6 research outputs found
New Type Photocatalyst PbBiO<sub>2</sub>Cl: Materials Design and Experimental Validation
A new kind of nanostructured photocatalyst,
PbBiO<sub>2</sub>Cl
is synthesized by a simple hydrothermal method. The proposed formation
mechanism of PbBiO<sub>2</sub>Cl is carried out by analyzing the XRD
patterns and SEM images of the products prepared under different conditions.
The PbBiO<sub>2</sub>Cl nanostructure behaves as a truncated bipyramid,
exposed with {002} and {103} facets. Moreover, theoretical calculation
and absorption spectrum indicate the PbBiO<sub>2</sub>Cl shows strong
absorption in the visible region with a band gap of 2.53 eV. The obtained
PbBiO<sub>2</sub>Cl nanostructures exhibit significantly enhanced
photocatalytic activity on degradation of methyl orange (MO) and 4-chlorophonel
(4-CP). This work may offer a paradigm on designing and synthesizing
visible photocatalyst exposed with reactive facets, which can be applied
in many fields
Doping Behavior of Zr<sup>4+</sup> Ions in Zr<sup>4+</sup>-Doped TiO<sub>2</sub> Nanoparticles
TiO<sub>2</sub> nanoparticles doped with different concentrations
of Zr<sup>4+</sup> ions were prepared by the sol–gel method
and annealed at different temperatures. X-ray diffraction (XRD), Raman
spectroscopy, X-ray photoelectron spectroscopy (XPS), and high resolution
transmission electron microscopy (HRTEM) techniques were used to investigate
the existing states and doping mechanism of dopants as well as the
phase transition of the Zr<sup>4+</sup>-doped TiO<sub>2</sub> samples.
It was revealed that the doping behavior of introduced Zr<sup>4+</sup> ions was closely related to the doping concentration. The Zr<sup>4+</sup> ions would replace the lattice Ti<sup>4+</sup> ions directly
in substitutional mode at a certain annealing temperature. Moreover,
if the concentration of doped Zr<sup>4+</sup> ions is high enough,
excess Zr<sup>4+</sup> ions would form ZrTiO<sub>4</sub> on the surface
of TiO<sub>2</sub>. In addition, the phase transition temperature
from anatase to rutile increases significantly after doping Zr<sup>4+</sup> ions, due to their larger electropositivity and radius than
those of Ti<sup>4+</sup> ions. Our results may afford a better understanding
on the doping mechanism and aid in the preparation of Zr-doped TiO<sub>2</sub> with high photoelectric performance
Modification of Pd and Mn on the Surface of TiO<sub>2</sub> with Enhanced Photocatalytic Activity for Photoreduction of CO<sub>2</sub> into CH<sub>4</sub>
The
novel Pd- and Mn-comodified TiO<sub>2</sub> photocatalyst (TiO<sub>2</sub>–Pd–Mn) was prepared via a simple sol–gel
method. The introduced Pd and Mn existed as the −O–Pd–O–
and −O–Mn–O– species on the surface of
the photocatalyst. The band structure and density of states are studied
by theoretical calculations, which is demonstrated by the experimental
results. The modification with Pd and Mn ions results in the strong
visible response and efficient separation of photogenerated carriers.
Thus, the TiO<sub>2</sub>–Pd–Mn exhibit improved photocatalytic
activity compared with pure TiO<sub>2</sub>, TiO<sub>2</sub>–Pd,
and TiO<sub>2</sub>–Mn for photoreduction of CO<sub>2</sub> and H<sub>2</sub>O into CH<sub>4</sub>. It is an effective method
on developing the highly active TiO<sub>2</sub>-based materials by
modification with double elements on the surface
Structure of Nitrogen and Zirconium Co-Doped Titania with Enhanced Visible-Light Photocatalytic Activity
Nitrogen
and zirconium co-doped TiO<sub>2</sub> (TiO<sub>2</sub>–N–<i>x</i>%Zr) photocatalysts were synthesized
via a sol–gel method. The existing states of the dopants (N
and Zr) and their corresponding band structures were investigated
via XRD, Raman, BET, XPS, TEM, FT-IR, UV–vis DRS, and PL techniques.
It was found that N existed only as a surface species (NO<sub><i>x</i></sub>) and Zr<sup>4+</sup> was doped in a substitutional
mode; the doping of Zr<sup>4+</sup> ions and modification of N extended
the absorption into the visible region and inhibited the recombination
of electrons and holes. Moreover, the excess Zr<sup>4+</sup> ions
existed as the ZrTiO<sub>4</sub> phase when the content of Zr was
sufficiently high, which could also contribute to the separation of
the charge carriers. Therefore, the TiO<sub>2</sub>–N–<i>x</i>%Zr samples show enhanced visible-light photocatalytic
activity compared with single-doped TiO<sub>2</sub>. These results
offer a paradigm for the design
and fabrication of optoelectronic functional materials such as solar
cells and photocatalysts
Adjustment and Matching of Energy Band of TiO<sub>2</sub>‑Based Photocatalysts by Metal Ions (Pd, Cu, Mn) for Photoreduction of CO<sub>2</sub> into CH<sub>4</sub>
A series of the metal ions (Pd, Cu,
and Mn) modified TiO<sub>2</sub> photocatalysts are synthesized via
simple sol–gel method.
Characterized by X-ray diffraction, Raman, UV–vis absorption
spectra, X-ray photoelectron spectroscopy, energy-dispersive X-ray
spectroscopy, time-resolved photoluminescence (PL) decay curves, and
PL, it was revealed these introduced metal ions existed as O–Me–O
species (Me: Pd, Cu, and Mn) on the surface of TiO<sub>2</sub>. The
corresponding theory calculation is used to investigate the electronic
density of states and band structure of the metal ions (Pd, Cu, and
Mn) modified TiO<sub>2</sub>. The modified TiO<sub>2</sub> photocatalysts
exhibit an improved photocatalytic performance on reduction of CO<sub>2</sub> and H<sub>2</sub>O into methane (CH<sub>4</sub>), attributed
to the contribution of surface species by enhancing the visible absorption
efficiently, separating charge carriers, and matching of the redox
potential on the photoreduction of CO<sub>2</sub> into CH<sub>4</sub>. This article could provide a wider understanding about the adjustment
and matching of the energy level for the synthesis and design of functional
materials with excellent photocatalytic performance
The Design of TiO<sub>2</sub> Nanostructures (Nanoparticle, Nanotube, and Nanosheet) and Their Photocatalytic Activity
Density
functional theory (DFT) calculation is carried out to access
the band structure and density of states (DOS) based on the models
of TiO<sub>2</sub> nanoparticle, nanotube, and nanosheet, predicting
the order of the photocatalytic activity for three different nanostructures.
Sol–gel method and hydrothermal method are used to achieve
desired morphologies: nanoparticles, nanotubes, and nanosheets (fragmentized
nanotubes). The photocatalytic activity ranks in the order of nanosheets
> nanotubes > nanoparticles, which is consistent with theoretical
prediction. It was revealed that the enlargement of band gap is caused
by the quantum confinement effect; the prolonged lifetime of photogenerated
electrons and increased specific surface areas are dependent on the
morphology of the nanostructure. All these factors contribute to the
improvement of the photocatalytic activity for nanostructures. Our
results can guide the design and selection of low-dimensional nanomaterials
with desired morphology and improved photoelectric functional properties,
which can be used in many fields, such as solar cells, photocatalysis,
and photosynthesis