Precious metal modified epitaxial titanium dioxide single crystal thin film, gas sensor and preparation method of noble metal modified epitaxial titanium dioxide single crystal thin film
Through the epitaxial titanium dioxide single crystal thin film modified by precious metals, the problem of difficulty in detecting low concentrations of hydrogen in the prior art is solved, and high sensitivity and selective detection of hydrogen is achieved, with good stability and applicability, and is suitable for early safety warning of thermal runaway in lithium-ion batteries.
Patent Information
- Application Number
- CN202510109653.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-23
- Publication Date
- 2025-05-27
AI Technical Summary
The prior art is difficult to detect low-concentration hydrogen quickly and selectively, especially in the case of thermal runaway of lithium-ion batteries, and lacks effective early safety warning methods.
The thin film of epitaxial titanium dioxide modified with precious metals is used as the sensitive layer, and the film is prepared by magnetron sputtering and electron beam evaporation technology. Combined with specific substrates and process conditions, high sensitivity and selective detection of low-concentration hydrogen is achieved.
It realizes rapid response and high selectivity detection of hydrogen below 100ppm, has good long-term stability and moisture resistance, and can be used for early safety warning of thermal runaway in lithium-ion batteries.
Smart Images
Figure CN120041933A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of gas sensors, and relates to a noble metal-modified epitaxial titanium dioxide single crystal thin film, a gas sensor and a preparation method thereof, which can be used in hydrogen detection, especially for low-concentration hydrogen detection and early safety warning of thermal runaway of lithium-ion batteries. Background Art
[0002] The safety problems caused by fire or explosion accidents of lithium-ion batteries (LIBs) have become the key problems hindering the further development of the energy storage field. When the battery is operated improperly, a large amount of heat and gas will be generated in a short time, thus triggering fires and explosions. This phenomenon is called thermal runaway and is the main cause of LIBs safety incidents. H 2 is a characteristic gas during the thermal runaway process. When the battery is overcharged, the lithium dendrites at the negative electrode continue to grow and finally react with the polymer binder, releasing a small amount of H 2 . Research shows that among the six common gases released during thermal runaway, namely H 2 , CO, CO 2 , HCl, HF and SO 2 , H 2 is the first to be detected, and the detection time is 639 s earlier than the smoke and 769 s earlier than the fire, which provides more valuable time for the early warning of thermal runaway. Therefore, for environmental protection and safety considerations, there is an urgent need for technical means capable of quickly and selectively detecting low-concentration hydrogen.
[0003] Based on this, the present invention proposes a titanium dioxide single crystal thin film and a gas sensor, which can be effectively used in the field of low-concentration hydrogen detection. Summary of the Invention
[0004] The purpose of the present invention is to provide, in view of the deficiencies of the prior art, a noble metal-modified epitaxial titanium dioxide single crystal thin film, a gas sensor and a preparation method thereof. The sensor of the present invention is based on a TiO 2 thin film modified with noble metals such as Pd, and has gas sensing properties of high sensitivity and selectivity, low detection limit, fast response, good long-term stability and moisture resistance, and is expected to be applied to low-concentration hydrogen detection and early safety warning of lithium-ion batteries.
[0005] The technical solution of the present invention is as follows:
[0006] A preparation method of a noble metal-modified epitaxial titanium dioxide single crystal thin film, comprising the following steps:
[0007] (1) Place the substrate in the vacuum chamber of a magnetron device. Use a Ti target as the Ti source. Heat the substrate and introduce argon and oxygen under high vacuum conditions. Through magnetron sputtering, apply an electric field and a magnetic field to generate argon ions. Through the bombardment of argon ions, titanium atoms on the surface of the target are detached from the target and react with the simultaneously introduced oxygen, thereby growing a titanium dioxide single crystal thin film on the substrate; the substrate is single crystal lanthanum aluminate (LAO) or single crystal magnesium oxide (MgO).
