Researchers led by Professor Yousung Jung at Seoul National University have proposed a catalyst-design principle that selectively suppresses hydrogen evolution while preserving the electrochemical reaction that converts nitrogen into ammonia. Their approach relies not on removing protons from the reaction environment, but on controlling how easily those protons can physically reach the electrode surface. The concept could offer a new route toward cleaner ammonia production powered by renewable electricity.

Ammonia is increasingly viewed as a practical carrier for hydrogen energy. It stores a large amount of hydrogen, remains liquid at room temperature under moderate conditions, and is easier to transport than gaseous hydrogen. Today, most ammonia is manufactured through the Haber–Bosch process, which requires high temperatures and pressures and consumes substantial amounts of energy. Because the process is commonly powered by fossil fuels, it also produces significant carbon dioxide emissions.

Electrochemical nitrogen reduction has emerged as a possible alternative. In principle, the process uses nitrogen, water and electricity to produce ammonia, potentially allowing production facilities to operate near wind or solar farms rather than relying on massive centralized chemical plants. The central obstacle, however, is that the electrode preferentially produces hydrogen instead of ammonia. This competing hydrogen evolution reaction consumes electrons and protons that would otherwise contribute to nitrogen reduction, sharply reducing ammonia yields.

Previous strategies have often attempted to control hydrogen evolution by changing the proton concentration or acidity of the electrolyte. That solution creates a fundamental trade-off: protons are needed not only to generate hydrogen but also to convert nitrogen into ammonia. Reducing their availability can therefore suppress both reactions. Jung’s team instead focused on the reaction interface—the narrow region where the electrolyte, catalyst and electrode meet—and asked whether the two reactions could be separated geometrically.

The researchers designed a reaction environment in which proton donors encounter greater steric hindrance as they approach the electrode surface. Steric hindrance occurs when the size and arrangement of molecules make it physically difficult for another molecule to reach a reactive site. In this case, the researchers effectively create a molecular gate around the electrode. Proton donors can still exist in the surrounding solution, but their paths toward the surface become restricted, making the initial step of hydrogen production less favorable.

That initial step is known as the Volmer reaction. During the Volmer reaction, a proton receives an electron and forms an adsorbed hydrogen atom on the electrode. Two such hydrogen atoms can subsequently combine to form molecular hydrogen, or an adsorbed hydrogen atom can react with another proton and electron. By making it harder for proton donors to reach the electrode, the new strategy raises the energy barrier for the Volmer reaction and slows the entire hydrogen evolution pathway.

The geometry of nitrogen reduction is different. According to the researchers, nitrogen molecules protrude outward from the catalyst environment, allowing protons to interact with nitrogen rather than needing to reach the electrode surface directly. This difference means that the same steric barrier that obstructs hydrogen evolution has a much smaller effect on nitrogen reduction. The result is a form of molecular selectivity based on access and positioning rather than solely on chemical composition.

The team used microkinetic modeling to examine how these competing pathways respond to changes in steric hindrance and applied voltage. Microkinetic models describe the rates of individual elementary reactions by tracking intermediates and solving differential equations for the overall reaction network. The simulations indicated that increasing steric hindrance can maintain high Faradaic efficiency across a broad voltage range. Faradaic efficiency measures the fraction of supplied electrical charge that produces the desired product—in this case, ammonia rather than hydrogen.

The findings could address a major limitation in electrochemical ammonia research, where Faradaic efficiencies have often remained near 70 percent or lower. The researchers report that their design principle could raise the value toward nearly 100 percent under modeled conditions, although future catalyst development and experimental validation will be essential. The strategy may also be transferable to other electrochemical systems in which a desired reaction competes with an unwanted one, including carbon dioxide reduction.

The study, published in the Journal of the American Chemical Society, presents the reaction interface itself as a programmable component of catalyst design. Rather than treating the electrolyte as a passive medium, the approach uses molecular shape to control which reactants can reach specific locations. Jung’s team plans to identify highly active catalyst materials that can incorporate this principle and to test the concept across additional reactions. If successful, the work could help bring renewable-powered ammonia production closer to practical use while offering a broader blueprint for controlling chemical reactions at the atomic scale.

Subject of Research: Electrochemical nitrogen reduction and selective suppression of the hydrogen evolution reaction

Article Title: Selective Suppression of Hydrogen Evolution in Electrochemical Nitrogen Reduction through Steric Control of Proton Donors

News Publication Date: July 22

Web References: https://doi.org/10.1021/jacs.6c07080

References: Journal of the American Chemical Society, DOI: 10.1021/jacs.6c07080

Image Credits: Seoul National University College of Engineering

Keywords

Electrochemical ammonia production, nitrogen reduction reaction, hydrogen evolution reaction, steric hindrance, catalyst design, green hydrogen, renewable energy, Faradaic efficiency, microkinetic modeling, Seoul National University

The appeal of ammonia (NH₃) as a hydrogen carrier lies in its liquid state under moderate conditions, rendering it far easier to store and transport compared to gaseous hydrogen. Unlike hydrocarbons, ammonia combustion emits almost no carbon dioxide, as its composition is solely nitrogen and hydrogen, thereby presenting a compelling option for sustainable energy infrastructure. However, until now, practical challenges such as degradation of nickel-based catalysts and sluggish reaction kinetics within fuel cells have stymied the widespread adoption of ammonia as a direct fuel.

