Pt / CMK-3 Nanocomposite for CO Detection Sensor, Its Preparation Method and Application

Abstract

The present invention provides a Pt / CMK-3 nanocomposite for a CO detection sensor, with metallic Pt as the carrier and CMK-3 as the additive loaded on the carrier. Among them, the mass ratio of the CMK-3 additive to the carrier Pt is 1-12:100. The preparation method is to first perform acidification pretreatment on CMK-3 to obtain the pretreated precursor CMK-3, and then load the precursor CMK-3 onto the noble metal Pt by a one-step hydrothermal method to obtain the Pt / CMK-3 nanocomposite. The Pt / CMK-3 nanocomposite of the present invention, as an electrode material for an electrochemical gas sensor, can improve the sensitivity to the target gas CO, shorten the response / recovery time, and can reduce the usage amount of platinum metal and lower the cost.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical gas sensors, and particularly relates to a Pt / CMK-3 nanocomposite material for a CO detection sensor, a preparation method thereof, and an application thereof. Background Art

[0002] With the continuous development of the national economy, the emissions of toxic gases (e.g., CO) have also increased rapidly, making the air pollution problem extremely prominent and attracting wide attention from all sectors of society. The World Health Organization (WHO) once predicted that air pollution is the main cause of premature human death. Such pollutants existing in the air will not only damage agriculture, industry, residential buildings, technical facilities, and historical sites, etc., but also affect human health, especially for those suffering from respiratory and cardiovascular diseases.

[0003] CO is a main component of air pollutants and one of the most harmful gases in the environment. It is colorless, odorless, non-irritating, flammable, and explosive, and is known as the "silent killer"; CO mainly comes from the incomplete combustion of carbon-based fuels used in household appliances, machinery, and heating equipment, etc.; when its concentration reaches a certain value, it is easy to contact with oxygen and explode. In addition, if a human inhales CO, CO will easily combine tightly with hemoglobin that carries oxygen in the blood to form carboxyhemoglobin, causing hemoglobin to lose its oxygen-carrying and other related abilities, resulting in dizziness, confusion, coma, and even death due to the inability to deliver oxygen to body tissues in time. Therefore, achieving accurate and real-time on-line monitoring of the CO concentration can avoid or reduce the harm caused to humans and environmental pollution.

[0004] Electrochemical gas sensors are a type of gas-sensitive sensing element with relatively higher detection accuracy, which can detect gas concentration changes in a timely, on-line, accurate, and continuous manner, and have the advantages of good selectivity, strong stability, high sensitivity, and room-temperature detection, etc., and are widely used in the fields of aerospace, food safety, environmental monitoring, and medical treatment. Its working principle is to utilize the oxidation or reduction reaction of the target gas at the gas-solid-liquid three-phase interface, and convert the chemical signal generated by the reaction into an electrical signal; based on the characteristic that there is a good linear relationship between the magnitude of the electrical signal and the gas concentration, we can achieve accurate and on-line monitoring of the concentration change of the target gas in a specific environment.

[0005] The electrode material used in traditional electrochemical CO gas sensors is generally pure platinum black, with a very high cost; at the same time, there are also problems such as long response / recovery time and low sensitivity in its sensing performance.

[0006] In view of this, it is necessary to develop a new type of electrode material to solve the above existing problems. Summary of the Invention

[0007] The object of the present invention is to provide a Pt / CMK-3 nanocomposite for a CO detection sensor. As an electrode material for an electrochemical gas sensor, it can improve the sensitivity to the target gas CO, shorten the response / recovery time, reduce the amount of platinum metal used, and lower the cost.

[0008] To solve the above problems, the technical solution of the present invention is as follows:

[0009] A Pt / CMK-3 nanocomposite for a CO detection sensor uses metallic Pt as the carrier and CMK-3 as the additive loaded on the carrier. Among them, the mass ratio of the CMK-3 additive to the carrier Pt is 1-12:100.

[0010] The present invention also provides a preparation method for a Pt / CMK-3 nanocomposite for a CO detection sensor, including the following steps:

[0011] Step S1: Place CMK-3 in a mixed solution of concentrated H2SO4 and concentrated HNO3, stir at room temperature for 18-48 h, centrifuge and wash until neutral, and then freeze-dry for 24-72 h to obtain the pretreated precursor CMK-3.

[0012] Step S2: Disperse an appropriate amount of the pretreated precursor CMK-3 in an aqueous solution of H2PtCl6·6H2O, stir and disperse, and then add an appropriate amount of PVP; after the PVP is completely dissolved, add a mixed solution of DMA and DMF, and continue to stir and disperse, where the mass ratio of the precursor CMK-3 to metallic Pt is 1-12:100.

[0013] Step S3: Transfer the solution prepared in Step S2 to a hydrothermal reaction kettle, heat-treat at 150-180 °C for 4-24 h, after the reaction ends and cools to room temperature, centrifuge and wash several times, and then freeze-dry for 24-72 h to obtain the Pt / CMK-3 nanocomposite.

