CN108031481B

CN108031481B - Ultrathin bismuth oxyhalide nanosheet photocatalyst stripped by silver intercalation and preparation method thereof

Info

Publication number: CN108031481B
Application number: CN201711380362.8A
Authority: CN
Inventors: 刘平; 王瑶珠; 冯文辉; 张璐璐; 王凯强; 王波
Original assignee: Fuzhou University
Current assignee: Fuzhou University
Priority date: 2017-12-20
Filing date: 2017-12-20
Publication date: 2019-12-31
Anticipated expiration: 2037-12-20
Also published as: CN108031481A

Abstract

The invention discloses an ultrathin Bi prepared by a silver intercalation stripping method₁₂O₁₇Cl₂A nano-sheet photocatalyst and application thereof belong to the field of photocatalysis. By using Ag⁺And Cl^‑The Ag is self-assembled in ethanol water solution under strong action force⁺Insert block Bi₁₂O₁₇Cl₂[ Bi ] of₁₂O₁₇]²⁺And [ Cl₂]^2‑Interlaminar and photoreduction of Ag⁺Converted into Ag simple substance, and the bulk Bi is formed along with nucleation and growth of the Ag simple substance between layers₁₂O₁₇Cl₂The nano-sheets are gradually stripped into ultrathin nano-sheets. The preparation method has the advantages of simple and convenient operation, low raw material cost, low energy consumption, realization of large-scale preparation and the like, and belongs to a green synthesis technology.

Description

Ultrathin bismuth oxyhalide nanosheet photocatalyst stripped by silver intercalation and preparation method thereof

Technical Field

The invention belongs to the field of photocatalysis, and particularly relates to ultrathin Bi prepared through silver intercalation stripping₁₂O₁₇Cl₂A nano-sheet photocatalyst, a preparation method and application thereof.

Background

With the rapid development of economy in China, the problems of environmental deterioration and energy shortage are increasingly highlighted. The two problems are solved, and the urgent needs of realizing sustainable development, improving the life quality of people and guaranteeing the national safety are met. The photocatalytic technology is considered to be one of the ideal solar energy conversion technologies in water treatment, air purification, water decomposition for hydrogen production, CO₂The method has potential advantages in the fields of reduction, artificial photosynthesis and the like.

Two-dimensional nanomaterials are a new class of materials with infinite planar dimensions, which can be considered as materials obtained by thinning a three-dimensional crystal down to the thickness of one or several atomic layers. Due to the unique thickness dimension and structural characteristics, not only can the intrinsic properties of the material be enhanced, but also new characteristics which are not possessed by bulk phase materials may be generated.

The photocatalytic redox reaction is carried out at the surface, so that the exposed surface structure of the semiconductor material has a decisive effect on its photocatalytic activity. The two-dimensional nano material has the characteristics of high specific surface area, high exposure proportion of active sites, extremely small migration distance of bulk photon-generated carriers and the like, and has potential application prospect in the aspect of photocatalytic application.

The preparation methods of the laminar two-dimensional nano-material reported so far mainly comprise a mechanical stripping method, a liquid-phase ultrasonic stripping method and an intercalation stripping method. Among them, the mechanical peeling method has low yield and is difficult to control in size; the liquid phase peeling method also has disadvantages such as low peeling efficiency and difficulty in controlling the thickness. The intercalation stripping method has relatively high yield, and the synthesized nano sheet has controllable thickness. The most widely used intercalation and exfoliation method is lithium intercalation and exfoliationLi J, Zhan G, Yu Y, et al. Superior visible light hydrogen evolution of Janus bilayer junctions via atomic-level charge flow steering[J]. Nature communications, 2016, 7.) However, the lithium intercalation reagent is usually a metal organic compound, and such a compound is very active and is very reactive with water and oxygen, which results in severe reaction conditions. Therefore, there is a need to find more suitable intercalating species, andsilver intercalation exfoliation rules may solve these problems well.

Disclosure of Invention

The invention aims to provide an ultrathin Bi prepared by silver intercalation aiming at the defects of the prior art₁₂O₁₇Cl₂A method of nano-sheet material.

