CN114904547A - Mixed crystal phase WO 3 @g-C 3 N 5 Preparation method of composite photocatalyst - Google Patents
Mixed crystal phase WO 3 @g-C 3 N 5 Preparation method of composite photocatalyst Download PDFInfo
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- 239000011941 photocatalyst Substances 0.000 title claims abstract description 95
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- 238000002360 preparation method Methods 0.000 title claims abstract description 45
- ZNOKGRXACCSDPY-UHFFFAOYSA-N tungsten trioxide Chemical compound O=[W](=O)=O ZNOKGRXACCSDPY-UHFFFAOYSA-N 0.000 claims abstract description 106
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/24—Nitrogen compounds
-
- B01J35/39—
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/30—Treatment of water, waste water, or sewage by irradiation
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/30—Organic compounds
- C02F2101/38—Organic compounds containing nitrogen
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/30—Organic compounds
- C02F2101/40—Organic compounds containing sulfur
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2305/00—Use of specific compounds during water treatment
- C02F2305/10—Photocatalysts
-
- 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
Abstract
The invention discloses mixed crystal phase WO 3 @g‑C 3 N 5 The preparation method of the composite photocatalyst comprises the following steps: step A: preparation of tungsten trioxide WO 3 (ii) a And B: preparation of g-C 3 N 5 (ii) a And C: tungsten trioxide WO 3 And g-C 3 N 5 Dispersing the mixture into absolute ethyl alcohol to obtain mixed dispersion liquid A, transferring the mixed dispersion liquid A into a high-pressure reaction kettle for hydrothermal reaction, washing and drying a solid product A obtained by the reaction after the reaction is finished to obtain a mixed crystal phase WO 3 @g‑C 3 N 5 A composite photocatalyst is provided. Mixed crystal phase WO prepared by the invention 3 @g‑C 3 N 5 The composite photocatalyst shows better catalytic stability, has higher catalytic utilization rate and is suitable for the catalytic reaction of the light-emitting diodeThe degradation rate of rhodamine B can reach 97 percent at most, and the rhodamine B is tungsten trioxide WO 3 And g-C 3 N 5 9.8 times and 2.5 times.
Description
Technical Field
The invention relates to the technical field of composite photocatalysts. In particular mixed crystal phase WO 3 @g-C 3 N 5 A preparation method of a composite photocatalyst.
Background
With the rapid development of modern industries, the amount and kinds of pollutants discharged into the environment are increasing, especially water pollution. In severe cases, the water ecosystem can be completely destroyed, and the water body loses functions. Water is a source of life, all life on the earth can not be boiled, but fresh water resources which can be used only comprise underground water and inland surface water, so that the problem of water pollution is increasingly concerned and valued by people. The water body pollutants are mainly composed of organic pollutants and inorganic pollutants according to the property classification of the substances. The most typical inorganic pollutants are heavy metal ions discharged into water, and once the heavy metal ions are absorbed by animals or human bodies seriously, heavy metal poisoning is caused and lives are threatened. The common organic pollutants comprise halogenated olefin, dye, medicine, antibiotic, pesticide and the like, most of the organic pollutants are substances which are difficult to naturally degrade and can be always remained in a water body, and the harmful substances can be transmitted through a food chain to cause great damage to the nature and the human health and are irreversible. Therefore, it is important to find a method for performing harmless treatment on sewage.
The current sewage treatment methods mainly comprise: (1) the physical method is that the dye in the water is removed by using an adsorbent, a filter net film, an extraction method and the like, but the organic substances in the water are only removed by phase transfer and are not converted into substances which do not pollute the environment; (2) the biological method is to decompose the wastewater into micromolecular carbon dioxide and water by using microorganisms or degrade the wastewater by using a microbial co-metabolism method, but the concentration of the industrial wastewater discharged into water is higher and the industrial wastewater is not a single pollutant, so the biological method has high toxicity to the microorganisms and sometimes cannot achieve the degradation effect; (3) the chemical precipitation method utilizes metal ions and organic matters in wastewater to form metal organic complexes to generate precipitates, so that the effect of sewage treatment is achieved, but the sensitivity is generally low, and the precipitated metal organic complexes need to be further treated. (4) The method is now accepted by many people by utilizing the environment-friendly solar photocatalytic system for degradation. Therefore, the method seeks an economic, effective, green and safe environment pollutant catalytic degradation material, solves the problem that the current refractory organic matters pollute the water body, and is a hot subject of wide attention and research of scholars at home and abroad at present.
Most of metal oxide semiconductor materials have the characteristics of no toxicity, no harm, proper forbidden band width, high photocatalytic activity and the like, and have good application prospect in the field of photocatalytic degradation, wherein WO 3 As a wide band gap n-type semiconductor material, the material has high surface area, good chemical stability and biocompatibility. In recent years, WO is being worked on by researchers 3 The intensive research on the photocatalytic performance of the material and the number of published articles are obviously increased, which shows that WO 3 The photocatalyst has great research value as a photocatalyst. However, the catalytic effect of the single metal oxide photocatalyst is not ideal, and agglomeration is easy to occur in the synthesis process, so that the specific surface area and the photocatalytic performance of the material are reduced. To improve WO 3 Has many methods for its photocatalytic activity, and is applied to WO 3 Such as noble metal doping, semiconductor material compounding, metal ion doping, etc., but these modification methods are generally costly, complicated to operate, and are compatible with WO 3 The photocatalytic activity of the photocatalyst is not sufficiently improved.
