Identifying In Situ Activity and Selectivity of Oxygen Reduction Catalysts at the Subparticle Level

Oxygen reduction reaction (ORR) plays a crucial role in both the chemical and energy industries. Despite substantial advancements in theoretical, computational, and experimental studies, identifying both the in situ activity and selectivity in ORR electrocatalysis remains a major challenge. Here, using a suite of correlative operando scanning electrochemical probe and electrochemiluminescence microscopy techniques, we establish a link between the morphological structure and the local ORR activity and selectivity of single Au and Au@Pt platelets at the subparticle level. It is clearly shown that the edge facets of Au and Au@Pt platelets exhibit higher activity for 4e- ORR compared to basal planes, whereas the basal planes of both Au and Au@Pt platelets demonstrate superior 2e- selectivity relative to the edge facets. These findings deepen our understanding of ORR activity and selectivity across different facets at the subparticle level, which offers valuable guidance for the rational design of highly efficient ORR electrocatalysts.