Membrane electrode for carbon monoxide electrochemical sensor, preparation method of membrane electrode, catalyst adopted by membrane electrode and preparation method of catalyst

Abstract

The invention provides a membrane electrode for a carbon monoxide electrochemical sensor, a preparation method of the membrane electrode, a catalyst adopted by the membrane electrode and a preparation method of the catalyst, and relates to the technical field of electrochemical sensors. The catalyst comprises a carrier and Pt particles attached to the surface of the carrier, wherein the carrier is a Mn / C composite material. The catalyst is prepared from the carrier and a chloroplatinic acid solution. The membrane electrode comprises a membrane and catalyst layers located on the two sides of the membrane, and the catalyst layers comprise catalysts. The preparation method of the membrane electrode comprises the following steps: coating two sides of a membrane with electrode slurry containing a catalyst, and drying. The Mn / C composite material is adopted as the carrier, the dispersity of Pt particles can be improved, active sites of reaction are increased, meanwhile, falling and migration of the Pt particles are inhibited through the strong interaction between the Pt particles and the metal carrier, the carbon monoxide toxicity resistance and stability of the sensor are greatly improved, and the service life of the sensor is greatly prolonged.

Description

Technical Field

[0001] The present application relates to the technical field of electrochemical sensors, and in particular to a membrane electrode for a carbon monoxide electrochemical sensor and a preparation method thereof, as well as a catalyst used in the membrane electrode and a preparation method thereof. Background Art

[0002] Carbon monoxide is a colorless and odorless gas. Because it has a high affinity with hemoglobin in the human body, when it is inhaled into the human body, it will compete for oxygen in the blood to form carbon monoxide hemoglobin, causing hypoxia and edema of the arterial wall, hindering blood flow, and causing fatigue, shortness of breath, nausea, dizziness and other adverse symptoms. Excessive inhalation of carbon monoxide in the body may even lead to death due to lack of oxygen. When the concentration of carbon monoxide in the air reaches 35ppm, it will damage the IQ of children. At the same time, carbon monoxide is also a flammable and explosive dangerous gas, and is one of the important signs of whether a spontaneous combustion fire occurs in a coal mine. Therefore, whether it is adding a carbon monoxide sensor to the underground coal mine monitoring system or timely and accurately monitoring and alarming the carbon monoxide concentration indoors, it has become an indispensable task to ensure the safety of people's lives and national property.

[0003] At present, fuel cell type carbon monoxide electrochemical sensors are in a blank stage in domestic technology. Most domestic companies use catalysts and membrane electrodes of hydrogen fuel cells as substitutes. However, carbon monoxide is highly toxic to the catalysts and membrane electrodes used in hydrogen fuel cells, which will have an irreversible impact on their performance. Since carbon monoxide electrochemical sensors are used in home and industrial environments, the environment is relatively complex and filled with a large number of toxic gases. Applying hydrogen fuel cell catalysts to carbon monoxide electrochemical sensors will cause the catalysts to be in long-term contact with some toxic substances, such as total sulfur, carbon monoxide, formaldehyde, formic acid, total halides, NH3, etc. Working under such conditions for a long time, the precious metals on the catalysts will react with such substances, resulting in the loss of active sites on the surface of the precious metals, resulting in activity attenuation and performance degradation. Among them, the membrane electrode is the core component of the sensor, and its performance directly determines the performance of the sensor, and may even endanger human life safety. Summary of the invention

[0004] In order to improve the problem that the catalyst used in the carbon monoxide electrochemical sensor has weak resistance to carbon monoxide poisoning, resulting in decreased sensor performance, the present application provides a membrane electrode for a carbon monoxide electrochemical sensor and a preparation method thereof, as well as a catalyst used in the membrane electrode and a preparation method thereof.

[0005] In a first aspect, the present application provides a catalyst for sensing carbon monoxide gas, which adopts the following technical solution: A catalyst for sensing carbon monoxide gas comprises a carrier and Pt particles attached to the surface of the carrier, wherein the carrier is a Mn / C composite material.

[0006] Compared with traditional catalysts, the catalyst for sensing carbon monoxide gas provided by the present invention adopts Mn / C composite material as a carrier, which can improve the dispersion of Pt particles and increase the active sites of the reaction. At the same time, the strong interaction between Pt particles and the metal carrier inhibits the shedding and migration of Pt particles, greatly improving the sensor's resistance to carbon monoxide toxicity, stability and lifespan.

[0007] Optionally, the carrier is prepared by washing and impregnating a manganese salt in an acid and then calcining the carrier with a carbon material in an inert atmosphere.

