Adsorption and interaction of CO₂ on rutile TiO₂(110) surfaces: a combined UHV-FTIRS and theoretical simulation study

Abstract

CO2 adsorption and interaction on rutile TiO2(110) surfaces was studied by UHV-FTIRS combined with theoretical simulations. With increasing CO2 exposure, CO2 adsorbs in succession at the oxygen vacancy (Vo) sites, on the five-coordinated Ti cation (Ti5c) sites and the bridging oxygen (Obr) sites at low temperature. The coupling has occurred between neighboring CO2 adsorbed on Ti5c sites from rather low CO2 coverage (∼0.5 ML), leading the ν3(OCO) asymmetric stretching vibrations to split into two absorption bands in IR spectra. Two kinds of coupled geometries of adjacent CO2 on Ti5c sites are determined by theoretical simulations. For the higher CO2 coverage (∼1.5 ML), the horizontal adsorption configuration along the [11[combining macron]0] azimuth of CO2 adsorbed on Obr sites is identified for the first time using polarization- and azimuth-resolved RAIRS in experiments. The significant deviation of CO2 from the top of Obr sites demonstrates the strong coupling between CO2 adsorbed on Obr and Ti5c sites.

Formation and evolution of orientation-specific CO2 chains on nonpolar ZnO(10͞10) surfaces

“…(See Figure S1 for the detailed judgements of the CO 2 vibration direction through the polarized IRRAS.) Our assignment is in accordance with previous HREELS and FTIR reports5678910111213141516171819.…”

“…studied the dynamic dipole-dipole-coupling of adjacent CO 2 molecules on MgO(100) and NaCl(100) surfaces13141516. Similar results were reported for CO 2 adsorption on rutile TiO 2 (110) surfaces in our previous work17. On the ZnO(100) surface, using the high resolution ultrahigh vacuum-Fourier transform infrared spectroscopy (UHV-FTIRS), Buchholz et al .…”

“…These dramatically lowered vibration frequencies of adsorbed CO 2 relative to that of gas-phase CO 2 (2349 cm −1 ) demonstrate evidently that CO 2 have chemically adsorbed on ZnO(100) surfaces. Based on the IR judgement principle on dielectric substrates1718, the vibrational bands at 1622, 1297 and 978 cm −1 for CO 2 on ZnO(100) surfaces are assigned respectively to the asymmetrical stretching mode (ν as (OCO), in-plane), symmetrical stretching mode (ν s (OCO), out-of-plane) and the stretching vibration between the carbon atom and the underneath surface O 3c atom (ν(CO 3c ), out-of-plane) for tridentate carbonates. (See Figure S1 for the detailed judgements of the CO 2 vibration direction through the polarized IRRAS.)…”

“…The experiments were carried out using an ultrahigh vacuum (UHV) system17 (the base pressure better than 6 × 10 −11 mbar) equipped with a vacuum Fourier transform infrared spectroscopy (FTIR) spectrometer (Bruker, VERTEX 80 v), a low energy electron diffraction (LEED)/Auger (AES) spectrometer with gain power of microchannel plates BDL 600IR-MCP. The clean mix-terminated ZnO(100) (8 × 8 × 1 mm, MTI) surface was prepared by repeated cycles of Ar + sputtering and annealing at 800 K under UHV conditions until no impurities were detected by AES and clear (1 × 1) LEED patterns were obtained.…”

Scenarios of polaron-involved molecular adsorption on reduced TiO2(110) surfaces

“…The contrast study on NO and CO adsorption will give more clear scenarios of polaron-involved molecular adsorption on single crystal oxide surfaces. We expect to throw new light on this important issue by probing the subtle interaction between CO/NO and polarons through detecting the vibration frequencies of adsorbed molecules by the highly sensitive ultra-high vacuum - Fourier transform infrared spectroscopy (UHV-FTIRS) 35, 36 .…”