Nickel hydroxide coupled loose nanocuboid assembly and preparation method and application thereof

Abstract

The application provides a loose nanometer cubic box coupled with single-layer nickel hydroxide and a preparation method and application thereof, and the preparation method comprises the following steps: dropping potassium ferricyanide aqueous solution into an aqueous solution in which polyvinylpyrrolidone, sodium citrate and nickel acetate are dissolved, and then standing and reacting at room temperature after the dropping is completed to obtain a precursor material of solid nanometer cubic; and then the precursor material is added into a vanadate solution to react; the loose nanometer cubic box of the application takes the single-layer nickel hydroxide as an assembly unit, not only realizes self-stabilization of the ultra-thin structure unit through the interaction between the two single layers to reduce the surface energy, but also exposes most of the atoms on the surface, and has the advantages of uniformity, increased interlayer spacing, cross-layer assembly mode, cubic box shape and loose structure, so that the loose nanometer cubic box has a higher atomic exposure ratio and has a wide application prospect in the energy storage field. The loose nanometer cubic box can exist alone without a substrate, and provides the possibility for further modification and combination.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials technology, specifically relating to a loose nanocube assembled with nickel hydroxide coupled monolayer, its preparation method, and its application. Background Technology

[0002] With the advent of graphene and its superior properties and broad application prospects, the study of two-dimensional materials has become a frontier and hot topic in materials science research in recent years. Subsequently, various two-dimensional metals and their oxides, sulfides, and hydroxides have been prepared in large quantities, but it is difficult to obtain their monolayer or ultrathin films with only a few monolayers. Currently, their synthesis methods are divided into top-down and bottom-up methods, including mechanical exfoliation, vapor deposition, and liquid-phase synthesis. The efficiency of various exfoliation methods in obtaining products is low, making it difficult to meet the requirements of practical application; the products obtained by vapor deposition often depend on the presence of a substrate, which greatly limits their further modification and composite; the liquid-phase method is more efficient, but it is difficult to obtain a large amount of uniform ultrathin materials in a controllable manner, and the products are prone to re-agglomeration during collection, causing many of their internal components to fail to play their functional roles.

[0003] Two-dimensional semiconductor nickel hydroxide has been extensively studied in energy storage and catalysis due to its excellent electrical properties. However, to maximize its functionality, it is often necessary to expose its internal atoms as stably as possible on the surface and utilize them effectively. Therefore, developing and providing simple and efficient, high-performance, substrate-free quasi-monolayer ultrathin nickel hydroxide functional nanomaterials and their preparation methods is essential for realizing their large-scale functional applications. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the primary objective of this invention is to provide a method for preparing a loose nanocube box coupled with nickel hydroxide monolayer assembly.

[0005] A secondary objective of the present invention is to provide the above-described loose nanocube assembled with nickel hydroxide coupling monolayer.

[0006] A third object of the present invention is to provide the use of the above-described nickel hydroxide-coupled monolayer assembled loose nanocube.

[0007] This invention uses a solid cube containing nickel iron as a precursor structure. Through competitive capture and synchronous intercalation reactions with anions such as hydroxide and provanadate in vanadate solution, it is transformed into a loose nanocube assembled with nickel hydroxide coupled monolayer as the structural unit, with a size of 200 nm.

[0008] To achieve the above objectives, the solution of the present invention is:

[0009] A method for preparing a loose nanocubic cell coupled with nickel hydroxide monolayer assembly includes the following steps:

[0010] (1) Polyvinylpyrrolidone, sodium citrate and nickel acetate were dissolved in 100 mL of deionized water and stirred until a clear and transparent solution A was formed; potassium ferricyanide was dissolved in 100 mL of deionized water and stirred until a clear and transparent solution B was formed; solution B was slowly added dropwise to solution A, and the mixed solution was allowed to stand at room temperature to react, then centrifuged, washed with water three times, and dried to obtain a precursor material with a solid nanostructure cubic morphology.

[0011] (2) Add the precursor material from step (1) to 100 mL of aqueous solution containing sodium vanadate to react and obtain a loose nanocube assembled with nickel hydroxide coupled monolayer.

[0012] Preferably, in step (1), the amount of polyvinylpyrrolidone added is 0.5-5g, the amount of sodium citrate added is 1-3g, and the amount of nickel acetate added is 0.5-3g.

[0013] Preferably, in step (1), the amount of potassium ferricyanide added is 0.2-2g.

[0014] Preferably, in step (1), the reaction time is 48-72 hours.

[0015] Preferably, in step (2), the amount of the precursor material of the solid nanocube is 200 mg.

