High-entropy sulfide and preparation method and application thereof

Abstract

The invention belongs to the field of photocatalytic materials, and particularly relates to a high-entropy sulfide and a preparation method and application thereof. The high-entropy sulfide is granular, the molecular general formula is (MnaFebCocCudZe) xS, x is equal to 1, and the atomic ratio of Mn to Fe to Co to Cu to Zn is a: b: c: d: e of (1-2): (1-2): (1-2): (1-2): (1-2): (1-2): (1-2). The preparation method comprises the following steps: S1, dissolving metal salt in a mixed solvent of isopropanol and glycerol according to the atomic ratio of metal elements, and carrying out solvothermal reaction to obtain a precursor; and S2, dispersing the precursor in ethanol, adding thioacetamide as a sulfur source, and carrying out solvothermal reaction to obtain the high-entropy sulfide. The high-entropy sulfide disclosed by the invention is used as a photocatalytic material and shows excellent photocatalytic performance.

Description

Technical Field

[0001] The present invention belongs to the field of photocatalytic materials, and in particular relates to a high-entropy sulfide and a preparation method and application thereof. Background Art

[0002] Global climate issues and energy crises have made CO2 resource utilization technology a research hotspot. Photocatalytic reduction of CO2 can convert greenhouse gases into high-value-added fuels (such as CH4, CO, formic acid, etc.), which has both environmental and economic benefits. However, traditional photocatalysts (such as TiO2 and ZnO) have problems such as narrow light absorption range (only responding to ultraviolet light), high carrier recombination rate, and insufficient active sites, resulting in low conversion efficiency and poor stability. High-entropy materials (containing five or more main elements) have shown great potential in the field of catalysis due to their unique "cocktail effect" and lattice distortion characteristics.

[0003] High-entropy materials have adjustable electronic structures: multi-metal synergy can optimize the band gap and broaden the light absorption range to the full spectrum. Enhanced stability: The uniform distribution of multiple elements in high-entropy sulfides can inhibit phase separation and improve the structural stability of the material during the reaction. Rich active sites: Nanoporous or heterojunction structures can expose more surface sites, promoting the adsorption and conversion of reaction intermediates. However, existing research on high-entropy sulfides is mostly focused on electrocatalysis (such as CO2 reduction, hydrogen evolution reaction) or energy storage (such as lithium / sodium ion batteries), and its application in photocatalytic CO2 reduction is still in the exploratory stage.

[0004] The current bottlenecks of high-entropy sulfides include synthetic complexity: traditional high-entropy sulfide preparation relies on high-temperature solid-phase methods or complex template methods, which easily lead to particle agglomeration, low porosity, and limited mass transfer efficiency. The photo-thermal-electric coupling mechanism is unclear: although some high-entropy sulfides improve their performance through photothermal effects, the mechanism linking the efficiency of photogenerated carrier separation and the CO2 reduction pathway is still unclear. Selective regulation is difficult: there is a lack of systematic research on the impact of multi-metal synergy on product selectivity. For example, the selectivity control of formic acid and CH4 still relies on empirical optimization.

[0005] Therefore, the development of a new high-entropy sulfide is of great significance. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to address the deficiencies of the existing technology and provide a pentasulfide photocatalytic material regulated by the high entropy effect. The photocatalytic material can be used in the photocatalytic reduction of carbon dioxide to selectively reduce carbon dioxide to a carbon dioxide product.

[0007] In order to solve the above technical problems, the present invention discloses a high entropy sulfide, which is in granular form and has a molecular formula of (Mn a Fe b Co cCu d Zn e ) x S, wherein x=1, and the atomic ratios a:b:c:d:e of Mn, Fe, Co, Cu, and Zn elements are (1-2):(1-2):(1-2):(1-2):(1-2).

[0008] The high entropy sulfide is in granular form, and the particle size is 40 to 50 nm.

