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

Abstract

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.

Molecular titanium nitrides: nucleophiles unleashed

“…1–7 Nitride reactivity can be tuned with the appropriate transition metal ion to render this site either nucleophilic or electrophilic. High oxidation states, generally, can be stabilized with this type of motif and are known to participate in reactivity spanning various transformations 8 such as N-atom transfer reactions and nitrile-alkyne cross-metathesis, 9,10 and also to act as surface supports that engage in important industrial processes such as Haber–Bosch 11–14 and hydrodenitrogenation and hydrodesulfurization.…”

Strain-Induced Isostructural and Magnetic Phase Transitions in Monolayer MoN2

“…As a new layered molybdenum dinitride material, the bulk single-crystal MoN 2 was successfully synthesized in recent experiment. 22 Subsequent study has shown that a monolayer MoN 2 could be realized and its ground state has a strong ferromagnetic ordering with a Curie temperature above 420 K. 23 Here, based on first-principles calculations, we discover that the monolayer MoN 2 actually exhibits two stable isostructural phases with extremely dissimilar N-N distances along the perpendicular direction: the ߙ-phase of a large N-N distance (݀ N-N ≅ 2.20 Å), corresponding to the ground state structure discussed in the previous study; 23 and a new ߚ-phase of a much shorter N-N distance (݀ N-N ≅ 1.54 Å). We show that the key difference between the two phases is on the N-N bonding status: the ߙ phase is with a nonbonding N-N state; whereas the ߚ-phase is with a N-N single bond state.…”

Synthesis of cubic sodium tungsten bronze NaxWO3 in air

“…Diffraction peaks corresponding to Na x WO 3 (PDF#05‐0367) can be clearly identified, revealing that an oxidation‐reduction process between B 4 C and W 6+ has occurred to form Na x WO 3 . Only some very weak peaks of the reaction byproduct NaBO 2 are detected as it is rather air sensitive, which makes the Bragg reflections almost invisible in the pattern …”