Method for preparing Ru-RuO2 core-shell nanosheet through gas-solid phase reaction

Abstract

The invention discloses a method for preparing Ru-RuO2 core-shell nanosheets through a gas-solid phase reaction. Carbon black with amino functionalized surface is used as a carrier,-NH2 functional groups grafted on the surface of the carbon black are used for inducing deposition, dispersion and nucleation growth of Ru metal, and the growth speed of a crystal face is changed by optimizing reduction conditions and kinetic parameters and utilizing selective adsorption of reducing gas to the Ru crystal face, so that the morphology of particles is regulated and controlled, and the Ru metal particles are obtained. And synthesizing the hexagonal Ru nanosheet without the surfactant. Ru nanosheets are partially oxidized, Ru-RuO2 core-shell nanosheet structures with different atomic layer thicknesses are further obtained, and RuO2 shells with different thicknesses can accurately regulate and control the surface strain of the catalyst. The Ru-RuO2 core-shell nanosheet has the advantages that the use of a surfactant is avoided in the synthesis process, the Ru-RuO2 core-shell nanosheet can be obtained through simple loading and calcination, the large-scale mass production can be realized, and the core-shell nanosheet can be used for efficiently catalyzing the acidic OER reaction.

Description

Technical Field

[0001] The invention relates to a method for preparing Ru-RuO2 core-shell nanosheets by gas-solid phase reaction, belonging to the technical field of 2D nano material preparation. Background Art

[0002] In the OER electrocatalytic process, the actual active material for catalyzing OER is RuO2, but RuO2 is unstable at high anodic potentials in acidic electrolytes, and the unstable RuO4 film formed on the surface of RuO2 will dissolve into the electrolyte. In order to solve the problem of catalyst dissolution, researchers have made extensive efforts in catalyst design and synthesis, from alloy and composition optimization to structure and morphology control. At present, a variety of Ru-based nanostructures have been synthesized, including metal RuCu nanosheets with rich channels, Ru-Ni nanosheet assemblies, etc. Inorganic ultrathin nanosheets can provide very large surface areas and 2D permeation channels for ion adsorption and transport, showing excellent catalytic performance. However, there are still great challenges in the synthesis of precious metal nanosheet catalysts at this stage. The wet chemical synthesis method currently developed in the experiment has low amplification capability and is not suitable for large-scale production of Ru-RuO2 core-shell nanosheet catalysts. In addition, most synthesis methods require the use of organic surfactants to control the particle morphology, but this will undoubtedly contaminate the catalyst surface, so careful cleaning is required before use to make the particles catalytically active. The complex synthesis and pollutant removal process increases the production cost, making these technologies difficult to implement industrially. This paper endeavors to propose a method for large-scale production of Ru-RuO2 core-shell nanosheet electrocatalysts by a scalable, surfactant-free, low-cost solid chemical synthesis method and demonstrates that the prepared catalysts have high acidic OER activity. Summary of the invention

[0003] The present invention aims to provide a method for preparing Ru-RuO2 core-shell nanosheets by gas-solid phase synthesis. By optimizing the reduction conditions and kinetic parameters, the selective adsorption of reducing gas on the Ru crystal surface is utilized to change the growth rate of the crystal surface so as to control the particle morphology and synthesize hexagonal Ru nanosheets without surfactant. By partially oxidizing the Ru nanosheets, Ru-RuO2 core-shell nanosheet structures with different atomic layer thicknesses are further obtained. The RuO2 shells with different thicknesses can accurately control the catalyst surface strain, and the obtained products have potential applications in the field of acidic OER electrocatalysis.

[0004] The implementation process of the present invention is as follows: A method for preparing Ru-RuO2 core-shell nanosheets comprises the following steps: (1) loading a soluble ruthenium salt onto a carrier, wherein the carrier is selected from carbon black, titanium carbide, titanium nitride, vanadium nitride, and niobium carbide; (2) reducing the carrier loaded with a soluble ruthenium salt in a reducing gas at 350–800 °C; (3) The product obtained in step (2) is partially oxidized at 100-350°C to obtain Ru-RuO2 core-shell nanosheets.

