Preparation And Characterization Of The Electrode Materials For High Performance Solid Oxide Fuel Cells

Solid oxide fuel cell(SOFC)can convert the chemical energy in fuels,e.g.hydrogen,hydrocarbon and carbon,directly into electric power with high efficiency and low emissions,which have the potential to accelerate the utilization of SOFCs as power sources in portable systems,transportations and distributed-power applications.However,the conventional Nibased SOFC anode is vulnerable to deactivation by carbon build-up(coking)from the direct oxidation of hydrocarbon fuels.Therefore,it is critical to explore a new anode material with good coking tolerance,excellent electronic conductivity and catalytic and a new cathode material with high oxygen reduction reaction(ORR)catalytic activityHerein,RP type layered perovskite(Pr0.4Sr0.6)3(Fe0.85Nb0.15)2O7(RP-PSFN)has been fabricated by reducing cubic perovskite Pr0.4Sr0.6Co0.2Fe0.7Nb0.1O3-?(P-PSCFN)in H2 at 900 oC for 2 h.Meanwhile,Co-Fe alloy(CFA)nanoparticles were formed in situ and homogenously coated on the RP-PSFN backbone.The open circuit voltages(OCV)at 800 oC are 1.08 V,for the SOFC with RP-PSFN-CFA as anode,using wet H2(3 vol.% H2O)as the fuel,close to the value calculated from the Nernst equation.At 800 oC,the peak power density of the cell with RP-PSFN-CFA as anode is 0.93 m W cm-2,being comparable to those of the prepared single cells with Ni-GDC as anode at the similar testing conditions.Moreover,the peak power densities of the RP-PSFN-CFA/LSGM/BCFN single cells with RP-PSFN-CFA as anode reached 0.92 W cm-2 in wet C3H8(3 vol.% H2O)fuel at 850 oC,the cell generated a stable power output for more than 100 h under a constant current load of 0.40 A cm-2 using wet C3H8 fuel at 800 oC,indicating the carbon deposit phenomenon could be greatly avoid on the RPPSFN-CFA ceramic anode.Herein,Nb-doped Ba0.5Sr0.5Co0.8Fe0.1Nb0.1O3-? perovskite oxides have been synthesized,to further improve the cathode ORR activity and thermal stability of BSCF.As seen from the figure,the cathode Rp decreases with the temperature from 0.18 ? cm2 at 600 o C to 0.07,0.04 and 0.02 ? cm2 at 650,700 and 750 o C,respectively.It is much smaller than that of the BSCF.Maximum power densities of 0.22,0.41,and 0.63 W cm-2 with OCV values of 1.08,1.07 and 1.06 V have been obtained at 600,650 and 700 oC,using wet H2(3 vol.% H2O)as the fuel.The cell voltage recorded under a constant current load of 0.6 A cm-2 for over 100 h at 650 oC,exhibited a stable performance and no detectable degradation was observed.