Hydrogen sensor and preparation method thereof
阅读说明：本技术 一种氢气传感器及其制备方法 (Hydrogen sensor and preparation method thereof ) 是由 谢波 丁伯胜 王一涛 于 2020-06-23 设计创作，主要内容包括：本发明涉及一种氢气传感器及其制备方法,包括氢气气敏膜、导电电极和绝缘衬底,所述氢气气敏膜附着于绝缘衬底表面,通过导电电极测量氢气气敏膜的电阻或导电值,所述氢气气敏膜包括至少一层钯基纳米粒子组装薄膜和至少一层金属有机物框架涂层,所述金属有机物框架涂层将钯基纳米粒子组装薄膜完全包裹。本发明中金属有机物框架涂层材料的多孔结构使其能在一定程度上隔离较大尺寸的气体分子,提高氢气气敏的选择性。此外,由于金属有机物框架材料对钯或合金粒子之间的表面修饰作用,还能提高纳米粒子气敏膜对氢气的响应值。(The invention relates to a hydrogen sensor and a preparation method thereof, and the hydrogen sensor comprises a hydrogen gas-sensitive film, a conductive electrode and an insulating substrate, wherein the hydrogen gas-sensitive film is attached to the surface of the insulating substrate, the resistance or the conductive value of the hydrogen gas-sensitive film is measured by the conductive electrode, the hydrogen gas-sensitive film comprises at least one layer of palladium-based nanoparticle assembly film and at least one layer of metal organic framework coating, and the palladium-based nanoparticle assembly film is completely wrapped by the metal organic framework coating. The porous structure of the metal organic framework coating material can isolate gas molecules with larger size to a certain extent, and the selectivity of hydrogen gas sensitivity is improved. In addition, the metal organic framework material can modify the surfaces of palladium or alloy particles, so that the response value of the nano particle gas-sensitive film to hydrogen can be improved.)
1. A hydrogen sensor, characterized by: the hydrogen-sensitive film is attached to the surface of an insulating substrate, the resistance or the conductivity value of the hydrogen-sensitive film is measured through the conductive electrode, the hydrogen-sensitive film comprises at least one layer of palladium-based nanoparticle assembly film and at least one layer of metal organic framework coating, the palladium-based nanoparticle assembly film is completely wrapped by the metal organic framework coating, and the palladium-based nanoparticle assembly film is embedded in the metal organic framework coating.
2. A hydrogen sensor according to claim 1, wherein: the hydrogen gas-sensitive film also comprises at least one layer of organic polymer coating, and the organic polymer coating covers the surface of the metal organic framework coating.
3. A hydrogen sensor according to claim 2, wherein: the thickness of the organic polymer coating is 1-100 nm.
4. A hydrogen sensor according to claim 1 or 2, wherein: the size of the nanoparticles in the palladium-based nanoparticle assembled film is 1-50 nm.
5. A hydrogen sensor according to claim 1 or 2, wherein: the pore diameter of the metal organic framework coating is larger than the kinetic size of hydrogen molecules.
6. A method for producing a hydrogen sensor as claimed in any one of claims 1 to 5, wherein the gas-sensitive film is produced by a process comprising the steps of:
(1) covering the metal organic matter frame coating on the surface of the palladium-based nano particle assembled film, and embedding the palladium-based nano particle assembled film in the metal organic matter frame coating;
(2) and covering the organic polymer solution on the surface of the metal organic framework coating to obtain the composite hydrogen gas-sensitive membrane.
7. The method of claim 6, wherein the palladium-based nanoparticle assembled film is prepared by a process comprising the steps of:
the palladium-based nanoparticles are prepared by adopting a magnetron plasma gas aggregation method, the sputtering gas is argon, the buffer gas is argon, the palladium-based nanoparticles are deposited on the surface of an insulating substrate with a pair of conductive electrodes, and the coverage rate of the palladium-based nanoparticles is determined by detecting the current value at two ends of the electrodes during deposition.
Technical Field
The invention relates to the technical field of gas sensing, in particular to construction and application of palladium-based nanoparticle assembled film @ metal organic framework composite hydrogen gas-sensitive film nanoparticles on a hydrogen sensor.
Background
Hydrogen, as a form of energy, has high combustion efficiency, and product water has the advantages of no pollution, etc., and has the potential to replace traditional fossil fuels. However, hydrogen is a flammable and explosive gas, has potential safety hazard problems in the production, storage and use processes, belongs to a colorless, odorless and tasteless gas, and cannot be detected by a human sensory system when hydrogen leakage occurs. Therefore, the development of a hydrogen sensing technology with practical application value is an important safety guarantee for realizing the large-scale application of hydrogen energy. Currently, palladium (Pd) based nano-structured hydrogen Sensors based on quantum tunneling effect are widely concerned by the Chemical industry and industry for their excellent sensing performance (see Sensors, 19 (2019), 4478-. However, such sensors still have common technical difficulties of poor sensing selectivity, which limits their commercialization progress. One way to improve the sensing selectivity is to arrange an isolation layer on the surface of a palladium-based sensitive material, and filter interfering gas components through the microporous structure of the isolation layer, and a typical example is to coat a palladium nanoparticle thin film with a polymethyl methacrylate (PMMA) organic film, so as to realize high selectivity response to hydrogen (see ACS Applied Materials & Interfaces, 9 (2017) 27193-27201). However, the encapsulation of organic substances has a negative effect on the response sensitivity and response speed of the sensor while achieving isolation of interfering gases. How to solve the problem of poor response selectivity of palladium-based hydrogen sensors without degrading the sensing performance is still a challenging task.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a hydrogen sensor, which achieves the aim of double optimization of hydrogen response selectivity and response performance.
