Preparation and application of potassium-doped inverse opal carbon nitride photocatalyst
阅读说明：本技术 一种钾掺杂的反蛋白石氮化碳光催化剂的制备与应用 (Preparation and application of potassium-doped inverse opal carbon nitride photocatalyst ) 是由 雷菊英 刘勇弟 陈斌 张金龙 王灵芝 周亮 丁宁恺 于 2019-08-14 设计创作，主要内容包括：本发明提供了一种钾掺杂的反蛋白石氮化碳(IO K-CN)光催化剂的制备方法,该催化剂在可见光作用下可以很好地用于左氧氟沙星(LVX)等抗生素污染物的降解。本发明以三维有序排列的二氧化硅(SiO<Sub>2</Sub>)作为硬模板,溴化钾(KBr)作为前驱体来合成钾掺杂的反蛋白石氮化碳。通过调控KBr的质量分数探究最佳负载量。本发明所述方法可以简单通过改变KBr的质量来控制掺入的钾的质量分数。制备的钾掺杂的反蛋白石氮化碳材料具有减小的带隙和较高的的光生电子-空穴对分离效率,表现出优异的光催化活性。通过将其应用于LVX废水的降解,发现其可以在可见光的驱动下快速降解抗生素,并具有比普通氮化碳(bulk CN)以及纯反蛋白石氮化碳(IO CN)材料更好的光催化活性。(The invention provides a preparation method of a potassium-doped inverse opal carbon nitride (IO K-CN) photocatalyst, and the catalyst can be well used for degrading antibiotic pollutants such as Levofloxacin (LVX) and the like under the action of visible light. The invention relates to silicon dioxide (SiO) arranged in three-dimensional order 2 ) As a hard template, potassium bromide (KBr) as a precursorPotassium-doped inverse opal carbon nitride. And (3) exploring the optimal loading capacity by regulating the mass fraction of KBr. The method of the invention can control the mass fraction of potassium incorporated simply by varying the mass of KBr. The prepared potassium-doped inverse opal carbon nitride material has a reduced band gap and higher separation efficiency of photo-generated electron-hole pairs, and shows excellent photocatalytic activity. By applying the material to degradation of LVX wastewater, the material is found to be capable of rapidly degrading antibiotics under the drive of visible light and has better photocatalytic activity than common carbon nitride (bulk CN) and pure inverse opal carbon nitride (IO CN) materials.)
1. A preparation method of a potassium-doped inverse opal carbon nitride photocatalyst is characterized by comprising the following steps:
(1) Uniformly mixing a certain amount of tetraethyl silicate (TEOS) and ethanol (EtOH) to form a solution A; mixing a certain amount of ethanol (EtOH) and water (H)2O) and ammonia (NH)3·H2O) mixing thoroughly to form a solution B; under magnetic stirring, adding the solution A into the solution B, reacting for a certain time, centrifuging and washing for a plurality of times after the reaction is finished, and drying for a period of time to obtain silicon dioxide spheres;
(2) Dispersing the obtained silicon dioxide spheres in water, pouring the water into a glass bottle, and performing evaporation arrangement at a certain temperature and time to obtain the orderly-arranged SiO2A pellet template;
(3) Weighing a certain amount of carbon nitride precursor, KBr and SiO2Uniformly mixing the small ball templates, putting the mixture into a porcelain ark, calcining the mixture at a certain temperature for a period of time at a certain heating rate in a certain atmosphere, calcining the mixture at a certain heating rate for a second time to a certain temperature, and then preserving the heat for a period of time to obtain a sample, etching the sample by using acid or alkali solution with a certain concentration for a period of time to remove SiO2A pellet template; and washing with water for several times, and drying for a certain time to obtain the potassium-doped inverse opal carbon nitride photocatalyst IO K-CN.
2. The method of claim 1, wherein in solution a of step (1), the amount of tetraethyl silicate TEOS is 1-100mL, and the amount of ethanol EtOH is 10-500 mL; in the solution B, the amount of ethanol EtOH is 10-500mL, and water H2O in an amount of 5-100mL, ammonia NH3·H2The amount of O is 1-100 mL; the reaction time is 10-25h, and the drying time is 8-40 h.
3. the method of claim 2, wherein in step (2), the SiO is2The amount of the small balls is 0.1-1.5g, and the amount of the deionized water is 50-350 mL; the SiO2The pellet arrangement temperature is 80-150 deg.C, and the arrangement time is 5-40 h.
