Mo single-atom doped two-dimensional ultrathin SnS2 nanosheet catalyst, preparation method and application thereof

Abstract

This invention discloses a Mo single-atom-doped two-dimensional ultrathin SnS2 nanosheet catalyst and its preparation method. Crystalline tin tetrachloride is dissolved in a mixed solvent of ethanol and water. L-cysteine ​​is vigorously stirred and heated to melt. The tin tetrachloride solution is added to the heated and stirred L-cysteine ​​melt. The product is washed and dried to obtain the two-dimensional ultrathin SnS2 nanosheet catalyst. The two-dimensional ultrathin SnS2 nanosheets are dispersed in a mixture of water and ethanol. Ammonium molybdate and L-cysteine ​​are dissolved in water to form a complex. This complex solution is added to the SnS2 dispersion for a solvothermal reaction. The product is centrifuged, washed, and dried to obtain the Mo single-atom-doped two-dimensional ultrathin SnS2 nanosheet catalyst. This invention utilizes a solvent-melt method to obtain two-dimensional ultrathin SnS2 nanosheets with a thickness of approximately 2 nm, and further dops the surface of the two-dimensional ultrathin SnS2 nanosheets with Mo single atoms. The Mo single atoms either substitute for S in the outer layer or anchor to S vacancies. This invention enables the doping of single-atom catalysts on the surface of two-dimensional ultrathin nanosheets, which has the advantages of readily available raw materials, low reaction temperature, low cost, simple equipment, and easy large-scale preparation, and exhibits good catalytic reduction performance for CO2.

Description

Technical Field

[0001] This invention belongs to the field of nanocatalyst development technology, and relates to a Mo single-atom doped two-dimensional ultrathin SnS2 nanosheet catalyst, its preparation method, and its application. Background Technology

[0002] Climate change is a major challenge facing humanity today, and one of the main causes of global climate change is the increase in atmospheric carbon dioxide (CO2) caused by industrial production. At the same time, the continued consumption of traditional fossil fuels has led to a global energy crisis. To address climate change and the energy crisis, in addition to carbon capture and storage technologies, converting CO2 into renewable fuels or valuable chemicals through photocatalysis is an effective solution that simultaneously reduces CO2 emissions, utilizes sustainable solar energy, and yields high-value-added products.

[0003] Ultrathin two-dimensional nanomaterials are a new class of nanomaterials, possessing sheet-like structures with lateral dimensions greater than 100 nm or up to several micrometers, but only a single atom or a few atoms thick. They have attracted widespread attention due to their high surface-to-metal atom volume ratio, abundant coordinated unsaturated atoms providing more active sites for interfacial catalytic reactions, unique photoelectric properties, and surface-interfacial effects. Preparing SnS2 into an ultrathin two-dimensional structure helps to fully expose active sites such as high-valence metal ions and defects on the surface. Since Academician Zhang Tao of the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, proposed the concept of single-atom catalysis in 2011 (Nature Chemistry, 2011, 3 634-641), single-atom catalysts have rapidly gained widespread attention. Single-atom catalysts possess a single, coordinated unsaturated active site, exhibiting extremely high activity. Furthermore, a single atom exposes all active sites, achieving maximum atom utilization. Single-atom catalysts supported on three-dimensional supports have been widely reported. Compared to three-dimensional materials supporting single atoms, two-dimensional materials, with their open sides, often exhibit more coordinated unsaturation of doped single atoms, thus potentially achieving higher catalytic performance. The open structure on both sides of the two-dimensional plane allows for faster mass transfer than single atoms on three-dimensional supports, theoretically ensuring 100% exposure of single atoms to reactants and maximizing the catalytic reaction rate. The catalytic properties of the active sites are essentially caused by the strong electronic interactions between the doped single atoms and the two-dimensional host structure. However, as the size of single atoms decreases, the surface energy of metal particles increases dramatically, leading to spontaneous aggregation into larger metal particles. Therefore, the difficulty in preparing single-atom catalysts limits their further large-scale application. To realize the practical application of single-atom catalysts, it is urgent to develop simple and efficient methods for their preparation. Furthermore, SnS2, as an important n-type transition metal sulfide semiconductor material, also suffers from drawbacks such as high photogenerated carrier recombination rate, slow transfer rate, and low photocatalytic efficiency. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a Mo single-atom doped two-dimensional ultrathin SnS2 nanosheet catalyst, its preparation method, and its application, thereby solving the technical problems of high recombination rate of photogenerated carriers, low photocatalytic efficiency, easy aggregation of single atoms, and difficult preparation in the prior art.

