Heterostructured composites consisting of In2O3 nanorods and reduced graphene oxide with enhanced interfacial electron transfer and photocatalytic performance

Article abstract of DOI:10.1039/c4ta04106b

A novel composite of In₂O₃ nanorods (INR) hybridized with reduced graphene oxide (RGO) was fabricated by a facile UV-assisted photoreduction method. The as-prepared samples were systematically characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and UV-vis diffuse reflectance spectroscopy. The one-dimensional INR with high surface-to-volume ratio anchored on the surface of RGO homogeneously, resulting in a nice interfacial contact between INR and RGO. The photocatalytic activities of the INR-RGO composites were investigated for 4-chlorophenol (4-CP) degradation under UV-vis or visible light irradiation. The photodegradation yield of the optimized photocatalyst reached 91.6%, which was about 1.9 times as high as that of INR under visible light irradiation (>400 nm). The enhanced photocatalytic activity of the INR-RGO composites can be ascribed to the efficient interfacial charge transfer from INR to RGO, which resulted in the prolonged lifetime of the photoinduced charge carriers.

Full text of DOI:10.1039/c4ta04106b

Journal of
Materials Chemistry A
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PAPER
Heterostructured composites consisting of In O
2
3
nanorods and reduced graphene oxide with
enhanced interfacial electron transfer and
photocatalytic performance
Cite this: DOI: 10.1039/c4ta04106b
ac
a
a
a
ab
a
Hui Huang, Zongkuan Yue, Gang Li, Xiaomei Wang, Jie Huang, Yukou Du
a
and Ping Yang*
A novel composite of In
2 3
O nanorods (INR) hybridized with reduced graphene oxide (RGO) was fabricated
by facile UV-assisted photoreduction method. The as-prepared samples were systematically
a
characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy,
Raman spectroscopy, X-ray photoelectron spectroscopy and UV-vis diffuse reflectance spectroscopy.
The one-dimensional INR with high surface-to-volume ratio anchored on the surface of RGO
homogeneously, resulting in a nice interfacial contact between INR and RGO. The photocatalytic
activities of the INR–RGO composites were investigated for 4-chlorophenol (4-CP) degradation under
UV-vis or visible light irradiation. The photodegradation yield of the optimized photocatalyst reached
Received 9th August 2014
Accepted 4th October 2014
9
1.6%, which was about 1.9 times as high as that of INR under visible light irradiation (>400 nm). The
enhanced photocatalytic activity of the INR–RGO composites can be ascribed to the efficient interfacial
charge transfer from INR to RGO, which resulted in the prolonged lifetime of the photoinduced charge
carriers.
DOI: 10.1039/c4ta04106b
www.rsc.org/MaterialsA
a-Fe
by Parida's group, and the optimized composite catalyst showed
In recent years, graphene has shown great applications in considerably higher photoactivity than that of the a-Fe O
2 3
2 3
O /graphene nanocomposites have also been synthesized
1
. Introduction
1
9–22
photocatalysis and energy conversation elds due to the unique nanorod.
However, for further improving the photocatalytic
2
sp hybrid carbon network, high carrier mobility, large theo- activity, designing and synthesizing novel graphene-based
retical specic surface area and excellent thermal conduc- photocatalysts are still needed.
1–6
tivity. In general, graphene oxide (GO) and reduced graphene
2 3
Indium oxide (In O ) has been regarded as a good candidate
oxide (RGO) exhibit many physicochemical properties similar to of photocatalysts for water splitting to produce hydrogen or
those of graphene. RGO can be prepared by reduction of GO, organic pollutants decomposition owing to its narrow band gap
which greatly improves the electron conductivity of the mate- energy (ca. 2.8 eV), stable physicochemical properties and low
7,8
23–27
rials. RGO has been considered as an ideal support and an toxicity.
