Molybdenum dioxide

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Molybdenum dioxide
Names
IUPAC name
Molybdenum(IV) oxide
Other names
Molybdenum dioxide
Tugarinovite
Identifiers
ECHA InfoCard 100.038.746 Edit this at Wikidata
Properties
MoO2
Molar mass 127.94 g/mol
Appearance brownish-violet solid
Density 6.47 g/cm3
Melting point 1,100 °C (2,010 °F; 1,370 K) decomposes
insoluble
Solubility insoluble in alkalies, HCl, HF
slightly soluble in hot H2SO4
+41.0·10−6 cm3/mol
Structure
Distorted rutile (monoclinic)
Octahedral (MoIV); trigonal (O−II)
Hazards
Flash point Non-flammable
Related compounds
Other anions
 Molybdenum disulfide
Other cations
 Chromium(IV) oxide
Tungsten(IV) oxide
"Molybdenum blue"
Molybdenum trioxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Molybdenum dioxide is the chemical compound with the formula MoO2. It is a violet-colored solid and is a metallic conductor. The mineralogical form of this compound is called tugarinovite, and is only very rarely found. The discovery and early studies of molybdenum dioxide date back to the late 18th and early 19th centuries. One of the notable figures in the history of molybdenum dioxide is the Hungarian chemist Jakob Joseph Winterl (1732-1809). Winterl, who was a professor of chemistry and botany at the University of Budapest, made significant contributions to the understanding of molybdenum compounds. In 1787, he proposed that copper was a compound of nickel, molybdenum, silica, and a volatile substance, showcasing his interest in molybdenum chemistry[1].

Structure[edit]

Molybdenum dioxide (MoO2) exists in various crystalline forms, with the most common being the monoclinic (α-MoO2) and hexagonal structures[2]. It crystallizes in a monoclinic cell, and has a distorted rutile, (TiO2) crystal structure. In TiO2 the oxide anions are close packed and titanium atoms occupy half of the octahedral interstices (holes). In MoO2 the octahedra are distorted, the Mo atoms are off-centre, leading to alternating short and long Mo – Mo distances and Mo-Mo bonding. The short Mo – Mo distance is 251 pm which is less than the Mo – Mo distance in the metal, 272.5 pm. The bond length is shorter than would be expected for a single bond. The bonding is complex and involves a delocalisation of some of the Mo electrons in a conductance band accounting for the metallic conductivity.[3]

Preparation[edit]

One common approach for synthesizing molybdenum dioxide (MoO2) is through the thermal decomposition of molybdenum-containing precursor compounds. For example, ammonium molybdate tetrahydrate ((NH4)6Mo7O24·4H2O) can be used as a precursor and thermally decomposed on an activated carbon support to form crystalline MoO2[4]. The decomposition typically occurs at temperatures in the range of 450-550°C[4]. The thermal behavior and decomposition mechanism of bis(alkylimido)-dichloromolybdenum(VI) adducts with neutral N,N'-chelating ligands has also been studied as precursors for MoO2[5]. It was found that the decomposition follows a general pathway, proceeding first by dissociation of the chelating ligand, then dimerization, intramolecular hydrogen transfer, and ultimately decomposition into molybdenum nitride or carbide species[5]. Understanding the thermal decomposition of Mo precursors is important for designing vapor-phase deposition processes for MoO2 thin films[5].

MoO2 can also be prepared :

  • by reduction of MoO3 with Mo over the course of 70 hours at 800 °C (1,470 °F). The tungsten analogue, WO2, is prepared similarly.
2 MoO3 + Mo → 3 MoO2
  • by reducing MoO3 with H2 or NH3 below 470 °C (878 °F) [6]

Single crystals are obtained by chemical transport using iodine. Iodine reversibly converts MoO2 into the volatile species MoO2I2.[7]

Uses[edit]

Electronic Applications

Molybdenum dioxide has shown promise in electronic applications due to its high work function and unique properties. In a study on symmetrical junction non-aligned double gate n-channel field effect transistors (NADGNFETs), researchers investigated the effects of metal work function and dielectric constant on device performance[8]. They found that using molybdenum, with a work function of 4.75 eV, as the gate metal significantly affected analog figures of merit such as ON current, ON/OFF current ratio, threshold voltage, and intrinsic gain.

Another study focused on the reliable synthesis of high work-function molybdenum dioxide via atomic layer deposition for next-generation electrode applications[9]. This highlights the potential of MoO2 in advanced electronic devices.

