CN115096956A - Hollow spherical nickel vanadate-nickel oxide heterogeneous material, preparation method and application thereof, and triethylamine gas sensor - Google Patents
Hollow spherical nickel vanadate-nickel oxide heterogeneous material, preparation method and application thereof, and triethylamine gas sensor Download PDFInfo
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
- G01N27/125—Composition of the body, e.g. the composition of its sensitive layer
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
- G01N27/125—Composition of the body, e.g. the composition of its sensitive layer
- G01N27/126—Composition of the body, e.g. the composition of its sensitive layer comprising organic polymers
Abstract
The invention provides a hollow spherical nickel vanadate-nickel oxide heterogeneous material, a preparation method and application thereof, and a triethylamine gas sensor, and relates to the technical field of gas sensitive materials. The invention provides a preparation method of a hollow spherical nickel vanadate-nickel oxide heterogeneous material, which comprises the following steps: mixing nickel nitrate, trimesic acid, polyvinylpyrrolidone, water, ethanol and N, N-dimethylformamide, and carrying out solvothermal reaction to obtain a Ni-MOF precursor product; mixing the Ni-MOF precursor product with a vanadate solution, and carrying out an ion exchange reaction to obtain a Ni-V-MOFs precursor product; and annealing the Ni-V-MOFs precursor product to obtain the hollow spherical nickel vanadate-nickel oxide heterogeneous material. Ni prepared by the invention 3 V 2 O 8 The NiO heterogeneous material has higher specific surface area and porosity and higher sensitivity to triethylamine gas.
Description
Technical Field
The invention relates to the technical field of gas-sensitive materials, in particular to a hollow spherical nickel vanadate-nickel oxide heterogeneous material, a preparation method and application thereof, and a triethylamine gas sensor.
Background
The gas sensor has no work in the aspects of monitoring environmental pollution, life safety and the like. Metal Oxide Semiconductor (MOS) gas sensors are the most advantageous means for monitoring toxic and harmful volatile organic gases (VOCs) due to their advantages of simplicity of manufacture, ease of operation, wide range of applications, and low cost. NiO is used as a p-type wide band gap MOS, and has excellent catalytic and electrical properties, so that the NiO has wide application prospect in the field of sensors. CN106006764B discloses a method for preparing a mesoporous silica material (SBA-15) with a specific surface area of 92.6m 2 g -1 The ordered mesoporous NiO nano material has high selectivity to acetone gas, but the working temperature is too high (T is 340 ℃), and the sensitivity is low (S is 4.3), so that the possibility of practical application is limited.
The pure NiO material prepared by the traditional method has the characteristics of small specific area and low porosity, and limits the reaction and gas diffusion between gas molecules and sensitive materials, so that the sensitivity of the pure NiO material to gas is poor, and the requirement of people on a high-sensitivity sensor cannot be met.
Disclosure of Invention
The invention aims to provide a hollow spherical nickel vanadate-nickel oxide heterogeneous material, a preparation method and application thereof, and a triethylamine gas sensor 3 V 2 O 8 -NiO) heterogeneous material has larger specific surface area and high porosity, and has higher sensitivity to triethylamine gas.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of a hollow spherical nickel vanadate-nickel oxide heterogeneous material, which comprises the following steps:
mixing nickel nitrate, trimesic acid, polyvinylpyrrolidone, water, ethanol and N, N-dimethylformamide, and carrying out solvothermal reaction to obtain a Ni-MOF precursor product;
mixing the Ni-MOF precursor product with a vanadate solution, and carrying out an ion exchange reaction to obtain a Ni-V-MOFs precursor product;
and annealing the Ni-V-MOFs precursor product to obtain the hollow spherical nickel vanadate-nickel oxide heterogeneous material.
Preferably, the molar ratio of the nickel nitrate to the trimesic acid to the polyvinylpyrrolidone is 4-39: 2-18: 1; the relative molecular mass of the polyvinylpyrrolidone is 40000.
Preferably, the volume ratio of the water to the ethanol to the N, N-dimethylformamide is (0.5-2): (1-2): 1-3).
Preferably, the temperature of the solvothermal reaction is 120-160 ℃, and the time is 12-16 h.
