Effects of temperature and pressure on the performance of a solid oxide fuel cell running on steam reformate of kerosene

A button solid oxide fuel cell with a La0.6Sr0.4Co0.2Fe0.8O3 cathode and a nickel-YSZ anode was tested over a range of temperatures from 650 to 800 °C and a range of pressures from 101 to 724 kPa. The fuel was simulated steam-reformed kerosene and the oxidant was air. The observed increases in open circuit voltages (OCVs) at elevated pressures were accurately predicted by the Nernst equation. Kinetics also increased with the pressure, although the power boost due to improved kinetics was just more than half as large as the boost due to increased OCV. The power boost increased almost linearly with the logarithm of pressure. At constant voltage the relative power boost due to increased pressure was higher at higher temperatures. At constant current the relative power boost was the same for all temperatures. When the pressure was increased from 101 to 724 kPa, the total power boost at 750 °C and 0.8 V was 66%. A significant decrease in electrodic losses at elevated pressures was observed by impedance spectroscopy. Complex impedance spectra were dominated by a combination of low frequency processes that decreased markedly with increasing pressure. A composite of high-frequency processes also decreased with pressure, but to a lesser extent.

► Tested button SOFC at pressures up to 724 kPa and temperatures from 650 °C to 800 °C.
► Open circuit voltages increased with pressure as predicted by the Nernst equation.
► At 750 °C, 0.8 V power boost due to kinetics was ∼1/2 as large as boost due to OCV.
► Impedance spectroscopy showed a decrease in electrodic losses at elevated pressures.
► Power densities increased nearly linearly with the logarithm of pressure.