Deconvolute the Impact of Microenvironment on Proton-Coupled Electron Transfers at Electrochemical Interfaces

Microenvironment at electrochemical interfaces has a critical impact on the elec-trode-mediated proton-coupled electron transfer (PCET) processes. However, understanding the convoluted effects by microenivornment remains challenging, and deploying the electron tranfer theory of the Marcus-Hush-Chidsey (MHC) framework is limited by its elusive link to experimentally accessible variables other than reaction rates. Herein, we report a general mech-anistic framework based on the MHC theory to deconvolute the effects of microenvironment on the interfacial PCET processes in terms of experimentally accessible variables, as illustrated by the model system of the cation effect on Au-catalyzed CO2 reduction reaction, for which we rationalize the trends by both inorganic and organic cations in a unified picture formulated by hydration free energy of cation and surface charge density.