Preferably, the concentration of the vanadate solution is 1.0-6.0 mmol/L; the molar ratio of vanadate in the nickel nitrate and vanadate solution is 17 (6-24).
Preferably, the annealing temperature is 300-400 ℃, and the heat preservation time is 1-3 h.
The invention provides a hollow spherical nickel vanadate-nickel oxide heterogeneous material prepared by the preparation method in the technical scheme, and the specific surface area of the hollow spherical nickel vanadate-nickel oxide heterogeneous material is 200-300 m 2 g -1 The porosity is 0.2-0.4 cm 3 g -1 。
The invention provides application of the hollow spherical nickel vanadate-nickel oxide heterogeneous material in a triethylamine gas sensor.
The invention provides a triethylamine gas sensor, and a sensitive material of the triethylamine gas sensor is a hollow spherical nickel vanadate-nickel oxide heterogeneous material in the technical scheme.
Preferably, the triethylamine gas sensor is of an indirectly heated structure.
The invention provides a preparation method of a hollow spherical nickel vanadate-nickel oxide heterogeneous material, which comprises the following steps: mixing nickel nitrate, trimesic acid, polyvinylpyrrolidone, water, ethanol and N, N-dimethylformamide, and carrying out solvothermal reaction to obtain a Ni-MOF precursor product; mixing the Ni-MOF precursor product with a vanadate solution, and carrying out an ion exchange reaction to obtain a Ni-V-MOFs precursor product; subjecting the Ni-V-MOFs precursor product toAnnealing to obtain the hollow spherical nickel vanadate-nickel oxide heterogeneous material. The invention introduces V object elements into single Ni-MOF by a cation exchange method to prepare bimetallic Ni-V-MOFs, and further converts the bimetallic Ni-V-MOFs into a hollow spherical nickel vanadate-nickel oxide heterogeneous material by an annealing process. Ni 3 V 2 O 8 NiO and Ni in NiO heterogeneous Material 3 V 2 O 8 The interface of the material forms a p-p heterojunction in a space charge region, plays an important role in regulating and controlling the carrier concentration and the conduction channel on the surface of the sensitive material, and is beneficial to improving the gas-sensitive performance. The preparation method provided by the invention is simple and low in cost, and the prepared Ni 3 V 2 O 8 The NiO heterogeneous material has higher specific surface area and porosity, and can provide a fully exposed interface and a more favorable channel for the adsorption and diffusion of triethylamine gas on the surface of the material. The results of the examples show that Ni according to the invention is used 3 V 2 O 8 The sensitivity of the triethylamine gas sensor prepared from the NiO heterogeneous material to 100ppm triethylamine is 15.0-43.7, which is 7.5-21.0 times of the sensitivity of a pure NiO-based gas sensor, the minimum concentration value of detection is 0.5ppm, and the lower limit of ppb detection is provided.
Drawings
FIG. 1 is an X-ray diffraction pattern of samples prepared in examples 1 to 3 of the present invention and comparative example 1;
FIG. 2 is an SEM image of samples prepared in examples 1 to 3 of the present invention and comparative example 1, wherein a is comparative example 1; b is example 1; c is example 2; d is example 3;
FIG. 3 is an EDX map and an EDS energy spectrum of a sample prepared in example 2 of the present invention, wherein a is the EDX map; b is an EDS energy spectrum;
FIG. 4 shows N values of samples prepared in examples 1 to 3 of the present invention and comparative example 1 2 Adsorption and desorption isotherms and pore size distribution maps, wherein a is N of comparative example 1 2 Adsorption and desorption isotherms; c is N of example 1 2 Adsorption and desorption isotherms; e is N of example 2 2 Adsorption and desorption isotherms; g is N of example 3 2 Adsorption and desorption isotherms; b. d, f and h are corresponding pore size distribution curves;
FIG. 5 is a schematic view of the structure of a triethylamine gas sensor according to the present invention;
FIG. 6 shows the gas-sensitive response of the triethylamine gas sensors of the samples prepared in examples 1 to 3 of the present invention and comparative example 1 to 100ppm triethylamine at different temperatures;
FIG. 7 is a graph showing recovery from transient dynamic response of triethylamine gas sensors prepared according to example 2 of the present invention when exposed to different concentrations of triethylamine vapor.
