Nanocatalysts on Two-Dimensional Supports Using APD

it is not easy to find clues for the observed difference in catalytic activities from only these structmal aspects. The XPS analysis in Fig. 3.9 shows that the impregnated and annealed Pt nanoparticles have inactive bulk oxide states, while the APD Pt nanoparticles are purely metallic. This oxide formation during annealing is considered the main reason for the difference in the catalytic activities. In order to improve catalytic activity, impregnated and annealed Pt nanoparticles on T1O2 films were reduced under 100 Torr of hydrogen at 250 °C for 1 h to decrease the oxidation state. However, the catalytic activity after reduction was stiU lower than that of the 

APD Pt nanoparticles (Fig. 3.8a). Furthermore, XPS survey spectra showed a very small peak for K on the impregnated Pt nanoparticles. The presence of K ions may have blocked active sites too [9]. This study showed that APD enabled the deposition of metallic Pt nanoparticles on TiOa films with neither oxidation due to annealing nor impurities commonly found in conventional wet-chemical processes. 

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