MICROCALORIMETRIC STUDY OF ETHYLENE ON PT(110)-(1X2)

The calorimetric heat of interaction for a hydrocarbon on a single-crystal surface is reported for the first time. For ethylene on Pt{110}-(1 × 2) at low coverages it is about 205 kJ/mol and drops in several steps to 120 kJ/mol with increasing coverage. Three stable species are identified on the surface, and the average bond dissociation energy of a Pt-C single bond is extracted for each. The mean value is about 223 kJ/mol, and we observe a systematic decrease from 235 to 214 kJ/mol as the number of single Pt-C bonds per adsorbate molecule increases from 2 to 4. © 1995 The American Physical Society.