Detailed Description
The invention provides a preparation method of a hollow spherical nickel vanadate-nickel oxide heterogeneous material, which comprises the following steps:
mixing nickel nitrate, trimesic acid, polyvinylpyrrolidone, water, ethanol and N, N-dimethylformamide, and carrying out solvothermal reaction to obtain a Ni-MOF precursor product;
mixing the Ni-MOF precursor product with a vanadate solution, and carrying out an ion exchange reaction to obtain a Ni-V-MOFs precursor product;
and annealing the Ni-V-MOFs precursor product to obtain the hollow spherical nickel vanadate-nickel oxide heterogeneous material.
The hollow spherical nickel vanadate-nickel oxide heterogeneous material obtained by the solvothermal and cation exchange two-step method can well reserve the similar hollow spherical structure of a Ni-MOF precursor product, and Ni 3 V 2 O 8 And NiO forms a p-p heterostructure, which is beneficial to improving the gas-sensitive performance of the sensor.
The method comprises the steps of mixing nickel nitrate, trimesic acid, polyvinylpyrrolidone, water, ethanol and N, N-dimethylformamide, and carrying out solvothermal reaction to obtain a Ni-MOF precursor product. In the invention, the molar ratio of the nickel nitrate to the trimesic acid to the polyvinylpyrrolidone is preferably 4-39: 2-18: 1, and more preferably 39:18: 1. In the present invention, the nickel nitrate is preferably nickel nitrate hexahydrate. In the present invention, the polyvinylpyrrolidone is preferably PVP-K30; the relative molecular mass (Mw) of the polyvinylpyrrolidone is preferably 40000.
In the invention, the volume ratio of the water, the ethanol and the N, N-dimethylformamide is preferably (0.5-2): (1-2): 1-3), and more preferably 1:1: 1.
In the present invention, the mixing of nickel nitrate, trimesic acid, polyvinylpyrrolidone, water, ethanol and N, N-dimethylformamide preferably comprises: dissolving nickel nitrate in a mixed solvent of water, ethanol and N, N-dimethylformamide, and then adding and mixing trimesic acid and polyvinylpyrrolidone. In the invention, the mixing temperature is preferably room temperature, and particularly preferably 20-35 ℃; the mixing is preferably carried out under stirring conditions; the mixing time is preferably 40 min. In the present invention, the usage ratio of the nickel nitrate to the mixed solvent of water, ethanol and N, N-dimethylformamide is preferably 1.5 mmol: 30 mL.
In the invention, the temperature of the solvothermal reaction is preferably 120-160 ℃, and more preferably 130-150 ℃; the time is preferably 12 to 16 hours, and more preferably 13 to 15 hours. In the present invention, the solvothermal reaction is preferably carried out in an autoclave. In the process of the solvent thermal reaction, Ni 2+ Coordinating with trimesic acid (BTC) to produce a metal organic framework material Ni-BTC.
According to the invention, preferably, after the solvothermal reaction, the obtained reaction product is sequentially subjected to centrifugal washing and drying to obtain a Ni-MOF precursor product. In the present invention, the centrifugal washing preferably includes washing with N, N-Dimethylformamide (DMF), absolute ethanol, and deionized water each three times, respectively; the rotation speed of the centrifugal washing is preferably 5000rpm, and the time required for each centrifugal washing is preferably 10 min. In the invention, the drying temperature is preferably 60-80 ℃; the drying time is preferably 8-16 h, and more preferably 12 h.
After a Ni-MOF precursor product is obtained, the Ni-MOF precursor product and a vanadate solution are mixed for ion exchange reaction, and a Ni-V-MOFs precursor product is obtained. In the invention, the concentration of the vanadate solution is preferably 1.0-6.0 mmol/L, and more preferably 1.5-4.5 mmol/L; the molar ratio of vanadate in the nickel nitrate and vanadate solution is preferably 17 (6-24). In the present invention, the vanadate is preferably ammonium vanadate (NH) 4 VO 3 )。
In the invention, the temperature of the ion exchange reaction is preferably room temperature, and particularly preferably 20-35 ℃; the time of the ion exchange reaction is preferably 2-5 h, and more preferably 3 h. In the present invention, the ion exchange reaction is preferably carried out under stirring conditions; the rate of stirring is preferably 40 rpm. In the ion exchange reaction process, the trimesic acid ligand in the Ni-MOF is nearby free VO 3 - And OH - And exchanging to form the Ni-V hydroxide composite material.
