Three-dimensional flower-like Ni x P y -Ni x S y Preparation methods and applications of composite structures

Abstract

This invention discloses a three-dimensional flower-like Ni x P y -Ni x S y Preparation methods and applications of composite structures belong to Ni x P y -Ni x S y In the field of composite material preparation, this method uses nickel nitrate hexahydrate, ammonium fluoride, and urea to prepare a reaction solution, and then conducts a high-temperature sealed reaction to prepare a sample, which reacts with phosphorus powder to produce pure-phase Ni. x P y And further react with sulfur powder to form Ni composite material. x P y -Ni x S y This process generates Ni atoms with regular morphology and excellent dispersion. x P y -Ni x S y The composite material has a relatively large specific surface area, forming more active contact points. At the same time, the reaction temperature of this synthesis method is much lower than the high temperature required by other methods, which makes it easier to control the particle size. Therefore, it is easier to estimate the turnover frequency and evaluate the relative reactivity of the crystal facets. It also reduces the emission of toxic and harmful gas PH3, significantly improves the phosphating efficiency, and for the first time applies transition metal phosphorus sulfides to the field of humidity sensing to construct a new type of humidity sensor.

Description

Technical Field

[0001] This invention relates to Ni x P y -Ni x S y In the field of composite material preparation, especially involving three-dimensional flower-like Ni x P y -Ni x S y Preparation methods and applications of composite structures. Background Technology

[0002] In recent years, transition metal oxides, hydroxides, phosphides, and sulfides have attracted widespread attention in the research community due to their excellent physicochemical properties. Among them, transition metal phosphides (TMPs), as an n-type semiconductor material, exhibit quasi-metallic properties compared to p-type semiconductor transition metal oxides or hydroxides, thus they are more conducive to electron transfer between interfaces. Nickel phosphide (Ni) is a particularly notable example. x P y Because of its unique d-orbital incompletely filled electron structure, nickel phosphide exhibits superior properties compared to other transition metal phosphides. Studies have shown that the surface of nickel phosphide has more unsaturated atoms, making it easier to transport electrons, and the strong Ni–P bonds improve its resistance to chemical corrosion and oxidation, while also increasing its thermal stability and hardness. It is even unaffected by strong acid or strong alkali environments. Due to its good electrical conductivity, excellent chemical stability and environmental friendliness, nickel phosphide is considered one of the most competitive candidate materials in the fields of batteries, electrocatalysis, and water electrolysis.

[0003] In addition, Ni in transition metal sulfides (TMSs) x S y Due to its superior redox properties, abundant edge active sites, and low cost, it has become another very popular candidate material. Studies have found that the heterostructure constructed from TMPs and TMSs can modulate the interaction between two anions with different electronegativity (S>P), optimizing the electronic structure of the interface and facilitating electron transfer on the composite material surface. Meanwhile, Ni... x P y After Ni x S y After modification, the charge on the heterostructure interface will redistribute, causing Ni to... x P y -Ni x S y Composite materials have superior physicochemical properties.

[0004] Combining the advantages of transition metal sulfides under alkaline conditions with rationally formulated composites of transition metal phosphides is a promising strategy for achieving high-performance composite materials. Therefore, Ni... x P y -Ni x S y The synthesis of composite materials is gradually emerging in a large number of articles.

[0005] Ni in the existing technology x P y -Ni x S y The main methods for synthesizing composite materials include electrodeposition, temperature-programmed reduction, chemical vapor deposition using NaH2PO2˙H2O as the phosphorus source, and stepwise hydrothermal methods. Electrodeposition is the process of electrochemically depositing metals from aqueous, non-aqueous, or molten salt solutions of their compounds. This process requires electrolyte conditions and is highly susceptible to factors such as electrolyte composition, pH, temperature, and current density. Therefore, transition metal phosphorus sulfides synthesized by electrodeposition often consist of aggregated solid particles of varying sizes, significantly reducing the number of active sites and hindering the improvement of composite material properties. A common method for obtaining phosphides using temperature-programmed reduction is the reduction of the corresponding phosphates with hydrogen gas. This synthesis method is characterized by high reaction temperatures. This can lead to the phosphide active phase particles becoming larger during formation, making it difficult to precisely control particle size. Consequently, it is difficult to estimate the turnover frequency and directly assess the relative reactivity of crystal planes. Chemical vapor deposition (CVD) using NaH2PO2˙H2O as the phosphorus source is the most common method for phosphorus sulfidation. Currently, NaH2PO2˙H2O is used as the phosphorus source for phosphating target substances. However, NaH2PO2˙H2O decomposes rapidly when heated above 200℃, releasing highly toxic and spontaneously combustible PH3 gas, posing a certain danger. The stepwise hydrothermal method commonly uses NaH2PO2˙H2O as the phosphorus source and Na2S as the sulfur source. Compared to CVD, its phosphorus sulfidation efficiency is very low, and it is also prone to side reactions within the reaction system. Summary of the Invention

