Preparation method and application of TiO2 / Ag-coated MoS2 composite photocatalyst

Abstract

The invention discloses a preparation method and application of a TiO2 / Ag-coated MoS2 composite photocatalyst, and relates to the technical field of catalysts.The method comprises the steps that titanium dioxide is evenly dispersed in an ethanol-water mixed solution to form turbid liquid; adding a silver nitrate solution and carrying out ultraviolet irradiation to carry out a photodeposition process; adding an ammonium tetrathiomolybdate precursor solution into the turbid liquid, carrying out ultraviolet irradiation, inducing MoS < 2-> to be subjected to an auto-oxidation reduction reaction through an electronic effect, generating an amorphous MoS2 shell on the surface of silver, and forming a core-shell Ag-coated MoS2 cocatalyst; and centrifuging, washing and drying to obtain the TiO2 / Ag-coated MoS2 composite photocatalyst. According to the Ag-coated MoS2 cocatalyst, the electron density of S atoms is higher, the strength of S (2 + delta)-Had bonds is weakened, and Had is more easily desorbed to form hydrogen; and the photocatalyst also has better light absorption and photo-generated charge separation efficiency, so that the photocatalyst shows better photocatalytic hydrogen evolution activity and stability.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and specifically relates to a preparation method and application of a TiO2 / Ag@MoS2 composite photocatalyst. Background Art

[0002] Hydrogen, as a clean energy source with high energy density and no carbon emissions, has received extensive attention. However, traditional hydrogen production methods (such as natural gas reforming and electrolysis of water) often rely on fossil fuels or consume a large amount of electric energy, which to a certain extent weakens their environmental friendliness. Photocatalytic water splitting for hydrogen production only requires water as a raw material and sunlight as an energy source, which is a clean hydrogen production method with great potential and has attracted a large number of scientific researchers to study.

[0003] Among them, metal sulfides have attracted attention as co-catalysts due to their unique electronic structure, narrow bandgap, and good photoelectrochemical properties. Research shows that the hydrogen evolution active site of metal sulfides as co-catalysts is on the S atom. During the photocatalytic hydrogen evolution process, the formation and dissociation of the S-H ad bond have an important impact on the hydrogen evolution efficiency. The strength of the S-H ad bond will directly affect the adsorption and desorption rates of H ad and thus affect the hydrogen production efficiency.

[0004] However, currently, the use of metal sulfides alone as co-catalysts to improve the catalytic activity has limited effects. This is because when metal sulfides are combined with photocatalysts, electrons will spontaneously transfer from S to the photocatalyst, thus forming an electron-deficient S (2 -δ)- site. Since the occupancy rate of the antibonding orbital of the S (2-δ)- site is lower than that of S,

[0005] S (2-δ)- -H ad bond strength will also be greater, and the formed H ad is more difficult to desorb from the S (2-δ)- -H ad bond, restricting the photocatalytic hydrogen evolution activity. Summary of the Invention

[0006] In order to weaken the strength of the S-H ad bond and enable H ad to more easily desorb from the S-H ad bond to combine and form hydrogen. In view of the fact that an electron-deficient S (2-δ)- site will be formed after the combination of metal sulfides and photocatalysts, the purpose of the present invention is to provide a preparation method and application of a TiO2 / Ag@MoS2 composite photocatalyst, and ingeniously introduce a noble metal between the metal sulfide and the photocatalyst to transfer electrons to the metal sulfide, forming an electron-rich S(2+δ)- sites, increasing the occupancy of the antibonding orbital, thereby weakening the S (2+δ)- -H ad bond strength and improving the H ad desorption efficiency.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] In the first aspect, the present invention provides a preparation method of a TiO2 / Ag@MoS2 composite photocatalyst, comprising the following steps:

[0009] 1) Uniformly disperse titanium dioxide in an ethanol-water mixed solution to form a suspension; add a silver nitrate solution and perform a photodeposition process under ultraviolet light irradiation, so that the color of the suspension changes from white to dark gray;

[0010] 2) Add an ammonium tetrathiomolybdate precursor solution to the suspension, and under ultraviolet light irradiation, induce the MoS4 2- to undergo a self-oxidation-reduction reaction to form an amorphous MoS2 shell on the silver surface, forming a core-shell Ag@MoS2 cocatalyst;

[0011] 3) After centrifugation, washing, and drying, obtain the TiO2 / Ag@MoS2 composite photocatalyst.

