MICROCALORIMETRIC AND CATALYTIC INVESTIGATIONS OF TRANSITION-METAL NANOPARTICLES INTERCALATED IN GRAPHITE

The distribution of the metal content of pristine and thermally treate d (medium-temperature reduction, MTR) Pt-, Pd- and Rh-graphite interca lation compounds (graphimets) was investigated by transmission electro n microscopy, H-2 titration and sorption microcalorimetry. It was esta blished that MTR resulted in a migration of interlayer metal atoms to the graphite surface accompanied by a moderate aggregation of the surf ace nanoparticles. Despite the increased metal content available for H -2 adsorption after MTR, the catalytic activities decreased substantia lly. Besides structural changes, the loss of catalytic performance was related to the increase of metal-hydrogen bond strengths suggested by the calorimetric data. (C) 1998 Elsevier Science B.V. All rights rese rved.