Bi selectively doped SrTiO3-x nanosheets enhance photocatalytic CO2 reduction under visible light

Converting CO2 into chemical energy by using solar energy is an environmental strategy to achieve carbon neutrality. In this paper, two dimensionality (2D) SrTiO3-x nanosheets with oxygen vacancies were synthesized successfully. Oxygen vacancies will generate defect levels in the band structure of SrTiO3-x. So, SrTiO3-x nanosheets have good photocatalytic CO2 reduction performance under visible light. In order to further improve its photocatalytic efficiency, Bi was used to dope Sr site and Ti site in SrTiO3-x nanosheets respectively. It is found that Sr site is the adsorption site of CO2 molecules. When Bi replaced Sr, CO2 adsorption on the surface of SrTiO3-x nanosheets was weakened. When Bi replaced Ti, there has no effect on CO2 adsorption. Due to the synergistic effect of Bi doping, oxygen vacancies, and Sr active site, the 1.0% Bi-doped Ti site in SrTiO3-x (1.0% Bi-Ti-STO) had the best photocatalytic performance under visible light (λ ≥ 420 nm). CO and CH4 yields were 5.58 umol/g/h and 0.36 umol/g/h. Photocatalytic CO2 reduction path has always been the focus of exploration. The in-situ FTIR spectrum proved the step of photocatalytic CO2 reduction and COO- and COOH are important intermediates in the photocatalytic CO2 reaction.