Artificial Photosynthetic System with Spatial Dual Reduction Site Enabling Enhanced Solar Hydrogen Production

Although S-scheme artificial photosynthesis shows promise for photocatalytic hydrogen production, traditional methods often overly concentrate on a single reduction site. This limitation results in inadequate redox capability and inefficient charge separation, which hampers the efficiency of the photocatalytic hydrogen evolution reaction. To overcome this limitation, a double S-scheme system is proposed that leverages dual reduction sites, thereby preserving energetic photo-electrons and holes to enhance apparent quantum efficiency. The design features a double S-scheme junction consisting of CdS nanospheres decorated with anatase TiO2 nanoparticles coupled with graphitic C3N4. The as-prepared catalyst exhibits a hydrogen evolution rate of 26.84 mmol g-1 h-1 and an apparent quantum efficiency of 40.2% at 365 nm. This enhanced photocatalytic hydrogen evolution is ascribed to the efficient charge separation and transport induced by the double S-scheme. Both theoretical calculations and comprehensive spectroscopy tests (both in situ and ex situ) affirm the efficient charge transport across the catalyst interface. Moreover, substituting the reduction-type catalyst CdS with other similar sulfides like ZnIn2S4, ZnS, MoS2 and In2S3 further confirms the feasibility of the proposed double S-scheme configuration. The findings provide a pathway to designing more effective double S-scheme artificial photosynthetic systems, opening up fresh perspectives in enhancing photocatalytic hydrogen evolution performance. Step-scheme heterojunctions, recognized for their efficient charge transport and high redox capacity, are considered a viable approach to improve photocatalytic hydrogen production. In this study, a double S-scheme heterojunction featuring spatial dual reduction sites is developed. This design enhances solar hydrogen production and yields a high apparent quantum efficiency. This work contributes a significant approach to the development of more effective S-scheme artificial photosynthetic systems.image