阅读说明：本技术 一种增强可见光响应的异质结构光催化剂及其制备方法 (Heterostructure photocatalyst for enhancing visible light response and preparation method thereof ) 是由 李文强 陈宁宁 詹美玲 张铎 黄朝晖 于 2020-04-17 设计创作，主要内容包括：本发明公开了一种CaBi<Sub>2</Sub>O<Sub>4</Sub>/BiOCl异质结复合光催化剂及其制备方法,属于光催化材料技术领域。包括以下步骤：将四水合硝酸钙溶于去离子水,五水合硝酸钡溶于稀硝酸,再将两者混合均匀。然后将稀氨水和混合溶液同时滴加入去离子水中,并不断搅拌,直至pH为6～8得白色悬浊液。将所得沉淀悬浮液搅拌陈化30min后,使用离心机进行固液分离得到白色沉淀,洗涤并稀释后置于反应釜中,于180～260℃条件下加热处理6h,经冷却干燥制得铋酸钙。将铋酸钙焙烧4h后,加入无水乙醇和去离子水超声处理。按不同摩尔分数加入所需体积盐酸,搅拌过滤洗涤干燥后,即可制得不同BiOCl含量的一系列CaBi<Sub>2</Sub>O<Sub>4</Sub>/BiOCl异质结光催化剂。该方法特点为制备温度低,工艺简单,所制得CaBi<Sub>2</Sub>O<Sub>4</Sub>/BiOCl异质结光催化剂增强了对可见光的吸收,对罗丹明B的降解性能也明显优于CaBi<Sub>2</Sub>O<Sub>4</Sub>。(The invention discloses a CaBi 2 O 4 A/BiOCl heterojunction composite photocatalyst and a preparation method thereof belong to the technical field of photocatalytic materials. The method comprises the following steps: dissolving calcium nitrate tetrahydrate in deionized water, dissolving barium nitrate pentahydrate in dilute nitric acid, and mixing the two solutions uniformly. And then, dropwise adding the diluted ammonia water and the mixed solution into deionized water at the same time, and continuously stirring until the pH value is 6-8 to obtain a white turbid liquid. Stirring and aging the obtained precipitate suspension for 30min, performing solid-liquid separation by using a centrifuge to obtain white precipitate, washing and diluting the white precipitate, placing the white precipitate in a reaction kettle, heating the white precipitate at 180-260 ℃ for 6h, and cooling and drying the white precipitate to obtain the calcium bismuthate. Roasting calcium bismuthate for 4 hours, and adding absolute ethyl alcohol and deionized water for ultrasonic treatment. Adding hydrochloric acid with required volume according to different mole fractions, stirring, filtering, washing and drying to obtain a series of CaBi with different BiOCl contents 2 O 4 /BiOCl heterojunctionA photocatalyst. The method is characterized by low preparation temperature, simple process and capability of preparing CaBi 2 O 4 the/BiOCl heterojunction photocatalyst enhances the absorption of visible light, and the degradation performance of the photocatalyst on rhodamine B is obviously superior to that of CaBi 2 O 4 。)

1. CaBi₂O₄The preparation method of the/BiOCl heterojunction photocatalyst material is characterized by comprising the following steps:

(1)CaBi₂O₄preparing powder material by adding Ca (NO) at a certain stoichiometric ratio₃)₂·4H₂Dissolving O in 50mL deionized water to obtain solution A, and dissolving Bi (NO)₃)₃·5H₂Dissolving O in 50mL of dilute nitric acid to obtain a solution B, mixing and stirring the solution A and the solution B for 30min to obtain a mixed solution C, adding the solution C and ammonia water together dropwise into 100mL of deionized water, continuously stirring to enable the pH value to be 6-8 to obtain a white precipitate suspension D, and continuously stirring and aging for 30 min; carrying out solid-liquid separation on the precipitate suspension D by using a centrifugal machine to obtain white precipitate, washing the white precipitate for 3-6 times by using deionized water, and diluting the precipitate to 100mL to obtain white precipitate suspension E; pouring the suspension E into a closed reaction kettle made of stainless steel and lined with white polytetrafluoroethylene for heat treatment at 180 ℃ for 6 hours, washing the suspension for 3-6 times by using deionized water after the treatment is finished and cooling the suspensionDrying in a drying oven at 50 deg.C for 10 hr to obtain white CaBi₂O₄A powder material;

