Metal Ru catalyst, preparation method and application thereof

Abstract

The invention provides a metal Ru catalyst as well as a preparation method and application thereof, and particularly, the metal Ru catalyst is prepared by using a specific carbon source and a ruthenium source as precursors through a simple one-step method. The method is simple in process, low in cost and high in controllability, the obtained metal Ru catalyst has excellent seawater electrolysis activity and stability, the overpotential (mV) shown under 10 mA cm <-2 > under the real seawater condition is 39 mV which is far lower than the overpotential (53 mV) shown under 10 mA cm <-2 > of commercial Pt / C, and the metal Ru catalyst can be applied to the cathodic hydrogen evolution reaction of seawater electrolysis.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic seawater electrolysis technology, and in particular to a metallic Ru catalyst, its preparation method, and its application. Background Technology

[0002] With the rapid development of industrial technology and the drastic consumption of fossil fuels, environmental and energy problems have become increasingly serious. Therefore, the development of clean, efficient, and safe energy conversion processes has received increasing attention and importance from countries around the world. Hydrogen energy, as a clean energy carrier, can be produced through water electrolysis (green hydrogen), a sustainable pathway. However, traditional electrolysis relies on freshwater, and global freshwater resources are limited. Seawater accounts for 96.5% of the Earth's water resources, making seawater electrolysis even more strategically significant.

[0003] The efficiency and power density of seawater electrolysis largely depend on the selection of electrolyte and catalyst materials, with the catalyst playing a crucial role; in a sense, catalyst selection limits the development of seawater electrolysis. Platinum-based materials are considered the best catalysts in electrocatalysis due to their excellent catalytic performance and are widely used, including being the earliest catalysts applied to water electrolysis. However, their high cost and scarcity restrict their large-scale commercial application. Therefore, developing high-performance, low-cost non-platinum-based catalysts to replace platinum-based materials in the electrocatalytic electrolysis of seawater is of paramount importance.

[0004] Ruthenium (Ru) and platinum (Pt) share similar physicochemical properties. Ruthenium is more abundant and relatively cheaper than platinum. Replacing platinum-based materials with ruthenium-based materials would be beneficial for advancing the electrocatalytic electrolysis of seawater. However, ruthenium atom catalysts exhibit unsatisfactory catalytic performance in the hydrogen evolution reaction (HER) of seawater electrolysis due to their unsuitable electronic structure. Numerous studies have shown that metal-supported carbon nanotubes are an effective measure to improve catalyst activity. Li et al. synthesized Ru / CNT nanoparticles through rapid Joule heating treatment at 10 mA cm⁻¹ under 1M KOH conditions. -2 The overpotential (mV) is only 9 mV, and it exhibits excellent long-term stability. Furthermore, Mahood et al. synthesized Ru@C2N nanoparticles via a condensation reaction between hexane-co-cyclohexane (HKH) and hexaaminobenzene (HAB) trihydrochloride, which showed excellent long-term stability at 10 mA cm⁻¹ under 1M KOH conditions. -2 The overpotential (mV) was only 17 mV, and no significant catalytic activity decay occurred after 10,000 cycles. Summary of the Invention

[0005] The purpose of this invention is to provide a solution to the technical problem of high price of currently available commercial Pt / C catalysts.

[0006] To achieve the above objectives, the present invention provides a metal Ru catalyst, a preparation method thereof, and its application.

[0007] 1. A metal Ru catalyst, which is obtained by supporting ruthenium in carboxylated carbon nanotubes.

[0008] 2. The specific steps of the aforementioned method for preparing a metal Ru catalyst are as follows: (1) Mix RuCl3 with carboxylated carbon nanotubes and stir for 10-15 hours; (2) Add NaBH4 solution to carry out the reduction reaction, filter the solid, grind it, and you will get the product.

[0009] Preferably, the mass ratio of NaBH4, RuCl3, and carboxylated carbon nanotubes in the NaBH4 solution is 8.0–8.2:0.9–1.1:1.25–2.5, more preferably 8.12:1:1.25–2.5, and the mass concentration of the NaBH4 solution is 10%.

[0010] Preferably, in step (1), the carboxylated carbon nanotubes are prepared by the following method: carbon nanotubes, concentrated nitric acid with a mass concentration of 60% to 70% and deionized water are stirred and mixed, heated under reflux reaction, naturally cooled to room temperature, filtered to obtain solid, and dried under vacuum at 60°C to obtain the final product.

[0011] More preferably, the mass ratio of carbon nanotubes to concentrated nitric acid is 0.05–0.15:1, and the volume ratio of concentrated nitric acid to deionized water is 1.5–2.0:1.

