Processing optimization of substrates for metal-supported SOFCs (MSCs)

Kurzfassung

Metal-supported SOFCs (MSCs) with high performance and low cost become more and more popular in the recent years. The properties of the metal substrate are of great importance. However, traditional processing method cannot ensure all the property require- ments including high electrical conductivity, high gas permeability, high porosity and a low-roughness surface. Suitable design and processing method should be developed to improve cell properties. The aim of this work is to optimize the selected processing routes to improve the mechanical stability, electrical conductivity, porosity related gas permeability, and the surface quality of metal substrates. A new metal-foam supported cell design has been proved to be successfully in increasing the mechanical stability of the substrate. The double-foam substrate supported half cells were tested to have a gas leak rate below the quality control threshold, 5 ×10−3 (hPa·dm3)/(s·cm2), with excellent processing reproducibility, which proves that the fab- rication process is already reliable for the manufacturing of cells with good gas tightness. Concentrated nickel nitrate solution was infiltrate into the substrate and the anode func- tional layer (AFL) to enhance the electrochemical catalytic activities. The desired effective Ni catalyst loading of at least 5 wt% is fulfilled after two times infiltration process. Rice starch was used as pore formers in the slurry to ensure high fuel gas permeability. Three types of pore former (Remy B, Remy DR and Remy FG P) were tested in this work. Remy DR was selected due to the highest specific surface area and good particle morphology. The porosity, average pore diameter and effective gas diffusion coefficient of hydrogen were significantly improved. The permeability of the substrate with 7.4 wt% Remy DR is 8.6E-10 m2, 78.8% higher than that of the substrate without pore former. With 10.7 wt% of Remy DR pore former in the impregnated materials, the permeability is increased by 3 times to 16.1E-10 m2 in comparison with the impregnated substrate without pore former. The porosity is increased to 41.1% from 25.0%, and the average pore diameter is enlarged to 529.9 nm from 328.3 nm. The calculated gas diffusion resistance is expected to be re- duced for 4 times. Through these optimization works, MSCs with high substrate permeability and excellent thin film electrolyte with high gas tightness can be fabricated, which is a promising alternative of MSCs.