Ce4Ce3

Ce4Ce3 is a descriptor used in discussions of cerium-containing materials, particularly cerium oxides, to denote a mixed-valence environment in which cerium ions exist in both +4 and +3 oxidation states. It is not a standard chemical formula for a discrete compound, but a qualitative representation of a region where the ratio of Ce4+ to Ce3+ ions is approximately four to three within a local structural motif. The notion reflects cerium’s tendency to undergo redox cycling between Ce4+ and Ce3+ during oxygen storage and release.

In ceria (CeO2) and related oxides, Ce4+ is dominant; partial reduction creates Ce3+ and oxygen vacancies to maintain charge balance. Mixed-valence states and oxygen vacancies underpin the material’s nonstoichiometry CeO2−δ, which enhances catalytic activity and ionic conductivity. The Ce4Ce3 description is used to discuss regions with specific valence distributions, affecting properties like color, optical absorption, redox behavior, and catalytic performance.

It is typically investigated using spectroscopic and electrochemical methods. Techniques such as X-ray absorption near-edge structure (XANES), X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR) provide information about the Ce4+/Ce3+ ratio. Thermogravimetric analysis or temperature-programmed reduction/oxidation experiments also reveal how valence ratios change under different atmospheres and temperatures.

Applications of cerium oxide materials rely on their mixed-valence chemistry, including automotive catalysts, solid oxide fuel cells, and environmental sensors. Ce4Ce3 is a useful conceptual shorthand for understanding how valence balance and oxygen vacancies govern performance, though it is not a fixed stoichiometric compound and varies with synthesis, temperature, and atmosphere.