A preparation method for synthesizing photocatalytic WO3 / NiCo2O4 nanospheres with visible light response by one-pot method

Abstract

This invention belongs to the field of photocatalyst preparation and discloses a one-pot method for synthesizing photocatalytic WO3 / NiCo2O4 nanospheres with visible light response. 4.04 g of sodium tungstate is dissolved in 25 mL of deionized water, and 0.274 g of oxalic acid is dissolved in 50 mL of deionized water. The mixture is stirred for 30 min, heated at 90 °C for 3 h, washed three times with ethanol and deionized water respectively, dried at 70 °C for 12 h, ground into powder, and placed at 500 °C for 1 h to obtain pure WO3. 1.5 mmol xylose, 0.5 mmol Ni(NO3)2·6H2O, and 1 mmol Co(NO3)2O2 are weighed. 3) Add 2·6H2O to 30mL of isopropanol and stir at room temperature for 1 hour. Add 1%, 2%, 3%, 4%, and 5% pure WO3. Solvent heat treatment at 180℃ for 24 hours, cool naturally to room temperature, wash several times with deionized water and ethanol, dry at 70℃ for 12 hours, grind into powder, and heat to 450℃ for 7 hours to obtain WO3 / NiCo2O4 nanospheres. These nanospheres have a large specific surface area and strong adsorption capacity. They also have better visible light absorption performance and greatly improve the ability to photocatalytically oxidize and degrade organic pollutants. The preparation method is relatively simple and easy to operate.

Description

Technical Field

[0001] This invention belongs to the field of photocatalyst preparation, and relates to a semiconductor photocatalyst for environmental pollution control and its preparation method. Specifically, it relates to a one-pot method for synthesizing photocatalytic WO3 / NiCo2O4 nanospheres with visible light response. Background Technology

[0002] Energy crisis and environmental problems are two serious issues that humanity must face. Effectively controlling and managing the pollution of the environment by various chemical pollutants is a key focus of comprehensive environmental governance. In recent years, semiconductor photocatalytic oxidation technology, as one of the advanced oxidation technologies, has been widely studied by scholars both domestically and internationally. This technology can use solar energy to degrade pollutants in the environment, effectively utilizing solar energy and reducing people's energy consumption.

[0003] Semiconductor photocatalytic oxidation technology originated from the discovery by Japanese scientists Fujishima and Honda that a TiO2 single-crystal electrode irradiated by light could decompose H2O. The use of TiO2 semiconductor photocatalysts to convert light energy into electrical and chemical energy has become a research hotspot in the field of semiconductor photocatalysis. However, anatase TiO2 has a band gap of 3.2 eV and an excitation wavelength of 387.5 nm, falling within the ultraviolet range of sunlight. Since solar energy is primarily concentrated in the visible light range of 400–600 nm, this significantly reduces the efficiency of TiO2 semiconductor photocatalysts. Therefore, developing novel semiconductor materials that respond to visible light is one of the key research areas in semiconductor photocatalysts.

[0004] Among the many newly developed semiconductor photocatalysts, researchers have developed tungstate compounds, finding that these catalysts have a small band gap and can fully utilize sunlight, making them a promising class of photocatalysts. However, with further research, most tungstate compounds have shown poor stability and susceptibility to photocorrosion, limiting their development. Summary of the Invention

[0005] The purpose of this invention is to provide a visible-light-responsive photocatalyst, WO3 / NiCo2O4 nanospheres, which not only exhibit visible-light response and the ability to degrade organic pollutants but also demonstrate good stability and resistance to corrosion, as well as a method for its preparation. This invention primarily achieves the above objective by improving the catalyst composition and preparation method.

[0006] I. The WO3 / NiCo2O4 nanospheres of the present invention are spherical nanoscale composites obtained by solvothermal reaction of synthesized WO3 in different mass ratios, namely WO3:NiCo2O4 nanosheets.

[0007] II. The specific preparation method of WO3 / NiCo2O4 nanospheres is as follows:

[0008] 1. Weigh 4.04 g of sodium tungstate (Na2WO4·2H2O) and dissolve it in 25 mL of deionized water (DI). Slowly add 25 mL of HCl to the sodium tungstate solution in deionized water using a guide rod and stir. Weigh 0.274 g of oxalic acid (H2C2O4) and dissolve it in 50 mL of deionized water. Mix the two solutions at room temperature for 30 minutes using a magnetic stirrer. Transfer the mixed solution to a 100 mL reactor and heat it at 90 °C for 3 hours in a constant temperature drying oven. Wash the mixture three times with ethanol and deionized water respectively using a multi-tube automatic balancing centrifuge. Dry it at 70 °C for 12 hours in a constant temperature drying oven. After drying, grind the powder into powder and place it in a muffle furnace at 500 °C for 1 hour with a heating rate of 5 °C / min to obtain pure WO3.

