Preparation method of an ionic liquid modified material and sensor application process

Abstract

The invention relates to the technical field related to ionic liquids, and in particular to a preparation method of an ionic liquid modified material and a sensor application process, comprising the following steps: weighing a certain amount of NiCo2O4 and γ-MnO2, dissolving them in deionized water; ultrasonically dispersing to obtain a mixed solution; transferring the obtained mixed solution to a stainless steel hydrothermal kettle lined with polytetrafluoroethylene to perform a constant temperature hydrothermal reaction; centrifugally washing the obtained substance after it is naturally cooled; drying the obtained sample under vacuum conditions; collecting the obtained solid matter to obtain a NiCo2O4 / γ-MnO2 composite nanomaterial; weighing a certain amount of [HOETMIM][BF4] and NiCo2O4 / γ-MnO2, and fully mixing them using a vortex mixer; ultrasonically treating the obtained mixture; and vacuum drying the obtained sample to obtain a NiCo2O4 / γ-MnO2 composite material. The modified material designed by the invention enables the ionic liquid to have better conductivity, repeatability, response recovery speed and long-term stability, and is applied to an ammonia detection sensor so that the overall performance of the ammonia detection sensor is significantly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of ionic liquids, and specifically to a preparation method of an ionic liquid modified material and a sensor application process. Background Technique

[0002] Ionic liquids are organic salts composed entirely of anions and cations and are liquid within a temperature range below 100°C. Ionic liquids have characteristics such as non-volatility, low vapor pressure, wide liquid range, high thermal stability, strong solubility, and adjustable structure and properties. In order to meet the requirements of different reactions, specific functional groups are grafted onto the cation or anion structure of ionic liquids to synthesize ionic liquids with unique properties, namely functionalized ionic liquids.

[0003] Existing ammonia detection sensors do not have good conductivity, repeatability, response and recovery speed, and long-term stability, etc., resulting in poor overall performance and unable to meet the actual use requirements. Therefore, in view of the above current situation, there is an urgent need to develop a preparation method of an ionic liquid modified material and a sensor application process to overcome the deficiencies in current practical applications. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method of an ionic liquid modified material and a sensor application process to solve the problems raised in the above background technique.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A preparation method of an ionic liquid modified material, the preparation method includes the following steps:

[0007] Step 1: Weigh a certain amount of NiCo2O4 and γ-MnO2 and dissolve them in deionized water;

[0008] Step 2: Obtain a mixed solution by ultrasonic dispersion;

[0009] Step 3: Transfer the mixed solution obtained in Step 2 to a stainless steel hydrothermal autoclave lined with polytetrafluoroethylene and carry out a constant temperature hydrothermal reaction;

[0010] Step 4: After the substance obtained in Step 3 is naturally cooled, perform multiple centrifugal washings on it;

[0011] Step 5: Dry the sample obtained in Step 4 at 80°C for 12 hours under vacuum conditions;

[0012] Step 6: Collect the solid substance obtained in Step 5, and thus obtain the NiCo2O4 / γ-MnO2 composite nanomaterial;

[0013] Step 7, weigh a certain amount of [HOETMIM][BF4] and NiCo2O4 / γ-MnO2, and mix them thoroughly using a vortex mixer;

[0014] Step 8, subjecting the mixture obtained in step 7 to ultrasonic treatment;

[0015] Step nine: vacuum dry the sample obtained in step eight at 60° C. for 12 hours to obtain a NiCo2O4 / γ-MnO2 composite material.

[0016] As a further solution of the present invention: in the step 1, the ratio of NiCo2O4 to γ-MnO2 is 1:1.

[0017] As a further solution of the present invention: the constant temperature hydrothermal reaction in step three is a hydrothermal reaction at a temperature of 120° C. for 24 hours.

[0018] As a further scheme of the present invention: In step one, the preparation method of NiCo2O4 is as follows: Ni(NO3)2·6H2O, Co(NO3)2·6H2O and polyvinylpyrrolidone PVP are dissolved in ethylene glycol and stirred for 30 minutes, the resulting solution is transferred to a stainless steel autoclave lined with polytetrafluoroethylene, the autoclave is sealed and maintained at 180°C for 12 hours, then cooled to room temperature, the final product is collected by centrifugation, washed several times with water and ethanol, and then dried in an oven at 60°C for 12 hours, and finally the prepared precursor is calcined at 300°C for 2 hours.

[0019] As a further scheme of the present invention: In step 1, the preparation method of γ-MnO2 is as follows: MnSO4·H2O and (NH4)2S2O8 are dissolved in deionized water and stirred for 30 minutes, the resulting solution is transferred to a polytetrafluoroethylene-lined autoclave and maintained at 90°C for 24 hours, after cooling, separated by a centrifuge to obtain a black precipitate, which is washed three times with deionized water, and then the sample is dried at 80°C for 12 hours, and finally, calcined at 350°C in air for 4 hours.

