Efficient Degradation of Phenol and 4-Nitrophenol by Surface Oxygen Vacancies and Plasmonic Silver Co-Modified Bi2MoO6 Photocatalysts

Article abstract of DOI:10.1002/chem.201804267

In this work, the surface plasmon resonance effect of metallic Ag, surface oxygen vacancies (SOVs), and Bi₂MoO₆ (BMO) material were rationally combined to construct new oxygen-vacancy-rich Ag/Bi₂MoO₆ (A/BMO-SOVs) photocatalysts. Their synergistic effect on the photocatalytic degradation of phenol and 4-nitrophenol under visible-light irradiation (λ≥420 nm) was also investigated. TEM, EPR, and Raman spectra demonstrate the co-existence of metallic Ag nanoparticles, surface oxygen vacancies, and Bi₂MoO₆ due to a controlled calcination process. The experimental results disclose that the 2 %A/BMO-SOVs-375 sample exhibited the highest photocatalytic activity for the degradation of both phenol and 4-nitrophenol under visible-light irradiation, achieving nearly 100 and 80 % removal efficiency, respectively, and demonstrated the apparent reaction rate constants (k_app) 183 and 26.5 times, respectively, higher than that of pure Bi₂MoO₆. The remarkable photodegradation performance of A/BMO-SOVs for organic substances is attributed to the synergistic effect between the surface oxygen vacancies, metallic Ag nanoparticles, and Bi₂MoO₆, which not only improves the visible-light response ability, but also facilitates charge separation. Thus, this work provides an effective strategy for the design and fabrication of highly efficient photocatalysts through integrating surface oxygen vacancies and the surface plasmon resonance effect of nanoparticles, which has the potential for both water treatment and air purification.

Full text of DOI:10.1002/chem.201804267

A Journal of
Accepted Article
Title: Efficient degradation of phenol and 4-nitrophenol by surface
oxygen vacancies and plasmonic silver co-modified Bi2MoO6
photocatalysts
Authors: Huidong Shen, Wenwen Xue, Feng Fu, Jiefang Sun,
Yanzhong Zhen, Danjun Wang, Bing Shao, and Junwang
Tang
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To be cited as: Chem. Eur. J. 10.1002/chem.201804267
Link to VoR: http://dx.doi.org/10.1002/chem.201804267
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Efficient degradation of phenol and 4-nitrophenol by surface
oxygen vacancies and plasmonic silver co-modified Bi2MoO6
photocatalysts
Huidong Shen,[a]† Wenwen Xue,[a]† Feng Fu,*[a] Jiefang Sun,[b,c] Yanzhong Zhen,[a] Danjun Wang,*[a]
Bing Shao,*[c] and Junwang Tang*[b]
Abstract: In this work, we rationally combined the surface plasmon decompose organic pollutants into carbon dioxide and H2O.[1-4]
resonance effect of metallic Ag, surface oxygen vacancies and
Bi2MoO6 photocatalyst together to construct novel oxygen vacancy-
rich Ag/Bi2MoO6 (A/BMO-SOVs) photocatalysts and further
From the viewpoint of solar energy utilization, it is desirable to
develop highly active and environment-friendly visible-light-
driven photocatalysts to meet the requirements of potential
investigated its synergistic effect on photocatalytic degradation of industrial applications.[5,
Among various semiconductor
6]
phenol and 4-nitrophenol under visible light irradiation (λ ≥ 420 nm). photocatalysis, bismuth-based semiconductors materials have
TEM, EPR and Raman spectra demonstrated the co-existence of attracted extensive attention over the past few years owing to
metallic Ag nanoparticles, surface oxygen vacancies and Bi2MoO6
due to a controlled calcination process. The experiment results the visible light region.[7,
their less toxicity, suitable band positions and photoresponse to
8]
Among these bismuth-based
disclosed that the 2%A/BMO-SOVs-375 sample exhibited the
compounds, Bi2MoO6 is a simplest member of the Aurivillius-
highest photocatalytic activity for the degradation of both phenol and type compounds, which is made up of alternate [Bi2O2]2+ layers
4-nitrophenol under visible light irradiation, achieving nearly 100% and MoO4 perovskite layers.[9] Recently, some studies have
2-
and 80% removal efficiency, respectively, and demonstrating the clearly revealed that Bi2MoO6 might be a promising candidate as
apparent reaction rate constants (kapp) of 183 and 26.5 times higher an excellent photocatalyst owing to a series of advantages, e.g.
than that of pure Bi2MoO6, respectively. The remarkable
photodegradation performance of A/BMO-SOVs for organic
high chemical durability, non-toxic, naturally abundant, and an
11]
appropriate band gap (2.5-2.8 eV).[10,
This material has
substance was attributed to the synergistic effect between the generally been used in many fields including Li-ion batteries,
surface oxygen vacancies, metallic Ag nanoparticles and Bi2MoO6, water splitting, hydrogen energy, and organic pollutant
which not only improves the visible light response ability, but also degradation.[12-16] Nevertheless, pure Bi2MoO6 suffers from low
facilitates charge separation. Thus this work provides an effective visible light utilization efficiency, the relatively rapid
strategy for the design and fabrication of highly efficient recombination of photoexcited electron-hole pairs, and slow
18]
photocatalysts through integrating surface oxygen vacancies and carrier transport, which limit its practical application.[17,
surface plasmon resonance effect of nanoparticles, which has a Therefore, to further extend the visible light response region and
potential to both water treatment and air purification.
improve the photocatalyitc activity of Bi2MoO6-based materials
are highly challenging while appealing.
In order to achieve such goal, the introduction of oxygen
vacancy on the semiconductor surface is proposed. It is widely
recognized that surface oxygen vacancies (SOVs) would play an
critical role in photocatalytic process, especially in terms of the
photo-catalytic degradation of pollutants,[19] owing that they can
narrow down the band gaps of semiconductors and tailor their
electronic structures.[20] Recently, some studies clearly
demonstrated that the introduction of SOVs within
semiconductor photocatalysts not only extended the visible light
response region, but also accelerated the separation of
photogenerated electrons and holes, leading to high
photocatalytic activity.[21-24] For example, Lv and co-workers
reported that the introduction of SOVs in BiPO4 via controllable
hydrogen reduction,[25] and the presence of oxygen vacancies in
BiPO4 resulted in broadening the valence band width and
narrowing the band gap, thus leading to an extended
photoresponse wavelength range and enhanced photocatalytic
performance. Recently, Yu and co-workers also introduced
oxygen vacancies into Bi2O2CO3 via a facile and scalable
precipitation approach with the assistance of glyoxal as
reductant, and further confirmed the favorable effect of oxygen
vacancies on extending the visible light response region and
accelerating the separation of photo-generated electrons and
Introduction
In recent years, semiconductor-based photocatalysis has been
regarded as one of the most promising technologies to address
the environmental contamination because it can completely
[a]
H.D. Shen, W.W. Xue, Prof.Dr. F. Fu, Y.Z. Zhen, Prof.Dr. D.J. Wang
Shaanxi Key Laboratory of Chemical Reaction Engineering, College
of Chemistry and Chemical Engineering
Yan’an University
Yan’an 716000, P. R. China
E-mail: yadxfufeng@126.com; wangdj761118@163.com;
shaobingch@sina.com; junwang.tang@ucl.ac.uk
Dr J.F. Sun, Prof. Dr. J.W. Tang
Department of Chemical Engineering
University College London
[b]
[c]
Torrington Place, London WC1E 7JE, UK.
Dr J.F. Sun, Prof. Dr B. Shao
Beijing Center for Diseaes Prevention and Control
Beijing 100013, P. R. China.
† These authors contributed equally to this work.
Supporting information for this article is given via a link at the end of
the document.
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10.1002/chem.201804267
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holes.[26] Therefore, it is sought-after to introduce the SOVs in Results and Discussion
the Bi2MoO6-based materials to extend its visible light response
Structure and morphology characterization
region and improve the photocatalyitc activity.
