Monatomic palladium-loaded titanium dioxide graded nanospheres for catalytic magnesium hydride

Abstract

The invention discloses a monatomic palladium-loaded titanium dioxide graded nanosphere for catalyzing magnesium hydride, and belongs to the technical field of hydrogen storage alloys and preparation thereof. The magnesium-based hydrogen storage material solves the problem that the existing magnesium-based hydrogen storage material has poor dynamic and thermodynamic properties and cannot meet the actual application requirements. The preparation method comprises the following steps: firstly, taking isopropyl titanate, diethylenetriamine and isopropanol as raw materials, preparing HA-TiO2 powder which exposes a large amount of {001} high-activity crystal faces by adopting a hydrothermal method, and further uniformly distributing monatomic Pd on the surface of the HA-TiO2 powder by adopting a chemical impregnation-reduction method to obtain Pd / TiO2 powder. The obtained Pd / TiO2 powder is used as a catalyst for catalyzing MgH2 hydrogen storage, the dehydrogenation temperature of a hydrogen storage material can be remarkably reduced, the hydrogen absorption / desorption rate is increased, and rapid hydrogen absorption at the room temperature is achieved.

Description

Technical Field

[0001] This invention relates to a single-atom palladium-supported titanium dioxide hierarchical nanosphere for catalytic magnesium hydride production, belonging to the field of hydrogen storage alloys and their preparation technology. Background Technology

[0002] Hydrogen energy, as a clean energy source, boasts advantages such as high calorific value, abundant resources, and good safety. The application of hydrogen energy mainly relies on three stages: production, storage, and utilization. Currently, hydrogen production and utilization technologies are relatively mature, but safe, economical, and efficient storage and transportation methods remain key issues for industrial development. Based on the physical state of hydrogen, common hydrogen storage methods include high-pressure gaseous hydrogen storage, liquid hydrogen storage, and solid-state hydrogen storage. High-pressure hydrogen storage technology was applied earlier, but it suffers from low volumetric hydrogen storage capacity and high safety risks. Liquid hydrogen storage, while possessing high volumetric density, requires complex low-temperature conditions or involves potential safety hazards related to organic matter, thus limiting its application. In contrast, solid-state hydrogen storage, due to its advantages in safety and hydrogen storage density, is considered one of the most promising solutions.

[0003] MgH2 has attracted widespread attention due to its high hydrogen storage density (7.6 wt.%) and excellent reversibility. However, its excessively high thermodynamic stability and high energy barrier during hydrogen absorption / desorption severely limit its practical applications. Therefore, effectively reducing the binding energy of the Mg–H bonds in MgH2, thereby improving its thermodynamic / kinetic hydrogen storage performance, is key to its industrial application. Summary of the Invention

[0004] To address the problem that existing MgH2 hydrogen storage materials have poor kinetic and thermodynamic properties and cannot meet the requirements of practical applications, this invention provides a single-atom palladium-supported titanium dioxide hierarchical nanosphere for catalytic magnesium hydride.

[0005] The technical solution of the present invention: One objective of this invention is to provide a single-atom palladium-supported titanium dioxide hierarchical nanosphere, specifically, the single-atom palladium-supported titanium dioxide hierarchical nanosphere includes TiO2 hierarchical nanospheres and single-atom Pd supported on the surface of TiO2 hierarchical nanospheres.

[0006] Further specifying, the particle size of TiO2 hierarchical nanospheres is 200-300 nm.

[0007] A second objective of this invention is to provide a method for preparing the above-mentioned single-atom palladium-supported titanium dioxide hierarchical nanospheres, the method comprising the following steps: Step 1: HA-TiO2 powder is prepared by hydrothermal method using isopropyl titanate, diethylenetriamine and isopropanol as raw materials; Step 2: Palladium(II) nitrate dihydrate is adsorbed onto the surface of HA-TiO2 powder by chemical impregnation-reduction method, and then calcined to obtain single-atom palladium-supported titanium dioxide hierarchical nanosphere powder, referred to as Pd / TiO2 powder.

[0008] Further specifying, in step one, the volume ratio of isopropyl titanate, diethylenetriamine, and isopropanol is 2 mL: 80 μL: 59 mL.

[0009] Further specifying, the hydrothermal reaction temperature in step one is 200-220℃, and the time is 24-26h.

[0010] Further specifying, the calcination atmosphere in step two is air, the temperature is 450-470℃, and the time is 2-3 hours.

