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How do cerium oxides help catalytic converters reduce vehicle emissions?

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A line graph showing electron probability distributions for gadolinium, with separate curves for 4f, 5s, 5p, 5d, and 6s orbitals. The x-axis shows distance from the nucleus in atomic units and the y-axis shows probability P2(r). — rare-earth element Electron probabilities, P²*(r)*, for the 4f, 5s, 5p, 5d, and 6s electrons of gadolinium.

Cerium oxides, specifically within the ${CeO}_{x}$ system, are essential components in automotive catalytic converters because they function as a portable oxygen source. Their effectiveness in reducing vehicle emissions is primarily due to their dual valence characteristics, which allow them to oscillate between the 3+ and 4+ oxidation states.12

This redox behavior enables the converter to manage the chemical composition of exhaust gases efficiently. Cerium oxides help facilitate the following processes:

Reduction: They assist in reducing nitrogen oxides into nitrogen gas.34
Oxidation: They promote the oxidation of carbon monoxide into carbon dioxide, as well as the oxidation of unburned hydrocarbons into carbon dioxide and water.34

By acting as an oxygen buffer, these compounds help the catalytic converter maintain the necessary chemical balance to effectively eliminate these environmentally harmful gases from gasoline-powered vehicles.12