A method for preparing an In2S3-Cu-Cu2O ternary heterojunction catalyst

Abstract

This invention belongs to the field of photocatalysis technology, specifically relating to a method for preparing an In2S3-Cu-Cu2O ternary heterojunction catalyst. The preparation method of this heterojunction catalyst is as follows: First, Cu2O is obtained by liquid-phase reduction, followed by the dropwise addition of sodium borohydride solution to partially reduce monovalent copper to obtain Cu-Cu2O powder; Indium nitrate hydrate and L-cysteine ​​are dissolved in deionized water, and the pH is adjusted with sodium hydroxide solution. The uniformly stirred solution is then transferred to a reaction vessel for hydrothermal preparation to obtain In2S3 powder; Finally, using Cu-Cu2O and In2S3 as raw materials, the In2S3-Cu-Cu2O ternary heterojunction catalyst is prepared by hydrothermal method. This invention introduces Cu... 0 As an “electron transfer station,” it works in conjunction with the built-in electric field of the ternary heterojunction to significantly enhance the separation efficiency and directional transport capability of photogenerated electron-hole pairs. Its catalytic performance is significantly better than that of pure Cu2O, In2S3 and binary heterojunction In2S3 / Cu2O under the same conditions.

Description

Technical Field

[0001] This invention belongs to the field of photocatalysis technology, specifically relating to a method for preparing an In2S3-Cu-Cu2O ternary heterojunction catalyst. Background Technology

[0002] Cuprous oxide (Cu2O), as an important p-type semiconductor material, has a narrow bandgap (approximately 2.0-2.2 eV) and shows broad application prospects in fields such as photocatalytic degradation of pollutants and electrocatalytic hydrogen evolution. However, single-phase Cu2O suffers from problems such as rapid recombination rates of photogenerated electron-hole pairs and photocorrosion, which severely restricts its practical applications.

[0003] To address the aforementioned issues, constructing heterojunction composite materials has become an effective strategy. Indium sulfide (In₂S₃) possesses easy tunability, a suitable band structure, and good chemical stability, making it suitable for enhancing catalytic performance through the construction of In₂S₃ / Cu₂O binary heterojunctions. The two materials exhibit a clear synergistic advantage: Cu₂O provides strong reducing power, while In₂S₃ provides stability and expands the light absorption range; the heterojunction interface is expected to promote the effective separation of photogenerated carriers. However, In₂S₃ / Cu₂O binary heterojunction catalysts still have significant limitations—the weak redox ability of photogenerated carriers leads to low catalytic efficiency, and the photocorrosion phenomenon of Cu₂O has not been effectively suppressed. These multiple issues mean that there is still great potential for improving catalytic performance. Summary of the Invention

[0004] Based on the analysis of the advantages and existing problems of the In2S3 / Cu2O composite system, and Cu 0 Based on the design concept of doping modification, this invention systematically optimizes the preparation process of In2S3-Cu-Cu2O ternary composite materials and provides a method for preparing a novel In2S3-Cu-Cu2O ternary heterojunction catalyst.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A method for preparing an In2S3-Cu-Cu2O ternary heterojunction catalyst includes the following steps:

[0007] Step 1: Preparation of Cu-Cu2O

[0008] Copper acetate monohydrate and sodium hydroxide were placed in deionized water to produce a dark precipitate. Then, d-glucose powder was added and the mixture was reacted in a water bath at 70-80 °C for 60-70 min to obtain a red solution. Subsequently, sodium borohydride solution was slowly added to the red solution and the mixture was heated and stirred for 30-50 min. After cooling to room temperature, a precipitate was obtained. The precipitate was washed and dried to obtain Cu-Cu2O.

[0009] Step 2: Preparation of In2S3

[0010] Indium nitrate hydrate and L-cysteine ​​were placed in deionized water and ultrasonically mixed. Sodium hydroxide solution was added dropwise to adjust the pH to 8-10. After stirring for 30-60 min, the solution turned pale yellow and was transferred to a reaction vessel. The reaction was carried out hydrothermally in an oven at 160-180 ℃ for 12-24 h. After cooling to room temperature, the solid was obtained by centrifugation and dried in an oven to obtain In2S3.

[0011] Step 3: Preparation of In2S3-Cu-Cu2O ternary heterojunction catalyst

[0012] Weigh the Cu-Cu2O from step 1 and the In2S3 from step 2 into deionized water, mix them ultrasonically and then mechanically, transfer them to a reactor for hydrothermal reaction, and cool them naturally to room temperature to obtain a mixed solution. Centrifuge the mixed solution and finally put the solid material obtained after centrifugation into an oven for drying. After grinding, the In2S3-Cu-Cu2O ternary heterojunction catalyst is obtained.

