Preparation method of nickel-based porous hollow cube nanomaterial based on phosphorus-sulfur modulation and application thereof in humidity sensing in wide temperature range from room temperature to high temperature

Abstract

A method for preparing nickel-based porous hollow cubic nanomaterials based on phosphorus and sulfur modulation and its application in humidity sensing over a wide temperature range from room temperature to high temperature is disclosed, belonging to the field of humidity sensor technology. This method addresses the problems of existing humidity sensor materials only being able to detect humidity at 100℃, with a significant decrease in response value as temperature increases; it also solves the problems of high cost and difficulty in precise control during the preparation of hollow cubic structures using existing sodium sulfide etching methods; it addresses the problem of introducing impurity ions during the synthesis of Ni-based Prussian blue analogs, which cannot be effectively removed; and it addresses the problem of difficulty in precisely controlling particle size during the synthesis of existing phosphides. The method involves: 1. Dissolving nickel chloride, polyvinylpyrrolidone, and sodium citrate in a solvent; 2. Dissolving potassium nickel cyanide in a solvent; 3. Calcination in air; 4. Calcination under an inert atmosphere. Application: It is used to prepare humidity sensors.

Description

Technical Field

[0001] This invention belongs to the field of humidity sensor technology. Background Technology

[0002] Humidity sensors are core components in environmental monitoring, healthcare, and smart wearables, and their performance is highly dependent on the intrinsic properties and structural design of the humidity-sensitive materials. Currently, humidity-sensing materials mainly include metal oxides, polymers, carbon-based materials, and transition metal phosphorus sulfides. The WO3-SnO2 humidity sensor prepared by Li et al. (H Li, B Liu, DP Cai, YR Wang, Y.Liu, L. Mei, LL Wang, DD Wang, QH Li, TH Wang, High-temperature humidity sensors based on WO3-SnO2 composite hollow nanospheres Journal of Materials Chemistry A, 2014, 2: 6854-6862) exhibited good performance at 80℃, but the response value decreased significantly with increasing temperature. This is because high temperatures cause lattice distortion, altering the electrical properties and affecting sensing accuracy and stability. Thorsten et al. (T. Wagner, S. Krotzky, A. Weiß, T. Sauerwald, CD Kohl, J. Roggenbuck, M. Tiemann, A High Temperature Capacitive Humidity Sensor Based on Mesoporous Silica, Sensors, 2011, 11:3136-3144.) proposed a capacitive sensor using mesoporous silica as the dielectric. This sensor can operate at 90°C, but its humidity detection range is only 25-50% RH. This is because when the ambient humidity is high, the hydroxyl groups on the silica surface undergo a dehydration reaction; for scenarios relying on surface hydroxyl groups for humidity sensing, this change directly destroys its ability to adsorb water molecules. VAISALA's HMP7, based on a polymer-sensitive membrane, is a leading product in the industry, capable of humidity detection at 100°C. However, when the temperature exceeds 100°C, the energy provided by the high temperature enhances the thermal motion of the polymer molecular chains, weakens intermolecular forces, and destroys the ordered structure, leading to material softening, melting, or a sharp decline in mechanical properties. Therefore, it is impossible to perform 100. oHumidity detection above 100°C. Transition metal phosphorus sulfides exhibit good humidity sensing potential due to their unique electronic structure and hydrophilicity. However, traditional materials suffer from poor stability, long response / recovery times, low sensitivity, and inability to detect humidity in high-temperature environments above 100°C. Currently, transition metal phosphorus sulfides are widely used in electrocatalysis, batteries, and other fields, but their research in humidity sensing is still in its early stages, and the reported humidity sensing performance is insufficient to meet the high-performance requirements over a wide temperature range.

[0003] Meanwhile, hierarchical porous structures such as hollow cubes are widely used to improve the adsorption capacity and response speed of humidity-sensitive materials due to their advantages such as high specific surface area and fast mass transfer channels. Currently, hollow cube structures are mostly prepared using sodium sulfide etching, and related hollow structure materials are mainly concentrated in metal oxides and Prussian blue analogues. For example, SnO2 hollow tubes are prepared by etching SnO2 with sodium sulfide. Furthermore, this type of construction strategy has not been reported in transition metal phosphorus sulfide systems, resulting in a lack of efficient and feasible structural control methods for improving the humidity-sensitive performance of such materials.

