Tunable Synthesis of Ultrathin BiOCl 2D Nanosheets for Efficient Photocatalytic Degradation of Carbamazepine upon Visible-Light Irradiation

Article abstract of DOI:10.1155/2020/1950645

A series of ultrathin BiOCl 2D nanosheet photocatalysts were prepared by the TBAOH-assisted hydrolysis method in water. The effects of tetrabutylammonium hydroxide (TBAOH) dosages, chlorine source, preparation pH value, ultrasonic treatment, and magnetic stirring on the photocatalytic degradation dynamics of carbamazepine were examined under visible-light irradiation to optimize the preparation parameters. It was found that ultrathin BiOCl prepared with TBAOH dosages of 1 mmol and chlorine source of NaCl in the pH of 2 upon magnetic stirring of 6 h displayed the highest photocatalytic degradation rate constant (0.0038 min-1) of carbamazepine, which is 7.6 times higher than that with the ordinary BiOCl (without TBAOH). To clarify the mechanism on the outstanding photocatalytic activity of ultrathin BiOCl, the elemental composition/state, micromorphology, and separation efficiency of photogenerated electron-hole pairs were investigated by X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), and photoluminescence (PL). Results showed that the presence of oxygen vacancy, ultrathin nanosheet structure, and improved separation efficiency of photogenerated electron-hole pairs contributed to the excellent photocatalytic degradation activity of ultrathin BiOCl. The obtained result provides a novel method to fabricate ultrathin BiOCl with excellent photocatalytic degradation activity of carbamazepine under visible-light irradiation.

Full text of DOI:10.1155/2020/1950645

Hindawi
Journal of Chemistry
Volume 2020, Article ID 1950645, 10 pages
https://doi.org/10.1155/2020/1950645
Research Article
Tunable Synthesis of Ultrathin BiOCl 2D Nanosheets for Efficient
Photocatalytic Degradation of Carbamazepine upon
Visible-Light Irradiation
Shuo Xu ,1 Xiaoya Gao,2 Wenfeng Xu ,1 Pengfei Jin ,1 and Yongmei Kuang1
1Department of Pharmaceutical Science, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine,
Chinese Academy of Medical Sciences, Beijing Key Laboratory of Drug Clinical Risk and Personalized Medication Evaluation,
Beijing 100730, China
2Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650500, China
Correspondence should be addressed to Shuo Xu; victoria06251226@163.com
Received 29 April 2020; Revised 8 July 2020; Accepted 15 July 2020; Published 13 August 2020
Guest Editor: Tapan Sarkar
Copyright © 2020 Shuo Xu et al. +is is an open access article distributed under the Creative Commons Attribution License, which
permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
A series of ultrathin BiOCl 2D nanosheet photocatalysts were prepared by the TBAOH-assisted hydrolysis method in water. +e
effects of tetrabutylammonium hydroxide (TBAOH) dosages, chlorine source, preparation pH value, ultrasonic treatment, and
magnetic stirring on the photocatalytic degradation dynamics of carbamazepine were examined under visible-light irradiation to
optimize the preparation parameters. It was found that ultrathin BiOCl prepared with TBAOH dosages of 1 mmol and chlorine
source of NaCl in the pH of 2 upon magnetic stirring of 6 h displayed the highest photocatalytic degradation rate constant
(0.0038 min−1) of carbamazepine, which is 7.6 times higher than that with the ordinary BiOCl (without TBAOH). To clarify the
mechanism on the outstanding photocatalytic activity of ultrathin BiOCl, the elemental composition/state, micromorphology,
and separation efficiency of photogenerated electron-hole pairs were investigated by X-ray photoelectron spectroscopy (XPS),
scanning electron microscope (SEM), and photoluminescence (PL). Results showed that the presence of oxygen vacancy, ultrathin
nanosheet structure, and improved separation efficiency of photogenerated electron-hole pairs contributed to the excellent
photocatalytic degradation activity of ultrathin BiOCl. +e obtained result provides a novel method to fabricate ultrathin BiOCl
with excellent photocatalytic degradation activity of carbamazepine under visible-light irradiation.
