High-sensitivity NO oxidation catalytic electrode as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of electrochemistry, and provides a high-sensitivity NO oxidation catalytic electrode and a preparation method and application thereof. The NO oxidation catalytic electrode provided by the invention comprises a catalytic layer and a catalytic protective layer, main raw material components of the catalytic layer comprise metal phthalocyanine, graphite and a binder, main raw material components of the catalytic protective layer comprise a hydrophilic porous carbon material and a perfluorosulfonic acid type polymer, and metal phthalocyanine and graphite are matched with each other, so that the catalytic performance of the catalytic electrode is improved. According to the present invention, the electrode has characteristics of good NO oxidation catalytic activity, good conductivity, good chemical stability, wide linear range and cost reduction, and is provided with the catalytic protection layer so as to effectively isolate the generation of the side reaction, improve the surface conductivity, reduce the background current generated by the electrode, and do not affect the response speed and the response time.

Description

Technical Field

[0001] The present invention relates to the field of electrochemical technology, and more specifically, to a highly sensitive NO oxidation catalytic electrode and a preparation method and application thereof. Background Art

[0002] Analyzing exhaled breath to detect human diseases (such as lung cancer, asthma, diabetes, etc.) is an emerging field of medical diagnosis. It is non-invasive, cost-effective, and a good alternative to traditional blood analysis methods.

[0003] Among the many detection methods of nitric oxide (NO), the detection by electrochemical sensor has the advantages of high sensitivity, simple operation and rapid detection. NO undergoes oxidation or reduction reaction on the electrode surface of the electrochemical sensor, causing changes in the electrochemical signal, and these changes are measured to know the changes in NO. NO electrochemical sensors are usually composed of working electrodes, auxiliary electrodes, reference electrodes, counter electrodes and other main parts. The core of NO electrochemical sensor research and development is to improve the sensitivity of the working electrode to NO, especially when detecting low concentrations of NO, the NO sensitivity and self-stability of the sensor are required to be higher. However, the commonly used carbon-based electrode materials (such as carbon nanotubes, graphene, graphyne, etc.) are too low in sensitivity; precious metal electrode materials (such as platinum, gold, etc.) often have the disadvantages of instability, high cost, high sensitivity and wide linearity; composite materials are often not used in practice due to complex processes, difficult mass production, and inability to ensure consistency; traditional electrodes prepared from metal phthalocyanines often produce large background currents.

[0004] Therefore, it is urgent to develop a working electrode for a NO electrochemical sensor with high sensitivity to NO, fast response speed, good stability, small background current and low cost. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides a highly sensitive NO oxidation catalytic electrode and a preparation method and application thereof. The highly sensitive NO oxidation catalytic electrode provided by the present invention has high sensitivity to NO, fast response speed, good stability, small background current, low cost, and a wide linear range, and can be further used to assemble a NO electrochemical sensor.

[0006] A first aspect of the present invention provides a highly sensitive NO oxidation catalytic electrode.

[0007] Specifically, a highly sensitive NO oxidation catalytic electrode includes a catalytic layer and a catalytic protective layer, wherein the raw material components of the catalytic layer include metal phthalocyanine, graphite and a binder; and the raw material components of the catalytic protective layer include a hydrophilic porous carbon material and a perfluorosulfonic acid polymer (Nafion).

[0008] The present invention uses graphite (Gp) as one of the main raw materials of the catalyst layer, which can give the electrode good conductivity and chemical stability. In addition, the carbon atoms on the graphite are SP 2 Hybridization, with a large π bond, has a certain adsorption effect on NO, and has a certain catalytic effect on NO oxidation. Metal phthalocyanine (MePC) is a transition metal macrocyclic complex. Its conjugated macrocyclic structure has good electrochemical activity and good catalytic activity for NO oxidation, but its conductivity is poor and it is difficult to transfer electrons during the reaction; while graphite has good conductivity and a large π bond, which can be combined with metal phthalocyanine with rich π electron substances through π-π stacking. After mutual combination, the electrode has excellent NO oxidation catalytic activity, good conductivity, high chemical stability, high sensitivity to NO, fast response speed, wide linear range, and can reduce costs. In addition, since the catalyst layer is mainly made of metal phthalocyanine and graphite, there are many internal groups and it is easy to produce side reactions. Therefore, the present invention also sets a catalytic protection layer connected to the catalyst layer to obtain a double-layer structure electrode. The catalytic protection layer can effectively isolate the generation of side reactions. For example, when sulfuric acid is used as an electrolyte, it can isolate sulfate from entering the catalyst layer; and since the catalytic protection layer is a hydrophilic porous structure with good surface conductivity, it can not affect the entry of water molecules into the catalyst layer to react with NO, and at the same time does not affect the transfer of reaction products such as hydrogen ions and electron transfer. Therefore, the catalytic protection layer can reduce the background current generated by the electrode, and at the same time does not affect the response speed and response time.

