Hydrogen Evolution and Interface Phenomena on a Nickel Cathode in 30 w/o KOH : I . Kinetics Parameters and Electrode Impedance Between 303 and 363 K

The hydrogen evolution reaction (HER) is investigated on a nickel cathode in 30 weight percent (w/o) KOH containing KOH metallic impurities. It is shown that the hydrogen evolution mechanism does not vary substantially between 303 and 363 K and that the apparent heat of activation is 21 kJ mol −1 . Reduction of the ferric impurity influences the log ( i ) ‐ E curves for the HER at low cathodic overpotentials and at temperatures higher than 323 K. Impedance measurements during water electrolysis confirm the limited influence of thermal energy on charge transfer kinetics and underline the effect of the hydrogen bubble layer on the accessible surface. A pseudocapacitive effect observed at low cathodic overpotentials and at anodic overpotentials is tentatively explained by hydrogen electrosorption and nickel oxidation.