阅读说明：本技术 一种氧化钨/氧化铋网-片复合材料及制备方法与用途 (Tungsten oxide/bismuth oxide net-sheet composite material and preparation method and application thereof ) 是由 陈敏 解仲凯 姜德立 李娣 孟素慈 徐菁 于 2019-10-24 设计创作，主要内容包括：本发明涉及一种氧化钨/氧化铋网-片复合材料及制备方法与用途,属于材料制备和光催化技术领域。本发明通过采用原位合成的方法制备了具有化学键异质结的Bi<Sub>2</Sub>O<Sub>3</Sub>/WO<Sub>3</Sub>光催化剂。该样品的合成是在反应进行到一半时终止,形成复合型光催化剂。该复合型光催化剂原料廉价,且合成方法简单,所制备的复合型光催化剂具有稳定的理化性质,无毒等优点。其光催化还原CO<Sub>2</Sub>活性高,生产过程绿色环保,既达到环境友好,又为可持续发展生产新能源提供了新思路,有望工业化生产。(The invention relates to a tungsten oxide/bismuth oxide net-sheet composite material, a preparation method and application thereof, belonging to the technical field of material preparation and photocatalysis. The invention prepares Bi with a chemical bond heterojunction by adopting an in-situ synthesis method 2 O 3 /WO 3 A photocatalyst. The synthesis of the sample is terminated when the reaction has progressed halfway, forming a composite photocatalyst. The composite photocatalyst has the advantages of cheap raw materials, simple synthesis method, stable physicochemical property, no toxicity and the like. Photocatalytic reduction of CO 2 The activity is high, the production process is green and environment-friendly, the environment is protected, a new idea is provided for sustainable development and production of new energy, and the method is expected to be applied to industrial production.)

1. The tungsten oxide/bismuth oxide net-sheet composite material is characterized by comprising a two-dimensional ultrathin structure Bi₂O₃Nanosheet and WO₃Composition of nano-mesh screen, WO₃Nanowire mesh and Bi₂O₃The nano sheets are connected by chemical bonds to form an in-situ heterojunction favorable for charge transmission.

2. The preparation method of the tungsten oxide/bismuth oxide net-sheet composite material according to claim 1, which comprises the following steps: weighing bismuth nitrate, sodium tungstate and hexadecyl trimethyl ammonium bromide, dissolving the bismuth nitrate, sodium tungstate and hexadecyl trimethyl ammonium bromide in deionized water, stirring by a stirrer, pouring the mixed solution into a polytetrafluoroethylene reaction kettle, placing the reaction kettle in a drying oven, carrying out hydrothermal reaction at 180 ℃, stopping the hydrothermal reaction when the hydrothermal reaction is carried out for 12 hours, and obtaining an intermediate transition state product WO₃/Bi₂O₃And the composite photocatalyst is obtained by centrifugally washing a sample by using deionized water and absolute ethyl alcohol and finally drying the sample to obtain the tungsten oxide/bismuth oxide net-sheet composite material.

3. The method of claim 2, wherein the stoichiometric ratio of bismuth to tungsten atoms is 2: 1.

4. the method of claim 2, wherein cetyl trimethylammonium bromide is added in an amount of 0.025 g; the stirring time of the stirrer is 30 min.

5. Use of a tungsten oxide/bismuth oxide mesh-sheet composite material according to claim 1 for photocatalytic reduction of carbon dioxide.

Technical Field

The invention relates to a tungsten oxide/bismuth oxide net-sheet composite material, a preparation method and application thereof, belonging to the technical field of material preparation and photocatalysis.

Background

CO realization by renewable solar energy₂Photocatalytic reduction is an important means to alleviate the problems of greenhouse effect, fuel shortage, and the like. Photocatalytic reduction of CO₂Can bring huge environmental protection and resource regeneration benefits to people. At present, TiO₂、g-C₃N₄ZnO, etc. have been widely reported. However, most of them have the disadvantages of high recombination rate of photogenerated carriers and no response to visible light. Therefore, it is of great significance to develop a photocatalyst with low visible light response and photocarrier recombination rate.

