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Sample records for polarographic oxygen electrodes

  1. Oxygen tension in human tumours measured with polarographic needle electrodes and its relationship to vascular density, necrosis and hypoxia

    International Nuclear Information System (INIS)

    Lyng, Heidi; Sundfoer, Kolbein; Rofstad, Einar K.

    1997-01-01

    Background and purpose: The use of polarographic needle electrodes for measurement of oxygen tension (pO 2 ) in tumours requires documentation of the validity of the method. In the present work the pO 2 values measured polarographically with the Eppendorf pO 2 histograph in human tumours were compared with the histological appearance of the tumour tissue, i.e. vascular density, fraction of necrosis and fraction of hypoxic tissue, to investigate whether the measurements reflected the expected pO 2 . Materials and methods: The pO 2 was measured in cervix tumours in patients and in human melanoma xenografted tumours in athymic mice. Vascular density was determined in the cervix tumours by histological analysis of biopsies from the pO 2 measurement tracks. Fraction of necrosis and fraction of hypoxic tissue, i.e. tissue binding the hypoxia marker pimonidazole, were determined in the melanomas by analysis of histological sections from the tumour planes in which the pO 2 measurements were performed. Results: The pO 2 distributions showed large intratumour heterogeneity. In cervix tumours, tumour regions with vascular density (vascular length per unit tissue volume) in the range of 47-77 mm/mm 3 showed higher pO 2 than tumour regions with vascular density in the range of 20-47 mm/mm 3 , which in turn showed higher pO 2 than tumour regions with vascular density in the range of 0-20 mm/mm 3 . In melanomas, tumour regions in which necrosis and hypoxia constituted more than 50% of the tissue showed lower pO 2 than other tumour regions. Conclusions: The pO 2 measured in the tumours was consistent with the histological appearance of the tissue in which the measurements were performed, suggesting that reliable pO 2 distributions of tumours can be obtained with polarographic needle electrodes

  2. Multi Frequency Phase Fluorimetry (MFPF) for Oxygen Partial Pressure Measurement: Ex Vivo Validation by Polarographic Clark-Type Electrode

    Science.gov (United States)

    Boehme, Stefan; Duenges, Bastian; Klein, Klaus U.; Hartwich, Volker; Mayr, Beate; Consiglio, Jolanda; Baumgardner, James E.; Markstaller, Klaus; Basciani, Reto; Vogt, Andreas

    2013-01-01

    Background Measurement of partial pressure of oxygen (PO2) at high temporal resolution remains a technological challenge. This study introduces a novel PO2 sensing technology based on Multi-Frequency Phase Fluorimetry (MFPF). The aim was to validate MFPF against polarographic Clark-type electrode (CTE) PO2 measurements. Methodology/Principal Findings MFPF technology was first investigated in N = 8 anaesthetised pigs at FIO2 of 0.21, 0.4, 0.6, 0.8 and 1.0. At each FIO2 level, blood samples were withdrawn and PO2 was measured in vitro with MFPF using two FOXY-AL300 probes immediately followed by CTE measurement. Secondly, MFPF-PO2 readings were compared to CTE in an artificial circulatory setup (human packed red blood cells, haematocrit of 30%). The impacts of temperature (20, 30, 40°C) and blood flow (0.8, 1.6, 2.4, 3.2, 4.0 L min−1) on MFPF-PO2 measurements were assessed. MFPF response time in the gas- and blood-phase was determined. Porcine MFPF-PO2 ranged from 63 to 749 mmHg; the corresponding CTE samples from 43 to 712 mmHg. Linear regression: CTE = 15.59+1.18*MFPF (R2 = 0.93; PPO2 ranged from 20 to 567 mmHg and CTE samples from 11 to 575 mmHg. Linear regression: CTE = −8.73+1.05*MFPF (R2 = 0.99; PPO2 due to variations of temperature were less than 6 mmHg (range 0–140 mmHg) and less than 35 mmHg (range 140–750 mmHg); differences due to variations in blood flow were less than 15 mmHg (all P-values>0.05). MFPF response-time (monoexponential) was 1.48±0.26 s for the gas-phase and 1.51±0.20 s for the blood-phase. Conclusions/Significance MFPF-derived PO2 readings were reproducible and showed excellent correlation and good agreement with Clark-type electrode-based PO2 measurements. There was no relevant impact of temperature and blood flow upon MFPF-PO2 measurements. The response time of the MFPF FOXY-AL300 probe was adequate for real-time sensing in the blood phase. PMID:23565259

  3. Determination of permeability and diffusivity of oxygen in polymers by polarographic method with inert gas by polarographic method with inert gas

    Czech Academy of Sciences Publication Activity Database

    Wichterlová, J.; Wichterle, K.; Michálek, Jiří

    2005-01-01

    Roč. 46, č. 23 (2005), s. 9974-9986 ISSN 0032-3861 R&D Projects: GA ČR GA106/00/1296 Institutional research plan: CEZ:AV0Z40500505 Keywords : oxygen permeability * oxygen diffusivity * polarographic method Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.849, year: 2005

  4. A dc polarographic study of the reduction of oxygen catalyzed by adsorbed Pb(II) species

    NARCIS (Netherlands)

    Pieterse, M.M.J.; Sluyters-Rehbach, M.; Sluyters, J.H.; A dc polarographic study of the reduction of oxygen catalyzed by adsorbed Pb(II) species

    1980-01-01

    The enhancement of the dc polarographic reduction current of oxygen by adsorbed Pb(II) species first observed by Strnad in 1939 and later studied qualitatively by a number of other authors has been reconsidered both experimentally and theoretically. A number of possible reaction mechanisms is

  5. Influence of pretreatment polarographically measured oxygenation levels in spontaneous canine tumors treated with radiation therapy

    Energy Technology Data Exchange (ETDEWEB)

    Bley, C.R.; Ohlerth, S.; Wergin, M.; Achermann, R.; Kaser-Hotz, B. [Section of Diagnostic Imaging and Radiation Oncology, Vetsuisse Faculty, Univ. of Zurich (Switzerland); Roos, M. [Biostatistics, ISPM, Univ. of Zurich (Switzerland)

    2006-09-15

    Background and purpose: the level of hypoxia in primary tumors has been described to influence response to treatment. The aim of the present study was to investigate the impact of pretreatment oxygen level measurements in spontaneous canine tumors on treatment outcome. Material and methods: data of pretreatment tumor oxygenation status and local tumor response after primary radiation therapy in a group of spontaneously occurring tumors in dogs (n = 52) was collected. Radiation therapy was given with curative (14-17 x 3-3.5 Gy) or palliative intent (3 x 8 Gy or 4-5 x 6 Gy). Progression-free interval and overall survival were correlated to polarographically measured tumor oxygenation status. Results: in the curatively irradiated group, tumors with median p0{sub 2} values {<=} 10 mmHg tended to have shorter median progression-free interval compared to better oxygenated tumors (246 vs. 739 days). The same trend could be shown for overall survival (330 vs. 745 days), indicating a cutoff value in this region. In the group treated with lower doses of radiation, the level of oxygen was no longer found to be of prognostic value; however, in this group hemoglobin had a significant impact on outcome. Conclusion: in curatively irradiated spontaneous canine tumors, tumor hypoxia was found to be a prognostic indicator, independent of tumor histologies and volume. (orig.)

  6. Robust high temperature oxygen sensor electrodes

    DEFF Research Database (Denmark)

    Lund, Anders

    Platinum is the most widely used material in high temperature oxygen sensor electrodes. However, platinum is expensive and the platinum electrode may, under certain conditions, suffer from poisoning, which is detrimental for an oxygen sensor. The objective of this thesis is to evaluate electrode...... materials as candidates for robust oxygen sensor electrodes. The present work focuses on characterising the electrochemical properties of a few electrode materials to understand which oxygen electrode processes are limiting for the response time of the sensor electrode. Three types of porous platinum......-Dansensor. The electrochemical properties of the electrodes were characterised by electrochemical impedance spectroscopy (EIS), and the structures were characterised by x-ray diffraction and electron microscopy. At an oxygen partial pressures of 0.2 bar, the response time of the sensor electrode was determined by oxygen...

  7. The relationship between temporal variation of hypoxia, polarographic measurements and predictions of tumour response to radiation

    Science.gov (United States)

    Toma-Dasu, Iuliana; Dasu, Alexandru; Karlsson, Mikael

    2004-10-01

    The polarographic oxygen sensor is one of the most used devices for in vivo measurements of oxygen and many other measurement techniques for measuring tumour hypoxia are correlated with electrode measurements. Little is known however about the relationship between electrode measurements and the real tissue oxygenation. This paper investigates the influence of the temporal change of the hypoxic pattern on the electrode measurements and the tumour response. Electrode measurements and tumour response were simulated using a computer program that allows both the calculation of the tissue oxygenation with respect to the two types of hypoxia that might arise in tumours and the virtual insertion of the electrode into the tissue. It was therefore possible to control the amount of each type of hypoxia in order to investigate their influence on the measurement results. Tissues with several vascular architectures ranging from well oxygenated to poorly oxygenated were taken into consideration as might be seen in practice. The influence of the electrode measurements on the treatment outcome was estimated by calculating the tumour control probability for the tumours characterized either by the real or by the measured tumour oxygenation. We have simulated electrode oxygen measurements in different types of tissues, covering a wide range of tumour oxygenations. The results of the simulations showed that the measured distribution depends on the details of the vascular network and not on the type of hypoxia. We have also simulated the effects of the temporal change of the acute hypoxic pattern due to the opening and the closure of different blood vessels during a full fractionated treatment. The results of this simulation suggested that the temporal variation of the hypoxic pattern does not lead to significantly different results for the electrode measurements or the predicted tumour control probabilities. In conclusion, it was found that the averaging effect of the electrode leads

  8. Bifunctional electrocatalyst for oxygen/air electrodes

    International Nuclear Information System (INIS)

    Sasikala, N.; Ramya, K.; Dhathathreyan, K.S.

    2014-01-01

    Highlights: • Nano-Silver powder was prepared by chemical method. • Ag catalyst was characterized by SEM and XRD studies. • Ag was investigated as bi-functional electrocatalyst for oxygen/air electrodes. • Ag shows good electrochemical activity towards OER and ORR reactions. - Abstract: Nano-Silver powder has been studied as bi-functional electrocatalyst for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline medium. Ag nano-powder has been prepared by a simple wet chemical method with Silver nitrate as precursor and Glucose as reducing agent. X-ray Diffraction and Scanning Electron Microscopy studies were carried out to characterize the Silver catalyst. Electrochemical oxygen evolution characterization shows anodic peak typically at the range between 0.350 and 0.514 V Vs Hg/HgO corresponding to Silver oxidation followed by the onset of oxygen evolution at 0.706 V. Oxygen reduction reaction studies carried out using Rotating Disc Electrode (RDE) confirm the four electron reaction mechanism. Ag catalyst shows promising characteristics for oxygen evolution and oxygen reduction

  9. Tumour oxygenation assessed by F-18-fluoromisonidazole PET and polarographic needle electrodes in human soft tissue tumours

    DEFF Research Database (Denmark)

    Bentzen, L; Keiding, S; Nordsmark, M

    2003-01-01

    patients with tumours suspected to be STS were examined by [F-18]FMISO PET scanning, and eleven of these patients completed a set of Eppendorf PO2 Histograph measurements following the scanning. Results and discussion: By histopathological diagnosis, seven tumours were shown to be STS and six tumours were...

  10. Automatic polarographic elucidation of electrode mechanisms by means of a knowledge-based system, part 3: Mechanisms ECE, EE and mechanisms involving adsorption

    NARCIS (Netherlands)

    Palys, M.J.; Palys, M.J.; Bos, M.; van der Linden, W.E.

    1993-01-01

    The previously described expert system has been extended: rules allowing the elucidation of a larger number of mechanisms have been added and automatic control of additional experimental parameters such as concentration and composition of the solution in the cell and the electrode size has been made

  11. Improved Internal Reference Oxygen Sensors with Composite Ceramic Electrodes

    DEFF Research Database (Denmark)

    Hu, Qiang; Jacobsen, Torben; Hansen, Karin Vels

    2012-01-01

    Potentiometric oxygen sensors with an internal reference electrode, which uses the equilibrium pO2 of the binary mixture of Ni/NiO as the reference, are demonstrated. The cells employ Pt or composite ceramics as the sensing electrode. The cells are fabricated by a flexible and potentially low cos...... and performance are highly reproducible. The composite ceramics, based on strontium doped manganite and yttria doped zirconia, are proven superior over Pt to serve as the electrode material.......Potentiometric oxygen sensors with an internal reference electrode, which uses the equilibrium pO2 of the binary mixture of Ni/NiO as the reference, are demonstrated. The cells employ Pt or composite ceramics as the sensing electrode. The cells are fabricated by a flexible and potentially low cost...

  12. The effect of X-irradiation on aqueous media containing traces of oxygen

    International Nuclear Information System (INIS)

    Evans, N.T.S.

    1981-01-01

    The effect of X-irradiation on small amounts of oxygen dissolved in 1 mM potassium chloride solution, tap water or Eagle's tissue culture medium has been followed with polarographic electrodes. Oxygen is removed from all these solutions down to concentrations corresponding to a few parts per million in the gas phase. Small amounts of hydrogen are also produced by irradiation and can be measured polarographically. Except in Eagle's medium, hydrogen peroxide is formed in the anoxic solutions, and molecular oxygen can be detected after irradiation when catalase is present in the solution. A non-volatile polarographically reducible substance is generated by irradiation of anoxic Eagle's medium. It is not decomposed by catalase but decays spontaneously in solution at a slow rate. (author)

  13. Polarographic measurement of ascorbate washout in isolated perfused rabbit hearts

    International Nuclear Information System (INIS)

    Arts, T.; Kuikka, J.T.; Reneman, R.S.; Bassingthwaighte, J.B.

    1985-01-01

    To study the myocardial washout of ascorbate, the applicability of polarographic detection of ascorbate ions by a platinum electrode (sensitive area 0.03 mm2) was investigated, in both a calibration setup (sampling flow along the electrode: 100 microliter X s-1) and isolated, retrogradely perfused rabbit hearts. In the calibration setup at pH 7.4, the sensitivity of the electrode was 70 microA/mol. This sensitivity increased moderately with increasing pH (13%/unit pH) and increasing sampling flow rate (14% at an increase from 100 to 150 microliter X s-1). In the isolated hearts, ascorbate infused into the aorta was detected in a right ventricular drain by the electrode as well as by the use of 14 C-labeled ascorbate. Both recorded time courses were similar except for a scaling factor dependent on flow velocity. During continuous infusion the arteriovenous difference of ascorbate was 2 +/- 2% (SD), indicating a relatively low consumption of ascorbate by the isolated heart. The authors conclude that polarographic measurement of ascorbate in the coronary effluent of an isolated rabbit heart can be performed on-line and relatively easily

  14. Correlation of pretreatment polarographically measured oxygen pressures with quantified contrast-enhanced power doppler ultrasonography in spontaneous canine tumors and their impact on outcome after radiation therapy

    Energy Technology Data Exchange (ETDEWEB)

    Rohrer Bley, Carla; Laluhova, Dagmar [Section of Radiooncology, Vetsuisse Faculty, Univ. of Zurich (Switzerland); Roos, Malgorzata [Inst. for Social and Preventive Medicine, Medical Faculty, Univ. of Zurich (Switzerland); Kaser-Hotz, Barbara [Section of Radiooncology, Vetsuisse Faculty, Univ. of Zurich (Switzerland); Section Imaging Diagnostics, Vetsuisse Faculty, Univ. of Zurich (Switzerland); Ohlerth, Stefanie [Section Imaging Diagnostics, Vetsuisse Faculty, Univ. of Zurich (Switzerland)

    2009-11-15

    Purpose: to evaluate the use of noninvasive quantified contrast-enhanced power Doppler ultrasonography as a surrogate in the estimation of tumor hypoxia measured by invasive pO{sub 2} histography in canine tumors. Material and methods: data of pretreatment tumor oxygenation status, tumor vascularity and blood volume, and tumor response after radiation therapy was collected in 48 spontaneous malignant oral tumors (Table 1). Tumor oxygenation status was correlated to vascularity and blood volume, and influences on outcome after treatment were analyzed. Results: although vascularity and blood volume correlated moderately with median pO{sub 2} (r = 0.51 and 0.61; p = 0.001 and < 0.0001) and percentage of pO{sub 2} readings {<=} 2.5, 5, and 10 mmHg (r = -0.37 to -0.42; p < 0.01-0.03) for all tumors, they did not correlate within the different histology groups (p = 0.06-0.9). For all tumors, pretreatment oxygenation status, vascularity and blood volume were not found to be of prognostic value. Conclusion: these analyses show that quantified contrast-enhanced power Doppler ultrasonography does not represent a non-invasive indirect method to assess tumor hypoxia measured by invasive pO{sub 2} histography. Both technologies were nonprognostic indicators in spontaneous malignant canine oral tumors. (orig.)

  15. Reduction of the Electrode Overpotential of the Oxygen Evolution Reaction by Electrode Surface Modification

    OpenAIRE

    Lu, Cian-Tong; Chiu, Yen-Wen; Li, Mei-Jing; Hsueh, Kan-Lin; Hung, Ju-Shei

    2017-01-01

    Metal–air batteries exhibit high potential for grid-scale energy storage because of their high theoretical energy density, their abundance in the earth’s crust, and their low cost. In these batteries, the oxygen evolution reaction (OER) occurs on the air electrode during charging. This study proposes a method for improving the OER electrode performance. The method involves sequentially depositing a Ni underlayer, Sn whiskers, and a Ni protection layer on the metal mesh. Small and uniform gas ...

  16. New Hypothesis for SOFC Ceramic Oxygen Electrode Mechanisms

    DEFF Research Database (Denmark)

    Mogensen, Mogens Bjerg; Chatzichristodoulou, Christodoulos; Graves, Christopher R.

    2016-01-01

    A new hypothesis for the electrochemical reaction mechanism in solid oxide cell ceramic oxygen electrodes is proposed based on literature including our own results. The hypothesis postulates that the observed thin layers of SrO-La2O3 on top of ceramic perovskite and other Ruddlesden-Popper...

  17. Polarographic determination of indium and thallium iodides in phosphor tablets

    International Nuclear Information System (INIS)

    Babich, G.A.; Dzhurka, G.F.; Kozhushko, G.M.; Kravtsova, K.F.; Magda, V.I.

    1984-01-01

    The technique of polarographic determination of indium and thallium iodides in phosphor tablets without preliminary separation of elements was developed. Mercury-dropping electrode was used as an indicator, and saturated calomel electrode was used as an auxiliary electrode. A recording of reduction currents was performed in the potential interval from -0.25 up to 1.15 V at potential sweep speed of 200 mV/min. Optimum conditions of sample acidic decomposition and polarography were presented. A solution of ethylene diamine (0.5 M), of ammonia (0.25 M) and of potassium chloride (0.05 M) served as a background electrolyte. The suggested technique allows one to determine component contents in tablets with a satisfactory accuracy. A period of one tablet analysis constitutes 1.5 h

  18. Reduction of the Electrode Overpotential of the Oxygen Evolution Reaction by Electrode Surface Modification

    Directory of Open Access Journals (Sweden)

    Cian-Tong Lu

    2017-01-01

    Full Text Available Metal–air batteries exhibit high potential for grid-scale energy storage because of their high theoretical energy density, their abundance in the earth’s crust, and their low cost. In these batteries, the oxygen evolution reaction (OER occurs on the air electrode during charging. This study proposes a method for improving the OER electrode performance. The method involves sequentially depositing a Ni underlayer, Sn whiskers, and a Ni protection layer on the metal mesh. Small and uniform gas bubbles form on the Ni/Sn/Ni mesh, leading to low overpotential and a decrease in the overall resistance of the OER electrode. The results of a simulated life cycle test indicate that the Ni/Sn/Ni mesh has a life cycle longer than 1,300 cycles when it is used as the OER electrode in 6 M KOH.

  19. The study of Cr3+/Cr2+ redox system by polarographic method

    Directory of Open Access Journals (Sweden)

    S. A. Pokhmyolkina

    2014-08-01

    Full Text Available Aim. The relevance of the theme is the ability to determine kinetic and thermodynamic parameters of the redox system on the example of Сr3/ Cr2in order to explain the reaction mechanism. In this paper, the electrochemical behavior of Cr+3/ Cr+2has been studied by polarography method. Polarogramshave been interpreted using the theory of irreversible polarographic waves and thermodynamically irreversible processes. Experiments have been carried out in a sealed cell with an outer casing for temperature control. Air oxygen removed from the feed solution for 15-20 minutes, purified nitrogen flowing from the cylinder. Characterization of the capillary in a 0.1N solution.H2SO4: mass flowing mercury m = 2,39 mg / sec; droplet formation period τ = 1,25 sec. Sulfate Cr (II was prepared by dissolving an electrolytic chromium 150 cm3 of water and 46 grams of 98 % sulphate acid. Thus a saturated solution formed a blue color. Sulfate salt solutions of two- and trivalent chromium in the medium of 0.1NH2SO4 give one wave. Anodic diffusion current sulfate Cr (II was 4,67μa, and half-wave potential E ½ = -0,44 V. The cathode current diffuse sulfate Cr (III, respectively - 7,65μa and E ½ = - 1,01 V. Inconsistency half-wave potentials of anodic and cathodic processes indicates its irreversibility. Half-wave potentials are given with respect to a saturated calomel electrode. Polarogramshave been investigated in the temperature range of 20-600C every 100C. Temperature coefficients have been calculated by the equation: Β% = idt –id20/ id20Δt, whereidtis diffusion current for a given concentration of the test solution at t0С; id20 is diffusion current for the same concentration at 200C; Δt - temperature change relative to 200C . Irreversibility, obviously due to the change in the electron configuration of chromium electrode is accompanying the redox process.Using the theory of irreversible polarographic waves we have determined the kinetic characteristics

  20. Pressure gap and electrode artefacts in the electrochemically induced oxygen spillover on Pt/YSZ electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Toghan, Arafat; Roesken, Liz; Imbihl, Ronald [Institut fuer Physikalische Chemie und Elektrochemie, Leibniz-Universitaet Hannover, Callinstr. 3 - 3a, D-30167 Hannover (Germany); Haevecker, Michael; Knop-Gericke, Axel [Fritz-Haber-Institut, Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin (Germany)

    2011-07-01

    Mechanistically, the electrochemical promotion of catalytic reactions (EPOC) on Pt/YSZ (yttrium stabilized zirconia) catalysts has been shown to be due to the spillover of oxygen from the solid electrolyte onto the Pt surface. This spillover has been studied on Pt/YSZ catalysts with photoemission electron microscope (PEEM) and with a differentially pumped x-ray photoelectron spectrometer (XPS) allowing to conduct in situ studies up to 1 mbar. PEEM revealed that upon electrochemical pumping not only the expected darkening of the Pt electrodes can be observed which is due to spillover oxygen but that also bright spots develop. These bright spots were attributed to metallic zirconium formed as electrically disconnected parts of the Pt electrode assume a negative potential thus causing a local reduction of zirconia. With XPS the main goal was to study whether a second special spillover species develops upon electrochemical pumping at high pressure which is different from chemisorbed oxygen. This special spillover species has been postulated by Vayenas et al. and was supposedly responsible for the non-Faradaic nature of EPOC. Up to now even at p=0.2 mbar only chemisorbed oxygen was detected.

  1. Iron oxide reference electrodes in solid electrolyte sensors designed to control the thermodynamic activity of oxygen

    International Nuclear Information System (INIS)

    Martynov, P.N.; Askhadullin, R.Sh.; Ivanov, K.D.; Chernov, M.E.; Ul'yanov, V.V.; Shelemet'ev, V.M.; Sadovnichij, R.P.; Cheporov, R.Yu.; Niyazov, S.-A.S.

    2012-01-01

    The paper presents results on the use of iron oxide reference electrode in the oxygen activity sensors used to measure the oxygen activity in heavy liquid metal coolants. The specific features of the operation of the sensor with iron oxide reference electrode are established and comparative characteristics with respect to other applicable reference electrodes are presented. Conclusions on the reasonability of its use for measurement of oxygen activity in liquid metal media are drawn [ru

  2. Early Polarographic Studies on Proteins

    Czech Academy of Sciences Publication Activity Database

    Heyrovský, Michael

    2004-01-01

    Roč. 16, 13/14 (2004), s. 1067-1073 ISSN 1040-0397 Institutional research plan: CEZ:AV0Z4040901 Keywords : proteins * dropping mercury electrode * peptides Subject RIV: CG - Electrochemistry Impact factor: 2.038, year: 2004

  3. Fundamental aspects of electrocatalysis of the hydrogen electrode reaction and oxygen electrode reaction on platinum

    Science.gov (United States)

    Bao, Jianer

    This dissertation work studies the fundamental aspects of the electrocatalysis of the hydrogen electrode reaction (HER) and oxygen electrode reaction (OER) on platinum over a wide temperature range from ambient up to 220°C. Previously, the majority of the work reported was restricted to temperatures below 70°C due to apparatus constraints, whereas the current operation temperature for proton exchange membrane fuel cells is around 100oC and is envisioned to operate at even higher temperatures. In this work, a special apparatus for controlled hydrodynamic study was constructed, which can keep the system in a single aqueous phase at elevated temperatures. The growth kinetics and mechanism of the anodic oxide film on platinum are studied under potential sweep conditions. By fitting the current equation derived based on the framework of the point defect model (PDM) on the linear polarization curves, the kinetic parameters for film growth and dissolution are extracted, which agree well with other findings. The kinetics and mechanism of the HER are investigated both at ambient temperature with a rotating ring disk electrode and at elevated temperatures with a platinized nickel electrode. Ambient results by micropolarization analysis agree well with findings in literature, and yield an exchange current density on the order of mA/cm2. An activation energy of 17.3kJ/mol is determined. This is comparable with that of a bulk platinum electrode, and is lower than sputtered platinum and single crystal platinum electrodes in alkaline solutions. Surprisingly, the apparent Tafel slope of the hydrogen evolution reaction is almost temperature independent. The most probable reason is that two parallel reactions with different activation energy and transfer coefficients are occurring at the interface. The OER on platinum is also studied by potential sweep method and potentiostatic polarization method. The sluggish nature of this reaction is postulated to be due to the existence of a

  4. Differential Pulse Polarographic Determination of Enalapril Maleate

    OpenAIRE

    ELMALI, Fikriye; ALPDOĞAN, Güzin

    2003-01-01

    A differential pulse polarographic (DPP) method has been developed for the quantitative analysis of enalapril maleate. Enalapril maleate gives a peak at -1.4 V in methanol. A calibration curve was constructed for the 20 -100 m g ml-1 concentration range. As a reference method, a reversed phase high performance liquid chromatographic procedure has been developed. Commercially available tablets were analysed by the two methods. Statistical evaluations indicated that there was no sign...

  5. Theory and development of fluorescence-based optochemical oxygen sensors: oxygen optodes.

    Science.gov (United States)

    Opitz, N; Lübbers, D W

    1987-01-01

    As the preceding considerations concerning the physical and technical features of oxygen optodes have demonstrated, fluorescence-based optochemical oxygen sensors possess certain advantages and peculiarities compared to conventionally applied electrochemical sensors such as polarographic oxygen electrodes. First, in contrast to oxygen electrodes, oxygen measurements with oxygen optodes do not suffer from distortions caused by the reference electrodes. In addition, because of the polarographic process, platinum electrodes continuously consume oxygen, which falsifies the results, especially when small sample volumes or long-term measurements, or both, are involved, whereas the sensor layer of oxygen optodes must only be equilibrated. Moreover, the surface of the platinum wire has to be catalytically clean in order to obtain a plateau of the polarogram and, consequently, to achieve a low rest current at zero PO2. Unfortunately, the demand for catalytically clean platinum surfaces turns out to be rather critical, since surface contamination occurs even with membranized electrodes, resulting in the well-known phenomenon of "electrode poisoning." The question of the specificity of oxygen electrodes also must be considered. In this context, CO2 and halothane may interfere with oxygen measurements, whereas fluorescence quenching is unaffected by CO2 and halothane affects the measurements only slightly, depending on the special indicator used. Furthermore, because of the flow dependence, oxygen measurements with the oxygen electrode show a distinct "stirring effect" caused by the turbulence in front of the electrode, which disturbs the diffusion field. Because of the completely different physical principle of fluorescence optical sensors, such influences are not observed with oxygen optodes. In addition, isolation and shielding of electrical circuits found in electrodes are not necessary for optodes. Furthermore, the sensitivity of oxygen optodes can be tuned to the desired

  6. High performance methanol-oxygen fuel cell with hollow fiber electrode

    Science.gov (United States)

    Lawson, Daniel D. (Inventor); Ingham, John D. (Inventor)

    1983-01-01

    A methanol/air-oxygen fuel cell including an electrode formed by open-ended ion-exchange hollow fibers having a layer of catalyst deposited on the inner surface thereof and a first current collector in contact with the catalyst layer. A second current collector external of said fibers is provided which is immersed along with the hollow fiber electrode in an aqueous electrolyte body. Upon passage of air or oxygen through the hollow fiber electrode and introduction of methanol into the aqueous electrolyte, a steady current output is obtained. Two embodiments of the fuel cell are disclosed. In the first embodiment the second metal electrode is displaced away from the hollow fiber in the electrolyte body while in the second embodiment a spiral-wrap electrode is provided about the outer surface of the hollow fiber electrode.

  7. Electroenzymatic Reactions With Oxygen on Laccase-Modified Electrodes in Anhydrous (Pure) Organic Solvent

    DEFF Research Database (Denmark)

    Yarapolov, A.; Shleev, S.; Zaitseva, E.

    2007-01-01

    glassy carbon and graphite electrodes with adsorbed laccase. The influence of the time for drying the laccase solution at the electrode surface on the electroreduction of oxygen was studied. Investigating the electroenzymatic oxidation reaction of catechol and hydroquinone in DMSO reveals the formation...

  8. Perovskites as electrodes of solid cells in sensitive elements of oxygen ion

    International Nuclear Information System (INIS)

    Gandurska, J.; Sniezynska, I.; Marek, A.; Szwagierczak, D.; Kulawik, J.

    1997-01-01

    The perovskite family comprises many compounds used in electronic applications. In this work perovskite materials based on LaCrO 3 were investigated, destined for electrodes of solid electrolyte oxygen sensors. lanthanum chromite powders modified by calcium, strontium and aluminium were prepared by the coprecipitation-calcination technique. The powders were examined using thermal analysis, x-ray diffraction analysis, scanning electron microscopy and transmission electron microscopy. Introductory studies of electromotive force of oxygen cells with yttria stabilized zirconia as solid electrolyte and perovskite-based electrodes proved that it is possible to replace expensive Pt electrodes by much cheaper perovskite ones. (author)

  9. Kinetics of oxygen reduction reaction at tin-adatoms-modified gold electrodes in acidic media

    International Nuclear Information System (INIS)

    Miah, Md. Rezwan; Ohsaka, Takeo

    2009-01-01

    In the present report, oxygen reduction reaction (ORR) at polycrystalline gold (Au (poly)) electrode in situ modified by the underpotential deposition (upd) of Sn-adatoms is addressed. The ORR was investigated at the Sn-adatoms-modified Au (poly) electrode by the hydrodynamic voltammetric technique with a view to evaluating the various related kinetic parameters. The results demonstrated that the underpotential deposited Sn-adatoms on the Au (poly) electrode substantially promoted the activity of the electrode towards an exclusive one-step four-electron ORR forming H 2 O as the final product.

  10. Kinetics of oxygen reduction reaction at tin-adatoms-modified gold electrodes in acidic media

    Energy Technology Data Exchange (ETDEWEB)

    Miah, Md. Rezwan [Department of Electronic Chemistry, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Mail Box G1-5, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502 (Japan)], E-mail: mrmche@yahoo.com; Ohsaka, Takeo [Department of Electronic Chemistry, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Mail Box G1-5, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502 (Japan)], E-mail: ohsaka@echem.titech.ac.jp

    2009-10-01

    In the present report, oxygen reduction reaction (ORR) at polycrystalline gold (Au (poly)) electrode in situ modified by the underpotential deposition (upd) of Sn-adatoms is addressed. The ORR was investigated at the Sn-adatoms-modified Au (poly) electrode by the hydrodynamic voltammetric technique with a view to evaluating the various related kinetic parameters. The results demonstrated that the underpotential deposited Sn-adatoms on the Au (poly) electrode substantially promoted the activity of the electrode towards an exclusive one-step four-electron ORR forming H{sub 2}O as the final product.

  11. Composite electrodes for oxygen evolution in metal electrowinning

    OpenAIRE

    Schmachtel, Sönke

    2017-01-01

    Oxygen evolution is the most common anode reaction in the electrowinning (EW) of metals from acidic sulfate based electrolytes and is a reaction that requires high activation overpotentials. Since the the oxygen evolution reaction contributes roughly 500-800 mV to the cell voltage which is roughly 15-25% of the total cell voltage, there has been increasing interest to replace the traditionally used lead anode by alternative anodes employing better electrocatalysts that show lower oxygen evolu...

  12. NanoCOT: Low-Cost Nanostructured Electrode Containing Carbon, Oxygen, and Titanium for Efficient Oxygen Evolution Reaction.

    Science.gov (United States)

    Shan, Zhichao; Archana, Panikar Sathyaseelan; Shen, Gang; Gupta, Arunava; Bakker, Martin G; Pan, Shanlin

    2015-09-23

    Developing high-efficiency, durable, and low-cost catalysts based on earth-abundant elements for the oxygen evolution reaction (OER) is essential for renewable energy conversion and energy storage devices. In this study, we report a highly active nanostructured electrode, NanoCOT, which contains carbon, oxygen, and titanium, for efficient OER in alkaline solution. The NanoCOT electrode is synthesized from carbon transformation of TiO2 in an atmosphere of methane, hydrogen, and nitrogen at a high temperature. The NanoCOT exhibits enhanced OER catalytic activity in alkaline solution, providing a current density of 1.33 mA/cm(2) at an overpotential of 0.42 V. This OER current density of a NanoCOT electrode is about 4 times higher than an oxidized Ir electrode and 15 times higher than a Pt electrode because of its nanostructured high surface area and favorable OER kinetics. The enhanced catalytic activity of NanoCOT is attributed to the presence of a continuous energy band of the titanium oxide electrode with predominantly reduced defect states of Ti (e.g., Ti(1+), Ti(2+), and Ti(3+)) formed by chemical reduction with hydrogen and carbon. The OER performance of NanoCOT can also be further enhanced by decreasing its overpotential by 150 mV at a current density of 1.0 mA/cm(2) after coating its surface electrophoretically with 2.0 nm IrOx nanoparticles.

  13. Analysis of molybdenum, chromium, vanadium and iron by polarographic techniques

    International Nuclear Information System (INIS)

    Al-Zand, T.K.

    1986-01-01

    The application of direct current Tast polarograph, differential pulse polarography and phase-selective alternative current Tast polarography to the problem of determining molybdenum, chromium, vanadium and iron in various supporting electrolytes is reported. The effect of the supporting electrolyte on the wave/peak potential and sensitivity of the metal ion have been examined. The polarographic methods were applied for simultaneous determination of chromium (3)/chromium (6), vanadium (4), vanadium (5) and iron (2)/iron (3) in different supporting electrolytes

  14. Composite oxygen electrode and method for preparing same

    DEFF Research Database (Denmark)

    2010-01-01

    on the surface of said backbone structure, wherein said electrocatalytic layer comprises first and second nanoparticles, wherein the first and second particles are randomly distributed throughout said layer. The present invention further comprises a method of producing the above composite electrode, comprising...

  15. Oxygen electrodes for ceramic fuel cells with proton and oxide ion conducting electrolytes

    OpenAIRE

    Strandbakke, Ragnar

    2014-01-01

    The overall aim of this work is to contribute to a better understanding of the reactions taking place at the oxygen electrode in proton ceramic fuel cells (PCFCs) and, moreover, to develop new materials with improved performance for this electrode. PCFCs and their cathode reactions are the main focus of the study, but these reactions are often running in parallel with reactions associated with other charge carriers that also need to be addressed. Most proton conducting ceramics exhibit also t...

  16. Composite Sr- and V-doped LaCrO3/YSZ sensor electrode operating at low oxygen levels

    DEFF Research Database (Denmark)

    Lund, Anders; Jacobsen, Torben; Hansen, Karin Vels

    2012-01-01

    A porous composite electrode of La0.8Sr0.2Cr0.97V0.03O3 -delta (LSCV) and yttria-stabilised zirconia (YSZ) was evaluated as a possible candidate for high-temperature potentiometric oxygen sensor measuring electrodes. The oxygen processes at the electrode were characterised by performing electroch....... The relatively low response time at 700º C at an oxygen partial pressure of around 5x10-6 bar and an inlet gas flow rate of 8 L h-1 makes the LSCV/YSZ electrode suitable for use as an potentiometric oxygen sensor electrodes.......A porous composite electrode of La0.8Sr0.2Cr0.97V0.03O3 -delta (LSCV) and yttria-stabilised zirconia (YSZ) was evaluated as a possible candidate for high-temperature potentiometric oxygen sensor measuring electrodes. The oxygen processes at the electrode were characterised by performing...... and 400 nm. At oxygen partial pressures around 0.2 bar at 700º C, the oxygen reaction is dominated by solid-state diffusion of oxide ions and surface reaction kinetics. At oxygen partial pressures around 10-5 bar above 800º C, gas phase mass transport processes dominate the impedance spectra...

  17. Comparison of the transcutaneous oxygen and carbon dioxide tension in different electrode locations during general anaesthesia.

    Science.gov (United States)

    Nishiyama, T; Nakamura, S; Yamashita, K

    2006-12-01

    The best place for the electrode of transcutaneous measurement of oxygen tension (tcPO2) and carbon dioxide tension (tcPCO2) during general anaesthesia was investigated in three different locations. Fifteen patients for major abdominal surgery in the supine position were studied. The electrode of the TCM4 (Radiometer, Copenhagen, Denmark) was put on the chest, upper arm or forearm. TcPO2, tcPCO2, end-tidal carbon dioxide tension (etCO2), percutaneous oxygen saturation (SaO2), arterial oxygen tension (PaO2 ) and arterial carbon dioxide tension (PaCO2) were simultaneously measured at four different etCO2 concentrations and inhaled oxygen percentages and the location of the electrode was changed to other places to repeat the same measurement. In total, 12 measurements for each patient and 60 measurements for each place were performed. TcPO2 correlated better than SaO2 (R2 = 0.58) with PaO2 (R2 = 0.76), and tcPCO2 correlated well with PaCO2 (R2 = 0.76) and etCO2 (R2 = 0.74) when the electrode was put on the chest, while not on the upper arm or forearm (R2 tcPCO2 (bias, -0.47; limits of agreement, 8.7, -9.64) as surrogate measures of PaO2 and PaCO2, respectively even when the electrode was put on the chest. When the electrode was put on the chest, tcPO2 and tcPCO2 might be available as non-invasive monitors of oxygenation and CO2 status during general anaesthesia, while the absolute values were not interchangeable with PaO2 and PaCO2, respectively.

  18. Brain Tissue Oxygen: In Vivo Monitoring with Carbon Paste Electrodes

    Directory of Open Access Journals (Sweden)

    John P. Lowry

    2005-11-01

    Full Text Available In this communication we review selected experiments involving the use ofcarbon paste electrodes (CPEs to monitor and measure brain tissue O2 levels in awakefreely-moving animals. Simultaneous measurements of rCBF were performed using the H2clearance technique. Voltammetric techniques used include both differential pulse (O2 andconstant potential amperometry (rCBF. Mild hypoxia and hyperoxia produced rapidchanges (decrease and increase respectively in the in vivo O2 signal. Neuronal activation(tail pinch and stimulated grooming produced similar increases in both O2 and rCBFindicating that CPE O2 currents provide an index of increases in rCBF when such increasesexceed O2 utilization. Saline injection produced a transient increase in the O2 signal whilechloral hydrate produced slower more long-lasting changes that accompanied the behavioralchanges associated with anaesthesia. Acetazolamide increased O2 levels through an increasein rCBF.

  19. Energy control of neutral oxygen particles passing through an aperture electrode

    Science.gov (United States)

    Ohno, Takeo; Nakayama, Daiki; Okada, Takeru; Samukawa, Seiji

    2018-03-01

    The kinetic energy of neutralized oxygen particles passing through an aperture electrode was measured by a quadrupole mass spectrometer. The peak energy position was controlled by changing the plasma source power, acceleration bias power, and gas pressure in the vacuum chamber.

  20. Oxygen electrosorption on Ag(111) and Ag(110) electrodes in in NaOH solution

    NARCIS (Netherlands)

    Droog, J.M.M.

    1980-01-01

    The first stages of the anodic oxidation of Ag(111) and Ag(110) electrodes in NaOH solution were studied by potential sweep voltammetry and ellipsometry. It was found that in the potential region studied, dissolution of silver species and electrosorption of oxygen occur. The (110) face is much more

  1. Oxygen evolution on Ru1-xNixO2-y nanocrystalline electrodes

    Czech Academy of Sciences Publication Activity Database

    Macounová, Kateřina; Jirkovský, Jakub; Makarova, Marina; Franc, Jiří; Krtil, Petr

    2009-01-01

    Roč. 13, č. 6 (2009), s. 959-965 ISSN 1432-8488 R&D Projects: GA AV ČR KAN100400702 Institutional research plan: CEZ:AV0Z40400503 Keywords : electrolysis * film electrodes * oxygen evolution Subject RIV: CG - Electrochemistry Impact factor: 1.821, year: 2009

  2. Nature and Distribution of Stable Subsurface Oxygen in Copper Electrodes During Electrochemical CO2 Reduction

    DEFF Research Database (Denmark)

    Cavalca, Filippo Carlo; Ferragut, Rafael; Aghion, Stefano

    2017-01-01

    Oxide-derived copper (OD-Cu) electrodes exhibit higher activity than pristine copper during the carbon dioxide reduction reaction (CO2RR) and higher selectivity towards ethylene. The presence of residual subsurface oxygen in OD-Cu has been proposed to be responsible for such improvements, although...

  3. Communications: Elementary oxygen electrode reactions in the aprotic Li-air battery

    DEFF Research Database (Denmark)

    Hummelshøj, Jens Strabo; Blomquist, Jakob; Datta, Soumendu

    2010-01-01

    We discuss the electrochemical reactions at the oxygen electrode of an aprotic Li-air battery. Using density functional theory to estimate the free energy of intermediates during the discharge and charge of the battery, we introduce a reaction free energy diagram and identify possible origins...

  4. Oxygen exchange and transport in dual phase ceramic composite electrodes.

    Science.gov (United States)

    Druce, John; Téllez, Helena; Ishihara, Tatsumi; Kilner, John A

    2015-01-01

    Composites consisting of a perovskite-based electronic or mixed conductor with a fluorite-structured ionic conductor are often used as electrodes in solid oxide electrochemical energy conversion devices. After sintering the materials, there is often evidence for inter-reaction between the two phases, or inter-diffusion of cations or impurities between the two phases. We studied the (18)O exchange properties of a composite consisting of CGO and LSCF in a 50 : 50 ratio. High resolution ToF-SIMS mapping reveals that the (18)O fraction at the very outer surface of grains of the CGO phase is much higher than expected from D* and k* values for the single-phase parent material. Surface compositional analysis by ToF-SIMS and low energy ion scattering (LEIS) spectroscopy suggests that the surfaces of the CGO grains in the composite do not show the impurities which typically segregate to the surface in single-phase CGO. Thus, the "cleaning" of impurities from the CGO surface by dissolution into the perovskite phase may be one explanation for the apparent enhanced surface exchange for CGO in these composites.

  5. Reversible potentiometric oxygen sensors based on polymeric and metallic film electrodes.

    Science.gov (United States)

    Yim, H S; Meyerhoff, M E

    1992-09-01

    Various materials and sensor configurations that exhibit reversible potentiometric responses to the partial pressure of oxygen at room temperature in neutral pH solution are examined. In one arrangement, platinum electrodes are coated with plasticized poly(vinyl chloride) films doped with a cobalt(II) tetraethylene pentamine complex. For such sensors, potentiometric oxygen response is attributed to a mixed potential originating from the underlying platinum electrode surface as well as a change in redox potential of the Co(II)-tetren-doped film as the complex binds oxygen reversibly. The response due to the platinum surface is prolonged by the presence of the Co(II)-tetren/PVC film. Alternately, thin films of metallic copper, electrochemically deposited on platinum and/or sputtered or vapor deposited on a single crystal silicon substrate, may be used for reversible oxygen sensing. The long-term reversibility and potentiometric stability of such copper film-based sensors is enhanced (up to 1 month) by preventing the formation of cuprous oxide on the surfaces via the application of an external nonpolarizing cathodic current through the working electrode or by specifically using sputtered copper films that have [100] preferred crystal structures as determined by X-ray diffraction. The implications of these findings in relation to fabricating analytically useful potentiometric oxygen sensors are discussed.

  6. Polarographic studies about indium (III) behaviour in aqueous media of sodium azide

    International Nuclear Information System (INIS)

    Tokoro, R.

    1988-01-01

    The present study shows some polarographic behavior of indium (III) in azide media that is close those observed in a thiocyanate solution. The presence of azide ligand decreases the overpotential in the discharge of indium whose catalytic character can be explained by formation of an azide bridge between electrode and indium (III) increasing the speed of electron transfer. The discharge of indium in azide media is diffusion controlled. As the azide concentration is increased the half wave potential displaces in the cathodic direction. This displacement is due to complex formation. The number of electrons, n, involved in the total process was estimates by the reversible polarographic equation to be 2,7. The potentiostatic coulometry of indium in azide/hydrazoic acid buffer showed a catalytic process where the chemistry regeneration was performed by reaction of hydrazoic acid and indium amalgam. The electrochemistry evidence was the constancy of current as the electrolysis proceeded. The chemistry aspect was the presence of ammonium cation in electrolysed solution. The catalytic process with chemistry regeneration and the formation of a bridge by azide could explain the higher value of current in azide media compared to perchlorate solution. (author) [pt

  7. An improved bifunctional oxygen (air) electrode for reversible alkaline fuel cell systems and for rechargeable metal-air batteries

    Science.gov (United States)

    Kordesch, K.; Steininger, K.-H.; Tomantschger, K.

    1988-10-01

    Electrodes with a nickel layer of dual pore structure on the electrolyte side and a PTFE-bonded carbon layer on the oxygen (air) side are discussed, with application to space energy storage. During the electrolyis stage, the oxygen fills the large pores of the porous Ni structure with gas. During the discharge cycle, the iron/air or zinc/air cell of the carbon layer operates as a regular oxygen electrode.

  8. Kinetics of oxygen evolution on electrodes of the ruthenium-titanium oxide anode (ORTA) type. Techniques for determining the rate of oxygen evolution in chloride solutions

    International Nuclear Information System (INIS)

    Kokoutina, D.V.; Bunakova, L.V.

    1985-01-01

    Two techniques are described for determining the rate of oxygen evolution on active electrodes of the ORTA type in chloride solutions. One of them is based on the equivalent acidification of the solution as a result of oxygen evolution and the other on the compensation by an anodic current of the deviation of the potential of the investigated electrode from the equilibrium value when the electrode is in contact with a chloride solution. Examples are given of the determination of the oxygen evolution current on RuO 2 and ORTA in NaCl solutions in the region of the equilibrium potentials of the chlorine reaction

  9. Influence of various metallic oxides on the kinetic of the oxygen evolution reaction on platinum electrodes

    Directory of Open Access Journals (Sweden)

    Kambire Ollo

    2015-08-01

    Full Text Available Pt, 50Pt-50RuO2 and 50Pt-50IrO2 electrodes were prepared on titanium (Ti substrate by thermal decomposition techniques. The micrographs of 50Pt-50RuO2 and 50Pt-50IrO2 have revealed that their surfaces are rough with cracked structures. That of platinum was smooth, compact and homogeneous. The richer the electrode ‘surface in platinum, thinner is the crack size and also more compact is the electrode’surface. The electrodes have also been characterized electrochemically by cyclic voltammetry in acid (HClO4 and in alkaline (KOH electrolytes. These characterizations showed that the surface of the 50Pt-50RuO2 and 50Pt-50IrO2 electrodes were composed by platinum and metal dioxide active sites. The Tafel slope obtained on Pt, 50Pt-50RuO2 and 50Pt-50IrO2 for the oxygen evolution reaction (OER were respectively 120, 90 and 44 mV/dec in acid electrolyte. In the alkaline electrolyte, they were 119, 87 and 42 mV/dec respectively on Pt, 50Pt-50RuO2 and 50Pt-50IrO2 electrodes indicating that for the prepared electrodes, Tafel slopes are the same in acid and in alkaline media. Moreover, in acid and in alkaline media, the kinetic of the oxygen evolution reaction was rapid on 50Pt-50RuO2 and 50Pt-50IrO2 than Pt owing to a synergetic effect of Pt and the oxides. That additional effect of the surface component 50Pt-50RuO2 and 50Pt-50IrO2 electrodes let them possess high electrocatalytic activity towards OER than Pt in the two media. Though the kinetic of the oxygen evolution reaction is practically the same in acidic and alkaline media for all the electrodes, OER occurred at lower overpotential in alkaline electrolyte than in acidic electrolyte on the prepared electrodes.

  10. Improvement of Electrochemical Properties of Lithium–Oxygen Batteries Using a Silver Electrode

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jin-Bum; Luo, Xiangyi; Lu, Jun; Shin, Chang Dae; Yoon, Chong Seung; Amine, Khalil; Sun, Yang-Kook

    2015-07-09

    Silver (Ag) electrodes are prepared by an electrodeposition method at -0.25 V versus SCE. To evaluate the effect of particle size on Li–air cells, deposition times are 3, 10, 30, and 300 s. When cycled at a current density of 0.032 mA cm–2, the Ag-deposited electrode for 300 s shows very low polarization corresponding to the oxygen evolution reaction potential at 3.6 V. X-ray diffraction studies confirm that the main discharge product is Li2O2, and the results of scanning electron microscopy and transmission electron microscopy of the discharged electrodes show lithium peroxides at different positions due to the limitation of active sites on silver particles.

  11. Studies on the oxygen reduction catalyst for zinc-air battery electrode

    Science.gov (United States)

    Wang, Xianyou; Sebastian, P. J.; Smit, Mascha A.; Yang, Hongping; Gamboa, S. A.

    In this paper, perovskite type La 0.6Ca 0.4CoO 3 as a catalyst of oxygen reduction was prepared, and the structure and performance of the catalysts was examined by means of IR, X-ray diffraction (XRD), and thermogravimetric (TG). Mixed catalysts doped, some metal oxides were put also used. The cathodic polarization curves for oxygen reduction on various catalytic electrodes were measured by linear sweep voltammetry (LSV). A Zn-air battery was made with various catalysts for oxygen reduction, and the performance of the battery was measured with a BS-9300SM rechargeable battery charge/discharge device. The results showed that the perovskite type catalyst (La 0.6Ca 0.4CoO 3) doped with metal oxide is an excellent catalyst for the zinc-air battery, and can effectively stimulate the reduction of oxygen and improve the properties of zinc-air batteries, such as discharge capacity, etc.

  12. Oxygen electrode as a new tool to evaluate hydroxyl radical-scavenging ability

    OpenAIRE

    Komagoe, Keiko; Takeuchi, Hiroaki; Katsu, Takashi

    2008-01-01

    An oxygen electrode was applied to determine hydroxyl radical ((OH)-O-center dot) levels for the first time. The method is based on the determination of (OH)-O-center dot generated by the Fenton reaction using the reaction of (OH)-O-center dot with a scavenger and the resulting radical consuming an oxygen molecule stoichiometrically. Thus, the (OH)-O-center dot-scavenging abilities of antioxidant reagents, as well as the concentration of (OH)-O-center dot, can be determined by the measurement...

  13. The electrode kinetics of the evolution and dissolution of oxygen at the urania-zirconia interfaces

    International Nuclear Information System (INIS)

    Badwal, S.P.S.; Bevan, D.J.M.; Bockris, J.O'M.

    1980-01-01

    In order to assess the potential of urania-yttria fluorite-type solid solutions as electrodes for high-temperature electrolysis of steam, oxygen evolution and dissolution reactions have been studied at the (Usub(0.7)Ysub(0.3))Osub (2+x)/YSZ interface. A current-interruption technique was used to separate overpotential and resistive potential drop. In oxygen and air the overpotential-current curves obey the Tafel law, suggesting that a charge-transfer process is rate determining. Activation energies of 120 kJ mole -1 and 165 kJ mole -1 were obtained for the cathodic reaction in oxygen and air respectively. The capacitance obtained from galvanostatic transients varied with potential, temperature, and oxygen partial pressure. The average value of n, the number of electrons involved in the overall charge-transfer reaction, was determined to be 4.01 from reversible potential measurements. The overpotential losses are small for porous electrodes at high psub(O 2 ). A mechanism for the oxygen transfer reaction has been proposed and its limitations discussed. (author)

  14. Electrocatalysis of oxygen electrode reactions by some perovskite oxides based on lanthanum manganate

    International Nuclear Information System (INIS)

    Raj, I.A.; Rao, K.V.; Venkatesan, V.K.

    1984-01-01

    In recent years, several electrocatalyst materials based on platinum, silver, tungsten bronzes, spinels, metal chelates, etc., have been studied for use as oxygen diffusion electrodes in alkaline fuel cells, secondary metal-air batteries, and water electrolyzers. However, virtually all catalysts of commercial importance are semiconducting transition metal oxides. The various oxide catalysts that have been studied can be grouped under mixed oxides, spinels, and perovskites

  15. The role of oxygen in porous molybdenum electrodes for the alkali metal thermoelectric converter

    International Nuclear Information System (INIS)

    Williams, R.M.; Nagasubramanian, G.; Khanna, S.K.; Bankston, C.P.; Thakoor, A.P.; Cole, T.

    1986-01-01

    The alkali metal thermoelectric converter is a direct energy conversion device, utilizing a high alkali metal activity gradient to generate electrical power. Its operation is based on the unique ion conductive properties of beta''-alumina solid electrolyte. The major barrier to application of this device is identification of an electrode which can maintain optimum power densities for operation times of >10,000h. Thin, porous molybdenum electrodes have shown the best performance characteristics, but show a variety of time dependent phenomena, including eventual degradation to power densities 3-5 times lower than initial values. Several Na-Mo-O compounds, including Na/sub 2/MoO/sub 4/ and Na/sub 2/Mo/sub 3/O/sub 6/, are formed during AMTEC operation. These compounds may be responsible for enhanced Na transport through Mo electrodes via sodium ion conduction, and eventual performance degradation due to their volatilization and decomposition. No decomposition of beta''-alumina has been observed under simulated AMTEC operating conditions up to 1373 K. In this paper, we present a model for chemical reactions occurring in porous molybdenum electrodes. The model is based on thermochemical and kinetic data, known sodium-molybdenum-oxygen chemistry, x-ray diffraction analysis of molybdenum and molybdenum oxide electrodes, and the electrochemical behavior of the cell

  16. Copper-substituted perovskite compositions for solid oxide fuel cell cathodes and oxygen reduction electrodes in other electrochemical devices

    Science.gov (United States)

    Rieke, Peter C [Pasco, WA; Coffey, Gregory W [Richland, WA; Pederson, Larry R [Kennewick, WA; Marina, Olga A [Richland, WA; Hardy, John S [Richland, WA; Singh, Prabhaker [Richland, WA; Thomsen, Edwin C [Richland, WA

    2010-07-20

    The present invention provides novel compositions that find advantageous use in making electrodes for electrochemical cells. Also provided are electrochemical devices that include active oxygen reduction electrodes, such as solid oxide fuel cells, sensors, pumps and the like. The compositions comprises a copper-substituted ferrite perovskite material. The invention also provides novel methods for making and using the electrode compositions and solid oxide fuel cells and solid oxide fuel cell assemblies having cathodes comprising the compositions.

  17. Effect of some organophosphorus pesticides on oxygen consumption of shrimp, Litopenaeus vannamei.

    Science.gov (United States)

    Galindo Reyes, José Guillermo; Dalla-Venezia, Luisella; Lazcano Alvarez, Maria Guadalupe

    2002-06-01

    Oxygen consumption was measured in adult specimens of Litopenaeus vannamei shrimps from a coastal lagoon of Sinaloa, Mexico, during exposure to sublethal concentrations of the organophosphorus pesticides, Diazinon, Folidol, and Gusathion. Each individual was used as a control of itself, to avoid differences between treatments being masked by individual variability. In all three treatments with pesticides, respiration rate, measured by a polarographic electrode, was significantly lower than in controls. This may, at least partly, explain the decrease in shrimp production observed in recent years in the coastal lagoons of Sinaloa. (c) 2002 Elsevier Science (USA).

  18. Freestanding eggshell membrane-based electrodes for high-performance supercapacitors and oxygen evolution reaction.

    Science.gov (United States)

    Geng, Jing; Wu, Hao; Al-Enizi, Abdullah M; Elzatahry, Ahmed A; Zheng, Gengfeng

    2015-09-14

    A type of freestanding, light-weight eggshell membrane-based electrode is demonstrated for supercapacitors and for oxygen evolution reaction (OER) catalysis. As a widely available daily waste, eggshell membranes have unique porous three-dimensional grid-like fibrous structures with relatively high surface area and abundant macropores, allowing for effective conjugation of carbon nanotubes and growth of NiCo2O4 nanowire arrays, an effective supercapacitor material and OER catalyst. The three-dimensional fibrous eggshell membrane frameworks with carbon nanotubes offer efficient pathways for charge transport, and the macropores between adjacent fibers are fully accessible for electrolytes and bubble evolution. As a supercapacitor, the eggshell membrane/carbon nanotube/NiCo2O4 electrode shows high specific capacitances at current densities from 1 to 20 A g(-1), with excellent capacitance retention (>90%) at 10 A g(-1) for over 10,000 cycles. When employed as an OER catalyst, this eggshell membrane-based electrode exhibits an OER onset potential of 1.53 V vs. the reversible hydrogen electrode (RHE), and a stable catalytic current density of 20 mA cm(-2) at 1.65 V vs. the RHE.

  19. Luminescent sensing and imaging of oxygen: fierce competition to the Clark electrode.

    Science.gov (United States)

    Wolfbeis, Otto S

    2015-08-01

    Luminescence-based sensing schemes for oxygen have experienced a fast growth and are in the process of replacing the Clark electrode in many fields. Unlike electrodes, sensing is not limited to point measurements via fiber optic microsensors, but includes additional features such as planar sensing, imaging, and intracellular assays using nanosized sensor particles. In this essay, I review and discuss the essentials of (i) common solid-state sensor approaches based on the use of luminescent indicator dyes and host polymers; (ii) fiber optic and planar sensing schemes; (iii) nanoparticle-based intracellular sensing; and (iv) common spectroscopies. Optical sensors are also capable of multiple simultaneous sensing (such as O2 and temperature). Sensors for O2 are produced nowadays in large quantities in industry. Fields of application include sensing of O2 in plant and animal physiology, in clinical chemistry, in marine sciences, in the chemical industry and in process biotechnology. © 2015 The Author. Bioessays published by WILEY Periodicals, Inc.

  20. Yeast-based Biochemical Oxygen Demand Sensors Using Gold-modified Boron-doped Diamond Electrodes.

    Science.gov (United States)

    Ivandini, Tribidasari A; Harmesa; Saepudin, Endang; Einaga, Yasuaki

    2015-01-01

    A gold nanoparticle modified boron-doped diamond electrode was developed as a transducer for biochemical oxygen demand (BOD) measurements. Rhodotorula mucilaginosa UICC Y-181 was immobilized in a sodium alginate matrix, and used as a biosensing agent. Cyclic voltammetry was applied to study the oxygen reduction reaction at the electrode, while amperometry was employed to detect oxygen, which was not consumed by the microorganisms. The optimum waiting time of 25 min was observed using 1-mm thickness of yeast film. A comparison against the system with free yeast cells shows less sensitivity of the current responses with a linear dynamic range (R(2) = 0.99) of from 0.10 mM to 0.90 mM glucose (equivalent to 10 - 90 mg/L BOD) with an estimated limit of detection of 1.90 mg/L BOD. However, a better stability of the current responses could be achieved with an RSD of 3.35%. Moreover, less influence from the presence of copper ions was observed. The results indicate that the yeast-immobilized BOD sensors is more suitable to be applied in a real condition.

  1. Electrochemical Reduction of Oxygen on Anthraquinone/Carbon Nanotubes Nanohybrid Modified Glassy Carbon Electrode in Neutral Medium

    Directory of Open Access Journals (Sweden)

    Zheng Gong

    2013-01-01

    Full Text Available The electrochemical behaviors of monohydroxy-anthraquinone/multiwall carbon nanotubes (MHAQ/MWCNTs nanohybrid modified glassy carbon (MHAQ/MWCNTs/GC electrodes in neutral medium were investigated; also reported was their application in the electrocatalysis of oxygen reduction reaction (ORR. The resulting MHAQ/MWCNTs nanohybrid was characterized by scanning electron microscope (SEM and transmission electron microscope (TEM. It was found that the ORR at the MHAQ/MWCNTs/GC electrode occurs irreversibly at a potential about 214 mV less negative than at a bare GC electrode in pH 7.0 buffer solution. Cyclic voltammetric and rotating disk electrode (RDE techniques indicated that the MHAQ/MWCNTs nanohybrid has high electrocatalytic activity for the two-electron reduction of oxygen in the studied potential range. The kinetic parameters of ORR at the MHAQ/MWCNTs nanohybrid modified GC electrode were also determined by RDE and EIS techniques.

  2. Advances in interactive supported electro-catalysis for hydrogen and oxygen electrode reactions

    Energy Technology Data Exchange (ETDEWEB)

    Nedeljko V Krstajic; Ljiljana M Vracar; Jelena M Jaksic; Milan M Jaksic [Faculty of Technology and Metallurgy, University of Belgrade, Belgrade, Serbia and Montenegro (Yugoslavia); Stelios G Neophytides; Miranda Labou; Jelena M Jaksic; Milan M Jaksic [Institute of Chemical Engineering and High Temperature Chemical Processes FORTH, and Department of Chemistry, University of Patras, 26500 Patras, (Greece); Reidar Tunold [University of Trondheim, NTNU, Institute of Industrial Electrochemistry, Trondheim, (Norway); Polycarpos Falaras [Institute of Physical Chemistry, NCSR Demokritos, Attikis, Athens, (Greece)

    2006-07-01

    Magneli phases have been introduced as an unique electron conductive and interactive support for electro-catalysis both in hydrogen (HELR) and oxygen (OELR) electrode reactions in water electrolysis and Low Temperature PEM Fuel Cells (LT PEM FC). The Strong Metal-Support Interaction (SMSI) that imposes the former implies: (i) the hypo-hyper-d inter-bonding effect and its catalytic consequences, and (ii) the interactive primary oxide (M-OH) spillover from the hypo-d-oxide support as a dynamic electrocatalytic contribution. The stronger the bonding, the more strained appear d-orbitals, thereby the less strong the intermediate adsorptive strength in the rate determining step (RDS), and consequently, the faster the facilitated catalytic electrode reaction arises. At the same time the primary oxide spillover transferred from the hypo-d-oxide support directly interferes and reacts either individually and directly to contribute to finish the oxygen reduction, or with other interactive species, like CO to contribute to the CO tolerance. In such a respect, the conditions to provide Au to act as the reversible hydrogen electrode have been proved either by its potentiodynamic surface reconstruction in a heavy water solution, or by the nano-structured SMSI Au on anatase titania with characteristic strained d-orbitals in such a hypo-hyper-d-interactive bonding (Au/TiO{sub 2}). In the same context, the monoatomic network dispersion of Pt upon Magneli phases makes it possible to produce an advanced interactive supported electro-catalyst for cathodic oxygen reduction (ORR). The strained hypo-hyper-d-inter-electronic and inter-d-orbital metal/hypo-d-oxide support bonding relative to the strength of the latter, has been inferred to be the basis of the synergistic electrocatalytic effect both in the HELR and ORR. (authors)

  3. Oxygen electrodes for energy conversion and storage. Annual report, 1 October 1977-30 September 1978

    Energy Technology Data Exchange (ETDEWEB)

    None

    1980-01-15

    Research on the development of high performance, long life O/sub 2/ cathodes for both alkaline and acid electrolytes for a spectrum of applications including industrial electrolysis, fuel cells, and metal-air batteries is described. Oxygen electrocatalysts studied include platinum, silver, underpotential deposited layers and alloy metal layers on noble metal substrates, intercalated graphite, transition metal macrocyclic complexes, and transition metal oxides. Research on gas fed electrodes is also described. Results are presented and discussed in detail. An appendix on the electrodeposition of platinum crystallites on graphite substrates is included. (WHK)

  4. Simple and inexpensive technique for measuring oxygen consumption rate in adherent cultured cells.

    Science.gov (United States)

    Takahashi, Eiji; Yamaoka, Yoshihisa

    2017-11-01

    Measurement of cellular oxygen consumption rate (OCR) is essential in assessing roles of mitochondria in physiology and pathophysiology. Classical techniques, in which polarographic oxygen electrode measures the extracellular oxygen concentration in a closed measuring vessel, require isolation and suspension of the cell. Because cell functions depend on the extracellular milieu including the extracellular matrix, isolation of cultured cells prior to the measurement may significantly affect the OCR. More recent techniques utilize optical methods in which oxygen-dependent quenching of fluorophores determines oxygen concentration in the medium at a few microns above the surface of the cultured cells. These techniques allow the OCR measurement in cultured cells adhered to the culture dish. However, this technique requires special equipment such as a fluorescence lifetime microplate reader or specialized integrated system, which are usually quite expensive. Here, we introduce a simple and inexpensive technique for measuring OCR in adherent cultured cells that utilizes conventional fluorescence microscopy and a glassware called a gap cover glass.

