CN115920931A - BiOBr/Bi 4 O 5 Br 2 Heterojunction photocatalyst and preparation method and application thereof - Google Patents
BiOBr/Bi 4 O 5 Br 2 Heterojunction photocatalyst and preparation method and application thereof Download PDFInfo
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W10/00—Technologies for wastewater treatment
- Y02W10/30—Wastewater or sewage treatment systems using renewable energies
- Y02W10/37—Wastewater or sewage treatment systems using renewable energies using solar energy
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Abstract
The invention provides BiOBr/Bi 4 O 5 Br 2 The heterojunction photocatalyst and the preparation method and the application thereof comprise the following steps: step 1, adding Bi (NO) 3 ) 3 ·5H 2 Dissolving O and NaBr in water to obtain a mixed solution; step 2, adjusting the pH value of the mixed solution to 3-9 by using an alkali solution to obtain a precursor solution; step 3, carrying out hydrothermal reaction on the precursor solution, washing and drying the obtained precipitate to obtain BiOBr/Bi 4 O 5 Br 2 A heterojunction photocatalyst. The preparation method of the invention needs short time, and the BiOBr/Bi containing oxygen vacancy is formed 4 O 5 Br 2 The Z-type heterojunction enhances the visible light absorption range and intensity, and can degrade antibiotics such as tetracycline and ciprofloxacin and organic dyes such as rhodamine B, methylene orange and methylene blue under the irradiation of visible light, store holes and electrons, degrade organic pollutants under the condition of dark light, and realize all-weather catalysis.
Description
Technical Field
The invention belongs to the field of functional materials, and particularly relates to BiOBr/Bi 4 O 5 Br 2 A heterojunction photocatalyst, a preparation method and application thereof.
Background
Antibiotics are widely used and easily generate drug resistance, and antibiotics such as tetracycline and ciprofloxacin are difficult to absorb by intestines and stomach after entering a human body, and about 75 percent of the antibiotics are discharged into sewage in the form of parent compounds. As a potential environmental ecological hazard, the method eliminates the antibiotic in water slowly, and the photocatalytic degradation of the antibiotic by the photocatalyst is an effective mode, so that the antibiotic in the water environment can be removed, and no secondary pollution is generated. The traditional photocatalyst needs continuous light irradiation (in the daytime) to drive a series of oxidation-reduction reactions, and when the light irradiation is limited (in the nighttime), the generation and separation of photogenerated carriers stop, so that the photogenerated carriers stop generating active species, immediately lose catalytic activity and limit practical use.
Br in BiOBr - Form [ Br ] 2 ] 2- Layer, bi and O are linked by a strong covalent bond to form [ Bi ] 2 O 2 ] 2+ Layer of [ Br ] in crystal 2 ] 2- Layer and [ Bi ] 2 O 2 ] 2+ The layers are connected through Van der Waals force and are alternately arranged, and due to the fact that the positive charge layer and the negative charge layer are alternately arranged, photoproduction electrons and holes are enabled to move towards different directions in the crystal under the action of electric field force, the combination of the photoproduction electrons and the holes is restrained, the photon efficiency is improved, and therefore the photocatalytic activity is enhanced. However, the original two-dimensional tetragonal phase BiOBr still has the problems of limited photoresponse rate, easy recombination of photocarriers and the like.
Bi x O y Br z The valence band of (a) is mainly composed of O2 p and Br 4p hybrid orbitals, and the conduction band thereof is composed of Bi 6p orbitals, therefore, by adding Bi x O y Br z Bi content in the material shifts the CB and VB edges upward, reducing the bandgap energy (E) g ) Thereby obtaining stronger visible light absorption and reduction capability. But only Bi x O y Br z The photocatalyst still has the problems of easy recombination of electron holes, high reduction potential and the like.
BiOBr/Bi is disclosed in the prior art 4 O 5 Br 2 The document CN108262050B discloses a two-dimensional composite visible-light-driven photocatalyst, a preparation method and application thereof, and discloses a two-dimensional BiOBr-Bi prepared by using bismuth nitrate as a bismuth source, adjusting the pH value of a solution, adding a surfactant cetyl trimethyl ammonium bromide as a bromine source and a coating agent to control the morphology 4 O 5 Br 2 The composite visible light catalyst cannot be in BiOBr-Bi state due to the use of an organic surfactant for controlling the appearance 4 O 5 Br 2 In the formation of defects, resulting in BiOBr-Bi 4 O 5 Br 2 The composite visible light catalyst is a type II heterojunction. Document CN108187699A discloses BiOX-Bi 4 O 5 X 2 Heterojunction and its preparation method and application, containing Bi 3+ One or more of bismuth nitrate, bismuth oxalate and bismuth oxide, X - Salts or containing X - The acid and the aqueous solution of glucose are heated and reacted; calcining the hydrothermal reaction product at 400-500 ℃ to prepare BiOX-Bi 4 O 5 X 2 Heterojunction, the defect of the heterojunction can not exist due to high-temperature treatment; document 201910898187.4 discloses a Bi for oil field wastewater treatment 4 O 5 Br 2 A preparation method of a BiOBr composite photocatalyst discloses that a glycerol solution containing a bromine compound is dropwise added into a glycerol solution containing a bismuth compound, the mixture is uniformly stirred, and hydrothermal reaction is carried out for 14 to 18 hours at 140 to 180 ℃ to obtain a precursor; adding distilled water into the precursor, and carrying out hydrolysis reaction for 21-26 h under the water bath condition of 40-70 ℃ to obtain Bi 4 O 5 Br 2 BiOBr composite photocatalyst, bi formed by hydrothermal and hydrolysis method 4 O 5 Br 2 BiOBr, long hydrolysis reaction, long time period for heterojunction formation. The application of the catalyst is to degrade pollutants under visible light, so that the service time and scene of the catalyst are limited, and the pollutants can be degraded only by continuous strong light.
Disclosure of Invention
The invention aims to provide BiOBr/Bi 4 O 5 Br 2 The preparation method of the invention needs short time, and the formed BiOBr/Bi containing oxygen vacancy 4 O 5 Br 2 The Z-type heterojunction can degrade organic matters under the conditions of dark light and illumination, and realizes all-weather catalysis.
