Facile Synthesis of BiOBr/Bi2Sn2O7 Heterojunction Photocatalysts with Improved Photocatalytic Activities

Article abstract of DOI:10.1111/jace.14431

BiOBr/Bi₂Sn₂O₇ heterojunction photocatalysts were successfully synthesized by treating hydrothermal as-prepared Bi₂Sn₂O₇ nanoparticles with hydrobromic acid (HBr). Partial Bi₂Sn<

Full text of DOI:10.1111/jace.14431

J. Am. Ceram. Soc., 1–7 (2016)
DOI: 10.1111/jace.14431
©
2016 The American Ceramic Society
ournal
J
Facile Synthesis of BiOBr/Bi Sn O Heterojunction Photocatalysts with
2
2
7
Improved Photocatalytic Activities
†
†
Dongdong Lv, Dafeng Zhang, Xipeng Pu, Yecheng Li, Jie Yin, Huiyan Ma, and Jianmin Dou
School of Materials Science and Engineering, Shandong Provincial Key Laboratory of Chemical Energy Storage and Novel Cell
Technology, Liaocheng University, Liaocheng, Shandong 252000, China
BiOBr/Bi
2
Sn
2
O
7
heterojunction photocatalysts were success-
contribution of Sn 5s to the conduction band (CB) and Bi 6s
2
0
fully synthesized by treating hydrothermal as-prepared
Bi Sn O nanoparticles with hydrobromic acid (HBr). Partial
to the valence band (VB). However, the poor light absorp-
tion and the rapid recombination of photogenerated
electrons and holes still limit its photocatalytic efficiency and
2
2
2
2
7
7
Bi
Sn
O
nanoparticles reacted with HBr to form the sheet-
Sn nanoparticles distributed evenly on
BiOBr sheets. BiOBr/Bi Sn O photocatalysts treated with
2
4
like BiOBr, and Bi
2
O
2 7
the practical applications. It has been proved that the con-
struction of heterojunction through combination of two
semiconductors is a promising technique to broaden respon-
2
2
7
different concentrations of HBr solution were successfully
obtained, and their structures, morphologies, optical, and visi-
ble light photocatalytic properties were characterized by XRD,
DRS, PL, SEM, and TEM. The experimental results showed
8
,25–27
sive spectrum and suppress the charge recombination.
On the basis of the alignment of the valence bands and
conduction bands of BiOBr and Bi Sn O , BiOBr/Bi Sn O
2
2
7
2
2
7
8
2
that the BiOBr/Bi
tocatalytic activity under visible light irradiation than pure
Bi Sn . The sample treated with 0.08 mol/L HBr solution
2
Sn
2
O
7
photocatalysts showed improved pho-
is expected to exhibit enhanced photocatalytic performance.
In this work, we synthesized a series of BiOBr/Bi Sn
composites by facially treating Bi Sn
acid (HBr) solution. We characterized the structures and
morphologies of as-synthesized BiOBr/Bi Sn composites.
2
2
O
7
2
2
O
7
2
2 7
O with hydrobromic
shows the best visible light photodegradation performance of
rhodamine B. In addition, the active species and photocatalytic
mechanism were discussed in detail.
2
2 7
O
It was found that BiOBr sheets were in situ obtained and
Bi Sn O nanoparticles were evenly distributed on the surface
of BiOBr sheets. Moreover, the catalytic mechanism of the
2
2
7
Keywords: BiOBr/Bi Sn O ; photocatalyst; heterojunction
2
2
7
BiOBr/Bi
2
Sn
2
O
7
composites have also been studied.
I. Introduction
NVIRONMENTAL pollution problems facing the world
today have attracted much attention and are getting
II. Experimental Procedure
E
All reagents of analytical grade were bought from Aladdin
Reagent Co. (Shanghai, China). Pure Bi Sn was synthe-
sized by a hydrothermal method. First, 0.04 mol SnCl H O
1–3
worse.
with TiO
Since Fujishima demonstrated the photocatalysis
under UV-light irradiation in 1970s, semiconduc-
2
2 7
O
2
20
.
