A Cu-Cu2O / Cu2Se photocatalyst and its preparation method

Abstract

This invention discloses a Cu-Cu₂O / Cu₂Se photocatalyst and its preparation method, comprising the following steps: Step 1, dissolving 3.5–4.5 mmol of copper salt in 10 mL of deionized water, then sequentially adding 0.05–0.1 mmol of selenium source, 0.05–0.1 mmol of disodium ethylenediaminetetraacetate, and 7–9 mmol of urea, stirring until homogeneous to obtain mixed solution A; Step 2, adding 7 mL of glycerol and 7 mL of ethanol to mixed solution A to obtain mixed solution B; Step 3, transferring mixed solution B to a hydrothermal reactor and sealing it, then placing the hydrothermal reactor in an oven and reacting at 150–170 °C for 7–9 h, and cooling the hydrothermal reactor to obtain product C; Step 4, washing and drying product C sequentially to obtain the Cu-Cu₂O / Cu₂Se photocatalyst. This invention employs a simple one-step solvothermal method, and the obtained Cu-Cu₂O / Cu₂Se photocatalyst exhibits stable and excellent photocatalytic activity.

Description

Technical Field

[0001] This invention belongs to the field of photocatalysis technology, specifically a Cu-Cu2O / Cu2Se photocatalyst and its preparation method. Background Technology

[0002] With the rapid development of modern industry, wastewater discharge poses a serious threat to the environment. Among industrial wastewater, dyeing and printing wastewater from textile, printing, and photography industries accounts for the largest proportion. Most dyes in dyeing and printing wastewater are organic synthetic products, such as azo dyes, fluorinated dyes, and benzene-based dyes, all of which have certain toxicity and carcinogenicity. If discharged directly into the environment without treatment, it will cause incalculable harm to the natural environment. Currently, many methods such as adsorption, chemical methods, biodegradation, and photocatalytic degradation technologies have been adopted to treat industrial wastewater. Among them, adsorption, chemical methods, and biodegradation methods have drawbacks such as the need to consume chemical oxidants, high costs, and the need for secondary treatment. Photocatalytic degradation technology, under light conditions, uses photocatalysts to generate active free radicals with strong oxidizing power. The photocatalytic oxidation reaction degrades organic pollutants in the aquatic environment into carbon dioxide and water, thereby achieving the purposes of pollutant purification, substance synthesis, and transformation. It is evident that photocatalytic degradation technology is a low-energy-consumption and environmentally friendly wastewater treatment technology, and therefore has received widespread attention from researchers.

[0003] In recent years, with the deepening research on semiconductor performance, semiconductor photocatalysts such as TiO2 and Cu2O have also come into focus. Cu2O, in particular, is a p-type semiconductor with a band gap of approximately 2.0–2.2 eV, capable of absorbing visible light, and has become one of the important photocatalytic materials. However, Cu2O powder suffers from drawbacks such as chemical instability, high electron-hole recombination rate, easy agglomeration, and easy deactivation, resulting in low and unstable catalytic activity, making it difficult to separate and recover, severely limiting the practical application of Cu2O in the field of photocatalysis. Currently, the main methods to improve the photocatalytic activity of Cu2O include heteroatom doping, noble metal deposition, and the introduction of defects. Among these, the preparation and performance research of heteroatom-doped materials still face some challenges and problems: First, the selection of heteroatoms and the precise control of doping positions are difficult points in the preparation process; second, the mechanism by which heteroatom doping affects the physical properties of materials is not yet clear and requires further theoretical research; third, efficient preparation processes and reliable quality control systems for heteroatom-doped materials have not yet been established, posing challenges to large-scale production and industrial application. At the same time, the manufacturing processes of methods such as precious metal deposition and the introduction of defects, as well as the cost of raw materials, also prevent its mass production.

[0004] Therefore, there is an urgent need to provide a simple and low-cost method to improve the photocatalytic activity of Cu2O in order to broaden the practical application of Cu2O-based photocatalytic materials in the field of photocatalysis technology. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a Cu-Cu2O / Cu2Se photocatalyst and its preparation method. The Cu-Cu2O / Cu2Se photocatalyst obtained by using a simple one-step solvothermal method exhibits stable and excellent photocatalytic activity.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] A method for preparing a Cu-Cu2O / Cu2Se photocatalyst includes the following steps:

[0008] Step 1: First, dissolve 3.5–4.5 mmol of copper salt in 10 mL of deionized water. Then, add 0.05–0.1 mmol of selenium source, 0.05–0.1 mmol of disodium ethylenediaminetetraacetate, and 7–9 mmol of urea in sequence, and stir to mix them evenly to obtain mixed solution A.

