Cerium(IV) oxide

Last updated
Cerium(IV) oxide
Cerium(IV) oxide.jpg
Ceria-3D-ionic.png
Names
IUPAC name
Cerium(IV) oxide
Other names
Ceric oxide,
Ceria,
Cerium dioxide
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.013.774 OOjs UI icon edit-ltr-progressive.svg
PubChem CID
UNII
  • InChI=1S/Ce.2O/q+4;2*-2 Yes check.svgY
    Key: OFJATJUUUCAKMK-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/Ce.2O/q+4;2*-2
    Key: OFJATJUUUCAKMK-UHFFFAOYAX
  • [O-2]=[Ce+4]=[O-2]
Properties
CeO2
Molar mass 172.115 g/mol
Appearancewhite or pale yellow solid,
slightly hygroscopic
Density 7.215 g/cm3
Melting point 2,400 °C (4,350 °F; 2,670 K)
Boiling point 3,500 °C (6,330 °F; 3,770 K)
insoluble
+26.0·10−6 cm3/mol
Structure
cubic crystal system, cF12 (fluorite) [1]
Fm3m, #225
a = 5.41 Å [2] , b = 5.41 Å, c = 5.41 Å
α = 90°, β = 90°, γ = 90°
Ce, 8, cubic
O, 4, tetrahedral
Hazards
NFPA 704 (fire diamond)
NFPA 704.svgHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
1
0
0
Related compounds
Related compounds
 Cerium(III) oxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Cerium(IV) oxide, also known as ceric oxide, ceric dioxide, ceria, cerium oxide or cerium dioxide, is an oxide of the rare-earth metal cerium. It is a pale yellow-white powder with the chemical formula CeO2. It is an important commercial product and an intermediate in the purification of the element from the ores. The distinctive property of this material is its reversible conversion to a non-stoichiometric oxide.

Contents

Production

Cerium occurs naturally as oxides, always as a mixture with other rare-earth elements. Its principal ores bastnaesite and monazite. After extraction of the metal ions into aqueous base, Ce is separated from that mixture by addition of an oxidant followed by adjustment of the pH. This step exploits the low solubility of CeO2 and the fact that other rare-earth elements resist oxidation. [3]

Cerium(IV) oxide is formed by the calcination of cerium oxalate or cerium hydroxide.

Cerium also forms cerium(III) oxide, Ce
2O
3, which is unstable and will oxidize to cerium(IV) oxide. [4]

Structure and defect behavior

Cerium oxide adopts the fluorite structure, space group Fm3m, #225 containing 8-coordinate Ce4+ and 4-coordinate O2−. At high temperatures it releases oxygen to give a non-stoichiometric, anion deficient form that retains the fluorite lattice. [5] This material has the formula CeO(2−x), where 0 < x < 0.28. [6] The value of x depends on both the temperature, surface termination and the oxygen partial pressure. The equation

has been shown to predict the equilibrium non-stoichiometry x over a wide range of oxygen partial pressures (103–10−4 Pa) and temperatures (1000–1900 °C). [7]

The non-stoichiometric form has a blue to black color, and exhibits both ionic and electronic conduction with ionic being the most significant at temperatures > 500 °C. [8]

The number of oxygen vacancies is frequently measured by using X-ray photoelectron spectroscopy to compare the ratio of Ce3+
to Ce4+
.

Defect chemistry

In the most stable fluorite phase of ceria, it exhibits several defects depending on partial pressure of oxygen or stress state of the material. [9] [10] [11] [12]

The primary defects of concern are oxygen vacancies and small polarons (electrons localized on cerium cations). Increasing the concentration of oxygen defects increases the diffusion rate of oxide anions in the lattice as reflected in an increase in ionic conductivity. These factors give ceria favorable performance in applications as a solid electrolyte in solid-oxide fuel cells. Undoped and doped ceria also exhibit high electronic conductivity at low partial pressures of oxygen due to reduction of the cerium ion leading to the formation of small polarons. Since the oxygen atoms in a ceria crystal occur in planes, diffusion of these anions is facile. The diffusion rate increases as the defect concentration increases.

