Applications of Scanning Electrochemical Microscopy in Energy-Relevant Electrocatalysis

Abstract Energy-relevant electrocatalytic reactions, such as hydrogen evolution, oxygen evolution, CO 2 reduction, and nitrate reduction, are fundamental to sustainable energy conversion and electrochemical manufacturing. Despite decades of progress, advances in electrocatalysis remain constrained by an incomplete understanding of active sites, reaction kinetics, and the interfacial microenvironment under operating electrochemical conditions. As an in situ characterization technique, scanning electrochemical microscopy (SECM) is well suited to addressing these challenges because of its submicron spatial resolution and rapid temporal response. Although SECM has been widely applied in recent years, reviews that systematically summarize these advances from the perspective of electrocatalytic reactions and their underlying mechanisms remain scarce. To bridge this gap, this review outlines the fundamental principles of SECM and reframes its functional applications in energy-relevant electrocatalysis through a mechanism-oriented framework. Building on recent progress, we highlight the key contributions of SECM in three areas: identification and quantification of active sites, determination of reaction kinetics, and in situ monitoring of the interfacial microenvironment evolution. Furthermore, we discuss several directions that are expected to shape the future development of SECM, including multimodal correlative characterization, integration of experimental measurements with theoretical modeling, innovations in probe technologies, and the extension of SECM applications from model systems to practical devices. These perspectives provide insight into electrocatalytic mechanisms and guide the design of next-generation electrocatalysts.