In the invention, preferably, after the ion exchange reaction, the obtained reaction solution is kept stand for precipitation, and the supernatant is removed; and sequentially carrying out centrifugal washing and drying on the residual solution to obtain a Ni-V-MOFs precursor product. In the present invention, the centrifugal washing preferably includes three times of washing with anhydrous ethanol and deionized water, respectively; the rotation speed of the centrifugal washing is preferably 5000 rpm; the time for each centrifugal washing is preferably 10 min. In the invention, the drying temperature is preferably 60-80 ℃; the drying time is preferably 8-16 h, and more preferably 12 h.
After obtaining the Ni-V-MOFs precursor product, annealing the Ni-V-MOFs precursor product to obtain the hollow spherical nickel vanadate-nickel oxide heterogeneous material. In the invention, the annealing temperature is preferably 300-400 ℃, and more preferably 350 ℃; the heat preservation time is preferably 1-3 h, and more preferably 2 h. In the present invention, the rate of temperature increase from room temperature to the annealing temperature is preferably 1 to 2 ℃/min. In the present invention, the atmosphere of the annealing is preferably an air atmosphere.
The invention provides the hollow spherical nickel vanadate-nickel oxide heterogeneous material prepared by the preparation method in the technical scheme, and the specific surface area of the hollow spherical nickel vanadate-nickel oxide heterogeneous material is 200-300 m 2 g -1 Preferably 243.8-275.9 m 2 g -1 (ii) a The porosity is 0.2-0.4 cm 3 g -1 . In the invention, the average diameter of the hollow spherical nickel vanadate-nickel oxide heterogeneous material is preferably 0.8-3 μm, and more preferably 1.1-2.3 μm; the average diameter of the inner hollow is preferably 0.4 to 1.0 μm, more preferably 0.5 to 0.823. mu.m. In the present invention, the hollow spherical nickel vanadate-oxideThe nickel heterogeneous material is preferably a mesoporous material; the average pore diameter of the mesopores is preferably 4.1 nm.
The invention also provides application of the hollow spherical nickel vanadate-nickel oxide heterogeneous material in the technical scheme in a triethylamine gas sensor.
The invention provides a triethylamine gas sensor, and a sensitive material of the triethylamine gas sensor is a hollow spherical nickel vanadate-nickel oxide heterogeneous material in the technical scheme. In the present invention, the triethylamine gas sensor is preferably an indirectly heated structure. As an embodiment of the present invention, the triethylamine gas sensor is shown in fig. 5, and includes a hollow ceramic tube, a gold electrode, a Ni — Cr heater wire, a platinum wire, a heating electrode, a measuring electrode, a base, and a gas sensitive coating; the gas-sensitive coating is formed by the hollow spherical nickel vanadate-nickel oxide heterogeneous material in the technical scheme.
In the invention, the thickness of the gas-sensitive coating is preferably 35.0-65.0 μm, and more preferably 40.0 μm.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Comparative example 1
0.432g of nickel nitrate hexahydrate Ni (NO) was added at room temperature 3 ) 2 ·6H 2 Dissolving O in 30mL of mixed solvent (the volume ratio of deionized water to ethanol to DMF is 1:1:1), after completely dissolving, slowly adding 150mg of trimesic acid and 1.5g of PVP-K30 into the solution, and violently stirring for 40min to uniformly disperse the solution; transferring the obtained light green mixture into a high-pressure reaction kettle with a polytetrafluoroethylene lining, and keeping the mixture in an oven for 15 hours at 150 ℃; after the reaction kettle is cooled to room temperature, centrifuging the obtained light green product for 10min at 5000rpm, respectively washing the product with DMF (dimethyl formamide), ethanol and deionized water for three times, and drying the product in an oven at 60 ℃ for 12h to obtain the light green productNi-MOF precursor product. Annealing for 2h at 350 ℃ in a tubular furnace at the heating rate of 1 ℃/min in the air atmosphere to obtain the MOFs-derived hollow sphere NiO material.
