Reactivity of thin-film TiO2(110)

The interaction of formic acid with TiO2 thin films and rutile TiO2(110) has been compared using high-resolution electron energy-loss spectroscopy (HREELS). Between 260 and 300 K the spectra are consistent with surface formate bonded to titanium sites, a consequence of dissociative chemisorption. For a four-layer TiO2(110) film, the 220 cm−1 separation of νs(OCO) and νa(OCO) at 260 K indicates that formate is bidentate-bonded, as it is to the surface of the bulk crystal, for which the bands have a 172 cm−1 separation at 300 K. In contrast, a three-layer c(2×6) film gives rise to a separation of about 282 cm−1, closer to the ν(CO)−ν(CO) separation expected for monodentate bonding.