CN117205957B - Preparation method and application of carbon nitride supported carbon dot anchored small-size Pt composite photocatalytic material - Google Patents
Preparation method and application of carbon nitride supported carbon dot anchored small-size Pt composite photocatalytic material Download PDFInfo
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- CN117205957B CN117205957B CN202311298461.7A CN202311298461A CN117205957B CN 117205957 B CN117205957 B CN 117205957B CN 202311298461 A CN202311298461 A CN 202311298461A CN 117205957 B CN117205957 B CN 117205957B
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- JMANVNJQNLATNU-UHFFFAOYSA-N oxalonitrile Chemical compound N#CC#N JMANVNJQNLATNU-UHFFFAOYSA-N 0.000 title claims abstract description 77
- 239000002131 composite material Substances 0.000 title claims abstract description 74
- 230000001699 photocatalysis Effects 0.000 title claims abstract description 74
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 66
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 66
- 239000000463 material Substances 0.000 title claims abstract description 52
- 238000002360 preparation method Methods 0.000 title claims abstract description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 37
- 239000002243 precursor Substances 0.000 claims abstract description 27
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 21
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 21
- 239000001257 hydrogen Substances 0.000 claims abstract description 21
- 238000000034 method Methods 0.000 claims abstract description 14
- 238000000197 pyrolysis Methods 0.000 claims abstract description 12
- 238000001354 calcination Methods 0.000 claims abstract description 8
- 239000011259 mixed solution Substances 0.000 claims description 45
- 239000000243 solution Substances 0.000 claims description 38
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 27
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 claims description 27
- 239000002244 precipitate Substances 0.000 claims description 26
- -1 polytetrafluoroethylene Polymers 0.000 claims description 20
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 20
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 20
- 239000008367 deionised water Substances 0.000 claims description 17
- 229910021641 deionized water Inorganic materials 0.000 claims description 17
- 238000001035 drying Methods 0.000 claims description 16
- GEYOCULIXLDCMW-UHFFFAOYSA-N 1,2-phenylenediamine Chemical compound NC1=CC=CC=C1N GEYOCULIXLDCMW-UHFFFAOYSA-N 0.000 claims description 14
- 238000001816 cooling Methods 0.000 claims description 14
- 238000010992 reflux Methods 0.000 claims description 14
- 238000003756 stirring Methods 0.000 claims description 14
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 13
- 150000001412 amines Chemical class 0.000 claims description 13
- 238000004108 freeze drying Methods 0.000 claims description 13
- 229910052698 phosphorus Inorganic materials 0.000 claims description 13
- 239000011574 phosphorus Substances 0.000 claims description 13
- 238000004321 preservation Methods 0.000 claims description 13
- 239000000203 mixture Substances 0.000 claims description 12
- 229910052573 porcelain Inorganic materials 0.000 claims description 10
- 238000010438 heat treatment Methods 0.000 claims description 9
- 238000002256 photodeposition Methods 0.000 claims description 9
- 238000000227 grinding Methods 0.000 claims description 5
- 238000002156 mixing Methods 0.000 claims description 5
- 229920000877 Melamine resin Polymers 0.000 claims description 4
- 238000005119 centrifugation Methods 0.000 claims description 4
- JDSHMPZPIAZGSV-UHFFFAOYSA-N melamine Chemical compound NC1=NC(N)=NC(N)=N1 JDSHMPZPIAZGSV-UHFFFAOYSA-N 0.000 claims description 4
- ISIJQEHRDSCQIU-UHFFFAOYSA-N tert-butyl 2,7-diazaspiro[4.5]decane-7-carboxylate Chemical compound C1N(C(=O)OC(C)(C)C)CCCC11CNCC1 ISIJQEHRDSCQIU-UHFFFAOYSA-N 0.000 claims description 4
- 229910052724 xenon Inorganic materials 0.000 claims description 4
- FHNFHKCVQCLJFQ-UHFFFAOYSA-N xenon atom Chemical compound [Xe] FHNFHKCVQCLJFQ-UHFFFAOYSA-N 0.000 claims description 4
- 238000004140 cleaning Methods 0.000 claims description 3
- 230000001678 irradiating effect Effects 0.000 claims description 2
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- 230000000630 rising effect Effects 0.000 claims description 2
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- 239000000969 carrier Substances 0.000 abstract description 3
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- 230000006798 recombination Effects 0.000 abstract description 3
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- 238000007146 photocatalysis Methods 0.000 description 4
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- 239000003054 catalyst Substances 0.000 description 3
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 3
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- 125000000524 functional group Chemical group 0.000 description 2
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Abstract
