How catalytic converters clean exhaust

Transcript

Inside the converter, exhaust is guided through a ceramic or metal honeycomb, which gives the gases a huge surface area to touch without creating much resistance. That honeycomb is coated with precious-metal catalysts such as platinum, palladium, and rhodium, which speed up reactions without being used up. On those surfaces, carbon monoxide becomes carbon dioxide, nitrogen oxides are reduced to nitrogen and oxygen, and hydrocarbons are oxidized into carbon dioxide and water vapor. But the converter works best when hot, usually around 400 to 800 degrees Celsius, because the reactions are too slow when it is cold, especially just after start-up.