CN115636440B - In+ doped (001) crystal plane exposed oxygen vacancies BiOCl nanosheet and preparation method thereof - Google Patents

Abstract

The invention discloses an In ⁺ doped (001) crystal plane exposed oxygen vacancy-containing BiOCl nanosheet visible light photocatalyst and a preparation method thereof. The method uses bismuth nitrate, indium nitrate and potassium chloride as precursors (the molar ratio of indium element to bismuth element is 1:100-5:100), and a mixed solution of ethylene glycol and water with a volume ratio of 1:8-1:3 is used as a solvent. The method reacts at 160 ^° C-180 ^° C for 10-30 hours to obtain In ³⁺ doped (001) crystal surface exposed BiOCl nanosheets. The obtained sample is irradiated with ultraviolet light for 1-4 hours to obtain In ⁺ doped (001) crystal surface exposed oxygen vacancy BiOCl nanosheets, the size of which is less than 200 nm and the thickness is 15-25 nm. In the (001) crystal surface exposed BiOCl nanosheets prepared by the method of the invention, In ⁺ and oxygen vacancies coexist, and the indium element replaces the position of the bismuth element, and the insecticide sodium pentachlorophenol can be efficiently degraded under visible light. The method of the invention has simple process, low cost, environmental friendliness, high yield, is suitable for large-scale production, meets actual production needs, and has great application potential.

Description

In+ doped (001) crystal plane exposed oxygen vacancies BiOCl nanosheet and preparation method thereof

Technical Field

The invention belongs to the technical field of photocatalytic material preparation, and in particular relates to In ⁺ doped (001) crystal plane exposed oxygen vacancy-containing BiOCl nanosheets and a preparation method thereof.

Background technique

BiOCl has attracted much attention due to its unique layered structure. It is used in the treatment of liquid and gas phase pollutants due to its wide bandgap, strong redox ability, and high photocatalytic activity. However, its wide bandgap reduces the utilization rate of sunlight, limiting its application. In recent years, studies have found that metal ion doping can regulate the band structure of BiOCl and improve its visible light photocatalytic performance.

For example, BiOCl doped with manganese, tungsten, cobalt and iron was prepared by hydrolysis method [Applied Surface Science 258 (2011) 247-253], solvothermal method [Phys. Chem. Chem. Phys. 16 (2014) 21349-21355], hydrothermal method [Applied Catalysis B: Environmental 221 (2018) 320-328] and combustion method [Separation and Purification Technology 162 (2016) 114-119] and its visible light catalytic activity was studied. Other BiOCl doped with alkali metals and rare earth metals [Chinese invention patent CN107597150A] has also been widely studied. Jingfa Li et al. calculated that indium-doped BiOCl can make its conduction band potential more negative [Chemical Physics Letter 705 (2018) 31-37], thereby improving the conduction band electron reduction efficiency. However, the increased bandgap width is not conducive to improving the visible light efficiency. Therefore, there has been no report on indium-doped BiOCl visible light catalysts so far.

Summary of the invention

In order to solve the above problems, the present invention adopts a solvothermal method of a mixed system of ethylene glycol and water to prepare In ³⁺ doped (001) crystal surface exposed BiOCl nanosheets, and obtains In ⁺ doped (001) crystal surface exposed oxygen vacancy BiOCl nanosheet visible light photocatalyst through ultraviolet irradiation at room temperature. The In ⁺ doped (001) crystal surface exposed oxygen vacancy BiOCl nanosheet prepared by the present invention can efficiently degrade high concentration of insecticide sodium pentachlorophenol under visible light. After half an hour of visible light irradiation, 20 mg/L of sodium pentachlorophenol can be almost completely degraded, and the degradation rate is 6.8 times that of undoped indium (001) crystal surface exposed oxygen vacancy BiOCl nanosheet and 27.4 times that of In ³⁺ doped (001) crystal surface exposed BiOCl nanosheet. The present invention has simple process, low cost, and is environmentally friendly, which is convenient for further expansion of production.

