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

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.