[0004] For example, existing transition metal sulfide humidity sensors utilize NiS to induce a phase transformation in ZnS, constructing a highly stable humidity sensor that solves the problem of poor stability of traditional ZnS in high humidity environments, achieving high sensitivity detection within the RH range of 11% to 97%. However, these materials still suffer from limitations such as limited response recovery speed, high detection limit, and poor thermal stability.

[0005] Existing transition metal phosphide catalysts, such as the unsupported and Laponite-supported NiPMoS catalysts, have shown good structural stability and catalytic activity by synergistically regulating the catalytic conversion performance of furfural HDO through phosphorus doping. However, this type of technology focuses on the hydrodeoxygenation catalytic reaction and does not address material design and performance optimization for humidity sensing. Furthermore, the synthesis methods require high temperatures, making precise control of particle size difficult.

[0006] In summary, existing humidity sensors and their fabrication methods have some drawbacks, such as:

[0007] (1) High temperature humidity sensor: Existing high temperature humidity sensors can only detect humidity at 100℃, and the response value of the material decreases significantly as the temperature increases.

[0008] (2) Preparation of hollow cubic structures by anhydrous sodium sulfide etching: The sodium sulfide etching method has significant limitations in the preparation of nanomaterials. Its disadvantages are mainly concentrated in two key aspects: cost and operation control. First, sodium sulfide itself is expensive, and its large-scale use will greatly increase the preparation cost of materials, which is not conducive to industrial promotion and practical application. Second, the amount of sodium sulfide is difficult to control precisely. If the amount of sodium sulfide is insufficient, the target material cannot be completely etched, and the remaining unetched part will destroy the preset structure of the material and affect the subsequent performance of the material. If the amount of sodium sulfide is too large, it will lead to over-etching, which will completely destroy the original morphology of the material and make it impossible to obtain nanomaterials with the expected structure.

[0009] (3) Ni-based Prussian blue analogs: Common Ni-based Prussian blue analogs are mainly synthesized from nickel salts and potassium cobalt cyanide using a precipitation method to synthesize nickel precursors. This method uses potassium cobalt cyanide to provide cyanide ions, which form Prussian blue analogs with nickel ions. However, Co is introduced into the system during this process. 2+ Furthermore, the ion was not removed during subsequent reaction and processing steps, which may have a potential impact on the material properties.

[0010] (4) Temperature-programmed reduction method: A common method to obtain phosphides is to reduce the corresponding phosphates by using hydrogen gas at a temperature-programmed rate. The significant feature of this synthesis method is that the reaction requires a high temperature. The high reaction temperature can easily cause the active phase particles of phosphides to agglomerate and increase in size during the growth and shaping process, making it difficult to accurately control the particle size. Summary of the Invention

[0011] This invention aims to address the problems of existing humidity sensor materials only being able to detect humidity at 100℃, and the response value decreasing significantly with increasing temperature; the problems of high cost and difficulty in precise control in the preparation of hollow cubic structures using existing sodium sulfide etching methods; the problem of introducing impurity ions in the synthesis process of existing Ni-based Prussian blue analogs that cannot be effectively removed; and the problem of difficulty in precisely controlling particle size in existing phosphide synthesis. Therefore, this invention provides a method for preparing nickel-based porous hollow cubic nanomaterials based on phosphorus-sulfur modulation and their application in humidity sensing over a wide temperature range from room temperature to high temperature.

[0012] 1. Dissolve nickel chloride, polyvinylpyrrolidone, and sodium citrate in a solvent to obtain precursor solution A;

[0013] 2. Dissolve potassium nickel cyanide in a solvent to obtain precursor solution B;

[0014] 3. Add precursor solution B dropwise to precursor solution A and stir evenly. Then, allow it to stand, centrifuge, wash and dry in sequence. Finally, calcine it in air to obtain hollow cubic NiPBA.

[0015] IV. A hollow cubic NiPBA is placed in one ceramic boat, and sulfur powder and red phosphorus are placed in another ceramic boat. Both ceramic boats are then placed simultaneously in a tube furnace and calcined under an inert atmosphere to obtain Ni. x P y -Ni x S y Porous hollow cubic nanomaterials.

[0016] An application of a phosphorus-sulfur-modulated nickel-based porous hollow cubic nanomaterial in humidity sensing over a wide temperature range from room temperature to high temperature is proposed, which is used to fabricate humidity sensors.

