Binary Transition Metal Nitrides Research Articles

Ammonia decomposition mediated at nitrogen vacancies on NaCl-type binary metal nitrides supporting transition metal nanoparticles.

The ability of NaCl-type binary transition metal nitrides (incorporating La, Ce, Y, Zr or Hf) to act as catalytic supports facilitating ammonia decomposition was examined. The effect of nitrogen vacancies formed on nitrides can be understood in terms of the ionic radii of the metal cations. A clear correlation between the N2 desorption temperature and catalytic activity was found.

Tailoring the plasmonic properties of complex transition metal nitrides: A theoretical and experimental approach

Transition metal nitrides (TMNs) are promising materials for developing next-generation photonic devices. A practical way toward high-performance TMNs is to tune their plasmonic properties through different compositions. Here, we investigate the electronic structures and optical properties of TMNs (Ti1-xZrxN and Ti1-xHfxN, x = 0, 0.25, 0.50, 0.75, and 1) computationally and experimentally. Our calculated dielectric permittivities and quality factors suggest that the overall performance of TMNs is well-tuned by their compositions, supported by our measured data obtained from the 50-nm thick TMN films deposited on sapphire (0001). Particularly, at the dielectric-metallic interface, Ti0.25Hf0.75N (ENZ of 401 nm) and Ti0.50Zr0.50N (ENZ of 406 nm) show a better dielectric response than the binary TMNs. Ti0.50Hf0.50N (ENZ of 457 nm) holds promise for applications requiring efficient energy absorption and enhanced wave manipulation in the near-infrared range. Using mixed ternary TMNs to tune plasmonic properties in the visible and near-infrared regions can thus achieve frequency-targeting photonics applications.

Two-dimensional binary transition metal nitride MN4 ( M = V, Cr, Mn, Fe, Co) with a graphenelike structure and strong magnetic properties

Binary transition metal nitride with a graphene-like structure and strong magnetic properties is rare. Based on the first-principles calculations, we design two kinds of $M{\mathrm{N}}_{4}$ ($M$ = transition metal) monolayers, which are transition metal nitrides with a planar structure, made up of $M{\mathrm{N}}_{4}$ units aligned in the rhombic and square patterns. The two structural lattices have robust stability and good compatibility with different metal atoms, and the underlying mechanism is the combination of $s{p}^{2}$ hybridization, coordinate bond, and $\ensuremath{\pi}$ conjugation. With the metal atom changing from V, Cr, Mn, Fe to Co, the total charge of $M{\mathrm{N}}_{4}$ system increases by one electron in turn, which results in continuous adjustability of the electronic and magnetic properties. The planar ligand field is another feature of the two $M{\mathrm{N}}_{4}$ lattices, which brings about the special splitting of five suborbitals of $3d$ metal atom and gives rise to strong magnetism. Moreover, room-temperature ferromagnetism in square-${\mathrm{CoN}}_{4}$ monolayer with the Curie temperatures of 321 K is determined by solving the Heisenberg model combined with Monte Carlo method.

Investigate the role of V in the Nitrogen-doped hierarchical porous carbon-supported binary transition metal nitrides catalyst for oxygen reduction reactions

N-doped carbon-supported titanium nitride (TiN/NC) is considered promising for its application in Zn-air batteries. However, the performance of TiN/NC cannot meet the practical application. To solve this problem, the catalytic activity and stability of the catalyst can be improved by introducing the second metal element V. In this paper, a high-performance catalyst (TixV1−xN/NC/C) was prepared by supporting titanium-vanadium binary transition metal nitride nanoparticles on nitrogen-doped carbon. The experimental results and density functional theory (DFT) calculations confirm that the electronic, atomic and microstructure of titanium nitride nanoparticles can be properly tuned by introducing V ions, which is beneficial to tune the adsorption/adsorption of oxygen intermediates on titanium nitride nanoparticles and decreasing the potential of the rate determining step, thereby increasing the catalytic activity. The TixV1−xN/NC/C composite exhibits excellent ORR performance with an onset potential (Eonset) and limiting current density of 0.91 V (vs. RHE) and 4.90 mA∙cm−2, respectively. The Ti0.85V0.15N/NC/C-based Zn-air battery exhibits the power density of 124.78 mW·cm−2, open circuit voltage of 1.34 V and high specific capacity of 731.38 mAh·g−1. More importantly, this work has deepened the understanding of the TMN-based catalytic mechanism and paved the way for enhancing the catalytic performance of TMN-based catalysts.

