Electronegativity drives charge polarization in indium single-atom catalysts for low-overpotential CO2 electroreduction

In/C-0.2 achieves 93.5% Faradaic efficiency for formate at -0.6 V vs. RHE with 400 mV overpotential and 80 h operation. • Indium dispersion regulates CO 2 adsorption and electron transfer, enabling low-overpotential formate production. • TOF-SIMS combined with FT-IR reveals that In sites promote *OCHO formation and suppress competing pathways. • Electronegativity-driven charge polarization stabilizes O-bound *OCHO and facilitates highly selective formate formation. Electrochemical CO 2 reduction to formate is limited by high overpotentials and competing reactions. Herein, we report an indium single-atom catalyst that modulates the adsorption geometry of CO 2 by engineering the charge state of the active site. The optimized catalyst achieves a Faradaic efficiency (FE) for formate of 93.5% at −0.6 V vs. RHE in a flow cell with 400 mV overpotential and maintains high selectivity across a wide potential window (-0.6 to −0.9 V). The overpotential of formate is highly sensitive to the initial dispersion of In atoms causing optimal CO 2 adsorption and fast electron transfer, and increases significantly when In clusters/particles become predominant species. In situ characterizations and theoretical calculations indicate that oxygen-coordinated isolated In sites induce significant interfacial charge polarization, which preferentially stabilizes a bidentate O-bound adsorption configuration of CO 2 -derived intermediates through strong In-O interactions and thereby enables highly selective conversion to formate. This work identifies electronegativity as a key descriptor for controlling intermediate adsorption on p-block single-atom catalysts and provides insights into the rational design of selective CO 2 RR electrocatalysts. Download: Download high-res image (296KB) Download: Download full-size image