A preparation method and application of a carbon nitride supported carbon dot anchored small-size Pt composite photocatalytic material relate to a preparation method and application of a composite photocatalytic material. The invention aims to solve the problems that the utilization efficiency of carbon nitride to visible light is low, the recombination rate of photoinduced carriers is high and the photocatalytic efficiency is severely limited in the photocatalytic process. The method comprises the following steps: 1. preparing a carbon dot solution; 2. preparing a carbon nitride precursor; 3. compounding; 4. calcining; 5. pt is loaded. The carbon nitride-supported carbon dot anchored small-size Pt composite photocatalytic material is used as a photocatalytic material for photocatalytic pyrolysis of water to produce hydrogen. The carbon nitride supported carbon dot anchored small-size Pt composite photocatalytic material prepared by the invention has good performance and excellent cycle stability of 1.352mmolh ‑1g‑1 of hydrogen production rate of photocatalytic pyrolysis water under the irradiation of visible light. The invention can obtain the carbon-nitride-supported carbon-dot-anchored small-size Pt composite photocatalytic material.
Description
Technical Field
The invention relates to a preparation method and application of a composite photocatalytic material.
Background
Hydrogen energy is considered as an ideal energy source for solving the future energy crisis and environmental problems, and photocatalytic water splitting hydrogen production is one of the important strategies for alleviating the energy crisis and the environmental pollution problems. Carbon nitride (C 3N4) is an effective semiconductor photocatalyst, and is widely studied in the field of photocatalytic hydrogen production due to its good chemical stability, non-toxicity and high photocatalytic activity. However, the light response range of C 3N4 is limited, the utilization efficiency of visible light in the photocatalysis process is low, the recombination rate of photocarriers is high, and the photocatalysis efficiency is severely limited. Finding a suitable method to widen its light absorption range and promote the separation of electron-hole pairs is a key to improving photocatalytic performance. Carbon dots are a hot spot of research due to their tunable light absorption range, good electrical conductivity, excellent light stability and low toxicity.
Disclosure of Invention
The invention aims to solve the problems that the utilization efficiency of carbon nitride to visible light is low, the recombination rate of photoinduced carriers is high and the photocatalytic efficiency is severely limited in the photocatalytic process, and provides a preparation method and application of a carbon nitride-supported carbon dot anchored small-size Pt composite photocatalytic material.
The preparation method of the carbon nitride supported carbon dot anchored small-size Pt composite photocatalytic material is specifically completed by the following steps:
1. Adding o-phenylenediamine into absolute ethyl alcohol, and stirring for a period of time to obtain an o-phenylenediamine absolute ethyl alcohol solution; transferring the o-phenylenediamine absolute ethanol solution into a polytetrafluoroethylene autoclave, then placing the polytetrafluoroethylene autoclave into a vacuum oven with the temperature of 170-200 ℃ for heat preservation for a period of time, and finally naturally cooling to room temperature to obtain a carbon dot solution;
2. mixing an amine source, a phosphorus source and deionized water, placing the mixture on a stirrer for stirring until the mixture forms a uniform solution, then placing the solution into a constant-temperature water bath kettle, setting the temperature to be 80-130 ℃, and keeping the temperature at 80-130 ℃ for a period of time to obtain a mixed solution; transferring the mixed solution into a polytetrafluoroethylene autoclave, then placing the autoclave into a vacuum oven with the temperature of 150-200 ℃ for heat preservation for a period of time, immediately cooling the autoclave to room temperature, collecting precipitate, cleaning the precipitate, and finally placing the precipitate into the vacuum oven for drying to obtain a carbon nitride precursor;
3. adding a carbon dot solution into a carbon nitride precursor, and then adding glycerol and absolute ethyl alcohol to obtain a mixed solution; refluxing the mixed solution for a period of time at constant temperature, and centrifuging the mixed solution obtained after refluxing to obtain a precipitate; placing the precipitate into a vacuum oven for drying to obtain a composite material;
4. fully grinding the obtained composite material, then placing the ground composite material into a porcelain boat, placing the porcelain boat into a muffle furnace, heating the muffle furnace, calcining in air for a period of time, and cooling to room temperature to obtain the carbon-dot-based carbon nitride composite material;
5. Adding an H 2PtCl6 solution into the carbon dot-based carbon nitride composite material to obtain a mixed solution; and performing photo-deposition on the mixed solution, and finally freeze-drying to obtain the carbon nitride supported carbon dot anchored small-size Pt composite photocatalytic material.
