Note: Descriptions are shown in the official language in which they were submitted.
Z-SCHEME HETEROSTRUCTURE PHOTOCATALYST, PREPARATION METHOD,
AND APPLICATION THEREOF
[0001]
FIELD
[0002] The present disclosure belongs to the technical field of
photoelectrocatalytic synthesis
of H202. It relates to a 1T/2H-MoSe2@Ti02 nanocomposite, method for preparing
the same, and
application thereof, and specifically to an in-situ synthesized all-solid-
state Z-scheme
hetero structure photocatalyst, method for preparing the same, and application
in
photoelectrocatalytic production of H202 thereof.
BACKGROUND
[0003] Currently, methods for industrial synthesis of hydrogen peroxide (H202)
mainly include
the anthraquinone process and the direct synthesis from hydrogen gas (H2) and
oxygen gas (02).
However, the anthraquinone process involves various hydrogenation and
oxidation reactions that
will consume a large amount of organic solvents and energy; and the direct
synthesis from
hydrogen gas (H2) and oxygen gas (02) is prone to explosion. Therefore, there
is always a need to
find a safe, enco-friendly, and energy-saving method for effectively
synthesizing H202 in this
field. In recent years, many researchers have proposed a lot of feasible
methods of producing
H202. Photocatalysis technology has become one of the most promising methods
for producing
H202 owing to its advantages of safety, enco-friendly and energy-saving. It
produces H202 on
semiconductor materials mainly using water (H20) and 02 as raw materials, as
the electrons
generated from a semiconductor material under light irradiation are able to
reduce 02 into H202.
This process may be divided into continuous two steps of single-step electron
oxygen reduction,
as shown in reaction equations (1) and (2), or a direct two-electron reduction
of 02, as shown in
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Date Recue/Date Received 2022-11-03
direct two-electron reduction of 02, as shown in reaction equation (3).
02 e- ¨> .02 (-0.33 V vs. NHE)
(1)
= 02-
+ 2H+ + e- ¨> H202 (2)
02 + 2H+ + 2e ¨> H202 (0.68 V vs .NHE)
(3)
[0004] Moreover, photoelectrochemistry (PEC) also can be used as an effective
method for
producing H202 by reduction of 02. In a PEC system, a semiconductor material
can generate
electron-hole pairs under light excitation, and then conduction band electrons
can transfer the
electrons to the counter electrode to reduce 02 and generate H202 by applying
a bias voltage,
and hence the electron-hole pairs can be more effectively separated.
[0005] So far, many alternative photocatalysts for reduction 02 to H202, e.g.,
graphite C3N4,
CdS/graphene, W03 and titanium dioxide (Ti02), have been proposed. Among these
semiconductor catalysts, Ti02-based photocatalysts have been extensively
studied due to their
low toxicity, high conduction band gap and high chemical stability. However,
the preparation
of H202 by TiO2 photocatalysis has a low yield, which is mainly attributed to
the following
three reasons: 1) due to inherent wide band gap (about 3.2 eV), absorption
spectra are limited
within the ultraviolet (UV) region; 2) photogenerated electrons and holes have
low separation
ability, and the electrons and holes are prone to recombine in the system; and
3) peroxide
(Ti-00H) is generated under light irradiation, which decomposes H202 adsorbed
on the
surface of Ti02.
[0006] Therefore, how to find a more suitable method to overcome these above
serious
shortcomings and improve the performance of TiO2 is widely concerned by these
skilled in
the art.
SUMMARY
[0007] In view of that, the technical problem to be solved by the present
disclosure is to
provide a 1T/2H-MoSe2@Ti02 nanocomposite, method for preparing the same, and
application thereof, and in particular an in-situ synthesized all-solid-state
Z-scheme
heterostructure photocatalyst. The 1T/2H-MoSe2@TiO2 nanocomposite prepared
according to
the present disclosure is a system of heterogeneous combination of
semiconductor TiO2 and
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MoSe2, which contains a 2H semiconductor phase and a 1T metal phase. It is an
all-solid-state
Z-scheme photocatalyst, and is capable of improving the photoelectrocatalytic
performance of
photocatalysts and increasing the yield of H202. Also, it can be prepared
using a simple
method with mild conditions and controllable processes, which is conducive to
industrialization and has broad practical prospects.
100081 The present disclosure provides a 1T/2H-MoSe2@TiO2 nanocomposite
comprising a
TiO2 nanorod and a MoSe2 nanoparticle compounded on the TiO2 nanorod; wherein
[0009] the MoSe2 nanoparticle includes a mixed-phase MoSe2 nanoparticle, and
the
mixed-phase contains a 1T metal phase and a 2H semiconductor phase.
[0010] Preferably, the TiO2 nanorod has a length of 1.8-2 pm.
[0011] The TiO2 nanorod has a diameter of 150-250 nm.
[0012] The 1T/2H-MoSe2@TiO2 nanocomposite includes a 1T/2H-MoSe2@TiO2
nanocomposite for photoelectrocatalysis.
[0013] The photoelectrocatalysis includes photoelectrocatalytic synthesis of
H202.
[0014] Preferably, the MoSe2 nanoparticle has a particle size of 15-25 nm.
[0015] The compounding includes coating.
[0016] The TiO2 includes rutile TiO2.
