Co-Exsolution Method Via Seeded Effect for Catalytically Active Anode in Protonic Ceramic Fuel Cells

Abstract

Protonic ceramic fuel cells (PCFCs) have great potential in terms of reducing the operating temperature (400-600oC), because of the low activation energy of proton conduction in oxides compared to oxygen ion conduction. These characteristics provide a pathway to overcome the limitation of conventional SOFC (600-1000oC) such as durability, degradation of catalysts. However, poor catalyst activity at low operating temperatures still remains a problem to be solved. One promising way to improve catalytic activity is in-situ exsolution of various metal nanoparticles. Exsolved nanoparticles not only increase the active catalytic area but also have excellent resistance to thermal agglomeration and carbon coking. Unfortunately, it is difficult to achieve a high population density of metal nanoparticles due to the low exsolution kinetics (diffusion, nucleation) in the anode atmospheres of PCFC. In this study, we designed an A-site deficiency proton-conducting oxide, Ba0.9(Zr0.1Ce0.7Y0.1Yb0.1)0.95M0.05O3-d, as a host material to maximize exsolution behaviors. In addition, a co-exsolution strategy with Cu, which has the highest reducibility among transition metals, was introduced to achieve a high population density of exsolved atoms at low temperatures. A single doped Ni metal in the designed host material exhibited a population density value of 1.13 particles/um2 in reducing atmosphere at 600oC. The single doped Cu metal showed 24.1 particles/um2, but Co-doped with Ni and Cu metal produced the highest particle population of 98.31/um2, which is 87 times greater than a single Ni doping. These results follow the seeded growth mechanism induced by the additional surface energy of pre-exsolved Cu. This suggests a new synergy effect on exsolution phenomena that enhances segregation and nucleation kinetics Figure 1