Despite the substantial merits, a major drawback of
electron mediator to construct novel photocatalysts. Very In is the fast recombination of photoexcited electron–hole
O
2 3
recently, semiconductor/RGO photocatalysts were proved to pairs, leading to a relatively low photoactivity. In general, well-
possess extended absorption in the visible light region and crystallized nanocrystals with controlled size and shape as well
9
–17
promoted photocatalytic performance.
have been made to combine RGO with semiconductor nano- the electron transfer and photocatalytic reaction.
Numerous attempts as with the increased density of active sites are favourable for
28–31
Recently,
2 3
An et al. reported various In O nanomaterials, such as nanowires, nanocubes
9,10,18
materials, such as TiO , Fe O , and WO .
2
2
3
3
that the WO -nanorods/RGO composites demonstrated signi- and nanorods, have been synthesized and used as photo-
3
cantly enhanced photocatalytic activity because of the improved catalysts because of their unique one-dimensional nano-
18
32–34
separation efficiency of the photogenerated charges. Various structure and promising functions.
Zhao et al. veried that
In O nanorods (INR) with high surface-to-volume ratio and
2
3
a
single crystal structure could provide a direct path for the
photoinduced charges transfer, resulting in enhanced photo-
catalytic activity. However, to the best of our knowledge, the
College of Chemistry, Chemical Engineering and Materials Science, Soochow
University, Suzhou 215123, China. E-mail: pyang@suda.edu.cn; Fax: +86-512-6588-
34
0
b
089; Tel: +86-512-6588-0361
Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, investigation about the composite prepared by hybridizing the
Suzhou 215123, China
c
Department of Chemistry, Nantong Vocational University, Nantong 226007, China
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one-dimensional INR with RGO and its application for visible- 2.3. Characterization
light-driven photocatalysis has not been reported.
X-ray diffraction (XRD) patterns of as-prepared samples were
obtained on a Philips diffractometer using Ni-ltered Cu Ka
radiation operating at 40 kV and 40 mA. The patterns were
Herein, we report fabrication, characterization and photo-
catalysis of a novel hybrid composed of In O nanorods (INR)
2
3
and reduced graphene oxide (RGO). The nanohybrid (INR–RGO)
ꢁ
ꢁ
recorded in the range 10 –80 (2q). The samples for XRD anal-
ysis were prepared by dropping the suspension of the sample on
a glass plate, which was dried under vacuum to form a thin lm.
Transmission electron microscopy (TEM) observation was con-
ducted using a Philips TECNAI-12 instrument. The samples for
TEM analysis were ultrasonically dispersed in EtOH for 30 min
and ca. 3 mL of the resulting suspension was dropped onto
carbon coated Cu grids, and then allowed to air dry. Field
emission scanning electron microscopy (FESEM) measure-
ments were taken on a Hitachi S-4700 microscope. The energy-
dispersive X-ray (EDX) analysis was performed on a KEVEX X-ray
energy detector. X-ray photoelectron spectroscopy (XPS)
measurements were carried out with an AXIS Ultra DLD system
was prepared through a two-step method: hydrothermal reac-
tion for preparing In O nanorods and UV-assisted reduction
2 3
GO to RGO and then coupling with INR. The one-dimensional
INR was uniformly anchored on the surface of RGO, and the two
moieties of the composite exhibited nice interfacial contacts. In
the INR–RGO composite, the RGO moiety acted as an electron
collector and transporter, which synergistically enhanced elec-
tron transfer from INR to RGO and decreased the recombina-
tion of electrons and holes, resulting in a greatly enhanced
photocatalytic activity of the degradation of 4-chlorophenol
(4-CP). Our research demonstrates a potential application of
INR–RGO composite as a novel photocatalyst to remove envi-
ronment contaminants.
(
Kratos Analytical Inc.) using monochromatic Al Ka radiation.
