A method for preparing a ruthenium-based alkaline bifunctional electrocatalyst

Abstract

The application discloses a preparation method of a ruthenium-based alkaline bifunctional electrocatalyst. The method is to use carbon nanotube coated nickel nanoparticles Ni@CNT as a carrier, and use ruthenium Ru as an active component. The Ru is loaded on the surface of the carbon nanotube through a replacement method, and the interface structure is optimized through low-temperature calcination treatment to obtain the ruthenium-based alkaline bifunctional electrocatalyst. The prepared catalyst can realize excellent HER and OER catalytic performance in an alkaline electrolyte. The synthesis process is simple. The carbon nanotube coated nickel nanoparticles are used as a carrier material. On the one hand, the carbon nanotube coated nickel nanoparticles have efficient mass transfer and electron transport functions. On the other hand, the carbon nanotube coated nickel nanoparticles have a strong carrier effect with the loaded Ru, which is helpful to improve the catalytic performance. In a 1.0M electrolyte, the HER and OER catalytic performance of the carbon nanotube coated nickel nanoparticles can be better than that of commercial Pt / C and RuO2 respectively.

Description

Technical Field

[0001] This invention relates to the technical field of new energy materials, and in particular to a method for preparing a ruthenium-based alkaline bifunctional electrocatalyst. Background Technology

[0002] Electrocatalytic water splitting processes include the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER); however, both OER and HER require highly active electrocatalysts to reduce their overpotentials. Furthermore, for continuous water electrolysis in practical applications, the reactions must take place in the same electrolyte (e.g., in an alkaline solution). Therefore, developing a highly efficient bifunctional electrocatalyst for water splitting in the same electrolyte is highly attractive for reducing costs and achieving large-scale hydrogen production.

[0003] Currently, Pt-based materials are the most widely used HER electrocatalysts; however, the scarcity and high cost of Pt limit its widespread application. To further promote the development of hydrogen production technology, it is necessary to find excellent alternatives to Pt-based materials. Ru, as the cheapest platinum group metal, possesses high theoretical intrinsic activity and exhibits strong corrosion resistance and an extremely low water dissociation energy barrier. Furthermore, numerous studies have shown that Ru oxides have excellent OER catalytic activity. Therefore, excellent bifunctional HER and OER catalytic activity can be achieved by modulating Ru. Supported Ru-based catalysts can improve the dispersion of active sites and reduce the amount of precious metals used; on the other hand, the synergistic effect between the catalyst and the support can further improve the catalytic activity and stability of the material. Chinese patent (publication number: CN115323394A) discloses a Fe-doped Co3O4-supported Ru bifunctional catalyst for electrocatalytic water splitting. Compared with carbon materials, such as carbon nanotubes, the Fe-doped Co3O4 support has dense particle packing and poor conductivity, which is detrimental to improving catalytic activity. Chinese Patent (Publication No.: CN114318411A) discloses a method for preparing and applying a cobalt / carbon nanotube / ruthenium electrocatalyst. It describes how carbon nanotubes obtained by lysozyme-assisted pyrolysis of a cobalt-based zeolite imidazolium ester framework are coated with Co and used to load Ru nanoparticles, enabling HER applications in a full-pH electrolyte. This demonstrates the potential of loading Ru onto metal particles using carbon nanotube coatings in the field of electrocatalysis. In contrast, the carbon nanotube-coated metal particles in this invention are obtained directly through the pyrolysis of a mixture of metal salt and carbon source, eliminating the need for crystal nucleation growth and the addition of auxiliary agents, thus simplifying the synthesis process. Furthermore, the nickel used in this invention is less expensive. In addition, the product of this invention exhibits excellent bifunctional electrocatalytic performance, enabling simultaneous application in HER and OER, rather than just HER. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings and deficiencies of the prior art and to propose a method for preparing a ruthenium-based alkaline bifunctional electrocatalyst. The synthesis process is simple, and the prepared catalyst can achieve excellent HER and OER catalytic performance in alkaline electrolytes.

[0005] To achieve the above objectives, the technical solution provided by this invention is as follows: a method for preparing a ruthenium-based alkaline bifunctional electrocatalyst. This method uses carbon nanotube-coated nickel nanoparticles (Ni@CNT) as a support and ruthenium (Ru) as the active component. Ru is loaded onto the surface of the carbon nanotubes by a substitution method, and the interface structure is optimized by low-temperature calcination to obtain a ruthenium-based alkaline bifunctional electrocatalyst. The prepared catalyst can achieve excellent HER and OER catalytic performance in alkaline electrolytes.

