A bifunctional M / Ti3C2T x / Zn3In2S6 composite photocatalyst and preparation method and application thereof

Abstract

The application belongs to the technical field of photocatalysis, and discloses a bifunctional M / Ti3C2T x / Zn3In2S6 composite photocatalyst as well as a preparation method and application thereof. (1), the Ti3C2T x powder is annealed in a reducing atmosphere; (2), the Ti3C2T x powder after annealing is added into water with a metal salt solution, and is uniformly dispersed under the protection of inert gas and then continuously stirred for 2-12 hours to obtain an M / Ti3C2T x composite material; (3), the M / Ti3C2T x composite material is dispersed in 1# water, is uniformly dispersed under the protection of inert gas, and then a solution A is obtained; zinc salt, indium salt and sulfur source are added into 2# water, are uniformly stirred, and then a solution B is formed; then, the solution A and the solution B are mixed in equal volume, a surfactant is added, is uniformly stirred at room temperature, and then is transferred into a high-pressure reaction kettle, is solvothermal reacted at 120-200 DEG C for 8-24 hours to obtain an M / Ti3C2T x / Zn3In2S6 composite photocatalyst. The catalyst disclosed by the application has stable structure and high cyclic stability, has high photocatalytic activity, can improve the generation efficiency of clean hydrogen energy, and can obtain products with high added value.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of photocatalysis, and particularly relates to a bifunctional M / Ti3C2T x / Zn3In2S6 composite photocatalyst and a preparation method and application thereof. BACKGROUND

[0002] Seeking clean and sustainable energy is a hot topic of current research. Among them, photocatalytic water splitting to produce hydrogen is considered as an economic and environmentally friendly technology. In the process of photocatalytic conversion, enhancing the charge separation and transfer ability is the key to improve the photocatalytic activity, especially constructing a heterojunction structure and modifying the interface is crucial to further enhance the charge separation and transfer. Indium zinc sulfide (Zn3In2S6) is a non-toxic n-type semiconductor photocatalyst, which has visible light response, adjustable energy band structure and other advantages, which has attracted extensive research. Unfortunately, due to the easy recombination of photo-generated electron-hole pairs, the photocatalytic activity of Zn3In2S6 alone is low.

[0003] In addition, the slow kinetics and high oxidation potential of the water oxidation half-reaction (H2O / O2, 1.23 V vs NHE) in the process of photocatalytic hydrogen production seriously inhibits the overall water splitting efficiency, and a series of hole sacrificial agents (such as triethanolamine, lactic acid, Na2S-Na2SO3 solution, etc.) are usually used to enhance the photocatalytic hydrogen evolution ability. However, this method not only increases the cost, but also wastes the oxidation ability of photo-generated holes, and increases the difficulty of reaction mechanism research. Therefore, it would be more meaningful and interesting to design a high-activity bifunctional catalyst to convert these originally wasted sacrificial agents into high-value-added chemicals by using the organic oxidation reaction of its holes. SUMMARY

[0004] In order to solve the low charge separation efficiency in single catalyst and the waste of hole energy in photocatalytic hydrogen evolution reaction, the purpose of the application is to provide a bifunctional M / Ti3C2T x / Zn3In2S6 composite photocatalyst and a preparation method and application thereof.

[0005] To achieve the above purpose, the technical scheme adopted by the application is as follows:

[0006] A bifunctional M / Ti3C2T x / Zn3In2S6 composite photocatalyst, M=metal, the metal is one or more of ruthenium, platinum, palladium, cobalt and copper; the composite photocatalyst is single-layer or few-layer (2-3 layers) sheet Ti3C2T x , and metal M nanopoints are dispersed on Ti3C2T x , and then Ti3C2T xThe Zn3In2S6 nanosheet is grown in situ; wherein, in the entire composite photocatalyst, the mass ratio of Ti3C2T x is 2-20 %, and the mass ratio of the metal M is 0.2-1.5 %.

[0007] The M / Ti3C2T x / Zn3In2S6 composite photocatalyst has the advantages of high photocatalytic activity, high stability, and the like.