[0005] This invention is achieved through the following technical solution:

[0006] A method for preparing a Mo single-atom-doped two-dimensional SnS2 nanosheet catalyst includes the following steps:

[0007] S1: Add tin tetrachloride solution to L-cysteine ​​melt and stir to react, thus obtaining two-dimensional SnS2 nanosheets;

[0008] S2: Ammonium molybdate and L-cysteine ​​are dissolved in water to form a Mo-L-cysteine ​​complex. The Mo-L-cysteine ​​complex is then added to the dispersion of the two-dimensional SnS2 nanosheets and subjected to a solvothermal reaction to obtain the Mo single-atom doped two-dimensional SnS2 nanosheet catalyst.

[0009] Preferably, the tin tetrachloride solution is prepared by dissolving tin tetrachloride in a mixed solvent of ethanol and water; the concentration of the tin tetrachloride solution is 0.003–0.01 mol / L; and the volume ratio of ethanol to water is (1–5):(5–1).

[0010] The L-cysteine ​​melt is prepared by heating L-cysteine ​​at 220–240°C and stirring until fully melted.

[0011] Preferably, in step S1, the molar ratio of tin tetrachloride to L-cysteine ​​is (0.07-0.1):1.

[0012] Preferably, in step S1, the process of adding tin tetrachloride solution to the L-cysteine ​​melt specifically involves injecting tin tetrachloride solution into the interior of the L-cysteine ​​melt while heating and stirring the L-cysteine ​​melt, wherein the injection rate of the tin tetrachloride solution is 1-3 mL / min.

[0013] Preferably, in step S1, the reaction temperature of tin tetrachloride and L-cysteine ​​is 220-240°C, the reaction time is 2-10 h, and the stirring rate during the reaction is 700-1500 rpm.

[0014] Preferably, in step S2, the dispersion of the two-dimensional SnS2 nanosheets is prepared by dispersing the two-dimensional SnS2 nanosheets in a mixture of water and ethanol; the concentration of the two-dimensional SnS2 nanosheet dispersion is 0.5 mg / mL.

[0015] Preferably, in step S2, the ratio of ammonium molybdate, L-cysteine ​​and water is 0.1 mmol:0.1 mmol:1 mL.

[0016] Preferably, in step S2, the reaction temperature is 160–180°C and the reaction time is 10–24 h.

[0017] A Mo single-atom doped two-dimensional SnS2 nanosheet catalyst was prepared by the method described above; the average thickness of the two-dimensional SnS2 nanosheet was 2 nm.

[0018] The above-mentioned application of a Mo single-atom doped two-dimensional SnS2 nanosheet catalyst in the field of carbon dioxide catalytic reduction.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects:

[0020] This invention provides a method for preparing Mo single-atom-doped two-dimensional SnS2 nanosheet catalysts. The method innovatively utilizes a solvent-melt method to prepare two-dimensional ultrathin SnS2 nanosheets. The ultrathin two-dimensional nanostructure facilitates the full exposure of surface active sites and overcomes the drawbacks of conventional solvothermal methods for preparing two-dimensional SnS2, such as the need for high temperatures and pressures, the reliance on surfactants for guiding effects, cumbersome processes, difficult waste disposal, and challenges in large-scale preparation. Furthermore, by anchoring Mo single atoms on the SnS2 surface using a low-concentration Mo-L-cysteine ​​complex, a Mo single-atom-doped two-dimensional ultrathin SnS2 nanosheet catalyst is prepared, achieving single-atom catalyst doping on the surface of the two-dimensional ultrathin nanosheet catalyst. This invention is simple to operate, requires simple equipment, uses readily available raw materials, operates at low temperatures, has low costs, and is easy to scale up, avoiding steps such as high-temperature calcination or hydrogen reduction, and providing mild reaction conditions. Two-dimensional ultrathin SnS2 materials doped with Mo single atoms exhibit a synergistic effect in their activity due to the newly integrated electronic states. The unique geometry and electronic structure of the two-dimensional material can modulate the catalytic performance of the confined single atom, while the confined single atom can, in turn, influence the intrinsic activity of the two-dimensional material. The presence of active sites on the metal single atom and the interaction between the single atom and the two-dimensional ultrathin nanosheet catalyst enable highly efficient photocatalytic carbon dioxide reduction. Preparing SnS2 into an ultrathin two-dimensional structure fully exposes the high-valence metal ions and defects on the surface, while the doping with Mo single atoms accelerates mass transfer in the ultrathin two-dimensional sheet structure and makes the single atom more coordinate-unsaturated. The combination of these two factors may lead to even higher catalytic performance.

