In situ/operando techniques for characterization of supported metal single-atom catalysts

This chapter presents the advances concerning in situ and operando characterization studies of supported single-atom catalysts (SAC), covering general information on the techniques which are currently used, and reviewing the range of recently published results that explore the understanding of both synthesis and structure-properties relationship. X-ray Absorption Spectroscopy is widely used since it is element specific and is able to study oxidation state, and bonding of metal atoms to ligands. Several IR studies are also present in the literature studying the bands associated with absorption of CO and the recent development of ambient pressure X-ray Photoelectron spectroscopy is promoting an increasing use of the technique. Electron microscopy techniques are used to probe supported SAC on an atomic scale, whether by imaging of structure, or by spectroscopic chemical analysis. The challenge of applying these techniques when the sample is not in a vacuum means that only a limited number of studies are available. Many of the recent studies show the advantages of combining more than one of these techniques.