4.7 Article

Electrochemical impedance characteristics and electroreduction of oxygen at tungsten carbide derived micromesoporous carbon electrodes

期刊

JOURNAL OF ELECTROANALYTICAL CHEMISTRY
卷 689, 期 -, 页码 176-184

出版社

ELSEVIER SCIENCE SA
DOI: 10.1016/j.jelechem.2012.09.039

关键词

Tungsten carbide; Oxygen electroreduction; Carbide derived carbon; Polymer electrolyte membrane fuel cell

资金

  1. Estonian Target Research Project [SF0180002s08]
  2. Estonian Centre of Excellence in Research Project [TK117T]
  3. Estonian Energy Technology Programme project [SLOKT 10209T]
  4. ETF [ETF8267]

向作者/读者索取更多资源

The electrical double layer characteristics and oxygen electroreduction kinetics in 0.5 M H2SO4 aqueous solution has been studied at micromesoporous tungsten carbide derived carbon C(WC) electrodes. Carbon powders with various specific surface areas (1280-2116 m(2) g(-1)) have been prepared from WC at chlorination temperatures 900 degrees C, 1000 degrees C and 1100 degrees C. The porous structure of carbon substrate was characterised using nitrogen sorption, X-ray diffraction, high resolution TEM, electron energy loss spectroscopy, selected area electron diffraction and scanning electron microscopy with energy-dispersive X-ray spectroscopy methods. Cyclic voltammograms at various potential scan rates from 2 to 70 mV s(-1), and rotating disc electrode data at rotation velocities from 0 to 3000 rev min(-1), were measured within the region of potentials from (+)0.4 V to -0.6 V vs. Hg vertical bar Hg2SO4 vertical bar sat.K2SO4 in H2O (MSE). At E > -0.2 V, the electroreduction of oxygen is mainly limited by the charge transfer step, and at -0.6 V < E < -0.2 V, by the mixed kinetics. The oxygen electroreduction mainly proceeds through the peroxide formation intermediate step on all electrodes studied. Despite of that the electrodes tested were very stable during the electrochemical experiment, indicating that the C(WC) is a suitable catalyst support material for polymer electrolyte membrane fuel cell. The electroreduction rate of oxygen depends strongly on the structure (graphitisation level) of carbide derived carbon used for preparation of an electrode and the oxygen reduction overvoltage decreases in the order C(WC) 1100 degrees C > C(WC) 1000 degrees C > degrees C(WC) 900 degrees C. Very high low-frequency capacitance values, independent of alternative current (ac) frequency at f < 0.1 Hz, have been established for C(WC) 1100 degrees C, demonstrating that at ac f -> 0, mainly pseudocapacitive behaviour with adsorption limited step of reaction intermediates has been observed. (C) 2012 Elsevier B.V. All rights reserved.

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