[0014] Further, in Step S2, the volume ratio of the amounts of DMA and DMF used is 0.01-2:10.

[0015] Further, in Step S2, the mass ratio of PVP to metallic Pt is 1-20:1.

[0016] Further, the specific surface area of the Pt / CMK-3 nanocomposite is greater than 42 m 2 / g, the average pore diameter is 5-10 nm, and the average particle size of the material is 2-10 nm.

[0017] The present invention also provides an application of the Pt / CMK-3 nanocomposite in an electrochemical sensor.

[0018] An electrochemical gas sensor includes a working electrode, a counter electrode, and a reference electrode. The working electrode, counter electrode, and reference electrode are gas diffusion electrodes, each including a polytetrafluoroethylene substrate film and a catalyst coating formed on the polytetrafluoroethylene substrate film. The material of the catalyst coating includes the Pt / CMK-3 nanocomposite for the CO detection sensor.

[0019] Further, the thickness of the catalyst coating is 12 - 20 μm.

[0020] Compared with the prior art, the Pt / CMK-3 nanocomposite for the CO detection sensor and its preparation method provided by the present invention have the following beneficial effects:

[0021] First, in the preparation method of the Pt / CMK-3 nanocomposite for the CO detection sensor provided by the present invention, CMK-3 is pretreated first, and then the precursor CMK-3 is doped into the aqueous solution of H2PtCl6·6H2O, and the Pt / CMK-3 nanocomposite is obtained by a one-pot hydrothermal method. The doping of an appropriate amount of CMK-3 can not only further improve the dispersion of platinum black, but also increase the specific surface area, pore volume of platinum black, and the number of active sites on the material surface, effectively improving the gas sensing performance.

[0022] Compared with the pure platinum black electrode material, it not only improves the sensitivity to the target gas CO, shortens the response / recovery time, but also can reduce the usage amount of Pt metal to a certain extent, further reducing the cost.

[0023] Second, the Pt / CMK-3 nanocomposite for the CO detection sensor provided by the present invention is synthesized by a one-step hydrothermal method, and the preparation method has a simple process flow and high reproducibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0025] Figure 1 It is a process flow chart for the preparation of the Pt / CMK-3 nanocomposite;

[0026] Figure 2 It is a schematic structural diagram of the ME-3 gas sensor of the present invention;

[0027] Figure 3 (a) is the SEM image of the self-made pure Pt black material in Example 1; Figure 3(b) SEM image of the Pt / CMK-3 nanocomposite of Example 2;

[0028] Figure 4 XRD patterns of the self-made pure Pt black material of Example 1 and the Pt / CMK-3 nanocomposites of Examples 2 and 3;

[0029] Figure 5 (a) Nitrogen isothermal adsorption-desorption curves of the self-made pure Pt black material of Example 1 and the Pt / CMK-3 nanocomposite of Example 2; Figure 5 (b) Pore size distribution curves of the self-made pure Pt black material of Example 1 and the Pt / CMK-3 nanocomposite of Example 2;

[0030] Figure 6 Dynamic response / recovery curves of the electrochemical gas sensors prepared in Examples 1-6 and Comparative Example 1 of the present invention to 100 ppm CO at room temperature;

[0031] Figure 7 Continuous 5-time response / recovery curves of the electrochemical gas sensor prepared in Example 2 of the present invention to 100 ppm CO at room temperature;

[0032] Figure 8 Continuous dynamic response-recovery curves of the electrochemical gas sensor prepared in Example 2 of the present invention to 5 - 400 ppm CO at room temperature. Detailed Description of the Invention

[0033] In order to enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention and make the above objects, features, and advantages of the present invention more obvious and understandable, the following further describes the specific embodiments of the present invention.

[0034] The endpoints and any values disclosed in this article are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the values between the endpoints of each range, between the endpoints of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this article.

[0035] Please refer to Figure 1 , which is the process flow chart for the preparation of the Pt / CMK-3 nanocomposite. A method for preparing a Pt / CMK-3 nanocomposite includes the following steps:

[0036] Step S1: Place CMK-3 (ordered mesoporous carbon material) in a mixed solution of concentrated H2SO4 and concentrated HNO3, stir at room temperature for 18 - 48 h, centrifuge and wash until neutral, and then freeze-dry for 24 - 72 h to obtain the pretreated precursor CMK-3;

[0037] Among them, the volume ratio of concentrated H2SO4 to concentrated HNO3 is 2 - 4:1, such as 2:1, 3:1 or 4:1, or other values within this range.

[0038] In order to make the surface of CMK-3 carry negatively charged functional groups such as -OH and -COOH, better generate electrostatic interaction with positive-valent Pt ions and regulate the electronic state of Pt, thereby improving the sensing performance. During the pretreatment process of the precursor CMK-3, the stirring duration is 18 - 48 h, which can be 18 h, 24 h, 30 h, 36 h, 42 h or 48 h, or other values within this range.

