Cerium Oxide
Cerium oxide, chemically known as cerium(IV) oxide or ceria, is an oxide of the rare earth metal cerium. Its chemical formula is CeO2, where cerium is in the +4 oxidation state. Here are some detailed points about cerium oxide:
Properties
- Appearance: It is a pale yellow-white powder, though it can appear darker when impure.
- Structure: Cerium oxide has a fluorite crystal structure, which contributes to its high melting point and hardness.
- Chemical Stability: It is relatively stable in air, but can be reduced to cerium(III) oxide (Ce2O3) under certain conditions, like high temperatures in the absence of oxygen.
- Catalytic Properties: It is used as a catalyst due to its ability to switch between Ce(IV) and Ce(III) oxidation states, making it effective in automotive catalytic converters for the oxidation of CO and hydrocarbons.
History
- Cerium was discovered in 1803 by Jöns Jakob Berzelius and Wilhelm Hisinger in Sweden, and independently by Martin Heinrich Klaproth in Germany. They named it after the dwarf planet Ceres, which was discovered around the same time.
- The oxide forms were later identified and characterized, with cerium oxide being recognized for its unique properties.
Applications
- Abrasive: Cerium oxide is widely used as a polishing agent for glass, lenses, and other optical surfaces due to its hardness and chemical inertness.
- UV Filter: In sunscreens, cerium oxide can act as a UV absorber.
- Catalyst: It plays a crucial role in the automotive industry as a component of three-way catalytic converters.
- Fuel Cells: Its ionic conductivity makes it useful in solid oxide fuel cells.
- Medical: There's research into its potential use in medical applications, particularly for its antioxidant properties.
Production
- Cerium oxide is typically produced by the thermal decomposition of cerium salts like cerium nitrate or cerium oxalate. The process involves heating these salts to high temperatures to yield CeO2.
Safety and Environmental Impact
- While cerium oxide itself is not highly toxic, care should be taken when handling powders due to potential respiratory hazards from inhalation.
- Its environmental impact is a subject of ongoing research, particularly concerning its use in automotive exhaust systems and its potential release into the environment.
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