CN119143186B - Au and Co Co-doped holmium ferrite gas-sensitive material and application thereof - Google Patents
Au and Co Co-doped holmium ferrite gas-sensitive material and application thereof Download PDFInfo
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Abstract
本发明公开了一种Au和Co共掺杂的铁酸钬气敏材料及其应用，涉及甲醛气体传感器技术领域。本发明采用硝酸钬、硝酸铁、硝酸钴作为反应原料，经溶胶‑凝胶法，制得Co掺杂的铁酸钬材料，再将其与氯金酸混合后煅烧，得Au和Co共掺杂的铁酸钬气敏材料。本发明利用Au的催化活化和Co的氧空位调控效应，材料的表面能够更稳定地吸附和分解甲醛分子，与非极性干扰气体相比展现出更好的选择性。同时，利用甲醛的分子特性与Au和Co掺杂的协同作用，不仅提升了材料对甲醛的响应灵敏度和选择性，还实现了对甲醛气体的快速低温检测，显著降低了气敏材料的能耗，使其在实际应用中具有较好的稳定性与长效性。
The invention discloses a Au and Co co-doped holmium ferrite gas-sensitive material and its application, and relates to the technical field of formaldehyde gas sensors. The invention adopts holmium nitrate, ferric nitrate and cobalt nitrate as reaction raw materials, and obtains Co-doped holmium ferrite material by sol-gel method, and then mixes it with chloroauric acid and calcines it to obtain Au and Co co-doped holmium ferrite gas-sensitive material. The invention utilizes the catalytic activation of Au and the oxygen vacancy regulation effect of Co, and the surface of the material can more stably adsorb and decompose formaldehyde molecules, showing better selectivity compared with non-polar interfering gases. At the same time, by utilizing the synergistic effect of the molecular characteristics of formaldehyde and the doping of Au and Co, not only the response sensitivity and selectivity of the material to formaldehyde are improved, but also the rapid low-temperature detection of formaldehyde gas is realized, and the energy consumption of the gas-sensitive material is significantly reduced, so that it has good stability and long-term performance in practical applications.
Description
Technical Field
The invention relates to the technical field of formaldehyde gas sensors, in particular to an Au and Co Co-doped holmium ferrite gas-sensitive material and application thereof.
Background
Formaldehyde (HCHO), also known as formic acid, is a toxic substance with high solubility and high volatility, and is a major health hazard to humans in stimulating skin and mucous membranes, affecting the central nervous system, inducing genopathy to cause tumors, and the like. Formaldehyde has been identified by the world health organization international cancer research institute as an carcinogenic and teratogenic substance. It can be seen that effective monitoring of formaldehyde concentration in the environment is particularly important for human health. The gas sensor is a device for converting the information about the concentration of specific gas into an electric signal and detecting the change of the concentration of the specific gas according to the electric signal, and is favored because the gas sensor has the advantages of being simple and convenient to operate, convenient to carry, capable of realizing quick and effective on-line monitoring and the like.
In the prior art, research on the influence of lanthanum ferrite modification on formaldehyde gas-sensitive performance (Lintao, university of Yunnan, 5 months 2012) discloses that a sol-gel method is combined with a microwave chemical method to prepare a synthetic Ag modified LaFeO 3 gas-sensitive material, wherein the optimal working temperature is 90 ℃, and the highest sensitivity to 1ppm formaldehyde at the optimal working temperature can reach about 20. Research shows that compared with single oxide, the composite oxide gas-sensitive material has better selectivity and thermal stability. Journal "preparation of holmium ferrite and samarium ferrite nanocrystalline and research on formaldehyde sensitivity characteristics thereof" (Jiang Dongli et al, chemical novel materials, volume 45, 10 th month 10 of 2007) discloses that the preparation of perovskite composite oxide holmium ferrite by adopting a solid phase reaction method has higher sensitivity to formaldehyde at the working temperature of 315 ℃, and the sensitivity to formaldehyde gas is 20.4. It can be seen that when the holmium ferrite alone is used as a gas-sensitive material for formaldehyde gas detection, the working temperature is up to 315 ℃, and therefore, the non-modified composite oxide material, holmium ferrite, is selected as the formaldehyde gas-sensitive material, the working temperature is up to 315 ℃, and the excessive temperature can cause the gas-sensitive material to sinter or oxidize, so that the sensitivity is reduced, and the energy consumption of the sensor is increased.