[0012] As a further solution of the present invention, uniformly disperse titanium dioxide in a 10 vol% ethanol-water mixed solution, add a silver nitrate solution and perform a photodeposition process under 365 nm ultraviolet light irradiation for 1 hour.

[0013] As a further solution of the present invention, add the ammonium tetrathiomolybdate precursor solution to the suspension and continue to irradiate with 365 nm ultraviolet light for 1 hour.

[0014] As a further solution of the present invention, the preparation method of the titanium dioxide comprises the following steps:

[0015] Dropwise add 50 mL of tetrabutyl titanate to 600 mL of deionized water under stirring, continue to stir the obtained suspension for 2 hours, and then leave it at room temperature for 18 hours;

[0016] Centrifuge and separate the obtained amorphous titanium dioxide, wash it with water and ethanol respectively, dry it in a drying oven at 60 °C for 24 hours, and calcine the obtained powder in a muffle furnace at a heating rate of 5 °C / min to 550 °C for 4 hours. The obtained white solid is anatase-phase titanium dioxide material.

[0017] As a further solution of the present invention, the preparation method of the titanium dioxide further comprises the following steps:

[0018] After placing the obtained powder in a crucible, wrap it with tin foil and then put it into a muffle furnace.

[0019] As a further aspect of the present invention, in the preparation method of the catalyst, the following steps are further included:

[0020] Before irradiating the suspension under ultraviolet light, seal the reaction system and introduce nitrogen to remove the air in the system.

[0021] As a further aspect of the present invention, in the preparation method of the catalyst, the concentration of the silver nitrate solution is 0.1 mol / L, and the concentration of the ammonium tetrathiomolybdate solution is 0.01 mol / L.

[0022] As a further aspect of the present invention, in the preparation method of the catalyst, the mass ratio of silver to titanium dioxide in the added silver nitrate solution is 5 - 0:100; the mass ratio of molybdenum to titanium dioxide in the added ammonium tetrathiomolybdate solution is 0 - 5:100, and the total mass of silver and molybdenum is 0 - 5% of titanium dioxide.

[0023] In the second aspect, the present invention also provides an application of the TiO2 / Ag@MoS2 composite photocatalyst, including:

[0024] Disperse the TiO2 / Ag@MoS2 composite photocatalyst prepared by the above preparation method of the composite photocatalyst evenly in a 10 vol% ethanol - aqueous solution, and introduce N2 into the reaction flask for 15 minutes to remove the air in the flask;

[0025] Under the condition of an ambient temperature of 25°C and stirring, irradiate with a 365 nm ultraviolet LED light source, and use a gas chromatograph to test the photocatalytic generation of H2.

[0026] As a further aspect of the present invention, when irradiating with a 365 nm ultraviolet LED light source under stirring, irradiate with 4 3W, 365 nm ultraviolet LED light sources. During cyclic testing, introduce nitrogen for 15 minutes after each reaction to discharge hydrogen, and repeat the light - induced hydrogen evolution process.

[0027] As a further aspect of the present invention, the photocatalytic hydrogen evolution activity of the TiO2 / Ag@MoS2 composite photocatalyst is characterized by PL spectra, transient photocurrent response, electrochemical impedance spectroscopy, and linear sweep voltammogram curves, and the results show that it has enhanced charge separation efficiency, reduced charge transfer resistance, and optimal cathodic current density.

