Cobalt-doped double-metal sulfide nanosheets, methods of making and using the same

Abstract

The application relates to the field of carbon dioxide resource utilization, in particular to a cobalt-doped double-metal sulfide nanosheet, a preparation method and application thereof. The preparation method of the double-metal sulfide nanosheet comprises the following steps: according to the molar ratio of Cu + :In 3+ : S being (0.5-1.5):(0.5-1.5):(2-3), fully dissolving Cu + source, In 3+ source and sublimated sulfur in triethylene glycol to obtain a mixed solution; moving the mixed solution into a high-pressure reaction kettle, sealing, reacting at 200 DEG C for 48 h, naturally cooling to room temperature, centrifugal separation, washing the precipitate with ethanol and water for several times, vacuum drying to obtain a double-metal sulfide nanosheet infrared photocatalyst, CuInS2 nanosheet. The double-metal sulfide nanosheet infrared photocatalyst prepared by the application can be used to catalytically reduce CO2 to generate C2 products under normal temperature and pressure by using infrared light.

Description

Technical Field

[0001] This invention relates to the field of carbon dioxide resource utilization, and particularly to a cobalt-doped bimetallic sulfide nanosheet, its preparation method and application. Background Technology

[0002] Utilizing solar energy to convert CO2 and H2O into carbon-based fuels is of paramount importance, not only for addressing environmental pollution but also for alleviating the energy crisis. However, the photocatalytic reduction efficiency of CO2 remains low, partly due to insufficient solar energy utilization. Current research on CO2 photocatalysis primarily focuses on the ultraviolet and visible light ranges, with few reports on infrared-driven CO2 reduction. In infrared photocatalysis, the band gap typically needs to be >1.8 eV, and such catalysts are not conducive to the utilization of infrared light. Therefore, traditional single-component photocatalysts struggle to achieve infrared-driven CO2 reduction without sacrificial agents. Furthermore, all current infrared-driven CO2 reduction methods only produce C1 products, severely impacting their economic viability. For example, existing technology reports that FeCoS2 nanosheets can catalytically reduce CO2 to C2H4 under visible light; however, they cannot effectively absorb and utilize infrared light, thus failing to achieve infrared-driven photocatalytic reduction of CO2 to C2H4 and other C2 products. Currently, there are no reports on the preparation of bimetallic sulfide nanosheets for infrared photocatalytic CO2 reduction. Summary of the Invention

[0003] Technical issues:

[0004] A method for preparing a bimetallic sulfide nanosheet infrared photocatalyst is provided. The prepared bimetallic sulfide nanosheet infrared photocatalyst can reduce CO2 to C2 products by infrared photocatalysis at room temperature and pressure.

[0005] Technical concept:

[0006] This invention designs and successfully prepares a cobalt-doped CuInS2 nanosheet with good structure and chemical stability. In the cobalt-doped CuInS2 nanosheet, Cu and In can provide dual active sites carrying different charges. Using a small amount of cobalt doping in CuInS2 nanosheet can further enhance the charge asymmetry on the active sites. The successful construction of asymmetric metal active sites not only overcomes the technical problem of the inability to generate C2 products from the infrared photocatalytic reduction of CO2, but also achieves a high C2H4 yield due to the increased charge asymmetry of the active sites.

[0007] Technical solution:

[0008] On the one hand, a method for preparing a bimetallic sulfide nanosheet infrared photocatalyst is provided, which includes the following steps: according to Cu + In 3+ The molar ratio of S is (0.5~1.5):(0.5~1.5):(2~3), and Cu... + Source, In 3+ Source and sublimed sulfur were fully dissolved in triethylene glycol and mixed to obtain a mixed solution. The mixed solution was transferred into a high-pressure reactor, sealed, and reacted at 200°C for 48 hours. After natural cooling to room temperature, the mixture was centrifuged, and the precipitate was washed several times with ethanol and water and dried under vacuum to obtain a bimetallic sulfide nanosheet infrared photocatalyst—CuInS2 nanosheets.