Recent results revealed that noble metal (Au, Ag etc.)
decoration of photocatalysts is another effective approach to
improve the photocatalytic performance owing to strongly
localized surface plasmonic resonance (LSPR) effect,[27-29] which
can extend the visible light response region and enhance the
separation of the photogenerated charge carriers of
photocatalysts.[30] In addition, Schottky junctions at the interface
between noble metal nanoparticles and semiconductors might
effectively promote transfer of electrons, thereby to some extent
inhibite the recombination rates of photogenerated electrons and
holes.[31] Among these metal nanoparticles, Ag nanoparticles are
relatively low-cost and widely employed to augment the
photocatalytic activity of semiconductor. For example, Chen and
co-workers prepared Ag nanoparticle decorated zinc oxide
nanostructures, and found that the nano-particulate composites
possessed enhancement in photocatalytic performance for the
oxidization of methane.[32] Wang and co-workers used a facile
The crystalline phase of as-obtained samples was investigated
by XRD analysis, and the results were displayed in Figure 1a. It
is clear to see that the BMO and 2%A/BMO-SOVs-375
composites show the same diffraction peaks, which can be
indexed to orthorhombic BMO (JCPDS card No.76-2388),
indicating that no obvious influence is observed on the
crystalline structure of BMO under a low content of Ag and
calcination at a low temperature (Figure 1a). It should be noted
that no obvious diffraction peaks of Ag are observed, which
might be attributed to the low loading amount, small particle size,
good dispersion and the dominant peaks of BMO in the obtained
samples.[39] However, for the patterns of 2%A/BMO-SOVs-375
(PD) and 2%A/BMO (PD), the intensity of diffraction peaks was
severely weakened, which might be attributed to the XRD
signals partially covered by Ag nanoparticles.[33] As can be seen
from Figure 1b, with increasing calcination temperature, the (131)
diffraction peak slightly shifts to a higher 2Theta angle in the
amplifying XRD patterns due to high temperature-induced the
displacement of oxygen atoms, resulting in lattice distortion and
oxygen vacancies.[40] Figure S1a shows the XRD patterns of
2%A/BMO-SOVs prepared at various calcination temperatures.
It was found that no impurity phase was formed when calcination
temperatures were below 375 ℃. However, when the
temperature reached 450℃, it was found that characteristic
peaks of metallic Ag marked with solid triangle appeared, which
are in good agreement with face-centered cubic Ag
corresponding to JCPDS files No. 04-0783 (Figure S1b), while
peaks marked with solid tetragonum agree well with monoclinic
AgO corresponding to JCPDS files No. 89-3081, which is due to
oxidation of Ag during calcination in air.
impregnation-roasting
method
to
prepare
Ag/g-C3N4
composite.[33] The obtained Ag/g-C3N4 composite exhibited
highly photocatalytic activities toward aerobic oxidative
amidation of aromatic aldehydes under visible light irradiation
owing to strongly LSPR effect of Ag. Recently, Di and co-
workers reported that the Ag quantum dots were deposited onto
the surface of BiOBr nanosheets to generate a heterostructured
Ag/BiOBr metal-semiconductor with an enhanced photocatalytic
performance.[34]
To achieve an optimally photocatalytic activity, the
combination of above-mentioned two strategies is applied to the
preparation of a heterostructured photocatalyst.[35-38] To our
knowledge, such
a design strategy for the visible driven
Bi2MoO6-based photocatalytic materials has seldom been
reported yet. Herein, inspired by the above impressive advances,
in this work, we have rationally designed and successfully
To further confirm the co-existence of Ag nanoparticles and
surface defects, XPS spectra of the as-obtained BMO and
A/BMO-SOVs were performed. The survey XPS curve in Figure
S1c clearly reveals that the 2%A/BMO-SOVs-375 composite is
mainly composed of Bi, Mo, O and Ag elements. Figure 1c and
1d present the high resolution spectra of Bi 4f and O 1s for the
samples BMO and 2%A/BMO-SOVs-375 samples. As shown in
Figure 1c, two asymmetric peaks located at 159.3 eV and 164.3
fabricated
photocatalyst with a high visible light driven photocatalytic
activity via facile solvothermal method combined with
a
novel oxygen vacancy-rich Ag/Bi2MoO6
a
impregnation-calcination approach. Phenol and 4-nitrophenol (4-
NP) were used as probe organic pollutants to assess the
photocatalytic activities of the prepared samples. Moreover, the
reaction parameters for phenol removal have been
systematically studied, such as calcination temperatures,
calcination time, metallic Ag contents and the dosage of
photocatalysts. The experiment results disclosed that the
eV belong to the binding energy of Bi 4f7/2 and Bi 4f5/2
,
respectively, suggesting that the Bi is in the form of Bi3+. The
corresponding peaks in the spectra of 2%A/BMO-SOVs-375
shifted to 159.4 and 164.7 eV, respectively, being 0.1 eV higher
than those of BMO, implying the existence of SOVs and the
strong interaction between Ag and BMO. As presented in Figure
S1d, two characteristic peaks of Mo 3d5/2 and Mo 3d3/2 from Mo6+
respectively centered at 232.5 and 235.6 eV are observed. The
asymmetric O 1s peak could be deconvoluted into three peaks
at 529.8, 530.6, and 531.9 eV (Figure 1d), which are ascribed to
the Bi-O, Mo-O, and OH group on the surface of BMO,
respectively.[41] However, the O 1s XPS spectra of 2%A/BMO-
SOVs-375 shifted to a higher binding energy from 530.20 eV to
530.48 eV (Figure 1d), which is attributed to the formation of
neighboring oxygen vacancies with a high electron-attracting
obtained
2%A/BMO-SOVs-375
exhibited
the
highest
photocatalytic activity for the degradation of phenol and 4-
nitrophenol under visible light irradiation, in which the apparent
reaction rate constants (kapp/min-1) are 183 and 26.5 times higher
than that of pure Bi2MoO6. The highly enhanced photocatalytic
efficiency observed in A/BMO-SOVs should be attributed to the
synergistic effect of the SOVs and SPR metallic Ag. This work
has been proven to be a new strategy, which is also applicable
to the design and fabrication of other photocatalytic systems to
enhance photocatalytic performance.
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effect.[42] The XPS Ag 3d spectrum of 2%A/BMO-SOVs-375 is
shown in Figure S1e, in which the two main peaks observed at
367.7 and 373.7 eV are ascribed to the binding energy of Ag
3d5/2 and Ag 3d3/2, respectively, and the result is in accordance
with previous reports.[43] The above XPS analysis demonstrated
that the 2%A/BMO-SOVs-375 nanocomposite was successfully
obtained.
Figure 2. FE-SEM images of as-prepared (a, b) BMO, and (c, d) 2%A/BMO-
SOVs-375 composites.
Figure 1. (a) XRD patterns of the samples BMO, BMO-SOVs-375, 2%A/BMO-
SOVs-375, 2%A/BMO-SOVs-375 (PD) and 2%A/BMO (PD), (b) XRD patterns
in a 2Theta range of 25°-32°, XPS spectra of (c) Bi 4f and (d) O 1s for the
samples BMO and 2%A/BMO-SOVs-375.
The morphology and microstructure of as-obtained samples
were revealed using SEM technology and the results were
illustrated in Figure 2. Figure 2a and 2b show that the pure BMO
sample is composed of well dispersed hierarchical microspheres
with average diameter of 1-2 μm, which are assembled with a
large amount of nanosheets with a thickness of 20-50 nm (inset
of Figure 2b). As seen from Figure 2c and 2d, the morphology of
2%A/BMO-SOVs-375 sample inherits the similar hierarchical
structure of BMO sample, indicating that the calcination process
does not give rise to obvious changes on the morphology and
size of BMO. However, compared to pure BMO, the surface of
the prepared 2%A/BMO-SOVs-375 composite becomes blurred
and disordered, which indicates that the surface structure is
damaged and SOVs are formed. In addition, some small
spherical Ag nanoparticles are observed on the surface of the
BMO hierarchical microspheres (inset of Figure 2d), indicating a
high dispersion of Ag nanoparticles. Furthermore, to further
analysis of elemental distribution on the 2%A/BMO-SOVs-375
sample, the corresponding EDS elemental mappings were also
performed. As shown in Figure 3a-3d, the Bi, Mo, O, and Ag
elements are all detected and uniformly dispersed, which gives a
very clear signal that the Ag nanoparticles are successfully
loaded on the surface of BMO after the impregnation-calcination
procedure. This finding is in good agreement with the XPS
results.
Figure 3. The corresponding EDS elemental mapping images of (a) Bi, (b) Mo,
(c) O and (d) Ag in sample 2%A/BMO-SOVs-375.
