Goldsmiths' Lecture Room 1
Speaker: Professor Bilge Yildiz, Massachusetts Institute of Technology, Cambridge, USA
Abstract:
Exsolution is an effective approach to fabricating oxide-supported metal nanoparticle (electro-)catalysts via phase precipitation out of a host oxide. A fundamental understanding and control of the exsolution kinetics are needed to engineer the size, density and composition of exsolved nanoparticles to obtain higher catalytic activity toward clean energy and fuel conversion reactions, such as in solid oxide fuel and electrolysis cells. Since oxygen release via oxygen vacancy formation in the host oxide is behind oxide reduction and metal exsolution, we hypothesize that the kinetics of metal exsolution should depend on the kinetics of oxygen release. In this work, we probe the surface exsolution kinetics both experimentally and theoretically using thin-film perovskite oxide model systems, show its relation to the oxygen evolution kinetics, and tune it by external drivers including elastic strain and ion irradiation. Using both drivers, we couple to the formation of point defects and defect clusters, that serve as nucleation sites for nanoparticle exsolution. As a result, we can controllably tune size, density, composition and position of the exsolved metal nanoparticles. This finding can guide the design of exsolution electrocatalysts to advance the performance and durability of solid oxide electrochemical cells.