Facile Synthesis of Carbon Dots@2D MoS2 Heterostructure with Enhanced Photocatalytic Properties

Article abstract of DOI:10.1021/acs.inorgchem.9b00111

To better utilize carbon dots (CDs) as efficient photocatalysts, an excellent strategy of constructing CDs@MoS₂ heterostructure is presented. Here a facile sonication-hydrothermal method is utilized to synthesize CDs@MoS₂. Such heter

Full text of DOI:10.1021/acs.inorgchem.9b00111

Article
pubs.acs.org/IC
Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX
Facile Synthesis of Carbon Dots@2D MoS2 Heterostructure with
Enhanced Photocatalytic Properties
Ning Li,*,†,‡ Zhengtang Liu,‡ Ming Liu,† Chaorui Xue,† Qing Chang,*,† Huiqi Wang,† Ying Li,†,§
Zhenchao Song,† and Shengliang Hu*,†
†School of Energy and Power Engineering & School of Material Science and Engineering, North University of China, Taiyuan
030051, P. R. China
‡State Key Lab of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, P. R. China
§CAS Key Laboratory of Carbon Materials, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, P. R. China
S
* Supporting Information
ABSTRACT: To better utilize carbon dots (CDs) as efficient
photocatalysts, an excellent strategy of constructing CDs@
MoS2 heterostructure is presented. Here a facile sonication−
hydrothermal method is utilized to synthesize CDs@MoS2.
Such heterostructure regulates the energy level configuration,
and visible light absorption and the separation and transfer of
photogenerated charges are enhanced remarkably, which is
propitious for the production of more photoinduced charges
and improvement of the heterogeneous photocatalytic activity. Meanwhile, the photocatalytic performance of CDs@MoS2 was
obviously improved in methylene blue degradation. On the basis of a series of contrast experiments, the possible mechanism of
the photocatalytic reaction is proposed. Therefore, this work offers a facile route for the design of a zero-dimensional/two-
dimensional heterojunction for the adjustment of the energy level structure and the improvement in photocatalytic
performance.
absorbance and photocatalytic efficiency. Moreover, intimate
interfacial contact in the layer-by-layer structure of CD-CdS
quantum dot heterojunction films facilitates efficient photo-
induced charge separation.19 By now, many CD-based
heterostructures and hybrid systems such as TiO2, Ag3PO4,
ZnFeO4, Fe2O3, C3N4, Bi2WO6, BiOCl, etc., have been
designed.1,4,21−24 However, CDs act only as decorated
accessories in these composites to heighten the photocatalytic
activity of the other compound, which runs counter to the
expectation of utilizing CDs adequately. Therefore, how to
better utilize and design CDs in the heterostructure is still
challenging.
Two-dimensional (2D) transition metal dichalcogenides
(TMDs) have advantages in terms of their large specific surface
area, strong visible light absorption, high-edge active sites, and
short migration distance of the photogenerated charge carrier,
which can be used to form heterostructures (or composites) by
combining with a metal or semiconductor to improve the
photocatalytic activity.25−28 Consequently, 2D MoS2 does
become the promotor of the CD-based hybridization. For
example, Atkin et al.29 synthesized the 2D WS2/CDs hybrids
by a two-step method of exfoliation followed by microwave
irradiation. These hybrids have enhanced photocatalytic
activity for Congo red (CR) dye. Moreover, Fang et al.30
1. INTRODUCTION
Carbon dots (CDs), due to their photoluminescence, photo-
stability, biocompatibility, nontoxicity, low cost, and potential
to capture, transfer, and convert light energy, have attracted a
tremendous amount of attention in the fields of fluorescence
imaging, sensing, and solar-to-energy conversion.1−13 For one
thing, as we know, CDs typically exhibit strong optical
absorption in the ultraviolet (UV) region (230−360 nm) with
a tail extending into the visible range,14 yet UV light is only 5%
of the whole solar spectrum, which restricts the photo-
absorption and the amount of photoinduced charge.15 For
another, highly efficient charge transfer is fundamental for
photocatalytic solar-to-energy conversion. Nevertheless, there
are plenty of recombination centers that work against the
separation and transfer of the photogenerated charge.9,14 In
view of these issues, many methods have been adopted to
enhance the visible light absorption and charge transfer
efficiency of CDs such as the creation of unique surface states,
doping with heteroatoms, construction of heterostructure,
etc.1,16−18 As part of these efforts, heterostructure not only can
manipulate the absorption of sunlight together with the
valence and conduction band positions but also possesses
unique interfacial properties for the separation and transfer of
photoinduced charges.4,12,19,20 For instance, Kang et al.4
fabricated the CDs-C3N4 composite. The optical properties,
valence, and conduction band energies of this composite
change, which is beneficial for the improvement of the light
Received: January 13, 2019
© XXXX American Chemical Society
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electrode was Pt foil, the reference electrode was the Ag/AgCl
reference electrode, and the working electrode was the prepared
sample. The working electrodes were prepared by overlaying a slurry
of the sample in ethanol onto an indium tin oxide (ITO) glass
electrode, and then they were dried under vacuum at 80 °C for 2 h.
