Effect of Fe, Ni and Zn dopants in La0·9Sr0·1CoO3 on the electrochemical performance of single-component solid oxide fuel cell

Fe-, Ni- and Zn- doped La0·9Sr0·1CoO3 are prepared and a single-component solid oxide fuel cell composed of 30 wt% perovskite oxide and 70 wt% samarium-doped ceria (SDC)-(Li0·67Na0.33)2CO3 is fabricated and characterized. When doping with either Fe, Ni or Zn, most cations occupy the Co3+ sites. X-ray photoelectron spectroscopy and oxygen temperature-programmed desorption characterizations show that Zn-doped La0·9Sr0·1CoO3 exhibits notably high surface oxygen, causing higher catalytic activity for oxygen reduction reaction (ORR) than that of nondoped La0·9Sr0·1CoO3. Fe or Ni doping into La0·9Sr0·1CoO3 decreases surface oxygen, resulting in a lower catalytic activity toward ORR than La0·9Sr0·1CoO3. Furthermore, X-ray diffraction, temperature-programmed reduction and transmission electron microscopy characterizations prove that after reduction, Fe-doped La0·9Sr0·1CoO3 is reduced to Co0·72Fe0.28 alloy-oxide core-shell nanoparticles, resulting in a high catalytic activity for hydrogen oxygen reaction (HOR). However, NiCo2O4 are formed during the reduction of Ni-doped La0·9Sr0·1CoO3, exhibiting a low catalytic activity for the HOR. Similarly, the low catalytic activity of reduced Zn-doped La0·9Sr0·1CoO3 for the HOR is caused by the formation of ZnCo2O4. A single component fuel cell composed with Fe-doped La0·9Sr0·1CoO3-SDC-(Li0·67Na0.33)2CO3 exhibits the highest Pmax of 239.1 mW cm−2 at 700 °C with H2 as fuel, indicating that HOR processes are rate-determining steps.