CN104692466A - A non-template method for preparing α-Fe2O3 hollow tubular nanofilms - Google Patents

Abstract

The invention belongs to the technical field of semiconductor nanomaterial preparation, and relates to a non-template method for _preparing α- _Fe2O3 hollow tubular nanofilm. Firstly, ferric chloride, sodium nitrate and sodium fluoride are respectively added into a beaker, and then distilled water is added to stir to prepare After forming a uniform solution, transfer it to a polytetrafluoroethylene liner reactor, then put the clean conductive substrate into the polytetrafluoroethylene liner reactor, seal it and transfer it to a high-pressure reactor, and put it in an oven for reaction. Take out the autoclave, cool it down to room temperature naturally, take out the conductive substrate, wash it with distilled water and dry it, then put the conductive substrate containing α-Fe ₂ O ₃ precursor film into the porcelain boat and put it into the muffle furnace Heating and heat preservation; finally take out the porcelain boat, cool naturally, and prepare α-Fe ₂ O ₃ hollow tubular nano-film on the conductive substrate; the preparation method is simple, the principle is scientific, the prepared nano-film has high stability, and is widely used.

Description

A non-template method for preparing α-Fe2O3 hollow tubular nanofilms

Technical field:

The invention belongs to the technical field of semiconductor nanomaterial preparation, and relates to a method for preparing a hollow tubular nanofilm, in particular to a method for _preparing an α- _Fe2O3 hollow tubular nanofilm without a template.

Background technique:

Since E. Becquerel discovered the photoelectric effect of semiconductors in 1839, the use of photoelectric effects of semiconductors to convert sunlight into electrical and chemical energy has aroused widespread concern among researchers in recent decades. Among many semiconductor materials, titanium dioxide (TiO ₂ ), as a standard material, has been extensively studied and applied in photochemistry. However, the energy band gap of TiO ₂ is 3.2eV, which can only absorb the ultraviolet part of sunlight, which greatly reduces the absorption rate of sunlight, resulting in a decrease in the utilization rate and conversion efficiency of solar energy. Therefore, more and more semiconducting nanomaterials have been extensively studied, among which iron trioxide (hematite, α-Fe ₂ O ₃ ) has a suitable energy band gap (2.2eV), which can absorb sunlight The visible part of the light can broaden the absorption range of light and increase the absorption efficiency in the visible region; the appropriate conduction band and valence band positions make it a photo-splitting water material; in addition, its chemical properties are stable, the storage capacity is abundant, and it is cheap and easy to obtain Compared with other semiconductors, iron trioxide (hematite, α-Fe ₂ O ₃ ) has more advantages in optoelectronic applications, such as solar cells, photochemical cells and photolysis of water. However, the iron trioxide (hematite, α-Fe ₂ O ₃ ) material itself also has the characteristics of easy recombination of photogenerated electrons and holes, short diffusion distance of carriers (2-4 nanometers) and easy recombination, low temperature at room temperature. The hole mobility (0.01cm ² V ^-1 s ^-1 ) and the existence of a certain overpotential, etc., these shortcomings greatly limit the application of α-Fe ₂ O ₃ .

At present, there are many ways to modify α-Fe ₂ O ₃ , which are generally divided into two categories: one is to improve the crystal structure of the material through element doping; the other is to modify the size and shape of α-Fe ₂ O ₃ The control of the material can effectively improve the photoelectric properties of the material through modification. For the first method, researchers have successfully doped elements such as Co, Pt, Ni, Ti and Si into the α-Fe ₂ O ₃ lattice, and found that the doping of different elements can effectively increase the Large carrier mobility, improving photoactivity; however, the most active absorbing layer is in the semiconductor-solution surface to 10 nm in the crystal, in addition, carriers at this thickness can effectively reach the surface of the semiconductor material, reducing the probability of its compounding. Therefore, controlling a certain thickness and size is the key to regulating the morphology of hematite. Among many structural forms, hollow nanostructures, such as nanotubes, nanospheres and other forms, have been prepared successively. Compared with other nanoforms, hollow nanostructures with thinner walls can effectively improve their photoactivity, showing better photoelectric conversion efficiency.

