Spherical nanoflower-like bimetallic (Mo,Ni)(S,O)3- sulfo-oxide catalysts for efficient hydrogen evolution under visible light

Photocatalytic H2O splitting by sulfide-based materials is a great challenge, because of the poor resilience of such materials against hole oxidation. Although sulfide ion of catalyst negatively shifts the valence band-edge relative to its oxide ion, the instability of sulfide ions during H2O oxidation is a critical obstacle to simultaneous evolution of H2 and O2. Here, active, stable, and spherical nanoflower-like bimetal (Mo,Ni)(S,O)3-x sulfo-oxide catalysts with a band gap of ∼2.1 eV and different concentrations of oxygen vacancy defects were synthesized for H2O splitting. (Mo,Ni)(S,O)3-x of 25 mg with a suitable amount of oxygen vacancy defects could evolve 587.5 μmol/h H2 under visible-light irradiation. This work demonstrated an example of converting an oxidation photocatalyst into a reduction one. Microstructure analysis showed that surface oxygen vacancy defects and the multiple-valence charges in Ni and Mo not only promoted effective separation, interface transfer, and reactions of photo-carriers but also reduced the charge build-up to avoid photo-corrosion during photocatalytic water decomposition.