[0009] 2. Weigh 1.5 mmol of xylose (C5H) using a balance. 10 0.5 mmol Ni(NO3)2·6H2O and 1 mmol Co(NO3)2·6H2O were added to 30 mL of isopropanol (IPA) and stirred with a magnetic stirrer at room temperature for 1 hour. 1%-5% pure WO3 was added, and the mixture was then added to 50 mL of polytetrafluoroethylene and placed in a stainless steel autoclave. The autoclave was then solvothermal treated at 180 °C for 24 hours. After natural cooling to room temperature, the brown powder was collected by centrifugation and washed several times with deionized (DI) water and ethanol. The powder was then dried in a heated constant-temperature drying oven at 70 °C for 12 hours. After drying, the powder was ground into powder and then heated to 450 °C for 7 hours in a muffle furnace at a temperature rise rate of 5 °C / min to obtain NiCo2O4 nanospheres.

[0010] Different mass ratios refer to adding WO3 at a ratio of 1%-5% based on NiCo2O4. The unit is determined according to the actual needs. The unit used here is grams (g). For specific required mass, please refer to Examples 4 and 5.

[0011] In this invention, WO3 / NiCo2O4 nanospheres with visible light response are synthesized by a one-pot method. By controlling the reaction time and temperature, a spherical morphology with a large specific surface area is formed, which makes the prepared material have a large specific surface area, which is beneficial to the adsorption and degradation of pollutants.

[0012] Method of using the WO3 / NiCo2O4 nanospheres of this invention:

[0013] 1. Catalytic degradation of gaseous pollutants, the specific procedure is as follows: WO3 / NiCO2O4 nanospheres are placed in a reactor. Inert gas is introduced into the reactor at a flow rate of 20–100 mL / min to purge the system until it stabilizes. Pollutants are introduced into the reactor at a flow rate of 1–10 μL / h. After 10–60 min, the inlet and outlet are closed, keeping the reactor sealed. The reactor is placed in the dark, allowing the gaseous pollutants to adsorb onto the solid surface of the WO3 / NiCO2O4 nanospheres for 0.5–3 h. Then, a xenon lamp is turned on to carry out a photocatalytic reaction. After 4–6 h, the xenon lamp is turned off. The pollutants include acetone, toluene, ethylbenzene, and formaldehyde, etc.

[0014] 2. Catalytic degradation of liquid-phase pollutants, the specific procedure is as follows: WO3 / NiCo2O4 nanospheres and pollutants are dissolved in a pollutant solution at a mass ratio of 10-50:1. The mixture is ultrasonically dispersed for 30 min, then magnetically stirred in the dark for 30 min. After stirring, 2 mL of the solution is taken, centrifuged at 3000 r / min for 5 min, and the absorbance is measured. Then, the solution is irradiated with a xenon lamp. Samples are taken every 20 min for centrifugation, and the absorbance is measured again. The pollutant content is calculated based on the absorbance. The pollutant is levofloxacin.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] ①WO3 / NiCo2O4 nanospheres have a large specific surface area and strong adsorption capacity;

[0017] ②Compared with traditional photocatalyst titanium dioxide, WO3 / NiCo2O4 nanospheres have better visible light absorption performance, which greatly improves the photocatalytic oxidation and degradation of organic pollutants;

[0018] ③The preparation method of WO3 / NiCo2O4 nanospheres is relatively simple, easy to operate, and suitable for industrial production. Attached Figure Description

[0019] Figure 1 The images shown are SEM images of the WO3 / NiCo2O4 nanospheres in Example 1 magnified to 200 nm. Image a is a SEM image of 4% WO3 / NiCo2O4; Image b is a magnified SEM image of a localized part of 4% WO3 / NiCo2O4.

[0020] Figure 2 The UV-vis diffuse reflectance spectra of NiCo2O4 and WO3 / NiCo2O4 in Examples 1 and 2 are shown.

[0021] Figure 3 TEM image of 4% WO3 / NiCo2O4 in Example 1;

[0022] Figure 4The PL spectra of NiCo2O4 and WO3 / NiCo2O4 in Example 1 are shown.

[0023] Figure 5 The photocatalytic levofloxacin curves of NiCo2O4 and WO3 / NiCo2O4 in Application Example 1;

[0024] Figure 6 The photocatalytic curves of levofloxacin using NiCo2O4 and WO3 / NiCo2O4 in Application Example 1 are shown. Detailed Implementation

[0025] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way. Unless otherwise specified, the experimental methods used in the present invention are conventional methods, and the experimental equipment, materials, reagents, etc. used are all commercially available.

