Ruthenium(IV) oxide is the inorganic compound with the formula RuO<sub>2</sub>. This black solid is the most common oxide of ruthenium. It is widely used as an electrocatalyst for producing chlorine, chlorine oxides, and O<sub>2</sub>. Like many dioxides, RuO<sub>2</sub> adopts the rutile structure.
It is usually prepared by oxidation of ruthenium trichloride. Nearly stoichiometric single crystals of RuO<sub>2</sub> can be obtained by chemical vapor transport, using O<sub>2</sub> as the transport agent:
Films of RuO<sub>2</sub> can be prepared by chemical vapor deposition (CVD) from volatile ruthenium compounds. RuO<sub>2</sub> can also be prepared through electroplating from a solution of ruthenium trichloride.
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 nm - 160 nm.
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.
RuO<sub>2</sub> can be used as catalyst in many other situations. Noteworthy reactions are the FischerâÂÂTropsch process, HaberâÂÂBosch process, and various manifestations of fuel cells.
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. 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. Average capacities of ruthenium(IV) oxide have reached 650 F/g when in sulfuric acid and annealed at temperatures lower than 200 ðC. In attempts to optimise its capacitive properties, prior work has looked at the hydration, crystallinity and particle size of ruthenium oxide.