Enhanced Photocatalytic Hydrogen Evolution over Twin-Crystal ZnCdS with Sulfur Vacancies Prepared by High-Gravity Technology

Photocatalytic hydrogen evolution via water splitting is considered an attractive method for addressing the increasing global energy crisis and environmental problems. The synthesis of efficient photocatalysts is currently a major focus and challenge in research. In this study, we utilized the impinging stream-rotating packed bed (IS-RPB) combined with the coprecipitation method to synthesize twin-crystal Zn0.5Cd0.5S solid solutions with rich sulfur vacancies, continuous and kilogram-scale process. At the optimal high-gravity factor and pH, a series of Zn0.5Cd0.5S with twin crystals, sulfur vacancies, and both were controllably synthesized by optimizing the initial impact velocity and crystallization time. This approach resulted in a steady increase in the performance of photocatalytic hydrogen evolution via water splitting. The formation of twin-crystal and sulfur vacancies together promotes the separation and transfer of photogenerated carriers, thereby enhancing photocatalytic performance. The optimal photocatalytic hydrogen evolution rate under visible light was 31.6 mmol g–1 h–1, and the largest apparent quantum yield (AQY) can reach a high value of 26.33% at 400 nm. In addition, it also exerts good stability in 12 h cycles. This unique in situ physical approach for constructing sulfur vacancies on twin crystals provides a new process for synthesizing highly efficient metal sulfide photocatalysts.