  5. Silver nanowire catalysts on carbon nanotubes-incorporated bacterial cellulose membrane electrodes for oxygen reduction reaction.

    Science.gov (United States)

    Kim, Bona; Choi, Youngeun; Cho, Se Youn; Yun, Young Soo; Jin, Hyoung-Joon

    2013-11-01

    Silver nanowires have unique electrical, thermal and optical properties, which support their potential application in numerous fields including catalysis, electronics, optoelectronics, sensing, and surface-enhanced spectroscopy. Especially, their application such as catalysts for alkaline fuel cells (AFCs) have attracted much interest because of their superior electrical conductivity over that of any metal and their lower cost compared to Pt. In this study, multiwalled carbon nanotubes (MWCNTs)-incorporated bacterial cellulose (BC) membrane electrode with silver nanowire catalyst was prepared. First, acid-treated MWCNTs were incorporated into BC membranes and then freeze-dried after solvent exchange to tert-butanol in order to maintain the 3D-network macroporous structure. Second, silver nanowires synthesized by polyol process were introduced onto the surface of the MWCNTs-incorporated BC membrane through easy vacuum filtration. Finally, thermal treatment was carried out to confirm the effect of the PVP on the silver nanowire catalysts toward oxygen reduction reaction. The electrode with thermally treated silver nanowire had great electrocatalytic activity compared with non-treated one. These results suggest that the MWCNTs-incorporated BC electrode with silver nanowire catalysts after thermal treatment could be potentially used in cathodes of AFCs.

  6. Development of a biochemical oxygen demand sensor using gold-modified boron doped diamond electrodes.

    Science.gov (United States)

    Ivandini, Tribidasari A; Saepudin, Endang; Wardah, Habibah; Harmesa; Dewangga, Netra; Einaga, Yasuaki

    2012-11-20

    Gold-modified boron doped diamond (BDD) electrodes were examined for the amperometric detection of oxygen as well as a detector for measuring biochemical oxygen demand (BOD) using Rhodotorula mucilaginosa UICC Y-181. An optimum potential of -0.5 V (vs Ag/AgCl) was applied, and the optimum waiting time was observed to be 20 min. A linear calibration curve for oxygen reduction was achieved with a sensitivity of 1.4 μA mg(-1) L oxygen. Furthermore, a linear calibration curve in the glucose concentration range of 0.1-0.5 mM (equivalent to 10-50 mg L(-1) BOD) was obtained with an estimated detection limit of 4 mg L(-1) BOD. Excellent reproducibility of the BOD sensor was shown with an RSD of 0.9%. Moreover, the BOD sensor showed good tolerance against the presence of copper ions up to a maximum concentration of 0.80 μM (equivalent to 50 ppb). The sensor was applied to BOD measurements of the water from a lake at the University of Indonesia in Jakarta, Indonesia, with results comparable to those made using a standard method for BOD measurement.

  7. Using electrochemistry - total internal refection imaging ellipsometry to monitor biochemical oxygen demand on the surface tethered polyelectrolyte modified electrode

    Science.gov (United States)

    Liu, Wei; Li, Meng; Lv, Bei'er; Chen, YanYan; Ma, Hongwei; Jin, Gang

    2015-03-01

    Our previous work has proposed an electrochemistry - total internal reflection imaging ellipsometry (EC-TIRIE) technique to observe the dissolved oxygen (DO) reduction on Clark electrode since high interface sensitivity makes TIRIE a useful tool to study redox reactions on the electrode surface. To amplify the optical signal noise ratio (OSNR), a surface tethered weak polyelectrolyte, carboxylated poly(oligo(ethylene glycol) methacrylate-random- 2-hydroxyethylmethacrylate) (abbreviated as carboxylated poly(OEGMA-r-HEMA)), has been introduced on the electrode surface. Since Clark electrode is widely used in biochemical oxygen demand (BOD) detection, we use this technique to measure BOD in the sample. The dynamic range of the system is from 0 ˜ 25 mg/L. Two samples have been measured. Compared with the conventional method, the deviation of both optical and electrical signals are less than 10%.

  8. Proton translocation stoichiometry of cytochrome oxidase: use of a fast-responding oxygen electrode.

    Science.gov (United States)

    Reynafarje, B; Alexandre, A; Davies, P; Lehninger, A L

    1982-01-01

    The mechanistic stoichiometry of vectorial H+ ejection coupled to electron transport from added ferrocytochrome c to oxygen by the cytochrome oxidase (EC 1.9.3.1) of rat liver mitoplasts was determined from measurements of the initial rates of electron flow and H+ ejection in the presence of K+ (with valinomycin). Three different methods of measuring electron flow were used: (a) dual-wavelength spectrophotometry of ferrocytochrome c oxidation, (b) uptake of scalar H+ for the reduction of O2 in the presence of a protonophore, and (c) a fast-responding membraneless oxygen electrode. The reliability of the rate measurements was first established against the known stoichiometry of the scalar reaction of cytochrome oxidase (2ferrocytochrome c + 2H+ + 1/2O2 leads to 2ferricytochrome c + H2O) in the presence of excess protonophore. With all three methods the directly observed vectorial H+/O ejection ratios in the presence of K+ + valinomycin significantly exceeded 3.0. However, because the rate of backflow of the ejected H+ into the mitoplasts is very high and increases with the increasing delta pH generated across the membrane, there is a very rapid decline in the observed H+/O ratio from the beginning of the reaction. Kinetic analysis of ferrocytochrome c oxidation by the mitoplasts, carried out with a fast-responding membraneless oxygen electrode, showed the reaction to be first order in O2 and allowed accurate extrapolation of the rates of O2 uptake and H+ ejection to zero time. At this point, at which there is zero delta pH across the membrane, the H+/O ejection ratio of the cytochrome oxidase reaction, obtained from the rates at zero time, is close to 4.0. PMID:6296824

  9. Oxygen Reduction on Gas-Diffusion Electrodes for Phosphoric Acid Fuel Cells by a Potential Decay Method

    DEFF Research Database (Denmark)

    Li, Qingfeng; Gang, Xiao; Hjuler, Hans Aage

    1995-01-01

    The reduction of gaseous oxygen on carbon supported platinum electrodes has been studied at 150 degrees C with polarization and potential decay measurements. The electrolyte was either 100 weight percent phosphoric acid or that acid with a fluorinated additive, potassium perfluorohexanesulfonate (C...... and the dependence of the double-layer capacitance on the overpotential depended on the electrode manufacture and the kind of electrolyte (whether containing the fluorinated additive or not)....

  10. Influence of the oxygen electrode and inter-diffusion barrier on the degradation of solid oxide electrolysis cells

    DEFF Research Database (Denmark)

    Hjalmarsson, Per; Sun, Xiufu; Liu, Yi-Lin

    2013-01-01

    -diffusion barrier sandwiched between the YSZ electrolyte and an LSCF:CGO oxygen electrode. Impedance Spectroscopy was used during the tests to diagnose the change in electrochemical response of the different components of the SOECs. The results showed a significantly lower degradation rate for the cell with an LSCF......Two Solid Oxide Electrolysis Cells (SOECs) with different oxygen electrodes have been tested in galvanostatic tests carried out at −1.5 Acm−2 and 800 °C converting 60% of a 50:50% mixture of H2O and CO2 (co-electrolysis). One of the cells had an LSM:YSZ oxygen electrode. The other had an CGO inter...

  11. Differential pulse polarographic determination of Sn (II) in DTPA radiopharmaceutical compound

    International Nuclear Information System (INIS)

    Mohamad Hadzri Yaacob; Fielden, P.R.

    1994-01-01

    A differential pulse polarographic technique has been developed for the assay of Sn(II). Acting as a reducing agent, Sn(II) is one of the most important components in radiopharmaceutical compounds. Under optimum conditions, Sn(II) undergoes reduction to form an amalgam at the dropping mercury electrode, producing a well-defined and characteristic peak at -0.45 + 0.030V, with respect to the standard calomel electrode (SCE) in 5M perchloric acid. For quantitative determination by this technique, a linear calibration graph was obtained over a concentration 0 to 70 ppm of stannous chloride for the analysis of diethylenetriamine pentaacetic acid (DTPA) samples. Average recovery from ten measurements of a fixed amount of standard solution was 90%. A detection limit of 2.3ppm which was fairly low compared to the actual content of Sn(II) which was 20 ppm, could be obtained. The analysis of the sample using this technique gave a well-defined Sn(II)peak without the interference of the chelate compounds present in the sample, and reproducible results with a typical coefficient variation of less than 7% for ten determinations. The results obtained demonstrated that the proposed DPP technique was a convenient, sensitive, accurate and rapid method. The results were in good agreement with those found by iodimetric titration. An advantage of this method is that it is free of interference from the other constituents of the sample, hence there is no need to separate the matrix

  12. Polarographic study of the electrochemical properties of plutonium; Etude polarographique des proprietes electrochimiques du plutonium

    Energy Technology Data Exchange (ETDEWEB)

    Guichard, C. [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1968-07-01

    The behaviour of the different degrees of oxidation of plutonium have been studied using a falling drop mercury electrode in a non-complexing medium: dilute perchloric acid. In this medium it is possible to carry out the polarographic determination of plutonium using the reduction step situated at - 0.54 V/ECS which corresponds to the passage from the degree of oxidation(V) to the degree(III). The modifications brought about by a complexing ion, acetate, are then observed and interpreted. The existence of two plutonium(IV) acetic complexes has been shown; one is a polymerized substance. (author) [French] Le comportement des differents degres d'oxydation du plutonium est etudie a l'electrode a gouttes de mercure dans un milieu non complexant: l'acide perchlorique dilue. Il est possible dans ce milieu d'effectuer le dosage polarographique du plutonium en utilisant la vague de reduction situee a - 0.54 V/ECS qui correspond au passage du degre d'oxydation(V) au degre(III). Les modifications apportees par un ion complexant, l'acetate, sont ensuite observees et interpretees. Deux complexes acetiques du plutonium(IV) ont ete mis en evidence, dont l'un est un compose polymerise. (auteur)

  13. Oxygen evolution on alpha-lead dioxide electrodes in methanesulfonic acid

    International Nuclear Information System (INIS)

    Oury, Alexandre; Kirchev, Angel; Bultel, Yann

    2012-01-01

    Highlights: ► Oxygen evolution on α-PbO 2 in methanesulfonic acid medium. ► The reaction kinetics is slower in MSA than in sulphuric acid. ► The hydrated lead dioxide layer affects the reaction kinetics. ► A high MSA concentration leads to lower O 2 evolution. - Abstract: This work examines the oxygen evolution reaction (OER) taking place on α-PbO 2 electrode in methanesulfonic acid (MSA) medium and in sulphuric acid as a comparison, by means of cyclic voltammetry (CVA) and electrochemical impedance spectroscopy (EIS), for soluble lead acid flow battery applications. The influence of MSA concentration on OER is studied. EIS measurements highlighted the impact of the hydrated lead dioxide layer upon decreasing MSA or sulphuric acid concentration. The evolution of the Tafel curves plotted from EIS measurements and quasi-stationary currents while varying acid concentration was interpreted in the light of this hydrated layer which could enhance the electrocatalytic activity when it is thin, and on the contrary act as an electronic barrier when growing for low acid concentration. Both EIS and CVA revealed that OER on lead dioxide is less favoured in MSA than in sulphuric acid. It is finally concluded that a high-concentrated MSA electrolyte is better for lead acid flow battery application in terms of oxygen evolution.

  14. Parallel oxygen and chlorine evolution on Ru1-xNixO2-y nanostructured electrodes

    International Nuclear Information System (INIS)

    Macounova, Katerina; Makarova, Marina; Jirkovsky, Jakub; Franc, Jiri; Krtil, Petr

    2008-01-01

    Nanocrystalline materials with chemical composition corresponding to formula Ru 1-x Ni x O 2-y (0.02 1-x Ni x O 2-y with respect to parallel oxygen (oxygen evolution reaction, OER) and chlorine (chlorine evolution reaction, CER) evolution in acidic media was studied by voltammetry combined with differential electrochemical mass spectrometry (DEMS). The DEMS data indicate a significant decrease of the over-voltage for chlorine evolution with respect to that of pure RuO 2 . The oxygen evolution is slightly hindered. The increasing Ni content affects the electrode material activity and selectivity. The overall material's activity increases with increasing Ni content. The activity of the Ru-Ni-O oxides towards Cl 2 evolution shows a distinguished maximum for material containing 10% of Ni. Further increase of Ni content results in suppression of Cl 2 evolution in favor of O 2 evolution. A model reflecting the cation-cation interactions resulting from Ni-doping is proposed to explain the observed trends in electrocatalytic behavior

  15. Electrocatalysis of oxygen reduction on nitrogen-containing multi-walled carbon nanotube modified glassy carbon electrodes

    International Nuclear Information System (INIS)

    Vikkisk, Merilin; Kruusenberg, Ivar; Joost, Urmas; Shulga, Eugene; Tammeveski, Kaido

    2013-01-01

    Highlights: ► Pyrolysis in the presence of urea was used for nitrogen doping of carbon nanotubes. ► N-doped carbon nanotubes were used as catalysts for the oxygen reduction reaction. ► N-doped carbon material showed a high catalytic activity for ORR in alkaline media. ► N-containing CNT material is an attractive cathode catalyst for alkaline membrane fuel cells. - Abstract: The electrochemical reduction of oxygen was studied on nitrogen-doped multi-walled carbon nanotube (NCNT) modified glassy carbon (GC) electrodes employing the rotating disk electrode (RDE) method. Nitrogen doping was achieved by simple pyrolysis of the carbon nanotube material in the presence of urea. The surface morphology and composition of the NCNT samples were investigated by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The SEM images revealed a rather uniform distribution of NCNTs on the GC electrode substrate. The XPS analysis showed a successful doping of carbon nanotubes with nitrogen species. The RDE results revealed that in alkaline solution the N-doped nanotube materials showed a remarkable electrocatalytic activity towards oxygen reduction. At low overpotentials the reduction of oxygen followed a two-electron pathway on undoped carbon nanotube modified GC electrodes, whereas on NCNT/GC electrodes a four-electron pathway of O 2 reduction predominated. The results obtained are significant for the development of nitrogen-doped carbon-based cathodes for alkaline membrane fuel cells.

  16. Topotactic Consolidation of Monocrystalline CoZn Hydroxides for Advanced Oxygen Evolution Electrodes.

    Science.gov (United States)

    Wang, Jing; Tan, Chuan Fu; Zhu, Ting; Ho, Ghim Wei

    2016-08-22

    We present a room temperature topotactic consolidation of cobalt and zinc constituents into monocrystalline CoZn hydroxide nanosheets, by a localized corrosion of zinc foils with cobalt precursors. By virtue of similar lattice orientation and structure coordination, the hybrid hydroxides amalgamate atomically without phase separation. Importantly, this in situ growth strategy, in combination with configurable percolated nanosheets, renders a high areal density of catalytic sites, immobilized structures, and conductive pathways between the nanosheets and underlying foils-all of which allow monocrystalline CoZn hydroxide nanosheet materials to function as effective electrodes for electrochemical oxygen evolution reactions. This convenient and eco-friendly topotactical transformation approach facilitates high-quality single crystal growth with improved multiphase purity and homogeneity, which can be extended to other transition metals for the fabrication of advanced functional nanocomposites. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. SiC-Si as a support material for oxygen evolution electrode in PEM steam electrolysers

    DEFF Research Database (Denmark)

    Nikiforov, Aleksey; Tomás García, Antonio Luis; Petrushina, Irina

    2011-01-01

    was synthesized following the Adams fusion method. The obtained powder was characterized with different techniques. XRD and Nitrogen adsorption experiments showed the influence of the support particles in the surface properties of the IrO2 particles, mainly affecting the IrO2 particle size. The prepared catalysts......The need of higher energy efficiency in hydrogen production has promoted the research on improved catalysts for water electrolysis. In this work, a novel supported catalyst for oxygen evolution electrodes was prepared and characterized with different techniques. IrO2 supported on a SiC/Si composite...... were electrochemically characterized by cyclic voltammetry experiments at 25, 80, 120 and 150°C. The results indicate an improvement in catalyst activity with the addition of the support. This was attributed to the mentioned variation in particle size and a different packing of catalyst particles...

  18. Electrochemical monitoring of native catalase activity in skin using skin covered oxygen electrode.

    Science.gov (United States)

    Nocchi, Sarah; Björklund, Sebastian; Svensson, Birgitta; Engblom, Johan; Ruzgas, Tautgirdas

    2017-07-15

    A skin covered oxygen electrode, SCOE, was constructed with the aim to study the enzyme catalase, which is part of the biological antioxidative system present in skin. The electrode was exposed to different concentrations of H 2 O 2 and the amperometric current response was recorded. The observed current is due to H 2 O 2 penetration through the outermost skin barrier (referred to as the stratum corneum, SC) and subsequent catalytic generation of O 2 by catalase present in the underlying viable epidermis and dermis. By tape-stripping the outermost skin layers we demonstrate that SC is a considerable diffusion barrier for H 2 O 2 penetration. Our experiments also indicate that skin contains a substantial amount of catalase, which is sufficient to detoxify H 2 O 2 that reaches the viable epidermis after exposure of skin to high concentrations of peroxide (0.5-1mM H 2 O 2 ). Further, we demonstrate that the catalase activity is reduced at acidic pH, as compared with the activity at pH 7.4. Finally, experiments with often used penetration enhancer thymol shows that this compound interferes with the catalase reaction. Health aspect of this is briefly discussed. Summarizing, the results of this work show that the SCOE can be utilized to study a broad spectrum of issues involving the function of skin catalase in particular, and the native biological antioxidative system in skin in general. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Heterostructured electrode with concentration gradient shell for highly efficient oxygen reduction at low temperature

    Science.gov (United States)

    Zhou, Wei; Liang, Fengli; Shao, Zongping; Chen, Jiuling; Zhu, Zhonghua

    2011-11-01

    Heterostructures of oxides have been widely investigated in optical, catalytic and electrochemical applications, because the heterostructured interfaces exhibit pronouncedly different transport, charge, and reactivity characteristics compared to the bulk of the oxides. Here we fabricated a three-dimensional (3D) heterostructured electrode with a concentration gradient shell. The concentration gradient shell with the composition of Ba0.5-xSr0.5-yCo0.8Fe0.2O3-δ (BSCF-D) was prepared by simply treating porous Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) backbone with microwave-plasma. Electrochemical impedance spectroscopy reveals that the oxygen surface exchange rate of the BSCF-D is enhanced by ~250% that of the pristine BSCF due to the appearance of the shell. The heterostructured electrode shows an interfacial resistance as low as 0.148 Ω cm2 at 550°C and an unchanged electrochemical performance after heating treatment for 200 h. This method offers potential to prepare heterostructured oxides not only for electrochemical devices but also for many other applications that use ceramic materials.

  20. Manufacturing of a LaNiO3 composite electrode for oxygen evolution in commercial alkaline water electrolysis

    DEFF Research Database (Denmark)

    Egelund, Sune; Caspersen, Michael; Nikiforov, Aleksey Valerievich

    2016-01-01

    The LaNiO3 perovskite was chosen for incorporation into a nickel matrix in order to obtain a metallic composite electrode suitable for improving the oxygen evolution reaction (OER) in commercial water electrolysis at elevated temperature. The manufactured LaNiO3 + Ni composite coatings were...

  1. Polarographic study of Cd(II)-Schiff base complexes and d.m.e. menthanol-water medium

    International Nuclear Information System (INIS)

    Patel, M.S.; Trivedi, T.; Vyas, D.N.

    1978-01-01

    Three Schiff base complexes of Cd 2+ have been investigated polarographically in 60% menthanol-water medium at 26 0 C. The Schiff bases used are salicyladehyde tris buffer (ST), benzaldehydetris buffer (BT) and vanillin tris buffer (VT). Cd-ST and Cd-VT complexes produce reversible reduction wave at dme, while Cd-BT gives a quasi reversible wave. Stability constants of the complexes have been determined and the standard overall electrode reaction rate constant (ksub(e)sup(o)) B of the Cd-BT complex is determined by three different methods. The log β values of complexes are : Cd-ST, 2.72; Cd-VT, 4.90; and Cd-BT, 4.41. (author)

  2. Polarographic determination of europium in the products of rare earths production

    International Nuclear Information System (INIS)

    Bruk, B.S.; Polishchuk, T.T.; Futerman, Yu.S.

    1977-01-01

    A procedure for polarographic determination of Eu in r.e.e. oxides and metals has been developed. It enables one to increase the threshold sensitivity of determination by one order (up to 3x10 -4 %). 3.4 g LiCl (anhydrous is placed in a 20 ml test-tube. 4 ml filtrate and 4.3 ml H 2 O are added, then the mixture is shaken until the LiCl is completely dissolved. The test solution is poured into a cell, and the polarogram of the a.c. is recorded in the range from 0.2 to 0.6 V relative to the external electrode filled with 10 M liCl. The europium content is determined by the addition method, for which purpose 1 ml of standard solution of europium with a concentration of 0.25 g/l is introduced into one of the two batches of one sample prier to dissolving, and an analysis is carried out with both samples according to the described pattern. In the range between 1.7x10 -3 and 1.6x10 -2 % the variation coefficient does not exceed 18.3%

  3. Oscillo-polarographic determination of boron based on its complex formation with polyphenol

    International Nuclear Information System (INIS)

    Fukushi, Norio

    1978-01-01

    A test solution in a 50-ml measuring flask contained the following reagents, 5 ml of 1 M KCl as a supporting electrolyte, 10 ml of NH 4 Cl-NH 3 buffer solution (pH 8 -- 10), 0 -- 5 ml of 10 -2 M H 3 BO 3 , and (1 -- 5) ml of 10 -3 M of a polyphenol, such as Pyrocatechol Violet (PV), Pyrogallol Red, Bromopyrogallol Red. Difference between the oscillopolarograms of the solutions containing and not containing boric acid together with certain amounts of a polyphenol was only the variation of the peak currents based on the electrode reaction of the polyphenol, being accompanied with some variation in their peak currents with time elapsed. In the case of using PV as the polyphenol, the relation between the concentration of PV and the peak current was quantitative at the peak potential of -0.69 V vs. SCE. The decrease of the peak current (Δi sub(p)) by the addition of boric acid in various concentrations was measured. To this procedure, the concentration ratio of PV to boric acid must be considered, too. Results obtained under various experimental conditions showed that an indirect determination of boron by oscillographic polarographic method is very promising. (author)

  4. Linear sweep polarographic determination of nucleic acids using acridine orange as a bioprobe

    Directory of Open Access Journals (Sweden)

    WEI SUN

    2007-11-01

    Full Text Available The interaction of acridine orange (AO with double-stranded (ds DNA in aqueous solution was investigated by linear sweep polarography (LSP on a dropping mercury working electrode (DME. In pH 2.5 Britton–Robinson (B–R buffer solution, AO had a sensitive linear sweep polarographic reductive peak at –0.89 V (vs. SCE, which could be greatly inhibited by the addition of dsDNA, with a positive shift of the peak potential. Based on the decrease of the reductive peak current, a new quantitative electrochemical determination method for dsDNA was developed with a linear range of 2.0−20.0 mg l-1 and the linear regression equation: ΔIp” (nA = 111.90 C (mg l-1+125.32 (n = 9, γ = 0.997. The influences of commonly co-existing substances, such as metal ions, amino acid, etc., on the determination were also investigated. The method is sensitive, rapid and simple with good selectivity. The new proposed method was further applied to the detection of RNA and three synthetic samples containing dsDNA with satisfactory results. The binding number and the equilibrium constant between dsDNA and AO were calculated by an electrochemical method.

  5. Polarographic study of hydrogen peroxide anodic current and its application to antioxidant activity determination.

    Science.gov (United States)

    Sužnjević, Desanka Ž; Pastor, Ferenc T; Gorjanović, Stanislava Ž

    2011-09-15

    Behavior of hydrogen peroxide in alkaline medium has been studied by direct current (DC) polarography with dropping mercury electrode (DME) aiming to apply it in antioxidant (AO) activity determination. Development of a peroxide anodic current having form of a peak, instead of common polarographic wave, has been investigated. As a base for this investigation the interaction of H(2)O(2) with anodically dissolved mercury was followed. Formation of mercury complex [Hg(O(2)H)(OH)] has been confirmed. The relevant experimental conditions, such as temperature, concentration and pH dependence, as well as time stability of hydrogen peroxide anodic current, have been assessed. Development of an AO assay based on decrease of anodic current of hydrogen peroxide in the presence of antioxidants (AOs) has been described. Under optimized working conditions, a series of benzoic acids along with corresponding cinnamate analogues have been tested for hydrogen peroxide scavenging activity. In addition, the assay versatility has been confirmed on various complex samples. Copyright © 2011 Elsevier B.V. All rights reserved.

  6. Phenomena and significance of intermediate spillover in electrocatalysis of oxygen and hydrogen electrode reactions

    Directory of Open Access Journals (Sweden)

    Jakšić Jelena M.

    2012-01-01

    Full Text Available Altervalent hypo-d-oxides of transition metal series impose spontaneous dissociative adsorption of water molecules and pronounced membrane spillover transferring properties instantaneously resulting with corresponding bronze type (Pt/HxWO3 under cathodic, and/or its hydrated state (Pt/W(OH6 responsible for the primary oxide (Pt-OH effusion, under anodic polarization, this way establishing instantaneous reversibly revertible alterpolar bronze features (Pt/H0.35WO3 Pt/W(OH6, and substantially advanced electrocatalytic properties of these composite interactive electrocatalysts. As the consequence, the new striking and unpredictable prospects both in law and medium temperature proton exchange membrane fuell cell (L&MT PEMFC and water electrolysis (WE have been opened by the interactive supported individual (Pt, Pd, Ni or prevailing hyper-d-electronic nanostructured intermetallic phase clusters (WPt3, NbPt3, HfPd3, ZrNi3, grafted upon and within high altervalent capacity hypo-d-oxides (WO3, Nb2O5, Ta2O5, TiO2 and their proper mixed valence compounds, to create a novel type of alterpolar interchangeable composite electrocatalysts for hydrogen and oxygen electrode reactions. Whereas in aqueous media Pt (Pt/C features either chemisorbed catalytic surface properties of H-adatoms (Pt-H, or surface oxide (Pt=O, missing any effusion of other interacting species, new generation and selection of composite and interactive strong metal-support interaction (SMSI electrocatalysts in condensed wet state primarily characterizes interchangeable extremely fast reversible spillover of either H-adatoms, or the primary oxides (Pt-OH, Au-OH, or the invertible bronze type behavior of these significant interactive electrocatalytic ingredients. Such nanostructured type electrocatalysts, even of mixed hypo-d-oxide structure (Pt/H0.35WO3/TiO2/C, Pt/HxNbO3/TiO2/C, have for the first time been synthesized by the sol-gel methods and shown rather high stability, electron

  7. Enhanced Cyclability of Lithium-Oxygen Batteries with Electrodes Protected by Surface Films Induced via In-Situ Electrochemical Process

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Bin; Xu, Wu; Tao, Jinhui; Yan, Pengfei; Zheng, Jianming; Engelhard, Mark H.; Lu, Dongping; Wang, Chongmin; Zhang, Jiguang

    2018-04-16

    Although the rechargeable lithium-oxygen (Li-O2) batteries have extremely high theoretical specific energy, the practical application of these batteries is still limited by the instability of their carbon-based air-electrode, Li metal anode, and electrolytes towards reduced oxygen species. Here we demonstrate a simple one-step in-situ electrochemical pre-charging strategy to generate thin protective films on both carbon nanotubes (CNTs) air-electrode and Li metal anode simultaneously under an inert atmosphere. Li-O2 cells after such pre-treatment demonstrate significantly extended cycle life of 110 and 180 cycles under the capacity-limited protocol of 1000 mAh g-1 and 500 mAh g-1, respectively, which is far more than those without pre-treatment. The thin-films formed from decomposition of electrolyte during in-situ electrochemical pre-charging process in an inert environment can protect both CNTs air-electrode and Li metal anode prior to conventional Li-O2 discharge/charge cycling where reactive reduced oxygen species are formed. This work provides a new approach for protections of carbon-based air-electrode and Li metal anode in practical Li-O2 batteries, and may also be applied to other battery systems.

  8. Roles of Bulk and Surface Chemistry in the Oxygen Exchange Kinetics and Related Properties of Mixed Conducting Perovskite Oxide Electrodes

    Directory of Open Access Journals (Sweden)

    Nicola H. Perry

    2016-10-01

    Full Text Available Mixed conducting perovskite oxides and related structures serving as electrodes for electrochemical oxygen incorporation and evolution in solid oxide fuel and electrolysis cells, respectively, play a significant role in determining the cell efficiency and lifetime. Desired improvements in catalytic activity for rapid surface oxygen exchange, fast bulk transport (electronic and ionic, and thermo-chemo-mechanical stability of oxygen electrodes will require increased understanding of the impact of both bulk and surface chemistry on these properties. This review highlights selected work at the International Institute for Carbon-Neutral Energy Research (I2CNER, Kyushu University, set in the context of work in the broader community, aiming to characterize and understand relationships between bulk and surface composition and oxygen electrode performance. Insights into aspects of bulk point defect chemistry, electronic structure, crystal structure, and cation choice that impact carrier concentrations and mobilities, surface exchange kinetics, and chemical expansion coefficients are emerging. At the same time, an understanding of the relationship between bulk and surface chemistry is being developed that may assist design of electrodes with more robust surface chemistries, e.g., impurity tolerance or limited surface segregation. Ion scattering techniques (e.g., secondary ion mass spectrometry, SIMS, or low energy ion scattering spectroscopy, LEIS with high surface sensitivity and increasing lateral resolution are proving useful for measuring surface exchange kinetics, diffusivity, and corresponding outer monolayer chemistry of electrodes exposed to typical operating conditions. Beyond consideration of chemical composition, the use of strain and/or a high density of active interfaces also show promise for enhancing performance.

  9. Electrocatalytic oxygen reduction and hydrogen evolution reactions on phthalocyanine modified electrodes: Electrochemical, in situ spectroelectrochemical, and in situ electrocolorimetric monitoring

    International Nuclear Information System (INIS)

    Koca, Atif; Kalkan, Ayfer; Bayir, Zehra Altuntas

    2011-01-01

    Highlights: → Electrochemical and in situ spectroelectrochemical characterizations of the metallophthalocyanines were performed. → The presence of O 2 influences both oxygen reduction reaction and the electrochemical behaviors of the complexes. → Homogeneous catalytic ORR process occurs via an 'inner sphere' chemical catalysis process. → CoPc and CuPc coated on a glassy carbon electrode decrease the overpotential of the working electrode for H + reduction. - Abstract: This study describes electrochemical, in situ spectroelectrochemical, and in situ electrocolorimetric monitoring of the electrocatalytic reduction of molecular oxygen and hydronium ion on the phthalocyanine-modified electrodes. For this purpose, electrochemical and in situ spectroelectrochemical characterizations of the metallophthalocyanines (MPc) bearing tetrakis-[4-((4'-trifluoromethyl)phenoxy)phenoxy] groups were performed. While CoPc gives both metal-based and ring-based redox processes, H 2 Pc, ZnPc and CuPc show only ring-based electron transfer processes. In situ electrocolorimetric method was applied to investigate the color of the electrogenerated anionic and cationic forms of the complexes. The presence of O 2 in the electrolyte system influences both oxygen reduction reaction and the electrochemical and spectral behaviors of the complexes, which indicate electrocatalytic activity of the complexes for the oxygen reduction reaction. Perchloric acid titrations monitored by voltammetry represent possible electrocatalytic activities of the complexes for hydrogen evolution reaction. CoPc and CuPc coated on a glassy carbon electrode decrease the overpotential of the working electrode for H + reduction. The nature of the metal center changes the electrocatalytic activities for hydrogen evolution reaction in aqueous solution. Although CuPc has an inactive metal center, its electrocatalytic activity is recorded more than CoPc for H + reduction in aqueous solution.

  10. Efficient direct oxygen reduction by laccases attached and oriented on pyrene-functionalized polypyrrole/carbon nanotube electrodes.

    Science.gov (United States)

    Lalaoui, Noémie; Elouarzaki, Kamal; Le Goff, Alan; Holzinger, Michael; Cosnier, Serge

    2013-10-18

    We report the functionalization of multi-walled carbon nanotube (MWCNT) electrodes by oxidative electropolymerization of pyrrole monomers bearing pyrene and N-hydroxysuccinimide groups. Both polymers were applied to the immobilization and electrical wiring of Trametes versicolor laccase via chemical grafting or non-covalent binding. A "pseudo" host-guest interaction of polymerized pyrene with a hydrophobic cavity of laccase was used for the oriented enzyme immobilization on MWCNT electrodes. The latter leads to higher catalytic current for oxygen reduction (1.85 mA cm(-2)) and higher electroenzymatic stability (50% after one month).

  11. Polarographic, spectrophotometric and coulometric studies of MoO=4 in H2SO4

    International Nuclear Information System (INIS)

    Tokoro, R.; Bertotti, M.

    1990-01-01

    This study characterizes the polarographic process of Mo O sup(=) sub(4) in H sub(2)SO sub(4) medium, determining which species is responsible by catalytic cycle. Spectrophotometric and coulometric studies are also described. (author)

  12. Polarographic methods for the analysis of beryllium metal and its alloys

    International Nuclear Information System (INIS)

    Wells, J.M.

    1975-10-01

    This report describes polarographic methods for the analysis of beryllium metal and its alloys. The elements covered by these methods are aluminium, bismuth, cadmium, cobalt, copper, iron, lead, molybdenum, nickel, thallium, tungsten, uranium, vanadium and zinc. (author)

  13. Free-standing, flexible β-Ni(OH)2/electrochemically-exfoliated graphene film electrode for efficient oxygen evolution

    Science.gov (United States)

    Wang, Lanlan; Zhang, Jian; Jiang, Weitao; Zhao, Hong; Liu, Hongzhong

    2018-03-01

    The oxidation of water into molecular oxygen (oxygen evolution reaction, OER) is a pivotal reaction in many energy conversion devices. The high cost of IrO2, however, seriously hinder its large-scale applications in water oxidation. Here, we have at first reported a free-standing and flexible film electrode consisting of 2D β-Ni(OH)2/electrochemically-exfoliated graphene hybrid nanosheets (NiG-2), which is synthesized by a solvothermal reaction and an assembly process. The as-obtained NiG-2 film electrode exhibited an excellent electrocatalytic OER activity with an extremely low OER onset overpotential of ∼250 mV in a 1 M KOH aqueous solution, which is lower than these of the commercial Ir/C (370 mV at 10 mA cm-2) catalyst.

  14. Spillover Phenomena and Its Striking Impacts in Electrocatalysis for Hydrogen and Oxygen Electrode Reactions

    Directory of Open Access Journals (Sweden)

    Georgios D. Papakonstantinou

    2011-01-01

    striking target issue of the present paper, has been shown to be the superior for substantiation of the revertible cell assembly for spontaneous reversible alterpolar interchanges between PEMFC and WE. The main target of the present thorough review study has been to throw some specific insight light on the overall spillover phenomena and their effects in electrocatalysis of oxygen and hydrogen electrode reactions from diverse angles of view and broad contemporary experimental methods and approaches (XPS, FTIR, DRIFT, XRD, potentiodynamic spectra, UHRTEM.

  15. Obesity Decreases Perioperative Tissue Oxygenation

    Science.gov (United States)

    Kabon, Barbara; Nagele, Angelika; Reddy, Dayakar; Eagon, Chris; Fleshman, James W.; Sessler, Daniel I.; Kurz, Andrea

    2005-01-01

    Background: Obesity is an important risk factor for surgical site infections. The incidence of surgical wound infections is directly related to tissue perfusion and oxygenation. Fat tissue mass expands without a concomitant increase in blood flow per cell, which might result in a relative hypoperfusion with decreased tissue oxygenation. Consequently, we tested the hypotheses that perioperative tissue oxygen tension is reduced in obese surgical patients. Furthermore, we compared the effect of supplemental oxygen administration on tissue oxygenation in obese and non-obese patients. Methods: Forty-six patients undergoing major abdominal surgery were assigned to one of two groups according to their body mass index (BMI): BMI < 30 kg/m2 (non-obese) and BMI ≥ 30 kg/m2 (obese). Intraoperative oxygen administration was adjusted to arterial oxygen tensions of ≈150 mmHg and ≈300 mmHg in random order. Anesthesia technique and perioperative fluid management were standardized. Subcutaneous tissue oxygen tension was measured with a polarographic electrode positioned within a subcutaneous tonometer in the lateral upper arm during surgery, in the recovery room, and on the first postoperative day. Postoperative tissue oxygen was also measured adjacent to the wound. Data were compared with unpaired two tailed t-tests and Wilcoxon rank-sum tests; P < 0.05 was considered statistically significant. Results: Intraoperative subcutaneous tissue oxygen tension was significantly less in the obese patients at baseline (36 vs. 57 mmHg, P = 0.002) and with supplemental oxygen administration (47 vs. 76 mmHg, P = 0.014). Immediate postoperative tissue oxygen tension was also significantly less in subcutaneous tissue of the upper arm (43 vs. 54 mmHg, P = 0.011) as well as near the incision (42 vs. 62 mmHg, P = 0.012) in obese patients. In contrast, tissue oxygen tension was comparable in each group on the first postoperative morning. Conclusion: Wound and tissue hypoxia were common in obese

  16. Oxygenated edge plane sites slow the electron transfer of the ferro-/ferricyanide redox couple at graphite electrodes.

    Science.gov (United States)

    Ji, Xiaobo; Banks, Craig E; Crossley, Alison; Compton, Richard G

    2006-06-12

    The electron transfer kinetics of ferrocyanide, potassium hexachloroiridate(III), hexaammineruthenium(III) chloride, and N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) have been examined at basal plane and edge plane pyrolytic graphite electrodes which have been allowed to oxidise in air for various periods of time. It is demonstrated via voltammetric and X-ray photoelectron spectroscopy (XPS) analysis that oxygenated species formed at edge plane sites/defects decrease the electron transfer kinetics of ferrocyanide but that the rates for potassium hexachloroiridate(III), hexaammineruthenium(III) chloride and TMPD are insensitive to the oxygenated species. The behaviour of the ferro-/ferricyanide couple contrasts with that seen on single-walled carbon nanotubes where oxygenation of the tube ends is known to speed up the electron transfer kinetics (A. Chou, T. Bocking, N. K. Singh, J. J. Gooding, Chem. Commun. 2005, 842); the possible reasons for this contrasting behaviour are discussed.

  17. Hydrogen Oxidation on Gas Diffusion Electrodes for Phosphoric Acid Fuel Cells in the Presence of Carbon Monoxide and Oxygen

    DEFF Research Database (Denmark)

    Gang, Xiao; Li, Qingfeng; Hjuler, Hans Aage

    1995-01-01

    Hydrogen oxidation has been studied on a carbon-supported platinum gas diffusion electrode in a phosphoric acidelectrolyte in the presence of carbon monoxide and oxygen in the feed gas. The poisoning effect of carbon monoxide presentin the feed gas was measured in the temperature range from 80...... to 150°C. It was found that throughout the temperaturerange, the potential loss due to the CO poisoning can be reduced to a great extent by the injection of small amounts ofgaseous oxygen into the hydrogen gas containing carbon monoxide. By adding 5 volume percent (v/o) oxygen, an almost......CO-free performance can be obtained for carbon monoxide concentrations up to 0.5 v/o CO at 130°C, 0.2 v/o CO at 100°C,and 0.1 v/o CO at 80°C, respectively....

  18. Vertically Aligned FeOOH/NiFe Layered Double Hydroxides Electrode for Highly Efficient Oxygen Evolution Reaction.

    Science.gov (United States)

    Chi, Jun; Yu, Hongmei; Qin, Bowen; Fu, Li; Jia, Jia; Yi, Baolian; Shao, Zhigang

    2017-01-11

    Employing a low-cost and highly efficient electrocatalyst to replace Ir-based catalysts for oxygen evolution reaction (OER) has drawn increasing interest in renewable energy storage. In this work, a vertically aligned FeOOH/NiFe layered double hydroxides (LDHs) nanosheets supported on Ni foam (VA FeOOH/NiFe LDHs-NF) is prepared as a highly effective OER electrode in alkaline electrolyte. The VA FeOOH/NiFe LDHs-NF represents nanosheet arrays on nickel foam with some interspace among them. The vertically aligned and interlayer-structured architecture is binder-free and contributes to facile strain relaxation, relieving the exfoliation of the catalysts layer caused by the oxygen evolution process. The as-prepared electrode shows current densities of 10 and 500 mA cm -2 at overpotentials of 208 and 288 mV, and good stability in a half-cell electrolyzer. Besides, the alkaline polymer electrolyte water electrolyzer (APEWE) with this electrode showed 1.71 V at 200 mA cm -2 , and 2.041 V at 500 mA cm -2 , exhibiting the corresponding energy efficiency of 86.0% and 72.0% (based on the lower heating value of hydrogen), which is better than the typical commercial alkaline water electrolyzer.

  19. Polarographic determination of Sn (II) and total Sn in PYRO and MDP radiopharmaceutical kits

    International Nuclear Information System (INIS)

    Sebastian, Maria V.A.; Lugon, Marcelo Di M.V.; Silva, Jose L. da; Fukumori, Neuza T.O.; Pereira, Nilda P.S. de; Silva, Constancia P.G. da; Matsuda, Margareth M.N.

    2007-01-01

    A sensitive, alternative method to atom absorption spectrometry, fluorimetry or potentiometry for the evaluation of tin(II) ions (0.1- 10 mg) and total tin in radiopharmaceutical kits was investigated. Differential pulse polarography was chosen. The supporting electrolyte was H 2 SO 4 3 mol L -1 and HCl 3 mol L -1 solution. The potential was swept from -250 to -800 mV vs Ag/AgCl/saturated KCl, using a dropping mercury electrode with 1 s drop time, 50 mV s -1 scan rate, -50 mV pulse amplitude, 40 ms pulse time and 10 mV step amplitude. Pure nitrogen was used to deaerate the polarographic cell solution for 5 min, before and after each sample introduction. Oxidation of Sn(II) was made in the same sample vial by adding H 2 O 2 (hydrogen peroxide) 10 mol L -1 , at 37 deg C, in order to quantify the total Sn. The calibration curve for Sn(II) and Sn(IV) was obtained in the concentration range of 0-10 ppm from a 1000 ppm standard solution. The detection limit of Sn(II) is 0.5 ppm and for Sn(IV) is 0.6 ppm. Differential pulse polarography was performed in the pyrophosphate (PYRO) and methylenediphosphonic acid (MDP) radiopharmaceutical kits, containing 2 mg and 1 mg of SnCl 2 .2H 2 O per vial, respectively. The described method for determination of stannous ion (Sn(II)), is selective, reproducible and adequate to be used in the quality control of lyophilized reagents and it shall be performed for other cold kits produced at IPEN. (author)

  20. Nanostructured carbon electrodes for laccase-catalyzed oxygen reduction without added mediators

    Energy Technology Data Exchange (ETDEWEB)

    Stolarczyk, Krzysztof; Nazaruk, Ewa [Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw (Poland); Rogalski, Jerzy [Department of Biochemistry, Maria Curie Sklodowska University, Sklodowskiej Sq 3, Lublin 20-031 (Poland); Bilewicz, Renata [Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw (Poland)], E-mail: bilewicz@chem.uw.edu.pl

    2008-04-20

    Reduction of dioxygen catalyzed by laccase was studied at carbon electrodes without any added mediators. On bare glassy carbon electrode (GCE) the catalytic reduction did not take place. However, when the same substrate was decorated with carbon nanotubes or carbon microcrystals the dioxygen reduction started at 0.6 V versus Ag/AgCl, which is close to the formal potential of the laccase used. Four different matrices: lecithin, hydrophobin, Nafion and lipid liquid-crystalline cubic phase were employed for hosting fungal laccase from Cerrena unicolor. The carbon nanotubes and nanoparticles present on the electrode provided electrical connectivity between the electrode and the enzyme active sites. Direct electrochemistry of the enzyme itself was observed in deoxygenated solutions and its catalytic activity towards dioxygen reduction was demonstrated. The stabilities of the hosted enzymes, the reduction potentials and ratios of catalytic to background currents were compared. The boron-doped diamond (BDD) electrodes prepolarized to high anodic potentials exhibited behavior similar to that of nanotube covered GCE pointing to the formation of nanostructures during the anodic pretreatment. BDD is a promising substrate in terms of potential of dioxygen reduction, however the catalytic current densities are not large enough for practical applications, therefore as shown in this paper, it should be additionally decorated with carbon particles being in direct contact with the electrode surface.

  1. Oxygen Reduction Kinetics of La2-xSrxNiO 4+delta Electrodes for Solid Oxide Fuel Cells

    Science.gov (United States)

    Guan, Bo

    In the development of intermediate temperature solid oxide fuel cell (IT-SOFC), mixed ionic-electronic conductors (MIEC) have drawn big interests due to their both ionic and electronic species transport which can enlarge the 3-dimension of the cathode network. This thesis presents an investigation of MIEC of Ruddlesden-popper (RP) phases like K2NiF4 type La2NiO4+delta (LNO)-based oxides which have interesting transport, catalytic properties and suitable thermal expansion coefficients. The motivation of this present work is to further understand the fundamental of the effect of Sr doing on the oxygen reduction reaction (ORR) kinetics of LNO cathode. Porous symmetrical cells of La2-xSrxNiO4+delta (0≤x≤0.4) were fabricated and characterized by electrochemical impedance spectroscopy (EIS) in different PO2 from temperature range of 600˜800°C. The spectra were analyzed based on the impedance model introduced by Adler et al. The rate determining steps (RDS) for ORR were proposed and the responsible reasons were discussed. The overall polarization resistances of doped samples increase with Sr level. Surface oxygen exchange and bulk ionic diffusion co-control the ORR kinetics. With high Sr content (x=0.3, 0.4), oxygen ion transfer resistance between nickelate/electrolyte is observed. However for porous symmetrical cells it is hard to associate the resistance from EIS directly to each ORR elementary processes because of the difficulty in describing the microstructure of the porous electrode. The dense electrode configuration was adopted in this thesis. By using the dense electrode, the surface area, the thickness of electrode, the interface between electrode and electrolyte and lastly the 3PB are theoretically well-defined. Through this method, there is a good chance to distinguish the contribution of surface exchange from other processes. Dense and thin electrode layers in thickness of ˜40 mum are fabricated by using a novel spray modified pressing method. Negligible

  2. Tailoring nanomaterial products through electrode material and oxygen partial pressure in a mini-arc plasma reactor

    International Nuclear Information System (INIS)

    Cui Shumao; Mattson, Eric C.; Lu, Ganhua; Hirschmugl, Carol; Gajdardziska-Josifovska, Marija; Chen Junhong

    2012-01-01

    Nanomaterials with controllable morphology and composition are synthesized by a simple one-step vapor condensation process using a mini-arc plasma source. Through systematic investigation of mini-arc reactor parameters, the roles of carrier gas, electrode material, and precursor on producing diverse nanomaterial products are revealed. Desired nanomaterial products, including tungsten oxide nanoparticles (NPs), tungsten oxide nanorods (NRs), tungsten oxide and tin oxide NP mixtures and pure tin dioxide NPs can thus be obtained by tailoring reaction conditions. The amount of oxygen in the reactor is critical to determining the final nanomaterial product. Without any precursor material present, a lower level of oxygen in the reactor favors the production of W 18 O 49 NRs with tungsten as cathode, while a high level of oxygen produces more round WO 3 NPs. With the presence of a precursor material, amorphous particles are favored with a high ratio of argon:oxygen. Oxygen is also found to affect tin oxide crystallization from its amorphous phase in the thermal annealing. Results from this study can be used for guiding gas phase nanomaterial synthesis in the future.

  3. A study of oxygen reduction on platinum-dispersed porous carbon electrodes at room and elevated temperatures by using a.c. impedance spectroscopy

    Science.gov (United States)

    Pyun, Su-Il; Ryu, Young-Gyoon

    Oxygen reduction on unwetted and pre-wetted platinum-dispersed porous carbon electrodes (Pt/C) is investigated in 1 M H 2SO 4 solution at room temperature by using a.c. impedance spectroscopy in combination with a current-decay transient technique (chronoamperometry). From the appearance of an inductive arc in Nyquist plots from the unwetted Pt/C electrode specimen, it is suggested that oxygen reduction proceeds via formation of an intermediate state. The a.c. impedance spectra are also obtained from the Pt/C electrode in 85% H 3PO 4 solution at 140°C, with and without oxygen and air blowings. In both cases, an inductive arc in the low-frequency range of the Nyquist plots is observed. The change in impedance spectra with pre-wetting treatment of the Pt/C electrode specimen in 1 M H 2SO 4 solution and the alteration of spectra without oxygen and air blowings in 85% H 3PO 4 solution are discussed in terms of the Epelboin model. From the analysis, it is concluded that as depletion of the dissolved oxygen occurs markedly within the narrow pores of the Pt/C electrode, the inductive arc moves towards the capacitive arc in the low-frequency range. The results of current-decay transients strongly suggest the occurrence of depletion of the dissolved oxygen within the narrow pores.

  4. New highly active oxygen reduction electrode for PEM fuel cell and Zn/air battery applications (NORA). Final report

    Energy Technology Data Exchange (ETDEWEB)

    Thiele, D.; Zuettel, A.

    2008-04-15

    This illustrated final report for the Swiss Federal Office of Energy (SFOE) presents the results of a project concerning a new, highly active oxygen reduction electrode for PEM fuel cell and zinc/air battery applications. The goal of this project was, according to the authors, to increase the efficiency of the oxygen reduction reaction by lowering the activation polarisation through the right choice of catalyst and by lowering the concentration polarisation. In this work, carbon nanotubes are used as support material. The use of these nanotubes grown on perovskites is discussed. Theoretical considerations regarding activation polarisation are discussed and alternatives to the use of platinum are examined. The results of experiments carried out are presented in graphical and tabular form. The paper is completed with a comprehensive list of references.

  5. Oxygen Transfer on Substituted ZrO2, Bi2O3, and CeO2 Electrolytes with Platinum Electrodes. I. Electrode Resistance by D-C Polarization

    NARCIS (Netherlands)

    Verkerk, M.J.; Hammink, W.J.; Burggraaf, A.J.

    1983-01-01

    The electrode behavior of Pt-sputtered and PT-gauze electrodes on ZrO2-Y2O3, Bi2O3-Er2O3, and CeO2-Gd2O3 solid electrolyteswas investigated by means of d-c measurements in the temperature region of 770–1050 K and in the oxygen partialpressure region of 10–5 – 1 atm O2 using N2-O2 mixtures. On these

  6. Oxygen electrode bifunctional electrocatalyst NiCo2O4 spinel

    Science.gov (United States)

    Fielder, William L.; Singer, Joseph

    1988-01-01

    A significant increase in energy density may be possible if a two-unit alkaline regenerative H2-O2 fuel cell is replaced with a single-unit system that uses passive means for H2O transfer and thermal control. For this single-unit system, new electrocatalysts for the O2 electrode will be required which are not only bifunctionally active but also chemically and electrochemically stable between the voltage range of about 0.7 and 1.5 V. NiCo2O4 spinel is reported to have certain characteristics that make it useful for a study of electrode fabrication techniques. High surface area NiCo2O4 powder was fabricated into unsupported, bifunctional, PTFE-bonded, porous gas fuel cell electrodes by commercial sources using varying PTFE contents and sintering temperatures. The object of this study is to measure the bifunctional activities of these electrodes and to observe what performance differences might result from different commercial electrode fabricators. O2 evolution and O2 reduction data were obtained at 80 C (31 percent KOH). An irreversible reaction (i.e., aging) occurred during O2 evolution at potentials greater than about 1.5 V. Anodic Tafel slopes of 0.06 and 0.12 V/decade were obtained for the aged electrodes. Within the range of 15 to 25 percent, the PTFE content was not a critical parameter for optimizing the electrode for O2 evolution activity. Sintering temperatures between 300 and 340 C may be adequate but heating at 275 C may not be sufficient to properly sinter the PTFE-NiCo2O4 mixture. Electrode disintegration was observed during O2 reduction. Transport of O2 to the NiCo2O4 surface became prohibitive at greater than about -0.02 A/sq cm. Cathodic Tafel slopes of -0.6 and -0.12 V/decade were assumed for the O2 reduction process. A PTFE content of 25 percent (or greater) appears to be preferable for sintering the PTFE-NiCo2O4 mixture.

  7. Methanol/Oxygen Enzymatic Biofuel Cell Using Laccase and NAD+-Dependent Dehydrogenase Cascades as Biocatalysts on Carbon Nanodots Electrodes.

    Science.gov (United States)

    Wu, Guozhi; Gao, Yue; Zhao, Dan; Ling, Pinghua; Gao, Feng

    2017-11-22

    The efficient immobilization of enzymes on favorable supporting materials to design enzyme electrodes endowed with specific catalysis performances such as deep oxidation of biofuels, and direct electron transfer (DET)-type bioelectrocatalysis is highly desired for fabricating enzymatic biofuel cells (BFCs). In this study, carbon nanodots (CNDs) have been used as the immobilizing matrixes and electron relays of enzymes to construct (NAD + )-dependent dehydrogenase cascades-based bioanode for the deep oxidation of methanol and DET-type laccase-based biocathode for oxygen reduction to water. At the bioanode, multiplex enzymes including alcohol dehydrogenase, aldehyde dehydrogenase, and formate dehydrogenase are coimmobilized on CNDs electrode which is previously coated with in situ polymerized methylene blue as the electrocatalyst for oxidizing NADH to NAD + . At the biocathode, fungal laccase is directly cast on CNDs and facilitated DET reaction is allowed. As a result, a novel membrane-less methanol/O 2 BFC has been assembled and displays a high open-circuit voltage of 0.71(±0.02) V and a maximum power density of 68.7 (±0.4) μW cm -2 . These investigated features imply that CNDs may act as new conductive architectures to elaborate enzyme electrodes for further bioelectrochemical applications.

  8. Study of an Ozone Composing Mechanism derived from the Third Element on Surface of Electrode using Oxygen Gas: Part 2

    Science.gov (United States)

    Murai, Akira; Nakajima, Tsuyoshi

    In our third experiment, we changed the density of nitrogen through the addition of heat energy to the anode. A computer simulation confirmed the same phenomenon. Then the copper anode was replaced with an antimony anode. We found that antimony worked better than nitrogen as a third element. Finally, in the fourth experiment, we used an industrial ozone generator including ceramic dielectrics and a titanium expanded metal electrode. A decrease in the temperature of the cooling water led to a proportional increase in ozone. It follows the formula of van't Hoff. After spattering the surface of the electrodes with argon gas and supplying the ozone generator with 99% oxygen, we were able to produce ozone which was more than 20% higher in concentration than primary state ozone under the same conditions. The ozone generator produced ozone in high yield efficiency due to the optimum density of a third element like nitrogen on the surface of the electrodes. Antimony works better than nitrogen does as a third element.

  9. Catalyst Stability Benchmarking for the Oxygen Evolution Reaction: The Importance of Backing Electrode Material and Dissolution in Accelerated Aging Studies.

    Science.gov (United States)

    Geiger, Simon; Kasian, Olga; Mingers, Andrea M; Nicley, Shannon S; Haenen, Ken; Mayrhofer, Karl J J; Cherevko, Serhiy

    2017-09-18

    In searching for alternative oxygen evolution reaction (OER) catalysts for acidic water splitting, fast screening of the material intrinsic activity and stability in half-cell tests is of vital importance. The screening process significantly accelerates the discovery of new promising materials without the need of time-consuming real-cell analysis. In commonly employed tests, a conclusion on the catalyst stability is drawn solely on the basis of electrochemical data, for example, by evaluating potential-versus-time profiles. Herein important limitations of such approaches, which are related to the degradation of the backing electrode material, are demonstrated. State-of-the-art Ir-black powder is investigated for OER activity and for dissolution as a function of the backing electrode material. Even at very short time intervals materials like glassy carbon passivate, increasing the contact resistance and concealing the degradation phenomena of the electrocatalyst itself. Alternative backing electrodes like gold and boron-doped diamond show better stability and are thus recommended for short accelerated aging investigations. Moreover, parallel quantification of dissolution products in the electrolyte is shown to be of great importance for comparing OER catalyst feasibility. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Parallel oxygen and chlorine evolution on Ru1-xNixO2-y nanostructured electrodes

    Czech Academy of Sciences Publication Activity Database

    Macounová, Kateřina; Makarova, Marina; Jirkovský, Jakub; Franc, Jiří; Krtil, Petr

    2008-01-01

    Roč. 53, č. 5 (2008), s. 6126-6134 ISSN 0013-4686 R&D Projects: GA AV ČR KAN100400702 Institutional research plan: CEZ:AV0Z40400503 Keywords : OER * CER * DEMS * ruthenium electrode Subject RIV: CG - Electrochemistry Impact factor: 3.078, year: 2008

  11. Influence of the Oxygen Electrode Open Ratio and Electrolyte Evaporation on the Performance of Li-O2 Batteries.

    Science.gov (United States)

    Mohazabrad, Farhad; Wang, Fangzhou; Li, Xianglin

    2017-05-10

    This study experimentally investigates and numerically simulates the influence of the cathode electrode open ratio (ratio of oxygen-opening area to the total electrode surface area) on the performance of Li-O 2 batteries at various discharge current densities. At the current density of 0.1 mA/cm 2 , the maximum discharge capacity is achieved at 25% open ratio among the tested open ratios (0-100%). As the open ratio increases from 25% to 100%, the specific discharge capacity decreases from 995 to 397 mA h/g carbon . A similar trend is observed at 0.3 mA/cm 2 , while the maximum discharge capacity is obtained at 3% open ratio among the tested open ratios. The model that assumes the electrode is always fully saturated by the electrolyte does not obtain similar trends with experimental results, while the model that considers electrolyte loss by evaporation and the volume change of the solid obtains the same trend with experimental observations. The open ratio governs not only availability of oxygen but also the evaporation of the electrolyte and the contact resistance. The faster evaporation of the electrolyte at a higher open ratio can be the main reason for the decrease of the discharge capacity, especially when the open ratio is relatively high (above 25%). Meanwhile, the contact resistance of the battery, measured by the electrochemical impedance spectroscopy (EIS), increases from 3.97 to 7.02 Ω when the open ratio increased from 3% to 95%. The increase of the Ohmic overpotential, however, is negligible (on the order of millivolts) because of the low discharge and charge current rates (on the order of 0.1 mA).

  12. Role of silver current collector on the operational stability of selected cobalt-containing oxide electrodes for oxygen reduction reaction

    Science.gov (United States)

    Chen, Yubo; Wang, Fucun; Chen, Dengjie; Dong, Feifei; Park, Hee Jung; Kwak, Chan; Shao, Zongping

    2012-07-01

    The long-term stability for oxygen reduction reaction (ORR) of two typical perovskite cathode materials of SOFCs, i.e., Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) and Sm0.5Sr0.5CoO3-δ (SSC), is investigated in a symmetric cell configuration under air condition at 700 °C using Sm0.2Ce0.8O1.9 (SDC) electrolyte substrate and silver current collectors. Moreover, two different methods of silver current collection are tested, i.e., whole electrode surface deposited with a diluted silver paste (CC-01) and a mesh-like current collector using concentrated silver paste (CC-02). Electrochemical impedance spectra are applied for stability investigations. With the CC-01 current collector, the performance of the electrode deteriorates significantly, although the initial performance is good. By contrast, fairly stable performance is obtained from symmetric cells with either BSCF or SSC + SDC electrodes using the CC-02 current collector, even though a phase transition is observed for BSCF. For instance, after approximately 800 h of continuous stability testing, the area-specific resistance of the BSCF electrode retains a value of approximately 0.065 Ω cm2, except for a slight fluctuation within the range of 0.06-0.07 Ω cm2. These findings reveal that both BSCF and SSC can be stably operated for ORR under symmetric cell conditions; however, an appropriate current collection method is crucial to achieving stable performance.

  13. Diagnosis on improved electrocatalytic activity of La2Ni0.8Cu0.2O4+δ electrodes towards oxygen reduction reaction

    Science.gov (United States)

    Wang, Ya-Ping; Xu, Qing; Huang, Duan-Ping; Zhao, Kai; Chen, Min; Kim, Bok-Hee

    2017-11-01

    La2Ni0.8Cu0.2O4+δ electrodes with different thicknesses were prepared on Ce0.8Sm0.2O1.9 electrolyte using screen printing technique. The electrocatalytic activity of La2Ni0.8Cu0.2O4+δ electrodes towards oxygen reduction reaction was investigated in comparison with La2NiO4+δ electrode. To understand the electrocatalytic activity of the two electrodes, chemical states of constituent elements on the surface of La2NiO4+δ and La2Ni0.8Cu0.2O4+δ were analyzed using X-ray photoelectron spectroscopy technique. La2Ni0.8Cu0.2O4+δ electrodes sintered at 920 °C exhibited improved electrocatalytic activity relative to literature results of the electrodes sintered at higher temperatures (e.g. 1200 °C). The Cu doping in La2NiO4+δ was validated to be effective in enhancing electrocatalytic activity. The electrocatalytic activity of La2Ni0.8Cu0.2O4+δ electrodes was found to be dependent on their thickness. Optimal electrocatalytic activity was achieved for the electrode with a thickness of 10 μm, showing a polarization resistance of 0.13 Ω cm2 at 800 °C. The effects of Cu doping and electrode thickness were diagnosed with respect to contributions of involved electrode reaction steps. The results of this work underscore that the electrocatalytic activity of La2Ni0.8Cu0.2O4+δ electrodes is dictated by dissociative adsorption process of molecular oxygen on the surface.

  14. A study of oxygen reduction on platinum-dispersed porous carbon electrodes at room and elevated temperatures by using a.c. impedance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Pyun, Su-Il [Korea Advanced Inst. of Science and Technology, Daejon (Korea, Republic of). Dept. of Materials Science and Engineering; Ryu, Young-Gyoon [Korea Advanced Inst. of Science and Technology, Daejon (Korea, Republic of). Dept. of Materials Science and Engineering

    1996-09-01

    Oxygen reduction on unwetted and pre-wetted platinum-dispersed porous carbon electrodes (Pt/C) is investigated in 1 M H{sub 2}SO{sub 4} solution at room temperature by using a.c. impedance spectroscopy in combination with a current-decay transient technique (chronoamperometry). From the appearance of an inductive arc in Nyquist plots form the unwetted Pt/C electrode specimen, it is suggested that oxygen reduction proceeds via formation on an intermediate state. The a.c. impedance spectra are also obtained form the Pt/C electrode in 85% H{sub 3}PO{sub 4} solution at 140 C, with and without oxygen and air blowings. In both cases, an inductive arc in the low-frequency range of the Nyquist plots is observed. The change in impedance spectra with pre-wetting treatment of the Pt/C electrode specimen in 1 M H{sub 2}SO{sub 4} solution and the alteration of spectra without oxygen and air blowings in 85% H{sub 3}PO{sub 4} solution are discussed in terms of the Epelboin model. From the analysis, it is concluded that as depletion of the dissolved oxygen occurs markedly within the narrow pores of the Pt/C electode, the inductive arc moves towards the capacitive arc in the low-frequency range. The results of current-decay transients strongly suggest the occurrence of depletion of the dissolved oxygen within the narrow pores. (orig.)

  15. Electrocatalysis of Oxygen Using Water Soluble Metal Porphyrins and Chemically Modified Porphyrin Electrodes.

    Science.gov (United States)

    1983-11-01

    important to model the proposed mechanism for oxygen electrocatalysis and to computer simulate the electrochemical response characteristics and compare...m .S " 3 -1 9 7 .8NOV W3 RF Project 761254/711380 Final Report ELECTROCATALYSIS OF OXYGEN * AND USING WATER SOLUBLE METAL...cobalt porphyrins, namely, iron and cobalt tetrakis(N-methyl- 4-pyridyllpcrphyrin. These prophyrins with the metal in the +3 oxidation state can be

  16. Anodic oxygen-transfer electrocatalysis at iron-doped lead dioxide electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Jianren [Iowa State Univ., Ames, IA (United States)

    1994-01-01

    The research illustrated in this thesis was performed under the guidance of Professor Dennis C. Johnson beginning in March 1987. Chapter 2 concentrates on the development and electrocatalytic properties of iron-doped β-PbO2 films on noble-metal substrates. Chapter 3 focuses attention on the preparation and characterization of iron-doped β-PbO2 films on titanium substrates (Fe-PbO2/Ti). Chapter 4 discusses anodic evolution of ozone at Fe-PbO2/Ti electrodes. Chapter 5 describes electrochemical incineration of p-benzoquinone (BQ) at Fe-PbO2/Ti electrodes. In addition, the Appendix includes another published paper which is a detailed study of α-PbO2 films deposited on various types of stainless steel substrates.

  17. Polarographic Determination of Composition and Thermodynamic Stability Constant of a Complex Metal Ion.

    Science.gov (United States)

    Marin, Dolores; Mendicuti, Francisco

    1988-01-01

    Describes a laboratory experiment designed to encourage laboratory cooperation among individual undergraduate students or groups. Notes each student contributes results individually and the exchange of data is essential to obtain final results. Uses the polarographic method for determining complex metal ions. (MVL)

  18. Simultaneous polarographic determination of micro amounts of vanadium(V) and molybdenum(VI)

    International Nuclear Information System (INIS)

    Rao, V.S.N.; Rao, S.B.

