Structure of a Model Dye/Titania Interface: Geometry of Benzoate on Rutile-TiO₂ (110)(1 × 1)

Abstract

Scanned-energy mode photoelectron diffraction (PhD) and ab initio density functional theory (DFT) calculations have been employed to investigate the adsorption geometry of benzoate ([C 6 H 5 COO] -) on rutile-TiO 2 (110)(1×1). PhD data indicate that the benzoate moiety binds to the surface through both of its oxygen atoms to two adjacent five-fold surface titanium atoms in an essentially upright geometry. Moreover, its phenyl (C 6 H 5 -) and carboxylate ([-COO] -) groups are determined to be coplanar, being aligned along the [001] azimuth. This experimental result is consistent with the benzoate geometry emerging from DFT calculations conducted for laterally rather well separated adsorbates. At shorter inter-adsorbate distances, the theoretical modeling predicts a more tilted and twisted adsorption geometry, where the phenyl and carboxylate groups are no longer coplanar, i.e. inter-adsorbate interactions influence the configuration of adsorbed benzoate.

Van der Waals Interaction Really Matters: Energetics of Benzoic Acid on TiO2 Rutile Surfaces

“…A nearly fully covered rutile (110) surface (θ ≈ 0.5 ML) can be prepared by slight heating to ≈370 K and further exposure to adsorbates. , The resulting structure gives rise to a 2 × 2 pattern in a recent low-energy electron diffraction (LEED) experiment . It is reported to diminish rapidly during electron bombardment and end up in a long-term stable 2 × 1 pattern, which is supposed to be identical to the previously reported ones. , Structures that yield a 2 × 2 pattern are clearly seen in scanning tunneling microscope (STM) experiments. ,, Those studies reveal pairwise (sometimes 3-fold) agglomerated benzoate rows, which run in [001] direction.…”

“…A nearly fully covered rutile (110) surface (θ ≈ 0.5 ML) can be prepared by slight heating to ≈370 K and further exposure to adsorbates. 12,16 The resulting structure gives rise to a 2 × 2 pattern in a recent low-energy electron diffraction (LEED) experiment. 15 It is reported to diminish rapidly during electron bombardment and end up in a long-term stable 2 × 1 pattern, which is supposed to be identical to the previously reported ones.…”

“…Typically, the adsorbate dissociates into a carboxylate species, binding toward two adjacent undercoordinated surface Ti atoms in a bidentate manner, and an H + forming a hydroxyl group at an undercoordinated, protruding surface oxygen atom, a “bridging oxygen”. That holds for formic acid (HCOOH), , acetic acid (CH 3 COOH), benzoic acid (C 6 H 5 COOH), , various amino acids, , and many others (e.g., see ref and references therein). As an example of this structure, acetic acid on TiO 2 (110) rutile is shown in Figure .…”

“…All attempts to verify, correct, or reject the structurally obvious “T”-type model suggested in ref are not satisfying. Especially, none of the existing density functional theory (DFT) studies concerning benzoic acid adsorption on TiO 2 ,,, can contribute sufficiently to this subject, because they all apply exchange-correlation functionals which are not able to account for the long-range vdW interactions.…”

Quantitative structure determination of adsorbed formate and surface hydroxyls on Fe3O4(001)

“…The dissociative adsorption of formic acid, according to LEED, lifted the SCV reconstruction giving a LEED pattern indicative of a bulk-like termination. A recently published surface X-ray diffraction (SXRD) study by Arndt et al 23 has shown that the formate is bound to two surface Fe oct cations through its two carboxylate oxygens, O HCOO , which is consistent with how formate [24][25][26][27][28][29] and more broadly the carboxylate functional group, [30][31][32][33][34][35][36][37] bonds with most surfaces. Moreover, they were able to determine that the formate molecule preferentially binds to one of the two bidentate adsorption sites, the 'tet' adsorption site, with the formate carbon atoms coincident with the 1st subsurface Fe tet in the [110] crystallographic direction, shown in Fig.…”