Exsolution versus particle segregation on (Ni,Co)-doped and undoped SrTi0.3Fe0.7O3-δ perovskites: Differences and influence of the reduction path on the final system nanostructure

Abstract

Exsolution is one of the most successful functionalization techniques to improve the catalytic activity of electrodes in solid oxide fuel and electrolyzer cells (SOFC/SOEC). The objective of this technique is to produce the highest possible number of metallic nanoparticles on the surface of a host-oxide, without significantly altering its structure. In this work, we compare three similar SOFC electrodes: STF (SrTi0.3Fe0.7O3), STFN (Sr0.93Ti0.3Fe0.63Ni0.07O3), and STFNC (Sr0.93Ti0.3Fe0.56Ni0.07Co0.07O3), revealing that there is a significant difference between Ni–Fe/Ni–Co–Fe nanoparticle formation in STFN/STFNC and pure Fe0 particle formation in STF, which is evidenced by the size and amount of produced nanoparticles, but also by their anchoring to the host-oxide. The terms exsolution and particle segregation will be used, respectively, to distinguish these phenomena. Next, we explore two different reduction methods and observe that the characteristics of exsolution do not only depend on temperature, atmosphere and reduction times, but also on the reduction path taken to reach such conditions.