Solvothermal synthesis of graphene/BiOCl0.75Br0.25 microspheres with excellent visible-light photocatalytic activity

Article abstract of DOI:10.1039/c5ra02852c

Three-dimensional BiOCl_0.75Br_0.25/graphene (BG) microspheres have been synthesized via a facile solvothermal route. The as-prepared samples were characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray Photoelectron Spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (UV-vis DRS) and Brunauer-Emmett-Teller (BET) area. The photocatalytic activities of the samples were evaluated by the degradation of Rhodamine B (RhB) under visible light irradiation. It was shown that the BG photocatalysts with 5.0 wt% graphene (BG5.0) exhibited the highest photocatalytic activity, which was almost up to 2.3 times than that of pure BiOCl_0.75Br_0.25. The enhanced photoactivity of BG5.0 was mainly attributed to the effective light absorption, the larger specific surface areas and the more efficient charge transportation and separation.

Full text of DOI:10.1039/c5ra02852c

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Solvothermal synthesis of graphene/BiOCl0.75Br0.25
microspheres with excellent visible-light
photocatalytic activity†
Cite this: RSC Adv., 2015, 5, 33696
ab
ab
ab
c
ab
Yang Liu, Xingzhong Yuan,* Hou Wang, Xiaohong Chen, Shansi Gu,
ab
ab
ab
ab
Qian Jiang, Zhibin Wu, Longbo Jiang and Guangming Zeng
Three-dimensional BiOCl0.75Br0.25/graphene (BG) microspheres have been synthesized via a facile
solvothermal route. The as-prepared samples were characterized by powder X-ray diffraction (XRD), field
emission scanning electron microscopy (FESEM), X-ray Photoelectron Spectroscopy (XPS), UV-vis diffuse
reflectance spectroscopy (UV-vis DRS) and Brunauer–Emmett–Teller (BET) area. The photocatalytic
activities of the samples were evaluated by the degradation of Rhodamine B (RhB) under visible light
irradiation. It was shown that the BG photocatalysts with 5.0 wt% graphene (BG5.0) exhibited the highest
photocatalytic activity, which was almost up to 2.3 times than that of pure BiOCl0.75Br0.25. The enhanced
photoactivity of BG5.0 was mainly attributed to the effective light absorption, the larger specific surface
areas and the more efficient charge transportation and separation.
Received 13th February 2015
Accepted 30th March 2015
DOI: 10.1039/c5ra02852c
www.rsc.org/advances
are also certied to be effective photocatalysts for the degra-
dation of pollutants under visible light irradiation. For example,
1
. Introduction
Recently, organic dyes have been extensively used to color Jia et al. successfully prepared BiOBr
products in the textile industry (nylon, wool, cotton, and silk) as vothermal and the BiOBr0.2 0.8 microspheres possessed the best
well as for varnish, waxes, plastics, etc. Since many N-containing photocatalytic activity under visible light irradiation. Kima et al.
dyes such as RhB are resistant to conventional chemical and found that the ower-like 3D-structure BiOCl 1ꢀx synthesized
x
I1ꢀx by a simple sol-
I
I
x
biological treatment, semiconductor-based photocatalysis in ethylene glycol (EG) owned better adsorption and photo-
captures great interest as a kind of “green” technology for catalytic performance than that of the stacked 2D plate-like
1,2
degrading toxic pollutants.
Among numerous semi- structures. Generally, the photocatalytic activity of the hybrids
conductors, bismuth oxyhalides have been extensively studied is superior to the monomer. Unfortunately, the fast recombi-
due to their cheap and environmental properties. The highly nation of photo-generated charge carriers still limits the appli-
anisotropic layered structure can also efficiently induce the cation of the photocatalysts. Therefore, increasing carbon
3–6
separation of photo-generated electron–hole pairs. Recently, materials as electron transport matrices are employed in
the coalescence of semiconductors concerned BiOX (X ¼ Cl, Br, retarding the recombination of electron–hole species.