The electrolyte solution was 0.5 M Na2SO4. Linear potential scans
were performed at a rate of 5 mV s−1 within a given potential window.
All of the electrochemical measurements were carried out on the Bio-
Logic (SP 120) electrochemical workstation.
2.4. Photocatalysis Experiments. First, a 0.01 mg/mL
methylene blue (MB) solution was prepared. Then, 2 mL of the
sample (CDs or CDs@MoS2 sample) was added to 25 mL of MB and
ceaselessly stirred for 1 h in the dark to establish an adsorption−
desorption equilibrium. The solution was irradiated for 5 min with a
300 W xenon lamp placed 30 cm away (wavelengths of <420 nm were
removed by a UV cutoff filter to obtain visible and near-infrared
light); the solution was constantly stirred during irradiation. The light
intensity reaching the solution was ∼100 mW cm−2. Subsequently, 3
mL of the solution was centrifuged at 1600 rpm for 5 min, and the
liquid supernatant was added to a quartz cell. Finally, the UV−vis
absorption spectrum was measured at set intervals.
demonstrated the effective transfer of photoexcited electrons
from the CDs to the MoS2 monolayers. Choosing zero-
dimensional (0D) carbon dots and 2D MoS2 to construct
heterostructures is based on the following. First, there are
strong interfacial coupling and high dispersion between
quantum-limited CDs and 2D MoS2,25 which further increase
the photocatalytic activity. Second, the ability of the CDs to
absorb sunlight improves, and more importantly, the rapid
recombination of photogenerated electron−hole pairs for both
CDs and MoS2 is inhibited.1,31 Third, it is generally known
that the energy band modulation is necessary to match the
different redox reaction and improve redox capabilities.
Considering the valence band-edge position of 2D MoS2
close to zero (−0.085 eV vs NHE32), constructing CDs/
MoS2 heterostructures to regulate band alignment could
facilitate preferable energy conversion. Therefore, CDs/MoS2
heterostructures can take advantage of each other and cover
the shortages.
In this work, we present a strategy for the in situ synthesis of
CDs@2D MoS2 heterostructures (named CDs@MoS2) and
demonstrate that the synthesized CDs@MoS2 possessed
superb photocatalytic activities compared with those of pure
CDs.
To detect the role of active species formed in the CDs@MoS2
samples, a series of trapping experiments were performed by utilizing
different scavengers in the photodegradation process; 0.1 mM
isopropanol (IPA), triethanolamine (TEOA), and orbenzoquinone
(BQ) were added to 25 mL of the MB solution to perform
degradation experiments for hydroxyl radical (•OH), hole (h+), and
2. EXPERIMENTAL SECTION
2.1. Synthesis of CDs. The preparation is shown in Scheme 1.
After sonication for 6 h at room temperature, 20 mL of an N,N-
−
superoxide radical (•O2 ), respectively. In the recycling experiments,
the tested sample was collected and washed several times and then
dried under vacuum at 80 °C for 8 h. Then, the collected sample was
measured accurately, and some fresh catalyst was added to ensure the
accuracy of the experiments because of the inevitable weight loss
during the experiment.
Scheme 1. Schematic Illustration of the Preparation of CDs
and CDs@MoS2
3. RESULTS AND DISCUSSION
XRD patterns of CDs, 2D MoS2, and CDs@MoS2 are shown
in Figure 1. As one can see, no significant diffraction peak
appears in the XRD pattern of CDs (Figure 1a). The XRD
pattern of MoS2 powder (Figure S1) reveals clear phase peaks
dimethylmethanamide (DMF) solution was transferred into a 50 mL
Teflon-lined stainless autoclave and then heated at 200 °C in oven for
6 h. The CD solution was obtained after the sample had cooled to
room temperature naturally.
