Fabrication Of Metal Nanoparticles/graphene Composite Catalysts And Their Applications In Electrocatalytic Aspects

Fuel cell is a kind of energy converse device, which can directly turn the chemical energy of the fuel into electrical energy. Fuel cell has very important significance in solving the two major problems of environmental pollution and energy crisis facing the world today, which has attracted considerable attention by reserachers all over the world. So far, Pt has been widely used as the anode catalyst for fuel cell. However, the nature reserves, high price and poor anti-poisonous of Pt severly hamper the commercialization of fuel cell. Therefore, decreasing the amount of Pt and increasing the catalytic activity of the catalyst have always been the research hotspots of fuel cell. Studies have shown that catalyst support plays a significant role in minimize the usage and maximize the catalytic activity of catalyst. Graphene has been considered as an ideal catalyst support for fuel cell owing to its large specific surface area, good electrical conductivity and excellent thermal/chemical stability.In this dissertation, chemical and electrochemical methods have been employed to prepare a series of metal/graphene composite catalysts by using graphene as the support. The electrocatalytic activities of as-prepared catalysts toward methanol and ethanol have been studied in detail. The main contents of this dissertation include the following five aspects:(1) PtAuRu/RGO catalyst has been prepared by simultaneous reduction of H2PtCl6, HAuCl4, RuCl3 and graphene oxide(GO) using ethanol as the reduction agent. The as-formed PtAuRu/RGO catalyst has been characterized by XRD, EDX, TEM, Raman and XPS. Electrochemical measurements reveal that the electrocatalytic activity and stability of the PtAuRu/RGO catalyst for the methanol oxidation reaction are superior to those of PtAu/RGO, PtRu/RGO and Pt/RGO catalysts.(2) PtPd/reduced graphene oxide(RGO) catalysts with different Pt/Pd ratios have been synthesized by a clean method without surfactants and stabilizing agents. The obtained catalysts were characterized by XRD, TEM, HRTEM, Raman, XPS and electrochemical measurements. The HRTEM measurements showed that all of the metallic nanoparticles exhibited well-defined crystalline structures. Both cyclic voltammetry and chronoamperometry results demonstrate that bimetallic PtPd catalysts have superior catalytic activity for the ethanol oxidation reaction compared to the monometallic Pt or Pd catalyst, with the best performance found with the PtPd(1:3)/RGO catalyst.(3) A novel poly(o-methoxyaniline)-modified graphene hybrid material(POMA/GE) has been fabricated by a facile electrochemical method, which was then used as the support for PtNi nanoparticles. The morphology and structure of the PtNi/POMA/GE have been analyzed by SEM, TEM, EDX and Raman spectroscopy. Electrochemical techniques such as cyclic voltammetry, chronoamperometry, chronopotentiometry and impedance spectroscopy have been employed to investigate the electrocatalytic activities of the catalyst for methanol oxidation. It was found that PtNi/POMA/GE/GC catalyst exhibits excellent electrocatalytic activity toward methanol oxidation as ompared to PtNi/GE/GC, PtNi/POMA/GC and PtNi/GC catalysts, showing that POMA/GE is a promising catalyst support material for use in methanol fuel cells.(4) Polydopamine reduced and modified graphene oxide composite(PDA-RGO) has been synthesized by a facile method, which was then used as the support for PtAu nanoparticles. The asprepared PtAu/PDA-RGO composites were extensively analyzed by TEM, HRTEM, Raman, EDX, XRD, XPS and electrochemical measurements. It is found that PDA plays an important role in enhancing the dispersion and stability of the catalyst. The bimetallic PtAu/PDA-RGO catalysts exhibits higher catalytic activity than the monometallic Pt/PDA-RGO toward methanol oxidation reaction, with the best performance found for the Pt/Au molar ratio of 3/1. Moreover, the PtAu(3:1)/PDA-RGO catalyst also shows better catalytic activity for MOR than PtAu(3:1)/RGO and PtAu(3:1)/C catalysts, suggesting that PDA-RGO can be a promising catalyst support for fuel cells.(5) A novel composite catalyst, Pd nanoparticles supported on 1,6-hexanediamine functionalized graphene(HD-RGO) has been synthesized. The as-synthesized composite catalyst has been extensively characterized by FTIR, XPS, SEM, TEM, XRD and electrochemical tests. Electrochemical tests reveal that the as-prepared Pd/HD-RGO catalyst diaplays higher electrocatalytic activity, better tolerance and better electrochemical stability toward ethanol oxidation in alkaline media in comparison with Pd/RGO and commercial Pd/C catalysts.