[0016] Preferably, in step (2), the amount of sodium vanadate added is 1-3g.

[0017] Preferably, in step (2), the reaction temperature is 20-80℃ and the time is 2-6h.

[0018] This invention first prepares a cubic nickel-iron precursor material. Then, using the precursor itself as a template and reactant, it undergoes simultaneous anion exchange and intercalation reactions in a sodium vanadate solution, ultimately transforming into a loosely assembled nanocube of nickel hydroxide coupled with a single layer. At the start of the transformation reaction, the six faces of the solid cubic precursor remain essentially unchanged, while its eight corners and twelve edges, due to their high curvature, exhibit high reactivity and thus react first with hydroxide ions in the solution to form a thin film of nickel hydroxide. Hydroxides then diffuse inward through the film covering the corners and edges, further competing to replace ferricyanide ions in the precursor, undergoing an exchange reaction until the final reaction is complete. Because the volume of hydroxide ions is much larger than that of ferricyanide ions, a loose, hollow structure is formed after hydroxide ions completely replace ferricyanide ions and react with nickel to form nickel hydroxide. Through the entire transformation process described above, a loosely assembled nanocube of coupled single layers is obtained for the first time. During the preparation process, both the preparation of the precursor and the transformation conditions play a crucial role in the formation of the product structure. In the precursor preparation process, sodium citrate can complex with nickel ions and then slowly release them during the reaction, playing a role in controlling crystal nucleation and growth. Meanwhile, polyvinylpyrrolidone (PVP) can adsorb around the crystal during crystal growth, hindering further growth and thus controlling crystal morphology and size. If the amount of sodium citrate and PPVP is too small, product agglomeration or even the formation of irregular large particles may occur, making it impossible to obtain a uniform nanocubic precursor. Secondly, in the conversion process from precursor to final product, the selected conversion reagent and the ratio of precursor to conversion reagent will ultimately affect the structure of the obtained nanomaterial. For conversion reagents, if strong alkaline reagents such as sodium hydroxide or potassium hydroxide are used, the final product is a compact structure assembled from particles, rather than a loose structure assembled from coupled monolayers. However, if conversion agents such as sodium metavanadate, sodium tungstate, or sodium molybdate are used, the conversion reaction cannot occur, and a product containing nickel hydroxide cannot be obtained. Regarding the feed ratio of precursor and conversion reagent, if the precursor is in excess, the reaction will not proceed completely, resulting in a core-shell structure with a nickel hydroxide shell and a nickel-iron core. Conversely, if the conversion reagent is used in excessive amounts, it will accelerate the conversion reaction, leading to increased assembly unit thickness and localized agglomeration. Therefore, only by using sodium orthovanadate as the conversion agent and applying an appropriate amount can a self-stabilizing, coupled monolayer assembled loose nanocube be obtained through the interaction of multiple reactions such as substitution and intercalation.

[0019] The loose nanocube of the present invention has the following characteristics: 1) It uses coupled monolayers as assembly units, which not only reduces the surface energy through the interaction between the two coupled monolayers to achieve self-stabilization of the ultrathin structural units, but also exposes most of its atoms on the surface; 2) The increased interlayer spacing can accelerate the diffusion rate of electrolyte ions during electrochemical reactions, thereby effectively improving the atomic utilization rate; 3) The coupled bilayer units are assembled into uniform nanocubes through cross-assembly, which not only avoids the re-aggregation of ultrathin assembly units, but also effectively enhances its structural stability; 4) It has a loose assembly structure with a large number of pores and channels inside, which is caused by the large number of void structures between assembly units, thus giving the material an extremely high specific surface area and a hierarchical porous structure; 5) It can exist independently of the substrate, which facilitates further composite and modification. In summary, the basic assembly unit of the loose nanocube is a nickel hydroxide coupled monolayer with increased interlayer spacing. These layers are cross-assembled into a loose, uniform nanocube. This structure not only prevents the aggregation of assembly units, thus exposing most of the atoms on the surface, but also has higher structural stability, enabling the material to have both ultra-high capacity and long-term cycling stability during electrochemical processes.

[0020] A loose nanocube assembled with nickel hydroxide-coupled monolayer is obtained by the above-described preparation method.

[0021] Application of the above-mentioned nickel hydroxide coupled monolayer assembly loose nanocube in the field of energy storage.

