A novel cobalt-free Ba_(0.5)Sr_(0.5)Fe_(0.9)Mo_(0.1)O_(3-δ)-BaZr_(0.1)Ce_(0.7)Y_(0.2)O_(3-α) composite cathode for solid oxide fuel cells

摘要

A new series of cobalt-free perovskite-type cathode materials Ba_(0.5)Sr_(0.5)Fe_(1-x)Mo_xO_(3-δ) (0≤x≤0.2) for proton conducting intermediate temperature solid oxide fuel cells (IT-SOFCs) are prepared by a citric-nitrate process. The conductivities of the cathode materials are measured as functions of temperature (300-800 ℃) and oxygen partial pressure (1-10~(-10)atm). It is found that partial substitution of Mo for Fe site obviously enhances the conductivities of the cathode materials. Among the series of samples, Ba_(0.5)Sr_(0.5)Fe_(0.9)Mo_(0.1)O_(3-δ) (BSFM10) has the highest conductivity to be 192Scm~(-1) in air at 400 C. The samples of 0≤x≤0.15 are p-type electronic conductors in the oxygen partial pressure range tested. An anode-supported Ba_(0.1)Ce_(0.7)Y_(0.2)O_(3-α) (BZCY) electrolyte membrane is successfully fabricated by a simple, cost-effective spin coating process. Peak power densities of the hydrogen/air fuel cell using BZCY electrolyte membrane and BSFM10-BZCY composite cathode reach 153 mW cm~(-2) at 600 C,253mWcm~(-2) at 650 C and 420 mWcm~(-2) at 700 C, respectively. The interfacial polarization resistance (R_p) for the fuel cell is as low as 0.15 Ω cm~(-2) at 700 ℃ under open circuit conditions.