[0017] The beneficial effects of this invention are:

[0018] 1. This invention introduces a hollow cubic multi-level porous structure into the transition metal phosphorus sulfide system for the first time. By precisely controlling the microstructure and porous structure of the material, the particle size is reduced to 100nm~300nm, and particle aggregation is effectively avoided. This greatly increases the specific surface area of ​​the material, optimizes the mass transfer channels, and thus effectively improves its humidity-sensitive performance, filling a gap in this field.

[0019] 2. The phosphorus-sulfur modulated hollow cubic nanomaterial prepared by this invention has a unique structure and composition that endows the material with excellent thermal stability, enabling it to work stably in a temperature range from room temperature to 200°C. This breaks through the limitation that the upper limit of the working temperature of existing transition metal sulfide sensors generally does not exceed 100°C, and its resistance only increases slightly with increasing temperature.

[0020] 3. The transition metal phosphorus sulfide system used in this invention significantly improves the chemical stability, humidity response speed and sensitivity of the material through the synergistic effect of phosphorus and sulfur. Its sensitivity is as high as 10,000, the response time is shortened to 100ms, and the detection humidity range is widened to 0%~97%RH. It exhibits good reversibility in the adsorption and desorption process, and solves the inherent defects of traditional metal oxides, polymers and other materials in terms of stability, response recovery time and sensitivity.

[0021] 4. This invention provides a novel preparation method that replaces the traditional complexing agent potassium cobalt cyanide with potassium nickel cyanide. The material is etched through calcination, effectively avoiding the problems of introducing impurity ions, using expensive and difficult-to-control sodium sulfide etching, and particle agglomeration and difficulty in particle size control due to high temperatures in traditional methods. Furthermore, the solvents used are water and ethanol, which are environmentally friendly and suitable for large-scale production. This method is simple, cost-controllable, and operates under mild conditions, which is conducive to industrial promotion and practical application. Attached Figure Description

[0022] Figure 1 Ni prepared in Example 1x P y -Ni x S y SEM images of porous hollow cubic nanomaterials;

[0023] Figure 2 Ni prepared in Example 1 x P y -Ni x S y XRD pattern of porous hollow cubic nanomaterials;

[0024] Figure 3 Under room temperature conditions, using Ni from Example 1 x P y -Ni x S y The response recovery curve of a humidity sensor made of porous hollow cubic nanomaterials over one cycle in the range of 0%~97%RH;

[0025] Figure 4 Under room temperature conditions, using Ni from Example 1 x P y -Ni x S y Response recovery curves of a humidity sensor fabricated from porous hollow cubic nanomaterials in the range of 0% to 97% RH;

[0026] Figure 5 Under room temperature conditions, using Ni from Example 1 x P y -Ni x S y Dynamic response recovery characteristics of a humidity sensor fabricated from porous hollow cubic nanomaterials;

[0027] Figure 6 Under room temperature conditions, using Ni from Example 1 x P y -Ni x S y Humidity hysteresis curve of a humidity sensor fabricated from porous hollow cubic nanomaterials;

[0028] Figure 7 Under room temperature conditions, using Ni from Example 1 x P y -Ni x S y Reproducibility of a humidity sensor fabricated from porous hollow cubic nanomaterials in the range of 0% to 97% RH;

[0029] Figure 8 This is a schematic diagram of the high-temperature humidity sensitivity testing device in Example 1;

[0030] Figure 9 To utilize Ni from Example 1 at different temperatures x P y -Ni x S y The response recovery curve of a humidity sensor made of porous hollow cubic nanomaterials in the humidity range of 0ppm to 18000ppm. Detailed Implementation

[0031] Specific Implementation Method 1: This implementation method is a preparation method of nickel-based porous hollow cubic nanomaterials based on phosphorus and sulfur modulation, which is carried out according to the following steps:

[0032] 1. Dissolve nickel chloride, polyvinylpyrrolidone, and sodium citrate in a solvent to obtain precursor solution A;

[0033] 2. Dissolve potassium nickel cyanide in a solvent to obtain precursor solution B;

[0034] 3. Add precursor solution B dropwise to precursor solution A and stir evenly. Then, allow it to stand, centrifuge, wash and dry in sequence. Finally, calcine it in air to obtain hollow cubic NiPBA.

[0035] IV. A hollow cubic NiPBA is placed in one ceramic boat, and sulfur powder and red phosphorus are placed in another ceramic boat. Both ceramic boats are then placed simultaneously in a tube furnace and calcined under an inert atmosphere to obtain Ni. x P y -Ni x S y Porous hollow cubic nanomaterials.

