A type of N,P-CQDs / WO 3-x Application of composite photoelectrode fabrication methods

Abstract

This invention belongs to the field of photoelectrocatalysis and discloses a method for preparing N,P-CQDs / WO 3‑x The method for preparing composite photoanodes includes the following steps: (1) first preparing N,P-CQDs using a hydrothermal method; (2) preparing WO3 with oxygen-containing vacancies using a hydrothermal method and a surface reduction method. 3‑x Photoanode; (3) Finally, N,P-CQDs / WO3 were prepared by hydrothermal method. 3‑x Composite photoanode. This invention utilizes the prepared N,P-CQDs / WO 3‑x Composite photoanodes were developed, and single-factor analysis was used to determine the preparation method of N,P-CQDs / WO 3‑x The optimal conditions for the composite photoanode were determined by methods such as scanning X-ray diffraction (XRD) to analyze the obtained N,P-CQDs / WO 3‑x The composite photoanodes were characterized and applied, and the N,P-CQDs / WO obtained in this invention were obtained. 3‑x The photoelectrocatalytic degradation capability and stability of composite photoanodes are improved, showing promising application prospects.

Description

Technical Field

[0001] This invention belongs to the field of photoelectrocatalysis and is a method for preparing a composite photoelectrode. Background Technology

[0002] Photoelectrocatalysis refers to advanced oxidation reactions that utilize the interaction of light and electricity. The structure of this system is consistent with that of electrocatalysis, requiring an electrode, a counter electrode, and an electrolyte. The difference is that this system also requires an additional light source to irradiate the reaction cell.

[0003] Carbon quantum dots are a novel type of nanoparticle with a spherical shape and a particle size of less than 10 nanometers. They have wide applications in ion detection, photoelectrocatalysis, and other fields. The main superior properties of this nanomaterial include wavelength-dependent photoluminescence (PL), chemical inertness and low toxicity, small particle size, good biocompatibility, and photoinduced electron transfer. Carbon quantum dots possess excellent physical and chemical properties; they exhibit not only high fluorescence intensity but also excellent photoelectric properties, making them promising candidates for photoelectrocatalysis. Currently, leveraging the advantages of carbon quantum dots, extensive research and applications have been conducted.

[0004] Tungsten trioxide (WO3) is a wide-bandgap n-type semiconductor, and its excellent sensitivity and selectivity make it an important metal oxide gas-sensitive material. Tungsten trioxide has a strong absorption capacity for electromagnetic waves, making it suitable for use as an excellent solar energy absorber and stealth material. Furthermore, with a bandgap energy of approximately 2.5 eV, tungsten trioxide possesses potential photocatalytic activity in the visible light spectrum (wavelengths < 500 nm). Therefore, tungsten trioxide shows promising applications in the treatment of organic dye-contaminated water.

[0005] Oxygen vacancies are a common and important catalyst defect, formed by the removal of oxygen atoms from the lattice of metal oxides. The introduction of such defects often helps to control the electronic and chemical properties of materials, alter adsorption energies, and enhance the intrinsic activity of their active sites, thereby improving catalytic performance. For example, studies have shown that abundant oxygen vacancies in metal hydroxides facilitate the adsorption of oxygen-containing intermediates onto active sites, significantly improving their OER activity. Oxygen vacancy engineering has proven to be an effective catalyst modification strategy, offering advantages in constructing low-coordination-number metal sites and modulating the adsorption energies of OER intermediates. However, the two effects of oxygen vacancy engineering—modulating the catalyst's electronic structure and acting as additional active sites—often coexist, making the differentiation and allocation of electronic structure modulation of active sites and electron transport in the catalyst challenging. Therefore, clarifying the contribution of each component and elucidating the key role of oxygen vacancy engineering is crucial for understanding electrocatalytic mechanisms and designing efficient OER catalysts.

[0006] This invention utilizes a hydrothermal method to prepare nitrogen-phosphorus-doped carbon quantum dots (N,P-CQDs), and then obtains oxygen-vacant tungsten trioxide (WO3) through a combination of hydrothermal and surface reduction methods. 3-x Finally, nitrogen-phosphorus doped carbon quantum dots and oxygen-vacant tungsten trioxide were combined using a hydrothermal method (N,P-CQDs / WO3). 3-x A composite photoelectrode was obtained. Summary of the Invention

[0007] This invention uses sugarcane bagasse as a matrix to prepare nitrogen and phosphorus-doped carbon quantum dots via a hydrothermal method. Then, tungsten trioxide containing oxygen vacancies is prepared as a carrier, and the nitrogen and phosphorus-doped carbon quantum dots are loaded onto the tungsten trioxide containing oxygen vacancies to prepare a composite photoelectrode with strong stability, good photoelectrocatalytic performance, and safety and non-toxicity. The composite photoelectrode is then applied to the degradation of wastewater.

