Atomically dispersed Ba sites as electron promoters to enhance the performance for photoreduction of CO2

Abstract

The highly photocatalytic conversion of CO₂ into valuable products is a promising method for mitigating the global greenhouse effect and increasing the energy supply. However, the utilization of electron-deficient active sites to activate CO₂ leads to lower photocatalytic efficiency and selectivity. One effective strategy to improve CO₂ photoreduction performance is making precise adjustments to the electronic structure of the photocatalyst. Herein, the defective TiO₂ modified with Cu, Ba, and CuBa metal sites is synthesized via a simple photo-deposition method and applied for photoreduction of CO₂. Among the prepared catalysts, Cu₁Ba₃/TiO₂-SBO (TiO₂-SBO: TiO₂ with surface and bulk oxygen vacancies) has been demonstrated to possess excellent photocatalytic conversion of CO₂, with the activity levels of the CO and CH₄ that are 8 and 6 times higher than the bare TiO₂-SBO, and the electron selectivity of CO is up to 53%. The results reveal that oxygen vacancies and CuBa bimetallic sites have a synergistic ability to facilitate the separation of photogenerated carriers. Furthermore, the electron-donor Ba metal enables modulation of the electronic structure of Cu co-catalysts, generating electron-rich Cu metal sites that accelerate the activation of CO₂. Meanwhile, the theoretical calculations prove that the Cu₁Ba₃/TiO₂-SBO has the stronger CO₂ adsorption energy, and its strengthened binding of *COOH and the markedly reduced formation energy of CO and *CO intermediates boost the conversion of COOH to CO and enhance the selectivity of CO. Thereby, the defective TiO₂ modified with CuBa bimetal represents a more effective measure for CO₂ reduction into valuable products.