Ultra-sensitive aerogel type hydrogen sensor material and preparation method thereof

Abstract

The invention discloses an ultra-sensitive aerogel type hydrogen sensor material and a preparation method thereof, and relates to the technical field of gas sensors. A preparation method of an ultra-sensitive aerogel type hydrogen sensor material comprises the following steps: S1, reducing divalent palladium ions in a solution into palladium atoms to prepare a palladium precursor solution; s2, mixing the palladium precursor solution with a divalent zinc ion precursor and a trivalent indium ion precursor, adding a template agent and a coagulant, and carrying out sol reaction to form palladium modified zinc oxide / indium oxide composite sol; s3, the obtained sol is subjected to standing forming, and gel is obtained; s4, performing aging and solvent replacement treatment on the gel, and further performing supercritical carbon dioxide drying to obtain an aerogel material; s5, the palladium modified zinc oxide / indium oxide aerogel material is subjected to high-temperature annealing, the structure has a large specific surface area and rich active sites, hydrogen molecules can be effectively adsorbed, and the response speed and sensitivity of the sensor to hydrogen are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of gas sensors, in particular to an ultra-sensitive aerogel-type hydrogen sensor material and a preparation method thereof. Background Art

[0002] Hydrogen is a colorless, tasteless, and odorless flammable gas. When exposed to fire, it explodes when the concentration of hydrogen in air is between 4% and 75%. Hydrogen has very low ignition energy: a 23 vol% hydrogen-air mixture (0.0017 mJ) has only one-tenth the ignition energy of other gasoline-air mixtures. Furthermore, as the smallest and lightest molecule, hydrogen is highly permeable to many materials. This makes hydrogen transportation and use highly prone to accidents.

[0003] Metal oxide semiconductors (MOS) are widely used as sensitive materials for gas sensors due to their excellent stability, low cost, simple preparation process, and ease of integration. They demonstrate enormous market potential. However, these sensors still face numerous challenges in practical applications, including slow device response and poor long-term stability, representing limitations.

[0004] The reason for this problem is that hydrogen's extremely high permeability allows it to diffuse rapidly into metal oxide semiconductor materials, but this rapid diffusion disrupts the material's original microstructure to a certain extent. Metal oxide semiconductor materials rely on their specific crystal structure and surface active sites to adsorb and react with gas molecules, thereby enabling hydrogen detection. The large-scale infiltration of hydrogen molecules changes the electronic structure and chemical composition of the material's surface, resulting in a reduction or inactivation of active sites, reducing the sensor's hydrogen adsorption efficiency and thus affecting its response speed. Therefore, we propose an ultrasensitive aerogel-based hydrogen sensor material and its preparation method to address this issue. Summary of the Invention

[0005] In response to the shortcomings of the existing technology, the present invention provides an ultra-sensitive aerogel-type hydrogen sensor material and a preparation method thereof, which solves the problem that the existing gas sensors use metal oxides as gas-sensitive materials, but the metal oxides have slow response speeds and poor long-term stability, which are limited.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions: an ultra-sensitive aerogel-type hydrogen sensor material and a preparation method thereof, comprising the following steps:

[0007] S1. Prepare a mother solution by adding 8 drops of 6 mol / L hydrochloric acid solution to a beaker, then adding 0.053 g of palladium chloride, letting it stand for 10 minutes to dissolve, then adding 15 mL of a reducing agent and ultrasonically dispersing it for 30 minutes to obtain a palladium precursor solution;

[0008] S2, composite sol preparation, adding 5 mL of deionized water to the palladium precursor solution and stirring and mixing;

[0009] After mixing, add 0.099g of indium trichloride and 4g of zinc chloride respectively, and continue stirring for 20min;

[0010] Add 4 mL of template into the beaker and continue stirring for 20 min;

[0011] Take 2mL of coagulant and add it to the beaker, stir for 3min to mix the solution evenly;

[0012] S3, sol forming, slowly pouring the mixed solution into a mold to obtain palladium-modified zinc oxide and indium oxide sol, and letting it stand to solidify to form a composite sol;

[0013] S4, static solidification, the palladium-modified zinc oxide and indium oxide sol are allowed to stand to form a gel;

[0014] S5, aerogel preparation, aging the gel and performing solvent replacement treatment, followed by drying, taking out the gel after aging, and then replacing it with anhydrous ethanol, and drying the gel with supercritical carbon dioxide to obtain aerogel;

[0015] S6, calcination and forming, high-temperature annealing of the aerogel, placing the aerogel in a tubular furnace for calcination, gradually increasing the temperature from room temperature to 500° C., and calcining at this temperature for 3 hours, and finally cooling naturally.

