| Abstract
| - Two groups of carbon-supported platinum nanoparticle catalysts have been prepared. In group I, catalysts Iand II were prepared using PtCl4 and H2PtCl6 as starting materials and 1-hexanethiol, HSCH2CH2CH2CH2CH2CH3, as a surfactant. For group II, the same platinum complexes were used as starting materials (catalystIII from PtCl4, catalyst IV from H2PtCl6) and tert-octanethiol, HSC(CH3)2CH2CH2CH2CH2CH3, was used asa surfactant for the first time. It has been found that the group II catalysts are between ∼2 and ∼3.3 timesmore active toward methanol oxidation reaction compared to other prepared and commercial catalysts.Transmission electron microscopy shows that the platinum nanoparticles are homogeneously dispersed onthe carbon support and exhibit a narrow size distribution; the average particle size was found to be 2 ± 0.4and 3 ± 0.4 nm in diameter for group I and group II catalysts, respectively. X-ray diffractogram analysisindicates that the platinum nanoparticles have a face centered cubic structure consistent with that of platinummetal itself. X-ray photoelectron spectra of the catalysts indicate two different types of platinum with the Pt4f7/2 binding energies of 71.1, 74.4 eV; 71.3, 74.3 eV; 71.0, 74.4 eV; and 71.5, 74.5 eV for catalysts I−IV,respectively. These have been identified as Pt(0) and Pt(IV), which could be platinum oxide or hydroxide.By looking at the oxidation state data, we found that catalysts I−IV consist of 71% Pt(0) and 29% Pt(IV);83% Pt(0) and 17% Pt(IV); 76% Pt(0) and 24% Pt(IV); and 65% Pt(0) and 35% Pt(IV), respectively.
|
