Wide-field imaging of active site distribution on semiconducting transition metal dichalcogenide nanosheets in electrocatalytic and photoelectrocatalytic processes.

Semiconducting transition metal dichalcogenide (TMD) nanosheets are promising materials for electrocatalysis and photoelectrocatalysis. However, the existing analytical approaches are inadequate at comprehensively describing the operation of narrow-bandgap semiconductors in these two processes. Furthermore, the distribution of the reactive sites on the electrode surface and the dynamic movement of carriers within these semiconductors during the reactions remain ambiguous. To plug these knowledge gaps, an widefield imaging technique was devised in this study to investigate the electron distribution in different types of TMDs; notably, the method permits high-spatiotemporal-resolution analyses of electron-induced metal-ion reduction reactions in both electrocatalysis and photoelectrocatalysis. The findings revealed a unique complementary distribution of the active sites on WSe nanosheets during the two different cathodic processes. Our facile imaging approach can provide insightful information on the heterogeneous structure-property relationship at the electrochemical interfaces, facilitating the rational design of high-performance electrocatalytic/photoelectrocatalytic materials.