A hydrogen-sensitive WO x / Pd nano-assembly material hydrogen sensor and preparation method thereof

Abstract

The invention discloses a hydrogen-sensitive WO x / Pd nano-assembled material hydrogen sensor and its preparation method, the WO x The Pd / WO nano-assembly material was prepared by cluster beam deposition technology. A dual-target cluster sputtering source was used to deposit WO on the surface of the interdigital electrode with an insulating substrate. x Nanoparticles and Pd nanoparticles can obtain WO with different mass ratios. x / Pd mixed nanoparticle assembly material; further, the material is used to realize gas sensing devices, and the WO x The tungsten oxide / Pd mixed nanoparticle assembly material is deposited on the surface of the interdigital electrode with an insulating substrate, which can be used for quantitative measurement of hydrogen concentration. Compared with the prior art, the tungsten oxide and palladium mixed nanoparticle assembly material system involved in the present invention has a larger specific surface area, and due to the catalytic dissociation ability of Pd nanoparticles to hydrogen, it also has more reaction sites than single tungsten oxide, and can achieve high sensitivity and fast response hydrogen sensing function at relatively low temperature.

Description

Technical Field

[0001] The present invention relates to the field of gas sensing, and in particular to a hydrogen gas-sensitive WO x / Pd nano-assembled material hydrogen sensor and preparation method thereof. Background Art

[0002] Hydrogen is a clean energy with broad application prospects. As a renewable energy source that can replace fossil fuels, hydrogen has been widely used in multiple industrial fields. However, as a colorless, odorless, flammable and explosive gas, hydrogen has an explosion range of 4%-75% in the air. However, due to the ultra-small molecular size of hydrogen, it is easy to leak during production, storage, transportation and use. How to quickly detect leaks on a large scale is crucial to the safe use of hydrogen energy.

[0003] Metal oxide semiconductor gas sensor is a classic chemical gas sensor. It has developed into the most practical and widely used gas sensor due to its advantages of high sensitivity, fast response speed, long life, simple preparation and low cost. Tungsten oxide is an important semiconductor material. Its excellent gas sensing properties have also been widely reported in the field of gas sensors. Traditional tungsten oxide bulk materials and continuous films have poor gas-sensitive response to hydrogen, and the response temperature is often above 250°C, which limits its application in the field of hydrogen sensing.

[0004] The present invention proposes to utilize the WO x Pd nanoparticles are deposited on the surface of nanoparticles to form a composite assembly material to achieve high-performance hydrogen sensing technology. x The nanoparticles play the role of hydrogen gas sensors, while the Pd nanoparticles play a synergistic catalytic role to enhance the hydrogen gas sensing performance and reduce the device operating temperature to 150°C, significantly reducing the device power consumption. Summary of the invention

[0005] The purpose of the present invention is to solve the problems of high working temperature and poor response performance of the conventional tungsten oxide hydrogen sensing material. x / Pd nano-assembly material hydrogen sensor and its preparation method. The present invention uses physical vapor deposition technology and proposes to prepare WO by cluster beam deposition technology x / Pd nanoparticles assemble materials and realize hydrogen sensing, which can greatly improve the hydrogen sensing performance of tungsten oxide, and the operating temperature can be reduced to 150°C.

[0006] The hydrogen-sensitive WO x / Pd nano-assembled material hydrogen sensor, including an interdigital electrode with an insulating substrate and tungsten oxide WO deposited successively on the surface of the interdigital electrodex Nanoparticles and Pd nanoparticles, tungsten oxide WO x Nanoparticles and Pd nanoparticles are combined into a disordered and uniform mixed structure to form WO x / Pd mixed nanoparticle assembly materials.

[0007] Furthermore, the WO x In the / Pd mixed nanoparticle assembly materials, the mass proportion of Pd nanoparticles is 0.5%~10%.