I) with apposite band potentials turned out to be an attractive
Currently, carbon black, activated carbon, carbon nanotubes
approach for the enhancement of pure BiOX. Coupled semi- and graphite are found to occupy a vital position in heteroge-
7
8
17
conductor systems such as BiOI/BiOBr, BiOCl/BiOBr, TiO /- neous catalysis as either catalysts or catalyst supports. Gra-
2
9,10
11
12
13
BiOX,
Bi S /BiOCl, N/BiOBr and Ag/BiOBr have been phene, a new carbon material with a monolayer of
2 3
2
reported to have higher photocatalytic activity than that of the sp -hybridized carbon atoms, has drawn much attention due to
individual semiconductor. Besides, bismuth oxyhalides-based its large specic surface area, high carrier mobility and superior
alloyed compounds containing more than one type of chemical stability. Our previous review has summarized the
14
15
16
halogen, namely BiOCl
x
I
1ꢀx
,
BiOBr
x
I
1ꢀx
,
and BiOCl
x
Br1ꢀx
recent advances of the graphene-based hybrids for the decon-
tamination of wastewater and researched the absorbability for
18–20
the heavy metal and organic dyes.
The specically two-
a
College of Environmental Science and Engineering, Hunan University, Changsha dimensional conjugated structure also guarantees its usage as
4
10082, PR China. E-mail: yxz@hnu.edu.cn; Fax: +86 731 88823701; Tel: +86 731 a supporting platform to disperse and stabilize semiconductors
8
8821413
21–27
for potential applications in catalysis.
b
Key Laboratory of Environment Biology and Pollution Control, Hunan University,
Ministry of Education, Changsha 410082, PR China
In the present study, we rstly realized the complex of
BiOCl0.75Br0.25 and graphene to improve the photocatalytic
activity of BiOCl0.75Br0.25 via a facile one-pot solvothermal
method. The samples were characterized by FESEM, XPS and
c
School of Business, Central South University, Changsha 410083, PR China
†
Electronic supplementary information (ESI) available. See DOI:
0.1039/c5ra02852c
1
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UV-vis DRS. The highly photocatalytic activities of BG with irradiation, the suspension was stirred for 1 h in the dark to
different amounts of graphene were evaluated by the degrada- attain adsorption–desorption equilibrium. The reactor was then
tion of RhB. The by-products in aqueous solution aer photo- exposed to a 500 W Xe lamp (CHF-XM500, Beijing) equipped
catalytic reaction were further analyzed by high-performance with a UV cutoff lter (l $ 420 nm) with magnetic stirring. At
liquid chromatography (HPLC). Finally, a feasible mechanism specic time intervals, 4 mL suspensions were sampled and
for the degradation of RhB on BG systems was proposed.
centrifuged at 8000 rpm for 5 min to remove the photocatalyst
powder. The concentration of RhB was determined based on the
absorption at 554 nm using a UV-vis spectrophotometer. The
HPLC analyses were performed using Agilent 1100 HPLC
instrument system equipped with UV-VIS detector. The system
2. Experimental
2.1 Preparation of BiOCl0.75Br0.25/graphene composites
All of the reagents were of analytical grade and used without any used a C18 inversed phase column and the column temperature
ꢁ
further purication. RhB was obtained from Tianjin Kemiou was set at 25 C. The mixture of methanol and H
O (7 : 3) was
2
ꢀ
1
Chemical Reagent Co., Ltd (Tianjin, China). Graphene oxide used as mobile phase with the ow rate of 0.8 mL min
GO) was synthesized from natural graphite powder according
to the modied Hummers method described in our previous
.
(
19
3. Results and discussion
report. Firstly, a set of BiOCl Br1ꢀx were straightforwardly
x
prepared by controlling the initial molar ratio of hexadecyl tri- 3.1 Characterization of the catalyst
methyl ammonium chloride (CTAC) and hexadecyl trimethyl
The purity and crystallinity of the as-prepared samples were
conrmed by XRD technique and were depicted in Fig. 1. All the
diffraction peaks for x ¼ 0.0 and 1.0 were readily indexed to the
structure of the BiOBr (JCPDS card no. 09-0393) and BiOCl
ammonium bromide (CTAB) in the preparation protocol. The
preliminary experiment conrmed that the BiOCl
x
Br1ꢀx
exhibited the highest photocatalytic activity at x ¼ 0.75. Thus,
various BG microspheres with different contents of graphene
were prepared. In a typical synthesis, 3.0 mmol of Bi
(JCPDS card no. 06-0249) respectively. In addition, the diffrac-
tion peaks of BiOCl Br1ꢀx shi gradually to larger angles with
x
3 3 2
(NO ) $5H O was dissolved into 40.0 mL of ethylene glycol (EG).
increasing x values, which demonstrated that there was no
Then, CTAC and CTAB with a total molar amount of 3 mmol
were added to the previous solution. Meanwhile, different mass
GO was dispersed in EG by sonication and then added to the
reacted-mixture. The mixture was poured into a 100 mL Teon-
separated phase and nucleation of BiOBr or BiOCl in the
28–30
formation of alloyed BiOCl0.75Br0.25 microspheres.
