Optical fiber hydrogen sensor for detecting hydrogen in water

Abstract

The invention belongs to the technical field of hydrogen detection sensing, and particularly relates to an optical fiber hydrogen sensor for detecting hydrogen in water. The optical fiber hydrogen sensor consists of a demodulator and a hydrogen-sensitive optical fiber, wherein the hydrogen-sensitive optical fiber consists of an optical fiber, a WO3 / Pt layer and an ePTFE hydrophobic breathable film from inside to outside, wherein the WO3 / Pt layer is coated outside the optical fiber, and the ePTFE hydrophobic breathable film is coated outside the WO3 / Pt layer. The optical fiber hydrogen sensor is small in size, and the defect that a traditional hydrogen sensor is not suitable for a narrow space in a small chamber of a water electrolysis hydrogen production tank is overcome. The problems of spectrum jitter and abnormal interference caused by the fact that a traditional optical fiber hydrogen sensor is affected by water in an electrolytic bath environment are solved through the hydrophobic breathable film. The hydrogen sensor disclosed by the invention provides a real-time and stable quantitative means for solving the problem that hydrogen concentration cannot be effectively measured due to mixing of hydrogen and oxygen in a small chamber, a water outlet and an oxygen outlet of a water electrolysis hydrogen production tank.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of hydrogen detection and sensing, and particularly relates to a fiber-optic hydrogen sensor for hydrogen detection in water. BACKGROUND

[0002] Hydrogen (H2) is a clean and efficient energy carrier and an important industrial raw material, and is increasingly widely used in new energy, chemical industry, aerospace and other fields. However, there are still many risks in the electrolytic hydrogen production system today, such as: 1) hydrogen itself has the characteristics of colorless and odorless, flammable and explosive (explosion limit in air is 4%~75%), small molecular weight, etc.; 2) the hydrogen-oxygen gas mixture in the electrolytic water hydrogen tank cell is extremely dangerous. Therefore, it is crucial to develop a real-time hydrogen monitoring technology with high sensitivity, fast response, intrinsic safety (explosion-proof), and stable performance.

[0003] Traditional electrical hydrogen sensors (such as semiconductor type and electrochemical type) have the disadvantages of large size and susceptibility to electromagnetic interference. Fiber-optic sensors, with their intrinsic safety (passive, no electricity), resistance to electromagnetic interference, corrosion resistance, small size, easy multiplexing and distributed sensing, have become an ideal choice for gas monitoring in harsh environments. By combining a hydrogen-sensitive film with a fiber-optic structure, high-sensitivity measurement of hydrogen concentration can be achieved. However, there is no precedent in the prior art for testing hydrogen concentration in hydrogen-oxygen mixed gas in an electrolytic tank environment, so it is of great significance to develop a fiber-optic hydrogen sensor for hydrogen detection in water. SUMMARY

[0004] The technical problem to be solved by the present application is to address the shortcomings of the prior art by combining a fiber-optic hydrogen sensor with excellent performance with a hydrophobic gas-permeable membrane, providing a new solution for measuring hydrogen concentration in hydrogen-oxygen mixed gas in an electrolytic water hydrogen tank cell, and breaking through the technical bottleneck of traditional sensors in measuring hydrogen concentration in hydrogen-oxygen mixed gas in an electrolytic tank environment.

[0005] To solve the above technical problems, the following technical solutions are adopted in the present application:

[0006] The present application provides a fiber-optic hydrogen sensor for hydrogen detection in water, which is composed of a demodulator and a hydrogen-sensitive optical fiber. The hydrogen-sensitive optical fiber is composed of an optical fiber, a WO3 / Pt layer coated on the outside of the optical fiber, and an ePTFE hydrophobic gas-permeable membrane coated on the outside of the WO3 / Pt layer.

[0007] The hydrogen-sensitive optical fiber is selected to have a structure of single-mode optical fiber-no-core optical fiber-single-mode optical fiber.

[0008] The diameter of the single-mode optical fiber is 60~300μm, and the diameter of the no-core optical fiber is 60~300μm.

