Design and construction of the sandwich-like Z-scheme multicomponent CdS/Ag/Bi2MoO6 heterostructure with enhanced photocatalytic performance in RhB photodegradation

Article abstract of DOI:10.1039/c6nj01893a

A sandwich-like Z-scheme tricomponent CdS/Ag/Bi₂MoO₆ photocatalytic system was rationally designed and successfully fabricated, in which Ag was loaded onto Bi₂MoO₆ microspheres by a facile photoreduction method and CdS was subsequently deposited onto the surface of Bi₂MoO₆ and Ag/Bi₂MoO₆ through a deposition-precipitation method. During this process, a series of Ag/Bi₂MoO₆ and CdS/Bi₂MoO₆ were also prepared. All the composites were characterized by XRD, TEM, SEM, EDX, XPS, UV-vis DRS, and IR spectra to confirm the successful integration of Ag or (and) CdS with Bi₂MoO₆, the alteration of morphology and the formation of a new phase before and after Ag or (and) CdS loading. The degradation of rhodamine B (RhB) dye under visible light irradiation (>420 nm) revealed that the CdS/Ag/Bi₂MoO₆ composite exhibited a highly visible-light-responsive photocatalytic performance compared to single Bi₂MoO₆ or CdS and dual Ag/Bi₂MoO₆ or CdS/Bi₂MoO₆. The enhanced photocatalytic performance of CdS/Ag/Bi₂MoO₆ was ascribed to its special structure-a typical Z-scheme photocatalytic system, in which Ag nanoparticles directly connected to the surface of CdS and Bi₂MoO₆ to form a solid-solid interface (ohmic contact), acting as a conductor that greatly shortened the distance for photogenerated electron transfer and combined photogenerated electrons from the CB of Bi₂MoO₆ with the photogenerated holes from the VB of CdS through ohmic contact, and thereby led to the efficient separation of photogenerated electrons and holes and showed stable and strong reducibility and oxidizability. Moreover, the surface plasmon resonance effect of metallic Ag nanoparticles also played an important role in the enhanced photocatalytic performance of RhB degradation under visible light irradiation. Furthermore, investigations on photoluminescence and photoelectrochemical properties also demonstrated indirectly the highly efficient separation of photogenerated electrons and holes in the Z-scheme CdS/Ag/Bi₂MoO₆ photocatalytic system. This new Z-scheme photocatalytic system will be applied to more photoreactions in further exploration.

Full text of DOI:10.1039/c6nj01893a

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New Journal of Chemistry
ARTICLE
Design and Construction of the Sandwich-Like Z-scheme
Multicomponent CdS/Ag/Bi MoO Heterostructure with
Enhanced Photocatalytic Performance in RhB
2
6
Received 00th January 20xx,
Accepted 00th January 20xx
Photodegradation
DOI: 10.1039/x0xx00000x
a
a
a
a
b
Danjun Wang, Huidong Shen, Li Guo, Feng Fu* and Yucang Liang*
A sandwichꢀlike Zꢀscheme tricomponent CdS/Ag/Bi MoO photocatalytic system was rationally designed and
successfully fabricated, in which Ag was loaded onto Bi MoO microspheres by a facile photoreduction
method and CdS was subsequently deposited onto the surface of Bi
depositionꢀprecipitation method. During this process, a series of Ag/Bi
www.rsc.org/
2
6
2
6
2
MoO
MoO
6
and Ag/Bi
and CdS/Bi
2
MoO through a
6
MoO were also
6
2
6
2
prepared. All composites were characterized by XRD, TEM, SEM, EDX, XPS, UVꢀvis DRS, and IR spectra
to confirm the successful integration of Ag or (and) CdS with Bi MoO and the alteration of morphology and
the formation of new phase before and after Ag or (and) CdS loading. The degradation of Rhodamine B (RhB)
dye under visible light irradiation (> 420 nm) revealed that CdS/Ag/Bi MoO composite exhibited a highly
visibleꢀlightꢀresponsive photocatalytic performance compared to single Bi MoO or CdS and dual
Ag/Bi MoO or CdS/Bi MoO . The enhanced photocatalytic performance of the CdS/Ag/Bi MoO was
ascribed to its special structure ― a typical Zꢀscheme photocatalytic system, in which Ag nanoparticles
directly connected to the surface of CdS and Bi MoO to form the solidꢀsolid interface (Ohmic contact) acting
as a conductor that greatly shortened the distance of photogenerated electron transfer and performed the
combination of photogenerated electrons from the CB of Bi MoO with the photogenerated holes from the VB
2
6
2
6
2
6
2
6
2
6
2
6
2
6
2
6
of CdS through the Ohmic contact, and thereby led to the efficient separation of photogenerated electrons and
holes and showed stable and strong reducibility and oxidizability. Moreover, the surface plasmon resonance
effect of metallic Ag nanoparticles also played an important role for the enhanced photocatalytic performance
of RhB degradation under visible light irradiation. Furthermore, the investigations on photoluminescence and
photoelectrochemical property also demonstrated indirectly the highly efficient separation of photogenerated
2 6
electrons and holes in the Zꢀscheme CdS/Ag/Bi MoO photocatalytic system. This new member of Zꢀscheme
photocatalytic system will be applied to more photoreactions in further exploration.
5
ꢀ7
exhibit low solar energy conversion efficiency; (ii) The high
1
Introduction
recombination of photogenerated electronꢀhole pairs in the
8
TiO
2
system leads to low quantum efficiency. These
Semiconductorꢀbased photocatalysis has been attracted
considerable attentions due to a promising pathway for solving
the increasingly serious energy and environmental problems.
shortcomings greatly limit its practical applications. Therefore,
the development of highly efficient, sustainable and visibleꢀ
lightꢀresponsive photocatalytic materials is urgent and
indispensable.
1
In these photocatalytic performances, TiO
photocatalyst that is widely used in H or O production and the
Unfortunately, TiO as
2
is a typical
2
ꢀ4
2
2
Bismuth molybdate (Bi MoO ) featured layered configuration
2
6
degradation of organic pollutants.
2
is a simplest member of the Aurivillius family of layered
photocatalyst shows two main drawbacks: (i) A wide band gap
of 3.2 eV, which can be photoactivated under UV light to
2
+
perovskites, which consists of [Bi
2
9,10
O
2
]
layers interleaved with
and displays an excellent
photocatalytic performance for completely degrading organic
2
ꢀ
perovskiteꢀlike [MoO
4
]
layers
1
0ꢀ13
pollutants in waste water under visible light irradiation.
Bi MoO as a semiconductor has a smaller band gap ranging
from 2.5 to 2.8 eV and is capable of capturing visible light.
2
6
1
4
Owing to the low visible light utilization efficiency and the
high recombination of photoꢀinduced electrons and holes, the
practical application of individual phase Bi
2
MoO
6
was
1
3,15,16
limited.
To overcome the intrinsic limitations of the
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2 6
singleꢀcomponent Bi MoO , the heterojuncted or multiꢀ photosystem II, and thereby carried out the efficient separation
2 6
component Bi MoO ꢀbased photocatalysts have been prepared of electrons and holes. This process markedly differs from the
to improve/enhance their property in repressing the conductor heterojunctionꢀtype charge transfer mechanism. Such
recombination of photogenerated electronꢀhole pairs through an a Zꢀscheme pathway of electron transfer can preserve the
efficient charge transfer process and thereby drive efficient oxidative holes in the lower VB and reductive electrons in the
photoꢀreduction and oxidation reactions at spatially separated higher CB, resulting in not only the great improvement of
1
4,17ꢀ20
sites.
singleꢀcomponent Bi
composites is becoming a pivotal strategy for improving their oxidizability of holes from photosystem II.
Hence the integration of heterocomposite into separation efficiency but also the strong reducibility of
2
MoO to prepare Bi MoO ꢀbased multiꢀ photogenerated electrons from photosystem I and the strong
6
2
6
2
0,29
Up to present,
photocatalytic performance in practical applications. CdS is an several Zꢀscheme photocatalytic systems containing silver have
important IIꢀVI semiconductive metal chalcogenide material been successfully designed and constructed for photocatalytic
regarded as a very promising class of visibleꢀlightꢀdriven convert of solar energy and photocatalytic degradation of
2
0,29,44ꢀ56
photocatalyst due to its wide light response (up to 520 nm or pollutants in waste water.
even longer).
2
1ꢀ23
But, the applications of pure CdS is Nevertheless, in a semiconductor heterojunction, the Zꢀscheme
encountering a enormous challenge — easy aggregation of charge transfer process usually faces the competition of the
2
4,25
29
smallꢀsized single CdS particles and its instability in air
due typical charge transfer process. A conductor or a contact
2
ꢀ
to easy oxidation of S in CdS. Note that CdS attached on the interface with low contact resistance can be applied as an
surface of the (non)metalꢀbased composite fabricated electron mediator to speed up the desirable specific carrier
4
3,45,52,56ꢀ58
heterojunction
CdS/Bi MoO ), efficiently showing an enhanced visible light conductivity and has been often used as a mediator in many Zꢀ
photocatalytic activity and photostability compared to pure scheme systems.
nanocomposites
(CdS@gꢀC
3
N
4
and transfer.
