Cu3MS4 (M=V, Nb, Ta) and its Solid Solutions with Sulvanite Structure for Photocatalytic and Photoelectrochemical H2 Evolution under Visible-Light Irradiation

Solid solutions with of Cu3VS4 with either Cu3NbS4 or Cu3TaS4 (Cu3Nb1-xVxS4 or Cu3Ta1-xVxS4) were prepared by a solid-state reaction and adopted a sulvanite structure. Their band gaps were 1.6-1.7eV corresponding to the absorption of a wide range of visible light. Ru cocatalyst-loaded Cu3MS4 (M=V, Nb, Ta), Cu3Nb1-xVxS4, and Cu3Ta1-xVxS4 showed photocatalytic activities for sacrificial H-2 evolution under visible-light irradiation. Most solid solutions showed better activities than the single-component Cu3MS4 (M=V, Nb, Ta). Cu3MS4 (M=V, Nb), Cu3Nb1-xVxS4, and Cu3Ta1-xVxS4 also functioned as photoelectrodes and gave cathodic photocurrents under visible-light irradiation, indicating a p-type semiconductor character. Cu3Nb0.9V0.1S4 showed the best photocatalytic and photoelectrochemical performances. When Ru-loaded Cu3Nb0.9V0.1S4 was used as a photocathode with a CoOx-loaded BiVO4 photoanode, photoelectrochemical water splitting proceeded under simulated sunlight irradiation without an external bias.