CN112142023B - Preparation method of ionized carbon nitride - Google Patents

Preparation method of ionized carbon nitride Download PDF

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CN112142023B
CN112142023B CN202010971633.2A CN202010971633A CN112142023B CN 112142023 B CN112142023 B CN 112142023B CN 202010971633 A CN202010971633 A CN 202010971633A CN 112142023 B CN112142023 B CN 112142023B
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carbon nitride
ionized carbon
ionized
sodium chloride
drying
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CN112142023A (en
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卢红斌
翟志敏
张佳佳
潘绍学
刘沛莹
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Fudan University
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    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B21/00Nitrogen; Compounds thereof
    • C01B21/082Compounds containing nitrogen and non-metals and optionally metals
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J27/00Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
    • B01J27/24Nitrogen compounds
    • B01J35/39

Abstract

The invention relates to a preparation method of ionized carbon nitride, which specifically comprises the following steps: dissolving urea in water, adding a mixture of sodium chloride and potassium chloride to fully dissolve the urea, and obtaining ionized carbon nitride under the condition of quickly heating the solution; and dialyzing, filtering or centrifuging to obtain an ionized carbon nitride aqueous solution; drying to obtain the ionized carbon nitride powder. The invention has the advantages of low price of raw materials, mild reaction conditions, no need of strong acid or strong alkali, no need of high pressure or vacuum and no pollution to the environment. It can be seen in the infrared spectrum that the ionized carbon nitride surface is modified with hydroxyl and cyano functional groups. In the fluorescence spectrum, the fluorescence intensity of ionized carbon nitride is reduced by about 10 times compared with that of common carbon nitride, the recombination of electrons and holes is inhibited, and the photocatalysis performance is improved. The ionized carbon nitride prepared by the invention can be applied to the fields of photoelectrocatalysis, chemical sensing, photoelectric devices and the like.

