CN107413325B - A kind of rare earth/carbon co-doped flexibility TiO2Nano fibrous membrane and preparation method thereof - Google Patents

Abstract

The invention relates to a rare earth/carbon co-doped flexible _TiO2 nanofiber membrane and a preparation method thereof. The steps are as follows: first, a precursor solution is prepared, and the precursor solution is composed of a titanium source, a rare earth metal salt, a carbon source, and a nonionic surfactant. and solvent; then electrospinning to obtain the precursor fiber film, apply a constant temperature thermal field of 50-100°C in the spinning interval during electrospinning and control the temperature of the receiving device to -10-0°C; finally in the air atmosphere Calcination yields rare earth/carbon co-doped flexible _TiO2 nanofiber membranes. The softness of the final product is 10-50mN, the tensile breaking strength is 3-5MPa, and the absorbable light absorption range is extended to 550-700nm. The preparation method of the present invention does not need to add polymers or aging, and does not need post-treatment, the process is simple, the cost is low, and the product has good tensile breaking strength, flexibility and visible light catalytic performance.

Description

A rare earth/carbon co-doped flexible TiO2 nanofiber membrane and its preparation method

technical field

The invention belongs to the field of new materials, and relates to a rare earth/carbon co-doped flexible _TiO2 nanofiber membrane and a preparation method thereof.

Background technique

Titanium dioxide (TiO ₂ ) one-dimensional nanomaterials are widely used in photocatalytic hydrogen production, volatile organic compounds (VOCs) in industry, and degradation of indoor and in-vehicle VOCs due to their stable photocatalytic properties, low price, and no biological toxicity. aroused widespread concern. But as a widely used photocatalytic material, it has the following main problems: 1) TiO ₂ has a wide band gap (Eg=3.0～3.2eV), so it can only be excited by ultraviolet light below 400 nanometer wavelength, and the solar energy utilization rate is low. Low. 2) Photogenerated electron-hole pairs are easy to recombine, resulting in low photon utilization efficiency, thereby reducing the catalytic activity of the material. 3) Most one-dimensional titania nanomaterials generally have the problems of high brittleness and low strength. The above-mentioned problems have become bottlenecks that limit the wide application of nano-titanium dioxide photocatalytic materials. To this end, people use element doping to realize the absorption of visible light by titanium dioxide, and effectively inhibit the recombination of photogenerated electron-hole pairs, thereby improving the catalytic activity and realizing the flexible preparation of fibers.

In the early research, it was mainly doped with a single metal or non-metal, such as C, S, N, Fe, Ni, Zn, La, Ce, etc. Maruska et al. reported that doping titanium dioxide with transition metals (Fe, Ni, etc.) can make it have a visible light catalytic response. Asahi et al. reported that after N substituting a small amount of O in the TiO ₂ lattice, the catalyst can have a visible light catalytic response. Then Lettmann et al. When doing N doping, it was accidentally discovered that there is also visible light catalytic activity in undoped samples, thus discovering the visible light catalytic activity of carbon-doped nano-TiO ₂ , and the research on the development of doped titanium dioxide with visible light catalytic response has caused extensive attention.

Patent CN 104607171 discloses a preparation method of a praseodymium-doped titanium dioxide composite nanofiber photocatalyst, and Applied Physics A 117 (2014) 1191-1201 reports a preparation method of a cerium-doped titanium dioxide nanofiber, in which a small amount of rare earth metal is incorporated into the In the lattice or lattice gap of TiO ₂ , the recombination of photogenerated electron-hole pairs is effectively suppressed, and the interaction between grain boundaries is enhanced, which improves the catalytic activity and expands its visible light absorption range, but its Visible light absorption wavelengths are mostly concentrated below 500nm.

