The morphology and photocatalytic performance of Zn(OH)F under different synthetic conditions

Article abstract of DOI:10.1016/j.jfluchem.2020.109600

Metal hydroxyfluorides have been widely used in the development of new functional materials, due to their diverse preparation methods and easy controlled morphologies. As an important zinc-based nanomaterial, zinc hydroxy fluoride (Zn(OH)F) is not only an

Full text of DOI:10.1016/j.jfluchem.2020.109600

JournalofFluorineChemistry237(2020)109600
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
The morphology and photocatalytic performance of Zn(OH)F under
different synthetic conditions
Yang Yanga, Sugang Menga,b,*, Xiuzhen Zhenga, Huihui Wua, Xianliang Fua, Shifu Chena,**
a Key Lab of Clean Energy and Green Circulation, Huaibei Normal University, Huaibei, 235000, China
b State Key Laboratory of Photocatalysis on Energy and Environment, Fuzhou University, Fuzhou, 350116, China
A R T I C L E I N F O
A B S T R A C T
Keywords:
Metal hydroxyfluorides have been widely used in the development of new functional materials, due to their
diverse preparation methods and easy controlled morphologies. As an important zinc-based nanomaterial, zinc
hydroxy fluoride (Zn(OH)F) is not only an important precursor for the synthesis of zinc oxide (ZnO) nanoma-
terials with special morphology, but also an effective photocatalyst in the degradation of organic pollutants. In
this article, many different morphologies of Zn(OH)F were synthesized by changing the synthetic conditions
(temperatures, reactants, surfactants), such as barklike, rod, cluster, ribbon, criss-cross, cross-assembled net-
work, thorn-ball and so on. Moreover, their photocatalytic performances were investigated and barklike Zn(OH)
F-T250 displayed good photocatalytic performance for liquid degradation (salicylic acid, rhodamine B, me-
thylene blue and phenol) and gaseous benzene removal under UV-light irradiation. Therefore, this study about
morphology control for metal hydroxyfluorides not only provides important theoretical value, but also performs
broad application prospects.
Morphology
Photocatalytic degradation
Surfactants
Zn source
Synthetic condition
1. Introduction
[16], liquid phase synthesis [21,22], electrochemical [12,13], and mi-
crowave radiation methods [23,24]. Correspondingly, a series shape of
Metal hydroxyfluorides have been widely used in the development
of new functional materials, due to the simple synthetic routes, easy
controllable morphology, strong oxidation resistance, stable presence in
the air, and unique electronic energy band structure [1–6]. Generally,
metal hydroxyfluorides are wide bandgap semiconductors and tend to
form layered structures with large specific surface area, which has been
widely applied in the fields of optoelectronic devices, photoluminescent
materials and degradation of organic pollutants [7–11]. Therefore, it is
great significance for us to extensive and deep research on the metal
hydroxyfluorides.
Zn(OH)F nanostructures were synthesized, such as rods [9], fibers [24],
flowers [21], ribbons [23], etc. [25]. However, it is still a major chal-
lenge on how to adopt a simple, efficient and relatively mild condition
to controllably synthesize Zn(OH)F nanostructures with different
morphologies.
Semiconductor-assisted photocatalytic oxidation of organic com-
pounds in water and air has attracted much attention as a promising
technology for pollution abatement [26–28]. Especially, some semi-
conductors contained OH group are reported as efficient photocatalysts
for wastewater and gaseous degradation, as OH group is conducive to
the generation of active species [29–31]. In this article, Zn(OH)F ma-
terial with OH group and many different morphologies were success-
fully synthesized by a simple hydrothermal method, for instance,
barklike, rod, cluster, ribbon, criss-cross, cross-assembled network,
thorn-ball and so on. Moreover, barklike Zn(OH)F catalyst exhibited
good performance for photocatalytic degradation of liquid (salicylic
acid, rhodamine B, methylene blue and phenol) and gaseous (benzene)
pollutants under UV-light irradiation, which was characterized by many
technologies (XRD, DRS, TG-DSC, FESEM, TEM and N2 adsorption-
desorption). To optimize the photocatalytic performance, the effects of
As an important zinc-based nanomaterial, Zn(OH)F is not only an
important precursor for the synthesis of ZnO nanomaterials with special
morphology [12–14], but also an effective photocatalyst in the de-
gradation of organic pollutants [15–17]. As is well known, the chemical
and physical properties of nanomaterials strongly depend on their
morphology, dimensions and surface properties [18]. The development
of controllable preparation methods for nanomaterials is of great sig-
nificance for the theoretical development and practical application.