[0012] A further preferred method is to reflux the reaction at 60–70°C for 5–6 hours.

[0013] More preferably, the heating and reflux reaction conditions are: reflux reaction at 70°C for 6 hours.

[0014] Preferably, in step (1), carboxylated carbon nanotubes are ultrasonically dispersed in anhydrous ethanol, and then RuCl3 is added and mixed and stirred; wherein the mass ratio of carboxylated carbon nanotubes to anhydrous ethanol is 1:412.

[0015] Further preferred mixing conditions are: stirring at 550 r / min for 12 hours.

[0016] Preferably, in step (2), the reduction reaction conditions are: stirring at 550 r / min for 3 to 4 hours.

[0017] Preferably, in step (2), after grinding, annealing is performed. The annealing conditions are: annealing at 600-900℃ for 1-2 hours under an argon atmosphere.

[0018] Further preferably, the temperature is increased to the annealing temperature at a rate of 5°C / min.

[0019] 3. The application of the aforementioned metal Ru catalyst in the electrolysis of seawater for hydrogen evolution.

[0020] The present invention has the following beneficial effects: This invention provides a metallic Ru catalyst, its preparation method, and its application. Specifically, it is prepared by a simple one-step method using specific carbon and ruthenium sources as precursors.

[0021] The method of this invention is simple, low-cost, and highly controllable. The resulting Ru metal catalyst exhibits excellent activity and stability in seawater electrolysis, demonstrating a 10 mA cm⁻¹ performance under real seawater conditions. -2 The overpotential (mV) is 39 mV, which is far lower than the 10 mA cm⁻¹ of commercial Pt / C. -2 The overpotential is 53 mV, which can be applied to the cathode hydrogen evolution reaction of seawater electrolysis.

[0022] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the figures. Attached Figure Description

[0023] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 Transmission electron microscopy (TEM) images of the materials prepared in Examples 1-6 are shown below. Specifically, a is a TEM image of Ru-CNT-R nanocrystals with a scale bar of 10 nm; b is a TEM image of Ru-CNT-P nanocrystals (900 ℃ / 2h) with a scale bar of 10 nm; c is a TEM image of Ru-CNT-P nanocrystals (600 ℃ / 1h) with a scale bar of 100 nm; d is a TEM image of Ru-CNT-P nanocrystals (950 ℃ / 3h) with a scale bar of 200 nm; e is a TEM image of Ru-CNT-P nanocrystals (700 ℃ / 2h) with a scale bar of 20 nm; and f is a TEM image of Ru-CNT-P nanocrystals (800 ℃ / 2h) with a scale bar of 50 nm.

[0024] Figure 2X-ray diffraction patterns of Ru-CNT-R, Ru-CNT-P (900 ℃ / 2h), Ru-CNT-P (600 ℃ / 1h), Ru-CNT-P (950 ℃ / 3h), Ru-CNT-P (700 ℃ / 2h), and Ru-CNT-P (800 ℃ / 2h) prepared in Examples 1-6.

[0025] Figure 3 The particle size distributions of Ru-CNT-R (a), Ru-CNT-P (900 ℃ / 2h) (b), Ru-CNT-P (600 ℃ / 1h) (c), Ru-CNT-P (950 ℃ / 3h) (d), Ru-CNT-P (700 ℃ / 2h) (e), and Ru-CNT-P (800 ℃ / 2h) (f) prepared in Examples 1-6 are shown.

[0026] Figure 4 LSV polarization curves of Ru-CNT-R, Ru-CNT-P (900 ℃ / 2h), Ru-CNT-P (600 ℃ / 1h), Ru-CNT-P (950 ℃ / 3h), Ru-CNT-P (700 ℃ / 2h), Ru-CNT-P (800 ℃ / 2h) and commercial Pt / C prepared in Examples 1-6 are shown.

[0027] Figure 5 Tafel slope polarization curves of RuCNT-R, Ru-CNT-P (900 ℃ / 2h), Ru-CNT-P (600 ℃ / 1h), Ru-CNT-P (950 ℃ / 3h), Ru-CNT-P (700 ℃ / 2h), and Ru-CNT-P (800 ℃ / 2h) prepared in Examples 1-6.

[0028] Figure 6 The images show transmission images of Ru-CR nanocrystals prepared using monolayer graphene as a carbon source. In the images, a is a transmission image of Ru-CR nanocrystals with a scale bar of 100 nm, and b is a transmission image of Ru-CR nanocrystals with a scale bar of 50 nm.

[0029] Figure 7 The LSV curves of the HER performance of the material obtained by replacing the carbon source with carbon nanotubes.

