(La,Sr)(Cr,Ni)O3/CeO2-Based Composite Anode with Various Ni Content and Mixing Ratio for SOFC

Abstract

Introduction Fuel cells are being developed as one of the power sources in the near future. Among them, solid oxide fuel cell (SOFC) is known for its high efficiency due to its high operating temperature. On the other hand, because of the high temperature, problems such as sintering, material compatibility, and mismatch of thermal expansion occurs. Generally, a so-called cerment is used for the anode material, which is a composite of metals and ceramics. Ni-YSZ (Yttria Stabilized Zirconia) is the most common cermet, but metal particles such as Ni would show degradation due to the sintering of the particles and/or due to expansion and contraction by thermal or redox cycling. As an alternative to Ni-YSZ anode, perovskite-type oxide has been attracting attention. Some perovskite type oxide show deposition of metal particles on the surface of the oxides in a reducing atmosphere, which is expected to increase catalytic activity. The deposited metal particles would dissolved in the structure in an oxidizing atmosphere. We have reported this repeating deposition and dissolution would recover the degradation using Pd doped lanthanum-chromite based perovskite type oxide. In this study, LSCN with different Ni composition ratio (La,Sr)(Cr,Ni)O3 were prepared, and their performance was compared. The performance of anode with different ratio of LSCN and doped ceria was also investigated. Experimental LSCN was prepared by citrate process. Crystal structure of the sample was determined using X-ray diffraction. Mixture of LSCN and GDC was used as the anode. Sm0.5Sr0.5CoO3 was used for the cathode. Electrochemical performance was investigated by measuring current-voltage characteristic at 900 ˚C. Terminal voltage change over time was measured during power generation at constant current for 16 h, followed by oxidation treatment, and another 16 h of power generation. Results Fig. 1 shows current density vs. time during power generation at constant current using anode with different mixing ratio of La0.85Sr0.15Cr1-x Ni x O3 (LSCNX , X = 100x). LSCN with higher Ni composition showed higher power generation performance, whereas LSCN with lower Ni composition showed higher resistance to degradation. The performance of anode with different ratio of LSCN and doped ceria was measured. Anode with mixing ratio of 60 % LSCN and 40 % GDC showed highest performance and resistance to degradation. References 1) Y. Nishihata et al, Nature, 418, 164 (2002) 2) H. Fukunaga et al, J. Chem. Eng. Jpn, 40, 1183 (2007) Figure 1