20 research outputs found
Bi<sub>2</sub>WO<sub>6</sub> Quantum Dots Decorated Reduced Graphene Oxide: Improved Charge Separation and Enhanced Photoconversion Efficiency
In this study, Bi<sub>2</sub>WO<sub>6</sub> quantum dots (QDs)
decorating reduced graphene oxide (RGO) sheets were produced by a
facile one-step hydrothermal synthesis process, which converts the
reactant precursors to Bi<sub>2</sub>WO<sub>6</sub> QDs and RGO simultaneously.
The Bi<sub>2</sub>WO<sub>6</sub> QDs with a size of 3–5 nm
anchored uniformly on the RGO sheets to form RGO-Bi<sub>2</sub>WO<sub>6</sub> QDs composites. The RGO sheets not only acted as a supporter
and stabilizer for the Bi<sub>2</sub>WO<sub>6</sub> QDs to prevent
them from being aggregation but also largely improved the charge separation
in the composite material. For this preponderance, the electron lifetime
in the RGO-Bi<sub>2</sub>WO<sub>6</sub> QDs composites was increased
8-fold compared with that of the pure Bi<sub>2</sub>WO<sub>6</sub> QDs. The much enhanced lifetime improved its performance in environmental
purification and photovoltaic conversion under the irradiation of
simulated sun light. This work not only provides a principle method
to produce graphene-composited multiple metal oxide QDs by one-step
process but also a route to obtain efficient functional material for
environmental purification and optoelectronic applications
Efficient Contaminant Removal by Bi<sub>2</sub>WO<sub>6</sub> Films with Nanoleaflike Structures through a Photoelectrocatalytic Process
Bi<sub>2</sub>WO<sub>6</sub> films with nanoleaflike
structures,
which are directly grown on a fluorinated tin oxide substrate, were
first realized by a solvothermal method. Because of the peculiar leaflike
structure, Bi<sub>2</sub>WO<sub>6</sub> films exhibited excellent
photocatalytic activity in the degradation of phenol, which is widely
used but slowly degradable in the natural environment. The degradation
of phenol could be further improved by a photoelectrocatalytic process,
along with a sharp decrease of total organic carbon. According to
the experimental results, a possible mechanism of the improved photoelectrocatalytic
activity on the phenol removal was proposed. The stability of the
directly grown leaflike Bi<sub>2</sub>WO<sub>6</sub> film is excellent.
As an immobilized film, it is easy to recycle for the next photoelectrocatalytic
process. This advantage, combining the excellent stability and photoelectrocatalytic
activity, makes it applicable in practical environmental purification
Internal Electric Field Assisted Photocatalytic Generation of Hydrogen Peroxide over BiOCl with HCOOH
Hydrogen peroxide
(H<sub>2</sub>O<sub>2</sub>) is a superb, clean,
and versatile reagent. However, large-scale production of H<sub>2</sub>O<sub>2</sub> is manufactured through nongreen methods that motivate
people to develop more efficient and green technologies as alternatives.
As a novel and green technology used for H<sub>2</sub>O<sub>2</sub> generation, the efficiency of photocatalysis is still far from satisfactory.
Here, we demonstrate a novel and efficient path of the generation
of H<sub>2</sub>O<sub>2</sub> in BiOCl photocatalysis but not the
direct electron reduction of O<sub>2</sub> or hole oxidation of OH<sup>–</sup> to H<sub>2</sub>O<sub>2</sub>. Super high production
(685 μmol/h) of H<sub>2</sub>O<sub>2</sub> by the addition of
HCOOH as the hole shuttle was realized over BiOCl nanoplates. In this
photocatalytic system, the BiOCl supplied abundant photoinduced holes
to initiate HCOO<sup>•</sup> radical. The HCOO<sup>•</sup> further reacts with OH<sup>–</sup> to •OH which is
proven to be the source of the H<sub>2</sub>O<sub>2</sub>. Apart from
HCOOH, O<sub>2</sub> also played important roles. The O<sub>2</sub> not only promoted the reaction through the cycle between Bi<sup>3+</sup> and Bi, which decreased the combination of carriers, but
also avoided the carbonation of surfaces, thus achieving the high
production of H<sub>2</sub>O<sub>2</sub> (1020 μmol/h). In this
work, we shed light on a deep understanding of the photocatalytic
evolution of H<sub>2</sub>O<sub>2</sub> in a novel perspective and
achieve high production
Descriptive statistics and correlations of the severity of PTSD, anxiety and depression symptoms.
*<p>P<0.05,</p>**<p>P<0.01; the parentheses include the number of items in each scale or subscale.</p
Bivariate logistic regression analyses of the effects of demographics, trauma exposure and social support on the odds of probable PTSD, anxiety and depression.
