(247y) Enhanced Oxygen Incorporation Near the Grain Boundary on Yttria-Stabilized Zirconia: A Density Functional Theory Study

Solid oxide fuel cell (SOFC) is a clean technology with less emission of air pollutants, but the high operating temperature (600~1000°C) causes significant issues related to materials stability and system cost. Since electrolyte conductivity and electrode kinetics are considerably deteriorated at lower temperature, improving the performance on them plays an important role in reducing the operating temperature of SOFC. The recently reported oxygen incorporation enhancement near the grain boundary (GB) of yttria-stabilized zirconia (YSZ) accelerated the realization of low temperature SOFC. However, the detailed reaction mechanism of the process is still not clear yet. To unravel it, we performed first-principles calculations to quantitatively access each elementary step of oxygen incorporation into YSZ, including yttrium dopant segregation, oxygen vacancy formation, and oxygen adsorption. We found that the doped yttrium which preferentially segregates towards GB facilitates to create the formation of oxygen vacancy between the yttrium pair. The oxygen is then easily adsorbed near the oxygen vacancies accumulated at GB, eventually incorporating into the vacancy sites. Our results will provide useful insight to unravel oxygen incorporation mechanism at the interfaces on defected oxide materials.