Addressing these hurdles, the KAIST team engineered a novel catalyst architecture that leverages a “high-entropy” oxide matrix. High-entropy materials are meticulously designed by blending multiple elements to produce a robust, stable structure that resists structural collapse and deactivation. Integrating this with spontaneously formed metal alloy nanoparticles on the catalyst surface, the researchers created a synergistic system that drastically improves ammonia decomposition and hydrogen ion conduction.

Detailed atomistic simulations using Density Functional Theory (DFT) revealed that the high-entropy oxide framework effectively lowers the activation energy barrier for ammonia decomposition. This expedites the initial breaking down of ammonia molecules into nitrogen and hydrogen, with concurrent formation and stabilization of metal nanoparticle alloys that exhibit superior catalytic activity compared to traditional single-metal catalysts. This dual mechanism enhances reaction rates and reinforces catalyst longevity.

Experimental investigations corroborated these computational insights. Fuel cells equipped with the new catalyst delivered an unprecedented maximum power density of 2.04 watts per square centimeter at 700°C — a remarkable level of power output for an ammonia-based PCFC. Such efficiency translates to substantial energy generation from a remarkably compact cell footprint, akin to the size of a fingernail, making it highly attractive for scalable energy applications.

Stability tests demonstrated sustained operation over 255 hours at 600°C under demanding conditions without significant performance decay, addressing the chronic problem of catalyst degradation encountered in prior designs. This stability is crucial for real-world deployment where long-term durability under thermal and chemical stress ensures reliability and cost-effectiveness.

The team’s innovation pivots on the carefully orchestrated interplay between the engineered high-entropy oxide and the in situ formed alloy nanoparticles. This design not only protects the catalyst’s structural integrity against ammonia’s detrimental effects but simultaneously fosters enhanced surface reactions that underpin efficient power generation. This breakthrough marks a paradigm shift in the practical use of ammonia fuel cells.

Professor Kang Taek Lee emphasized the transformative potential of this synergy, stating that their catalyst design could accelerate the commercial viability of ammonia-based power generation technologies and spur widespread adoption of carbon-neutral hydrogen energy systems. The societal and environmental implications are profound, offering a viable pathway to mitigate reliance on fossil fuels and reduce greenhouse gas emissions globally.

This research effort was a collaborative enterprise comprising multidisciplinary expertise from KAIST, the Korea Institute of Ceramic Engineering and Technology (KICET), and the Korea Institute of Geoscience and Mineral Resources (KIGAM). The interdisciplinary approach facilitated innovative materials design, advanced theoretical modeling, and rigorous experimental validation, demonstrating the integrated nature of contemporary energy research.

The results are documented in a scientific paper titled “Entropy-Modulated Oxide–Metal Catalyst Architectures for Direct Ammonia Protonic Ceramic Fuel Cells,” published in the high-impact journal Nano-Micro Letters. The publication reflects a significant contribution to the energy materials research community and opens avenues for further exploration and refinement of fuel cell catalysts tailored for ammonia and other hydrogen carriers.

Supported by multiple funding initiatives, including the Mid-Career Researcher Program of the Ministry of Science and ICT and the Global Basic Research Laboratory Program, this study exemplifies how strategic investments in foundational science can yield technological breakthroughs with far-reaching economic and ecological benefits. The research sets a new benchmark for ammonia fuel cell performance and durability, inspiring optimistic prospects for a sustainable hydrogen economy.

The advent of high-entropy oxide–metal hybrid catalysts heralds a new chapter in clean energy technologies, potentially enabling efficient, stable, and practical ammonia-based fuel cells. By overcoming the intrinsic limitations of previous materials, this innovation paves the way for scalable implementation of carbon-free power generation, offering a glimpse into a future where ammonia serves as a cornerstone of sustainable energy infrastructure worldwide.

