Study On The Preparation Of Pd Catalysts Modified By Transition Metal Oxides And Their Catalytic Oxidation Of Methanol

Direct methanol fuel cell?DMFC?has the advantages of high energy density,small size,light weight,low cost and corrosion resistance,it has a broad development prospects due to the convenient storage and transportation security.Anode catalysts directly determine the performance of DMFC.The present study modified the Pd/C catalyst by doping transition metal oxides and improving the preparationmethod;and finally achieved enhanced oxidation methanol performance,catalytic stability and toxicity resistance,meanwhilereduced the cost.In the present study,Y₂O₃ was doped into the Pd/C catalyst,and Pd-Y₂O₃/C catalystwas successfully prepared through microwave-assisted ethylene glycol reduction process.Pd-Y₂O₃/C with 20 wt.% Y₂O₃ gave the highest catalytic current density of 145.97 mA cm-2;witch was ca.1.5 times than that of the commercialPd/C catalysts.The catalytic stability of Pd-Y₂O₃/C-20% was ca.2 times than that of the commercialPd/C catalysts.The electrochemical active surface area?EASA?of Pd-Y₂O₃/C-20% was increased to 70.25 m2 g-1.Physical characterizations revealed that the basic reasonfor the improved catalytic performance of Pd-Y₂O₃/C was the strong electronic effect between Pd and Y₂O₃.Pd-V₂O₅/C catalyst was also investigated in this study.The V₂O₅/C support was prepared by the means of liquid phase reaction that usually used in the industry production of extracting vanadium from stone coal.Then Pd was loaded on the V₂O₅/C support by microwave-assisted ethylene glycol reduction process.Pd-V₂O₅/C with 30 wt.% V₂O₅ obtained the highest catalytic current density of 198.51 mA cm-2witch was approximately 2 times than that of the commercialPd/C catalysts.The catalytic stability of Pd-V₂O₅/C-30% was ca.3 times than that of the commercial Pd/C catalysts.The EASA of Pd-V₂O₅/C-30% was increased to 120.03 m2 g-1.Physical characterizations revealed that the basic reasonfor the improved catalytic performance of Pd-V₂O₅/C was the strong electronic effect between Pd and V₂O₅ and the bifunctional mechanism of the catalyst.On the basis of Pd-V₂O₅/C,different carbon materials were employed as catalyst support and their co-catalysis effect was studied and compared.Electrochemical analysis indicated that the co-catalysis effect was in a notable order of graphene> multi-walled carbon nanotubes> carbon powder > carbon nanofibers.When graphene was used as catalyst support,the Pd-V₂O₅/rGOachieved the highest catalytic current density of 231.20 mA cm-2 and exhibited higher catalytic stability and larger EASA of 123.31 m2 g-1.Physical characterizations revealed that the difference of catalytic performance between catalysts was mainly attributed to the grain size effect.Above all,the catalytic performance was significantly improved by dopting transition metal oxides into traditional Pd/C catalyst and improving the preparation method.The study of this paper provided theoretical support for the commercial application of DMFC.