[0006] Preferably, the preparation method of the ruthenium-based basic bifunctional electrocatalyst includes the following steps:

[0007] 1) Mix the metallic nickel salt and dicyandiamine evenly, grind them, and place them in a tube furnace for pyrolysis under an inert atmosphere to obtain Ni@CNT;

[0008] 2) Ni@CNT was added to an aqueous solution of ruthenium salt for a displacement reaction, then filtered, washed and dried. Finally, the dried product was placed in a tube furnace and calcined in air to obtain a ruthenium-based basic bifunctional electrocatalyst.

[0009] Preferably, in step 1), the nickel salt is selected from nickel nitrate, nickel chloride, nickel sulfate, and nickel acetate.

[0010] Preferably, in step 1), the molar ratio of the nickel salt to dicyandiamine is 1:2-6 mmol.

[0011] Preferably, in step 1), the pyrolysis process is as follows: the dried product is placed in a tube furnace and heated to 500-550°C at a heating rate of 5°C / min under an argon atmosphere, held for 0.5-2 hours, then heated to 600-900°C at a heating rate of 3°C / min, held for 1-3 hours, and then cooled naturally.

[0012] Preferably, in step 2), the ruthenium salt is selected from ruthenium chloride and ruthenium acetate.

[0013] Preferably, in step 2), the mass ratio of Ni@CNT to ruthenium salt is 4:1-3.

[0014] Preferably, in step 2), the volume of the aqueous solution of the ruthenium salt is 10-100 mL.

[0015] Preferably, in step 2), the reaction conditions for the ruthenium salt and Ni@CNT are: stirring, shaking or standing at 30°C for 24-48 hours.

[0016] Preferably, in step 2), the dried product is placed in a tube furnace and heated to 200-250°C at a heating rate of 5°C / min under an air atmosphere, held at that temperature for 0.5-2 hours, and then allowed to cool naturally.

[0017] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0018] The synthesis process of this invention is simple. Carbon nanotubes coated with nickel nanoparticles serve as the carrier material, which on the one hand has efficient mass transfer and electron transport, and on the other hand has a strong carrier effect with the supported Ru, which helps to improve catalytic performance. In a 1.0M electrolyte, it can achieve HER and OER catalytic performance superior to commercial Pt / C and RuO2, respectively, and is worth promoting. Attached Figure Description

[0019] Figure 1 The images show the XRD characterization patterns of Ni@CNT and Ni@CNT / Ru prepared in Example 1.

[0020] Figure 2 The images show SEM images of Ni@CNT and Ni@CNT / Ru prepared in Example 1.

[0021] Figure 3 The graph shows the hydrogen evolution polarization curves of Ni@CNT / Ru prepared in Example 1 and commercial 20wt% Pt / C in 1.0M KOH.

[0022] Figure 4 The graph shows the oxygen evolution polarization curves of Ni@CNT / Ru prepared in Example 1 and commercial RuO2 in 1.0M KOH. Detailed Implementation

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments, but the implementation of the present invention is not limited thereto. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0024] Example 1

[0025] 1) Preparation of Ni@CNT: 1.1632g of nickel nitrate hexahydrate and 1.3453g of dicyandiamine were mixed evenly, ground, and the powder was transferred to a tube furnace. The temperature was increased to 550℃ at a heating rate of 5℃ / min and held for 1h. Then the temperature was increased to 650℃ at a heating rate of 3℃ / min and held for 2h. After natural cooling, Ni@CNT was obtained.

[0026] 2) Preparation of Ni@CNT / Ru: 100 mg Ni@CNT was ultrasonically dispersed in 50 mL of an aqueous solution containing 50 mg RuCl3, and then shaken at 30 °C for 48 h. After the reaction was completed, the mixture was filtered, washed with water, and dried in an oven at 60 °C. The dried product was then transferred to a tube furnace and calcined at 250 °C in air for 0.5 h to obtain Ni@CNT / Ru (i.e., ruthenium-based basic bifunctional electrocatalyst).

[0027] Morphology, structure, and performance characterization of catalysts:

[0028] The phase composition of the material was analyzed by X-ray diffraction (XRD). The XRD diffraction peaks of Ni and Ru in the standard PDF card were basically coincident, and the XRD of the material did not change significantly before and after the introduction of Ru (see Figure 1 The morphology of Ni@CNT and Ni@CNT / Ru was observed using scanning electron microscopy (see figure). Figure 2 As shown in the figure, the carbon nanotubes coated with Ni nanoparticles prepared in this embodiment have smooth tube walls and a diameter of 100-200 nm. After the introduction of Ru, the carbon tube walls become rough, which indicates that Ru nanoparticles were successfully loaded onto the tube walls.

