Ammonia Synthesis via an Associative Mechanism on Alkaline Earth Metal Sites of Ca3CrN3H

Typically, transition metals are considered as the centers for the activation of dinitrogen. Here we demonstrate that the nitride hydride compound Ca3CrN3H, with robust ammonia synthesis activity, can activate dinitrogen through active sites where calcium provides the primary coordination environment. DFT calculations also reveal that an associative mechanism is favorable, distinct from the dissociative mechanism found in traditional Ru or Fe catalysts. This work shows the potential of alkaline earth metal hydride catalysts and other related 1 D hydride/electrides for ammonia synthesis. Earthbound: Ca3CrN3H exhibits catalytic ammonia synthesis activity, despite the lack of Ru/Fe centers. DFT calculations reveal that N2 activation and hydrogenation over Ca3CrN3H proceeds though an associative mechanism on the alkaline earth cations Ca, rather than the Cr sites as one would normally expect.