Preparation And Reasearch Of Graphene Supported Platium-based Electrocatalysts For Methanol Electrooxidation Reaction In Acidic Medium

Direct methanol fuel cells(DMFCs)using methanol as raw materials has been considered as a promising green technology to replace traditional fossil fuel technologies,which is an approach that converts directly the chemical energy into electrical energy.Due to its safe storage and transportation,abundant sources,high energy conversion rate and energy density,low pollution,easy and fast operation et al,DMFCs has possessed the wide application prospect as the mobile power source.At present,there are two main approaches to increase the rate of methanol electrocatalytic oxidation:one is the study of the electrocatalyst carrier;and the research of the kind and preparation methods of the electrocatalysts is second.Pt-based catalyst is widely regarded as the state-of-the-art anode catalyst for DMFCs,so we mainly outline the DMFCs Pt-based anode catalysts.In addition,we promote the electrocatalytic activity of Pt-based anode catalysts for DMFCs via adding second and third component or selecting graphene as support.There are mainly two parts in this thesis,including the advances in DMFCs Pt-based anode catalysts and the research paper.The detailed explanation is as follows:Section one:We mainly aim at reasearching the DMFCs background,structure,working principle and applications and so on.Moreover,the study of the DMFCs Pt-based anode catalysts are introduced in detail,including the reaction mechanism,species,preparation method,application and the kinds and research progress of the carrier.Section two:Research papers,including the preparation of PtNi alloy catalysts with increased electrocatalytic performance for the methanol oxidation reaction in acidic medium,one-pot synthesis of graphene supported PtCu and PtNiCu nanoparticles for highly efficient electrooxidation of methanol in acidic medium.Concrete content is as follows:1.The different proportions of PtNi alloy catalysts have been prepared by a one-pot hydrothermal method.Electrochemical measurement results indicate that the Pt3Ni alloy catalyst has not only the higher catalytic and stability to methanol oxidation compared to other proportions of PtNi alloy catalysts,but also the lower initial oxidation potential,which has the highest peak current density(501 mA mg-1).Scanning electron microscope(SEM)and Transmission electron microscope(TEM)results indicate that Pt3Ni alloy catalyst has high dispersion,uniform distribution and no obvious agglomeration phenomenon.X-ray energy dispersive spectrum(EDS),X-ray photoelectron spectroscopy(XPS)and Inductively coupled plasma emission spectroscopy(ICP)results indicate that the catalyst is constituted of Pt and Ni elements,which has the similar proportion to the theoretical value(3:1),and the main valence state of the two elements is zero.X-ray diffraction(XRD)result indicates the formation of Pt3Ni alloy.2.PtCu/rGO catalyst has been prepared by a one-pot hydrothermal method,which constructed by using reduced graphene oxide(rGO)as the carrier,N,N-dimethylformamide as the reducing agent,ethylene glycol solution of NaOH to control the pH value.SEM and TEM results indicate that PtCu/rGO catalyst has high dispersion,uniform distribution and no obvious agglomeration phenomenon.XRD result indicates the formation of PtCu alloy.XPS result indicates that PtCu/rGO catalyst is constituted of C,O,Pt and Cu elements,moreover,the main valence state of Pt and Cu elements is zero.Cyclic voltammetry result shows that PtCu/rGO catalyst has good electro-catalytic activity for methanol and the positive peak current density is 809 mA mg-1,about 3.9 times of the Pt/XC-72 catalyst.Furthermore,chronoamperometry result indicates that PtCu/rGO catalyst has higher electro-catalytic activity and stability for the electro-oxidation of methanol in acid solution compared to PtCu/XC-72 and Pt/XC-72 catalysts.3.Using highly reduced graphene(HG)as the carrier,the PtCuNi/HG catalyst has been successfully prepared by a two step process.Firstly,PtCuNi nanoparticles were prepared by a one-pot hydrothermal method.Then,the PtCuNi/HG catalyst was achieved by using HG as the carrier.SEM and TEM results indicate that PtCuNi nanoparticles on the surface of HG have high dispersion and uniform distribution.XPS result indicates that PtCuNi/HG catalyst is constituted of C,O,Pt,Cu and Ni elements,moreover,the main valence state of Pt,Cu and Ni elements is zero.XRD result indicates the formation of PtCuNi alloy.Electrochemical measurement results indicate that PtCuNi/HG catalyst has higher electro-catalytic activity,more excellent tolerance ability for CO poisoning and enhanced stability for the electro-oxidation of methanol in acid solution compared to PtCu/HG,PtNi/HG and Pt/XC-72 catalysts,which has the highest peak current density(1022 mA mg-1)and the lowest initial oxidation potential(0.25 V).