Self-assembled layered structure materials and their preparation methods and applications

Abstract

The present invention discloses a self-assembled layered structure material, a preparation method thereof and an application thereof. The preparation method of the self-assembled layered structure material comprises: mixing and etching an intermetallic electronide RTX with a strong acid to obtain a self-assembled layered structure material; wherein, R comprises at least one of lanthanide elements, T comprises at least one of transition metals, and X comprises at least one of silicon and germanium. By using this method, a self-assembled layered structure material with a large specific surface area, stable structure and small particle size can be prepared. Moreover, this method is simple to operate and the raw materials are easy to obtain. A catalyst comprising the self-assembled layered structure material has excellent catalytic performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and particularly relates to a self-assembled layered structure material, a preparation method thereof, and an application thereof. Background Art

[0002] The intermetallic electride RTX is a large class of intermetallic compounds with a tetragonal crystal structure (P4 / nmm) pioneered by the research team of Professor H. Hosono. It has attracted wide attention due to its relatively low work function, high concentration of surface anion electrons, extremely strong thermal stability, stability in aqueous solution, and extremely large regulation space. However, there is currently no method to prepare a two-dimensional metal-silicon structure material at a relatively low temperature (room temperature), with a small particle size and a large specific surface area of the two-dimensional metal-silicon structure material.

[0003] Therefore, the existing technology for preparing two-dimensional metal-silicon structure materials still needs to be improved and developed. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems in the related art to some extent. For this purpose, an object of the present invention is to provide a self-assembled layered structure material, a preparation method thereof, and an application thereof. By using this method, a self-assembled layered structure material with a large specific surface area, stable structure, and small particle size can be prepared. Moreover, the method is simple to operate, and the raw materials are easily available. The catalyst including this self-assembled layered structure material has excellent catalytic performance.

[0005] In one aspect of the present invention, a method for preparing a self-assembled layered structure material is provided. According to an embodiment of the present invention, the method includes:

[0006] Mixing and etching the intermetallic electride RTX with a strong acid to obtain a self-assembled layered structure material;

[0007] Wherein, R includes at least one of lanthanide elements, T includes at least one of transition metals, and X includes at least one of silicon and germanium.

[0008] According to the method of the above embodiments of the present invention, the intermetallic electronide RTX is mixed and etched with a strong acid. R includes at least one of the lanthanide elements, T includes at least one of the transition metals, and X includes at least one of silicon and germanium. The strong acid has a strong etching ability for the lanthanide elements in the intermetallic electronide RTX, and will not etch the transition metals, silicon, and germanium. That is, the strong acid performs directional etching on R in the intermetallic electronide RTX, removing the R element in the structure. T and X in the same layer respectively aggregate inward to form an alternating structure of T layer and X layer, that is, a highly ordered self-assembled two-dimensional metal T-X structure material is obtained. This material is almost entirely composed of T and X elements, and the molar content of the R element is less than 1%. During the etching process, the entire crystal structure of the intermetallic electronide is reorganized, completely losing its original crystal structure and electronide characteristics, forming a unique self-assembled layered structure. This self-assembled layered structure has a highly periodic transition metal-silicon / germanium layered feature, and the specific surface area is also greatly improved. The structure is stable and the particle size is small. Therefore, by using this method, a self-assembled layered structure material with a large specific surface area, stable structure, and small particle size can be prepared. Moreover, this method is simple to operate, the raw materials are easily available, and it is suitable for large-scale preparation. The catalyst including this self-assembled layered structure material has excellent catalytic performance.

[0009] In addition, the method for preparing the self-assembled layered structure material according to the above embodiments of the present invention may further have the following technical features:

[0010] In some embodiments of the present invention, the R includes at least one of La, Ce, and Pr, and the T includes at least one of Ni, Fe, Co, Mo, Mn, Cu, and Ru.

[0011] In some embodiments of the present invention, the strong acid includes at least one of hydrochloric acid, nitric acid, sulfuric acid, perchloric acid, hydroiodic acid, hydrobromic acid, and p-toluenesulfonic acid. Thus, a self-assembled layered structure material with a large specific surface area, stable structure, and small particle size can be prepared.

[0012] In some embodiments of the present invention, the concentration of the strong acid is 0.01 mol / L - 10 mol / L. Thus, a self-assembled layered structure material with a large specific surface area, stable structure, and small particle size can be prepared.

