Journal of Physical Chemistry B, Vol.109, No.19, 9581-9588, 2005
Vibrational analysis of H-2 and D-2 adsorption on Pt/SiO2
Vibrational properties of surface species formed upon H-2 and D-2 exposure of silica supported platinum particles have been investigated with in situ diffuse reflection infrared Fourier transform spectroscopy. Experiments have been performed at 50-250 degrees C, using different platinum loading of the samples in the absence and presence of oxygen. In addition, electronic structure calculations and vibrational analysis have been performed within the density functional theory for H adsorption on a silica cluster, (HO)(3)SiOSi(OH)(3). The spectroscopy experiments showed reversible formation of isolated OH and OD groups on the silica surface when the samples were exposed to H-2 and D-2, respectively. In addition to the absorption peak corresponding to isolated OH and OD groups, an intense broad band was observed around 3270 cm(-1) (2500 cm(-1)) during H-2 (D-2) exposure. Supported by the calculations, this band was assigned to perturbed OH groups on the silica surface. The surface coverage of new OH groups was found to correlate to the platinum loading in the samples, indicating that the new silanol groups were formed in the vicinity of the Pt particles. In the investigated temperature interval, the formation rate of CH groups was not found to be temperature dependent.