Study Of Catalyst And Low Temperature Adaptability Of Proton Exchange Membrane Fuel Cells

Due to the outstanding advantages, proton exchange membrane fuel cells (PEMFCs) are playing essential roles in many fields. Lately, PEMFCs have become the most hopeful clean technology to be used in vehicles to substitute the combustion engine.The state-of-the-art PEMFC catalyst is carbon supported Pt (Pt/C). Despite the high catalytic performance of the Pt catalyst, it is prone to be poisoned by CO. And the carbon support is easy to be oxidized during the operating process, too. So the first portion of this dissertation is about the innovation of the catalyst and the support. The research was mainly about the Pt based catalyst, such as the preparation and characterization of Pt-Au/C, Pt-Au-TiO₂/C and the Pt+W_xC_y catalyst. The result showed that the catalyst of Pt-Au-TiO₂/C prepared by chemical method exhibited favorable CO-resistant performance. The introduction of tungsten carbide in the Pt based catalyst can promote the catalytic procedure of hydrogen oxidation. In addition, tungsten carbide showed excellent oxidation resistance than the carbon support.The second portion of the dissertation is about the adaptability of the PEMFC in subzero environment. The research included the influences of subzero temperature on the key components and the effects of purging method on protecting the fuel cell. It was found that the electrode damage was immediately caused by the water inside the fuel cell when deposited in subzero environment. The repeating freeze-thaw cycles could result in the pore size distribution shift of the electrode. Gas purging can remove most of the water in the porous electrode and the flow field of PEMFCs. Therefore, it can reduce the negative effect brought by the freeze-thaw cycles. Furthermore, the heating effect of electroosmotic pumping on PEMFC was also investigated in this section. The result showed that the gas flow rate is the most sensitive factor which could determine the heating efficiency. And repetitious electroosmotic pumping process did not engender any destructive effect to the component and the performance of the fuel cell.