Adsorption Configurations and Reactions of Boric Acid on a TiO₂ Anatase (101) Surface

Abstract

This study investigates the adsorption and reactions of the monomer and dimer of B(OH)3 on a TiO2 anatase (101) surface by first-principles calculations based on the density functional theory and pseudopotential method. On the clean surface, the most stable adsorption structure for B(OH)3 is a molecular monodentate configuration with one hydrogen bonded to a neighboring surface bridging oxygen. The adsorbed B(OH)3 molecule can dissociate into the bidentate adsorption configuration, Ti−OB(OH)O−Ti(a), in which the −OB(OH)O− moiety binds to the surface through two Ti−O bonds with the two dissociated H atoms on neighboring bridged surface oxygen atoms following two successive H migrations. The overall exothermicity is 10.8 kcal/mol; significantly the adsorption energy for Ti−OB(OH)O−Ti(a) with 2 H’s on two O2c surface atoms is 140.1 kcal/mol. In the case of the dimer, there are two identical molecules like the monodentate configuration of B(OH)3 adsorbed on two 5-fold-coordinated Ti atoms of the surface. The Ti−OB(OH)OB(OH)O−Ti binding with 2 H’s on two neighboring O2c surface atoms is very strong like the monomer case, with 150.0 kcal/mol of adsorption energy. Thus, both Ti−OB(OH)O−Ti and Ti−OB(OH)OB(OH)O−Ti adsorbates can be employed as strong linkers between semiconductor quantum dots such as InN and TiO2 nanoparticles. The energeties and mechanisms of these surface reactions have also been explicitly predicted with the computed potential energy surfaces. Most of the B(OH)3 reactions on the anatase surface are exothermic.

Computational investigation of the adsorption and reactions of SiHx (x = 0–4) on TiO2 anatase (101) and rutile (110) surfaces

“…As summarized in Table 1, the adsorption energy with hydrogen attaching to a neighboring oxygen site decreases in the range of 0.2-11.9 kcal/mol. These results indicate that the hydrogen coadsorption may destabilize the SiH x adsorption on the TiO 2 anatase (101) surface, unlike the enhancement effects of H-coadsorption on the binding of OH, [57,58] HS, [19] NO 3 , [21] and HOBO 2 [16] species with titania. …”

“…To improve the heterogeneous interface between a QD and TiO 2 and achieve higher efficiencies, there have been attempts to search for a variety of linkers (e.g., H 3 BO 3 , [16,17] BCl x , [18] H 2 S, [19] H 2 O 2 , [20] and HNO 3 , [21] ). An alternative material, the well-known silicon has been studied extensively for the solar cell applications.…”

“…[16,21,38,39] The electronic orbitals were represented by the plane-wave expansion including all the plane waves with their kinetic energies smaller than the chosen cutoff energy, hk 2 /2m \ E cut , which ensures the convergence. The calculations were carried out with a 500 eV cutoff energy using the (4 Â 4 Â 4) and (3 Â 3 Â 1) MonkhorstPack k-points for the bulk and (101) surface of anatase, whereas the (2 Â 4 Â 2) and (4 Â 3 Â 1) Monkhorst-Pack kpoints with the same cutoff energy were chosen for bulk and (110) surface of rutile, respectively.…”

Optimization of boron-doping process of titania nanotubes via electrochemical method toward enhanced photoactivity

“…The luminescence intensity is strongly related with the radiative recombination of photogenerated electrons and holes, so the higher the intensity of PL, the greater the likelihood of occurrence of electron-hole recombination processes [44]. For both materials, the registered PL spectra are characterized by a broad band in the range of 480-600 nm with a maximum at 530 nm that is attributed to activity of surface states [45]. The doped titania nanotubes exhibit lower intensity of photoluminescence than pure TiO 2 .…”

Hybrid density-functional calculations of formic acid on anatase TiO2 (101) surfaces

“…A density functional tight binding study of acetic acid on TiO2 on anatase (101), rutile (110), and brookite (001) identified a bidentate configuration(4) on all politypes. First-principles calculations using DFT+U show a molecular monodentate geometry of formic acid on TiO2,(5, 6) while standard GGA calculations (7,8) and tight-binding(9) predicted a bidentate geometry.…”