[0036] In this specific embodiment, a nanoscale cubic nickel precursor with a large specific surface area was synthesized by precipitation and by adjusting the ratio of polyvinylpyrrolidone and sodium citrate in the raw materials. Subsequently, the precursor was calcined at a slow heating rate to form a hollow cubic structure. Finally, Ni was successfully synthesized in one step using red phosphorus as the phosphorus source and sulfur powder as the sulfur source. x P y -Ni x S y Porous hollow cubic nanomaterials. These hollow and porous humidity-sensitive materials possess a relatively large specific surface area, promoting the penetration and diffusion of water molecules while also providing more adsorption sites, thus enhancing sensor performance. Furthermore, Ni... x P y with Ni x S y After recombination, Ni x P y -Nix S y Composite materials possess more covalent properties, making it easier to adsorb water molecules and thus contributing to improved humidity sensing performance. Furthermore, breakthroughs have been made in the humidity-sensing properties of transition metal phosphorus sulfides. Compared to previously reported Ni2P-NiS humidity sensors, the fabricated humidity sensor significantly improves detection sensitivity, shortens response / recovery time, and lowers the humidity detection limit. It also achieves stable operation under both room temperature and high temperature conditions, providing reliable experimental data support and theoretical reference for the development of high-performance, wide-temperature-range transition metal phosphorus sulfide humidity sensors.

[0037] The beneficial effects of this embodiment are:

[0038] 1. This embodiment introduces a hollow cubic multi-level pore structure into the transition metal phosphorus sulfide system for the first time. By precisely controlling the microstructure and pore structure of the material, the particle size is reduced to 100nm~300nm, and particle aggregation is effectively avoided. This greatly increases the specific surface area of ​​the material, optimizes the mass transfer channels, and thus effectively improves its humidity-sensitive performance, filling a gap in this field.

[0039] 2. The phosphorus-sulfur modulated hollow cubic nanomaterial prepared in this embodiment has a unique structure and composition that endows the material with excellent thermal stability, enabling it to work stably in a temperature range from room temperature to 200°C. This breaks through the limitation that the upper limit of the working temperature of existing transition metal sulfide sensors generally does not exceed 100°C, and its resistance only increases slightly with increasing temperature.

[0040] 3. The transition metal phosphorus sulfide system used in this embodiment significantly improves the chemical stability, humidity response speed and sensitivity of the material through the synergistic effect of phosphorus and sulfur. Its sensitivity is as high as 10,000, the response time is shortened to 100ms, and the detection humidity range is widened to 0%~97%RH. It exhibits good reversibility in the adsorption and desorption process, and solves the inherent defects of traditional metal oxides, polymers and other materials in terms of stability, response recovery time and sensitivity.

[0041] 4. This embodiment provides a novel preparation method that replaces the traditional complexing agent potassium cobalt cyanide with potassium nickel cyanide. The material is etched through calcination, effectively avoiding the problems of introducing impurity ions, using expensive and difficult-to-control sodium sulfide etching, and particle agglomeration and difficulty in controlling particle size due to high temperatures, which are inherent in traditional methods. Furthermore, the solvents used are water and ethanol, which are environmentally friendly and suitable for large-scale production. This method is simple, cost-effective, and operates under mild conditions, making it conducive to industrial promotion and practical application.

[0042] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that: the molar ratio of nickel chloride to polyvinylpyrrolidone in step one is 1:(0.5~2); the molar ratio of nickel chloride to sodium citrate in step one is 1:(0.5~1); the molar ratio of nickel chloride to solvent volume in step one is 1 mmol:(10~30) mL; and the solvent in step one is a mixed solvent of ethanol and deionized water, with an ethanol concentration of 30wt%~60wt%. Everything else is the same as in Specific Implementation Method One.

[0043] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that: the molar ratio of potassium nickel cyanide to solvent in step 2 is 1 mmol:(10~30) mL; the solvent in step 2 is a mixed solvent of ethanol and deionized water, and the concentration of ethanol in the solvent is 10 wt%~40 wt%. Everything else is the same as in Specific Implementation Method 1 or 2.

[0044] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the molar ratio of nickel chloride to potassium nickel cyanide in precursor solution B and precursor solution A in step three is 1:(1~2). Everything else is the same as in Specific Implementation Methods One to Three.

