Sulfur Vacancy-Enriched Rhombohedral ZnIn₂S₄ Nanosheets for Highly Efficient Photocatalytic Overall Water Splitting under Visible Light Irradiation

Crystal phase and vacancies play an important role in regulating photocatalytic activity. In this work, sulfur vacancy-enriched rhombohedral ZnIn2S4 was obtained by calcining hexagonal ZnIn2S4 with poor sulfur vacancies under a nitrogen atmosphere. Based on the results of theoretical calculations and photocatalytic performance, it was found that the synergy of crystal phase and sulfur vacancies resulted in highly efficient photocatalytic overall water splitting under visible light irradiation. The lighter average effective mass of photogenerated electrons and holes in the rhombohedral ZnIn2S4 accelerates the separation of photogenerated carriers, which plays a major role in achieving overall water splitting activity. An appropriate amount of sulfur vacancies can further improve the overall water splitting performance, which plays a supplementary role. More importantly, the solar-to-hydrogen conversion efficiency of sulfur vacancy-enriched rhombohedral ZnIn2S4 reaches 0.021%, which is the highest reported efficiency for single-phase ZnIn2S4.