Advanced in-situ electrochemical scanning probe microscopies in electrocatalysis

Electrocatalysis is critical in improving the energy conversion efficiency, decreasing carbon emissions, and promoting the development of the green energy industry. A deep understanding of the electrocatalytic processes at nanostructured electrochemical interfaces (electrodes) is required to elucidate the electrocatalytic mechanism and facilitate the rational design of electrocatalysts. Electrocatalytic surfaces, which are structurally and compositionally heterogeneous, are usually analyzed using classical macroscopic electrochemical methods that lack the high spatial resolution and temporal sensitivity required for localized electrochemical measurements. In this regard, advances in electrochemical scanning probe microscopy, including electrochemical scanning tunneling, electrochemical atomic force, scanning electrochemical, and scanning electrochemical cell microscopies, offer significant opportunities to study electrocatalytic phenomena at nanometer and ultimately atomic scales during the reaction process. In this review, we first introduce the basic principles, features, and advantages and disadvantages of each technique of these scanning probe microscopies and outline the key advancements of each technique, particularly in investigating electrocatalysis. Subsequently, hybrid techniques of probe microscopy with synergistic effects are introduced. Then, we summarize the recent progress in the application of in-situ characterization methods in electrocatalysis, including hydrogen evolution/oxidation, oxygen evolution, and CO2 reduction reactions, focusing on the structure-activity correlation, structure evolution/stability, adsorption of the reactants or intermediates, preferred reaction pathways, and selectivity. Finally, the challenges and future developments of in-situ scanning probe microscopy in electrocatalysis are discussed.