Bi-deposited potassium niobate for synthesizing potassium bismuth niobate photocatalytic material and preparation method thereof

Abstract

The application discloses a kind of bismuth deposition potassium niobate synthesis potassium niobate bismuth photocatalytic material and preparation method thereof, comprising the following steps: step 1: by hydrothermal synthesis potassium niobate, bismuth nitrate is dissolved in solvent respectively to form A solution and B solution, ultrasonic or stirring 0.5-2.5h;Step 2: B solution is added to A solution to form mixed solution, ultrasonic or stirring 0.5-1.5h;Step 3: mixed solution in step 2 is transferred to hydrothermal reaction kettle, 150~250 ℃ under reaction 1~24h, after cooling, filtration, washing, drying, obtain potassium niobate bismuth photocatalytic material.The application is introduced by bismuth deposition surface defect such as oxygen vacancy, change the migration direction of photo-generated charge, reduce photo-generated charge recombination rate and expose more active sites, to accelerate the surface photocatalytic reaction.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photocatalysts, in particular to a bismuth-deposited potassium niobate photocatalyst material and a preparation method thereof. BACKGROUND

[0002] Photocatalysis is a way to realize the conversion of substances by using common light energy, such as water splitting to produce hydrogen, carbon dioxide reduction, organic matter decomposition and mineralization, and selective photosynthesis. The photocatalytic process can be roughly divided into three main steps: light energy absorption, photo-generated charge separation and surface reaction. Whether the photo-generated charges can be effectively separated directly restricts the efficiency of the entire photocatalytic process. Potassium niobate is a stable polar material. Since the positive and negative charge centers do not coincide, the built-in electric field of the polar photocatalyst provides a driving force for the separation of photo-generated electrons and holes, so that a high-efficiency photocatalyst can be obtained. At the same time, the layer-by-layer stacking mode in the potassium niobate crystal makes the crystal lattice easy to deform in the stacking direction, which brings the possibility of regulating the built-in electric field and improving the photocatalytic efficiency. However, due to the large difference in electronegativity between K-O and Nb-O, potassium niobate has a wide band gap of 3.06-3.24 eV, resulting in low light utilization efficiency in the ultraviolet region. The current feasible methods to improve the photocatalytic efficiency are to extend the light absorption range by semiconductor coupling, noble metal deposition and element doping, and to regulate the crystalline structure.

[0003] At present, constructing crystal defects such as element doping, vacancies and lattice distortion is the most effective method to regulate the band structure and photocatalytic activity of the material. At the same time, element doping has been proved to be an effective method to extend the light absorption to the visible light region. The doped elements are mainly exposed on the surface to avoid the formation of recombination centers of photo-generated charges in the interior of the material due to excessive doping elements. Through relevant calculations, it is proved that the metal elements with 3d or 4d orbitals such as bismuthate can significantly reduce the band gap of potassium niobate material. This is because the hybridization of Bi's 6s orbital and O's 2p orbital makes the VB of potassium niobate shift upwards, thereby reducing the band gap. In addition, doping also introduces surface defects such as oxygen vacancies, which can reduce the coordination around the atom and change the migration direction of photo-generated charges, reduce the recombination rate of photo-generated charges and expose more active sites, thereby accelerating the surface photocatalytic reaction. Therefore, by selecting appropriate doping elements and doping amounts, the main contradiction of improving the photocatalytic activity of potassium niobate can be solved, that is, reducing the band gap of the material to improve the light utilization rate while maintaining the photocatalytic activity of the material. SUMMARY

[0004] In view of the above problems, the present application provides a method,

[0005] A preparation method of a bismuth-deposited potassium niobate photocatalyst material, comprising the following steps:

[0006] Step 1: dissolve the potassium niobate and bismuth nitrate synthesized by the hydrothermal method into a solvent respectively to form solution A and solution B, and ultrasonic or stir for 0.5-2.5 hours;

[0007] Step 2: drop solution B into solution A to form a mixed solution, and ultrasonic or stir for 0.5-1.5 hours;

[0008] Step 3: transfer the mixed solution in step 2 to a hydrothermal reactor, and react at 150-250 DEG C for 1-24 hours, then filter, wash and dry to obtain the potassium bismuth niobate photocatalytic material.

