CN108445060B - Preparation method of sensor electrode for detecting formaldehyde content in air - Google Patents
Preparation method of sensor electrode for detecting formaldehyde content in air Download PDFInfo
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Abstract
The invention discloses a preparation method of a sensor electrode for detecting formaldehyde content in air, which is characterized in that a catalyst used by the electrode is a superconducting carbon-supported tin oxide-copper oxide-zinc oxide-cobalt oxide catalyst, and a base material is a sulfonated polyether sulfone compound ion exchange membrane.
Description
Technical Field
The invention relates to the field of sensors, in particular to a preparation method of an electrochemical formaldehyde sensor electrode for detecting the content of formaldehyde in air.
Background
At normal temperature, formaldehyde is colorless and easily soluble irritant gas, can be absorbed by respiratory tract, can be combined with biological cell protein, is a protoplasm substance with strong toxicity, is listed as one of carcinogenic substances by the international cancer research institute, and is located at the second place controlled by a virulent substance. Formaldehyde is a protosome poison which destroys biological cell proteins, and under normal conditions, pure formaldehyde is a colorless gas with a suffocating smell, can cause damage to the skin, respiratory tract and internal organs of people, and the damage degree of the formaldehyde is closely related to the concentration of the formaldehyde in the air and the contact time. The formaldehyde also has teratogenic and carcinogenic effects, the probability of suffering from nasal cavity, oral cavity, nasopharynx, throat, skin and digestive tract cancers is higher than that of ordinary people for people who contact the formaldehyde for a long time, chronic respiratory diseases, female menstrual disorder and pregnancy syndrome can be caused by long-term contact of low formaldehyde by the people, the physique of newborns is reduced, the chromosome is abnormal, even the nasopharyngeal carcinoma is caused, and the high-concentration formaldehyde has toxic and harmful effects on a nervous system, an immune system, a liver and the like.
0.01-3.1 mg/m3, namely 0.008-2 ppm, causes headache, dizziness and insomnia;
0.06-0.07 mg/m3, i.e. 0.05-0.06 ppm, asthma of children occurs;
0.12 to 1.2 mglm3, i.e., 0.1 to 1ppm, can cause liver function, lung function abnormality, and immune system abnormality. The maximum allowable concentration of formaldehyde in air is 0.1 ppm, and the standard of the air quality is 0.08 ppm.
The main sources of formaldehyde are:
the sources of formaldehyde in outdoor air are mainly combustion of petroleum, coal, natural gas, etc., oxidative decomposition of lubricating oil, automobile emissions, atmospheric photochemical reactions and some of the plants producing formaldehyde, novolac resins, chemical fibers, dyes, rubber products, plastics, inks, spray paints, coatings, etc.
Indoor formaldehyde is mainly derived from some building materials, furniture, various adhesive coatings, synthetic textiles and the like. Such as various artificial boards, carpet compositions, cleaning agents, cosmetics, and the like.
Research shows that the release period of formaldehyde contained in decoration and furniture is as long as 3-15 years, and the detection rate of formaldehyde is 100% in newly built unfinished houses and houses after being decorated in China, so that the formaldehyde becomes a recognized 'home decoration first killer'.
The concentration of formaldehyde in the air of indoor environment and operation place is mostly tested by adopting an air sampling method, namely, a sampling pump is utilized to extract a certain volume of air sample, the air sample passes through a formaldehyde absorption bottle, and then the air sample is returned to a laboratory and is subjected to quantitative analysis by chemical colorimetry or gas chromatography, and the air sample can also be directly detected on site. The method needs professional personnel and professional equipment to perform analysis and test, is long in time consumption and high in cost, and is not suitable for common families.
The lowest detection of the existing formaldehyde detector is 10ppm and is affected by SO in the air2、H2S、NH3NO, etc. have great influence on the content detection, and are also greatly influenced by temperature and humidity, and the active substances of the used sensor are mainly noble metals such as platinum, gold, etc. and have high cost.
Therefore, the development of a sensor for detecting formaldehyde, which has high accuracy, high sensitivity, high selectivity and low cost, is urgently needed.
Disclosure of Invention
In order to solve the technical problems of low accuracy, sensitivity and selectivity and high manufacturing cost in the existing formaldehyde detection technology, the manufacturing method of the sensor for detecting the formaldehyde content is provided.