[0008] (1) annealing the Ti3C2T x powder in a reducing atmosphere;

[0009] (2) adding the annealed Ti3C2T x powder and a metal salt solution into water, uniformly dispersing under inert gas protection, continuously stirring for 2-12 h, and then obtaining the M / Ti3C2T x composite material through centrifugation, washing, and drying; wherein, the metal salt solution is a salt solution of the metal M, the mass ratio of the Ti3C2T x powder, the metal salt solution, and water is (5-200) mg:(0.5-4.0) mL:(15-40) mL, and the concentration of the metal salt solution is 5-30 mM in terms of the metal M therein;

[0010] (3) dispersing the M / Ti3C2T x composite material in 1# water, uniformly dispersing under inert gas protection, obtaining solution A; adding zinc salt, indium salt, and sulfur source into 2# water, stirring uniformly, and forming solution B; then mixing solution A and solution B in equal volume, adding a surfactant, stirring uniformly at room temperature, transferring to a high-pressure reaction kettle, and performing solvothermal reaction at 120-200 ℃ for 8-24 h; after the reaction liquid is cooled to room temperature, the M / Ti3C2T x / Zn3In2S6 composite photocatalyst is obtained through centrifugation, washing, and drying; wherein, the mass ratio of M / Ti3C2T x , 1# water, zinc salt, indium salt, sulfur source, and surfactant is (5-50) mg:(15-40) mL:0.9 mmol:0.6 mmol:(1.5-2.5) mmol:(20-200) mg, and the molar amount of the aforementioned zinc salt, indium salt, and sulfur source is calculated in terms of Zn, In, and S therein.

[0011] Preferably, in step (1), the reducing atmosphere is hydrogen, hydrogen / nitrogen mixed gas, or hydrogen / argon mixed gas, the volume ratio of hydrogen in the mixed gas is 5-20 %, the annealing temperature is 150-400 ℃, and the annealing time is 2-8 h.

[0012] Preferably, in step (2), the metal salt is one or more of nitrate, chloride, sulfate, acetate.

[0013] Preferably, in step (2), the inert gas is nitrogen or argon.

[0014] Preferably, in step (3), the zinc salt is zinc sulfate, zinc acetate or zinc nitrate; the indium salt is indium nitrate, indium chloride or indium sulfate; the sulfur source is thioacetamide or thiourea.

[0015] Preferably, in step (3), the surfactant is cetyltrimethylammonium bromide, polyvinylpyrrolidone, sodium citrate, cetyltrimethylammonium chloride.

[0016] Preferably, in step (1), the Ti3C2T x The powder is prepared by the following method: commercial Ti3AlC2 powder is added to an acid solution, etching treatment is carried out in a 20-70 ℃ water bath with continuous stirring for 12-48 h, and then Ti3C2T x powder is obtained by centrifugation, washing and drying; wherein Ti3AlC2: acid solution = (0.1-1) g: (5-30) mL; the acid solution is a 35-60 wt% hydrofluoric acid solution or a hydrochloric acid-lithium fluoride mixed solution, wherein the hydrochloric acid-lithium fluoride mixed solution refers to lithium fluoride powder dissolved in a 6-12 M hydrochloric acid solution, and the concentration of lithium fluoride in the mixed solution is 2-10 M.

[0017] The bifunctional M / Ti3C2T x / Zn3In2S6 composite photocatalyst is used in the preparation of DFF by photocatalytic water splitting to produce hydrogen and selective oxidation of HMF.

[0018] Preferably, the M / Ti3C2T x / Zn3In2S6 composite photocatalyst and HMF are uniformly dispersed in water, and the photocatalytic reaction is carried out in an air-tight atmosphere for 3-5 h; wherein M / Ti3C2T x / Zn3In2S6 composite photocatalyst: HMF: water = (10-50) mg: (0.1-2) mmol: 100 mL.

[0019] Advantages:

[0020] (1) The Ti3C2T xAnnealing of the powder in a reducing atmosphere can modulate the surface properties of titanium carbide, increasing the number of surface titanium defects. These defects, exhibiting high instability and reducing power, can reduce some adsorbed metal ions on the surface into metal nanoparticles without the addition of additional reducing agents. Therefore, annealing is beneficial for subsequent self-reduction and anchoring of the metal. This invention utilizes Ti3C2T... x The reduction-selective anchoring of titanium defect vacancies in the metal cocatalyst to form nanodots can effectively promote the dispersion of the cocatalyst and improve its utilization rate, which is beneficial to enhancing the photocatalytic reaction activity and efficiency.