[0017] The 1T/2H-MoSe2@TiO2 nanocomposite is an all-solid-state Z-scheme
heterostructure photocatalyst.
[0018] The 1T/2H-MoSe2@TiO2 nanocomposite is prepared by performing
hydrothermal
process and element-doping on raw materials.
[0019] The present disclosure provides a method for preparing 1T/2H-MoSe2@TiO2
nanocomposite comprising the following steps:
[0020] 1) placing a conductive substrate in a TiO2 precursor solution to
perform a
hydrothermal reaction, and then performing an annealing treatment, to obtain a
TiO2 nanorod;
[0021] 2) mixing a selenium powder solution with a molybdate solution to
obtain a
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Date Recue/Date Received 2021-09-24
precursor solution, and placing the TiO2 nanorod obtained in step 1) in the
precursor solution
to perform a second hydrothermal reaction, and then performing a second
annealing treatment,
to obtain an intermediate product 2H-MoSe2@Ti 02; and
[0022] 3) under an atmosphere containing ammonia, performing a third annealing
treatment
on the intermediate product obtained in step 2), to obtain a 1T/2H-MoSe2@TiO2
nanocomposite.
[0023] Preferably, a manner of placing the conductive substrate includes
placing the
conductive substrate with a conductive surface thereof facing downwards and
leaning against
an inner wall of a reaction vessel;
[0024] the TiO2 precursor solution contains a titanium source, acid and water;
[0025] the titanium source includes tetrabutyl titanate;
[0026] the acid includes hydrochloric acid; and
[0027] the titanium source, the acid and water are present in a volume ratio
of 0.4: (5-15):
(5-15).
[0028] Preferably, the hydrothermal reaction is performed at a temperature of
150-180 C;
[0029] the hydrothermal reaction is performed for a duration of 15-24 hours;
[0030] the annealing treatment includes annealing treatment under an air
atmosphere;
[0031] the annealing treatment is performed for a duration of 2-3 hours; and
[0032] the annealing treatment is performed at a temperature of 400-500 C.
[0033] Preferably, the selenium powder solution includes a solution of
selenium powder in
hydrazine hydrate, in which the selenium powder and hydrazine hydrate are
present in a ratio
of mass to volume of (0.025-0.034) g: 1 mL;
[0034] the molybdate solution includes an aqueous solution of sodium molybdate
dihydrate
in which the sodium molybdate dihydrate and water are present in a ratio of
mass to volume
of (0.009-0.012) g: 1 mL; and
[0035] the selenium powder and molybdate are present in a mass ratio of (0.65-
0.7): 1.
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Date Recue/Date Received 2021-09-24
[0036] Preferably, the second hydrothermal reaction is performed at a
temperature of
170-190 C;
[0037] the second hydrothermal reaction is performed for a duration of 0.5-2
hours;
[0038] the second annealing treatment is performed for a duration of 2-3
hours;
[0039] the second annealing treatment is performed at a temperature of 400-450
C;
[0040] the second annealing treatment includes annealing treatment under an
argon gas
atmosphere;
[0041] the TiO2 nanorod has an array structure.
[0042] Preferably, the third annealing treatment is performed for a duration
of 0.5-2 hours;
[0043] the third annealing treatment is performed at a temperature of 400-450
C;
[0044] the third annealing treatment is performed at a heating rate of 5-10
C/min;
[0045] the atmosphere containing ammonia has a flow rate of 50-150 mL/min; and
[0046] the 1T/2H-MoSe2@TiO2 nanocomposite has an array structure.
[0047] The present disclosure further provides use of the 1T/2H-MoSe2@TiO2
nanocomposite according to any one of the above technical solutions or the
1T/2H-MoSe2@TiO2 nanocomposite prepared by using the method according to any
one of
the above technical solutions in a photocatalyst field.
[0048] The present disclosure provides a 1T/2H-MoSe2@TiO2 nanocomposite
comprising a
TiO2 nanorod and a MoSe2 nanoparticle compounded on the TiO2 nanorod; wherein
the
MoSe2 nanoparticle includes a mixed-phase MoSe2 nanoparticle containing a 1T
metal phase
and a 2H semiconductor phase. Compared with the prior art, the present
disclosure is made
based on the following problems in the existing semiconductor catalysts.
Although TiO2
photocatalysts have features such as low toxicity, high conduction band gap
and high
chemical stability, the preparation of H202 by photocatalysis has a defect of
low yield, and the
current modification for TiO2 photocatalysts, such as construction of
heterojunction,
modification with noble metals and element doping, still has problems that are
not conducive
to the preparation of H202. The research of the present disclosure found that
the currently
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dominant method for improving the photocatalytic performance of TiO2 is to
construct type II
heteroj unction, but this kind of heterostructure does not conducive to
formation of active free
radicals, and hence is not conducive to the preparation of H202 (hydrogen
peroxide).
