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 O-2c 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(bH)O-Ti binding with 2 H's on two neighboring O-2c 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.