4
2
tor-based photocatalytic technique has been considered to be
one of the reliable and ultimate solutions to dealing with glo-
was dissolved in 20 mL deionized water under vigorous stir-
ring to obtain a transparent solution. White Sn(OH) precipi-
tation was quickly formed after 80 mL NaOH solution
2 mol/L) was added. The as-prepared white precipitation
and 0.04 mol bismuth nitrate pentahydrate [Bi(NO O]
were added into 40 mL deionized water under vigorous stir-
ring. Then, the pH value of the mixture was adjusted to 12
by the addition of 4 mol/L NaOH solution. After 10 min
stirring, the suspension was transferred into a Teflon-lined
autoclave (100 mL capacity) and kept at 200°C for 24 h. The
resulting yellowish powder was collected by filtering, washed
with DI water, and then dried at 80°C for further use. A
4
–6
4
bal environmental pollution.
ductor owning improved photocatalytic activities for the
2
TiO is a famous semicon-
(
7
,8
oxidative degradation of organic compounds.
TiO with band gap of 3.2 eV has poor nature solar effi-
ciency and slow reaction rate, which hinders its further appli-
However,
3
)
3
ꢀ5H
2
2
9,10
cations.
Thus, in order to utilize abundant and clean solar
energy, the research and development of visible light respon-
sive photocatalysts has become an appealing challenge.
Recently, bismuth-based semiconductors, including BiOX
1
1–14
15
16,17
(
X = Cl, Br, and I),
Bi Sn O
2 2 7,
BiVO4,
Bi WO
,
and
have attracted much attention due to their
2
6
1
8–21
2 2 7
total quantity of 0.001 mol Bi Sn O (0.7674 g) was added
outstanding photo-oxidation activity. Bi-based semiconduc-
tors are believed to possess the hybridized energy band struc-
tures, which can effectively suppress the recombination of
into 40 mL HBr solution followed by 20 min ultrasonication.
Then, the suspension was kept at 90°C for 30 min. The resul-
tant sample was washed with DI water and dried at 80°C for
further characterization. The concentrations of HBr solution
are 0, 0.05, 0.08, 0.1, and 0.15 mol/L and the corresponding
2
2
photogenerated electrons and holes. The characteristic lay-
2
+
ered structure of (Bi
tric field that contributes to the efficient separation of
2
O
2
)
can also produce an internal elec-
samples were labeled as Bi
.15-BiOBr/Bi Sn , respectively.
X-ray powder diffraction (XRD) patterns were measured
2 2 7
Sn O , 0.05-, 0.08-, 0.1-, and
2
3
photogenerated electrons and holes.
Bi Sn belongs to the pyrochlore oxides with 352 atoms
2 2 7
per unit cell. As a Bi-based semiconductor, Bi Sn O has
0
2
2 7
O
2
2 7
O
18,20
on a D8 diffractometer (Bruker Co., Karlsruhe, Germany)
with CuKa-radiation. Field-emission scanning (FE-SEM) and
transmission electron microscopy (TEM) were carried out on
a Gemini microscope (Zeiss Ltd., Oberkochen, Germany)
quipped with an energy-dispersive X-ray spectrometer (EDX)
and a JEM-2100 microscope (JEOL Ltd., Tokyo, Japan),
respectively. Ultraviolet–visible diffuse reflectance spectra
shown its potential application in photocatalysis due to the
R.-J. Xie—contributing editor
(
UV–vis DRS) of samples and the absorption spectra of RhB
solution were recorded on a UV-3600 spectrophotometer
Shimadzu Co., Kyoto, Japan). The photoluminescence (PL)
Manuscript No. 38575. Received May 10, 2016; approved July 6, 2016.