[0011] Further specifying, the process of adsorbing palladium(II) dihydrate on the surface of HA-TiO2 powder by chemical impregnation-reduction in step two is as follows: palladium(II) dihydrate is dissolved in anhydrous ethanol, then HA-TiO2 powder is added, stirred at room temperature, and then centrifuged, washed and dried.

[0012] The third objective of this invention is to provide an application of the above-mentioned single-atom palladium-supported titanium dioxide hierarchical nanospheres, specifically as a catalyst for catalyzing magnesium hydride hydrogen storage materials.

[0013] The fourth objective of this invention is to provide a magnesium-based hydrogen storage material, wherein the HA-TiO2 powder is composed of the above-mentioned single-atom palladium-supported titanium dioxide hierarchical nanospheres and MgH2 powder.

[0014] Further specifying, the proportion of single-atom palladium-supported titanium dioxide hierarchical nanospheres in magnesium-based hydrogen storage materials is 5-15 wt.%.

[0015] The fifth objective of this invention is to provide a method for preparing the above-mentioned magnesium-based hydrogen storage material, which is obtained by high-energy ball milling of titanium dioxide hierarchical nanospheres supported on single-atom palladium and MgH2 powder.

[0016] Further specify the high-energy ball milling conditions as follows: under a protective atmosphere, with a ball-to-material ratio of 60:1 and a rotation speed of 400-500 rpm, using an intermittent ball milling method, with each ball milling session lasting 20 minutes followed by a 10-minute rest, for a total ball milling time of 8-12 hours.

[0017] Beneficial effects: This invention first uses isopropyl titanate, diethylenetriamine, and isopropanol as raw materials to prepare HA-TiO2 powder with a large number of exposed {001} highly active crystal planes via a hydrothermal method. Then, single-atom Pd is uniformly distributed on the surface of the HA-TiO2 powder through a chemical impregnation-reduction method to obtain Pd / TiO2 powder. Using the obtained Pd / TiO2 powder as a catalyst for MgH2 hydrogen storage can significantly reduce the dehydrogenation temperature of the hydrogen storage material and increase the hydrogen absorption / desorption rate, achieving rapid hydrogen absorption at room temperature. Compared with the prior art, this invention also has the following advantages: (1) This invention uses a hydrothermal method to prepare HA-TiO2 powder with a large number of {001} highly active crystal planes. It utilizes multivalent metal Ti as an electron transfer medium and the characteristic that some TiO2 can react with MgH2 to form hydrogen diffusion channels MgTi2O4 to improve the hydrogen absorption / desorption rate of the hydrogen storage material. At the same time, the presence of single-atom Pd reduces the dissociation energy of hydrogen, providing sufficient impetus for the subsequent binding of dissociated hydrogen atoms with magnesium and providing a channel for the diffusion of hydrogen atoms into the Mg substrate. Loading Pd on the TiO2 surface in the form of single atoms can form highly dispersed and uniform catalytic sites, and inhibit metal agglomeration through strong interaction with the support, thereby enhancing structural stability. At the same time, this structure can effectively reduce the binding energy of Mg–H bonds and significantly improve the thermal / kinetic performance of hydrogen storage. Experimental results show that using Pd / TiO2 powder as a catalyst for MgH2 hydrogen storage reduces the initial hydrogen desorption temperature of commercial MgH2 powder from 415℃ to 179℃, and only 3.5 min is needed to release 6.0 wt.% of hydrogen at 250℃. Meanwhile, at 25°C, the hydrogen absorption rate reached as high as 1.2 wt.% within 5 minutes.

[0018] (2) The magnesium-based hydrogen storage material prepared by the present invention has a simple process and low raw material cost, providing a new strategy for the low-cost and high-performance practical application of magnesium-based hydrogen storage materials. Attached Figure Description

[0019] Figure 1 Transmission electron microscope image of Pd / TiO2 powder prepared in Example 1; Figure 2 High-resolution transmission electron microscope image of Pd / TiO2 powder prepared in Example 1; Figure 3 Fourier transform of the extended X-ray absorption fine structure spectrum of the Pd / TiO2 powder prepared in Example 1; Figure 4 A comparison of temperature-dependent hydrogen desorption curves of magnesium-based hydrogen storage materials prepared in Example 1 and Comparative Examples 1-2; Figure 5 Isothermal dehydrogenation curves of magnesium-based hydrogen storage materials prepared in Example 1 and Comparative Examples 1-2 at 200°C; Figure 6 Isothermal hydrogen desorption curves at different temperatures for magnesium-based hydrogen storage materials prepared in Example 1; Figure 7 Isothermal hydrogen absorption curves of magnesium-based hydrogen storage materials prepared in Example 1 at a hydrogen pressure of 3 MPa and different temperatures; Figure 8 Transmission electron microscope image of TiO2 powder prepared for Comparative Example 2; Figure 9 High-resolution transmission electron microscope image of TiO2 powder prepared for Comparative Example 2. Detailed Implementation

