chemisorbed

Chemisorption, or chemical adsorption, is a process in which molecules or atoms adhere to a solid surface through the formation of chemical bonds with surface atoms. This bonding typically involves electron sharing or transfer, creating a new chemical species at the surface and often altering the electronic structure of the substrate.

It typically involves activation energy and a substantial adsorption energy, usually tens to hundreds of kilojoules per mole, much greater than physisorption. The binding is often localized to specific sites and can be dissociative (a molecule splits on the surface) or non-dissociative.

Chemisorption differs from physisorption in that it is highly dependent on the chemical identity of the adsorbate and surface, may cause electronic and structural changes on the surface, is less easily reversed, and often forms a monolayer of adsorbate. The process is usually slower to reach equilibrium and more sensitive to temperature and surface structure.

The concept is central to heterogeneous catalysis and surface chemistry. Examples include hydrogen chemisorption on metal surfaces, carbon monoxide chemisorption on noble metals, and oxygen chemisorption on transition metals. Chemisorbed species can influence catalytic activity, selectivity, and the work function or reactivity of the surface.

Characterization methods such as temperature-programmed desorption, X-ray photoelectron spectroscopy, infrared spectroscopy, and scanning probe microscopy are used to study chemisorption and to identify chemisorbed bonds, binding energies, and surface coverages.