阅读说明：本技术 一种铁酸铋纤维状热释电催化剂的制备方法及应用 (Preparation method and application of bismuth ferrite fibrous pyroelectric catalyst ) 是由 郝洪顺 胡宇彤 赵一睿 杨航 闵敬凯 侯红漫 张公亮 毕景然 闫爽 于 2021-08-16 设计创作，主要内容包括：本发明公开一种铁酸铋纤维状热释电催化剂的制备方法及应用,利用五水硝酸铋、九水硝酸铁为主要原料,溶解于有机溶剂中,并将PVP溶解于乙醇和DMF的混合溶液中,形成铁酸铋纤维的纺前溶液,将溶液置于注射器中,放至静电纺丝机上,由注射器喷出,锡纸收集、高温煅烧后得到铁酸铋纤维。在制备过程中控制纺前液配料比、静电纺丝电压、煅烧温度等工艺参数,制得铁酸铋纤维状热释电催化剂。本发明工艺流程简单,易操作,可重复性强,成本低,产物重复利用率高,是一种具有商业前景的制备方法。所制备的铁酸铋纤维在热释电催化杀菌和降解有机污染物及增强光催化等方面有重要的应用价值,在应用时可借助昼夜温差激发热释电效应,实现热释电催化,易于操作。(The invention discloses a preparation method and application of bismuth ferrite fibrous pyroelectric catalyst, which comprises the steps of dissolving bismuth nitrate pentahydrate and ferric nitrate nonahydrate serving as main raw materials in an organic solvent, dissolving PVP in a mixed solution of ethanol and DMF to form a solution before spinning of bismuth ferrite fibers, placing the solution in an injector, placing the solution on an electrostatic spinning machine, spraying the solution by the injector, collecting tin foil, and calcining at high temperature to obtain the bismuth ferrite fibers. And in the preparation process, technological parameters such as the proportioning ratio of the solution before spinning, electrostatic spinning voltage, calcination temperature and the like are controlled to prepare the bismuth ferrite fibrous pyroelectric catalyst. The invention has simple process flow, easy operation, strong repeatability, low cost and high product recycling rate, and is a preparation method with commercial prospect. The prepared bismuth ferrite fiber has important application values in the aspects of pyroelectric catalytic sterilization, organic pollutant degradation, photocatalysis enhancement and the like, can excite the pyroelectric effect by means of day and night temperature difference during application, realizes pyroelectric catalysis, and is easy to operate.)

1. The preparation method of the bismuth ferrite fibrous pyroelectric catalyst is characterized by comprising the following steps

a. Preparation of a solution before spinning: adding bismuth nitrate pentahydrate (Bi (NO)₃·5H₂O) and iron nitrate nonahydrate (Fe (NO)₃·9H₂O) dissolving the bismuth nitrate pentahydrate and the ferric nitrate nonahydrate in a 2-methoxy glycol solution, wherein the stoichiometric ratio of the bismuth nitrate pentahydrate to the ferric nitrate nonahydrate is 1.05-1.1: 1, dropwise adding ethylene glycol amine into the solution to adjust the pH value to be 3-5, then adding glacial acetic acid to control the viscosity of the solution, and then mechanically stirring the solution at room temperature for 2 hours to obtain a solution A; adding polyvinylpyrrolidone (PVP) into a mixed solution of N-N Dimethylformamide (DMF) and ethanol, and stirring for 1 hour to obtain a solution B; after the two solutions are uniformly mixed, slowly adding the solution A into the solution B, and after uniform mixing, forming BiFeO₃The solution before spinning of (1); the mass fraction of the spinning precursor solution is 13-15%.

b. Preparing bismuth ferrite fiber, namely preparing the BiFeO prepared in the step a₃The solution before spinning is moved into an injector, and BiFeO is obtained by an electrostatic spinning method₃The as-spun fiber of (a); the electrostatic spinning parameters are as follows: the spinning distance is 10-15 cm, the working voltage is 12-17V, and the advancing speed is 0.3-0.5 mL/h. The obtained BiFeO is subjected to₃Placing the nascent fiber in an oven for drying, and then calcining by a muffle furnace, wherein the calcining process parameters are as follows; the calcination temperature is 550-750 ℃, the heat preservation time is 1.5-2.5 h, and the atmosphere is air. After calcination, the mixture is naturally cooled to room temperature to finally obtain BiFeO₃A fiber.

2. The method according to claim 2, wherein the bismuth nitrate pentahydrate and the iron nitrate nonahydrate in step a are water-soluble salts, and anions in the salts are reacted and are not doped in the bismuth ferrite fiber.

