View source for Ruthenium(IV) oxide



{{Chembox new
|   Name = Ruthenium(IV) oxide
|   IUPACName = Ruthenium(IV) oxide
| Section2 = {{Chembox Properties
|   Formula = RuO<sub>2</sub>
|   MolarMass = 133.07 g/mol (anhydrous)
|   Appearance = Black crystalline solid
|   Density = 6.97 g/cm³ (solid)
|   Solubility = insoluble
|   MeltingPt = 1200<sup>o</sup>C (sublimes)
|   BoilingPt = decomposes
  }}
| Section7 = {{Chembox Hazards
|   ExternalMSDS = [http://www.jmcatalysts.com/pct/pdfs/msds/422.pdf External MSDS]
|   EUClass = not listed
  }}
| Section8 = {{Chembox Related
|   OtherCpds = '''RuO<sub>4</sub>''','''RuCl<sub>3</sub>'''}}
}}

'''Ruthenium(IV) oxide''' ([[Ruthenium|Ru]][[Oxygen|O<sub>2</sub>]]) is a black [[chemical compound]] containing the rare metal [[ruthenium]] and [[oxygen]].  The most often
used O<sub>2</sub> catalyst is ruthenium(IV) oxide, however care must be taken since hydrates of this oxide exist.<ref>Mills, A.; ''Chem. Sot. Rev.,'''''1989''', ''18'', 285.</ref><br />
RuO<sub>2</sub> is generally used as a [[catalyst]] in various industrial applications or an [[electrode]] in [[electrochemical]] processes.   RuO<sub>2</sub> is highly reactive with [[reducing]] agents, due to its [[oxidizing]] properties.

==Structure and Physical Properties==
Ruthenium(IV) oxide takes on the [[rutile]] crystal structure<ref> Wyckoff, R.W.G.. ''Crystal Structures'', Vol. 1. Interscience, John Wiley & Sons: 1963.</ref><ref>Wells, A.F. ''Structural Inorganic Chemistry'', 4th ed., Oxford: 1975.</ref>, similar to [[titanium dioxide]] and several other metal oxides. Due to its structure, ruthenium(IV) oxide easily forms hydrates.
<!-- Image with unknown copyright status removed:[[Image:RuO2_structure.jpg|200px|center]] -->

Ruthenium(IV) oxide is a (nearly black) purple crystalline solid at room temperature.  The hydrates of RuO<sub>2</sub> have a blue color to them.  RuO<sub>2</sub> sublimes at 1200°C under standard conditions (and does not have boiling point).  Ruthenium(IV) oxide has a density of about 6970 kg/m³ or 6.970 g/cm³.</br>

Ruthenium oxide has great capacity to store charge when used in aqueous solutions.<ref> Matthey, Johnson. ''Platinum Metals Review.'' '''2002''', ''46'', 3, 105</ref> Average capacities of ruthenium(IV) oxide have reached 650 F/g when in H<sub>2</sub>SO<sub>4</sub> solution and annealed at temperatures lower than 200<sup>o</sup>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 of ruthenium oxide, its crystallinity and particle size. <!-- As ruthenium is considered a rare metal and is costly, when used it is often combined with other elements. PROBABLY NOT RELEVENT TO THIS ARTICLE-->

The mass percent composition is as follows: Ruthenium 75.96%, Oxygen 24.04%</br>

Ruthenium(IV) oxide is insoluble in water.

==Preparation==
There are various ways in preparing ruthenium(IV) oxide. 
The following processes described below are for preparing RuO<sub>2</sub> as a film.

1. The [[chemical vapor deposition]] (CVD) of RuO<sub>2</sub> from suitable voltile ruthenium compounds.<ref> Pizzini, S.; Buzzancae, g.; ''Mat. Res. Bull.'', '''1972,''' ''7'', 449-462.</ref>

2. The [[pyrolysis]], or heating of ruthenium halides, suitably deposited on the substrate by spraying on the heated substrate a solution of the halide . The most commonly used halide is [[ruthenium(III) chloride]] to form RuO<sub>2</sub>.<br />
This technique has in fact been developed by Schafer for the preparation
of nearly stoichiometric RuO<sub>2</sub> single crystals.<ref> Schafer, H., ''Z.an.allg. Chem.'' '''1963''', ''319'', 327</ref>
<br />
Both process follow the same reaction mechanism:

Ru<sup>+(IV)</sup> + O<sub>2</sub> (heat)→ RuO<sub>2</sub>
<br />
High temperature flashes of heat up to 1500<sup>o</sup>C can remove all oxides and contaminants, and form a new oxide layer on the ruthenium.

3. Another way to prepare RuO<sub>2</sub> is through [[electroplating]]. Films can be electroplated from a solution of RuCl<sub>3</sub><sup>.</sup>xH<sub>2</sub>O. Pt gauze was used
as the counter electrode and Ag/AgCl as the reference electrode.<ref>Leea, Se-Hee; Liu, Ping.; ''Solid State Ionics'' '''2003''', ''165'', 217-221.</ref>

==Uses==
RuO<sub>2</sub> 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> De Nora,O.; ''Chem. Eng. Techn.'', '''1970''', ''42'', 222.</ref><ref>Iles, G.S.; ''Platinum Met. Rev.'', '''1967''',''11'',126.</ref>

Ruthenium(IV) oxide is a versatile catalyst and doping agent. [[hydrogen sulfide]] can be split by light by using a [[photocatalyst]] of CdS particles doped with ruthenium(IV) oxide loaded with ruthenium dioxide.<ref> Park, Dae-chul; Baeg, Jin-ook., ''U.S. Pat. Appl. Publ.'', '''2001''',6 pp.</ref>  This may be useful in the removal of H<sub>2</sub>S from oil refineries and from other industrial processes.  The hydrogen produced could be used to synthesize ammonia, methanol, and possibly fuel a future hydrogen economy.

Ruthenium (IV) oxide is being used as the main component in the catalyst of the [[ Deacon process]] which produces [[ chlorine]] by the oxidation of [[ hydrogen chloride ]].

==Oxidative Catalyst==
RuO<sub>2</sub> by itself is a poor catalyst because without the presence of a hydrate its surface area is greatly decreased.  To get pure ruthenium(IV) oxide, it needs to be [[annealed]] at 900<sup>o</sup>C.  The best catalyst for electrochemical processes is to have some hydrate present, but not a completely hydrous one.<ref>Mills, A.; Davies, H.; ''Inorganica. Chimica. Acta.,'' '''1991''', ''189'', 149-155</ref>
RuO<sub>2</sub> can be used as catalyst in multiple reactions.  Such noteworthy reactions are the [[Fischer-Tropsch process]] and [[fuel cells]].

==Precautions==
Use personal protection equipment when handling. Conditions and substances to avoid are: extreme [[heat]], [[fire]], [[acid]]s, [[aqua regia]], [[organic solvent]]s.

==Suppliers==
RuO<sub>2</sub> and its hydrates can be purchased commercially.  Such suppliers are [[Alfa Aesar]] and [[American Elements]].

==References==
{{reflist|2}}

==External links==
* [http://periodic.lanl.gov/elements/44.html Los Alamos National Laboratory &ndash; Ruthenium]<br />[http://www.alfa.com/alf/laboratory_chemical_suppliers.htm Alfa Aesar - chemical supplier]<br />[http://www.americanelements.com/ American Elements - rare metal supplier]

[[Category:Oxides]]
[[Category:Ruthenium compounds]]
[[Category:Inorganic compound stubs]]


[[fr:Dioxyde de ruthénium]]

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