It was
worth-noting that no apparent peaks of GO were observed in
BiOCl0.75Br0.25/graphene samples, implying that the GO was
almost reduced under the hydrothermal conditions. However,
ꢁ
lined stainless steel autoclave and maintained at 160 C for
10 h, and then cooled to room temperature naturally. The
the main peak assigned to reduced graphene oxide (RGO, 2q ¼
precipitate was collected by centrifugation, washed with
deionized water and anhydrous ethanol. Finally, the products
ꢁ
2
6 ) may be overlapped with the peak of tetragonal BiOCl at
ꢁ
17
2
5.8 . In addition, it may also due to the low amount and
ꢁ
were dried under vacuum at 80 C. The BiOCl0.75Br0.25/graphene
relatively weak diffraction intensity of graphene in the
composite.
The morphology of the samples was determined by FESEM
and the typical images were delineated in Fig. 2a and b. Clearly,
the pristine BiOCl0.75Br0.25 exhibited lots of scattered
samples with 2.0, 5.0, 10.0 wt% of graphene, were labeled as
BG2.0, BG5.0 and BG10.0, respectively.
2.2 Catalysts characterization
The surface morphologies of the prepared samples were char-
acterized by a eld emission scanning electron microscopy
(FESEM) (JSM-7001F, Japan). The X-ray diffraction (XRD)
patterns were obtained with Bruker AXS D8 Advance diffrac-
˚
tometer using Cu-Ka source (l ¼ 1.541 A). The surface
elemental composition analyses were conducted based on the
X-ray Photoelectron Spectroscopy spectra (XPS) (Thermo Fisher
Scientic, UK). UV-visible diffuse-reectance spectra (UV-vis
DRS) of the samples were recorded using a Varian Cary
300 spectrometer outtted with an integrating sphere. The
Brunauer–Emmett–Teller (BET) specic surface area and pore
size of the samples were measured with an automatic instru-
ment (ASAP2020, Micromeritics, USA).
2.3 Photocatalytic test and analysis
The photocatalytic activities of the as-obtained samples were
evaluated by the degradation of RhB under visible light irradi-
ation. Typically, 50 mg of the photocatalyst was suspended in a
Fig.
1 XRD patterns of GO, BiOBr, BiOCl0.75Br0.25, BiOCl and
ꢀ
1
1
50 mL of RhB aqueous solution (50 mg L ). Prior to BiOCl0.75Br0.25/graphene (BG2.0, BG5.0, BG10.0) samples.
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Fig. 2 FESEM and TEM image of (a), and (d) BiOCl0.75Br0.25, (b), and (e) BG5.0, (c) the EDX spectrum of BG5.0 and HRTEM (f) image of BG5.0.
microspheres with the diameters of around 3–4 mm (Fig. 2a). bonded carbon at 284.5 eV, (b) the carbon in epoxy/hydroxyls
The morphology of the BiOCl0.75Br0.25 and BG5.0 samples was (C–O) at 286.2 eV, and (c) the carbonyl carbon (C]O) at
34,35
further investigated by TEM. As can be clearly seen in Fig. 2b 288.4 eV.
In the XPS spectrum of C 1s from BG5.0 (Fig. 3f),
and e, the RGO displayed intrinsic microscopic wrinkles and the oxygenated functional groups decreased markedly and the
owned a well-dened layered structure. The microspheres of distinct peak at 284.5 eV corresponding to graphitic carbon
BiOCl0.75Br0.25 were randomly distributed on both sides of the were prominent, conrming the deoxygenation of GO during
graphene sheets, exhibiting strong chemical interactions with the solvothermal synthesis process. All the characterizations
the RGO sheets. The HRTEM image showed the characteristic above indicated the successful combination of BiOCl0.75Br0.25
lattice fringes of BiOCl0.75Br0.25 in the graphene nanosheets and graphene in the products. BiOCl0.75Br0.25 microspheres
matrix (Fig. 2f). The lattice spacing was calculated to be were achieved with the aid of CTAB and CTAC, which served as
0
.322 nm. Moreover, the EDX spectrum of the BG5.0 sample bromide and chloride suppliers and also as structure-directing
16
showed the presence of Bi, O, Br, Cl and C elements, conrming agents. Meanwhile, the reduction of GO and the assembly
the formation of BiOCl0.75Br0.25/graphene composites. The precipitation of the BiOCl0.75Br0.25 on graphene were success-
elemental mapping of the BG5.0 sample was also presented in fully completed. They rmly contacted with each other with the
Fig. S1.†
The XPS analysis of BG5.0 powder was further performed for tion, such as Bi–C, C–Cl veried by XPS.
