Engineering surface defect active sites in SnS2 nanosheets with electron-donating groups for efficient photoelectrochemical water splitting

Lack of surface charge and poor carrier separation efficiency limit the photoelectrochemical (PEC) water splitting performance. Therefore, enhancing the charge density around the surface-active sites is an important strategy to boost the PEC performance. Herein, an in-situ strategy to construct surface S vacancies (S_v) and introduce hydroxyl groups (–OH) on the SnS₂ photoanode is designed, and its PEC water splitting activity has significantly improved, reaching a maximum photocurrent density of 1.44 mA·cm⁻² at 1.23 V_RHE, which is 8.47 times greater than in terms of pure SnS₂, and the onset potential has an obvious negative shift. Complete theoretical simulations and detailed experimental tests show that the –OH groups, as strong electron donors, transfer charge to the S vacancy sites and increase the surface charge density. Effective separation and transport of the photoinduced carriers are achieved. The ability of S_v active sites to activate and stabilize H₂O molecules and reaction intermediates is also effectively improved to ensure the smooth progress of the water oxidation reaction. This work offers a novel approach for the synthesis of effective photoanodes by modifying surface defect active sites with electron donor groups.