Photocatalytic optical fiber and method for manufacturing the same

Abstract

The application discloses a kind of photocatalytic optical fibers, including optical fiber core, photocatalytic layer, optical fiber cladding and light reflection film;The optical fiber core is hollow structure, and the optical fiber core outer periphery side is surrounded by optical fiber cladding;The interface of the optical fiber cladding and optical fiber core is coated with photocatalytic layer, and the outer surface of the optical fiber cladding away from optical fiber core is coated with light reflection film;The two ends of the optical fiber core are gas input end and light input end respectively, the gas can enter optical fiber core by gas input end, and can contact with photocatalytic layer and occur photocatalytic reduction reaction;The light can enter optical fiber core by light input end, and can be reflected by light reflection film;The optical fiber structure of the application can effectively enhance the utilization efficiency of light energy, increase the contact frequency of reactant and catalyst, thereby improve the reaction rate of photocatalytic reaction, and further improve the conversion efficiency of CO2.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of photocatalytic optical fiber, and in particular to a photocatalytic optical fiber and a preparation method thereof. BACKGROUND

[0002] Energy is the driving force for the progress of human society. Global annual energy consumption has grown from 172.6 billion tons of coal equivalent in 2010 to 199.2 billion tons of coal equivalent at present, of which fossil fuel energy consumption accounts for more than 84%. The excessive consumption of fossil fuels by humans not only leads to global energy crisis, but also causes environmental problems due to large CO2 emissions. Since 2010, global CO2 emissions have exceeded 3 billion tons per year and continue to increase, contributing more than 60% to global warming. At present, different strategies have been taken to reduce the impact of CO2 on the environment, including reducing CO2 emissions from the source, CO2 capture and storage, and electrochemical or photocatalytic technology to convert CO2 into renewable hydrocarbon fuels for reuse.

[0003] Among them, the photocatalytic technology utilizes excess renewable solar energy at room temperature and pressure to combine the reduction half-reaction of CO2 conversion with the oxidation half-reaction of H2O at the interface of the semiconductor photocatalyst, realizing the molecular conversion of CO2+H2O→C x H y O z to produce synthetic alcohol ether fuel, alkane diesel, aviation fuel and other hydrocarbon fuels. Therefore, the semiconductor photocatalytic technology realizes the molecular conversion of CO2+H2O→C x H y O z , which provides a practical and feasible solution to global energy and environmental problems. This technology is of great significance to the sustainable development of CO2 emission reduction and renewable fuel production, energy, environment and economy.

[0004] In the immobilized photocatalytic reduction of CO2 reactor, the photocatalyst is fixed on the surface of the carrier, and H2O and CO2 are in gas phase. The immobilized photocatalytic reduction of CO2 technology can effectively enhance the transmission of light and CO2, improve the light energy utilization efficiency, quantum efficiency, CO2 conversion efficiency and system operation stability, and greatly promote the development of photocatalytic reduction of CO2 technology.

[0005] However, the photocatalytic reduction of CO2 technology can utilize solar energy to produce hydrocarbon fuels, but the photocatalytic reduction of CO2 reaction process has the bottleneck problem of low CO2 conversion performance due to limited light transmission in the porous photocatalytic layer.

[0006] In order to enhance light transmission, improve light energy utilization efficiency and CO2 catalytic conversion efficiency, the side-emitting optical fiber and the photocatalytic reduction CO2 coupling technology are rapidly developed. In the photocatalytic and side-emitting optical fiber coupling system, the photocatalyst is coated on the surface of the side-emitting optical fiber, and the side-emitting optical fiber serves as a light transmission medium to provide light energy for the photocatalyst coated on the surface of the optical fiber. The photocatalyst generates electron-hole pairs under light excitation, thereby promoting the reaction of CO2 and H2O adsorbed on the surface of the catalyst to generate carbon hydrocarbon fuel. Although the catalyst coated on the surface of the optical fiber can effectively capture the light energy radiated from the surface of the optical fiber, there are the following three shortcomings in using the photocatalyst coated on the surface of the side-emitting optical fiber for photocatalytic reduction of CO2:

[0007] Firstly, due to the low light radiation intensity and low light transmission depth on the surface of the optical fiber, and due to the intrinsic absorption of the optical fiber core and cladding material to light, especially the large ultraviolet light absorption coefficient, the effective excitation light intensity in the photocatalytic layer on the surface of the optical fiber is low.

[0008] Secondly, when the photocatalyst is coated on the surface of the optical fiber, the light in the photocatalytic layer is transmitted from inside to outside, that is, the light intensity is the strongest at the interface between the optical fiber and the catalyst thin film, that is, the light at the bottom layer of the catalyst is the strongest, and the light at the surface of the catalyst thin film is the weakest, which limits the light intensity at the surface layer of the catalyst; at the same time, the electron-hole pairs generated at the bottom layer of the catalyst are greatly lost in the transmission process to the surface layer of the catalyst thin film, and the number of electron-hole pairs generated at the surface layer of the catalyst is limited due to the limitation of light.

