La 2NiO 4+ δ potential cathode material on La 0.9Sr 0.1Ga 0.8Mg 0.2O 2.85 electrolyte for intermediate temperature solid oxide fuel cell

Abstract

La 2NiO 4+ δ , a mixed ionic-electronic conducting oxide with K 2NiF 4 type structure, has been studied as cathode material with La 0.9Sr 0.1Ga 0.8Mg 0.2O 2.85 (LSGM) electrolyte for intermediate solid oxide fuel cells (IT-SOFCs). XRD results reveal excellent chemical compatibility between the La 2NiO 4+ δ sample and LSGM electrolyte. A single cell (0.22 cm 2 active area) was fabricated with La 2NiO 4+ δ as cathode, Ni–Sm 0.2Ce 0.8O 1.9 (2:1; w/w) as anode and LSGM as electrolyte. A thin buffer layer of Sm 0.2Ce 0.8O 1.9 (SDC) between anode and electrolyte was used to avoid possible interfacial reactions. The cell was tested under humidified H 2 and stationary air as fuel and oxidant, respectively. The electrochemical behaviour was evaluated by means of current–voltage curves and impedance spectroscopy. Microstructure and morphology of the cell components were analysed by SEM-EDX after testing. The maximum power densities were 160, 226, and 322 mW cm −2 at 750, 800 and 850 °C, respectively with total polarisation resistances of 0.77, 0.48 and 0.31 Ω cm 2 at these temperatures. Cell performance remained stable when a current density of 448 mA cm −2 was demanded for 144 h at 800 °C, causing no apparent degradation in the cell. The performance of this material may be further improved by reducing the electrolyte thickness and optimisation of the electrode microstructure.