Cobalt-nickel sulfide-indium oxide composite nanosheet material, preparation method and application thereof

Abstract

The application provides a cobalt-nickel sulfide-indium oxide composite nanosheet material, a preparation method and application thereof. The preparation method of the cobalt-nickel sulfide-indium oxide composite nanosheet material comprises the following steps: synthesizing CoNi2S4 nanosheet powder; synthesizing In2O3 nanosheet powder; compounding the CoNi2S4 nanosheet and the In2O3 nanosheet: the CoNi2S4 nanosheet powder and the In2O3 nanosheet powder are fully dispersed in water according to a molar ratio of (1-2):(1:2), are placed in a light-transmitting container, are irradiated with visible light for 1 h, and then are centrifugally separated to obtain a precipitate, are washed with water, and are vacuum dried to obtain the cobalt-nickel sulfide-indium oxide composite nanosheet material. The cobalt-nickel sulfide-indium oxide composite nanosheet material prepared by the method can catalytically reduce carbon dioxide into carbon monoxide and methanol under visible light irradiation, the yield of methanol can reach 129.73 μg·g ‑1 ·h ‑1 , the selectivity and the electronic selectivity of methanol can reach 52.65% and 76.29%, respectively, and the methanol production performance does not show attenuation at least for 30 h.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of carbon dioxide resource utilization, in particular to a cobalt-nickel sulfide-indium oxide composite nanosheet material, a preparation method and application thereof. BACKGROUND

[0002] The carbon dioxide (CO2) photocatalytic reduction technology has double benefits, which can not only inhibit the greenhouse effect, but also produce valuable chemical substances to offset the technical cost. At the same time, the photocatalytic reduction of CO2 has the advantages of simple operation, mild reaction conditions, inexhaustible solar energy and clean and cheap. Due to the complexity of the reduction pathway, the products of CO2 photoreduction are usually a mixture of carbon hydrides such as carbon monoxide (CO), methane (CH4) and methanol (CH3OH). CH3OH is considered to be one of the most ideal energy storage substances due to its high energy density, relatively low toxicity, easy storage, wide adaptability and low risk. It is an important raw material and alternative energy source in chemical, transportation and power industries, and can be used as a raw material for producing acetic acid, formaldehyde, fatty acid methyl ester and other chemicals. It can also be used for producing dimethyl ether, and is widely used for manufacturing daily chemicals, including plastics, coatings and organosilicon, etc.

[0003] The traditional metal oxide or sulfide catalyst has a single metal site (denoted as M) on the surface which is easy to combine with the carbon atom or oxygen atom of the adsorbed CO2, usually forming a M-C-O or M-O-C intermediate. In this case, the relatively weak M-C or M-O bond is more likely to break than the highly stable C-O bond, thus facilitating the generation of CO. At present, establishing a composite material with a double metal site may be a potential strategy to improve the photocatalytic reduction of CO2 to produce methanol.

[0004] In the prior art, most of the composite materials are designed as heterojunctions, because the heterojunctions not only help to broaden the band edge position, but also can accelerate the separation of carriers, thereby improving the performance of CO2 photoreduction. However, in the heterojunction, the double active sites are generally stacked through the bonding effect and closely connected, i.e. there is no gap between them, which causes the CO2 molecules to be adsorbed on the single active site of the exposed surface of the heterojunction, making it difficult to fully exert the advantages of the double active sites. SUMMARY

[0005] Technical problem:

[0006] The present disclosure provides a preparation method of a composite nanosheet material, and the obtained composite nanosheet material can efficiently photocatalytically reduce carbon dioxide to produce carbon monoxide and methanol under visible light at room temperature and normal pressure, has a high yield of methanol, and has good stability in photocatalytic production of methanol.

[0007] Technical solution:

[0008] In one aspect, a method for preparing a cobalt nickel sulfide-indium oxide composite nanosheet material is provided, comprising the following steps:

[0009] (1) synthesizing CoNi2S4 nanosheet powder;

[0010] (2) synthesizing In2O3 nanosheet powder;

[0011] (3) combining CoNi2S4 nanosheet and In2O3 nanosheet: dispersing CoNi2S4 nanosheet powder and In2O3 nanosheet powder in water according to a molar ratio of (1-2):(1-2), placing them in a light-transmitting container, irradiating them with visible light for 1 h, then centrifugally separating the precipitate, washing it with water, and vacuum drying to obtain a cobalt nickel sulfide-indium oxide composite nanosheet material.

