Hollow high-entropy transition metal hydroxide crystal and preparation method thereof

Abstract

The invention relates to a hollow high-entropy transition metal hydroxide crystal and a preparation method thereof. The preparation method comprises the following steps: providing a cuprous oxide crystal; the preparation method comprises the following steps: respectively adding a nickel salt precursor, a cobalt salt precursor, a chromium salt precursor, a manganese salt and / or iron salt precursor and cuprous oxide crystals into an ethanol / water mixed solvent to prepare uniformly dispersed suspension liquid; adding polyvinylpyrrolidone into the suspension, and fully mixing to obtain a mixed solution; and dropwise adding a reactant containing thiosulfate radicals into the mixed solution, reacting, and separating to obtain the hollow high-entropy transition metal hydroxide crystal. The method is simple in process, mild in condition, short in reaction time, low in requirement for precision of equipment and instruments, high in controllability of product morphology, good in repeatability and especially suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention relates to a method for preparing hollow high-entropy transition metal hydroxide crystals. Background Technology

[0002] High-entropy transition metal hydroxides, as a novel class of multifunctional materials, have shown broad application prospects in electrochemical energy storage, catalysis, and sensing due to their unique electronic synergistic effect, high active site density, and tunable chemical composition. Compared with single / bimetallic hydroxides, high-entropy materials, through atomic-level homogeneous mixing of five or more transition metal elements, can significantly improve the intrinsic activity and catalytic stability of the materials. However, the controllable synthesis of high-entropy hydroxide crystals still faces significant challenges: First, the differential hydrolysis rates of multimetallic precursors easily lead to elemental segregation, making it difficult to achieve atomic-level homogeneous dispersion; second, the high-temperature conditions of traditional hydrothermal / solvothermal methods (typically reaction temperatures ≥100 ℃) easily induce excessive grain growth, making it difficult to precisely control crystal morphology and exposed crystal faces; third, existing template methods have limited ability to construct complex shell structures, making it difficult to simultaneously achieve uniform loading of high-entropy components and directional growth of structures.

[0003] Currently, the preparation methods for high-entropy hydroxides mainly fall into two categories: The first is a synthesis strategy based on co-precipitation, such as patent CN118341439A, which uses co-precipitation to precipitate a mixed metal salt solution in high-concentration sodium hydroxide to form high-entropy hydroxides. These are then subjected to high-temperature calcination and ball milling to obtain spherical high-entropy oxide materials with high specific surface area and numerous oxygen defects. However, the products are large in size and easily form amorphous aggregates, resulting in low specific surface area and low density of exposed active sites. The second is a topological transformation method based on sacrificial templates, such as patent CN119530855A, which uses a two-dimensional high-entropy hydroxide template to controllably prepare two-dimensional high-entropy sulfides. Porous high-entropy hydroxides are then prepared through ion exchange and oxidation treatment. However, this method is complex, costly, and the template removal process easily damages the structural integrity. Furthermore, the excessive use of surfactants in existing technologies can cover the active sites on the material surface, and subsequent high-temperature annealing may induce phase separation, both of which severely restrict the performance improvement of high-entropy hydroxides.

[0004] It is worth noting that cuprous oxide (Cu₂O) crystals, due to their tunable morphology (such as cubic, octahedral, and cubic octahedral) and controllable etching properties under mild conditions, have been widely used in recent years as ideal templates for synthesizing hollow / porous nanostructures. For example, patent CN107954463A utilized the acidic etching properties of Cu₂O templates to prepare hollow polyhedral structures, but its etching process relies on a strong acid environment (such as HCl), which easily leads to premature precipitation of transition metal ions, making it difficult to adapt to the multi-metal synergistic introduction requirements of high-entropy systems. Traditional thiosulfate (S₂O₃) 2-The coordination reagent can mildly etch Cu2O under neutral conditions, but the matching mechanism between its etching kinetics and the nucleation rate of polymetallic hydroxides is still unclear, making it difficult to achieve both uniform loading of high-entropy components and accurate replication of template morphology.

[0005] Therefore, there is an urgent need to develop a method for the controllable preparation of hollow high-entropy transition metal hydroxide crystals under ambient temperature and mild conditions. Summary of the Invention

[0006] One of the objectives of this invention is to provide a controllable preparation method for hollow high-entropy transition metal hydroxide crystals, which achieves atomic-level uniform dispersion of multiple metal elements and precise control of structure through a mild coordination etching strategy.