The presence of oxygen vacancies at terminating ceria planes governs the energetics of ceria interactions with adsorbate molecules, and its wettability. Controlling such surface interactions is key to harnessing ceria in catalytic applications. [13]

Natural occurrence

Cerium(IV) oxide occurs naturally as the mineral cerianite-(Ce). [14] [15] It is a rare example of tetravalent cerium mineral, the other examples being stetindite-(Ce) and dyrnaesite-(La). The "-(Ce)" suffix is known as Levinson modifier and is used to show which element dominates in a particular site in the structure. [16] It is often found in names of minerals bearing rare earth elements (REEs). Occurrence of cerianite-(Ce) is related to some examples of cerium anomaly, where Ce - which is oxidized easily - is separated from other REEs that remain trivalent and thus fit to structures of other minerals than cerianite-(Ce). [17] [14] [15]

Applications

Cerium has two main applications, which are listed below.

The principal industrial application of ceria is for polishing, especially chemical-mechanical planarization (CMP). [3] For this purpose, it has displaced many other oxides that were previously used, such as iron oxide and zirconia. For hobbyists, it is also known as "opticians' rouge". [18] [19]

In its other main application, CeO2 is used to decolorize glass. It functions by converting green-tinted ferrous impurities to nearly colorless ferric oxides. [3]

Other niche and emerging applications

Catalysis

CeO2 has attracted much attention in the area of heterogeneous catalysis. It catalyses the water-gas shift reaction. It oxidizes carbon monoxide. Its reduced derivative Ce2O3 reduces water, with release of hydrogen. [20] [21] [22] [23]

The interconvertibility of CeOx materials is the basis of the use of ceria for an oxidation catalyst. One small but illustrative use is its use in the walls of self-cleaning ovens as a hydrocarbon oxidation catalyst during the high-temperature cleaning process. Another small scale but famous example is its role in oxidation of natural gas in gas mantles. [24]

A glowing Coleman white gas lantern mantle. The glowing element is mainly ThO2 doped with CeO2, heated by the Ce-catalyzed oxidation of the natural gas with air. Glowing gas mantle.jpg
A glowing Coleman white gas lantern mantle. The glowing element is mainly ThO2 doped with CeO2, heated by the Ce-catalyzed oxidation of the natural gas with air.

Building on its distinct surface interactions, ceria finds further use as a sensor in catalytic converters in automotive applications, controlling the air-exhaust ratio to reduce NOx and carbon monoxide emissions. [25]

Energy & fuels

Due to the significant ionic and electronic conduction of cerium oxide, it is well suited to be used as a mixed conductor. [26] As such, cerium oxide is a material of interest for solid oxide fuel cells (SOFCs) in comparison to zirconium oxide. [27]

Thermochemically, the cerium(IV) oxide–cerium(III) oxide cycle or CeO2/Ce2O3 cycle is a two-step water splitting process that has been used for hydrogen production. [28] Because it leverages the oxygen vacancies between systems, this allows ceria in water to form hydroxyl (OH) groups. [29] The hydroxyl groups can then be released as oxygen oxidizes, thus providing a source of clean energy.

Optics

Cerium oxide has found use in infrared filters and as a replacement for thorium dioxide in incandescent mantles [30]

Welding

Cerium oxide is used as an addition to tungsten electrodes for Gas Tungsten Arc Welding. It provides advantages over pure Tungsten electrodes such as reducing electrode consumption rate and easier arc starting & stability. Ceria electrodes were first introduced in the US market in 1987, and are useful in AC, DC Electrode Positive, and DC Electrode Negative.

