Morphology and facet tailoring of CaSnO₃assembled in molten salt with defect-mediated photocatalytic activity

Modulation of perovskite oxide toward controlled active facets and defects has attracted much attention. However, the influence of facets and defects on the photocatalytic activity are still ambiguous, especially for the alkaline-earth stannates. In this work, a high-efficiency CaSnO3 semiconductor photocatalyst was prepared by a facile one-step molten salt method without adding a capping agent. By simply varying the solutes, three kinds of CaSnO3 with different morphology were successfully synthesized, including sphere, cube, and cuboctahedron. Meanwhile, both the facet exposure and formation of defects affected the photocatalytic performance of CaSnO3 samples. The formation mechanism for various CaSnO3 morphology and their facet-dependent photocatalytic performances were explored in detail, which indicated that the formation of {100} facets was beneficial for the photocatalytic performance rather than {111}. Although these samples showed similar absorption edges, the varying amount of oxygen vacancy was one of the reasons for the diverse photocatalytic activity. The distortion of crystal structure of CaSnO3 was due to the formation of reduced Sn, which could influence the bond and angle of Sn-O-Sn and subsequently the photocatalytic activity. Different scavengers were also used to identify the role of active species in the photo-degradation process. The relationships between surface electronic structure, oxygen vacancy, and oxidation state of B site with the photocatalytic activity of tin stannate were clearly revealed.