[0008] Optionally, the mass ratio of the manganese salt to the carbon material is 1:(2-10).

[0009] Optionally, the mass ratio of the manganese salt to the carbon material is 1:10.

[0010] Optionally, the manganese salt is manganese chloride; and the carbon material is a mesoporous carbon material.

[0011] Optionally, the Pt particles are supported on the carrier by a chemical reduction method.

[0012] Optionally, the mass ratio of the Pt particles to the carrier is (1-6):4.

[0013] Optionally, the preparation method of the carrier is as follows: take manganese chloride and add it into hydrochloric acid for impregnation, add mesoporous carbon material, mix and stir in a beaker, heat to 100°C until the solvent evaporates, and finally place the mixture in a tube furnace and calcine in an argon atmosphere to obtain the target Mn / C material.

[0014] Optionally, the calcination temperature is 800° C. and the calcination time is 2 h.

[0015] The present application uses manganese salts and carbon materials to composite, thereby improving the structure and surface chemical properties of the carbon material, so that the catalytic material exhibits higher stability.

[0016] In a second aspect, the present application provides a method for preparing a catalyst for sensing carbon monoxide gas, using the following technical solution: The preparation method of a catalyst for sensing carbon monoxide gas comprises the following steps: The carrier is mixed with chloroplatinic acid solution and ethylene glycol to obtain solution A; Under low temperature stirring conditions, adding the prepared sodium hydroxide solution to the solution A, adjusting the pH value to neutral, to obtain solution B; The solution B is subjected to shear dispersion and emulsification under low temperature conditions, and then heated to boiling to obtain a solution C; After the solution C is cooled to room temperature, hydrochloric acid is added, and water is added and filtered repeatedly 3-4 times by positive pressure filtration to obtain a precipitate, which is then dried.

[0017] In a third aspect, the present application provides an application of a catalyst for sensing carbon monoxide gas, using the following technical solution: The catalyst is used as a sensitive material for preparing a membrane electrode of a carbon monoxide electrochemical sensor.

[0018] In a fourth aspect, the present application provides a membrane electrode for a carbon monoxide electrochemical sensor, which adopts the following technical solution: The membrane electrode of the carbon monoxide electrochemical sensor comprises a membrane and catalyst layers located on both sides of the membrane, wherein the catalyst layers comprise the catalyst for sensing carbon monoxide gas.

[0019] Optionally, the membrane is a Nafion membrane.

[0020] Optionally, the membrane is a Nafion 115 membrane.

[0021] In a fifth aspect, the present application provides a method for preparing a membrane electrode of a carbon monoxide electrochemical sensor, using the following technical solution: A method for preparing a membrane electrode of a carbon monoxide electrochemical sensor comprises the following steps: The membrane is pretreated to remove ionic impurities on the surface and dried for later use; The catalyst for sensing carbon monoxide gas is wetted with deionized water, and a dispersant and a binder are added in sequence and mixed and dispersed evenly to prepare an electrode slurry; The electrode slurry is coated on both sides of the membrane respectively and dried to obtain a carbon monoxide electrochemical sensor membrane electrode.

[0022] Optionally, for every 1 mg of catalyst in the electrode slurry, (0.05-0.5) ml of deionized water, (0.01-0.5) ml of dispersant and (0.01-0.5) ml of binder are added.

[0023] Optionally, the dispersant is isopropanol, and the binder includes Nafion solution or PTFE.

[0024] Optionally, the electrode slurries coated on both sides of the membrane are used as an anode and a cathode, respectively, and the mass ratio of the Pt particles contained in the cathode and the anode is (1-4):4.

[0025] Optionally, the membrane is a Nafion membrane.

[0026] Optionally, the membrane is a Nafion 115 membrane.

[0027] Optionally, the film has a thickness of 50-200 μm.

[0028] In a sixth aspect, the present application provides a carbon monoxide electrochemical sensor, which adopts the following technical solution: The membrane electrode thereof adopts the membrane electrode of the carbon monoxide electrochemical sensor.

[0029] The sensor provided by the present invention improves the catalyst's resistance to CO poisoning by improving the structural components of the carbon carrier in the catalyst composition. It has better stability in complex air environments and has the advantages of high sensitivity, rapid response and long service life. It has strong market application potential and can greatly promote the update and iteration of fuel cell type CO sensors.

[0030] In summary, the present application includes at least one of the following beneficial effects: 1. The catalyst for sensing carbon monoxide gas provided by the present invention adopts Mn / C composite material as a carrier, which can improve the dispersibility of Pt particles and increase the active sites of the reaction. At the same time, the strong interaction between Pt particles and the metal carrier inhibits the shedding and migration of Pt particles, greatly improving the sensor's resistance to carbon monoxide toxicity, stability and life.

