Design Of High-efficiency Methanol Fuel Cell Anode Catalyst Based On Strong Metal Support Interaction

Energy and environmental issues are two extremely important issues facing human society in the 21st century.With the advancement of the industrialization of various countries in the past half century,traditional energy sources such as oil,coal,andnatural gas have been continuously consumed,so many countries have continuously explored new forms of energy,such as solar,wind,and tidal energy.In this context,direct methanol fuel cells(DMFCs)emerged as an efficient energy conversion device.DMFCSs have attracted much research attention owing to the advantages of low pollution,not restricted by the Carnot cycle,wide source of raw materials,high specific energy density,convenient storage and transportation,and environmental friendliness.Pt presents the state-of-the art catalysts for methanol electrooxidation.However,the high price of Pt,low earth abundance,and easy poisoned by carbon-containing intermediate species greatly limits the commercialization process of DMFCs.Therefore,reducing the use of precious metals,improving the catalytic efficiency and prolonging life have become urgent problems which have to be solved.From the perspective of DMFCs catalyst support design,composition,and synthesis,this paper uses strong metal support interaction(SMSI)to study the performance of two Pt-based catalysts to catalyze methanol oxidation.The main contents are listed as follows:1.Carbon-oxide(C-CeO2)composite supports were prepared by direct pyrolysis of the mixture of sugar and metal salt for Pt-based MOR catalysts.Carbon-oxide(C-CeO2)composite support materials were prepared by the high-temeparture pyrolysis of a mixture of natural carbohydrate molecules(glucose,sucrose,a-cyclodextrin(CD)and soluble starch)and metal salts(cerium nitrate,niobium chloride,zirconium chloride,vanadium chloride and aluminum nitrate).The CD-CeO2 composite was selected as a typical support for loading Pt nanoparticles by ethylene glycol(EG)reduction.The methanol oxidation reaction(MOR)activity of the Pt/CD-CeO2 catalyst for methanol oxidation under acidic conditions(1.13 A·mg-1 Pt)is much higher than that of commercial JM-Pt/C(0.31 A·mg-1 Pt),which can be attributed to the fact that CeO2 can activate water molecules effectively for producing hydroxyl adsorption species(OHads)to transfer and consume carbon-containing intermediate species(COads)adsorbed on Pt.In addition,we conducted X-ray photoelectron spectroscopy(XPS)and extended X-ray absorption fine structure(EXAFS)to study the catalyst and infer the presence of SMSI in the metal Pt and composite support.We used high-resolution transmission electron microscopy(HRTEM)to characterize and observe the Pt-oxide-carbon interface,further revealing the microscopic mechanism of the high activity of methanol electrooxidation.We also observed the Pt-oxide-carbon interface by using HRTEM and further revealed the microscopic mechanism for the high activity of methanol electrooxidation.2.Based on the strong interaction between sulfur and metal on the carbon support,a small-sized PtCu3 intermetallic compound(IMC)was synthesized for methanol electrooxidation.Through the mesoporous sulfur-doped carbon support(SC)developed previously in our laboratory,the PtCu3 intermetallic compound was synthesized by the traditional wet impregnation method and a high-temperature reducing atmosphere.Characterizations such as powder X-ray diffraction(PXRD)and spherical aberration corrected high-angle annular dark field image(Cs-STEM-HAADF)confirmed that the ordered PtCu3 nanoparticles with an average particle size of 4.9 nm was uniformly dispersed on the carbon support.By comparing with the loading effect of commercial carbon black,we can infer that the strong interaction between S and Pt in the meso-SC is the main reason for inhibiting particle agglomeration during the reduction process.Compared with commercial JM-Pt/C(0.31 A·mg-1 Pt),SC-PtCu3(2.42 A·mg-1 Pt)showed excellent activity and stability in methanol oxidation reaction.On the one hand,the introduction of Cu reduces the use of precious metal Pt.On the other hand,Cu can activate water to produce OHads to promote the conversion of COads adsorbed on Pt,accelerate the reaction process,reduce poisoning,and extend the li fe of the catalyst.In addition,the mass activity of SC-PtCu3(1.53 A·mg-1 Pt)in the oxygen reduction reaction(ORR)is 3.9 times than that of JM-Pt/C(0.39 A·mg-1 Pt).