[0009] Step 2: Add 7 mL of glycerol and 7 mL of ethanol to mixed solution A to obtain mixed solution B;

[0010] Step 3: First, transfer the mixed solution B to a hydrothermal reactor and seal it. Then, place the hydrothermal reactor in an oven and react at 150-170°C for 7-9 hours. After the hydrothermal reactor cools down, product C is obtained.

[0011] Step 4: Wash and dry product C sequentially to obtain Cu-Cu2O / Cu2Se photocatalyst.

[0012] Furthermore, the copper salt in step 1 is (CH3COO)2Cu·H2O, Cu(No3)2, or CuCl2.

[0013] Furthermore, the selenium source in step 1 is selenium powder, SeO2, or Na2SeO3.

[0014] Furthermore, the washing in step 4 involves alternating between deionized water and anhydrous ethanol at least three times.

[0015] Furthermore, the drying in step 4 is carried out in a vacuum drying oven at 50–70°C for 8–12 hours.

[0016] A Cu-Cu2O / Cu2Se photocatalyst.

[0017] Compared with the prior art, the present invention has the following technical effects:

[0018] On the one hand, this invention uses deionized water, ethanol, and glycerol as solvents. Ethanol and glycerol not only act as solvents but also as template agents controlling the product morphology. In the solvothermal reaction, disodium ethylenediaminetetraacetate (EDTA) is used as a chelating agent, where copper ions first form a Cu(EDTA)²⁻ complex, which then further reacts to yield the product. On the other hand, urea is used as a mineralizing agent to enhance the recrystallization of Cu in the solvothermal system. Simultaneously, urea also acts as a reducing agent, reducing a portion of divalent copper to elemental copper. Elemental copper has good conductivity, which improves the electron transport rate of the material and reduces the recombination probability of electrons and holes. A portion of divalent copper is also reduced to monovalent copper, which reacts with Se. 2- Cu₂Se is generated; furthermore, the selenium source alters the chelation environment and recrystallization process of copper ions, resulting in Cu-Cu₂O / Cu₂Se with a larger specific surface area, thereby improving its adsorption capacity, photocatalytic activity, and degradation efficiency for organic pollutants. In short, the Cu-Cu₂O / Cu₂Se prepared in this invention solves the problems of low electron transport rate, small specific surface area, and easy electron-hole recombination of Cu₂O as a photocatalyst; simultaneously, because the preparation method is a simple one-step solvothermal method with low reaction temperature and short time, it is more suitable for large-scale mass production.

[0019] Compared with ordinary Cu2O particles, the Cu-Cu2O / Cu2Se prepared by this invention has a stronger absorption capacity for ultraviolet and visible light. Photocatalytic degradation utilizes light energy to excite electron-hole pairs on the surface of semiconductor materials, thereby promoting chemical reactions. Therefore, it has more significant photocatalytic activity and improves the photocatalytic degradation performance of organic pollutants.

[0020] In photocatalytic degradation, when the light energy absorbed by a semiconductor material is equal to or exceeds the semiconductor's own band gap energy (Eg), the semiconductor valence band (VB) is excited by the light energy to generate electrons (e). - Afterwards, photogenerated electrons jump to the conduction band (CB) of the semiconductor, generating photogenerated holes (h). + Without undergoing a transition, the electrons and holes remain within the semiconductor VB. These electrons and holes possess reducing and oxidizing capabilities, and can react with molecules such as H₂O, OH⁻, and O₂ on the semiconductor surface to generate various active groups, including hydroxyl radicals (·OH) and superoxide radicals (·O₂). - Active groups such as ions and hydrogen peroxide (H2O2) react with organic pollutants through redox reactions, thereby achieving the purpose of degrading pollutants. Therefore, in practical applications, the solvothermal system environment can be changed by adjusting the reaction conditions such as solvents, mineralizers, and chelating agents to change the metal ion chelation process, thereby changing the recrystallization and morphology of the substance, and further improving the photocatalytic degradation performance of Cu-Cu2O / Cu2Se. Attached Figure Description

[0021] Figure 1 XRD patterns of Cu-Cu2O / Cu2Se prepared in Example 1 and Cu-Cu2O prepared in Comparative Example 1;

[0022] Figure 2 SEM image of Cu-Cu2O prepared in Comparative Example 1;

[0023] Figure 3 SEM image of Cu-Cu2O / Cu2Se prepared in Example 1;

[0024] Figure 4 UV-Vis diffuse reflectance spectra of Cu-Cu2O / Cu2Se prepared in Example 1 and Cu-Cu2O prepared in Comparative Example 1;

[0025] Figure 5 Degradation curves of methyl orange by Cu-Cu2O / Cu2Se prepared in Example 1 and Cu-Cu2O prepared in Comparative Example 1 under visible light irradiation;

[0026] Figure 6 Photocurrent density diagrams of Cu-Cu2O / Cu2Se prepared in Example 1 and Cu-Cu2O prepared in Comparative Example 1;

[0027] Figure 7 Electrochemical impedance spectroscopy curves of Cu-Cu2O / Cu2Se prepared in Example 1 and Cu-Cu2O prepared in Comparative Example 1. Detailed Implementation

[0028] The specific content of the present invention will be further explained in detail below with reference to the embodiments.

