The electrolysis of saline water such as seawater and oilfield produced water is an important way to generate green hydrogen energy towards the future carbon-neutral society. However, the corrosive environment of saline water electrolyte imposes strict requirements on the electrode materials, especially for the electrocatalysts for saline water oxidation (SWO). Even the most stable noble metal RuO2 catalysts encounter with two major technical challenges in saline water electrolysis: the high energy consumption caused by the high electrocatalytic overpotential, and the poor catalytic stability caused by the Cl--induced corrosion. The development of materials with low electrocatalytic overpotential and high corrosion resistance is of great importance for both active and stable SWO electrocatalysis.
The intrinsic activity of a material for catalytic reactions is highly dependent on the number of the active sites and the intrinsic activity of the catalytic sites. For instance, ultrathin ternary NiFeCo layered double hydroxide (LDH) nanosheet materials have been demonstrated to be intrinsically active for oxygen evolution electrocatalysis, due to the high surface area of the ultrathin structure and the high intrinsic activity of ternary Ni/Fe/Co sites. Through these materials displayed low electrocatalytic overpotential for water oxidation, they suffered from Cl--induced corrosion issues in saline water electrolytes. What's more, the Cl--induced corrosion rates generally exhibit a positive correlation with the surface area of electrocatalysts. This creates a fundamental conflict where high surface area architectures, while advantageous for catalytic activity, paradoxically accelerate material degradation through corrosion pathways. This intrinsic limitation presents a significant obstacle in developing active and stable SWO electrocatalysts that reconcile the competing requirements of high surface area and corrosion resistance in saline water environments.
A team of material scientists led by Zhao Cai from China University of Geosciences in Wuhan, China recently addressed this issue by developing a ternary NiFeCo hydroxychloride-derived electrocatalyst with high surface area and anti-corrosion merits was developed, which was both active and stable for SWO electrocatalysis. The Ni,Fe-doped Co2(OH)3Cl nanomaterials was prepared via a simple one-step precipitation method, and exhibited an overpotential of 369 mV at a SWO current density of 100 mA cm-2 and a small Tafel slope of 49.9 mV dec-1, outperforming NiFeCo LDH (474 mV, 81.6 mV dec-1) and RuO2 catalysts (523 mV, 103.7 mV dec-1) under the same test condition. It was revealed that the lattice Cl- of NiFe-Co2(OH)3Cl was leached during catalysis, leading to the transformation of hydroxychloride to layered hydroxide with 35.5% larger electrochemical surface area (ECSA), which contributed to the improved SWO activity. Moreover, in-situ Raman suggested that the electrolyte Cl- was further incorporated to the lattice of the catalysts, which stabilized the crystal structure and reduced the Cl--induced corrosion of the catalysts, resulting in the enhanced electrocatalytic stability for 100 h. The combination of the facile synthesis and performance advantages endows the as-demonstrated ternary NiFeCo hydroxychloride material as a promising pre-electrocatalyst for both active and stable saline water electrolysis.
The team published this work in Carbon Future on August 04, 2025.
"We believe the results in this study not only offer a new choice in selecting highly efficient SWO electrocatalysts, but also expand the application of hydroxyloride materials to the field of saline water electrolysis hydrogen production." said Zhao Cai, senior author of the research paper, Professor in the Faculty of Materials Science and Chemistry at China University of Geosciences.
This work was supported by the National Natural Science Foundation of China (No. 22205068), the "CUG Scholar" Scientific Research Funds at China University of Geosciences (Wuhan) (Project No. 2022118), and the Fundamental Research Funds for National Universities, China University of Geosciences (No. 2024XLB70).
About the Author
Zhao Cai gained his B.S. degree and Ph.D in Chemistry from Beijing University of Chemical Technology in 2012 and 2018, respectively. After working as a visiting scholar at Yale University and postdoctoral researcher at Wuhan National Laboratory for Optoelectronics, he joined China University of Geosciences (Wuhan) as a Professor of Chemistry in 2022. His research focuses on developing novel transition metal nanostructures for key energy conversion and storage processes, such as electrocatalysis and aqueous batteries. To date, he has published 40+ papers as first/corresponding author in top-tier international journals (e.g. J. Am. Chem. Soc., Angew. Chem. Int. Ed.) and leading Chinese flagship journals (e.g. Sci. Bull., eScience), with >7,000 citations. These include 8 ESI Highly Cited Papers and 2 Hot Papers. He ranks among Stanford Top 2% Scientists Worldwide (2024), presides 7 national/provincial scientific research projects, owns 5 invention patents and co-authors 2 academic monographs.
About Carbon Future
Carbon Future is an open access, peer-reviewed, and international interdisciplinary journal Sponsored by Tsinghua University, published by Tsinghua University Press, and exclusively available via SciOpen. It serves as a platform for researchers, scientists, and industry professionals to share their findings and insights on carbon-related materials and processes, including catalysis, energy storage and conversion, as well as low carbon emission process and engineering. It features cutting-edge research articles, insightful reviews, perspectives, highlights, and news and views. The article publishing charge is covered by the Tsinghua University Press.
