Catalyst Electronic Surface Structure Under Gas and Liquid Environments

Abstract

In this chapter we demonstrate the potential of ambient pressure X-ray photoelectron spectroscopy (AP-XPS) for the estimation of the electronic structure of gas–solid and liquid–solid interfaces active in catalytic processes. Within the last 10 years a strong increase in applications of synchrotron radiation based AP-XPS was observed in studies related to the characterization of heterogeneous catalytic reactions. In particular the correlation of the electronic structure of the active catalyst surfaces and the catalytic performance obtained by in situ studies has provided new insights into reaction mechanisms of heterogeneous catalytic reactions. The huge potential of this technique has led many synchrotron radiation facilities to implement dedicated beamlines with infrastructure for AP-XPS measurements. More recently a demand for investigations of electrochemically active liquid–solid interfaces occurred due to the development of energy storage facilities like electrolyzers. Therefore the evolution of electrochemical in situ cells was triggered and the first studies have recently appeared in the literature. This chapter consists of three parts. Part one describes a study of the CO oxidation over Au nanoparticles. Part two gives a general overview about techniques and related in situ cells which can be applied to the characterization of electrochemically active solid–liquid interfaces. The last part summarizes studies of Pt and IrOx anodes used in the oxygen evolution reaction (OER). The study clearly shows correlations between the evolved oxygen and the electronic structure of the active anodes. In this contribution we will introduce examples of in situ measurements performed at the synchrotron radiation facility BESSY II in Berlin, Germany.