[0021] (2) In this invention, the addition of surfactant can effectively regulate the defect concentration in Zn3In2S6. The introduction of defects is beneficial to the adsorption and activity of organic reactants, thereby promoting the organic oxidation reaction of the holes left on Zn3In2S6.

[0022] (3) The present invention utilizes a directional self-reduction strategy in conjunction with an in-situ solvothermal reaction to prepare M / Ti3C2T selectively supported by a metal co-catalyst M. x The M / Ti3C2T composite photocatalyst constructs an efficient directional charge transfer pathway, effectively promoting the separation and rapid transfer of photogenerated electrons and holes while inhibiting the rapid recombination of photogenerated carriers, thereby promoting the M / Ti3C2T... x In the Zn3In2S6 composite system, photogenerated electrons and holes are simultaneously used for efficient hydrogen production and value-added biomass chemicals; the photocatalytic activity of this system is higher than that of Zn3In2S6 and Ti3C2T alone. x Both Zn3In2S6 and Zn3In2S6 have been significantly improved, providing a new solution for achieving industrial production as soon as possible; therefore, this invention is a very meaningful technology for efficiently obtaining clean energy.

[0023] (4) In this invention, HMF is introduced to replace the sacrificial agent during photocatalytic hydrogen evolution. This can not only avoid the waste of sacrificial agent and the generation of environmentally unfriendly organic products, but also obtain products with high added value while improving the efficiency of clean hydrogen energy generation. This method provides a green technology for the efficient conversion of biomass resources.

[0024] (5) The catalyst in this invention has a stable structure and high cycle stability. As a highly efficient bifunctional photocatalyst, it can simultaneously utilize photogenerated electrons and holes to achieve a combination of hydrogen production and organic conversion. Furthermore, the liquid products and gaseous products can be automatically separated, which has potential application prospects in actual production. Attached Figure Description

[0025] Figure 1 : Ti3C2T prepared in Example 1 x Scanning electron microscope image.

[0026] Figure 2 : Scanning electron microscope image of Zn3In2S6 prepared in Comparative Example 2.

[0027] Figure 3 : Transmission electron microscope image, high-resolution transmission electron microscope image and elemental mapping of Ru / Ti3C2T x / Zn3In2S6 prepared in Example 1, wherein TC represents Ti3C2T x .

[0028] Figure 4 : X-ray diffraction (XRD) pattern of the samples Ti3C2T x , Ru / Ti3C2T x / Zn3In2S6, Zn3In2S6 and Ti3C2T x / Zn3In2S6 prepared in Example 1, Comparative Examples 2 and 3.

[0029] Figure 5 : Electron paramagnetic resonance (EPR) spectrum of Ru / Ti3C2T x / Zn3In2S6 prepared in Example 1 with addition of a surfactant (A) and Comparative Example 1 without addition of a surfactant (B).

[0030] Figure 6 : Photocatalytic performance of the catalyst Ru / Ti3C2T x / Zn3In2S6, Zn3In2S6, Ti3C2T x / Zn3In2S6 and Ru-Zn3In2S6 in the photocatalytic hydrogen production and HMF oxidation reaction, wherein TC represents Ti3C2T x , and ZIS represents Zn3In2S6.

[0031] Figure 7 : Photocatalytic cyclic stability of the catalyst Ru / Ti3C2T x / Zn3In2S6 and Zn3In2S6 prepared in Example 1 and Comparative Example 2. DETAILED DESCRIPTION

[0032] In order to make the present application clearer and more explicit, the present application will be further described in detail below. It should be understood that the specific examples described here are only used to explain the present application and are not used to limit the present application.

[0033] Example 1

[0034] A method for preparing a Ru / Ti3C2T x / Zn3In2S6 composite photocatalyst, comprising the following steps:

[0035] (1), 1.6 g of lithium fluoride was added into 20 mL of 10 M hydrochloric acid and stirred until completely dissolved, then 1.0 g of commercial Ti3AlC2 was added, and etching treatment was carried out by continuously stirring in a 40 ℃ water bath for 24 h, after which Ti3C2T x powder was obtained by centrifugation, washing and drying;

[0036] (2), the Ti3C2T x powder obtained in step (1) was annealed at 300 o C for 4 h in a H2 / N2 mixed atmosphere (H2 accounted for 10 vol%) ;