[0021] Furthermore, the tin tetrachloride solution is prepared by dissolving tin tetrachloride in a mixed solvent of ethanol and water; the concentration of the tin tetrachloride solution is 0.003–0.01 mol / L, which allows the material to dissolve fully; the volume ratio of ethanol to water is (1–5):(5–1), which allows the solvent to evaporate smoothly during the solvent-melt reaction; the L-cysteine ​​melt is prepared by heating L-cysteine ​​at 220–240°C and stirring until fully melted, which allows the material to form a molten state better.

[0022] Furthermore, the molar ratio of tin tetrachloride to L-cysteine ​​is (0.07-0.1):1, which allows the tin source to fully participate in the reaction and effectively controls the reaction rate of both at the molecular level, thus inhibiting the growth of SnS2 into thicker nanosheets.

[0023] Furthermore, in step S1, during the process of adding the tin tetrachloride solution to the L-cysteine ​​melt, the addition rate of the tin tetrachloride solution is 1-3 mL / min. This slow addition rate can, on the one hand, slow down the rapid reaction between the tin source and the sulfur source, effectively control the reaction rate of both, inhibit the growth of SnS2 nanosheets in the longitudinal height, and promote the formation of two-dimensional ultrathin nanosheets. On the other hand, it can also reduce the crystallinity of the nanosheets, promote the formation of surface defect structures, and help construct active sites.

[0024] Furthermore, in step S1, the reaction temperature of tin tetrachloride and L-cysteine ​​is 220–240 °C, the reaction time is 2–10 h, and the stirring rate is 700–1500 rpm. The relatively low reaction temperature and fast stirring rate can, on the one hand, slow down the rapid reaction of the tin source and sulfur source, effectively control the reaction rate of both, inhibit the growth of SnS2 nanosheets in the longitudinal height, and promote the formation of two-dimensional ultrathin nanosheets. On the other hand, it can also reduce the crystallinity of the nanosheets, promote the formation of surface defect structures, and help construct active sites.

[0025] Furthermore, in step S2, the dispersion of the two-dimensional SnS2 nanosheets is prepared by dispersing the two-dimensional SnS2 nanosheets in a mixture of water and ethanol. The concentration of the two-dimensional SnS2 nanosheet dispersion is 0.5 mg / mL, which allows the two-dimensional ultrathin SnS2 nanosheets to be fully dispersed and facilitates the uniform doping of Mo single atoms.

[0026] Furthermore, in step S2, the ratio of ammonium molybdate, L-cysteine, and water is 0.1 mmol:0.1 mmol:1 mL. This low concentration of the Mo-L-cysteine ​​complex allows Mo atoms to be anchored to defects in SnS2. If the concentration is too high, the generated Mo atoms will induce self-nucleation. During the solvothermal process, due to the high molecular affinity of defect vacancies, especially for thiol molecules, the Mo-L-cysteine ​​complex fills the sulfur vacancies on the SnS2 surface, effectively achieving the bonding of Mo with the two-dimensional SnS2 nanosheets.

[0027] Furthermore, in step S2, the solvothermal reaction process is carried out at a reaction temperature of 160–180°C and a reaction time of 10–24 h, which can both preserve the two-dimensional ultrathin nanosheet structure of SnS2 and promote the generation of Mo single atoms. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic flowchart of a method for preparing a Mo single-atom doped two-dimensional SnS2 nanosheet catalyst according to the present invention.

[0030] Figure 2 This is the X-ray diffraction (XRD) pattern of the Mo single-atom doped two-dimensional ultrathin SnS2 prepared in Example 1 of this invention.

[0031] Figure 3 The images are scanning electron microscope (SEM) images of two-dimensional ultrathin SnS2 nanosheets doped with Mo single atoms; where (a) is a two-dimensional ultrathin SnS2 nanosheet and (b) is a SnS2 nanosheet doped with Mo single atoms.

