Modulation of charge structure in Bi/Bi₂O₃-In₂O₃@C for efficient CO₂ electroreduction to formate

Electrocatalytic CO₂ reduction reaction (ECO₂RR) to value-added chemicals is of significant importance to control CO₂ emission and reach carbon neutrality. Herein, Bi/Bi₂O₃-In₂O₃@C electrocatalyst with nanosheet arrays is successfully fabricated by a facile solvothermal with subsequent calcination process. It is found that the electron structure of Bi/Bi₂O₃-In₂O₃@C can be adjusted by the synergistic effects of Bi-In hetero-diatoms, which can significantly enhance its inherent catalytic activity. As expected, it requires a maximum HCOOH faradaic efficiency (FE_HCOOH) of 97.6 % at -1.1 V vs. Reversible Hydrogen Electrode (RHE), which further delivers over 90 % at a wide potential range of -0.8 to -1.4 V vs. RHE, and exhibits high stability of 90.1 % over 60-h long-term test. In-situ Raman analysis is performed to explore the mechanism of its excellent stability. Meanwhile, in-situ attenuated total reflection-Fourier-transform infrared (ATR-FTIR) analysis combined with theoretical calculations reveal that the hetero-bridging absorption of *OCHO and d-d orbital coupling effect can regulate d-band center of Bi/Bi₂O₃-In₂O₃@C and improve its density of states around E_f, moderating free energy of intermediates, thereby the improved formate production performance can be seen.