[0009] Preferably, the mass ratio of the metal phthalocyanine to graphite is (10-1):(90-99).

[0010] Further preferably, the mass ratio of the metal phthalocyanine to graphite is (5-3): (95-97).

[0011] Preferably, the metal phthalocyanine includes at least one of ferrous phthalocyanine (Fe(II)Pc), copper phthalocyanine (Cu(II)Pc), and nickel phthalocyanine (Ni(II)Pc). The electrode prepared from ferrous phthalocyanine will transform from Fe(II)Pc to Fe(II)Pc during operation. 1+ status.

[0012] Preferably, the mass ratio of the total mass of metal phthalocyanine and graphite to the mass ratio of the binder in the catalyst layer is (70-95): (30-5).

[0013] Further preferably, the mass ratio of the total mass of metal phthalocyanine and graphite in the catalyst layer to the mass ratio of the binder is (90-95):(10-5).

[0014] Preferably, the binder is a perfluorosulfonic acid type polymer.

[0015] Preferably, the binder is perfluorosulfonic acid resin (PFSA).

[0016] Preferably, the mass ratio of the hydrophilic porous carbon material and the perfluorosulfonic acid polymer in the catalytic protection layer is (0.5-3): (0.5-3) Further preferably, the mass ratio of the hydrophilic porous carbon material to the perfluorosulfonic acid type polymer in the catalytic protection layer is (1-2): (1-2).

[0017] Preferably, the perfluorosulfonic acid polymer is polyperfluorosulfonic acid resin (PFSA).

[0018] Preferably, the hydrophilic porous carbon material includes at least one of graphite oxide, graphene, and multi-walled carbon nanotubes.

[0019] Preferably, the particle size of the hydrophilic porous carbon material is 300-500 mesh.

[0020] Further preferably, the particle size of the hydrophilic porous carbon material is 400-450 mesh.

[0021] Preferably, in step (1), the particle size of the graphite is 400-600 mesh.

[0022] Further preferably, in step (1), the particle size of the graphite is 450-500 mesh.

[0023] Preferably, the NO oxidation catalytic electrode further includes a carrier, which is arranged in the order of a catalytic protection layer, a catalytic layer and a carrier.

[0024] Preferably, the carrier is a polytetrafluoroethylene (PTFE) membrane.

[0025] Preferably, the thickness of the catalytic layer is 20-30 μm.

[0026] Preferably, the thickness of the catalytic protection layer is 10-15 μm.

[0027] Preferably, the thickness of the carrier is 240-260 μm.

[0028] Preferably, the resistance of the catalytic layer is 500-600Ω, and / or the air permeability of the catalytic layer is 250-270 mL / min.

[0029] Preferably, the resistance of the NO oxidation catalytic electrode is 400-500Ω, and / or the air permeability of the NO oxidation catalytic electrode is 100-120 mL / min.

[0030] A second aspect of the present invention provides a method for preparing a highly sensitive NO oxidation catalytic electrode.

[0031] A method for preparing a highly sensitive NO oxidation catalytic electrode comprises the following steps: (1) mixing a metal phthalocyanine solution with graphite to prepare a solution containing a metal phthalocyanine / graphite mixture; Mixing a hydrophilic porous carbon material with a perfluorosulfonic acid type polymer solution to prepare a hydrophilic porous carbon material / perfluorosulfonic acid type polymer slurry; (2) Co-assembling a solution containing a metal phthalocyanine / graphite mixture to obtain a metal phthalocyanine / graphite composite material, mixing the metal phthalocyanine / graphite composite material with a binder, and drying to obtain the catalytic layer; then loading the hydrophilic porous carbon material / perfluorosulfonic acid type polymer slurry on the catalytic layer, and drying to obtain the oxidation catalytic electrode.