Safety aspects

Cerium oxide nanoparticles (nanoceria) have been investigated for their antibacterial and antioxidant activity. [31] [32] [33] [34]

Nanoceria is a prospective replacement of zinc oxide and titanium dioxide in sunscreens, as it has lower photocatalytic activity. [35]

See also

Related Research Articles

<span class="mw-page-title-main">Catalysis</span> Process of increasing the rate of a chemical reaction

Catalysis is the increase in rate of a chemical reaction due to an added substance known as a catalyst. Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quickly, very small amounts of catalyst often suffice; mixing, surface area, and temperature are important factors in reaction rate. Catalysts generally react with one or more reactants to form intermediates that subsequently give the final reaction product, in the process of regenerating the catalyst.

<span class="mw-page-title-main">Silicon dioxide</span> Oxide of silicon

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<span class="mw-page-title-main">Zirconium dioxide</span> Chemical compound

Zirconium dioxide is a white crystalline oxide of zirconium. Its most naturally occurring form, with a monoclinic crystalline structure, is the mineral baddeleyite. A dopant stabilized cubic structured zirconia, cubic zirconia, is synthesized in various colours for use as a gemstone and a diamond simulant.

<span class="mw-page-title-main">Thorium dioxide</span> Chemical compound

Thorium dioxide (ThO2), also called thorium(IV) oxide, is a crystalline solid, often white or yellow in colour. Also known as thoria, it is produced mainly as a by-product of lanthanide and uranium production. Thorianite is the name of the mineralogical form of thorium dioxide. It is moderately rare and crystallizes in an isometric system. The melting point of thorium oxide is 3300 °C – the highest of all known oxides. Only a few elements (including tungsten and carbon) and a few compounds (including tantalum carbide) have higher melting points. All thorium compounds, including the dioxide, are radioactive because there are no stable isotopes of thorium.

<span class="mw-page-title-main">Solid oxide fuel cell</span> Fuel cell that produces electricity by oxidization

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<span class="mw-page-title-main">Bismuth(III) oxide</span> Chemical compound

Bismuth(III) oxide is perhaps the most industrially important compound of bismuth. It is also a common starting point for bismuth chemistry. It is found naturally as the mineral bismite (monoclinic) and sphaerobismoite, but it is usually obtained as a by-product of the smelting of copper and lead ores. Dibismuth trioxide is commonly used to produce the "Dragon's eggs" effect in fireworks, as a replacement of red lead.

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<span class="mw-page-title-main">Cerium(IV) oxide–cerium(III) oxide cycle</span> Chemical reaction

The cerium(IV) oxide–cerium(III) oxide cycle or CeO2/Ce2O3 cycle is a two-step thermochemical process that employs cerium(IV) oxide and cerium(III) oxide for hydrogen production. The cerium-based cycle allows the separation of H2 and O2 in two steps, making high-temperature gas separation redundant.

<span class="mw-page-title-main">Cerium(III) oxide</span> Chemical compound

Cerium(III) oxide, also known as cerium oxide, cerium trioxide, cerium sesquioxide, cerous oxide or dicerium trioxide, is an oxide of the rare-earth metal cerium. It has chemical formula Ce2O3 and is gold-yellow in color.

<span class="mw-page-title-main">Cerium</span> Chemical element, symbol Ce and atomic number 58

Cerium is a chemical element with the symbol Ce and atomic number 58. Cerium is a soft, ductile, and silvery-white metal that tarnishes when exposed to air. Cerium is the second element in the lanthanide series, and while it often shows the oxidation state of +3 characteristic of the series, it also has a stable +4 state that does not oxidize water. It is also considered one of the rare-earth elements. Cerium has no known biological role in humans but is not particularly toxic, except with intense or continued exposure.

