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Lowering the temperature for nitrogen splitting on paper

Computer simulations predict a new light-activated catalyst could make the Haber-Bosch process obsolete

by Sam Lemonick
January 8, 2018 | A version of this story appeared in Volume 96, Issue 2

Credit: Adapted from Sci. Adv.
A predicted molybdenum-doped gold nanoparticle catalyst can split a dinitrogen molecule.
A nitrogen atom coordinated to and split by a gold-molybdenum catalyst.
Credit: Adapted from Sci. Adv.
A predicted molybdenum-doped gold nanoparticle catalyst can split a dinitrogen molecule.

The world relies on the Haber-Bosch process to reduce atmospheric nitrogen to ammonia to make fertilizer, pharmaceuticals, and other industrially important chemicals. But the process requires high temperature and thereby consumes a tremendous amount of energy—about 1% of the world’s electricity every year. A new light-activated catalyst could dramatically reduce the temperature needed to drive the reaction, according to computer simulations (Sci. Adv. 2017, DOI: 10.1126/sciadv.aao4710). John Mark P. Martirez and Emily A. Carter at Princeton University have proposed that a gold-molybdenum catalyst could split dinitrogen’s triple bond at room temperature using visible light. That dissociation step is the primary limit on the Haber-Bosch process’s reaction rate. Their catalyst relies on a phenomenon called surface plasmon resonance, in which the valence electrons on a nanoparticle—made of molybdenum-doped gold in this case—oscillate in unison when excited by a photon. Harnessed correctly, that excitation energy could push the nitrogen dissociation reaction over its high activation energy barrier, Carter says. The researchers evaluated the dissociation reaction for nitrogen in different excited states that are accessible at gold nanoparticle plasmon frequencies (models shown). Their calculations suggest that the catalyst can lower the energy needed to split nitrogen by about 80 to 90%. Carter says plans are in the works to collaborate with Naomi Halas and Peter Nordlander of Rice University to test the predictions.


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