[0032] Preferably, in step (1), the method for preparing the metal phthalocyanine solution comprises: dispersing the metal phthalocyanine in a solvent to obtain the metal phthalocyanine solution.

[0033] Further preferably, in step (1), the method for preparing the metal phthalocyanine solution comprises: dispersing the metal phthalocyanine in a solvent at 60-80° C. and stirring at a speed of 300-500 rpm to obtain the metal phthalocyanine solution.

[0034] Preferably, the solvent is at least one of tetrahydrofuran (THF), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO).

[0035] More preferably, the solvent is N,N-dimethylformamide (DMF).

[0036] Preferably, the solid-liquid ratio of the metal phthalocyanine to the solvent is 1 g: (200-300) mL.

[0037] Preferably, in step (1), the perfluorosulfonic acid polymer is first prepared into a perfluorosulfonic acid polymer solution with a mass concentration of 9-11%, and then the hydrophilic porous carbon material and the perfluorosulfonic acid polymer solution are mixed, and stirred at a speed of 800-1000 rpm for 6-8 hours to obtain a hydrophilic porous carbon material / perfluorosulfonic acid polymer slurry.

[0038] Preferably, in step (1), the viscosity of the hydrophilic porous carbon material / perfluorosulfonic acid polymer slurry is 7000-8000 mPa.s.

[0039] Preferably, in step (2), the co-assembly temperature is 70-90°C, and the co-assembly pressure is 0.05-0.1Mpa. Inducing the co-assembly of metal phthalocyanine and graphite, during this process, metal phthalocyanine slowly precipitates from the solution, and the molecular chain re-forms a three-dimensional structure, at which many groups are exposed, rather than simply physically mixing. The obtained metal phthalocyanine / graphite composite material helps to improve the stability and catalytic effect of the catalytic layer, while removing the solvent.

[0040] Preferably, in step (2), the co-assembly is performed by evaporation.

[0041] Preferably, the evaporation is a rotary evaporation, and the rotation speed of the rotary evaporation is 200-250 rpm. The rotary evaporation helps to promote uniform mixing between the components.

[0042] Preferably, in step (2), the solution containing the metal phthalocyanine / graphite mixture is co-assembled by evaporation to obtain a metal phthalocyanine / graphite composite material, and then a binder with a mass concentration of 6-8% is added and mixed to obtain a metal phthalocyanine / graphite / perfluorosulfonic acid type polymer slurry, which is coated on a carrier and dried to obtain the catalyst layer.

[0043] Further preferably, in step (2), the solution containing the metal phthalocyanine / graphite mixture is co-assembled by evaporation to obtain a metal phthalocyanine / graphite composite material, and then a binder with a mass concentration of 6.5-7.5% is added and mixed at 20-30°C, and stirred at a speed of 800-1000 rpm for 8-11 hours to obtain a metal phthalocyanine / graphite / perfluorosulfonic acid type polymer slurry, which is coated on a carrier and vacuum dried to obtain the catalyst layer.

[0044] Preferably, the viscosity of the metal phthalocyanine / graphite / perfluorosulfonic acid type polymer slurry is 6000-10000 mPa.s.

[0045] Further preferably, the viscosity of the metal phthalocyanine / graphite / perfluorosulfonic acid type polymer slurry is 7000-8000 mPa.s.

[0046] Preferably, the carrier is a polytetrafluoroethylene (PTFE) membrane.

[0047] Preferably, the air permeability of the carrier tested at 7 kPa is 300-800 mL / min, and / or the thickness of the carrier is 0.15-0.3 mm.

[0048] Further preferably, the air permeability of the carrier tested at 7 kPa is 400-600 mL / min, and / or the thickness of the carrier is 0.25-0.3 mm.

[0049] Preferably, the coating is performed on the carrier by blade coating or screen printing.

[0050] Preferably, the coating has a thickness of 0.4-0.8 mm.

[0051] Further preferably, the coating has a thickness of 0.6-0.7 mm.

[0052] Preferably, the mold used for coating is a circular mold with a diameter of 16-20 mm.

[0053] Further preferably, the mold used for the coating is a circular mold with a diameter of 18-19 mm.

[0054] Preferably, the vacuum drying temperature is 60-80° C., and the vacuum drying time is 2-3 h.

