ELECTRON-PARAMAGNETIC-RESONANCE SPECTROSCOPY OF CATALYTIC SURFACES

A review is presented of the application of electron paramagnetic reso nance (EPR) spectroscopy to study surfaces of catalytic interest. Spec tra of Mo(V) in supported molybdena catalysts illustrate how EPR can a ssist in the characterization of such materials. The spectra of an ads orbed stable radical, the superoxide ion, are used to show how surface sites on catalysts can be probed by EPR. Unstable radicals which are conceivable intermediates in catalytic reaction mechanisms can be iden tified via spin trapping experiments, either chemical or matrix isolat ion. The mobility of adsorbed radicals on surfaces can be studied by E PR. Finally, recent progress in observing EPR spectra from well-define d single-crystal surfaces is discussed.