Direct Propane Micro-Tubular Solid Oxide Fuel Cell

Solid oxide fuel cell?SOFC?is a kind of energy conversion device that directly converts the chemical energy stored in fuel into electrical energy.Since there are only H₂O and CO₂ after operation,they have a small impact on environment.The fuel cell has the reputation of green energy technology at 21st century.The operating temperature of the SOFC is at intermediate temperature?500⁷00°C?or high temperature??700°C?.When the temperature is higher than 600°C,the hydrocarbon fuel can be reformed to produce H₂ by partial oxidation reaction,providing a possibility for hydrocarbons as a direct fuel.Therefore,SOFC has a wide of fuel sources,such as hydrocarbon fuel,CO,syngas,solid carbon,which greatly increases the flexibility selection of SOFC's fuel.Although the nickel phase of the SOFC anode can be used as a reforming catalyst for the hydrocarbon fuel,internal reforming causes carbon deposition on the surface of the nickel catalyst under hydrocarbon fuel atmosphere,which can deactivate the battery.Thus,a foam ceramic reforming reactor need to be prepared and embedded in the SOFC gas inlet,which help to convert the hydrocarbon fuel into a hydrogen-rich reformed gas.And then reformed gas was passed into a fuel cell to react with oxygen ions from the cathode.The?-Al₂O₃ foam ceramic carrier was prepared by double impregnation method.The foamed ceramic has a cross-folded pore structure,which can improve the heat rate and reduce pressure drop.A foam ceramic reforming reactor with Ni-Fe as catalyst was prepared by hydrothermal method with nickel nitrate hexahydrate and iron nitrate nonahydrate as raw materials.Through complete randomalized design,the best synthesis conditions were obtained:the nickel-iron atomic ratio was 0.9:0.1,the annealing temperature was 500°C,the reduction temperature was 600°C,and the mole ratio of propane:oxidation was 1:1.78.The hydrogen production was about 3000?mol.The Ni_0.9Fe_0.1/?-Al₂O₃ catalyst has good catalytic performance and no obvious decrease in1500 min.It is worthy to note that the hydrogen production of the Ni_0.9Fe_0.1/?-Al₂O₃catalyst is similar to the hydrogen production of the commercial Pt catalyst.The surface morphology of the catalyst was characterized by SEM and the Ni-Fe nanoshees were uniformly distributed on the surface of the foamed ceramic.Further,the reduced Ni_0.9Fe_0.1/?-Al₂O₃ catalyst was analyzed by XRD and Ni₃Fe alloy phase was found.At 700°C,the maximum power density of the mixed hydrogen?20 vol%H₂+80 vol%Ar,800 ml/min?flow was 0.64 W/cm².Using reformed propane as a fuel,maximum power density was 0.67 W/cm²,which is higher than that of using hydrogen as a fuel.At the same time,it can run for about 80 hours.The SEM was used to characterize the anode microstructure of SOFC after testing with different fuels.The surface of the anode after propane testing was deposited with two types of carbon structures.Amorphous carbon was obeseved at the outlet and inlet and a small amount of fibrous carbon was deposited at the collector current.The anode structure after hydrogen test was the same as the anode structure after reduction.As Ni-Fe nanosheets catalyst supported foam ceramic was used to produce hydrogen,carbon was deposited on surface of catalyst.These carbon depositions were mainly nanotubes.When the molar ratio of propane to oxygen was 1:1.5,high density carbon nanotubes are obtained.As the oxygen increased,the amount of synthesized carbon nanotubes decreased and more spheric graphite carbon was found.The carbon nanotubes are twisted and the growth direction is random.The diameter is in the range of 20-50 nm.