[0055] Preferably, in step (2), the hydrophilic porous carbon material / perfluorosulfonic acid type polymer slurry is loaded on the catalyst layer with a thickness of 0.4-0.6 mm.

[0056] Further preferably, in step (2), the hydrophilic porous carbon material / perfluorosulfonic acid type polymer slurry is loaded on the catalytic layer with a thickness of 0.5-0.55 mm.

[0057] Preferably, in step (2), the hydrophilic porous carbon material / perfluorosulfonic acid polymer slurry is loaded on the catalyst layer and vacuum dried at 60-80° C. for 2-3 h to obtain the oxidation catalytic electrode.

[0058] A third aspect of the present invention provides an application of a highly sensitive NO oxidation catalytic electrode.

[0059] The invention discloses an application of a highly sensitive NO oxidation catalytic electrode in the field of NO detection.

[0060] A NO electrochemical sensor comprises an auxiliary electrode, a working electrode, a reference electrode and a counter electrode. The materials of the auxiliary electrode and the working electrode are both the NO oxidation catalytic electrode.

[0061] A NO detection device comprises the NO electrochemical sensor.

[0062] Preferably, the NO detection equipment includes at least one of a NO detector and an environmental pollution gas source detector.

[0063] NO detectors are mainly used in medicine for breath testing.

[0064] Environmental pollution gas source detector is an industrial equipment, mainly used to detect environmental pollution gas source.

[0065] Compared with the prior art, the beneficial effects of the present invention are as follows: The NO oxidation catalytic electrode provided by the present invention comprises a catalytic layer and a catalytic protective layer, wherein the main raw material components of the catalytic layer comprise metal phthalocyanine, graphite and a binder, and the main raw material components of the catalytic protective layer comprise a hydrophilic porous carbon material and a perfluorosulfonic acid type polymer. By utilizing the mutual coordination of metal phthalocyanine and graphite, the electrode not only has good catalytic activity for NO oxidation, but also has good electrical conductivity and chemical stability, has a wide linear range, and can reduce costs. In addition, a catalytic protective layer is also provided to effectively isolate the generation of side reactions, improve surface electrical conductivity, and reduce the background current generated by the electrode, while not affecting the response speed and response time. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 This is a schematic diagram of the structure of the NO oxidation catalytic electrode prepared in Example 1 of the present invention; Figure 2 It is a structural schematic diagram of the electrochemical performance testing device made by the present invention; Figure 3 The current-time relationship diagram of the NO electrochemical sensor assembled with the NO oxidation catalytic electrode prepared in Example 1 of the present invention at different NO concentrations; Figure 4 A total output current-NO concentration relationship diagram of a NO electrochemical sensor assembled from the NO oxidation catalytic electrode prepared in Example 1 of the present invention; Figure 5 The current-time relationship diagram of the NO electrochemical sensor assembled with the NO oxidation catalytic electrode prepared in Example 2 of the present invention at different NO concentrations; Figure 6 A total output current-NO concentration relationship diagram of a NO electrochemical sensor assembled from a NO oxidation catalytic electrode prepared in Example 2 of the present invention; Figure 7 This is a current-time relationship diagram of a NO electrochemical sensor assembled with a NO oxidation catalytic electrode prepared in Example 3 of the present invention at different NO concentrations; Figure 8 A total output current-NO concentration relationship diagram of a NO electrochemical sensor assembled from a NO oxidation catalytic electrode prepared in Example 3 of the present invention; Fig. 9 This is the current-time relationship diagram of the commercially available ppb-level NO four-electrode sensor at different NO concentrations; Fig.10 The total output current-NO concentration relationship diagram of the commercially available ppb-level NO four-electrode sensor; Fig.11This is a current-time relationship diagram of the NO electrochemical sensor assembled with the NO oxidation catalytic electrode of Comparative Example 1 at different NO concentrations; Fig.12 This is a relationship diagram between the total output current and NO concentration of the NO electrochemical sensor assembled with the NO oxidation catalytic electrode of Comparative Example 1; Fig.13 This is a scanning electron microscope image (SEM) of the NO oxidation catalytic electrode of Example 1 of the present invention; Fig.14 This is an X-ray energy spectrum (EDS) of the NO oxidation catalytic electrode of Example 1 of the present invention; Fig.15 This is a surface contact angle diagram of the catalytic protection layer of the NO oxidation catalytic electrode prepared in Example 1 of the present invention; Fig.16 This is the surface contact angle diagram of the NO oxidation catalytic electrode of Comparative Example 1. Implementation

[0067] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.

