Preparation Of Pt-based Catalysts And Electrocatalytic Properties

Direct methanol fuel cells(DMFC)have attracted enormous research interest as portable power sources.However,the cost and activity issues of anode catalysts still impede the large-scale commercialization.In this thesis,the research is devoted to enhancing the electrocatalytic activity of catalysts for DMFC electrocatalysts.Firstly,a polyol process activated by microwave irradiation was implemented to prepare efficient Pt/CNTs and PtRu/CNTs for methanol electro-oxidation.For the electrode with Pt loading 12.75 ?g·cm-2,Nafion loading 55%,Pt/CNTs showed the highest activity for methanol electro-oxidation.The methanol oxidation reaction on Pt/CNTs was a typical diffusion controlled process.The activity of PtRu catalysts are independent of their particle size.The activity of methanol electro-oxidation was highest over 3Pt1Ru/CNTs.Secondly,PtM/CNTs(M=Co?Sn?Cu?Fe?Ni)have been prepared by microwave irradiation method.The activity of methanol electro-oxidation was highest over PtSn/CNTs.It can be concluded that a fraction of Sn would be Sn(0)alloyed with Pt,and the remaining Sn would be Sn oxides bounded to the support.The catalytic activity of PtSn for methanol electro-oxidation is not only related to the particle size,but also to the structural characteristics(phase composition)of Pt-Sn.Thirdly,PtPd/CNTs were prepared by ascorbic acid reduction.The average size of PtPd was 68 nm,composed of a large number of tiny nanoparticles,which were uniformly dispersed on CNTs.XRD and XPS showed that the formation of PtPd bimetallic alloy phase,and that platinum atoms were concentrated on the surface of the alloy.The morphology of the catalysts have been influenced by NaOH,ascorbic acid,CTAB and Pt/Pd atomic ratio.PtPd/CNTs exhibited efficient electrocatalytic activity toward methanol electro-oxidation in alkaline media.