Cerium(III) oxide, also known as cerium oxide, cerium trioxide, cerium sesquioxide, cerous oxide or dicerium trioxide, is an oxide of the

rare-earth metal The rare-earth elements (REE), also called the rare-earth metals or rare earths, and sometimes the lanthanides or lanthanoids (although scandium and yttrium, which do not belong to this series, are usually included as rare earths), are a set of ...

cerium Cerium is a chemical element; it has Chemical symbol, symbol Ce and atomic number 58. It is a hardness, soft, ductile, and silvery-white metal that tarnishes when exposed to air. Cerium is the second element in the lanthanide series, and while it ...

. It has

chemical formula A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...

and is gold-yellow in color. According to

X-ray crystallography X-ray crystallography is the experimental science of determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to Diffraction, diffract in specific directions. By measuring th ...

, the Ce(III) ions are seven-coordinate, a motif typical for other trivalent lanthanide oxides.

Applications

Cerium oxide is of commercial interest as a catalyst for oxidation of carbon monoxide and reduction of . These applications exploit the facility of the Ce(III)/Ce(IV) redox couple. It is used in

catalytic converter A catalytic converter part is an vehicle emissions control, exhaust emission control device which converts toxic gases and pollutants in exhaust gas from an internal combustion engine into less-toxic pollutants by catalysis, catalyzing a redox ...

s ("three-way catalytic converter") 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, also known as ceric oxide, ceric dioxide, ceria, cerium oxide or cerium dioxide, is an oxide of the rare-earth metal cerium. It is a pale yellow-white powder with the chemical formula CeO2. It is an important commercial produc ...

oxidizes

carbon monoxide Carbon monoxide (chemical formula CO) is a poisonous, flammable gas that is colorless, odorless, tasteless, and slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the si ...

to the benign dioxide: : When oxygen is in surplus, the process is reversed and cerium(III) oxide is oxidized to cerium(IV) oxide: : Cerium oxide-based catalysts have been intensively investigated for selective catalytic reduction (SCR) of . Such technologies, which tend to use vanadium oxide-based catalysts rather than ceria, are associated with power plants, foundries, cement factories and other energy-intensive facilities. Cerium oxide finds use as a fuel additive to

diesel fuel Diesel fuel, also called diesel oil, heavy oil (historically) or simply diesel, is any liquid fuel specifically designed for use in a diesel engine, a type of internal combustion engine in which fuel ignition takes place without a spark as a re ...

s, which results in increased

fuel efficiency Fuel efficiency (or fuel economy) is a form of thermal efficiency, meaning the ratio of effort to result of a process that converts chemical energy, chemical potential energy contained in a carrier (fuel) into kinetic energy or Mechanical work, w ...

and decreased hydrocarbon derived

particulate matter Particulate matter (PM) or particulates are microscopic particles of solid or liquid matter suspended in the air. An ''aerosol'' is a mixture of particulates and air, as opposed to the particulate matter alone, though it is sometimes defin ...

emissions, however the health effects of the cerium oxide bearing engine exhaust is a point of study and dispute.

Other properties

Water splitting

The cerium(IV) oxide–cerium(III) oxide cycle or cycle is a two step thermochemical water splitting process based on

and cerium(III) oxide for

hydrogen production Hydrogen gas is produced by several industrial methods. Nearly all of the world's current supply of hydrogen is created from fossil fuels. Article in press. Most hydrogen is ''gray hydrogen'' made through steam methane reforming. In this process, ...

Photoluminescence

Cerium(III) oxide combined with tin(II) oxide (SnO) in

ceramic A ceramic is any of the various hard, brittle, heat-resistant, and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcela ...

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.

Production

Cerium(III) oxide is produced by the reduction of

with

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

at approximately . Samples produced in this way are only slowly air-oxidized back to the dioxide at room temperature.

References

External links

Transformation of CeO2(1 1 1) to Ce2O3(0 0 0 1) films
{{DEFAULTSORT:Cerium(Iii) Oxide Cerium(III) compounds Sesquioxides