    1979-01-01

    A simple and sensitive polarographic method has been developed for the determination of micro quantities of vanadium(V) and molybdenum(VI), based on the reduction of bromate, which is catalysed by these metal ions in the presence of 2,4-dihydroxyacetophenone oxime. Interference by various cations and anions has been investigated. (author)

  19. Development of a Novel Cu(II Complex Modified Electrode and a Portable Electrochemical Analyzer for the Determination of Dissolved Oxygen (DO in Water

    Directory of Open Access Journals (Sweden)

    Salvatore Gianluca Leonardi

    2016-04-01

    Full Text Available The development of an electrochemical dissolved oxygen (DO sensor based on a novel Cu(II complex-modified screen printed carbon electrode is reported. The voltammetric behavior of the modified electrode was investigated at different scan rates and oxygen concentrations in PBS (pH = 7. An increase of cathodic current (at about −0.4 vs. Ag/AgCl with the addition of oxygen was observed. The modified Cu(II complex electrode was demonstrated for the determination of DO in water using chronoamperometry. A small size and low power consumption home-made portable electrochemical analyzer based on custom electronics for sensor interfacing and operating in voltammetry and amperometry modes has been also designed and fabricated. Its performances in the monitoring of DO in water were compared with a commercial one.

  20. Limiting Current of Oxygen Reduction on Gas-Diffusion Electrodes for Phosphoric Acid Fuel Cells

    DEFF Research Database (Denmark)

    Li, Qingfeng; Gang, Xiao; Hjuler, Hans Aage

    1994-01-01

    on polytetrafluorine-ethyl bonded gas-diffusion electordes in phosphoric acid with and without fluorinated additives. This provides an alternative to estimate the film thickness by combining it with the acid-adsorption measurements and the porosity analysis of the catalyst layer. It was noticed that the limiting...... expression for the limiting current density. The acid-film thickness estimated this way was found to be of 0.1 mum order of magnitude for the two types of electrodes used in phosphoric acid with and without fluorinated additives at 150-degrees-C....

  1. Heterostructured electrode with concentration gradient shell for highly efficient oxygen reduction at low temperature

    OpenAIRE

    Zhou, Wei; Liang, Fengli; Shao, Zongping; Chen, Jiuling; Zhu, Zhonghua

    2011-01-01

    Heterostructures of oxides have been widely investigated in optical, catalytic and electrochemical applications, because the heterostructured interfaces exhibit pronouncedly different transport, charge, and reactivity characteristics compared to the bulk of the oxides. Here we fabricated a three-dimensional (3D) heterostructured electrode with a concentration gradient shell. The concentration gradient shell with the composition of Ba0.5-xSr0.5-yCo0.8Fe0.2O3-? (BSCF-D) was prepared by simply t...

  2. Micro-Membrane Electrode Assembly Design to Precisely Measure the in Situ Activity of Oxygen Reduction Reaction Electrocatalysts for PEMFC.

    Science.gov (United States)

    Long, Zhi; Li, Yankai; Deng, Guangrong; Liu, Changpeng; Ge, Junjie; Ma, Shuhua; Xing, Wei

    2017-06-20

    An in situ micro-MEA technique, which could precisely measure the performance of ORR electrocatalyst using Nafion as electrolyte, was designed and compared with regular thin-film rotating-disk electrode (TFRDE) (0.1 M HClO 4 ) and normal in situ membrane electrode assembly (MEA) tests. Compared to the traditional TFRDE method, the micro-MEA technique makes the acquisition of catalysts' behavior at low potential values easily achieved without being limited by the solubility of O 2 in water. At the same time, it successfully mimics the structure of regular MEAs and obtains similar results to a regular MEA, thus providing a new technique to simply measure the electrode activity without being bothered by complicated fabrication of regular MEA. In order to further understand the importance of in situ measurement, Fe-N-C as a typical oxygen reduction reaction (ORR) free-Pt catalyst was evaluated by TFRDE and micro-MEA. The results show that the half wave potential of Fe-N-C only shifted negatively by -135 mV in comparison with state-of-the-art Pt/C catalysts from TFRDE tests. However, the active site density, mass transfer of O 2 , and the proton transfer conductivity are found to strongly influence the catalyst activity in the micro-MEA, thereby resulting in a much lower limiting current density than Pt/C (8.7 times lower). Hence, it is suggested that the micro-MEA is better in evaluating the in situ ORR performance, where the catalysts are characterized more thoroughly in terms of intrinsic activity, active site density, proton transfer, and mass transfer properties.

  3. Stability and Performance of Oxygen Electrodes for Reversible Solid Oxide Cells

    Science.gov (United States)

    Railsback, Justin Gary

    Worldwide, governments are beginning to take action to reduce anthropogenic CO2 emissions in order to mitigate the extent of global climate change. The largest fraction of global CO2 emission comes from electrical power generation, which is rapidly being converted to wind and solar installations. The intermittent nature of renewable resources requires that large scale energy storage be implemented to ensure grid stability. Pumped hydro storage is currently the only technology available for large scale energy storage; however, pumped hydro remains geographically confined and susceptible to seasonal fluctuations and offers limited discharge hours. Recent system level models predict that reversible solid oxide cells may be a competitive solution, but two key advancements are required to realize the technology: low cell resistance (system is desirable to achieve high round-trip efficiency. The electrochemical performance of mixed electronic-ionic conducting electrodes has not been reported above 1 atm. Four candidate electrodes are examined under pressurization up to 10 atm: Pr2NiO4 infiltrated La0.9Sr0.1 Ga0.8Mg0.2O3, Sm0.5Sr 0.5CoO3 infiltrated Ce0.9Gd0.1O 2, single phase La0.6Sr0.4Co0.2Fe 0.8O3, and single phase Nd2NiO4. The role of the ion conduction mechanism (vacancy or interstitial) is explored in relation to the decrease in polarization resistance with increased pressure. Current switched life-tests designed to emulate reversible solid oxide cell operating conditions were performed for a range of current densities and overpotentials on three candidate systems: composite La0.7Sr 0.3MnO3-Zr0.84Y0.16O2, single phase La0.6Sr0.4Co0.2Fe0.8O 3, and La2NiO4 infiltrated La0.9Sr 0.1Ga0.8Mg0.2O3. The degradation mode of each system is determined by impedance spectroscopy and post-test microstructural analysis. Operating regions of improved stability are identified for each system based on the measured degradation rates. Overpotential is determined to be the major

  4. Screen-Printed Graphite Electrodes as Low-Cost Devices for Oxygen Gas Detection in Room-Temperature Ionic Liquids

    Directory of Open Access Journals (Sweden)

    Junqiao Lee

    2017-11-01

    Full Text Available Screen-printed graphite electrodes (SPGEs have been used for the first time as platforms to detect oxygen gas in room-temperature ionic liquids (RTILs. Up until now, carbon-based SPEs have shown inferior behaviour compared to platinum and gold SPEs for gas sensing with RTIL solvents. The electrochemical reduction of oxygen (O2 in a range of RTILs has therefore been explored on home-made SPGEs, and is compared to the behaviour on commercially-available carbon SPEs (C-SPEs. Six common RTILs are initially employed for O2 detection using cyclic voltammetry (CV, and two RTILs ([C2mim][NTf2] and [C4mim][PF6] chosen for further detailed analytical studies. Long-term chronoamperometry (LTCA was also performed to test the ability of the sensor surface for real-time gas monitoring. Both CV and LTCA gave linear calibration graphs—for CV in the 10–100% vol. range, and for LTCA in the 0.1–20% vol. range—on the SPGE. The responses on the SPGE were far superior to the commercial C-SPEs; more instability in the electrochemical responses were observed on the C-SPEs, together with some breaking-up or dissolution of the electrode surface materials. This study highlights that not all screen-printed ink formulations are compatible with RTIL solvents for longer-term electrochemical experiments, and that the choice of RTIL is also important. Overall, the low-cost SPGEs appear to be promising platforms for the detection of O2, particularly in [C4mim][PF6].

  5. Screen-Printed Graphite Electrodes as Low-Cost Devices for Oxygen Gas Detection in Room-Temperature Ionic Liquids.

    Science.gov (United States)

    Lee, Junqiao; Hussain, Ghulam; Banks, Craig E; Silvester, Debbie S

    2017-11-26

    Screen-printed graphite electrodes (SPGEs) have been used for the first time as platforms to detect oxygen gas in room-temperature ionic liquids (RTILs). Up until now, carbon-based SPEs have shown inferior behaviour compared to platinum and gold SPEs for gas sensing with RTIL solvents. The electrochemical reduction of oxygen (O₂) in a range of RTILs has therefore been explored on home-made SPGEs, and is compared to the behaviour on commercially-available carbon SPEs (C-SPEs). Six common RTILs are initially employed for O₂ detection using cyclic voltammetry (CV), and two RTILs ([C₂mim][NTf₂] and [C₄mim][PF₆]) chosen for further detailed analytical studies. Long-term chronoamperometry (LTCA) was also performed to test the ability of the sensor surface for real-time gas monitoring. Both CV and LTCA gave linear calibration graphs-for CV in the 10-100% vol. range, and for LTCA in the 0.1-20% vol. range-on the SPGE. The responses on the SPGE were far superior to the commercial C-SPEs; more instability in the electrochemical responses were observed on the C-SPEs, together with some breaking-up or dissolution of the electrode surface materials. This study highlights that not all screen-printed ink formulations are compatible with RTIL solvents for longer-term electrochemical experiments, and that the choice of RTIL is also important. Overall, the low-cost SPGEs appear to be promising platforms for the detection of O₂, particularly in [C₄mim][PF₆].

  6. In Situ-Grown ZnCo2O4 on Single-Walled Carbon Nanotubes as Air Electrode Materials for Rechargeable Lithium–Oxygen Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Bin; Xu, Wu; Yan, Pengfei; Bhattacharya, Priyanka; Cao, Ruiguo; Bowden, Mark E.; Engelhard, Mark H.; Wang, Chong M.; Zhang, Jiguang

    2015-10-12

    Although lithium-oxygen (Li-O2) batteries have great potential to be used as one of the next generation energy storage systems due to their ultrahigh theoretical specific energy, there are still many significant barriers before their practical applications. These barriers include electrolyte and electrode instability, poor ORR/OER efficiency and cycling capability, etc. Development of a highly efficient catalyst will not only enhance ORR/OER efficiency, it may also improve the stability of electrolyte because the reduced charge voltage. Here we report the synthesis of nano-sheet-assembled ZnCo2O4 spheres/single walled carbon nanotubes (ZCO/SWCNTs) composites as high performance air electrode materials for Li-O2 batteries. The ZCO catalyzed SWCNTs electrodes delivered high discharge capacities, decreased the onset of oxygen evolution reaction by 0.9 V during charge processes, and led to more stable cycling stability. These results indicate that ZCO/SWCNTs composite can be used as highly efficient air electrode for oxygen reduction and evolution reactions. The highly enhanced catalytic activity by uniformly dispersed ZnCo2O4 catalyst on nanostructured electrodes is expected to inspire

  7. In Situ-Grown ZnCo2O4 on Single-Walled Carbon Nanotubes as Air Electrode Materials for Rechargeable Lithium-Oxygen Batteries.

    Science.gov (United States)

    Liu, Bin; Xu, Wu; Yan, Pengfei; Bhattacharya, Priyanka; Cao, Ruiguo; Bowden, Mark E; Engelhard, Mark H; Wang, Chong-Min; Zhang, Ji-Guang

    2015-11-01

    The development of highly efficient catalysts is critical for the practical application of lithium-oxygen (Li-O2) batteries. Nanosheet-assembled ZnCo2O4 (ZCO) microspheres and thin films grown in situ on single-walled carbon nanotube (ZCO/SWCNT) composites as high-performance air electrode materials for Li-O2 batteries are reported. The in situ grown ZCO/SWCNT electrodes delivered high discharge capacities, decreased the onset of the oxygen evolution reaction by 0.9 V during the charging process, and led to longer cycling stability. These results indicate that in situ grown ZCO/SWCNT composites can be used as highly efficient air electrode materials for oxygen reduction and evolution reactions. The enhanced catalytic activity displayed by the uniformly dispersed ZCO catalyst on nanostructured electrodes is expected to inspire further development of other catalyzed electrodes for Li-O2 batteries and other applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Oxygenation of spontaneous canine tumors during fractionated radiation therapy

    International Nuclear Information System (INIS)

    Achermann, R.E.; Ohlerth, S.M.; Bley, C.R.; Inteeworn, N.; Schaerz, M.; Wergin, M.C.; Kaser-Hotz, B.; Gassmann, M.; Roos, M.

    2004-01-01

    Background and purpose: tumor oxygenation predicts treatment outcome, and reoxygenation is considered important in the efficacy of fractionated radiation therapy. Therefore, the purpose of this study was to document the changes of the oxygenation status in spontaneous canine tumors during fractionated radiation therapy using polarographic needle electrodes. Material and methods: tumor oxygen partial pressure (pO 2 ) measurements were performed with the eppendorf-pO 2 -Histograph. The measurements were done under general anesthesia, and probe tracks were guided with ultrasound. pO 2 was measured before radiation therapy in all dogs. In patients treated with curative intent, measurements were done sequentially up to eight times (total dose: 45-59.5 Gy). Oxygenation status of the palliative patient group was examined before each fraction of radiation therapy up to five times (total dose: 24-30 Gy). Results: 15/26 tumors had a pretreatment median pO 2 ≤ 10 mmHg. The pO 2 values appeared to be quite variable in individual tumors during fractionated radiation therapy. The pO 2 of initially hypoxic tumors (pretreatment median pO 2 ≤ 10 mmHg) remained unchanged during fractionated radiotherapy, whereas in initially normoxic tumors the pO 2 decreased. Conclusion: hypoxia is common in spontaneous canine tumors, as 57.7% of the recorded values were ≥ 10 mmHg. The data of this study showed that initially hypoxic tumors remained hypoxic, whereas normoxic tumors became more hypoxic. (orig.)

  9. Preparation of biofilm electrode with Xanthomonas sp. and carbon nanotubes and the application to rapid biochemical oxygen demand analysis in high-salt condition.

    Science.gov (United States)

    Chen, Jing; Yu, Zhiguo; Sun, Jinfeng; Jia, Jianbo; Li, Genxi

    2008-08-01

    A Xanthomonas sp. was isolated from the sludge on the drain outlet of a pharmaceutical factory. Then, the bacterium and carbon nanotubes (CNTs) were co-attached to an oxygen electrode for rapid analysis of biochemical oxygen demand (BOD). The response current was linear with BOD values in the range 10 to 300 mg/L for standard BOD solution with a response time of 35 seconds (R = 0.9994) and 20 to 580 mg/L for pharmaceutical wastewater with a response time < or =200 seconds (R = 0.9985), which means that this modified electrode might be used for online BOD analysis of pharmaceutical wastewater. Further studies revealed that the modified electrode can be used for BOD measurement in a high-salt condition. Also, the bacterium/CNTs biofilm can maintain its activity and good performance, even after being sealed and stored at 4 degrees C for 50 days.

  10. Electrocatalytic reduction of oxygen at glassy carbon electrode modified by polypyrrole/anthraquinones composite film in various pH media

    International Nuclear Information System (INIS)

    Valarselvan, S.; Manisankar, P.

    2011-01-01

    Graphical abstract: The electrocatalytic reduction of dioxygen by one mono and four dihydroxy derivatives of 9,10-anthraquinone (AQ) incorporated in polypyrrole (PPy) matrix on glassy carbon electrode has been investigated. AQ and PPy composite film showed excellent electrocatalytic performance for the reduction of O 2 to H 2 O 2 . Highlights: → Hydroxyl derivatives of anthraquinones as electrocatalysts for dioxygen reduction. → AQ/PPy composite film on GC electrode exhibits potent electrocatalytic activity. → Substituent groups influence electrocatalytic dioxygen reduction. → Surface coverage varies the rate of electrocatalytic dioxygen reduction. - Abstract: The electrocatalytic reduction of dioxygen by one mono and four dihydroxy derivatives of 9,10-anthraquinone (AQ) incorporated in polypyrrole (PPy) matrix on glassy carbon electrode has been investigated. The electrochemical behaviour of the modified electrodes was examined in various pH media and both the formal potential of anthraquinones and reduction potential of dioxygen exhibited pH dependence. AQ and PPy composite film showed excellent electrocatalytic performance for the reduction of O 2 to H 2 O 2 . pH 6.0 was chosen as the most suitable medium to study the electrocatalysis by comparing the peak potential of oxygen reduction and enhancement in peak current for oxygen reduction. The diffusion coefficient values of AQ at the modified electrodes and the number of electrons involved in AQ reduction were evaluated by chronoamperometric and chronocoulometric techniques, respectively. In addition, hydrodynamic voltammetric studies showed the involvement of two electrons in O 2 reduction. The mass specific activity of AQ used, the diffusion coefficient of oxygen and the heterogeneous rate constants for the oxygen reduction at the surface of modified electrodes were also determined by rotating disk voltammetry.

  11. Surface oxygen exchange properties of bismuth oxide-based solid electrolytes and electrode materials

    NARCIS (Netherlands)

    Boukamp, Bernard A.; Vinke, I.C.; de Vries, K.J.; Burggraaf, A.J.

    1989-01-01

    The surface oxygen exchange coefficient, ks, has been measured for the solid solution (Bi2O3)0.75(Er2O3)0.25 and (Bi2O3)0.6(Tb2O3)0.4 (abbreviated BE25 and BT40), using gas-phase 18O exchange techniques. The activation enth alpy of ks amounts to ΔE=110 kJ/molforBT40 andΔE=130 kJ/molforBE25. The

  12. Polarographic determination of the titanium and niobium content of zirconium alloys

    International Nuclear Information System (INIS)

    Levin, R; Gabra, J.

    1978-03-01

    A method is described for the polarographic determination of titanium and niobium in zirconium alloys in the concentration range of 0.1% to 4% of each of the determined metals. To assure the complete dissolution of the sample a mixture of nitric acid and hydrofluoric acid is used. After evaporating these acids in the presence of sulphuric acid, the contents are determined polarographically with a supporting electrolyte solution of 0.1M EDTA, 0.33M potassium sulfate and 0.4M sodium acetate, buffered to pH 4 with acetic acid. The half-wave potential (Esub(1/2)) of titanium is -0.35V and that of niobium is -0.67 V. (author)

  13. Modified polarographic method of determining O/U ratio of uranium oxide-based nuclear fuels

    International Nuclear Information System (INIS)

    Papez, V.; Vecernik, J.; Krtil, J.

    1983-01-01

    Following the dissolution of UO 2 in concentrated H 3 PO 4 the solution contains not only U(VI) but also a large excess of U(IV). The polarographic method was used to determine the concentration of U(VI) in the initial sample. Then an accurate amount of cerium sulphate was added to the sample. Part of the U(VI) was converted into U(VI) which was again determined using polarography. The remaining U(IV) was determined by amperometrical titration in the same sample using Ce(SO 4 ) 2 . This method makes po-sible a simple and quick determination of the O/U ratio in uranium oxides. It is suitable for routine analyses and may be performed on routine polarographical instruments. (E.S.)

  14. Characteristics of the oxygen evolution reaction on synthetic copper - cobalt - oxide electrodes for water electrolysis

    Science.gov (United States)

    Park, Yoo Sei; Park, Chan Su; Kim, Chi Ho; Kim, Yang Do; Park, Sungkyun; Lee, Jae Ho

    2016-10-01

    A nano-sized Cu0.7Co2.3O4 powder was prepared using a thermal decomposition method to achieve an efficient anode catalyst for an economical water electrolysis system for high-purity hydrogen-gas production without using a noble-metal catalyst. This study showed that the calcination temperature should be maintained under 400 °C to obtain a spinel copper - cobalt oxide structure without secondary oxide phases. The powder calcined at 250 °C showed the highest current density at the oxygen evolution reaction. This was due mainly to the increased number of available active sites and the active surface area of the powders. Further systematic analyses of the electrochemical characteristics of Cu x Co3- x O4 synthesized by using the fusion method were performed to assess it as potential anode material for use in alkaline-anion-exchange-membrane water electrolysis.

  15. Electrocatalysis of anodic oxygen-transfer reactions at modified lead dioxide electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Hsiao, Yun-Lin.

    1990-09-21

    The electrocatalytic activities were compared for pure and chloride-doped beta-PbO{sub 2} (Cl-PbO{sub 2}) films on gold and platinum substrates. Rate constants were increased significantly for oxidations of Mn{sup 2+}, toluene, benzyl alcohol, dimethylsulphoxide (DMSO) and benzaldehyde in acidic media by the incorporation of Cl{sup {minus}} into the oxide films. These reactions are concluded to occur by the electrocatalytic transfer of oxygen from H{sub 2}O to the reaction products. Results of x-ray diffraction studies indicate the Cl-PbO{sub 2} film continues to have the slightly distorted rutile structure of pure beta-PbO{sub 2}. The observed electrocatalytic phenomena are concluded to be the beneficial consequence of surface defects generated when Cl{sup {minus}} serves for charge compensation within the surface matrix and, thereby, increases the number of surface sites capable of adsorbing hydroxyl radicals which are transferred in the electrocatalytic O-transfer reactions. 91 refs., 44 figs., 10 tabs.

  16. Generation of Transparent Oxygen Evolution Electrode Consisting of Regularly Ordered Nanoparticles from Self-Assembly Cobalt Phthalocyanine as a Template

    KAUST Repository

    Ziani, Ahmed

    2016-11-04

    The decoration of (photo)electrodes for efficient photoresponse requires the use of electrocatalysts with good dispersion and high transparency for efficient light absorption by the photoelectrode. As a result of the ease of thermal evaporation and particulate self-assembly growth, the phthalocyanine molecular species can be uniformly deposited layer-by-layer on the surface of substrates. This structure can be used as a template to achieve a tunable amount of catalysts, high dispersion of the nanoparticles, and transparency of the catalysts. In this study, we present a systematic study of the structural and optical properties, surface morphologies, and electrochemical oxygen evolution reaction (OER) performance of cobalt oxide prepared from a phthalocyanine metal precursor. Cobalt phthalocyanine (CoPc) films with different thicknesses were deposited by thermal evaporation on different substrates. The films were annealed at 400 °C in air to form a material with the cobalt oxide phase. The final Co oxide catalysts exhibit high transparency after thermal treatment. Their OER measurements demonstrate well expected mass activity for OER. Thermally evaporated and treated transition metal oxide nanoparticles are attractive for the functionalization of (photo)anodes for water oxidation.

  17. A novel stainless steel mesh/cobalt oxide hybrid electrode for efficient catalysis of oxygen reduction in a microbial fuel cell.

    Science.gov (United States)

    Gong, Xiao-Bo; You, Shi-Jie; Wang, Xiu-Heng; Zhang, Jin-Na; Gan, Yang; Ren, Nan-Qi

    2014-05-15

    To explore efficient and cost-effective cathode material for microbial fuel cells (MFCs), the present study fabricates a new type of binder-free gas diffusion electrode made of cobalt oxide (Co3O4) micro-particles directly grown on stainless steel mesh (SSM) by using an ammonia-evaporation-induced method. In various electrochemical analyses and evaluations in batch-fed dual-chamber MFCs, the SSM/Co3O4 hybrid electrode demonstrates improved performances in terms of electrocatalytic activity, selectivity, durability and economics toward oxygen reduction reaction (ORR) in pH-neutral solution, in comparison with conventional carbon supported platinum catalyst. This study suggests a new strategy to fabricate a more effective electrode for ORR in MFCs, making it more technically and economically viable to produce electrical energy from organic materials for practical applications. Copyright © 2013 Elsevier B.V. All rights reserved.

  18. Stability of a Cu0.7Co2.3O4 electrode during the oxygen evolution reaction for alkaline anion-exchange membrane water electrolysis

    Science.gov (United States)

    Kang, Kyoung Eun; Kim, Chi Ho; Lee, Myung Sup; Jung, Chang Wook; Kim, Yang Do; Lee, Jae Ho

    2018-01-01

    The electrode materials for oxygen evolution, especially non-platinum group metal oxides, have attracted increasing attention. Among the spinel-type transition metal oxides, Cu0.7Co2.3O4 powders were evaluated as a potential replacement for expensive dimensionally stabilized anode materials. Cu0.7Co2.3O4 powder for use as an electrode material for oxygen evolution in an alkaline anion-exchange membrane water electrolyzer was prepared using a thermal decomposition method. The Cu0.7Co2.3O4 powders heat-treated at 250 °C exhibited the same X-ray diffraction patterns without any secondary phases as the Co3O4 spinel structure did. The Cu0.7Co2.3O4 powders heat-treated at 250 °C for 30 minutes showed the smallest mean particle size of approximately 376 nm with the powders having a homogeneous shape and size distribution. The fine powders with a relatively homogeneous size distribution showed a higher current density during the oxygen evolution reaction. The lifetime of the Cu0.7Co2.3O4 electrode was relatively long at a low current density, but was quickly shortened due to physical detachment of the Cu0.7Co2.3O4 powders as the current density was increased. This study showed that the efficiency and the stability of Cu0.7Co2.3O4 powders during the oxygen evolution reaction were related directly to the active electrode area.

  19. Investigation of the Alkaline Electrochemical Interface and Development of Composite Metal/Metal-Oxides for Hydrogen and Oxygen Electrodes

    Science.gov (United States)

    Bates, Michael

    electrolyte. The HER kinetics of numerous binary & ternary Ni-alloys and composite Ni/metal-oxide/C samples were evaluated in aqueous 0.1 M KOH electrolyte. Furthermore a model of the double layer interface is proposed, which helps explain the observed ensemble effect in the presence of AEI. In Chapter 3, Ni-Fe and Ni-Fe-Co mixed-metal-oxide (MMO) films were investigated for oxygen evolution reaction (OER) activity in 0.1M KOH on high surface area Raney-Nickel supports. During investigations of MMO activity, aniline was identified as a useful "capping agent" for synthesis of high-surface area MMO-polyaniline (PANI) composite materials. A Ni-Fe-Co/PANI-Raney-Ni catalyst was developed which exhibits enhanced mass-activity compared to state-of-the-art Ni-Fe OER electrocatalysts reported to date. The morphology of the MMO catalyst film on PANI/Raney-Ni support provides excellent dispersion of active-sites and should maintain high active-site utilization for catalyst loading on gas-diffusion electrodes. In Chapter 4, the de-activation of reversible-hydrogen electrode catalysts was investigated and the development of a Pt-Ir-Nx/C catalyst is reported, which exhibits significantly increased stability in the HBr/Br 2 electrolyte. In contrast a Pt-Ir/C catalyst exhibited increased tolerance to high-voltage cycling and in particular showed recovery of electrocatalytic activity after reversible de-activation (presumably from bromide adsorption and subsequent oxidative bromide stripping). Under the harshest testing conditions of high-voltage cycling or exposure to Br2 the Pt-based catalyst showed a trend in stability: Pt < Pt-Ir < Pt-Ir-Nx. (Abstract shortened by UMI.).

  20. Transcriptional analysis of Shewanella oneidensis MR-1 with an electrode compared to Fe(IIIcitrate or oxygen as terminal electron acceptor.

    Directory of Open Access Journals (Sweden)

    Miriam A Rosenbaum

    Full Text Available Shewanella oneidensis is a target of extensive research in the fields of bioelectrochemical systems and bioremediation because of its versatile metabolic capabilities, especially with regard to respiration with extracellular electron acceptors. The physiological activity of S. oneidensis to respire at electrodes is of great interest, but the growth conditions in thin-layer biofilms make physiological analyses experimentally challenging. Here, we took a global approach to evaluate physiological activity with an electrode as terminal electron acceptor for the generation of electric current. We performed expression analysis with DNA microarrays to compare the overall gene expression with an electrode to that with soluble iron(III or oxygen as the electron acceptor and applied new hierarchical model-based statistics for the differential expression analysis. We confirmed the differential expression of many genes that have previously been reported to be involved in electrode respiration, such as the entire mtr operon. We also formulate hypotheses on other possible gene involvements in electrode respiration, for example, a role of ScyA in inter-protein electron transfer and a regulatory role of the cbb3-type cytochrome c oxidase under anaerobic conditions. Further, we hypothesize that electrode respiration imposes a significant stress on S. oneidensis, resulting in higher energetic costs for electrode respiration than for soluble iron(III respiration, which fosters a higher metabolic turnover to cover energy needs. Our hypotheses now require experimental verification, but this expression analysis provides a fundamental platform for further studies into the molecular mechanisms of S. oneidensis electron transfer and the physiologically special situation of growth on a poised-potential surface.

  1. Sensor employing internal reference electrode

    DEFF Research Database (Denmark)

    2013-01-01

    The present invention concerns a novel internal reference electrode as well as a novel sensing electrode for an improved internal reference oxygen sensor and the sensor employing same.......The present invention concerns a novel internal reference electrode as well as a novel sensing electrode for an improved internal reference oxygen sensor and the sensor employing same....

  2. Fluctuations in pO2 in poorly and well-oxygenated spontaneous canine tumors before and during fractionated radiation therapy.

    Science.gov (United States)

    Brurberg, Kjetil G; Skogmo, Hege K; Graff, Bjørn A; Olsen, Dag R; Rofstad, Einar K

    2005-11-01

    The spatial heterogeneity in oxygen tension (pO2) in tumor tissue has been studied extensively, whereas, the information about the temporal heterogeneity is sparse. The purpose of the present study was to search for pO2 fluctuations in untreated and irradiated spontaneous canine tumors, and to investigate whether there is a relationship between overall tumor oxygenation status and pO2 fluctuation pattern. Six dogs scheduled for radiation therapy of head and neck cancer were included in the study. The primary tumors were irradiated with 18 fractions of 3 Gy. Eppendorf polarographic electrodes and OxyLite fluorescence probes were used to measure overall oxygenation status and pO2 fluctuation pattern, respectively. Tissue pO2 was recorded at three subsequent days prior to treatment, and immediately before radiation fraction 4, 7, and 10. Overall oxygenation status differed substantially among the tumors. Radiation therapy had no consistent effect on overall oxygenation status. Fluctuations in pO2 were detected in untreated as well as irradiated tumors, and independent of whether the tumors were poorly or well oxygenated. Fluctuations in pO2 can occur in untreated and irradiated spontaneous canine tumors. There is no correlation between pO2 fluctuation pattern and overall tumor oxygenation status.

  3. Polarographic behaviour and determination of selenite and tellurite in simple solutions or in a binary mixture

    International Nuclear Information System (INIS)

    Hassan, A.

    1991-01-01

    The polarographic behaviour of simple solutions of selenite and tellurite in 1 M ammonium salts of formate, acetate, tartrate, oxalate, and benzoate solutions in absence and in presence of Triton X-100 as a maximum suppressor and a temperature of 25 O C has been investigated. Schemes for the mechanism of reductions occuring at the DME have been deduced. A method for analytical determination of selenite and tellurite in simple solutions as well as in a binary mixture in the presence of 4-14 . 10 -3 % Triton X-100 is reported. (author)

  4. Role of the adsorbed oxygen species in the selective electrochemical reduction of CO{sub 2} to alcohols and carbonyls on copper electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Le Duff, Cecile S.; Lawrence, Matthew J.; Rodriguez, Paramaconi [School of Chemistry, University of Birmingham, Edgbaston (United Kingdom)

    2017-10-09

    The electrochemical reduction of CO{sub 2} into fuels has gained significant attention recently as source of renewable carbon-based fuels. The unique high selectivity of copper in the electrochemical reduction of CO{sub 2} to hydrocarbons has called much interest in discovering its mechanism. In order to provide significant information about the role of oxygen in the electrochemical reduction of CO{sub 2} on Cu electrodes, the conditions of the surface structure and the composition of the Cu single crystal electrodes were controlled over time. This was achieved using pulsed voltammetry, since the pulse sequence can be programmed to guarantee reproducible initial conditions for the reaction at every fraction of time and at a given frequency. In contrast to the selectivity of CO{sub 2} reduction using cyclic voltammetry and chronoamperometric methods, a large selection of oxygenated hydrocarbons was found under alternating voltage conditions. Product selectivity towards the formation of oxygenated hydrocarbon was associated to the coverage of oxygen species, which is surface-structure- and potential-dependent. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Oxygen evolution reaction of Ti/IrO2–SnO2 electrode: a study by ...

    Indian Academy of Sciences (India)

    Typical electric circuits are modelled to the oxide electrode elements that describe the ohmic resistance associated with solution and the oxide film, as well as the .... scan rate. To assess the electrode stability of the prepared anodes, open circuit potential (OCP) was per- formed. Anodic performance was measured by using ...

  6. Uptake rate of cationic mitochondrial inhibitor MKT-077 determines cellular oxygen consumption change in carcinoma cells.

    Directory of Open Access Journals (Sweden)

    John L Chunta

    Full Text Available OBJECTIVE: Since tumor radiation response is oxygen-dependent, radiosensitivity can be enhanced by increasing tumor oxygenation. Theoretically, inhibiting cellular oxygen consumption is the most efficient way to increase oxygen levels. The cationic, rhodacyanine dye-analog MKT-077 inhibits mitochondrial respiration and could be an effective metabolic inhibitor. However, the relationship between cellular MKT-077 uptake and metabolic inhibition is unknown. We hypothesized that rat and human mammary carcinoma cells would take up MKT-077, causing a decrease in oxygen metabolism related to drug uptake. METHODS: R3230Ac rat breast adenocarcinoma cells were exposed to MKT-077. Cellular MKT-077 concentration was quantified using spectroscopy, and oxygen consumption was measured using polarographic electrodes. MKT-077 uptake kinetics were modeled by accounting for uptake due to both the concentration and potential gradients across the plasma and mitochondrial membranes. These kinetic parameters were used to model the relationship between MKT-077 uptake and metabolic inhibition. MKT-077-induced changes in oxygen consumption were also characterized in MDA-MB231 human breast carcinoma cells. RESULTS: Cells took up MKT-077 with a time constant of ∼1 hr, and modeling showed that over 90% of intracellular MKT-077 was bound or sequestered, likely by the mitochondria. The uptake resulted in a rapid decrease in oxygen consumption, with a time constant of ∼30 minutes. Surprisingly the change in oxygen consumption was proportional to uptake rate, not cellular concentration. MKT-077 proved a potent metabolic inhibitor, with dose-dependent decreases of 45-73% (p = 0.003. CONCLUSIONS: MKT-077 caused an uptake rate-dependent decrease in cellular metabolism, suggesting potential efficacy for increasing tumor oxygen levels and radiosensitivity in vivo.

  7. Bubble dynamic templated deposition of three-dimensional palladium nanostructure catalysts: Approach to oxygen reduction using macro-, micro-, and nano-architectures on electrode surfaces

    International Nuclear Information System (INIS)

    Yang Guimei; Chen Xing; Li Jie; Guo Zheng; Liu Jinhuai; Huang Xingjiu

    2011-01-01

    Highlights: → We synthesize the Pd nanostructures by bubbles dynamic templated. → We obtain Pd nanobuds and Pd nanodendrites by changing the reaction precursor. → We obtain Pd macroelectrode voltammertric behavior using small amount of Pd materials. → We proved a ECE process. → The Pd nanostructures/GCE for O 2 reduction is a 2-step 4-electron process. - Abstract: Three-dimensional (3D) palladium (Pd) nanostructures (that is, nano-buds or nano-dendrites) are fabricated by bubble dynamic templated deposition of Pd onto a glassy carbon electrode (GCE). The morphology can be tailored by changing the precursor concentration and reaction time. Scanning electron microscopy images reveal that nano-buds or nano-dendrites consist of nanoparticles of 40-70 nm in diameter. The electrochemical reduction of oxygen is reported at such kinds of 3D nanostructure electrodes in aqueous solution. Data were collected using cyclic voltammetry. We demonstrate the Pd macroelectrode behavior of Pd nanostructure modified electrode by exploiting the diffusion model of macro-, micro-, and nano-architectures. In contrast to bare GCE, a significant positive shift and splitting of the oxygen reduction peak (vs Ag/AgCl/saturated KCl) at Pd nanostructure modified GCE was observed.

  8. Polarographic and potentiometric studies on some binary and ternary complex systems of dioxouranium(VI)

    International Nuclear Information System (INIS)

    Janarthanam, M.; Sivasankar, B.; Rengaraj, K.; Nair, M.S.

    1995-01-01

    The relative coordinating abilities of donor sites in the potentially tridentate ligands viz., asparagine, glutamine, aspartic acid and glutamic acid towards uranyl ion have been investigated by polarographic and pH-metric techniques. The metal ion forms 1:2 complexes under polarographic conditions. However, only 1:1 complex is observed under pH-metric conditions, where 1:2 complexes do not proceed due to extensive hydrolysis of the metal ion. The relative variations of ΔE 1/2 with pH and ligand concentration supported by conductometric titration data indicate that the primary amino groups in the amino acids are not involved in coordination with uranyl ion. Further, the amide groups in asparagine and glutamine also do not participate in coordination thus rendering these ligands unidentate. In aspartic and glutamic acid complexes, seven- and eight- membered chelate rings are formed involving two terminal carboxyl groups. The mixed ligand complex equilibria of uranyl ion involving aspartic acid/glutamic acid as primary ligands (A) and maleic acid, malonic acid, succinic acid and lactic acid as secondary ligands (B) have also been studied by computer based numerical evaluation of pH titration data. The concentration profiles have indicated the favorability of the formation of ternary complexes in general as reflected in the Δlog K values. (author). 10 refs., 1 fig., 1 tab

  9. Main alloy elements in covered electrodes in terms of the amount of oxygen in weld metal deposits (WMD

    Directory of Open Access Journals (Sweden)

    T. Węgrzyn

    2012-04-01

    Full Text Available There were investigated properties of WMD, especially metallographic structure, toughness and fatigue strength of welds with various oxygen amount. The connection between the properties of welds with the content of oxygen in WMD were carried out. The research results indicate that it should be limited oxygen content in steel welds. Subsequent researchers could find more precisely the most beneficial oxygen amount in the welds in terms of the amount of acicular ferrite in welds.

  10. Insights into an autonomously formed oxygen-evacuated Cu2O electrode for the selective production of C2H4 from CO2.

    Science.gov (United States)

    Kim, Dahee; Lee, Seunghwa; Ocon, Joey D; Jeong, Beomgyun; Lee, Jae Kwang; Lee, Jaeyoung

    2015-01-14

    Electrochemical conversion of carbon dioxide (CO2) to small organic fuels (e.g. formate, methanol, ethylene, ethanol) is touted as one of the most promising approaches for solving the problems of climate change and energy security. In this study, we report the highly efficient electrochemical reduction of CO2 using cuprous oxide (Cu2O) electrodes to produce ethylene (C2H4) primarily. During CO2 electrolysis using electrodeposited Cu2O on a carbon electrode, we observe the transformation of a compact metal oxide layer to a metal oxide structure with oxygen vacant sites at the bulk region. In contrast to previous studies, our results clearly indicate that Cu2O remains at the surface of the catalyst and it efficiently catalyzes the conversion process of CO2 at low overpotential, exhibiting a high selective faradaic efficiency of over 20% towards C2H4 formation even in long-term electrolysis.

  11. Studies on the heterogeneous electron transport and oxygen reduction reaction at metal (Co, Fe) octabutylsulphonylphthalocyanines supported on multi-walled carbon nanotube modified graphite electrode

    Energy Technology Data Exchange (ETDEWEB)

    Mamuru, Solomon A. [Department of Chemistry, University of Pretoria, Pretoria 0002 (South Africa); Ozoemena, Kenneth I., E-mail: kozoemena@csir.co.z [Department of Chemistry, University of Pretoria, Pretoria 0002 (South Africa)] [Energy and Processes Unit, Materials Science and Manufacturing, Council for Scientific and Industrial Research (CSIR), Pretoria 0001 (South Africa); Fukuda, Takamitsu; Kobayashi, Nagao [Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578 (Japan); Nyokong, Tebello [Department of Chemistry, Rhodes University, Grahamstown 6140 (South Africa)

    2010-09-01

    Heterogeneous electron transfer dynamics and oxygen reduction reaction (ORR) activities using octabutylsulphonylphthalocyanine complexes of iron (FeOBSPc) and cobalt (CoOBSPc) supported on multi-walled carbon nanotube (MWCNT) platforms have been described. The MWCNT-based electrodes (MWCNT-CoOBSPc and MWCNT-FeOBSPc) showed larger Faradaic current responses than the electrodes without the MWCNTs, interpreted as a consequence of the trapped electrolyte species within the porous layers of MWCNTs undergoing a redox process. The EPPGE-MWCNT-FeOBSPc showed onset potential (-0.01 V vs Ag|AgCl) which is comparable and even much lower than recent reports. The MWCNT-FeOBSPc showed the best ORR activity involving a direct 4-electron mechanism, with a Tafel slope of about 124 mV, indicating a 1-electron process in the rate-determining step.

  12. Control of oxygen octahedral rotation in BiFeO3 films using modulation of SrRuO3 bottom electrode layer

    Science.gov (United States)

    Lee, Sungsu; Jo, Ji Young

    2015-03-01

    Oxygen octahedral rotation of multiferroic BiFeO3 (BFO) has attracted great attention due to changes of electrical and magnetic properties. Coupling of octahedral rotation in BFO-bottom electrode layer interface remains unexplored. Recently, there have been reported the control of octahedral rotation in SrRuO3 (SRO) film on SrTiO3 (001) substrate by coherently controlling the oxygen pressure during growth and interfacial coupling. Here we demonstrate that the octahedral rotation of BFO film is changed using tetragonal a0a0c- tilted-SRO bottom electrodes. In this work, BFO/SRO heterostructure is fabricated to SrTiO3 (001) single crystal substrates by pulsed laser deposition at different oxygen partial pressures. The rotation pattern of FeO6 and the structural symmetry are identified from half-integer reflections using high-resolution X-ray diffraction. The effects depending on octahedral tilting of BFO films on the magnetic and ferroelectric properties will be presented.

  13. FY 1998 annual report on the development of novel, high-activity oxygen electrode by ion-implantation; 1998 nendo ion chunyuho ni yoru shinkina kokassei sanso denkyoku no kaihatsu chosa hokokusho

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1999-03-01

    An attempt has been made to develop an electrode material having high activity for oxygen generating reactions by ion-implantation, which is used to form the bulk defects (fine gaps at the atomic level) on the electrode surface, considered to serve as the active sites. It is found that implantation of the Co{sup +} or Zn{sup +} ion into a compound oxide electrode of Ti and Ru is accompanied by decreased overvoltage for oxygen generation by 50 to 100 mV. The Co{sup +} and Zn{sup +} ions, when implanted, cause damage of similar density in the thin film, decreasing its overvoltage to a similar extent, in spite of their different chemical properties, from which it is considered that the effect of ion implantation is not to change chemical properties of the film but to form a structural defect therein. A thin-film electrode of ruthenium dioxide, which is considered to be the oxygen generating electrode of the highest activity at present, is prepared and implanted with the Ru{sup +} ion, to observe the effect. The ion implantation also decreases the overvoltage by 50 to 70 mV, demonstrating its effect. The same principle is expected to be applicable to development of high-activity oxygen reducing electrode (electrode for fuel cell). (NEDO)

  14. pH matters: The influence of the catalyst ink on the oxygen reduction activity determined in thin film rotating disk electrode measurements

    Science.gov (United States)

    Inaba, Masanori; Quinson, Jonathan; Arenz, Matthias

    2017-06-01

    We investigated the influence of the ink properties of proton exchange membrane fuel cell (PEMFC) catalysts on the oxygen reduction reaction (ORR) activity determined in thin film rotating disk electrode (TF-RDE) measurements. It was found that the adaption of a previously reported ink recipe to home-made catalysts does not lead to satisfying results, although reported work could be reproduced using commercial catalyst samples. It is demonstrated that the pH of the catalyst ink, which has not been addressed in previous TF-RDE studies, is an important parameter that needs to be carefully controlled to determine the intrinsic ORR activity of high surface area catalysts.

  15. Development of Novel Electrode Materials for the Electrocatalysis of Oxygen-Transfer and Hydrogen-Transfer Reactions

    Energy Technology Data Exchange (ETDEWEB)

    Simpson, Brett Kimball [Iowa State Univ., Ames, IA (United States)

    2002-01-01

    Throughout this thesis, the fundamental aspects involved in the electrocatalysis of anodic O-transfer reactions and cathodic H-transfer reactions have been studied. The investigation into anodic O-transfer reactions at undoped and Fe(III)[doped MnO2 films] revealed that MnO2 film electrodes prepared by a cycling voltammetry deposition show improved response for DMSO oxidation at the film electrodes vs. the Au substrate. Doping of the MnO2 films with Fe(III) further enhanced electrode activity. Reasons for this increase are believed to involve the adsorption of DMSO by the Fe(III) sites. The investigation into anodic O-transfer reactions at undoped and Fe(III)-doped RuO2 films showed that the Fe(III)-doped RuO2-film electrodes are applicable for anodic detection of sulfur compounds. The Fe(III) sites in the Fe-RuO2 films are speculated to act as adsorption sites for the sulfur species while the Ru(IV) sites function for anodic discharge of H2O to generate the adsorbed OH species. The investigation into cathodic H-transfer reactions, specifically nitrate reduction, at various pure metals and their alloys demonstrated that the incorporation of metals into alloy materials can create a material that exhibits bifunctional properties for the various steps involved in the overall nitrate reduction reaction. The Sb10Sn20Ti70, Cu63Ni37 and Cu25Ni75 alloy electrodes exhibited improved activity for nitrate reduction as compared to their pure component metals. The Cu63Ni37 alloy displayed the highest activity for nitrate reduction. The final investigation was a detailed study of the electrocatalytic activity of cathodic H-transfer reactions (nitrate reduction) at various compositions of Cu-Ni alloy electrodes. Voltammetric response for NO3- at the Cu-Ni alloy electrode is superior to

  16. Interplay of tumor vascular oxygenation and tumor pO2 observed using near-infrared spectroscopy, an oxygen needle electrode, and 19F MR pO2 mapping.

    Science.gov (United States)

    Kim, Jae G; Zhao, Dawen; Song, Yulin; Constantinescu, Anca; Mason, Ralph P; Liu, Hanli

    2003-01-01

    This study investigates the correlation of tumor blood oxygenation and tumor pO(2) with respect to carbogen inhalation. After having refined and validated the algorithms for calculating hemoglobin concentrations, we used near-infrared spectroscopy (NIRS) to measure changes of oxygenated hemoglobin concentration (delta[HbO(2)]) and used an oxygen needle electrode and (19)F MRI for pO(2) measurements in tumors. The measurements were taken from Dunning prostate R3327 tumors implanted in rats, while the anesthetized rats breathed air or carbogen. The NIRS results from tumor measurements showed significant changes in tumor vascular oxygenation in response to carbogen inhalation, while the pO(2) electrode results showed an apparent heterogeneity for tumor pO(2) response to carbogen inhalation, which was also confirmed by (19)F MR pO(2) mapping. Furthermore, we developed algorithms to estimate hemoglobin oxygen saturation, sO(2), during gas intervention based on the measured values of delta[HbO(2)] and pO(2). The algorithms have been validated through a tissue-simulating phantom and used to estimate the values of sO(2) in the animal tumor measurement based on the NIRS and global mean pO(2) values. This study demonstrates that the NIRS technology can provide an efficient, real-time, noninvasive approach to monitoring tumor physiology and is complementary to other techniques, while it also demonstrates the need for an NIR imaging technique to study spatial heterogeneity of tumor vasculature under therapeutic interventions. Copyright 2003 Society of Photo-Optical Instrumentation Engineers

  17. Active Salt/Silica-Templated 2D Mesoporous FeCo-Nx-Carbon as Bifunctional Oxygen Electrodes for Zinc-Air Batteries.

    Science.gov (United States)

    Li, Shuang; Cheng, Chong; Zhao, Xiaojia; Schmidt, Johannes; Thomas, Arne

    2018-02-12

    Two types of templates, an active metal salt and silica nanoparticles, are used concurrently to achieve the facile synthesis of hierarchical meso/microporous FeCo-N x -carbon nanosheets (meso/micro-FeCo-N x -CN) with highly dispersed metal sites. The resulting meso/micro-FeCo-N x -CN shows high and reversible oxygen electrocatalytic performances for both ORR and OER, thus having potential for applications in rechargeable Zn-air battery. Our approach creates a new pathway to fabricate 2D meso/microporous structured carbon architectures for bifunctional oxygen electrodes in rechargeable Zn-air battery as well as opens avenues to the scale-up production of rationally designed heteroatom-doped catalytic materials for a broad range of applications. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Poly(3,4-ethylenedioxythiophene) based enzyme-electrode configuration for enhanced direct electron transfer type biocatalysis of oxygen reduction

    International Nuclear Information System (INIS)

    Latonen, Rose-Marie; Wang, Xiaoju; Sjöberg-Eerola, Pia; Eriksson, Jan-Erik; Bergelin, Mikael; Bobacka, Johan

    2012-01-01

    An O 2 -consuming cathode for biofuel cell applications consisting of Trametes hirsuta laccase (ThL) immobilized in an electropolymerized fine-tuned poly(3,4-ethylenedioxythiophene) (PEDOT) bilayer structure as the catalyst was studied. A NO 3 − -doped PEDOT layer with a relatively porous structure was used as the immobilization matrix on which the enzyme was added by solution casting. A capping layer of polystyrene sulphonate, PSS − -doped PEDOT was then electrodeposited on top of the first PEDOT layer in order to entrap the ThL between the layers. The PEDOT-NO 3 − /ThL/PEDOT-PSS − enzyme electrode is reported to be able to promote direct electron transfer (DET) between ThL and the current collector and it catalyzes the reduction of O 2 into water. The applicability of the PEDOT-NO 3 − /ThL/PEDOT-PSS − enzyme electrode structure on ITO glass with a geometrical surface area of 1 cm 2 as the electrode material was studied. The influence of different enzyme electrode fabrication parameters, such as the dopant ion used during electropolymerization, different combinations of PEDOT films, the thickness of both PEDOT layers and ThL loading on the enzyme electrode performance were investigated by chronoamperometric and cyclic voltammetric measurements. The optimum working pH for the enzyme electrode was found to be in the pH range 3.0–3.5. No enhanced cell performance was recorded when 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) was used as mediator compared to DET in the PEDOT bilayer structure.

  19. The oxygen sensitivity of a multipoint antimony electrode for tissue pH measurements. A study of the sensitivity for in vivo PO2 variations below 6 kPa.

    Science.gov (United States)

    Sjöberg, F; Edwall, G; Lund, N

    1987-02-01

    Monocrystalline micro antimony electrodes in a multipoint arrangement as described by Lund et al. were placed on the skeletal muscle surface of the rabbit. Tissue oxygen levels were measured simultaneously with the MDO (Mehrdraht Dortmund Oberfläche) oxygen electrode. The sensitivity for variations in tissue PO2 (PO2(t)) was evaluated for the antimony metal-metal oxide sensor. The sensitivity (delta E/delta log10 PO2)+/- SE was found to be 21.8 +/- 1.2 mV in the interval between 0.1 kPa and 1 kPa and 53 +/- 5 mV in the interval between 1 kPa and 6 kPa. These results are not consistent with the oxygen sensitivity of monocrystalline antimony described in vitro, but are in agreement with the findings of Nilsson & Edwall. A plausible explanation for the S-shaped oxygen sensitivity curve of antimony at oxygen levels below 10 kPa could be an interaction, at the electrode surface, between the dissolved oxygen and the oxygen bound to haemoglobin. If this is the case, the use of an antimony electrode would make possible the determination of the dissociation of oxyhaemoglobin in tissues.

  20. Complete Decomposition of Li 2 CO 3 in Li–O 2 Batteries Using Ir/B 4 C as Noncarbon-Based Oxygen Electrode

    Energy Technology Data Exchange (ETDEWEB)

    Song, Shidong; Xu, Wu; Zheng, Jianming; Luo, Langli; Engelhard, Mark H.; Bowden, Mark E.; Liu, Bin; Wang, Chong-Min; Zhang, Ji-Guang

    2017-02-10

    Incomplete decomposition of Li2CO3 during charge process is a critical barrier for rechargeable Li-O2 batteries. Here we report complete decomposition of Li2CO3 in Li-O2 batteries using ultrafine iridium-decorated boron carbide (Ir/B4C) nanocomposite as oxygen electrode. The systematic investigation on charging the Li2CO3 preloaded Ir/B4C electrode in an ether-based electrolyte demonstrates that Ir/B4C electrode can decompose Li2CO3 with an efficiency close to 100% at below 4.37 V. In contrast, the bare B4C without Ir electrocatalyst can only decompose 4.7% of preloaded Li2CO3. The reaction mechanism of Li2CO3 decomposition in the presence of Ir/B4C electrocatalyst has been further investigated. A Li-O2 battery using Ir/B4C as oxygen electrode material shows highly enhanced cycling stability than that using bare B4C oxygen electrode. These results clearly demonstrate that Ir/B4C is an effecitive oxygen electrode amterial to completely decompose Li2CO3 at relatively low charge voltages and is of significant importance in improving the cycle performanc of aprotic Li-O2 batteries.

  1. Fabrication of three-dimensional ordered macroporous spinel CoFe2O4as efficient bifunctional catalysts for the positive electrode of lithium-oxygen batteries.

    Science.gov (United States)

    Kim, Jong Guk; Noh, Yuseong; Kim, Youngmin; Lee, Seonhwa; Kim, Won Bae

    2017-04-20

    Three-dimensionally ordered macroporous (3DOM) CoFe 2 O 4 (CFO) catalysts were prepared by using the colloidal crystal templating method to be used as bifunctional catalysts of Li-O 2 battery positive electrodes. In order to study the relationship between the macropore diameter and charge/discharge behavior, 3DOM CFO catalysts with two different pore diameters of 140 and 60 nm were prepared. The physicochemical properties of the 3DOM CFO catalysts were investigated by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy. When the 3DOM CFO catalyst with a pore diameter of 140 nm (CFO@140) was used in the O 2 -electrode of Li-O 2 batteries, it exhibited a substantially enhanced discharge capacity (ca. 11 658.5 mA h g -1 ) in the first cycle. Moreover, the Li-O 2 cells with the CFO@140 catalyst showed cycling stability over 47 cycles at a limited capacity of 500 mA h g -1 with a reduced potential polarization of 1.13 V, as compared with that with Ketjen Black carbon and the 3DOM CFO of 60 nm pore diameter (CFO@60). Their high cycling stability, low overpotential, high round-trip efficiency, and high rate performance suggest that these 3DOM CFO catalysts could be promising O 2 -electrode catalysts for next-generation lithium-oxygen batteries.

  2. Polarographic behaviour of Aceclofenac, Tenoxicam and Droxicam in a methanol-water mixture.

    Science.gov (United States)

    Acuña, J A; Vázquez, M D; Tascón, M L; Sánchez-Batanero, P

    2004-09-21

    A polarographic study about how three anti-inflammatories, such as Aceclofenac, Tenoxicam and Droxicam behave, using tast polarography (TP) and differential pulse polarography (DPP) was carried out. These studies were always carried out in a media formed by Methanol-Britton-Robinson aqueous buffer (0.1M) (4:96 (v/v)) due to the low solubility of these drugs in water. A strong influence of pH on analytical signals was observed, showing that the optimal pH values were between 4 and 5. Using DPP in the optimal experimental conditions, a detection limit of 10 ppb for Tenoxicam and Droxicam and 52 ppb for Aceclofenac was reached. The DPP proposed method was successfully applied to the determination of the active compounds in commercial drugs.

  3. Polarographic determination of selenium and tellurium in silver-gold alloys

    International Nuclear Information System (INIS)

    Gornostaeva, T.D.; Shmargun, S.V.

    1986-01-01

    The determination of selenium and tellurium is of importance in monitoring the composition of silver-gold alloys (SGA) since these elements are harmful impurities in the pure metals. Tellurium is determined in silver alloys by atomic absorption and atomic emmission methods; selenium determination is made by atomic absorption methods. This paper examines the polarographic determination of silver and tellurium in SGA containing platinum metals and copper. Copper and the bulk of the platinum and palladium were removed by precipitating selenium and tellurium with potassium hypophosphite in the elementary state from 6 M HC1. The results of an analysis of samples of SGA according to the proposed method were compared with the results obtained by the atomic absorption method. the relative deviation in the determination of 0.02-1.0% by weight selenium and tellurium does not exceed 0.12 (n = 5)

  4. Rhodium nanoparticle-modified screen-printed graphite electrodes for the determination of hydrogen peroxide in tea extracts in the presence of oxygen.

    Science.gov (United States)

    Gatselou, Vasiliki A; Giokas, Dimothenis L; Vlessidis, Athanasios G; Prodromidis, Mamas I

    2015-03-01

    In this work we describe the fabrication of nanostructured electrocatalytic surfaces based on polyethyleneimine (PEI)-supported rhodium nanoparticles (Rh-NP) over graphite screen-printed electrodes (SPEs) for the determination of hydrogen peroxide in the presence of oxygen. Rh-NP, electrostatically stabilized by citrate anions, were immobilized over graphite SPEs, through coulombic attraction on a thin film of positively charged PEI. The functionalized sensors, polarized at 0.0 V vs. Ag/AgCl/3 M KCl, exhibited a linear response to H2O2 over the concentration range from 5 to 600 μmol L(-1) H2O2 in the presence of oxygen. The 3σ limit of detection was 2 μmol L(-1) H2O2, while the reproducibility of the method at the concentration level of 10 μmol L(-1) H2O2 (n=10) and between different sensors (n=4) was lower than 3 and 5%, respectively. Most importantly, the sensors showed an excellent working and storage stability at ambient conditions and they were successfully applied to the determination of H2O2 produced by autooxidation of polylphenols in tea extracts with ageing. Recovery rates ranged between 97 and 104% suggesting that the as-prepared electrodes can be used for the development of small-scale, low-cost chemical sensors for use in on-site applications. Copyright © 2014 Elsevier B.V. All rights reserved.

  5. One-Step Growth of Iron-Nickel Bimetallic Nanoparticles on FeNi Alloy Foils: Highly Efficient Advanced Electrodes for the Oxygen Evolution Reaction.

    Science.gov (United States)

    Qazi, Umair Yaqub; Yuan, Cheng-Zong; Ullah, Naseeb; Jiang, Yi-Fan; Imran, Muhammad; Zeb, Akif; Zhao, Sheng-Jie; Javaid, Rahat; Xu, An-Wu

    2017-08-30

    Electrochemical water splitting is an important process to produce hydrogen and oxygen for energy storage and conversion devices. However, it is often restricted by the oxygen evolution reaction (OER) due to its sluggish kinetics. To overcome the problem, precious metal oxide-based electrocatalysts, such as RuO 2 and IrO 2 , are widely used. The lack of availability and the high cost of precious metals compel researchers to find other resources for the development of cost-effective, environmentally friendly, earth-abundant, nonprecious electrocatalysts for OER. Such catalysts should have high OER performance and good stability in comparison to those of available commercial precious metal-based electrocatalysts. Herein, we report an inexpensive fabrication of bimetallic iron-nickel nanoparticles on FeNi-foil (FeNi 4.34 @FeNi-foil) as an integrated OER electrode using a one-step calcination process. FeNi 4.34 @FeNi-foil obtained at 900 °C shows superior OER activity in alkaline solution with an overpotential as low as 283 mV to achieve a current density of 10 mA cm -2 and a small Tafel slope of 53 mV dec -1 . The high performance and durability of the as-prepared nonprecious metal electrode even exceeds those of the available commercial RuO 2 and IrO 2 catalysts, showing great potential in replacing the expensive noble metal-based electrocatalysts for OER.

  6. Microwave exposure as a fast and cost-effective alternative of oxygen plasma treatment of indium-tin oxide electrode for application in organic solar cells

    Science.gov (United States)

    Soultati, Anastasia; Kostis, Ioannis; Papadimitropoulos, Giorgos; Zeniou, Angelos; Gogolides, Evangelos; Alexandropoulos, Dimitris; Vainos, Nikos; Davazoglou, Dimitris; Speliotis, Thanassis; Stathopoulos, Nikolaos A.; Argitis, Panagiotis; Vasilopoulou, Maria

    2017-12-01

    Pre-treatment methods are commonly employed to clean as well as to modify electrode surfaces. Many previous reports suggest that modifying the surface properties of indium tin oxide (ITO) by oxygen plasma treatment is a crucial step for the fabrication of high performance organic solar cells. In this work, we propose a fast and cost-effective microwave exposure step for the modification of the surface properties of ITO anode electrodes used in organic solar cells. It is demonstrated that a short microwave exposure improves the hydrophilicity and reduces the roughness of the ITO surface, as revealed by contact angle and atomic force microscopy (AFM) measurements, respectively, leading to a better quality of the PEDOT:PSS film coated on top of it. Similar results were obtained with the commonly used oxygen plasma treatment of ITO suggesting that microwave exposure is an effective process for modifying the surface properties of ITO with the benefits of low-cost, easy and fast processing. In addition, the influence of the microwave exposure of ITO anode electrode on the performance of an organic solar cell based on the poly(3-hexylthiophene):[6,6]-phenyl C70 butyric acid methyl ester (P3HT:PC70BM) blend is investigated. The 71% efficiency enhancement obtained in the microwave annealed-ITO based device as compared to the device with the as-received ITO was mainly attributed to the improvement in the short circuit current (J sc) and decreased leakage current caused by the reduced series and the increased shunt resistances and also by the higher charge generation efficiency, and the reduced recombination losses.

  7. One-Step Fabrication of Monolithic Electrodes Comprising Co9S8Particles Supported on Cobalt Foam for Efficient and Durable Oxygen Evolution Reaction.

    Science.gov (United States)

    Xiong, Dehua; Zhang, Qingqing; Thalluri, Sitaramanjaneya Mouli; Xu, Junyuan; Li, Wei; Fu, Xiuli; Liu, Lifeng

    2017-06-27

    A very easy and cost-effective approach to the fabrication of monolithic Co 9 S 8 water oxidation electrodes (Co@Co 9 S 8 ), fabricated by one-step hydrothermal treatment of commercially available cobalt foam in the presence of thiourea, is reported. The morphology, crystal structure, microstructure, and composition of as-fabricated Co@Co 9 S 8 electrodes were examined by using scanning electron microscopy (SEM), powder X-ray diffractometry (XRD), transmission electron microscope (TEM), and X-ray photoelectron spectroscopy (XPS), and their electrochemical properties were investigated by cyclic voltammetry (CV), chronopotentiometry (CP), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). When used to catalyze the oxygen evolution reaction (OER) in alkaline solution, the Co@Co 9 S 8 electrode with an optimal Co 9 S 8 loading exhibits outstanding catalytic activity, requiring a low overpotential of 350 mV to deliver an anodic current density of 10 mA cm -2 and showing fast kinetics for OER with a small Tafel slope (55 mV dec -1 ) and charge-transfer resistance (0.44 Ω cm -2 ), which outperforms many sulfide-based OER catalysts and some state-of-the-art noble metal catalysts recently reported in the literature. Importantly, the electrodes show excellent long-term stability, and are capable of operating at both a low current density and a high current density relevant to industrial water electrolysis up to 100 hours. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. In situ formation of a 3D core-shell and triple-conducting oxygen reduction reaction electrode for proton-conducting SOFCs

    Science.gov (United States)

    Zhang, Zhenbao; Wang, Jian; Chen, Yubo; Tan, Shaozao; Shao, Zongping; Chen, Dengjie

    2018-05-01

    BaZrxCeyY1-x-yO3-δ are recognized proton-conducting electrolyte materials for proton-conducting solid oxide fuel cells (H+-SOFCs) below 650 °C. Here Co cations are incorporated into the BaZr0.4Ce0.4Y0.2O3-δ (BZCY) scaffold to generate a 3D core-shell and triple-conducting (H+/O2-/e-) electrode in situ via infiltrating and reactive sintering. The core is the bulk BZCY scaffold, while the shell is composed of the cubic Ba(Zr0.4Ce0.4Y0.2)1-xCoxO3-δ, cubic spinel Co3O4 and cubic fluorite (Ce, Zr, Y)O2. The obtained electrode exhibits an excellent compatibility with the BZCY electrolyte, and performs well in yielding a low and stable polarization resistance for oxygen reduction reaction for intermediate-temperature H+-SOFCs. In particular, it achieves polarization resistances as low as 0.094 and 0.198 Ω cm2 at 650 and 600 °C in wet air (3% H2O) when the sintering temperature for the electrode is 900 °C. In addition, a symmetrical cell also exhibits operation stability of 70 h at 650 °C. Furthermore, a fuel cell assembled with the 3D core-shell and triple-conducting electrode delivers a peak power density of ∼330 mW cm-2 at 650 °C. The substantially improved electrochemical performance and high stability are ascribed to the unique core-shell structure and the formation of Ba(Zr0.4Ce0.4Y0.2)1-xCoxO3-δ in the shell.

  9. Oxygenation of spontaneous canine tumors during fractionated radiation therapy

    Energy Technology Data Exchange (ETDEWEB)

    Achermann, R.E.; Ohlerth, S.M.; Bley, C.R.; Inteeworn, N.; Schaerz, M.; Wergin, M.C.; Kaser-Hotz, B. [Section of Diagnostic Imaging and Radiation Oncology, Veterinary School, Univ. of Zurich (Switzerland); Gassmann, M. [Inst. for Veterinary Physiology, Univ. of Zurich (Switzerland); Roos, M. [Inst. for Social and Preventive Medicine, Univ. of Zurich (Switzerland)

    2004-05-01

    Background and purpose: tumor oxygenation predicts treatment outcome, and reoxygenation is considered important in the efficacy of fractionated radiation therapy. Therefore, the purpose of this study was to document the changes of the oxygenation status in spontaneous canine tumors during fractionated radiation therapy using polarographic needle electrodes. Material and methods: tumor oxygen partial pressure (pO{sub 2}) measurements were performed with the eppendorf-pO{sub 2}-Histograph. The measurements were done under general anesthesia, and probe tracks were guided with ultrasound. pO{sub 2} was measured before radiation therapy in all dogs. In patients treated with curative intent, measurements were done sequentially up to eight times (total dose: 45-59.5 Gy). Oxygenation status of the palliative patient group was examined before each fraction of radiation therapy up to five times (total dose: 24-30 Gy). Results: 15/26 tumors had a pretreatment median pO{sub 2} {<=} 10 mmHg. The pO{sub 2} values appeared to be quite variable in individual tumors during fractionated radiation therapy. The pO{sub 2} of initially hypoxic tumors (pretreatment median pO{sub 2} {<=} 10 mmHg) remained unchanged during fractionated radiotherapy, whereas in initially normoxic tumors the pO{sub 2} decreased. Conclusion: hypoxia is common in spontaneous canine tumors, as 57.7% of the recorded values were {>=} 10 mmHg. The data of this study showed that initially hypoxic tumors remained hypoxic, whereas normoxic tumors became more hypoxic. (orig.)