[0022] Due to the adoption of the above solution, the beneficial effects of the present invention are:

[0023] First, the porous nanocubic cell of this invention possesses both ultra-high atomic surface exposure and self-stabilizing properties, making it promising for use in energy storage materials while exhibiting high specific capacity and cycle stability. Using nickel hydroxide-coupled monolayers as assembly units, it not only reduces surface energy through the interaction between the two coupled monolayers to achieve self-stabilization of the ultrathin structural unit, but also exposes the vast majority of its atoms on the surface, resulting in uniformity, increased interlayer spacing, a cross-layer assembly pattern, a cubic shape, and a porous structure. This leads to a higher atomic exposure ratio and a stable structure, making it a promising candidate for applications in the energy storage field. Furthermore, its ability to exist independently of a substrate provides possibilities for further modification and composite application.

[0024] Secondly, the preparation method of this invention is simple, easy to control, mild, efficient, green and environmentally friendly, and low in cost. It provides a reference for the synthesis of other quasi-monolayer transition metal compounds and can also be extended to the synthesis of other similar nanomaterials. Attached Figure Description

[0025] Figure 1 The image shows the precursor material obtained in Example 2 at a magnification of 500 nm.

[0026] Figure 2 This is a SEM image of the loose nanocube assembled by nickel hydroxide coupled monolayer in Example 2 at a magnification of 1 μm.

[0027] Figure 3 This is a TEM image of the loose nanocube assembled with nickel hydroxide coupled monolayer in Example 2 at a magnification of 10 nm.

[0028] Figure 4 This is a TEM image of the loose nanocube assembled with nickel hydroxide coupled monolayer in Example 2 at a magnification of 2 nm.

[0029] Figure 5 The graph shows the constant current charge-discharge curves of the loose nanocube assembled with nickel hydroxide coupled with a single layer in Example 2 at different current densities.

[0030] Figure 6 The graph shows the cycling performance of the loose nanocube assembled with nickel hydroxide coupled to a single layer in Example 2. Detailed Implementation

[0031] The technical solution of the present invention will be further described in detail below with reference to several embodiments. These embodiments are implemented on the premise of the technical solution of the invention, and detailed implementation methods and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0032] The technical solution of the loose nanocube box with nickel hydroxide coupling monolayer assembly of the present invention will be further described below with reference to specific embodiments and accompanying drawings.

[0033] All reagents used in this invention were purchased from Sinopharm Chemical Reagent Co., Ltd., including: polyvinylpyrrolidone K30, GR (Wokai); sodium citrate, 98% (Wokai); nickel acetate, AR (Hushi), ≥98.0%; potassium ferricyanide, AR (Hushi), ≥99.5%; and sodium orthovanadate, AR (Wokai). All instruments used in this invention are conventional chemical instruments.

[0034] Example 1

[0035] (1) Dissolve 0.5g polyvinylpyrrolidone, 1g sodium citrate and 0.5g nickel acetate in 100mL of deionized water and stir until a clear and transparent solution A is formed.

[0036] (2) Dissolve 0.2g potassium ferricyanide in 100mL of deionized water and stir until a clear and transparent solution B is formed;

[0037] (3) Slowly add the B solution obtained in step (2) to the A solution obtained in step (1), and let the mixed solution stand at room temperature for 48 hours. Then centrifuge, wash with water three times, and dry to obtain a precursor material with a solid nanostructure cubic morphology.

[0038] (4) Take 200 mg of the precursor material from step (3) and add it to 100 mL of deionized water containing 1 g of sodium orthovanadate. React at 20 °C for 5 h to obtain the target product.

[0039] Example 2

[0040] (1) Dissolve 1.5g polyvinylpyrrolidone, 1.5g sodium citrate and 0.8g nickel acetate in 100mL of deionized water and stir until a clear and transparent solution A is formed.

[0041] (2) Dissolve 0.5g potassium ferricyanide in 100mL of deionized water and stir until a clear and transparent solution B is formed;

[0042] (3) Slowly add the B solution obtained in step (2) to the A solution obtained in step (1), and let the mixed solution stand at room temperature for 60 h, then centrifuge, wash with water three times, and dry to obtain a precursor material with a solid nanostructure cubic morphology.

[0043] (4) Take 200mg of the precursor material from step (3) and add it to 100mL of deionized water containing 2g of sodium orthovanadate. React at 40℃ for 3h to obtain the target product, a loose nanocube assembled with nickel hydroxide coupling monolayer.

[0044] This embodiment, as the recommended optimal embodiment of the present invention, is analyzed based on experimental data as follows:

[0045] Figure 1 The image shows a SEM image of the precursor material obtained in step (3) of Example 2 at a magnification of 500 nm. As can be seen from the image, the precursor has a solid cubic structure and is a metal-organic complex formed by nickel ions and ferricyanide ions through coordination bonds, with a side length of approximately 200 nm.