[0045] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that: In step three, precursor solution B is added dropwise to precursor solution A at a dropping rate of 1 drop / s to 2 drops / s, and stirred at a speed of 100 r / min to 800 r / min for 0.5 h to 2 h. Then, it is allowed to stand at room temperature for 1 h to 48 h. Next, it is centrifuged and washed with deionized water and ethanol at a speed of 4000 r / min to 12000 r / min, respectively. Then, it is dried at a temperature of 40℃ to 100℃. Finally, it is calcined in air at a heating rate of 1℃ / min to 10℃ / min to 200℃ to 500℃ for 1 h to 2 h. The rest is the same as in Specific Implementation Methods One to Four.

[0046] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that: the mass ratio of hollow cubic NiPBA to phosphoric acid powder in step four is 1:(5~30); the mass ratio of hollow cubic NiPBA to sulfur powder in step four is 1:(5~30). Everything else is the same as in Specific Implementation Methods One to Five.

[0047] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the calcination in an inert atmosphere in step four is specifically carried out as follows: Under an inert atmosphere, the temperature is increased to 200℃ to 500℃ at a heating rate of 1℃ / min to 10℃ / min, and calcined for 0.5h to 3h under the conditions of an inert atmosphere and a temperature of 200℃ to 500℃; the inert atmosphere is one or a combination of several of argon, nitrogen, helium, neon, krypton, and xenon. Everything else is the same as in Specific Implementation Methods One to Six.

[0048] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One through Seven in that: the Ni prepared in step four... x P y -Ni x S y The porous hollow cubic nanomaterial has a particle size of 100nm~300nm and a shell thickness of 20nm~30nm. Other aspects are the same as in specific embodiments one to seven.

[0049] Specific Implementation Method Nine: This implementation method describes an application of a nickel-based porous hollow cubic nanomaterial based on phosphorus and sulfur modulation, which is used to prepare a humidity sensor.

[0050] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Method Nine in that the humidity sensor has a humidity detection range of 0%~97% RH and an operating temperature range of room temperature to 200℃. Everything else is the same as in Specific Implementation Method Nine.

[0051] The beneficial effects of the present invention are verified using the following embodiments:

[0052] Example 1:

[0053] A method for preparing nickel-based porous hollow cubic nanomaterials based on phosphorus and sulfur modulation, comprising the following steps:

[0054] 1. Dissolve nickel chloride, polyvinylpyrrolidone, and sodium citrate in a solvent to obtain precursor solution A;

[0055] The molar ratio of nickel chloride to polyvinylpyrrolidone is 1:1.5; the molar ratio of nickel chloride to sodium citrate is 1:1; the volume ratio of the molar ratio of nickel chloride to the solvent is 1 mmol: 20 mL; the solvent is a mixture of ethanol and deionized water, and the concentration of ethanol in the solvent is 45 wt%.

[0056] 2. Dissolve potassium nickel cyanide in a solvent to obtain precursor solution B;

[0057] The molar ratio of potassium nickel cyanide to the volume ratio of the solvent is 1 mmol: 20 mL; the solvent is a mixture of ethanol and deionized water, and the concentration of ethanol in the solvent is 20 wt%.

[0058] 3. Precursor solution B was added to precursor solution A at a dropping rate of 1 drop / s, and stirred for 1 h at a speed of 600 r / min. Then, it was allowed to stand at room temperature for 24 h. After that, it was washed by centrifugation with deionized water and ethanol at a speed of 800 r / min. Then, it was dried at a temperature of 60℃. Finally, it was heated to 400℃ in air at a heating rate of 2℃ / min and calcined for 2 h in air at a temperature of 400℃ to obtain hollow cubic NiPBA.

[0059] The molar ratio of nickel chloride to potassium nickel cyanide in precursor solution B and precursor solution A is 1:1;

[0060] IV. A hollow cubic NiPBA was placed in one ceramic boat, and sulfur powder and red phosphorus were placed in another ceramic boat. Both boats were then placed simultaneously in a tube furnace, and under an argon atmosphere, the temperature was increased to 400°C at a rate of 1°C / min. The furnace was then calcined for 2 hours under an argon atmosphere and at 400°C to obtain Ni. x P y -Ni x S y Porous hollow cubic nanomaterials;

[0061] The mass ratio of the hollow cubic NiPBA to phosphorus powder is 1:20; the mass ratio of the hollow cubic NiPBA to sulfur powder is 1:10.

