ELECTROCHEMICAL STUDIES OF A NICKEL ELECTRODE FOR THE HYDROGEN EVOLUTION REACTION

The mechanism of the hydrogen evolution and reduction reactions on a nickel electrode has been examined several times, mainly because of the potential application of this material in water electrolysers and fuel cells. This work presents the results of electrochemical studies of hydrogen evolution and reduction on nickel plate in 30 wt% KOH at different temperatures ranging from 28 to 77 degrees C. Kinetic parameters were obtained by steady state polarization experiments, complemented by cyclic voltammetry. Nickel showed an improved performance with increasing temperature. It has been observed that a temperature increase from 28 to 77 degrees C results in an almost equal Tafel slope of 80 mV dec(-1). This behaviour could be the impact of such factors as variation of the adsorbed hydrogen coverage with potential or the entropic contribution to the free energy of activation. However, some controversy still remains. Current density values increase with increasing temperature. A current-time dependence curve shows that the current density is constant up to 200 s, then it decreases with time. However, after 1000 s, current density is again constant and remains so up to 3000s. The apparent energy of activation Delta H was calculated from the Arrhenius plot.