Computational study on the reactions of H₂O₂ on TiO₂ anatase (101) and rutile (110) surfaces

This study investigates the adsorption and reactions of H₂O ₂ on TiO₂ 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 H₂O₂ and its fragments on both surfaces are analyzed. It is found that H₂O ₂, H₂O, 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 TiO₂ and the hydroxylated TiO₂, are produced with the H₂O ₂ dehydration and deoxidation, respectively. The formation of main products, H₂O(g) and the 1/3 ML oxygen covered TiO₂ 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 H₂O₂ 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 cm³ molecule^-1 s^-1.