Fabrication of a heterostructured Ag/AgCl/Bi2MoO6 plasmonic photocatalyst with efficient visible light activity towards dyes

Article abstract of DOI:10.1039/c4ra15821k

A ternary Ag/AgCl/Bi₂MoO₆ plasmonic photocatalyst was successfully fabricated through a two-step synthesis method. The obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and ultraviolet-visible diffuse reflectance spectroscopy (DRS). The DRS results showed that the visible light absorption of the Ag/AgCl/Bi₂MoO₆ composite had been greatly enhanced owing to the surface plasmonic resonance (SPR) of Ag⁰ particles. The SEM and TEM images showed that the obtained flower-like Bi₂MoO₆ microspheres were composed of nanoplates, on the surface of which Ag/AgCl particles were distributed. In the photocatalytic degradation of dyes, Ag/AgCl/Bi₂MoO₆ photocatalysts exhibited significantly enhanced activities compared with Bi₂MoO₆. It was also found that the components of Ag/AgCl/Bi₂MoO₆ have a great influence on the activity. Controlled experiments proved that the degradation of pollutants over Ag/AgCl/Bi₂MoO₆ was mainly ascribed to the strong oxidation ability of photo-generated holes. On the basis of band structure analysis and active species trapping experimental results, a photocatalytic mechanism is also proposed. This journal is

Full text of DOI:10.1039/c4ra15821k

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Fabrication of a heterostructured Ag/AgCl/
Bi2MoO6 plasmonic photocatalyst with efficient
Cite this: RSC Adv., 2015, 5, 17245
visible light activity towards dyes
a
ab
Tao Yan,a Mengmeng Li,c Liangguo Yan,a Dong Weia
*
Qing Yan, Meng Sun,
a
*
and Bin Du
A ternary Ag/AgCl/Bi2MoO6 plasmonic photocatalyst was successfully fabricated through a two-step
synthesis method. The obtained samples were characterized by X-ray diffraction (XRD), scanning
electron microscopy (SEM), transmission electron microscopy (TEM), and ultraviolet-visible diffuse
reflectance spectroscopy (DRS). The DRS results showed that the visible light absorption of the Ag/AgCl/
Bi2MoO6 composite had been greatly enhanced owing to the surface plasmonic resonance (SPR) of Ag0
particles. The SEM and TEM images showed that the obtained flower-like Bi2MoO6 microspheres were
composed of nanoplates, on the surface of which Ag/AgCl particles were distributed. In the
photocatalytic degradation of dyes, Ag/AgCl/Bi2MoO6 photocatalysts exhibited significantly enhanced
activities compared with Bi2MoO6. It was also found that the components of Ag/AgCl/Bi2MoO6 have a
great influence on the activity. Controlled experiments proved that the degradation of pollutants over
Ag/AgCl/Bi2MoO6 was mainly ascribed to the strong oxidation ability of photo-generated holes. On the
basis of band structure analysis and active species trapping experimental results, a photocatalytic
mechanism is also proposed.
Received 5th December 2014
Accepted 2nd February 2015
DOI: 10.1039/c4ra15821k
www.rsc.org/advances
Therefore, it is an urgent topic to develop visible-light driven
photocatalysts for the practical utilization of solar energy.
Introduction
Recently, noble metals with localized surface plasmonic
resonance properties have attracted considerable attention
because of their strong absorption of visible light.12–15 Among
which, Ag/AgCl-based composites have exhibited the most
outstanding photocatalytic activity and stability.16,17 Huang et al.
