Understanding electrochemical switchability of perovskite-type exsolution catalysts

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. Exsolution, nanoparticle precipitation from oxide materials during reduction, offers a promising approach to heterogeneous catalysis. Here, authors examine the switching behavior between high and low activity and correlate the electro-catalytic activity to exsolved phases from complex oxides.