First catalytic example of nitrogen reduction by rare earth metals

April 9, 2024

Illustration of robot carrying out active nitrogen reduction catalysis

Photo: Earth-abundant metals, including rare earths for the first time, can convert abundant nitrogen gas into amines at room temperature. Illustration by Dr. Amy Kynman

The row of elements nearly at the bottom of the periodic table are called the rare earth metals, and most are classified as critical materials by the high-tech economies – those that rely on advanced technology and innovation – because of their unique electronic structure. For example, rare earths make incredibly strong magnets for electric cars and wind turbines and the active supports in catalytic converters for gas-powered cars. Luckily, they are, in fact, relatively plentiful in the earth’s crust, but they earned their name because they are typically dispersed.

“They are difficult to separate from each other due to their physical similarity,” says Polly Arnold, professor of chemistry. “It is still difficult to predict their behavior because of their complicated electronic structures.”

Arnold and her team have discovered that these rare earth metals can form active nitrogen reduction catalysts. This is the process of converting nitrogen gas, which is the normally unreactive, major component of air, into forms that are useful for living organisms, like ammonia or other nitrogen-containing compounds.

“For hundreds of years, chemists have been trying to emulate nature,” says Arnold. “We aren’t the only ones trying to do this.” Metals such as iron, molybdenum, and vanadium are known to form active nitrogen reduction catalysts. Arnold and her team are the first to show that this can also be done with other metals – those that are less toxic and more abundant. Discoveries like these represent a step change in our understanding of these complicated metals.

Ammonia is a crucial component in fertilizers, which are essential for promoting plant growth and increasing crop yields. By converting nitrogen gas from the air into usable forms, chemists help ensure enough nutrients are available for plants to grow, ultimately supporting food production and addressing global food security challenges.

To find out how the team made their discovery, read the full article in Chem Catalysis.