[0037] (3), 100 mg of the annealed Ti3C2T x powder obtained in step (2) was added to 20 mL of deionized water with a ruthenium trichloride aqueous solution (3 mL, 20 mM), and after ultrasonic treatment for 0.5 h under nitrogen protection, it was continuously stirred for 8 h, and finally the reaction liquid was centrifuged, washed to near neutral pH, and vacuum dried to obtain Ru / Ti3C2T x ;

[0038] (4), 20 mg of the Ru / Ti3C2T x obtained in step (3) was added to 15 mL of deionized water and ultrasonically dispersed for 0.5 h under nitrogen protection to obtain solution A; 0.9 mmol of zinc chloride, 0.6 mmol of indium trichloride, and 1.8 mmol of thioacetamide were sequentially added to 15 mL of deionized water, and after stirring for 0.5 h, solution B was obtained; After mixing solution A and solution B, 50 mg of cetyltrimethylammonium bromide was added, and after stirring uniformly, it was transferred to a high-pressure hydrothermal kettle and solvothermal reacted at 160 o C for 12 h, and after the reaction liquid was cooled to room temperature, the product Ru / Ti3C2T x / Zn3In2S6 was obtained by centrifugation, washing and drying, and the mass fraction of Ru in it was 0.72% measured by inductively coupled plasma spectrometer (ICP).

[0039] Example 2

[0040] The difference from Example 1 is that the amount of Ru / Ti3C2T x in step (4) is changed to 10 mg, and the others are the same as Example 1.

[0041] Example 3

[0042] The difference from Example 1 is that the amount of Ru / Ti3C2T x in step (4) is changed to 30 mg, and the others are the same as Example 1.

[0043] Example 4

[0044] The difference from Example 1 is that the amount of Ru / Ti3C2T x in step (4) is changed to 40 mg, and the others are the same as Example 1.

[0045] Comparative Example 1

[0046] The difference from Example 1 is that in step (4), after mixing solution A and solution B, no cetyltrimethylammonium bromide is added, and the subsequent solvothermal reaction is directly carried out; and the others are the same as Example 1.

[0047] Comparative Example 2

[0048] The preparation method of Zn3In2S6 catalyst is as follows: 0.9 mmol of zinc chloride, 0.6 mmol of indium trichloride, and 1.8 mmol of thioacetamide are sequentially added to 30 mL of deionized water, and after stirring for 0.5 h, 50 mg of cetyltrimethylammonium bromide is added, and after stirring uniformly, it is transferred to a high-pressure hydrothermal kettle for 160 o C solvothermal reaction for 12 h, and after the reaction solution is cooled to room temperature, the product Zn3In2S6 is obtained through centrifugation, washing, and drying.

[0049] Comparative Example 3

[0050] The preparation method of Ti3C2T x / Zn3In2S6 composite photocatalyst is as follows:

[0051] Steps (1) and (2) are the same as Example 1;

[0052] (3), 20 mg of annealed Ti3C2T x obtained in step (2) is added to 15 mL of deionized water, ultrasonically dispersed for 0.5 h under nitrogen protection to obtain solution A; 0.9 mmol of zinc chloride, 0.6 mmol of indium trichloride, and 1.8 mmol of thioacetamide are sequentially added to 15 mL of deionized water, and after stirring for 0.5 h, solution B is obtained; after mixing solution A and solution B, 50 mg of cetyltrimethylammonium bromide is added, and after stirring uniformly, it is transferred to a high-pressure hydrothermal kettle for 160 o C solvothermal reaction for 12 h, and after the reaction solution is cooled to room temperature, the product Ti3C2T x / Zn3In2S6 is obtained through centrifugation, washing, and drying.

[0053] Comparative Example 4

[0054] Preparation method of Ru-Zn3In2S6 catalyst: 100 mg of Zn3In2S6 obtained in Comparative Example 2 was dispersed in 50 mL of deionized water, and then ruthenium trichloride aqueous solution (0.75 mL, 10 mM) was added. After stirring for 0.5 h, the mixture was irradiated with a xenon lamp as a light source for 2 h. The reaction solution was centrifuged, washed and dried to obtain the product Ru-Zn3In2S6 (Ru loading was 0.73 wt%).

[0055] Product Characterization

[0056] Figure 1 Ti3C2T prepared in Example 1 x Scanning electron microscope image. From Figure 1 As can be seen from this: Ti3C2T x It exhibits a two-dimensional sheet-like structure with a single layer or few layers (2 to 3 layers) and a lateral dimension of 1.0 to 2.0 micrometers.