In order to achieve the technical purpose, the technical scheme is as follows:
a preparation method of a sensor electrode for detecting the content of formaldehyde in air, wherein a catalyst used by the electrode is a superconducting carbon-supported tin oxide-copper oxide-zinc oxide-cobalt oxide catalyst, a base material is a sulfonated polyether sulfone compound ion exchange membrane, and the preparation process comprises the following specific steps:
step 1, weighing tin oxide powder, copper nitrate, zinc nitrate and cobalt oxide powder into a unified beaker, and weighing excessive oxalic acid and adding into the beaker; then transferring the mixture to a ball mill for ball milling, taking out the mixture, drying the mixture at 100-130 ℃, and grinding the mixture for 10-12 hours for later use;
step 2, weighing the product obtained in the step 1 and the superconducting carbon with the same mass in a beaker, dripping a strong sodium oxide solution into the beaker, uniformly stirring, putting the beaker in a water bath, and taking out the beaker after the colloid in the beaker is dried;
step 3, transferring the catalyst powder taken out in the step 2 into a ceramic vessel, preserving the temperature for 4-6 hours at the temperature of 700-800 ℃ in a muffle furnace, cooling, taking out, transferring to a ball mill for ball milling, taking out, placing in a crucible, adding 1-5% Nafion solution into the crucible, stirring the mixture uniformly to prepare a catalyst material, and then uniformly coating the catalyst on a waterproof breathable film by using a weighing spoon;
step 4, putting the treated sulfonated polyether sulfone compound ion exchange membrane into a beaker with deionized water, putting the beaker into a water bath for heat preservation, and then fishing out for later use;
and 5, sticking the catalyst-coated waterproof breathable film in the step 3, and a reference electrode and a counter electrode which are manufactured by the same method on the sulfonated polyether sulfone compound ion exchange membrane formed in the step 3 for hot pressing, sticking the catalyst-sprayed waterproof breathable film on two sides of the sulfonated polyether sulfone compound ion exchange membrane respectively, sticking one catalyst-sprayed waterproof breathable film on one side and two catalyst-sprayed waterproof breathable films on the other side, and placing at room temperature after hot pressing, so that the electrochemical formaldehyde gas sensor electrode is manufactured.
Preferably, the mass ratio of the tin oxide powder, the copper nitrate, the zinc nitrate and the cobalt oxide powder in the step 1 is 1-3: 4-6: 8-9: 0.1-0.8.
Preferably, the concentration of the sodium hydroxide solution in the step 2 is 1-5 g/ml, and the addition amount is 50-60 ml/g of the catalyst; the temperature of the water bath kettle is 90-100 ℃.
Preferably, the sulfonated polyether sulfone compound ion exchange membrane treated in the step 4 is pretreated, and the sulfonated polyether sulfone compound ion exchange membrane is firstly placed into boiling H with the concentration of 3-5%2O2Treating the solution for 0.5 to 1 hour at the temperature of 80 ℃; then soaking the membrane in 0.5-1M sulfuric acid at the temperature of 80 ℃ for 0.5-1 hour, washing the residual acid solution on the surface of the membrane with deionized water, and then putting the membrane into deionized water for later use.
Preferably, the sulfonated polyether sulfone compound ion exchange membrane comprises the following raw materials, by weight, 60-80 parts of a sulfonated polyether sulfone compound; 1-10 parts of thiophene ionic liquid; 10-30 parts of a film-making solvent;
preferably, the sulfonated polyether sulfone compound is prepared by the following method: 18-20 g of 3,3' -sodium disulfonate-4, 4' -dichlorodiphenyl sulfone, 5-15 g of 4, 4' -dichlorodiphenyl disulfide, 10-15 g of 3,3' -diamino-4, 4' -dichlorodiphenyl sulfone, 10-15 g of 3,3', 5' -tetramethylbiphenol, 16-20 g of anhydrous sodium carbonate, 200-250 mL of N, N-dimethylformamide and 150-200 mL of dichlorotoluene are mixed, and heated to 200-210 ℃ for reflux water diversion for 2-3 hours. Distilling to remove dichlorotoluene, keeping the reaction temperature at 200-210 ℃, and reacting for 30-40 hours. Stopping heating and stirring, and naturally cooling to room temperature. Slowly pouring the reaction solution into 2-3L of deionized water to obtain a white fibrous polymer, soaking 4-6L of deionized water at 80 ℃ for 6-8 hours, repeating for three times, filtering, drying, and vacuum drying at 110-120 ℃ for 20-30 hours to obtain a light yellow fibrous polymer.