Authors to whom correspondence should be addressed. e-mails: xipengpu@hotmail.com
and dougroup@163.com
†
(
1

2
Journal of the American Ceramic Society—Lv et al.
spectra of samples were recorded on an F-7000 spectrometer
The photocatalytic performance of samples were charac-
terized on a home-made photocatalytic reaction box using
RhB as a model pollutant. A 300 W xenon lamp with a UV
cutoff filter (JB450) was used as irradiation source. Solid cat-
alyst (0.1 g) was dispersed in 100 mL aqueous solution of
RhB (10 mg/L). The suspension was stirred for 30 min in
dark to ensure the adsorption–desorption equilibrium
between the organic molecules and the catalyst surface, and
then transferred to a cylindrical container with a circulating
water jacket under the xenon lamp. The absorption of RhB
solution was analyzed by recording the absorption band
maximum (554 nm) in the absorption spectra and taken as
(Hitachi Ltd., Tokyo, Japan). The Brunauer–Emmett–Teller
(BET) specific surface areas of samples were measured with a
Quantachrome Autosorb IQ-C nitrogen adsorption appara-
tus (Quantachrome Co., Boynton Beach, FL). The photocur-
rent analysis and the electrochemical impedance spectroscopy
(
workstation (Chenhua Co., Shanghai, China), using
EIS) were carried out on an CHI-660C electrochemical
a
conventional three-electrode cell. ITO glass coated with the
as-prepared samples served as the working electrode. The
counter and the reference electrodes were a platinum wire
and a saturated Ag–AgCl electrode, respectively. A 0.1M
Na SO aqueous solution was used as electrolyte. A 300 W
xenon lamp with a UV cutoff filter (JB450, Fuchen Co.,
Changchun, China) was used as the photosource.
2
4
0
the initial concentration (C ). During the photocatalysis, the
absorption of suspension was measured at an interval of
10 min, and the normalized concentration changes (C/C ) of
0
2 2 7
RhB were calculated. The photostability of BiOBr/Bi Sn O
photocatalyst was further characterized through a 6-cycle
photodegradation. After each cycle, photocatalyst was
washed by DI water and alcohol several times, and then
redispersed in fresh RhB solution for another cycle. The
ꢁ
2ꢁ
ꢁ
effects of foreign anions of 0.1M (Cl , SO
4
, NO , and
3
ꢁ
+
HCO3 ) using Na as cation on the photodegradation reac-
tion were studied under the same conditions.
III. Results and Discussion
The XRD patterns of the synthesized heterostructured com-
posites, as well as the pure Bi
2 2 7
Sn O , are shown in Fig. 1.
The XRD peaks of Bi Sn O at around 28.8°, 33.4°, 47.9°,
2
2
7
and 56.9° can be indexed as the (2 2 2), (4 0 0), (4 4 0), and
(
6 2 2) diffractions of a pure cubic phase of Bi Sn
2
2 7
O
(
JCPDS No. 87-0284). In the case of BiOBr/Bi Sn O , one
2
2 7
new set of diffraction peaks was observed and can be indexed
to the tetragonal BiOBr (JCPDS No. 09-0393), which proves
the formation of BiOBr/Bi
reaction between Bi
follows:
2
Sn
2 7
O composites. The suggested
2 2 7
Sn O and HBr can be formulated as
2 2 7 2 2 7
Fig. 1. XRD patterns of BiOBr, Bi Sn O , and BiOBr/Bi Sn O
composites.
(
a)
(b)
(
c)
(d)
2 2 7 2 2 7 2 2 7
Fig. 2. SEM images of (a) pure Bi Sn O and (b) 0.08-BiOBr/Bi Sn O . (c, d) TEM images of 0.08-BiOBr/Bi Sn O .

Synthesis of BiOBr/Bi Sn O
7
3
2
2
coefficient, band-gap energy, photon energy, and a constant,
respectively. Among them, n depends on the characteristics
of the transition in a semiconductor (n = 1 for direct transi-
tion or n = 1/2 for indirect transition). For BiOBr and
Bi2Sn2O7 þ 10HBr ! 2BiOBr þ 2SnBr4 þ 5H2O
(1)
FE-SEM and TEM were employed to directly analyze the
morphology and microstructure of the samples, as shown in
Fig. 2. From Fig. 2(a), a large number of agglomerated
nanoparticles with an estimated diameter ranging from 15 to
Bi
tions.