  10. Temperature dependence of the electrode kinetics of oxygen reduction at the platinum/Nafion interface - A microelectrode investigation

    Science.gov (United States)

    Parthasarathy, Arvind; Srinivasan, Supramanian; Appleby, A. J.; Martin, Charles R.

    1992-01-01

    Results of a study of the temperature dependence of the oxygen reduction kinetics at the Pt/Nafion interface are presented. This study was carried out in the temperature range of 30-80 C and at 5 atm of oxygen pressure. The results showed a linear increase of the Tafel slope with temperature in the low current density region, but the Tafel slope was found to be independent of temperature in the high current density region. The values of the activation energy for oxygen reduction at the platinum/Nafion interface are nearly the same as those obtained at the platinum/trifluoromethane sulfonic acid interface but less than values obtained at the Pt/H3PO4 and Pt/HClO4 interfaces. The diffusion coefficient of oxygen in Nafion increases with temperature while its solubility decreases with temperature. These temperatures also depend on the water content of the membrane.

  11. Mass-Producible 2D-MoS2-Impregnated Screen-Printed Electrodes That Demonstrate Efficient Electrocatalysis toward the Oxygen Reduction Reaction.

    Science.gov (United States)

    Rowley-Neale, Samuel J; Smith, Graham C; Banks, Craig E

    2017-07-12

    Two-dimensional molybdenum disulfide (2D-MoS 2 ) screen-printed electrodes (2D-MoS 2 -SPEs) have been designed, fabricated, and evaluated toward the electrochemical oxygen reduction reaction (ORR) within acidic aqueous media. A screen-printable ink has been developed that allows for the tailoring of the 2D-MoS 2 content/mass used in the fabrication of the 2D-MoS 2 -SPEs, which critically affects the observed ORR performance. In comparison to the graphite SPEs (G-SPEs), the 2D-MoS 2 -SPEs are shown to exhibit an electrocatalytic behavior toward the ORR which is found, critically, to be reliant upon the percentage mass incorporation of 2D-MoS 2 in the 2D-MoS 2 -SPEs; a greater percentage mass of 2D-MoS 2 incorporated into the 2D-MoS 2 -SPEs results in a significantly less electronegative ORR onset potential and a greater signal output (current density). Using optimally fabricated 2D-MoS 2 -SPEs, an ORR onset and a peak current of approximately +0.16 V [vs saturated calomel electrode (SCE)] and -1.62 mA cm -2 , respectively, are observed, which exceeds the -0.53 V (vs SCE) and -635 μA cm -2 performance of unmodified G-SPEs, indicating an electrocatalytic response toward the ORR utilizing the 2D-MoS 2 -SPEs. An investigation of the underlying electrochemical reaction mechanism of the ORR within acidic aqueous solutions reveals that the reaction proceeds via a direct four-electron process for all of the 2D-MoS 2 -SPE variants studied herein, where oxygen is electrochemically favorably reduced to water. The fabricated 2D-MoS 2 -SPEs are found to exhibit no degradation in the observed achievable current over the course of 1000 repeat scans. The production of such inks and the resultant mass-producible 2D-MoS 2 -SPEs mitigates the need to modify post hoc an electrode via the drop-casting technique that has been previously shown to result in a loss of achievable current over the course of 1000 repeat scans. The 2D-MoS 2 -SPEs designed, fabricated, and tested herein could

  12. Synthesis and characterization of the WxRuySez from the electrochemical reduction of oxygen and their possible application as electrode in fuel cell

    International Nuclear Information System (INIS)

    Ramirez R, S.D.

    1995-01-01

    In this communication the synthesis of the W 0.03 RuSe 0.47 O 0.3 from the transition metal carbonyl compounds and the chalcogenide in m Xylene, the chemical characterization of the novel material was performed by neutron activation analysis (NAA), using the TRIGA Mark III Reactor from the Nuclear Center of Mexico. The oxygen present in the material was determined by Rutherford Backscattering Spectrometry (RBS). Also the RuSe 5.7 y WSe 2 were synthesized and characterized by NAA. The electro kinetic oxygen reduction behaviour of the W 0.03 RuSe 0.47 O 0.3 deposited in glassy carbon was investigated in aqueous H 2 SO 4 0.5M. The rotating disk electrode electrochemical technique was used for determining the kinetic parameters: The reaction was of first order which implied that the rate determining step is the transfer of one electron, the Tafel slope was 0.115 V/decade; the electron transfer coefficient found was of 0.5, and the activation energy in the oxygen reduction reaction was 0.47 eV. (Author)

  13. Potential of porous platinum electrode in contact with 0.9ZrO2-0.1Y2O3 solid electrolyte in atmosphere with changing oxygen content

    International Nuclear Information System (INIS)

    Glumov, M.V.; Brajnin, M.I.

    1996-01-01

    Polarization dependences of platinum electrode on the 0.9ZrO 2 -0.1Y 2 O 3 electrolyte in gaseous mixtures with free oxygen and impurity in the form of steam or carbon dioxide have been obtained in the course of oxygen removal from gaseous volume of a cell. Electrolytic flow of oxygen proved to be the polarizing factor. Polarization curves have the maximum near the point of the gas mixture equivalence. The behaviour of the polarization maximum, depending on the rate of oxygen removal and gas composition, has been considered. The results are compared with the character of stationary polarization curves. 16 refs.; 5 figs

  14. Oxygen evolution reaction of Ti/IrO2–SnO2 electrode: a study by ...

    Indian Academy of Sciences (India)

    electrochemical industry. An interest in Ti/IrO2 type DSAs for oxygen evolution has been ... as oxidizing organics in wastewater, even the wastewater contains low amount of chloride ions. To the best of our knowledge, ... Subsequently chemical treatment was carried out using 5% (w/w) oxalic acid solution for. 10 min and ...

  15. Accurate Assessment of the Oxygen Reduction Electrocatalytic Activity of Mn/Polypyrrole Nanocomposites Based on Rotating Disk Electrode Measurements, Complemented with Multitechnique Structural Characterizations

    Directory of Open Access Journals (Sweden)

    Patrizia Bocchetta

    2016-01-01

    Full Text Available This paper reports on the quantitative assessment of the oxygen reduction reaction (ORR electrocatalytic activity of electrodeposited Mn/polypyrrole (PPy nanocomposites for alkaline aqueous solutions, based on the Rotating Disk Electrode (RDE method and accompanied by structural characterizations relevant to the establishment of structure-function relationships. The characterization of Mn/PPy films is addressed to the following: (i morphology, as assessed by Field-Emission Scanning Electron Microscopy (FE-SEM and Atomic Force Microscope (AFM; (ii local electrical conductivity, as measured by Scanning Probe Microscopy (SPM; and (iii molecular structure, accessed by Raman Spectroscopy; these data provide the background against which the electrocatalytic activity can be rationalised. For comparison, the properties of Mn/PPy are gauged against those of graphite, PPy, and polycrystalline-Pt (poly-Pt. Due to the literature lack of accepted protocols for precise catalytic activity measurement at poly-Pt electrode in alkaline solution using the RDE methodology, we have also worked on the obtainment of an intralaboratory benchmark by evidencing some of the time-consuming parameters which drastically affect the reliability and repeatability of the measurement.

  16. Efficient oxidative dissolution of V2O3 by the in situ electro-generated reactive oxygen species on N-doped carbon felt electrodes

    International Nuclear Information System (INIS)

    Xue, Yudong; Wang, Yunting; Zheng, Shili; Sun, Zhi; Zhang, Yi; Jin, Wei

    2017-01-01

    Highlights: • Novel alkaline electro-Fenton-like was applied for V 2 O 3 oxidative dissolution. • N-doped carbon felt electrode was fabricated for the two-electron ORR. • ROS including ·OH and HO 2 − was in-situ generated from the electrochemical system. • A significant enhancement of V 2 O 3 dissolution was achieved due to the ROS. - Abstract: Oxidative dissolution is a critical step for the efficient remediation of heavy metal oxides in large-scale solid wastes. In the present study, a novel electro-oxidative dissolution process of V 2 O 3 to VO 4 3− is achieved by the in-situ generated reactive oxygen species on the N-doped carbon felt cathode in alkaline media. The electro-catalytic HO 2 − generation and hydrophilic behavior were significantly enhanced by the introduction of nitrogen-containing functional groups. Besides, the mechanism of electrochemical vanadium conversion is systematically illustrated, and a vanadium self-induced electro-Fenton-like reaction is proposed. By employing the radical quenching and ESR measurements, the contributions for V(III) dissolution is determined to be 43.5% by HO 2 − and 56.5% by hydroxyl radicals, respectively. It should be noted that the V 2 O 3 solid particles can be efficiently dissolved via adsorption-reaction scheme on the carbon felt electrode. This novel electrochemical strategy provides a promising solution for the heavy metal oxide treatment and further understanding for the in situ reactive oxygen species.

  17. Oxygen evolution reaction catalysis

    Science.gov (United States)

    Haber, Joel A.; Jin, Jian; Xiang, Chengxiang; Gregoire, John M.; Jones, Ryan J.; Guevarra, Dan W.; Shinde, Aniketa A.

    2016-09-06

    An Oxygen Evolution Reaction (OER) catalyst includes a metal oxide that includes oxygen, cerium, and one or more second metals. In some instances, the cerium is 10 to 80 molar % of the metals in the metal oxide and/or the catalyst includes two or more second metals. The OER catalyst can be included in or on an electrode. The electrode can be arranged in an oxygen evolution system such that the Oxygen Evolution Reaction occurs at the electrode.

  18. Oxygen-assisted low-pressure chemical vapor deposition for the low-temperature direct growth of graphitic nanofibers on fluorine-doped tin oxide glass as a counter electrode for dye-sensitized solar cell

    Science.gov (United States)

    Chen, Chih-Sheng; Hsieh, Chien-Kuo

    2014-11-01

    In this paper, we report an oxygen-assisted low-pressure chemical vapor deposition (LPCVD) method for the direct growth of graphitic nanofibers (GNFs) on a fluorine-doped tin oxide (FTO) glass substrate at a low temperature (550 °C). By adding moderate concentrations of oxygen in a gas mixture of argon, ethylene, and hydrogen during LPCVD, an extremely dense GNF forest can be obtained on a nickel-coated FTO glass substrate. Though this process, the graphitic nanofibers are grown homogenously on a large area of FTO glass. It was observed that oxygen-assisted LPCVD leads to the direct growth of high-quality GNFs as a counter electrode for dye-sensitized solar cells (DSSCs). In combination with an N719 dye-sensitized TiO2 working electrode and an iodine-based electrolyte, the DSSC with a GNF counter electrode showed a power conversion efficiency of 5.51% under AM 1.5 (100 mW cm-2) illumination, which approached that of the DSSC with a Pt counter electrode (5.44%). The results demonstrated that our directly grown GNFs could be promising candidates for counter electrodes to achieve high performance in DSSCs.

  19. Molecule-Level g-C3N4 Coordinated Transition Metals as a New Class of Electrocatalysts for Oxygen Electrode Reactions

    KAUST Repository

    Zheng, Yao

    2017-02-21

    Organometallic complexes with metal-nitrogen/carbon (M-N/C) coordination are the most important alternatives to precious metal catalysts for oxygen reduction and evolution reactions (ORR and OER) in energy conversion devices. Here, we designed and developed a range of molecule-level graphitic carbon nitride (g-C3N4) coordinated transition metals (M-C3N4) as a new generation of M-N/C catalysts for these oxygen electrode reactions. As a proof-of-concept example, we conducted theoretical evaluation and experimental validation on a cobalt-C3N4 catalyst with a desired molecular configuration, which possesses comparable electrocatalytic activity to that of precious metal benchmarks for the ORR and OER in alkaline media. The correlation of experimental and computational results confirms that this high activity originates from the precise M-N2 coordination in the g-C3N4 matrix. Moreover, the reversible ORR/OER activity trend for a wide variety of M-C3N4 complexes has been constructed to provide guidance for the molecular design of this promising class of catalysts.

  20. Direct detection of ammonium ion by means of oxygen electrocatalysis at a copper-polyaniline composite on a screen-printed electrode

    International Nuclear Information System (INIS)

    Zhybak, Mykhailo T.; Vagin, Mikhail Yu.; Beni, Valerio; Liu, Xianjie; Turner, Anthony P. F.; Dempsey, Eithne; Korpan, Yaroslav I.

    2016-01-01

    We describe a composite material for use in electrochemical oxygen reduction. A screen-printed electrode (SPE) was consecutively modified with electrodeposited copper, a Nafion membrane and electropolymerized polyaniline (PANi) to give an electrocatalytic composite of type PANi/Nafion/Cu 2 O/SPE that displays good electrical conductivity at neutral pH values. It is found that the presence of ammonia causes complex formation with Cu(I), and this causes electroreduction of oxygen to result in an increased cathodic current. The finding was applied to the quantification of ammonium ions in the 1 to 1000 μM concentration range by amperometry at −0.45 V (vs. Ag/AgCl). This Faradaic phenomenon offers the advantage of direct voltammetric detection, one of the lowest known limits of detection (0.5 μM), and high sensitivity (250 mA∙M −1 ∙cm −2 ). It was applied to the determination of ammonium ion in human serum where it compared well with the photometric routine approach for clinical analysis using glutamate dehydrogenase. (author)

  1. Assay of Aliphatic Phthalates in Polymer Products by Sensitive Polarographic Method: Health and Environmental Issue

    Directory of Open Access Journals (Sweden)

    Munawar Saeed

    2010-06-01

    Full Text Available A faster, simpler and sensitive method was developed for determination of aliphatic phthalates using differential pulse polarography (DPP as standard technique. The choice and concentration of base electrolyte, solvent, initial potential, effect of water addition and interference by other phthalates were the main parameters to optimize for enhancement of peak current and to obtain well-defined polarogram with lower background current using 1.3 x 10-4 M di-butyl phthalate (DBP solution. Best results were obtained in the presence of tetra methyl ammonium bromide (TMAB as electrolyte in methanol solvent with initial potential, -1.4 V. A linear calibration plot was observed in the range of 3 x 10-7 – 1.6 x 10-4 M DBP solution as aliphatic phthalates with lower detection limit of 5.9 x 10-8 M and linear regression coefficient of 0.9987. The developed polarographic method was successfully applied for analysis of aliphtaic phthalates in various samples of locally available polymer products such as baby toys, nipples, teethers, infusion blood bags and shopping bags. The results of the current method were compared with those obtained by a reported method and good agreement was found between them.

  2. Determination of Sn in 99mTc Radiopharmaceutical Kits by Polarographic Methods

    International Nuclear Information System (INIS)

    Castro, M.; Cruz, J.; Sanchez, M.

    2009-01-01

    Kits of 99 m Tc radiopharmaceuticals are used in nuclear medicine for diagnosis of different diseases. Sn (II) is one of the essential components in their formulations, which is used for reduction 99 m Tc-pertechnetate in cold kits for on-site preparation 99 m Tc-pertechnetate radiopharmaceuticals. Usually, these cold kits contain different additives (complexing agents, antioxidants, buffers, etc.) and the amount of Sn (II) varies from kit to kit. The determination of Sn in these products is essential in assessing their quality. We report here the development of a new polarographic method for the determination of Sn (II) and total Sn in representative radiopharmaceuticals kits (for the content of Sn and chemical composition) produced at the Center of Isotopes of Cuba (CENTIS). These methods were validated by analysis of variance and recovery techniques. From the results of the validation, the characteristic functions of uncertainties and fits are considered for the established methods, which give the necessary evidences to demonstrate the usefulness of these methods according to the current trends in Analytical Chemistry. This work provides practical results of great importance for CENTIS. After the speciation of Sn in the MAG3 radiopharmaceuticals kit is inferred that the production process is affected by uncontrolled factors that influence in the product stability, which demonstrates the necessity for analytical tools for the characterization of products and processes. (Author) 57 refs.

  3. Tissue oxygen tension in the stria vascularis.

    Science.gov (United States)

    Nagahara, K; Miyake, Y; Aoyama, T; Ogino, F

    1988-01-01

    Tissue oxygen tension in the stria vascularis was successfully measured in cats using the polarographic technique. A correlation study using the differential coefficient between oxygen tension in the stria vascularis and systemic blood pressure proved that vascular autoregulation is present in the mean systemic blood pressure range between 40 and 80 mmHg. The anatomical findings and the response patterns to different gas inhalations indicated that the type of vascular regulation present is more closely related to chemical control than to auto-regulation.

  4. Dosing of traces of oxygenated water by polarography

    International Nuclear Information System (INIS)

    Faure, A.M.; Malterre, J.

    1960-01-01

    As dosing oxygenated water by using polarography has been envisaged within the framework of water purity controls for the Melusine pile, the objective of the authors is here to see whether the polarographic method could be satisfying for routine analyses, and would result in a higher dosing sensitivity. They describe the polarography principle, indicate devices which are used, specify and comment conditions under which polarography is performed [fr

  5. Evaluation of H2O2-generation during oxygen reduction at electrodeposited Pt particles on mask scratched electrodes

    Science.gov (United States)

    Kishi, Akira; Inoue, Mitsuhiro; Umeda, Minoru

    2013-08-01

    In this study, the Pt particle deposition was systematically performed by our proposed mask scratch and subsequent Pt electrodeposition in order to investigate the H2O2-byproduct generation efficiency during O2 reduction. By peeling a part of polymer layer coated on a glassy carbon substrate using an atomic force microscope cantilever, scratched areas are regularly made. The Pt particles are deposited only on the above-mentioned scratched areas, indicating that the controlled Pt deposition has been achieved. The background cyclic voltammetry of the prepared electrodes showed that the deposited nanoparticles are certainly composed of Pt. Moreover, the electrochemical surface area of the deposited Pt (Pt-ESA) linearly increases with the increasing scratched area, revealing that the Pt-ESAs can be controlled by the mask scratch-based Pt electrodeposition method. It should be noted that an increase in the Pt-ESA not only increases the O2 reduction currents, but also enhances the H2O2 generation efficiency.

  6. Cu3Mo2O9Nanosheet Array as a High-Efficiency Oxygen Evolution Electrode in Alkaline Solution.

    Science.gov (United States)

    Gou, Ying; Yang, Lin; Liu, Zhiang; Asiri, Abdullah M; Hu, Jianming; Sun, Xuping

    2018-02-05

    Developing highly active and sustained oxygen evolution reaction (OER) catalysts for energy-saving electrolytic hydrogen generation is highly attractive. In this work, we report the development of a Cu 3 Mo 2 O 9 nanosheet array on nickel foam (Cu 3 Mo 2 O 9 /NF) as a highly active OER catalyst. Such Cu 3 Mo 2 O 9 /NF shows high catalytic activity in 1.0 M KOH, passing 50 mA cm -2 at an overpotential of 325 mV. It also shows superior long-term durability more than 24 h with a turnover frequency (TOF) of 0.09 mol O 2 s -1 at overpotential of 400 mV.

  7. Electron transfer number control of the oxygen reduction reaction on nitrogen-doped reduced graphene oxides for the air electrodes of zinc-air batteries and organic degradation

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Sheng-Hui; Li, Po-Chieh; Hu, Chi-Chang, E-mail: cchu@che.nthu.edu.tw

    2016-11-01

    The mean electron transfer number (n) of the oxygen reduction reaction (ORR) on reduced graphene oxide (rGO) is controlled by nitrogen doping for the air electrodes of Zn-air batteries and electrochemical organic degradation. Melamine and pyrrole are employed as the nitrogen sources for fabricating N-doped rGO (N-rGO) by microwave-assisted hydrothermal synthesis (MAHS). The n value of the ORR is determined by the rotating ring-disk electrode (RRDE) voltammetry and is successfully controlled from 2.34 to 3.93 by preparation variables. The N-doped structures are examined by the x-ray photoelectron spectroscopic (XPS) analysis. The morphology and the defect degree of N-rGOs are characterized by high resolution transmission electron microscopy (HR-TEM) and Raman spectroscopy. N-rGOs with high and low n values are employed as the air electrode catalysts of zinc-air batteries and in-situ hydrogen peroxide (H{sub 2}O{sub 2}) generation, respectively. The highest discharge cell voltage of 1.235 V for a Zn-air battery is obtained at 2 mA cm{sup −2} meanwhile the current efficiency of H{sub 2}O{sub 2} generation in 1-h electrolysis at 0 V (vs. RHE) reaches 43%. The electrocatalytic degradation of orange G (OG), analyzed by UV-VIS absorption spectra, reveals a high decoloration degree from the relative absorbance of 0.38 for the azo π-conjugation structure of OG. - Highlights: • The mean electron transfer number (n) is controlled by nitrogen doping. • Melamine and pyrrole are used as the nitrogen sources for fabricating N-rGO. • The n value is successfully controlled from 2.34 to 3.93 by preparation variables. • The highest discharge cell voltage of 1.235 V for a Zn-air battery. • The current efficiency of H{sub 2}O{sub 2} generation 1-h electrolysis reaches 43%.

  8. Polarographic study of simple and mixed ligand complexes of Eu(III) with imidazole and succinate

    International Nuclear Information System (INIS)

    Shivhare, Madhu; Singh, Mukhtar

    1982-01-01

    The formation of simple and mixed ligand complexes of Eu(III) with imidazole (Im) and succinate (Succ 2- ) has been studied polarographically at 25deg C+-0.1deg C, μ=1.0 (NaClO 4 ) and pH=6. The reduction of the complexes at d.m.e. is quasi-reversible and diffusion-controlled. Eu(III) forms six successive complexes with Im, viz. [Eu(Im)] 3+ , [Eu(Im) 2 ] 3+ , [Eu(Im) 2 ] 3+ , [Eu(Im) 3 ] 3+ , [Eu(Im) 4 ] 3+ , [Eu(Im) 5 ] 3+ , and[Eu(Im) 6 ] 3+ . Their stability constant values are: logβ 10 =3.6, logβ 20 =4.6, logβ 30 =6.5, logβ 40 =7.8, logβ 50 =8.4 and logβ 60 =9.6 respectively. With succ 2- , Eu(III) forms four successive complexes; [Eu(Succ)] + , [Eu(Succ) 2 ] - , [Eu(Succ) 3 ] 3- and [Eu(Succ) 4 ] 5- with the stability constants, logβ 01 =3.8, logβ 02 =4.6, logβ 03 =5.3 and logβ 04 =6.9 respectively. Eu(III) forms five mixed ligand complexes; [Eu(Im)(Succ) 2 ] - , Eu(Im) 2 (Succ) 2 ] - , [Eu(Im) 3 (Succ) 2 ], [Eu(Im) 4 (Succ) 2 ] and [Eu(Im) 5 (Succ)] + with stability constants, logβ 12 =6.1, logβ 22 =8.0, logβ 32 =9.5, logβ 42 =10.9 and logβ 51 =10.2 respectively. (author)

  9. Fabrication and characterization of nanostructured mechanically alloyed Pt-Co catalyst for oxygen gas-diffusion-electrode

    International Nuclear Information System (INIS)

    Pharkya, P.; Farhat, Z.; Czech, E.; Hawthorne, H.; Alfantazi, A.

    2003-01-01

    The use of PEM fuel cells depends largely upon the cost of materials, processing and fabrication. The cost of Pt catalyst is a significant cost of a fuel cell. Alternative low cost catalyst that promotes high rate of oxygen reduction is needed. To achieve this, a mechanochemical technique was employed to refine the catalyst layer structure (i.e. increasing the effective catalyst surface area) and reducing the amount of Pt used, by alloying with a cheaper element. An investigation is carried out to study the relationship between the new catalyst structure refinement, morphology, microstructure and its electrocatalytic behaviour. Nanostructured Pt, Co and Pt 0.2 5 Co 0.75 alloy was fabricated from high purity Pt (99.9%) and Co (99.5%) powders using a Laboratory Planetary Ball Mill 'Pulverisette 6'. Optimum milling conditions, that produce fine, uniform and mechanically alloyed microstructure, were determined during fabrication, by varying process parameters (i.e., rpm, milling time, ball to powder ratio, milling atmosphere, surface-agents and milling/cooling cycle). Mechanically induced chemical and physical reactions and thermal effects were monitored 'in-situ' using a GTM system, which recorded temperature and pressure changes during milling. The alloy catalysts were characterized using TEM, SEM, EDX, XRD and BET techniques. Electrochemical tests were carried out on prepared powders. Exchange currents were determined from a potentiodynamic polarization tests and used to compare relative electrocatalytic behaviour of the new catalyst. Structure/property relationships were discussed and conclusions were drawn on the production of improved low cost catalyst. (author)

  10. Oxygen Transfer on Substituted ZrO2, Bi2O3, and CeO2 Electrolytes with Platinum Electrodes II. A-C Impedance Study

    NARCIS (Netherlands)

    Verkerk, M.J.; Burggraaf, A.J.

    1983-01-01

    An equivalent electrical circuit that describes the electrode processes on different electrolytes, using porous Pt electrodes,is given. Diffusional processes are important and have to be presented by Warburg components in the circuit. Theoverall electrode process is rate limited by diffusion of

  11. Oxygen and chlorine evolution on RuO2 + TiO2 + CeO2 + Nb2O5 mixed oxide electrodes

    International Nuclear Information System (INIS)

    Santana, Mario H.P.; Faria, Luiz A. de

    2006-01-01

    A systematic investigation was conducted on the mechanism and electrocatalytic properties of O 2 and Cl 2 evolution on mixed oxide electrodes of nominal composition: Ti/[Ru (0.3) Ti (0.6) Ce (0.1-x) ]O 2 [Nb 2 O 5 ] (x) (0 ≤ x ≤ 0.1). For the oxygen evolution, a 30 mV Tafel slope is obtained in the presence of CeO 2 , while in its absence a 40 mV coefficient is observed. The intrinsic electrocatalytic activity is mainly due to electronic factors, as result of the synergism between Ru and Ce oxides. For chlorine evolution, the Tafel slope (30 mV) is independent on oxide composition. The best global electrocatalytic activity for ClER was observed in the absence of Nb 2 O 5 additive. Variation of the voltammetric charge throughout the experiments confirms high CeO 2 content compositions are fragile, due mainly to the porosity caused by CeO 2 presence. On the other hand, Nb 2 O 5 addition decreases considerably this instability

  12. Influence of Oxygen Concentration on the Performance of Ultra-Thin RF Magnetron Sputter Deposited Indium Tin Oxide Films as a Top Electrode for Photovoltaic Devices

    Directory of Open Access Journals (Sweden)

    Jephias Gwamuri

    2016-01-01

    Full Text Available The opportunity for substantial efficiency enhancements of thin film hydrogenated amorphous silicon (a-Si:H solar photovoltaic (PV cells using plasmonic absorbers requires ultra-thin transparent conducting oxide top electrodes with low resistivity and high transmittances in the visible range of the electromagnetic spectrum. Fabricating ultra-thin indium tin oxide (ITO films (sub-50 nm using conventional methods has presented a number of challenges; however, a novel method involving chemical shaving of thicker (greater than 80 nm RF sputter deposited high-quality ITO films has been demonstrated. This study investigates the effect of oxygen concentration on the etch rates of RF sputter deposited ITO films to provide a detailed understanding of the interaction of all critical experimental parameters to help create even thinner layers to allow for more finely tune plasmonic resonances. ITO films were deposited on silicon substrates with a 98-nm, thermally grown oxide using RF magnetron sputtering with oxygen concentrations of 0, 0.4 and 1.0 sccm and annealed at 300 °C air ambient. Then the films were etched using a combination of water and hydrochloric and nitric acids for 1, 3, 5 and 8 min at room temperature. In-between each etching process cycle, the films were characterized by X-ray diffraction, atomic force microscopy, Raman Spectroscopy, 4-point probe (electrical conductivity, and variable angle spectroscopic ellipsometry. All the films were polycrystalline in nature and highly oriented along the (222 reflection. Ultra-thin ITO films with record low resistivity values (as low as 5.83 × 10−4 Ω·cm were obtained and high optical transparency is exhibited in the 300–1000 nm wavelength region for all the ITO films. The etch rate, preferred crystal lattice growth plane, d-spacing and lattice distortion were also observed to be highly dependent on the nature of growth environment for RF sputter deposited ITO films. The structural, electrical

  13. Oxygen evolution on Co{sub 3}O{sub 4} and Li-doped Co{sub 3}O{sub 4} coated electrodes in an alkaline solution

    Energy Technology Data Exchange (ETDEWEB)

    Bocca, C.; Cerisola, G.; Barbucci, A. [Genova Univ. (Italy). Inst. of Chemistry; Magnone, E. [Genova Univ. (Italy). INFM; Genova Univ. (Italy). Dept. of Chemistry and Industrial Chemistry

    1999-08-01

    The oxygen evolution reaction (OER) was investigated at 60{sup o}C in 15 wt% NaOH solution on Co{sub 3}O{sub 4}, Li-doped Co{sub 3}O{sub 4} and perovskite-type oxide (LaNiO{sub 3}) electrodes. Cobalt and Li-doped cobalt oxides were obtained by different preparation techniques and were applied to chemically-pickled nickel plates. The obtained phases were structurally characterized by X-ray powder diffraction. The electrodes were subjected to electrochemical measurements, before and after electrochemical ageing (21 days, 150 mA cm{sup -2}). The correlation between the coating preparations and their electrocatalytic activity was investigated. The efficiency of the studied electrodes seems to depend on the preparation method. Two Tafel slopes for the OER were observed in most cases. This behaviour was interpreted on the basis of a change in the valence state of the surface oxide. (author)

  14. Real-time monitoring of nitric oxide (NO) and pO2 levels under ischemic conditions associated with small bowel ischemia/reperfusion injury using selective electrodes for NO and oxygen molecules.

    Science.gov (United States)

    Watanabe, T; Owada, S; Kobayashi, H; Ishiuchi, A; Nakano, H; Asakuta, T; Shimamura, T; Asano, T; Koizumi, S; Jinnouchi, Y; Katayama, M; Kamibayasi, M; Murakami, E; Otsubo, T

    2007-12-01

    The present study demonstrated the feasibility of monitoring nitric oxide (NO) and pO2 levels under ischemic conditions associated with small bowel ischemia/reperfusion (I/R) injury through the use of selective electrodes for NO and oxygen molecules. NO levels gradually increased during ischemia. When reperfusion was started, the NO level decreased suddenly and returned to pre-ischemia values within 10 minutes. After clamping, pO2 decreased rapidly. When reperfusion was started, pO2 increased suddenly, returning to pre-ischemia values within 10 minutes. We concluded that it is feasible to monitor NO and pO2 levels under ischemic conditions of small bowel I/R injury through the use of electrodes selective for NO and oxygen molecules.

  15. Deconvolution of polarographic peaks by means of multi-parametric fitting; Deconvolution de pics polarographiques par regression multiparametrique

    Energy Technology Data Exchange (ETDEWEB)

    Petitfour, B.; Rahier, A.

    1996-08-01

    The non-linear multi-parametric fitting method has been applied to the deconvolution of differential pulse polarographic peaks. In the practice, it has been observed that even the powerful modified Marquardt method often fails to find a coherent set of parameters. An extensive analysis of the objective function reveals clearly a hyper-volcano shape with the solution located inside the crater. This explains why classical methods often fail to find the solution when the initial values given to the parameters are too far from their exact values. A sequential optimization has been combined to the Marquardt``s method, resulting in convergence in most cases, though all problems are not entirely solved. It has been demonstrated that the sequence chosen to preliminary optimize each parameter before using the Marquardt``s method influences both the speed and the accuracy of the convergence process.

  16. Polarographic determination of Iodide and Iodate, in Solutions Coming from Aerosols in Fission Products Containment Studies in Nuclear Power Stations

    International Nuclear Information System (INIS)

    Sanchez, M.; Ballesteros, O.; Fernandez, M.; Clavero, M.A.; Gonzalez, A.M.

    2000-01-01

    A polarographic method is described for the iodine species determination, iodide and iodate in water solutions. the iodate can be determined by differential pulse polarography. Calibration curves and the detection and determination limits have been obtained. Iodides is oxidized to iodate with sodium hypochlorite and the excess of oxidizing agent is destroyed with sodium sulphide. The concentration of iodide is calculated as the difference between the concentration of iodate in the sample before and after the oxidation. As an application, species of iodine in samples coming from the experimental plants GIRS (Gaseous Iodine Removal by Sprays) of Nuclear Fission Department of the CIEMAT, dedicated to fission products containment studies in nuclear power station, were determined. (Author) 10 refs

  17. [Effect of solcoseryl on oxygen metabolism and growth of experimental tumors].

    Science.gov (United States)

    Mosienko, V S; Zagoruĭko, L I; Todor, I N; Khasanova, L T

    1987-01-01

    Antihypoxant and antitumour properties of solcoseryl were studied on intact and tumour-bearing rats and mice. By the polarographic method it is found that solcoseryl increases the oxygen metabolism only in animal hypoxic tissues and improves, probably, energy production of their mitochondria. On many tumour strains it is shown that the injections of solcoseryl decelerate the growth of some tumours, inhibit the metastatic process and produce no toxic effect on the animals.

  18. A Combined Variable-Temperature Neutron Diffraction and Thermogravimetric Analysis Study on a Promising Oxygen Electrode, SrCo0.9Nb0.1O3-δ, for Reversible Solid Oxide Fuel Cells.

    Science.gov (United States)

    Yang, Tianrang; Wang, Jie; Chen, Yan; An, Ke; Ma, Dong; Vogt, Thomas; Huang, Kevin

    2017-10-11

    The present study investigates the temperature-structure-stoichiometry relationship of a promising oxygen electrode SrCo 0.9 Nb 0.1 O 3-δ over a temperature (T) range from room temperature (RT) to 900 °C. The techniques employed are variable-temperature neutron diffraction (VTND) and thermogravimetric analysis (TGA). At T < 75 °C, VTND reveals a tetragonal (P4/mmm) structure with a G-type magnetic ordering. Above 75 °C, the nucleus structure remains the same, while the magnetic ordering disappears. A phase transition from tetragonal (P4/mmm) to cubic (Pm3̅m) is observed at 412 °C, where the two Co sites and three O sites in the P4/mmm phase converge to one equivalent site, respectively. The phase transition temperature coincides with the peak temperature of oxygen uptake obtained by TGA. It is also observed that the Nb dopant has no preferred Co site to occupy. The oxygen vacancies are mostly located at the O3 site surrounding the Co2 site in the P4/mmm structure. The intermediate-spin state of Co 3+ at the Co2 site is responsible for the observed distortions of CoO 6 octahedra, i.e., elongation of Co2O 6 octahedra and shortening of Co1O 6 octahedra along the c-axis, which is a phenomenon known as Jahn-Teller distortion. At high temperatures, large thermal displacement factor for O 2- is observed with high concentration of oxygen vacancies, providing a structural environment favorable to high O 2- conductivity in Nb-doped SrCoO 3 -based oxygen electrode materials.

  19. ELECTROCHEMISTRY OF FUEL CELL ELECTRODES.

    Science.gov (United States)

    optimization of fuel cell electrodes. Hydrogen oxidation and reduction, the reduction of oxygen, and the oxidation of formic acid, a soluble organic...substance, were selected for these studiees because of their relevance to fuel cell systems and because of their relative simplicity. The electrodes

  20. Use of lanthanide catalysts in air electrodes

    International Nuclear Information System (INIS)

    Souza Parente, L.T. de

    1982-01-01

    A review on the lanthanide catalysts suitable for the reduction catalysis of oxygen in air electrodes is presented. The kinds of lanthanide indicated to be used as catalysts of oxygen reduction are shown. (A.R.H.) [pt

  1. Polarographic behavior of tris(acetylacetonato)ruthenium(III) in aqueous and acetonitrile solutions

    International Nuclear Information System (INIS)

    Endo, Akira; Watanabe, Masayuki; Hayashi, Sadayuki; Shimizu, Kunio; Sato, G.P.

    1978-01-01

    In tetraethylammonium perchlorate-acetonitrile solution, [Ru(acac) 3 ] was reversibly reduced at the dropping mercury electrode to [Ru(acac) 3 ] - with a conditional electrode reaction rate-constant estimated to be ca. 0.2 cm s -1 or larger. The reduced form was stable in the solution under an inert gas atmosphere. In aqueous solutions, [Ru(acac) 3 ] was reduced reversibly when the depolarizer concentration was less than 0.07 mol m -3 at 25 0 C. At higher depolarizer concentrations, [Ru(acac) 3 ] molecules were adsorbed onto the mercury surface, and the free molecules in solution were reduced through the adsorbed layer at a smaller rate; the adsorbed layer was removed at a certain negative potential, and the reversible reduction took place normally at the bare surface. The difference between reversible half-wave potentials observed in acetonitrile and aqueous solutions was discussed in terms of solvation energies of the oxidized and reduced forms. (auth.)

  2. Influence of Nafion film on oxygen reduction reaction and hydrogen peroxide formation on Pt electrode for proton exchange membrane fuel cell

    International Nuclear Information System (INIS)

    Ohma, Atsushi; Fushinobu, Kazuyoshi; Okazaki, Ken

    2010-01-01

    The influence of Nafion film on ORR kinetics and H 2 O 2 formation on a Pt electrode was investigated using RRDE in 0.1 M HClO 4 . It was found that the Nafion-coated Pt system showed lower apparent ORR activity and more H 2 O 2 production than the bare Pt electrode system. From the temperature sensitivity, it was revealed that the apparent activation energies of ORR in the Nafion-coated Pt system were lower than the bare Pt electrode system, and the H 2 O 2 formation was suppressed with the increase of the temperature. In order to analyze the results furthermore, other systems (0.1/1.0 M, HClO 4 /CF 3 SO 3 H) with the bare Pt electrodes were also examined as references. It was exhibited that the ORR kinetic current, the H 2 O 2 formation, and the apparent activation energies of 1.0 M CF 3 SO 3 H system were close to those of the Nafion-coated Pt system. We concluded that the orientation of anion species of Nafion and CF 3 SO 3 H to the Pt surface via water molecules, as well as a fluorocarbon polymer network of Nafion, might block O 2 adsorption, resulting in the smaller effective surface area of the Pt electrode for ORR, the smaller ORR kinetic current, and the more H 2 O 2 production.

  3. Polarographic study of the Cu(II)/Cu(I) system in the presence of 1-ascorbic acid and 0,1 M ClK

    International Nuclear Information System (INIS)

    Alonso Lopez, J.

    1969-01-01

    While studying the catalytic effect of Cu ↓ 2 ions on the oxidation process of 1-ascorbic acid, it has been observed that, in a 0,1 M solution of K1 at a pH 6 to 7, the above acid gives rise in the presence of Cu ↓ 2 ions to a polarographic wave of half-wave potential of -0,41 V (vs. S.C.E.). (Author) 14 refs

  4. Regional perfusion and oxygenation of tumors upon methylxanthine derivative administration

    International Nuclear Information System (INIS)

    Kelleher, Debra K.; Thews, Oliver; Vaupel, Peter

    1998-01-01

    Purpose: The use of methylxanthine derivatives has been postulated as a means of increasing tumor perfusion and thus ameliorating tumor hypoxia. The aim of this study was to quantify and compare the effects of three methylxanthine derivatives: pentoxifylline (PX), torbafylline (TB), and HWA 138 (HW) on tumor perfusion and oxygenation. Methods and Materials: Anesthetized Sprague Dawley rats with DS-sarcomas implanted subcutaneously onto the hind foot dorsum were used in this study. Mean arterial blood pressure (MABP) was measured throughout experiments. Regional red blood cell (RBC) flux was monitored using a multichannel laser Doppler device and tumor oxygenation on a more global level was assessed polarographically using an O 2 -sensitive catheter electrode. The methylxanthine derivatives were administered as a single dose intraperitoneally (for PX 50 mg/kg; for TB and HW 75 mg/kg). Results: Following drug administration, initial decreases in MABP down to 75% of baseline values were observed for all three substances. PX, HW, and TB caused initial transient reductions in mean RBC flux followed by gradual increases to values of 137 ± 27 %, 139 ± 14 %, and 122 ± 14 % respectively at t = 60 min. Following a small initial decrease upon drug administration, O 2 partial pressure (pO 2 ) rose to 160 ± 31 %, 153 ± 34 %, and 121 ± 11 % for PX, HW, and TB, respectively at t = 60 min. At the end of the observation period (t = 90 min), increases in RBC flux and pO 2 were still evident. When individual tumors were considered, a variety of patterns (including opposing effects) for changes in RBC flux were seen, not necessarily reflected in the mean values. Thus, while the methylxanthine derivatives caused an increased average tumor perfusion, there is evidence suggesting that a redistribution of tumor blood flow occurs which may amplify preexisting heterogeneity. Conclusions: Substantial improvements in tumor oxygenation and perfusion were observed after administration of

  5. Severe anemia is associated with poor tumor oxygenation in head and neck squamous cell carcinomas

    International Nuclear Information System (INIS)

    Becker, Axel; Stadler, Peter; Lavey, Robert S.; Haensgen, Gabriele; Kuhnt, Thomas; Lautenschlaeger, Christine; Feldmann, Horst Juergen; Molls, Michael; Dunst, Juergen

    2000-01-01

    Purpose: To investigate the relationship between tumor oxygenation and the blood hemoglobin (Hb) concentration in patients with squamous cell carcinoma of the head and neck (SCCHN). Methods and Materials: A total of 133 patients with SCCHN underwent pretreatment polarographic pO 2 measurements of their tumors. In 66 patients measurements were also made in sternocleidomastoid muscles. The patients were divided into three groups according to their Hb concentration--severe anemia (Hb 2 . Conclusion: Our data suggest that a low Hb concentration and cigarette smoking contribute to inadequate oxygenation of SCCHN and thus for increased radioresistance. Consequently, Hb correction and abstinence from smoking may significantly improve tumor oxygenation

  6. Characterization and Electrocatalytic Properties of Titanium-Based Ru0.3Co0.7−xCex Mixed Oxide Electrodes for Oxygen Evolution in Alkaline Solution

    Directory of Open Access Journals (Sweden)

    Hongjun Wu

    2011-01-01

    Full Text Available Ti-supported RuO2-Co3O4-CeO2 (Ru0.3Co0.7−xCex oxide, 0≤x≤0.7 electrodes were prepared by sol-gel process. The phase structure, surface morphology, and microstructure of the oxide layer were characterized by X-ray diffraction (XRD and scanning electron microscopy (SEM. Electrocatalytic activity and oxygen evolution reaction (OER kinetics on these electrodes in 1.0 mol⋅dm−3 KOH solution were studied by recording open-circuit potential, cyclic voltammetry, and polarisation curves. The results showed that the appropriate content of CeO2 could reduce the grain size and increase active surface area. The electrocatalytic activity shows a strong dependence on the CeO2 content in the film. Catalytic performance of mixed oxide electrodes with 40 mol % CeO2 was the best, with the greatest voltammetric charge, 86.23 mC⋅cm−2, and the smallest apparent activation energy for OER at 0.60 V was 22.76 kJ⋅mol−1.

  7. Studies on the heterogeneous electron transport and oxygen reduction reaction at metal (Co, Fe) octabutylsulphonylphthalocyanines supported on multi-walled carbon nanotube modified graphite electrode

    CSIR Research Space (South Africa)

    Mamuru, SA

    2010-09-01

    Full Text Available Heterogeneous electron transfer dynamics and oxygen reduction reaction (ORR) activities using octabutylsulphonylphthalocyanine complexes of iron (FeOBSPc) and cobalt (CoOBSPc) supported on multi-walled carbon nanotube (MWCNT) platforms have been...

  8. Modeling of Impedance of Porous Electrodes

    Science.gov (United States)

    Lasia, Andrzej

    Porous electrodes are very important in practical applications of electrocatalysis, where an increase in the real surface area leads to an increase in catalytic activity. Porous electrodes are used in gas evolution (water electrolysis, hydrogen and oxygen evolution, chlorine evolution), electrocatalytic hydrogenation or oxidation of organic compounds, in batteries, fuel cells, etc. Good knowledge of the porous electrode theory permits for the construction of the electrodes with optimal utilization of the active electrode material. The porous electrode model was first developed by several authors for dc conditions (1-6) and later applied to the impedance studies.

  9. Surface Characterization and Electrocatalytic Properties of the Ti/Ir0.3Ti(0.7-xPbx O2-Coated Electrodes for Oxygen Evolution Reaction in Acidic Media

    Directory of Open Access Journals (Sweden)

    Oliveira-Sousa Adriana de

    2002-01-01

    Full Text Available In this work a systematic investigation was carried out of the surface characterization and electrocatalytic activity of Ti/Ir0.3Ti(0.7-xPb x O2-coated electrodes (0 <= x <= 0.7, using the oxygen evolution reaction (OER in 0.5 mol dm-3 H2SO4 as model. The electrodes were prepared by thermal decomposition of IrCl3, TiCl3 and Pb(NO32 at 600 °C for 1 h using Ti as support. X-ray diffraction shows that the layers are crystalline and that the corresponding metal oxides are present. The surface morphology of the samples, before and after use under extensive oxygen evolution (Tafel experiment, was characterized by Scanning Electron Microscopy and the micrograph analyses show that the OER promotes the dissolution of the oxide layer. The redox processes occurring on the surface were characterized by cyclic voltammetry at 20 mV s-1 in 0.5 mol dm-3 aqueous H2SO4, at room temperature, and were controlled by the Ir3+/Ir4+ couple. The measured anodic voltammetric charge is related to the active area of the electrode showing that the replacement of TiO2 by PbO2 increases the surface area with the higher value being at 50 mol% PbO2. After oxygen evolution, the surface area increases slightly. Tafel slopes are independent of Pb content with the values around 60 mV decade-1, which suggest that only Ir sites are active for OER. The values of normalized current (i/q a show some inhibition of the OER as TiO2 is replaced by PbO2 suggesting that PbO2, can be a good choice, with potential to improve the selectivity of the system. The reaction order with respect to H+ ion is zero at constant overpotential and ionic strength. The values of Tafel slope and reaction order indicate that a single reaction mechanism is operating.

  10. Comparison between La0.6Sr0.4CoO3-d and LaNi0.6Co0.4O3-d infiltrated oxygen electrodes for long-term durable solid oxide fuel cells

    DEFF Research Database (Denmark)

    Ovtar, Simona; Hauch, Anne; Veltzé, Sune

    2018-01-01

    The degradation of infiltrated oxygen electrodes during long-term operation of solid oxide fuel cells (SOFCs) was studied. The infiltrated oxygen electrodes were prepared by infiltration of the electro-catalysts La0.6Sr0.4CoO3-d (LSC) and LaNi0.6Co0.4O3-d (LCN) into a porous yttria stabilized...... conducted and the change of resistance was followed by electrochemical impedance spectroscopy under current load. The cell performance degradation profiles of the LSC and LCN infiltrated cells showed significant differences. The performance of the LSC infiltrated cell stabilized after 700 h of operation...

  11. Enhancement of anodic current attributed to oxygen evolution on α-Fe2O3 electrode by microwave oscillating electric field

    Science.gov (United States)

    Kishimoto, Fuminao; Matsuhisa, Masayuki; Kawamura, Shinichiro; Fujii, Satoshi; Tsubaki, Shuntaro; Maitani, Masato M.; Suzuki, Eiichi; Wada, Yuji

    2016-01-01

    Various microwave effects on chemical reactions have been observed, reported and compared to those carried out under conventional heating. These effects are classified into thermal effects, which arise from the temperature rise caused by microwaves, and non-thermal effects, which are attributed to interactions between substances and the oscillating electromagnetic fields of microwaves. However, there have been no direct or intrinsic demonstrations of the non-thermal effects based on physical insights. Here we demonstrate the microwave enhancement of oxidation current of water to generate dioxygen with using an α-Fe2O3 electrode induced by pulsed microwave irradiation under constantly applied potential. The rectangular waves of current density under pulsed microwave irradiation were observed, in other words the oxidation current of water was increased instantaneously at the moment of the introduction of microwaves, and stayed stably at the plateau under continuous microwave irradiation. The microwave enhancement was observed only for the α-Fe2O3 electrode with the specific surface electronic structure evaluated by electrochemical impedance spectroscopy. This discovery provides a firm evidence of the microwave special non-thermal effect on the electron transfer reactions caused by interaction of oscillating microwaves and irradiated samples. PMID:27739529

  12. Electrochemical characterisation of solid oxide cell electrodes for hydrogen production

    DEFF Research Database (Denmark)

    Bernuy-Lopez, Carlos; Knibbe, Ruth; He, Zeming

    2011-01-01

    Oxygen electrodes and steam electrodes are designed and tested to develop improved solid oxide electrolysis cells for H2 production with the cell support on the oxygen electrode. The electrode performance is evaluated by impedance spectroscopy testing of symmetric cells at open circuit voltage (OCV...... and impregnated with CGO/Ni, with an Rp of 0.08 Ω cm2 at 850 °C in 3% H2O/H2....

  13. Bias polarization study of steam electrolysis by composite oxygen electrode Ba0.5Sr0.5Co0.8Fe0.2O3-δ/BaCe0.4Zr0.4Y0.2O3-δ

    Science.gov (United States)

    Yang, Tao; Shaula, Aliaksandr; Pukazhselvan, D.; Ramasamy, Devaraj; Deng, Jiguang; da Silva, E. L.; Duarte, Ricardo; Saraiva, Jorge A.

    2017-12-01

    The polarization behavior of Ba0.5Sr0.5Co0.8Fe0.2O3-δ-BaCe0.4Zr0.4Y0.2O3-δ (BSCF-BCZY) electrode under steam electrolysis conditions was studied in detail. The composite oxygen electrode supported by BCZY electrolyzer has been assessed as a function of temperature (T), water vapor partial pressures (pH2O), and bias polarization voltage for electrodes of comparable microstructure. The Electrochemical impedance spectra show two depressed arcs in general without bias polarization. And the electrode resistance became smaller with the increase of the bias polarization under the same water vapor partial pressures. The total resistance of the electrode was shown to be significantly affected by temperature, with the same level of pH2O and bias polarization voltage. This result highlights BSCF-BCZY as an effective oxygen electrode under moderate polarization and pH2O conditions.

  14. Long life lithium batteries with stabilized electrodes

    Science.gov (United States)

    Amine, Khalil [Downers Grove, IL; Liu, Jun [Naperville, IL; Vissers, Donald R [Naperville, IL; Lu, Wenquan [Darien, IL

    2009-03-24

    The present invention relates to non-aqueous electrolytes having electrode stabilizing additives, stabilized electrodes, and electrochemical devices containing the same. Thus the present invention provides electrolytes containing an alkali metal salt, a polar aprotic solvent, and an electrode stabilizing additive. In some embodiments the additives include a substituted or unsubstituted cyclic or spirocyclic hydrocarbon containing at least one oxygen atom and at least one alkenyl or alkynyl group. When used in electrochemical devices with, e.g., lithium manganese oxide spinel electrodes or olivine or carbon-coated olivine electrodes, the new electrolytes provide batteries with improved calendar and cycle life.

  15. Development and Study of Tantalum and Niobium Carbides as Electrocatalyst Supports for the Oxygen Electrode for PEM Water Electrolysis at Elevated Temperatures

    DEFF Research Database (Denmark)

    Nikiforov, Aleksey; Petrushina, Irina; Prag, Carsten Brorson

    2013-01-01

    . Resistance to oxidation of the TaC and NbC was investigated by exposing them to air at 84 and 150 °C. Subsequently, their electrical conductivity was measured as the indicator of oxidation. Change in specific surface area and conductivity was measured after different periods of ball milling. We found...... that the TaC was significantly more resistant to oxidation than the NbC. Eventually, both materials retained relatively high electrical conductivity even with the oxidized surface. TaC can thus be recommended as an electrocatalyst support for the oxygen evolution reaction and both materials are proposed...

  16. Electrochemical reduction of imazamethabenz methyl on mercury and carbon electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Ruiz Montoya, Mercedes, E-mail: mmontoya@uhu.e [Departamento de Ingenieria Quimica, Quimica Fisica y Quimica Organica, Universidad de Huelva, Campus El Carmen, Facultad de Ciencias Experimentales, E-21071 Huelva (Spain); Pintado, Sara; Rodriguez Mellado, Jose Miguel [Departamento de Quimica Fisica y Termodinamica Aplicada, Universidad de Cordoba, Campus Universitario de Rabanales, edificio ' Marie Curie' , E-14014 Cordoba (Spain)

    2010-03-30

    This paper presents polarographic and voltammetric studies of the reduction of the herbicide imazamethabenz methyl (2/3-methyl-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-p-toluate), on mercury and carbon electrodes. The electrochemical studies were performed in strongly acidic media (0.1-2.7 M H{sub 2}SO{sub 4}) as well as in the pH range of 1-12. The overall reduction process involves the uptake of two electrons. The results obtained in polarography show that there is the reduction of two species, related via an acid-base equilibrium, and having very close reduction potentials. The voltammetric results obtained with a glassy carbon electrode were very similar to those observed on mercury electrodes. The reducible group in the molecule is the imidazolinone ring. In strongly acidic media (pH < pK{sub a}), the reaction mechanism proposed is the reduction of the protonated herbicide by an electrochemical-chemical-electrochemical (ECE) process, being the r.d.s. the second electron transfer. At pH > pK{sub a} the neutral form of the herbicide is reduced and the second electron transfer becomes reversible or quasi-reversible. In basic media, the species reduced is the deprotonated imazamethabenz methyl and the r.d.s. is the second electron transfer.

  17. Oxygen tension in transplanted mouse osteosarcomas during fractionated high-LET- and low-LET radiotherapy - predictive aspects for choosing beam quality?

    International Nuclear Information System (INIS)

    Auberger, T.; Thuerriegel, B.; Freude, T.; Weissfloch, L.; Kneschaurek, P.; Molls, M.; Senekowitsch-Schmidtke, R.; Wagner, F.M.

    1999-01-01

    Murine OTS64 - osteosarcomas were tranplanted in 102 balb-C mice and irradiated by 36 Gy of photons in fractions of 3 Gy five times a week (group P-36/3) or by 12 Gy of reactor fission neutrons in fractions of 2 Gy two times a week (group N-12/2). Irradiations started at a tumor volume of 500 to 600 mm 3 . A third group received no radiotherapy, but all investigations (group CG). Tumor volume and tumor oxygenation were measured once a week under therapy and during three weeks after therapy. For in vivo-evaluation of oxygen status a computerized polarographic needle electrode system (KIMOC pO 2 histograph, Eppendorf) was used. The median pO 2 and the hypoxic fraction (pO 2 values 2 decreased from 20 mm to 8 mm Hg and the hypoxic fraction increased from 7% to 31%. After fractionated photon therapy a growth delay of three weeks was observed. Six weeks after beginning of the irradiation the median tumor volume had been doubled again. After fission neutron therapy growth delay continued until the end of the follow-up period. In both of the irradiated groups a significant decrease of median pO 2 values and an increase of the hypoxic fraction were observed under radiotherapy. Hypoxia was more intensive after neutrons with a decrease of the median pO 2 from 20 mm Hg to 1 mm Hg vs. 10 mm Hg after photon therapy and with an increase of the hypoxic fraction from 7% to 78% vs. 36% respectively. Two weeks after the end of therapy the median pO 2 and the hypoxic fraction of both treated groups reached the levels prior to irradiation indicating a complete reoxygenation. (orig.)

  18. Activated carbon from orange peels as supercapacitor electrode and catalyst support for oxygen reduction reaction in proton exchange membrane fuel cell

    Directory of Open Access Journals (Sweden)

    M. Dhelipan

    2017-05-01

    Full Text Available Activated carbon is synthesized using orange peel as precursor through chemical activation using H3PO4 and its ability as electrocatalyst support for ORR reaction is examined. The prepared material was subjected to various structural, compositional, morphological and electrochemical studies. For ORR activity, the platinum loaded on activated carbon (Pt/OP-AC was investigated by cyclic voltammograms (CVs recorded in N2 and O2 saturated 0.1 M aqueous HClO4. For supercapacitor performance, three electrode systems was tested in aqueous H2SO4 for feasibility determination and showed electrochemical double layer capacitance (EDLC behaviour which is expected for activated carbon like materials. Electrochemical surface area (ECSA of the activated carbon from orange peel is measured using CV. The physical properties of the prepared carbon are studied using SEM (scanning electron microscope, XRD (X-ray diffraction, Fourier transform infrared (FT-IR spectroscopy and Raman spectroscopy. The AC derived from orange peels delivered a high specific capacitance of 275 F g−1 at 10 mV s-1 scan rate. Hence, this study suggested that orange peels may be considered not only as a potential alternative source for synthesizing carbon supported catalyst for fuel cell application but also highlight the production of low-cost carbon for further applications like supercapacitors.

  19. Coatings of nanostructured pristine graphene-IrOx hybrids for neural electrodes: Layered stacking and the role of non-oxygenated graphene.

    Science.gov (United States)

    Pérez, E; Lichtenstein, M P; Suñol, C; Casañ-Pastor, N

    2015-10-01

    The need to enhance charge capacity in neural stimulation-electrodes is promoting the formation of new materials and coatings. Among all the possible types of graphene, pristine graphene prepared by graphite electrochemical exfoliation, is used in this work to form a new nanostructured IrOx-graphene hybrid (IrOx-eG). Graphene is stabilized in suspension by IrOx nanoparticles without surfactants. Anodic electrodeposition results in coatings with much smaller roughness than IrOx-graphene oxide. Exfoliated pristine graphene (eG), does not electrodeposit in absence of iridium, but IrOx-nanoparticle adhesion on graphene flakes drives the process. IrOx-eG has a significantly different electronic state than graphene oxide, and different coordination for carbon. Electron diffraction shows the reflection features expected for graphene. IrOx 1-2 nm cluster/nanoparticles are oxohydroxo-species and adhere to 10nm graphene platelets. eG induces charge storage capacity values five times larger than in pure IrOx, and if calculated per carbon atom, this enhancement is one order magnitude larger than the induced by graphene oxide. IrOx-eG coatings show optimal in vitro neural cell viability and function as cell culture substrates. The fully straightforward electrochemical exfoliation and electrodeposition constitutes a step towards the application of graphene in biomedical systems, expanding the knowledge of pristine graphene vs. graphene oxide, in bioelectrodes. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. La0.8Sr0.2Co0.8Ni0.2O3-δ impregnated oxygen electrode for H2O/CO2 co-electrolysis in solid oxide electrolysis cells

    Science.gov (United States)

    Zheng, Haoyu; Tian, Yunfeng; Zhang, Lingling; Chi, Bo; Pu, Jian; Jian, Li

    2018-04-01

    High-temperature H2O/CO2 co-electrolysis through reversible solid oxide electrolysis cell (SOEC) provides potentially a feasible and eco-friendly way to convert electrical energy into chemicals stored in syngas. In this work, La0.8Sr0.2Co0.8Ni0.2O3-δ (LSCN) impregnated Gd0.1Ce0.9O1.95 (GDC)-(La0.8Sr0.2)0.95MnO3-δ (LSM) composite oxygen electrode is studied as high-performance electrode for H2O/CO2 co-electrolysis. The LSCN impregnated cell exhibits competitive performance with the peak power density of 1057 mW cm-2 at 800 °C in solid oxide fuel cell (SOFC) mode; in co-electrolysis mode, the current density can reach 1.60 A cm-2 at 1.5 V at 800 °C with H2O/CO2 ratio of 2/1. With LSCN nanoparticles dispersed on the surface of GDC-LSM to maximize the reaction active sites, the LSCN impregnated cell shows significant enhanced electrochemical performance at both SOEC and SOFC modes. The influence of feed gas composition (H2O-H2-CO2) and operating voltages on the performance of co-electrolysis are discussed in detail. The cell shows a very stable performance without obvious degradation for more than 100 h. Post-test characterization is analyzed in detail by multiple measurements.

  1. Reação de geração de oxigênio em eletrodos de Mn2O3 suportados em aço inoxidável Oxygen evolution reaction on Mn2O3 electrodes supported on stainless steel

    Directory of Open Access Journals (Sweden)

    Hamilton Varela

    2000-12-01

    Full Text Available A study of the kinetics of oxygen evolution in alkaline conditions from ceramic films of Mn2O3 supported on stainless steel was carried out. This study has been done through the determination of transfer coefficients, Tafel slopes and exchange currents using potentiodynamic and quasi-potentiostatic measurements. The activation energy was determined as a function of the overpotential and, additionally, the electrode active surface was estimated. The results are consistent with data already published for other electrodes, implying that the methods used in this work were reliable and precise.

  2. Early diagenesis in the Congo deep-sea fan sediments dominated by massive terrigenous deposits: Part I - Oxygen consumption and organic carbon mineralization using a micro-electrode approach

    Science.gov (United States)

    Pozzato, Lara; Cathalot, Cécile; Berrached, Chabha; Toussaint, Flora; Stetten, Elsa; Caprais, Jean-Claude; Pastor, Lucie; Olu, Karine; Rabouille, Christophe

    2017-08-01

    Organic matter (OM) transfer from the continent to the ocean occurs across margins which constitute a major area of OM recycling and burial. The lobe complex of the Congo deep-sea fan is connected to the river mouth by a canyon and alimented by recurrent turbidity currents, containing a large proportion of labile terrigenous OM and producing high sedimentation rates. These inputs support the development of ecosystems harboring rich assemblages of vesicomyid bivalves and bacterial mats, called Habitats. Here, we present O2 microprofiles and diffusive oxygen uptake rates (DOUs) obtained during the CONGOLOBE project at six sites of this active lobe complex by in situ and on-board methods based on micro-electrode profiling. The dataset is used to determine remineralization rates and study the biogeochemical dynamics of different ecosystems of the lobe area, in order to compare levee and background sediments to the Habitats developed on the flanks of the main turbiditic channel. Levee and background sediments are characterized by significantly higher DOUs than abyssal sediments at 5000 m meters depth (2-5 mmol O2 m-2 d-1versus 1.5-2.5 mmol O2 m-2 d-1) and the Habitats are hotspots of OM remineralization with DOU values ranging between 8 and 40 mmol O2 m-2 d-1. By comparing sites near the active channel to a site located 50 km away, we show that the lobe connection to the main turbiditic channel is vital to the dense benthic communities.

  3. Magnetohydrodynamic electrode

    International Nuclear Information System (INIS)

    1980-01-01

    The object of the invention is the provision of a material capable of withstanding a high-temperature, corrosive and erosive environment for use as a ceramic-metal composite electrode current collector in the channel of a magnetohydrodynamic generator. (U.K.)

  4. FUEL CELL ELECTRODES FOR ACID MEDIA

    Science.gov (United States)

    fuel cell electrodes for acid media. Activated carbon electrodes were prepared, wetproofed with paraffin or Teflon, and catalyzed with platinum. The wetproofing agent was applied by immersion or electrodeposition and the catalyst applied by chemical decomposition of H2P+Cl6 solutions. Half cell studies with hydrogen anodes and oxygen (air) cathodes showed that electrochemical performance is essentially the same for paraffin and Teflontreated electrodes; however, the life of the Teflon-treated electrodes under equal conditions of load is greater than that for

  5. Carbon aerogel electrodes for direct energy conversion

    Science.gov (United States)

    Mayer, Steven T.; Kaschmitter, James L.; Pekala, Richard W.

    1997-01-01

    A direct energy conversion device, such as a fuel cell, using carbon aerogel electrodes, wherein the carbon aerogel is loaded with a noble catalyst, such as platinum or rhodium and soaked with phosphoric acid, for example. A separator is located between the electrodes, which are placed in a cylinder having plate current collectors positioned adjacent the electrodes and connected to a power supply, and a pair of gas manifolds, containing hydrogen and oxygen positioned adjacent the current collectors. Due to the high surface area and excellent electrical conductivity of carbon aerogels, the problems relative to high polarization resistance of carbon composite electrodes conventionally used in fuel cells are overcome.

  6. Perovskite electrodes and method of making the same

    Science.gov (United States)

    Seabaugh, Matthew M.; Swartz, Scott L.

    2005-09-20

    The invention relates to perovskite oxide electrode materials in which one or more of the elements Mg, Ni, Cu, and Zn are present as minority components that enhance electrochemical performance, as well as electrode products with these compositions and methods of making the electrode materials. Such electrodes are useful in electrochemical system applications such as solid oxide fuel cells, ceramic oxygen generation systems, gas sensors, ceramic membrane reactors, and ceramic electrochemical gas separation systems.

  7. Catalytic polarographic currents of platinum metal complexes and their application to determination of trace concentrations of the elements

    International Nuclear Information System (INIS)

    Ezerskaya, N.A.; Kiseleva, I.N.

    1984-01-01

    Several types of catalytic electrode processes with the participation of platinum metal complexes and used for the determination of the element microconcentrations have been considered in the review. It is pointed out that to measure catalytic currents of hydrogen solutions nitroso compounds, which are prepared by heating chloride complexes of Ru(3) and (4) with NaNO 2 are used. The method is applicable for ruthenium determination in commercial nitric acid solutions. Ru determination in solution of ruthenium (4) dimeric chloride complex on graphite electrode, using catalytic currents of hydrogen, surpasses in sensitivity the determination of the element, using the method of inversion voltammetry. Certain other complexes of Ru and determination methods of ruthenium in them are considered. Hydrogen catalytic currents in the complexes solutions with organic ligands are the most perspective for analysis

  8. New Materials for Oxygen Reduction Electrodes

    DEFF Research Database (Denmark)

    Johansson, Tobias Peter

    indicated a 1:88 x 1:88 R30 degree structure compared to Pt(111). CO TPD measurements showed a distinct peak at 295 K and a general weaker bonding of CO (on the order of 120 K) compared to Pt(111). The ORR activity of the annealed Y/Pt(111) was measured to be comparable to that of sputter cleaned bulk...... polycrystalline Pt3Y. The angle resolved x-ray photoelectron spectroscopy (ARXPS) depth profile after the electrochemical measurements showed the formation of a thick Pt overlayer. Finally, the possible changes in the surface morphology of Pt nanoparticles by annealing in high pressures of CO was correlated...... with measurements done on a sputtered Pt(111) crystal. For the Pt(111), crystal high pressures of CO was seen to enhance the annealing of the defect sites, whereas for nanoparticles a slight roughening was observed....

