Fundamentals in Adsorption at the Solid-Gas Interface. Concepts and Thermodynamics

Some fundamental concepts about the features of a solid material surface and the adsorption at the gas-solid interface are illustrated. The basic tools dealing with the thermodynamics aspects of adsorption processes are also discussed. The stepwise adsorption microcalorimetry technique, which is a tool of greatest quantitative merit in surface chemistry studies, is described in detail through a selection of gas-solid interface systems, taken from different materials science fields. Criteria for discriminating physical and chemical adsorption are given, based on the nature of the forces involved in the process and the heat of adsorption values. The molecular interpretation of the volumetric-calorimetric data, favored by the joint use of adsorption microcalorimetry, spectroscopic and/or ab initio modeling techniques, is also stressed by illustrating a number of examples dealing with either physical or associative/dissociative chemical adsorption.