Therefore, developing a formaldehyde sensor based on a novel gas-sensitive material is particularly important to reduce the working temperature to enhance the long-term stability of the formaldehyde sensor so as to better adapt to the requirements of various application scenes while ensuring the sensitivity and selectivity of the formaldehyde sensor for detecting formaldehyde gas.
Disclosure of Invention
Aiming at the prior art, the invention aims to provide an Au and Co Co-doped holmium ferrite gas-sensitive material and application thereof. According to the invention, holmium nitrate, ferric nitrate and cobalt nitrate are used as reaction raw materials, a Co-doped holmium ferrite material is prepared by a sol-gel method, and then the Co-doped holmium ferrite material is mixed with chloroauric acid, and after grinding and calcining, the Au and Co Co-doped holmium ferrite gas-sensitive material is obtained. According to the invention, the complex oxide holmium ferrite is doped and modified with Au element and Co element, and the surface of the material can more stably adsorb and decompose formaldehyde molecules by utilizing the catalytic activation of Au and the oxygen vacancy regulation effect of Co, so that the material has better selectivity compared with nonpolar interference gas. Meanwhile, by utilizing the synergistic effect of the molecular characteristics of formaldehyde and Au and Co doping, the response sensitivity and selectivity of the material to formaldehyde are improved, the rapid low-temperature detection of formaldehyde gas is realized, the energy consumption of the gas-sensitive material is obviously reduced, and the gas-sensitive material has better stability and long-acting property in practical application.
In order to achieve the above purpose, the invention adopts the following technical scheme:
according to the first aspect of the invention, a Au and Co Co-doped holmium ferrite gas-sensitive material is provided, and the Au and Co Co-doped holmium ferrite gas-sensitive material is prepared by the following method:
(1) Mixing holmium nitrate, ferric nitrate, cobalt nitrate and citric acid to obtain a mixture, adding the mixture into dilute nitric acid, and stirring to uniformly mix the mixture to obtain a precursor solution;
(2) Calcining the solid at 650-1050 ℃ for 3-12 hours, and grinding to obtain a Co-doped holmium ferrite material;
(3) Mixing a Co-doped holmium ferrite material with chloroauric acid, grinding for the first time, calcining for 3-12 hours at 650-1050 ℃, and grinding for the second time to obtain an Au-Co Co-doped holmium ferrite gas-sensitive material;
Wherein, the addition ratio of holmium nitrate, ferric nitrate, cobalt nitrate, chloroauric acid, citric acid and dilute nitric acid is (0.01-5) mol, (0.05-5) mol, (0.01-100) g (20-100) g (50-200) mL.
Preferably, in the step (1), the mass fraction of the dilute nitric acid is 8-9%.
Preferably, in the step (1), the stirring time is 6-12h.
Preferably, in the step (2), the precursor solution is stirred in the water bath heating process, the stirring speed is 500-600r/min, and the stirring time is 2-8h.
Preferably, in step (2), the milling time is 2-6 hours.
Preferably, in the step (3), the time of the primary grinding and the time of the secondary grinding are 2-6 hours.
In a second aspect of the invention, the application of the Au and Co Co-doped holmium ferrite gas-sensitive material in formaldehyde gas detection is provided.
Preferably, the concentration of the formaldehyde gas is 0.5-1.5ppm.
In a third aspect of the invention, the application of the Au and Co Co-doped holmium ferrite gas-sensitive material in preparing formaldehyde gas-sensitive sensors is provided.