Non-metallic g-C with graphite-like structure 3 N 4 The star material in the field of energy and environment application is formed by good chemical stability, stable chemical structure, low preparation cost, high corrosion resistance and unique electronic energy band structure. But g-C 3 N 4 Insufficient visible light utilization, and therefore, low band gap nitrogen-rich graphitic carbonitride g-C 3 N 5 Has attracted great research attention in the field of photocatalysis. By means of g-C 3 N 5 The morphology adjustability can be made different by different synthesis meansStructural morphology g-C 3 N 5 The combination of the characteristics of different morphologies can accelerate electron transfer and broaden the optical response (the band gap value is 1.70eV) of a visible light region, thereby realizing the improvement of the photocatalytic performance of the material. Synthesis of g-C with 3-amino-1, 2, 4-triazole by Wei et al 3 N 5 Successful preparation of Er 3+ /Tb 3+ @BiOBr-g-C 3 N 5 The photocatalysis experiment result shows that the material has good degradation effect on sulfamethoxazole, and the removal rate can reach 94.2% after visible light irradiation for 60 min. But now on how to utilize the low band gap nitrogen rich graphitic carbonitride g-C 3 N 5 To WO 3 The compound photocatalyst with better catalytic effect can be obtained by modification has not been reported.
Disclosure of Invention
To this end, the invention provides a mixed crystal phase WO 3 @g-C 3 N 5 A preparation method of a composite photocatalyst, aiming at solving the problem of the prior WO 3 The modified catalyst has the problems of unsatisfactory catalytic effect, poor catalytic stability and the like.
In order to solve the technical problems, the invention provides the following technical scheme:
mixed crystal phase WO 3 @g-C 3 N 5 The preparation method of the composite photocatalyst comprises the following steps:
step A: preparation of mixed-crystal phase tungsten trioxide WO 3 ；
And B: preparation of g-C 3 N 5 ；
And C: mixing the mixed crystal phase tungsten trioxide WO 3 And g-C 3 N 5 Dispersing the mixed dispersion liquid A into absolute ethyl alcohol to obtain mixed dispersion liquid A, then transferring the mixed dispersion liquid A into a high-pressure reaction kettle to carry out hydrothermal reaction, after the reaction is finished, washing and drying a solid product A obtained by the reaction to obtain a mixed crystal phase WO 3 @g-C 3 N 5 A composite photocatalyst is provided.
The mixed crystal phase WO 3 @g-C 3 N 5 The preparation method of the composite photocatalyst comprises the step C of mixing crystal phase tungsten trioxide WO 3 And g-C 3 N 5 Quality of (1)The ratio of the amounts is 1: 0.25 to 4.
The mixed crystal phase WO 3 @g-C 3 N 5 The preparation method of the composite photocatalyst comprises the step C of mixing the mixed dispersion liquid A with the mixed crystal phase tungsten trioxide WO 3 The content of (a) is 0.01-0.05 g/mL; the use of absolute ethanol as a solvent enables the pressure in the reaction vessel to be increased during the hydrothermal reaction in order to obtain a mixed crystal phase of tungsten trioxide, WO 3 And g-C 3 N 5 Better combination of the two materials forms mixed crystal phase WO 3 @g-C 3 N 5 A composite photocatalyst.
The mixed crystal phase WO 3 @g-C 3 N 5 In the step C, the hydrothermal reaction conditions are as follows: the reaction temperature is 100-200 ℃, and the reaction time is 6-16 h; the hydrothermal reaction temperature is higher than 200 ℃ or lower than 150 ℃, and the reaction temperature is lower than 6h or higher than 16h, so that the prepared mixed crystal phase WO is reduced 3 @g-C 3 N 5 The photocatalytic activity of the composite photocatalyst.
The mixed crystal phase WO 3 @g-C 3 N 5 The preparation method of the composite photocatalyst comprises the step C of mixing the crystal phase of tungsten trioxide WO 3 And g-C 3 N 5 When the tungsten trioxide is dispersed into absolute ethyl alcohol, stirring is carried out for 50-70 min in a magnetic stirring mode, and mixed crystal phase tungsten trioxide WO is obtained 3 And g-C 3 N 5 The more uniform the dispersion in the absolute ethyl alcohol, the more beneficial the hydrothermal reaction to form a homogeneous composite photocatalyst, and if the dispersion uniformity is not good, the mixed crystal phase tungsten trioxide WO can be caused 3 And g-C 3 N 5 The hydrothermal reaction is not completely compounded, so that the catalytic activity of the prepared composite photocatalyst is reduced to a certain extent; when the magnetic stirring mode is adopted for stirring for 50-70 min, the two materials are sufficiently dispersed to be fully contacted in absolute ethyl alcohol, and if the stirring time is too short, the two materials are not fully contacted, so that the composite effect is influenced; after the reaction is finished, washing the solid product A obtained by the reaction for 3 times by using absolute ethyl alcohol, so that impurities on the surface of the product can be cleaned, and the subsequent drying is accelerated after the absolute ethyl alcohol is adopted for washing; then theDrying for 10-12 h at the temperature of 75-85 ℃; drying at a temperature of 75-85 ℃ close to the boiling point of ethanol can accelerate the volatilization of the ethanol, and if the temperature is too low, the drying time is influenced, so that the activation of the composite photocatalyst material is influenced.
The mixed crystal phase WO 3 @g-C 3 N 5 A preparation method of the composite photocatalyst comprises the step A of mixing a crystal phase of tungsten trioxide WO 3 The preparation method comprises the following steps:
step A-1: putting tungstic acid and sodium sulfate into distilled water, and uniformly stirring to obtain a mixed dispersion liquid B;
step A-2: transferring the mixed dispersion liquid B into a high-pressure reaction kettle, carrying out hydrothermal reaction, and obtaining a solid product B after the reaction is finished;
step A-3: washing the solid product B with distilled water and absolute ethyl alcohol alternately in sequence, drying the washed solid product B, and grinding after drying to obtain the mixed crystal phase tungsten trioxide WO 3 . The mixed crystal phase tungsten trioxide WO prepared by the preparation method 3 Has mixed crystal phase, while the commercial tungsten trioxide is usually single crystal phase and can not be used for preparing the mixed crystal phase WO 3 @g-C 3 N 5 A composite photocatalyst is provided.
