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

In acidic CO2 electroreduction reaction (CO2RR), excessive H* adsorption from high proton concentrations suppresses *CO coverage on Cu-based catalysts, limiting multicarbon (C2+) 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 C2+ 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 C2+ products in a flow cell. This work highlights a novel cation regulation strategy for advancing the acidic CO2RR efficiency.