Seawater electrolysis hydrogen production catalyst based on metal ruthenium doped copper nanowire composite structure and synthesis method thereof

Abstract

The invention relates to a catalyst for hydrogen production through seawater electrolysis based on a metal ruthenium-doped copper nanowire composite structure and a synthesis method thereof, and belongs to the technical field of catalysis, the catalyst is composed of a copper nanowire skeleton derived from foamy copper and metal ruthenium clusters uniformly distributed on the surface of the copper nanowire skeleton; the method comprises the following steps: placing foamy copper in a solution containing sodium hydroxide and an oxidizing agent to generate a copper hydroxide nanowire; metal ruthenium is introduced by dipping in a solution containing ruthenium salt; and carrying out inert atmosphere heat treatment and electrochemical reduction to obtain the ruthenium-cluster-loaded copper nanowire composite catalyst. The fine regulation and control of the structure and components of the catalyst are realized by adjusting the concentration of the reaction solution, the dipping time and the treatment conditions. The electrocatalyst shows excellent hydrogen evolution activity and long-term stability under the acidic seawater electrolysis condition, the problems that a nickel-based current collector is prone to corrosion in an acidic medium and a traditional platinum-based catalyst is prone to inactivation in natural seawater are effectively solved, and a new technical scheme is provided for efficient and stable seawater electrolysis hydrogen production.

Description

Technical Field

[0001] This invention belongs to the fields of nanomaterials, electrochemical energy and catalysis technology, and relates to an electrolytic seawater hydrogen production catalyst based on a ruthenium-doped copper nanowire composite structure and its synthesis method. Background Technology

[0002] Hydrogen energy, due to its cleanliness, efficiency, safety, and sustainability, is considered one of the most promising new energy sources of the 21st century. Currently, industrial hydrogen production mainly includes water electrolysis, coal gasification, and natural gas steam reforming. Among these, water electrolysis offers advantages such as a clean process and high hydrogen purity, making it a crucial technological route for achieving green hydrogen production. However, the catalysts currently used in industrial water electrolysis are primarily precious metals such as platinum and iridium, which are costly and scarce, severely hindering the large-scale application of this technology. Therefore, developing low-cost, highly active, and highly stable catalysts for water electrolysis is of great significance.

[0003] Compared to the increasingly scarce freshwater resources, seawater accounts for over 97% of the Earth's total water resources, making its direct use for hydrogen electrolysis an inevitable trend in future hydrogen production technology development. However, the complex ionic composition and near-neutral electrolysis environment of seawater place higher demands on the activity and durability of the hydrogen evolution electrode. Existing precious metal hydrogen evolution catalysts are prone to deactivation or corrosion in seawater environments, exhibiting insufficient stability. Therefore, there is an urgent need to develop high-performance hydrogen evolution catalysts suitable for seawater conditions.

[0004] Nanostructured materials exhibit superior performance in electrocatalysis due to their high specific surface area, abundant active sites, and tunable electronic structure. In particular, one-dimensional metal nanowire structures possess continuous electron transport paths and good structural stability, which are beneficial for improving the kinetics of electrocatalytic reactions. Copper is abundant and has excellent electrical conductivity, but its hydrogen evolution activity is relatively low. By introducing small amounts of noble metal elements for doping or surface modification, its electronic structure can be effectively controlled, and its catalytic performance can be significantly improved.

[0005] Ruthenium, a relatively inexpensive precious metal, exhibits excellent hydrogen evolution catalytic activity. Introducing ruthenium atoms into copper nanowire structures promises to achieve a balance between high activity and high stability while maintaining low cost. However, achieving uniform ruthenium doping in copper nanowires and maintaining structural and performance stability under seawater electrolysis conditions remains a critical technical challenge that urgently needs to be addressed. Summary of the Invention