  9. Cobalt Phthalocyanine Modified Electrodes Utilised in Electroanalysis: Nano-Structured Modified Electrodes vs. Bulk Modified Screen-Printed Electrodes

    Science.gov (United States)

    Foster, Christopher W.; Pillay, Jeseelan; Metters, Jonathan P.; Banks, Craig E.

    2014-01-01

    Cobalt phthalocyanine (CoPC) compounds have been reported to provide electrocatalytic performances towards a substantial number of analytes. In these configurations, electrodes are typically constructed via drop casting the CoPC onto a supporting electrode substrate, while in other cases the CoPC complex is incorporated within the ink of a screen-printed sensor, providing a one-shot economical and disposable electrode configuration. In this paper we critically compare CoPC modified electrodes prepared by drop casting CoPC nanoparticles (nano-CoPC) onto a range of carbon based electrode substrates with that of CoPC bulk modified screen-printed electrodes in the sensing of the model analytes l-ascorbic acid, oxygen and hydrazine. It is found that no “electrocatalysis” is observed towards l-ascorbic acid using either of these CoPC modified electrode configurations and that the bare underlying carbon electrode is the origin of the obtained voltammetric signal, which gives rise to useful electroanalytical signatures, providing new insights into literature reports where “electrocatalysis” has been reported with no clear control experiments undertaken. On the other hand true electrocatalysis is observed towards hydrazine, where no such voltammetric features are witnessed on the bare underlying electrode substrate. PMID:25414969

  10. Cobalt phthalocyanine modified electrodes utilised in electroanalysis: nano-structured modified electrodes vs. bulk modified screen-printed electrodes.

    Science.gov (United States)

    Foster, Christopher W; Pillay, Jeseelan; Metters, Jonathan P; Banks, Craig E

    2014-11-19

    Cobalt phthalocyanine (CoPC) compounds have been reported to provide electrocatalytic performances towards a substantial number of analytes. In these configurations, electrodes are typically constructed via drop casting the CoPC onto a supporting electrode substrate, while in other cases the CoPC complex is incorporated within the ink of a screen-printed sensor, providing a one-shot economical and disposable electrode configuration. In this paper we critically compare CoPC modified electrodes prepared by drop casting CoPC nanoparticles (nano-CoPC) onto a range of carbon based electrode substrates with that of CoPC bulk modified screen-printed electrodes in the sensing of the model analytes L-ascorbic acid, oxygen and hydrazine. It is found that no "electrocatalysis" is observed towards L-ascorbic acid using either of these CoPC modified electrode configurations and that the bare underlying carbon electrode is the origin of the obtained voltammetric signal, which gives rise to useful electroanalytical signatures, providing new insights into literature reports where "electrocatalysis" has been reported with no clear control experiments undertaken. On the other hand true electrocatalysis is observed towards hydrazine, where no such voltammetric features are witnessed on the bare underlying electrode substrate.

  11. Cobalt Phthalocyanine Modified Electrodes Utilised in Electroanalysis: Nano-Structured Modified Electrodes vs. Bulk Modified Screen-Printed Electrodes

    Directory of Open Access Journals (Sweden)

    Christopher W. Foster

    2014-11-01

    Full Text Available Cobalt phthalocyanine (CoPC compounds have been reported to provide electrocatalytic performances towards a substantial number of analytes. In these configurations, electrodes are typically constructed via drop casting the CoPC onto a supporting electrode substrate, while in other cases the CoPC complex is incorporated within the ink of a screen-printed sensor, providing a one-shot economical and disposable electrode configuration. In this paper we critically compare CoPC modified electrodes prepared by drop casting CoPC nanoparticles (nano-CoPC onto a range of carbon based electrode substrates with that of CoPC bulk modified screen-printed electrodes in the sensing of the model analytes L-ascorbic acid, oxygen and hydrazine. It is found that no “electrocatalysis” is observed towards L-ascorbic acid using either of these CoPC modified electrode configurations and that the bare underlying carbon electrode is the origin of the obtained voltammetric signal, which gives rise to useful electroanalytical signatures, providing new insights into literature reports where “electrocatalysis” has been reported with no clear control experiments undertaken. On the other hand true electrocatalysis is observed towards hydrazine, where no such voltammetric features are witnessed on the bare underlying electrode substrate.

  12. Low resistance electrode construction

    Science.gov (United States)

    Redey, Laszlo; Karell, Eric J.

    2002-01-01

    An electrochemical cell having a cathode and an anode in contact with an electrolyte. Both electrodes or one of them has an electrically conducting non-metal receptacle defining a chamber with a first metal having a melting point in the range of from about room temperature to about 800.degree. C. inside said receptacle chamber. A second metal with a melting point greater than about 800.degree. C. is in contact with the first metal inside the receptacle chamber and extends outside of the receptacle chamber to form a terminal for the anode. The electrolyte may include the oxides, halides or mixtures thereof of one or more of Li, V, U, Al and the lanthanides. Metal may be produced at the cathode during operation of the cell and oxygen or chlorine at the anode.

  13. Differential pulse polarographic determination of trace antimony in standard biological samples after preconcentration using 2-nitroso-1-naphthol-4-sulfonic acid

    International Nuclear Information System (INIS)

    Taher, M. A.

    2003-01-01

    A highly selective, rapid and economical differential polarographic method has been developed for the determination of trace amounts of antimony in various standard alloys and biological samples after of its 2-naphthol-4 sulfonic acid tetradecyl dimethylbenzylammonium chloride on microcrystalline naphthalene in the ph range of 7.5-11.0. After filtration, the solid mass is shaken with 8-10 ml of 1 M hydrochloric acid (with preconcentration factor of 10) and antimony is determined by differential pulse polarography. Antimony can alternatively be quantitatively absorbed on 2-nitroso-1-naphthol-4-sulfonic acid tetradecyl dimethylbenzylammonium-naphthalene absorbed packed in a column (with preconcentration factor of 30) and determined similarly. In this case, 1.5 μg of antimony can be concentrated in a column from 300 ml of aqueous sample, where its concentration is as low as 5 ng/ml. Characterization of the electro active process included an examination of the degree of reversibility. The results show that the irreversibility of antimony. Various parameters such as the effect of ph, volume of aqueous phase, HCl concentration, reagent concentration, naphthalene concentration, shaking time and interference of a number of metal ions on the determination of antimony have been studied in detail to optimize the conditions for determination in standard alloys and standard biological samples

  14. Determination of Sn in 99{sup m}Tc Radiopharmaceutical Kits by Polarographic Methods; Determinacion de Estano en Radiofarmacos de 99{sup m}Tc mediante Metodos Polarograficos

    Energy Technology Data Exchange (ETDEWEB)

    Castro, M.; Cruz, J.; Sanchez, M.

    2009-07-01

    Kits of 99{sup m}Tc radiopharmaceuticals are used in nuclear medicine for diagnosis of different diseases. Sn (II) is one of the essential components in their formulations, which is used for reduction 99{sup m}Tc-pertechnetate in cold kits for on-site preparation 99{sup m}Tc-pertechnetate radiopharmaceuticals. Usually, these cold kits contain different additives (complexing agents, antioxidants, buffers, etc.) and the amount of Sn (II) varies from kit to kit. The determination of Sn in these products is essential in assessing their quality. We report here the development of a new polarographic method for the determination of Sn (II) and total Sn in representative radiopharmaceuticals kits (for the content of Sn and chemical composition) produced at the Center of Isotopes of Cuba (CENTIS). These methods were validated by analysis of variance and recovery techniques. From the results of the validation, the characteristic functions of uncertainties and fits are considered for the established methods, which give the necessary evidences to demonstrate the usefulness of these methods according to the current trends in Analytical Chemistry. This work provides practical results of great importance for CENTIS. After the speciation of Sn in the MAG3 radiopharmaceuticals kit is inferred that the production process is affected by uncontrolled factors that influence in the product stability, which demonstrates the necessity for analytical tools for the characterization of products and processes. (Author) 57 refs.

  15. Performance of solid oxide electrolysis cells based on composite La{sub 0.8}Sr{sub 0.2}MnO{sub 3-{delta}} - yttria stabilized zirconia and Ba{sub 0.5}Sr{sub 0.5}Co{sub 0.8}Fe{sub 0.2}O{sub 3-{delta}} oxygen electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Kim-Lohsoontorn, P. [Department of Chemical Engineering, Mahidol University, Nakorn Pathom 73170 (Thailand); KI for Eco-Energy, Korea Advanced Institute of Science and Technology, Daejeon 305-701 (Korea); Brett, D.J.L. [Department of Chemical Engineering, University College London, WC1E 7JE (United Kingdom); Laosiripojana, N. [The Joint Graduate School of Energy and Environment, King Mongkut' s University of Technology Thonburi, Bangkok 10140 (Thailand); Kim, Y-M. [Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305-701 (Korea); Bae, J-M. [KI for Eco-Energy, Korea Advanced Institute of Science and Technology, Daejeon 305-701 (Korea); Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon 305-701 (Korea)

    2010-05-15

    The electrochemical performance of solid oxide electrolysis cells (SOECs) having barium strontium cobalt ferrite (Ba{sub 0.5}Sr{sub 0.5}Co{sub 0.8}Fe{sub 0.2}O{sub 3-{delta}}) and composite lanthanum strontium manganite-yttria stabilized zirconia (La{sub 0.8}Sr{sub 0.2}MnO{sub 3-{delta}}-YSZ) oxygen electrodes has been studied over a range of operating conditions. Increasing the operating temperature (973 K to 1173 K) significantly increased electrochemical performance and hydrogen generation efficiency for both systems. The presence of water in the hydrogen electrode was found to have a marked positive effect on the EIS response of solid oxide cell (SOC) under open circuit voltage (OCV). The difference in operation between electrolytic and galvanic modes was investigated. Cells having BSCF oxygen electrodes (Ni-YSZ/YSZ/BSCF) showed greater performance than LSM-YSZ-based cells (Ni-YSZ/YSZ/LSM-YSZ) over the range of temperatures, in both galvanic and electrolytic regimes of operation. The area specific resistance (ASR) of the LSM-YSZ-based cells remained unchanged when transitioning between electrolyser and fuel cell modes; however, the BSCF cells exhibited an overall increase in cell ASR of {proportional_to}2.5 times when entering electrolysis mode. Durability studies of cells in electrolysis mode were made over 20 h periods. Significant degradation of the BSCF cell was observed (0.02 V h{sup -1}) while the LSM-YSZ cell exhibited more stable performance under the same operating conditions (0.3 A cm{sup -2}, 1123 K, and H{sub 2}O/H{sub 2} = 70/30). Increasing the electrolysis current density accelerated performance degradation. Electrochemical impedance spectroscopy measurements and microstructure analysis were used to investigate the cause of performance degradation, with evidence emerging of microstructural change in the case of the BSCF electrode. (author)

  16. Graphene-based battery electrodes having continuous flow paths

    Science.gov (United States)

    Zhang, Jiguang; Xiao, Jie; Liu, Jun; Xu, Wu; Li, Xiaolin; Wang, Deyu

    2014-05-24

    Some batteries can exhibit greatly improved performance by utilizing electrodes having randomly arranged graphene nanosheets forming a network of channels defining continuous flow paths through the electrode. The network of channels can provide a diffusion pathway for the liquid electrolyte and/or for reactant gases. Metal-air batteries can benefit from such electrodes. In particular Li-air batteries show extremely high capacities, wherein the network of channels allow oxygen to diffuse through the electrode and mesopores in the electrode can store discharge products.

  17. Oxygen Therapy

    Science.gov (United States)

    ... best for you. Oxygen is usually delivered through nasal prongs (an oxygen cannula) or a face mask. Oxygen equipment can attach to other medical equipment such as CPAP machines and ventilators. Oxygen therapy can help you ...

  18. Compatibility of RuO2 electrodes with PZT ceramics

    Indian Academy of Sciences (India)

    Administrator

    zation fatigue after repeated switching cycles (Taylor et al 1995). The use of conducting oxides such as RuO2,. IrO2 and (La,Sr)CoO3 improves fatigue properties (Al- shareef et al 1995; Law et al 1999). Oxide electrodes inhibit fatigue primarily by acting as sinks for oxygen vacancies. However, these oxide electrodes are ...

  19. Flexible retinal electrode array

    Science.gov (United States)

    Okandan, Murat [Albuquerque, NM; Wessendorf, Kurt O [Albuquerque, NM; Christenson, Todd R [Albuquerque, NM

    2006-10-24

    An electrode array which has applications for neural stimulation and sensing. The electrode array can include a large number of electrodes each of which is flexibly attached to a common substrate using a plurality of springs to allow the electrodes to move independently. The electrode array can be formed from a combination of bulk and surface micromachining, with electrode tips that can include an electroplated metal (e.g. platinum, iridium, gold or titanium) or a metal oxide (e.g. iridium oxide) for biocompatibility. The electrode array can be used to form a part of a neural prosthesis, and is particularly well adapted for use in an implantable retinal prosthesis where the electrodes can be tailored to provide a uniform gentle contact pressure with optional sensing of this contact pressure at one or more of the electrodes.

  20. Micromachined electrode array

    Science.gov (United States)

    Okandan, Murat; Wessendorf, Kurt O.

    2007-12-11

    An electrode array is disclosed which has applications for neural stimulation and sensing. The electrode array, in certain embodiments, can include a plurality of electrodes each of which is flexibly attached to a common substrate using a plurality of springs to allow the electrodes to move independently. In other embodiments of the electrode array, the electrodes can be fixed to the substrate. The electrode array can be formed from a combination of bulk and surface micromachining, and can include electrode tips having an electroplated metal (e.g. platinum, iridium, gold or titanium) or a metal oxide (e.g. iridium oxide) for biocompatibility. The electrode array can be used to form a part of a neural prosthesis, and is particularly well adapted for use in an implantable retinal prosthesis.

  1. Oxygen delivery to the fish eye: root effect as crucial factor for elevated retinal PO2.

    Science.gov (United States)

    Waser, W; Heisler, N

    2005-11-01

    Although the retina has one of the highest metabolic rates among tissues, certain teleost fishes lack any vascular supply to this organ which, in combination with the overall thickness of the organ, results in extremely long diffusion distances. As the only way to compensate for these obstacles, oxygen partial pressure (PO2) in the eyes of such fish is elevated far above atmospheric values. Although not supported by any direct evidence, the enhancement of PO2 is considered to be related to the Root effect, the release upon acidification of Hb-bound O2 into physical dissolution, possibly supported by counter-current multiplication similar to the loop of Henle. The present study evaluates the magnitude of intraocular PO2 enhancement under tightly controlled physiological conditions, to directly confirm the involvement of the Root effect on intraocular PO2 in the retina of rainbow trout Oncorhynchus mykiss. Intraocular PO2 was determined with special polarographic microelectrodes inserted into the eye. PO2 profiles established in vivo by driving electrodes through the entire retina yielded average PO2 values between 10 mmHg (1.3 kPa) at the inner retinal surface and 382 mmHg (50.9 kPa) close to the outer retinal limit (Bruch's membrane). According to estimates on the basis of the diffusion distances determined from sections of the retina (approximately 436 microm at the site of PO2 measurement) and literature data on specific oxygen consumption, the in vivo determined values would be sufficient to cover the oxygen demand of the retina with some safety margin. For a clear and direct in-tissue-test as to the involvement of the Root effect, an isolated in vitro eye preparation was established in order to avoid the problem of indirect blood supply to the eye from the dorsal aorta only via the pseudobranch, a hemibranch thought to modulate blood composition before entry of the eye. Any humoral effects (e.g. catecholamines) were eliminated by perfusing isolated eyes

  2. Discrepancies between measured changes of radiobiological hypoxic fraction and oxygen tension monitoring using two assay systems

    International Nuclear Information System (INIS)

    Sasai, K.; Brown, J.M.

    1994-01-01

    This study was conducted to assess the ability of computerized pO 2 histography to measure changes in tumor oxygenation produced by low oxygen breathing. Female syngeneic C3H/Km mice bearing SCC VII/St carcinomas were used in these experiments. Changes in tumor oxygenation produced by the mice breathing 10% oxygen were assessed with computerized pO2 histography, 3 H-misonidazole binding, and the paired survival curve assay of radiosensitivity. The hypoxic cell fraction of the tumors in mice breathing 10% oxygen was 3.1 times higher than that of tumors in mice breathing normal air determined by an in vivo-in vitro clonogenic assay. Binding of radiolabeled misonidazole to the tumors in mice breathing 10% oxygen was also significantly higher than that to tumors in mice breathing normal air (p 2 value for the tumor. The number of pO 2 readings lower than 5 mmHg in the tumor was not affected by the 10% oxygen breathing. These findings indicate that increases in radiobiological hypoxic fraction produced by lower blood oxygen levels may not correlate well with the results of polarographic measurements of tumor pO 2 levels. 29 refs., 4 figs., 1 tab

  3. FUEL CELL ELECTRODE MATERIALS

    Science.gov (United States)

    FUEL CELL ELECTRODE MATERIALS. RAW MATERIAL SELECTION INFLUENCES POLARIZATION BUT IS NOT A SINGLE CONTROLLING FACTOR. AVAILABLE...DATA INDICATES THAT AN INTERRELATIONSHIP OF POROSITY, AVERAGE PORE VOLUME, AND PERMEABILITY CONTRIBUTES TO ELECTRODE FUEL CELL BEHAVIOR.

  4. A Simple Hydrogen Electrode

    Science.gov (United States)

    Eggen, Per-Odd

    2009-01-01

    This article describes the construction of an inexpensive, robust, and simple hydrogen electrode, as well as the use of this electrode to measure "standard" potentials. In the experiment described here the students can measure the reduction potentials of metal-metal ion pairs directly, without using a secondary reference electrode. Measurements…

  5. The Composite Insertion Electrode

    DEFF Research Database (Denmark)

    Atlung, Sven; Zachau-Christiansen, Birgit; West, Keld

    1984-01-01

    The specific energy obtainable by discharge of porous insertion electrodes is limited by electrolyte depletion in thepores. This can be overcome using a solid ion conductor as electrolyte. The term "composite" is used to distinguishthese electrodes from porous electrodes with liquid electrolyte...

  6. Oxygen transport and transfer properties of erbia-stabilized bismuth oxide

    NARCIS (Netherlands)

    Vinke, I.C.; Bakiewicz, J.L.; Boukamp, Bernard A.; de Vries, K.J.; Burggraaf, A.J.

    1990-01-01

    The electrode resistances of solid solutions of 75 mol% Bi2O3−25 mol% Er2O3 with sputtered and with copressed gold gauze electrodes were compared. In contrast with literature no enhancement of the electrode process could be observed for the copressed electrodes. The measurements show an oxygen

  7. Electrode reaction mechanisms in molten carbonate fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Selman, J.R.; Nishina, T.; Lin, Y.P.; Yeager, E.B.; Tryk, D.A.

    1989-07-01

    This report describes the results of a joint research effort at Illinois Institute of Technology (IIT) and Case Western Reserve University (CWRU) to elucidate the reaction mechanism of oxygen reduction at the cathode of the molten carbonate fuel cell (MCFC). This research project was aimed at developing novel experimental approaches to the chemistry and electrode kinetics of oxygen reduction under MCFC conditions, and improving our fundamental understanding of the reaction mechanism as it applies to the MCFC. IIT's contribution was focused on developing and using rotating electrodes with well-defined mass-transfer properties, to characterize the electrode kinetics of oxygen reduction in molten carbonate. CWRU's contribution was focused on developing and using micro-electrodes for the same purpose, and also on developing spectroscopic cells and carrying out various types of spectroscopic measurements to characterize the oxygen species in molten carbonate under MCFC conditions. This report is divided into two main parts. Part 1 provides the technical background of the questions concerning oxygen reduction in molten carbonate as they apply to the MCFC system. The methodological approach and the objectives of the research are also presented. The second part describes the development of the rotating electrodes, micro-electrodes and spectroscopic cells and the results of measurements, as well as the interpretation of the data. Conclusions of this project, including some recommendations for further research, are also given in this part. 111 refs., 69 figs., 7 tabs.

  8. Mn valence state and electrode performance of perovskite-type ...

    Indian Academy of Sciences (India)

    increase in the oxidation state of Mn ions was due to the formation of Mn4+ ions and oxygen vacancies. The addition of Cu ions to LSM systems could lead to enhanced electrode performance for oxygen reduction reactions originating from the change in valence of Mn ions. Keywords. Cu-doped LSM; electrical conductivity; ...

  9. Oxygen-induced doping on reduced PEDOT.

    Science.gov (United States)

    Mitraka, E; Jafari, M J; Vagin, M; Liu, X; Fahlman, M; Ederth, T; Berggren, M; Jonsson, M P; Crispin, X

    2017-03-07

    The conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) has shown promise as air electrode in renewable energy technologies like metal-air batteries and fuel cells. PEDOT is based on atomic elements of high abundance and is synthesized at low temperature from solution. The mechanism of oxygen reduction reaction (ORR) over chemically polymerized PEDOT:Cl still remains controversial with eventual role of transition metal impurities. However, regardless of the mechanistic route, we here demonstrate yet another key active role of PEDOT in the ORR mechanism. Our study demonstrates the decoupling of conductivity (intrinsic property) from electrocatalysis (as an extrinsic phenomenon) yielding the evidence of doping of the polymer by oxygen during ORR. Hence, the PEDOT electrode is electrochemically reduced (undoped) in the voltage range of ORR regime, but O 2 keeps it conducting; ensuring PEDOT to act as an electrode for the ORR. The interaction of oxygen with the polymer electrode is investigated with a battery of spectroscopic techniques.

  10. Oxygen consumption of Callianassa kraussi Stebbing ...

    African Journals Online (AJOL)

    Oxygen consumption experiments were performed on the thalassinid prawn, Callianassa kraussi Stabbing, using an open flow system coupled to a Radiometer electrode and a continuous recorder. The effect of starvation, sex, body size, salinity, temperature, seasons and reduced oxygen tensions on the respiratory rates of ...

  11. Response behaviour of oxygen sensing solid electrolytes

    NARCIS (Netherlands)

    Winnubst, Aloysius J.A.; Scharenborg, A.H.A.; Burggraaf, A.J.

    1985-01-01

    The response time (t r) after a step change in oxygen partial pressure was investigated for some solid electrolytes used in Nernst type oxygen sensors. The electrolyte as well as the (porous) electrode material affect the value oft r. Stabilized Bi2O3 materials exhibit slower response rates (largert

  12. Methods and systems for in-situ electroplating of electrodes

    Science.gov (United States)

    Zappi, Guillermo Daniel; Zarnoch, Kenneth Paul; Huntley, Christian Andrew; Swalla, Dana Ray

    2015-06-02

    The present techniques provide electrochemical devices having enhanced electrodes with surfaces that facilitate operation, such as by formation of a porous nickel layer on an operative surface, particularly of the cathode. The porous metal layer increases the surface area of the electrode, which may result in increasing the efficiency of the electrochemical devices. The formation of the porous metal layer is performed in situ, that is, after the assembly of the electrodes into an electrochemical device. The in situ process offers a number of advantages, including the ability to protect the porous metal layer on the electrode surface from damage during assembly of the electrochemical device. The enhanced electrode and the method for its processing may be used in any number of electrochemical devices, and is particularly well suited for electrodes in an electrolyzer useful for splitting water into hydrogen and oxygen.

  13. Oxygen evolution on nanocrystalline RuO2 and Ru0.9Ni0.1O2−δ electrodes – DEMS approach to reaction mechanism determination

    Czech Academy of Sciences Publication Activity Database

    Macounová, Kateřina; Makarova, Marina; Krtil, Petr

    2009-01-01

    Roč. 11, č. 10 (2009), s. 1865-1868 ISSN 1388-2481 R&D Projects: GA AV ČR KAN100400702; GA AV ČR IAA400400906 Institutional research plan: CEZ:AV0Z40400503 Keywords : oxygen evolution * DEMS * ruthenium dioxide * electrocatalysis Subject RIV: CG - Electrochemistry Impact factor: 4.243, year: 2009

  14. Reversible operation of microtubular solid oxide cells using La0.6Sr0.4Co0.2Fe0.8O3-δ-Ce0.9Gd0.1O2-δ oxygen electrodes

    Science.gov (United States)

    López-Robledo, M. J.; Laguna-Bercero, M. A.; Larrea, A.; Orera, V. M.

    2018-02-01

    Yttria stabilized zirconia (YSZ) based microtubular solid oxide fuel cells (mT-SOFCs) using La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) and Ce0.9Gd0.1O2-δ (GDC) as the oxygen electrode, along with a porous GDC electrolyte-electrode barrier layer, were fabricated and characterized in both fuel cell (SOFC) and electrolysis (SOEC) operation modes. The cells were anode-supported, the NiO-YSZ microtubular supports being made by Powder Extrusion Moulding (PEM). The cells showed power densities of 695 mW cm-2 at 800 °C and 0.7 V in SOFC mode, and of 845 mA cm-2 at 800 °C and 1.3 V in SOEC mode. AC impedance experiments performed under different potential loads demonstrated the reversibility of the cells. These results showed that these cells, prepared with a method suitable for using on an industrial scale, are highly reproducible and reliable, as well as very competitive as reversible SOFC-SOEC devices operating at intermediate temperatures.

  15. DC Polarographic and Plane Polarographic investigation of the ...

    African Journals Online (AJOL)

    The reduction behavior Thallium (I) at DME has been studied by several authors with different equivalent circuits and arrived at varying results. The complexity is due to the rapid reduction process and the adsorption behavior in the mercury solution interface. So, a thorough investigation was carried out on the reduction ...

  16. DC Polarographic and Plane Polarographic investigation of the ...

    African Journals Online (AJOL)

    Bheema

    com). ABSTRACT. The reduction behavior Thallium (I) at DME has been ... In all the systems, Thallium (I) proceeds with high degree of reversibility and the values ... Later they investigated the problem with Laitinen and reported a value for.

  17. Limitations of potentiometric oxygen sensors operating at low oxygen levels

    DEFF Research Database (Denmark)

    Lund, Anders; Jacobsen, Torben; Hansen, Karin Vels

    2011-01-01

    The electrochemical processes that limit the range of oxygen partial pressures in which potentiometric oxygen sensors can be used, were analysed using a theoretical and an experimental approach. Electrochemical impedance spectroscopy was performed on porous Pt/yttria stabilised zirconia (YSZ......) electrodes between 10−6 and 0.2 bar and at temperatures between 500 and 950 °C. The flow of oxide ions and electron holes through a sensor cell, with a YSZ electrolyte, were calculated under similar conditions. The oxygen permeation of the sensor cell was insignificant at an oxygen partial pressure of 10......−6 bar for an inlet flow rate higher than 2 L h−1 between 600 and 800 °C. The polarisation resistance measured between 10−6 and 10−4 bar was found to be inversely proportional to the oxygen partial pressure, nearly temperature independent and inversely proportional to the inlet gas flow rate, which shows...

  18. Determination of dissolved oxygen in saline waters applying mathematical methods and as a membrane electrode sensor; Determinacion de oxigeno disuelto en aguas salinas aplicando modelos matematicos y como sensor electrodo de membrana

    Energy Technology Data Exchange (ETDEWEB)

    Mayari, R.; Espinosa, M. C.; Ruiz, M. [Centro Nacional de Investigaciones Ceintificas. La Habana (Cuba); Romero, E. [Universidad de Huelva (Spain)

    2000-07-01

    This work shows as specific methodology for the determination of dissolved oxygen in saline waters that allows to consider the variations of temperature and of concentration of salts. Both factors influence the solubility of the gases in water, making possible in place measurements, in bodies of water with content of salts unto of the concentration of sea water, with greater dependability. The mathematical models obtained are shown, the errors due to equipment, as well as the results obtained when applying this methodology in saline waters with diverse levels of contamination this allows to discern when the decrease of dissolved oxygen levels is due to an increase in the salinity or to an increase in the contamination of the water body. (Author) 7 refs.

  19. Handbook of reference electrodes

    CERN Document Server

    Inzelt, György; Scholz, Fritz

    2013-01-01

    Reference Electrodes are a crucial part of any electrochemical system, yet an up-to-date and comprehensive handbook is long overdue. Here, an experienced team of electrochemists provides an in-depth source of information and data for the proper choice and construction of reference electrodes. This includes all kinds of applications such as aqueous and non-aqueous solutions, ionic liquids, glass melts, solid electrolyte systems, and membrane electrodes. Advanced technologies such as miniaturized, conducting-polymer-based, screen-printed or disposable reference electrodes are also covered. Essen

  20. A study of oxygen transport in mixed conducting oxides using isotopic exchange and conductivity relaxation

    NARCIS (Netherlands)

    den Otter, M.W.

    2000-01-01

    Mixed conducting oxygen ion conductors can be applied as membranes for the separation of oxygen from air, as electrodes for both oxygen pumps and solid oxide fuel cells. In these applications, oxygen molecules dissociate on the surface of the material. The atomic oxygen species pick up two electrons

  1. Automatic measurement of the red cell oxygen dissociation curve identical with the whole blood curve.

    Science.gov (United States)

    Mawjood, A H; Imai, K

    1999-08-01

    Automatic measurement of the entire oxygen dissociation curve (ODC) of blood and hemoglobin provides a useful means for evaluating their gas-transport function. The automatic oxygenation apparatus previously developed by Imai et al. (1970, 1981), which uses a polarographic determination of partial pressure of oxygen and a spectrophotometric determination of oxygen saturation of hemoglobin, has mostly been used for the measurement of accurate ODCs of hemoglobin solution. However, it was not suitable for red cell suspension because a significant noise was superimposed on the absorbance signal due to light-scattering by red cells. In the present study, we have overcome this problem by using an integrating sphere for the photometric system. Through extensive tests we found the optimal experimental conditions for obtaining the red cell oxygenation data that were identical with the whole blood data with respect to the position (oxygen affinity) and shape (sigmoid character) of the ODC and its pH-dependence (the Bohr effect). The accuracy was higher than that of commercially available automatic apparatuses such as the "Hemox-Analyzer" (Technical Consulting Service) and "Hem-O-Scan" (Aminco). Thus, our method provides an easy and convenient means for obtaining accurate ODCs mimicking the whole blood ODCs from one drop of whole blood. An application of our method to the effect of blood storage on ODC is presented, demonstrating the usefulness of our method.

  2. Application of SIMS analyses on oxygen transport in SOFC materials

    International Nuclear Information System (INIS)

    Sakai, N.; Yamaji, K.; Horita, T.; Kishimoto, H.; Brito, M.E.; Yokokawa, H.; Uchimoto, Y.

    2006-01-01

    The oxygen transport was investigated for modelled interface of striped metal electrode on a solid oxide electrolyte by oxygen tracer exchange and three dimensional imaging techniques by using a secondary ion mass spectrometry (SIMS). The gold or platinum electrode on yttrium stabilized zirconia (YSZ) electrolyte were stable, and acted as a blocking layer of 18 O diffusion during the treatments in dry atmosphere at T = 873 K in p( 18 O 2 ) = 7 kPa. The oxygen flow via triple phase boundary was clearly observed for both electrodes. The treatment in humid atmosphere (T = 773 K, p( 18 O 2 ) = 7 kPa, p(H 2 18 O) = 2 kPa) raised the flux of oxygen diffusion through YSZ surface, however, it did not affect on the role of electrode on the oxygen transport properties

  3. Oxygen Therapy

    Science.gov (United States)

    ... oxygen at very high altitudes (like in the mountains or in an airplane) even if you do ... an arterial blood gas (ABG) measurement. The ABG measures your oxygen level directly from your blood and ...

  4. Temporal changes in tumor oxygenation and perfusion upon normo- and hyperbaric inspiratory hyperoxia

    Energy Technology Data Exchange (ETDEWEB)

    Thews, Oliver [University of Halle, Institute of Physiology, Halle (Saale) (Germany); Vaupel, Peter [University Medical Center Mainz, Department of Radiooncology and Radiotherapy, Tumor Pathophysiology Section, Mainz (Germany)

    2016-03-15

    Inspiratory hyperoxia under hyperbaric conditions has been shown to effectively reduce tumor hypoxia and to improve radiosensitivity. However, applying irradiation (RT) under hyperbaric conditions is technically difficult in the clinical setting since RT after decompression may be effective only if tumor pO{sub 2} remains elevated for a certain period of time. The aim of the present study was to analyze the time course of tumor oxygenation and perfusion during and after hyperbaric hyperoxia. Tumor oxygenation, red blood cell (RBC) flux for perfusion monitoring, and vascular resistance were assessed continuously in experimental rat DS-sarcomas by polarographic catheter electrodes and laser Doppler flowmetry at 1 and 2 atm (bar) of environmental pressure during breathing of pure O{sub 2} or carbogen (95 % O{sub 2} + 5 % CO{sub 2}). During room air breathing, the tumor pO{sub 2} followed very rapidly within a few minutes the change of the ambient pressure during compression or decompression. With O{sub 2} breathing under hyperbaric conditions, the tumor pO{sub 2} increased more than expected based on the rise of the environmental pressure, although the time course was comparably rapid. Breathing carbogen, the tumor pO{sub 2} followed with a slight delay of the pressure change, and within 10 min after decompression the baseline values were reached again. RBC flux increased during carbogen breathing but remained almost constant with pure O{sub 2}, indicating a vasodilation (decrease in vascular resistance) with carbogen but a vasoconstriction (increase in vascular resistance) with O{sub 2} during hyperbaric conditions. Since the tumor pO{sub 2} directly followed the environmental pressure, teletherapy after hyperbaric conditions does not seem to be promising as the pO{sub 2} reaches baseline values again within 5-10 min after decompression. (orig.) [German] Inspiratorische Hyperoxie unter hyperbaren Bedingungen reduziert sehr effektiv die Tumorhypoxie und erhoeht die

  5. Disposable biomedical electrode

    Science.gov (United States)

    Frost, J. D., Jr.; Hillman, C. E., Jr.

    1977-01-01

    Reusable recording cap equipped with compressible snap-on bioelectronic electrodes is worn by patient to allow remote monitoring of electroencephalogram and electro-oculogram waveforms. Electrodes can be attached to inside surface of stretch-textile cap at twelve monitoring positions and at one or two ground positions.

  6. Durable fuel electrode

    DEFF Research Database (Denmark)

    2017-01-01

    the composite. The invention also relates to the use of the composite as a fuel electrode, solid oxide fuel cell, and/or solid oxide electrolyser. The invention discloses a composite for an electrode, comprising a three-dimensional network of dispersed metal particles, stabilised zirconia particles and pores...

  7. Electrode Kinetics and Gas Conversion in Solid Oxide Cells

    DEFF Research Database (Denmark)

    Njodzefon, Jean-Claude

    that the kinetics at the fuel electrode were exactly the same in both reformates. This means that chemical equilibrium reactions were much faster than the electrochemical reactions. The electrode displayed slightly faster kinetics in hydrogen/steam fuel than in the reformate fuels. To minimize the influence of (i...... slower reaction kinetics under cathodic mode operation at 50 mV overvoltage than in anodic mode. The trend was opposite for the lower performing La0.58Sr0.4Co0.2Fe0.8O3 (LSCF) oxygen electrode. However, with decreasing oxygen partial pressure both electrodes displayed increasing asymmetry between anodic...... and cathodic modes. It could be shown that surface exchange kinetics were the major cause of the decreasing kinetics with decreasing pO2 and that the cathodic mode kinetics were slowed down much more than the anodic branch kinetics thus increasing the asymmetry. Independent of operation mode, commercialization...

  8. Kinetic and geometric aspects of solid oxide fuel cell electrodes

    DEFF Research Database (Denmark)

    Mogensen, Mogens Bjerg; Skaarup, Steen

    1996-01-01

    the size of the polarisation resistance greatly and may also change the rate limiting step for oxygen reduction as evidenced by the change in dependence on oxygen partial pressure and in the apparent activation energy. O-16/O-19 isotope exchange measurements have shown that oxygen surface exchange takes...... are is much more dependent on the structure than the low frequency arcs. In the case of LSM-YSZ composite it has been demonstrated that both the ratio of LSM to YSZ and the conductivity of the YSZ is of major importance. The length and the nature of the three-phase-boundary between LSM, YSZ and air influence...... place with significant rates on both electrodes and electrolyte types of materials. Results from pointed electrodes indicate that the electrochemical reaction occurs on both the solid electrolyte and the electrode materials but only in a narrow zone (few mu m) along the three-phase-boundary....

  9. Direct reform of graphite oxide electrodes by using ambient plasma for supercapacitor applications

    Science.gov (United States)

    Kim, Ho Jun; Jeong, Hae Kyung

    2017-10-01

    Ambient plasma is applied to graphite oxide electrodes directly to improve electrochemical properties for supercapacitor applications. Surface morphology of the electrodes after the plasma treatment changes dramatically and amount of oxygen reduced significantly, demonstrating a reduction effect on the graphite oxide electrode by the ambient plasma. Equivalent series resistance of the electrode also reduced from 108 Ω to 84 Ω after the plasma treatment. Corresponding specific capacitance, therefore, increases from 0.45 F cm-2 to 0.85 F cm-2, proving that the ambient plasma treatment is very efficient, clean, economic, and environment-friendly method to reform the graphite oxide electrodes directly for the supercapacitor applications.

  10. Metal | polypyrrole battery with the air regenerated positive electrode

    Science.gov (United States)

    Grgur, Branimir N.

    2014-12-01

    Recharge characteristics of the battery based on the electrochemically synthesized polypyrrole cathode and aluminum, zinc, or magnesium anode in 2 M NH4Cl are investigated. It is shown that polypyrrole electrode can be regenerated by the reoxidation with the dissolved oxygen from the air. Using the polypyrrole synthesized on high surface graphite-felt electrode under modest discharge conditions, stable discharge voltage of 1.1 V is obtained. Such behavior is explained by the complex interaction of polypyrrole and hydrogen peroxide produced by the oxygen reduction reaction. The electrochemical characteristics are compared with the zinc-manganese dioxide and zinc-air systems.

  11. Catalysts for electrochemical generation of oxygen

    Science.gov (United States)

    Hagans, P.; Yeager, E.

    1979-01-01

    Several aspects of the electrolytic evolution of oxygen for use in life support systems are analyzed including kinetic studies of various metal and nonmetal electrode materials, the formation of underpotential films on electrodes, and electrode surface morphology and the use of single crystal metals. In order to investigate the role of surface morphology to electrochemical reactions, a low energy electron diffraction and an Auger electron spectrometer are combined with an electrochemical thin-layer cell allowing initial characterization of the surface, reaction run, and then a comparative surface analysis.

  12. The contents of sesamol and related lignans in sesame, tahina and halva as determined by a newly developed polarographic and stripping voltammetric analysis

    Directory of Open Access Journals (Sweden)

    2009-06-01

    Full Text Available The contents of antioxidant lignans (Sesamol in sesame, commercial formulations of tahina and halva, which are processed tahina foods, were determined by Differential Pulse Polarography (DPP with a capillary hanging mercury drop electrode (HMDE. A platinum wire was used as the counter electrode and Ag/AgCl was the reference electrode. Samples have been analyzed by standard addition procedures and found to be quantitative (p2=0.9999 (pSe determinó el contenido del lignano antioxidante (Sesamol en sésamo, formulaciones comerciales de tahina y halva, que es el producto procesado de tahina, por polarografía de pulsos diferencial (DPP con un capilar conteniendo un electrodo de gota de mercurio (HMDE. Un hilo de platino fué usado como el electrodo contador y Ag/AgCl como electrodo de referencia. Las muestras fueron analizadas por procedimientos de adición de patrones y se encontró que wl procedimiento era cuantitativo (p2= 0.9999 (p< 0.01. El método polarográfico propuesto (DPP es un método rápido y reproducible para la determinación simultánea de lignanos fenólicos en sésamo y otros productos alimentarios que contienen sésamo. Éste proporciona una detección cuantitativa adecuada y sensible de este compuesto nutraceútico en alimentos comerciales.

  13. A Roadmap for Achieving Sustainable Energy Conversion and Storage: Graphene-Based Composites Used Both as an Electrocatalyst for Oxygen Reduction Reactions and an Electrode Material for a Supercapacitor

    Directory of Open Access Journals (Sweden)

    Peipei Huo

    2018-01-01

    Full Text Available Based on its unique features including 2D planar geometry, high specific surface area and electron conductivity, graphene has been intensively studied as oxygen reduction reaction (ORR electrocatalyst and supercapacitor material. On the one hand, graphene possesses standalone electrocatalytic activity. It can also provide a good support for combining with other materials to generate graphene-based electrocatalysts, where the catalyst-support structure improves the stability and performance of electrocatalysts for ORR. On the other hand, graphene itself and its derivatives demonstrate a promising electrochemical capability as supercapacitors including electric double-layer capacitors (EDLCs and pseudosupercapacitors. A hybrid supercapacitor (HS is underlined and the advantages are elaborated. Graphene endows many materials that are capable of faradaic redox reactions with an outstanding pseudocapacitance behavior. In addition, the characteristics of graphene-based composite are also utilized in many respects to provide a porous 3D structure, formulate a novel supercapacitor with innovative design, and construct a flexible and tailorable device. In this review, we will present an overview of the use of graphene-based composites for sustainable energy conversion and storage.

  14. Oxygen transport through soft contact lens and cornea: Lens characterization and metabolic modeling

    Science.gov (United States)

    Chhabra, Mahendra

    The human cornea requires oxygen to sustain metabolic processes critical for its normal functioning. Any restriction to corneal oxygen supply from the external environment (e.g., by wearing a low oxygen-permeability contact lens) can lead to hypoxia, which may cause corneal edema (swelling), limbal hyperemia, neovascularization, and corneal acidosis. The need for adequate oxygen to the cornea is a major driving force for research and development of hypertransmissible soft contact lenses (SCLs). Currently, there is no standard technique for measuring oxygen permeability (Dk) of hypertransmissible silicone-hydrogel SCLs. In this work, an electrochemistry-based polarographic apparatus was designed, built, and operated to measure oxygen permeability in hypertransmissible SCLs. Unlike conventional methods where a range of lens thickness is needed for determining oxygen permeabilities of SCLs, this apparatus requires only a single lens thickness. The single-lens permeameter provides a reliable, efficient, and economic tool for measuring oxygen permeabilities of commercial hypertransmissible SCLs. The single-lens permeameter measures not only the product Dk, but, following modification, it measures separately diffusivity, D, and solubility, k, of oxygen in hypertransmissible SCLs. These properties are critical for designing better lens materials that ensure sufficient oxygen supply to the cornea. Metabolism of oxygen in the cornea is influenced by contact-lens-induced hypoxia, diseases such as diabetes, surgery, and drug treatment, Thus, estimation of the in-vivo corneal oxygen consumption rate is essential for gauging adequate oxygen supply to the cornea. Therefore, we have developed an unsteady-state reactive-diffusion model for the cornea-contact-lens system to determine in-vivo human corneal oxygen-consumption rate. Finally, a metabolic model was developed to determine the relation between contact-lens oxygen transmissibility (Dk/L) and corneal oxygen deficiency. A

  15. Metal-air flow batteries using oxygen enriched electrolyte

    Science.gov (United States)

    Zheng, Jian-ping; Andrei, Petru; Shellikeri, Annadanesh; Chen, Xujie

    2017-08-01

    A metal air flow battery includes an electrochemical reaction unit and an oxygen exchange unit. The electrochemical reaction unit includes an anode electrode, a cathode electrode, and an ionic conductive membrane between the anode and the cathode, an anode electrolyte, and a cathode electrolyte. The oxygen exchange unit contacts the cathode electrolyte with oxygen separate from the electrochemical reaction unit. At least one pump is provided for pumping cathode electrolyte between the electrochemical reaction unit and the oxygen exchange unit. A method for producing an electrical current is also disclosed.

  16. Plastic-bonded electrodes for nickel-cadmium accumulators. Pt. 8

    Energy Technology Data Exchange (ETDEWEB)

    Mrha, J.; Musilova, M.; Jindra, J.; Polydorova, M.; Peizker, J.; Garche, J.; Hauptmann, M.

    1982-07-01

    The oxygen recombination (reduction) rate on plastic-bonded cadmium electrodes in sealed Ni-Cd systems can be controlled by the use of a catalytic mix consisting of active carbon and carbon black either in the pure state or mixed with PTFE. This catalytic mix is either rolled onto the gas side of the plastic-bonded cadmium electrode or added to the active material prior to the preparation of the electrode by a rolling technique. The highest oxygen recombination rate, which surpassed that obtained with commercial pocket-type electrodes, was obtained in both cases by the use of an active carbon, carbon black and PTFE catalytic mix. In this case an optimum three-phase boundary, well known from oxygen electrodes for fuel cells, was established.

  17. electrocatalytic reduction of oxygen at vapor phase polymerized poly ...

    African Journals Online (AJOL)

    Preferred Customer

    ABSTRACT. We successfully polymerized poly(3,4-ethylenedioxidethiophene) by vapor phase polymerization technique on rotating glassy carbon disk electrode. The catalytic activity of this electrode towards oxygen reduction reaction was investigated and showed remarkable activity. Rotating disk voltammetry was used to ...

  18. Electrocatalytic reduction of oxygen at vapor phase polymerized ...

    African Journals Online (AJOL)

    We successfully polymerized poly(3,4-ethylenedioxidethiophene) by vapor phase polymerization technique on rotating glassy carbon disk electrode. The catalytic activity of this electrode towards oxygen reduction reaction was investigated and showed remarkable activity. Rotating disk voltammetry was used to study the ...

  19. Erosion on spark plug electrodes; Funkenerosion an Zuendkerzenelektroden

    Energy Technology Data Exchange (ETDEWEB)

    Rager, J.

    2006-07-01

    Durability of spark plugs is mainly determined by spark gap widening, caused by electrode wear. Knowledge about the erosion mechanisms of spark plug materials is of fundamental interest for the development of materials with a high resistance against electrode erosion. It is therefore crucial to identify those parameters which significantly influence the erosion behaviour of a material. In this work, a reliable and reproducible testing method is presented which produces and characterizes electrode wear under well-defined conditions and which is capable of altering parameters specifically. Endurance tests were carried out to study the dependence of the wear behaviour of pure nickel and platinum on the electrode temperature, gas, electrode gap, electrode diameter, atmospheric pressure, and partial pressure of oxygen. It was shown that erosion under nitrogen is negligible, irrespective of the material. This disproves all common mechanism discussed in the literature explaining material loss of spark plug electrodes. Based on this observation and the variation of the mentioned parameters a new erosion model was deduced. This relies on an oxidation of the electrode material and describes the erosion of nickel and platinum separately. For nickel, electrode wear is caused by the removal of an oxide layer by the spark. In the case of platinum, material loss occurs due to the plasma-assisted formation and subsequent evaporation of volatile oxides in the cathode spot. On the basis of this mechanism a new composite material was developed whose erosion resistance is superior to pure platinum. Oxidation resistant metal oxide particles were added to a platinum matrix, thus leading to a higher erosion resistance of the composite. However, this can be decreased by a side reaction, the separation of oxygen from the metal oxides, which effectively assists the oxidation of the matrix. This reaction can be suppressed by using highly stable oxides, characterized by a large negative Gibbs

  20. Antibacterial validation of electrogenerated hypochlorite using carbon-based electrodes.

    Science.gov (United States)

    Locker, J; Fitzgerald, P; Sharp, D

    2014-12-01

    This proof-of-concept study explores the novel use of carbon-based electrodes for the electrochemical generation of hypochlorite and compares the antimicrobial efficacy against commercial hypochlorite solution. Antimicrobial concentrations of hypochlorite were generated using pad-printed carbon and carbon fibre electrodes, yielding up to 0·027% hypochlorite in 60 min and 0·1% hypochlorite in 15 min, respectively, in a nondivided assembly. The minimum inhibitory concentration (MIC) of the electrogenerated hypochlorite produced using carbon fibre electrodes was established for four medically important bacteria (Pseudomonas aeruginosa and Staphylococcus aureus approx. 0·025%, Escherichia coli and Enterococcus faecalis approx. 0·012%) and found to be in agreement with those determined using commercial hypochlorite solution. Therefore, carbon-based electrodes, particularly carbon fibre, have proven effective for the generation of antimicrobial concentrations of hypochlorite. The similarity of the MIC values to commercial hypochlorite solutions suggests that the antimicrobial efficacy is derived from the quantified hypochlorite generated and not due to marked cogeneration of reactive oxygen species, as identified for other assemblies. As such, the application of carbon electrodes may be suitable for the local production of hypochlorite for healthcare antisepsis. Carbon fibre electrodes can rapidly generate antimicrobial concentrations of hypochlorite; as such, these cheap and commercially available electrodes are proposed for the local production of hypochlorite for healthcare antisepsis. Importantly, the antimicrobial properties of the electrochemically generated hypochlorite mirror those of commercial hypochlorite, suggesting this is not enhanced by the cogeneration of reactive oxygen species. This illustrates the potential use of disposable carbon electrodes for localized small-volume production of hypochlorite for surface and skin cleansing, and opens a broader

  1. In-situ formed Ce0.8Gd0.2O1.9 barrier layers on yttria stabilized zirconia backbones by infiltration - A promising path to high performing oxygen electrodes of solid oxide cell

    DEFF Research Database (Denmark)

    Ovtar, Simona; Chen, Ming; Samson, Alfred Junio

    2017-01-01

    Oxygen electrodes for solid oxide cells were prepared by a consecutive infiltration of a gadolinium doped ceria (Ce0.8Gd0.2O1.9, CGO) barrier layer and a lanthanum cobalt nickelate (La0.95Co0.4Ni0.6O3, LCN) electro catalyst layer into a porous yttrium doped zirconia (YSZ) backbone. The influences...... of the following parameters on the microstructure of the formed CGO barrier layer and on the electrochemical performance of the cells were studied: i) surfactants and wetting agents, ii) ceria/gadolinia coverage, iii) calcination profiles and iv) exposure temperature during testing. The infiltration process...... performance and only a small increase of the cell-resistance with increasing exposure temperatures during testing were obtained. A complete and homogenous covering of the YSZ backbone with Ce0.8Gd0.2O1.9 was found to be necessary to maintain high performance also at higher exposure temperatures (> 800 °C)....

  2. Fabrication and electrochemical characterization of multi-walled carbon nanotube electrodes for applications to nano-electrochemical sensing

    International Nuclear Information System (INIS)

    Hwang, Sookhyun; Choi, Hyonkwang; Jeon, Minhyon; Vedala, Harindra; Kim, Taehyung; Choi, Wonbong

    2010-01-01

    In this study, we fabricated and electrochemically characterized two types of individual carbon nanotube electrodes: an as-produced multi-walled carbon nanotube (MWNT) electrode and a modified MWNT electrode. As-produced MWNTs were electrically contacted with Au/Ti layers by using nanolithography and RF magnetron sputtering. Open-ended modified MWNT electrodes were fabricated by using a reactive ion etching treatment under an oxygen atmosphere. We also performed cyclic voltammetry measurements to detect aqueous dopamine solutions with different concentrations. We found that an individual MWNT electrode, which had a small effective area, showed good electrochemical performance. The electrocatalytic behavior of the modified electrode, which had 'broken' open ends were better than that of the as-produced electrode with respect to sensitivity. The modified electrode was capable of detecting dopamine at the picomolar level. Therefore, an individual modified MWNT electrode has potential for applications to active components in nanobiosensors.

  3. Composite carbon foam electrode

    Science.gov (United States)

    Mayer, Steven T.; Pekala, Richard W.; Kaschmitter, James L.

    1997-01-01

    Carbon aerogels used as a binder for granularized materials, including other forms of carbon and metal additives, are cast onto carbon or metal fiber substrates to form composite carbon thin film sheets. The thin film sheets are utilized in electrochemical energy storage applications, such as electrochemical double layer capacitors (aerocapacitors), lithium based battery insertion electrodes, fuel cell electrodes, and electrocapacitive deionization electrodes. The composite carbon foam may be formed by prior known processes, but with the solid particles being added during the liquid phase of the process, i.e. prior to gelation. The other forms of carbon may include carbon microspheres, carbon powder, carbon aerogel powder or particles, graphite carbons. Metal and/or carbon fibers may be added for increased conductivity. The choice of materials and fibers will depend on the electrolyte used and the relative trade off of system resistivty and power to system energy.

  4. Ion-selective electrodes

    CERN Document Server

    Mikhelson, Konstantin N

    2013-01-01

    Ion-selective electrodes (ISEs) have a wide range of applications in clinical, environmental, food and pharmaceutical analysis as well as further uses in chemistry and life sciences. Based on his profound experience as a researcher in ISEs and a course instructor, the author summarizes current knowledge for advanced teaching and training purposes with a particular focus on ionophore-based ISEs. Coverage includes the basics of measuring with ISEs, essential membrane potential theory and a comprehensive overview of the various classes of ion-selective electrodes. The principles of constructing I

  5. Single Electrode Heat Effects

    DEFF Research Database (Denmark)

    Jacobsen, Torben; Broers, G. H. J.

    1977-01-01

    The heat evolution at a single irreversibly working electrode is treated onthe basis of the Brønsted heat principle. The resulting equation is analogous to the expression for the total heat evolution in a galvanic cellwith the exception that –DeltaS is substituted by the Peltier entropy, Delta......SP, of theelectrode reaction. eta is the overvoltage at the electrode. This equation is appliedto a high temperature carbonate fuel cell. It is shown that the Peltier entropyterm by far exceeds the heat production due to the irreversible losses, and thatthe main part of heat evolved at the cathode is reabsorbed...

  6. Aluminum reference electrode

    Science.gov (United States)

    Sadoway, Donald R.

    1988-01-01

    A stable reference electrode for use in monitoring and controlling the process of electrolytic reduction of a metal. In the case of Hall cell reduction of aluminum, the reference electrode comprises a pool of molten aluminum and a solution of molten cryolite, Na.sub.3 AlF.sub.6, wherein the electrical connection to the molten aluminum does not contact the highly corrosive molten salt solution. This is accomplished by altering the density of either the aluminum (decreasing the density) or the electrolyte (increasing the density) so that the aluminum floats on top of the molten salt solution.

  7. Electrical properties of textile electrodes.

    Science.gov (United States)

    Rattfalt, Linda; Chedid, Michel; Hult, Peter; Lindén, Maria; Ask, Per

    2007-01-01

    In this study we aim to explain the behavior of textile electrodes due to their construction techniques. Three textile electrodes were tested for electrode impedance and polarization potentials. The multifilament yarn (A) is favorable for its low thread resistance. Although, when knitted into electrodes, the staple fiber yarn (B) showed a comparable and satisfiable electrode impedance. The multifilament yarn had however a lower polarization potential drift then the other specimens. The monofilament yarn (C) had high electrode impedance and varying mean polarization potentials due to its conductive material and small contact area with the skin.

  8. Exploring single electrode reactions in polymer electrolyte fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Kuhn, H.; Wokaun, A.; Scherer, G.G. [Paul Scherrer Institute, Electrochemistry Laboratory, 5232 Villigen (Switzerland)

    2007-01-20

    Utilising a pseudo-reference electrode in polymer electrolyte fuel cells allows for the separation of anodic and cathodic contributions to the entire cell impedance. Modelling the impedance responses by using equivalent circuits inhibits the investigation of kinetic parameters of the basic electrochemical reactions, which take place at single electrode-electrolyte interfaces. Therefore, we evaluate single electrode impedance measurements by a kinetic model, which is based on specific reaction pathways, either for the oxygen reduction reaction (ORR) or the hydrogen oxidation reaction (HOR). As a consequence, it is possible to obtain kinetic parameters for the specific reaction of interest. Furthermore, the information gained from the single electrode impedance measurements and the kinetic model can give insight into single reactions steps. In particular, the ORR has to include a chemical step in the reaction pathway. (author)

  9. Electrode materials for microbial fuel cells: nanomaterial approach

    KAUST Repository

    Mustakeem, Mustakeem

    2015-11-05

    Microbial fuel cell (MFC) technology has the potential to become a major renewable energy resource by degrading organic pollutants in wastewater. The performance of MFC directly depends on the kinetics of the electrode reactions within the fuel cell, with the performance of the electrodes heavily influenced by the materials they are made from. A wide range of materials have been tested to improve the performance of MFCs. In the past decade, carbon-based nanomaterials have emerged as promising materials for both anode and cathode construction. Composite materials have also shown to have the potential to become materials of choice for electrode manufacture. Various transition metal oxides have been investigated as alternatives to conventional expensive metals like platinum for oxygen reduction reaction. In this review, different carbon-based nanomaterials and composite materials are discussed for their potential use as MFC electrodes.

  10. Dry EEG Electrodes

    Directory of Open Access Journals (Sweden)

    M. A. Lopez-Gordo

    2014-07-01

    Full Text Available Electroencephalography (EEG emerged in the second decade of the 20th century as a technique for recording the neurophysiological response. Since then, there has been little variation in the physical principles that sustain the signal acquisition probes, otherwise called electrodes. Currently, new advances in technology have brought new unexpected fields of applications apart from the clinical, for which new aspects such as usability and gel-free operation are first order priorities. Thanks to new advances in materials and integrated electronic systems technologies, a new generation of dry electrodes has been developed to fulfill the need. In this manuscript, we review current approaches to develop dry EEG electrodes for clinical and other applications, including information about measurement methods and evaluation reports. We conclude that, although a broad and non-homogeneous diversity of approaches has been evaluated without a consensus in procedures and methodology, their performances are not far from those obtained with wet electrodes, which are considered the gold standard, thus enabling the former to be a useful tool in a variety of novel applications.

  11. Electrochemistry on nanopillared electrodes

    Directory of Open Access Journals (Sweden)

    Chandni Lotwala

    2017-02-01

    Full Text Available The addition of nanopillars to electrodes increases their electrochemical capabilities through an increase in electroactive surface area. The nanopillars can be applied on either cathodes or anodes to engage in reduction-oxidation reactions. This minireview summaries some work on cyclic voltammetry, chronoamperometry, impedance change on nanopillared surface and compared their electrochemistry behavior on planar surfaces.

  12. The oxygen-binding properties of hemocyanin from the mollusk Concholepas concholepas.

    Science.gov (United States)

    González, Andrea; Nova, Esteban; Del Campo, Miguel; Manubens, Augusto; De Ioannes, Alfredo; Ferreira, Jorge; Becker, María Inés

    2017-12-01

    Hemocyanins have highly conserved copper-containing active sites that bind oxygen. However, structural differences among the hemocyanins of various mollusks may affect their physicochemical properties. Here, we studied the oxygen-binding cooperativity and affinity of Concholepas concholepas hemocyanin (CCH) and its two isolated subunits over a wide range of temperatures and pH values. Considering the differences in the quaternary structures of CCH and keyhole limpet hemocyanin (KLH), we hypothesized that the heterodidecameric CCH has different oxygen-binding parameters than the homodidecameric KLH. A novel modification of the polarographic method was applied in which rat liver submitochondrial particles containing cytochrome c oxidase were introduced to totally deplete oxygen of the test solution using ascorbate as the electron donor. This method was both sensitive and reproducible. The results showed that CCH, like other hemocyanins, exhibits cooperativity, showing an inverse relationship between the oxygen-binding parameters and temperature. According to their Hill coefficients, KLH has greater cooperativity than CCH at physiological pH; however, CCH is less sensitive to pH changes than KLH. Appreciable differences in binding behavior were found between the CCH subunits: the cooperativity of CCH-A was not only almost double that of CCH-B, but it was also slightly superior to that of CCH, thus suggesting that the oxygen-binding domains of the CCH subunits are different in their primary structure. Collectively, these data suggest that CCH-A is the main oxygen-binding domain in CCH; CCH-B may play a more structural role, perhaps utilizing its surprising predisposition to form tubular polymers, unlike CCH-A, as demonstrated here using electron microscopy. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Ion-selective electrode reviews

    CERN Document Server

    Thomas, J D R

    1985-01-01

    Ion-Selective Electrode Reviews, Volume 7 is a collection of papers that covers the applications of electrochemical sensors, along with the versatility of ion-selective electrodes. The coverage of the text includes solid contact in membrane ion-selective electrodes; immobilized enzyme probes for determining inhibitors; potentiometric titrations based on ion-pair formation; and application of ion-selective electrodes in soil science, kinetics, and kinetic analysis. The text will be of great use to chemists and chemical engineers.

  14. Characterization of dry biopotential electrodes.

    Science.gov (United States)

    Xie, Li; Yang, Geng; Xu, Linlin; Seoane, Fernando; Chen, Qiang; Zheng, Lirong

    2013-01-01

    Driven by the increased interest in wearable long-term healthcare monitoring systems, varieties of dry electrodes are proposed based on different materials with different patterns and structures. Most of the studies reported in the literature focus on proposing new electrodes and comparing its performance with commercial electrodes. Few papers are about detailed comparison among different dry electrodes. In this paper, printed metal-plate electrodes, textile based electrodes, and spiked electrodes are for the first time evaluated and compared under the same experimental setup. The contact impedance and noise characterization are measured. The in-vivo electrocardiogram (ECG) measurement is applied to evaluate the overall performance of different electrodes. Textile electrodes and printed electrodes gain comparable high-quality ECG signals. The ECG signal obtained by spiked electrodes is noisier. However, a clear ECG envelope can be observed and the signal quality can be easily improved by backend signal processing. The features of each type of electrodes are analyzed and the suitable application scenario is addressed.

  15. Zinc electrode in alkaline electrolyte

    Energy Technology Data Exchange (ETDEWEB)

    McBreen, J.

    1995-12-31

    The zinc electrode in alkaline electrolyte is unusual in that supersaturated zincate solutions can form during discharge and spongy or mossy zinc deposits can form on charge at low overvoltages. The effect of additives on regular pasted ZnO electrodes and calcium zincate electrodes is discussed. The paper also reports on in situ x-ray absorption (XAS) results on mossy zinc deposits.

  16. Determination of sulfite by pervaporation-flow injection with amperometric detection using copper hexacyanoferrate-carbon nanotube modified carbon paste electrode.

    Science.gov (United States)

    Alamo, Lori Shayne T; Tangkuaram, Tanin; Satienperakul, Sakchai

    2010-06-15

    A pervaporation-flow injection (PFI) method was developed for the determination of sulfite in selected food samples using a copper hexacyanoferrate-carbon nanotube (CuHCF-CNT)-modified carbon paste electrode. The electrochemical behavior of the modified electrode was observed using cyclic voltammetry in comparison to a CuHCF-modified carbon paste electrode and a bare carbon paste electrode at a scan rate of 100mVs(-1) in 0.10M KNO(3). The bare carbon paste electrode gave the lowest response to sulfite, while the presence of CuHCF made the detection of sulfite possible through electrocatalytic oxidation by the hexacyanoferrate in the modified electrodes. The presence of CNT in the CuHCF-CNT-modified sensor gave the most remarkable current for the detection of sulfite and was then used as a working electrode in the amperometric flow-through cell in the pervaporation flow injection system. The PFI method involves the injection of a standard or sample sulfite solution into a sulfuric acid donor stream to generate sulfur dioxide gas and evaporate into the headspace of the pervaporation unit. The sulfur dioxide diffuses through the PTFE hydrophobic membrane into a potassium nitrate acceptor stream and reverts to the sulfite form, which, subsequently, is transported to the electrochemical flow cell where it is analyzed amperometrically at a CuHCF-CNT-modified electrode at +0.55V (vs. Ag/AgCl). The detection was determined to be applicable in the sulfite concentration range of 0.5-50mgL(-1). The sensitivity, detection limit, and sample throughput were determined to be 2.105nALmg(-1), 0.40mgL(-1) and 11h(-1), respectively. The developed PFI method, coupled with the CuHCF-CNT-modified carbon paste electrode, was applied in the determination of sulfite content in sulfite-containing food products. The results agreed well with those obtained through the officially recommended differential pulse polarographic method.

  17. Ion-selective electrode reviews

    CERN Document Server

    Thomas, J D R

    1983-01-01

    Ion-Selective Electrode Reviews, Volume 5 is a collection of articles that covers ion-speciation. The book aims to present the advancements of the range and capabilities of selective ion-sensors. The topics covered in the selection are neutral carrier based ion-selective electrodes; reference electrodes and liquid junction effects in ion-selective electrode potentiometry; ion transfer across water/organic phase boundaries and analytical; and carbon substrate ion-selective electrodes. The text will be of great use to chemists and chemical engineers.

  18. Oxygen safety

    Science.gov (United States)

    ... sure you have working smoke detectors and a working fire extinguisher in your home. If you move around the house with your oxygen, you may need more than one fire extinguisher in different locations. Smoking can be very dangerous. No one should smoke ...

  19. Electrostatic Levitator Electrode Layout

    Science.gov (United States)

    1998-01-01

    Schematic of Electrostatic Levitator (ESL) electrodes and controls system. The ESL uses static electricity to suspend an object (about 2-3 mm in diameter) inside a vacuum chamber while a laser heats the sample until it melts. This lets scientists record a wide range of physical properties without the sample contacting the container or any instruments, conditions that would alter the readings. The Electrostatic Levitator is one of several tools used in NASA's microgravity materials science program.