[0009] On the other hand, a method for preparing a cobalt-doped bimetallic sulfide nanosheet infrared photocatalyst is provided, comprising the following steps: according to Co... 2+ Cu + In 3+ The molar ratio of S is (0.01~0.05):(0.5~1.5):(0.5~1.5):(2~3), and Co is... 2+ Source, Cu + Source, In 3+ Source and sublimed sulfur were fully dissolved in triethylene glycol and mixed to obtain a mixed solution. The mixed solution was transferred into a high-pressure reactor, sealed, and reacted at 200°C for 48 hours. After natural cooling to room temperature, the mixture was centrifuged, and the precipitate was washed several times with ethanol and water and dried under vacuum to obtain a cobalt-doped bimetallic sulfide nanosheet infrared photocatalyst—cobalt-doped CuInS2 nanosheets.

[0010] In some embodiments, the amount of triethylene glycol used in the mixed solution is 20 to 100 mL.

[0011] In some embodiments, Cu + In 3+ The molar ratio of S to S is 1:1:2.5.

[0012] In some embodiments, Co 2+ Cu + In 3+ The molar ratio of S to S is 0.04:1:1:2.5.

[0013] In some embodiments, the Cu + The source is cuprous chloride.

[0014] In some embodiments, the In 3+ The source is indium chloride tetrahydrate.

[0015] In some embodiments, the Co 2+The source is at least one of cobalt chloride hexahydrate, cobalt nitrate, or cobalt sulfate.

[0016] On the other hand, an infrared photocatalyst prepared by the aforementioned method is provided.

[0017] On the other hand, the application of the aforementioned infrared photocatalyst in the infrared photocatalytic reduction of carbon dioxide to ethylene is provided.

[0018] In some embodiments, the aforementioned infrared photocatalyst is used as the photocatalyst, and water and carbon dioxide are used as raw materials to reduce carbon dioxide to ethylene and carbon monoxide at room temperature and pressure using infrared photocatalysis.

[0019] Beneficial effects:

[0020] (1) This invention designs and successfully prepares a cobalt-doped CuInS2 nanosheet with good structure and chemical stability. In the cobalt-doped CuInS2 nanosheet, Cu and In can provide dual active sites carrying different charges. Using a small amount of cobalt doping in CuInS2 nanosheet can further enhance the charge asymmetry on the active sites. The successful construction of asymmetric metal active sites not only overcomes the technical problem that infrared photocatalytic reduction of CO2 cannot generate C2 products, but also obtains a high C2H4 yield due to the increased charge asymmetry of the active sites;

[0021] (2) This invention provides a simple and easy method for preparing bimetallic sulfide nanosheet infrared photocatalysts and cobalt-doped bimetallic sulfide nanosheet infrared photocatalysts, which utilizes a hydrothermal method to controllably synthesize CuInS2 nanosheets or cobalt-doped CuInS2 nanosheets in one step.

[0022] (3) This invention has found that undoped CuInS2 nanosheets can achieve infrared photocatalytic reduction of carbon dioxide to ethylene under ambient temperature and pressure with water as a reducing agent: undoped CuInS2 nanosheets, under ambient temperature and pressure and infrared light irradiation with water as a reducing agent, can catalytically reduce CO2 to carbon monoxide and ethylene, with an ethylene yield of approximately 1.17 μmol g. -1 h -1 The ethylene selectivity was approximately 32.86%. Compared to undoped CuInS2 nanosheets, cobalt-doped CuInS2 nanosheets exhibited superior infrared photocatalytic reduction of carbon dioxide to ethylene: under ambient temperature and pressure and infrared irradiation, cobalt-doped CuInS2 nanosheets, using water as a reducing agent, could catalytically reduce CO2 to carbon monoxide and ethylene, with an ethylene production rate of approximately 5.06 μmol g. -1 h -1 The C2H4 selectivity is approximately 49.13%;

[0023] (3) Based on the infrared photocatalyst of the present invention and the infrared photocatalytic reduction method of the present invention, only water is needed as a reducing agent. At room temperature and pressure, CO2 can be catalytically reduced to carbon monoxide and ethylene by infrared light. The ethylene production efficiency is high, the stability is high, and it is environmentally friendly and sustainable. Compared with the traditional visible light driven photocatalyst, the energy utilization rate is higher and the economic efficiency is higher. Attached Figure Description

[0024] Figure 1 XRD diffraction patterns of different samples: undoped CuInS2 nanosheets a prepared in Example 2 and cobalt-doped CuInS2 nanosheets b prepared in Example 1;

[0025] Figure 2 Microscopic images of different samples: A, Transmission electron microscopy (TEM) image of undoped CuInS2 nanosheets prepared in Example 2; B, High-resolution transmission electron microscopy (HRTEM) image of undoped CuInS2 nanosheets prepared in Example 2; C, Transmission electron microscopy (TEM) image of cobalt-doped CuInS2 nanosheets prepared in Example 1; and D, High-resolution transmission electron microscopy (HRTEM) image of cobalt-doped CuInS2 nanosheets prepared in Example 1.

