Computational study on the reactions of H_2O_2 on TiO_2 anatase (101) and rutile (110) surfaces

摘要

This study investigates the adsorption and reactions of H_2O _2 on TiO_2 anatase (101) and rutile (110) surfaces by first-principles calculations based on the density functional theory in conjunction with the projected augmented wave approach, using PW91, PBE, and revPBE functionals. Adsorption mechanisms of H_2O_2 and its fragments on both surfaces are analyzed. It is found that H_2O _2, H_2O, and HO preferentially adsorb at the Ti 5c site, meanwhile HOO, O, and H preferentially adsorb at the (O _(2c))(Ti_(5c)), (Ti_(5c))_2, and O _(2c) sites, respectively. Potential energy profiles of the adsorption processes on both surfaces have been constructed using the nudged elastic band method. The two restructured surfaces, the 1/3 ML oxygen covered TiO_2 and the hydroxylated TiO_2, are produced with the H_2O _2 dehydration and deoxidation, respectively. The formation of main products, H_2O(g) and the 1/3 ML oxygen covered TiO_2 surface, is exothermic by 2.8 and 5.0 kcal/mol, requiring energy barriers of 0.8 and 1.1 kcal/mol on the rutile (110) and anatase (101) surface, respectively. The rate constants for the H_2O_2 dehydration processes have been predicted to be 6.65 × 10~(-27) T~(4.38) exp(-0.14 kcal mol~(-1)/RT) and 3.18 × 10~(-23) T~(5.60) exp(-2.92 kcal mol~(-1)/RT) respectively, in units of cm~3 molecule~(-1) s~(-1).