Proton conduction at the surface of Y-doped BaCeO3

In our work, 25 mol % of Y3+-doped BaCeO3 (BCY25) showed an extremely low activation energy of 0.3 eV for proton conduction at the surface. The resulting overall conductivity at the surface reached 8.24 x 10(-3) S cm(-1) at 400 degreesC, which was 3, 8, and 28 times higher than conductivities in the bulk of BCY25, 20 mol % Sm3+-doped ceria, and 8 mol % yttriia-stabilized zirconia, respectively. A large H/D isotope effect strongly suggested that the enhanced proton conductivities were due to an advantageous jump of protons between adjacent oxide ions at the surface. Such fast proton conduction enabled an air/fuel sensor using BCY25 as the solid electrolyte to work at 200 degreesC or less.