100491 1T/2H-MoSe2@TiO2 nanocomposite is creatively prepared according to the
present
disclosure. This composite material has a specific morphology, structure and Z-
scheme
heterostructure, and is a system of heterogeneous combination of semiconductor
TiO2 and
MoSe2 obtained by heterogeneous combining semiconductor TiO2 and 2H-MoSe2. The
nanocomposite provided by the present disclosure is an all-solid-state Z-
scheme composite
material containing a 2H semiconductor phase and a 1T metal phase. The
composite material
provided by the present disclosure is a photocatalyst, in which a small part
of 2H-MoSe2 is
converted into 1T-MoSe2, and the synthesis of 1T phase acts as an electron
transferring bridge,
which further promotes the separation of electron-hole pairs. Hence, the
constructed
photoelectrocatalysis system can greatly improve the photoelectrocatalytic
performance,
thereby increasing the yield of H202, which is more conducive to the
production of H202. In
addition, the preparation method provided by the present disclosure is simple,
and has mild
conditions and controllable processes, which is conducive to industrialization
and has broad
practical prospects.
100501 The 1T/2H-MoSe2@TiO2 nanocomposite provided by the present disclosure
is an
all-solid-state Z-scheme composite system photocatalyst. The all-solid-state Z-
scheme system
photocatalyst is prepared by coupling 2H-MoSe2 and TiO2, and further
introducing the 1T
metal phase MoSe2 by using in-situ generation method, which is used for
photoelectrocatalytic preparation of H202.
100511 The experimental results shows that the 1T/2H-MoSe2@TiO2 nanocomposite
prepared according to the present disclosure, as an in-situ synthesized all-
solid-state Z-scheme
heterostructure photocatalyst, has a better photoelectrocatalytic performance
of producing
H202.
BRIEF DESCRIPTION OF DRAWINGS
[0052] FIG. 1 is a schematic diagram showing the preparation process of
1T/2H-MoSe2@TiO2 according to the present disclosure;
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[0053] FIG. 2 is a scanning electron micrograph of TiO2, 2H-MoSe2@TiO2 and
1T/2H-MoSe2@TiO2 prepared according to the present disclosure;
[0054] FIG. 3 is TEM, HRTEM, and element mapping images of the 1T metal phase
and
the 2H semiconductor phase, which coexist in MoSe2 nanoparticles and are
successfully
modified on TiO2, prepared in examples of the present disclosure;
[0055] FIG. 4 is a graph showing transient photocurrent curves of 2H-
MoSe2@TiO2
prepared at different hydrothermal reaction time in examples of the present
disclosure;
[0056] FIG. 5 is a bar graph showing concentrations of the H202 produced by
using
2H-MoSe2@TiO2 prepared at different hydrothermal reaction time in examples of
the present
disclosure;
[0057] FIG. 6 is a graph showing the comparison of H202 yields using the
catalyst
1T/2H-MoSe2@TiO2 prepared in Example 1 of the present disclosure, and using
other
catalysts or without catalysts;
[0058] FIG. 7 is a graph showing the comparison of ability of photoelectric
catalytic
degradation of H202 by the catalyst 1T/2H-MoSe2@TiO2 prepared in Example 1 of
the
present disclosure, and other catalysts or without catalysts; and
[0059] FIG. 8 is a graph showing cycle stability test on the H202 prepared by
using
1T/2H-MoSe2@TiO2 prepared in Example 1 of the present disclosure.
DETAILED DESCRIPTION
[0060] For further understanding of the present disclosure, preferred
embodiments of the
present disclosure will be described below in conjunction with examples.
However, it should
be understood that these descriptions are only for further illustrating the
features and
advantages the present invention, rather than limiting the claims of the
present invention.
[0061] The source of the raw materials used in the present disclosure is not
particularly
limited, and the raw materials may be the ones available in market or prepared
by using the
conventional methods well known to these skilled in the art.
[0062] The purity of the raw materials used in the present disclosure is not
particularly
limited, and analytically pure or conventional purity in the field of
preparation of
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Date Recue/Date Received 2021-09-24
photocatalysts is preferred in the present disclosure.
[0063] The brand names and abbreviations of the raw materials used in the
present
disclosure are conventional brand names and abbreviations in the field. Each
brand name and
abbreviation are clearly and definite in the field of its related use. Those
skilled in the art can
purchase them from market or prepare them using conventional methods, based on
these
brand names, abbreviations or their related applications.
[0064] The abbreviations of the processes in the present disclosure are
conventional
abbreviations in the field. Each abbreviation is clearly and definite in the
field of its related
use. Those skilled in the art can understand their conventional procedures
based on these
abbreviations.
[0065] The present disclosure provides a 1T/2H-MoSe2@TiO2 nanocomposite
comprising a
TiO2 nanorod and a MoSe2 nanoparticle compounded on the TiO2 nanorod; wherein
[0066] the MoSe2 nanoparticle include a mixed-phase MoSe2 nanoparticle;
[0067] the mixed-phase contains a 1T metal phase and a 2H semiconductor phase.
[0068] The 1T/2H-MoSe2@TiO2 nanocomposite according to the present disclosure
comprises a TiO2 nanorod.
[0069] In the present disclosure, the TiO2 nanorod preferably has a length of
1.8-2 gm,
more preferably 1.82-1.98 gm, further more preferably 1.85-1.95 gm, and even
more
preferably 1.87-1.93 gm.
[0070] In the present disclosure, the TiO2 nanorod preferably has a diameter
of 150-250 nm,
more preferably170-230 nm, and further more preferably 190-210 nm.