ple can be thus estimated from a plot of (ahm)
2 2 7
Sn O , the value of n is 1/2 for their indirect transi-
24,30
g
The band-gap energy (E ) of the as-prepared sam-
1/2
versus
3
0 nm were observed in pure Bi
treated with 0.08 mol/L HBr, the sheet-like BiOBr can be
observed, as shown in Fig. 2(b). As a result, Bi Sn
nanoparticles were distributed evenly on BiOBr sheets. This
suppresses the agglomeration of Bi Sn and provides more
2 2 7 2 2 7
Sn O . After Bi Sn O was
photon energy (hm). The intersect of the two tangents of the
curve gives a good approximation of the band-gap energy
2
2 7
O
for the sample. The optical band gap of pure Bi
estimated to be 2.83 eV, and those of 0.05-, 0.08-, 0.1-, 0.15-
BiOBr/Bi Sn are 2.81, 2.85, 2.85, and 2.84 eV, respec-
tively. Obviously, the band gap of BiOBr/Bi Sn samples
is slightly larger than that of pure Bi Sn , which is consis-
tent with the color changed from yellowish color of Bi Sn O
2 2 7
Sn O is
2
2 7
O
2
2 7
O
active sites for the photocatalytic reaction. The photogener-
ated electrons and holes under visible light can transfer easily
between BiOBr and Bi Sn O , which is beneficial for the
2
2 7
O
2
2 7
O
2
2
7
2
2
7
separation of charges.
The TEM images of 0.08-BiOBr/Bi
Fig. 2(c) and (d). Bi Sn O nanoparticles and BiOBr sheets
to light yellow of BiOBr/Bi
Fig. 3(a).
2 2 7
Sn O , as shown in the inset of
2 2 7
Sn O were given in
2
2
7
The decreased recombination rate of photoinduced elec-
trons and holes is a crucially important factor for the
enhanced photocatalytic activity of photocatalysts. The PL
spectrum is usually applied to probe the recombination rate
of electron-hole pairs. PL emission spectra of as-obtained
samples were measured in the wavelength region of 400–
can be observed in the samples. From Fig. 2(d), the lattice
fringes of 0.344 and 0.283 nm coincide with the fringe spac-
ings of the (101) and (102) lattice planes of the tetragonal
BiOBr, respectively. The fringes of 0.325 nm can be indexed
to (311) crystal plane of the cubic Bi Sn O .
2 2 7
Figure 3(a) presents the DRS spectra of as-synthesized
samples. All samples showed the steep absorption edges at
5
50 nm with an excitation wavelength of 350 nm, as shown
in Fig. 4. The photoluminescence at ~460 nm can be attribu-
ted to the recombination of the photogenerated electron-hole
~375 nm. Their steep shape indicates that the optical absorp-
tion is due to the band-gap transition rather than a transition
24
pairs from localized surface states. The emission intensity
2
from the impurity level. The optical band gaps of samples
9
became weaker with the increasing HBr concentration. It is
clear that the BiOBr/Bi Sn O photocatalysts show lower
emission intensity than the pristine Bi Sn O , suggesting the
n
can be calculated from the following equation: (ahm) = A
2
2
7
(
hm ꢁ E ), in which a, E , hm, and A are the absorption
g
g
2
2
7
more efficient charge separation in the BiOBr/Bi
2 2 7
Sn O sys-
tem. The Bi Sn treated with 0.08M HBr exhibits the
2
2 7
O
weakest emission, implying that more photoinduced charges
can be utilized in the photocatalytic reaction.
For each kind of samples, the adsorption experiments were
performed in the presence of the photocatalysts in the dark,
as shown in Fig. 5. Obviously, BiOBr/Bi Sn O samples exhi-
2
2
7
bit the better adsorption property than pure Bi
can be ascribed to the inhibited agglomeration of Bi
2
Sn
2
O
7
, which
Sn
2
2 7
O
nanoparticles through attaching evenly on the surface of
BiOBr sheets. The 0.08-BiOBr/Bi Sn O sample exhibits the
2
2
7
best adsorption property, which agrees with the BET results.
