Bifunctional Gas Diffusion Electrode Enables In-situ Separation and Conversion of CO 2 to Ethylene from Dilute Stream.

The requirement of concentrated CO 2 feedstock significantly limits the economic feasibility of electrochemical CO 2 reduction (eCO 2 R) as it often involves multiple intermediate processes, including CO 2 capture, energy intensive regeneration, compression, and transportation steps. Herein, we report on a bifunctional gas diffusion electrode (BGDE) for separation and electrolysis of CO 2 from a low concentration CO 2 stream (∼10 vol%). We demonstrate a BGDE for selective production of ethylene (C 2 H 4 ) by combining high density polyethylene-derived porous carbon (HPC) as a physisorbent with polycrystalline copper as conversion catalyst. Our BGDE shows substantial tolerance to 10 vol% CO 2 exhibiting a Faradaic efficiency of ∼45% towards C 2 H 4 at a current density of 80 mA/cm 2 over 11 hrs, outperforming previous reports that utilised such partial pressure (P CO2 = 0.1 atm and above) at ambient conditions and unaltered polycrystalline copper as catalyst. Molecular dynamics simulation and mixed gas permeability assessment reveal that such selective performance is ensured by high CO 2 uptake of microporous HPC as well as continuous desorption owing to molecular diffusion and concentration gradient created by binary flow (CO 2 |N 2 ) within sorbent boundary. We conclude based on detailed technoeconomic analysis that our in-situ process has the potential to be economically compelling by precluding the C 2 H 4 production cost associated with the energy intensive intermediate steps of conventional decoupled process. This article is protected by copyright. All rights reserved.