[0016] Preferably, the divalent palladium ions in step S1 are derived from chloropalladic acid generated by dissolving palladium chloride in a hydrochloric acid solution, and the reducing agent used in step S1 is ethanol.

[0017] Preferably, in step S2, the divalent zinc ion precursor is a zinc-containing inorganic salt, and the trivalent indium ion precursor is an indium-containing inorganic salt. The molar ratio of the sol palladium to zinc in step 2 is 1%-3%, and the molar ratio of indium to zinc is 15%. In step 2, the stirring device inside the beaker is a magnetic stirrer, and the stirring conditions of the palladium precursor solution and deionized water are continuous stirring at a speed of 600 rpm for 5 minutes at room temperature.

[0018] Preferably, the template agent in step S2 is polyacrylic acid, and the coagulant is propylene oxide.

[0019] Preferably, the time it takes for the sol to be formed into gel by static standing in step S3 is 30 minutes to 1 hour.

[0020] Preferably, the aging time in step S4 is 12 hours to 24 hours.

[0021] Preferably, the solvent replacement in step S4 is performed using anhydrous ethanol, each time for more than 12 hours, and repeated 7 to 8 times.

[0022] Preferably, the supercritical carbon dioxide drying process of the solvent in step S4 is carried out at a temperature of 40 to 45° C. and a pressure of 8 to 12 MPa, and the drying time is 8 to 24 hours.

[0023] Preferably, the calcination atmosphere in step S5 is air, and the heating rate during the calcination process is set to 1°C / min.

[0024] Preferably, the material is obtained by the preparation method described in claims 1-9, wherein palladium is uniformly dispersed in the zinc oxide / indium oxide aerogel network in a nanometer state, and can achieve high-sensitivity detection of hydrogen under low temperature conditions.

[0025] The present invention discloses an ultra-sensitive aerogel-type hydrogen sensor material and a preparation method thereof, which has the following beneficial effects:

[0026] 1. The device utilizes a unique fabrication process to uniformly disperse palladium in a nanostructured state within a zinc oxide / indium oxide aerogel network. This structure, with its large surface area and abundant active sites, effectively adsorbs hydrogen molecules, improving the sensor's response speed and sensitivity to hydrogen.

[0027] 2. The aerogel's three-dimensional network structure has excellent stability, which can resist the damage of hydrogen molecular diffusion to the material structure, ensuring the long-term stability of the sensor. In addition, the material can achieve highly sensitive hydrogen detection under low temperature conditions, broadening the application range of hydrogen sensors and reducing their use costs, which has practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 This is a schematic diagram of the preparation process of the present invention;

[0030] Figure 2 Response curve of the palladium-modified zinc oxide / indium oxide aerogel prepared in Example 3 to a hydrogen concentration of 100-200 ppm at 175° C.;

[0031] Figure 3Response curve of the palladium-modified zinc oxide / indium oxide aerogel prepared in Example 3 to a hydrogen concentration of 200-1000 ppm at 175° C.;

[0032] Figure 4 This is a scanning electron microscope characterization image of the palladium-modified zinc oxide / indium oxide aerogel material prepared in the present invention. DETAILED DESCRIPTION

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0034] The embodiments of the present application provide an ultra-sensitive aerogel-type hydrogen sensor material and a preparation method thereof, thereby solving the problem that existing gas sensors use metal oxides as gas-sensitive materials, but the metal oxides have slow response speeds and poor long-term stability, which are limited.

[0035] In order to better understand the above technical solution, the above technical solution will be described in detail below with reference to the accompanying drawings and specific implementation methods.

[0036] The present invention discloses an ultra-sensitive aerogel type hydrogen sensor material and a preparation method thereof. Figure 1-2 As shown;

[0037] Example 1: comprising the following steps:

[0038] S1. Prepare a mother solution by adding 8 drops of 6 mol / L hydrochloric acid solution to a beaker, then adding 0.053 g of palladium chloride, letting it stand for 10 minutes to dissolve, then adding 15 mL of a reducing agent and ultrasonically dispersing it for 30 minutes to obtain a palladium precursor solution;

[0039] S2, composite sol preparation, adding 5 mL of deionized water to the palladium precursor solution and stirring and mixing;

[0040] After mixing, add 0.099g of indium trichloride and 4g of zinc chloride respectively, and continue stirring for 20min;

[0041] Add 4 mL of template into the beaker and continue stirring for 20 min;

[0042] Take 2mL of coagulant and add it to the beaker, stir for 3min to mix the solution evenly;