All binding energies (BE) were referenced to the C 1s peak at
84.6 eV. Fourier transform infrared (FTIR) spectra of the
2
2. Experimental
samples were obtained with a Thermo Scientic Nicolet 6700
instrument. The solid samples were dried in vacuum at room
temperature for 2 h, and then dispersed in KBr and compressed
into a thin disk for the measurement. Raman spectra of the
samples were measured with a JobinYvon HR-800 spectrometer
using a He–Ne laser (l ¼ 633 nm, spot size ꢂ1 mm). UV-vis
diffuse reectance spectra (DRS) of the samples were measured
on a UV-1800 SPC spectrophotometer. Photoelectrochemical
measurements of the samples were carried out on a CHI 660 B
potentiostat/galvanostat electrochemical analyzer in a three-
electrode system, consisting of an indium tin oxide (ITO) glass
covered with the sample, a platinum wire, and a Ag/AgCl elec-
trode. The ITO covered sample acted as a working electrode, the
platinum wire as the counter electrode, and Ag/AgCl as the
reference electrode. The electrodes were immersed in 1 M
2.1. Materials
InCl $4H O (A.R., 99.99%), urea and graphite powder (Alfa
3
2
Aesar, 325 mesh, 99.9995%) were purchased and used without
further purication.
2.2. Synthesis of INR–RGO
In O nanorods were prepared via the hydrothermal method. In
2
3
ꢀ
1
a typical procedure, 50 mL of InCl (0.25 mol L ) solution was
mixed with 50 mL of urea solution (2.4 mol L ) under magnetic
3
ꢀ
1
stirring. Then the mixture was transferred into a 150 mL Teon-
ꢁ
lined stainless steel autoclave and heated at 130 C for 12 h. The
solid was collected by centrifugation and washed with distilled
ꢁ
water and ethanol several times, dried at 80 C for 24 h in air,
Na
2 4
SO solution. The working electrode was irradiated with a
ꢁ
then annealed in air at 350 C for 3 h, resulting in In
2
O
3
150 W GY-10 xenon lamp during the measurement. A 400 nm
nanorods (INR). Graphene oxide (GO) was synthesized using
cut-off lter was set between the lamp and the working elec-
trode for the visible light irradiation. The electrochemical
impedance spectroscopy (EIS) was carried out using a similar
system for the measurement of photoelectrical response under
the perturbation signal of 5 mV over the frequency range from
graphite powder as the starting material by a modied
35
Hummers method.
INR/RGO nanohybrid was fabricated via an UV-assisted
reduction and coupling method. In a typical experiment, a
ꢀ1
certain amount of GO solution (0.5 g L ), 0.2 g of INR and 50
mL of ethanol were added into a 100 mL cylindrical quartz glass
vessel. The mixture was sonicated for 30 min, and then irradi-
ated by a 500 W high pressure Hg lamp with the main wave crest
10 Hz to 10 MHz.
2.4. Measurements of photocatalytic activities
at 365 nm for 8 h under magnetic stirring. Aer UV light irra- The photocatalytic degradation of 4-chlorophenol (4-CP) was
diation, it was found that the color of the suspension had carried out in a 50 mL quartz photochemical reactor containing
ꢀ
1
ꢀ1
changed into greyish-black, indicating the successful chemical 50 mL of 4-CP (25 mg L ) and the catalyst (Ccatal ¼ 1.0 g L ). A
reduction of GO to RGO. Finally, the mixture was ltered, and water-cooling system was used to maintain the solution at room
the solid was rinsed by deionized water several times and dried temperature. The pH value of the system was adjusted by the
under vacuum at room temperature. The resulting samples addition of hydrochloric acid or sodium hydroxide solution.
were labelled as INR–RGO-x, where x stands for the weight The system was stirred continuously with air bubbling into the
percentage of RGO in the composite, which may vary from 0 to reaction solution and irradiated by a 150 W Xe lamp at 298 K
5, depending on the ratio of the starting materials in the and atmospheric pressure. The visible light irradiation was
synthesis. For comparison, RGO was also prepared using the obtained from the xenon lamp equipped with a UV cut-off lter
same UV-assisted reduction method.