(2) preparing a CaBi2O4/BiOCl heterojunction photocatalyst material for enhancing visible light response, weighing CaBi2O4 powder, adding 20mL of absolute ethyl alcohol and 10mL of deionized water, carrying out ultrasonic treatment for 30min, and stirring for 30 min; and then adding a concentrated hydrochloric acid solution, stirring for 1h at room temperature, filtering the obtained product, washing for 3-6 times by using absolute ethyl alcohol and deionized water, and drying for 6h at 80 ℃ to obtain the CaBi2O4/BiOCl heterojunction photocatalyst with enhanced visible light response.

2. The enhanced visible light response CaBi of claim 1₂O₄The preparation method of the/BiOCl heterojunction photocatalyst is characterized by comprising the following steps: the volume of the concentrated hydrochloric acid solution and the CaBi in the step (2)₂O₄The mass ratio of the powder material is 0.065-0.260mL:0.76 g.

3. The enhanced visible light response CaBi of claim 1₂O₄The preparation method of the/BiOCl heterojunction photocatalyst is characterized by comprising the following steps: the mass concentration of the concentrated hydrochloric acid solution in the step (2) is 36%.

Technical Field

The invention relates to the technical field of preparation of novel photocatalysts, in particular to a method for synthesizing CaBi by taking calcium nitrate tetrahydrate, bismuth nitrate pentahydrate, ammonia water, dilute nitric acid and deionized water as raw materials₂O₄A method for preparing a BiOCl heterojunction composite photocatalyst.

Background

The semiconductor photocatalysis technology is used for degrading organic pollutants, and people pay more and more attention to energy conservation and high efficiency. Wherein, TiO₂The method has the advantages of no toxicity, low price, easy obtainment, good thermal stability and the like, thereby arousing great interest in the early research of heterogeneous photocatalysis. But TiO 2₂The forbidden band width is large, and the utilization rate of visible light is low; in addition, TiO₂The high recombination rate of photogenerated carriers also results in a decrease in its photocatalytic efficiency. These inherent drawbacks limit their application in the field of photocatalysis.

In the course of research on novel photocatalytic materials, Bi-based compounds have received attention because of their special layered structure and appropriate size of forbidden band width. BiOCl is an indirect band gap semiconductor, has a highly anisotropic layered structure, and is very beneficial to the separation of photon-generated carriers; meanwhile, the photocatalyst has the advantages of no toxicity, low cost and the like, so that the photocatalyst attracts attention in the field of photocatalysis in recent years. Researches find that the activity of BiOCl for degrading methyl orange under ultraviolet light is even better than that of TiO₂. BiOCl is a wide bandgap semiconductor material, and the generated holes have strong oxidation capability due to the high valence band potential. However, the larger forbidden band width of BiOCl also limits the utilization of visible light, and constructing a heterojunction type photocatalyst by compounding the BiOCl with a narrow forbidden band semiconductor is a good method for improving the photocatalytic efficiency of the heterojunction type photocatalyst. Therefore, the search for good narrow bandgap semiconductors becomes the main research direction of the BiOCl photocatalytic material at present.

Disclosure of Invention

In view of the above technical problems in the prior art, it is an object of the present invention to provide a method for enhancing visible light responseCaBi₂O₄The preparation method of the/BiOCl heterojunction composite photocatalyst comprises the step of mixing CaBi₂O₄A heterostructure photocatalyst is constructed with BiOCl to improve the absorption of visible light and greatly enhance the utilization of solar energy; on the other hand, CaBi₂O₄The heterojunction formed after the heterojunction is compounded with BiOCl can promote the separation of photon-generated carriers and improve the photocatalytic efficiency. The problem of thereby the wide influence of BiOCl forbidden band is to visible light absorption among the prior art is solved.

In order to achieve the purpose, the technical scheme adopted by the invention for solving the technical problem is as follows: a preparation method of a heterostructure photocatalyst for enhancing visible light response comprises the following steps:

(1) weighing a certain amount of Ca (NO) according to a stoichiometric ratio₃)₂·4H₂O and Bi (NO)₃)₃·5H₂O, first Ca (NO)₃)₂·4H₂Dissolving O in deionized water to obtain transparent solution, and dissolving Bi (NO)₃)₃·5H₂O is dissolved in the freshly prepared dilute nitric acid solution.