[0029] The hydrogen evolution activity and oxygen evolution activity of the catalyst were determined using a three-electrode system in 1.0 M KOH. The results are shown in [Figure number missing]. Figure 3 and Figure 4 As shown. The catalyst prepared in this example operates at 10 mA / cm². -2 The hydrogen evolution overpotential at current density is 44 mV, which is superior to that of a commercial 20% platinum-carbon catalyst (46 mV); at 10 mA / cm -2 The oxygen evolution overpotential at current density is 252 mV, which is superior to that of commercial ruthenium dioxide catalysts (376 mV).

[0030] Example 2

[0031] 1) Preparation of Ni@CNT: 0.4754 g of nickel chloride hexahydrate and 1.0089 g of dicyandiamine were mixed evenly, ground, and the powder was transferred to a tube furnace. The temperature was increased to 500°C at a heating rate of 5°C / min and held for 2 h. Then the temperature was increased to 600°C at a heating rate of 3°C / min and held for 1 h. Ni@CNT was then obtained by natural cooling.

[0032] 2) Preparation of Ni@CNT / Ru: 100 mg Ni@CNT was ultrasonically dispersed in 10 mL of an aqueous solution containing 25 mg RuCl3, and then allowed to stand at 30 °C for 48 h. After the reaction was completed, the sample was filtered, washed with water, and dried in an oven at 60 °C. The dried sample was then transferred to a tube furnace and calcined at 200 °C in air for 1 h to obtain Ni@CNT / Ru (i.e., ruthenium-based basic bifunctional electrocatalyst).

[0033] Morphology, structure, and performance characterization of the catalyst: The morphology and phase of the catalyst prepared in this example are similar to those in Example 1. Electrochemical test results show that at 10 mA / cm², the catalyst exhibits good performance. -2 The hydrogen evolution overpotential at current density is 47 mV, comparable to that of a commercial 20% platinum-carbon catalyst; at 10 mA / cm², the overpotential is... -2 The oxygen evolution overpotential at current density is 279 mV, which is superior to that of commercial ruthenium dioxide catalysts.

[0034] Example 3

[0035] 1) Preparation of Ni@CNT: 1.0486g of nickel sulfate hexahydrate and 1.0089g of dicyandiamine were mixed evenly, ground, and the powder was transferred to a tube furnace. The temperature was increased to 500℃ at a heating rate of 5℃ / min and held for 0.5h. Then the temperature was increased to 900℃ at a heating rate of 3℃ / min and held for 3h. After natural cooling, Ni@CNT was obtained.

[0036] 2) Preparation of Ni@CNT / Ru: 100 mg Ni@CNT was ultrasonically dispersed in 100 mL of an aqueous solution containing 75 mg ruthenium acetate, and then stirred at 30 °C for 24 h. After the reaction was completed, the sample was filtered, washed with water, and dried in an oven at 60 °C. The dried sample was then transferred to a tube furnace and calcined at 200 °C in air for 2 h to obtain Ni@CNT / Ru (i.e., ruthenium-based basic bifunctional electrocatalyst).

[0037] Electrochemical test results show that at 10 mA / cm -2 The hydrogen evolution overpotential at current density is 50 mV, comparable to that of a commercial 20% platinum-carbon catalyst; at 10 mA / cm², the overpotential is... -2 The oxygen evolution overpotential at current density is 300 mV, which is superior to that of commercial ruthenium dioxide catalysts.

[0038] Example 4

[0039] Except for the low-temperature calcination temperature of 200℃, the preparation and testing methods in this embodiment are exactly the same as in Example 1. Electrochemical test results show that at 10 mA / cm²... -2 The hydrogen evolution overpotential at current density is 48 mV, comparable to that of a commercial 20% platinum-carbon catalyst; at 10 mA / cm², the overpotential is... -2The oxygen evolution overpotential at current density is 260 mV, which is superior to that of commercial ruthenium dioxide catalysts.

[0040] Example 5

[0041] Except for the use of nickel acetate as the nickel salt, the preparation and testing methods in this embodiment are exactly the same as in Example 2. Electrochemical test results show that at 10 mA / cm²... -2 The hydrogen evolution overpotential at current density is 49 mV, comparable to that of a commercial 20% platinum-carbon catalyst; at 10 mA / cm², the overpotential is... -2 The oxygen evolution overpotential at current density is 265 mV, which is superior to that of commercial ruthenium dioxide catalysts.