At present, the methods for preparing hollow structure nano-α-Fe ₂ O ₃ in the prior art include template method, self-assembly method and electrochemical oxidation method, etc. Among them, the template method is the most direct method, and one of the methods is to use zinc oxide (ZnO) is used as a template to prepare hollow α-Fe ₂ O ₃ , but the nanometer wall thickness of its preparation exceeds 10 nanometers, and the template needs to be removed in the subsequent process; another preparation method first synthesizes nano-carbon spheres of a certain size or other organic compound nanospheres, and then wrap them to obtain α-Fe ₂ O ₃ hollow nanospheres with a certain thickness. This method is simple to prepare, but requires high-temperature calcination, and the synthesized materials have poor crystallinity, which affects the photoelectric conversion efficiency. The electrochemical method is to prepare a certain thickness of α-Fe ₂ O ₃ nanotubes by controlling a certain voltage and current density, but it cannot form a hollow structure, and the crystallinity of the nanomaterials is poor, and it will affect the chemical stability of the material. Therefore, a non-template method for preparing α-Fe ₂ O ₃ hollow tubular nanofilms is sought, using a simple synthetic route without using any template, and using vertically arranged α-Fe ₂ O ₃ on conductive glass (FTO) Hollow nanotubular materials.

Invention content:

The purpose of the present invention is to overcome the shortcomings of the prior art, to seek to design a simple and feasible method for preparing α-Fe ₂ O ₃ hollow tubular nano-films on conductive glass without using any template, first through the selection of different additives Precursor materials were prepared under control, followed by heat treatment, and finally a α-Fe ₂ O ₃ hollow tubular nanofilm with a tube wall of 10 nanometers and vertically arranged on the surface of the FTO conductive glass was synthesized.

In order to achieve the above object, the preparation process of the present invention comprises the following steps:

(1), first cut the FTO conductive glass with a size of 2cm×2cm, and use the prior art to clean the FTO conductive glass sequentially with detergent, deionized water, acetone, deionized water and isoalcohol, and then dry it naturally to form clean conductive substrate;

(2), 0.324g ferric chloride, 0.170g sodium nitrate and 0.016g sodium fluoride are added to beaker respectively, then add 20ml distilled water and be mixed with homogeneous solution under the stirring of magnetic stirrer;

(3), the homogeneous solution that step (2) obtains is transferred in the polytetrafluoroethylene liner reactor;

(4), then put the clean conductive substrate face up into the polytetrafluoroethylene liner reactor, then seal the polytetrafluoroethylene liner reactor and transfer it to the high-pressure reactor, and put it in an oven at 95 Reaction at ℃ for 6 hours;

(5) Take out the autoclave from the oven, cool it down to room temperature naturally, open the autoclave, take out the conductive substrate with tweezers, wash it with distilled water, and dry it to obtain a conductive substrate containing the α- _{Fe2O3 precursor} film ;

(6) Put the conductive substrate containing the α-Fe ₂ O ₃ precursor film into the porcelain boat and then put it into the muffle furnace, raise the temperature at a rate of 5°C per minute, heat it to 550°C in the air, and keep it warm for 2 Hour;

(7) Finally, the porcelain boat was taken out, cooled naturally in the air, and dark red, vertically arranged α-Fe ₂ O ₃ hollow tubular nano-films were prepared on the conductive substrate.

Compared with the prior art, the present invention adopts a simple synthesis route and synthesizes vertically arranged α-Fe ₂ O ₃ hollow nanotubular nano-films on conductive glass (FTO) without using any template. The preparation method is simple, The principle is scientific, the prepared nano-film has high stability and is widely used, and has potential application prospects in many fields such as photocatalysis, inorganic solar cells and photolysis of water.

Description of drawings:

Fig. 1 is an electron photograph of the α-Fe ₂ O ₃ precursor film (left picture) and the α-Fe ₂ O ₃ hollow tubular nanofilm (right picture) described in Example 1 of the present invention.

Fig. 2 is a transmission electron microscope (TEM) photo of the α-Fe ₂ O ₃ hollow tubular nano-film prepared by the present invention, the inset shows that the thickness of the tube wall is about 10 nanometers.

Figure 3 is the X-ray diffraction pattern of the α-Fe ₂ O ₃ precursor film and α-Fe ₂ O ₃ hollow tubular nanofilm (2 in the figure) prepared by the present invention, wherein 1 is the α-Fe ₂ O ₃ precursor film (sample before high temperature treatment), 2 is α-Fe ₂ O ₃ hollow tubular nano film (sample after high temperature treatment), ﹟ represents the SnO ₂ diffraction peak on the FTO surface, ◆ represents the generated α-Fe ₂ O ₃ diffraction peak .