For example, Ag has an excellent electron
2
6
2
0,45ꢀ56
Moreover, Ag nanoparticles with
The improvement of the photocatalytic efficiency of localized surface plasmon resonance (SPR) properties have a
2
6ꢀ28
CdS.
photocatalysts is performed by promoting the fast effective strong absorption under visible light.
separation of photogenerated electrons and holes (impeding the advantages, Ag particles as conductor have attracted
5
9,60
On the basis of these
2
0,45,47ꢀ57,61
recombination of electron and hole as much as possible). In considerable attention.
fact, photocatalysis is a lightꢀdriven chemical process over the In this paper, we rationally designed and successfully fabricated
surface of a photocatalyst or is the acceleration of a an allꢀsolidꢀstate Zꢀscheme CdSꢀAgꢀBi
photoinduced chemical reaction in the presence of catalyst, and system including CdS and Bi MoO as the visibleꢀlight active
photoinduction reaction is activated by absorption of a photon photocatalysts and Ag as a solid electron mediator, and showed
2
9
2 6
MoO photocatalytic
2
6
3
0
31ꢀ33
with sufficient energy — water can produce hydrogen,
an enhanced photocatalytic performance for degrading organic
can be pollutants compared with singleꢀcomponent Bi MoO , dual
and organic pollutants can be Ag/Bi MoO and CdS/Bi MoO . The enhanced performance of
The absorption leads to a charge separation — the CdS/Ag/Bi MoO was ascribed to the separation efficiency
3
4,35
solar energy can convert into electric energy,
CO
2
2
6
3
6ꢀ38
reduced to organic fuels
2
6
2
6
3
9ꢀ41
degraded.
2
6
the formation of negative electron in the conduction band and of photoinduced carriers and the strong reducibility and
of positive hole in valence band of the semiconductor catalyst. oxidizability of the photogenerated electrons and holes. A Zꢀ
It is known that the electrons in less negative conduction band scheme charge transfer mechanism for efficiently separation of
(
CB) and holes in less positive valence band (VB) show weak photogenerated electrons and holes was suggested to elucidate
2
0
redox ability.
2 6
Consequently, the typical semiconductor photocatalytic reactions over CdS/Ag/Bi MoO photocatalyst
heterojunction displays a fatal shortcoming — the reduced by photoluminescence (PL) spectra, photocurrent generation
redox ability of transferred electrons and holes, which and electrochemical impedance spectroscopy (EIS). Hence the
4
2
negatively affect the photocatalytic reactions. Thus, it is an combination of all advantage of the visibleꢀlightꢀresponsive Ag,
enormous challenge to establish a photocatalytic system with Bi MoO and CdS photocatalysts in CdSꢀAgꢀBi MoO system
2
6
2
6
both fast electronꢀhole separation and strong redox ability. might be a promising strategy for improving highly efficient
Hence, the singleꢀcomponent photocatalyst is very difficult to separation of electrons and holes and performing quick
simultaneously satisfy all strict requirements — ‘‘a wide photodegradation of organic pollutants such as rhodamine B
absorption range, longꢀterm stability, high chargeꢀseparation and methyl orange.
efficiency and strong redox ability’’, the multicomposite
photocatalytic systems are becoming more and more important,
especially, the allꢀsolidꢀstate Zꢀscheme photocatalytic systems.
In 2006, an allꢀsolidꢀstate photosystemꢀconductorꢀphotosystem
2
Experimental
2
.1 Sample preparation
(
PSꢀCꢀPS) system — a soꢀcalled Zꢀscheme CdSꢀAuꢀTiO
system was reported for the first time, in which PSI(CdS),
PSII(TiO ) and the electronꢀtransfer system (Au) were spatially
fixed. After that the artificial heterogeneous allꢀsolidꢀstate Zꢀ
2
2
.1.1 Preparation of Bi
2
MoO
6
All the chemicals were analytical grade and used as received.
Distilled water was used in all experiments. Bi MoO
microspheres were prepared according to slightly modified
literature procedures.
stoichiometric of Bi(NO
2
4
3
2
6
2
9
scheme photocatalytic system has been widely investigated.
Especially note that the photogenerated electrons and holes are
respectively left in the CB of photosystem I and the VB of
1
9
In
a
typical process,
a certain
O was dissolved in 13.0 mL of
3
)
3
·5H
2
2
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ethylene glycol (EG) under vigorous stirring, and 0.65 mmol of photoelectron spectroscopy (XPS) was recorded on a PHIꢀ5400
Na MoO ·2H O powder was then added and continuously Xꢀray photoelectron spectrometer. Field emission scanning
2
4
2
stirred for 30 min until a transparent solution was formed. electron microscope (FEꢀSEM) images were recorded on a
Afterwards, 32.5 mL of ethanol was added and the mixture was JSMꢀ6700F scanning electron microscope. Highꢀresolution
stirred for another 30 min. Finally, the miscible solution was transmission electron microscope (HRTEM) images and
transferred into
a 65.0 mL Teflonꢀlined stainless steel selected area electron diffraction (SAED) patterns were
autoclave. The autoclave was sealed and maintained at 160 °C recorded on a JEMꢀ2100 electron microscope operated at an
for 12 h, and then naturally cooled down to room temperature. accelerating voltage of 200 kV. The UVꢀVis diffuse reflectance
The resulting precipitates were separated by centrifugation and spectra (UVꢀVisꢀDRS) of the samples were obtained using
washed with deionized water for several times and then dried at Shimadzu UVꢀ2550 UVꢀVis spectrophotometer. BaSO
0 °C for 12 h in a vacuum oven. used as a reflectance standard. Photoluminescence (PL) spectra
.1.2 Synthesis of Ag/Bi MoO photocatalysts
Silver nanoparticles deposited on the surface of Bi
prepared by a photoreduction process according to our previous
4
was
6
2
2
6
were measured using a Fꢀ4500 spectrophotometer (Hitachi,
6
MoO was Japan) at an excitation at 400 nm.
2
6
2
work. To a aqueous suspension of Bi
2 6
MoO (1.0 mmol), an 2.3 Photocurrent-time measurement
ꢀ4
ꢀ1
appropriate amounts of AgNO solution (18 mL, 10 g·mL )
3
Photocurrent measurements were performed on an
electrochemical analyzer (CHI660D, CHI Shanghai, Inc.) in a
standard threeꢀelectrode configuration with a platinum wire as a
counter electrode and a saturated calomel electrode (in
saturated KCl) as a reference electrode. A 400W xenon lamp
with an UV cutoff filter (λ > 420 nm) is employed as the light
were added under stirring. Then the suspension was irradiated
at ambient temperature for 3 h using a 400W xenon lamp under
stirring. During the irradiation, the supernatant was collected
+
and tested until Ag was precipitated completely. After
completed photoreduction process, the Agꢀloaded Bi
2 6
MoO
were filtered and washed with water to completely remove
2 4
source. Na SO (0.1 M) aqueous solution was used as the
ꢀ
NO
theoretically deposited amount of Ag is 1.0 at% to Bi
and the resulted sample Ag/Bi MoO was noted as A/BMO.
.1.3 Fabrication of CdS/Ag/Bi MoO photocatalyst
All the CdS/Ag/Bi MoO photocatalyst were fabricated via a
depositionꢀprecipitation method. A detail procedure is as
follows: the obtained Ag/Bi MoO (0.6099 g) was dispersed in
5 mL of absolute ethanol solution for 1 h under stirring, and
an appropriate amounts of Cd(CH COO) ·2H O were then
3
ions, and dried at 60 °C for 12 h in a vacuum oven. The
electrolyte. The typical working electrode was prepared as
follows: the 10 mg ground sample was dispersed ultrasonically
in 2 mL of distilled water to make a slurry. The slurry was then
dispersed onto an ITO glass electrode with an active area of
2
MoO ,
6
2
6
2
2
6
2
6
2
about 1.0 cm , and the electrode was dried at 60 °C for 6 h.
Electrochemical impedance spectra (EIS) were measured.
