Mechanochemical Synthesis of Nanocrystalline Nickel Molybdates.

Abstract

Mechanochemistry H 3000Mechanochemical Synthesis of Nanocrystalline Nickel Molybdates. -NiMoO4 catalysts are prepared from 1:1 mixtures of NiO and MoO3 by intense mechanical treatment in air using a planetary ball mill for different periods of time ranging from 2.5 to 5 h. The samples are characterized by XRD, IR, and XPS. Single-phase α-NiMoO4 is obtained after 5 h milling at room temperature. Mechanochemical activation for 2.5 h results in the high-temperature β-NiMoO 4 phase. -(KLISSURSKI, D.; MANCHEVA*, M.; IORDANOVA, R.; TYULIEV, G.; KUNEV, B.; J. Alloys

Urea-Assisted Room Temperature Stabilized Metastable β-NiMoO4: Experimental and Theoretical Insights into its Unique Bifunctional Activity toward Oxygen Evolution and Supercapacitor

“…Such phase transitions in the case of nickel molybdates has previously been discussed by many researchers. 22,39 While the breaking of Mo−O bonds in the Mo coordination sphere at steep temperature could be one of the driving factor behind the phase shift, a low temperature transition to β-phase from NiMoO 4 .xH 2 O is also probable via much lower (∼280 °C) thermal treatment approach. 40 To the β-variant obtained here, no symmetry group has been assigned yet and thus no indexing has been carried out.…”

“…Besides the ternary metal oxides mentioned in the previous section, compounds like CoMoO 4 , MnMoO 4 , and NiMoO 4 , etc., collectively termed as molybdates are known for their excellent catalytic properties of industrial repute. 22,23 They are complex in both nature and structure, which keeps them in a distinguished category of mixed-metal oxides. Among them, NiMoO 4 shows better prospect for both supercapacitor electrode material and OER catalyst due to the dynamicity and superior electrochemical activity shown by its cations.…”

“…24 Apart from that, NiMoO 4 has got a huge number of polymorphs and two of them, that is, α-NiMoO 4 and β-NiMoO 4 , are noteworthy because of their peculiar lattice arrangement and mechanochemical transition effect. 22 The basic structural difference between these two polymorphs is the coordination state of Mo cation. In α-NiMoO 4 , the molybdenum ions coordinate with the oxygen atoms to form a pseudo-octahedral symmetry, 25 whereas in the case of β-NiMoO 4 , the molybdenum ions are coordinated in a distorted tetrahedral manner.…”

Synergistic effects of nanoarchitecture and oxygen vacancy in nickel molybdate hollow sphere towards a high‐performance hybrid supercapacitor

“…The sharp peak observed at 1396 cm −1 is assigned to the C‐H bending or Mo‐O‐Mo stretching vibration 33 . The series of peaks noticed at 960, 885, 805, 709, 615, and 486 cm −1 are assigned to the vibrational modes of distorted MoO 6 octahedra, Mo‐O‐Mo, Mo‐O, Ni‐O, and Mo‐O‐Ni, respectively 34‐36 …”

“…33 The series of peaks noticed at 960, 885, 805, 709, 615, and 486 cm À1 are assigned to the vibrational modes of distorted MoO 6 octahedra, Mo-O-Mo, Mo-O, Ni-O, and Mo-O-Ni, respectively. [34][35][36] The electrochemical performance of the Ov-NiMoO 4 and b-NiMoO 4 electrodes was further investigated by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) in a three-electrode setup into 6 M KOH as aqueous electrolyte, as presented in Figure 4 and Figure S2. The comparative CVs of the Ov-NiMoO 4 and b-NiMoO 4 electrodes at a constant scan rate of 25 mV s À1 are exhibited in Figure 4A.…”