Single-step fabrication and characterisations of electrolyte/anode dual-layer hollow fibres for micro-tubular solid oxide fuel cells

An electrolyte/anode hollow fibre (HF) for micro-tubular solid oxide fuel cells (SOFCs), i.e. a cerium–gadolinium oxide (CGO)/Ni–CGO dual-layer HF, has been developed in this study via a novel single-step co-extrusion and co-sintering technique, and followed by a reduction process. The microstructure of the developed dual-layer HFs, which are co-sintered at 1450–1550 °C, can be characterised by an electrolyte outer layer of approximately 80 μm supported by an anode inner layer of around 220 μm. Benefiting from the advantages of this fabrication technique, great adhesion between the anode layer and the electrolyte layer can be achieved without any crack formation during the co-sintering. Moreover, no elemental inter-diffusion between layers, such as Ni, was observed even at 1550 °C. With the increasing co-sintering temperature, mechanical strength of the developed dual-layer HF, gas-tightness of the electrolyte layer and electrical conductivity of the anode layer are increased. However, gas permeability through the anode layer decreases dramatically with the increasing temperature, which may greatly reduce the efficiency of the related micro-tubular SOFC. According to the investigations on the effects of co-sintering temperature on the mechanical, structural and electrical conducting properties of the dual-layer HFs, a co-sintering temperature at 1500 °C is recommended for the construction of the electrolyte/anode half-cell for micro-tubular solid oxide fuel cells (SOFCs).