Bifunctional Gas Diffusion Electrode Enables In-situ Separation and Conversion of CO2 to Ethylene from Dilute Stream.

Abstract

The requirement of concentrated CO2 feedstock significantly limits the economic feasibility of electrochemical CO2 reduction (eCO2 R) as it often involves multiple intermediate processes, including CO2 capture, energy intensive regeneration, compression, and transportation steps. Herein, we report on a bifunctional gas diffusion electrode (BGDE) for separation and electrolysis of CO2 from a low concentration CO2 stream (∼10 vol%). We demonstrate a BGDE for selective production of ethylene (C2 H4 ) 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% CO2 exhibiting a Faradaic efficiency of ∼45% towards C2 H4 at a current density of 80mA/cm2 over 11hrs, outperforming previous reports that utilised such partial pressure (PCO2 = 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 CO2 uptake of microporous HPC as well as continuous desorption owing to molecular diffusion and concentration gradient created by binary flow (CO2 |N2 ) 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 C2 H4 production cost associated with the energy intensive intermediate steps of conventional decoupled process. This article is protected by copyright. All rights reserved.