3. The bismuth ferrite fiber-shaped pyroelectric catalyst prepared by the method according to any claim 1 to 2, characterized in that the bismuth ferrite fibers of the bismuth ferrite fiber-shaped pyroelectric catalyst are closely arranged together, the surfaces of the fibers are smooth and straight and have no fracture; the fiber diameter is about 100-400 nm;

the bismuth ferrite fibrous pyroelectric catalyst is respectively matched with BiFeO at diffraction angles of 2 theta 22.44 degrees, 31.80 degrees, 39.02 degrees, 45.79 degrees, 51.38 degrees, 56.47 degrees and 66.44 degrees₃The characteristic peaks of the (010), (110), (111), (020), (120), (121) and (220) crystal planes of the crystal face are matched.

4. Use of the bismuth ferrite fibrous thermoelectric catalyst of claim 3, wherein the BiFeO₃The fibrous catalyst is applied to pyroelectric catalytic sterilization, degradation of organic dye in dye wastewater and enhancement of photocatalysis.

5. Use of the bismuth ferrite fibrous thermoelectric catalyst of claim 4, wherein the BiFeO is₃The fibrous catalyst is used for treating wastewater containing rhodamine (RhB), and the treatment process is carried out under the condition of a certain temperature difference, wherein the temperature difference is 20-40 ℃.

6. Use of the bismuth ferrite fibrous thermoelectric catalyst according to claim 4, wherein the treatment is carried out under natural diurnal temperature differences.

Technical Field

The invention belongs to the technical field of novel functional materials, and particularly relates to a preparation method and application of a bismuth ferrite fibrous pyroelectric catalyst.

Background

At present, rapid development of industry and consumption of fossil fuel accelerate environmental pollution and energy dilemma. In order to alleviate the above two serious problems, some researchers have been dedicated to find methods and products for treating environmental sewage, such as photocatalytic, thermocatalytic, piezoelectric catalytic products, etc.

Unlike the above techniques, pyroelectric catalysis can be triggered by temperature fluctuations to generate thermally generated positive and negative charges for redox reactions. The temperature change causes a slight spatial movement of atoms in the crystal structure, resulting in a change in the polarization inside the pyroelectric body and an induced pyroelectric charge on the surface of the pyroelectric material. The perovskite substance is represented by a pyroelectric catalyst, and the general formula of the perovskite substance is ABX₃The smaller transition metal ion at the B site is located in the co-angular octahedron of the X anion, and the larger a site cation is a species having 12-fold coordination as X. CaTiO₃Is the first mineral found in this structural family. The space point group of the perovskite structure is Pm3m, and the perovskite oxide group has a flexible electronic structureDifferent physical and chemical properties are shown in different situations, including ferroelectric giant magnetoresistance, ion conductivity of protons, etc. BiFeO, one of the perovskite structures₃Not only has the rhombohedral perovskite structure, but also is a multiferroic substance. BiFeO₃Has an energy band gap of about 2.013eV, belongs to a semiconductor having a narrow band gap, and has an antiferromagnet property. BiFeO₃Is paid much attention for its superior properties such as good visible light absorption efficiency, spontaneous polarization, low cost and nontoxicity, and is commonly used for water decomposition and degradation of organic pollutants, but the conventional BiFeO₃The preparation method is prepared in a powder form, has the problems of large size and small specific surface area, and is easy to agglomerate during wastewater treatment, thereby seriously influencing the wastewater treatment effect.

Disclosure of Invention

The invention aims to provide a preparation method and application of a bismuth ferrite fibrous pyroelectric catalyst by using bismuth nitrate pentahydrate and ferric nitrate nonahydrate as main raw materials.

The technical scheme adopted by the invention is as follows:

the bismuth ferrite fibrous pyroelectric catalyst is prepared by electrostatic spinning and high temperature calcination method, and has a chemical composition of BiFeO₃。

a. Preparation of a solution before spinning: adding bismuth nitrate pentahydrate (Bi (NO)₃·5H₂O) and iron nitrate nonahydrate (Fe (NO)₃·9H₂O) dissolving in a 2-methoxy ethylene glycol solution, dropwise adding ethylene glycol amine into the solution to adjust the pH value, adding glacial acetic acid to control the viscosity of the solution, and mechanically stirring the solution at room temperature for 2 hours to obtain a solution A; adding polyvinylpyrrolidone (PVP) into a mixed solution of N-N Dimethylformamide (DMF) and ethanol, and stirring for 1 hour to obtain a solution B; after the two solutions are uniformly mixed, slowly adding the solution A into the solution B, and after uniform mixing, forming BiFeO₃The solution before spinning of (1);

b. preparing bismuth ferrite fiber, namely preparing the BiFeO prepared in the step a₃The solution before spinning is moved into an injector, and BiFeO is obtained by an electrostatic spinning method₃For the first birth ofFibers; the obtained BiFeO is subjected to₃Drying the nascent fiber in an oven, calcining the nascent fiber in a muffle furnace, naturally cooling the nascent fiber to room temperature after calcining, and finally obtaining BiFeO₃A fiber.

