| To solve the problems of energy shortage and environmental pollution in the world, the direct liquid fuel cell were paid much attention and investigated widely. They have wide applications in the portable equipment, electric car and field power etc. due to the low-pollution, abundant sources, high energy efficiency, the easy storage and transportation of the fuel. However, the low electrochemical activity and high cost of the electrocatalysts are still the key issues hindering the commercial application of fuel cell. Therefore, the improvement of the electrocatalytic activity of the electrocatalysts and the decrease of the loading mass of noble metals are the effective routes for the commercial application of fuel cells.In this dissertation, the assistant catalysts, new structure of classical catalysts and new catalyst supports in fuel cells have been developed and investigated. The micrographs, structure and properties of the catalysts applications have been investigated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), cyclic voltammetry (CV), chronoamperometry and polarization method, etc. The main points in this dissertation are summarized as follows:(1) Based on the good stability of SiO2 in acid solution, SiO2, as the second catalyst, was introduced into the preparation of Pt catalyst for ethanol electrooxidation and the resulted catalyst was investigated by electrochemical methods. For the same loading mass of catalyst, the peak current of ethanol oxidation on the Pt/SiO2/graphite electrode is about 3.4, 2 and 4.4 times as high as that on the E-TEK Pt/C/graphite, E-TEK PtRu/C/graphite and Pt/graphite electrodes, respectively. Moreover, Pt/SiO2 catalyst shows excellent anti-poisoning ability and long-term cycle stability.(2) MgO was introduced in the anodic electrocatalyst system for ethanol oxidation in alkaline solution and the resulting Pt-MgO-CNTs/graphite electrode was investigated by electrochemical methods. For the same loading mass of platinum catalyst, the best electrocatalytic activity on Pt-MgO-CNTs/graphite electrode is obtained when the mass ratio between Pt and MgO is 1:4. And the better long-term cycle stability can be obtained at the Pt-MgO-CNTs/graphite electrode, as compared to the electrode without MgO. (3) Based on the special structure of CNTs, MnO2-C hybrid catalyst with 1D nanostructure was prepared by the redox reaction between CNTs and KMnO4. And the electrocatalytic activity of the MnO2-C/glassy carbon electrode for oxygen reduction reaction (ORR) in alkaline solutions was investigated by electrochemical methods. The results indicate that the MnO2-C composite shows good electrochemical properties for ORR when the mass ratio of CNTs, KMnO4 and HNO3 is 20: 1: 4。The electron number (n) involved in the O2 reduction was calculated to be 3.4, which is close to the theoretical value for four-electron-reduction of O2.(4) With the organic molecule triphenylphosphine as the linker, Pt nanoparticles were assembled uniformly on the graphene sheets and used as the electrocatalyst for oxygen reduction reaction (ORR). The electrocatalytic properties of the Pt/G catalyst for ORR have been evaluated by typical electrochemical methods. With the same Pt mass loading, the current of ORR at the Pt/G catalyst (70.4μA) was about 8 times as high as that at the Pt/C catalyst (8.1μA) at 0.6 V. The results indicate that the Pt/G catalyst has excellent electrocatalytic properties for ORR and the number of electrons involved in ORR is 3.94 based on the results from the rotating ring-disk electrode (RRDE) investigation.(5) Graphene was used as the catalyst support for catalytic oxidation of formic acid in acidic solution and investigated by electrochemical methods. The PtPd nanoparticles loaded on the surface of the graphene exhibit higher electrocatalytic activity for formic acid oxidation than the Pt catalyst supported on CNTs. With the equivalent loading mass of Pt, the current at 0.35 V on PtPd/G catalyst (1.71 mA) is higher than that of the PtPd/CNTs (1.29 mA). The corresponding results imply that the electrochemical performance (high electrocatalytic activity, better long-term cycle stability) of PtPd nanoparticles for formic acid oxidation is improved by the new graphene support.(6) Carbon nanotubes supported PtPd hollow nanospheres have been prepared by a replacement reaction between sacrificial cobalt nanoparticles and PtCl62-, Pd2+ ions. The electrocatalytic properties of the PtPd hollow nanospheres have been investigated by typical electrochemical methods, respectively. The results indicate that the CNTs supported PtPd hollow nanospheres have excellent electrochemical properties for the electrooxidation of formic acid (high electrocatalytic activity and excellent stability) due to the high surface area resulted from the hollow nanosphere structure with porous shell. For the same loading mass of catalyst, the peak current of formic acid oxidation on the PtPd hollow nanospheres catalyst supported on the CNTs is about 5 and 10.7 times as high as that on the E-TEK PtRu/C and E-TEK Pt/C catalysts, respectively. Moreover, PtPd hollow nanospheres catalyst supported on CNTs showed excellent long-term cycle stability.
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