The mixed crystal phase WO 3 @g-C 3 N 5 In the step A-1, the mass ratio of tungstic acid to sodium sulfate is 1: 1.5-2.5, the sodium sulfate can play a role of a morphology guiding agent, and the crystal phase of the generated tungsten trioxide is adjusted by regulating the ratio of tungstic acid to sodium sulfate; if the mass ratio of tungstic acid to sodium sulfate is beyond the range, the generation of crystal phase in the material during the synthesis process is influenced, and the mixed crystal phase WO finally prepared is influenced 3 @g-C 3 N 5 The catalytic performance of the composite photocatalyst; in the mixed dispersion liquid B, the content of tungstic acid is 0.05-0.08 g/mL, which is beneficial to WO 3 Generating mixed crystal phase of (2);
in the step A-2, the hydrothermal reaction conditions are as follows: the reaction temperature is 150-200 ℃, and the reaction time is 10-15 h; the hydrothermal reaction temperature is too high or too low, and the hydrothermal reaction time is too long or too shortInfluencing WO 3 The crystal phase composition of the photocatalyst, thereby influencing the photocatalytic activity of the prepared composite photocatalyst.
In the step A-3, the drying temperature of the solid product B is 75-85 ℃, and the drying time is 7.5-8.5 h; too low drying temperature or too short drying time can result in incomplete evaporation of water and affect activation of the material, and too high drying temperature or too long drying time can affect WO 3 The crystal phase composition of (a); mixed crystal phase tungsten trioxide WO 3 Has a particle diameter of 90 to 110 [ mu ] m and is in the range of the particle diameter 3 Can better react with g-C 3 N 5 Complex to form mixed crystal phase WO 3 @g-C 3 N 5 A composite photocatalyst is provided.
The mixed crystal phase WO 3 @g-C 3 N 5 Preparation method of composite photocatalyst, in step B, g-C 3 N 5 The preparation method comprises the following steps:
step B-1: adding 3-amino-1, 2, 4-triazole into deionized water, and stirring for dissolving to obtain a mixed dispersion liquid C;
step B-2: heating the mixed dispersion liquid C and magnetically stirring to completely evaporate the water in the mixed dispersion liquid C, and grinding the residual solid after the water is evaporated to dryness to obtain a solid product C; the reason that the 3-amino-1, 2, 4-triazole is dissolved and then the water is evaporated to dryness at a specific temperature is to recrystallize the 3-amino-1, 2, 4-triazole, and the internal structure of the crystal may be changed to some extent after the crystallization, so that g-C obtained by calcination 3 N 5 Can be better mixed with mixed crystal phase WO 3 Compounding to generate a composite photocatalyst with better photocatalytic activity;
step B-3: putting the solid product C into a tubular furnace for high-temperature calcination; calcining to obtain yellow solid powder, i.e. g-C 3 N 5 . g-C prepared by the preparation method 3 N 5 Can be mixed with mixed crystal phase WO 3 Complex to form mixed crystal phase WO 3 @g-C 3 N 5 Composite photocatalyst and g-C prepared by adopting preparation method of invention 3 N 5 With mixed crystal phases WO 3 In the compounding process, WO 3 The monoclinic phase in the mixed crystal phase is easier to be converted into the hexagonal phase, so that the mixed crystal phase WO with better catalytic activity and catalytic stability is prepared 3 @g-C 3 N 5 A composite photocatalyst is provided.
The mixed crystal phase WO 3 @g-C 3 N 5 In the step B-1, the mass fraction of 3-amino-1, 2, 4-triazole in the mixed dispersion liquid C is 2-8 wt%; if the mass fraction of the 3-amino-1, 2, 4-triazole is too high, the rate of evaporative crystallization is affected, whereas if the mass fraction of the 3-amino-1, 2, 4-triazole is too low, the amount after crystallization is too small, and the yield is affected;
in the step B-2, the heating temperature of the mixed dispersion liquid C is 75-85 ℃, and if the heating temperature is too high or too low, the crystallization effect is influenced, so that the g-C prepared by the method is influenced 3 N 5 The structure of the composite photocatalyst is not beneficial to preparing the composite photocatalyst with good catalytic performance, and the particle size of the solid product C is 80-120 microns; controlling the particle size of the solid product C within this range allows all ingredients to be heated uniformly during calcination, which can lead to non-uniform particle size of the material if not sufficiently ground, which can lead to non-uniform heating of the material during calcination, resulting in g-C being produced 3 N 5 The catalyst performance becomes poor;
in the step B-3, during high-temperature calcination, the temperature is increased to 480-560 ℃ at the heating rate of 4-6 ℃/min, and then the temperature is kept for 2.5-3.5 hours; during calcination, the internal structure of the material is affected by too fast or too slow heating rate, and the structure is formed imperfectly if the temperature is too fast, and g-C is caused if the temperature is too slow 3 N 5 Build-up of internal structures, detrimental to obtaining g-C of desired structure 3 N 5 (ii) a In tests it was found that g-C is obtained if the calcination temperature is lower than 480 ℃ or higher than 560 ℃ 3 N 5 With mixed crystal phases WO 3 Mixed crystal phase WO obtained by compounding 3 @g-C 3 N 5 The catalytic performance of the composite photocatalyst is relatively poor.