reported the synthesis of Ag/AgCl photocatalyst using ion-
exchange method, which exhibited efficient activity for the
degradation of methyl orange.18 In order to further improve its
activity, many researchers have focused on the morphology-
controlled fabrication of Ag/AgCl.16,19 Therefore, many
Over the past years, the water pollution problem becomes more
and more severe because of the rapid development of industri-
alization and urbanization. The organic pollutants in contami-
nated wastewater are usually found to be toxic synthetic dyes,
which are harmful to the environment and human health. Thus,
great efforts have been made to explore green and economic
methods for treating the organic pollutants discharged into the
environment. For example, numerous studies have focused on
the photocatalytic degradation of stable organic pollutants,1–4
which are difficult to remove using traditional treatment
methods. TiO2, as an efficient photocatalyst, has been widely
studied and applied in the photocatalysis eld because of its
unique surface structure characteristics, high chemical stability,
nontoxicity, and prefect photocatalytic activity.5–8 However, its
wide band gap (3.2 eV for anatase TiO2) and low quantum effi-
ciency have greatly hindered its practical application.9–11
Ag/AgCl-based
hierarchical
nanostructures,
such
as
Ag/AgCl/WO3,20 AgCl/Ag/TaON,21 and Ag/AgCl/Bi20TiO32,22 have
been fabricated and exhibited efficient activity. Furthermore,
Ag/AgCl has also been successfully used to combine with ower-
like semiconductors, such as Bi2WO6 (ref. 23) and BiOBr,24 and
the photocatalytic activity has been greatly improved by the
synergy effect of SPR effect driving from Ag nanoparticles and
light scattering effect driving from ower-like structure.
aSchool of Resources and Environment, University of Jinan, Shandong Provincial
Engineering Technology Research Center for Ecological Carbon Sink and Capture
Utilization, Jinan 250022, P. R. China. E-mail: smlcu@163.com; bindu61@gmail.
com; Fax: +86-531-82765969; Tel: +86-531-82769235
In this work, Ag/AgCl has also been used to couple with a
ower-like Bi2MoO6 photocatalyst via
a two-step route.
Bi2MoO6, with a narrow band gap of 2.5–2.8 eV, has been
reported as an excellent photocatalyst from the viewpoint of
utilizing visible light. It could serve as a solar-energy-conversion
material for water splitting and the decomposition of organic
compounds under visible-light irradiation.25–27 Unfortunately,
bFujian Provincial Key Laboratory of Photocatalysis-State Key Laboratory Breeding
Base, FuzhouUniversity, Fuzhou 350002, P. R. China
cSchool of Civil Engineering and Architecture, University of Jinan, Jinan 250022, P. R.
China
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the rapid recombination of electrons and holes aer photo- reectance spectroscopy (DRS) were measured at room temper-
excitation leads to the low efficiency of Bi2MoO6. Thus, it was ature in the range of 200–700 nm on a UV-vis spectrophotometer
used to couple with Ag/AgCl to enhance the visible light (Cary 500 Scan Spectrophotometers, Varian, and U.S.A) equip-
responsive photocatalytic activity. The obtained Ag/AgCl/Bi2- ped with an integrating sphere attachment. X-ray photoelectron
MoO6 composites have exhibited efficient activities in photo- spectroscopy (XPS) analysis was conducted on an ESCALAB
catalytic decomposing of Rhodamine B (RhB) dye under visible 250 photoelectron spectroscopy (Thermo Fisher Scientic) at
light illumination. Aer 40 min of reaction, the degradation 3.0 ꢂ 10ꢁ10 mbar using Al Ka X-ray beam (1486.6 eV).
ratio of RhB was up to 99%. The activity improvement should be
ascribed to the SPR effect of Ag0 and the formation of hetero-
junction, which respectively improved the visible light absorp-
Evaluation of photocatalytic performance
Photocatalytic reactions were conducted in a customized
reactor. The visible light photocatalytic activity of Ag/AgCl/
Bi2MoO6 composites were evaluated by the degradation of dyes,
tion and separation efficiency of photo-generated carriers.
Experimental section
a 300 W xenon lamp (PLS-SXE300C, Beijing Perfect Light Co.
