Ruthenium(IV) oxide is the

inorganic compound An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''. Inorgan ...

with the formula Ru O₂. This black solid is the most common oxide of

ruthenium Ruthenium is a chemical element; it has symbol Ru and atomic number 44. It is a rare transition metal belonging to the platinum group of the periodic table. Like the other metals of the platinum group, ruthenium is unreactive to most chem ...

. It is widely used as an electrocatalyst for producing chlorine, chlorine oxides, and O₂. Like many dioxides, RuO₂ adopts the

rutile Rutile is an oxide mineral composed of titanium dioxide (TiO2), the most common natural form of TiO2. Rarer polymorphs of TiO2 are known, including anatase, akaogiite, and brookite. Rutile has one of the highest refractive indices at vis ...

structure.

Preparation

It is usually prepared by oxidation of

ruthenium trichloride Ruthenium(III) chloride is the chemical compound with the formula RuCl3. "Ruthenium(III) chloride" more commonly refers to the hydrate RuCl3·''x''H2O. Both the anhydrous and hydrated species are dark brown or black solids. The hydrate, with a var ...

. Nearly stoichiometric single crystals of RuO₂ can be obtained by

chemical vapor transport In chemistry, a chemical transport reaction describes a process for purification and crystallization of non-volatility (chemistry), volatile solids. The process is also responsible for certain aspects of mineral growth from the effluent of volca ...

, using O₂ as the transport agent: :RuO₂ + O₂ RuO₄ Films of RuO₂ can be prepared by

chemical vapor deposition Chemical vapor deposition (CVD) is a vacuum deposition method used to produce high-quality, and high-performance, solid materials. The process is often used in the semiconductor industry to produce thin films. In typical CVD, the wafer (electro ...

(CVD) from volatile ruthenium compounds. RuO₂ can also be prepared through

electroplating Electroplating, also known as electrochemical deposition or electrodeposition, is a process for producing a metal coating on a solid substrate through the redox, reduction of cations of that metal by means of a direct current, direct electric cur ...

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.

Uses

Ruthenium(IV) oxide is being used as the main component in the catalyst of the Sumitomo-

Deacon process The Deacon process, invented by Henry Deacon, is a process used during the manufacture of alkalis (the initial end product was sodium carbonate) by the Leblanc process. Hydrogen chloride gas was converted to chlorine gas, which was then used to m ...

which produces

chlorine Chlorine is a chemical element; it has Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between ...

by the oxidation of

hydrogen chloride The Chemical compound, compound hydrogen chloride has the chemical formula and as such is a hydrogen halide. At room temperature, it is a colorless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric water vapor. Hyd ...

. RuO₂ can be used as catalyst in many other situations. Noteworthy reactions are the

Fischer–Tropsch process The Fischer–Tropsch process (FT) is a collection of chemical reactions that converts a mixture of carbon monoxide and hydrogen, known as syngas, into liquid hydrocarbons. These reactions occur in the presence of metal catalysts, typically at te ...

Haber–Bosch process The Haber process, also called the Haber–Bosch process, is the main industrial procedure for the production of ammonia. It converts atmospheric nitrogen (N2) to ammonia (NH3) by a reaction with hydrogen (H2) using finely divided iron metal as ...

, and various manifestations of

fuel cells A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen) and an oxidizing agent (often oxygen) into electricity through a pair of redox reactions. Fuel cells are different from most batteries in req ...

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 A resistor is a passive two-terminal electronic component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active e ...

integrated circuits An integrated circuit (IC), also known as a microchip or simply chip, is a set of electronic circuits, consisting of various electronic components (such as transistors, resistors, and capacitors) and their interconnections. These components a ...

. 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 Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...

and annealed at temperatures lower than 200 °C.Kim, Il-Hwan; Kim, Kwang-Bum; ''Electrochem. Solid-State Lett.,'' 2001, ''4'', 5, A62-A64 In attempts to optimise its capacitive properties, prior work has looked at the hydration, crystallinity and particle size of ruthenium oxide.

References

External links

Los Alamos National Laboratory – Ruthenium
{{Ruthenium compounds Ruthenium(IV) compounds Transition metal oxides