[0006] The purpose of this invention is to provide a three-dimensional flower-like Ni x P y -Ni x S y Preparation methods and applications of composite structures to solve the problems caused by existing synthesis methods for Ni x P y -Ni x S yComposite materials have few active contacts and irregular surfaces. They also require a high-temperature environment for guidance. During the synthesis process, a large amount of toxic and harmful gas PH3 is emitted, phosphating efficiency is low, and humidity sensors made of transition metals have poor response recovery time and sensing performance, which prevents them from being applied in practice.

[0007] This invention provides three-dimensional flower-shaped Ni x P y -Ni x S y The preparation method and application of the composite structure are carried out according to the following steps:

[0008] 1. Prepare the reaction solution by dissolving nickel nitrate hexahydrate, ammonium fluoride and urea in a solvent and stirring magnetically on a stirring table until dissolved to obtain a uniformly mixed solution.

[0009] Wherein, the molar ratio of nickel nitrate hexahydrate to urea is set to 1:(0.5-2); the molar ratio of nickel nitrate hexahydrate to ammonium fluoride is 1:(0.5-2); the total molar ratio of nickel nitrate hexahydrate to urea to the volume ratio of solvent is 1:(7-20), and the solvent is composed of ethanol and deionized water; wherein the total volume of ethanol and deionized water is 30 mL, and the concentration of ethanol is (10-50) wt%.

[0010] II. Sample preparation: The solution was stirred and mixed evenly in a stainless steel reactor and then sealed at high temperature for reaction. After cooling to room temperature, the mixture was thoroughly washed with a cleaning solution to remove impurities, centrifuged, and then dried.

[0011] The high temperature is between 120-200℃, the reaction time is between 1-24h, the stainless steel reactor lining is made of polytetrafluoroethylene, and the cleaning solution is a mixture of deionized water and ethanol.

[0012] III. Production of pure-phase Ni x P y The dried sample and phosphorus powder were placed in a tube furnace and heated under inert gas conditions for several hours to obtain pure-phase Ni. x P y .

[0013] The sulfur powder is 10-30 times the mass of the dried sample, and is calcined in an inert gas environment at a heating rate of 1-10℃ / min to above 450℃ to obtain a smooth, flower-like Ni. x P y .

[0014] IV. Composite Material Ni x P y -Nix S y Generation: Ni x P y Sulfur powder was placed in a tube furnace and heated and held at that temperature for several hours under inert gas conditions to obtain the composite material Ni. x P y -Ni x S y .

[0015] Wherein, Ni x P y The sulfur powder and the sulfur powder are respectively loaded into two alumina ceramic boats, wherein the mass of the sulfur powder is Ni. x P y The concentration is 10-30 times that of Ni, and calcined at a heating rate of 1-10℃ / min to above 450℃ in an inert gas environment to obtain flower-like Ni with small particles attached to the surface. x P y -Ni x S y Composite materials.

[0016] V. The three-dimensional flower-shaped Ni x P y -Ni x S y The composite material powder is ground into a paste with a small amount of anhydrous ethanol. The mixture is then drop-coated onto an Au interdigitated electrode and dried at 70°C to be used in the field of humidity sensing to construct a new type of humidity sensor.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] This invention combines the advantages of hydrothermal reaction and chemical vapor deposition, forming composite materials with regular morphologies. These composite materials exhibit excellent particle dispersion, a relatively large specific surface area, and numerous active contact sites. This promotes water molecule penetration and diffusion while providing more adsorption sites. Furthermore, the reaction temperature is significantly lower than the high temperatures required by temperature-programmed reduction methods, avoiding the problem of phosphide active phase particles growing larger during formation. This facilitates particle size control, making it easier to estimate turnover frequency and assess the relative reactivity of crystal faces. In the field of material synthesis, traditional phosphating processes generate toxic and harmful PH3 gas, which not only pollutes the environment but also threatens the health of operators. The innovative use of phosphate powder instead of NaH2PO2·H2O reduces the emission of toxic and harmful PH3 gas. This means that the production process can reduce harmful substances. The emission of these materials can reduce pressure on the ecosystem, achieve environmental protection, and mitigate potential harm to the environment and human health. By optimizing the conditions and processes of the phosphating reaction and using phosphoric acid powder instead of NaH2PO2 in production, this method significantly improves phosphating efficiency. This means that a higher conversion rate can be achieved in a shorter time, producing more target products, thereby reducing production costs and improving production efficiency. More importantly, the material has excellent humidity sensitivity performance and is the first to apply transition metal phosphorus sulfides to the field of humidity sensing under high-temperature conditions to construct a new type of humidity sensor. Furthermore, the synthesized composite material can effectively reduce the response recovery time of the humidity sensor and improve sensing performance, thus opening up a new path for transition metal phosphorus sulfides in the field of humidity sensing under high-temperature conditions. In addition, the material synthesis method is simple, efficient, and environmentally friendly. The solvents used are water and ethanol, which are environmentally friendly and suitable for large-scale production. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 To prepare three-dimensional flower-like Ni x P y -Ni x S y Flowchart of composite structure preparation;