Ltd., Beijing) with two cutoff lters (420 nm < l < 800 nm) has
been used as light source. In each experiment, 100 mg of pho-
tocatalyst was added into 100 mL of RhB dye aqueous solution
(2 ꢂ 10ꢁ5 M). Before irradiation, the suspensions were
magnetically stirred in dark for 60 min to ensure the estab-
lishment of an adsorption–desorption equilibrium between the
photocatalyst and dye. During reaction under visible light irra-
diation, 3 mL of suspension was sampled and centrifuged to
remove the photocatalyst particles at given time intervals. The
resulting clear liquor was analyzed on a PerkinElmer UV-vis
spectrophotometer (model: Lambda 35) to record the concen-
tration changes of dyes. The percentage of degradation is
reported as C/C0. C is the absorption of RhB absorption spec-
trum at 554 nm. And C0 is the absorption of the starting
concentration when adsorption–desorption equilibrium is
achieved.
Synthesis of ower-like Bi2MoO6 microspheres
All chemical reagents were analytical grade and used without
further purications. For the synthesis of ower-like Bi2MoO6
microspheres, 2 mmol of Bi(NO3)3$5H2O and 1 mmol of
(NH4)6MoO4$4H2O were dissolved in 20 mL of ethylene glycol
and stirred for 120 min. Then 50 mL of ethanol was added into
it. The mixture was stirred for another 10 min. The resulting
solution was transferred into a ꢀ100 mL Teon-lined stainless
steel autoclave and kept at 160 C for 12 h. Subsequently, the
autoclave was cooled to room temperature naturally. The
obtained samples were ltered, washed with deionized water for
ꢀ
several times, and nally dried at 80 C in air.
Synthesis of heterostructured Ag/AgCl/Bi2MoO6 composites
In a typical synthesis of Ag/AgCl/Bi2MoO6 composites, 0.4 g
of Bi2MoO6 powders and 0.075
g of hexadecyltrimethyl-
ammoniumchloride (CTAC) were added into 200 mL of deion-
ized water and stirred for 60 min. Then 2.0 mL of 0.1 M AgNO3
was quickly added into the above mixture. During this process,
the excessive surfactant CTAC adsorbed onto the surface of
Bi2MoO6 and induced Clꢁ to react with Ag+ to produce AgCl
particles in the suspension. Aer 60 min of continuous stirring,
the resulting suspension was then exposed to UV-vis light
emitted by a 300 W Xe lamp for a certain time to deoxidize Ag+ to
Ag0 on the surface of AgCl particles. The suspension was ltered,
Results and discussion
Structural characterization
Fig. 1 shows the XRD patterns of the obtained Bi2MoO6, Ag/AgCl
and Ag/AgCl/Bi2MoO6 photocatalysts. As we can see, all the
diffraction peaks of the obtained Bi2MoO6 sample located at
10.9, 23.6, 28.2, 32.5, 36.0, 46.8, 55.4, and 58.4ꢀ can be assigned
to orthorhombic-phase Bi2MoO6 (JCPDS no. 76-2388). No
ꢀ
washed with deionized water, and dried at 80 C for 12 h. The
illumination time has great inuence on the reduction of Ag+,
the obtained samples illuminated for 10, 30, and 50 min were
marked as AAB-10, AAB-30, and AAB-50, respectively.
Characterization of photocatalysts
X-ray diffraction (XRD) patterns of the obtained products were
recorded on a Bruker D8 Advance X-ray diffractometer under
the conditions of generator voltage ¼ 40 kV; generator current ¼
˚
40 mA; divergence slit ¼ 1.0 mm; Cu Ka (l ¼ 1.5406 A). The
morphologies and microstructures were examined with a
Hitachi S-4800 scanning electron microscopy (SEM). The
transmission electron microscopy (TEM) and high-resolution
transmission electron microscopy (HRTEM) images were
measured by a JEOL model JEM 2010 EX instrument at an
accelerating voltage of 200 kV. Carbon-coated copper grid was
Fig. 1 XRD patterns of pure Bi2MoO6, Ag/AgCl, and Ag/AgCl/Bi2MoO6
used as the sample holder. The ultraviolet-visible diffuse composites.
