Researchers boost CO₂ conversion in acidic media by keeping ion traffic under control
One promising strategy to mitigate and eventually reverse greenhouse effects associated with carbon emissions is the capture and electrochemical conversion of CO₂ into valuable chemicals, for instance via carbon dioxide electroreduction.
ICFO researchers now tackle the challenge of performing this reaction in acidic media by controlling how ions move at the catalyst surface, a fundamentally different approach complementing catalyst design and optimization. The strategy, presented in ACS Energy Letters, improves carbon efficiency, reduces parasitic reactions and maintains stability, all under industrially relevant conditions.
Carbon dioxide electroreduction (CO2E) has recently emerged as a promising way to convert CO2 into useful multicarbon compounds, such as ethylene (the world’s most widely produced organic compound, used as a precursor in the polymer industry) and ethanol (which can be readily used as a fuel and incorporated into existing supply chains).
The medium pH, however, strongly influences how the CO2E reaction unfolds, affecting both its efficiency and potential for large-scale deployment. Acidic CO2E is particularly attractive because it avoids the formation of unwanted carbonates, which severely limit the production of desired products in neutral and alkaline systems. As a downside, the high concentration of protons in acidic environments favours the formation of hydrogen gas (H₂), consuming electricity that should be destined to convert CO2 into multicarbons instead.
ICFO researchers, Blanca Belsa, Dr. Anku Guha, Dr. Bárbara Polesso, Ranit Ram, Dr. Viktoria Golovanova, Dr. Marinos Dimitropoulos, Dr. Sunil Kadam, Prathama Haldar, led by ICFO Prof. F. Pelayo García de Arquer, have recently proposed interfacial ion transport as a new path for addressing the challenges of acidic CO2E. Instead of modifying the catalyst itself (the element that accelerates otherwise inefficient reactions), the novel approach introduces ion management channels to control how ions and water move near the catalyst surface. Published in ACS Energy Letters, this strategy creates a well-balanced chemical environment, suppressing parasitic reactions like H2 formation while preserving the intrinsic efficiency advantage of acidic operation, even under industrially relevant conditions.
“You can think of ion management channels as traffic controllers at the reaction interface,” explains Blanca Belsa, first author of the article. “The ions still move, but their movement is guided in a way that promotes the desired chemical reaction,” she clarifies.
In particular, hydroxyl (*OH) species, which can accumulate at the catalyst surface and block the active sites where multicarbon products form, are given a clear pathway away from the catalyst. Protons (H+), in turn, are guided towards the hydroxyls, recombining to create water (H₂O). In this way, protons cannot reach the catalyst surface, where they would otherwise form hydrogen gas (H₂). As a result, CO2 and key reaction intermediates (like *CO) can access active sites more easily, enabling an efficient formation of ethylene, ethanol, or similar compounds.
Overall, the study demonstrates that high carbon efficiency (80±4%) in acidic CO2 electrolysis can be maintained at industrially relevant current densities (0.5 A·cm−2) by engineering ion management channels near the catalyst surface. Importantly, the reaction’s performance remains stable over 70 hours of continuous operation.
“By proposing a new design principle that goes beyond optimising catalysts or operating conditions, we have opened a complementary research direction in the field,” claims Prof. Pelayo García de Arquer, lead researcher of the study. “This foundational advance could eventually lead to efficient and selective CO2 conversion technologies suitable for real-world applications, an effort we are already pursuing through research projects such as ICONIC or Helva.”
Reference:
Blanca Belsa, Anku Guha, Barbara Polesso, Ranit Ram, Viktoria Golovanova, Marinos Dimitropoulos, Sunil Kadam, Prathama Haldar, Aliaksandr S. Bandarenka, and F. Pelayo García de Arquer, Carbon Efficient CO2 Interfaces in Acid through Ion Management Channels, ACS Energy Letters, 2026 11 (1), 498-507.
DOI: 10.1021/acsenergylett.5c02981
Acknowledgements:
ICFO thanks CEX2024-001490-S and PID2022-138127NAI00 [MCIN/AEI/10.13039/ 501100011033], Fundació Cellex, Fundació Mir-Puig, BIST Ignite (7th edition), Generalitat de Catalunya through CERCA (SGR 2021 01455); the European Union: NASCENT (101077243) and ICONIC (101115204) projects. Funding through MCIN/AEI/10.13039/501100011033 supported the following programmes and grants: CEX2024-001490-S, PID2022-138127NA-I00, and CEX2019-000910-S; PCI2023-143410, cofunded by the European Union within M-ERA.NET 3 (H2020 grant 958174); PRE2019-088522 (FSE “El FSE invierte en tu futuro”); JDC2023-052976-I. V.G. acknowledges a Severo Ochoa Excellence Postdoctoral Fellowship (CEX2019-000910-S). A.S.B. acknowledges the EU project ICONIC (no. 101115204). M.D. acknowledges funding from Marie Skłodowska-Curie actions grant WILDCAT, (101150029).