Preparation And Research Of High Activity Nano-structured Cathode For SOFC And Its Cr Resistance

The development of high electrocatalytic ability of the cathode is the only way for SOFC application in low temperature (800 C). Aiming at the catalytic ability of ITSOFC cathode is small, and the stability is poor, Cr poison resistance ability is poor, using infiltration as main methods of modification to optimize electrochemical behavior, micro structure and the preparation of coating structure for various cathode. Study on nano modified structure, redox mechanism, performance stable period, anti Cr poisoning performance etc.. The promotion of catalytic activity of the traditional LNF cathode and the LSCF Cr anti poisoning ability improvement were achieved. According to the research direction can be divided into the following three aspects:1. The strengthening mechanism of the electrochemical properties of the impregnated cathode is studied. The porous electrodes of LNF were impregnated with mixed ionic electronic conductor materials and ionic conductor materials. Under the condition of 750℃, the polarization resistance of the pure LNF cathode can reach 1.49 Ωcm2, the polarization resistance of BSCF and BLF impregnated LNF can reach 0.12 Ωcm2 and 0.35 Ωcm2 and the polarization resistance of PO and SDC impregnated LNF can reach 0.09 Ωcm2 and 0.19 Ωcm2. Among them, the material with ionic conductivity and various valencies element has a good oxygen diffusion capacity, and thus be able to for the cathodic system with electronic-chemistry behavior of reinforced.2.The formation of LNF@BSC coating and its electrochemical properties were studied. BSC and LNF have good chemical stability under low temperature condition (800 ℃). After high temperature calcination, the cobalt acid salt and nickel iron ore in situ reaction to form a new phase of perovskite. The electrochemical performance and stability of the system have been improved. Its initial value of polarization resistance is 0.37 Ωcm2, degenerated to 0.5 Ωcm2 after 70h, far better than the LNF@PO system. Although BSC is an A doped SC, there is no difference in the performance of the two impregnated cathodes, the initial Rp values of LNF@SC and LNF@BSC can reach about 0.4 Ωcm2, and both reduced to 0.5 Ωcm2 after 70h. The activation energy of the system can be reduced by about 2 KJmol-1 when the impregnation solution using PVP as an additive. However, LNF impregnated cathode of resistance to Cr poisoning itself insurmountable. The recession rate of LNF@BSC in Cr pollution is even faster.3. Study on LSCF coating forming and its resistance to Cr poisoning. The oxide of nickel and iron in low temperature conditions (800℃) and LSCF have good chemical compatibility, when the calcination temperature reached 1000℃, Fe will replace Co in LSCF and Co will separate out and combine with the remaining nickel oxide to produce B doped cobalt acid salt, which is ionic conductivity. The electrochemical performance of LSCF@NF can be similar at any processing conditions. Under 750℃ and Cr pollution, the LSCF@NF will decline to 5 Ω2cm2 far better than LSCF which is 10 Ωcm2. The deposition of Cr is about 5% for LSCF@NF better than 9% for LSCF. It can effectively prevent the destruction of the porous structure of the cathode by the formation of the coating on the LSCF.