The research team of Professor Lee Kwang-ryeol of the Department of Chemistry at Korea University (President Dong-won Kim) has developed a non-precious metal-based nano catalyst that will advance the green hydrogen economy through joint research with KIST and KAIST. The study was recognized for its importance and was published on December 8 (Sunday) in the world-renowned academic journal in the field of materials science, 'Advanced Energy Materials' (Impact Factor: 24.4). *Paper title: Boosting Hydrogen Evolution Reaction on Co9S8 in Neutral Media Leveraging Oxophilic CrOx Mosaic Dopant*DOI: https://onlinelibrary.wiley.com/doi/abs/10.1002/aenm.202405035Hydrogen is attracting attention as an eco-friendly and sustainable energy source, but the electrochemical hydrogen evolution reaction (HER) that produces it has several limitations. In particular, in the case of electrolytes under neutral pH conditions, the ion concentration is low and the reactants are not well adsorbed on the catalyst surface, which slows down the electrochemical reaction rate and ultimately hinders hydrogen production.To overcome this, existing catalysts were manufactured based on precious metals. However, precious metal-based catalysts have the disadvantage of being difficult to commercialize due to high cost and limited durability. Here, the research team developed a non-precious metal-based heterostructure nano catalyst by combining chromium oxide (CrOx) and cobalt sulfide (Co9S8) using a synthetic method called 'cation substitution reaction'. The catalyst binds to cobalt sulfide in the form of clusters, which are small structures formed by atoms or molecules coming together, and as a result, it has a structure in which the interface where chromium oxide and cobalt sulfide come into contact is maximized. This caused a synergy effect between the two substances, resulting in a much higher hydrogen production efficiency than existing catalysts. The catalyst effectively adsorbed and decomposed water molecules on its surface as a result of the performance evaluation. It also promoted the movement of reaction intermediates, greatly increasing the hydrogen production efficiency. In particular, it demonstrated excellent electrochemical performance and fast reaction speed that surpassed commercial platinum catalysts for HER by recording low overvoltage (37 mV) and small Tafel slope (49 mV/dec-1) even in a neutral pH environment. In addition, it showed high durability by operating stably for more than 60 hours.The research team demonstrated that the catalyst can also be used in seawater electrolysis experiments using natural resources such as seawater. In particular, it showed excellent HER activity similar to that of commercial platinum catalysts not only in neutral pH but also in simulated seawater and actual seawater environments. These results indicate that the developed catalyst is useful for practical hydrogen production applications in seawater environments as well as in neutral pH electrolytes. Professor Lee Kwang-ryeol of the Department of Chemistry said, "Non-precious metal-based catalysts that operate effectively under neutral conditions are much more economical than existing precious metal catalysts." He continued, "This research is significant in that it opens up new possibilities for non-precious metal-based high-efficiency nanocatalysts, which will help increase the efficiency of the hydrogen production process and bring us one step closer to commercializing green hydrogen technology."This research was conducted with the support of the Leader Research Project, the University Key Research Institute Support Project, the Basic Science Research Group Project, the Future Hydrogen Source Technology Development Project, the Ministry of Trade, Industry and Energy Energy Technology Development Project, and the Sejong Science Fellowship.