Transition metal oxides are compounds composed of oxygen atoms bound to transition metals. They are commonly utilized for their catalytic activity and semiconducting properties. Transition metal oxides are also frequently used as pigments in paints and plastics, most notably titanium dioxide. Transition metal oxides have a wide variety of surface structures which affect the surface energy of these compounds and influence their chemical properties. The relative acidity and basicity of the atoms present on the surface of metal oxides are also affected by the coordination of the metal cation and oxygen anion, which alter the catalytic properties of these compounds. For this reason, structural defects in transition metal oxides greatly influence their catalytic properties. The acidic and basic sites on the surface of metal oxides are commonly characterized via infrared spectroscopy, calorimetry among other techniques. Transition metal oxides can also undergo photo-assisted adsorption and desorption that alter their electrical conductivity. One of the more researched properties of these compounds is their response to electromagnetic radiation, which makes them useful catalysts for redox reactions, isotope exchange and specialized surfaces.

Gadolinium-doped ceria (GDC) (known alternatively as gadolinia-doped ceria, gadolinium-doped cerium oxide (GCO), cerium-gadolinium oxide (CGO), or cerium(IV) oxide, gadolinium-doped, formula Gd:CeO2) is a ceramic electrolyte used in solid oxide fuel cells (SOFCs). It has a cubic structure and a density of around 7.2 g/cm3 in its oxidised form. It is one of a class of ceria-doped electrolytes with higher ionic conductivity and lower operating temperatures (<700 °C) than those of yttria-stabilized zirconia, the material most commonly used in SOFCs. Because YSZ requires operating temperatures of 800–1000 °C to achieve maximal ionic conductivity, the associated energy and costs make GDC a more optimal (even "irreplaceable", according to researchers from the Fraunhofer Society) material for commercially viable SOFCs.

<span class="mw-page-title-main">Ceria-zirconia</span>

Ceria-zirconia is a solid solution of cerium(IV) oxide (CeO2, also known as ceria) and zirconium oxide (ZrO2, also known as zirconia).

<span class="mw-page-title-main">Cerianite-(Ce)</span> Oxide mineral

Cerianite-(Ce) is a relatively rare oxide mineral, belonging to uraninite group with the formula (Ce,Th)O
2. It is one of a few currently known minerals containing essential tetravalent cerium, the other examples being stetindite and dyrnaesite-(La).

<span class="mw-page-title-main">Mixed conductor</span>

Mixed conductors, also known as mixed ion-electron conductors(MIEC), are a single-phase material that has significant conduction ionically and electronically. Due to the mixed conduction, a formally neutral species can transport in a solid and therefore mass storage and redistribution are enabled. Mixed conductors are well known in conjugation with high-temperature superconductivity and are able to capacitate rapid solid-state reactions.

Maria Flytzani-Stephanopoulos was a Greek chemical engineer and, at the time of her death, had been the Robert and Marcy Haber Endowed Professor in Energy Sustainability and a distinguished professor at Tufts University. Flytzani-Stephanopoulos had also been the Raytheon Professor of Pollution Prevention at Tufts. She published more than 160 scientific articles with over 14,000 citations as of April 2018. She was a Fellow of AIChE, the American Association for the Advancement of Science and American Institute of Chemical Engineers. She lived in the Greater Boston Area with her husband, Professor Gregory Stephanopoulos of MIT.

Praseodymium(III,IV) oxide is the inorganic compound with the formula Pr6O11 that is insoluble in water. It has a cubic fluorite structure. It is the most stable form of praseodymium oxide at ambient temperature and pressure.

Cerium compounds are compounds containing the element cerium (Ce), a lanthanide. Cerium exists in two main oxidation states, Ce(III) and Ce(IV). This pair of adjacent oxidation states dominates several aspects of the chemistry of this element. Cerium(IV) aqueous solutions may be prepared by reacting cerium(III) solutions with the strong oxidizing agents peroxodisulfate or bismuthate. The value of E⦵(Ce4+/Ce3+) varies widely depending on conditions due to the relative ease of complexation and hydrolysis with various anions, although +1.72 V is representative. Cerium is the only lanthanide which has important aqueous and coordination chemistry in the +4 oxidation state.

