A catalytic converter is a device that uses a catalyst to convert three harmful compounds in car exhaust into harmless compounds.
The three harmful compounds are:
In a catalytic converter, the catalyst (in the form of platinum and palladium) is coated onto a ceramic honeycomb or ceramic beads that are housed in a muffler-like package attached to the exhaust pipe. The catalyst helps to convert carbon monoxide into carbon dioxide. It converts the hydrocarbons into carbon dioxide and water. It also converts the nitrogen oxides back into nitrogen and oxygen.
Here are some interesting links: