Enriching Surface‐Accessible CO 2 in the Zero‐Gap Anion‐Exchange‐Membrane‐Based CO 2 Electrolyzer

Abstract

Zero‐gap anion exchange membrane (AEM)‐based CO 2 electrolysis is a promising technology for CO production, however, their performance at elevated current densities still suffers from the low local CO 2 concentration due to heavy CO 2 neutralization. Herein, via modulating the CO 2 feed mode and quantitative analyzing CO 2 utilization with the aid of mass transport modeling, we develop a descriptor denoted as the surface‐accessible CO 2 concentration ([CO 2 ] SA ), which enables us to indicate the transient state of the local [CO 2 ]/[OH − ] ratio and helps define the limits of CO 2 ‐to‐CO conversion. To enrich the [CO 2 ] SA , we developed three general strategies: (1) increasing catalyst layer thickness, (2) elevating CO 2 pressure, and (3) applying a pulsed electrochemical (PE) method. Notably, an optimized PE method allows to keep the [CO 2 ] SA at a high level by utilizing the dynamic balance period of CO 2 neutralization. A maximum j CO of 368±28 mA cm geo −2 was achieved using a commercial silver catalyst.