Coordination of Palladium on Carbon Fibrils as Determined by XAFS Spectroscopy

To investigate the anchoring of precious metals onto carbon fibrils Pd/C-fibril samples were investigated in both the precursor and the reduced state by X-ray absorption fine structure (XAFS) spectroscopy. Analysis of the XAFS data of the freshly prepared catalyst showed a palladium–tetraamine complex in interaction with carbon. The proposed model involves [Pd(NH3)4]2+ coordinated to the carbon fibril surface, most probably stabilised by the carboxylic groups (through O–H bridging and charge balance) and the π-electron system of the support. After insitu reduction, analysis pointed to small palladium particles of ca. 15 A present on the fibrils with a significant Pd–C interaction.