[0026] Figure 3 X-ray photoelectron spectroscopy (XPS) of undoped CuInS2 nanosheets a prepared in Example 2 and cobalt-doped CuInS2 nanosheets b prepared in Example 1: A, Co spectrum; B, S spectrum; C, In spectrum; D, Cu spectrum.

[0027] Figure 4 The graph shows the yields of carbon monoxide (gray) and ethylene (white) obtained from the infrared photocatalytic reduction of carbon dioxide in Example 3 and Comparative Example 1.

[0028] Figure 5 Characterization images of the powder prepared in Comparative Example 2: A, Transmission Electron Microscopy (TEM); B, XRD diffraction pattern.

[0029] Figure 6 Characterization images of the powder prepared in Comparative Example 3: A, Transmission Electron Microscopy (TEM); B, XRD diffraction pattern.

[0030] Figure 7 Characterization images of the powder prepared in Comparative Example 4: A, Transmission Electron Microscopy (TEM); B, XRD diffraction pattern. Detailed Implementation

[0031] Example 1

[0032] A method for preparing cobalt-doped CuInS2 nanosheets includes the following steps:

[0033] 10 mg cobalt chloride hexahydrate, 99 mg cuprous chloride, 293 mg indium chloride tetrahydrate, and 80 mg sublimed sulfur were thoroughly dissolved in 30 mL of triethylene glycol and mixed to obtain a mixed solution (Co 2+ Cu + In 3+ The molar ratio of CuInS to S is 0.04:1:1:2.5. The mixed solution is transferred to a 40 mL high-pressure reactor, sealed, and reacted at 200 °C (hydrothermal reaction temperature) for 48 h (hydrothermal reaction time). After natural cooling to room temperature, the mixture is centrifuged, and the precipitate is washed several times with ethanol and water and dried under vacuum. The resulting powder is cobalt-doped CuInS2 nanosheets, which are stored in a desiccator for later use.

[0034] The structure of the powder obtained in Example 1 was identified, and the results are shown in the figure. Figures 1-3 .

[0035] The XRD diffraction pattern of the cobalt-doped CuInS2 nanosheets prepared in Example 1 is shown below. Figure 1 As shown in b.

[0036] Microscopic morphology images of cobalt-doped CuInS2 nanosheets prepared in Example 1 are shown below. Figure 2 C and Figure 2 As shown in D. From a microscopic morphology perspective, the obtained product is nanosheets.

[0037] X-ray photoelectron spectroscopy (XPS) of cobalt-doped CuInS2 nanosheets prepared in Example 1 is as follows: Figure 3 As shown, it is labeled b. Wherein, Figure 3 X-ray photoelectron spectroscopy of Co 2p corresponding to A confirmed that cobalt was successfully doped into CuInS2 nanosheets.

[0038] Example 2

[0039] A method for preparing undoped CuInS2 nanosheets, referring to Example 1, except that the addition of cobalt chloride hexahydrate is omitted, yielding undoped CuInS2 nanosheets; the specific steps are as follows:

[0040] Dissolve 99 mg cuprous chloride, 293 mg indium chloride tetrahydrate, and 80 mg sublimed sulfur thoroughly in 30 mL of triethylene glycol, mix well, and obtain a mixed solution (Cu). + In 3+ The molar ratio of CuInS to S is 1:1:2.5. The mixed solution is transferred to a 40 mL high-pressure reactor, sealed, and reacted at 200 °C for 48 h. After naturally cooling to room temperature, it is separated by centrifugation. The precipitate is washed several times with ethanol and water and dried under vacuum. The powder obtained is the undoped CuInS2 nanosheets, which are stored in a desiccator for later use.

[0041] The structure of the powder obtained in Example 2 was identified, and the results are shown in the figure. Figures 1-3 .

[0042] The XRD diffraction pattern of the undoped CuInS2 nanosheets prepared in Example 2 is shown below. Figure 1 As shown in figure a, its diffraction pattern, compared with the standard CuInS2 diffraction pattern, shows no additional diffraction peaks.

