Working electrode of ammonia gas electrochemical gas sensor suitable for high-temperature and low-humidity environment and preparation method of working electrode
By using a conductive layer and catalytic layer design of graphene/carbon nanotube composite and manganese sulfate in an ammonia electrochemical gas sensor, combined with diffusion control of polytetrafluoroethylene film, the problem of sensor instability under high temperature and low humidity conditions was solved, achieving high sensitivity and long lifespan detection effect.
Patent Information
- Application Number
- CN202511032876.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-25
- Publication Date
- 2025-10-31
AI Technical Summary
Existing ammonia electrochemical gas sensors are unstable in high-temperature and low-humidity environments, and are prone to false alarms and missed alarms, making it difficult to meet the detection needs of special scenarios such as high-temperature industrial workshops and desert areas.
A graphene/carbon nanotube composite was used as a conductive agent, combined with manganese sulfate and manganese carbonate as active materials. The conductive layer and catalytic layer were prepared using ultrasonic spraying and screen printing techniques, and a hot-melt polytetrafluoroethylene film was placed on top to control ammonia diffusion and prevent moisture and impurities from entering.
This improves the stability and sensitivity of the sensor in high-temperature and low-humidity environments, shortens the detection time, enhances the durability and selectivity of the sensor, and ensures the accuracy of the detection.
Smart Images
Figure CN120870276A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of electrochemical sensor technology, specifically relating to a working electrode of an ammonia electrochemical gas sensor suitable for high-temperature and low-humidity environments and its preparation method. Background Technology
[0002] Ammonia, a colorless gas widely used in industry, agriculture, and daily life, has attracted much attention due to its unique physicochemical properties. Ammonia has a strong, pungent odor, exists as a gas at room temperature and pressure, and is readily soluble in water to form ammonia water. This characteristic makes it indispensable in many fields such as refrigeration, fertilizer production, pharmaceuticals, and food processing. However, ammonia is also a highly hazardous chemical substance, with potential threats affecting multiple aspects including human health, the ecological environment, and public safety.
[0003] To effectively monitor and prevent ammonia risks, electrochemical gas sensors, with their advantages of high sensitivity, fast response, and low power consumption, have become one of the core technologies for ammonia detection, widely used in industrial leak monitoring, agricultural environmental control, and environmental quality monitoring. However, the actual application environment of electrochemical gas sensors is complex, especially in extreme conditions of high temperature and low humidity, which poses a severe challenge to sensor performance. Under high temperature conditions, the chemical reaction rate of electrode materials accelerates, leading to accelerated aging and corrosion, thus shortening the sensor's lifespan. In low humidity environments, the aqueous solutions or gel electrolytes commonly used in sensors are prone to water evaporation, causing dehydration and a significant decrease in ionic conductivity. This not only reduces the detection sensitivity of electrochemical gas sensors but also impairs their stability and selectivity, leading to false alarms or missed alarms. Currently, commercially available NH3 electrochemical gas sensors struggle to maintain stable and accurate detection performance under extreme high temperature and low humidity conditions, failing to meet the stringent requirements of special scenarios such as high-temperature industrial workshops and environmental monitoring in desert areas. Therefore, developing a high-performance NH3 electrochemical gas sensor capable of withstanding high temperature and low humidity environments is particularly urgent. Summary of the Invention
[0004] The first objective of this invention is to provide a working electrode for an ammonia electrochemical gas sensor suitable for high-temperature and low-humidity environments, in order to solve the technical problem that existing ammonia electrochemical gas sensors are unstable in high-temperature and low-humidity environments, and are prone to false alarms and missed alarms.
[0005] The second objective of this invention is to provide a method for preparing the working electrode of an ammonia electrochemical gas sensor suitable for high-temperature and low-humidity environments.
[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0007] A method for preparing a working electrode for an ammonia electrochemical gas sensor suitable for high-temperature and low-humidity environments includes the following steps:
[0008] S1: Preparation of conductive layer: Mix dispersant solution, polymer solution, conductive agent one, and binder one to prepare conductive layer slurry. Coat the conductive layer slurry onto the substrate and dry to obtain the conductive layer.
[0009] S2: Preparation of the catalyst layer: The active material, conductive agent II, catalyst, polymer, solvent and binder II are mixed to prepare the catalyst layer slurry. The catalyst layer slurry is coated on the conductive layer and dried to obtain the working electrode.
