The Application Research Of Cerium Oxide Powder And Composite Cathodes For SOFCs

The solid oxide fuel cells(SOFCs),an efficient and pollution-free power generation device,directly convert the chemical energy into electric energy.The crucial factors to affect the performance of the cell are the gadolinium-doped ceria(GDC)barrier layer and the cathode material.In this paper,the mass production of the GDC nanoparticles and the improvement on densification of GDC barrier layer were investigated.In view of the Sr element segregation and the high price of Co element,a kind of Sr,Co-free Ba_0.5La_0.125Zn_0.375NiO₃ perovskite cathode material was tested.To avoid the high temperature sintering of the GDC barrier layer and simplify the process,Cu_1.4Mn_1.6O₄ spinel and SmMn₂O₅ mullite cathode materials lacking the barrier layer were studied.Nanocrystalline GDC(Ce_0.9Gd_0.1O_1.95)was synthesized with an economy and pollution-free solid–liquid method.The gluconic acid(GA),instead of traditional citric acid(CA),was used as complexing agent to form metal-complex compounds.X-ray diffractometry(XRD),thermogravimetry/differential thermal analysis(TG/DTA),scanning electron microscopy(SEM)were applied to analyze the powders.The pure GDC powder was gained after sintering at 800°C.The varying amounts of polyethylene glycol(PEG)were applied to improve the morphologies of powders.The density of GDC pellet calcined at 1450°C was high and the conduction was 0.021S/cm at 650°C.The asymmetric GDC interlayers printed screen on the flat substrate and flat tube substrate were sintered at 1300°C to research different structures of substrate affect the densification of GDC interlayers.The constrained sintering of asymmetric GDC laminate and symmetric GDC laminate on the flat tube substrates was studied to confirm different structures of GDC interlayers affect the densification.The order of density of GDC interlayers from large to small is symmetric GDC laminate on the flat tube substrate,asymmetric GDC laminate on the flat tube substrate,asymmetric GDC laminate on the flat substrate.The constrained sintering modes were applied to explain the disparity of microstructures on the GDC interlayers.A Sr,Co-free electrode material perovskite oxide Ba_0.5La_0.125Zn_0.375NiO₃ was synthesized by solid–liquid method.The Ba_0.5La_0.125Zn_0.375NiO₃,mixed GDC powders,intended to test the performance of the composite oxygen electrode.The polarization resistance(Rp)of Ba_0.5La_0.125Zn_0.375NiO₃-GDC composite cathode is 0.33?cm² at 700°C on the symmetrical cell.A flat tube based on double-sided Ba_0.5La_0.125Zn_0.375NiO₃-GDC cathodes operated at 750°C,achieving a power density 125mW/cm² at 0.6V.The total power of the single cell reached to 6.88W.Spinel Cu_1.4Mn_1.6O₄ and mullite SmMn₂O₅ were synthesized.GDC interlayer-free Cu_1.4Mn_1.6O₄-GDC and SmMn₂O₅-GDC composite cathodes were prepared to test the performances on the cell.The Cu_1.4Mn_1.6O₄-GDC(3:7),mass ratio 3:7,was sintered at 1000°C on the symmetrical cell.The polarization resistance(R_P)was 2.6?cm² at 700°C.The SmMn₂O₅-GDC(4:6),Mass ratio 4:6,sintered at 1050°C on the symmetrical cell with R_P=0.48?cm² at 700°C.These three kinds of cathode materials have the potential to apply in the Solid oxide fuel cells(SOFCs).