Energy Storage

Molybdenum dioxide has been explored as a component in energy storage systems, particularly in lithium-sulfur (Li-S) batteries. One study prepared one-dimensional molybdenum dioxide–carbon nanofibers (MoO2–CNFs) using an electrospinning technique. When used as a matrix in sulfur/MoO2–CNF cathodes for Li-S batteries, these nanofibers acted as polysulfide reservoirs to alleviate the shuttle effect and improve electrochemical reaction kinetics during charge–discharge processes. The sulfur/MoO2–CNF composites demonstrated high lithium-ion diffusion coefficients, low interfacial resistance, and better electrochemical performance compared to pristine sulfur cathodes.

Another study synthesized nanocomposites of carbon nanotubes (CNTs) with homogeneously anchored MoO2 nanoparticles using a hydrothermal method[10]. When used as an anode in lithium-ion batteries, these MoO2/CNT nanocomposites delivered a higher reversible capacity compared to MoO3 nanobelt/CNT composites and pure MoO2 nanoparticles. The enhanced performance was attributed to the nanocomposite structure, which efficiently enhanced electrical conductivity, lithium-ion diffusion, and maintained electrode integrity during cycling.

Catalysis

Molybdenum dioxide and related compounds have shown catalytic properties in various reactions. One study investigated supported molybdenum carbide and nitride catalysts for carbon dioxide hydrogenation[11]. The catalysts, prepared by wet impregnation followed by thermal treatment, were able to produce CO, methane, methanol, and ethane from CO2. The carbide activity increased with lower carburizing alkane concentration and temperature, and enhanced performance was obtained with pure anatase titania support.

Another study explored the use of liquid or supercritical carbon dioxide (scCO2) as a reaction medium for ring-opening metathesis polymerization (ROMP) and ring-closing olefin metathesis (RCM) reactions using well-defined metal catalysts, including a molybdenum alkylidene complex[12]. The unique properties of scCO2 provided advantages such as convenient workup procedures, catalyst immobilization, and reaction tuning by density control.

Molybdenum dioxide is a constituent of "technical molybdenum trioxide" produced during the industrial processing of MoS2:[13][14]

2 MoS2 + 7 O2 → 2 MoO3 + 4 SO2
MoS2 + 6 MoO3 → 7 MoO2 + 2 SO2
2 MoO2 + O2 → 2 MoO3

MoO2 has been reported as catalysing the dehydrogenation of alcohols,[15] the reformation of hydrocarbons[16] and biodiesel.[17] Molybdenum nano-wires have been produced by reducing MoO2 deposited on graphite.[18] Molybdenum dioxide has also been suggested as possible anode material for Li-ion batteries.[19][20]

References[edit]

