Cerium(IV) oxide

Cerium(IV) oxide (CeO₂), also called ceria, is a pale yellow-white solid whose crystal lattice can reversibly lose oxygen, enabling uses in catalysis, polishing, and electrochemical devices.

Oxygen vacancy: A missing oxygen atom in a crystal lattice that leaves a locally altered electronic structure. Removing lattice oxygen from ceria creates these defects and changes its reactivity.
Three-way catalyst: An automotive exhaust catalyst that oxidizes carbon monoxide and hydrocarbons while reducing nitrogen oxides. Ceria helps the catalyst maintain effective oxygen availability as exhaust composition changes.
Cerium: A soft, silvery rare-earth metal with atomic number 58 and several accessible oxidation states. Cerium’s variable oxidation states underpin the reversible chemistry of its dioxide.
Zirconium dioxide: A refractory ceramic oxide of zirconium, commonly called zirconia, used in structural and electrochemical applications. Zirconia is a common alternative support and electrolyte, but its redox chemistry differs from ceria’s.
Ce³⁺/Ce⁴⁺ redox couple: The reversible interconversion between cerium ions in the +3 and +4 oxidation states. Ceria accommodates oxygen loss partly by reducing Ce⁴⁺ to Ce³⁺.
Chemical mechanical polishing: A manufacturing process that combines chemical reactions and mechanical abrasion to planarize a surface. Ceria abrasives polish glass and silicon dioxide through coupled chemical and mechanical action.
Oxide: A chemical compound in which oxygen is bonded to at least one other element. Cerium(IV) oxide is the dioxide formed when cerium and oxygen combine.
Titanium dioxide: A white titanium oxide used as a pigment, photocatalyst, and functional ceramic. Titania is another reducible oxide, but ceria is especially valued for oxygen buffering.
Oxygen storage capacity: A material’s ability to absorb and release oxygen under changing chemical conditions. Ceria’s oxygen-storage capacity buffers oxygen fluctuations in exhaust catalysts.
Solid oxide fuel cell: An electrochemical device that converts fuel and oxygen into electricity through a solid oxide electrolyte. Doped ceria conducts oxide ions and can serve as an electrolyte or interlayer.

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