[0013] Preferably, in step 3, the mass ratio of In2S3 to Cu-Cu2O is 1:2 to 1:19;

[0014] Preferably, the ultrasonic mixing time in step 3 is 20-40 min;

[0015] Preferably, the mechanical stirring time in step 3 is 40-60 min;

[0016] Preferably, the hydrothermal reaction in step 3 is carried out at a temperature of 150-180 °C for 2-5 h.

[0017] Preferably, in step 3, the centrifugation speed is 4000~6000 rpm, the centrifugation time is 3~6 min, the oven drying temperature is 60~80 ℃, and the drying time is 6~8 h;

[0018] Preferably, step 3 further includes: during centrifugation, the mixture is washed alternately with deionized water and anhydrous ethanol, and the number of washes is 3 to 5.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] 1. This invention proposes metallic copper (Cu) 0 Optimization path for doping modification of copper (Cu). 0As an electron "transfer station," it can alleviate localized carrier accumulation and achieve a dual solution of "targeted defects + enhanced performance": on the one hand, it directly addresses the essence of Cu2O photocorrosion through efficient electron transfer. This process is achieved in the electron capture stage after photoexcitation: when Cu2O is exposed to light and generates photogenerated electron-hole pairs, Cu... 0 With its unique electronic structure and low electron affinity, it becomes a "highly efficient trapping center" for conduction band electrons, rapidly adsorbing free photogenerated electrons from the Cu2O conduction band. This rapid trapping process avoids localized electron accumulation in the conduction band, reducing the relative enrichment of photogenerated holes in the valence band at the source. Excessive accumulation of holes is precisely what triggers the self-oxidation of Cu2O (Cu2O). + Oxidized to Cu 2+ This addresses the fundamental cause of lattice destruction, thus suppressing photocorrosion mechanistically; on the other hand, it enhances catalytic performance by promoting efficient carrier separation. This efficiency is achieved during the carrier migration and reaction participation stages: Cu 0 It exhibits excellent electrical conductivity, and its internal electron migration resistance is much lower than that of semiconductor substrates, making it suitable for use with Cu. 0 The captured electrons can be rapidly transferred from the semiconductor to Cu. 0 On the surface, the electrons are further directionally transferred to heterojunction components such as In2S3 or reactant molecules. This efficient transport significantly reduces the recombination probability of photogenerated electron-hole pairs, enabling more charge carriers to participate in redox reactions. This not only enhances the catalytic active site function of the material but also improves the carrier utilization rate, effectively solving the problem of low efficiency in traditional catalysts. This dual effect simultaneously improves the material's stability and reaction efficiency, compensating for the corrosion susceptibility of Cu2O as a single component and overcoming the problem of incomplete carrier separation in binary heterojunctions, fully leveraging the synergistic innovation value of the ternary system.

[0021] 2. The In2S3-Cu-Cu2O ternary heterojunction catalyst prepared in this invention exhibits excellent photocatalytic degradation performance: within 100 min of visible light irradiation, the ternary catalyst achieves a degradation efficiency of up to 93% for tetracycline (TC) at an initial concentration of 20 mg / L, significantly outperforming single-component Cu2O (12%), In2S3 (41%), and the binary heterojunction catalyst In2S3 / Cu2O (59%). This data fully confirms that Cu... 0 The introduction of In2S3 creates an efficient electron transport channel, maximizing the visible light absorption advantage of In2S3 and the catalytic activity of Cu2O, fully demonstrating the synergistic effect of the ternary heterojunction system. Attached Figure Description

[0022] The invention will be further described below with reference to the accompanying drawings.

[0023] Figure 1These are X-ray diffraction (XRD) patterns of the In2S3-Cu-Cu2O ternary heterojunction catalysts prepared in Examples 1-4 of this invention.

[0024] Figure 2 These are scanning electron microscope (SEM) images and EDS spectra of the In2S3-Cu-Cu2O ternary heterojunction catalysts prepared in Examples 1-4 of this invention.

[0025] (A) is a scanning electron microscope (SEM) image, and (B) is a detailed SEM image and an EDS energy spectrum.