(l > 400 nm). During irradiation, ca. 1.5 mL of the suspension
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was taken from the reactor with a syringe at a regular time
interval for analysis. The sample taken out of the reactor was
centrifuged to separate the solid photocatalyst from the
suspension. The solution was analyzed with a high pressure
liquid chromatograph (P680ALPG4) equipped with a UVD170U
analysis detector and a C18 column.
3. Results and discussion
3.1. Structure and morphology of the samples
The crystalline phase and structure of the as-prepared samples
were examined by powder X-ray diffraction (XRD). The XRD
patterns of INR and the INR–RGO-2 composite are shown in
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
Fig. 1. The peaks at 21.4 , 30.5 , 35.4 , 50.9 and 60.5 corre-
spond to the (211), (222), (400), (440) and (622) planes of the
36
2 3
cubic In O (JCPDS no. 71-2194). Furthermore, no character-
istic diffraction of carbon species has been detected from
INR–RGO-2, which may be attributed to the relatively low
37
amount and weak intensity of RGO in the composite.
SEM and TEM were taken to analyze the morphology and the
microscopic structure of INR and INR–RGO-2, and the results
are displayed in Fig. 2. It can be observed from Fig. 2A that INRs
with a well-dened morphology are successfully synthesized.
2 3
The as-prepared In O demonstrated a rodlike shape with a
diameter of ca. 200 nm and a length about 1.5–2.5 mm. As for
INR–RGO-2 composite, the addition of RGO during the
synthesis process did not affect the morphology of INR. It can
be seen from Fig. 2B that the INRs have homogeneously
anchored on the RGO sheets, and the two-dimensional struc-
ture of RGO sheets with obvious wrinkles are still retained aer
the UV-assisted photoreduction treatment. The SAED pattern
Fig. 2 (A) SEM image of INR, (B and C) TEM image of INR–RGO-2,
(
(
inset of (C)) the selected area diffraction (SAED), (D) HRTEM image and
E) EDX spectra of INR–RGO-2.
(
inset Fig. 2C) recorded on the marked area of Fig. 2B reveals
that INR possesses single crystal structure. As observed in the
HRTEM (Fig. 2D), the measured lattice fringe spacing of The XPS analysis was further employed to determine the
.275 nm in INR–RGO-2 composite corresponds to the cubic composition and the surface electronic state of the as-synthe-
3.2. XPS analysis
0
34
INR. Chemical composition analysis of INR–RGO-2 composite sized samples. Survey XPS spectrum (Fig. 3A) indicates that the
by EDX spectroscopy shows the presence of In, O and C INR–RGO-2 composite consists of C, In, and O elements. To
elements in the composites (Fig. 2E), conrming that the investigate the degree of reduction of the RGO sheets in the
obtained composite consists of RGO and INR.
composites, the high-resolution C 1s spectrum of GO and
INR–RGO are shown in Fig. 3B. Evidently, the C 1s spectrum of
GO can be deconvolved into four peaks corresponding to carbon
atoms in different functional groups: the non-oxygenated ring C
(
284.6 eV), the C atom in the C–O bond (286.5 eV), the carbonyl
38
C (C]O, 288.3 eV) and the carboxylate C (O–C]O, 289.1 eV).
Aer the hybridization with INR and the photoreduction treat-
ment, the intensity of the C–O peak is dramatically decreased,
indicating the GO have been reduced to RGO sheets. Fig. 3C
shows the In 3d core level photoelectron spectra of INR and
INR–RGO-2. The spectrum of the INR sample may be tted with
two peaks corresponding to In 3d5/2 centered at 443.7 eV and In
3+
19
3
d3/2 at 451.1 eV, indicating the presence of In . Furthermore,
the peak corresponding to C–O in INR–RGO-2 composite
Fig. 3B) exhibited an evident shi to a lower binding energy
(
position compared with that of the GO. Simultaneously, the fact
Fig. 1 Wide-angle XRD patterns of INR and INR–RGO-2.