Preferably, the formaldehyde gas sensor is prepared by mixing Au and Co Co-doped holmium ferrite gas sensitive material, deionized water and terpineol to obtain a mixture, spin-coating the mixture on a substrate to form a gas sensitive film, and aging the gas sensitive film to obtain the formaldehyde gas sensor.
Further preferably, the addition ratio of the Au and Co Co-doped holmium ferrite gas sensitive material, deionized water and terpineol is (1-5) g (3-15) mL (1-5) mL.
Further preferably, the aging temperature is 200-240 ℃ and the aging time is 10-24 hours.
Preferably, the working temperature of the formaldehyde gas sensor is 80-200 ℃.
The invention has the beneficial effects that:
According to the invention, holmium nitrate, ferric nitrate and cobalt nitrate are used as reaction raw materials, a Co-doped holmium ferrite material is prepared by a sol-gel method, and then the Co-doped holmium ferrite material is mixed with chloroauric acid, and after grinding and calcining, the Au and Co Co-doped holmium ferrite gas-sensitive material is obtained. The invention carries out doping modification of Au element and Co element on the holmium ferrite composite oxide, and reduces the working temperature to enhance the long-term stability of the formaldehyde sensor while guaranteeing the sensitivity and selectivity of the holmium ferrite composite oxide for detecting formaldehyde gas, thereby being particularly important to better meet the requirements of various application scenes. Specifically, the Au and Co Co-doped holmium ferrite gas-sensitive material prepared by the invention has good selectivity to formaldehyde gas, and the optimal working temperature is 140 ℃, and the response to 1ppm formaldehyde gas is 5.96 at the working temperature.
Drawings
FIG. 1 is an XRD pattern of Au and Co Co-doped holmium ferrite gas sensitive material prepared in example 1;
FIG. 2 is an SEM image of the Au and Co Co-doped holmium ferrite gas-sensitive material prepared in example 1;
FIG. 3 is a EDS MAPPING diagram of gold element and cobalt element of the Au and Co Co-doped holmium ferrite gas-sensitive material prepared in example 1;
FIG. 4 is a graph showing the relationship between the gas-sensitive properties and the temperature of the formaldehyde gas of 1 ppm in the gas-sensitive materials prepared in example 1 and comparative examples 1 to 3;
FIG. 5 is a graph showing the relationship between the gas sensitivity and humidity of Au and Co Co-doped holmium ferrite gas sensitive material prepared in example 1 to formaldehyde gas of 1 ppm;
FIG. 6 is a graph showing the response of the Au and Co Co-doped holmium ferrite gas-sensitive material prepared in example 1 to various gases of 1 ppm;
FIG. 7 is a schematic diagram showing the long-term gas-sensitive stability of Au and Co Co-doped holmium ferrite gas-sensitive material prepared in example 1 to formaldehyde gas.
Detailed Description
It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the application. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
In the prior art, compared with single oxide, the composite oxide gas-sensitive material has better selectivity and thermal stability. Although the holmium ferrite material prepared by adopting the solid phase reaction method has higher sensitivity to formaldehyde, the working temperature is 315 ℃, and the high working temperature can cause sintering or oxidization of the holmium ferrite material, so that the sensitivity is reduced, and meanwhile, the energy consumption of the gas sensor is increased.
Based on the above, the invention provides the Au and Co Co-doped holmium ferrite gas-sensitive material, and the invention carries out doping modification on the Au element and the Co element of the composite oxide holmium ferrite, so that the invention is particularly important to better meet the requirements of various application scenes by reducing the working temperature to enhance the long-term stability of the formaldehyde sensor while ensuring the sensitivity and the selectivity of the composite oxide holmium ferrite for detecting formaldehyde gas. Specifically, the Au and Co Co-doped holmium ferrite gas-sensitive material prepared by the invention has good selectivity to formaldehyde gas, and the optimal working temperature is 140 ℃, and the response to 1ppm formaldehyde gas is 5.96 at the working temperature.