[0068] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods. Example

[0069] A highly sensitive NO oxidation catalytic electrode comprises a catalytic layer and a catalytic protective layer, wherein the raw material components of the catalytic layer comprise ferrous phthalocyanine (Fe(II)Pc), graphite (Gp), and Nafion, wherein the mass ratio of ferrous phthalocyanine (Fe(II)Pc) to graphite (Gp) is 3:97, and the mass ratio of the Fe(II)Pc / Gp mixture to Nafion is 90:10; the raw material components of the catalytic protective layer comprise graphite oxide and Nafion in a mass ratio of 1:1.

[0070] The method for preparing the highly sensitive NO oxidation catalytic electrode comprises the following steps: (1) a. Preparation of a solution containing a mixture of metal phthalocyanine / graphite (Fe(II)Pc / Gp): 1 g of ferrous phthalocyanine (Fe(II)Pc) was dispersed by stirring in 100 mL of N,N-dimethylformamide (DMF) at 75°C, with a solid-liquid ratio of 1 g:210 mL and a magnetic stirring speed of 400 rpm to obtain a metal phthalocyanine solution; The metal phthalocyanine solution and graphite (500 mesh) were mixed at a mass ratio of Fe(II)Pc:Gp=3:97 to obtain a solution containing a metal phthalocyanine / graphite mixture, and the mixed solution was subjected to rotary evaporation (rotary evaporation) at 85°C, 240rpm, and 0.09Mpa by an evaporation-induced co-assembly method of Fe(II)Pc and graphite, and after rotary evaporation and drying, a co-assembled Fe(II)Pc / Gp composite material was obtained; b. Preparation of graphite oxide / Nafion slurry: Add 400 mesh graphite oxide into Nafion solution (mass concentration 10%), with a mass ratio of graphite oxide: Nafion = 1:1, and stir at 900 rpm for 7 hours to obtain 7000 mPa.s graphite oxide / Nafion slurry; (2) a. Preparation of catalytic layer: The above Fe(II)Pc / Gp mixture was mixed with Nafion solution (mass concentration 6.5%), with a solid mass ratio of Fe(II)Pc / Gp mixture: Nafion = 90:10, and the mixture was stirred at room temperature for 10 h until uniformly mixed, with a rotation speed of 900 rpm, to obtain a slurry with a viscosity of 7100-7200 mPa.s; the slurry was scraped, the mold was circular, with a diameter of 18 mm, the scraping thickness was 0.6 mm, and the bottom receiving carrier was a PTFE membrane with an air permeability of 400 mL / min and a thickness of 0.25 mm; The electrode sheet formed by scraping is vacuum dried at a temperature of 75°C for 3 hours to obtain a catalytic layer. After drying, an electrode containing a catalytic layer is obtained, which has a thickness of 27 μm (the thickness of the electrode containing a PTFE membrane is 270-280 μm), a resistance of 540-560Ω, and an air permeability of 100-104 mL / min.

[0071] b. Preparation of a catalytic protective layer: Place the electrode sheet containing the catalytic layer prepared in step (2) in a scraping mold (0.5 mm thick, 18 mm in diameter), then scrape the graphite oxide / Nafion slurry on the surface of the catalytic layer, and dry it according to the drying conditions of step (2) to obtain a NO oxidation catalytic electrode, which comprises a catalytic protective layer, a catalytic layer, and a carrier in sequence. The total thickness of the final NO oxidation catalytic electrode is 287 μm (the electrode thickness excluding the PTFE membrane is 42 μm), the resistance is 300-320Ω, and the air permeability is 100-102 mL / min.

[0072] The structural schematic diagram of the NO oxidation catalytic electrode prepared in Example 1 is as follows Figure 1 As shown, from top to bottom are the catalytic protective layer (or protective layer), the catalytic layer (or Fe / Pc catalytic layer) and the PTFE membrane. Example

[0073] A NO oxidation catalytic electrode, which differs from Example 1 in that ferrous phthalocyanine (Fe(II)Pc) is replaced by copper phthalocyanine (Cu(II)Pc), and the mass ratio (Cu(II)Pc):Gp=3:97. Example

[0074] A NO oxidation catalytic electrode, which differs from Example 1 in that in step (1), the mass ratio of Fe(II)Pc:Gp is ​​replaced with 5:95.