The mixed crystal phase WO 3 @g-C 3 N 5 The preparation method of the composite photocatalyst comprises the step C of mixing crystal phase tungsten trioxideWO 3 And g-C 3 N 5 The mass ratio of (1): 2; in the mixed dispersion liquid A, tungsten trioxide WO of mixed crystal phase 3 The content of (b) is 0.033 g/mL; the conditions of the hydrothermal reaction are as follows: the reaction temperature is 180 ℃, and the reaction time is 12 h; mixing the mixed crystal phase tungsten trioxide WO 3 And g-C 3 N 5 When the mixture is dispersed into absolute ethyl alcohol, stirring for 60min in a magnetic stirring mode; after the reaction is finished, washing a solid product A obtained by the reaction for 3 times by using absolute ethyl alcohol; then drying for 10h at the temperature of 80 ℃;
in step A, mixed crystal phase tungsten trioxide WO 3 The preparation method comprises the following steps:
step A-1: putting tungstic acid and sodium sulfate into distilled water, and uniformly stirring to obtain a mixed dispersion liquid B; the mass ratio of the tungstic acid to the sodium sulfate is 1:2, and the content of the tungstic acid in the mixed dispersion liquid B is 0.067 g/mL;
step A-2: transferring the mixed dispersion liquid B into a high-pressure reaction kettle, carrying out hydrothermal reaction, and obtaining a solid product B after the reaction is finished; the conditions of the hydrothermal reaction are as follows: the reaction temperature is 180 ℃, and the reaction time is 12 hours;
step A-3: washing the solid product B with distilled water and absolute ethyl alcohol alternately in sequence, drying the washed solid product B, and grinding after drying to obtain the mixed crystal phase tungsten trioxide WO 3 (ii) a The drying temperature of the solid product B is 80 ℃, and the drying time is 8 h; mixed crystal phase tungsten trioxide WO 3 The particle size of the particles is 90-110 mu m;
in step B, g to C 3 N 5 The preparation method comprises the following steps:
step B-1: adding 3-amino-1, 2, 4-triazole into deionized water, and stirring for dissolving to obtain a mixed dispersion liquid C; the mass fraction of the 3-amino-1, 2, 4-triazole in the mixed dispersion liquid C is 5 wt%;
step B-2: heating the mixed dispersion liquid C and magnetically stirring to completely evaporate the water in the mixed dispersion liquid C, and grinding the residual solid after the water is evaporated to dryness to obtain a solid product C; the heating temperature of the mixed dispersion liquid C is 80 ℃, and the particle size of the solid product C is 80-120 mu m;
step B-3: putting the solid product C into a tube furnace for high-temperature calcination; calcining to obtain yellow solid powder, i.e. g-C 3 N 5 (ii) a During high-temperature calcination, the temperature is raised to 540 ℃ at the heating rate of 5 ℃/min, and then the temperature is kept at 540 ℃ for 3 h.
The technical scheme of the invention achieves the following beneficial technical effects:
1. the invention mixes the crystal phase tungsten trioxide WO 3 And g-C 3 N 5 The mixed crystal phase WO is prepared by hydrothermal reaction 3 @g-C 3 N 5 Composite photocatalyst, and mixed crystal phase tungsten trioxide WO 3 And g-C 3 N 5 Compared with the prior art, the mixed crystal phase composite photocatalyst shows better catalytic activity when catalyzing rhodamine B: under the condition that a 500W xenon lamp is used as an irradiation light source, the highest degradation rate of rhodamine B in 120min can reach 97 percent, and the rhodamine B is respectively tungsten trioxide WO with mixed crystal phases 3 And g-C 3 N 5 9.8 times and 2.5 times.
2. The mixed crystal phase WO prepared by the invention 3 @g-C 3 N 5 (1:2) when the composite photocatalyst repeatedly degrades rhodamine B, the more the composite photocatalyst is repeatedly used, the better the photocatalytic effect on rhodamine B is; and after degrading rhodamine B repeatedly for six times, the method still has good degradation effect on tetracycline and methylene blue: WO after degrading rhodamine B repeatedly for six times 3 @g-C 3 N 5 (1:2) the composite photocatalyst has the degradation rate of 73% for tetracycline and 90% for methylene blue within 120 min; WO prepared according to the invention 3 @g-C 3 N 5 (1:2) the composite photocatalyst shows better catalytic stability and has higher catalytic utilization rate.
3. The invention respectively regulates and controls the tungsten trioxide WO with mixed crystal phase 3 And g-C 3 N 5 Preparation method of (5) tungsten trioxide WO having a mixed crystal phase 3 Mixed crystal phase tungsten trioxide WO 3 And g-C prepared by the invention 3 N 5 When hydrothermal reaction is carried out, mixed crystal phase WO with good catalytic activity and catalytic stability can be obtained in a compounding way 3 @g-C 3 N 5 A composite photocatalyst; tungsten trioxide WO in the hydrothermal reaction process 3 And g-C 3 N 5 The mass ratio of the tungsten trioxide and the tungsten trioxide, the hydrothermal reaction temperature, the reaction time, the drying temperature and the like are controlled within a specific range, so that the tungsten trioxide WO 3 In the presence of g-C 3 N 5 Monoclinic phase in the mixed crystal phase is converted to hexagonal phase during compounding, so that the prepared WO is 3 @g-C 3 N 5 The composite photocatalyst has higher photocatalytic activity and photocatalytic stability; the WO 3 @g-C 3 N 5 In the process of catalyzing rhodamine B degradation by the composite photocatalyst, along with the increase of catalysis times, the mixed crystal phase WO 3 @g-C 3 N 5 Monoclinic phase in the composite photocatalyst is converted towards hexagonal phase, so that the hexagonal phase is increased along with the increase of the photocatalytic times, and the catalytic activity of the composite photocatalyst is enhanced along with the increase of the catalytic times.
