Defect‐Rich Porous Cu with Abundant Cu(100) for Acidic CO2 Electroreduction in Membrane Electrode Assembly

Abstract Acidic electrocatalytic CO 2 reduction (CO 2 RR) faces slow C‐C coupling kinetics and dominant hydrogen evolution, resulting in low C 2+ yields and selectivity. Here, the porous copper nanosheets (pCu NS) are reported with abundant Cu(100) and defect sites for efficient acidic CO 2 RR to C 2+ products. In a membrane electrode assembly (MEA), the pCu NS electrodes achieved a remarkable 75.01% C 2+ production Faradaic efficiency (FE) at a current density of 300 mA cm −2 with a full‐cell voltage of 3.8 V. A CO 2 single‐pass conversion efficiency of up to 74.38% is achieved. In situ Raman spectra and density functional theory calculations revealed that pCu NS not only gives abundant nanopores and defect sites but also preferentially exposes Cu(100) facets, synergistically creating local alkaline microenvironment, maximizing the *CO intermediate coverage, and promoting *CO hydrogenation for C 2+ production. This work offers a crucial insight for designing an efficient catalyst for efficient acidic CO 2 ‐to‐C 2+ conversion.