Enhanced electrochemical performance of BaZr_(0.1)Ce_(0.7)Y_(0.1)Yb_(0.1)O_(3-δ) electrodes for hydrogen and methane oxidation in solid oxide fuel cells by Pd or Cu_(0.5)Pd_(0.5) impregnation

摘要

The anode material BaZr_(0.1)Ce_(0.7)Y_(0.1)Yb_(0.1)O_(3-δ) (BZCYYb) for solid oxide fuel cells (SOFCs) is prepared by solid state reaction method and its chemical compatibility with Y_2O_3 stabilized ZrO_2 (YSZ) is evaluated. The electrochemical performance of the pure and Pd- and Cu_(0.5)Pd_(0.5)-impreganated BZCYYb electrodes is characterized in the temperature range between 650 and 750 ℃ by AC impedance spectroscopy in H_2 and/or CH_4 atmospheres, respectively, under the condition of open circuit. It is confirmed that the BZCYYb is chemically compatible with the YSZ at temperatures below 1000 C. The polarization resistance of the BZCYYb anode in H_2 is decreased from 2.08 to 0.51 Ω cm~2 as the measuring temperature increases from 650 to 750 C with an activation energy of 117 kJ moh~(-1). With Pd- or Cu_(0.5)Pd_(0.5)-impregnation, the polarization resistance of the BZCYYb electrode in H_2 is reduced significantly to approximately 0.40Ω cm~2 at 650 ℃ and 0.12 Ω cm~2 at 750 ℃. With dry CH_4 as the fuel, the polarization resistance of the Pd- and Cu_(0.5) Pd_(0.5)-impregnated BZCYYb anodes is obviously increased below 1.00 Ω cm~2 at 650 ℃ and 0.22 Ω cm~2 at 750 ℃. Both Pd and Cu-0.5 Pd_(0.5) impregnations are equivalently effective in enhancing the electrochemical performance of the BZCYYb anode.