Drawings
FIG. 1 XRD spectra of different photocatalysts in the examples of the present invention;
FIG. 2a photocatalyst WO in the example of the invention 3 Scanning electron microscope images of (a);
FIG. 2b photocatalyst g-C in an example of the invention 3 N 5 Scanning electron microscope images of;
FIG. 2c photocatalyst WO in the example of the present invention 3 @g-C 3 N 5 (1:2) scanning electron micrographs;
FIG. 3a photocatalyst WO in the example of the present invention 3 @g-C 3 N 5 (1:2) EDX spectrum (tungsten W element);
FIG. 3b photocatalyst WO in the example of the present invention 3 @g-C 3 N 5 (1:2) EDX spectrum (oxygen O element);
FIG. 3c photocatalyst WO in the example of the present invention 3 @g-C 3 N 5 (1:2) EDX spectrum (carbon C element);
FIG. 3d photocatalyst WO in the example of the invention 3 @g-C 3 N 5 EDX spectrum (nitrogen N element) of (1: 2).
FIG. 4 is a UV-vis DRS spectrum of different photocatalysts in an example of the present invention;
FIG. 5 is a graph showing degradation curves of different photocatalysts on rhodamine B in the embodiment of the invention;
FIG. 6a photocatalyst WO in the example of the present invention 3 @g-C 3 N 5 (1:2) a stability test result graph;
FIG. 6b photocatalyst WO in the example of the present invention 3 @g-C 3 N 5 (1:2) a test result curve diagram of a catalytic degradation mechanism;
FIG. 6c shows that the photocatalyst WO is a photocatalyst after degrading rhodamine B (RhB) for six times in the embodiment of the invention 3 @g-C 3 N 5 (1:2), a graph of the results of the catalytic degradation tests on Tetracycline (TC) and Methylene Blue (MB);
FIG. 6d example WO of the invention 3 @g-C 3 N 5 (1:2) comparison of XRD spectrograms before use (Fresh) and after repeated degradation of rhodamine B six times (Recycle 6 th).
Detailed Description
1. Experimental part
1.1 pure tungsten trioxide WO 3 Preparation of
Weighing 2g of tungstic acid and 4g of sodium sulfate, placing the tungstic acid and the sodium sulfate into a beaker filled with 30mL of distilled water, and stirring to uniformly disperse the tungstic acid and the sodium sulfate to obtain a mixed dispersion liquid B; transferring the mixed dispersion liquid B into a high-pressure reaction kettle, carrying out hydrothermal reaction for 12h at the temperature of 180 ℃, after the reaction is finished, alternately washing a solid product B obtained by the reaction with distilled water and absolute ethyl alcohol for several times, drying for 8h at the temperature of 80 ℃, grinding after drying to ensure that the particle size of the product reaches 90-110 mu m, and obtaining the tungsten trioxide WO 3 And (3) powder.
1.2 pure g-C 3 N 5 Preparation of
Adding 1.5g of 3-amino-1, 2, 4-triazole into 30mL of deionized water, and stirring to fully dissolve the mixture to obtain a mixed dispersion liquid C; magnetically stirring the mixed dispersion liquid C at 80 ℃, and grinding the mixed dispersion liquid C until the particle size of the powder is 80-120 mu m after the water is evaporated to dryness to obtain a solid product C; putting the solid product C into a tube furnace, heating to 540 ℃ at the heating rate of 5 ℃/min, and then heating to 5 DEG CKeeping the temperature at 40 ℃ for 3h to obtain yellow g-C 3 N 5 And (5) naturally cooling the powder for later use.
1.3 Mixed crystalline phases WO 3 @g-C 3 N 5 Preparation of composite photocatalyst
1g of tungsten trioxide WO is weighed out respectively 3 And 2g of pure g-C 3 N 5 Placing in a beaker filled with 30mL of absolute ethyl alcohol, magnetically stirring for 1h to obtain a mixed dispersion liquid A, transferring the mixed dispersion liquid A into a high-pressure reaction kettle, carrying out hydrothermal reaction at 180 ℃ for 12h, washing the obtained solid product A with absolute ethyl alcohol for 3 times, and drying at 80 ℃ for 10h to obtain a mixed crystal phase WO 3 @g-C 3 N 5 Composite photocatalyst, designated WO 3 :g-C 3 N 5 (1:2). In the same way, by varying g-C 3 N 5 0.25 g, 0.5g, 1g, 3g and 4g, respectively to prepare a mixed crystal phase WO 3 @g-C 3 N 5 The composite photocatalyst comprises: WO 3 :g-C 3 N 5 (1:0.25)、WO 3 :g-C 3 N 5 (1:0.5)、WO 3 :g-C 3 N 5 (1:1)、WO 3 :g-C 3 N 5 (1:3)、 WO 3 :g-C 3 N 5 (1:4)。
1.4 photocatalytic Performance test
In this example, rhodamine B (RhB) was chosen as the mimic contaminant for g-C 3 N 5 、WO 3 、 WO 3 @g-C 3 N 5 The degradation performance of three photocatalysts was tested: respectively adding 20mg of photocatalyst into 40mL of rhodamine B with the concentration of 10mg/mL, and respectively stirring for 30min in the dark to ensure that the rhodamine B achieves absorption-desorption balance on the surface of the photocatalyst, thereby obtaining a sample solution. Taking a sample (5mL) from the sample solution every 15min by using a 500W xenon lamp as a light source (a 420nm filter); the sampled samples were centrifuged to remove the catalyst added to the samples, and the supernatants were collected and measured for absorbance at the maximum absorption wavelength of rhodamine B (λ max ═ 554nm) using an ultraviolet-visible spectrophotometer.