[0009] Further, in step 1, the solvent is any one of water, ethylene glycol, ethanol and acetic acid.

[0010] Further, in step 1, the concentration of the potassium niobate in the solvent is 1000-6000 mg / L.

[0011] Further, in step 2, the mass ratio of the potassium niobate to the bismuth nitrate in the mixed solution is (1-10):(1-10).

[0012] Another aspect of the present application provides a potassium bismuth niobate photocatalytic material, and the micro-morphology of the potassium bismuth niobate photocatalytic material is 30 μm spherical, and the surface is hair line or needle-shaped.

[0013] The present application has the following beneficial effects:

[0014] 1. By using the hybrid of the 6s orbit of Bi and the 2p orbit of O, the VB of potassium niobate is moved up to reduce the band gap, and the light absorption range of the photocatalytic material is greatly improved.

[0015] 2. By depositing Bi to introduce surface defects such as oxygen vacancies, the migration direction of photo-generated charges is changed, the photo-generated charge recombination rate is reduced, and more active sites are exposed, thereby accelerating the surface photocatalytic reaction. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings described below only relate to some embodiments of the present application, but not limit the present application.

[0017] Figure 1 The micro-morphology schematic diagram of the potassium bismuth niobate photocatalytic material prepared in the embodiment 1 of the present application;

[0018] Figure 2 The micro-morphology schematic diagram of the potassium bismuth niobate photocatalytic material prepared in the embodiment 2 of the present application;

[0019] Figure 3The ultraviolet absorption curve schematic diagram of the potassium bismuth niobate photocatalytic material of the embodiment 1 of the present application and KNbO3 of the comparative example 1;

[0020] Figure 4 The fluorescence spectrum schematic diagram of the potassium bismuth niobate photocatalytic material of the embodiment 1 of the present application and KNbO3 of the comparative example 1;

[0021] Figure 5 The Zeta potential schematic diagram of the potassium bismuth niobate and potassium niobate of the present application;

[0022] Figure 6 The activity comparison schematic diagram of different catalysts for degrading polypropylene into CO; DETAILED DESCRIPTION

[0023] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme of the embodiments of the present application will be described clearly and completely below in combination with the drawings of the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the described embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without any creative effort belong to the scope of protection of the present application.

[0024] The present application will be further described below in combination with the drawings and embodiments.

[0025] A preparation method of a potassium bismuth niobate photocatalytic material synthesized by bismuth deposition of potassium niobate, comprising the following steps:

[0026] Step 1: potassium niobate and bismuth nitrate synthesized by a hydrothermal method are respectively dissolved in a solvent to form A solution and B solution, and ultrasonic or stirring is performed for 0.5-2.5 h.

[0027] The solvent is any one of water, ethylene glycol, ethanol and acetic acid; the concentration of the potassium niobate in the solvent is 1000-6000 mg / L.

[0028] Step 2: the B solution is added dropwise into the A solution to form a mixed solution, and ultrasonic or stirring is performed for 0.5-1.5 h.

[0029] The mass ratio of the potassium niobate to the bismuth nitrate in the mixed solution is (1-10):(1-10).

[0030] Step 3: the mixed solution in step 2 is transferred into a hydrothermal reaction kettle, and reaction is performed at 150-250 ℃ for 1-24 h, and then filtration, washing and drying are performed after cooling to obtain the potassium bismuth niobate photocatalytic material.

[0031] Embodiment 1

[0032] Step 1: 1.5g of potassium niobate and 0.15g of bismuth nitrate were respectively dissolved in 30mL of ethylene glycol solution and continuously stirred for 1h to obtain a potassium niobate solution and a bismuth nitrate solution.

[0033] Step 2: The bismuth nitrate solution was added to the potassium niobate solution to form a mixed solution, and the mass ratio of potassium niobate to bismuth nitrate was 10:1, and ultrasonic or stirring was performed for 0.5h.

