Preparation And Electrochemical Performance Of Palladium Copper Anode Nanocatalysts For Direct Ethanol Fuel Cells

Direct ethanol fuel cells(DEFCs) are a new type of low-temperature fuel cells using ethanol as fuel energy. DEFCs have become the very promising green energy, owing to their wide fuel source, non-polluting, high energy conversion rate, and convenient to carry and store. Nowadays, the anode catalysts in DEFCs are often made up of platinum-based metals. Nevertheless, Pt with the significantly high costs, finite resource on earth, and low poisoning resistance have seriously limit the commercial development of DEFC. Therefore, to find a kind of non-platinum catalyst replacing Pt-based catalysts has become a hot research topic. As we all know, palladium has the same properties as Pt. Furthermore, its price is lower than Pt, and its catalytic activity and stability for ethanol oxidation in alkaline medium are higher than Pt. Consequently, in order to reduce the production cost and improve the catalytic activity and stability of the catalysts, the research of the Pd-based catalysts in the alkaline direct ethanol fuel cells(ADEFC) has important practical significance.In this thesis, we studied the palladium-copper alloy catalysts from a series of strategies such as morphology control, carbon materials support including carbon black and carbon nanotubes. Moreover, we explored the preparation and electrochemical performance of these Pd-Cu catalysts. The aim of our research is to reduce the amount of precious metals and enhance their catalytic performance at the same time. The main work is as following:(1) Pd-Cu alloy near-spherical, nanorods, and nanowire networks structure were successfully synthesized through regulating the concentration of KOH/EG in the ethylene glycol(EG) solution. X-ray Diffraction(XRD), Energy Dispersive Spectrometer(EDS), and Transmission Electron Microscope(TEM) were used to characterize the physical properties of the catalysts, such as the composition, phase structure and surface morphology. The analysis results show that the dispersion of the three kinds of catalysts is good, and there is no obvious agglomeration. The catalytic activity and stability of the catalysts were investigated by the cyclic voltammetry(CV). The results show that the three kinds of catalysts exhibit much better catalytic activity and stability toward ethanol oxidation compared with the commercial Pd/C catalyst in alkaline medium. Especially, the Pd-Cu alloy near-spherical shows the best catalytic performance, followed by nanorods and nanowire networks.(2) With the use of carbon black modified by ionic liquids, porous carbon supported Pd-Cu composite catalyst(Pd-Cu/C) was successfully prepared through the reduction of NaBH4. The results of XRD, EDS and TEM show a good alloy formation between Pd and Cu which has small size and high dispersion particles. The electrochemical measurement of ethanol oxidation indicates that the Pd-Cu/C catalyst exhibits an extremely high catalytic activity about 3.1 times higher than the commercial Pd/C catalyst in alkaline medium. Furthermore, three kinds of carbon supported Pd-Cu composite catalysts(Pd_xCu_y/C) were successfully prepared by only increasing the concentration of reducing agent. Form the TEM characterization results, it can be seen that the Pd_xCu_y/C catalysts have small particles and good dispersion. The electrochemical results show that the Pd_xCu_y/C catalysts exhibit much higher catalytic performance toward the oxidation of ethanol in alkaline medium. Especially, the Pd1Cu1/C catalyst shows the highest catalytic performance.(3) A one-pot solvothermal strategy is developed for the preparation of carbon nanotubes supported Pd-Cu alloy catalyst(Pd-Cu/CNTs) with the activated carbon nanotube as catalyst support. The morphology, composition and structure of the catalyst were characterized by using SEM, TEM, XRD and EDS, and the catalytic performance of the catalysts was analyzed by CV and chronoamperograms(CA). The results show that, the Pd-Cu alloy nanoparticles are uniformly dispersed on the CNTs, and have no obvious agglomeration. Besides, the catalytic activity and stability of Pd-Cu/CNTs catalyst for ethanol oxidation are higher than the commercial Pd/C catalyst in alkaline medium.