[0009] In some embodiments of the present invention, the single-mode optical fiber has a diameter of 125 μm and a length of 30 cm; the coreless optical fiber has a diameter of 125 μm and a length of 5 cm.

[0010] The WO3 / Pt layer is located on the surface of the coreless optical fiber; the thickness of the WO3 layer is 10nm~500μm; and the thickness of the Pt layer is 1nm~50μm.

[0011] In some embodiments of the present invention, the thickness of the WO3 layer is 50 nm and the thickness of the Pt layer is 5 nm.

[0012] The ePTFE hydrophobic and breathable membrane has a thickness of 10~100μm and a pore size of 0.2~1μm.

[0013] In some embodiments of the present invention, the ePTFE hydrophobic and breathable membrane has a thickness of 30 μm, a pore size of 0.45 μm, and a length of 10 cm.

[0014] In some embodiments of the present invention, the working steps of the optical fiber hydrogen sensor in the electrolytic cell are as follows: one end of the hydrogen-sensitive optical fiber is connected to the electrolytic cell, and the other end is connected to the demodulator. It is ensured that the hydrogen-sensitive optical fiber is completely sealed in the small chamber of the electrolytic cell and the outlet. The surface of the hydrogen-sensitive optical fiber can react with hydrogen, thereby changing the optical properties and affecting the optical fiber spectrum. By analyzing the changes in the optical signal transmitted back by the optical fiber through the demodulator, the concentration of hydrogen in the gas flow inside the electrolytic cell and at the outlet can be monitored.

[0015] In some embodiments of the present invention, the WO3 layer readily reacts with hydrogen to form hydrogen tungsten bronze, thereby causing a change in refractive index. The optical fiber is affected by the change in refractive index, and the spectrum will change.

[0016] In some embodiments of the present invention, the Pt layer is a hydrogen activator, which facilitates the decomposition of hydrogen molecules into hydrogen atoms, thereby enabling a more efficient reaction with the WO3 layer.

[0017] The second aspect of this invention provides a method for fabricating an optical fiber hydrogen sensor, comprising the following steps: fusion splicing two single-mode optical fibers and a coreless optical fiber to obtain a single-mode optical fiber-coreless optical fiber-single-mode optical fiber structure; constructing a WO3 layer on the surface of the coreless optical fiber using a radio frequency magnetron sputtering process; and finally constructing a Pt layer on the surface of the WO3 layer using a DC magnetron sputtering process. At this point, the coreless optical fiber, the WO3 layer, and the Pt layer together constitute the optical fiber sensing region of the optical fiber hydrogen sensor. The optical fiber sensing region is then coated with an ePTFE hydrophobic and gas-permeable membrane to obtain a hydrogen-sensitive optical fiber. The hydrogen-sensitive optical fiber is fixed in the environment to be tested and connected to a demodulator, thus completing the fabrication of the optical fiber hydrogen sensor.

[0018] In some embodiments of the present invention, the fusion splicing includes the following steps: placing the stripped fiber on a fiber cleaver, making the fiber end face flat by cutting, and placing the single-mode fiber and the coreless fiber on the fiber fusion splicer in the order of single-mode-coreless-single-mode for fusion splicing, with fiber loss less than 0.05dB.

[0019] The radio frequency magnetron sputtering process is characterized by the following conditions: the pressure in the reaction chamber is controlled below 4.5 μTorr, Ar is introduced at 10-20 scmm and O2 at 0-5 sccm, the power is 50-150 W, and the time is 10-240 min.

[0020] In some embodiments of the present invention, the radio frequency magnetron sputtering process is performed under the following conditions: the pressure in the reaction chamber is controlled below 4.5 μTorr, 15 scmm of Ar and 1 sccm of O2 are introduced, the power is 80 W, and the time is 15 min.

[0021] The DC magnetron sputtering process is characterized by the following conditions: the pressure in the reaction chamber is controlled below 4.5 μTorr, 10-20 scmm of Ar is introduced, the power is 50-150 W, and the time is 10-240 s.

[0022] In some embodiments of the present invention, the DC magnetron sputtering process is performed under the following conditions: the pressure in the reaction chamber is controlled below 4.5 μTorr, 15 scmm of Ar is introduced, the power is 100 W, and the time is 1 min.

