Ab initio insight into mechanisms of ozone interaction with a surface of dehydrated nanocrystalline TiO2 (original) (raw)
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Infrared Study of Ozone Adsorption on TiO2 (Anatase)
The Journal of Physical Chemistry, 1995
Ozone adsorption at 77 K on titania (anatase) surface dehydrated at different temperatures or preexposed to pyridine, acetonitrile, and CO has been studied by infrared spectroscopy in order to characterize ozone interaction with Lewis acid sites of different strength. With weaker sites, ozone molecules form coordinative complexes bound via the terminal oxygen atom. The observed vibrational frequencies (about 1145 and 990 cm-I), as well as the isotopic shifts observed for ozone enriched by '*O, reveal a strong distortion of the molecule in this complex. No molecular adsorption of ozone on strong Lewis sites was detected. Data obtained provide evidence for ozone dissociation on these sites. Formation of atomic oxygen is suggested. It participates in oxidation of CO on the Ti02 surface.
Computational investigation of water and oxygen adsorption on the anatase TiO2 (1 0 0) surface
In this work, a computational technique based on semiempirical SCF MO method MSINDO, has been adopted for adsorption of water and oxygen molecules on the anatase TiO2 (1 00) surface. We employed free and saturated cluster models for simulation of TiO2 (1 0 0) surface. In accordance with other experimental and theoretical methods, the adsorption of dissociated form of water molecule is energetically more favoured than that of molecular form. Furthermore, the hydrogen bonding of water molecule with surface titanium ion plays a significant role in stabilization of water molecule adsorption. We have also investigated the adsorption of atomic and molecular, singlet and superoxide, oxygen. The results reveal that, the adsorption of atomic and molecular oxygen on TiO2 (1 00) surface is energetically possible. Further, the peroxo type adsorption of molecular oxygen at four-fold coordinated titanium (Ti4C) atom, being predominant.
Effect of oxygen vacancy on the adsorption of O2 on anatase TiO2(001): A DFT-based study
Surface Science, 2015
We performed density functional theory (DFT) based calculations to investigate the effects of O-vacancies on the adsorption of O 2 on anatase TiO 2 (001). Our calculation results show that we can promote O 2 adsorption on an initially inert stoichiometric TiO 2 (001) by introducing O-vacancy. The resulting excess electrons from the introduction of the O-vacancy redistribute around the neighboring Ti ions. An incoming O 2 can then adsorb at the O-vacancy site, either in the superoxide state (O − 2) or the peroxide state (O 2− 2). In the O − 2 state, the O-O bond is oriented parallel to the surface, along [010]. In the O 2− 2 state, the O-O bond is oriented perpendicular to the surface, along [001]. Healing of the surface occurs when one of the O atoms of the perpendicularly adsorbed O 2 fills the vacant site and the other atom diffuses, recovering the stoichiometric surface.
Israel Journal of Chemistry, 2005
We review the adsorption and desorption of molecular oxygen on a reduced TiO 2 (110) surface. This system is known to play a fundamental role in heterogeneous photocatalysis. Periodic calculations are performed with the objective of characterizing the variety of stable species of O 2 that are known to exist on the TiO 2 surface. The implications of our results for recent experiments are discussed. We also consider a direct optical excitation mechanism for the ultraviolet (UV) light-desorption process and model the most stable O 2 /TiO 2-x system as a cluster. High-level ab initio calculations of the excited states and interaction matrix elements are performed using different orbitals, separately optimized for the target states. The nonadiabatic and dipole-moment couplings are calculated directly from the correlated wave functions by a special transformation to bi-orthonormal (dual) orbital sets to preserve their structure. The method used for the electronic structure calculations is described in detail. Finally, the effect of the electronic coupling in the UVphotodesorption dynamics is analyzed in detail.
