Grand canonical view on electrochemical energetics at applied potential in a nutshell

In this review, I summarize the foundations and motivation of modern grand canonical descriptions of electrified interfaces, which represent a thermodynamically consistent framework for assessing electronically adiabatic energetics and kinetics as a function of the applied electrode potential. The discussion will center around the ubiquitous coupled proton-electron transfer process at electrified metal-water interfaces and highlight the conceptual differences to the classical understanding and viewpoint. Finally, I present a range of important recent insights about the energetics of protons along their (adiabatic) adsorption path. • Elaboration of problematic approximations and concepts in classical electrochemistry descriptions. • Summary of the central cornerstones of the modern, grand canonical description of processes at electrified interfaces. • Prototypical features of the adiabatic free energy landscape for adsorbing protons from interfacial water.