Reaction Pathways of Hydrogen-Evolving Electrocatalysts: Electrochemical and Spectroscopic Studies of Proton-Coupled Electron Transfer Processes

Proton-coupled electron transfer (PCET) reactions are at the heart of the catalytic processes involved in hydrogen evolution. In this Perspective, the state-of-the-art spectroscopic and electrochemical methods available to elucidate the mechanisms of PCET reactions of fuel-forming catalysts are presented. Through examples of our recent work, the applications of these methods are discussed with a focus on the type of information and the accuracy that can be obtained from each. Three case studies are presented to illustrate different possible origins for peak shifts observed in cyclic voltammograms.