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impurity has been detected from the diffraction patterns. For the microsphere morphology, and the average diameter of the
obtained Ag/AgCl sample, ve characteristic diffraction peaks microspheres was about 1.5 mm. The HRTEM image showing
located at 27.8, 32.2, 46.2, 54.8, and 57.5ꢀ have been observed, clear lattice planes was shown in Fig. 3b. The uniform fringe with
which indexed to the (111), (200), (220), (311), and (222) planes of an interval of 0.327 nm was indexed to the (140) facet of
cubic phase AgCl (JCPDS no. 31-1238). In addition, a very weak Bi2MoO6. Another set of clear fringes with an inter-planer
diffraction peak of cubic phase Ag (JCPDS no. 65-2871) located at spacing of 0.277 nm corresponded to the (200) lattice plane of
38.1ꢀ has also been observed, this result was in accordance with AgCl, while the fringe of 0.204 nm could be ascribed to the (200)
the experimental phenomena that the color of AgCl changed facet of Ag. Fig. 3b implies that obvious interfaces between
from white to gray during light irradiation. As for the Ag/AgCl/ Bi2MoO6 and Ag/AgCl can be observed. This result suggests that
Bi2MoO6 photocatalysts, it is difficult to distinguish which the heterojunction is actually formed at the interfaces of those
diffraction peak was ascribed to Ag/AgCl or Bi2MoO6 because of materials. The elemental mapping has been performed to
the overlapping of their main diffraction peaks (see Fig. 1).
investigate the distribution of Ag/AgCl over Ag/AgCl/Bi2MoO6
composites. Fig. 3 also displays the elemental mapping images
for the Ag/AgCl/Bi2MoO6 sample. The cyan, red, and yellow-
brown color of the images was respectively acquired at the
K-line spectra of Ag, Cl, and O elements, while that for the
magenta and green color was respectively acquired at the L-line
spectra of Bi and Mo elements. This result provides solid
evidence that Ag/AgCl were successfully combined with Bi2MoO6.
Morphology and microstructure
The morphologies of Bi2MoO6, Ag/AgCl and Ag/AgCl/Bi2MoO6
composites have been characterized by SEM. Fig. 2a shows that
the obtained Bi2MoO6 exhibited ower-like microsphere
morphology. The microspheres with average diameter of 1–2 mm
were composed of large amount of nanoplates. Meanwhile,
Fig. 2b shows that the obtained Ag/AgCl exhibited particle
morphology with smaller sizes of 400–500 nm compared with
Bi2MoO6. Even smaller Ag nanoparticles (average diameter of 50
nm) have also been observed on the surface of AgCl. Fig. 2c
shows that when Ag/AgCl was coupled with Bi2MoO6, the
Ag/AgCl particles would be decorated on the surfaces of ower-
like Bi2MoO6 structures. The element composition of the
Ag/AgCl/Bi2MoO6 composites has been measured using energy-
dispersive X-ray (EDX) spectroscopy, and the corresponding
result was shown in Fig. 2d. It shows that the composites are
mainly consisted of Bi, O, Mo, Cl, and Ag elements.
DRS and BET surface analysis
The UV-vis diffuse reectance spectra (DRS) have been per-
formed to investigate the optical properties of the as-prepared
samples. As shown in Fig. 4a, the absorption edge of Bi2MoO6
was estimated to 485 nm showing a strong absorption in the UV
range, while Ag/AgCl exhibited strong light absorption in the
visible light region. When Ag/AgCl combined with Bi2MoO6, the
The morphology and nanostructures of Ag/AgCl/Bi2MoO6
composite were further investigated by TEM and HRTEM.
Fig. 3a shows that the Ag/AgCl/Bi2MoO6 composite possessed
Fig. 3 TEM and HRTEM images of the as-prepared sample: (a) TEM
micrographs of Ag/AgCl/Bi2MoO6 composites, (b) HRTEM image of
Fig. 2 SEM images of the as-prepared sample: (a) pure Bi2MoO6, (b) Ag/AgCl/Bi2MoO6 composites showing the formation of heterojunc-
Ag/AgCl, (c) Ag/AgCl/Bi2MoO6 composite, and (d) corresponding EDX tion structure, and corresponding elemental mapping images of Ag, Cl,
spectrum for Ag/AgCl/Bi2MoO6 composite.