For further investigating the morphological and structural
characteristics of BMO and 2%A/BMO-SOVs-375, TEM and
HRTEM analyses were carried out and the results are shown in
Figure 4. Figure 4a and 4c show the TEM images of BMO and
2%A/BMO-SOVs-375, revealing
a hierarchical microsphere
structure. Figure 4b indicated the HRTEM images of BMO. It can
be clearly observed that the lattice spacing is measured to be
0.315 nm, which corresponds to the (131) crystal plane of BMO
(inset of Figure 4b).[44] Figure 4d shows the HRTEM image of
2%A/BMO-SOVs-375. It can be clearly indicates that the Ag
nanoparticles were located on the surface of BMO (the red
dotted line mark). Besides, the lattice fringe spacing of 0.236 nm
can be observed on the surface, which matched with the (111)
39]
crystal plane of metal Ag (inset of Figure 4d).[32,
The results
demonstrated that metallic Ag was successfully loaded on the
surface of BMO microspheres, which promoted the effective
electrons and holes separation.
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with previous report.[50] From the Raman vibrations of the BMO-
SOVs-375, it shows the similar Raman vibration modes.
Furthermore, the vibrating peaks of BMO-SOVs-375 are
stronger than BMO, indicating that the BMO-SOVs-375 contain
more MoO6 octahedral structures. The increase in the intensities
of these vibrational modes for the calcined samples suggested
the deformation of the crystal structure after calcination, which
could be attributed to the contribution of surface oxygen
vacancies.[51] Compared with BMO, the characteristic peaks of
2%A/BMO-SOVs-375 and 2%A/BMO (PD) display the
enhancement of peak intensity, which is attributed to the strong
interaction between metal Ag and BMO interface as well as the
energy coupling process to enhance the Raman signals.[52]
Based on the results from TEM, EPR, and Raman spectra
analyses, both SOVs and metallic Ag were successfully
produced on the A/BMO-SOVs via a reliable calcination process.
Figure 4. TEM and HR-TEM images of (a, b) BMO and (c, d) 2%A/BMO-
SOVs-375 composites.
Formation of Surface Oxygen Vacancy
As shown in Figure 5a and 5b, the HRTEM image clearly
reveals that both BMO and BMO-SOVs-375 are highly
crystalline structure. However, it can be seen clearly that pure
BMO sample displays a perfect lattice feature, while the edge of
lattice fringe for BMO-SOVs-375 appears a disordered layer of
about 2.794 nm thickness. This phenomenon indicates the
surface structure is damaged and maybe SOVs are formed.
Hence, the generation of SOVs stems from the calcination
process.
To provide a direct and solid evidence for the existence of
oxygen vacancies, EPR spectra analysis was carried out. It has
been reported that EPR can be directly and accurately detected
the presence of oxygen vacancies in semiconductors.[45] Figure
5c shows the EPR spectra of BMO, BMO-SOVs-375, and
2%A/BMO-SOVs-375. It can be found that only very weak EPR
signal with a small g-value of 1.991 can be observed for BMO,
which could be ascribed to the existence of oxygen vacancies.[40]
Compared to BMO, a strong symmetric peak centered at g value
of around 2.004 for BMO-SOVs-375 and 2%A/BMO-SOVs-375
Figure 5. HR-TEM images of (a) BMO and (b) BMO-SOVs-375, (c) EPR
spectra of BMO, BMO-SOVs-375, and 2%A/BMO-SOVs-375 at 77 K, (d)
Raman spectra of BMO, BMO-SOVs-375, 2%A/BMO-SOVs-375 and
2%A/BMO (PD).
To investigate the optical band gap and absorption
properties of the as-obtained samples, the UV-vis DRS spectra
were provided and the results were illustrated in Figure 6a and
Figure S2. It can be seen clearly that the adsorption edge of
pure BMO appears at around 470 nm. Interestingly, compared
with pure BMO, the main absorption edge of BMO-SOVs-375
changes little. More importantly, the 2%A/BMO-SOVs-375
exhibits a significant enhancement of visible light absorption at
420-800 nm after treated by calcination as a result of the
introduction of SOVs and metallic Ag nanoparticles. Furthermore,
it can be found that 2%A/BMO-SOVs-375, 2%A/BMO-SOVs-375
(PD), and 2%A/BMO (PD) display a stronger absorption about
550 nm, which could be attributed to the strong SPR due to
metallic Ag nanoparticles.[27-29] From the inset of Figure 6a, the
color changes a little from BMO to BMO-SOVs-375, consistent
with the edge absoprtion observed. The color of powder
changes from pale yellow of BMO to gray of 2%A/BMO-SOVs-
375, indicating the existence of metallic Ag.[52] To prove the
change of band gap structure, the band gap energy (Eg) of BMO,
were observed, which is a typical peak of surface oxygen
47]
vacancies.[46,
In addition, it can be easily seen that the
intensity of EPR signal for 2%A/BMO-SOVs-375 is considerably
stronger than that of BMO-SOVs-375, which was gradually
enhanced with increasing SOVs’ concentration.[48] This result
further corroborates that the successful formation of oxygen
vacancies on BMO surface via a facile impregnation-calcination
method.
In order to further investigate the crystal defects and the
distortion of crystal structure, Raman spectroscopy were
performed and the results were illustrated in Figure 5d. It was
found that pure BMO exhibited many characteristic peaks at 138,
282, 351, 399, 714, 798 and 844 cm-1 (Figure 5d). The
characteristic peaks at 714, 798 and 844 cm-1 were correspond
to the asymmetric, symmetric and asymmetric stretching
vibrations of the MoO6 octahedrons, respectively.[49] Additionally,
the characteristic peaks below 400 cm-1 can be attributed to both
Bi-O stretches and lattice modes, which is in good accordance
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BMO-SOVs-375 and 2%A/BMO-SOVs-375 were calculated by
plots of (αhν)1/2 versus energy (hν), and the results were
illustrated in Figure 6b. It can be clearly observed that the Eg
values of BMO, BMO-SOVs-375 and 2%A/BMO-SOVs-375 are
about 2.45, 2.49 and 2.33 eV, respectively. The above results
can be ascribed to the synergistic effect between SOVs and
metallic Ag co-modification and coupling with BMO, which
somehow improves the visible light response ability. Figure 6c
shows the valence band X-ray photoelectron spectra (VB-XPS)
of BMO and BMO-SOVs-375 photocatalysts. It can be seen that
the positions of valence band (VB) of BMO and BMO-SOVs-375
are about 1.95 and 1.85 eV vs NHE, respectively. Meanwhile,
the conduction band (CB) edges of BMO and BMO-SOVs-375
are calculated to be -0.50 and -0.64 eV, respectively, based on
their band gaps. This result can be ascribed to the introduction
of SOVs elevates the both conduction and valence bands. A
similar phenomenon was also observed on BiOCl.[53] According
to the characterization findings, we can describe the band
photocatalytic activity in the degradation of phenol compared to
BMO, BMO-SOVs-375, 2%A/BMO-SOVs-375 (PD), and
2%A/BMO (PD). The improved photocatalytic activity of
2%A/BMO-SOVs-375 is attributed to the synergistic effect
between the SOVs, metallic Ag and BMO, which not only
improves the visible light response ability, but also utilizes the
strong SPR effect in metallic Ag nanoparticles, promoting the
efficient separation of photogenerated electron-hole pairs.
As shown in Figure 7b, the typical evolution of the
absorption spectra of phenol with BMO, BMO-SOVs-375, and
2%A/BMO-SOVs-375 under visible light irradiation (λ ≥ 420 nm).
It is found that the characteristic absorption peak is observed at
507 nm at the beginning of photodegradation of phenol. With
increasing irradiation time, the absorption peak of 2%A/BMO-
SOVs-375 obviously decreases and virtually no peak could be
observed after 180 min irradiation than pure BMO, in which
slightly decreases. This result confirms that the complete
photocatalytic degradation of phenol by 2%A/BMO-SOVs-375
during the irradiation.
structure of BMO and BMO-SOVs-375 using
diagram (Figure 6d).
a schematic
Figure 7. (a) Photocatalytic degradation efficiency of phenol by BMO, BMO-
SOVs-375, 2%A/BMO-SOVs-375, 2%A/BMO-SOVs-375 (PD), and 2%A/BMO
(PD), (b) The change of the absorption spectra of photodegradated phenol
with increasing irradiation time under visible light using BMO, BMO-SOVs-375,
and 2%A/BMO-SOVs-375 as catalysts, respectively, (c) Kinetic plot of C/C0
versus irradiation time for the photodegradation of phenol with different
catalysts, (d) The rate constants of the photodegradation of phenol using
different catalysts.