The invention is realized by the following technical scheme:
BiOBr/Bi 4 O 5 Br 2 The preparation method of the heterojunction photocatalyst comprises the following steps:
Preferably, in step 1, bi (NO) 3 ) 3 ·5H 2 The molar ratio of O to NaBr is (0.5-1.5): (0.5-1.5).
Preferably, in step 1, bi (NO) in the solution is mixed 3 ) 3 ·5H 2 The concentrations of O and NaBr are respectively (0.0125-0.05) mol.L -1 、(0.0125-0.05)mol·L -1 。
Preferably, in step 2, the alkaline solution is a NaOH solution.
Preferably, in the step 3, the temperature of the hydrothermal reaction is 120-200 ℃ and the time is 8-20h.
Preferably, in step 3, the washing is performed by using deionized water and absolute ethyl alcohol respectively.
BiOBr/Bi obtained by the preparation method 4 O 5 Br 2 A heterojunction photocatalyst of said BiOBr/Bi 4 O 5 Br 2 BiOBr and Bi in heterojunction photocatalyst 4 O 5 Br 2 Two phases co-existing, biOBr and Bi 4 O 5 Br 2 A Z-type heterojunction is formed between the two layers, and the Z-type heterojunction contains oxygen vacancy and Bi 4 O 5 Br 2 Store h + BiOBr store e - 。
The BiOBr/Bi 4 O 5 Br 2 The application of the heterojunction photocatalyst in catalyzing and degrading organic matters under the condition of dark light or illumination realizes 'all-weather catalysis'.
Preferably, the lighting condition is visible light.
Preferably, the organic substance is an antibiotic or an organic dye.
Preferably, the antibiotic is tetracycline or ciprofloxacin, and the organic dye is rhodamine B, methylene orange or methylene blue.
Compared with the prior art, the invention has the following beneficial effects:
the invention takes bismuth nitrate as a bismuth source, inorganic salt NaBr as a bromine source, and no surfactant is added, and bismuth nitrate is controlled to hydrolyze by adjusting the pH of a mixed solution to form BiO + Polymer ions and one-time hydrothermal preparation of BiOBr/Bi containing oxygen vacancies 4 O 5 Br 2 And the Z-type heterojunction has short reaction time. The present invention utilizes Bi (NO) 3 ) 3 ·5H 2 O hydrolysis of polymer ion change in precursor solution with different pH value to form BiOBr [ ((BiO) in BiOBr crystal nucleus 2 )·((BiO) 3 )·(BiO) 4 ]Br 7 (OH) 5 Micelle is subjected to saturation crystallization in the hydrothermal reaction process to form BiOBr/Bi 4 O 5 Br 2 Crystals exist in a double diffusion electric layer, and BiOBr and [ ((BiO)) 2 )·((BiO) 3 )·(BiO) 4 ] 9+ Forming an interface electric field, forming OVs by the BiOBr due to hydrothermal anoxic environment, and transferring the electrons bound by the BiOBr to Bi under the action of the interface electric field 4 O 5 Br 2 Making BiOBr/Bi 4 O 5 Br 2 Bi of medium BiOBr 3+ Increase in concentration of Bi 4 O 5 Br 2 Of Bi +(3-x) The concentration is increased to form BiOBr/Bi containing oxygen vacancy 4 O 5 Br 2 Z-type heterojunction photocatalyst, and Bi 4 O 5 Br 2 Store h + BiOBr store e - . The carrier separation capacity is improved under the condition of keeping the original high oxidation reduction capacity. BiOBr/Bi containing oxygen vacancy prepared by the method 4 O 5 Br 2 The Z-type heterojunction enhances the visible light absorption range and intensity, and degrades antibiotics such as tetracycline and ciprofloxacin and organic dyes such as rhodamine B, methylene orange, methylene blue under the irradiation of visible light, so that the photocatalytic performance is obviously improved, the selective degradation of tetracycline is enhanced, and the method is simple and efficient. And in the preparation process of the photocatalyst, biOBr/Bi 4 O 5 Br 2 Bi in the photocatalyst 4 O 5 Br 2 Store h + BiOBr store e - . In dark light, bi 4 O 5 Br 2 Store h + Can release e for oxidizing and degrading pollutants and storing BiOBr - The released oxygen reacts with dissolved oxygen to form O 2 - Free radicals, degrading pollutants.
Realizes 'all-weather catalysis'
The BiOBr/Bi of the invention 4 O 5 Br 2 Heterojunction photocatalyst, biOBr and Bi in comparison to pure phase 4 O 5 Br 2 The concentration of oxygen vacancies increases and the binding energy shifts to the right, forming Bi 4 O 5 Br 2 An interface electric field pointing to BiOBr, under the irradiation of visible light, biOBr and Bi 4 O 5 Br 2 Can be excited to generate electrons and holes, which are respectively transferred to their own conduction band and valence band in BiOBr and Bi 4 O 5 Br 2 Under the action of interface electric field, electrons on BiOBr conduction band and Bi 4 O 5 Br 2 Composition of empty points above valence band, bi 4 O 5 Br 2 The photoproduction electrons reserved on the conduction band of the organic silicon solar cell keep stronger reduction capability and can be matched with O 2 Reaction to produce O 2 - The hole on VB of BiOBr reacts with water to generate OH, thereby realizing BiOBr/Bi 4 O 5 Br 2 High carrier separation efficiency and strong oxidation-reduction capability of the photocatalyst. Therefore, the invention combines BiOBr and Bi 4 O 5 Br 2 Forming a Z-type heterojunction, bi 4 O 5 Br 2 The band gap energy is lower than that of a BiOBr (2.74 eV) photocatalyst, the absorption range of heterojunction visible light is expanded, the redox capability is improved, antibiotics and organic dyes can be degraded under dark and visible light irradiation, and the method can be applied to a method for treating water pollution through photocatalysis.
Drawings
FIG. 1 is an XRD pattern of the photocatalysts prepared in comparative example 1, examples 1 to 3 and comparative examples 2 and 3 according to the present invention.
Fig. 2 is an SEM image of the photocatalyst prepared in comparative example 1 of the present invention.
