Preparation method and application of Ni2P / NiO heterostructure nanosheet gas-sensitive material

Abstract

The present invention provides a preparation method and application of a Ni2P / NiO heterostructure nanosheet gas-sensitive material, comprising the following steps: Based on the pre-obtained BP nanosheets, disperse them in 1-methyl-2-pyrrolidone, denoted as dispersion A; Disperse a certain amount of metal salt in 1-methyl-2-pyrrolidone, mix dispersion A and dispersion C and stir evenly to obtain a reaction precursor; Place the precursor mixture in a flask, and under the protection of an argon atmosphere, put it in a laboratory microwave oven, microwave-heat the reaction for a period of time, and centrifuge and wash the reactant with ethanol to obtain in-situ topologically transformed Ni2P / NiO heterostructure nanosheets. The preparation method and application of a Ni2P / NiO heterostructure nanosheet gas-sensitive material provided by the present invention are obtained by a two-step method of microwave in-situ topological transformation and high-temperature oxidation, retaining the original two-dimensional nanosheet morphology of BP, and greatly improving its gas-sensitive performance towards H2S.

Description

Technical Field

[0001] The present invention relates to the field of gas sensitivity sensing, and in particular to a preparation method and application of a Ni2P / NiO heterostructure nanosheet gas-sensitive material. Background Art

[0002] With the development of society and the advancement of science and technology, the advancement of global industrialization has led to the over-exploitation of resources and the emission of polluting gases, which has caused serious damage to the ecological environment and has affected human health and sustainable development. Monitoring polluting gases is the fundamental source of effectively controlling gas emissions and purifying the atmospheric environment. Among them, H2S gas is an inevitable toxic gas in industrial production, agricultural activities and microbial decomposition. In recent years, effective detection and real-time monitoring of H2S have become a demand for industrial production and daily life. Based on this, exploring and developing cheap, highly reactive and durable gas sensors has become the focus of detection. At present, common gas-sensitive sensing materials have the problems of high production and preparation costs, high effective working temperature and long response time, which cannot meet the needs of real-time and rapid detection of target gases.

[0003] Metal oxide semiconductor materials, such as NiO, SnO2, ZnO, etc., have shown certain performance application potential in the field of gas sensing. However, a single metal oxide has a specific electronic structure and coordination environment, which leads to a series of defects such as certain response, but often limited by temperature and concentration, and poor stability. Therefore, the construction of adjustable heterostructures is expected to achieve adjustable gas sensitive properties. Among them, transition metal phosphides show some metallic properties and can provide the same sensitization properties as precious metals. Therefore, this metal phosphide composite material with advantages such as good conductivity, stable structure, and easy preparation is expected to become an advantageous material for improving NiO-based H2S gas sensitive materials. In addition, since O has a higher electronegativity than P, under high-temperature oxidation conditions, O has the possibility of replacing P in metal phosphorus compounds. Therefore, the preparation of metal phosphide and oxide heterojunctions by in-situ means can not only achieve electronic structure adjustment, but also ensure interface lattice adaptation and achieve structural stability.

[0004] Therefore, it is necessary to provide a method for preparing Ni2P / NiO heterostructure nanosheet gas-sensitive materials to solve the above technical problems. Summary of the invention

[0005] The present invention provides a method for preparing a Ni2P / NiO heterostructure nanosheet gas-sensitive material, which solves the problems of high production and preparation cost, high effective working temperature, long recovery time and inability to meet the demand for real-time rapid detection of target gas in currently common gas-sensitive sensing materials.

[0006] In order to solve the above technical problems, the present invention provides a method for preparing a Ni2P / NiO heterostructure nanosheet gas-sensitive material, comprising the following steps:

[0007] S1. Dispersing the BP nanosheets obtained in advance in 1-methyl-2-pyrrolidone, which is referred to as mixed solution A; dispersing a certain amount of metal salt in 1-methyl-2-pyrrolidone, which is referred to as mixed solution C; mixing the A and C dispersions and stirring them evenly to obtain a reactant mixed solution;

[0008] S2, placing the reactant mixture in a flask, and placing it in an experimental microwave oven under the protection of an argon atmosphere, heating the reaction in the microwave for a period of time, and washing the reactant by centrifugation with ethanol to obtain a precursor material Ni2P / Ni12P5 heterostructure;

[0009] S3. The obtained precursor material Ni2P / Ni12P5 heterostructure is placed in an air furnace for high-temperature calcination, and after oxidation, an in-situ transformed Ni2P / NiO heterostructure nanosheet is obtained.

