Synthesis Of Nitrogen-doped Graphene Supported Pt-Sn Composite Catalyst And Study Of Their Electrocatalytic Properties

With the shortage of fossil fuels and environmental pollution problems continue to increase, direct ethanol fuel cells(DEFCs) have attracted much attention for the potential energy device due to their high energy exchange efficiency and low pollution. However, the research status of the high cost and low performance anode catalyst restricts the mass commercialization of DEFCs. In recent years, graphene become an ideal supporting material to be used to construct efficient composite catalyst in DEFCs owe to its high specific surface area, excellent conductivity, good thermal stability and rich doped properties and so on. A large number of literature and experimental study that the nitrogen functional groups of nitrogen-doped graphene to provide additional anchoring for precious metal particles, thus make more the metal particles load to the graphene layer, so as to improve the utilization of metal platinum. The nitrogen content of nitrogen-doped graphene also affects the morphology of the precious metal catalyst, dispersion degree and particle size, is closely related to the fuel cell electric catalytic performance. In addition, in order to reduce costs and improve the CO tolerance of Pt catalyst, to adding other transition metals in Pt to synthesis binary or ternary composite catalyst, and to promote the further commercialization of DEFCs.Therefore, in order to reduce cost and improve the catalytic efficiency, this experiment mainly using hydrazine hydrate reduction graphene oxide(GO) which was prepared by modified Hummers, and simultaneously doping made a series of different nitrogen content of graphene, then to load Pt-Sn metal particles by ethylene glycol reduction metal precursors, one-step synthesis nitrogen-doped graphite alkenyl Pt-Sn catalysts(Pt-Sn/G-N). And the structure, morphology and composition of the catalysts have been characterized, the electrocatalytic properties of catalysts was studied.The experimental results indicate that: when the mass ratio of GO and hydrazine hydrate is 1:7, it have the highest nitrogen content, and the N/C atomic ratio is 1:10. Metal particles uniform load to the graphene surface, the average particle size is only 1.8 nm. Platinum tin content are the highest in Pt-Sn/G-N(1:7) catalyst, its overall metal load rate is 77.6%. Compare to the undoped Pt-Sn/G catalyst, an enhanced electrocatalytic activity and stability for ethanol oxidation was obtained in the case of the Pt-Sn/G-N(1:7) with optimized composition and nanostructure. This is because nitrogen content added, there will be the more nucleation sites of metal nanoparticles, and can load more homogenous and smaller particles, consequently, increasing the specific surface area of Pt nanoparticles, promoted the synergy of bimetallic Pt-Sn, to improve the electrochemical active area, CO poisoning tolerance and stability of the catalyst.