Micro-Raman spectroscopy of Pd-B/SiO2 amorphous alloy catalyst

Multi-channel confocal micro-Raman spectroscopy was used to characterize si lica-supported PdCl2 powder (PdCl2/SiO2) and Pd-B amorphous alloy catalyst (Pd-B/SiO2) which is formed by reducing PdCl2/SiO2 with KBH4. The results s how that PdCl2/SiO2 gives mainly a complicated broad nu (PdCl) bands in the 150-650 cm(-1) region arising from surface palladium complex species such as [PdCl4](2-) and/or its various hydrolysis products. The Raman spectrum o f Pd-B/SiO2 amorphous alloy shows broad bands in the 300-500 cm(-1) and ca 800 cm(-1) regions. They may be assigned to Pd-B vibration overlapping that of the amorphous SiO2 support compared with the Raman spectra of unsupport ed Pd-B amorphous ahoy and SiO2 support calcined at 873 K, Pd-B/SiO2 would be gradually converted to metallic Pd and elemental boron containing a cert ain amount of positive boron ions upon heating in Nz from 673 to 873 K. The effects of laser power and irradiation time on Pd-B and Pd-B/SiO2 show tha t Pd-B/SiO2 has better thermal stability than the unsupported material. Cop yright (C) 2000 John Whey & Sons, Ltd.