2
6
2
2
.4 Photocatalytic activity
3
2
2
The evaluation of the photocatalytic performance of samples
for photocatalytic decolorization of RhB aqueous solution was
performed as follows: A 400W halogen lamp was used as the
visibleꢀlight source with a cutoff filter to cut off the light below
added. After being stirred at ambient temperature for 2 h,
equimolar thioacetamide (TAA) ethanol solution (0.133 M) was
added to the above suspension and stirred at room temperature
for another 1 h. The suspension was sealed in a Teflonꢀlined
stainless steel vessel and heated at 180 °C for 10 h. After
cooled down to room temperature, the asꢀprepared product was
centrifugally separated and washed with water and absolute
ethanol for several times. Finally, the asꢀmade sample was
4
20 nm. The suspension containing 200 mg of photocatalyst
ꢀ1
and 200 mL of fresh aqueous solution of RhB (10 mg L ) were
continuously stirred in the dark for 1.0 h to establish an
adsorption/desorption equilibrium of RhB solution. After this
period of time, the light source was turned on. During the
reaction, 5.0 mL of samples were taken at given time intervals
dried at 60 °C in a vacuum oven to obtain CdS/Ag/Bi
C/A/BMO). The CdS/Ag/Bi MoO composites with molar
ratio of CdS to Ag/Bi MoO of 80, 100, 120, 140 and 160 %
2 6
MoO
(
2
6
2 6
and the photocatalysts (Bi MoO ) were then separated by
centrifugation. The supernatant solution was decanted and the
absorbance of RhB was determined through its maximum
2
6
were marked as 80 at% C/A/BMO, 100 at% C/A/BMO, 120
at% C/A/BMO, 140 at% C/A/BMO and 160 at% C/A/BMO,
respectively. The same procedure was used to prepare 120 at%
absorption band using
a
Shimadzu 2550 UVꢀvisible
spectrophotometer and the absorption peak at 553 nm was
CdS/Bi
Bi MoO
C/BMO. For comparison, single CdS was prepared via a similar
procedure in the absence of Bi MoO
2
MoO
6
by depositing CdS on the surface of pure
6
3
monitored to obtain the photocatalytic degradation efficiency.
2
6
, and the obtained product was marked as 120 at%
2
6
.
3
Results and discussion
3
.1 Determination of Z-scheme CdS/Ag/Bi
analysis
Fig. 1 shows XRD patterns of singleꢀcomponent Bi
CdS, dual CdS/Bi MoO (120 at% C/BMO) and Ag/Bi
and triꢀcomponent CdS/Ag/Bi MoO (120 at% C/A/BMO). All
the diffraction peaks can be attributed to single composite
2 6
MoO using XRD
2
.2 Characterization
Powder Xꢀray diffraction (XRD) was carried out on a
Shimadzu XRDꢀ7000 Xꢀray diffractometer using Cu Kα
radiation (λ = 0.15418 nm) at a scanning rate of 2° min in a 2θ
range of 5° ꢀ 80°. The accelerating voltage and the applied
current were 40 kV and 30 mA, respectively. Xꢀray
2
MoO
6
and
ꢀ1
2
6
2
MoO ,
6
2
6
Bi
2
MoO
6
(JCPDS card No.76ꢀ2388), Ag (JCPDS card No.04ꢀ
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0
783) and CdS (JCPDS card No. 89ꢀ0440), respectively. For without uniform size, and these small nanospheres are
samples A/BMO, C/BMO and C/A/BMO, the characteristic aggregated together to form bulk clusters (Fig. S2a). Compared
diffraction peaks of BMO still preserve. However the XRD with the pure Bi MoO , the morphology of Ag/Bi MoO
pattern of sample Ag/Bi MoO indicates two weak wellꢀ composite is quite similar to that of precursor Bi MoO in a
resolved diffraction peaks at 2θ = 38.12° and 44.28°, which are large area (Fig. 2c, 2d), but some small spherical Ag particles
indexed as the (111) and (200) reflection planes of faceꢀ loaded onto the surface of the Bi MoO architectures are
2
6
2
6
2
6
2
6
2
6
centered cubic Ag particles with Fmꢀ3m space group (marked observed anywhere, indicating that Ag nanoparticles were
with the triangle ▼). For C/BMO heterostructure, the successfully prepared and highly dispersed on the surface of the
diffraction peaks corresponded to CdS phase (JCPDS card No. Bi
2 6
MoO nanoarchitectures, which is well consistent with the
8
9ꢀ0440) are observed, confirming the deposition of CdS phase XRD results. For the asꢀmade C/A/BMO composite, the SEM
on BMO. For C/A/BMO composite, after deposited CdS on the images clearly indicate that many irregularly spherical CdS
surface of A/BMO, some new diffraction peaks appear at 2θ particles deposited on the surface of A/BMO performed the
angle of 26.46°, 43.89° and 51.98°, which can be indexed as partial or complete coverage of A/BMO, showing the formation
(111), (220) and (311) reflection planes of faceꢀcentered cubic of obvious agglomerations (Fig. 2e, 2f). To further identify the
CdS crystalline particles with Fꢀ43d symmetry. The XRD presence of CdS and Ag on the surface of Bi MoO6
2
patterns of other Zꢀscheme C/A/BMO (80 at%, 100 at%, 140 microspheres, the microanalysis of the C/A/BMO composite
at%, 160 at%) are similar to that of 120 at% C/A/BMO (Fig. was examined by the energy dispersive Xꢀray (EDX)
S1). Owing to the overlap of diffraction peaks of Ag and CdS spectroscopy. The EDX spectrum came from Fig. 2f is shown
phases, the positions of diffraction peaks are slightly shifted in Fig. 2g, confirming that the composite contained elements
compared to a single Ag and CdS composite. These results Ag, Bi, Mo, O, Cd and S.
based on XRD analysis clearly corroborate that Zꢀscheme
C/A/BMO composites were successfully synthesized.
Fig. 1 XRD patterns of pure Bi
2 6
MoO and CdS, dual A/BMO and 120 at%
C/BMO, ternary 120 at% C/A/BMO composites.
3
.2 Morphology and microstructure of Z-scheme C/A/BMO
composite by FE-SEM and TEM analysis
The morphology and microstructure of the pure Bi MoO and
2
6
CdS, dual A/BMO and asꢀprepared C/A/BMO composites are Fig. 2 FEꢀSEM images of (a, b) asꢀprepared pure Bi MoO , (c, d) A/BMO, (e, f)
2
6
1
20 at% C/A/BMO composites, and (g) EDX profile of 120 at% C/A/BMO.
directly investigated by SEM and (HR)TEM. The Bi MoO6
2
To further identify the microstructure of the asꢀsynthesized
C/A/BMO composite, transmission electron microscopy (TEM)
was performed and the representative TEM images are shown
microspheres with average diameter of 1 ꢀ 2 ꢁm are composed
of a large amount of nanoplates with the thickness of 20 ꢀ 50
nm (Fig. 2a, 2b). The asꢀmade CdS consists of nanospheres
4
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2 6
in Fig. 3. For the pure Bi MoO , a flowerꢀlike microsphere
structure is observed (Fig. 3a). Singleꢀcomponent CdS is
composed of irregular nanoparticles with the size of about 10
nm (Fig. S2b). For Zꢀscheme photocatalytic system C/A/BMO
the representative (HR)TEM images are presented in Fig. 3b
and 3c. The measured lattice fringes of the (131) plane of
Bi
with
ꢀspacing of 0.337 nm, are in better agreement with that from
the wide angle PXRD data, further demonstrating the presence
of faceꢀcentered cubic Ag and CdS phases in Bi MoO
2
MoO
6
with dꢀspacing of 0.317 nm, of the (200) plane of Ag
d
ꢀspacing of 0.204 nm, and of the (111) plane of CdS with
d
2
6
composite. Moreover, for 120 at% C/A/BMO nanocomposite,
the highꢀangle annular dark field scanning transmission
electron microscopy (HAADFꢀSTEM) image in Fig. 3d and the
spatial distribution of the element composition along the edge
of the particles in Fig. 3e investigated by lineꢀscanning
elemental mappings, clearly corroborated
a wellꢀdefined
composition profile of C/A/BMO nanostructures. The profiles
of Bi, Mo and O show a narrow bandꢀlike peak at the center,
whereas the profiles of Ag, S and Cd show slightly sharp peaks
at the right and left sides with a broad valley at the center,
showing
a clear interface between CdS and Bi MoO6
2
components of the heterostructures.
Fig. 4 XPS spectra of sample 120 at% C/A/BMO: (a) The survey spectrum, (b) Bi
4
f and S 2p, (c) Mo 3d, (d) O 1s, (e) Ag 3d, and (f) Cd 3d.
3
.3 XPS analysis
XPS spectra of the samples are performed to investigate the
surface valence state and the chemical composition. As shown
in Fig. 4a, the XPS survey spectra are mainly composed of Bi,
Mo, O, Ag, S and Cd elements, which are consistent with the
chemical composition of the photocatalysts. The C element
came from the adventitious hydrocarbon of the XPS instrument
itself. The high resolution spectra of Bi 4f, Mo 3d, O 1s, Ag 3d,
and Cd 3d of sample 120 at% C/A/BMO are shown in Fig. 4bꢀf,
respectively. As viewed in Fig. 4b, two strong peaks at around
1
58.5 and 163.7 eV are observed, which can be assigned to the
6
4
binding energy of Bi 4f7/2 and Bi 4f5/2, respectively. Two
bands at 232.2 and 235.3 eV in Fig. 4c are ascribed to Mo 3d5/2
6
5
and Mo 3d3/2, respectively. The observed two O 1s peaks at
31.2 and 529.9 eV in Fig. 4d are in agreement with OH
hydroxyl groups and oxygen species in the lattice oxygen,
5
6
6
respectively. Moreover, the Ag 3d spectrum monitored is very
weak due to a very low loading of Ag (Fig. 4e). However, the
XPS spectrum of Cd 3d clearly indicates two characteristic
bands at 404.9 and 412.3 eV, which can be assigned to the Cd
ions in CdS. Furthermore, the S element can also be detected
by XPS spectrum in Fig. 4b at around 160.5 and 159.5 eV,
2
+
6
7
revealing binding energy of characteristic S 2p3/2 and S 2p1/2
,
6
8,69
respectively.