Description

Preparation method of ionized carbon nitride
Technical Field
The invention belongs to the technical field of materials, and particularly relates to a preparation method of ionized carbon nitride.
Background
Graphitized carbo-nitriding (g-C) 3 N 4 ) Is an interesting non-metal photocatalyst, and has attracted extensive attention due to its simple preparation process, low production cost, good energy band gap and good chemical stability. However, the photocatalytic activity of pristine g-C3N4 is limited due to its inherent pi-pi conjugated electron system, resulting in slow separation and migration of photogenerated carriers. In order to compensate for the inherent defects of g-C3N4 to improve its performance, it is common practice to heterojunction with other semiconductors to facilitate the separation of electrons and holes. This approach requires the involvement of more than two materials and the bonding at the interface is not ideal. The carbon nitride can be charged on the surface, so that an electric field can be formed inside and outside to promote the separation of electrons and holes.
Carbon nitride is very stable due to hydrogen bonds and van der waals forces, and is difficult to disperse in aqueous solution, usually at a concentration of 0.2 g/l, which relatively affects its photocatalytic performance and its compounding with other materials. For this purpose, a series of methods, for example: such as sonication, heating or acid treatment, at least partially effectively achieve this goal, but these methods inevitably result in a decrease in the yield of carbon nitride due to losses occurring during stripping or etching, do not allow a truly uniformly dispersed carbon nitride solution to be achieved, and in addition, the use of acids and bases causes environmental pollution. In order to realize high-concentration dispersion of carbon nitride in water and inhibit recombination of electrons and holes in the carbon nitride, it is important to develop a preparation method with mild conditions, no pollution and low cost.
Disclosure of Invention
The invention aims to overcome the defects that the traditional carbon nitride is difficult to disperse in water and electrons and holes are easy to recombine under the action of light, and provides a preparation method of an ionized carbon nitride material, which has good dispersity in water and can improve the separation of the electrons and the holes. The invention takes urea with mild reaction condition, no environmental pollution and low cost as a precursor, and prepares the ionized carbon nitride by direct and rapid solution heating method through aqueous solutions of urea, sodium chloride and potassium chloride with different proportions.
The invention provides a preparation method of ionized carbon nitride, which comprises the following specific steps:
(1) Adding sodium chloride and potassium chloride into an aqueous solution containing urea, uniformly mixing, and reacting under the direct and rapid heating condition of the solution to obtain ionized carbon nitride; wherein: the concentration of the urea is 0.1-18 mol/L, the concentration of the sodium chloride is 0.01-6.16 mol/L, and the concentration of the potassium chloride is 0.01-4.58 mol/L;
(2) Dialyzing, centrifuging or filtering the ionized carbon nitride obtained in the step (1) to remove impurities to obtain an ionized carbon nitride aqueous solution;
(3) Drying the ionized carbon nitride aqueous solution obtained in the step (2) to obtain ionized carbon nitride powder;
(4) Dispersing the ionized carbon nitride powder obtained in the step (3) in water at high concentration to obtain ionized carbon nitride gel.
In the present invention, the contents of sodium chloride and potassium chloride in step (1) may exceed their own saturation concentrations, i.e., some of sodium chloride and potassium chloride may be undissolved.
In the invention, the solution in the step (1) is directly and rapidly heated to react for 10 to 20 minutes at the temperature of between 200 and 300 ℃, and then the temperature is raised to between 400 and 600 ℃ at the speed of between 2 and 10 ℃/minute, and the heating reaction time is between 2 and 5 hours.
In the invention, the heating condition in the step (1) is air.
In the invention, the drying treatment in the step (3) is one or a combination of freeze drying, spray drying or supercritical carbon dioxide drying.
The invention has the beneficial effects that: aiming at the defects in the prior art, the inventor provides the technical method of the invention through long-term practice and research, and the method can realize that the carbon nitride surface has negative charges, has good dispersibility in water, and can inhibit the recombination of electrons and holes. In the technical route of the invention, harmful reaction conditions such as acid and alkali are avoided, the key problems of scale preparation and structure regulation of ionized carbon nitride are solved, and an effective way is provided for the application of carbon nitride in the fields of catalysis, sensing, photoelectricity and the like. The invention has the advantages of low price of raw materials, mild reaction conditions, no need of strong acid or strong alkali, no need of high pressure or vacuum and no pollution to the environment. The obtained ionized carbon nitride has sheet structure with size of 50-200 nm, and can be uniformly dispersed in water solution, and when the concentration is up to 200 mg/ml, no cross-linking agent is needed to be added, and gel can be formed at room temperature within 5 min. It can be seen in the infrared spectrum that the ionized carbon nitride surface is modified with hydroxyl and cyano functional groups. In the fluorescence spectrum, the ionized carbon nitride is observed to have fluorescence intensity reduced by about 10 times compared with the common carbon nitride, so that the recombination of electrons and holes is inhibited, and the photocatalysis performance is improved. The ionized carbon nitride prepared by the invention can be applied to the fields of photoelectrocatalysis, chemical sensing, photoelectric devices and the like. The excellent dispersion property endows the carbon nitride with the ability of forming a composite material with other substances, and the surface charge can inhibit the recombination of electrons and holes, which is beneficial to the photocatalysis performance.
Drawings
FIG. 1 is a transmission electron micrograph of the resulting ionized carbon nitride.
FIG. 2 is an infrared spectrum of ionized carbon nitride and ordinary carbon nitride.
