Enhanced electrochemical activity and stability of LSCF cathodes by Mo doping for intermediate temperature solid oxide fuel cells

La0.6Sr0.4Co0.2Fe0.8O3-delta (LSCF), La0.6Sr0.4Co0.2Fe0.78Mo0.02O3-delta (LSCFM02), La0.6Sr0.4Co0.2Fe0.75Mo0.05O3-delta (LSCFM05) cathodes were prepared and their electrochemical performance and stability were investigated. Mo doping into LSCF, which is confirmed by X-ray diffraction (XRD) and Rietveld refinement, increases unit cell parameters from 3.893 to 3.924 angstrom, causing expansion of unit cell volume. Polarization resistance (R-p) value of LSCFM05 cathodes is less that of LSCF cathodes at 750 degrees C, indicating that Mo-doped LSCF exhibits enhanced electrochemical performance. X-ray photoelectron spectroscopy (XPS) analysis shows that high electrocatalytic activity for oxygen reduction reaction of Mo-doped LSCF cathodes is related to mixed-valent Mo5+/Mo6+. LSCFM05 cathodes have less degradation rate during 20 h testing at 700 degrees C in air compared to LSCF cathodes. XPS results show that Mo doping reduces Sr surface segregation and is responsible for the stability enhancement of LSCF cathodes. [GRAPHICS] .