[0026] Figure 3 These are the photocatalytic degradation diagrams of the In2S3-Cu-Cu2O ternary heterojunction catalysts prepared in Examples 1-4 and Comparative Examples 1-3 of this invention. Detailed Implementation

[0027] The present invention will now be further described with reference to specific embodiments. These embodiments are intended to illustrate the invention and not to further limit it. In the photocatalytic degradation method for wastewater in this invention, tetracycline (TC) aqueous solution is used as model wastewater to evaluate the photocatalytic activity of the catalyst. The experimental conditions are as follows: two portions each of 40 mg catalyst and 100 mL of TC solution with a concentration of 20 mg / L are prepared and placed in a photocatalytic reactor with a rotor speed of 900 r / min for dark adsorption for 0.5 h. After adsorption equilibrium, the solution is irradiated with simulated visible light for 100 min using a xenon lamp with an output power of 300 W. The degradation rate is calculated by taking the solution after photocatalytic degradation.

[0028] Example 1:

[0029] (1) Preparation of Cu-Cu2O: 45 mmol of copper acetate monohydrate was dissolved in 60 mL of deionized water, and 30 mL of sodium hydroxide (9M) solution and 1.8 g of d-glucose powder were added sequentially. The mixture was stirred continuously in a water bath at 70 °C for 60 min. Then, 30 mL of sodium borohydride solution (0.1M) was added dropwise, and the mixture was stirred for another 30 min. After the reaction was completed, Cu-Cu2O was obtained by centrifugation, drying, and grinding.

[0030] (2) Preparation of In2S3: 902.49 mg of indium nitrate hydrate and 726.96 mg of L-cysteine ​​were dissolved in 40 ml of deionized water and stirred at room temperature for 40 min to obtain a homogeneous solution. Then, the pH of the solution was adjusted to 8 with 1 mol / L sodium hydroxide and stirred for another 30 min to obtain a pale yellow solution. The solution was transferred to a reaction vessel and hydrothermally reacted in an oven at 180 °C for 12 h. After cooling to room temperature, the solid was obtained by centrifugation and dried in an oven to obtain In2S3.

[0031] (3) Preparation of In2S3-Cu-Cu2O-1 ternary heterojunction catalyst: Weigh Cu-Cu2O from step 1 and In2S3 from step 2 into 30 mL of deionized water. The mass ratio of In2S3 to Cu-Cu2O is 1:19. Mix ultrasonically for 20 min and then mechanically stir for 40 min. Transfer to a reactor and perform hydrothermal reaction at 180 °C for 2 h. Cool naturally to room temperature. Centrifuge the mixture at 4000 rpm for 5 min and discard the supernatant. Wash the solid material with deionized water and anhydrous ethanol 5 times each (20 mL each time) and then dry in an oven at 60 °C for 8 h to obtain the target product, labeled as In2S3-Cu-Cu2O-1.

[0032] Example 2:

[0033] The operation steps are the same as in Example 1, except that in step (3), the mass ratio of In2S3 to Cu-Cu2O is 1:9. The mixture is first ultrasonically mixed for 20 min and then mechanically stirred for 60 min. It is then transferred to a reaction vessel for hydrothermal reaction at 180 °C for 2 h. After natural cooling to room temperature, the mixture is centrifuged at 6000 rpm for 3 min and the supernatant is discarded. The solid material is washed 5 times each with deionized water and anhydrous ethanol (20 mL each time) and then dried in an oven at 60 °C for 8 h to obtain the target product, which is labeled as In2S3-Cu-Cu2O-2.

[0034] Example 3:

[0035] The operation steps are the same as in Example 1, except that in step (3), the mass ratio of In2S3 to Cu-Cu2O is 1:4. The mixture is first ultrasonically mixed for 40 min and then mechanically stirred for 40 min. It is then transferred to a reaction vessel for hydrothermal reaction at 150 °C for 5 h. After natural cooling to room temperature, the mixture is centrifuged at 6000 rpm for 3 min and the supernatant is discarded. The solid material is washed three times each with deionized water and anhydrous ethanol (20 mL each time) and then dried in an oven at 80 °C for 6 h to obtain the target product, which is labeled as In2S3-Cu-Cu2O-3.

[0036] Example 4:

[0037] The operation steps are the same as in Example 1, except that in step (3), the mass ratio of In2S3 to Cu-Cu2O is 1:2. The mixture is first ultrasonically mixed for 40 min and then mechanically stirred for 60 min. It is then transferred to a reaction vessel for hydrothermal reaction at 150 °C for 2 h. After natural cooling to room temperature, the mixture is centrifuged at 4000 rpm for 5 min and the supernatant is discarded. The solid material is washed three times each with deionized water and anhydrous ethanol (20 mL each time) and then dried in an oven at 80 °C for 6 h to obtain the target product, which is labeled as In2S3-Cu-Cu2O-4.