According to the invention, a sol-gel method is utilized, noble metal Au is utilized to carry out HoFeO 3 surface loading and modification, and meanwhile, co element is doped on the B site. Through the composite doping design of the noble metal and the B site, the prepared formaldehyde gas-sensitive material shows excellent sensitivity in detecting HCHO gas, and can effectively distinguish HCHO gas from other interference gases, and meanwhile, the prepared formaldehyde gas-sensitive material can reduce the working temperature of the sensor to 80-200 ℃, reduce the energy consumption of the sensor and is suitable for portable or low-power-consumption equipment.
Formaldehyde (HCHO) is a small molecule, highly polar and chemically active gas, and its carbonyl group (c=o) has remarkable electron attraction properties, and is liable to react with active sites on the surface of a gas sensitive material. According to the invention, au and Co Co are Co-doped to modify holmium ferrite, and a synergistic effect is generated between the molecular characteristics of formaldehyde and doping elements, so that the gas sensitivity of the material to formaldehyde is remarkably improved.
First, au acts as a noble metal, exerting a remarkable catalytic sensitization on the material surface. The carbonyl groups of formaldehyde molecules are easily adsorbed and activated by the Au surface to form reactive oxygen species (such as O -), which accelerates the oxidation reaction of formaldehyde molecules on the material surface. Meanwhile, due to the catalytic effect of Au, the activation energy of formaldehyde is greatly reduced, so that the material can efficiently detect formaldehyde at a lower temperature. The rapid oxidation reaction causes the material resistance to change obviously, thereby effectively improving the sensitivity and speed of gas-sensitive response, and leading the material to respond to formaldehyde sensitively under the low temperature condition of 100-200 ℃.
In addition, the Co doping introduces a large amount of oxygen vacancies in the material, thereby further improving the gas-sensitive performance. Formaldehyde molecules have oxygen affinity and are easy to combine with the oxygen vacancies to form substances such as adsorbed formic acid (HCOO -), so that the decomposition and conversion processes of formaldehyde are accelerated. The oxygen vacancy not only provides sufficient active sites for the oxidation reaction of formaldehyde, but also optimizes the conductivity of the material, so that the oxidation reaction of formaldehyde is more efficient. The oxygen vacancy effect obviously enhances the adsorption and reaction speed of formaldehyde, and further improves the low-temperature response performance of the material.
Through the catalytic activation of Au and the oxygen vacancy regulation effect of Co, the surface of the material can more stably adsorb and decompose formaldehyde molecules, and the material has better selectivity compared with nonpolar interference gases (such as methane, ethane and the like). The molecular characteristics of formaldehyde and Au and Co doping synergistic effect not only improves the response sensitivity and selectivity of the material to formaldehyde, but also realizes the rapid low-temperature detection of formaldehyde gas, and obviously reduces the energy consumption of the gas-sensitive material, so that the gas-sensitive material has better stability and long-acting property in practical application.
In order to enable those skilled in the art to more clearly understand the technical scheme of the present invention, the technical scheme of the present invention will be described in detail with reference to specific embodiments.
The experimental materials used in the embodiment of the invention are all conventional in the field and can be purchased through commercial channels.
EXAMPLE 1 preparation of Au and Co Co-doped holmium ferrite gas sensitive Material
(1) Mixing holmium nitrate, ferric nitrate, cobalt nitrate and citric acid to obtain a mixture, adding the mixture into dilute nitric acid with the mass fraction of 8.5%, and stirring for 8 hours to uniformly mix the mixture to obtain a precursor solution;
(2) Heating the precursor solution in a water bath at 80 ℃, stirring for 6 hours at a rotating speed of 500r/min in the water bath heating process, cooling to room temperature to obtain a solid, calcining the solid at 900 ℃ for 8 hours, and grinding for 3 hours to obtain a Co-doped holmium ferrite material;
(3) Mixing a Co-doped holmium ferrite material with chloroauric acid, grinding for 3 hours, calcining at 900 ℃ for 8 hours, and grinding for 3 hours to obtain an Au-Co Co-doped holmium ferrite gas-sensitive material;
Wherein, the addition ratio of holmium nitrate, ferric nitrate, cobalt nitrate, chloroauric acid, citric acid and dilute nitric acid is 39.29g:19.35g:3.65g:2.29g:60g:50mL.