the measurement of surface compositions and chemical states
new chemical bonds formed during the hydrothermal reduc-
of the sample (Fig. 3). The survey XPS spectrum revealed that 3.2 Optical properties of the samples
the BG5.0 composites were composed of Bi, O, Cl, Br, and C
Fig. 4a displayed the UV-vis DRS of the pure BiOCl0.75Br0.25 and
the BG hybrids. Compared to the pure BiOCl0.75Br0.25, BG
hybrids exhibited a strong absorption in both UV and visible
range. This phenomenon can be explained by the fact that the
introduced graphene might act as photosensitizer chemically
bonded with BiOCl0.75Br0.25 and thus contribute to the visible
light absorption. The optical absorption near the band edge
followed the formula:
(Fig. 3a). A high-resolution Bi 4f spectrum in Fig. 3b showed that
the bands located at binding energies of 164.74 eV and 159.44
eV were assigned to the Bi 4f S ¼ 5/2 and 7/2 spin-orbital
31
splitting photoelectrons in the BiOCl Br
chemical state.
0
.75 0.25
Apart from the two characteristic peaks, two other weak peaks
centered at 164.01 eV and 158.43 eV were found, which may
31,32
arise from the Bi–C bond on the lm surface of graphene.
The Br 3d peak associated with the binding energy at 68.92 eV
ꢀ
4
n/2
(
Fig. 3c) can be ascribed to Br in BiOCl0.75Br0.25 material. The
ahv ¼ A(hv ꢀ Eg)
(1)
XPS signal of Cl 2p (Fig. 3d) tted with the peak at binding
ꢀ
energy of 198.13 eV and 199.75 eV were characteristic for Cl
g
where a, v, E and A were absorption coefficient, light frequency,
anions in Bi–Cl and C–Cl, separately. Fig. 3e showed that the band gap energy, and a constant, respectively. Among them,
XPS spectrum for the O 1s region was matched with two peaks at n was determined by the type of optical transition of a semi-
5
32.0 eV and 530.2 eV. The main peak at 532.0 eV was related to conductor (n ¼ 1 for direct transition and n ¼ 4 for indirect
36
2 2
g
the Bi–O bonds in [Bi O ] slabs of BiOX layered structure. The transition). The E of the as-prepared samples can be calcu-
peak centered at 530.2 eV was assigned to the oxygen-containing lated from a plot depicting (ahv) versus (hv), as shown in
groups (hydroxyl groups or water molecules adsorbed on the Fig. 4b. The band gap energies (E values) of BiOCl0.75Br0.25
surface of the sample). Generally, the C 1s core-level spectra of BG2.0, BG5.0 and BG10.0 were estimated to be 3.05, 2.02, 2.43
GO can be devolved into three peaks: (a) the non-oxygenated sp
1
/2
,
g
33
2
and 1.56 eV.
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Fig. 3 XPS spectra of BG5.0: (a) survey spectrum, (b) Bi 4f, (c) Br 3d, (d) Cl 2p, (e) O 1s and (f) C 1s.
To further investigate the separation capacity of the photo- of 404 nm. The PL spectrum of pure BiOCl0.75Br0.25 showed a
induced carriers in semiconductors, the PL spectra of the strong emission. However, with the introduction of graphene,
samples were obtained. Fig. S2† presented the PL spectra for the emission intensity of the BG photocatalysts signicantly
pure BiOCl0.75Br0.25 and BG hybrids at an excitation wavelength decreased, with the BG5.0 sample having the weakest intensity.
g
Fig. 4 (a) UV-vis diffuse reflectance spectra of the samples; (b) the band gaps (E ) of different samples.