[0039] And in order to maintain the surface structure of platinum black particles, the drying form of the precursor CMK-3 is freeze-drying, where the freeze-drying duration is 24 - 72 h, which can be 24 h, 30 h, 36 h, 42 h, 48 h, 54 h, 60 h, 66 h or 72 h, or other values within this range.

[0040] Step S2: Disperse an appropriate amount of the pretreated precursor CMK-3 in an aqueous solution of H2PtCl6·6H2O, stir and disperse, and then add an appropriate amount of PVP (polyvinyl pyrrolidone); after PVP is completely dissolved, add a mixed solution of DMA (N,N-dimethylacetamide) and DMF (N,N-dimethylformamide), and continue to stir and disperse, where the mass ratio of the precursor CMK-3 to metallic Pt is 1 - 12:100;

[0041] Among them, the mass ratio of the precursor CMK-3 to metallic Pt is 1 - 12:100; for example, the addition amount of CMK-3 can be 1%, 2%, 4%, 6%, 8%, 10% or 12% of metallic Pt, or other values within this range. Preferably, the mass ratio of the precursor CMK-3 to metallic Pt is 2 - 8:100, such as 2:100, 3:100, 4.5:100, 6:100 or 8:100.

[0042] The role of adding PVP is to enhance the dispersion of platinum particles. PVP is mainly adsorbed on the surface of Pt nanoparticles by forming coordination bonds through the lone pair electrons provided by N and O atoms in its molecular structure with the surface atoms of Pt nanoparticles, leaving the C-H long chains stretching out fully in all directions in the solvent, preventing the mutual aggregation of Pt nanoparticles, and thus playing a dispersing role. If too much PVP is added, it will increase the difficulty of the subsequent centrifugal washing process of Pt particles; if too little PVP is added, the dispersing effect cannot be achieved. Therefore, in the present invention, the mass ratio of PVP to metallic Pt is designed to be 1-20:1. For example, the addition amount of PVP can be 1, 4, 8, 12, 16 or 20 times that of metallic Pt, or other values within this range.

[0043] To reduce Pt ions to elemental Pt, the reducing agent added is a mixed solution of DMA and DMF. Due to the polarization of the carbon-oxygen double bond in the aldehyde group of DMF, the carbon carries a small amount of positive charge, and the carbon-oxygen double bond can attract electrons and be opened to have certain reducibility; in addition, compared with DMF, DMA has the characteristics of strong reducibility, good thermal stability and low toxicity. Therefore, the introduction of DMA helps the reduction of Pt ions. If the content of DMA is too high, it will cause significant changes in the crystal form and sensing performance of Pt nanoparticles. The volume ratio of DMA to DMF can be selected as 0.01-2:10, that is, the volume fraction of DMA can be 0.1%, 1%, 5%, 10%, 15% or 20%, or other values within this range; preferably, the volume ratio of the dosage of DMA to DMF is 0.1-1.25:10, such as 0.1:10, 0.5:10, 1.0:10 or 1.25:10, or other ratios within this range.

[0044] Step S3: Transfer the solution prepared in step S2 to a hydrothermal reaction kettle, heat-treat it at 150-180 °C for 4-24 h. After the reaction ends and cools to room temperature, centrifuge and wash it several times alternately with water and ethanol, and then freeze-dry it for 24-72 h to obtain the Pt / CMK-3 nanocomposite.

[0045] In the present invention, the Pt / CMK-3 nanocomposite is prepared by a one-pot hydrothermal method, where the hydrothermal reaction temperature is 150-180 °C, which can be 150 °C, 160 °C, 170 °C or 180 °C, or other values within this range.

[0046] The hydrothermal treatment time is 4-24 h, which can be 4 h, 8 h, 12 h, 16 h, 20 h or 24 h, or other values within this range.

[0047] To more completely remove the PVP existing on the surface of platinum black, the reacted material needs to be centrifuged and washed several times with water and ethanol, and a mixed solution of acetone-ethanol can also be used when necessary.

[0048] The freeze-drying duration is 24 - 72 h, which can be 24 h, 30 h, 36 h, 42 h, 48 h, 54 h, 60 h, 66 h or 72 h, or other values within this range.

[0049] The specific surface area of the Pt / CMK-3 nanocomposite prepared by the present invention is greater than 42 m 2 / g, the average pore diameter is 5 - 10 nm, and the average particle size of the material is 2 - 10 nm.

[0050] The Pt / CMK-3 nanocomposite of the present invention is applied in CO detection, and its working principle is as follows:

[0051] When the electrochemical CO sensor works, CO diffuses through the gas permeable membrane to the gas-solid-liquid three-phase interface of the working electrode, and undergoes an oxidation reaction to generate CO2 under the catalysis of the catalyst on the electrode. CO2 diffuses through the gas film into the gas phase, and H + diffuses through the liquid film into the electrolyte. At the same time, H + needs to diffuse to the counter electrode and undergo a corresponding electron gain reduction reaction on the counter electrode.