The carbon nitride-supported carbon dot anchored small-size Pt composite photocatalytic material is used as a photocatalytic material for photocatalytic pyrolysis of water to produce hydrogen.
The principle of the invention is as follows:
The invention reasonably constructs the carbon dot/C 3N4 composite material, can effectively widen the light absorption range of the material, promote the rapid separation of photon-generated carriers, and has important significance for improving the photocatalysis hydrogen production efficiency of the material. In addition, the surface of the carbon dot is provided with changeable functional groups, so that the metal cocatalyst can be effectively dispersed, and the efficiency of the cocatalyst in the photocatalysis process is improved. Therefore, a proper carbon dot/C 3N4 composite material is constructed, a small-size Pt-promoted material is anchored by utilizing the functional groups on the surface of the carbon dot, the light absorption range of the material is widened, the carrier separation efficiency is improved, the promoter efficiency is effectively improved, and the method is very important for realizing high-efficiency photocatalytic hydrogen production.
The invention has the advantages that:
1. The carbon dots used in the invention have unique structure and physical and chemical properties, such as low toxicity, excellent light stability, photoinduction electron transfer characteristic and wider visible light response range, thus opening up new possibility for developing a catalyst with better photocatalytic activity;
2. The controllable synthesis of the composite photocatalytic material serving as the catalyst for anchoring the carbon dots can be realized by regulating and controlling variables such as the material feeding proportion, the heat treatment heating rate and the like;
3. Compared with the traditional synthesis method, the method has the characteristics of relatively simplicity, environmental friendliness and the like, and can save a large amount of experimental materials;
4. The carbon nitride supported carbon dot anchored small-size Pt composite photocatalytic material prepared when the volume ratio of the carbon dot solution to the porous few-layer carrier (precursor) is 0.5mL:0.6g shows good performance and excellent cycle stability of 1.352mmolh -1g-1 of hydrogen production rate of photocatalytic cracking water under the irradiation of visible light, and compared with a control test: under the irradiation of visible light, the hydrogen production rate of the photocatalytic cracking water is 0.729mmol h -1g-1, and the prepared composite photocatalytic material with the carbon dot anchoring serving as a catalyst plays an important role in improving the hydrogen production rate.
Drawings
FIG. 1 is an SEM image of a carbon nitride precursor prepared in step one of comparative example 1;
FIG. 2 is an SEM image of a carbon-supported carbon-dot anchored small-sized Pt composite photocatalytic material prepared in example 1;
FIG. 3 is an ultraviolet-visible light absorption spectrum of the carbon nitride prepared in step three of comparative example 1 and the carbon dot-based carbon nitride composite prepared in step four of example 1;
fig. 4 is a graph of hydrogen production rate of photocatalytic pyrolysis water under simulated sunlight irradiation, in which fig. 1 is a carbon nitride supported carbon dot anchored small-sized Pt composite photocatalytic material prepared in step five of example 1, and fig. 2 is a carbon nitride composite photocatalytic material prepared in step four of comparative example 1.
Detailed Description
The following examples further illustrate the invention but are not to be construed as limiting the invention. Modifications and substitutions to methods, procedures, or conditions of the present invention without departing from the spirit of the invention are intended to be within the scope of the present invention.
