A method for preparing a nanoporous two-dimensional palladium metalene
By controlling the ultrasonic frequency and carbon monoxide gas flow rate using an ultrasonic-assisted chemical method, nanoporous two-dimensional palladium metal olefins were prepared, solving the problem of difficult control of the defect density of two-dimensional palladium metal olefins. This achieved synergistic optimization of the material structure and hydrogen sensing performance, improving the sensitivity and response performance of the hydrogen sensor.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANGHAI INST OF MICROSYSTEM & INFORMATION TECH CHINESE ACAD OF SCI
- Filing Date
- 2026-02-10
- Publication Date
- 2026-06-16
Smart Images
Figure CN122209384A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of two-dimensional metal materials technology, and specifically relates to a method for preparing nanoporous two-dimensional palladium metal olefins. Background Technology
[0002] Two-dimensional metallic materials, due to their ultrathin structure, high specific surface area, and abundant surface active sites, show significant application potential in catalysis and gas sensing. Two-dimensional palladium metalenes, as representative materials, combine the excellent intrinsic catalytic performance of palladium metal with the unique physicochemical properties endowed by their two-dimensional structure. Especially in the field of hydrogen sensing, palladium materials' efficient adsorption and dissociation of hydrogen molecules make them ideal sensing materials, and two-dimensional palladium metalenes, with their continuous conductive network and highly activated surface, are expected to show significant advantages in achieving highly sensitive, low-power hydrogen detection at room temperature.
[0003] Currently, the main methods for preparing two-dimensional palladium metalloenes include solution chemistry, template-assisted methods, and surface confinement growth. Among these, solution chemistry is widely used due to its mild reaction conditions and simple operation; however, existing research mainly focuses on the formation and morphology control of the two-dimensional structure, with limited ability to precisely regulate defect structures. Existing defect construction strategies typically rely on post-processing methods such as etching, plasma treatment, or high-energy beam irradiation, which generally suffer from complex processes, insufficient reproducibility, and easy destruction of the two-dimensional continuous structure. Studies have shown that appropriate and controllable defects can significantly increase the density of active sites and optimize the electronic structure, thereby effectively improving catalytic activity. However, achieving precise control of defect type and defect density while maintaining the integrity of the two-dimensional structure remains a significant challenge. Therefore, there is an urgent need to develop a simple, parameter-controllable, highly reproducible, and scalable method for controlling defects in two-dimensional palladium metalloenes to achieve synergistic optimization of material structure and room-temperature hydrogen sensing performance.
[0004] Ultrasonic-assisted chemistry, through the instantaneous high temperature, high pressure, and strong shearing effects generated by cavitation, can significantly influence the nucleation and growth processes of materials, providing a new approach for the in-situ construction and control of defects. However, current research lacks reports on the systematic control of the defect structure of two-dimensional palladium metalloenes using key parameters such as ultrasonic frequency, and further studies on its room-temperature hydrogen sensing performance. Summary of the Invention
[0005] This invention provides a method for preparing nanoporous two-dimensional palladium metal olefins, which solves the problem that existing methods for preparing two-dimensional palladium metal olefins lack a simple, controllable, and repeatable method to adjust the defect density while maintaining the integrity of the two-dimensional continuous structure. This makes it difficult to achieve the joint optimization of material structure and sensing performance in applications such as room temperature hydrogen sensing.
[0006] This invention provides a method for preparing nanoporous two-dimensional palladium metal olefins, comprising the following steps:
[0007] (1) Weigh palladium acetylacetonate and add it to a clean and dry reaction vessel. Add organic solvent and ligand modifier to the reaction vessel in sequence. Stir magnetically at room temperature until palladium acetylacetonate is completely dissolved to form a homogeneous and transparent reaction precursor.
[0008] (2) Seal the reaction vessel and continuously introduce carbon monoxide gas into the reaction precursor through a gas introduction device;
[0009] (3) Place the reaction vessel in an ultrasonic cleaning tank and perform ultrasonic-assisted treatment on the reaction precursor under ultrasonic conditions, while heating the reaction precursor and maintaining the reaction under these conditions.
[0010] (4) After the reaction is complete, stop heating and ultrasonic treatment, allow the reaction precursor to cool naturally to room temperature, then centrifuge, wash and dry to obtain nanoporous two-dimensional palladium metalene.