[0052] The sensitivity is the ratio of the response platform current value to the target gas concentration; the response time is the time taken for the response current value to reach 90% of the full-scale value; the recovery time is the time taken for the response current value to recover to 10% of the full-scale value.

[0053] Based on the above-mentioned Pt / CMK-3 nanocomposite, the present invention also provides a gas-sensitive element.

[0054] Please refer to Figure 2 , which is a schematic structural diagram of the electrochemical gas sensor of the present invention. The electrochemical gas sensor of the present invention includes a working electrode 1, a reference electrode 2, a counter electrode 3, a liquid storage chamber 4, an air inlet hole 5, a filter membrane 6, and an electrolyte 7. The working electrode 1, the reference electrode 2, and the counter electrode 3 are respectively connected to the corresponding pins. Among them, the working electrode is the place for providing the oxidation reaction, the reference electrode is used to maintain the potential stability between the working electrode and the reference electrode, and the counter electrode is the place for providing the reduction reaction; the air inlet hole provides an air inlet channel for the target gas; the function of the filter membrane is to filter interfering gases and dust and improve the cross-selectivity of the sensor; the electrolyte is used to maintain the progress of the electrolytic reaction and effectively transfer ionic charges to the electrodes.

[0055] The structure of the sensor is the same as the prior art. The difference is that the working electrode, the counter electrode, and the reference electrode of the present invention are gas diffusion electrodes, which respectively include a polytetrafluoroethylene base film and a catalyst coating formed on the polytetrafluoroethylene base film. The material of the catalyst coating includes the above-mentioned Pt / CMK-3 nanocomposite.

[0056] Specifically, the electrochemical gas sensor of the present invention is a three-electrode sensor based on MEMS technology (abbreviated as ME-3), and its assembly process includes the following steps:

[0057] 1. Mix the Pt / CMK-3 nanocomposite with a solvent (including a binder, a surfactant, and water), and spray the electrode paste on a polytetrafluoroethylene substrate film with an airbrush to form a catalyst layer, and the coating thickness of the catalyst layer is 12-20 μm;

[0058] Among them, the binder can be one or more of PTFE emulsion, styrene-butadiene rubber emulsion, methyl cellulose, carboxymethyl cellulose, and polyvinyl alcohol;

[0059] The surfactant can be one or more of polysorbate-20, lauryl polyoxyethylene ether, Triton X-100, and perfluoroalkyl carboxylate sodium;

[0060] 2. Further dry (50 °C) and sinter (250 °C) the sprayed electrode to obtain a gas diffusion electrode;

[0061] 3. Assemble the internal components of the sensor, and then perform liquid injection and aging treatment.

[0062] The following elaborates in detail on the Pt / CMK-3 nanocomposite provided by the present invention and its application in CO detection through specific examples.

[0063] Example 1

[0064] Synthesize a pure Pt black electrode material by a one-pot hydrothermal method to fabricate a gas diffusion electrode and a sensor. The specific process is as follows:

[0065] (1) Take 25 ml of an aqueous solution of H2PtCl6·6H2O (0.0193 M) in a 100 ml beaker, add 0.5 g of PVP, and after the PVP is completely dissolved, add 20.5 ml of a mixed solution of DMA and DMF (where the volume ratio of DMA to DMF is 0.5:20), and stir for 1 h;

[0066] (2) Transfer the solution prepared in step (1) to a hydrothermal reaction kettle, react at 160 °C for 8 h, then cool to room temperature, wash alternately by centrifugation with water and ethanol several times, and then perform freeze-drying for 36 h to obtain a pure Pt black electrode material;

[0067] (3) Mix the pure Pt black electrode material with a binder, a surfactant, and water in a certain mass ratio, and spray the electrode paste on a polytetrafluoroethylene substrate film with an airbrush to form a catalyst layer, and the coating thickness of the catalyst layer is 15 μm;

[0068] Among them, the binder is methyl cellulose, and the surfactant is Triton.

[0069] In addition, the mass ratio of methylcellulose, Triton, and water is 1:4:260.

[0070] (4) Dry and sinter the sprayed electrode to obtain a gas diffusion electrode;

[0071] (5) Load the internal components of the sensor in sequence. Ensure good contact between the gas diffusion electrode and the wire. Then slowly inject 350 μl of electrolyte into the sensor through the injection hole, and finally age for three days.

