Bromine‐Enhanced Generation and Epoxidation of Ethylene in Tandem CO2 Electrolysis toward Ethylene Oxide

The indirect electro‐epoxidation of ethylene (C2H4), produced from CO2 electroreduction (CO2R), holds immense promise for CO2 upcycling to valuable ethylene oxide (EO). However, this process currently faces mediocre Faradaic efficiency (FE) due to sluggish formation and rapid dissociation of active species, as well as reductive deactivation of Cu‐based electrocatalysts during the conversion of C2H4‐to‐EO and CO2‐to‐C2H4, respectively. Herein, we report a bromine‐induced dual‐enhancement strategy designed to concurrently promote both C2H4‐to‐EO and CO2‐to‐C2H4 conversions, thereby improving EO generation, using single‐atom Pt on N‐doped CNTs (Pt1/NCNT) and Br−‐beared porous Cu2O as anode and cathode electrocatalysts, respectively. Physicochemical characterizations including synchrotron X‐ray absorption, operando infrared spectroscopy, and quasi‐in situ Raman spectroscopy/electron paramagnetic resonance with theoretical calculations reveal that the favorable Br2/HBrO generation over Pt1/NCNT with optimal intermediates binding facilitates C2H4‐to‐EO conversion with a high FE of 92.2%, and concomitantly, the Br− with strong nucleophilicity protects active Cu+ species in Cu2O effectively for improved CO2‐to‐C2H4 conversion with a FE of 66.9% at 800 mA cm−2, superior to those in traditional chloride‐mediated case. Consequently, a single‐pass FE high to 41.1% for CO2‐to‐EO conversion can be achieved in a tandem system.