First-principles study of vacancy ordered structures, mechanical properties and electronic properties of ternary Hf-C-N system

The thermal-mechanical properties of transition metal carbonitrides can be affected by the concentration and ordering of vacancies besides the C/N atomic ratio. However, there are few reports on the vacancy ordered structure of ternary transition metal carbonitrides. In the present paper, the first-principles method is used to study the vacancy ordered structures, mechanical properties, electronic properties and the effect of vacancies on the ternary Hf-C-N system. Firstly, the crystal structures of Hf-C-N system is examined by the first-principles and evolutionary algorithms implemented in USPEX under ambient pressure, and eight thermodynamical stable vacancy ordered structures are found, each of which has a rock-salt structure, and is also dynamical and mechanical stable, which are verified by the calculations of their phonon dispersion curves and elastic constants. The vacancies are occupied at the [Hf<sub>6</sub>] octahedral interstices, which replace the positions of non-metal atoms. Their crystallographic data such as space group, lattice constants are also predicted. To the best of our knowledge, there is no report on the Hf-C-N vacancy ordered structures and these structures investigated here in this work are all found for the first time. Then their mechanical properties are calculated. The Hf-C-N vacancy ordered structures all have very high bulk, shear and elastic modulus and hardness. It is found that except for C∶N = 1∶4, for the Hf-C-N system with the same C/N ratio the moduli, Vickers hardness values, and Pugh’s ratios decrease with the increase of the concentration of vacancy. However, the Vickers hardness of Hf<sub>6</sub>CN<sub>4</sub> (the concentration of vacancy is equal to 1/6) is higher than that of Hf<sub>5</sub>CN<sub>4</sub> (no vacancy), that is so-called vacancy hardening. Finally, the electronic density of states and the crystal orbital Hamilton populations are calculated. The chemical bonding of Hf-C-N vacancy ordered structure is analyzed, which is a mixture of covalence and metallic and is similar to that of binary transition metal carbides and nitrides. With the increase of the concentration of vacancy, the total bond strength decreases, and then the modulus decreases for Hf-C-N compound.

High-performance Ti0.95Co0.05N@NC–based ORR catalysts: organic-nitrogen nitrogenize and their application in rechargeable Zn-air batteries

The exploration of cheap, stable, and highly efficient non-precious metal catalyst is conducive to extending the practical applications of zinc-air batteries (ZABs). Herein, a simple, environmental friendly and low-cost method was proposed to fabricate nitrogen-doped carbon–coated TiN nanoparticle composites (TiN@NC). Dicyandiamide was applied as the nitrogen source instead of ammonia reduction, based on which Ti0.95Co0.05N@NC was synthesized. Oxygen reduction reaction (ORR) measurement shows that the onset potential of Ti0.95Co0.05N@NC was 30 mV higher compared to TiN@NC, which is attributed: (i) Cobalt was doped into TiN lattice. (ii) After cobalt doping, the graphitization degree of carbon was increased to facilitate electron transport. (iii) Controlling the reservation of nitrogen to form more N-C active sites in Ti0.95Co0.05N@NC may further promote the performance of ORR. The performance of the ZABs was effectively improved after cobalt doping. It is believed to make it more convenient to prepare binary transition metal nitride nanostructures.

Substrate Mediated Synthesis of Ti–Si–N Nano‐and‐Micro Structures for Optoelectronic Applications