3. Results and analysis
3.1 XRD analysis
In order to determine the crystal structure of the prepared photocatalyst, the prepared photocatalyst was subjected to XRD characterization, the test results are shown in FIG. 1, and the analysis of the graph shows that pure g-C 3 N 5 One peak appears at 2 theta-12.8 deg., indicating the synthesized g-C 3 N 5 The internal structure is ordered, a peak appears at 27.4 degrees 2 theta, the corresponding crystal plane is 002, and g-C is illustrated 3 N 5 A good crystal structure is formed and stacked between layers in the form of conjugated chains in the CN backbone. From WO 3 The characteristic diffraction peaks appeared at 2 θ of 22.9(002), 23.49(020) and 24.15(200), which is attributed to WO of monoclinic phase 3 Conforms to the standard card JCPDS-83-0950; diffraction peaks appearing at 2 θ of 13.74(100), 27.83(101), 28.82 (200), 31.92(111), 33.64(201), 36.33(210) are attributed to WO in the hexagonal phase 3 In conformity with the standard card JCPDS-33-1387, the description is given of the tungsten trioxide WO prepared in this example 3 Has monoclinic crystal phase and hexagonal crystal phase at the same time, and is a mixed crystal phase WO 3 . Meanwhile, the XRD diffraction peak analysis of the composite catalyst can obtain: with g-C 3 N 5 Increase in doping amount, m-WO 3 The intensities of the three diffraction peaks 22.9, 23.49 and 24.15 show a tendency of increasing first and decreasing. At the same time due to g-C 3 N 5 Doping of h-WO 3 The intensity of the characteristic diffraction peak at 27.83 is gradually increased, and the diffraction peak is also widened to a certain extent, which indicates that the g-C 3 N 5 With WO 3 After compounding, the WO is affected 3 In the middle of the crystal structure, with g-C 3 N 5 Increase in doping amount WO 3 Mainly towards the hexagonal phase (h-WO) 3 ) And (4) increasing. For g-C 3 N 5 The diffraction peak of the 002 crystal face is probably caused by h-WO 3 The diffraction peak positions of the 101 crystal face are similar, so that after the two materials are compounded, g-C 3 N 5 The diffraction peak of the 002 crystal face is shifted with h-WO 3 The diffraction peaks of the 101 crystal plane overlap, which further illustrates WO 3 And g-C 3 N 5 Good couplingTogether.
2.2 SEM analysis
For determining the surface morphology of the catalyst prepared, the catalyst prepared is treated with tungsten trioxide WO 3 、 g-C 3 N 5 And WO 3 @g-C 3 N 5 (1:2) SEM analysis was performed, and the results are shown in FIGS. 2a to 2 c. As can be seen from FIG. 2a, tungsten trioxide WO prepared by the above-described method 3 The catalyst is in a rod-shaped structure, and is agglomerated in a hydrothermal process, so that the size of the catalyst is large. As can be seen from FIG. 2b, g-C is produced 3 N 5 Presenting a sheet-like stacked porous structure. From FIG. 2c, it can be seen that when WO is applied 3 And g-C 3 N 5 After compounding, the shape is changed from a rod-like structure into particles, the shape is changed, and simultaneously g-C 3 N 5 The gaps among the layers are enlarged, the composite catalyst presents a certain gap structure, and the adsorption of degradation pairs is facilitated in a photocatalytic degradation experiment, so that the photocatalytic activity of the material is improved.
Based on the above results, in order to confirm the types and distribution of elements present in the composite catalyst, WO was applied 3 @g-C 3 N 5 Energy dispersive X-ray (EDX) imaging was performed (1:2) verifying the presence of W, O, C, N elements (fig. 3a to 3 d). At the same time from EDX-map analysis, in this region WO 3 In g-C 3 N 5 Medium to high dispersion.
2.3 UV-vis DRS spectrogram analysis
FIG. 4 is a UV-visible diffuse reflectance spectrum of the prepared photocatalyst, and it can be seen from an analysis of FIG. 4 that the light absorption value of the prepared composite catalyst in the visible light region is less than that of pure g-C 3 N 5 Greater than pure WO 3 . The reason for this is probably firstly that of WO 3 And g-C 3 N 5 The recombination affects the optical band gap of the semiconductor, thereby showing red shift of the ultraviolet-visible spectrum; the second possibility is due to g-C 3 N 5 The higher nitrogen content in the structure enhances the charge transfer capability and thus the photocatalytic activity, which indicates that WO 3 @g-C 3 N 5 Can be in the visible rangeThe sunlight is fully utilized in the inner part. Meanwhile, the analysis of DRS test results of the composite catalyst after being repeatedly used for six times shows that the light absorption value of the composite material after being repeatedly used is increased, which shows that the photocatalytic degradation effect of the composite catalyst after being used is improved, and is consistent with the subsequent experimental results.
2.4 photocatalytic Performance testing
In order to detect the optical activity of the prepared photocatalyst, in this example, the performance of the photocatalyst was tested by mainly using rhodamine B as a simulated pollutant and using a 500W xenon lamp as an irradiation light source, and the experimental result is shown in fig. 5, and it can be seen from fig. 5 that when WO is used as a reference, the performance of the photocatalyst is tested 3 And g-C 3 N 5 After the composition is carried out, the WO is compared with pure WO 3 And pure g-C 3 N 5 Has good photocatalytic effect, when WO is used 3 And g-C 3 N 5 When the mass ratio of (A) to (B) is 1:2, the removal rate of rhodamine B can reach 97 percent (within 120 min), and the rhodamine B is pure WO respectively 3 And pure g-C 3 N 5 9.8 times and 2.5 times.
2.5 stability test
Stability is one of the important indicators for measuring the performance of the photocatalyst, and therefore this example shows the photocatalyst WO 3 @g-C 3 N 5 The stability of (1:2) is tested, the experimental result is shown in figure 6a, the experimental result shows that the photocatalytic effect of rhodamine B tends to become better along with the increase of the use times of the material, and when the material is used for 5 times, the degradation performance of the composite photocatalyst is basically stable, so that the catalyst WO can be greatly improved 3 @g-C 3 N 5 (1:2) utilization ratio.
