Single-step fabrication and characterisations of triple-layer ceramic hollow fibres for micro-tubular solid oxide fuel cells (SOFCs)

In this study, a phase-inversion assisted co-extrusion/co-sintering technique has been employed to fabricate a triple-layer ceramic hollow fibre in one step for micro-tubular solid oxide fuel cells (SOFCs). The fibres developed consist of an exterior symmetric electrolyte layer (CGO), a symmetric anode functional layer (AFL, NiO(40 wt%)/CGO(60 wt%)) and an interior asymmetric anode layer (NiO(60 wt%)/CGO(40 wt%)) where radical finger-like voids provide lower fuel diffusion resistance. In addition to more triple-phase boundary (TPB) for electrochemical reactions, the AFL forms a graded porosity with better conductivity and sintering behaviours, leading to greater bounding characteristics between the electrolyte and anode. AFL between 19.1 and 77.5 µm can be achieved by simply adjusting its extrusion rate during co-extrusion, with no cracks or delamination observed after co-sintering. Moreover, the effects of AFL thickness on physical and electrochemical properties of the obtained triple-layer s were investigated systematically using various characterisation techniques. The results illustrate that the AFL between anode and electrolyte improves the mechanical strength of the whole and gas-tightness of the electrolyte, despite for slight drops in electrical conductivity and average porosity of anode and AFL.