[0013] In some embodiments of the present invention, the molar ratio of the strong acid to the intermetallic electronide RTX is not less than 3. Thus, a self-assembled layered structure material with a large specific surface area, stable structure, and small particle size can be prepared.

[0014] In some embodiments of the present invention, the temperature of the mixed etching is -20°C to 100°C. Thus, a self-assembled layered structure material with a large specific surface area, stable structure, and small particle size can be prepared.

[0015] In some embodiments of the present invention, the time of the mixed etching is 3 h - 24 h. Thus, a self-assembled layered structure material with a large specific surface area, stable structure and small particle size can be prepared.

[0016] In some embodiments of the present invention, the mixed etching includes at least one of static treatment, ultrasonic treatment and stirring treatment.

[0017] In the second aspect of the present invention, the present invention provides a self-assembled layered structure material. According to the embodiments of the present invention, the self-assembled layered structure material is prepared by the above method. Thus, the self-assembled layered structure material has a large specific surface area, small particle size and stable structure.

[0018] In the third aspect of the present invention, the present invention provides a catalyst. According to the embodiments of the present invention, the catalyst includes the above self-assembled layered structure material. Thus, the catalyst has excellent catalytic performance.

[0019] The additional aspects and advantages of the present invention will be partly given in the following description, partly will become obvious from the following description, or be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and / or additional aspects and advantages of the present invention will become obvious and easy to understand from the description of the embodiments in conjunction with the following drawings, wherein:

[0021] Figure 1 is a schematic diagram of the change mechanism of the bulk phase during the deep etching of LaRuSi in Example 1 of the present invention with hydrochloric acid;

[0022] Figure 2 is an XRD characterization diagram of the crystal structure change after the deep etching of LaRuSi in Example 1 of the present invention with hydrochloric acid;

[0023] Figure 3 is a description diagram of the structural change during the deep etching of LaRuSi in Example 1 of the present invention with hydrochloric acid;

[0024] Figure 4 is a scanning electron microscope image of the layered structure material obtained after the deep etching of LaRuSi in Example 1 of the present invention with hydrochloric acid;

[0025] Figure 5 is a high-resolution transmission electron microscope image of the layered structure material obtained after the deep etching of LaRuSi in Example 1 of the present invention with hydrochloric acid;

[0026] Figure 6 is a high-angle annular dark-field image of the scanning transmission electron microscope of the layered structure material obtained after the deep etching of LaRuSi in Example 1 of the present invention with hydrochloric acid;

[0027] Figure 7 is Figure 6 The elemental linear distribution diagram of the elements in the part of the middle - lined square box;

[0028] Figure 8 is the elemental distribution diagram of the layered structure material obtained after deep etching of LaRuSi in Example 1 of the present invention with hydrochloric acid;

[0029] Figure 9 is the test result diagram of the catalytic performance of the layered structure material obtained after deep etching of LaRuSi in Example 1 of the present invention with hydrochloric acid;

[0030] Figure 10 is Figure 9 The corresponding Tafel slope diagram;

[0031] Figure 11 is the test result diagram of the catalytic performance of the layered structure material in Example 2 of the present invention;

[0032] Figure 12 is the test result diagram of the catalytic performance of the layered structure material in Example 3 of the present invention. Detailed implementation manners

[0033] The embodiments of the present invention are described in detail below, which are intended to explain the present invention and should not be construed as limiting the present invention.

[0034] In one aspect of the present invention, a method for preparing a self - assembled layered structure material is proposed. According to an embodiment of the present invention, the method includes:

[0035] Mixing and etching the intermetallic electronide RTX with a strong acid to obtain a self - assembled layered structure material;

[0036] wherein, R includes at least one of lanthanide elements, T includes at least one of transition metals, and X includes at least one of silicon and germanium.