EXAMPLE 2 preparation of Au and Co Co-doped holmium ferrite gas sensitive Material
(1) Mixing holmium nitrate, ferric nitrate, cobalt nitrate and citric acid to obtain a mixture, adding the mixture into 8 mass percent dilute nitric acid, and stirring for 8 hours to uniformly mix the mixture to obtain a precursor solution;
(2) Heating the precursor solution in a water bath at 50 ℃, stirring at 600r/min for 8 hours in the water bath heating process, cooling to room temperature to obtain a solid, calcining the solid at 650 ℃ for 10 hours, and grinding for 2 hours to obtain a Co-doped holmium ferrite material;
(3) Mixing a Co-doped holmium ferrite material with chloroauric acid, grinding for 2 hours, calcining at 650 ℃ for 10 hours, and grinding for 2 hours to obtain an Au-Co Co-doped holmium ferrite gas-sensitive material;
Wherein, the addition ratio of holmium nitrate, ferric nitrate, cobalt nitrate, chloroauric acid, citric acid and dilute nitric acid is 39.29g:14.51g:7.32g:4.58g:80 mL.
Example 3 preparation of Au and Co-doped holmium ferrite gas sensitive Material
(1) Mixing holmium nitrate, ferric nitrate, cobalt nitrate and citric acid to obtain a mixture, adding the mixture into 9 mass percent dilute nitric acid, and stirring for 6 hours to uniformly mix the mixture to obtain a precursor solution;
(2) Heating the precursor solution in a water bath at 85 ℃, stirring at a rotating speed of 550r/min for 2 hours in the water bath heating process, cooling to room temperature to obtain a solid, calcining the solid at 1050 ℃ for 3 hours, and grinding for 6 hours to obtain a Co-doped holmium ferrite material;
(3) Mixing a Co-doped holmium ferrite material with chloroauric acid, grinding for 6 hours, calcining for 3 hours at 1050 ℃ and grinding for 6 hours again to obtain an Au-Co Co-doped holmium ferrite gas-sensitive material;
Wherein, the addition ratio of holmium nitrate, ferric nitrate, cobalt nitrate, chloroauric acid, citric acid and dilute nitric acid is 39.29g:21.77g:1.83g:0.92g:90 mL.
EXAMPLE 4 preparation of Formaldehyde gas sensor
The Au and Co Co-doped holmium ferrite gas-sensitive material prepared in the example 1, deionized water and terpineol are mixed according to the addition amount of 1g:3mL:1mL to obtain a mixture, the mixture is spin-coated on an Al 2O3 substrate at the rotating speed of 600rpm to form a gas-sensitive film with the thickness of 263 mu m, and then the gas-sensitive film is placed in air and aged for 20 hours at 220 ℃ to obtain the formaldehyde gas-sensitive sensor.
Comparative example 1 preparation of holmium ferrite gas sensitive material HoFeO 3
(1) Mixing holmium nitrate, ferric nitrate and citric acid to obtain a mixture, adding the mixture into 8.5 mass percent dilute nitric acid, and stirring for 12 hours to uniformly mix the mixture to obtain a precursor solution;
(2) Heating the precursor solution in a water bath at 80 ℃, stirring for 6 hours at a rotating speed of 500r/min in the water bath heating process, and cooling to room temperature to obtain a solid, calcining the solid at 900 ℃ for 8 hours, and grinding for 3 hours to obtain a holmium ferrite material;
Wherein, the addition ratio of holmium nitrate, ferric nitrate, citric acid and dilute nitric acid is 39.29g:19.35g:60g:50mL.