As comparison, the highꢀresolution XPS
2 6
Fig. 3 TEM image of (a) Bi MoO , (b) C/A/BMO, (c) HRTEM image of
C/A/BMO, (d) HAADFꢀSTEM image of C/A/BMO composite, and (e) EDX lineꢀ spectra of Cd 3d of pristine CdS, Bi 4f of pristine Bi MoO and
2
6
scanning elemental mappings of a single C/A/BMO particle (indicated by red line
in (b)).
1
20 at% C/A/BMO are shown in Fig. S3. The binding energy
of Bi 4f5/2 and Bi 4f7/2 of Bi
2
MoO
6
is lower (0.2 eV) than those
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of the 120 at% C/A/BMO (Fig. S3a). Note that the binding in the UV range. The multicomposites A/BMO, 120 at%
energy of the Cd 3d3/2 and Cd 3d5/2 from pure CdS is higher C/BMO, and 120 at% C/A/BMO and other Zꢀscheme
(
0.25 eV) than those from the 120 at % C/A/BMO (Fig. S3b). C/A/BMO (80 at%, 100 at%, 140 at%, 160 at%) respectively
These results imply that the deposited CdS nanoparticles are exhibit a strong absorption ability in the range of 400ꢀ800 nm
probably attached on the surface of BMO, not via a simply compared to pure Bi MoO , indicating that the loading of Ag
physical mixture. Based on these XPS results, Ag and CdS and CdS can effectively enhance the visibleꢀlight absorption.
have been successfully loaded on the surface of Bi MoO to For A/BMO, it is noteworthy that an extra absorption peak at
fabricate a Zꢀscheme C/A/BMO photocatalytic system which the visibleꢀlight absorption region (about 540 nm) is found and
has been confirmed by the HRTEM and EDX measurement. can be ascribed to the surface plasmon resonance (SPR)
2
6
7
0
2
6
5
9,60
absorption of the Ag nanoparticles.
However, for C/A/BMO
3
.4 FT-IR spectra analysis
composite, the SPR absorption significantly broadens and
occurs a redꢀshift of the Ag surface plasmon band of about 100
nm compared with A/BMO, suggesting a strong electronic
To investigate the chemical composition and characteristic
chemistry bonding of the composites, the Fourier transform
infrared spectroscopy (FTꢀIR) was carried out. Fig. 5a shows
the FTꢀIR spectra of the asꢀprepared pure Bi MoO , A/BMO,
4
3,75
interaction between Ag and CdS.
Therefore, this
phenomenon corroborates that the Ag nanoparticles deposited
on Bi MoO are coated by CdS.
2
6
2
6
1
20 at% C/BMO, 120 at% C/A/BMO and pure CdS. For pure
Bi MoO , the characteristic MoꢀO asymmetric and symmetric
2
6
stretching vibrations of MoO octahedron involving vibration
6
ꢀ1
of the apical oxygen atoms appear at 843 and 797 cm ,
7
1ꢀ73
ꢀ1
respectively.
Moreover, the bands, at 734 cm attributed to
the MoꢀO asymmetric stretching mode involving vibrations of
the equatorial oxygen atoms from MoO , and at 603 and 570
6
ꢀ1
cm assigned to the bending vibration of MoO , as well as at
55 cm belonged to the BiꢀO stretching and bending
6
ꢀ1
4
vibrations from BiO6 unit, are observed as previous study
7
3
reported by Zhu and coꢀworkers. For singleꢀcomponent CdS,
ꢀ1 74
the characteristic CdꢀS bond appears at 1384 and 1118 cm .
Owing to surface adsorption of water on CdS, the OꢀH bending
ꢀ1 26
vibration appears at 1630 cm . It is worth noting that a
ꢀ1
absorption peak appears at about 1045 cm for A/BMO and
20 at% C/A/BMO, which can be attributed to the resonance
absorption of Ag nanoparticles. For samples Ag/Bi MoO ,
1
2
6
C/BMO and C/A/BMO, the correspondingly characteristic
chemistry bonding vibrations (MoꢀO, CdꢀS and BiꢀO) appear in
2 6
Fig.6 (a) Photocatalytic degradation efficiency of RhB by pure Bi MoO ,
their IR spectra, clearly verifying the successful synthesis of A/BMO, 120 at% C/BMO, 120 at% C/A/BMO composites and single CdS; (b)
0
kinetic plot of C/C versus irradiation time for the photodegradation of RhB with
corresponding composites. These results are in good agreement
with data from the XRD, SEM and (HR)TEM analysis.
different photocatalysts, (c) Rate constants of the photodegradation of RhB using
different photocatalysts, and (d) The change of the absorption spectra of
photodegradated RhB with increasing irradiation time under visible light using
1
20 at% C/A/BMO composite as a photocatalyst.
g
The band gap energy (E ) of the semiconductors are calculated
2
/n
from a plot of (αhν) versus energy (hv) (Fig. 5b, inset)
according to the equation of the optical absorption near band
n/2 76
edge:
α
hν = A(hν ꢀ Eg)
,
g
where α, hv, E and A are the
optical absorption coefficient, photonic energy, photonic energy
band gap, and proportionality constant, respectively. In this
equation,
or indirect (
CdS is an direct optical transition type semiconductor.
direct band gaps of pure Bi MoO
n
depends on whether the transition is direct (
n
= 1)
and
The
n
= 4). As shown in the literature, Bi MoO
2
6
7
7,78
Fig. 5 (a) FTꢀIR spectra and (b) UVꢀvis DRS spectra of pure Bi
2 6
MoO and CdS,
2
6
2
and CdS can be obtained
dual A/BMO and 120 at% C/BMO, and Zꢀscheme ternary 120 at% C/A/BMO
2
composites. The inset is the plot of absorption (αhν) versus energy (hν) for the from the chart of absorption (αhν) versus energy hν (Fig. 5b,
2 6
band gap energy of pure Bi MoO and CdS.
inset). Thus, the band gaps of pure Bi MoO and CdS are
2
6
3
.4 UV-vis-DRS analysis
determined to be 2.10 and 2.50 eV, respectively.
The typical UVꢀvis diffuse reflectance spectroscopy (UVꢀvisꢀ
DRS) is a useful method to reflect the optical absorption
properties of the asꢀprepared samples. As viewed in Fig. 5b and
3
.5 Photocatalytic activity
Photocatalytic decomposition of RhB on various samples as
photocatalysts is evaluated under visible light irradiation (λ >
4
Fig. S4, the absorption edge of pure Bi
2
MoO
6
is estimated to be
470 nm, while pure CdS shows a strong absorption at 556 nm
20 nm). Fig. 6a presents the photocatalytic degradation results
6
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2 6
of RhB over single component CdS, pure Bi MoO , A/BMO, Owing to the photoluminescence (PL) emission originates from
1
20 at% C/BMO, and 120 at% C/A/BMO composites. The the recombination of free charge carriers, PL spectra is often
results indicate that the photocatalytic degradation efficiency of used to investigate the efficiency of separation and transfer of
RhB was approximately 40% using pure Bi MoO as a photogenerated charge carrier and the fate of photogenerated
photocatalyst after irradiation for 80 min. Low yield is probably electrons and holes in semiconductors.
caused by the rapid recombination of photogenerated electrons that the lower PL intensity indicates less recombination rate of
and holes of the Bi MoO microspheres. As compared to the photogenerated electronꢀhole pairs and thereby shows high
pure Bi MoO both A/BMO and C/BMO as catalysts photocatalytic activity. Hence we measured the PL emission
significantly improve the photocatalytic activity, proving that spectra of pure Bi MoO , Ag/Bi MoO , C/BMO (120 at%),
Ag nanoparticles and CdS acted as an important role to enhance C/A/BMO (120 at%) composite and single CdS as shown in
the photocatalytic performance. It is interesting to note that the Fig. 7. For the pure Bi MoO , one characteristic emission peak
20 at% C/A/BMO as a photocatalyst displays the highest centred at about 460 nm is observed, which is in accordance
2
6
6
9,71,82
It’s well known
2
6
6
4
2
6
,
2
6
2
6
2
6
1
7
1,83
photocatalytic degradation efficiency compared to pure with previously reported results.