[0010] Preferably, the mixed solution A in S1 is prepared by dispersing 20 mg of BP nanosheets in every 20 mL of 1-methyl-2-pyrrolidone.

[0011] Preferably, the mixed solution C in S1, wherein the metal salt is NiCl2·6H2O, is prepared by dispersing 2.6146 g of NiCl2·6H2O metal salt in every 10 mL of 1-methyl-2-pyrrolidone.

[0012] Preferably, the microwave heating power in S2 is 800 W and the reaction time is 10 min.

[0013] Preferably, the calcination temperature in the air furnace in S3 is 650° C., and the calcination time is selected in the range of 4 to 16 hours.

[0014] Preferably, the metal salt in S1 further comprises a phosphorus source-related metal salt, and the phosphorus source-related metal salt is selected from at least one of sodium phosphate, potassium phosphate, and sodium phosphite, which is used to regulate the phosphorus content in the product, thereby optimizing the gas-sensing properties of the Ni2P / NiO heterostructure nanosheets.

[0015] Preferably, the air humidity in the S3 air furnace is controlled within a specified range to prevent water vapor from adversely affecting the high-temperature calcination process and product structure.

[0016] An application of a Ni2P / NiO heterostructure nanosheet gas-sensitive material, a Ni2P / NiO heterostructure nanosheet gas-sensitive material prepared by the preparation method of the Ni2P / NiO heterostructure nanosheet gas-sensitive material, and the Ni2P / NiO heterostructure nanosheet gas-sensitive material is used to detect H2S.

[0017] Compared with the related art, the preparation method of the Ni2P / NiO heterostructure nanosheet gas-sensitive material provided by the present invention has the following beneficial effects:

[0018] The present invention provides a method for preparing a Ni2P / NiO heterostructure nanosheet gas-sensitive material, which is obtained by a two-step method of microwave in-situ topological transformation and high-temperature oxidation, retaining the original two-dimensional nanosheet morphology of BP and transforming it into Ni2P / NiO heterostructure nanosheets, thereby greatly improving its gas sensitivity to H2S.

[0019] The excessive amount of Ni metal source used in S1 of the present invention is to meet the basic requirements of in-situ topological transformation. In the high-concentration nearly saturated NiCl2·6H2O solution, the Ni source can be continuously provided to the reaction, resulting in Ni2P / NiO basically retaining the original two-dimensional morphology of BP. And due to undersaturation, part of BP is not fully combined with the Ni source, and many microporous defects are generated on the surface of the heterostructure. The above two points are beneficial to the contact between gas and device and the conduction of gas during gas sensitive detection. On the other hand, the high-temperature calcination method uses Ni2P / NiO heterostructure as a precursor, and the obtained Ni2P / NiO retains the original two-dimensional morphology, forming a Ni2P-modified Ni2P / NiO heterostructure, which has an adjustable electronic structure, and is conducive to providing higher carrier migration, and can play a synergistic role to enable the heterostructure material to exhibit excellent gas sensitive sensing performance.

[0020] The Ni2P / NiO heterostructure nanosheet of the present invention presents a thinner two-dimensional nanosheet morphology, has a high surface exposure, can provide more adsorption and desorption sites for the target gas, and thus has a high response sensitivity. In addition, a nn heterostructure is formed between Ni2P and NiO, which produces an adjustable electronic state, so that the material body can be conducive to the adsorption and desorption response of a specific gas.