Photocatalytic technology has been reported to effec-
tively degrade environmental pollutants due to the pro-
duction of highly active redox species, such as electron (e−),
hole (h+), hydroxyl radical (·OH), and superoxide radical
(O2−) [4–6]. Compared with the traditional physical ad-
sorption method, the photocatalysis technology can not only
completely mineralize many pollutants but also exhibit the
advantages of simple operation, high efficiency, and low
operation cost. More importantly, photocatalytic technology
takes the green renewable energy solar energy as the driving
force. +erefore, photocatalytic technology has been favored
by researchers all over the world and is expected to become
one of the effective methods to solve environmental crisis.
+e core of photocatalytic technology is fabricating the
efficient photocatalyst. Up to date, many new and efficient
1. Introduction
Pharmaceutical and personal care products (PPCPs) as a
new type of pollutants have been of growing concerns be-
cause of the biological toxicity and biorefractory nature [1].
Particularly, an antiepileptic drug of carbamazepine is a
typical representative of PPCPs [2]. Carbamazepine is hard
to be degraded from current wastewater treatment processes
and appears to be remarkably persistent in a variety of water
bodies including surface water, effluent from sewage
treatment plant, and even in drinking water. +e presence of
carbamazepine is always associated with chronic toxicity to
human and ecological environment [3]. +erefore, it is
urgent to find a green and environmentally friendly method
to degrade carbamazepine in water.

2
Journal of Chemistry
photocatalysts have been fabricated by researchers [7–11].
Bismuth oxychloride (BiOCl), as a new type of semicon-
ductor materials, has attracted great attention due to its
unique microstructure and good photocatalytic perfor-
mance [12–14]. However, in practical applications, BiOCl
still fails to respond to visible light, which restricted the
application of solar energy to degrade environmental pol-
lutants [15].
Furthermore, the ultrasonic treatment (1, 2, and 3 h) and
magnetic stirring (3, 6, and 12 h) were also optimized.
BiOCl prepared in the optimal preparation conditions
was denoted as ultrathin BiOCl. And the BiOCl sample
prepared without TBAOH (TBAOH concentrations of 0)
was denoted as ordinary BiOCl.
2.2. Characterization. +e micromorphology of the samples
was observed using SEM (America FEI, Quanta 200). XPS
analysis (ESCALab250Xi, Al Ka) was used to examine the
chemical composition and element state of the as-prepared
BiOCl samples. +e adventitious carbon signal (C1s peak) at
284.8 eV as an internal standard was used to calibrate the
shift of the binding energy. +e separation efficiency of
photogenerated electron-hole pairs was evaluated by the PL
spectrums using an Edinburgh FLS980 fluorescence
spectrophotometer.
To fabricate visible-light-driven BiOCl, many strategies
have been explored. With the assistance of other semi-
conductors, BiOCl composite heterojunction was always
constructed to improve the photocatalytic activity upon
visible-light irradiation. For example, Dong et al. prepared
H-TiO2/BiOCl heterojunction with improved photocatalytic
activity under the visible light by a facile solvothermal
method [16]. Elemental doping is also an efficient method to
improve the visible-light-driven photocatalytic activity of
BiOCl, since its intrinsic light absorption is improved. Re-
cently, Xu et al. described a novel bulk doping strategy to
extend the light by bulk W-doping of BiOCl [17]. However,
these methods are associated with massive organic solvents,
high cost, or cumbersome procedures.