And (b) in the step a, the anions in the bismuth nitrate pentahydrate and the ferric nitrate nonahydrate can be removed after reaction, and are not doped in the bismuth ferrite.

In the step a, the stoichiometric ratio of bismuth nitrate pentahydrate to ferric nitrate nonahydrate is 1.05-1.1: 1, and the mass fraction of the spinning precursor solution is 13-15%.

And b, adding ethylene glycol amine to adjust the pH of the solution to 3-4 in the step a.

The electrostatic spinning parameters in the step b are as follows: the spinning distance is 10-15 cm, the working voltage is 12-17V, and the advancing speed is 0.3-0.5 mL/h.

The calcination process parameters in the step b are as follows: the calcining temperature is 550-750 ℃, the time is 1.5-2.5 h, and the atmosphere is air.

Bismuth ferrite fibers of the bismuth ferrite fiber-shaped pyroelectric catalyst are closely arranged together, the surfaces of the fibers are smooth and straight, and no fracture occurs; the fiber bundle diameter is small.

The bismuth ferrite fibrous pyroelectric catalyst is matched with characteristic peaks of (010), (110), (111), (020), (120), (121) and (220) crystal faces of BiFeO3 at diffraction angles 2 theta of 22.44 degrees, 31.80 degrees, 39.02 degrees, 45.79 degrees, 51.38 degrees, 56.47 degrees and 66.44 degrees respectively.

The BiFeO₃The fibrous catalyst is applied to pyroelectric catalytic sterilization, degradation of organic dye in dye wastewater and enhancement of photocatalysis.

The treatment process is carried out under the condition of a certain temperature difference, and the temperature difference is 20-40 ℃. Preferably, the method can be completed under the condition of natural temperature difference between day and night.

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

(1) the invention aims at the existing BiFeO₃The powder has large form size, small specific surface area and easy agglomeration, and the BiFeO is prepared by adopting the processes of electrostatic spinning and high-temperature calcination₃Fibrous pyroelectric catalysts formedThe fibrous product improves the specific surface area, does not agglomerate and obviously improves the wastewater treatment effect.

(2) The preparation method of the invention explores the optimized and reasonable preparation parameters, BiFeO₃The fibrous pyroelectric catalyst has high purity, the fiber surface is smooth and straight and can not agglomerate, meanwhile, organic matters on the fiber surface are volatilized and dispersed by high-temperature calcination, and the obtained product does not have any other impurity peak and has very good purity as seen by XRD. The pyroelectric catalytic film has obvious effects on the aspects of pyroelectric catalytic sterilization, organic pollutant degradation and photocatalysis enhancement, can excite the pyroelectric effect only by day and night temperature difference in industrial application, realizes pyroelectric catalysis, and is easy to operate.

(3) The invention adopts bismuth nitrate pentahydrate and ferric nitrate nonahydrate as main raw materials, and has the advantages of simple raw materials, low price, simple overall process and flow, easy control of reaction and strong repeatability.

Drawings

FIG. 1 BiFeO prepared by the invention₃XRD pattern of fibrous pyroelectric catalyst.

FIG. 2 BiFeO prepared by the invention₃SEM image of fibrous pyroelectric catalyst.

FIG. 3 BiFeO prepared by the invention₃And (3) a degradation diagram of the fibrous pyroelectric catalyst to the rhodamine B aqueous solution.

Detailed Description

The invention aims to provide a preparation method and application of a bismuth ferrite fibrous pyroelectric catalyst.

The bismuth ferrite fibrous pyroelectric catalyst is prepared by electrostatic spinning and a high-temperature calcination method, generates temperature difference through pyroelectric catalytic reaction, promotes the coupling of the required electrochemical oxidation reduction reaction and the pyroelectric effect, increases the value of thermal energy delta Q along with the increase of the temperature difference due to the fact that the delta Q is c.m.delta t, and is beneficial to the degradation of organic dyes. Meanwhile, BiFeO is caused₃The fibrous pyroelectric catalyst has smooth surface, is not easy to agglomerate and has good reusability; while pyroelectric catalysis can be realized industrially by means of day and night temperature difference. The method has simple preparation process and low cost of raw materials, and can be used for treating organic pollutantsThe method has good application prospect.

