AVS 52nd International Symposium
    Surface Science Monday Sessions
       Session SS-MoP

Paper SS-MoP29
Chain Structure of Surface Hydroxyl Groups on TiO@sub 2@(110) with Line Oxygen Vacancy Studied by in-situ Noncontact Atomic Force Microscopy (NC-AFM)

Monday, October 31, 2005, 5:00 pm, Room Exhibit Hall C&D

Session: Surface Science Poster Session
Presenter: Y. Namai, Mitsui Chemicals, Inc., Japan
Authors: Y. Namai, Mitsui Chemicals, Inc., Japan
O. Matsuoka, Mitsui Chemicals, Inc., Japan
Correspondent: Click to Email
Surface hydroxyl groups are essential species in many catalytic reactions. Especially, in oxide surfaces, they play a crucial role in reforming of the surface reactivity due to the adsorption of hydrogen adatoms at oxygen ion (anion) sites. Therefore controlling of the surface hydroxyl on catalysis surfaces is important in the reactivity and the selectivity. As a model surface to control hydroxyl groups, a slightly reduced TiO@sub 2@(110) surface was utilized. By repeating many cleaning cycles, surface oxygen atoms on bridge oxygen rows of the TiO@sub 2@(110) linearly desorbed, and the line vacancy structures were obtained. The line vacancy was formed by increasing of the density of oxygen vacancies on the TiO@sub 2@(110) surface. After exposing H@sub 2@O (1.0 x 10@super -4@ Pa for 120 s), hydroxyl chain structure, which is linearly arranged hydroxyl groups into two rows on bridge oxygen rows, were formed on the TiO@sub 2@(110) surface with the line oxygen vacancy. In-situ NC-AFM measurements at RT to 1.0 x 10@super -7@ Pa H2O revealed that the hydroxyl chain structure was formed at the line vacancy site. After H@sub 2@O exposure, annealing at above 500 K was sufficient to remove the hydroxyl chains on the TiO@sub 2@(110) surface, and then line vacancy structures reappeared on the surface. Before published STM and other experimental results supported that dissociative adsorption of water occurs on oxygen vacancy sites of the TiO@sub 2@(110). Therefore these results concluded that the hydroxyl chain structure was formed at the line vacancy site. Thus the formation of the hydroxyl chain structure suggests that controlling of surface hydroxyl groups on catalysis surfaces is possible.