Bi MoO A/BMO and C/BMO. Highly photocatalytic nanoparticles and CdS onto the surface of Bi
performance is attributed to the positive synergism of Ag and intensity of the PL emission of C/A/BMO composites is
CdS on the surface of Bi MoO Hence for the obviously lower than that of other samples, implying that the
photodegradation of RhB the photocatalytic activity of all incorporation of Ag and CdS nanoparticles on BMO composite
catalysts used is as follows in order from slow to fast: Bi MoO can effectively repress the recombination of electronꢀhole pairs
A/BMO < CdS < 120 at% C/BMO< 120 at% C/A/BMO In and thereby generate a higher photocatalytic activity, which is
After introduced Ag
2
6
,
2
MoO , the
6
2
6
.
2
6
<
.
addition, the screening of all the Zꢀscheme C/A/BMO in good agreement with the result from RhB photodegradation
photocatalysts with different amounts of CdS for the enhanced experiment.
photocatalytic activities is shown in Fig. S5, clearly revealing
Bi
A/BMO
20 at% C/BMO
120 at% C/A/BMO
CdS
2 6
MoO
that 120 at% C/A/BMO is a best photocatalyst. Furthermore, in
order to better compare the photocatalytic efficiency of the all
samples, the reaction kinetics of RhB degradation was
investigated. According to the LangmuirꢀHinshelwood (LꢀH)
1
7
9,80
kinetics model,
the pseudo firstꢀorder kinetics equation is
/C) = , where app denotes the apparent
and C are the RhB concentrations (mg
= 0 and represents the irradiation
time (min). With increasing irradiation time the plot of ln(C /C)
expressed as ln(C
0
k
app
·
t
k
ꢀ1
rate constant (min ), C
0
ꢀ1
L ) in solution at time
t
t = t, t
0
versus irradiation time (t) for RhB degradation over different
photocatalysts is shown in Fig. 6b. The results reveal that the
photodegradation of RhB is a typical pseudo firstꢀorder reaction
400
425
450
475
500
525
550
Wavelength (nm)
2 6
Fig. 7 PL spectra of pure Bi MoO and CdS, A/BMO, 120 at% C/BMO and 120
in the presence of photocatalysts (Bi
and C/A/BMO). The corresponding rate constants (
photodegradation of RhB are shown in Fig. 6c, the
2
MoO
6
, A/BMO, C/BMO at% C/A/BMO composite.
k
app) of the
6
5
4
3
2
1
0
Bi MoO6
A/BMO
CdS
2
off
C/BMO
C/A/BMO
on
ꢀ3
ꢀ2
corresponding rate constants
2
kapp are 6.92×10 , 1.43×10 ,
.146×10 , 2.534×10 and 4.155×10 min for pure Bi MoO ,
2 6
A/BMO, singleꢀphase CdS, 120 at% C/BMO and 120 at%
C/A/BMO, respectively. These findings clearly confirm that
C/A/BMO composite is a highest active photocatalyst for the
photocatalytic degradation of RhB, its activity is approximately
ꢀ2
ꢀ2
ꢀ2
ꢀ1
6
2 6
times higher than that of pure Bi MoO .
The temporal evolution of the absorption spectra of
photodegradated RhB with increasing irradiation time are
illustrated in Fig. 6d in the presence of catalyst 120 at%
C/A/BMO composite. At the beginning of photodegradation,
the strongest absorbance of RhB locates at 554 nm, and with
0
20
40
60
80
100
Irradiation (sec)
increasing irradiation time the absorption peak gradually Fig. 8 Comparison of transient photocurrent responses of pure Bi
2
MoO
A/BMO, 120 at% C/BMO, and 120 at% C/A/BMO composite under visible light
irradiation (λ > 420 nm, [Na SO ] = 0.1 M).
6
and CdS,
decreases and takes place a blueꢀshift until 498 nm after 80 min
irradiation. The blueꢀshift is caused by the Nꢀdeethylation and
deethylation of RhB during irradiation.
2
4
8
1
3
.7 Photoelectrochemical property
3.6 Photoluminescence analysis
The photocurrent measurements are usually utilized to
investigate the interfacial charge transfer dynamics. A high
photocurrent implies a high separation efficiency of electrons
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8
4
and holes, showing a high photocatalytic activity. Fig. 8
displays the transient photocurrent responses of pure Bi MoO
20 at% C/BMO, 120 at% C/A/BMO and single CdS with
several onꢀoff cycles of visible light illumination. In
comparison with pure Bi MoO and single CdS, C/A/BMO
2
6
,
1
2
6
exhibits a significantly enhanced transient photocurrent density,
which is about 3 times and 2 times higher than that of the pure
Bi MoO and single CdS, respectively. The results reveal that
2 6
the C/A/BMO possesses the higher separation efficiency of
photogenerated electrons and holes, further corroborating that
Fig. 10 Trapping experiments of active species for RhB photodegradation in the
the synergism of Ag and CdS on the surface of Bi
2
MoO
6
is far presence of photocatalyst (a) 120 at% C/BMO, (b) 120 at% C/A/BMO under
visible light irradiation.
superior to that of pure Bi
single CdS.
2
MoO
6
, CdS/Bi
2
MoO
6
composite and
3
.8 Photocatalytic mechanism
During the photodegradation process of organic pollutants, the
1
6000
ꢀ
2
active species including superoxide anion radicals (·O ),
+
positive holes (h ) and hydroxyl radicals (·OH) are playing a
crucial role. To further reveal the possible mechanism of the
enhanced photocatalytic performance, the trapping experiment
for identifying main active species was performed. The
sacrificial agents, such as disodium ethylene diamineꢀ
tetraacetate (EDTAꢀ2Na), isopropanol (IPA) and benzoquinone
1
2000
8
4
000
000
0
aDark
aLight
bDark
bLight
cDark
cLight
dDark
dLight
eDark
eLight
+
ꢀ
(
2
BQ), are utilized as the scavengers of h , ·OH and ·O ,
8
9,90
respectively.
The trapping experiments of active species
upon the photocatalytic reactions of the samples shown in Fig.
10 indicates that IPA is almost not affect on photocatalytic
efficiency, while the photocatalytic activity of the samples are
0
5000
10000
Z' (Ohm)
15000
20000
obviously inhibited by the addition of the EDTAꢀ2Na and BQ.
ꢀ
This fact demonstrates that superoxide anion radicals ·O
2
and
+
positive holes h are mainly active species and are playing key
Fig. 9 Electrochemical impedance Nyqusit plots of samples (a) pure Bi
2 6
MoO , (b)
A/BMO; (c) CdS, (d) 120 at% C/A/BMO, (e) 120 at% C/BMO electrodes under roles in the RhB photodegradation process to compare with
2 4
dark and light irradiation in the 0.5 M Na SO electrolyte.
hydroxyl radical ·OH in the presence of composites 120 at%
C/BMO or 120 at% C/A/BMO under visible light irradiation.
Nevertheless, the addition of EDTAꢀ2Na quickly represses RhB
degradation compared to that with the addition of BQ, revealing
Moreover, the migration and transfer processes of
photogenerated electrons and holes in a semiconductor can also
be verified by the typical electrochemical impedance spectrum
8
5
(
EIS). The radius of the arc in the EIS reflects the interface
+
that positive holes h play a more important role than hydroxyl
layer resistance occurred on the surface of electrode. The
previous studies revealed that the smaller radius of the arc
implied the higher efficiency of charge transfer.
ꢀ
radical ·O
2
in the photocatalytic reactions.
8
6ꢀ88
As shown
6
MoO ,
in Fig. 9, the typical EIS Nyquist plots of the pure Bi
2
A/BMO, 120 at% C/BMO, 120 at% C/A/BMO and single CdS
before and after visible light irradiation, clearly show that the
arc radius of A/BMO and C/BMO is smaller than that of the
2 6
pure Bi MoO and CdS under light or dark conditions, but is
bigger than that of C/A/BMO composite, implying that sample
C/A/BMO (120 at%) possesses a stronger ability in separation
and transfer of photogenerated electronꢀhole pairs. This result
indicates that the incorporation of Ag and CdS on the surface of
2 6
Bi MoO can effectively enhance the separation and transfer of
photogenerated electronꢀhole pairs and thereby leads to the
improvement of photocatalytic degradation efficiency. The
results of the EIS are in accordance with the aforementioned PL
and photocurrent. Subsequently, the photocurrent generation
and EIS experiments better demonstrate the electron excitation
and the charge transport characteristics of 120 at% C/A/BMO
samples.
Fig. 11 Schematic illustration for the charge transfer in samples (a) C/BMO and
(
b) C/A/BMO under visible light irradiation.
To further confirm the formation of the Zꢀscheme C/A/BMO,
the energy band levels of the Bi
As shown in Fig. 11a, the band gaps of Bi
.5 and 2.16 eV, respectively. The calculated VB positions of
2
MoO
6
and CdS are determined.