2.2. In Situ Synthesis of CDs@MoS2 Heterostructure. As
shown in Scheme 1, after sonication for 6 h at room temperature, 22
mL of a DMF solution supplemented with 80 mg of bulk MoS2
powder (Alfa Aesar, 99% pure) was centrifuged at 3000 rpm for 20
min. The 2D MoS2 suspension was prepared immediately. Then 20
mL of the supernatant was transferred into a 50 mL Teflon-lined
stainless autoclave and heated at 200 °C in an oven for 6 h. The
CDs@MoS2 solution was obtained after the sample had cooled to
room temperature naturally.
2.3. Characterization. X-ray diffraction (XRD) was conducted
for structure analysis with monochromatic Cu Kα radiation (40 kV,
30 mA). Transmission electron microscopy (TEM) was performed
for the microstructure analysis on a Tecnai G2 F20 S-Twin
microscope with a field-emission gun operating at 200 kV. The
compositions and chemical states of the samples were analyzed using
X-ray photoelectron spectroscopy (XPS) with a monochromatic Al
Kα (1486.6 eV) X-ray source. UV−visible (UV−vis) absorption
spectra and photoluminescence (PL) were recorded on a Shimadzu
UV-2550 spectrometer and a Hitachi F4500 fluorescence spectropho-
tometer, respectively. Electrochemical measurements were performed
in a three-electrode electrochemical system in which the counter
Figure 1. XRD patterns of (a) CDs and (b) 2D MoS2 and CD@
MoS2.
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at 14.4°, 29.0°, 32.7°, 33.5°, 39.5°, 44.2°, 49.8°, 58.3°, and
60.1° that can be indexed to (002), (004), (100), (101),
(103), (006), (105), (110), and (008) planes of the hexagonal
phase of MoS2, respectively (PDF Card 37-1492).33,34 Figure
1b displays (002), (004), (006), and (008) planes of 2D MoS2,
which exhibits a (002) preferred orientation. Interestingly, the
exfoliated 2D MoS2 has an enhanced planar crystal structure
compared with that of bulk MoS2. Moreover, XRD peak
positions of CDs@MoS2 are in agreement with those of 2D
MoS2, whereas the (002) peak intensity dropped markedly,
which can be attributed to the fact that CDs not only cover the
surface of 2D MoS2 but also enter between different MoS2
layers.35 This phenomenon confirms the formation of CDs@
MoS2 heterostructure.21,35 To perform TEM, dilute 2D MoS2
or CDs@MoS2 solutions were dropped onto carbon-coated
copper grids. A planar view of the lattice planes in multilayer
stacked MoS2 is illustrated in Figure 2a. The fast Fourier
Figure 3. (a and b) XPS spectra of CDs and CDs@MoS2. (c and d)
XPS spectra of Mo 3d and S 2p of CD@MoS2.
to C 1s, N 1s, and O 1s, respectively.6 Figure 3b shows the
XPS spectrum of CDs@MoS2. There are Mo 3d, S 2p, Mo 3p,
C 1s, N 1s, and O 1s peaks in the spectrum. The high-
resolution XPS spectra for Mo 3d and S 2p of CDs@MoS2 are
displayed in panels c and d of Figure 3. Mo 3d spectra can be
resolved into two spin−orbit doublets and one extra peak.
Peaks at 229.2 and 232.3 eV, 231.4 and 234.5 eV, and 226.5 eV
correspond to Mo 3d5/2 and Mo 3d
of MoS2 and S 2s of
3/2
MoOx, respectively.38−42 The S 2p is only fitted into one
doublet corresponding to S−Mo of MoS2 (Figure 3d),
suggesting that a chemical bond (for example, a S−C bond)
may not form between CDs and 2D MoS2. Binding energies
(BEs) of S 2p
(162.0 eV) and S 2p
(163.2 eV) are in
3/2
1/2
agreement with the reported BEs of MoS2,34,38 further
illustrating the chemical states of Mo cations. In view of our
XPS analysis and the inert basal planes of MoS2,43 there may
be an intermolecular force between the evenly distributed CDs
and the 2D MoS2 surface.
Figure 4a shows the UV−vis absorption spectra of CDs, 2D
MoS2, and CDs@MoS2. One can see that CDs exhibit strong
optical absorption in the UV region of 230−360 nm with a tail
extending into the visible range. In contrast, there is higher
absorption intensity in the ultraviolet and visible region for 2D
MoS2, and the peaks at 398 and 443 nm and at 608 and 667
nm are attributed to direct transition from the deep valence
band to the conduction band and to the K point of the
Brillouin zone, respectively.44 Therefore, because of the
adjustment of the energy band structure, the absorption
intensity of CDs@MoS2 increases remarkably in the visible
region compared with that of CDs, which is extremely
propitious for the production of more photoinduced charges.