In order to solve the above purpose, the invention adopts the following technical scheme:

(1) preparation of bulk Bi₁₂O₁₇Cl₂Nano-sheet

Adding BiCl at room temperature₃Adding into weakly acidic ethanol aqueous solution, adding polyethylene glycol 4000, dissolving completely, adding into strongly basic ethanol aqueous solution dropwise to obtain mixed solution, stirring, transferring into polytetrafluoroethylene reaction kettle, heating to 80 deg.C ~ 160 deg.C, maintaining for 2 ~ 5 h, naturally cooling to room temperature, washing with deionized water and anhydrous ethanol for several times, centrifuging, precipitating, collecting, and vacuum drying at 60 ~ 80 deg.C;

(2) preparation of ultra-thin Bi₁₂O₁₇Cl₂Nano-sheet

The block Bi obtained in the step (1)₁₂O₁₇Cl₂The nano-sheet is ultrasonically dispersed in ethanol water solution, and then AgNO is subjected to shading condition₃The aqueous ethanol solution was added dropwise, stirred at room temperature for 0.5 ~ 2 h, and then illuminated (lambda)>= 420 nm) for 0.5 ~ 2 h, centrifugally separated, washed by deionized water, and dried in vacuum to obtain ultrathin Bi₁₂O₁₇Cl₂A nanosheet photocatalyst;

the volume ratio of ethanol to water in the ethanol water solution is 1: 1;

the weakly acidic ethanol aqueous solution in the step (1) is an ethanol aqueous solution adjusted by dilute HCl, and the pH =4 ~ 6;

the strongly alkaline ethanol aqueous solution in the step (1) is an ethanol aqueous solution adjusted by NaOH or KOH, and has the pH =12 ~ 14.

Ultrathin Bi prepared in step (2)₁₂O₁₇Cl₂The mass fraction of silver in the nanosheets is 0.1% ~ 1%.

Block Bi₁₂O₁₇Cl₂The thickness of the nanoplatelets is 20 ~ 40 nm.

Ultra-thin Bi₁₂O₁₇Cl₂The thickness of the nanosheets was 3 ~ 4 nm.

The invention provides the ultrathin Bi₁₂O₁₇Cl₂Nanosheet photocatalyst and ultrathin Bi prepared by preparation method₁₂O₁₇Cl₂The application of the nanosheet photocatalyst in degrading rhodamine B. The application comprises the following steps: the ultra-thin Bi₁₂O₁₇Cl₂Mixing and adsorbing the nanosheet photocatalyst and the rhodamine B solution under a light-proof condition; the mixed solution is irradiated under a xenon lamp of 300W (lambda)>= 420 nm) for 5-60 min to finish the degradation of rhodamine B.

The innovation points of the invention are as follows: the invention firstly proposes that the method for preparing the ultrathin Bi by adopting silver intercalation stripping₁₂O₁₇Cl₂The method not only realizes thickness regulation, but also successfully introduces silver elementary substance between the nanosheets, and under the coupling action of the two factors, the ultrathin Bi is obtained₁₂O₁₇Cl₂The photocatalytic performance of the nanosheets is comparable to bulk Bi₁₂O₁₇Cl₂The nano-sheet is greatly improved.

Compared with the prior art, the invention has the advantages that:

(1) the invention firstly utilizes Ag⁺And Cl^-Under the condition of strong force, Ag is prepared by self-assembly technology in ethanol water solution⁺Insert block Bi₁₂O₁₇Cl₂Nanosheet [ Bi ]₁₂O₁₇]²⁺And [ Cl₂]^2-Interlaminar and photoreduction of Ag⁺Converted into Ag simple substance, Bi grows along with nucleation of the Ag simple substance between layers₁₂O₁₇Cl₂The interlayer spacing of the nano-sheets is increased, and the Van der Waals force between the layers is weakened, so that the Bi can be stripped₁₂O₁₇Cl₂The function of the nano-sheet. The preparation method has the advantages of simple and convenient operation, low cost of raw materials, low energy consumption, realization of large-scale preparation and the like, and belongs to a green synthesis technology;

(2) the ultrathin Bi of the invention₁₂O₁₇Cl₂The nano-sheet photocatalyst has excellent photocatalytic effect, and the ultrathin Bi is obtained under the same conditions₁₂O₁₇Cl₂The nanosheet photocatalyst catalyzes and degrades 87.2 percent of rhodamine B within 20 min, and the block Bi₁₂O₁₇Cl₂The nano-sheet photocatalyst only catalyzes and degrades 38.0 percent within 20 min.

