Three Way Catalytic (TWC) Converter

The TWC converter contains either platinum (Pt) and rhodium (Rh) or palladium (Pd) and rhodium (Rh). The TWC converter catalyzes the oxidation reactions of unburned HCs and CO and the reduction reaction of NO _x . The 3 way conversion can be best accomplished by always operating the engine air fuel ratio at or close to stoichiometry.