The BET specific surface areas of pure Bi Sn , 0.05-, 0.08-
0.1-, and 0.15-BiOBr/Bi Sn O , are 40.353, 41.825, 47.144,
2
2 7
O
,
2
2
7
2
4
of higher HBr concentration, much more Bi
2.803, and 42.638 m /g, respectively. However, in the case
Sn nanopar-
2
2 7
O
ticles transformed to BiOBr of larger sizes, which decreases
the specific surface area of sample and thus leads to poor
adsorption capacity. The excellent adsorption properties
1
/2
Fig. 3. (a) DRS spectra and (b) corresponding plots of (ahm)
versus photon energy (hm) of Bi Sn and BiOBr/Bi Sn
composites. Inset is the photos of pure Bi Sn and 0.08-BiOBr/
Bi Sn
2
2
O
7
2
2 7
O
2
2
O
7
2 2 7
Fig. 4. PL spectra of neat BiOBr and BiOBr/Bi Sn O composites
upon 350 nm excitation.
2
2
O
7
.

4
Journal of the American Ceramic Society—Lv et al.
favor the diffusion of dye molecules from the solution to the
active sites in the surface of photocatalysts, which has a ben-
eficial effect on the enhanced photoactivity. Moreover, the
adsorption/desorption equilibration can be established in
30 min. In this way, the influence of RhB adsorption on the
photocatalysts could be neglected during the following
photocatalytic process.
3
1
As shown in Fig. 6, the photoactivities of all samples were
evaluated by photocatalytic degradation of RhB under visible
light irradiation. As can be seen, after 120 min of visible
light irradiation, Bi Sn O showed the poorest photodegrada-
2
2
7
tion performance, and only 10% RhB was degraded, which
can be ascribed to the high recombination rate of electrons
and holes. In contrast, after Bi
solution, the as-obtained BiOBr/Bi Sn O composites show
2 2 7
Sn O was treated by HBr
2
2
7
higher photocatalytic efficiency. As discussed in the DRS sec-
tion, the optical band gap of BiOBr/Bi Sn is a little
higher than pure Bi Sn , suggesting that the utilization of
visible light for BiOBr/Bi Sn O is not enhanced. Conse-
2
2 7
O
2
2 7
O
2
2
7
2 2 7
quently, the improved photoactivity of BiOBr/Bi Sn O
should only be ascribed to the formation of the BiOBr/
Bi Sn O heterojunction, which will be further discussed in
2
2
7
the following section. Figures 6(b)–(e) shows the absorption
spectra of aqueous RhB solutions in the presence of 0.05-,
0
.08-, 0.1-, and 0.15-BiOBr/Bi
ation. All the samples exhibit a large blue shift from 554 to
20 nm after 10 min irradiation, and the absorption peak
2 2 7
Sn O under visible light irradi-
5
of the dye solution dramatically dropped. Generally, RhB
molecules usually have two different degradation pathways,
Fig. 5. The adsorption properties of the as-synthesized samples for
RhB.
Fig. 6. (a) Photodegradation curves of RhB for the as-synthesized samples. Absorbance curves of RhB under visible light irradiation in the
presence of (b) 0.05-, (c) 0.08-, (d) 0.1- (e) 0.15-BiOBr/Bi Sn . (f) Photodegradation curves of 0.08-BiOBr/Bi Sn when reused six times.
2
2
O
7
2
2 7
O

Synthesis of BiOBr/Bi Sn O
7
5
2
2
including the de-ethylation and the degradation of chro-
3
2
mophore processes. The large blue shift is considered to be
the characteristic of de-ethylation process. Obviously, 0.08-
BiOBr/Bi Sn O shows the highest degradation efficiency. To
2
2
7
research the stability of the as-synthesized samples, a 6-cycle
photodegradation experiment for 0.08-BiOBr/Bi Sn was
2
2 7
O
carried out, as shown in Fig. 6(f). No obvious deterioration
is observed, indicating the excellent stability of the as-synthe-
sized BiOBr/Bi
The influences of various foreign anions (Cl , SO
2 2 7
Sn O photocatalysts.