Figure 6. (a) UV-vis diffuse reflectance spectra of BMO, BMO-SOVs-375,
2%A/BMO-SOVs-375, 2%A/BMO-SOVs-375 (PD), and 2%A/BMO (PD) (inset:
the color of the photocatalysts), (b) The band gap value estimated by the
curve of (αhν)1/2 versus photon energy plotted, (c) Valence band XPS spectra,
and (d) Schematic illustration of the band structures of BMO and BMO-SOVs-
375, respectively.
Photocatalytic activity and degradation mechanism
In addition, the kinetic behaviors of as-obtained samples for
photodegradation of phenol were investigated. It can be seen
clearly that all of them fit well with the pseudo-first-order kinetics
model[54]: ln(C0/C) = kapp·t, where kapp denotes the apparent rate
constant (min-1), C0 represents the initial phenol concentration
(mg·L-1) and C represents the final concentration of phenol in
solution after irradiation time t minute. Figure 7c illustrates the
plot of ln(C0/C) versus irradiation time (t), using BMO, BMO-
SOVs-375, 2%A/BMO-SOVs-375, 2%A/BMO-SOVs-375 (PD),
and 2%A/BMO (PD) photocatalysts. Figure 7d shows the kapp
values of as-obtained samples for photodegradation of phenol.
The kapp values of BMO, BMO-SOVs-375, 2%A/BMO-SOVs-375,
To evaluate the photocatalytic activities of as-obtained samples,
phenol was chosen as a representative organic pollutant for
photocatalytic degradation. Figure 7a shows the variation of
phenol concentration (C/C0) over BMO, BMO-SOVs-375,
2%A/BMO-SOVs-375,
2%A/BMO-SOVs-375
(PD),
and
2%A/BMO (PD) photocatalysts against reaction time under
visible light irradiation (λ ≥ 420 nm). It can be clearly observed
that pure BMO exhibits 4.8% of phenol decrease efficiency after
180 min, and BMO-SOVs-375 and 2%A/BMO-SOVs-375
composites both displayed superior photocatalytic activities.
Especially, for the 2%A/BMO-SOVs-375 exhibited the highest
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2%A/BMO-SOVs-375 (PD), and 2%A/BMO (PD) are 1.88×10-4,
70.3×10-4, 343.9×10-4, 111.2×10-4, and 4.73×10-4 min-1,
respectively. It can be found that the kapp value of 2%A/BMO-
SOVs-375 is much higher than other samples, which is
approximately 183 times higher than that of pure BMO.
Simulated results of kapp for each process, in the presence of
different photocatalysts with regard to phenol, were summarized
in Table S1. The dramatically enhanced photocatalytic activity is
attributed to the synergistic effect between the SOVs, metallic
Ag and BMO, which not only improves the visible light response
ability, but also utilizes the strong SPR effect in metallic Ag
acquired and are shown in Figure 8b. It can be found that the
crystal structure of the 2%A/BMO-SOVs-375 photocatalyst
showed no obvious changes during the photocatalytic reaction.
Consequently, the 2%A/BMO-SOVs-375 composite is a quite
stable and reusable photocatalyst, which can be utilized to
degrade organic pollutants during practical applications.
nanoparticles,
promoting
the
efficient
separation
of
photogenerated electron-hole pairs.
The variation of phenol concentration (C/C0) photocatalysts
against reaction time over 2%A/BMO-SOVs with different
calcination temperatures for 2 h and different calcination times at
375℃ are shown in Figure S3a and S3b, respectively. With the
increase of calcination temperature, the activity of the as-
obtained samples first increases and then decreases and the
activity of 2%A/BMO-SOVs calcinated at 375℃ is the best. As
displayed in Figure S3b, with the increase of calcination time,
the photocatalytic activities of 2%A/BMO-SOVs-375 samples
slightly enhanced. These results indicate that the introduction of
SOVs and SPR effect of metallic Ag nanoparticles due to
controlled calcination temperatures act as pivotal roles for the
enhanced photocatalytic performance.
Figure S3c illustrates the photocatalytic activities of the as-
prepared A/BMO-SOVs-375 nanocomposites with different
metallic Ag contents at 375℃ for 2h for the photocatalytic
degradation of phenol under visible light irradiation. We can see
that when the mole ratio of Ag increased from 0.5% to 2% in the
composites, photocatalytic degradation efficiency of phenol was
obviously improved. However, when the mole ratio of Ag was
further increased to 5%, the photocatalytic activity decreased. It
can be attributed to the the excessive amount of Ag
nanoparticles on the surface acts as recombination center for
photogenerated electrons and holes,[16, 39] resulting in decreased
photocatalytic performance.
To investigate the influence of different initial dosages of
2%A/BMO-SOVs-375 on the photocatalytic degradation
efficiency, a series of experiments were performed and the
results are shown in Figure S3d. It can be clearly observed that
when the amount of 2%A/BMO-SOVs-375 was increased from
0.50 to 1.00 g·L-1, the degradation efficiency of phenol was
improved accordingly, which is due to that more active sites
would be provided. However, when the amount of 2%A/BMO-
SOVs-375 further increased and more than 1.00 g·L-1, the
degradation rate would slightly decrease due to the scattering of
light, and would severely reduce the intensity of light penetrating
through the phenol solution.[55]
From the viewpoint of practical application, it is of significant
importance to investigate the stability of prepared 2%A/BMO-
SOVs-375. Figure 8a illustrates five successively photocatalytic
degradation experiments. It can see clearly that the
photocatalytic performance shows a slight decrease after five
cycles. In addition, the XRD patterns of 2%A/BMO-SOVs-375
samples before and after photodegradation of phenol were
Figure 8. (a) Photocatalytic degradation of phenol with the 2%A/BMO-SOVs-
375 sample for five cycles, (b) XRD patterns of the 2%A/BMO-SOVs-375
samples before and after photodegradation of phenol under visible light
irradiation (λ ≥ 420 nm).
In addition, 4-NP was used as the second model pollutant to
further evaluate the visible light photocatalytic performance of
the as-prepared samples, and the results are displayed in Figure
9. Figure 9a illustrates the variation of 4-NP concentration (C/C0)
over BMO, BMO-SOVs-375, 2%A/BMO-SOVs-375, 2%A/BMO-
SOVs-375 (PD), and 2%A/BMO (PD) photocatalysts against
reaction time under light irradiation (λ ≥ 420 nm). It can be easily
seen that the 2%A/BMO-SOVs-375 exhibited the highest
photocatalytic activity in the degradation of 4-NP compared to
those photocatalysts, which is in good agreement with the
photocatalytic degradation of phenol experiments results. Figure
9b illustrates the typical evolution of the absorption spectra of 4-
NP with 2%A/BMO-SOVs-375 under visible light irradiation (λ ≥
420 nm). It is obvious that the main band of 4-NP at 318 nm
decreased monotonously with irradiation time, indicating that 4-
NP was photodegraded.
Figure 9c illustrates the photocatalytic degradation curves of
4-NP in the form of ln(C0/C) versus irradiation time (t), using
BMO, BMO-SOVs-375, 2%A/BMO-SOVs-375, 2%A/BMO-
SOVs-375 (PD), and 2%A/BMO (PD) photocatalysts. Figure 9d
shows the kapp values of as-obtained samples for
photodegradation of 4-NP. It can be easily seen that the kapp
values of 2%A/BMO-SOVs-375 is much higher than other
samples, which is approximately 27 times higher than that of
pure BMO. Simulated results of kapp for each process, in the
presence of different photocatalysts with regard to 4-NP, are
summarized in Table S1. The remarkable photodegradation
performance is attributed to the synergistic effect between the
SOVs, metallic Ag and BMO, which not only improves the visible
light response ability, but also utilizes the strong SPR effect in
metallic Ag nanoparticles, promoting the efficient separation of
photogenerated electron-hole pairs. This result is in good
accordance with that the photocatalytic degradation of phenol
experiments results.
To further evaluate the mineralization rate of phenol and 4-
NP over BMO and 2%A/BMO-SOVs-375, Total organic carbon
(TOC) analyses were carried out, which monitored the
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10.1002/chem.201804267
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concentration of remained organic substance in the aqueous
solution and the degree of mineralization can be calculated that
is displayed in Figure 10. It can be observed that 57.1 % and
48.7% of carbon contents in phenol and 4-NP were eliminated in
the presence of 2%A/BMO-SOVs-375, which was much higher
than that of BMO (2.5% and 4.7%), further indicating the
enhanced photocatalytic performance. It should also be noted
that 2%A/BMO-SOVs-375 shows higher photocatalytic and
mineralization performances toward phenol and 4-NP, which is
again attributed to the synergistic effect between the SOVs,
metallic Ag and BMO.
