Defect Control And Photocatalytic Performance Of Alkaline Earth Metal Stannate Materials

With the increasing environmental pollution and energy crisis,photocatalytic technology stands out as a powerful weapon for repairing the environment and solving the energy crisis.So far,hundreds of photocatalysts have been reported,mainly for water decomposition and environmental remediation.Currently,commercial TiO₂ photocatalysts have been widely used because of their non-toxicity,low cost,high efficiency and good stability.However,the photon energy conversion of photocatalyst is far from the practical level at this stage.The key reason is to limit the migration of photogenerated charges from the inside to the surface of the semiconductor.In order to achieve optical drive catalytic activation,the solar-chemical energy conversion process on the oxide catalyst should be better utilized,the efficiency of which depends on the energy coupling between photons,excitons and active species.In response to photon-exciton energy conversion,solar energy capture efficiencies can be optimized by designing band structures,such as the generation of defect states and the formation of heterojunctions.Among many photocatalyst materials,perovskite oxides have shown excellent prospects for photocatalysis due to their unique crystal structure and electronic properties.The perovskite crystal structure provides a good framework in which the band gap values are adjusted so that the visible light absorption and band edge potentials can meet the needs of a particular photocatalytic reaction.Furthermore,lattice distortion in perovskite compounds strongly influences the separation of photogenerated charge carriers.Usually the transfer of energy to oxygen species is considered to be a critical step in the O₂·-driven photocatalytic reaction process,so it is very important to develop and design oxygen-induced photocatalysts to improve the oxidative adsorption performance.In this paper,the alkaline earth metal stannate perovskite material was selected as the research object,and the CaSnO₃ photocatalyst was mainly studied.The photocatalyst was synthesized by hydrothermal method in the form of non-stoichiometric ratio.Defects are induced in this way to form shallow capture centers,enhance electron and hole separation transmission rates,and regulate the performance of photocatalysts.The MSnO₃ catalyst controlled by oxide defects converts light into chemical energy by improving the chemical adsorption of substances on the surface.CaSnO₃ with a Ca/Sn ratio of 2.7?2.7-CaSnO₃?with oxygen-rich vacancies exhibits high photocurrent performance and effective photocatalytic activity.A superior photo efficiency is achieved for 2.7-CaSnO₃,which reduces 93.9%MB dyes within 30 min under 100 mW/cm²white LED light irradiation,approximately 3.2 times larger than its stoichiometric one.Under the same LED light irradiation,577.4?molh^-11 g^-11 of H₂ and 62.0?molh^-11 g^-11 of O₂ are realized over2.7-CaSnO₃.The chemisorption improved by oxygen defects in 2.7-CaSnO₃ enables the transfer of photogenerated electrons to oxygen species in space.Therefore,oxygen molecules are activated into superoxide radicals on the oxygen defect-rich MSnO₃ successfully.After more oxygen defects doping,the hydrogen evolution rate increases from 553.3 to 1152.7?molh^-1g^-1,while O₂production rates increases from 62.0 to 129.1?molh^-1g^-1.The hydrogen reduction treatment further revealed that the enhancement of both hydrogen and oxygen evolution was realized by introducing more oxygen vacancies into 2.7-CaSnO₃.The modified MSnO₃ can enhance photocatalytic activity by chemical adsorption and activation of molecular oxygen on surface defects.Here,we provide a new strategy for oxide defect modulating MSnO₃ catalysts.