[0008] To achieve the above objectives, the present invention provides the following solution:

[0009] (1) Preparation of nitrogen-phosphorus-doped carbon quantum dots (N,P-CQDs): 1.2g of sugarcane bagasse powder was placed in a beaker, and 0.96g of (NH4)2HPO4 and 30ml of deionized water were added. After stirring evenly, the mixture was transferred into a PPL liner and then placed in a reactor. Finally, the reactor was placed in a muffle furnace and reacted at 260℃ for 12h. After the reactor cooled down, the product in the PPL liner was removed, filtered by vacuum pump, and the supernatant was collected. Dialyzed with a dialysis bag (500Da) for 12h to obtain a yellowish-brown clear liquid. The deionized water was replaced every 6h to obtain an N,P-CQDs solution. The N,P-CQDs solution was freeze-dried to obtain solid N,P-CQDs.

[0010] (2) Preparation of oxygen-vacancy tungsten trioxide photoelectrode (WO3) 3-x First, dissolve 0.4 g of Na₂WO₄·2H₂O and 0.2 g of (NH₄)₂C₂O₄ in 33 mL of deionized water. Then, add 9 mL of HCl to the solution, resulting in the formation of a yellow precipitate. Next, add 8 mL of H₂O₂ to the mixture, and the solution becomes colorless and clear. Finally, add 30 mL of anhydrous ethanol to the solution and stir continuously for 30 min. Simultaneously, prepare a 2×4 cm⁻¹ container... 2 The FTO conductive glass was placed in a beaker. The prepared solution was poured into this beaker containing the FTO conductive glass, and the mixture was transferred to an 85°C constant temperature water bath for a water bath reaction for 2 hours. After natural cooling, the beaker was removed, and the electrode surface was repeatedly rinsed with deionized water. After drying the WO3 at room temperature, it was calcined at 500°C for 2 hours under a nitrogen atmosphere. The final sample obtained was WO3. 3-x Photoanode;

[0011] (3) Preparation of tungsten trioxide composite photoelectrodes (N,P-CQDs / WO3) with oxygen vacancies loaded with nitrogen and phosphorus doped carbon quantum dots. 3-x ): Place the WO3-x photoanode in a beaker, add 15 ml of 1.5 g / L N,P-CQDs aqueous solution, seal, and react at 80 °C for 14 h. After the solution cools to room temperature, remove it and place it in an oven to dry at 60 °C to obtain N,P-CQDs / WO3. 3-x .

[0012] 1. Preferred: The mass ratio of sugarcane bagasse, diammonium hydrogen phosphate and water in step (1) is 5:4:125.

[0013] 2. Preferably: The heating reaction temperature of the nitrogen-phosphorus doped carbon quantum dots in step (1) is 260°C.

[0014] 3. Specifically: The heating reaction time of the nitrogen-phosphorus doped carbon quantum dots in step (1) is 12 hours.

[0015] 4. Preferably, the heating reaction temperature in step (2) is 85°C.

[0016] 5. Preferably, the heating reaction time in step (2) is 2 hours.

[0017] 6. Specifically: The atmosphere for high-temperature calcination in step (2) is nitrogen.

[0018] 7. Specifically: The concentration of the nitrogen-phosphorus doped carbon quantum dot solution in step (3) is 1.5 g / L.

[0019] 8. Preferably, the heating reaction temperature in step (3) is 80°C.

[0020] 9. Preferably, the heating reaction time in step (3) is 14 hours.

[0021] 10. Preferably, the immobilization time in step (3) is 10 hours.

