Bromine-Enhanced Generation and Epoxidation of Ethylene in Tandem CO Electrolysis Towards Ethylene Oxide.

The indirect electro-epoxidation of ethylene (C H ), produced from CO electroreduction (CO R), holds immense promise for CO upcycling to valuable ethylene oxide (EO). However, this process currently has a 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 C H to EO and CO to C H , respectively. Herein, we report a bromine-induced dual-enhancement strategy designed to concurrently promote both C H -to-EO and CO -to-C H conversions, thereby improving EO generation, using single-atom Pt on N-doped CNTs (Pt /NCNT) and Br -bearing porous Cu O 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 Br /HBrO generation over Pt /NCNT with optimal intermediate binding facilitates C H -to-EO conversion with a high FE of 92.2 %, and concomitantly, the Br with strong nucleophilicity protects active Cu species in Cu O effectively for improved CO -to-C H conversion with a FE of 66.9 % at 800 mA cm , superior to those in the traditional chloride-mediated case. Consequently, a single-pass FE as high as 41.1 % for CO -to-EO conversion can be achieved in a tandem system.