A new insight into the chemical degradation of proton exchange membranes in water electrolyzers

Abstract

The chemical degradation of the proton exchange membrane (PEM) in a water electrolyzer is a significant issue that can lead to device failure and pose safety risks due to increased gas permeability. Currently, it is generally believed that chemical degradation of PEMs occurs primarily at the cathode. However, there is a lack of research on the actual location of degradation and more in-depth investigation into the mechanisms of membrane degradation. By investigating the chemical degradation in different operation modes, as well as the in situ electrochemical H₂O₂ detection, we discovered that both the cathode and anode electrodes can generate H₂O₂ during operation. Furthermore, membrane degradation can be effectively mitigated by doping CeO₂ in either catalyst layer. Based on the analysis and summary of the observed phenomena in the durability tests, we propose a new model for the membrane degradation process, encompassing H₂O₂ formation and fluoride emission. A 1-D model was also established for quantitative comprehension of the model. This model considers both cathodic and anodic membrane degradation, which could be beneficial for the design of highly durable PEM water electrolyzers.