Investigation Of Pt-based And Pd-based Electrocatalyst For Direct Ethanol Fuel Cell

Direct ethanol fuel cell(DEFC) is promising power sources for portable and electric cars because of its environmentally friendly, and high energy density, and easiness in fuel supply,storage and transportation and other characteristics. DEFC has a great significance for the energy shortage and environmental problems. At present, Pt-based materials are the most commonly used catalysts in DEFC. However, challenging issues, especially the low fuel efficiency and the poisoning problem of some CO-like intermediate species at the catalyst surface, obstruct the commercialization of DEFC. Therefore, there are still great significances in improving the activity and durability of catalysts for the development of DEFC. On the other hand, platinum metal is pretty costly and less abundant on the earth. It is imperative to design and synthesis of low loading Pt-based catalysts and non-Pt catalysts. In this thesis,numerous studies have been dedicated to screening more efficient catalytic materials considering(concerning)the activity, stability and cost of catalysts. The main research content is as follows:(1) In this chapter, mesoporous Sn O2 was synthesized via a water-evaporating process.Mesoporous Pt Sn O2/C electrocatalyst was prepared by the glycol-reduction route. The morphology and elemental composition of the catalyst was characterized by X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), transmission electron microscopy(TEM),and inductively coupled plasma atomic emission spectroscopy(ICP-AES). It was proved that the mesoporous Sn O2 and Pt nanoparticles were immobilized on the carbon carrier successfully. The electrochemical performance test showed that the electrochemical surface area(ECSA) of catalyst decreased significantly, but the activity and anti-poisoning ability have obvious improvement due to the addition of mesoporous Sn O2. The enhanced EOR activity could be attributed to the mesoporous structure of Sn O2 and the strong chemical interaction between Pt and Sn O2. The improved anti-poisoning ability of the mesoporous Pt Sn O2/C catalysts may be explained by the bifunctional mechanism and high activity of mesoporous Sn O2 provide OH species.(2) In this chapter, Pd Cu hollow nanospheres were synthesized by the vesicles template method and chemical reduction method. Hollow Pd Cu/C catalyst was prepared with water as solvent and Vulcan XC-72 carbon black as the carrier at room temperature. TEM and HAADF STEM show that the synthesized Pd Cu nanospheres have hollow spherical structure, and both Pd and Cu were relatively uniformly distributed in the as-prepared sphere, and the hollow Pd Cu remained hollow structure after load. Compared to the commercial Pd/C catalyst, the synthesized Pd Cu/C exhibited a higher electrocatalytic activity for oxidation-reduction reaction(ORR). The stability of the Pd1Cu1/C catalyst was investigated by subjecting it to3000 CV cycles, a current loss of 24.8% for Pd Cu/C was observed. The steady state current ofthe Pd Cu/C catalyst was much higher than Pd/C and Pt/C catalysts. The higher electrochemical activity should attribute to both the hollow porous structure and the dispersion of Pd increased because of the addition of Cu, which provided more Pd active sites for the reactants.(3) In this chapter, the synthetic strategy was based on a one-pot hydrothermal process involving polyvinylpyrrolidone(PVP), KBr, K2 Pt Cl4, Pd Cl2, and Cu Cl2. Pt Pd Cu concave nanocubes were obtained by simply adjusting the amount of hydrochloric acid. The XRD characterization proved that the Pt Pd Cu/C-1 and Pt Pd Cu/C-2 catalysts all present alloy phase.In comparison with commercial Pt/C catalyst, the Pt Pd Cu/C-1 and Pt Pd Cu/C-2 catalysts showed higher catalytic activity in the ORR. The enhanced ORR activity was mainly due to its high-index facets and the electronic effects.