4. The method according to the preceding claim, wherein in step (3) the carbon nitride precursor is selected from dicyanodiamide (DCDA), urea (urea), thiourea (thiourea), melamine (melamine), cyanamide (monocyanamide), guanidine hydrochloride (guanidine hydrochloride) in an amount of 0.3-2.5g, KBr in an amount of 0.1-0.2g, SiO in an amount of 0.1-0.2g2The addition amount of the small balls is 0.5-5 g; the atmosphere is selected from nitrogen (N2) and argon (Ar), the calcining temperature is 300-700 ℃, the heat preservation time is 0.5-9h, and the heating rate is 0.2-9 ℃ per minute-1(ii) a The etching SiO2The acid solution used for the template is selected from hydrofluoric acid (HF), ammonium hydrogen fluoride (NH)4HF2) The concentration range is 3-10mol/L, the alkali solution is NaOH solution, the concentration range is 3-8mol/L, and the etching time is 10-96 h.
5. A potassium-doped inverse opal carbon nitride photocatalyst obtainable by a process as claimed in any one of claims 1 to 4.
6. Use of a potassium-doped inverse opal carbon nitride photocatalyst obtained by the method according to any one of claims 1 to 4 for photocatalytic degradation of LVX, photocatalytic degradation of organic contaminants, photocatalytic hydrogen peroxide production, photocatalytic water splitting hydrogen production, in particular photocatalytic LVX degradation.
Technical Field
The invention relates to a photocatalyst for photocatalytic degradation of LVX, in particular to a potassium-doped inverse opal carbon nitride photocatalyst, belonging to the field of nano materials and the technical field of photocatalysis.
Background
In recent years, the application of semiconductor photocatalysts to the degradation of antibiotic wastewater is receiving wide attention, because the process can fully utilize clean sunlight as the reaction power. Moreover, the method for degrading the antibiotic pollutants by photocatalysis does not generate toxic byproducts, and can be regarded as a safe and green method.
Graphite phase carbon nitride (g-C)3N4) The N-type semiconductor is an n-type semiconductor without metal, and has good physical and chemical stability and environmental friendliness. However, ordinary g-C3N4There are two drawbacks: (1) the visible light absorption capacity is low; (2) the visible light utilization efficiency is low. Combining the inverse opal structure of the photonic crystal with g-C3N4In combination, the potassium-doped inverse opal carbon nitride prepared by simultaneously doping proper amount of potassium can effectively solve the two defects. The potassium is doped to promote the absorption capability of visible light, and the special forbidden band scattering effect and the slow light effect of the inverse opal structure can effectively improve the utilization efficiency of the visible light.
Due to the improvement of the visible light absorption capacity, the improvement of the visible light utilization efficiency and the improvement of the separation efficiency of photo-generated electrons and holes, the improvement of the activity of the photocatalyst formed by combining the inverse opal structure and potassium doping is foreseeable.
Therefore, based on the above research background, the present invention prepares a potassium-doped inverse opal carbon nitride photocatalyst and uses the potassium-doped inverse opal carbon nitride photocatalyst for photocatalytic degradation of LVX under visible light excitation, and simultaneously systematically compares the difference of the potassium-doped inverse opal carbon nitride photocatalyst from the degradation of LVX by other carbon nitride photocatalysts. On one hand, the inverse opal structure has a periodic pore channel structure, so that the separation of photo-generated electrons and holes can be promoted, and the specific forbidden band scattering effect and the 'slow light effect' of the inverse opal structure can effectively improve the utilization efficiency of visible light; on the other hand, the incorporation of potassium promotes the absorption capability of visible light. The potassium-doped inverse opal carbon nitride photocatalyst prepared by the invention has larger specific surface area, higher visible light absorption capacity, higher visible light utilization efficiency and higher separation efficiency of photo-generated electrons and holes, thereby having excellent capacity of degrading LVX and providing a new way for green and safe treatment of LVX wastewater.
disclosure of Invention
In order to improve the effect of photocatalytic degradation of LVX under the excitation of visible light, the invention provides a preparation method of a potassium-doped inverse opal carbon nitride (IO K-CN) photocatalyst, and the catalyst can be well used for degradation of antibiotic pollutants such as Levofloxacin (LVX) and the like under the action of visible light. The invention relates to silicon dioxide (SiO) arranged in three-dimensional order2) As a hard template, dicyanodiamide (DCDA), potassium bromide (KBr) was used as a precursor to synthesize potassium-doped inverse opal carbon nitride. And (3) exploring the optimal loading capacity by regulating the mass fraction of KBr. The method of the invention can control the mass fraction of potassium incorporated simply by varying the mass of KBr. The potassium-doped inverse opal carbon nitride photocatalyst is prepared by a method of calcining a precursor and a hard template in an inert atmosphere and is applied to degradation of antibiotic pollutants. And simultaneously compared with the degradation LVX of other carbon nitride photocatalysts. The method can simply prepare the potassium-doped inverse opal carbon nitride photocatalyst by calcining the hard template and the precursor in an inert atmosphere. The inverse opal structure and the doped potassium improve the separation efficiency of photon-generated carriers together, thereby improving the photocatalytic activity. Preparation ofThe potassium-doped inverse opal carbon nitride material has reduced band gap and higher separation efficiency of photo-generated electron-hole pairs, and shows excellent photocatalytic activity. By applying the material to degradation of LVX wastewater, the material is found to be capable of rapidly degrading antibiotics under the drive of visible light and has better photocatalytic activity than common carbon nitride (bulk CN) and pure inverse opal carbon nitride (IO CN) materials.