Drawings

FIG. 1 shows bulk Bi synthesized in example 1₁₂O₁₇Cl₂Nanosheet (BOC), ultra-thin Bi₁₂O₁₇Cl₂Field emission scanning electron microscopy (FE-SEM) of nanoplatelets (U-BOC).

FIG. 2 shows bulk Bi synthesized in example 1₁₂O₁₇Cl₂Nanosheet (BOC), ultra-thin Bi₁₂O₁₇Cl₂Atomic Force Microscopy (AFM) of nanoplatelets (U-BOC).

FIG. 3 shows bulk Bi synthesized in example 1₁₂O₁₇Cl₂Nanosheet (BOC), ultra-thin Bi₁₂O₁₇Cl₂X-ray powder diffraction Pattern (XRD) of the nanoplatelets (U-BOC).

FIG. 4 shows bulk Bi synthesized in example 1₁₂O₁₇Cl₂Nanosheet (BOC), ultra-thin Bi₁₂O₁₇Cl₂A rate diagram of photocatalytic degradation of rhodamine B by nanosheet (U-BOC).

Detailed Description

In order to more clearly and completely describe the present invention, some embodiments will be described in detail below with reference to the accompanying drawings.

Example 1

Preparation:

the first step is as follows: preparation of bulk Bi₁₂O₁₇Cl₂Nanosheet (BOC)

(1) Preparing a reaction precursor solution: 2.5 mmol of BiCl at room temperature₃Dissolving in 25 mL of weakly acidic ethanol aqueous solution (pH = 5), adding 1 g of polyethylene glycol 4000, and completely dissolvingAfter decomposition, 25 mL of strongly basic ethanol aqueous solution (pH = 13) is added dropwise, and the mixture is fully stirred for 1 h to form a reaction precursor solution;

(2) hydrothermal reaction: transferring the obtained precursor solution into a polytetrafluoroethylene reaction kettle with the capacity of 100 mL, heating to 120 ℃, and preserving heat for 3 hours;

(4) washing and collecting the precipitate: naturally cooling the product to room temperature, washing with deionized water and absolute ethyl alcohol for several times, centrifuging, collecting precipitate, and vacuum drying at 60 deg.C to obtain block Bi₁₂O₁₇Cl₂Nanosheets.

The second step is that: preparation of ultra-thin Bi of Ag intercalation₁₂O₁₇Cl₂Nanosheet (U-BOC)

The block Bi obtained in the first step₁₂O₁₇Cl₂The nano-sheet is dispersed in 50 mL ethanol water solution by ultrasonic, and 50 mL AgNO is added under the condition of keeping out of the sun₃Adding 90 mg/L ethanol aqueous solution dropwise, stirring for 2 h, placing under a xenon lamp equipped with a 420 nm optical filter for illumination for 1 h, centrifugally separating the obtained product, washing with deionized water, and vacuum drying at 60 ℃ to obtain Ag intercalated ultrathin Bi₁₂O₁₇Cl₂Nanosheets.

The application comprises the following steps:

weighing 30 mg of ultrathin Bi₁₂O₁₇Cl₂Adding the nanosheet photocatalyst into 60 mL of 5 mg/L rhodamine B solution, stirring and adsorbing for 1 h under a dark condition, providing a visible light source by using a xenon lamp provided with a 420 nm optical filter, and researching the degradation condition of rhodamine B. As shown in FIG. 4, under the same conditions, ultra-thin Bi₁₂O₁₇Cl₂The nanosheet photocatalyst catalyzes and degrades 87.2 percent of rhodamine B within 20 min, and Bi₁₂O₁₇Cl₂The nano-sheet photocatalyst only catalyzes and degrades 38.0 percent within 20 min.

Example 2

The bulk Bi obtained in example 1₁₂O₁₇Cl₂Nanosheets and ultrathin Bi₁₂O₁₇Cl₂The nanosheets were respectively subjected to field emission scanning electron microscope characterization, and the results are shown in fig. 1. It can be seen that through silver insertionAfter layer treatment, Bi₁₂O₁₇Cl₂The thickness of the nano-sheet is obviously changed, and the thickness of the ultrathin nano-sheet is within 10 nm.

Example 3

The bulk Bi obtained in example 1₁₂O₁₇Cl₂Nanosheets and ultrathin Bi₁₂O₁₇Cl₂And nanosheets, each subjected to atomic force microscopy characterization, as shown in fig. 2. From the figure, it can be seen that bulk Bi₁₂O₁₇Cl₂The thickness of the thick nano-sheet is between 20 ~ 40 nm, and the thickness of the nano-sheet obtained after silver intercalation treatment is about 3 ~ 4 nm₁₂O₁₇Cl₂Nanosheets.