+is paper provided a new strategy to fabricate ul-
trathin BiOCl 2D nanosheets for efficient photocatalytic
degradation of carbamazepine upon visible-light irradi-
ation by regulating the growth process of BiOCl. To
optimize the preparation parameters, the effects of tet-
rabutylammonium hydroxide (TBAOH) dosages, chlo-
rine source, preparation pH value, ultrasonic treatment,
and magnetic stirring on the photocatalytic degradation
of carbamazepine were examined under visible-light ir-
radiation. Finally, X-ray photoelectron spectroscopy
(XPS), scanning electron microscope (SEM), and pho-
toluminescence (PL) were employed to clarify the ele-
mental composition/state, micromorphology, and
separation efficiency of photogenerated electron-hole
pairs of the as-prepared BiOCl samples.
2.3. Photocatalytic Activity. +e photocatalytic performance
was evaluated by photocatalytic degradation of carbamaz-
epine solution (2.5 mg/L). A 300 W xenon lamp with a
420 nm filter was used as the visible light source of the
experiment. +e liquid phase photocatalytic degradation of
carbamazepine was carried out in a 50 mL of beaker, which
was placed in a water bath pot to maintain 25°
C throughout
the reaction process. To examine the photocatalytic activity
of the as-prepared BiOCl, 0.04 g of photocatalyst powders
was added in the above carbamazepine solution. Before il-
lumination, the solution was stirred in the dark for an hour
to achieve the equilibrium of adsorption-desorption be-
tween carbamazepine and BiOCl photocatalyst powders.
+en, the solution was irradiated upon visible light. +e
carbamazepine solution was sampled every 30 minutes (3 ml
each time), which underwent centrifugation to remove the
photocatalyst powders. Finally, the residual concentration
was measured using an ultraviolet visible spectrophotometer
(UV-vis, Puxi TU-1901).
2. Experimental
+e kinetics of photocatalytic degradation was evaluated
by the apparent pseudo-first-order model expressed by
following equation:
2.1. Preparation of Ultrathin BiOCl 2D Nanosheet
Photocatalysts. BiOCl samples were synthesized using a
facile hydrolysis method in water. Typically, TBAOH was
dissolved in ultrapure water. +en, 1 mmol of
Bi(NO3)3·5H2O and KCl was introduced to the above
TBAOH solution with ultrasonic treatment or magnetic
stirring. +en, the white suspension was agitated at atmo-
spheric environment to obtain precipitates. Finally, the
precipitates were collected, washed, and dried in an oven.
To evaluate the effects of TBAOH dosages on the
photocatalytic activity of BiOCl, the concentrations of
TBAOH were set at 0, 0.5, 1, and 2 mmol.
To evaluate the effects of chlorine source on the pho-
tocatalytic activity, BiOCl samples were prepared by the
same procedure except that KCl was changed to HCl, NaCl,
and choline chloride.
+e pH value of catalyst preparation reaction solution
was tested on 1, 2, and 3 by changing the pH value with
NaOH.
C0
C
(1)
ln
� kt,
ꢀ
ꢁ
where C0, C, and k are the original carbamazepine
concentration (2.5 mg/L), carbamazepine concentration at
reaction time t, and pseudo-first-order degradation rate
constant.
3. Results and Discussion
3.1. Optimization of Preparation Parameters
3.1.1. TBAOH Dosages. Figure 1 shows the effects of
TBAOH dosages on the carbamazepine degradation ki-
netics. It can be seen that the addition of TBAOH promoted
the carbamazepine degradation kinetics under the photo-
catalytic reaction of BiOCl, as the degradation rate constant
increased over the BiOCl samples prepared in the presence

Journal of Chemistry
3
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Time (min)
Irradiation time (min)
0mmoL
0.5mmoL
1mmoL
2mmoL
0mmoL k = 0.0004min–1
0.5mmoL k = 0.0016min–1
1mmoL k = 0.0030min–1
2mmoL k = 0.0025min–1
(a)
(b)
Figure 1: Effects of TBAOH dosages on the carbamazepine degradation kinetics.
