Cerium(III) oxide
Cerium oxide is an oxide of the rare earth metal cerium
Cerium is a chemical element with the symbol Ce and atomic number 58. It is a soft, silvery, ductile metal which easily oxidizes in air. Cerium was named after the dwarf planet . Cerium is the most abundant of the rare earth elements, making up about 0.0046% of the Earth's crust by weight...

. It has chemical formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

 Ce2O3, and is gold-yellow in color.

Exhaust catalysts

Cerium oxide is used as a catalytic converter
Catalytic converter
A catalytic converter is a device used to convert toxic exhaust emissions from an internal combustion engine into non-toxic substances. Inside a catalytic converter, a catalyst stimulates a chemical reaction in which noxious byproducts of combustion are converted to less toxic substances by dint...

 for the minimisation of CO emissions in the exhaust gases from motor vehicles.

When there is a shortage of oxygen, cerium(IV) oxide
Cerium(IV) oxide
Cerium oxide, also known as ceric oxide, ceria, cerium oxide or cerium dioxide, is an oxide of the rare earth metal cerium...

 is reduced by carbon monoxide
Carbon monoxide
Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...

 to cerium(III) oxide:
2 + CO → +

When there is an oxygen surplus, the process is reversed and cerium(III) oxide is oxidized to cerium(IV) oxide:
2 + → 4

Water splitting

The cerium(IV) oxide-cerium(III) oxide cycle
Cerium(IV) oxide-cerium(III) oxide cycle
The cerium oxide–cerium oxide cycle or CeO2/Ce2O3 cycle is a two step thermochemical process based on cerium oxide and cerium oxide for hydrogen production...

 or CeO2/Ce2O3 cycle is a two step thermochemical
Thermochemistry is the study of the energy and heat associated with chemical reactions and/or physical transformations. A reaction may release or absorb energy, and a phase change may do the same, such as in melting and boiling. Thermochemistry focuses on these energy changes, particularly on the...

 water splitting
Water splitting
Water splitting is the general term for a chemical reaction in which water is separated into oxygen and hydrogen. Efficient and economical water splitting would be a key technology component of a hydrogen economy. Various techniques for water splitting have been issued in water splitting patents in...

 process based on cerium(IV) oxide
Cerium(IV) oxide
Cerium oxide, also known as ceric oxide, ceria, cerium oxide or cerium dioxide, is an oxide of the rare earth metal cerium...

 and cerium(III) oxide for hydrogen production
Hydrogen production
Hydrogen production is the family of industrial methods for generating hydrogen. Currently the dominant technology for direct production is steam reforming from hydrocarbons. Many other methods are known including electrolysis and thermolysis...



Cerium(III) oxide combined with tin(II) oxide
Tin(II) oxide
Tin oxide is a compound of tin and oxygen where tin has the oxidation state of +2. There are two forms, a stable blue-black form and a metastable red form.-Preparation and reactions:...

 (SnO) in ceramic
A ceramic is an inorganic, nonmetallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous...

 form is used for illumination with UV light. It absorbs light with a wavelength of 320 nm and emits light with a wavelength of 412 nm. This combination of cerium(III) oxide and tin(II) oxide is rare, and obtained only with difficulty on a laboratory scale.


Cerium(III) oxide is produced by the reduction
Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....

 of cerium(IV) oxide
Cerium(IV) oxide
Cerium oxide, also known as ceric oxide, ceria, cerium oxide or cerium dioxide, is an oxide of the rare earth metal cerium...

 with hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

 at approximately 1400 °C (2,552 °F) to make air stable cerium(III) oxide. Production at other temperatures results in pyrophoric cerium(III) oxide.

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