[0009] Thirdly, CO2 molecules and H2O molecules are attached to the surface of the photocatalytic layer, and the number of electron-hole pairs generated at the bottom layer of the photocatalytic thin film is large, and the number of electron-hole pairs generated at the surface of the photocatalytic thin film is small due to the limitation of light, which results in the waste of the electron-hole pairs generated at the bottom layer of the photocatalytic thin film, and the number of electron-hole pairs for reducing CO2 molecules and oxidizing H2O molecules at the surface of the photocatalytic thin film is limited.

[0010] Due to the above three shortcomings, the light energy utilization efficiency and CO2 conversion efficiency of the side-emitting optical fiber and the photocatalytic reduction CO2 coupling technology are still low. SUMMARY

[0011] The present application aims to provide a photocatalytic optical fiber and a preparation method thereof, to solve the technical problem of low CO2 conversion efficiency in the application of the side-emitting optical fiber coated with a photocatalyst to the photocatalytic reduction of CO2.

[0012] In order to solve the above technical problem, the technical scheme adopted by the present application is as follows:

[0013] A photocatalytic optical fiber, comprising an optical fiber core 1, a photocatalytic layer 2, an optical fiber cladding 3 and a light reflection film 4.

[0014] The optical fiber core 1 is a hollow structure, and the optical fiber cladding 3 is arranged on the outer periphery of the optical fiber core 1;

[0015] The interface between the optical fiber cladding 3 and the optical fiber core 1 is coated with a photocatalytic layer 2, and the outer surface of the optical fiber cladding 3 away from the optical fiber core 1 is coated with a light reflection film 4;

[0016] The two ends of the optical fiber core 1 are a gas input end 5 and a light input end 6, respectively, the gas can enter the optical fiber core 1 through the gas input end 5, and can contact the photocatalytic layer 2 to occur a photocatalytic reduction reaction;

[0017] The light can enter the optical fiber core 1 through the light input end 6, and can be reflected by the light reflection film 4.

[0018] The working principle of the application is that the refractive index of the photocatalytic layer 2 is greater than the refractive index of the optical fiber core 1 and the optical fiber cladding 3, and the surface of the optical fiber cladding 3 has the light reflection film 4, thereby limiting the light entering the optical fiber inside to be transmitted inside the optical fiber; Figure 2 As shown in the figure, the light 61 enters the optical fiber from the light input end 6, because the refractive index of the photocatalytic layer 2 is greater than the refractive index of the optical fiber core 1, the light beam is refracted into the photocatalytic layer 2, when the light beam not absorbed by the photocatalytic layer 2 continues to transmit to the interface between the photocatalytic layer 2 and the optical fiber cladding 3, the light beam is refracted into the optical fiber cladding 3, because the material of the optical fiber cladding 3 is quartz, the absorption of light can be ignored; therefore, the light beam continues to transmit to the interface between the optical fiber cladding 3 and the light reflection film 4, is reflected by the light reflection film 4 into the optical fiber cladding 3, that is, the light beam is limited to be transmitted inside the optical fiber, and is absorbed by the photocatalyst in the photocatalytic layer 2, thereby generating electron and hole pairs, thereby avoiding the loss of light transmission, and effectively enhancing the light energy utilization efficiency.

[0019] Preferably, the photocatalytic layer 2 is a semiconductor photocatalyst coated on the photocatalytic film formed by the interface between the optical fiber cladding 3 and the optical fiber core 1.

[0020] Preferably, the photocatalytic layer 2 is prepared from a noble metal / N-TiO2 composite material, and the noble metal / N-TiO2 composite material is prepared by adding noble metal particles into N-TiO2 sol.

[0021] Preferably, the noble metal particles are silver nanoparticles, and the particle size of the silver nanoparticles is less than 8 nm.

[0022] Preferably, the thickness of the photocatalytic layer 2 is 10-30 μm, and the thickness of the light reflection film 4 is 20-200 nm.

[0023] The application also discloses a preparation method of the photocatalytic optical fiber.

[0024] S1, adding titanium isopropoxide into preheated ethylene glycol, and heating the ethylene glycol / titanium isopropoxide mixed solution while stirring;

[0025] S2, adding citric acid monohydrate into the ethylene glycol / titanium isopropoxide mixed solution, and stirring until the mixed solution is clear;

[0026] S3, adding N-TiO2 powder into the mixed solution obtained in step S2, and stirring to obtain a photocatalytic N-TiO2 sol;

[0027] S4, adding silver nanoparticles into the photocatalytic N-TiO2 sol obtained in step S3 to obtain an Ag / N-TiO2 composite material, i.e. a photocatalytic layer 2 raw material, and coating the photocatalytic layer 2 raw material on the interface between the optical fiber cladding 3 and the optical fiber core 1;

[0028] S5, coating the outer surface of the optical fiber cladding 3 coated with the photocatalytic layer 2 obtained in step S4 with a light reflecting film 4, to obtain a photocatalytic optical fiber.