of TBAOH. When the TBAOH dosages increased from 0.5
to 1 mmol, TBAOH displayed a positive effect on the deg-
radation of carbamazepine with the degradation rate con-
stant of carbamazepine increasing significantly from 0.0016
to 0.0030 min−1. However, the degradation kinetics became
slow with a further increased TBAOH dosage from 1 to
2 mmol. +e degradation rate constant of carbamazepine
decreased to 0.0025 min−1 upon the excited BiOCl prepared
by adding TBAOH of 2 mmol. To sum up, the highest
degradation rate constant of carbamazepine was obtained at
0.0030 min−1. +e absorption spectra for the degradation of
carbamazepine at various times of irradiation are shown in
Figure S1. As shown in the figure, the absorption spectra of
carbamazepine decreased upon the light excited BiOCl.
Hence, it is important to add TBAOH in the preparation
procedure of BiOCl for the high degradation kinetics of
carbamazepine. +e role of TBAOH in regulating the growth
process of BiOCl will be discussed further in the charac-
terization results from XPS and SEM.
Figure 2 presents the degradation kinetics of carba-
mazepine by BiOCl prepared with different chlorine sources.
As exhibited, the degradation kinetics is the highest in BiOCl
prepared using NaCl as chlorine source, with a degradation
rate constant of 0.0038 min−1. +e degradation rate constant
of carbamazepine is 0.0018, 0.0034, and 0.0025 min−1 in the
BiOCl prepared using HCl, KCl, and choline chloride as
chlorine source, respectively. It should be noted that the
difference in photocatalytic degradation kinetics of BiOCl
prepared in various chlorine sources did not originate from
the alteration of pH caused by chlorine source, as the pH was
adjusted to the same value during the preparation of BiOCl.
3.1.3. Effect of pH. Nucleation and crystallization process
of BiOCl are highly dependent on the solution pH [22].
Hence, the effects of pH value within ranges of 1–3 on the
degradation activity of BiOCl were examined under vis-
ible-light irradiation. As shown in Figure 3, the highest
degradation kinetics of carbamazepine was found in the
BiOCl prepared in solution pH value of 2. +e degradation
rate constant of carbamazepine is 0.0030, 0.0033, and
0.0031 min−1 in the BiOCl prepared in pH value of 1, 2,
and 3, respectively.
+e pH of catalyst preparation reaction solution (bis-
muth nitrate + TBAOH) was about 1 without adjustment
(because of the existence of TBAOH, the catalyst preparation
reaction solution gave pH 1). +en, NaOH was added into
the reaction solution to adjust pH value from 2 to 3. In the
preparation of BiOCl, it was found that white precipitates
could be immediately formed after adding NaOH (the in-
volved reaction is shown in the supplementary information
files). Massive NaOH could speed up the nucleation and
crystallization process excessively, which does not favor the
controlled growth of BiOCl. So, NaOH was added cautiously
during the preparation of BiOCl. And the pH values were
tested within acid ranges of 1–3.
3.1.2. Chlorine Source. For the preparation of BiOCl, both
bismuth source and chlorine source were required. Be-
cause of low cost, Bi(NO3)3·5H2O is the most widely used
bismuth source, while chlorine source can be different
based on the preparation route [18–21]. As reported in the
literatures, HCl, NaCl, KCl, and choline chloride can
provide chlorine to the fabrication of BiOCl. Chlorine
source is important for the preparation of BiOCl, for it can
coordinate with bismuth source, control the concentra-
tion of reaction species in the reaction system, and in-
fluence the dynamic behavior in the process of BiOCl
crystallization, finally affecting the microstructure and
determining its photocatalytic performance. Here, the
effects of chlorine sources on the photocatalytic activity of
BiOCl were evaluated according to the degradation ki-
netics of carbamazepine.

4
Journal of Chemistry
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0
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200
0
30
60
90
120
150
180
Time (min)
Irradiation time (min)
HCl
NaCl
KCl
Choline chloride
HCl k = 0.0018min–1
NaCl k = 0.0038min–1
KCl k = 0.0034min–1
Choline chloride
k = 0.0025min–1
(a)
(b)
Figure 2: Effects of chlorine source on the carbamazepine degradation kinetics.