[0012] In some embodiments, in step (3), the molar ratio of CoNi2S4 nanosheet powder and In2O3 nanosheet powder is 1:1.

[0013] In some embodiments, in step (3), the visible light is sunlight or a 300W xenon lamp.

[0014] In some embodiments, in step (3), CoNi2S4 nanosheet powder and In2O3 nanosheet powder are both dispersed in water according to a ratio of 1 mmol nanosheet powder per 100 mL water.

[0015] In some embodiments, step (1) is specifically: synthesizing CoNi2S4 nanosheet powder: dissolving cobalt nitrate hexahydrate, nickel nitrate hexahydrate, and anhydrous sodium acetate in a mixed solution of ethylene glycol and polyethylene glycol, mixing well, moving the obtained mixed solution into a high-pressure reaction kettle, sealing the high-pressure reaction kettle, reacting at 200℃ for 16 h, naturally cooling to room temperature, centrifugally separating the precipitate, washing it with water and ethanol, and vacuum drying; dispersing the obtained powder after vacuum drying in ethanol according to a ratio of 60 mg per 40 mL, adding thioacetamide, wherein the mass ratio of thioacetamide to the obtained powder after vacuum drying is 2:1, mixing well, moving the obtained mixed solution into a high-pressure reaction kettle, sealing the high-pressure reaction kettle, reacting at 200℃ for 24 h, naturally cooling to room temperature, centrifugally separating the precipitate, washing it with water and ethanol, and vacuum drying to obtain CoNi2S4 nanosheet powder; wherein: the volume ratio of ethylene glycol to polyethylene glycol in the mixed solution of ethylene glycol and polyethylene glycol is 1:1; the molar ratio of cobalt nitrate hexahydrate, nickel nitrate hexahydrate, and anhydrous sodium acetate is 1:1:4.

[0016] In some embodiments, step (1) is specifically: synthesizing CoNi2S4 nanosheet powder: 1.455 g of cobalt nitrate hexahydrate, 1.454 g of nickel nitrate hexahydrate and 1.64 g of anhydrous sodium acetate are dissolved in a mixture of 20 mL of ethylene glycol and 20 mL of polyethylene glycol, mixed well, and the resulting mixed solution is moved into a 40 mL high-pressure reaction kettle. The high-pressure reaction kettle is sealed, reacted at 200°C for 16 h, naturally cooled to room temperature, centrifuged to obtain a precipitate, washed with water and ethanol for several times, and vacuum dried; 60 mg of the powder obtained by vacuum drying is taken and dispersed in 40 mL of ethanol, 120 mg of thioacetamide is added, mixed well, and the resulting mixed solution is moved into a 40 mL high-pressure reaction kettle. The high-pressure reaction kettle is sealed, reacted at 200°C for 24 h, naturally cooled to room temperature, centrifuged to obtain a precipitate, washed with water and ethanol for several times, and vacuum dried to obtain CoNi2S4 nanosheet powder.

[0017] In some embodiments, step (2) is specifically: synthesizing In2O3 nanosheet powder: indium chloride tetrahydrate is dissolved in water to prepare a 0.025 M indium chloride aqueous solution; the 0.025 M indium chloride aqueous solution is slowly added to a 0.1 M NaOH aqueous solution, wherein the volume ratio of the indium chloride aqueous solution to the 0.1 M NaOH aqueous solution is 2:3, stirred for 5 h, centrifuged to obtain a precipitate, washed with water, vacuum dried, and then placed in a muffle furnace and calcined at 400°C in an air atmosphere for 4 min to obtain In2O3 nanosheet powder.

[0018] In some embodiments, step (2) is specifically: synthesizing In2O3 nanosheet powder: 293 mg of indium chloride tetrahydrate is dissolved in 40 mL of water, slowly added to 60 mL of 0.1 M NaOH aqueous solution, stirred for 5 h, centrifuged to obtain a precipitate, washed with water for several times, vacuum dried, and then placed in a muffle furnace and calcined at 400°C in an air atmosphere for 4 min to obtain In2O3 nanosheet powder.

