Photodriven Ammonia Synthesis from N<sub>2</sub> and H<sub>2</sub>: Recycling of a Molecular Molybdenum Nitride
Junho Kim, Grace B. Panetti, Nidhi Kaul, Sangmin Kim, Paul J. Chirik
Abstract
The synthesis of ammonia from its elements, N 2 and H 2, is the most atom-economical and thermodynamically preferred route but presents a high kinetic barrier and thus is rare using molecular compounds. Irradiation of a molecular molybdenum nitride prepared from N 2 cleavage with visible light in the presence of an iridium photocatalyst and 1–4 atm of H 2 produced high yields of ammonia along with the formation of a cationic, formally molybdenum(VI) pentahydride as the major molybdenum-containing product. Continued irradiation of the molybdenum hydride under an N 2 atmosphere resulted in regeneration of the molybdenum nitride that was recycled and used for additional hydrogenation to generate more ammonia, demonstrating superstoichiometric batch ammonia synthesis using only N 2 and H 2 with molecular compounds under ambient conditions.