[0028] In the above technical solution, for the preparation method and application of the TiO2 / Ag@MoS2 composite photocatalyst provided by the present invention, the beneficial effects are:

[0029] 1. The core-shell Ag@MoS2 co-catalyst provided by the present invention is successfully loaded on TiO2 to form a TiO2 / Ag@MoS2 composite photocatalyst. The synthesis only requires simple photodeposition and photoelectron reduction methods, which are simpler and safer than other synthesis methods. At the same time, compared with single-component TiO2, the synthesized composite photocatalyst has stronger light absorption ability. The formation of the core-shell structure also improves the separation and transfer efficiency of photogenerated charges in this material, making it have more excellent optoelectronic properties.

[0030] 2. The core-shell Ag@MoS2 co-catalyst provided by the present invention successfully weakens the strength of the S-H ad bond. By introducing a noble metal between the metal sulfide and the photocatalyst, electrons are directionally transferred to the metal sulfide, forming electron-rich S (2+δ)- sites, increasing the occupancy rate of the antibonding orbital, thereby weakening the S (2+δ)- -H ad bond strength and improving the H ad desorption efficiency. This significantly improves the photocatalytic hydrogen evolution performance of the modified photocatalyst.

[0031] These aspects or other aspects of the present invention will be more clearly understood in the following description of the embodiments. It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings.

[0033] Figure 1 It is a schematic flow diagram of the TiO2 / Ag@MoS2 composite photocatalyst according to the embodiment of the present invention.

[0034] Figure 2 It is an X-ray diffraction (XRD) test chart of the TiO2 / Ag@MoS2 composite photocatalyst provided by the embodiment of the present invention.

[0035] Figure 3 It is a scanning electron microscope (SEM) test chart of the TiO2 / Ag@MoS2 composite photocatalyst provided by the embodiment of the present invention.

[0036] Figure 4 It is a transmission electron microscope (TEM) test chart of the TiO2 / Ag@MoS2 composite photocatalyst provided by the embodiment of the present invention.

[0037] Figure 5 This is a high-resolution transmission electron microscope (HRTEM) test image of the TiO2 / Ag@MoS2 composite photocatalyst provided by the embodiments of the present invention.

[0038] Figure 6 This is the ultraviolet-visible diffuse reflectance spectrum provided by the embodiments of the present invention.

[0039] Figure 7 This is the photocatalytic hydrogen evolution rate graph provided by the embodiments of the present invention.

[0040] Figure 8 This is the photocatalytic cycle stability graph provided by the embodiments of the present invention.

[0041] Figure 9 This is the PL spectrum, transient photocurrent response (i-t), electrochemical impedance spectrum (EIS), and linear sweep voltammetry curve (LSV) provided by the embodiments of the present invention.

[0042] Figure 10 This is a schematic diagram of the principle of the TiO2 / Ag@MoS2 composite photocatalyst provided by the embodiments of the present invention to increase the occupancy rate of the antibonding orbital of S. Detailed implementation manners

[0043] In order to make the technical problems to be solved, technical solutions, and beneficial effects of this application clearer, the following further elaborates on this application in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not used to limit this application.

[0044] In some processes described in the specification, claims, and above-mentioned drawings of the present invention, multiple operations appear in a specific order. However, it should be clearly understood that these operations can be executed not in the order in which they appear herein or in parallel. The serial numbers of the operations, such as 101, 102, etc., are only used to distinguish different operations, and the serial numbers themselves do not represent any execution order. In addition, these processes may include more or fewer operations, and these operations can be executed in sequence or in parallel. It should be noted that the descriptions such as "first" and "second" in this article are used to distinguish different messages, devices, modules, etc., and do not represent a sequence, nor do they limit that "first" and "second" are of different types.

[0045] Next, the technical solutions in the exemplary embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the exemplary embodiments of the present invention. Obviously, the described exemplary embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present invention.

[0046] To weaken the S-H ad bond strength so that H ad can be more easily desorbed from the S-H ad bond to combine and form hydrogen gas, the present invention proposes a preparation method and application of a TiO2 / Ag@MoS2 composite photocatalyst. By ingeniously introducing a noble metal between the metal sulfide and the photocatalyst, electrons are transferred to the metal sulfide to form electron-rich S (2+δ)- sites, increasing the occupancy rate of the antibonding orbital, thereby weakening the S (2+δ)- -H ad bond strength and improving the H ad desorption efficiency.