[0019] In some embodiments, the method for preparing the cobalt-nickel sulfide-indium oxide composite nanosheet material comprises the following steps:

[0020] (1) Synthesis of CoNi2S4 nanosheets: 1.4-1.5 g of cobalt nitrate hexahydrate, 1.4-1.5 g of nickel nitrate hexahydrate and 1.6-1.7 g of sodium acetate anhydrous were dissolved in a mixture of 20 mL of ethylene glycol and 20 mL of polyethylene glycol, mixed well, and the obtained mixed solution was transferred into a 40 mL high-pressure reaction kettle. The high-pressure reaction kettle was sealed, and reacted at 200°C for 16 h. After natural cooling to room temperature, the precipitate was separated by centrifugation, washed with water and ethanol for several times, and vacuum dried. 60 mg of the powder obtained by vacuum drying was taken and dispersed in 40 mL of ethanol, 120 mg of thioacetamide was added, mixed well, and the obtained mixed solution was transferred into a 40 mL high-pressure reaction kettle. The high-pressure reaction kettle was sealed, and reacted at 200°C for 24 h. After natural cooling to room temperature, the precipitate was separated by centrifugation, washed with water and ethanol for several times, and vacuum dried to obtain CoNi2S4 nanosheet powder, which was stored in a desiccator for standby use.

[0021] (2) Synthesis of In2O3 nanosheets: 200-300 mg of indium chloride tetrahydrate was dissolved in 40 mL of water, and 60 mL of 0.1M NaOH aqueous solution was slowly added. After stirring for 5 h, the precipitate was separated by centrifugation, washed with water for several times, vacuum dried, and then calcined in a muffle furnace at 400°C in air atmosphere for 4 min to obtain In2O3 nanosheet powder, which was stored in a desiccator for standby use.

[0022] (3) Composite CoNi2S4 nanosheets and In2O3 nanosheets: 50-130 mg of CoNi2S4 nanosheet powder and 50-120 mg of In2O3 nanosheet powder were dissolved in 20 mL of water, and placed in a light-transmitting container. A 300 W xenon lamp was used to simulate sunlight for 1 h, and then the precipitate was separated by centrifugation, washed with water for several times, and vacuum dried to obtain CoNi2S4-In2O3 composite nanosheets, which were stored in a desiccator for standby use.

[0023] In another aspect, the application provides a CoNi2S4-In2O3 composite nanosheet material prepared by the above preparation method.

[0024] In yet another aspect, the application provides an application of the above CoNi2S4-In2O3 composite nanosheet material in photocatalytic reduction of carbon dioxide.

[0025] Beneficial effects:

[0026] (1) The present disclosure designs and successfully synthesizes a cobalt nickel sulfide (CoNi2S4)-indium oxide (In2O3) composite nanosheet material combined by van der Waals force. Compared with the single cobalt nickel sulfide (CoNi2S4) nanosheet and the single indium oxide (In2O3) nanosheet before compounding, which can only reduce carbon dioxide to carbon monoxide, the intermediate layer of the nanosheet after compounding can produce a synergistic anchoring effect with the reaction intermediates, thereby reducing carbon dioxide to methanol and carbon monoxide, and the selectivity and stability of methanol are greatly improved: under normal temperature and pressure, under visible light irradiation, carbon dioxide can be catalytically reduced to methanol and carbon monoxide, and the methanol yield can be as high as 129.73 μg·g -1 ·h -1 , the selectivity and electronic selectivity of methanol are as high as 52.65% and 76.29% respectively, and the methanol production performance does not decay at least for 30h;

[0027] (2) The preparation method of the cobalt nickel sulfide-indium oxide composite nanosheet material of the present disclosure is simple, mainly including the following steps: dispersing CoNi2S4 nanosheet powder and In2O3 nanosheet powder in water, visible light irradiation, centrifugal separation of the precipitate, and drying. The preparation method is relatively simple. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The characterization graphs of the CoNi2S4-In2O3 composite nanosheet material with a ratio of 1:1 prepared in Example 1 are: A transmission electron microscope (TEM) and B XRD diffraction pattern;

[0029] Figure 2 The characterization graphs of the CoNi2S4-In2O3 composite nanosheet material with a ratio of 2:1 prepared in Example 3 are: A transmission electron microscope (TEM) and B XRD diffraction pattern;

[0030] Figure 3 The characterization graphs of the CoNi2S4-In2O3 composite nanosheet material with a ratio of 1:2 prepared in Example 4 are: A transmission electron microscope (TEM) and B XRD diffraction pattern;

[0031] Figure 4 The characterization graphs of the CoNi2S4 nanosheet powder prepared in Comparative Example 1 are: A transmission electron microscope (TEM) and B XRD diffraction pattern;

[0032] Figure 5 The characterization graphs of the In2O3 nanosheet powder prepared in Comparative Example 2 are: A transmission electron microscope (TEM) and B XRD diffraction pattern;

[0033] Figure 6 The carbon monoxide (gray) and methanol (white) yield graphs of different materials for photocatalytic reduction of carbon dioxide;

