Microfludic Synthesis And Electrochemical Performance Study Of PtSn Intermetallic Compounds

It is well known that the energy produced by the direct ethanol fuel cell?DEFC?is theoretically higher than that of the direct methanol fuel cell,but the complete oxidation of ethanol becomes difficult because of the ethanol structure and so on.In order to change this situation and increase the oxidation rate of ethanol,many researchers try to overcome the difficulty of cracking C-C bond by continuously improving the catalyst.At present,the commercial catalyst for DEFC is Pt/C,however,due to the high price of Pt and the low anti-toxicity to CO,the intermediate product of fuel oxidation,the Pt based metal alloy?Pt-M?has become a hot spot in the research of anode and cathode electrocatalyst for fuel cell.Among them,intermetallic compound alloys have attracted much attention because of their specific element composition,special geometry and electronic structure.Unlike disordered solid solution alloys,intermetallic compounds have higher enthalpy of mixing and better structural stability due to the definite distance and arrangement of their internal atoms.Studies have shown that the leaching amount of ordered intermetallic compounds in acidic or alkaline electrolytes is much smaller than that of disordered alloys,which not only reduces the non-toxic effect of the catalyst to the electrolyte,but also increases the stability of the catalytic process.Moreover,the ordered intermetallic compounds synthesized with the same proportion of the same active metals have higher catalytic activity than the disordered solid solution alloys,which is due to the ordered and stable structure of the intermetallic compounds,and many researchers have also demonstrated this.Among the numerous Pt-M intermetallic compounds,PtSn is considered to be one of the most suitable catalysts for ethanol oxidation,and more and more attention has been paid to the synthesis of PtSn intermetallic compounds.At present,most of the methods of synthesis of PtSn intermetallic compounds are obtained by high temperature annealing after the preparation of alloys.In this paper,PtSn intermetallic compounds were synthesized by microfluidic method under the condition of no surfactant.The main contents and conclusions of this paper include the following parts:1)the unsupported ptsn intermetallic compounds were successfully synthesized by using microfluidic reaction apparatus with crystalline tin tetrachloride?SnCl₄?5H₂O?and platinum acetylacetonate?Pt?acac?₂?dissolved in ethylene glycol as metal precursors,and the synthesis parameters including reaction temperature and capillary length were changed,and determine the minimum synthesis temperature of pure phase intermetallic phase is 250?.According to the characterization results of the synthesized samples,the formation process and formation mechanism of the target product nanochains were theoretically analyzed;The PtSn intermetallic compounds were synthesized with polyethylene glycol 400 and polyethylene glycol 600 as solvents respectively.The results show that the pure phase target product can be synthesized at higher temperature when polyethylene glycol 400 is used as solvent.Moreover,the chain width of the product was wider than that of the synthetic product in the solvent of ethylene glycol,but when polyethylene glycol 600 was used as the solvent,no pure phase intermetallics was synthesized.The morphology of the synthesized products is greatly affected by the capillary itself.Compared with the phase and morphology of the synthesized products with several solvents,the effects of solvent reductivity and viscosity on the synthesis of PtSn intermetallic compounds were analyzed.2)The supported PtSn/C intermetallic compounds were successfully synthesized with polyethylene glycol 400 as solvent,SnCl₄?5H₂O and Pt?acac?₂ as precursors of two metal elements,respectively,and functionalized carbon black Vulcan XC-72 as support by microfluidic reaction device.The effects of precursor ratio,intake pressure and capillary length on the synthesis of pure phase intermetallics were investigated,and the temperature and its synthesis conditions of PtSn/C intermetallic materials were determined,that is,the pure phase PtSn/C intermetallics can be prepared at the300?under the conditions of the 1:5 of precursors ratio and 5 cycles of capillary length?157 cm?at 200 Psi pressure;The synthesis of highly dispersible supported PtSn/C intermetallic compounds was preliminarily explored by two-step synthesis,increasing the amount of support carbon and adding a little distilled water to the precursor solution,respectively.It was found that water addition had a great influence on the dispersion of particles.However,the most uniform dispersion based on the pure phase has not been achieved yet,and further exploration is needed.