Understanding electrochemical switchability of perovskite-type exsolution catalysts
Alexander Karl Opitz, Andreas Nenning, Vedran Vonk, S. A. Volkov, Florian Bertram, Harald Summerer, Sabine Schwarz, Andreas Steiger‐Thirsfeld, Johannes Bernardi, Andreas Stierle, Jürgen Fleig
Abstract
Abstract Exsolution of metal nanoparticles from perovskite-type oxides is a very promising approach to obtain catalysts with superior properties. One particularly interesting property of exsolution catalysts is the possibility of electrochemical switching between different activity states. In this work, synchrotron-based in-situ X-ray diffraction experiments on electrochemically polarized La 0.6 Sr 0.4 FeO 3-δ thin film electrodes are performed, in order to simultaneously obtain insights into the phase composition and the catalytic activity of the electrode surface. This shows that reversible electrochemical switching between a high and low activity state is accompanied by a phase change of exsolved particles between metallic α-Fe and Fe-oxides. Reintegration of iron into the perovskite lattice is thus not required for obtaining a switchable catalyst, making this process especially interesting for intermediate temperature applications. These measurements also reveal how metallic particles on La 0.6 Sr 0.4 FeO 3-δ electrodes affect the H 2 oxidation and H 2 O splitting mechanism and why the particle size plays a minor role.