[0005] In the above step (1), the carrier is immersed in a soluble ruthenium salt aqueous solution to obtain a carrier loaded with a soluble ruthenium salt. The carrier is preferably carbon black or titanium carbide, and the carbon black is hydrothermally treated with ammonia water before use.

[0006] The hydrothermal treatment of carbon black in aqueous ammonia is to add carbon black to concentrated aqueous ammonia and treat it at 100-250°C in a closed reactor.

[0007] In the above step (1), the soluble ruthenium salt is preferably selected from ruthenium chloride or ruthenium acetate.

[0008] In the above step (2), the reducing gas is selected from H2 or CO.

[0009] In the above step (2), the reduction treatment temperature is 350–600 ºC.

[0010] The Ru-RuO2 core-shell nanosheets prepared by the above method exhibited excellent catalytic performance in the acidic OER reaction. -2 The overpotential is only 275 mV.

[0011] The application of the above-mentioned Ru-RuO2 core-shell nanosheets in electrocatalytic water decomposition.

[0012] The above method promotes the nucleation of RuO2 on the surface of Ru core and the surface diffusion efficiency by regulating the growth temperature, time and heating rate during the growth of RuO2 shell, thereby forming a uniform and continuous RuO2 shell.

[0013] Beneficial effects of the present invention: Compared with the prior art, the present invention is a scalable, surfactant-free, low-cost solid chemical synthesis method. The synthesized Ru nanosheets have a regular hexagonal morphology. The hexagonal Ru nanosheets can be oxidized in an O2 atmosphere to obtain Ru-RuO2 core-shell nanosheets with different atomic layer thicknesses, and exhibit excellent acidic OER performance. When the current density reaches 10 mA·cm -2 The overpotential is only 275 mV. The present invention provides a simple and efficient new method for preparing Ru-RuO2 core-shell nanosheets with excellent two-dimensional structural properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1is a TEM image of Ru@CB-NH2 nanosheets obtained by CO reduction in Example 1; Figure 2 is the XRD spectrum of Ru-RuO2@CB-NH2 nanosheets after partial oxidation in Example 1; Figure 3 is a TEM image of Ru@CB obtained by CO reduction in Example 2; Figure 4 is a TEM image of Ru@TiC-NH2 nanosheets obtained by CO reduction in Example 3; Figure 5 is a TEM image of Ru@ITO-NH2 obtained by CO reduction in Example 4; Figure 6 is a TEM image of Ru@CB-NH2 obtained by CO reduction of ruthenium acetylacetonate in Example 5; Figure 7 is a TEM image of Ru@CB-NH2 obtained by NH3 reduction in Example 6; Figure 8 is the TEM image of Ru@CB-NH2 obtained by NO reduction in Example 7; Fig. 9 is a TEM image of Ru@CB-NH2 obtained by H2 reduction in Example 8; Fig.10 This is the electrochemical performance diagram of the Ru-RuO2@CB-NH2 nanosheets after partial oxidation in Example 1. DETAILED DESCRIPTION

[0015] The technical solution of the present invention is further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0016] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the art can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be purchased commercially. Example 1

[0017] Weigh 130 mg of RuCl3·3H2O and dissolve it in 20 ml of deionized water. Ultrasonicate for 20 min to completely dissolve RuCl3·3H2O. Add 100 ml of deionized water to a 200 ml beaker, disperse 200 mg of carbon black treated with ammonia in deionized water, ultrasonicate for 30 min, and mix the completely dissolved RuCl3·3H2O aqueous solution with the ultrasonicated carbon black for 1 h. Then transfer the stirred solution to an eggplant-shaped bottle and evaporate it at a speed of 100 rpm and a temperature of 60 ºC until the water is completely evaporated, and then dry it in a vacuum drying oven for 15 h to obtain RuCl3@CB powder.

