Improving Proton Conductivity by Navigating Proton Trapping in High Scandium-Doped Barium Zirconate Electrolytes

Proton-conductingoxides are used in intermediate-temperature (300 & DEG;C < T < 700 & DEG;C) applications offuel cells, electrolyzers, membrane reactors, hydrogen pumps, andsensors. The proton conductivity of doped ABO(3) perovskitesis partly dependent on the proton concentration and hence on the levelof material hydration. However, how the material hydration abilityis affected by differences in doping is not fully understood. Here,we show the prospect of proton trapping and detrapping that influencesmaterial hydration and dehydration. The proton-trapping influenceis significant for Sc-doped BaZrO3 compared to Y-dopedBaZrO(3). Our work offers a perspective to understand howdefect interaction/associations influence the hydration ability ofproton-conducting oxides. Furthermore, positron annihilation lifetimespectroscopy was revealed to be a valuable technique for studyingthe proton-trapping phenomena and the defect chemistry of dense protonconductors. Density functional theory calculations also showed thata high hydration level in Sc-doped BaZrO3 boosts protonmigration. In contrast, the effect of boosting the proton migrationdue to increased hydration is limited for Y-doped BaZrO3. This effect, in turn, might explain the trend of conductivity withdopant concentration in doped BaZrO3.