Ruthenium(IV) oxide hydrate
[CAS# 32740-79-7]

Identification

• Classification: Inorganic chemical industry >> Inorganic salt >> Oxides of rare earth metals, yttrium or scandium
• Name: Ruthenium(IV) oxide hydrate
• Synonyms: Hydrous ruthenium oxide
• Molecular Formula: RuO₂.H₂O
• Molecular Weight: 151.08
• CAS Registry Number: 32740-79-7
• EC Number: 629-041-8
• SMILES: O.O=[Ru]=O

Properties

• Solubility: Insoluble (water.), Soluble (HCl) (Expl.)

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H319
• Safety Statements: P305+P351+P338

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Eye irritation	Eye Irrit.	2	H319
Skin irritation	Skin Irrit.	2	H315
Oxidising solids	Ox. Sol.	2	H272

Discovery and Applications

Ruthenium(IV) oxide hydrate is a hydrated form of ruthenium dioxide (RuO₂), a compound composed of ruthenium in the +4 oxidation state bonded to oxygen atoms. The hydrated variant contains water molecules integrated within its crystalline or amorphous structure, affecting its physical and chemical properties. Ruthenium(IV) oxide and its hydrates are important materials in catalysis, electronics, and electrochemistry.

Ruthenium dioxide is a dark gray to black solid known for its high electrical conductivity, chemical stability, and catalytic activity. The hydrate form typically appears as a black or dark brown powder with varying amounts of adsorbed or bound water. The precise hydration state can depend on synthesis methods and environmental conditions such as humidity and temperature.

The synthesis of ruthenium(IV) oxide hydrate commonly involves the hydrolysis of ruthenium precursors such as ruthenium trichloride or ruthenium tetroxide in aqueous media. Alternatively, it can form during the partial hydration of ruthenium dioxide powders exposed to moisture. Controlled thermal treatments can remove water to yield anhydrous RuO₂.

Ruthenium(IV) oxide hydrate retains much of the catalytic and conductive properties of the anhydrous oxide but may exhibit differences in surface area, porosity, and reactivity. The presence of water molecules can influence proton conduction and facilitate redox reactions, which are useful in electrochemical applications.

One of the primary applications of ruthenium(IV) oxide hydrate is as a catalyst or catalyst support in various oxidation reactions. It is employed in processes such as the oxygen evolution reaction (OER) in electrolyzers for water splitting, where it aids in the generation of oxygen gas from water under an applied voltage. The hydrated form often displays enhanced catalytic activity due to increased surface hydroxyl groups and higher surface area compared to the anhydrous oxide.

Additionally, ruthenium dioxide hydrates are utilized in the fabrication of supercapacitors and mixed metal oxide electrodes. Their excellent electrical conductivity and chemical robustness make them suitable materials for energy storage devices and sensors. They are also studied for applications in resistors and conductive coatings.

In environmental chemistry, RuO₂ hydrates can catalyze the degradation of pollutants via advanced oxidation processes. Their catalytic efficiency and stability under harsh conditions make them attractive for wastewater treatment and environmental remediation.

Physically, ruthenium(IV) oxide hydrate is insoluble in water and most organic solvents but can interact strongly with moisture due to its hydrophilic surface. It exhibits thermal stability up to several hundred degrees Celsius, beyond which dehydration and structural changes occur.

Safety considerations include handling as a fine powder, which may pose inhalation risks. Ruthenium compounds should be handled with appropriate protective equipment, and waste disposal should follow regulations for heavy metals and hazardous materials.

In summary, ruthenium(IV) oxide hydrate is a hydrated form of RuO₂ valued for its catalytic, electrochemical, and conductive properties. Its hydration affects physical characteristics and can enhance performance in applications such as water splitting catalysts, energy storage, and environmental catalysis.

References

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