OXYGEN CHEMICAL-POTENTIAL PROFILE IN A SOLID OXIDE FUEL-CELL AND SIMULATION OF ELECTROCHEMICAL PERFORMANCE

Based on the reported kinetic equations on the air and fuel electrodes, simulation was made on the oxygen potential profile in a solid oxide fuel cell (SOFC) and the electrochemical performance. As a model for simulation, we considered the SOFC of the type, H2-H2O/porous Pt electrode/YSZ/porous La0.6Ca0.4MnO3/O2(g). In the previous papers, we reported the empirical rate equations calculated from the results of the complex impedance due to electrode reaction and the steady-state polarization for the O2(g)/porous La0.6Ca0.4MnO3/YSZ electrode and for the H2-H2O/porous Pt/YSZ electrode. They were expressed using oxygen activity, aO, in YSZ at the electrode/YSZ interface and the partial pressures of gaseous components: I=kO(aO-a-1OPO) for the air electrode, and I=kH{PHP- 1 2HKaO-P- 1 2HPH(K aO)- 1 2 for the fuel electrode, where I is the steady-state current density, kO and kH are the rate constants and K is the equilibrium constant of H2-H2O-O2 system. Here, kO and kH were related to the electrode interface conductivities σE(O) and σE(H) by σ(O)=4FkOP 1 2O/RTand σE(H)=3Fk HP 1 2H/RT. Using the above equations and the relationship of μO=(RT/2) ln PO, the μO profiles in SOFC were calculated with current density and the interface conductivities as parameters. Also, I-V curves of SOFC were simulated with the electrolyte thickness as the additional parameter to predict the performance of SOFC with any cell construction. © 1990.