[0071] The 1T/2H-MoSe2@TiO2 nanocomposite according to the present disclosure
further
comprises a MoSe2 nanoparticle compounded on the TiO2 nanorod. In the present
disclosure,
the MoSe2 nanoparticle includes a mixed-phase MoSe2 nanoparticle. The MoSe2
nanoparticle
is a mixed phase, and the mixed phase contains a 1T metal phase and a 2H
semiconductor
phase.
[0072] In the present disclosure, the MoSe2 nanoparticle preferably has a
particle size of
15-25 nm, further more preferably 17-23 nm, and even more preferably 19-21 nm.
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Date Recue/Date Received 2021-09-24
[0073] In the present disclosure, the compounding specifically is coating.
[0074] In the present disclosure, the TiO2 preferably includes rutile TiO2.
[0075] In the present disclosure, the TiO2 nanorod has an array structure.
Further, the
1T/2H-MoSe2@TiO2 nanocomposite also has an array structure.
.. [0076] In the present disclosure, the 1T/2H-MoSe2@TiO2 nanocomposite
preferably
includes a 1T/2H-MoSe2@TiO2 nanocomposite for photoelectrocatalysis.
Specifically, the
1T/2H-MoSe2@TiO2 nanocomposite is preferably an all-solid-state Z-scheme
heterostructure
photocatalyst. More specifically, the photoelectrocatalysis preferably
includes
photoelectrocatalytic synthesis of H202.
[0077] In the present disclosure, the 1T/2H-MoSe2@TiO2 nanocomposite is
prepared by
performing hydrothermal process and element-doping on raw materials.
[0078] The present disclosure provides a method for preparing 1T/2H-MoSe2@TiO2
nanocomposite, comprising the following steps:
[0079] 1) placing a conductive substrate in a TiO2 precursor solution to
perform a
hydrothermal reaction, and then performing an annealing treatment, to obtain a
TiO2 nanorod;
[0080] 2) mixing a selenium powder solution with a molybdate solution to
obtain a
precursor solution, placing the TiO2 nanorod obtained in step 1) in the
precursor solution to
perform a second hydrothermal reaction, and then performing a second annealing
treatment,
to obtain an intermediate product 2H-MoSe2@Ti02; and
[0081] 3) under an atmosphere containing ammonia, performing a third annealing
treatment
on the intermediate product obtained in step 2), to obtain a 1T/2H-MoSe2@TiO2
nanocomposite.
[0082] In the present disclosure, a conductive substrate is first placed in a
TiO2 precursor
solution to perform a hydrothermal reaction, and then an annealing treatment
is preformed, to
.. obtain a TiO2 nanorod.
[0083] In the present disclosure, the conductive substrate preferably includes
conductive
glasses (FTO).
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Date Recue/Date Received 2021-09-24
[0084] In the present disclosure, a manner of placing the conductive substrate
preferably
includes placing the conductive substrate with its conductive surface facing
downwards and
leaning against an inner wall of a reaction vessel.
[0085] In the present disclosure, the TiO2 precursor solution preferably
contains a titanium
source, acid, and water, wherein the titanium source includes tetrabutyl
titanate, and the acid
includes hydrochloric acid.
[0086] In the present disclosure, the titanium source and the acid preferably
has a volume
ratio of 0.4: (5-15), more preferably 0.4: (7-13), and even more preferably
0.4: (9-11).
[0087] In the present disclosure, the titanium source and water preferably has
a volume
ratio of 0.4: (5-15), more preferably 0.4: (7-13), and even more preferably
0.4: (9-11).
[0088] In the present disclosure, the hydrothermal reaction are preferably
performed at a
temperature of 150-180 C, more preferably 155-175 C, and even more preferably
160-170 C.
[0089] In the present disclosure, the hydrothermal reaction are preferably
performed for a
duration of 15-24 hours, more preferably 17-22 hours, and even more preferably
19-20 hours.
[0090] In the present disclosure, the annealing treatment preferably includes
annealing
treatment under an air atmosphere.
[0091] In the present disclosure, the annealing treatment is preferably
performed for a
duration of 2-3 hours, more preferably 2.2-2.8 hours, and even more preferably
2.4-2.6 hours.
[0092] In the present disclosure, the annealing treatment is preferably
performed at a
temperature of 400-500 C, more preferably 420-480 C, and even more preferably
440-460 C.
[0093] In the present disclosure, subsequently, a selenium powder solution is
mixed with a
molybdate solution to obtain a precursor solution, and the TiO2 nanorod
obtained in step 1) is
palced in the precursor solution to perform a second hydrothermal reaction,
and then a second
annealing treatment is performed, to obtain an intermediate product 2H-
MoSe2@Ti02.
[0094] In the present disclosure, the selenium powder solution preferably
includes a
solution of selenium powder in hydrazine hydrate.
[0095] In the present disclosure, the selenium powder and hydrazine hydrate
are preferably
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Date Recue/Date Received 2021-09-24
present in a ratio of mass to volume of (0.025-0.034) g: 1 mL, more preferably
(0.027-0.032)
g: 1 mL, and even more preferably (0.029-0.030) g: 1 mL.
[0096] In the present disclosure, the molybdate solution preferably includes
an aqueous
solution of sodium molybdate dihydrate.
