Enriching Surface‐Accessible CO₂ in the Zero‐Gap Anion‐Exchange‐Membrane‐Based CO₂ 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 À ] 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 À 2 was achieved using a commercial silver catalyst.

Benchmarking the pH–Stability Relationship of Metal Oxide Anodes in Anion Exchange Membrane Water Electrolysis

“…Furthermore, NiFe 2 O 4 displays a higher level of surface reconstruction in both pure water and alkaline electrolytes in contrast to Ni 0.5 Co 1.5 FeO 4 . In the AEMWE system, the determining electron-charge transfer step occurs on the catalyst/polymer electrolyte interface and thus the catalyst structure plays an important role on the interfacial stability. − Any poor structural evolution of the catalyst is likely to ruin the catalyst/ionomer/membrane interface, leading to the loss of the active site and degradation. − Therefore, we assume that the variable pH–stability response of metal oxides should come from their diverse reconstructions that result in the different contact interfaces, for example, the reconstructed Fe species (e.g., FeOOH) are prone to leach out from the crystal structure …”