[0008] (2) Place the titanium dioxide single crystal thin film in the vacuum chamber of an electron beam evaporation device. Evaporate noble metal particles by the method of electron beam evaporation and deposit them on the surface of the material to form dispersed clusters; thus, a noble metal-modified epitaxial titanium dioxide single crystal thin film is obtained.
[0009] Further, in step (1), place the substrate in the vacuum chamber of a magnetron sputtering device and heat the substrate to 400 - 600 °C at a heating rate of 30 °C / min.
[0010] Further, in step (1), the substrate is any one of a (100)-oriented single crystal lanthanum aluminate substrate and a (100)-oriented single crystal magnesium oxide substrate. When the substrate is a (100)-oriented single crystal lanthanum aluminate, the obtained titanium dioxide single crystal thin film has a (001) crystal plane orientation. When the substrate is a (100)-oriented single crystal magnesium oxide, the obtained titanium dioxide single crystal thin film has a (100) crystal plane orientation.
[0011] Further, in step (1), the magnetron sputtering is carried out by using the DC magnetron sputtering method, and at the same time, adjust the oxygen pressure ratio in the growth chamber to be 10% - 30%; wherein, the total pressure is 0.6 - 1.5 Pa, the power is 100 - 300 W, and the sputtering time is 1 - 4 h.
[0012] Further, in step (1), before the formal sputtering, use a power of 100 W and introduce only pure Ar to pre-sputter the Ti target for 5 min for cleaning.
[0013] Further, in step (1), before placing the substrate in the vacuum chamber of the deposition device, it also includes washing the substrate successively with acetone, absolute ethanol, and deionized water.
[0014] Further, in step (2), evaporate the noble metal particles in the crucible by the electron beam evaporation method and deposit them on the surface of the titanium dioxide single crystal thin film at a deposition rate of 0.1 Å / s.
[0015] A noble metal-modified titanium dioxide single crystal thin film is prepared by the above method, and the single crystal titanium dioxide thin film has a specific crystal plane orientation.
[0016] A gas sensor uses the above-mentioned noble metal-modified titanium dioxide single crystal thin film material as the sensitive layer material.
[0017] The above gas sensor can be used for hydrogen detection, especially for low-concentration hydrogen detection and early safety warning of thermal runaway of lithium-ion batteries. The low concentration is usually less than 100 ppm.
[0018] Preparation of the sensor and gas detection:
[0019] Using the method of thermal evaporation deposition, deposit Al / Au interdigital electrodes on the surface of the obtained thin film to construct the sensor. Perform gas-sensing measurement on the obtained sample, and use the intelligent gas-sensing analysis system CGS-MT for detection. Alternately fill a certain amount of hydrogen or dry air in the laboratory, and use the gas-liquid distribution system DGL-Ⅴ with automatic humidity control. In typical tests, the humidity is dynamically controlled by the dual-flow dynamic humidity generator DHD-Ⅱ. The response value is defined as the resistance R of the gas sensor in the air background a and the resistance R in the target gas hydrogen environment g ratio.
[0020] The beneficial effects of the present invention are as follows:
[0021] (1) The preparation of single crystal TiO thin films with different crystal plane orientations is realized. The prepared single crystal is anatase phase, with more defect vacancies, which can generate oxygen vacancies to capture electrons and have high activity, and has a wider energy band and smaller effective electron mass, and also has a higher carrier mobility. 2 The preparation method of the present invention is simple and controllable, the process conditions are mild, the energy consumption is low, the production cycle is short, the requirements for equipment are low, there is no pollution to the environment, its preparation method is simple, and it is suitable for large-scale preparation.
[0022] (2) The preparation method of the present invention is simple and controllable, the process conditions are mild, the energy consumption is low, the production cycle is short, the requirements for equipment are low, there is no pollution to the environment, its preparation method is simple, and it is suitable for large-scale preparation.
[0023] (3) The present invention uses noble metal nano-ions for modification, provides rich active centers on the surface of the titanium dioxide thin film, and effectively reduces the activation energy of hydrogen adsorption.