In order to determine the degradation mechanism of the photo-composite catalyst, in this example, the photo-catalytic mechanism of the photo-composite catalyst was tested by using disodium ethylenediaminetetraacetate (EDTA-2Na) as a hole inhibitor, tert-butyl alcohol (TBA) as a hydroxyl inhibitor, and p-Benzoquinone (BQ) as a superoxide radical inhibitor, and the experimental result is shown in fig. 6b, from which it can be seen that in the degradation process h + 、·OH、O 2 All play a role, but the main role is OH.
In order to further test the performance of the composite photocatalyst after six times of degradation of rhodamine B (RhB), the composite photocatalyst after six times of degradation is used for carrying out photocatalytic degradation performance detection on Tetracycline (TC) and Methylene Blue (MB), and the experimental result is shown in FIG. 6 c. This shows that the composite photocatalyst prepared in this example has good stability, and the utilization rate of the composite photocatalyst can be greatly improved.
FIG. 6d shows the composite photocatalyst after six times of reuse and before reuse (WO) 3 @g-C 3 N 5 (1:2)), and analysis shows that after six times of repeated use, the internal crystal structure composition of the photocatalyst changes, the original peak intensities of the crystal faces of the hexagonal crystal phases 100 and 101 become larger, the peak widths become narrower, and the peak corresponding to the 111 crystal face disappears, which indicates that the crystal of the composite photocatalyst is converted from the monoclinic phase to the hexagonal phase during the use process, and further indicates that WO of the hexagonal phase is combined with the stability test result 3 The photocatalysis performance is better.
Claims (10)
1. Mixed crystal phase WO 3 @g-C 3 N 5 The preparation method of the composite photocatalyst is characterized by comprising the following steps:
step A: preparation of mixed-crystal phase tungsten trioxide WO 3 ；
And B: preparation of g-C 3 N 5 ；
And C: mixing the mixed crystal phase tungsten trioxide WO 3 And g-C 3 N 5 Dispersing the mixture into absolute ethyl alcohol to obtain mixed dispersion liquid A, transferring the mixed dispersion liquid A into a high-pressure reaction kettle for hydrothermal reaction, washing and drying a solid product A obtained by the reaction after the reaction is finished to obtain a mixed crystal phase WO 3 @g-C 3 N 5 A composite photocatalyst is provided.
2. According toA mixed crystal phase WO as claimed in claim 1 3 @g-C 3 N 5 The preparation method of the composite photocatalyst is characterized in that in the step C, tungsten trioxide WO with mixed crystal phase 3 And g-C 3 N 5 The mass ratio of (1): 0.25 to 4.
3. Mixed crystal phase WO according to claim 2 3 @g-C 3 N 5 The preparation method of the composite photocatalyst is characterized in that in the step C, tungsten trioxide WO with mixed crystal phase is added into the mixed dispersion liquid A 3 The content of (b) is 0.01-0.05 g/mL.
4. The mixed crystal phase WO of claim 3 3 @g-C 3 N 5 The preparation method of the composite photocatalyst is characterized in that in the step C, the hydrothermal reaction conditions are as follows: the reaction temperature is 100-200 ℃, and the reaction time is 6-16 h.
5. Mixed crystal phase WO according to claim 4 3 @g-C 3 N 5 The preparation method of the composite photocatalyst is characterized in that in the step C, tungsten trioxide WO with mixed crystal phase 3 And g-C 3 N 5 When the dispersion is dispersed into absolute ethyl alcohol, stirring for 50-70 min by adopting a magnetic stirring mode; after the reaction is finished, washing the solid product A obtained by the reaction for 3 times by using absolute ethyl alcohol; and then drying for 10-12 h at the temperature of 75-85 ℃.
6. Mixed crystal phase WO as claimed in claim 1 3 @g-C 3 N 5 The preparation method of the composite photocatalyst is characterized in that in the step A, tungsten trioxide WO in a mixed crystal phase 3 The preparation method comprises the following steps:
step A-1: putting tungstic acid and sodium sulfate into distilled water, and uniformly stirring to obtain a mixed dispersion liquid B;
step A-2: transferring the mixed dispersion liquid B into a high-pressure reaction kettle, carrying out hydrothermal reaction, and obtaining a solid product B after the reaction is finished;
step A-3: mixing the solid productWashing the solid product B with distilled water and absolute ethyl alcohol alternately in sequence, drying the washed solid product B, and grinding the dried solid product B to obtain the mixed crystal phase tungsten trioxide WO 3 。
7. The mixed crystal phase WO of claim 6 3 @g-C 3 N 5 The preparation method of the composite photocatalyst is characterized in that in the step A-1, the mass ratio of tungstic acid to sodium sulfate is 1: 1.5-2.5; in the mixed dispersion liquid B, the content of tungstic acid is 0.05-0.08 g/mL;
in the step A-2, the hydrothermal reaction conditions are as follows: the reaction temperature is 150-200 ℃, and the reaction time is 10-15 h;
in the step A-3, the drying temperature of the solid product B is 75-85 ℃, and the drying time is 7.5-8.5 h; mixed crystal phase tungsten trioxide WO 3 The particle size of (A) is 90 to 110 μm.
