Preparation method and application of CoO / black phosphorus catalyst

Abstract

The present invention belongs to the technical field of environmental chemical photocatalytic water treatment, and discloses a preparation method and application of a CoO / black phosphorus catalyst. A series of CoO / BP composite photocatalysts are prepared using CoO and Black Phosphoru (BP) as precursor reactants. The BP catalyst is prepared by a simple hydrothermal method, and then Co(CH3COO)2·4H2O and BP are calcined in different proportions to generate a composite CoO / BP photocatalyst. It is analyzed that CoO has been loaded onto the BP layer and a composite structure has been formed. Under visible light conditions, tetracycline hydrochloride is degraded using each of the prepared catalysts, and the catalytic activity of the composite photocatalyst is observed. The results show that among the photocatalysts with different loading amounts of CoO / BP, 50%-CoO / BP has the best photocatalytic degradation effect, and the degradation rate in 4 hours reaches 86.55%, which is 7.76 times and 2.06 times the degradation rates of pure CoO and BP, respectively. This shows that the present invention successfully prepares a highly efficient composite catalyst.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental chemical photocatalytic water treatment, relates to generating clean gas by visible light treatment, and particularly relates to a preparation method and application of a CoO / black phosphorus catalyst. Background Art

[0002] As industrialization continues to expand in line with production needs, the volume of industrial wastewater discharged from industries such as papermaking, petrochemicals, and printing and dyeing is growing annually. A significant portion of this wastewater is organically contaminated, with organic pollutants persisting in water bodies for extended periods and affecting a wide range of areas. The chemicals involved are numerous and numerous, and the reaction mechanisms and physicochemical properties involved in organic degradation are complex. Currently, traditional methods for treating organic pollutants are often costly. However, photocatalysis is rapidly emerging as an environmentally friendly and cost-effective tool for harnessing renewable energy from sunlight. Its vast potential to harvest solar energy for a variety of applications, coupled with its sustainability and cleanliness, has led to its rapid global development. Its prominent role in solar energy conversion is its potential to convert solar energy into renewable energy, overcoming environmental pollution and energy shortages, and aligning with the water / wastewater industry's "100% utilization" strategy.

[0003] Black phosphorus (BP) is a naturally occurring form of elemental phosphorus, an allotrope of the common, flammable red phosphorus. The preparation of BP crystals began over a century ago. BP crystals are composed of single layers of black phosphorus. BP is a p-type semiconductor. Research has shown that its properties are independent of the number and size of the layers, but its bandgap is dependent on the number of layers. Therefore, by controlling the number of BP layers, the BP bandgap width can be tuned. This makes BP a tunable bandgap semiconductor, ranging from 2.1 eV for a single BP layer to 0.3 eV for a bulk crystal. By adjusting the BP bandgap, its absorption range spans the ultraviolet, visible, and near-infrared regions, a significant advantage over other semiconductors. While BP exhibits excellent photocatalytic properties, it is susceptible to oxidative decomposition in oxygen-containing air, water, and visible light, resulting in inactivity and instability. Therefore, further research is needed to modify BP to preserve its original photocatalytic properties while improving its stability.

[0004] As a common metal material, cobalt has attracted widespread attention in recent years. Cobalt oxide is a very promising electrocatalytic material and one of the most intensively studied materials for electrocatalysis. In recent years, cobalt oxide has also been used in photocatalysis and is currently a hot topic of research. Despite this, only a few studies have used CoO as a candidate material for the photocatalytic degradation of organic pollutants because the synthesis method of CoO nanoparticles is complex and the synthesis conditions are harsh. In addition, due to the severe aggregation and chemical instability of CoO nanoparticles, they are easily deactivated. This results in an extremely short lifespan of as low as 1 hour. Therefore, the problem of preparing efficient, stable and readily available CoO photocatalysts remains to be solved. Summary of the Invention