[0034] Figure 7 The selectivity (solid) and electron selectivity (hollow) of methanol produced by photocatalytic reduction of carbon dioxide using the CoNi2S4-In2O3 ratio (1:1) composite nanosheet material prepared in Example 1 at different times;

[0035] Figure 8 Characterization graphs of the powder prepared for Comparative Example 3: A transmission electron microscope (TEM) and B XRD diffraction pattern;

[0036] Figure 9 Characterization graphs of the powder prepared for Comparative Example 4: A transmission electron microscope (TEM) and B XRD diffraction pattern;

[0037] Figure 10 Characterization graphs of the powder prepared for Comparative Example 5: A transmission electron microscope (TEM) and B XRD diffraction pattern. DETAILED DESCRIPTION

[0038] Preparation of CoNi2S4-In2O3 ratio (1:1) composite nanosheet of Example 1

[0039] A method for preparing a cobalt nickel sulfide (CoNi2S4)-indium oxide (In2O3) composite nanosheet material, comprising the following steps:

[0040] (1) Synthesis of CoNi2S4 nanosheet: 1.455 g of cobalt nitrate hexahydrate, 1.454 g of nickel nitrate hexahydrate and 1.64 g of anhydrous sodium acetate were dissolved in a mixture of 20 mL of ethylene glycol and 20 mL of polyethylene glycol, mixed well, and the resulting mixed solution was transferred into a 40 mL high-pressure reaction kettle. The high-pressure reaction kettle was sealed, and reacted at 200°C for 16 h. It was naturally cooled to room temperature, centrifuged to obtain a precipitate, washed with water and ethanol for several times, and vacuum dried. 60 mg of the powder obtained by vacuum drying was taken and dispersed in 40 mL of ethanol, 120 mg of thioacetamide was added, mixed well, and the resulting mixture was transferred into a 40 mL high-pressure reaction kettle. The high-pressure reaction kettle was sealed, and reacted at 200°C for 24 h. It was naturally cooled to room temperature, centrifuged to obtain a precipitate, washed with water and ethanol for several times, and vacuum dried to obtain CoNi2S4 nanosheet powder, which was stored in a desiccator for standby;

[0041] (2) Synthesis of In2O3 nanosheet: 293 mg of indium chloride tetrahydrate was dissolved in 40 mL of water, and 60 mL of 0.1M NaOH aqueous solution was slowly added. It was stirred for 5 h, centrifuged to obtain a precipitate, washed with water for several times, vacuum dried, and then calcined in a muffle furnace at 400°C in air atmosphere for 4 min to obtain In2O3 nanosheet powder, which was stored in a desiccator for standby;

[0042] (3) CoNi2S4 nanosheet and In2O3 nanosheet composite: 61 mg of CoNi2S4 nanosheet powder and 55 mg of In2O3 nanosheet powder were dispersed in 20 mL of water, placed in a light-transmitting container, irradiated with a 300 W xenon lamp to simulate sunlight for 1 h, and then centrifuged to obtain a precipitate, which was washed with water several times and vacuum dried to obtain CoNi2S4-In2O3 composite nanosheet material, wherein the mixed molar ratio of CoNi2S4 nanosheet powder and In2O3 nanosheet powder was 1:1, denoted as CoNi2S4-In2O3 ratio (1:1) composite nanosheet, which was stored in a desiccator for standby.

[0043] The CoNi2S4-In2O3 ratio (1:1) composite nanosheet material prepared in Example 1 was subjected to structural identification, and the results are shown in Figure 1 . Figure 1 It was confirmed that the composition of the composite nanosheet material was CoNi2S4 and In2O3, and no new substance was generated, indicating that the CoNi2S4-In2O3 composite nanosheet material combined by van der Waals force was successfully synthesized.

[0044] Example 2

[0045] The application of a CoNi2S4-In2O3 composite nanosheet material in photocatalytic reduction of carbon dioxide includes the following steps: 5 mg of CoNi2S4-In2O3 ratio (1:1) composite nanosheet material powder prepared in Example 1 was uniformly dispersed on a glass sheet, placed in a glass container with good airtightness, 2 mL of water was injected into the container, and high-purity (concentration > 99.999%) carbon dioxide was filled and vacuumed, and the operation was repeated for 3 times. When the pressure in the glass container was close to normal pressure, the glass container was sealed. A 300 W xenon lamp was used to simulate sunlight for continuous irradiation for 30 h. The products carbon monoxide and methanol were detected, and the yield of carbon monoxide and methanol, as well as the methanol selectivity and electron selectivity were calculated, and the results are shown in Figure 6 and Figure 7 .

