Review on the Application of Electron Paramagnetic Resonance in Surface Chemistry Research

Electron paramagnetic resonance (EPR) is a technique for studying the microscopic structures by detecting the transitions of the spin magnetic moments of unpaired electrons. Since its discovery by E. K. Zavoisky in 1944, EPR has evolved from a tool for analyzing atomic structures in physics into a core characterization method in the fields of chemistry, biology, and materials science. In surface chemistry, due to its high sensitivity to the local environment, EPR has become a unique technique for elucidating surface-active sites, free radical intermediates, and defect structures. However, for many chemists, EPR testing and analysis, which are based on mathematical and physical principles, is not an easy field to engage in due to its high level of specialization. Some introductory textbooks provide excellent and comprehensive explanations of the basic knowledge, and recent work reports have also demonstrated the continuously developing magnetic resonance spectroscopy methods. Nevertheless, they are not intended to provide a brief and clear overview through a wide range of examples. To bridge the knowledge gap between EPR spectroscopists and chemists unfamiliar with EPR, this work reviews the progress in the application of EPR in surface chemistry, discussing its principles, applications, innovative cases and future challenges. It is hoped that nonprofessionals would gain certain knowledge and technical accumulation from this work, thereby promoting the development of surface chemistry.