Current Developments in Operando Electron Paramagnetic Resonance Spectroscopy

Abstract

Electron paramagnetic resonance (EPR) spectroscopy is a powerful tool for in situ/operando tracking of catalytic reactions that involve paramagnetic species either as a catalyst (e.g. transition metal ions or defects), reaction intermediates (radicals) or poisoning agents such as coke. This article provides a summary of recent experimental examples and developments in resonator design as well as detection schemes that were carried out in our group. Opportunities for applying this technique are illustrated by examples, including studies of transition metal exchanged zeolites and metal-free zeolites as well as metal oxide catalysts. The inherent limitations of EPR applied at high temperatures are discussed, as well as strategies in reducing or lifting these restrictions are evaluated and ideas for future improvements and methodologies are discussed.

Keywords

• Defect sites
• EPR instrumentation
• Operando spectroscopy
• Transition metal ions