Derui Zhou

Sealing Glass of Barium-Calcium-Aluminosilicate System for Solid Oxide Fuel Cells

Abstract Glass-ceramic materials were developed as a sealant in the solid oxide fuel cell (SOFC) in the temperature range of 800 ∼ 850 °C. The glass materials were based on the glass and glass-ceramic in the BaO-CaO-Al 2 O 3 -SiO 2 -La 2 O 3 -B 2 O 3 system. The thermal expansion coefficient (TEC) decreased with lower Ba 2+ content and higher Ca 2+ content, but the glass transition temperature and crystallization temperature increased greatly with an increase in Ca 2+ content and a decrease in Ba 2+ content, when the other components in the sealant were invariable. The TEC of the sealant with Ba 2+ content of 25.4% was 10.8 × 10 −6 K −1 (temperature range from 25 to 850 °C), and its softening temperature was 950 °C. The TEC of the sealant accorded well with that of La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3 - 6 (LSGM) with a mismatch of only 3%. The sealant had superior stability and compatibility with the LSGM electrolyte during the process of operation in SOFC. The weight loss of the sealant with Ba 2+ content of 25.4% was approximately zero after heat-treated at 800 °C for 500 h in H 2 and O 2 atmosphere, respectively.

Electrochemical and microstructural characterization of cyclic redox behaviour of SOFC anodes

Abstract The oxidation of Ni to NiO in solid oxide fuel cell (SOFC) anode will result in large bulk volume change, which may change the interfaces of the two phases in the anode cermet and thus may cause significant performance degradation. The reduction and oxidation (redox) of the Ni/YSZ cermet were studied at 800 °C. Anodic polarization measurements were performed before and after redox cycles. The anode current density at an overpotential of 100 mV kept decreasing during the whole redox treatment. It decreased from 19.11 to 7.95 mA·cm −2 after two redox cycles. Anode supported unit cell was assembled for cells discharge measurements. Cell performance declined after each redox cycle. The maximum power density decreased from 126.28 to 40.32 mW·cm −2 . The microstructural changes after redox cycling were recorded using scanning electron microscopy (SEM). The results reveal that after re-oxidation, the Ni gets coarse and has a higher porosity; the nickel network structure turns to be desultory.

Fabrication and performance of La0.8Sr0.2MnO3/YSZ graded composite cathodes for SOFC

Abstract The performance of multi-layer (1 − x) La0.8Sr0.2MnO3/x YSZ graded composite cathodes was studied as electrode materials for intermediate solid oxide fuel cells (SOFC). The thermal expansion coefficient, electrical conductivity, and electrochemical performance of multi-layer composite cathodes were investigated. The thermal expansion coefficient and electrical conductivity decreased with the increase in YSZ content. The (1 -x)La0.8Sr0.2MnO3/x YSZ composite cathode greatly increased the length of the active triple phase boundary line (TPBL) among electrode, electrolyte, and gas phase, leading to a decrease in polarization resistance and an increase in polarization current density. The polarization current density of the triple-layer graded composite cathode (0.77 A/cm2) was the highest and that of the monolayer cathode (0.13 A/cm2) was the lowest. The polarization resistance (Rp) of the triple-layer graded composite cathode was only 0.182 ω·cm2 and that of the monolayer composite cathode was 0.323 ω·cm2. The power density of the triple-layer graded composite cathode was the highest and that of the monolayer composite cathode was the lowest. The triple-layer graded composite cathode had superior performance.

Electrochemical properties of La0.8Sr0.2FeO3-δ based composite cathode for intermediate temperature SOFC

Abstract La0.8 Sr0.2FeO3-δ is a new kind of cathode material for intermediate SOFC, but its electrochemical activity is relative poor for the lanthanum gallate based solid oxide fuel cell. In this paper, a novel composite cathode of La0.8Sr0.2FeO3-δ/La0.9Sr0.1 Ga0.8Mg0.2O3-δ was prepared on the LSGM electrolyte substrate by screen-printing method. The results of cathodic polarization measurements show that the overpotential decreases significantly when the composite cathode is used instead of the La0.8Sr0.2 FeO3-δ single layer cathode. The cathodic overpotential of the composite La0.8Sr0.2FeO3-δ/La0.9Sr0.1Ga0.8Mg0.2O3-δ cathode is 150 mV at the current density of 0.2 A·cm−2 at 800 °C, while the cathodic overpotential of the La0.8Sr0.2 FeO3-δ single layer cathode is higher than 260 mV at the same condition. The electrochemical impedance spectroscopy was employed to investigate the polarization resistance of the cathode. The polarization resistance of the composite cathode is 1.20 ω·cm2 in open circuit condition, while the value of the single La0.8 Sr0.2FeO3-δ cathode is 1.235 ω·cm2.