Homojunction and Vacancy Traps in Zn0.5Cd0.5S for Efficient Photocatalytic Hydrogen Generation

The advancement of photocatalysts for solar fuel production is fundamentally limited by inefficient charge separation and sluggish surface kinetics. Herein, we propose a defect-engineering paradigm to develop Zn 0.5 Cd 0.5 S photocatalysts with exceptional photocatalytic hydrogen activity. The alternating zinc-blende/wurtzite homojunction, induced by ordered stacking faults, is revealed to enable a periodic internal electric field that facilitates directional bulk charge transport and superior photogenerated carrier separation. This design is validated through the subsequent hydrothermal synthesis of twined Zn 0.5 Cd 0.5 S samples with the targeted homojunctions and significantly enhanced photocatalytic performance. Mechanistic investigations further demonstrate that a fine-tuned density of vacancies, serving as selective charge traps, is essential to maximize efficiency. Accordingly, a superior hydrogen evolution rate of 192.11 mmol/h/g, along with remarkable stability (>36 h), has been achieved in our synthesized samples, substantially surpassing previously reported ZnCdS-based photocatalysts. The work highlights the potential of tailoring homojunction and vacancy traps to boost the photocatalytic efficiency, and paves an alternative way to design high-performance photocatalysts for scalable hydrogen evolution from water.