Preferably, the preparation method of the sulfonated polyether sulfone compound ion exchange membrane comprises the following preparation steps:
A. dissolving a sulfonated polyether sulfone compound in a film-making solvent to prepare a film-making solution with the mass percent concentration of 5.0-35.0%;
B. adding thiophene ionic liquid into the membrane preparation liquid obtained in the step A, stirring for 10-24 hours at 85-95 ℃ under the protection of inert atmosphere, cooling to room temperature, carrying out suction filtration to remove insoluble substances, and drying to obtain a thiophene ionic liquid doped sulfonated polyether sulfone compound ion exchange membrane material;
C. b, performing tape casting or pressing on the ion exchange membrane material obtained in the step B to form a membrane, and volatilizing the solvent at the temperature of 40-90 ℃ to obtain a wet membrane; drying the obtained wet film at the constant temperature of 50-100 ℃ for 2-24 h; or drying for 10-12 h at 50-70 ℃, and then heating to 70-120 ℃ for drying for 4-10 h to obtain the thiophene ionic liquid doped sulfonated polyether sulfone compound proton exchange membrane.
Preferably, the thiophene ionic liquid is named as: tetrahydrothiophene ionic liquid or S-alkyl thiophene ionic liquid.
Preferably, the film-forming solvents used are: one or more of amyl formate, amyl acetate, xylene and trichloroethylene.
Preferably, the film-forming solvents used are: xylene.
Has the advantages that:
the electrode is used for measuring formaldehyde on a sensor, and has the advantages of high sensitivity, wide detection range, high accuracy, good linearity, good selectivity and good stability.
Drawings
FIG. 1 is a linear graph showing the concentration of formaldehyde gas detected by the electrode of example 2.
DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION
Example 1 preparation method of sensor electrode for detecting formaldehyde content in air
A preparation method of a sensor electrode for detecting the content of formaldehyde in air, wherein a catalyst used by the electrode is a superconducting carbon-supported tin oxide-copper oxide-zinc oxide-cobalt oxide catalyst, a base material is a sulfonated polyether sulfone compound ion exchange membrane, and the preparation process comprises the following specific steps:
step 1, weighing tin oxide powder, copper nitrate, zinc nitrate and cobalt oxide powder into a unified beaker, and weighing excessive oxalic acid and adding into the beaker; then transferring the mixture to a ball mill for ball milling, taking out the mixture, drying the mixture at 100 ℃, and grinding the mixture for 10 to 12 hours for later use;
step 2, weighing the product obtained in the step 1 and the superconducting carbon with the same mass in a beaker, dripping a strong sodium oxide solution into the beaker, uniformly stirring, putting the beaker in a water bath, and taking out the beaker after the colloid in the beaker is dried;
step 3, transferring the catalyst powder taken out in the step 2 into a ceramic vessel, preserving the temperature for 4 hours in a muffle furnace at the temperature of 700 ℃, cooling, taking out, transferring to a ball mill for ball milling, taking out, placing in a crucible, adding 1% Nafion solution, stirring uniformly to prepare a catalyst material, and then uniformly coating the catalyst on a waterproof breathable film by using a weighing spoon;
step 4, putting the treated sulfonated polyether sulfone compound ion exchange membrane into a beaker with deionized water, putting the beaker into a water bath for heat preservation, and then fishing out for later use;
and 5, sticking the catalyst-coated waterproof breathable film in the step 3, and a reference electrode and a counter electrode which are manufactured by the same method on the sulfonated polyether sulfone compound ion exchange membrane formed in the step 3 for hot pressing, sticking the catalyst-sprayed waterproof breathable film on two sides of the sulfonated polyether sulfone compound ion exchange membrane respectively, sticking one catalyst-sprayed waterproof breathable film on one side and two catalyst-sprayed waterproof breathable films on the other side, and placing at room temperature after hot pressing, so that the electrochemical formaldehyde gas sensor electrode is manufactured.
The mass ratio of the tin oxide powder, the copper nitrate, the zinc nitrate and the cobalt oxide powder in the step 1 is 1:4:8: 0.1.
The concentration of the sodium hydroxide solution in the step 2 is 1g/ml, and the addition amount is 50ml/g of catalyst; the temperature of the water bath was 90 ℃.
The sulfonated polyether sulfone compound ion exchange membrane treated in the step 4 is a p-sulfonated polyether sulfone compound ion exchange membranePretreating the ion exchange membrane of polyethersulfone compound by putting it in boiling 3% H2O2Treating the solution for 0.5h at the temperature of 80 ℃; then soaking the membrane in 0.5M sulfuric acid at the temperature of 80 ℃ for 0.5 hour, washing the residual acid solution on the surface of the membrane by deionized water, and then putting the membrane into the deionized water for later use.
