Enhanced And Synergistic Electrocatalysis Of Tiny Platinum Nanoparticles Supported On Polyaniline/Polypyrrole Hybrid For Methanol Oxidation

Direct methanol fuel cells(DMFCs)are considered as an effective energy conversion device to solve the problem of air pollution and global warming due to its advantages of high energy density,rich source and environmental friendliness.In DMFCs,Pt-base catalysts have high electric catalytic activity and stability,thus caused wide attention.However,on the one hand,Pt-based catalysts are easy to be poisoned when catalyzing methanol,which result in a significant decrease in catalytic activity,on the other hand,the high cost and scarcity of precious metals platinum hinder its large-scale industrial application.Conductive polymers such as polyaniline(PANI)and polypyrrole(PPy)have the advantages of larger specific surface area,good stability and unique conjugate π structure,which can be used to modify Pt-based catalysts.In this paper,Pt nanoparticles(Pt NPs)were firstly prepared by liquid phase reduction method.Then Pt@PANI/PPy,Pt@PANI and Pt@PPy nanocomposites with core-shell structure were further prepared by chemical oxidation polymerization.They were characterized by XRD,SEM,TEM,HRTEM,FT-IR,TGA,XPS,and other methods.The results showed that during the copolymerization of polyaniline and polypyrrole,Pt NPs with a diameter of 4-5 nm were highly dispersed in the polyaniline and polypyrrole matrix in the form of multiple particles,and further formed spherical nanocomposites with core-shell structure(Pt@PANI/PPy).What’s more,both Pt NPs and PANI/PPy copolymers maintained their respective chemical properties without no new chemical bonds but Pt@PANI/PPy showed better crystallization properties.Based on the above research,Pt@PANI/PPy/C,Pt@PANI/C and Pt@PPy/C electrodes were assembled on the basis of carbon cloth,and their electrochemical catalytic oxidation of methanol in acidic solution were studied.The electrochemical experimental results indicate that within a certain range of the methanol concentration at room temperature,compared to the catalysts of Pt@PANI/C,Pt@PPy/C and Pt/C,Pt@PANI/PPy/C has obvious superior catalytic properties,and the current density is 1.5 times higher than Pt@PPy/C,2.0 times higher than Pt@PANI/C.The results of stability test show that the current retention rate of Pt@PANI/PPy/C is more than 85%,and in the case of Pt@PANI/C and Pt@PPy/C,the value is more than 70%and 80%,respectively.Moreover,its steady state current density is higher than that of Pt@PANI/C and Pt@PPy/C.At the same time,it has the advantages of good stability,long service life,showing its potential as anode material for direct methanol fuel cells(DMFCs).According to my analysis,its excellent catalytic performance comes from the modification of PANI/PPy copolymer,which can reduce the toxic effect of CO on Pt NPs,reduce the polarization of electrode,and enhance the reversiblity of electrode.