Bi, O, and Mo elements.
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absorption edges of Ag/AgCl/Bi2MoO6 composites were red-
shied. The visible light adsorption has also been greatly
enhanced compared with pure Bi2MoO6. Fig. 4b shows the
nitrogen adsorption isotherm for the as-synthesized AAB-30 and
Bi2MoO6 sample, which exhibited the stepwise adsorption and
desorption (type-IV isotherm). The pore-size distribution plot
(inset) showed that the samples had exhibited a mean pore
diameter of 16 nm with a narrow distribution of pore size. The
BET specic surface area of AAB-30 was 50.4 m2 gꢁ1, larger than
that of Bi2MoO6 (35.7 m2 gꢁ1).
Photocatalytic activity tests
To investigate the inuences of Ag/AgCl on the photocatalytic
activities, Ag/AgCl/Bi2MoO6 composites prepared under
different conditions have been used to decompose RhB in water
under visible light irradiation. Fig. 6 shows the photocatalytic
degradation results of RhB over pure Bi2MoO6, Ag/AgCl, and
Ag/AgCl/Bi2MoO6 composites. As we can see, all of the
Ag/AgCl/Bi2MoO6 composites have exhibited efficient activities,
which were higher than that for pure Bi2MoO6 or Ag/AgCl. Aer
45 min of visible light irradiation, the degradation ratio of RhB
over Ag/AgCl and Bi2MoO6 was only about 70 and 20%,
respectively. As for the Ag/AgCl/Bi2MoO6 composites, the AAB-
30 sample exhibited the best activity, and the degradation
ratio of RhB was nearly to 100%. That is to say, the amount of
Ag/AgCl has great inuence on the photocatalytic activity. Fig. 7
shows the temporal evolution of the spectral changes of RhB
mediated by AAB-30. It exhibited that the absorption peak of
RhB located at 554 nm gradually blue-shied to 499 nm within
30 min of reaction. This hypsochromic shi of absorption
maximum was caused by the N-deethylation of RhB during
irradiation, which has been conrmed by Watanabe and
co-workers.31,32 Aer that the peak decreased in the following
degradation process and nally disappeared.
XPS characterization
The XPS characterization was performed to investigate the
chemical composition of Ag/AgCl/Bi2MoO6 sample and identify
the chemical state of the Ag element. The results have been
added into the revised manuscript. Fig. 5a shows the XPS survey
spectra of AAB-30 sample. As we can see, the sample contains Bi,
Mo, O, Ag, Cl and C elements. The C element should be
attributed to the adventitious hydrocarbon from the XPS
instrument itself. Fig. 5b shows that Ag 3d peak locates at the
binding energy of 367.2 eV. Compared with that for bulk Ag
(368.2 eV), it shows a peak shis to the lower binding energy.
Very similar phenomenon has also been reported,28–30 and the
shi of the binding energy of Ag 3d should be primarily
attributed to the interactions among the Ag, AgCl and Bi2MoO6.
The reaction kinetics study shows that the photocatalytic
degradation of RhB dye over those photocatalysts followed
pseudo-rst-order kinetic model. The rate constant (k) can be
calculated by the formula of ꢁln(C/C0) ¼ kt.33 k is kinetic
constant (minꢁ1), while t represents the irradiation time (min).
Fig. 4 (a) UV-vis diffuse reflectance spectra of Bi2MoO6, Ag/AgCl, and
Ag/AgCl/Bi2MoO6 composites. (b) N2 adsorption–desorption isotherm
and the pore size distribution plot for AAB-30 and Bi2MoO6. The pore
size distribution was estimated from the desorption branch of the Fig. 5 XPS spectra of Ag/AgCl/Bi2MoO6 photocatalyst (a) survey
isotherm.
spectrum and (b) Ag 3d.
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Fig. 6 Degradation rates of RhB under visible light irradiation using
Bi2MoO6, Ag/AgCl, and Ag/AgCl/Bi2MoO6 composites.