Patent CN 102021676A discloses a preparation method of titanium dioxide/activated carbon composite nanofiber membrane, and Synthetic Metals 193 (2014) 125-131 reports a preparation method of titanium dioxide/carbon nanotube nanofiber. In the co-doped nano-TiO ₂ material, a small amount of C enters the TiO ₂ lattice to form a Ti-C bond and form a doping energy level, which narrows the forbidden band width and is beneficial to its absorption of visible light. Although the introduction of C The light absorption range of the catalyst can be enlarged and extended to more than 700nm, but the presence of C leads to a decrease in the catalytic activity of the catalyst.

In recent years, multi-element doping has received increasing attention. In particular, doping with carbon and rare earth elements is more popular. Increased fiber strength. However, there are few reports on the preparation and research of rare earth/carbon co-doped flexible titania nanofibers. Therefore, it is of great significance to develop a rare earth/carbon co-doped flexible TiO ₂ nanofiber material.

Contents of the invention

The purpose of the present invention is to overcome the defects of relatively complex process, high cost and poor product performance in the prior art, and provide a rare earth/carbon co-doping with simple production process, low cost, good photocatalytic performance and flexibility of the product Flexible _TiO2 nanofibrous membrane and method for its preparation.

To achieve the above object, the present invention adopts the following technical solutions:

A preparation method of rare earth/carbon co-doped flexible _TiO nanofiber membrane, the steps are as follows:

(1) prepare precursor solution, described precursor solution is made up of titanium source, rare earth metal salt, carbon source, nonionic surfactant and solvent;

(2) Electrospinning is carried out to obtain a precursor fiber film. During the electrospinning, a constant temperature thermal field is applied in the spinning interval and the temperature of the receiving device is controlled. The temperature of the constant temperature thermal field is 50-100°C. The temperature of the device is -10～0℃;

(3) Rare earth/carbon co-doped flexible _TiO2 nanofiber membranes were obtained by calcination under air atmosphere.

As a preferred technical solution:

A method for preparing rare earth/carbon co-doped flexible _TiO nanofiber membranes as described above, the specific operation of preparing the precursor solution is: dissolving the titanium source and the rare earth metal salt in a solvent and stirring for 30 to 150 minutes, and then Add carbon source and non-ionic surfactant in sequence and stir for 10-90 minutes to mix evenly.

The purpose of first dissolving the titanium source and the rare earth metal salt in the solvent is to partially hydrolyze the titanium source to generate hydroxyl groups, and on the other hand to mix the rare earth metal salt and the titanium source evenly. If titanium source, rare earth metal salt, carbon source and non-ionic surfactant are added to the solvent at the same time, it is not conducive to the hydrolysis of titanium source, affecting the growth of colloidal particles, and is not conducive to the uniform distribution of rare earth metal ions.

The preparation method of rare earth/carbon co-doped flexible _TiO2 nanofiber membrane as described above, the molar ratio of titanium source, rare earth metal salt and solvent in the precursor solution is 1:0.001～0.1:10～100, titanium source , The molar ratio of the carbon source to the nonionic surfactant is 1:0.001-0.1:0.05-0.25.

Rare earth/carbon co-doped flexible _TiO as mentioned above The preparation method of the nanofiber membrane, the titanium source is titanium isopropoxide, tetrabutyl titanate, titanium tetrachloride, titanium trichloride or titanyl sulfate;

The rare earth metal salt is lanthanum salt, cerium salt, gadolinium salt, erbium salt, praseodymium salt, strontium salt or neodymium salt;

The solvent is ethanol, ethylene glycol, isopropanol, glycerol, acetic acid or N,N-dimethylformamide;

The carbon source is graphene, single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon quantum dots, activated carbon or carbon black;

The nonionic surfactant is polyethylene oxide-polypropylene oxide-polyoxyethylene triblock copolymer, polyoxyethylene polyoxypropylene, glycerol polyoxyethylene polyoxypropylene block copolymer substances, ethylenediamine polyoxyethylene polyoxypropylene block polyether or propylene glycol polyoxyethylene polyoxypropylene ether.