[0057] Figure 2 Scanning electron microscope image of Zn3In2S6 prepared for control example 2. From Figure 2 As can be seen, the original Zn3In2S6 exhibits a typical micron-shaped flower structure assembled from nanosheets, with a small number of unassembled sheet structures appearing. The particle size of the flower structure is approximately 1.0~1.2 micrometers.

[0058] Figure 3 Ru / Ti3C2T prepared in Example 1 x Transmission electron microscopy image of / Zn3In2S6, where TC represents Ti3C2T. x .from Figure 3 It can be seen from this that: Ru / Ti3C2T x / Zn3In2S6 exhibits a typical 2D / 2D stacked lamellar morphology, while Ti3C2T x The surface and edges are covered with nanosheet-like Zn3In2S6 layers, and the two phases are in close contact. The lattice spacing of 0.318 nm corresponds to the (102) crystal plane of Zn3In2S6, and the lattice spacings of 0.206 nm and 0.266 nm correspond to Ti3C2T x The (002) and (0110) crystal planes together indicate that the two-dimensional Ti3C2T x The formation of the Zn3In2S6 heterostructure; although in Figure 3 No obvious Ru particles were observed, but Ru elements were visible in the mapping plot, which may be due to their relatively low content or high dispersion.

[0059] Figure 4Samples of Ti3C2T x , Ru / Ti3C2T x / Zn3In2S6, Zn3In2S6 and Ti3C2T x X-ray diffraction (XRD) patterns of Ru / Ti3C2T Figure 4 It can be seen that the diffraction peak at 7.0° corresponds to the (002) crystal plane of Ti3C2T x , and the diffraction peaks at 20.6°, 27.1°, 47.2°, 56.0° and 76.3° correspond to the (005), (100), (110), (203) and (213) crystal planes of Zn3In2S6, respectively. The characteristic peaks of Ru are difficult to see in Ru / Ti3C2T x / Zn3In2S6, which may be due to the small amount of Ru and good dispersion, which further confirms the successful synthesis of the composite material.

[0060] Figure 5 Electron paramagnetic resonance (EPR) spectra of Ru / Ti3C2T x / Zn3In2S6 prepared under the condition of adding surfactant (A) in Example 1 and not adding surfactant (B) in Comparative Example 1. From the EPR graph, it can be seen that Ru / Ti3C2T x / Zn3In2S6 in Example 1 has a clear signal peak at g value of 2.003, corresponding to S defects, but the sample in Comparative Example 1 has basically no signal peak, indicating that the Ru / Ti3C2T x / Zn3In2S6 sample prepared in Example 1 contains S defects, while the Ru / Ti3C2T x / Zn3In2S6 sample prepared in Comparative Example 1 does not contain S defects. The introduction of defects is beneficial to the adsorption and activity of organic reactants, thereby promoting the organic oxidation reaction of the holes left on Zn3In2S6. This feature is also confirmed in related literature (Appl. Catal. B Environ., 2019, 243, 10–18; Int. J. Hydrogen Energy, 2021, 46, 37782–37791; J. Mater. Chem. A, 2023, 11, 21677–21685).

[0061] Application Example 1

[0062] 25 mg catalyst and 0.5 mmol HMF were added into 100 mL deionized water, and after ultrasonic dispersion for 20 min, they were poured into a 250 mL Beijing Pheilite photocatalytic reactor, then vacuum was applied to remove air, and a 300 W xenon lamp was used to provide full-spectrum light source. Liquid and gas samples were taken at certain intervals and quantitatively analyzed by high-performance liquid chromatography and gas chromatography, respectively.

