In-Situ EXAFS Observation of the Microscopic Surface Structure of CdS and ZnS Semiconductor Nanocrystalline Photocatalysts in N, N-Dimethylformamide

Abstract

In-situ EXAFS analysis of colloidal CdS and ZnS nanocrystallites in N, N-dimethylformamide (DMF) was performed to clarify their microscopic surface structure. Analyses revealed that CdS and ZnS nanocrystallites are stabilized by solvation of the oxygen atoms of DMF to the cadmium and zinc atoms on the surface of nanocrystallites, respectively. The solvated surface structure of CdS nanocrystallites was affected by the addition of pentafluorothiophenol or H₂S to the system. In the system of ZnS nanocrystallite, the structural parameters, such as atomic distances and coordination numbers of the Zn-S and Zn-O shcll, depend on the coexistent counter anions dereived from the starting zinc salts. These characteristics were correlated to their catalytic activity for photoreduction of carbon dioxide to carbon monoxide or/and formate.