[0047] To enable those skilled in the art to better understand the solution of the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention.

[0048] Example 1

[0049] The embodiment of the present invention provides a preparation method of a TiO2 / Ag@MoS2 composite photocatalyst, including the following steps:

[0050] Disperse 50 mg of titanium dioxide uniformly in a 10 vol% ethanol-water mixed solution to form a white suspension. Subsequently, add 127.5 μL of silver nitrate solution (0.1 mol / L) and carry out a photodeposition process under 365 nm ultraviolet light irradiation for 1 hour. The color of the suspension changes from white to dark gray.

[0051] On this basis, add 130.3 μL of ammonium tetrathiomolybdate precursor solution (0.01 mol / L) to the suspension. Continue to irradiate with 365 nm ultraviolet light for 1 hour, and induce the reduction reaction of MoS4 2- through the electronic effect. Finally, an amorphous MoS2 shell is formed on the silver surface to form a core-shell Ag@MoS2 cocatalyst. Then, after centrifugation, washing, and drying, a TiO2 / Ag@MoS2 composite photocatalyst is obtained, where the mass ratio of silver and molybdenum to titanium dioxide is 2.75:0.25:100.

[0052] Example 2

[0053] The embodiment of the present invention provides a preparation method of a TiO2 / Ag@MoS2 composite photocatalyst, which is different from Example 1 and includes the following steps:

[0054] 50 mg of titanium dioxide was uniformly dispersed in a 10 vol% ethanol-water mixed solution to form a white suspension. Subsequently, 139 μL of silver nitrate solution (0.1 mol / L) was added and photo-deposition was carried out under ultraviolet light irradiation at 365 nm for 1 hour. The color of the suspension changed from white to dark gray. Then, after centrifugation, washing, and drying, a TiO2 / Ag photocatalyst was obtained, and at this time, the mass ratio of silver to titanium dioxide was 3:100.

[0055] Example 3

[0056] An embodiment of the present invention provides a preparation method of a TiO2 / Ag@MoS2 composite photocatalyst. Different from Example 1, it includes the following steps:

[0057] 50 mg of titanium dioxide was uniformly dispersed in a 10 vol% ethanol-water mixed solution to form a white suspension. Subsequently, 1563 μL of ammonium tetrathiomolybdate solution (0.01 mol / L) was added and photo-deposition was carried out under ultraviolet light irradiation at 365 nm for 1 hour. The color of the suspension changed from white to brown. Then, after centrifugation, washing, and drying, a TiO2 / MoS2 photocatalyst was obtained, and at this time, the mass ratio of molybdenum to titanium dioxide was 3:100.

[0058] Example 4

[0059] An embodiment of the present invention provides a preparation method of a TiO2 / Ag@MoS2 composite photocatalyst. The preparation method is the same as that shown in Example 1, except that the proportions of the silver nitrate solution and ammonium tetrathiomolybdate solution added in the steps are different. Among them, the addition amount of the silver nitrate solution is 134.5 μL, and the addition amount of the ammonium tetrathiomolybdate solution is 52.1 μL.

[0060] Example 5

[0061] An embodiment of the present invention provides a preparation method of a TiO2 / Ag@MoS2 composite photocatalyst. The preparation method is the same as that shown in Example 1, except that the proportions of the silver nitrate solution and ammonium tetrathiomolybdate solution added in the steps are different. Among them, the addition amount of the silver nitrate solution is 116 μL, and the addition amount of the ammonium tetrathiomolybdate solution is 261 μL.

[0062] Example 6

[0063] An embodiment of the present invention provides a preparation method of a TiO2 / Ag@MoS2 composite photocatalyst. The preparation method is the same as that shown in Example 1, except that the proportions of the silver nitrate solution and ammonium tetrathiomolybdate solution added in the steps are different. Among them, the addition amount of the silver nitrate solution is 46 μL, and the addition amount of the ammonium tetrathiomolybdate solution is 1042 μL.

