Mixed-conductive membrane composed of natural hematite and Ni0.8Co0.15Al0.05LiO2-δ for electrolyte layer-free fuel cell

Abstract

Very recently, natural hematite has been developed as an electrolyte candidate for solid oxide fuel cells (SOFCs), because of its considerable ionic conductivity. In this work, to exploit more practical applications of natural hematite, we report a novel mixed-conductive composite made of natural hematite (α-Fe2O3) and semiconductor Ni0.8Co0.15Al0.05LiO2-δ (NCAL) to act as membrane layer in a new SOFC technology, electrolyte-layer free fuel cell (EFFC). The Hematite-NCAL composite was synthesized directly from natural hematite and commercial NCAL by solid-state blending and high-temperature calcination. The EFFC were constructed into a sandwich architecture with Hematite-NCAL as the membrane and NCAL pasted-Ni foams as the electrodes. Electrochemical impedance spectra (EIS) and direct current (DC) polarization measurements were carried out to investigate the electrical conductivity of the composite. A high ionic conductivity of 0.16 S cm -1 is achieved by the composite at 600 o C with mass ratios of 7:3 (7Hematite: 3NCAL). When operated at low temperatures, the as-designed fuel cell demonstrated superior power densities of 554 mW cm -2 at 600 o C and 342 mW cm -2 at 500 o C. Considering the competitive cost, abundant resource and eco-friendliness of natural hematite, our findings indicate the Hematite-NCAL can be a highly promising candidate for advanced low-temperature SOFC applications.