[0005] Since BP is easily oxidized and decomposed in oxygen-containing air, water and visible light, resulting in ineffectiveness and unstable properties, research has been conducted to modify BP in a way that not only retains its original photocatalytic properties but also improves its stability. The synthesis method of CoO nanoparticles is complex and the synthesis conditions are harsh. In addition, due to the severe aggregation and chemical instability of CoO nanoparticles, they are easily deactivated, resulting in an extremely short lifespan of as low as 1 hour. BP, which has a large specific surface area and a flexible two-dimensional structure, can effectively prevent the aggregation of nanoparticles. Studies have shown that after BP sheets can be wrapped by CoO nanoparticles, the lone pair electrons will be protected, which may improve the stability of BP. The present invention combines the two to avoid the shortcomings of each other and produce a highly efficient composite metal photocatalyst. The effects of different concentrations of CoO combined with BP on the degradation and photocatalytic performance of tetracycline hydrochloride wastewater were experimentally studied.

[0006] In order to solve the problems mentioned in the background technology, the purpose of the present invention is to provide a CoO / BP catalyst and a preparation method having good photocatalytic properties and providing new ideas for subsequent wastewater degradation.

[0007] The present invention mainly achieves the above-mentioned object by improving the catalyst composition and preparation method. To achieve this object, the present invention provides:

[0008] A CoO / black phosphorus catalyst is prepared by first synthesizing BP particles, then synthesizing CoO particles, and finally loading BP on them. The CoO material is in the form of nanoparticles, and the BP has a clear layered structure. The composite CoO / BP has a layered structure inlaid with nanoparticles.

[0009] On the other hand, a method for preparing the composite photocatalyst CoO / BP is provided, comprising the following steps:

[0010] (1) Preparation of BP: 0.25-0.75 g of red phosphorus was first ground into powder using a pestle and mortar, and then 70-80 mL of ethylenediamine was added. After vigorous stirring with a magnetic stirrer for 30 min, the mixture was transferred to a 100 mL polytetrafluoroethylene-lined stainless steel autoclave and placed in a constant temperature drying oven. After heating at 165°C for 24 h, the mixture was rapidly cooled to room temperature and the product was collected with cold water. After centrifugation, the product was washed three times with ethanol to remove the residual solvent ethylenediamine. The final product was dried in a vacuum at 40°C.

[0011] (2) Preparation of CoO / BP: Composite materials with different mass ratios of BP and CoO were prepared by changing the CoO content of the mixed solution before calcination while keeping the BP content unchanged. The CoO / BP composite catalyst was prepared by the following method: 0.27-7.75g of Co(CH3COO)2·4H2O and 1g of the prepared BP powder were added to a mixed solvent containing 10-20mL of n-octanol and 60-70mL of ethanol, and stirred with a magnetic stirrer for 2h. The resulting slurry was transferred to a 100mL tetrafluoroethylene-lined stainless steel autoclave, then placed in a vacuum drying oven and heated at 220℃ for 4h. The resulting mixture was centrifuged to obtain the composite material, washed three times with ethanol, and finally dried in an oven at 70℃. Pure CoO was prepared using the same method, but without BP, and the sample preparation was completed.

[0012] On the other hand, a CoO / black phosphorus catalyst is provided for photocatalytic degradation of antibiotic wastewater.

[0013] More specifically, the application in photocatalytic degradation of tetracycline hydrochloride wastewater. First, 3-5mg of pure CoO, pure BP and a composite of CoO / BP with different ratios were added to 100mL tetracycline hydrochloride (10mg / L). The 3-5mg synthesized catalyst was dispersed in 100mL tetracycline hydrochloride (10mg / L) by ultrasonic treatment. The adsorption-desorption equilibrium between the catalyst and the tetracycline hydrochloride solution was then established by stirring for 60min under dark conditions. A 500w xenon lamp was placed vertically 15cm above the solution. 4mL was sampled at regular intervals and transferred to a centrifuge tube for centrifugation to separate the photocatalyst. Finally, an ultraviolet-visible spectrophotometer was used to measure the absorbance at 356nm. The variation in tetracycline hydrochloride concentration was determined by absorbance to analyze the degradation efficiency of the photocatalyst.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] 1. The composite CoO / BP catalyst is composed of CoO particles and BP particles. The BP particles are prepared first and then loaded with CoO.

