Use of a Pd-TiO2 in the preparation of a hydrogen and / or methane sensor

Abstract

The application discloses application of Pd-TiO2 in preparation of a hydrogen and / or methane sensor, wherein surface-coordinated monopalladium atom-based TiO2 can quickly detect methane and / or hydrogen at a lower temperature condition, and excellent sensitivity and reliable stability are exhibited, energy consumption is reduced, and safety and environmental protection are further improved.

Description

Technical Field

[0001] This application relates to the application of Pd-TiO2 in the preparation of hydrogen and / or methane sensors, belonging to the field of gas sensor technology. Background Technology

[0002] Methane emissions and leaks not only negatively impact air quality and contribute to global warming, but also affect numerous industries and applications. For example, detecting methane leaks is crucial in natural gas extraction, transportation, and power generation. In the chemical industry, the production of methanol, syngas, acetic acid, and other commercial chemicals relies on methane gas sensors to confirm the effective and safe operation of production processes. The coal industry requires the detection and monitoring of hazardous gases such as gas explosions and toxic gas leaks at each stage of production, processing, transportation, and use. Furthermore, natural gas (primarily composed of methane) is widely used as fuel in production and daily life, but accidents caused by natural gas leaks occur frequently. Therefore, measuring atmospheric methane levels to monitor changes in environmental conditions is essential. When using fuels with methane as a primary component, strict detection and monitoring of gas leaks must be implemented during production, transportation, and storage to eliminate safety hazards and ensure the safety of life and property for businesses, employees, and the public.

[0003] The problems with hydrogen as a fuel stem from the unavoidable hydrogen leaks during production, storage, and the use of hydrogen fuel cells, which can easily lead to dangers such as hydrogen refueling station explosions, chemical plant fires, fuel cell accidents, and environmental impacts. Given the widespread use of hydrogen in food safety, energy, and military defense, and its inherent safety concerns, hydrogen concentration must be monitored during use. To ensure the safety of future hydrogen fuel cell vehicles and related infrastructure, it is essential to detect even minute amounts of hydrogen in the air, and hydrogen sensors must have a sufficiently fast response time to detect leaks before a fire occurs.

[0004] Chemical resistance sensors are a real-time detection technology with advantages such as high sensitivity, fast response speed, convenient operation, and low production cost. Representative sensing materials, such as metal oxides (MO), typically require high operating temperatures (usually >250℃) to promote the activity of reactive oxygen species (O2). - O - and O2 -High operating temperatures not only increase the ignition risk when detecting combustible gases, but also complicate device manufacturing and increase energy consumption. Supporting catalytically active metal nanoparticles is one of the most common methods to improve room-temperature sensing performance. However, metal nanoparticles typically exhibit relatively low catalytic activity at room temperature. Furthermore, many factors, such as different crystal facets of metal nanoparticles, synergistic effects of adjacent metal atoms, and the uneven distribution of different metal atoms in alloy nanoparticles, lead to multiple catalytically active sites that can simultaneously activate various analytes and reduce their selectivity. Currently, the sensitivity and selectivity of MOs supported on metal NP catalysts at room temperature remain unsatisfactory.

[0005] Single-atom catalysts possess high catalytic activity and selectivity, showing great potential in various catalyst-related applications such as energy and organic conversion. Single-atom catalysts can achieve near-100% atom utilization, enabling higher catalytic efficiency. Furthermore, surface-coordinated single-atom catalysts possess pure, isolated, and structurally recognizable catalytic active sites. The influence of nitrogen atom catalysts on different reactants can be flexibly tuned by selecting the metal atom, substituting the supporting substrate, and altering the metal atom coordination environment. Unfortunately, research on gas-sensitive materials based on single-atom catalysts is still in its early stages; previous work still requires additional heating, which complicates device fabrication. Summary of the Invention

[0006] According to one aspect of this application, an application of Pd-TiO2 in the preparation of hydrogen and / or methane sensors is provided. In this application, the surface-coordinated single Pd atom-based TiO2 can rapidly detect methane and / or hydrogen at lower temperature conditions and exhibits excellent sensitivity and reliable stability. It not only reduces energy consumption but is also safer and more environmentally friendly.

