In Situ Electron Paramagnetic Resonance Spectroscopy in Catalysis

This chapter provides readers with the fundamental knowledge of electron paramagnetic resonance (EPR) techniques and its applications in the field of heterogeneous catalysis. It introduces the principal EPR theory, which is needed to understand the EPR spectra of the various examples provided. The chapter also introduces different EPR methods generally applied and the basic setup of the equipment, which is also followed by in situ setup with its advantages and challenges. It shows examples of EPR application with two main classes of active species, paramagnetic transition metal ions (TMIs) and radicals, in heterogeneous catalysis study utilizing in situ EPR. EPR spectroscopy has long been used to characterize catalysts in a wide range of fields, from heterogeneous catalysis, via homogeneous, to biological systems of enzymes. Two main classes of EPR-active species that are relevant to catalysis and can be detected under in situ conditions are radicals and TMIs.