Single‐Site Molybdenum on Solid Support Materials for Catalytic Hydrogenation of N₂‐into‐NH₃

Abstract

Very stable in operando and low‐loaded atomic molybdenum on solid‐support materials have been prepared and tested to be catalytically active for N2‐into‐NH3 hydrogenation. Ammonia synthesis is reported at atmospheric pressure and 400 °C with NH3 rates of approximately 1.3×103 μmol h−1 gMo−1 using a well‐defined Mo‐hydride grafted on silica (SiO2‐700). DFT modelling on the reaction mechanism suggests that N2 spontaneously binds on monopodal [(≡Si−O‐)MoH3]. Based on calculations, the fourth hydrogenation step involving the release of the first NH3 molecule represents the rate‐limiting step of the whole reaction. The inclusion of cobalt co‐catalyst and an alkali caesium additive impregnated on a mesoporous SBA‐15 support increases the formation of NH3 with rates of circa 3.5×103 μmol h−1 gMo−1 under similar operating conditions and maximum yield of 29×103 μmol h−1 gMo−1 when the pressure is increased to 30 atm.

N2 Electroreduction to NH3 by Selenium Vacancy‐Rich ReSe2 Catalysis at an Abrupt Interface

“…[15,16] Until now,the development of NRR is mainly focused on exploring advanced electrocatalysts to activate dinitrogen for alleviated energy barriers. [17,18] Among them, transition metal based electrocatalysts are regarded as promising species towards the NRR process, [19][20][21][22][23] due to their available d-orbital electrons for p-back donation process.H owever, their practical applications are still hindered by low NH 3 yield and Faradaic efficiency,w hich originates from the following two perspectives: ( 1) the binding force between transition metals and nonpolar dinitrogen is too weak to break the strong NN triple bond due to the poorly optimized structure of the electrocatalyst; [24] (2) the adverse hydrogen evolution reaction (HER) is regarded as an intense-competing reaction towards NRR due to the preferential adsorption of the hydrogen (H) atom over an itrogen (N) atom. [8,25] Fora n enhanced interfacial force towards nitrogen, one effective strategy is to tailor the electronic structure of the transition metal based electrocatalysts by incorporating defect structures (such as anionic vacancies).…”

Recent progress towards mild-condition ammonia synthesis

“…was recently demonstrated to be catalytically active for the conversion of N 2 to NH 3 using dihydrogen, in which an associative mechanism was suggested by DFT calculations [76] . Mechanistic investigations on LiH-Fe composite catalyst was also performed.…”

Atomic Modulation, Structural Design, and Systematic Optimization for Efficient Electrochemical Nitrogen Reduction

“…In the alternating pathway, the two nitrogen atoms concurrently undergo hydrogenation to form two ammonia molecules, during which a variable amount of hydrazine may also be produced by possible shunts from diazene. Recently, a mixed distal and alternating pathway was found . Dinitrogen is side‐on coordinated in the enzymatic pathway, followed by hydrogenation steps similar to the alternating pathway .…”