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0021] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0022] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0023] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0024] Example 1: Preparation of hierarchical titanium dioxide nanospheres supported on single-atom palladium: 59 mL of isopropanol and 80 μL of diethylenetriamine were mixed thoroughly, and 2 mL of isopropyl titanate was added dropwise to the above solution. Subsequently, the mixture was transferred to a 100 mL autoclave and reacted at 200 °C for 24 h. After the reaction was completed, the mixture was centrifuged, washed, and dried to obtain HA-TiO2 powder.

[0025] 100 mg of HA-TiO2 powder was dissolved in 20 mL of anhydrous ethanol solution containing 1 mg of palladium(II) nitrate dihydrate. The mixture was stirred at room temperature for 1 h. After the reaction, the mixture was centrifuged, washed, and dried. Finally, it was calcined in air at 450 °C for 2 h to obtain single-atom palladium-supported titanium dioxide hierarchical nanosphere powder, abbreviated as Pd / TiO2 powder.

[0026] The structure of the obtained Pd / TiO2 powder was characterized, and the results are as follows: Figures 1-3 As shown. Figure 1 This is a transmission electron microscope image of Pd / TiO2 powder, by... Figure 1 It can be seen that its morphology is nanosphere-shaped. Figure 2 Here is a high-resolution transmission electron microscope image of Pd / TiO2 powder, by [source missing]. Figure 2 It can be seen that the nanosphere mainly exposes the {001} active crystal facet. Figure 3 Fourier transform of the extended X-ray absorption fine structure spectrum of the Pd / TiO2 hierarchical nanosphere catalyst, by Figure 3 It can be seen that Pd mainly exists in the form of single atoms.

[0027] Preparation of magnesium-based hydrogen storage materials: Under an argon atmosphere, Pd / TiO2 powder and MgH2 powder were mixed at mass fractions of 10 wt.% and 90 wt.%, respectively. A certain amount of zirconia beads were weighed and placed in a ball mill jar at a ball milling ratio of 60:1. High-energy ball milling was carried out at a speed of 450 rpm using an intermittent ball milling method. Specifically, each ball milling session lasted 20 minutes, followed by a 10-minute rest, for a total ball milling time of 10 hours, to obtain MgH2-10 wt.% Pd / TiO2 magnesium-based hydrogen storage material.

[0028] Comparative Example 1: This comparative example uses commercially available MgH2 hydrogen storage material as the magnesium-based hydrogen storage material.

[0029] Comparative Example 2: The difference between this comparative example and Example 1 is that: (1) no single-atom Pd loading was performed, and only TiO2 hierarchical nanosphere powder (referred to as TiO2 powder) was obtained. The remaining process steps and parameter settings were the same as in Example 1, and MgH2-10wt.% TiO2 magnesium-based hydrogen storage material was obtained.

[0030] The specific process of (1) in this comparative example is as follows: 59 mL of isopropanol and 80 μL of diethylenetriamine were mixed thoroughly, and 2 mL of isopropyl titanate was added dropwise to the above solution. Subsequently, the mixed solution was transferred to a 100 mL autoclave, reacted at 200 °C for 24 h, and then centrifuged, washed and dried to obtain HA-TiO2 powder.

[0031] 100 mg of HA-TiO2 was calcined in air at 450 °C for 2 h to obtain TiO2 graded nanosphere powder, referred to as TiO2 powder.

[0032] The structure of the TiO2 powder prepared in Comparative Example 2 was characterized, and the results are as follows: Figure 8 and Figure 9 As shown. Figure 8 The image shows a transmission electron microscope image of TiO2 powder, which reveals that the morphology of TiO2 is also nanosphere-like. Figure 9 The image shows a high-resolution transmission electron microscope image of TiO2 powder. As can be seen from the image, the nanospheres mainly expose the {001} active crystal planes.

[0033] The performance of the magnesium-based hydrogen storage materials prepared in Example 1 and Comparative Examples 1-2 was characterized, and the specific test results are as follows: Figures 4-7 As shown.

