Ruthenium(IV) oxide

{{About |RuO₂|RuO₄|Ruthenium tetroxide}}

{{chembox | Verifiedfields = changed | Watchedfields = changed | verifiedrevid = 428796180 | ImageFile = Ruthenium(IV)-oxide-unit-cell-3D-vdW.png | ImageSize = | IUPACName = Ruthenium(IV) oxide | OtherNames = Ruthenium dioxide |Section1={{Chembox Identifiers | CASNo = 12036-10-1 | CASNo_Ref = {{cascite|correct|CAS}} | ChemSpiderID = 74760 | PubChem = 82848 | EINECS = 234-840-6 | InChI = 1S/2O.Ru | StdInChIKey = WOCIAKWEIIZHES-UHFFFAOYSA-N | SMILES = O=[Ru]=O }} |Section2={{Chembox Properties | Formula = RuO₂ | MolarMass = 133.0688 g/mol | Appearance = blue-black solid | Density = 6.97 g/cm³ | Solubility = insoluble | BoilingPtC = 1200 | BoilingPt_notes = sublimates | MagSus = +162.0·10⁻⁶ cm³/mol }} |Section3={{Chembox Structure | CrystalStruct = Rutile (tetragonal), tP6 | SpaceGroup = ''P''4₂/''mnm'', No. 136 | Coordination = Octahedral (Ru^IV); trigonal planar (O²⁻) | LattConst_a = | LattConst_c = }} |Section7={{Chembox Hazards | FlashPt = Non-flammable | GHS_ref = <ref>{{Cite web |last=PubChem |title=Ruthenium dioxide |url=https://pubchem.ncbi.nlm.nih.gov/compound/82848 |access-date=2026-02-02 |website=pubchem.ncbi.nlm.nih.gov |language=en}}</ref> | GHSPictograms = {{GHS03}}{{GHS07}} | GHSSignalWord = Danger | HPhrases = {{H-phrases|H272|H319|H413}} | PPhrases = {{P-phrases|P210|P220|P264+P265|P273|P280|P305+P351+P338|P337+P317|P370+P378|P501}} }} |Section8={{Chembox Related | OtherAnions = Ruthenium disulfide | OtherCations = Osmium(IV) oxide | OtherFunction = Ruthenium tetroxide | OtherFunction_label = ruthenium oxides | OtherCompounds = }} }} '''Ruthenium(IV) oxide''' is the inorganic compound with the formula RuO₂. This black solid is the most common oxide of ruthenium. It is widely used as an electrocatalyst for producing chlorine, chlorine oxides, and O₂.<ref>{{cite journal | last=Mills | first=Andrew | title=Heterogeneous redox catalysts for oxygen and chlorine evolution | journal=Chemical Society Reviews | publisher=Royal Society of Chemistry (RSC) | volume=18 | year=1989 | issn=0306-0012 | doi=10.1039/cs9891800285 | page=285}}</ref> Like many dioxides, RuO₂ adopts the rutile structure.<ref>Wyckoff, R.W.G.. ''Crystal Structures'', Vol. 1. Interscience, John Wiley & Sons: 1963.</ref><ref>{{Wells4th}}</ref>

==Preparation== It is usually prepared by oxidation of ruthenium trichloride. Nearly stoichiometric single crystals of RuO₂ can be obtained by chemical vapor transport, using O₂ as the transport agent:<ref>{{cite journal | last1=Schäfer | first1=Harald | last2=Schneidereit | first2=Gerd | last3=Gerhardt | first3=Wilfried | title=Zur Chemie der Platinmetalle. RuO2 Chemischer Transport, Eigenschaften, thermischer Zerfall | journal=Zeitschrift für anorganische und allgemeine Chemie | publisher=Wiley | volume=319 | issue=5–6 | year=1963 | issn=0044-2313 | doi=10.1002/zaac.19633190514 | pages=327–336 | bibcode=1963ZAACh.319..327S | language=de}}</ref><ref>{{cite book | last1 = Rogers | first1 = D. B. | last2 = Butler | first2 = S. R. | last3 = Shannon | first3 = R. D. | title = Inorganic Syntheses | year = 1972 | chapter = Single Crystals of Transition-Metal Dioxides | volume = XIII | pages = 135–145 | doi = 10.1002/9780470132449.ch27 | isbn = 9780470132449 }}</ref>

:RuO₂ + O₂ {{eqm}} RuO₄

Films of RuO₂ can be prepared by chemical vapor deposition (CVD) from volatile ruthenium compounds.<ref>{{cite journal | last1=Pizzini | first1=S. | last2=Buzzanca | first2=G. | last3=Mari | first3=C. | last4=Rossi | first4=L. | last5=Torchio | first5=S. | title=Preparation, structure and electrical properties of thick ruthenium dioxide films | journal=Materials Research Bulletin | publisher=Elsevier BV | volume=7 | issue=5 | year=1972 | issn=0025-5408 | doi=10.1016/0025-5408(72)90147-x | pages=449–462}}</ref> RuO₂ can also be prepared through electroplating from a solution of ruthenium trichloride.<ref>{{Cite journal | last1 = Lee | first1 = S. | doi = 10.1016/j.ssi.2003.08.035 | title = Electrochromism of amorphous ruthenium oxide thin films | journal = Solid State Ionics | volume = 165 | issue = 1–4 | pages = 217–221 | year = 2003 | url = https://zenodo.org/record/1259365 }}</ref>

