Sustainable fabrication of triple-layer hollow fiber micro-tubular SOFCs: Tailoring cathode microstructure through graphite pore formers and bore fluid optimization

Co-sintering triple-layer hollow fiber (TLHF) consisting of anode, electrolyte, and cathode; fabricated through a single-step phase inversion-based co-extrusion might cause the densification of the cathode. To address this, varying graphite pore former loadings in the initial cathode suspension and bore fluid flow rates were investigated to optimize cathode porosity and assess its impact on the overall performance of micro-tubular solid oxide fuel cells (MT-SOFCs). Different graphite loadings (2.5–15 wt%) were added to the cathode suspension to improve its structure. A series of characterizations were conducted, encompassing suspension viscosity, morphology, bending strength, and gas-tightness properties. A 2.5 wt% graphite enhanced the cathode structure by generating fine microscopic pores uniformly distributed across the cathode. However, graphite addition influenced shrinkage behavior, reducing the size of the TLHFgr, as seen in SEM images. Bore fluid flow rates between 8 and 16 ml min⁻¹ were varied to improve the TLHFgr structure, with 12 ml min⁻¹ identified as optimal. Stability analysis over 24 h at 800 °C confirmed that TLHF fabricated via this simplified technique maintained structural integrity. Despite successfully improving the cathode structure, graphite addition slightly reduced overall SOFC performance. Consequently, further research is crucial to leverage the pore former's addition to the oxygen electrode and enhance MT-SOFC performance. Nonetheless, the approach supports the development of compact, durable, thermally stable SOFCs for clean energy applications. This work contributes to environmentally conscious technologies by promoting low emission power systems and ceramic processing, offering potential pathways toward sustainable fuel cell fabrication and reducing carbon impact through hydrogen-based solutions.