[0008] The present invention also provides a hydrogen-sensitive WO x The invention discloses a method for preparing a hydrogen sensor of a WO3 / Pd nano-assembly material. The preparation process is as follows: placing a high-purity WO3 target material and a high-purity Pd target material on two sputtering guns of a cluster beam deposition device respectively, placing an interdigital electrode with an insulating substrate in a deposition chamber of the cluster beam deposition system, evacuating the entire device, and after the vacuum degree reaches a standard, respectively introducing high-purity argon gas as a sputtering gas and a buffer gas into the two target guns, and applying a voltage, successively partially vaporizing the WO3 target material and the Pd target material into gaseous molecules or atoms, and then colliding the buffer gas with the target material to form nanoparticles, and forming a nanoparticle beam by a differential exhaust method, and then guiding the beam into the deposition chamber of the cluster beam deposition device, and depositing it on the surface of the interdigital electrode placed thereon, thereby obtaining a WO3 / Pd nano-particle assembly material. After the preparation is completed, the interdigital electrodes are taken out and placed in the test chamber. A stable voltage is connected to the interdigital electrodes using a Keithley digital source meter. After hydrogen is introduced, the hydrogen reacts with the adsorbed oxygen on the surface of the material, causing the material resistance to change, thereby causing the current displayed on the source meter to change. According to the formula:

[0009]

[0010] in I 0 is the current value displayed on the source meter before hydrogen is passed. I 1 is the current value displayed on the source meter after hydrogen is passed, which can be used to calculate the response performance of the material to hydrogen.

[0011] Furthermore, the WO x In the preparation method of the hydrogen sensor made of Pd / Pd nano-assembly material, the gas pressure in the sputtering chamber is maintained at 40~120Pa.

[0012] Furthermore, the WO x In the preparation method of the hydrogen sensor made of WO3 / Pd nano-assembly material, the sputtering power of the WO3 target is set to 20~25W, the sputtering current is 0.045~0.05A, the sputtering voltage is 450~500V, and the sputtering time is 180~250s.

[0013] Furthermore, the WO x In the preparation method of the hydrogen sensor made of Pd / Pd nano-assembly material, the sputtering power of the Pd target is set to 10-15 W, the sputtering current is 0.035-0.042 A, and the sputtering voltage is 300-360 V.

[0014] The beneficial effects achieved by the present invention are as follows: the present invention uses vapor deposition technology to deposit nanoparticle assembly materials, and compared with traditional wet chemical methods, the prepared materials are purer and compatible with existing microelectronic processes. Since the nanoparticle assembly materials formed by sputtering have a higher specific surface area than thin films, the contact opportunities with hydrogen can be greatly increased, more reaction sites can be created, and since the Pd loaded on the surface is used as a catalyst, the selectivity and sensitivity to hydrogen are enhanced, and the operating temperature is greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the structure of the nanoparticle assembly material prepared by the present invention.

[0016] Figure 2a It is the response curve of the nanoparticle assembly material prepared by the present invention to different hydrogen concentrations.

[0017] Figure 2b It is the linear fitting relationship between the responsiveness and the hydrogen concentration when the nanoparticle assembly material prepared by the present invention is tested for different hydrogen concentrations.

[0018] Figure 1 Middle: 1 is interdigital electrode, 2 is WO X Nanoparticles, 3 are Pd nanoparticles. DETAILED DESCRIPTION

[0019] The present invention will be further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0020] Embodiment 1:

[0021] A hydrogen-sensitive WO x The preparation of Pd / Pd nanoparticle assembly material and sensor device thereof comprises the following steps:

[0022] (1) WO x Preparation of Pd / WO nanoparticle assembly materials: High-purity WO3 target and high-purity Pd target were placed on two sputtering guns of cluster beam deposition equipment, respectively. The interdigital electrode was placed in the deposition chamber of the cluster beam deposition system. The entire device was evacuated to a vacuum of 2×10 -4 Pa.

[0023] 70 sccm of sputtering gas was introduced into the sputtering gun equipped with WO3 target, and 100 sccm of buffer gas was introduced into the sputtering chamber. At this time, the pressure in the sputtering chamber was 110 Pa. Then, 22 W of power was introduced into the sputtering gun equipped with WO3 target. At this time, the sputtering current was 0.048 A and the sputtering voltage was 465 V. The sputtering time was 200 s. The sputtering gas and power were turned off.

[0024] Then, 70 sccm of sputtering gas was introduced into the sputtering gun equipped with the Pd target. At this time, the pressure in the sputtering chamber was 110 Pa. Then, 12 W of power was introduced into it. At this time, the sputtering current was 0.036 A, the sputtering voltage was 323 V, and the deposition time was 10 s. WO was obtained. x / Pd nanoparticle assembly material, in which the mass proportion of Pd nanoparticles is 2%.

