Photocatalytic H₂ generation via CoP quantum-dot-modified g-C₃N₄ synthesized by electroless plating

Photocatalytic water splitting is a promising method for hydrogen production. Numerous efficient photocatalysts have been synthesized and utilized. However, photocatalysts without a noble metal as the co-catalyst have been rarely reported. Herein, a CoP co-catalyst-modified graphitic-C₃N₄ (g-C₃N₄/CoP) is investigated for photocatalytic water splitting to produce H₂. The g-C₃N₄/CoP composite is synthesized in two steps. The first step is related to thermal decomposition, and the second step involves an electroless plating technique. The photocatalytic activity for hydrogen evolution reactions of g-C₃N₄ is distinctly increased by loading the appropriate amount of CoP quantum dots (QDs). Among the as-synthesized samples, the optimized one (g-C₃N₄/CoP-4%) shows exceptional photocatalytic activity as compared with pristine g-C₃N₄, generating H₂ at a rate of 936 μ mol g⁻¹ h⁻¹, even higher than that of g-C₃N₄ with 4 wt% Pt (665 μmol g⁻¹ h⁻¹). The UV-visible and optical absorption behavior confirms that g-C₃N₄ has an absorption edge at 451 nm, but after being composited with CoP, g-C₃N₄/CoP-4% has an absorption edge at 497 nm. Furthermore, photoluminescence and photocurrent measurements confirm that loading CoP QDs to pristine g-C₃N₄ not only enhances the charge separation, but also improves the transfer of photogenerated e⁻-h⁺ pairs, thus improving the photocatalytic performance of the catalyst to generate H₂. This work demonstrates a feasible strategy for the synthesis of highly efficient metal phosphide-loaded g-C₃N₄ for hydrogen generation.