[0011] Preferably, the reaction vessel in step (1) is a small glass vial with a sealed cap to ensure the stability of the atmosphere during the reaction.
[0012] Preferably, the organic solvent in step (1) is N,N-dimethylformamide (DMF); the ligand modifier is acetic acid. DMF acts as a solvent and also has a weak reducing effect, while acetic acid acts as a ligand modifier to regulate the coordination environment and crystal growth behavior of the palladium precursor.
[0013] Preferably, the ratio of palladium acetylacetonate, organic solvent and ligand modifier in step (1) is 10-15 mg, 8-10 mL and 2-5 mL.
[0014] Preferably, the flow rate of carbon monoxide gas in step (2) is controlled at 10-30 sccm. As a structure directing agent, carbon monoxide preferentially adsorbs onto specific crystal faces of the palladium crystal, inhibiting its vertical growth.
[0015] Preferably, the ultrasonic frequency in step (3) is 1-120 kHz. Under the action of ultrasonic cavitation effect and local mechanical stress, the palladium precursor undergoes nucleation and two-dimensional growth under the synergistic effect of mild reduction by DMF and selective adsorption of carbon monoxide on crystal planes, and introduces abundant pores and lattice defect structures during the growth process.
[0016] Preferably, the reaction precursor in step (3) is heated to 50-60°C and the reaction time is 1-2 hours.
[0017] Preferably, the nanoporous two-dimensional palladium metalene obtained in step (4) is used to prepare a room temperature sensor, as shown in the schematic diagram below. Figure 1 As shown.
[0018] Preferably, the method for preparing the room temperature sensor includes: loading the nanoporous two-dimensional palladium metalene onto the sensitive region of a MEMS single-crystal silicon thermopile by spotting, and then drying and fixing it.
[0019] The principle of this invention is as follows:
[0020] (1) Using ultrasonic frequency as the core control parameter: This invention introduces ultrasonic frequency into the preparation process of two-dimensional palladium metal olefins and uses it as the key process parameter that determines the defect density. By selecting different working frequencies to control the cavitation intensity, local mechanical stress and mass transfer behavior in the reaction precursor, the controllable preparation of low-defect, medium-defect and high-defect palladium metal olefins can be achieved in the same chemical system, which effectively solves the problem that the defect structure is difficult to adjust precisely in the prior art.
[0021] (2) Realize the correlation and optimization of material defect structure and room temperature hydrogen sensing performance: By precisely controlling the defect density, the present invention effectively increases the low coordination active sites on the surface of two-dimensional palladium metal olefin, optimizes its electronic structure and hydrogen molecule adsorption / dissociation behavior, thereby significantly improving the hydrogen sensing sensitivity and response performance of the material under room temperature conditions, and realizing the synergistic optimization of material structure design and sensing performance improvement.
[0022] Through the above-mentioned innovations, this invention introduces ultrasonic frequency modulation to construct a two-dimensional palladium metal olefin defect modulation method that is simple in process, has controllable parameters, and is highly repeatable. This effectively solves the problems of difficult controllable defect construction and limited performance in room temperature hydrogen sensing applications in the prior art.
[0023] Beneficial effects
[0024] (1) More precise and repeatable defect control: Existing technologies mostly rely on template methods, etching methods or high-energy post-processing to introduce defects, which makes it difficult to achieve precise control of defect density. This invention can achieve stable preparation of palladium metal olefins in the same chemical system by controlling the single and precisely controllable process parameter of ultrasonic frequency, and the defect control process has high repeatability.
[0025] (2) Introducing high-density active defects while maintaining the integrity of the two-dimensional structure: Existing high-defect construction methods are often accompanied by the destruction of the two-dimensional structure or the fracture of the lamellar structure, making it difficult to balance structural integrity and defect abundance. This invention achieves in-situ introduction of defects while ensuring the continuous two-dimensional growth of palladium metal olefins through the synergistic effect of ultrasonic physical field and carbon monoxide structure guidance, so that the material has both an ultrathin two-dimensional structure and abundant low-coordination active sites.
[0026] (3) The process route is simple and does not require complex templates or post-processing: Compared with the multi-step template construction, etching or high-temperature annealing methods commonly used in the prior art, the present invention does not require additional templates, etching or post-processing steps, has fewer reaction steps and is easy to operate, effectively reducing process complexity and preparation cost.