[0009] Preferably, the molecular formula of the high entropy sulfide includes any one of (MnFeCoCuZn)S, (Mn2FeCoCuZn)S, (MnFe2CoCuZn)S, (MnFeCo2CuZn)S, (MnFeCoCu2Zn)S, (MnFeCoCuZn2)S, (Mn2FeCoCu2Zn)S, (MnFe2CoCu2Zn)S, (MnFeCo2Cu2Zn)S and (MnFeCoCu2Zn2)S.

[0010] More preferably, the molecular formula of the high entropy sulfide is (Mn2FeCoCu2Zn)S.

[0011] Furthermore, the preparation method of the above-mentioned high-entropy sulfide is also within the scope of protection of the present invention; the preparation method comprises the following steps: S1. dissolving the metal salt in a mixed solvent of isopropanol and glycerol according to the atomic ratio of the metal elements, and obtaining a precursor through a solvent thermal reaction; S2. dispersing the precursor in ethanol, adding thioacetamide as a sulfur source, and obtaining a high-entropy sulfide through a solvent thermal reaction.

[0012] Wherein, the metal salt is metal nitrate or metal hydrochloride.

[0013] In some embodiments of the present invention, the metal salt is a metal nitrate, specifically including manganese nitrate, iron nitrate, cobalt nitrate, copper nitrate and zinc nitrate; the molar ratio of manganese nitrate, iron nitrate, cobalt nitrate, copper nitrate and zinc nitrate is (1-2):(1-2):(1-2):(1-2):(1-2).

[0014] In S1, the volume ratio of isopropanol to glycerol in the mixed solvent is 34:(2-8); the solvent thermal reaction has a reaction temperature of 160-200° C. and a reaction time of 8-12 h.

[0015] In some embodiments of the present invention, in S1, the volume ratio of isopropanol to glycerol in the mixed solvent is 34:6; the solvent thermal reaction has a reaction temperature of 180° C. and a reaction time of 10 h.

[0016] In S1, after the solvothermal reaction is completed, the reaction product is centrifuged and washed with anhydrous ethanol, and then dried to obtain a precursor.

[0017] Among them, in S2, the mass volume ratio of the precursor to ethanol is 100:(45~55) in mg / mL; the mass ratio of the precursor to thioacetamide is 1:1; the solvent thermal reaction has a reaction temperature of 160~200℃ and a reaction time of 8~12h.

[0018] In some embodiments of the present invention, in S2, the mass volume ratio of the precursor to ethanol is 100:50 in mg / mL; the mass ratio of the precursor to thioacetamide is 1:1; the solvent thermal reaction has a reaction temperature of 180° C. and a reaction time of 10 h.

[0019] Among them, in S2, after the solvent thermal reaction is completed, the reaction product is centrifuged and washed with anhydrous ethanol and water, and then dried to obtain high entropy sulfide.

[0020] Furthermore, the application of the above-mentioned high-entropy sulfide as a photocatalytic material in the photocatalytic reduction of carbon dioxide is also within the protection scope of the present invention; wherein, the high-entropy sulfide is used as a photocatalytic material to selectively reduce carbon dioxide to carbon two under photocatalytic conditions; the carbon two refers to a compound containing two carbon atoms, including but not limited to acetylene, ethylene, and ethane; carbon one refers to a substance containing one carbon atom, including but not limited to methane and carbon monoxide.

[0021] Specifically, in some embodiments of the present invention, a variety of high-entropy sulfides were prepared by the above-mentioned preparation method. By testing the photocatalytic activity and photocatalytic stability of the prepared high-entropy sulfides, it was shown that the high-entropy sulfides provided by the present invention have good CO2 reduction performance and can still maintain good photocatalytic activity after multiple uses, which proves the application prospect of the high-entropy sulfides provided by the present invention as photocatalytic materials in the photocatalytic reduction of carbon dioxide.