[0031] 2. The carbon monoxide electrochemical sensor of the present invention uses a membrane electrode as a sensitive material, and the constructed fuel cell type carbon monoxide sensor has the characteristics of high precision, simple structure and long life.

[0032] 3. The carbon monoxide electrochemical sensor using Pt / MnC as a catalyst in the present application has the advantages of good linearity, excellent stability, fast response time and short recovery time. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 TEM image of the Mn / C material prepared in Example 1 of the present invention; Figure 2 TEM image of the Pt (50%) / MnC material prepared in Example 1 of the present invention; Figure 3 Response recovery curves of the Pt (50%) / MnC material sensor prepared in Example 1 of the present invention and the Pt (50%) / C sensor prepared in Comparative Example 1 to 10ppm-200ppm carbon monoxide; Figure 4 The linear fitting curves between the response current and the carbon monoxide concentration of the Pt (50%) / MnC material sensor prepared in Example 1 of the present invention and the Pt (50%) / C sensor prepared in Comparative Example 1; Figure 5 The curves of the response current value of the Pt (50%) / MnC material sensor prepared in Example 1 of the present invention and the Pt (50%) / C sensor prepared in Comparative Example 1 to 100 ppm carbon monoxide over time within 12 hours; Figure 6 This is the short-term continuous response recovery curve of the Pt (50%) / MnC material sensor prepared in Example 1 of the present invention under the condition of 100 ppm carbon monoxide; Figure 7 The response recovery curves of the Pt (50%) / MnC material sensor prepared in Example 1 of the present invention to 100 ppm at 15 days, 30 days, and 60 days; Figure 8 Comparison of response recovery curves of the Pt (50%) / MnC sensor prepared in Example 1 of the present invention and the Pt (20%) / MnC sensor prepared in Example 2 under 100 ppm carbon monoxide; Fig. 9 Comparison of response recovery curves of the Pt (20%) / MnC sensor prepared in Example 2 of the present invention and the Pt (20%) / nC sensor prepared in Comparative Example 2 under 100 ppm carbon monoxide; Fig.10 Comparison of response recovery curves of the Pt (50%) / MnC sensor prepared in Example 1 of the present invention and the PtRu (50%) / C sensor prepared in Comparative Example 3 under 100 ppm carbon monoxide. DETAILED DESCRIPTION

[0034] From the following preferred embodiments in conjunction with the accompanying drawings, the above and other purposes, features and advantages of the present invention will be more clearly understood. However, the present invention is not limited to the embodiments disclosed herein and can be modified into different forms. These embodiments are provided to thoroughly explain the present invention and fully convey the spirit of the present invention to those skilled in the art.

[0035] Example 1 (1) Preparation of Mn / C materials: Take 0.1g of manganese chloride and add it to 20ml of hydrochloric acid for impregnation, add 1g of mesoporous carbon material, mix and stir in a beaker for 8h, heat to 100℃ until the solvent evaporates, and finally place the mixture in a tube furnace and calcine it at 800℃ for 2h in an argon atmosphere to obtain the target Mn / C material. Figure 1 It can be seen that the metal elements are uniformly composited on the mesoporous carbon material.

[0036] (2) Preparation of Pt (50%) / MnC catalyst: S1: Take 0.2g of Mn / C material, add 30ml of chloroplatinic acid solution (prepared by 0.5g of 40% Pt chloroplatinic acid and 27.5g of ethylene glycol), mix and stir evenly, add 20ml of ethylene glycol and 15ml of water and stir well for 20 minutes to obtain solution A; S2: placing the solution A obtained in step S1 in an ice bath, slowly adding 0.1 mol / L sodium hydroxide solution and stirring thoroughly, adjusting the pH value to 7, to obtain solution B; S3: The solution B obtained in step S2 is subjected to shear dispersion by controlling the temperature at 0-10° C., and the speed is controlled at 2000 rpm for 10 min, and then heated to boiling by microwave to obtain solution C; S4: Place the solution C obtained in step S3 in a low-temperature cooling circulation agitator, control the temperature to 0-10°C, control the speed to 500 rpm, and stir for 10 hours, then add 1.5 ml of hydrochloric acid, let it stand for 2 hours, pour out the supernatant, filter the precipitate, add water to wash and filter it repeatedly for 3 times, and then vacuum dry it at 85°C for 12 hours to obtain a Pt (50%) / MnC catalyst, that is, the mass ratio of Pt element to carbon material is 1:1. Figure 2 It can be seen that Pt is uniformly loaded on the Mn / C material.