[0029] Preferably, in step S2, the weight ratio of ethylene glycol, titanium isopropoxide, and citric acid monohydrate is in the range of 10:1:8-4:1:3; in step S3, the weight ratio of the mixed solution obtained in step S2 and N-TiO2 powder is in the range of 1.0:1-1.6:1; and in step S4, the weight ratio of the photocatalytic N-TiO2 sol and silver nanoparticles is in the range of 160:1-200:1.

[0030] Preferably, in step S4, coating the photocatalytic layer 2 raw material on the interface between the optical fiber cladding 3 and the optical fiber core 1 comprises the following steps:

[0031] S4.1, sealing the outer surface of the optical fiber cladding 3 with paraffin wax, and cleaning and drying the paraffin wax with a sodium hydroxide solution;

[0032] S4.2, immersing the optical fiber cladding 3 in the photocatalytic layer 2 raw material by a plating film lifting method, so that the interface between the optical fiber cladding 3 and the optical fiber core 1 is coated with the photocatalytic layer 2 raw material, and then sintering to obtain the optical fiber cladding 3 with the photocatalytic layer 2.

[0033] Preferably, in step S5, coating the outer surface of the optical fiber cladding 3 coated with the photocatalytic layer 2 obtained in step S4 with a light reflecting film 4 comprises the following steps:

[0034] S5.1, temporarily plugging the two ends of the optical fiber core 1 with plugs;

[0035] S5.2, cleaning the paraffin wax on the outer surface of the optical fiber cladding 3, and drying the outer surface of the optical fiber cladding 3;

[0036] S5.3. Using magnetron sputtering, a light-reflecting film 4 is sputtered onto the outer surface of the fiber cladding 3. Then, the plugs used to seal both ends of the fiber core 1 are removed to obtain the photocatalytic fiber.

[0037] Preferably, the thickness of the photocatalytic layer 2 is 10–30 μm, and the thickness of the light-reflecting film 4 is 20–200 nm.

[0038] The present invention has the following beneficial effects:

[0039] 1. The photocatalytic layer of the photocatalytic optical fiber disclosed in this invention has a refractive index greater than that of the fiber core and the fiber cladding. At the same time, the surface of the optical fiber has a silver reflective film, which confines the light inside the optical fiber to the photocatalytic layer for transmission, thereby avoiding light transmission loss, effectively enhancing the light energy utilization efficiency, and thus improving the CO2 conversion rate.

[0040] 2. The photocatalytic optical fiber disclosed in this invention has the strongest light intensity on the surface of the photocatalytic layer because the light transmission process in the optical fiber is first transmitted from the fiber core to the photocatalytic layer, and the number of electron-hole pairs generated is the largest, thereby improving the reaction rate and improving the CO2 conversion efficiency.

[0041] 3. The photocatalytic optical fiber disclosed in this invention transmits gas molecules from the fiber core, which are adsorbed on the photocatalytic layer. This causes the electron and hole pairs generated by photocatalysis to react directly with the gas molecules to generate hydrocarbon fuels, effectively improving CO2 conversion efficiency. Attached Figure Description

[0042] To make the objectives, technical solutions, and advantages of the invention clearer, the invention will now be described in further detail with reference to the accompanying drawings, wherein:

[0043] Figure 1 This is a schematic diagram of the photocatalytic optical fiber structure of the present invention.

[0044] Figure 2 This is a schematic diagram of the light and gas transmission path of the present invention.

[0045] Figure 3 This is a schematic diagram of the ethylene glycol molecular structure of the present invention.

[0046] Figure 4 This is a schematic diagram of the isopropoxide titanium molecule structure of the present invention.

[0047] Figure 5 This is a schematic diagram of the molecular structure of citric acid monohydrate according to the present invention.

[0048] Figure 6 This is a graph showing the yield relationship of CO2 reduction to CH4 using a hollow optical fiber in an embodiment of the present invention.

[0049] Explanation of reference numerals in the attached diagram: 1. Fiber core; 2. Fiber cladding; 3. Photocatalytic layer; 4. Light reflective film; 5. Gas input end; 51. CO2 gas molecule; 52. H2O gas molecule; 6. Light input end; 61. Light ray. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0051] It should be noted that similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the figures, or the orientation or positional relationship commonly used when the product is in use. They are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance. In addition, the terms "horizontal," "vertical," etc., do not indicate that the component is required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted. In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0052] This invention solves the technical problem of low CO2 conversion efficiency when side-emitting optical fibers coated with photocatalysts are applied to the photocatalytic reduction of CO2.

[0053] The application discloses a photocatalytic optical fiber, and aims to improve the conversion efficiency of CO2.

[0054] As shown in the accompanying drawings, Figure 1 The application discloses a photocatalytic optical fiber, which comprises a fiber core 1, a photocatalytic layer 2, a fiber cladding 3 and a light reflection film 4.

[0055] The fiber core 1 is a hollow structure, and the fiber cladding 3 is arranged around the outer periphery of the fiber core 1.

