Visualizing light-induced dynamic structural transformations of Au clusters-based photocatalyst via in situ TEM

Ultrasmall gold (Au) clusters have been regarded as one of the prototypes materials for solar energy conversion due to their unique strong molecular-like light absorption properties. However, light-induced aggregation Au into nanoparticles is most important factors that restricts its application in photocatalysis. Although has widely demonstrated, underlying mechanism cluster fusion still unclear lack experimental evidence. Herein, we report direct observation on TiO2 nanosheets aggregating when used visible photocatalysts reduction nitroaromatics. Through situ high-resolution transmission electron microscopy (TEM), coexistence two mechanisms under ultraviolet-visible (UV-Vis) irradiation air identified, i.e., migration and coalescence (MC) Ostwald ripening (OR). Additionally, correlation between photostability reaction atmospheres investigated, among which higher stability an inert N2 atmosphere or vacuum than oxidizing (i.e., O2). These results indicate inherent during photocatalysis, instability comes from consuming ligand layer. This work not only discloses sintering but also provides guidelines enhancing metal clusters-based stability.