The Mechanism of Hydrogen Evolution Reaction on a Modified Raney Nickel Composite‐Coated Electrode by AC Impedance

The hydrogen evolution reaction (HER) on a modified Raney nickel electrode, consisting of Ni‐Al‐Cu‐Cr alloy, was investigated with ac impedance measurements and by dc polarization current behavior in 5.36 M solution at 70°C. Comparative measurements also were carried out on commercial Raney nickel (Ni‐Al). The rate constants of the forward and backward reactions of Volmer, Heyrovsky, and Tafel steps were estimated by a nonlinear fitting method. The modified Raney nickel composite‐coated electrode provides a lower overpotential for the HER than the commercial Raney nickel‐coated electrode. The main pathway for the HER is Volmer‐Tafel with Volmer as the rate determining step.