[0022] The N,P-CQDs / WO prepared by this invention 3-x The composite photoelectrode is uniform in size and has good photoelectrocatalytic performance, while retaining the characteristics of tungsten trioxide and possessing high stability. It is highly reusable and can be used in the photoelectrocatalytic wastewater treatment industry to treat toxic and harmful wastewater. Attached Figure Description

[0023] Figure 1 The relationship between N,P-carbon quantum dot concentration and N,P-CQDs / WO 3-x The effect of photoanodic degradation of 4-chlorophenol;

[0024] Figure 2 For WO3, WO 3-x and N,P-CQDs / WO 3-x Photoelectrochemical degradation effect of 4-chlorophenol;

[0025] Figure 3 For WO3, WO 3-x and N,P-CQDs / WO 3-x XRD pattern of the surface;

[0026] Figure 4 For WO3, WO 3-x and N,P-CQDs / WO 3-x UV-Vis diffuse reflectance spectrum;

[0027] Figure 5 For WO3, WO 3-x and N,P-CQDs / WO 3-x Tauc curve; Detailed Implementation

[0028] The present invention will be further described below with reference to examples:

[0029] Example 1

[0030] A type of N,P-CQDs / WO 3-x The method for preparing a composite photoelectrode includes the following steps:

[0031] 1) Preparation of nitrogen-phosphorus-doped carbon quantum dots (N,P-CQDs): 1.2g of sugarcane bagasse powder was placed in a beaker, along with 0.96g of (NH4)2HPO4 and 30ml of deionized water. After stirring until homogeneous, the mixture was transferred to a PPL liner and placed in a reactor. The reactor was then placed in a muffle furnace and reacted at 260℃ for 12h. After the reactor cooled, the product was removed from the PPL liner and filtered using a vacuum pump. The supernatant was collected. Dialyzed using a dialysis bag (500Da) for 12h to obtain a yellowish-brown supernatant. The deionized water was replaced every 6h to obtain an N,P-CQDs solution. The N,P-CQDs solution was freeze-dried to obtain solid N,P-CQDs.

[0032] (2) Preparation of oxygen-vacancy tungsten trioxide photoelectrode (WO3) 3-x First, dissolve 0.4 g of Na₂WO₄·2H₂O and 0.2 g of (NH₄)₂C₂O₄ in 33 mL of deionized water. Then, add 9 mL of HCl to the solution, resulting in the formation of a yellow precipitate. Next, add 8 mL of H₂O₂ to the mixture, and the solution becomes colorless and clear. Finally, add 30 mL of anhydrous ethanol to the solution and stir continuously for 30 min. Simultaneously, prepare a 2×4 cm⁻¹ container... 2The FTO conductive glass was placed in a beaker. The prepared solution was poured into this beaker containing the FTO conductive glass, and the mixture was transferred to an 85°C constant temperature water bath for a water bath reaction for 2 hours. After natural cooling, the beaker was removed, and the electrode surface was repeatedly rinsed with deionized water. After drying the WO3 at room temperature, it was calcined at 500°C for 2 hours under a nitrogen atmosphere. The final sample obtained was WO3. 3-x Photoanode;

[0033] (3) Preparation of tungsten trioxide composite photoelectrodes (N,P-CQDs / WO3) with oxygen vacancies loaded with nitrogen and phosphorus doped carbon quantum dots. 3-x ): will WO 3-x The photoanode was placed in a beaker, and 15 ml of a 1.5 g / L N,P-CQDs aqueous solution was added. The beaker was sealed and reacted at 80 °C for 14 h. After the solution cooled to room temperature, it was removed and placed in an oven to dry at 60 °C to obtain N,P-CQDs / WO 3-x .

[0034] Example 2

[0035] The difference from Example 1 is that the dialysis time in step (1) is 18 hours, while the other parameters and operating steps are the same.

[0036] Example 3

[0037] The difference from Example 1 is that the amount of hydrochloric acid in step (2) is 3 ml, 6 ml, 12 ml and 15 ml, while the other parameters and operating steps are the same.

[0038] Example 4

[0039] The difference from Example 1 is that the reaction temperatures of 55°C, 65°C, 95°C and 105°C in step (2) are the same as the other parameters and operating steps.

[0040] Example 5

[0041] The difference from Example 1 is that the reaction time in step (2) is 3h, 4h, 5h and 6h, while the other parameters and operating steps are the same.

[0042] Example 6

[0043] The difference from Example 1 is that the concentration of N,P-CQDs aqueous solution in step (3) is 0.5 g / L, 1 g / L, 2 g / L and 2.5 g / L, while the other parameters and operating steps are the same.

[0044] Example 7

[0045] The difference from Example 1 is that the heating temperature in step (3) is 60°C, 70°C, 90°C and 100°C, while the other parameters and operating steps are the same.

[0046] Example 8

[0047] The difference from Example 1 is that the heating time in step (3) is 6h, 8h, 10h and 12h, while the other parameters and operating steps are the same.

