CeO2x

CeO2x refers to cerium oxide in a non-stoichiometric form, meaning the ratio of cerium to oxygen is not exactly 2:1. This non-stoichiometry arises from the ability of cerium to exist in multiple oxidation states, primarily Ce3+ and Ce4+. In the ideal CeO2 structure, all cerium ions are in the +4 oxidation state. However, under certain conditions, some Ce4+ ions can be reduced to Ce3+, creating oxygen vacancies in the crystal lattice. This presence of oxygen vacancies and the coexistence of different cerium oxidation states are responsible for the unique properties of CeO2x.

These oxygen vacancies are mobile and can be easily filled or emptied by oxygen ions, making cerium oxide a highly effective oxygen storage material. This property is crucial for its applications in three-way catalytic converters in automobiles, where it helps to store and release oxygen to optimize the conversion of harmful exhaust gases like carbon monoxide, nitrogen oxides, and unburned hydrocarbons into less harmful substances. The redox cycling between Ce3+ and Ce4+ is the fundamental mechanism behind this oxygen storage capacity.

Beyond catalysis, CeO2x exhibits other interesting properties such as its strong UV absorption, which makes it useful as a sunscreen agent in cosmetics and sunscreens. Its ability to scavenge reactive oxygen species has also led to research into its potential as an antioxidant in biomedical applications. The precise oxygen content and resulting defect structure of CeO2x can be tuned through synthesis methods, allowing for the optimization of its properties for specific applications.