[0072] Example 2

[0073] Use the Pt / CMK-3 nanocomposite material to fabricate a gas diffusion electrode and a sensor. The preparation process is as follows:

[0074] (1) First, place 0.3 g of CMK-3 in a mixed solution of 40 ml of concentrated H2SO4 and concentrated HNO3 (where the volume ratio of concentrated H2SO4 to concentrated HNO3 is 3:1). Stir at room temperature for 24 h, wash with water by centrifugation until neutral, and then freeze-dry for 36 h to obtain the pretreated precursor CMK-3;

[0075] (2) Disperse 3 mg of the precursor CMK-3 in 25 ml of an aqueous solution of H2PtCl6·6H2O (0.0193 M), stir and disperse for 4 h, then add 0.5 g of PVP. After PVP is completely dissolved, add 20.5 ml of a mixed solution of DMA and DMF (where the volume ratio of DMA to DMF is 0.5:20), and continue to stir for 1 h;

[0076] (3) Transfer the solution prepared in step (2) to a hydrothermal reaction kettle, react at 160 °C for 8 h, then cool to room temperature, wash with water and ethanol alternately by centrifugation several times, and then perform freeze-drying for 36 h to obtain the Pt / CMK-3 nanocomposite material;

[0077] (4) Mix the Pt / CMK-3 nanocomposite material with a binder, a surfactant, and water in a certain mass ratio, and spray the electrode paste on a polytetrafluoroethylene substrate film with an airbrush to form a catalyst layer. The coating thickness of the catalyst layer is 15 μm;

[0078] Among them, the binder is methylcellulose, and the surfactant is Triton.

[0079] In addition, the mass ratio of methylcellulose, Triton, and water is 1:4:260.

[0080] (5) Dry and sinter the sprayed electrode to obtain a gas diffusion electrode;

[0081] (6) Load the internal components of the sensor in sequence. Ensure good contact between the gas diffusion electrode and the wire. Then, slowly inject 350 μl of electrolyte into the sensor through the injection hole. Finally, age for three days.

[0082] Example 3

[0083] Fabricate the gas diffusion electrode and the sensor using the Pt / CMK-3 nanocomposite. The preparation process is as follows:

[0084] (1) First, place 0.3 g of CMK-3 in a mixed solution of 40 ml of concentrated H2SO4 and concentrated HNO3 (where the volume ratio of concentrated H2SO4 to concentrated HNO3 is 3:1). Stir at room temperature for 24 h, wash by centrifugation with water until neutral, and then freeze-dry for 36 h to obtain the pretreated precursor CMK-3.

[0085] (2) Disperse 3 mg of the precursor CMK-3 in 25 ml of an aqueous solution of H2PtCl6·6H2O (0.0193 M), stir for 4 h, add 0.5 g of PVP, and after PVP is completely dissolved, add 21.5 ml of a mixed solution of DMA and DMF (where the volume ratio of DMA to DMF is 1.5:20), and continue to stir for 1 h.

[0086] (3) Transfer the solution prepared in step (2) to a hydrothermal reaction kettle, react at 160 °C for 8 h, then cool to room temperature, wash by centrifugation with water and ethanol alternately several times, and then freeze-dry for 36 h to obtain the Pt / CMK-3 nanocomposite.

[0087] (4) Mix the Pt / CMK-3 nanocomposite with a binder, a surfactant, and water in a certain mass ratio, and spray the electrode paste on a polytetrafluoroethylene substrate film using an airbrush to form a catalyst layer. The coating thickness of the catalyst layer is 15 μm.

[0088] Among them, the binder is methyl cellulose, and the surfactant is Triton.

[0089] In addition, the mass ratio of methyl cellulose, Triton, and water is 1:4:260.

[0090] (5) Dry and sinter the sprayed electrode to obtain the gas diffusion electrode.

[0091] (6) Load the internal components of the sensor in sequence. Ensure good contact between the gas diffusion electrode and the wire. Then, slowly inject 350 μl of electrolyte into the sensor through the injection hole. Finally, age for three days.

[0092] Example 4

[0093] A gas diffusion electrode and a sensor are fabricated using a Pt / CMK-3 nanocomposite, and the preparation process is as follows:

[0094] (1) First, 0.3 g of CMK-3 is placed in a mixed solution of 40 ml of concentrated H2SO4 and concentrated HNO3 (where the volume ratio of concentrated H2SO4 to concentrated HNO3 is 3:1), stirred at room temperature for 24 h, centrifugally washed with water until neutral, and then freeze-dried for 36 h to obtain the pretreated precursor CMK-3;

[0095] (2) 3 mg of the precursor CMK-3 is dispersed in 25 ml of an aqueous solution of H2PtCl6·6H2O (0.0193 M), stirred for 4 h, then 0.5 g of PVP is added. After the PVP is completely dissolved, 22.5 ml of a mixed solution of DMA and DMF (where the volume ratio of DMA to DMF is 2.5:20) is added, and stirring is continued for 1 h;

[0096] (3) The solution prepared in step (2) is transferred to a hydrothermal reaction kettle, reacted at 160 °C for 8 h, then cooled to room temperature, centrifugally washed several times with water and ethanol alternately, and then freeze-dried for 36 h to obtain the Pt / CMK-3 nanocomposite;

[0097] (4) The Pt / CMK-3 nanocomposite is mixed with a binder, a surfactant, and water in a certain mass ratio, and the electrode paste is sprayed onto a polytetrafluoroethylene substrate film using an airbrush to form a catalyst layer, and the coating thickness of the catalyst layer is 15 μm;

[0098] Among them, the binder is methylcellulose, and the surfactant is Triton.