  1. ^ Snelders, H. A. M. (July 1970). "The Influence of the Dualistic System of Jakob Joseph Winterl (1732-1809) on the German Romantic Era". Isis. 61 (2): 231–240. doi:10.1086/350622. ISSN 0021-1753.
  2. ^ Lüdtke, Tobias; Wiedemann, Dennis; Efthimiopoulos, Ilias; Becker, Nils; Seidel, Stefan; Janka, Oliver; Pöttgen, Rainer; Dronskowski, Richard; Koch-Müller, Monika; Lerch, Martin (2017-02-20). "HP-MoO2: A High-Pressure Polymorph of Molybdenum Dioxide". Inorganic Chemistry. 56 (4): 2321–2327. doi:10.1021/acs.inorgchem.6b03067. ISSN 1520-510X. PMID 28181799.
  3. ^ Oxides: Solid state chemistry McCarroll W.H. Encyclopedia of Inorganic Chemistry Ed R. Bruce King, (1994), John Wiley & sons ISBN 0-471-93620-0
  4. ^ a b Moulahi, Ali (2020). "Controlled Hydrothermal Synthesis of Nano-MoO2 as Anode for Lithium Ion Battery". Indian Journal of Science and Technology. 13 (3): 277–285. doi:10.17485/ijst/2020/v13i03/149476. S2CID 222117900.
  5. ^ a b c Land, Michael A.; Bačić, Goran; Robertson, Katherine N.; Barry, Seán T. (2022-10-24). "Origin of Decomposition in a Family of Molybdenum Precursor Compounds". Inorganic Chemistry. 61 (42): 16607–16621. doi:10.1021/acs.inorgchem.2c01967. ISSN 1520-510X. PMID 36223133.
  6. ^ Cotton, F. Albert; Wilkinson, Geoffrey; Murillo, Carlos A.; Bochmann, Manfred (1999), Advanced Inorganic Chemistry (6th ed.), New York: Wiley-Interscience, ISBN 0-471-19957-5
  7. ^ Conroy, L. E.; Ben-Dor, L. "Molybdenum(IV) Oxide and Tungsten(IV) Oxides Single-Crystals" Inorganic Syntheses 1995, volume 30, pp. 105–107. ISBN 0-471-30508-1
  8. ^ Sinha, Arun Kumar; Naik, Banoth Vasu (2023-12-14). "Evaluating Performance Using kϕ Index Parameter for a Symmetrical Junction NADGFET: A 3D TCAD Simulation Analysis". 2023 International Conference on Next Generation Electronics (NEleX). IEEE. pp. 1–5. doi:10.1109/nelex59773.2023.10420946. ISBN 979-8-3503-1908-8.
  9. ^ Kim, Ye Won; Lee, Ae Jin; Han, Dong Hee; Lee, Dae Cheol; Hwang, Ji Hyeon; Kim, Youngjin; Moon, Songyi; Youn, Taewon; Lee, Minyung; Jeon, Woojin (2022). "Correction: Reliable high work-function molybdenum dioxide synthesis via template-effect-utilizing atomic layer deposition for next-generation electrode applications". Journal of Materials Chemistry C. 10 (36): 13268–13269. doi:10.1039/d2tc90174a. ISSN 2050-7526.
  10. ^ Qiu, Song; Lu, Guixia; Liu, Jiurong; Lyu, Hailong; Hu, Chenxi; Li, Bo; Yan, Xingru; Guo, Jiang; Guo, Zhanhu (2015-10-13). "Enhanced electrochemical performances of MoO2 nanoparticles composited with carbon nanotubes for lithium-ion battery anodes". RSC Advances. 5 (106): 87286–87294. doi:10.1039/C5RA17147D. ISSN 2046-2069.
  11. ^ Abou Hamdan, Marwa; Nassereddine, Abdallah; Checa, Ruben; Jahjah, Mohamad; Pinel, Catherine; Piccolo, Laurent; Perret, Noémie (2020). "Supported Molybdenum Carbide and Nitride Catalysts for Carbon Dioxide Hydrogenation". Frontiers in Chemistry. 8. doi:10.3389/fchem.2020.00452. ISSN 2296-2646. PMID 32582635.
  12. ^ Fürstner, A.; Ackermann, L.; Beck, K.; Hori, H.; Koch, D.; Langemann, K.; Liebl, M.; Six, C.; Leitner, W. (2001-09-19). "Olefin metathesis in supercritical carbon dioxide". Journal of the American Chemical Society. 123 (37): 9000–9006. doi:10.1021/ja010952k. ISSN 0002-7863. PMID 11552807.
  13. ^ Metallurgical furnaces Jorg Grzella, Peter Sturm, Joachim Kruger, Markus A. Reuter, Carina Kogler, Thomas Probst, Ullmans Encyclopedia of Industrial Chemistry
  14. ^ "Thermal Analysis and Kinetics of Oxidation of Molybdenum Sulfides" Y. Shigegaki, S.K. Basu, M.Wakihara and M. Taniguchi, J. Therm. Analysis 34 (1988), 1427-1440
  15. ^ A. A. Balandin and I. D. Rozhdestvenskaya, Russian Chemical Bulletin, 8, 11, (1959), 1573 doi:10.1007/BF00914749
  16. ^ Molybdenum based catalysts. I. MoO2 as the active species in the reforming of hydrocarbons A. Katrib, P. Leflaive, L. Hilaire and G. Maire Catalysis Letters, 38, 1–2, (1996) doi:10.1007/BF00806906
  17. ^ Catalytic partial oxidation of a biodiesel surrogate over molybdenum dioxide, C.M. Cuba-Torres, et al, Fuel (2015), doi:10.1016/j.fuel.2015.01.003
  18. ^ Synthesis of Molybdenum Nanowires with Millimeter-Scale Lengths Using Electrochemical Step Edge Decoration M. P. Zach, K. Inazu, K. H. Ng, J. C. Hemminger, and R. M. Penner Chem. Mater. (2002),14, 3206 doi:10.1021/cm020249a
  19. ^ Shi, Yifeng; Guo, Bingkun; Corr, Serena A.; Shi, Qihui; Hu, Yong-Sheng; Heier, Kevin R.; Chen, Liquan; Seshadri, Ram; Stucky, Galen D. (2009-12-09). "Ordered Mesoporous Metallic MoO2 Materials with Highly Reversible Lithium Storage Capacity". Nano Letters. 9 (12): 4215–4220. doi:10.1021/nl902423a. ISSN 1530-6984. PMID 19775084.
  20. ^ Kim, Hyung-Seok; Cook, John B.; Tolbert, Sarah H.; Dunn, Bruce (2015-01-01). "The Development of Pseudocapacitive Properties in Nanosized-MoO2". Journal of the Electrochemical Society. 162 (5): A5083–A5090. doi:10.1149/2.0141505jes. ISSN 0013-4651. OSTI 1370243.
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