A team led by Stanford University researchers has demonstrated a prototype device that manufactures ammonia by using wind energy to draw air through a catalyst-coated mesh.
The portable, patented device operates at room temperature and standard atmospheric pressure and requires no external voltage to run.
The mesh is composed of magnetite (Fe3O4) and Nafion polymer. The polymer is made of perfluorosulfonic acid, which is noted for its good chemical stability and is often used in formulations for fuel cell membranes and a variety of electrochemical applications.
When air is passed through the mesh, microdroplets from water vapor condense and combine with nitrogen from the air, making ammonia.
In tests around the Stanford campus, its concentration ranged from 25-120 μM/hr, depending on local relative humidity.
In laboratory experiments, the researchers further optimized the reaction conditions and scaled up the process. After two hours of spraying water mist, the ammonia concentration increased to 270.2 ± 25.1 μM, which they say is adequate for some agricultural purposes.
The research, published in a recent Science Advances notes that in the field the device collected 20 ml/hr of ammonia, and in the lab, 500 ml/hr, although the belief is that this could be hugely increased with suitable engineering.
According to study co-author Chanbasha Basheer, a professor at the King Fahd University of Petroleum and Minerals in Dhahran, Saudi Arabia, the device is two to three years away from being market-ready. In the meantime, the researchers plan to use increasingly large mesh systems to produce more ammonia.
“The most important task now is to scale up the volume production of ammonia dissolved in water,” said Richard N Zare, the Marguerite Blake Wilbur Professor in Natural Science at the Stanford School of Humanities and Sciences.
“I truly hope we can make a device that can be used in the field/farm as a source of fertilizer. We are also working on related technologies that take nitrogen from the air to make nitrate and take nitrogen and carbon dioxide to make urea,” he added.
Ammonia's importance extends beyond fertilizers, not least as a clean energy.
"Green ammonia represents a new frontier in sustainability," Zare said. "This method, if it can be scaled up economically, could drastically reduce our reliance on fossil fuels across multiple sectors."
Meanwhile Zare says that he has been overwhelmed with people interested in exploring and commercializing the mesh approach to ammonia production.