2
MoO and CdS are
6
2
Bi
2
MoO
6
and CdS are approximately 2.29 and 1.7 eV,
8
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ARTICLE
e
respectively, via the equation
E
CB = χ −
E
−
E
g
, and their the VB of Bi
2
MoO
6
to make a holeꢀrich region and therefore
corresponding CB edge levels (ECB vs NHE) are calculated to protect Bi
be −0.21 and −0.46eV, respectively, via the equation
CB, where CB is the CB edge potential, VB is the VB edge photoꢀreduction and photoꢀoxidation, respectively, indicating a
potential, and χ is the electronegativity of the semiconductor.
is the energy of free electrons on the hydrogen scale ≈ 4.5 eV circular photoꢀreduction and photoꢀoxidation. Moreover the
2
MoO
6
from the photoꢀreduction. Hence the electronꢀ
E
VB
=
E
g
rich region and the holeꢀrich region readily take place strong
+
E
E
E
e
E
high photocatalytic performance with a spontaneous and
7
0,91
and
E
g
is the band gap of the semiconductor.
2 6
Based on the photogenerated electrons from the CB of Bi MoO can directly
energy band levels of the Bi
2
MoO and CdS and the aboveꢀ recombine with the photogenerated holes from the VB of CdS
6
mentioned the trapping experiments of active species, herein, through the Ohmic contact Ag nanoparticles, which greatly
we suggest that the photogenerated charge migration in the reduces the distance of Zꢀscheme electron transfer. This further
C/BMO composite is similar to the typical charge migration improves efficient separation of electrons from CB of CdS and
mechanism of a semiconductor heterojunction (Fig. 11a). When holes from the VB of Bi
the Bi MoO and CdS are excited by visible light irradiation, C/A/BMO indicates a highest photocatalytic performance in
the photogenerated electrons on the CB of CdS can easily RhB photodegradation compared to C/BMO (Fig. 6a).
migrate to the CB of Bi MoO , while the photogenerated holes Contrarily, addition of EDTAꢀ2Na or BQ faster represses the
in the VB of Bi MoO can transfer to the VB of CdS. As a rate of RhB photodegradation in the presence of
result, the photogenerated electrons and holes are spatially CdS/Ag/Bi MoO compared to that in the presence of
separated and greatly weakened undesirable recombination. But CdS/Bi MoO (Fig. 10). It is noteworthy that the Zꢀscheme
in the CdSꢀBi MoO system, due to that the top of the valence charge transfer pathway not only greatly improves the
band potential of CdS is less positive than that of Bi MoO and separation of electronꢀhole pairs, but also preserves strong and
the bottom of conduction band potential of Bi MoO is less continuous redox ability. According to the aboveꢀmentioned
negative than that of CdS, it is difficult to simultaneously discussion, the Zꢀscheme CdS/Ag/Bi MoO ꢀcatalyzed RhB
2 6
MoO . This is why Zꢀscheme catalyst
2
6
2
6
2
6
2
6
2
6
2
6
2
6
2
6
2
6
possess the high chargeꢀseparation efficiency and strong redox photodegradation can be proposed as follows:
ability, and thereby show a weak redox ability, especially after
ꢀ
+
C/A/BMO+ hν (visible light) →C/A/BMO (e + h ) .........(1)
charge transfer. As shown in Fig. 11a, the holes density in the
VB of Bi MoO
CdS is enhanced during the photocatalytic process, hence, the
+
2
6
is depleted while holes density in the VB of RhB + h → degradation ....................................................(2)
ꢀ
ꢀ
O
2
+ e → ·O
2
.....................................................................(3)
4
2,92
redox ability of transferred electrons and holes are reduced,
ꢀ
2
showing a negative effect for the photocatalytic reactions. Note RhB + ·O
that the catalytic performance of this type of photocatalyst is
much higher than that of single semiconductor and singleꢀ
→ degradation ..................................................(4)
Conclusions
component catalyst. As a result, for the RhB photodegradation,
the catalytic performance shown in Fig. 6a clearly reveals that
the heterojunctionꢀtype C/BMO catalyst displays a higher
photocatalytic behavior than single semiconductor CdS and
In summary,
a
novel Zꢀscheme photocatalytic system
CdS/Ag/Bi MoO (C/A/BMO) was rationally designed and
2 6
successfully prepared. As comparison, a series of singleꢀ
component CdS and Bi MoO dual component
CdS/Bi MoO (C/BMO) and Ag/Bi MoO (A/BMO) were also
2 6
single Bi MoO due to the effective separation of the
2
6
,
photogenerated electrons and holes. For C/A/BMO
photocatalytic system, a different mechanism is suggested as
shown in Fig. 11b. Although the spatial separation of
photogenerated electrons and holes in Zꢀscheme C/A/BMO are
similar to that from the heterojunctionꢀtype catalyst C/BMO
under light irradiation, the photogenerated electrons from the
CB of Bi MoO can readily recombine with the photogenerated
2 6
holes from the VB of CdS by Ohmic contact Ag NPs as
conductor, because on the one hand, equilibrium of the Fermi
2
6
2
6
synthesized. All composites were characterized by XRD, SEM,
TEM, XPS, EDX, IR and UV visible spectrum to confirm their
phase composite, morphology and structure. The results
revealed that Ag and CdS were successfully integrated to the
surface of Bi
Bi MoO (C/BMO) as well as CdSꢀAg solidꢀsolid contact
interfaces in different composite materials Ag/Bi MoO (A/
BMO), CdS/Bi MoO (C//BMO) and CdS/Ag/Bi MoO (C/A/
2 6 2 6
MoO to form AgꢀBi MoO (A/BMO) and CdSꢀ
2
6
2
6
2
6
2
6
2 6
levels has established at the solidꢀsolid interfaces of Bi MoO ,
BMO), respectively. All materials can be used as photocatlysts
for the degradation of RhB dye under visible light irradiations.
Owing to the high electronic mobility and strong SPR effect of
Ag nanoparticles, the introduction of Ag NPs provides a highꢀ
Ag and CdS before light irradiation. On the other hand, the
strong SPR effect of Ag nanoparticles results in an enhanced
local electric field around the solidꢀsolid interfaces, which can
drive the excited electrons of Ag to inject into the VB of CdS to
recombine with holes or into the CB of CdS via direct electron
2 6
speed charge transfer channel in CdS/Ag/Bi MoO (C/A/BMO)
heterostructure and thereby leads to more efficiently spatial
separation of the electrons and holes. Moreover, the
photodegradation of RhB dye under visible light irradiation
2
0,93
transfer or plasmonꢀinduced resonant energy transfer.
As a
result, the photogenerated electrons in the VB of CdS
continuously transit to the CB of CdS under light irradiation,
and the photogenerated electrons aggregate in the CB of CdS to
form an electronꢀrich region and thereby suppress the photoꢀ
oxidation of CdS, while the photogenerated holes aggregate in
revealed that the multicomposites CdSꢀAgꢀBi
photocatalytic system exhibited highest efficient
photocatalytic activity compared to the single CdS and
Bi MoO , and dual Ag/Bi MoO (A/BMO) and CdS/Bi MoO
6
2 6
MoO (C/A/BMO)
a
2
6
2
6
2
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New Journal of Chemistry
(
C/BMO), showing the highly efficient separation of the 20 J. W. Fu, S. W. Cao, J. G. Yu, Journal of Materiomics, 2015,
1
, 124–133.
photogenerated electrons and holes, and stable and strong
reducibility and oxidizability in the Zꢀscheme photocatalytic
2
2
1 Y. Zhang, Y. Tang, X. Liu, Z. Dong, H. H. Hng, Z. Chen, T.
C. Sum and X. Chen, Small, 2013, 9, 996–1002.
2 X. Wang, C. Liow, D. Qi, B. Zhu, W. R. Leow, H. Wang, C.
Xue, X. Chen and S. Li, Adv. Mater., 2014, 26, 3506–3512.
system CdSꢀAgꢀBi
2
MoO
6
(C/A/BMO). Hence a highly efficient
MoO (C/A/BMO)
photocatalytic performance of CdSꢀAgꢀBi
2
6
can be explained by Zꢀscheme charge transfer mechanism. 23 Y. Hu, X. Gao, L. Yu, Y. Wang, J. Ning, S. Xu and X. W.
Lou, Angew. Chem., Int. Ed., 2013, 52, 5636–5639.
Furthermore,
photoelectrochemical properties of single CdS and Bi
dual Ag/Bi MoO (A/BMO) and CdS/Bi MoO (C/BMO) and
triꢀcomposite CdS/Ag/Bi MoO (C/A/BMO) were
investigated in detail, indirectly corroborating the highly
the
photoluminescence
properties
and
2
4 Q. Li, B. Guo, J. G. Yu, J. R. Ran, B. H. Zhang, H. J. Yan
and J. R. Gong, J. Am. Chem. Soc., 2011, 133, 10878–10884.
5 A. Kudo and Y. Miseki, Chem. Soc. Rev., 2009, 38, 253–278.
2
MoO ,
6
2
6
2
6
2
2
6
also 26 M. L. Lu, Z. X. Pei, S. X. Weng, W. H. Feng, Z. B. Fang, Z.
Y. Zheng, M. L. Huang and P. Liu, Phys. Chem. Chem. Phys.,
014, 16, 21280–21288.
