| Proton exchange membrane fuel cell, as a kind of clean energy technology with high efficiencyã€environment friendly fast start at room temperature, has become the hot area of the research in the field of the new energy now, but the working life of cell is great obstacle to restrict its commercial. With the deeper research of PEMFC, fuel cell is likely to take place starvation in the its working process, and the starvation will lead to producing the negative voltage. The emergence of the negative voltage is likely to lead to the attenuation of the performance of the catalyst the degradation and breakdown of the proton exchange membrane phenomena, such as thus greatly reduce fuel the life of the cell. Therefore, in order to improve the working life of the fuel cell, we should try to reduce the damage due to starvation of fuel cell. Here, we present a method of the semiconductor diode shielding the negative voltage that starvation produces, by inhibiting the negative voltage to achieve the function of protecting the fuel cell. This paper mainly compare and analysis the damage of the MEA of PEMFC in the both cases of anode starvation with and without diode protection.This paper mainly divides into three parts:The first part mainly introduces the working principle, structure of the PEMFC and the mechanism of formation of the negative voltage under starvation; through consulting literature material about producing negative voltage due to starvation and shielding negative voltage at home and abroad, we find the great influence of negative voltage on the performance of MEA, and summarize the mechanism that diode shielding negative voltage of fuel cell. The second part discuss the influence of different anode gas flow on the performance of the fuel cell by changing the hydrogen gas flow, we find that the fuel cell begins to appear negative voltage when the stoichiomestry is1.1and along with the stoichiomestry decreases, ultimately stable negative voltage value of fuel cell reduces gradually. Through the polarization curve test of the fuel cell, the test of CV curve and the characterization of SEM, TEM, we study the influence of different time of negative voltage on the performance of MEA of fuel cell when the stoichiomestry is0.5, find that the negative voltage due to starvation has a great influence on catalyst layers of fuel cell, especially to the cathode catalyst layers of MEA, With the extension of negative voltage time, the damage of catalyst layers also increases significantly. The third part mainly researches the dynamic response of the fuel cell with the presence of diode and contracts the attenuation level of the performance of MEA under the condition with and without a diode protection. We find that the diodes reversely parallel in the two poles of cell has the response mechanism of fast start and break; and it can effectively restrain the growth of the negative pressure, keep the negative voltage value in about-0.37V. At the same time, the attenuation of the performance of the cell is smaller, the damages of catalyst layers in MEA are reduced in the presence of diodes, which indicates that the diode can effectively reduce the influence of the negative voltage on the performance of the cell, so as to increase the life and durability of fuel cell. |
