A DFT study of gas molecules adsorption on the anatase (0 0 1) nanotube arrays

Abstract First-principles density functional theory (DFT) calculations have been performed on the structural and electronic properties of anatase (0 0 1) TiO 2 nanotube arrays (TNTAs) without and with the adsorption of various gas molecules including O 2 , H 2 , CO, NO, H 2 O, CO 2 , NO 2 , N 2 O, NH 3 and CH 4 in details. Our study shows that the (12,0) and (18,0) TNTAs are semiconductors with indirect band gaps higher and lower than that of the bulk TiO 2 , respectively. The adsorption of the same gas molecule on (18,0) TNTAs is relatively stronger than that on (12,0) TNTAs due to the surface curvature effect. H 2 O and NH 3 are chemisorbed while other gases are physisorbed. In addition, all the studied gases are charge donors to the TNTAs. The electronic and transport properties of both TNTAs are sensitive to the adsorption of certain gases such as O 2 , NO and NO 2 . In contrast, other gases have little effect on modifying the electronic structures of TNTAs.