[0075] A NO oxidation catalytic electrode, which differs from Example 1 in that it does not contain a catalytic protection layer.

[0076] A four-electrode NO electrochemical sensor comprises a working electrode (WE), an auxiliary electrode (AE), a reference electrode (RE) and a counter electrode (CE). The auxiliary electrode is made of the same material as the working electrode, both of which are the NO oxidation catalytic electrode of Example 1. The reference electrode is made of the same material as the counter electrode, both of which are platinum black electrodes.

[0077] A four-electrode NO electrochemical sensor is different from Application Example 1 in that the materials of the auxiliary electrode and the working electrode are replaced with the NO oxidation catalytic electrode of Example 2.

[0078] A four-electrode NO electrochemical sensor is different from Application Example 1 in that the materials of the auxiliary electrode and the working electrode are replaced with the NO oxidation catalytic electrode of Example 3.

[0079] The difference from Application Example 1 is that both the working electrode and the auxiliary electrode are replaced with the NO oxidation catalytic electrode of Comparative Example 1.

[0080] 1. Electrochemical performance: A self-made electrochemical performance test device was used to test the electrochemical performance of the four-electrode NO electrochemical sensor assembled in the above-mentioned application example 1 and the application comparative example 1 by the following method (the structure of the test device is as follows: Figure 2 As shown in the figure): A certain flow of compressed air is introduced into the closed test box for 200-300s, and the current when there is no NO is read. The flow rate of NO standard gas is controlled by adjusting the flow meter, and the target NO gas concentration can be obtained by mixing with compressed air. A NO analyzer is connected to the mixing point to accurately determine the mixed gas concentration. A total of 5 NO gas concentrations are tested: 0, 20, 50, 200, and 500 ppb. In addition, the host terminal reads three currents, namely: I out (total output current of the sensor), I ae (auxiliary electrode output current), I we (working electrode output current), where I out =I we -I ae .

[0081] The test results of the four-electrode NO electrochemical sensor of Application Example 1 are as follows: Figure 3 and Figure 4 As shown, the background current I generated by the working electrode and the auxiliary electrode we ,I ae The sensitivity is 1.9602nA / ppb, which is high, the zero current is 30nA, and the linearity for NO gas 0-500ppb is 0.9996. 90 The time required for the sensor to rise from a reading of 0 to 90% of the gas concentration measured in the environment is 3s, with a fast response speed and good conductivity.

[0082] The test results of the four-electrode NO electrochemical sensor of Application Example 2 are as follows: Figure 5 and Figure 6 As shown, the background current I generated by the working electrode and the auxiliary electrode we ,I ae They are 510nA and 500nA respectively, and the sensitivity is 1.5882nA / ppb. Compared with the background current of Application Example 1, it has increased and the sensitivity has decreased.

[0083] The test results of the four-electrode NO electrochemical sensor of Application Example 3 are as follows: Figure 7 and Figure 8 As shown, the background current I generated by the working electrode and the auxiliary electrode we ,I ae They are 920nA and 860nA respectively, and the sensitivity is 1.5843nA / ppb. Compared with the background current of Application Example 1, it has increased and the sensitivity has decreased.

[0084] From the above, it can be seen that the NO electrochemical sensors prepared in Application Examples 1-3 of the present invention have high sensitivity, wide linear range, short response time, fast response speed and low zero-point current.

[0085] The above electrochemical performance test was repeated using a commercially available ppb-level NO four-electrode sensor (UK City, model MNO-LO) with a surface resistance of 240-300Ω and a permeability of 100-200mL / min. The results are as follows: Fig. 9 and Fig.10 As shown, the background current I generated by the working electrode and the auxiliary electrode we ,I ae The currents are 730nA and 610nA respectively, and both are decreasing slowly, showing an unstable state, but the total output is stable. Through calculation, it can be obtained that its sensitivity is 1.4800nA / ppb, the zero current is 80nA, and the linearity for NO gas 0-500ppb is 0.9988, T 90It can be seen that compared with the four-electrode NO electrochemical sensor provided in Application Example 1 of the present invention, the commercially available ppb-level NO four-electrode sensor not only has a large background current but also has a low sensitivity.