[0037] By mixing and etching the intermetallic electronide RTX with a strong acid, where R includes at least one of the lanthanide elements, T includes at least one of the transition metals, and X includes at least one of silicon and germanium, the inventors found that the strong acid has a strong etching ability for the lanthanide elements in the intermetallic electronide RTX and does not etch the transition metals, silicon, and germanium. That is, the strong acid performs directional etching on R in the intermetallic electronide RTX to remove the R element in the structure. T and X in the same layer respectively aggregate inward to form an alternating structure of T layer and X layer, that is, a highly ordered self-assembled two-dimensional metal T-X structure material is obtained. This material is almost entirely composed of T and X elements, and the molar content of the R element is less than 1%. During the etching process, the entire crystal structure of the intermetallic electronide is reorganized, completely losing its original crystal structure and electronide characteristics, forming a unique self-assembled layered structure. This self-assembled layered structure has a highly periodic transition metal-silicon / germanium layered feature, and the specific surface area is also greatly improved. The structure is stable, and the particle size is small. At the same time, this application can prepare the metal-silicon / germanium layered structure material at a relatively low temperature, avoiding high-temperature reactions, saving consumables and costs. Specifically, the temperature of the mixed etching is -20°C to 100°C, indicating that this application can prepare the metal-silicon / germanium layered structure material at room temperature or below room temperature. Thus, by using this method, a self-assembled layered structure material with a large specific surface area, stable structure, and small particle size can be prepared. Moreover, this method is simple to operate, the raw materials are easy to obtain, and it is suitable for large-scale preparation. The catalyst including this self-assembled layered structure material has excellent catalytic performance.

[0038] Furthermore, R includes at least one of La, Ce, and Pr, and T includes at least one of Ni, Fe, Co, Mo, Mn, Cu, and Ru. It should be noted that before mixing and etching the intermetallic electronide RTX with a strong acid, the intermetallic electronide RTX is ground. Grinding is a conventional operation method in the art. For example, in this application, the intermetallic electronide RTX is manually ground in a glove box or ball-milled under the protection of an inert gas to obtain RTX powder. The strong acid is a conventional reagent in the art, and those skilled in the art can select according to the actual situation. For example, the strong acid includes at least one of hydrochloric acid, nitric acid, sulfuric acid, perchloric acid, hydroiodic acid, hydrobromic acid, and p-toluenesulfonic acid. Thus, directional etching of the lanthanide elements can be carried out.

[0039] According to an embodiment of the present invention, the concentration of the strong acid is 0.01 mol / L - 10 mol / L. The inventors have found that if the concentration of the strong acid is too small, it will affect the progress of the etching reaction. Controlling the concentration of the strong acid within 0.01 mol / L - 10 mol / L can increase the efficiency of the etching reaction. Thus, by using a strong acid with a concentration of 0.01 mol / L - 10 mol / L in this application, a self-assembled layered structure material with a large specific surface area, stable structure, and small particle size can be prepared. Further, the molar ratio of the strong acid to the intermetallic electron compound RTX is not less than 3, which is beneficial to the progress of the etching reaction.

[0040] According to an embodiment of the present invention, the time for mixed etching is 3 h - 24 h. The inventors have found that if the time for mixed etching is too short, the etching is incomplete and the material properties are affected; if the time for mixed etching is too long, the etching reaction has been completed, increasing the time cost. Thus, by using a time for mixed etching of 3 h - 24 h in this application, a self-assembled layered structure material with a large specific surface area, stable structure, and small particle size can be prepared. Further, the mixed etching includes at least one of static treatment, ultrasonic treatment, and stirring treatment. It should be noted that static treatment, ultrasonic treatment, and stirring treatment are conventional treatment methods in the art. For the parameter conditions in the specific treatment process, those skilled in the art can select according to the specific method used. At the same time, those skilled in the art can understand that after mixing and etching the intermetallic electron compound RTX with the strong acid to obtain a precipitate of the self-assembled layered structure material, the precipitate of the self-assembled layered structure material can be subjected to centrifugation, washing, and drying treatments. For example, the washing solvent is deionized water and ethanol, and the precipitate is washed with deionized water and ethanol in sequence and repeated multiple times; the drying is vacuum drying, which is carried out at room temperature, and the drying time is 10 - 12 hours.

[0041] In the second aspect of the present invention, the present invention provides a self-assembled layered structure material. According to an embodiment of the present invention, the self-assembled layered structure material is prepared by the above method. Thus, the self-assembled layered structure material has a large specific surface area, small particle size, and stable structure. It should be noted that the features and advantages described above for the method of preparing the self-assembled layered structure material also apply to the self-assembled layered structure material, and will not be repeated here.

[0042] In the third aspect of the present invention, the present invention provides a catalyst. According to an embodiment of the present invention, the catalyst includes the above self-assembled layered structure material. Thus, the catalyst has excellent catalytic performance. It should be noted that the features and advantages described above for the self-assembled layered structure material and its preparation method also apply to the catalyst, and will not be repeated here.

[0043] The present invention will be described below with reference to specific embodiments. It should be noted that these embodiments are merely illustrative and do not limit the present invention in any way.