[0043] S3, sol forming, slowly pouring the mixed solution into a mold to obtain palladium-modified zinc oxide and indium oxide sol, and letting it stand to solidify to form a composite sol;

[0044] S4, static solidification, the palladium-modified zinc oxide and indium oxide sol are allowed to stand to form a gel;

[0045] S5, aerogel preparation, aging the gel and performing solvent replacement treatment, followed by drying, taking out the gel after aging, and then replacing it with anhydrous ethanol, and drying the gel with supercritical carbon dioxide to obtain aerogel;

[0046] S6, calcination and forming, high-temperature annealing of the aerogel, placing the aerogel in a tubular furnace for calcination, gradually increasing the temperature from room temperature to 500° C., and calcining at this temperature for 3 hours, and finally cooling naturally.

[0047] The divalent palladium ions in step S1 are derived from chloropalladic acid generated by dissolving palladium chloride in a hydrochloric acid solution. The reducing agent used in step S1 is ethanol. The divalent zinc ion precursor in step S2 is a zinc-containing inorganic salt, and the trivalent indium ion precursor is an indium-containing inorganic salt. The molar ratio of palladium to zinc in the sol in step 2 is 1%, and the molar ratio of indium to zinc is 15%. In step 2, the stirring device inside the beaker is a magnetic stirrer. The stirring conditions of the palladium precursor solution and deionized water are: stirring at a speed of 600 rpm for 5 minutes at room temperature. The template in step S2 is polyacrylic acid, and the coagulant is propylene oxide. In step S3, the sol is allowed to stand and form into a gel. The time is 30 minutes to 1 hour, the aging time of step S4 is 12 hours to 24 hours, the solvent replacement in step S4 is carried out using anhydrous ethanol, each time for more than 12 hours, and repeated 7 to 8 times, the solvent supercritical carbon dioxide drying process in step S4 is carried out under the conditions of a temperature of 40 to 45°C and a pressure of 8 to 12 MPa, and the drying time is 8 to 24 hours, the calcination atmosphere in step S5 is air, and the heating rate is set to 1°C / min during the calcination process. The material is obtained by the preparation method of claims 1 to 9, the palladium in the material is uniformly dispersed in the zinc oxide / indium oxide aerogel network in a nano state, and can achieve high-sensitivity detection of hydrogen under low temperature conditions.

[0048] In addition to the above preparation method, the second preparation method is as follows:

[0049] S1. Add 8 drops of 6 mol / L hydrochloric acid solution to a beaker, then add 0.0106 g of palladium chloride and let it stand for 10 minutes to dissolve. Then, add 15 mL of anhydrous ethanol to the beaker and ultrasonically disperse for 30 minutes to obtain a palladium precursor solution.

[0050] S2. Add 5 mL of deionized water to the palladium precursor solution. Place the beaker on a magnetic stirrer and stir at 600 rpm for 5 minutes at room temperature to ensure that the solution is initially mixed.

[0051] After the solution is evenly mixed, continue to weigh 0.099g of indium trichloride and 4g of zinc chloride and add them separately, and continue stirring for 20 minutes. Add 4mL of polyacrylic acid to the above system and continue stirring for 20 minutes under the same conditions. Continue to use a rubber-tipped dropper to measure 2mL of propylene oxide and add it to the system, stir for 3 minutes to mix the solution evenly. Slowly pour the evenly mixed solution into the mold to obtain palladium-modified zinc oxide / indium oxide sol, and let it stand to set. The molar ratio of palladium to zinc in the sol is 2%, and the molar ratio of indium to zinc is 15%

[0052] S3. The palladium-modified zinc oxide / indium oxide sol turns into gel after standing for 30 minutes.

[0053] S4. After aging for 24 hours, the gel can be removed from the mold and replaced with anhydrous ethanol for 12 hours each time, repeating this step 7 times. The gel is then dried with supercritical carbon dioxide at a temperature of 45°C and a pressure of 12 MPa for 24 hours.

[0054] S5. The palladium-modified zinc oxide / indium oxide aerogels were placed in a tubular furnace for calcination. The calcination atmosphere was air. During the calcination process, the heating rate was set at 1°C / min, and the temperature was gradually increased from room temperature to 500°C. The aerogels were kept at this temperature for 3 hours and then cooled naturally.