8. Mixed crystal phase WO according to claim 1 3 @g-C 3 N 5 The preparation method of the composite photocatalyst is characterized in that in the step B, g-C 3 N 5 The preparation method comprises the following steps:
step B-1: adding 3-amino-1, 2, 4-triazole into deionized water, and stirring for dissolving to obtain a mixed dispersion liquid C;
step B-2: heating the mixed dispersion liquid C and magnetically stirring the mixed dispersion liquid C at the same time to completely evaporate the water in the mixed dispersion liquid C, and grinding the residual solid after the water is evaporated to dryness to obtain a solid product C;
step B-3: putting the solid product C into a tubular furnace for high-temperature calcination; calcining to obtain yellow solid powder, i.e. g-C 3 N 5 。
9. The mixed crystal phase WO according to claim 8 3 @g-C 3 N 5 The preparation method of the composite photocatalyst is characterized in that in the step B-1, the mass fraction of the 3-amino-1, 2, 4-triazole in the mixed dispersion liquid C is 2-8 wt%;
in the step B-2, the heating temperature of the mixed dispersion liquid C is 75-85 ℃, and the particle size of the solid product C is 80-120 mu m;
in the step B-3, during high-temperature calcination, the temperature is raised to 480-560 ℃ at the heating rate of 4-6 ℃/min, and then the temperature is kept for 2.5-3.5 h.
10. The mixed crystal phase WO according to any of claims 1 to 9 3 @g-C 3 N 5 The preparation method of the composite photocatalyst is characterized in that in the step C, tungsten trioxide WO with mixed crystal phase 3 And g-C 3 N 5 The mass ratio of (1): 2; in the mixed dispersion liquid A, tungsten trioxide WO of mixed crystal phase 3 The content of (b) is 0.033 g/mL; the conditions of the hydrothermal reaction are as follows: the reaction temperature is 180 ℃, and the reaction time is 12 hours; mixing the mixed crystal phase tungsten trioxide WO 3 And g-C 3 N 5 When the mixture is dispersed into absolute ethyl alcohol, stirring for 60min in a magnetic stirring mode; after the reaction is finished, washing the solid product A obtained by the reaction for 3 times by using absolute ethyl alcohol; then drying for 10h at the temperature of 80 ℃;
in step A, mixed crystal phase tungsten trioxide WO 3 The preparation method comprises the following steps:
step A-1: putting tungstic acid and sodium sulfate into distilled water, and uniformly stirring to obtain a mixed dispersion liquid B; the mass ratio of the tungstic acid to the sodium sulfate is 1:2, and the content of the tungstic acid in the mixed dispersion liquid B is 0.067 g/mL;
step A-2: transferring the mixed dispersion liquid B into a high-pressure reaction kettle, carrying out hydrothermal reaction, and obtaining a solid product B after the reaction is finished; the conditions of the hydrothermal reaction are as follows: the reaction temperature is 180 ℃, and the reaction time is 12 hours;
step A-3: washing the solid product B with distilled water and absolute ethyl alcohol alternately in sequence, drying the washed solid product B, and grinding after drying to obtain the mixed crystal phase tungsten trioxide WO 3 (ii) a The drying temperature of the solid product B is 80 ℃, and the drying time is 8 h; mixed crystal phase tungsten trioxide WO 3 The particle size of the particles is 90-110 mu m;
in step B, g to C 3 N 5 The preparation method comprises the following steps:
step B-1: adding 3-amino-1, 2, 4-triazole into deionized water, and stirring for dissolving to obtain a mixed dispersion liquid C; the mass fraction of 3-amino-1, 2, 4-triazole in the mixed dispersion liquid C is 5 wt%;
step B-2: heating the mixed dispersion liquid C and magnetically stirring to completely evaporate the water in the mixed dispersion liquid C, and grinding the residual solid after the water is evaporated to dryness to obtain a solid product C; the heating temperature of the mixed dispersion liquid C is 80 ℃, and the particle size of the solid product C is 80-120 mu m;
step B-3: putting the solid product C into a tubular furnace for high-temperature calcination; calcining to obtain yellow solid powder, i.e. g-C 3 N 5 (ii) a During high-temperature calcination, the temperature is raised to 540 ℃ at the heating rate of 5 ℃/min, and then the temperature is kept at 540 ℃ for 3 h.
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| CN104772158A (en) * | 2015-03-23 | 2015-07-15 | 上海应用技术学院 | Preparation method of WO3/C3N4 mixed photocatalyst |
| CN110339853A (en) * | 2019-07-22 | 2019-10-18 | 成都理工大学 | C3N5Material and its preparation method and application |
| CN112221531A (en) * | 2020-11-13 | 2021-01-15 | 长沙学院 | Heterogeneous core-shell g-C3N5@MnO2Composite and preparation method thereof |
| CN112495420A (en) * | 2020-12-09 | 2021-03-16 | 北华大学 | Preparation method of nitrogen-rich graphite phase carbon nitride/silver metavanadate composite photocatalyst |
| CN113751048A (en) * | 2021-10-15 | 2021-12-07 | 阜阳师范大学 | Molybdenum trioxide in-situ intercalation carbon nitride composite catalyst and preparation method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104772158A (en) * | 2015-03-23 | 2015-07-15 | 上海应用技术学院 | Preparation method of WO3/C3N4 mixed photocatalyst |
| CN110339853A (en) * | 2019-07-22 | 2019-10-18 | 成都理工大学 | C3N5Material and its preparation method and application |
| CN112221531A (en) * | 2020-11-13 | 2021-01-15 | 长沙学院 | Heterogeneous core-shell g-C3N5@MnO2Composite and preparation method thereof |
| CN112495420A (en) * | 2020-12-09 | 2021-03-16 | 北华大学 | Preparation method of nitrogen-rich graphite phase carbon nitride/silver metavanadate composite photocatalyst |
| CN113751048A (en) * | 2021-10-15 | 2021-12-07 | 阜阳师范大学 | Molybdenum trioxide in-situ intercalation carbon nitride composite catalyst and preparation method thereof |
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