| AVS 66th International Symposium & Exhibition | |
| Surface Science Division | Tuesday Sessions |
| Session SS+2D+HC-TuM |
| Session: | Atom Manipulation and Synthesis/Oxide Surface Reactions & Flash Session |
| Presenter: | Katsuyuki Fukutani, Institute of Industrial Science, The University of Tokyo, Japan |
| Authors: | N. Nagatsuka, Institute of Industrial Science, The University of Tokyo, Japan Y. Ohashi, Institute of Industrial Science, The University of Tokyo, Japan M. Fujimoto, Tokyo Gakugei University, Japan M. Matsumoto, Tokyo Gakugei University, Japan K. Fukutani, Institute of Industrial Science, The University of Tokyo, Japan |
| Correspondent: | Click to Email |
Interaction of hydrogen with TiO2 surfaces is of interest and importance in view of photocatalytic H2 generation and hydrogen sensors. Furthermore, hydrogenated TiO2 has recently acquired much attention due to its excellent photocatalytic activity [1]. In our previous study, we have investigated the interaction of hydrogen with the rutile TiO2(110) surface with nuclear reaction analysis (NRA) and ultraviolet photoemission (UPS) [2]. Whereas the former allows us to quantify hydrogen in the sample in a depth-resolved manner [3], the latter provides us with the information on the electronic states. In the present study, we have studied interaction of low-energy hydrogen ions with TiO2 single-crystal surfaces, where the hydrogen ion penetrates the surface being distributed in the near-surface region [4]. We also report atomic hydrogen interaction with TiO2 nanoparticles in relation with hydrogenation of TiO2.
When the rutile TiO2(110) and anatase TiO2(101) surfaces are exposed to atomic hydrogen, NRA shows adsorption of hydrogen on the surfaces with a coverage of about 0.5 monolayer [2]. When the rutile TiO2(110) surface is exposed to a hydrogen ion beam at 500 eV, on the other hand, NRA reveals a maximum at a depth of about 1 nm extending to ∼30 nm with an average concentration of 5.6 at. % and UPS shows an in-gap state (IGS) at ∼0.8 eV below the Fermi level with a downward band-bending by 0.5 eV. The IGS intensity is about ten times as large as that of the H-adsorbed surface. Upon annealing at 673 K, the IGS intensity is reduced by about 40 % and H with a coverage of 1.4 monolayer remains in the near-surface region, which suggests stable H occupation of subsurface sites. When the H-ion-irradiated surface is exposed to oxygen molecules, on the hand, the hydrogen distribution remains unchanged although the IGS intensity is substantially reduced. The effect of hydrogen in the near-surface region on the surface electronic state is discussed.
[1] Z. Wang et al., Adv. Func. Mater. 23, 5444 (2013).
[2] K. Fukada et al., J. Phys. Soc. Jpn. 84, 064716 (2015); N. Nagatsuka et al., in preparation.
[3] M. Wilde, K. Fukutani, Surf. Sci. Rep. 69, 196 (2014).
[4] Y. Ohashi et al., J. Phys. Chem. C in press.