[0056] The interface between the fiber cladding 3 and the fiber core 1 is coated with the photocatalytic layer 2, and the outer surface of the fiber cladding 3 away from the fiber core 1 is coated with the light reflection film 4.

[0057] The two ends of the fiber core 1 are respectively a gas input end 5 and a light input end 6.

[0058] The light can enter the fiber core 1 through the light input end 6 and can be reflected by the light reflection film 4.

[0059] In specific implementation, the fiber core 1 is air, the fiber cladding 3 is quartz, and the light reflection film 4 is silver.

[0060] In the prior art, the photocatalytic layer 2 is coated on the outer surface of the fiber cladding 3, and the interface between the fiber cladding 3 and the photocatalytic layer 2 strongly attenuates or even completely absorbs the light for photocatalytic reduction of CO2, so that there is almost no light for exciting the photocatalyst to generate electron-hole pairs on the outer surface of the photocatalytic layer 2, the electron-hole pairs generated at the interface between the fiber cladding 3 and the photocatalytic layer 2 are greatly lost in the transmission process to the surface layer of the catalytic film, and the number of the electron-hole pairs generated by the surface layer catalyst is limited due to the light limitation, so that the efficiency of photocatalytic reduction of CO2 is low.

[0061] Compared with the prior art, the photocatalytic layer 2 is coated on the inner surface of the fiber cladding 3, and the specific working principle is that the refractive index of the photocatalytic layer 2 is greater than the refractive indexes of the fiber core 1 and the fiber cladding 3, and the fiber cladding 3 is provided with the light reflection film 4, so as to limit the light entering the fiber to be transmitted in the fiber. Figure 2As shown, the light ray 61 enters the optical fiber from the light input end 6, and due to the fact that the refractive index of the photocatalytic layer 2 is greater than the refractive index of the optical fiber core 1, the light beam is refracted into the photocatalytic layer 2, and when the light beam that is not absorbed by the photocatalytic layer 2 continues to transmit to the interface between the photocatalytic layer 2 and the optical fiber cladding 3, the light beam is refracted into the optical fiber cladding 3, and since the material of the optical fiber cladding 3 is quartz, the absorption of light can be ignored; therefore, the light beam continues to transmit to the interface between the optical fiber cladding 3 and the light reflection film 4, is reflected by the light reflection film 4 into the optical fiber cladding 3, that is, the light beam is limited to transmit inside the optical fiber, and is absorbed by the photocatalyst in the photocatalytic layer 2, thereby generating electron-hole pairs, thereby avoiding the loss of light transmission and effectively enhancing the light energy utilization efficiency.

[0062] Since the transmission process of light in the optical fiber is first transmitted from the optical fiber core to the interface between the optical fiber core 1 and the photocatalytic layer 2, the surface light intensity of the photocatalytic layer 2 is the strongest, and the number of generated electron-hole pairs is the most; after the light beam that is not absorbed by the photocatalytic layer 2 is reflected by the light reflection film 4, it is shot to the interface between the photocatalytic layer 2 and the optical fiber cladding 3, so that both surfaces of the photocatalytic layer 2 can be in contact with light, thereby increasing the contact area of light and catalyst, thereby generating more electron-hole pairs, thereby avoiding the loss of light transmission and effectively enhancing the light energy utilization efficiency.

[0063] In addition, taking the reaction of producing hydrocarbon fuel by photocatalytic reaction as an example, in the reaction process, CO2 and H2O gas molecules are often simultaneously input as initial reaction raw materials of the photocatalytic reaction, such as Figure 2 As shown, the CO2 and H2O gas molecules transmitted from the optical fiber core are also adsorbed on the surface of the photocatalytic layer 2, thereby promoting the photocatalytic generated electron-hole pairs to directly react with CO2 and H2O gas molecules to generate hydrocarbon fuel, and the hydrocarbon fuel (such as CH4, C2H6, C3H8, etc.) can be separated from the surface of the photocatalytic layer 2 in time, thereby avoiding inhibiting the photocatalytic generated electron-hole pairs in the photocatalytic layer 2 from reducing reaction with CO2 and H2O gas molecules, and effectively improving the conversion efficiency of CO2 in the photocatalytic reduction reaction.

[0064] And the light reflection film 4 is coated on the outer surface of the optical fiber cladding 3 and does not contact the photocatalytic layer 2, so that the light reflection film 4 does not hinder the direct contact of water molecules and CO2 with the photocatalyst, thereby not hindering the conversion of CO2 in the photocatalytic reduction reaction.

[0065] The photocatalytic optical fiber disclosed in the present application can also be used for the digestion and conversion of gas pollutants, thereby realizing the treatment of gas pollutants, such as ammonia, hydrogen sulfide, volatile toxic organic pollutants and other gas pollutants that can be oxidized or reduced.

[0066] As a preferred, the photocatalytic layer 2 is a photocatalytic film formed by coating the semiconductor photocatalyst on the interface between the optical fiber cladding 3 and the optical fiber core 1.

