Lab‐based electrochemical X‐ray photoelectron spectroscopy for in‐situ probing of redox processes at the electrified solid/liquid interface

Abstract

Abstract A profound understanding of the solid/liquid interface is central in electrochemistry and electrocatalysis, as the interfacial properties ultimately determine the electro‐reactivity of a system. Although numerous electrochemical methods exist to characterize this interface under operating conditions, tools for the in‐situ observation of the surface chemistry, that is, chemical composition and oxidation state, are still scarce, and currently exclusively available at synchrotron facilities. Here, we demonstrate the ability of laboratory‐based near‐ambient pressure X‐ray photoelectron spectroscopy to track changes in oxidation states in‐situ with respect to the applied potential. In this proof‐of‐principle study with polycrystalline gold (Au) as the best‐studied electrochemical standard, we show that during the oxygen evolution reaction (OER), at high OER overpotentials, Au 3+ governs the interfacial chemistry, while, at lower overpotentials, Au + dominates.