Ligand-defect synergistic catalyst for localized CO2 concentration enhancement in electrochemical reduction of low concentration CO2

Abstract

Electrochemical CO₂ reduction reaction (CO₂RR) is a potential strategy for mitigating severe greenhouse effect. Despite its potential, CO₂RR encounters critical challenges to convert low CO₂ concentrations in practical scenarios, due to the CO₂ mass transfer limitations. Herein, we prepared a reduced 2-aminoterephthalic acid modified bismuth coordination compound (Re-BiBDC-NH₂) for CO₂RR in low CO₂ concentrations. Retained amino groups after in situ reduction induce abundant unsaturated coordination sites, enhancing CO₂ adsorption and enabling localized concentration enhancement even under low CO₂ supply concentrations. As such, the optimized Re-BiBDC-NH₂ achieves a Faradaic efficiency for formate (FE_formate) of > 80% at a wide potential range of 700 mV, FE_formate of >75% across 15%–100% CO₂ concentrations. Furthermore, in a flow cell at a current density of 300 mA cm⁻² and across a wide pH range (pH = 1.7, 7, and 14), the Re-BiBDC-NH₂ catalyst achieved FE_formate > 95%, with a single-pass carbon efficiency (SPCE) reaching 71.6% in acidic electrolyte (pH = 1.7). In situ spectroscopies and Density functional theory calculations reveal that dynamically frustrated Lewis pairs formed by amino groups and defects concentrate CO₂, and stabilize *OCHO intermediates to reduce energy barriers, thereby not only enhancing the CO₂RR performance but also allowing reaction to operate under low CO₂ concentrations. This work presents a promising ligand-defect synergistic catalyst for low-concentration CO₂RR, offering insights for bridging catalyst research and practical CO₂ conversion.