[0043] Microscopic morphology images of undoped CuInS2 nanosheets prepared in Example 2 are shown below. Figure 2 A and Figure 2 As shown in B. From a microscopic morphology perspective, the obtained product is nanosheets.

[0044] X-ray photoelectron spectroscopy (XPS) of the undoped CuInS2 nanosheets prepared in Example 2 is as follows: Figure 3 As shown, it is labeled a. Wherein, Figure 3 X-ray photoelectron spectroscopy of Co 2p corresponding to A confirmed that the undoped CuInS2 nanosheets did not contain cobalt.

[0045] Example 3

[0046] The application of cobalt-doped CuInS2 nanosheets prepared in Example 1 in the infrared photocatalytic reduction of carbon dioxide to ethylene includes the following steps:

[0047] 10 mg of the powder (cobalt-doped CuInS2 nanosheets) prepared in Example 1 was uniformly dispersed on a glass slide and placed in a well-sealed glass instrument. 2 mL of water was injected into the instrument, followed by the introduction of high-purity (≥99.999%) CO2 and then evacuation. This process was repeated three times until the pressure inside the sealed glass instrument approached atmospheric pressure. The instrument was then sealed. At room temperature and pressure, a 300 W xenon lamp with an 800 nm cutoff filter was used to simulate infrared light as the light source for the reaction. Infrared light was continuously irradiated for a period of time (e.g., 2 hours) to perform photocatalytic CO2 reduction. The composition of the gas after the reaction was collected using a syringe, and gas chromatography was used to analyze and calculate the product yield. The average yields of carbon monoxide (CO) and ethylene (C2H4) obtained after 2 hours of infrared photocatalysis are shown below. Figure 4 As shown.

[0048] Comparative Example 1

[0049] The application of undoped CuInS2 nanosheets prepared in Example 2 in the infrared photocatalytic reduction of carbon dioxide is the same as that in Example 3, except that the photocatalyst is replaced with undoped CuInS2 nanosheets prepared in Example 2 instead of the cobalt-doped CuInS2 nanosheets prepared in Example 1. All other steps and conditions remain unchanged. The yields of carbon monoxide (CO) and ethylene (C2H4) are as follows: Figure 4 As shown.

[0050] Comparative Example 2

[0051] A method for preparing a material, referring to Example 1, differs only in that the hydrothermal reaction temperature is adjusted to 180°C, while the other steps remain unchanged, to obtain powder.

[0052] The structure of the powder obtained in Comparative Example 2 was identified, and the results are shown in the figure. Figure 5 . Figure 5 Characterization images of the powder obtained in Comparative Example 2: A, Transmission Electron Microscopy (TEM); B, XRD diffraction pattern. From Figure 5 As can be seen from A, in addition to nanosheets, the powder obtained in Comparative Example 2 also contains some columnar products; from Figure 5 As can be seen from B, compared with the standard CuInS2 diffraction pattern, the XRD diffraction pattern of the powder prepared in Comparative Example 2 has additional diffraction peaks, indicating that other impurities were generated. The powder prepared in Comparative Example 2 is not cobalt-doped CuInS2 nanosheets.

[0053] Comparative Example 3

[0054] A method for preparing a material, referring to Example 1, differs only in that the hydrothermal reaction time is adjusted to 12 hours, while the other steps remain unchanged, to obtain powder.

[0055] The structure of the powder prepared in Comparative Example 3 was identified, and the results are shown in the figure. Figure 6 . Figure 6 Characterization images of the powder prepared in Comparative Example 3: A, Transmission Electron Microscopy (TEM); B, XRD diffraction pattern. From Figure 6 As can be seen from A, in addition to nanosheets, the powder prepared in Comparative Example 3 also contained some columnar products; from Figure 6 As can be seen from B, compared with the standard diffraction pattern of CuInS2, the XRD diffraction pattern of the powder prepared in Comparative Example 3 has additional diffraction peaks, indicating that the powder prepared in Comparative Example 3 is not a cobalt-doped CuInS2 nanosheet.

[0056] Comparative Example 4

[0057] A method for preparing a material, referring to Example 1, differs only in that the amount of cobalt chloride hexahydrate used is adjusted to 150 mg, and the corresponding mixed solution contains (Co) 2+ Cu+ In 3+ The molar ratio of S to S is 0.6:1:1:2.5, and the remaining steps remain unchanged to obtain powder.

