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 La 0·9 Sr 0·1 CoO 3 are prepared and a single-component solid oxide fuel cell composed of 30 wt% perovskite oxide and 70 wt% samarium-doped ceria (SDC)-(Li 0·67 Na 0.33 ) 2 CO 3 is fabricated and characterized. When doping with either Fe, Ni or Zn, most cations occupy the Co 3+ sites. X-ray photoelectron spectroscopy and oxygen temperature-programmed desorption characterizations show that Zn-doped La 0·9 Sr 0·1 CoO 3 exhibits notably high surface oxygen, causing higher catalytic activity for oxygen reduction reaction (ORR) than that of nondoped La 0·9 Sr 0·1 CoO 3 . Fe or Ni doping into La 0·9 Sr 0·1 CoO 3 decreases surface oxygen, resulting in a lower catalytic activity toward ORR than La 0·9 Sr 0·1 CoO 3 . Furthermore, X-ray diffraction, temperature-programmed reduction and transmission electron microscopy characterizations prove that after reduction, Fe-doped La 0·9 Sr 0·1 CoO 3 is reduced to Co 0·72 Fe 0.28 alloy-oxide core-shell nanoparticles , resulting in a high catalytic activity for hydrogen oxygen reaction (HOR). However, NiCo 2 O 4 are formed during the reduction of Ni-doped La 0·9 Sr 0·1 CoO 3 , exhibiting a low catalytic activity for the HOR. Similarly, the low catalytic activity of reduced Zn-doped La 0·9 Sr 0·1 CoO 3 for the HOR is caused by the formation of ZnCo 2 O 4 . A single component fuel cell composed with Fe-doped La 0·9 Sr 0·1 CoO 3 -SDC-(Li 0·67 Na 0.33 ) 2 CO 3 exhibits the highest P max of 239.1 mW cm −2 at 700 °C with H 2 as fuel, indicating that HOR processes are rate-determining steps.