[0067] As a preferred, the thickness of the photocatalytic layer 2 is 10-30 μm.

[0068] Specifically, the semiconductor photocatalyst material includes one of the following semiconductor materials:

[0069] (1) "O" type, such as WO3, which has a positive valence band potential and strong oxidation ability;

[0070] (2) "R" type, such as GaAs, which has a negative conduction band potential and strong reduction ability;

[0071] (3) "RO" type, such as TiO2, SrTiO3, which has a better matching energy band structure with the redox potential of water.

[0072] As a preferred, the photocatalytic layer 2 is prepared from a noble metal / N-TiO2 composite material, which is prepared by adding noble metal particles to N-TiO2 sol.

[0073] Depositing noble metal particles, such as Ag, Au, Pt, Pd, Rh, Ru, etc., on the surface of nano-TiO2 can effectively separate the photo-generated electron-hole pairs and inhibit the recombination between them. In addition, depositing a certain specific noble metal particle can also improve the visible light response of TiO2.

[0074] After the noble metal is deposited on the surface of TiO2, a photo-generated electron accumulation center is formed, which can better capture photo-generated electrons. In addition, because the individual charge transfer after the deposition of noble metal particles causes the Fermi level of the noble metal particles to be lower than the conduction band of the semiconductor TiO2, electrons continuously transfer from the inside of TiO2 to the loaded noble metal nanoparticles after being excited by external conditions, which will continue until the new Fermi level reaches equilibrium. At the same time, a Schottky barrier is formed at the junction of the noble metal particles and TiO2, which causes the photo-generated electrons to continue to accumulate at the noble metal particles, while the holes also migrate to the surface of TiO2, thereby inhibiting the recombination of electron-hole pairs. After being excited, the electrons can overcome the barrier and flow from TiO2 to the noble metal particles, but on the contrary, the electrons will be blocked by the barrier and cannot return.

[0075] Therefore, the efficient photo-generated electron-hole pairs will produce a large number of ·O2 - and ·OH active free radicals to participate in redox reactions, thereby improving the photocatalytic performance.

[0076] N-doped TiO2 (N-TiO2) can effectively replace oxygen atoms in the TiO2 lattice without high energy, because N has a suitable atomic radius. The energy band position formed after N-doping is shallow, which can ensure the effective migration of photo-generated carriers. Moreover, N-doped TiO2 can change the band gap of TiO2. Therefore, N-doped TiO2 is the most effective way to make TiO2 respond to visible light.

[0077] In specific implementation, the N-TiO2 is in powder form, and the particle size is less than 30 nm. The particle size of the noble metal particles is less than 8 nm.

[0078] Preferably, the photocatalytic layer 2 is prepared from Ag / N-TiO2 composite material, which is prepared by adding silver nanoparticles to N-TiO2 sol.

[0079] Preferably, the light reflection film 4 is formed by sputtering silver on the surface of the optical fiber cladding 3 by a magnetron sputtering method. The thickness of the light reflection film 4 is 20-200 nm.

[0080] Preferably, the diameter of the optical fiber core 1 is 0.2-10 mm, and the thickness of the optical fiber cladding 3 is 0.2-5 mm.

[0081] Specifically, the TiO2 refers to silicon dioxide, the English name is titanium oxide, the CAS number is 12065-65-5, and the molecular weight is 223.598.

[0082] The application also discloses a preparation method of the photocatalytic optical fiber.

[0083] S1, adding titanium isopropoxide to preheated ethylene glycol, and heating the ethylene glycol / titanium isopropoxide mixed solution while stirring;

[0084] S2, adding citric acid monohydrate to the ethylene glycol / titanium isopropoxide mixed solution, and stirring until the mixed solution is colorless and transparent;

[0085] S3, adding N-TiO2 powder to the mixed solution obtained in step S2, and stirring to obtain photocatalytic N-TiO2 sol;

[0086] S4, adding silver nanoparticles to the photocatalytic N-TiO2 sol obtained in step S3 to obtain Ag / N-TiO2 composite material, that is, to obtain the raw material for preparing the photocatalytic layer 2, and coating the raw material for preparing the photocatalytic layer 2 on the interface between the optical fiber cladding 3 and the optical fiber core 1.

[0087] S5, coating the outer surface of the optical fiber cladding 3 coated with the photocatalytic layer 2 obtained in step S4 with a light reflection film 4, to obtain a photocatalytic optical fiber.

[0088] Specifically, in step S1, the weight ratio of ethylene glycol to titanium isopropoxide is in the range of 10:1 to 4:1.

[0089] Specifically, in step S1, the preheating temperature of ethylene glycol is 55-65 ℃, and the ethylene glycol needs to be continuously stirred when heated; after adding titanium isopropoxide, the mixed solution of ethylene glycol / titanium isopropoxide is heated to 85-95 ℃.

