Graphitic C₃N₄ Decorated with CoP Co-catalyst: Enhanced and Stable Photocatalytic H₂ Evolution Activity from Water under Visible-light Irradiation

In this work, graphitic C₃N₄ decorated with a CoP co-catalyst (g-C₃N₄/CoP) is reported for photocatalytic H₂ evolution reaction based on two-step hydrothermal and phosphidation method. The structure of g-C₃N₄/CoP is well confirmed by XRD, FTIR, TEM, XPS, and UV/Vis diffuse reflection spectra techniques. When the weight percentage of CoP loading is 3.4 wt % (g-C₃N₄/CoP-3.4 %), the highest H₂ evolution amount of 8.4×10² μmol g⁻¹ is obtained, which is 1.1×10³ times than that over pure g-C₃N₄. This value also is comparable with that of g-C₃N₄ loaded by the same amount of Pt. In cycling experiments, g-C₃N₄/CoP-3.4 % shows a stable photocatalytic activity. In addition, g-C₃N₄/CoP-3.4 % is an efficient photocatalyst for H₂ evolution under irradiation with natural solar light. Based on comparative photoluminescence emission spectra, photoelectrochemical I–t curves, EIS Nyquist plots, and polarization curves between g-C₃N₄/CoP-3.4 % and pure g-C₃N₄, it is concluded that the presence of the CoP co-catalyst accelerates the separation and transfer of photogenerated electrons of g-C₃N₄, thus resulting in improved photocatalytic activity in the H₂ evolution reaction.