Preparation And Catalytic Properties Of Pt-Co Alloy Nanocatalysts

Fuel cells is one of the most attractive new green energy.The fuel cells is regarded as a new generation of the most environmentally friendly green power energy conversion device because of its low operating temperature,high starting speed,high power density and low environmental pollution.However,due to the scarcity of Pt resources,the cost of Pt based catalyst is high,which restricts the development and popularization of the proton exchange membrane fuel,and the fuel cell cans not be used in large-scale commercial applications.In the process of fuel cell commercialization,the key problem is to improve the catalytic performance and reduce the dosage of Pt.The reaction rate of cathodic oxygen reduction reaction(ORR)in proton exchange membrane fuel cell(PEMFC)is slow,but the direct methanol fuel cell anode Pt catalyst(MOR)activity is low and easy to CO poisoning.Therefore,it is of great significance to improve the utilization of Pt and reduce the usage of Pt,and to develop a new type of high performance and low cost Pt catalyst to promote the development of low temperature fuel cells.In order to reduce the amount of Pt,the main purpose is to reduce the cost and improve the catalytic performance of Pt based alloy catalysts with small size and uniform distribution by Pt and transition metal M(M=Fe,Co,Cu,Ni)alloying.In addition,Pt based alloy can be used to control the surface segregation of Pt to induce the surface segregation of Pt based alloy nano catalyst in the reducing atmosphere.This paper uses acetylacetonate platinum and cobalt acetate as precursor by chemical reduction method,synthesis Pt3Co/C,PtCo/C,PtCo3/C catalyst,the Pt,Co atomic ratio of which were 3:1,1:1,1:3.The surface composition of Pt-Co alloy nano catalyst was controlled in the reduction atmosphere at 400℃ with 2h,4h and 6h.Use the TEM,XRD,XPS and other analysis methods to study Pt-Co alloy particle size,morphology,chemical composition and chemical valence,and catalytic property of nano Pt-Co alloy catalyst was tested by electrochemical methods(ORR,MOR activity).The results are as follows:(1)The Pt-Co nano alloy catalysts with different ratios of Pt and Co(3:1,1:1,3:1)were synthesized by chemical thermal reduction method,and the average size was less than 3nm;(2)The carbon supported Pt-Co alloy nano catalyst was confirmed by XRD analysis.It was confirmed that Co had been incorporated into the lattice of Pt to form Pt-Co alloy.The results showed that the Pt-Co catalyst was synthesized by chemical thermal reduction method.Electrochemical tests show that the synthesized carbon supported Pt-Co alloy nano catalysts have higher activity on ORR and MOR.Among them,the ORR activity of PtCo3/C was the best,while the MOR activity of Pt3Co/C was the best;(3)The carbon supported Pt-Co nano alloy catalyst was obtained by heat treatment at 400 ℃ in the reducing atmosphere.The TEM analysis showed that the size of the Pt-Co alloy nanoparticles was not obviously grown.ORR activity test showed that with the increase of incubation time,the activity of ORR was significantly increased,but the long incubation time led to the decrease of ORR activity.The MOR activity test showed that with the increase of the holding time,the activity of MOR increased significantly,but the holding time is too long will lead to the decrease of MOR activity,the MOR activity of Pt-Co nano alloy catalyst which was heated by 2h is best,and PtCo3/C is the best catalyst of MOR performance.