In order to achieve the purpose, the invention provides a hydrogen sensor which comprises a hydrogen gas-sensitive film, a conductive electrode and an insulating substrate, wherein the hydrogen gas-sensitive film is attached to the surface of the insulating substrate, the resistance or the conductive value of the hydrogen gas-sensitive film is measured through the conductive electrode, the hydrogen gas-sensitive film comprises at least one layer of palladium-based nanoparticle assembly film and at least one layer of metal organic framework coating, the palladium-based nanoparticle assembly film is completely wrapped by the metal organic framework coating, and the palladium-based nanoparticle assembly film is embedded in the metal organic framework coating.
The innovation points of the invention are as follows: the metal organic framework coating has an adjustable pore channel structure and has the great advantage of gas separation, the metal organic framework and the palladium-based nanoparticle assembled film are combined in a complete wrapping and embedding mode to form a hydrogen gas-sensitive film, and the hydrogen gas-sensitive film is applied to a hydrogen sensor, when the hydrogen gas-sensitive film contacts hydrogen with certain concentration, hydrogen molecules can penetrate through the metal organic framework coating and are further dissolved in the palladium-based nanoparticle assembled film through diffusion to cause lattice expansion, the surface distance between particles in the assembled film is changed, the integral resistance or conductance value of the film is changed, the chemical activity of the nanoparticles is improved, and the sensitivity and the response speed of hydrogen response can be obviously enhanced; in addition, the pore structure of the metal organic matter frame coating can effectively filter other gases, so that more active sites can be exposed on the surface of the nanoparticles, and the response selectivity and the sensing performance of the device are further improved; the quantum tunneling in the nano particle lattice is the main conducting mechanism, and the number density of the nano particles is greater than the percolation threshold, so that the current in the assembled film can be measured.
Preferably, the metal-organic framework coating further comprises at least one organic polymer coating, and the organic polymer coating covers the surface of the metal-organic framework coating. The organic polymer coating is used for coating the palladium-based nanoparticle assembly film and the metal organic framework coating, a stable and firm film structure is formed on the surface of the hydrogen gas-sensitive film, and the sensing selection is further improved, and certain waterproof and moistureproof effects are achieved.
Preferably, the organic polymer coating layer has a thickness of 1 to 100nm, and the organic polymer coating layer has a good hydrogen permeability, for example, polymethyl methacrylate, polydimethylsiloxane, polyvinylpyrrolidone, or the like.
Preferably, the size of the nanoparticles in the palladium-based nanoparticle assembled film is 1-50 nm.
Preferably, the pore diameter of the metal organic framework coating is larger than the kinetic size of hydrogen molecules, the metal organic framework coating plays a role in filtering gas molecules and improving the sensing selectivity, and the pore diameter of the metal organic framework coating is larger than the kinetic size (0.29nm) of the hydrogen molecules, such as ZIF-8, ZIF-67 and the like, so that hydrogen can interact with the palladium-based nanoparticle assembly film through a diffusion mechanism, the selective adsorption of the hydrogen molecules on the surfaces of the nanoparticles can be achieved, and the sensor can obtain higher selectivity. In addition, the chemical activity of the metal organic matter framework coating is enhanced due to the chemical modification effect on the surface of the nano particle, so that the hydrogen sensing performance of the palladium-based nano particle assembled film is also improved.
A preparation method of a hydrogen sensor comprises the following steps: (1) covering the metal organic matter frame coating on the surface of the palladium-based nano particle assembled film, and embedding the palladium-based nano particle assembled film in the metal organic matter frame coating;
(2) and covering the organic polymer solution on the surface of the metal organic framework coating to obtain the composite hydrogen gas-sensitive membrane.
Preferably, the preparation process of the palladium-based nanoparticle assembled film comprises the following steps:
the palladium-based nanoparticles are prepared by adopting a magnetron plasma gas aggregation method, the sputtering gas is argon, the buffer gas is argon, the palladium-based nanoparticles are deposited on the surface of an insulating substrate with a pair of conductive electrodes, and the coverage rate of the palladium-based nanoparticles is determined by detecting the current value at two ends of the electrodes during deposition.
