Construction of Co9S8/MoS2/Ni2P double S-scheme heterojunction for enhanced photocatalytic hydrogen evolution

Rational design of composite catalysts with efficient charge separation and transfer and good light collection ability is of great significance to achieve high photoelectrochemical conversion efficiency. In this paper, a Co9S8/MoS2/Ni2P dual S-scheme heterojunction photocatalyst was successfully synthesized by a simple sulfidation and hydrothermal method. The optimized Co9S8/MoS2/Ni2P composite with hierarchical structure, large surface area and numerous reactive active sites showed a good photocatalytic hydrogen evolution rate of 5.69 mmol g−1 h−1, which is 2.28, 4.12 and 10.74 times higher than that of pure Co9S8, MoS2 and Ni2P, respectively. A combination of time-resolved photoluminescence (TRPL) spectroscopy, valence band XPS (VB-XPS), ultraviolet photoelectron spectroscopy (UPS), and density-functional theory (DFT) calculations confirms that the formation of the Co9S8/MoS2/Ni2P double S-scheme greatly facilitates charge migration and spatial separation, and improves the oxidation and reduction ability. This work will provide insights into the development of PBA-based dual S-scheme heterojunction catalysts for photocatalytic hydrogen evolution.