[0022] Beneficial effects:

[0023] This invention provides a granular high-entropy sulfide in which the atomic-level uniform distribution of five metal elements (Mn, Fe, Co, Cu, and Zn) produces a significant high-entropy effect. The local stress field formed by lattice distortion can regulate the band structure, expanding the material's light absorption sidebands and exhibiting a broad spectrum response in the visible-near-infrared region. Furthermore, the electronic synergy between the multiple elements increases the carrier mobility, significantly enhancing the kinetics of photocatalytic reactions.

[0024] The unique granular morphology of high-entropy sulfides significantly increases the material's specific surface area, providing abundant active site exposure and efficient material transport channels. Compared to traditional sulfides, this structure reduces the recombination rate of photogenerated electron-hole pairs, effectively enhancing photocatalytic activity.

[0025] The present invention also provides a method for preparing the high-entropy sulfide with a granular structure. The method adopts an isopropyl alcohol-glycerol mixed solvent system, avoids the use of highly toxic organic reagents, and the process route of low-temperature decomposition and sulfurization of thioacetamide has the characteristics of low energy consumption, conforms to the concept of green chemical synthesis, and is suitable for large-scale production.

[0026] The high-entropy sulfides, characterized by their specific morphology and particle size, achieved through the combination of metal elements and preparation methods, exhibit excellent CO2 reduction catalytic performance as photocatalytic materials. In particular, by adjusting the atomic ratio of the metal elements, the electronic structure of the material can be optimized, achieving precise control of product selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more apparent.

[0028] Figure 1 This is the SEM image of (Mn2FeCoCu2Zn)S prepared in Example 7 of the present invention.

[0029] Figure 2 UV-vis graphs of (MnFeCoCuZn)S, (Mn2FeCoCuZn)S, (MnFeCoCu2Zn)S and (Mn2FeCoCu2Zn)S prepared in Examples 1, 2, 5 and 7 of the present invention.

[0030] Figure 3 These are the XRD patterns of (MnFeCoCuZn)S, (MnFeCoCu2Zn)S and (Mn2FeCoCu2Zn)S prepared in Examples 1, 5 and 7 of the present invention.

[0031] Figure 4 This is a diagram of the CO2 reduction performance of (MnFeCoCuZn)S and (Mn2FeCoCu2Zn)S prepared in Examples 1 and 7 of the present invention.

[0032] Figure 5 This is a graph showing the CO2 reduction performance of (Mn2FeCoCu2Zn)S prepared in Example 7 of the present invention after a 5-hour photocatalytic reaction. DETAILED DESCRIPTION

[0033] The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials are commercially available unless otherwise specified.

[0034] Manganese nitrate hexahydrate, iron nitrate nonahydrate, cobalt nitrate hexahydrate, copper nitrate trihydrate, zinc nitrate hexahydrate, isopropyl alcohol, glycerol, and thioacetamide used in the following examples were all of analytical grade and purchased from Sinopharm Chemical Reagent Co., Ltd.; CO2 with a purity of 99.9% was purchased from Zhenjiang Zhongpu Special Gas Co., Ltd.

[0035] Example 1: Preparation of high entropy sulfide (MnFeCoCuZn)S

[0036] The method for preparing high entropy sulfide provided in this embodiment comprises the following steps:

[0037] S1. Dissolve manganese nitrate hexahydrate, iron nitrate nonahydrate, cobalt nitrate hexahydrate, copper nitrate trihydrate, and zinc nitrate hexahydrate (1 mmol each) in a molar ratio of 1:1:1:1:1 in a mixed solvent consisting of 34 mL of isopropanol and 6 mL of glycerol, and stir magnetically for 30 min to obtain a homogeneous solution. Transfer the solution to a 100 mL polytetrafluoroethylene autoclave and perform a solvothermal reaction at 180°C for 10 h. After centrifugation, the reaction product was washed three times with anhydrous ethanol and dried in vacuo at 60°C for 24 h to obtain a precursor.

