Combustion Synthesis and Electrical Behavior of Nanometric β-NiMoO₄

Abstract

Metallic molybdates are of great importance for their potential use as catalysts of selective nature. The synthesis of the β-NiMoO4 phase is not simple and has been approached employing different methods; however, combustion synthesis has never been proposed before. This work describes the synthesis of nanometric β-NiMoO4 powders from mixtures of Ni (II) and Mo (VI) acetylacetonates as cation precursors and urea as fuel. The characterization of the as-prepared combustion product showed that the combustion synthesis provides a straightforward method for the achievement of β-NiMoO4. This phase, prepared by this method, is stable at room temperature in the absence of NiO. The as-prepared powders are nanometric (∼6 nm as observed by TEM) and have a specific surface area of 31 ± 7 m2/g. Both parameters are crucial for an enhancement of its catalyst activity. As the β-NiMoO4 phase is not stable at room temperature its preparation is discussed taking into account its evolution with temperature and the synthesis conditions which promote metastable phases due to a high exothermic energy release followed by a rapid cooling. The electrical conductivity is determined in air as a function of temperature and discussed in relation with the phase transition that takes place promoted by temperature.

Bimetallic single-source precursor for the synthesis of pure nanocrystalline room temperature-stabilized β-NiMoO 4

“…Metal molybdates are important ternary oxide ceramics with unique chemical and physical properties [1][2][3][4][5][6][7] that enable their use as catalysts for the catalytic oxidative dehydrogenation (ODH) of light alkanes to their corresponding olefins [8][9][10][11][12][13]. Nickel molybdate (NiMoO 4 ) is the most active and selective catalyst of these for converting propane to propylene [14,15].…”

Phase-pure β-NiMoO4 yolk-shell spheres for high-performance anode materials in lithium-ion batteries

“…Two phases (a and b) usually exist at atmospheric pressure, which are both monoclinic but exhibit different Mo coordination, i.e., of octahedral and tetrahedral sites, respectively [15][16][17][18][19][20][21][22][23]. The a phase is stable at room temperature, whereas the b phase starts to crystallize between 550 and 670 C. The electrochemical properties of the materials are closely dependent on their crystal structures and morphologies.…”

“…The a phase is stable at room temperature, whereas the b phase starts to crystallize between 550 and 670 C. The electrochemical properties of the materials are closely dependent on their crystal structures and morphologies. However, there have only been a few studies on a and b phase mixtures for LIB anode materials because of the difficulties involved in preparing the pure b phase [23][24][25]. For example, Haetge et al [15] prepared nanocrystalline a/b-NiMoO 4 thin film anodes with 3D honeycomb structures using polymer templates, and Park et al [18] suggested a/b-NiMoO 4 with a nanowire structure for the anode material.…”

Polyol‐Mediated Synthesis and Properties of Nanoscale Molybdates/Tungstates: Color, Luminescence, Catalysis

“…Studies on the synthesis, characterization, and properties of nanoscale metal molybdates and tungstates, however, have comparably limited to date. Most often nanoscale molybdates and tungstates have been gained via simple water-based precipitation, [ 3 ] freeze-drying, [ 8 ] hydrothermal/solvothermal reactions, [ 9 ] thermal combustion, [ 10 ] or mechanochemical treatment. [ 11 ] Quite often the described materials were obtained with comparably large diameter (i.e., greater than 80 nm), and broad size distribution.…”