Adsorption of CO, H 2, N 2O, NH 3 and CH 4 on the anatase TiO 2 (0 0 1) and (1 0 1) surfaces and their competitive adsorption predicted by periodic DFT calculations

Abstract

The adsorption of CO, H 2, N 2O, NH 3 and CH 4 gases on the anatase TiO 2 (0 0 1) and (1 0 1) surfaces was investigated by two-dimensionally periodic slab model DFT calculation. The most energetically favorable positions of these gases on the anatase TiO 2 surface computed using two different optimization models were obtained. The relative adsorption energies of these gases on the anatase TiO 2 (0 0 1) and (1 0 1) surfaces are in orders: NH 3 (Δ E ads = −26.6 kcal mol −1) ≫ CO (Δ E ads = −9.7 kcal mol −1) ≫ H 2 ≈ CH 4 ≈ N 2O and NH 3 (Δ E ads = −24.3 kcal mol −1) ≫ CO (Δ E ads = −6.8 kcal mol −1) ≈ N 2O > CH 4, respectively. The N 2O energetically likes better to adsorb on the TiO 2 (1 0 1) than the (0 0 1) surface. The H 2 dislike to adsorb on the TiO 2 (1 0 1) but weakly adsorb on the TiO 2 (0 0 1) surface. The CH 4 weakly adsorbs on the TiO 2 (0 0 1) surface but very weakly adsorbs on the TiO 2 (1 0 1). Two configurations for co-adsorption of N 2O and CO as [O N N⋯CO] and [CO⋯O N N] were found.