[0064] Based on this, in Example 4, the mass ratio of silver, molybdenum to titanium dioxide is 2.9:0.1:100; in Example 5, the mass ratio of silver, molybdenum to titanium dioxide is 2.5:0.5:100; in Example 6, the mass ratio of silver, molybdenum to titanium dioxide is 1:2:100.

[0065] Comparative Example 1

[0066] Preparation of anatase phase nano-titanium dioxide: 50 mL of tetrabutyl titanate was added dropwise to 600 mL of deionized water under stirring, and the resulting suspension was continuously stirred for 2 hours and then left at room temperature for 18 hours. The obtained amorphous titanium dioxide was centrifuged and washed with water and ethanol respectively, dried in a drying oven at 60 °C for 24 hours, and the obtained powder was calcined in a muffle furnace at a heating rate of 5 °C / min to 550 °C for 4 hours. The resulting white solid is the anatase phase titanium dioxide material. It was compared with the modified composite photocatalyst.

[0067] Comparative Example 2

[0068] Preparation of amorphous MoS2: 20 mg of ammonium tetrathiomolybdate was added to 20 mL of deionized water, and 20 mL of lactic acid solution (10 vol%) was added dropwise to the resulting dark red solution. After sufficient stirring, it was left overnight. The obtained black solid was filtered, washed with water and ethanol, and then vacuum dried for 12 hours to obtain amorphous MoS2. It was compared with the modified composite photocatalyst.

[0069] Sample characterization:

[0070] As shown in the figure, as Figure 1 shown is the process schematic diagram of preparing the TiO2 / Ag@MoS2 composite photocatalyst in Example 1. The TiO2 / Ag@MoS2, TiO2 / Ag, TiO2 / MoS2, TiO2 and MoS2 prepared in the examples were characterized, and the XRD patterns as Figure 2 shown, Figure 3 the SEM patterns as Figure 4 and 5 the TEM and HRTEM patterns as Figure 6 and the UV-vis patterns were obtained.

[0071] From Figure 2 the XRD patterns, it can be clearly seen that TiO2 / Ag@MoS2, TiO2 / Ag, TiO2 / MoS2 and TiO2 all have obvious TiO2 diffraction peaks; TiO2 / Ag@MoS2 and TiO2 / Ag have a diffraction peak representing silver at 44.3°, indicating the successful composite of silver.

[0072] From Figure 3 the SEM images and Figure 4The TEM image of Figure 5 shows that TiO2 / Ag@MoS2 are nanoparticles with a size ranging from 20 to 50 nm. Meanwhile, in the

[0073] Figure 6 high-resolution transmission electron microscope, the lattice fringes of TiO2 / Ag@MoS2 can be observed. The measured d-value of 0.347 nm corresponds to the (101) crystal plane of TiO2, and the d-value of 0.242 nm corresponds to the (111) crystal plane of Ag.

[0074] (1) Photocatalytic hydrogen evolution performance test:

[0075] Among the materials and evidence used in this example, the test equipment is a gas chromatograph (SP-6801A type) from Ruihong Instruments, and the light source used is 4 3W LED light sources (λ = 365 nm).

[0076] Add 50 mg of the catalyst into a three-necked flask containing 72 mL of deionized water and 8 mL of ethanol, and ultrasonically treat for 5 minutes to uniformly mix the catalyst in the solution to form a white suspension.

[0077] Seal the three-necked flask, displace the air with nitrogen for 15 minutes to fill the system with nitrogen. Subsequently, place the sample under stirring under 4 3W 365 nm wavelength LED light sources for the photocatalytic hydrogen evolution process.

[0078] Every 30 minutes, use the gas chromatograph to extract the gas in the system to test the hydrogen production amount. A total of 4 sets of data are tested in 2 hours, and the photocatalytic hydrogen evolution activity diagram as shown in Figure 7 is obtained.

