Adsorption properties of trifluoroacetic acid on anatase (101) and (001) surfaces: a density functional theory study

Abstract

The interaction of trifluoroacetic acid with anatase TiO2(101) and TiO2(001) surfaces has been studied by means of periodic density functional theory based calculations. On the former, the interaction is weak with the adsorbed molecules in a configuration almost indistinguishable from the gas phase structure. On the latter, the interaction is very strong; the molecule adsorbs as trifluoroacetate and releases a proton that binds an oxygen surface atom with a significant distortion of the substrate. The difference in adsorption the mode and strength can be understood from the different structural features of both surfaces and provides arguments to the role of trifluoroacetic as a morphological control agent in the solvothermal synthesis of TiO2 nanoparticles with predominant (001) facets. This, in turn, has a very significant impact on industrial production strategies of value-added TiO2 for photocatalytic applications. Analysis of calculated core level binding energies for F(1s) confirms the experimental assignment to F at the surface as F(-) at Ti surface sites and to F in -CF3 groups of the adsorbed molecule.

Effect of Solvent and Substrate on the Surface Binding Mode of Carboxylate-Functionalized Aromatic Molecules

“…Dye molecules and MOF linkers need to be able to anchor to the TiO 2 surface to facilitate charge injection; this is typically achieved by a covalent bond of a carboxylic acid group to a surface metal atom. The preferred binding mode for carboxylic-acid-containing adsorbates on these substrates has been much discussed in the literature, − and there is debate over whether the acid group will be protonated or deprotonated upon adsorption. The incorporation of solvation effects (or lack thereof) and differences between cluster and periodic approaches taken in prior modeling studies make comparing published results difficult.…”

Solvothermal synthesis of soluble, surface modified anatase and transition metal doped anatase hybrid nanocrystals

“…This corresponds to an empirical formula of TiO(OH)(CF 3 COO), analogous to many titanium( iv ) oxo carboxylate clusters; clusters which invariably involve bridging bidentate carboxylate groups. 69–72…”

“…This corresponds to an empirical formula of TiO(OH)(CF 3 COO), analogous to many titanium(IV) oxo carboxylate clusters; clusters which invariably involve bridging bidentate carboxylate groups. [69][70][71][72] Taking the fully crystalline triuoroacetate modied anatase samples prepared by solvothermal treatment at 150 °C for 24 hours and at 200 °C for 6 or more hours, it is possible to estimate the degree of surface coverage achieved by this system. Based on the 150 °C sample the average crystallite diameters calculated from the XRD pattern of 4.5 nm gives the volume and surface area of the "average" modied anatase nanoparticle as 48 nm 3 and 64 nm 2 , respectively.…”

The crystal facet-dependent electrochemical performance of TiO2 nanocrystals for heavy metal detection: Theoretical prediction and experimental proof

“…When 1.5mL HF was added into the precursor, the as-prepared samples (named HF1.5) became stocky, and the percentage of exposed (001) facets was increased to 35% (Figure 5h). This is because fluorine ions are efficient capping agents, which are favorable for the growth of (001)-faceted surfaces [31,38,39]. As shown in Figure 5i, further increasing the volume of HF to 3 mL resulted in rectangle TiO2 nanosheets with up to 80% of (001) facets (noted as HF3).…”

“…It is usually exposed to low index facets such as (001) and (101) [23]. The facet-dependent performance has been deeply investigated in term of surface structure, computational and experimental science [28][29][30][31]. Moreover, the synthesis technology of TiO2 nanocrystals with specific facets is relatively rich and mature.…”