Synthesis, electrical and electrochemical properties of Ba_(0.5)Sr_(0.5)Zn_(0.2)Fe_(0.8)O_(3-δ) perovskite oxide for IT-SOFC cathode

摘要

The Ba_(0.5)Sr_(0.5)Zn_(0.2)Fe_(0.8)O_(3-δ) (BSZF) complex oxide with cubic perovskite structure was synthesized and examined as a new cobalt-free cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The electrical conductivity was relatively low with a peak value of 9.4 S cm~(-1) at about 590 ℃, which was mainly caused by the high concentration of oxygen vacancy and the doping of bivalent zinc in B-sites. At 650℃ and under open circuit condition, symmetrical BSZF cathode on Sm-doped ceria (SDC) electrolyte showed polarization resistances (R_p) of 0.48 Ω cm~2 and 0.35 Ω cm~2 in air and oxygen, respectively. The dependence of R_p with oxygen partial pressure indicated that the rate-limiting step for oxygen reduction was oxygen adsorption/desorption kinetics. Using BSZF as the cathode, the wet hydrogen fueled Ni + SDC anode-supported single cell exhibited peak power densities of 392 mW cm~(-2) and 626 mW cm~(-2) at 650 ℃ when stationary air and oxygen flux were used as oxidants, respectively.