Britannica
Sources used in this answer
How do catalyst poisons interfere with reactions on catalytic surfaces?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
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 the context of surface chemistry, catalyst poisons reduce the effectiveness of a catalyst by accumulating on its surface. Because heterogeneous catalytic reactions occur specifically at the surface of a solid catalyst, the presence of these foreign substances interferes with the process in several ways:1
- Preferential Adsorption: Poisons are often minor constituents of the reacting system or unwanted reaction products that bind to the catalyst's active sites more strongly than the reactants. By occupying these sites and resisting removal, they prevent the necessary reactants from adsorbing and undergoing the reaction.2
- Electronic Modification: A poison may also reduce catalytic activity by adversely modifying the electronic properties of the catalyst surface.2
- Complex Formation: Poisoning can occur through the formation of stable complexes between the catalyst and the inhibitor, effectively removing the catalyst from the reaction environment.3
When a catalyst's effectiveness drops due to such poisoning, it often becomes necessary to remove the accumulated substances or replenish the active components of the catalyst.1