However, this shift of paradigm results in an even more pressing need for experimental tools that would allow one to probe the composition, structure, and dynamics of catalysts under realistic reaction conditions. (1−9) The concept of catalysts being dynamic systems that actively transform and respond to the reaction conditions, rather than just a static arrangement of atoms, is almost commonplace now. Such advanced new methods have allowed us to gain deeper insight into the complex processes that take place in thermal- and electro-catalysts while at work. The last decades have been marked by drastic developments in experimental in situ and operando characterization techniques as well as great progress in theory.
More specifically, we will discuss applications of in situ and operando XAS to probe the catalyst’s interactions with the environment (support, electrolyte, ligands, adsorbates, reaction products, and intermediates) and its structural, chemical, and electronic transformations as it adapts to the reaction conditions. This review will highlight the new insight that can be gained with XAS on complex real-world electrocatalysts including their working mechanisms and the dynamic processes taking place in the course of a chemical reaction.
The latter is a rapidly developing field with immense industrial applications but also unique challenges in terms of the experimental characterization restrictions and advanced modeling approaches required. Recent usages of XAS in the field of heterogeneous catalysis, with emphasis on examples concerning electrocatalysis, will be presented. Here we discuss the fundamental principles of the XAS method and describe the progress in the instrumentation and data analysis approaches undertaken for deciphering X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra. During the last decades, X-ray absorption spectroscopy (XAS) has become an indispensable method for probing the structure and composition of heterogeneous catalysts, revealing the nature of the active sites and establishing links between structural motifs in a catalyst, local electronic structure, and catalytic properties.