[0027] (4) Low equipment requirements and suitable for large-scale preparation: Some existing methods rely on special reactors or high-energy equipment, which makes it difficult to scale up the preparation. This invention only requires conventional reaction vessels and multi-frequency ultrasonic cleaning tanks to achieve defect control. The equipment is highly versatile, the process conditions are mild, and it has good market application feasibility. Attached Figure Description
[0028] Figure 1 A schematic diagram illustrating the principle of preparing a room-temperature hydrogen sensor using the nanoporous two-dimensional palladiumene of this invention.
[0029] Figure 2 TEM image of the low-defect two-dimensional palladium metalene prepared for Comparative Example 1 and its response recovery time curve to 1% hydrogen at room temperature.
[0030] Figure 3 TEM image of the moderately defective two-dimensional palladium metal olefin prepared in Example 1 and its response recovery time curve to 1% hydrogen at room temperature.
[0031] Figure 4 TEM image of the high-defect nanoporous two-dimensional palladium metalene prepared in Example 2 and its response recovery time curve to 1% hydrogen at room temperature.
[0032] Figure 5 The gas-sensing performance of the high-defect nanoporous two-dimensional palladium metalene prepared in Example 2 was characterized at room temperature; wherein, (a) the continuous dynamic response curve to hydrogen in the concentration range of 25 ppb-2%; (b) the fitting relationship between the sensor response value and the hydrogen concentration; (c) the repeatability test for 1% hydrogen concentration; and (d) the comparison of selective response to different gases. Detailed Implementation
[0033] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.
[0034] Comparative Example 1
[0035] Preparation of low-defect two-dimensional palladium metalene under ultrasound-free conditions:
[0036] 10 mg of palladium acetylacetone was weighed and added to a reaction vessel, along with 8 mL of DMF and 2 mL of acetic acid. The mixture was magnetically stirred at room temperature for 10-20 min to form a homogeneous and transparent reaction precursor. The precursor was then placed in a sealed environment, and a gas mixture of 10% carbon monoxide (the remainder being inert carrier gas) was introduced through a gas inlet device at a flow rate of 20 sccm. The system was heated to 50 °C and reacted for 1 h without sonication. After the reaction, the mixture was allowed to cool naturally to room temperature, centrifuged, washed, and solvent-displaced to obtain a two-dimensional palladium metal olefin material. The obtained material exhibits a continuous two-dimensional layered structure with a complete lattice and low defect density. Figure 2 As shown.
[0037] Example 1
[0038] High-frequency ultrasound-assisted preparation of moderately defective two-dimensional palladium metalene:
[0039] The precursor solution was prepared using the same method as in Comparative Example 1. The reaction vessel was placed in a multi-frequency ultrasonic cleaning tank, and the high-frequency ultrasonic mode was selected at a frequency of 120 kHz. Carbon monoxide gas (the remainder being inert carrier gas) was introduced under high-frequency ultrasonic conditions at a flow rate of 20 sccm, and the reaction temperature was controlled at 50℃ for 1 h. After the reaction, the ultrasonication was stopped, and the product was separated and purified. Because the cavitation bubbles induced by high-frequency ultrasound are smaller in size and the collapse process is more gentle, their lattice-destructive effect is weaker than that of low-frequency ultrasound. Therefore, the obtained two-dimensional palladium metallene maintains a continuous structure while exhibiting moderate defects, such as... Figure 3 As shown.
[0040] Example 2
[0041] Low-frequency ultrasound-assisted preparation of highly defective nanoporous two-dimensional palladium metalene:
[0042] The precursor solution was prepared using the same method as in Comparative Example 1. The reaction vessel was placed in a multi-frequency ultrasonic cleaning tank, and the low-frequency ultrasonic mode was selected at a frequency of 40 kHz. Carbon monoxide gas (the remainder being inert carrier gas) was introduced under continuous low-frequency ultrasonic conditions at a flow rate of 20 sccm, and the reaction temperature was maintained at 50℃ for 1 h. After the reaction, ultrasonication was stopped, and the products were separated and purified. The strong cavitation effect and localized mechanical stress generated by low-frequency ultrasound can introduce defect structures such as nanopores, edge serrations, and lattice distortions into the two-dimensional palladium metallene sheets. The resulting material has a high defect density and abundant low-coordination active sites, such as… Figure 4 As shown.