References

  1. ↑ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN   0-07-049439-8
  2. ↑ E. A. Kümmerle and G. Heger, “The Structures of C-Ce2O3+δ, Ce7O12, and Ce11O20,” Journal of Solid State Chemistry, vol. 147, no. 2, pp. 485–500, 1999.
  3. 1 2 3 Reinhardt, Klaus; Winkler, Herwig (2000). "Cerium Mischmetal, Cerium Alloys, and Cerium Compounds". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. doi:10.1002/14356007.a06_139..
  4. ↑ "Standard Thermodynamic Properties of Chemical Substances" (PDF). Archived from the original (PDF) on October 29, 2013.
  5. ↑ DFT study of Cerium Oxide Surfaces Applied surface science 2019 vol 478
  6. ↑ Defects and Defect Processes in Nonmetallic Solids By William Hayes, A. M. Stoneham Courier Dover Publications, 2004.
  7. ↑ Bulfin, B.; Lowe, A. J.; Keogh, K. A.; Murphy, B. E.; Lübben, O.; Krasnikov, S. A.; Shvets, I. V. (2013). "Analytical Model of CeO2 Oxidation and Reduction". The Journal of Physical Chemistry C. 117 (46): 24129–24137. doi:10.1021/jp406578z. hdl: 2262/76279 .
  8. ↑ Ghillanyova, K.; Galusek, D. (2011). "Chapter 1: Ceramic oxides". In Riedel, Ralf; Chen, I-Wie (eds.). Ceramics Science and Technology, Materials and Properties, vol 2. John Wiley & Sons. ISBN   978-3-527-31156-9.
  9. ↑ Munnings, C.; Badwal, S.P.S.; Fini, D. (2014). "Spontaneous stress-induced oxidation of Ce ions in Gd-doped ceria at room temperature". Ionics. 20 (8): 1117–1126. doi:10.1007/s11581-014-1079-2. S2CID   95469920.
  10. ↑ Badwal, S.P.S.; Daniel Fini; Fabio Ciacchi; Christopher Munnings; Justin Kimpton; John Drennan (2013). "Structural and microstructural stability of ceria – gadolinia electrolyte exposed to reducing environments of high temperature fuel cells". J. Mater. Chem. A. 1 (36): 10768–10782. doi:10.1039/C3TA11752A.
  11. ↑ Anandkumar, Mariappan; Bhattacharya, Saswata; Deshpande, Atul Suresh (2019-08-23). "Low temperature synthesis and characterization of single phase multi-component fluorite oxide nanoparticle sols". RSC Advances. 9 (46): 26825–26830. Bibcode:2019RSCAd...926825A. doi: 10.1039/C9RA04636D . ISSN   2046-2069. PMC   9070433 . PMID   35528557.
  12. ↑ Pinto, Felipe M (2019). "Oxygen Defects and Surface Chemistry of Reducible Oxides". Frontiers in Materials. 6: 260. Bibcode:2019FrMat...6..260P. doi: 10.3389/fmats.2019.00260 . S2CID   204754299.
  13. ↑ Fronzi, Marco; Assadi, M. Hussein N.; Hanaor, Dorian A.H. (2019). "Theoretical insights into the hydrophobicity of low index CeO2 surfaces" (PDF). Applied Surface Science. 478: 68–74. arXiv: 1902.02662 . Bibcode:2019ApSS..478...68F. doi:10.1016/j.apsusc.2019.01.208. S2CID   118895100.
  14. 1 2 "Cerianite-(Ce)". www.mindat.org. Retrieved 2020-11-12.
  15. 1 2 "List of Minerals". www.ima-mineralogy.org. 2011-03-21. Retrieved 2020-11-12.
  16. ↑ Burke, Ernst (2008). "The use of suffixes in mineral names" (PDF). Elements. 4 (2): 96.
  17. ↑ Pan, Yuanming; Stauffer, Mel R. (2000). "Cerium anomaly and Th/U fractionation in the 1.85 Ga Flin Flon Paleosol: Clues from REE- and U-rich accessory minerals and implications for paleoatmospheric reconstruction". American Mineralogist. 85 (7): 898–911. Bibcode:2000AmMin..85..898P. doi:10.2138/am-2000-0703. S2CID   41920305.
