Reactivity of thin-film TiO2(110)

The interaction of formic acid with TiO2 thin films and rutile TiO2(110) ha s been compared using high-resolution electron energy-loss spectroscopy (HR EELS). Between 260 and 300 K the spectra are consistent with surface format e bonded to titanium sites, a consequence of dissociative chemisorption. Fo r a four-layer TiO2,(110) film,, the 220 cm(-1) separation of nu(s)(OCO) an d nu(a)(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) s eparation at 300 K. In contrast, a three-layer c(2 x 6) film gives rise to a separation of about 282 cm(-1), closer to the nu(C=O)-nu(CO) separation e xpected for monodentate bonding. (C) 2000 Elsevier Science B.V. All rights reserved.