[0079] (2) Photocatalytic stability test:

[0080] Perform a photocatalytic hydrogen evolution cycle test with 50 mg of the catalyst. The test steps are basically the same as those of the photocatalytic hydrogen evolution activity test. Add 50 mg of the catalyst into a three-necked flask containing 72 mL of deionized water and 8 mL of ethanol, and ultrasonically treat for 5 minutes to uniformly mix the catalyst in the solution to form a white suspension. Seal the three-necked flask, displace the air with nitrogen for 15 minutes to fill the system with nitrogen.

[0081] Subsequently, place the sample under stirring under 4 3W 365 nm wavelength LED light sources for the photocatalytic hydrogen evolution process, and test the photocatalytic hydrogen evolution activity once every 2 hours. After the test, pass nitrogen for 15 minutes again to remove the hydrogen in the system, and continue light irradiation for 2 hours to test the photocatalytic hydrogen production amount. Repeat four times in total. Taking the first hydrogen production amount as 100%, the result as shown inFigure 8 Photocatalytic cycle test diagram shown

[0082] The addition amounts of the solutions in each example are shown in Table 1

[0083] (3) Photoelectrochemical test:

[0084] See Figure 9 shown Figure 9 are the PL spectrum, transient photocurrent response diagram (i-t), electrochemical impedance diagram (EIS) and linear sweep voltammogram (LSV) of the sample. The photoluminescence (PL) spectrum shows that each sample has peaks at 520 nm and 700 nm. A higher PL intensity indicates faster electron-hole pair recombination, meaning that the photocatalytic effect is weakened. While the PL intensity of TiO2 / Ag@MoS2 is lower, indicating that its charge recombination is inhibited and the charge separation efficiency is significantly improved Figure 9 The transient photocurrent response of the sample in b under multiple periodic illuminations shows that TiO2 / Ag@MoS2 has the highest photocurrent density, indicating that its carrier separation and transport ability is the best. The electrochemical impedance spectrum shows that compared with pure TiO2, the arc radius of the composite catalyst decreases, indicating a reduction in charge transfer resistance, and the arc radius of TiO2 / Ag@MoS2 is the smallest, with a smaller internal resistance of charge transport, showing the highest charge separation and transport efficiency, which helps to improve the photocatalytic hydrogen evolution performance. The results of linear sweep voltammetry show that TiO2 / Ag@MoS2 exhibits the lowest overpotential and the best cathodic current density, indicating that the combination of Ag and MoS2 significantly improves the synergistic catalytic efficiency of the S site

[0085] It should be noted that: Figure 10 is the schematic diagram of the highest photocatalytic activity exhibited by TiO2 / Ag@MoS2. The introduction of silver atoms transfers electrons to the S site to form an electron-rich S (2+δ)- active site, increasing the occupancy rate of the antibonding orbital of S, thereby weakening the S (2+δ)- -H ad bond, promoting the rapid desorption of H ad to generate free H, which finally combines to produce hydrogen, improving the photocatalytic hydrogen evolution efficiency

[0086] The core-shell Ag@MoS2 cocatalyst provided by the present invention is successfully loaded on TiO2 to form a TiO2 / Ag@MoS2 composite photocatalyst. The synthesis only requires simple photodeposition and photoelectron reduction methods, which are simpler and safer than other synthesis methods. At the same time, compared with single-component TiO2, the synthesized composite photocatalyst has stronger light absorption ability. The formation of the core-shell structure also improves the separation and transport efficiency of the photogenerated charges of the material, making it have more excellent optoelectronic properties. The core-shell Ag@MoS2 cocatalyst provided by the present invention successfully weakens the S-Had The strength of the bond. Since a noble metal is introduced between the metal sulfide and the photocatalyst, electrons are directionally transferred to the metal sulfide, forming an electron-rich S (2+δ)- site, increasing the occupancy rate of the antibonding orbital, thereby weakening the S (2+δ)- -H ad bond strength and improving the H ad desorption efficiency. The photocatalytic hydrogen evolution performance of the modified photocatalyst is significantly improved.

