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How do precious metal catalysts help reduce pollutants in automobile exhaust?

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dissociation of E–N — reaction mechanism Possible energy diagram for the dissociation of a covalent molecule, E–N, into its ions E⁺ and N⁻ (see text).

Precious metal catalysts—typically platinum, palladium, and rhodium—are essential components of an automobile's catalytic converter. These metals are coated onto honeycomb structures or refractory pellets within the exhaust system to promote the conversion of harmful pollutants into less toxic substances through oxidation and reduction reaction mechanisms.12

The process functions as follows:

Oxidation: Unburned hydrocarbons and carbon monoxide are oxidized to form water vapor and carbon dioxide.123
Reduction: Nitrogen oxides are reduced to nitrogen and oxygen.23

By providing a surface that facilitates these chemical interactions, the catalyst increases the rate of these reactions without being consumed itself. This effectively reduces the discharge of noxious gases from the internal-combustion engine into the environment.3425