FIG. 3 is an SEM image of a photocatalyst prepared in example 2 of the present invention.
Fig. 4 is an SEM image of the photocatalyst prepared in comparative example 2 of the present invention.
FIG. 5 is a high resolution O1s XPS spectrum of the photocatalysts prepared in comparative examples 1, 2 and 2 of the present invention.
FIG. 6 is a high resolution Bi 4f XPS spectrum of the photocatalysts prepared in comparative examples 1, 2 and 2 of the present invention.
FIG. 7 is a Raman diagram of the photocatalysts prepared in comparative example 1, examples 1-3 and comparative example 2 of the present invention.
FIG. 8 is a graph of photocurrents i-t under visible light irradiation for the photocatalysts prepared in comparative example 1, example 2 and comparative example 2 of the present invention.
FIG. 9 is a graph showing the tetracycline removal curves of the photocatalysts prepared in comparative example 1, examples 1 to 3, and comparative examples 2 and 3 according to the present invention under visible light irradiation.
FIG. 10 is an apparent rate constant of tetracycline degradation under visible light irradiation of the photocatalyst powders prepared in comparative example 1, examples 1 to 3, and comparative examples 2 and 3 of the present invention.
FIG. 11 is a graph showing the removal curves of ciprofloxacin by the photocatalysts prepared in comparative example 1, examples 1 to 3 and comparative examples 2 and 3 according to the present invention under irradiation of visible light.
FIG. 12 is an apparent rate constant of degradation of ciprofloxacin by the photocatalyst powders prepared in comparative example 1, examples 1 to 3, and comparative examples 2 and 3 according to the present invention under irradiation of visible light.
Fig. 13 shows the degradation rates of the photocatalyst powder prepared in example 2 of the present invention to rhodamine B, methylene orange, and methylene blue under the irradiation of visible light.
FIG. 14 is a graph showing the detection of active species in visible light degradation of tetracycline by the photocatalyst prepared in example 2 of the present invention.
FIG. 15 is a UV-VIS diffuse reflectance spectrum of the photocatalyst powders prepared in comparative example 1, examples 1 to 3, and comparative examples 2 and 3 of the present invention.
Fig. 16 is a band gap diagram of the photocatalysts of comparative examples 1 and 2 of the present invention.
FIG. 17 is an XPS VB chart of a photocatalyst of comparative example 1 of the present invention.
FIG. 18 is an XPS VB chart of a photocatalyst of comparative example 2 of the present invention.
FIG. 19 shows BiOBr/Bi prepared according to the present invention 4 O 5 Br 2 A photocatalysis mechanism diagram of the heterojunction photocatalyst under visible light.
FIG. 20 is a graph showing the tetracycline removal curves of the photocatalysts prepared in comparative example 1, examples 1 to 3, and comparative examples 2 and 3 according to the present invention under dark light.
FIG. 21 is an apparent rate constant for tetracycline degradation in dark light for the photocatalysts prepared in comparative example 1, examples 1-3, and comparative examples 2 and 3 in accordance with the present invention.
FIG. 22 is a graph of the TOC removal rate of tetracycline degradation by the photocatalyst prepared in example 2 of the present invention in the dark.
FIG. 23 is a graph showing the removal curves of ciprofloxacin by the photocatalysts prepared in comparative example 1, examples 1 to 3 and comparative examples 2 and 3 according to the present invention in dark light.
FIG. 24 is an apparent rate constant of degradation of ciprofloxacin in dark light by the photocatalysts prepared in comparative example 1, examples 1 to 3, and comparative examples 2 and 3 of the present invention.
FIG. 25 is a chart of the TOC removal rate of degradation of ciprofloxacin by the photocatalyst prepared in example 2 of the present invention in dark light.
Fig. 26 shows the degradation rates of the photocatalyst powder prepared in example 2 of the present invention for rhodamine B, methylene orange, and methylene blue in dark light.
FIG. 27 is a graph showing the detection of active species for the degradation of tetracycline by the photocatalyst prepared in example 2 of the present invention in the dark.
FIG. 28 shows BiOBr/Bi prepared according to the present invention 4 O 5 Br 2 A photocatalysis mechanism diagram of the heterojunction photocatalyst under dark light.
Detailed Description
For a further understanding of the invention, reference will now be made to the following examples, which are provided to illustrate further features and advantages of the invention, and are not intended to limit the scope of the invention as set forth in the following claims.
BiOBr/Bi 4 O 5 Br 2 The preparation method of the heterojunction photocatalyst comprises the following steps:
In step 1, bi (NO) in the mixed solution 3 ) 3 ·5H 2 The concentrations of O and NaBr are respectively (0.0125-0.05) mol.L -1 、(0.0125-0.05)mol·L -1 。Bi(NO 3 ) 3 ·5H 2 The molar ratio of O to NaBr is (0.5-1.5): (0.5-1.5).
In step 2, the concentration of NaOH solution is 1mol L -1 。
The temperature of the hydrothermal reaction in the step 3 is 120-200 ℃, and the hydrothermal reaction time is 8-20h; washing is carried out by using deionized water and absolute ethyl alcohol respectively.
BiOBr/Bi obtained by the invention 4 O 5 Br 2 In the heterojunction photocatalyst, biOBr and Bi 4 O 5 Br 2 Coexistence of two phases, biOBr and Bi 4 O 5 Br 2 A Z-shaped heterojunction is formed between the two layers; biOBr belongs to a tetragonal phase, and a space point group is P4/nmm (129); bi 4 O 5 Br 2 The single oblique phase is formed, and the space point group is P21 (4).
The BiOBr/Bi 4 O 5 Br 2 Heterojunction photocatalysts can degrade antibiotics and organic dyes in dark light and visible light. The antibiotic is tetracycline or ciprofloxacin and the like, and the organic dye is rhodamine B, methylene orange, methylene blue and the like.
Comparative example 1
and 2, carrying out hydrothermal reaction on the mixed solution at 160 ℃ for 12h with the filling rate of 80%, finally sequentially collecting precipitates in the reaction solution, and respectively washing, drying and grinding the precipitates for 3 times by using deionized water and absolute ethyl alcohol to obtain the BiOBr powder.