(2) Mixing the two transparent solutions, and continuously stirring until the two transparent solutions are uniformly mixed. Taking a proper amount of deionized water as a base solution, and mixing the mixed solution with 3-4 mol/L ammonia water (NH)₃·H₂And O) dripping the two solutions into the base solution, continuously stirring to uniformly mix the precipitation reactants, controlling the dripping speed of the two solutions to keep the pH value between 6 and 8, and continuously stirring and aging the precipitation suspension obtained after the titration for 30 min.

(3) Separating the obtained suspension with a centrifuge, washing the obtained white precipitate with deionized water and anhydrous ethanol to remove NH⁴⁺And NO^3-And repeating the washing for 4-6 times. Diluting the precipitate after washing and centrifugal separation to a certain concentration to obtain white precipitate suspension, then putting the suspension into a closed reaction kettle made of stainless steel and lined with white polytetrafluoroethylene for heat treatment at 160-200 ℃ for 6-8 h, and cooling and drying after the treatment to obtain CaBi₂O₄White powder.

(4) Preparing the mass fraction of36% hydrochloric acid, and storing in shade for later use. Accurately weighing a certain amount of CaBi₂O₄And (3) roasting the white powder at a certain temperature for 4 hours, adding 20mL of absolute ethyl alcohol and 10mL of primary distilled water, carrying out ultrasonic treatment for 30min, and stirring at room temperature for 30 min. Respectively according to Bi³⁺With Cl^-The molar ratio is 1: 0.00,1: 0.25,1: 0.5,1: 0.75 addition of the desired volume (0.000, 0.065, 0.130, 0.195mL) of hydrochloric acid [ preparation of pure BiOCl requires addition of sufficient (0.26mL) hydrochloric acid]The mixture was stirred at room temperature for 1 hour. After the reaction is finished, filtering the obtained product, washing the product for a plurality of times by using absolute ethyl alcohol and deionized water in sequence, and drying the product for 6 hours at the temperature of 80 ℃ to obtain CaBi with different BiOCl contents₂O₄a/BiOCl heterojunction photocatalyst.

(4) 5mg/L of rhodamine B is used as an organic pollutant, and a set of equipment which is used for separating a photocatalyst from a pollutant solution and can circularly and uninterruptedly carry out photocatalytic degradation reaction is adopted. The device reactor is divided into two parts, and the upper part and the lower part are connected through frosted openings, so that the rhodamine B solution is prevented from overflowing. The light source adopts a parallel visible light source, can provide stable photon energy, and enables the photocatalyst to generate photo-generated electrons and holes. After the visible light is irradiated for 70min, the degradation rate of the photocatalyst on rhodamine B reaches about 90%.

The invention has the beneficial effects that:

the invention adopts the common hydrothermal synthesis method to prepare CaBi₂O₄the/BiOCl heterostructure photocatalyst has lower forbidden band width and higher visible light absorption response. The low forbidden band width reduces the transmission distance of the photoproduction electron holes, improves the separation efficiency of the photoproduction electron holes, reduces the recombination rate, improves the photon utilization rate due to high visible light absorption response, improves the electron hole pair generation rate, and greatly improves the photocatalytic activity under visible light. The catalyst prepared by the method has good stability and stable chemical property.

Drawings

FIG. 1 shows the visible light response CaBi prepared by the present invention₂O₄SEM scanning electron microscope image of/BiOCl heterojunction photocatalyst shows that after HCl is added,in CaBi₂O₄The two structures are closely overlapped, so that the structure is not only favorable for adsorbing reactants, but also favorable for effectively separating photoproduction electrons from holes, and plays a role of two-dimensional photocatalysis.

FIG. 2 shows that the prepared CaBi can respond to light₂O₄SEM partial enlarged view of/BiOCl heterojunction photocatalyst.

Detailed Description

The present invention will be described in detail below with reference to examples to enable those skilled in the art to better understand the present invention, but the present invention is not limited to the following examples.