Formic acid (HCOOH) dissociated on the rutile TiO2(110) surface into formate (HCOO) and H. Certain ordered structures for HCOO were observed for different coverages. In the present work, the role of hydrogen in the stability of these structures and also in the process of HCOO diffusion was studied by means of ab initio density functional calculations. The calculations showed that co-adsorption of H was necessary to stabilize the high-coverage p(2 x 1) geometry. They furthermore explained the observed high mobility of HCOO in a p(2 x 1)-like environment which was caused by a rather complex movement of HCOO together with H. This process cannot operate at lower coverages and for isolated molecules, which therefore made HCOO immobile, as suggested by experiment.

Dissociative Adsorption of Formic Acid and Diffusion of Formate on the TiO2(110) Surface: the Role of Hydrogen. Käckell, P., Terakura, K.: Surface Science, 2000, 461[1-3], 191-8

Table 2

Electrotransport of 110mAg in TiO2

under an applied gradient of 250V/mm