Preparation Of Low-Pt Modified Core-shell Nanocatalysts And Research On Its Catalytic Performance

Fuel cell,as a promising power generation device,has received extensive attention in recent years.Among them,the electricity catalyst is the key to the development of fuel cell.Platinum-based electrocatalysts are an essential part of fuel cells.However,it’s expensive and scarce,acquiring low platinum with high performance catalysts has become the key to reducing the cost of fuel cells.In recent years,the nanostructure control of precious metal catalysts has received great attention from researchers.In particular,the M@Pt catalysts with a non-precious metal as the core exhibit excellent catalytic performance.At the same time,the use of inexpensive transition metals instead of precious metals as the core can significantly reduce the use of platinum.In this paper,the seed growth method was used to prepare Ni@Pt core-shell structure.The experiment adopts an integrated reaction path,we prepared polyhedron nickel particles with 30 nm as nucleation in oil ammonia solution,then,we restored the Pt atom and wrapped it on the surface of the nickel crystal core.In the first group of experiments,Pt（acac）₂ was used as precursor,according to the different Pt/Ni mole ratios,we could obtain nanoparticles with multiple dendritic,island-like core-shells and dendritic morphology.The paper discusses the process of formation of various topographies and the effect of the surfactant CTAB on the morphology of nanoparticles,and we find that the amount of surfactant added will affect the morphology and growth rate of nanoparticles.When the core-shell structure is prepared by the seed method,a proper amount of CTAB can reduce the platinum reduction rate,induce platinum atoms to assemble on the surface of nickel particles,and form a Ni@Pt core-shell structure.Electrochemical tests showed that the PtNi₃ nanoparticles exhibited the highest activity due to their core-shell structure.The second set of experiments used H₂PtCl₆·6H₂O as a precursor,it was found that platinum easily exchanged with the nickel nucleus and evenly encapsulated several nanometer platinum layers on the surface of nickel particles.There was a coherent relationship between the surface platinum layer and the inner Ni of Ni@Pt core-shell nanoparticles which were obtained by the substitution reaction.This not only helps to form a dense layer to prevent the nickel core from being corroded,moreover,the lattice mismatch between the inner and outer layers can form a stress effect and an electron effect,thereby greatly improving the catalytic activity.The displacement reaction is an effective method for preparing Ni@Pt core-shell nanoparticles.The Ni@Pt core-shell nanoparticles can also be obtained by changing the ratio of Pt and Ni in the precursors 1:3,1:2,and 1:1.Electrochemical tests show that the Ni@Pt core-shell structure can greatly increase the catalytic activity of the precious metal and effectively reduce the platinum content of the fuel cell catalyst.Among them,the smaller size of Ni₂@Pt works best.Studies have shown that the growth of the platinum shell of the core-shell structure is mainly controlled by kinetic factors.When Pt（acac）₂ was used as precursor,rapid decomposition of explosive nucleation resulted in a large number of 5 nm nanoparticles,island-like nano-particles with platinum nanoparticles attached to the surface of nickel large particles are prepared.When H₂PtCl₆·6H₂O is used as a precursor,this enables platinum ions to react with nickel nuclei and can encapsulate several nano platinum layers on the surface of nickel particles.Controlling the reduction rate of Pt is the key to form core-shell structure.