Efficient spatial charge separation and transfer in ultrathin g-C3N4 nanosheets modified with Cu2MoS4 as a noble metal-free co-catalyst for superior visible light-driven photocatalytic water splitting

Abstract

Developing photocatalysts with efficient spatial charge separation and transfer as well as a high light-harvesting ability remains a key challenge. Here, we report a facile in situ process to decorate ultrathin g-C₃N₄ nanosheets (NSs) with a co-catalyst, Cu₂MoS₄, for photocatalytic water splitting. The as-obtained Cu₂MoS₄/g-C₃N₄ exhibits a superior photocatalytic H₂ evolution rate of 2170.5 μmol h⁻¹ g⁻¹ under visible light irradiation, which is nearly 677 and 34 times higher than that of bulk g-C₃N₄ and g-C₃N₄ NSs, respectively, and far exceeds that of most g-C₃N₄ catalysts modified with other sulphide co-catalysts reported in the literature, demonstrating that Cu₂MoS₄ can serve as a promising non-noble metal co-catalyst to couple with g-C₃N₄ for highly efficient photocatalysts. Structural characterization confirms the well-defined morphology of Cu₂MoS₄/g-C₃N₄ in which Cu₂MoS₄ hollow spheres are uniformly attached on the ultrathin g-C₃N₄ NSs with numerous micropores and vacancies. The optical properties indicate that Cu₂MoS₄/g-C₃N₄ possesses a superb visible light absorption ability. The photoluminescence spectra, photocurrent response, and electrochemical impedance spectra combine to prove the highly efficient separation and migration of photogenerated electrons and holes. All these factors synergistically enhance the photocatalytic activity of Cu₂MoS₄/g-C₃N₄ for photocatalytic water splitting, providing new insights into the rational design of high-performance visible light-driven photocatalysts based on earth-abundant elements.