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The result indicated that the efficient transfer of photo-induced
electrons between BiOCl0.75Br0.25 and graphene facilitated the
electron–hole separation, and thus improves the photocatalytic where k (min ) and t (min) were the apparent rst-order rate
activity.
ꢀln(C /C ) ¼ kt
(2)
t
0
ꢀ
1
ꢀ
1
ꢀ1
0 t
constant and irradiation time, C (mg L ) and C (mg L ) were
the initial concentration of RhB and the remaining concentra-
3
8–40
tions of RhB at each time, respectively.
plots and corresponding k values were shown in Fig. 6c and d.
The ability of photocatalysts to adsorb target pollutants was The initial removal constants were calculated to be 0.068, 0.118,
The model tting
3.3
2
N sorption isotherms
ꢀ
1
another noticeable factor in affecting its photocatalytic perfor- 0.151, and 0.098 min for BiOCl0.75Br0.25, BG2.0, BG5.0, and
mance. The specic surface area and porosity of BiOCl0.75Br0.25 BG10.0, respectively.
and BG5.0 were investigated by using nitrogen adsorption and
The result suggested that the introduction of graphene can
desorption isotherms (as shown in Fig. 5). The isotherms can be efficiently enhance the photocatalytic performance of
categorized as type IV with a distinct hysteresis loop observed in BiOCl0.75Br0.25. This may be ascribed to the increased active
the range of 0.4–1.0 p/p , implying the presence of mesopores in adsorption sites and photocatalytic reaction centers offered by
0
37
the size range of 2–50 nm. The corresponding porosity graphene. Besides, graphene can act as an electronic “high way”
distribution of the samples was shown in the insets of Fig. 5. and decrease the recombination of the photoexcited electron–
The average pore diameter was calculated to be 5.946 nm and hole pairs. BG5.0 showed the highest RhB removal efficiency
4
.868 nm for BiOCl0.75Br0.25 and BG5.0. The Brunauer–Emmett– (97.8%). However, a further increase in graphene amount
Teller (BET) surface areas of the samples calculated from N
(10 wt%) led to a decrease in photocatalytic efficiency of the
2
2
ꢀ1
2
ꢀ1
isotherms were 20.26 m g and 35.0 m g , respectively. Such composite. The reason was that the excessive graphene could
mesoporous architecture and the larger surface area of BG5.0 act as a kind of recombination center and promote the recom-
played an important role in the adsorption process and the bination of electron–hole pairs in graphene (Fig. S2, ESI†).
34
catalyst reaction.
Additionally, the large of black may weaken the intensity of light
through the depth of the reaction solution, which would lead to
a decreased photocatalytic activity.
In addition, as illustrated in Fig. 7, the by-products in
41,42
3.4 Photocatalytic activity of RhB under visible lights
To determine the photocatalytic activity of the as-prepared aqueous solution aer photocatalytic reaction were further
samples, the degradation of RhB was investigated under analyzed by HPLC. Obviously, some incomplete mineralized
visible light irradiation. Fig. 6a presented the variation of the intermediates of RhB formed during the irradiation process,
RhB concentration (C/C
0
) as a function of the irradiation time which was answerable for the blue shi of the absorption peak
over BG photocatalysts. The dark experiment with no signicant (Fig. S3, ESI†). The intensity of RhB peak decreased quickly
changes conrmed that the adsorption–desorption equilibrium while the concentration of other intermediates rst increased
can be achieved aer 60 min stirring at dark. As shown in and subsequently decreased with further irradiation. It was
Fig. 6a, BG2.0, BG5.0, and BG10.0 could remove 94.7%, 97.8%, generally reported that the decomposition was mainly a de-
36,43
and 91.2% of RhB which were better than the pure ethylated process.
In addition to RhB, ve intermediates
BiOCl0.75Br0.25. The temporal evolution of the spectral changes were evidently observed (Fig. 7b). The result may correspond to
of the RhB mediated by the samples was also detected (Fig. S3, the N-deethylated products during the de-ethylated process.
0
0
ESI†).
Namely, N,N-diethyl-N -ethylrhodamine (DER), N-ethyl-N -
To quantitatively understand the reaction kinetics of the RhB ethylrhodamine (EER), N,N-diethylrhodamine (DR), N-ethyl-
degradation, the pseudo-rst-order kinetics model was used to rhodamine (ER), and rhodamine (R), corresponded to peaks
44,45

t the photodegradation data, the equation is:
b–f, respectively.