Subject of Research: Development of high-performance catalysts for ammonia-based protonic ceramic fuel cells enabling direct ammonia utilization

Article Title: Entropy-Modulated Oxide–Metal Catalyst Architectures for Direct Ammonia Protonic Ceramic Fuel Cells

News Publication Date: 20-May-2026

Web References: http://dx.doi.org/10.1007/s40820-026-02194-9

Image Credits: KAIST

Keywords

Protonic Ceramic Fuel Cells, Ammonia Fuel, High-Entropy Oxide Catalyst, Metal Nanoparticles, Catalyst Durability, Hydrogen Economy, Carbon-Free Power Generation, Density Functional Theory, Ammonia Decomposition, Catalyst Stability, Fuel Cell Performance, Sustainable Energy

The pursuit of safe and efficient hydrogen storage and transportation is crucial for a sustainable hydrogen economy. Ammonia, with its high hydrogen density and ease of liquefaction, is a promising carrier, but its decomposition into hydrogen typically requires high temperatures (400–700 °C). Electrochemical liquid ammonia decomposition (ELADH) offers a promising route for room-temperature, on-site hydrogen release with a low theoretical voltage. However, its development has been hampered by sluggish kinetics, poor catalyst stability, and corrosive reaction environments.

Recently, a research team led by Prof. Jun-Min Yan from Jilin University and Prof. Hai-Xia Zhong from the Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, demonstrated a highly efficient and stable ELADH system. Through density functional theory calculations, they identified Ru as a superior catalyst compared to Pt, Rh, and Ir, with the Ru (101) facet exhibiting a low energy barrier for N–H bond cleavage and optimal hydrogen adsorption. Guided by this, they synthesized nitrogen-doped carbon-supported Ru nanoparticle catalysts (Ru NPs-CN) via a two-step pyrolysis method.

The Ru NPs-CN catalyst, featuring predominantly exposed (101) facets and a porous structure, achieved outstanding performance in an optimized electrochemical system using a graphite plate anode and NH₄PF₆ electrolyte in liquid ammonia. It delivered a high current density of -910 mA cm^-2 at –1.47 V and a low overpotential of –1.01 V at -10 mA cm^-2, significantly outperforming Ru single-atom and commercial Pt/C catalysts. Crucially, the system maintained stable hydrogen evolution for over 100 hours in a two-electrode configuration, showcasing remarkable durability. This work provides a feasible strategy for mild-condition hydrogen production from ammonia and deepens the understanding of the electrochemical ammonia splitting process. The results were published in Chinese Journal of Catalysis (DOI: 10.1016/S1872-2067(25)64915-1).

About the journal

Chinese Journal of Catalysis is co-sponsored by Dalian Institute of Chemical Physics, Chinese Academy of Sciences and Chinese Chemical Society, and it is currently published by Elsevier group. This monthly journal publishes in English timely contributions of original and rigorously reviewed manuscripts covering all areas of catalysis. The journal publishes Reviews, Accounts, Communications, Articles, Highlights, Perspectives, and Viewpoints of highly scientific values that help understanding and defining of new concepts in both fundamental issues and practical applications of catalysis. Chinese Journal of Catalysis ranks among the top six journals in Applied Chemistry with a current SCI impact factor of 17.7.

At Elsevier

Manuscript submission

Journal

Chinese Journal of Catalysis

DOI

10.1016/S1872-2067(25)64915-1

Transporting hydrogen safely over long distances presents a formidable challenge due to hydrogen’s low energy density and high flammability. Ammonia, composed of nitrogen and hydrogen atoms, offers a compelling alternative because it can store twice the energy density of compressed hydrogen and be transported using existing infrastructure more efficiently. Scientists envision using ammonia as a molecular shuttle: hydrogen can be chemically embedded within ammonia and then released on demand wherever needed. This paradigm shift could transform the energy landscape by decentralizing hydrogen production, minimizing the scale and complexity of industrial facilities, and reducing the associated costs and risks of hydrogen transportation.

Historically, ammonia synthesis has relied heavily on the Haber-Bosch process, which requires extreme temperatures exceeding 400°C and pressures over 150 atmospheres. This method demands massive, centralized plants equipped with expensive machinery and substantial energy inputs. The energy-intensive nature of Haber-Bosch poses scalability and sustainability challenges, particularly as the world seeks greener industrial methods. The new plasma-catalyzed approach devised by a multidisciplinary team from the Princeton Plasma Physics Laboratory (PPPL), Rutgers University, Oak Ridge National Laboratory, Rowan University, and Princeton University promises a low-energy, highly efficient alternative. This innovation utilizes low-temperature plasma, electric energy, water, and nitrogen to facilitate ammonia formation at or near room temperature.

Plasma, often referred to as the fourth state of matter, consists of a partially ionized gas in which electrons attain very high energies while the bulk gas remains relatively cold. This unique environment enables chemical reactions that are inaccessible under conventional conditions. By harnessing plasma’s energetic electrons, researchers induce fundamental changes in catalyst surfaces, triggering atomic rearrangements that promote ammonia synthesis. The process creates reactive sites on the catalyst where nitrogen molecules from the air can be activated and combined with hydrogen atoms derived from water. This method not only reduces the synthesis temperature and pressure but also dramatically accelerates the reaction rate.

