Unveiling The Effect of Dopants on the Hydration Reaction and Proton Conduction of Nd and Y Co-Doped BaZrO3 in Solid Oxide Fuel Cells

Abstract

Both surface and bulk properties on hydration reaction and proton conduction of Nd and Y co-doped BaZrO3 (BZNY) were investigated for the first time by first-principles calculations. The effects of Nd and Y on oxygen vacancies in BaZrO3 are opposite to those in BaCeO3, which allows us to break away from the traditional misunderstanding that the larger the radius of the doped ion, the easier it is to form oxygen vacancies. We can also infer from the calculation that the hydration reaction has a negative correlation with the formation of oxygen vacancies. Both oxygen vacancies and protons were calculated to have a tendency to accumulate on the BZNY surface, which facilitates promoting surface hydration reaction. It is worth noting that Nd and Y reduce the difference in proton stability of the layers near the surface, therefore promote proton transmission. Unexpectedly, Y3+ (0.900 Å) was calculated to be more likely to segregate in BZNY than Nd3+ (0.983 Å), which subverts our traditional view that doped ions with larger radius are easier to segregate. Moreover, for proton transport though the grain boundaries, the segregation of Nd and Y were also predicted to have beneficial effects in BZNY.