Constructing Robust Bi Active Sites In Situ on -Bi2O3 for Efficient and Selective Photoreduction of CO2 to CH4 via Directional Transfer of Electrons

Photocatalytic CO2 reduction is an ideal strategy to reduce greenhouse effects and realize carbon neutralization. Constructing active sites with specific designs is highly desired and challenging to achieve with high activity and selectivity of photoreduction. Herein, our studies find that a series of Bi-based materials with different compositions, structures, and morphologies can be prepared by adjusting the pH. At pH 12.5, Bi nanocluster (NC)-modified Bi2O3 (Bi NCs/Bi2O3) are obtained, and the active site has changed from O of Bi2O3 to Bi of Bi NCs. Experimental and theoretical analyses suggest that photogenerated electrons in Bi NCs/Bi2O3 efficiently and directionally transfer from Bi2O3 to Bi NCs. As an outcome, Bi NCs/Bi2O3 possess outstanding adsorption and activation capacity of CO2, it achieves 94.8% of selectivity for visible light-driven CO2 reduction to CH4. According to the number of transferred electrons, the catalytic activity of Bi NCs/Bi2O3 is an amazing 210 times that of pure Bi2O3. It was found that the intermediate of *CO at Bi sites tended to be hydrogenated to form *CHO species in thermodynamics, and the intermediates of *CHO and *CH2OH/*CH3OH further formed on Bi NCs/Bi2O3, thus generating CH4 as a product. Whereas the above process is difficult to occur on Bi2O3, because the *CO easily desorbs to form CO. The results demonstrate that the evolution of active sites successfully leads to the change of CO2 photoreduction pathway.