To achieve the above object, the preparation method of the In ⁺ doped (001) crystal plane exposed oxygen vacancies BiOCl nanosheets of the present invention adopts the following technical means, including the following steps:

Preparation method of In ⁺ doped (001) crystal plane exposed oxygen vacancies containing BiOCl nanosheets,

1) Bismuth nitrate, indium nitrate and potassium chloride are added to a mixed solution of water and ethylene glycol to form a suspension under magnetic stirring, wherein the volume ratio of water to ethylene glycol is 1:8 to 1:3;

2) placing the suspension obtained in step 1) in a polytetrafluoroethylene reactor and allowing it to stand in an atmosphere of 160 ^° C to 180 ^° C for 10 to 30 hours to form a precipitate;

3) washing and drying the precipitate obtained in step 2) to obtain In ³⁺ doped (001) crystal surface exposed BiOCl nanosheets;

4) The sample obtained in step 3) is irradiated with ultraviolet light to obtain In ⁺ doped (001) crystal plane exposed oxygen vacancies containing BiOCl nanosheets.

As a further improvement of the In ⁺ doped (001) crystal plane exposed oxygen vacancies BiOCl nanosheets of the present invention: in the step 1), the molar ratio of indium element to bismuth element is 1:100 to 5:100, the total volume is 40 mL, and the sum of the moles of bismuth nitrate and indium nitrate is equal to the mole of potassium chloride.

As a further improvement of the In ⁺ doped (001) crystal plane exposed oxygen vacancies BiOCl nanosheets of the present invention: the ultraviolet irradiation in the step 4) is carried out at room temperature, the sample is within 10 cm from the light source and continuously irradiated with ultraviolet light emitted by a 300-watt mercury lamp for 1 to 4 hours, and the ultraviolet light wavelength range of the mercury lamp is 350 nm to 450 nm, and the peak wavelength is 365 nm.

The invention discloses an In ⁺ doped (001) crystal plane exposed BiOCl nanosheet containing oxygen vacancies, characterized in that the In3 ⁺ doped (001) crystal plane exposed BiOCl nanosheet is irradiated with ultraviolet light to form an In ⁺ doped (001) crystal plane exposed BiOCl nanosheet containing oxygen vacancies, the size of which is less than 200 nm and the thickness is 15 to 25 nm.

The In ⁺ doped (001) crystal plane exposed oxygen vacancies in the BiOCl nanosheets as visible light photocatalysts.

Beneficial Effects

Compared with the prior art, the present invention has the following beneficial effects:

First, the In ⁺ doped (001) crystal surface exposed oxygen vacancies BiOCl nanosheets prepared by the present invention have a size of less than 200 nm and a thickness of 15 to 25 nm, which is about half the size of P doped BiOCl nanosheets prepared by similar methods. The specific surface area is increased, which is beneficial to improving its photocatalytic activity. In the In ⁺ doped (001) crystal surface exposed oxygen vacancies BiOCl nanosheets prepared by the present invention, the indium element replaces the bismuth element in the lattice, and 20 mg/L of sodium pentachlorophenol can be almost completely degraded in half an hour under visible light, and the degradation rate is 6.8 times that of the undoped indium (001) crystal surface exposed oxygen vacancies BiOCl nanosheets, and 27.4 times that of the In ^{3 +} doped (001) crystal surface exposed BiOCl nanosheets.

Second, in the preparation of the In ⁺ doped (001) crystal plane exposed oxygen vacancies BiOCl nanosheets described in the present invention, the volume ratio of water to ethylene glycol is set to 1:8 to 1:3. After a large number of experiments, it is found that if the volume ratio of ethylene glycol is higher than this range, it is easy to generate a graded spherical structure of BiOCl, while if it is lower than this range, the size of the BiOCl sheet will be significantly increased, which will reduce the specific surface area and photocatalytic activity of the sample. In addition, the presence of ethylene glycol also avoids the formation of In(OH) ₃ precipitation, ensuring that indium is doped into BiOCl in the form of ions. At the same time, when the molar ratio of indium element to bismuth element is higher than 5:100, impurities are easily generated.