[0055] Example 2: comprising the following steps:

[0056] S1. Prepare a mother solution by adding 8 drops of 6 mol / L hydrochloric acid solution to a beaker, then adding 0.053 g of palladium chloride, letting it stand for 10 minutes to dissolve, then adding 15 mL of a reducing agent and ultrasonically dispersing it for 30 minutes to obtain a palladium precursor solution;

[0057] S2. Mix the solutions and perform a sol reaction to form a composite sol. Add 5 mL of deionized water to the palladium precursor solution. Place the beaker on a magnetic stirrer and stir at 600 rpm for 5 minutes at room temperature.

[0058] After mixing, add 0.099g of indium trichloride and 4g of zinc chloride, stirring continuously for 20 minutes. Add 4mL of template agent to the beaker and continue stirring for 20 minutes. Add 2mL of coagulant to the beaker and stir for 3 minutes to mix the solution thoroughly. Slowly pour the mixed solution into a mold to obtain a palladium-modified zinc oxide / indium oxide sol, which is then allowed to set.

[0059] S3, palladium-modified zinc oxide / indium oxide sol turns into gel after standing;

[0060] S4, aging the gel and performing solvent replacement treatment, followed by drying. After the gel is aged, it is taken out and replaced with anhydrous ethanol. The gel is dried with supercritical carbon dioxide to obtain an aerogel;

[0061] S5. Perform high-temperature annealing on the aerogel. Place the aerogel in a tubular furnace for calcination. Increase the temperature gradually from room temperature to 500° C., calcine at this temperature for 3 hours, and finally cool naturally.

[0062] In addition to the above preparation methods, the third preparation method is as follows:

[0063] S1. Add 8 drops of 6 mol / L hydrochloric acid solution to a beaker, then add 0.0159 g of palladium chloride and let it stand for 10 minutes to dissolve. Then, add 15 mL of anhydrous ethanol to the beaker and ultrasonically disperse for 30 minutes to obtain a palladium precursor solution.

[0064] S2. Add 5 mL of deionized water to the palladium precursor solution. Place the beaker on a magnetic stirrer and stir at 600 rpm for 5 minutes at room temperature to ensure that the solution is initially mixed.

[0065] After the solution is evenly mixed, continue to weigh 0.099g of indium trichloride and 4g of zinc chloride and add them separately, and continue stirring for 20 minutes. Add 4mL of polyacrylic acid to the above system and continue stirring for 20 minutes under the same conditions. Continue to use a rubber-tipped dropper to measure 2mL of propylene oxide and add it to the system, stir for 3 minutes to mix the solution evenly. Slowly pour the evenly mixed solution into the mold to obtain palladium-modified zinc oxide / indium oxide sol, and let it stand to set. The molar ratio of palladium to zinc in the sol is 3%, and the molar ratio of indium to zinc is 15%.

[0066] S3. The palladium-modified zinc oxide / indium oxide sol turns into gel after standing for 30 minutes.

[0067] S4. After aging for 24 hours, the gel can be removed from the mold and replaced with anhydrous ethanol for 12 hours each time, repeating this step 7 times. The gel is then dried with supercritical carbon dioxide at a temperature of 45°C and a pressure of 12 MPa for 24 hours.

[0068] S5. The palladium-modified zinc oxide / indium oxide aerogels were placed in a tubular furnace for calcination. The calcination atmosphere was air. During the calcination process, the heating rate was set at 1°C / min, and the temperature was gradually increased from room temperature to 500°C. The aerogels were kept at this temperature for 3 hours and then cooled naturally.

[0069] The calculation method of the sensor response value in this patent is:

[0070] S=(Ra-Rg) / Ra, Ra is the resistance of the sensor in air atmosphere, and Rg is the resistance of the sensor in hydrogen atmosphere.

[0071] from Figure 1 It can be seen that the prepared aerogel particles are evenly distributed and retain certain pores between each other, presenting a porous structure with nanoparticles agglomerated.

[0072] from Figure 2 It can be seen that the gas sensor has a response value of up to 29 to 100ppm hydrogen.

[0073] from Figure 3 As can be seen from the figure, the gas sensor has excellent response characteristics to hydrogen. For 1000ppm hydrogen, the response even reaches 2^10 4 .

[0074] It should be noted that the template agent in step S2 can be polyacrylic acid or citric acid. The coagulant can be any one of propylene oxide, 2,3-butylene oxide, 1,2-propylene oxide, or 1,4-butylene oxide. The operator can select the template agent and coagulant according to the material requirements. The functions, mechanisms of action, and effects of polyacrylic acid on the material are as follows: 1. Regulating the pore structure, carboxyl groups chelate with metal ions to form a steric network, forming high-specific-surface-area mesopores, and improving hydrogen adsorption capacity.

[0075] 2. Inhibit agglomeration, stabilize metal ions through electrostatic repulsion, prevent excessive growth of nanoparticles, and ensure uniform dispersion of propylene oxide nanoparticles.