[0021] Figure 2 Ni(OH)2-Ni in Example 2 of this invention x Py XRD patterns;

[0022] Figure 3 The SEM image (a) Fe in Embodiment 3 of the present invention x P y -Fe x S y (b)Co x P y -Co x S y (c)Cu x P y -Cu x S y ,(d)Zn x P y -Zn x S y ;

[0023] Figure 4 Pure phase Ni in Example 1 of this invention x P y SEM images;

[0024] Figure 5 Pure phase Ni in Example 1 of this invention x P y XRD patterns;

[0025] Figure 6 Ni in Embodiment 1 of the present invention x P y -Ni x S y SEN image of the composite material;

[0026] Figure 7 Ni prepared in Example 1 of this invention x P y -Ni x S y XRD pattern of the composite material;

[0027] Figure 8 Ni prepared in Example 3 of this invention x P y -Ni x S y The response recovery curve of the composite material over one cycle in the range of 11-97%RH;

[0028] Figure 9 Example 3Ni of the present invention x P y -Ni x S y Response recovery curves of the composite material in the range of 11-97% RH;

[0029] Figure 10 Example 4Ni of the present invention x P y -Ni x S y Dynamic response recovery characteristics of composite materials;

[0030] Figure 11 Ni prepared in Example 4 of this invention x P y -Ni x S y Humidity hysteresis curve of composite materials;

[0031] Figure 12 Ni prepared in Example 4 of this invention x P y -Ni x S y Reproducibility of composite materials in the range of 11-97% RH;

[0032] Figure 13 Ni prepared as Comparative Example 1 of this invention x P y -Ni x S y Complex impedance curves of composite materials in different humidity ranges. Detailed Implementation

[0033] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0034] The components of the embodiments of the invention described and shown in the accompanying drawings can typically be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of the invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.

[0035] Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] The following is combined with Figures 1 to 13 As shown, this embodiment of the invention provides a three-dimensional flower-shaped Ni x P y -Ni x S y The preparation method and application of the composite structure, and all raw materials used in the examples of this invention, are commercially available unless otherwise specified.

[0037] Example 1:

[0038] Raw materials: nickel nitrate hexahydrate, urea, ammonium fluoride, ethanol and deionized water.

[0039] This embodiment provides a method for three-dimensional flower-shaped Ni x P y -Ni x S y The composite structure is prepared according to the following steps:

[0040] 1. Dissolve nickel nitrate hexahydrate, urea and ammonium fluoride in a molar ratio of 1:2:1 in a solvent composed of ethanol and deionized water, wherein the concentration of ethanol is (10-50)wt%. Stir magnetically until dissolved to obtain a uniformly mixed solution.

[0041] 2. Transfer the well-stirred solution from step 1 to a stainless steel reactor lined with polytetrafluoroethylene, seal it, and react it under high temperature. After naturally cooling to room temperature, wash the reacted solution thoroughly with deionized water and ethanol, and dry it in an oven at 70°C for 12 hours to obtain a three-dimensional micron-shaped Ni(OH)2 precursor.

[0042] 3. The Ni(OH)₂ precursor and phosphorus powder obtained in step 2 are respectively loaded into two alumina ceramic boats, wherein the mass of phosphorus powder is 10-30 times that of the Ni(OH)₂ precursor. The boats are then calcined in an inert atmosphere at a heating rate of 1-10℃ / min to above 450℃ to obtain a smooth, flower-like Ni. x P y .

[0043] IV. The Ni obtained in step three x P y Sulfur powder and nitrogen are separately loaded into two alumina ceramic boats, wherein the mass of sulfur powder is Ni. x P y The concentration is 10-30 times that of Ni, and it is calcined at a heating rate of 1-10℃ / min to above 450℃ in an inert atmosphere to obtain flower-like Ni with small particles attached to the surface. x P y -Ni x S y Composite materials.

