Hydrogen adsorption on TiO2 anatase(101)

Full text: Titanium dioxide is a prototypical material in photocatalysis. The most stable polymorph of TiO2 – rutile – has been widely investigated in surface science, while the metastable anatase is preferred in applications due to its higher efficiency. It has been shown that water only adsorbs molecularly on the TiO2 anatase(101) surface. Dissociation of H2O, which usually is the most common channel for formation of terminal hydroxyl groups, does not occur on anatase(101). While STM images of the anatase(101) surface do not show any signature of hydroxyl groups, other methods such as XPS or IR spectroscopy do. Here the anatase(101) surface is exposed to atomic hydrogen at low temperatures (100 K). This results in the creation of terminal hydroxyl groups, which are identified by means of low temperature scanning tunneling microscopy. The hydroxyls disappear from the surface after annealing to room temperature. The possibility of hydrogen migration to step edges or to the bulk is discussed. (author)