Barium Carbonate Nanoparticles as Synergistic Catalysts for the Oxygen Reduction Reaction on La0.6Sr0.4Co0.2Fe0.8O3-δ Solid-Oxide Fuel Cell Cathodes

Barium carbonate (BaCO3) nanoparticles have been demonstrated to have excellent synergistic catalytic activity for the oxygen reduction reaction on La0.6Sr0.4Co0.2Fe0.8O3-delta (LSCF) and LSCF-SDC (SDC=Sm0.2Ce0.8O1.9), which are typical mixed conducting electrode materials for solid-oxide fuel cells (SOFCs). The BaCO3 nanoparticles were deposited into the porous electrodes through an infiltration/impregnation method with barium acetate as the precursor. Electrochemical impedance analysis indicated that BaCO3 dramatically reduced the resistance associated with the low-frequency response, which suggests that BaCO3 greatly enhances the kinetics of the surface reaction process. Electrical conductivity relaxation experiments revealed that BaCO3 particles enlarged the oxygen chemical surface exchange coefficient by a factor of up to eight. As a result, the interfacial polarization resistance of both the LSCF and LSCF-SDC electrodes was greatly reduced, from 0.28 and 0.13 to 0.12 and 0.047 Omega cm(2), respectively, at 700 degrees C. In addition, the single-cell performance was also improved and demonstrated peak power density from 0.66 and 0.71 to 0.73 and 0.81 W cm(2) for the LSCF and LSCF-SDC cathodes, respectively, at 700 degrees C. The LSCF electrode infiltrated with BaCO3 nanoparticles also exhibited higher stability than the bare LSCF electrode in tests conducted under typical SOFC conditions for over 340 h of operation.