ZnIn₂S₄ with oxygen atom doping and surface sulfur vacancies for overall water splitting under visible light irradiation

Previous reports have found that surface sulfur vacancies can improve the hydrogen production performance of ZnIn2S4, and oxygen atom doping can improve its water oxidation ability. However, the simultaneous introduction of these two factors to achieve photocatalytic overall water splitting under visible-light irradiation has not been reported. In this work, we introduce surface sulfur vacancies and oxygen atom doping simultaneously via calcination of the ZnIn2S4 obtained by a hydrothermal method under an air atmosphere. Their synergistic effect on the photocatalytic overall water splitting activity is investigated in detail by controlling the calcination temperature and calcination time. Both surface sulfur vacancies and oxygen atom doping can inhibit carrier recombination, and oxygen atom doping can increase the photogenerated carrier concentration. Surface sulfur vacancies and oxygen atom doping can increase the photocatalytic rate 2-3 times, respectively, confirming that the two are equally important for the improvement of photocatalytic activity. More importantly, the synergistic effect of sulfur vacancies and oxygen atom doping results in a solar-to-hydrogen (STH) efficiency of similar to 0.035% (the highest efficiency reported so far for single-phase ZnIn2S4) and a stable photocatalytic overall water splitting performance.