[0034] Figure 4 The graph shows a comparison of the temperature-dependent hydrogen desorption curves of the magnesium-based hydrogen storage materials prepared in Example 1 and Comparative Examples 1-2. As can be seen from the graph, the initial hydrogen desorption temperature of pure MgH2 is as high as 415℃, with a total hydrogen desorption of 7.4 wt.%. The initial hydrogen desorption temperature of the MgH2-10 wt.% Pd / TiO2 magnesium-based hydrogen storage material is reduced to 179℃, a decrease of approximately 236℃ compared to pure MgH2, demonstrating excellent dehydrogenation thermodynamic performance. Under the same test conditions, the initial hydrogen desorption temperature of the MgH2-10 wt.% TiO2 magnesium-based hydrogen storage material is 198℃, higher than that of the MgH2-10 wt.% Pd / TiO2 magnesium-based hydrogen storage material. This indicates that the introduction of single-atom Pd lowers the initial hydrogen desorption temperature of the hydrogen storage material.

[0035] Figure 5 The figures show the isothermal dehydrogenation curves of the magnesium-based hydrogen storage materials prepared in Examples 1-2 and Comparative Example 1 at 200°C. As can be seen from the figures, under the same test conditions, the hydrogen release of the MgH2-10wt.% Pd / TiO2 magnesium-based hydrogen storage material reached 2.7wt.% within 10 min at 200°C, while the hydrogen release of the MgH2-10wt.% TiO2 magnesium-based hydrogen storage material was only 1.0wt.%.

[0036] Figure 6 The figure shows the isothermal hydrogen release curves of the magnesium-based hydrogen storage material prepared in Example 1 at different temperatures. As can be seen from the figure, the MgH2-10wt.% Pd / TiO2 magnesium-based hydrogen storage material can release 6.0wt.% hydrogen in only 3.5 minutes at 250℃.

[0037] Figure 7The isothermal hydrogen absorption curves of the magnesium-based hydrogen storage material prepared in Example 1 at a hydrogen pressure of 3 MPa and different temperatures are shown in the figure. As can be seen from the figure, the hydrogen absorption capacity is as high as 1.2 wt.% within 5 minutes at 25°C.

[0038] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A hierarchical titanium dioxide nanosphere supported on a single atom palladium, characterized in that, It includes TiO2 hierarchical nanospheres and single-atom Pd loaded on the surface of the TiO2 hierarchical nanospheres.

2. The single-atom palladium-supported titanium dioxide hierarchical nanospheres according to claim 1, characterized in that, The TiO2 hierarchical nanospheres have a particle size of 200-300 nm.

3. A method for preparing single-atom palladium-supported titanium dioxide hierarchical nanospheres as described in claim 1 or 2, characterized in that, include: Step 1: HA-TiO2 powder is prepared by hydrothermal method using isopropyl titanate, diethylenetriamine and isopropanol as raw materials; Step 2: Single-atom palladium-loaded titanium dioxide hierarchical nanosphere powder is obtained by impregnating the surface of HA-TiO2 powder with palladium(II) dihydrate and then reducing and calcining it.

4. The preparation method according to claim 3, characterized in that, In step one, the volume ratio of isopropyl titanate, diethylenetriamine, and isopropanol is 2 mL: 80 μL: 59 mL; the hydrothermal reaction temperature is 200-220℃, and the time is 24-26 h.

5. The preparation method according to claim 3, characterized in that, In step two, the reduction and calcination atmosphere is air, the temperature is 450-470℃, and the time is 2-3 hours.

6. An application of the single-atom palladium-supported titanium dioxide hierarchical nanospheres as described in claim 1 or 2, characterized in that, Magnesium as a catalyst for catalytic hydration of hydrogen storage materials.

7. A magnesium-based hydrogen storage material, characterized in that, It is composed of titanium dioxide hierarchical nanospheres supported on single-atom palladium as described in claim 1 or 2 and MgH2 powder.

8. The magnesium-based hydrogen storage material according to claim 7, characterized in that, In magnesium-based hydrogen storage materials, the proportion of single-atom palladium-supported titanium dioxide hierarchical nanospheres is 5-15 wt.%.

9. A method for preparing the magnesium-based hydrogen storage material according to claim 7 or 8, characterized in that, The titanium dioxide hierarchical nanospheres supported on single-atom palladium and MgH2 powder were obtained by high-energy ball milling.

10. The preparation method according to claim 9, characterized in that, The high-energy ball milling conditions are as follows: under a protective atmosphere, a ball-to-material ratio of 60:1, and a rotation speed of 400-500 rpm, the ball milling is carried out in an intermittent manner, with each ball milling session lasting 20 minutes and followed by a 10-minute rest, for a total ball milling time of 8-12 hours.

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