Homomorphic heterojunction photocatalyst and preparation method and application thereof
阅读说明：本技术 一种同素异质结光催化剂及其制备方法和应用 (Homomorphic heterojunction photocatalyst and preparation method and application thereof ) 是由 张静 许紫竹 王芳芳 陈雪冰 于 2019-10-23 设计创作，主要内容包括：本发明涉及光催化剂技术领域,尤其涉及一种同素异质结光催化剂及其制备方法和应用。本发明提供的同素异质结光催化剂,包括Bi<Sub>2</Sub>O<Sub>3</Sub>和Bi<Sub>5</Sub>O<Sub>7</Sub>I；所述Bi<Sub>2</Sub>O<Sub>3</Sub>和Bi<Sub>5</Sub>O<Sub>7</Sub>I的质量比为(0.4～0.8)：(0.2～0.6)。本发明所述的光催化剂具有较高的光催化活性,能够快速、高效的降解污染物。根据实施例的记载,本发明提供的同素异质结光催化剂在60min的光照时间内,对40mg/L甲基橙的降解率最高可达100％,对10mg/L 4-氯苯酚的降解率最高可达100％,实现了对污染物的快速、高效降解。(The invention relates to the technical field of photocatalysts, in particular to a homomorphic heterojunction photocatalyst and a preparation method and application thereof. The homomorphic heterojunction photocatalyst provided by the invention comprises Bi 2 O 3 And Bi 5 O 7 I; the Bi 2 O 3 And Bi 5 O 7 The mass ratio of I is (0.4-0.8): (0.2-0.6). The photocatalyst has higher photocatalytic activity and can degrade pollutants quickly and efficiently. According to the description of the embodiment, the degradation rate of the homological heterojunction photocatalyst provided by the invention to 40mg/L methyl orange can reach 100% at most, and the degradation rate to 10 mg/L4-chlorophenol can reach 100% at most within 60min of illumination time100 percent, and realizes the rapid and high-efficiency degradation of pollutants.)
1. A homomorphic heterojunction photocatalyst is characterized by comprising Bi2O3And Bi5O7I; the Bi2O3And Bi5O7The mass ratio of I is (0.4-0.8): (0.2-0.6).
2. The method of preparing a homological heterojunction photocatalyst as claimed in claim 1, comprising the steps of:
gamma-Bi2O3Mixing the potassium iodide solution and absolute ethyl alcohol, and carrying out a displacement reaction to obtain the homological heterojunction photocatalyst.
3. The method of claim 2, wherein the γ -Bi is2O3The mass ratio of the potassium iodide to the potassium iodide in the potassium iodide solution is 1.45 (1-1.45).
4. The method according to claim 2 or 3, wherein the volume ratio of potassium iodide to water in the potassium iodide solution is (0.166 to 0.322) g: (10-20) mL.
5. The method according to claim 2, wherein the volume ratio of the mass of potassium iodide in the potassium iodide solution to the absolute ethyl alcohol is (0.166 to 0.322) g: 5 mL.
6. The method according to claim 2, wherein the metathesis reaction is carried out under stirring;
the temperature of the displacement reaction is room temperature, and the time of the displacement reaction is 5-30 h.
7. The method according to claim 2 or 6, further comprising, before the substitution reaction, subjecting the mixed solution obtained by the mixing to ultrasound.
8. The method according to claim 2 or 3, wherein the γ -Bi2O3The preparation method comprises the following steps:
mixing the bismuth nitrate pentahydrate solution and the sodium hydroxide solution, and performing liquid-phase precipitation to obtain gamma-Bi2O3。
9. The preparation method according to claim 8, wherein the temperature of the liquid phase precipitation is 75-85 ℃, and the time of the liquid phase precipitation is 2.5-6 h;
the solvent of the bismuth nitrate pentahydrate solution is a nitric acid solution, and the solute is bismuth nitrate pentahydrate;
the dosage ratio of the bismuth nitrate pentahydrate to the nitric acid solution is (10-20) g: (50-100) mL.
10. The use of the homorph heterojunction photocatalyst of claim 1 or the homorph heterojunction photocatalyst prepared by the preparation method of any one of claims 2 to 9 in photocatalytic degradation of water body pollutants.
Technical Field
The invention relates to the technical field of photocatalysts, in particular to a homomorphic heterojunction photocatalyst and a preparation method and application thereof.
Background
The bismuth-based semiconductor photocatalytic material has the natural advantages of safety, no toxicity, rich reserves, low price and the like; and bismuth (Bi) oxide in a bismuth-based photocatalytic material2O3) The preparation method is simple and easy to obtain, and the energy band absorption boundary is in a visible light range, so that the organic pollutant can be well degraded in a visible light wavelength range, and the preparation method has important application in the field of photocatalytic degradation of organic pollutants. However, the bismuth oxide has low transmission efficiency of photogenerated electrons, so that the recombination efficiency of photogenerated carriers is high, and the quantum efficiency is low. These factors limit their practical application in the field of photocatalysis.