ꢁ
42ꢁ
,
ꢁ
2ꢁ
ꢁ
NO3 , CO3 , and HCO3 ) on RhB photodegradation by
the catalyst system of 0.08-BiOBr/Bi Sn were examined,
as showed in Fig. 7. The photocatalytic efficiency toward
2
2 7
O
ꢁ
2ꢁ
2ꢁ
RhB degradation was almost not affected by Cl , SO
NO3 , but was decreased significantly when CO3
4
, or
or
ꢁ
ꢁ
HCO
the presence of Cl , SO
3
was added. The pH values of the RhB solution in
ꢁ
2ꢁ
ꢁ
2ꢁ
ꢁ
were
, 7, 7, 13, and 9, respectively. Thus, the pH value plays a
4
, NO
3
, CO
3
, and HCO
3
7
crucial role in the catalytic efficiency and further study is
needed to clarify the mechanism.
The electrons transfer from VB to CB under visible light
excitation, leaving holes in valence bands, and the photocur-
rent generates in this process. The appropriate heterojunction
composites have the better electron and hole separation effi-
ciency so that the composites showed the higher photocur-
rent and higher photocatalytic activity. Figure 8(a) clearly
illustrates the photocurrent responses of pure Bi
.08-BiOBr/Bi Sn heterojunction composite under visible
light irradiation. As can be seen, the 0.08-BiOBr/Bi Sn O
2 2 7
Sn O and
0
2
2 7
O
2
2
7
heterojunction composite shows higher current compared to
the pure Bi Sn sample, which indicates that 0.08-BiOBr/
Bi Sn heterojunction composite has a lower recombina-
2
2 7
O
2
2 7
O
tion rate of electrons and holes. The result agrees well with
the photocatalytic activity for RhB degradation and PL
results. Figure 8(b) demonstrates the EIS Nyquist plots of
the as-synthesized samples. The high-frequency semicycles
are related to the resistance of the electrodes. As shown in
Fig. 8(b), the radius on EIS Nyquist plot of composites is
3
3
Fig. 8. (a) Photocurrent responses and (b) the EIS curves of pure
Bi Sn and 0.08-BiOBr/Bi Sn composite in 0.1M Na SO
solution under visible light irradiation.
2
2
O
7
2
2
O
7
2
4
smaller than that of pure Bi
2 2 7
Sn O , which implies that the
introduction of Bi Sn has a beneficial effect on the charge
2
2 7
O
ethylenediaminetetraacetate (Na
2
-EDTA), and isopropyl
transfer and thus results in higher charge separation effi-
ciency. The result is consistent with the photocurrent
responses.
ꢁ
+
alcohol (IPA) were used as trap for ∙O , h , and ∙OH,
2
1
4,24
respectively.
1
As shown in Fig. 9, in the presence of
mM of Na -EDTA as a h scavenger, pronounced deterio-
+
The type of reactive species, such as hydroxyl radicals
2
ꢁ
+
ration in the photodegradation of RhB can be observed.
However, in the presence of 1 mM of BZQ or IPA, the
degradation of RhB was just slightly depressed. The results
indicate that the dominant active species is h but not ∙O
or ∙OH radicals in the photocatalytic reaction.
(
∙OH), superoxide radicals (∙O2 ), and holes (h ), plays a
crucial role in the process of photodegradation process of
dye molecules. Herein, to study the dominant reactive species
in our work, the scavenger experiments were carried out.
Three different chemicals, p-benzoquinone (BZQ), disodium
+
ꢁ
2
Fig. 7. Degradation ratios of RhB for 0.08-BiOBr/Bi
, NO
2
Sn
2
O
7
in the
) after
ꢁ
2ꢁ
ꢁ
2ꢁ
ꢁ
presence of anions (Cl , SO
90 min of visible light irradiation.
4
3
, CO
3
, and HCO
3
Fig. 9. Photocatalytic activities of 0.08-BiOBr/Bi
different quenchers.