Fig. 8 showed the kinetic plots for RhB degradation over
different photocatalysts. The rate constant of the photocatalytic
degradation of RhB over AAB-30 photocatalyst is 0.1295 minꢁ1
,
which is much higher than that of Bi2MoO6 (0.0036 minꢁ1),
Ag/AgCl (0.0200 minꢁ1), or other Ag/AgCl/Bi2MoO6 composites
(0.0435 and 0.0639 minꢁ1 for AAB-10 and AAB-50, respectively).
Thus, Ag/AgCl/Bi2MoO6 composite photocatalysts exhibited the
enhanced photocatalytic activities, among of which AAB-30 was
the most efficient. That is to say, the irradiation time played an
important role in improving the activities, with too long or too
short illumination time should be avoided. With a shorter
illumination time as to 10 min, only a very small amount of Ag0
would be produced over the sample, leading to weak light
absorption ability and a lower activity. However, when the
illumination time was longer than 50 min, too much of AgCl
would be photo-reduced to form Ag/AgCl nano-clusters. The
Ag/AgCl clusters might further agglomerated and shaded the
active sties on the surface of Bi2MoO6.34,35 Therefore, the
degradation rates would be depressed accordingly.
Fig. 8 (a) Plots of ꢁln(C/C0) vs. the irradiation time for RhB aqueous
solution over different samples under visible light irradiation (420 nm
< l < 800 nm); (b) the kinetic constant k (minꢁ1) for different samples.
was accordingly improved when the amount of AAB-30 added
was increased from 0.025 to 0.100 g, and nearly 100% of RhB
has been decomposed within 30 min of reaction. The activity
increased with photocatalyst concentration enhancement was a
characteristic of heterogeneous catalysis. This phenomenon
can be rationalized in relation to the amount of surface active
cites as well as the light penetration into the suspensions.
The stability of a photocatalyst is very important for its
practical application. In this work, Ag/AgCl/Bi2MoO6 composite
photocatalyst was recycled for four times in the photocatalytic
degradation experiments. Fig. 10 showed the life-time test
results. The photocatalytic activity of AAB-30 composite only
deteriorated slightly in the reuse cycles. Fig. 11 showed the XRD
patterns of AAB-30 composites before and aer RhB degrada-
tion. It illustrated that the crystal structure of the AAB-30 pho-
tocatalyst had not changed during the photocatalytic reaction.
In order to study the degradation mechanism of RhB over
AAB-30 photocatalyst, diagnostic experiments have also been
performed with different active scavenger added. Herein, tert-
butanol (TBA), p-benzoquinone (PBQ), and oxalate was respec-
tively used as hydroxyl radical, superoxide radical, and hole
scavengers.36,37 Fig. 12 presented the inuences of active species
(such as cOH, cO2ꢁ, and hVB+) on the degradation rates of RhB.
Fig. 9 showed the photocatalytic degradation of RhB at
different dosages of AAB-30 photocatalyst under visible light
irradiation. It was obviously that the degradation rate of RhB
Fig. 7 The absorption spectra of RhB in the presence of AAB-30 under
exposure to visible light (420 nm < l < 800 nm).
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Fig. 11 XRD patterns of AAB-30 before and after photocatalytic
degradation of RhB.
Fig. 9 Photocatalytic degradation of RhB with different dosages of
AAB-30 under the visible light (420 nm < l < 800 nm) irradiation.