[0062] Figure 1 Ni prepared in Example 1 x P y -Ni x S y SEM images of the porous hollow cubic nanomaterials; as shown in the images, the prepared material exhibits a uniform morphology, displaying typical characteristics of a porous hollow cubic structure with clear edges and sharp corners. The cubic structure contains obvious pores, with pore sizes approximately 1 / 2 to 2 / 3 of the cubic's side length, allowing direct observation of the internal cavities. The shell has a certain thickness, forming a cage-like structure of "square outside, hollow inside," with cavities penetrating the entire cubic structure, presenting a complete hollow cubic morphology. The cubic particle size is 100 nm, and the shell thickness is approximately 20 nm to 30 nm. The surface is covered with numerous interconnected mesoporous structures, without obvious aggregation or morphological collapse.

[0063] Figure 2 Ni prepared in Example 1 x Py -Ni x S y XRD pattern of porous hollow cubic nanomaterial; as shown in the figure, after calcination, the crystallization is complete, and the XRD diffraction peaks are consistent with those of Ni. x P y -Ni x S y There is a very good response.

[0064] Humidity sensitivity test: The Ni prepared in Example 1 was used for humidity sensitivity testing. x P y -Ni x S y Porous hollow cubic nanomaterials are ground into a paste mixture with a small amount of anhydrous ethanol. The paste mixture is then drop-coated onto an Au interdigitated electrode and dried at 70°C to obtain a humidity sensor.

[0065] Room temperature humidity sensitivity test:

[0066] Table 1. Preparation of different relative humidity levels

[0067]

[0068] The humidity sensor's performance was tested by placing it in wide-mouthed glass bottles containing different saturated salt solutions (LiCl, CH3COOK, MgCl2, K2CO3, Mg(NO3)2, KI, NaCl, KCl, and Pb(NO3)2). The relative humidity (RH) values ​​of these saturated salt solutions at room temperature (25°C) were 11%, 22%, 32%, 43%, 54%, 69%, 75%, 84%, and 97%, respectively, with 0% provided by a desiccant. All tests were conducted at room temperature (25°C). The sensitivity was calculated using the formula S=R. 0% / R 97% Among them, R 0% R represents the stable impedance value of the humidity sensor in the presence of a desiccant. 97% This represents the stable impedance value of the humidity sensor at 97% relative humidity; the calculation method is similar for other humidity levels. The response time and recovery time correspond to the change in resistance from R when the humidity sensor is placed in the measured relative humidity. 0% Change to R 0% -90% (R 0% -R 97% The required time and the resistance after removal from the gas being measured are determined by R. 97% Change to R 97% +90% (R) 0% -R 97%The required time was determined. The humidity sensor's humidity sensitivity performance was tested using an LCR digital bridge instrument analyzer (TH2829A, Changzhou, China) under AC voltage of 1V and operating frequency range of 20Hz~200kHz.

[0069] Figure 3 Under room temperature conditions, using Ni from Example 1 x P y -Ni x S y The response recovery curve of the humidity sensor made of porous hollow cubic nanomaterials in the range of 0%~97%RH over one cycle is shown in the figure. As can be seen from the figure, the humidity sensor can respond quickly to the change in humidity within 100ms and the recovery time is 1s.

[0070] Figure 4 Under room temperature conditions, using Ni from Example 1 x P y -Ni x S y The response recovery curves of a humidity sensor fabricated from porous hollow cubic nanomaterials are shown in the RH range of 0%–97%. The humidity sensor was stabilized in a 0% RH environment for 60 seconds, then placed in an 11% RH environment for 120 seconds, and finally returned to a 0% RH environment. The same testing procedure was then followed for subsequent humidity measurements (22%, 32%, 43%, 54%, 69%, 75%, 84%, and 97%). The graphs show that the sensor resistance changes instantaneously when transitioning from a low-humidity environment to a high-humidity environment, but completely recovers to its initial value when transitioning from a high-humidity environment to a low-humidity environment. This indicates that the sensor has good reversibility and rapid response recovery characteristics. The response values ​​of the sensor at 11%, 22%, 32%, 43%, 54%, 69%, 75%, 84%, and 97% RH are 1.53, 3.94, 10.83, 32.50, 76.47, 260, 520, 1818, and 10000, respectively. This indicates that the sensor has good reversibility and fast response recovery characteristics.

