Controllable Synthesis And Electro-catalytic Properties Study Of Iridum-and Platinum-Based Nanocrystals

Noble metal iridium and platinum are platinum group elements,content in the crust are rare but exhibit excellent catalytic performance.In recent years,they have been widely used in fuel cell,petrochemical and pharmaceutical fields.The efficient utilization of iridium and platinum has become a scientific problem to be solved.Many studies have reported that the catalytic activity of iridium-and platinum-based nanocrystals is closely related to their morphology,size and surface defects electronic structure.Therefore,the design and synthesis of nanocrystal structure is very important to ensure the efficient use of precious metals and to improve the catalytic activity.In this thesis,iridium and platinum as the research objects,iridium and platinum alloy nanocrystals with special structures were synthesized.The relationship between the structure and properties of the catalysts was investigated by the electro-catalytic reaction.The design,synthesis and catalysis of iridium based bimetallic nanoframe structure.The framework provides a very good reaction environment in the catalytic reaction.In this chapter,we have controllable synthesized the Ir-Cu nanoframe structure catalysts which presented highly open,uniform morphology and size of about 5nm.The subsequent characterization revealed that substantial unsaturated atoms were exposed in the framework of the nanocrystals,which was favorable for the molecular approach and greatly increased the collision probability.The oxygen evolution reaction(OER)was chosen as the model reaction,and the catalytic activity of the Ir-Cu nanoframe catalysts was found to be better than that of Ir-Cu nanoparticles in alkaline electrolyte.At the same time,the three metal Ir-Cu-Au nanoframes were constructed by using the bimetallic skeleton as the template,and the synthesis method of Ir based nanocrystals was extended.The controllable synthesis and catalytic of ultrathin platinum based bimetallic nanowire structure.One dimensional(ID)ultrafine nanowires have many advantages,such as high aspect ratio,high electron and mass conductivity,large number of surface defects and unique electronic effects.The bimetallic nanowires with one-dimensional ultrafine structure,on the one hand,provide massive reactive sites,on the one hand,improve the utilization of precious metals.In this chapter,we prepared the wavy ultrafine Pt-Zn nanowires.With the evolution of reaction time,Pt-Zn nanowires was formed by the initiation of particle aggregates oriented attachment,and the synergistic growth mechanism of"reduction-orientation attachment " was proposed.Ethanol oxidation(EOR)and formic acid oxidation were chosen as the probe reaction.It was found that the catalytic activity and stability of ultrathin Pt-Zn nanowires were much higher than those of commercial catalysts Pt/C and Pt black.Because of the difference of the reduction potential between metals,it is difficult to controllable synthesis of multi-metal ultrafine nanocrystals.We constructed Pt-Zn-Au and Pt-Zn-Pd trimetallic nanowire catalysts with Pt-Zn as the template,which provided the direction for the preparation of the new type of fuel cell catalysts.