Preparation And Properties Of Cathode Materials Of Solid Oxide Fuel Cell For Treating Automobile Exhaust

Automobile exhaust contains a large number of NOX, HCs and CO, which affects the ecological environment and endangers human health. At present, the most commonly used catalytic method of exhaust is the three way catalytic method, CO and HCs are oxidized to CO₂ and water, and NO_x is reduced to N₂ and O₂ in this method. But the catalyst used in the three way catalytic are mainly precious metals which are expensive and shortage of reserve. What's more, under the background of lean-burn technology is widely used at present, Three way catalyst can simultaneously be effective catalytic purification for the nitrogen oxide, carbon monoxide and hydrocarbon which only be in a narrow window range of air fuel ratio ?A/F at around 14.6?,which cause its application has been challenged. In this paper, it is proposed that CO and NO of exhaust were treated by the solid oxide fuel cell, decreasing the concentration of CO and NO while generating electricity, and to achieve energy conservation and pollution reducing.LSCF series perovskite type catalysts prepared by sol-gel method and applied as cathode materials for solid oxide fuel cell, according to different Cu element doping amount, five different cathode powders have been prepared, which were La_0.6Sr_0.4Co_0.2Fe_0.8O₃, La_0.6Sr_0.4Co_0.2Fe_0.6Cu_0.2O₃, La_0.6Sr_0.4Co_0.2Fe_0.4Cu_0.4O₃, La_0.6Sr_0.4Co_0.2Fe_0.2Cu_0.6O₃ and La_0.6Sr_0.4Co_0.2Cu_0.8O₃. The properties of five kinds of cathode have been test by electrochemical impedance spectroscopy ?EIS? in the NO and air atmosphere respectively. The influence of temperature and Cu doping ratio to the cathode structure and impedance characteristics have been researched. On one hand, with the temperature increases, the ohm resistance and activation polarization impedances of cathode are both monotonically decreasing; on the other hand, with the increase of amount of Cu doped, cathode ohm resistance monotonically increasing, activation polarization impedance monotonically decreasing. Furthermore, we have prepared GDC powders with sol gel method and co-precipitation, and prepared to LSCF-GDC composite cathode, through the analysis of XRD and EIS, the conclusion is drawn that compared with the co-precipitation method, GDC prepared by sol-gel method has purer crystalline phase and more excellent electrochemical properties.AC impedance of La_0.6Sr_0.4Co_0.2Fe_0.4Cu_0.4O₃ cathode and LSCF cathode in air, oxygen and nitric oxide atmosphere were tested respectively, through the comparison and analysis of AC impedance spectra we draw the conclusion:Cu containing and Cu-free cathode material exhibited the same law in varies atmosphere, the activation polarization resistance?Rct? NO <?Rct? O₂<?Rct?air, Nitric oxide is more easily dissociated than oxygen, LSCF material is suitable for processing nitric oxide pollutants.Prepared tubular solid oxide fuel cell A and cell B with impregnation method, while LSCF as cathode for cell A and La_0.6Sr_0.4Co_0.2Fe_0.4Cu_0.4O₃ as cathode for cell B. Both tubular cells length were 10cm while diameter were 1cm, the effective area of both cells were 20.93cm².withing CO gas as fuel, NO gas as oxidizing gas, test AC impedance and output power of the battery under three kinds of temperature ?600?,700?,800??.Through the analysis of the two cells output performance curve, we conclude that _0.8V voltage and _0.65W/cm² power density generated when NO and CO as the oxidation gas and fuel gas of solid oxide fuel cell, tubular solid oxide fuel cell A has better catalytic effect at low temperature, solid oxide fuel cell B tend to run well in high temperature period.