The photocatalytic properties of CDs and CDs@MoS2 are
investigated by the degradation (oxidation) of methylene blue
(MB). The MB solution reaches the equilibrium adsorption
state after being stirred for 30 min (Figure S3). As shown in
Figure 4b, the photodegradation of MB in the presence of CDs
is very slow, and the degradation rate is only 10.2% after
irradiation for 35 min (Figure S4b). The degradation effect
through 2D MoS2 is also poor (Figure S4b). By comparison,
the MB containing the same amount of CDs@MoS2 degrades
quickly and the rate reaches 91.1% within 35 min upon
irradiation (Figure 4c and Figure S4b). In Figure 4d, a linear
Figure 2. (a) TEM image of 2D MoS2. The insets are the
corresponding fast Fourier transformation (FFT) and HRTEM
images. (b) Atomic configurations of the MoS2 model. (c and d)
TEM and HRTEM images of CDs@MoS2.
transformation (FFT) pattern and high-resolution (HR) image
(shown in the inset of Figure 2a) suggest a hexagonal lattice
structure with a d spacing of 0.27 nm for lattice planes (100),36
which is consistent with the XRD results. Meanwhile, the
distance between the two neighboring circle dots in the TEM
image is 3.17 Å, which is equal to that of the two S atoms in
the atomic model [3.168 Å (Figure 2b)]. Figure 2c and Figure
S2 show that CDs with average diameters of ∼2.85 nm are
uniformly dispersed on the lamellar surface of the 2D MoS2. As
illustrated in the inset of Figure 2d, the obtained HRTEM
image of CDs reveals visible crystalline lattice fringes and the
interlayer spacing of 0.21 nm corresponds to the in-plane
lattice spacing of graphene in the (100) diffraction facets of
graphite carbon.37
The chemical composition and chemical states of the CDs
and CDs@MoS2 were studied by XPS analysis. As displayed in
the XPS spectra of CDs (Figure 3a), the sample possesses
three peaks at 284.1, 398.2, and 532.3 eV, which are attributed
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Figure 4. (a) Absorption spectra of the CDs, 2D MoS2, and CDs@
MoS2. (b and c) UV−vis spectra of MB degradation vs irradiation
time in the presence of CDs and CDs@MoS2, respectively. (d)
Pseudo-first-order kinetic rate plots of the photocatalytic degradation
of the MB solution for CDs, 2D MoS2, and CDs@MoS2.
characteristic is observed for each sample, indicating that the
decomposition kinetics follows the first-order law of ln(C/C0)
= kt,6 where k is the pesudo-first-order rate constant and t is
the time. Notably, the degradation rate constants of CDs, 2D
MoS2, and CDs@MoS2 are −0.0030, −0.0034, and −0.072
min−1, respectively. It is not hard to find that the photocatalytic
activity is obviously enhanced after the hybridization of CDs
and MoS2. Then, the stability of CDs@MoS2 was evaluated via
recycling experiments. We tested the highest-performance
CDs@MoS2 sample, and its degradation efficiency was >90%
(Figure S5a), indicating that the CDs@MoS2 sample remains
photocatalytic and stable. As shown in Figures 1−3 and Figure
S5b−g, the position and intensity of the (002) preferential
peak, the binding energies of Mo 3d and S 2p, and the
morphology of the CDs@MoS2 sample were almost the same
before and after the photocatalytic experiments. Thus, the
stability of CDs@MoS2 could be further validated through the
XRD, TEM, and XPS results. In addition, PL spectra of the
CDs, CDs@MoS2, and 2D MoS2 were measured. As one can
see, an overt emission maximum at ∼415 nm is observed when
CDs are excited at 340 nm (Figure S6a). However, the
intensity of the emission peak maximum (∼413 nm) decreases
significantly (Figure S6b) after combination with 2D MoS2
[the PL peak of the 2D MoS2 sample is extremely low (Figure
S6c)], suggesting that the intimate interaction between CDs
and 2D MoS2 promotes the effective separation and transfer of
the photoinduced electron−hole and inhibits the recombina-
tion. This is an indirect explanation for the increment in the
photocatalytic efficiency of CDs@MoS2.
