A New Molybdenum Nitride Catalyst with Rhombohedral MoS₂ Structure for Hydrogenation Applications

Nitrogen-rich transition-metal nitrides hold great promise to be the next-generation catalysts for clean and renewable energy applications. However, incorporation of nitrogen into the crystalline lattices of transition metals is thermodynamically unfavorable at atmospheric pressure; most of the known transition metal nitrides are nitrogen-deficient with molar ratios of N:metal less than a unity. In this work, we have formulated a high-pressure route for the synthesis of a nitrogen-rich molybdenum nitride through a solid-state ion-exchange reaction. The newly discovered nitride, 3R-MoN₂, adopts a rhombohedral R3m structure, isotypic with MoS₂. This new nitride exhibits catalytic activities that are three times more active than the traditional catalyst MoS₂ for the hydrodesulfurization of dibenzothiophene and more than twice as high in the selectivity to hydrogenation. The nitride is also catalytically active in sour methanation of syngas with >80% CO and H₂ conversion at 723 K. Our formulated route for the synthesis of 3R-MoN₂ is at a moderate pressure of 3.5 GPa and, thus, is feasible for industrial-scale catalyst production.