The Study Of Multicomponent Gas Diffusing In The Porous Electrode

Solid oxide fuel cell is a new type,efficient energy conversion device and plays an important role in reducing the global fossil energy shortage.Therefore,it is significant to improve the efficiency of the solid oxide fuel cell.The diffusion of gas in the porous electrode is a very big loss that affects the efficiency of the battery.Therefore,the study of diffusion mechanism of the gas in the electrode to reduce the concentration polarization of the cell and improve the working efficiency of the SOFC has become a hot issue.Based on the above,the main research work of this paper is as follows?1?Based on the simplified two dimensional theory of accurate dusty gas model?DGM?,the relationship between the effective diffusion coefficient of the gas through and the gas pressure difference on both sides of the electrode is deduced and the experimental method has used to measure the diffusion coefficient of binary system N₂-O₂.The influence of the porosity and experimental temperature on the effective diffusion coefficient of the gas has been investigated.The diffusion theory of the multicomponent gas system has been analyzed.The results showed that the porosity of the electrode was very important to improve the effective diffusion coefficient of the gas.At the same time,the effective diffusion coefficient could be improved by increasing the experimental temperature,but when the temperature was too high,it could produce defects such as electrode sintering.?2?Based on the experimental data,the influence of electrode thickness,electrode porosity and working current on the concentration polarization has been analyzed systematically.The optimal combination of parameters has been selected according to the experimental results.The results show that the smaller the thickness of the electrode,the larger the porosity of the electrode,the smaller the tortuosity of the electrode,the smaller the working current density can reduce the polarization loss of the electrode.The optimum combination of parameters: thickness 200 ?m,porosity characteristics 0.4/2.64,operating temperature 650?.?3?The process of the gas diffusing through the porous electrode has been simulated by using the comsol software.The simulation results were compared with the experimental results,In addition,a three-dimensional model has been established for the SOFC single cell,and the real-time status of the SOFC has been simulated.A series of studies have been carried out about the properties of the electrode was changed according to the experimental data.The performance of the battery,gas mass transfer process,the current density distribution.The results showed that the simulated correction value of gas diffusion was in good agreement with the experimental data.When the porosity is about 40%,the SOFC with hydrogen as fuel showed good gas diffusion and current conduction characteristics,and the corresponding output voltage,power density were also higher.