Comparative example 2
Comparative example 3
Example 1
and 3, placing the precursor solution into a hydrothermal reaction kettle with the filling rate of 80%, carrying out hydrothermal reaction for 12 hours at 160 ℃, finally sequentially collecting precipitates in the reaction solution, and respectively washing, drying and grinding with deionized water and absolute ethyl alcohol for 3 times to obtain BiOBr/Bi 4 O 5 Br 2 A heterojunction.
Example 2
Example 3
Example 4
Example 5
Example 6
Example 7
Example 8
Example 9
Example 10
Example 11
Example 12
Example 13
Example 14
Example 15
and 3, carrying out hydrothermal reaction on the precursor solution at 160 ℃ for 8h with the filling rate of 80%, finally sequentially collecting precipitates in the reaction solution, and respectively washing, drying and grinding the precipitates for 3 times by using deionized water and absolute ethyl alcohol to obtain BiOBr/Bi 4 O 5 Br 2 A heterojunction.
Example 16
Example 17
FIG. 1 is an XRD pattern of the photocatalysts prepared in comparative examples 1, 1-3 and 2, 3 of the present invention, wherein a corresponds to comparative examples 1, b-d corresponds to examples 1-3, and e, f corresponds to powders prepared in comparative examples 2, 3. Examples 1 to 3 exhibited diffraction peaks corresponding to the (001), (102) and (110) crystal planes of tetragonal BiOBr (JCPDS No. 09-0393) at 10.9 °, 31.7 and 32.22 °, and the spatial point group was P4/nmm (129); bi in which corresponding monoclinic phases appear at 29.55 °, 29.70 °, 31.67 ° and 31.81 ° 4 O 5 Br 2 (JCPDS No. 37-0699) (11-3), (41-1), (402) and (020) crystal plane diffraction peaks, the space point group is P21 (4), when the pH value is higher<3 BiOBr was prepared, comparative example 1; biOBr/Bi is prepared at pH =3-9 4 O 5 Br 2 And with increasing pH, bi 4 O 5 Br 2 Gradually increases, and when the pH =12, only Bi appears 4 O 5 Br 2 The phase of (1), comparative example 2; when pH =14, comparative example 3, cubic phase Bi appeared at 29.072 °, 32.594 ° and 38.784 ° 2 O 3 (JCPDS No. 74-1375) with diffraction peaks on the (220), (013) and (123) crystal planes, which indicates that the hydrothermal preparation of the precursor solution with pH =14 is cubic phase Bi 2 O 3 I.e. comparative example 3.
Bi(NO 3 ) 3 ·5H 2 Dissolving O in water, hydrolyzing to form BiO + Equation (1) hydrolysis of NaBr to Br - And Na + Reaction of equation (2), biO + With Br - Forming BiOBr colloidal particles, reacting according to equation (3), and hydrothermally forming BiOBr crystals of comparative example 1; some BiO when the pH of the precursor solution is adjusted to 3-9 + With Br - Rapid formation of BiOBr nuclei, other BiO nuclei in aqueous solution + Will gradually form dimer ions (BiO) 2 2+ Trimer ion (BiO) 3 3+ Tetramer ion formation (BiO) 4 4+ The reaction of equations (3) to (6) causes the ions to adsorb on the surface of the BiOBr crystal nucleus to form an adsorption layer, which constitutes BiOBr [ (BiO) 2 (BiO) 3 (BiO) 4 ] 9+ Micelles, equation (7), which are positively charged, will then adsorb Br from solution - And OH - Forming a diffusion double layer, forming a micelle BiOBr [ ((BiO) 2 )·((BiO) 3 )·(BiO) 4 ]Br 7 (OH) 5 Equation (8), saturation crystallization in hydrothermal reaction system, micelle formation BiOBr/Bi 4 O 5 Br 2 The crystal, equation (9), is BiOBr and [ ((BiO) at the colloidal particle solid-liquid interface due to the presence of a double diffused layer 2 )·((BiO) 3 )·(BiO) 4 ] 9+ Forming an interface electric field, wherein the direction of the interface electric field points to BiOBr; when the pH is =12, the BiO in the reaction system + All polymerize to form tetramers (BiO) 4 + Ion, (BiO) 4 + With Br-formation (BiO) 4 Br 2 (OH) 2 Saturation and crystallization in hydrothermal reaction system to form Bi 4 O 5 Br 2 Crystal, equation (10); when pH =14, biO + Form an amorphous BiOOH with OH-, (BiO) 2 2+ 、(BiO) 3 3+ 、(BiO) 4 4+ Also reacts with OH-to form amorphous BiOOH, equations (11) to (14), hydrothermally forms cubic phase crystal Bi 2 O 3 Equation (15).
Bi(NO 3 ) 3 +H 2 O＝BiONO 3 +2H + +NO 3 - (1)
NaBr+H 2 O＝Br - +Na + (2)
BiO + +Br - ＝BiOBr (3)
BiO + +BiO + ＝(BiO) 2 2+ (4)
(BiO) 2 2+ +BiO+＝(BiO) 3 3+ (5)
(BiO) 3 3+ +BiO+＝(BiO) 4 4+ (6)
[(BiO) 2 ] 2+ +[(BiO) 3 ] 3+ +[(BiO) 4 ]4 + +BiOBr＝
BiOBr[((BiO) 2 )·((BiO) 3 )·(BiO) 4 ] 9+ (7)
BiOBr[((BiO) 2 )·((BiO) 3 )·(BiO) 4 ] 9+ +Br - +OH - +H 2 O＝
BiOBr[((BiO) 2 )·((BiO) 3 )·(BiO) 4 ] 9+ (Br) 7 (OH) 5 (8)
BiOBr[((BiO) 2 )·((BiO) 3 )·(BiO) 4 ] 9+ (Br) 7 (OH) 5 ++H 2 O＝BiOBr/
Bi 4 O 5 Br 2 (9)
(BiO) 4 4+ +2Br - +H 2 O＝(BiO) 4 (Br) 2 (OH) 2 ＝Bi 4 O 5 Br 2 (10)
BiO + +OH - ＝BiOOH (11)
(BiO) 2 2+ +2OH - ＝(BiO) 2 (OH) 2 ＝2BiOOH (12)
(BiO) 3 3+ +3OH - ＝(BiO) 3 (OH) 3 ＝3BiOOH (13)
(BiO) 4 4+ +4OH - ＝(BiO) 4 (OH) 4 ＝4BiOOH (14)
2BiO + +2OH - ＝2BiOOH＝Bi 2 O 3 +H 2 O (15)
Fig. 2, 3 and 4 are SEM images of the photocatalysts prepared in comparative example 1, example 2 and comparative example 2. Figure 2 is a pure phase BiOBr flower shaped insert, but with a thicker sheet. FIG. 3 shows BiOBr/Bi 4 O 5 Br 2 The heterojunction nanosheet layer becomes thinner, the area of a single nanosheet becomes smaller, the specific surface area is increased, and the increase in pH promotes the nucleation of BiOBr, resulting in the reduction of the grain size, possibly due to the differential nucleation process of BiOBr. When pH =12, it becomes Bi in pure phase 4 O 5 Br 2 When used, the individual nanoplatelets are reduced in area and thinner, exhibiting a more open structure, as shown in fig. 4.