[0010] Furthermore, the thickness of the conductive layer in S1 is 0.03-0.05 mm, and the thickness of the working electrode of the ammonia electrochemical gas sensor suitable for high temperature and low humidity environments is 0.1-0.3 mm.
[0011] Furthermore, the drying described in S1 and S2 is performed at 200-265℃ for 1-3 hours.
[0012] Furthermore, in S1, the conductive layer slurry is coated onto the substrate by ultrasonic spraying, and the substrate is a polytetrafluoroethylene film; in S2, the catalyst layer slurry is coated onto the conductive layer by screen printing.
[0013] Furthermore, in S1, the dispersant solution is a polyvinylpyrrolidone solution, the polymer solution is a polyacrylamide solution, the first conductive agent is a graphene / carbon nanotube composite, and the first binder is a polytetrafluoroethylene emulsion; in S2, the active substances are manganese sulfate and manganese carbonate, with a mass ratio of manganese sulfate to manganese carbonate of 0.1:0.1; the second conductive agent is graphene, the catalyst is ruthenium black, the polymer is polyacrylamide, the solvent is glycerol, and the second binder is a perfluorosulfonic acid polymer solution.
[0014] Furthermore, the concentration of the dispersant solution is 0.01-0.02 g / mL, the concentration of the polymer solution is 0.01-0.02 g / mL, and the solid content of the first binder is 35-55%; each g of the first conductive agent corresponds to 0.75-3 mL of the dispersant solution, each g of the first conductive agent corresponds to 0.75-3 mL of the polymer solution, and each g of the first conductive agent corresponds to 1-4 mL of the first binder.
[0015] Furthermore, in S2, the mass ratio of the active material to the conductive agent II is 0.2:0.2; the mass ratio of the active material to the catalyst is 0.2:0.01; the mass ratio of the active material to the polymer is 0.2:0.02; 5 mL of the solvent is added per gram of the active material; and 1.5 mL of the binder II is added per gram of the active material; the solid content of the binder II is 20%.
[0016] A working electrode for an ammonia electrochemical gas sensor suitable for high-temperature and low-humidity environments is prepared using the above-described method for preparing a working electrode for an ammonia electrochemical gas sensor suitable for high-temperature and low-humidity environments.
[0017] An ammonia electrochemical gas sensor suitable for high-temperature and low-humidity environments includes the aforementioned working electrode of the ammonia electrochemical gas sensor suitable for high-temperature and low-humidity environments; the ammonia electrochemical gas sensor suitable for high-temperature and low-humidity environments also includes a top cover, the top cover being thermally fused with a polytetrafluoroethylene film, and the working electrode of the ammonia electrochemical gas sensor suitable for high-temperature and low-humidity environments is located below the polytetrafluoroethylene film.
[0018] Furthermore, the polytetrafluoroethylene membrane has a pore size of 0.05 μm and an air permeability of 1-6 mL / min / cm. 2 .
[0019] The beneficial effects of this invention are:
[0020] Graphene possesses an extremely high specific surface area and excellent conductivity, providing abundant active sites for the adsorption and reaction of ammonia. The ultra-thin conductive layer facilitates rapid diffusion of ammonia and electron transport. The composite structure of the working electrode shortens the detection time for ammonia and enhances its stability under high temperature and low humidity conditions. The T90 of the ammonia electrochemical gas sensor of this invention is approximately 30 seconds.
[0021] Traditional electrochemical gas sensors directly fuse the working electrode to the top cover, which can lead to cracks or detachment of the working electrode. This invention fuses a blank polytetrafluoroethylene (PTFE) membrane to the top cover of the ammonia electrochemical gas sensor. By controlling the pore size and permeability of the PTFE membrane, ammonia gas can diffuse evenly and slowly to the surface of the working electrode, while effectively preventing the entry of external moisture and impurities and the evaporation of internal moisture in low-humidity environments. Attached Figure Description
[0022] Figure 1 The response recovery curves are shown for Examples 1-5, Comparative Example 1, and the ammonia electrochemical gas sensor in the competing products.
[0023] Figure 2The graph shows the sensitivity changes of the ammonia electrochemical gas sensors in Examples 1, 4, 5, Comparative Example 1, and competing products.
