Controlled Synthesis Of Ultrathin Platinum-based Nanowires And Their Electrocatalytic Properties

Developing hydrogen energy to replace the existing fossil energy provides a vital solution for achieving national"dual carbon"go al.However,fuel cell device in the hydrogen energy conversion technology and electrolyzer device for efficient hydrogen production rely on scarce and expensive platinum materials as cathodic catalysts,which seriously hinder deployment of those tech nologies.At present,Pt is still the irreplaceable catalyst in these energy conversion devices.In this context,the design and development of Pt-based catalysts with high activity and long durability are imminent,which however face great challenges.Alloying Pt with transition metals and designing nanostructure are two main strategies to improve catalytic activity,nevertheless it is hard to balance activity and stability.To this end,our works focus on advancing development of platinum-based nanowires catalysts with high mass activity and long durability simultaneously,starting with precise and controllable synthesis methods in the first place.By regulating the geometric structure and chemical composition of platinum-based catalysts and revealing the intrinsic relationship between atomic structure and catalytic performance,thus constructing an active and durable platinum-based nanowires catalysts.Moreover,the developed seed-mediated diffusion method of surface autocatalytic reduction is further exte nded to the synthesis of palladium-based intermetallic nanocrystals so as to creat a novel catalysts system for energy conversion.The specific research work of this paper is as follows:（1）By proposing a new strategy of"strong p-d orbital interaction to suppress the dissolution of active metals",we develop a synthetic method based on atomic precise diffusion and further prepare ultrathin PtGa NWs with strong p-d orbital interaction.In the oxygen reduction reaction（ORR）tests,the mass activity and specific activity of the Pt_4.31Ga NWs/C catalyst are 10.5 and 12.1 times higher than that of the commercial Pt/C catalyst,respectively.Stability testing shows that the mass a ctivity of the Pt_4.31Ga NWs/C catalyst loses only 15.8%after 30,000 cycles of accelerated durability tests（ADTs）,which markedly outperforms stability of Pt/C with 79.6%of activity loss.Mechanism studies show that the strong p-d orbital interaction between Ga and Pt atoms optimizes the surface electronic structure and suppresses the atomic migration of lattice Ga,thus explaining the origin of activity and stability of PtGa NWs.（2）A universal preparation method for the synthesis of Pt-based ultrathin nanowires was developed,including monometallic Pt NWs,bimetallic nanowires（Pt Ni NWs,Pt Fe NWs,and Pt Co NWs）,trimetallic nanowires（Pt Ni Ga NWs,Pt Fe Rh NWs,and Pt Co Re NWs）,and tetrametallic nanowires（Pt Ni Ga Re NWs,Pt Ni Sn Rh NWs,Pt Fe Ga Re NWs,and Pt Co Ga Rh NWs）,in which the trimetallic and tetrametallic NWs in the present work are new catalytic systems.In the ORR tests,the mass activity of the optimized ultrathin Pt Ni Ga Re NWs/C catalyst is found to be 19.6times higher than that of Pt/C,and it only lo ses 10.6%after 20,000 cycles of ADTs.The above perfomance is further verified in fuel-cell membrane electrode system,indicating the practical application potential of the nanowires as cathodic cataltst.Theoretical calculations show that the trace dopin g of Re into Pt Ni Ga NWs weaken the adsorption binding strength of oxygenated species and elevate dissolution potential,well rationalizing the great enhancements in activity and durability.（3）A autocatalytic surface reduction-assisted strategy was used to realize the incorporation of W element with large reduction potentials into Pt NWs,enabling the precise synthesis of ultrathin PtW alloy nanowires.The experimental evidence and density functional theory calculations demonstrate that the preformed Pt NWs in the synthesis serve as the catalyst to facilitate the reduction of W^x+species through the autocatalytic surface reduction mechanism.Using the alkaline hydrogen evolution reaction as a model reaction,the as-synthesized PtW NWs/C catalyst shows an ultralow overpotential of 18 m V at 10 m A cm^–2 and a high mass activity of 6.13 A mg_Pt^–1 at an overpotential of 100 m V.The dual roles of alloyed W atoms are further uncovered by theoretical simulations,involving the ensemble effect for accelerating H₂O dissociation and a ligand effect for optimizing the hydrogen adsorption strength.（4）The developed seed-mediated diffusion synthesis method for autocatalytic surface reduction was extended to the synthesis of Pd-based intermetallic nanocrystal,futher realizing the rapidly synthesis of Pd₃Pb,Pd₃Sn and Pd Cd ultrathin porous intermetallic nanosheets（UPINs）of with tunable sizes.This strategy uses preformed seeds,which act as the template to control the deposition of foreign atoms and the subsequent interatom ic diffusion.Using the ORR as a model reaction,the as-synthesized Pd₃Pb UPINs exhibite excellent activity,durability,and methanol tolerance.Theoretical studies suggest that the favored geometric structure and strong interatomic interaction between Pd and Pb atoms in Pd₃Pb UPINs are conclude to account for the enhanced ORR performance.