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–50
0
50
100
150
200
0
30
60
90
120
150
180
Time (min)
Irradiation time (min)
pH = 1
pH = 2
pH = 3
pH = 1 k = 0.0030min–1
pH = 2 k = 0.0033min–1
pH = 3 k = 0.0031min–1
(a)
(b)
Figure 3: Effects of pH of reaction solution on the carbamazepine degradation kinetics.
3.1.4. Effect of Ultrasonic Treatment or Magnetic Stirring.
Ultrasonic treatment or magnetic stirring is the ordinary
treatment in the growth process of photocatalytic material
[23–25]. Here, effects of ultrasonic treatment or magnetic
stirring on the photocatalytic activity were also evaluated. As
shown in Figure 4, different times of ultrasonic treatment
were detected on 1, 2, and 3 h. +e highest degradation
kinetics of carbamazepine was found in BiOCl prepared in
ultrasonic treatment of 2 h, with a degradation rate constant
of 0.0035 min−1, which is higher than 0.0032 and
0.0029 min−1 for BiOCl prepared in ultrasonic treatment of 1
and 3 h, respectively.
+e magnetic stirring was also performed in the
preparation of BiOCl, as shown in Figure 5. +e degra-
dation rate constants are 0.0032, 0.0038, and 0.0037 min−1
in the BiOCl prepared in magnetic stirring of 3, 6, and
12 h, respectively. Obviously, BiOCl prepared in magnetic
stirring of 6 h exhibited the highest photocatalytic deg-
radation rate constants of carbamazepine under visible-
light irradiation. +is is also superior to the highest
degradation rate constant of 0.0035 min−1 in the BiOCl
prepared in ultrasonic treatment of 2 h. Hence, magnetic
stirring of 6 h was set as the optimal treatment in the
growth process of BiOCl.

Journal of Chemistry
5
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–20
0
20 40 60 80 100 120 140 160 180 200
Irradiation time (min)
Time (min)
U 1
U 2
U 3
U 1 k = 0.0035min–1
U 2 k = 0.0032min–1
U 3 k = 0.0029min–1
(a)
(b)
Figure 4: Effect of ultrasonic treatment on the carbamazepine degradation kinetics.
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0
20 40 60 80 100 120 140 160 180 200
Irradiation time (min)
Time (min)
S 3 k = 0.0032min–1
S 6 k = 0.0038min–1
S 12 k = 0.0037min–1
S 3
S 6
S 12
(a)
(b)
Figure 5: Effect of magnetic stirring on the carbamazepine degradation kinetics.
Taken together, the fastest degradation kinetics of
carbamazepine can be obtained in the BiOCl prepared
with TBAOH dosages of 1 mmoL and chlorine source of
NaCl in the pH of 2 upon magnetic stirring of 6 h
(denoted as ultrathin BiOCl). Ultrathin BiOCl displayed
the highest photocatalytic degradation rate constant
(0.0038 min−1) of carbamazepine, which is 7.6 times
higher than that with the ordinary BiOCl (prepared
without TBAOH). To clarify the contributors to the
outstanding photocatalytic activity, XPS, SEM, and PL
were carried out to examine the elemental composition/
state, micromorphologies, and separation efficiency of
photogenerated electron-hole pairs.
