Time‐Dependent Energy Efficiency Losses at Nickel Cathodes in Alkaline Water Electrolysis Systems

Water electrolysis in alkaline solutions is an important hydrogen production method. One difficulty encountered in systems employing nickel electrodes in electrolytes is the continual decrease in operating efficiency with time. The major component of this decrease is the rise in cathodic overpotential at constant cell current. It was found that the kinetic parameters of Tafel slope and exchange current density increase markedly with the decline of efficiency. Four mechanisms have previously been postulated as being responsible for this phenomenon. In the present work, it was found that the loss of efficiency can be completely recovered, and an examination of the recovery mechanism supports the theory of hydrogen absorption's being responsible for the efficiency decline.