[0006] To address the problems of insufficient activity, poor stability, and high cost of existing seawater electrolysis catalysts for hydrogen production, this invention provides a seawater electrolysis catalyst based on a ruthenium-doped copper nanowire composite structure and its synthesis method. The catalyst prepared by this invention consists of a one-dimensional nanostructure network composed of copper nanowires uniformly doped with ruthenium atoms. The nanowires have a diameter of tens of nanometers and a length of several micrometers, possessing continuous electron transport channels and abundant surface active sites. The introduction of ruthenium effectively modulates the electronic structure of the copper nanowires, significantly reducing the energy barrier of the hydrogen evolution reaction, while simultaneously improving the catalyst's corrosion resistance and long-term operational stability in seawater environments. The synthesis method proposed in this invention is simple, operates under mild conditions, and is highly controllable, making it suitable for large-scale preparation. The obtained catalyst exhibits excellent hydrogen evolution catalytic activity and long-term stability in near-neutral natural seawater, achieving stable hydrogen production at low overpotentials.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A seawater electrolysis hydrogen production catalyst based on a ruthenium-doped copper nanowire composite structure, comprising a foamed copper current collector and an in-situ grown copper nanowire array on its surface, wherein ruthenium or ruthenium-based nanoclusters are uniformly loaded on the surface of the copper nanowires; wherein: The copper nanowires are constructed in situ from copper foam through chemical oxidation, thermal conversion and electrochemical reduction processes. The copper nanowires have a diameter of 40–100 nm and a length greater than 500 nm. The ruthenium is distributed on the surface or near the surface of the copper nanowires in the form of metallic ruthenium or clusters; the size of the clusters is 2–5 nm. The ruthenium mass loading is 0.05–0.8 mg cm⁻¹. -2 ; The catalyst for producing hydrogen through seawater electrolysis has an integral self-supporting electrode structure and requires no binder.

[0008] A method for synthesizing a catalyst for hydrogen production by seawater electrolysis based on a ruthenium-doped copper nanowire composite structure includes the following steps: The first step is to ultrasonically clean the foamed copper in sequence with ethanol, dilute hydrochloric acid solution and deionized water to remove surface organic contaminants and oxide layer; The second step involves immersing the foamed copper treated in the first step into an alkaline oxidation solution containing ammonium persulfate and sodium hydroxide, and reacting at room temperature for 0.5–2 h to generate an in-situ copper hydroxide nanowire array on the surface of the foamed copper, which serves as a self-supporting electrode for the copper hydroxide nanowires. Furthermore, in the alkaline oxidizing solution, the concentration of ammonium persulfate is 0.05–0.2 M; Furthermore, the concentration of sodium hydroxide in the alkaline oxidizing solution is 0.5–2 M; Furthermore, in the alkaline oxidizing solution, the molar ratio of ammonium persulfate to sodium hydroxide is 1:10.

[0009] The third step involves immersing the copper hydroxide nanowire self-supporting electrode obtained in the second step into an aqueous solution containing ruthenium salt for ion exchange reaction. The reaction is allowed to proceed under ambient temperature and pressure for 2–24 h to uniformly introduce ruthenium species onto the surface of the copper-based nanostructure, thereby obtaining a ruthenium-doped copper hydroxide nanowire electrode. Furthermore, in the aqueous solution containing ruthenium salt, the concentration of ruthenium salt is 5–60 mM; Furthermore, the ruthenium salt is ruthenium chloride.

[0010] The fourth step involves subjecting the ruthenium-doped copper hydroxide nanowire electrode obtained in the third step to low-temperature heat treatment under inert gas protection, transforming it into an oxide nanowire structure to obtain a ruthenium-doped copper oxide nanowire electrode. The low-temperature heat treatment is carried out under an argon atmosphere at a temperature of 150–400 °C for 1–5 h.

[0011] The fifth step involves immersing the copper oxide nanowire electrode obtained in the fourth step in a potassium bicarbonate electrolyte and converting the oxide nanowire into metallic copper nanowire through constant current electrochemical reduction. At the same time, ruthenium clusters are formed and stably loaded on its surface, ultimately obtaining a ruthenium-doped copper nanowire composite electrode. Furthermore, the concentration of the potassium bicarbonate electrolyte is 0.25–1 M; Furthermore, the current density of the constant current treatment is 300–800 mA cm⁻¹. -2 The constant current treatment time is 3–24 h.

