Independent Optimization of the Redox Reaction Sites for Simultaneous Production of Value-Added Organic Compounds and Hydrogen with High Activity and Selectivity

Developing integrated photocatalytic systems for the simultaneous production of value-added organic compounds and hydrogen is a promising approach to efficient solar energy utilization. However, it also proves to be highly challenging, since it requires catalytic surface sites that are optimized for both photocatalytic oxidation and reduction reactions. Here, we addressed this challenge by constructing a hollow S-scheme heterojunction photocatalyst composed of hollow WO2.72 (WOHS) and CdS. The key benefit of this heterojunction is that it enabled directional charge transfer between WOHS and CdS, which allowed the reaction sites for oxidation and reduction reaction to be effectively separated from each other. Exploiting this advantage enabled further optimization of the oxidation and reduction reaction sites independently, which was achieved by depositing Ni and Co3O4 selectively on the CdS and WOHS surface. We demonstrated that this not only enhanced charge-separation efficiency but also significantly lowered the activity energy for proton reduction and •CH(OH)Ph radical dehydrogenation. The resulting heterojunction therefore exhibited high activity for hydrogen evolution and BA-to-BAD oxidation with selectivity that is unachievable with each of the component photocatalyst separately.