Example 1
A greenish Ni-MOF precursor product was prepared according to the method of comparative example 1.
0.1g of the pale green Ni-MOF precursor product and 0.014g NH 4 VO 3 Placing the solution in a beaker filled with 80mL of deionized water, magnetically stirring the solution for 3 hours, standing the solution for precipitation, and pouring out supernatant; and centrifuging the residual uniformly mixed solution at 5000rpm for 10min, respectively washing the solution with ethanol and deionized water for three times, and drying the solution in an oven at 60 ℃ for 12h to obtain a Ni-V-MOFs precursor product.
Annealing at 350 ℃ for 2h in a tubular furnace at the heating rate of 1 ℃/min in the air atmosphere, and collecting to obtain hollow spherical Ni derived from bimetallic MOFs 3 V 2 O 8 -NiO heterogeneous material.
Example 2
A greenish-colored Ni-MOF precursor product was prepared according to the method of comparative example 1.
0.1g of the pale green Ni-MOF precursor product and 0.028g NH 4 VO 3 Placing the solution in a beaker filled with 80mL of deionized water, magnetically stirring the solution for 3 hours, standing the solution for precipitation, and pouring out supernatant; and centrifuging the residual uniformly mixed solution at 5000rpm for 10min, respectively washing the solution with ethanol and deionized water for three times, and drying the solution in an oven at 60 ℃ for 12h to obtain a Ni-V-MOFs precursor product.
Annealing at 350 ℃ for 2h in a tube furnace at the heating rate of 1 ℃/min in the air atmosphere, and collecting to obtain hollow spherical Ni derived from bimetallic MOFs 3 V 2 O 8 -NiO heterogeneous material.
Example 3
A greenish Ni-MOF precursor product was prepared according to the method of comparative example 1.
0.1g of the greenish Ni-MOF precursor product and 0.042g of NH 4 VO 3 Placing the solution in a beaker filled with 80mL of deionized water, magnetically stirring the solution for 3 hours, and pouring out supernatant after the solution is kept stand and precipitated; the remaining mixed solution was centrifuged at 5000rpm 10And min, respectively washing the precursor with ethanol and deionized water for three times, and drying the precursor in an oven at 60 ℃ for 12h to obtain the Ni-V-MOFs precursor product.
Annealing at 350 ℃ for 2h in a tube furnace at the heating rate of 1 ℃/min in the air atmosphere, and collecting to obtain hollow spherical Ni derived from bimetallic MOFs 3 V 2 O 8 -NiO heterogeneous material.
Test example
The microscopic morphologies and crystal structures of the products obtained in the examples and comparative examples were characterized. The micro-morphology is characterized on a FEI Verios G4 model transmission scanning electron microscope of FEI company in USA, and the crystal structure is characterized on a powder X-ray diffractometer of X' Pert Pro MPD model of Pynaudiaceae company in the Netherlands. The specific surface area and pore size distribution were characterized on a nitrogen adsorption desorption analyzer model TriStar II 3020 from Macco USA. The gas sensitive test was characterized on a WS-30B gas sensitive tester from Weisheng electronics, Inc., China. The results are shown in FIGS. 1 to 6.
FIG. 1 is X-ray diffraction patterns of samples prepared in examples 1 to 3 of the present invention and comparative example 1, and it can be seen that the pure NiO crystal structure prepared in comparative example 1 is a cubic structure, five distinct characteristic peaks completely coincide with face-centered cubic phase NiO standard card (JCPDS: 47-1049), and 5 characteristic peaks are respectively indexed to the (111), (200), (220), (311) and (222) crystal faces. Due to Ni 3 V 2 O 8 Has a low concentration of compounds of (1), Ni 3 V 2 O 8 The diffraction peak of (A) is not obvious in the map, but the hollow spherical Ni 3 V 2 O 8 The diffraction peak intensity of the NiO heterogeneous material is reduced and the peak is widened compared with that of pure NiO. The absence of the relevant impurity diffraction peaks in all the samples synthesized indicates that the purity of the material produced is higher.