Chemical Physics Letters, 2018
DFT study on O 2 adsorption on a nanocrystalline titania is presented for the first time. The dioxide's nanoparticle is modeled via the nanocluster Ti 8 O 16. According to the calculations, O 2 physisorbs on the nanocluster Ti 8 O 16 in S 0 and T 0 states and chemisorbs on the nanocluster in S 1 state. The computed adsorption enthalpies, O 2 vibrational frequencies, and O 2 À g-tensor agree well with available data. In contrast to the axial O 2 orientation on a surface of titania with oxygen vacancies, in the chemisorption complex O 2 is oriented laterally. We explain this by the sterical hindrance of the Ti 3+ centers in the former case.
Chemical Physics, 2008
The adsorption and photocleavage of chlorobenzene (CB) molecule on the anatase TiO 2 (0 0 1), (1 0 0) and surfaces are studied with semiempirical SCF MO method, MSINDO. The surfaces have been modeled with two saturated clusters Ti 21 O 58 H 32 and Ti 36 O 90 H 36 . The dissociative perpendicular adsorption of CB on TiO 2 and surfaces revealed comparable stabilities and much higher than on the (0 0 1) surface. The aromatic ring cleavage by atomic oxygen, singlet oxygen and superoxide anion molecules has been investigated computationally and relevant mechanisms are proposed. Molecular dynamics (MD) simulations have been implemented for the adsorption models and the early stages of photocleavage mechanisms. The oxygen-type chemistry is involved actively in the water mediated photocleavage step upon excitation. The O ÅÀ 2 radical anion dependant ring opening mechanism, through the dioxetane intermediate, is thermodynamically the most favourable.
In this work, we studied the adsorption of water molecule onto the (1 0 0), (0 1 0) and (0 0 1) surfaces of nano-sized anatase TiO2 with semiempirical SCF MO method, MSINDO. The anatase TiO2 particles are modeled with free clusters (TiO2)n, where n = 20–80. Whereas, the surfaces have been modeled with two saturated clusters, Ti21O58H32 and Ti36O90H36. The surface lattice fivefold coordinated titanium atoms (Ti5C), which represent the Lewis acid sites, are selected as adsorption centers. We also investigated the effect of TiO2 cluster size on the computed band gap energy. Results reveal that the electronic properties of a cluster in the lowest excited state differ from that of the ground state. Furthermore, the MSINDO band gap energies of 3.68–3.77 eV for the anatase TiO2 are in a fair accordance with other literature data. In agreement with other computational and experimental studies, the dissociated form of water molecule adsorption on anatase TiO2 surfaces is always more stabilized than the molecular form
High-affinity adsorption leads to molecularly ordered interfaces on TiO2 in air and solution
Science
Researchers around the world have observed the formation of molecularly ordered structures of unknown origin on the surface of titanium dioxide (TiO2) photocatalysts exposed to air and solution. Using a combination of atomic-scale microscopy and spectroscopy, we show that TiO2 selectively adsorbs atmospheric carboxylic acids that are typically present in parts-per-billion concentrations while effectively repelling other adsorbates, such as alcohols, that are present in much higher concentrations. The high affinity of the surface for carboxylic acids is attributed to their bidentate binding. These self-assembled monolayers have the unusual property of being both hydrophobic and highly water-soluble, which may contribute to the self-cleaning properties of TiO2. This finding is relevant to TiO2 photocatalysis, because the self-assembled carboxylate monolayers block the undercoordinated surface cation sites typically implicated in photocatalysis.
Journal of Physics: Condensed Matter, 2022
A variety of OH containing molecules in their different modes of adsorption onto the rutile TiO2(110) are studied by means of density functional theory. A special focus is given to ethanol, ethylene glycol and glycerol. The different species were analyzed with respect to the adsorption energy, work function, and atomic Bader charges. Our results show that dissociated adsorption is favored in all cases. Within these modes, the strongest binding is observed in the case of bidentate fully dissociated adsorption, followed by bidentate partially dissociated then the monodentate dissociated modes. The dependence is also noted upon charge transfer analysis. Species adsorbing with two dissociated OH groups show a negative charge which is roughly twice as large compared to those exhibiting only one dissociated group. In the case of molecular adsorption, we find a small positive charge on the adsorbate. The change in work functions obtained is found to be negative in all studied cases. We obs...