A rare earth/carbon co-doped flexible _TiO nanofiber membrane as described above, the lanthanum salt is lanthanum nitrate hexahydrate, lanthanum acetate or lanthanum chloride heptahydrate, and the cerium salt is cerium nitrate hexahydrate Or cerium chloride heptahydrate, the gadolinium salt is gadolinium nitrate hexahydrate, gadolinium chloride hexahydrate or gadolinium sulfate octahydrate, the erbium salt is erbium nitrate pentahydrate or erbium chloride hexahydrate, and the praseodymium salt is hexahydrate Praseodymium nitrate hydrate or praseodymium sulfate octahydrate, the strontium salt is strontium chloride hexahydrate or strontium bromide hexahydrate, and the neodymium salt is neodymium nitrate hexahydrate or neodymium chloride hexahydrate.

The preparation method of a rare earth/carbon co-doped flexible _TiO2 nanofiber membrane as described above, the parameters of the electrospinning are: relative humidity 20-70%, perfusion speed 0.1-15mL/h, voltage 10-60kV , the distance between the receiving device and the spinneret is 20-40cm, and the receiving device is a metal drum or a metal plate.

As mentioned above, a rare earth/carbon co-doped flexible _TiO2 nanofiber membrane preparation method, the temperature of the calcination is gradually increased from room temperature to 400-1000 °C, the heating rate is 0.1-10 °C/min, and at the highest Keep at the calcination temperature for 10-360 minutes.

The present invention also provides a rare earth/carbon co-doped flexible _TiO2 nanofiber membrane prepared by the above preparation method, the softness of the rare earth/carbon co-doped flexible _TiO2 nanofiber membrane is 10-50mN, The tensile fracture strength of the doped flexible TiO ₂ nanofiber film is 3-5MPa, and the absorbable light absorption range is extended to 550-700nm.

As a preferred technical solution:

The rare earth/carbon co-doped flexible _TiO2 nanofiber membrane as described above, the average diameter of the fibers in the rare earth/carbon co-doped flexible _TiO2 nanofiber membrane is 10-400nm, and the relative standard deviation is 1-5% , The internal grain size is 10-80nm. The fiber diameter range indicates the fiber thickness, the smaller the fiber diameter, the better the softness of the single fiber, which is conducive to the improvement of the softness of the fiber film; the relative standard deviation is used to characterize the uniformity of the fiber diameter distribution, the smaller the deviation value, the better the fiber uniformity. Good; the grain size is closely related to the mechanical properties of the fiber membrane, and the reduction of the grain size is also conducive to the improvement of the photocatalytic performance.

Invention principle:

In the first step of the present invention, the titanium source is added to the solvent, and a hydrolysis condensation reaction occurs under stirring. The purpose of adding the rare earth metal salt is to reduce the micro-defects on the fiber surface during the subsequent calcination process, inhibit the growth of _TiO2 grains, and the grain size The smaller the grain size, the higher the specific surface area of the grains, the more the number of surface active sites, and the corresponding improvement in photocatalytic activity. After adding carbon source and surfactant, titanium source, carbon source and surfactant will form Hydrogen bonds make the carbon source evenly distributed in the precursor solution to obtain a uniform and stable spinning solution; a constant temperature thermal field of 50-100°C is applied in the spinning range during electrospinning, which promotes the rapid volatilization of the solvent in the spinning jet , so that the surfactant concentration reaches the critical micelle concentration, and then the micelles are formed by self-assembly, and are regularly arranged along the axial direction of the fiber under the rapid drawing of the electric field force. The micellar units in the fiber are parallel to each other and have a one-dimensional In addition, the thermal field and electrostatic field coupling induction can promote the formation of strong hydrogen bonds or covalent bonds between the hydroxyl groups in the TiO ₂ precursor in the spinning solution and the carbon source, so that the TiO ₂ precursor and The carbon source is uniformly aggregated and distributed on the surface of the micelles. When the fibers are collected on the receiving device, due to the low temperature (-10-0°C) of the receiving device, the ordered self-assembled structure inside the precursor fiber can be instantly consolidated and retained.