[0030] Figure 8 The image shows the material obtained by replacing the carbon source with a single layer of graphene. a is a scale bar of 100 nm and b is a scale bar of 50 nm.

[0031] Figure 9 The HER performance LSV curve of the material obtained by replacing the carbon source with monolayer graphene. Detailed Implementation

[0032] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered by the claims.

[0033] Example 1 A method for preparing ultrasmall Ru-CNT-R nanomaterials, the specific steps of which are as follows: 10 mg of carboxylated carbon nanotubes (0.833 mmol carbon) and 6.16 mg of RuCl3 powder (0.021 mmol ruthenium) were used as precursors. The carboxylated carbon nanotubes were first added to a glass reagent bottle containing an appropriate amount of anhydrous ethanol and sonicated to form a homogeneous solution. Then, the prepared RuCl3 solution was added and stirred for 12 h. 500 μL of NaBH4 solution was added to the stirred solution for reduction for 3 h. After filtration and vacuum drying, the solution was ground into powder to obtain the final nanomaterial, named Ru-CNT-R.

[0034] Example 2 A method for preparing particulate Ru-CNT-P (900℃) nanomaterials, the specific steps of which are as follows: 10 mg of carboxylated carbon nanotubes (0.833 mmol carbon) and 6.16 mg of RuCl3 powder (0.021 mmol ruthenium) were used as precursors. The carboxylated carbon nanotubes were first added to a glass reagent bottle containing an appropriate amount of anhydrous ethanol and sonicated to form a homogeneous solution. Then, the prepared RuCl3 solution was added and stirred for 12 h. 500 μL of NaBH4 solution was added to the stirred solution for reduction for 3 h. After filtration and vacuum drying, the solution was ground into powder. The powder was then placed in a tube furnace, and Ar was introduced to replace the air. The temperature was increased to 900 °C at a rate of 5 °C / min and held for 2 h for annealing to obtain the final nanomaterial, named Ru-CNT-P (900 °C / 2 h).

[0035] Example 3 A method for preparing particulate Ru-CNT-P (600℃) nanomaterials, the specific steps of which are as follows: 10 mg of carboxylated carbon nanotubes (0.833 mmol carbon) and 6.16 mg of RuCl3 powder (0.021 mmol ruthenium) were used as precursors. The carboxylated carbon nanotubes were first added to a glass reagent bottle containing an appropriate amount of anhydrous ethanol and sonicated to form a homogeneous solution. Then, the prepared RuCl3 solution was added and stirred for 12 h. 500 μL of NaBH4 solution was added to the stirred solution for reduction for 3 h. After filtration and vacuum drying, the solution was ground into powder. The powder was then placed in a tube furnace, and after replacing the air with Ar, the temperature was increased to 600 °C at a rate of 5 °C / min and held for 1 h for annealing to obtain the final nanomaterial, named Ru-CNT-P (600 °C / 1 h).

[0036] Example 4 A method for preparing particulate Ru-CNT-P (900℃) nanomaterials, the specific steps of which are as follows: 10 mg of carboxylated carbon nanotubes (0.833 mmol carbon) and 6.16 mg of RuCl3 powder (0.021 mmol ruthenium) were used as precursors. The carboxylated carbon nanotubes were first added to a glass reagent bottle containing an appropriate amount of anhydrous ethanol and sonicated to form a homogeneous solution. Then, the prepared RuCl3 solution was added and stirred for 12 h. 500 μL of NaBH4 solution was added to the stirred solution for reduction for 3 h. After filtration and vacuum drying, the solution was ground into powder. The powder was then placed in a tube furnace, and Ar was introduced to replace the air. The temperature was increased to 950 °C at a rate of 5 °C / min and held for 3 h for annealing to obtain the final nanomaterial, named Ru-CNT-P (950 °C / 3 h).

[0037] Example 5 A method for preparing particulate Ru-CNT-P (700℃) nanomaterials, the specific steps of which are as follows: 10 mg of carboxylated carbon nanotubes (0.833 mmol carbon) and 6.16 mg of RuCl3 powder (0.021 mmol ruthenium) were used as precursors. The carboxylated carbon nanotubes were first added to a glass reagent bottle containing an appropriate amount of anhydrous ethanol and sonicated to form a homogeneous solution. Then, the prepared RuCl3 solution was added and stirred for 12 h. 500 μL of NaBH4 solution was added to the stirred solution for reduction for 3 h. After filtration and vacuum drying, the solution was ground into powder. The powder was then placed in a tube furnace, and after replacing the air with Ar, the temperature was increased to 700 °C at a rate of 5 °C / min and held for 2 h for annealing to obtain the final nanomaterial, named Ru-CNT-P (700 °C / 2 h).