FIG. 5 is a high resolution O1s XPS spectrum of the photocatalysts prepared in comparative examples 1, 2 and 2 of the present invention. Wherein a, c and e represent BiOBr, biOBr/Bi synthesized according to comparative example 1, example 2 and comparative example 2, respectively 4 O 5 Br 2 And Bi 4 O 5 Br 2 A photocatalyst. The pure phase BiOBr O1s atlas can be fitted with two peaks corresponding to oxygen vacancy and [ Bi ] at 532.42eV and 530.26eV respectively 2 O 2 ] 2+ The lattice of the layer has an oxygen vacancy concentration of about 10.44%. Pure phase Bi 4 O 5 Br 2 The O1s spectra can be fitted as two peaks corresponding to oxygen vacancies, [ Bi ] at 532.25eV and 529.63eV, respectively 2 O 2 ] 2+ The lattice of the layer has an oxygen vacancy concentration of about 3.84%. BiOBr/Bi 4 O 5 Br 2 The O1s spectra can be fitted to two peaks, corresponding to oxygen vacancies, [ Bi ] at 531.17eV, 528.73eV, respectively 2 O 2 ] 2+ The oxygen vacancy concentration of the lattice oxygen atoms of the layer is about 14.46%, compared to the pure phase of BiOBr and Bi 4 O 5 Br 2 The concentration of oxygen vacancies is increased and the binding energy is shifted to the right, proving BiOBr/Bi 4 O 5 Br 2 Middle Bi 4 O 5 Br 2 The charge density of O of (2) increases.
FIG. 6 is a high resolution Bi 4f XPS spectrum of the photocatalysts prepared in comparative examples 1, 2 and 2 of the present invention. The pure phase BiOBr shows two strong peaks at about 164eV and 158eV, which are respectively attributed to Bi 3+ 4f 7/2 and Bi 3+ 4f 5/2, which after fitting can be divided into 163.43eV and 158.12eV, 162.25eV and 156.90eV 4 binding energies, 163.43eV and 158.12eV which are assigned to Bi 3+ ，Bi 3+ The concentration is about 63.03 percent, and is 162.25eVAnd 156.90eV is due to the low charge of Bi ions (Bi) in the compound +(3-x) )，Bi +(3-x) The concentration was about 36.97%. In BiOBr/Bi 4 O 5 Br 2 In the heterojunction, the peaks of 162.03 and 156.74eV are ascribed to Bi 3+ ，Bi 3+ The concentration is about 60.93%, and the peaks of 160.58 and 155.29eV are attributed to Bi +(3-x) ，Bi +(3-x) The binding energy shifts to the right and the concentration increases at a concentration of about 39.07%, demonstrating BiOBr/Bi 4 O 5 Br 2 The interface interaction between the two causes the chemical environment of Bi to change. Bi 4 O 5 Br 2 Can also be divided into 161.81eV and 156.42eV (Bi) 3+ ) 160.66eV and 155.25eV (Bi) +(3-x) )，Bi 3+ Concentration of about 70.28%, bi +(3-x) The concentration was about 29.72%. Illustrating the formation of BiOBr/Bi 4 O 5 Br 2 In the presence of double diffusion layers, biOBr and [ ((BiO)) are formed at the solid-liquid interface of colloidal particles 2 )·((BiO) 3 )·(BiO) 4 ] 9+ Forming an interface electric field, forming OVs by the BiOBr due to hydrothermal anoxic environment, and transferring the electrons bound by the BiOBr to Bi under the action of the interface electric field 4 O 5 Br 2 Making BiOBr/Bi 4 O 5 Br 2 Bi of medium BiOBr 3+ Increase in concentration of Bi 4 O 5 Br 2 Of Bi +(3-x) The concentration is increased until the Fermi levels of the two reach the equilibrium to form BiOBr/Bi 4 O 5 Br 2 A heterojunction.
FIG. 7 is a Raman diagram of photocatalysts prepared in comparative example 1, examples 1 to 3 and comparative example 2 of the present invention, in which a corresponds to comparative example 1, b to d correspond to examples 1 to 3, and e to f correspond to powders prepared in comparative examples 2 to 3. Pure phase BiOBr at 114cm -1 The strong Raman peak at is attributed to A 1g Internal Bi-O stretch mode, 161.681cm -1 The Raman peak at is due to E g Internal Bi-O stretching mode, with [ Bi ] 2 O 2 ] 2+ Layer and double halide [ Br ] 2 ] 2- The compressive movement of the layer is related to oxygen atoms at 367cm -1 Left-right movement produced E g And B 1g The bands were very weak and not apparent. With increasing pH，110cm -1 A of (A) 1g Characteristic peaks gradually decreased and shifted to the right, 156cm -1 Of (E) g The characteristic peak is gradually enhanced and shifted to the left, and the two vibration peaks are both in parallel with [ Bi ] 2 O 2 ] 2+ Layer and [ Br 2 ] 2- Layer related due to BiOBr and Bi 4 O 5 Br 2 The difference of the crystal structures indicates that the BiOBr structure is changed to generate BiOBr/Bi 4 O 5 Br 2 Heterojunction, consistent with XRD results.