[0044] Among them, Ni in step three is obtained by scanning electron microscopy. x P y Sample surface images, showing the microscopic morphology and structural features of the sample surface, are shown in the SEM images. Figure 4 Its XRD test Figure 5 It can be seen that after calcination, crystallization is complete, and the XRD diffraction peaks are consistent with those of Ni.x P y There is a very good response.

[0045] Simultaneously, Ni in step three was obtained using scanning electron microscopy. x P y -Ni x S y Images of the composite material sample surface, showing the microstructure and structural features of the Ni sample surface. x P y -Ni x S y The SEM image of the composite material is shown below. Figure 6 Its XRD test Figure 7 It can be seen that after calcination, crystallization is complete, and the XRD diffraction peaks are consistent with those of Ni. x P y -Ni x S y There are good corresponding options for each.

[0046] Example 2:

[0047] In this embodiment, phosphoric acid powder is used instead of NaH2PO2 during the phosphating process, which can improve the phosphating efficiency.

[0048] Theoretically, 1 mol of phosphorus powder can generate 1 mol of Ni. x P y However, for NaH2PO2˙H2O, the formation of 1 mol Ni x P y Approximately 2.7 mol of NaH₂PO₂˙H₂O is required. (See the reaction equation below.)

[0049] 8H2PO2 - →4PH3 + 4HPO4 2- ①

[0050] 3 x Ni2 + +12OH - +4PH3→3Ni x P y +6H₂O + P↑ ②

[0051] yP+xNi2+→Ni x P y ③

[0052] The above conclusions have also been confirmed by experiments:

[0053] 1 mol of NaH2PO2 was weighed and used to phosphate Ni(OH)2, and the result was characterized by XRD. The characterization results are as follows: Figure 2It can be seen that the product is composed of Ni(OH)2 and Ni x P y It consists of two phases. This indicates that Ni(OH)2 was not completely converted into Ni. x P y .

[0054] Example 3:

[0055] This invention discloses a method for synthesizing Ni with a three-dimensional flower-like structure. x P y -Ni x S y The method for preparing composite materials is not limited to specific metals but can also be widely applied to the phosphating and sulfidation processes of various transition metals, demonstrating excellent versatility. This unique composite material structure endows the materials with distinctive physical and chemical properties, enabling them to play important roles in various application fields, such as... Figure 3 The microstructures of these composite materials exhibit rich diversity and complexity. When discussing the core value of this invention, several key points need to be emphasized. First, the universality of this method means it can be extended to a variety of transition metals, providing a wide range of material choices for research and industrial applications. Second, the three-dimensional flower-like Ni prepared by this method... x P y -Ni x S y Composite materials, due to their unique structural characteristics, exhibit excellent performance in various fields such as catalysis, energy storage, and sensors. Furthermore, Figure 3 The microstructure images of the composite materials shown not only confirm the complexity and diversity of materials but also reflect the precision and controllability of the preparation method. These images provide intuitive evidence for studying the relationship between the structure and properties of materials, and thus provide important information for optimizing the performance and applications of materials. In summary, the preparation method provided by this invention not only provides three-dimensional flower-like Ni x P y -Ni x S y The production of composite materials provides an efficient and universal approach, and drives innovative development in materials science, offering new solutions to material needs in various fields. This is achieved through detailed analysis. Figure 3 The composite material structures shown can be further explored and expanded to explore the potential applications of these materials and contribute to scientific and technological progress.

[0056] Example 4:

[0057] Three-dimensional flower-like Ni x P y -Ni x S ySpecific implementation of humidity sensitivity testing for composite structures:

[0058] Step 1: Preparation of Humidity Sensing Element

[0059] The three-dimensional flower-shaped Ni x P y -Ni x S y The composite material powder is ground into a paste with a small amount of anhydrous ethanol. The mixture is then drop-coated onto an Au interdigitated electrode and dried at 70°C to be used in the field of humidity sensing to construct a new type of humidity sensor.