[0026] Example 1

[0027] Weigh 4.04 g of sodium tungstate (Na2WO4·2H2O) and dissolve it in 25 mL of deionized water (DI). Slowly add 25 mL of HCl to the sodium tungstate solution in deionized water using a guide rod and stir. Weigh 0.274 g of oxalic acid (H2C2O4) and dissolve it in 50 mL of deionized water. Mix the two solutions at room temperature for 30 minutes using a magnetic stirrer. Transfer the mixed solution to a 100 mL reactor and place it in a heated constant temperature drying oven at 90 °C for 3 hours. Wash the mixture three times with ethanol and deionized water respectively using a multi-tube automatic balancing centrifuge. Dry the mixture in a heated constant temperature drying oven at 70 °C for 12 hours. After drying, grind the mixture into powder and place it in a muffle furnace at 500 °C for 1 hour at a heating rate of 5 °C / min. Pure WO3 was obtained; then, WO3 / NiCo2O4 nanospheres were prepared, and the synthesis steps were as follows: 1.5 mmol of xylose (C5H) was weighed using a balance. 10 O5), 0.5 mmol Ni(NO3)2·6H2O and 1 mmol Co(NO3)2·6H2O were added to 30 mL of isopropanol (IPA) and stirred with a magnetic stirrer at room temperature for 1 hour. 4% pure WO3 was added, and the mixture was then added to 50 mL of polytetrafluoroethylene (PTFE) and placed in a stainless steel autoclave. The autoclave was then solvothermal treated at 180 °C for 24 hours. After natural cooling to room temperature, the brown powder was collected by centrifugation and washed several times with deionized (DI) water and ethanol. The powder was then dried in a heated oven at 70 °C for 12 hours. After drying, the powder was ground into a fine powder. WO3 / NiCo2O4 nanospheres were obtained by heating the precursor to 450 °C for 7 hours in a muffle furnace at a temperature rise rate of 5 °C / min. From Figure 1As shown in Figure a, the three small spheres are very close together, and their surfaces are enriched with small lumps. Based on experimental methods and relevant data, pure NiCo₂O₄ should be spherical, so the small sphere should be NiCo₂O₄, and the small lumps on the outside should be WO₃. To better observe their enrichment, the material was magnified locally. Figure 1 As can be seen in image b, WO3 is more clearly loaded on nickel cobalt oxide, and the quantity is relatively large and the distribution is uniform. The surface of the binuclear spherical NiCo2O4 material has a material loaded on it, exhibiting a small arc shape and a bumpy surface. At the same time, the shape of NiCo2O4 remains unchanged. Based on the above, it can be preliminarily confirmed that WO3 and NiCo2O4 were successfully synthesized.

[0028] Example 2

[0029] To further investigate the microstructure and structure of NiCo2O4 and WO3 / NiCo2O4, TEM was used for characterization. Figure 3 The central position clearly shows the distinct binuclear spherical shape of NiCo2O4. It also reveals a high surface compatibility between WO3 and NiCo2O4. While the structural shape of NiCo2O4 remains largely unchanged after composite formation, the spacing between the inner and outer cores alters, likely due to the reaction with WO3. The image also shows that the WO3 enriched on the outer core has a blocky shape, with some small particles also enriched on the outer layer of the material. Combined with SEM, this indicates that the surface area and contact space of the WO3 / NiCo2O4 composite photocatalyst are increased.

[0030] Example 3

[0031] Following the preparation method of the present invention in Example 1, except without the addition of WO3, pure NiCo2O4 nanosphere photocatalyst was obtained.

[0032] Example 4

[0033] The preparation method of the present invention in Example 1 was followed, except that the amount of WO3 was increased to 0.1153g to obtain 5% [the product / product / method].

[0034] WO3 / NiCo2O4 nanosphere photocatalyst.

[0035] Example 5

[0036] The preparation method of the present invention in Example 1 was followed, except that the amount of WO3 was reduced to 0.0159g to obtain 1% [the product / product].

[0037] WO3 / NiCo2O4 nanosphere photocatalyst.

[0038] Application Example 1

[0039] Levofloxacin solution was purchased and used directly in a photocatalytic reaction without any treatment.

[0040] The degradation of levofloxacin solution was analyzed under visible light irradiation (λ=520nm) to better analyze the properties of pure NiCo2O4 and WO3 / NiCo2O4 composite photocatalysts.

