In Situ/Operando Studies for Designing Next-Generation Electrocatalysts

It has been widely acknowledged that most electrocatalysts would undergo a structural reconstruction during the water splitting as well as carbon dioxide (CO2) reduction reactions. Recently developed in situ and/or operando methods are gaining increasing interest as judicious tools for investigations of heterogeneous electrocatalysis. In this Perspective, recent applications of various in situ characterization techniques in tracking the structural reconstruction of the catalysts, identifying real active sites, and recording intermediates formed during water electrolysis and CO2 reduction reaction are thoroughly summarized. Finally, on the basis of the unique capabilities as well as limitations of each in situ or operando technique, we established an "in situ probing map" for the corresponding in situ technologies in liquid–solid interfaces and offer guidelines for the successful development of next-generation efficient catalysts.