Bifunctional Gas Diffusion Electrode Enables In Situ Separation and Conversion of CO<sub>2</sub> to Ethylene from Dilute Stream
Shariful Kibria Nabil, Soumyabrata Roy, Wala A. Algozeeb, Tareq A. Al‐Attas, Md Abdullah Al Bari, Ali Shayesteh Zeraati, Karthick Kannimuthu, Pedro Guerra Demingos, Adwitiya Rao, Thien Tran, Xiaowei Wu, Praveen Bollini, Haiqing Lin, Chandra Veer Singh, James M. Tour, Pulickel M. Ajayan, Md Golam Kibria
Abstract
Abstract The requirement of concentrated carbon dioxide (CO 2 ) feedstock significantly limits the economic feasibility of electrochemical CO 2 reduction (eCO 2 R) which often involves multiple intermediate processes, including CO 2 capture, energy‐intensive regeneration, compression, and transportation. Herein, a bifunctional gas diffusion electrode (BGDE) for separation and eCO 2 R from a low‐concentration CO 2 stream is reported. The BGDE is demonstrated for the selective production of ethylene (C 2 H 4 ) by combining high‐density‐polyethylene‐derived porous carbon (HPC) as a physisorbent with polycrystalline copper as a conversion catalyst. The BGDE shows substantial tolerance to 10 vol% CO 2 exhibiting a Faradaic efficiency of ≈45% toward C 2 H 4 at a current density of 80 mA cm −2 , outperforming previous reports that utilized such partial pressure ( P CO2 = 0.1 atm and above) and unaltered polycrystalline copper. Molecular dynamics simulation and mixed gas permeability assessment reveal that such selective performance is ensured by high CO 2 uptake of the microporous HPC as well as continuous desorption owing to the molecular diffusion and concentration gradient created by the binary flow of CO 2 and nitrogen (CO 2 |N 2 ) within the sorbent boundary. Based on detailed techno‐economic analysis, it is concluded that this in situ process can be economically compelling by precluding the C 2 H 4 production cost associated with the energy‐intensive intermediate steps of the conventional decoupled process.