Temperature-Dependent Kinetic Parameters for the Alkaline Oxygen Evolution Reaction on NiFeOOH

Kinetic parameters of the oxygen evolution reaction on NiFeOOH remain elusive. Here, we studied the temperature dependence of this reaction to extract kinetic parameters, such as the temperature-dependent Tafel slopes, transfer coefficients, (standard) apparent activation energies, and pre-exponential factors. We observe a linear increase in the Tafel slope (∼30 mV/dec at room temperature) with increasing temperature when nonkinetic effects were excluded, whereas the trend reverses when significant nonkinetic effects were involved. Standard apparent activation energies of ∼75 kJ/mol were found. This has to be interpreted with regards to the mechanism containing two electrochemical presteps prior to a chemical rate-determining step (EEC or E²C) and consists mostly of the free energy of the pre-equilibrium steps. The apparent activation energy at an overpotential of 0.265 V then decreased to ∼13 kJ/mol. Therefore, temperature-dependent studies can provide important mechanistic insights into electrocatalytic reactions, provided care is taken that nonkinetic effects are eliminated.