Challenges and recent progress in unraveling the intrinsic pH effect in electrocatalysis

The kinetics of many electrode reactions, especially those involving the consumption/production of H⁺/OH^?, show significant pH dependence. Systematic studies of the pH effect over a wide pH range can provide very useful information about their reaction mechanism(s) and help figure out the optimum reaction conditions. For fast electrode reactions in solutions of medium pH and low buffer capacity, correcting the effects induced from the shift of local pH near the electrode?electrolyte interface (pH^s) is a prerequisite for unraveling the intrinsic kinetics and its pH dependence. In this review, recent progress on how to estimate the pH^s, how to eliminate the effect induced by pH^s shift and how to deduce the pH dependent intrinsic reaction kinetics are summarized. Mechanistic and kinetic implication of pH effect on electrocatalytic processes will be discussed by taking formic acid/formate oxidation at Pt electrode as an example.