The Preparing Of Fuel Cell Cathodic Catalysts For Oxygen Reduction Reaction And The Study Of Its Electrochemical Performance

In recent years, fuel cell systems have attracted significant attentions due to the easy device, portal transportation and high energy density. To date, Pt-based materials are the most proverbially used electrocatalysts, especially for the cathodic oxygen reduction reaction (ORR). However, the commercialization of fuel cells has been heavily prevented by the high cost of the precious catalysts. Other problems, such as the low stability of Pt-based precious electrocatalysts are still the biggest obstacle for their application of fuel cells. Consequently, developing non-precious metal electrocatalysts to rival Pt-based catalysts is very important for the commercialization of fuel cells in future. In this thesis, in order to solve these problems, we developed a series of electrocatalysts with high price/performance ratio for ORR and assembled alkaline direct methanol fuel cells (ADMFCs). The concrete results are showed in the following text:(1) Hetero-atom N and Fe doped carbon materials is one of the hot topics in recent years for ORR. However, the high Fe content directly results in the instability and the waste of Fe sources. By tuning the Fe content from 0.02 to 20 wt%, we found, in addition to the previously reported optimal Fe content in a high concentration range, that there is a second or real optimal value in an extremely low concentration range. When the Fe concentration is about 0.05 wt%, the CN-NFe electrocatalysts show the best ORR performance; these electrocatalysts are the one with the best performance and the lowest Fe concentration for ORR at present. The ADMFC with CB-NFe.the best CB-NF as cathode outperforms the one with commercial Pt/C based.We believed that the energetic effect between N and Fe greatly enhanced the ORR activity for the high utilization of Fe in these electrocatalysts open a new way for developing other non-precious metal catalysts.(2) The acid oxidation and the following heat treatment of carbon support is a common pretreatment technology for preparation of carbon-based electrocatalysts. Herein, we obtain a series of carbon supports by oxidizing carbon support Vulcan XC-72 (VXC-72) once or twice by Hummer method with or without heat-treatment under N2 flow. Rotation Ring-Disk Electrode (RRDE) measurement, Elemental analysis and Brunauer-Emmett-Teller (BET) analyses indicate a delicate relationship between the oxidation treatment and the electrocatalytic activities of the carbon catalysts for oxygen reduction reaction (ORR). It is found that nitrogen atoms could be doped into carbon through the oxidation treatment. The N-doped carbon itself shows improved electrocatalytical activities for ORR. The results obtained may help designing and analyzing other carbon-based catalysts.