3.2. Characterization
3.2.1. Chemical Composition and Elemental State. +e
chemical composition and elemental state in the samples
were determined by XPS analysis, as shown in Figure 6. +e
XPS analysis suggested that only the elements of Bi, O, and
Cl were found in the ordinary and ultrathin samples, which

6
Journal of Chemistry
1 × 105
9 × 104
8 × 104
7 × 104
6 × 104
5 × 104
2.5 × 105
2.0 × 105
1.5 × 105
1.0 × 105
Bi 4f
Cl 2p
5.0 × 104
0.0
158
160
162
164
166
195
196
197
198
199
200
201
202
Binding energy (eV)
Binding energy (eV)
Ordinary BiOCl
Ultrathin BiOCl
Ordinary BiOCl
Ultrathin BiOCl
(a)
(b)
5 × 105
4 × 104
3 × 104
2 × 104
2.5 × 105
2.0 × 104
1.5 × 104
1.0 × 104
Ordinary BiOCl
Ultrathin BiOCl
1 × 104
0
5.0 × 103
0.0
528
529
530
531
532
533
534
535
528
529
530
531
532
533
534
535
Binding energy (eV)
Binding energy (eV)
O 1s XPS spectra
Lattice oxygen
Oxygen vacancy
O 1s XPS spectra
Lattice oxygen
Oxygen vacancy
Chemisorbed oxygen
Chemisorbed oxygen
(c)
(d)
Figure 6: High-resolution Bi 4f (a), Cl 2p (b), and O1s (c, d) XPS spectra of ordinary BiOCl and ultrathin BiOCl.
confirmed the formation of BiOCl with high purity. +e
high-resolution spectra of Bi 4f, Cl 2p, and O1s are shown in
Figures 6(a)–6(d), respectively.
ordinary BiOCl and 198.0 eV in ultrathin BiOCl corre-
sponded to Cl 2p1/2, while Cl 2p3/2 was confirmed by the
high binding energy of 199.4 and 199.7 eV in ordinary BiOCl
and ultrathin BiOCl samples, respectively [28]. Compared
with ordinary BiOCl, the two peaks of Cl 2p1/2 and Cl 2p3/2
shifted to relatively higher binding energy in the ultrathin
BiOCl samples. +e Cl peak at a higher binding energy may
be explained by the following: Cl ions are more tightly
bonded to ultrathin BiOCl due to the introduction of
positively charged ions originated from the dissociation of
TBAOH.
It can be seen from Figure 6(a) that the spectra of Bi 4f
were deconvoluted into two peaks in both ordinary BiOCl
and ultrathin BiOCl. +e two peaks were assigned to Bi 4f5/2
and Bi 4f7/2, respectively [26]. Compared with 159.2 and
164.5 eV in ordinary BiOCl, these two peaks shifted to lower
binding energy of 159.0 and 164.3 eV in ultrathin BiOCl.
Lower binding energy of Bi is classically attributed to the
formation of lower charge Bi(3−x)+ ions caused by oxygen
vacancies [27].
Figures 6(c) and 6(d) show the O1s spectra of ordinary
BiOCl and ultrathin BiOCl samples, respectively. +e O1s
spectra can be deconvoluted into three peaks, namely, lattice
oxygen, oxygen vacancy, and chemisorbed oxygen, which
As shown in Figure 6(b), Cl 2p in ordinary BiOCl and
ultrathin BiOCl samples also exhibited two peaks between
195.0 and 202.0 eV. +e lower binding energy of 197.8 eV in

Journal of Chemistry
7
be 9.64 and 20.32 m2
can be assigned to 530, 531.4, and 533.3 eV in the ordinary
BiOCl samples [29]. And the three peaks shifted to 530.3,
531.5, and 533.1 eV in ultrathin BiOCl. Obviously, the O1s
peak became larger in the ultrathin BiOCl samples. Par-
ticularly, the intensity of peak assigned to oxygen vacancy
improved significantly in ultrathin BiOCl. +is indicated
that massive oxygen vacancies were introduced in the ul-
trathin BiOCl samples, which could be benefited from the
addition of TBAOH. To further confirm the formation of the
presence of oxygen vacancy, TPO was applied and is shown
in Figure S2. As can be seen from the figure, both BiOCl
samples show one peak centered at 87°C, which could be
attributed to the oxidation of cation vacancies [30]. And this
peak became much larger in ultrathin BiOCl than that in
ordinary BiOCl, which indicated more oxygen vacancies in
ultrathin BiOCl. +is is in accordance with the XPS results.