[0032] Figure 4 This is an atomic force microscope (AFM) image of the Mo single-atom doped two-dimensional ultrathin SnS2 nanosheet catalyst prepared in Example 1 of this invention;

[0033] Figure 5 The graphs show the photocatalytic reduction performance of CO2 on two-dimensional ultrathin SnS2 nanosheets and Mo single-atom-doped two-dimensional ultrathin SnS2 nanosheets prepared in Example 1 of this invention. Detailed Implementation

[0034] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0035] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0036] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0037] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0038] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0039] like Figure 1 As shown, this invention provides a method for preparing a Mo single-atom-doped two-dimensional SnS2 nanosheet catalyst, comprising the following steps:

[0040] S1: Add crystalline tin tetrachloride to a mixed solvent of ethanol and water, and dissolve it completely to obtain a tin tetrachloride solution with a concentration of 0.003-0.01 mol / L, wherein the volume ratio of ethanol to water is (1-5):(5-1), and the tin tetrachloride here can be crystalline tin tetrachloride; add L-cysteine ​​to a high-temperature resistant crucible, heat at 220-240℃, and stir until fully melted to obtain an L-cysteine ​​melt;

[0041] A tin tetrachloride solution is added to a heated and stirred L-cysteine ​​molten solution at a rate of 1–3 mL / min. In a preferred embodiment, the tin tetrachloride solution is injected into the interior of the L-cysteine ​​molten solution while it is being heated and stirred. This significantly increases the contact area between the tin tetrachloride solution and the L-cysteine ​​molten solution, improving the uniformity of the reaction and resulting in a product with good homogeneity. The molar ratio of tin tetrachloride to L-cysteine ​​is (0.07–0.1):1. The reaction is continued with heating and stirring at a temperature of 220–240 °C for 2–10 h, and a stirring rate of 700–1500 rpm. The product is then washed three times with ethanol and deionized water, and dried to obtain two-dimensional SnS2 nanosheets. Specifically, this step can be achieved by adding the tin tetrachloride solution to the heated and stirred L-cysteine ​​molten solution using a disposable syringe.

[0042] S2: Two-dimensional SnS2 nanosheets were prepared by dispersing them in a mixture of water and ethanol; the concentration of the two-dimensional SnS2 nanosheet dispersion was 0.5 mg / mL. Ammonium molybdate and L-cysteine ​​were dissolved in water to form a Mo-L-cysteine ​​complex, wherein the ratio of ammonium molybdate, L-cysteine, and water was 0.1 mmol:0.1 mmol:1 mL. The Mo-L-cysteine ​​complex was then added to the two-dimensional SnS2 nanosheet dispersion, and a solvothermal reaction was carried out at 160–180 °C for 10–24 h to obtain a Mo single-atom-doped two-dimensional SnS2 nanosheet catalyst. The average thickness of the obtained two-dimensional SnS2 nanosheets was 2 nm.

[0043] This invention discloses a Mo single-atom-doped two-dimensional ultrathin SnS2 nanosheet catalyst and its preparation method. Crystalline tin tetrachloride is dissolved in a mixed solvent of ethanol and water. L-cysteine ​​is vigorously stirred and heated to melt. The tin tetrachloride solution is added to the heated and stirred L-cysteine ​​melt. The product is washed and dried to obtain the two-dimensional ultrathin SnS2 nanosheet catalyst. The two-dimensional ultrathin SnS2 nanosheets are dispersed in a mixture of water and ethanol. Ammonium molybdate and L-cysteine ​​are dissolved in water to form a complex. This complex solution is added to the SnS2 dispersion for a solvothermal reaction. The product is centrifuged, washed, and dried to obtain the Mo single-atom-doped two-dimensional ultrathin SnS2 nanosheet catalyst. This invention utilizes a solvent-melt method to obtain two-dimensional ultrathin SnS2 nanosheets with a thickness of approximately 2 nm, and further dops the surface of the two-dimensional ultrathin SnS2 nanosheets with Mo single atoms. The Mo single atoms either substitute for S in the outer layer or are anchored at S vacancies. This invention achieves the doping of single-atom catalysts on the surface of two-dimensional ultrathin nanosheets, offering advantages such as readily available raw materials, low reaction temperature, low cost, simple equipment, and ease of large-scale preparation. It also exhibits excellent catalytic reduction performance for CO2. This invention utilizes a simple and efficient synthesis method, first preparing two-dimensional ultrathin SnS2 nanosheets using a solvent-melt method, and then further doping the SnS2 surface with Mo single atoms. Due to the presence of active sites on the metal single atoms and the interaction between the single atoms and the two-dimensional ultrathin nanosheets, highly efficient photocatalytic carbon dioxide reduction can be achieved.