2
photocatalytic
CdS/Ag/Bi MoO
performance
6
(C/A/BMO).
of
Zꢀscheme
catalyst
2
7 Y. G. Li, X. L. Wei, H. J. Li, R. R. Wang, J. Feng, H. Yun
and A. N. Zhou, RSC Adv., 2015, 5, 14074–14080.
2
2
8 Y. Feng, X. Yan, C. B. Liu, Y. Z. Hong, L. Zhu, M. J. Zhou
and W. D. Shi, Appl. Surf. Sci., 2015, 353, 87–94.
Acknowledgements
29 P. Zhou, J. G. Yu and M. Jaroniec. Adv. Mater., 2014, 26,
4
920–4935.
This work was supported by the National Natural Science
Foundation of China (No. 21373159) and the Project of Science
3
0 T. Van Gerven, G. Mul, J. Moulijn and A. Stankiewicz,
Chem. Eng. Process., 2007, 46, 781–789.
&
Technology Office of Shaanxi Province (No. 2015SF291, 31 H. Tong, S. Ouyang, Y. Bi, N. Umezawa, M. Oshikiri, J. Ye,
2
013K11ꢀ08, 2013SZS20ꢀP01) and Natural Science Program of
Adv. Mater., 2012, 24, 229–251.
2 Q. J. Xiang, J. G. Yu and M. Jaroniec, J. Am. Chem. Soc.,
3
3
Education Department of Shaanxi Province (No. 15JS119).
2
012, 134, 6575–6578.
3 M. G. Kibria, H. P. T. Nguyen, K. Cui, S. Zhao, D. Liu, H.
Guo, M. L. Trudeau, S. Paradis, A. R. Hakima and Z. Mi,
ACS Nano, 2013, 7, 7886–7893.
References
1
2
3
4
5
6
7
8
A. Kubacka, M. FernandezꢀGarcia and G. Colon, Chem. Rev., 34 Q. Zhang, E. Uchaker, S. L. Candelaria and G. Cao, Chem.
Soc. Rev., 2013, 42, 3127–3171.
2
012, 112, 1555–1614.
J. Chen, H. B. Yang, J. Miao, H. Y. Wang and B. Liu, J. Am. 35 J. A. Christians, R. C. M. Fung and P. V. Kamat, J. Am.
Chem. Soc., 2014, 136, 15310–15318.
B. Liu, A. Khare and E. S. Aydil, ACS Appl. Mater. Inter.,
Chem. Soc., 2014, 136, 758–764.
3
6 S. C. Roy, O. K. Varghese, M. Paulose and C. A. Grimes,
2011, 3, 4444–4450.
ACS Nano, 2010, 4, 1259–1270.
H. Zhang, X. Liu, Y. Li, Q. Sun, Y. Wang, B. J. Wood and H. 37 A. Dhakshinamoorthy, S. Navalon, A. Corma and H. Garcia,
Energy Environ. Sci., 2012, 5, 9217–9233.
R. Zhou, Q. Zhang, E. Uchaker, J. Lan, M. Yin and G. Cao, J. 38 E. V. Kondratenko, G. Mul, J. Baltrusaitis, G. O. Larrazábal
Zhao, J. Mater. Chem., 2012, 22, 2465–2472.
Mater. Chem. A, 2014, 2, 2517–2525.
L. Yang, C. McCue, Q. Zhang, E. Uchaker, Y. Mai and G.
Cao, Nanoscale, 2015, 7, 3173–3180.
and J. PérezꢀRamírez, Energy Environ. Sci., 2013, 6, 3112–
135.
39 J. Kim, J. Lee and W. Choi, Chem. Commun., 2008, 756–758.
3
B. Liu, L. M. Liu, X. F. Lang, H. Y. Wang, X. W. Lou and E. 40 J. G. Yu and X. X. Yu, Environ. Sci. Technol., 2008, 42,
4
902–4907.
S. Aydil, Energy Environ. Sci., 2014, 7, 2592–2597.
X. B. Chen and S. S. Mao, Chem. Rev., 2007, 107, 2891– 41 Y. Bi, S. Ouyang, N. Umezawa, J. Cao and J. Ye, J. Am.
2959.
Chem., Soc., 2011, 133, 6490–6492.
2 X. Li, J. G. Yu, J. X. Low, Y. P. Fang , J. Xiao and X. B.
4
9
1
B. Frit and J. P. Mercorio, J. Alloys Compd.,1992, 188, 27ꢀ35.
0 Y. Shimodaira, H. Kato, H. Kobayashi and A. Kudo, J. Phys.
Chem. B, 2006, 110, 17790–17797.
Chen, J Mater Chem. A, 2015, 3, 2485–2534.
43 H. Tada, T. Mitsui, T. Kiyonaga, T. Akita and K. Tanaka,
Nat. Mater., 2006, 5, 782–786.
1
1 H. P. Li, Q. H. Deng, J. Y. Liu, W. G. Hou, N. Du, R. J.
Zhang and X. T. Tao, Catal. Sci. Technol., 2014, 4, 1028– 44 P. Li, Y. Zhou, H. J. Li, Q. F. Xu, X. G. Meng, X. Y. Wang,
1037.
M. Xiao and Z. G. Zou, Chem. Commun., 2015, 51, 800–803.
5 H. L. Lin, J. Cao, B. D. Luo, B. Y. Xu and S. F. Chen, Catal.
Commun., 2012, 21, 91–95.
4
1
2 J. C. Jung, H. Kim, A. S. Choi, Y.ꢀM. Chung, T. J. Kim, S. J.
Lee, S.ꢀH. Oh and I. K. Song, Catal. Commun., 2007, 8, 625–
628.
46 Y. M. He, L. H. Zhang, B. T. Teng and M. H. Fan, Environ.
Sci. Technol., 2015, 49, 649–656.
47 Z. H. Cheng, F. Bing, Q. Liu, Z. G. Zhang and X. M. Fang, J.
Mater. Chem. A, 2015, 3, 4652–4658.
1
1
1
1
1
1
1
3 G. H. Tian, Y. J. Chen, W. Zhou, K. Pan, Y. Z. Dong, C. G.
Tian and H. G. Fu, J. Mater. Chem., 2011, 21, 887–892.
4 D. Yue, D. M. Chen, Z. H. Wang, H. Ding, R. L. Zong and Y.
F. Zhu, Phys.Chem.Chem.Phys., 2014, 16, 26314–26321.
5 L. J. Xie, J. F. Ma and G. J. Xu, Mater. Chem. Phys., 2008,
4
8 J. Zhang, C. G. Niu, J. Ke, L. F. Zhou and G. M. Zeng, Catal.
Commun., 2015, 59, 30–34.
49 R. Y. Xie, L. P. Zhang, H. Xu, Y. Zhong, X. F. Sui and Z. P.
Mao, J. Mole. Catal. A: Chem., 2015, 406, 194–203.
50 Y. X. Yang, W. Guo, Y. N. Guo, Y. H. Zhao, X. Yuan and Y.
H. Guo, J. Hazard. Mater., 2014, 271, 150–159.
1
10, 197–200.
6 W. Z. Yin, W. Z. Wang and S. M. Sun, Catal. Commun.,
010, 11, 647–650.
2
7 T. Yan, Q. Yan, X. D. Wang, H. Y. Liu, M. M. Li, S. X. Lu,
W. G. Xu and M. Sun, Dalton Trans., 2015,44, 1601–1611.
8 J. Tian, P. Hao, N. Wei, H. Z. Cui and H. Liu, ACS Catal.,
5
1 J. J. Li, Y. L. Xie, Y. J. Zhong and Y. Hu, J. Mater. Chem. A,
2015, 3, 5474–5481.
52 X. F. Wang , S. F. Li , Y. Q. Ma, H. G. Yu and J. G. Yu, J.
Phys. Chem. C, 2011, 115, 14648–14655.
2015, 5, 4530–4536.
9 Q. Yan, M. Sun, T. Yan, M. M. Li, L. G. Yan, D. Wei and B.
Du, RSC Adv., 2015, 5, 17245–17252.
1
0 | New J. Chem. 2016, 00, xx
This journal is © The Royal Society of Chemistry 2016
Please do not adjust margins

Page 11 of 13
New Journal of Chemistry
New Journal of Chemistry
View Article Online
DOI: 10.1039/C6NJ01893A
ARTICLE
5
5
5
3 Y. Y. Bu, Z. Y. Chen, C. J. Sun, Appl. Catal. B: Environ., 85 T. Yan, M. Sun, H. Y. Liu, T. T. Wu, X. J. Liu, Q. Yan, W.
015, 179, 363–371. G. Xu and B. Du, J. Alloy Compd., 2015, 634, 223–231.
4 H. J. Cheng, J. G. Hou, H. M. Zhu and X. M. Guo, RSC Adv., 86 Z. Hosseini, N. Taghavinia, N. Sharifi, M. Chavoshi and M.
014, 4, 41622–41630. Rahman, J. Phys. Chem. C, 2008, 112, 18686–18689.
5 J. G. Hou, C. Yang, Z. Wang, Q. H. Ji, Y. T. Li, G. C. Huang, 87 X. J. Bai, L. Wang, R. L. Zong, Y. H. Lv, Y. Q. Sun and Y.