Third, the In ⁺ doped (001) crystal planes prepared by the present invention expose oxygen vacancies in the BiOCl nanosheets, realizing the visible light photocatalytic activity of indium doped BiOCl, and greatly improving the efficiency of degrading high-concentration water pollutants such as the pesticide sodium pentachlorophenol, providing a new photocatalytic material for environmental water pollution control.

Fourthly, the ultraviolet irradiation for 1 to 4 hours described in the present invention generates oxygen vacancies in BiOCl and simultaneously excites the intrinsic energy band of BiOCl to promote the generation of photogenerated electrons, which reduces In ³⁺ to In ⁺ . The presence of In ⁺ further improves the separation efficiency of electrons and holes in the visible light catalytic reaction and improves the visible light catalytic activity.

Fifth, the entire process is simple and easy to control, consumes less energy, has high yield, and low cost, which meets actual production needs.

Sixth, the raw materials of the present invention are cheap and easy to obtain, the reaction conditions are mild, the energy consumption is low, and the equipment requirements are low. The coexistence of In ⁺ and oxygen vacancies in the (001) crystal surface exposed BiOCl nanosheets greatly improves the separation efficiency of electrons and holes under visible light, can quickly degrade high-concentration water pollutants, and has good application prospects.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is an XRD diffraction pattern of the In ³⁺ doped (001) crystal plane exposed BiOCl nanosheets prepared in Example 2, the In ⁺ doped (001) crystal plane exposed oxygen vacancies BiOCl nanosheets prepared in Example 4, and the (001) crystal plane exposed oxygen vacancies BiOCl nanosheet samples prepared in Example 1.

FIG. 2 is the full XPS spectrum of the samples obtained in Example 2 and Example 4 and the high-resolution energy spectrum of In 3d.

FIG3 is TEM, SAED and HRTEM images of the samples obtained in Example 2 (3a, 3b, 3c) and Example 4 (3d, 3e, 3f).

FIG. 4 is an EPR spectrum of the sample obtained in Example 4.

FIG5 is a graph of the UV-visible absorption spectra of the In ³⁺ doped (001) crystal plane exposed BiOCl nanosheets prepared in Example 2 and the In ⁺ doped (001) crystal plane exposed oxygen vacancies BiOCl nanosheets prepared in Example 4.

FIG6 is a comparison of the degradation effects of the pesticide sodium pentachlorophenol under visible light by the In ⁺ doped (001) crystal plane exposed oxygen vacancies BiOCl nanosheets obtained in Example 4, the In3 ⁺ doped (001) crystal plane exposed BiOCl nanosheets prepared in Example 2, and the (001) crystal plane exposed oxygen vacancies BiOCl nanosheets prepared in Example 1.

FIG. 7 is a comparison of the photocatalytic activities of the In ⁺ -doped (001) crystal plane-exposed oxygen vacancies-containing BiOCl nanosheet samples prepared in Examples 3, 4, 5 and 6.

Detailed ways

The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. This embodiment is based on the technical solution of the present invention and provides a detailed implementation method.

The invention discloses an In ⁺ doped (001) crystal surface exposed BiOCl nanosheet and a preparation method thereof, and an application of the In ⁺ doped (001) crystal surface exposed BiOCl nanosheet as a photocatalyst to efficiently degrade high-concentration water pollutants such as the pesticide sodium pentachlorophenol, thereby providing a new photocatalytic material for environmental water pollution control.

In the present application, Example 1 and Example 2 respectively prepare BiOCl nanosheets with (001) crystal plane exposed oxygen vacancies and In ³⁺ doped (001) crystal plane exposed BiOCl nanosheets, which are used as experimental control groups for In ⁺ doped (001) crystal plane exposed BiOCl nanosheets to be protected by the present patent application.