Comparative example 2 preparation of Co-doped holmium ferrite gas sensitive material
(1) Mixing holmium nitrate, ferric nitrate, cobalt nitrate and citric acid to obtain a mixture, adding the mixture into dilute nitric acid with the mass fraction of 8.5%, and stirring for 12 hours to uniformly mix the mixture to obtain a precursor solution;
(2) Heating the precursor solution in a water bath at 80 ℃, stirring for 6 hours at a rotating speed of 500r/min in the water bath heating process, cooling to room temperature to obtain a solid, calcining the solid at 900 ℃ for 8 hours, and grinding for 3 hours to obtain a Co-doped holmium ferrite gas-sensitive material;
Wherein, the addition ratio of holmium nitrate, ferric nitrate, chloroauric acid, citric acid and dilute nitric acid is 39.29g:19.35g:3.65g:60g:50mL.
Comparative example 3 preparation of Au-doped holmium ferrite gas-sensitive material
(1) Mixing holmium nitrate, ferric nitrate and citric acid to obtain a mixture, adding the mixture into 8.5 mass percent dilute nitric acid, and stirring for 12 hours to uniformly mix the mixture to obtain a precursor solution;
(2) Heating the precursor solution in a water bath at 80 ℃, stirring for 6 hours at a rotating speed of 500r/min in the water bath heating process, and cooling to room temperature to obtain a solid, calcining the solid at 900 ℃ for 8 hours, and grinding for 3 hours to obtain a holmium ferrite material;
(3) Mixing a holmium ferrite material with chloroauric acid, grinding for 3 hours, calcining for 8 hours at 900 ℃ and grinding for 3 hours to obtain an Au-doped holmium ferrite gas-sensitive material;
Wherein, the addition ratio of holmium nitrate, ferric nitrate, cobalt nitrate, chloroauric acid, citric acid and dilute nitric acid is 39.29g:19.35g:2.29g:60g:50mL.
Test example 1:
The Au and Co Co-doped holmium ferrite gas-sensitive material prepared in example 1 is subjected to structural characterization, and the results are shown in fig. 1-3.
Fig. 1 is an XRD pattern of the formaldehyde gas-sensitive material prepared in example 1, and as can be seen from fig. 1, crystallization peaks correspond to crystalline phases (112), (111) and (200) of HoFeO 3 (No. 46-0115), and fig. 2 is an SEM pattern of the formaldehyde gas-sensitive material prepared in example 1 at 60K and 100K magnifications, and as can be seen from fig. 2, the formaldehyde gas-sensitive material exhibits a typical nanoparticle structure, the specific surface area and porosity of the material are large, and the reaction sites and transmission channels of gas molecules are many. As can be seen from the XPS schematic diagram of the gold and cobalt elements of fig. 3, au and Co elements are present in the material, indicating that both elements are doped in.
Test example 2:
The gas-sensitive materials prepared in example 1 and comparative examples 1 to 3 were coated on a sensing film, and the gas-sensitive responses (Rg/Ra) of each gas-sensitive material to 1ppm of a gas such as formaldehyde, nitrogen, etc., were measured, respectively, and the results are shown in FIGS. 4 to 7. Wherein Ra is the resistance of the sensor in the air, and Rg is the resistance of the measured gas. The experimental environment is RH of 20% and the ambient temperature of 20 ℃.
1. Operating temperature
The response of each gas sensitive material to formaldehyde gas at 1.0ppm at different temperatures is shown in FIG. 4. As can be seen from fig. 4, the optimum operating temperature of the gas-sensitive material prepared according to the present invention is 140 ℃.
At the working temperature of 140 ℃, the response value of the gas-sensitive material prepared by the invention to formaldehyde gas of 1 ppm is 5.96, the response value of the gas-sensitive material HoFeO 3 prepared by comparative example 1 to formaldehyde gas of 1 ppm is 1.86, the response value of the gas-sensitive material prepared by doping Co element HoFeO 3 material only in comparative example 2 to formaldehyde gas of 1 ppm is 2.53, and the response value of the gas-sensitive material prepared by doping Au element HoFeO 3 material only in comparative example 3 to formaldehyde gas of 1 ppm is 4.22. Therefore, au element and Co element are adopted to carry out combined doping modification on HoFeO 3 material, and the synergistic effect is achieved on improving the response value of the gas-sensitive material to formaldehyde gas.
