The Synthesis Of Palladium-based Catalysts Supported On Carbon Nanotubes And The Study Of The Influence On Their Electrocatalysis For The Ethanol

As a kind of new energy, fuel cells have become a safe and reliable energy installationgradually because of their efficiency and environmentally friendly property. However, due to thehigh cost of the precious metal catalysts, the process of commercial application of the fuel cells isblocked. Therefore, how to reduce the amount of precious metals or to improve their utilizationhas become the focus of the current study. On the other hand, it is necessary to possess a suitablecarrier for the efficient catalyst, and carbon nanotubes would be the preferred catalyst supportaccordingly for their good electrical conductivity and thermal stability and high specific surfacearea, on the research.In this dissertation, the main research strategy is: Pd and Pd-based catalysts，which arepossessing small particle size, large specific surface area and different morphology and controlledprepared with the appropriate additives which are selected in terms of the basic principle, and thecatalysts manily are nanoscale Pd particles, nano-Pd-Co alloy hollow-spheres and Pd-Cu alloyhollow-spheres carried on the SnO₂nanorods. High-power transmission electron microscopy（HR-TEM）, X-ray powder diffraction （XRD）, fourier transform infrared spectroscopy （FTIR）,scanning electron microscope （SEM）, X-rayphotoelectron spectroscopy （XPS）, thermalgravimetric analysis （TGA） and cyclic voltammetry （CV）, chronoamperometry are used tocharacterize the morphology and test the catalytic activity and stability of the catalysts, and wediscusse the synthesis mechanism and catalytic essence. The main contents are as follows:（1） We introduced the knowledge about the DEFCs and the preparation and the progress ofthe catalysts of the fuel cells.（2） The Pd catalysts supported on the MWCNTs were prepared by reduction method at theroom temperature in the presence of diphenyl phosphorus propane （DPPP）, the particle size isabout2.5nm. From the physical characterizations and electrocatalytic performance tests, wefound that with the additive, the active surface area of the catalyst can be achieved to32.7m²g^-1Pd,the current density was102.2mAcm^-2, which is about1.6times higher than that of the catalystprepared without the additive, and the stability was also improved. It showed that the appropriateadditives can play the role of regulating the catalyst particle size and dispersion, to improve the electrocatalytic performance of the catalyst.（3） The soft-template method was used to prepare Pd-Co hollow sphere catalyst dispersed onthe surface of multi-wall carbon nanotubes. Cetyl trimethyl ammonium bromide （CTAB） was usedas additive, surfactant and template, ethylene glycol （EG） as solvent and reducing agent in thesynthesis system. The size of the catalyst was about100nm, with narrow size distribution, thespecific surface area was66.51m²/g, which was two times higher than that of the non-hollowcatalyst prepared under the same conditions. The catalysts of hollow-spheres exhabited higherelectrocatalytic activity and stability, the current density was212mAcm^-2, about1.8times higherthan that of the non-hollow catalysts. It showed that the soft template method is a good way toimprove the catalyst utilization.（4） The rod-like tin dioxide was prepared by the solvent thermal method using SnCl₂.5H₂Oin the aqueous solution of glucose. Then the Pd-Cu hollow spheres catalyst was fabricated on theSnO₂by using the glutamic acid as additive, glycol as reducing agent. The size of the catalyst wasabout100nm, with narrow size distribution, the specific surface area was43.97m²/g, which wasabout1.4times higher than that of the catalyst carried without SnO₂. From the electrocatalyticperformance tests with carbon nanotubes as catalyst conductive agent, the catalysts exhabitedhigher electrocatalytic activity and stability, the current density was119.4mAcm^-2. It showed thatthe introduction of a suitable metal oxide may release more active sites of the catalyst to improvethe electrocatalytic activity of the catalyst.It had a try to improve the utilization of the precious metal catalyst and solve the problem ofcatalyst poisoning through the above experimental study, thus it could provide new methods andideas for commercial application of the fuel cells.