The sulfonated polyether sulfone compound ion exchange membrane comprises the following raw materials, by weight, 60 parts of a sulfonated polyether sulfone compound; 1 part of thiophene ionic liquid; 10 parts of a film-making solvent;
the sulfonated polyether sulfone compound is prepared by the following method: 18g of 3,3' -disulfonic acid sodium-4, 4' -dichlorodiphenyl sulfone, 5g of 4, 4' -dichlorodiphenyl disulfide, 10g of 3,3' -diamino-4, 4' -dichlorodiphenyl sulfone, 10g of 3,3', 5' -tetramethylbiphenol, 16g of anhydrous sodium carbonate, 200mL of N, N-dimethylformamide and 150mL of dichlorotoluene were mixed, heated to 200 ℃ and refluxed for water diversion for 2 hours. The dichlorotoluene was distilled off, and the reaction temperature was maintained at 200 ℃ for 30 hours. Stopping heating and stirring, and naturally cooling to room temperature. Slowly pouring the reaction solution into 2L of deionized water to obtain a white fibrous polymer, soaking 4L of deionized water at 80 ℃ for 6 hours, repeating the soaking three times, filtering, drying, and performing vacuum drying at 110 ℃ for 20 hours to obtain a light yellow fibrous polymer.
The preparation method of the sulfonated polyether sulfone compound ion exchange membrane comprises the following preparation steps:
A. dissolving a sulfonated polyether sulfone compound in a membrane preparation solvent to prepare a membrane preparation liquid with the mass percent concentration of 5.0%;
B. adding thiophene ionic liquid into the membrane-making liquid obtained in the step A, stirring for 10 hours at 85 ℃ under the protection of inert atmosphere, cooling to room temperature, carrying out suction filtration to remove insoluble substances, and drying to obtain a thiophene ionic liquid doped sulfonated polyether sulfone compound ion exchange membrane material;
C. b, performing tape casting or pressing on the ion exchange membrane material obtained in the step B to form a membrane, and volatilizing the solvent at 40 ℃ to obtain a wet membrane; drying the obtained wet film at the constant temperature of 50 ℃ for 2 hours; or drying at 50 ℃ for 10h, and then heating to 70 ℃ for drying for 4h to obtain the imidazole thiophene ionic liquid doped sulfonated polyether sulfone compound proton exchange membrane.
The thiophene ionic liquid is named as: tetrahydrothiophene ionic liquid.
The film-forming solvents used were: pentyl formate.
When formaldehyde is detected by using the sensor made of the electrode prepared in the embodiment, the linear relation between the current (I, uA) and the formaldehyde content (C, ppm) is as follows within the range of 0.0001ppm to 20 ppm: i =65C +7.8 (R =0.9997, n = 6).
And (3) selectivity: SO (SO)2、H2And S, no interference is generated to detection.
The sensor prepared by the electrode is used for testing the response performance of formaldehyde gas. The test conditions are room temperature conditions, and the operation steps are as follows: introducing clean air, and sequentially introducing 20ppm SO2Gas, 20ppmH2S gas, the change value of the response signal of the sensor is basically zero, and the change value of the response of the sensor when 2ppm of formaldehyde gas is introduced is 137.8 uA.
When formaldehyde detection was performed with a commercially available formaldehyde electrode sensor: introducing clean air, and sequentially introducing 20ppm SO2Gas and 20ppmH2The more the change value of the response signal of the sensor was about 120 uA for S gas, the more 257.8uA the change value of the sensor response when 2ppm of formaldehyde gas was introduced.
As can be seen, a commercially available formaldehyde sensor, SO, was used2、H2S can seriously affect the detection of formaldehyde gas.
Embodiment 2 preparation method of sensor electrode for detecting content of formaldehyde in air
A preparation method of a sensor electrode for detecting the content of formaldehyde in air, wherein a catalyst used by the electrode is a superconducting carbon-supported tin oxide-copper oxide-zinc oxide-cobalt oxide catalyst, a base material is a sulfonated polyether sulfone compound ion exchange membrane, and the preparation process comprises the following specific steps:
step 1, weighing tin oxide powder, copper nitrate, zinc nitrate and cobalt oxide powder into a unified beaker, and weighing excessive oxalic acid and adding into the beaker; then transferring the mixture to a ball mill for ball milling, taking out the mixture, drying the mixture at 120 ℃, and grinding the mixture for 11 hours for later use;
step 2, weighing the product obtained in the step 1 and the superconducting carbon with the same mass in a beaker, dripping a strong sodium oxide solution into the beaker, uniformly stirring, putting the beaker in a water bath, and taking out the beaker after the colloid in the beaker is dried;
step 3, transferring the catalyst powder taken out in the step 2 into a ceramic vessel, preserving heat for 5 hours at 750 ℃ in a muffle furnace, cooling, taking out, transferring to a ball mill, ball-milling, taking out, placing in a crucible, adding 4% Nafion solution, stirring uniformly to prepare a catalyst material, and then uniformly coating the catalyst on a waterproof breathable film by using a weighing spoon;
step 4, putting the treated sulfonated polyether sulfone compound ion exchange membrane into a beaker with deionized water, putting the beaker into a water bath for heat preservation, and then fishing out for later use;
and 5, sticking the catalyst-coated waterproof breathable film in the step 3, and a reference electrode and a counter electrode which are manufactured by the same method on the sulfonated polyether sulfone compound ion exchange membrane formed in the step 3 for hot pressing, sticking the catalyst-sprayed waterproof breathable film on two sides of the sulfonated polyether sulfone compound ion exchange membrane respectively, sticking one catalyst-sprayed waterproof breathable film on one side and two catalyst-sprayed waterproof breathable films on the other side, and placing at room temperature after hot pressing, so that the electrochemical formaldehyde gas sensor electrode is manufactured.