Being one of the strongest materials, ternary TiSiN exhibits a very interesting family of binary transition metal nitride and silicide systems. A novel technique to fabricate morphologically fascinating nano and micro structures of TiSiN is reported here. The referred TiSiN films, majorly constituted with cubic TiN phase, are enriched with crystalline nanoparticles, micro‐flowers, and faceted micro‐crystals which possess attractive functionalities toward plasmon mediated optoelectronic applications. Reactivity of titanium to silicon nitride‐based dielectric topping on the substrate at high temperature plays the key role in nitride formation for the demonstrated protocol. The optoelectronic response for these morphologically enriched composite films indicates an influential role of photo‐induced surface plasmon polaritons (SPPs) on their dc transport properties. A plasmonically tuned resistive switching, controlled by the surface morphology in association with the film thickness, is observed under light illumination. Using Drude's modified frequency dependent bulk electron scattering rates and surface mediated SPPs‐electron scattering rates, a generic model is proposed for addressing unambiguously the increased device resistance in response to light. The featured synthesis process opens a new direction toward the growth of transition metal nitrides while the proposed model serves as a basic platform to understand photo‐induced electron scattering mechanisms in metal.

First-principles study of mechanical and magnetic properties of transition metal (M) nitrides in the cubic M4N structure

We report results from systematic calculations performed by density functional theory on mechanical properties of twenty-eight 3 d, 4 d and 5 d transition metal (M) nitrides (TMNs) in metal-rich cubic M4N structure as novel candidates for hard coatings materials. We have computed lattice constants, elastic constants, derived moduli and ratios which characterize mechanical properties, and other properties like magnetic moments, formation energies, Debye temperature and Bader charge transfer. Our calculations indicate that all M4N-type metal nitrides except V4N, Nb4N, and Pt4N are mechanically stable. All Group 7 TMNs in the M4N structure are found to have high Vickers hardness values with the highest being 24.3 GPa for Re4N. Our computed lattice constants and magnetic dipole moments for Mn4N and Fe4N, the two compounds for which experimental measurements exist, are consistent with their measured values. Spin-polarized computations reduce the hardness of some magnetic compounds like Mn4N and Fe4N. The total density of states calculation reveals that all 28 M4N phases are metallic. The hybridization of metal d and nitrogen 2p orbitals is found to be the key factor in determining mechanical stability and hardness in these compounds. In contrast, ionicity, as computed by Bader charge transfer, does not correlate with hardness. Our comprehensive database for binary transition metal nitrides in M4N structure offers wide possibilities for experimental synthesis of such materials with desirable physical properties for the hard-coatings application.

Valence electron concentration as an indicator for mechanical properties in rocksalt structure nitrides, carbides and carbonitrides

First-principles calculations are employed to determine the mechanical properties of rock-salt structure binary and ternary transition metal nitrides, carbides, and carbonitrides from groups 4 to 12, predicting a unified indicator for mechanical properties: the valence electron concentration (VEC). Pugh's and Poisson's ratios indicate an increasing ductility with increasing VEC, with a brittle-to-ductile transition at a critical VEC = 10. The calculated C44 of carbonitrides and ternary nitrides monotonically decreases from 164 ± 12 GPa at VEC = 8 to −39 ± 46 GPa at VEC = 11, indicating a transition to mechanical instability at VEC = 10.6. Similarly, the average isotropic elastic modulus decreases slightly from 420 GPa for VEC = 8 to 388 GPa for VEC = 10, but then steeply to −98 GPa for VEC = 11, while the corresponding hardness decreases from 25 to 12 to 2 GPa. The overall softening with increasing VEC is attributed to the increasing electron density in d–t2g orbitals, which overlap upon shear and cause a decrease in C44. Phonon dispersion curves, calculated at 0 K for binary nitrides and carbides, exhibit imaginary frequencies for VEC ≥10, indicating a dynamical stability-to-instability transition between VEC = 9 and 10, which is smaller than the critical VEC = 10.6 for the mechanical stability-instability transition. In addition, mechanical stability is increased by magnetic ordering but decreased when accounting for on-site Coulomb repulsion, while temperature and vacancies cause a reduction in the magnitude of C44 for both stable and unstable compounds, likely leading to an increase in the critical VEC for the stability-instability transition. The overall results indicate a narrow region between VEC = 9 and 10 where rocksalt carbonitrides are ductile but also exhibit a high hardness, mechanical and dynamical stability, and therefore are expected to exhibit the highest toughness.