Disclosure of Invention
The invention aims to provide a homomorphic heterojunction photocatalyst, and a preparation method and application thereof.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a homomorphic heterojunction photocatalyst which comprises Bi2O3And Bi5O7I; the Bi2O3And Bi5O7The mass ratio of I is (0.4-0.8): (0.2-0.6).
The invention also provides a preparation method of the homological heterojunction photocatalyst in the technical scheme, which comprises the following steps:
gamma-Bi2O3Mixing the potassium iodide solution and absolute ethyl alcohol, and carrying out a displacement reaction to obtain the homological heterojunction photocatalyst.
Preferably, the gamma-Bi2O3The mass ratio of the potassium iodide to the potassium iodide in the potassium iodide solution is 1.45 (1-1.45).
Preferably, the volume ratio of the mass of the potassium iodide to the water in the potassium iodide solution is (0.166-0.322) g: (10-20) mL.
Preferably, the volume ratio of the mass of the potassium iodide in the potassium iodide solution to the absolute ethyl alcohol is (0.166-0.322) g: 5 mL.
Preferably, the displacement reaction is carried out under stirring conditions;
the temperature of the displacement reaction is room temperature, and the time of the displacement reaction is 5-30 h.
Preferably, before the displacement reaction, the method further comprises subjecting the mixed solution obtained by mixing to ultrasound.
Preferably, the gamma-Bi2O3The preparation method comprises the following steps:
mixing the bismuth nitrate pentahydrate solution and the sodium hydroxide solution, and performing liquid-phase precipitation to obtain gamma-Bi2O3。
Preferably, the temperature of the liquid-phase precipitation is 75-85 ℃, and the time of the liquid-phase precipitation is 2.5-6 h;
the solvent of the bismuth nitrate pentahydrate solution is a nitric acid solution, and the solute is bismuth nitrate pentahydrate;
the dosage ratio of the bismuth nitrate pentahydrate to the nitric acid solution is (10-20) g: (50-100) mL.
The invention also provides the application of the homomorphic heterojunction photocatalyst in the technical scheme or the homomorphic heterojunction photocatalyst prepared by the preparation method in the technical scheme in photocatalytic degradation of water pollutants.
The invention provides a homomorphic heterojunction photocatalyst which comprises Bi2O3And Bi5O7I; the Bi2O3And Bi5O7The mass ratio of I is (0.4-0.8): (0.2-0.6). Bi of the present invention2O3And Bi5O7The valence band and the conduction band of I are in proper positions, and Bi can be ensured2O3And Bi5O7I forms a homomorphic heterojunction (noted as Bi)2O3-Bi5O7I heterojunction), proper valence and conduction band positions reduce Bi2O3-Bi5O7The built-in electric field provides more energy for the migration of photo-generated electrons by the migration path of the photo-carriers in the I heterojunction, so that the photo-carriers have higher energy and longer service life, thereby improving the service life of the photo-carriersThe photocatalytic activity of the photocatalyst provided by the invention enables the photocatalyst provided by the invention to degrade pollutants quickly and efficiently. According to the description of the embodiment, the degradation rate of the homological heterojunction photocatalyst provided by the invention to 40mg/L methyl orange can reach 100% at most, and the degradation rate to 10 mg/L4-chlorophenol can reach 100% at most in 60min of illumination time, so that the rapid and efficient degradation of pollutants is realized.
Drawings
FIG. 1 shows homorph heterojunction photocatalysts obtained in examples 1, 2, 4 and 6 and gamma-Bi described in comparative example 12O3Bi as described in comparative example 25O7I and alpha-Bi as described in comparative example 32O3XRD pattern of (a);
FIG. 2 is an SEM photograph of the homojunction photocatalyst obtained in example 1;
FIG. 3 shows homomorphic heterojunction photocatalysts of examples 1 to 7 and gamma-Bi of comparative example 12O3Bi as described in comparative example 25O7I and alpha-Bi as described in comparative example 32O3Histogram of the degradation rate of 4-chlorophenol.
Detailed Description
The invention provides a homomorphic heterojunction photocatalyst which comprises Bi2O3And Bi5O7I; the Bi2O3And Bi5O7The mass ratio of I is (0.4-0.8): (0.2-0.6).
The invention also provides a preparation method of the homological heterojunction photocatalyst in the technical scheme, which comprises the following steps:
gamma-Bi2O3Mixing the potassium iodide solution and absolute ethyl alcohol, and carrying out a displacement reaction to obtain the homological heterojunction photocatalyst.
In the present invention, all the raw material components are commercially available products well known to those skilled in the art unless otherwise specified.
