THE HYDROGEN EVOLUTION REACTION ON NICKEL SURFACES STABILIZED BY H-ABSORPTION

The hydrogen evolution reaction (her) was studied on bright nickel electrodes in alkaline solutions at several temperatures. The formation of nickel hydrides in the potential region of the her was previously analyzed by cyclic voltammetry and the electrode surface was pre-conditioned to minimize the effect of the hydrides in the experimental response of the system. Data from polarization curves was conveniently analyzed by non-linear regression fitting resulting in a Volmer-Heyrovsky mechanism in which the second reaction must be the rds to explain the characteristics of the hydride formation. The calculated value of the rate constant for the electrochemical desorption step was 1.65 x 10(-11) mol cm2 s-1 at 25-degrees-C. The apparent energy of activation was 58 kJ mol-1, a value somewhat higher than those in the literature and that was justified in terms of the specific pre-treatment of the surface. A voltammetric method for determining the real electrochemical active area of Ni electrodes is also described.