[0090] Specifically, in step S1, the ethylene glycol used has the English name Ethylene glycol, the molecular formula C2H6O2, the molecular weight 62.068, the CAS number 107-21-1, and the Chinese alias 1,2-ethanediol / glycol / ethyl glycol / ethylene glycol / ethylene glycol. The molecular structure of ethylene glycol is shown in Figure 3 .

[0091] Specifically, in step S1, the titanium isopropoxide used has the common name titanium isopropoxide, the English name Titanium(4+) tetrapropan-2-olate, Chemical Formula C 12 H 28 O4Ti, the molecular weight is 284.215, the CAS number is 546-68-9, and the Chinese alias has titanium isopropoxide / titanium(IV) isopropoxide / titanium isopropoxide / titanium isopropoxide. The molecular structure of titanium isopropoxide is shown in Figure 4 .

[0092] Specifically, in step S2, the weight ratio of ethylene glycol, titanium isopropoxide, and citric acid monohydrate is in the range of 10:1:8 to 4:1:3.

[0093] Specifically, in step S2, after adding citric acid monohydrate to the mixed solution obtained in step S1, continuous stirring is required until the solution is clear.

[0094] Specifically, in step S2, the citric acid monohydrate used is a natural preservative and food acid enhancer, with the English name Citric acid monohydrate, the molecular formula C6H 10 O8, the molecular weight is 210.139, the CAS number is 5949-29-1, and the Chinese alias has citric acid / citric acid. The molecular structure of citric acid monohydrate is shown in Figure 5 .

[0095] Specifically, in step S3, the N-TiO2 is in powder form with a particle size less than 30 nm, and the weight ratio of the mixed solution obtained in step S2 to the N-TiO2 powder ranges from 1.0:1 to 1.6:1, preferably 1.54, and the stirring time ranges from 3 to 5 hours.

[0096] Specifically, in step S4, the silver nanoparticles have a particle size less than 5 nm, and the weight ratio of the photocatalytic N-TiO2 sol to the silver nanoparticles ranges from 160:1 to 200:1.

[0097] The Ag / N-TiO2 composite material obtained in step S4 can enhance the adhesion strength between the photocatalytic layer 2 and the optical fiber cladding 3, and can also inhibit the recombination of photo-generated electron-hole pairs.

[0098] Specifically, in step S4, the optical fiber cladding 3 is a hollow quartz tube with an inner diameter of 0.2-10 mm, a thickness of 0.2-5 mm, and a length of 2-200 cm.

[0099] Specifically, in step S4, coating the photocatalytic layer 2 raw material on the interface between the optical fiber cladding 3 and the optical fiber core 1 includes the following steps:

[0100] S4.1, sealing the outer surface of the optical fiber cladding 3 with paraffin wax, and cleaning with a sodium hydroxide solution and air-drying;

[0101] S4.2, using a plating method, immersing the optical fiber cladding 3 in the photocatalytic layer 2 raw material, so that the interface between the optical fiber cladding 3 and the optical fiber core 1 is coated with the photocatalytic layer 2 raw material, and then sintering to obtain the optical fiber cladding 3 with the photocatalytic layer 2.

[0102] Specifically, in step S4.1, the concentration of sodium hydroxide is 1-2 mol / L, the cleaning time is 20-40 minutes, and the cleaning temperature is room temperature; after cleaning, the optical fiber cladding 3 is taken out and rinsed with deionized water and air-dried.

[0103] The optical fiber is cleaned with sodium hydroxide to hydroxylize the surface of the optical fiber and enhance the adhesion strength between the photocatalyst and the optical fiber.

[0104] Specifically, in step S4.2, the thickness of the photocatalytic layer 2 is 10-30 μm.

[0105] Specifically, in step S4.2, the sintering temperature is 250-350 ℃, and the sintering time is 2-3 hours.

[0106] Specifically, in step S5, coating a light reflecting film 4 on the outer surface of the optical fiber cladding 3 coated with the photocatalytic layer 2 obtained in step S4 includes the following steps:

[0107] S5.1, temporarily seal the two ends of the optical fiber core 1 with plugs;

[0108] S5.2, clean the paraffin wax on the outer surface of the optical fiber cladding 3, and dry the outer surface of the optical fiber cladding 3;

[0109] S5.3, use a magnetron sputtering method to sputter a light reflecting film 4 on the outer surface of the optical fiber cladding 3, and then remove the plugs used to seal the two ends of the optical fiber core 1, thereby obtaining a photocatalytic optical fiber.

[0110] Specifically, in step S5.1, the plugs are plastic plugs, and the two ends of the optical fiber core 1 are temporarily sealed with plastic plugs to prevent external substances from contaminating the photocatalytic layer 2 coated on the inner surface of the quartz tube.

[0111] Specifically, in step S5.2, the outer surface of the sealed optical fiber cladding 3 is cleaned with alcohol and dried with nitrogen.

[0112] Specifically, in step S5.3, the thickness of the light reflecting film 4 is 20-200 nm, and the light reflecting film 4 is a silver film.