[0099] In addition, the mass ratio of methylcellulose, Triton, and water is 1:4:260.

[0100] (5) The sprayed electrode is dried and sintered to obtain a gas diffusion electrode;

[0101] (6) The internal components of the sensor are filled in sequence. The gas diffusion electrode and the wire need to be in good contact. Then, 350 μl of electrolyte is slowly injected into the sensor through the injection hole, and finally aged for three days.

[0102] Example 5

[0103] A gas diffusion electrode and a sensor are fabricated using a Pt / CMK-3 nanocomposite, and the preparation process is as follows:

[0104] (1) First, place 0.3 g of CMK-3 in a mixed solution of 40 ml of concentrated H2SO4 and concentrated HNO3 (where the volume ratio of concentrated H2SO4 to concentrated HNO3 is 3:1), stir at room temperature for 24 h, wash by centrifugation with water until neutral, and then freeze-dry for 36 h to obtain the pretreated precursor CMK-3;

[0105] (2) Disperse 4.5 mg of the precursor CMK-3 in 25 ml of an aqueous solution of H2PtCl6·6H2O (0.0193 M), stir and disperse for 4 h, then add 0.5 g of PVP. After the PVP is completely dissolved, add 20.5 ml of a mixed solution of DMA and DMF (where the volume ratio of DMA to DMF is 0.5:20), and continue to stir for 1 h;

[0106] (3) Transfer the solution prepared in step (2) to a hydrothermal reaction kettle, react at 160 °C for 8 h, then cool to room temperature, wash by centrifugation with water and ethanol alternately several times, and then freeze-dry for 36 h to obtain the Pt / CMK-3 nanocomposite;

[0107] (4) Mix the Pt / CMK-3 nanocomposite with a binder, a surfactant, and water in a certain mass ratio, and spray the electrode paste on a polytetrafluoroethylene substrate film with an airbrush to form a catalyst layer, and the coating thickness of the catalyst layer is 15 μm;

[0108] Among them, the binder is methyl cellulose, and the surfactant is Triton.

[0109] In addition, the mass ratio of methyl cellulose, Triton, and water is 1:4:260.

[0110] (5) Dry and sinter the sprayed electrode to obtain a gas diffusion electrode.

[0111] (6) Fill the internal components of the sensor in sequence, ensure good contact between the gas diffusion electrode and the wire, then slowly inject 350 μl of electrolyte into the sensor through the injection hole, and finally age for three days.

[0112] Example 6

[0113] Fabricate a gas diffusion electrode and a sensor using the Pt / CMK-3 nanocomposite, and the preparation process is as follows:

[0114] (1) First, place 0.3 g of CMK-3 in a mixed solution of 40 ml of concentrated H2SO4 and concentrated HNO3 (where the volume ratio of concentrated H2SO4 to concentrated HNO3 is 3:1), stir at room temperature for 24 h, wash by centrifugation with water until neutral, and then freeze-dry for 36 h to obtain the pretreated precursor CMK-3;

[0115] (2) Disperse 6 mg of the precursor CMK-3 in 25 ml of an aqueous solution of H2PtCl6·6H2O (0.0193 M), stir and disperse for 4 h, then add 0.5 g of PVP. After the PVP is completely dissolved, add 20.5 ml of a mixed solution of DMA and DMF (where the volume ratio of DMA to DMF is 0.5:20), and continue stirring for 1 h;

[0116] (3) Transfer the solution prepared in step (2) to a hydrothermal reactor, react at 160 °C for 8 h, then cool to room temperature, wash it several times by centrifugation with water and ethanol alternately, and then perform freeze-drying for 36 h to obtain the Pt / CMK-3 nanocomposite;

[0117] (4) Mix the Pt / CMK-3 nanocomposite with a binder, a surfactant, and water in a certain mass ratio, and spray the electrode paste on a polytetrafluoroethylene substrate film with an airbrush to form a catalyst layer, and the coating thickness of the catalyst layer is 15 μm;

[0118] Among them, the binder is methyl cellulose, and the surfactant is Triton.

[0119] In addition, the mass ratio of methyl cellulose, Triton, and water is 1:4:260.

[0120] (5) Dry and sinter the sprayed electrode to obtain a gas diffusion electrode.

[0121] (6) Fill the internal fittings of the sensor in sequence. The gas diffusion electrode and the wire need to be in good contact. Then, slowly inject 350 μl of the electrolyte into the sensor through the injection hole, and finally age for three days.