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Fig. 4 FTIR spectra of GO, RGO and INR–RGO-2.
42
skeletal vibration of the RGO sheets. These results indicated
that the oxygen functional groups in GO were removed, and GO
43
was reduced during the formation of INR–RGO-2 composite.
The interaction between INR and RGO was further
conrmed by the Raman spectral analysis (Fig. 5). For INR, the
ꢀ
1

ve distinct peaks located at 131, 308, 367, 497, and 630 cm
could be detected. As is expected, RGO displays two prominent
G and D bands, which are generally assigned to the E2 photon
g
2
of sp bonds of carbon atoms, and a breathing mode of k-point
phonons of A1g symmetry, respectively. Compared with RGO
sheets, it could be observed that the D- and G-band of
44
ꢀ1
ꢀ1
INR–RGO-2 slightly up-shis to 1351 cm and 1601 cm
,
respectively, which provides more evidence of superior inter-
actions between INR and RGO.
Fig. 3 (A) XPS spectra of the survey spectra of the INR and INR–RGO-
2, (B) C 1s peaks of the GO and INR–RGO-2 and (C) In 3d peaks of the
INR and INR–RGO-2.
3.4. Optical and photoelectrochemical properties of the
samples
The UV-vis diffuse reectance spectra of INR and INR–RGO-x
composites with various contents of RGO are shown in Fig. 6A.
It can be seen that the absorption intensity of INR–RGO-x
composites increases with the augment of RGO content. The
red-shi of the absorption edge of INR–RGO-x composites may
be ascribed to some restoration of the p–p conjugation network
that both the peaks of In 3d5/2 and 3d3/2 have a shi of 0.4 eV to
the higher bonding energy (Fig. 3C) demonstrates chemical
39
bonding between INR and RGO in the hybrid. The chemical
interaction between GO and INR may be attributed to the
formation of an In–O–C chemical bond. The similar phenom-
40
2
enon was also observed from the TiO –RGO system.
3.3. FTIR and Raman spectra
The FTIR spectra of the samples are shown in Fig. 4. The
characteristic absorption bands of GO are observed at 1048
ꢀ
1
(
C–OH), 1578 (C]C) and 1719 cm (C]O). For the photo-
reduced RGO, the intensity of the absorption bands corre-
sponding to C–OH and C]O groups decreases signicantly,
and the absorption band corresponding to C]C vibration
ꢀ
1
slightly red-shis to 1576 cm . For the INR–RGO-2 hybrid, the
broad IR band at low frequency reects the stretching vibration
ꢀ1
of In–O–In bonds, and the bond at 556 cm can be assigned to
41
In–O vibration. Moreover, the peaks corresponding to C]O
ꢀ
1
and C–OH vibrations at 1719 and 1048 cm , respectively, in the
INR–RGO-2 composite are not observed, and a new absorption
ꢀ
1
band appeared at 1642 cm , which might be attributed to the Fig. 5 Raman spectra of RGO, INR and INR–RGO-2.
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Fig. 7 Photocurrents of (a) INR, (b) INR–RGO-1, (c) INR–RGO-2 and
(
d) INR–RGO-5 under visible light irradiation (l > 400 nm) at 1.2 V. The
ꢀ2
power of the lamp with a 400 nm cut-off filter is ca. 100 mW cm
.
indicates higher charge separation efficiency and prolonged
lifetime of the photogenerated electrons and holes. With the
extensive two-dimensional p–p conjugation structure, RGO
serves as an acceptor and transporter of the electrons generated
from the In
generated charges separation.
