Defective TiO2 Nanotube Arrays for Efficient Photoelectrochemical Degradation of Organic Pollutants

Oxygen vacancies (OVs) are one of the most critical factorsthatenhance the electrical and catalytic characteristics of metal oxide-basedphotoelectrodes. In this work, a simple procedure was applied to preparereduced TiO2 nanotube arrays (NTAs) (TiO2-x ) via a one-step reduction method using NaBH4. A series of characterization techniques were used to studythe structural, optical, and electronic properties of TiO2-x NTAs. X-ray photoelectron spectroscopy confirmedthe presence of defects in TiO2-x NTAs. Photoacoustic measurements were used to estimate the electron-trapdensity in the NTAs. Photoelectrochemical studies show that the photocurrentdensity of TiO2-x NTAs was nearly3 times higher than that of pristine TiO2. It was foundthat increasing OVs in TiO2 affects the surface recombinationcenters, enhances electrical conductivity, and improves charge transport.For the first time, a TiO2-x photoanodewas used in the photoelectrochemical (PEC) degradation of a textiledye (basic blue 41, B41) and ibuprofen (IBF) pharmaceutical usingin situ generated reactive chlorine species (RCS). Liquid chromatographycoupled with mass spectrometry was used to study the mechanisms forthe degradation of B41 and IBF. Phytotoxicity tests of B41 and IBFsolutions were performed using Lepidium sativum L. to evaluate the potential acute toxicity before and after thePEC treatment. The present work provides efficient PEC degradationof the B41 dye and IBF in the presence of RCS without generating harmfulproducts.

Automated summary

Oxygen vacancies (OVs) are critical for enhancing the electrical and catalytic properties of metal oxide-based photoelectrodes. In this study, reduced TiO2 nanotube arrays (NTAs) (TiO2-x) were prepared using a one-step reduction method. Characterization techniques confirmed the presence of defects in TiO2-x NTAs, and photoelectrochemical studies showed a significantly improved photocurrent density compared to pristine TiO2. The increased OVs in TiO2-x affected surface recombination centers, enhanced electrical conductivity, and improved charge transport. The TiO2-x photoanode was successfully used for the photoelectrochemical degradation of a textile dye and a pharmaceutical compound.