Facet-defined AgCl nanocrystals with surface-electronic-structure-dominated photoreactivities

The conventional understanding of facet effects on photocatalysts is that semiconductor micro/nanocrystals exposed with high-reactivity facets usually exhibit excellent photocatalytic activities. However, this point of view is being challenged in some circumstances. Herein, two types of facet-defined AgCl nanocrystals, AgCl nanocubes exposed with six {100} facets and AgCl octahedrons enclosed by eight {111} facets have been successfully prepared. The comparative studies of their photocatalytic properties reveal an unusual higher photoreactivity of AgCl nanocubes than that of AgCl octahedrons, although AgCl {100} facets have lower theoretical surface energy than the AgCl {111} facets. The further mechanism investigation suggests that the much decreased reduction potential of {111} facet would result in insufficient consumption of photo-excited electrons and hence depress the involvement of holes in photooxidation reactions. Consequently, the surface electronic structures dominate the photoreactivities of AgCl {111} and {100} facets. Our work reveals the true photoreactivities of AgCl {111} and {100} facets by direct experimental evidence, and the proposed mechanism will facilitate further development of highly efficient AgCl photocatalysts.