Platinum decorated hierarchical porous structures composed of ultrathin titanium nitride nanoflakes for efficient methanol oxidation reaction

Alloying Pt electrocatalysts with the second transition metal (e.g., Fe, Co, Ni and Cu) is an effective strategy to boost the methanol oxidation reaction (MOR) and simultaneously reduce the catalyst cost for the direct methanol fuel cells. However, the durability issues caused by the leaching of the transition metals for prolonged time and carbon corrosion hinder the practical applications of the Pt alloys. Herein, for the first time, a facile and robust strategy is developed to synthesize titanium nitride and copper doped titanium nitride with porous and hierarchical tubular structures (labeled as TiN NFs and Ti0.9Cu0.1N NFs, respectively). When used as the Pt support, both of Pt/TiN NFs and Pt/Ti0.9Cu0.1N NFs exhibit much enhanced activity and durability compared with the commercial Pt/C catalyst. The experimental data confirms that the leaching of the transition metal can be significantly impeded by this strategy while their advantageous properties that favors MOR activity for the Pt based catalysts are maintained. This work opens a new path for maximizing the MOR activity and stability by introducing porous binary transition metal nitride as the Pt support, which integrates the advantages of high stability, co-catalysis and doping effects.

Thermal stability and mechanical properties of Ti-Al-B-N thin films

The increasing demand in machining and drilling operations calls for new developments of protective coatings with outstanding properties. Meeting these challenging requirements, nitride based thin films have been well established and investigated. In recent years, this development has led - from binary transition metal nitrides (e.g. TiN, CrN) - to multinary alloyed thin films. The oxidation resistance and high temperature hardness of TiN was significantly improved through the addition of aluminum, to form supersaturated c-Ti1−xAlxN thin films. This system allows for age-hardening processes (via spinodally formed cubic Al- and Ti-rich domains) and increased oxidation resistance due to the formation of protective Al2O3-containing oxide scales.In this study, we investigate the influence of boron addition to further improve the already excellent thermal and mechanical properties of Ti1−xAlxN, using reactive magnetron sputtering of B-alloyed Ti1−xAlx targets. In addition to detailed experimental investigations, we study the preferred lattice sites of boron and the influence on phase stability by density functional theory (DFT) calculations.The calculations suggest that energetically, boron prefers the metal sublattice (hence, the formation of (Ti1−xAlx)1−yByN is preferred over Ti1−xAlxByN1−y). The cubic-to-wurtzite phase transition is unchanged for Ti1−xAlxByN1−y solid solutions, but shifts to lower Al contents for (Ti1−xAlx)1−yByN solid solutions, with increasing B. Furthermore, the experimental results show, that due to the addition of boron, the hardness of a w-Ti1−xAlxN thin film significantly increases to ~31GPa after annealing at 1000°C.

Atomic defects and dopants in ternary Z-phase transition-metal nitrides CrMN with M=V , Nb, Ta investigated with density functional theory

A density functional theory study of atomic defects and dopants in ternary Z-phase transition-metal nitrides CrMN with M=V, Nb, or Ta is presented. Various defect formation energies of native point defects and of substitutional atoms of other metal elements which are abundant in the steel as well, are evaluated. The dependence thereof on the thermodynamic environment, i.e. the chemical conditions of a growing Z-phase precipitate, is studied and different growth scenarios are compared. The results obtained may help to relate results of experimental atomic-scale analysis, by atom probe tomography or transmission electron microscopy, to the theoretical modeling of the formation process of the Z phase from binary transition metal nitrides.

Activated Carbon Supported Mo-Ti-N Binary Transition Metal Nitride as Catalyst for Acetylene Hydrochlorination

Recently, many scientists have focused on the development of green industrial technology. However, the process of synthesizing vinyl chloride faces the problem of Hg pollution. Via a novel approach, we used two elements Mo and Ti to prepare an inexpensive and green binary transition metal nitride (BTMN) as the active ingredient in a catalyst with nano-sized particles and an excellent degree of activation, which was supported on activated carbon. When the Mo/Ti mole ratio was 3:1, the conversion of acetylene reached 89% and the selectivity exceeded 98.5%. The doping of Ti in Mo-based catalysts reduced the capacity of adsorption for acetylene and also increased the adsorption of hydrogen chloride. Most importantly, the performance of the BTMN excelled those of the individual transition metal nitrides, due to the synergistic activity between Mo and Ti. This will expand the new epoch of the employment of transition metal nitrides as catalysts in the hydrochlorination of acetylene reaction.