[0063] The test results are shown in Table 1. It can be seen that: the conversion rate of HMF is only 12.8% after 5 h of illumination of Zn3In2S6 alone, and under the same conditions, the photocatalytic hydrogen evolution activity and HMF oxidation activity of Ti3C2T x / Zn3In2S6 and Ru-Zn3In2S6 are significantly improved, and the photocatalytic hydrogen evolution and HMF oxidation activity of Ru / Ti3C2T x / Zn3In2S6 is the best, and the photocatalytic hydrogen evolution rate of Ru / Ti3C2T x / Zn3In2S6 photocatalyst can reach 2.91 mmol g x h ‒1 , and the conversion rate of HMF can reach 72.4 %; the photocatalytic hydrogen evolution and HMF oxidation activity of the Ru / Ti3C2T ‒1 / Zn3In2S6 catalyst prepared in Examples 1-4 are ranked from low to high in terms of Ru / Ti3C2T x content, and the reaction activity will increase, but if the content of Ru / Ti3C2T x is further increased, the reaction activity will decrease instead, which may be because excessive Ti3C2T x will block the main catalyst Zn3In2S6, thereby affecting its light absorption capacity and the number of surface active sites; compared with Example 1, the photocatalytic activity of Ru / Ti3C2T x / Zn3In2S6 prepared in Comparative Example 1 is reduced, which may be because the Ru / Ti3C2T x content in the Ru / Ti3C2T x / Zn3In2S6 prepared in Example 1 is higher; compared with Example 1, the photocatalytic activity of Ru / Ti3C2T x / Zn3In2S6 prepared in Comparative Example 1 is reduced, which may be because the Zn3In2S6 in the Ru / Ti3C2T x / Zn3In2S6 prepared in Example 1 contains some defects, while the Zn3In2S6 in the catalyst prepared in Comparative Example 1 has no defect structure, and the defect structure is beneficial to the adsorption and activation of HMF in the photocatalytic reaction, which may be the main reason for the difference in activity between the catalysts in Comparative Example 1 and Example 1.

[0064]

[0065] Figure 6 Catalyst Ru / Ti3C2T x / Zn3In2S6, Zn3In2S6, Ti3C2T x and Ru-Zn3In2S6. The figure of photocatalytic hydrogen evolution and HMF oxidation performance of the catalysts, wherein TC represents Ti3C2T x , ZIS represents Zn3In2S6. It can be seen from Figure 6 that compared with Zn3In2S6, the introduction of Ti3C2T x and Ru can significantly enhance the photocatalytic reaction activity of Zn3In2S6, and the hydrogen evolution rate of Ru / Ti3C2T x / Zn3In2S6 can reach 2.91 mmol g ‒1 h ‒1 , and the stoichiometric DFF value-added product can be generated.

[0066] Application Example 2 - Cycle stability test

[0067] Catalyst Ru / Ti3C2T x / Zn3In2S6 and Zn3In2S6, the reaction liquid after the reaction in the above application example 1 is centrifuged and washed with deionized water, dried to obtain regenerated catalyst, and the second cycle catalytic reaction is carried out according to the reaction conditions of application example 1, and the same operation is continuously cycled for five times, 3 h for each cycle, and 15 h in total.

[0068] Figure 7 Catalyst Ru / Ti3C2T x / Zn3In2S6 and Zn3In2S6. The figure of photocatalytic cycle stability of the catalysts, wherein TC represents Ti3C2T Figure 7 It can be seen from the figure that the activity of the catalyst prepared in the embodiment 1 of the present application basically remains unchanged after five times of continuous cycle, that is, the catalyst does not show obvious deactivation phenomenon, which indicates that the catalyst has good cycle stability.

Claims

1. A bifunctional M / Ti3C2T x A method for preparing a dual functional M / Ti3C2T M=metal, the metal is one or more of ruthenium, platinum, palladium, cobalt, copper; the composite photocatalyst is in a single layer or a few layers of sheet Ti3C2T x is a substrate, and metal M nanodots are dispersed in Ti3C2T x , and the Ti3C2T x above has Zn3In2S6 nanosheets grown in situ; wherein, in the entire composite photocatalyst, the mass ratio of Ti3C2T x is 2-20%, and the mass ratio of metal M is 0.2-1.5%; the dual function refers to the fact that the M / Ti3C2T x / Zn3In2S6 composite photocatalyst can simultaneously utilize photo-generated electrons and holes to realize hydrogen production and organic conversion combination; the preparation steps are as follows: (1) Ti3C2T x powder is annealed in a reducing atmosphere; (2), the Ti3C2T x powder and the metal salt solution are added into water, uniformly dispersed under ultrasonic treatment in nitrogen or inert gas protection, then continuously stirred for 2-12 h, and then centrifuged, washed and dried to obtain M / Ti3C2T x composites; wherein the metal salt solution is a salt solution of metal M, Ti3C2T x powder: metal salt solution: water = (5-200) mg: (0.5-4.0) mL: (15-40) mL, and the concentration of the metal salt solution is 5-30 mM in terms of the metal M therein. (3), M / Ti3C2T x The composite material is dispersed in 1# water, ultrasonically dispersed uniformly under nitrogen or inert gas protection to obtain solution A; zinc salt, indium salt and sulfur source are added to 2# water, stirred uniformly to form solution B; then solution A and solution B are mixed in equal volume, and then a surfactant is added, stirred uniformly at room temperature, and then transferred to a high-pressure reaction kettle, and then solvent thermal reaction is carried out at 120-200 ℃ for 8-24 h, and then the reaction liquid is cooled to room temperature, and then centrifuged, washed and dried to obtain M / Ti3C2T x / Zn3In2S6 composite photocatalyst; wherein, M / Ti3C2T x 1# water: zinc salt: indium salt: sulfur source: surfactant = (5-50) mg: (15-40) mL: 0.9 mmol: 0.6 mmol: (1.5-2.5) mmol: (20-200) mg, the molar amount of the foregoing zinc salt, indium salt and sulfur source is calculated according to Zn, In and S therein.