2. Relative humidity of
The response of the Au and Co Co-doped holmium ferrite gas-sensitive material prepared in example 1 to 1.0ppm formaldehyde gas at different relative humidities is shown in FIG. 5.
As can be seen from fig. 5, the gas-sensitive performance gradually decreases as the relative humidity increases. When the relative humidity exceeds 40%, the gas-sensitive performance is drastically reduced, but within 40%, the formaldehyde gas-sensitive performance change rate of the material is within 5%, which indicates that the material has extremely high gas-sensitive relative humidity resistance.
3. Selectivity of
The response of the Au and Co Co-doped holmium ferrite gas-sensitive material prepared in example 1 to 1.0ppm of different gases is shown in fig. 6, and as can be seen from fig. 6, when the Au and Co-doped holmium ferrite gas-sensitive material prepared in the invention contacts various gases, the selectivity of the Au and Co-doped holmium ferrite gas-sensitive material to 1 ppm formaldehyde gas is obviously higher than that of the gases including CH 5N、C2H7 N and the like, so that the gas-sensitive material prepared in the invention has good selectivity to formaldehyde gas.
4. Long term stability
As can be seen from FIG. 7, the Au and Co Co-doped holmium ferrite gas-sensitive material prepared by the invention has long-term stability to 1 ppm formaldehyde gas. It can be seen that the response value change rate of the formaldehyde gas-sensitive material prepared by the invention to the formaldehyde gas of 1 ppm is within 2% within one month, which indicates that the material has extremely high long-term stability of gas sensitivity.
The above description is only of the preferred embodiments of the present application and is not intended to limit the present application, but various modifications and variations can be made to the present application by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.
Claims (9)
1. The Au and Co Co-doped holmium ferrite gas-sensitive material is characterized by being prepared by the following method:
(1) Mixing holmium nitrate, ferric nitrate, cobalt nitrate and citric acid to obtain a mixture, adding the mixture into dilute nitric acid, and stirring to uniformly mix the mixture to obtain a precursor solution;
(2) Calcining the solid at 650-1050 ℃ for 3-12 hours, and grinding to obtain a Co-doped holmium ferrite material;
(3) Mixing a Co-doped holmium ferrite material with chloroauric acid, grinding for the first time, calcining for 3-12 hours at 650-1050 ℃, and grinding for the second time to obtain an Au-Co Co-doped holmium ferrite gas-sensitive material;
Wherein, the addition ratio of holmium nitrate, ferric nitrate, cobalt nitrate, chloroauric acid, citric acid and dilute nitric acid is (0.01-5) mol, (0.05-5) mol, (0.01-100) g (20-100) g (50-200) mL.
2. The Au and Co-doped holmium ferrite gas-sensitive material according to claim 1, wherein in the step (1), the mass fraction of the dilute nitric acid is 8-9%, and the stirring time is 6-12h.
3. The Au and Co-doped holmium ferrite gas-sensitive material according to claim 1, wherein in the step (2), the precursor solution is stirred during the water bath heating process, the stirring speed is 500-600r/min, and the stirring time is 2-8h.
4. The Au and Co-doped holmium ferrite gas sensitive material according to claim 1, wherein in the step (2), the milling time is 2-6h.
5. The Au and Co-doped holmium ferrite gas sensitive material according to claim 1, wherein in the step (3), the time of the primary grinding and the secondary grinding is 2-6 hours.
6. Use of the Au and Co-doped holmium ferrite gas-sensitive material according to any one of claims 1-5 in formaldehyde gas detection.
7. The use according to claim 6, wherein the formaldehyde gas has a concentration of 0.5 to 1.5ppm.
8. Use of the Au and Co-doped holmium ferrite gas-sensitive material according to any one of claims 1-5 for the preparation of formaldehyde gas-sensitive sensors.
9. The use according to claim 8, wherein the formaldehyde gas sensor has an operating temperature of 80-200 ℃.
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