Preferably, the mass ratio of the tin oxide powder, the copper nitrate, the zinc nitrate and the cobalt oxide powder in the step 1 is 2:5:8.5: 0.5.
Preferably, the concentration of the sodium hydroxide solution in the step 2 is 1-5 g/ml, and the addition amount is 50-60 ml/g of the catalyst; the temperature of the water bath was 95 ℃.
The sulfonated polyether sulfone compound ion exchange membrane treated in the step 4 is pretreated by firstly putting the sulfonated polyether sulfone compound ion exchange membrane into boiling 4 percent of H2O2Treating the solution for 0.8h at the temperature of 80 ℃; then soaking in 0.5M sulfuric acid at 80 deg.C for 0.5 hr, and washing off the surface of the membrane with deionized waterAnd (4) putting the residual acid solution into deionized water for later use.
The sulfonated polyether sulfone compound ion exchange membrane comprises the following raw materials, by weight, 70 parts of a sulfonated polyether sulfone compound; 1 part of thiophene ionic liquid; 10 parts of a film-making solvent;
the sulfonated polyether sulfone compound is prepared by the following method: 19g of 3,3' -sodium disulfonate-4, 4' -dichlorodiphenyl sulfone, 10g of 4, 4' -dichlorodiphenyl disulfide, 12g of 3,3' -diamino-4, 4' -dichlorodiphenyl sulfone, 13g of 3,3', 5' -tetramethylbiphenol, 18g of anhydrous sodium carbonate, 230mL of N, N-dimethylformamide and 180mL of dichlorotoluene are mixed, heated to 205 ℃, refluxed and dehydrated for 2-3 hours. The dichlorotoluene was distilled off, and the reaction temperature was maintained at 205 ℃ for 35 hours. Stopping heating and stirring, and naturally cooling to room temperature. Slowly pouring the reaction solution into 2.5L of deionized water to obtain a white fibrous polymer, soaking 5L of deionized water at 80 ℃ for 7 hours, repeating the soaking for three times, filtering, drying, and performing vacuum drying at 115 ℃ for 25 hours to obtain a light yellow fibrous polymer.
The preparation method of the sulfonated polyether sulfone compound ion exchange membrane comprises the following preparation steps:
A. dissolving a sulfonated polyether sulfone compound in a membrane preparation solvent to prepare a membrane preparation solution with the mass percent concentration of 25%;
B. adding thiophene ionic liquid into the membrane-making liquid obtained in the step A, stirring for 15 hours at 90 ℃ under the protection of inert atmosphere, cooling to room temperature, carrying out suction filtration to remove insoluble substances, and drying to obtain a thiophene ionic liquid doped sulfonated polyether sulfone compound ion exchange membrane material;
C. b, performing tape casting or pressing on the ion exchange membrane material obtained in the step B to form a membrane, and volatilizing the solvent at 80 ℃ to obtain a wet membrane; drying the obtained wet film at the constant temperature of 80 ℃ for 10 hours; or drying at 55 ℃ for 11h, heating to 100 ℃ and drying for 6h to obtain the thiophene ionic liquid doped sulfonated polyether sulfone compound proton exchange membrane.
The thiophene ionic liquid is named as: tetrahydrothiophene ionic liquid or S-alkyl thiophene ionic liquid.
The film-forming solvents used were: xylene.
When formaldehyde is detected by using the sensor made of the electrode prepared in the embodiment, the linear relation between the current (I, uA) and the formaldehyde content (C, ppm) is as follows within the range of 0.0001 ppm-30 ppm: i =75C +8.9 (R =0.9999, n = 6).
And (3) selectivity: SO (SO)2、H2S 、NH3NO was not interfering with the detection.
