Surface-sensitive vibrational sum-frequency spectroscopy (vSFS) has been utilized to study the adsorption behavior of methanol on anatase TiO2 thin films under ambient temperature and pressure condition. The vSF spectra in the C–H region establish the presence of both molecular methanol and dissociated methoxy adsorbates. Spectra for the isotopologues of methanol also support the deprotonatation process at the surface. Furthermore, by a systematic study of the vSF spectra of methanol isotopologues in the C–H and C–D stretching regions, we clarify that in the CH spectral region the molecular signal coherently interferes with the near-resonant one from hydrogen bonded OH. The latter is due to adsorption from the water vapor present in the background and its interaction with surface OH.

Surface-sensitive vibrational sum frequency spectroscopy (vSFS) has been utilized to study the adsorption chemistry of small alcohols, namely, methanol, ethanol, 1propanol, and 2-propanol on TiO 2 thin films under near-ambient conditions. The vSF spectra in the C−H region reveal that methanol and ethanol adsorb both molecularly and dissociatively, while 1-propanol and 2-propanol are solely detected in the molecular form. The different adsorption behavior suggests that the extent of dissociation decreases from methanol to propanol. Moreover, polarization analysis of the spectra reveals that the methyl groups are preferentially oriented with their symmetry axis pointing in a direction close to the surface normal for methanol, ethanol, and 1-propanol. However, for 2-propanol, the methyl groups exhibit a larger tilt angle.

The interaction of 2-propanol with Co3O4(001) was studied by vibrational sum fre-quency spectroscopy (vSFS) and by ab initio molecular dynamics (AIMD) simulations of 2-propanol dissolved in a water film to gain insight at the molecular level into the pathways of catalytic oxidation. The experimental study has been performed under near ambient condition, where the presence of water vapor is unavoidable, resulting in a water film on the sample and thereby allowing us to mimic the solution-water interface. Both experiment and theory conclude that 2-propanol adsorbs molecularly. The lack of dissociation is attributed to the adsorption geometry of 2-propanol in which the O-H bond does not point towards the surface. Furthermore, the copresent water not only competitively adsorbs on the surface but also inhibits 2-propanol deprotonation. The calculations reveal that the presence of water deactivates the lattice oxygen, thereby reducing the surface activity. This finding sheds light on the multifaceted role of water at the interface for the electrochemical oxidation of 2-propanol in aqueous solution as recently reported. At higher temperatures 2-propanol remains molecularly adsorbedon Co3O4(001) until it desorbs with increasing surface temperature.

The interaction of 2-propanol with Co3O4(001) was studied by vibrational sum frequency spectroscopy and ab initio molecular dynamics simulations of 2-propanol dissolved in a water film to gain an insight, at the molecular level, into the pathways of catalytic oxidation. The experimental study has been performed under near ambient conditions, where the presence of water vapor is unavoidable, resulting in a water film on the sample and, thereby, allowing us to mimic the solution–water interface. Both experiment and theory conclude that 2-propanol adsorbs molecularly. The lack of dissociation is attributed to the adsorption geometry of 2-propanol in which the O–H bond does not point toward the surface. Furthermore, the copresent water not only competitively adsorbs on the surface but also inhibits 2-propanol deprotonation. The calculations reveal that the presence of water deactivates the lattice oxygen, thereby reducing the surface activity. This finding sheds light on the multifaceted role of water at the interface for the electrochemical oxidation of 2-propanol in aqueous solution as recently reported [Falk et al., ChemCatChem 13, 2942–2951 (2021)]. At higher temperatures, 2-propanol remains molecularly adsorbed on Co3O4(001) until it desorbs with increasing surface temperature.

The interaction of 2-propanol with SrTiO3(100) surfaces is studied with a focus on the role of different surface terminations in the deprotonation upon adsorption.