<p>OR = odds ratio; CIs = confidence intervals.</p>*<p>P<0.05,</p>**<p>P<0.01.</p>#<p>Numbers within categories may not add up to 505 for some variables due to missing data.</p
Insights into the Surface-Defect Dependence of Photoreactivity over CeO<sub>2</sub> Nanocrystals with Well-Defined Crystal Facets
Crystal
facet engineering (CFE) has been widely employed to regulate the photoreactivity
of crystalline materials, mostly concerning the surface atomic and
electronic structures. However, surface defects ubiquitous in real
catalysts have long been less recognized. An integrated examination
of various influence factors is necessary for the elucidation of an
accurate structure–function relationship. Herein, we carefully
studied the heterogeneous photoreactivity of CeO<sub>2</sub> nanocrystals
(NCs) with well-defined crystal facets in multiple processes, including
photocatalytic oxidation of volatile organic compounds (VOCs), O<sub>2</sub> evolution, and ·OH generation. Variable reactivity priorities
were found between different nanoshapes as well as samples of identical
nanoshapes. With integrated examinations of the coexisting surface
factors (i.e., atomic, electronic, and defect structures), surface
defects were evidently proved to compete with other surface factors
in deciding the final photoreactivity orders. Surface-defect structure
(e.g., Ce<sup>3+</sup> ions and O vacancies) was suggested to greatly
influence the surface properties of ceria NCs, including the activation
of reactants as well as the mobility of surface lattice oxygen. The
results clearly confirm the surface-defect dependence of photoreactivity
and provide further insights into the complex surface effects in semiconductor
photocatalysis. It also underscores the significance of surface-defect
structure as an essential supplement to the traditional CFE strategy
for achieving desired solar energy utilization
Participant demographic information (n = 505).
<p>Participant demographic information (n = 505).</p
Multivariate logistic regression analyses of the factors significantly associated with PTSD, anxiety and depression.
<p>All significant univariate logistic analysis variables (i.e., P-values equal to 0.05 or less) were included in the multivariate logistic regression.</p
Bismuth-Induced Integration of Solar Energy Conversion with Synergistic Low-Temperature Catalysis in Ce<sub>1–<i>x</i></sub>Bi<sub><i>x</i></sub>O<sub>2−δ</sub> Nanorods
For
conventional photocatalysis, the energy threshold rather than
merely the spectral response is always restricted that the infrared
part (48% of solar energy) has never been efficiently utilized, undesirably
elevating the temperature and damaging the photon-to-electron conversion.
It remains challenging to conquer the IR-related contradiction and
integrate the infrared energy into the solar energy conversion. Herein,
we logically designed a Bi-induced synergistic photo/thermocatalyst
(fluorite Ce<sub>1–<i>x</i></sub>Bi<sub><i>x</i></sub>O<sub>2−δ</sub> nanorods), where the coupled ionic
conductivity accompanying highly reductive Bi and concomitant oxygen
vacancies helped bring about integration of photocatalysis with synergistic
low temperature (20–80 °C, IR-driven) catalysis, promising
for the effective utilization of infrared energy. More generally,
through our results a feasible methodology is verified in detail that
integration of semiconductor photocatalysis with solid state ionics
may help design brand new catalysts, shedding light on the practical
solar energy conversion
Equilibrating the Plasmonic and Catalytic Roles of Metallic Nanostructures in Photocatalytic Oxidation over Au-Modified CeO<sub>2</sub>
Finite amounts of noble metals have
been widely introduced as surface
plasmon resonance (SPR) mediators and reductive cocatalysts for solar-driven
energy conversion. At present, knowledge of the roles of metal loading
is multifarious and may be one-sided in some cases. In addition, the
catalytic roles which metals play in photocatalytic oxidation have
been rarely discussed. It is necessary to explore the equilibrium
between plasmon resonance and surface catalysis over metallic nanostructures.
Herein, Au NPs with various loading amounts (0.25–1 wt %) and
particle sizes (3–20 nm) were attached to CeO<sub>2</sub> by
photodeposition. Aerobic oxidations of propylene under simulated sunlight
and visible (>420 nm) light irradiation were selected as probe
reactions.
Both processes exhibited similar humplike activity dependence upon
Au NP addition, with a peak at 0.67 wt % loading and a size of 8.4
nm. Modifications to the whole photocatalytic process brought by metal
attachment have been integrally examined, concerning both the photoexcitation
and surface catalysis steps. With an increase of Au loading, the induced
SPR photoabsorption, charge separation, and resonant energy transfer
were enhanced, whereas outgrown Au NPs (>10 nm) led to the saturation
of exposed active sites for reactant adsorption as well as distinct
passivity to O<sub>2</sub> dissociation. Therefore, photoexcitation
and surface catalysis present opposite dependence on Au NP size and
codetermine the final photocatalytic performance in propylene oxidation.
An integral consideration of the above two aspects should be instructive
for a better understanding of SPR-enhanced photocatalysis and the
design of efficient metal–semiconductor systems for ideal solar
energy conversion