Electrochemical Performance of La2NiO4‐based Cathode for Solid Oxide Fuel Cells. Single Cell Test

Abstract

AbstractThe electrochemical performance of La2NiO4‐Ce0.8Sm0.2O1.9 composite cathode material with Ce0.8Sm0.2O1.9 electrolyte and Ni‐Ce0.8Sm0.2O1.9 anode has been studied. Powders of La2NiO4 were prepared by a nitrate‐citrate route whereas commercial Ce0.8Sm0.2O1.9 was used to prepare the electrolyte and composites/cermets of cathode and anode, respectively. Fuel cell tests were performed with stationary air as oxidant and humidified hydrogen as fuel using single cells with 450 μm‐thick electrolytes. Values of maximum power density higher than 130, 200 and 275 mW cm–2 were obtained for temperatures of 750, 800 and 850 °C, respectively. Impedance spectroscopy under open cell voltage (OCV) conditions and with different current loads was used as a complementary tool to study the different contributions to the voltage loss of the system. The ohmic loss was revealed as the main important contribution to the internal voltage loss of the single cell even at lower temperatures due to the use of a 450 μm‐thick electrolyte. Decreasing the electrolyte thickness to values in the order of 150 μm is expected to produce a decrease higher than 45% in the total cell resistance under OCV conditions, improving the maximum power density to 190 mW cm–2 at 750 °C. The performance of the cell was affected by the hydrogen flux as was made evident by changing the flow rate of the fuel in the range 8–66 ml min–1. An increase higher than 20% in the maximum power density was directly obtained by simply increasing the hydrogen flux from 8 to 66 ml min–1. However, the increase in the hydrogen flow rate produced a decrease in the fuel utilisation. Very good stability of the single cell was also obtained after operation times higher than 40 h with the cell producing the maximum power density.