[0021] The Ni2P / NiO heterostructure nanosheet of the present invention is used to assemble a gas-sensitive sensor device to detect H2S gas. It has a ppm-level H2S gas response at an optimal working temperature of 150°C, a rapid response, and a short recovery time, which indicates that the Ni2P / NiO heterostructure nanosheet of the present invention has excellent H2S gas sensing sensitivity. In addition, after a long-term sensitivity stability test, the Ni2P / NiO heterostructure nanosheet of the present invention has a durability of up to 5 weeks without obvious attenuation. In order to further evaluate the high selectivity of the heterostructure nanosheet for H2S gas, NH3 and CO comparison gases are introduced. The results show that the Ni2P / NiO heterostructure nanosheet of the present invention has an extremely high sensitivity with high selectivity for H2S and has a special value for preventing H2S gas leakage in industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic structural diagram of a preferred embodiment of a method for preparing a Ni2P / NiO heterostructure nanosheet gas-sensitive material provided by the present invention;

[0023] Figure 2 Transmission electron microscope (TEM) images of (a) the Ni2P / Ni12P5 heterostructure of Example 6, (b) the Ni2P / NiO-4h heterostructure of Example 1, and (c) the Ni2P / NiO-16h heterostructure of Example 2;

[0024] Figure 3 High-resolution TEM (HRTEM) images of (a) the Ni2P / Ni12P5 heterostructure of Example 6, (b) the Ni2P / NiO-4h heterostructure of Example 1, and (c) the Ni2P / NiO-16h heterostructure of Example 2;

[0025] Figure 4 Gas sensitivity test of samples prepared for Example 1, Example 2 and Example 6, (a) response-recovery curve of Example 1 when exposed to 5 ppm concentration of H2S gas at different temperatures, (b) gas sensing performance of Example 1, Example 2 and Example 6 at a temperature of 150°C;

[0026] Figure 5 (a) Short-term response recovery and (b) long-term sensitivity stability test diagram of the Ni2P / NiO-4h heterostructure prepared in Example 1;

[0027] Figure 6 Gas sensitivity response curve tests of the Ni2P / NiO heterostructure nanosheets prepared in Example 1 and Example 2 to different gases H2S, NH3 and CO. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with the accompanying drawings and implementation modes.

[0029] First embodiment

[0030] Please refer to Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 and Figure 6 ,in, Figure 1 A schematic structural diagram of a preferred embodiment of a method for preparing a Ni2P / NiO heterostructure nanosheet gas-sensitive material provided by the present invention; Figure 2Transmission electron microscope (TEM) images of (a) the Ni2P / Ni12P5 heterostructure of Example 6, (b) the Ni2P / NiO-4h heterostructure of Example 1, and (c) the Ni2P / NiO-16h heterostructure of Example 2; Figure 3 High-resolution TEM (HRTEM) images of (a) the Ni2P / Ni12P5 heterostructure of Example 6, (b) the Ni2P / NiO-4h heterostructure of Example 1, and (c) the Ni2P / NiO-16h heterostructure of Example 2; Figure 4 Gas sensitivity test of samples prepared for Example 1, Example 2 and Example 6, (a) response-recovery curve of Example 1 when exposed to 5 ppm concentration of H2S gas at different temperatures, (b) gas sensing performance of Example 1, Example 2 and Example 6 at a temperature of 150°C; Figure 5 (a) Short-term response recovery and (b) long-term sensitivity stability test diagram of the Ni2P / NiO-4h heterostructure prepared in Example 1; Figure 6 The gas sensitivity response curves of the Ni2P / NiO heterostructure nanosheets prepared in Example 1 and Example 2 to different gases H2S, NH3 and CO were tested. A method for preparing a Ni2P / NiO heterostructure nanosheet gas-sensitive material comprises the following steps:

[0031] S1. Dispersing the BP nanosheets obtained in advance in 1-methyl-2-pyrrolidone, which is referred to as mixed solution A; dispersing a certain amount of metal salt in 1-methyl-2-pyrrolidone, which is referred to as mixed solution C; mixing the A and C dispersions and stirring them evenly to obtain a reactant mixed solution;

[0032] S2, placing the reactant mixture in a flask, and placing it in an experimental microwave oven under the protection of an argon atmosphere, heating the reaction in the microwave for a period of time, and washing the reactant by centrifugation with ethanol to obtain a precursor material Ni2P / Ni12P5 heterostructure;

[0033] S3. The obtained precursor material Ni2P / Ni12P5 heterostructure is placed in an air furnace for high-temperature calcination, and after oxidation, an in-situ transformed Ni2P / NiO heterostructure nanosheet is obtained.

