CN110732330A - Preparation method of WO3/Ag/AgCl photocatalytic thin film material - Google Patents

Abstract

The invention discloses a preparation method of a WO ₃ /Ag/AgCl photocatalytic film material. The method uses tungstic acid as a precursor, hydrogen peroxide as a solvent, and polyvinyl alcohol as a binder to dissolve the three into a slurry, prepare a WO ₃ film on the surface of a glass substrate by spin coating and high temperature treatment technology, and then mix WO ₃ The film material was repeatedly soaked in equal concentrations of NaCl and AgNO ₃ solutions, and dried to obtain a WO ₃ /AgCl film. Finally, the film was exposed to light to obtain a WO ₃ /Ag/AgCl photocatalytic film material. The WO ₃ /Ag/AgCl thin film material prepared by the method of the invention can overcome the disadvantage that traditional powder materials are difficult to separate and recycle, has good repeatability, simple preparation process, low cost, relatively stable photocatalytic performance, and is expected to be applied in sterilization, gas sensors, etc.

Description

Preparation method of WO3/Ag/AgCl photocatalytic thin film material

technical field

The invention belongs to the field of photocatalytic thin film composite material synthesis, in particular to a preparation method of a WO ₃ /Ag/AgCl photocatalytic thin film material.

Background technique

Pollutants in water mainly come from waste dyes discharged from paper and textile industries. Photocatalytic technology is a promising and effective method to degrade organic pollutants in water. Semiconductors such as TiO ₂ , ZnO, SnO ₂ , WO ₃ , Bi ₂ O ₃ are widely used for photocatalytic degradation of dyes in water.

The band gap width of WO ₃ is relatively low, 2.4-2.8 eV, and has a relatively high valence band (+3.1-3.2 eV), which makes its oxidation potential high and can absorb blue light in sunlight. Due to its excellent optoelectronic properties and good chemical stability and thermal stability, it has a wide range of applications in the fields of photocatalysts, gas sensors, photochromic and electrocatalysis. However, WO ₃ has a poor ability to separate photogenerated holes from electrons due to its lower conduction band position. Therefore, it is necessary to improve the photocatalytic performance of WO ₃ by means of modification.

Due to its ability to absorb visible light, Ag/AgCl has excellent properties that make Ag/AgCl a good combination with other semiconductors to improve the stability, photocatalytic activity and repeatability of photocatalysts.

Bowen Ma et al. (Applied Catalysis B Environmental, 2012, 123-124(30): 193-199.) prepared Ag-AgCl/WO ₃ hollow spheres with flower-like structure by a two-step method under calcination conditions. Due to its unique hollow sphere structure, the utilization rate of incident light is improved, and its photocatalytic performance is greatly improved, and its photocatalytic effect can completely degrade p-chlorophenol within half an hour. Qingyong Li et al. (Journal of Energy Chemistry (2017).) prepared _Ag /AgCl/WO nanosheet photocatalysts by using the hydrothermal method under the ultrasonic-assisted method with geothermal water as the source of chlorine element, and the obtained catalyst had good It can effectively degrade p-aminobenzoic acid under visible light irradiation.

However, the above catalysts are all in powder form, and it takes a lot of time and energy to separate them from the catalytic phase after being degraded, and at the same time, it is not conducive to their repeated use, which increases the cost.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a preparation method of WO ₃ /Ag/AgCl photocatalytic thin film material.

The technical solution that realizes the object of the present invention is as follows:

A preparation method of WO ₃ /Ag/AgCl photocatalytic film material, using tungstic acid as a precursor, hydrogen peroxide as a solvent, and polyvinyl alcohol as a binder, a layer of WO is prepared on a glass substrate by a spin coating process and a high-temperature calcination method ₃ films, and then repeatedly immersed in NaCl and AgNO ₃ solutions to obtain a WO ₃ /AgCl film, and finally illuminated to obtain a WO ₃ /Ag/AgCl film with photocatalytic properties. The specific steps are as follows:

Step 1), dissolving polyvinyl alcohol and tungstic acid in hydrogen peroxide, the obtained mixed solution is coated on the surface of a clean glass substrate, spin-coated at a speed of 500-800 rpm, dried, and then calcined at 550-600 ° C for 4- 6h, naturally cooling the glass substrate coated with WO ₃ ;

Step 2), soak the glass substrate coated with WO ₃ in NaCl and AgNO ₃ solutions with the same concentration and a concentration of 0.02M-0.05M in turn for 30-60min, soak completely, and illuminate to obtain WO ₃ /Ag/AgCl Photocatalytic thin film materials.

