Zilin Zhao, Ruikuan Xie, Weixiao Lin, Houhong Song, Nengji Liu, Yifei Xu, Cheng-Jie Yang, Chung‐Li Dong, Bin Yang, Zhongjian Li, Xiahan Sang, Lecheng Lei, Bingjun Xu, Guoliang Chai, P. Samorì, Yuanjun Chen, Yang Hou
Acidic CO 2 electroreduction (CO 2 ER) enhances carbon utilization but faces significant challenges: intense hydrogen evolution reaction competition and poor multicarbon (C 2+ ) product selectivity. We identify that this stems primarily from acid-induced destabilization of the critical *CO intermediate, exacerbated by adsorbed hydrogen. Here, we propose a dual-modification “molecular-fence” strategy to reconfigure the catalyst–electrolyte interface. We first engineer atomically dispersed Lewis acid Zr sites on Cu to electronically accelerate *CO formation. Subsequently, we anchor π-conjugated benzo-2,1,3-thiadiazole (BTD) molecules, which form a physical fence that spatially confines *CO intermediates and electrogenerated OH – . This synergy creates and sustains a localized, highly alkaline microenvironment in bulk acidic media, which concentrates *CO coverage and strengthens *CO binding to accelerate C–C coupling kinetics for acidic CO 2 ER. As a result, we achieve Faradaic efficiencies of 57.0% for ethylene (C 2 H 4 ) and 74.9% for total C 2+ products at 600 mA cm –2 . Single-pass carbon efficiencies reach 64.2% for C 2 H 4 and 79.9% for C 2+ . Remarkably, a high C 2 H 4 selectivity (>52.0%) is sustained across a wide current density range of 400 to 700 mA cm –2 . This work establishes the molecular-fence strategy as a broadly applicable paradigm for regulating interfacial microenvironments to enable efficient and selective CO 2 ER in challenging acidic media.