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

This study investigates the adsorption and reactions of the monomer and dimer of B(OH) 3 on a TiO 2 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(OH)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 TiO 2 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.