[0046] Figure 2 The image shows a SEM image of the loose nanocube obtained by nickel hydroxide coupled monolayer assembly in step (4) of Example 2 at a multiple of 1 μm. As can be seen from the image, the product has a uniform cubic structure and the surface becomes a wrinkled structure.

[0047] at the same time, Figure 3 The image shows a TEM image of the loose nanocube assembled by nickel hydroxide coupled monolayer at a magnification of 10 nm. As can be seen from the image, the product is a loose hollow cubic box assembled by cross-assembly of ultrathin films.

[0048] at the same time, Figure 4 This is a TEM image of the loosely packed nanocubic cell assembled from a nickel hydroxide-coupled monolayer at a magnification of 2 nm. The high-resolution results show that the structural units of the coupled monolayer have an interlayer spacing of 1 nm, which is much larger than the typical interlayer spacing of 0.78 nm for α-Ni(OH)₂.

[0049] The aforementioned nickel hydroxide coupled monolayer, as an assembly unit, not only reduces the surface energy through the interaction between the two coupled monolayers to achieve self-stabilization of the ultrathin structural unit, but also exposes the vast majority of its atoms on the surface, resulting in uniformity, increased interlayer spacing, cross-layer assembly mode, cubic box shape, and loose structure, thus simultaneously possessing a higher atomic exposure ratio and a stable structure.

[0050] Testing showed that this loosely packed nanocubic cell, coupled with a single layer of nickel hydroxide, exhibited excellent electrochemical performance as a cathode material in an alkaline aqueous battery in 6M KOH electrolyte. Figure 5 As shown, its maximum specific capacity at a current density of 1 A / g is as high as 280 mAh / g, which is close to its theoretical specific capacity. Figure 6 The specific capacity change curves during 10,000 charge-discharge cycles are shown, demonstrating its excellent cycle stability. These superior high capacity and highly stable electrochemical properties give this material broad application prospects in the energy storage field. This dual high performance is also consistent with its high surface atom exposure ratio and self-stabilizing structural characteristics.

[0051] Example 3

[0052] (1) Dissolve 3g polyvinylpyrrolidone, 3g sodium citrate and 2g nickel acetate in 100mL of deionized water and stir until a clear and transparent solution A is formed.

[0053] (2) Dissolve 1.5g of potassium ferricyanide in 100mL of deionized water and stir until a clear and transparent solution B is formed;

[0054] (3) Slowly add the B solution obtained in step (2) to the A solution obtained in step (1), and let the mixed solution stand at room temperature for 72 hours. Then centrifuge, wash with water three times, and dry to obtain a precursor material with a solid nanostructure cubic morphology.

[0055] (4) Take 200 mg of the precursor material from step (3) and add it to 100 mL of deionized water containing 3 g of sodium orthovanadate. React at 60 °C for 2 h to obtain the target product.

[0056] The above description of the embodiments is intended to enable those skilled in the art to understand and use the present invention. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing nickel hydroxide coupled single-layer assembled loose nanocuboid, characterized in that, It comprises the following steps: (1) polyvinylpyrrolidone, sodium citrate, nickel acetate are dissolved in deionized water in turn, stirring to form a clear transparent solution A; potassium ferricyanide is dissolved in deionized water, stirring to form a clear transparent solution B; B solution is added dropwise to the A solution, and the mixed solution is placed at room temperature for reaction, then centrifuged, washed with water three times, dried to obtain a solid nanostructure cubic precursor material; (2) the precursor material of step (1) is added to the aqueous solution containing sodium orthovanadate for reaction, to obtain a loose nanocubic box coupled with single-layer assembled nickel hydroxide.

2. The production method according to claim 1, characterized by, In step (1), the addition amount of polyvinylpyrrolidone is 0.5-5g, the addition amount of sodium citrate is 1-3g, and the addition amount of nickel acetate is 0.5-3g.

3. The preparation method according to claim 1, characterized in that, In step (1), the addition amount of potassium ferricyanide is 0.2-2g.

4. The production method according to claim 1, characterized by, In step (1), the reaction time is 48-72h.

5. The preparation method according to claim 1, characterized in that, In step (2), the addition amount of the precursor material is 200mg.

6. The method of claim 1, wherein, In step (2), the addition amount of sodium orthovanadate is 1-3g.

7. The preparation method according to claim 1, characterized in that, In step (2), the reaction temperature is 20-80℃, and the reaction time is 2-6h.

8. A loose nanocuboctahedron of nickel hydroxide coupled monolayer assembly, characterized by, It is obtained by the preparation method of any one of claims 1-7.

9. The application of a loose nanocubic box coupled with single-layer assembled nickel hydroxide in the field of energy storage according to claim 8.

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