Cerium(III) oxide
Cerium(III) oxide
IUPAC name
Cerium(III) oxide
Other names
Cerium sesquioxide
3D model (JSmol)
ECHA InfoCard 100.014.289 Edit this at Wikidata
EC Number
  • 234-374-3
  • InChI=1S/2Ce.3O/q2*+3;3*-2
  • [O-2].[O-2].[O-2].[Ce+3].[Ce+3]
Molar mass 328.229 g·mol−1
Appearance yellow-green dust[citation needed]
Density 6.2 g/cm3
Melting point 2,177 °C (3,951 °F; 2,450 K)
Boiling point 3,730 °C (6,750 °F; 4,000 K)
Solubility in sulfuric acid soluble
Solubility in hydrochloric acid insoluble
Hexagonal, hP5
P3m1, No. 164
GHS labelling:
GHS07: Exclamation markGHS09: Environmental hazard
Related compounds
Other anions
Cerium(III) chloride
Other cations
Lanthanum(III) oxide, Praseodymium(III) oxide
Related compounds
Cerium(IV) oxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

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 cerium. It has chemical formula Ce2O3 and is gold-yellow in color.


Engine and exhaust catalysts

Cerium oxide is used as a 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 is reduced by carbon monoxide to cerium(III) oxide:

2 CeO2 + CO → Ce2O3 + CO2

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

2 Ce2O3 + O2 → 4 CeO2

Major automotive applications for cerium(III) oxide are as a catalytic converter for the oxidation of CO and NOx emissions in the exhaust gases from motor vehicles,[1][2] and secondly, cerium oxide finds use as a fuel additive to diesel fuels, which results in increased fuel efficiency and decreased hydrocarbon derived particulate matter emissions,[3] however the health effects of the cerium oxide bearing engine exhaust is a point of study and dispute.[4][5][6]

Water splitting

The cerium(IV) oxide–cerium(III) oxide cycle or CeO2/Ce2O3 cycle is a two step thermochemical water splitting process based on cerium(IV) oxide and cerium(III) oxide for hydrogen production.[7]


Cerium(III) oxide combined with tin(II) oxide (SnO) in ceramic 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.[8] This combination of cerium(III) oxide and tin(II) oxide is rare, and obtained only with difficulty on a laboratory scale.[citation needed]


Cerium(III) oxide is produced by the reduction of cerium(IV) oxide with hydrogen at approximately 1,400 °C (2,550 °F). Samples produced in this way are only slowly air-oxidized back to the dioxide at room temperature.[9]


  1. ^ Bleiwas, D.I. (2013). Potential for Recovery of Cerium Contained in Automotive Catalytic Converters. Reston, Va.: U.S. Department of the Interior, U.S. Geological Survey.
  2. ^ "Argonne's deNOx Catalyst Begins Extensive Diesel Engine Exhaust Testing". Archived from the original on 2015-09-07. Retrieved 2014-06-02.
  3. ^ "Exploring Nano-sized Fuel Additives EPA scientists examine nanoparticle impacts on vehicle emissions and air pollution".
  4. ^ "Nanoparticles used as additives in diesel fuels can travel from lungs to liver, November 18, 2011. Marshall University Research Corporation".
  5. ^ Park, B.; Donaldson, K.; Duffin, R.; Tran, L.; Kelly, F.; Mudway, I.; Morin, J. P.; Guest, R.; Jenkinson, P.; Samaras, Z.; Giannouli, M.; Kouridis, H.; Martin, P. (Apr 2008). "Hazard and risk assessment of a nanoparticulate cerium oxide-based diesel fuel additive - a case study". Inhal Toxicol. 20 (6): 547–66. doi:10.1080/08958370801915309. PMID 18444008.
  6. ^ "Exploring Nano-sized Fuel Additives EPA scientists examine nanoparticle impacts on vehicle emissions and air pollution".
  7. ^ Hydrogen production from solar thermochemical water splitting cycles Archived August 30, 2009, at the Wayback Machine
  8. ^ Peplinski, D.R.; Wozniak, W. T.; Moser, J. B. (1980). "Spectral Studies of New Luminophors for Dental Porcelain". Journal of Dental Research. 59 (9): 1501–1509. doi:10.1177/00220345800590090801. PMID 6931128.
  9. ^ Y. Wetzel (1963). "Scandium, Yttrium, Rare Earths". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 1. NY, NY: Academic Press. p. 1151.