First-Principles Insight into the Hydration Ability and Proton Conduction of the Solid State Proton Conductor, Y and Sn Co-Doped BaZrO3

Y and Sn co-doped BaZrO3 (BZSY) has recently been shown to exhibit superior hydration ability and improved power output performance compared to those of the traditional solid oxide fuel cell (SOFC) electrolyte, Y-doped BaZrO3. The fact that BZSY is also chemically stable in both H2O and CO2 atmospheres further illustrates the great potential for BZSY as a future electrolyte material in proton-conducting SOFCs. In this work, we conducted comprehensive density functional theory calculations to analyze the energetics of hydration and proton migration in BZSY. The energy of hydration is calculated at four different locations in the cell to better assess the specific contributions of each defect type. For all locations tested, hydration is found to be strongly exothermic and is most favorable when Y ions are in the vicinity. The calculated energies of hydration (-1.72 to -1.11 eV) are significantly lower than any previously calculated for acceptor-doped BaZrO3-based electrolytes. Nudged elastic band calculations confirm low proton reorientation energies (0.080.24 eV) and low intraoctahedral hopping energies (0.210.41 eV) and that these diffusion barriers are at minimum when the proton is migrating to an oxygen ion in a YO6 octahedron. Our results show how the synergy of the Sn and Y dopant ions produces the excellent hydration and conduction performance of BZSY and fully support its potential application in next-generation SOFCs.