[0122] Comparative Example 1

[0123] Use a commercial pure platinum black electrode material to make a gas diffusion electrode and a sensor. The specific preparation process is as follows:

[0124] The manufacturing steps of filling the gas diffusion electrode and the sensor are the same as those in steps (4)-(6) of Example 1, and will not be elaborated here.

[0125] Test the performance of the electrode materials of Example 1 and Comparative Example 1, as well as the ME-3 electrochemical gas sensor made of the Pt / CMK-3 electrode material.

[0126] Please refer to Figure 3 , Figure 3 (a) is the SEM image of the self-made pure platinum black material in Example 1; Figure (b) is the SEM image of the Pt / CMK-3 nanocomposite in Example 2. From Figure 3(a) It can be seen that the pure Pt black powder is composed of nanoparticles with relatively uniform particle sizes; from Fig. (b), it can be seen that the introduction of an appropriate amount of CMK-3 can disperse the Pt particles to a certain extent.

[0127] Please refer to Figure 4 , for the XRD patterns of the self-made pure Pt black material in Example 1 and the Pt / CMK-3 nanocomposites in Examples 2 and 3. As Figure 4 can be seen, the diffraction peak positions of the pure Pt black material and the Pt / CMK-3 nanocomposites correspond to the diffraction peak positions of the Pt standard card (PDF#04-0802) with a face-centered cubic structure. However, the presence of CMK-3 material was not detected in the Pt / CMK-3 nanocomposites, because the doping amount of CMK-3 was less or the dispersion of CMK-3 in platinum black was better; Example 2 shows that the introduction of a small amount of CMK-3 did not affect the intensity of the diffraction peaks of pure platinum black, and the crystal form did not change significantly; but in Example 3, due to the increase in the amount of DMA added, obvious changes occurred in the crystal form and diffraction peak intensity of Pt; in addition, the grain sizes of Pt in Examples 1, 2, and 3 were calculated by the Scherrer formula to be 4.2 nm, 4.4 nm, and 4.1 nm, respectively.

[0128] Please refer to Figure 5 , Figure 5 (a) is the nitrogen isothermal adsorption and desorption curve of the self-made pure Pt black material in Example 1 and the Pt / CMK-3 nanocomposite in Example 2; Figure 5 (b) is the pore size distribution diagram of the self-made pure Pt black material in Example 1 and the Pt / CMK-3 nanocomposite in Example 2. As Figure 5 (a) can be seen, the introduction of CMK-3 increases the specific surface area and pore volume of the Pt black material; as Figure 5 (b) can be seen, the doping of CMK-3 will reduce the pore size of pure platinum black, but it is still a mesoporous material.

[0129] Please refer to Figure 6 , for the dynamic response / recovery curves of the electrochemical gas sensors prepared in Examples 1-6 and Comparative Example 1 of the present invention at room temperature to 100 ppm CO, where T 90 , F 90 The response / recovery time values from top to bottom represent Comparative Example 1, Examples 1-6 in turn. As Figure 6It can be seen that Example 1 and Comparative Example 1 have similar sensing performances; doping with an appropriate amount of CMK-3 (i.e., Example 2) can exhibit better gas sensing performance compared to Example 1 and Comparative Example 1; there are significant differences in the sensing performances between Example 2 and Examples 3 and 4, indicating that excessive addition of DMA will reduce the sensing performance: if the doping amount of CMK-3 is excessive (i.e., Example 6), the number of active sites of the Pt / CMK-3 nanocomposite at the gas-solid-liquid three-phase interface will decrease, resulting in poor sensing performance. The electrochemical gas sensor prepared in Example 2 has the highest response current value and the shortest response / recovery time, and its sensing performance is the best.

[0130] Therefore, in the present invention, the volume ratio of the amounts of DMA and DMF is further optimized and designed to be 0.1 - 1.25:10; the mass ratio of the precursor CMK-3 to metal Pt is optimized and designed to be 2 - 8:100.

[0131] Please refer to Figure 7 , which is the continuous 5 - time response / recovery curve of the electrochemical gas sensor prepared in Example 2 of the present invention to 100 ppm CO at room temperature. From Figure 7 It can be seen that the repeatability of the electrochemical gas sensor prepared in Example 2 is very good.

[0132] Please refer to Figure 8 , which is the continuous dynamic response-recovery curve of the electrochemical gas sensor prepared in Example 2 of the present invention to 5 - 400 ppm CO at room temperature. From Figure 8 It can be seen that the response current value of the electrochemical gas sensor prepared in Example 2 increases with the increase of the target gas concentration, and there is a good linear relationship between the response current value and the concentration.

[0133] Compared with the prior art, the Pt / CMK-3 nanocomposite for a CO detection sensor, its preparation method and application provided by the present invention have the following beneficial effects:

[0134] (1) The preparation method of the Pt / CMK-3 nanocomposite provided by the present invention uses metal Pt as the carrier and CMK-3 as the additive, which changes the characteristic of the conventional preparation method that only noble metal Pt is used as the active component in the past, reduces the usage amount of metal Pt, and can significantly reduce the production cost.

