Investigation Of Ni-Co Cermet Anode Materials For Solid Oxide Fuel Cell

Ni based cermet has is an important anode material for SOFCs due to its excellent catalytic properties for fuel oxidation,compatible coefficient of thermal expansion with electrolyte and high electronic conductivity.Conventional Ni-based anode encounters a great challege of carbon deposition when fueled with hydrocarbons,and Ni particles can get sintering readily at high temperature,leading to the degradation of the anode catalytic activity.Aimed at improving the anode resistance to carbon formation and the stability of the cell,Ni_1-x-x Co_xO-Ce_0.8Sm_0.2O_1.9?SDC?composite has been sythesised and investigated as the anode material for solid oxide fuel cells with methanol as fuel.Furthermore,a new Ni coating anode LaNi_0.9Co_0.1O₃?LNC?-SDC with low Ni contents is proposed and explored.Ni_1-x-x Co_xO-SDC composite with different Co contents has been sythesised with the hydrothermal method and applied as the anode of a single cell with a configuration of Ni_1-xCo_xO-SDC|SDC-(Li_0.66Na_0.34)₂CO₃|LiNiO₂-SDC-(Li_0.66Na_0.34)₂-CO₃.The results indicate that a small amount of Co dissolves into NiO and forms Ni-Co alloy after H₂ reduction.The interaction between NiO and SDC phases is enhanced by the existence of Co.Besides,Co reduces the particle size and improves the dispersion of Ni_1-x-x Co_xO by inhibiting the growth of NiO grains,which results in a larger three-phase boundary in the anode layer.Co also increases the resistance to carbon deposition of the anode and decreases the graphitization degree of deposited carbon when methanol is used as fuel.Maximum power densities of 514,582,625and 371mW cm^-2 are achieved by the single cells with Ni_1-x-x Co_xO-SDC anode at700^oC with methanol as fuel,coresoponding to x values of 0,0.05,0.1 and 0.2,respectively.Compared to the Ni-SDC anode,with a life-time about 260 min,the cell with the Co doped anode exhibits a stable performance during a 500-min discharge period.LaNi_0.9Co_0.1O₃?LNC?coated SDC composite with different Ni contents were systhesised through impregnation and used as the anode precursor for a single cell withtheconfigurationofLNC-SDC|SDC-(Li_0.66Na_0.34)₂CO₃|LiNiO₂-SDC-(Li_0.66Na_0.34)₂CO₃.Expenrimential results show that perovskite type oxide LNC forms on the SDC surface after impregnation and calcination.Highly dispersed Ni-Co particles with a size of about 5 nm are obtained from the reduction of LNC.TGA result indicates that the amount of carbon deposition on the anode is directly related to the Ni content,and higher Ni contents lead to more carbon deposition.The EIS result shows that sufficient electron conductivity is achieved when the loading amount of Ni reaches 10 wt%.Due to the high dispersion of Ni,the catalytic activity of the anode is obviously improved compared with that of the conventional Ni-based anode.When fueled with methanol at 700 ^oC,a maximum power density of 511,453,745 and872mW cm^-2 are achieved with single cells with LNC-SDC,2LNC-SDC,10LNC-SDC and 20LNC-SDC anode,respectively.