[0044] To evaluate the catalytic performance of the Mo single-atom doped two-dimensional SnS2 nanosheet catalyst obtained in this invention, the photocatalytic reduction performance of the prepared catalyst for CO2 was evaluated in a stainless steel reactor. The reaction chamber had a volume of 200 mL, with a stainless steel bottom and sides, and a quartz window (50 mm in diameter) on the top surface. 0.01 g of catalyst was uniformly dispersed in 3 mL of deionized water and then poured into a 60 mm diameter petri dish to dry, ensuring the sample evenly covered the petri dish. The petri dish was then placed in the reaction chamber, and 100 μL of deionized water was added dropwise. The reaction chamber was rinsed six times with high-purity carbon dioxide (99.999%). Subsequently, a certain amount of high-purity carbon dioxide was injected into the reaction chamber, maintaining a pressure of 0.1 MPa. The reaction was induced by irradiating the sample surface through the quartz window using a xenon lamp light source. The products were detected using a gas chromatograph (7890B, Agilent, USA). The yields of CH4 and CO were detected using a flame ionization detector (FID). The CO2 reduction product production rate was expressed as μmol / g. -1 h -1 express.

[0045] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0046] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0047] Example 1

[0048] (1) Prepare 30 mL of a mixed solvent with a volume ratio of ethanol and water of 1:2. Weigh an appropriate amount of crystalline tin tetrachloride and add it to the mixed solvent to dissolve it completely. The concentration of the tin tetrachloride solution is 0.005 mol / L. Add L-cysteine ​​to a high-temperature resistant crucible, add a high-temperature resistant magnetic ball, and heat at 220°C with vigorous stirring until completely melted.

[0049] (2) The above tin tetrachloride solution was added to the L-cysteine ​​melt under heating and stirring using a disposable syringe at an injection rate of 1 mL / min. The mixture was stirred vigorously. The molar ratio of tin tetrachloride to L-cysteine ​​was 0.075:1. The product was obtained after reacting at 220℃ for 4 h. The product was then washed three times with ethanol and deionized water, and dried to obtain a two-dimensional ultrathin SnS2 nanosheet catalyst.

[0050] (3) Prepare 50 mL of a mixture of deionized water and ethanol in a volume ratio of 1:1. Weigh 0.025 g of two-dimensional ultrathin SnS2 nanosheets and disperse them in the mixture to prepare a dispersion with a concentration of 0.5 mg / mL. Add 0.1 mmol of ammonium molybdate and 0.1 mmol of L-cysteine ​​to 1 mL of water to dissolve and form a complex. Then add the complex solution to the SnS2 dispersion and carry out a solvothermal reaction at 160 °C for 10 h. Wash the product three times with ethanol and deionized water respectively, and dry it to obtain a Mo single-atom doped two-dimensional ultrathin SnS2 nanosheet catalyst.

[0051] XRD analysis was performed on the Mo single-atom-doped two-dimensional ultrathin SnS2 nanosheet catalyst, and the results are as follows: Figure 2 As shown, from Figure 2It can be seen that the diffraction peaks of the Mo single-atom-doped two-dimensional ultrathin SnS2 nanosheet catalyst obtained in Example 1 are consistent with the diffraction peaks of JSPDS card No. 23-2677 in the database, indicating that SnS2 has been successfully synthesized. Due to the low doping amount of Mo single atoms, no Mo diffraction peaks were detected in the XRD pattern.

[0052] SEM analysis was performed on two-dimensional ultrathin SnS2 nanosheets and Mo single-atom-doped two-dimensional ultrathin SnS2 nanosheet catalysts. The results are as follows: Figure 3 As shown, both the SnS2 nanosheets and the Mo single-atom-doped SnS2 nanosheets obtained in Example 1 are two-dimensional ultrathin nanosheets.

[0053] The thickness of Mo single-atom-doped two-dimensional ultrathin SnS2 nanosheets was measured using atomic force microscopy, and the results are as follows: Figure 4 As shown in the figure, the thickness of the prepared nanosheets is approximately 2 nm.

[0054] Photocatalytic reduction of CO2 was tested on two-dimensional ultrathin SnS2 nanosheets and Mo single-atom-doped two-dimensional ultrathin SnS2 nanosheet catalysts. The results are as follows: Figure 5 As shown, the CO yield of Mo single-atom doped two-dimensional ultrathin SnS2 nanosheets was found to be 8.48 μmol / g. -1 h -1 It is a pure two-dimensional ultrathin SnS2 nanosheet (0.56 μmol g). -1 h -1 The yield of CH4 was 15.1 times that of 1,800 μmol / g, with a yield of 4.80 μmol / g. -1 h -1 It is a pure two-dimensional ultrathin SnS2 nanosheet (0.13 μmol g). -1 h -1 The concentration of Mo was 36.9 times that of catalytic performance, demonstrating that the introduction of Mo significantly improves catalytic performance.

