Electrospun-based TiO2 nanofibers for organic pollutant photodegradation: a comprehensive review

Titanium dioxide (TiO2) is commonly used as a photocatalyst in the removal of organic pollutants. However, weaknesses of TiO2 such as fast charge recombination and low visible light usage limit its industrial application. Furthermore, photocatalysts that are lost during the treatment of pollutants create the problem of secondary pollutants. Electrospun-based TiO2 fiber is a promising alternative to immobilize TiO2 and to improve its performance in photodegradation. Some strategies have been employed in fabricating the photocatalytic fibers by producing hollow fibers, porous fibers, composite TiO2 with magnetic materials, graphene oxide, as well as doping TiO2 with metal. The modification of TiO2 can improve the absorption of TiO2 to the visible light area, act as an electron acceptor, provide large surface area, and promote the phase transformation of TiO2. The improvement of TiO2 properties can enhance carrier transfer rate which reduces the recombination and promotes the generation of radicals that potentially degrade organic pollutants. The recyclability of fibers, calcination effect, photocatalytic reactors used, operation parameters involved in photodegradation as well as the commercialization potential of TiO2 fibers are also discussed in this review.

In Situ Fabrication of Branched TiO2 /C Nanofibers as Binder-Free and Free-Standing Anodes for High-Performance Sodium-Ion Batteries

Herein, 1D free-standing and binder-free hierarchically branched TiO₂ /C nanofibers (denoted as BT/C NFs) based on an in situ fabrication method as an anode for sodium-ion batteries are reported. The in situ fabrication endows this material with large surface area and strong structural stability, providing this material with abundant active sites and smooth channels for fast ion transportation. As a result, BT/C NFs with the character of free-standing membranes are directly used as binder-free anode for sodium-ion batteries, delivering a capacity of 284 mA h g^-1 at a current density of 200 mA g^-1 after 1000 cycles. Even at a high current density of 2000 mA g^-1 , the reversible capacity can still achieve as high as 204 mA h g^-1 . By means of kinetic analysis, it is demonstrated that the remarkable surface pseudocapacitive behavior is also a major factor to achieve excellent performance. The rationally designed structure coupled with the inherent pseudocapacitive behavior gives this material potential for sodium-ion batteries.

Characterization and Computation of Yb/TiO₂ and Its Photocatalytic Degradation with Benzohydroxamic Acid

Yb-doped TiO₂ (Yb/TiO₂) compositions were synthesized by sol-gel method, and the prepared materials were characterized by X-ray Diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-visible diffuse-reflectance spectrum (UV-Vis DRS), transmission electron microscope (TEM) and high resolution transmission electron microscope (HRTEM), energy dispersive spectrometer (EDS), and N₂ adsorption. A beneficiation reagent of benzohydroxamic acid (BHA) was used to test the photocatalytic activity of Yb/TiO₂. The characterizations indicate that the doping of Yb could inhibit the crystal growth of TiO₂, enhance the specific surface area, increase the binding energy of Ti2p, and also slightly expand the adsorption ranges to visible light. Furthermore, the computation of band structure also indicates that Yb-doped TiO₂ could make the forbidden band narrower than pure anatase TiO₂, which presents a red shift in the absorption spectrum. As a result of the photodegradation experiment on BHA, Yb/TiO₂ (0.50% in mass) sintered at 450 °C displayed the highest catalytic activity for BHA when compared with pure TiO₂ or other doped Yb/TiO₂ compositions, and more than 89.2% of the total organic carbon was removed after 120 min. Almost all anions, including Cl⁻, HCO₃⁻, NO₃⁻, and SO₄²⁻, inhibited the degradation of BHA by Yb/TiO₂, and their inhibition effects followed the order of HCO₃⁻ > NO₃⁻ > SO₄²⁻ > Cl⁻. Cations of Na⁺, K⁺, Ca²⁺, and Mg²⁺ displayed a slight suppressing effect due to the impact of Cl⁻ coexisting in the solution. In addition, Yb/TiO₂ maintained a high photocatalytic ability with respect to BHA after four runs. It is hypothesized that ·OH is one of the main species involved in the photodegradation of BHA, and the mutual transformation of Yb³⁺ and Yb²⁺ could promote the separation of electron-hole pairs.