Synthesis of transition metal nitride by nitridation of metastable oxide precursor

Transition Metal Nitrides for Electrocatalytic Application: Progress and Rational Design

The energy crisis and environmental issues are becoming more severe due to the long-term consumption of fossil fuels. Therefore, novel energy-conversion devices with high energy density and environmental friendliness are expected to provide reliable alternatives to traditional fossil-based energy systems. However, because of the inevitable use of costly precious metals as the electrode catalysts for such devices, their popularization is seriously hindered. Transition metal nitrides (TMNs) exhibit similar surface and adsorption properties to noble metals because the atomic distance between metal atoms increases and the d-band center of metal atoms downshifts after nitrogen atoms enter the metal lattice. TMNs have become one of the best electrode materials to replace noble metal-based electrocatalysts in next-generation energy-storage and energy-conversion devices. In this review, the recent developments in the electrocatalytic application of TMNs are covered. First, we discuss the structure and activity origin of TMNs and introduce the common synthesis methods for the preparation of TMNs. Subsequently, we illustrate the applications of mono-metallic TMNs and multi-metallic TMNs in oxygen-reduction reaction, oxygen-evolution reaction, and bifunctional oxygen reduction and evolution reactions. Finally, we summarize the challenges of TMNs encountered at the present stage, and expect their future development.

Study of Chemical and Morphological Transformations during Ni2Mo3N Synthesis via an Oxide Precursor Nitration Route

Chemical and morphological transformations during Ni2Mo3N synthesis were studied in this work. Nitride samples were synthesized from oxide precursors in H2/N2 flow and were analyzed by thermogravimetry, X-ray diffraction analysis, scanning electron microscopy, and energy dispersive X-ray spectroscopy methods. In addition, physical and chemical adsorption properties were studied using low-temperature N2 physisorption and NH3 temperature-programmed desorption. It was shown that nitride formation proceeds through a sequence of phase transformations: NiMoO4 + MoO3 → Ni + NiMo + MoO2 → Ni + NiMo + Mo2N → Ni2Mo3N. The weight changes that were calculated from the proposed reactions were in agreement with the experimental data from thermogravimetry. The morphology of the powder changed from platelets and spheres for the oxide sample, to aggregates of needle-like particles for the intermediate product, to porous particles with an extended surface area for the nitride final product. The obtained results should prove useful for subsequent Ni2Mo3N based catalysts production process optimization.

Metal non-oxide nanostructures developed from organic-inorganic hybrids and their catalytic application

The rational design of metal non-oxides is important for their catalytic application, which is however limited by the fact that the current synthetic strategies are short of effective control over formation reactions. Recently, the hybrids evenly integrating organic with inorganic molecules on a nanoscale significantly provided quasi-homogeneous reactions towards well-defined nanocatalysts of metal non-oxides, in which their structures and properties can be modulated in a wide range. Focusing on the nanostructures and the related catalytic behaviors, this feature article seeks to provide some control on the key structures and properties of metal non-oxides (e.g. carbides, nitrides, sulfides and selenides). It is thus anticipated to shed some light on the development of emerging materials for efficient catalysis, especially those used in energy utilization.

Atomic layer deposited molybdenum nitride thin film: a promising anode material for Li ion batteries

Molybdenum nitride (MoNx) thin films are deposited by atomic layer deposition (ALD) using molybdenum hexacarbonyl [Mo(CO)6] and ammonia [NH3] at varied temperatures. A relatively narrow ALD temperature window is observed. In situ quartz crystal microbalance (QCM) measurements reveal the self-limiting growth nature of the deposition that is further verified with ex situ spectroscopic ellipsometry and X-ray reflectivity (XRR) measurements. A saturated growth rate of 2 Å/cycle at 170 °C is obtained. The deposition chemistry is studied by the in situ Fourier transform infrared spectroscopy (FTIR) that investigates the surface bound reactions during each half cycle. As deposited films are amorphous as observed from X-ray diffraction (XRD) and transmission electron microscopy electron diffraction (TEM ED) studies, which get converted to hexagonal-MoN upon annealing at 400 °C under NH3 atmosphere. As grown thin films are found to have notable potential as a carbon and binder free anode material in a Li ion battery. Under half-cell configuration, a stable discharge capacity of 700 mAh g(-1) was achieved after 100 charge-discharge cycles, at a current density of 100 μA cm(-2).