Visualisation and quantification of flooding phenomena in gas diffusion electrodes used for electrochemical CO2 reduction: A combined EDX/ICP–MS approach

• Published in: Journal of catalysis Vol. 408; pp. 1 - 8
• Main Authors: Kong, Ying, Hu, Huifang, Liu, Menglong, Hou, Yuhui, Kolivoška, Viliam, Vesztergom, Soma, Broekmann, Peter
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.04.2022
• Subjects: Carbon dioxide electroreduction; Flooding; Gas diffusion electrodes; Precipitate formation; Carbon dioxide electroreduction; Precipitate formation; Flooding; Gas diffusion electrodes
• ISSN: 0021-9517
• DOI: 10.1016/j.jcat.2022.02.014

[Display omitted] •The flooding of GDEs used for CO2 electrolysis causes unstable electrolyser behavior and, with time, the loss of Faradaic efficiency for CO production.•Flooding is closely related to the formation of potassium carbonate and bicarbonate salts in the GDE structure that causes hydrophobicity loss.•The cross-sectional elemental (K) mapping of GDEs by EDX helps the visualization of K salt penetration inside a GDE structure, but does not allow quantitative comparison.•By combining EDX mapping with ICP-MS based total K content determination, quantitative and comparable depth profiles can be obtained.•The combined EDX/ICP-MS approach is used to study two different GDLs: one with a cracked, and another with a compact microporous layer.•The analysis indicates better water management for the cracked GDL. The most promising strategy to scale up the electrochemical CO2 reduction reaction (ec-CO2RR) is based on the use of gas diffusion electrodes (GDEs) that allow current densities close to the range of 1 A/cm2 to be reached. At such high current densities, however, the flooding of the GDE cathode is often observed in CO2 electrolysers. Flooding hinders the access of CO2 to the catalyst, and by thus leaving space for (unwanted) hydrogen evolution, it usually leads to a decrease of the observable Faradaic efficiency of CO2 reduction products. To avoid flooding as much as possible has thus become one of the most important aims of to-date ec-CO2RR engineering, and robust analytical methods that can quantitatively assess flooding are now in demand. As flooding is very closely related to the formation of carbonate salts within the GDE structure, in this paper we use alkali (in particular, potassium) carbonates as a tracer of flooding. We present a novel analytical approach —based on the combination of cross-sectional energy-dispersive X-ray (EDX) mapping and inductively coupled plasma mass spectrometry (ICP–MS) analysis— that can not only visualise, but can also quantitatively describe the electrolysis time dependent flooding in GDEs, leading to a better understanding of electrolyser malfunctions.