Spatial distribution of oxygen chemical potential under potential gradients and performance of solid oxide fuel cells with Ce0.9Gd0.1O2-delta electrolyte

摘要

In this work, maximum power density as the function of electrolyte thickness of a solid oxide fuel cell (SOFC) with Ce0.9Gd0.1O2-delta (GDC10) electrolyte was calculated by integrating partial conductivities of charge carriers under various DC bias conditions at a fixed oxygen chemical potential gradient at both sides of the electrolyte. Partial conductivities as a function of temperature and oxygen partial pressure (P-O2) were calculated using Hebb-Wagner polarization method and spatial distribution of P-O2 across the electrolyte was calculated based on Choudhury and Patterson's model [1] by considering reversible electrode conditions. At terminal voltages corresponding to SOFC and electrolysis cell operation modes, the oxygen chemical potential gradient at a electronic-stoichiometric point became maximum and minimum to compensate the contribution from electrochemical potential gradient of electron. The current-voltage characteristics in different fuel cell conditions with temperature and thickness dependence were calculated with cathodic and anodic P-O2 of 0.21 and 10(-22) atm, respectively. The theoretical maximum power density increased from 1.26 W.cm(-2) at 500 degrees C to 7.39 W.cm(-2) at 700 degrees C. Similarly, at 500 degrees C, power density increased two fold on reducing electrolyte thickness from 20 mu m to 10 mu m. The implications of these results on the development of GDC10 based SOFC systems was discussed.