Figure 5. Cathodic and anodic scans of (a and b) 2D MoS2, (c and d)
CDs, and (e and f) CDs@MoS2, respectively. (g) Schematic energy
level diagram of the three prepared samples. (h) EIS Nyquist plots of
CDs and CDs@MoS2.
equivalent to −0.08 and 1.51 V, −1.37 and 1.14 V, −0.36 and
1.21 V (vs NHE), respectively. The energy gaps of the three
samples determined from the potential scan are 1.59, 2.51, and
1.57 eV, respectively. In succession, we plot the schematic
energy level diagram of 2D MoS2, CDs, and CDs@MoS2
(Figure 5g). This plot clearly shows that the energy level
configuration has been regulated and a typical type II band
alignment1,30,42,46−48 is formed between 2D MoS2 and CDs,
which facilitates the transfer of photoexcited holes from MoS2
to CDs and photogenerated electrons from CDs to MoS2,
resulting in an effective oxidation ability under visible light
irradiation. Furthermore, EIS measurements were carried out
to further investigate the separation efficiency of the charge
carriers. The arc radius on the EIS Nyquist plot of CDs@MoS2
is smaller than that of CDs (Figure 5h), illustrating that the
former sample has the lower interfacial charge transfer
resistance and subsequently causes the effective separation of
photogenerated electron−hole pairs.6−8,45,49 A reasonably
theoretical simulation based on density functional theory can
study the nature of the material properties and demonstrate
experimental results. The just reported work50 can be the
auxiliary support for the experimental results of energy level
configuration and charge transfer.
To thoroughly understand the behaviors of photogenerated
charges and the oxidation mechanism, the band alignment [the
conduction band minimum (CBM) and the valence band
maximum (VBM) levels] and electrochemical property are
estimated through linear potential scans and electrochemical
impedance spectroscopy (EIS).6−8,45 Panels a and b, c and d,
and e and f of Figure 5 show the cathodic and anodic scan
results of 2D MoS2, CDs, and CDs@MoS2, respectively. The
CBM and VBM values of these three samples are
approximately −0.28 and 1.31 V, −1.57 and 0.94 V, and
−0.56 and 1.01 V (vs Ag/AgCl), respectively, which are
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From the analysis presented above, the possible degradation
mechanism is shown in Figure 5g. First, samples of CDs, 2D
MoS2, and CD@MoS2 could be excited, and simultaneously,
the holes (h+) and electrons (e−) were produced under visible
light irradiation (λ > 420 nm). However, the abilities of
photoinduced e−−h+ pairs are different due to the absorption
capacity. The better the absorption ability, the more the
photoinduced charges produce. Then, the photogenerated
electrons would participate in the following reaction:51,52
can see that the photocatalytic activities are restrained most
seriously by the BQ, suggesting that •O2 plays the most
−
important role in photodegradation. Meanwhile, the active
species h+ and •OH are also responsible for the final
breakdown of the MB. Therefore, MB molecules are degraded
22,35,47,51−53,55
•
− •
by O2 , OH, and h+.
On the basis of the analysis presented above, the
photocatalytic activities of CDs@MoS2 can be significantly
enhanced. The modulation of the valence band-edge position
(from −0.08 to −0.36 eV vs NHE) enhances the ability to
•
−
O2 + e− → O2
produce •O2 compared with that of 2D MoS2, and the
−
(1)
(2)
increment in the absorption, separation, and transfer of
photoinduced charges boosts the effective MB degradation in
contrast to that of CDs. Therefore, we can conclude that the
construction of the CDs@MoS2 heterostructure is propitious
for the improvement of solar energy absorption and
conversion.
•O2 + 2H2O + 2e− → 3OH− + OH
−
•
In view of the CBM values of 2D MoS2, CDs, and CDs@
MoS2 (−0.08, −1.37, and −0.36 V vs NHE, respectively), the
photogenerated electrons reacted with absorbed O2 on the
•
−
−
surface of photocatalysts to form O2 (O2/•O2 , −0.046 eV
vs NHE24). Due to the lower reduction potential of 2D MoS2
and the worse visible absorption of CDs, the capacities of
reducing dissolved O2 are both poor. For CDs@MoS2, the
separation and transfer of photoinduced charges promote the
generation of enough •O2− radicals. To quantify the amount of
4. CONCLUSION
In summary, we present a facile sonication−hydrothermal
method for synthesizing CDs@MoS2 heterostructure. The
results show that CDs loaded onto the 2D MoS2 not only can
extend and enhance visible light absorption but also can
produce higher separation and transfer efficiency of photo-
induced charges compared with that of pure CDs. The linear
potential scans illustrate that a staggered type II band
alignment is formed near the CDs 2D MoS2 interface, and
we know that electrons are transferred from the conduction
band minimum of CDs to that of 2D MoS2. As a consequence,
the proper band-edge positions of CDs@MoS2 are conducive
to the production of adequate active radicals to participate in
degradation. Meanwhile, the possible mechanism of the
photocatalytic reaction is proposed. Finally, we can conclude
that the construction of the CDs@MoS2 heterostructure
enhances the solar energy absorption and conversion on the
basis of this work.
