Surface-Reconstructed, Mesoporous In1.8Bi0.2O3 Nanocubes as Electrocatalysts for Efficient CO2 Conversion to Formate

Precise control and understanding of surface changes in indium (In)-based catalysts during the electrocatalytic CO2 reduction reaction (CO2RR) process are challenging. This study presents a series of surface-reconstructed In2O3–Bi electrocatalysts, created by doping mesoporous In2O3 nanocubes with bismuth (Bi). This doping introduces abundant bimetallic In–Bi sites at the crystal–amorphous interfaces, enhancing the CO2-to-formate conversion selectivity. Bi atoms accelerate the surface reconstruction of In2O3, reduce the charge density around In atoms, and promote partial amorphization. In situ X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR) measurements and density functional theory (DFT) calculations show that the bimetallic In–Bi sites lower the energy barrier for the HCOOH* intermediate, enhance H2O dissociation, and inhibit the hydrogen evolution reaction (HER). The surface-reconstructed In1.8Bi0.2O3 electrocatalyst demonstrates a Faradaic efficiency (FE) of 92.6% and a partial current density of −28.5 mA·cm–2 and operates stably for 110 h in a H-type cell. In a flow cell, it achieves an FE of formate (FEformate) of 97.6% at −1.4 VRHE and maintains above 94% FEformate over a potential window of 800 mV (from −1.0 to −1.8 V vs RHE). This study offers an effective approach for designing high-performance electrocatalysts for the CO2RR based on surface reconstruction.