[0029] Example 1

[0030] Step 1: First, dissolve 3.5 mmol (CH3COO)2Cu·H2O in 10 mL of deionized water. Then, add 0.05 mmol SeO2, 0.05 mmol disodium ethylenediaminetetraacetate and 7 mmol urea in sequence, and stir to mix them evenly to obtain mixed solution A.

[0031] Step 2: Add 7 mL of glycerol and 7 mL of ethanol to mixed solution A to obtain mixed solution B;

[0032] Step 3: First, transfer the mixed solution B to a hydrothermal reactor and seal it. Then, place the hydrothermal reactor in an oven and react at 170°C for 7 hours. After the hydrothermal reactor cools down, product C is obtained.

[0033] Step 4: First, wash product C three times alternately with deionized water and anhydrous ethanol, then dry it in a vacuum drying oven at 50°C for 12 hours to obtain a black powder Cu-Cu2O / Cu2Se photocatalyst.

[0034] Example 2

[0035] Step 1: First, dissolve 4.5 mmol Cu(NO3)2 in 10 mL of deionized water, then add 0.1 mmol selenium powder, 0.1 mmol disodium ethylenediaminetetraacetate and 9 mmol urea in sequence, and stir to mix evenly to obtain mixed solution A;

[0036] Step 2: Add 7 mL of glycerol and 7 mL of ethanol to mixed solution A to obtain mixed solution B;

[0037] Step 3: First, transfer the mixed solution B to a hydrothermal reactor and seal it. Then, place the hydrothermal reactor in an oven and react at 160°C for 8 hours. After the hydrothermal reactor cools down, product C is obtained.

[0038] Step 4: First, wash product C three times alternately with deionized water and anhydrous ethanol, then dry it in a vacuum drying oven at 60°C for 10 hours to obtain a black powder Cu-Cu2O / Cu2Se photocatalyst.

[0039] Example 3

[0040] Step 1: First, dissolve 4 mmol CuCl2 in 10 mL of deionized water, then add 0.075 mmol Na2SeO3, 0.075 mmol disodium ethylenediaminetetraacetate and 8 mmol urea in sequence, and stir to mix them evenly to obtain mixed solution A;

[0041] Step 2: Add 7 mL of glycerol and 7 mL of ethanol to mixed solution A to obtain mixed solution B;

[0042] Step 3: First, transfer the mixed solution B to a hydrothermal reactor and seal it. Then, place the hydrothermal reactor in an oven and react at 150°C for 9 hours. After the hydrothermal reactor cools down, product C is obtained.

[0043] Step 4: First, wash product C three times alternately with deionized water and anhydrous ethanol, then dry it in a vacuum drying oven at 70°C for 8 hours to obtain a black powder Cu-Cu2O / Cu2Se photocatalyst.

[0044] Comparative Example 1

[0045] Step 1: First, dissolve 3.5 mmol (CH3COO)2Cu·H2O in 10 mL of deionized water, then add 0.05 mmol disodium ethylenediaminetetraacetate and 7 mmol urea in sequence, stir to mix evenly, and obtain mixed solution D;

[0046] Step 2: Add 7 mL of glycerol and 7 mL of ethanol to mixed solution D to obtain mixed solution E;

[0047] Step 3: First, transfer the mixed solution E to a hydrothermal reactor and seal it. Then, place the hydrothermal reactor in an oven and react at 170°C for 7 hours. After the hydrothermal reactor cools down, product F is obtained.

[0048] Step 4: First, wash product F three times alternately with deionized water and anhydrous ethanol, then dry it in a vacuum drying oven at 50°C for 12 hours to obtain a dark brown powdery Cu-Cu2O photocatalyst.