2. The bifunctional M / Ti3C2T x The application relates to a preparation method of a dual-functional M / Ti3C2T In step (1), the reducing atmosphere is hydrogen, hydrogen / nitrogen mixed gas or hydrogen / argon mixed gas, the volume ratio of hydrogen in the mixed gas is 5-20%, the annealing temperature is 150-400 ℃, and the annealing time is 2-8 h.

3. The bifunctional M / Ti3C2T x The application relates to a preparation method of a bifunctional M / Ti3C2T In step (2), the metal salt is one or more of nitrate, chloride, sulfate and acetate.

4. The bifunctional M / Ti3C2T x The application relates to a preparation method of a dual-functional M / Ti3C2T In step (2), the inert gas is argon.

5. The bifunctional M / Ti3C2T x The application relates to a preparation method of a bifunctional M / Ti3C2T In step (3), the zinc salt is zinc sulfate, zinc acetate or zinc nitrate; the indium salt is indium nitrate, indium chloride or indium sulfate; and the sulfur source is thioacetamide or thiourea.

6. The bifunctional M / Ti3C2T x The application relates to a preparation method of a dual-functional M / Ti3C2T In step (3), the surfactant is cetyltrimethylammonium bromide, polyvinylpyrrolidone, sodium citrate or cetyltrimethylammonium chloride.

7. The bifunctional M / Ti3C2T x A method for preparing a dual-functional M / Ti3C2T In step (1), the Ti3C2T x The powder is prepared by the following method: commercial Ti3AlC2 powder is added to an acid solution, etching treatment is carried out by continuously stirring in a 20-70 ℃ water bath for 12-48 h, and then Ti3C2T x powder is obtained by centrifugation, washing and drying; wherein Ti3AlC2: acid solution = (0.1-1) g: (5-30) mL; the acid solution is a 35-60 wt% hydrofluoric acid solution or a hydrochloric acid-lithium fluoride mixed solution, wherein the hydrochloric acid-lithium fluoride mixed solution refers to dissolving lithium fluoride powder in a 6-12 M hydrochloric acid solution, and the concentration of lithium fluoride in the mixed solution is 2-10 M.

8. A bifunctional M / Ti3C2T x / Zn3In2S6 composite photocatalyst, characterized in that: M is metal, which is one or more of ruthenium, platinum, palladium, cobalt and copper; the composite photocatalyst is in a single layer or a few layers of sheet Ti3C2T x is a substrate, and metal M nanodots are dispersed in Ti3C2T x , and Zn3In2S6nanosheets are in-situ grown on Ti3C2T x , wherein the mass ratio of Ti3C2T x is 2-20%, and the mass ratio of metal M is 0.2-1.5%; the dual function refers to that the M / Ti3C2T x / Zn3In2S6composite photocatalyst can simultaneously utilize photo-generated electrons and holes to realize hydrogen production and organic conversion combination; the dual function M / Ti3C2T x / Zn3In2S6composite photocatalyst is used for photocatalytic water splitting to produce hydrogen and simultaneously prepare DFF through selective oxidation of HMF.

9. The bifunctional M / Ti3C2T x The application relates to an application of a dual-function M / Ti3C2T M / Ti3C2T x The M / Ti3C2T x The M / Ti3C2T / Zn3In2S6 composite photocatalyst: HMF: water = (10-50) mg: (0.1-2) mmol: 100 mL.

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