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Why do catalytic converter supports need a very large surface area?

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advanced structural ceramics Figure 1: Resistance to cracking in transformation-toughened zirconia. In a ceramic composed of tetragonal zirconia dispersed in a zirconia matrix, the stress field advancing ahead of a propagating crack transforms the small tetragonal particles to larger monoclinic particles. The larger particles exert a crack-closing force in the process zone behind the crack tip, effectively resisting propagation of the crack.

In the context of advanced structural ceramics, catalytic converter supports require a very large surface area to maximize the efficiency of the conversion process.1

Because heterogeneous catalytic reactions occur specifically at the interface between the exhaust gases and the catalyst, the rate of these reactions is directly proportional to the accessible surface area available for the reactants. To achieve this, engineers utilize microstructural engineering to create highly porous ceramic structures, such as pellets or honeycomb monoliths.21

By maximizing the internal pore surface area, manufacturers can effectively disperse expensive platinum-group metals as finely divided particles across the ceramic support. This ensures that a greater number of active sites are available for the oxidation of carbon monoxide and hydrocarbons, as well as the reduction of nitrogen oxides, thereby significantly improving the overall performance of the emission control system.13