The first embodiment is as follows: the preparation method of the carbon nitride supported carbon dot anchored small-size Pt composite photocatalytic material in the embodiment is specifically completed by the following steps:
1. Adding o-phenylenediamine into absolute ethyl alcohol, and stirring for a period of time to obtain an o-phenylenediamine absolute ethyl alcohol solution; transferring the o-phenylenediamine absolute ethanol solution into a polytetrafluoroethylene autoclave, then placing the polytetrafluoroethylene autoclave into a vacuum oven with the temperature of 170-200 ℃ for heat preservation for a period of time, and finally naturally cooling to room temperature to obtain a carbon dot solution;
2. mixing an amine source, a phosphorus source and deionized water, placing the mixture on a stirrer for stirring until the mixture forms a uniform solution, then placing the solution into a constant-temperature water bath kettle, setting the temperature to be 80-130 ℃, and keeping the temperature at 80-130 ℃ for a period of time to obtain a mixed solution; transferring the mixed solution into a polytetrafluoroethylene autoclave, then placing the autoclave into a vacuum oven with the temperature of 150-200 ℃ for heat preservation for a period of time, immediately cooling the autoclave to room temperature, collecting precipitate, cleaning the precipitate, and finally placing the precipitate into the vacuum oven for drying to obtain a carbon nitride precursor;
3. adding a carbon dot solution into a carbon nitride precursor, and then adding glycerol and absolute ethyl alcohol to obtain a mixed solution; refluxing the mixed solution for a period of time at constant temperature, and centrifuging the mixed solution obtained after refluxing to obtain a precipitate; placing the precipitate into a vacuum oven for drying to obtain a composite material;
4. fully grinding the obtained composite material, then placing the ground composite material into a porcelain boat, placing the porcelain boat into a muffle furnace, heating the muffle furnace, calcining in air for a period of time, and cooling to room temperature to obtain the carbon-dot-based carbon nitride composite material;
5. Adding an H 2PtCl6 solution into the carbon dot-based carbon nitride composite material to obtain a mixed solution; and performing photo-deposition on the mixed solution, and finally freeze-drying to obtain the carbon nitride supported carbon dot anchored small-size Pt composite photocatalytic material.
The second embodiment is as follows: the present embodiment differs from the specific embodiment in that: the volume ratio of the mass of the o-phenylenediamine to the absolute ethyl alcohol in the first step is 1.5g (100 mL-200 mL); the stirring time in the first step is 0.5-2 h, and the stirring speed is 100-300 r/min; and in the first step, the mixture is put into a vacuum oven with the temperature of 170-200 ℃ for heat preservation for 9-12 h. The other steps are the same as in the first embodiment.
And a third specific embodiment: this embodiment differs from the first or second embodiment in that: the amine source in the second step is melamine; the volume ratio of the mass of the amine source to the deionized water in the second step is 1.0g (60 mL-120 mL); the phosphorus source in the second step is phosphorous acid; the volume ratio of the mass of the phosphorus source to the deionized water in the second step is 1.2g (60 mL-120 mL). The other steps are the same as those of the first or second embodiment.
The specific embodiment IV is as follows: one difference between this embodiment and the first to third embodiments is that: in the second step, the constant temperature is kept at 80-130 ℃ for 0.5-2 h; and step two, transferring the mixed solution into a polytetrafluoroethylene autoclave, and then placing the polytetrafluoroethylene autoclave into a vacuum oven with the temperature of 150-200 ℃ for heat preservation for 7-12 h. The other steps are the same as those of the first to third embodiments.
Fifth embodiment: one to four differences between the present embodiment and the specific embodiment are: in the second step, the sediment is respectively washed by deionized water and absolute ethyl alcohol for 2 to 6 times, and the centrifugal speed is 3000r/min to 6000r/min; and in the second step, the temperature for drying the precipitate is 45-65 ℃. Other steps are the same as those of the first to fourth embodiments.
Specific embodiment six: the present embodiment differs from the first to fifth embodiments in that: the volume ratio of the mass of the carbon nitride precursor to the glycerol in the third step is (0.4 g-0.8 g) 5mL; the volume ratio of the mass of the carbon nitride precursor to the absolute ethyl alcohol in the third step is (0.4 g-0.8 g) 15mL; the volume ratio of the mass of the carbon nitride precursor to the carbon dot solution in the third step is (0.4 g-0.8 g) 0.5mL. Other steps are the same as those of the first to fifth embodiments.
