Language
Country/Area
No result found
The Janus-Side of Cerium Oxide: How Does It Release Oxygen at High Temperature?
Cerium oxide, with the chemical formula CeO2, is a pale yellowish white powder and is an oxide of the rare earth metal cerium. The material is commercially important and serves as an intermediate in the extraction of cerium from its ore. A special feature of it is its reversible conversion into non-stoichiometric oxides. As research deepens, the dual nature of cerium oxide has received more and more attention, especially its ability to release oxygen in high-temperature environments, making it a star material in many industrial applications.
Production process
Cerium is usually found in oxides of rare earth metals, and the main ores include cerium and monoxene. During the extraction process, cerium is mixed with other rare earth elements. After immersing the metal ions in an aqueous alkaline solution, cerium is separated by adding an oxidizing agent and adjusting the pH. This step takes advantage of the low solubility of cerium oxide, in contrast to the oxidation resistance of other rare earth elements. Cerium oxide can be formed by calcination of cerium oxalate or cerium hydroxide.
Characteristics and structure
. At high temperatures, it can release oxygen, forming a non-stoichiometric ion defect form and maintaining the fluorite lattice. The formula for this material is CeO(2−x), where 0 < x < 0.28. The value of x depends on the temperature, surface termination and the partial pressure of oxygen.Cerium oxide adopts a fluorite structure with a Fm3m space group, containing 8-coordinated Ce4+ and 4-coordinated O2−
Defect Chemistry
In the stable fluorite phase of cerium oxide, several defects are shown depending on the partial pressure of oxygen or the stress state of the material. Defects of primary concern include oxygen defects and small polarons (localized electrons present on the cerium cation). Increasing the concentration of oxygen defects increases the diffusion rate of oxide cations in the lattice, which reflects the improvement of ionic conductivity, making cerium oxides superior in solid oxide fuel cell applications.
Natural conditions and applications
In nature, cerium oxide exists in the form of zircon cerium ore (cerianite), which is a tetravalent cerium mineral. Its applications are wide-ranging, mainly including grinding and decolorizing glass. In grinding, cerium oxide replaces the previously commonly used iron oxide and zirconium oxide. In addition, cerium oxides have also attracted attention in catalysis and energy production, especially for the two-step splitting of water in hydrogen production.
Emerging Uses
Cerium oxide has attracted much attention in the catalytic field, where it catalyzes the water-gas change reaction, and is also used in automotive catalytic converters to help control the ratio of air to exhaust gases to reduce emissions of nitrogen dioxide and carbon monoxide. In the optical industry, cerium oxide is widely used to polish glass surfaces and excels in durability. Its application in welding is also gaining more and more attention, especially when used in combination with tungsten electrodes to provide a smooth and stable arc.
Safety considerations
Cerium oxide nanoparticles (nanoceria) are gradually entering the market and are a potential alternative for use in products such as sunscreens, given their antibacterial and antioxidant activities, due to their impact on photocatalytic activity. Smaller.
As we explore the potential of cerium oxide in different fields, coupled with its application in energy production and catalytic reactions, will cerium oxide become a key material in solving modern technological challenges in the future?