2
2
S. Q. Jiao and H. M. Zhu, Appl. Catal. B: Environ., 2013,
42-143, 579–589.
F. Zhu, Langmuir, 2013, 29, 3097–3105.
88 Z. Dai, F. Qin, H. P. Zhao, F. Tian, Y. L. Liu and R. Chen,
Nanoscale, 2015, 7, 11991ꢀ11999.
1
56 L. Q. Ye, Ji. Y. Liu, C. Q. Gong, L. H. Tian, T. Y. Peng and
L. Zan, ACS Catal., 2012, 2, 1677–1683.
89 P. Ji, J. Zhang, F. Chen and M. Anpo, Appl. Catal. B:
Environ., 2009, 85, 148–154.
57 K. P. Xie , Q. Wu, Y. Y. Wang, W. X. Guo, M. Y. Wang, L.
Sun and C. J. Lin, Electrochem. Commun., 2011, 13, 1469– 90 M. C. Yin, Z. S. Li, J. H. Kou and Z. G. Zou, Environ. Sci.
472. Technol., 2009, 43, 8361–8366.
8 X. W. Wang, G. Liu, L. Z. Wang, Z. G. Chen, G. Q. Lu and 91 J. Jin , J. G Yu, D. P. Guo, C. Cui and W. K. Ho, Small, 2015,
H. M. Cheng, Adv. Energy Mater., 2012, 2, 42–46. 11, 39, 5262–5271.
9 M. R. Jones, K. D. Osberg, R. J. Macfarlane, M. R. Langille 92 J. Xing, Z. P. Chen, F. Y. Xiao, X. Y. Ma, C. Z. Wen, Z. Li
and C. A. Mirkin, Chem. Rev., 2011, 111 , 3736–3827. and H. G. Yang, ChemꢀAsian. J., 2013, 8, 1265–1270.
0 W. B. Hou and S. B. Cronin, Adv. Funct. Mater., 2013 , 23 , 93 J. T. Li, S. K. Cushing, J. Bright, F. Meng, T. R. Senty, P.
1
5
5
6
6
6
6
6
6
1
612–1619.
Zheng, A. D. Bristow and N. Q. Wu, ACS Catal., 2013, 3,
47–51.
1 H. F. Li, H. T. Yu, X. Quan, S. Chen and Y. B. Zhang, ACS
Appl. Mater. Interfaces, 2016, 8, 2111−2119.
2 D. J. Wang, G. L. Xue, Y. Z. Zhen, F. Fu and D. S. Li, J.
Mater. Chem., 2012, 22, 4751–4758.
3 H. Xu, Y. G. Xu, H. M. Li, J. X. Xia, J. Xiong, S. Yin, C. J.
Huang and H. L. Wan, Dalton Trans., 2012, 41, 3387–3394.
4 Y. S. Xu and W. D. Zhang, Dalton Trans., 2013, 42, 1094–
1101.
5 M. Y. Zhang, C. L. Shao, J. B. Mu, X. M. Huang, Z. Y.
Zhang, Z. C. Guo, P. Zhang and Y. C. Liu, J. Mater. Chem.,
2
012, 22, 577–584.
6
6 S. Guo, X. F. Li, H. Q. Wang, F. Dong and Z. B. Wu, J.
Colloid Interf. Sci., 2012, 369, 373–380.
67 A. Thomas, A. Fischer, F. Goettmann, M. Antonietti, J. O.
Muller, R. Schlogl and J. M. Carlsson, J. Mater. Chem., 2008,
18, 4893–4908.
6
8 Z. Fang, Y. F. Liu, Y. T. Fan, Y. H. Ni, X. W. Wei, K. B.
Tang, J. M. Shen and Y. Chen, J. Phys. Chem. C, 2011, 115,
1
3968–13976.
9 R. M. Mohamed and F. M. Ibrahim, Int. J. Hydrogen Energ.,
014, 39, 14479–14486.
0 H. P. Li, T. X. Hu, R. J. Zhang, J. Q. Liu and W. G. Hou,
Appl. Catal. B: Environ., 2016, 188, 313–323.
1 F. Chen, C. G. Niu, Q. Yang, X. M. Li and G. M. Zeng,
Ceram. Int., 2016, 42, 2515–2525.
2 M. Y. Zhang, L. Li, Y. Liu, L. L. Xu and X. T. Zhang, J. Mol.
Catal. A: Chem., 2015, 400, 154–161.
3 L.W. Zhang, T. G. Xua, X. Zhao and Y. F. Zhu, Appl. Catal.
B: Environ., 2010, 98,138–146.
6
7
7
7
7
7
7
2
4 J. Fu, B. B. Chang, Y. L. Tian, F. N. Xi and X. P. Dong, J.
Mater. Chem. A, 2013, 1, 3083–3090.
5 I. Honma, T. Sano, and H. Komiyama, J. Phys. Chem., 1993,
9
7, 6692–6695.
7
7
6 M. A. Butler, J. Appl. Phys., 1977, 48, 1914–1920.
7 H. W. Huang, L. Y. Liu, Y. H. Zhang and N. Tian, J. Alloy
Compd., 2015, 619, 807–811.
7
7
8
8
8
8
8
8 S. Kumar, S. Khanchandani, M. Thirumal and A. K. Ganguli,
ACS Appl. Mater. Inter., 2014, 6, 13221–13233.
9 Y. He, Y. H. Zhang, H. W. Huang, N. Tian and Y. Luo,
Inorg. Chem. Commun., 2014, 40, 55–58.
0 H. W. Huang, G. Chen and Y. H. Zhang, Chem. Commun.
014, 44, 46–49.
,
2
1 X. F. Hu, T. Mohamood, W. H. Ma, C. C. Chen and J. C.
Zhao, J. Phys. Chem. B, 2006, 110, 26012–26018.
2 J. W. Tang, Z. G. Zou and J. H. Ye, J. Phys. Chem. B, 2003,
1
07, 14265–14269.
Z. Dai, F. Qin, H. P. Zhao, J. Ding, Y. L. Liu and R. Chen,
ACS Catal., 2016, , 3180−3192.
4 Q. J. Xiang, J. G. Yu and M. Jaroniec, J. Phys. Chem. C,
011, 115, 7355–7363.
3
6
2
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New Journal of Chemistry
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DOI: 10.1039/C6NJ01893A
Manuscript for New Journal of Chemistry
Design and Construction of the Sandwich-Like Z-scheme
Multicomponent CdS/Ag/Bi MoO Heterostructure with Enhanced
2
6
Photocatalytic Performance in RhB Photodegradation
a
a
a
a
b
Danjun Wang, Huidong Shen, Li Guo, Feng Fu* and Yucang Liang*
a
College of Chemistry &Chemical Engineering, Yan'an University, Shaanxi Key Laboratory of
Chemical Reaction Engineering, Yan’an 716000, China
b
Institut für Anorganische Chemie, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 18,
7
2076 Tübingen, Germany
Corresponding Author
Dr. Yucang Liang
Institut für Anorganische Chemie, Eberhard Karls Universität Tübingen
Auf der Morgenstelle 18, 72076 Tübingen, Germany
Fax: +49(0)7071 292436
E-mail: yucang.liang@uni-tuebingen.de
Prof. Dr. Feng Fu
College of Chemistry &Chemical Engineering, Yan'an University
Shaanxi Key Laboratory of Chemical Reaction Engineering, Yan’an 716000, China
E-mail: yadxfufeng@126.com
1

Page 13 of 13
New Journal of Chemistry
View Article Online
DOI: 10.1039/C6NJ01893A
For table of contents use only:
Design and Construction of the Sandwich-Like Z-scheme Multicomponent
CdS/Ag/Bi MoO Heterostructure with Enhanced Photocatalytic Performance
2
6
in RhB Photodegradation
a
a
a
a
b
Danjun Wang, Huidong Shen, Li Guo, Feng Fu* and Yucang Liang*
Summary:
A rationally designed and successfully fabricated all-solid-state Z-scheme photocatalyst
CdS/Ag/Bi MoO with sandwich-like multicomponent heterostructure shows an enhanced
2
6
photocatalytic performance in RhB photodegradation due to a highly efficient separation of the
photogenerated electrons and holes.
e-
-
-
-
-
-
-
e e e
e e e
CB
(-0.46eV)
e-
-
-
-
ECB
-
-
-
e e e
e e e
ECB
CB
-0.21 eV)
(
2
.16 eV
2.16 eV
CdS
Ag
CdS
Bi MoO
2
.50 eV
6
Bi MoO
2
6
2
.50 eV
2
VB
(1.7eV)
+
+
+
EVB
+
+
+
h h h
h+
h+
h h h
EVB
VB
2.29 eV)
+
+
+
+
+
+
h h h
h h h
(
(
a )
( b )
Charge transfer of (a) CdS/Bi MoO and (b) CdS/Ag/Bi MoO
6
2
6
2
during photocatalytic process
2