[0046] Figure 6 The yield of carbon monoxide (gray) and methanol (white) obtained by photocatalytic reduction of carbon dioxide of the CoNi2S4-In2O3 ratio (1:1) composite nanosheet material of Example 1 is shown in the figure. As can be seen from the figure, the CoNi2S4-In2O3 ratio (1:1) composite nanosheet material of Example 1 can reduce carbon dioxide into carbon monoxide and methanol under normal temperature and pressure and visible light irradiation, and has high selectivity for the product methanol, with a methanol yield as high as 129.73 μg·g -1 ·h -1 .

[0047] Figure 7 The selectivity (solid) and electron selectivity (hollow) of methanol produced by the photocatalytic reduction of carbon dioxide by the CoNi2S4-In2O3 ratio (1:1) composite nanosheet material of Example 1 are shown, wherein the electron selectivity is the ratio of electrons used to generate the target product to the total transferred electrons. As can be seen from the figure, the selectivity and electron selectivity of methanol when the CoNi2S4-In2O3 ratio (1:1) composite nanosheet material of Example 1 photocatalytically reduces carbon dioxide are as high as 52.65% and 76.29%, respectively, and at least 30 h of methanol production performance has not been observed to decay, proving that the stability of the CoNi2S4-In2O3 ratio (1:1) composite nanosheet material of Example 1 in photocatalytically reducing carbon dioxide to produce methanol is excellent.

[0048] Preparation of CoNi2S4 nanosheets of Comparative Example 1

[0049] A method for preparing CoNi2S4 nanosheets, referring to step (1) of Example 1.

[0050] The CoNi2S4 nanosheet powder prepared in Comparative Example 1 was subjected to structural identification, and the results are shown in Figure 4 .

[0051] Preparation of In2O3 nanosheets of Comparative Example 2

[0052] A method for preparing In2O3 nanosheets, referring to step (2) of Example 1.

[0053] The In2O3 nanosheet powder prepared in Comparative Example 2 was subjected to structural identification, and the results are shown in Figure 5 .

[0054] Test of Comparative Example 1

[0055] Referring to the method of Example 2, the only difference is that the CoNi2S4-In2O3 ratio (1:1) composite nanosheet material powder prepared in Example 1 is replaced by the CoNi2S4 nanosheet powder prepared in Comparative Example 1 or the In2O3 nanosheet powder prepared in Comparative Example 2, so as to respectively apply the CoNi2S4 nanosheet powder prepared in Comparative Example 1 and the In2O3 nanosheet powder prepared in Comparative Example 2 to photocatalytic reduction of carbon dioxide, detect the products carbon monoxide and methanol, and calculate the yield of carbon monoxide and methanol, as well as the selectivity and electron selectivity of methanol, and the results are shown in Figure 6 .

[0056] From Figure 6It is evident that the CoNi2S4 nanosheet powder prepared in Comparative Example 1 and the In2O3 nanosheet powder prepared in Comparative Example 2 can only reduce carbon dioxide to carbon monoxide under normal temperature, pressure, and light irradiation, but cannot generate methanol. Comparing the performance of the CoNi2S4-In2O3 (1:1) composite nanosheet powder prepared in Example 1, the CoNi2S4 nanosheet powder prepared in Comparative Example 1, and the In2O3 nanosheet powder prepared in Comparative Example 2 reveals that under the same photocatalytic conditions, neither CoNi2S4 nanosheets nor In2O3 nanosheets alone possess the ability to produce methanol. However, the CoNi2S4-In2O3 (1:1) composite nanosheet powder prepared using the method of Example 1 exhibits a new property (i.e., methanol production), and the methanol yield is relatively high, confirming that the method of this invention can achieve synergistic effects.

[0057] Example 3: Preparation of CoNi2S4-In2O3 composite nanosheets in a ratio of 2:1

[0058] A method for preparing a cobalt-nickel sulfide (CoNi2S4)-indium oxide (In2O3) composite nanosheet material is described, referring to Example 1, except that the molar ratio of CoNi2S4 nanosheet powder to In2O3 nanosheet powder is adjusted to 2:1, i.e., step (3) is adjusted as follows:

[0059] (3) Composite CoNi2S4 nanosheets and In2O3 nanosheets: 122 mg CoNi2S4 nanosheet powder and 55 mg In2O3 nanosheet powder were dissolved in 20 mL of water and placed in a transparent container. The container was irradiated with a 300 W xenon lamp to simulate sunlight for 1 h. The precipitate was then separated by centrifugation, washed several times with water, and dried under vacuum to obtain CoNi2S4-In2O3 composite nanosheet material, which was denoted as CoNi2S4-In2O3 ratio (2:1) composite nanosheet. It was stored in a desiccator for later use.

