(Invited) Controlling the Size and Dispersion of Exsolved Catalyst Particles By Electrochemistry and By Strain

Abstract

Increasing the performance of Solid Oxide Electrolysis Cells (SOECs) for the production of hydrogen (H2) from water (H2O) splitting requires the use of cathodes with low polarization resistance. In-situ growth of metal catalysts from perovskite oxides (termed catalyst exsolution) has been proposed as a means to decorate the porous electrode with highly dispersed, nanometer-sized catalytic particles [1-3]. These particles are highly active towards reactions of interest and show increased resistance to agglomeration due to their socketed nature [4].In this work, we investigate the in-situ, on demand exsolution of catalysts by using fuel and electrochemistry as a means to decrease the temperature and duration required to grow catalytic particles on the surface of electrodes. We study the performance, stability, particle morphology and distribution as a function of electrochemical polarization applied at the electrode. Substantial improvement of reaction kinetics is found, consistent with previous reports [5]. In addition, we probe the effect of electrochemical and temperature conditions on the particle size, shape and distribution. In addition, we propose tuning the reducibility of parent oxides to be a good strategy in controlling the size and dispersion of the exsolved particles, and demonstrate this approach on epitaxial perovskite thin films. Moreover, our observations suggest oxygen vacancies to be the potential nucleation sites of the exsolved particles.The present study provides a new direction towards the generation of nanoparticle-size catalysts on the surface of perovskite oxides given the increasing demand for active and durable catalysts in the field of solid oxide cells and in other energy and fuels conversion processes.