[0055] Example 2

[0056] (1) Prepare 30 mL of a mixed solvent of ethanol and water in a volume ratio of 1:1. Weigh an appropriate amount of crystalline tin tetrachloride and add it to the mixed solvent to dissolve it completely. The concentration of the tin tetrachloride solution is 0.005 mol / L. Add L-cysteine ​​to a high-temperature resistant crucible, add a high-temperature resistant magnetic ball, and heat at 230°C with vigorous stirring until completely melted.

[0057] (2) The above tin tetrachloride solution was added to the L-cysteine ​​melt under heating and stirring using a disposable syringe at an injection rate of 3 mL / min. The mixture was stirred vigorously. The molar ratio of tin tetrachloride to L-cysteine ​​was 0.08:1. The product was obtained after reacting at 230℃ for 6 h. The product was then washed three times with ethanol and deionized water, and dried to obtain a two-dimensional ultrathin SnS2 nanosheet catalyst.

[0058] (3) Prepare 50 mL of a mixture of deionized water and ethanol in a volume ratio of 1:1. Weigh 0.025 g of two-dimensional ultrathin SnS2 nanosheets and disperse them in the mixture to prepare a dispersion with a concentration of 0.5 mg / mL. Add 0.1 mmol of ammonium molybdate and 0.1 mmol of L-cysteine ​​to 1 mL of water to dissolve and form a complex. Then add the complex solution to the SnS2 dispersion and carry out a solvothermal reaction at 160 °C for 12 h. Wash the product three times with ethanol and deionized water respectively, and dry it to obtain a Mo single-atom doped two-dimensional ultrathin SnS2 nanosheet catalyst.

[0059] The resulting Mo single-atom-doped two-dimensional ultrathin SnS2 nanosheets were approximately 2 nm thick, and the CO yield in the photocatalytic reduction of CO2 test was 7.81 μmol g. -1 h -1 It is a pure two-dimensional ultrathin SnS2 nanosheet (0.56 μmol g). -1 h -1 The yield of CH4 was 13.9 times that of 13.9 μmol g, with a yield of 3.20 μmol g. -1 h -1 It is a pure two-dimensional ultrathin SnS2 nanosheet (0.13 μmol g). -1 h -1 The concentration of Mo was 24.6 times that of catalytic performance, demonstrating that the introduction of Mo significantly improves catalytic performance.

[0060] Example 3

[0061] (1) Prepare 30 mL of a mixed solvent with a volume ratio of ethanol and water of 2:1. Weigh an appropriate amount of crystalline tin tetrachloride and add it to the mixed solvent to dissolve it completely. The concentration of the tin tetrachloride solution is 0.003 mol / L. Add L-cysteine ​​to a high-temperature resistant crucible, add a high-temperature resistant magnetic ball, and heat at 220°C with vigorous stirring until completely melted.

[0062] (2) The above tin tetrachloride solution was added to the heated and stirred L-cysteine ​​melt using a disposable syringe at an injection rate of 2 mL / min. The mixture was stirred vigorously. The molar ratio of tin tetrachloride to L-cysteine ​​was 0.07:1. The product was obtained after reacting at 220℃ for 2 h. The product was then washed three times with ethanol and deionized water, and dried to obtain a two-dimensional ultrathin SnS2 nanosheet catalyst.

[0063] (3) Prepare 50 mL of a mixture of deionized water and ethanol in a volume ratio of 1:1. Weigh 0.025 g of two-dimensional ultrathin SnS2 nanosheets and disperse them in the mixture to prepare a dispersion with a concentration of 0.5 mg / mL. Add 0.1 mmol of ammonium molybdate and 0.1 mmol of L-cysteine ​​to 1 mL of water to dissolve and form a complex. Then add the complex solution to the SnS2 dispersion and carry out a solvothermal reaction at 170 °C for 24 h. Wash the product three times with ethanol and deionized water respectively, and dry it to obtain a Mo single-atom doped two-dimensional ultrathin SnS2 nanosheet catalyst.

[0064] The resulting Mo single-atom-doped two-dimensional ultrathin SnS2 nanosheets were approximately 2 nm thick, and the CO yield in the photocatalytic reduction of CO2 test was 8.12 μmol g. -1 h -1 It is a pure two-dimensional ultrathin SnS2 nanosheet (0.56 μmol g). -1 h -1 The yield of CH4 was 14.5 times that of 14.5 μmol g, with a yield of 3.05 μmol g. -1 h -1 It is a pure two-dimensional ultrathin SnS2 nanosheet (0.13 μmol g). -1 h -1 The concentration of Mo was 23.5 times that of catalytic performance, demonstrating that the introduction of Mo significantly improves catalytic performance.

