Preparation And Electrocatalytic Performance Of Pt-based Alloy Catalysts For Methanol Oxidation

With the development of economy,the problem of environment is more serious,which puts forward new requirements for energy.As a new and green energy conversion device,fuel cell have already drawn plenty of interests of researchers,among which alkaline direct methanol fuel cells have a very extensive commercial application,due to their high energy conversion efficiency,low working temperature,low pollution,long service life and rich source of fuel methanol.However,the further development of the alkaline direct methanol fuel cells is hindered by the anode catalyst problem.The traditional catalysts of platinum and its alloy have been limited by the abundance,high price and low activity,so it is important for us to study an anode catalyst with low Pt usage and high activity.In this dissertation,the reduction of cost and improvement of catalytic performance are mainly caused by modifying or alloying Pt with foreign metal and adding an appropriate catalyst support.The specific work includes the following three aspects:（1）The Pt_xPb_y/MWCNTs catalysts have been prepared by using PVP as capping agent in the DMF and water medium.The physical characterization and electrochemical performance of catalysts were analyzed by TEM,XRD,XPS,EDX,ICP-AES and electrochemical tests.The characterized results show that the atomic ratio of Pt to Pb has a strong influence on the morphology of catalyst.When the feed ratio of Pt to Pb is 5:1,the Pt₇₆Pb₂₄/MWCNTs catalyst with worm-like nanowire morphology exhibits superior electrocatalytic activity about 3.024 A mg_Pt^-1,better than the commercial PtRu/C(0.830 A mg_Pt^-1)and Pt/MWCNTs(1.16 A mg_Pt^-1).（2）A simple and efficient chemical reduction method has been presented to synthesize the PtPd₃/N-RGO catalyst,in which the support is the nitrogen doped graphene（N-RGO）and the reductants are KI and ascorbic acid.The characterization results of catalysts show that PtPd₃ nanoparticles were successfully synthesized and distributed uniformly on the surface of N-RGO.The electrochemical performance of PtPd₃/N-RGO catalysts was tested in alkaline media.The results show that the current density of PtPd₃/N-RGO toward methanol oxidation was 1.79 and 1.76 times as high as that of commercial PtRu/C and Pt/N-RGO.（3）Based on the influence of supports,we prepared the Pt/Fe,N-RGO catalysts,using the Fe-N codoped graphene as support（Fe,N-RGO）.The electrochemical properties of Pt/Fe,N-RGO toward methanol oxidation were studied in KOH medium.The results show that the the catalytic activity and stability of Pt/Fe,N-RGO on methanol oxidation reaction were better than Pt/N-RGO,Pt/RGO and commercial PtRu/C,which can be attributed to the codoping of Fe-N elements and interaction between the support and Pt nanoparticles.