An amorphous MoSx modified g-C3N4 composite for efficient photocatalytic hydrogen evolution under visible light

In this work, an MoSx/g-C3N4 composite photocatalyst was successfully fabricated by a sonochemical approach, where amorphous MoSx was synthesized using a hydrothermal method with Na2MoO4·H2O, H4SiO4(W3O9)4 and CH3CSNH2 as precursors, and g-C3N4 nanosheets were produced using a two-step thermal polycondensation method. The hydrogen-evolution performance of the MoSx/g-C3N4 composite was tested under visible light. The results show that the H2-evolution rate of the MoSx/g-C3N4 (7 wt%) photocatalyst reaches a maximum value of 1586 μmol g−1 h−1, which is about 70 times that of pure g-C3N4 nanosheets. The main reason is that amorphous MoSx forms intimate heterojunctions with g-C3N4 nanosheets, and the introduction of MoSx into g-C3N4 nanosheets not only enhances the ability to convert H+ into H2, but also promotes the separation of photoinduced electron–hole pairs for the photocatalyst. BET analysis shows that the specific surface area and pore volume of g-C3N4 are decreased in the presence of MoSx. XPS analysis manifests that MoSx provides a number of active sites. Mott–Schottky plots show that the conduction band of MoSx (−0.18 V vs. EAg/AgCl, pH = 7) is more negative than that of g-C3N4 nanosheets.