[0038] S2. Disperse 100 mg of the precursor obtained in step S1 in 50 mL of ethanol. Add 100 mg of thioacetamide as a sulfur source at a 1:1 mass ratio. Ultrasonic dispersion is performed on the mixture for 30 minutes, followed by transfer to an autoclave for a solvothermal reaction at 180°C for 10 hours. The reaction product is centrifuged, washed with ethanol and deionized water, and then vacuum-dried at 60°C for 24 hours to obtain a granular (MnFeCoCuZn)S high-entropy sulfide.

[0039] Example 2 to Example 10:

[0040] Table 1 shows the molecular formulas of the high entropy sulfides prepared in Examples 1 to 10.

[0041] Table 1 Molecular formula of high entropy sulfides prepared in Examples 1 to 10

[0042] Example High entropy sulfides 1 (MnFeCoCuZn)S 2 <![CDATA[(Mn2FeCoCuZn)S <!-- 3 -->]]> 3 <![CDATA[(MnFe2CoCuZn)S]]> 4 <![CDATA[(MnFeCo2CuZn)S]]> 5 <![CDATA[(MnFeCoCu2Zn)S]]> 6 <![CDATA[(MnFeCoCuZn2)S]]> 7 <![CDATA[(Mn2FeCoCu2Zn)S]]> 8 <![CDATA[(MnFe2CoCu2Zn)S]]> 9 <![CDATA[(MnFeCo2Cu2Zn)S]]> 10 <![CDATA[(MnFeCoCu2Zn2)S]]>

[0043] The preparation methods of the high-entropy sulfides described in Examples 2 to 10 differ from the method described in Example 1 only in that the molar ratios of manganese nitrate hexahydrate, iron nitrate nonahydrate, cobalt nitrate hexahydrate, copper nitrate trihydrate, and zinc nitrate hexahydrate in S1 are different from those in Example 1, and the other steps and parameters are the same as those in Example 1; specifically, the molar ratios of the above-mentioned metal salts are the same as the atomic ratios of the metal elements in the final high-entropy sulfide molecular formula obtained in Table 1.

[0044] The micromorphology of the high entropy sulfide (Mn2FeCoCu2Zn)S prepared in Example 7 was characterized by scanning electron microscopy (SEM). Figure 1 This is the SEM image of (Mn2FeCoCu2Zn)S prepared in Example 7, where Figure 1 a and Figure 1 b in the figure is the SEM image of (Mn2FeCoCu2Zn)S at different magnifications. Figure 1 It can be seen that the particle size of the (Mn2FeCoCu2Zn)S is 40-50 nm.

[0045] The (MnFeCoCuZn)S, (Mn2FeCoCuZn)S, (MnFeCoCu2Zn)S and (Mn2FeCoCu2Zn)S prepared in Example 1, Example 2, Example 5 and Example 7 were tested for UV-visible absorption by a UV-visible spectrophotometer. Figure 2 The UV-vis diagrams of (MnFeCoCuZn)S, (Mn2FeCoCuZn)S, (MnFeCoCu2Zn)S and (Mn2FeCoCu2Zn)S are shown in Figure 2. Figure 2 It can be seen that (Mn2FeCoCu2Zn)S has the strongest visible light absorption capacity, which is conducive to improving the photocatalytic performance and promoting the photocatalytic CC coupling reaction, thereby greatly improving the ethylene production efficiency.

[0046] The (MnFeCoCuZn)S, (MnFeCoCu2Zn)S and (Mn2FeCoCu2Zn)S prepared in Example 1, Example 5 and Example 7 were tested by X-ray diffractometer. Figure 3 The XRD patterns of (MnFeCoCuZn)S, (MnFeCoCu2Zn)S and (Mn2FeCoCu2Zn)S are shown in Figure 2. Figure 3It can be seen that the diffraction peak of the high-entropy sulfide belongs to CoS (PDF#76-1725), indicating that the synthesized high-entropy sulfide is a material with a CoS crystal configuration. The crystal structure of the high-entropy sulfide itself did not change after changing the ratio. The intensity of the CoS2 characteristic peak (such as 2θ≈27.8°) of (MnFeCoCu2Zn)S is significantly higher than that of the base material (MnFeCoCuZn)S, indicating that the increase of Cu promotes the formation of the CoS2 crystal phase and the improvement of crystallinity; while the CoS2 peak in the (Mn2FeCoCu2Zn)S sample with further introduction of Mn is significantly weakened, suggesting that the synergistic effect of Mn-Cu may induce lattice distortion or form a local disordered structure of cobalt. This structural feature is closely related to its high ethylene catalytic activity (8.75μmol·g -1 h -1 ) have a potential association.