[0024] (4) The noble metal-modified titanium dioxide single crystal thin film sensors with (001) and (100) crystal plane orientations prepared by the present invention have response values to hydrogen of 353 and 52.1 (100 °C, 100 ppm) respectively, and the response speed is 8 s. In addition, the sensor based on Pd / TiO 2 has good selectivity and long-term stability performance of more than 30 days. The sensor based on Pd / TiO 2 has a high response value and a low detection limit (1 ppm) at low concentrations, and can be used for early safety warning of thermal runaway of lithium-ion batteries.
[0025] (4) The noble metal-modified titanium dioxide single crystal thin film provided by the present invention is expected to be applied to the detection of low-concentration hydrogen and the early safety warning of thermal runaway of lithium-ion batteries. Description of the Drawings
[0026] Figure 1 XRD diffraction patterns of titanium dioxide thin films grown on two different substrates respectively.
[0027] Figure 2 They are AFM images of TiO thin films with (001) orientation (a) and (100) orientation (b). 2 thin films.
[0028] Figure 3 They are the response values of sensors based on Pd / TiO 2 (001) and Pd / TiO 2 (100) to 100 ppm hydrogen at different working temperatures (a), the response values of sensors based on Pd / TiO 2 (001) and Pd / TiO 2 (100) to 100 ppm hydrogen under different humidity conditions (b), the dynamic response curves of sensors based on Pd / TiO 2 (001) and Pd / TiO 2 (100) to 100 ppm hydrogen at the optimal working temperature (c)(d).
[0029] Figure 4 They are the dynamic response curves of sensors based on Pd / TiO 2 (001) to 1 - 2000 ppm (insert Figure 1-1 0 ppm) hydrogen at the optimal working temperature (a) and the curve of response value changing with hydrogen concentration (c), the repeatability curve of sensors based on Pd / TiO 2 (001) to 100 ppm hydrogen at the optimal working temperature (b), the selectivity of sensors based on Pd / TiO 2 (001) and Pd / TiO 2 (100) to 100 ppm hydrogen and various interfering gases (d), the long-term stability of sensors based on Pd / TiO 2 (001) to 100 ppm hydrogen (e). Detailed Embodiments
[0030] The technical solution of the present invention will be further described below in conjunction with the drawings and specific embodiments.
[0031] Example 1
[0032] Synthesis of the sensitive layer material and preparation of the gas sensor:
[0033] (1) Ultrasonically clean a single-crystal LAO substrate with a (100) orientation of 1 mm * 1 mm and a single-crystal MgO substrate successively with acetone, absolute ethanol, and deionized water for 20 min.
[0034] (2) Place the two substrates in the vacuum chamber of a magnetron sputtering device and place a Ti target.
[0035] (3) Then evacuate the chamber. When a certain vacuum degree is reached, raise the temperature to 600 °C at a rate of 30 °C / min.
[0036] (4) After the vacuum degree reaches 1 * 10 -3 Pa, set the flow rate of oxygen to 10 sccm and the flow rate of argon to 50 sccm, and open the inlet valve.
[0037] (5) Control the vacuum degree of the thin-film gauge to 2 Pa, observe whether the surface of the target starts to glow, and then modify the vacuum degree of the thin-film gauge to 1.2 Pa.
[0038] (6) Set the DC power supply power to 200 W and the bias voltage to 100 V, start the DC power supply and the bias voltage power supply, and sputter for 2 h.
[0039] (7) Place the two differently oriented titanium dioxide thin films taken out in the vacuum chamber of an electron beam evaporation device, and deposit 5 nm of Pd nanoparticles on the surface of the thin films.
[0040] (8) Place a mask template of interdigital electrodes on the surface of the material, and deposit 20 nm of Al / 20 nm of Au on the surface of the material by thermal evaporation to fabricate a sensor.
[0041] (9) Finally, heat the fabricated sensor at 300 °C for 10 min to age the sensor.