[0016] 2. The composite CoO / BP catalyst has strong light adsorption ability and high electron-hole separation efficiency. This makes the material structure stable, the photogenerated carriers transport fast, and can effectively inhibit the recombination of photogenerated carriers.

[0017] 3. Compared with the common photocatalyst g-C3N4 and pure CoO and BP, the composite CoO / BP catalyst has better visible light absorption performance and greatly improves the photocatalytic degradation of tetracycline hydrochloride solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 are scanning electron micrographs, (a) is a scanning electron micrograph of CoO in Example 1, (b) is a transmission electron micrograph of BP at 50 nm, (c) is a transmission electron micrograph of BP at 5 nm, (d) is a scanning electron micrograph of CoO / BP, (e) is a transmission electron micrograph at 100 nm, and (f) is a transmission electron micrograph at 500 nm;

[0019] Figure 2 The photoelectron spectra of CoO, BP, and CoO / BP in Example 1 are shown in Figure (a) as the overall spectrum, Figure (b) as the Co 2p spectrum, Figure (c) as the O1s spectrum, and Figure (d) as the P 2p spectrum.

[0020] Figure 3 The fluorescence spectra of all samples in Example 1 are shown in FIG.

[0021] Figure 4 The UV-visible diffuse reflectance spectra of all samples in Example 1 are shown in FIG.

[0022] Figure 5 is the X-ray diffraction spectrum of all samples in Example 1;

[0023] Figure 6 Figures 2 and 3 are the degradation effect diagrams of different catalysts under visible light irradiation, (a) is the removal rate diagram of tetracycline hydrochloride degradation by different catalysts under visible light irradiation in Example 1, and (b) is the first-order kinetic curve of tetracycline hydrochloride degradation by different catalysts under visible light irradiation in Example 1. DETAILED DESCRIPTION

[0024] The following non-limiting examples are provided to provide a more comprehensive understanding of the present invention to those skilled in the art, but are not intended to limit the present invention in any way. Unless otherwise specified, the experimental methods employed in the present invention are conventional methods, and the experimental equipment, materials, and reagents used are all commercially available.

[0025] Example 1

[0026] The preparation method of the composite CoO / BP photocatalyst is as follows:

[0027] The prepared photocatalysts are denoted as CoO / BP(x:y), where x:y is the mass ratio of CoO to BP. CoO / BP composite catalysts with different mass ratios (0%, 7.5%, 15%, 30%, 50%, and 70%) were prepared using the following method: Different masses of Co(CH3COO)2·4H2O (0, 0.27, 0.58, 1.43, 3.32, and 7.75 g) and 1 g of the prepared BP powder were added to a mixture of 16 mL of n-octanol and 64 mL of ethanol and stirred with a magnetic stirrer for 2 hours. The resulting slurry was transferred to a 100 mL Teflon-lined stainless steel autoclave, then placed in a vacuum drying oven and heated at 220°C for 4 hours. The resulting mixture was centrifuged, the composites were washed three times with ethanol, and finally dried in an oven at 70°C. Pure CoO, but without BP, was prepared using the same method to complete the sample preparation.

[0028] Example 2

[0029] 0.5 g of red phosphorus was ground into a powder using a pestle and mortar, followed by the addition of 75 mL of ethylenediamine. After vigorous stirring with a magnetic stirrer for 30 minutes, the mixture was transferred to a 100 mL Teflon-lined stainless steel autoclave and placed in a constant-temperature drying oven. After heating at 165°C for 24 hours, the mixture was rapidly cooled to room temperature and collected with cold water. After centrifugation, the product was washed three times with ethanol to remove residual ethylenediamine solvent. The final product was dried in a vacuum at 40°C to obtain BP. Figure 1 The scanning electron microscope image of CoO, the transmission electron microscope image of BP, and the scanning electron microscope image and transmission electron microscope image of CoO / BP in Example 1 are shown; Figure 1 a, is the SEM image of CoO nanomaterial at 1 μm. It can be seen from the figure that the CoO material is in the form of nanoparticles. Figure 1 b is the TEM image of BP material at 50nm. It can be seen from the figure that BP has a clear layered structure. Figure 1 c, TEM image of BP at 5 nm, shows that the lattice spacing of the prepared BP material is approximately 0.256 nm, corresponding to the (040) crystal plane, consistent with the XRD pattern of BP. (d), (e), and (f), 1μm SEM images, 100nm TEM images, and 500nm TEM images of the CoO / BP composite material, clearly show a rougher surface. Analysis of the CoO / BP composite structure reveals that CoO nanoparticles are adsorbed on the layered BP.