[0049] from Figure 1 It can be seen that the characteristic peaks of the Cu-Cu2O / Cu2Se photocatalyst prepared in Example 1 are completely consistent with the PDF standard cards No. 05-0667 (Cu2O), No. 29-0575 (Cu2Se) and No. 04-0836 (Cu). Furthermore, the diffraction peaks in the composite Cu-Cu2O / Cu2Se correspond to the (110), (111), (200), (220), (311) and (222) crystal planes of Cu2O, and the (111) and (200) crystal planes of Cu, respectively. This indicates that the Cu-Cu2O / Cu2Se photocatalyst was successfully prepared in Example 1, and the crystal phase of Cu-Cu2O in Cu-Cu2O / Cu2Se was not changed.

[0050] from Figure 2 and Figure 3 It can be seen that the Cu-Cu2O prepared in Comparative Example 1 has a multifaceted cubic structure, while the Cu-Cu2O / Cu2Se prepared in Example 1 has hexagonal nanosheets. Compared with Cu-Cu2O, Cu-Cu2O / Cu2Se has a larger specific surface area, which increases the contact area between the catalyst and organic pollutants and improves the adsorption and photocatalytic degradation performance of the catalyst for organic matter.

[0051] from Figure 4 It can be seen that the Cu-Cu2O / Cu2Se prepared in Example 1 has a stronger visible light absorption capacity than the Cu-Cu2O prepared in Comparative Example 1.

[0052] Take 25 mg each of Cu-Cu2O / Cu2Se prepared in Example 1 and Cu-Cu2O prepared in Comparative Example 1, and place them in 50 mL test tubes containing 20 mg / L methyl orange solution (the volume ratio of methyl orange pollutant to catalyst is 2:1). Stir for 10 min in the dark to reach adsorption equilibrium. Then place the tubes in a photocatalytic reactor equipped with a 500W mercury lamp and perform photocatalytic degradation experiments under magnetic stirring. Take samples every 10 min and measure the absorbance using a UV-Vis spectrophotometer. The results are as follows: Figure 5 As shown, when visible light catalysis is carried out for 50 minutes, the degradation rate of methyl orange by Cu-Cu2O / Cu2Se reaches 80.6%, which is 3.2 times that of Cu-Cu2O for methyl orange.

[0053] from Figure 6 It can be seen that under visible light irradiation, Cu-Cu2O / Cu2Se has a larger photocurrent density than Cu-Cu2O, indicating that Cu-Cu2O / Cu2Se has a higher absorption rate in the visible light range, which is more conducive to the separation and transport of photogenerated electrons and holes, and can improve the photocatalytic reaction rate.

[0054] Since electrochemical impedance spectroscopy reflects the resistance during the separation and transport of photogenerated electrons and holes, having the smallest radius of curvature is beneficial for the separation and transport of photogenerated electrons and holes. Figure 7 It can be seen that Cu-Cu2O / Cu2Se has the smallest radius of curvature, indicating that it has the lowest resistance during electron transport, which is more conducive to the separation and transport of photogenerated electrons and holes, and thus has better photocatalytic activity.

Claims

1. A method for preparing a Cu-Cu2O / Cu2Se photocatalyst, characterized in that, Includes the following steps: Step 1: First, dissolve 3.5–4.5 mmol of copper salt in 10 mL of deionized water. Then, add 0.05–0.1 mmol of selenium source, 0.05–0.1 mmol of disodium ethylenediaminetetraacetate, and 7–9 mmol of urea in sequence, and stir to mix them evenly to obtain mixed solution A. Step 2: Add 7 mL of glycerol and 7 mL of ethanol to mixed solution A to obtain mixed solution B; Step 3: First, transfer the mixed solution B to a hydrothermal reactor and seal it. Then, place the hydrothermal reactor in an oven and react at 150-170°C for 7-9 hours. After the hydrothermal reactor cools down, product C is obtained. Step 4: Wash and dry product C sequentially to obtain Cu-Cu2O / Cu2Se photocatalyst.

2. The preparation method of the Cu-Cu2O / Cu2Se photocatalyst according to claim 1, characterized in that, The copper salt in step 1 is (CH3COO)2Cu·H2O, Cu(NO3)2, or CuCl2.

3. The method for preparing the Cu-Cu₂O / Cu₂Se photocatalyst according to claim 1, characterized in that, The selenium source in step 1 is selenium powder, SeO2, or Na2SeO3.

4. The preparation method of the Cu-Cu2O / Cu2Se photocatalyst according to claim 1, characterized in that, The washing in step 4 involves alternating between deionized water and anhydrous ethanol at least three times.

5. The method for preparing the Cu-Cu₂O / Cu₂Se photocatalyst according to claim 1, characterized in that, The drying in step 4 is carried out in a vacuum drying oven at 50-70°C for 8-12 hours.

6. A Cu-Cu2O / Cu2Se photocatalyst prepared by the method according to any one of claims 1 to 5.

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