Seventh embodiment: one difference between the present embodiment and the first to sixth embodiments is that: in the third step, the mixed solution is subjected to constant temperature reflux at 80-130 ℃ for 2-6 h; in the third step, the mixed solution obtained after the reflux is centrifuged for 2 to 6 times, the time of each centrifugation is 2 to 6 minutes, and the speed of the centrifugation is 3000 to 6000r/min; and thirdly, placing the precipitate into a vacuum oven for drying, wherein the drying temperature is 45-65 ℃ and the drying time is 8-12 h. Other steps are the same as those of embodiments one to six.
Eighth embodiment: one difference between the present embodiment and the first to seventh embodiments is that: in the fourth step, the temperature rising rate of the muffle furnace is 0.5-5 ℃/min; and step four, calcining in air at 300-600 ℃ for 1-4 h. The other steps are the same as those of embodiments one to seven.
Detailed description nine: one of the differences between this embodiment and the first to eighth embodiments is: the mass ratio of H 2PtCl6 and the carbon dot-based carbon nitride composite material in the mixed solution in the fifth step is 0.5-1.5%; the photo-deposition in the fifth step is specifically: irradiating for 30-50 min under a xenon lamp by using a cut420 optical filter; and step five, the freeze drying temperature is-15 ℃ to-35 ℃ and the freeze drying time is 24h to 48h. Other steps are the same as those of embodiments one to eight.
Detailed description ten: the present embodiment differs from the first to ninth embodiments in that: the carbon nitride-supported carbon dot anchored small-size Pt composite photocatalytic material is used as a photocatalytic material for photocatalytic pyrolysis of water to produce hydrogen. The other steps are the same as those of embodiments one to nine.
The following examples are used to verify the benefits of the present invention:
Example 1: the preparation method of the carbon nitride supported carbon dot anchored small-size Pt composite photocatalytic material is specifically completed by the following steps:
1. Adding 1.5g of o-phenylenediamine into 150mL of absolute ethyl alcohol, and stirring for 1h at the stirring speed of 250r/min to obtain an o-phenylenediamine absolute ethyl alcohol solution; transferring the o-phenylenediamine absolute ethanol solution into a polytetrafluoroethylene autoclave, then placing the autoclave into a vacuum oven with the temperature of 180 ℃ for heat preservation for 12 hours, and finally naturally cooling to room temperature to obtain a carbon dot solution;
2. mixing an amine source, a phosphorus source and deionized water, placing the mixture on a stirrer for stirring until the mixture forms a uniform solution, then placing the solution into a constant-temperature water bath kettle, setting the temperature to be 80 ℃, and keeping the temperature at 80 ℃ for 1h to obtain a mixed solution; transferring the mixed solution into a polytetrafluoroethylene autoclave, then placing the polytetrafluoroethylene autoclave into a vacuum oven with the temperature of 180 ℃ for heat preservation for 10 hours, immediately cooling the polytetrafluoroethylene autoclave to room temperature, collecting sediment, and centrifugally flushing the sediment for 3 times by using deionized water and absolute ethyl alcohol respectively, wherein the centrifugal speed is 4000r/min; finally, placing the precipitate in a vacuum oven to dry for 10 hours at the temperature of 60 ℃ to obtain a carbon nitride precursor;
the amine source in the second step is melamine;
The volume ratio of the mass of the amine source to the deionized water in the second step is 1.0g to 100mL;
The phosphorus source in the second step is phosphorous acid;
the volume ratio of the mass of the phosphorus source to the deionized water in the second step is 1.2g to 100mL;
3. adding a carbon dot solution into a carbon nitride precursor, and then adding glycerol and absolute ethyl alcohol to obtain a mixed solution; refluxing the mixed solution at a constant temperature of 90 ℃ for 3 hours, and centrifuging the mixed solution obtained after refluxing for 3 times, wherein the centrifuging time is 4min each time, and the centrifuging speed is 4000r/min to obtain a precipitate; placing the precipitate into a vacuum oven for drying for 10 hours at the temperature of 60 ℃ to obtain a composite material;
the volume ratio of the mass of the carbon nitride precursor to the glycerol in the third step is 0.6g to 5mL;
The volume ratio of the mass of the carbon nitride precursor to the absolute ethyl alcohol in the third step is 0.6g:15mL;
The volume ratio of the mass of the carbon nitride precursor to the carbon dot solution in the third step is 0.6g:0.5mL;
4. fully grinding the obtained composite material, then placing the ground composite material into a porcelain boat, placing the porcelain boat into a muffle furnace, heating the muffle furnace to 500 ℃ at a heating rate of 2 ℃/min, calcining in air for 2 hours, and cooling to room temperature to obtain a carbon dot-based carbon nitride composite material (CDs/C 3N4);
5. Adding an H 2PtCl6 solution into the carbon dot-based carbon nitride composite material to obtain a mixed solution; performing photo-deposition on the mixed solution, and finally freeze-drying to obtain the carbon nitride supported carbon dot anchored small-size Pt composite photocatalytic material;
the mass ratio of H 2PtCl6 to the carbon dot-based carbon nitride composite material in the mixed solution in the fifth step is 1%;
the photo-deposition in the fifth step is specifically: irradiation under a xenon lamp (PLS-SXE 300) for 40min using a cut420 filter;
the temperature of the freeze drying in the fifth step is-25 ℃, and the time of the freeze drying is 40 hours.