[0034] The mixed solution A in S1 is prepared by dispersing 20 mg of BP nanosheets in every 20 mL of 1-methyl-2-pyrrolidone.

[0035] The mixed solution C in S1, wherein the metal salt is NiCl2·6H2O, is prepared by dispersing 2.6146 g of NiCl2·6H2O metal salt in every 10 mL of 1-methyl-2-pyrrolidone.

[0036] The microwave heating power in S2 is 800 W, and the reaction time is 10 min.

[0037] In S3, the calcination temperature in the air furnace is 650° C., and the calcination time is selected in the range of 4 to 16 hours.

[0038] The metal salt in S1 also includes a phosphorus source-related metal salt, and the phosphorus source-related metal salt is selected from at least one of sodium phosphate, potassium phosphate, and sodium phosphite, which is used to regulate the phosphorus content in the product, thereby optimizing the gas sensing performance of the Ni2P / NiO heterostructure nanosheets.

[0039] The air humidity in the S3 air furnace is controlled within a specified range to prevent water vapor from adversely affecting the high-temperature calcination process and product structure.

[0040] An application of a Ni2P / NiO heterostructure nanosheet gas-sensitive material, a Ni2P / NiO heterostructure nanosheet gas-sensitive material prepared by the preparation method of the Ni2P / NiO heterostructure nanosheet gas-sensitive material, and the Ni2P / NiO heterostructure nanosheet gas-sensitive material is used to detect H2S.

[0041] Embodiment 1

[0042] S1. Prepare the reactant mixture

[0043] 10 mg of BP nanosheets (based on the two-dimensional nanosheet BP obtained in previous studies) was dispersed in 20 mL of 1-methyl-2-pyrrolidone and stirred for 30 min. The resulting mixed solution was recorded as A. 2.6146 g of NiCl2·6H2O metal salt was dispersed in 10 mL of 1-methyl-2-pyrrolidone and stirred for 30 min. The resulting mixed solution was recorded as C. The mixed solution C was slowly injected into the mixed solution A and stirred evenly to obtain a reactant mixed solution.

[0044] S2. Preparation of precursors

[0045] The mixed solution was transferred to a 50 mL flask, and a reaction device was built under argon atmosphere protection, and then placed in an experimental microwave oven. The experimental conditions set the microwave reaction power to 800 W and the reaction time to 10 min. No stirring was performed during the reaction. The reaction mixture was centrifuged and washed with ethanol, and then dried in a vacuum drying oven at 60 ° C for 12 h to finally obtain the precursor material Ni2P / Ni 12 P5 heterostructure.

[0046] S3, high temperature oxidation

[0047] The Ni2P / Ni 12The P5 heterostructure precursor powder was placed in an air furnace. The air furnace was set to heat up at a rate of 5°C / min, heated to 650°C and kept for 4 hours, and then cooled naturally to room temperature. The sample was taken out to obtain powder, which was recorded as Ni2P / NiO-4h.

[0048] Embodiment 2

[0049] S1. Prepare the reactant mixture

[0050] 10 mg of BP nanosheets (based on the two-dimensional nanosheet BP obtained in previous studies) was dispersed in 20 mL of 1-methyl-2-pyrrolidone and stirred for 30 min. The resulting mixed solution was recorded as A. 2.6146 g of NiCl2·6H2O metal salt was dispersed in 10 mL of 1-methyl-2-pyrrolidone and stirred for 30 min. The resulting mixed solution was recorded as C. The mixed solution C was slowly injected into the mixed solution A and stirred evenly to obtain a reactant mixed solution.

[0051] S2. Preparation of precursors

[0052] The mixed solution was transferred to a 50 mL flask, and a reaction device was built under argon atmosphere protection, and then placed in an experimental microwave oven. The experimental conditions set the microwave reaction power to 800 W and the reaction time to 10 min. No stirring was performed during the reaction. The reaction mixture was centrifuged and washed with ethanol, and then dried in a vacuum drying oven at 60 ° C for 12 h to finally obtain the precursor material Ni2P / Ni 12 P5 heterostructure.