[0060] The structure of the CoNi2S4-In2O3 (2:1) composite nanosheet material prepared in Example 2 was identified, and the results are shown in the figure. Figure 2 . Figure 2 The composition of the composite nanosheet material was confirmed to be CoNi2S4 and In2O3, and no new substances were generated, indicating that the cobalt nickel sulfide (CoNi2S4)-indium oxide (In2O3) composite nanosheet material bonded by van der Waals forces was successfully synthesized.

[0061] Example 4: Preparation of CoNi2S4-In2O3 composite nanosheets in a ratio of 1:2

[0062] A method for preparing a cobalt nickel sulfide (CoNi2S4)-indium oxide (In2O3) composite nanosheet material, referring to Example 1, the only difference is that the mixing molar ratio of CoNi2S4 nanosheet powder and In2O3 nanosheet powder is adjusted to 1:2, that is, step (3) is adjusted to:

[0063] (3) Composite CoNi2S4 nanosheet and In2O3 nanosheet: 61 mg of CoNi2S4 nanosheet powder and 110 mg of In2O3 nanosheet powder were dissolved in 20 mL of water, placed in a light-transmitting container, irradiated with a 300 W xenon lamp to simulate sunlight for 1 h, then centrifuged to obtain a precipitate, washed with water several times, and vacuum dried to obtain a CoNi2S4-In2O3 composite nanosheet material, denoted as CoNi2S4-In2O3 ratio (1:2) composite nanosheet, which was stored in a desiccator for later use.

[0064] The CoNi2S4-In2O3 ratio (1:2) composite nanosheet material prepared in Example 4 was subjected to structural identification, and the results are shown in Figure 3 . Figure 3 It was confirmed that the composition of the composite nanosheet material was CoNi2S4 and In2O3, and no new substance was generated, indicating that the cobalt nickel sulfide (CoNi2S4)-indium oxide (In2O3) composite nanosheet material combined by van der Waals force was successfully synthesized.

[0065] Test Comparative Example 2

[0066] Referring to the method of Example 2, the only difference is that the CoNi2S4-In2O3 ratio (1:1) composite nanosheet material powder prepared in Example 1 is replaced by the CoNi2S4-In2O3 ratio (2:1) composite nanosheet powder prepared in Example 3 or the CoNi2S4-In2O3 ratio (1:2) composite nanosheet powder prepared in Example 4, so as to apply the CoNi2S4-In2O3 ratio (2:1) composite nanosheet prepared in Example 3 and the CoNi2S4-In2O3 ratio (1:2) composite nanosheet prepared in Example 4 to the photocatalytic reduction of carbon dioxide, respectively, to detect the products carbon monoxide and methanol, and to calculate the yield of carbon monoxide and methanol, as well as the methanol selectivity and electron selectivity, and the results are shown in Figure 6 .

[0067] From Figure 6 It can be seen that the CoNi2S4-In2O3 composite nanosheet materials with different mixing molar ratios of CoNi2S4 nanosheet powder and In2O3 nanosheet powder have a methanol yield of not less than 50 μg·g -1 ·h -1The CoNi2S4-In2O3 composite nanosheet material with different mixing molar ratios of CoNi2S4 nanosheet powder and In2O3 nanosheet powder was prepared, and it was found that when the mixing molar ratio of CoNi2S4 nanosheet powder and In2O3 nanosheet powder was 1:1, the yield of methanol was the highest.

[0068] Comparative Example 3

[0069] A powder was prepared according to the steps of Example 1, with the difference that in the second hydrothermal reaction, the hydrothermal temperature was adjusted to 100°C, i.e.:

[0070] 1.455 g of cobalt nitrate hexahydrate, 1.454 g of nickel nitrate hexahydrate and 1.64 g of anhydrous sodium acetate were dissolved in a mixture of 20 mL of ethylene glycol and 20 mL of polyethylene glycol, mixed well, and the obtained mixed solution was transferred into a 40 mL high-pressure reaction kettle. The high-pressure reaction kettle was sealed, and the reaction was carried out at 200°C for 16 h. After natural cooling to room temperature, centrifugal separation was performed to obtain a precipitate, which was washed with water and ethanol for several times and vacuum dried. 60 mg of the powder obtained by vacuum drying was taken and dispersed in 40 mL of ethanol, and 120 mg of thioacetamide was added and mixed well. The obtained mixed solution was transferred into a 40 mL high-pressure reaction kettle, and the high-pressure reaction kettle was sealed. The reaction was carried out at 100°C for 24 h, and the reaction kettle was naturally cooled to room temperature. Centrifugal separation was performed to obtain a precipitate, which was washed with water and ethanol for several times and vacuum dried to obtain a powder, which was stored in a desiccator for standby.

