3 research outputs found
Enhancement of Activity of Activated Carbon Fiber for Electro-Fenton Process by Loading it with SiO<sub>2</sub> having Tunable Hydrophobic/Hydrophilic Moieties
Electro-Fenton (EF) process is promising
for achieving satisfactory
oxidation of organic contaminants. However, the sluggish kinetics
of in situ production of H2O2 and slow rate
of Fe2+ regeneration remain its limitations. In this work,
SiO2 with tunable methyl and hydroxyl moieties on the surface
(MxOHSiO2; x denotes the mass ratio of diethoxydimethylsilane to tetraethyl orthosilicate)
was successfully loaded onto activated carbon fiber (ACF) to construct
an ACF-supported cathode (MxOHSiO2/ACF) for the degradation of bisphenol A (BPA). The MxOHSiO2/ACF exhibited substantially
higher activity than bare ACF in the EF process. The removal of BPA
proceeded most rapidly with M0.75OHSiO2/ACF
with an initial pH of 3.0, an electrolyzing voltage of 20 V, and an
Fe2+ dosage of 0.5 mM. The mineralization efficiency was
79.3% after 360 min, with the complete disappearance of BPA recorded
at 60 min during the EF process. In addition, the M0.75OHSiO2/ACF catalytic electrode remained stable for five
successive cycling tests. Because of the synergistic effect of the
hydrophobic methyl moiety and electron-rich hydroxyl moiety on SiO2, the H2O2 electro-generation and Fe2+ regeneration at M0.75OHSiO2/ACF were
simultaneously improved. This work provides an effective strategy
for the application of EF technology in future
Photocatalytic Reduction of CO<sub>2</sub> in Aqueous Solution on Surface-Fluorinated Anatase TiO<sub>2</sub> Nanosheets with Exposed {001} Facets
Photocatalytic
reduction of carbon dioxide can activate chemically
inert carbon dioxide by the use of renewable energy. In the present
work, the main products of photocatalytic reduction of CO<sub>2</sub> in aqueous TiO<sub>2</sub> suspensions were found to be methane,
methanol, formaldehyde, carbon monoxide, and H<sub>2</sub>. Anatase
TiO<sub>2</sub> catalysts with various morphologies, such as nanoparticle,
nanotube, and nanosheet, were synthesized through a hydrothermal method.
The TiO<sub>2</sub> nanosheets were more active than the nanotubes
or nanoparticles in the reduction of CO<sub>2</sub> in aqueous solution.
This is because the photogenerated carriers prefer to flow to the
specific facets. The TiO<sub>2</sub> sheet with high-energy exposed
{001} facets facilitates the oxidative dissolution of H<sub>2</sub>O with photogenerated holes, leaving more photogenerated electrons
available for the reduction of CO<sub>2</sub> on {101} facets. Moreover,
surface fluorination promotes the formation of Ti<sup>3+</sup> species,
which is helpful in the reduction of CO<sub>2</sub> to CO<sub>2</sub><sup>–</sup> and in extending the lifetime of photogenerated
electron–hole pairs. The optimum ratio of exposed {001} to
{101} facets for surface-fluorinated TiO<sub>2</sub> nanosheets was
found to be ∼72:28, which corresponds to an initial F/Ti ratio
of 1. From our analysis of the effect of adding of known intermediates
on the photocatalytic reduction of CO<sub>2</sub>, we propose that
the photocatalytic reduction of CO<sub>2</sub> with H<sub>2</sub>O
on surface-fluorinated TiO<sub>2</sub> nanosheets proceeds via a mechanism
involving generation of hydrogen radicals and carbon radicals
Photocatalytic Degradation of Toluene by a TiO<sub>2</sub> p‑n Homojunction Nanostructure
The development of catalysts for the treatment of volatile
organic
compounds (VOCs) by photocatalytic oxidation is very important for
treating industrial flue gases. Although defect engineering has been
developed into an effective method to improve the photocatalytic activity
of TiO2 semiconductor materials, few holistic studies have
been performed on the structure and properties of TiO2.
Herein, a one-step hydrothermal method was used to synthesize three
types of nanoscale TiO2 (p-TiO2 with only Ti
vacancies, n-TiO2 with only O vacancies, and pn-TiO2 with dual Ti/O vacancies) for the photocatalytic removal
of gaseous toluene to determine the relationship between the redox
capacity of the electron–hole pairs and the type of conductive
semiconductors. It was found that pn-TiO2 exhibited a higher
gaseous toluene conversion (99.6%) within 2 h, with 2.8-fold faster
photocatalytic kinetics than p-TiO2 and 1.26-fold faster
than n-TiO2. Based on the results of an experimental study
and theoretical calculations, it was verified that the dual vacancies
in pn-TiO2 enabled the valence and conduction bands to
be fully exploited to generate ·OH and ·O2–, respectively, for the synergistic
degradation of gaseous toluene. Because of the characteristics of
the p-n homojunction, charge transfer and separation were efficiently
increased in pn-TiO2, resulting in the effective treatment
of gaseous toluene. In addition, after five cycles of photocatalytic
degradation of toluene, the degradation rate by pn-TiO2 remained over 80%, indicating potential applications for pn-TiO2. In this study, a rational pathway is demonstrated for photocatalysts
containing dual vacancies to degrade toluene based on the synergistic
effect of free radicals, providing an inspiration for designing materials
with vacancies or homojunctions and providing means of eliminating
VOCs in practical applications