•
−
formed O2 , the nitro blue tetrazolium (NBT) was used as a
•
−
probe for O2 on the basis of the formation of the insoluble
formazan dye.53,54 As displayed in panels a and b of Figure S7,
the absorption bulge at ∼650 nm refers to the characteristic
peak of formazan. When the CDs@MoS2 sample was added to
the NBT/NaOH mixture, the adsorption intensity of formazan
increased more evidently than those of the CD sample and 2D
MoS2, indicating the more beneficial effect of CDs@MoS2 in
•
−
•
−
the generation of O2 . In addition, O2 radicals of the three
kinds of samples could react with H2O and e− to generate
52
strongly oxidative OH (•O2 /•OH, 0.9 V vs NHE ). The
•
−
•
presence of OH radicals can be determined by terephthalic
acid (TA). After reaction, TA transforms to 2-hydroxytereph-
thalic acid (TAOH), which emits fluorescence at 426 nm.51
Panels c and d of Figure S7 illustrate the fluorescence spectra
of the TA solution irradiated at different times after the
addition of samples of CDs, CDs@MoS2, and 2D MoS2. The
fluorescence intensity of 426 nm generated from CDs@MoS2
is much stronger than those of the CDs and 2D MoS2.
To detect the main active species formed in the CDs@MoS2
samples and comprehend the degradation mechanism, a series
of trapping experiments were performed by utilizing diff•erent
scavengers in the photodegradation process: IPA for OH,
ASSOCIATED CONTENT
■
S
* Supporting Information
The Supporting Information is available free of charge on
the ACS Publications website at DOI: 10.1021/acs.inorg-
chem.9b00111.
XRD patterns of MoS2 powder, TEM image of CDs@
MoS2, size distribution of CDs, dark adsorption curve,
degradation rates, recycling experiments, XRD, XPS, and
TEM images of the CDs@MoS2 sample after photo-
degradation, PL spectra, and quantification of active
species (PDF)
TEOA for h+, and BQ for •O2 .32,55 As shown in Figure 6, one
−
AUTHOR INFORMATION
■
Corresponding Authors
*E-mail: lnlong2834@yeah.net.
*E-mail: changneu@gmail.com.
*E-mail: hsliang@yeah.net.
ORCID
Ning Li: 0000-0002-4046-4825
Huiqi Wang: 0000-0003-1232-7572
Shengliang Hu: 0000-0002-2838-4072
Notes
Figure 6. Trapping of active species during the photocatalytic
•
•
−
degradation of MB: IPA for OH, TEOA for h+, and BQ for O2 .
The authors declare no competing financial interest.
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Performance of N-Doped Carbon Quantum Dot/TiO2 Composites
for Photocatalytic Hydrogen Evolution. ChemSusChem 2017, 10,
4650−4656.
ACKNOWLEDGMENTS
■
This work was financially supported by the National Natural
Science Foundation of China (U1510125, 51272301,
51502270, and 21703209) and the fund of the State Key
Laboratory of Solidification Processing in NWPU
(SKLSP201719). The authors also appreciate the financial
support by the Shanxi Province Science Foundation
(201601D021059), Key Research and Development (R&D)
Projects of Shanxi Province (201803D121037 and
201803D421091), the Shanxi Province Science Foundation
for Youths (201701D221087, 201701D221085, and
201801D221085), the Specialized Research Fund for Sanjin
Scholars Program of Shanxi Province, the Program for the
Outstanding Innovative Teams of Higher Learning Institutions
of Shanxi, the Fund of CAS Key Laboratory of Carbon
Materials (KLCMKFJJ1709), the North University of China
Fund for Distinguished Young Scholars, and “333” talent
project research. This work was part of the Ph.D. degree of Jin
(2017) and North University of China Fund for Scientific
Innovation Team.
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