[0018] 30 mg of dried RuCl3@CB-NH2 powder was weighed and placed in a quartz boat. Reducing gas CO was introduced into a tube furnace for calcination at a temperature of 400 °C and a heating rate of 5 °C min. -1 , gas flow rate is 20 sccm, and the holding time is 2 h to obtain Ru@CB-NH2 powder. The TEM image of Ru@CB-NH2 powder after reduction is shown in Figure 1 As shown, it can be seen that the Ru nanosheets prepared by the gas-solid phase synthesis method are hexagonal, with a lateral size range of 30‒50 nm and a thickness distribution of 5–7 nm.

[0019] The Ru@CB-NH2 powder was partially oxidized. 20 mg of Ru@CB-NH2 powder was weighed and placed in a quartz boat. O2 was introduced into a tube furnace for calcination at a temperature of 200 °C and a heating rate of 1 °C min. -1 , the gas flow rate was 20 sccm, and the holding time was 12 h. Figure 2 The XRD spectra of Ru nanosheets and Ru-RuO2 core-shell nanosheets show that the characteristic peak of RuO2 (110) crystal plane is at 28.01°, while the carbon characteristic peak is in the range of 16–29°. Therefore, when the oxidation temperature is between 100–300°C, there is no obvious characteristic peak of RuO2, but the peak position of the carbon characteristic peak gradually shifts to a higher angle as the oxidation temperature increases. After peak separation of the characteristic peaks in the range of 16–29°, the characteristic peaks of RuO2 are obtained. As the oxidation temperature increases, the characteristic peaks of RuO2 also shift to a higher angle, and the characteristic peak intensity of 35.05° ((101) crystal plane) also gradually increases, indicating that the Ru shell has been partially oxidized between 100–300°C, and the oxidation intensity gradually increases. XRD analysis shows that the gas-solid phase synthesis has successfully prepared Ru-RuO2 core-shell nanosheets with different atomic layer thicknesses. Example 2

[0020] Weigh 130 mg of RuCl3·3H2O and dissolve it in 20 ml of deionized water. Ultrasonicate for 20 min to completely dissolve RuCl3·3H2O. Add 100 ml of deionized water to a 200 ml beaker, disperse 200 mg of carbon black in the deionized water, ultrasonicate for 30 min, mix and stir the completely dissolved RuCl3·3H2O aqueous solution and the ultrasonicated carbon black for 1 h. Then transfer the stirred solution to an eggplant-shaped bottle and evaporate it at a speed of 100 rpm and a temperature of 60 ºC until the water is completely evaporated, and then dry it in a vacuum drying oven for 15 h to obtain RuCl3@CB powder.

[0021] 30 mg of dried RuCl3@CB powder was weighed and placed in a quartz boat. Reducing gas CO was introduced into a tube furnace for calcination to obtain Ru@CB. The temperature was 400 ºC and the heating rate was 5 ºC·min. -1 , gas flow rate is 20 sccm, and holding time is 2 h to obtain Ru@CB powder.

[0022] TEM characterization results show that Ru-RuO2 core-shell nanosheets cannot be obtained ( Figure 3 ). Example 3

[0023] Weigh 130 mg of RuCl3·3H2O and dissolve it in 20 ml of deionized water. Ultrasonicate for 20 min to completely dissolve RuCl3·3H2O. Add 100 ml of deionized water to a 200 ml beaker, disperse 200 mg of titanium carbide treated with ammonia in deionized water, ultrasonicate for 30 min, and mix the completely dissolved RuCl3·3H2O aqueous solution with the ultrasonicated carbon black for 1 h. Then transfer the stirred solution to an eggplant-shaped bottle and evaporate it at a speed of 100 rpm and a temperature of 60 ºC until the water is completely evaporated, and then dry it in a vacuum drying oven for 15 h to obtain RuCl3@TiC-NH2 powder.

[0024] 30 mg of dried RuCl3@TiC-NH2 powder was weighed and placed in a quartz boat. Reducing gas CO was introduced into a tube furnace for calcination at a temperature of 400 °C and a heating rate of 5 °C min. -1 , gas flow rate is 20 sccm, and the holding time is 2h to obtain Ru@TiC-NH2 powder.

[0025] Similar to Example 1, TEM characterization results show that the Ru-RuO2 core-shell nanosheets ( Figure 4 ).

