Electron Paramagnetic Resonance

Abstract

This chapter presents an overview of electron paramagnetic resonance (EPR) technique. EPR has been applied to surface chemistry and catalysis to study a variety of paramagnetic species including typically: (1) Adsorbed atoms, molecules and/or ions, which are in some cases intermediates of catalytic reactions; (2) intrinsic surface defects or defects formed by irradiation, grinding etc.; (3) transition metal ions supported on an oxide surface or included in the solid; and (4) spin labels interacting with a surface. In this chapter, the basic principles of EPR are given with particular emphasis on the interpretation of the spectra of polycrystalline materials, which are those most usually encountered in surface chemistry and catalysis work. In the chapter, characterization of catalytic surfaces by adsorption of probe molecules is considered without, however, attempting an exhaustive literature review of the field. Attention is devoted to the approaches used for studying important properties, such as surface crystal field, surface redox properties, active site identification, and surface groups' morphology, mobility of adsorbed species and coordination of surface metal ions. © 1990, Elsevier Science & Technology. All rights reserved.