Carbonate dual-phase improves the ionic conductivity and performance of mixed ionic and semiconductor single-layer fuel cell

Abstract

A mixed ionic and semiconducting composite in a single-layer configuration has been shown to work as a fuel cell at a lower temperature (500-600 oC) than a traditional solid-oxide fuel cell. The performance of such single-layer fuel cell (SLFC) is often limited by high resistive losses. Here, an eutectic mixture of alkali-carbonates was added to SLFC to improve the ionic conductivity. The dualphase composite ionic conductor consisted of a ternary carbonate (sodium lithium potassium carbonate, NLKC) mixed with gadolinium-doped cerium oxide (GDC). Lithium nickel zinc oxide (LNZ) was used as the semiconducting material. The LNZ-GDC-NLKC SLFC reached a high power density, 582 mW/cm2 (conductivity 0.22 S/cm) at 600 °C, which is more than 30 times better than without the carbonate. The best results were obtained with the ternary carbonate which decreased the ohmic losses of the cell by more than 95%, whereas a binary carbonate (sodium lithium carbonate, NLC) showed a lower conductivity and performance (243 mW/cm2, 0.17 S/cm at 600°C). It is concluded that adding carbonates to the LNZ-GDC will improve the ionic conductivity and positively contribute to the cell performance. These results will help to design better-performing SLFCs in the future and highlight the potential of SLFCs as a candidate for future electricity generation.