[0038] Comparative Example 1:

[0039] 45 mmol of copper acetate monohydrate was dissolved in 60 mL of deionized water, followed by the addition of 30 mL of sodium hydroxide (9M) solution and 1.8 g of d-glucose powder. The mixture was stirred continuously in an 80 °C water bath for 70 min to obtain a red solution. After centrifugation, drying, and grinding, pure cuprous oxide was obtained and labeled as Cu2O.

[0040] Comparative Example 2:

[0041] Indium nitrate hydrate and L-cysteine ​​were dissolved in 40 ml of deionized water and mixed and stirred at room temperature for 40 min to obtain a homogeneous solution. The pH of the solution was then adjusted to 10 with 1 mol / L sodium hydroxide and stirred for another 60 min to obtain a pale yellow solution. The solution was then subjected to hydrothermal reaction at 160 °C for 24 h. The target product was obtained by centrifugation, drying, and grinding, and labeled as In2S3.

[0042] Comparative Example 3:

[0043] Cu₂O and In₂S₃ were ultrasonically mixed into 30 mL of deionized water and subjected to a hydrothermal reaction at 180 °C for 2 h in an oven. The resulting product was obtained by centrifugation, drying, and grinding. The mass ratio of In₂S₃ to Cu₂O was 1:4, and the mixture was labeled as In₂S₃ / Cu₂O.

[0044] observe Figure 1 It can be seen that in the In2S3-Cu-Cu2O ternary heterojunction catalyst prepared by this invention, Cu2O and Cu... 0 The characteristic peaks of Cu₂O and In₂S₃ agree well with their standard PDF cards (#97-001-5028, #85-1326, #91-001-2148), respectively. Therefore, it can be demonstrated that the composite catalyst contains Cu₂O and Cu. 0 The presence of In2S3 indicates the successful preparation of the In2S3-Cu-Cu2O ternary heterojunction catalyst; with increasing In2S3 content, the XRD peaks of In2S3 gradually appear, while those of Cu2O and Cu... 0 The characteristic peaks are still clearly visible, proving that Cu-Cu2O was not severely damaged during the composite process. This further demonstrates the successful preparation of the In2S3-Cu-Cu2O ternary heterojunction catalyst.

[0045] observe Figure 2 As can be seen from A, (a) In2S3 has a morphology of embroidered nanosheets, (b) Cu2O has a morphology of smooth octahedrons, and (cd) the surface of Cu-Cu2O becomes rough. (eh) — In2S3-Cu-Cu2O ternary heterojunction catalysts prepared in Examples 1-4; Figure 2B shows detailed SEM images and EDS spectra of the In2S3-Cu-Cu2O ternary heterojunction catalysts from Examples 1-4, for observation. Figure 2 As shown in Figure B, In₂S₃ nanosheets were successfully loaded onto the Cu-Cu₂O surface. Furthermore, with increasing In₂S₃ content, the number of In₂S₃ nanosheets on the Cu-Cu₂O surface gradually increased without disrupting the original octahedral structure of Cu₂O. EDS spectroscopy results revealed the presence of four elements: O, Cu, S, and In in the In₂S₃-Cu-Cu₂O ternary heterojunction catalyst. Further analysis showed that O and Cu elements were mainly distributed on the Cu₂O surface, while the characteristic signals of S and In elements gradually increased with increasing In₂S₃ loading. These results collectively confirm the successful synthesis of the In₂S₃-Cu-Cu₂O ternary heterojunction catalyst.

[0046] observe Figure 3 By comparison Figure 3 The photocatalytic degradation performance of tetracycline in different samples shows that the In2S3-Cu-Cu2O ternary heterojunction catalysts prepared in Examples 1-4 exhibit significantly better photocatalytic activity than comparative examples 1-3 (pure Cu2O, pure In2S3, and In2S3 / Cu2O binary heterojunction catalysts). Among them, Example 2 (In2S3-Cu-Cu2O-2) is the best example: under the same light conditions (100 min), its tetracycline degradation rate reached 93%, far exceeding that of comparative example 1 (pure Cu2O, 12%), comparative example 2 (pure In2S3, 41%), and comparative example 3 (In2S3 / Cu2O, 59%), demonstrating the best catalytic degradation performance. This optimal result can be obtained through... Figure 2 The SEM characterization results of B(b) clearly confirm that the surface roughness of the catalyst in Example 2 (In2S3-Cu-Cu2O-2) was adjusted to a suitable range, without the problem of insufficient interfacial contact caused by excessive dispersion or the problem of active site shielding caused by excessive agglomeration. This exposed more active sites that could participate in the reaction, providing an excellent structural basis for the efficient separation and migration of photogenerated carriers and the full contact between reactants and active sites.

