Noble Metal/Graphene Nanocatalysts: Synthesis And Application In Electrocatalysis

Noble metal/graphene nanohybrids combine the advantages of graphene andnoble metal nanoparticles, and show very important applications in electrocatalysis ofdirect alcohol fuel cells （DAFC）. Platinum （Pt） and palladium （Pd） have been widelystudied as anode catalysts in DAFCs. However, the nature reserves and the price of Ptlimit its wide application as catalyst material. To solve these problems, the researcherspay more attention to the electrocatalytic activity of Pd nanomaterial. The smallermetal particle size and more uniform dispersion, the higher the electrocatalyticactivity of catalyst. According to the literatures, oxide doped plays an important rolein increasing the activity of metal catalysts, mainly because the oxide can promote thedispersion of metal nanoparticles, on the other hand, it will play an important role inthe oxidation of alcohols.In this thesis, the improvement of carrier material and metal oxide doped areused to improve the activity of metal catalysts. The main research results are asfollows:（1） Graphene oxide （GO） was prepared by a mobified Hummers method.Graphene oxide scrolls （GSSO） were prepared by a facile and novel microexplosionmethod using GO as the raw material. Pd nanoparticles supported on the GSS（Pd/GSS） were synthesized successfully by co-reduction of GSSO and ammoniumchloropalladate （NH）4PdCl6. The micrograph of Pd/GSS nanohybrids and theirelectrocatalytic properties for ethanol oxidation were characterized by scanningelectron microscopy （SEM）、 transmission electron microscopy （TEM）、 X-raydiffraction （XRD）、 cyclic voltammetry （CV） and chronoamperometry （CA）,respectively. The results show that Pd nanoparticles dispersed uniformly in the GSSand the average size of particles is about5nm. Compared with Pd/G material, Pd/GSShas better catalytic activity and ability of resistance to poisoning.（2） MnO₂modifed GO （MnO₂-GO） was prepared by chemical reduction method.Using MnO₂-GO as supporting materials, Pd/MnO₂-RGO was fabricated for the frsttime by co-reduction of MnO₂-GO and （NH）4PdCl6. The micrograph ofPd/MnO₂-RGO nanohybrids and their electrocatalytic properties for methanoloxidation were characterized by SEM、TEM、XRD、CV and CA, respectively. Theresults show that Pd nanoparticles dispersed uniformly in the MnO₂modifed graphene and the average size of particles is about5nm. Compared with Pd/RGOmaterial, Pd/MnO₂-RGO has better electrocatalytic activity and electrochemicalstability. Pd/MnO₂-RGO exhibits the highest catalytic activity when the weight ratioof MnO₂to RGO is1:7.（3） Using MgO doped graphene materials as supporting materials, Pd/MgO-RGOnanohybrids were fabricated for the frst time by co-reduction method. Themicrograph of Pd/MgO-RGO nanohybrids and their electrocatalytic properties formethanol oxidation were characterized by SEM, X-ray energy dispersive spectrometer（EDS）、CV and CA, respectively. The results show that Pd and MgO are stably loadedon graphene. Compared with Pd/RGO material, Pd/MgO-RGO has betterelectrocatalytic activity and electrochemical stability. The reaction of methanol on thesurface of Pd/MgO-RGO nanocomposite catalyst is controlled by the diffusion step ofmethanol.