Preparation And Catalytic Performance Of Ni@Pt Core-shell Fuel Cell Catalyst

Proton exchange membrane fuel cell(PEMFC)is the most likely and widely used energy conversion device with low pollution and high efficiency.The cost of the device is mainly on the catalyst,because the Pt is expensive and resource lackly,the research and development of fuel cell depends on obtaining the catalyst with low platinum and high activity.The activity of noble metal and alloy catalysts is related to the morphology,crystal structure,surface state,particle size and load dispersion.At present,a large number of studies have been carried out to reduce the amount of Pt in the catalyst,but this is not enough to reduce the cost of fuel cell.The research shows that the morphology of nanoparticles can improve the surface area and the high index surface of the catalyst,which can improve the electrochemical activity.The reaction of catalyst in use occurs on the surface,the precious metals inside the particles are in a state of uselessness.Core-shell structure is designed for this feature,which can effectively reduce the use of platinum.In this study,a series of PtNi alloys are used as the research object to obtain the catalyst with high activity.A variety of morphologies of PtNi nanoparticles are obtained by two-step method.The effect of molar ratio of Pt/Ni on morpholobgy is studied.The study finds:Only when the molarratio ofPt/Ni alloy is 1:1,it will tend to.generate dendritic strcture,dendritic structure is grown in the direction of a particular crystal,containing only platinum.Addition of CTAB and diphenyl ether promote the synthesis of core-shell strcture nanoparticles with the uniform shell.when the molar ratio of Pt/Ni alloy is 1:3,the thickness of the platinum layer is about 6 nm.This article also studies the effect of heat treatment temperature,time and atmosphere to the electrochemical activity of PtNi/C catalyst The optimal electrochemical activity of PtNi is obtained after heat treatment at 400? for 4 hours in N2/H2 atmosphere,the half wave potential of 0.74 eV and the current density of 4.45 mA·cm-2.Too long heating time will lead to agglomeration of metal particles,and high heat treatment temperature will lead to the growth of PtNi nanoparticles.In this paper,XPS is used to analyze the oxidation states ofpjatinum and the ratio of Pt/Ni on the surface of PftNi/C catalyst under different states.The heat treatment in the N2/H2 atmosphere can reduce the amount of the surface oxidation state,and under some conditions,the metal reduction state can be obtained entirely.The ratib of Pt/Ni on the surface shows that PtNi nanoparticles occurred surface segregation and formed alloy core-shell structure.