[0007] According to a first aspect of the present invention, a method for preparing a hollow high-entropy transition metal hydroxide crystal is provided, comprising: Provides cuprous oxide crystals; Nickel salt precursor, cobalt salt precursor, chromium salt precursor, manganese salt and / or iron salt precursor, and cuprous oxide crystals were respectively added to an ethanol / water mixed solvent to prepare a uniformly dispersed suspension. Polyvinylpyrrolidone was added to the above suspension and mixed thoroughly to obtain a mixed solution; Then, the reactant containing thiosulfate is added dropwise to the above mixed solution, and after the reaction, hollow high-entropy transition metal hydroxide crystals are obtained by separation.

[0008] Based on the interaction mechanism of soft and hard acids and bases, this invention uses thiosulfate as a coordinating agent for cuprous oxide template, and achieves the controllable preparation of hollow high-entropy transition metal hydroxide crystals under mild reaction conditions and in a short time.

[0009] According to a preferred embodiment of the preparation method of the present invention, the volume ratio of ethanol to water in the ethanol / water mixed solvent is 1:1, and the suspension contains: 0.9~1.1 mg / mL of cuprous oxide crystals; 0.08~0.1 mg / mL of NiCl2, 0.08~0.1 mg / mL of CoCl2, 0.06~0.08 mg / mL of MnCl2 and 0.05~0.07 mg / mL of CrCl3, and the mixed solution contains 30~35 mg / mL of polyvinylpyrrolidone.

[0010] In another preferred embodiment of the preparation method according to the present invention, the volume ratio of ethanol to water in the ethanol / water mixed solvent is 1:1, and the suspension contains: 0.9~1.1 mg / mL cuprous oxide crystals; 0.08~0.1 mg / mL NiCl2, 0.08~0.1 mg / mL CoCl2, 0.05~0.07 mg / mL FeCl3 and 0.05~0.07 mg / mL CrCl3, and the mixed solution contains 30~35 mg / mL polyvinylpyrrolidone.

[0011] According to the preparation method of the present invention, the reactant added dropwise to the mixed solution is preferably a 1.0 mol / L Na2S2O3 solution, the volume ratio of the added reactant to the ethanol / water mixed solvent is (35~45):100, the reaction time is 15~25 min, more preferably 20 min under a water bath at 25°C.

[0012] According to the preparation method of the present invention, cuprous oxide crystals can be provided by the following method: providing an aqueous solution containing NaOH and CuCl2·2H2O, wherein the concentration of NaOH is 0.15~0.23 mol / L and the concentration of CuCl2·2H2O is 0.008~0.01 mol / L; The above aqueous solution was stirred and reacted in a water bath at 55℃~65℃ for 20~40 min to obtain a water bath reaction solution; Then, ascorbic acid solution is added dropwise to the above water bath reaction solution to obtain a mixed reaction solution, wherein the concentration of ascorbic acid is 0.04~0.06 mol / L; After continuing the reaction of the mixed reaction solution under the above water bath conditions for 0.5 to 2 hours, cubic cuprous oxide crystals were obtained by separation.

[0013] According to the preparation method of the present invention, cuprous oxide crystals can also be provided by the following method: providing an aqueous solution containing NaOH, polyvinylpyrrolidone and CuCl2·2H2O, wherein the concentration of NaOH is 0.15~0.23 mol / L, the concentration of polyvinylpyrrolidone is 25~30 mg / mL, and the concentration of CuCl2·2H2O is 0.008~0.01 mol / L; The above aqueous solution was stirred and reacted in a water bath at 55℃~65℃ for 20~40 min to obtain a water bath reaction solution; Then, ascorbic acid solution is added dropwise to the above water bath reaction solution to obtain a mixed reaction solution, wherein the concentration of ascorbic acid is 0.04~0.06 mol / L; After continuing the reaction of the mixed reaction solution under the above water bath conditions for 0.5 to 2 hours, octahedral cuprous oxide crystals were obtained by separation.

[0014] According to another aspect of the present invention, a hollow high-entropy transition metal hydroxide crystal prepared according to the above method is also provided, which preferably has a cubic or octahedral morphology.

