Calorimetric measurements of the adsorption heat for ethene on Pt{211} andPt{311}

The sticking probability and heat of adsorption for C2H4 on the stepped Pt( 211) and Pt(311)-(1 x 2) surfaces have been measured for the first time. Ad sorption on Pt(211) leads to the formation of several different species as a function of coverage, whereas adsorption on Pt(311)-(1 x 2) leads to the formation of only one species on the surface over the whole coverage range. The initial heats of adsorption for C-2,H-4 on Pt(211) and Pt(311)-(1 x 2) have been measured as 180 and 220 kJ mol(-1), respectively. The initial st icking probabilities are 0.84 for both surfaces. The most likely species to be formed on Pt(211) as a function of coverage are quad-a acetylene follow ed by ethylidyne whereas on Pt(311)-(1 x 2) ethylylidyne forms at all cover ages. (C) 1999 Elsevier Science B.V. All rights reserved.