Currently, a variety of preparation methods are used to synthesize Zn
(OH)F nanomaterials, including hydrothermal [19,20], solvothermal
⁎ Corresponding author.
⁎⁎ Corresponding author.
E-mail addresses: mengsugang@126.com (S. Meng), chshifu@chnu.edu.cn (S. Chen).
https://doi.org/10.1016/j.jfluchem.2020.109600
Received 19 May 2020; Received in revised form 9 July 2020; Accepted 9 July 2020
Availableonline12July2020
0022-1139/©2020ElsevierB.V.Allrightsreserved.

Y. Yang, et al.
JournalofFluorineChemistry237(2020)109600
Fig. 1. SEM images of Zn(OH)F materials obtained at 100 ℃ with different hydrothermal time: (a) 0 h, (b) 10 min, (c) 0.5 h, (d) 1 h, (e) 2 h, (f) 6 h.
hydrothermal temperature, calcination temperature, Zn sources, sol-
vent, alkali source and surfactants were considered in the process of
synthesis.
2.2. Characterization of Zn(OH)F samples
X-ray diffraction (XRD) patterns of the samples were obtained on a
Bruker D8 Advance X-ray diffract meter with Cu Kα radiation (λ
=1.5406 Å). UV–vis diffuse reflection spectra (UV–vis DRS) were re-
corded using a Hitachi UV-365 spectrophotometer with BaSO4 as re-
ference. Scanning electron microscopy (SEM) images of the samples
were obtained by a field emission SEM (FESEM, FEI Nova NANOSEM
230). Transmission electron microscopy (TEM) and high-resolution
transmission electron microscopy (HRTEM) images were performed on
a JEM-ARM200 F electron microscope operated at an acceleration
voltage of 200 kV. N2 physisorption measurements were carried out at
77 K using a Micromeritics Tristar II 3020 surface area analyzer.
Multipoint Brunauer-Emmett-Teller (BET) specific surface areas were
then determined from the adsorption isotherms.
2. Experimental section
2.1. Preparation of Zn(OH)F samples with different morphology
All chemicals in this work were of analytical grade and purchased
from Sinopharm company, which were used without further purifica-
tion. Deionized water was used throughout this study. Zn(OH)F with
different synthetic conditions are described as following:
The synthesis of barklike Zn(OH)F: 0.661 g Zn(NO3)2∙6H2O, 0.822 g
NH4F were firstly dissolved into 82 mL H2O, and the pH value was
adjusted by NaOH (when NaOH amount is 0.176 g, PH = 7). After
continuous stirring for 2 h, the solution was transferred into a Teflon-
lined stainless steel autoclave with 100 mL capacity. The autoclave was
sealed and maintained at 100 ℃ for 6 h, and then cooling down natu-
rally. The obtained products were collected by centrifugation and wa-
shed with deionized water and ethanol for several times, and dried at
60 °C for 8 h.
2.3. Photocatalytic activity of Zn(OH)F samples
The liquid-phase photocatalytic activities of Zn(OH)F samples were
mainly evaluated by the degradation of organic pollutants under UV
light. A cylindrical glass vessel as the reactor was surrounded by four
UV lamps (Philips, TUV 4 W/G4 T5), and the wavelength centered at
254 nm. 100 mg catalyst was added into the vessel which contained
150 mL organic pollutants. The initial concentration of salicylic acid
(SA), rhodamine B (RhB), Methylene blue (MB) and phenol were 1.0 ×
The influence of calcination temperature: the above obtained Zn
(OH)F was calcinated at 200 ℃, 250 ℃, 300 ℃ and 400 ℃ with 1 ℃
min–1, respectively.
