Study On Controllable Preparation And Electrocatalytic Performance Of Pdlladium-silver Nanocatalysts

Direct alcohol fuel cells?DAFCs?have received wide attention due to its high energy conversion efficiency,high energy density,system simplicity and environmental friendliness.Compared to acid medium,in alkaline medium,alcohol has excellent reaction kinetics and more kinds of catalysts can be used.Furthermore,the electrocatalytic performance of catalysts is better than that in acid medium.The activity and the cost of catalysts are two key issues for DAFCs commercialization.Pd has attracted much attention in recent years due to their higher abundance,lower cost,good electrocatalytic activities and great resistance to CO in alkaline environment.It is well-known that the electrocatalytic properties of the nanostructured electrocatalysts highly depend on their shape,surface structure,size and composition.Accordingly,the preparation of architecturally controlled multimetallic Pd-based alloy electrocatalys is of great significance for further improving their elctrocatalytical performance.Galvanic replacement offers a facile and versatile route to prepare a variety of advanced multifunctional metallic nanomaterials.In this thesis,based on galvanic replacement,we focus on the study on the controllable preparation of palladium-silver alloy nanomaterials and their electrocatalytical performance.The related studies are as follows:?1?Firstly,silver nanoparticles?NPs?are synthesized via polyol process.Then Pd-Ag nanoparticles with different composition?PdxAgy-ANPs?are prepared using Galvanic replacement.Research results revealed PdxAgy-ANPs were PdAg alloy nanoparticles with hollow interiors and porous structure.The electrochemical experiments showed that three kinds of catalyst with different component exhibited good electrocatalytic performance and the performance order is as follows: Pd1Ag1-ANPs >Pd₂Ag₁-ANPs > Pd1Ag2-ANPs.?2?Secondly,silver nanowires?NWs?are synthesized using polyol process,and then PdAg-NTs and Au@PdAg-NTs were prepared based on Galvanic replacement.Research results revealed PdAg-ANTs were PdAg alloy nanotubes with hollow interior and porous walls and Au@PdAg-NTs were novel nanotubes comprised of Au core and three-dimensionally PdAg alloy dendritic shell.The results showed that,compare to commercial Pd/C catalyst,the PdAg-ANTs and the Au@PdAg-NTs have exhibited superior electrocatalytic performance for the ethanol electrooxidation and methanol electrooxidation,respectively.?3?Coralline-like and dendritic-like Ag hierarchical nanomaterials are synthesized using hydrothermal process,and then,based on Galvanic replacement,PdAg catalysts with different hierarchical nanostructure are successfully prepared.Results showed that the shape of coralline-like and dendritic PdAg nanostructures were three-dimensional hollow,porous structure.Electrochemical studies indicated that as-prepared two kinds of catalyst have showed better electrocatalytic activity and stability towards ethanol electrooxidation in alkaline environment than that of commercial Pd/C catalyst.