Preparation And Properties Of Nano Carbon Loaded Pt-Au Core-Shell Structure Catalyst

Energy and environmental crisis has increasingly become a notable characteristicof the times of the early21st century. Looking for an alternative energy is a task need tobe discussed imeadieatly. Among many solutions, fuel cell is one of the mostpromising candidates because it’s clean and efficient. However, the high cost ofthe electro-catalysts is one of the major obstacles hindering its commercialization.Currently, Pt or Pt-based catalysts is still the best option for fuel cells because ofits high catalytic activity and stability in methanol oxidation and oxygen reduction.However, due to the small reserves of Pt in nature, it is too expensive to apply.Therefore, the study of how to improve the utilization efficiency, the catalytic activityand stability of Pt is very necessary.We synthesized Pt monolayer and sub-monolayer on Au/C core-shell nanoparticleelectrocatalysts for DMFC. Carbon-supported Au nanoparticles were synthesized bychemical reduction using NaBH4as reducing agent and sodium citrate as protectiveagent. Au nanoparticles were characterized by Transmission Electron Microscope(TEM). The Pt Monolayer or sub-monolayer was deposited on Au/C nanoparticles bygalvanic replacement of underpotential deposited Cu on the Au surface. MAPPINGimages showed that the core-shell structure of catalyst had been prepared successfully.Series of Ptn@Au/C (where n=number of UPD-redox replacement cycles) weresynthesized and their electrochemical properties for Hydrogen adsorption and Oxygenreduction reaction (ORR) were investigated by electrochemical measurements. Duringthe experiments, it was found that a perfect UPD adlayer of Cu was not easy to get. TheCu atoms in adlayer could not be oxidized to Cu2+completely by H2PtCl6, because ofthe presence of Cl which will lead to the formation of{CuCl}-2.After characterization of oxygen reducing ability on different Pt@Au/C catalysts,we found that: the oxygen reducing ability of catalyst promoted with the increased of Ptlayer thickness, but the utilization efficiency of Pt decreased; For sub-monolayerPt@Au/C catalysts, the situation is the same. When the surface of the Pt and Au is closeto the atomic ratio of1:1, we obtained the maximum oxygen reduction currentindicating the stabilizing effect of Au in Pt oxygen-reduction.