[0053] S3, high temperature oxidation

[0054] The Ni2P / Ni 12 The P5 heterostructure precursor powder was placed in an air furnace. The air furnace was set to heat up at a rate of 5°C / min, heated to 650°C and kept for 16 hours, and then cooled naturally to room temperature. The sample was taken out to obtain powder, which was recorded as Ni2P / NiO-16h.

[0055] Embodiment 3

[0056] S1. Prepare the reactant mixture

[0057] 10 mg of BP nanosheets (based on the two-dimensional nanosheet BP obtained in previous studies) was dispersed in 20 mL of 1-methyl-2-pyrrolidone and stirred for 30 min. The resulting mixed solution was recorded as A. 2.6146 g of NiCl2·6H2O metal salt was dispersed in 10 mL of 1-methyl-2-pyrrolidone and stirred for 30 min. The resulting mixed solution was recorded as C. The mixed solution C was slowly injected into the mixed solution A and stirred evenly to obtain a reactant mixed solution.

[0058] S2. Preparation of precursors

[0059] The mixed solution was transferred to a 50 mL flask, and a reaction device was built under argon atmosphere protection, and then placed in an experimental microwave oven. The experimental conditions set the microwave reaction power to 800 W and the reaction time to 10 min. Stirring was added halfway. The reaction mixture was centrifugally washed with ethanol, and then dried in a vacuum drying oven at 60 ° C for 12 h to finally obtain the precursor material Ni2P / Ni 12 P5 heterostructure.

[0060] S3, high temperature oxidation

[0061] The Ni2P / Ni 12 The P5 heterostructure precursor powder was placed in an air furnace. The air furnace was set to heat up at a rate of 5°C / min, heated to 650°C and kept for 4 hours, and then naturally cooled to room temperature with the furnace to obtain the final agglomerated Ni2P / NiO powder.

[0062] Embodiment 4

[0063] S1. Prepare the reactant mixture

[0064] 10 mg of BP nanosheets (based on the two-dimensional nanosheet BP obtained in previous studies) was dispersed in 20 mL of 1-methyl-2-pyrrolidone and stirred for 30 min. The resulting mixed solution was recorded as A. 2.6146 g of NiCl2·6H2O metal salt was dispersed in 10 mL of 1-methyl-2-pyrrolidone and stirred for 30 min. The resulting mixed solution was recorded as C. The mixed solution C was slowly injected into the mixed solution A and stirred evenly to obtain a reactant mixed solution.

[0065] S2. Preparation of precursors

[0066] The mixed solution was transferred to a 50 mL flask, and a reaction device was built under argon atmosphere protection, and then placed in an experimental microwave oven. The experimental conditions set the microwave reaction power to 800 W and the reaction time to 10 min. No stirring was performed during the reaction. The reaction mixture was centrifuged and washed with ethanol, and then dried in a vacuum drying oven at 60 ° C for 12 h to finally obtain the precursor material Ni2P / Ni 12 P5 heterostructure.

[0067] S3, high temperature oxidation

[0068] The Ni2P / Ni 12 The P5 heterostructure precursor powder was placed in an air furnace. The air furnace was set to heat up at a rate of 5°C / min, heated to 450°C and kept for 4 hours, and then naturally cooled to room temperature with the furnace to obtain the final Ni2P / NiO powder.

[0069] Embodiment 5

[0070] S1. Prepare the reactant mixture

[0071] 10 mg of BP nanosheets (based on the two-dimensional nanosheet BP obtained in previous studies) was dispersed in 20 mL of 1-methyl-2-pyrrolidone and stirred for 30 min. The resulting mixed solution was recorded as A. 2.6146 g of NiCl2·6H2O metal salt was dispersed in 10 mL of 1-methyl-2-pyrrolidone and stirred for 30 min. The resulting mixed solution was recorded as C. The mixed solution C was slowly injected into the mixed solution A and stirred evenly to obtain a reactant mixed solution.