Electrostatically stabilized hydrosols of pristine ruthenium dioxide hydrate have been prepared by exploiting the autocatalytic reduction of ruthenium tetroxide in aqueous solution. The resulting particle populations may be controlled to comprise substantially monodisperse, uniform spheres with diameters in the range 40&nbsp;nm - 160&nbsp;nm.<ref>{{ cite journal |author1=McMurray, H. N. | title = Uniform colloids of ruthenium dioxide hydrate evolved by the surface-catalyzed reduction of ruthenium tetroxide| journal = The Journal of Physical Chemistry | year = 1993 | volume = 97 | issue = 30 | pages = 8039–8045 | doi = 10.1021/j100132a038}}</ref>

==Uses== Ruthenium(IV) oxide is being used as the main component in the catalyst of the Sumitomo-Deacon process which produces chlorine by the oxidation of hydrogen chloride.<ref>{{citation | last1=Vogt | first1=Helmut | last2=Balej | first2=Jan | last3=Bennett | first3=John E. | last4=Wintzer | first4=Peter | last5=Sheikh | first5=Saeed Akbar | last6=Gallone | first6=Patrizio | title=Ullmann's Encyclopedia of Industrial Chemistry | chapter=Chlorine Oxides and Chlorine Oxygen Acids | publisher=Wiley-VCH Verlag GmbH & Co. KGaA | publication-place=Weinheim, Germany | date=2000-06-15 | doi=10.1002/14356007.a06_483 | page=| isbn=3527306730 }}</ref><ref>{{cite journal | last=Seki | first=Kohei | title=Development of RuO2/Rutile-TiO2 Catalyst for Industrial HCl Oxidation Process | journal=Catalysis Surveys from Asia | publisher=Springer Science and Business Media LLC | volume=14 | issue=3–4 | date=2010-05-29 | issn=1571-1013 | doi=10.1007/s10563-010-9091-7 | pages=168–175| s2cid=93115959 }}</ref>

RuO₂ can be used as catalyst in many other situations. Noteworthy reactions are the Fischer–Tropsch process, Haber–Bosch process, and various manifestations of fuel cells.

===Aspirational and niche applications=== RuO₂ is extensively used for the coating of titanium anodes for the electrolytic production of chlorine and for the preparation of resistors or integrated circuits.<ref>{{cite journal | last=De Nora | first=O. | title=Anwendung maßbeständiger aktivierter Titan-Anoden bei der Chloralkali-Elektrolyse | journal=Chemie Ingenieur Technik | publisher=Wiley | volume=42 | issue=4 | year=1970 | issn=0009-286X | doi=10.1002/cite.330420417 | pages=222–226}}</ref><ref>{{cite journal|last1=Iles|first1=G.S.|journal=Platinum Metals Review|year=1967|volume=11|issue=4|page=126|title=Ruthenium Oxide Glaze Resistors|doi=10.1595/003214067X114126129 |url=https://www.technology.matthey.com/article/11/4/126-129/|url-access=subscription}}</ref> Ruthenium oxide resistors can be used as sensitive thermometers in the temperature range .02 < T < 4 K. It can be also used as active material in supercapacitor because it has very high charge transfer capability. Ruthenium oxide has great capacity to store charge when used in aqueous solutions.<ref>{{cite journal|last1=Matthey|first1=Johnson|url=http://www.platinummetalsreview.com/article/46/3/105-105-1/|journal=Platinum Metals Review|year=2002|volume=46|issue=3|page=105|title=Nanocrystalline Ruthenium Supercapacitor Material|doi=10.1595/003214002X463105105a |access-date=2013-09-16|archive-date=2015-09-24|archive-url=https://web.archive.org/web/20150924074119/http://www.platinummetalsreview.com/article/46/3/105-105-1/|url-status=dead|doi-access=free}}</ref> Average capacities of ruthenium(IV) oxide have reached 650&nbsp;F/g when in sulfuric acid and annealed at temperatures lower than 200&nbsp;°C.<ref>Kim, Il-Hwan; Kim, Kwang-Bum; ''Electrochem. Solid-State Lett.,'' '''2001''', ''4'', 5, A62-A64</ref> In attempts to optimise its capacitive properties, prior work has looked at the hydration, crystallinity and particle size of ruthenium oxide.

==References== {{reflist}}

==External links== {{Commons category|Ruthenium(IV) oxide}} * [http://periodic.lanl.gov/elements/44.html Los Alamos National Laboratory – Ruthenium] {{Webarchive|url=https://web.archive.org/web/20070405104929/http://periodic.lanl.gov/elements/44.html |date=2007-04-05 }}

{{Ruthenium compounds}}

Category:Ruthenium(IV) compounds Category:Transition metal oxides