Titanium vanadium nitride electrode for micro-supercapacitors

Here we report on the synthesis of binary transition metal nitride electrodes based on titanium vanadium nitride (TiVN) thin films. These films were deposited by a method compatible with micro-electronic processes which consists of DC co-sputtering of vanadium (V) and titanium (Ti) targets. TiVN films with different Ti/V ratio were deposited. A dependence of the capacitance and the cycling stability with the Ti/V atomic ratio in the films was established. While V rich sample exhibits a Faradic behavior that limits its cycling ability despite a high areal and volumetric capacity, the addition of Ti in the film drastically improves the cycling ability with virtually no fade in capacitance after 10,000cycles. Furthermore, a 1.1 Ti/V ratio leads to an areal capacitance up to 15mF·cm−2 in 1M KOH electrolyte solution. Such electrodes shed light on the use of binary transition metal nitrides as candidate electrodes for micro-supercapacitor.

A high-performance composite ORR catalyst based on the synergy between binary transition metal nitride and nitrogen-doped reduced graphene oxide

The synergy between binary transition metal nitride and nitrogen-doped reduced graphene oxide makes TiCoNx/N-rGO an outstanding ORR catalyst.

Platinum nanoparticles decorated robust binary transition metal nitride–carbon nanotubes hybrid as an efficient electrocatalyst for the methanol oxidation reaction

Abstract Titanium cobalt nitride (TiCoN)–CNTs hybrid support is prepared by a facile and efficient method, including a one-pot solvothermal process followed by a nitriding process, and this hybrid support is further decorated with Pt nanoparticles to catalyze the oxidation of methanol. The catalyst is characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. Notably, Pt/CNTs@TiCoN catalyst exhibits a much higher mass activity and durability than that of the conventional Pt/C (JM) for methanol oxidation. The experimental data indicates that the CNTs@TiCoN hybrid support combines the merits of the CNTs’s high conductivity and the superb corrosion resistance of external TiCoN coating.

Plasmonic spectral tunability of conductive ternary nitrides

Conductive binary transition metal nitrides, such as TiN and ZrN, have emerged as a category of promising alternative plasmonic materials. In this work, we show that ternary transition metal nitrides such as TixTa1−xN, TixZr1−xN, TixAl1−xN, and ZrxTa1−xN share the important plasmonic features with their binary counterparts, while having the additional asset of the exceptional spectral tunability in the entire visible (400–700 nm) and UVA (315–400 nm) spectral ranges depending on their net valence electrons. In particular, we demonstrate that such ternary nitrides can exhibit maximum field enhancement factors comparable with gold in the aforementioned broadband range. We also critically evaluate the structural features that affect the quality factor of the plasmon resonance and we provide rules of thumb for the selection and growth of materials for nitride plasmonics.

Binary transition metal nitrides with enhanced activity and durability for the oxygen reduction reaction

Binary transition metal nitrides demonstrate high activity and stability/durability for the oxygen reduction reaction in both acid and alkaline media.

Trends in the elastic response of binary early transition metal nitrides

Motivated by an increasing demand for coherent data that can be used for selecting materials with properties tailored for specific application requirements, we studied elastic response of nine binary early transition metal nitrides (ScN, TiN, VN, YN, ZrN, NbN, LaN, HfN, and TaN) and AlN. In particular, single crystal elastic constants, Young's modulus in different crystallographic directions, polycrystalline values of shear and Young's moduli, and the elastic anisotropy factor were calculated. Additionally, we provide estimates of the third order elastic constants for the ten binary nitrides.

Synthesis of Binary Transition Metal Nitrides, Carbides and Borides from the Elements in the Laser-Heated Diamond Anvil Cell and Their Structure-Property Relations.

Transition metal nitrides, carbides and borides have a high potential for industrial applications as they not only have a high melting point but are generally harder and less compressible than the pure metals. Here we summarize recent advances in the synthesis of binary transition metal nitrides, carbides and borides focusing on the reaction of the elements at extreme conditions generated within the laser-heated diamond anvil cell. The current knowledge of their structures and high-pressure properties like high-() stability, compressibility and hardness is described as obtained from experiments.