[0030] Figure 2 The photoelectron spectra of CoO, BP and CoO / BP in Example 1 confirm the presence of Co, O and P elements in the CoO / BP structure.

[0031] Figure 3The fluorescence spectra of all samples in Example 1 are shown. As shown, the PL intensity of BP is higher than that of the CoO / BP composite, while the PL intensity of the CoO / BP composite decreases. The 50%-CoO / BP composite has the lowest PL intensity, indicating that the presence of CoO reduces the PL intensity, effectively separating photogenerated electron-hole pairs and reducing recombination, thereby achieving efficient electron transfer. The 70%-CoO / BP composite exhibits slightly higher PL intensity than the 50%-CoO / BP composite, indicating good electron transfer.

[0032] Figure 4 The UV-visible diffuse reflectance spectra of all samples in Example 1 are as follows; black phosphorus has a wide range of light absorption and excellent light absorption ability. The light absorption range of CoO is 400-600nm, and its light absorption ability is relatively weak. The absorption edge of 50%, 70% and 30%-CoO / BP in the composite material has red-shifted relative to the absorption edge of pure CoO material, and the light absorption range is 450-700nm. The light absorption ability of the CoO / BP-50% composite material is stronger than that of CoO. The visible light utilization rate of the surface composite material 50%-CoO / BP is significantly improved compared with CoO.

[0033] Figure 5 The X-ray diffraction spectra of all samples in Example 1 are shown in the figure. As shown in the figure, the characteristic peaks are 16.9°, 26.5°, and 35.0°, corresponding to the (020), (021), and (040) crystal planes, respectively, indicating that BP was successfully prepared. In the XRD spectrum of the CoO nanomaterial, all diffraction peaks at 36.4°, 42.3°, 61.4°, 73.6°, and 77.5° correspond to the (111), (200), (220), (311), and (222) crystal planes, and no miscellaneous peaks appear, indicating that the CoO nanomaterial was successfully prepared. The characteristic peaks of BP and CoO nanomaterials can be observed in the spectrum of the CoO / BP composite material in the figure, indicating that the layered BP material and the CoO nanomaterial are successfully composited. The synthesized composite material does not change the crystal structure of the BP material and the CoO nanomaterial. In the composite drug, the characteristic peak of the CoO material at (220) becomes more and more obvious as the proportion of CoO increases, indicating that the CoO component is successfully synthesized in the composite component.

[0034] Figure 6 The figure shows the removal rate and first-order kinetic curve of tetracycline hydrochloride degradation by different catalysts under visible light irradiation in Example 1;

[0035] Application Example 1

[0036] First, 3 mg of pure CoO, pure BP, and CoO / BP composite catalysts with different ratios (0%, 7.5%, 15%, 30%, 50%, and 70%) were added to 100 mL of tetracycline hydrochloride (10 mg / L). 3 mg of the synthesized catalyst was dispersed in 100 mL of tetracycline hydrochloride (10 mg / L) by ultrasonic treatment. The adsorption-desorption equilibrium between the catalyst and the tetracycline hydrochloride solution was then established by stirring for 60 min under dark conditions. A 500W xenon lamp was placed vertically 15 cm above the solution. 4 mL of the sample was taken at regular intervals and transferred to a centrifuge tube. The photocatalyst was separated by centrifugation. Finally, the absorbance at 356 nm was measured using a UV-visible spectrophotometer. The change in tetracycline hydrochloride concentration was determined by absorbance to analyze the degradation efficiency of the photocatalyst.

