Organic chemistry

Activation energy

Adsorption

Catalysis

Physical chemistry

Ammonia production

Chemistry

Ammonia

Nitride

Dissociative

Layer (electronics)

Associative substitution

Reaction mechanism

Medicine

Photochemistry

Pharmacology

Journal of the American Chemical Society

The current catalytic reaction mechanism for ammonia synthesis relies on either dissociative or associative routes, in which adsorbed N2 dissociates directly or is hydrogenated step-by-step until it is broken upon the release of NH3 through associative adsorption. Here, we propose a concerted mechanism of associative and dissociative routes for ammonia synthesis over a cobalt-loaded nitride catalyst. Isotope exchange experiments reveal that the adsorbed N2 can be activated on both Co metal and the nitride support, which leads to superior low-temperature catalytic performance. The cooperation of the surface low work function (2.6 eV) feature and the formation of surface nitrogen vacancies on the CeN support gives rise to a dual pathway for N2 activation with much reduced activation energy (45 kJ·mol–1) over that of Co-based catalysts reported so far, which results in efficient ammonia synthesis under mild conditions.

Dissociative and Associative Concerted Mechanism for Ammonia Synthesis over Co-Based Catalyst