Controllable Synthesis And Electrocatalytic Properties Of Platinum-Bismuth And Platinum-Cobalt Alloy Nanocrystals

Pt has shown excellent catalytic performance in the field of electrocatalysis.However,it cannot be utilized widely because its rare reserve,expensive price and easy to CO poisoning.Therefore,how to increase the catalytic activity of Pt while reducing the usage has become intractable.Many reports have demonstrated that alloying of Pt with other less expensive metals can significantly reduce the usage of Pt and enhance catalytic activity because of the modification of electronic structure and synergistic effect of alloying metals.Therefore,it has great significance to study of Pt-based alloys.On the other hand,the catalytic performance of Pt-based alloy nanocrystals is closely related to the alloy components and the surface structure.Therefore,we can obtaine better electrocatalyst by adjusting these two aspects.The optimal composition is related to the highest atomic utilization and the lowest usage of Pt.In terms of surface structure,nanocrystals with an excavated morphology are often favored in the field of catalysis due to the advantages of exposing high-energy planes,large specific surface area and not easy agglomeration.Therefore,this thesis focuses on the Pt-based alloy nanocrystals,which explores the effects of the alloy components and surface structure to the electrocatalytic performance.The research results are listed as follows:1.In the oleylamine-octadecene system,composition tunable PtBi(Pt51Bi49,Pt62Bi38,Pt67Bi33,Pt81Bi19 and Pt87Bi13 nanoplates with thick edges were successfully synthesized through co-reduction of Pt and Bi precursors.The selective adsorption of Br" ions,selective deposition of Pt atoms and adjustment of the initial ratio of precursors play important roles in the formation of those hcp-PtBi@fcc-Pt heteronanostructures.The PtBi alloys show better catalytic performance than commercial Pt/C in the formic acid oxidation under acidic condition.Among all those hcp-PtBi@fcc-Pt heteronanostructures,Pt87Bi13 nanoplates exhibite best catalytic activity,the mass activity(1.49 A mg-1 Pt)is 3.2 times higher than that of commercial Pt/C and 3.1 times higher than that of Pt92Bi8(which shape is not a nanoplate).The enhanced catalytic activity should be partially contributed to the incorporation of Bi which changes the electronic structure and geometric structure of Pt,and thereby improves the anti-poisoning ability of CO,and partially to the unique heteronanostructure.2.The PtCo excavated nanocubes were successfully synthesized by co-reduction of Pt and Co precursors in the presence of adding acetic acid and n-butylamine in DMF system.The synergistic effect of acetic acid and n-butylamine are the key factors in the formation of excavated morphology.The synthesized samples were annealed at low temperature in hydrogen atmosphere.Comparing the untreated sample and commercial Pt/C,the untreated sample exhibited better ORR performance.It was due to the alloying of Co and excavated morphology exposes the {110} plane.Among the hydrogen treated samples have better ORR catalytic performance than the untreated samples,which may be due to the reduction of oxidation state Pt on surface in a reductive atmosphere.