FIG. 8 is a graph of photocurrents i-t of photocatalysts prepared in comparative example 1, example 2 and comparative example 2 of the present invention under irradiation of visible light, wherein a corresponds to comparative example 1, c corresponds to example 2 and e corresponds to powder prepared in comparative example 2. Fig. 8 shows that all samples have a photocurrent response under visible light, indicating that they are capable of generating photo-generated charges and that photo-generated electrons are capable of directionally migrating. BiOBr/Bi compared to the pure phase sample 4 O 5 Br 2 The photocurrent of the photocatalyst was significantly enhanced, which indicates that its photocurrent separation rate and mobility were the largest.
FIG. 9 shows the concentration of 20 mg. Multidot.L in visible light irradiation of the photocatalyst powders prepared in comparative example 1, examples 1 to 3, and comparative examples 2 and 3 of the present invention -1 The degradation curve of the tetracycline is shown in FIG. 10, wherein a corresponds to comparative example 1, b-d corresponds to examples 1-3, and e-f corresponds to the degradation curve and apparent rate constant of the powder prepared in comparative examples 2-3, and it can be seen that after 20min of visible light irradiation, 0.5g of pure-phase BiOBr and pure-phase Bi are observed 4 O 5 Br 2 Pure phase Bi 2 O 3 BiOBr/Bi prepared in examples 1 to 3 4 O 5 Br 2 The degradation efficiency of the tetracycline is respectively 28.26 percent, 12.29 percent, 12.56 percent, 50.69 percent, 69.48 percent and 58.51 percent, and the corresponding apparent rate constants are respectively 0.01427min -1 、0.0052min -1 、0.00339min -1 、0.02683min -1 、0.04826min -1 、0.03752min -1 。BiOBr/Bi 4 O 5 Br 2 The degradation activity of the heterojunction to tetracycline under the irradiation of visible light is obviously higher than that of BiOBr、Bi 4 O 5 Br 2 And Bi 2 O 3 Wherein BiOBr/Bi prepared in example 2 4 O 5 Br 2 The degradation efficiency of the photocatalyst on the tetracycline can reach 69.48 percent, and the corresponding apparent rate constant is 0.04826min -1 。
FIG. 11 shows the concentration of 10 mg. L of the photocatalyst powders prepared in comparative example 1, examples 1 to 3, and comparative examples 2 and 3 according to the present invention under irradiation of visible light -1 The degradation curve of ciprofloxacin in the graph is shown in FIG. 12 as the corresponding apparent rate constants, wherein a corresponds to comparative example 1, b-d corresponds to examples 1-3, and e-f corresponds to the degradation curve and the apparent rate constants of the powder prepared in comparative examples 2-3 to ciprofloxacin, and as can be seen from the graph, after visible light irradiation for 180min, 0.5g of pure-phase BiOBr and pure-phase Bi are obtained 4 O 5 Br 2 Pure phase Bi 2 O 3 BiOBr/Bi prepared in examples 1 to 3 4 O 5 Br 2 The degradation efficiency of the ciprofloxacin is 23.15 percent, 33.68 percent, 17.24 percent, 45.83 percent, 72.47 percent and 66.23 percent respectively, and the corresponding apparent rate constants are 0.00037min -1 、0.00085min -1 、0.00058min -1 、0.00145min -1 、0.00409min -1 、0.0033min -1 。BiOBr/Bi 4 O 5 Br 2 The degradation activity of the heterojunction to ciprofloxacin under the irradiation of visible light is obviously higher than that of pure-phase BiOBr and Bi 4 O 5 Br 2 And Bi 2 O 3 Wherein BiOBr/Bi prepared in example 2 4 O 5 Br 2 The degradation efficiency of the photocatalyst on the tetracycline can reach 72.47 percent, and the corresponding apparent rate constant is 0.00409min -1 。
FIG. 13 shows the results of the measurement of the concentration of 0.5g of the photocatalyst powder prepared in example 2 of the present invention in a range of 10 mg.L under irradiation with visible light -1 Rhodamine B, 10 mg. L -1 Methylene orange, 10 mg.L -1 Degradation rate of methylene blue, biOBr/Bi 4 O 5 Br 2 The degradation rate of the photocatalyst on rhodamine B is 67.32 percent, the degradation rate on methylene orange is 67.39 percent, and the degradation rate on methylene blue is 60.22 percent, so that the prepared BiOBr/Bi 4 O 5 Br 2 The photocatalyst also has good degradation capability to dyes.
FIG. 14 is a diagram showing the trapping of tetracycline degrading active species by visible light of the photocatalyst powder prepared in example 2 of the present invention, with benzoquinone added as O 2 - Free radical scavenger, sodium oxalate as h + The scavenging agent, tert-butyl alcohol as OH scavenging agent, has different degrees of inhibition to photodegradation reaction, and the contribution of active species to tetracycline removal is O 2 - >h + >·OH。
FIG. 15 is a UV-VIS diffuse reflectance spectrum of the photocatalyst powders prepared in comparative example 1, examples 1 to 3, and comparative examples 2 and 3 of the present invention, in which a corresponds to comparative example 1, b to d corresponds to examples 1 to 3, and e to f correspond to powders prepared in comparative examples 2 to 3. The pure phase BiOBr has a small absorption range in the visible light region, the absorption edge is 437.29nm, and the pure phase Bi 4 O 5 Br 2 The absorption edge is 472.63nm. BiOBr/Bi 4 O 5 Br 2 The heterojunction photocatalyst is subjected to red shift in a visible light absorption range, the absorption edge is red-shifted to 480.12nm, and the absorption intensity of the heterojunction photocatalyst on visible light is enhanced.