[0135] (2) The Pt / CMK-3 nanocomposite provided by the present invention first performs acid pretreatment on CMK-3 to obtain the pretreated precursor CMK-3, and then loads the precursor CMK-3 onto the noble metal Pt through a one-step hydrothermal method to obtain the Pt / CMK-3 nanocomposite. The doping of an appropriate amount of CMK-3 not only improves the dispersion of Pt nanoparticles, but also increases the specific surface area, pore volume, and the number of defects and active sites on the surface of the Pt nanomaterial, thereby improving its gas-sensing performance towards CO. Compared with the existing pure Pt black electrode material, the Pt / CMK-3 nanocomposite provided by the present invention has a significantly improved detection sensitivity towards CO, shows a shorter response / recovery time, and has good gas-sensing performance.

[0136] (3) In terms of the preparation process, the Pt / CMK-3 nanocomposite provided by the present invention is synthesized by a one-step hydrothermal method, and the preparation method has a simple process flow and high reproducibility.

[0137] The above has made a detailed description of the embodiments of the present invention, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations made to these embodiments without departing from the principle and spirit of the present invention still fall within the protection scope of the present invention.

Claims

1. A Pt / CMK-3 nanocomposite for a CO detection sensor, characterized in that, Using metallic Pt as the carrier and CMK-3 as the additive loaded on the carrier, wherein the mass ratio of the CMK-3 additive to the carrier Pt is 2-8:100; The Pt / CMK-3 nanocomposite for the CO detection sensor is prepared by the following method: Step S1: Place CMK-3 in a mixed solution of concentrated H2SO4 and concentrated HNO3, stir at room temperature for 18-48 h, centrifuge and wash until neutral, and then freeze-dry for 24-72 h to obtain the pretreated precursor CMK-3; Step S2: Disperse an appropriate amount of the pretreated precursor CMK-3 in an aqueous solution of H2PtCl6·6H2O, add an appropriate amount of PVP after stirring and dispersing; after the PVP is completely dissolved, add a mixed solution of DMA and DMF, and continue to stir and disperse, wherein the mass ratio of the precursor CMK-3 to metallic Pt is 2-8:100, and the volume ratio of the amounts of DMA and DMF used is 0.1-1.25:10; Step S3: Transfer the solution prepared in Step S2 to a hydrothermal reaction kettle, heat-treat at 150-180 °C for 4-24 h, after the reaction ends and cools to room temperature, centrifuge and wash several times, and then freeze-dry for 24-72 h to obtain the Pt / CMK-3 nanocomposite; The specific surface area of the Pt / CMK-3 nanocomposite is greater than 42 m 2 / g, the average pore diameter is 5-10 nm, and the average particle size of the material is 2-10 nm.

2. A preparation method of a Pt / CMK-3 nanocomposite for a CO detection sensor, characterized in that, Comprising the following steps: Step S1: Place CMK-3 in a mixed solution of concentrated H2SO4 and concentrated HNO3, stir at room temperature for 18-48 h, centrifuge and wash until neutral, and then freeze-dry for 24-72 h to obtain the pretreated precursor CMK-3; Step S2: Disperse an appropriate amount of the pretreated precursor CMK-3 in an aqueous solution of H2PtCl6·6H2O, add an appropriate amount of PVP after stirring and dispersing; after the PVP is completely dissolved, add a mixed solution of DMA and DMF, and continue to stir and disperse, wherein the mass ratio of the precursor CMK-3 to metallic Pt is 2-8:100, and the volume ratio of the amounts of DMA and DMF used is 0.1-1.25:10; Step S3: Transfer the solution prepared in Step S2 to a hydrothermal reaction kettle, heat-treat at 150-180 °C for 4-24 h, after the reaction ends and cools to room temperature, centrifuge and wash several times, and then freeze-dry for 24-72 h to obtain the Pt / CMK-3 nanocomposite; The specific surface area of the Pt / CMK-3 nanocomposite is greater than 42 m 2 / g, the average pore diameter is 5-10 nm, and the average particle size of the material is 2-10 nm.

3. The preparation method of the Pt / CMK-3 nanocomposite material for a CO detection sensor according to claim 2, characterized in that, In Step S2, the mass ratio of PVP to metallic Pt is 1-20:

1.

4. An electrochemical gas sensor, characterized in that, Comprising a working electrode, a counter electrode and a reference electrode, wherein the working electrode, the counter electrode and the reference electrode are gas diffusion electrodes, each comprising a polytetrafluoroethylene substrate film and a catalyst coating formed on the polytetrafluoroethylene substrate film, and the material of the catalyst coating comprises the Pt / CMK-3 nanocomposite for the CO detection sensor described in Claim 1.

5. The electrochemical gas sensor according to claim 4, characterized in that, The thickness of the catalyst coating is 12-20 μm.

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