[0037] (3) Membrane electrode preparation: T1: Take a 10cm×10cm Nafion 115 membrane and boil it in 5wt% hydrogen peroxide at 80℃ for 1h, then put it in deionized water for 0.5h, and finally boil it in 5wt% sulfuric acid for 1h, wash it repeatedly with deionized water 3-4 times, and store it in water for later use; T2: Take 0.5g Pt (50%) / MnC powder, add 6.2ml deionized water to moisten it, then add 15ml isopropanol and 10ml Nafion solution, mix and stir evenly, and ultrasonicate for 20min to obtain electrode slurry; T3: The electrode slurry obtained in step T2 is coated on both sides of the Nafion membrane treated in step T1 by an ultrasonic sprayer at a temperature of 80° C. The amount of electrode slurry on both sides is the same, and a carbon monoxide electrochemical sensor membrane electrode is obtained.

[0038] (4) Sensor assembly: The structure of the sensor from top to bottom is pins, current collecting layer, filter layer, membrane electrode, filter layer, current collecting layer, and shell. After the membrane electrode obtained in step 3 is assembled in sequence, it is tightly packaged with a sealing ring to obtain a sensor.

[0039] (5) Sensor test: The sensor was placed at room temperature, purged with air at a controlled flow rate of 500 ml / min for 6 hours, placed in an environmental chamber, connected to an electrochemical workstation, and tested using the static gas distribution method. The sensor was tested with carbon monoxide gas of different concentrations. The test results are shown in Figure 2. Figures 3 to 7 . The response recovery curve of the sensor at different concentrations (10ppm-200ppm) performed well, and the linear relationship between the response value and the concentration of carbon monoxide was excellent. The prepared carbon monoxide sensor was subjected to a continuous response test, and the sensor showed good repeated response recovery performance. The response current of the sensor was tested every hour, and the results showed that the performance of the sensor was very stable in the short term. It was stored under constant environmental conditions (temperature: 25±2℃, humidity: 55±5%RH), and response tests were carried out at 15 days, 30 days, and 60 days respectively. The response current of the sensor to 100ppm carbon monoxide was tested, and the results showed that the long-term stability of the sensor was good. This shows that the fuel cell type carbon monoxide sensor prepared based on Pt / MnC catalyst and its membrane electrode performs very well in the detection of carbon monoxide and has great application potential.

[0040] Example 2 (1) Preparation of Mn / C material: same as in Example 1.

[0041] (2) Preparation of Pt (20%) / MnC catalyst: S1: Take 0.2g of Mn / C material, add 7.5ml of chloroplatinic acid solution (prepared by 0.125g of 40% Pt chloroplatinic acid and 6.875g of ethylene glycol), mix and stir evenly, add 20ml of ethylene glycol and 15ml of water and stir well for 20 minutes to obtain solution A; S2: placing the solution A obtained in step S1 in an ice bath, slowly adding 0.1 mol / L sodium hydroxide solution and stirring thoroughly, adjusting the pH to 7, to obtain solution B; S3: The solution B obtained in step S2 is subjected to shear dispersion by controlling the temperature at 0-10° C., and the speed is controlled at 2000 rpm for 10 min, and then heated to boiling by microwave to obtain solution C; S4: Place the solution C obtained in step S3 in a low-temperature cooling circulating agitator, control the temperature to 0-10°C, control the speed to 500 rpm and stir for 10 hours, then add 1.5 ml of hydrochloric acid, let it stand for 2 hours, pour out the supernatant, filter the precipitate, add water to wash and filter it repeatedly for 3 times, and then vacuum dry it at 85°C for 12 hours to obtain a Pt (20%) / MnC catalyst, that is, the mass ratio of Pt element to carbon material is 1:4.

[0042] (3) Membrane electrode preparation: same as in Example 1.

[0043] (4) Sensor assembly: same as in Example 1.

[0044] (5) Sensor test: The test method is the same as that of Example 1. The results are as follows: Figure 8 .from Figure 8 It can be seen that the response value of Pt (20%) / MnC sensor at 100 ppm carbon monoxide is lower than that of Pt (50%) / MnC, but its recovery performance is better.

[0045] Comparative Example 1 (1) The electrode material is commercially purchased platinum carbon Pt (50%) / C, and the mass ratio of Pt element to carbon material is 1:1.

[0046] (2) Membrane electrode preparation: same as in Example 1.