[0020] As a further solution of the present invention: the ultrasonic treatment time in step 2 and step 8 is 30 minutes.

[0021] A process for applying an ionic liquid modified material in a sensor. The sensor consists of a shell, an electrode, blotting paper, a waterproof and breathable membrane, and a modified ionic liquid electrolyte solution. Before assembly, a working electrode is punched out from a dried polytetrafluoroethylene membrane using a manual press and a 17mm punch. The blotting paper is punched out using the same method, and a reference electrode and a counter electrode are cut out to assemble the sensor.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The modified material designed in this application enables ionic liquids to have better conductivity, repeatability, response recovery speed, and long-term stability. Applying it to ammonia gas detection sensors significantly improves the overall performance of the ammonia gas detection sensors. Description of the Drawings

[0024] Figure 1 It is the output signal baseline diagram of the ammonia gas detection sensor based on the modified ionic liquid.

[0025] Figure 2 It is the repeatability test diagram of the ammonia gas detection sensor based on the modified ionic liquid.

[0026] Figure 3 It is the response and recovery test diagram of the ammonia gas detection sensor based on the modified ionic liquid.

[0027] Figure 4 It is the long-term stability test diagram of the ammonia gas detection sensor based on the modified ionic liquid.

[0028] Figure 5 It is the output signal baseline diagram of the ammonia gas detection sensor with ILs / NiCo2O4 as the electrolyte.

[0029] Figure 6 It is the output signal baseline diagram of the ammonia gas detection sensor with ILs / γ-MnO2 as the electrolyte.

[0030] Figure 7 It is the output signal baseline diagram of the ammonia gas detection sensor with ILs as the electrolyte.

[0031] Figure 8 It is the impedance spectrum diagram of the ammonia gas sensor based on different electrolytes under 50 ppm NH3. Detailed Embodiments

[0032] The technical solution of this application will be further described in detail below in combination with specific embodiments.

[0033] The embodiments of this application will be described in detail below. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions from beginning to end. The embodiments described below by referring to the drawings are exemplary and are only used to explain this application and should not be construed as limiting this application.

[0034] In one embodiment of the present invention, a preparation method of an ionic liquid modified material, the preparation method includes the following steps:

[0035] Step 1: Weigh 1.5 g of NiCo2O4 and 1.5 g of γ-MnO2, and dissolve them in 60 mL of deionized water;

[0036] Step 2: Ultrasonically disperse for 30 min to obtain a mixed solution;

[0037] Step 3: Transfer the mixed solution obtained in Step 2 into a stainless-steel hydrothermal autoclave lined with polytetrafluoroethylene and conduct a constant-temperature hydrothermal reaction;

[0038] Step 4: After the substance obtained in Step 3 is naturally cooled, conduct multiple centrifugal washings on it;

[0039] Step 5: Dry the sample obtained in Step 4 at 80 °C for 12 hours under vacuum conditions;

[0040] Step 6: Collect the solid substance obtained in Step 5, and thus obtain the NiCo2O4 / γ-MnO2 composite nanomaterial;

[0041] Step 7: Weigh 2.85 g of [HOETMIM][BF4] and 0.15 g of NiCo2O4 / γ-MnO2, and use a vortex mixer to fully mix them;

[0042] Step 8: Ultrasonically treat the mixture obtained in Step 7 for 30 min;

[0043] Step 9: Vacuum-dry the sample obtained in Step 8 at 60 °C for 12 hours to obtain the NiCo2O4 / γ-MnO2 composite material.

[0044] In one embodiment of the present invention, the constant-temperature hydrothermal reaction in Step 3 is a hydrothermal reaction at 120 °C for 24 hours.

[0045] In one embodiment of the present invention, the preparation method of NiCo2O4 is as follows: Dissolve 1.163 g of Ni(NO3)2·6H2O, 2.328 g of Co(NO3)2·6H2O, and 0.0474 g of polyvinylpyrrolidone PVP in 80 ml of ethylene glycol and stir for 30 min. Transfer the obtained solution into a stainless-steel autoclave lined with polytetrafluoroethylene. Seal the autoclave and maintain it at 180 °C for 12 hours, then cool it to room temperature. Centrifuge to collect the final product, wash it several times with water and ethanol, then dry it in an oven at 60 °C for 12 hours. Finally, calcine the prepared precursor at 300 °C for 2 hours.

[0046] In one embodiment of the present invention, the preparation method of γ-MnO2 is as follows: Dissolve MnSO4·H2O (3.38 g, 20.0 mmol) and (NH4)2S2O8 (4.564 g, 20.0 mmol) in 70 ml of deionized water and stir for 30 min. Transfer the resulting solution to a polytetrafluoroethylene-lined autoclave (with a capacity of 100 ml) and maintain it at 90 °C for 24 hours. After cooling, separate by a centrifuge to obtain a black precipitate, wash it three times with deionized water, then dry the sample at 80 °C for 12 hours. Finally, calcine it in air at 350 °C for 4 hours.