[0076] 3. Gel enhancement and long-chain polymers increase sol viscosity, delay phase separation, and obtain complete aerogel blocks with low shrinkage

[0077] It should be noted that polyacrylic acid releases heat when used and requires an ice bath to maintain 25°C. In addition, aerosolized polyacrylic acid irritates the respiratory tract and must be operated in a fume hood.

[0078] Propylene oxide is used as a coagulant in aerogel preparation. Its core function is to drive the transformation of sol to gel through a controllable acid-base catalytic mechanism. Propylene oxide has the best compatibility with polyacrylic acid templates, and the 20-minute gel time is consistent with the static molding requirements. However, safety precautions should be taken during operation. Propylene oxide is flammable and explosive. The specific handling process is ice bath cooling + dropwise addition under nitrogen protection. The addition should be done dropwise at a rate of <0.5 mL / min to avoid localized aggregation. Propylene oxide is a Class 2 carcinogen and must be operated in a fume hood and with a gas mask.

[0079] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an ultrasensitive aerogel-type hydrogen sensor material, characterized in that: The following steps are involved: S1. Prepare a mother solution by adding 8 drops of 6 mol / L hydrochloric acid solution to a beaker, then adding 0.053 g of palladium chloride, letting it stand for 10 minutes to dissolve, then adding 15 mL of a reducing agent and ultrasonically dispersing it for 30 minutes to obtain a palladium precursor solution; S2, composite sol preparation, adding 5 mL of deionized water to the palladium precursor solution and stirring and mixing; After mixing, add 0.099g of indium trichloride and 4g of zinc chloride respectively, and continue stirring for 20min; Add 4 mL of template into the beaker and continue stirring for 20 min; Take 2mL of coagulant and add it to the beaker, stir for 3min to mix the solution evenly; S3, sol forming, slowly pouring the mixed solution into a mold to obtain palladium-modified zinc oxide and indium oxide sol, and letting it stand to solidify to form a composite sol; S4, static solidification, the palladium-modified zinc oxide and indium oxide sol are allowed to stand to form a gel; S5, aerogel preparation, aging the gel and performing solvent replacement treatment, followed by drying, taking out the gel after aging, and then replacing it with anhydrous ethanol, and drying the gel with supercritical carbon dioxide to obtain aerogel; S6, calcination and forming, high-temperature annealing of the aerogel, placing the aerogel in a tubular furnace for calcination, gradually increasing the temperature from room temperature to 500° C., and calcining at this temperature for 3 hours, and finally cooling naturally.

2. The preparation method according to claim 1, wherein: The divalent palladium ions in step S1 are derived from chloropalladic acid generated by dissolving palladium chloride in a hydrochloric acid solution, and the reducing agent used in step S1 is ethanol.

3. The preparation method according to claim 1, wherein: In step S2, the divalent zinc ion precursor is a zinc-containing inorganic salt, and the trivalent indium ion precursor is an indium-containing inorganic salt. The molar ratio of the sol palladium to zinc in step 2 is 1%-3%, and the molar ratio of indium to zinc is 15%. In step 2, the stirring device inside the beaker is a magnetic stirrer, and the stirring conditions of the palladium precursor solution and deionized water are continuous stirring at a speed of 600 rpm for 5 minutes at room temperature.

4. The preparation method according to claim 1, wherein: In step S2, the template agent is polyacrylic acid and the coagulant is propylene oxide.

5. The preparation method according to claim 1, wherein: The time for the sol to be formed into gel by standing still in step S3 is 30 minutes to 1 hour.

6. The preparation method according to claim 1, wherein: The aging time in step S4 is 12 hours to 24 hours.

7. The preparation method according to claim 1, wherein: The solvent replacement in step S4 is performed using anhydrous ethanol, each time for more than 12 hours, and repeated 7 to 8 times.

8. The preparation method according to claim 1, wherein: The supercritical carbon dioxide drying process of the solvent in step S4 is carried out at a temperature of 40 to 45° C. and a pressure of 8 to 12 MPa, and the drying time is 8 to 24 hours.

9. The preparation method according to claim 1, wherein: The calcination atmosphere in step S5 is air, and the heating rate during the calcination process is set to 1°C / min.

10. An ultra-sensitive aerogel-type hydrogen sensor material, characterized in that: The material is obtained by the preparation method according to claims 1-9, wherein palladium is uniformly dispersed in the zinc oxide / indium oxide aerogel network in a nanometer state, and can achieve high-sensitivity detection of hydrogen under low temperature conditions.

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