Optical in situ deciphering of the surface reconstruction-assistant multielectron transfer event of single CoO nanoparticles.

Surface reconstruction determines the fate of catalytic sites on the near-surface during the oxygen evolution reaction. However, deciphering the conversion mechanism of various intermediate-states during surface reconstruction remains a challenge. Herein, we employed an optical imaging technique to draw the landscape of dynamic surface reconstruction on individual CoO nanoparticles. By regulating the surface states of CoO nanoparticles, we explored dynamic growth of the CoO(OH) sublayer on single CoO nanoparticles and directly identified the conversion between two dynamics. Rich oxygen vacancies induced more active sites on the surface and prolonged surface reconstruction, which enhanced electrochemical redox and oxygen evolution. These results were further verified by in situ electrochemical extinction spectroscopy of single CoO nanoparticles. We elucidate the heterogeneous evolution of surface reconstruction on individual CoO nanoparticles and present a unique perspective to understand the fate of catalytic species on the nanosurface, which is of enduring significance for investigating the heterogeneity of multielectron-transfer events.