Example 1

The preparation method of the (001) crystal plane exposed oxygen vacancies BiOCl nanosheets in this embodiment is to add bismuth nitrate and potassium chloride (wherein the molar ratio of bismuth nitrate to potassium chloride is 1:1) to a mixed solution of water and ethylene glycol (the volume ratio of ethylene glycol to water is 1:8) to form a suspension under magnetic stirring, and the volume of the suspension is 40 mL; the suspension is allowed to stand for 20 hours in an atmosphere of 160 ^o C to form a precipitate, and the obtained precipitate is dried to obtain the (001) crystal plane exposed BiOCl nanosheets, and then irradiated under ultraviolet light (300-watt mercury lamp) for 2 hours to obtain the (001) crystal plane exposed oxygen vacancies BiOCl nanosheets.

Example 2

In this embodiment, the preparation method of In ⁺ doped (001) crystal plane exposed oxygen vacancies BiOCl nanosheets is to add bismuth nitrate, indium nitrate and potassium chloride (wherein the molar ratio of bismuth nitrate to indium nitrate is 1:100) to a mixed solution of water and ethylene glycol (the volume ratio of ethylene glycol to water is 1:8), and form a suspension under magnetic stirring, the volume of the suspension is 40 mL; stand in an atmosphere of 160 ^o C for 20 hours to form a precipitate, and the obtained precipitate is dried to obtain In3 ⁺ doped (001) crystal plane exposed BiOCl nanosheets.

Example 3

In this embodiment, the preparation method of In ⁺ doped (001) crystal surface exposed oxygen vacancies BiOCl nanosheets is as follows: bismuth nitrate, indium nitrate and potassium chloride (wherein the molar ratio of bismuth nitrate to indium nitrate is 1:100, and the sum of the molar ratio of bismuth nitrate and indium nitrate is equal to the molar ratio of potassium chloride) are added to a mixed solution of water and ethylene glycol (the volume ratio of ethylene glycol to water is 1:8), and a suspension is formed under magnetic stirring, and the volume of the suspension is 40 mL; the suspension is allowed to stand for 20 hours in an atmosphere of 160 ^o C to form a precipitate, and the obtained precipitate is dried to obtain In ³⁺ doped (001) crystal surface exposed BiOCl nanosheets, and then irradiated under ultraviolet light (300-watt mercury lamp) for 1 hour to obtain In ⁺ doped (001) crystal surface exposed oxygen vacancies BiOCl nanosheets. Specifically, the sample ultraviolet irradiation process is carried out at room temperature, and the sample is within 10 cm from the light source and continuously irradiated under the ultraviolet light source emitted by a 300-watt mercury lamp for 1 hour to obtain In 3+ doped (001) crystal surface exposed oxygen vacancies BiOCl nanosheets. ⁺ doped (001) planes expose BiOCl nanosheets containing oxygen vacancies.

Example 4

In this embodiment, the preparation method of In ⁺ doped (001) crystal plane exposed oxygen vacancies BiOCl nanosheets is as follows: bismuth nitrate, indium nitrate and potassium chloride (wherein the molar ratio of bismuth nitrate to indium nitrate is 1:100, and the sum of the molar ratio of bismuth nitrate and indium nitrate is equal to the molar ratio of potassium chloride) are added to a mixed solution of water and ethylene glycol (the volume ratio of ethylene glycol to water is 1:8), and a suspension is formed under magnetic stirring, and the volume of the suspension is 40 mL; the suspension is allowed to stand for 20 hours in an atmosphere of 160 ^o C to form a precipitate, and the obtained precipitate is dried to obtain In ³⁺ doped (001) crystal plane exposed BiOCl nanosheets, and then the sample is exposed to an ultraviolet light source within 10 cm at room temperature, and continuously irradiated under ultraviolet light (300-watt mercury lamp) for 2 hours to obtain In ⁺ doped (001) crystal plane exposed oxygen vacancies BiOCl nanosheets.

