Analysis On Cathode Characteristic Of PEM Fuel Cell

Fussil energy becomes increasingly deficiency and its consumption leads to serious environmental problems. Many countries began to develop new clean energy to resolve these environmental problems. Hydrogen energy is regarded as the most potential foreground energy due to its abundance, environment-friendly and wide application. Currently, researches based on proton exchange membrane fuel cell (PEMFC or PEM fuel cell) have obtained a great progress. In this paper, the influence of channel and spine in PEM fuel cell on its performance, and the mechanism and procedure of oxygen reduction in the cathode are studied by the experiment and molecular simulations.In this thesis, on the basis of reading informaton about PEM fuel cell, its working principles, characters and application are generalized and summarized, and its structure, function and characters of materials and key parts in PEM fuel cell are introduced. Calculating theory of PEM fuel cell, such as the thermodynamics, reaction dynamic, efficiency and reactant gas flux in PEM fuel cell are stated.In this thesis, three groups of single fuel cell covered with catalyst in different positions are designed, and the U-J curves and electrochemical impedance spectroscopy of these fuel cells were tested to analyse the effects of operational parameters on theses performances used by the fuel cell test station. The results show that when catalyst covers the corresponding zone of diffusion layer contacted with channel only, current density is slightly higher than that with spine only; the total current when catalyst is distributed both ways is almost equal to the sum current when diffusion layer is covered with catalyst. Meanwhile, when catalyst is distributed the area corresponding to channel and spine, parameters such as current impedance, resistance of electric charge transfer, concentration polarization in cathode and the three dimension effect of electrochemistry reactions are various.In this thesis, a model of oxygen reduction path in the fuel cell cathode is established based on the intersection with the molecular dynamics and quantum mechanics simulation to simulate mechanism and process of oxygen reduction reaction in PEM fuel cell cathode by molecular simulation software and finally optimize structure and energy of rection states. The simulating results show that all the reactions in oxygen reduction path are exothermic reactions; the two of the four reactions have the transition state, and the first reaction step is the rate-controlling step. The study also find that the reduction rate of oxygen is very slowly in PEM fuel cell cathode. It indicates that the catalyst need to be added to improve the reaction rate.