[0072] S2. Preparation of precursors

[0073] The mixed solution was transferred to a 50 mL flask, and a reaction device was built under argon atmosphere protection, and then placed in an experimental microwave oven. The experimental conditions set the microwave reaction power to 800 W and the reaction time to 10 min. No stirring was performed during the reaction. The reaction mixture was centrifuged and washed with ethanol, and then dried in a vacuum drying oven at 60 ° C for 12 h to finally obtain the precursor material Ni2P / Ni 12 P5 heterostructure.

[0074] S3, high temperature oxidation

[0075] The Ni2P / Ni 12 The P5 heterostructure precursor powder was placed in an air furnace. The air furnace was set to heat up at a rate of 5°C / min, heated to 550°C and kept for 4 hours, and then naturally cooled to room temperature with the furnace to obtain the final Ni2P / NiO powder.

[0076] Embodiment 6

[0077] S1. Prepare the reactant mixture

[0078] 10 mg of BP nanosheets (based on the two-dimensional nanosheet BP obtained in previous studies) was dispersed in 20 mL of 1-methyl-2-pyrrolidone and stirred for 30 min. The resulting mixed solution was recorded as A. 2.6146 g of NiCl2·6H2O metal salt was dispersed in 10 mL of 1-methyl-2-pyrrolidone and stirred for 30 min. The resulting mixed solution was recorded as C. The mixed solution C was slowly injected into the mixed solution A and stirred evenly to obtain a reactant mixed solution.

[0079] S2. Preparation of precursors

[0080] The mixed solution was transferred to a 50 mL flask, and a reaction device was built under argon atmosphere protection, and then placed in an experimental microwave oven. The experimental conditions set the microwave reaction power to 800 W and the reaction time to 10 min. No stirring was performed during the reaction. The reaction mixture was centrifuged and washed with ethanol, and then dried in a vacuum drying oven at 60 ° C for 12 h to finally obtain powdered Ni2P / Ni 12 P5 heterostructure.

[0081] The samples prepared in Example 1 were characterized and tested, and the results were as follows:

[0082] See also Figure 1 , Figure 1 The Ni2P / NiO-4h, Ni2P / NiO-16h and Ni2P / Ni of Example 1, Example 2 and Example 6 are 12 XRD characterization of P5. The results show that the phase structure of the precursor corresponds to Ni2P and Ni 12 The samples after high temperature oxidation correspond to Ni2P and NiO phases, while Ni 12 The P5 substance disappears. The extension of high-temperature oxidation time causes the characteristic peak of Ni2P to almost disappear, and the substance content is extremely low, with NiO as the main phase.

[0083] See also Figure 2 , Figure 2 (a) is the Ni2P / Ni of Example 6 12 The TEM image of the P5 heterostructure shows a two-dimensional layered structure with a rough surface and many micropores. Figure 2 (b) is a TEM image of the partially oxidized Ni2P / NiO-4h heterostructure of Example 1, which shows that the structure has not collapsed, the two-dimensional morphology of the precursor is retained, and a large number of microporous structures still exist on the surface. Figure 2 (c) is the TEM image of the nearly completely oxidized Ni2P / NiO-16h nanoparticle heterojunction of Example 2.

[0084] See also Figure 3 , Figure 3 (a) is the Ni2P / Ni of Example 6 12 High-resolution TEM image of the P5 heterostructure. The lattice spacing is measured and it is known that 0.222nm corresponds to the (111) crystal plane of Ni2P and 0.253nm corresponds to the Ni 12 P5 (002) crystal plane, and there is a clear interface, indicating that Ni2P / Ni 12 Formation of P5 heterostructures. Figure 3(b) is a high-resolution TEM image of the Ni2P / NiO-4h heterostructure of Example 1. Under high resolution, it can be clearly seen that multiple local patches are distributed on the Ni2P substrate, corresponding to the (200) crystal plane of NiO distributed on the (111) crystal plane of Ni2P to form a heterostructure. Figure 3 (c) is a high-resolution TEM image of the Ni2P / NiO-16h heterostructure of Example 2, exposing a large area of ​​0.209nm lattice fringe spacing, corresponding to the (200) crystal plane of NiO, indicating that it is almost completely oxidized to form NiO with very little Ni2P content.

