Preparation And Study Of Pd-based Nanocomposites With High Electrocatalytic Activity

Noble metal nanoparticles(NPs) composites supported by graphene nanosheets(GNS) or carbon nanotubes(CNTs) has shown the bright future in electrocatalysis, heterogeneous catalysis and chemo/biosensing. Especially in the case of anode catalysts of direct alcohol fuel cells(DAFC), the Pt NPs has obtained a Long-term study and became the most widely used catalytic material. However, considering the inevitable defects of Pt NPs, high cost, limited resources and easy to poisoning, it is a very important project to seek a substitution for Pt NPs with low cost and high catalytic efficiency. Up to now, according to the researches, Pd will be an ideal substitute for Pt NPs, not only because of it’s low price, but also the good catalytic activity and the better ability to resist poisoning which have been showed in many of the catalytic applications. But the study on Pd-based catalysts is still not enough at present, how to synthesize lowcost Pd NPs composites with high electrocatalytic performance is still a urgent problem.In order to solve the above problem, we developed several methods including metal oxide decorated GNS and high-molecular polymer surface functionalized CNTs in this dissertation. By these ways, we achieved the high dispersion and small particle size of Pd NPs on GNS or CNTs, and reduced the amount of Pd used. Additionally, the morphologies、Compositions and the electrocatalytic properties towards the electrooxidation of ethanol or methanol of the prepared Pd NPs composites have been studied in detail. The main points in this dissertation are summarized as follows:(1) Taking chitosan, CNTs under ultrasounding and stirring conditions to synthesize CNTs-Chit. Using ethylene glycol as reducing agent, obtained Pd/CNTs-Chit composite catalysts under a heating condition, and applied it to the electric catalytic oxidation of methanol. The micrograph and composition of Pd/CNTs-Chit nanohybrids characterized by fourier transform infrared spectroscopy(FTIR), transform electron microscopy(TEM) and X-ray diffraction(XRD), respectively. And its electrocatalytic properties for methanol oxidation under alkaline condition were tested by cyclic voltammetry(CV) and linear sweep voltammetry(LSV). The results shown that: chitosan on CNTs can provided well dispersed anchor points for Pd NPs, made Pd NPs with an average diameter of 3.9 nm highly dispersed on CNTs-Chit surface. The activity of Pd/CNTs-Chit nanohybrids towards methanol electrooxidation is 1.5 times higher than Pd/CNTs nanohybrids.(2) Taking manganese acetate, graphene oxide(GO) under stirring and heating conditions to synthesize Mn3O4/GO,using ethylene glycol as reducing agent, obtained Pd-Mn3O4/GNS composite catalysts under a heated to reflux condition, and applied it to the electric catalytic oxidation of ethanol. The micrograph and composition of Pd-Mn3O4/GNS nanohybrids characterized by TEM and XRD, respectively. And its electrocatalytic properties for ethanol oxidation under alkaline condition were tested by CV and LSV. The results shown that: Mn3O4 on GNS can not only provided well dispersed anchor points for Pd NPs, made Pd NPs with an average diameter of 6.7 nm highly dispersed on Mn3O4/GNS surface, but also formed a synergistic effect with Pd NPs to improve the catalytic performance. The activity of Pd-Mn3O4/GNS nanohybrids towards ethanol electrooxidation is 1.9 times higher than Pd/GNS nanohybrids.(3) Using tantalum chloride, GO under stirring and evaporation conditions to synthesize Ta2O5/GO, taking microwave reactor as auxiliary reducing equipment to obtained Pd-Ta2O5/GNS composite catalysts,and applied it to the electric catalytic oxidation of ethanol. The micrograph and composition of Pd-Ta2O5/GNS nanohybrids characterized by TEM and XRD, respectively. And its electrocatalytic properties for ethanol oxidation under alkaline condition were tested by CV and LSV. The results shown that: Ta2O5 on GNS can not only provided well dispersed anchor points for Pd NPs, made Pd NPs with an average diameter of 3.1 nm highly dispersed on Ta2O5/GNS surface, but also formed a synergistic effect with Pd NPs to improve the catalytic performance. The activity of Pd- Ta2O5/GNS nanohybrids towards ethanol electrooxidation is 2.2 times higher than Pd/GNS nanohybrids.