[0071] Figure 5 Under room temperature conditions, using Ni from Example 1 x P y -Ni x S yThe dynamic response recovery characteristics of a humidity sensor fabricated from porous hollow cubic nanomaterials were investigated. The sensor was first stabilized in a 0% RH environment for 60 seconds, and then sequentially placed in environments with 11%, 22%, 32%, 43%, 54%, 69%, 75%, 84%, and 97% RH, and held for 120 seconds each. As shown in the figure, the sensor exhibits good reversibility during adsorption and desorption. During adsorption, the impedance values ​​at various RH levels from 0% to 97% were 13 MΩ, 8.5 MΩ, 3.3 MΩ, 1.2 MΩ, 400 kΩ, 170 kΩ, 50 kΩ, 25 kΩ, 11 kΩ, and 1.3 kΩ, respectively. During desorption, the impedance values ​​were 13 MΩ, 8.5 MΩ, 3.28 MΩ, 1.2 MΩ, 400 kΩ, 170 kΩ, 50 kΩ, 25 kΩ, 11 kΩ, and 1.3 kΩ, respectively.

[0072] Figure 6 Under room temperature conditions, using Ni from Example 1 x P y -Ni x S y Humidity hysteresis curve of humidity sensor made of porous hollow cubic nanomaterial; as shown in the figure, the sensor exhibits maximum humidity hysteresis of only 0.69% RH when the relative humidity is 34%, and the small humidity hysteresis indicates that the sensor has good reliability.

[0073] Figure 7 Under room temperature conditions, using Ni from Example 1 x P y -Ni x S y The reproducibility of a humidity sensor fabricated from porous hollow cubic nanomaterials within the 0%–97% RH range was demonstrated. Ten consecutive tests were performed within this range, and the sensor's resistance consistently recovered to its initial value each time. The response values ​​for the ten tests were 10157, 10138, 10145, 9920, 10138, 9945, 10120, 9985, 10265, and 10148, with a relative standard deviation of 1.08%, proving the effectiveness of Ni... x P y -Ni x S y The sensor has good reproducibility.

[0074] High-temperature humidity sensitivity test: The humidity sensor is placed in a high-temperature chamber. The ambient temperature required for the test is set through the high-temperature chamber. The ambient humidity is precisely controlled by adjusting the ratio of the water tank and the desiccant mass flow meters. The specific ratio is shown in Table 2. Figure 8This is a schematic diagram of the high-temperature humidity sensitivity testing device in Example 1. The humidity sensitivity of the humidity sensor was tested using an LCR digital bridge instrument analyzer (TH2829A, Changzhou, China) under conditions of AC voltage of 1V and operating frequency range of 200Hz~200kHz.

[0075] The formula for calculating the water vapor concentration (humidity, parts per million) in a gas mixture is as follows:

[0076]

[0077] Where Q1 represents the flow rate (L / min) of the water tank branch, Q2 represents the flow rate (L / min) of the desiccant branch, and φ sat It is 0.0317 (volume fraction of saturated water vapor at 25°C and 1 atmosphere).

[0078] Table 2 Relationship between flow rate and humidity of the flow meter

[0079]

[0080] Figure 9 To utilize Ni from Example 1 at different temperatures x P y -Ni x S y The response recovery curves of a humidity sensor fabricated from porous hollow cubic nanomaterials are shown in the humidity range of 0 ppm to 18000 ppm. The humidity sensor was stabilized in a high-temperature furnace with a dry gas flow for 60 s, then placed in a 3000 ppm environment for 120 s, followed by another 60 s of dry gas flow. The same procedure was then repeated for subsequent humidity measurements (6000 ppm, 9000 ppm, 12000 ppm, 15000 ppm, and 18000 ppm). At room temperature, the response values ​​for 3000 ppm to 18000 ppm were 2.89, 10, 32.5, 130, 650, and 4333, respectively. At 200℃, the response values ​​for 3000 ppm to 18000 ppm were 2.73, 9.85, 31.2, 129, 648, and 4332, respectively. Within the temperature range of room temperature to 200℃, the humidity sensor exhibits excellent response recovery characteristics under different temperature conditions, and its resistance only increases slightly with increasing temperature. This slight signal drift is mainly caused by the increased thermal motion of water molecules. In high-temperature environments, the interaction forces between materials and molecules weaken, making it more difficult for water molecules to be captured and adsorbed.

