Hybrid Density Functional Calculations of Formic Acid on Anatase TiO<sub>2</sub>(101) Surfaces

Kou, Liangzhi; Frauenheim, Thomas; Rosa, A. L.; Lima, Erika Nascimento

doi:10.1021/acs.jpcc.7b06957

Cited by 12 publications

(11 citation statements)

References 24 publications

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“…34 In contrast, hybrid density functional theory calculations predicted MD dissociative adsorption on both the defect-free and reduced surfaces as the lowest-energy configuration. 31 To explore the effect of surface reduction on FA adsorption, we examined HCOOH on reduced anatase with a V O in the subsurface. 54,55 As shown in Table 1, deprotonated MD becomes slightly (0.06 eV) more stable than molecular MD on the reduced surface.…”

Section: Methodsmentioning

confidence: 99%

Binding of Formic Acid on Anatase TiO₂(101)

et al. 2020

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The adsorption of formic acid (FA) and the formation of formate species on metal oxide surfaces are of great interest in catalysis. Formic acid is used to probe the adsorption properties of surface sites, and formates are common intermediates in many catalytic reactions. Here we focus on the interaction of FA with a prototypical anatase TiO 2 (101) surface by using a combination of scanning tunneling microscopy (STM), infrared reflection absorption spectroscopy (IRAS), electron-stimulated desorption (ESD), and density functional theory (DFT) to assess the coverage-dependent evolution of different FA-derived surface species at low temperatures (80−240 K). We find that isolated FA adsorbs at 80 K in both monodentate (MD) and bidentate (BD) configurations on top of undercoordinated Ti sites (Ti 5c ). The MD form is likely deprotonated and readily converts upon annealing to deprotonated bridging BD on two neighboring Ti 5c sites. DFT calculations show that molecularly bound MD FA is metastable and readily converts to a deprotonated state in the proximity of subsurface oxygen vacancy. The stability of the MD species increases as the availability of the paired Ti 5c sites for BD formation diminishes at high coverages. Upon surface saturation, a mixed configuration of alternating MD and BD species with a coverage of 2/3 FA/Ti 5c represents the most favorable configuration. This is in contrast with the adsorption of FA on rutile TiO 2 (110) and many other oxides, where bidentate formate species dominate.

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Section: Methodsmentioning

confidence: 99%

Binding of Formic Acid on Anatase TiO₂(101)

et al. 2020

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“…The adsorption of small molecules such as H2O, 39 O2, 40 methanol, 41 and formic acid 42 on TiO2 surfaces has been studied extensively due to the application of such processes in catalysis, using both experimental and theoretical methods. 43,44 In particular, the interaction of water with TiO2 surfaces has been the subject of many studies, with the aim of understanding the mechanism of photochemical water splitting on such surfaces.…”

Section: Introductionmentioning

confidence: 99%

Linear Correlations between Adsorption Energies and HOMO Levels for the Adsorption of Small Molecules on TiO₂ Surfaces

et al. 2019

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Adsorption is a fundamental step in catalysis on a solid surface, and therefore its understanding is important to explaining its behavior. This work investigated the adsorption of various small molecules, including H2, N2, CO, CO2, CH4, NH3, H2O, H2S, DMSO, alkanes, alkenes, alkynes, aromatic compounds, alcohols, aldehydes, ketones, nitriles, carboxylic acids, amides, and amines, on the anatase (101) and rutile (110) surfaces of TiO2, using periodic density functional theory calculations and statistical methods. Adsorption energies were computed at the same level of theory to obtain a clean and consistent data set. A linear relationship was observed between the adsorption energies of these molecules and their highest occupied molecular orbital (HOMO) levels, whereas no obvious correlation was evident for the lowest unoccupied molecular orbital (LUMO) levels. Improved correlations between the adsorption energies and the HOMO levels were generated by dividing these molecules into two subgroups: hydrocarbons and heteroatom-containing compounds. Interactions between frontier molecular orbitals and the surfaces were considered, to gain a better understanding of the significant correlations that were identified. The data show that these relationships can be primarily ascribed to interactions between the HOMO of the small molecule and conduction state of the TiO2 surface. Statistical analysis using machine learning demonstrated that the HOMO and the dipole moment are the first and second most important properties, respectively, in terms of rationalizing and predicting the adsorption energies.

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“…The energetic effects of O vacancies on the catalytic activity of TiO 2 surfaces have been investigated in both experimental and theoretical studies. For example, defects are expected to strongly affect molecules containing an O atom; therefore, the literature contains numerous reports of the adsorption of molecules such as air pollutants, , carbonyl compounds, − and alcohols , onto TiO 2 surfaces. Although many researchers have reported the adsorption of various molecules on TiO 2 surfaces, as mentioned, systematic studies are rare.…”

Section: Introductionmentioning

confidence: 99%

Effect of Oxygen Vacancies on Adsorption of Small Molecules on Anatase and Rutile TiO₂ Surfaces: A Frontier Orbital Approach

et al. 2021

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Adsorption is a critical step in the initial stage of a catalytic reaction. Oxygen vacancies often become a central topic of discussion with respect to the reaction mechanism on metal oxide surfaces because oxygen vacancies change the surface electronic properties and affect the adsorption process. In this study, we use first-principles calculations and regression analyses to investigate the effect of oxygen vacancies on a metal oxide surface on the adsorption of small molecules. We adopt the anatase (101) and rutile (110) TiO2 surfaces as research targets. The calculation results show that the removal of an oxygen atom causes a large difference in the electronic structure due to the presence of two unpaired electrons. Our previous study showed that the adsorption energy of a defect-free surface is linearly correlated with the energy of the highest occupied molecular orbital for small adsorbed molecules. In the case of a defective anatase surface, we found that the energy of the lowest unoccupied molecular orbital also plays an important role in enhancing the adsorption of small molecules, especially those with an unpaired electron. Notably, our results demonstrate that hardness is a prime descriptor to explain the adsorption of various molecules by TiO2 surfaces.

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Hybrid Density Functional Calculations of Formic Acid on Anatase TiO₂(101) Surfaces

Cited by 12 publications

References 24 publications

Binding of Formic Acid on Anatase TiO₂(101)

Binding of Formic Acid on Anatase TiO₂(101)

Linear Correlations between Adsorption Energies and HOMO Levels for the Adsorption of Small Molecules on TiO₂ Surfaces

Effect of Oxygen Vacancies on Adsorption of Small Molecules on Anatase and Rutile TiO₂ Surfaces: A Frontier Orbital Approach

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Hybrid Density Functional Calculations of Formic Acid on Anatase TiO2(101) Surfaces

Cited by 12 publications

References 24 publications

Binding of Formic Acid on Anatase TiO2(101)

Binding of Formic Acid on Anatase TiO2(101)

Linear Correlations between Adsorption Energies and HOMO Levels for the Adsorption of Small Molecules on TiO2 Surfaces

Effect of Oxygen Vacancies on Adsorption of Small Molecules on Anatase and Rutile TiO2 Surfaces: A Frontier Orbital Approach

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Hybrid Density Functional Calculations of Formic Acid on Anatase TiO₂(101) Surfaces

Binding of Formic Acid on Anatase TiO₂(101)

Binding of Formic Acid on Anatase TiO₂(101)

Linear Correlations between Adsorption Energies and HOMO Levels for the Adsorption of Small Molecules on TiO₂ Surfaces

Effect of Oxygen Vacancies on Adsorption of Small Molecules on Anatase and Rutile TiO₂ Surfaces: A Frontier Orbital Approach