Rod-shaped CoS_x/TiO_x@ZIS core-Shell dual S-scheme heterojunctions for solar-driven water splitting to produce hydrogen and photothermal conversion

Developing efficient photocatalysts capable of promoting electron transfer and enhancing redox reaction performance is a crucial approach to achieve photocatalytic water splitting for hydrogen production. In this study, a rod-shaped CoS_x/TiO_x@ZnIn₂S₄ (CoS_x/TiO_x@ZIS) core-shell dual S-scheme heterojunction was successfully constructed using an oil bath-high temperature sulfiding method. The random distribution of CoS_x and TiO_x nanoparticles ensured intimate contact, improving the smoothness of interfacial transfer and the effective separation of photoelectron-hole pairs. The ultrathin ZnIn₂S₄ nanosheets were tightly coated on the surface of CoS_x/TiO_x nanorods, constructing a dual built-in electric field to further enhance the separation rate of photogenerated carriers. Simultaneously, the photothermal effect of CoS_x created a high-temperature environment locally, significantly enhancing the reaction kinetics. Photocatalytic performance tests revealed that the optimized catalyst achieved a hydrogen production rate of ~42.947 mmol g⁻¹·h⁻¹, which was ~203.5 times and ~8.3 times higher than that of pure CoS_x/TiO_x and ZnIn₂S₄, respectively. This performance enhancement was attributed to the synergistic effect of the S-scheme heterojunction, enhanced light absorption capability, and photothermal effect. Under an irradiation of 0.3 W·cm⁻², the photothermal conversion efficiency of CoS_x/TiO_x@ZIS reached 60.30%, which is ~1.3 times higher than that of pure ZIS. At 380 nm, its apparent quantum efficiency(AQE) reached ~49.8%, significantly outperforming most reported similar photocatalysts. Furthermore, after four consecutive cycles of testing, the degradation rate of its catalytic performance was less than ~7.9%, demonstrating excellent stability. The results of this study indicate that the dual S-scheme heterojunction structure promotes effective separation of spatial charges and utilization of light energy, enhancing the synergistic photocatalytic performance of photothermal catalysis.