| As an all solid state chemical power generation device,Solid oxide fuel cell(SOFC)could convert the chemical energy stored in fuel and oxidant into electrical energy.Anode is the place where the fuel is oxidized in SOFC.Therefore,the performance of anode material can directly affect the overall energy utilization of SOFC.When H2 is used as fuel of Ni based metal ceramic composite anode,it has better catalytic activity and higher output performance.However,hydrogen fuel has the problems of high cost,difficult storage and transportation,which has become an obstacle to SOFC commercialization.Among many perovskites that have been studied as substitutes for nickel anodes,La Cr O3 based materials of the perovskite family of ABO3 have mixed ion electron conductivity and good stability,to catalyze hydrocarbon fuel well,and inhibit carbon deposition and sulfur poisoning on the anode,so they are widely concerned.In order to improve the electrochemical performance of the anode,La0.75Sr0.25Cr0.5Mn0.5O3-?(LSCM)based anode with nanofiber structure was constructed to improve the anode structure and increase the catalytic activity area.The main results are as follows:(1)La1-x Srx Cr0.5Mn0.5O3-x(x=0,0.2,0.25,0.4,0.6 and 0.8)xerogel powders were prepared by sol-gel method,and the effects of calcination temperature and Sr doping amount on the phase of LSCM powders were investigated.The results showed that the pure perovskite structure with high crystallinity could be obtained when the doping amount of Sr is x=0.25 after calcination at 1100 and 1200 ?.Taking La0.75Sr0.25Cr0.5Mn0.5O3-? as the research object,LSCM powder obtained by calcining at900 ? for 2 hours could obtain pure perovskite phase with small grain size;with the increase of calcination temperature,LSCM grain gradually growed up and crystallinity gradually increased.(2)LSCM nanofibers were prepared by electrospinning under 5 kinds of electrospinning fluids and heat-treated at high temperature.SEM analysis showed that the diameter of LSCM fibers were decreased with the increase of calcination temperature.After calcination at 1150 ? for 2 h,the fibers prepared by electrostatic spinning separately using LSCM sol and PVP,LSCM powder and PVP aqueous solution present the serious fracture.And separately through nitrate solution and PVP aqueous solution,nitrate solution,PVP solution and dispersant as the electrospinning liquid,the fibers remain fibrous,connected by small particles.After calcination at 1250 ? for 2 h,using nitrate solution,PVP solution and dispersant for the electrospinning solution preparation,the LSCM fiber fibrous remain the same fibrous.With the increase of contact pointbetween particles,it has good high temperature resistance and large aspect ratio.(3)LSCM powder,LSCM nanofiber and La0.75Sr0.25Cr0.5Mn0.5O3-?-Ce0.9Gd0.1O2-?(LSCM-GDC)composite nanofiber were used as anodes to assemble LSCM||GDC||LSCF+GDC and LSCM+GDC||GDC||LSCF+GDC single cells,and to compare their electrochemical performance.The results showed that with wet hydrogen(3 vol.% H2O)as fuel gas at 700 ?,LSCM fiber as anode shows better electrochemical performance,and the maximum power density and polarization impedance of the single cell are 63.42 m W·cm-2 and 3.64 ?·cm2,respectively,which are better than those with LSCM powder as anode(32.05 m W·cm-2 and 8.31 ?·cm2).LSCM +GDC||GDC||LSCF+GDC single cell has a maximum power density of 149.93 m W·cm-2and a polarization resistance of 1.35 ?·cm2 at 700 ?.The results showed that the continuous path of ion and electron conduction could be formed and the three interface reaction areas could be effectively increased by introducing GDC into LSCM fiber skeleton,which could decrease polarization resistance,and then improve the electrochemical performance of the anode. |
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