Enhanced photocatalytic hydrogen evolution under visible light irradiation by p-type MoS₂/n-type Ni₂P doped g-C₃N₄

Solar energy conversion by photocatalytic hydrogen generation provides a clean alternative to fossil fuels. However, designing more efficient, chemically stable and affordable catalytic systems remains a great challenge for industrial application. In this study, p-type MoS₂ is innovatively introduced on the n-type g-C₃N₄ loaded with Ni₂P, which forms a new earth-abundant and environmentally benign photocatalyst for solar hydrogen generation. Firstly, we prepared the ternary MoS₂–g-C₃N₄/Ni₂P composite by ultrasonically mixing MoS₂ nanosheets with g-C₃N₄/Ni₂P by simple annealing process. The as-synthesized MoS₂–g-C₃N₄/Ni₂P catalyst is well characterized by X-Ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), UV–vis diffuse reflectance spectroscopy (DRS) and photoluminescence spectroscopy (PL). The 2% MoS₂–g-C₃N₄/Ni₂P exhibited the best hydrogen generation rate of 298.1 μmol·g⁻¹·h⁻¹ under visible light illumination, which is 69 times more than that of pure g-C₃N₄. Based on the evaluation of hydrogen generation rate and characteristic results, a possible mechanism is proposed, where 2D MoS₂–g-C₃N₄ p-n heterojunction could efficiently promote the electron-hole pair separation and Ni₂P could significantly accelerate the hydrogen reduction step. The mechanism is supported by the results of PL and electrochemical analyses.