[0007] An application of Pd-TiO2 in the preparation of hydrogen and / or methane sensors, wherein the Pd-TiO2 comprises Pd single atoms and TiO2;

[0008] The Pd single atom is coordinated on the surface of the TiO2.

[0009] Optionally, the single Pd atom is a +1 valence Pd single atom Pd1.

[0010] Optionally, the TiO2 has a nanoflower morphology.

[0011] Optionally, the particle size of the TiO2 is 100–500 nm.

[0012] Optionally, the particle size of the TiO2 is selected from any value of 100nm, 200nm, 300nm, 400nm, 500nm or a range between any two values.

[0013] Optionally, in the Pd-TiO2, the loading of the Pd single atom is 0.1–5 wt.%.

[0014] Optionally, the loading of the Pd single atom is selected from any value or a range between any two values ​​of 0.1wt.%, 0.2wt.%, 0.3wt.%, 0.4wt.%, 1wt.%, 2wt.%, 3wt.%, 4wt.%, and 5wt.%.

[0015] Optionally, the detection conditions of the sensor include:

[0016] Temperature 20~30℃.

[0017] Optionally, the temperature is selected from any value of 20℃, 23℃, 25℃, 26℃, 28℃, or 30℃, or a range between any two values.

[0018] Optionally, the detection conditions of the sensor include:

[0019] Temperature 23~26℃.

[0020] Optionally, the detection conditions of the sensor include:

[0021] The bias voltage is 1 to 5V.

[0022] Optionally, the bias voltage is selected from any value of 1V, 2V, 3V, 4V, 5V or a range between any two values.

[0023] Optionally, the detection conditions of the sensor include:

[0024] The detection airflow is 200–600 mL / min. -1 .

[0025] Optionally, the detection gas flow is selected from 200 mL min. -1 300mL min -1 400mL min -1 600mL min -1 Any value in the range or any two values.

[0026] Optionally, at 25±1℃, the sensor has a detection limit for methane as low as 0.815ppm;

[0027] The sensor has a detection limit of 0.35 ppm for hydrogen.

[0028] Optionally, the preparation method of the Pd-TiO2 includes the following steps:

[0029] The mixture containing TiO2 and Pd salt is obtained by irradiating it under ultraviolet light for 3 to 8 minutes.

[0030] Optionally, the Pd salt includes H2PdCl4.

[0031] Optionally, the power density of the ultraviolet light is 5–12 mW / cm². -2 The wavelength is 298–415 nm.

[0032] As one implementation scheme, this application proposes a method for detecting hydrogen and methane at room temperature. By using surface-coordinated single Pd atom-based TiO2 nanoflower (Pd1-TiO2) materials, hydrogen and methane can be detected at room temperature, thereby improving the safety and sensitivity of hydrogen and methane detection and reducing energy consumption.

[0033] To overcome the sensitivity limitations of room-temperature chemielectric resistivity sensing materials for hydrogen and methane sensing at room temperature, this study, for the first time, utilizes surface-coordinated single-Pd atom-based TiO2 nanoflowers (Pd1-TiO2) to achieve highly active detection of hydrogen and methane at room temperature. Compared to Pd nanoparticles (Pd NPs), single Pd atoms significantly enhance the sensing performance of TiO2 at room temperature. This work may open a general pathway for designing next-generation hydrogen and methane sensing materials and devices urgently needed for environmental monitoring in the Internet of Things (IoT).

[0034] As one implementation scheme, the technical problem this application aims to solve is: rapid real-time detection of hydrogen and methane at room temperature.

