Hydrogenation of Ethylene and Dehydrogenation and Hydrogenolysis of Ethane on Pt(111) and Pt(211): A Density Functional Theory Study

Hydrogenation of ethylene and dehydrogenation and hydrogenolysis of ethane on Pt(111) and Pt(211) have been studied using density functional theory (DFT) calculations. Adsorption of CH x and C 2 H x species on Pt(111) and Pt(211) has been investigated. All the dehydrogenation and hydrogenation elementary-like reactions of C 2 species, all the C−C bond-cleavage reactions and isomerization reactions between C 2 species have been calculated. The following have been found: (i) CH 3 C is the most stable C 2 species on Pt(111) and Pt(211); (ii) on Pt(211), ethane dissociation to CH 2 CH 2 and CH 3 CH is a rapid process at low surface temperatures; (iii) on Pt(111), CH 3 CH is expected to be rapidly consumed by dehydrogenation to CH 3 C, which is difficult to be further dehydrogenated to CH 2 C or hydrogenated to CH 3 CH; (iv) isomerization reactions are not energetically favored on Pt; (v) on Pt(111), the lowest barrier of C−C cleavage is 0.9 eV in CHC, whereas on Pt(211) the lowest barrier of C−C cleavage is 1.1 eV in CH 3 CH 2 . These results suggest that at high temperatures, C−C cleavage can happen most possibly via CHCH, CH 3 CH, and CH 3 CH 2 intermediates.