Paper SS-TuA1
A Density Functional Theory Study of Stability and Reactivity of H-C=O and C-OH Surface Reaction Intermediates on Pt(111) and Effects of Water on the Intermediates

Tuesday, October 29, 2013, 2:00 pm, Room 201 A

Two forms of the reaction intermediate with H:C:O stoichiometry were studied on Pt(111) using density functional theory. Three cases were studied: the intermediate on a clean surface, the intermediate and one water molecule on the surface and the intermediate with a water bilayer. Both the H-C=O (formyl) and C-OH configurations were found to be stable on clean Pt(111) and when coadsorbed with a single water molecule. On the clean surface interconversion between the two forms goes through stable a CO_ads and H_ads intermediates so although both HCO and COH are stable on the clean surface they will not interconvert without coadsorbed water. In the presence of coadsorbed water molecule the activation barrier for the interconversion from HCO to COH was found to be much lower or 0.62 eV. The HCO configuration is stable in the presence of a water bilayer with slight preference for bridge over atop adsorption site. The COH configuration is unstable under the water bilayer and dissociates into CO_ads and H that structurally diffuses into the water bilayer. That suggest that, in the presence of water, the HCO form will be the only stable form of the reaction intermediate of H:C:O stoichiometry. Various reactions paths for both of the reaction intermediates with OH and H₂O eventually leading to CO or CO₂ formation are also investigated.