X-ray photoelectron spectroscopy as a useful tool to study surfaces and model systems for heterogeneous catalysts: A review and perspective

After a brief recapitulation of the historic development of photoelectron spectroscopy, we review the attempts to interpret, in particular, x-ray photoelectron spectra to extract information on electronic structure and constitution, i.e. stoichiometry of materials systems. We focus on materials systems, specifically in the area of heterogeneous catalysis, and modelling their complexity by designing single crystal-based model systems with well-defined structures. This allows us to relate measured chemical shifts observed in X-ray photoelectron spectra, obtained with both laboratory and synchrotron radiation, to structures and also allows us to test those against theory. We discuss a number of systems by combing experimental observations and theory and demonstrate the usefulness of combined theory/experiment approach. We also point out a number of issues, that are often ignored in previous and present studies published in the field of heterogeneous catalysis.