Platinum catalyst particle size effect

Maillard F, Martin M, Gloaguen F, Leger JM. 2002. Oxygen electroreduction on carbon-sup-ported platinum catalysts. Particle-size effect on the tolerance to methanol competition. Electrochim Acta 47 3431-3440. 

In nanoscale catalyst particles the ratio of the different crystallographic faces are depending on the particle size thus giving an explanation for the particle size effects observed in electrolytes containing adsorbing anions. Since the perfluorinated polymer sulfonic acids are not adsorbing to the platinum sxuface, particle size effects are not so prominent in PEFC. 

Yano H, Inukai J, Uchida H, Watanabe M, Babu PK, Kobayashi T, Chung JH, Oldfield E, Wieckowski A. 2006b. Particle-size effect of nanoscale platinum catalysts in oxygen reduction reaction an electrochemical and Pt EC-NMR study. Phys Chem Chem Phys 8 4932-4939. 

Frelink T, Visscher W, vanVeen JAR. 1995. Particle-size effect of carbon-supported platinum catalysts for the electrooxidation of methanol. J Electroanal Chem 382 65-72. 

As already pointed out, the first particle size effect in skeletal rearrangement was found for the hydrogenolysis of methylcyclopentane (55). Nonselective hydrogenolysis takes place on highly dispersed catalysts, with a metal loading smaller than 0.6%, while selective rupture of bisecondary C-C bonds occurs on heavily loaded catalysts (more than 6% platinum on alumina). 

The particle size effect in the case of supported platinum catalysts prepared from chloroplatinic acid was questioned by Dautzenberg and Platteeuw (131), who claimed that the difference of behavior between the 0.2% and the... 

Particle-size effects may also be addressed in terms of the model outlined in Schemes 13.2-5. In the case of the reference platinum catalysts, a decrease in size was accompanied by a marked decrease in S2 and in 5i, and in F this implies stronger hydrogen chemisorption on the Pt/Al203 reforming catalyst. On rhodium and iridium, however, the effect of size on S2 and F (Table 13.9) is more probably due to a change in the surface s ability to accommodate multiple C=M bonds. 

Markovic et al. [17] review the data on platinum particles and suggest that the data in dilute sulfuric acid is consistent with Kinoshita s model and further suggest that essentially all of the reactivity can be attributed to the (100) surface. They go on to suggest that this difference in reactivity between the crystal faces is due to structure sensitivity of anion adsorption that impedes the reaction. They point out that in PEM systems, where anion adsorption by the sulfonic acid groups is unlikely, there might be considerably less of a particle-size effect. Still, most PEM catalyst layers employ platinum particles on the order of 3nm, roughly the same size as the maximum in mass activity identified by Kinoshita. 

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. 

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