[0071] The powder prepared in Comparative Example 3 was subjected to structure identification, and the results are shown in Figure 8 .

[0072] From Figure 8 It can be seen that the powder prepared in Comparative Example 3 is not an ultrathin nanosheet, and there are additional diffraction peaks compared with the standard diffraction pattern of CoNi2S4, indicating that the powder is not a CoNi2S4 ultrathin nanosheet. Therefore, it is proved that CoNi2S4 ultrathin nanosheets cannot be successfully prepared after the hydrothermal temperature is adjusted to 100°C in the second hydrothermal reaction.

[0073] Comparative Example 4

[0074] A powder was prepared according to the steps of Example 1, with the difference that in the second hydrothermal reaction, the hydrothermal reaction time was adjusted to 3 h, i.e.:

[0075] Dissolve 1.455 g of cobalt nitrate hexahydrate, 1.454 g of nickel nitrate hexahydrate, and 1.64 g of anhydrous sodium acetate in a mixture of 20 mL of ethylene glycol and 20 mL of polyethylene glycol. Mix well and transfer the resulting solution to a 40 mL high-pressure reactor. Seal the reactor and react at 200 °C for 16 h. Allow to cool naturally to room temperature, centrifuge to obtain a precipitate, wash several times with water and ethanol, and vacuum dry. Take 60 mg of the aforementioned vacuum-dried powder and disperse it in 40 mL of ethanol. Add 120 mg of thioacetamide and mix well. Transfer the resulting solution to a 40 mL high-pressure reactor, seal the reactor, and react at 200 °C for 3 h. Allow to cool naturally to room temperature, centrifuge to obtain a precipitate, wash several times with water and ethanol, and vacuum dry to obtain a powder. Store the powder in a desiccator for later use.

[0076] The structure of the powder obtained in Comparative Example 4 was identified, and the results are shown in the figure. Figure 9 .

[0077] Depend on Figure 9 It is evident that the powder obtained in Comparative Example 4 is not an ultrathin nanosheet; furthermore, compared with the standard diffraction pattern of CoNi2S4, there are additional diffraction peaks, indicating that the powder is not a CoNi2S4 ultrathin nanosheet. This proves that in the second hydrothermal reaction, adjusting the hydrothermal reaction time to 3 hours cannot successfully prepare CoNi2S4 ultrathin nanosheets.

[0078] Comparative Example 5

[0079] A method for preparing a powder, referring to step (2) of Example 1, except that the calcination temperature in the muffle furnace is adjusted to 300°C, that is:

[0080] 293 mg of indium chloride tetrahydrate was dissolved in 40 mL of water, and 60 mL of 0.1 M NaOH aqueous solution was slowly added. The mixture was stirred for 5 h, centrifuged to obtain a precipitate, washed several times with water, vacuum dried, and then calcined in a muffle furnace at 300 °C in air for 4 min to obtain In2O3 nanosheet powder, which was stored in a desiccator for later use.

[0081] The structure of the powder obtained in Comparative Example 5 was identified, and the results are shown in the figure. Figure 10 .

[0082] Depend on Figure 10 It is evident that the powder obtained in Comparative Example 5 is not an ultrathin nanosheet; furthermore, compared with the standard In2O3 diffraction pattern, the powder exhibits additional diffraction peaks, indicating that it is not an In2O3 ultrathin nanosheet. This demonstrates that adjusting the muffle furnace calcination temperature to 300℃ fails to successfully prepare In2O3 ultrathin nanosheets.

