Sn-Doped Bi₂O₃ nanosheets for highly efficient electrochemical CO₂ reduction toward formate production

Electrocatalytic CO₂ reduction to formate is considered as a perfect route for efficient conversion of the greenhouse gas CO₂ to value-added chemicals. However, it still remains a huge challenge to design a catalyst with both high catalytic activity and selectivity for target products. Here we report a unique Sn-doped Bi₂O₃ nanosheet (NS) electrocatalyst with different atomic percentages of Sn (1.2, 2.5, and 3.8%) prepared by a simple solvothermal method for highly efficient electrochemical reduction of CO₂ to formate. Of them, the 2.5% Sn-doped Bi₂O₃ NSs exhibited the highest faradaic efficiency (FE) of 93.4% with a current density of 24.3 mA cm^-2 for formate at -0.97 V in the H-cell and a maximum current density of nearly 50 mA cm^-2 was achieved at -1.27 V. The formate FE is stable maintained at over 90% in a wide potential range from -0.87 V to -1.17 V. Electrochemical and density functional theory (DFT) analyses of undoped and Sn doped Bi₂O₃ NSs indicated that the strong synergistic effect between Sn and Bi is responsible for the enhancement in the adsorption capacity of the OCHO* intermediate, and thus the activity for formate production. In addition, we coupled 2.5% Sn-doped Bi₂O₃ NSs with a dimensionally stable anode (DSA) to realize battery-driven highly active CO₂RR and OER with decent activity and efficiency.