Investigation of oxide ion flux at cathode/electrolyte interface in solid oxide fuel cell

Abstract

Oxide ion flux at cathode/electrolyte interface of solid oxide fuel cell (SOFC) is investigated through quenching reaction and oxygen isotope labeling. A YSZ (yttria-stabilized zirconia) electrolyte-supported cell with LSM (strontium-doped lanthanum manganite)/YSZ porous cathode is operated by supplying 18O2 at 973 K and abruptly quenched to room temperature by a direct helium gas-impinging jet to the cell. The 18O concentration distribution in the cross section of the cathode/electrolyte interface is obtained by secondary ion mass spectrometry (SIMS) with a spatial resolution of 50 nm. From the analysis of oxygen isotope diffusion profiles in YSZ electrolyte, oxide ion flux incorporated from a cathode/electrolyte interface to an electrolyte is first estimated. The obtained flux 1.01–1.43 × 10−3 mol m−2 s−1 at a current density of 0.09 A cm−2 indicates that 22–31% of the overall electrochemical reaction occurs at the cathode/electrolyte interface, while the remaining 69–78% of those proceeds inside the porous cathode under the present experimental condition.