Study On Anodic Electro-Catalyst In Direct Methanol Fuel Cells

Direct methanol fuel cell (DMFC) is a promising candidate to satisfy the ever-increasing energy demand in future because of its relatively low pollutant emissions, system simplicity, high-energy conversion efficiency, widely available resources of the fuel and safety for the storage and transportations. However, there are still several barriers in DMFC practical applications, of which the poor activity and the high-price of the anodic catalysts currently used are the most serious ones. Therefore, it is necessary to develop catalysts with high activity and low metal loading, or to find alternative catalysts, which are both efficient ways to reduce the cost of fuel cell devices. In this thesis, in order to solve the problems mentioned above, new anodic catalysts were fabricated and their electrochemical properties were studied in detail. The main results obtained in this thesis are presented as follows:1. Au@Pt nanoparticles were prepared by successive reduction of HAuCl4 and H2PtCl6 precursors. The morphology of Au@Pt nanoparticles was characterized by scanning electron microscopy(SEM) and transmission electron microscopy(TEM) and core (Au) - shell (Pt) like structure was observed. The electrocatalytic properties of Au@Pt catalyst for methanol oxidation were investigated by cyclic voltammetry (CV). The effects of atomic ratio of gold to platinum, methanol concentration and CV scan rate on the peak current density of methanol oxidation and long-term cycle stability of Au@Pt catalyst were also studied. The results show that the presence of Au improves the electrocatalytic activity of Pt catalyst for methanol oxidation, and the best atomic ratio of Au to Pt is 1/2.25. Moreover, Au@Pt catalyst showed good long-term cycle stability and 98.6% value of peak current density of methanol oxidation remains after 500 cycles.2. Ethylene diamine (ED) molecular was selected to modify carbon nanotubes (CNTs), which were employed as support of the Pt-Ru catalyst. The cyclic voltammetry (CV) and Fourier transform infrared spectroscopy (FTIR) were employed to study the interaction between ED and CNT surface. The morphology and elemental composition of the as-prepared Pt-Ru/ED/CNT electrode were characterized by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The electrocatalytic properties of Pt-Ru/ED/CNT electrode for methanol electro-oxidation were investigated by CV, polarization method and electrochemical impedance spectroscopy (EIS). The long-term stability of the Pt-Ru/ED/CNT electrode was also evaluated. Compared with Pt-Ru/CNT electrode, the Pt-Ru/ED/CNT electrode exhibited better electrocatalytic properties and long-term stability. These results show that ED-grafted CNTs are promising catalyst support for methanol electro-oxidation.3. Au doped CeO2 were prepared by coprecipitation(CP) method. The morphology and elemental composition of as-prepared Pt/Aux-Ce1-xO2 electrode were characterized by SEM and EDS. The electrochemical properties of Pt/Aux-Ce1-xO2 electrode were investigated by cyclic voltammetry. The effects of methanol concentration and CV scan rate on catalytic activity and the long-term cycle stability were also studied. The results show that compared with Pt/CeO2 electrode, Pt/Aux-Ce1-xO2 electrode has a better catalytic activity on methanol oxidation. Moreover, it also showed good long-term cycle stability.