[0047] Further analysis of the effect of the mass ratio of In2S3 to Cu-Cu2O on the catalytic effect: The SEM characterization results of Example 1 (In2S3-Cu-Cu2O-1) are as follows: Figure 2 As shown in B(a), the distribution of S and In elements is not obvious. This is because the In2S3 loading is too low, resulting in insufficient interfacial contact area of ​​the ternary heterojunction, limiting the separation efficiency of photogenerated electron-hole pairs, and thus weakening the catalytic activity. The SEM characterization results of Example 3 (In2S3-Cu-Cu2O-3) are as follows: Figure 2As shown in B(c), with the increase of In2S3 loading, the catalyst particle agglomeration intensifies, some active sites are masked, the interfacial synergy between In2S3 and Cu-Cu2O is destroyed, and the catalytic performance decreases; the SEM characterization results of Example 4 (In2S3-Cu-Cu2O-4) are as follows. Figure 2 As shown in B(d), due to the excessive In2S3 loading, the catalyst surface was completely covered by In2S3 and the aggregation was severe, resulting in a large number of active sites being buried, which led to a photocatalytic efficiency that was significantly lower than that of Examples 1-3.

[0048] In summary, the mass ratio of In2S3 to Cu-Cu2O is a key parameter for regulating the microstructure and catalytic performance of the In2S3-Cu-Cu2O ternary heterostructure. Only when the mass ratio is within a suitable range (such as the parameter condition of 1:9 mass ratio of In2S3 to Cu-Cu2O in Example 2) can an optimal microstructure with sufficient interfacial contact and sufficient exposure of active sites be constructed, thereby achieving the best photocatalytic degradation effect.

[0049] The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for preparing an In2S3-Cu-Cu2O ternary heterojunction catalyst, characterized in that, Includes the following steps: Step 1: Preparation of Cu-Cu2O Copper acetate monohydrate and sodium hydroxide were placed in deionized water to produce a dark precipitate. d-glucose powder was then added, and the mixture was reacted in a water bath at 70-80 °C for 60-70 min to obtain a red solution. Subsequently, sodium borohydride solution was slowly added to the red solution, and the mixture was heated and stirred for 30-50 min. After cooling to room temperature, a precipitate was obtained. The precipitate was washed and dried to obtain Cu-Cu2O. Step 2: Preparation of In2S3 Indium nitrate hydrate and L-cysteine ​​were placed in deionized water and ultrasonically mixed. Sodium hydroxide solution was added dropwise to adjust the pH to 8-10. After stirring for 30-60 min until the solution turned pale yellow, it was transferred to a reaction vessel and hydrothermally reacted in an oven at 160-180 ℃ for 12-24 h. After cooling to room temperature, the solid was obtained by centrifugation and dried in an oven to obtain In2S3. Step 3: Preparation of In2S3-Cu-Cu2O ternary heterojunction catalyst Weigh the Cu-Cu2O from step 1 and the In2S3 from step 2 into deionized water, mix them ultrasonically and then mechanically, transfer them to a reaction vessel for hydrothermal reaction, and obtain a mixed solution after natural cooling to room temperature. Centrifuge the mixed solution and finally put the solid material obtained after centrifugation into an oven for drying. After grinding, the In2S3-Cu-Cu2O ternary heterojunction catalyst is obtained. The hydrothermal reaction temperature is 150~180 ℃, and the reaction time is 2~5 h.

2. The method according to claim 1, characterized in that, In step 3, the mass ratio of In2S3 to Cu-Cu2O is 1:2 to 1:

19.

3. The method according to claim 1, characterized in that, In step 3, the ultrasonic mixing time is 20-40 minutes.

4. The method according to claim 1, characterized in that, The mechanical stirring time in step 3 is 40-60 minutes.

5. The method according to claim 1, characterized in that, In step 3, the centrifugation speed is 4000~6000 rpm and the centrifugation time is 3~6 min; the drying temperature in the oven is 60~80 ℃ and the drying time is 6~8 h.

6. The method according to claim 5, characterized in that, Step 3 further includes: during the centrifugation process, the mixture is washed alternately with deionized water and anhydrous ethanol, and the number of washes is 3 to 5.

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