Research On Performance Of The Ni-LCCM/LSCM-GDC Composite Anode And Its Reaction Kinetics For Intermediate Temperature Solid Oxide Fuel Cell

In this thesis, the properties of composite anode materials were investigated in order to improve the anode performance. At the same time the anode tail gas of single cell and four ranks pile were also detected. Series of research work have been conducted to explore the kinetics which happened on the surface of composite anode.This thesis carried out the Sol-Gel Method to synthesize La_1-xCe_xCr_0.5Mn_0.5O_3-δ (x=0.05, 0.10, 0.15, 0.20) (LCCM) and La_0.75Sr_0.25Cr_0.5Mn_0.5O_3-δ (LSCM) nanopowders as the anode materials of Solid Oxide Fuel Cell (SOFC). The anode materials that active carbon supported rare earth oxides, M₂O₃/C (M=La, Ce, Pr, Nd, Sm, Eu), were prepared by immersion method. The NiO-La_0.9Ce_0.1Cr_0.5Mn_0.5O_3-δ (L90C10CM)-Ce_0.8Gd_0.2O_2-δ (GDC), NiO-LSCM-GDC and NiO-M₂O₃-Ce_0.8Sm_0.2O_2-δ (SDC) anode-supported cells were fabricated by co-press and co-sinter method with GDC as electrolyte and La_0.8Sr_0.2Co_0.8Fe_0.2O_3-δ (LSCF)-GDC as cathode. The four ranks pile was assembled by using four single cell made up of NiO-LSCM-GDC composite anode. The thermal decomposition process was characterized by thermal analysis (TG-DTA), from which the optimum calcination temperature was obtained. The phase structures of synthetic anode powders were identified by X-ray diffraction (XRD). The topography of calcined L90C10CM powder and single cell were characterized with transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. The performances of single cell and four ranks pile were tested in the temperature range from 500℃to 750℃.The results show that the optimum temperature to calcine powders is 800℃. The shape of LSCM particles appears to be spheres with good homogeneity and good dispersion. The La_1-xCe_xCr_0.5Mn_0.5O_3-δ (x≤0.1) and LSCM powders calcined at 1300℃with perovskite structure can also be obtained. The maximum current densities and the maximum power densities attain the maximum value simultaneously among all single cells at 700℃, especially, the NiO(50%)-Nd₂O₃/C(5%)-SDC(45%) anode-supported cell demonstrates the best electrochemical performance. The maximum current density and the maximum power density are 154.25 mA·cm^-2 and 31.21 mW·cm^-2 tested at 700℃, respectively. Carbon monoxide (CO) and carbon dioxide (CO₂) were detected in the anode tail gas at 500-750℃. The contents of CO and CO₂ attain the maximum value when the temperature up to 700℃. As the ranks increasing, the contents of CH₄ decreasing, while the contents of CO, CO₂, C₂H₄, C₂H₆ and C₃H₆ increasing. The kinetics results indicate that the reaction which happened on the surface of composite anode for CH₄ is approximate to the second order.