Plasma Treated Carbon Supported Noble Metal Catalyst and Its Application
|Keywords||noble metal catalyst plasma reduction glucose oxidation|
Catalyst is an essential part of modern industry, in which the supportedcatalyst of noble metal has been a hot topic recently. To form nanoparticles ofmetal on support as small as possible, so far, the technologys like colloid,micromicell et, al have succeed in synthesizing well dispersed nanoparticles.However, in these cases, losts of chemicals are needed, like reductant, polymerprotectant, so are the complicated steps like deposition, precipitation, repetivewashing and activation. All of these mean that they are hard to control the costand would have a serious problem on environment when commercialized. In thiswork, incipient-wetness impregnation was followed by glow discharge plasma toprepare supported nanoparticles of metal. The thesis of this work is to find out ifit is excutable to reduce the metal on the support and form nanoparticles withhigh catalytic reactivity.The plasma treated Au/C catalysts with different loading of gold have shownbetter activity than hydrogen reduced one in the reaction of glucose oxidation,especially for low loading of metal. In XPS and FT-IR analysis, gold wasevidenced to concentrate on the surface of meso-pore and macro-pore of support,and the hydrophilicity of carbon was enhanced. As a result, in aquousheterogeneous reaction, oxygen and glucose could move to the catalytic sitesmore easily and rapid, which lead to the better activity.After Pd/C catalyst supported on activated carbon was treated by plasma,there was still oxidized palladium, but most of it was reduced and formed asmetallic nanoparticles with excellent dispersion. Both determinations of XRDand TEM shown that plasma reduced particles were smaller than hydrogenreduced ones. And similar to the Au/C catalyst, palladium was found toaccumulate on the surface of carbon, too, which was certified by the XPSexaminations. In the estimation of activity for reaction, plasma treated catalystperformed better than hydrogen treated one.On the bimetallic Pt-Ru/C catalyst prepared by plasma, platinum and a littleruthenium was reduced together and formed bimetallic nanoparticles, while most of Ruthenium was not reduced at all. Smaller particles were obtained on plasmatreated catalyst, comparing with hydrogen reduced one. The inferior activity inelectro-chemical test of plasma treated catalyst was attributed to the worsecrystallography of Pt-Ru bimetallic particles reduced by plasma.In summary, for Au, Pd and Pt on carbon support, plasma is an impressivetechnique for catalyst preparation, which could decompose the precursors, reducethe metal and build nanoparticles, excluding the ineffectiveness in reducing Ru.As a conclusion, the degree of metal reduced by plasma is determined by thestandard electrode potential (SEP) of metal anion. Compared with Au Pd and Pt,the SEP of Ru is much lower, so it is more difficult for Ru to obtain electron andreduced in plasma Nevertheless, plasma still offers a promising alternativetechnique for preparation of noble metal catalyst owing to its easy operation, timesaving, low cost, low energy consumption and no pollution.