[0042] Gas-sensing test:
[0043] Perform gas-sensing measurements on the obtained samples using an intelligent gas-sensing analysis system: a micro multi-functional detection station CGS-MT for detection, alternately filling a certain amount of hydrogen or dry air into the chamber, and a gas-liquid distribution system DGL-Ⅴ for automatically controlling humidity. During the operation, first place the test device in the center of the heating stage, raise the temperature to the required working temperature of 300 °C, and make its resistance stable in an air atmosphere. In a typical test, first introduce nitrogen into the pneumatic valve to open the valve in the device. The humidity is dynamically controlled by a dual-flow dynamic humidity generator DHD-Ⅱ. The response value is defined as the ratio of the resistance R a of the gas sensor in the air background to the resistance R g in the target gas hydrogen environment. The response time and the recovery time are defined as the time required for a 90% change in the resistance value during the response and recovery processes.
[0044] Result analysis:
[0045] (1) XRD analysis: The crystal structures of titanium dioxide films grown on two different substrates were studied by XRD. As Figure 1 shown, the materials exhibited distinct XRD peaks. The titanium dioxide grown on the LAO(100) substrate corresponded to the anatase phase (001) lattice plane, and the titanium dioxide grown on the MgO(100) substrate corresponded to the anatase phase (100) lattice plane, which was in line with the standard card (PDF#21-1272).
[0046] (2) AFM analysis: As Figure 2 , the surface morphologies of TiO 2 (001) and TiO 2 (100) were different. Since the (001) plane was a highly active plane, the particles tended to grow outwards, and the surface roughness was relatively high, while the (100) plane was relatively flat.
[0047] (3) Gas-sensing performance: As Figure 3 (a) shown, the optimal operating temperatures of the Pd / TiO 2 (001) and Pd / TiO 2 (100) sensors were both 100 °C. As the temperature increased, the response values of the sensors both exhibited a typical volcano-like behavior, first increasing and then decreasing. This could be attributed to the competition between the adsorption accumulation rate of oxygen active sites and the desorption rate of gas molecules. As the temperature increased, the adsorption rate was first higher than the desorption rate and then lower than the desorption rate. At 100 °C, the response value of the Pd / TiO 2 (001) sensor to 100 ppm hydrogen reached 353, which was 6.78 times higher than that of Pd / TiO 2 (100). Figure 3 (b) shows the response values of the Pd / TiO 2 (001) and Pd / TiO 2 (100) sensors to 100 ppm hydrogen under different relative humidity conditions. It can be seen that as the relative humidity increased, the sensing response gradually decreased. This was because there was moisture in the air, and moisture had a strong affinity for the surface of metal oxides. By forming -OH groups to occupy the active sites on the material surface, it hindered the adsorption of hydrogen molecules. As Figure 3 (c) and (d) shown, at the optimal operating temperature, the response time and recovery time of the Pd / TiO 2 (001) and Pd / TiO 2 (100) sensors to 100 ppm hydrogen were 8 / 640, 9 / 56 s respectively.
[0048] Figure 4(a) shows the dynamic response curves of the sensor prepared at the optimal working temperature to hydrogen with concentrations ranging from 1 to 2000 ppm. Based on the Pd / TiO 2 (001) sensor, the response values to hydrogen concentrations of 1, 2, 5, 10, 20, 50, 100, 200, 500, 1000, and 2000 ppm are 1.31, 2.7, 13.8, 44.5, 160, 274, 351, 419, 553, 920, and 1695 respectively. Figure 4 (b) shows the repeatability of the Pd / TiO 2 (001) sensor at a hydrogen concentration of 100 ppm during six cycles of air - hydrogen - air exposure at the optimal working temperature. It can be observed that the response to hydrogen remains consistent without obvious attenuation, indicating good repeatability. By exposing to 100 ppm hydrogen or interfering gases such as carbon monoxide, carbon dioxide, methane, and ethylene, the gas selectivity of the Pd / TiO 2 (001) sensor was studied. As Figure 4 (d) shows, the Pd / TiO 2 (001) sensor has the best response to hydrogen (353). Figure 4 (e) shows the long - term stability of the Pd / TiO 2 (001) sensor to 100 ppm hydrogen at the optimal working temperature. Even after continuous use for 30 days, at the optimal working temperature, the response value of the sensor can still reach about 350, indicating significant stability of the sensor.
