Copper phosphide decorated g-C₃N₄ catalysts for highly efficient photocatalytic H₂ evolution

Designing functional heterojunctions to enhance photocatalytic hydrogen evolution is still a key challenge in the field of efficient solar energy utilization. Copper phosphides become an ideal material to serve as the cocatalysts during photocatalytic hydrogen evolution by virtue of the lower prices. In this study, we synthesized graphitic carbon nitride (g-C₃N₄) based catalysts loaded with copper phosphide (Cu₃P, Cu₉₇P₃), which exhibit superior performance in photocatalytic H₂ evolution. Ultraviolet (UV)-visible spectroscopy illustrated that the absorption of light strengthened after the loading of copper phosphide, and the time-resolved transient photoluminescence (PL) spectra showed that the separation and transfer of the photoexcited carriers greatly improved. Moreover, both copper phosphide/g-C₃N₄ photocatalysts exhibited a relatively high H₂ evolution rate: Cu₃P/g-C₃N₄ (maximum 343 μmol h⁻¹ g⁻¹), Cu₉₇P₃/g-C₃N₄ (162.9 μmol h⁻¹ g⁻¹) while copper phosphide themself exhibit no photocatalytic activity. Thus, the copper phosphides (Cu₃P, Cu₉₇P₃) work as a cocatalyst during photocatalytic H₂ evolution. The cycling experiments illustrated that both copper phosphide/g-C₃N₄ photocatalysts perform excellent stability in the photocatalytic H₂ evolution. It is worth noting that while the NaH₂PO₂ was heated in the tube furnace for phosphorization to obtain Cu₃P, the excessive PH₃ could pass through the solution of CuSO₄ to obtain Cu₉₇P₃ at the same time, which significantly improved the utilization of PH₃ and reduced the risk of toxicity. This work could provide new strategies to design photocatalysts decorated with copper phosphide for highly efficient visible-light-driven hydrogen evolution.