[0097] In the present disclosure, the sodium molybdate dihydrate and water are
preferably
present in a ratio of mass to volume of (0.009-0.012) g: 1 mL, more preferably
(0.009-0.011)
g: 1 mL, and even more preferably (0.01-0.012) g: 1 mL.
[0098] In the present disclosure, the selenium powder and molybdate are
preferably in a
mass ratio of (0.65-0.7): 1, more preferably (0.66-0.69): 1, and even more
preferably
(0.67-0.68): 1.
[0099] In the present disclosure, the second hydrothermal reaction are
preferably performed
at a temperature of 170-190 C, more preferably 172-188 C, further more
preferably
175-185 C, and even more preferably 177-183 C.
[0100] In the present disclosure, the second hydrothermal reaction are
preferably performed
for a duration of 0.5-2 hours, more preferably 0.7-1.8 hours, and even more
preferably 1.0-1.5
hours.
[0101] In the present disclosure, the second annealing treatment is preferably
performed for
a duration of 2-3 hours, more preferably 2.2-2.8 hours, and even more
preferably 2.4-2.6
hours.
[0102] In the present disclosure, the second annealing treatment is preferably
performed at a
temperature of 400-450 C, more preferably 410-440 C, and even more preferably
420-430 C.
[0103] In the present disclosure, the annealing treatment preferably includes
annealing
treatment under an argon gas atmosphere.
[0104] At last, in the present disclosure, under an atmosphere containing
ammonia, a third
annealing treatment is performed on the intermediate product obtained in step
2) to obtain a
1T/2H-MoSe2@TiO2 nanocomposite.
[0105] In the present disclosure, the third annealing treatment is preferably
performed for a
duration of 0.5-2 hours, more preferably 0.7-1.8 hours, and even more
preferably 1.0-1.5
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Date Recue/Date Received 2021-09-24
hours.
[0106] In the present disclosure, the third annealing treatment is preferably
performed at a
temperature of 400-450 C, more preferably 410-440 C, and even more preferably
420-430 C.
[0107] In the present disclosure, the third annealing treatment is preferably
performed at a
heating rate of 5-10 C/min, more preferably 6-9 C/min, and even more
preferably 7-8 C/min.
[0108] In the present disclosure, the atmosphere containing ammonia preferably
has a flow
rate of 50-150 mL/min, more preferably 70-130 mL/min, and even more preferably
90-110
mL/min.
[0109] In the present disclosure, in order to provide a better complete and
detailed technical
solution, well ensure the structure and morphology of the 1T/2H-MoSe2@TiO2
nanocomposite, and improve the photocatalytic performance of the 1T/2H-
MoSe2@TiO2
nanocomposite, the above-mentioned method for preparing the 1T/2H-MoSe2@TiO2
nanocomposite may specifically comprises the following steps:
[0110] (1) Preparation of the TiO2 nanorod material by hydrothermal process:
[0111] preparing a precursor solution by selecting a conductive glass (PTO) as
a substrate
for growing TiO2 nanorods and using tetrabutyl titanate as a titanium source,
transferring the
precursor solution into an autoclave with a polytetrafluoroethylene liner, and
performing
reaction for 15-24 hours; and at last, nnealing the sample inside a muffle
furnace under an air
atmosphere to obtain rutile TiO2. Specifically, the reaction may be performed
at a temperature
of 150 C; and the annealing may be performed at a temperature of 450 C.
[0112] (2) Preparation of the 2H-MoSe2@TiO2 material by hydrothermal process
[0113] mixing a selenium powder solution and a sodium molybdate dihydrate
solution, and
stirring to obtain a precursor solution; transferring the precursor solution
into an autoclave
with a polytetrafluoroethylene liner; immersing the TiO2 material prepared in
step (1) into the
precursor solution inside the polytetrafluoroethylene line, and performing
reaction for 0.5-2
hours; and at last, annealing the sample inside a tube furnace under an argon
gas atmosphere
to obtain a highly crystalline 2H-MoSe2@Ti02. Specifically, the stiffing may
be performed
for a duration of 30 min; the reaction may be performed at a temperature of
180 C; and the
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Date Recue/Date Received 2021-09-24
annealing may be performed at a temperature of 450 C.
[0114] (3) Preparation of the 1T/2H-MoSe2@TiO2 material by N-doping
[0115] annealing the prepared 2H-MoSe2@TiO2 sample inside a tube furnace,
under an
NH3 gas atmosphere for 0.5-2 hours, to obtain a T/2H-MoSe2@TiO2 material.
Specifically,
the annealing may be performed at a temperature of 400 C.
[0116] In the step (1), the precursor in the Ti source precursor solution is
formulated from
tetrabutyl titanate, hydrochloric acid and water, and the volume ratio of them
can be
controlled at 0.4: 10: 10.
[0117] In the step (2), the selenium powder solution may be specifically
formulated from
0.158 g of selenium powder and 5 mL of hydrazine hydrate; and the sodium
molybdate
dihydrate solution may be specifically formulated from 0.242 g of ammonium
molybdate
dihydrate and 25 mL of deionized water.
[0118] In the step (3), in the annealing conditions, the heating rate can be
specifically
10 C/min, and the NH3 flow rate can be specifically 100 mL/min.
[0119] Preferably, in the preparation of TiO2 nanorod array photocatalyst by
hydrothermal
process, tetrabutyl titanate is selected as the Ti source to prepare the
precursor solution; and
then the precursor solution is transferred into the autoclave with a
polytetrafluoroethylene
liner, to perform reaction at 150 C for 15-24 h.