[0023] The third aspect of this invention provides an application of an optical fiber hydrogen sensor in real-time monitoring of hydrogen concentration in a hydrogen-oxygen mixture in an electrolytic hydrogen production system.

[0024] In some embodiments of this invention, an optical fiber hydrogen sensor was successfully fabricated using the above-described preparation method and applied to hydrogen detection in water within an electrolyzer. The ePTFE hydrophobic and breathable membrane on the surface of the hydrogen-sensitive optical fiber blocks liquid water, water vapor, and impurities from entering the fiber's interior, while allowing hydrogen molecules to pass through rapidly, achieving a gas-permeable but water-impermeable effect. After selective hydrogen selection, the optical properties are altered using a WO3 / Pt layer, thereby affecting the optical fiber spectrum. By analyzing the changes in the optical signal transmitted back from the fiber using a demodulator, the hydrogen concentration inside the electrolyzer and in the outlet gas flow was successfully monitored. This demonstrates the promising application of the optical fiber hydrogen sensor in real-time monitoring of hydrogen concentration in hydrogen-oxygen mixtures within an electrolytic hydrogen production system.

[0025] Beneficial effects:

[0026] The fiber optic hydrogen sensor provided by this invention is small in size, overcoming the limitation of traditional hydrogen sensors being unsuitable for the confined space of a water electrolysis hydrogen production cell. It utilizes a hydrophobic and breathable membrane to overcome the spectral fluctuations and abnormal interference problems caused by water in the electrolysis cell environment of traditional fiber optic hydrogen sensors. This invention provides a real-time and stable quantitative method to address the problem of ineffective hydrogen concentration measurement in the water electrolysis hydrogen production cell, at the water outlet, and at the oxygen outlet due to hydrogen and oxygen gas mixing. Attached Figure Description

[0027] The present invention will be further described in detail below with reference to the accompanying drawings, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0028] Figure 1 This is a cross-sectional view of the optical fiber sensing area in an embodiment of the present invention, wherein 1 is a coreless optical fiber, 2 is a WO3 layer, 3 is a Pt layer, and 4 is an ePTFE hydrophobic and breathable membrane.

[0029] Figure 2 This is a schematic diagram of the operation of the fiber optic hydrogen sensor for hydrogen detection in water in an embodiment of the present invention.

[0030] Figure 3 This is a curve showing the change of the optical fiber hydrogen sensor spectrum with hydrogen concentration in an embodiment of the present invention. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0032] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and materials described are commercially available unless otherwise specified.

[0033] This invention provides an optical fiber hydrogen sensor for hydrogen detection in water, specifically comprising a demodulator and a hydrogen-sensitive optical fiber. The hydrogen-sensitive optical fiber is a composite of a hydrogen-sensitive thin film and optical fibers of different structures. Specifically, the different optical fiber structures include any one of single-mode coreless-single-mode fiber, multi-mode coreless-multi-mode fiber, Bragg fiber grating, and long-period fiber grating. The hydrogen-sensitive thin film includes any one or a combination of several of the following: WO3 / Pt thin film, WO3 / Pd thin film, SnO2 (tin oxide) thin film, WO3 (tungsten oxide) thin film, ZnO (zinc oxide) thin film, In2O3 (indium oxide) thin film, TiO2 (titanium oxide) thin film, Pd thin film, PdAg thin film, PdAu thin film, and PdNi thin film. To overcome the spectral fluctuations caused by water in the electrolyzer environment of traditional optical fiber hydrogen sensors, this invention coats the sensing region of the hydrogen-sensitive optical fiber with a hydrophobic and gas-permeable membrane, thereby achieving stable testing of the optical fiber hydrogen sensor. Hydrophobic and breathable membranes include any one or a combination of several of TPU films, ePTFE films, and polyolefin films.