FIG. 2 is an SEM image of samples prepared in examples 1 to 3 of the present invention and comparative example 1, and it can be seen that pure NiO is a hollow sphere having a diameter of about 2.2 μm and a hollow diameter of about 0.84. mu.m. The formation of the hollow structure depends on the Ostwald mature theory, under the existence of PVP-K30 stabilizer, Ni ions are firstly coordinated with organic ligand trimesic acid to form amorphous solid spheres, and the amorphous solid spheres are easily crystallized to form more stable solid spheres through the solvothermal reaction processThe internal part of the sphere gradually dissolves and diffuses to the surface to form a hollow sphere in the crystallization process. For hollow spherical Ni 3 V 2 O 8 -NiO heterogeneous material, average diameter of 2.3 μm for the samples prepared in example 1, average diameter of the internal hollows of 0.82 μm, average diameter of 1.3 μm for the samples prepared in example 2, average diameter of the internal hollows of 0.6 μm, average diameter of 1.1 μm for the samples prepared in example 3, average diameter of the internal hollows of 0.5 μm. Therefore, the derivative composite material obtained by the solvothermal and cation exchange two-step method can well keep the initial state hollow structure and is accompanied with Ni 3 V 2 O 8 The hollow sphere size gradually decreased with increasing concentration.
A in fig. 3 is an EDX map of the sample prepared in example 2 of the present invention, showing that three elements of Ni, O and V are uniformly distributed. The EDS spectrum of b in FIG. 3 further confirms the presence of three elements, Ni, O and V, Ni 3 V 2 O 8 The weight percentages of Ni, V and O in the NiO heterogeneous material were 64.24%, 8.72% and 27.04%, respectively, and the atomic percentages were 37.02%, 5.79% and 57.19%, respectively.
FIG. 4 shows N values of samples prepared in examples 1 to 3 of the present invention and comparative example 1 2 Adsorption and desorption isotherms and pore size distribution maps. According to the IUPAC classification, the four materials all exhibit type IV isotherms and H4 hysteresis loops, and the peaks of narrow pore size for the four samples are concentrated on average at 4.1nm, indicating that there is a relatively uniform and narrowly distributed mesoporous structure in the synthesized material, as evidenced by b, d, f, and H in fig. 4. Hollow spherical Ni prepared in examples 1 to 3 3 V 2 O 8 The specific surface areas of the NiO heterogeneous materials are 275.9m respectively 2 g -1 、270.5m 2 g -1 And 243.8m 2 g -1 All larger than the specific surface area (128.7 m) of NiO prepared in example 1 2 g -1 )。
FIG. 5 is a schematic structural diagram of the triethylamine gas sensor according to the present invention, which is composed of a hollow ceramic tube, a gold electrode, a Ni-Cr heater wire, a platinum wire, a heating electrode, a measuring electrode, a base and a gas sensitive coating; the gas-sensitive coating comprises examples 1-3 and a comparative example1, forming the hollow spherical nickel vanadate-nickel oxide heterogeneous material; the gold electrode is arranged on the outer surface of the hollow ceramic tube; the number of the gold electrodes is two; the two gold electrodes are mutually parallel and surround the two ends of the hollow ceramic tube; the Ni-Cr heating wire penetrates through the hollow ceramic tube; the number of the platinum wires is 4, and the platinum wires are arranged on the outer surface of the hollow ceramic tube; the 4 platinum wires are averagely divided into two groups, and each group is connected with a gold electrode; the hollow ceramic tube, the heating electrode and the measuring electrode are all arranged on the base; the number of the heating electrodes is preferably 2; the number of the measuring electrodes is preferably 4; two ends of the Ni-Cr heating wire are respectively connected with two heating electrodes; the 4 platinum wires are respectively connected with 4 measuring electrodes; the gas-sensitive coating covers the outer surfaces of the hollow ceramic tube and the gold electrode; the thickness of the gas-sensitive coating is 40.0 μm. The preparation method of the sensor comprises the following steps: respectively ultrasonically mixing 0.003g of the materials prepared in the examples 1-3 and the comparative example 1 with 0.15mL of deionized water to form uniform slurry; transferring 12 mu L of slurry as a gas-sensitive material by using a liquid-transferring gun to be uniformly coated on a hollow ceramic tube with two parallel gold electrodes and four platinum wires; welding a platinum wire coated with a gas-sensitive material on the surface of the hollow ceramic tube on a measuring electrode of the base, passing a Ni-Cr heating wire through the ceramic tube from the inside of the ceramic tube and welding the heating wire on the heating electrode of the base, and carrying out stabilizing treatment on the heating electrode on an aging table at the temperature of 100 ℃ for 24 hours to obtain the triethylamine gas sensor shown in figure 5. FIG. 6 shows the gas sensitive response of triethylamine gas sensors based on samples prepared in examples 1 to 3 of the present invention and comparative example 1 to 100ppm triethylamine at different temperatures. It can be seen that the gas sensitive response of all triethylamine gas sensors showed a changing trend of volcanic "increase-maximum-decrease". The results showed that the optimum operating temperatures of the triethylamine gas sensors prepared in comparative example 1 and examples 1 to 3 were 160 ℃, 260 ℃, 240 ℃ and 200 ℃, respectively, and the corresponding sensitivities were 2.08, 15, 43.7 and 21.8, respectively. Thus, it can be seen that the hollow spherical Ni 3 V 2 O 8 The sensitivity of the sensor prepared from the NiO heterogeneous material is improved by 7.5-21 times compared with that of a sensor prepared from pure NiO.