The influence of Zn sources, solvent, alkali sources and surfactants
are investigated, and other condition is similar with the above synthesis
of barklike Zn(OH)F without calcination. These differences are shown
in the following: (1) different zinc sources are added to replace Zn
(NO3)2∙6H2O, and the corresponding mass are 0.310 g, 0.639 g, 0.488 g
and 0.590 g for ZnCl2, ZnSO4∙7H2O, zinc acetate (Zn(Ac)2) and zinc
acetylacetone (Zn(Ah)2), respectively. (2) The methanol and H2O as the
solvent is added, and the volume are 20 mL and 62 mL, respectively. (3)
Different alkali source (3-butylamine, oleylamine and ethylenediami-
netetraacetic acid disodium salt (EDTA-2Na)) is added to replace
NaOH, and the amount is 0.176 g. (4) The surfactants are added after
the dissolution of Zn(NO3)2∙6H2O and 0.83 g NH4F in water, and their
mass for P123, cetyl brominated ammonium (CTAB), sodium dodecyl
benzene sulfonate (DBS), D-glucose (D-Glu), polyethylene pyrrole
(PVP) and sodium dodecylsulphonate (SDS) are 2 g, 1 g, 0.5 g, 1 g, 0.5 g
and 1 g, respectively.
10−4 mol L–1, 1.0 × 10-5 mol L–1, 10 ppm and 1.0 × 10–4 mol L–1
,
respectively. Prior to irradiation, the suspension was stirred con-
tinuously in the dark for 30 min to ensure the establishment of the
adsorption/desorption equilibrium. After specific time intervals of ir-
radiation, a 3-mL suspension was withdrawn and then centrifuged to
remove the catalyst during the photocatalytic degradation progress. A
Varian Cary 50 Scan UV–vis spectrophotometer was used to record the
concentration changes of the resulting degraded solution. The de-
gradation rate was marked as C/C0. C was the maximum absorption
intensity of degraded solution (SA, RhB, MB and phenol) for each ir-
radiated time interval at 297 nm, 554 nm, 664 nm and 269 nm, and C0
was the absorption intensity of the initial concentration when adsorp-
tion/desorption equilibrium was achieved.
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Y. Yang, et al.
JournalofFluorineChemistry237(2020)109600
olivelike Zn(OH)F is dissolved to form barklike, clearly observed from
Fig. 1d and Fig. S1. With the shape changing, the material is also
transformed from ZnO (labeled by in the XRD pattern) to Zn(OH)F
(labeled with in Fig. 2). Meanwhile, no impurity phase can be found
under the hydrothermal condition at 100 ℃ for 6 h (Fig. S2). The 2-
theta of 20.6°, 32.5°, 33.7° and 35.5° are well corresponding to the
crystal plane of (110), (310), (201) and (111) of Zn(OH)F (JPCDS No.
74-1816), respectively [29]. By calculated, its cell parameters are 10.17
× 4.72 × 3.11 < 90 × 90 × 90 > , and the average size is about 24.4
nm.
Moreover, different amount of NaOH was added to investigate the
optimal value of alkali source (Fig. S3-S5). As the amount of NaOH is in
0∼0.088 g (acidity), Zn(OH)F material with impurity phase was ap-
peared (Fig. S3 at 35°). With the NaOH amount increasing from 0.132
to 0.264 g, pure Zn(OH)F is obtained. The morphology remains bark-
like, without much changing (Fig. S4). When the quantity of NaOH is
more than 0.30 g (e.g., 0.308 g and 0.352 g, strong basicity), ZnO is
generated. Herein, Zn(OH)F and ZnO are simultaneously existed in the
samples. The photocatalytic performance of Zn(OH)F prepared with
different NaOH amount are further explored (Fig. S5), which exhibit
good degraded ability in RhB solution. When the mass of NaOH is 0.176
g, Zn(OH)F performs the highest activity. Thus, the optimal amount of
NaOH addition in Zn(OH)F preparation is 0.176 g.
Fig. 2. XRD patterns of Zn(OH)F nanomaterials obtained from different hy-
drothermal time, and the standard card shown in the bottom of XRD patterns:
red line for Zn(OH)F (JPCDS No. 74-1816) and black line for ZnO (JPCDS No.
36-1451).