Further, in step 1), the molar ratio of the hydrogen peroxide to the tungstic acid is 5-8:1, and the mass ratio of the tungstic acid to the polyvinyl alcohol is 2-3:1.

Further, in step 1), the spin coating time is 8-15s.

Further, in step 1), the drying temperature is 60-80° C., and the drying time is 1-2 h.

Further, in step 1), the heating rate during the calcination is 3-5°C/min.

Further, in step 2), the illumination time is 5-10 min.

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

(1) The WO ₃ /Ag/AgCl thin film prepared by the present invention is uniform, has good transparency and high stability, is easy to catalyze phase separation, and is convenient for recycling and reuse;

(2) The WO ₃ /Ag/AgCl film prepared by the present invention has good degradation performance to organic dyes under visible light irradiation: the highest degradation effect of the prepared WO ₃ /Ag/AgCl film is 98% in 3 hours, and the concentration is 5mol/L methyl orange (MO) and 2.5 hours can degrade 95% of 5mol/L Rhodamine B (RhB).

Description of drawings

Figure 1 is the optical image of WO ₃ thin film and WO ₃ /Ag/AgCl thin film material at different concentrations.

Figure 2 shows WO ₃ films (a and b) and 1-WO ₃ /Ag/AgCl films (c and d), 2-WO ₃ /Ag/AgCl films (e and f), 3-WO ₃ /Ag/AgCl films SEM images of thin films (g and h) (wherein: 1-WO ₃ /Ag/AgCl, 2-WO ₃ /Ag/AgCl and 3-WO ₃ /Ag/AgCl, the numbers in front of them from small to large represent the experimental ones, respectively AgNO3 and _NaCl solution concentration from low to high, the same below).

3 is the XRD patterns of the WO ₃ thin film, the 1-WO ₃ /Ag/AgCl thin film, the 2-WO ₃ /Ag/AgCl thin film, and the 3-WO ₃ /Ag/AgCl thin film.

FIG. 4 is the UV-Vis absorption spectra of WO ₃ thin film and three WO ₃ /Ag/AgCl thin films.

Figure 5 is the degradation diagram of different catalysts for the catalytic degradation of methyl orange (a) and rhodamine B (b) under visible light irradiation.

Fig. 6 is a graph showing the results of the repeatability experiment of 3-WO ₃ /Ag/AgCl thin film catalyzing methyl orange (a) and rhodamine B (b) under visible light irradiation; 3-WO ₃ /Ag/AgCl before five repeated experiments SEM image (c) of the film and SEM image (d) of the 3-WO ₃ /Ag/AgCl film after five repeated experiments.

Detailed ways

The following examples and figures further illustrate the present invention.

Example 1

10.0 g of tungstic acid and 5.0 g of polyvinyl alcohol were weighed and added to 20 mL of hydrogen peroxide under constant stirring, and the stirring was continued for about 24 hours until the tungstic acid and polyvinyl alcohol were completely dissolved. The prepared solution was coated on the surface of clean silicate glass, spin-coated at 800rmp for 8s with a spin coater, then dried at 80°C for 1h, and then placed in a muffle furnace and calcined at 550°C for 4h. Cool naturally.

The optical physical image of the prepared WO ₃ film is shown in Figure 1a, and it can be seen that a nearly transparent film is attached to the glass surface _; It can be seen that there is a layer of WO ₃ crystal particles uniformly attached to the surface of the glass.

