A series of catalysts, Pt-Al2O3, with various particle size distributions has been studied by electron microscopy and infrared spectroscopy and chemisorption measurements. Well-characterized narrow distributions have been obtained in the range 15-35 Å. The stretching vibration of NO irreversibly adsorbed on these supported metals is particle size dependent: the larger the size, the lower the ν(NO) vibration. This result is interpreted by assuming that the extent of the back-donation to the π* orbitals of NO+ depends on the collective properties of the crystallites. This interpretation is corroborated by the spectroscopic results obtained with platinum carbonyl clusters.
ASJC Scopus subject areas
- Colloid and Surface Chemistry