This chapter discusses gas adsorption by solid surfaces. It describes some key ideas relating to the interaction of gases with solids, starting with the Langmuir adsorption isotherm. The Langmuir isotherm has been used successfully to interpret equilibrium adsorption behaviour of a number of systems and in determining the total surface area of solid surfaces, particularly high surface area solids often used as heterogeneous catalysts. Meanwhile, the Brunauer, Emmett and Teller (BET) isotherm provides an extension of the Langmuir monolayer model to multilayer adsorption. The chapter then looks at the types of bonding interactions formed between gas molecules and solid surfaces, as well as the rate at which vacant adsorption sites are filled. Two broad classifications of adsorbate bonding may be distinguished depending on the magnitude of their enthalpies of adsorption: physisorption and chemisorption. The chapter also considers single crystal surfaces, the problem of surface sensitivity, and adsorbate–adsorbate interactions.
Chapter
Gas adsorption at solid surfaces
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.
