Preparation And Alcohol Oxidation Performance Research Of Platinum-based Ternary Metal Catalysts

Direct alcohol fuel cells(DAFCs)have become one of the most promising portable power sources due to their unique advantages,including high energy density,diversity of fuel options,lower operating temperature and low pollutant emissions.Anode platinum(Pt)-based precious metal catalysts,because of their superior electrocatalytic performance,have been widely studied and applied to methanol oxidation reaction(MOR)and ethanol oxidation reaction(EOR)of DAFCs anodes.However,Pt is a rare precious metal,and its reserves on the earth are scarce and expensive.Therefore,reducing the consumption of Pt in the electrocatalyst while improving catalytic activity is the key to reducing the cost of DAFCs.With the rapid advance of nanomaterial preparation technology,it is possible to construct a highly efficient multicomponent Ptbased precious metal nanocatalysts with a rational design by tuning the elemental composition and precisely controlling the formation of nanostructures.In this thesis,Pt is alloyed with oxyphilic metals,such as copper(Cu)and silver(Ag),and rhodium(Rh)is introduced to form PtRh-M(M = Cu,Ag)ternary metal catalysts.The reducing agent and the capping agent were used to rehulate the composition and morphology growth of the nanomaterials,and the catalytic activity of the nanomaterials for the oxidation of alcohols was studied.The specific research contents are as follows:(1)The Rh-strengthened PtCuRh rhombohedral dodecahedrons with nanodendrites(RDD)were synthesized through a one-pot solvothermal method,which could be etched to obtain totally open nanoframe PtCuRh rhombohedral dodecahedrons with nanodendrites(RDND).More interestingly,the growth of the nanodendrites can be easily controlled through changing the reaction temperature.Meanwhile,the length of the nanodendrites can be controlled through adjusting the amount of cetyltrimethyl ammonium bromide(CTAB)and the reaction time.In addition,synergistic effects between Pt,Cu and Rh modified the electronic structure and downshifted the d-band center of Pt,which weakened the adsorption of toxic intermediates by the catalyst.In particular Rh metal oxide on the surface contributes heavily towards improving the electrocatalytic efficiency.Therefore the as-prepared catalyst PtCuRh RDND shows superior catalytic performance towards the methanol oxidation reaction(MOR)as well as the ethanol oxidation reaction(EOR)compared to TKK-commercial Pt/C.Remarkably,after 1000 electrochemical cycles of the MOR,the superior mass activity of PtCuRh RDND surpasses that of TKK-commercial Pt/C by 2.6 times,benefiting from enhanced CO tolerance and the stable structure.This work provides a facile and feasible strategy for synthesizing stable and efficient nanoframe catalysts.(2)One-pot solvothermal reduction method was used to synthesize Ag nanocube enclosed by PtRh nanoparticles as trimetallic Ag@PtRh Ag nanocube(NC)core-shell catalysts toward methanol oxidation reaction(MOR).The core-shell structure is formed due to the presence of N-NDimethylacetamide(DMA),which promotes the preferential reduction of Ag by changing the reduction potential of Ag.Meanwhile,the bromide ions originating from CTAB controlled the growth of the cubic morphology.Benefiting from the pleated exterior providing more active sites and the synergistic effect among Pt,Rh and Ag,the mass and specific activities of Ag@PtRh Ag NC exhibit 4.22 and 3.78 times higher than that of commercial Pt/C,respectively.More impressively,due to the better CO tolerance,Ag@PtRh Ag NC displays a strengthened durability by maintaining 84.9% mass activity after 1000 MOR cycles compared to the initial value.The present work provides a one-step strategy to synthesize core-shell nanostructure catalyst enhancing the MOR activity.