[0015] This invention utilizes the dual-functional properties of coordination etching and complexation of thiosulfate ions to achieve simultaneous control of atomic-level uniform dispersion and morphology of high-entropy hydroxides at room temperature, overcoming the grain coarsening limitations of traditional high-temperature methods (≥100℃). Furthermore, this invention employs an ethanol / water mixed solvent system, eliminating the need for high-pressure / high-temperature equipment, resulting in a short reaction time (<30 min), and avoiding the generation of strong acid / base waste liquids through in-situ consumption of the template reactant.

[0016] In summary, the present invention features a simple process, mild conditions, short reaction time, low requirements for equipment precision, high controllability of product morphology, and good repeatability, making it particularly suitable for large-scale industrial production. Attached Figure Description

[0017] Figure 1a This is a scanning electron microscope image of a Cu2O cube prepared according to the present invention; Figure 1b This is its XRD phase analysis diagram.

[0018] Figure 2a and Figure 2b The images shown are scanning electron microscope (SEM) images and transmission electron microscope (TEM) images of the hollow high-entropy transition metal hydroxide cubes prepared according to Example 1 of the present invention. Figure 2c , Figure 2d , Figure 2e , Figure 2f , Figure 2g and Figure 2h These are the energy dispersive X-ray energy (EDS) spectra of Co, Mn, Ni, Cu, Cr, and O, respectively.

[0019] Figure 3 This is a scanning electron microscope image of the hollow high-entropy hydroxide cube prepared according to Example 2 of the present invention.

[0020] Figure 4a This is a scanning electron microscope image of a hollow high-entropy transition metal hydroxide cube prepared according to Example 3 of the present invention; Figure 4b , Figure 4c , Figure 4d , Figure 4e , Figure 4f , Figure 4g and Figure 4h These are the energy dispersive X-ray energy (EDS) spectra of Cu, Fe, Co, Ni, Cr, O, and the mixed energy of each element.

[0021] Figure 5 This is a scanning electron microscope image of the hollow high-entropy hydroxide octahedron prepared according to Example 4 of the present invention. Detailed Implementation

[0022] The preparation method of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings, but it is not intended to limit the present invention.

[0023] Example 1 (1) Add 2.0 mol / L 10 mL NaOH solution to 0.01 mol / L 100 mL CuCl2·2H2O aqueous solution, stir and react for 0.5 h in a water bath at 60 °C, then add 0.6 mol / L 10 mL ascorbic acid solution dropwise, continue the reaction in a water bath for about 1 h, and centrifuge, wash and dry the product to obtain cubic cuprous oxide crystals.

[0024] Figure 1a This is a scanning electron microscope image of the Cu2O cubes prepared above; Figure 1b This is its XRD phase analysis diagram. For example... Figure 1a and Figure 1b As shown: The obtained Cu2O crystals have uniform size and morphology, with an average particle size of 432.04 nm. The position of its diffraction peak is completely consistent with the standard diffraction peak of cuprous oxide (JPCDS05-0667). The 2θ angles of its three main diffraction peaks are 30°, 36° and 42°, respectively, which correspond to the (110), (111) and (200) crystal planes of copper.

[0025] (2) Disperse 100 mg of the above-prepared Cu2O, 9 mg of NiCl2, 9 mg of CoCl2, 7 mg of MnCl2 and 6 mg of CrCl3 in 100 mL of ethanol / water (volume ratio 1:1) mixed solvent, and sonicate to form a uniform suspension.

[0026] (3) Add 3.33g of polyvinylpyrrolidone (PVP) to the obtained suspension and stir for 10min to obtain a mixed solution.

[0027] (4) Under the condition of 25℃ water bath, add 40mL of 1.0mol / L Na2S2O3 solution to the above mixed solution, and (etch) the reaction for 20min to obtain the product.

[0028] (5) The product was centrifuged and washed with ethanol and deionized water in sequence. After vacuum drying at 60°C, hollow high-entropy hydroxide cubes were obtained.

[0029] Figure 2a and Figure 2b The images shown are scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the hollow high-entropy transition metal hydroxide cubes prepared above. Figure 2c , Figure 2d , Figure 2e , Figure 2f , Figure 2g and Figure 2h These are the energy dispersive X-ray energy (EDS) spectra of Co, Mn, Ni, Cu, Cr, and O, respectively.

