Heterostructured ZnFe2O4/TiO2 nanotube arrays with remarkable visible-light photoelectrocatalytic performance and stability

Abstract

A series of heterostructured ZnFe2O4/TiO2-nanotube arrays (NTAs) with remarkable visible-light photoelectrocatalytic (PEC) activity were successfully prepared via a two-step process of anodization and impregnation, followed by annealing. The structure and morphology of the as-prepared ZnFe2O4/TiO2-NTAs samples, PEC degradation abilities and photoelectrochemical performances, as well as long-term stabilities toward degradation of methyl orange (MO) solution under visible-light irradiation were deeply investigated. Results showed that forming a heterojunction by combination of TiO2-NTAs with ZnFe2O4 successfully extended the absorption edge of TiO2-NTAs to visible-light region. Among all the ZnFe2O4/TiO2-NTAs samples, the 2-ZnFe2O4/TiO2-NTAs sample, named ZT(2), obtained the best PEC activity and the highest photocurrent density under visible-light irradiation. Moreover, the ZT(2) sample retained a good reproducibility and high stability after 20days of PEC degradation. The outstanding visible-light PEC activity and photocurrent response of the ZT(2) sample were attributed to the proper amount of ZnFe2O4 nanoparticles loaded onto the TiO2-NTAs, which not only dramatically improved the visible-light absorption of TiO2-NTAs, but also assisted the separation of photo-induced electron-hole pairs and reduced their recombination by forming a ZnFe2O4/TiO2-NTAs heterojunction. The reaction mechanism responsible for the enhanced visible-light PEC performance of the ZnFe2O4/TiO2-NTAs heterostructure was also discussed.