Phase Effect of NixPy Hybridized with g-C3N4 for Photocatalytic Hydrogen Generation

The use of noble metal-free nickel phosphides (Ni_xP_y) as suitable cocatalysts in photocatalytic hydrogen (H₂) generation has gained a lot of interest. In this paper, for the first time, three different crystalline phases of nickel phosphides, Ni₂P, Ni₁₂P₅, and Ni₃P, were synthesized and then hybridized with g-C₃N₄ to investigate the phase effect of Ni_xP_y on photocatalytic H₂ generation. It has been found that all three phases of Ni_xP_y work as effective cocatalysts for the enhancement of visible light H₂ generation with g-C₃N₄. The effective charge transfer between g-C₃N₄ and Ni_xP_y, demonstrated by photoelectrochemical properties, photoluminescence, and time-resolved diffused reflectance, contributes to the enhanced photocatalytic H₂ generation performance. Interestingly, Ni₂P/g-C₃N₄ showed the highest photocatalytic activity among the three Ni_xP_y/g-C₃N₄. Ni_xP_y with a higher ratio of phosphorus (Ni₂P) can accelerate charge transfer and provide more Ni-P bonds, leading to a preferable H₂ generation performance.