[0038] Example 6 A method for preparing particulate Ru-CNT-P (800℃) nanomaterials, the specific steps of which are as follows: 10 mg of carboxylated carbon nanotubes (0.833 mmol carbon) and 6.16 mg of RuCl3 powder (0.021 mmol ruthenium) were used as precursors. The carboxylated carbon nanotubes were first added to a glass reagent bottle containing an appropriate amount of anhydrous ethanol and sonicated to form a homogeneous solution. Then, the prepared RuCl3 solution was added and stirred for 12 h. 500 μL of NaBH4 solution was added to the stirred solution for reduction for 3 h. After filtration and vacuum drying, the solution was ground into powder. The powder was then placed in a tube furnace, and Ar was introduced to replace the air. The temperature was increased to 800 °C at a rate of 5 °C / min and held for 2 h for annealing to obtain the final nanomaterial, named Ru-CNT-P (800 °C / 2 h).

[0039] Figure 1 Figures a, b, c, d, e, and f in the figures are transmission electron microscopy (TEM) images of the microstructures of RuCNT-R, Ru-CNT-P (900℃ / 2h), Ru-CNT-P (600℃ / 1h), Ru-CNT-P (950℃ / 3h), Ru-CNT-P (700℃ / 2h), and Ru-CNT-P (800℃ / 2h) prepared in Examples 1-6, respectively. From these TEM images, it can be seen that by adjusting the annealing temperature and time, Ru-CNT nanoparticles with significantly different metal particle shapes were obtained. The results show that when no annealing treatment was performed, its shape was as follows: Figure 1 As shown in Figure a, extremely small Ru nanoparticles are formed and loaded onto carbon nanotubes. When the annealing temperature is 900 °C, their shape is as follows... Figure 1 As shown in Figure b, smaller nanostructures are formed. When the annealing temperature is 600 °C, its shape is as follows. Figure 1 As shown in Figure c, irregular nanoparticles are formed. When the annealing temperature is 950 °C, their shape is as follows: Figure 1 As shown in d, larger nanoparticles are formed. When the annealing temperature is 700 ℃, their shape is as follows... Figure 1 As shown in Figure e, slightly larger nanoparticles are formed and uniformly distributed. When the annealing temperature is 800 ℃, their shape is as follows: Figure 1 As shown in f, larger Ru nanoparticles are formed, with significant size differences and poor distribution regularity.

[0040] Figure 2The X-ray diffraction patterns of Ru-CNT-R, Ru-CNT-P (900 ℃ / 2h), Ru-CNT-P (600 ℃ / 1h), Ru-CNT-P (950 ℃ / 3h), Ru-CNT-P (700 ℃ / 2h), and Ru-CNT-P (800 ℃ / 2h) are shown. Their phase information can be obtained from their diffraction peaks. From the main diffraction peaks, it can be seen that the diffraction peaks show the positions of elemental C and Ru. However, Ru-CNT-R does not show the peak position of elemental Ru. This indicates that the Ru elemental nanoparticles of Ru-CNT-R are too small, and the X-ray diffraction pattern cannot show its peak position. The other five materials all show the phase of elemental Ru well.

[0041] Figure 3 The figure shows the particle size distribution of Ru metal in Ru-CNT-R, Ru-CNT-P (900 ℃ / 2h), Ru-CNT-P (600 ℃ / 1h), Ru-CNT-P (950 ℃ / 3h), Ru-CNT-P (700 ℃ / 2h), and Ru-CNT-P (800 ℃ / 2h). The figure shows that Ru nanoparticles in Ru-CNT-R have the smallest particle size, with an average particle size of only 0.97 nm. This is followed by Ru-CNT-P (900 ℃ / 2h), with an average particle size of approximately 2.89 nm. The average particle size gradually increases from Ru-CNT-P (600 ℃ / 1h) to Ru-CNT-P (950 ℃ / 3h), reaching 5.72 nm, 10.59 nm, 20.46 nm, and 56.13 nm, respectively.

