In situ light-assisted preparation of MoS2 on graphitic C3N4 nanosheets for enhanced photocatalytic H-2 production from water

MoS2-decorated graphitic C3N4 (g-C3N4/MoS2) photocatalysts were prepared by a simple and scalable in situ light-assisted method. In this process, MoS2 was formed from the reduction of [MoS4](2-) by photogenerated electrons, and was then loaded in situ on the electron outlet points of g-C3N4. The g-C3N4/MoS2 composite was well characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy (Raman), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), and ultraviolet visible diffuse reflection spectroscopy (UV-DRS). The g-C3N4/MoS2 photocatalysts showed good photocatalytic H-2 evolution activity. When the loading amount of MoS2 was increased to 2.89 wt% (g-C3N4/MoS2-2.89%), the highest H-2 evolution rate (252 mu mol g(-1) h(-1)) was obtained. In addition, g-C3N4/MoS2-2.89% presented stable photocatalytic H-2 evolution ability (no noticeable degradation of photocatalytic H-2 evolution was detected in 18 h) and good natural light driven H-2 evolution ability (the H-2 evolution rate was 320 mu mol g(-1) h(-1)). A possible photocatalytic mechanism of the MoS2 cocatalyst for the improvement of the photocatalytic activity of g-C3N4 is proposed, where MoS2 can efficiently promote the separation of the photogenerated electrons and holes of g-C3N4, consequently enhancing the H-2 evolution activity; this mechanism is supported by the photoluminescence spectroscopy and photoelectrochemical analyses.