HKU Engineering Team Unveils Self-protecting Catalyst Advancing Durable and Affordable Green Hydrogen
An international research team led by Professor Philip C.Y. Chow at The University of Hong Kong (HKU) has unveiled a new catalyst that overcomes a major challenge in producing green hydrogen at scale. This innovation makes the process of producing oxygen efficiently and reliably in the harsh acidic environment used by today's most promising industrial electrolysers.
Green hydrogen is seen as a clean fuel that can help reduce carbon emissions across industries like steelmaking, chemical production, long-distance transportation, and seasonal energy storage. Proton exchange membrane (PEM) electrolysers are preferred for their compact design and rapid response, but they operate in acidic conditions that are exceptionally demanding on the oxygen evolution reaction (OER) catalyst. Currently, the best catalysts use rare and expensive metals like iridium. Alternative materials often break down quickly, making green hydrogen too expensive for widespread use. Finding a catalyst that's both durable and affordable is crucial for scaling up green hydrogen production.
The research team's solution is a new catalyst made with single atoms of ruthenium (a platinum-group metal) spread across tiny particles of manganese oxybromide (Mn7.5O10Br3), also known as Ru‑MOB. During operation, the catalyst "self-adjusts" its surface, forming a thin protective layer of modified manganese dioxide (γ‑MnO2). This dynamic layer acts like a skin that shields the catalyst from damage while remaining highly active, allowing it to produce oxygen efficiently and stay stable over time.
Using advanced testing techniques and computer simulations, the researchers showed that this self‑formed layer guides the chemical reactions down a safer, more efficient pathway. It favours the formation of oxygen directly from water, while preventing destructive reactions that can damage the catalyst.
In laboratory tests, the Ru‑MOB catalyst required only a small extra voltage—just 208.3 millivolts—to produce hydrogen efficiently at a typical current density. It also demonstrated exceptional durability, running for more than 1,400 hours at a standard operating level without significant degradation, and over 200 hours at higher current levels. This combination of high efficiency and long-lasting performance in acidic conditions, while using a minimal amount of ruthenium, is a major step toward making affordable, reliable green hydrogen a reality.
Beyond these impressive performance results, the study offers a powerful blueprint for designing durable catalysts: using a self-reconstructing mechanism and single‑atom tuning to regulate the reactions happen and protect the catalyst during operation.
Professor Philip Chow commented, "This approach can guide the development of the next-generation materials for clean hydrogen and other electrochemical processes, accelerating the adoption of green energy solutions across industries such as shipping, aviation, power grids, and long‑term energy storage."
Spearheaded by Ci Lin, a PhD student in HKU's Department of Mechanical Engineering, the team's work was published in ACS Energy Letters on April 30, 2025.
Article details:
C. Lin, T.-Y. Chen, T. Zhou, Y. Wu, C. K. T. Wun, W. Chen, H. Chen, V. Tung, Z. Guo, T. W. B. Lo, L. Cai, Y. Deng, P. C. Y. Chow, Regulating the Oxygen Evolution Mechanism through In Situ Reconstruction of Ru-Modified Manganese Oxybromide. ACS Energy Lett. 10, 2641–2649 (2025).
Link: https://pubs.acs.org/doi/10.1021/acsenergylett.5c00957
About Professor Philip C.Y. Chow
Professor Philip Chi Yung Chow received his B.Sc. from Imperial College London, and M.Phil. and Ph.D. in Physics from the University of Cambridge. He is currently an Assistant Professor in the Department of Mechanical Engineering at HKU. His multidisciplinary research group at HKU focuses on the study and development of optoelectronic and photonic devices with applications in solar energy, wearable electronics and green buildings. He was awarded the UK EPSRC Doctoral Training Award in 2010, JSPS Overseas Postdoctoral Research Fellowship in 2016, the Hong Kong RGC Early Career Scheme in 2022, and the NSFC Excellent Young Scientist Fund in 2022. He is recognised among Clarivate's Top 1% Scientists worldwide for his research impact.
