Redox and Catalytic Properties of Copper Molybdates with Various Composition

Sołtys, E.; Urazov, Kh. Kh.; Kharlamova, Tamara; Vodyankina, O. V.

doi:10.1134/s0023158418010111

Cited by 13 publications

(5 citation statements)

References 45 publications

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“…Cu1 and Cu3 sites form four long (2.054(4) -2.376(3) Å) and two short (1.898(2) -1.935(4) Å) bonds each, which is rather uncommon. A similar coordination was also observed for Cu 2+ in the structures of CuMoO 4 (Soltys et al 2018) and in Cu-doped Zn 3 O(MoO 4 ) 2 (Sohnel et al 1996). Cu [4+2] coordination is also observed in the structure of volborthite (Basso et al 1988), wherein Cu1 atom forms four long equatorial bonds of 2.172(6) Å, and two short apical bonds of 1.938(6) Å.…”

Section: Vergasovaite Mineral Sample (Vm)supporting

confidence: 68%

Vergasovaite to cupromolybdite topotactic transformation with crystal shape preservation

Nazarchuk,

Siidra,

Charkin

et al. 2024

American Mineralogist

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Thermal behavior of vergasovaite, ideally Cu 3 O(SO 4 )(MoO 4 ), and its synthetic analogue has been studied by high-temperature single crystal X-ray diffraction in the temperature range of 300-1100 K. According to the EMPA results, the empirical formulas are (Cu 2.36 Zn 0.61 ) ∑=2.97 O[(Mo 0.91 S 0.08 V 0.04 ) ∑=1.03 O 4 ](SO 4 ) for vergasovaite and Cu 2.97 O[(Mo 0.92 S 0.09 ) ∑=1.01 O 4 ](SO 4 ) for its synthetic analogue. The mineral is stable until 950±15 K; at 975 K, the unit-cell parameters and volume increase abruptly due to topotactic transformation of vergasovaite into cupromolybdite, Cu 3 O(MoO 4 ) 2 . The transformation is accompanied by loss of sulfur (and excess copper) without destruction of the crystal. The thermal expansion of the vergasovaite structure is strongly anisotropic, being minimal along the [O 2 Cu 6 ] 8+ chains comprised of vertex-sharing OCu 4 tetrahedra. The peculiarities of the thermal expansion of vergasovaite can be explained by the anisotropy of bond length evolution in the Cu1O 6 and Cu3O 6 octahedra and flexibility of the S-O-Cu and Mo-O-Cu bond angles. Synthetic Zn-and V-free analogue demonstrates negative thermal expansion at 425-625 K and melts at as low temperature as 700 K with no indication of transformation or recrystallization at least below 1200 K.

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Section: Vergasovaite Mineral Sample (Vm)supporting

confidence: 68%

Vergasovaite to cupromolybdite topotactic transformation with crystal shape preservation

Nazarchuk,

Siidra,

Charkin

et al. 2024

American Mineralogist

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“…In the last decades, the optical, magnetic, and semiconductor properties of materials containing copper ions have been associated with many applications. − In this context, antimicrobial, photoluminescent, catalytic, magnetic, and solar cell applications have been reported. Therefore, solid solutions with copper ions have been associated with an increase of optical, structural, catalytic, and magnetic properties, when compared with the pure structures.…”

Section: Introductionmentioning

confidence: 99%

Structural and Optical Properties of Ca_0.9Cu_0.01WO₄ Solid Solution Synthesized by Sonochemistry Method at Room Temperature

Nobre¹,

Nogueira

Souza

et al. 2020

Inorg. Chem.

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In this work, we report the room-temperature synthesis of pure calcium tungstate (CaWO 4 ) and copper-doped calcium tungstate solid solution (Ca 0.99 Cu 0.01 WO 4 ) by using a sonochemistry method. These materials were structurally characterized by X-ray diffraction (XRD) and Raman spectroscopy. The obtained XRD patterns were submitted to a Rietveld refinement showing, in both materials, a tetragonal phase with space group and point group of I4 1 /a and C 4h 6 , respectively. Microscopy images of both materials, obtained by field emission scanning electron microscopy, showed spherical agglomerated structures composed by spherical nanoparticles, while calcium and tungstate elements were identified by energy-dispersive X-ray spectroscopy for pure calcium tungstate and copper, calcium, and tungstate for Ca 0.99 Cu 0.01 WO 4 solid solution. The decrease of optical band gap (E gap ) from 4.0 eV (CaWO 4 ) to 3.45 eV (Ca 0.99 Cu 0.01 WO 4 ) confirmed the substitution of calcium atoms for copper atoms in the clusters [CaO 8 ]. Maximum photoluminescence (PL) emission was shifted from 522 nm in the pure CaWO 4 to 475 nm in the Ca 0.99 Cu 0.01 WO 4 solid solution. Consequently, there was an increase of PL emissions intensity in the blue and green regions of the visible spectrum, due to electronic transitions between the orbitals O 2p, Cu 3d, and W 5d.