[0035] To solve the above-mentioned technical problems, the technical solution provided in this application is as follows:

[0036] TiO2 was selected as the semiconductor material for gas sensing. The nanoflower morphology of TiO2 provides a large specific surface area to support Pd single atoms. Pd single atoms are coordinated on the surface of the TiO2 nanoflowers (denoted as Pd1-TiO2). The effective Pd-O-Ti interface is constructed through surface coordination between Pd atoms and TiO2 to enhance the catalytic oxidation of hydrogen and methane at room temperature. Pd1-TiO2 exhibits rapid response and high sensitivity in the detection of hydrogen and methane.

[0037] Preparation of TiO2 nanoflowers: TiCl3 (1 mL) and ethylene glycol (20 mL) were mixed and stirred for 10 minutes, then 1 mL of water was added. The resulting pale yellow solution was transferred to a polytetrafluoroethylene-lined stainless steel autoclave and reacted at 160 °C for 6 hours. The mixture was then cooled to room temperature over 12 hours. A white product was obtained by centrifugation at 8000 rpm for 5 minutes and further washed with water and ethanol. After drying in a vacuum oven, the TiO2 nanoflowers were collected.

[0038] Preparation of Pd1-TiO2 nanoflowers: First, 17.4 mg of TiO2 nanoflowers were dispersed in 10 mL of water. Then, H2PdCl4 solution (0.845 mL, 5 mmol / L) was added with stirring. -1 The power density of the mixture exposed to light while stirred was approximately 10 mW / cm². -2 Irradiate with 365 nm ultraviolet light for 5 minutes. Centrifuge to obtain a light gray product, which is then washed with water. Pd1-TiO2 nanoflowers are dried in a vacuum oven and collected.

[0039] Most current chemiluminescence resistivity sensors sensitive to methane and hydrogen require testing temperatures exceeding 150 degrees Celsius. Pd1-TiO2, however, can rapidly and sensitively detect methane and hydrogen at room temperature, exhibiting excellent sensitivity and reliable stability. This not only reduces energy consumption but also makes it safer and more environmentally friendly.

[0040] The beneficial effects that this application can produce include:

[0041] (1) The application of Pd-TiO2 provided in this application in the preparation of hydrogen and / or methane sensors: the surface-coordinated single Pd atom-based TiO2 can quickly detect methane and / or hydrogen under low temperature conditions, and exhibits excellent sensitivity and reliable stability. It not only reduces energy consumption, but is also safer and more environmentally friendly. Attached Figure Description

[0042] Figure 1 This is a dynamic response-recovery curve of Pd1-TiO2 devices to a wide concentration (1-100ppm) of methane.

[0043] Figure 2 This is the normalized response-recovery curve of the Pd1-TiO2 device to methane at a concentration of 100 ppm.

[0044] Figure 3 This is a double logarithmic curve of the response of the Pd1-TiO2 device to methane concentration.

[0045] Figure 4This is a dynamic response-recovery curve of Pd1-TiO2 devices to a wide concentration (1-100ppm) of hydrogen.

[0046] Figure 5 This is the normalized response-recovery curve of the Pd1-TiO2 device to hydrogen gas at a concentration of 100 ppm.

[0047] Figure 6 This is a double logarithmic curve of the response of the Pd1-TiO2 device to hydrogen concentration.

[0048] Figure 7 This is a graph showing the response time and recovery time of a Pd1-TiO2 device to different concentrations of hydrogen gas.

[0049] Figure 8 The dynamic response-recovery curves of Pd NPs-TiO2 at room temperature to 100 ppm methane and 100 ppm hydrogen are shown.

[0050] Figure 9 The dynamic response-recovery curves of TiO2 nanoflowers at room temperature to 100 ppm methane and 100 ppm hydrogen are shown.