The sensor prepared by the electrode is used for testing the response performance of formaldehyde gas. Test conditions
The method comprises the following steps of: introducing clean air, and respectively introducing 40ppm SO2、40ppmH2S、40ppm NH340ppm NO, the change in the response signal of the sensor was substantially zero, and the change in the response of the sensor when 3ppm of formaldehyde gas was introduced was 233.9 uA.
When formaldehyde detection was performed with a commercially available formaldehyde electrode sensor: introducing clean air, and respectively introducing 40ppm SO2、40ppmH2S、40ppm NH3The more the change value of the response signal of the sensor was 250uA and the more the change value of the response signal of the sensor was 483.9uA when 3ppm of formaldehyde gas was introduced.
As can be seen, a commercially available formaldehyde sensor, SO, was used2、H2S 、NH3NO can seriously affect the detection of formaldehyde gas.
Embodiment 3 a method for manufacturing a sensor for detecting formaldehyde content in air
A method for preparing a sensor for detecting the content of formaldehyde in air comprises the following steps of:
step 1, weighing tin oxide powder, copper nitrate, zinc nitrate and cobalt oxide powder into a unified beaker, and weighing excessive oxalic acid and adding into the beaker; then transferring the mixture to a ball mill for ball milling, taking out the mixture, drying the mixture at 130 ℃, and grinding the mixture for 12 hours for later use;
step 2, weighing the product obtained in the step 1 and the superconducting carbon with the same mass in a beaker, dripping a strong sodium oxide solution into the beaker, uniformly stirring, putting the beaker in a water bath, and taking out the beaker after the colloid in the beaker is dried;
step 3, transferring the catalyst powder taken out in the step 2 into a ceramic vessel, preserving the temperature for 6 hours in a muffle furnace at 800 ℃, cooling, taking out, transferring to a ball mill for ball milling, taking out, placing in a crucible, adding 5% Nafion solution, stirring uniformly to prepare a catalyst material, and then uniformly coating the catalyst on a waterproof breathable film by using a weighing spoon;
step 4, putting the treated sulfonated polyether sulfone compound ion exchange membrane into a beaker with deionized water, putting the beaker into a water bath for heat preservation, and then fishing out for later use;
and 5, sticking the catalyst-coated waterproof breathable film in the step 3, and a reference electrode and a counter electrode which are manufactured by the same method on the sulfonated polyether sulfone compound ion exchange membrane formed in the step 3 for hot pressing, sticking the catalyst-sprayed waterproof breathable film on two sides of the sulfonated polyether sulfone compound ion exchange membrane respectively, sticking one catalyst-sprayed waterproof breathable film on one side and two catalyst-sprayed waterproof breathable films on the other side, and placing at room temperature after hot pressing, so that the electrochemical formaldehyde gas sensor electrode is manufactured.
The mass ratio of the tin oxide powder, the copper nitrate, the zinc nitrate and the cobalt oxide powder in the step 1 is 3: 6: 9: 0.8.
The concentration of the sodium hydroxide solution in the step 2 is 5g/ml, and the adding amount is 60ml/g of catalyst; the temperature of the water bath was 100 ℃.
The sulfonated polyether sulfone compound ion exchange membrane treated in the step 4 is pretreated, and is firstly put into boiling H with the concentration of 5 percent2O2Treating the solution for 1h at the temperature of 80 ℃; then soaking the membrane in 1M sulfuric acid at the temperature of 80 ℃ for 1 hour, washing the residual acid solution on the surface of the membrane with deionized water, and then putting the membrane into deionized water for later use.
The sulfonated polyether sulfone compound ion exchange membrane comprises the following raw materials, by weight, 80 parts of a sulfonated polyether sulfone compound; 10 parts of thiophene ionic liquid; 30 parts of a film-making solvent;
the sulfonated polyether sulfone compound is prepared by the following method: 20g of 3,3 '-disulfonic acid sodium-4, 4' -dichlorodiphenyl sulfone, 15g of 4, 4-dichlorodiphenyl disulfide, 15g of 3,3 '-diamino-4, 4' -dichlorodiphenyl sulfone and 200mL of dichlorotoluene were mixed, heated to 210 ℃ and refluxed for water diversion for 3 hours. The dichlorotoluene was distilled off, and the reaction temperature was maintained at 210 ℃ for 40 hours. Stopping heating and stirring, and naturally cooling to room temperature. Slowly pouring the reaction solution into 3L of deionized water to obtain a white fibrous polymer, soaking 6L of deionized water at 80 ℃ for 8 hours, repeating the soaking three times, filtering, drying, and performing vacuum drying at 120 ℃ for 30 hours to obtain a light yellow fibrous polymer.