[0060] Step 2: Humidity Sensitivity Test

[0061] reagents LiCl <![CDATA[CH3COOK]]> <![CDATA[MgCl2]]> <![CDATA[K2CO3]]> <![CDATA[Mg(NO3)2]]> Relative humidity (%RH) 11 22 32 43 54 reagents KI NaCl KCl <![CDATA[Pb(NO3)2]]> Relative humidity (%RH) 69 75 84 97

[0062] Table 1. Configurations for Different Relative Humidities

[0063] The device was placed in nine wide-mouthed glass bottles containing different saturated salt solutions (LiCl, CH3COOK, MgCl2, K2CO3, Mg(NO3)2, KI, NaCl, KCl, and Pb(NO3)2) to test its humidity sensing performance. The relative humidity (RH) values ​​of the nine saturated salt solutions at room temperature (25℃) were 11%, 22%, 32%, 43%, 54%, 69%, 75%, 84%, and 97%, respectively. The humidity sensor's performance was tested using an LCR digital bridge analyzer (TH2829A, Changzhou, China) under AC voltage of 1V and a working frequency range of 200Hz-200kHz. The test results are presented in six graphs. Figures 8 to 13 These charts record in detail the material's response under different relative humidity conditions, thus comprehensively demonstrating the material's performance as a humidity sensor. These data show that the material of this invention can accurately sense changes in different humidity levels and exhibits good stability and reliability. In summary, humidity sensing performance tests conducted in a series of saturated salt solutions fully verified the excellent performance of the material of this invention in humidity detection. These test results not only demonstrate the material's high sensitivity to humidity changes but also show its potential for significant applications in environmental monitoring and control.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. Three-dimensional flower-like Ni x P y -Ni x S y The method for preparing the composite structure is characterized by: Includes the following steps: Sp1: Preparation of reaction solution: Dissolve nickel nitrate hexahydrate, ammonium fluoride and urea in ethanol solvent, place on a stirring table and stir magnetically until dissolved to obtain a uniformly mixed solution; Sp2: Sample preparation: The homogeneous solution obtained in Sp1 is placed in a stainless steel reactor and sealed for reaction at high temperature. Then it is cooled to room temperature, and the mixture is thoroughly washed with a cleaning solution to remove impurities. After centrifugation, it is dried to obtain the sample. Sp3: Creating pure phase Ni x P y The dried sample and phosphorus powder were placed in a tube furnace and heated and held at that temperature for several hours under inert gas conditions to obtain pure-phase Ni. x P y ; Sp4: Ni composite material x P y -Ni x S y Generation: Ni x P y Sulfur powder is placed in a tube furnace and heated and held at that temperature for several hours under inert gas conditions to obtain the composite material Ni. x P y -Ni x S y .

2. The three-dimensional flower-shaped Ni according to claim 1 x P y -Ni x S y The method for preparing the composite structure is characterized by: In step Sp1, the molar ratio of nickel nitrate hexahydrate to urea is 1:(0.5-2), the molar ratio of nickel nitrate hexahydrate to ammonium fluoride is 1:(0.5-2), and the total molar number of nickel nitrate hexahydrate and urea to the volume ratio of ethanol solvent is 1:(7-20).

3. The three-dimensional flower-shaped Ni according to claim 1 x P y -Ni x S y The method for preparing the composite structure is characterized by: In step Sp1, the ethanol solvent is composed of ethanol and deionized water, wherein the total volume of the ethanol and the deionized water is 30 mL, and the concentration of the ethanol is (10-50) wt%.

4. The three-dimensional flower-like Ni according to claim 1 x P y -Ni x S y The method for preparing the composite structure is characterized by: In the sample preparation step of Sp2, the dried sample and the phosphorus powder are heated at a temperature between 120-200°C under the conditions of a tube furnace and an inert gas, and the reaction time is between 1-24 hours.

5. The three-dimensional flower-shaped Ni according to claim 1 x P y -Ni x S y The method for preparing the composite structure is characterized by: In the sample preparation step of Sp2, the cleaning solution is a mixture of deionized water and ethanol.

6. The three-dimensional flower-like Ni according to claim 1 x P y -Ni x S y The method for preparing the composite structure is characterized by: The Sp3 was used to produce pure phase Ni. x P y During the process, the heating temperature shall not be lower than 350℃.

7. The three-dimensional flower-shaped Ni according to claim 1 x P y -Ni x S y The method for preparing the composite structure is characterized by: The composite material Ni of Sp4 x P y -Ni x S y During the generation process, the heating temperature shall not be lower than 350℃.

8. The three-dimensional flower-shaped Ni according to claim 1 x P y -Ni x S y The method for preparing the composite structure is characterized by: The stainless steel reactor is lined with polytetrafluoroethylene.

9. Three-dimensional flower-like Ni x P y -Ni x S y The application of composite structures to three-dimensional flower-like Ni x P y -Ni x S y The composite structure is applied in the field of humidity sensing, characterized by: The three-dimensional flower-shaped Ni x P y -Ni x S y The composite structural material powder was mixed and ground with a small amount of anhydrous ethanol to form a paste. The paste is then dripped onto the Au interdigitated electrode and dried at 70°C. After processing, it can be applied to the field of humidity sensing to build a new type of humidity sensor.

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