Acid–Base Catalysis and Kinetic Buffering in Stepwise Proton Coupled Electron Transfer

In investigations of stepwise proton coupled electron transfer (PCET) reactions, it is often assumed, explicitly or implicitly, that the proton transfer (PT) step is at equilibrium, meaning that the buffering conditions are examined from a strictly thermodynamic perspective. In the present work, the implications of the Brönsted acid–base catalysis on the voltammetric responses of reversible (fast electron transfer) electroactive species are examined in the context of a 1 e − , 1 H + square scheme, by numerical simulations accounting explicitly for the PT kinetics. Depending on the p K a ’s of the electroactive species and those of the buffer components, PT kinetics can be slowed down to such an extent that voltammetric features akin to non-buffered conditions can appear even at high buffering capacities. This kinetic buffering is intrinsically asymmetric, the PT rate being affected only in one direction as a natural consequence of the Brönsted catalysis mechanism.