[0043] The two-dimensional palladium metalloenes prepared in Comparative Example 1 and Examples 1-2 were dispersed in ethanol to prepare a catalytic material dispersion of a predetermined mass concentration. This dispersion was then ultrasonically treated to form a uniformly dispersed and stable suspension. Subsequently, using a micro-spotting method, the dispersion was precisely loaded onto the sensitive hot end region of a MEMS single-crystal silicon thermopile chip, ensuring full contact between the two-dimensional palladium metalloene and the thermopile hot end to construct a stable catalytic sensing layer. After spotting, the device was placed in a constant-temperature oven for low-temperature drying to effectively remove residual solvent and enhance the adhesion stability between the sensitive material and the substrate. The dried device was further subjected to static or electrically aging treatments to gradually stabilize the sensitive layer structure and its interface with the thermopile, thereby improving the repeatability and long-term reliability of the sensor during actual operation.
[0044] The TEM morphology of the palladium metalenes prepared in Comparative Example 1 and Examples 1-2, and their response-recovery characteristics to 1% hydrogen at room temperature are as follows: Figure 2 , Figure 3 and Figure 4 As shown in the figure. Test results indicate that the hydrogen sensor constructed based on high-defect two-dimensional palladium metalene exhibits significantly superior dynamic response performance compared to medium-defect and low-defect palladium metalene sensors, with response times reduced to approximately 60.5% and 50% of the latter two, respectively. Furthermore, at room temperature and a 1% hydrogen concentration, the response amplitude (551 mV) of the high-defect two-dimensional palladium metalene sensor is 122% and 180% of that of the medium-defect (453 mV) and low-defect (318 mV) palladium metalene sensors, respectively, demonstrating the significant advantage of defect structures in improving hydrogen sensing sensitivity and response kinetics. And as... Figure 5 As shown, the hydrogen sensor using high-defect two-dimensional palladium metal olefin as a catalyst exhibits excellent overall performance, with both an ultra-wide detection range (25 ppb-2%) and excellent gas selectivity.
Claims
1. A method for preparing nanoporous two-dimensional palladium metalloene, characterized in that, Includes the following steps: (1) Weigh palladium acetylacetonate and add it to a clean and dry reaction vessel. Add organic solvent and ligand modifier to the reaction vessel in sequence. Stir magnetically at room temperature until palladium acetylacetonate is completely dissolved to form a homogeneous and transparent reaction precursor. (2) Seal the reaction vessel and continuously introduce carbon monoxide gas into the reaction precursor through a gas introduction device; (3) Place the reaction vessel in an ultrasonic cleaning tank and perform ultrasonic-assisted treatment on the reaction precursor under ultrasonic conditions, while heating the reaction precursor and maintaining the reaction under these conditions. (4) After the reaction is complete, stop heating and ultrasonic treatment, allow the reaction precursor to cool naturally to room temperature, then centrifuge, wash and dry to obtain nanoporous two-dimensional palladium metalene.
2. The preparation method according to claim 1, characterized in that, The reaction vessel in step (1) is a small glass vial with a sealed cap.
3. The preparation method according to claim 1, characterized in that, The organic solvent in step (1) is N,N-dimethylformamide; the ligand modifier is acetic acid.
4. The preparation method according to claim 1, characterized in that, In step (1), the ratio of palladium acetylacetone, organic solvent, and ligand modifier is 10-15 mg, 8-10 mL, and 2-5 mL, respectively.
5. The preparation method according to claim 1, characterized in that, The flow rate of carbon monoxide gas in step (2) is controlled to be 10-30 sccm.
6. The preparation method according to claim 1, characterized in that, The ultrasonic frequency in step (3) is 1-120kHz.
7. The preparation method according to claim 1, characterized in that, In step (3), the reaction precursor is heated to 50-60°C and the reaction time is 1-2 hours.
8. The preparation method according to claim 1, characterized in that, The nanoporous two-dimensional palladium metalene obtained in step (4) is used to prepare a room temperature sensor.
9. The preparation method according to claim 8, characterized in that, The method for preparing the room temperature sensor includes: loading the nanoporous two-dimensional palladium metalene onto the sensitive region of a MEMS single-crystal silicon thermopile by spotting, and then drying and fixing it.