[0113] Magnetron sputtering is a type of physical vapor deposition (PVD). General sputtering methods can be used to prepare multiple materials such as metals, semiconductors, and insulators, and have the advantages of simple equipment, easy control, large coating area, and strong adhesion. The magnetron sputtering method developed in the 1970s achieves high speed, low temperature, and low damage.

[0114] Magnetron sputtering specifically refers to the addition of a closed magnetic field parallel to the target surface in diode sputtering, which uses the orthogonal electromagnetic field formed on the target surface to confine the secondary electron beam in a specific area of the target surface to enhance ionization efficiency, increase ion density and energy, and thus achieve a high-speed sputtering process.

[0115] The working principle of magnetron sputtering is that electrons, under the action of an electric field E, collide with argon atoms during their flight to the substrate, causing ionization to produce Ar positive ions and new electrons; new electrons fly to the substrate, and Ar ions accelerate to the cathode target under the action of the electric field and bombard the target surface with high energy, causing the target material to sputter. Since the sputtered atoms are exchanged with positive ions with tens of electron volts of energy, the sputtered atoms have high energy, which is beneficial to improving the diffusion ability of the atoms during deposition and improving the compactness of the deposited structure, allowing the prepared thin film to have strong adhesion to the substrate.

[0116] The application adopts the magnetron sputtering method to sputter the light reflection film 4 to the outer surface of the optical fiber cladding 3, which can ensure that the light reflection film 4 is closely combined with the outer surface of the optical fiber cladding 3 and does not occur damage or shedding phenomenon, thereby ensuring the stability of the transmission path of the light in the optical fiber, and further ensuring the reaction efficiency of the photocatalytic reduction reaction.

[0117] The photocatalytic optical fiber and the preparation method thereof have the following technical effects: the optical fiber core 1 is air, the photocatalytic layer 2 is composed of a semiconductor photocatalyst, the optical fiber cladding 3 is composed of quartz, and the optical fiber surface light reflection film 4 is composed of a silver film, thereby limiting the light in the optical fiber to be transmitted in the photocatalytic layer 2, and the light on the surface layer of the photocatalytic layer 2 is the strongest and the number of electron-hole pairs is the most; the application overcomes the defects of the traditional photocatalytic optical fiber that the photocatalytic layer 2 is coated on the outer surface of the optical fiber, which results in that the light on the surface layer of the photocatalytic layer 2 is the weakest and the number of electron-hole pairs is the least, thereby reducing the light energy utilization efficiency and the performance of photocatalytic reduction of CO2 to prepare carbon-hydrogen fuel.

[0118] In addition, the application can not only be used for the preparation of carbon-hydrogen fuel by CO2 reduction, but also be used for the treatment of gas pollutants, such as ammonia, hydrogen sulfide and volatile toxic organic pollutants. Embodiment

[0119] The photocatalytic optical fiber is prepared according to the following steps:

[0120] S1, 3 mL of titanium isopropoxide is added to the preheated 13 mL of ethylene glycol, and the ethylene glycol / titanium isopropoxide mixed solution is heated while stirring;

[0121] S2, 12.6 g of citric acid monohydrate is added to the ethylene glycol / titanium isopropoxide mixed solution, and the mixed solution is stirred until the color is clear;

[0122] S3, 20 g of N-TiO2 powder with a particle size of 20 nm is added to the mixed solution obtained in step S2, and the photocatalytic N-TiO2 sol is obtained after stirring;

[0123] S4, 0.15 g of silver nanoparticles with a particle size of 4 nm is added to the photocatalytic N-TiO2 sol obtained in step S3 to obtain Ag / N-TiO2 composite material, that is, the preparation of photocatalytic layer 2 raw material, and the photocatalytic layer 2 raw material is coated on the interface between the optical fiber cladding 3 and the optical fiber core 1, and the thickness of the photocatalytic layer 2 is 15 μm;

[0124] S4.1, the outer surface of the optical fiber cladding 3 is sealed with paraffin, and washed with sodium hydroxide solution and dried, the diameter of the optical fiber core 1 in the optical fiber cladding 3 is 1 mm, the wall thickness of the optical fiber cladding 3 is 1 mm, and the length of the optical fiber cladding 3 is 20 cm;

[0125] S4.2. Using the coating extraction method, the optical fiber cladding 3 is immersed in the raw material of the photocatalytic layer 2, so that the interface between the optical fiber cladding 3 and the optical fiber core 1 is coated with the raw material of the photocatalytic layer 2, and then sintering is performed to obtain the optical fiber cladding 3 with the photocatalytic layer 2.

[0126] S5. Coat the outer surface of the optical fiber cladding 3 coated with the photocatalytic layer 2 obtained in step S4 with a light reflection film 4. The thickness of the light reflection film 4 is 100 nm, thus obtaining the photocatalytic optical fiber.

[0127] S5.1 Temporarily seal both ends of fiber core 1 with plugs;

[0128] S5.2 Clean the paraffin wax on the outer surface of the optical fiber cladding 3 and dry the outer surface of the optical fiber cladding 3.

