In situ light-assisted preparation of MoS2 on graphitic C3N4 nanosheets for enhanced photocatalytic H2 production from water

Abstract

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 H₂ evolution activity. When the loading amount of MoS₂ was increased to 2.89 wt% (g-C₃N₄/MoS₂-2.89%), the highest H₂ evolution rate (252 μmol g⁻¹ h⁻¹) was obtained. In addition, g-C₃N₄/MoS₂-2.89% presented stable photocatalytic H₂ evolution ability (no noticeable degradation of photocatalytic H₂ evolution was detected in 18 h) and good natural light driven H₂ evolution ability (the H₂ evolution rate was 320 μmol 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 H₂ evolution activity; this mechanism is supported by the photoluminescence spectroscopy and photoelectrochemical analyses.