Preparation And Reasearch Of Graphene Supported Copper-based Electrocatalysis For Oxygen Reduction Reaction In Alkaline Medium

Direct methanol fuel cell(DMFCs)is a new type of PEMFC,which is based on low price and renewable methanol liquid as fuel and directly converts the chemical energy into electric energy.DMFCs can be used as one of the most promising renewable green energy to replace non renewable fossil fuels,due to significant advantages of the liquid fuel is convenient and safe to carry and fill,abundant resources,low cost,mild reaction conditions,the product is almost zero pollution and overall fuel energy conversion efficiency,long service life,low emissions,simple postprocessing process.Although DMFCs has many significant advantages,it is still facing many daunting challenges in order to commercialize it.At present,there are two main ways to improve the electrocatalytic performance of ORR:one is the study of the electrocatalytic supports,the other is the study of the types and preparation methods of the catalyst.In this paper,we mainly study the cathodic oxygen reduction reaction(ORR)electrocatalyst for DMFCs,Study on the preparation of Cu based alloy with reduced graphene oxide(rGO)as carrier and its sulfide and its oxygen reduction in alkaline medium.The research aims to design and prepare a novel ORR catalyst with high activity and low cost,which is non Pt and methanol resistant.This thesis consists of two parts:Patrt 1:We mainly introduce the research background,basic structure,working principle and advantages and disadvantages of DMFCs.In addition,the cathode reaction mechanism of DMFCs,the design and research of cathode electrocatalyst,and the research progress of catalyst carrier are introduced in detail.Patrt 2:Research papers including the preparation of reduced graphene oxide supported PdCu nanocatalyst by simple room temperature co reduction method and its application for ORR,Preparation of highly dispersed CuI derived Cu turned PdCux/rGO nanocomposites and their superior ORR properties,the preparation of CuCo2S4/rGO nanocomposites by one pot method and its properties for ORR in alkaline medium.Specific contents are as follows:1.PdCu/rGO electrocatalyst was successfully prepared by by simple room temperature co reduction method.The results of TEM show that the Pd-Cu alloy is densely and uniformly loaded on the surface of rGO,and their size is very small.The diffraction peaks of graphene and PdCu alloys in the XRD diagram are very obvious,and one-to-one correspondence,indicating that the PdCu alloy was successfully loaded on the reduced graphene oxide(rGO).The characterization of XPS further proves that the PdCu/rGO electrocatalyst is composed of four elements:C,O,Cu,Pd,and Pd and Cu mainly exist in zero valent state.The prepared PdCu/rGO catalysts were tested by cyclic voltammetry,linear sweep voltammetry and chronoamperometry,respectively,and compared with PdCu/XC-72 and Commercial Pd/C in 0.1 M KOH solution.These results show that the ORR activity and stability of PdCu/rGO are better than other catalysts,and PdCu/rGO undergos four-electron-transfer pathway for the ORR.2.PdCuxIy/rGO nano electrocatalysts have been synthesized by a simple one pot solvothermal method.The key of this experiment is that KI can form a small amount of CuI with Cu+ in the synthesis process,Using different amounts of KI to produce different amounts of Cul can affect the atomic ratio of the PdCux,and then affect the properties of the catalyst.SEM and TEM were used to characterize the microstructure and morphology of GO and PdCuxIy/rGO nano catalysts,respectively.XRD and XPS were used to analyze the crystal structure of the catalyst and the valence of elements for characterization of samples.Raman spectroscopy was used to characterize the structure and disorder of graphene in the synthesized PdCu216/rGO catalyst.All the results show that the addition of appropriate amount of KI and the amount of the precursor of the reactive metal in the process of preparing the PdCuxly/rGO catalyst is beneficial to improve the uniformity and dispersion of the nanoparticles.The performance test of ORR in alkaline medium showed that PdCu2I6/rGO with the optimal atomic ratio and the amount of KI,has a better ORR catalytic activity than that of commercial Pt/C,and it shows that PdCu216/rGO has superior catalytic activity in alkaline medium.3.CuCo2S4/rGO nanocomposites were successfully prepared by a simple one pot two step solvothermal method which constructed by Co(OAC)2 and Cu(OAC)2 as precursors of metal,TAA as S source,rGO as carrier.Characterization of the composition and surface electronic states of the prepared CuCo2S4/rGO electrocatalyst by XPS.The results show that Cu is Cu+and Cu2+,Co is CO2+and Co3+,S is in the form of metal sulfide,which proves that the synthesis of CUCo2S4 nanoparticles.The diffraction peaks corresponding to the CUCo2S4 in the XRD diagram are sharp and strong which shows that the crystal form of the catalyst is very good.The ORR properties of the CuCo2S4/rGO nanocomposites were tested in alkaline medium,and compared with Commercial Pd/C.The test results show that the CuCo2S4/rGO exhibits a superior overall electrocatalytic performance of ORR,and has high selectivity to ORR in alkaline medium,and it has excellent resistance to methanol poisoning.