3. Results and discussion
Additionally, the calcination temperatures of Zn(OH)F sample
(synthesized at 100 ℃ for 6 h) are also investigated. When the calci-
nated temperature is lower than 250 ℃, pure Zn(OH)F is obtained
(Fig. 3a). For Zn(OH)F-T250, its cell parameters are 10.12 × 4.74 ×
3.12 < 90 × 90 × 90 > , and the average size is about 29.2 nm (292
Å). Compared with Zn(OH)F, the cell parameters are slightly changed,
and the size is increased after calcination. As the temperature rising to
The morphology of Zn(OH)F synthesized at 100 ℃ with different
hydrothermal time are shown in Fig. 1. The morphology of Zn(OH)F is
changed from block to barklike at microscale. With the extension of
hydrothermal time, the morphology is changed greatly (block → oli-
velike → barklike). This is a self-dissolution and regrowth process, fa-
voring to form the “thermodynamically stable” phase [32], in which the
Fig. 3. The XRD patterns (a) of Zn(OH)F with different calcinated temperatures (the XRD standard card shown in the bottom: red line for Zn(OH)F and black for
ZnO), the decomposition temperature of Zn(OH)F (b), and the photocatalytic performances of Zn(OH)F at different calcination temperatures (c) and organic
pollutants (d).
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Y. Yang, et al.
JournalofFluorineChemistry237(2020)109600
Fig. 4. The Eg value (a) of Zn(OH)F and Zn(OH)F-T250, SEM (b) and TEM (c-d) images of Zn(OH)F-T250.
%
Fig. 5. The detection of H2O2 and OH (b) on Zn(OH)F and Zn(OH)F-T250 samples.
300 ℃, Zn(OH)F is partially decomposed to ZnO, which is observed in
the crystal structure ( ). The decomposition temperature in this work
(307 ℃, Fig. 3b) is much lower than the reported temperature (about
400 ℃) [17], which may be influenced by the preparation condition
and sample size. Moreover, the photocatalytic activity of RhB de-
gradation for Zn(OH)F after heat treatment is investigated, which is
following the order: Zn(OH)F-T250 > Zn(OH)F-T200 > Zn(OH)F
(Fig. 3c), meaning that the degradation activity of Zn(OH)F sample is
improved after heat treatment. Meanwhile, it shows good performance
in degrade other organic pollutants (MB, SA and phenol, Fig. 3d). After
120 min of phenol degradation, the mineralization rate for Zn(OH)F-
T250 (87 %, Fig. S6) is higher than Zn(OH)F (76 %) and P25 (84 %).
Especially, it can also degrade the gaseous benzene under UV light, and
exhibit higher activity and mineralization rate than P25 (Fig. S7).
To explore the enhanced reasons of photocatalytic activity, some
physical properties of Zn(OH)F after calcination (at 250 ℃) are char-
acterized, such as Eg value, morphology and BET surface areas. Band
energy of the samples before and after heat treatment are almost the
same (about 3.2 eV, Fig. 4a), but the F(R) value of the heated sample is
stronger than the original sample, indicating that the light absorption of
Zn(OH)F-T250 is stronger than that of Zn(OH)F. The barklike mor-
phology is not changed much after calcination, which is confirmed by
SEM and TEM images (Fig. 4b and 4c). Moreover, many different
crystallographic spacing can be found that allowed for identification of
Zn(OH)F. The lattice fringes with 0.260 nm, 0.265 nm and 0.209 nm
are observed (Fig. 4d and S8), which respectively correspond to the
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Y. Yang, et al.
JournalofFluorineChemistry237(2020)109600
Fig. 6. SEM images (a-d), XRD patterns (e) and photocatalytic activity (f) of Zn(OH)F obtained from different Zn sources: (a) ZnCl2, (b) Zn(AC)2, (c) ZnSO4 and (d) Zn
(Ah)2.
Fig. 7. The morphology (a-e) and XRD patterns (f) of Zn(OH)F with different synthetic conditions: solvent (a, methanol), alkali source (b, 3-butylamine; c, oley-
lamine; d, EDTA-2Na) and surfactant (e, P123).
(011), (201) and (311) plane of Zn(OH)F-T250. Meanwhile, the BET
surface areas of ZnFOH and Zn(OH)F-T250 samples are 19.6 and 20.8
m2 g–1, respectively (Fig. S9). Thus, the band gap, morphology and
surface areas perform no significant changes before and after heat
treatment, which are not the main reasons for the activity enhance-
ment. In the depth exploration, Zn(OH)F-T250 possesses more number
Besides, the Zn(OH)F morphology synthesized at 140 ℃ for 12 h
with different conditions (Zn sources, solvent, alkali source and sur-
factant) without calcination are investigated and shown in Fig. 6–8 as
its photocatalytic activity is almost equal with the above sample syn-
thesized at 100 ℃ (Fig. S10). Firstly, Zn(OH)F nanomaterial with dif-
ferent morphologies is explored by changing the zinc source. The zinc
sources are respectively ZnCl2, Zn(Ac)2, ZnSO4∙7H2O and Zn(Ah)2, and
their morphological characteristics are obviously different. Fig. 6a-d are
the FESEM images of Zn(OH)F nanomaterial obtained by using different
zinc sources, and the morphology are random belts for ZnCl2 and thatch
%
of active species (H2O2 [33] and OH, Fig. 5) than Zn(OH)F [34,35].