[0085] See also Figure 4 , Figure 4 Gas sensitivity test of samples prepared for Example 1, Example 2 and Example 6; Figure 4 (a) Response-recovery curves of Ni2P / NiO-4h heterostructures exposed to 5 ppm H2S gas at different temperatures. The results show that the sample has the highest sensitivity to H2S gas at 150°C. Figure 4 (b) Ni2P / NiO-4h heterostructure and Ni2P / Ni 12 The gas sensing performance of P5 and Ni2P / NiO-16h at a temperature of 150°C shows that the Ni2P / NiO-4h heterostructure surface has the shortest response time and recovery time, and has better H2S gas sensitivity.

[0086] See also Figure 5 , Figure 5 This is a test diagram of the short-term response recovery and long-term sensitivity stability of the Ni2P / NiO-4h heterostructure prepared in Example 1. Figure 5 (a) is the short-term response recovery curve of the Ni2P / NiO-4h heterostructure. The results show that under the conditions of H2S gas concentration of 5ppm and working temperature of 150℃, after multiple adsorption and desorption gas sensitive tests, the gas sensitivity and recovery time of the Ni2P / NiO-4h heterostructure did not change significantly, indicating good response recovery stability. Figure 5 (b) is the long-term response sensitivity test curve of the Ni2P / NiO-4h heterostructure. The gas-sensitive response value fluctuates in about 2-3 weeks, and the response value shows a downward trend as the number of days increases. Due to its long-term exposure, the gas-sensitive performance will decay, but it has a high long-term stability overall.

[0087] See also Figure 6 , Figure 6 Gas sensitivity response curve tests of the Ni2P / NiO heterostructure nanosheets prepared in Example 1 and Example 2 to different gases H2S, NH3 and CO. Figure 6(a) is the sensitivity response curve of the Ni2P / NiO-16h heterostructure nanosheet of Example 2 to different gases. The results show that the sample has extremely low response values ​​to all three gases, and there is almost no difference between the three gases. Figure 6 (b) is the sensitivity response curve of the Ni2P / NiO-4h heterostructure nanosheet of Example 1 to different gases. The results show that the sample has a high sensitivity response to H2S gas, which is much higher than the response values ​​of NH3 and CO gas, indicating that the high-concentration heterostructure Ni2P / NiO-4h two-dimensional nanosheet has a special gas sensitivity selectivity to H2S gas. Therefore, Ni2P / NiO heterostructure materials have special value in preventing H2S gas leakage in industry.

[0088] Compared with the related art, the preparation method of the Ni2P / NiO heterostructure nanosheet gas-sensitive material provided by the present invention has the following beneficial effects:

[0089] The present invention provides a method for preparing a Ni2P / NiO heterostructure nanosheet gas-sensitive material, which is obtained by a two-step method of microwave in-situ topological transformation and high-temperature oxidation, retaining the original two-dimensional nanosheet morphology of BP and transforming it into Ni2P / NiO heterostructure nanosheets, thereby greatly improving its gas sensitivity to H2S.

[0090] The excessive amount of Ni metal source used in S1 of the present invention is to meet the basic requirements of in-situ topological transformation. In the high-concentration nearly saturated NiCl2·6H2O solution, the Ni source can be continuously provided to the reaction, resulting in Ni2P / NiO basically retaining the original two-dimensional morphology of BP. And due to undersaturation, part of BP is not fully combined with the Ni source, and many microporous defects are generated on the surface of the heterostructure. The above two points are beneficial to the contact between gas and device and the conduction of gas during gas sensitive detection. On the other hand, the high-temperature calcination method uses Ni2P / NiO heterostructure as a precursor, and the obtained Ni2P / NiO retains the original two-dimensional morphology, forming a Ni2P-modified Ni2P / NiO heterostructure, which has an adjustable electronic structure, and is conducive to providing higher carrier migration, and can play a synergistic role to enable the heterostructure material to exhibit excellent gas sensitive sensing performance.

[0091] The Ni2P / NiO heterostructure nanosheet of the present invention presents a thinner two-dimensional nanosheet morphology, has a high surface exposure, can provide more adsorption and desorption sites for the target gas, and thus has a high response sensitivity. In addition, a nn heterostructure is formed between Ni2P and NiO, which produces an adjustable electronic state, so that the material body can be conducive to the adsorption and desorption response of a specific gas.