[0120] Preferably, in the preparation of 2H-MoSe2@TiO2 photocatalyst by
hydrothermal
process, the TiO2 photocatalyst prepared in the above step is immersed in a
mixed solution of
the Se powder and sodium molybdate dihydrate, and subjected to hydrothermal
treatment
after being stand for 1 hour; and at last, the annealing is performed at high
temperature under
an argon gas atmosphere.
[0121] Preferably, in the preparation of the 1T/2H-MoSe2@TiO2 photocatalyst by
N-doping,
the 2H-MoSe2@TiO2 photocatalyst prepared in the above step is annealed inside
a tube
furnace under an NH3 gas atmosphere for 1 hour.
[0122] Reference is made to FIG. 1, which is a schematic diagram showing the
preparation
process of 1T/2H-MoSe2@TiO2 according to the present disclosure.
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[0123] The 1T/2H-MoSe2@TiO2 nanocomposite provided by the present disclosure
is an
all-solid-state Z-scheme heterojunction photocatalyst which is a system of
heterogeneous
combination of semiconductor TiO2 and 1T/2H-MoSe2, in which the 1T metal phase
MoSe2 is
in-situ introduced between TiO2 and 2H-MoSe2 in a way of N-doping. The N-
doping uses
NH3 as N source, and annealing time is preferably 0.5-2 h.
[0124] The research of the present disclosure found that although TiO2-based
catalysts has
the advantages of low toxicity, high conduction band gap and high chemical
stability, and also
their photoelectrocatalytic performance can be effectively improved by
constructing
heterojunction, the decreases in potential of the photogenerated holes in
valence band (VB)
and in potential of electrons in the conduction band are inevitable, which is
not conducive to
the formation of active free radicals, and thus maintaining the energy band
structure of TiO2
plays an important role in the production of hydrogen peroxide. In the present
disclosure,
firstly the TiO2 nanorod is prepared on FTO through hydrothermal process, and
the TiO2
nanorod is subjected to annealing, to obtain rutile TiO2; subsequently MoSe2
is modified on
the TiO2 nanorod through hydrothermal process again, to construct and obtain Z-
scheme
2H-MoSe2@Ti02; and at last part of the 2H-MoSe2 is converted into 1T-MoSe2
through
N-doping method, to construct and obtain the 1T/2H-MoSe2@TiO2 all-solid-state
Z-scheme
heterostructure photocatalyst. The synthesis of the 1T phase acts as an
electron transferring
bridge, and further promotes the separation of electron-hole pairs, thereby
being more
conducive to the production of H202.
[0125] The present disclosure further provides use of the 1T/2H-MoSe2@TiO2
nanocomposite according to any one of the above technical solutions or the
1T/2H-MoSe2@TiO2 nanocomposite prepared by using the method according to any
one of
the above technical solutions in a photocatalyst
[0126] The all-solid-state Z-scheme heterostructure photocatalyst provided by
the present
disclosure is a system of heterogeneous combination of semiconductor TiO2 and
MoSe2. The
T/2H-MoSe2@TiO2 all-solid-state Z-scheme photocatalyst is prepared by
modifying MoSe2
nanoparticles on the TiO2 nanorod, and subsequently performing annealing under
an NH3 gas
atmosphere to transform a small part of the 2H semiconductor phase MoSe2 into
the IT metal
phase MoSe2.
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Date Recue/Date Received 2021-09-24
[0127] In the above-mentioned steps of the present disclosure, an in-situ
synthesized
all-solid-state Z-scheme heterostructure photocatalyst and preparation method
thereof, and
use in photoelectrocatalytic production of H202 thereof are provided. The
1T/2H-MoSe2@TiO2 nanocomposite provided by the present disclosure has a
specific
morphology, structure and Z-scheme heterostructure, which is a system of
heterogeneous
combination of semiconductor TiO2 and MoSe2 obtained by heterogeneous
combining
semiconductor TiO2 and 2H-MoSe2. In the present disclosure, a hydrothermal
process and
element doping are combined, to prepare the 1T/2H-MoSe2@TiO2 all-solid-state Z-
scheme
heterojunction photocatalyst. Heterogeneous combining semiconductor TiO2 and
2H-MoSe2,
and in-situ transforming a small part of the 2H-MoSe2 into 1T-MoSe2 through
doping, which
can be used as an electron-transferring bridge to construct a
photoelectrocatalytic system,
thereby greatly improving photoelectrocatalytic performance of the
photocatalyst and
increasing the yield of H202.
[0128] The nanocomposite provided by the present disclosure contains a 2H
semiconductor
phase and a 1T metal phase, which is a 1T/2H-MoSe2@TiO2 all-solid-state Z-
scheme
composite material. The composite material is a photocatalyst, in which a
small part of
2H-MoSe2 is converted into 1T-MoSe2, and the synthesis of 1T phase acts as an
electron
transferring bridge, which further promotes the separation of electron-hole
pairs. Hence, the
constructed photoelectrocatalysis system can greatly improve the
photoelectrocatalytic
performance, thereby increasing the yield of H202, which is more conducive to
the production
of H202. In addition, the preparation method provided by the present
disclosure is simple, and
has mild conditions and controllable processes, which is conducive to
industrialization and
has broad practical prospects.