Claims

1. A method for preparing nickel-based porous hollow cubic nanomaterials based on phosphorus and sulfur modulation, characterized in that... It is done in the following steps:

1. Dissolve nickel chloride, polyvinylpyrrolidone, and sodium citrate in a solvent to obtain precursor solution A; 2. Dissolve potassium nickel cyanide in a solvent to obtain precursor solution B; 3. Add precursor solution B dropwise to precursor solution A and stir evenly. Then, allow it to stand, centrifuge, wash and dry in sequence. Finally, calcine it in air to obtain hollow cubic NiPBA. IV. A hollow cubic NiPBA is placed in one ceramic boat, and sulfur powder and red phosphorus are placed in another ceramic boat. Both ceramic boats are then placed simultaneously in a tube furnace and calcined under an inert atmosphere to obtain Ni. x P y -Ni x S y Porous hollow cubic nanomaterials.

2. The method for preparing a nickel-based porous hollow cubic nanomaterial based on phosphorus and sulfur modulation according to claim 1, characterized in that... The molar ratio of nickel chloride to polyvinylpyrrolidone in step one is 1:(0.5~2); the molar ratio of nickel chloride to sodium citrate in step one is 1:(0.5~1); the molar ratio of nickel chloride to solvent in step one is 1 mmol:(10~30) mL; the solvent in step one is a mixed solvent of ethanol and deionized water, and the concentration of ethanol in the solvent is 30wt%~60wt%.

3. The method for preparing a nickel-based porous hollow cubic nanomaterial based on phosphorus and sulfur modulation according to claim 1, characterized in that... The molar ratio of potassium nickel cyanide to solvent in step two is 1 mmol: (10~30) mL; the solvent in step two is a mixed solvent of ethanol and deionized water, and the concentration of ethanol in the solvent is 10 wt%~40 wt%.

4. The method for preparing a nickel-based porous hollow cubic nanomaterial based on phosphorus and sulfur modulation according to claim 1, characterized in that... The molar ratio of nickel chloride to potassium nickel cyanide in precursor solution B and precursor solution A mentioned in step three is 1:(1~2).

5. The method for preparing a nickel-based porous hollow cubic nanomaterial based on phosphorus and sulfur modulation according to claim 1, characterized in that... In step three, precursor solution B is added dropwise to precursor solution A at a dropping rate of 1 drop / s to 2 drops / s, and stirred at a speed of 100 r / min to 800 r / min for 0.5 h to 2 h. Then, it is allowed to stand at room temperature for 1 h to 48 h. Next, it is centrifuged and washed with deionized water and ethanol at a speed of 4000 r / min to 12000 r / min. Then, it is dried at a temperature of 40℃ to 100℃. Finally, it is calcined in air at a heating rate of 1℃ / min to 10℃ / min to 200℃ to 500℃ for 1 h to 2 h.

6. The method for preparing a nickel-based porous hollow cubic nanomaterial based on phosphorus and sulfur modulation according to claim 1, characterized in that... The mass ratio of hollow cubic NiPBA to phosphorus powder in step four is 1:(5~30); the mass ratio of hollow cubic NiPBA to sulfur powder in step four is 1:(5~30).

7. The method for preparing a nickel-based porous hollow cubic nanomaterial based on phosphorus and sulfur modulation according to claim 1, characterized in that... Step four, calcination under an inert atmosphere, is carried out in the following steps: under an inert atmosphere, the temperature is increased to 200℃~500℃ at a heating rate of 1℃ / min~10℃ / min, and calcined for 0.5h~3h under the conditions of an inert atmosphere and a temperature of 200℃~500℃; the inert atmosphere is one or a combination of several of argon, nitrogen, helium, neon, krypton and xenon.

8. The method for preparing a nickel-based porous hollow cubic nanomaterial based on phosphorus and sulfur modulation according to claim 1, characterized in that... Ni prepared in step four x P y -Ni x S y The porous hollow cubic nanomaterials have a particle size of 100nm~300nm and a shell thickness of 20nm~30nm.

9. The application of a phosphorus-sulfur modulated nickel-based porous hollow cubic nanomaterial as described in claim 1 in humidity sensing over a wide temperature range from room temperature to high temperature, characterized in that... It is used to manufacture humidity sensors.

10. The application of a phosphorus-sulfur modulated nickel-based porous hollow cubic nanomaterial according to claim 9 in humidity sensing over a wide temperature range from room temperature to high temperature, characterized in that... The humidity sensor has a humidity detection range of 0% to 97% RH and an operating temperature range of room temperature to 200°C.

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