[0049] The above - described embodiments have detailed the technical solutions and beneficial effects of the present invention. It should be understood that the above - described are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, supplements, equivalent replacements, etc. made within the scope of the principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing a noble metal modified epitaxial titanium dioxide single crystal thin film, characterized in that: The following steps are involved: (1) placing a substrate in a vacuum chamber of a magnetron device, using a Ti target as a Ti source, heating the substrate, and introducing argon and oxygen under high vacuum conditions, so that titanium atoms on the surface of the target are separated from the target by magnetron sputtering and react with the oxygen introduced at the same time, thereby growing a titanium dioxide single crystal thin film on the substrate; the substrate is single crystal lanthanum aluminate or single crystal magnesium oxide; (2) Placing a titanium dioxide single crystal film in a vacuum chamber of an electron beam evaporation device, evaporating precious metal particles by electron beam evaporation, and depositing them on the surface of the film to form dispersed clusters; thereby obtaining a precious metal-modified epitaxial titanium dioxide single crystal film.
2. The method for preparing a noble metal-modified epitaxial titanium dioxide single crystal thin film according to claim 1, characterized in that: The substrate heating temperature is 400-600° C., and the heating rate is 30° C. / min.
3. The method for preparing a noble metal-modified epitaxial titanium dioxide single crystal thin film according to claim 1, characterized in that: The substrate is any one of a (100)-oriented single crystal lanthanum aluminate substrate and a (100)-oriented single crystal magnesium oxide substrate. When the substrate is a (100)-oriented single crystal lanthanum aluminate, the obtained titanium dioxide single crystal film has a (001) crystal plane orientation. When the substrate is a (100)-oriented single crystal magnesium oxide, the obtained titanium dioxide single crystal film has a (100) crystal plane orientation.
4. The method for preparing a titanium dioxide single crystal thin film according to claim 1, characterized in that: Neutral atoms are bombarded from the Ti target by DC magnetron sputtering, and argon and oxygen are introduced into the vacuum chamber at the same time, and the oxygen pressure in the growth chamber is adjusted to 10%-30%; the total pressure is 0.6-1.5Pa, the power is 100-300W, and the sputtering time is 1-4h.
5. The method for preparing a noble metal-modified epitaxial titanium dioxide single crystal thin film according to claim 1, characterized in that: Before the formal sputtering, the power was 100 W, and only pure Ar was introduced to pre-sputter the Ti target for 5 minutes for cleaning.
6. The method for preparing a noble metal-modified epitaxial titanium dioxide single crystal thin film according to claim 1, characterized in that: Before placing the substrate in the vacuum chamber of the deposition equipment, the method further includes cleaning the substrate with acetone, anhydrous ethanol and deionized water in sequence.
7. The method for preparing a noble metal-modified epitaxial titanium dioxide single crystal thin film according to claim 1, characterized in that: The precious metal particles in the crucible are evaporated by electron beam evaporation and deposited on the surface of the titanium dioxide single crystal film at a deposition rate of 0.1 A / s.
8. A titanium dioxide single crystal film modified with a noble metal, characterized in that: The single crystal film is prepared by the method according to any one of claims 1 to 7, and has a specific orientation and can be combined with precious metals.
9. A gas sensor, characterized in that: The titanium dioxide single crystal thin film material modified with a noble metal as claimed in claim 8 is used as a sensitive layer material.
10. The gas sensor according to claim 9, characterized in that: The sensor is used for hydrogen detection or early safety warning of thermal runaway of lithium-ion batteries.