  20. Improved Internal Reference Oxygen Sensors Using Composite Oxides as Electrodes

    DEFF Research Database (Denmark)

    Hu, Qiang

    good reproducibility. Apart from the excellent performance the IROSes are fabricated by an inexpensive and flexible method. Therefore, the IROSes present in this thesis may be commercialized in the future. Theoretical investigations on IROS are carried out. The electronic leak of an electrolyte made...... from 8YSZ is evaluated quantitatively and figures that may be used to design the depletion period of an IROS due to the electronic leak of 8YSZ are provided. One dimensional numerical simulations are performed to study the variation in cell voltage during the process of gas mixing, and the asymmetric...... the application of IROSes are provided. Based on the concepts and fundamentals of the IROS, internal reference sensors that detect other gas species such as hydrogen, chlorine and bromine may be developed....

  1. Single crystal studies of platinum alloys for oxygen reduction electrodes

    DEFF Research Database (Denmark)

    Ulrikkeholm, Elisabeth Therese

    the behavior of bulk single crystals, deposition of yttrium and gadolinium on a clean, annealed Pt(111) crystal were investigated in UHV. PtxY and PtxGd alloys terminated with a single atomic layer of platinum were formed after annealing to 500 °C in UHV. These alloys will be referred to as Y/Pt(111) and Gd.......89×1.89 structure, and the Gd/Pt(111) sample has formed a 1.90×1.90 structure compared to pure platinum. From the XPS measurements, it is most likely that alloys with the Pt5Y and Pt5Gd stoichiometry have been formed. The reactivity of the surfaces were probed using TPD. These measurements showed sharp desorption...

  2. Flexible transparent electrode

    Science.gov (United States)

    Demiryont, Hulya; Shannon, Kenneth C., III; Moorehead, David; Bratcher, Matthew

    2011-06-01

    This paper presents the properties of the EclipseTECTM transparent conductor. EclipseTECTM is a room temperature deposited nanostructured thin film coating system comprised of metal-oxide semiconductor elements. The system possesses metal-like conductivity and glass-like transparency in the visible region. These highly conductive TEC films exhibit high shielding efficiency (35dB at 1 to 100GHz). EclipseTECTM can be deposited on rigid or flexible substrates. For example, EclipseTECTM deposited on polyethylene terephthalate (PET) is extremely flexible that can be rolled around a 9mm diameter cylinder with little or no reduction in electrical conductivity and that can assume pre-extension states after an applied stress is relieved. The TEC is colorless and has been tailored to have high visible transmittance which matches the eye sensitivity curve and allows the viewing of true background colors through the coating. EclipseTECTM is flexible, durable and can be tailored at the interface for applications such as electron- or hole-injecting OLED electrodes as well as electrodes in flexible displays. Tunable work function and optical design flexibility also make EclipseTECTM well-suited as a candidate for grid electrode replacement in next-generation photovoltaic cells.

  3. ETEM Studies of Electrodes and Electro-catalysts

    DEFF Research Database (Denmark)

    Jooss, Christian; Mildner, Stephanie; Beleggia, Marco

    2016-01-01

    Environmental TEM is an excellent tool for gaining insight into the atomic and electronic structure of electro-catalysts under operating conditions. Several electrochemical reactions such as oxidation/reduction processes of electrodes, heterogeneous gas phase catalysis of water splitting/oxygen...... evolution and electrochemical corrosion processes of materials have been studied in some pioneering experiments which will be summarized in this chapter. These experiments often reveal a strong change of the electrode due to the adsorption of gas species from the environment as well as due to the impact...

  4. Dual mode antimony electrode for simultaneous measurements of PO2 and pH.

    Science.gov (United States)

    Sjöberg, F; Nilsson, G

    2000-01-01

    In biomedical research and clinical medicine there is a demand for potent sensors to measure the components that make up blood gas analyses. Today, as when the electrochemical PO2, PCO2 and pH electrodes were first introduced, these measurements are usually made with the same type of sensor technology. The aims of the present study were, firstly, to find out whether the platinum cathode in the Clark electrode can be replaced by antimony for oxygen measurements (amperometry (A)); secondly, whether, during oxygen measurements, the inherent corrosion potential of the antimony metal can be used for measurement of pH in the same measurement area (potentiometry (P)). An electrode of purified, crystallographically orientated monocrystalline antimony (COMA) connected to a reference electrode (silver-silver chloride) was used for the P measurements. Measurements of A (at -900 mV) and P were made in an aqueous environment regulated for oxygen, pH, and temperature. Reproducible oxygen sensitivities of 0.925 nA/% oxygen (2% CV (coefficient of variation)) (A), 10.7 mV/% (P), and 0.7 mV/% (P) were found in the oxygen range: 0-21%, <5%, and above 5%, respectively. The pH sensitivity was 57 mV/pH unit (P). Oxygen and pH measurements were less accurate at oxygen concentrations close to 0%. Both the oxygen and pH part of the composite electrode signal can be identified by this dual mode technique (A and P). The sensor seems to be promising as it provides measurements of two separate variables (oxygen and pH) and also has the desirable characteristics of a solid state sensor.

  5. Mathematical modeling of oxygen transport in solid oxide fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Svensson, Ann Mari

    1997-12-31

    This thesis develops mathematical models to describe the electrochemical performance of a solid oxide fuel cell cathode based on electrochemical kinetics and mass transfer. The individual effects of various coupled processes are investigated. A one-dimensional model is developed based on porous electrode theory. Two different mechanisms are investigated for the charge transfer reaction. One of these assumes that intermediately adsorbed oxygen atoms are reduced at the electrode/electrolyte interface, similar to the models proposed for metal electrodes. Simulated polarization curves exhibit limited currents due to depletion of oxygen adsorbates at high cathodic overvoltages. An empirical correlation is confirmed to exist between the limiting current an the oxygen partial pressure, however, a similar correlation often assumed to exist between the measured polarization resistance and the oxygen partial pressure could not be justified. For the other model, oxygen vacancies are assumed to be exchanged directly at the electrode/electrolyte interface. The electrochemical behaviour is improved by reducing the oxygen partial pressure, due to increased vacancy concentration of the electrode material. Simulated polarization curves exhibit Tafel-like slopes in the cathodic direction, which are due to polarization concentration, and not activation polarization in the conventional sense. Anodic limiting currents are predicted due to lack of available free sites for vacancy exchange at the cathode side. The thesis also presents a theoretical treatment of current and potential distributions in simple two-dimensional cell geometries, and a two-dimensional model for a porous electrode-electrolyte system for investigation of the effect of interfacial diffusion of adsorbates along the electrode/electrolyte interface. 172 refs., 60 figs., 11 tabs.

  6. Influence of Tear Protein Deposition on the Oxygen Permeability of Soft Contact Lenses

    Directory of Open Access Journals (Sweden)

    Se Eun Lee

    2017-01-01

    Full Text Available Purpose. To investigate the effect of tear protein deposition on the change in oxygen permeability (Dk of soft contact lenses (SCL. Methods. Three hydrogel lenses (polymacon, nelfilcon A, and etafilcon A and two silicon hydrogel lenses (lotrafilcon A and balafilcon A were investigated. Etafilcon A lenses were incubated in artificial tear solution for 1, 6, 12, and 48 h, whereas the other SCL were incubated for 1, 3, 7, and 14 days. Oxygen permeability was measured using the polarographic method, and lenses were stacked in four layers to correct the boundary effect. Results. The Dk of all investigated SCL was decreased by the protein deposition. Silicone hydrogel lenses showed a smaller deposition of artificial tear proteins than conventional hydrogel lenses. However, their Dk was reduced twofold than those of 3 conventional hydrogel lenses when compared at the same level of protein deposition. Despite a large amount of total deposited protein in etafilcon A lenses, their Dk was more stable than other SCL. Conclusions. From the results, it was revealed that the Dk of SCL is different from the value provided by manufacturers because of the tear protein deposition on surface and/or in pore of SCL; however, the degree of Dk change in SCL was not simply correlated with the amount of tear protein deposition. Thus, it is considered that the correlation between tear protein deposition and properties of lens materials affects Dk change.

  7. Reductive cleavage of chlorine from 6-chloronicotinic acid on mercury electrodes

    International Nuclear Information System (INIS)

    Ruiz Montoya, M.; Pintado, S.; Rodriguez Mellado, J.M.

    2011-01-01

    Highlights: → Dissociation constants (as pK) of 6 chloronicotinic acid (6CNA) obtained by UV-vis spectroscopy: -0.80 ± 0.05 (-COOH group) and 3.2 ± 0.1 (pyridinic nitrogen). → Electrolysis of 6CNA evidenced the reductive cleavage of chlorine from the molecule. → Kinetic parameters (Tafel slopes and reaction orders) determined at the foot of the waves. → Reduction pathways have been proposed. - Abstract: This paper presents polarographic (direct current, dc, and differential pulse, DP) and voltammetric (linear-sweep cyclic voltammetry) studies on the electroreduction of 6-chloronicotinic acid (6CNA) on mercury electrodes. In order to obtain the dissociation constants of 6CNA, UV-vis spectra were recorded as a function of pH. pK values of -0.80 ± 0.05 (-COOH group) and 3.2 ± 0.1 (pyridinic nitrogen) were obtained. The electrochemical studies were performed in the acidity range 6 M H 2 SO 4 to pH 8. Above the last pH value no signals were obtained. Electrolysis made at potentials corresponding to the limiting current of the first wave indicates that there is a reductive cleavage of chlorine from the molecule. This was confirmed by dc and DP polarografic results and also by voltammetric results. Kinetic parameters such as Tafel slopes and electrochemical reaction orders have been determined at potentials corresponding to the foot of the waves. From these results, together with those obtained by cyclic voltammetry, a reaction pathway is proposed, in which the rate-determining step of the process is the release of a chloride ion from the radical formed after the uptake of a H + ion and an electron.

  8. Reductive cleavage of chlorine from 6-chloronicotinic acid on mercury electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Ruiz Montoya, M., E-mail: mmontoya@uhu.e [Departamento de Ingenieria Quimica, Quimica Fisica y Quimica Organica, Universidad de Huelva, Campus El Carmen, Facultad de Ciencias Experimentales, E-21071 Huelva (Spain); Pintado, S., E-mail: q02pibes@uco.e [Departamento de Quimica Fisica y Termodinamica Aplicada, Universidad de Cordoba, Campus Universitario de Rabanales, edificio ' Marie Curie' ., E-14014 Cordoba (Spain); Rodriguez Mellado, J.M., E-mail: jmrodriguez@uco.e [Departamento de Quimica Fisica y Termodinamica Aplicada, Universidad de Cordoba, Campus Universitario de Rabanales, edificio ' Marie Curie' ., E-14014 Cordoba (Spain)

    2011-04-30

    Highlights: Dissociation constants (as pK) of 6 chloronicotinic acid (6CNA) obtained by UV-vis spectroscopy: -0.80 {+-} 0.05 (-COOH group) and 3.2 {+-} 0.1 (pyridinic nitrogen). Electrolysis of 6CNA evidenced the reductive cleavage of chlorine from the molecule. Kinetic parameters (Tafel slopes and reaction orders) determined at the foot of the waves. Reduction pathways have been proposed. - Abstract: This paper presents polarographic (direct current, dc, and differential pulse, DP) and voltammetric (linear-sweep cyclic voltammetry) studies on the electroreduction of 6-chloronicotinic acid (6CNA) on mercury electrodes. In order to obtain the dissociation constants of 6CNA, UV-vis spectra were recorded as a function of pH. pK values of -0.80 {+-} 0.05 (-COOH group) and 3.2 {+-} 0.1 (pyridinic nitrogen) were obtained. The electrochemical studies were performed in the acidity range 6 M H{sub 2}SO{sub 4} to pH 8. Above the last pH value no signals were obtained. Electrolysis made at potentials corresponding to the limiting current of the first wave indicates that there is a reductive cleavage of chlorine from the molecule. This was confirmed by dc and DP polarografic results and also by voltammetric results. Kinetic parameters such as Tafel slopes and electrochemical reaction orders have been determined at potentials corresponding to the foot of the waves. From these results, together with those obtained by cyclic voltammetry, a reaction pathway is proposed, in which the rate-determining step of the process is the release of a chloride ion from the radical formed after the uptake of a H{sup +} ion and an electron.

  9. Transparent Electrodes for Efficient Optoelectronics

    KAUST Repository

    Morales-Masis, Monica

    2017-03-30

    With the development of new generations of optoelectronic devices that combine high performance and novel functionalities (e.g., flexibility/bendability, adaptability, semi or full transparency), several classes of transparent electrodes have been developed in recent years. These range from optimized transparent conductive oxides (TCOs), which are historically the most commonly used transparent electrodes, to new electrodes made from nano- and 2D materials (e.g., metal nanowire networks and graphene), and to hybrid electrodes that integrate TCOs or dielectrics with nanowires, metal grids, or ultrathin metal films. Here, the most relevant transparent electrodes developed to date are introduced, their fundamental properties are described, and their materials are classified according to specific application requirements in high efficiency solar cells and flexible organic light-emitting diodes (OLEDs). This information serves as a guideline for selecting and developing appropriate transparent electrodes according to intended application requirements and functionality.

  10. Modulating indium doped tin oxide electrode properties for laccase electron transfer enhancement

    International Nuclear Information System (INIS)

    Diaconu, Mirela; Chira, Ana; Radu, Lucian

    2014-01-01

    Indium doped tin oxide (ITO) electrodes were functionalized with gold nanoparticles (GNPs) and cysteamine monolayer to enhance the heterogeneous electron transfer process of laccase from Trametes versicolor. The assembly of GNP on ITO support was performed through generation of H + species at the electrode surface by hydroquinone electrooxidation at 0.9 V vs Ag/AgCl. Uniform distribution of gold nanoparticle aggregates on electrode surfaces was confirmed by atomic force microscopy. The size of GNP aggregates was in the range of 200–500 nm. The enhanced charge transfer at the GNP functionalized ITO electrodes was observed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy. Electrocatalytic behavior of laccase immobilized on ITO modified electrode toward oxygen reduction reaction was evaluated using CV in the presence of 2,2′-azino-bis 3-ethylbenzothiazoline-6-sulfuric acid (ABTS). The obtained sigmoidal-shaped voltammograms for ABTS reduction in oxygen saturated buffer solution are characteristic for a catalytic process. The intensity of catalytic current increased linearly with mediator concentration up to 6.2 × 10 −4 M. The registered voltammogram in the absence of ABTS mediator clearly showed a significant faradaic current which is the evidence of the interfacial oxygen reduction. - Highlights: • Assembly of gold nanoparticles on indium tin oxide support at positive potentials • Electrochemical and morphological evaluation of the gold nanoparticle layer assembly • Bioelectrocatalytic oxygen reduction on laccase modified electrode

  11. Modulating indium doped tin oxide electrode properties for laccase electron transfer enhancement

    Energy Technology Data Exchange (ETDEWEB)

    Diaconu, Mirela [National Institute for Biological Sciences, Centre of Bioanalysis, 296 Spl. Independentei, Bucharest 060031 (Romania); Chira, Ana [National Institute for Biological Sciences, Centre of Bioanalysis, 296 Spl. Independentei, Bucharest 060031 (Romania); Politehnica University of Bucharest, Faculty of Applied Chemistry and Materials Science, 1-7 Polizu Str., 011061 (Romania); Radu, Lucian, E-mail: gl_radu@chim.upb.ro [Politehnica University of Bucharest, Faculty of Applied Chemistry and Materials Science, 1-7 Polizu Str., 011061 (Romania)

    2014-08-28

    Indium doped tin oxide (ITO) electrodes were functionalized with gold nanoparticles (GNPs) and cysteamine monolayer to enhance the heterogeneous electron transfer process of laccase from Trametes versicolor. The assembly of GNP on ITO support was performed through generation of H{sup +} species at the electrode surface by hydroquinone electrooxidation at 0.9 V vs Ag/AgCl. Uniform distribution of gold nanoparticle aggregates on electrode surfaces was confirmed by atomic force microscopy. The size of GNP aggregates was in the range of 200–500 nm. The enhanced charge transfer at the GNP functionalized ITO electrodes was observed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy. Electrocatalytic behavior of laccase immobilized on ITO modified electrode toward oxygen reduction reaction was evaluated using CV in the presence of 2,2′-azino-bis 3-ethylbenzothiazoline-6-sulfuric acid (ABTS). The obtained sigmoidal-shaped voltammograms for ABTS reduction in oxygen saturated buffer solution are characteristic for a catalytic process. The intensity of catalytic current increased linearly with mediator concentration up to 6.2 × 10{sup −4} M. The registered voltammogram in the absence of ABTS mediator clearly showed a significant faradaic current which is the evidence of the interfacial oxygen reduction. - Highlights: • Assembly of gold nanoparticles on indium tin oxide support at positive potentials • Electrochemical and morphological evaluation of the gold nanoparticle layer assembly • Bioelectrocatalytic oxygen reduction on laccase modified electrode.

  12. Oxygen-depleted zones inside reproductive structures of Brassicaceae: implications for oxygen control of seed development

    Science.gov (United States)

    Porterfield, D. M.; Kuang, A.; Smith, P. J.; Crispi, M. L.; Musgrave, M. E.

    1999-01-01

    Growth of Arabidopsis thaliana (L.) Heynh. in decreasing oxygen partial pressures revealed a linear decrease in seed production below 15 kPa, with a complete absence of seed production at 2.5 kPa oxygen. This control of plant reproduction by oxygen had previously been attributed to an oxygen effect on the partitioning between vegetative and reproductive growth. However, plants grown in a series of decreasing oxygen concentrations produced progressively smaller embryos that had stopped developing at progressively younger stages, suggesting instead that their growth is limited by oxygen. Internal oxygen concentrations of buds, pistils, and developing siliques of Brassica rapa L. and siliques of Arabidopsis were measured using a small-diameter glass electrode that was moved into the structures using a micromanipulator. Oxygen partial pressures were found to be lowest in the developing perianth (11.1 kPa) and pistils (15.2 kPa) of the unopened buds. Pollination reduced oxygen concentration inside the pistils by 3 kPa after just 24 h. Inside Brassica silique locules, partial pressures of oxygen averaged 12.2 kPa in darkness, and increased linearly with increasing light levels to 16.2 kPa. Measurements inside Arabidopsis siliques averaged 6.1 kPa in the dark and rose to 12.2 kPa with light. Hypoxia in these microenvironments is postulated to be the point of control of plant reproduction by oxygen.

  13. Polarographic study of the Cu(II)/Cu(I) system in the presence of 1-ascorbic acid and 0,1 M ClK; Estudio polarografico del sistema Cu(II)/Cu(I) en presencia del acido 1-ascorbico y en ClK 0,1 M

    Energy Technology Data Exchange (ETDEWEB)

    Alonso Lopez, J.

    1969-07-01

    While studying the catalytic effect of Cu{sup {down_arrow}}2 ions on the oxidation process of 1-ascorbic acid, it has been observed that, in a 0,1 M solution of K1 at a pH 6 to 7, the above acid gives rise in the presence of Cu{sup {down_arrow}}2 ions to a polarographic wave of half-wave potential of -0,41 V (vs. S.C.E.). (Author) 14 refs.

  14. Steel Collet For Welding Electrodes

    Science.gov (United States)

    Gilbert, Jeffrey L.; Gutow, David A.; Burley, Richard K.; Fogul, Irving

    1992-01-01

    Improved steel collet holds electrode for tungsten inert-gas welding but allows quick and easy replacement. Also ensures reliable arc starting. Slip-on compression ring compresses tapered section of body of collet around inner end of welding electrode. Collet mounted in receptacle below stack of lenses and filters in coaxial-vision welding torch. Blind hole in collet protects outermost lens from damage by electrode.

  15. Amperometric detection and electrochemical oxidation of aliphatic amines and ammonia on silver-lead oxide thin-film electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Ge, Jisheng [Iowa State Univ., Ames, IA (United States)

    1996-01-08

    This thesis comprises three parts: Electrocatalysis of anodic oxygen-transfer reactions: aliphatic amines at mixed Ag-Pb oxide thin-film electrodes; oxidation of ammonia at anodized Ag-Pb eutectic alloy electrodes; and temperature effects on oxidation of ethylamine, alanine, and aquated ammonia.

  16. Kinetic investigation of oxygen evolution at titanium-ruthenium oxide anodes. Oxygen evolution kinetics at RuO2 and titaniumruthenium oxide anodes in chloride solutions

    International Nuclear Information System (INIS)

    Kokoulina, D.V.

    1986-01-01

    Oxygen evolution kinetics was studied at 70 degrees C at RuO 2 and titaniumruthenium oxide anodes in chlorinated chloride solutions (1 M NaCl, pH 1.4 to 2.25) by recording polarization curves. The reaction orders were determined. The kinetics of anodic oxygen evolution is important for an understanding of electrode behavior and for an estimate of possible current yields of oxygen under the different conditions of electrolysis of NaCl solutions. The results obtained demonstrate that substantial oxygen evolution can occur in chlorinated chloride solutions at active electrodes because of the coupled reaction of chlorine reduction

  17. Ion-selective electrode reviews

    CERN Document Server

    Thomas, J D R

    1982-01-01

    Ion-Selective Electrode Reviews, Volume 3, provides a review of articles on ion-selective electrodes (ISEs). The volume begins with an article on methods based on titration procedures for surfactant analysis, which have been developed for discrete batch operation and for continuous AutoAnalyser use. Separate chapters deal with detection limits of ion-selective electrodes; the possibility of using inorganic ion-exchange materials as ion-sensors; and the effect of solvent on potentials of cells with ion-selective electrodes. Also included is a chapter on advances in calibration procedures, the d

  18. Coated carbon nanotube array electrodes

    Science.gov (United States)

    Ren, Zhifeng [Newton, MA; Wen, Jian [Newton, MA; Chen, Jinghua [Chestnut Hill, MA; Huang, Zhongping [Belmont, MA; Wang, Dezhi [Wellesley, MA

    2008-10-28

    The present invention provides conductive carbon nanotube (CNT) electrode materials comprising aligned CNT substrates coated with an electrically conducting polymer, and the fabrication of electrodes for use in high performance electrical energy storage devices. In particular, the present invention provides conductive CNTs electrode material whose electrical properties render them especially suitable for use in high efficiency rechargeable batteries. The present invention also provides methods for obtaining surface modified conductive CNT electrode materials comprising an array of individual linear, aligned CNTs having a uniform surface coating of an electrically conductive polymer such as polypyrrole, and their use in electrical energy storage devices.

  19. Continuous monitoring of the partial pressure of oxygen in cerebral venous blood.

    Science.gov (United States)

    Rieger, A; Menzel, M; Rainov, N G; Sanchin, L; Rot, S; Furka, I; Görömbey, Z; Burkert, W

    1997-08-01

    Clinical oxygen monitoring in the injured brain is somewhat difficult. However, ischemia is one of the major factors responsible for secondary tissue damage after head injury or subarachnoid hemorrhage. Therefore, the aim of the present study was to investigate the value of continuously monitoring the partial pressure of oxygen in cerebral venous blood (PcvO2) during changes in intracranial pressure (ICP). In eight domestic pigs with Clark type probes placed in the posterior third of the superior sagittal sinus, PcvO2 was continuously registered while ICP was stepwise elevated by an inflatable balloon placed below the tentorium. Arterial blood pressure was continuously monitored, cerebral perfusion pressure (CPP) was calculated, and arterial partial carbon dioxide pressure and partial pressure of oxygen were registered intermittently. The mean intraparenchymal ICP before the start of balloon inflation was 5 +/- 1 mm Hg, the mean CPP was 80 +/- 15 mm Hg, and the mean PcvO2 was 36 +/- 3 mm Hg. At maximum ICP elevation, CPP decreased to 20 +/- 12 mm Hg, PcvO2 decreased to 10 +/- 6 mm Hg, and ICP increased to 90 +/- 10 mm Hg. Strong linear correlations between ICP and PcvO2 and between CPP and PcvO2 were revealed, and mean correlation coefficients of 0.89 for ICP/PcvO2 and 0.73 for CPP/PcvO2 were calculated. The present study demonstrates that polarographic PcvO2 monitoring in the superior sagittal sinus is a reliable method for the early detection of reduced CPP during ICP elevation. This technique is capable of registering the global oxygen supply and oxygen consumption of the brain. It seems superior to jugular venous oxymetry and is better suited for clinical use because of a somewhat low artifact susceptibility.

  20. Ultramicroelectrode studies of oxygen reduction in polyelectrolyte membranes

    Energy Technology Data Exchange (ETDEWEB)

    Holdcroft, S.; Abdou, M.S.; Beattie, P.; Basura, V. [Simon Fraser Univ., Burnaby, BC (Canada). Dept. of Chemistry

    1997-12-31

    A study on the oxygen reduction reaction in a solid state electrochemical cell was presented. The oxygen reduction reaction is a rate limiting reaction in the operation of solid polymer electrolyte fuel cells which use H{sub 2} and O{sub 2}. Interest in the oxygen reduction reaction of platinum electrodes in contact with Nafion electrolytes stems from its role in fuel cell technology. The kinetics of the oxygen reduction reaction in different polyelectrolyte membranes, such as Nafion and non-Nafion membranes, were compared. The electrode kinetics and mass transport parameters of the oxygen reduction reaction in polyelectrolyte membranes were measured by ultramicroelectrode techniques. The major difference found between these two classes of membrane was the percentage of water, which is suggestive of superior electrochemical mass transport properties of the non-Nafion membranes. 2 refs. 1 fig.

  1. Optic nerve pH and PO2

    DEFF Research Database (Denmark)

    Pedersen, Daniella B; Stefánsson, Einar; Kiilgaard, Jens Folke

    2006-01-01

    Earlier studies have demonstrated that carbonic anhydrase inhibitors (CAIs) increase optic nerve oxygen tension (ONPO(2)) in pigs. We hypothesized that the mechanism of this effect was either a CO(2) increase or a pH decrease in tissue and blood. To test this hypothesis we investigated and compared...... how optic nerve pH (ONpH) and ONPO(2) are affected by: (1) carbonic anhydrase inhibition; (2) respiratory acidosis, and (3) metabolic acidosis. We measured ONpH with a glass pH electrode and ONPO(2) with a polarographic oxygen electrode. One of the electrodes was placed in the vitreous cavity 0.5 mm...

  2. Gas sensor with multiple internal reference electrodes and sensing electrodes

    DEFF Research Database (Denmark)

    2016-01-01

    The invention relates to a potentiometric gas sensor, or potentiometric gas detection element, with multiple internal reference electrodes and multiple sensing electrodes for determining the concentrations of gas components in a gaseous mixture. The sensor for gas detection comprises: a solid...

  3. APPLICATION OF FLOW-THROUGH THREE-DIMENSIONAL ELECTRODES FOR REGENERATION OF PLATING IRON ELECTROLYTES: 1. MATHEMATICAL MODEL

    Directory of Open Access Journals (Sweden)

    Alexandr Kоshev

    2014-12-01

    Full Text Available The mathematical model of electrochemical processes distribution within the three-dimensional flow-through electrode for the system Fe(III/Fe(II/Fe is described in this paper, considering also the electrochemical reactions of hydrogen and molecular oxygen reduction. Possible dynamic changes in the parameters of electrode, electrolyte and the process are taken into account in the mathematical model, such as electro-conductivity of electrode material, electrolyte flow rate, material porosity and specific electrode surface, concentrations of electro-active substances and other characteristics within the local volume of electrode. Electrode and process characteristics are treated as time and coordinate functions within the electrode volume. The results of calculations and experimental studies of iron electro-reduction are given, the analysis of the numerical modeling is provided.

  4. Light addressable gold electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Khalid, Waqas

    2011-07-01

    The main objective carried out in this dissertation was to fabricate Light Amplified Potentiometric sensors (LAPS) based upon the semiconductor nanoparticles (quantum dots) instead of its bulk form. Quantum dots (QDs) were opted for this device fabrication because of their superior fluorescent, electric and catalytic properties. Also in comparison to their bulk counterparts they will make device small, light weighted and power consumption is much lower. QDs were immobilized on a Au substrate via 1,4 benzene dithiol (BDT) molecule. Initially a self-assembled monolayer (SAM) of BDT was established on Au substrate. Because of SAM, the conductivity of Au substrate decreased dramatically. Furthermore QDs were anchored with the help of BDT molecule on Au substrate. When QDs immobilized on Au substrate (QD/Au) via BDT molecule were irradiated with UV-visible light, electron-hole pairs were generated in QDs. The surface defect states in QDs trapped the excited electrons and long lived electron-hole pairs were formed. By the application of an appropriate bias potential on Au substrate the electrons could be supplied or extracted from the QDs via tunneling through BDT. Thus a cathodic or anodic current could be observed depending upon bias potential under illumination. However without light illumination the QD/Au electrode remained an insulator. To improve the device different modifications were made, including different substrates (Au evaporated on glass, Au evaporated on mica sheets and Au sputtered on SiO{sub 2}/Si) and different dithiol molecules (capped and uncapped biphenyl 4,4' dithiol and capped and uncapped 4,4' dimercaptostilbenes) were tried. Also different QD immobilization techniques (normal incubation, spin coating, layer by layer assembly (LbL) of polyelectrolytes and heat immobilization) were employed. This device was able to detect electrochemically different analytes depending upon the QDs incorporated. For example CdS QDs were able to detect 4

  5. Characterization and optimization of polymer electrolyte fuel cell electrodes

    Science.gov (United States)

    Boyer, Christopher Carter

    Experimental characterization and modeling were combined to find a procedure for optimizing the design of polymer electrolyte membrane fuel cell (PEMFC) electrodes. The mass transfer and kinetic properties of the active layer used in electrodes fabricated at the Center for Electrochemical Systems and Hydrogen Research (CESHR) were characterized as a function of electrolyte polymer content NafionRTM, DuPont, Fayetteville, NC) and catalyst loading for different types of platinum catalysts (E-Tek, Natick, MA). Expressions from limiting cases of the fuel cell model showed the combination of electrode materials for maximum current density at maximum catalyst utilization. Models describing the fuel cell behavior were selected and used to explain how different operating pressures affect the system power density and efficiency. An "inert layer" method was developed to determine the effective proton conductivity of the active layer. A "buffer layer" method was developed to determine the oxygen diffusivity in the gas pores. A review of the literature and experiments at CESHR was used to determine the oxygen reduction activity of the active layer. Finally, a fitting method was developed to measure the agglomerate diffusivity from cell tests. A PEMFC model demonstrated that operating the fuel cell pressurized can improve the power density at high currents because of oxygen mass transport. limitations in the substrate. However. as better electrode designs improve oxygen mass transfer, pressurized operation will lose this advantage. In addition, the model confirmed that oxygen enrichment systems require too much energy to separate oxygen from air to improve the net performance of a fuel cell. From limiting approximations of the solutions of the differential material balances in the fuel cell model, a simple set of analytical expressions were derived that predict the optimum active layer thickness and maximum current density based on the materials of construction and operating

  6. Precordial electrode placement in women.

    Science.gov (United States)

    Macfarlane, P W; Colaco, R; Stevens, K; Reay, P; Beckett, C; Aitchison, T

    2003-03-01

    Precordial ECG electrode positioning was standardised in the early 1940s. However, it has been customary for the V 3 to V 6 electrodes to be placed under the left breast in women rather than in the correct anatomical positions relating to the 4th and 5th interspaces. For this reason, a comparison between the two approaches to chest electrode positioning in women was undertaken. In total 84 women were recruited and ECGs recorded with electrodes in the correct anatomical position and also in the more commonly used positions under the breast. As a separate study, 299 healthy women were recruited to study normal limits of leads V 3 to V 6 recorded with electrodes in the correct anatomical positions and compare them with published normal limits with electrodes in the more commonly used locations. It was shown that there was less variability with electrodes in the correct anatomical positions and that there were significant differences between the new limits of normality compared with the old established limits. Expansion of the database and further analysis of the data is required to make a definitive recommendation with respect to precordial electrode placement in women.

  7. EDM Electrode for Internal Grooves

    Science.gov (United States)

    Ramani, V.; Werner, A.

    1985-01-01

    Electroerosive process inexpensive alternative to broaching. Hollow brass electrodes, soldered at one end to stainless-steel holding ring, held in grooves in mandrel. These electrodes used to machine grooves electrically in stainless-steel tube three-eights inch (9.5 millimeters) in diameter. Tool used on tubes already in place in equipment.

  8. Making EDM Electrodes By Stereolithography

    Science.gov (United States)

    Barlas, Philip A.

    1988-01-01

    Stereolithography is computer-aided manufacturing technique. Used to make models and molds of electrodes for electrical-discharge machining (EDM). Eliminates intermediate steps in fabrication of plastic model of object used in making EDM electrode to manufacture object or mold for object.

  9. Influence of structure and hydrophobic properties on the characteristics of carbon-air electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Shteinberg, G.V.; Dribinsky, A.V.; Kukushkina, I.A.; Musiliva, M.; Mrha, J.

    1982-07-01

    The electrochemical parameters of carbon-oxygen gas-diffusion electrodes can be controlled over a wide range by varying the structure of the active carbon catalyst and the ratio of lyophilic and lyophobic pores in the catalyst particles. Two typical representatives of active carbon catalysts with significantly different hydrophobic properties have been investigated by mercury-alkali intrusion porosimetry and tested both in model floating electrodes and as the hydrophilic component of the active layer of two-layer, gas-diffusion working electrodes. The optimal electrolyte content in the active layer ensuring the maximum electrical characteristics of working electrodes has been found to depend on the structure and hydrophobic properties of the carbon catalyst. The gas pores in the carbon catalyst have been shown to play an essential role in the oxygen mass transfer process in the active layer.

  10. Multi electrode semiconductors detectors

    CERN Document Server

    Amendolia, S R; Bertolucci, Ennio; Bosisio, L; Bradaschia, C; Budinich, M; Fidecaro, F; Foà, L; Focardi, E; Giazotto, A; Giorgi, M A; Marrocchesi, P S; Menzione, A; Ristori, L; Rolandi, Luigi; Scribano, A; Stefanini, A; Vincelli, M L

    1981-01-01

    Detectors with very high space resolution have been built in this laboratory and tested at CERN in order to investigate their possible use in high energy physics experiments. These detectors consist of thin layers of silicon crystals acting as ionization chambers. Thin electrodes, structured in strips or in more fancy shapes are applied to their surfaces by metal coating. The space resolution which could be reached is of the order of a few microns. An interesting feature of these solid state detectors is that they can work under very high or low external pressure or at very low temperature. The use of these detectors would strongly reduce the dimensions and the cost of high energy experiments. (3 refs).

  11. Multi electrode semiconductor detectors

    International Nuclear Information System (INIS)

    Amendolia, S.R.; Batignani, G.; Bertolucci, E.; Bosisio, L.; Budinich, M.; Bradaschia, C.; Fidecaro, F.; Foa, L.; Focardi, E.; Giazotto, A.; Giorgi, M.A.; Marrocchesi, P.S.; Menzione, A.; Ristori, L.; Rolandi, L.; Scribano, A.; Stefanini, A.; Vincelli, M.L.

    1981-01-01

    Detectors with very high space resolution have been built in the laboratory and tested at CERN in order to investigate their possible use in high energy physics experiments. These detectors consist of thin layers of silicon crystals acting as ionization chambers. Thin electrodes, structured in strips or in more fancy shapes are applied to their surfaces by metal coating. The space resolution which could be reached is of the order of a few microns. An interesting feature of these solid state detectors is that they can work under very high or low external pressure or at very low temperature. The use of these detectors would strongly reduce the dimensions and the cost of high energy experiments. (Auth.)

  12. Electrode for a lithium cell

    Science.gov (United States)

    Thackeray, Michael M [Naperville, IL; Vaughey, John T [Elmhurst, IL; Dees, Dennis W [Downers Grove, IL

    2008-10-14

    This invention relates to a positive electrode for an electrochemical cell or battery, and to an electrochemical cell or battery; the invention relates more specifically to a positive electrode for a non-aqueous lithium cell or battery when the electrode is used therein. The positive electrode includes a composite metal oxide containing AgV.sub.3O.sub.8 as one component and one or more other components consisting of LiV.sub.3O.sub.8, Ag.sub.2V.sub.4O.sub.11, MnO.sub.2, CF.sub.x, AgF or Ag.sub.2O to increase the energy density of the cell, optionally in the presence of silver powder and/or silver foil to assist in current collection at the electrode and to improve the power capability of the cell or battery.

  13. Composite electrode/electrolyte structure

    Science.gov (United States)

    Visco, Steven J.; Jacobson, Craig P.; DeJonghe, Lutgard C.

    2004-01-27

    Provided is an electrode fabricated from highly electronically conductive materials such as metals, metal alloys, or electronically conductive ceramics. The electronic conductivity of the electrode substrate is maximized. Onto this electrode in the green state, a green ionic (e.g., electrolyte) film is deposited and the assembly is co-fired at a temperature suitable to fully densify the film while the substrate retains porosity. Subsequently, a catalytic material is added to the electrode structure by infiltration of a metal salt and subsequent low temperature firing. The invention allows for an electrode with high electronic conductivity and sufficient catalytic activity to achieve high power density in ionic (electrochemical) devices such as fuel cells and electrolytic gas separation systems.

  14. Metabolic Prosthesis for Oxygenation of Ischemic Tissue

    Energy Technology Data Exchange (ETDEWEB)

    Greenbaum, Elias [ORNL

    2009-01-01

    This communication discloses new ideas and preliminary results on the development of a "metabolic prosthesis" for local oxygenation of ischemic tissue under physiological neutral conditions. We report for the first time the selective electrolysis of physiological saline by repetitively pulsed charge-limited electrolysis for the production of oxygen and suppression of free chlorine. For example, using 800 A amplitude current pulses and <200 sec pulse durations, we demonstrated prompt oxygen production and delayed chlorine production at the surface of a shiny 0.85 mm diameter spherical platinum electrode. The data, interpreted in terms of the ionic structure of the electric double layer, suggest a strategy for in situ production of metabolic oxygen via a new class of "smart" prosthetic implants for dealing with ischemic disease such as diabetic retinopathy. We also present data indicating that drift of the local pH of the oxygenated environment can be held constant using a feedback-controlled three electrode electrolysis system that chooses anode and cathode pair based on pH data provided by local microsensors. The work is discussed in the context of diabetic retinopathy since surgical techniques for multielectrode prosthetic implants aimed at retinal degenerative diseases have been developed.

  15. Advantage of four-electrode over two-electrode defibrillators

    Science.gov (United States)

    Bragard, J.; Šimić, A.; Laroze, D.; Elorza, J.

    2015-12-01

    Defibrillation is the standard clinical treatment used to stop ventricular fibrillation. An electrical device delivers a controlled amount of electrical energy via a pair of electrodes in order to reestablish a normal heart rate. We propose a technique that is a combination of biphasic shocks applied with a four-electrode system rather than the standard two-electrode system. We use a numerical model of a one-dimensional ring of cardiac tissue in order to test and evaluate the benefit of this technique. We compare three different shock protocols, namely a monophasic and two types of biphasic shocks. The results obtained by using a four-electrode system are compared quantitatively with those obtained with the standard two-electrode system. We find that a huge reduction in defibrillation threshold is achieved with the four-electrode system. For the most efficient protocol (asymmetric biphasic), we obtain a reduction in excess of 80% in the energy required for a defibrillation success rate of 90%. The mechanisms of successful defibrillation are also analyzed. This reveals that the advantage of asymmetric biphasic shocks with four electrodes lies in the duration of the cathodal and anodal phase of the shock.

  16. Efficient oxygen reduction reaction using ruthenium tetrakis(diaquaplatinum)octacarboxyphthalocyanine catalyst supported on MWCNT platform

    CSIR Research Space (South Africa)

    Maxakato, NW

    2011-02-01

    Full Text Available Electrocatalytic reduction of molecular oxygen in alkaline solution using a novel ruthenium tetrakis(diaquaplatinum) octacarboxyphthalocyanine (RuOCPcPt) electrocatalyst supported on multi-walled carbon nanotube electrode has been described. We show...

  17. Treating refinery wastewaters in microbial fuel cells using separator electrode assembly or spaced electrode configurations

    KAUST Repository

    Zhang, Fang

    2014-01-01

    The effectiveness of refinery wastewater (RW) treatment using air-cathode, microbial fuel cells (MFCs) was examined relative to previous tests based on completely anaerobic microbial electrolysis cells (MECs). MFCs were configured with separator electrode assembly (SEA) or spaced electrode (SPA) configurations to measure power production and relative impacts of oxygen crossover on organics removal. The SEA configuration produced a higher maximum power density (280±6mW/m2; 16.3±0.4W/m3) than the SPA arrangement (255±2mW/m2) due to lower internal resistance. Power production in both configurations was lower than that obtained with the domestic wastewater (positive control) due to less favorable (more positive) anode potentials, indicating poorer biodegradability of the RW. MFCs with RW achieved up to 84% total COD removal, 73% soluble COD removal and 92% HBOD removal. These removals were higher than those previously obtained in mini-MEC tests, as oxygen crossover from the cathode enhanced degradation in MFCs compared to MECs. © 2013 Elsevier Ltd.

  18. Estudo polarográfico sobre a determinação de Fe(III utilizando-se a técnica da polarografia de pulso diferencial Polarographic study about the determination of Fe(III using the technique of differencial pulse polarography

    Directory of Open Access Journals (Sweden)

    Luiz Manoel Aleixo

    2001-12-01

    Full Text Available A differential pulse polarographic study with the objective to determine iron (III in presense of copper (II in a supporting electrolyte based on citrate - EDTA was made. The best experimental conditions found were a supporting electrolyte of citrate 0.25 mol L-1, EDTA 0.050 mol L-1 and KNO3 0.50 mol L-1, pH 5.00. In this media iron (III showed a polarographic peak in -0.08 V and the copper (II in -0.34 V, both vs. Ag/AgCl (saturated KCl. Thus, a analytical method was developed and applied to determine iron (III in brass alloy, a matrix were copper is in large excess over iron. The results obtained showed no interference of copper in the iron determination. The value of 0.21% of iron in the sample alloy composition was obtained and the method was validated by atomic absortion and recovery test, and the results exhibited a good agreement with the proposed method.

  19. Oxygen Reduction Reaction Activity of Platinum Thin Films with Different Densities

    Energy Technology Data Exchange (ETDEWEB)

    Ergul, Busra; Begum, Mahbuba; Kariuki, Nancy; Myers, Deborah J.; Karabacak, Tansel

    2017-08-24

    Platinum thin films with different densities were grown on glassy carbon electrodes by high pressure sputtering deposition and evaluated as oxygen reduction reaction catalysts for polymer electrolyte fuel cells using cyclic voltammetry and rotating disk electrode techniques in aqueous perchloric acid electrolyte. The electrochemically active surface area, ORR mass activity (MA) and specific activity (SA) of the thin film electrodes were obtained. MA and SA were found to be higher for low-density films than for high-density film.

  20. Comparison of electrocatalytic characterization of boron-doped diamond and SnO2 electrodes

    International Nuclear Information System (INIS)

    Lv, Jiangwei; Feng, Yujie; Liu, Junfeng; Qu, Youpeng; Cui, Fuyi

    2013-01-01

    Boron-doped diamond (BDD) and SnO 2 electrodes were prepared by direct current plasma chemical vapor deposition (DC-PCVD) and sol–gel method, respectively. Electrochemical characterization of the two electrodes were investigated by phenol electrochemical degradation, accelerated service life test, cyclic voltammetry (CV) in phenol solution, polarization curves in H 2 SO 4 . The surface morphology and crystal structure of two electrodes were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis. The results showed a considerable difference between the two electrodes in their electrocatalytic activity, electrochemical stability and surface properties. Phenol was readily mineralized to CO 2 at BDD electrode, favoring electrochemical combustion, but its degradation was much slower at SnO 2 electrode. The service life of BDD electrode was 10 times longer than that of SnO 2 . Higher electrocatalytic activity and electrochemical stability of BDD electrode arise from its high oxygen evolution potential and the physically absorbed hydroxyl radicals (·OH) on electrode surface.

  1. Altering Anode Thickness To Improve Power Production in Microbial Fuel Cells with Different Electrode Distances

    KAUST Repository

    Ahn, Yongtae

    2013-01-17

    A better understanding of how anode and separator physical properties affect power production is needed to improve energy and power production by microbial fuel cells (MFCs). Oxygen crossover from the cathode can limit power production by bacteria on the anode when using closely spaced electrodes [separator electrode assembly (SEA)]. Thick graphite fiber brush anodes, as opposed to thin carbon cloth, and separators have previously been examined as methods to reduce the impact of oxygen crossover on power generation. We examined here whether the thickness of the anode could be an important factor in reducing the effect of oxygen crossover on power production, because bacteria deep in the electrode could better maintain anaerobic conditions. Carbon felt anodes with three different thicknesses were examined to see the effects of thicker anodes in two configurations: widely spaced electrodes and SEA. Power increased with anode thickness, with maximum power densities (604 mW/m 2, 0.32 cm; 764 mW/m2, 0.64 cm; and 1048 mW/m2, 1.27 cm), when widely spaced electrodes (4 cm) were used, where oxygen crossover does not affect power generation. Performance improved slightly using thicker anodes in the SEA configuration, but power was lower (maximum of 689 mW/m2) than with widely spaced electrodes, despite a reduction in ohmic resistance to 10 Ω (SEA) from 51-62 Ω (widely spaced electrodes). These results show that thicker anodes can work better than thinner anodes but only when the anodes are not adversely affected by proximity to the cathode. This suggests that reducing oxygen crossover and improving SEA MFC performance will require better separators. © 2012 American Chemical Society.

  2. Noise properties of textile, capacitive EEG electrodes

    OpenAIRE

    Asl Sara Nazari; Ludwig Frank; Schilling Meinhard

    2015-01-01

    The rigid surface of the conventional PCB-based capacitive electrode produces an undefined distance between the skin and the electrode surface. Therefore, the capacitance introduced by them is uncertain and can vary from electrode to electrode due to their different positions on the scalp. However, textile electrodes which use conductive fabric as electrode surfaces, are bendable over the scalp. Therefore, it provides a certain value of the capacitance which is predictable and calculable accu...

  3. Preset Electrodes for Electrical-Discharge Machining

    Science.gov (United States)

    Coker, Bill E.

    1987-01-01

    New electrode holder for electrical-discharge machining (EDM) provides for repeatable loading and setting of many electrodes. New holder is rotating-index tool carrying six, eight, or more electrodes. Before use, all electrodes set with aid of ring surrounding tool, and locked in position with screws. When electrode replaced, EDM operator pulls spring-loaded pin on tool so it rotates about center pin. Fresh electrode then rotated into position against workpiece.

  4. A model to predict the removal of oxygen from air using a zirconia solid electrolyte membrane

    Science.gov (United States)

    Marner, W. J.; Suitor, J. W.; Glazer, C. R.

    1988-01-01

    A finite difference mathematical model has been developed to predict the removal of oxygen from air using a zirconia separation cell. The model predicts the electrical and mass transfer processes in circular disk cells with either axial or radial current flow in the electrodes and in tubular cells with axial current flow in the electrodes. Representative results are presented and discussed.

  5. Surface effects of electrode-dependent switching behavior of resistive random-access memory

    KAUST Repository

    Ke, Jr Jian

    2016-09-26

    The surface effects of ZnO-based resistive random-access memory (ReRAM) were investigated using various electrodes. Pt electrodes were found to have better performance in terms of the device\\'s switching functionality. A thermodynamic model of the oxygen chemisorption process was proposed to explain this electrode-dependent switching behavior. The temperature-dependent switching voltage demonstrates that the ReRAM devices fabricated with Pt electrodes have a lower activation energy for the chemisorption process, resulting in a better resistive switching performance. These findings provide an in-depth understanding of electrode-dependent switching behaviors and can serve as design guidelines for future ReRAM devices.

  6. ELECTROD FLUOR-SELECTIV

    Directory of Open Access Journals (Sweden)

    Mariana DÎRU

    2018-03-01

    Full Text Available A fost preparat un senzor anionic specific, bazat pe pivalatul trinuclear al cromului(III ca material electro­activ încorporat în membrana PVC plastifiată. Senzorul prezintă răspuns Nernstian (55,78 mV/decadă în intervalul de concentrație 10-1-10-4 mol/L cu limita de detecție 2,0∙10-5 mol/L pentru anionul fluorură. Domeniul optim de pH de funcţionare a electrodului asamblat este ˃5. Senzorul dat are un timp de răspuns de 30-60 s și reproductibilitatea rezultatelor se menține timp de 3 luni. Coeficienții potențiometrici ai selectivității au fost determinați prin metoda soluțiilor separate. A fost realizată aplicarea acestor electrozi la analiza pastei de dinți ce conține fluorură și rezultatele experimentale au fost comparate cu datele de pe prospect.FLUORIDE-SELECTIVE ELECTRODEA specific anionic sensor has been prepared, based on trinuclearchromium(III pivalate as sensing material incorpo­rated into the plasticized PVC-membrane. The sensor exhibited Nernstian response (55,78 mV/decade in the region between 10-1-10-4 mol/L with a detection limit of 2,0∙10-5 mol/L for fluoride. The working pH of the electrode was in the 5-6 range. The sensor has a response time 30-60 s and can be used for least 3 month. The potentiometric selectivity coefficients were determined by separate solution method. Application of these electrodes to the analysis of toothpaste containing fluoride has been realized and experimental results have been compared with the data on the prospectus.

  7. New electrodes for biofuel cells

    Science.gov (United States)

    Stom, D. I.; Zhdanova, G. O.; Lashin, A. F.

    2017-11-01

    Two new types of electrodes for biofuel elements (BFC) are proposed. One of them is based on a microchannel plate (MCP). Its peculiarity is a special structure with a large number of glass channels being 6-10 μm in diameter with an internal semiconducting surface. The MCP operation is based on the principle of the channel secondary emission multiplication of the electrons. The second type of electrode presented in the work is made of silicon carbide. This type of electrodes has a developed porous structure. The electrode pores account for at least 30% of the total volume. The pore size varies from 10 to 100 μm. Such porosity greatly increases the anode area and volume. This allows us to achieve sorption of a larger number of microorganisms interacting with the anode and transformed by electron donors. The work of the electrodes developed in BFC was tested, their effectiveness was estimated. A comparison is made with electrodes made of carbon cloth, the most widely used material for working with BFC. It is shown that the MCP based electrode is not inferior to the power characteristics of carbon cloth. The generated power when using silicon carbide was slightly lower than the other two electrodes. However, the stability of silicon carbide to aggressive media (alkalis, acids, strong oxidants, etc.), as well as to mechanical damages gives additional advantages to such electrodes compared to the materials that are commonly used in BFC. The noted features are extremely important for the BFC to work in harsh conditions of treatment facilities and to utilize wastewater components.

  8. Studies of pyrrole black electrodes as possible battery positive electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Mengoli, G.; Musiani, M.M.; Fleischmann, M.; Pletcher, D.

    1984-05-01

    It is shown that a polypyrrole, pyrrole black, may be formed anodically in several aqueous acids. The polypyrrole film shows a redox couple at less positive potentials than that required to form the film and the charge associated with these reduction and oxidation processes together with their stabilty to cycling varies with the anion in solution and the potential where the polypyrrole is formed; over-oxidation of the film caused by taking its potential too positive has a particularly disadvantageous affect. In the acids HBr and HI, the polypyrrole films can act as a storage medium for Br/sub 2/ or I/sub 2/ so that they may be used as a substrate for a X/sub 2//X/sup -/ electrode. Such electrodes may be charge/discharge cycled and the pyrrole/Br/sub 2/ electrode shows promise as a battery positive electrode.

  9. Connecting electrodes with light: one wire, many electrodes.

    Science.gov (United States)

    Choudhury, Moinul H; Ciampi, Simone; Yang, Ying; Tavallaie, Roya; Zhu, Ying; Zarei, Leila; Gonçales, Vinicius R; Gooding, J Justin

    2015-12-01

    The requirement of a wire to each electrode is central to the design of any electronic device but can also be a major restriction. For example it entails space restrictions and rigid device architecture in multi-electrode devices. The finite space that is taken up by the array of electrical terminals and conductive pads also severely limits the achievable density of electrodes in the device. Here it is shown that a travelling light pointer can be used to form transient electrical connections anywhere on a monolithic semiconductor electrode that is fitted with a single peripheral electrical terminal. This is achieved using hydrogen terminated silicon electrodes that are modified with well-defined organic monolayers. It is shown that electrochemical information can be either read from or written onto these surfaces. Using this concept it is possible to form devices that are equivalent to a conventional electrode array but that do not require a predetermined architecture, and where each element of the array is temporally "connected" using light stimulus; a step change in capability for electrochemistry.

  10. Development of high temperature reference electrodes for in-pile application: Part I. Feasibility study of the external pressure balanced Ag/AgCl reference electrode (EPBRE) and the cathodically charged Palladium hydrogen electrode

    Energy Technology Data Exchange (ETDEWEB)

    Bosch, R.W.; Van Nieuwenhove, R

    1998-10-01

    The main problems connected with corrosion potential measurements at elevated temperatures and pressures are related to the stability and lifetime of the reference electrode and the correct estimation of the potential related to the Standard Hydrogen Scale (SHE). Under Pressurised Water Reactor (PWR) conditions of 300 degrees Celsius and 150 bar, the choice of materials is also a limiting factor due to the influence of radiation. Investigations on two reference electrodes that can be used under PWR conditions are reported: the cathodically charged palladium hydrogen electrode, and the external pressure balanced silver/silver chloride electrode. Preliminary investigations with the Pd-electrode were focused on the calculation of the required charging time and the influence of dissolved oxygen. High temperature applications are discussed on the basis of results reported in the literature. Investigations with the silver/silver chloride reference electrode mainly dealt with the salt bridge which is necessary to connect the reference electrode with the testing solution. It is shown that the thermal junction potential is independent of the length of the salt bridge. In addition, the high temperature contributes to an increase of the conductivity of the solution, which is beneficial for the salt bridge connection.

  11. Electrode materials for rechargeable batteries

    Science.gov (United States)

    Abouimrane, Ali; Amine, Khalil

    2015-04-14

    Selenium or selenium-containing compounds may be used as electroactive materials in electrodes or electrochemical devices. The selenium or selenium-containing compound is mixed with a carbon material.

  12. Composite substrate for bipolar electrodes

    Science.gov (United States)

    Tekkanat, Bora; Bolstad, James J.

    1992-12-22

    Substrates for electrode systems, particularly those to be used for bipolar electrodes in zinc-bromine batteries, are disclosed. The substrates preferably include carbon-black as a conductive filler in a polymeric matrix, with reinforcing materials such as glass fibers. Warpage of the zinc-bromine electrodes which was experienced in the prior art and which was believed to be caused by physical expansion of the electrodes due to bromine absorption by the carbon-black, is substantially eliminated when new substrate fabrication techniques are employed. In the pesent invention, substrates are prepared using a lamination process known as glass mat reinforced thermoplastics technology or, in an alternate embodiment, the substrate is made using a slurry process.

  13. Oxygen reduction of several gold alloys in 1-molar potassium hydroxide

    Science.gov (United States)

    Miller, R. O.

    1975-01-01

    With rotated disk-and-ring equipment, polarograms and other electrochemical measurements were made of oxygen reduction in 1-molar potassium hydroxide on an equiatomic gold-copper (Au-Cu) alloy and a Au-Cu alloy doped with either indium (In) or cobalt (Co) and on Au doped with either nickel (Ni) or platinum (Pt). The results were compared with those for pure Au and pure Pt. The two-electron reaction dominated on all Au alloys as it did on Au. The polarographic results at lower polarization potentials were compared, assuming exclusively a two-step reduction. A qualified ranking of cathodic electrocatalytic activity on the freshly polished reduced disks was indicated: anodized Au Au-Cu-In Au-Cu Au-Cu-Co is equivalent or equal to Au-Pt Au-Ni. Aging in distilled water improved the electrocatalytic efficiency of Au-Cu-Co, Au-Cu, and (to a lesser extent) Au-Cu-In.

  14. Amodiaquine polymeric membrane electrode.

    Science.gov (United States)

    Malongo, T Kimbeni; Blankert, B; Kambu, O; Amighi, K; Nsangu, J; Kauffmann, J-M

    2006-04-11

    The construction and electrochemical response characteristics of two types of poly(vinyl chloride) (PVC) membrane sensors for the determination of amodiaquine hydrochloride (ADQ.2HCl) are described. The sensing membrane comprised an ion-pair formed between the cationic drug and sodium tetraphenyl borate (NaTPB) or potassium tetrakis(4-chlorophenyl) borate (KTCPB) in a plasticized PVC matrix. Eight PVC membrane ion-selective electrodes were fabricated and studied. Several plasticizers were studied namely, dioctyl phthalate (DOP), 2-nitrophenyl octyl ether (NPOE), dioctyl phenylphosphonate (DOPP) and bis(2-ethylhexyl)adipate (EHA). The sensors display a fast, stable and near-Nernstian response over a relative wide ADQ concentration range (3.2 x 10(-6) to 2.0 x 10(-2) M), with slopes comprised between 28.5 and 31.4 mV dec(-1) in a pH range comprised between pH 3.7 and 5.5. The assay of amodiaquine hydrochloride in pharmaceutical dosage forms using one of the proposed sensors gave average recoveries of 104.3 and 99.9 with R.S.D. of 0.3 and 0.6% for tablets (Malaritab) and a reconstituted powder containing ADQ.2HCl, respectively. The sensor was also used for dissolution profile studies of two drug formulations. The sensor proved to have a good selectivity for ADQ.2HCl over some inorganic and organic compounds, however, berberine chloride interfered significantly. The results were validated by comparison with a spectrophotometric assay according to the USP pharmacopoeia.

  15. Variations in tumour oxygen tension (pO2) during accelerated radiotherapy of head and neck carcinoma

    International Nuclear Information System (INIS)

    Guichard, M.; Eschwege, F.; Luboinski, B.; Wibault, P.; Weeger, P.; Lusinchi, A.; Lartigau, E.

    1998-01-01

    The study was performed to assess the effect of accelerated radiotherapy on oxygenation of primary tumours and metastatic nodes in patients with advanced head and neck tumours. In 14 patients with head and neck tumour, oxygen tension (pO 2 ) was evaluated in normal tissues and tumours (primary tumour or metastatic neck node) before (0 Gy) and after 2 weeks (32 Gy) of accelerated radiotherapy (70 Gy in 3.5 weeks, with three daily fractions). Radiotherapy was combined with carbogen breathing in 5 patients. pO 2 was measured using a polarographic technique. For pooled normal tissues, median pO 2 was 38 mmHg before treatment and 46 mmHg after 2 weeks. For tumours, very low values ( 2 12 mmHg before treatment versus 26 mmHg after 2 weeks, P 2 was 44 mmHg at 2 weeks, compared with 13.5 mmHg before treatment (P=0.05). Very low pO 2 values, corresponding to tumour hypoxia, were found in the tumours (primary and metastatic neck nodes) prior to accelerated treatment. During the first 2 weeks of accelerated treatment, an increase in median pO 2 was found in nine of the 14 tumours, together with a decrease in the frequency of very low values. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

  16. Voltammetric and impedance behaviours of surface-treated nano-crystalline diamond film electrodes

    Directory of Open Access Journals (Sweden)

    F. B. Liu

    2015-04-01

    Full Text Available The electrochemical performances of hydrogen- and oxygen-terminated nano-crystalline diamond film electrodes were investigated by cyclic voltammetry and AC impedance spectroscopy. In addition, the surface morphologies, phase structures, and chemical states of the two diamond films were analysed by scanning probe microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy, respectively. The results indicated that the potential window is narrower for the hydrogen-terminated nano-crystalline diamond film than for the oxygen-terminated one. The diamond film resistance and capacitance of oxygen-terminated diamond film are much larger than those of the hydrogen-terminated diamond film, and the polarization resistances and double-layer capacitance corresponding to oxygen-terminated diamond film are both one order of magnitude larger than those corresponding to the hydrogen-terminated diamond film. The electrochemical behaviours of the two diamond film electrodes are discussed.

  17. Voltammetry at micro-mesh electrodes

    Directory of Open Access Journals (Sweden)

    Wadhawan Jay D.

    2003-01-01

    Full Text Available The voltammetry at three micro-mesh electrodes is explored. It is found that at sufficiently short experimental durations, the micro-mesh working electrode first behaves as an ensemble of microband electrodes, then follows the behaviour anticipated for an array of diffusion-independent micro-ring electrodes of the same perimeter as individual grid-squares within the mesh. During prolonged electrolysis, the micro-mesh electrode follows that behaviour anticipated theoretically for a cubically-packed partially-blocked electrode. Application of the micro-mesh electrode for the electrochemical determination of carbon dioxide in DMSO electrolyte solutions is further illustrated.

  18. Stimulation and recording electrodes for neural prostheses

    CERN Document Server

    Pour Aryan, Naser; Rothermel, Albrecht

    2015-01-01

    This book provides readers with basic principles of the electrochemistry of the electrodes used in modern, implantable neural prostheses. The authors discuss the boundaries and conditions in which the electrodes continue to function properly for long time spans, which are required when designing neural stimulator devices for long-term in vivo applications. Two kinds of electrode materials, titanium nitride and iridium are discussed extensively, both qualitatively and quantitatively. The influence of the counter electrode on the safety margins and electrode lifetime in a two electrode system is explained. Electrode modeling is handled in a final chapter.

  19. Influence of Electric Fields on Biofouling of Carbonaceous Electrodes.

    Science.gov (United States)

    Pandit, Soumya; Shanbhag, Sneha; Mauter, Meagan; Oren, Yoram; Herzberg, Moshe

    2017-09-05

    Biofouling commonly occurs on carbonaceous capacitive deionization electrodes in the process of treating natural waters. Although previous work reported the effect of electric fields on bacterial mortality for a variety of medical and engineered applications, the effect of electrode surface properties and the magnitude and polarity of applied electric fields on biofilm development has not been comprehensively investigated. This paper studies the formation of a Pseudomonas aeruginosa biofilm on a Papyex graphite (PA) and a carbon aerogel (CA) in the presence and the absence of an electric field. The experiments were conducted using a two-electrode flow cell with a voltage window of ±0.9 V. The CA was less susceptible to biofilm formation compared to the PA due to its lower surface roughness, lower hydrophobicity, and significant antimicrobial properties. For both positive and negative applied potentials, we observed an inverse relationship between biofilm formation and the magnitude of the applied potential. The effect is particularly strong for the CA electrodes and may be a result of cumulative effects between material toxicity and the stress experienced by cells at high applied potentials. Under the applied potentials for both electrodes, high production of endogenous reactive oxygen species (ROS) was indicative of bacterial stress. For both electrodes, the elevated specific ROS activity was lowest for the open circuit potential condition, elevated when cathodically and anodically polarized, and highest for the ±0.9 V cases. These high applied potentials are believed to affect the redox potential across the cell membrane and disrupt redox homeostasis, thereby inhibiting bacterial growth.

  20. Preparation and Performance of Sb-SnO2 / Ti Electrode Modified with Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    WEI Jin-zhi

    2017-06-01

    Full Text Available In order to improve the electro-catalytic oxidation activity and stability of Sb-SnO2 /Ti electrode,the CNTs-Sb-SnO2 /Ti electrode was prepared by sol-gel-thermal decomposition method. The microstructure and electrochemical properties of the modified electrode was characterized via SEM electrochemical impedance spectroscope ( EIS ,polarization curve and congo red degradation experiments. Furthermore,its the stability was investigated by accelerated life test. The results indicate that when the optimal doping amount of CNTs is 2. 0 g /L the congo red removal rate increases by 14. 7% using the CNTs-Sb-SnO2 /Ti electrode compared with the Sb-SnO2 /Ti electrode. Meanwhile pore structure appears and roughness increases on the surface of modified electrodes leading to larger specific surface area of electrode. Then the modified electrodes exhibit higher oxygen evolution potential and lower charge transfer resistance. Additionally,accelerated life tests reveal that the modified electrode has better electro-catalytic stability while the service life increases by

  1. Dissolved oxygen detection by galvanic displacement-induced ...

    Indian Academy of Sciences (India)

    This paper proposed a simple, efficient and sensitive electrochemical sensor for dissolved oxygen (DO) detection based on a galvanic displacement synthesized reduced graphene oxide–silver nanoparticles (RGO/Ag) composite modified grassy carbon electrode (GCE). The synthesized RGO/Ag nanocomposite was ...

  2. Label-free electrochemical detection of singlet oxygen protein damage

    Czech Academy of Sciences Publication Activity Database

    Vargová, Veronika; Gimenez, R.E.; Černocká, Hana; Trujillo, D.C.; Tulli, F.; Zanini, V.I.P.; Paleček, Emil; Borsarelli, C.D.; Ostatná, Veronika

    2016-01-01

    Roč. 187, JAN 2016 (2016), s. 662-669 ISSN 0013-4686 R&D Projects: GA ČR GA13-00956S Institutional support: RVO:68081707 Keywords : singlet oxygen protein damage * surface-attached protein stability * mercury and carbon electrodes Subject RIV: BO - Biophysics Impact factor: 4.798, year: 2016

  3. Tissue oxygen tensions under physiological and pathological conditions

    NARCIS (Netherlands)

    M. Fennema (Michael)

    1988-01-01

    textabstractThe aims of this thesis are twofold: One - to describe a reliable micro-electrode system for determination of oxygen partial pressures in the micro-area of the tissue and to demonstrate that it is applicable in exxerimental and clinical situations. Two - to demonstrate that

  4. Performance of mixed conducting electrochemical filters for YSZ oxygen sensors

    Energy Technology Data Exchange (ETDEWEB)

    Costa, A.D.S. [ESTGAD, Caldas da Rainha (Portugal). Inst. Politecnico Leiria; Labrincha, J.A.; Marques, F.M.B. [Dept. Eng. Ceramica e do Vidro, Univ. de Aveiro (Portugal)

    1997-12-31

    Oxygen sensors based on yttria stabilized zirconia (YSZ), used in some industrial applications, can be protected by dense filters with high electrochemical permeability to ensure longer lifetime. However, the performance of such sensors can be affected by the surface properties of the filter. This work reports on the relevance of surface processes on the overall oxygen transport rate across the filter. Different materials (filter and electrodes) were tested for this purpose, involving LaCoO{sub 3} (LC) and Ce{sub 0.8}Gd{sub 0.2}O{sub 2} (GCO) single phase or composite filters (combination of both phases), and different deposited electrode materials ((La,Sr)MnO{sub 3} and Pt). For a typical combination involving an ionic conductor as filter (GCO) and electronic conductors as electrodes, the cathodic process seems to be more relevant than the anodic one in determining the protected sensor performance. (orig.) 7 refs.