Example 2

15.0 g of tungstic acid and 5.0 g of polyvinyl alcohol were weighed and added to 20 mL of 30% hydrogen peroxide with constant stirring, and the stirring was continued for about 24 hours until the tungstic acid and polyvinyl alcohol were completely dissolved. The prepared solution was coated on the surface of clean silicate glass, spin-coated at 700 rpm for 10 s with a glue spinner, then dried at 80 °C for 1 h, and then placed in a muffle furnace and calcined at 550 °C for 6 h. Cool naturally. The prepared WO ₃ films were immersed in NaCl and AgNO ₃ solutions with concentrations of 0.005M, 0.01M, and 0.02M in turn for 30 min, and the steps were repeated 3 times respectively, and then irradiated under a 300W xenon lamp for 10 min to obtain 1-WO ₃ /Ag/AgCl thin film, 2-WO ₃ /Ag/AgCl thin film, 3-WO ₃ /Ag/AgCl thin film samples.

The optical images of the prepared 1-WO ₃ /Ag/AgCl thin film, 2-WO ₃ /Ag/AgCl thin film, and 3-WO ₃ /Ag/AgCl thin film samples are shown in Figure 1(b,c,d), it can be seen that With the increase of the concentration of NaCl and AgNO ₃ solution, the color of the film on the glass surface became darker and darker, indicating that more and more elemental silver was reduced by light; the prepared 1-WO ₃ /Ag/AgCl thin film, 2-WO The SEM of ₃ /Ag/AgCl thin film and 3-WO ₃ /Ag/AgCl thin film samples are shown in Figure 2 (c, d, e, f, g, h), it can be seen that WO ₃ and Ag/AgCl are all uniform Distributed on the surface of the glass, and with the increase of the concentration of NaCl and AgNO ₃ solutions, the amount of Ag/AgCl on the film surface also increased.

Example 3

10.0 g of tungstic acid and 5.0 g of polyvinyl alcohol were weighed and added to 30 mL of 30% hydrogen peroxide with constant stirring, and the stirring was continued for about 24 hours until the tungstic acid and polyvinyl alcohol were completely dissolved. The prepared solution was coated on the surface of clean silicate glass, spin-coated at 500 rpm for 15 s with a glue spinner, then dried at 80 °C for 1 h, and then placed in a muffle furnace and calcined at 580 °C for 5 h. Cool naturally. The prepared WO ₃ films were immersed in NaCl and AgNO ₃ solutions with concentrations of 0.005M, 0.01M, and 0.02M in turn for 30 min, and the steps were repeated 3 times respectively, and then irradiated under a 300W xenon lamp for 10 min to obtain 1-WO ₃ /Ag/AgCl thin film, 2-WO ₃ /Ag/AgCl thin film, 3-WO ₃ /Ag/AgCl thin film samples.

The XRD patterns of the prepared WO ₃ thin film, 1-WO ₃ /Ag/AgCl thin film, 2-WO ₃ /Ag/AgCl thin film, and 3-WO ₃ /Ag/AgCl thin film are shown in Figure 3, which can be clearly seen from the figure The peaks corresponding to WO ₃ and AgCl, while the peaks corresponding to Ag are relatively insignificant. The possible reason is that the amount of Ag is relatively small, and with the increase of the concentration of NaCl and AgNO ₃ solutions, the peaks of AgCl become stronger and stronger. , while the peak of WO ₃ is getting weaker and weaker.

Example 4

15.0 g of tungstic acid and 5.0 g of polyvinyl alcohol were weighed and added to 30 mL of 30% hydrogen peroxide under constant stirring, and the stirring was continued for about 24 hours until the tungstic acid and polyvinyl alcohol were completely dissolved. The prepared solution was coated on the surface of clean silicate glass, spin-coated at 700 rpm for 8 s with a glue spinner, then dried at 80 °C for 1 h, and then placed in a muffle furnace and calcined at 600 °C for 4 h. Cool naturally. The prepared WO ₃ film was immersed in NaCl and AgNO ₃ solutions with concentrations of 0.005M, 0.01M, and 0.02M in turn for 60 min, and the steps were repeated 3 times, and then irradiated under a 300W xenon lamp for 5 min to obtain 1-WO ₃ /Ag/AgCl thin film, 2-WO ₃ /Ag/AgCl thin film, 3-WO ₃ /Ag/AgCl thin film samples.

The UV spectra of the prepared WO ₃ thin films and 1-WO ₃ /Ag/AgCl thin films, 2-WO ₃ /Ag/AgCl thin films, and 3-WO ₃ /Ag/AgCl thin films are shown in Figure 4, and it can be seen from the figure The reason is that the absorption range of WO ₃ film increases when Ag/AgCl is loaded, and it can absorb visible light, and it can be concluded from the figure that the forbidden band width of WO ₃ is 2.61eV.