[0065] Example 4

[0066] (1) Prepare 30 mL of a mixed solvent with a volume ratio of ethanol and water of 1:5. Weigh an appropriate amount of crystalline tin tetrachloride and add it to the mixed solvent to dissolve it completely. The concentration of the tin tetrachloride solution is 0.01 mol / L. Add L-cysteine ​​to a high-temperature resistant crucible, add a high-temperature resistant magnetic ball, and heat at 240°C with vigorous stirring until completely melted.

[0067] (2) The above tin tetrachloride solution was added to the heated and stirred L-cysteine ​​melt using a disposable syringe at an injection rate of 2 mL / min. The mixture was stirred vigorously. The molar ratio of tin tetrachloride to L-cysteine ​​was 0.1:1. The product was obtained after reacting at 240℃ for 10 h. The product was then washed three times with ethanol and deionized water, and dried to obtain a two-dimensional ultrathin SnS2 nanosheet catalyst.

[0068] (3) Prepare 50 mL of a mixture of deionized water and ethanol in a volume ratio of 1:1. Weigh 0.025 g of two-dimensional ultrathin SnS2 nanosheets and disperse them in the mixture to prepare a dispersion with a concentration of 0.5 mg / mL. Add 0.1 mmol of ammonium molybdate and 0.1 mmol of L-cysteine ​​to 1 mL of water to dissolve and form a complex. Then add the complex solution to the SnS2 dispersion and carry out a solvothermal reaction at 180 °C for 10 h. Wash the product three times with ethanol and deionized water respectively, and dry it to obtain a Mo single-atom doped two-dimensional ultrathin SnS2 nanosheet catalyst.

[0069] The resulting Mo single-atom-doped two-dimensional ultrathin SnS2 nanosheets were approximately 2 nm thick, and the CO yield in the photocatalytic reduction of CO2 test was 7.20 μmol / g. -1 h -1 It is a pure two-dimensional ultrathin SnS2 nanosheet (0.56 μmol g). -1 h -1 The yield of CH4 was 12.9 times that of 12.9 μmol g, with a yield of 2.65 μmol g. -1 h -1 The molar content is 20.4 times that of pure two-dimensional ultrathin SnS2 nanosheets (0.13 μmol g⁻¹ h⁻¹), demonstrating that the introduction of Mo significantly improves catalytic performance.

[0070] Example 5

[0071] (1) Prepare 30 mL of a mixed solvent with a volume ratio of ethanol and water of 5:1. Weigh an appropriate amount of crystalline tin tetrachloride and add it to the mixed solvent to dissolve it completely. The concentration of the tin tetrachloride solution is 0.007 mol / L. Add L-cysteine ​​to a high-temperature resistant crucible, add a high-temperature resistant magnetic ball, and heat at 230°C with vigorous stirring until completely melted.

[0072] (2) The above tin tetrachloride solution was added to the L-cysteine ​​melt under heating and stirring using a disposable syringe at an injection rate of 1 mL / min. The mixture was stirred vigorously. The molar ratio of tin tetrachloride to L-cysteine ​​was 0.09:1. The product was obtained after reacting at 230℃ for 8 h. The product was then washed three times with ethanol and deionized water, and dried to obtain a two-dimensional ultrathin SnS2 nanosheet catalyst.

[0073] (3) Prepare 50 mL of a mixture of deionized water and ethanol in a volume ratio of 1:1. Weigh 0.025 g of two-dimensional ultrathin SnS2 nanosheets and disperse them in the mixture to prepare a dispersion with a concentration of 0.5 mg / mL. Add 0.1 mmol of ammonium molybdate and 0.1 mmol of L-cysteine ​​to 1 mL of water to dissolve and form a complex. Then add the complex solution to the SnS2 dispersion and carry out a solvothermal reaction at 160 °C for 16 h. Wash the product three times with ethanol and deionized water respectively, and dry it to obtain a Mo single-atom doped two-dimensional ultrathin SnS2 nanosheet catalyst.