[0129] The 1T/2H-MoSe2@TiO2 nanocomposite provided by the present disclosure
is an
all-solid-state Z-scheme composite system photocatalyst. The all-solid-state Z-
scheme system
photocatalyst is prepared by coupling 2H-MoSe2 and TiO2, and further
introducing the 1T
metal phase MoSe2 by using in-situ generation method, which is used for
photoelectrocatalytic preparation of H202.
[0130] The experimental results shows that the 1T/2H-MoSe2@TiO2 nanocomposite
prepared according to the present disclosure, as an in-situ synthesized all-
solid-state Z-scheme
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Date Recue/Date Received 2021-09-24
heterostructure photocatalyst, has a better photoelectrocatalytic performance
of producing
H202.
[0131] In order to further describe the present disclosure, the 1T/2H-
MoSe2@TiO2
nanocomposite, preparation method, and use thereof provided by the present
disclosure will
be described in detail below in conjunction with examples. It should be
understood that these
examples are implemented under the premise of the technical solution of the
present
disclosure, and that the detailed implementation modes and specific operating
procedures are
given, merely for illustrating the features and advantages of the present
disclosure, rather than
limiting the claims of the invention, and that the scope of protection of the
invention is not
.. limited to the following examples.
Examples
[0132] (1) Preparation of TiO2 material by hydrothermal process
[0133] The FTO substrate needed to be washed, and the steps for washing were
washing
with acetone, ethanol and deionized water in sequence through ultrasonication
for 10 min. A
precursor solution of TiO2 was prepared and transferred into an autoclave with
a
polytetrafluoroethylene liner. Subsequently, the washed FTO was placed to the
polytetrafluoroethylene liner, with its conductive surface facing downwards
and being leaned
against the liner at a predetermined degree. After being tightened, the
reaction kettle was
placed in a blast drying oven, to perform reaction for 15-24 hours at 150 C.
After natural
cooling, the prepared sample was taken out and washed with deionized water and
ethanol in
sequence. Subsequently, the sample was dried in a vacuum dry box for 12 hours,
and at last
annealed in a muffle furnace at 450 C at a heating rate of 2 C/min under an
air atmosphere to
obtain rutile TiO2.
[0134] The precursor solution of TiO2 was formulated from tetrabutyl titanate,
hydrochloric
acid and water, with their volume ratio controlled at 0.4: 10: 10. After
hydrochloric acid and
water were well mixed, tetrabutyl titan ate was added and mixed for 5 min
before being taken
out.
[0135] (2) Preparation of 2H-MoSe2@TiO2 material by hydrothermal process
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Date Recue/Date Received 2021-09-24
[0136] A sodium molybdate dihydrate solution and a selenium powder solution
were mixed,
and stirred for 30 min to obtain a MoSe2 precursor solution. The precursor
solution was then
transferred into an autoclave with a polytetrafluoroethylene liner. The rutile
TiO2 material
prepared in step (1) was immersed in the precursor solution in the
polytetrafluoroethylene
liner, with the surface for growing TiO2 facing downwards and being leaned
against the liner.
After being tightened, the reaction kettle was placed in a blast drying oven,
with heating rate
program set to 3 C/min, to perform reaction at a temperature of 180 C and for
a duration of
0.5-2 hours. For a duration of 30 min, 60 min, 90 min and 120 min, 4 groups of
samples were
prepared respectively. After the reaction was completed, the prepared samples
were allowed
to naturally cool to room temperature before being taken out. The prepared
samples were
taken out and washed with deionized water and ethanol in sequence.
Subsequently, the
samples were dried for 12 hours in a vacuum dry box, and at last annealed in a
tube furnace at
450 C under an argon gas atmosphere to obtain a highly crystalline 2H-
MoSe2@Ti02.
[0137] The ammonium molybdate aqueous solution was prepared by mixing 0.242 g
of
ammonium molybdate dihydrate and 25 mL of deionized water with magnetic
stirring for 30
min. The selenium powder aqueous solution was prepared by mixing 0.158 g of
selenium
powder and 5 mL of hydrazine hydrate followed by 5 min of ultrasonication to
well mix them.
In addition, in the precursor solution, Mo and Se were present in a molar
ratio of 1: 2.
[0138] (3) Preparation of 1T/2H-MoSe2@TiO2 material by N-doping:
[0139] The prepared 2H-MoSe2@TiO2 sample was annealed under an NH3 gas
atmosphere
at 400 C for 0.5-2 hours in a tube furnace, to obtain a T/2H-MoSe2@TiO2
material.
[0140] The flow rate of NH3 was controlled at 100 mL/min. The heating rate was
controlled
at 10 C/min. The preferred annealing time for 1T/2H-MoSe2@TiO2 photocatalysis
was 1 h.
[0141] The 1T/2H-MoSe2@TiO2 composite material prepared according to the
present
.. disclosure was characterized.
[0142] Reference is made to FIG. 2, which is a scanning electron micrograph of
TiO2,
2H-MoSe2@TiO2 and 1T/2H-MoSe2@TiO2 prepared according to the present
disclosure.