[0026] Similar results were obtained by changing the carrier titanium carbide to titanium nitride, vanadium nitride or niobium carbide. Example 4

[0027] Similar to Example 1, except that the carrier is indium tin oxide (ITO), Ru-RuO2 core-shell nanosheets cannot be obtained under the same preparation conditions. Figure 5 shown. Example 5

[0028] Similar to Example 1, the difference is that the soluble ruthenium salt is ruthenium acetylacetonate. Under the same preparation conditions, ruthenium acetylacetonate decomposes at 260 ºC and cannot be reduced to obtain Ru@CB powder. Figure 6 shown. Example 6

[0029] Similar to Example 1, except that the reducing gas is ammonia, Ru-RuO2 core-shell nanosheets cannot be obtained under the same preparation conditions (reduction at 400 ºC). Increasing the reduction temperature causes the carbon black carrier to react with ammonia, such as Figure 7 shown.

[0030] Using NO as the reducing gas, the results are similar to those of ammonia, such as Figure 8 shown. Example 7

[0031] Similar to Example 1, except that the reducing gas is hydrogen, Ru-RuO2 core-shell nanosheets cannot be obtained under the same preparation conditions (reduction at 400 ºC), but Ru-RuO2 core-shell nanosheets can be obtained by increasing the reduction temperature to 700 ºC, as shown in FIG. Fig. 9 shown. Example 8

[0032] The Ru-RuO2@CB-NH2 nanosheets prepared in Example 1 were subjected to electrochemical performance tests. Fig.10 As shown in the figure, when the oxidation temperature is 150 ºC, the catalyst performance begins to decay after only one cycle of LSV testing, which is similar to the LSV curve of the unoxidized Ru@CB-NH2 powder. When the oxidation temperature is 200 ºC, the overpotential of Ru-RuO2 nanosheets is 275 mV. When the oxidation temperature is further increased (250 ºC), the OER activity of Ru-RuO2@CB-NH2 nanosheets decreases. Ru-RuO2 nanosheets have the best OER activity at an oxidation temperature of 200 ºC.

Claims

1. A method for preparing Ru-RuO2 core-shell nanosheets, characterized in that The following steps are involved: (1) loading a soluble ruthenium salt onto a carrier, wherein the carrier is selected from carbon black, titanium carbide, titanium nitride, vanadium nitride, and niobium carbide; (2) reducing the carrier loaded with a soluble ruthenium salt in a reducing gas at 350–800 °C; (3) The product obtained in step (2) is partially oxidized at 100-350°C to obtain Ru-RuO2 core-shell nanosheets.

2. The method for preparing Ru-RuO2 core-shell nanosheets according to claim 1, characterized in that: In step (1), the carrier is immersed in a soluble ruthenium salt aqueous solution to obtain a carrier loaded with a soluble ruthenium salt.

3. The method for preparing Ru-RuO2 core-shell nanosheets according to claim 1, characterized in that: The carrier is selected from carbon black or titanium carbide.

4. The method for preparing Ru-RuO2 core-shell nanosheets according to claim 1, characterized in that: The carbon black is subjected to hydrothermal treatment with ammonia water before use.

5. The method for preparing Ru-RuO2 core-shell nanosheets according to claim 1, characterized in that: The soluble ruthenium salt is selected from ruthenium chloride or ruthenium acetate.

6. The method for preparing Ru-RuO2 core-shell nanosheets according to claim 1, characterized in that: In step (2), the reducing gas is selected from H2 or CO.

7. The method for preparing Ru-RuO2 core-shell nanosheets according to claim 1, characterized in that: In step (2), the reduction treatment temperature is 350–600 ºC.

8. The Ru-RuO2 core-shell nanosheets prepared by the method according to any one of claims 1 to 7.

9. The two-dimensional ruthenium nanosheet according to claim 8, characterized in that: The Ru-RuO2 core-shell nanosheets exhibited excellent catalytic performance in the acidic OER reaction when the current density reached 10 mA cm -2 The overpotential is only 275 mV.

10. Use of the Ru-RuO2 core-shell nanosheets according to claim 8 in electrocatalytic water decomposition.

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