A central breakthrough enabling this technology revolves around the design and fabrication of a specialized catalyst exhibiting a heterogeneous interfacial complexion (HIC). The catalysts, primarily composed of tungsten oxide and tungsten oxynitride, are not new as materials; however, their configuration and preparation method represent a major advancement. The plasma-enabled synthesis technique allows precise control over the catalyst’s surface structure at the atomic level, facilitating the creation of nitrogen vacancies—tiny voids perfectly sized to trap nitrogen molecules. Hydrogen atoms generated on the catalyst readily occupy adjacent sites, prompting an efficient conversion of nitrogen into ammonia molecules.

The synergy between nitrogen vacancies and active hydrogen atoms is the cornerstone of this catalyst’s enhanced performance. The vacancies act as attractors, binding nitrogen molecules and holding them in place, while the hydrogen atoms rapidly interact with these activated nitrogen centers. This cooperative effect minimizes the occurrence of undesirable side reactions, such as hydrogen gas formation, which traditionally compete with ammonia production. Consequently, the method not only increases the yield of ammonia but also improves selectivity and energy efficiency, marking a significant leap beyond existing catalytic technologies.

Time efficiency is another critical asset of the plasma-based approach. Traditional catalyst preparation can take upwards of two days under specialized conditions, hindering rapid experimentation and scale-up. In contrast, the plasma-enabled fabrication process drastically reduces this timeframe to mere minutes. This rapid synthesis capability accelerates research cycles and opens avenues for mass production, making it highly attractive for industrial adaptation. Early experimental results, as outlined by doctoral candidate and lead researcher Zhiyuan Zhang, demonstrate that ammonia output surpasses that of catalysts produced by conventional methods, indicating the method’s practical value.

Fundamental to understanding and optimizing these developments are high-fidelity simulations performed at the atomic scale. Modeling the complex quantum chemistry involved in plasma catalysis requires detailed observation of atomic interactions during ammonia synthesis. PPPL’s research physicist Mark Martirez is spearheading simulation efforts that elucidate the precise mechanisms at play, clarifying how plasma-excited electrons modify catalyst surfaces and how hydrogen and nitrogen atoms migrate and interact. Such computational insight is instrumental in guiding catalyst design and process parameters to maximize efficiency and scalability.

The plasma approach also offers potential sustainability advantages. Because it relies on electricity rather than fossil-fuel-derived heat, it integrates well with renewable energy sources such as solar and wind. Coupling plasma-driven ammonia synthesis with renewable electricity could substantially lower the carbon footprint of fertilizer and hydrogen production, supporting broader climate goals. Moreover, the decentralized nature of the technology could democratize ammonia and hydrogen supply chains, enabling localized production in remote or underserved regions.

The collaborative effort behind this research exemplifies the convergence of plasma physics, materials science, chemistry, and engineering. Institutions such as the U.S. Department of Energy’s PPPL and Oak Ridge National Laboratory have contributed unique expertise, alongside academic partners at Rutgers and Princeton Universities. This multidisciplinary synergy accelerates innovation, blending theoretical modeling, experimental plasma generation, catalyst synthesis, and advanced characterization techniques.

Looking ahead, challenges remain in scaling up the plasma catalysis process for commercial applications. Researchers are focused on refining catalyst durability, optimizing plasma reactor designs, and integrating ammonia decomposition technologies for onsite hydrogen retrieval. Continued research will expand understanding of plasma-material interactions and explore ways to tailor catalysts for broader chemical pathways. The ultimate goal is to establish comprehensive energy systems where ammonia serves as a versatile, safe energy carrier bridging production, storage, transportation, and utilization.

As the world races to find sustainable solutions for energy and chemical manufacturing, plasma-enabled ammonia synthesis represents a compelling milestone. By radically changing how ammonia is produced and harnessed, this innovation has the potential to reshape global energy infrastructure, making hydrogen storage and distribution less hazardous, more efficient, and economically viable. This exciting development heralds a future where plasma catalysis underpins not only fertilizer production but also the clean energy transition, ultimately contributing to a more sustainable and resilient energy ecosystem.

Subject of Research: Plasma catalysis for ammonia synthesis and hydrogen storage
Article Title: (Not provided)
News Publication Date: 22-Jun-2025
Web References:
– U.S. Department of Energy: https://www.energy.gov/
– Princeton Plasma Physics Laboratory: https://www.pppl.gov/
– DOI: http://dx.doi.org/10.1021/acsenergylett.5c01034

References:
ACS Energy Letters, DOI: 10.1021/acsenergylett.5c01034

Keywords:
Energy, Chemical compounds, Chemical processes, Electricity, Ammonia, Hydrogen