[0030] like Figures 2a-2h As shown, Ni, Co, Cu, Mn and Cr elements are evenly distributed, the edges of the cube are clearly visible, and its surface is composed of interlaced nanosheets, exhibiting a typical open porous structure with obvious internal cavities, indicating that the controllable preparation of hollow high-entropy hydroxide cubes has been successfully achieved.

[0031] Example 2 The rest is the same as in Example 1; the difference is that the reaction time in step (4) of Example 1 is changed to 10 min. Figure 3 The image shows a scanning electron microscope (SEM) image of the corresponding hollow high-entropy hydroxide cubes. Figure 3 As shown: Some cubic particles still contain incompletely etched Cu2O inside, forming a transitional structure similar to "egg yolk-eggshell".

[0032] Example 3 (1): Same as step (1) in Example 1.

[0033] (2) 100 mg Cu2O, 9 mg NiCl2, 9 mg CoCl2, 6 mg FeCl3 and 6 mg CrCl3 were dispersed in 100 mL of ethanol / water (volume ratio 1:1) mixed solvent and ultrasonically treated to form a uniform suspension.

[0034] (3) Add 3.33g PVP to the obtained suspension and stir for 10min to obtain a mixed solution.

[0035] (4) Under the condition of 25℃ water bath, 40mL of 1.0mol / L Na2S2O3 solution was added dropwise to the above mixed solution, and the product was obtained after reacting for 20min.

[0036] (5) The product was centrifuged and washed with ethanol and deionized water in sequence. After vacuum drying at 60°C, a hollow high-entropy hydroxide cube containing Fe, Ni, Co, Cr and Cu was obtained.

[0037] Figure 4a Here is a scanning electron microscope image of the hollow high-entropy transition metal hydroxide prepared above; Figure 4b , Figure 4c , Figure 4d , Figure 4e , Figure 4f , Figure 4g and Figure 4hThese are the energy dispersive X-ray energy (EDS) spectra of Cu, Fe, Co, Ni, Cr, O, and the mixed energy of each element.

[0038] like Figures 4a-4h As shown, the obtained product has good morphology and size uniformity, exhibiting a complete and regular cubic framework structure, and the Fe, Ni, Co, Cr and Cu elements are uniformly distributed, consistent with the morphology of the high-entropy hydroxide sample in Example 1, proving that the method has good universality and scalability in the control of high-entropy hydroxide components.

[0039] Example 4 (1) Add 2.0 mol / L 10 mL NaOH solution and 3 g PVP to 0.01 mol / L 100 mL CuCl2·2H2O aqueous solution. Stir the reaction in a 60℃ water bath for 0.5 h. Then add 0.6 mol / L 10 mL ascorbic acid dropwise to the aqueous solution and continue the reaction in a water bath for about 1 h. After centrifuging, washing and drying the product, octahedral cuprous oxide crystals are obtained.

[0040] (2) Disperse 100 mg of Cu2O, 9 mg of NiCl2, 9 mg of CoCl2, 6 mg of FeCl3 and 6 mg of CrCl3 prepared above in 100 mL of ethanol / water (volume ratio 1:1) mixed solvent, and sonicate to form a uniform suspension.

[0041] (3) Add 3.33g PVP to the obtained suspension and stir for 10min to obtain a mixed solution.

[0042] (4) Add 40 mL of 1.0 mol / L Na2S2O3 solution to the above mixed solution at room temperature and react for 20 min.

[0043] (5) The product was centrifuged and washed with ethanol and deionized water in sequence. After vacuum drying at 60°C, hollow high-entropy transition hydroxide octahedrons were obtained.

[0044] Figure 5 The image shows a scanning electron microscope (SEM) image of the corresponding hollow high-entropy hydroxide octahedron. Figure 5 As shown, the obtained product has good morphology and size uniformity, exhibiting a complete and regular octahedral morphology.

[0045] This invention utilizes Cu2O with (pre-synthesized) cubic, octahedral, or other morphologies as templates to form a suspension with a multi-metal salt precursor. The template surface is controlled by PVP surfactant, and dynamic coordination etching is performed using thiosulfate ions. This simultaneously achieves Cu2O template etching and heterogeneous nucleation of multi-metal hydroxides to obtain a high-entropy hydroxide crystal with a complete hollow structure.

