Ultra-Violet-Assisted Scalable Method to Fabricate Oxygen-Vacancy-Rich Titanium-Dioxide Semiconductor Film for Water Decontamination under Natural Sunlight Irradiation

Abstract

This work reports the fabrication of titanium dioxide (TiO2) nanoparticle (NPs) films using a scalable drop-casting method followed by ultra-violet (UV) irradiation for creating defective oxygen vacancies on the surface of a fabricated TiO2 semiconductor film using an UV lamp with a wavelength oof 255 nm for 3 h. The success of the use of the proposed scalable strategy to fabricate oxygen-vacancy-rich TiO2 films was assessed through UV–Vis spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The Ti 2p XPS spectra acquired from the UV-treated sample showed the presence of additional Ti3+ ions compared with the untreated sample, which contained only Ti4+ ions. The band gap of the untreated TiO2 film was reduced from 3.2 to 2.95 eV after UV exposure due to the created oxygen vacancies, as evident from the presence of Ti3+ ions. Radiation exposure has no significant influence on sample morphology and peak pattern, as revealed by the SEM and XRD analyses, respectively. Furthermore, the photocatalytic activity of the fabricated TiO2 films for methylene-blue-dye removal was found to be 99% for the UV-treated TiO2 films and compared with untreated TiO2 film, which demonstrated only 77% at the same operating conditions under natural-sunlight irradiation. The proposed UV-radiation method of oxygen vacancy has the potential to promote the wider application of photo-catalytic TiO2 semiconductor films under visible-light irradiation for solving many environmental and energy-crisis challenges for many industrial and technological applications.

A Comprehensive Review on the Boosted Effects of Anion Vacancy in the Heterogeneous Photocatalytic Degradation, Part II: Focus on Oxygen Vacancy

“…The induced OVs promoted the photodegradation efficiency of the Z-scheme mechanism (between TiO 2 nanorods/g-C 3 N 4 nanosheets) toward phenol under visible light illumination. 225 Oxygen vacancy-mediated sandwich-structured TiO 2−x /ultrathin g-C 3 N 4 /TiO 2-x showed a direct Z-scheme photocatalytic mechanism with an excellent TC photodegradation efficiency (87.7% for 90 min) employing • O 2 − , h + and • OH reactive species (by Ni et al). This excellent activity is related to the special 3D structure, the Z-scheme heterojunction expediting charge transfer, and enhanced active species formation.…”

“…Similarly, the TiO 2– x /g-C 3 N 4 nanorod array photoelectrode was fabricated by Qi et al via urea drop calcination and NaBH 4 reduction. The induced OVs promoted the photodegradation efficiency of the Z-scheme mechanism (between TiO 2 nanorods/g-C 3 N 4 nanosheets) toward phenol under visible light illumination …”

Unveiling the Role of Sulfur Vacancies in Enhanced Photocatalytic Activity of Hybrids Photocatalysts

“…Among these, microscope techniques, such as atomic-resolution spherical aberration-corrected transmission electron microscopy, scanning transmission electron microscopy (STEM), and scanning tunneling microscopy, are employed to verify the presence of vacancies [ 33 ]. Spectroscopy techniques, on the other hand, encompass electron spin resonance (ESR) spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure (XAFS), in situ electron energy loss spectroscopy, transient absorption, Raman spectroscopy, thermogravimetric, time-resolved absorption, and fluorescence spectroscopy [ 34 , 35 ]. For instance, STEM, with the aid of probe-forming aberration correctors, can distinguish between surface and bulk vacancies, offering insights into local atomic structure and chemical composition at the atomic level.…”

Special Issue “Synthesis of TiO2 Nanoparticles and Their Catalytic Activity”

“…Under visible light irradiation, the as-synthesized heterojunctions significantly enhanced the photodegradation activity of rhodamine B, thereby providing the possibility of the removal of photocatalytic pollutants using solar light [ 2 ]. In another study, Alyami reported an ultra-violet-assisted scalable method to construct TiO 2 photocatalysts with abundant oxygen vacancies for photocatalytic dye removal [ 3 ]. The defective TiO 2 with Ti 3+ exhibited stronger visible light absorption and much higher removal efficiency of methylene blue under visible light illumination than pristine TiO 2 [ 3 ].…”

“…In another study, Alyami reported an ultra-violet-assisted scalable method to construct TiO 2 photocatalysts with abundant oxygen vacancies for photocatalytic dye removal [ 3 ]. The defective TiO 2 with Ti 3+ exhibited stronger visible light absorption and much higher removal efficiency of methylene blue under visible light illumination than pristine TiO 2 [ 3 ]. Similarly, Wang et al developed B-doped g-C 3 N 4 /black TiO 2 Z-Scheme heterojunctions with enhanced charge separation efficiency and increased tetracycline sorption ability [ 4 ].…”