enhancement mechanism of Ag/AgCl/Bi2MoO6 photocatalyst
was proposed (shown in Scheme 1). Bi2MoO6 possessed a band
gap of 2.58 eV, and the conduction band (CB) and valence band
(VB) energy levels are ca. ꢁ0.13 and 2.45 eV (vs. NHE).26 The
positive potential endows the VB holes of Bi2MoO6 with high
oxidation ability. That is to say, the holes generated over could
directly react with pollutants absorbed on its surface. As for
Ag/AgCl, it has been reported as an efficient visible light pho-
tocatalyst result in the strong surface plasmon resonance of
metallic Ag0 species. With a large band gap of 3.26 eV, AgCl
cannot be excited by visible light, but its lower CB potential
(ꢁ0.06 vs. NHE) enabled the plasmon-induced electrons over Ag
In the presence of AO (1.0 mL added), the peak blue-shi of RhB
became very slow during the degradation process, meaning that
the N-deethylation of RhB becoming more difficult. What was
worse, the blue-shi absorption peak of RhB did not disappear
aer 90 min of reaction, but observed with relatively higher
peak intensity. When PBQ was added into the system, a very
similar situation was observed, but the degradation rate was
further decreased. However, when certain amount of TBA was
added into the system, it could hardly affect the N-deethylation
process and degradation rates of RhꢁB. That is to say, during the
+
degradation process of RhB, cO2 and hVB played more
important role compared with other active species.
As discussed above, Ag/AgCl/Bi2MoO6 composites have
exhibited enhanced photocatalytic activity for decomposing
RhB dye compared with pure Bi2MoO6. This activity enhance-
ment should be ascribed to two main reasons, including their
suitable band potentials and the SPR effect of Ag. According to
the band gap structure of Ag/AgCl/Bi2MoO6 and the effects of
scavengers, a possible pathway for the photocatalytic activity
Fig. 12 The absorption spectra of RhB in the presence of AAB-30
Fig. 10 Photocatalytic performances of AAB-30 composite photo- under exposure to visible light (420 nm < l < 800 nm) with different
catalyst in the first four reuse cycles.
active scavenger added, such as AO, PBQ, and TBA.
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to transfer to the CB of AgCl.26 On the other hand, metallic Ag
specie could strongly absorb visible light because of its surface
plasmon resonance effect, which was also benecial for activity
enhancement. The electrons transferred to the surface of AgCl
ꢁ
could be further captured by dissolved oxygen to produce cO2
.
Because the CB potential of Bi2MoO6 was more negative than
that of Ag+/Ag (+0.799 eV vs. NHE), the CB electrons over
Bi2MoO6 should transfer to the VB of metallic Ag and captured
by the holes generated, leaving the VB holes generated over
Bi2MoO6 directly to react with surface absorbed pollutants.
17 Y. Tang, Z. Jiang, G. Xing, A. Li, P. D. Kanhere, Y. Zhang,
T. C. Sum, S. Li, X. Chen, Z. Dong and Z. Chen, Adv. Funct.
Mater., 2013, 23, 2932.
Conclusions
Novel visible-light responsive Ag/AgCl/Bi2MoO6 plasmonic
photocatalyst was successfully fabricated through a two-step
synthesis method. Aer combination of Ag/AgCl, the
18 P. Wang, B. Huang, X. Qin, X. Zhang, Y. Dai, J. Wei and
M. H. Whangbo, Angew. Chem., Int. Ed., 2008, 47, 7931.
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22 J. Hou, Z. Wang, C. Yang, W. Zhou, S. Jiao and H. Zhu,
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Ag/AgCl/Bi2MoO6 photocatalyst possessed
a
signicantly
enhanced visible light activity in decomposing dyes. The highest
degradation efficiency was observed for the AAB-30 sample. The
activity enhancement was mainly attributed to the SPR effect of
Ag0, and high separation efficiency of electron–hole pairs on
their heterojunction interfaces.
A possible photocatalytic
degradation mechanism was proposed based on the band
potentials of Ag/AgCl and Bi2MoO6. This method was expected to
be extended for other Ag/AgCl loaded materials, which might
have potential applications in removing pollutants.
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Acknowledgements
This work was nancially supported by the Scientic Research
Reward Fund for Excellent Young and Middle-Aged Scientists of
Shandong Province (BS2012HZ001), National Natural Science
Foundation of China (no. 21103069, 21075052, 21175057, and
40672158), and Scientic Research Foundation for Doctors of
University of Jinan (XBS1037 and XKY1043).
28 Y. H. Zheng, L. R. Zheng, Y. Y. Zhan, X. Y. Lin, Q. Zheng and
K. M. Wei, Inorg. Chem., 2007, 46, 6980.
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