Harnessing Interfacial Cl⁻ Ions for Concurrent Formate Production at Industrial Level via CO₂ Reduction and Methanol Oxidation

The efficient electrocatalytic conversion of CO₂ to formate is often impeded by the high energy requirements of the oxygen evolution reaction (OER) and the limited activity and selectivity of CO₂ reduction reaction (CO₂RR). Herein, a novel strategy to enhance formate production by substituting the OER with the methanol oxidation reaction (MOR) and optimizing the cathodic microenvironment with interfacial Cl⁻ ions is presented. Through theoretical analysis, binder-free Bi and NiOOH electrodes that achieve remarkable Faradaic efficiencies (FE_formate) exceeding 90% at current densities of 50–250 mA·cm⁻² for CO₂RR and MOR, respectively, are identified. These combined experimental and theoretical investigations demonstrate that interfacial Cl⁻ enrichment on the Bi electrode modulates the local electronic structure, fostering a microenvironment conducive to CO₂RR. The Bi–NiOOH full cell maintains a FE_formate above 90% at industry-level current densities (100–300 mA·cm⁻²), enabling concurrent formate electrosynthesis at both electrodes. This work highlights the critical role of local anion environments in electrocatalysis and provides a strategic framework for the synergistic engineering of electrochemical systems.