The preparation method of the sulfonated polyether sulfone compound ion exchange membrane comprises the following preparation steps:
A. dissolving a sulfonated polyether sulfone compound in a membrane preparation solvent to prepare a membrane preparation liquid with the mass percent concentration of 35.0%;
B. and D, adding thiophene ionic liquid into the membrane preparation liquid obtained in the step A, stirring for 24 hours at 95 ℃ under the protection of inert atmosphere, cooling to room temperature, carrying out suction filtration to remove insoluble substances, and drying to obtain the thiophene ionic liquid doped sulfonated polyether sulfone compound ion exchange membrane material.
C. B, performing tape casting or pressing on the ion exchange membrane material obtained in the step B to form a membrane, and volatilizing the solvent at 90 ℃ to obtain a wet membrane; drying the obtained wet film at the constant temperature of 100 ℃ for 24 hours; or drying at 70 ℃ for 12h, heating to 120 ℃ and drying for 10h to obtain the thiophene ionic liquid doped sulfonated polyether sulfone compound proton exchange membrane.
The thiophene ionic liquid is named as: s-alkyl thiophene ionic liquid.
The film-forming solvents used were: amyl acetate and trichloroethylene.
When formaldehyde is detected by using the sensor made of the electrode prepared in the embodiment, the linear relation between the current (I, uA) and the formaldehyde content (C, ppm) is as follows within the range of 0.0001ppm to 25 ppm: i =68C +7.3 (R =0.9996, n = 6).
And (3) selectivity: SO (SO)2、H2S 、NH3NO was not interfering with the detection.
The sensor prepared by the electrode is used for testing the response performance of formaldehyde gas. Test conditions
The method comprises the following steps of: introducing clean air, and sequentially introducing 30ppm SO2、30ppmH2S、30ppm NH330ppm NO, the change in the response signal of the sensor was substantially zero, and the change in the response of the sensor when 3ppm of formaldehyde gas was introduced was 211.3 uA.
When formaldehyde detection was performed with a commercially available formaldehyde electrode sensor: introducing clean air, and respectively introducing 40ppm SO2、40ppmH2S、40ppm NH340ppm NO, the response signal of the sensor changed by substantially about 250uA, and the response of the sensor when 3ppm formaldehyde gas was introduced changed by 461.3 uA.
As can be seen, a commercially available formaldehyde sensor, SO, was used2、H2S 、NH3NO can seriously affect the detection of formaldehyde gas.
Claims (9)
1. A preparation method of a sensor electrode for detecting formaldehyde content in air is characterized in that a catalyst used by the electrode is a superconducting carbon-supported tin oxide-copper oxide-zinc oxide-cobalt oxide catalyst, a base material is a sulfonated polyether sulfone compound ion exchange membrane, and the preparation process comprises the following specific steps:
step 1, weighing tin oxide powder, copper nitrate, zinc nitrate and cobalt oxide powder into a unified beaker, and weighing excessive oxalic acid and adding into the beaker; then transferring the mixture to a ball mill for ball milling, taking out the mixture, drying the mixture at 100-130 ℃, and grinding the mixture for 10-12 hours for later use;
step 2, weighing the product obtained in the step 1 and the superconducting carbon with the same mass in a beaker, dripping a sodium hydroxide solution into the beaker, uniformly stirring, putting the beaker in a water bath, and taking out the beaker after the colloid in the beaker is dried;
step 3, transferring the catalyst powder taken out in the step 2 into a ceramic vessel, preserving the temperature for 4-6 hours at the temperature of 700-800 ℃ in a muffle furnace, cooling, taking out, transferring to a ball mill for ball milling, taking out, placing in a crucible, adding 1-5% Nafion solution into the crucible, stirring the mixture uniformly to prepare a catalyst material, and then uniformly coating the catalyst on a waterproof breathable film by using a weighing spoon;
step 4, putting the treated sulfonated polyether sulfone compound ion exchange membrane into a beaker with deionized water, putting the beaker into a water bath for heat preservation, and then fishing out for later use;
step 5, sticking the catalyst-coated waterproof breathable film in the step 3, and a reference electrode and a counter electrode which are manufactured by the same method on the sulfonated polyether sulfone compound ion exchange membrane formed in the step 3 for hot pressing, sticking the catalyst-sprayed waterproof breathable film on two sides of the sulfonated polyether sulfone compound ion exchange membrane respectively, sticking one catalyst-sprayed waterproof breathable film on one side and two catalyst-sprayed waterproof breathable films on the other side, and placing the membrane at room temperature after hot pressing, so that the electrochemical formaldehyde gas sensor electrode is manufactured;
the sulfonated polyether sulfone compound ion exchange membrane comprises the following raw materials in parts by weight: 60-80 parts of a sulfonated polyether sulfone compound; 1-10 parts of thiophene ionic liquid; 10-30 parts of a film-forming solvent.