Beneficial effect:

(1) The preparation method of a rare earth/carbon co-doped flexible _TiO2 nanofiber membrane of the present invention does not require adding polymers or aging, and does not require post-treatment, by applying a constant temperature thermal field during the spinning process and lowering the receiving substrate Temperature, so that the carbon source is evenly distributed and consolidated in the precursor fiber, and the titanium content in the spinning solution is high, the yield of titanium dioxide nanofibers is high, the preparation process is simple, and the cost is low;

(2) A rare earth/carbon co-doped flexible _TiO2 nanofiber membrane of the present invention has good tensile breaking strength, flexibility and visible light catalytic performance.

Detailed ways

The present invention will be further described below in combination with specific embodiments. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Example 1

A preparation method of rare earth/carbon co-doped flexible _TiO nanofiber membrane, the steps are as follows:

(1) Dissolve titanium source titanium isopropoxide and rare earth metal salt lanthanum nitrate hexahydrate in solvent ethanol and stir for 30 minutes, then add carbon source graphene and nonionic surfactant polyethylene oxide-polypropylene oxide- The polyethylene oxide triblock copolymer was stirred for 90min and mixed uniformly to obtain a precursor solution, wherein the molar ratio of titanium source, rare earth metal salt, solvent, carbon source and nonionic surfactant in the solution was 1:0.001:100: 0.001:0.25;

(2) Prepare the precursor fiber film by electrospinning the above precursor solution, apply a constant temperature thermal field of 50°C in the spinning interval during electrospinning and control the temperature of the metal drum receiving device to 0°C; The parameters are: relative humidity 20%, perfusion speed 15mL/h, voltage 10kV, distance between receiving device and spinneret 40cm;

(3) Put the above precursor fiber film in the air atmosphere and calcinate to obtain the rare earth/carbon co-doped flexible _TiO2 nanofiber film. Calcination means that the temperature of calcination is gradually increased from room temperature to 650 °C, and the heating rate is 10 °C/min , and kept at the highest calcination temperature for 120min.

The average diameter of the fiber in the final rare earth/carbon co-doped flexible _TiO2 nanofiber film is 200nm, and the relative standard deviation is 1%, the grain size inside the fiber is 10nm, and the rare earth/carbon co-doped flexible _TiO2nm The softness of the fiber membrane is 10mN, the tensile breaking strength is 5MPa, and the absorption range of visible light is extended to 700nm.

Comparative example 1

A preparation method of rare earth/carbon co-doped flexible _TiO2 nanofiber membrane, its basic steps and parameters are the same as in Example 1, the difference is that a constant temperature thermal field is not set during the electrospinning process, and the temperature of the receiving device is set to room temperature.

The average diameter of the fiber in the rare earth/carbon co-doped flexible _TiO2 nanofiber film prepared by it is 300nm, and the relative standard deviation is 3%, the grain size inside the fiber is 45nm, and the rare earth/carbon co-doped flexible _TiO2 The softness of the nanofiber film is 50mN, the tensile breaking strength is 0.8MPa, and the absorption range of visible light is extended to 500nm. By comparing with Example 1, it can be found that the rare earth/carbon co-doped flexible film prepared in Example 1 While ensuring a certain degree of flexibility, the _TiO2 nanofiber membrane greatly improves its absorption range for visible light, and its photocatalytic performance is far superior to that of the rare earth/carbon co-doped flexible _TiO2 nanofiber membrane.

Example 2

A preparation method of rare earth/carbon co-doped flexible _TiO nanofiber membrane, the steps are as follows:

(1) Dissolve titanium source tetrabutyl titanate and rare earth metal salt lanthanum acetate in solvent ethylene glycol and stir for 150 minutes, then add carbon source single-walled carbon nanotubes and nonionic surfactant polyoxyethylene polyoxypropylene successively and stir Mix evenly for 10 minutes to prepare a precursor solution, wherein the molar ratio of titanium source, rare earth metal salt, solvent, carbon source and nonionic surfactant in the solution is 1:0.1:10:0.1:0.05;

