AVS 59th Annual International Symposium and Exhibition
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP30
Active Sites for H2 Dissociation on Gold Model Catalyst

Tuesday, October 30, 2012, 6:00 pm, Room Central Hall

Session: Surface Science Poster Session
Presenter: I. Nakamura, AIST, Japan
Authors: I. Nakamura, AIST, Japan
T. Fujitani, AIST, Japan
Correspondent: Click to Email
Au nanoparticles supported on metal oxides are highly active for various hydrogenation reactions. The dissociation of H2 molecules is one of the most important elementary steps in hydrogenation reactions, and the nature of H2 dissociation sites has been the subject of various studies. Recently, we demonstrated using Au/TiO2(110) that the perimeter interface between Au and TiO2 was the active sites for H2 dissociation. However, the oxidation state of Ti and the structure of Ti oxide at the perimeter interface are not entirely clear. Here, we performed H2–D2 exchange reaction using TiOx/Au(111) and TiOx/Au(100) (x = 0–2), and clarified the influence of the oxidation state of Ti and the Au and TiO2 structures on the creation of active sites for H2 dissociation. We found that the presence of stoichiometric TiO2 was essential for the creation of H2 dissociation sites over the Au surfaces. The activation energies (Ea) for HD formation over TiO2/Au(111) and TiO2/Au(100) were consistent with each other, and these Ea agreed well with that for Au/TiO2(110). This result shows that the active sites for H2 dissociation created on TiO2/Au(111) and TiO2/Au(100) were identical to those formed on Au/TiO2(110). Furthermore, we demonstrated that turnover frequencies (TOFs) for HD formation were close among these three surfaces, where TOFs were calculated by normalizing the number of HD molecules formed per second to the total number of Au atoms at the perimeter interfaces. These results clearly indicate that the active sites for H2 dissociation over TiO2/Au(111) and TiO2/Au(100) were the perimeter interface between TiO2 and Au. Concerning the structure of TiO2 on Au surfaces, LEED observations showed that the TiO2 produced on Au(111) was the ordered structure, in contrast to disordered TiO2 structure on Au(100). Thus, the creation of active sites for H2 dissociation was independent of the Au and TiO2 structures consisting perimeter interface. We concluded that local bonds between Au and O atoms of stoichiometric TiO2 (Au–O–Ti) create the active sites for H2 dissociation.