Preparation And Performance Of Micro/nano-structured Electrodes For Intermediate/Low Temperature SOFCs

To achieve low temperature operation and utilization of hydrocarbon gas as a fuel is the trend of development of SOFCs. The problems that hinder the development are that cell impedance increases greatly at low temperatures and a lot of carbon deposite on anode when the hydrocarbon gas as fuel. To solve the two problems, one of the effective approaches is to optimize the microstructure of the existing cells. In this paper, introducing micro/nano-structure to the anode-supported SOFC with Sm doped CeO2 (SDC) electrolyte for improving its electrochemical performance and carbon deposition resistance ability. The researches are summarized as:Suspension spin coating method was used to prepared nanostructural cathode with both porosity gradient and the composition gradient. Such cathode with 200nm particles had micro/nano pore structure. The outer layer had high SSC content and large pores in 0.3-0.8μm, while the inner layer had high SDC content and small pores in 0.1～0.3μm. And a composite thin layer formed at the interface. The alternate spin-coating and heat treatment at low temperature was critical for the formation of gradient.300 mW-cm-2 maximum power density was obtained with H2 as fuel at 600℃for a single cell with the graded cathode. Compare to the single cell without graded cathode, the maximum power density has a 13.3% increase.PS microspheres, PMMA microspheres and starch microspheres were used as templates to fabricate the porous supported style Ni-Cu alloy-based anodes. Only PS microspheres as templates led to an anode with connected large and small pores in the micro/nano-structure. The main reason is that the good affinity resulted in uniformly distribution of the nano anode powder on the surface of a single PS sphere, and after pressing and sintering, a porous micro/nano-structured skeleton was formed. The optimized anode with 735 nm PS had specific surface area of 1.50 m-2/g and porosity of 51.4%.With the porous Nio.95Cu0.05/SDC cermet as precursor framework, Cu(NO3)2 solution was impregnated, and then a reducing treatment was carried out at high temperature. The Cu/Ni0.95Cu0.05/SDC anode with nano particles on the surface could be obtained. The nano particles preferentially distributed on the surface of Ni0.95Cu0.05 grains. The nano particles were the Cu-rich Cu-Ni alloy phase with the size of 10～50 nm. The amount of nano particles could be controlled by the impregnation cycle times. Carbon deposition test results showed that carbon was obviously inhibited when Cu existed as the form of Cu and Cu alloy in the Cu/Ni0.95Cu0.05 anode. And with increase of the impregnation cycle times, the resistance ability to carbon deposition was enhanced. When 4 times of the impregnation cycle, the carbon deposition was only 13%, less than 1/10 of that in Ni0.95Cu0.05 based anode and 1/20 in Ni-based anode. In addition, the reduction temperature of nano Cu modified Ni0.95Cu0.05/SDC anode affected the resistance ability to carbon deposition significantly. As the reduction temperature increased, the resistance ability was enhanced. The 800℃reduction treated anode had the relative carbon deposition of 3%,only 1% of that in Ni-based anode.