[0051] Figure 10 The images show the characterization results of TiO2 nanoflowers, Pd1-TiO2, and Pd NPs-TiO2. Among them, a is a scanning electron microscope image of TiO2, b is a transmission electron microscope image of Pd1-TiO2, c is a transmission electron microscope image of Pd NPs-TiO2, d is an XPS image of Pd1-TiO2, e is an aberration-corrected high-angle annular dark-field STEM image of Pd1-TiO2, and f is a STEM-EDS elemental mapping map of Pd1-TiO2. Detailed Implementation

[0052] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0053] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0054] In this application, the room temperature is (25±1)℃.

[0055] The sensor performance testing system was prepared according to the references Yao, M.-S.; Tang, W.-X.; Wang, G.-E.; Nath, B.; Xu, G., MOF Thin Film-Coated Metal Oxide Nanowire Array: Significantly Improved Chemiresistor Sensor Performance. Adv. Mater. 2016, 28, 5229-5234.

[0056] Morphological detail analysis was performed using a JEOL JSM-6700F field emission scanning electron microscope and a FEI TECNAI G2 F20 field emission transmission electron microscope. High-angle annular dark-field scanning transmission electron microscopy images and aberration-corrected high-angle annular dark-field scanning transmission electron microscopy images were obtained using a JEOL JEM-2100F scanning transmission electron microscope equipped with a CEOS probe corrector. X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy data were obtained from a Thermo Scientific ESCALAB 250Xi XPS system [monochromatic Al Kα X-ray (1486.6 eV), operating voltage 15 kV, basic pressure 5.0 × 10⁻⁶]. –8 [Pa]. Before XPS and UPS testing, the samples were first dried in a vacuum oven for 8 hours.

[0057] Palladium chloride [PdCl2, 98%] was purchased from Sigma Aldrich. Titanium trichloride (III) (15.0–20.0% TiCl3 dissolved in 30% HCl) and ethylene glycol (EG) were purchased from Alfa Aesar. Hydrochloric acid (HCl–35%) and ethanol were purchased from Xin-weicheng Co., Ltd. (Fuzhou, China).

[0058] All aqueous solutions were prepared using Milli-Q water (18.2 MΩ). 200 μm channel Ag-Pd interdigitated electrode plates were purchased from Hangzhou Jinbo Technology Co., Ltd., China. The electrode plates were rinsed with water and dried with nitrogen before use.

[0059] Example 1

[0060] Preparation of TiO2 nanoflowers: A TiCl3 solution (15.0–20.0% TiCl3 dissolved in 30% HCl) (1 mL) and ethylene glycol (20 mL) were mixed and stirred for 10 minutes, then 1 mL of water was added. The resulting pale yellow solution was transferred to a polytetrafluoroethylene-lined stainless steel autoclave and reacted at 160 °C for 6 hours. The mixture was then cooled to room temperature over 12 hours. The product was centrifuged at 8000 rpm for 5 minutes to obtain a white product, which was then washed three times with 10 mL of water and three times with 10 mL of ethanol. After drying in a vacuum oven, the TiO2 nanoflowers were collected.

[0061] Preparation of Pd1-TiO2 nanoflowers: First, 17.4 mg of TiO2 nanoflowers were dispersed in 10 mL of water. Then, H2PdCl4 solution (0.845 mL, 5 mmol / L) was added with stirring. -1 The power density of the mixture exposed to light while stirred was approximately 10 mW / cm². -2 Irradiate with 365 nm ultraviolet light for 5 minutes. Centrifuge to obtain a light gray product, which is then washed with water. Pd1-TiO2 nanoflowers are dried in a vacuum oven and collected.

