Probing Pd-carbon interaction in Pd/C catalysts by EXAFS

The Pd/C catalyst prepared by PdCl2 impregnation was examined with extended X-ray absorption fine structure (EXAFS) analysis. The model of precursor anchoring by surface oxygen groups is not supported by EXAFS. A Pd-C interaction at around 3.6 angstrom can be included in the fitting of the fresh catalyst. This Pd-C interaction remained after the fresh PdCl2/C was washed and reduced by NaBH4. However, a further hydrogen treatment at 338 K removed this Pd-C interaction and Pd sintering was indicated with increasing hydrogen treatment temperature. This Pd-C interaction was originally proposed [B.L. Mojet, M.S. Hoogenraad, AJ. van Dillen, J.W. Geus, D.C. Koningsberger, J. Chem. Soc., Faraday Trans. 93 (1997) 4271] for Pd(NH3)(4)Cl-2/C and was also found in the Pd/C prepared by Pd(NO3)(2) impregnation in this study. This suggests a similar Pd-C interaction while preparing Pd/C catalyst from cationic, anionic and neutral I'd species. (c) 2005 Elsevier B.V. All rights reserved.