[0087] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of a TiO2 / Ag@MoS2 composite photocatalyst, characterized in that, It includes the following steps: 1) Uniformly disperse titanium dioxide in an ethanol-water mixed solution to form a suspension; add silver nitrate solution and irradiate with ultraviolet light for a photodeposition process, causing the color of the suspension to change from white to dark gray; 2) Add ammonium tetrathiomolybdate precursor solution to the suspension. After ultraviolet light irradiation, induce the self-oxidation-reduction reaction of MoS4 2- through the electronic effect, and form an amorphous MoS2 shell on the silver surface to form a core-shell Ag@MoS2 cocatalyst; 3) After centrifugation, washing, and drying, obtain the TiO2 / Ag@MoS2 composite photocatalyst.

2. The preparation method of a TiO2 / Ag@MoS2 composite photocatalyst according to claim 1, characterized in that, Uniformly disperse titanium dioxide in a 10 vol% ethanol-water mixed solution, add silver nitrate solution, and irradiate with 365 nm ultraviolet light for 1 hour for the photodeposition process.

3. The preparation method of a TiO2 / Ag@MoS2 composite photocatalyst according to claim 2, characterized in that, Add the ammonium tetrathiomolybdate precursor solution to the suspension and continue to irradiate with 365 nm ultraviolet light for 1 hour.

4. The preparation method of a TiO2 / Ag@MoS2 composite photocatalyst according to claim 1, characterized in that The preparation method of the titanium dioxide includes the following steps: Dropwise add 50 mL of tetrabutyl titanate to 600 mL of deionized water under stirring, continue to stir the obtained suspension for 2 hours, and then leave it at room temperature for 18 hours; Centrifuge and separate the obtained amorphous titanium dioxide, wash it with water and ethanol respectively, dry it in a drying oven at 60 °C for 24 hours, heat the obtained powder in a muffle furnace to 550 °C at a rate of 5 °C / min for 4 hours, and the obtained white solid is the anatase-phase titanium dioxide material.

5. The preparation method of a TiO2 / Ag@MoS2 composite photocatalyst according to claim 4, characterized in that, The preparation method of the titanium dioxide further includes the following steps: Place the obtained powder in a crucible, wrap it with tin foil, and then put it into a muffle furnace.

6. The preparation method of a TiO2 / Ag@MoS2 composite photocatalyst according to claim 1, characterized in that, In the preparation method of the catalyst, the following steps are further included: Before irradiating the suspension with ultraviolet light, close the reaction system and introduce nitrogen to remove the air in the system.

7. The preparation method of a TiO2 / Ag@MoS2 composite photocatalyst according to claim 6, characterized in that, In the preparation method of the catalyst, the concentration of the silver nitrate solution is 0.1 mol / L, and the concentration of the ammonium tetrathiomolybdate solution is 0.01 mol / L.

8. The preparation method of a TiO2 / Ag@MoS2 composite photocatalyst according to claim 7, characterized in that, In the preparation method of the catalyst, the mass ratio of silver to titanium dioxide in the added silver nitrate solution is 5 - 0:100; the mass ratio of molybdenum to titanium dioxide in the added ammonium tetrathiomolybdate solution is 0 - 5:100, and the total mass of silver and molybdenum is 0 - 5% of titanium dioxide.

9. Application of a TiO2 / Ag@MoS2 composite photocatalyst, characterized in that, It includes: Uniformly disperse the TiO2 / Ag@MoS2 composite photocatalyst prepared by the preparation method of the composite photocatalyst according to any one of claims 1 - 8 in a 10 vol% ethanol-water solution, introduce N2 into the reaction flask for 15 minutes to remove the air in the flask; Under the condition that the ambient temperature is 25 °C and under stirring, irradiate with a 365 nm ultraviolet LED light source, and use a gas chromatograph to test the photocatalytic generation of H2.

10. Use of a TiO2 / Ag@MoS2 composite photocatalyst according to claim 9, characterized in that, When irradiating with a 365 nm ultraviolet LED light source under stirring, irradiate with 4 3W, 365 nm ultraviolet LED light sources. During the cyclic test, introduce nitrogen for 15 minutes after each reaction to discharge hydrogen, and repeat the light irradiation hydrogen evolution process.

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