Graphite-supported platinum catalysts

J. H. Vleeming, B. F. M. Kuster, and G. B. Marin, Oxidation of methyl and n-octyl a-D-glucopyranoside over graphite-supported platinum catalysts effect of the alkyl substituent on activity and selectivity, Carbohydr. Res., 303 (1997) 175-183. 

F.A. Debruijn, G.B. Marin, J.W. Niemantsverdriet, W. Visscher, J.A.R. Vanveen, Characterization of graphite-supported platinum catalysts by electrochemical methods and XPS. Surface and Interface Analysis 1992, 19(1-12), 537-542. 

In the present article, the size and the loading efficiency of metal particles were investigated by changing the preparation method of carbon-supported platinum catalysts. First, the effect of acid/base treatment on carbon blacks supports on the preparation and electroactivity of platinum catalysts. Secondly, binary carbon-supported platinum (Pt) nanoparticles were prepared using two types of carbon materials such as carbon blacks (CBs) and graphite nanofibers (GNFs) to check the influence of carbon supports on the electroactivity of catalyst electrodes. Lastly, plasma treatment or oxyfluorination treatment effects of carbon supports on the nano structure as well as the electroactivity of the carbon supported platinum catalysts for DMFCs were studied. 

The catalyst is platinum-based for both the anode and cathode. To promote hydrogen oxidation, the anode uses either pure platinum metal catalyst or, as is common in most modem PEFC catalysts, a supported platinum catalyst, typically on carbon or graphite for pure hydrogen feed streams. For other fuels, such as reformate (containing H2, CO2, CO, and N2), the desired catalyst is an alloy of platinum containing mthenium. Oxygen reduction at the cathode may use either the platinum metal or the supported catalyst. 

Many studies report the effect of porosity and surface area on metal dispersion and catalytic activity. Linares-Solano et al. [10] prepared platinum catalysts supported on a graphitized carbon black (V3G), which was subjected to various degrees of activation in air to increase the surface area. They observed that as the surface area of the parent sample increased from 62 m /g to 136 m /g,... 

Basically, the construction of PAFCs differs little from what was said in Section 1.4 about fuel cells with liquid acidic electrolyte. In the development of PAFCs and two decades later in the development of PEMFCs (described in Chapter 3), many similar steps can be distinguished, such as the change from pure platinum catalysts to catalysts consisting of highly disperse platinum deposited on a carbon support with a gradual reduction of platinum content in the catalyst from 4 to 0.4 and then to 0.25 mg/cm, and the change from pure platinum to Pt-Ru catalysts. The bipolar graphite plates that have special channels for reactant snpply and distribution over the entire electrode surface now used widely in PEMFC stacks were first used in PAFCs. 

Low-temperature oxidation (below 200°C) of carbon has received attention from research workers not only because of its potential utility in DCFCs but also because of the harm it does in many types of fuel cells and other electrochemical devices where platinum catalysts on carbon supports are used. It was in this connection that Choo et al. (2007) studied the anodic oxidation mechanism of graphite in sulfuric acid. 

X-Ray studies confirm that platinum crystallites exist on carbon supports at least down to a metal content of about 0.03% (2). On the other hand, it has been claimed that nickel crystallites do not exist in nickel/carbon catalysts (50). This requires verification, but it does draw attention to the fact that carbon is not inert toward many metals which can form carbides or intercalation compounds with graphite. In general, it is only with the noble group VIII metals that one can feel reasonably confident that a substantial amount of the metal will be retained on the carbon surface in its elemental form. Judging from Moss s (35) electron micrographs of a reduced 5% platinum charcoal catalyst, the platinum crystallites appear to be at least as finely dispersed on charcoal as on silica or alumina, or possibly more so, but both platinum and palladium (51) supported on carbon appear to be very sensitive to sintering. 

An interesting catalyst is the platinum supported on graphite. Fig. 12 shows a bright field image. The... 

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