This chapter examines adsorption and desorption. There are several possible outcomes when an atom or a molecule hits a surface, including elastic and inelastic scattering. However, the outcome of an atomic or a molecular collision that results in the retention of the molecule on the surface is of far greater importance to the study of surface chemistry. There are two types of interactions that can occur: physical adsorption (or physisorption) and chemisorption. In each case, the atom or molecule being adsorbed on the surface is usually described as the adsorbate; the adsorbing surface is usually termed the adsorbent or substrate. The chapter then looks at adsorption isotherms, before considering the measurement of heats of adsorption, isosteres, and desorption rates. It also discusses adsorption sites and geometries. Finally, the chapter highlights two methods which can provide information on surface chemical composition: auger electron spectroscopy (AES) and secondary ion mass spectrometry (SIMS).
Chapter
Adsorption and desorption
Book
Elaine M. McCash
Surface Chemistry conveys the fundamental concepts of surface chemistry. It describes solid surfaces, their properties at macroscopic and microscopic levels and their interrelation, and reflects the striking advances made in recent years through the study of well-defined single crystal surfaces. It begins with a discussion of the clean surface, its electronic and structural properties and goes on to describe adsorption, desorption, reactions, and reactivity at the surface. In the final section, the growth and properties of ultrathin films is introduced. Starting with the established concepts in terms of kinetics and thermodynamics, the book develops to look at phenomena such as surface dynamics and photochemistry. Important techniques which are applied to surfaces are also covered; this is a concept-driven rather than technique-driven approach.