Taken together, both XPS and TPO confirm the formation of
the presence of oxygen vacancy.
In the growth process of BiOCl, TBAOH acted as a
structure-directing agent inducing the formation of oxygen
vacancies. +is is similar to the previous reported trietha-
nolamine (TEOA), which induced the production of oxygen
vacancies on the surface of BiOCl nanosheets [31]. +e
presence of oxygen vacancies is favored for the reduction of
oxygen molecule to produce massive active species, which
are important for the photocatalytic degradation of carba-
mazepine [32].
/g for ordinary BiOCl and ultrathin
BiOCl, respectively. Larger surface area always means more
active sites, so the improved surface area of ultrathin BiOCl
could be favored for the photocatalytic degradation of
carbamazepine.
3.2.3. Separation of Photogenerated Electron-Hole Pairs.
+e optical properties of ordinary BiOCl and ultrathin
BiOCl photocatalysts were evaluated using UV-diffuse ab-
sorption spectra (DRS) technique, as shown in the sup-
plementary information files (Figure S6). Obviously, the
light absorption band edge shifted to the long wavelength
region. To determine the visible-light responsibility, the
energy gaps of the samples were calculated based on the UV-
vis DRS of the Kubelka–Munk function versus the photo
energy. +e energy gaps of the samples were estimated to be
2.98 and 3.20 eV in ultrathin BiOCl and ordinary BiOCl,
respectively. +e narrow band gap in ultrathin BiOCl can be
ascribed to the existence of oxygen vacancy, which formed a
new Bi 6p electronic state in the forbidden band of BiOCl
[33].
Upon irradiation, photogenerated electron-hole pairs
can be formed. +e photocatalytic activities of semicon-
ductor materials are highly dependent on the separation of
photogenerated electron-hole pairs, which can be measured
by PL spectrum. PL emission signal is originated from the
recombination of photogenerated electron-hole pairs.
Hence, the stronger emission signal in PL corresponded to
the higher recombination efficiency of photogenerated
electron-hole pairs [34].
3.2.2. Microstructure and Morphology. +e XRD patterns of
BiOCl samples are shown in Figure S3. As shown in the
figure, both ordinary BiOCl and ultrathin BiOCl exhibited
tetragonal structure (JCPDS No. 85-0861) with high purity
(no other impurity diffraction peaks). SEM images were
taken to examine the microstructure and morphology of the
as-prepared samples. Figures 7(a) and 7(c) present the
microstructure and morphology of ordinary BiOCl in dif-
ferent magnifications. And images in Figures 7(b) and 7(d)
were taken for ultrathin BiOCl. As shown in the figures, both
BiOCl samples were composed of 2D nanosheet-shaped
structures. In comparison with ordinary BiOCl, the nano-
sheets became much thinner and more uniform in ultrathin
BiOCl.
Figure 8 shows the PL emission spectra of the ordinary
BiOCl and ultrathin BiOCl. As shown in the figure, ultrathin
BiOCl displayed significantly diminished PL emission in-
tensity. +is indicated the decreased recombination rate of
photogenerated electron-hole pairs and increased separation
efficiency of photogenerated electron-hole pairs. Hence, the
improved separation efficiency of photogenerated electron-
hole pairs contributed to the excellent photocatalytic activity
of ultrathin BiOCl.