[0024] Figure 3 This is a photograph of the conductive layer of the working electrode of the ammonia electrochemical gas sensor in Example 1.
[0025] Figure 4 This is a photograph of the working electrode of the ammonia electrochemical gas sensor in Example 1. Detailed Implementation
[0026] The present invention will be further described below with reference to the embodiments and accompanying drawings.
[0027] Example 1
[0028] The preparation method of the working electrode of the ammonia electrochemical gas sensor suitable for high temperature and low humidity environments in Example 1 includes the following steps:
[0029] Preparation of the conductive layer: 0.4 g of polyvinylpyrrolidone was dissolved in 20 mL of deionized water to obtain a polyvinylpyrrolidone solution. 0.4 g of polyacrylamide was dissolved in 20 mL of deionized water to obtain a polyacrylamide solution. 0.1 g of commercially available graphene / carbon nanotube composite, 0.3 mL of polyvinylpyrrolidone solution, 0.3 mL of polyacrylamide solution, and 0.4 mL of polytetrafluoroethylene (PTFE) emulsion were mixed and homogenized in a vacuum mixer to obtain a conductive layer slurry. The conductive layer slurry was ultrasonically sprayed onto a PTFE membrane to prepare a coating with a diameter of 7 mm and a thickness of 0.04 mm. The coating was cured at 245 °C for 2 h to form the conductive layer. The solid content of the PTFE emulsion was 35-55%.
[0030] Preparation of the catalyst layer: 0.1 g of manganese sulfate, 0.1 g of manganese carbonate, 0.2 g of graphene, 0.01 g of ruthenium black, 0.02 g of polyacrylamide, 1 mL of glycerol, and 0.3 mL of perfluorosulfonic acid polymer solution (Nafion solution) were mixed in a vacuum mixer to form a catalyst layer slurry. The catalyst layer slurry was then screen-printed onto the conductive layer and cured at 245 °C for 2 hours to obtain a working electrode with a diameter of 7 mm and a thickness of 0.2 mm. The solid content of the Nafion solution was 20%.
[0031] Example 1 describes an ammonia electrochemical gas sensor for high-temperature, low-humidity environments, comprising a working electrode and a top cover. The top cover has a blank polytetrafluoroethylene (PTFE) membrane heat-fused to it. The working electrode is located below the PTFE membrane. The PTFE membrane has a pore size of 0.05 μm and a permeability of 2 mL / min / cm². 2.
[0032] Example 2
[0033] The preparation method of the working electrode of the ammonia electrochemical gas sensor suitable for high temperature and low humidity environments in Example 2 includes the following steps:
[0034] Preparation of the conductive layer: 0.4 g of polyvinylpyrrolidone was dissolved in 20 mL of deionized water to obtain a polyvinylpyrrolidone solution, and 0.4 g of polyacrylamide was dissolved in 20 mL of deionized water to obtain a polyacrylamide solution. 0.1 g of graphene / carbon nanotube composite, 0.3 mL of polyvinylpyrrolidone solution, 0.3 mL of polyacrylamide solution and 0.4 mL of PTFE emulsion were mixed and homogenized in a vacuum mixer to obtain a conductive layer slurry. The conductive layer slurry was ultrasonically sprayed onto a PTFE film to prepare a coating with a diameter of 7 mm and a thickness of 0.04 mm. The coating was cured at 245 °C for 2 h to form a conductive layer.
[0035] Preparation of the catalyst layer: 0.1 g of manganese sulfate, 0.1 g of manganese carbonate, 0.2 g of graphene, 0.01 g of ruthenium black, 0.02 g of polyacrylamide, 1 mL of glycerol, and 0.3 mL of perfluorosulfonic acid polymer solution were mixed in a vacuum mixer to form a catalyst layer slurry. The catalyst layer slurry was then screen-printed onto the conductive layer and cured at 245 °C for 2 h to obtain a working electrode with a diameter of 7 mm and a thickness of 0.1 mm. The Nafion solution had a solid content of 20%.
[0036] Example 2 illustrates an ammonia electrochemical gas sensor for high-temperature, low-humidity environments, comprising a working electrode and a top cover. The top cover is heat-fused with a blank polytetrafluoroethylene (PTFE) membrane. The working electrode is located below the PTFE membrane. The PTFE membrane has a pore size of 0.05 μm and a permeability of 2 mL / min / cm². 2 .
