Just add water to make ammonia

Published online 12 April 2023

A lab-scale demonstration reveals a surprisingly simple way to make ammonia from nitrogen and water.

Andrew Scott

Experimental setup for making ammonia by spraying water microdroplets with nitrogen gas onto a graphite mesh coated with iron oxide (magnetite) and Nafion.
Experimental setup for making ammonia by spraying water microdroplets with nitrogen gas onto a graphite mesh coated with iron oxide (magnetite) and Nafion.
Richard N. Zare Enlarge image
More than 150 million metric tons of ammonia are produced by the chemical industry each year in a reaction called the Haber-Bosch process, which accounts for around 2% of global energy consumption and 1% of carbon dioxide emissions. Researchers from Stanford University, USA, and King Fahd University of Petroleum and Minerals in Saudi Arabia, have discovered a simpler and greener reaction that combines water and nitrogen to make ammonia.

Ammonia is used to make fertilisers that provide the essential nitrogen needed by plants in a form they can absorb, since they cannot directly take up and use the nitrogen that comprises 78% of the air by volume. It is also a major feedstock for making a wide variety of other industrial chemicals.

Nitrogen molecules are extremely stable, with their two nitrogen atoms held together by three strong covalent bonds. This stability is overcome in the Haber-Bosch process by combining nitrogen with hydrogen at around 400oC and more than 150 atmospheres of pressure with the assistance of an iron-based catalyst. The new method works when water droplets at room temperature are mixed with nitrogen and sprayed through a graphite mesh coated with iron oxide (magnetite) and a polymer called Nafion (a sulfonated tetrafluoroethylene-based fluoropolymer copolymer).

“I was thrilled to discover that a simple room-temperature and atmospheric-pressure process could turn [nitrogen] into ammonia,” says chemist, Richard Zare of the Stanford team. The work reveals that the simple trick of applying water in the form of micro-droplets sufficiently increases its chemical reactivity for the reaction to proceed on the surface of the catalyst mesh.

At present, the reaction has been achieved as only a very small-scale laboratory demonstration, with the creation of ammonia detected using a sophisticated instrument called a mass spectrometer. The team is now investigating whether the process could feasibly be scaled up and the ammonia concentrated sufficiently for commercial application.

Chanbasha Basheer, a chemist at King Fahd University of Petroleum and Minerals, who was also involved in the study, says that ammonia production from air, using water as a source of hydrogen, could become more sustainable and efficient with further improvements in catalysts, energy efficiency and scale-up.


Song, X. et al. Making ammonia from nitrogen and water microdroplets. PNAS 120, e2301206120 (2023).