Definition

1. Noun:
   • A type of adsorption: A process in which atoms, ions, or molecules from a gas or liquid adhere to a surface. Specifically, chemisorption involves the formation of strong, often irreversible, chemical bonds between the adsorbate (the substance being adsorbed) and the surface of the adsorbent (the material doing the adsorbing). This distinguishes it from physisorption, which involves weaker physical forces.

Usage Examples

• Noun:
  • The chemisorption of oxygen onto the metal surface created a stable oxide layer.
  • Hydrogen storage in some materials relies on the principle of chemisorption.
  • The catalyst's activity depends on the chemisorption of reactant molecules.

Advanced Usage

• Irreversibility: Chemisorption is often difficult to reverse without applying significant energy (e.g., high temperature) to break the chemical bonds formed.
  • The chemisorption of carbon monoxide on the platinum catalyst was so strong it required a high-temperature treatment to remove it.
• Monolayer Formation: Unlike physisorption, which can form multiple layers, chemisorption typically results in only a single molecular layer (a monolayer) on the surface because the chemical bonds saturate the available surface sites.
  • The data indicated that chemisorption had occurred, as the uptake corresponded to a complete monolayer.

Variants and Related Words

• Chemisorb (verb): To take up or hold by chemisorption.
  • Nitrogen molecules chemisorb onto the iron catalyst.
• Chemisorptive (adjective): Relating to or characterized by chemisorption.
  • The material exhibited strong chemisorptive properties.

Synonyms

• Chemical adsorption: The full technical term synonymous with chemisorption.
• Activated adsorption: An older term sometimes used to emphasize that chemisorption often requires an activation energy to initiate the bond formation.

Related Terms (for contrast)

• Physisorption (noun): Adsorption via weak physical forces (e.g., van der Waals forces), which is typically reversible and can form multilayers.
• Adsorbate (noun): The substance that is adsorbed onto a surface.
• Adsorbent (noun): The material on whose surface adsorption occurs.
• Sorption (noun): A general term encompassing both adsorption and absorption.

Noun

1. adsorption (especially when irreversible) by means of chemical instead of physical forces
   • chemisorption of gaseous nitrogen on iron catalysts