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How can an inhibitor poison a catalyst?
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catalysis
Nanoparticles of a gold-palladium (yellow-blue) alloy supported on acid-treated carbon (gray) directly catalyzing hydrogen peroxide formation from hydrogen (white) and oxygen (red) while shutting off unwanted hydrogen peroxide decomposition.
An inhibitor, often referred to as a catalyst poison, reduces the effectiveness of a catalyst by decreasing the concentration of active catalytic sites available for a chemical reaction.12
This process typically occurs through the following mechanisms:
- Complex Formation: The inhibitor may form a chemical complex with the catalyst, effectively removing it from the reaction process.2
- Surface Accumulation: In heterogeneous catalysis, poisonsâwhich may originate from reactants or reaction productsâpreferentially adsorb onto the catalyst's surface. By occupying these reaction sites and resisting removal, they block the reactants from accessing the catalyst.13
- Electronic Modification: A poison can also reduce catalytic activity by adversely altering the electronic properties of the catalyst material.3
- Structural Distortion: In enzymatic reactions, inhibitors can bind to allosteric sites, causing a change in the enzyme's shape that misaligns the catalytic groups, or they may distort the active site by affecting essential binding groups, preventing the substrate from interacting with the enzyme.4
When a catalyst's effectiveness drops significantly, the poison must be removed or the catalyst component replenished to restore activity.1