[0062] Gas sensing performance measurement: The gas sensor was manufactured using a traditional drop-coating method. 1.0 mg of prepared Pd1-TiO2 nanoflower sample was dispersed in 1 mL of ethanol to obtain a dispersion. Subsequently, the dispersion containing 1.0 mg of the sample was drop-coated onto an Ag-Pd interdigitated electrode. The obtained Pd1-TiO2 sensor was aged at 80 °C for 8 hours before testing. The sensor performance testing conditions were: constant gas flow of 600 mL / min. -1 The bias on the sensor was set to 5V, and data acquisition was performed using a Keithley 2602B source meter. The target gas was mixed with dry air in a specific ratio using a mass flow controller to produce a gas of accurate concentration, which was then injected into the quartz tube. All tests were performed at (25±1)℃. The response (R) of Pd1-TiO2 to the analyte was determined by the change in detection resistance, defined as R(%) = (r... gas / r air -1)×100 reducing gas (where r air and r gas These are the resistances of Pd1-TiO2 in air and the target gas, respectively. The response and recovery times of Pd1-TiO2 refer to the time required to achieve 90% of the total resistance change.

[0063] Results: Using methane as the standard gas, the methane sensing performance of the Pd1-TiO2 device tested with a self-made gas sensing test device is as follows: Figures 1-3 As shown. Figure 1The dynamic response-recovery curves of Pd1-TiO2 to a wide range of methane concentrations from 1 to 100 ppm (specific methane concentrations detected were 1.0, 2.5, 5, 7.5, 10, and 100 ppm) at room temperature are shown. The resistivity of Pd1-TiO2 increases significantly upon exposure to methane but recovers to its initial value upon purging with dry air, indicating good reversibility. The fabricated device exhibits a response value as high as 3970% to methane at a concentration of 100 ppm.

[0064] The normalized response recovery curve ( Figure 2 As can be seen, Pd1-TiO2 exhibits a very fast response and recovery to methane gas at room temperature. The response time to 100 ppm methane is only 20 seconds, and the recovery time is only 64 seconds. By plotting double logarithmic curves of concentration and response values, and setting the response to 10% (…),… Figure 3 The linear fit of the plot shows that the detection limit of Pd1-TiO2 for methane at room temperature is as low as 0.815 ppm.

[0065] Similarly, when hydrogen is used as the standard gas for testing, the hydrogen sensing performance of the Pd1-TiO2 device, as tested using a self-made gas sensing test apparatus, is as follows: Figures 4-7 As shown. The dynamic response-recovery curves of hydrogen over a wide concentration range of 1-100 ppm (the specific hydrogen concentrations detected were 1, 3, 5, 10, and 100 ppm) are presented. Figure 4 As can be seen, the Pd1-TiO2 device is highly sensitive to hydrogen, with its response value increasing with increasing hydrogen concentration and exhibiting good reversibility. The response value to 100 ppm hydrogen is as high as 1209%. The normalized response recovery curve for 100 ppm hydrogen is shown in the figure. Figure 5 It can be seen that Pd1-TiO2 exhibits a relatively fast response and recovery to hydrogen gas at room temperature. Its response time is 0.7 minutes, and its recovery time is 5.52 minutes. Furthermore, from... Figure 7 It can be seen that the Pd1-TiO2 device exhibits different response and recovery rates to different concentrations of hydrogen. It shows faster response and recovery rates at low concentrations, while higher concentrations result in increased response and recovery times. For example, with 1 ppm hydrogen, the response time is only 0.37 minutes and the recovery time is 4.02 minutes. However, as the hydrogen concentration increases to 100 ppm, both the response and recovery times increase to 0.7 minutes and 5.52 minutes, respectively. Furthermore, by plotting a double logarithmic curve of hydrogen concentration and response value, and setting the response to 10% (… Figure 6 The linear fit of the plot shows that the detection limit of Pd1-TiO2 for hydrogen at room temperature is as low as 0.35 ppm.

[0066] Comparative Example 1

[0067] Preparation of TiO2 nanoflowers: A TiCl3 solution (15.0–20.0% TiCl3 dissolved in 30% HCl) (1 mL) and ethylene glycol (20 mL) were mixed and stirred for 10 minutes, then 1 mL of water was added. The resulting pale yellow solution was transferred to a polytetrafluoroethylene-lined stainless steel autoclave and reacted at 160 °C for 6 hours. The mixture was then cooled to room temperature over 12 hours. The product was centrifuged at 8000 rpm for 5 minutes to obtain a white product, which was then washed three times with 10 mL of water and three times with 10 mL of ethanol. After drying in a vacuum oven, the TiO2 nanoflowers were collected.

