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

Abstract

In this work, an MoS_x/g-C₃N₄ composite photocatalyst was successfully fabricated by a sonochemical approach, where amorphous MoS_x 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 MoS_x/g-C₃N₄ composite was tested under visible light. The results show that the H₂-evolution rate of the MoS_x/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 MoS_x forms intimate heterojunctions with g-C₃N₄ nanosheets, and the introduction of MoS_x 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 MoS_x. XPS analysis manifests that MoS_x provides a number of active sites. Mott–Schottky plots show that the conduction band of MoS_x (−0.18 V vs. E_Ag/AgCl, pH = 7) is more negative than that of g-C₃N₄ nanosheets.