[0037] The experimental results are shown in Figure 6 As shown in the figure, a mixture of catalyst and tetracycline hydrochloride was placed under a 500W xenon lamp. It can be clearly seen from the figure that the efficiency of pure black phosphorus and CoO in degrading tetracycline hydrochloride was only 41.45% and 11.14% respectively, while the CoO / black phosphorus composite material was significantly higher than the two pure samples. Among them, the highest composite material 50%-CoO / BP had an efficiency of up to 86.55%. The degradation rate of the common photocatalyst g-C3N4 was 44% for the degradation of tetracycline hydrochloride solution, and the degradation rate of 50%-CoO / BP was 1.97 times that of g-C3N4. The degradation percentage of the composite materials was 50%-CoO / BP (86.55%) > 30%-CoO / BP (78.38%) > 70%-CoO / BP (72.36%) > 15% CoO / BP (55.46%) > 7.5%-CoO / BP (47.67%). From this, we can analyze that as the proportion of CoO added to black phosphorus increases, the degradation efficiency of tetracycline hydrochloride gradually increases, but as the CoO ratio increases to 70%, the degradation efficiency decreases, indicating that excessively loaded CoO nanoparticles will burden the composite material. Too much CoO arranged together will increase the recombination efficiency of photoelectrons and holes and reduce the photocatalytic activity. Using the kinetic first-order model ln(C / C0)=kt to fit Figure 6 (b) shows the fitting curve. The slope of the fitting curve can be used to determine the photocatalytic degradation reaction rate. The degradation rate of the composite material 50%-CoO / BP is the highest at 0.172h. -1 The degradation rate of pure black phosphorus and cobalt oxide is 0.053h -1 and 0.029h -1 .

[0038] The above-described embodiments are only preferred embodiments of the present invention, and are not intended to be all feasible embodiments of the present invention. Any obvious modifications made by a person skilled in the art without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.

Claims

1. An application of CoO / black phosphorus catalyst, characterized in that, The CoO / black phosphorus catalyst is used for photocatalytic degradation of antibiotic wastewater; The preparation method of the CoO / black phosphorus catalyst comprises the following steps: first synthesizing black phosphorus particles, and then preparing the CoO / black phosphorus catalyst; the CoO material is in the form of nanoparticles, the black phosphorus is in a layered structure, and the CoO / black phosphorus catalyst is in the form of nanoparticles embedded in the layered structure; The method for preparing the CoO / black phosphorus catalyst comprises the following steps: 0.27-7.75 g of Co(CH3COO)2·4H2O and 1 g of prepared black phosphorus powder were added to a mixed solvent containing 10-20 mL of n-octanol and 60-70 mL of ethanol. The resulting slurry was stirred evenly and heated at 220°C for 4 h. The resulting mixture was centrifuged to obtain the composite material, washed with ethanol, and finally dried in an oven at 70°C.

2. The use according to claim 1, characterized in that The synthesis of black phosphorus particles includes the following steps: 0.25-0.75 g of red phosphorus powder was added to 70-80 mL of ethylenediamine. The mixture was then heated at 165°C for 24 hours. The mixture was then rapidly cooled to room temperature, collected with cold water, centrifuged, and washed with ethanol to remove the residual solvent ethylenediamine. The final product was dried in a vacuum at 40°C.

3. The use according to claim 2, characterized in that The heated reaction mixture in the synthesis of black phosphorus particles is mixed evenly and then transferred to a polytetrafluoroethylene-lined stainless steel high-pressure reactor and placed in a constant temperature drying oven.

4. The use according to claim 1, characterized in that The slurry of the heating reaction in the preparation of the CoO / black phosphorus catalyst was transferred to a tetrafluoroethylene-lined stainless steel autoclave and placed in a vacuum drying oven.

5. The use according to claim 1, characterized in that The antibiotic is tetracycline hydrochloride.

6. The use according to claim 5, characterized in that 3-5 mg of the synthesized CoO / black phosphorus catalyst was dispersed in 100 mL of a 10 mg / L tetracycline hydrochloride solution by ultrasonic treatment and stirred for 60 min in the dark to establish the adsorption-desorption equilibrium between the CoO / black phosphorus catalyst and the tetracycline hydrochloride solution. The mixture was then irradiated vertically with a xenon lamp.

7. The use according to claim 6, characterized in that Add a magnetic stirring bar to the tetracycline hydrochloride solution and place it on a magnetic stirrer to continue stirring the reaction.

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