{"paper_id":"5abeb648-3435-44cd-a597-c190ef9a22f4","body_text":"The Olympic challenge of reverse-bias bipolar membranes for CO2 electrolysis | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article The Olympic challenge of reverse-bias bipolar membranes for CO 2 electrolysis Thomas Burdyny, Gerard Prats Vergel, Huan Mu, Nikita Kolobov, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6872030/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 17 Nov, 2025 Read the published version in Nature Chemical Engineering → Version 1 posted You are reading this latest preprint version Abstract Bipolar membranes operated under reverse-bias (r-BPM) provide the only potential route to use PGM-free anodes in CO 2 electrolyzers when paired with the oxygen evolution reaction (OER). Under 100% water dissociation efficiency (WDE) conditions, the OH - generated by a r-BPM fully replenishes the OH - consumed by the OER, maintaining an alkaline anolyte. However, unwanted co-ion crossover leads to <100% WDEs, gradually causing anolyte acidification and nickel-based anodes to corrode over time. Here we experimentally measure the WDE of r-BPMs in a membrane-electrode assembly configuration as a function of current density, anolyte concentration and cation identity, finding that the highest measured WDE of 98% is insufficient to maintain an alkaline environment over extended operation. We further highlight through modelling that WDEs >99.8% are required to operate for >10,000 hours with reasonable anolyte volumes. Our results show that r-BPMs CO 2 electrolyzers require additional strategies, such as reverting to PGM anodes or regenerating anolyte, to operate stably at an industrial scale. Physical sciences/Chemistry/Electrochemistry/Electrocatalysis Physical sciences/Engineering/Chemical engineering Bipolar membranes CO2 electrolysis mass transport platinum group metals Full Text Additional Declarations There is NO Competing Interest. Supplementary Files P01PaperSIrBPMWDElongtermstabilityPGMFreeCO2ERforsubmission.docx Supplementary Information Cite Share Download PDF Status: Published Journal Publication published 17 Nov, 2025 Read the published version in Nature Chemical Engineering → Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {\"props\":{\"pageProps\":{\"initialData\":{\"identity\":\"rs-6872030\",\"acceptedTermsAndConditions\":true,\"allowDirectSubmit\":false,\"archivedVersions\":[],\"articleType\":\"Article\",\"associatedPublications\":[],\"authors\":[{\"id\":473394622,\"identity\":\"521c8714-abc0-4422-acf2-5a8e96d6ae47\",\"order_by\":0,\"name\":\"Thomas 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