The interfaces of different semiconductors are connected by chemical bonds to promote rapid separation of charges, defined as a heterojunction, whose effect is the built-in electric field from the atomic thin interface. Research has shown that heterojunctions reduce the recombination rate of photo-generated electron holes. Chemical bond in-situ heterojunctions composed of different ultra-thin 2D materials have attracted a wide interest compared to conventional heterojunction materials. Bi₂WO₆Is prepared from [ BiO]⁺-[WO₄]^2--[BiO]⁺A typical Aurivillius phase oxide of composition, [ BiO]⁺Monomolecular layer with [ WO₄]^2-The monolayers are tightly connected by chemical bonds. Meanwhile, different monomolecular layers are easily stacked together by van der waals force, the number of reaction sites is reduced, and the carrier recombination rate is increased, resulting in a decrease in activity. On the basis, the development of a photocatalyst with more catalytic active centers and chemical bond in-situ heterojunction is urgently needed to achieve the purposes of high activity and high stability. However, research on photocatalysts having these characteristics is still lacking at present.

To date, some studies have employed strong chemical bonds to prevent monolayer film stacking. To prevent [ BiO]⁺The monolayer films are stacked together and have been studied by attaching the surfactant CTAB to [ BiO ]]⁺A single film surface such that [ BiO]⁺Large amount of CTA on the surface of monolayer film⁺，[BiO]⁺CTA of monolayer film surface⁺Can prevent [ BiO]⁺Deposition between single-layer films to form Bi having an ultra-thin structure₂WO₆Nanosheets. However,in Bi₂WO₆In the nano-sheet with sandwich molecular layer structure, when excited by visible light, two sides [ BiO ]]⁺Electrons of the monolayer film will be transferred to the intermediate WO₄ ^2-The single-layer film has higher separation rate of photon-generated carriers. And [ BiO ]]⁺-WO₄ ^2--[BiO]⁺Both sides of (1) [ BiO ]]⁺The monolayers all have the same coulomb force, which comes from the intervening WO₄ ^2-Attraction of the monolayer. { [ BiO]⁺-WO₄ ^2-And { WO } and { WO₄ ^2--[BiO]⁺The attractive force of W atoms is weakened by the interaction between the W atoms, so that the migration rate of photon-generated carriers is slow, and the carriers are easy to recombine. In addition, CO₂The reduction reaction sites are distributed only in Bi₂WO₆Intermediate WO₄ ^2-The reduction performance is poor at the layer edge position. The aim of the research is to prepare an asymmetric structure photocatalyst, a large number of active sites can be exposed out of the catalyst, and different ultrathin monomolecular layers are directly connected through chemical bonds to form an in-situ heterojunction which is tightly connected and is beneficial to charge transmission.

Bi with chemical bond heterojunction is prepared by adopting in-situ synthesis method₂O₃/WO₃A photocatalyst. The synthesis of the sample is terminated when the reaction has progressed halfway, forming a composite photocatalyst. The composite photocatalyst has the advantages of cheap raw materials, simple synthesis method, stable physicochemical property, no toxicity and the like. Photocatalytic reduction of CO₂The activity is high, the production process is green and environment-friendly, the environment is protected, a new idea is provided for sustainable development and production of new energy, and the method is expected to be applied to industrial production.

Disclosure of Invention

The invention aims to provide a simple WO (WO) two-dimensional mesh screen synthesized by a one-step hydrothermal method₃/Bi₂O₃A method for preparing a nano-sheet composite semiconductor material.

The invention is realized by the following technologies:

by forming a stable sandwich structure Bi₂WO₆Of two-dimensional ultrathin nanosheetsDuring the hydrothermal reaction, the reaction is terminated and WO is formed in the intermediate transition state of the reaction₃/Bi₂O₃A composite photocatalyst. And by adding a cationic surfactant CTAB, a two-dimensional WO with an ultrathin structure is formed₃Mesh screen and Bi₂O₃Nanosheets.

The invention is realized by the following steps:

synthesis of WO₃/Bi₂O₃: weighing bismuth nitrate, sodium tungstate and hexadecyl trimethyl ammonium bromide, dissolving the bismuth nitrate, sodium tungstate and hexadecyl trimethyl ammonium bromide in deionized water, stirring by a stirrer, pouring the mixed solution into a polytetrafluoroethylene reaction kettle, placing the reaction kettle in an oven, and carrying out 24-hour hydrothermal reaction at 180 ℃ to obtain Bi with a sandwich structure₂WO₆If the hydrothermal reaction is terminated when the reaction is carried out for 12 hours, the intermediate transition state product WO can be obtained₃/Bi2O₃And after the reaction of the composite photocatalyst is finished, the sample is centrifugally washed by deionized water and absolute ethyl alcohol. Finally, the sample was dried.

The stoichiometric ratio of bismuth to tungsten atoms is 2: 1.

cetyl trimethylammonium bromide was dosed in an amount of 0.025 g.

