ceramic autocatalyst - Johnson Matthey

Diesel engines normally run lean (more air than fuel), and therefore a diesel autocatalyst usually operates as an oxidation catalyst (which is why it is known as a diesel oxidation catalyst or DOC) cutting CO and HC emissions by more than 90%.

CO + ½ O2 → CO2

[HC] + O2 → CO2 + H2O

Many diesel particulate filter (DPF) systems incorporate an oxidation catalyst, either as a coating on the filter or as a separate element.