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How does catalyst surface area affect the rate of a heterogeneous catalytic reaction?

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Moon rock crystals — surface analysis A scanning-electron-microscope photograph of pyroxene and plagioclase crystals (the long and the short crystals, respectively) that grew in a cavity in a fragment of Moon rock gathered during the Apollo 14 mission.

In heterogeneous catalysis, where reactants and the catalyst exist in different phases, the reaction occurs specifically at the interface between the two. Because the surface is the site of the chemical transformation, the rate of a heterogeneously catalyzed reaction is directly proportional to the accessible surface area of the catalyst.12

To maximize this rate, catalysts are typically prepared as highly porous solids, finely divided metals, or metallic films to achieve a large surface area per unit of mass, sometimes reaching several hundred square metres per gram.1

While increasing the total surface area generally enhances the reaction rate, the specific nature of the surface also plays a critical role. The effectiveness of a catalyst can be influenced by:

Promoters: Minor constituents that can extend the effective surface area or improve the quality of the surface for a specific reaction.1
Poisons: Substances that adsorb preferentially onto active sites, blocking them and reducing the reaction rate.1
Structure Sensitivity: For some reactions, known as "demanding reactions," the rate and selectivity depend on the specific arrangement of atoms on the surface (such as specific crystal facets) rather than just the total surface area.3