The invention has the beneficial effects that: the hydrogen gas-sensitive membrane formed by mutually combining the palladium-based nano particle assembled membrane, the metal organic matter frame coating and the organic polymer coating has good selectivity on hydrogen, and meanwhile, the metal organic matter frame coating coats the palladium-based nano particle assembled membrane, so that the hydrogen sensing performance is further improved, the hydrogen response selectivity and response performance are improved, and the performance of a hydrogen sensing device is improved; the organic polymer coating forms a stable and firm film structure on the surface of the hydrogen gas-sensitive film, and further improves the sensing selection and plays a certain role in water and moisture prevention.
The features and advantages of the invention will be described in detail by the embodiments and the accompanying drawings.
Drawings
Fig. 1 is a schematic structural view of the present invention.
FIG. 2 is a graph of the real-time current response of a gas-sensitive membrane.
FIG. 3 is a graph of the response of the gas sensitive membrane.
FIG. 4 is a graphical representation of the selective response of a gas sensitive membrane.
1-hydrogen gas-sensitive film, 2-conductive electrode, 3-insulating substrate, 11-palladium-based nanoparticle assembled film, 12-metal organic frame coating and 13-organic polymer coating.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail by examples below. It should be understood, however, that the description herein of specific embodiments is only intended to illustrate the invention and not to limit the scope of the invention. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present invention.
As shown in fig. 1, the hydrogen sensor of the present invention comprises a hydrogen-
For better understanding of the present invention, the palladium-based
(1) preparation of palladium (Pd) -based nanoparticle assembled film 11: the Pd-based nanoparticles are prepared by adopting a magnetron plasma gas aggregation method, the sputtering gas is argon, the buffer gas is argon, the sputtering power is 20-30 w, the Pd nanoparticles are deposited on the surface of an
(2) Preparation of Metal Organic Framework (MOF): taking ZIF-8 of a class of zeolite imidazole ester framework materials (ZIFs) in MOF as an example, a chemical synthesis method is adopted, a certain amount of Zn (NO3) 2.6H 2O and 2-methylimidazole are dissolved in a methanol solvent, magnetic stirring is carried out for several hours to ensure that the reaction is complete, and then, multiple centrifugation and washing operations are carried out subsequently.
(3) Preparation of organic polymer solution: for example, polymethyl methacrylate (PMMA): PMMA powder with different molecular weights is dissolved in an anisole solvent, and PMMA solutions with different mass percentages can be prepared by controlling the mass of PMMA added.
(4) The preparation method of the Pd nano particle assembled film with the composite material layer structure comprises the following steps: and (2) covering the surface of the ZIF-8 nano-crystal on the surface of the Pd nano-particle by a spin coating method by using a desk type spin coater with the rotating speed controlled at 1000-4000 r/min, embedding the Pd nano-particle in the MOF, and covering the PMMA solution on the surface of the ZIF-8 coating by using a spin coating process to obtain the Pd @ [email protected] PMMA composite hydrogen gas-
And (3) testing the performance of the Pd @ [email protected] PMMA composite hydrogen gas-
(1) Hydrogen response test of gas sensitive film: and placing the gas-sensitive film in a cavity, introducing a certain amount of hydrogen, applying bias voltage to electrodes at two ends, and respectively measuring the current values of the Pd nano particles, the Pd nano particles with the ZIF-8 coating and the Pd nano particle assembled film with the PMMA and ZIF-8 coating. The change of current value reflects the gas-sensitive film pairResponse performance of hydrogen gas, wherein response value = (h)I H2－I 0) /I 0× 0.9.9 0.9 × 100%, as shown in FIG. 2 and FIG. 3, which respectively show the real-time current response curve and response value of the gas sensitive film to 6000 ppm hydrogen concentration under 20sccm flow rate, it can be seen that the hydrogen response value of the composite film containing the ZIF-8 coating is significantly higher than that of the elemental palladium nanoparticle film.
(2) Hydrogen selectivity test of gas-sensitive membranes: carbon monoxide (CO) is an interfering gas that is likely to cause Pd poisoning to lose responsiveness. Therefore, a certain amount of CO is introduced into the cavity while a certain amount of hydrogen is introduced into the cavity, bias voltages are applied to the electrodes at the two ends, the current values of the Pd nanoparticles and the Pd nanoparticle gas-sensitive film with PMMA and ZIF-8 coatings are respectively measured, and fig. 4 shows the selective response value of the gas-sensitive film to 6000 ppm hydrogen concentration and 1% CO concentration under the flow of 20 sccm. The result shows that the response value of the Pd nano particle film to hydrogen is obviously reduced by about 30% under the condition of introducing CO; and the response value of the composite film with the ZIF-8 and PMMA coatings is only slightly reduced under the condition of introducing CO. The composite gas-sensitive film has better CO isolation performance and embodies better hydrogen selectivity.
Therefore, the hydrogen sensor with the composite gas-sensitive film can improve the sensing performance of hydrogen, improve the response selectivity and response performance of hydrogen, and has certain waterproof and moistureproof effects.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents or improvements made within the spirit and principle of the present invention should be included in the scope of the present invention.