The surface acidity of solid oxides and its characterization by IR spectroscopic methods. An attempt at systematization

The bases of IR spectroscopic methods for the characterization of the surface acidity, of the Lewis type and of the Brønsted type, of solid, simple and mixed oxides are briefly reviewed. The results are described and a systematization is proposed. The surface acidity is essentially associated with the ionicity/covalency of the element–oxygen bond, mainly affected by the size and charge of the cation.