Near-Edge X-Ray Absorption Spectroscopy in Catalysis

Abstract

Near-edge X-ray absorption (XAS) spectroscopy and techniques related to it by an extension of the photoelectron energy range or a modification in the experimental detection mode have all matured in the past years. The contributions of near-edge X-ray absorption spectroscopy to catalysis and surface science have grown considerably, essentially since the development of synchrotron radiation sources. On a low interpretative level the application of threshold fine-structure effects to catalyst diagnostics has rapidly taken off as atoms in different structural or bonding conditions result in fingerprints that can readily be used for analysis of their structural and chemical state. The near-edge spectroscopy is at its best as an adjunct to other physicochemical characterization methods, such as other XAS techniques, and in combination with XRD, STEM, Auger electron spectroscopy (AES), thermal desorption, and catalytic activity measurements, can expect to bring new insights into the nature of basic catalytic reaction processes. In situ X-ray absorption near edge experiments have the considerable advantage over others that they can be applied to real catalytic problems, sensing changes in the bonding electron distribution and coordination of the environment of the absorber and resulting in more closely matching models of structure and reaction processes.