[0068] Preparation of Pd NPs-TiO2: First, 17.4 mg of TiO2 nanoflowers were dispersed in 10 mL of water. Then, H2PdCl4 solution (0.845 mL, 5 mmol / L) was added with stirring. -1 The power density of the mixture exposed to light while stirred was approximately 10 mW / cm². -2 Irradiate with 365 nm ultraviolet light for 30 minutes. Centrifuge to obtain a light gray product, which is then washed with water. NPs-TiO2 nanoflowers are dried in a vacuum oven and collected.

[0069] Gas sensing performance measurement: The gas sensor was manufactured using a traditional drop-coating method. 1.0 mg of a prepared Pd NPs-TiO2 sample was dispersed in 1 mL of ethanol to obtain a dispersion. Subsequently, the dispersion containing 1.0 mg of the sample was drop-coated onto an Ag-Pd interdigitated electrode. The obtained Pd NPs-TiO2 sensor was aged at 80°C for 8 hours before testing. The sensor performance testing conditions were: constant gas flow of 600 mL / min. -1 The bias on the sensor was set to 5V, and data acquisition was performed using a Keithley 2602B source meter. The target gas was mixed with dry air in a specific ratio using a mass flow controller to produce a gas of accurate concentration, which was then injected into the quartz tube. All tests were performed at (25±1)℃. The response (R) of Pd NPs-TiO2 to the analyte was determined by the change in detection resistance, defined as R(%) = (r... gas / r air -1)×100 reducing gas (where r air and r gas These are the resistances of Pd NPs-TiO2 in air and the target gas, respectively. The response and recovery times of Pd NPs-TiO2 refer to the time required to achieve 90% of the total resistance change.

[0070] Results: Using methane and hydrogen as standard gases, the methane sensing performance of the Pd NPs-TiO2 device is as follows: Figure 8 As shown. Figure 8 The dynamic response-recovery curves of Pd NPs-TiO2 at room temperature to 100 ppm methane and 100 ppm hydrogen are shown. The resistivity of Pd1-TiO2 increases significantly upon exposure to methane and hydrogen, but recovers to its initial value upon purging with dry air, indicating good reversibility. However, the response value of the Pd NPs-TiO2 device to 100 ppm methane is only 53%, a 75-fold decrease compared to Pd1-TiO2. The response value of the Pd NPs-TiO2 device to 100 ppm hydrogen is only 21.6%, a 56-fold decrease compared to Pd1-TiO2.

[0071] Comparative Example 2

[0072] Preparation of TiO2 nanoflowers: A TiCl3 solution (15.0–20.0% TiCl3 dissolved in 30% HCl) (1 mL) and ethylene glycol (20 mL) were mixed and stirred for 10 minutes, then 1 mL of water was added. The resulting pale yellow solution was transferred to a polytetrafluoroethylene-lined stainless steel autoclave and reacted at 160 °C for 6 hours. The mixture was then cooled to room temperature over 12 hours. The product was centrifuged at 8000 rpm for 5 minutes to obtain a white product, which was then washed three times with 10 mL of water, followed by three washes with 10 mL of ethanol. After drying in a vacuum oven, the TiO2 nanoflowers were collected for characterization and further experiments.