Fig. 16 is a band gap diagram of the photocatalysts of comparative examples 1 and 2 of the present invention. In the figure, a and e correspond to BiOBr and Bi prepared in comparative example 1 and comparative example 2 respectively 4 O 5 Br 2 A photocatalyst powder. The band gap of BiOBr is 2.68eV 4 O 5 Br 2 The band gap of (A) is 2.25eV. Fig. 17 and 18 are band gap diagrams of the photocatalysts of comparative examples 1 and 2 of the present invention. The valence band position of BiOBr is +2.59eV 4 O 5 Br 2 The valence band position of (2) is +1.49eV. According to the formula E CB ＝E VB -E g BiOBr and Bi 4 O 5 Br 2 The conduction bands of (A) are-0.09 eV and-0.76 eV, respectively. Under illumination, biOBr and Bi 4 O 5 Br 2 The valence band electrons are excited into the conduction band leaving a corresponding hole in the valence band. If Bi is present 4 O 5 Br 2 Conduction band electrons are transferred to conduction band of BiOBr, and BiOBr valence band holes are transferred to Bi 4 O 5 Br 2 The valence band of (a), forms a conventional type II heterojunction, but this is not in line with the active species results.Thus, bi 4 O 5 Br 2 And BiOBr form a Z-type heterojunction.
FIG. 19 shows BiOBr/Bi prepared according to the present invention 4 O 5 Br 2 A photocatalysis mechanism diagram of the heterojunction photocatalyst under visible light. In the preparation process of the photocatalyst, bi is formed due to the existence of a diffused double electric layer 4 O 5 Br 2 An interface electric field directed to BiOBr. Under irradiation of visible light, biOBr and Bi 4 O 5 Br 2 Both can be excited to generate electrons and holes, which are transferred to their own conduction and valence bands, respectively, in BiOBr and Bi 4 O 5 Br 2 Under the action of interface electric field, electrons on BiOBr conduction band and Bi 4 O 5 Br 2 Composition of empty points above valence band, bi 4 O 5 Br 2 The photo-generated electrons reserved on the conduction band have strong reducing capability and can be dissolved with O in solution 2 Reaction to produce O 2 - The photoproduction holes reserved on the valence band of BiOBr react with water to generate OH with strong oxidation capacity, thereby realizing BiOBr/Bi 4 O 5 Br 2 The photocatalyst has high carrier separation efficiency and strong oxidation-reduction capability.
FIG. 20 shows the concentration of 20 mg. Multidot.L in dark light for photocatalysts prepared in comparative example 1, examples 1 to 3 and comparative examples 2 and 3 in accordance with the present invention -1 FIG. 21 shows the corresponding apparent rate constants, where a corresponds to comparative example 1, b-d corresponds to examples 1-3, and e-f corresponds to the degradation curves and apparent rate constants of the powders prepared in comparative examples 2-3. As can be seen from the figure, after 50min of dark light, 0.5g of pure phase BiOBr and pure phase Bi 4 O 5 Br 2 Pure phase Bi 2 O 3 BiOBr/Bi prepared in examples 1-3 4 O 5 Br 2 The degradation efficiency of the tetracycline is 32.93 percent, 40.52 percent, 24.35 percent, 57.12 percent, 63.44 percent and 47.69 percent respectively, and the corresponding apparent rate constants are 0.00867min -1 、0.01175min -1 、0.00569min -1 、0.02024min -1 、0.02351min -1 、0.01565min -1 。BiOBr/Bi 4 O 5 Br 2 The degradation activity of the heterojunction to tetracycline in dark light is obviously higher than that of BiOBr and Bi 4 O 5 Br 2 And Bi 2 O 3 Wherein BiOBr/Bi prepared in example 2 4 O 5 Br 2 The degradation efficiency of the photocatalyst to the tetracycline can reach 63.44 percent, and the corresponding apparent rate constant is 0.02351min -1 . FIG. 22 shows the concentration of the photocatalyst prepared in example 2 of the present invention in dark light versus 40 mg.L -1 Graph of TOC removal of tetracycline. BiOBr/Bi by TOC test 4 O 5 Br 2 The mineralization capability of the photocatalyst is further verified, and after 50min of dark light, biOBr/Bi 4 O 5 Br 2 The TOC removal rate of the photocatalyst to 40mg/L tetracycline can reach 28.86%, which proves that BiOBr/Bi 4 O 5 Br 2 The photocatalyst has higher mineralization ability under dark light.
FIG. 23 shows the concentration of 10 mg. Multidot.L in dark light for the photocatalyst powders prepared in comparative example 1, examples 1 to 3, and comparative examples 2 and 3 of the present invention -1 The degradation curve of ciprofloxacin in the graph is shown in FIG. 24 as the corresponding apparent rate constants, in the graph, a corresponds to comparative example 1, b-d corresponds to examples 1-3, and e-f corresponds to the degradation curve and the apparent rate constants of the powder prepared in comparative examples 2-3 to ciprofloxacin, and as can be seen from the graph, after dark light for 25min, 0.5g of pure-phase BiOBr and pure-phase Bi are obtained 4 O 5 Br 2 Pure phase Bi 2 O 3 BiOBr/Bi prepared in examples 1-3 4 O 5 Br 2 The degradation efficiency of ciprofloxacin is 56.42%, 45.69%, 26.14%, 63.56%, 75.95%, 60.37%, respectively, and the corresponding apparent rate constants are 0.04218min -1 、0.02805min -1 、0.0147min -1 、0.0499min -1 、0.0729min -1 、0.04487min -1 。BiOBr/Bi 4 O 5 Br 2 The degradation activity of the heterojunction on the ciprofloxacin under dark light is obviously higher than that of pure-phase BiOBr and Bi 4 O 5 Br 2 And Bi 2 O 3 Wherein BiOBr/Bi prepared in example 2 4 O 5 Br 2 The degradation efficiency of the photocatalyst on the tetracycline can reach 75.95 percent, and the corresponding rate is correspondingly improvedApparent rate constant of 0.0729min -1 . FIG. 25 shows the concentration of the photocatalyst prepared in example 2 of the present invention in dark light versus the concentration of 20 mg.L -1 Graph of TOC removal of ciprofloxacin. BiOBr/Bi by TOC test 4 O 5 Br 2 The mineralization capability of the photocatalyst is further verified, and after dark light for 25min, biOBr/Bi 4 O 5 Br 2 The TOC removal rate of the photocatalyst to 20mg/L ciprofloxacin can reach 44.52 percent, which proves that BiOBr/Bi 4 O 5 Br 2 The photocatalyst has higher mineralization capability under dark light.