[0034] Step 3: The mixed solution was poured into a hydrothermal reaction kettle, heated at 200℃ for 12h, and after natural cooling, filtration, washing and drying, a potassium bismuth niobate photocatalytic material was obtained.

[0035] Example 2

[0036] Step 1: 1.5g of potassium niobate and 0.15g of bismuth nitrate were respectively dissolved in 30mL of ethylene glycol solution and 30mL of deionized water and continuously stirred for 1h to obtain a potassium niobate solution and a bismuth nitrate solution.

[0037] Step 2: The bismuth nitrate solution was added to the potassium niobate solution to form a mixed solution, and the mass ratio of potassium niobate to bismuth nitrate was 10:1, and ultrasonic or stirring was performed for 0.5h.

[0038] Step 3: The mixed solution was poured into a hydrothermal reaction kettle, heated at 200℃ for 12h, and after natural cooling, filtration, washing and drying, a potassium bismuth niobate photocatalytic material was obtained.

[0039] Example 3

[0040] Step 1: 1.5g of potassium niobate and 0.15g of bismuth nitrate were respectively dissolved in 30mL of ethylene glycol solution and continuously stirred for 0.5h to obtain a potassium niobate solution and a bismuth nitrate solution.

[0041] Step 2: The bismuth nitrate solution was added to the potassium niobate solution to form a mixed solution, and the mass ratio of potassium niobate to bismuth nitrate was 10:10, and ultrasonic or stirring was performed for 1.5h.

[0042] Step 3: The mixed solution was poured into a hydrothermal reaction kettle, heated at 150℃ for 24h, and after natural cooling, filtration, washing and drying, a potassium bismuth niobate photocatalytic material was obtained.

[0043] Example 4

[0044] Step 1: 1.5g of potassium niobate and 0.15g of bismuth nitrate were respectively dissolved in 30mL of ethylene glycol solution and continuously stirred for 2.5h to obtain a potassium niobate solution and a bismuth nitrate solution.

[0045] Step 2: The bismuth nitrate solution was added to the potassium niobate solution to form a mixed solution, and the mass ratio of potassium niobate to bismuth nitrate was 1:10, and ultrasonic or stirring was performed for 1.5h.

[0046] Step 3: Pour the mixed solution into a hydrothermal reactor, heat at 250°C for 1 hour, and after natural cooling, filter, wash, and dry to obtain potassium bismuth niobate photocatalyst material.

[0047] Example 5

[0048] Step 1: Dissolve 1.5g of potassium niobate and 0.15g of bismuth nitrate in 30mL of ethylene glycol solution and stir continuously for 2.5h to obtain potassium niobate solution and bismuth nitrate solution.

[0049] Step 2: Add bismuth nitrate solution to potassium niobate solution to form a mixed solution. The mass ratio of potassium niobate to bismuth nitrate is 1:1. Sonicate or stir for 1.5 hours.

[0050] Step 3: Pour the mixed solution into a hydrothermal reactor, heat at 250°C for 1 hour, and after natural cooling, filter, wash, and dry to obtain potassium bismuth niobate photocatalyst material.

[0051] Comparative Example 1

[0052] KNbO3 was prepared by hydrothermal synthesis and used as a control sample without any modifications.

[0053] Figure 1 and Figure 2 These are microscopic morphology images of the potassium bismuth niobate photocatalyst materials synthesized from bismuth deposited potassium niobate prepared in Examples 1 and 2. As can be seen from the SEM images, the potassium bismuth niobate photocatalyst material exhibits a 30 μm spherical morphology with a fuzzy or needle-like surface. The spherical structure increases the contact area with waste polypropylene, providing more reaction sites. Figure 5 Analysis shows that the Zeta potential of potassium bismuth niobate is much higher than that of potassium niobate. The higher the absolute value of the Zeta potential, the more electrostatic forces cause ions with the same charge to repel each other, resulting in excellent dispersion stability of potassium bismuth niobate in aqueous solution.

