A research team led by Professor Yousung Jung from the Department of Chemical and Biological Engineering at Seoul National University College of Engineering has developed a new catalyst design principle that suppresses the hydrogen evolution reaction, which interferes with ammonia production, while maintaining the nitrogen reduction reaction that produces ammonia.
Ammonia can store large amounts of hydrogen and remains in liquid state at room temperature, making it easy to transport. For this reason, it has gained attention as a next-generation eco-friendly energy carrier capable of delivering energy generated from renewable sources such as wind and solar power. However, the conventional ammonia synthesis method (the Haber–Bosch process) requires high temperature and pressure, as well as overall high energy consumption and carbon emissions.
As an alternative, the electrochemical nitrogen reduction reaction (NRR)—which produces ammonia using only water, nitrogen, and electricity—has attracted attention. However, a major limitation has been that hydrogen is produced preferentially over ammonia, significantly lowering production efficiency.
*Nitrogen reduction reaction (NRR): A technology that electrochemically reduces nitrogen in the air to synthesize ammonia.
The research team proposed a new catalyst design principle that selectively suppresses hydrogen evolution by controlling the structure of molecules participating in the reaction. This study is expected to overcome efficiency limitations in eco-friendly ammonia production and provide a foundation for the stable supply of carbon-free ammonia-based hydrogen energy to households and industrial sites.
The study was published on July 22 in the Journal of the American Chemical Society (JACS), a leading international journal of the American Chemical Society established in 1879.
Unlike conventional approaches, the research team focused on a new strategy of designing the reaction environment itself.
Previous studies primarily attempted to suppress hydrogen evolution by controlling protons, such as adjusting the acidity of the electrolyte. However, because protons are also required for ammonia synthesis, reducing them suppresses both hydrogen evolution and nitrogen reduction simultaneously.
To overcome this limitation, the team proposed a new approach that selectively blocks only the hydrogen evolution reaction while preserving nitrogen reduction activity. The idea was inspired by nature: proteins often act as catalysts and selectively react only with substrates that fit their shapes. The researchers applied this principle to electrochemical reactions.
The team successfully increased the energy barrier of the Volmer reaction, the first step in hydrogen evolution, by controlling the steric structure of proton donors.
*Proton donor: A substance that acts as an acid by donating protons (hydrogen ions) to other materials.
*Volmer reaction: The first step of the hydrogen evolution reaction, in which hydrogen atoms are adsorbed onto the electrode surface.
The key lies in the geometric positioning of reactants. Similar to how incorrectly placed blocks in a game of Tetris hinder progress, increased steric hindrance makes it difficult for protons to approach the electrode surface, significantly slowing the hydrogen evolution reaction.
In contrast, the nitrogen reduction reaction is minimally affected because protons interact with nitrogen molecules that protrude outward from the catalyst surface rather than the electrode surface itself. In other words, by selectively blocking access to the electrode surface through steric hindrance, the researchers were able to suppress hydrogen evolution while maintaining nitrogen reduction.
In addition, microkinetic modeling simulations confirmed that greater steric hindrance allows high Faradaic efficiency to be maintained stably over a wide voltage range.
*Microkinetic modeling: A modeling technique that analyzes chemical reaction behavior by solving differential equations for the reaction rates of intermediates.
*Faradaic efficiency: The proportion of total supplied charge that is actually used to produce the desired chemical product.
This study is significant in that it proposes a design principle capable of increasing the Faradaic efficiency of electrochemical nitrogen reduction—from previously around 70%—to nearly 100%. The findings are expected to enable localized production of eco-friendly ammonia near renewable energy sources, eliminating the need for large-scale chemical plants and contributing to the realization of a clean hydrogen economy.
The approach is also expected to be widely applicable to other electrochemical catalytic systems, such as carbon dioxide reduction, where controlling competing reactions is critical.
Professor Jung’s team plans to expand this concept to other electrochemical reactions and accelerate commercialization by identifying highly active catalyst materials that can incorporate this design principle, ultimately developing catalytic systems with both high selectivity and high activity.
Professor Yousung Jung commented,
“This study is significant in that it proposes a precise interfacial design strategy capable of selectively suppressing only competing reactions in electrochemical nitrogen reduction, where technical limitations have long been evident.”
He added,
“It will serve as a foundational technology not only for eco-friendly ammonia production but also for improving the efficiency of a wide range of interfacial electrochemical reactions.”
The paper was co-first authored by Dongmin Park, Ph.D., and Changhyeok Choi, a Ph.D. graduate from Professor Jung’s lab currently at the University of Toronto. Dr. Park, now a researcher at the Institute of Chemical Process Technology at SNU, conducts catalyst research using density functional theory and multiscale simulations. Dr. Choi is conducting research on AI-driven materials discovery and autonomous laboratories at the University of Toronto.
This research was supported by the National Research Foundation of Korea (NRF) through the SRC program (2021R1A5A1030054), the Digital Research Innovation Leading Institution Program (RS-2023-00283902), and the STEAM Research Program (RS-2024-00464386), and utilized the Nurion supercomputer (No. 5) provided by the Korea Institute of Science and Technology Information (KISTI).
□ Introduction to the SNU College of Engineering
Seoul National University (SNU) founded in 1946 is the first national university in South Korea. The College of Engineering at SNU has worked tirelessly to achieve its goal of ‘fostering leaders for global industry and society.’ In 12 departments, 323 internationally recognized full-time professors lead the development of cutting-edge technology in South Korea and serving as a driving force for international development.
Journal of the American Chemical Society
Computational simulation/modeling
Not applicable
The authors declare no competing financial interest.