Engineering the Ag/Cu microenvironment for efficient CO ₂ electroreduction to CO in a three‐membrane electrolyzer producing Na ₂ CO ₃ and Cl ₂ by‐products

Abstract A three‐membrane electrolyzer has been designed for carbon dioxide (CO 2 ) electroreduction to carbon monoxide (CO) in an organic electrolyte, with sodium carbonate (Na 2 CO 3 ) and chlorine (Cl 2 ) generated as by‐products. In order to improve the performance of the electrolyzer, a heterostructured Ag/Cu catalyst was synthesized by growing spherical assemblies of Ag/Cu nanoflowers on Cu foam (AgNFs@CF). Experimental results combined with density functional theory (DFT) calculations reveal that tailoring the electric double‐layer structure of the catalyst modulates the local microenvironment and effectively suppresses the hydrogen evolution reaction in the organic medium. Moreover, the synergistic interaction at the curved and interlaced interface between the Cu support and the Ag layer facilitates charge separation, thereby increasing the electron density at Ag sites. As a result, AgNFs@CF delivered a high CO partial current density of 162.68 mA cm −2 at −2.4 V (vs. SHE), with a Faradaic efficiency of 92.6%, maintaining stability under prolonged electrolysis. This work provides both theoretical and experimental insights into designing the microenvironment of the Ag/Cu catalyst for efficient and eco‐friendly CO production, while offering an industrially feasible route for converting CO 2 into high‐value products.