(2) Prepare the precursor fiber film by electrospinning the above precursor solution, apply a constant temperature thermal field of 100°C in the spinning interval during electrospinning and control the temperature of the metal plate receiving device to -10°C; The parameters of silk are: relative humidity 70%, infusion speed 0.1mL/h, voltage 60kV, distance between receiving device and spinneret 20cm;

(3) Put the above precursor fiber film in an air atmosphere and calcinate to obtain a rare earth/carbon co-doped flexible _TiO2 nanofiber film. Calcination means that the temperature of calcination is gradually increased from room temperature to 1000 °C, and the heating rate is 0.1 °C/min , and kept at the highest calcination temperature for 360min.

The average diameter of the fibers in the final rare earth/carbon co-doped flexible _TiO2 nanofiber film is 300nm, and the relative standard deviation is 5%, the grain size inside the fiber is 80nm, and the rare earth/carbon co-doped flexible _TiO2nm The softness of the fiber membrane is 50mN, the tensile breaking strength is 3MPa, and the absorption range of visible light is extended to 580nm.

Example 3

A preparation method of rare earth/carbon co-doped flexible _TiO nanofiber membrane, the steps are as follows:

(1) Stir the titanium source titanium tetrachloride and the rare earth metal salt lanthanum chloride heptahydrate in the solvent ethylene glycol for 90 minutes, then add the carbon source multi-walled carbon nanotubes and the nonionic surfactant glycerol polyoxyethylene successively The polyoxypropylene block copolymer was stirred for 50 minutes and mixed evenly to obtain a precursor solution, wherein the molar ratio of titanium source, rare earth metal salt, solvent, carbon source and nonionic surfactant in the solution was 1:0.05:55:0.05: 0.15;

(2) Prepare the precursor fiber film by electrospinning the above precursor solution, apply a constant temperature thermal field of 75°C in the spinning interval and control the temperature of the metal drum receiving device to -5°C during electrospinning; The parameters of silk are: relative humidity 45%, perfusion speed 7.5mL/h, voltage 35kV, distance between receiving device and spinneret 30cm;

(3) Put the above precursor fiber film in an air atmosphere and calcinate to obtain a rare earth/carbon co-doped flexible _TiO2 nanofiber film. Calcination means that the temperature of calcination is gradually increased from room temperature to 700 °C, and the heating rate is 5 °C/min , and kept at the highest calcination temperature for 185min.

The average diameter of the fiber in the final rare earth/carbon co-doped flexible _TiO2 nanofiber film is 205nm, and the relative standard deviation is 3%, the grain size inside the fiber is 45nm, and the rare earth/carbon co-doped flexible _TiO2nm The softness of the fiber membrane is 40mN, the tensile breaking strength is 3.5MPa, and the absorption range of visible light is extended to 650nm.

Examples 4-27

The preparation steps of Examples 4 to 27 are the same as in Example 1, wherein the preparation parameters of precursor solution, electrospinning parameters, calcination parameters and rare earth/carbon co-doped flexible _TiO2 nanofiber membrane performance parameters are shown in Tables 1 to 6 ( Note: Stirring time 1 is the stirring time after titanium source and rare earth metal salt are dissolved in the solvent, stirring time 2 is the stirring time after adding carbon source and nonionic surfactant)

Table 1

Table 2

table 3

Table 4

table 5

Table 6

Claims (9)

1. a kind of rare earth/carbon co-doped flexibility TiO₂The preparation method of nano fibrous membrane, characterized in that steps are as follows:

(1) prepare precursor solution, the precursor solution by titanium source, rare earth metal salt, carbon source, nonionic surfactant and Solvent composition；

(2) it carries out electrostatic spinning and obtains precursor fibre film, when electrostatic spinning applies constant temperature thermal field in spinning section and controls The temperature of reception device processed, the temperature of the constant temperature thermal field are 50~100 DEG C, and the temperature of the reception device is -10~0 DEG C；

(3) calcining obtains rare earth/carbon co-doped flexibility TiO in air atmosphere₂Nano fibrous membrane.

