Effect of post-treatments on the photocatalytic activity of Sm 2Ti2S2O5 for the hydrogen evolution reaction

Abstract

The oxysulphide photocatalyst Sm2Ti2S 2O5 was synthesized by sulphurizing an amorphous Sm 2Ti2O7 prepared using a polymerized complex method under a H2S flow and was used as a H2 evolution photocatalyst in the sacrificial H2 evolution and Z-scheme water splitting reactions. The H2 evolution activity of Rh-loaded Sm 2Ti2S2O5 was improved by annealing with sulphur powder and etching with nitric acid. Characterization using XRD, SEM, DRS and XPS suggested that annealing with sulphur decreased the density of the reduced Ti species in Sm2Ti2S2O5 and etching with nitric acid removed the amorphous phases and excessive sulphur species on the surface. After the two post-treatments, platinized Sm 2Ti2S2O5 combined with rutile-type TiO2 and NaI showed activity for Z-scheme water splitting under UV irradiation. Although UV irradiation was necessary owing to the use of TiO 2, this work provided the first evidence that an oxysulphide photocatalyst was applicable to Z-scheme water splitting. © 2014 the Partner Organisations.