SOVs-375 exhibits the lowest PL signal in comparison with BMO
and BMO-SOVs-375, suggesting that the recombination rate of
photoinduced electron-hole pairs was efficiently inhibited via the
modification of SOVs and metallic Ag nanoparticles on the
surface of BMO. This effect can be further confirmed by the TR-
PL analysis. Moreover, a blue-shift in the PL emission peak of
2%A/BMO-SOVs-375 was observed in comparison with BMO,
which could be mainly attributed to the recombination of the
photogenerated holes with the single electron oxygen
58, 59]
vacancy.[37,
This result is in good accordance with TEM,
EPR, Raman and UV-vis analysis.
Additionally, to further confirm the recombination process of
photogenerated electron and hole pairs, time-resolved PL decay
spectra were performed (Figure 11b). These spectra are in good
agreement with the two-exponential decay models,[14] and the
fitting results are shown in Table S2. As shown in Figure 11b
and Table S2, the lifetime of 2%A/BMO-SOVs-375 is 13.09 ns,
which is much longer than that of BMO (i.e., 3.39 ns) and BMO-
SOVs-375 (i.e., 4.36 ns), respectively. The prolonged lifetime is
attributed to the synergistic effect between SOVs and metallic
Ag nanoparticles, which effectively accelerates the separation of
photogenerated electron and hole. The results are in
accordance with the observation from the PL measurements.
Figure 9. (a) Photocatalytic degradation efficiency of 4-NP by BMO, BMO-
SOVs-375, 2%A/BMO-SOVs-375, 2%A/BMO-SOVs-375 (PD), and 2%A/BMO
(PD), (b) The change of the absorption spectra of photodegradated 4-NP with
increasing irradiation time under visible light using 2%A/BMO-SOVs-375 as a
catalyst, respectively, (c) Kinetic plot of C/C0 versus irradiation time for the
photodegradation of 4-NP with different catalysts, (d) The rate constants of the
photodegradation of 4-NP using different catalysts.
Figure 11. (a) Photoluminescence spectra, (b) Time-resolved fluorescence
decay spectra of BMO, BMO-SOVs and 2%A/BMO-SOVs-375.
To further investigate the underlying mechanism of the
excellent photocatalytic activities of 2%A/BMO-SOVs-375, active
species trapping experiments were carried out. In this study,
ethylenediaminetetraacetic acid disodium salt (EDTA-2Na),
benzoquinone (BQ), and isopropanol (IPA) were applied as the
-
scavengers of holes (h+), superoxide radicals (·O2 ) and hydroxyl
radicals (·OH), respectively.[60] Figure 12 illustrates the active
species trapping experiments in photocatalytic degradation of
phenol with 2%A/BMO-SOVs-375. The experimental results
show that the addition of EDTA-2Na slightly hindered the
photocatalytic activity, while the addition of BQ and IPA largely
suppressed the photocatalytic degradation efficiency of phenol.
Figure 10. TOC measurement during mineralisation of phenol and 4-NP over
BMO and 2%A/BMO-SOVs-375 composites under visible light illumination (λ ≥
420 nm).
-
Thus, it could be inferred that ·O2 and ·OH- were the main
reaction species in the phenol photodegradation process over
A/BMO-SOVs.
To further verify the presence of ·OH and ·O2- radicals in the
In order to investigate the generation, transfer, and
recombination of photogenerated electron-hole pairs on the
semiconductor,[56] PL emission spectra were recorded and the
results are shown in Figure 11a. Recent results revealed that the
higher intensity means the higher rate of photogenerated
electron and hole recombination.[57] It is clear that 2%A/BMO-
photocatalytic reaction systems, the spin-trapping ESR
62]
technique was carried out,[61,
and the results were shown in
Figure 13 and Figure S4. Experiment was first conducted under
dark condition and visible light irradiation of 4 min, 8 min, and 12
min. Figure 13 and Figure S4 show the results of BMO, BMO-
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10.1002/chem.201804267
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SOVs-375, and 2%A/BMO-SOVs-375. It can be clearly
observed that the characteristic ESR signals were not detectable
On the basis of the above-mentioned semiconductor band
structure analysis and the ESR results, the remarkable
photocatalytic performance of the 2%A/BMO-SOVs-375
photocatalysts may be attributed to the synergistic effect of
SOVs and metallic Ag nanoparticles, and the possible
photocatalytic mechanism describing the charge transfer and
separation process is proposed in Scheme 1. According to the
results reported by Zhu et al.,[66] the SOV is a shallow defect,
which may be near the conduction band minimum (CBM) or
-
in the dark, while the light was on, the ·O2 and ·OH radicals
-
signals could be observed, further confirming the forming of ·O2
and ·OH during the photodegradation process. As shown in
-
Figure 13a and 13b, BMO shows very weak the ·O2 and ·OH
-
radicals signals, indicating that the ·O2 and ·OH were barely
generated in the photocatalysis process. However, for
2%A/BMO-SOVs-375, the intensity of radical signals gradually
enhanced as the irradiation time prolonged (Figure 13c and 13d). above the valence band maximum (VBM). As manifested in our
After visible light irradiation for 12 min, the special spectrum with previous works, the existence of SOVs would induce the
relative intensities of 1 : 1 : 1 : 1 quartet signal was clearly
formation of sub-bands above VB.[40] A similar phenomenon has
-
66, 67]
observed, which is characteristic of DMPO ·O2 adduct.[63]
also been observed on Bi2O2CO3, BiPO4 and BiFeO3.[26,
Meanwhile, the ·OH radical was captured to form DMPO ·OH
adduct with relative intensities of 1 : 2 : 2 : 1 quadruplet signal.[64,
Our experimental results show that BMO-SOVs-375
photocatalytic performance is evidently increased compared with
pure BMO, which is attributed to the efficient separation of
photogenerated electron-hole pairs and transfer.[66] Furthermore,
when metallic Ag nanoparticles are deposited on BMO-SOVs-
375 surface, due to the Fermi level equilibrium between BMO
65]
-
The ESR results indicate that ·O2 and ·OH radicals are both
produced over 2%A/BMO-SOVs-375, which is in good
agreement with the active species trapping experimental results.
-
Figure S4 shows the DMPO-·O2 and DMPO-·OH characteristic
peaks of BMO-SOVs-375. Sample BMO-SOVs-375 shows a
highly intensive ·O2 and ·OH radical signals compared to those
and Ag nanoparticles, and Schottky barriers formed at a metal-
-
69]
semiconductor junction.[68,
This unique metal-semiconductor
of BMO under visible light irradiation.
interface allows only the movement of electrons from the
semiconductor to metal particles and hinders electron transfer
back across the Schottky barrier, and thereby preventing from
the recombination of the photogenerated electron-hole pairs.[40]
Therefore, the resulting 2%A/BMO-SOVs-375 photocatalyst
shows a very high photocatalytic activity via a synergetic effect
of SOVs and metallic Ag nanoparticles. Consequently, the
enhanced photocatalytic activity for phenol and 4-NP
degradation with 2%A/BMO-SOVs-375 could be explained as
follows.
Under visible light irradiation, the BMO-SOVs-375 can be
excited to generate photoexcited electron-hole pairs.
Subsequently, the electrons from the CB of BMO-SOVs-375 flow
into metallic Ag nanoparticles surface due to a Schottky barrier
at the metal-semiconductor interface,[70] and thus reducing the
recombination possibility with photogenerated holes, which was
confirmed by the PL and TR-PL spectra (Figure 11). The
photogenerated electrons could react with the dissolved oxygen
Figure 12. Kinetic curves of the 2%A/BMO-SOVs-375 composite on the
degradation of phenol in the presence of different radical scavengers under
visible light irradiation ( λ ≥ 420 nm).
-
molecules (O2) from the environment to generate ∙O2 radicals,
while the valence holes photogenerated on the surface of BMO-
SOVs-375 could not react with OH- or H2O molecules to form
∙OH radicals, which can be ascribed to the reason that the
photo-induced hole (h+) of BMO-SOVs-375 (1.85 eV vs. NHE) is
more negative than that of ·OH/OH- potential (1.99 eV vs NHE,
pH = 7).[71] Nevertheless, the typical characteristic peaks of
DMPO-∙OH adducts (Figure 13d and Figure S4b) were also
observed, indicating that the ∙OH radicals are also produced in
both BMO-SOVs-375 and 2%A/BMO-SOVs-375 reaction
systems. It is believed that the observed ∙OH radicals originate
-
-
73]
from the further reduction of ∙O2 via ∙O2 → H2O2 → ∙OH.[72,
Meanwhile, the phenol and 4-NP molecules can be directly
degraded by the strong oxidizing holes (h+) from the VB of BMO.
