Solid Oxide Fuel Cell Directly Operated On Propane With High Fuel Utilization

Solid oxide fuel cell?SOFC?is a kind of device that converts chemical energy of fuels into electrical energy with high efficiency.The relatively high operating temperature of SOFC leads to fast ion exchange ratio and high chemical activity,so that there is no need for noble metal such as platinum or palladium.The SOFC is also called“A Strong Man with Non-picky Stomach”,which means SOFC could be operated on not only hydrogen,but also other kind of fuels,in harsh conditions.This characteristic signifies the great potential of SOFC on commercial applications.Propane is one of the popular fuels in daily life.Compressed liquid propane is usually used as fuel of portable devices such as portable stoves,lighters.In recent years,unmanned aerial vehicle?UAV?is widely used in commercial and military applications due to its small volume and convenience.Considering the strict demand of UAV on power and energy density,SOFC fueled with propane is one of the promising power sources.However,traditional Ni-based-anode SOFCs get problems on carbon deposition,which could result microstructure destruction that deactivates the anode.There have been many efforts on the mechanism of how carbon deposition deactivates the anode.Based on the existing research,we proposed a novel SOFC operated directly on propane with Ag-based anode and investigated the mechanism of the novel SOFC.Then,we verified the feasibility of direct-carbon solid oxide fuel cell?DC-SOFC?operated on carbon produced form propane pyrolysis,and investigated the mechanism of DC-SOFC.Finally,we proposed a two-step SOFC directly operated on propane with high fuel utilazation by combining SOFC directly operated on propane and that operated on carbon from propane pyrolysis.What we did is very important for speeding up the commercial process of SOFC.First,we proposed an easy to prepare,extremely stable Ag-based anode material for SOFC.It has been proved that deposited carbon diffuses through and dissolves in the bulk of nickel is the main reason leading to deactivation of Ni-based anode.We prepared Ag-GDC anode slurry by simply grinding and painted it on SOFC by brush-painting.The prepared Ag-GDC anode,electrolyte-supporting SOFC was operated on dry propane without reforming.It could discharge at 103 mA cm^-2,800°C for 160 h without any obvious decay.By analyzing the reaction mechanismof the cells based on GC,SEM,Raman measurements,we assumethat the good stability of the cell with Ag-GDC anode is maintainedby the electrochemical oxidation of hydrogen which comes fromthe pyrolysis of propane.There is still deposited carbon being produced during SOFC discharging.However,deposited carbon mainly deposited on the surface of Ag-GDC anode and formed a thin layer with breakages,without influence on the electrochemical performance or stability of SOFC.Then,we make two related research on DC-SOFC.One is verifying the feasibility of DC-SOFC operated on carbon produced form propane pyrolysis by adding Ni catalyst to promote the pyrolysis reaction of propane,and we found it could make it.The other is proposing a two-step DC-SOFC system to investigate the operation process of DC-SOFC.This two-step system means a low-temperature SOFC settled at low-temperature region in the anode chamber of the former DC-SOFC's.In this way,the low-temperature SOFC works on the CO in tailed gas of high-temperature one.It show that the low-temperature SOFC could achieve a reasonable output even the amount of CO in tailed gas is relatively low.The electrochemical performance of low-temperature SOFC could also respond sensitively to changes of carbon fuels,including the change on the amount and the production rate of CO.It is a very significant study on investigating the process of DC-SOFC.Finally,based on our former conclusions,we added Fe catalyst into anode chamber of SOFC to get a better performance.On the one hand,Fe catalyst could promote the pyrolysis reaction of propane to generate more hydrogen to fuel SOFCs.On the other hand,the isolated carbon could deposit on Fe catalyst,and Fe catalyst could also promote the reaction rate of Boudouard's reactions.Thus,we divided the operation of SOFC fueled with propane into two steps.Step one is SOFC discharges,fueled with propane,while carbon deposition also happens at the same time.Step two is that the supply of propane is paused,and the SOFC discharges on the deposited carbon just like a DC-SOFC.We prepared such a two-step SOFC operated on propane with high fuel utilization.We ran this SOFC at 1 A,800°C in 3 cycle of discharging with propane fueled for 30 min followed by without propane fueled for about 20min,and got a much higher propane utilization.