FIG. 3 is a graph of the dispersion of the resulting ionized carbon nitride in water and the Tyndall effect.
FIG. 4 is a graph of the resulting gel formed by the high concentration of ionized carbon nitride (from left to right: ionized carbon nitride forms a gel, conventional carbon nitride does not form a gel).
FIG. 5 is a graph showing fluorescence spectra of conventional carbonitride and ionized carbonitride (from top to bottom: conventional carbonitride, ionized carbonitride).
Detailed Description
The technical solution of the present invention is illustrated by the following specific examples. It is to be understood that one or more of the steps referred to in the present application do not exclude the presence of other methods or steps before or after said combination of steps or that other methods or steps may be intervening between those steps specifically referred to. It should also be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Unless otherwise indicated, the numbering of the method steps is only for the purpose of identifying the steps, and is not intended to limit the order of arrangement of each method or the scope of the implementation of the invention, and changes or modifications in the relative relationship thereof, without substantial technical changes, should also be considered as the scope of the implementation of the invention.
Example 1:
(1) Dissolving 4g of sodium chloride, 4g of potassium chloride and 8g of urea in 10 ml of deionized water, and stirring until the sodium chloride, the potassium chloride and the urea can not be dissolved again to obtain precursor mother liquor;
(2) Rapidly heating the precursor mother liquor obtained in the step (1) in a muffle furnace at 300 ℃ for 15 minutes, then heating to 500 ℃ at a speed of 10 ℃/minute, sintering at 500 ℃ for 120 minutes, then taking out, and naturally cooling at room temperature;
(3) Filtering the carbon nitride obtained in the step (2);
(4) And (4) freeze-drying the carbon nitride obtained in the step (3).
The transmission electron micrograph of the ionized carbon nitride prepared in this example is shown in FIG. 1.
The infrared spectrum of the ionized carbon nitride prepared in this example is shown in FIG. 2. The oscillation peaks of the amino and hydroxyl groups can be seen in the figure.
The ionized carbon nitride prepared in this example was dispersed in water at a concentration of 1 mg/ml to produce the tyndall effect, as shown in figure 3.
Example 2:
(1) Dissolving 4g of sodium chloride, 4g of potassium chloride and 8g of urea in 10 ml of deionized water, and stirring until the sodium chloride, the potassium chloride and the urea can not be dissolved again to obtain precursor mother liquor;
(2) Rapidly heating the precursor mother liquor obtained in the step (1) in a muffle furnace at 300 ℃ for 15 minutes, then heating to 500 ℃ at a speed of 10 ℃/minute, sintering at 500 ℃ for 120 minutes, then taking out, and naturally cooling at room temperature;
(3) Filtering the carbon nitride obtained in the step (2);
(4) Freeze-drying the carbon nitride obtained in the step (3);
(5) The carbon nitride powder obtained in step (4) was dispersed in water at 200 mg/ml, and a gel was formed within 5 minutes.
The gel formed by the ionized carbon nitride prepared in this example is shown in FIG. 4.
The fluorescence spectrum of the ionized carbon nitride prepared in this example is shown in FIG. 5. It can be seen that the fluorescence intensity is reduced by approximately 10 times as compared with the intensity of conventional carbon nitride, and recombination of electrons and holes is suppressed.
Example 3:
(1) Dissolving 3g of sodium chloride, 3g of potassium chloride and 8g of urea in 10 ml of deionized water, and stirring until the sodium chloride, the potassium chloride and the urea are completely dissolved to obtain precursor mother liquor;
(2) Rapidly heating the precursor mother liquor obtained in the step (1) in a muffle furnace at 300 ℃ for 15 minutes, then heating to 500 ℃ at a speed of 10 ℃/minute, sintering at 500 ℃ for 120 minutes, then taking out, and naturally cooling at room temperature;
(3) Filtering the carbon nitride obtained in the step (2);
(4) And (4) freeze-drying the carbon nitride obtained in the step (3).
Example 4:
(1) Dissolving 2g of sodium chloride, 2g of potassium chloride and 8g of urea in 10 ml of deionized water, stirring until the sodium chloride, the potassium chloride and the urea are completely dissolved, and uniformly mixing to obtain precursor mother liquor;
(2) Rapidly heating the precursor mother liquor obtained in the step (1) in a muffle furnace at 300 ℃ for 15 minutes, then heating to 500 ℃ at a speed of 10 ℃/minute, sintering at 500 ℃ for 120 minutes, then taking out, and naturally cooling at room temperature;
(3) Filtering the carbon nitride obtained in the step (2);
(4) And (4) freeze-drying the carbon nitride obtained in the step (3).
Example 5
(1) Dissolving 2.5g of sodium chloride, 2.5g of potassium chloride and 8g of urea in 10 ml of deionized water, stirring until the sodium chloride, the potassium chloride and the urea are completely dissolved, and uniformly mixing to obtain precursor mother liquor;
(2) Rapidly heating the precursor mother liquor obtained in the step (1) in a muffle furnace at 300 ℃ for 15 minutes, then heating to 500 ℃ at a speed of 10 ℃/minute, sintering at 500 ℃ for 120 minutes, then taking out, and naturally cooling at room temperature;
(3) Filtering the carbon nitride obtained in the step (2);
(4) And (4) freeze-drying the carbon nitride obtained in the step (3).
Comparative example 1:
(1) Putting 8g urea solid in a crucible, putting the crucible in a muffle furnace at 20 ℃, heating the crucible to 500 ℃ at 10 ℃/min, sintering the crucible at 500 ℃ for 120 min, taking out the crucible, and naturally cooling the crucible at room temperature.
(2) And (2) grinding the carbon nitride obtained in the step (1) in a mortar to obtain carbon nitride powder.
The infrared spectrum of the conventional carbon nitride prepared in this example is shown in FIG. 2.
The non-gel pattern of the conventional carbon nitride prepared in this example is shown in fig. 4.
The fluorescence spectrum of the conventional carbon nitride prepared in this example is shown in FIG. 5.
Comparative example 2:
(1) 8g urea was dissolved in 10 ml of an aqueous solution, placed in a muffle furnace at 20 ℃ and then heated to 500 ℃ at 10 ℃/min, sintered at 500 ℃ for 120 minutes, and then removed and naturally cooled at room temperature.
(2) And (2) grinding the carbon nitride obtained in the step (1) in a mortar to obtain carbon nitride powder.

