Synergistic surface oxygen defect and bulk Ti3+ defect engineering on SrTiO3 for enhancing photocatalytic overall water splitting

Abstract

SrTiO₃ as a photocatalytic overall water splitting material has received extensive attention in recent years, while effectively suppressing Ti³⁺ is the key to enhancing the photocatalytic performance. Herein, a polymerizable complexation method is employed to enable Al³⁺ uniformly enter into SrTiO₃ lattice for reducing Ti³⁺, and substituting Ti⁴⁺ with the formation of oxygen vacancy. Thus, the photogenerated carrier transport is promoted, and the resulting appropriate surface oxygen vacancy is also conducive to the adsorption of water molecules and OH*. The optimized 2% Al³⁺-doped SrTiO₃ possesses a lower Ti³⁺ concentration, compared with the same sample prepared by the solid-phase griding method. Consequently, 2% Al-STO sample deposited co-catalysts achieves the highest activity and durability with the H₂ and O₂ evolution rates of 1.256 mmol·h^-1 and 0.692 mmol·h^-1 (0.04 g catalyst), respectively, corresponding to the AQE value of 55.46% at 365 nm. The characterizations and DFT calculation results reveal that the uniform Al³⁺ doping promotes the increase in the surface oxygen vacancy, which is beneficial for accelerating the reduction reaction and facilitating carrier separation and migration, therefore enhancing the overall water splitting reaction.

Keywords: Al(3+) doping; DFT calculation; Overall water splitting; Polymerizable complexation method; SrTiO(3).