Based on these physical and chemical characterization, the stronger
light absorption and more active species may be the main reasons of Zn
(OH)F-T250 performed higher photocatalytic activity.
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Y. Yang, et al.
JournalofFluorineChemistry237(2020)109600
Fig. 8. SEM images of different hydrothermal reaction time for Zn(OH)F synthesis with EDTA-2Na as alkali source: (a) 1 h, (b) 1.5 h, (c) 3 h, (d) 4 h, (e) 5 h, (f) 6 h,
(g) 7 h, (h) 9 h, (i) 9 h (the enlarged part of the dotted frame in the h figure), (j) 12 h and (k) 16 h.
Fig. 10. The photocatalytic RhB degradation of Zn(OH)F samples with different
additives: methanol as solvent, 3-butylamine, oleylamine and EDTA-2Na as
alkali source, and P123 as surfactant.
Fig. 9. The XRD patterns of different hydrothermal reaction time for Zn(OH)F
synthesis with EDTA-2Na as alkali source.
morphology, not improve the photocatalytic performance, illuminating
that Zn(NO3)2 are the suitable zinc source for Zn(OH)F synthesis.
Moreover, the effect of morphology and photocatalytic performance
on solvent, alkali sources and surfactants are also investigated. With the
addition of methanol (as solvent, Fig. 7a), 3-butylamine and oleylamine
(as alkali source, Fig. 7b and 7c), the cluster structure is formed and
consisted with rods. However, the addition of EDTA-2Na (as alkali
source, Fig. 7d) and P123 (as surfactant, Fig. 7e) make the morphology
change to ribbons, and the length can reach to tens of micron for P123
(Fig. S11). The morphologies are different with the synthetic conditions
leaf shape for Zn(Ac)2. As the zinc source is ZnSO4∙7H2O (Fig. 6c), the
obtained Zn(OH)F sample is a rigid rod, and the cross-assembled net-
work structure is observed. In Fig. 6d, the prepared Zn(OH)F material is
cluster shape composed of ribbon structure, with Zn(Ah)2 as the Zn
source. Compared with the standard card (JCPDS No.: 74–1816), all the
diffraction peaks in the XRD patterns are corresponded well to Zn(OH)F
(Fig. 6e), indicating that these zinc sources can all used to synthesize
pure phase Zn(OH)F. However, in the photocatalytic activities of RhB
degradation (Fig. 6f), Zn(NO3)2 as the Zn source performs the optimal
activity. Change the Zn sources can only regulate the Zn(OH)F
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Y. Yang, et al.
JournalofFluorineChemistry237(2020)109600
Fig. 11. SEM images of Zn(OH)F obtained from different condition: (a) glycerol as solvent, (2) n-butylamine as alkali source, (c and d) low magnification images of
EDTA-2Na as alkali source with hydrothermal time of 6 h and 9 h, (e) PVP (1 g) as surfactant and (f) Zn(Ah)2 as Zn source.
changed, and the crystal structure are not the same accordingly
(Fig. 7f). Among these samples, Zn(OH)F with EDTA-2Na as alkali
source performs the highest diffraction peak in XRD patterns due to the
high crystallinity.
catalyst and degraded pollutant [38–40]. Therefore, the changes of the
synthetic conditions (Zn sources, solvent, alkali sources and surfac-
tants) cannot improve the photocatalytic performance, and the syn-
thetic condition for Zn(OH)F with the best activity is obtained: Zn
(NO3)2 as Zn source, NaOH as alkali sources, H2O as solvent, no sur-
factant addition, the hydrothermal temperature controlled at 100 ℃
and calcination at 250 ℃.