  18. ↑ "Properties of Common Abrasives (Boston Museum of Fine Arts)" (PDF).
  19. ↑ "Ceric oxide - CAMEO". cameo.mfa.org.
  20. ↑ Ruosi Peng; et a. (2018). "Size effect of Pt nanoparticles on the catalytic oxidation of toluene over Pt/CeO2 catalysts". Applied Catalysis B: Environmental. 220.
  21. ↑ Montini, Tiziano; Melchionna, Michele; Monai, Matteo; Fornasiero, Paolo (2016). "Fundamentals and Catalytic Applications of CeO2-Based Materials". Chemical Reviews. 116 (10): 5987–6041. doi:10.1021/acs.chemrev.5b00603. hdl: 11368/2890051 . PMID   27120134.
  22. ↑ Paier, Joachim; Penschke, Christopher; Sauer, Joachim (2013). "Oxygen Defects and Surface Chemistry of Ceria: Quantum Chemical Studies Compared to Experiment". Chemical Reviews. 113 (6): 3949–3985. doi:10.1021/cr3004949. PMID   23651311.
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  24. ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN   978-0-08-037941-8.
  25. ↑ Twigg, Martyn V. (2011). "Catalytic control of emissions from cars". Catalysis Today. 163: 33–41. doi:10.1016/j.cattod.2010.12.044.
  26. ↑ "Mixed conductors". Max Planck institute for solid state research. Retrieved 16 September 2016.
  27. ↑ Arachi, Y. (June 1999). "Electrical conductivity of the ZrO2–Ln2O3 (Ln=lanthanides) system". Solid State Ionics. 121 (1–4): 133–139. doi:10.1016/S0167-2738(98)00540-2.
  28. ↑ "Hydrogen production from solar thermochemical water splitting cycles". SolarPACES. Archived from the original on August 30, 2009.
  29. ↑ "New discoveries made on the role of Cerium Oxide in Hydrogen production". Ceric. 2018-07-01. Retrieved 2022-09-22.
  30. ↑ "Cerium dioxide". DaNa. Archived from the original on 2013-03-02.
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  32. ↑ Karakoti, A. S.; Monteiro-Riviere, N. A.; Aggarwal, R.; Davis, J. P.; Narayan, R. J.; Self, W. T.; McGinnis, J.; Seal, S. (2008). "Nanoceria as antioxidant: synthesis and biomedical applications". JOM. 60 (3): 33–37. Bibcode:2008JOM....60c..33K. doi:10.1007/s11837-008-0029-8. PMC   2898180 . PMID   20617106.
  33. ↑ Rajeshkumar, S.; Naik, Poonam (2017-11-29). "Synthesis and biomedical applications of Cerium oxide nanoparticles – A Review". Biotechnology Reports. 17: 1–5. doi:10.1016/j.btre.2017.11.008. ISSN   2215-017X. PMC   5723353 . PMID   29234605.
  34. ↑ Hussain S, Al-Nsour F, Rice AB, Marshburn J, Yingling B, Ji Z, Zink JI, Walker NJ, Garantziotis S (2012). "Cerium dioxide nanoparticles induce apoptosis and autophagy in human peripheral blood monocytes". ACS Nano. 6 (7): 5820–9. doi:10.1021/nn302235u. PMC   4582414 . PMID   22717232.
  35. ↑ Zholobak, N.M.; Ivanov, V.K.; Shcherbakov, A.B.; Shaporev, A.S.; Polezhaeva, O.S.; Baranchikov, A.Ye.; Spivak, N.Ya.; Tretyakov, Yu.D. (2011). "UV-shielding property, photocatalytic activity and photocytotoxicity of ceria colloid solutions". Journal of Photochemistry and Photobiology B: Biology. 102 (1): 32–38. doi:10.1016/j.jphotobiol.2010.09.002. PMID   20926307.
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