Study On High-activity Anode Catalyst And Methanol-blocking Of Membrane Electrode Assembly Of Direct Methanol Fuel Cell

Nowadays the increasing consumption of fossil fuel drives people to look for new alternative energy resource because of the fossil fuel energy reservation is progressively reduced and will inevitably reach exhaustion in hundreds ofyears in the future.Therefore, as an alternatively new energy, the Direct Methanol Fuel Cell,(referred to DMFC) has become a hot research topic in the energy and other related areas with many advantages such as eco-friendly, efficiency, high energy density, abundant reserves, convenient for storage and transport. However, the key challenges for the intensively research of DMFC is the performance of a DMFCis always unable to achieve its optimal values even in the laboratory level, for the industry’s application, the situation becomes worse. The main reason is that the core component of a DMFC, membrane electrode assembly(MEA), can not meet the requirements of the performances of a DMFC. To be specific, there are two main reasons: firstly, the activity and stability of anode catalyst is relatively low; secondly, the methylalcohol near the anode permeates to the cathode directly through the proton exchange membrane. To solve this problems, This paper deeply focus on the research of enhancing the performance of the anode catalysts and increasehighalcohol resistance characteristics ofproton membrane exchange needle.Graphene is widely believed to be a potential catalyst support to enhance the activity of chemical reaction due to its extrodinary high electronic conductance, high chemical stability and ultra-large specific surface area. But the graphene-supported catalysts encounters a problem during the utilization process which is mainly about the unwanted adsorption and stacked between various graphene sheets.The effect of porosity of catalysts on anode mass transfer and performance of the DMFC was intensively analyzed and studied. The simulation results indicated that the activity of electrochemical reaction and the permeation of methane were remarkably enhanced with increasing the porosity of catalysts. After that, this paper intends to explore amorphous carbon derived from high temperature carbonization of glucose and acetylaniline polymerization in acid environment to conduct the chemical modification of the graphene supported platinum catalyst(Pt / G). It is found that this modification process can significantly increase the posority of the anode catalyst, reduce the adsorption and stacking of graphene sheets with various areas. The experimental data indicates that the catalytic activity and stability of catalyst were largely improved, which is agreed with the results obtained by theotical analysis. Moreover, the preparation process of two modification metholds for graphene-supported catalysts was optimized to achieve the optimal parameters at which the catalyst can run at peak performance.In order to maximize the performance of desorption and unpacking of stacked graphene sheets, graphene oxide aero-gels with three-dimensional porous structure were synthesized and prepared, which was successfully used as an anode catalyst with three-dimensional porous structure. In addition, this kind of anode catalyst has been proved that exhibit extreme high posority, enhanced stability and especially the catalytic activity for oxidation of methanol. The electrochemical active area and the current density for catalytic oxidation of methanol have reached a impressive 93.5 m2 g-1and 876.5 m A mg-1Pt respectively. The catalyst activity reached about 5 times of that of the ordinary graphene supported platinum catalyst, and the chemical stability has reached 3 times of that of the graphene supported platinum catalyst.As the performance of the catalyst is improved, a serious problem of leaking of methanol resulting from massive large porosity emerges. Aiming at this problem, this paper explores the impregnation reduction method to enhance the overall performance and reduce permeability of methanol by introducing Pd nano-particles into the proton exchange membrane without reducing the rate of the proton conductivity of proton exchange membrane. Systematically studies were performed to determine the influence of various parameters of condition of impregnation reduction method on the performance and properties of the proton exchange membranes electrode. Based on these studies, the further reduction of permeation of methanol was achieved by introducing more Pd ions into the proton exchange membrane due to the more transport capacity of Pd ions assisted by application of external electrical field during the impregnation process based on the findings mentioned above. Confirmed by experimental investigation, it is proved that the permeability of methanol can be significantly reduced after a reduction modification treatment used in the proton exchange membrane. Meanwhile, the condition parameters such as temperature, concentration, frequency of pulse signal at both ends of the system for soaking Pd Cl2 and signal voltage amplitude were systematically studied to determine the optimal process condition. Compared with the traditional impregnation reduction method, the modified method can significantly improve the performance of the modified membrane and Direct Methanol Fuel Cell.