[0042] Figure 4The polarization curves of Ru-CNT-R, Ru-CNT-P (900 ℃ / 2h), Ru-CNT-P (600 ℃ / 1h), Ru-CNT-P (700 ℃ / 2h), Ru-CNT-P (800 ℃ / 2h), Ru-CNT-P (950 ℃ / 3h), and commercial Pt / C were tested in real seawater. Compared with commercial Pt / C with a mass fraction of 40%, it can be found that Ru-CNT-R (10 mA cm-2 / 39 mV) has a smaller overpotential than commercial Pt / C (10 mA cm-2 / 53 mV). (The overpotential at 10 mA cm-2 can be used to qualitatively analyze the electrocatalytic hydrogen evolution activity of the material; the smaller the overpotential, the better the catalytic activity of the material). The specific results are shown in Table 1. In particular, the overpotential of Ru-CNT-R at 10 mA cm⁻² is 39 mV, which is much lower than that of commercial Pt / C, indicating that these catalysts have higher activity than commercial Pt / C. This may be because their unique structure and composition generate electronic effects, coordination effects, and stress effects, which can regulate the adsorption energy between intermediate products and catalysts, thereby greatly improving their electrocatalytic hydrogen evolution activity.

[0043] Figure 5 The Tafel slopes of the Ru-CNT-R, Ru-CNT-P (900 ℃ / 2h), Ru-CNT-P (600 ℃ / 1h), Ru-CNT-P (700 ℃ / 2h), Ru-CNT-P (800 ℃ / 2h), and Ru-CNT-P (950 ℃ / 3h) alloy nanomaterials prepared in Example 1 and the commercial Pt / C electrode were calculated. It was found that the Ru-CNT-R alloy nanomaterial prepared in Example 1 exhibited the smallest Tafel slope (the Tafel slope can qualitatively analyze the electrocatalytic hydrogen evolution activity of the material; the smaller the slope, the better the catalytic activity of the material).

[0044] Table 1. 10 mA cm⁻¹ of nanomaterials obtained in Examples 1-6 and commercial Pt / C -2 Overpotential (mV) results Comparative Example 1: Effect of different carbon sources on nanomaterials (carbon nanotubes without carboxylation treatment) Referring to Example 1, the carbon source was replaced with uncarboxylated carbon nanotubes, and the corresponding material was prepared in the same manner as in Example 1.

[0045] The results showed that: Figure 6 As shown, the number of Ru nanoparticles loaded on carbon nanotubes is relatively small, and the HER performance in seawater was found to be significantly different from that of carboxylated carbon nanotube materials. LSV, for example... Figure 7As shown, this indicates that carboxylated carbon nanotubes play a crucial role as a carbon source in this system.

[0046] Comparative Example 2: The effect of different carbon sources on nanomaterials (monolayer graphene) Referring to Example 1, the carbon source was replaced with monolayer graphene (Maclean), and the corresponding material was prepared in the same manner as in Example 1.

[0047] The results showed that: Figure 8 As shown, some sheet-like nanoparticles were obtained. When testing the HER performance in seawater, it was found to be worse than that of commercial Pt / C, and LSV was as follows. Figure 9 As shown, carbon nanotubes play a crucial role as a carbon source in this system.

[0048] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A metal Ru catalyst, characterized in that, It is obtained by loading ruthenium onto carboxylated carbon nanotubes.

2. The method for preparing a metal Ru catalyst according to claim 1, characterized in that, The specific steps are as follows: (1) Mix RuCl3 with carboxylated carbon nanotubes and stir for 10-15 hours; (2) Add NaBH4 solution to carry out the reduction reaction, filter the solid, grind it, and you will get the product.

3. The preparation method according to claim 2, characterized in that, The NaBH4 solution contains NaBH4, RuCl3, and carboxylated carbon nanotubes in a mass ratio of 8.0–8.2:0.9–1.1:1.25–2.5, and the NaBH4 solution has a mass concentration of 10%.

4. The preparation method according to claim 2, characterized in that, In step (1), the carboxylated carbon nanotubes are prepared by the following method: carbon nanotubes, concentrated nitric acid and deionized water are stirred and mixed, heated and refluxed, cooled naturally to room temperature, filtered to obtain solid, and vacuum dried to obtain the final product.

5. The preparation method according to claim 4, characterized in that, The mass ratio of carbon nanotubes to concentrated nitric acid is 0.05–0.15:1, and the volume ratio of concentrated nitric acid to deionized water is 1.5–2.0:

1.

6. The preparation method according to claim 4, characterized in that, The heating and reflux reaction conditions are: reflux reaction at 60-70℃ for 5-6 hours.

7. The preparation method according to claim 2, characterized in that, In step (1), carboxylated carbon nanotubes are ultrasonically dispersed in anhydrous ethanol, and RuCl3 is added and mixed and stirred; wherein the mass ratio of carboxylated carbon nanotubes to anhydrous ethanol is 1:

412.

8. The preparation method according to claim 2, characterized in that, In step (2), the reduction reaction conditions are: stirring at 550 rpm for 3 to 4 hours.

9. The application of the metal Ru catalyst according to claim 1 in the electrolysis of seawater for hydrogen evolution.

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