[0034] Example 1:

[0035] This embodiment provides an optical fiber hydrogen sensor for hydrogen detection in water. The optical fiber hydrogen sensor includes a demodulator and a hydrogen-sensitive optical fiber. Specifically, the optical fiber of the hydrogen-sensitive fiber adopts a single-mode coreless-single-mode fiber structure, and the thin film sensitive to hydrogen is a WO3 / Pt thin film. The specific preparation steps are as follows:

[0036] First, using wire strippers, the cladding of the two single-mode and coreless optical fibers is stripped. The stripped fibers are then placed on a fiber cleaver and cut to make the fiber ends flat. The single-mode and coreless fibers are then placed on a fiber fusion splicer in the order of single-mode-coreless-single-mode for splicing. The fiber loss is less than 0.05dB, resulting in a single-mode-coreless-single-mode fiber structure. The single-mode fiber has a diameter of 125μm and a length of 30cm; the coreless fiber has a diameter of 125μm and a length of 5cm.

[0037] Furthermore, a WO3 / Pt thin film and a hydrophobic and breathable film are constructed on the surface of the coreless fiber in the single-mode-coreless-single-mode fiber structure to obtain the fiber sensing area of ​​the hydrogen-sensitive fiber. Figure 1The image shows a cross-sectional view of the fiber optic sensing region, where 1 represents the coreless fiber, 2 the WO3 layer, 3 the Pt layer, and 4 the ePTFE hydrophobic and breathable membrane. First, a WO3 layer with a thickness of 50 nm was constructed on the surface of the coreless fiber using radio frequency magnetron sputtering. Specific process parameters were as follows: the pressure in the magnetron sputtering reaction chamber was reduced to below 4.5 μTorr using a vacuum pump; then, 15 scmm of Ar and 1 sccm of O2 were introduced; the radio frequency magnetron sputtering power was turned on and set to 80 W; and the deposition time was 15 min to prepare a 50 nm thick WO3 layer. Subsequently, a Pt layer with a thickness of 5 nm was constructed on the surface of the WO3 layer using DC magnetron sputtering. Specific process parameters were as follows: the pressure in the magnetron sputtering reaction chamber was reduced to below 4.5 μTorr using a vacuum pump; then, 15 scmm of Ar was introduced; the DC magnetron sputtering power was turned on and set to 100 W; and the deposition time was 1 min to prepare a 5 nm thick Pt layer. At this point, the coreless optical fiber, the WO3 layer, and the Pt layer constitute the optical fiber sensing region of the optical fiber hydrogen sensor. The ePTFE hydrophobic and breathable membrane is then wrapped around the optical fiber sensing region, thus completing the construction of the hydrogen-sensitive optical fiber. The ePTFE hydrophobic and breathable membrane is 10 cm long, has a pore size of 0.45 μm, and a thickness of 30 μm.

[0038] Figure 2 This is a schematic diagram of the operation of the fiber optic hydrogen sensor for hydrogen detection in water provided by the present invention. The system mainly consists of an electrolytic cell, a water supply and drainage unit, a detection unit, and a power supply. The electrolytic cell is the core reaction vessel of the entire device, with a water inlet on its right side and a hydrogen outlet, a water outlet, and an oxygen outlet on its left side. A water pump is connected to the water inlet via a pipe and is responsible for pumping deionized water into the electrolytic cell. The power supply provides the electrical energy required for the operation of the electrolytic cell and the water pump. During electrolysis, the hydrogen generated at the cathode is drawn out separately from the hydrogen outlet on the left side, while the oxygen generated at the anode mixes with the water and flows out together from the water outlet and the oxygen outlet on the lower left.

[0039] During electrolysis, one end of a hydrogen-sensitive optical fiber is connected to the electrolytic cell, and the other end is connected to a demodulator above it. This fiber is completely sealed within the electrolytic cell chamber, the water outlet, and the oxygen outlet. The hydrogen-sensitive thin film on its surface reacts with hydrogen gas, altering its optical properties and thus affecting the fiber's spectrum. By analyzing the changes in the optical signal transmitted back from the fiber, the demodulator can achieve real-time, quantitative monitoring of the hydrogen concentration inside the electrolytic cell and in the outlet gas flow.