Example 5

In this embodiment, the preparation method of In ⁺ doped (001) crystal plane exposed oxygen vacancies BiOCl nanosheets is to add bismuth nitrate, indium nitrate and potassium chloride (wherein the molar ratio of bismuth nitrate and indium nitrate is 5:100, and the sum of the molar amounts of bismuth nitrate and indium nitrate is equal to the molar amount of potassium chloride) to a mixed solution of water and ethylene glycol (the volume ratio of ethylene glycol to water is 1:5), and form a suspension under magnetic stirring, and the volume of the suspension is 40 mL; the suspension is allowed to stand for 20 hours in an atmosphere of 160 ^o C to form a precipitate, and the obtained precipitate is dried to obtain In ³⁺ doped (001) crystal plane exposed BiOCl nanosheets, and then the sample is exposed to an ultraviolet light source within 10 cm at room temperature, and illuminated under ultraviolet light (300-watt mercury lamp) for 4 hours to obtain In ⁺ doped (001) crystal plane exposed BiOCl nanosheets.

Example 6

In this embodiment, the preparation method of In ⁺ doped (001) crystal plane exposed oxygen vacancies BiOCl nanosheets is to add bismuth nitrate, indium nitrate and potassium chloride (wherein the molar ratio of bismuth nitrate to indium nitrate is 5:100, and the sum of the molar ratio of bismuth nitrate and indium nitrate is equal to the molar ratio of potassium chloride) to a mixed solution of water and ethylene glycol (the volume ratio of ethylene glycol to water is 1:3), and form a suspension under magnetic stirring, and the volume of the suspension is 40 mL; the suspension is allowed to stand for 20 hours in an atmosphere of 180 ^o C to form a precipitate, and the obtained precipitate is dried to obtain In ³⁺ doped (001) crystal plane exposed BiOCl nanosheets, and then the sample is exposed to an ultraviolet light source within 10 cm at room temperature, and irradiated under ultraviolet light (300-watt mercury lamp) for 4 hours to obtain In ⁺ doped (001) crystal plane exposed BiOCl nanosheets.

The present invention uses the above embodiment to prepare In ⁺ doped (001) crystal plane exposed oxygen vacancies containing BiOCl nanosheets and conduct data analysis:

As shown in Figure 1, the XRD diffraction analysis of various BiOCl nanosheet samples is carried out. By comparing the data with the standard card, it can be seen that the diffraction peaks of the two samples in the figure are consistent with the standard spectrum of BiOCl (JCPDS No: 6-249), and there is no other impurity phase. The diffraction peaks of the BiOCl samples doped with In ³⁺ and In ⁺ in the XRD graph move to the high angle direction, proving that In replaces Bi and enters the BiOCl lattice.

The presence of indium can be seen from the full spectrum in Figure 2. By comparing the high-resolution energy spectrum of In 3d, it can be found that the binding energy of In 3d in the In ⁺ doped (001) crystal plane exposed oxygen vacancies BiOCl nanosheets is about 0.4 electron Ford lower than that in the In ³⁺ doped (001) crystal plane exposed BiOCl nanosheets, confirming that the indium element in the sample prepared in Example 4 exists in the In ⁺ state.

In Figure 3, it can be seen from TEM that the size of the prepared In ³⁺ doped (001) crystal plane exposed BiOCl nanosheets and In ⁺ doped (001) crystal plane exposed oxygen vacancies BiOCl nanosheets are both less than 200 nm and the thickness is about 20 nm. From the HRTEM and SAED images, it can be seen that the upper and lower surfaces of the nanosheets prepared in Example 2 and Example 4 are both (001) crystal planes.

The EPR spectrum in Figure 4 confirms the existence of oxygen vacancies in the In ⁺ doped (001) crystal plane exposed oxygen vacancies in the BiOCl nanosheets after UV irradiation.