[0143] In FIG. 2, (a, d) stands for TiO2, (b, e) stands for 2H-MoSe2@Ti02, and
(c, f) stands
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Date Recue/Date Received 2021-09-24
for 1T/2H-MoSe2@TiO2.
[0144] Reference is made to FIG. 3, which is TEM, HRTEM, and element mapping
images
of the 1T metal phase and the 2H semiconductor phase, which coexist in MoSe2
nanoparticles
and are successfully modified on TiO2, prepared in examples of the present
disclosure.
[0145] In FIG. 3, (a) stands for a TEM image; (b, c) stands for HRTEM images;
and (d)
stands for mapping images.
[0146] The 1T/2H-MoSe2@TiO2 composite material prepared by Example 1 of the
present
disclosure was tested on its performance.
[0147] Test on Photoelectrocatalytic Performance of Preparation of H202
[0148] TiO2, the prepared 2H-MoSe2@Ti02, and 1T/2H-MoSe2@TiO2 were used as
photoanode materials. Pt sheet and Ag/AgC1 were used as a counter electrode
and a reference
electrode, respectively. The reaction cell was a quartz cell. The three-
electrode system was
connected with an ultraviolet lamp source, a peristaltic pump, an oxygen
source and an
electrochemical workstation, to construct a photoelectrocatalytic test system.
The peristaltic
pump can take out the aqueous solution samples at different reaction times,
for detection of
H202 concentrations. The concentration detection method was iodine reduction
method. The
method included steps of taking 1 mL of reaction solution, adding 1 mL of KI
(0.1 M) and 50
[IL of ammonium molyb date (0.01 M) solution, well mixing, followed by
standing for 15 min
until the reaction was completed, and measuring absorbance by ultraviolet-
visible
.. spectrophotometry. The test result will show an absorption peak at 353nm,
and then it was
compared with calibration curves to obtain H202 concentrations. The
performance test results
of MoSe2@TiO2 photocatalysts are shown in FIGs. 4-6.
[0149] Reference is made to FIG. 4, which is a graph showing transient
photocurrent curves
of 2H-MoSe2@TiO2 prepared at different hydrothermal reaction time in examples
of the
present disclosure.
[0150] Reference is made to FIG. 5, which is a bar graph showing
concentrations of the
H202 produced by using 2H-MoSe2@TiO2 prepared at different hydrothermal
reaction time in
examples of the present disclosure.
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Date Recue/Date Received 2021-09-24
[0151] In FIG. 5, the 2H-MoSe2@TiO2 sample with a hydrothermal reaction time
of 1 hour
has the highest H202 yield.
[0152] Reference is made to FIG. 6, which is a graph showing the comparison of
H202
yields using the catalyst 1T/2H-MoSe2@TiO2 prepared in Example 1 of the
present disclosure,
and using other catalysts or without catalysts.
[0153] In FIG. 6, (a) is the curves showing the change of H202 generation
concentration
over time, under the condition of light illumination or without light
illumination; and (b)
shows the net H202 yields from different samples after removing that from the
blank sample.
[0154] It can be seen from FIG. 6 that the H202 yields from 1T/2H-MoSe2@TiO2
reached
to 4.7 times of that from TiO2 catalyst.
[0155] Reference is made to FIG. 7, which is a graph showing the comparison of
ability of
photoelectric catalytic degradation of H202 by the catalyst 1T/2H-MoSe2@TiO2
prepared in
Example 1 of the present disclosure, and other catalysts or without
catalystss.
[0156] It can be seen from FIG. 7 that in terms of degradation of H202, the
degradation
ability of 1T/2H-MoSe2@TiO2 is worse than that of TiO2, demonstrating that
1T/2H-MoSe2@TiO2 has less degradation of H202 generated in real time, which is
one reason
for the increase in H202 yield.
[0157] Reference is made to FIG. 8, which is a graph showing cycle stability
test on the
H202 prepared by using 1T/2H-MoSe2@TiO2 prepared in Example 1 of the present
disclosure.
[0158] It can be seen from FIG. 8 that 1T/2H-MoSe2@TiO2 (60 min of
hydrothermal
reaction and 1 hour of annealing) prepared according to the present disclosure
exhibits good
cycle stability.
[0159] The above provides a detailed introduction to the in-situ synthesized
all-solid-state
Z-scheme heterostructure photocatalyst provided by the present disclosure and
preparation
method thereof, as well as use in photoelectrocatalytic production of H202
thereof. To
illustrate the principle and implementation of the present disclosure, the
specific examples are
used herein, their description above is only intended to facilitate
understanding of the method
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Date Recue/Date Received 2021-09-24
and core concept of the present invention, including the best implementation
mode, and to
enable any one of the skilled in the art to implement the present invention
including any
device or system in manufacture and use, as well as any combined methods. It
should be
noted that for those skilled in the art, various improvements and
modifications may be made
without departing from the principle of the present disclosure, and these
improvements and
modifications should fall within the scope of protection of the present
disclosure. The
protection scope of this patent is defined by the claims and can include other
embodiments
that a person skilled in the art would know. The said other embodiments should
also be
included in the scope of the claims, if they contain structural elements that
are not different
.. from the literal expression of claims, or equivalent structural elements
that are not
substantially different from the literal expression of the claims.
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