[0041] like Figure 5 The pure nickel cobalt oxide shown has low visible light efficiency, resulting in poor degradation of levofloxacin. Pure NiC... O2 The O4 sample showed a pollutant conversion rate of 25.18% after 180 minutes of reaction. The composite material doped with WO3 showed a higher conversion rate after 180 minutes of reaction. Among the five ratios (1% WO3 / NiCo2O4, 2% WO3 / NiCo2O4, 3% WO3 / NiCo2O4, 4% WO3 / NiCo2O4, and 5% WO3 / NiCo2O4), the 4% WO3 / NiCo2O4 ratio stood out, exhibiting the highest photocatalytic activity at 48.80%.

[0042] Meanwhile, the 180-minute reaction time reveals that some intermediate products are adsorbed on the surface of the catalyst, and the reaction kinetics can also be explored. The Langmuir-Hinshelwood model is selected to determine the photocatalytic reaction rate equation, where C0 is the initial concentration of levofloxacin, Ct is the final concentration of photocatalytic degradation, k is the first-order kinetic constant, and t is the reaction time.

[0043] from Figure 6 As can be seen, NiCo2O4 and different ratios of WO3 / NiCo2O4 all follow a first-order curve, with 4% WO3 / NiCo2O4 (0.00239 min) showing the best performance. -1 () is pure nickel cobalt oxide (NiCo2O4) (0.0017 min) -1 The 1.94-fold increase indicates that after pure nickel cobalt oxide is coupled with WO3, the WO3 / NiCo2O4 photocatalysis has a significant effect on levofloxacin.

[0044] The embodiments described above are merely preferred embodiments of the present invention, and not all feasible embodiments of the present invention. Any obvious modifications made by those 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. A one-pot method for synthesizing photocatalytic WO3 / NiCo2O4 nanospheres with visible light response, characterized in that: Spherical nanoscale composites were obtained by solvothermal reaction of synthesized WO3 in different mass ratios, namely WO3:NiCo2O4. The preparation method includes the following steps: 1) Weigh 4.04 g of sodium tungstate and dissolve it in 25 mL of deionized water. Slowly add 25 mL of HCl to the sodium tungstate solution dissolved in deionized water and stir. Weigh 0.274 g of oxalic acid and dissolve it in 50 mL of deionized water. Mix the two solutions at room temperature and stir for 30 minutes. Transfer the mixed solution to a reaction vessel and heat it at 90 °C for 3 hours in a constant temperature drying oven. Wash it three times with ethanol and deionized water respectively. Dry it in a constant temperature drying oven at 70 °C for 12 hours. After drying, grind it into powder. Place the powder in a muffle furnace at 500 °C for 1 hour with a heating rate of 5 °C / min to obtain pure WO3. 2) Weigh 1.5 mmol xylose, 0.5 mmol Ni(NO3)2·6H2O and 1 mmol Co(NO3)2·6H2O using a balance and add them to 30 mL of isopropanol. Stir with a magnetic stirrer at room temperature for 1 hour. Add pure WO3 and then add the mixture to 50 mL of polytetrafluoroethylene. Place the mixture into a stainless steel autoclave and solvothermal treat it at 180 °C for 24 hours in a constant temperature oven. After naturally cooling to room temperature, collect the brown powder by centrifugation and wash it several times with deionized water and ethanol. Then dry it in a constant temperature drying oven at 70 °C for 12 hours. After removing it, grind it into powder. Heat the precursor to 450 °C for 7 hours in a muffle furnace at a temperature rise rate of 5 °C / min to obtain WO3 / NiCo2O4 nanospheres. The microstructure of the WO3 / NiCo2O4 nanospheres is binuclear spherical.

2. The one-pot synthesis of photocatalyst WO3 / NiC with visible light response according to claim 1 O2 The method for preparing O4 nanospheres is characterized by, The addition of pure WO3 refers to adding pure WO3 at a ratio of 1%-5%.

3. The application of the photocatalytic WO3 / NiCo2O4 nanospheres with visible light response synthesized by the preparation method according to claim 1, characterized in that: Used to decompose levofloxacin.

4. The application of the photocatalytic WO3 / NiCo2O4 nanospheres with visible light response synthesized by the preparation method according to claim 3, characterized in that: When used to decompose levofloxacin, WO3 / NiCo2O4 nanospheres and pollutants are dissolved in a solution containing pollutants at a mass ratio of 10-50:

1. The mixture is ultrasonically dispersed for 30 min, and then magnetically stirred in the dark for 30 min. After stirring, 2 mL of the solution is taken, centrifuged at 3000 r / min for 5 min, and the absorbance is measured. Then, the solution is irradiated with a xenon lamp as the light source. Samples are taken every 20 min for centrifugation and absorbance is measured. The pollutant content is calculated based on the absorbance until the pollutant removal standard is met.

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