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

With the increasing of energy crisis and environmental problem,human has to find ideal alternative energy sources and develop efficient energy conversion devices.Fuel cells have already drawn plenty of attention on account of high energy conversion efficiency,low noise and environmental friendliness.Among them,direct methanol fuel cells have important applications in portable and fixed electronic equipments because of their high energy density,simple structure,low operating temperature and rich source of methanol.At present,Pt and Pt-based catalysts are usually used as anode catalysts in direct methanol fuel cells.However,Pt is expensive and poisoned easily by intermediate products CO,which prevent the practical application of direct methanol fuel cells.Therefore,it is important to develop the anode catalyst which can not only reduce the use of Pt but also improve the catalytic performance toward methanol oxidation.In this paper,the catalytic performance of catalysts for methanol oxidation is improved mainly by adding the second component metal or supports,and changing the structure and morphology of catalysts.The specific work includes the following aspects.(1)A facile one-pot solvothermal method has been presented to synthesize Pt Ru nanoflower catalysts by using oleylamine as the coordinating solvent,reductant and surfactant.The morphology,composition and electrochemical performance of the PtRu catalysts have been characterized by XRD,XPS,TEM,EDX,ICP-AES and electrochemical methods.The results indicate that the obtained PtRu catalysts show flower-like nanostructures and exhibit different morphologies at different ratios of Pt to Ru,among which the PtRu nanoflowers composed of nanodendrites(8-10 nm in diameter)show superior electrocatalytic properties toward methanol electro-oxidation.(2)An effective one-pot solvothermal method has been developed to prepare three-dimensional(3D)bimetallic PtNi nanoparticles via the co-reduction of H2PtCl6·6H2O and Ni(NO3)2·6H2O by using oleylamine as the reducing agent.Due to the unique 3D interconnected structure and the bimetallic synergetic effect between Pt and Ni,the obtained 3D PtNi alloy dendric nanocrystals display higher electrocatalytic activity and stability for methanol oxidation and better tolerance towards reaction intermediates than the commercial PtRu/C catalyst.(3)A simple chemical reduction method has been adopted to prepare Pt-Co/MWCNTs composite catalysts with different ratios of Pt to Co by using sodium borohydride as the reducing agent and multiwalled carbon nanotubes(MWCNTs)as the support.The structure and electrochemical characterization of Pt-Co/MWCNTs catalysts were carried out by XRD,XPS,TEM and electrochemical methods.The results show that Pt3Co/MWCNTs with the molar ratio of Pt to Co at 3:1 exhibit excellent catalytic performance for methanol oxidation in alkaline electrolyte.