Comparative example 1: the preparation of the carbon nitride composite photocatalytic material is completed according to the following steps:
1. Mixing an amine source, a phosphorus source and deionized water, placing the mixture on a stirrer for stirring until the mixture forms a uniform solution, then placing the solution into a constant-temperature water bath kettle, setting the temperature to be 80 ℃, and keeping the temperature at 80 ℃ for 1h to obtain a mixed solution; transferring the mixed solution into a polytetrafluoroethylene autoclave, then placing the polytetrafluoroethylene autoclave into a vacuum oven with the temperature of 180 ℃ for heat preservation for 10 hours, immediately cooling the polytetrafluoroethylene autoclave to room temperature, collecting sediment, and centrifugally flushing the sediment for 3 times by using deionized water and absolute ethyl alcohol respectively, wherein the centrifugal speed is 4000r/min; finally, placing the precipitate in a vacuum oven to dry for 10 hours at the temperature of 60 ℃ to obtain a carbon nitride precursor;
the amine source in the first step is melamine;
the volume ratio of the mass of the amine source to the deionized water in the first step is 1.0g to 100mL;
The phosphorus source in the first step is phosphorous acid;
The volume ratio of the mass of the phosphorus source to the deionized water in the first step is 1.2g to 100mL;
2. Adding glycerol and absolute ethyl alcohol into the carbon nitride precursor to obtain a mixed solution; refluxing the mixed solution at a constant temperature of 90 ℃ for 3 hours, and centrifuging the mixed solution obtained after refluxing for 3 times, wherein the centrifuging time is 4min each time, and the centrifuging speed is 4000r/min to obtain a precipitate; placing the precipitate into a vacuum oven for drying for 10 hours at the temperature of 60 ℃ to obtain a composite material;
the volume ratio of the mass of the precursor to the glycerol in the second step is 0.6g to 5mL;
The volume ratio of the mass of the precursor to the absolute ethyl alcohol in the second step is 0.6g to 15mL;
3. fully grinding the obtained composite material, then placing the ground composite material into a porcelain boat, placing the porcelain boat into a muffle furnace, heating the muffle furnace to 500 ℃ at a heating rate of 2 ℃/min, calcining in air for 2 hours, and cooling to room temperature to obtain carbon nitride;
4. Adding an H 2PtCl6 solution into carbon nitride to obtain a mixed solution; performing photo-deposition on the mixed solution, and finally freeze-drying to obtain a carbon nitride composite photocatalytic material;
the mass ratio of H 2PtCl6 to carbon nitride in the mixed solution in the fourth step is 1%;
The photo-deposition in the fourth step is specifically: irradiation under a xenon lamp (PLS-SXE 300) for 40min using a cut420 filter;
The temperature of the freeze drying in the step four is minus 25 ℃, and the time of the freeze drying is 40 hours.
FIG. 1 is an SEM image of a carbon nitride precursor prepared in step one of comparative example 1;
FIG. 2 is an SEM image of a carbon-supported carbon-dot anchored small-sized Pt composite photocatalytic material prepared in example 1;
As can be seen from fig. 1 and 2: the surface of the carrier is provided with a lamellar structure, and carbon points are added to ensure that the surface of the carrier is more loose, and the spinning and stripping are more obvious.
