Phases TinO2n Research Articles

Magnéli phases Ti O2−1 as novel ozonation catalysts for effective mineralization of phenol

Magnéli phases TinO2n−1 have been demonstrated as promising environmentally friendly materials in advanced oxidation processes. In this study, Magnéli phases TinO2n−1 have been used as catalysts for the ozonation of phenol in aqueous solution for the first time. The materials exhibited excellent catalytic ozonation activities both in phenol degradation and mineralization. When Ti4O7 was added, the reaction rate was six-fold higher than that of with ozone alone, while the total organic carbon removal rate was substantially elevated from around 19.2% to 92%. By virtue of the good chemical stability of the materials, a low metal leaching of less than 0.15 mg·L− 1 could effectively avoid the secondary pollution by metal ions. Radical quenching tests revealed O2− and 1O2 to be active oxygen species for phenol degradation at pH 5. As semiconductor catalysts, TinO2n−1 materials show electronic transfer capability. Ozone adsorbed at B-acid sites of the catalyst surface can capture an electron from the conversion of Ti(III) to Ti(IV), and is thereby broken into the active oxygen species. It was interesting to observe that TinO2n−1 exhibit better catalytic activity for phenol degradation and mineralization with lower n value. The difference in electrical conductivity can be considered as a major factor for the catalytic performances. More highly conductive catalysts show a faster electron-transfer rate and better catalytic activity. Thus, significant evidences have been obtained for a single-electron-transfer mechanism of catalytic ozonation with Magnéli phases TinO2n−1.

Bandgap engineering of Magnéli phase TinO2n−1: Electron-hole self-compensation

An electron-hole self-compensation effect is revealed and confirmed in nitrogen doped Magnéli phase TinO2n−1 (n = 7, 8, and 9) by using hybrid density functional theory calculations. We found that the self-compensation effect between the free electrons in Magnéli phase TinO2n−1 (n = 7, 8, and 9) and the holes induced by p-type nitrogen doping could not only prevent the recombination of photo-generated electron-hole pairs, but also lead to an effective bandgap reduction. This novel electron-hole self-compensation effect may provide a new approach for bandgap engineering of Magnéli phase metal suboxides.

Cathodic electrochemical deposition of Magnéli phases TinO2n−1 thin films at different temperatures in acetonitrile solution

The Magnéli phase titanium oxide films prepared by cathodic electrodeposition on indium–tin-oxide coated glass substrates from saturated peroxo-titanium solution in acetonitrile. Electrodeposited brownish semi-conductor thin films were identified via X-ray diffraction, Raman spectroscopy, UV–vis spectroscopy and scanning electron microscopy (SEM). The effects of different potentials and temperatures on the crystallinity of the thin films have been discussed. Ti3O5, Ti4O7 and Ti5O9 as the most favorable forms of the TinO2n−1 were electrodeposited on ITO electrode at electrochemical deposition potentials and different temperatures. The present investigation reveals that the electrochemical deposition of crystalline TinO2n−1 films by a simple one-step electrodeposition method (without any heat treatment) in acetonitrile solution is possible and very promising as a preparation method for electrochemical applications.