2 3
O semiconductor, which enhances the photo-
46
The electrochemical impedance spectrum (EIS) is another
powerful tool to study the charge transfer process. As shown in
Fig. 8, the radius of the Nyquist curve of INR–RGO-2 is
considerably smaller than that of INR, indicating the fast
interfacial electron transfer between INR and RGO and efficient
Fig. 6 (A) UV-vis diffuse reflectance spectra of the as-prepared INR,
INR–RGO-1, INR–RGO-2 and INR–RGO-5 composites. (B) The plots
of (ahn) versus energy hn for INR and INR–RGO-2 composite.
2
47
hindrance of the charge recombination in the hybrid.
45
of the RGO in the hybrid. Moreover, Fig. 6B shows the plots of
2
(
ahn) versus photon energy, which demonstrate that the band
gap of the INR is 2.71 eV, whereas the band gap of the INR–RGO-
composite has been consequently reduced to 2.37 eV. The
3.5. Photocatalytic activity
2
The photocatalytic degradation of 4-CP was investigated under
UV-vis and visible light (>400 nm) irradiation, respectively.
From Fig. 9A we can see that the 4-CP photodegradation yield of
INR is 58.1% aer 2 h UV-vis light irradiation. However, the
narrowing of the band gap in the case of INR–RGO-2 composite
was attributed to the interaction between INR and RGO.
Therefore, hybridization of INR and RGO to form a composite
may also change the band gap and light absorption property of
the materials.
The results of photoelectrochemical experiments performed
under visible light illumination are shown in Fig. 7. Under
visible light irradiation (l > 400 nm) and 1.2 V applied voltage,
blank experiments conducted with the bare ITO electrode do
not produce photocurrent. It is found that the INR electrode
demonstrated prompt but weak photocurrent responses under
visible light irradiation. However, enhanced photocurrent
responses for INR–RGO electrodes are detected evidently. As the
content of RGO in the INR–RGO composites increased from 1%
to 2 wt%, the corresponding photocurrent density increased
ꢀ2
from 12.23 to 15.41 mA cm . The order of photocurrent
response is INR–RGO-2 > INR–RGO-1 > INR–RGO-5 > INR. The
maximum photocurrent density for the INR–RGO-2 electrode is
ca. 6 times as high as that of the INR electrode under the same
irradiation conditions, suggesting positive synergetic effect
between INR and RGO components in the hybrid. The
enhancement of the photocurrent for INR–RGO electrodes
Fig. 8 Nyquist plots of electrochemical impedance spectra (EIS) for
the electrodes covered with INR and INR–RGO-2 composites in 0.5 M
Na SO electrolyte.
2 4
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Fig. 9 Photodegradation 4-CP yields over the as-prepared INP, INR
and INR–RGO-x composites under UV-vis light (A) and visible light (B) Fig. 10 (A) Effect of the pH values on photodegradation of 4-CP under
l > 400 nm) irradiation. Reaction conditions: mcatalyst ¼ 50 mg, T ¼ visible light and (B) cycling measurements of the yields of 4-CP
98 K, pH ¼ 3, light source: 150 W Xe lamp (a cut-off filter (l > 400 nm) degradation under visible light irradiation by INR–RGO-2 composite.
used for visible light irriadiation).
Reaction conditions: mcatalyst ¼ 50 mg, T ¼ 298 K, pH ¼ 3, light source:
50 W Xe lamp with cut-off filter (l > 400 nm).
(
2
1
4
-CP photodegradation yields of INR–RGO-1 reached 91.9%. In
maximum average photodegradation yield of 4-CP was achieved
at a pH of 3. The reason that organic contaminants photo-
degradation should occur at an optimized pH may be attributed
addition, along with the increase of RGO in the composite, the
photocatalytic activity of INR–RGO composites reached a
summit and then decreased. The optimized RGO content in the
INR–RGO composite is ca. 2 wt% and the 4-CP degradation yield
of the catalyst under 2 h UV-vis irradiation is 96.2%, which gives
approximately 38% increase compared with that of INR under
the same conditions.