[0129] S5.3. Using magnetron sputtering, a light-reflecting film 4 is sputtered onto the outer surface of the fiber cladding 3. Then, the plugs used to seal both ends of the fiber core 1 are removed to obtain the photocatalytic fiber.

[0130] The experimental curves of CO2 conversion performance (CH4 production rate) of the photocatalytic optical fiber prepared according to the above steps under 5mW UV-Vis excitation are shown below. Figure 6 As shown.

[0131] Depend on Figure 6 It can be seen that the production rate of CH4 is linearly related to time. The production rate of CH4 gradually increases with time, and the growth rate of production does not change. This shows that the photocatalytic optical fiber prepared by the present invention can effectively improve the conversion efficiency of CO2 in the photocatalytic reduction reaction.

[0132] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Under the teachings of the present invention, modifications can be made to these features and embodiments to adapt to specific situations and materials without departing from the spirit and scope of the invention. The embodiments described in this invention are only a part of the embodiments of the invention, not all of them. The components of the embodiments of the invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. Therefore, the invention is not limited to the specific embodiments disclosed herein, and all other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A photocatalytic optical fiber, characterized in that, It includes an optical fiber core (1), a photocatalytic layer (2), an optical fiber cladding (3), and a light-reflecting film (4); The fiber core (1) is a hollow structure, and the fiber core (1) is surrounded by an optical fiber cladding (3) on its outer periphery; The interface between the optical fiber cladding (3) and the optical fiber core (1) is coated with a photocatalytic layer (2), and the outer surface of the optical fiber cladding (3) away from the optical fiber core (1) is coated with a light-reflecting film (4). The two ends of the fiber core (1) are a gas input end (5) and a light input end (6), respectively. The gas can enter the fiber core (1) through the gas input end (5) and can come into contact with the photocatalytic layer (2) to undergo a photocatalytic reduction reaction. The light can enter the fiber core (1) through the light input end (6) and can be reflected by the light reflection film (4); The photocatalytic layer (2) is a photocatalytic thin film formed by coating a semiconductor photocatalyst at the interface between the optical fiber cladding (3) and the optical fiber core (1); the photocatalytic layer (2) is made of a noble metal / N-TiO2 composite material, which is prepared by adding noble metal particles to N-TiO2 sol; the noble metal particles are silver nanoparticles with a particle size of less than 8 nm; The fabrication method of this photocatalytic optical fiber includes the following steps: S1. Add titanium isopropoxide to preheated ethylene glycol, and heat the ethylene glycol / titanium isopropoxide mixture while stirring. S2. Add citric acid monohydrate to the ethylene glycol / titanium isopropoxide mixed solution and stir until the mixed solution is clear; the weight ratio of ethylene glycol, titanium isopropoxide and citric acid monohydrate is in the range of 10:1:8 to 4:1:

3. S3. Add N-TiO2 powder to the mixed solution obtained in step S2, and stir to obtain photocatalytic N-TiO2 sol; the weight ratio of the mixed solution to N-TiO2 powder is in the range of 1.0:1 to 1.6:

1. S4. Add silver nanoparticles to the photocatalytic N-TiO2 sol obtained in step S3 to obtain Ag / N-TiO2 composite material, which is the raw material for preparing photocatalytic layer (2). The weight ratio of photocatalytic N-TiO2 sol to silver nanoparticles is 160:1 to 200:

1. Coat the raw material for photocatalytic layer (2) at the interface between the optical fiber cladding (3) and the optical fiber core (1). This step specifically includes: S4.1 Seal the outer surface of the optical fiber cladding (3) with paraffin wax, and clean and dry it with sodium hydroxide solution; S4.

2. Using the coating extraction method, the optical fiber cladding (3) is immersed in the photocatalytic layer (2) material, so that the interface between the optical fiber cladding (3) and the optical fiber core (1) is coated with the photocatalytic layer (2) material, and then sintering is performed to obtain an optical fiber cladding (3) with a photocatalytic layer (2). S5. Coat the outer surface of the optical fiber cladding (3) coated with the photocatalytic layer (2) obtained in step S4 with a light reflection film (4) to obtain the photocatalytic optical fiber.

2. The photocatalytic optical fiber according to claim 1, characterized in that, The thickness of the photocatalytic layer (2) is 10-30 μm, and the thickness of the light reflection film (4) is 20-200 nm.

3. The photocatalytic optical fiber according to claim 1, characterized in that, In step S5, coating the outer surface of the optical fiber cladding (3) coated with the photocatalytic layer (2) obtained in step S4 with a light-reflecting film (4) includes the following steps: S5.1 Temporarily seal both ends of the optical fiber core (1) with plugs; S5.2 Clean the paraffin wax on the outer surface of the fiber cladding (3) and dry the outer surface of the fiber cladding (3); S5.

3. Using magnetron sputtering, a light-reflecting film (4) is sputtered onto the outer surface of the fiber cladding (3). Then, the plugs used to seal both ends of the fiber core (1) are removed to obtain the photocatalytic fiber.

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