Impact of Anodic Oxidation Reactions in the Performance Evaluation of High-Rate CO2/CO Electrolysis
Qiucheng Xu a, Brian Seger a
a Department of Energy Conversion and Storage (DTU Energy), Technical University of Denmark, Anker Engelunds Vej 301, 2800 Kongens Lyngby, Denmark
Materials for Sustainable Development Conference (MATSUS)
Proceedings of MATSUS Fall 2023 Conference (MATSUSFall23)
#CO2X - Frontier developments in Electrochemical CO2 reduction and the utilization
Torremolinos, Spain, 2023 October 16th - 20th
Organizers: Alexander Bagger and Yu Katayama
Oral, Qiucheng Xu, presentation 362
DOI: https://doi.org/10.29363/nanoge.matsus.2023.362
Publication date: 18th July 2023

The membrane-electrode assembly (MEA) approach appears to be the most promising technique to realize the high-rate CO2/CO electrolysis, however there are major challenges related to the crossover of ions and liquid products from cathode to anode via the membrane and the concomitant anodic oxidation reactions (AORs). In this perspective, by combining experimental and theoretical analyses, we elaborate on several impacts of anodic oxidation of liquid products in terms of performance evaluation. Firstly, we analyzed the crossover behavior of several typical liquid products through an anion-exchange membrane. Subsequently, two instructive examples (introducing formate or ethanol oxidation during electrolysis) reveals that the dynamic change of the anolyte (i.e., pH and composition) not only brings a slight shift of anodic potentials (i.e., change of competing reactions), but also affects the chemical stability of the anode catalyst. Anodic oxidation of liquid products can also cause either over- or under-estimation of the faradaic efficiency, leading to an inaccurate assessment of overall performance. To comprehensively understand fundamentals of AORs, we further develop a theoretical guideline with hierarchical indicators to predict and regulate the possible AORs in an electrolyzer. We conclude by giving some suggestions on rigorous performance evaluations for high-rate CO2/CO electrolysis in the MEA-based setup.

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