Boosting the hydrogen peroxide production over In2S3 crystals under visible light illumination by gallium ions doping and sulfur vacancies modulation

Hydrogen peroxide (H2O2) is a green oxidant that is widely used in daily life and industry. Artificial photocatalytic synthesis of H2O2 is a green and sustainable scheme, but the high complexation rate of electron-hole pairs during photocatalysis and the low activation capacity of the catalyst for O2 greatly inhibit the oxygen reduction reaction. Herein, the first synergistic modification of In2S3 using ion doping and vacancy modulation is used in this paper. An In2S3-based photocatalyst containing S vacancies and Ga3+ ions is designed and synthesized. After continuous irradiation under visible light (λ ≥ 420 nm) for 1 h, the H2O2 concentration of the system reaches 352.58 μmol L–1, which is 7.5 times than that of pure In2S3, and the apparent quantum yield at 450 nm is 4.64%. Appropriate concentrations of S vacancies promoted O2 adsorption, and theoretical calculations demonstrates that Ga3+ ions and S vacancies synergistically promote O2 activation and more favorable for 2e– oxygen reduction reaction. All these phenomena facilitate H2O2 generation. Furthermore, ESR analysis and radical trapping experiments show that the interaction between superoxide anion radicals (•O2–), singlet oxygen (1O2), h+, and proton donor (isopropanol) in the solution phase plays a key role in the photocatalytic synthesis of H2O2, which has been largely neglected in previous studies. We suggest that the S vacancy-regulated Ga3+ ion-doped In2S3 catalyst could provide a reference for the design of high-performance materials for the photocatalytic production of hydrogen peroxide.