Degradation of a Bipolar Membrane in a Hybrid Acid/Alkali Electrolyzer Studied by X-ray Computed Tomography.

The use of a bipolar membrane (BPM) in a hybrid acid/alkali electrolyzer is widely considered as a promising energy technology for efficient hydrogen production. The stability of a BPM is often believed to be largely limited by the anion exchange layer (AEL) due to the hydrophilic attack of AEL polymers by hydroxide groups in alkaline. In this study, we employ X-ray computed tomography (CT) to investigate the degradation behaviors of BPM and found that the cation exchange layer (CEL) experiences more pronounced degradation compared with the AEL during water splitting operations. Despite its chemical stability in both acidic and alkaline environments, the CEL is more prone to electrochemical corrosion under the influence of applied voltages. This susceptibility leads to the formation of micropores and a consequent increase in the porosity. The results of this work provide a new perspective on and highlight the complexity of the degradation behaviors of BPMs in hybrid acid/alkali electrolyzers.