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

Hydrogen peroxide (H 2 O 2 ) is a green oxidant that is widely used in daily life and industry. Artificial photocatalytic synthesis of H 2 O 2 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 O 2 greatly inhibit the oxygen reduction reaction. Herein, the first synergistic modification of In 2 S 3 using ion doping and vacancy modulation is used in this paper. An In 2 S 3 -based photocatalyst containing S vacancies and Ga 3+ ions is designed and synthesized. After continuous irradiation under visible light ( λ ≥ 420 nm) for 1 h, the H 2 O 2 concentration of the system reaches 352.58 μmol L –1 , which is 7.5 times than that of pure In 2 S 3 , and the apparent quantum yield at 450 nm is 4.64%. Appropriate concentrations of S vacancies promoted O 2 adsorption, and theoretical calculations demonstrates that Ga 3+ ions and S vacancies synergistically promote O 2 activation and more favorable for 2e – oxygen reduction reaction. All these phenomena facilitate H 2 O 2 generation. Furthermore, ESR analysis and radical trapping experiments show that the interaction between superoxide anion radicals (•O 2 – ), singlet oxygen ( 1 O 2 ), h + , and proton donor (isopropanol) in the solution phase plays a key role in the photocatalytic synthesis of H 2 O 2 , which has been largely neglected in previous studies. We suggest that the S vacancy-regulated Ga 3+ ion-doped In 2 S 3 catalyst could provide a reference for the design of high-performance materials for the photocatalytic production of hydrogen peroxide.