FIG. 7 is a graph showing recovery from transient dynamic response of a triethylamine gas sensor of a sample prepared in example 2 of the present invention when exposed to triethylamine vapor having different concentrations. As is clear from the figure, the triethylamine gas sensor showed excellent reversible recovery characteristics for different concentrations of triethylamine gas, and further, the triethylamine gas sensor showed a sensitivity of 1.3 for 500ppb of triethylamine, indicating that the hollow spherical Ni 3 V 2 O 8 The sensor prepared from the NiO heterogeneous material has the lower limit of ppb detection level, and the detection limit is low.
As is apparent from the above examples and comparative examples, the hollow spherical Ni prepared by the present invention 3 V 2 O 8 The NiO heterogeneous material has higher specific surface area and porosity, has a mesoporous structure, has high sensitivity and ppb level detection limit on triethylamine gas, and has wide application prospect in the field of triethylamine sensing.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A preparation method of a hollow spherical nickel vanadate-nickel oxide heterogeneous material comprises the following steps:
mixing nickel nitrate, trimesic acid, polyvinylpyrrolidone, water, ethanol and N, N-dimethylformamide, and carrying out solvothermal reaction to obtain a Ni-MOF precursor product;
mixing the Ni-MOF precursor product with a vanadate solution, and carrying out an ion exchange reaction to obtain a Ni-V-MOFs precursor product;
and annealing the Ni-V-MOFs precursor product to obtain the hollow spherical nickel vanadate-nickel oxide heterogeneous material.
2. The preparation method according to claim 1, wherein the molar ratio of the nickel nitrate to the trimesic acid to the polyvinylpyrrolidone is 4-39: 2-18: 1; the relative molecular mass of the polyvinylpyrrolidone is 40000.
3. The method according to claim 1, wherein the volume ratio of the water, the ethanol and the N, N-dimethylformamide is (0.5-2): 1-2: 1-3.
4. The preparation method according to claim 1, wherein the temperature of the solvothermal reaction is 120-160 ℃ and the time is 12-16 h.
5. The method according to claim 1, wherein the concentration of the vanadate solution is 1.0 to 6.0 mmol/L; the molar ratio of vanadate in the nickel nitrate and vanadate solution is 17 (6-24).
6. The preparation method according to claim 1, wherein the annealing temperature is 300-400 ℃, and the holding time is 1-3 h.
7. The hollow spherical nickel vanadate-nickel oxide heterogeneous material prepared by the preparation method of any one of claims 1 to 6 has a specific surface area of 200 to 300m 2 g -1 Porosity of 0.2-0.4 cm 3 g -1 。
8. The use of the hollow spherical nickel vanadate-nickel oxide heterogeneous material according to claim 7 in a triethylamine gas sensor.
9. A triethylamine gas sensor, characterized in that the sensitive material of the triethylamine gas sensor is the hollow spherical nickel vanadate-nickel oxide heterogeneous material according to claim 7.
10. The triethylamine gas sensor according to claim 9, wherein the triethylamine gas sensor has an indirectly heated structure.
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