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“…Copper is known to replace O atoms within the crystalline matrix, forming copper molybdates. [40][41][42] The alloy formation can be associated with Cu y MoO 3 quasi-ternary system as suggested in previous studies [43] that results in formation of Mo 5+ and is accompanied by formation of the MoO 2 sub-oxidation. The increase of the oxygen partial pressure results in re-oxidation of the MoO 2 sub-oxide as well as diffusion of the oxygen to the substrate and oxidation of the copper while the saturated ternary phase remains persistent.…”

Section: Discussionmentioning

confidence: 99%

Metallic Interface Induced Ionic Redistribution within Amorphous MoO₃ Films

Paparoni

Mijiti

Minicucci

et al. 2022

Adv Materials Inter

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molybdenum oxides recently attracted the attention, due to the peculiar features of this class of oxide, originating from the interplay between the large variety of lattice configuration and the multiple valence states of Mo. [5][6][7] Even though MoO 3 is a high-k dielectric insulator, its electronic structure can be adjusted by modifying the oxygen substoichiometry (MoO 3−x ), introducing electronic gap states that modifies the oxide's electrical conductivity. [8,9] The stoichiometric MoO 3 is an n-type material with an equilibrium concentration of defects (mainly oxygen vacancies), which cause the formation of Mo 5+ , that partially occupies Mo 4d band creating gap states. These states play as n-type dopant, push the MoO 3 Fermi level closer to the conduction band. A continuous removal of oxygen may reduce MoO 3 to MoO 2 , the lowest stable molybdenum oxide, which contains Mo 4+ cations, that give rise to a partially filled 4d band resulting in semi-metallic states.The consequent electronic properties of the vacancy formation have shown applicability across a number of technological fields, including promising electrochromic, battery cathode material, and gas sensors. [10,11] It has also been shown thatThe phase evolution and ionic redistribution in amorphous MoO 3 films, deposited on metallic aluminium (Al) and copper (Cu) substrates and subjected to distinct thermal treatments, are systematically investigated in this work. It is shown that the metallic interface significantly modifies the formation and dynamics of oxygen vacancies within the resulted structure, reducing the oxygen content of the MoO 3 up to x < 2.94. The concentration of the oxygen vacancies can also be extended to the bulk via thermal treatment up to 400 °C. It is demonstrated that the MoO 3 structure on metallic substrates is affected either by the diffusion of the metallic atoms inserted from the interface, which results in a formation of the meta-stable alloy phases in case of Cu, or by the introduction of the oxygen vacancies into the crystalline matrix in case of Al. The oxygen vacancy density in the MoO 3 films with a metallic interface can be tuned via optimal choice of the metal and treatment parameters such as temperature and oxygen partial pressure. Furthermore, the intrinsic defects present in the amorphous structure enhance the ionic mobility and diffusion of the metallic ions inside the crystalline structure.

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Redox and Catalytic Properties of Copper Molybdates with Various Composition

Cited by 13 publications

References 45 publications

Vergasovaite to cupromolybdite topotactic transformation with crystal shape preservation

Vergasovaite to cupromolybdite topotactic transformation with crystal shape preservation

Structural and Optical Properties of Ca_0.9Cu_0.01WO₄ Solid Solution Synthesized by Sonochemistry Method at Room Temperature

Metallic Interface Induced Ionic Redistribution within Amorphous MoO₃ Films

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Redox and Catalytic Properties of Copper Molybdates with Various Composition

Cited by 13 publications

References 45 publications

Vergasovaite to cupromolybdite topotactic transformation with crystal shape preservation

Vergasovaite to cupromolybdite topotactic transformation with crystal shape preservation

Structural and Optical Properties of Ca0.9Cu0.01WO4 Solid Solution Synthesized by Sonochemistry Method at Room Temperature

Metallic Interface Induced Ionic Redistribution within Amorphous MoO3 Films

Contact Info

Product

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Structural and Optical Properties of Ca_0.9Cu_0.01WO₄ Solid Solution Synthesized by Sonochemistry Method at Room Temperature

Metallic Interface Induced Ionic Redistribution within Amorphous MoO₃ Films