Study On Platinum-based Nanocrystals With Controllable Electronic Structure And Active Site Density And Their Electrocatalytic Properties

Proton Exchange Membrane Fuel Cell（PEMFC）is a kind of Fuel Cell which can cleanly and efficiently convert the chemical energy in the Fuel into electric energy.Its working principle is equivalent to the"reverse device"of water electrolysis.It is a major requirement for national energy security,sustainable economic and social development,and promotion of energy conservation and emission reduction.In commercial electrodes,the precious metal Ptis mainly used as a catalyst,because of its high catalytic performance and durability.However,the high cost,toxic inactivity and poor catalyst stability of Pthindered its large-scale commercial development.The poor stability of the catalyst hinders its large Large-scale commercial development.Therefore,it is of great significance to improve the catalytic activity,utilization rate,anti-poisoning ability and stability of Pt.Therefore,this thesis uses atom-dispersed metalphilic and low-cost transition metals to precisely synthesize platinum-based nanocrystalline catalyst materials with controllable electronic structure and active site density using a simple and environmentally friendly method.The specific research contents are as follows:（1）Here,we report a facile one-pot method to implant atomic dispersed Ru in PtNi colloidal nanocrystal clusters with different Ru/Pt/Ni molar ratios,which highly reduces the dosages of Ptand Ru,and further improves their catalytic performances for the electro-oxidation of formic acid and methanol.By simply controlling the amount of Ni（acac）₂precursor,trimetallic Ru_0.3Pt_70.5Ni_29.2CNCs,Ru_0.6Pt_55.9Ni_43.5CNCs,Ru_0.2Pt_77.3Ni_22.5CNCs and Ru_0.9Pt_27.3Ni_71.8CNCs are obtained.Particularly,the Ru_0.3Pt_70.5Ni_29.2CNCs exhibit the excellent specific activities for formic acid and methanol electro-oxidation,14.2-and15.3-fold higher than those of Pt/C catalyst,respectively.Moreover,the Ru_0.3Pt_70.5Ni_29.2CNCs also possess better anti-CO-poisoning property and superior diffusion ability than those of other Ru PtNi CNCs.（2）An environmentally friendly and flexible one-step synthesis method is used to prepare a PtCuFe nano-frame structure（NFs）with adjustable structure and defect density.The method enhances the catalytic activity and stability of the catalyst.Two kinds of PTCuFe NFs with different open frame structures were obtained by changing the nucleation/growth kinetics by changing the heating methods and the types of alcohols.Among them,the dendritic nanoframework（d-NFs）showed excellent electrocatalytic activity for methanol electrooxidation（MOR）and formic acid electrooxidation（FAOR）,which were 8.34 times and3.68 times higher than commercial Pt/C,respectively,and the stability was also greatly improved.The excellent electrocatalytic activity of d-NFS is attributed to a number of factors,including high defect site,large specific surface area,suitable d-band center and open frame structure.（3）Using an environmentally friendly and flexible one-step synthesis method,the growth kinetics was changed by changing the heating method and the type of sodium halide,and three different open-frame PtCuMn nano-frame structures with adjustable surface electronic structure and active site density were obtained.Cuand Mn enter the crystal lattice of Ptto optimize the electronic structure of Pt;at the same time,it exposes more defect sites and thus has a higher energy density,which improves the electrocatalytic activity,stability and resistance to CO poisoning of the catalyst.Among them,PtCuMn sawtooth hexapod nanoframes（sh-NFs）show excellent electrocatalytic activity for methanol electrooxidation（MOR）and formic acid electrooxidation（FAOR）,which are 7.76 times and 3.53 times higher than commercial Pt/C,respectively,and are stable Sex has also been greatly improved.This is mainly attributed to the fact that sh-NFs have more active sites on the crystal surface with high exponent and the coordination between Ptand Cuand Mn modulated the electronic structure of Ptsurface.