The most effective catalyst for the oxidation reaction of carbon monoxide CO to carbon dioxide CO2 in a gas mixture containing both CO and CO2 is platinum Pt supported on a metal oxide, such as alumina Al2O3 or ceria CeO2 . This catalyst is widely used in automotive catalytic converters to reduce harmful emissions, including converting CO to CO2. Other noble metals, such as palladium Pd and rhodium Rh , can also be effective catalysts for this reaction.