Example 4

The bulk Bi obtained in example 1₁₂O₁₇Cl₂Nanosheets and ultrathin Bi₁₂O₁₇Cl₂The nanosheets were analyzed by X-ray diffraction, and the results are shown in fig. 3. Proves that the method for stripping silver intercalation provided by the invention does not change Bi₁₂O₁₇Cl₂The crystal form, but the peak intensity of the {0012} plane is obviously enhanced, probably because the {0012} plane is more exposed in the thinning process of the nanosheet, the crystal plane orientation is changed.

The above description is only for the purpose of illustrating the present invention and is not intended to limit the scope of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be covered by the present invention without creative efforts.

Claims

1. Ultrathin Bi stripped by silver intercalation₁₂O₁₇Cl₂The preparation method of the nanosheet photocatalyst is characterized by comprising the following steps of: by using Ag⁺And Cl^-The Ag is self-assembled in ethanol water solution under strong action force⁺Insert block Bi₁₂O₁₇Cl₂[ Bi ] of₁₂O₁₇]²⁺And [ Cl₂]^2-Interlaminar and photoreduction of Ag⁺Converted into Ag simple substance, and the bulk Bi is formed along with nucleation and growth of the Ag simple substance between layers₁₂O₁₇Cl₂The nano sheets are gradually stripped into ultrathin nano sheets; the method comprises the following two steps:

(1) preparation of bulk Bi₁₂O₁₇Cl₂Nano-sheet

2.5 mmol of BiCl₃Adding the mixture into 25 mL of weakly acidic ethanol aqueous solution, then adding 1 g of polyethylene glycol 4000, after completely dissolving, dropwise adding 25 mL of strongly basic ethanol aqueous solution to obtain mixed solution, uniformly stirring, transferring the mixed solution into a polytetrafluoroethylene reaction kettle, and carrying out hydrothermal reaction; naturally cooling the obtained product to room temperature, washing the product with deionized water and absolute ethyl alcohol for multiple times respectively, centrifugally precipitating, collecting and drying the precipitate;

(2) preparation of ultra-thin Bi₁₂O₁₇Cl₂Nano-sheet

The block Bi obtained in the step (1)₁₂O₁₇Cl₂The nano-sheets are ultrasonically dispersed in 50 mL ethanol water solution, and then AgNO is subjected to shading₃Dropwise adding an ethanol water solution, stirring at room temperature and illuminating to strip the block into nanosheets; the product is washed by deionized water after centrifugal separation and dried in vacuum to prepare the ultrathin Bi₁₂O₁₇Cl₂A nanosheet photocatalyst;

the pH value of the weak acidic ethanol aqueous solution in the step (1) is 4 ~ 6;

the pH value of the strong alkaline ethanol aqueous solution in the step (1) is 12 ~ 14;

ultra-thin Bi₁₂O₁₇Cl₂The thickness of the nano-sheet is 3 ~ 4 nm, the hydrothermal reaction temperature in the step (1) is 80 ℃, ~ 160 ℃, the hydrothermal reaction time is 2 ~ 5 h, and the ultrathin Bi prepared in the step (2)₁₂O₁₇Cl₂The mass fraction of silver in the nanosheets is 0.1% ~ 1%.

2. The ultra-thin Bi of claim 1 stripped from silver intercalation₁₂O₁₇Cl₂The preparation method of the nanosheet photocatalyst is characterized by comprising the following steps of: the volume ratio of ethanol to water in the ethanol water solution is 1: 1.

3. The ultra-thin Bi of claim 1 stripped from silver intercalation₁₂O₁₇Cl₂The preparation method of the nanosheet photocatalyst is characterized by comprising the following steps of: step (1) Block Bi₁₂O₁₇Cl₂The drying temperature of the nano-sheets is 60 ℃ and ~ 100 ℃ is 100 ℃.

4. The ultra-thin Bi of claim 1 stripped from silver intercalation₁₂O₁₇Cl₂The preparation method of the nanosheet photocatalyst is characterized by comprising the following steps of: step (2) ultra-thin Bi₁₂O₁₇Cl₂The light wavelength of the nanosheet is 200 nm ~ 700 nm during the nanosheet peeling operation, and the peeling time is 0.5-3 h.