[0074] The resulting Mo single-atom-doped two-dimensional ultrathin SnS2 nanosheets were approximately 2 nm thick, and the CO yield in the photocatalytic reduction of CO2 test was 7.62 μmol / g. -1 h -1 It is a pure two-dimensional ultrathin SnS2 nanosheet (0.56 μmol g). -1 h -1 The yield of CH4 was 13.6 times that of 13.6 μmol g, with a yield of 3.90 μmol g. -1 h -1 It is a pure two-dimensional ultrathin SnS2 nanosheet (0.13 μmol g). -1 h -1 The result shows that the catalytic performance is 30 times that of the previous one, proving that the introduction of Mo has a significant effect on catalytic performance.

[0075] This invention utilizes a solvent-melt method to obtain two-dimensional ultrathin SnS2 nanosheets with a thickness of approximately 2 nm, overcoming the drawbacks of conventional solvothermal methods for preparing two-dimensional SnS2, such as the need for high temperatures and pressures, the reliance on surfactants for guiding effects, cumbersome processes, difficult waste disposal, and challenges in large-scale preparation. Further doping with Mo single atoms, where Mo single atoms substitute for S in the outer layer or anchor on S vacancies, avoids steps such as high-temperature calcination or hydrogen reduction, resulting in milder reaction conditions. The integration of single-atom-doped two-dimensional materials leads to a mutually beneficial relationship in their activity; that is, the unique geometry and electronic structure of the two-dimensional material can modulate the catalytic performance of the confined single atom, while the confined single atom can, in turn, influence the intrinsic activity of the two-dimensional material. Due to the presence of active sites on the metal single atom and the interaction between the single atom and the two-dimensional ultrathin nanosheet, highly efficient photocatalytic carbon dioxide reduction can be achieved.

[0076] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a Mo single-atom-doped two-dimensional SnS2 nanosheet catalyst, characterized in that, Includes the following steps: S1: Add tin tetrachloride solution to L-cysteine ​​melt and stir to react, thus obtaining two-dimensional SnS2 nanosheets; S2: Ammonium molybdate and L-cysteine ​​are dissolved in water to form a Mo-L-cysteine ​​complex. The Mo-L-cysteine ​​complex is then added to the dispersion of the two-dimensional SnS2 nanosheets and subjected to a solvothermal reaction to obtain the Mo single-atom doped two-dimensional SnS2 nanosheet catalyst. The tin tetrachloride solution is prepared by dissolving tin tetrachloride in a mixed solvent of ethanol and water; the concentration of the tin tetrachloride solution is 0.003~0.01mol / L; the volume ratio of ethanol to water is (1~5):(5~1); The average thickness of the two-dimensional SnS2 nanosheets is 2 nm; In step S1, adding tin tetrachloride solution to the L-cysteine ​​melt specifically involves injecting tin tetrachloride solution into the interior of the L-cysteine ​​melt while heating and stirring the L-cysteine ​​melt, with the injection rate of tin tetrachloride solution being 1~3 mL / min. In step S1, the reaction temperature of tin tetrachloride and L-cysteine ​​is 220~240℃, the reaction time is 2~10h, and the stirring rate during the reaction is 700~1500rpm. In step S2, the dispersion of the two-dimensional SnS2 nanosheets is prepared by dispersing the two-dimensional SnS2 nanosheets in a mixture of water and ethanol. In step S2, the ratio of ammonium molybdate, L-cysteine, and water is 0.1 mmol:0.1 mmol:1 mL; In step S2, the reaction temperature is 160~180℃ and the reaction time is 10~24 h.

2. The method for preparing a Mo single-atom-doped two-dimensional SnS2 nanosheet catalyst according to claim 1, characterized in that, The L-cysteine ​​melt is prepared by heating L-cysteine ​​at 220~240℃ and stirring until it is fully melted.

3. The method for preparing a Mo single-atom-doped two-dimensional SnS2 nanosheet catalyst according to claim 1, characterized in that, In step S1, the molar ratio of tin tetrachloride to L-cysteine ​​is (0.07~0.1):

1.

4. The method for preparing a Mo single-atom-doped two-dimensional SnS2 nanosheet catalyst according to claim 1, characterized in that, The concentration of the two-dimensional SnS2 nanosheet dispersion is 0.5 mg / mL.

5. A Mo single-atom-doped two-dimensional SnS2 nanosheet catalyst, characterized in that, The two-dimensional SnS2 nanosheets are prepared by the method described in any one of claims 1 to 4; the average thickness of the two-dimensional SnS2 nanosheets is 2 nm.

6. The application of the Mo single-atom doped two-dimensional SnS2 nanosheet catalyst as described in claim 5 in the field of carbon dioxide catalytic reduction.

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