+
to the fact that the concentration of H in the solution may
inuence the transfer of photoinduced electrons and redox
potential of the contaminant and thus affect the photocatalytic
48,49
activity of the catalyst.
The stability of INR–RGO-2 composite for the photo-
degradation of 4-CP is shown in Fig. 10B. The results of ve
cycles of photocatalytic experiments demonstrate that the
INR–RGO-2 composite is very stable and thus suitable for
treatment of organic contaminants in wastewater.
According to the above results, the photocatalytic mecha-
nism is illustrated in Scheme 1. Photodegradation of 4-CP is
2
believed to be initiated by cOH radicals. In the presence of O ,
In order to further investigate the photocatalytic properties
of the as-prepared samples, analogous experiments are con-
ducted under visible light irradiation (l > 400 nm). As shown in
Fig. 9B, the 4-CP photodegradation yield of INR–RGO-2 under 4
h visible-light irradiation is ca. 91.6%, which is ca. 1.9 times as
high as that of INR under similar conditions. These results
demonstrate that the INR–RGO composites possess very nice
visible-light photocatalytic activity for photodegradation of
the cOH radicals are generated in the following photochemical
reactions:
4-CP.
In general, the enhancement of photocatalytic activity of
INR–RGO under UV-vis or visible light irradiation for 4-CP
ꢀ
+
(e + h )
In
2
O
3
+ hn / In
2
O
3
(1)
(2)
(3)
(4)
(5)
degradation could be attributed to the excellent electronic
3
conductivity and large specic surface area of RGO, which
ꢀ
ꢀ
2
In O
3
(e ) + RGO / In
2
O
3
+ e (RGO)
enhance the photoinduced electrons transport from INR to the
RGO sheets, thus inhibiting the recombination of photoin-
duced electrons and holes.
Fig. 10 A shows the effect of the pH values on the photo-
degradation yields of 4-CP under visible light irradiation. The
pH value of the system inuences the photodegradation yields
of 4-CP signicantly. When pH value varies from 1 to 7, the
ꢀ
ꢀ
e
+ O / cO
2 2
ꢀ
ꢀ
2cO2 + 2H O / H O + O + 2OH
2
2
2
2
H
O / 2cOH
2
2
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Acknowledgements
The authors gratefully acknowledge nancial support of this
research by the National Natural Science Foundation of China
(21373143 and 51273141), the Priority Academic Program
Development of Jiangsu Higher Education Institutions (PAPD),
the Project of Scientic and Technologic Infrastructure of
Suzhou (SZS201207), and Qing Lan Project of Jiangsu Province.
Notes and references
1
2
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3
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F. Miao and C. N. Lau, Nano Lett., 2008, 8, 902.
Scheme
1 Schematic photoexcited electron transfer and 4-CP
degradation over the INR–RGO photocatalyst under visible light
irradiation.
4 X. Q. An and J. C. Yu, RSC Adv., 2011, 1, 1426.
Q. J. Xiang, J. G. Yu and M. Jaroniec, Chem. Soc. Rev., 2012,
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E. J. Zimney, E. A. Stach, R. D. Piner, S. T. Nguyen and
R. S. Ruoff, Nature, 2006, 442, 282.
5
4
+
h + H
+
2
O / cOH + H
(6)
(7)
(8)
+
ꢀ
h + OH / cOH
7
8
9
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4
-CP + cOH / CO + H O
2 2
2
014, 1.
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37.
ꢀ
Under UV-vis or visible light illumination, electrons (e )
can be excited from the valence band (VB) to the conduction
band (CB) of INR, producing the same number of holes (h ) in
the VB of the semiconductor. The photogenerated electrons in
the conduction band of INR transfer to RGO and then react
with oxygen molecules dissolved in the solution to yield
superoxide cO
role in the photodegradation of 4-CP.
molecules may also be oxidized by the holes immigrating to
the surface of INR.
4
+
1
1
1
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ꢀ
2
and nally form cOH, which may play a major
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0,51
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