FIG. 3 is an ultraviolet-visible light absorption spectrum of the carbon nitride prepared in step three of comparative example 1 and the carbon dot-based carbon nitride composite prepared in step four of example 1;
as can be seen from fig. 3: the addition of the carbon dot solution obviously widens the visible light absorption range of the composite material.
The hydrogen production rate of the carbon nitride supported carbon dot anchored small-size Pt composite photocatalytic material prepared in the step five of the example 1 and the carbon nitride composite photocatalytic material prepared in the step four of the comparative example 1 under the irradiation of visible light is shown in fig. 4;
fig. 4 is a graph of hydrogen production rate of photocatalytic pyrolysis water under simulated sunlight irradiation, in which fig. 1 is a carbon nitride supported carbon dot anchored small-sized Pt composite photocatalytic material prepared in step five of example 1, and fig. 2 is a carbon nitride composite photocatalytic material prepared in step four of comparative example 1.
As can be seen from fig. 4, the carbon nitride supported carbon dot anchored small-sized Pt composite photocatalytic material prepared in example 1 has a hydrogen production rate of 1.352mmolh -1g-1 in photocatalytic pyrolysis water under simulated visible light irradiation, and the carbon nitride composite photocatalytic material prepared in comparative example 1 has a hydrogen production rate of only 0.729mmolh -1g-1 in photocatalytic pyrolysis water under visible light irradiation. Compared with a single porous few-layer C 3N4 photocatalyst, the photocatalytic pyrolysis water hydrogen production rate of the carbon nitride supported carbon dot anchored small-size Pt composite photocatalytic material can be improved by more than about one time.
Comparative example 2: the difference between this embodiment and embodiment 1 is that: the volume ratio of the mass of the carbon nitride precursor to the carbon dot solution in the step three is 0.6 g/0.05 mL. Other steps and parameters were the same as in example 1.
Comparative example 3: the difference between this embodiment and embodiment 1 is that: the volume ratio of the mass of the carbon nitride precursor to the carbon dot solution in the step three is 0.6g:0.3mL. Other steps and parameters were the same as in example 1.
The small-size Pt composite photocatalytic material with carbon dot anchoring on carbon nitride prepared in comparative example 2 has a hydrogen production rate of 0.806mmolh -1g-1 in photocatalytic pyrolysis water under simulated visible light irradiation.
The carbon nitride supported carbon dot anchored small-size Pt composite photocatalytic material prepared in comparative example 3 has a hydrogen production rate of 1.103mmolh -1g-1 in photocatalytic pyrolysis water under simulated visible light irradiation.
Claims (6)
1. The preparation method of the carbon nitride supported carbon dot anchored small-size Pt composite photocatalytic material is characterized by comprising the following steps of:
1. Adding o-phenylenediamine into absolute ethyl alcohol, and stirring for a period of time to obtain an o-phenylenediamine absolute ethyl alcohol solution; transferring the o-phenylenediamine absolute ethanol solution into a polytetrafluoroethylene autoclave, then placing the polytetrafluoroethylene autoclave into a vacuum oven with the temperature of 170-200 ℃ for heat preservation for a period of time, and finally naturally cooling to room temperature to obtain a carbon dot solution;
2. mixing an amine source, a phosphorus source and deionized water, placing the mixture on a stirrer for stirring until the mixture forms a uniform solution, then placing the solution into a constant-temperature water bath kettle, setting the temperature to be 80-130 ℃, and keeping the temperature at 80-130 ℃ for a period of time to obtain a mixed solution; transferring the mixed solution into a polytetrafluoroethylene autoclave, then placing the autoclave into a vacuum oven with the temperature of 150-200 ℃ for heat preservation for a period of time, immediately cooling the autoclave to room temperature, collecting precipitate, cleaning the precipitate, and finally placing the precipitate into the vacuum oven for drying to obtain a carbon nitride precursor;
the amine source in the second step is melamine; the volume ratio of the mass of the amine source to the deionized water in the second step is 1.0g (60 mL-120 mL);
