Investigation Of The Preparation Technology Of Cathodic Co@Pt/C Catalysts For Direct Methanol Fuel Cell

The direct methanol fuel cell (DMFC) is a good candidate as a power source for applications in transportation and in portable electronic devices because methanol is an abundant, inexpensive liquid fuel and its high-energy efficiency and low-temperature operation. Although good progress has been made in the development of DMFCs, the commercialization of DMFCs is, however, still hindered by a number of basic problems, including the poor kinetics of the cathode reaction, the high-cost catalysts, and the cross-over of methanol from the anode to the cathode through the proton exchange membranes. To avoid these problems, one strategy is the development of oxygen reduction catalysts, which have a high catalystic activity for oxygen reduction reaction (ORR), a high methanol tolerance, and a high electrochemical stability. The work in this dissertation is devoted to these issues by developing a novel cathodic catalyst with core-shell structure.The particle size, lattice parameter, composition, and micro-morphology of the Co@Pt/C catalysts were determined by X-ray diffraction (XRD), energy dispersive analysis of X-ray (EDAX), and transmission electron microscopy (TEM), respectively.The CHI-650C electrochemical analyzer was used to test the electrochemical performance of homemade Co@Pt/C catalysts. The electrochemical surface area (ESA) of catalysts were also tested by using a glassy carbon electrode through CV curves in a solution of 0.5 mol·L-1H2SO4. Their performances of oxygen reduction reaction were evaluated by rotating disc electrode (RDE) through linear sweep curves in an oxygen-saturated solution of 0.5 mol·L-1 H2SO4. Their performances of methanol tolerance were tested by rotating disc electrode (RDE) through linear sweep curves in an oxygen-saturated solution of 0.5 mol·L-1H2SO4+0.1 mol·L-1 CH3OH.Compared with Co@Pt/C catalyst prepared by water phase method, the Co@Pt/C catalyst prepared by EG colloid method under high temperature had higher catalystic performance of oxygen reduction reaction which was due to the higher dispersion and an even size distribution with small average diameter. Keeping argon atmosphere through the whole preparation process of Co@Pt/C catalyst was very essential.Compared with Pt/C catalyst, the Co@Pt/C catalyst prepared by EG colloid method has higher dispersion on the carbon support, an even size distribution with small average diameter, no aggregation phenomenon, reduced amount of Pt and higher catalystic performance of oxygen reduction reaction. Hence, Co@Pt/C catalyst with core-shell structure has definite research and practical application value. The optimized preparation technology was obtained by comparing the physical and electrochemical characterizations of electrocatalysts that were prepared under different preparation condition. The best pH value of the solution was about 10.0 and the optimized amount of PVP was about 1.67 mg·mL-1. Experimental results indicated that Co@Pt/C catalyst prepared under the optimized preparation technology showed higher performances of methanol tolerance than 20 wt% Pt/C.Co@Pt/C catalyst with core-shell structure will become a new research direction on DMFC cathodic catalyst due to its advantages of high catalystic activity for oxygen reduction reaction, reduced amount of noble metal and high performance of methanol tolerance.