-
It has been reported that both ∙OH and ∙O2 have strong
oxidation capacity, which can mineralize phenol and 4-NP to
H2O, CO2 and other inoganic anions (Figure 10). Hence, the
2%A/BMO-SOVs-375 exhibits the highest visible light
Figure 13. DMPO spin-trapping ESR spectra of (a) BMO and (c) 2%A/BMO-
SOVs-375 in methanol dispersion for DMPO-·O2 , DMPO spin-trapping ESR
spectra of (b) BMO and (d) 2%A/BMO-SOVs-375 in aqueous dispersion for
DMPO-·OH.
-
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10.1002/chem.201804267
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Preparation of Bi2MoO6 (BMO). All the chemicals were analytical grade
and used as received. Distilled water was used in all experiments. The
pure Bi2MoO6 was synthesized according to our previous work.[40] In brief,
1.3 mmol of Bi(NO3)3·5H2O and 0.65 mmol of Na2MoO4·2H2O were
dissolved in 13.0 mL of ethylene glycol (EG) under vigorously stirring.
Afterwards, 32.5 mL of ethanol was added and the colourless solution
was stirred for another 30 min at room temperature. Finally, the miscible
responsive photocatalytic performance, which can be attributed
to the synergistic effect between the SOVs, metallic Ag
nanoparticles and BMO. This synergistic effect not only
improves the visible light absorption ability, but also produces
the SPR effect and Schottky barriers, greatly promoting the
efficient separation of photogenerated electron-hole pairs and
resulting in the very high photocatalytic performance.
solution was transferred into
a 65.0 mL Teflon-lined stainless steel
autoclave, which was maintained at 160 ºC for 12 h under autogenous
pressure. After completion of the reaction, the autoclave naturally cooled
down to room temperature. The resulting precipitates were collected and
washed with ethanol and deionized water for three times and then dried
at 60 ºC for 12 h in a vacuum oven. The obtained product was marked as
BMO.
Synthesis of oxygen vacancy-rich Ag/Bi2MoO6 (A/BMO-SOVs)
photocatalysts. The A/BMO-SOVs composite photocatalysts were
prepared through a facile impregnation-calcination method. First, 0.61 g
pure BMO powers were dispersed into 60 mL aqueous solution that
containing various amount of AgNO3 (10-3 g·mL-1) in a beaker under
vigorous stirring. Then, the suspension was stirred vigorously at 70℃ to
evaporate the water. After that, the precipitates were calcined at 300℃,
350℃, 375℃, 400℃, 425℃ and 450℃ in air-rich atmosphere with the
heating rate of 2°C/min for 2 h in the muffle furnace to obtain the final
A/BMO-SOVs composite. The products were denoted as 2%A/BMO-
SOVs-X ( X=300℃, 350℃, 375℃, 400℃, 425℃, 450℃). Following the
Scheme 1. Schematic illustration of hole-electron separation and transfer
process for the 2%A/BMO-SOVs-375 photocatalysts under visible light
irradiation ( λ ≥ 420 nm).
similar procedure, we fixed calcination temperature at 375
℃ and
controlled the molar ratio of Ag nanoparticles deposit on BMO-SOVs at
0.5%, 1%, 2%, 3% and 5%, respectively. The obtained samples were
denoted as Y%A/BMO-SOVs-375 (Y = 0, 0.5, 1, 2, 3, 5). In addition, to
investigate the effect of calcination time on the photocatlaytic activities on
the series 2%A/BMO-SOVs-375 photocatalysts, we fixed the calcination
temperatures at 375℃and changed the calcination time to 1h, 2h, 3h and
5h, respectively. The resulted products were denoted as 2%A/BMO-
SOVs-Z (Z = 1h, 2h, 3h, 5h).
Conclusions
In summary, novel A/BMO-SOVs photocatalysts were
successfully fabricated via
a reliable solvothermal method
followed by a mild impregnation-calcination treatment. TEM,
EPR, and Raman spectra analyses results confirmed the co-
existence of SOVs, metallic Ag nanoparticles and BMO after
controlled calcination process. The 2%A/BMO-SOVs-375
showed the optimal efficiency of phenol and 4-NP degradation
under visible light irradiation, achieving about 100% and 80%
degration of these organic substance within 180 min,
respectively, and the kapp are 183 and 26.5 times higher than
that of pure BMO. The reason for the remarkable photocatalytic
activity is reasonably attributed to the synergistic effect between
the SOVs, metallic Ag nanoparticles and BMO. These results
For comparison, two controllable samples were also prepared according
to our previous work.[40] Briefly, 1.0 mmol of the pure BMO (BMO-SOVs)
and a certain amount of AgNO3 solution (3.5 mL, 10-3 g·mL-1) were added
into 20 mL of deionized water under stirring. The suspension was stirred
for 30 min in the dark, and then irradiated at ambient temperature for 2 h
using a 400W xenon lamp under stirring. During the irradiation, the
supernatant was collected and tested until Ag+ ions were precipitated
completely. After completed photoreduction process, the samples were
-
collected, washed with water to completely remove NO3 ions, and finally
dried at 60 ºC for 12 h in a vacuum oven. The theoretical deposited
amount of Ag is 2% to pure BMO (BMO-SOVs), and the resulted
samples were denoted as 2%A/BMO (PD) and 2%A/BMO-SOVs-375
(PD), respectively. Herein A/BMO-SOVs indicates that Ag nanoparticles
was deposited on the surface of oxygen vacancy-rich Bi2MoO6
photocatalysts via a impregnation-calcination treatment, while A/BMO-
SOVs (PD) means that Ag nanoparticles was deposited on the surface of
were further demonstrated by 57.1
% and 48.7 removal
efficiency of phenol and 4-NP by TOC measurement,
respectively. This heterojunction not only improves the visible
light absorption, but also produces the SPR effect and Schottky
barriers, which significantly promote the separation of
photogenerated electrons and holes, and simultaneously
suppress the recombination of electrons and holes, thus
resulting in the high photocatalytic performance on 2%A/BMO-
SOVs-375. In addition, this work provides an effective strategy
for the design and fabrication of highly efficient photocatalysts
through integrating SOVs and SPR metallic Ag nanoparticles
and the potential to other environment pollutants’ removal.
oxygen vacancy-rich Bi2MoO6 photocatalysts via
process.
a photoreduction
Characterization of photocatalysts
Powder X-ray diffraction (XRD) was carried out on a Shimadzu XRD-
7000 X-ray diffractometer using Cu Kα radiation (λ = 0.15418 nm) at a
scanning rate of 2° min-1 in a 2θ range of 10° - 80°. The accelerating
voltage and the applied current were 40 kV and 30 mA, respectively. X-
ray photoelectron spectroscopy (XPS) was recorded on a PHI-5400 X-
ray photoelectron spectrometer. Field emission scanning electron
microscope (FE-SEM) images were recorded on a JSM-6700F scanning
Experimental Section
Synthesis of photocatalysts
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10.1002/chem.201804267
Chemistry - A European Journal
FULL PAPER
electron microscope. Energy-dispersive X-ray (EDS) spectra were
obtained using a JEOL-2100 at an accelerating voltage of 200 kV. High-
resolution transmission electron microscope (HRTEM) images were
[3]
[4]
[5]
[6]
[7]
[8]
[9]
H.L. Wang, L.S. Zhang, Z.G. Chen, J.Q. Hu, S.J. Li, Z.H. Wang, J.S.
Liu, X.C. Wang, Chem. Soc. Rev. 2014, 43, 5234-5244.
D.J. Martin, G.G. Liu, S.J.A. Moniz, Y.P. Bi, A.M. Beale, J.H. Ye, J.W.
