Synthesis And Characterization Of Sulfide Anode For SOFC

As a kind of high efficiency and clean electrochemical energy conversion device, solid oxide fuel cell(SOFC) is promising as the next generation power system which generates electricity from fuel directly. However, the performance of the most commonly used anode--Ni/yttria-stabilized zirconia(Ni/YSZ) is very sensitive to sulfur: at 750 oC, the performance drops dramatically in few minutes by H2 S at levels as low as 0.05 ppm. It is then crucial and necessary to find a new SOFC anode catalyst which is chemically stable in H2S-containing fuels and has a high catalytic activity for the oxidation of H2 and H2 S. The main research content and results are as follows:1、YSZ electrolyte skeleton with different porosity was made by screen printing and impregnated with Ni O in different mass ratio.The performance of impregnated anode was increased with the mass ratio of Ni O. The best electrochemical performance was obtained when the electrolyte skeleton was made from 70 wt. % YSZ and 30 wt. % of stach and impregnated till the mass ratio of Ni O: YSZ to be 1.75: 1.2、Single cells and symmetrical cells were prepared with Mo S2 as anode. The polarization resistance of Mo S2 anode was 3.51 Ω cm2 in 50 ppm H2S-H2 at 850 oC,which was better than 4.25 Ω cm2 when tested in pure H2. Unlike the symmetrical cell, the stability test for the single cell showed that the potential didn’t change with time while loading 40 m A/cm2. The max power density was even higher after durability test(50.3 m W/cm2 vs. 45.2 m W/cm2), indicating that Mo S2 can remain stable in 50 ppm H2S-H2.3、(Co, Ni)9S8 and Co9S8 were synthesized by hydrothermal method and mixed with Mo S2 as SOFC anode. XRD patterns showed that the product of(Co, Ni)9S8 contained Ni3S2 impurity, in contrast, Co9S8 was pure phase. Whether(Co, Ni)9S8 or Co9S8 mixed with Mo S2 as anode, the performance was higher than Mo S2 alone. Once the ratio of Mo S2 in the mixture was reduced, the conductivity was increased obviously and the polarization resistance was decreased at the same time.4、A new electrode preparation method was studied: The electrolyte skeleton was screen printed and calcined on the electrolyte support at first, and then the anode was screen printed on the skeleton and calcined. Symmetrical cell test indicted that anode has electrochemical activity even at as low as 650 °C. The morphology of Co9S8 product varied with different synthesis parameters of hydrothermal reaction, which had no effect on the performance of electrode at high temperature.5、Co9S8 particles were deposited on to the YSZ skeleton directly by using hydrothermal impregnation method and adhered to the skeleton closely after heat treating in N2. The symmetrical cells were measured in the present of 50 ppm H2S-H2 at intermediate temperatures. The polarization resistance was only 0.34 Ω cm2 at 650 °C.