Self-standing bipolar membranes for water electrolysis Bhavin Siritanaratkul , Dora Alicia Garcia-Osorio, Alexander J. Cowan Stephenson Institute for Renewable Energy and Department of Chemistry, University of Liverpool, UK
Bipolar membranes (BPM), composed of a cation exchange layer and an anion exchange layer, can enable steady-state operation at different pHs at the cathode and anode in a water electrolyzer. This allows optimizing the cathode and anode catalysts for acidic and alkaline environments, respectively, which increases the scope for low-cost materials. Commercially available BPMs are operational only in a limited current range, therefore we aimed to develop custom BPMs for higher currents that are easily fabricated, mechanically stable, and suitable for storage in dry form. We used commercial single membranes combined with TiO 2 as the water dissociation catalyst in the junction, and found that spin-coating of TiO 2 yielded reproduceable interfaces for water dissociation. Electrochemical Impedance Spectroscopy (EIS) was used to deconvolute the water dissociation resistance from other processes, leading to better understanding of the parameters that determine BPM performance. Hot- pressing of the BPM led to stronger adhesion of the two membrane layers, creating a durable self-standing BPM. Using this workflow, future high-performance BPMs can be developed and investigated, for use not only in water electrolyzers but also CO 2 electrolyzers where BPMs are required for higher CO 2 utilization efficiency.
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© The Author(s), 2025
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