+e photocatalytic degradation mechanism was sys-
tematically studied based on the different radical scavengers
and N2 purging. As shown in Figure S7, AgNO3 decreased
the photocatalytic degradation of CBZ indicating the im-
portance of e− in the degradation reaction. +e involvement
of h+ was confirmed by the reduced photocatalytic degra-
dation efficiency by adding HCOONa. Importantly, ·OH was
produced in the CBZ degradation process, for IPA ham-
pered the photocatalytic degradation of CBZ. In General,
·OH is hard to be generated in BiOCl because of the more
TEM images of ultrathin BiOCl and ordinary BiOCl are
shown in the revised supplementary information files. As
shown in Figure S4, the morphology of ultrathin BiOCl and
ordinary BiOCl was composed by ultrathin nanosheets. In
comparison with ordinary BiOCl, the lower contrast in the
TEM images of ultrathin BiOCl suggested the thinner thick-
ness, which is consistent with the SEM results. +e average
thickness of samples was characterized to approximately
1.5 nm by atomic force microscope (AFM, Figure S5). +is can
be ascribed by the TBAOH participation in the growth process
of BiOCl. TBAOH can be dissociated to positively charged
ions, facilitating its adsorption on the negative (001) plane. +is
retarded the (001) crystal growth and directed the formation of
much thinner BiOCl nanosheets [21].
negative redox potential of BiV
/BiIII (+1.59 eV) than
·OH/OH (+1.99 eV). +e production of ·OH in ultrathin
BiOCl could be benefited from the ultrathin nanosheet
structure, which shortens the transfer path of e−. +is
promoted the generation of ·OH through multielectron
reduction of O2. In this reaction process, O2 is a crucial
factor, which was supported by N2 purging. Taken together,
the active species of e−, h+, and ·OH dominated the pho-
tocatalytic degradation of CBZ over ultrathin BiOCl.
Generally, ultrathin BiOCl exhibits high surface area.
+e surface areas of BiOCl and BiOCl-T were determined to

8
Journal of Chemistry
Figure 7: SEM images of ordinary BiOCl (a, c) and ultrathin BiOCl (b, d) samples.
oxygen vacancy, ultrathin nanosheet structure, and
improved separation efficiency of photogenerated electron-
hole pairs contributed to the excellent photocatalytic
degradation activity of ultrathin BiOCl. +e obtained result
provides a new strategy of regulating the growth process of
BiOCl to fabricate ultrathin nanosheet structures with ex-
cellent photocatalytic degradation activity of carbamazepine
under visible-light irradiation.
3.2 × 105
2.8 × 105
2.4 × 105
2.0 × 105
1.6 × 105
1.2 × 105
8.0 × 104
Data Availability
+e experimental data used to support the findings of this
study are included in the article. Other data are available
from the corresponding author upon request.
492
494
496
498
500
502
504
Wavelength (nm)
Conflicts of Interest
Ordinary BiOCl
Ultrathin BiOCl
+e authors declare that they have no conflicts of interest.
Authors’ Contributions
Figure 8: PL spectra of ordinary BiOCl and ultrathin BiOCl
samples.
Shuo Xu and Xiaoya Gao contributed equally to this study.
Acknowledgments
4. Conclusions
+e authors gratefully acknowledge the financial support of
the High-Level Scientific Research Foundation for Talent
Introduction (10978172).
In summary, a series of ultrathin BiOCl 2D nanosheet
photocatalysts were readily synthesized by the TBAOH-
assisted hydrolysis method in water. +e preparation pa-
rameters were optimized to TBAOH dosages of 1 mmoL and
chlorine source of NaCl in the pH of 2 upon magnetic
stirring of 6 h. +e obtained ultrathin BiOCl displayed the
highest photocatalytic degradation rate constant
(0.0038 min−1) of carbamazepine, which is 7.6 times higher
than that with the ordinary BiOCl. From the characteriza-
tion of XPS, SEM, and PL, it was found that the presence of
Supplementary Materials
Figure S1: the absorption spectra for the degradation of
carbamazepine over ultrathin BiOCl. Figure S2: the ab-
sorption spectra for the degradation of carbamazepine over
ultrathin BiOCl. Figure S3: XRD patterns of the as-syn-
thesized BiOCl samples. Figure S4: TEM images of the as-

Journal of Chemistry
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