Original Synthesis of Molybdenum Nitrides Using Metal Cluster Compounds as Precursors: Applications in Heterogeneous Catalysis

Abstract

Transition metal nitrides (TMN) form a class of materials with unique physical and chemical properties. Among them, molybdenum nitrides are mainly used as high-performance magnets or catalysts for a wide range of reactions. This work aims at developing innovative syntheses to prepare nanostructured TMN from metallic clusters for heterogeneous catalysis. The use of a nanoscale precursor such as (TBA)2Mo6Br14 (TBA = tetrabutylammonium = (C4H9)4N +) enables to reach different molybdenum nitride compositions (Mo2N, Mo5N6) by thermal reaction under ammonia at relatively low temperatures. Such a novel synthetic approach highlights the prime importance of the starting material to stabilize specific stoichiometries. The impact of this new synthetic route is characterized by several techniques including electron probe microanalysis and high-resolution transmission microscopy. Moreover, catalytic properties of these potential cost-effective catalysts are investigated for the Water-Gas Shift Reaction.

Transition Metal Nitrides for Electrocatalytic Application: Progress and Rational Design

“…The rational design of TMNs’ nanocrystalline-based electrocatalysts can not only notably reduce the consumption of precious metals, but also improve the ionic conductivity of materials by shortening the diffusion length of ions in the electrocatalytic process. Therefore, the design of favorable nanostructures for electrode materials can significantly improve electrocatalytic performance [ 31 , 32 , 33 ]. The unique nanostructure will provide new features of the electrocatalytic surface, which can significantly enhance the activity of the electrocatalyst, and lead to a large specific surface area and more adsorption and reaction sites [ 34 ].…”

Utility of NaMoO3F as a Precursor for Homogeneous Distribution of Cobalt Dopants in Molybdenum Oxynitrides

“…These reports imply that the phase, the crystallinity, and the Co/O dopant state in the MoN should be controlled simultaneously for further improvement of molybdenum nitride‐based ORR catalytic activity. Although nitridation of MoCl 5, [5c] MoS 2, [6] Cs 2 Mo 6 Br 14 , [7] Cs 2 Mo 6 Cl 14 [7] , and MoO 3 with NaCl [8] has been converted into hexagonal MoN phase, the synthetic process of MoN has been very limited until now. This limitation can dramatically suppress the simultaneous control.…”

Phase-Controllable Synthesis of Ultrathin Molybdenum Nitride Crystals Via Atomic Substitution of MoS2

“…MXenes have drawn tremendous interest among researchers by virtue of their excellent electrical, optical, and mechanical properties, − with potential in various applications including energy storage, transparent conductors, and gas sensors. − Among a variety of synthetic strategies, selective etching of bulk MAX phase precursors is the most widely used one to make MXenes. − Nevertheless, molybdenum-based MXenes, especially molybdenum nitrides (MoN x ), are hardly accessible through this approach due to the rarity of stable MAX precursors from theoretical predictions. , Thus, alternative synthetic strategies beyond the selective etching method are in demand. Growing efforts have been spent on designing rational synthetic routes for 2D molybdenum-based MXenes very recently. − Synthesis of 2D Mo 2 C has been achieved through a chemical vapor deposition (CVD) process. − With regard to MoN x , Hong et al developed an approach to grow monolayer MoSi 2 N 4 by introducing silicon during the deposition of Mo 2 N film using the CVD technique . The presence of silicon atoms passivates the surface and hence enables the lateral growth of the film.…”

“…A variety of MoN x with different stoichiometries and crystal structures have been reported in either bulk or 2D forms, including MoN 2 , Mo 5 N 6 , δ-MoN, β-Mo 2 N, and γ-Mo 2 N. − ,− All MoN x are composed of host Mo atoms and interstitial N atoms. Three of the polymorphisms (MoN 2 , Mo 5 N 6 , and δ-MoN) belong to the hexagonal crystal system, while β-Mo 2 N belongs to the tetragonal crystal system, and γ-Mo 2 N belongs to the cubic crystal system.…”

“…With the density of states around the Fermi level being significantly modified by the interstitial N atoms, the concentration of nitrogen has a remarkable impact on the electrical properties of MoN x (e.g., electrical conductivity) . Nonetheless, reports on achieving the different phases of ultrathin MoN x , especially those with satisfactory lateral dimensions for electronic devices, are very rare. , Guy et al synthesized different phases of nanostructured Mo 2 N and Mo 5 N 6 in a powder form by using metalorganic clusters as precursors, and Jin et al reported that the addition of foreign elements in nitrogen-deficient δ-MoN nanosheets could result in the formation of nitrogen-rich Mo 5 N 6 nanosheets . Note that these works are not focusing on the lateral size of the materials (mostly below 500 nm), and hence the as-synthesized materials do not meet the requirements for solid-state electronic devices.…”