[0086] Depend on Fig.11 and Fig.12 It can be seen that when the NO electrochemical sensor of Comparative Example 1 is used, the background current I generated by the working electrode and the auxiliary electrode we ,I ae The values ​​are 880nA and 870nA respectively, and the sensitivity is 1.9090nA / ppb, indicating that the background current is significantly increased because the working electrode and the auxiliary electrode are not coated with the catalytic protective layer. However, the background current generated by the working electrode and the auxiliary electrode of the present invention is significantly reduced after being treated with the catalytic protective layer, and the sensitivity is not affected.

[0087] Depend on Fig.13 a and Fig.13 b It can be seen that the surface of the electrode prepared in Example 1 is a porous structure. EDS results show that ferrous phthalocyanine has been incorporated into graphite ( Fig.14 ).in Fig.13 In (ab), Selected Area 1 is the selected area, that is, the area within the white box.

[0088] 2. Hydrophilicity of the catalytic protective layer Using a contact angle tester, water drops were dropped on the surfaces of the electrodes prepared in Example 1 and Comparative Example 1 to test the contact angles of the electrode surfaces.

[0089] Depend on Fig.15 and Fig.16 It can be seen that the contact angle of the surface of the electrode prepared in Example 1 (i.e., the catalytic protective layer) is 85°, while the contact angle of the surface of the uncoated electrode in Comparative Example 1 is 125°, indicating that the catalytic protective layer covered on the surface of the electrode of the present invention has good hydrophilicity, which helps to improve the conductivity of the electrode, thereby reducing the background current generated by the electrode without affecting the response speed and response time.

Claims

1. A NO oxidation catalytic electrode, characterized in that: The invention comprises a catalytic layer and a catalytic protective layer. The raw material components of the catalytic layer comprise metal phthalocyanine, graphite and a binder; the raw material components of the catalytic protective layer comprise hydrophilic porous carbon material and perfluorosulfonic acid type polymer.

2. The NO oxidation catalytic electrode according to claim 1, characterized in that: The mass ratio of the metal phthalocyanine to graphite is (10-1): (90-99).

3. The NO oxidation catalytic electrode according to claim 1, characterized in that: The catalytic layer also includes a perfluorosulfonic acid type polymer, and the mass ratio of the total mass of metal phthalocyanine and graphite in the catalytic layer to the perfluorosulfonic acid type polymer is (70-95): (30-5).

4. The NO oxidation catalytic electrode according to claim 1, characterized in that: The mass ratio of the hydrophilic porous carbon material to the perfluorosulfonic acid polymer in the catalytic protection layer is (0.5-3): (0.5-3).

5. The NO oxidation catalytic electrode according to claim 1, characterized in that: The NO oxidation catalytic electrode further includes a carrier, which is arranged in the order of a protective layer, a catalytic layer and a carrier.

6. The method for preparing the NO oxidation catalytic electrode according to any one of claims 1 to 5, characterized in that: The steps include: (1) mixing a metal phthalocyanine solution with graphite to prepare a solution containing a metal phthalocyanine / graphite mixture; Mixing a hydrophilic porous carbon material with a perfluorosulfonic acid type polymer solution to prepare a hydrophilic porous carbon material / perfluorosulfonic acid type polymer slurry; (2) Co-assembling a solution containing a metal phthalocyanine / graphite mixture to obtain a metal phthalocyanine / graphite composite material, mixing the metal phthalocyanine / graphite composite material with a binder, and drying to obtain the catalytic layer; then loading the hydrophilic porous carbon material / perfluorosulfonic acid type polymer slurry on the catalytic layer, and drying to obtain the oxidation catalytic electrode.

7. The preparation method according to claim 6, characterized in that: In step (2), the co-assembly temperature is 70-90° C., and the co-assembly pressure is 0.05-0.1 MPa.

8. Use of the NO oxidation catalytic electrode according to any one of claims 1 to 5 in the field of NO detection.

9. A NO electrochemical sensor, characterized in that: It comprises a working electrode, an auxiliary electrode, a reference electrode and a counter electrode, and the materials of the working electrode and the auxiliary electrode are the NO oxidation catalytic electrode according to any one of claims 1 to 5.

10. A NO detection device, characterized in that: The invention comprises the NO electrochemical sensor as claimed in claim 9.

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