[0058] The structure of the powder obtained in Comparative Example 4 was identified, and the results are shown in the figure. Figure 7 . Figure 7 Characterization images of the powder obtained in Comparative Example 4: A, Transmission Electron Microscopy (TEM); B, XRD diffraction pattern. From Figure 7 As can be seen from A, the powder obtained in Comparative Example 4 is not nanosheets; from Figure 7 As can be seen from B, compared with the standard diffraction pattern of CuInS2, the XRD diffraction pattern of the powder prepared in Comparative Example 4 has additional diffraction peaks, indicating that the powder prepared in Comparative Example 4 is not a cobalt-doped CuInS2 nanosheet.

[0059] Comparative Example 5

[0060] A method for preparing a material, referring to Example 1, differs only in that cobalt chloride hexahydrate is replaced with nickel chloride, the mass of nickel chloride remains 10 mg, a mixed solution is obtained, the remaining steps remain unchanged, and a powder is obtained.

[0061] The application of the powder prepared in Comparative Example 5 in the infrared photocatalytic reduction of carbon dioxide was the same as that in Example 3, except that the photocatalyst was replaced by the cobalt-doped CuInS2 nanosheets prepared in Example 1 with the powder prepared in Comparative Example 5, while the other steps and conditions remained unchanged. Tests showed that the average yields of carbon monoxide (CO) and ethylene (C2H4) obtained by the powder prepared in Comparative Example 5 under the same conditions were significantly lower than those of the powder prepared in Example 1 (cobalt-doped CuInS2 nanosheets).

[0062] Comparative Example 6

[0063] A method for preparing a material, referring to Example 1, differs only in that cobalt chloride hexahydrate is replaced with ferrous chloride, the mass of ferrous chloride remains 10 mg, a mixed solution is obtained, the remaining steps remain unchanged, and a powder is obtained.

[0064] The application of the powder prepared in Comparative Example 6 in the infrared photocatalytic reduction of carbon dioxide was the same as that in Example 3, except that the photocatalyst was replaced with the cobalt-doped CuInS2 nanosheets prepared in Example 1, while the other steps and conditions remained unchanged. Tests showed that the average yields of carbon monoxide (CO) and ethylene (C2H4) obtained from the powder prepared in Comparative Example 6 under the same conditions were significantly lower than those from the powder prepared in Example 1 (cobalt-doped CuInS2 nanosheets).

[0065] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A method for preparing an infrared photocatalyst for the infrared photocatalytic reduction of carbon dioxide to ethylene from cobalt-doped bimetallic sulfide nanosheets, characterized in that, Includes the following steps: According to Co 2+ Cu + In 3+ The molar ratio of S is 0.04:1:1:2.

5. Co... 2+ Source, Cu + Source, In 3+ Source and sublimed sulfur were fully dissolved in triethylene glycol and mixed to obtain a mixed solution. The mixed solution was transferred into a high-pressure reactor, sealed, and reacted at 200 °C for 48 h. After natural cooling to room temperature, the mixture was centrifuged, and the precipitate was washed several times with ethanol and water and dried under vacuum to obtain a cobalt-doped bimetallic sulfide nanosheet infrared photocatalyst—cobalt-doped CuInS2 nanosheets; which have asymmetric metal active sites.

2. The method for preparing the infrared photocatalyst according to claim 1, characterized in that, The Cu + The source is cuprous chloride.

3. The method for preparing the infrared photocatalyst according to claim 1, characterized in that, The In 3+ The source is indium chloride tetrahydrate.

4. The method for preparing the infrared photocatalyst according to claim 1, characterized in that, The Co 2+ The source is at least one of cobalt chloride hexahydrate, cobalt nitrate, or cobalt sulfate.

5. The infrared photocatalyst for the infrared photocatalytic reduction of carbon dioxide to ethylene prepared by the method of any one of claims 1-4.

6. The application of the infrared photocatalyst according to claim 5 in the infrared photocatalytic reduction of carbon dioxide to ethylene, characterized in that, Using the infrared photocatalyst described in claim 5 as a photocatalyst, and water and carbon dioxide as raw materials, ethylene and carbon monoxide are obtained by infrared photocatalysis of carbon dioxide reduction at room temperature and pressure. The ethylene formation rate was 5.06 μmol g. -1 h -1 The C2H4 selectivity was 49.13%.

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