Carbon Nanocage Supported Asymmetrically Coordinated Nickel Single‐Atom for Enhanced CO 2 Electroreduction in Membrane Electrode Assembly

Abstract Designing efficient catalysts for operating CO 2 electroreduction in membrane electrode assembly (MEA) faces significant obstacles. Herein, we propose an asymmetrically coordinated Ni single‐atom catalyst featuring axial Br coordination at NiN 4 Br sites anchoring onto hollow Br/N co‐doped carbon nanocages, achieved through a NaBr‐assisted confined‐pyrolysis strategy. The Ni‐NBr‐C catalyst exhibits a high CO Faradaic efficiency (FE CO >97 %) over the current density range of 50 to 350 mA cm −2 in the MEA device. Furthermore, Ni‐NBr‐C shows a stable cell voltage of 2.66±0.2 V while delivering a large current density of 350 mA cm −2 over an 85‐hour long‐term operation, demonstrating its potential for industrial‐scale applications. Advanced characterization techniques and theoretical calculations reveal that the coordination and doping of Br not only enhance the intrinsic activity but also highlight that the unique pore structure improves mass transfer efficiency.