Construction Of Pt-based Ternary Alloy Nanoframes And Electrocatalytic Performance

Proton Exchange Membrane Fuel Cell(PEMFC)is a high-efficiency power generation device that directly converts chemical energy stored in small molecular fuels into electrical energy.It has the advantages of high energy density,low environmental pollution,and low temperature operation.It provides new ideas for solving environmental problems and energy crisis.In the pursuit of PEMFC anode catalyst,Pt is considered as the most ideal metal component because of its high catalytic activity and stability.However,Pt catalysts still have the problems of high cost due to low intrinsic catalytic activity and poor stability due to poisoning and inactivation of substances such as CO produced in the middle of the reaction,which restricts the large-scale application of this technology.Therefore,further improving the utilization rate of Pt atoms and improving the electrocatalytic activity and stability are the key points of current research.At present,introducing cheap transition metal elements and constructing specific surface structures and surface coordination unsaturated active sites is an ideal strategy.In this thesis,the Pt-based ternary nanoframes with high specific surface area and high-index facets was precisely controlled and synthesized by one-step method.The main research contents are as follows:(1)A one-step microwave-assisted wet chemical method was used to prepare PtCuCo nanoframes with tunable defect-density and structure,which has enhanced activity and durability for the electro-oxidation reaction of methanol(MOR)and formic acid(FAOR).The density of the high-index facets can be facilely controlled by different kinds/amounts of reducing agents and structure-directing agents.Studies have found that I~-has a unique guiding effect on the formation of nanoparticles.In addition,compared with commercial Pt/C,the prepared PtCuCo NFs showed enhanced performance in both MOR and FAOR.In particular,the prepared PtCuCo rh-NFs exhibited excellent specific activities towards MOR and FAOR,7.25 and 5.20 times higher than those of benchmark Pt/C,respectively.(2)A facile,environmental and one-pot approach to fabricate PtCuNi NFs with tunable external and internal surface structures by flexibly adjusting coordination and reducing agents.Alcohol species were clarified to play the dominant role in governing the internal structure of PtCuNi NFs,while the glycine and NaI species were demonstrated as the main factors in controlling the external architecture of PtCuNi NFs.Electrocatalytic results show that PtCuNi nanoparticles with a variable external structure exhibit higher activity and stability than nanoparticles with a tunable internal structure and commercial Pt/C.In particular,the prepared PtCuNi eb-NFs exhibit higher catalytic activity for MOR and FAOR,10.7 times and7.9 times higher than commercial Pt/C,respectively,and have excellent durability.(3)PtCuCr NFs with high-index faces was synthesized in a single step in the aqueous phase.Cu and Cr enter the lattice of Pt,and compressive strain occurs,which is conducive to improving the catalytic activity of the nanoparticles.At the same time,compressive strain produces defect sites that are conducive to stable coordination unsaturation.By comparing the strain levels of the two nanoframework structures,it was found that particles with larger compressive strain exhibited better catalytic activity.The prepared PtCuCr h-NFs showed 7.9times and 7.0 times higher catalytic activity for MOR and FAOR than commercial Pt/C.