[0047] Comparative Example 1 to Comparative Example 3:

[0048] Table 2 shows the molecular formulas of the high entropy sulfides prepared in Comparative Examples 1 to 3.

[0049] Table 2 Molecular formula of high entropy sulfides prepared in Comparative Examples 1 to 3

[0050] Comparative Example High entropy sulfides 1 (MnFeCoCuNi)S 2 (FeCoNiCuCd)S 3 (MnFeCoCuCr)S

[0051] The high-entropy sulfides described in Comparative Examples 1 to 3 were prepared using the method of Example 1. The only difference from Example 1 was the added metal salts and the molar ratio of the metal salts. The other steps and parameters were the same as those in Example 1. Specifically, the metal salts and the molar ratios of the metal salts used in Comparative Examples 1 to 3 were based on the types of metal elements and the atomic ratios of the metal elements in the final high-entropy sulfide molecular formula obtained in Table 2.

[0052] The photocatalytic activity and photocatalytic stability of the high entropy sulfides prepared in Examples 1 to 10 and Comparative Examples 1 to 3 were evaluated. The evaluation conditions and results are shown below:

[0053] Photocatalytic activity test: The performance test of reducing CO2 using high entropy sulfide as a photocatalyst was carried out in a reaction vessel with a capacity of 100 mL. The reaction light source used was a xenon lamp with a power of 300 W to simulate sunlight. The reaction solution for each experiment consisted of 18 mL of deionized water and 2 mL of triethanolamine as an electron sacrificial agent. The mass of the high entropy sulfide catalyst used in the reduction experiment was 10 mg. The above solution was added to a dedicated quartz container. The reactor was installed in a CEL-SPH2N photocatalytic reduction reaction device. Within 5 hours of the photoreaction, 1 mL of the gas in the reactor was taken every hour, and the generated gas was detected by a gas chromatograph GC-2030 equipped with a thermal conductivity detector and a flame ionization detector to obtain an accurate yield of the reduced gas product. Table 3 shows the photocatalytic activity data of the high-entropy sulfides prepared in Examples 1 to 10 and Comparative Examples 1 to 3. It can be seen from Table 3 that in the high-entropy sulfide catalytic system, Cu is the core factor driving the production of C2 (such as ethylene), which can significantly increase the ethylene yield to 8.75; at the same time, Ni can inhibit the methanation reaction (CH4 as low as 0.83), and the introduction of Mn and Zn elements further synergistically reduces the methane selectivity (CH4 can be reduced to 0.51), thereby achieving directional optimization of the C2 product selectivity.

[0054] Table 3 Photocatalytic activity data of high entropy sulfides prepared in Examples 1 to 10 and Comparative Examples 1 to 3 (unit: μmol·g -1 h -1 )

[0055]

[0056] The CO2 reduction performance of (MnFeCoCuZn)S and (Mn2FeCoCu2Zn)S prepared in Example 1 and Example 7 was further studied. Figure 4 The CO2 reduction performance diagram of (MnFeCoCuZn)S and (Mn2FeCoCu2Zn)S prepared in Example 1 and Example 7 is shown in FIG. Figure 4 It can be seen that under the action of (Mn2FeCoCu2Zn)S catalyst, the C2H4 yield (8.75μmol·g -1 h -1 ) reaches 4.86 times that of the basic material (MnFeCoCuZn)S, and the selectivity of the catalyst for ethylene (C2H4) is significantly higher than that for other products.

