Kinetics of hydrogen evolution on submicron size Co, Ni, Pd and Co–Ni alloy powder electrodes by d.c. polarization and a.c. impedance studies
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- Elumalai, P., Vasan, H., Munichandraiah, N. et al. Journal of Applied Electrochemistry (2002) 32: 1005. doi:10.1023/A:1020935218149
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Submicron size Co, Ni and Co–Ni alloy powders have been synthesized by the polyol method using the corresponding metal malonates and Pd powder by reduction of PdOx in methanol. The kinetics of the hydrogen evolution reaction (HER) in 6 M KOH electrolyte have been studied on electrodes made from the pressed powders. The d.c. polarization measurements have resulted in a value close to 120 mV decade−1 for the Tafel slope, suggesting that the HER follows the Volmer–Heyrovsky mechanism. The values of exchange current density (io) are in the range 1–10 mA cm−2 for electrodes fabricated in the study. The a.c. impedance spectra measured at several potentials in the HER region showed a single semicircle in the Nyquist plots. Exchange current density (io) and energy transfer coefficient (α) have been calculated by employing a nonlinear least square-fitting program.