Noble-metal-free Cu2S-modified photocatalysts for enhanced photocatalytic hydrogen production by forming nanoscale p–n junction structure

Abstract

Developing efficient noble-metal-free photocatalysts is of great importance for the large-scale application of photocatalytic hydrogen production. Herein, low-cost and environment-friendly p-type Cu₂S was successfully loaded on n-type CdS photocatalyst by an in situ method to achieve efficient Cu₂S/CdS hybrid photocatalysts. Cu₂S nanoparticles of ca. 50 nm were intimately assembled on the surface of polyhedral CdS nanocrystals, giving rise to the formation of numerous nanoscale p–n junctions between p-type Cu₂S and n-type CdS. Compared to single CdS, Cu₂S/CdS exhibited increased photocatalytic hydrogen production under visible light irradiation. The generated nanoscale p–n junctions in Cu₂S/CdS, leading to the enhanced charge separation efficiency and better utilization of visible light, were crucial to the improved photocatalytic activity. During the photocatalytic reaction, Cu₂S nanoparticles captured the photogenerated holes in CdS and served as the active sites for the surface oxidation reaction. The photocatalytic property of Cu₂S/CdS photocatalysts was influenced by the Cu/Cd molar ratio, with the optimal one of 0.05. P-type Cu₂S could also be utilized for improving the photocatalytic activities of n-type ZnIn₂S₄ and n-type TiO₂ by forming efficient p–n junctions, indicating the general applicability of p-type Cu₂S. This work demonstrates that forming p–n junction structure was a useful strategy for developing efficient noble-metal-free hybrid photocatalysts.