Novel Synthesis and Photocatalytic Activity of Oxysulfide Sm₂Ti₂S₂O₅

The oxysulfide Sm 2 Ti 2 S 2 O 5 was synthesized by sulfurization of Sm 2 Ti 2 O 7 under H 2 S flow. Amorphous Sm 2 Ti 2 O 7 was found to be the most appropriate precursor for the synthesis of Sm 2 Ti 2 S 2 O 5 at temperatures above 1073 K. The relationship between the preparation conditions and the photocatalytic activities for H + reduction to H 2 and H 2 O oxidation to O 2 was investigated, and the highest activities for both H 2 and O 2 evolution were obtained at a sulfurization temperature of 1123 K. Subsequent heating of Sm 2 Ti 2 S 2 O 5 in air enhanced the activities further. Sulfurization by H 2 S allows for synthesis of Sm 2 Ti 2 S 2 O 5 at lower temperatures with a significantly shorter heating period (1 h) than that of conventional solid-state reaction.