[0046] In summary, the preparation method of the present invention designs a reaction system that combines coordination etching and metal complexation functions, simultaneously controls the etching kinetics of Cu2O templates and the nucleation process of multi-metal hydrogen-based oxides, and balances the uniformity of high-entropy components and structural integrity through synergistic optimization of the composition of metal precursors and solvents.

Claims

1. A method for preparing a hollow high-entropy transition metal hydroxide crystal, comprising: Provides cuprous oxide crystals; Nickel salt precursor, cobalt salt precursor, chromium salt precursor, manganese salt and / or iron salt precursor, and cuprous oxide crystals were respectively added to an ethanol / water mixed solvent to prepare a uniformly dispersed suspension. Polyvinylpyrrolidone was added to the above suspension and mixed thoroughly to obtain a mixed solution; Then, the reactant containing thiosulfate is added dropwise to the above mixed solution, and after the reaction, hollow high-entropy transition metal hydroxide crystals are obtained by separation.

2. According to the preparation method of claim 1, the volume ratio of ethanol to water in the ethanol / water mixed solvent is 1:1, and the suspension contains: 0.9~1.1 mg / mL of cuprous oxide crystals; 0.08~0.1 mg / mL of NiCl2, 0.08~0.1 mg / mL of CoCl2, 0.06~0.08 mg / mL of MnCl2 and 0.05~0.07 mg / mL of CrCl3, and the mixed solution contains 30~35 mg / mL of polyvinylpyrrolidone.

3. According to the preparation method of claim 1, the volume ratio of ethanol to water in the ethanol / water mixed solvent is 1:1, and the suspension contains: 0.9~1.1 mg / mL of cuprous oxide crystals; 0.08~0.1 mg / mL of NiCl2, 0.08~0.1 mg / mL of CoCl2, 0.05~0.07 mg / mL of FeCl3 and 0.05~0.07 mg / mL of CrCl3, and the mixed solution contains 30~35 mg / mL of polyvinylpyrrolidone.

4. According to the preparation method of claim 2 or 3, the reactant added dropwise to the mixed solution is a 1.0 mol / L Na2S2O3 solution, the volume ratio of the added reactant to the ethanol / water mixed solvent is (35~45):100, and the reaction time is 15~25 min.

5. The preparation method according to claim 4, wherein the reaction is carried out in a water bath at 25°C for 20 min.

6. The preparation method according to claim 1, wherein cuprous oxide crystals are provided by the following method: Provide an aqueous solution containing NaOH and CuCl2·2H2O, wherein the concentration of NaOH is 0.15~0.23 mol / L and the concentration of CuCl2·2H2O is 0.008~0.01 mol / L; The above aqueous solution was stirred and reacted in a water bath at 55℃~65℃ for 20~40 min to obtain a water bath reaction solution; Then, ascorbic acid solution is added dropwise to the above water bath reaction solution to obtain a mixed reaction solution, wherein the concentration of ascorbic acid is 0.04~0.06 mol / L; After continuing the reaction of the mixed reaction solution under the above water bath conditions for 0.5 to 2 hours, cubic cuprous oxide crystals were obtained by separation.

7. The preparation method according to claim 1, wherein cuprous oxide crystals are provided by the following method: Provide an aqueous solution containing NaOH, polyvinylpyrrolidone, and CuCl2·2H2O, wherein the concentration of NaOH is 0.15~0.23 mol / L, the concentration of polyvinylpyrrolidone is 25~30 mg / mL, and the concentration of CuCl2·2H2O is 0.008~0.01 mol / L; The above aqueous solution was stirred and reacted in a water bath at 55℃~65℃ for 20~40 min to obtain a water bath reaction solution; Then, ascorbic acid solution is added dropwise to the above water bath reaction solution to obtain a mixed reaction solution, wherein the concentration of ascorbic acid is 0.04~0.06 mol / L; After continuing the reaction of the mixed reaction solution under the above water bath conditions for 0.5 to 2 hours, octahedral cuprous oxide crystals were obtained by separation.

8. A hollow high-entropy transition metal hydroxide crystal, prepared by the method according to any one of claims 1-7.

9. A hollow high-entropy transition metal hydroxide crystal, which has a cubic or octahedral morphology.

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