Study On The Supporter Of Nickel-based Cermet Anodes For Intermediate Temperature Solid Oxide Fuel Cells

A solid oxide fuel cell(SOFC)is a novel kind of power generating device that converts chemical energy in fuels directly into electric energy with high efficiency and low emission.Nickel-based cermet composites are the most widely used anode materials in SOFC.However,its catalytic performance is still insufficient with hydrocarbon fuels in the intermediate and low temperature region,hindering the commercialization of SOFC.In this work,rare-earth elements such as Pr,La and Nd are added into Ce_0.8Sm_0.2O_2-?,a widely used supporter in traditional nickel-based cermet anodes.The catalytic activity of the anode towards the oxidation of hydrocarbon fuels is improved by adjusting the oxygen activity and oxygen ionic conductivity of the ceramic phase.Ce_0.8Pr_xSm_0.2-xO_2-?(x=0-0.15)is studied as the anode supporter of solid oxide fuel cells.The doping of Pr improves the reactivity of the surface oxygen on the ceramic phase,facilitating the chemical oxidation of CH₃OH.Pr improves the oxygen surface exchange coefficient(k_s)and oxygen chemical diffusion coefficient(D_chem)of Ce_0.8Sm_0.2O_2-?simultaneously.Nevertheless,the ionic conductivity of the ceramic phase decreases with the doping of Pr owing to the decreased concentration of oxygen vacancy.The doping of Pr shows negligible influence on the performance of the cell fed with H₂ due to the high reactivity of H₂.However,the maximum power density of the cell with methanol as the fuel increases significantly with the addition of Pr in the anode,demonstrating the high importance of the oxygen activity of the supporter when hydrocarbon fuels are used.A Ce_0.8Sm_0.2O_2-?-carbonate electrolyte-supported single cell with Ni O-Ce_0.8Pr_0.1Sm_0.1O_2-?anode shows a maximum power density of 792 m W cm^-2 at 650 ^oC with methanol as the fuel.Ce0.8La0.1Sm0.1O2-?and Ce0.8Nd0.1Sm0.1O2-?ceramic materials with porous structure are prepared via EDTA-citric acid sol-gel method.The doping of La and Nd promotes the oxygen ionic conduction and accelerates the oxygen bulk diffusion process,whereas the oxygen surface reaction is not influenced significantly.Moreover,the content of the absorbed oxygen species on the anode surface is increased with the addition of La.Compared with Ni O-Ce0.8Sm0.2O2-?anode,Ni O-Ce0.8La0.1Sm0.1O2-?anode shows a higher catalytic activity for the electrochemical oxidation of CH₄,proving that enhancing the oxygen ionic conductivity of the supporter facilitates the oxidation of fuel remarkably.