Theoretical studies of stability and reactivity of C-2 hydrocarbon specieson Pt clusters, Pt(111), and Pt(211)

Quantum chemical calculations employing density functional theory were perf ormed to investigate the interactions of C2Hx(ads) species on Pt-10 cluster s and on Pt(111) and Pt(211) slabs. We calculate the binding energies of ex perimentally observed surface species, such as di-a-bonded ethylene, ethyli dyne species, and di-sigma/pi vinylidene species. In addition, we calculate the binding energies of the other species, such as ethyl, ethylidene, and vinyl species, that are postulated to be reactive intermediates in surface reactions. Furthermore, we calculate the activation energies for C-C bond d issociation of various C2Hx(ads) species. We show that the bonding energies are dependent on the geometry of the surface, leading to the observed stru cture sensitivity of ethane hydrogenolysis. We show that the underlying par ameter for understanding the stronger binding of various species on the ste p edge of Pt(211) compared to Pt(111) is the position of the metal d-band c enter. With estimates from these DFT calculations of the potential energy s urface involved in the formation and reactivity of various C2Hx(ads) specie s on Pt, we show that the primary reaction pathways for ethane hydrogenolys is on platinum involve highly hydrogenated species, such as C2H5(ads).