Fig. 4 is an X-ray energy spectrum (EDX) of Sn, Fe and O elements involved in the present invention.

Fig. 5 is a transmission electron microscope (TEM) photo of the α-Fe ₂ O ₃ powder prepared in Example 4 of the present invention.

Detailed ways:

The present invention will be further elaborated below through specific embodiments and in conjunction with the accompanying drawings.

Example 1:

The specific process for preparing α-Fe ₂ O ₃ hollow tubular nano-films in this example includes the following steps:

(1), first cut the FTO conductive glass with a size of 2cm×2cm, and use the prior art to clean the FTO conductive glass sequentially with detergent, deionized water, acetone, deionized water and isoalcohol, and then dry it naturally to form clean conductive substrate;

(2), 0.324g ferric chloride, 0.170g sodium nitrate and 0.016g sodium fluoride are added to the beaker respectively, then add 20ml distilled water and be mixed with a homogeneous solution under the stirring of a magnetic stirrer, the homogeneous solution obtained is iron red, and has presence of tiny particles;

(3), the homogeneous solution that step (2) is obtained is rapidly transferred in the polytetrafluoroethylene liner reactor;

(4), then put the clean conductive substrate face up into the polytetrafluoroethylene liner reactor, then seal the polytetrafluoroethylene liner reactor and transfer it to the high-pressure reactor, and put it in an oven at 95 Reaction at ℃ for 6 hours;

(5) Take out the autoclave from the oven, cool it down to room temperature naturally, open the autoclave, take out the conductive substrate with tweezers, wash it with distilled water, and dry it to obtain a conductive substrate containing the α- _{Fe2O3 precursor} film ; As can be seen from the left figure of Figure 1, there is a light yellow film on the conductive substrate;

(6) Put the conductive substrate containing the α-Fe ₂ O ₃ precursor film into the porcelain boat and then put it into the muffle furnace, raise the temperature at a rate of 5°C per minute, heat it to 550°C in the air, and keep it warm for 2 Hour;

(7) Finally, the porcelain boat was taken out and cooled naturally in the air, that is, deep red vertically arranged α-Fe ₂ O ₃ hollow tubular nano-films were prepared on the conductive substrate, as shown in the right figure of Figure 1.

The α-Fe ₂ O ₃ hollow tubular nano-film transmission electron microscope (TEM) photos prepared in this embodiment are shown in Figure 2, as can be seen from the figure, the wall thickness of α-Fe ₂ O ₃ hollow tubular nano-film is less than 10 Nano.

Example 2:

This embodiment is the same as steps (1)-(5) in Example 1, only adding slowly in the homogeneous solution obtained in step (2) is 10 milliliters of dilute hydrochloric acid that is 10% by weight percent concentration, to dissolve and produce The precipitation, its specific steps are as follows:

(1), first cut the FTO conductive glass with a size of 2cm×2cm, and use the prior art to clean the FTO conductive glass sequentially with detergent, deionized water, acetone, deionized water and isoalcohol, and then dry it naturally to form clean conductive substrate;

(2), 0.324g ferric chloride, 0.170g sodium nitrate and 0.016g sodium fluoride are added to the beaker respectively, then add 20ml distilled water and be mixed with a homogeneous solution under the stirring of a magnetic stirrer, the homogeneous solution obtained is iron red, and has Tiny particles exist; then slowly add 10 ml of 10% dilute hydrochloric acid dropwise to dissolve the precipitate;

(3), the homogeneous solution that step (2) is obtained is rapidly transferred in the polytetrafluoroethylene liner reactor;

(4), then put the clean conductive substrate face up into the polytetrafluoroethylene liner reactor, then seal the polytetrafluoroethylene liner reactor and transfer it to the high-pressure reactor, and put it in an oven at 95 Reaction at ℃ for 6 hours;

(5) Take out the autoclave from the oven, cool it down to room temperature naturally, open the autoclave and take out the conductive substrate with tweezers, wash it with distilled water, and dry it in the air. There is no substance formed on the conductive substrate, which means adding dilute hydrochloric acid After that, the α-Fe ₂ O ₃ precursor film cannot be formed on the surface of the FTO conductive glass.

