Synthesis,Surface Modification And Synergistic Of Bifunctiional Pt-based Catalytic Nanomaterials And Their Electrocatalytic Performance

In recent years,severe global energy crisis and environmental pollution issues have ignited great passion for developing environmentally,benign and sustainable energy conversion and storage devices,such as polymer electrolyte membrane fuel cells(PEMFCs).It has been established that Pt-based alloys are considered as excellent electrocatalysts.However,a number of obstacles associated with their scarcity,high cost,low catalytic efficiency,and ready poisoning by intermediates still hinder their commercial application.Therefore,it is the highest priority to explore low cost catalyst materials with high electrocatalytic activity and stability.To solve the above problem,we selected the relatively cheap transition metal and synthesized dual-functional Pt-M alloy catalytic nanomaterials through the optimization of reaction conditions(including the structure,morphology,composition,heteroatomic surface modification,and facets).Futhermore,their electrocatalytic performance toward methanol oxidation reaction(MOR)and oxygen reduction reaction(ORR)which used as the model reactions have been studied systematically.The RuMPt(M= Fe,Ni,Cu,Co)catalysts,PtNi-N nanoflowers catalysts,and hierarchical PtNiCo@C-N catalysts were prepared and investigated in this paper.The main points in this thesis are summarized in the following aspects:(1)The ternary RuMPt(M = Fe,Co,Ni,and Cu)nanodendrities(NDs)catalysts were synthesized by a facile method,which are not only suitable for MOR but also for ORR.Benefiting from their unique nanodendrities,and enhanced synergistic catalytic effects among Pt,M,and Ru atoms,these catalysts manifest increasing surface active sites,highly efficient electrocatalytic performance and stability.The as-prepared ternary RuCoPt alloy catalyst shows excellent catalytic performance and stability for methanol oxidation and oxygen reduction reaction.(2)A highly active nitrogen species decorated Pt-Ni-N electrocatalyst with tunable architectures and facets was prepared by a facile solvothermal method.The influences of Ni2+,the volume ratios of water to ethylene glycol(R),the dosage of KI,the reaction time,and the composition on the nanoflowers structures,high-index crystal facets and decorating of surface nitrogen species were investigated.Pt-Ni-N electrocatalysts showed nanoflowers and nanoparticles which bounded to high-energy crystal facets(111)and(220)with varying different parameters.The results show that the Pt-Ni-N electrocatalysts exhibited superior electrocatalytic activity than that of PtNi,Pt-N and Pt/C catalysts for MOR and ORR.To further specify the molecular mechanism for enhanced catalytic activity towards the MOR,Density functional theory(DFT)was used to calculate the surface reaction energies for the(111)and(220)facets attributed to nanoflowers(NFs)and nanoparticles(NPs).(3)A novel ternary hierarchical carbon and nitrogen adsorbed PtNiCo@C-N nanocomposites with a tunable morphology have been successfully synthesized.The nanocube structure and the high index(111)facet can be achieved by controlling the volume ratio of OAm/OA.The surface etching technology(XPS)and ligand exchange strategies were proposed to establish the location,content,and the bonding mode for the carbon,nitrogen atoms and Pt atoms.The catalytic results indicated the PtNiCo@C-N nanocube nanocomposites exhibited superior electrocatalytic activity as well as outstanding durability towards the MOR and ORR.