2. a kind of rare earth according to claim 1/carbon co-doped flexibility TiO₂The preparation method of nano fibrous membrane, feature Be, it is described prepare precursor solution concrete operations are as follows: by titanium source and rare earth metal salt dissolution in a solvent stirring 30~ 150min, then sequentially adds carbon source and nonionic surfactant stirs 10~90min and is uniformly mixed.

3. a kind of rare earth according to claim 1/carbon co-doped flexibility TiO₂The preparation method of nano fibrous membrane, feature It is, the molar ratio of titanium source, rare earth metal salt and solvent is 1:0.001~0.1:10~100, titanium in the precursor solution The molar ratio in source, carbon source and nonionic surfactant is 1:0.001~0.1:0.05~0.25.

4. a kind of rare earth according to claim 3/carbon co-doped flexibility TiO₂The preparation method of nano fibrous membrane, feature It is, the titanium source is isopropyl titanate, butyl titanate, titanium tetrachloride, titanium trichloride or titanyl sulfate；

The rare earth metal salt is lanthanum salt, cerium salt, gadolinium salt, erbium salt, praseodymium salt or neodymium salt；

The solvent is ethyl alcohol, ethylene glycol, isopropanol, glycerine, acetic acid or N,N-dimethylformamide；

The carbon source is graphene, single-walled carbon nanotube, multi-walled carbon nanotube, carbon quantum dot, active carbon or carbon black；

The nonionic surfactant is polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, polyoxy second Alkene polyoxypropylene, glycerine polyoxyethylene polyoxypropylene blocked copolymer, ethylenediamine polyoxyethylene oxypropylene block formula are poly- Ether or propylene glycol polyoxyethylene poly-oxygen propylene aether.

5. a kind of rare earth according to claim 4/carbon co-doped flexibility TiO₂The preparation method of nano fibrous membrane, feature It is, the lanthanum salt is lanthanum nitrate hexahydrate, lanthanum acetate or seven hydrated lanthanum chlorides, and the cerium salt is six nitric hydrate ceriums or seven water Cerium chloride is closed, the gadolinium salt is gadolinium nitrate hexahydrate, six chloride hydrate gadoliniums or eight hydrated sulfuric acid gadoliniums, and the erbium salt is five hydration nitre Sour erbium or six chloride hydrate erbiums, the praseodymium salt are six nitric hydrate praseodymiums or eight hydrated sulfuric acid praseodymiums, and the neodymium salt is six nitric hydrates Neodymium or six Neodymium chloride hydrates.

6. a kind of rare earth according to claim 1/carbon co-doped flexibility TiO₂The preparation method of nano fibrous membrane, feature It is, the parameter of the electrostatic spinning are as follows: relative humidity 20~70%, 0.1~15mL/h of rate of flooding, 10~60kV of voltage, Reception device between spinning nozzle at a distance from 20~40cm, the reception device be metal roller or metal plate.

7. a kind of rare earth according to claim 1/carbon co-doped flexibility TiO₂The preparation method of nano fibrous membrane, feature It is, the temperature of the calcining gradually rises to 400~1000 DEG C from room temperature, and heating rate is 0.1~10 DEG C/min, and most 10~360min is kept under high calcination temperature.

8. using rare earth/carbon co-doped flexibility TiO made from preparation method as described in any one of claims 1 to 7₂Nanowire Film is tieed up, it is characterized in that: rare earth/carbon co-doped flexibility TiO₂The pliability of nano fibrous membrane is 10~50mN, rare earth/carbon co-doped Flexible TiO₂The tensile break strength of nano fibrous membrane is 3~5MPa, and absorbable light abstraction width is expanded to 550~700nm.

9. rare earth according to claim 8/carbon co-doped flexibility TiO₂Nano fibrous membrane, which is characterized in that the rare earth/ Carbon co-doped flexibility TiO₂The average diameter of fiber is 10~400nm in nano fibrous membrane, and relative standard deviation is 1~5%, Internal grain is having a size of 10~80nm.