Comprehensive analysis (aerobic/anaerobic, molecular recognitions, band-position and degradation-mechanism) of undoped and Co-doped anatase-brookite - An experimental/theoretical evaluation of the less-studied TiO2 mixed phase

Abstract

The molecular recognition (MRec) effect is required in the initial phase of organic reactions. The second stage involves molecular-orientations and molecular-orbitals energy-levels (MOrbE). The components of a reaction must be compatible in terms MRec and MOrbE. Therefore, the comprehension of photocatalytic systems applied in wastewater treatment will be improved if the MRec effect is also considered as an important factor. The purpose of this study is to provide a comprehensive understanding of the less studied anatase-brookite mixed-phase (doped and undoped). Anatase/brookite photocatalytic systems were evaluated utilizing experimental/theoretical approaches in H2O (aerobic/anaerobic) environments with Vis-light and the organic pollutant (OrPo) methyl orange (MO). The compatibility of MRec and MOrbE of anatase-brookite mixed-phase (with the different reactive system components) confirmed this is the optimal combination for photocatalytic application. Using the sol-gel method, AM-TiO2NP (amorphous), TiO2NP (crystalline), and TiO2NP-Co0.1 at% (crystalline Co-doped) anatase-brookite mixed-phase photocatalysts were obtained. The morphology and surface were characterized using XRD, BET, SEM, HR-TEM, FT-IR and XPS. Employing UV–vis DRS and PL, photo-response and electron-hole recombination were studied. LVS and Mott-Schottky plot were employed to determine photo-electrochemical activity. The results of TiO2NP photocatalytic degradation in both aerobic and anaerobic environments are remarkable. The results of molecular dynamics (MD) simulation and Fukui Function (FF) based on density functional theory (DFT) validate the remarkable photocatalytic MO degradation.