Observing dynamic electric field changes in bipolar membranes for water electrolysis Nathaniel J. D. Hill 1,2 , Adrian M. Gardner 2 , Paul M. Donaldson 3 , Alexander J. Cowan 1 * 1 Stephenson Institute for Renewable Energy (SIRE) and the Department of Chemistry, University of Liverpool,Liverpool L69 7ZF, United Kingdom, 2 Early Career Laser Laboratory and Surface Science Research Centre, University of Liverpool, Liverpool, Liverpool L69 3BX, United Kingdom, 3 Central Laser Facility, Science and Technology Facilities Council, Research Complex at Harwell, Rutherford Appleton Laboratory, Didcot, United Kingdom *acowan@liverpool.ac.uk Bipolar Membranes (BPMs) are a form of partially permeable membrane which have been commonly employed in water electrolysers to divide the cell into a separate pH regions, by controlling the diffusion and migration of charged particles. 1 BPMs consist of a Cationic Exchange Layer (CEL), which selectively permits the transport of cations, an Anionic Exchange Layer (AEL), which selectively permits the transport of anions, and often a central Catalyst Layer to aid Water Dissociation (WD). 2 pH segregation allows oxygen evolution to occur at high pH at the anode and hydrogen evolution at low pH at the cathode, which facilitates these reactions in the absence of platinum group metals. WD at the interface between the AEL and the CEL replenishes the ions to preserve the pH gradient, and is the key process which limits the energy efficiency of current BPM electrolyzers. 3 In conjunction with catalytic effects, the local electric field, arising from large local ion concentration gradients, is thought to play an important role in promoting WD, however this role and the properties of these electric fields are not well understood. Understanding and modelling the interfacial dynamics using common electrochemical techniques is challenging since the BPM interfaces are not traditional electrode-electrolyte interfaces. Despite this, it is crucial for aiding membrane design and the development of BPM based electrolysers. By using operando , Electric Field Induced Second Harmonic Generation (EFISHG) spectroscopy, we have developed a non-invasive method for observing dynamic changes in the electric field and interfacial ionic environment of the BPMs. References 1. E. J. Park, C. G. Arges, H. Xu and Y. S. Kim ACS Energy Lett. 2022, 7, 10, 3447–3457. 2. J. C. Bui, E. W. Lees, D. H. Marin, T. N. Stovall, L. Chen, A. Kusoglu, A. C. Nielander, T. F. Jaramillo, S. W. Boettcher, A. T. Bell and A. Z. Weber, Nat Chem Eng, 2024, 1, 45–60. 3. L. Chen, Q. Xu, S. Z. Oener, K. Fabrizio and S. W. Boettcher, Nat Commun, 2022, 13, 3846.
P41
© The Author(s), 2025
Made with FlippingBook Learn more on our blog