The stirring time of the stirrer is 30 min.

The method comprises the following steps of analyzing the morphology and structure of a product by using an X-ray diffractometer (XRD), a Transmission Electron Microscope (TEM) and a high-resolution transmission electron microscope (HRTEM), irradiating and reducing carbon dioxide by using a xenon lamp to perform a photocatalytic activity experiment, determining the type of the reduced product by using the CEAULIGHT GC-7920 gas chromatography retention time, and comparing the actual measurement peak area with the standard peak area to determine the efficiency of reducing carbon dioxide so as to evaluate the performance of the photocatalytic reduction of carbon dioxide.

Compared with the prior art, the prepared Bi with the two-dimensional ultrathin structure₂O₃Nanosheet and WO₃And (3) a nano-mesh screen, wherein a large number of synergetic unsaturated Bi atoms and W atoms are exposed on the surface of the nano-mesh screen as active sites. Bi₂O₃CTA of surfaces⁺Inhibition of Bi₂O₃The stacking between the single-layer films,bi for forming ultrathin structure₂O₃Nanosheets. And a symmetrical sandwich structure Bi₂WO₆In contrast, WO₃/Bi₂O₃Is free from Bi₂O₃The charge competition between the single layers can obtain high-efficiency and quick photon-generated carrier separation efficiency. The photocatalyst not only has double active centers (cooperating with unsaturated Bi atoms and a large number of exposed W atoms), but also has a strong chemical bond in-situ heterojunction, and is essentially different from a mechanical composite photocatalyst. A synergistic effect can be formed between the double sites, and the redox capability is improved. Meanwhile, the heterojunction synthesized in situ has high efficiency of electron hole separation rate. In general, the experiment provides reference and guidance for researching an intermediate transition state system of the multi-metal oxide and forming the composite metal oxide semiconductor photocatalyst with multi-site and high activity.

Drawings

FIG. 1 shows WO prepared₃/Bi₂O₃XRD diffraction pattern of the composite material. It can be seen from the figure that the diffraction peak of the composite photocatalyst corresponds to the monomer WO₃(JCPDS NO.83-0951) and Bi₂O₃(JCPDSNO.71-0147). It can be seen that the composite nano photocatalytic material has been successfully prepared, and the composite sample has high crystallinity and no impurities.

FIG. 2 shows WO prepared₃/Bi₂O₃Transmission electron microscope photo and high resolution transmission electron microscope photo of the composite material, (a, b, c) are WO₃/Bi₂O₃The pictures of the transmission electron microscope of the sample under different scales show that the composite photocatalyst is successfully prepared, and the mesh screen and the pieces are tightly connected; (d, e, f) is WO₃/Bi₂O₃High resolution TEM image with WO clearly visible₃And Bi₂O₃And lattice stripes show the successful preparation of the composite photocatalyst.

FIG. 3 shows WO prepared₃/Bi₂O₃XPS energy spectrum of the composite material, and further analyzing the element composition and chemical state of the sample. (a) Monomer Bi₂O₃Has a binding energy of 158.1eV and 163.5eV, respectively, while the characteristic peaks of WBC-12h and WBC-24h are located at 159.1eV and 164.5eV, respectively. The reason why the binding energy of Bi is increased is that Bi atoms are bound to surface Br atoms, and WBC-12h and WBC-24h (Bi)₂WO₆) Have the same binding energy. (b) W4 f_5/2And W4 f_7/2The shoulder peaks (37.6eV and 35.4eV) appeared at higher binding energies, and WBC-12h and WBC-24h had the same binding energy. The WBC-12h and WBC-24h have the same binding energy of W and Bi, which shows that the WBC-12h and Bi₂WO₆With the same heterogeneous interface (chemical bond interface). Thus, WO having a chemical bond in-situ heterojunction was successfully prepared₃/Bi₂O₃A composite photocatalyst.

FIG. 4 shows photocatalytic CO₂Reduction activity diagram, (a) monomer WO₃And monomer Bi₂O₃And a composite photocatalyst WO₃/Bi₂O₃Graph of CO yield of; (b) monomer WO₃And monomer Bi₂O₃And a composite photocatalyst WO₃/Bi₂O₃CO generation rate map of (1). The WO₃/Bi₂O₃The CO generation rate of the composite photocatalyst after reaction for two hours reaches 35 mu mol g^-1The CO generation rate is as high as 16.65 mu mol g^-1·h^-1The photocatalytic activity being of the monomer WO₃And Bi₂O₃10 times of the catalyst.

Detailed Description