[0057] Figure 5 The CO2 reduction performance diagram of the (Mn2FeCoCu2Zn)S prepared in Example 7 after a 5-hour photocatalytic reaction is shown. Figure 5It can be seen that among the products of (Mn2FeCoCu2Zn)S, the output of C2H4 far exceeds that of other products, which intuitively verifies the selective enhancement effect of the Cu2+Mn2 combination on ethylene production.

[0058] Photocatalytic stability test:

[0059] After the photocatalytic reduction of CO₂ was completed, the reaction solution was centrifuged to obtain the high-entropy sulfide photocatalyst. The solution was then washed several times with ethanol and water to remove any impurities remaining on the surface of the photocatalyst. The solution was then dried in a 60°C vacuum oven. This photocatalyst was then used in the next 5-hour test cycle. Multiple cycles of photocatalytic reduction experiments were performed continuously.

[0060] The stability cycle experiment of (Mn2FeCoCu2Zn)S prepared in Example 7 showed that after 5 cycle experiments, the activity retention rate of the material as a catalyst was greater than 92%, and there was no significant element segregation on the surface, showing excellent chemical stability.

[0061] The present invention provides a high-entropy sulfide, its preparation method, and its application. There are many methods and approaches to implement this technical solution. The above is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are also considered to be within the scope of protection of the present invention. Any components not specified in this embodiment may be implemented using existing technologies.

Claims

1. A high entropy sulfide, characterized in that: The high entropy sulfide is in granular form and has the general molecular formula (Mn a Fe b Co c Cu d Zn e ) x S, wherein x=1, and the atomic ratios a:b:c:d:e of Mn, Fe, Co, Cu, and Zn elements are (1-2):(1-2):(1-2):(1-2):(1-2).

2. The high entropy sulfide according to claim 1, characterized in that The high entropy sulfide is in granular form, and the particle size is 40 to 50 nm.

3. The high entropy sulfide according to claim 1, characterized in that The molecular formula of the high entropy sulfide includes any one of (MnFeCoCuZn)S, (Mn2FeCoCuZn)S, (MnFe2CoCuZn)S, (MnFeCo2CuZn)S, (MnFeCoCu2Zn)S, (MnFeCoCuZn2)S, (Mn2FeCoCu2Zn)S, (MnFe2CoCu2Zn)S, (MnFeCo2Cu2Zn)S and (MnFeCoCu2Zn2)S.

4. The high entropy sulfide according to claim 3, characterized in that The molecular formula of the high entropy sulfide is (Mn2FeCoCu2Zn)S.

5. The method for preparing high entropy sulfide according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: S1. dissolving a metal salt in a mixed solvent of isopropanol and glycerol according to the atomic ratio of the metal elements, and obtaining a precursor through a solvent thermal reaction; S2. dispersing the precursor in ethanol, adding thioacetamide as a sulfur source, and obtaining a high-entropy sulfide through a solvent thermal reaction.

6. The preparation method according to claim 5, characterized in that The metal salt is metal nitrate or metal hydrochloride.

7. The preparation method according to claim 5, characterized in that In S1, the volume ratio of isopropyl alcohol to glycerol in the mixed solvent is 34:(2-8); the solvent thermal reaction has a reaction temperature of 160-200° C. and a reaction time of 8-12 h.

8. The preparation method according to claim 5, characterized in that In S2, the mass volume ratio of the precursor to ethanol is 100:(45-55) in mg / mL; the mass ratio of the precursor to thioacetamide is 1:1; the solvent thermal reaction has a reaction temperature of 160-200° C. and a reaction time of 8-12 h.

9. Use of the high entropy sulfide according to any one of claims 1 to 4 as a photocatalytic material in the photocatalytic reduction of carbon dioxide.

10. The use according to claim 9, characterized in that The high entropy sulfide is used as a photocatalytic material to selectively reduce carbon dioxide to carbon dioxide under photocatalytic conditions.

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