Coaxial Fe2O3/TiO2 nanotubes for enhanced photo-Fenton degradation of electron-deficient organic contaminant

Abstract

Coaxial Fe2O3/TiO2 nanotubes (Fe2O3/TiO2 NTs) were prepared by two anodic oxidation processes. The synthesized Fe2O3/TiO2 NTs catalysts showed high photocatalytic activity in heterogeneous photo-Fenton system. With the help of Fe2O3/TiO2 NTs, 4-nitrophenol (10 mg·L−1, 50 ml), a typical electron-deficient organic contaminant, can be completely removed by adding only 0.4 mmol·L−1 of H2O2 under irradiation. Investigation results clarify that the calculated position of Fe2O3/TiO2 NTs valence band is at 2.944 eV, its potential is higher than the potential of OH−/·OH (2.800 eV), thereby ensuring the generation of ·OH. Meanwhile, the transformation of photogenerated electrons from the conduction band of TiO2 to Fe2O3 accelerates the reduction of Fe3+ to Fe2+. The unstable Fe2+ can be oxidized by H2O2 to produce high yields of ·OH. Therefore, both the coaxial heterojunction and fast Fe2+/Fe3+ conversion provide abundant ·OH to effective attack the electron-deficient benzene ring passivated by the nitro group. Thus, surface-catalyzed degradation of 4-nitrophenol can be carried out step by step. This work contributes a detailed understanding of charge transfer in semiconductor composites and degradation of organic contaminants.