Surface-Reconstructed,\nMesoporous In<sub>1.8</sub>Bi<sub>0.2</sub>O<sub>3</sub> Nanocubes\nas Electrocatalysts for Efficient\nCO<sub>2</sub> Conversion to Formate

Precise\ncontrol and understanding of surface changes in indium\n(In)-based catalysts during the electrocatalytic CO<sub>2</sub> reduction\nreaction (CO<sub>2</sub>RR) process are challenging. This study presents\na series of surface-reconstructed In<sub>2</sub>O<sub>3</sub>–Bi\nelectrocatalysts, created by doping mesoporous In<sub>2</sub>O<sub>3</sub> nanocubes with bismuth (Bi). This doping introduces abundant\nbimetallic In–Bi sites at the crystal–amorphous interfaces,\nenhancing the CO<sub>2</sub>-to-formate conversion selectivity. Bi\natoms accelerate the surface reconstruction of In<sub>2</sub>O<sub>3</sub>, reduce the charge density around In atoms, and promote partial\namorphization. <i>In situ</i> X-ray diffraction (XRD) and\nFourier-transform infrared spectroscopy (FT-IR) measurements and density\nfunctional theory (DFT) calculations show that the bimetallic In–Bi\nsites lower the energy barrier for the HCOOH* intermediate, enhance\nH<sub>2</sub>O dissociation, and inhibit the hydrogen evolution reaction\n(HER). The surface-reconstructed In<sub>1.8</sub>Bi<sub>0.2</sub>O<sub>3</sub> electrocatalyst demonstrates a Faradaic efficiency (FE) of\n92.6% and a partial current density of −28.5 mA·cm<sup>–2</sup> and operates stably for 110 h in a H-type cell. In\na flow cell, it achieves an FE of formate (FE<sub>formate</sub>) of\n97.6% at −1.4 V<sub>RHE</sub> and maintains above 94% FE<sub>formate</sub> over a potential window of 800 mV (from −1.0\nto −1.8 V vs RHE). This study offers an effective approach\nfor designing high-performance electrocatalysts for the CO<sub>2</sub>RR based on surface reconstruction.