TWC operates based on heterogeneous catalysis principles. The catalyst is typically composed of precious metal nanoparticles like platinum (Pt), palladium (Pd), and rhodium (Rh) dispersed on a high surface area support material such as alumina. When exhaust gases pass over the catalyst, the following reactions occur:
Oxidation of CO: 2CO + O2 → 2CO2 Oxidation of HC: CxHy + (x + y/4)O2 → xCO2 + y/2H2O Reduction of NOx: 2NO + 2CO → N2 + 2CO2
