Preparation And Electrocatalytic Performance Of Reduced Graphene Oxide Supported Pd-M Nanocomposites

Reduced graphene oxide (RGO) has attracted wide concern because of its high specific surface area, excellent electrical conductivity and thermostability. One of the hot research areas is taking RGO as the carrier of noble nanoparticles and then being applied to fuel cell area. The graphene supported Pt nanocomposite yields better result than conventional Pt/C and Pt/CNTs catalysts in the way of electrocatalytic acitivity, stability and tolerance to CO as fuel cell catalyst. However, the widespread application of Pt noble metal in fuel cell area is restricted because of its limited resource and high cost. In order to realize this goal of reducing the catalyst cost, the graphene supported Pd nanocomposite turns into one of significant study contents. In this thesis, taking the reduced graphene oxide as support, the electrocatalytic performances of the Pd based bimetal nanoparticles toward ethanol oxidation are studied. The main study results in the thesis are presented as follows:(1) Palladium-silver bimetallic nanoparticles loaded on reduced graphene oxide (Pd-Ag/RGO) were prepared by co-reduction of mixed metal salts and graphene oxide (GO) with urea-assisted ethylene glycol. The as-obtained Pd-Ag/RGO nanocomposites were characterized by X-ray diffraction, transmission electronic microscopy, and UV-Vis absorption spectroscopy. The results show that the nanoparticles with an average particle size of5nm are dispersed on the surface of RGO highly uniformly. The electrochemical activities of the as-prepared nanocomposites for ethanol oxidation were investigated by using cyclic voltammetry and chronoamperometry in alkaline solution. Compared to the Pd-Ag/E-tek carbon (Pd-Ag/C) and Pd-Ag/multi-walled carbon nanotubes (Pd-Ag/MWCNTs) which were fabricated by the same method, the Pd-Ag/RGO exhibits much higher electrocatalytic activity, stronger tolerance to CO and better stability during the ethanol electrooxidation reaction in alkaline media. The electrocatalytic performances of Pd-Ag/RGO with different mass ratios of Pd-Ag toward ethanol oxidation in alkaline media were also studied. The results indicate that the electrocatalytic activity of Pd-Ag/RGO with1:1mass ratio of Pd-Ag is the best.(2) The Pd-Ag/RGO catalyst was synthesized by using microwave-assisted ethylene glycol one step co-reduction method. The morphologies and compositions of the as-prepared nanocomposites were characterized by scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (XRD) and UV-Vis absorption spectroscopy. The results show that the Pd-Ag bimetal nanoparticles with an average particle size of8nm are loaded on the surface of corrugated RGO, the value of pH has a certain effect on the formed morphology of the Pd-Ag bimetal nanoparticles and the microwave reduction time influences the reduction degree of GO. The electrocatalytic performances of the as-obtained nanocomposites toward ethanol oxidation in alkaline media were investigated by cyclic voltammetry and chronoamperometry. The Pd-Ag/RGO catalyst exhibits much higher electrocatalytic activity, stronger tolerance to CO and better stability toward ethanol electrooxidation reaction in comparison with Pd/RGO and Pd-Ag/MWCNTs catalysts. The optimal conditions for preparing the Pd-Ag/RG catalyst with the best electrocatalytic activity through this method are pH=10, the microwave treated time=15min and the amount of the reductant ethylene glycol=30mL(3) Monolayer Pd on electrochemical reduced graphene oxidte supported Au nanoparticles (m-Pd-Au/ERG) was designed by a simple and effective route, which produces electrocatalyst with a considerably low Pd loading and good catalytic performance for ethanol electrooxidation. The as-obtained m-Pd-Au/ERG nanocompostie was characterized by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The results show that high-density m-Pd-Au nanoparticles are dispersed on the surface of ERG uniformly, besides the monolayer Pd has little effect on the morphology and distribution of the Au nanoparticles on the ERG surface. The electrochemical activities of the as-prepared nanocomposites toward ethanol oxidation in alkaline media were investigated by using cyclic voltammetry and chronoamperometric techniques. The results demonstrate that the m-Pd-Au/ERG catalyst shows much higher electrocatalytic activity, stronger tolerance to CO than the m-Pd-Au and b-Pd-Au/ERG catalysts prepared by bulk deposition-replacement method for ethanol oxidation reaction.