Structural study of co-extruded dual-layer hollow fibre for micro-tubular solid oxide fuel cell

Abstract

This study provides information on the structure of solid oxide fuel cell (SOFC). Porous anode provides active site reaction while dense electrolyte layer prevents direct flow of gases through one electrode to another. Therefore, anode and electrolyte structural modifications were thoroughly investigated using different types of pore formers and various ceramic particle sizes, respectively. In the preliminary study, 0 to 10 wt.% corn starch and polyetherethylketone (PEEK) functioned as pore former were added into nickel oxide-yttria-stabilized zirconia (NiO-YSZ) anode suspensions. The results showed that high loading of pore former increased the porosity in anode but reduced the mechanical strength. As compared to using corn starch, addition of 2 wt.% PEEK produced anode with better porous structure by generating more connected open pores and the hollow fibre (HF) was 67 % stronger. The electrolyte of dual-layer HF was subsequently modified by varying the loading of YSZ particle sizes (i.e. micron, submicron and nano-sized) during suspension preparation. The most promising electrolyte layer with thin, dense, gas-tight and defect-free was comprised of 70 % submicron-YSZ and 30 % nano-YSZ. The HF yielded the highest mechanical strength of 85 MPa, good gas-tightness behaviour of 3.16x10-6 molm-2s-1Pa-1 and successfully reduced the co-sintering temperature from 1450 to 1400 °C. Lastly, the anode suspension consist of 2 wt.% PEEK and electrolyte suspension composed of a mixture of particle sizes of micron, submicron and nano-sized YSZ in a ratio of 3:4:3 were co-extruded and co-sintered to produce the structural modified electrolyte/anode. Results revealed that the connected open pores at the entrance of anode inner surface resulted from the addition of pore former was significantly contributed to gas permeability of anode. However, the electrolyte was not fully densified due to less efficient electrolyte packing particles which resulted to the reduction in mechanical strength and integrity of HF.