[0042] Comparative Example 1

[0043] Unlike Example 1, step 2) does not introduce Ru. Electrochemical test results show that Ni@CNT at 10 mA / cm -2 The hydrogen evolution overpotential at the current density is 395 mV, and the oxygen evolution overpotential is 466 mV.

[0044] Comparative Example 2

[0045] 20 mg of commercial carbon nanotubes were dispersed in 30 ml of an aqueous solution containing 20 mg of ruthenium chloride. After stirring at room temperature for 30 min, 10 ml of an aqueous solution containing 40 mg of NaBH4 was added. After the reaction was complete, the mixture was filtered, washed with water, and dried in a 60 °C oven. The dried sample was then transferred to a tube furnace and calcined at 250 °C for 0.5 h in air to obtain CNT / Ru. Electrochemical tests showed that CNT / Ru exhibited good performance at 10 mA / cm². -2 The hydrogen evolution overpotential at the current density is 75mV, and the oxygen evolution overpotential is 350mV.

[0046] Table 1 Comparison of alkaline electrochemical performance tests between the examples and the comparative examples.

[0047]

[0048]

[0049] Examples 1, 2, 3, 4, and 5 used different reaction conditions and metal salts, and all showed performance comparable to or even better than commercial catalysts. Comparing Example 1 with Comparative Examples 1 and 2, it can be seen that the introduction of Ru greatly improved the catalytic performance of the Ni@CNT support; however, the CNT / Ru obtained by simply reducing Ru onto the carbon nanotube support showed worse performance than Ni@CNT / Ru. This indicates that both the carbon nanotube-coated Ni nanoparticles and the Ru-supported material are indispensable for the realization of the basic bifunctional electrocatalyst in this invention.

[0050] The embodiments of the present invention are merely examples for clearly illustrating the invention and are not intended to limit the implementation of the invention. Those skilled in the art will recognize that other variations or modifications can be made based on the above embodiments, and it is neither necessary nor possible to exhaustively describe all possible implementations here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a ruthenium-based basic bifunctional electrocatalyst, characterized in that, This method uses nickel nanoparticles (Ni@CNT) coated with carbon nanotubes as a support and ruthenium (Ru) as the active component. Ru is loaded onto the surface of the carbon nanotubes via a substitution method, and the interfacial structure is optimized through low-temperature calcination to obtain a ruthenium-based alkaline bifunctional electrocatalyst. The prepared catalyst exhibits excellent HER and OER catalytic performance in alkaline electrolytes. The method includes the following steps: 1) Mix the nickel salt and dicyandiamine evenly, grind them, and place them in a tube furnace for pyrolysis under an inert atmosphere to obtain Ni@CNT; wherein the molar ratio of the nickel salt and dicyandiamine is 1:2-6 mmol. 2) Ni@CNT is added to an aqueous solution of ruthenium salt for a displacement reaction, followed by filtration, washing, and drying. Finally, the dried product is placed in a tube furnace and calcined in air to obtain a ruthenium-based basic bifunctional electrocatalyst. The mass ratio of Ni@CNT to ruthenium salt is 4:1-3.

2. The method for preparing a ruthenium-based basic bifunctional electrocatalyst according to claim 1, characterized in that: In step 1), the nickel salt is selected from one of nickel nitrate, nickel chloride, nickel sulfate, and nickel acetate.

3. The method for preparing a ruthenium-based basic bifunctional electrocatalyst according to claim 1, characterized in that: In step 1), the pyrolysis process is as follows: the dried product is placed in a tube furnace and heated to 500-550°C at a heating rate of 5°C / min under an argon atmosphere, held for 0.5-2 hours, then heated to 600-900°C at a heating rate of 3°C / min, held for 1-3 hours, and then cooled naturally.

4. The method for preparing a ruthenium-based basic bifunctional electrocatalyst according to claim 1, characterized in that: In step 2), the ruthenium salt is selected from ruthenium chloride and ruthenium acetate.

5. The method for preparing a ruthenium-based basic bifunctional electrocatalyst according to claim 1, characterized in that: In step 2), the volume of the aqueous solution of the ruthenium salt is 10-100 mL.

6. The method for preparing a ruthenium-based basic bifunctional electrocatalyst according to claim 1, characterized in that: In step 2), the reaction conditions for the ruthenium salt and Ni@CNT are: stirring, shaking or standing at 30°C for 24-48 hours.

7. The method for preparing a ruthenium-based basic bifunctional electrocatalyst according to claim 1, characterized in that: In step 2), the dried product is placed in a tube furnace and heated to 200-250°C at a heating rate of 5°C / min under an air atmosphere, held at that temperature for 0.5-2 hours, and then allowed to cool naturally.

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