[0073] Gas sensing performance measurement: The gas sensor was manufactured using a traditional drop-coating method. 1.0 mg of the prepared TiO2 nanoflower sample was dispersed in 1 mL of ethanol. Subsequently, the dispersion containing 1.0 mg of the sample was drop-coated onto an Ag-Pd interdigitated electrode. The obtained TiO2 nanoflower sensor was aged at 80 °C for 8 hours before testing. The sensor performance testing conditions were: constant gas flow of 600 mL / min. -1 The bias on the sensor was set to 5V, and data acquisition was performed using a Keithley 2602B source meter. The target gas was mixed with dry air in a specific ratio using a mass flow controller to generate a gas with accurate concentration, which was then injected into the quartz tube. All tests were performed at (25±1)℃. The response (R) of the TiO2 nanoflowers to the analyte was determined by the change in detection resistance, defined as R(%) = (r... gas / r air -1)×100 reducing gas (where r air and r gasThese are the resistances of TiO2 nanoflowers in air and the target gas, respectively. The response and recovery times of TiO2 nanoflowers refer to the time required to achieve 90% of the total resistance change.

[0074] Results: Using methane and hydrogen as standard gases, the methane sensing performance of the TiO2 nanoflower device was tested as follows: Figure 9 As shown. Figure 9 The dynamic response-recovery curves of TiO2 nanoflowers to 100 ppm methane and 100 ppm hydrogen at room temperature are shown. The resistivity of the TiO2 nanoflowers increases significantly upon exposure to methane and hydrogen, but recovers to its initial value upon purging with dry air, indicating good reversibility. However, the response value of the TiO2 nanoflower device to 100 ppm methane is only 17.04%, a decrease of 233 times compared to Pd1-TiO2. The response value of the TiO2 nanoflower device to 100 ppm hydrogen is only 16.31%, a decrease of 74 times compared to Pd1-TiO2.

[0075] Characterization: Scanning electron microscopy measurements of TiO2 showed a similar nanoflower morphology, with particle sizes ranging from 100 to 500 nm. Figure 10 a). From the transmission electron microscope image, in Pd1-TiO2 ( Figure 10 No Pd NPs were found in b). In contrast, 5 nm Pd particles were found in PdNPs-TiO2. Figure 10 c) These particles exhibit 0.221 nm lattice fringes, belonging to the d111 spacing of PdNPs. Aberration-corrected high-angle annular dark-field STEM images of Pd1-TiO2 show ultra-small bright spots uniformly dispersed on TiO2 nanoflows. Figure 10 e) indicates that Pd exists in the form of isolated single atoms. STEM-EDS elemental mapping of Pd1-TiO2 ( Figure 10 f) indicates that Ti, O, and Pd elements are well distributed throughout the nanoflowers. In XPS, the Pd3d spectrum of Pd1-TiO2 exhibits two main signals (3d... 5 / 2 and 3D 3 / 2 ), located at 336.2 and 341.4 eV respectively, between Pd 2+ and Pd 0 Between these, it is indicated that some Pd atoms are anchored in the oxidized state ( Figure 10 d).

[0076] ICP-AES (Inductively Coupled Plasma Atomic Emission Spectroscopy) measurements showed that the Pd1 loading in Pd1-TiO2 was 0.34 wt.%.

[0077] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. Use of Pd-TiO2 for the preparation of a hydrogen and / or methane sensor, characterized in that, The Pd-TiO2 comprises Pd single atoms and TiO2; The Pd single atom is coordinated on the surface of the TiO2; The single Pd atom is a Pd single atom with a +1 valence, Pd1; The TiO2 has a nanoflower morphology; The particle size of the TiO2 is 100~500 nm; In the Pd-TiO2, the loading of Pd single atoms is 0.1~5wt%.

2. Use according to claim 1, characterized in that, The detection conditions of the sensor include: Temperature 20~30℃.

3. The use according to claim 1, characterized in that, The detection conditions of the sensor include: Temperature 23~26℃.

4. The application according to claim 1, characterized in that, The detection conditions of the sensor include: The bias voltage is 1~5 V.

5. The application according to claim 1, characterized in that, The detection conditions of the sensor include: The detection airflow is 200~600mL / min.

6. The application according to claim 1, characterized in that, At 25±1℃, the sensor's detection limit for methane is as low as 0.815ppm; The sensor has a detection limit of 0.35 ppm for hydrogen.

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