  5. Kinetics of oxygen reduction reaction at electrochemically fabricated tin-palladium bimetallic electrocatalyst in acidic media

    Energy Technology Data Exchange (ETDEWEB)

    Miah, Md. Rezwan, E-mail: mrmche@yahoo.co [Department of Electronic Chemistry, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Mail Box G1-5, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502 (Japan); Masud, Jahangir [Department of Electronic Chemistry, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Mail Box G1-5, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502 (Japan); Ohsaka, Takeo, E-mail: ohsaka@echem.titech.ac.j [Department of Electronic Chemistry, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Mail Box G1-5, 4259 Nagatsuta, Midori-ku, Yokohama 226-8502 (Japan)

    2010-12-15

    In the present article, oxygen reduction reaction (ORR) at electrochemically fabricated tin-palladium (Sn-Pd) bimetallic electrocatalyst-modified glassy carbon (GC) electrode (Sn-Pd/GC electrode) in acidic media is addressed. Hydrodynamic voltammetric measurements were employed with a view to evaluating various kinetic parameters of the ORR at the Sn-Pd/GC electrode. The obtained results obviously demonstrated that the Sn-Pd bimetallic electrocatalyt substantially promoted the activity of the GC electrode and drove the ORR through an exclusive one-step four-electron pathway forming H{sub 2}O as the final product.

  6. Kinetics of oxygen reduction reaction at electrochemically fabricated tin-palladium bimetallic electrocatalyst in acidic media

    International Nuclear Information System (INIS)

    Miah, Md. Rezwan; Masud, Jahangir; Ohsaka, Takeo

    2010-01-01

    In the present article, oxygen reduction reaction (ORR) at electrochemically fabricated tin-palladium (Sn-Pd) bimetallic electrocatalyst-modified glassy carbon (GC) electrode (Sn-Pd/GC electrode) in acidic media is addressed. Hydrodynamic voltammetric measurements were employed with a view to evaluating various kinetic parameters of the ORR at the Sn-Pd/GC electrode. The obtained results obviously demonstrated that the Sn-Pd bimetallic electrocatalyt substantially promoted the activity of the GC electrode and drove the ORR through an exclusive one-step four-electron pathway forming H 2 O as the final product.

  7. All conducting polymer electrodes for asymmetric solid-state supercapacitors

    KAUST Repository

    Kurra, Narendra

    2015-02-16

    In this study, we report the fabrication of solid-state asymmetric supercapacitors (ASCs) based on conducting polymer electrodes on a plastic substrate. Nanostructured conducting polymers of poly(3,4-ethylenedioxythiophene), PEDOT, and polyaniline (PANI) are deposited electrochemically over Au-coated polyethylene naphthalate (PEN) plastic substrates. Due to the electron donating nature of the oxygen groups in the PEDOT, reduction potentials are higher, allowing it to be used as a negative electrode material. In addition, the high stability of PEDOT in its oxidised state makes it capable to exhibit electrochemical activity in a wide potential window. This can qualify PEDOT to be used as a negative electrode in fabricating asymmetric solid state supercapacitors with PANI as a positive electrode while employing polyvinyl alcohol (PVA)/H2SO4 gel electrolyte. The ASCs exhibit a maximum power density of 2.8 W cm−3 at an energy density of 9 mW h cm−3, which is superior to the carbonaceous and metal oxide based ASC solid state devices. Furthermore, the tandem configuration of asymmetric supercapacitors is shown to be capable of powering a red light emitting diode for about 1 minute after charging for 10 seconds.

  8. Point Electrode Studies of the Solid Electrolyte-Electrode Interface

    DEFF Research Database (Denmark)

    Jacobsen, Torben

    may be masked by memory effects. The aim of the present work is clarify to what extent the picture of a point electrode as a surface in intimate contact surrounded by a reaction zone is influenced by these processes, and to obtain more information on the mechanisms. The basic idea....... A condition for this to work in a reproducible manner is that the properties of the reaction zone are stable. Recent studies have shown that the activity of the reaction zone is influenced by the electrode reaction itself and changes in the morphology have been observed by AFM (1,2,3). As consequence results...

  9. Effects of buffer composition, pH and temperature on oxygen binding ...

    African Journals Online (AJOL)

    1989-03-14

    Mar 14, 1989 ... optical fibre cluster (Schott Mainz, Model KL, West. Germany). Oxygen-binding equilibria of the snail haemoglobins were measured using a thin-layer technique (Dolman &. Gill 1978). A Clark-type oxygen-electrode (Model E. 5046, Radiometer, Denmark) was installed next to the optical cell containing the ...

  10. Artificial oxygen transport protein

    Science.gov (United States)

    Dutton, P. Leslie

    2014-09-30

    This invention provides heme-containing peptides capable of binding molecular oxygen at room temperature. These compounds may be useful in the absorption of molecular oxygen from molecular oxygen-containing atmospheres. Also included in the invention are methods for treating an oxygen transport deficiency in a mammal.

  11. Control of edge effects of oxidant electrode

    Science.gov (United States)

    Carr, Peter; Chi, Chen H.

    1981-09-08

    Described is an electrode assembly comprising; a. a porous electrode having a first and second exterior face with a cavity formed in the interior between said exterior faces thereby having first and second interior faces positioned opposite the first and second exterior faces; b. a counter electrode positioned facing each of the first and second exterior faces of the porous electrode; c. means for passing an oxidant through said porous electrode; and d. screening means for blocking the interior face of the porous electrode a greater amount than the blocking of the respective exterior face of the porous electrode, thereby maintaining a differential of oxidant electrode surface between the interior face and the exterior face. The electrode assembly is useful in a metal, halogen, halogen hydrate electrical energy storage device.

  12. Polarographic determination of Iodide and Iodate, in Solutions Coming from Aerosols in Fission Products Containment Studies in Nuclear Power Stations; Determinacion Polarografica de Especies de Iodo (Ioduro y Iodato) en Soluciones Procedentes de Aerosoles, para Estudios de Contencion de Productos de Fision en Centrales Nucleares

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez, M.; Ballesteros, O.; Fernandez, M.; Clavero, M.; Gonzalez, A. M. [Ciemat, Madrid (Spain)

    2000-07-01

    A polarographic method is described for the iodine species determination, iodide and iodate in water solutions. the iodate can be determined by differential pulse polarography. Calibration curves and the detection and determination limits have been obtained. Iodides is oxidized to iodate with sodium hypochlorite and the excess of oxidizing agent is destroyed with sodium sulphide. The concentration of iodide is calculated as the difference between the concentration of iodate in the sample before and after the oxidation. As an application, species of iodine in samples coming from the experimental plants GIRS (Gaseous Iodine Removal by Sprays) of Nuclear Fission Department of the CIEMAT, dedicated to fission products containment studies in nuclear power station, were determined. (Author) 10 refs.

  13. Electrocatalysis of anodic and cathodic oxygen-transfer reactions

    Energy Technology Data Exchange (ETDEWEB)

    Wels, B.R.

    1990-09-21

    The electrocatalysis of oxygen-transfer reactions is discussed in two parts. In Part I, the reduction of iodate (IO{sub 3}{sup {minus}}) is examined as an example of cathodic oxygen transfer. On oxide-covered Pt electrodes (PtO), a large cathodic current is observed in the presence of IO{sub 3}{sup {minus}} to coincide with the reduction of PtO. The total cathodic charge exceeds the amount required for reduction of PtO and IO{sub 3}{sup {minus}} to produce an adsorbed product. An electrocatalytic link between reduction of IO{sub 3}{sup {minus}} and reduction of PtO is indicated. In addition, on oxide-free Pt electrodes, the reduction of IO{sub 3}{sup {minus}} is determined to be sensitive to surface treatment. The electrocatalytic oxidation of CN{sup {minus}} is presented as an example of anodic oxygen transfer in Part II. The voltametric response of CN{sup {minus}} is virtually nonexistent at PbO{sub 2} electrodes. The response is significantly improved by doping PbO{sub 2} with Cu. Cyanide is also oxidized effectively at CuO-film electrodes. Copper is concluded to serve as an adsorption site for CN{sup {minus}}. It is proposed that an oxygen tunneling mechanism comparable to electron tunneling does not occur at the electrode-solution interface. The adsorption of CN{sup {minus}} is therefore considered to be a necessary prerequisite for oxygen transfer. 201 refs., 23 figs., 2 tabs.

  14. A cold plasma plume with a highly conductive liquid electrode

    International Nuclear Information System (INIS)

    Chen Guangliang; Chen Wenxing; Chen Shihua; Yang Size

    2008-01-01

    A cold dielectric barrier discharge (DBD) plasma plume with one highly conductive liquid electrode has been developed to treat thermally sensitive materials, and its preliminary discharging characteristics have been studied. The averaged electron temperature and density is estimated to be 0.6eV and 10 11 /cm 3 , respectively. The length of plasma plume can reach 5 cm with helium gas (He), and the conductivity of the outer electrode affects the plume length obviously. This plasma plume could be touched by bare hand without causing any burning or painful sensation, which may provide potential application for safe aseptic skin care. Moreover, the oxidative particles (e.g., OH, O * , O 3 ) in the downstream oxygen (O2) gas of the plume have been applied to treat the landfill leachate. The results show that the activated O 2 gas can degrade the landfill leachate effectively, and the chemical oxygen demand (COD), conductivity, biochemical oxygen demand (BOD), and suspended solid (SS) can be decreased by 52%, 57%, 76% and 92%, respectively. (fluids, plasmas and electric discharges)

  15. Composite Electrodes for Electrochemical Supercapacitors

    Directory of Open Access Journals (Sweden)

    Yang QuanMin

    2010-01-01

    Full Text Available Abstract Manganese dioxide nanofibers with length ranged from 0.1 to 1 μm and a diameter of about 4–6 nm were prepared by a chemical precipitation method. Composite electrodes for electrochemical supercapacitors were fabricated by impregnation of the manganese dioxide nanofibers and multiwalled carbon nanotubes (MWCNT into porous Ni plaque current collectors. Obtained composite electrodes, containing 85% of manganese dioxide and 15 mass% of MWCNT, as a conductive additive, with total mass loading of 7–15 mg cm−2, showed a capacitive behavior in 0.5-M Na2SO4 solutions. The decrease in stirring time during precipitation of the nanofibers resulted in reduced agglomeration and higher specific capacitance (SC. The highest SC of 185 F g−1 was obtained at a scan rate of 2 mV s−1 for mass loading of 7 mg cm−2. The SC decreased with increasing scan rate and increasing electrode mass.

  16. RETGEM with polyvinylchloride (PVC) electrodes

    CERN Document Server

    Razin, V I; Reshetin, A I; Filippov, S N

    2009-01-01

    This paper presents a new design of the RETGEM (Resistive Electrode Thick GEM) based on electrodes made of a polyvinylchloride material (PVC). Our device can operate with gains of 10E5 as a conventional TGEM at low counting rates and as RPC in the case of high counting rates without of the transit to the violent sparks. The distinct feature of present RETGEM is the absent of the metal coating and lithographic technology for manufacturing of the protective dielectric rms. The electrodes from PVC permit to do the holes by a simple drilling machine. Detectors on a RETGEM basis could be useful in many fields of an application requiring a more cheap manufacturing and safe operation, for example, in a large neutrino experiments, in TPC, RICH systems.

  17. Nanofiber membrane-electrode-assembly and method of fabricating same

    Science.gov (United States)

    Pintauro, Peter N.; Ballengee, Jason; Brodt, Matthew

    2016-02-02

    In one aspect of the present invention, a fuel cell membrane-electrode-assembly (MEA) has an anode electrode, a cathode electrode, and a membrane disposed between the anode electrode and the cathode electrode. At least one of the anode electrode, the cathode electrode and the membrane is formed of electrospun nanofibers.

  18. Double layer of platinum electrodes: Non-monotonic surface charging phenomena and negative double layer capacitance

    Science.gov (United States)

    Huang, Jun; Zhou, Tao; Zhang, Jianbo; Eikerling, Michael

    2018-01-01

    In this study, a refined double layer model of platinum electrodes accounting for chemisorbed oxygen species, oriented interfacial water molecules, and ion size effects in solution is presented. It results in a non-monotonic surface charging relation and a peculiar capacitance vs. potential curve with a maximum and possibly negative values in the potential regime of oxide-formation.

  19. Electrokinetic and impedimetric dynamics of FeCo-nanoparticles on glassy carbon electrode

    CSIR Research Space (South Africa)

    Ikpo, CO

    2013-01-01

    Full Text Available voltammetric experiments revealed a diffusion-controlled electron transfer process on the GCE/FeCo electrode surface. Further interrogation on the electrochemical properties of the FeCo nanoelectrode in an oxygen saturated 1 M LiClO4 containing 1:1 v/v ethylene-carbonate...

  20. Oxygen-enhanced combustion

    CERN Document Server

    Baukal, Charles E

    2013-01-01

    Combustion technology has traditionally been dominated by air/fuel combustion. However, two developments have increased the significance of oxygen-enhanced combustion-new technologies that produce oxygen less expensively and the increased importance of environmental regulations. Advantages of oxygen-enhanced combustion include less pollutant emissions as well as increased energy efficiency and productivity. Oxygen-Enhanced Combustion, Second Edition compiles information about using oxygen to enhance industrial heating and melting processes. It integrates fundamental principles, applications, a

  1. Production method of nickel electrode

    Science.gov (United States)

    Ikeda, H.; Ohira, T.

    1982-01-01

    A nickel electrode having improved charging efficiency, an increased coefficient of discharging utilization, and large capacity is disclosed. Nickel hydroxide or nickel oxide is retained in a porous nickel substrate which is immersed in an aqueous solution of cobalt acetate with a pH 4.0 to 6.8. The electrode thus obtained is then immersed in an alkaline solution or heated to change cobalt acetate into cobalt hydroxide or cobalt oxide whereby the surface of nickel active material is covered with cobalt crystals and alloying of cobalt and nickel is promoted at the same time.

  2. Nanofiber membrane-electrode-assembly and method of fabricating same

    Energy Technology Data Exchange (ETDEWEB)

    Pintauro, Peter N.; Ballengee, Jason; Brodt, Matthew

    2018-01-23

    In one aspect of the present invention, a method of fabricating a fuel cell membrane-electrode-assembly (MEA) having an anode electrode, a cathode electrode, and a membrane disposed between the anode electrode and the cathode electrode, includes fabricating each of the anode electrode, the cathode electrode, and the membrane separately by electrospinning; and placing the membrane between the anode electrode and the cathode electrode, and pressing then together to form the fuel cell MEA.

  3. On the noise performance of pt electrodes.

    Science.gov (United States)

    Liu, Xiao; Demosthenous, Andreas; Donaldson, Nick

    2007-01-01

    We measured the noise and impedance from Pt electrode pairs in a frequency band from 100 Hz to 10 kHz, containing the ENG band (500 Hz 5 kHz). The results show that the Pt electrode noise is the same as the thermal noise from the real part of the electrode impedance, which is a summation of the polarisation resistance and the access resistance. This differs from Ag-AgCl electrodes for which the electrode noise has been reported to be higher than the thermal noise. Our study shows that Pt electrodes are suitable for neural recording.

  4. Heterogeneous electron transfer and oxygen reduction reaction at nanostructured iron(II) phthalocyanine and its MWCNTs nanocomposites

    CSIR Research Space (South Africa)

    Mamuru, SA

    2010-05-01

    Full Text Available Electron transfer and oxygen reduction dynamics at nanostructured iron(II) phthalocyanine/multi-walled carbon nanotubes composite supported on an edge plane pyrolytic graphite electrode (EPPGE-MWCNT-nanoFePc) platform have been reported. All...

  5. Electrochemical capacity fading of polyaniline electrode in supercapacitor: An XPS analysis

    Directory of Open Access Journals (Sweden)

    Jinxing Deng

    2017-04-01

    Full Text Available To understand the electrochemical capacity fading of the polyaniline (PANI electrodes in supercapacitors, for the first time, their chemical structure change during electrochemical cycles was traced with XPS analysis after the HCl doped PANI electrodes were subjected to the cyclic voltammetry test in 1.0 M H2SO4 electrolyte for different cycle numbers. The results showed that the chlorine disappeared in the electrode surface, while the surface element contents of sulfur and oxygen increased with the electrochemical cycles increased. It demonstrated that the hydrolytic degradation of the PANI chains and exchange of dopant occurred during the electrochemical cycling, causing the fading in the mechanical and electrochemical performance of the PANI electrodes. This understanding should lead to better design of the conductive polymer-based energy storage devices.

  6. Membrane-electrode structures for molecular catalysts for use in fuel cells and other electrochemical devices

    Energy Technology Data Exchange (ETDEWEB)

    Kerr, John B.; Zhu, Xiaobing; Hwang, Gi Suk; Martin, Zulima; He, Qinggang; Driscoll, Peter; Weber, Adam; Clark, Kyle

    2016-09-27

    Water soluble catalysts, (M)meso-tetra(N-Methyl-4-Pyridyl)Porphinepentachloride (M=Fe, Co, Mn & Cu), have been incorporated into the polymer binder of oxygen reduction cathodes in membrane electrode assemblies used in PEM fuel cells and found to support encouragingly high current densities. The voltages achieved are low compared to commercial platinum catalysts but entirely consistent with the behavior observed in electroanalytical measurements of the homogeneous catalysts. A model of the dynamics of the electrode action has been developed and validated and this allows the MEA electrodes to be optimized for any chemistry that has been demonstrated in solution. It has been shown that improvements to the performance will come from modifications to the structure of the catalyst combined with optimization of the electrode structure and a well-founded pathway to practical non-platinum group metal catalysts exists.

  7. Characterization of porous texture of cermet electrode for steam electrolysis at intermediate temperature

    International Nuclear Information System (INIS)

    Deslouis, C.; Keddam, M.; Rahmouni, K.; Takenouti, H.; Grasset, F.; Lacroix, O.; Sala, B.

    2011-01-01

    Electrodes designed for PCEC (Proton Conducting Electrolyzing Cell) should ensure both electron and proton conductions and also allowed the supply or the draining of gaseous phase such as steam, hydrogen and oxygen. Porous cermet electrodes fulfil these requirements: percolated metallic phase for electron conduction, ceramic for proton conduction, and pores for transport of reactant and products in gas phase. The electrochemical reactions will take place at boundaries of these three phases, commonly named triple points. Therefore, the cermet electrode has to possess a sufficient open porosity and the expanded metallic surface area exposed to pores as large as possible. In this work, the pore texture of cermet electrodes was characterized by means of Electrochemical Impedance Spectroscopy in aprotic liquid medium. The parameter regression calculation based on de Levie's transmission-line model allowed us to determine the pore texture characterized by expanded surface area, number, mean radius of pores, and open porosity.

  8. Analysis of SOFCs Using Reference Electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Finklea, H.; Chen, X.; Gerdes, K.; Pakalapati, S.; Celik, I.

    2013-01-01

    Reference electrodes are frequently applied to isolate the performance of one electrode in a solid oxide fuel cell. However, reference electrode simulations raise doubt to veracity of data collected using reference electrodes. The simulations predict that the reported performance for the one electrode will frequently contain performance of both electrodes. Nonetheless, recent reports persistently treat data so collected as ideally isolated. This work confirms the predictions of the reference electrode simulations on two SOFC designs, and to provides a method of validating the data measured in the 3-electrode configuration. Validation is based on the assumption that a change in gas composition to one electrode does not affect the impedance of the other electrode at open circuit voltage. This assumption is supported by a full physics simulation of the SOFC. Three configurations of reference electrode and cell design are experimentally examined using various gas flows and two temperatures. Impedance data are subjected to deconvolution analysis and equivalent circuit fitting and approximate polarization resistances of the cathode and anode are determined. The results demonstrate that the utility of reference electrodes is limited and often wholly inappropriate. Reported impedances and single electrode polarization values must be scrutinized on this basis.

  9. Production and characterization of TI/PbO2 electrodes by a thermal-electrochemical method

    Directory of Open Access Journals (Sweden)

    Laurindo Edison A.

    2000-01-01

    Full Text Available Looking for electrodes with a high overpotential for the oxygen evolution reaction (OER, useful for the oxidation of organic pollutants, Ti/PbO2 electrodes were prepared by a thermal-electrochemical method and their performance was compared with that of electrodeposited electrodes. The open-circuit potential for these electrodes in 0.5 mol L-1 H2SO4 presented quite stable similar values. X-ray diffraction analyses showed the thermal-electrochemical oxide to be a mixture of ort-PbO, tetr-PbO and ort-PbO2. On the other hand, the electrodes obtained by electrodeposition were in the tetr-PbO2 form. Analyses by scanning electron microscopy showed that the basic morphology of the thermal-electrochemical PbO2 is determined in the thermal step, being quite distinct from that of the electrodeposited electrodes. Polarization curves in 0.5 mol L-1 H2SO4 showed that in the case of the thermal-electrochemical PbO2 electrodes the OER was shifted to more positive potentials. However, the values of the Tafel slopes, quite high, indicate that passivating films were possibly formed on the Ti substrates, which could eventually explain the somewhat low current values for OER.

  10. Research on PEG modified Bi-doping lead dioxide electrode and mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Yang Weihua, E-mail: yangwh@hqu.edu.cn [College of Materials Science and Engineering, Huaqiao University, Xiamen 361021 (China); Yang Wutao; Lin Xiaoyan [College of Materials Science and Engineering, Huaqiao University, Xiamen 361021 (China)

    2012-05-15

    Bi-doping PbO{sub 2} electrode, which is called Bi-PbO{sub 2} for short, modified with different concentrations of polyethylene glycol (PEG) was prepared by electrodeposition method in this paper. The microstructure and electrochemical properties of the different modified electrodes were investigated using scanning electron microscopy, X-ray diffraction, Mott-Schottky, electrochemical impedance spectroscopy and linear sweep voltammetry techniques. The results show that adulteration of PEG has a noticeable improvement in the morphology of Bi-PbO{sub 2} electrode which can greatly decrease its particle size and enlarge its active surface area. Phenol degradation experiments reveal that the modified electrodes have excellent electro-catalytic activity and stability, and the optimal adulterate concentration of PEG is 8 g L{sup -1}. Electrochemical performance tests show that the modified electrodes exhibit more negative flatband potential (E{sub fb}), larger adsorption pseudo capacitance, lower adsorption resistance and higher oxygen evolution potential, and these characteristics promote the electro-catalytic activity of the Bi-PbO{sub 2} electrode. Finally, accelerated lifetime tests demonstrate that PEG modification can highly lengthen the service life of Bi-PbO{sub 2} electrode in its practical application.

  11. Electrodeposited nanostructured raspberry-like gold-modified electrodes for electrocatalytic applications

    International Nuclear Information System (INIS)

    Manivannan, Shanmugam; Ramaraj, Ramasamy

    2013-01-01

    A facile method for fabrication of raspberry-like Au nanostructures (Au NRBs)-modified electrode by electrodeposition and its applications toward the electrocatalytic oxidation of methanol (MOR) in alkaline medium and oxygen reduction reaction (ORR) in both alkaline and acidic media are demonstrated. The Au NRBs are characterized by UV–Vis absorption spectra, SEM, X-ray diffraction, and electrochemical measurements. The growth of Au NRBs was monitored by recording the in-situ absorption spectral changes during electrodeposition using spectroelectrochemical technique. Here we systematically studied the MOR by varying several reaction parameters such as potential scan rate and methanol concentration. The electrocatalytic poisoning effect due to the MOR products are not observed at the Au NRBs-modified electrode. At the alkaline medium the Au NRBs-modified electrode shows the better catalytic activities toward the MOR and ORR when compared to the poly crystalline gold and bare glassy carbon electrodes. The Au NRBs-modified electrode is a promising and inexpensive electrode material for other electrocatalytic applications.Graphical AbstractRaspberry-like Au nanostructures modified electrode is prepared and used for electrocatalytic applications

  12. Activation method of the fuel electrode of a methanol fuel cell. Methanol nenryo denchi no nenryokyoku no kasseika hoho

    Energy Technology Data Exchange (ETDEWEB)

    Ozeki, H.; Tanizaki, K.; Dokoshi, H. (Aisin AW Co. Ltd., Aichi (Japan))

    1992-09-04

    It is known that, with the addition of 1-2% of oxygen to the fuel in a methanol fuel cell, carbon monoxide adsorbed on a platinum catalyst is oxidized to carbon dioxide, liberated from the platinum catalyst and exhausted from the fuel chamber. However, in this method, the efficiency of the fuel cell decreases because oxygen is always contained in the fuel and burnt directly in the fuel electrode. Moreover, in case platinum-ruthenium is used as a catalyst in the fuel electrode, the catalyst adsorbs oxygen very well and a small amount of hydrogen or oxygen should be supplied from the outside in order to activate the catalyst. The invention concerns an activation method of the oxygen-adsorbing fuel electrode of a methanol fuel cell, in which water in the electrolyte solution in the methanol fuel cell is eletrolyzed by the use of the fuel cell as a cathode with an external power supply so as to remove the oxygen adsorbed in the fuel electrode. 7 figs.

  13. Surface intermediates on metal electrodes at high temperatures

    DEFF Research Database (Denmark)

    Zachau-Christiansen, Birgit; Jacobsen, Torben; Bay, Lasse

    1998-01-01

    The mechanisms widely conceived for the O(2)-reduction or H(2)-oxidation reactions in SOFC's involve intermediate O/H species adsorbed on the electrode surface. The presence of these intermediates is investigated by linear sweep voltammetry. In air at moderate temperatures (500 degrees C) Pt...... in contact with YSZ is covered with adsorbed oxygen which vanishes at high temperature (1000 degrees C). On Ni (YSZ) a specific layer of NiO is observed above the equilibrium potential while no surface species involving hydrogen can be identified at SOFC anode conditions. (C) 1998 Published by Elsevier...... Science B.V. All rights reserved....

  14. Luminescence studies of semiconductor electrodes

    NARCIS (Netherlands)

    Kelly, J.J.; Kooij, Ernst S.; Meulenkamp, E.A.

    1999-01-01

    In this paper we review our recent results of in-situ luminescence studies of semiconductor electrodes. Three classes of materials are considered: single crystal compound semiconductors, porous silicon and semiconducting oxides doped with luminescent ions. We show how photoluminescence (PL) and

  15. Efficient degassing of dissolved oxygen in aqueous media by microwave irradiation and the effect of microwaves on a reaction catalyzed by Wilkinson's catalyst

    International Nuclear Information System (INIS)

    Horikoshi, Satoshi; Matsuzaki, Shohei; Sakamoto, Shintaro; Serpone, Nick

    2014-01-01

    To the extent that some reactions are oxygen-sensitive, we herein examined the degassing of dissolved oxygen in water and in 2-propanol solvent by microwave heating with regard to the effects of the microwave frequency (2.45 GHz versus 915 MHz), and with regard to when samples are subjected to electric-field-rich and magnetic-field rich 2.45-GHz microwaves. Changes in the quantity of dissolved oxygen were ascertained by monitoring its concentration in such solvents when exposed to microwave and conventional heating using a polarographic technique and by the chemical oxygen demand (COD) method. The specific microwave (non-thermal) effect played a role in the degassing process on comparing results between microwave heating and conventional heating under identical temperature conditions. The 915-MHz microwaves were more effective, at least at 60 °C, owing to their greater penetration into the solutions. No significant differences were found when degassing was carried out on exposing the water sample to 2.45-GHz microwaves with the sample located within the waveguide at positions rich in either the electric field or the magnetic field (T=80 °C). Conversion of cyclohexanone to cyclohexanol via hydrogen transfer in the presence of Wilkinson's catalyst and 2-propanol solvent (hydrogen source) was also investigated to assess the effect(s) that microwaves might have on this oxygen-sensitive reaction with respect to product yields in contrast to conventional heating by the oil-bath method. - Highlights: • Degassing dissolved oxygen in water was enhanced when using microwave heating. • Degassing was more effective with lower frequency microwaves. • Synthesis of cyclohexanol with Wilkinson's catalyst was investigated under microwave irradiation

  16. Noise properties of textile, capacitive EEG electrodes

    Directory of Open Access Journals (Sweden)

    Asl Sara Nazari

    2015-09-01

    Full Text Available The rigid surface of the conventional PCB-based capacitive electrode produces an undefined distance between the skin and the electrode surface. Therefore, the capacitance introduced by them is uncertain and can vary from electrode to electrode due to their different positions on the scalp. However, textile electrodes which use conductive fabric as electrode surfaces, are bendable over the scalp. Therefore, it provides a certain value of the capacitance which is predictable and calculable accurately if the effective distance to the scalp surface can be determined. In this paper noise characteristics of textile electrodes with different fabric sizes as electrode’s surface and capacity calculations related to each size are presented to determine the effective distances for each electrode size.

  17. Integral skin electrode for electrocardiography is expendable

    Science.gov (United States)

    1966-01-01

    Inexpensive, expendable skin electrode for use in electrocardiography combines an electrical contact, conductive paste, and a skin-attachment adhesive. Application of the electrode requires only degreasing of the skin area.

  18. Recovery of fluoride ion selective electrode

    International Nuclear Information System (INIS)

    Monteiro, R.P.G.

    1988-01-01

    A recovery procedure of fluoride ion selective electrode based upon the body radiography of inactive electrode and introduction of suitable internal regeneration solution, is developed. The recovered electrode was tested in standard solutions of fluoride ions (10 sup5) to 10 -1M showing as good performance as the new one. The fluor determination by potentiometric measurements with selective electrode is used in nuclear fuel cycle for quality control of thorium and uranium mixed oxide pellets and pellets of uranium dioxides. (author) [pt

  19. Alkali metal ion battery with bimetallic electrode

    Science.gov (United States)

    Boysen, Dane A; Bradwell, David J; Jiang, Kai; Kim, Hojong; Ortiz, Luis A; Sadoway, Donald R; Tomaszowska, Alina A; Wei, Weifeng; Wang, Kangli

    2015-04-07

    Electrochemical cells having molten electrodes having an alkali metal provide receipt and delivery of power by transporting atoms of the alkali metal between electrode environments of disparate chemical potentials through an electrochemical pathway comprising a salt of the alkali metal. The chemical potential of the alkali metal is decreased when combined with one or more non-alkali metals, thus producing a voltage between an electrode comprising the molten the alkali metal and the electrode comprising the combined alkali/non-alkali metals.

  20. Minimizing electrode contamination in an electrochemical cell

    Science.gov (United States)

    Kim, Yu Seung; Zelenay, Piotr; Johnston, Christina

    2014-12-09

    An electrochemical cell assembly that is expected to prevent or at least minimize electrode contamination includes one or more getters that trap a component or components leached from a first electrode and prevents or at least minimizes them from contaminating a second electrode.

  1. Fluctuations at Electrode-YSZ Interfaces

    DEFF Research Database (Denmark)

    Jacobsen, Torben; Hansen, Karin Vels; Skou, Eivind

    in performance [\\ref{McEvoy}, \\ref{Adler}]. This sensitivity to the pre-history is probably one of the explanations for the discrepancies between results reported for single electrode studies. The mechanism behind the activation is still an unresolved problem. In the case of point electrodes, i.e. electrodes...

  2. Measurement of noise and impedance of dry and wet textile electrodes, and textile electrodes with hydrogel.

    Science.gov (United States)

    Puurtinen, Merja M; Komulainen, Satu M; Kauppinen, Pasi K; Malmivuo, Jaakko A V; Hyttinen, Jari A K

    2006-01-01

    Textile sensors, when embedded into clothing, can provide new ways of monitoring physiological signals, and improve the usability and comfort of such monitoring systems in the areas of medical, occupational health and sports. However, good electrical and mechanical contact between the electrode and the skin is very important, as it often determines the quality of the signal. This paper introduces a study where the properties of dry textile electrodes, textile electrodes moistened with water, and textile electrodes covered with hydrogel were studied with five different electrode sizes. The aim was to study how the electrode size and preparation of the electrode (dry electrode/wet electrode/electrode covered with hydrogel membrane) affect the measurement noise, and the skin-electrode impedance. The measurement noise and skin-electrode impedance were determined from surface biopotential measurements. These preliminary results indicate that noise level increases as the electrode size decreases. The noise level is high in dry textile electrodes, as expected. Yet, the noise level of wet textile electrodes is quite low and similar to that of textile electrodes covered with hydrogel. Hydrogel does not seem to improve noise properties, however it may have effects on movement artifacts. Thus, it is feasible to use textile embedded sensors in physiological monitoring applications when moistening or hydrogel is applied.

  3. Oxygen transport membrane

    DEFF Research Database (Denmark)

    2015-01-01

    The present invention relates to a novel composite oxygen transport membrane as well as its preparation and uses thereof.......The present invention relates to a novel composite oxygen transport membrane as well as its preparation and uses thereof....

  4. Miniature oxygen resuscitator

    Science.gov (United States)

    Johnson, G.; Teegen, J. T.; Waddell, H.

    1969-01-01

    Miniature, portable resuscitation system is used during evacuation of patients to medical facilities. A carrying case contains a modified resuscitator head, cylinder of oxygen, two-stage oxygen regulator, low pressure tube, and a mask for mouth and nose.

  5. Apparatus for Screening Multiple Oxygen-Reduction Catalysts

    Science.gov (United States)

    Whitacre, Jay; Narayanan, Sekharipuram

    2009-01-01

    An apparatus that includes an array of multiple electrodes has been invented as a means of simultaneously testing multiple materials for their utility as oxygen-reduction catalysts in fuel cells. The apparatus ensures comparability of test results by exposing all the catalyst-material specimens to the same electrolytic test solution at the same potential. Heretofore, it has been possible to test only one specimen at a time, using a precise rotating disk electrode that provides a controlled flux of solution to the surface of the specimen.

  6. Cryptococcus neoformans and oxygen

    OpenAIRE

    Vladislav,Raclavsky

    2006-01-01

    Oxygen is essential to life of all organisms except for obligate anaerobic species, because it is necessary for energy generation and also for some biosynthetic pathways. However, sensitivity to low oxygen levels can vary widely in different organisms and cell types. The pathogenic yeast species Cryptococcus neoformans is known to love oxygen. In response to the lack of oxygen (hypoxia), this yeast delays budding without resigning DNA replication, which eventually results in unique cell cycle...

  7. Proterozoic atmospheric oxygen

    DEFF Research Database (Denmark)

    Canfield, Donald Eugene

    2014-01-01

    This article is concerned with the evolution of atmospheric oxygen concentrations through the Proterozoic Eon. In particular, this article will seek to place the history of atmospheric oxygenation through the Proterozoic Eon in the context of the evolving physical environment including the history...... of continental growth and volcanic outgassing, as well as biogeochemical processing of elements within the oceans. The author will seek to explore constraints on the history of oxygenation and understand which processes have regulated oxygen through this eon....

  8. [Domiciliary oxygen therapy].

    Science.gov (United States)

    Abdel Kafi, S

    2010-09-01

    In Belgium, oxygen therapy is becoming more and more accessible. When oxygen is needed for short periods or for special indications as palliative care, an agreement between mutual insurance companies and pharmacists allows the practitioner the home installation of gazeous oxygen cylinder or of oxygen concentrator. When long term oxygen therapy (LTOT) is indicated for patients with respiratory insufficiency, the pneumologist must first ask the INAMI the authorization to install one of the following modalities: oxygen concentrator with or without demand oxygen delivery cylinder and liquid oxygen. The goal of LTOT is to increase survival and quality of life. The principal and well accepted indication for LTOT is severe hypoxemia. The beneficial effects of oxygen therapy limited at night or on exertion are controversial. In order to increase patient's autonomy, oxygen can be prescribed for ambulation, respecting prescription's rules. At each step of oxygen therapy implementing (indication, choice of the device and follow-up) the patient under oxygen may benefit from a joint approach between the general practitioner and the chest specialist.

  9. Oxygen sensitive microwells.

    Science.gov (United States)

    Sinkala, Elly; Eddington, David T

    2010-12-07

    Oxygen tension is critical in a number of cell pathways but is often overlooked in cell culture. One reason for this is the difficulty in modulating and assessing oxygen tensions without disturbing the culture conditions. Toward this end, a simple method to generate oxygen-sensitive microwells was developed through embossing polystyrene (PS) and platinum(ii) octaethylporphyrin ketone (PtOEPK) thin films. In addition to monitoring the oxygen tension, microwells were employed in order to isolate uniform clusters of cells in microwells. The depth and width of the microwells can be adapted to different experimental parameters easily by altering the thin film processing or embossing stamp geometries. The thin oxygen sensitive microwell substrate is also compatible with high magnification modalities such as confocal imaging. The incorporation of the oxygen sensor into the microwells produces measurements of the oxygen tension near the cell surface. The oxygen sensitive microwells were calibrated and used to monitor oxygen tensions of Madin-Darby Canine Kidney Cells (MDCKs) cultured at high and low densities as a proof of concept. Wells 500 µm in diameter seeded with an average of 330 cells exhibited an oxygen level of 12.6% whereas wells seeded with an average of 20 cells per well exhibited an oxygen level of 19.5%, a 35.7% difference. This platform represents a new tool for culturing cells in microwells in a format amenable to high magnification imaging while monitoring the oxygen state of the culture media.

  10. Electrochemical pretreatment of heavy oil refinery wastewater using a three-dimensional electrode reactor

    International Nuclear Information System (INIS)

    Wei Lingyong; Guo Shaohui; Yan Guangxu; Chen Chunmao; Jiang Xiaoyan

    2010-01-01

    The pretreatment of heavy oil refinery wastewater (HORW) was experimentally investigated using a three-dimensional electrode reactor (TDER) with granular activated carbon (GAC) and porous ceramsite particle (PCP) as the combination particle electrode and DSA type anodes as the anode. The results showed that higher chemical oxygen demand (COD) removal was obtained in TDER comparing with the two-dimensional electrode reactor (without particle electrodes packed), and combination particle electrode was favorable to improve the COD removal efficiency and reduce the energy consumption. The treated HORW under the optimal experimental condition (GAC percentage = 75%, current density = 30 mA/cm 2 , pH not adjusted and treatment time = 100 min) presented that the removal efficiencies of COD, total organic carbon and toxicity units were 45.5%, 43.3% and 67.2%, respectively, and the ratio of 5-day biochemical oxygen demand to COD was increased from 0.10 to 0.29, which is beneficial for further biological treatment. Furthermore, the application of electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry to characterize polar compounds in HORW and their oxidation products was well demonstrated to reveal the composition variation.

  11. Reversible Decomposition of Secondary Phases in BaO Infiltrated LSM Electrodes-Polarization Effects

    DEFF Research Database (Denmark)

    Traulsen, Marie Lund; McIntyre, Melissa D.; Norrman, Kion

    2016-01-01

    potential. A changing electrode surface is observed during operation as the Ba3Mn2O8 secondary phase decomposes and manganese oxide accumulates on the electrode surface during cathodic polarization. The observed changes are reversible. These results suggest that the formation of Ba3Mn2O8 is responsible...... and Raman spectroscopy reveal the formation of a secondary phase, Ba3Mn2O8, on the electrode. During the in operando Raman investigation of the BaO-infiltrated La0.85Sr0.15MnO3±δ electrodes, experiments are performed at 300 and 500 °C with oxygen partial pressure 0.1 atm and with −1 or +1 V Applied...... for the reduced polarization resistance observed at open Circuit voltage (OCV) in an oxygen containing atmosphere. Furthermore, the results illustrate the dramatic differences between the electrode surface composition at OCV and during cathodic polarization. Overall, the results highlight the dynamic interactions...

  12. Piercing by composite electrode tool

    International Nuclear Information System (INIS)

    Abdukarimov, Eh.T.; Krakov, B.G.; Saidinov, S.Ya.

    1990-01-01

    The construction of the electrode consisting of a dielectric shell, where a working liquid enters, and a metal rod is designed for precision super-deep piercing by the electroerosion treatment method. Technological parameters of piercing with small diameter (0.5-1.9 mm) for 12Kh18N10T steel, copper and tungsten are presented. A possibility to use a new tool for treating components of any form and sizes is marked

  13. Potentiometric titration with polarized electrodes

    International Nuclear Information System (INIS)

    Chikryzova, E.G.

    1977-01-01

    Based on the analysis of the works carried out during 1911-75 consideration is given to the present state of the method of potentiometric titration with polarized electrodes. The material is generalized in the tabular form indicating the elments of interest, titration conditions and the objects to be analyzed. The list and classification of the potentiometric titration methods intended for determining organic and inorganic substances are presented

  14. Surface modification of recording electrodes

    Directory of Open Access Journals (Sweden)

    Iaci Miranda Pereira

    2013-01-01

    Full Text Available Waterborne Polyurethanes (PUs are a family of polymers that contains urethane linkages synthesized in an aqueous environment and are thus free of organic solvents. Recently, waterborne PUs have been extensively studied for biomedical applications because of their biocompatibility. The present work investigates the following: (1 the impact on electrical performance of electrode materials (platinum and silicon modified chemically by a layer of waterborne PU, and (2 the behavior of rat cardiac fibroblasts and rat cardiomyocytes when in contact with an electrode surface. Diisocyanate and poly(caprolactone diol were the main reagents for producing PUs. The electrochemical impedance of the electrode/electrolyte interface was accessed by electrochemical impedance spectroscopy. The cellular viability, proliferation, and morphology changes were investigated using an MTT assay. Cardiomyocyte adherence was observed by scanning electron microscopy. The obtained surface was uniform, flat, and transparent. The film showed good adhesion, and no peeling was detected. The electrochemical impedance decreased over time and was influenced by the ionic permeability of the PU layer. The five samples did not show cytotoxicity when in contact with neonatal rat cells.

  15. Variations in tumour oxygen tension (pO{sub 2}) during accelerated radiotherapy of head and neck carcinoma

    Energy Technology Data Exchange (ETDEWEB)

    Guichard, M. [Laboratory of Radiobiology, Institut Gustave Roussy, 94800 Villejuif (France); Eschwege, F. [Department of Radiotherapy, Institut Gustave Roussy, 94800 Villejuif (France); Luboinski, B. [Department of Head and Neck Surgery, Institut Gustave Roussy, 94800 Villejuif (France); Wibault, P. [Department of Radiotherapy, Institut Gustave Roussy, 94800 Villejuif (France); Weeger, P. [Department of Head and Neck Surgery, Institut Gustave Roussy, 94800 Villejuif (France); Lusinchi, A.; Lartigau, E. [Department of Radiotherapy, Institut Gustave Roussy, 94800 Villejuif (France)

    1998-05-01

    The study was performed to assess the effect of accelerated radiotherapy on oxygenation of primary tumours and metastatic nodes in patients with advanced head and neck tumours. In 14 patients with head and neck tumour, oxygen tension (pO{sub 2}) was evaluated in normal tissues and tumours (primary tumour or metastatic neck node) before (0 Gy) and after 2 weeks (32 Gy) of accelerated radiotherapy (70 Gy in 3.5 weeks, with three daily fractions). Radiotherapy was combined with carbogen breathing in 5 patients. pO{sub 2} was measured using a polarographic technique. For pooled normal tissues, median pO{sub 2} was 38 mmHg before treatment and 46 mmHg after 2 weeks. For tumours, very low values (<2 mmHg) represented 20% of the recorded values before treatment and 10% after 2 weeks. The relative increase in tumour oxygenation was more pronounced for primary tumours (median pO{sub 2} 12 mmHg before treatment versus 26 mmHg after 2 weeks, P<0.05) than for metastatic nodes (respectively, 20 and 27 mmHg P=0.1). For the 5 patients who breathed carbogen during accelerated radiotherapy, the median pO{sub 2} was 44 mmHg at 2 weeks, compared with 13.5 mmHg before treatment (P=0.05). Very low pO{sub 2} values, corresponding to tumour hypoxia, were found in the tumours (primary and metastatic neck nodes) prior to accelerated treatment. During the first 2 weeks of accelerated treatment, an increase in median pO{sub 2} was found in nine of the 14 tumours, together with a decrease in the frequency of very low values. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

  16. Different electrode configurations to optimize performance of multi-electrode microbial fuel cells for generating power or treating domestic wastewater

    KAUST Repository

    Ahn, Yongtae

    2014-03-01

    Scaling-up of microbial fuel cells (MFCs) for practical applications requires compact, multiple-electrode designs. Two possible configurations are a separator electrode assembly (SEA) or closely spaced electrodes (SPA) that lack a separator. It is shown here that the optimal configuration depends on whether the goal is power production or rate of wastewater treatment. SEA MFCs produced a 16% higher maximum power density (328 ± 11 mW m-2) than SPA MFCs (282 ± 29 mW m-2), and higher coulombic efficiencies (SEAs, 9-31%; SPAs, 2-23%) with domestic wastewater. However, treatment was accomplished in only 12 h with the SPA MFC, compared to 36 h with the SEA configuration. Ohmic resistance was not a main factor in performance as this component contributed only 4-7% of the total internal resistance. Transport simulations indicated that hindered oxygen diffusion into the SEA reactor was the primary reason for the increased treatment time. However, a reduction in the overall rate of substrate diffusion also may contribute to the long treatment time with the SEA reactor. These results suggest that SEA designs can more effectively capture energy from wastewater, but SPA configurations will be superior in terms of treatment efficiency due to a greatly reduced time needed for treatment. © 2013 Elsevier B.V. All rights reserved.

  17. Schiff Base modified on CPE electrode and PCB gold electrode for selective determination of silver ion

    Science.gov (United States)

    Leepheng, Piyawan; Suramitr, Songwut; Phromyothin, Darinee

    2017-09-01

    The schiff base was synthesized by 2,5-thiophenedicarboxaldehyde and 1,2,4-thiadiazole-3,5-diamine with condensation method. There was modified on carbon paste electrode (CPE) and Printed circuit board (PCB) gold electrode for determination silver ion. The schiff base modified electrodes was characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM), respectively. The electrochemical study was reported by cyclic voltammetry method and impedance spectroscopy using modified electrode as working electrode, platinum wire and Ag/AgCl as counter electrode and reference electrode, respectively. The modified electrodes have suitable detection for Ag+. The determination of silver ions using the modified electrodes depended linearly on Ag+ concentration in the range 1×10-10 M to 1×10-7 M, with cyclic voltammetry sensitivity were 2.51×108 μAM-1 and 1.88×108 μAM-1 for PCB gold electrode and CPE electrode, respectively, limits of detection were 5.33×10-9 M and 1.99×10-8 M for PCB gold electrode and CPE electrode, respectively. The modified electrodes have high accuracy, inexpensive and can applied to detection Ag+ in real samples.

  18. Catalyst evaluation for oxygen reduction reaction in concentrated phosphoric acid at elevated temperatures

    DEFF Research Database (Denmark)

    Hu, Yang; Jiang, Yiliang; Jensen, Jens Oluf

    2018-01-01

    temperatures and hence is not suitable for catalyst evaluation for HT-PEMFCs. In this study, we have designed and constructed a half-cell setup to measure the intrinsic activities of catalysts towards the oxygen reduction reaction (ORR) in conditions close to HT-PEMFC cathodes. By optimization......-cell electrode than that observed in fuel cells, indicating the feasibility of the technique as well as the potential for further improvement of fuel cell electrode performance....

  19. Determination of nonmetallic elements in actinide complexes by oxygen flask combustion (OFC) (Part 2). Sulphur

    International Nuclear Information System (INIS)

    Ruikar, P.B.; Nagar, M.S.; Subramanian, M.S.

    1989-01-01

    This report describes the determination of sulphur in metallic complexes by oxygen flask combustion followed by conductivity titration with standard barium acetate solution in alcoholic medium and lead electrode titration using a lead ion sensitive electrode. Various organic ligands and uranyl and plutonyl synergistic complexes have been analysed by both these methods and the precision and accuracy of the results have been found to be satisfactory. (author). 12 refs., 12 tabs

  20. Boron-doped diamond electrode: synthesis, characterization, functionalization and analytical applications.

    Science.gov (United States)

    Luong, John H T; Male, Keith B; Glennon, Jeremy D

    2009-10-01

    In recent years, conductive diamond electrodes for electrochemical applications have been a major focus of research and development. The impetus behind such endeavors could be attributed to their wide potential window, low background current, chemical inertness, and mechanical durability. Several analytes can be oxidized by conducting diamond compared to other carbon-based materials before the breakdown of water in aqueous electrolytes. This is important for detecting and/or identifying species in solution since oxygen and hydrogen evolution do not interfere with the analysis. Thus, conductive diamond electrodes take electrochemical detection into new areas and extend their usefulness to analytes which are not feasible with conventional electrode materials. Different types of diamond electrodes, polycrystalline, microcrystalline, nanocrystalline and ultrananocrystalline, have been synthesized and characterized. Of particular interest is the synthesis of boron-doped diamond (BDD) films by chemical vapor deposition on various substrates. In the tetrahedral diamond lattice, each carbon atom is covalently bonded to its neighbors forming an extremely robust crystalline structure. Some carbon atoms in the lattice are substituted with boron to provide electrical conductivity. Modification strategies of doped diamond electrodes with metallic nanoparticles and/or electropolymerized films are of importance to impart novel characteristics or to improve the performance of diamond electrodes. Biofunctionalization of diamond films is also feasible to foster several useful bioanalytical applications. A plethora of opportunities for nanoscale analytical devices based on conducting diamond is anticipated in the very near future.

  1. Characterization of carbon pastes as matrices in composite electrodes for use in electrochemical capacitors.

    Directory of Open Access Journals (Sweden)

    M. Miranda-Hernandez

    2008-06-01

    Full Text Available Carbon paste electrodes (CPEs were prepared from carbon black powder with different binders (Silicon Oil or Nujol.Cyclic voltammetry, chronoamperometry and chronopotentiometry techniques and different electrolytes (1M HClO4 and 1MLiClO4 were used to characterize the capacitive response and evaluate the capacitance (F/cm2, F/g of CPEs, with andwithout surface modification. The surface modification was carried out by applying a potential pulse (1.35 V vs. saturatedcalomel electrode, SCE at a time of 300 s, where the growth of carbon-oxygen (C-O species were induced on the surface ofthe electrode. The results show that modified electrodes enhanced the capacitance and the electrolytic system has animportant influence in the stability and reactivity of electrodes. The modified electrodes shows an importantpseudocapacitive behavior as result of a diffusion processes that involved an interfacial reaction between the C-O speciesformed during the electrochemical surface treatment and the protons present in the electrolyte.

  2. Anodic oxidation of anthraquinone dye Alizarin Red S at Ti/BDD electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Sun Jianrui; Lu Haiyan [College of Chemistry, Jilin University, Changchun 130012 (China); Du Lili [State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China); Lin Haibo, E-mail: lhb910@jlu.edu.cn [College of Chemistry, Jilin University, Changchun 130012 (China); State Key Laboratory of Theoretical and Computational Chemistry, Jilin University, Changchun 130012 (China); Li Hongdong, E-mail: hdli@jlu.edu.cn [State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China)

    2011-05-15

    The boron-doped diamond (BDD) thin-film electrode with high quality using industrially titanium plate (Ti/BDD) as substrate has been prepared and firstly used in the oxidation of anthraquinone dye Alizarin Red S (ARS) in wastewaters. The Ti/BDD electrodes are shown to have high concentration of sp{sup 3}-bonded carbon and wide electrochemical window. The results of the cyclic voltammetries show that BDD has unique properties such as high anodic stability and the production of active intermediates at the high potential. The oxidation regions of ARS and water are significantly separated at the Ti/BDD electrode, and the peak current increases linearly with increasing ARS concentration. The bulk electrolysis shows that removal of chemical oxygen demand (COD) and color can be completely reached and the electrooxidation of ARS behaves as a mass-transfer-controlled process at the Ti/BDD electrode. It is demonstrated that the performances of the Ti/BDD electrode for anodic oxidation ARS have been significantly improved with respect to the traditional electrodes.

  3. Design of Perovskite Oxides as Anion-Intercalation-Type Electrodes for Supercapacitors: Cation Leaching Effect.

    Science.gov (United States)

    Liu, Yu; Dinh, Jim; Tade, Moses O; Shao, Zongping

    2016-09-14

    Oxygen ions can be exploited as a charge carrier to effectively realize a new type of anion-intercalation supercapacitor. In this study, to get some useful guidelines for future materials development, we comparatively studied SrCoO3-δ (SC), Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF), and Co3O4 as electrodes in supercapacitors with aqueous alkaline electrolyte. The effect of interaction between the electrode materials with the alkaline solution was focused on the structure and specific surface area of the electrode material, and ultimately the electrochemical performance was emphasized. Both BSCF and SC were found to experience cation leaching in alkaline solution, resulting in an increase in the specific surface area of the material, but overleaching caused the damage of perovskite structure of BSCF. Barium leaching was more serious than strontium, and the cation leaching was component dependent. Although high initial capacitance was achieved for BSCF, it was not a good candidate as intercalation-type electrode for supercapacitor because of poor cycling stability from serious Ba(2+) and Sr(2+) leaching. Instead, SC was a favorable electrode candidate for practical use in supercapacitors due to its high capacity and proper cation leaching capacity, which brought beneficial effect on cycling stability. It is suggested that cation leaching effect should be seriously considered in the development of new perovskite materials as electrodes for supercapacitors.

  4. Enhanced performance of electrospun carbon fibers modified with carbon nanotubes: promising electrodes for enzymatic biofuel cells.

    Science.gov (United States)

    Engel, A Both; Cherifi, A; Tingry, S; Cornu, D; Peigney, A; Laurent, Ch

    2013-06-21

    New nanostructured electrodes, promising for the production of clean and renewable energy in biofuel cells, were developed with success. For this purpose, carbon nanofibers were produced by the electrospinning of polyacrylonitrile solution followed by convenient thermal treatments (stabilization followed by carbonization at 1000, 1200 and 1400° C), and carbon nanotubes were adsorbed on the surfaces of the fibers by a dipping method. The morphology of the developed electrodes was characterized by several techniques (SEM, Raman spectroscopy, electrical conductivity measurement). The electrochemical properties were evaluated through cyclic voltammetry, where the influence of the carbonization temperature of the fibers and the beneficial contribution of the carbon nanotubes were observed through the reversibility and size of the redox peaks of K3Fe(CN)6 versus Ag/AgCl. Subsequently, redox enzymes were immobilized on the electrodes and the electroreduction of oxygen to water was realized as a test of their efficiency as biocathodes. Due to the fibrous and porous structure of these new electrodes, and to the fact that carbon nanotubes may have the ability to promote electron transfer reactions of redox biomolecules, the new electrodes developed were capable of producing higher current densities than an electrode composed only of electrospun carbon fibers.

  5. Electrochemical degradation of Ibuprofen on Ti/Pt/PbO2 and Si/BDD electrodes

    International Nuclear Information System (INIS)

    Ciriaco, L.; Anjo, C.; Correia, J.; Pacheco, M.J.; Lopes, A.

    2009-01-01

    The electrochemical oxidation of Ibuprofen (Ibu) was performed using a Ti/Pt/PbO 2 electrode as the anode, prepared according to literature, and a boron doped diamond (BDD) electrode, commercially available at Adamant Technologies. Tests were performed with model solutions of Ibu, with concentrations ranging from 0.22 to 1.75 mM for the Ti/Pt/PbO 2 electrode and 1.75 mM for the BDD electrode, using 0.035 M Na 2 SO 4 as the electrolyte, in a batch cell, at different current densities (10, 20 and 30 mA cm -2 ). Absorbance measurements, Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) tests were conducted for all samples. The results have shown a very good degradation of Ibu, with COD removals between 60 and 95% and TOC removals varying from 48 to 92%, in 6 h experiments, with higher values obtained with the BDD electrode. General Current Efficiency and Mineralization Current Efficiency, determined for both electrodes, show a similar behaviour for 20 mA cm -2 but a very different one at 30 mA cm -2 . The combustion efficiency was also determined for both anodes, and found to be slightly higher with BDD at lower current density and equal to 100% for both anodes at 30 mA cm -2

  6. Electrocatalytic behavior of thin Co-Te-O films in oxygen evolution and reduction reactions

    International Nuclear Information System (INIS)

    Rashkova, V.; Kitova, S.; Vitanov, T.

    2007-01-01

    Co-Te-O catalytic films, obtain by vacuum co-evaporation of Co and TeO 2 are investigated as electrocatalysts for oxygen reactions in alkaline media. Bifunctional gas-diffusion oxygen electrodes (gde) are prepared by direct deposition of catalyst films on gas-diffusion membranes (gdm) consisting of hydrophobized carbon blacks or hydrophobized 'Ebonex' (suboxides of titanium dioxide). Thus obtained electrodes with different atomic ratio R Co/Te of the catalyst, treated at different temperatures were electrochemically tested by means of cyclic voltammetry and steady-state voltammetry. It is shown that the electrodes exhibit high catalytic activity toward oxygen evolution and reduction reaction despite very low catalyst loading of about 0.05-0.5 mg cm -2

  7. Effects of poly-1,5-diaminoanthraquinone morphology on oxygen reduction in acidic solution

    International Nuclear Information System (INIS)

    Gao Mingming; Yang Fenglin; Zhang Guoquan; Liu Lifen; Wang Xinhua

    2009-01-01

    The poly-1,5-diaminoanthraquinone (P15DAAQ) modified Pt electrodes show electrocatalytic activity for oxygen reduction reaction (ORR) with oxygen reduction peak at about 0.39 V in 0.1 M H 2 SO 4 . The P15DAAQ with different thickness has different morphology. The effects of morphologies on the electrocatalytic behaviors of P15DAAQ for oxygen reduction reaction are investigated using cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) measurements. We propose two different O 2 -transport processes on electrodes modified with thin P15DAAQ and thick P15DAAQ. Together with the quantitative analysis with O 2 -transport dynamics, electron-transfer resistance, and catalytic reaction rate during ORR, thin P15DAAQ electrode performs better electrocatalysis for ORR, although thick P15DAAQ provides higher real surface area and more reactive sites which is beneficial for ORR within a short time

  8. Effects of electrode geometry on the performance of dielectric barrier/packed-bed discharge plasmas in benzene degradation.

    Science.gov (United States)

    Jiang, Nan; Lu, Na; Shang, Kefeng; Li, Jie; Wu, Yan

    2013-11-15

    In this study, the effects of electrode geometry on benzene degradation in a dielectric barrier/packed-bed discharge plasma reactor with different electrodes were systematically investigated. Three electrodes were employed in the experiments, these were coil, bolt, and rod geometries. The reactor using the coil electrode showed better performance in reducing the dielectric loss in the barrier compared to that using the bolt or rod electrodes. In the case of the coil electrode, both the benzene degradation efficiency and energy yield were higher than those for the other electrodes, which can be attributed to the increased role of surface mediated reactions. Irrespective of the electrode geometry, the packed-bed discharge plasma was superior to the dielectric barrier discharge plasma in benzene degradation at any specific applied voltage. The main gaseous products of benzene degradation were CO, CO2, H2O, and formic acid. Discharge products such as O3, N2O, N2O5, and HNO3 were also detected in the outlet gas. Moreover, the presence of benzene inhibited the formation of ozone because of the competing reaction of oxygen atoms with benzene. This study is expected to offer an optimized approach combining dielectric barrier discharge and packed-bed discharge to improve the degradation of gaseous pollutants. Copyright © 2013 Elsevier B.V. All rights reserved.

  9. Biotic and abiotic characterization of bioanodes formed on oxidized carbon electrodes as a basis to predict their performance.

    Science.gov (United States)

    Cercado, Bibiana; Cházaro-Ruiz, Luis Felipe; Ruiz, Vianey; López-Prieto, Israel de Jesús; Buitrón, Germán; Razo-Flores, Elías

    2013-12-15

    Bioelectrochemical systems (BESs) are based on the catalytic activity of biofilm on electrodes, or the so-called bioelectrodes, to produce electricity and other valuable products. In order to increase bioanode performance, diverse electrode materials and modification methods have been implemented; however, the factors directly affecting performance are yet unclear. In this work carbon cloth electrodes were modified by thermal, chemical, and electrochemical oxidation to enhance oxygenated surface groups, to modify the electrode texture, and consequently the electron transfer rate and biofilm adhesion. The oxidized electrodes were physically, chemically, and electrochemically characterized, then bioanodes were formed at +0.1 V vs. Ag/AgCl using domestic wastewater amended with acetate. The bioanode performance was evaluated according to the current and charge generated. The efficacy of the treatments were in the order Thermal>Electrochemical>Untreated>Chemical oxidation. The maximum current observed with untreated electrode was 0.152±0.026 mA (380±92 mA m(-2)), and it was increased by 78% and 28% with thermal and electrochemical oxidized electrodes, respectively. Moreover, the volatile solids correlated significantly with the maximum current obtained, and the electrode texture was revealed as a critical factor for increasing the bioanode performance. Copyright © 2013 Elsevier B.V. All rights reserved.

  10. HVDC Ground Electrodes and Tectonic Setting

    Science.gov (United States)

    Freire, P. F.; Pereira, S. Y.

    2017-12-01

    Ground electrodes in HVDC transmission are huge grounding systems for the DC part of the converter substation, about 1 km wide, sized to inject in the ground DC currents up to 3.5 kA. This work presents an analysis of how the tectonic setting at converter substation location is determinant for the search of the best electrode location (Site Selection) and on its design and performance. It will briefly present the author experience on HVDC electrode design, summarized as follows: Itaipu - Foz do Iguaçu electrodes (transmitter side) located in the middle of Paraná Sedimentary Basin, and Ibiúna electrodes (receiving side) on the border of the basin, 6 km from the geological strike, where the crystalline basement outcrops in São Paulo state; Madeira River - North electrodes (transmitting side) located on the Northwest border of South Amazon Craton, where the crystalline basement is below a shallow sediments layer, and South electrodes (receiving side) located within Paraná Sedimentary Basin; Chile - electrodes located on the Andean forearc, where the Nazca Plate plunges under the South American Plate; Kenya - Ethiopia - electrodes located in the African Rift; Belo Monte - North electrodes (transmitter side) located within the Amazonian Sedimentary Basin, about 35 km of its South border, and South electrodes (receiving side) within Paraná Sedimentary Basin (bipole 1) and on crystalline metamorphic terrain "Brasília Belt" (bipole 2). This diversity of geological conditions results on ground electrodes of different topologies and dimensions, with quite different electrical and thermal performances. A brief study of the geology of the converter stations regions, the so-called Desktop Study, allows for the preview of several important parameters for the site selection and design of the electrodes, such as localization, type, size and estimate of the interference area, which are important predictors of the investment to be made and indications of the design to be

  11. Diffusion-free mediator based miniature biofuel cell anode fabricated on a carbon-MEMS electrode.

    Science.gov (United States)

    Bisht, Gobind S; Holmberg, Sunny; Kulinsky, Lawrence; Madou, Marc

    2012-10-02

    concentration of the enzyme on the electrode surface during incubation. The electrodes were finally protected with a gelatin based hydrogel film. The anode half-cell was tested using cyclic voltammetry in deoxygenated phosphate buffer saline solution pH 7.4 to minimize oxygen interference and to simulate the pH environment of the body. The electrodes that yielded the highest anodic current were prepared by enzyme attachment method with dry spotting incubation. A polarization response was generated for this anodic half-cell and exhibits operation close to maximum efficiency that is limited by the mass transport of glucose to the electrode.

  12. Electrolysis of lunar soil to produce oxygen and metals

    Science.gov (United States)

    Colson, Russell O.; Haskin, Larry A.; Keller, R.

    1991-01-01

    The discussion of melt electrolysis consists of three sections. The implications of the chemistry and physics of fluxed and raw melts on melt electrolysis are discussed first. This includes discussion of the factor that influence melt resistivity, melt viscosity, oxygen production efficiency, and the theoretical energy required to produce oxygen. Second, the implications of phase equilibria and solubilities in silicate melts on the selection of materials for container and electrodes are discussed. The implications of proposed container and electrode materials on melt composition and how this effects expected resistivities, viscosities, as outlined in the first section are discussed. Finally, a general discussion of the basic features of both the fluxed and unfluxed melt electrolysis is given, including their advantages and disadvantages and how they compare with alternative processes.

  13. Ambient oxygen promotes tumorigenesis.

    Directory of Open Access Journals (Sweden)

    Ho Joong Sung

    2011-05-01

    Full Text Available Oxygen serves as an essential factor for oxidative stress, and it has been shown to be a mutagen in bacteria. While it is well established that ambient oxygen can also cause genomic instability in cultured mammalian cells, its effect on de novo tumorigenesis at the organismal level is unclear. Herein, by decreasing ambient oxygen exposure, we report a ∼50% increase in the median tumor-free survival time of p53-/- mice. In the thymus, reducing oxygen exposure decreased the levels of oxidative DNA damage and RAG recombinase, both of which are known to promote lymphomagenesis in p53-/- mice. Oxygen is further shown to be associated with genomic instability in two additional cancer models involving the APC tumor suppressor gene and chemical carcinogenesis. Together, these observations represent the first report directly testing the effect of ambient oxygen on de novo tumorigenesis and provide important physiologic evidence demonstrating its critical role in increasing genomic instability in vivo.

