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How does chemisorption allow reactants to react on the surface of a solid 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.
In heterogeneous catalysis, chemisorption is the process by which at least one reactant is held to the surface of a solid catalyst by chemical forces. This interaction allows reactants to undergo chemical transformation through several mechanisms:1
- Bond Formation and Activation: Chemisorption involves the making and breaking of chemical bonds. By forming specific chemical bonds with the catalyst surface, the reactant molecules are activated, which often lowers the activation energy required for the reaction to proceed compared to an uncatalyzed process.12
- Surface Interaction: Once adsorbed, the reactants may interact with each other while adjacent on the surface, or an impinging molecule may react with a species already held on the surface. The specific form of this attachment—and the resulting reactivity—depends on the electronic properties of the catalyst, such as the availability of free electrons or holes in the lattice of semiconductor catalysts.13
- Reaction and Release: After the reaction occurs on the surface, the catalyst must release the products. If the products are not released readily, they remain on the surface and can act as poisons, inhibiting further catalytic activity.1
Ultimately, the efficiency of this process is tied to the catalyst's accessible surface area and the specific nature of the chemical bonds formed between the adsorbate and the catalyst surface.31