Synthesis of Oxygen Deficient TiO2 for Improved Photocatalytic Efficiency in Solar Radiation

Abstract

The photocatalytic activities of TiO2 have been limited mainly to absorbing in the ultraviolet spectrum which accounts for only 5% of solar radiation. High energy band gap and electron recombination in TiO2 nanoparticles are responsible for its limitations as a photocatalyst. An oxygen deficient surface can be artificially created on the titanium oxide by zero valent nano iron through the donation of its excess electrons. A visible light active TiO2 nanoparticle was synthesized in the current investigation through simple chemical reduction using sodium boro-hydride. The physical and textural properties of the synthesized oxygen deficient TiO2 photocatalyst was measured using scanning/ transmission electron microscopy while FTIR, XRD and nitrogen sorption methods (BET) were employed for its further characterizations. Photochemical decoloration of orange II sodium dye solution in the presence of the synthesized TiO2 was measured using an UV spectrophotometer. The resulting oxygen deficient TiO2 has a lower energy band-gap, smaller pore sizes, and enhanced photo-catalytic properties. The decoloration (88%) of orange (II) sodium salt solution (pH 2) under simulated solar light was possible at 20 min. This study highlights the effect of surface oxygen defects, crystal size and energy band-gap on the photo-catalytical property of TiO2 nanoparticles as impacted by nano zero valent iron. It opens a new window in the exploitation of instability in the dopant ions for creation of a visible light active TiO2 photocatalyst.

Microwave assisted synthesis of bismuth titanate nanosheets and its photocatalytic effects

“…This is because the oxygen deficient sites that form at the crystallite faces of the nanosheets due to imperfections in the structure, produce a band of new electronic states, in effect, lowering the band gap of the material. This effect has been seen in action previously in titania and certain bismuth titanates (Bark, 2013;Han & Bark, 2014;Choi et al, 2012;Badmus et al, 2021;Yao et al, 2020). This in turn brings the band gap of the material closer to the values of pristine bismuth titanate (Murugesan et al, 2010).…”

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

“…220 The OVs induced in TiO 2 NPs by sodium borohydride treatment caused a lower energy band gap, smaller pore sizes, and improved photocatalytic activity in orange II sodium salt degradation. 221 In another work, OVs were induced in TiO 2 films by CaH 2 as a reducing agent, resulting in a 340% photodegradation enhancement toward benzene under UV light. A band-bending model as a p−n junction between the bulk and the surface layer with OVs was confirmed by the density functional theory (DFT) calculations.…”

“…Further, its high electronic energy band gap and e/h recombination are other limitations of it as a photocatalyst. One strategy to overcome these problems is producing an oxygen-deficient surface, which critically changes the band gap position and the color of catalysts, resulting in an extended absorption wavelength range. , For example, inducing OVs in black TiO 2 (B-TiO 2 ) via a facile approach introduced by Chen and co-workers significantly improved its visible–IR light absorption efficiency. The decrease in e/h recombination is due to the localized states in the bandgap induced by OVs, which act as trap centers (Figure a).…”

“…Thus, the engineering of OVs plays critical roles in various fields such as supercapacitors, 163 electrocatalysis, 164 and photo(electro)catalysis, 165 including photoelectrochemical (PEC) water splitting 166 and photodegradation. 167 5.1.1. Strategies for Creating Vacancies.…”

Role of Post-Hydrothermal Treatment on the Microstructures and Photocatalytic Activity of TiO2-Based Nanotubes

“…Substantial work has been performed over the last several decades to develop novel materials with an aim to improve photocatalytic activity or to find additional ways to improve the effectiveness of existing photocatalysts [10,11]. It has now been established that by controlling photocatalyst features, such as morphology, shape, size, surface area and its functionalization, and so forth, the photocatalytic activity can be significantly improved [12][13][14][15][16].…”