[0044] Example 1

[0045] Weigh 2.8 g of metallic lump La, 2.02 g of Ru, and 0.56 g of silicon. Mix them evenly and put them into a metal melting furnace. Under an Ar atmosphere, melt them multiple times until LaRuSi forms a uniform elliptical bulk material. After cooling, take out the mixed bulk, manually break it and grind it into a uniform powder (without obvious granular feeling) in a glove box environment.

[0046] Take an appropriate amount of the powder and press it into a block with a diameter of about 6 mm and a height of 5 mm in the glove box. The re-pressed sample is wrapped with a clean metal Mo sheet and placed in a quartz tube with one end sealed and one end open, with a length of 20 cm and a thickness of 1.5 mm. The quartz tube is evacuated, and a high-temperature hydrogen-oxygen flame is used for sealing to ensure vacuum. Then, anneal it in a box furnace at 1000 °C for 10 days to obtain a purified sample.

[0047] After the annealing is completed, manually grind the sample into a uniform powder (without obvious granular feeling) in a glove box environment. Weigh 500 mg of the obtained sample powder and place it in a 50 mL graduated plastic centrifuge tube. Then, add 50 mL of a hydrochloric acid solution with a concentration of 1 mol / L, stir evenly, and let it stand at room temperature for 3 h.

[0048] Centrifuge the processed sample to obtain the bottom solid, and repeatedly wash the product 6 times with deionized water and ethanol. Vacuum-dry the washed sample.

[0049] The intermetallic electron compound LaRuSi in Example 1 is etched with hydrochloric acid, and the change mechanism of the bulk phase is as Figure 1 shown. It can be seen from Figure 1 that the two-dimensional La-electron-La layer is etched, and then the Ru layer and the Si layer are recombined.

[0050] The XRD characterization of the crystal structure change after the intermetallic electron compound LaRuSi is deeply etched with hydrochloric acid is as Figure 2 shown. It can be seen from Figure 2 that the product is amorphous.

[0051] The structure change description diagram of the intermetallic electron compound LaRuSi during the process of deep etching with hydrochloric acid is as Figure 3 shown. It can be seen from Figure 3 that the product is a heterojunction with Ru and Si stacked in a 2D / 2D layered structure.

[0052] The scanning electron microscope image of the layered structure material obtained after the intermetallic electron compound LaRuSi is deeply etched with hydrochloric acid is as Figure 4 shown. It can be seen fromFigure 4 It can be seen that the product has a layered structure.

[0053] The high-resolution transmission electron microscope image of the layered structure material obtained by deeply etching the intermetallic electron compound LaRuSi with hydrochloric acid is as Figure 5 shown. From Figure 5 it can be seen that the product has a heterojunction with layered stacking.

[0054] The high-angle annular dark-field image of the scanning transmission electron microscope of the layered structure material obtained by deeply etching the intermetallic electron compound LaRuSi with hydrochloric acid is as Figure 6 shown. From Figure 6 it can be seen that the heterojunction is composed of Ru layer and Si respectively. Figure 6 The elemental line distribution map of the part in the underlined square box is as Figure 7 shown.

[0055] The elemental distribution map of the layered structure material obtained by deeply etching the intermetallic electron compound LaRuSi with hydrochloric acid is as Figure 8 shown. From Figure 8 it can be seen that the heterojunction is composed of Ru layer and Si respectively.

[0056] The electrocatalytic hydrogen evolution reaction was adopted to verify the catalytic performance of the layered structure material prepared in Example 1. Commercial Ru / C, Pt / C, LaRuSi and the layered structure material (RSHS) prepared in Example 1 were respectively selected for electrocatalytic hydrogen evolution in 1 mol / L KOH solution. The results of the above electrocatalytic hydrogen evolution linear voltammetry curves are shown in Figure 9 , Figure 9 and the corresponding Tafel slope graph is as Figure 10 shown. From Figure 9 and Figure 10 it can be seen that the potential of the layered structure material (RSHS) prepared in Example 1 is significantly lower than that of Ru / C, Pt / C, and LaRuSi. The potential of RSHS is as low as 15 mV, indicating that the layered structure material (RSHS) prepared in Example 1 has excellent catalytic performance.