FIG. 26 shows the results of a graph of the results of comparison of 0.5g of the photocatalyst powder prepared in example 2 of the present invention with 10 mg.L in a dark light -1 Rhodamine B, 10 mg. L -1 Methylene orange, 10 mg.L -1 Degradation rate of methylene blue, biOBr/Bi 4 O 5 Br 2 The degradation rate of the photocatalyst on rhodamine B is 64.54 percent, the degradation rate on methylene orange is 57.75 percent, and the degradation rate on methylene blue is 58.4 percent, so that the prepared BiOBr/Bi 4 O 5 Br 2 The photocatalyst also has good degradation capability on dyes under dark light.
FIG. 27 is a diagram showing the trapping of tetracycline degrading active species in the dark of the photocatalyst powder prepared in example 2 of the present invention, with benzoquinone added as O 2 - Free radical scavenger, sodium oxalate as h + The scavenging agent, tert-butyl alcohol as OH scavenging agent, has different degrees of inhibition to dark light reaction, and the contribution of active species to tetracycline removal is h + >·O 2 - 。
FIG. 28 shows BiOBr/Bi prepared according to the present invention 4 O 5 Br 2 A photocatalysis mechanism diagram of the heterojunction photocatalyst under dark light. In the preparation process of the photocatalyst, biOBr and [ ((BiO)) are generated at the solid-liquid interface of colloidal particles due to the existence of a diffusion double electric layer 2 )·((BiO) 3 )·(BiO) 4 ] 9+ Forming an interface electric field, forming OVs by BiOBr due to hydrothermal anoxic environment, and transferring the E bound by BiOBr to Bi under the action of the interface electric field 4 O 5 Br 2 Making BiOBr/Bi 4 O 5 Br 2 Bi of medium BiOBr 3+ Increase in concentration of Bi 4 O 5 Br 2 Of Bi +(3-x) The concentration is increased until the Fermi levels of the two reach the equilibrium to form BiOBr/Bi 4 O 5 Br 2 Heterojunction of Bi 4 O 5 Br 2 Middle Bi +(3-x) The concentration increases to form Bi +(3-x) Doping with Bi 4 O 5 Br 2 The material forms a negative charge center and forms an acceptor level at the top of the valence band, so BiOBr/Bi 4 O 5 Br 2 Bi in the photocatalyst 4 O 5 Br 2 Store h + BiOBr store e - . In dark light, bi 4 O 5 Br 2 Store h + Can release the e stored by BiOBr for oxidizing and degrading pollutants - The released oxygen reacts with dissolved oxygen to form O 2 - Free radicals, degrading pollutants.
The above description is only one embodiment of the present invention, and not all or only one embodiment, and any equivalent modifications of the technical solutions of the present invention, which are made by a person skilled in the art through reading the present specification, are all covered by the claims of the present invention.
Claims (10)
1. BiOBr/Bi 4 O 5 Br 2 The preparation method of the heterojunction photocatalyst is characterized by comprising the following steps:
step 1, adding Bi (NO) 3 ) 3 ·5H 2 Dissolving O and NaBr in water to obtain a mixed solution;
step 2, adjusting the pH value of the mixed solution to 3-9 by using an alkali solution to obtain a precursor solution;
step 3, carrying out hydrothermal reaction on the precursor solution, washing and drying the obtained precipitate to obtain BiOBr/Bi 4 O 5 Br 2 A heterojunction photocatalyst.
2. The BiOBr/Bi of claim 1 4 O 5 Br 2 The preparation method of the heterojunction photocatalyst is characterized in that in the step 1, bi (NO) 3 ) 3 ·5H 2 The molar ratio of O to NaBr is (0.5-1.5): (0.5-1.5).
3. The BiOBr/Bi of claim 1 4 O 5 Br 2 The preparation method of the heterojunction photocatalyst is characterized in that in the step 1, bi (NO) in the mixed solution 3 ) 3 ·5H 2 The concentrations of O and NaBr are respectively (0.0125-0.05) mol.L -1 、(0.0125-0.05)mol·L -1 。
4. The BiOBr/Bi of claim 1 4 O 5 Br 2 The preparation method of the heterojunction photocatalyst is characterized in that in the step 2, the alkali solution is NaOH solution.
5. The BiOBr/Bi of claim 1 4 O 5 Br 2 The preparation method of the heterojunction photocatalyst is characterized in that in the step 3, the temperature of the hydrothermal reaction is 120-200 ℃ and the time is 8-20h.
6. BiOBr/Bi obtained by the production method according to any one of claims 1 to 5 4 O 5 Br 2 A heterojunction photocatalyst, characterized in that said BiOBr/Bi 4 O 5 Br 2 BiOBr and Bi in heterojunction photocatalyst 4 O 5 Br 2 Coexistence of two phases, biOBr and Bi 4 O 5 Br 2 A Z-type heterojunction is formed between the two electrodes, and the Z-type heterojunction contains oxygen vacancies.
7. The BiOBr/Bi of claim 6 4 O 5 Br 2 The application of the heterojunction photocatalyst in catalyzing and degrading organic matters under the condition of dark light or illumination.
8. Use according to claim 7, wherein the lighting conditions are visible light.
9. Use according to claim 7, wherein the organic substance is an antibiotic or an organic dye.
10. The use of claim 9, wherein the antibiotic is tetracycline or ciprofloxacin and the organic dye is rhodamine B, methylene orange or methylene blue.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN202211457607.3A CN115920931B (en) | 2022-11-21 | 2022-11-21 | BiOBr/Bi4O5Br2Heterojunction photocatalyst, preparation method and application thereof |
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| CN108262050A (en) * | 2018-01-03 | 2018-07-10 | 东南大学 | A kind of two dimension composite visible light catalyst and preparation method and application |
| CN109590005A (en) * | 2018-12-14 | 2019-04-09 | 江苏大学 | A kind of high electron-transporting type nucleocapsid ZnIn2S4Nanometer sheet/Ta3N5The preparation method and application of composite photo-catalyst |
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