This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Ammonia is one of the most important chemicals produced in the world, ranking second only to sulfuric acid in the total volume produced each year. It is used mostly to make fertilizer, which is essential to feeding the world's population.
Yet its production accounts for up to 2% of the world's energy consumption and about 1.5% of greenhouse gas emissions, so the search has been underway for ways to produce ammonia more sustainably. The traditional way of making ammonia, in use for more than a century and accounting for the vast majority of production, is the Haber–Bosch process, which relies on fossil fuels to provide the needed heat. Hydrogen used in the process is also largely produced from fossil fuels.
There is another way, using electrochemistry instead of heat and pressure, but so far this method has not been anywhere near economically competitive at the scales needed. Now, researchers at MIT have developed a way to predict which materials could be most promising as catalysts in electrochemical ammonia production. Catalysts help drive chemical reactions, and their properties determine how efficiently those reactions proceed.
Rather than using trial and error to test each possible combination out of the millions of possible alloys—which can take years—the new approach could greatly speed up the search for materials that could make this low-emissions method competitive with the Haber–Bosch process. "Our approach identifies the key physical properties that drive catalytic activity in ammonia production," says Bilge Yildiz, the Breen M. Kerr Professor in the departments of Nuclear Science and Engineering and Materials Science and Engineering (DMSE).
The results can guide the search for new and more effective catalyst compounds. The open-access findings were published Aug. 11 in the Royal Society of Chemistry journal EES Catalysis, in a paper by Yildiz and doctoral students Constantine Athanitis of DMSE and Filip Grajkowski of the Department of Chemistry. As the world's population grows, Athanitis says, "we're just going to need more and more food, and the only reason we're able to sustain so many people is because of fertilizer." But more than 90% of the ammonia needed for fertilizer is still made by that energy-intensive Haber–Bosch process, which "has been hyper-optimized since it first came out more than a century ago," he says.
"If we're trying to keep in line with society's sustainability and energy targets and climate change targets, we really need to come up with another alternative," he explains. The world currently uses about 200 million metric tons of ammonia each year, "so ideally we want to be able to find a way to produce the same amount of ammonia, or even more, but in a more energy-efficient way and also with lower CO2 emissions," he says. Using electricity to produce ammonia is not a new idea.
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