[0092] The Ni2P / NiO heterostructure nanosheet of the present invention is used to assemble a gas-sensitive sensor device to detect H2S gas. It has a ppm-level H2S gas response at an optimal working temperature of 150°C, a rapid response, and a short recovery time, which indicates that the Ni2P / NiO heterostructure nanosheet of the present invention has excellent H2S gas sensing sensitivity. In addition, after a long-term sensitivity stability test, the Ni2P / NiO heterostructure nanosheet of the present invention has a durability of up to 5 weeks without obvious attenuation. In order to further evaluate the high selectivity of the heterostructure nanosheet for H2S gas, NH3 and CO comparison gases are introduced. The results show that the Ni2P / NiO heterostructure nanosheet of the present invention has an extremely high sensitivity with high selectivity for H2S and has a special value for preventing H2S gas leakage in industry.

[0093] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing a Ni2P / NiO heterostructure nanosheet gas-sensitive material, characterized in that: The following steps are involved: S1. Dispersing the BP nanosheets obtained in advance in 1-methyl-2-pyrrolidone, which is referred to as mixed solution A; dispersing a certain amount of metal salt in 1-methyl-2-pyrrolidone, which is referred to as mixed solution C; mixing the A and C dispersions and stirring them evenly to obtain a reactant mixed solution; S2, placing the reactant mixture in a flask, and placing it in an experimental microwave oven under the protection of an argon atmosphere, heating the reaction in the microwave for a period of time, and washing the reactant by centrifugation with ethanol to obtain a precursor material Ni2P / Ni12P5 heterostructure; S3. The obtained precursor material Ni2P / Ni12P5 heterostructure is placed in an air furnace for high-temperature calcination, and after oxidation, an in-situ transformed Ni2P / NiO heterostructure nanosheet is obtained.

2. The method for preparing the Ni2P / NiO heterostructure nanosheet gas-sensitive material according to claim 1, characterized in that: The mixed solution A in S1 is prepared by dispersing 20 mg of BP nanosheets in every 20 mL of 1-methyl-2-pyrrolidone.

3. The method for preparing the Ni2P / NiO heterostructure nanosheet gas-sensitive material according to claim 1, characterized in that: The mixed solution C in S1, wherein the metal salt is NiCl2·6H2O, is prepared by dispersing 2.6146 g of NiCl2·6H2O metal salt in every 10 mL of 1-methyl-2-pyrrolidone.

4. The method for preparing the Ni2P / NiO heterostructure nanosheet gas-sensitive material according to claim 1, characterized in that: The microwave heating power in S2 is 800 W, and the reaction time is 10 min.

5. The method for preparing the Ni2P / NiO heterostructure nanosheet gas-sensitive material according to claim 1, characterized in that: In S3, the calcination temperature in the air furnace is 650° C., and the calcination time is selected in the range of 4 to 16 hours.

6. The method for preparing the Ni2P / NiO heterostructure nanosheet gas-sensitive material according to claim 1, characterized in that: The metal salt in S1 also includes a phosphorus source-related metal salt, and the phosphorus source-related metal salt is selected from at least one of sodium phosphate, potassium phosphate, and sodium phosphite, which is used to regulate the phosphorus content in the product, thereby optimizing the gas sensing performance of the Ni2P / NiO heterostructure nanosheets.

7. The method for preparing the Ni2P / NiO heterostructure nanosheet gas-sensitive material according to claim 1, characterized in that: The air humidity in the S3 air furnace is controlled within a specified range to prevent water vapor from adversely affecting the high-temperature calcination process and product structure.

8. An application of Ni2P / NiO heterostructure nanosheet gas-sensitive material, characterized in that: The Ni2P / NiO heterostructure nanosheet gas-sensitive material is prepared by the preparation method of the Ni2P / NiO heterostructure nanosheet gas-sensitive material as described in any one of claims 1 to 7, and the Ni2P / NiO heterostructure nanosheet gas-sensitive material is used to detect H2S.

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