The preparation method of the potassium-doped inverse opal carbon nitride photocatalyst provided by the invention comprises the following steps:
(1) Uniformly mixing a certain amount of tetraethyl silicate (TEOS) and ethanol (EtOH) to form a solution A; mixing a certain amount of ethanol (EtOH) and water (H)2O) and ammonia (NH)3·H2O) mixing thoroughly to form a solution B; under magnetic stirring, adding the solution A into the solution B, reacting for a certain time, centrifuging and washing for a plurality of times after the reaction is finished, and drying for a period of time to obtain silicon dioxide spheres;
(2) Dispersing the obtained silicon dioxide spheres in water, pouring the water into a glass bottle, and performing evaporation arrangement at a certain temperature and time to obtain the orderly-arranged SiO2A pellet template;
(3) Weighing a certain amount of carbon nitride precursor, KBr and SiO2Uniformly mixing the small ball templates, putting the mixture into a porcelain ark, calcining the mixture at a certain temperature for a period of time at a certain heating rate in a certain atmosphere, calcining the mixture at a certain heating rate for a second time to a certain temperature, and then preserving the heat for a period of time to obtain a sample, etching the sample by using acid or alkali solution with a certain concentration for a period of time to remove SiO2A pellet template; and washing with water for several times, and drying for a certain time to obtain the potassium-doped inverse opal carbon nitride photocatalyst IO K-CN.
In the solution A in the step (1), the amount of tetraethyl silicate TEOS is 1-100mL, and the amount of ethanol EtOH is 10-500 mL; in the solution B, the amount of ethanol EtOH is 10-500mL, and water H2O in an amount of 5-100mL, ammonia NH3·H2The amount of O is 1-100 mL; the reaction time is 10-25h, and the drying time is 8-40 h;
In the step (2), the SiO2The amount of the small ball is 0.1-1.5g, and the amount of the deionized water50-350 mL; the SiO2The pellet arrangement temperature is 80-150 deg.C, and the arrangement time is 5-40 h.
In the step (3), the carbon nitride precursor is selected from dicyandiamide (DCDA), urea (urea), thiourea (thiourea), melamine (melamine), cyanamide (monocyanamide) and guanidine hydrochloride (guanidinehydrochloride), the adding amount of the carbon nitride precursor is 0.3-2.5g, the adding amount of KBr is 0.1-0.2g, and SiO is2The addition amount of the small balls is 0.5-5 g; the atmosphere is selected from nitrogen (N2) and argon (Ar), the calcining temperature is 300-700 ℃, the heat preservation time is 0.5-9h, and the heating rate is 0.2-9 ℃ per minute-1(ii) a The etching SiO2The acid solution used for the template is selected from hydrofluoric acid (HF), ammonium hydrogen fluoride (NH)4HF2) The concentration range is 3-10mol/L, the alkali solution is NaOH solution, the concentration range is 3-8mol/L, and the etching time is 10-96 h.
The potassium-doped inverse opal carbon nitride photocatalyst obtained by the method is applied to photocatalytic degradation of LVX, photocatalytic degradation of organic pollutants, photocatalytic generation of hydrogen peroxide, photocatalytic decomposition of water for hydrogen production and the like.
The invention has the following beneficial effects:
1) the inventor unexpectedly finds that the potassium-doped inverse opal carbon nitride photocatalyst prepared by the method has extremely strong catalytic capability on the photocatalytic degradation of LVX by doping potassium, and the visible light absorption efficiency of the photocatalyst is greatly enhanced by doping potassium, so that a practical and feasible solution is provided for green treatment of antibiotic wastewater.
2) The alkali metal potassium is embedded into the carbon nitride layers to generate an internal electric field which can serve as an electron transfer channel for carrier diffusion, so that the separation efficiency of photo-generated electrons and holes is effectively improved. In addition, the band gap of the semiconductor material can be obviously reduced by doping potassium ions, so that the visible light absorption capability of the photocatalytic material is obviously enhanced. Meanwhile, the oxidation performance of the material is further enhanced by increasing the valence band potential, which is beneficial to the full degradation of organic matters. Compared with a pure inverse opal carbon nitride material, the potassium-doped inverse opal carbon nitride material can further improve the separation efficiency of photo-generated electrons and holes, and the band gap and the valence band oxidation capability of the material.
