The origin of 1560cm−1 band in experimental IR spectra of water adsorbed on TiO2 surface: Ab initio assessment

Highlights: • We perform DFT study on vibrational spectrum of water layer on Ti₈O₁₆ nanocluster. • The calculated v2 frequency agrees well with experimental IR spectral feature at 1560 cm⁻¹. • The v2 frequency depends linearly on a distance between water molecules and the TiO₂ surface. We present DFT study on vibrational spectrum of water layer on a surface of TiO₂ which is modeled via Ti₈O₁₆ nanocluster. In contrast to ν₂ mode's frequency of liquid water (1645 cm⁻¹) for the water layer theory predicts considerably lower ν₂ frequency (1570 cm⁻¹) which matches experimentally observed shoulder in IR spectrum (1560 cm⁻¹). We demonstrate that the calculated ν₂ frequencies depend linearly on a distance between adsorbed water molecules and a surface of Ti₈O₁₆ nanocluster! We also show that hydrogen bonding strongly affects ν₁ vibrational frequencies but leaves ν₂ and ν₃ ones almost intact.