Effect of Cu doping on YBaCo2O5+δ as cathode for intermediate-temperature solid oxide fuel cells

• DOI: 10.1016/j.electacta.2014.04.126
• Publication Date: 2014-04-30T19:31:50Z
• Authors: Yongjun Zhang; Bo Yu; Shiquan Lü; Xiangwei Meng; Xiaoyu Zhao; Yuan Ji; Yaxin Wang; Chengwei Fu; Xiaoyan Liu; Xiuyan Li; Yingrui Sui; Jihui Lang; Jinghai Yang
• Keywords: 13. Climate action; 02 engineering and technology; 0210 nano-technology; 01 natural sciences; 7. Clean energy; 0104 chemical sciences; 3. Good health

Abstract Layered-perovskites YBaCo 2-x Cu x O 5+δ (YBCCO, x = 0.0, 0.2, 0.4, 0.6, 0.8) are synthesized by the sol-gel method and are assessed as potential cathode materials for utilization in intermediate-temperature solid oxide fuel cells (IT-SOFCs) on the La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3-δ (LSGM) electrolyte. With increasing x from 0.0 to 0.8, the structure does not change but the lattice parameters and unit-cell volumes increase. From X-ray photoelectron spectra, it can be seen that both Cu and Co exist in a mixed oxidation state. Cu ions are prone to low oxidation state (Cu + and Cu 2+ ), while Co ions basically exhibit high oxidation state (Co 3+ and Co 4+ ). The conductivity of the YBCCO samples decreases with increasing Cu content, and the maximum conductivity of YBCCO is 143 S cm −1 at 300 °C for the x = 0.0 sample. The thermal expansion coefficient of samples significantly decreases from 17.8 × 10 −6 K −1 for x = 0.0 to 13.4 × 10 −6 K −1 for x = 0.8 in the temperature range of 30–850 °C. With increasing Cu substitution content for Co, the electrode polarization resistance ( R p ) increases. The R p values of the YBCCO ( x =0.6) cathode on the LSGM electrolyte are 0.125 Ω cm 2 and 0.076 Ω cm 2 at 700 °C and 750 °C, respectively. The maximum power densities of the single cells fabricated with the LSGM electrolyte, Ce 0.8 Gd 0.2 O 1.9 (GDC) interlayer, NiO/GDC anode and YBCCO ( x = 0.6) cathode reach 815, 642 and 479 mW cm −2 at 850, 800 and 750 °C, respectively. This study suggests that the layered-perovskites YBCCO can be potential candidates for utilization as IT-SOFC cathodes.