3) Due to the problems of difficult degradation and high toxicity of degradation products of antibiotics, the potassium-doped inverse opal carbon nitride material prepared by the method can more efficiently degrade antibiotic wastewater represented by levofloxacin on the basis of a pure inverse opal carbon nitride material, the degradation products are more complete, and the toxicity of degradation intermediates is lower. Furthermore, the ability of pure inverse opal carbon nitride materials to be reduced has been demonstrated, but the oxidative properties remain inadequate. The potassium-doped inverse opal carbon nitride material prepared by the method is greatly improved in oxidation capacity, so that the potassium-doped inverse opal carbon nitride material can be applied to efficient degradation of organic pollutants represented by antibiotics.
4) The use of a hard template SiO in the process of the invention2The inverse protein carbon nitride obtained by carrying out secondary calcination and etching on the globule and the carbon nitride precursor has larger specific surface area, better visible light utilization efficiency and stronger photon-generated carrier separation efficiency.
5) The prepared inverse opal carbon nitride photocatalytic material enhances the visible light utilization efficiency of the photocatalyst due to the slow photon effect and the stop band scattering effect, and the template method enables the specific surface area to be remarkably increased and provides more active sites for the photocatalyst.
6) The inventor finds that the KBr is selected as the potassium source, so that the doping of potassium can be effectively realized, the visible light absorption efficiency can be effectively improved, and in addition, the potassium source is compared with other potassium sources (KNO)3KOH, etc.), the use of KBr as a potassium source compares, on the one hand, to KNO3It is more safe and stable because of KNO3As an easily explosive drug, it is easy to cause production accidents. On the other hand, compared with KOH as a potassium source, KBr is more environment-friendly, and KOH as a strong alkaline medicine is easy to cause environmental pollution.
7) The raw materials used in the method are low in price and easy to obtain, and the prepared photocatalyst is green and environment-friendly, and a series of preparation experiments have strong operability.
8) The potassium-doped inverse opal carbon nitride photocatalyst prepared by the invention has excellent effect on photocatalytic degradation of LVX, and can be used for photocatalytic degradation of organic pollutants, photocatalytic generation of hydrogen peroxide, photocatalytic decomposition of water for hydrogen production and other fields.
Drawings
FIG. 1 is an SEM photograph, TEM photograph and FESEM photograph of IO K-CN (7.5) of example 2.
FIG. 2 is an XRD pattern of samples obtained in examples 1-4 and comparative example 3.
FIG. 3 is an XPS spectrum of IO K-CN (7.5) obtained from example 2.
FIG. 4 is a graph showing the degradation of the samples obtained in examples 1-4 and comparative examples 1-3 to a 10mg/L LVX solution.
FIG. 5 shows the solid UV spectrum, band gap spectrum and Mott Schottky spectrum of the samples obtained in examples 1 to 4 and comparative example 3.
Fig. 6 is a nitrogen adsorption-desorption curve of the samples obtained in example 2 and comparative example 2.
FIG. 7 is a Fourier infrared spectrum of samples obtained in examples 1-4 and comparative example 3.
FIG. 8 shows the results of the cycle stability test of the sample obtained in example 2 and the XRD, SEM and TEM images of IO K-CN (7.5) after 5 cycles.
FIG. 9 is a fluorescence spectrum of samples obtained in examples 1 to 4 and comparative examples 1 to 3.
FIG. 10 is a photocurrent graph and an electrochemical impedance graph of the samples obtained in examples 1 to 4 and comparative example 3.
Detailed Description
The present invention will be described in more detail below with reference to specific examples, but the scope of the present invention is not limited to these examples.
SiO2Preparation of pellet template
8mL of tetraethyl silicate (TEOS) was added to 92mL of ethanol (EtOH) and the solution was mixed well with stirring to form solution A, then 56.6mL of ethanol (EtOH), 29.4mL of water, and 14mL of ammonia were added to a 250mL round bottom flask to form solution B. The solution A was quickly added to the solution B and stirred continuously for 24h at 25 ℃ in an oil bath. After the reaction was completed, the prepared silica spheres were washed with water by centrifugation 3 times. After centrifugal drying, the silica spheres are dispersed in water according to 5 wt%, addedPutting the mixture into a 10mL straight screw-top glass bottle, putting the glass bottle into a 110 ℃ electrothermal blowing dry box for evaporation arrangement, and obtaining the solid on the wall of the glass bottle after evaporation to dryness, namely the orderly-arranged SiO2And (4) a small ball template.