MoS2 as non-noble-metal co-catalyst for photocatalytic hydrogen evolution over hexagonal ZnIn2S4 under visible light irradiations

MoS2/ZnIn2S4 nanocomposites were prepared by impregnating the hydrothermally prepared hexagonal ZnIn2S4 microspheres with an aqueous solution of (NH4)2MoS4, followed by a treatment in H2S flow at high temperatures to transform Mo(VI) to Mo(IV). The as-prepared MoS2/ZnIn2S4 nanocomposites were characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). Their photocatalytic performance for hydrogen evolution under visible light irradiations was also investigated. It was found that the photocatalytic hydrogen evolution activity over hexagonal ZnIn2S4 can be significantly increased by loading MoS2 as a co-catalyst and the photocatalytic activity of MoS2/ZnIn2S4 nanocomposites could be even higher than that of Pt/ZnIn2S4 under similar reaction condition. Amorphous MoS2 was for the first time shown to exhibit excellent promoting effect for photocatalytic hydrogen evolution. The promoting effect played by amorphous MoS2 can be ascribed to the existence of many defect sites in amorphous MoS2 which can act as adsorption sites for hydrogen atoms and eventually leads to hydrogen evolution. This work demonstrates a high potential of the developing of environmental friendly, cheap noble metal-free co-catalyst for semiconductor-based photocatalytic hydrogen evolution.