[0047] (3) Sensor assembly: Same as Example 1 (4) Sensor test: The sensor prepared in Comparative Example 1 was tested under the same conditions as in Example 1. The results are shown in Figure 3-Figure 5 As shown, the response value of the sensor based on Pt (50%) / C to carbon monoxide is lower than that based on Pt (50%) / MnC, and Pt (50%) / C recovers slowly at high concentrations. Figure 4 The slope of the fitting curve of Example 1 is higher, which indicates that its response is more sensitive under the same gas concentration. The stability of the sensor based on Pt (50%) / C is not as good as that of the sensor based on Pt (50%) / MnC, and the response current value of the sensor based on Pt (50%) / C has a significant downward trend. This shows that the catalyst Pt / MnC prepared in the present invention has better performance than traditional platinum carbon materials.

[0048] Comparative Example 2 (1) The electrode material is commercially purchased platinum carbon Pt (20%) / C, the mass ratio of Pt element to carbon material is 1:4, and the carbon carrier is graphitized porous carbon.

[0049] (2) Membrane electrode preparation: same as in Example 1.

[0050] (3) Sensor assembly: same as in Example 1.

[0051] (4) Sensor test: The sensor prepared in Comparative Example 2 was tested under the same conditions as in Example 1. The results are shown in Table 1. Fig. 9 As shown, the Pt (20%) / MnC based sensor has better stability and recovery than Pt (20%) / C, indicating that the MnC carbon support has better resistance to carbon monoxide toxicity than graphitized porous carbon.

[0052] Comparative Example 3 (1) The electrode material is commercially purchased platinum ruthenium PtRu (50%) / C, and the mass ratio of PtRu element to carbon material is 1:1.

[0053] (2) Membrane electrode preparation: same as in Example 1.

[0054] (3) Sensor assembly: same as in Example 1.

[0055] (4) Sensor test: The sensor prepared in Comparative Example 3 was tested under the same conditions as in Example 1. The results are shown in Fig.10 As shown, the Pt (50%) / MnC based sensor has a higher response value than that of PtRu (50%) / C, but its recovery performance is slightly worse.

[0056] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A catalyst for sensing carbon monoxide gas, characterized in that: The invention comprises a carrier and Pt particles attached to the surface of the carrier, wherein the carrier is a Mn / C composite material.

2. The catalyst for sensing carbon monoxide gas according to claim 1, characterized in that: The carrier is prepared by washing and impregnating the carrier with a manganese salt in an acid and then calcining the carrier with a carbon material in an inert atmosphere.

3. The catalyst for sensing carbon monoxide gas according to claim 2, characterized in that: The mass ratio of the manganese salt to the carbon material is 1:(2-10).

4. The catalyst for sensing carbon monoxide gas according to claim 1, characterized in that: The Pt particles are supported on the support by a chemical reduction method.

5. The catalyst for sensing carbon monoxide gas according to claim 1, characterized in that: The mass ratio of the Pt particles to the carrier is (1-6):

4.

6. The method for preparing a catalyst for sensing carbon monoxide gas according to any one of claims 1 to 5, characterized in that: The following steps are involved: The carrier is mixed with chloroplatinic acid solution and ethylene glycol to obtain solution A; Under low temperature stirring conditions, adding the prepared sodium hydroxide solution to the solution A, adjusting the pH value to neutral, to obtain solution B; The solution B is subjected to shear dispersion and emulsification under low temperature conditions, and then heated to boiling to obtain a solution C; After the solution C is cooled to room temperature, hydrochloric acid is added, and water is added and filtered repeatedly 3-4 times by positive pressure filtration to obtain a precipitate, which is then dried.

7. Use of a catalyst for sensing carbon monoxide gas according to any one of claims 1 to 5, characterized in that: The catalyst is used as a sensitive material for preparing a membrane electrode of a carbon monoxide electrochemical sensor.

8. A membrane electrode for a carbon monoxide electrochemical sensor, characterized in that: The invention comprises a membrane and catalyst layers located on both sides of the membrane, wherein the catalyst layers comprise the catalyst for sensing carbon monoxide gas according to any one of claims 1 to 5.

9. A method for preparing a membrane electrode for a carbon monoxide electrochemical sensor according to claim 8, characterized in that: The steps include: The membrane is pretreated to remove ionic impurities on the surface and dried for later use; The catalyst for sensing carbon monoxide gas is wetted with deionized water, and a dispersant and a binder are added in sequence and mixed and dispersed evenly to prepare an electrode slurry; The electrode slurry is coated on both sides of the membrane respectively and dried to obtain a carbon monoxide electrochemical sensor membrane electrode.

10. A carbon monoxide electrochemical sensor, characterized in that: The membrane electrode thereof adopts the membrane electrode of the carbon monoxide electrochemical sensor as claimed in claim 8.

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