[0040] Figure 3 The curve of the spectrum of the fiber optic hydrogen sensor as a function of hydrogen concentration is shown below. Figure 3It can be seen that as the hydrogen concentration increases, the spectral wavelength shifts towards shorter wavelengths. This is because the refractive index of the WO3 / Pt film decreases with increasing hydrogen concentration, which in turn reduces the effective refractive index difference between interference modes. The interference condition requires the wavelength to shift towards shorter wavelengths to maintain phase matching, thus causing a shift in the resonant wavelength.

[0041] This invention provides a concept and method for a fiber optic hydrogen sensor for hydrogen detection in water. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. An optical fiber hydrogen sensor for hydrogen detection in water, characterized by, The optical fiber hydrogen sensor is composed of a demodulator and a hydrogen-sensitive optical fiber, which is composed of an optical fiber, a WO3 / Pt layer coated outside the optical fiber, and an ePTFE hydrophobic and air-permeable film coated outside the WO3 / Pt layer from inside to outside.

2. The optical fiber hydrogen sensor of claim 1, wherein, The hydrogen-sensitive optical fiber is selected to have a structure of single-mode optical fiber-no-core optical fiber-single-mode optical fiber.

3. The optical fiber hydrogen sensor of claim 2, wherein, The single-mode optical fiber has a diameter of 60-300 μm, and the no-core optical fiber has a diameter of 60-300 μm.

4. The optical fiber hydrogen sensor according to any one of claims 1 to 3, wherein The WO3 / Pt layer is located on the surface of the no-core optical fiber, and in the WO3 / Pt layer, the thickness of the WO3 layer is 10 nm-500 μm, and the thickness of the Pt layer is 1 nm-50 μm.

5. The optical fiber hydrogen sensor according to any one of claims 1 to 3, wherein The ePTFE hydrophobic and air-permeable film has a thickness of 10-100 μm and a pore size of 0.2-1 μm.

6. The optical fiber hydrogen sensor of claim 1, wherein, The optical fiber hydrogen sensor has the following working steps in an electrolytic cell: one end of the hydrogen-sensitive optical fiber is connected to the electrolytic cell, and the other end is connected to the demodulator, so as to ensure that the hydrogen-sensitive optical fiber is completely sealed in the electrolytic cell chamber and the water outlet, the surface layer of the hydrogen-sensitive optical fiber reacts with hydrogen to change the optical properties, thereby affecting the optical spectrum of the optical fiber, and the change of the light signal returned by the optical fiber is analyzed by the demodulator, so as to realize the monitoring of the hydrogen concentration in the electrolytic cell and the outlet gas flow.

7. The method of claim 1 to 6, wherein the optical fiber hydrogen sensor is prepared by the steps of: The method comprises the following steps: fusing two single-mode optical fibers and a no-core optical fiber to obtain a structure of single-mode optical fiber-no-core optical fiber-single-mode optical fiber; constructing a WO3 layer on the surface of the no-core optical fiber by a radio frequency magnetron sputtering process; and finally constructing a Pt layer on the surface of the WO3 layer by a direct current magnetron sputtering process, so that the no-core optical fiber, the WO3 layer, and the Pt layer together form an optical fiber sensing area of the optical fiber hydrogen sensor, an ePTFE hydrophobic and air-permeable film is coated on the optical fiber sensing area, a hydrogen-sensitive optical fiber is obtained, the hydrogen-sensitive optical fiber is fixed to the environment to be measured, and a demodulator is connected, so as to complete the preparation of the optical fiber hydrogen sensor.

8. The preparation method according to claim 7, characterized in that, The radio frequency magnetron sputtering process has the following conditions: the pressure in the reaction chamber is controlled below 4.5 μTorr, 10-20 sccm of Ar and 0-5 sccm of O2 are introduced, the power is 50-150 W, and the time is 10-240 min.

9. The preparation method according to claim 7, characterized in that, The direct current magnetron sputtering process has the following conditions: the pressure in the reaction chamber is controlled below 4.5 μTorr, 10-20 sccm of Ar is introduced, the power is 50-150 W, and the time is 10-240 s.

10. The optical fiber hydrogen sensor according to any one of claims 1-6 is used for real-time monitoring of the hydrogen concentration in the hydrogen-oxygen mixed gas in an electrolytic hydrogen production system.

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