[0025] (2) The WO obtained above x / Pd nanoparticles assembled materials for hydrogen sensitivity testing:

[0026] The deposited WO x The interdigital electrodes of the Pd / Pd nanoparticle assembly material are placed in the test chamber, and the temperature in the test chamber is heated to 150°C using a ceramic heater. The two ends of the electrode are connected to a Keithley digital source meter, and a stable voltage of 1 V is applied to the two ends of the interdigital electrodes using the source meter, and the current at the two ends of the assembly material is read through the source meter.

[0027] The hydrogen flow and air flow are controlled by a flow meter. A mixed gas containing a certain concentration of hydrogen (the mixed gas pressure is normal pressure) is introduced into the test chamber. The current value before and after ventilation is recorded. Use:

[0028]

[0029] in I 0 is the current value displayed on the source meter before hydrogen is passed. I 1 is the current value displayed on the source meter after hydrogen is passed. x / Pd nanoparticle assembly material to the quantitative response of hydrogen. The measured results are shown in Figure 2a ( Figure 2a kpa in the curve represents the unit of partial pressure of H2 in the mixed gas) and Figure 2b From the figure, we can see that the detection range is 0~100000ppm, and the response time is T 90 <40s, responsiveness is 0%~1766%.

[0030] The best response temperature of WOx thin film prepared by traditional chemical method to hydrogen is as high as 250℃, the response time is 180 s, and the maximum response is 87% when the hydrogen concentration is 100ppm. For example, the literature: Rhushikesh Godbole, Sadia Ameen, Umesh T. Nakate, M. Shaheer Akhtar, Hyung-Shik Shin, Low temperature HFCVD synthesis of tungsten oxide thin film for high response hydrogen gas sensor application, Materials Letters, Volume 254, 2019, Pages 398-401.

[0031] In summary, it can be seen that compared with the gas-sensitive response effect of the tungsten oxide continuous film in the prior art to hydrogen, the present invention is based on WO x The sensor composed of Pd / Pd nanoparticles can greatly improve the hydrogen sensing performance. The tested response temperature can be as low as 150°C, and the selectivity and sensitivity to hydrogen are greatly enhanced.

[0032] The contents described in this specification are merely an enumeration of implementation forms of the inventive concept, and the protection scope of the present invention should not be regarded as being limited to the specific forms described in the embodiments.

Claims

1. A hydrogen-sensitive WO x / Pd nano-assembled material hydrogen sensor, characterized in that The invention comprises a forked electrode with an insulating substrate and tungsten oxide WO deposited on the surface of the forked electrode. x Nanoparticles and Pd nanoparticles, tungsten oxide WO x Nanoparticles and Pd nanoparticles are combined into a disordered and uniform mixed structure to form WO x / Pd mixed nanoparticle assembly materials; The WO x In the / Pd mixed nanoparticle assembly material, the mass proportion of Pd nanoparticles is 0.5%~10%; The WO x The preparation method of the hydrogen sensor of the Pd / Pd nano-assembly material comprises the following steps: (1) High-purity WO3 and Pd targets are placed on two sputtering guns of the cluster beam deposition equipment, respectively, the interdigital electrodes are placed in the deposition chamber of the cluster beam deposition system, and the entire device is evacuated; (2) Sputtering gas is introduced into both sputtering guns, and buffer gas is introduced into the sputtering chamber of the cluster beam deposition system; (3) WO3 and Pd targets were sputtered successively to deposit WOx and Pd nanoparticles on the surface of the interdigital electrodes.

2. A hydrogen-sensitive WO as claimed in claim 1 x / Pd nano-assembled material hydrogen sensor, characterized in that In step (2), high-purity argon gas with a purity of more than 99.99% is used as sputtering gas and buffer gas, and the gas pressure in the sputtering chamber is maintained at 40~120Pa.

3. A hydrogen-sensitive WO as claimed in claim 1 x / Pd nano-assembled material hydrogen sensor, characterized in that In step (3), the sputtering power of the WO3 target is set to 20-25 W, the sputtering current is 0.045-0.05 A, the sputtering voltage is 450-500 V, and the sputtering time is 180-250 s.

4. A hydrogen-sensitive WO as claimed in claim 1 x / Pd nano-assembled material hydrogen sensor, characterized in that In step (3), the sputtering power of the Pd target is set to 10-15 W, the sputtering current is set to 0.035-0.042 A, and the sputtering voltage is set to 300-360 V.

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