[0047] The principle of the ionic liquid electrochemical ammonia detection sensor is as follows: NH3 diffuses from the air vent on the sensor lid through the waterproof and breathable membrane to the surface of the working electrode. Catalyzed by the catalytic layer of the working electrode, an oxidation reaction occurs to generate ammonium ions (NH 4+ ) and nitrogen gas (N2). NH 4+ is deprotonated to generate ammonia gas and hydrogen ions (H+). The hydrogen ions and electrons flow through the electrolyte to the counter electrode, and a reduction reaction occurs on the electrode surface. The mechanism is as follows:

[0048]

[0049] NH4 + →NH3(g)+H +

[0050]

[0051] An application process of an ionic liquid modified material in a sensor. The sensor is composed of a housing, electrodes, absorbent paper, a waterproof and breathable membrane, and a modified ionic liquid electrolyte solution. Before assembly, use a manual press and a 17 mm punch to punch out the working electrode from the dried polytetrafluoroethylene membrane. Using the same method, punch out the absorbent paper, cut out the reference electrode and the counter electrode, assemble to obtain the sensor, and conduct conductivity, repeatability, response recovery speed, and long-term stability tests on the sensor. Among them, the ammonia gas concentration used in the experiment is 200 ppm. Connect the aged sensor to an electrochemical workstation, and use a gas distribution device to configure ammonia to an appropriate concentration. Then test the ammonia performance through the electrochemical workstation, and the test temperature is 25 °C.

[0052] The test method is as follows: Real-time current measurement of electrochemical ammonia sensors with different electrolytes for ammonia at a concentration of 50 ppm at room temperature.

[0053] 1. The electrolyte is [HOETMIM][BF4], its peak current is 6.2 μA, its baseline is unstable, the response time is long, and the sensitivity does not meet the requirements.

[0054] 2. The electrolyte is γ-MnO2 doped with 5wt%, 10wt%, 15wt%, 20wt%, and 25wt% of [HOETMIM][BF4]. The test results are as follows: the peak currents correspond to 6.2 μA, 5.8 μA, 1.9 μA, 1.7 μA, and 2 μA respectively. The sensitivity of 10wt% meets the requirements, but the response time is long.

[0055] 3. The electrolyte is NiCo2O4 doped with 5wt%, 10wt%, 15wt%, 20wt%, and 25wt% of [HOETMIM][BF4]. The test results are as follows: the peak currents correspond to 5 μA, 4.7 μA, 4.3 μA, 3.9 μA, and 3.8 μA respectively. The sensitivities of 5wt%, 10wt%, and 15wt% meet the requirements, but there is a problem of decreasing peak current.

[0056] 4. The electrolyte is a NiCo2O4 / γ-MnO2 composite doped with 5wt%, 10wt%, 15wt%, 20wt%, and 25wt% of [HOETMIM][BF4]. The test results are as follows: the peak currents correspond to 4.56 μA, 3.7 μA, 5 μA, 3 μA, and 2.7 μA respectively. The sensitivities of 5wt% and 15wt% meet the requirements. After comparison, the response and recovery time of 5wt% is better than that of 15wt%. The response time of 5wt% is 41 s, the recovery time is 37 s, and the sensitivity is 0.0912 uA / ppm.

[0057] The electrolyte is a NiCo2O4 / γ-MnO2 composite doped with 5wt% of [HOETMIM][BF4]. The sensor performs real-time current measurement on ammonia gas with a concentration range of 0 to 100 ppm at room temperature. When the sensor is exposed to concentrations of 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100 ppm, the corresponding current values are approximately 1.36 uA, 2.34 uA, 3.27 uA, 4.32 uA, 5.42 uA, 6.32 uA, 7.49 uA, 8.61 uA, 9.62 uA, and 10.5 uA respectively. Without a doubt, as the ammonia concentration increases, the current value also increases. The functional fitting of the current value Y and the ammonia concentration X can be expressed as Y = 0.13864 + 0.10435X, and the fitting correlation coefficient R2 is 0.99921. This fitting result indicates that there is a good linear relationship between the response value of the sensor and the ammonia concentration. The test results are shown in the attached figures:

[0058] Combined with the attached Figure 1 、attached Figure 5 、attached Figure 6 and attached Figure 7 it can be seen that the baseline of the output signal of the ammonia gas detection sensor based on the modified ionic liquid can be well maintained stable. Combined with the attached Figure 2It can be seen that the ammonia detection sensor based on the modified ionic liquid has excellent repeatability. Combining with the attached Figure 3 It can be seen that the ammonia detection sensor based on the modified ionic liquid has a fast response and recovery speed. Combining with the attached Figure 4 It can be seen that the ammonia detection sensor based on the modified ionic liquid has excellent long-term stability. In summary, this modified material enables the ionic liquid to have better conductivity, repeatability, response and recovery speed, and long-term stability. Applying it to the ammonia detection sensor significantly improves the overall performance of the ammonia detection sensor.