Example 5:

10.0 g of tungstic acid and 5.0 g of polyvinyl alcohol were weighed and added to 30 mL of 30% hydrogen peroxide with constant stirring, and the stirring was continued for about 24 hours until the tungstic acid and polyvinyl alcohol were completely dissolved. The prepared solution was coated on the surface of clean silicate glass, spin-coated at 800 rpm for 10 s with a glue spinner, then dried at 80 °C for 1 h, and then placed in a muffle furnace and calcined at 600 °C for 6 h. Cool naturally. The prepared WO ₃ film was immersed in NaCl and AgNO ₃ solutions with concentrations of 0.005M, 0.02M, and 0.05M in turn for 30 min, and the steps were repeated 3 times, and then irradiated under a 300W xenon lamp for 5 min to obtain 1-WO ₃ /Ag/AgCl thin film, 2-WO ₃ /Ag/AgCl thin film, 3-WO ₃ /Ag/AgCl thin film samples.

The prepared WO ₃ films, as well as 1-WO ₃ /Ag/AgCl films, 2-WO ₃ /Ag/AgCl films, and 3-WO ₃ /Ag/AgCl films were highly sensitive to methyl orange (MO) and rhodamine B (RhB). The degradation effect under visible light is shown in Figure 5. It can be seen from the figure that the catalytic performance of the modified photocatalyst has been greatly improved, and the 3-WO ₃ /Ag/AgCl thin film sample has the best catalytic performance , the degradation rate of MO and RhBd can reach 98% and 95%, respectively, while the degradation efficiency of 1-WO ₃ /Ag/AgCl film sample is only 79% and 81%, indicating that under the condition of 0.005M NaCl and AgNO ₃ solutions The effect of the prepared photocatalyst is not ideal. And it shows the electron movement process during the reaction process. Under illumination conditions, the photogenerated electrons on the conduction band of WO ₃ will combine with the holes on the Ag nanoparticles, and the plasmonic electrons on the Ag nanoparticles will enter the conduction band of AgCl. . Figure 6(a and b) are the degradation efficiencies of methyl orange (MO) and rhodamine B (RhB) for the 3-WO ₃ /Ag/AgCl thin film sample repeated five times, respectively. It can be seen from the figure that the fifth The effect of the second degradation is almost the same as that of the first degradation, indicating that the catalyst has good repeatability. Figure 6(c and d) are the SEM images of the 3-WO ₃ /Ag/AgCl thin film sample before and after repeated experiments, respectively. It can be seen that there is almost no change in the film on the glass surface before and after the repeated experiments, which further reflects the stability of the prepared photocatalyst. very good.

Claims (6)

1.WO₃The preparation method of the/Ag/AgCl photocatalytic film material is characterized by comprising the following specific steps:

step 1), dissolving polyvinyl alcohol and tungstic acid in hydrogen peroxide to obtain a mixed solution, coating the mixed solution on the surface of a clean glass substrate, spin-coating at the rotating speed of 500-800 rpm, drying, calcining at the temperature of 550-600 ℃ for 4-6 h, and naturally cooling and coating WO₃The glass substrate of (1);

step 2) will be coated with WO₃The glass substrate is sequentially soaked in NaCl and AgNO with the same concentration and the concentration of 0.02M to 0.05M₃Soaking in the solution for 30-60 min, and illuminating to obtain WO₃the/Ag/AgCl photocatalysis film material.

2. The preparation method according to claim 1, wherein in the step 1), the molar ratio of hydrogen peroxide to tungstic acid is 5-8: 1, the mass ratio of the tungstic acid to the polyvinyl alcohol is 2-3: 1.

3. the preparation method according to claim 1, wherein in the step 1), the spin coating time is 8-15 s.

4. The preparation method according to claim 1, wherein in the step 1), the drying temperature is 60-80 ℃ and the drying time is 1-2 h.

5. The preparation method according to claim 1, wherein in the step 1), the temperature rise rate during the calcination is 3 to 5 ℃/min.

6. The preparation method according to claim 1, wherein in the step 2), the illumination time is 5-10 min.

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