Tang, Chem. Soc. Rev. 2015, 44, 7808-7828.
recorded on
a
JEM-2100 electron microscope operated at an
accelerating voltage of 200 kV. In situ electron paramagnetic resonance
(EPR) measurement was took in an Endor spectrometer (JEOL ES-
ED3X). The g factor was obtained by taking the signal of manganese as
standard. The electron spin resonance (ESR) signals of radicals spin-
trapped by spin-trap reagent DMPO (5, 5′- dimethyl -1-pirroline-N-oxide)
(Sigma Chemical Co.) in water were examined on a Bruker model ESR
JES-FA200 spectrometer equipped with a quanta-Ray Nd: YAG laser
system as the irradiation source (λ > 410 nm). To minimize experimental
errors, the same type of quartz capillary tube was used for all ESR
measurements. Raman spectra were recorded by using a Horiba Jobin-
Yvon LabRam HR800 Raman microspectrometer, with laser excitation at
320 nm. The UV-Vis diffuse reflectance spectra (UV-Vis-DRS) of the
W.J. Ong, L.L. Tan, Y.H. Ng, S.T. Yong, S.P. Chai, Chem. Rev. 2016,
116, 7159-7329.
Y.H. Li, K.L. Lv, W.K. Ho, F. Dong, X.F. Wu, Y. Xia, Appl. Catal. B:
Environ. 2017, 202, 611-619.
Y. Ma, Y.L. Jia, Z.B. Jiao, M. Yang, Y.X. Qi, Y.P. Bi, Chem. Commun.
2015, 51, 6655-6658.
Z. Dai, F. Qin, H.P. Zhao, F. Tian, Y.L. Liu, R. Chen, Nanoscale 2015, 7,
11991-11999.
D.J. Wang, H.D. Shen, L. Guo, F. Fu, Y.C. Liang, New J. Chem. 2016,
40, 8614-8624.
[10] C.S. Guo, J. Xu, S.F. Wang, L. Li, Y. Zhang, X.C. Li, CrystEngComm
2012, 14, 3602-3608.
samples
were
obtained
using
Shimadzu
UV-2550
UV-Vis
[11] G.H. Tian, Y.J. Chen, W. Zhou, K. Pan, Y.Z. Dong, C.G. Tian, H.G. Fu,
J. Mater. Chem. 2011, 21, 887-892.
spectrophotometer. BaSO4 was used as a reflectance standard. Room-
temperature photoluminescence spectra (PL) and time-resolved
photoluminescence spectra (TR-PL) were detected with
FLTCSPC fluorescence spectrophotometer.
[12] S. Yuan, Y. Zhao, W.B. Chen, C. Wu, X.Y. Wang, L.N. Zhang, Q. Wang,
ACS Appl. Mater. Interfaces 2017, 9, 21781-21790.
a Horiba
[13] Y. Zheng, T.F. Zhou, X.D. Zhao, W.K. Pang, H. Gao, S.A. Li, Z. Zhou,
H.K. Liu, Z.P. Guo, Adv. Mater. 2017, 29, 1700396-1700404.
[14] X.L. Wu, J.N. Hart, X.M. Wen, L. Wang, Y. Du, S.X. Dou, Y.H. Ng, R.
Amal, J. Scott, ACS Appl. Mater. Interfaces 2018, 10, 9342-9352.
[15] J.L. Lv, J.F. Zhang, J. Liu, Z. Li, K. Dai, C.H. Liang, ACS Sustainable
Chem. Eng. 2018, 6, 696-706.
Measurements of photocatalytic activity
Phenol and 4-NP were used as probe organic pollutants to assess the
photocatalytic activities. 400W halogen lamp (Nanjing XuJiang
A
[16] X.C. Meng, Z.S. Zhang, Appl. Catal. B: Environ. 2017, 209, 383-393.
[17] X.X. Chang, T. Wang, P. Zhang, J.J. Zhang, A. Li, J.L. Gong, J. Am.
Chem. Soc. 2015, 137, 8356-8359.
electrical and mechanical plant, Nanjing, P. R. China) with a 420 nm
cutoff filter was chosen as the visible light source. The suspension
containing 200 mg of photocatalyst and 200 mL of 10 mg·L-1 phenol or 4-
NP (1.0 gcat/Lsolution) fresh aqueous solution was continuously stirred in the
dark for 30 min to establish an adsorption/desorption equilibrium of
phenol or 4-NP solution. After this period of time, the light source was
turned on. During the reaction, 5.0 mL of samples was taken at given
time intervals and the photocatalysts were then separated by
centrifugation. The residual concentration of phenol in solution was
estimated using absorption at 507 nm by a Shimadzu 2550 UV-visible
spectrophotometer following the 4-aminoantipyrine colorimetric method.
The remaining concentration of 4-NP was monitored using a Shimadzu
2550 UV-visible spectrophotometer at the wavelength of 318 nm. TOC in
the phenol solution was recorded by automatic total organic carbon
analyzer (VARIO, Elementar, Germany).
[18] Z. Dai, F. Qin, H.P. Zhao, J. Ding, Y.L. Liu, R. Chen, ACS Catal. 2016,
6, 3180-3192.
[19] G.M. Wang, Y.C. Ling, Y. Li, Nanoscale 2012, 4, 6682-6691.
[20] J. Liao, L. Chen, M. Sun, B. Lei, X. Zeng, Y. Sun, F. Dong, Chin. J.
Catal. 2018, 4, 779-789
[21] M.L. Guan, C. Xiao, J. Zhang, S.J. Fan, R. An, Q.M. Cheng, J.F. Xie, M.
Zhou, B.J. Ye, Y. Xie, J. Am. Chem. Soc. 2013, 135, 10411-10417.
[22] Y.Y. Zhu, Q. Ling, Y.F. Liu, H. Wang, Y.F. Zhu, Appl. Catal. B: Environ.
2016, 187, 204-211.
[23] J. Ding, Z. Dai, F. Qin, H.P. Zhao, S. Zhao, R. Chen, Appl. Catal. B:
Environ. 2017, 205, 281-291.
[24] J. Ding, Z. Dai, F. Tian, B. Zhou, B. Zhao, H.P. Zhao, Z.Q. Chen, Y.L.
Liu, R. Chen, J. Mater. Chem. A 2017, 5, 23453-23459.
[25] Y.H. Lv, Y.F. Liu, Y.Y. Zhu, Y.F. Zhu, J. Mater. Chem. A 2014, 2, 1174-
1182.
[26] S.X. Yu, Y.H. Zhang, F. Dong, M. Li, T.R. Zhang, H.W. Huang, Appl.
Catal. B: Environ. 2018, 226, 441-450.
Acknowledgements
[27] M. Rycenga, C.M. Cobley, J. Zeng, W.Y. Li, C.H. Moran, Q. Zhang, D.
Qin, Y.N. Xia, Chem. Rev. 2011, 111, 3669-3712.
This work was supported by the National Natural Science
Foundation of China (No. 21663030, 21666039) and the Project
of Science & Technology Office of Shaanxi Province (No.
2018TSCXL-NY-02-01, 2015SF291) and Natural Science
Program of the Education Department of Shaanxi Province (No.
15JS119).
[28] Y.G. Sun, Chem. Soc. Rev. 2013, 42, 2497-2511.
[29] Z.W. Seh, S.H. Liu, M.C. Low, S.Y. Zhang, Z.L. Liu, A. Mlayah, M.Y.
Han, Adv. Mater. 2012, 24, 2310-2314.
[30] V. Vaianoa, M. Matarangoloa, J.J. Murciab, H. Rojasb, J.A. Navíoc,
M.C. Hidalgo, Appl. Catal. B: Environ. 2018, 225, 197-206.
[31] Y.Y. Bu, Z.Y. Chen, W.B. Li, Appl. Catal. B: Environ. 2014, 144, 622-
630.
Keywords: Oxygen vacancy-rich Ag/Bi2MoO6 • Surface oxygen
vacancy • Surface plasmon resonance • Synergistic effect •
Phenol and 4-nitrophenol degradation
[32] X.X. Chen, Y.P. Li, X.Y. Pan, D. Cortie, X.T. Huang, Z.G. Yi, Nat.
Commun. 2016, 7, 12273-12281.
[33] L.L. Wang, M. Yu, C.L. Wu, N. Deng, C. Wang, X.Q. Yao, Adv. Synth.
Catal. 2016, 358, 2631-2641.
[34] J. Di, J.X. Xia, M.X. Ji, B. Wang, S. Yin, Y. Huang, Z.G. Chen, H.M. Li,
Appl. Catal. B: Environ. 2016, 188, 376-387.
[1]
[2]
Z.G. Yi, J.H. Ye, N. Kikugawa, T. Kako, S.X. Ouyang, H.S. Williams, H.
Yang, J.Y. Cao, W.J. Luo, Z.S. Li, Y. Liu, R.L. Withers, Nat. Mater.
2010, 9, 559-564.