Example 3:

The present embodiment only carries out the step (1)-(5) of embodiment 1, does not carry out high-temperature treatment again, and concrete process is:

(1), first cut the FTO conductive glass with a size of 2cm×2cm, and use the prior art to clean the FTO conductive glass sequentially with detergent, deionized water, acetone, deionized water and isoalcohol, and then dry it naturally to form clean conductive substrate;

(2), 0.324g ferric chloride, 0.170g sodium nitrate and 0.016g sodium fluoride are added to the beaker respectively, then add 20ml distilled water and be mixed with a homogeneous solution under the stirring of a magnetic stirrer, the homogeneous solution obtained is iron red, and has presence of tiny particles;

(3), the homogeneous solution that step (2) is obtained is rapidly transferred in the polytetrafluoroethylene liner reactor;

(4), then put the clean conductive substrate face up into the polytetrafluoroethylene liner reactor, then seal the polytetrafluoroethylene liner reactor and transfer it to the high-pressure reactor, and put it in an oven at 95 Reaction at ℃ for 6 hours;

(5), the autoclave is taken out from the oven, after naturally cooling to room temperature, the autoclave is opened and the conductive substrate is taken out with tweezers, washed with distilled water and dried to form a light yellow film on the surface of the conductive substrate. According to XRD analysis, there is no α-Fe ₂ O ₃ hollow tubular nanofilm formed on the surface.

Example 4:

In this embodiment, α-Fe ₂ O ₃ nanometer films are not generated on the surface of the FTO conductive glass, and other steps are the same as in the embodiment steps (2)-(7), and the specific process is

(1), 0.324g ferric chloride, 0.170g sodium nitrate and 0.016g sodium fluoride are added to the beaker respectively, then add 20ml distilled water and be mixed with a homogeneous solution under the stirring of a magnetic stirrer, the homogeneous solution obtained is iron red, and has presence of tiny particles;

(2), the homogeneous solution that step (2) obtains is transferred rapidly in the polytetrafluoroethylene liner reactor;

(3), then put the clean conductive substrate face up into the polytetrafluoroethylene liner reactor, then transfer the polytetrafluoroethylene liner reactor to the high-pressure reactor, and put it into the oven at 95 Reaction at ℃ for 6 hours;

(4), take out the autoclave from the oven, cool down to room temperature naturally, and obtain the α-Fe ₂ O ₃ precursor powder, wash the α-Fe ₂ O ₃ precursor powder with 5 ml of water and ethanol, respectively three spares;

(5) Put the α-Fe ₂ O ₃ precursor powder prepared in step (4) into a porcelain boat, put them into a muffle furnace together, raise the temperature at a rate of 5°C per minute, and heat it to 550°C in air ℃, keep warm for 2 hours;

(6) Take out the porcelain boat and cool it naturally in the air. It can be observed that red α-Fe ₂ O ₃ powder is generated, as shown in Figure 5; after testing, in the absence of FTO conductive glass, its The sample clusters are relatively strong, and the shape of the sample does not show a hollow nanostructure.

Claims (1)

1. a non-template prepares α-Fe ₂o ₃the method of hollow tubular nano thin-film, is characterized in that preparation technology comprises the following steps:

(1), first cut lengths are the FTO conductive glass of 2cm × 2cm, naturally dry, the conductive substrates of formation cleaning to FTO conductive glass after adopting prior art to carry out ultrasonic cleaning with washing composition, deionized water, acetone, deionized water and different alcohol successively;

(2), by 0.324g iron(ic) chloride, 0.170g SODIUMNITRATE and 0.016g Sodium Fluoride add beaker respectively, then add 20ml distilled water be mixed with homogeneous solution under the stirring of magnetic stirrer;

(3), the homogeneous solution that step (2) obtains is proceeded in polytetrafluoroethylliner liner reactor;

(4) face up, again by the conductive substrates of cleaning and put into polytetrafluoroethylliner liner reactor, then the sealing of polytetrafluoroethylliner liner reactor is transferred in autoclave, and put into baking oven and react 6 hours under 95 DEG C of conditions;

(5), by autoclave take out from baking oven, after naturally cooling to room temperature, open autoclave tweezers and take out conductive substrates, with distilled water wash, dry, obtain containing α-Fe ₂o ₃the conductive substrates of precursor film;

(6), will containing α-Fe ₂o ₃put into retort furnace again after the conductive substrates of precursor film puts into porcelain boat, with the ramp of per minute 5 DEG C, be heated to 550 DEG C in atmosphere, be incubated 2 hours;

(7), finally taken out by porcelain boat, naturally cooling in atmosphere, conductive substrates prepares scarlet, vertically disposed α-Fe ₂o ₃hollow tubular nano thin-film.