= 아 래 =
1. 일 시 : 2014. 11. 28 (금), 11:00 ~
2. 장 소 : 신소재 공학과 2427호
3. 연 사 : 오태식 박사 (University of Pennsylvania)
4. 제 목 : Metal exsolution from oxides and its applications
Transition metal cations can exsolve from a host oxide lattice under reducing conditions, and this process can be used to decorate the oxide surface with catalytically active metal nanoparticles. Upon oxidation, the exsolved particles re-dissolve into the lattice for regeneration of nanoparticles in the following reduction step. This reversibility makes them attractive for any catalytic application where catalyst coarsening is of concern. ABO3 perovskites are natural choice for host material since they provide wide-ranged tunability in nonstoichiometry and solubility for many metal cations. In solid oxide fuel cell community, many perovskite oxides have been considered as candidates to replace conventional nickel-YSZ (yttria stabilized zirconia) composite anode owing to their appropriate transport property. Accordingly, perovskite fuel cell anodes with exsolution particles were tested and showed great anti-coarsening property. In addition, it has been shown that one can, by redox cycling, recover the initial fuel cell anode performance after performance degradation. In this presentation, I demonstrate unique anti-coking behavior of nickel particles exsolved from lanthanum strontium titanate upon dry methane exposure. This has a direct impact on hydrocarbon reforming. Utilizing imaging tools, I show how metal particles nucleate to come out of the perovskite lattice. One has to consider the energy balance between surface energy and strain energy to explain observed morphology evolution. Potential applications of this phenomenon will also be discussed including bulk transport property tuning.