Influência da dopagem do ferro nas propriedades estruturais e eletrônicas do TiO2 anatase:rutilo

Abstract

In the present work is presented a study on the doping of the iron atom (F e) in the crystalline structure of the anatase: rutile T iO2, through the theory of the functional of the density (DFT). The electronic structures of the T iO2 cells were analyzed with T iO2-P25 R network and doped with Fe atom. A tension-type stress was observed with doping, in this sense a study was carried out with the unit cell with parameters of a compressive stress type. Using a PW91 functional with Hubbard correction (PW91 + U) a band gap value of 3,17 eV and 2,95 eV was obtained for the anatase and rutile TiO2-P25, which the experimental value is determined as 3,20 eV and 3,00 eV, respectively. For T iO2 with tensile and compressive stress process an increase and decrease of band-gap value were observed, respectively. In order to study the doping process with Fe, a supercell with 48 atoms was constructed for anatase: rutile. With calculations of band structure and projected density of state (PDOS), it was observed that doping introduced a defect between the valence band and conduction. For the study of water photolysis on the surfaces of T iO2 and T iO2 − F e, the NEB (Nudged Elastic band) method was used. The water splitting surface was simulated to evaluate its reactivity in relation to water adsorption (H2O). The initial steps of the reaction mechanism and the transition states were determined taking into account the species involved H2O, OH∗ e and H+ on the surface of T iO2. For the pure T iO2 an energy value of activation of 0,29 eV and for the Fe atom doped T iO2, an activation energy value of 0.08 eV was obtained.