  14. Integrated turbomachine oxygen plant

    Science.gov (United States)

    Anand, Ashok Kumar; DePuy, Richard Anthony; Muthaiah, Veerappan

    2014-06-17

    An integrated turbomachine oxygen plant includes a turbomachine and an air separation unit. One or more compressor pathways flow compressed air from a compressor through one or more of a combustor and a turbine expander to cool the combustor and/or the turbine expander. An air separation unit is operably connected to the one or more compressor pathways and is configured to separate the compressed air into oxygen and oxygen-depleted air. A method of air separation in an integrated turbomachine oxygen plant includes compressing a flow of air in a compressor of a turbomachine. The compressed flow of air is flowed through one or more of a combustor and a turbine expander of the turbomachine to cool the combustor and/or the turbine expander. The compressed flow of air is directed to an air separation unit and is separated into oxygen and oxygen-depleted air.

  15. [The oxygen consumption of ostrich embryos during incubation].

    Science.gov (United States)

    Reiner, G; Dzapo, V

    1995-02-01

    This work deals with the oxygen consumption of ostrich chicks during incubation. Brood eggs were incubated in a hermetic isolated acrylic-glass cylinder. Reduction of oxygen content in the air surrounding the egg was measured using an oxygen-sensitive electrode. A sigmoid curve could be drawn during incubation, with the steepest phase being around day 26. Maximum oxygen consumption was reached on day 36. It was slightly decreased until day 39, when the embryo switches to lung circulation, followed again by an increase until hatching. Average oxygen consumptions for the whole brood interval were calculated to 63.6 liters. Oxygen volumes consumed on day 36 result in a demand about to 240 liters of fresh air per egg and day. Oxygen consumption of the embryos on day 36 was significantly positive correlated with their vitality. Numb or less vital embryos could be clearly differentiated from others. The higher a chick's oxygen consumption, the earlier and shorter its hatching. Possible applications of the method in regard to the evaluation of incubation parameters or chicken constitution are discussed.

  16. Growth of oxygen bubbles during recharge process in zinc-air battery

    Science.gov (United States)

    Wang, Keliang; Pei, Pucheng; Ma, Ze; Chen, Huicui; Xu, Huachi; Chen, Dongfang; Xing, Haoqiang

    2015-11-01

    Rechargeable zinc-air battery used for energy storage has a serious problem of charging capacity limited by oxygen bubble coalescence. Fast removal of oxygen bubbles adhered to the charging electrode surface is of great importance for improving the charging performance of the battery. Here we show that the law of oxygen bubble growth can be achieved by means of phase-field simulation, revealing two phenomena of bubble detachment and bubble coalescence located in the charging electrode on both sides. Hydrodynamic electrolyte and partial insulation structure of the charging electrode are investigated to solve the problem of oxygen bubble coalescence during charging. Two types of rechargeable zinc-air battery are developed on the basis of different tri-electrode configurations, demonstrating that the charging performance of the battery with electrolyte flow (Ⅰ) is better than that of the battery with the partially insulated electrode (Ⅱ), while the battery Ⅱ is superior to the battery Ⅰ in the discharging performance, cost and portability. The proposed solutions and results would be available for promoting commercial application of rechargeable zinc-air batteries or other metal-air batteries.

  17. Impedance pneumography using textile electrodes.

    Science.gov (United States)

    Fiedler, P; Biller, S; Griebel, S; Haueisen, J

    2012-01-01

    The acquisition of physiological parameters using textile and textile-integrated sensors has become an important alternative for mobile and long-term monitoring. We analyzed to different commercially available electrically conductive textiles concerning their applicability for textile-based impedance pneumography. We immersed the textiles to four corroding solutions and observed no considerable changes in the absolute value as well as the phase shift of the material impedances. Subsequently, we performed impedance pneumography tests with different current amplitudes and frequencies. Using silver coated synthetic textile electrodes it was possible to detect the correct respiration frequency during normal, flat as well as slow, deep respiration.

  18. Aluminum-carbon composite electrode

    Science.gov (United States)

    Farahmandi, C.J.; Dispennette, J.M.

    1998-07-07

    A high performance double layer capacitor having an electric double layer formed in the interface between activated carbon and an electrolyte is disclosed. The high performance double layer capacitor includes a pair of aluminum impregnated carbon composite electrodes having an evenly distributed and continuous path of aluminum impregnated within an activated carbon fiber preform saturated with a high performance electrolytic solution. The high performance double layer capacitor is capable of delivering at least 5 Wh/kg of useful energy at power ratings of at least 600 W/kg. 3 figs.

  19. Aluminum-carbon composite electrode

    Science.gov (United States)

    Farahmandi, C. Joseph; Dispennette, John M.

    1998-07-07

    A high performance double layer capacitor having an electric double layer formed in the interface between activated carbon and an electrolyte is disclosed. The high performance double layer capacitor includes a pair of aluminum impregnated carbon composite electrodes having an evenly distributed and continuous path of aluminum impregnated within an activated carbon fiber preform saturated with a high performance electrolytic solution. The high performance double layer capacitor is capable of delivering at least 5 Wh/kg of useful energy at power ratings of at least 600 W/kg.

  20. Evaluation of silver as a miniature direct methanol full cell electrode

    Science.gov (United States)

    Gao, Yong; Kong, Xiangxing; Munroe, Norman; Jones, Kinzy

    Miniature direct methanol fuel cells (DMFCs) and direct hydrogen fuel cells are promising candidates for future polymer electrolyte membrane (PEM) based micro-power sources. Currently, most miniature DMFCs are developed using a silicon based microelectromechanical system (MEMS) technique, which requires complex and precise processing. Low temperature cofire ceramic (LTCC) technology offers an attractive alternative for a ceramics MEMS construction, allowing the integration of high density interconnect and embedded electronic components with microchannels and hermetic cavities from the meso- to the microscale. Silver is a major metallization source for LTCC, which can be fabricated in a range of configurations, from a solid hermetic layer to a porous open structure with microchannels that can easily be integrated into the structures. Silver based LTCC provides an ideal technology for the fabrication of an integrated fuel cell into a high density ceramic-based microelectronic assembly. A silver electrode was evaluated in a simulated DMFC operating environment and found to exhibit good corrosion resistance and chemical stability, essential properties for electrode systems. Potentiodynamic analysis of a catalyzed silver electrode (prepared by thermal decomposition of a Pt/Ru resinate) revealed excellent corrosion resistance under anodic and cathodic DMFC operating conditions. The Pt/Ru catalyst on the silver electrode enhanced the methanol oxidation reaction (MOR) as well as oxygen reduction reaction (ORR) as compared with similar reactions on carbon electrodes. The potential at which methanol is oxidized was lower than the silver oxidation potential, which served to protect the silver electrode. The determination of a contact angle of 30° on the silver electrode indicated wettability, which is deleterious for its application in DMFCs. Nevertheless, the results of good corrosion resistance derived from this investigation as well as the high electrical and thermal

  1. Silver manganese oxide electrodes for lithium batteries

    Science.gov (United States)

    Thackeray, Michael M.; Vaughey, John T.; Dees, Dennis W.

    2006-05-09

    This invention relates to electrodes for non-aqueous lithium cells and batteries with silver manganese oxide positive electrodes, denoted AgxMnOy, in which x and y are such that the manganese ions in the charged or partially charged electrodes cells have an average oxidation state greater than 3.5. The silver manganese oxide electrodes optionally contain silver powder and/or silver foil to assist in current collection at the electrodes and to improve the power capability of the cells or batteries. The invention relates also to a method for preparing AgxMnOy electrodes by decomposition of a permanganate salt, such as AgMnO4, or by the decomposition of KMnO4 or LiMnO4 in the presence of a silver salt.

  2. Amperometric noise at thin film band electrodes.

    Science.gov (United States)

    Larsen, Simon T; Heien, Michael L; Taboryski, Rafael

    2012-09-18

    Background current noise is often a significant limitation when using constant-potential amperometry for biosensor application such as amperometric recordings of transmitter release from single cells through exocytosis. In this paper, we fabricated thin-film electrodes of gold and conductive polymers and measured the current noise in physiological buffer solution for a wide range of different electrode areas. The noise measurements could be modeled by an analytical expression, representing the electrochemical cell as a resistor and capacitor in series. The studies revealed three domains; for electrodes with low capacitance, the amplifier noise dominated, for electrodes with large capacitances, the noise from the resistance of the electrochemical cell was dominant, while in the intermediate region, the current noise scaled with electrode capacitance. The experimental results and the model presented here can be used for choosing an electrode material and dimensions and when designing chip-based devices for low-noise current measurements.

  3. IR-doped ruthenium oxide catalyst for oxygen evolution

    Science.gov (United States)

    Valdez, Thomas I. (Inventor); Narayanan, Sekharipuram R. (Inventor)

    2012-01-01

    A method for preparing a metal-doped ruthenium oxide material by heating a mixture of a doping metal and a source of ruthenium under an inert atmosphere. In some embodiments, the doping metal is in the form of iridium black or lead powder, and the source of ruthenium is a powdered ruthenium oxide. An iridium-doped or lead-doped ruthenium oxide material can perform as an oxygen evolution catalyst and can be fabricated into electrodes for electrolysis cells.

  4. Microstructure of plastic bonded nickel electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Kulcsar, S.; Agh, J.; Fazekas, A.; Vigh, J.; Bujdoso, Z.

    1982-07-01

    Structure is of great importance in the characteristics of plastic bonded nickel electrodes. On the basis of SEM tests it has been established that in pressed Ni electrodes some tenth of a millimetre-long PTFE fibres can be found with a diameter smaller than 500 nm. These form a net-like structure in the electrode which holds the active material together without any decrease in the conductivity. The formation and arrangement of this structure can be influenced by technological parameters.

  5. Electrocatalytic activity of bismuth doped silver electrodes

    CERN Document Server

    Amjad, M

    2002-01-01

    Investigation of redox reactions on silver, and bismuth doped silver electrodes in aqueous KOH solutions, by using potentiostatic steady-state polarization technique, has been carried out. The redox wave potential and current displacements along with multiplicity of the latter have been examined. These electrodes were employed for the oxidation of organic molecules such as ethylamine in alkaline media. Subsequently, these electrodes were ranked with respect to their activity for the redox reactions. (author)

  6. Oxygen permeability of soft contact lenses in different pH, osmolality and buffering solution

    Directory of Open Access Journals (Sweden)

    Se Eun Lee

    2015-10-01

    Full Text Available AIM: To determine the effect of pH, osmolality, and buffering system on the oxygen permeability (Dk of soft contact lenses.METHODS: Two hydrogel lenses (nelfilcon A and etafilcon A and 2 silicone hydrogel lenses (lotrafilcon A and balafilcon A were used in the study. These lenses were incubated in phosphate-buffered saline (PBS and borate-buffered saline (BBS solutions adjusted by 0.8 pH increments to a pH in the range of 5.8-9.0 or in hypotonic (280 mOsmol/kg, isotonic (310 mOsmol/kg and hypertonic (380 mOsmol/kg PBS solutions. Polarographic method was used for measuring the Dk and lenses were stacked as 4 layers to correct the boundary effect.RESULTS: Dk values of all contact lenses measured in BBS solutions were more stable than those in PBS solutions. Especially the etafilcon A lens showed a relative big change compared with other types of contact lenses at the same conditions. When the osmolality of PBS solution increased from hypotonic to hypertonic, Dk of all contact lenses decreased. Variations in Dk existed depending on lens materials, etafilcon A lens was the most affected and nelfilcon A was the least affected by osmolality.CONCLUSION:From the result obtained, it is revealed that Dk of contact lenses is changed by the pH, osmolality, and buffering condition of tear. Thus, Dk of contact lens can be varied by the lens wearers'' physiological and/or pathological conditions.

  7. Alkaline Electrochemical Capacitor and Electrode Fabrication

    National Research Council Canada - National Science Library

    Finello, D

    1999-01-01

    .... The subject low cost alkaline electrochemical capacitor designs are based upon titanium nitride electrodes which exhibit 125 mF/sq cm surface capacitance density and remarkable electrochemical...

  8. Charged Water Droplets can Melt Metallic Electrodes

    Science.gov (United States)

    Elton, Eric; Rosenberg, Ethan; Ristenpart, William

    2016-11-01

    A water drop, when immersed in an insulating fluid, acquires charge when it contacts an energized electrode. Provided the electric field is strong enough, the drop will move away to the opposite electrode, acquire the opposite charge, and repeat the process, effectively 'bouncing' back and forth between the electrodes. A key implicit assumption, dating back to Maxwell, has been that the electrode remains unaltered by the charging process. Here we demonstrate that the electrode is physically deformed during each charge transfer event with an individual water droplet or other conducting object. We used optical, electron, and atomic force microscopy to characterize a variety of different metallic electrodes before and after drops were electrically bounced on them. Although the electrodes appear unchanged to the naked eye, the microscopy reveals that each charge transfer event yielded a crater approximately 1 micron wide and 50 nm deep, with the exact dimensions proportional to the applied field strength. We present evidence that the craters are formed by localized melting of the electrodes via Joule heating in the metal and concurrent dielectric breakdown of the surrounding fluid, suggesting that the electrode locally achieves temperatures exceeding 3400°C. Present address: Dept. Materials Sci. Engineering, MIT.

  9. Fabricating solid carbon porous electrodes from powders

    Science.gov (United States)

    Kaschmitter, James L.; Tran, Tri D.; Feikert, John H.; Mayer, Steven T.

    1997-01-01

    Fabrication of conductive solid porous carbon electrodes for use in batteries, double layer capacitors, fuel cells, capacitive dionization, and waste treatment. Electrodes fabricated from low surface area (Electrodes having a higher surface area, fabricated from powdered carbon blacks, such as carbon aerogel powder, carbon aerogel microspheres, activated carbons, etc. yield high conductivity carbon compositives with excellent double layer capacity, and can be used in double layer capacitors, or for capacitive deionization and/or waste treatment of liquid streams. By adding metallic catalysts to be high surface area carbons, fuel cell electrodes can be produced.

  10. Electrode assemblies, plasma apparatuses and systems including electrode assemblies, and methods for generating plasma

    Science.gov (United States)

    Kong, Peter C; Grandy, Jon D; Detering, Brent A; Zuck, Larry D

    2013-09-17

    Electrode assemblies for plasma reactors include a structure or device for constraining an arc endpoint to a selected area or region on an electrode. In some embodiments, the structure or device may comprise one or more insulating members covering a portion of an electrode. In additional embodiments, the structure or device may provide a magnetic field configured to control a location of an arc endpoint on the electrode. Plasma generating modules, apparatus, and systems include such electrode assemblies. Methods for generating a plasma include covering at least a portion of a surface of an electrode with an electrically insulating member to constrain a location of an arc endpoint on the electrode. Additional methods for generating a plasma include generating a magnetic field to constrain a location of an arc endpoint on an electrode.

  11. Changes in tumor oxygen tension during radiotherapy of uterine cervical cancer: relationships to changes in vascular density, cell density, and frequency of mitosis and apoptosis

    International Nuclear Information System (INIS)

    Lyng, Heidi; Sundfoer, Kolbein; Rofstad, Einar K.

    2000-01-01

    Purpose: Changes in oxygen tension (pO 2 ) during the early phase of fractionated radiotherapy were studied in 22 patients with uterine cervical cancer. The aims were to investigate (a) whether possible changes in pO 2 differed among and within tumors and (b) whether the changes could be attributed to changes in vascular density, cell density, and frequency of mitosis and apoptosis. Methods and Materials: The pO 2 was measured polarographically in four regions of the tumors before treatment and after 2 weeks of radiotherapy. The vascular density, cell density, and frequency of mitosis and apoptosis were determined from biopsies taken from the tumor regions after each pO 2 measurement. Results: The changes in pO 2 during therapy differed among the tumors and were correlated to pO 2 before treatment (p 2 and vice versa. The tumors with increased pO 2 (n = 10) had a large decrease in cell density and a significant increase in apoptotic frequency. In contrast, the tumors with decreased pO 2 (n = 10) had a smaller decrease in cell density (p = 0.014) and no significant increase in apoptotic frequency. Vascular density and mitotic frequency showed no change during therapy; however, vascular damage other than decreased vascular density was observed. Conclusion: These results indicate that the oxygenation of cervix tumors generally changes during the early phase of radiotherapy. The change depends on the balance between the factor leading to an increase and that leading to a decrease in oxygenation; i.e., decreased cell density and vascular damage, respectively. Increased apoptotic frequency may contribute to a large decrease in cell density and hence increased oxygenation during therapy

  12. Polystyrene Based Silver Selective Electrodes

    Directory of Open Access Journals (Sweden)

    Shiva Agarwal

    2002-06-01

    Full Text Available Silver(I selective sensors have been fabricated from polystyrene matrix membranes containing macrocycle, Me6(14 diene.2HClO4 as ionophore. Best performance was exhibited by the membrane having a composition macrocycle : Polystyrene in the ratio 15:1. This membrane worked well over a wide concentration range 5.0×10-6–1.0×10-1M of Ag+ with a near-Nernstian slope of 53.0 ± 1.0 mV per decade of Ag+ activity. The response time of the sensor is <15 s and the membrane can be used over a period of four months with good reproducibility. The proposed electrode works well in a wide pH range 2.5-9.0 and demonstrates good discriminating power over a number of mono-, di-, and trivalent cations. The sensor has also been used as an indicator electrode in the potentiometric titration of silver(II ions against NaCl solution. The sensor can also be used in non-aqueous medium with no significant change in the value of slope or working concentration range for the estimation of Ag+ in solution having up to 25% (v/v nonaqueous fraction.

  13. Textile electrodes as substrates for the electrodeposition of porous ZnO.

    Science.gov (United States)

    Loewenstein, Thomas; Hastall, Andreas; Mingebach, Markus; Zimmermann, Yvonne; Neudeck, Andreas; Schlettwein, Derck

    2008-04-14

    Metal-coated polyamide threads and filaments were chosen as substrate electrodes to deposit highly porous ZnO films for photovoltaic application. The films were electrodeposited at 70 degrees C from oxygen-saturated aqueous zinc salt solutions containing EosinY as a structure directing agent. The current density during deposition was increased compared with planar electrodes by enhanced diffusion at the filaments operating as cylindrical microelectrodes. Analysis by scanning electron microscopy showed an influence of geometrical constraints within the textiles and the hydrodynamic flow rate in the deposition solution on the film morphology. Photoelectrochemical characterization of sensitized films revealed the feasibility of the presented approach and indicated further steps needed for electrode optimization.

  14. Influence of water on the anodic oxidation mechanism of diethylenetriamine (deta on platinum electrode

    Directory of Open Access Journals (Sweden)

    Lassine Ouattara

    2006-12-01

    Full Text Available Diethylenetriamine was oxidised in different electrolytes on platinum electrode. In non-aqueous electrolyte, an irreversible oxidation peak characteristic of DETA oxidation appears on the voltammogram followed by a constant current until the higher limit of the sweeping potential domain is attained. The following successive scans showed a high decrease of the current intensity and that is due to the formation of an insulating coating layer on the electrode surface. When water is added to the non-aqueous electrolyte, a DETA oxidation wave appears on the voltammograms. That oxidation wave is observed on the following scans. Indeed, DETA oxidation mechanism seems to be different either the electrolyte is free or not of water. In non-aqueous electrolyte, DETA oxidation leads to electrode surface covering by a thin polymeric film but in water containing electrolyte, oxygen evolution occurs and DETA oxidation leads to uncoated surface by producing aldehyde and amine through imine hydrolysis.

  15. Effects of electrode material and configuration on the characteristics of planar resistive switching devices

    KAUST Repository

    Peng, H.Y.

    2013-11-13

    We report that electrode engineering, particularly tailoring the metal work function, measurement configuration and geometric shape, has significant effects on the bipolar resistive switching (RS) in lateral memory devices based on self-doped SrTiO3 (STO) single crystals. Metals with different work functions (Ti and Pt) and their combinations are used to control the junction transport (either ohmic or Schottky-like). We find that the electric bias is effective in manipulating the concentration of oxygen vacancies at the metal/STO interface, influencing the RS characteristics. Furthermore, we show that the geometric shapes of electrodes (e.g., rectangular, circular, or triangular) affect the electric field distribution at the metal/oxide interface, thus plays an important role in RS. These systematic results suggest that electrode engineering should be deemed as a powerful approach toward controlling and improving the characteristics of RS memories. 2013 Author(s).

  16. Method of preparation of carbon materials for use as electrodes in rechargeable batteries

    Science.gov (United States)

    Doddapaneni, Narayan; Wang, James C. F.; Crocker, Robert W.; Ingersoll, David; Firsich, David W.

    1999-01-01

    A method of producing carbon materials for use as electrodes in rechargeable batteries. Electrodes prepared from these carbon materials exhibit intercalation efficiencies of .apprxeq.80% for lithium, low irreversible loss of lithium, long cycle life, are capable of sustaining a high rates of discharge and are cheap and easy to manufacture. The method comprises a novel two-step stabilization process in which polymeric precursor materials are stabilized by first heating in an inert atmosphere and subsequently heating in air. During the stabilization process, the polymeric precursor material can be agitated to reduce particle fusion and promote mass transfer of oxygen and water vapor. The stabilized, polymeric precursor materials can then be converted to a synthetic carbon, suitable for fabricating electrodes for use in rechargeable batteries, by heating to a high temperature in a flowing inert atmosphere.

  17. Carbon Deposition during CO2 Electrolysis in Ni-Based Solid-Oxide-Cell Electrodes

    DEFF Research Database (Denmark)

    Skafte, Theis Løye; Graves, Christopher R.; Blennow, P.

    2015-01-01

    -stabilized zirconia (Ni-YSZ) cermets were supplied by Haldor Topsoe A/S and the operating conditions were chosen so as to take stack relevant considerations into account. Formation of carbon nanotubes in Ni containing fuel electrodes has previously been observed in co-electrolysis of H2O and CO2 [1]. Hence....... Electrochemical impedance spectroscopy in both H2/H2O and CO/CO2 revealed an increase in resistance of the fuel electrode after each CO2 electrolysis current-voltage curve, indicating possible carbon deposition. The difference in partial oxygen pressure between inlet and outlet was analyzed to verify carbon...... in detail. In an attempt to mitigate the degradation due to carbon deposition, the Ni-YSZ electrode was infiltrated with a gadolinium doped ceria (CGO) solution. Initial results indicate that the coking tolerance was not enhanced, but it is still unclear whether infiltrated cells degrade less. However...

  18. Simultaneous Production of High-Performance Flexible Textile Electrodes and Fiber Electrodes for Wearable Energy Storage.

    Science.gov (United States)

    Dong, Liubing; Xu, Chengjun; Li, Yang; Wu, Changle; Jiang, Baozheng; Yang, Qian; Zhou, Enlou; Kang, Feiyu; Yang, Quan-Hong

    2016-02-24

    High-performance flexible textile electrodes and fiber electrodes are produced simultaneously by a newly proposed effective strategy. Activated carbon fiber cloth (ACFC)/carbon nanotubes (CNTs) and ACFC/MnO2/CNTs composites are designed as high-performance flexible textile electrodes. Theses textiles can also be easily dismantled into individual fiber bundles used as high-performance flexible fiber electrodes. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Effects of motexafin gadolinium on tumor oxygenation and cellular oxygen consumption

    International Nuclear Information System (INIS)

    Donnelly, E.T.; Liu, Y.; Rockwell, S.; Magda, D.

    2003-01-01

    Full text: Recent work in our laboratory showed that motexafin gadolinium (MGd, Xcytrin), a drug currently in Phase III clinical trials as an adjuvant to radiation therapy, modulates the oxygen tensions in EMT6 tumors. The median pO 2 increased from the control value of 1.5±0.4 mmHg to 7.4 ± 3.8 mmHg six hours after treatment with 40 μmol/kg MGd and the percentage of severely hypoxic readings in the tumors ( 7 plateau phase EMT6 cells in 3 mL Dulbecco's Modified Eagle's Medium supplemented with 10% dialyzed fetal bovine serum, which contains no ascorbic acid. In the absence of ascorbic acid, 100 μM MGd did not alter the cellular oxygen consumption rate for EMT6 cells significantly. Marked inhibition of cellular oxygen consumption was observed when cells were incubated with 100 μM MGd in medium supplemented with equimolar ascorbic acid (a 31.5% decrease in consumption was observed after 6 hours of treatment). The 5% mannitol vehicle solution with equimolar ascorbic acid had no discernible effect on cellular oxygen consumption. Ascorbic acid may facilitate cellular uptake of MGd via the intermediate formation of a MGd-oxalate complex. These studies suggest that changes in cellular oxygen consumption could contribute to the changes in tumor oxygenation seen after administration of MGd. These experiments were supported by Pharmacyclics and training grant T32CA09085 from the NIH (E.T.D.). We thank Dr. Raymond Russell for allowing us to use his oxygen electrode apparatus

  20. A Novel AED Electrode Design Significantly Improves Laypersons Abillities to Correctly Place AED Electrodes

    DEFF Research Database (Denmark)

    Bødtker, Henrik; Stærk, Mathilde; Glerup Lauridsen, Kasper

    2017-01-01

    electrode designs on a 10 point-scale. The primary endpoint was ratio of correct left apical AED electrode placement defined as ≤5 cm from the recommended position.Results: In total, 84 participants were randomized to novel (n=39, female: 62% median age: 41.5 years (±10.3)) and standard (n=45, female: 64......% median age: 43.5 (±8.2)) electrodes. The left apical AED electrode placement was improved when using novel electrodes with pictures compared with standard electrodes (51% vs 18%, (P<0.0001). No significant difference in right AED electrode placement was observed. Time to AED electrode placement...... was faster using novel electrodes with pictures (difference: 7.9 sec, P<0.0001). User-friendliness was rated higher in novel AED electrodes with pictures compared to conventional electrodes (9 (8;10) vs. 7 (6;8)) (P=0.001).Conclusion: A novel AED electrode design with pictures results in faster and better...

  1. Comparison of Biocomposite Electrode Sensor for the Detection of Oxidative Reactions

    Directory of Open Access Journals (Sweden)

    Solomon W. LEUNG

    2015-12-01

    Full Text Available Hemoglobin has a very strong affinity with oxygen and thus is a good catalyst to carry oxygen for many oxidation reactions. Many researchers have explored this property of hemoglobin to develop sensors for the detection of nitrite and peroxide that are important in biomedical and environmental monitoring. We have previously reported the development of biosensors that can detect nitrite and peroxide with a lower detecting limit below 1´1012 M, that were among the best detectors at the time. With a similar sensor platform, we have now developed a biosensor that can detect the oxidation reaction orders of magnitude better than the previous sensors. The sensor comprises layers of biocomposite made up of a polymer, nanogold particles, and a complex protein on the surface of an electrode. The performance of this electrode biosensor is compared with the previously developed sensors, the durability and other factors that can affect the performance and fabrication of this biosensor are discussed.

  2. Reduced Graphene Oxide on Nickel Foam for Supercapacitor Electrodes

    Directory of Open Access Journals (Sweden)

    Uma Ramabadran

    2017-11-01

    Full Text Available The focus of this paper is the investigation of reduced graphene oxide (GO/nickel foam (RGON samples for use as supercapacitor electrodes. Nickel foam samples were soaked in a GO suspension and dried before being subjected to two different methods to remove oxygen. Atmospheric pressure annealed (APA samples were treated with a varying number (10–18 of nitrogen plasma jet scans, where sample temperatures did not exceed 280 °C. Furnace annealed (FA samples were processed in an atmosphere of hydrogen and argon, at temperatures ranging from 600 °C to 900 °C. Environmental Scanning Electron Microscope (ESEM data indicated that the carbon to oxygen (C:O ratio for APA samples was minimized at an intermediate number of plasma scans. Fourier Transform Infrared Spectroscopic (FTIR and Raman spectroscopic data supported this finding. ESEM analysis from FA samples showed that with increasing temperatures of annealing, GO is transformed to reduced graphene oxide (RGO, with C:O ratios exceeding 35:1. X-ray Photoelectron Spectroscopy (XPS and X-ray diffraction (XRD data indicated the formation of RGO with an increasing annealing temperature until 800 °C, when oxygen reincorporation in the surface atomic layers becomes an issue. Supercapacitors, constructed using the FA samples, demonstrated performances that correlated with surface atomic layer optimization of the C:O ratio.

  3. Production of Manual Metal Arc Welding Electrodes with Local Raw ...

    African Journals Online (AJOL)

    The basic characteristic test criteria for determining the performance of any electrode were carried out. ... It was observed that manganese based flux covered electrode (a local electrode) with tensile strength of 585.8 N/mm2 was able to compete effectively with titanium dioxide based electrode (a foreign electrode) with ...

  4. Oxygen enrichment incineration

    International Nuclear Information System (INIS)

    Kim, Jeong Guk; Yang, Hee Chul; Park, Geun Il; Kim, Joon Hyung

    2000-10-01

    Oxygen enriched combustion technology has recently been used in waste incineration. To apply the oxygen enrichment on alpha-bearing waste incineration, which is being developed, a state-of-an-art review has been performed. The use of oxygen or oxygen-enriched air instead of air in incineration would result in increase of combustion efficiency and capacity, and reduction of off-gas product. Especially, the off-gas could be reduced below a quarter, which might reduce off-gas treatment facilities, and also increase an efficiency of off-gas treatment. However, the use of oxygen might also lead to local overheating and high nitrogen oxides (NOx) formation. To overcome these problems, an application of low NOx oxy-fuel burner and recycling of a part of off-gas to combustion chamber have been suggested

  5. Oxygen enrichment incineration

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jeong Guk; Yang, Hee Chul; Park, Geun Il; Kim, Joon Hyung

    2000-10-01

    Oxygen enriched combustion technology has recently been used in waste incineration. To apply the oxygen enrichment on alpha-bearing waste incineration, which is being developed, a state-of-an-art review has been performed. The use of oxygen or oxygen-enriched air instead of air in incineration would result in increase of combustion efficiency and capacity, and reduction of off-gas product. Especially, the off-gas could be reduced below a quarter, which might reduce off-gas treatment facilities, and also increase an efficiency of off-gas treatment. However, the use of oxygen might also lead to local overheating and high nitrogen oxides (NOx) formation. To overcome these problems, an application of low NOx oxy-fuel burner and recycling of a part of off-gas to combustion chamber have been suggested.

  6. Oxygen Dependent Biocatalytic Processes

    DEFF Research Database (Denmark)

    Pedersen, Asbjørn Toftgaard

    temperature and pressure. A significant number of enzymes carrying out redox reactions (oxidoreductases) requiring molecular oxygen as an electron acceptor – those termed oxidases, monooxygenases and dioxygenases. These enzymes catalyze a range of industrially relevant reactions, such as oxidation of alcohols...... to aldehydes and ketones, oxyfunctionalization of C-H bonds, and epoxidation of C-C double bonds. Although oxygen dependent biocatalysis offers many possibilities, there are numerous chal-lenges to be overcome before an enzyme can be implemented in an industrial process. These challenges requires the combined...... is the requirement for oxygen, because the transfer of oxygen from the gas-phase (typically air) to the aqueous phase, where the reaction takes place, is notoriously slow due to the low aqueous solubility of oxygen at am-bient conditions. Therefore, vigorous agitation and aeration is required to create a large in...

  7. Towards Synergistic Electrode-Electrolyte Design Principles for Nonaqueous Li-O[Formula: see text] batteries.

    Science.gov (United States)

    Khetan, Abhishek; Krishnamurthy, Dilip; Viswanathan, Venkatasubramanian

    2018-03-20

    One route toward sustainable land and aerial transportation is based on electrified vehicles. To enable electrification in transportation, there is a need for high-energy-density batteries, and this has led to an enormous interest in lithium-oxygen batteries. Several critical challenges remain with respect to realizing a practical lithium-oxygen battery. In this article, we present a detailed overview of theoretical efforts to formulate design principles for identifying stable electrolytes and electrodes with the desired functionality and stability. We discuss design principles relating to electrolytes and the additional stability challenges that arise at the cathode-electrolyte interface. Based on a thermodynamic analysis, we discuss two important requirements for the cathode: the ability to nucleate the desired discharge product, Li[Formula: see text]O[Formula: see text], and the ability to selectively activate only this discharge product while suppressing lithium oxide, the undesired secondary discharge product. We propose preliminary guidelines for determining the chemical stability of the electrode and illustrate the challenge associated with electrode selection using the examples of carbon cathodes and transition metals. We believe that a synergistic design framework for identifying electrolyte-electrode formulations is needed to realize a practical Li-O[Formula: see text] battery.

  8. Fabrication and characterization of buckypaper-based nanostructured electrodes as a novel material for biofuel cell applications.

    Science.gov (United States)

    Hussein, Laith; Urban, Gerald; Krüger, Michael

    2011-04-07

    The fabrication process of buckypapers (BPs) made from stable suspensions of as-received or functionalized multi-walled carbon nanotubes (MWCNTs) with high purity (97.5 wt%, Baytubes), their characterization and their utilization towards novel biofuel cell electrode applications are reported. The BPs can vary in thickness between 1 μm and 200 μm, are mechanically robust, flexible, stable in solvents, possess high meso-porosities as well as high apparent electrical conductivities of up to 2500 S m(-1). Potentiodynamic measurements of biocathodes based on bilirubin oxidase (BOD)-decorated BPs for the oxygen reduction reaction (ORR) in neutral media (phosphate buffer solution) containing glucose indicate that BP electrodes based on functionalized MWCNTs (fBPs) perform better than BP electrodes of as-received MWCNTs and have high potential as an effective electrode material in biofuel cells and biosensors.

  9. Effects of electrode geometry on the performance of dielectric barrier/packed-bed discharge plasmas in benzene degradation

    International Nuclear Information System (INIS)

    Jiang, Nan; Lu, Na; Shang, Kefeng; Li, Jie; Wu, Yan

    2013-01-01

    Highlights: • Benzene was successfully degraded by dielectric barrier/packed-bed discharge plasmas. • Different electrode geometry has distinct effect on plasmas oxidation performance. • Benzene degradation and energy performance were enhanced when using the coil electrode. • The reaction products were well determined by online FTIR analysis. -- Abstract: In this study, the effects of electrode geometry on benzene degradation in a dielectric barrier/packed-bed discharge plasma reactor with different electrodes were systematically investigated. Three electrodes were employed in the experiments, these were coil, bolt, and rod geometries. The reactor using the coil electrode showed better performance in reducing the dielectric loss in the barrier compared to that using the bolt or rod electrodes. In the case of the coil electrode, both the benzene degradation efficiency and energy yield were higher than those for the other electrodes, which can be attributed to the increased role of surface mediated reactions. Irrespective of the electrode geometry, the packed-bed discharge plasma was superior to the dielectric barrier discharge plasma in benzene degradation at any specific applied voltage. The main gaseous products of benzene degradation were CO, CO 2 , H 2 O, and formic acid. Discharge products such as O 3 , N 2 O, N 2 O 5 , and HNO 3 were also detected in the outlet gas. Moreover, the presence of benzene inhibited the formation of ozone because of the competing reaction of oxygen atoms with benzene. This study is expected to offer an optimized approach combining dielectric barrier discharge and packed-bed discharge to improve the degradation of gaseous pollutants

  10. Electrode modifications to lower electrode impedance and improve neural signal recording sensitivity

    Science.gov (United States)

    Chung, T.; Wang, J. Q.; Wang, J.; Cao, B.; Li, Y.; Pang, S. W.

    2015-10-01

    Objective. Although electrode size should be miniaturized to provide higher selectivity for neural signal recording and to avoid tissue damage, small sized electrodes induce high impedance, which decreases recording quality. In this work, the electrode surface was modified to increase the effective surface area to lower the electrode impedance and to improve the neural signal detection quality by optimizing plasma conditions. Approach. A tetrafluoromethane (CF4) plasma was used to increase the effective surface area of gold electrode sites of polyimide-based neural probes. In vitro electrode impedance and in vivo neural signal recording and stimulation were characterized. Main results. For 15 μm diameter (dia.) electrode size, the average surface roughness could be increased from 1.7 to 22 nm after plasma treatment, and the electrode impedance was decreased by 98%. Averaged background noise power in the range of 1 to 1000 Hz was decreased to -106 dB after the 30 μm dia. electrodes were plasma modified—lower than the noise level of -86 dB without plasma treatment. Neural probes with plasma-modified electrode sites of 15 and 30 μm dia. were implanted to the anterior cingulate cortex (ACC) region for acute recording of spontaneous and electrical evoked local field potential (LFP) of neural signals. Spontaneous LFP recorded in vivo by the plasma-modified electrodes of 30 μm dia. was two times higher compared to electrodes without treatment. For a stimulation current of 400 μA, electrically evoked LFP recorded by the plasma-modified electrodes was seven times higher than those without plasma exposure. Significance. A controllable technology was developed to increase the effective surface area of electrodes using a CF4 plasma. Plasma-modified electrodes improved the quality of the neural probe recording and more sensitive to record spontaneous and evoked LFP in the ACC region.

  11. Low Energy Desalination Using Battery Electrode Deionization

    KAUST Repository

    Kim, Taeyoung

    2017-09-21

    New electrochemical technologies that use capacitive or battery electrodes are being developed to minimize energy requirements for desalinating brackish waters. When a pair of electrodes is charged in capacitive deionization (CDI) systems, cations bind to the cathode and anions bind to the anode, but high applied voltages (>1.2 V) result in parasitic reactions and irreversible electrode oxidation. In the battery electrode deionization (BDI) system developed here, two identical copper hexacyanoferrate (CuHCF) battery electrodes were used that release and bind cations, with anion separation occurring via an anion exchange membrane. The system used an applied voltage of 0.6 V, which avoided parasitic reactions, achieved high electrode desalination capacities (up to 100 mg-NaCl/g-electrode, 50 mM NaCl influent), and consumed less energy than CDI. Simultaneous production of desalinated and concentrated solutions in two channels avoided a two-cycle approach needed for CDI. Stacking additional membranes between CuHCF electrodes (up to three anion and two cation exchange membranes) reduced energy consumption to only 0.02 kWh/m3 (approximately an order of magnitude lower than values reported for CDI), for an influent desalination similar to CDI (25 mM decreased to 17 mM). These results show that BDI could be effective as a very low energy method for brackish water desalination.

  12. Reverse electrodialysis : evaluation of suitable electrode systems

    NARCIS (Netherlands)

    Veerman, J.; Saakes, M.; Metz, S. J.; Harmsen, G. J.

    Reverse electrodialysis (RED) is a method for directly extracting electrical energy from salinity gradients, especially from sea and river water. For the commercial implementation of RED, the electrode system is a key component. In this paper, novel electrode systems for RED were compared with

  13. Microneedle array electrode for human EEG recording.

    NARCIS (Netherlands)

    Lüttge, Regina; van Nieuwkasteele-Bystrova, Svetlana Nikolajevna; van Putten, Michel Johannes Antonius Maria; Vander Sloten, Jos; Verdonck, Pascal; Nyssen, Marc; Haueisen, Jens

    2009-01-01

    Microneedle array electrodes for EEG significantly reduce the mounting time, particularly by circumvention of the need for skin preparation by scrubbing. We designed a new replication process for numerous types of microneedle arrays. Here, polymer microneedle array electrodes with 64 microneedles,

  14. Testing of Electrodes, Cells and Short Stacks

    DEFF Research Database (Denmark)

    Hauch, Anne; Mogensen, Mogens Bjerg

    2017-01-01

    The present contribution describes the electrochemical testing and characterization of electrodes, cells, and short stacks. To achieve the maximum insight and results from testing of electrodes and cells, it is obviously necessary to have a good understanding of the fundamental principles...

  15. Doped graphene electrodes for organic solar cells

    International Nuclear Information System (INIS)

    Park, Hyesung; Kim, Ki Kang; Bulovic, Vladimir; Kong, Jing; Rowehl, Jill A

    2010-01-01

    In this work graphene sheets grown by chemical vapor deposition (CVD) with controlled numbers of layers were used as transparent electrodes in organic photovoltaic (OPV) devices. It was found that for devices with pristine graphene electrodes, the power conversion efficiency (PCE) is comparable to their counterparts with indium tin oxide (ITO) electrodes. Nevertheless, the chances for failure in OPVs with pristine graphene electrodes are higher than for those with ITO electrodes, due to the surface wetting challenge between the hole-transporting layer and the graphene electrodes. Various alternative routes were investigated and it was found that AuCl 3 doping on graphene can alter the graphene surface wetting properties such that a uniform coating of the hole-transporting layer can be achieved and device success rate can be increased. Furthermore, the doping both improves the conductivity and shifts the work function of the graphene electrode, resulting in improved overall PCE performance of the OPV devices. This work brings us one step further toward the future use of graphene transparent electrodes as a replacement for ITO.

  16. Nanometer-spaced electrodes with calibrated separation

    NARCIS (Netherlands)

    Kervennic, Y.V.; Van der Zant, H.S.J.; Morpurgo, A.F.; Gurevich, L.; Kouwenhoven, L.P.

    2002-01-01

    We have fabricated pairs of platinum electrodes with separation between 20 and 3.5 nm. Our technique combines electron beam lithography and chemical electrodeposition. We show that the measurement of the conductance between the two electrodes through the electrolyte provides an accurate and

  17. APPLICATIONS OF A SINGLE CARBON ELECTRODE

    African Journals Online (AJOL)

    Preferred Customer

    applications: welding, spot welding, hole piercing, etc. The metal tube holding the carbon electrodes is banded with a piece of copper tubing that has been flattened into a strap and fitted with a screw for tightening. The perpendicular free end of the copper strap is inserted into the jaws of the electrode holder of an arc welder ...

  18. Synthesis of carbon nanotubes bridging metal electrodes

    International Nuclear Information System (INIS)

    Kotlar, M.; Vojs, M.; Marton, M.; Vesel, M.; Redhammer, R.

    2012-01-01

    In our work we demonstrate growth of carbon nanotubes that can conductively bridge the metal electrodes. The role of different catalysts was examined. Interdigitated metal electrodes are made from copper and we are using bimetal Al/Ni as catalyst for growth of carbon nanotubes. We are using this catalyst composition for growth of the single-walled carbon nanotube network. (authors)

  19. Composite supercapacitor electrodes made of activated carbon ...

    Indian Academy of Sciences (India)

    ... in PEDOT improved the storage performance of the composite electrode well over that of PEDOT:PSS. The composite electrodes were characterized for their electrochemical behaviour, structural and morphological details and electronic conductivity and showed promise as high-performance energy storage systems.

  20. mwnts composite film modified glassy carbon electrode

    African Journals Online (AJOL)

    Preferred Customer

    ABSTRACT: A poly p-aminosalicylic acid (Poly(p-ASA)) and multiwall carbon nanotubes. (MWCNTs) composite modified glassy carbon (GC) electrode was constructed by casting the MWNTs on the GC electrode surface followed by electropolymerization of the p-ASA on the MWCNTs/GCE. The electrochemical behaviours ...

  1. Bipolar Electrode Sample Preparation Devices

    Science.gov (United States)

    Wang, Yi (Inventor); Song, Hongjun (Inventor); Pant, Kapil (Inventor)

    2017-01-01

    An analyte selection device can include: a body defining a fluid channel having a channel inlet and channel outlet; a bipolar electrode (BPE) between the inlet and outlet; one of an anode or cathode electrically coupled with the BPE on a channel inlet side of the BPE and the other of the anode or cathode electrically coupled with the BPE on a channel outlet side of the BPE; and an electronic system operably coupled with the anode and cathode so as to polarize the BPE. The fluid channel can have any shape or dimension. The channel inlet and channel outlet can be longitudinal or lateral with respect to the longitudinal axis of the channel. The BPE can be any metallic member, such as a flat plate on a wall or mesh as a barrier BPE. The anode and cathode can be located at a position that polarizes the BPE.

  2. Steady-state oxidation of cholesterol catalyzed by cholesterol oxidase in lipid bilayer membranes on platinum electrodes

    International Nuclear Information System (INIS)

    Bokoch, Michael P.; Devadoss, Anando; Palencsar, Mariela S.; Burgess, James D.

    2004-01-01

    Cholesterol oxidase is immobilized in electrode-supported lipid bilayer membranes. Platinum electrodes are initially modified with a self-assembled monolayer of thiolipid. A vesicle fusion method is used to deposit an outer leaflet of phospholipids onto the thiolipid monolayer forming a thiolipid/lipid bilayer membrane on the electrode surface. Cholesterol oxidase spontaneously inserts into the electrode-supported lipid bilayer membrane from solution and is consequently immobilized to the electrode surface. Cholesterol partitions into the membrane from buffer solutions containing cyclodextrin. Cholesterol oxidase catalyzes the oxidation of cholesterol by molecular oxygen, forming hydrogen peroxide as a product. Amperometric detection of hydrogen peroxide for continuous solution flow experiments are presented, where flow was alternated between cholesterol solution and buffer containing no cholesterol. Steady-state anodic currents were observed during exposures of cholesterol solutions ranging in concentration from 10 to 1000 μM. These data are consistent with the Michaelis-Menten kinetic model for oxidation of cholesterol as catalyzed by cholesterol oxidase immobilized in the lipid bilayer membrane. The cholesterol detection limit is below 1 μM for cholesterol solution prepared in buffered cyclodextrin. The response of the electrodes to low density lipoprotein solutions is increased upon addition of cyclodextrin. Evidence for adsorption of low density lipoprotein to the electrode surface is presented

  3. Applicability of boron-doped diamond electrode to the degradation of chloride-mediated and chloride-free wastewaters

    International Nuclear Information System (INIS)

    Wu Meifen; Zhao Guohua; Li Mingfang; Liu Lei; Li Dongming

    2009-01-01

    The electrochemical degradation of chloride-mediated and chloride-free dye wastewaters was investigated on a boron-doped diamond (BDD) electrode in comparison with that on a dimensionally stable anode (DSA), and the applicability of BDD electrode to the degradation of these two kinds of wastewaters was explored. In chloride-free wastewater, the electrochemical degradation efficiency of dye on BDD electrode was much higher than that on DSA, with a chemical oxygen demand (COD) removal of 100% and 26% for BDD and DSA, respectively. In chloride-mediated dye wastewater, COD removal was faster than that in chloride-free wastewater on both BDD and DSA electrodes with COD removal efficiencies higher than 95%, whereas the rate of COD removal on DSA was faster than that on BDD electrode. The investigation indicates that DSA is more suitable than BDD electrode in degradation of originally chloride contained dye wastewaters for the sake of energy and time saving. However, for chloride-free dye wastewaters, with the aim of environmental protection, BDD electrode is more appropriate to realize complete mineralization. At the same time, the secondary pollution can be avoided

  4. Platinum Porous Electrodes for Fuel Cells

    DEFF Research Database (Denmark)

    Andersen, Shuang Ma

    Fuel cell energy bears the merits of renewability, cleanness and high efficiency. Proton Exchange Membrane Fuel Cell (PEMFC) is one of the most promising candidates as the power source in the near future. A fine management of different transports and electrochemical reactions in PEM fuel cells...... determination; morphology; oxidation state of components and stability.  Electrode composition investigation: optimization on ionomer content and electrode protonic conductivity.  Interaction between electrode components  Morphology of electrode surface and MEA cross section. The above efforts all contribute...... to a genuine picture of a working PEM fuel cell catalyst layer. These, in turn, enrich the knowledge of Three-Phase-Boundary, provide efficient tool for the electrode selection and eventually will contribute the advancement of PEMFC technology....

  5. Pierce electrodes for a multigap accelerating system

    International Nuclear Information System (INIS)

    Davydenko, V.I.; Ivanov, A.A.; Kotelnikov, I.A.; Tiunov, M.A.

    2007-01-01

    A well-known Pierce's solution that allows to focus a beam of charged particles using properly shaped electrodes outside the beam is generalized to the case of multigap accelerating system. Simple parametric formulae for Pierce electrodes are derived for an accelerating system with current density, limited either by space charge or by emitting property of the cathode. As an example of general approach, Pierce electrodes shape is analyzed for a system with two accelerating gaps. It is shown that precise Pierce's solution exists if acceleration rate within second gap is lower than within first gap. In the opposite case quasi-Pierce solution can be implemented using non-equipotential electrode between the gaps, and guidelines, based on numerical simulations, for the design of equipotential focusing electrodes are given

  6. Study and development of a hydrogen/oxygen fuel cell in solid polymer electrolyte technology

    Energy Technology Data Exchange (ETDEWEB)

    Mosdale, R.

    1992-10-29

    The hydrogen/oxygen fuel cell appears today as the best candidate to the replacing of the internal combustion engine for automobile traction. This system uses the non explosive electrochemical recombination of hydrogen and oxygen. It is a clean generator whom only reactive product is water. This thesis shows a theoretical study of this system, the synthesis of different kinds of used electrodes and finally an analysis of water movements in polymer electrolyte by different original technologies. 70 refs., 73 figs., 15 tabs.

  7. Telemetry-based oxygen sensor for continuous monitoring of kidney oxygenation in conscious rats.

    Science.gov (United States)

    Koeners, Maarten P; Ow, Connie P C; Russell, David M; Abdelkader, Amany; Eppel, Gabriela A; Ludbrook, John; Malpas, Simon C; Evans, Roger G

    2013-06-15

    The precise roles of hypoxia in the initiation and progression of kidney disease remain unresolved. A major technical limitation has been the absence of methods allowing long-term measurement of kidney tissue oxygen tension (Po₂) in unrestrained animals. We developed a telemetric method for the measurement of kidney tissue Po₂ in unrestrained rats, using carbon paste electrodes (CPEs). After acute implantation in anesthetized rats, tissue Po₂ measured by CPE-telemetry in the inner cortex and medulla was in close agreement with that provided by the "gold standard" Clark electrode. The CPE-telemetry system could detect small changes in renal tissue Po₂ evoked by mild hypoxemia. In unanesthetized rats, CPE-telemetry provided stable measurements of medullary tissue Po₂ over days 5-19 after implantation. It also provided reproducible responses to systemic hypoxia and hyperoxia over this time period. There was little evidence of fibrosis or scarring after 3 wk of electrode implantation. However, because medullary Po₂ measured by CPE-telemetry was greater than that documented from previous studies in anesthetized animals, this method is presently best suited for monitoring relative changes rather than absolute values. Nevertheless, this new technology provides, for the first time, the opportunity to examine the temporal relationships between tissue hypoxia and the progression of renal disease.

  8. Textile electrode characterization: dependencies in the skin-clothing-electrode interface

    International Nuclear Information System (INIS)

    Macías, R; Fernández, M; Bragós, R

    2013-01-01

    Given the advances in the technology known as smart textiles, the use of textile electrodes is more and more common. However this kind of electrodes presents some differences regarding the standard ones as the Ag-AgCl electrodes. Therefore to characterize them as best as possible is required. In order to make the characterization reproducible and repetitive, a skin dummy made of agar-agar and a standardized measurement set-up is used in this article. Thus, some dependencies in the skin-electrode interface are described. These dependencies are related to the surface of the textile electrode, the conductive material and the applied pressure. Furthermore, the dependencies on clothing in the skin-textile electrode interface are also analyzed. Thus, based on some parameters such as textile material, width and number of layers, the behavior of the interface made up by the skin, the textile electrode and clothing is depicted.

  9. Textile electrode characterization: dependencies in the skin-clothing-electrode interface

    Science.gov (United States)

    Macías, R.; Fernández, M.; Bragós, R.

    2013-04-01

    Given the advances in the technology known as smart textiles, the use of textile electrodes is more and more common. However this kind of electrodes presents some differences regarding the standard ones as the Ag-AgCl electrodes. Therefore to characterize them as best as possible is required. In order to make the characterization reproducible and repetitive, a skin dummy made of agar-agar and a standardized measurement set-up is used in this article. Thus, some dependencies in the skin-electrode interface are described. These dependencies are related to the surface of the textile electrode, the conductive material and the applied pressure. Furthermore, the dependencies on clothing in the skin-textile electrode interface are also analyzed. Thus, based on some parameters such as textile material, width and number of layers, the behavior of the interface made up by the skin, the textile electrode and clothing is depicted.

  10. The electrochemical property of the electrodeposited magnetite electrode with different pH values

    International Nuclear Information System (INIS)

    Kim, Myong-Jin; Kim, Dong Jin; Kim, Hong Pyo

    2014-01-01

    Flow accelerated corrosion (FAC) is influenced by many factors such as the water chemistry (temperature, pH, dissolved oxygen (D.O.) in a solution, and etc.), chemical composition of carbon steel, and fluid dynamics. Magnetite is formed at the inner surface of carbon steel, and protects the integrity of pipes from damage. The magnetite has a stable state at each equilibrium condition, so that it can be dissolved into the fluid under conditions that satisfy the equilibrium state. The iron solubility can be calculated by considering the reaction equilibrium constants for prediction of the change in the magnetite layer. On the other hand, it is necessary to measure the experimental solubility to compare the theoretical data and the experimental data. In addition, the solubility of magnetite can be predicted by measuring the electrochemical experiments. However, there are few studies related to the electrochemical property of magnetite owing to the difficulty of the electrode fabrication. In the present work, a magnetite electrode was prepared using the electrochemical-assisted precipitation method, and the electrochemical property of the fabricated magnetite electrode was measured in an alkaline solution. The magnetite electrode was fabricated by using the electrochemical-assisted precipitation method for the measurement of the solubility of the magnetite. The prepared magnetite electrode showed the characteristic of the magnetite by an XRD spectrum

  11. Prolongation of electrode lifetime in biofuel cells by periodic enzyme renewal

    Energy Technology Data Exchange (ETDEWEB)

    Rubenwolf, S.; Sane, S.; Kestel, J.; Stetten, F. von; Kerzenmacher, S. [Freiburg Univ. (Germany). Lab. for MEMS Applications; Hussein, L.; Urban, G.; Krueger, M. [Freiburg Univ. (Germany). Freiburg Materials Research Centre (FMF); Freiburg Univ. (Germany). Lab. for Sensors; Zengerle, R. [Freiburg Univ. (Germany). Lab. for MEMS Applications; Freiburg Univ. (Germany). BIOSS Centre for Biological Signalling Studies

    2012-11-15

    Enzymatically catalyzed biofuel cells show unique specificity and promise high power densities, but suffer from a limited lifetime due to enzyme deactivation. In the present work, we demonstrate a novel concept to extend the lifetime of a laccase-catalyzed oxygen reduction cathode in which we decouple the electrode lifetime from the limited enzyme lifetime by a regular resupply of fresh enzymes. Thereto, the adsorption behavior of laccase from Trametes versicolor to buckypaper electrode material, as well as its time-dependent deactivation characteristics, has been investigated. Laccase shows a Langmuir-type adsorption to the carbon nanotube-based buckypaper electrodes, with a mean residence time of 2 days per molecule. In a citrate buffer of pH 5, laccase does not show any deactivation at room temperature for 2 days and exhibits a half-life of 9 days. In a long-term experiment, the laccase electrodes were operated at a constant galvanostatic load. The laccase-containing catholyte was periodically exchanged against a freshly prepared one every second day to provide sufficient active enzymes in the catholyte for the replacement of desorbed inactive enzymes. Compared to a corresponding control experiment without catholyte exchange, this procedure resulted in a 2.5 times longer cathode lifetime of 19 {+-} 9 days in which the electrode showed a potential above 0.744 V vs. normal hydrogen electrode at 110 {mu}A cm{sup -2}. This clearly indicates the successful exchange of molecules by desorption and re-adsorption and is a first step toward the realization of a self-regenerating enzymatic biofuel cell in which enzyme-producing microorganisms are integrated into the electrode to continuously resupply fresh enzymes. (orig.)

  12. Graphene-modified nickel foam electrode for cathodic degradation of nitrofuranzone: Kinetics, transformation products and toxicity

    Directory of Open Access Journals (Sweden)

    Ya Ma

    2017-12-01

    Full Text Available Simple, efficient, and durable electrodes are highly demanded for practical electro­chemical process. In this study, a reduced graphene oxide modified nickel foam electrode (GR‑Ni foam was facilely prepared via one-step cyclic voltammetry electrodeposition of gra­phene oxide suspension onto the Ni foam. The electrochemical degradation of nitrofuran­zone (NFZ, a kind of typical antibiotics was studied on the GR-Ni foam cathode. The cyclic voltammetry and electrochemical impedance spectra analysis confirmed that presence of GR loading accelerated the electron transfer from the cathode surface to NFZ. With the applied cathode potential of −1.25 V (vs. Ag/AgCl, the removal efficiency of NFZ (C0 = 20 mg L−1 at the GR-Ni foam electrode reached up to 99 % within 30 min, showing a higher reaction rate constant (0.1297 min−1 than 0.0870 min−1 at the Pd-Ni foam and 0.0186 min−1 at the Ni foam electrode. It was also found that the pH, dissolved oxygen and NFZ initial concentration have slight effect on NFZ degradation at the GR-Ni foam electrode. The reactions first occurred at nitro groups (-NO2, unsaturated C=N bonds and N-N bonds to generate furan ring-containing products, and then these products were transformed into linear diamine products. The direct reduction by electrons was mainly responsible for NFZ reduction at the GR-Ni foam electrode. Even after 18 cycles, the removal efficiency of NFZ still reached up to 98 % within 1 h. In addition, the cathodic degradation process could eliminate the antibacterial activity of NFZ. The GR-Ni foam electrode would have a great potential in electrochemical process for treating wastewater containing furan antibiotics.

  13. Electrode assembly for a lithium ion battery, process for the production of such electrode assembly, and lithium ion battery comprising such electrode assemblies

    NARCIS (Netherlands)

    Mulder, F.M.; Wagemaker, M.

    2013-01-01

    The invention provides an electrode assembly for a lithium ion battery, the electrode assembly comprising a lithium storage electrode layer on a current collector, wherein the lithium storage electrode layer is a porous layer having a porosity in the range of -35 %, with pores having pore widths in

  14. Oxygen bridges between NiO nanosheets and graphene for improvement of lithium storage.

    Science.gov (United States)

    Zhou, Guangmin; Wang, Da-Wei; Yin, Li-Chang; Li, Na; Li, Feng; Cheng, Hui-Ming

    2012-04-24

    Graphene has been widely used to dramatically improve the capacity, rate capability, and cycling performance of nearly any electrode material for batteries. However, the binding between graphene and these electrode materials has not been clearly elucidated. Here we report oxygen bridges between graphene with oxygen functional groups and NiO from analysis by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy and confirm the conformation of oxygen bridges by the first-principles calculations. We found that NiO nanosheets (NiO NSs) are bonded strongly to graphene through oxygen bridges. The oxygen bridges mainly originate from the pinning of hydroxyl/epoxy groups from graphene on the Ni atoms of NiO NSs. The calculated adsorption energies (1.37 and 1.84 eV for graphene with hydroxyl and epoxy) of a Ni adatom on oxygenated graphene by binding with oxygen are comparable with that on graphene (1.26 eV). However, the calculated diffusion barriers of the Ni adatom on the oxygenated graphene surface (2.23 and 1.69 eV for graphene with hydroxyl and epoxy) are much larger than that on the graphene (0.19 eV). Therefore, the NiO NS is anchored strongly on the graphene through a C-O-Ni bridge, which allows a high reversible capacity and excellent rate performance. The easy binding/difficult dissociating characteristic of Ni adatoms on the oxygenated graphene facilitates fast electron hopping from graphene to NiO and thus the reversible lithiation and delithiation of NiO. We believe that the understanding of this oxygen bridge between graphene and NiO will lead to the development of other high-performance electrode materials.

  15. Electrochemical oxidation of textile industry wastewater by graphite electrodes.

    Science.gov (United States)

    Bhatnagar, Rajendra; Joshi, Himanshu; Mall, Indra D; Srivastava, Vimal C

    2014-01-01

    In the present article, studies have been performed on the electrochemical (EC) oxidation of actual textile industry wastewater by graphite electrodes. Multi-response optimization of four independent parameters namely initial pH (pHo): 4-10, current density (j): 27.78-138.89 A/m(2), NaCl concentration (w): 0-2 g/L and electrolysis time (t): 10-130 min have been performed using Box-Behnken (BB) experimental design. It was aimed to simultaneously maximize the chemical oxygen demand (COD) and color removal efficiencies and minimize specific energy consumption using desirability function approach. Pareto analysis of variance (ANOVA) showed a high coefficient of determination value for COD (R(2) = 0.8418), color (R(2) = 0.7010) and specific energy (R(2) = 0.9125) between the experimental values and the predicted values by a second-order regression model. Maximum COD and color removal and minimum specific energy consumed was 90.78%, 96.27% and 23.58 kWh/kg COD removed, respectively, were observed at optimum conditions. The wastewater, sludge and scum obtained after treatment at optimum condition have been characterized by various techniques. UV-visible study showed that all azo bonds of the dyes present in the wastewater were totally broken and most of the aromatic rings were mineralized during EC oxidation with graphite electrode. Carbon balance showed that out of the total carbon eroded from the graphite electrodes, 27-29.2% goes to the scum, 71.1-73.3% goes into the sludge and rest goes to the treated wastewater. Thermogravimetric analysis showed that the generated sludge and scum can be dried and used as a fuel in the boilers/incinerators.

  16. Characteristics of Honeycomb-Type Oxygen Generator with Electrolyte Based on Doped Bismuth Oxide

    Science.gov (United States)

    Chen, Yu-Wen; Liu, Yi-Xin; Wang, Sea-Fue; Devasenathipathy, Rajkumar

    2018-03-01

    An oxygen generator using Y-doped Bi2O3 as electrolyte to transport oxygen ions has been developed, having honeycomb-type structure with dimensions of 40 mm × 35 mm × 30 mm and consisting of 13 × 12 channels. External wire circuitry for the channels arrayed using parallel, series, and hybrid connection was evaluated to achieve the best oxygen separation efficiency. It was observed that the oxygen generator with hybrid connection facilitated evolution of oxygen at maximum of 117 sccm and high purity > 99.9% at 550°C under current flow of 14 A. Addition of 5 wt.% silane and 3 wt.% glass-ceramic powder to the Ag slurry used at both electrodes not only increased the coverage of the metal electrode on the ceramic substrate during dip coating but also prevented cracking at the electrode layer of the module under stress from the electric field and temperature during high-temperature operation, thus reducing the decay rate of the oxygen generator in durability testing.

  17. Positive role of oxygen vacancy in electrochemical performance of CoMn2O4 cathodes for Li-O2 batteries

    Science.gov (United States)

    Sadighi, Zoya; Huang, Jiaqiang; Qin, Lei; Yao, Shanshan; Cui, Jiang; Kim, Jang-Kyo

    2017-10-01

    The thermally induced oxygen vacancies present across the intra/inter-crystalline sites and surface of ultrafine CoMn2O4 (CMO) electrodes ameliorate electrochemical performance of Li-O2 batteries (LOBs). Oxygen deficient CMOs are synthesized via a two-step process: in situ reduction to achieve a large surface area of 151.3 m2 g-1 and thermal treatment at 400 °C in pure Ar. The oxygen deficient CMO electrode presents a higher initial capacity, lower overpotential, better cyclic stability, higher Coulombic efficiencies and higher rate capabilities than the as-prepared CMO electrode without heat treatment. While the CMO electrode presents an excellent catalytic behavior in oxygen reduction reaction (ORR), the oxygen vacancies mitigate the migration of Li+ ions and electrons and act as active sites for O2 in the oxygen evolution reaction (OER). The ex situ characterization also proves a lower kinetic charge transfer resistance and higher catalytic activities of the oxygen deficient CMO electrodes in the decomposition of discharge products during the discharge/charge cycles.

  18. The water decomposition reactions on boron-doped diamond electrodes

    Directory of Open Access Journals (Sweden)

    Suffredini Hugo B

    2004-01-01

    Full Text Available The electrochemical processes occurring at both edges of the wide electrochemical window of the boron doped diamond (BDD electrode were studied by polarization curves experiments to evaluate the apparent energy of activation for the rate determining step in each reaction. It was found that the hydrogen evolution reaction occurs by a Volmer-Heyrovsky mechanism with the first step being the RDS. Moreover, the apparent energy of activation calculated from the Tafel plots presented a value as high as 150 kJ mol-1, indicating the formation of the M-H intermediate that is characteristic for the Volmer step. On the other hand, the apparent energy of activation for the oxygen evolution reaction was found to be 106 kJ mol-1 suggesting that the RDS in this mechanism is the initial adsorption step. In this way, it was demonstrated that the interaction between water molecules and the electrode surface is strongly inhibited on BDD thus justifying the extended potential window observed for this material.

  19. Electrodic behaviour of RuZr in acid

    International Nuclear Information System (INIS)

    Manoharan, Ramasamy; Goodenough, John B.

    1998-01-01

    The electrochemical properties of RuZr alloy in acidic solution have been investigated by means of steady-state polarization measurements and cyclic voltammetry. The current potential profiles for the formation/reduction of surface oxides and the deposition/dissolution of hydrogen at a virgin RuZr electrode are basically similar to those at an elemental Ru electrode. The onset of the oxygen evolution reaction and Ru-corrosion reactions are well resolved on RuZr alloy; the Ru-corrosion reaction is shifted positively by about 1.12 V. This is attributed to the presence of more basic Zr-O-Ru bonds in the gelatinous oxyhydroxide film that is formed during the anodic polarization. The film thus formed exists permanently on the surface, and it plays a vital role in catalysing the electrochemical reaction by virtue of its ability to exhibit three redox couples. The film is capable of catalysing the hydrogen evolution reaction. RuZr does not catalyse the methanol- oxidation reaction. (author)

  20. High Selectivity Oxygen Delignification

    Energy Technology Data Exchange (ETDEWEB)

    Lucian A. Lucia

    2005-11-15

    Project Objective: The objectives of this project are as follows: (1) Examine the physical and chemical characteristics of a partner mill pre- and post-oxygen delignified pulp and compare them to lab generated oxygen delignified pulps; (2) Apply the chemical selectivity enhancement system to the partner pre-oxygen delignified pulps under mill conditions (with and without any predetermined amounts of carryover) to determine how efficiently viscosity is preserved, how well selectivity is enhanced, if strength is improved, measure any yield differences and/or bleachability differences; and (3) Initiate a mill scale oxygen delignification run using the selectivity enhancement agent, collect the mill data, analyze it, and propose any future plans for implementation.