Claims (4)

1. A preparation method of ionized carbon nitride is characterized by comprising the following specific steps:
(1) Adding sodium chloride and potassium chloride into an aqueous solution containing urea, uniformly mixing, and reacting under the direct and rapid heating condition of the solution to obtain ionized carbon nitride; wherein: the concentration of the urea is 0.1-18 mol/L, the concentration of the sodium chloride is 0.01-6.16 mol/L, and the concentration of the potassium chloride is 0.01-4.58 mol/L; the direct rapid heating condition is that the rapid reaction is carried out for 10 to 20 minutes at the temperature of between 200 and 300 ℃, then the temperature is raised to between 400 and 600 ℃ at the speed of between 2 and 10 ℃/minute, and the heating reaction time is between 2 and 5 hours;
(2) Dialyzing, centrifuging or filtering the ionized carbon nitride obtained in the step (1) to remove impurities to obtain an ionized carbon nitride aqueous solution;
(3) Drying the ionized carbon nitride aqueous solution obtained in the step (2) to obtain ionized carbon nitride powder;
(4) Dispersing the ionized carbon nitride powder obtained in the step (3) in water at high concentration to obtain ionized carbon nitride gel.
2. A method of producing ionized carbon nitride in accordance with claim 1, wherein the sodium chloride and potassium chloride in step (1) are contained in excess of their own saturation concentrations, i.e., a part of the sodium chloride and potassium chloride is not dissolved.
3. The method according to claim 1, wherein the heating condition in step (1) is air.
4. The method of claim 1, wherein the drying process in step (3) is one or a combination of freeze drying, spray drying and supercritical carbon dioxide drying.
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011049085A1 (en) * 2009-10-20 2011-04-28 独立行政法人産業技術総合研究所 Photocatalyst containing carbon nitride, method for producing same, and air purification method using the photocatalyst
CN110215929A (en) * 2019-06-04 2019-09-10 中国石油大学(华东) A kind of preparation method of the carbonitride of a large amount of negative electrical charges of surface band
CN111359652A (en) * 2020-04-29 2020-07-03 中国计量大学 Carbon nitride-based nickel-gold bimetallic supported catalyst and preparation method thereof
CN111514917A (en) * 2020-05-15 2020-08-11 扬州大学 Na and Fe co-doped carbon nitride Fenton reaction catalyst and preparation method thereof

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011049085A1 (en) * 2009-10-20 2011-04-28 独立行政法人産業技術総合研究所 Photocatalyst containing carbon nitride, method for producing same, and air purification method using the photocatalyst
CN110215929A (en) * 2019-06-04 2019-09-10 中国石油大学(华东) A kind of preparation method of the carbonitride of a large amount of negative electrical charges of surface band
CN111359652A (en) * 2020-04-29 2020-07-03 中国计量大学 Carbon nitride-based nickel-gold bimetallic supported catalyst and preparation method thereof
CN111514917A (en) * 2020-05-15 2020-08-11 扬州大学 Na and Fe co-doped carbon nitride Fenton reaction catalyst and preparation method thereof

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