[0048] The N,P-CQDs / WO prepared in Examples 1-8 above 3-x The composite photoelectrode was tested and analyzed. The reagents and instruments used in the experiment are as follows:

[0049] Sugarcane bagasse powder: This powder was obtained from sugarcane bagasse from the Nanning Sugar Factory in Guangxi, processed using methods optimized by our research group. Sodium tungstate: Shanghai Aladdin Biochemical Technology Co., Ltd.; Ammonium oxalate: Sinopharm Chemical Reagent Co., Ltd.; Diammonium hydrogen phosphate: Sinopharm Chemical Reagent Co., Ltd.; Hydrochloric acid: Sinopharm Chemical Reagent Co., Ltd.; Anhydrous ethanol: Sinopharm Chemical Reagent Co., Ltd.; Hydrogen peroxide (30%): Sinopharm Chemical Reagent Co., Ltd. Freeze dryer: FD-1A-50+, Boyikang Instrument Co., Ltd.; X-ray diffractometer: Rigaku miniflex600 (Japan); UV-Vis-DRS: RG5000J.

[0050] N,P-CQDs / WO 3-x Analysis of the effect and structure of composite photoelectrode:

[0051] 1. The effect of N,P-carbon quantum dot concentration on N,P-CQDs / WO 3-x Effects of photoanodic degradation of 4-chlorophenol

[0052] N,P-CQDs / WO were prepared according to the method described in Implementation Case 1. 3-x WO3 photoanodes were placed in beakers, and 10 ml of N,P-CQDs aqueous solutions with concentrations of 0.5, 1, 1.5, 2, and 2.5 g / L were added. The beakers were sealed and reacted at 85°C for 14 h. After the solution cooled to room temperature, it was removed and placed in an oven to dry at 60°C, finally yielding N,P-CQDs / WO3. The removal rate of 4-chlorophenol under 60 min conditions was used as the evaluation index to investigate the removal effect of photoanodes with different N,P-CQDs concentrations on 4-chlorophenol. The electrolysis conditions were: 100 mL of 4-chlorophenol with an initial concentration of 10 mg / L, Na2SO4 concentration of 2 g / L, and a bias voltage of 1.2 V. The photoelectrocatalysis experiment was conducted in a photoelectrochemical reactor using a 300 W xenon lamp light source. A filter was used to filter out light with wavelengths less than 420 nm. The electrolysis time was 60 min. After the test, the degradation rate of 4-CP by the photoanode was calculated using the following formula: (initial 4-CP concentration - 4-CP concentration at 60 minutes) / initial 4-CP concentration. Figure 1It can be seen that under the condition of electrolysis time of 60 min, the degradation effect is the best when the N,P-CQDs concentration is 1.5 g / L, with a degradation effect of 25.7%.

[0053] 2. WO3. WO 3-x and N,P-CQDs / WO 3-x Measurement of photoelectrochemical degradation effect of photoelectrode

[0054] Depend on Figure 2 It can be seen that loading N,P-CQDs onto WO3 improved the degradation effect. After 150 min of reaction, the degradation rate of 4-CP increased from 43.45% to 65.33%, an increase of 21.88%. This is because the doping of N,P-CQDs promoted charge conduction on the catalyst surface, providing more reactive sites and improving the catalytic efficiency for 4-CP. WO3 containing oxygen vacancies... 3-x The N,P-CQDs-loaded photoanode exhibited a 72.71% 4-CP degradation rate, which is 7.38% higher than the 65.33% 4-CP removal efficiency of the WO3 / N,P-CQDs photoanode. This means that WO3... 3-x Oxygen vacancies in the photoanode can improve the catalytic performance in the photoelectrocatalytic system and increase the degradation efficiency of pollutants by the photoanode.

[0055] 3. X-ray diffraction (XRD) analysis of WO3 and WO 3-x and N,P-CQDs / WO 3-x Crystal structure of photoelectrode