Claims

1. A method for preparing a cobalt nickel sulfide-indium oxide composite nanosheet material, characterized in that, Includes the following steps: (1) Synthesis of CoNi2S4 nanosheet powder; (2) Synthesis of In2O3 nanosheet powder; (3) Composite CoNi2S4 nanosheets and In2O3 nanosheets: CoNi2S4 nanosheet powder and In2O3 nanosheet powder were fully dispersed in water at a molar ratio of (1~2):(1~2), placed in a light-transmitting container, irradiated with visible light for 1 h, and then centrifuged to obtain the precipitate. The precipitate was washed with water and vacuum dried to obtain cobalt nickel sulfide-indium oxide composite nanosheet material. Step (1) is as follows: Synthesis of CoNi2S4 nanosheet powder: Cobalt nitrate hexahydrate, nickel nitrate hexahydrate, and anhydrous sodium acetate were dissolved in a mixture of ethylene glycol and polyethylene glycol, mixed thoroughly, and the resulting solution was transferred to a high-pressure reactor. The reactor was sealed and reacted at 200 °C for 16 h. After natural cooling to room temperature, the precipitate was obtained by centrifugation, washed with water and ethanol, and vacuum dried. The vacuum-dried powder was dispersed in ethanol at a ratio of 60 mg powder / 40 mL ethanol, and thioacetamide was added, wherein the mass ratio of thioacetamide to the vacuum-dried powder was 2:

1. The mixture was mixed thoroughly, and the resulting solution was transferred to a high-pressure reactor. The reactor was sealed and reacted at 200 °C for 24 h. After natural cooling to room temperature, the precipitate was obtained by centrifugation, washed with water and ethanol, and vacuum dried to obtain CoNi2S4 nanosheet powder. The volume ratio of ethylene glycol to polyethylene glycol in the mixture of ethylene glycol and polyethylene glycol is 1:1; The molar ratio of cobalt nitrate hexahydrate, nickel nitrate hexahydrate, and anhydrous sodium acetate is 1:1:

4.

2. The preparation method according to claim 1, characterized in that, In step (3), the molar ratio of CoNi2S4 nanosheet powder to In2O3 nanosheet powder is 1:

1.

3. The preparation method according to claim 1, characterized in that, In step (3), the visible light is sunlight or a 300W xenon lamp.

4. The preparation method according to claim 1, characterized in that, In step (3), CoNi2S4 nanosheet powder and In2O3 nanosheet powder are mixed and dispersed in water at a ratio of 1 mmol nanosheet powder / 100 mL water.

5. The preparation method according to claim 1, characterized in that, Step (1) is as follows: Synthesis of CoNi2S4 nanosheet powder: 1.455 g of cobalt nitrate hexahydrate, 1.454 g of nickel nitrate hexahydrate, and 1.64 g of anhydrous sodium acetate were dissolved in a mixture of 20 mL of ethylene glycol and 20 mL of polyethylene glycol. The mixture was stirred and transferred to a 40 mL high-pressure reactor. The reactor was sealed and reacted at 200 °C for 16 h. After natural cooling to room temperature, the precipitate was obtained by centrifugation, washed with water and ethanol, and dried under vacuum. 60 mg of the vacuum-dried powder was taken and dispersed in 40 mL of ethanol. 120 mg of thioacetamide was added and mixed. The resulting mixture was transferred to a 40 mL high-pressure reactor, sealed, and reacted at 200 °C for 24 h. After natural cooling to room temperature, the precipitate was obtained by centrifugation, washed with water and ethanol, and dried under vacuum to obtain CoNi2S4 nanosheet powder.

6. The preparation method according to claim 1, characterized in that, Step (2) specifically involves: Synthesis of In2O3 nanosheet powder: Indium chloride tetrahydrate was dissolved in water to prepare a 0.025 M indium chloride aqueous solution; the 0.025 M indium chloride aqueous solution was slowly added to a 0.1 M NaOH aqueous solution, wherein the volume ratio of the indium chloride aqueous solution to the 0.1 M NaOH aqueous solution was 2:

3. The mixture was stirred for 5 h, centrifuged to obtain a precipitate, washed with water, vacuum dried, and then calcined in a muffle furnace at 400 ℃ in air atmosphere for 4 min to obtain In2O3 nanosheet powder.

7. The preparation method according to claim 6, characterized in that, Step (2) specifically involves: Synthesis of In2O3 nanosheet powder: 293 mg of indium chloride tetrahydrate was dissolved in 40 mL of water, and 60 mL of 0.1 M NaOH aqueous solution was slowly added. The mixture was stirred for 5 h, centrifuged to obtain the precipitate, washed with water, vacuum dried, and then calcined in a muffle furnace at 400 °C in air atmosphere for 4 min to obtain In2O3 nanosheet powder.

8. The cobalt nickel sulfide-indium oxide composite nanosheet material prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the cobalt nickel sulfide-indium oxide composite nanosheet material according to claim 8 in the photocatalytic reduction of carbon dioxide.

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