[0037] Example 3
[0038] The preparation method of the working electrode of the ammonia electrochemical gas sensor suitable for high temperature and low humidity environments in Example 3 includes the following steps:
[0039] Preparation of the conductive layer: 0.4 g of polyvinylpyrrolidone was dissolved in 20 mL of deionized water to obtain a dispersant solution, and 0.2 g of polyacrylamide was dissolved in 20 mL of deionized water to obtain a polyacrylamide solution. 0.4 g of graphene / carbon nanotube composite, 0.3 mL of dispersant solution, 0.3 mL of polyacrylamide solution and 0.4 mL of PTFE emulsion were mixed and homogenized in a vacuum mixer to obtain a conductive layer slurry. The conductive layer slurry was ultrasonically sprayed onto a PTFE film to prepare a coating with a diameter of 7 mm and a thickness of 0.04 mm. The coating was cured at 245 °C for 2 h to form a conductive layer.
[0040] Preparation of the catalyst layer: 0.1 g of manganese sulfate, 0.1 g of manganese carbonate, 0.2 g of graphene, 0.01 g of ruthenium black, 0.02 g of polyacrylamide, 1 mL of glycerol, and 0.3 mL of Nafion solution were mixed in a vacuum mixer to form a catalyst layer slurry. The catalyst layer slurry was then screen-printed onto the conductive layer and cured at 245 °C for 2 h to obtain a working electrode with a diameter of 7 mm and a thickness of 0.3 mm. The solid content of the Nafion solution was 20%.
[0041] Example 3 describes an ammonia electrochemical gas sensor for high-temperature, low-humidity environments. It includes a working electrode and a top cover. The top cover has a blank polytetrafluoroethylene (PTFE) membrane heat-fused to it. The working electrode is located below the PTFE membrane. The PTFE membrane has a pore size of 0.05 μm and a permeability of 2 mL / min / cm². 2 .
[0042] Example 4
[0043] Example 4 uses the same electrodes and assembly method as Example 1. The polytetrafluoroethylene (PTFE) membrane for the top cover is heat-fused and has a pore size of 0.05 μm and an air permeability of 1 mL / min / cm. 2 .
[0044] Example 5
[0045] Example 5 uses the same electrodes and assembly method as Example 1. The polytetrafluoroethylene (PTFE) membrane for the top cover is heat-fused and has a pore size of 0.05 μm and an air permeability of 6 mL / min / cm. 2 .
[0046] Comparative Example 1
[0047] The structure of the ammonia electrochemical gas sensor in Comparative Example 1 is roughly the same as that in Example 1. The difference between the structure of the ammonia electrochemical gas sensor in Comparative Example 1 and that in Example 1 is that the ammonia electrochemical gas sensor in Comparative Example 1 does not have a blank polytetrafluoroethylene film heat-fused to the top cover.
[0048] from Figure 1 It can be seen that the response and recovery times of the ammonia electrochemical gas sensor in Example 1 are significantly better than those of competing sensors, while the difference between Example 1 and Comparative Example 1 is not significant. The sensors in Examples 1 and 3 have significantly higher sensitivity than the sensor in Example 2. However, the working electrode in Example 3 is too thick, which poses a risk of electrode detachment. Considering cost, the working electrode of Example 1 is the optimal choice. For the polytetrafluoroethylene film of different specifications for heat-fused top cover, the response and recovery times of Examples 1 and 5 are significantly better.
[0049] from Figure 2 It can be seen that, under conditions of 50℃ and 15% RH, the sensitivity of competing products decreased to 70% of the original after half a month, and to less than 50% after one month. In contrast, the ammonia electrochemical gas sensor of Example 1, resistant to high temperature and low humidity, regained approximately 95% of its original sensitivity after three months under the same conditions. Example 4 showed performance similar to Example 1, but its response and recovery times were longer. The ammonia electrochemical gas sensor of Example 5, resistant to high temperature and low humidity, regained approximately 90% of its original sensitivity after three months under the same conditions. The ammonia electrochemical gas sensor of Comparative Example 1, under the same conditions, regained 85% of its original sensitivity after three months under the same conditions. The ammonia electrochemical gas sensor of this invention exhibits significantly improved high temperature and low humidity resistance.
