Chemisorption

Name:
Chemisorption
Detailed information:
The formation of bonds between the surface molecules of a metal (or other material of high surface energy) and another substance (gas or liquid) in contact with it. These bonds are comparable in strength to ordinary chemical bonds and much stronger than the Van der Waals type characterizing physical adsorption. Chemisorbed molecules are often altered. Hydrogen is chemisorbed on metal surfaces as hydrogen atoms. Chemisorption of hydrocarbons may result in formation of chemisorbed hydrogen atoms and hydrocarbon fragments. Even when dissociation does not occur, the properties of the molecules are changed by the surface in important ways. This mechanism is the activating force of catalysis. An example of chemisorption is the boundary lubrication of moving metal parts in machinery. An oil film forms a chemisorbed layer at the interface and averts the high frictional forces that would otherwise exist. Solids with high surface energies are necessary for chemisorption to occur, e.g., nickel, silver, platinum, iron.See Catalysis.