, Volume 32, Issue 9, pp 1005-1010

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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Abstract

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 PdO x 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 (i o) 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 (i o) and energy transfer coefficient (α) have been calculated by employing a nonlinear least square-fitting program.