Engineering Interlayer Electric Fields to Enhance K+ Insertion for Efficient Acidic CO2 Reduction

In acidic CO 2 electroreduction reaction (CO 2 RR), excessive H* adsorption from high proton concentrations suppresses *CO coverage on Cu-based catalysts, limiting multicarbon (C 2+ ) product formation. Here, we introduce a K + insertion strategy via an interlayer electric field (IEF) between the layers of Cu nanosheets (K + -Cu NS) to strengthen *CO adsorption and boost C 2+ selectivity. Finite element method (FEM) simulations verified the role of the IEF in enriching K + ions, meanwhile density functional theory (DFT) calculations demonstrated these enriched K + ions facilitate stronger *CO adsorption. Ar + ion-etching-assisted X-ray photoelectron spectroscopy (XPS) and operando Raman spectroscopy confirmed the structured K + stuffing. Operando attenuated total reflection infrared spectroscopy (ATR-IR) demonstrated the enhanced *CO adsorption on K + -Cu NS. As a result, the K + -Cu NS catalyst achieved an ultrahigh cathodic energy efficiency of 42.5% and a remarkable Faradaic efficiency of 80.3% for C 2+ products in a flow cell. This work highlights a novel cation regulation strategy for advancing the acidic CO 2 RR efficiency.