[0056] Figure 3 XRD patterns of WO3 and N,P-CQDs / WO3 are shown. The WO3 sample exhibits diffraction peaks at 23.1°, 23.5°, 24.3°, 42.6°, 50.2°, and 56.2°, corresponding to the (002), (020), (200), (222), (232), and (241) crystal planes of monoclinic WO3, respectively. This result demonstrates the successful synthesis of WO3 thin films in the laboratory via in-situ hydrothermal method. The strong and sharp diffraction peaks indicate that the obtained WO3 thin films possess good crystallinity. 3-x The successful preparation altered some of the crystal forms of WO3 while still retaining its characteristic peaks. In addition, the N,P-CQDs / WO3 composite sample was also characterized by XRD. Figure 3As can be seen, after modifying N,P-CQDs by surface adsorption, the N,P-CQDs / WO3 sample still conforms to the characteristic peak shape of typical WO3, indicating that the crystal structure of WO3 itself is well maintained during the surface modification process. Meanwhile, due to the low content and high dispersion of N,P-CQDs in the sample, the characteristic diffraction peaks corresponding to N,P-CQDs cannot be observed in the XRD pattern. In summary, the experiment successfully prepared well-crystallized WO3. The surface composite of N,P-CQDs did not affect the lattice structure of WO3 (N,P-CQDs did not enter the interior of the WO3 lattice but only composited on the surface), and no other impurities appeared in the samples, indicating that the prepared catalyst has high purity.

[0057] 4. WO3, WO 3-x and N,P-CQDs / WO 3-x UV-Vis diffuse reflectance spectrum

[0058] Figure 4 The results show that after oxygen vacancies form, oxygen atoms escape from the WO3 structure, increasing the specific surface area of ​​WO3 and thus improving its absorbance in the visible light region. N,P-CQDs / WO 3-x The absorbance intensity of the photoanode in the visible light region is significantly increased, which may be due to the N,P-CQDs promoting electron transfer and upconversion effects.

[0059] 5. WO3, WO 3-x and N,P-CQDs / WO 3-x Tauc curve

[0060] Depend on Figure 5 It can be seen that WO3 and WO 3-x and N, P-CQDs / WO 3-x The band gap values ​​were 2.33, 2.25, and 1.57, respectively. The formation of oxygen vacancies and the loading of N, P-CQDs all reduced the band gap of WO3, making WO3... 3-x and N,P-CQDs / WO 3-x The reduced energy required for electron transfer and the faster efficiency of electron transfer significantly enhance the photoelectrocatalytic activity of WO3, which can be reasonably explained. Figure 2 N,P-CQDs / WO 3-x The principle behind the best degradation effect.

[0061] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. An N,P-CQDs / WO with good photoelectrocatalytic effect 3-x A method for preparing a composite photoanode, characterized in that: Includes the following steps: (1) Preparation of N,P-CQDs: Take 1.2g of sugarcane bagasse powder into a beaker, add 0.96g of (NH4)2HPO4 and 30ml of deionized water and stir evenly. Transfer the resulting mixture into the PPL liner and then place it into the reactor. Finally, place the reactor in a muffle furnace and react at 260℃ for 12h. After the reactor cools down, take out the product from the PPL liner, filter it with a vacuum pump, take the supernatant, and dialyze it with a dialysis bag for 12h to obtain a yellowish-brown clear liquid. Replace the deionized water every 6h to obtain an N,P-CQDs solution. Freeze-dry the N,P-CQDs solution to obtain solid N,P-CQDs. (2) Preparation of WO 3-x First, dissolve 0.4g Na₂WO₄·2H₂O and 0.2g (NH₄)₂C₂O₄ in 33mL of deionized water. Then, add 9mL of HCl to the solution, resulting in the formation of a yellow precipitate. Next, add 8mL of H₂O₂ to the mixture, and the solution becomes colorless and clear. Finally, add 30mL of anhydrous ethanol to this solution and stir continuously for 30 minutes. Simultaneously, prepare a 2×4cm... 2 FTO conductive glass was placed on the wall of a 15mL beaker. The prepared solution was poured into this 15mL beaker containing FTO conductive glass, and the mixture was transferred to an 85℃ constant temperature water bath for a water bath reaction for 2 hours. After natural cooling, the beaker was removed, and the anode surface was repeatedly rinsed with deionized water. After drying at room temperature, it was calcined at 400℃ for 2 hours under a nitrogen atmosphere. The final sample obtained was WO3. 3-x Photoanode; (3) Preparation of N,P-CQDs / WO 3-x Composite photoanode: WO3 3-x The photoanode was placed in a beaker, and 15 ml of a 1.5 g / L N,P-CQDs aqueous solution was added. The beaker was sealed and reacted at 80 °C for 14 h. After the solution cooled to room temperature, it was removed and placed in an oven to dry at 60 °C to obtain N,P-CQDs / WO 3-x .

2. N,P-CQDs / WO prepared by the method according to claim 1 3-x Application of composite photoanodes in the photoelectric degradation of wastewater.

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