To detailly study the morphology changing of EDTA-2Na as alkali
source, all other conditions remain unchanged except that NaOH is
replaced by EDTA-2Na. The morphology observed from SEM images is
changed from rod → criss-cross → branch → ribbon with a dis-
solution–growth process, by controlling the hydrothermal reaction time
from 1 h to 16 h. The prepared Zn(OH)F nanomaterials firstly perform
rods shape (Fig. 8a), and then grow small branches in the middle of the
rods. With the extension of reaction time, number of small branches
increase and the twigs grow out (Fig. 8b-g). When the reaction time
reaches 9 h, the superstructure keeps on self-dissolve and restructure
(Fig. 8h-j), and finally grows into a ribbon structure (Fig. 8k). Thus, the
formation mechanism of the Zn(OH)F material is a growth-dissolution-
growth process, and the morphology can be controlled by changing the
reaction time. The one-dimensional rod-shaped morphology undergoes
a two-dimensional hierarchical structure and finally forms a one-di-
mensional ribbon structure. Meanwhile, the intensities of XRD patterns
are changed (increase → decrease → increase) with the synthetic pro-
cess (Fig. 9).
Based on the above description, different additives, reaction time
and temperature have an important impact on the morphology, and the
construction of morphology is very vital for the material. There are
some typical morphologies are also synthesized, which may provide
reference for Zn(OH)F material design and application. As shown in
Fig. 11, some beautiful morphology of Zn(OH)F synthesized at 140 ℃
for 6 h can be observed. Fig. 11a shows a short rod-shape with glycerol
as solvent, and its synthesis is similar with the methanol as solvent.
When n-butylamine is chosen as the alkali source (Fig. 11b), the mor-
phology exhibits two-dimensional flattened bucket-like hierarchical
structure, different from the flower structure (Fig. 7b, with 3-butyla-
mine as alkali source). Fig. 11c and 11d are the low magnification
images of Zn(OH)F (corresponding to Fig. 8f and 8 h, reaction time is 6
h and 9 h) with EDTA-2Na as alkali source, which exhibit two-dimen-
sional cruciform micro-nano hierarchical structure. When P123 (1 g) as
surfactant is added, the two-dimensional interweave network structure
is obtained (Fig. 11e). The thorn-ball hierarchical structure composed
of swords shape is formed with Zn(Ah)2 as Zn source with 6 h reaction
time (Fig. 11f and Fig. S13,), which decompose to form a cluster
structure (Fig. 6d) when the reaction time prolongs to 12 h.
However, the photocatalytic activities in RhB degradation (Fig. 10)
are also decreased after the respective addition of solvent (methanol),
alkali source (3-butylamine, oleylamine and EDTA-2Na) and surfactant
(P123). This may be due to that these added materials can capture
active species (e.g., methanol and EDTA-2Na are the hole scavengers
[36,37]) or decrease the production of active species, resulting to the
poor photocatalytic performance. Except P123, some surfactants
(CTAB, PVP, SDS, DBS or D-Glu) were also respectively added into the
reaction system, pure Zn(OH)F can be obtained (Fig. S12 a). The pho-
tocatalytic performances (RhB degradation) of Zn(OH)F prepared with
different surfactants are following the order: no surfactant > PVP >
CTAB > DBS > D-Glu (Fig. S12 b). The activity is also much lower than
that of pure Zn(OH)F without no surfactant addition (the degradation
efficiency is 97 % after 60 min reaction, Fig. 6f). This decrease may be
due to that the surfactant is attached on the surface of Zn(OH)F and
cover the surface-active sites of catalyst, preventing the contact of
4. Conclusions
Many different morphologies of Zn(OH)F were successfully syn-
thesized by the low temperature hydrothermal method. The synthesis
conditions (temperature, reactants and surfactants) were investigated
to improve the photocatalytic activity, and barklike Zn(OH)F sample
obtained at 100 ℃ for 6 h showed higher activity in the liquid de-
gradation. Especially, the heat treatment process can improve the
photocatalytic performance, which is much higher than the commercial
P25 in phenol and benzene degradation, resulting from the stronger
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Y. Yang, et al.
JournalofFluorineChemistry237(2020)109600
light absorption and more active species. To further optimize the syn-
thesized condition, the effects of hydrothermal temperature, Zn
sources, solvent, alkali source and surfactants were detailly in-
vestigated. Although the morphology and crystal structure is sig-
nificantly changed, the photocatalytic performances are not improved
with these conditions changing.
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Appendix A. Supplementary data
Supplementary material related to this article can be found, in the
online version, at doi:https://doi.org/10.1016/j.jfluchem.2020.
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