Ammonia sits at the center of a hard climate problem. It is one of the most widely produced chemicals in the world, used mostly for fertilizer, yet making it consumes up to 2 percent of the world’s energy and produces about 1.5 percent of greenhouse gas emissions.
Researchers at MIT now say they have a way to make the search for greener ammonia catalysts less dependent on slow trial and error. Their approach uses computer modeling and machine learning to identify material properties that may point toward better catalysts for electrochemical ammonia production.
Why ammonia is difficult to decarbonize
The dominant method for making ammonia is the Haber-Bosch process. It has been in use for more than a century and accounts for the vast majority of ammonia production. The process relies on fossil fuels for heat, and the hydrogen used in it is also largely produced from fossil fuels.
That matters because ammonia is not a niche chemical. It ranks second only to sulfuric acid in annual production volume, and fertilizer made from ammonia is essential to feeding the world’s population.
Constantine Athanitis, a doctoral student in MIT’s Department of Materials Science and Engineering, put the pressure plainly: “we’re just going to need more and more food, and the only reason why we’re able to sustain so many people is because of fertilizer.”
More than 90 percent of the ammonia needed for fertilizer is still produced through Haber-Bosch, which Athanitis says “has been hyper-optimized since it first came out more than a century ago.” The world currently uses about 200 million metric tons of ammonia each year, so any alternative has to be more than scientifically interesting. It has to work at enormous scale.
The promise and problem of electrochemical ammonia
Electrochemical ammonia production offers another route. Instead of relying on heat and pressure in the same way as Haber-Bosch, it uses electricity to drive reactions in devices that follow the same basic principles as electrolyzers.
Athanitis describes it as “the electrochemical reaction between proton-electron pairs and nitrogen gas.” The technology exists, but it has not yet reached the performance needed for industrial production.
The main barriers are practical. Production rates and yields are still too low, and a cleaner method will not be adopted widely unless it can compete economically. As Athanitis puts it, “Even though a technology might be better for the world or for the climate, companies and capitalism won’t really allow it unless it’s cost competitive.”
This is where catalysts become central. A catalyst helps drive a chemical reaction, and its properties shape how efficiently the reaction proceeds. For electrochemical ammonia, the goal is to find a metallic catalyst that lowers the energy required and favors ammonia production over unwanted side reactions.
What MIT’s method changes
The challenge is not simply to pick one known metal and improve it slightly. Researchers are looking across many possible alloys, including combinations that could improve different parts of the reaction pathway. Searching through millions of options by making and testing each one could take years.
MIT’s approach aims to narrow that search before materials are made in the lab. The open-access findings were published Aug. 11 in the Royal Society of Chemistry journal EES Catalysis, in a paper by Bilge Yildiz, Constantine Athanitis, and Filip Grajkowski.
Yildiz, the Breen M. Kerr Professor in the departments of Nuclear Science and Engineering and Materials Science and Engineering, says the work identifies the physical properties that matter most for catalytic activity. In her words, “Our approach identifies the key physical properties that drive catalytic activity in ammonia production.”
The researchers focused on transition metal nitrides. According to Yildiz, “Metal nitride compounds make an ideal material system for this reaction and for identifying the electronic, chemical, and structural properties that determine reactivity in nitrogen reduction and ammonia electrosynthesis.”
These materials are promising because the nitrogen already present in the catalyst becomes part of the reaction. That creates a sequence in which one chemical step can help supply part of the energy needed for the next. In plain terms, the catalyst is not just a surface where the reaction happens; it participates in the process.
From quantum models to candidate materials
The study uses density functional theory, a computational method based on quantum mechanics, to simulate material properties and behavior. This lets researchers predict how different atomic arrangements may perform before committing to laboratory synthesis.
The team also used machine learning to connect microscopic material properties with reaction bottlenecks. Those bottlenecks include nitrogen dissociation and hydrogen transfer, both of which limit the reaction pathway.
For greener ammonia production, this matters because the nitrogen reduction reaction faces a major energy challenge: breaking the strong bonds in nitrogen molecules. Better catalysts could reduce the amount of input energy needed and make the process more selective for ammonia.
The logic of the work is straightforward:
- Ammonia demand is large because fertilizer is central to food production.
- The current Haber-Bosch process is energy-intensive and tied to fossil fuels.
- Electrochemical ammonia production could offer a lower-emissions path.
- Better catalysts are needed to improve production rates, yields, and selectivity.
- Computational screening can help researchers focus on the most promising alloys.
What still has to happen
The study is still theoretical. The researchers have used models to identify promising alloys, but those materials still need to be made and tested.
Dane Morgan, a professor of engineering at the University of Wisconsin who was not involved in this study, called the approach “exciting work.” He says it could help build a foundation for designing new catalysts for ammonia production.
Morgan also notes the gap between calculations and real systems. “This work helps clarify how fundamental electronic properties of a material relate to its role as a catalyst in making ammonia,” he says. But he cautions that “translating these calculations into practical catalysts will require many additional steps, so meaningful real-world impact is likely still some distance away.”
That makes the MIT work a step in the search, not the endpoint. Its importance lies in direction: instead of testing catalyst candidates one by one, researchers may be able to use physical insight and computation to focus on materials with a better chance of making electrochemical ammonia viable at scale.