Then, the conjugated structure of RhB was
Fig. 5
2
N adsorption and desorption isotherms of the (a) BiOCl0.75Br0.25 (b) BG5.0. Insets: the corresponding pore-size distribution.
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Fig. 6 (a) Photocatalytic degradation of RhB over BiOCl0.75Br0.25/graphene composites under visible light (l $ 420 nm) irradiation; (b) pho-
tocatalytic degradation of RhB (100 mL, 50 ppm) with BG5.0 in the absence and presence of different scavengers. (c) Pseudo first-order kinetics
fitting plots and (d) apparent first-order rate constants for various photocatalysts.
assault and some organic acidic molecules were produced due photodegradation of BG5.0 for RhB upon addition of various
4
6,47
to the process of opening-ring.
Finally, these organic acidic scavengers. Apparently, the RhB degradation was almost
+
ꢀ
molecules were further mineralized to water and carbon totally suppressed aer trapping h by adding EDTA. BQ (cO2
dioxide. On the basis of the above results, one rational pathway scavenger) also appeared signicantly suppressed on the dye
for the visible light induced photocatalytic degradation of RhB degradation. However, IPA acted as cOH trapping agent pre-
was put forward and depicted in Fig. 8.
.4.1 Major active species and photocatalytic mechanism.
sented no inuence on photoactivity.
3
On the basis of the aforementioned results and analysis, a
The photodegradation of organic pollutants may involve one possible mechanism was proposed as Scheme 1 to explain the
+
ꢀ11
or more of the reactive species cOH, h , and cO
2
. An alter- process of BG5.0 removing RhB under visible light irradiation.
native chemical method by adding scavengers was used to
investigate the role of the active species in the disintegration
of RhB. Isopropyl alcohol (IPA), benzoquinone (BQ) and EDTA
+
BiOCl0.75Br0.25 + visible light / BiOCl0.75Br0.25
(eCBꢀ
+ hVB
)
(3)
ꢀ
+
as scavengers for cOH, cO2 and h were dissolved in the
CBꢀ
CBꢀ
)
1
4,40
BiOCl0.75Br0.25(e
) + graphene / graphene(e
(4)
reaction solution, respectively.
Fig. 6b displayed
Fig. 7 HPLC chromatograms of the RhB (a) and (b) the N-deethylated intermediates recorded at 554 nm at 15 and 25 m.
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Fig. 8 Proposed pathway for the photocatalytic degradation of RhB dye under visible light.
CBꢀ
2
2ꢀ
e
+ adsorbed O
(surface O) / cO
(5) the photogenerated electron–hole pairs. The ow electrons
accumulated on the surface of graphene could be captured by
(6) the surface-absorbed molecular (or atomic) oxygen to yield
+
+
H O + BiOCl0.75Br0.25(hVB ) / H + cOH
2
ꢀ
cO
2
. The superoxide radical anion acted as an oxidant to attack
2ꢀ
+
cO + H / cOH
(7)
(8)
(9)
38
the pollutants and the pollutants were degraded gradually.
The activated cO2 further proceeded to form active cOH radi-
cals via a series of reaction with H . The adsorbed OH species
may also capture the hole to form cOH radicals. However, the
ꢀ
ꢀ
+
OH + BiOCl0.75Br0.25(hVB ) / cOH
+
ꢀ
36
+
ꢀ
+
h ,cO2 + adsorbed dye/dye / degradation products
cOH radical did not participated in the dye degradation since
ꢀ
there was no cOH scavenger effect. To summarize, the cO
2
and
+
CBꢀ
h as dominant active species undergo the main responsibility
to degrade the dye.
Once the material was irradiated, the electrons (e
) can be
excited to the conduction band (CB) from the valence band (VB)
of the BiOCl0.75Br0.25, leaving behind a hole in the valence band
simultaneously. Then, graphene accepted the photogenerated
electrons from BiOCl0.75Br0.25 and transported apace to separate
3.4.2 Stability of the catalyst. Reuse activity was an impor-
tant parameter for photocatalytic materials. According to the
experimental data, BG5.0 showed the highest photocatalytic
activity. Thus, BG5.0 was selected as model and undergone the
Scheme
1 The photocatalytic mechanism of RhB over BG
composites.
Fig. 9 Recycling test of BG5.0 in photocatalytic degradation of RhB.
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2
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