2. The method for preparing the sensor electrode for detecting the formaldehyde content in the air as claimed in claim 1, wherein the mass ratio of the tin oxide powder, the copper nitrate, the zinc nitrate and the cobalt oxide powder in the step 1 is 1-3: 4-6: 8-9: 0.1-0.8.
3. The method for preparing the sensor electrode for detecting the formaldehyde content in the air according to claim 1, wherein the concentration of the sodium hydroxide solution in the step 2 is 1-5 g/ml, and the addition amount of the sodium hydroxide solution is 50-60 ml/g of the catalyst; the temperature of the water bath kettle is 90-100 ℃.
4. The method for preparing the sensor electrode for detecting the formaldehyde content in the air according to claim 1, wherein the sulfonated polyether sulfone compound ion exchange membrane treated in the step 4 is treated by performing ion exchange treatment on the sulfonated polyether sulfone compound ion exchange membranePerforming pretreatment, namely putting the sulfonated polyether sulfone compound ion exchange membrane into boiling H with the concentration of 3-5%2O2Treating the solution for 0.5 to 1 hour at the temperature of 80 ℃; then soaking the membrane in 0.5-1M sulfuric acid at the temperature of 80 ℃ for 0.5-1 hour, washing the residual acid solution on the surface of the membrane with deionized water, and then putting the membrane into deionized water for later use.
5. The method for preparing the sensor electrode for detecting the formaldehyde content in the air according to claim 1, wherein the sulfonated polyether sulfone compound is prepared by the following method: 18-20 g of 3,3 '-sodium disulfonate-4, 4' -dichlorodiphenyl sulfone, 5-15 g of 4, 4, -dichlorodiphenyl disulfide, 10-15 g of 3,3 '-diamino-4, 4' -dichlorodiphenyl sulfone, 10-15 g of 3,3', 5' -tetramethylbiphenyl diphenol, 16-20 g of anhydrous sodium carbonate, 200-250 mL of N, N-dimethylformamide and 150-200 mL of dichlorotoluene are mixed, heated to 200-210 ℃ for reflux and water diversion for 2-3 hours, dichlorotoluene is removed by distillation, the reaction temperature is kept at 200-210 ℃, the reaction is carried out for 30-40 hours, heating and stirring are stopped, the mixture is naturally cooled to the room temperature, the reaction liquid is slowly poured into 2-3L of deionized water to obtain a white fibrous polymer, 4-6L of deionized water is soaked for 6-8 hours at 80 ℃, repeating the steps for three times, filtering, drying, and then performing vacuum drying at the temperature of 110-120 ℃ for 20-30 hours to obtain the light yellow fibrous polymer.
6. The method for preparing the sensor electrode for detecting the formaldehyde content in the air according to claim 1, wherein the method for preparing the sulfonated polyether sulfone compound ion exchange membrane comprises the following steps:
A. dissolving a sulfonated polyether sulfone compound in a film-making solvent to prepare a film-making solution with the mass percent concentration of 5.0-35.0%;
B. adding thiophene ionic liquid into the membrane preparation liquid obtained in the step A, stirring for 10-24 hours at 85-95 ℃ under the protection of inert atmosphere, cooling to room temperature, carrying out suction filtration to remove insoluble substances, and drying to obtain a thiophene ionic liquid doped sulfonated polyether sulfone compound ion exchange membrane material;
C. b, performing tape casting or pressing on the ion exchange membrane material obtained in the step B to form a membrane, and volatilizing the solvent at the temperature of 40-90 ℃ to obtain a wet membrane; drying the obtained wet film at the constant temperature of 50-100 ℃ for 2-24 h; or drying for 10-12 h at 50-70 ℃, and then heating to 70-120 ℃ for drying for 4-10 h to obtain the thiophene ionic liquid doped sulfonated polyether sulfone compound proton exchange membrane.
7. The method for preparing the sensor electrode for detecting the formaldehyde content in the air as claimed in claim 6, wherein the thiophene ionic liquid is named as: tetrahydrothiophene ionic liquid or S-alkyl thiophene ionic liquid.
8. The method for manufacturing the sensor electrode for detecting the formaldehyde content in the air as claimed in claim 6, wherein the film-forming solvents used are: one or more of amyl formate, amyl acetate, xylene and trichloroethylene.
9. The method for manufacturing the sensor electrode for detecting the formaldehyde content in the air as claimed in claim 6, wherein the film-forming solvents used are: xylene.
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