[35] X.N. Wang, R. Long, D. Liu, D. Yang, C.M. Wang, Y.J. Xiong, Nano
Energy 2016, 24, 87-93.
S. J. A. Moniz, J. Tang, ChemCatChem, 2015, 7, 1659-1667..
[36] C.C. Li, T. Wang, Z.J. Zhao, W.M. Yang, J.F. Li, A. Li, Z.L. Yang, G.A.
Ozin, J.L. Gong, Angew. Chem. Int. Ed. 2018, 19, 5376-5380.
This article is protected by copyright. All rights reserved.

10.1002/chem.201804267
Chemistry - A European Journal
FULL PAPER
[37] Y.Y. Duan, M. Zhang, L. Wang, F. Wang, L.P. Yang, X.Y. Li, C.Y.
Wang, Appl. Catal. B: Environ. 2017, 204, 67-77.
[56] X. Feng, W.D. Zhang, Y.J. Sun, H.W. Huang, F. Dong, Environ. Sci.:
Nano 2017, 4, 604-612.
[38] J.W. Wan, W.X. Chen, C.Y. Jia, L.R. Zheng, J.C. Dong, X.S. Zheng, Y.
Wang, W.S. Yan, C. Chen, Q. Peng, D.S. Wang, Y.D. Li, Adv. Mater.
2018, 30, 1705369-1705377.
[57] Z.F. Jiang, W.M. Wan, W. Wei, K.M. Chen, H.M. Li, P.K. Wong, J.M.
Xie, Appl. Catal. B: Environ. 2017, 204, 283-295.
[58] F.C. Lei, Y.F. Sun, K.T. Liu, S. Gao, L. Liang, B.C. Pan, Y. Xie, J. Am.
Chem. Soc. 2014, 136, 6826-6829.
[39] Y.C. Deng, L. Tang, G.M. Zeng, C.Y. Feng, H.R. Dong, J.J. Wang, H.P.
Feng, Y.N. Liu, Y.Y. Zhou, Y. Pang, Environ. Sci.: Nano 2017, 4, 1494-
1511.
[59] G.S. Huang, X.L. Wu, Y.F. Mei, X.F. Shao, G.G. Siu, J. Appl. Phys.,
2003, 93, 582-585.
[40] D.J. Wang, H.D. Shen, L. Guo, C. Wang, F. Fu, Y.C. Liang, Appl. Surf.
Sci. 2018, 436, 536-547.
[60] L.Q. Jing, Y.G. Xu, S.Q. Huang, M. Xie, M.Q. He, H. Xu, H.M. Li, Q.
Zhang, Appl. Catal. B: Environ. 2016, 199, 11-22.
[41] Y.S. Xu, W.D. Zhang, Dalton Trans. 2013, 42, 1094-1101.
[42] Y.H. Lv, W.Q. Yao, R.L. Zong, Y.F. Zhu, Sci. Rep. 2016, 6, 19347.
[43] H.Y. Mou, C.X. Song, Y.H. Zhou, B. Zhang, D.B. Wang, Appl. Catal. B:
Environ. 2018, 221, 565-573.
[61] J.J. Yang, D.M. Chen, Y. Zhu, Y.M. Zhang, Y.F. Zhu, Appl. Catal. B:
Environ. 2017, 205, 228-237.
[62] H.W. Huang, X.W. Li, J.J. Wang, F. Dong, P.K. Chu, T.R. Zhang, Y.H.
Zhang, ACS Catal. 2015, 5, 4094-4103.
[44] H.P. Li, J.Y. Liu, W.G. Hou, N. Du, R.J. Zhang, X.T. Tao, Appl. Catal. B:
Environ. 2014, 160-161, 89-97.
[63] W.W. He, H.M. Jia, W.G. Wamer, Z. Zheng, P.J. Li, J.H. Callahan, J.J.
Yin, J. Catal. 2014, 320, 97-105.
[45] C. Zhang, Y.F. Zhu, Chem. Mater. 2005, 17, 3537-3545.
[46] J.G. Hou, S.Y. Cao, Y.Z. Wu, F. Liang, Y.F. Sun, Z.S. Lin, L.C. Sun,
Nano Energy 2017, 32, 359-366.
[64] P.X. Qiu, C.M. Xu, H. Chen, F. Jiang, X. Wang, R.F. Lu, X.R. Zhang,
Appl. Catal. B: Environ. 2017, 206, 319-327.
[65] P.H. Shao, Z.J. Ren, J.Y. Tian, S.S. Gao, X.B. Luo, W.X. Shi, B.Y. Yan,
J. Li, F.Y. Cui, Chem. Eng. J. 2017, 323, 64-73.
[47] W.T. Bi, C.M. Ye, C. Xiao, W. Tong, X.D. Zhang, W. Shao, Y. Xie,
Small 2014, 10, 2820-2825.
[66] Y.H. Lv, Y.Y. Zhu, Y.F. Zhu, J. Phys. Chem. C 2013, 117, 18520-18528.
[67] D. Chen, F. Niu, L.S. Qin, S. Wang, N. Zhang, Y.X. Huang, Sol. Energy
Mater. Sol. Cells 2017, 171, 24-32.
[48] H. Li, J. Li, Z.H. Ai, F.L. Jia, L.Z. Zhang, Angew. Chem. Int. Ed. 2018,
57, 122-138.
[49] X.B. Zhang, L. Zhang, J.S. Hu, X.H. Huang, RSC Adv. 2016, 6, 32349-
32357.
[68] Q.J. Xiang, J.G. Yu, B. Cheng, H.C. Ong, Chem. Asian J. 2010, 5,
1466-1474.
[50] Y.C. Miao, G.F. Pan, Y.N. Huo, H.X. Li, Dyes Pigm. 2013, 99, 382-389.
[51] Z. Wei, Y.F. Liu, J. Wang, R.L. Zong, W.Q. Yao, J. Wang, Y.F. Zhu,
Nanoscale 2015, 7, 13943-13950.
[69] L.G. Devi, R. Kavitha, Appl. Surf. Sci. 2016, 360, 601-622.
[70] B. Yuan, C.H. Wang, Y. Qi, X.L. Song, K. Mu, P. Guo, L.T. Meng, H.M.
Xi, Colloids and Surfaces A: Physicochem. Eng. Aspects 2013, 425,
99-107.
[52] Y.Z. Wang, X.Y. Huang, K.Q. Wang, L.L. Zhang, B. Wang, Z.B. Fang, Y.
Zhao, F. Gao, P. Liu, W.H. Feng, J. Mater. Chem. A 2018, 6, 9200-
9208.
[71] X.L. Hu, J. Tian, Y.J. Xue, Y.J. Li, H.Z. Cui, ChemCatChem 2017, 9,
1511-1516.
[53] Z.Y. Ma, P.H. Li, L.Q. Ye, Y. Zhou, F.Y. Su, C.H. Ding, H.Q. Xie, Y. Bai,
P.K. Wong, J. Mater. Chem. A 2017, 5, 24995-25004.
[54] C.W. Tan, G.Q. Zhu, M. Hojamberdiev, K. Okada, J. Liang, X.C. Luo, P.
Liu, Appl. Catal. B: Environ. 2014, 152-153, 425-436.
[55] T. Yan, Q. Yan, X.D. Wang, H.Y. Liu, M.M. Li, S.X. Lu, W.G. Xu, M.
Sun, Dalton Trans. 2015, 44, 1601-1611.
[72] X. Ding, K. Zhao, L.Z. Zhang, Environ. Sci. Technol. 2014, 48, 5823-
5831.
[73] Z.F. Jia, F.M. Wang, F. Xin, B.Q. Zhang, Ind. Eng. Chem. Res. 2011,
50, 6688-6694.
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A novel oxygen vacancy-rich
Ag/Bi2MoO6 was firstly fabricated via a
reliable solvothermal process
Huidong Shen,a† Wenwen Xue,a† Feng
Fu,*a Jiefang Sun,b,c, Yanzhong Zhen,a
Danjun Wang,*a Bing Shao, *c and
Junwang Tang*b
combined with impregnation-
calcination approach, which exhibited
excellent visible-light-driven
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photocatalytic performances for both
phenol and 4-nitrophenol degradation
due to synergistic effect stemming
from the integration of individual
advantages of SOVs, metallic Ag
nanoparticles and BMO.
Efficient degradation of phenol and 4-
nitrophenol by surface oxygen vacancies
and plasmonic silver co-modified
Bi2MoO6 photocatalysts
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Author(s), Corresponding Author(s)*
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