Example 1:

preparation of BiFeO by electrostatic spinning method₃Solution before spinning fiber:

2.43g of Bi (NO)₃·5H₂O and 2.02g Fe (NO)₃·9H₂Dissolving O in 10mL of 2-methoxy glycol solution, dropwise adding glycol amine into the solution to adjust the pH of the solution to 3.5, then adding 5mL of glacial acetic acid to control the viscosity of the solution, and then mechanically stirring the solution at room temperature for about 2 hours to obtain a solution A; adding 2g of polyvinylpyrrolidone into a mixed solution of 11g N-N dimethylformamide and ethanol, and stirring for 1 hour to obtain a solution B; after the two solutions are uniformly mixed, slowly adding the solution A into the solution B, and after uniform mixing, forming BiFeO₃The solution before spinning.

Example 2:

high-temperature calcination method for preparing BiFeO₃Fibrous pyroelectric catalyst:

BiFeO prepared in example 1₃The solution before spinning is moved into an injector, the distance between the needle head of the injector and a tinfoil collecting plate is set to be 10cm, the electrostatic spinning voltage is 12V, the advancing speed of the injector is 0.4mL/h, the environmental temperature and humidity in the spinning process are kept constant, and BiFeO is obtained₃The as-spun fiber of (a); the obtained BiFeO is subjected to₃Placing the nascent fiber in a 60 ℃ oven for drying, placing the dried fiber in a muffle furnace for calcining, setting the calcining temperature of the muffle furnace to 600 ℃, keeping the temperature for 2 hours, fully removing organic substances contained in the nascent fiber, and improving BiFeO₃The purity of the fiber is naturally cooled to room temperature after calcination, and BiFeO is finally obtained₃A fibrous pyroelectric catalyst.

FIG. 1 shows BiFeO₃As can be seen from fig. 1, the XRD patterns of the fibrous pyroelectric catalysts, when the diffraction peak positions were compared with the PDF #72-2035 standard card, were found to be respectively equal to BiFeO at diffraction angles 2 θ of 22.44 °, 31.80 °, 39.02 °, 45.79 °, 51.38 °, 56.47 ° and 66.44 ° of₃The characteristic peaks of the (010), (110), (111), (020), (120), (121) and (220) crystal planes of the crystal face are matched. BiFe can be determinedO₃The XRD spectrum of the fibrous pyroelectric catalyst does not have any other impurity peak, and the purity is good.

FIG. 2 shows BiFeO obtained after high-temperature calcination₃SEM image of the fibrous pyroelectric catalyst, from which BiFeO can be found₃The fibers are closely arranged together, the surfaces of the fibers are smooth and straight and are not broken; the diameter of the fiber bundle is very small, and the diameter of the fiber is about 220nm, which is caused by volatilization and dispersion of organic matters on the surface of the fiber after high-temperature calcination.

Application example 1:

BiFeO obtained as described above₃The fibrous pyroelectric catalyst is applied to treating organic pollutants in wastewater and degrading rhodamine (RhB) aqueous solution.

50mL of 5mg/L rhodamine B solution is taken, and 0.05g of BiFeO is added into the rhodamine B solution₃The fibrous pyroelectric catalyst is prepared through circulating the solution in cold water at 20 deg.c and hot water at 60 deg.c, and repeating every 10min while keeping the solution in dark. The supernatant of the solution was taken every 1h, and after centrifuging the supernatant at 8000r/min for 3min, the absorbance was measured by UV spectrometer at 554 nm.

Comparative application example 1:

BiFeO obtained as described above₃The fibrous pyroelectric catalyst is applied to treating organic pollutants in wastewater and degrading rhodamine (RhB) aqueous solution.

50mL of 5mg/L rhodamine B solution is taken, and 0.05g of BiFeO is added into the rhodamine B solution₃Fibrous thermoelectric catalyst, the solution was stirred in the dark. The supernatant of the solution was taken every 1h, and after centrifuging the supernatant at 8000r/min for 3min, the absorbance was measured by UV spectrometer at 554 nm.

FIG. 3 shows BiFeO₃A graph of degradation of rhodamine B aqueous solution by the fibrous pyroelectric catalyst. As can be seen from FIG. 3, BiFeO is present under the condition of pyroelectric catalysis₃The degradation of the fibrous thermoelectric catalyst to the rhodamine B aqueous solution is obviously higher than that under the dark stirring condition in the comparative application 1, and after the pyroelectric catalyst is used for 7 hours, BiFeO₃The degradation rate of the fibrous pyroelectric catalyst to rhodamine B water solution can reach 85.6 percent.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, changes and equivalent structural changes made to the above embodiment according to the technical spirit of the present invention still fall within the protection scope of the technical solution of the present invention.