Claims
1. A method for preparing a working electrode for an ammonia electrochemical gas sensor suitable for high-temperature and low-humidity environments, characterized in that, Includes the following steps: S1: Preparation of conductive layer: Mix dispersant solution, polymer solution, conductive agent one, and binder one to prepare conductive layer slurry. Coat the conductive layer slurry onto the substrate and dry to obtain the conductive layer. S2: Preparation of the catalyst layer: The active material, conductive agent II, catalyst, polymer, solvent and binder II are mixed to prepare the catalyst layer slurry. The catalyst layer slurry is coated on the conductive layer and dried to obtain the working electrode.
2. The method for preparing the working electrode of the ammonia electrochemical gas sensor suitable for high temperature and low humidity environments according to claim 1, characterized in that, The thickness of the conductive layer in S1 is 0.03-0.05 mm, and the thickness of the working electrode of the ammonia electrochemical gas sensor suitable for high temperature and low humidity environments is 0.1-0.3 mm.
3. The method for preparing the working electrode of the ammonia electrochemical gas sensor suitable for high temperature and low humidity environments according to claim 1, characterized in that, The drying process described in S1 and S2 involves drying at 200-265℃ for 1-3 hours.
4. The method for preparing the working electrode of the ammonia electrochemical gas sensor suitable for high temperature and low humidity environments according to claim 1, characterized in that, The conductive layer slurry in S1 is coated onto the substrate by ultrasonic spraying, and the substrate is a polytetrafluoroethylene film; the catalyst layer slurry in S2 is coated onto the conductive layer by screen printing.
5. The method for preparing the working electrode of the ammonia electrochemical gas sensor suitable for high temperature and low humidity environments according to claim 1, characterized in that, In S1, the dispersant solution is a polyvinylpyrrolidone solution, the polymer solution is a polyacrylamide solution, the first conductive agent is a graphene / carbon nanotube composite, and the first binder is a polytetrafluoroethylene emulsion; in S2, the active substances are manganese sulfate and manganese carbonate, with a mass ratio of 0.1:0.1; the second conductive agent is graphene, the catalyst is ruthenium black, the polymer is polyacrylamide, the solvent is glycerol, and the second binder is a perfluorosulfonic acid polymer solution.
6. The method for preparing the working electrode of the ammonia electrochemical gas sensor suitable for high temperature and low humidity environments according to claim 1, characterized in that, The concentration of the dispersant solution is 0.01-0.02 g / mL, the concentration of the polymer solution is 0.01-0.02 g / mL, and the solid content of the first binder is 35-55%. For every g of the first conductive agent, 0.75-3 mL of the dispersant solution, 0.75-3 mL of the polymer solution, and 1-4 mL of the first binder are added.
7. The method for preparing the working electrode of the ammonia electrochemical gas sensor suitable for high temperature and low humidity environments according to claim 1, characterized in that, In S2, the mass ratio of the active material to the conductive agent II is 0.2:0.2; the mass ratio of the active material to the catalyst is 0.2:0.01; the mass ratio of the active material to the polymer is 0.2:0.02; 5 mL of the solvent is added per gram of the active material; 1.5 mL of the binder II is added per gram of the active material; the solid content of the binder II is 20%.
8. A working electrode for an ammonia electrochemical gas sensor suitable for high-temperature and low-humidity environments, characterized in that, The working electrode of the ammonia electrochemical gas sensor suitable for high temperature and low humidity environments, as described in any one of claims 1-7, is prepared using the method described in claims 1-7.
9. An ammonia electrochemical gas sensor suitable for high-temperature and low-humidity environments, characterized in that, The ammonia electrochemical gas sensor suitable for high temperature and low humidity environments, as described in claim 8, includes a working electrode; the ammonia electrochemical gas sensor suitable for high temperature and low humidity environments further includes a top cover, the top cover being thermally fused with a polytetrafluoroethylene film, and the working electrode of the ammonia electrochemical gas sensor suitable for high temperature and low humidity environments is located below the polytetrafluoroethylene film.
10. The ammonia electrochemical gas sensor suitable for high temperature and low humidity environments according to claim 9, characterized in that, The polytetrafluoroethylene membrane has a pore size of 0.05 μm and an air permeability of 1-6 mL / min / cm. 2 .