Investigation of active electrocatalytic centers under reaction conditions using operando microscopies

Electrocatalysis is crucial for transitioning from a fossil fuel-based to a renewable energy society. In situ identification of electrocatalytic active centers is required to realize this vision, enabling observing the catalytic behavior comprehensively and continuously in real-time under relevant reaction conditions and providing insight into reaction steps. Operando methodology incorporates in situ analysis and simultaneous measurements of catalytic performance. In this manuscript, we analyze the recent progress in the observation of active sites in a wide range of electrocatalysts and various electrocatalytic reactions by employing operando microscopies, including liquid cell transmission electron microscopy (LCTEM), electrochemical scanning tunneling microscopy (EC-STM), scanning electrochemical microscopy (SECM) and scanning electrochemical cell microscopy (SECCM). We showcase their capability to correlate the electrocatalytic activity with catalyst topological and structural properties.