In the present invention, the gamma-Bi2O3The preparation method preferably comprises the following steps:
will fiveMixing the aqueous bismuth nitrate solution and the sodium hydroxide solution, and performing liquid-phase precipitation to obtain gamma-Bi2O3。
In the invention, the solvent of the bismuth nitrate pentahydrate solution is preferably nitric acid solution, and the solute is preferably bismuth nitrate pentahydrate; the concentration of the nitric acid solution is preferably 1 mol/L; the preferable dosage ratio of the bismuth nitrate pentahydrate to the nitric acid solution is (10-20) g: (50-100) mL, more preferably (12-18) g: (60-90) mL, most preferably (14-16) g: (70-80) mL. In the invention, the concentration of the sodium hydroxide solution is preferably 2-6 mol/L, more preferably 2-4 mol/L, and most preferably 2-3 mol/L.
In the invention, the volume ratio of the bismuth nitrate pentahydrate solution to the sodium hydroxide solution is preferably (1-3): (2-6), more preferably (2-3): (4-6).
In the invention, the mixing of the bismuth nitrate pentahydrate solution and the sodium hydroxide solution is preferably to drop the bismuth nitrate pentahydrate solution into the sodium hydroxide solution; in the invention, the dripping mode is preferably dropwise dripping, and the dripping speed is preferably 2-3 s/drop. In the present invention, the above-mentioned dropping rate can make the reaction between sodium hydroxide and bismuth nitrate more sufficient.
The dropping is not particularly limited in the present invention, and may be carried out by a procedure well known to those skilled in the art.
In the invention, the temperature of the liquid phase precipitation is preferably 75-85 ℃, more preferably 75 ℃, the time of the liquid phase precipitation is preferably 2.5-6 h, more preferably 6h, and the initial time of the liquid phase precipitation is preferably counted when the dropwise addition is completed.
After the liquid phase precipitation is completed, the present invention preferably washes and dries the resulting product system. In the present invention, the washing is preferably 5 times with deionized water; the drying temperature is preferably 55-60 ℃, more preferably 60 ℃, and the drying time is preferably 8-15 hours, more preferably 10-12 hours.
In the present invention, the gamma-Bi2O3The potassium iodide solution and the absolute ethyl alcohol are preferably mixed firstlyThen is mixed with gamma-Bi2O3And (4) mixing. In the present invention, the potassium iodide solution is preferably an aqueous solution of potassium iodide; the volume ratio of the mass of the potassium iodide in the potassium iodide solution to the water is preferably (0.166-0.322) g: (10-20) mL, more preferably (0.2-0.3) g: (12-18) mL, most preferably (0.24-0.28) g: (14-16) mL. In the invention, the volume ratio of the mass of potassium iodide in the potassium iodide solution to the pentahydrate ethanol is preferably (0.166-0.322) g: 5mL, more preferably (0.2 to 0.3) g: 5mL, most preferably (0.24-0.28) g: 5 mL. In the present invention, the gamma-Bi2O3The mass ratio of the potassium iodide to the potassium iodide in the potassium iodide solution is preferably 1.45 (1-1.45), and more preferably 1.45: 1.
After the mixing is completed, the present invention preferably further comprises subjecting the obtained mixed solution to ultrasonic treatment, and the ultrasonic treatment is performed by a process well known to those skilled in the art without any particular limitation in the present invention. In the invention, the ultrasonic treatment can further dissolve potassium iodide in a mixed solution of deionized water and absolute ethyl alcohol and can also enable gamma-Bi to be dissolved2O3The dispersion in the mixed liquid is more uniform.
In the present invention, the metathesis reaction is preferably carried out under stirring; the temperature of the replacement reaction is preferably room temperature, and the time of the replacement reaction is preferably 5-30 h, more preferably 10-25 h, and most preferably 15-20 h. The stirring is not particularly limited in the present invention, and may be carried out by a procedure well known to those skilled in the art. In the present invention, the stirring conditions may further allow the reaction of bismuth oxide and potassium iodide to be more complete.
After the replacement reaction is finished, the obtained solid product is preferably washed and dried; the washing and drying are not particularly limited in the present invention and may be performed by a process well known to those skilled in the art.
The invention also provides the application of the homomorphic heterojunction photocatalyst in the technical scheme or the homomorphic heterojunction photocatalyst prepared by the preparation method in the technical scheme in photocatalytic degradation of water pollutants.
In the invention, the water body pollutant is preferably methyl orange and/or 4-chlorophenol.
In the present invention, the process of the application is preferably: and placing the homomorphic heterojunction photocatalyst in a water body to be treated, and degrading under the condition of illumination. In the invention, the ratio of the mass of the photocatalyst to the concentration of water pollutants is preferably (0.02-0.1) g: (10-50) mg/L, more preferably (0.04-0.05) g: (10-40) mg/L. In the present invention, the illumination is preferably performed using a xenon lamp.
The homojunction heterojunction photocatalyst provided by the present invention, the preparation method and the application thereof are described in detail below with reference to the examples, but they should not be construed as limiting the scope of the present invention.