The phosphorus source in the second step is phosphorous acid; the volume ratio of the mass of the phosphorus source to the deionized water in the second step is 1.2g (60 mL-120 mL);
3. adding a carbon dot solution into a carbon nitride precursor, and then adding glycerol and absolute ethyl alcohol to obtain a mixed solution; refluxing the mixed solution for a period of time at constant temperature, and centrifuging the mixed solution obtained after refluxing to obtain a precipitate; placing the precipitate into a vacuum oven for drying to obtain a composite material;
the volume ratio of the mass of the carbon nitride precursor to the glycerol in the third step is (0.4 g-0.8 g) 5mL;
The volume ratio of the mass of the carbon nitride precursor to the absolute ethyl alcohol in the third step is (0.4 g-0.8 g) 15mL;
the volume ratio of the mass of the carbon nitride precursor to the carbon dot solution in the third step is (0.4 g-0.8 g) 0.5mL;
In the third step, the mixed solution is subjected to constant temperature reflux at 80-130 ℃ for 2-6 h;
4. fully grinding the obtained composite material, then placing the ground composite material into a porcelain boat, placing the porcelain boat into a muffle furnace, heating the muffle furnace, calcining in air for a period of time, and cooling to room temperature to obtain the carbon-dot-based carbon nitride composite material;
In the fourth step, the temperature rising rate of the muffle furnace is 0.5-5 ℃/min; in the fourth step, the calcination is carried out in air at the temperature of 300-600 ℃ for 1-4 hours;
5. Adding an H 2PtCl6 solution into the carbon dot-based carbon nitride composite material to obtain a mixed solution; performing photo-deposition on the mixed solution, and finally freeze-drying to obtain the carbon nitride supported carbon dot anchored small-size Pt composite photocatalytic material;
the mass ratio of H 2PtCl6 and the carbon dot-based carbon nitride composite material in the mixed solution in the fifth step is 0.5-1.5%;
The photo-deposition in the fifth step is specifically: irradiating for 30-50 min under a xenon lamp by using a cut420 optical filter;
and step five, the freeze drying temperature is-15 ℃ to-35 ℃ and the freeze drying time is 24h to 48h.
2. The method for preparing the carbon nitride supported carbon dot anchored small-size Pt composite photocatalytic material according to claim 1, wherein the volume ratio of the mass of the o-phenylenediamine to the volume of the absolute ethyl alcohol in the first step is 1.5g (100 mL-200 mL); the stirring time in the first step is 0.5-2 h, and the stirring speed is 100-300 r/min; and in the first step, the mixture is put into a vacuum oven with the temperature of 170-200 ℃ for heat preservation for 9-12 h.
3. The method for preparing the carbon nitride supported carbon dot anchored small-size Pt composite photocatalytic material according to claim 1, wherein in the second step, the constant temperature is maintained at 80-130 ℃ for 0.5-2 hours; and step two, transferring the mixed solution into a polytetrafluoroethylene autoclave, and then placing the polytetrafluoroethylene autoclave into a vacuum oven with the temperature of 150-200 ℃ for heat preservation for 7-12 h.
4. The method for preparing the carbon nitride supported carbon dot anchored small-size Pt composite photocatalytic material according to claim 1, wherein in the second step, the precipitate is centrifugally washed 2-6 times by deionized water and absolute ethyl alcohol respectively, and the centrifugal speed is 3000-6000 r/min; and in the second step, the temperature for drying the precipitate is 45-65 ℃.
5. The method for preparing the carbon nitride supported carbon dot anchored small-size Pt composite photocatalytic material according to claim 1, wherein the mixed solution obtained after reflux in the third step is centrifuged for 2-6 times, the time of each centrifugation is 2-6 min, and the speed of centrifugation is 3000-6000 r/min; and thirdly, placing the precipitate into a vacuum oven for drying, wherein the drying temperature is 45-65 ℃ and the drying time is 8-12 h.
6. The application of the carbon nitride supported carbon dot anchored small-size Pt composite photocatalytic material prepared by the preparation method as claimed in claim 1, wherein the carbon nitride supported carbon dot anchored small-size Pt composite photocatalytic material is used for photocatalytic pyrolysis of water to produce hydrogen.
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