[0059] In addition, the impedance spectrum includes a linear part representing the diffusion-limited process and a semicircular part (Rct) representing the charge-transfer-limited process. Figure 8 The Nyquist plots of the Pt-Ru electrode in different electrolytes are described. Due to the poor conductivity of NiCo2O4, the impedance of ILs / NiCo2O4 (curve c) is the largest. For pure ILs (curve a), a well-defined semicircle with an Rct of 6.5 Ω was found, revealing the obvious influence of the interfacial resistance on electron transfer. As for ILs / γ-MnO2 (curve b), its impedance is greatly reduced due to the improved electron transfer efficiency of the conductive ILs and γ-MnO2. In contrast, ILs / NiCo2O4 / γ-MnO2 (curve d) is almost linear and the Rct value is very small. Therefore, it can be considered that the synergistic effect of the components in ILs / NiCo2O4 / γ-MnO2 promotes electron transfer.

[0060] The above are only the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicality of the patent.

Claims

1. A method for preparing an ionic liquid modified material, characterized in that: The preparation method comprises the following steps: Step 1: Weigh a certain amount of NiCo2O4 and γ-MnO2 and dissolve them in deionized water; Step 2: Ultrasonic dispersion to obtain a mixed solution; Step 3, transferring the mixed solution obtained in step 2 to a stainless steel hydrothermal kettle lined with polytetrafluoroethylene to perform a constant temperature hydrothermal reaction; Step 4, after the material obtained in step 3 is cooled naturally, centrifuge and wash it several times; Step 5: drying the sample obtained in step 4 at 80°C under vacuum conditions for 12 hours; Step 6: Collect the solid material obtained in step 5 to obtain NiCo2O4 / γ-MnO2 composite nanomaterial; Step 7, weigh a certain amount of [HOEtmim][BF4] and NiCo2O4 / γ-MnO2, and mix them thoroughly using a vortex mixer; Step 8, subjecting the mixture obtained in step 7 to ultrasonic treatment; Step nine: vacuum dry the sample obtained in step eight at 60° C. for 12 hours to obtain a NiCo2O4 / γ-MnO2 composite material.

2. The method for preparing the ionic liquid modified material according to claim 1, characterized in that: In the step 1, the ratio of NiCo2O4 to γ-MnO2 is 1:

1.

3. The method for preparing the ionic liquid modified material according to claim 2, characterized in that: The constant temperature hydrothermal reaction in step 3 is a hydrothermal reaction at a temperature of 120° C. for 24 hours.

4. The method for preparing the ionic liquid modified material according to claim 1, characterized in that: In step 1, the preparation method of NiCo2O4 is as follows: Ni(NO3)2·6H2O, Co(NO3)2·6H2O and polyvinylpyrrolidone PVP are dissolved in ethylene glycol and stirred for 30 minutes, the resulting solution is transferred to a stainless steel autoclave lined with polytetrafluoroethylene, the autoclave is sealed and maintained at 180°C for 12 hours, then cooled to room temperature, the final product is collected by centrifugation, washed several times with water and ethanol, and then dried in an oven at 60°C for 12 hours, and finally the prepared precursor is calcined at 300°C for 2 hours.

5. The method for preparing the ionic liquid modified material according to claim 1, characterized in that: In step 1, the preparation method of γ-MnO2 is as follows: MnSO4·H2O and (NH4)2S2O8 are dissolved in deionized water and stirred for 30 minutes, the resulting solution is transferred to a polytetrafluoroethylene-lined autoclave and maintained at 90°C for 24 hours, after cooling, separated by a centrifuge to obtain a black precipitate, which is washed three times with deionized water, and then the sample is dried at 80°C for 12 hours, and finally, calcined at 350°C in air for 4 hours.

6. The method for preparing the ionic liquid modified material according to claim 1, characterized in that: The ultrasonic treatment time in step 2 and step 8 is 30 minutes.

7. A process for using the ionic liquid modified material obtained by the preparation method as claimed in claim 1 in a sensor, characterized in that: The sensor consists of a shell, electrodes, blotting paper, a waterproof and breathable membrane and a modified ionic liquid electrolyte solution. Before assembly, a manual press and a 17mm punch are used to punch out the working electrode from the dried polytetrafluoroethylene membrane. The same method is used to punch out the blotting paper, cut out the reference electrode and the counter electrode, and assemble the sensor.

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