Dual-layer hollow fibres with different anode structures for micro-tubular solid oxide fuel cells

In this study, a high performance micro-tubular solid oxide fuel cell (SOFC) has been developed by depositing a multi-layer cathode onto an improved electrolyte/anode dual-layer hollow fibre fabricated via a single-step co-extrusion/co-sintering technique. The use of 0-20 wt.% of ethanol in the inner layer spinning suspension allows the control over the asymmetric structure of the Ni-CGO anode layer, i.e. finger-like voids structure covering about 50-85% of the anode layer thickness with the rest volume occupied by sponge-like structure, and at the same time affects the morphology of the CGO electrolyte layer. The presence of finger-like voids significantly facilitates the fuel gas diffusion inside the anode, and as a result, the maximum power density increases from 1.84 W m ^-2 to 2.32 W cm ^-2, when the finger-like voids is increased from 50% to 70% of the asymmetric anode layer. However, further growth of finger-like voids, i.e. 85% of the anode layer, dramatically reduce the number of triple-phase boundary (TPB) region and conductivity in the anode, as well as the gas-tightness property of the electrolyte, which consequently decreases the maximum power density to 0.99 W cm ^-2. Based on the results obtained, therefore, dual-layer hollow fibres with 50-70% of finger-like voids in the anode layer can be considered as the ideal structure for producing high performance micro-tubular SOFCs.