It can be seen from the UV-visible absorption spectrum of Figure 5 that compared with the In ³⁺ doped (001) crystal plane exposed BiOCl nanosheets, although the energy band of the In ⁺ doped (001) crystal plane exposed oxygen vacancies BiOCl nanosheets has no obvious change, it has a strong impurity energy level absorption phenomenon in the visible light range.

Figure 6 shows a comparison of the effects of BiOCl nanosheets on the degradation of sodium pentachlorophenol under visible light. The photocatalyst activity was tested by degrading sodium pentachlorophenol under visible light, where a 500 W xenon lamp was used as the light source, and a filter was added to filter out light with a wavelength less than 420 nm, thereby obtaining visible light. The amount of catalyst used was 0.05 g, the concentration of the sodium pentachlorophenol solution was 20 mg/L, and the volume was 50 mL. It can be seen from the figure that after half an hour of visible light irradiation, the In ⁺ doped (001) crystal surface exposed oxygen vacancies BiOCl nanosheets in Example 4 can almost completely degrade sodium pentachlorophenol, and its degradation rate is 6.8 times that of the (001) crystal surface exposed oxygen vacancies BiOCl nanosheets in Example 1, and 27.4 times that of the In ³⁺ doped (001) crystal surface exposed BiOCl nanosheets in Example 2.

The photocatalytic activities of the In ⁺ doped (001) crystal plane exposed oxygen vacancies BiOCl nanosheet samples prepared in Examples 3, 4, 5 and 6 are compared (as shown in FIG7 ). It can be seen that the photocatalytic activity of the sample prepared by ultraviolet irradiation for 1 hour in Example 3 is the weakest, and the efficiency of photocatalytic degradation of the pesticide sodium pentachlorophenol under visible light of the samples irradiated with ultraviolet light for more than 2 hours is comparable. Within the range of the ratio of ethylene glycol to water, the range of the ratio of bismuth to indium, and the range of the thermal reaction temperature of dissolution given in this example, the changes in these three conditions have no obvious effect on the catalytic activity.

The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims (2)

1. A method for preparing In ⁺ doped (001) crystal plane exposed oxygen vacancies BiOCl nanosheets, characterized by comprising the following steps: 1) adding bismuth nitrate, indium nitrate and potassium chloride to a mixed solution of water and ethylene glycol to form a 40 mL suspension under magnetic stirring, wherein the volume ratio of water to ethylene glycol is 1:8 to 1:3; 2) placing the suspension obtained in step 1) in a polytetrafluoroethylene reaction kettle, and standing in an atmosphere of 160° C. to 180° C. for 10 to 30 hours to form a precipitate; 3) washing and drying the precipitate obtained in step 2) to obtain an In ³⁺ doped (001) crystal plane exposed BiOCl nanosheet sample; 4) The sample obtained in step 3) is subjected to ultraviolet light to obtain In ⁺ doped (001) crystal plane exposed oxygen vacancies containing BiOCl nanosheets with a size of less than 200 nm and a thickness of 15 to 25 nm; wherein the sum of the amounts of bismuth nitrate and indium nitrate in step 1) is equal to the amount of potassium chloride, and the molar ratio of indium element to bismuth element is 1:100 to 5:100; In step 4), the ultraviolet irradiation is carried out at room temperature, the sample is within 10 cm from the light source and is continuously irradiated for 1 to 4 hours under ultraviolet light emitted by a 300-watt mercury lamp, the wavelength range of the ultraviolet light of the mercury lamp is 350 nm to 450 nm, and the peak wavelength is 365 nm. 2. An application of the In ⁺ doped (001) crystal plane exposed oxygen vacancies BiOCl nanosheet as claimed in claim 1, characterized in that: the In ⁺ doped (001) crystal plane exposed oxygen vacancies BiOCl nanosheet is used as a visible light catalyst.