Simulation And Analysis Of The Performance Of The Solid Oxide Fuel Cell

Through simulating and analyzing the SOFC,one can have a better understanding of the working mechanism of the SOFC and gain some instructions on the SOFC design.In this thesis,we firstly simulated the discharging curve of the SOFC from a macro-scale,then we elaborated how to determine the electrode polarization resistance of the SOFC from a micro-scale,and subsequently,we used the density functional theory(DFT)calculation to investigate the electrode reaction mechanism and kinetics of the SOFC from an atomic scale,and finally,we discussed how to use the DFT calculation to simulate the overall performance of the SOFC.In chapter 2,an anode-supported SOFC with 60?m samarium doped ceria(Ce0.8Sm0.2O1.9,SDC)thin film electrolyte was fabricated with the co-pressing technique.The discharging curves of the SOFC at different temperatures show high linearity.A linear discharging model of the SOFC was derived,and the model fits the measured discharging curves very well with relative errors smaller than 1.5%.The possible power losses of the SOFC were calculated.When the SOFC operates at low current density,the major power loss of the SOFC results from the internal short-circuiting of the SOFC,and when the SOFC operates at high current density,the electrode polarization power losses and the electrolyte ohmic resistance power loss are the major power losses of the SOFC.In chapter 3,according to the reported data of the conductivities of the SDC electrolyte material,the diagram showing the relationship between the electronic resistance,ionic resistance and electrode polarization resistance of the SDC electrolyte supported SOFC was simulated.A real SDC electrolyte supported SOFC was fabricated and the electrochemical impedance spectroscopies(EIS)of the cell were measured under open circuit conditions at different temperatures.Finally,based on the parameters calculated from the measured EIS and the above-mentioned relationship diagram,the anode and the cathode polarization resistances were respectively determined.In chapter 4,the mechanism and kinetics of the electrochemical oxidation of methane on the Sr2FeMoO6-?(SFMO)(001)surface were investigated with DFT+U calculations and micro-kinetic simulation techniques.In the SOFC operation condition,the calculated composition of the SFMO(001)slab is Sr2FeMoO5.75.Two pathways of methane oxidation were considered in this chapter.The effects of temperature,pressure and electrode overpotential on the rate of methane oxidation were simulated.Campell's analyzing method was employed to analyze the rate-determining steps of the methane oxidation reactions at different cell voltages.In chapter 5,how to simulate the overall performance of a SOFC was discussed.In this chapter,the widely researched Sr2FeMoO6-?(SFMO),La0.5Sr0.5MnO3(LSM)and yttria stabilized zirconia(YSZ)were chosen respectively as the anode,cathode and electrolyte materials,then DFT calculations were used to simulate the discharging curve of the SOFC(H2,SFMO|YSZ|LSM,O2).The relationship between the power output and the thickness of the YSZ electrolyte was discussed,and the classic electrochemical analysis was performed on the polarization curves of the electrodes.