中温固体氧化物燃料电池NiO/YSZ阳极的还原过程

The Reduction Process of a NiO/YSZ Anode for Intermediate Temperature Solid Oxide Fuel Cells

以氢气程序升温还原(H2-TPR)为手段,研究了中温固体氧化物燃料电池烧结NiO/YSZ阳极的还原过程,并通过对电池开路电位和阻抗的原位监测考察了电池中阳极的还原过程.H2-TPR结果表明,阳极烧结温度升高,阳极中的NiO变得难以还原,但当温度提高到1500℃时,NiO还原峰的峰温降低.阳极NiO含量越高,NiO越容易被还原.这是由于烧结过程中NiO颗粒长大和NiO/YSZ界面分离共同作用的结果.电池原位还原过程中开路电位的变化表明,具有高NiO含量的阳极还原较慢.这主要是由于高NiO含量的阳极具有较大的收缩率和大的NiO粒子,导致还原初期产生的大量H2O不能被及时排出,从而抑制了还原过程.电池还原过程中交流阻抗谱的变化表明,50%NiO/YSZ阳极具有最稳定的还原过程.30%和70%NiO/YSZ电池都有一个极化电阻逐渐增大的过程,前者的极化电阻在还原600min后逐渐稳定,而后者并不能稳定.

The reduction behavior of a sintered NiO/YSZ anode used for intermediate temperature solid oxide fuel cells was studied by hydrogen temperature-programmed reduction （H2-TPR）. The reduction process of the NiO/YSZ anode in the cell was in situ monitored by open circuit voltage （OCV） and electrochemical impedance spectroscopy （EIS）. H2-TPR results show that the higher sintering temperature of the NiO/YSZ anode results in a slower reduction of NiO to metallic Ni. However, when the sintering temperature is elevated to 1 500 ℃ , the reduction of sintered NiO/YSZ anode powder instead becomes easier. The higher NiO content in the anode leads to the more rapid reduction of the corresponding anode powder. The above H2-TPR results can be attributed to the combined effects of the growth up of NiO particles and the interface separation between NiO and YSZ caused by the anode sintering. The variation of OCVs reveals that for the cells, the anode with higher NiO content has a slower reduction process, which can be ascribed to the retarding effect of excessive H2O produced during the initial reduction period. It was found from the EIS results that the 50 % NiO/YSZ anode has a most stable reduction process, whereas for the cells with 30 % and 70 % NiO/YSZ anodes, both the polarization resistances gradually increase after experiencing an initial decrease for a short period. The cell polarization resistance with 30 % NiO/ YSZ anode keeps no change any more after reduction for 600 min, whereas the cell polarization resistance with 70 % NiO/YSZ anode increases continuously.