Tuning reduction conditions to understand and control Ni exsolution from Sr0.8La0.1Ca0.1Ti0.94Ni0.06O3−δ

Abstract

Ceramic-supported metal catalysts formed by exsolution of metal nanoparticles from perovskites are promising materials for energy and chemical conversion applications. However, our incomplete understanding of the exsolution mechanism presents a roadblock to engineering exsolution nanoparticle properties. We investigated the influence of reduction conditions on the properties of Ni nanoparticles exsolved on the fracture surfaces of Sr_0.8La_0.1Ca_0.1Ti_0.94Ni_0.06O_3−δ. We first carried out exsolution at 25 different temperatures and oxygen chemical potentials. We found that reduction at lower temperatures and moderate oxygen chemical potentials produced more numerous, smaller nanoparticles. We then fit our data to a LaMer nucleation model where the number of nanoparticles formed depends on Ni surface segregation, reduction of Ni-rich surfaces, and nanoparticle growth. Finally, we demonstrated prediction of the energetics of these processes with density functional theory calculations. Our experiments and modelling build understanding of the exsolution mechanism and are a step towards computational design of supported metal catalysts made via exsolution.