The bigger picture
Current methods for characterization of single-atom catalysts (SACs) often fail to accurately describe critical features necessary for understanding and optimizing their performance. These features include metal dispersion, geometries and electronic structure of active sites, and support functionalities responsible for metal coordination or co-catalytic roles. Combining different ex situ and operando electron paramagnetic resonance (EPR) methods, including continuous wave and pulse techniques, can help address this gap. This integration enhances understanding of the structures and reactivity of SACs when used alongside other methods, and this approach can potentially become a standard tool for investigating SACs. This will stimulate the development of new EPR methods and further advance the field of catalytic materials investigation.
Summary
Single-atom catalysts (SACs) are an important material class, lying at the forefront of precision design for heterogeneous catalysis research. Despite extensive investigations of their structure and reactivity using state-of-the-art analytical tools, new approaches are sought to improve the understanding of their properties and catalytic behavior. This review highlights the often-overlooked potential of electron paramagnetic resonance (EPR) spectroscopy, which is exceptionally suited to studying isolated paramagnetic species. EPR provides valuable complementary insights into SACs, including metal oxidation state, dispersion degree, local coordination environment, and catalytically relevant features of support materials. To enhance the technique’s accessibility, we provide a tutorial on EPR, summarize significant findings to date, place them within a broader methodological framework for SAC applications, and identify key directions for future research.
M. Agrachev, V. Giulimondi, I. Surin, S. Mitchell, G. Jeschke, J. Pérez-Ramírez, Electron paramagnetic resonance spectroscopy for the analysis of single-atom catalysts, Chem Catalysis, 2024, 101136. DOI: 10.1016/j.checat.2024.101136.
