ReS2 with unique trion behavior as a co-catalyst for enhanced sunlight hydrogen production

The interfacial catalytic reaction plays a crucial role in determining hydrogen production efficiency of a photocatalyst. In this work, hollow spherical nano-shell composite (g-C3N4/CdS/ReS2) formed by graphitic carbon nitride (g-C3N4), cadmium sulfide (CdS), and rhenium disulfide (ReS2) was prepared for photocatalytic hydrogen production, with ReS2 introduced as a relatively inexpensive co-catalyst with excellent performance. It was found that two-electron catalytic reaction took place in this photocatalytic system due to the unique trion behavior of ReS2 co-catalyst, which greatly enhances the rate of photocatalytic hydrogen production. The tightly bound excitons in the ReS2 co-catalyst could easily capture the photogenerated electrons in the photocatalytic system to form trions, while g-C3N4 in the inner shell and CdS in the middle shell provided sufficient electrons for the formation of trions. The active edge sites of ReS2 also facilitated the generation and desorption of hydrogen, which creates conditions favoring two-electron catalytic reaction. In addition, oxidation and reduction reactions occurred inside and outside of the hollow spherical nano-shell, respectively, which effectively inhibits the recombination of photogenerated carriers. The unique trion behavior of ReS2 alters the interfacial catalytic reaction compared to the widely used platinum (Pt) co-catalyst in photocatalytic hydrogen production, which provides a new approach for enhancing the activity of photocatalytic systems.