Study On The Preparation And Performance Of The Methanol Oxidation Eleetrocatalyst

Direct methanol fuel cells （DMFCs） possess a wide application prospect as thepower source in portable electronic products due to the high energy efficiency, lightweight, small size, ambient operating condition and easy storage of the fuel. However,the low activity and the CO poisoning of the anode catalysts lead to high noble metalloadings, which hinders the commercialization of DMFCs. In order to improve theactivity and stability of the PtRu catalyst and reduce the noble metal loadings, thepreparation methods of catalysts and the addition of transition metals were studied inthis dissertation. Several kinds of PtRuM/C (M=W, Mo, PW₁₂and PMo₁₂) catalystswere prepared. The structures and compositions of the prepared catalysts werecharacterized by transmission electron microscopy （TEM） and X-ray photoelectronspectra （XPS）. Electrochemical measurements including cyclic voltammetry （CV）,linear sweep voltammetry （LSV） and chronoamperometry （CA） were carried out toinvestigate the activity and stability of the catalysts. The main results obtained areoutlined as follows:（1）Different reductants were used to prepare PtRu/C catalysts.The catalysts prepa-red by ethylene glycol reduction displayed a homogeneously dispersion of the metalparticles. The average particle size was2.1nm and the distribution range was relativelynarrow. It showed high activity toward methanol electrooxidation.（2）The results of the optimization of PtRuM/C （M=W, Mo） catalysts indicated thatthe prepared PtRuM/C catalyst with the Pt:Ru:M molar ratio of about1:1:0.2had agood catalytic activity toward methanol electrooxidation. XPS analysis showed that Ptexistsed mainly in the form of metal and there were abundant oxide species on theRu surface.（3）The PtRuM/C (M=PW₁₂、PMo₁₂)catalysts were prepared by depositing PtRunano particles and heteropoly acids onto the carbon support in different sequences. Theresults showed that the PtRu/C-M catalysts had homogeneous distributions of metalparticles and exhibited high methanol oxidation activities and stabilities. Heteropolyacids formed negativly charged monolayer on the catalyst surface, which promoted the catalytic activity of PtRu/C catalyst and prevent the dissolution of metal species to someextent.（4）The influences of the treating temperature of tungsten and molybdenumcomponents on the catalyst performances were studied. It is found that the contents ofmetal oxides increased with the temperature. They provided oxygen species so as tomitigate the CO poisoning of the catalysts.