Auto exhaust catalysts operate through heterogeneous catalysis, where the phase of the catalyst differs from the phase of the reactants. In this case, the solid catalyst is in contact with gaseous emissions. The catalyst typically contains precious metals like platinum, palladium, and rhodium, which facilitate the chemical reactions. The key reactions include:
1. Oxidation of carbon monoxide to carbon dioxide: \[ 2CO + O_2 \rightarrow 2CO_2 \]
2. Oxidation of unburnt hydrocarbons to carbon dioxide and water: \[ C_xH_y + (x + \frac{y}{4})O_2 \rightarrow xCO_2 + \frac{y}{2}H_2O \]
3. Reduction of nitrogen oxides to nitrogen and oxygen: \[ 2NO_x \rightarrow xO_2 + N_2 \]