[0057] Example 2

[0058] Weigh 2.78 g of metal pellets of Ce, 2.02 g of Ru, and 0.56 g of silicon, mix them evenly and put them into a metal melting furnace. Melt them multiple times under an Ar atmosphere until CeRuSi forms a uniform elliptical bulk material. After cooling, take out the mixed bulk, and manually break and grind it into a uniform powder (without obvious particle feeling) in a glove box environment.

[0059] Take an appropriate amount of powder and press it into a block with a diameter of about 6 mm and a height of 5 mm in a glove box. The re-pressed sample is wrapped with a clean metal Mo sheet and placed in a quartz tube with one end sealed and one end open, a length of 20 cm and a thickness of 1.5 mm. The quartz tube is evacuated and sealed with a high-temperature hydrogen-oxygen flame to ensure vacuum, and then annealed in a box furnace at 1000 °C for 10 days to obtain a purified sample.

[0060] After the annealing is completed, manually grind the sample into a uniform powder (without obvious granularity) in a glove box environment. Weigh 500 mg of the obtained sample powder and place it in a 50 mL graduated plastic centrifuge tube, then add 50 mL of a hydrochloric acid solution with a concentration of 1 mol / L, stir evenly and let it stand at room temperature for 3 h.

[0061] Centrifuge the processed sample to obtain the bottom solid, and repeatedly wash the product 6 times with deionized water and ethanol. Vacuum dry the washed sample.

[0062] Verify the catalytic performance of the layered structure material prepared in Example 2 by performing an electrocatalytic hydrogen evolution reaction. The catalytic performance test results are as Figure 11 shown. It can be seen from Figure 11 that the potential of the layered structure material prepared in Example 2 is as low as 24 mV, indicating that the layered structure material prepared in Example 2 has excellent catalytic performance.

[0063] Example 3

[0064] Weigh 2.76 g of metal lump Pr, 2.02 g of Ru, and 0.56 g of silicon, mix them evenly and put them into a metal melting furnace, and melt them multiple times in an Ar atmosphere until PrRuSi forms a uniform elliptical bulk material. After cooling, take out the mixed bulk, manually break it and grind it into a uniform powder (without obvious granularity) in a glove box environment.

[0065] Take an appropriate amount of powder and press it into a block with a diameter of about 6 mm and a height of 5 mm in a glove box. The re-pressed sample is wrapped with a clean metal Mo sheet and placed in a quartz tube with one end sealed and one end open, a length of 20 cm and a thickness of 1.5 mm. The quartz tube is evacuated and sealed with a high-temperature hydrogen-oxygen flame to ensure vacuum, and then annealed in a box furnace at 1000 °C for 10 days to obtain a purified sample.

[0066] After the annealing is completed, manually grind the sample into a uniform powder (without obvious granularity) in a glove box environment. Weigh 500 mg of the obtained sample powder and place it in a 50 mL graduated plastic centrifuge tube, then add 50 mL of a hydrochloric acid solution with a concentration of 1 mol / L, stir evenly and let it stand at room temperature for 3 h.

[0067] The sample after processing was centrifuged to obtain the bottom solid, and the product was washed repeatedly with deionized water and ethanol 6 times. The washed sample was dried in vacuo.

[0068] The electrocatalytic hydrogen evolution reaction was adopted to verify the catalytic performance of the layered structure material prepared in Example 2. The test results of the catalytic performance are as Figure 12 shown. It can be seen from Figure 12 that the potential of the layered structure material prepared in Example 3 is as low as 36 mV, indicating that the layered structure material prepared in Example 3 has excellent catalytic performance.

[0069] In the description of this specification, the descriptions referring to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, without conflict, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples.

[0070] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. Application of a self-assembled layered structure material as a catalyst in an electrocatalytic hydrogen evolution reaction, characterized in that, The preparation method of the self-assembled layered structure material includes: Mixing the intermetallic electronide RTX with a strong acid to etch away R to obtain the self-assembled layered structure material; The molar ratio of the strong acid to the intermetallic electronide RTX is not less than 3; The concentration of the strong acid is 1 mol / L - 10 mol / L; The temperature of the mixed etching is -20°C to 100°C; The time of the mixed etching is 3 h to 24 h; The strong acid is hydrochloric acid; Wherein, R includes at least one of lanthanide elements, T is Ru element, and X is silicon element.

2. Use of the self-assembled layered structure material as claimed in claim 1 as a catalyst in an electrocatalytic hydrogen evolution reaction, characterized in that, The mixed etching includes at least one of static treatment, ultrasonic treatment, and stirring treatment.

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