[0054] Figure 3 The images show the UV absorption curves of potassium bismuth niobate synthesized by bismuth deposition in Example 1 and potassium bismuth niobate without bismuth deposition in Comparative Example 1. It can be seen that the UV absorption curve of potassium bismuth niobate after bismuth deposition is significantly higher than that of potassium niobate without bismuth deposition. This indicates that bismuth deposition can significantly increase the VBM (Vibration Bandwidth), thereby reducing the band gap of potassium niobate and broadening the absorption capacity of the photocatalytic material in the visible and infrared regions. This proves that elemental deposition is an effective means to improve the light utilization rate of materials.

[0055] Figure 4The fluorescence spectra of the bismuth-deposited potassium niobate of Example 1 and the non-bismuth-deposited potassium niobate of Comparative Example 1 are shown in the figure. It can be seen that the fluorescence peak of the bismuth-deposited potassium niobate is significantly lower than that of the non-bismuth-deposited potassium niobate, which indicates that the bismuth deposition widens the absorption capacity of the photocatalytic material in the visible and infrared regions, and the surface defects introduced promote the charge transfer of the bismuth-deposited potassium niobate photocatalytic material, further improving the separation efficiency of the photo-generated charges, effectively proving that the bismuth deposition not only widens the light absorption of the material, but also further improves the separation efficiency of the photo-generated charges, balancing the contradiction between the two.

[0056] The photocatalytic degradation of polypropylene was carried out under the same conditions using the two catalysts of Example 1 and Comparative Example 1, and the carbon monoxide generation rate was calculated. The two catalysts were the bismuth-deposited potassium niobate photocatalytic material of Example 1 and the non-deposited KNbO3 material of Comparative Example 1. The mass ratio of polypropylene to catalyst was 10 / 1, the 300W xenon lamp was the light source, and the photocatalytic degradation experiment was carried out for 6h. The gas generated during the degradation process was analyzed and quantified by gas chromatography. The experimental results are shown in the figure. Figure 6 It can be seen that the CO generation rate of the bismuth-deposited potassium niobate is significantly higher than that of the non-bismuth-deposited potassium niobate, which proves that the bismuth deposition can significantly improve the photocatalytic activity of the bismuth-deposited potassium niobate catalyst.

[0057] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical solution of the present application, and any simple modification, equivalent change and modification of the above embodiments based on the technical essence of the present application are still within the scope of the technical solution of the present application.

Claims

1. Application of a bismuth deposited potassium niobate synthetic potassium bismuth niobate photocatalytic material in photocatalytic degradation of polypropylene, characterized in that, The preparation method of the potassium bismuth niobate photocatalytic material comprises the following steps: Step 1: potassium niobate and bismuth nitrate synthesized by a hydrothermal method are respectively dissolved in a solvent to form A solution and B solution, and ultrasonic or stirring is performed for 0.5-2.5 h; Step 2: the B solution is added dropwise into the A solution to form a mixed solution, and ultrasonic or stirring is performed for 0.5-1.5 h; Step 3: the mixed solution in step 2 is transferred into a hydrothermal reaction kettle, and reaction is performed at 150-250 DEG C for 1-24 h, and after cooling, filtration, washing and drying, the potassium bismuth niobate photocatalytic material is obtained; The micro-morphology of the potassium bismuth niobate photocatalytic material is 30 μm spherical, and the surface is hair line or needle-like.

2. The application of bismuth deposited potassium niobate synthesized potassium niobate bismuth photocatalytic material in photocatalytic degradation of polypropylene according to claim 1, characterized in that, In step 1, the solvent is any one of water, ethylene glycol, ethanol and acetic acid. 3.The application of the bismuth deposited potassium niobate synthesized potassium niobate bismuth photocatalytic material in photocatalytic degradation of polypropylene according to claim 1, characterized in that, In step 1, the concentration of the potassium niobate in the solvent is 1000-6000 mg / L.

4. The use of the bismuth-deposited potassium niobate synthesized potassium niobate bismuth photocatalytic material in photocatalytic degradation of polypropylene according to claim 1, characterized in that, In step 2, the mass ratio of the potassium niobate to the bismuth nitrate in the mixed solution is 1-10:1-10.

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