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

La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3− δ (LSCF), La 0.6 Sr 0.4 Co 0.2 Fe 0.78 Mo 0.02 O 3− δ (LSCFM02), La 0.6 Sr 0.4 Co 0.2 Fe 0.75 Mo 0.05 O 3− δ (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 Å, causing expansion of unit cell volume. Polarization resistance ( R p ) value of LSCFM05 cathodes is less that of LSCF cathodes at 750 °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 Mo 5+ /Mo 6+ . LSCFM05 cathodes have less degradation rate during 20 h testing at 700 °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. Graphic Abstract