2
Sn O
2 7
with

6
Journal of the American Ceramic Society—Lv et al.
Innovation Foundation of Liaocheng University (26312151912). Undergradu-
ate Training Programs for Innovation and Entrepreneurship of Liaocheng
University (CXCY2015029).
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2
both absorb visible light. With the irradiation of visible light,
the electrons in the VB of BiOBr and Bi Sn O were excited
9
2
Photocatalyst
2
2
7
to CB. The levels of conduction band (CB) and valence band
VB) of BiOBr are 0.28 and 3.19 eV, respectively. By con-
trast, the VB level of Bi Sn O is lower by 0.23 eV than that
9
6, 50–7 (2012).
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(
10
2
2
7
2 3 2
of Bi S /SnS Heterojunction Photocatalysts with Efficient Photocatalytic
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of BiOBr. Although the difference for the VB potential
energy positions is a little small, it can drive the transfer of
photogenerated charges, which was confirmed by the pho-
todegradation and photocurrent results. Hence, holes in the
1
1
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2
1
2
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3
O
4
2
VB of BiOBr can transfer to VB of Bi
react with OH to produce the ∙OH radicals. The CB of
2
Sn
2
O
7
, and further
ꢁ
ble Light Photocatalytic Properties,” Mater. Chem. Phys., 148, 896–902 (2014).
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13
2 2 7
BiOBr is more positive than that of Bi Sn O so that elec-
I. Lee, “Heterojunctioned BiOCl/Bi
2
O
3
, a New Visible Light Photocatalyst,”
trons can flow onto CB of BiOBr and then react with dis-
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ꢁ
14
N
3 4
3 4
/Fe O /
2
radicals. The
generated under visible
ꢁ
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photogenerated holes, ∙OH, and ∙O
2
irradiation can further remove RhB. This heterojunction
structure can result in an effective separation of photogener-
ated electrons and holes, which leads to more efficient photo-
1
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Sn
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.
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IV. Conclusion
We present a facile method to synthesize the BiOBr/Bi
heterojunction photocatalysts through treating Bi Sn O
17
2 2 6
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2
Sn
2
O
7
7
18
2
2
nanoparticles by HBr solution with different concentrations.
After treated with HBr, part of Bi Sn nanoparticles were
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d 2 7
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2
2 7
O
1
9
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2
2
7
2
2
O
7
3
can distribute evenly on BiOBr sheets, which inhibits the
agglomeration of Bi Sn . The DRS results show that the
optical band gaps of BiOBr/Bi Sn composites are slightly
larger than that of pure Bi Sn O sample. However, the pho-
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todegradation performance of BiOBr/Bi
cantly enhanced. The PL and photocurrent results showed that
2
Sn
2
O
7
was signifi-
21
W. Xu, J. Fang, Y. Chen, S. Lu, G. Zhou, et al., “Novel Heterostructured
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Bi
2
S
3
2
2 7
O
ꢁ
+
the recombination of photoinduced e and h was suppressed,
due to the formation of BiOBr/Bi Sn O heterojunction. Based
2
2
H. Tian, F. Teng, J. Xu, S. Lou, N. Li, et al., “An Innovative Anion Reg-
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2
2
7
2 3
O
2 2 7
on the alignment of CB and VB of BiOBr and Bi Sn O , a
2
2
2
4
3
plausible photocatalytic mechanism of enhanced photoactivity
of the as-obtained BiOBr/Bi Sn O was discussed. Moreover,
through the scavenger experiments and 6-cycle photodegrada-
2
2
7
7
24
2 2 7
H. Liu, Z. Jin, Y. Su, and Y. Wang, “Visible Light-Driven Bi Sn O /
+
tion, the dominant active specie (h ) in this work and the
excellent photostability of the as-obtained BiOBr/Bi
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Sn
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2
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Designed 1D Ag@AgVO Nanowire/Graphene/Protonated g-C Nanosheet
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51303076), a project of Shandong Province Higher Educational Science and
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h