[0012] Compared with the prior art, the present invention has the following beneficial effects: 1) This invention constructs a self-supporting electrode structure by in-situ grown copper nanowire array, which significantly reduces interface resistance and improves the stability of high current density operation. 2) In this invention, ruthenium is loaded onto the surface of copper nanowires in the form of highly dispersed nanoclusters, thereby achieving efficient utilization of the noble metal and regulation of its electronic structure. 3) The catalyst obtained by this invention exhibits excellent hydrogen evolution activity and long-term stability in acidic and natural seawater environments, and is suitable for continuous operation at high current. 4) This invention can achieve precise control over the microstructure and chemical composition of the seawater electrolysis hydrogen production catalyst based on the ruthenium-doped copper nanowire composite structure. The process is simple, green and environmentally friendly, and easy to scale up. It can be applied not only to seawater electrolysis hydrogen production technology, but also has broad application prospects in other catalytic hydrogen evolution fields such as chlor-alkali industry and solar water electrolysis. Attached Figure Description

[0013] Figure 1 This is a scanning electron microscope image of the ruthenium-doped copper nanowire composite nanocatalyst prepared in Example 1 of this invention; Figure 2 This is a transmission electron microscope image of the ruthenium-doped copper nanowire composite nanocatalyst prepared in Example 1 of this invention; Figure 3 This is a scanning transmission electron microscope image in bright field mode of the ruthenium-doped copper nanowire composite nanocatalyst prepared in Example 1 of this invention. Figure 4 This is a high-magnification transmission electron microscope image of the ruthenium-doped copper nanowire composite nanocatalyst prepared in Example 1 of this invention, wherein the circled areas represent Ru nanoclusters. Figure 5 This is a high-magnification transmission electron microscope image of the ruthenium-doped copper nanowire composite nanocatalyst prepared in Example 1 of this invention. The lattice fringe spacing of the copper nanowire support conforms to the Cu(111) crystal plane. Figure 6 This invention relates to Example 1, which characterizes the catalytic activity of a ruthenium-doped copper nanowire composite nanocatalyst for hydrogen production via seawater electrolysis and compares its activity with that of a commercial Ru / C catalyst. Test method: A three-electrode system was used, with natural seawater and 0.5 M sulfuric acid as the electrolyte. The working electrode was the self-supported ruthenium-doped copper nanowire composite nanocatalyst, the Hg / Hg₂SO₄ electrode was the reference electrode, and the ruthenium-iridium-titanium sheet electrode was the counter electrode. The scan rate was 5 mV / s. -1 The electrochemical workstation used was a CHI760E. As shown in the figure, the catalyst obtained in this invention operates at a current density of 500 mA cm⁻¹. -1 Its overpotential is 207 mV, which is lower than the overpotential of commercial Ru / C catalysts at the same current density (242 mV, vs. RHE). Therefore, the catalyst obtained in this invention exhibits superior catalytic activity for hydrogen production from water electrolysis in seawater compared to commercial noble metal Ru / C catalysts. Figure 7 This invention relates to the stability characterization of the ruthenium-doped copper nanowire composite nanocatalyst prepared in Example 1 of the present invention for hydrogen production by seawater electrolysis. Test method: A three-electrode system was used, with natural seawater and 0.5 M sulfuric acid as the electrolyte. The working electrode was the self-supported ruthenium-doped copper nanowire composite nanocatalyst, the Hg / Hg₂SO₄ electrode was the reference electrode, and the ruthenium-iridium-titanium sheet electrode was the counter electrode. The scan rate was 5 mV / s. -1 The electrochemical workstation used was a CHI760E. As shown in the figure, the catalyst obtained in this invention operates at a current density of 500 mA cm⁻¹. -2 After 400 h, the overpotential remained essentially unchanged, indicating that the catalyst obtained in this invention exhibits excellent stability in hydrogen production via water electrolysis in seawater. Detailed Implementation

[0014] In view of the many shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The following will further explain and illustrate this technical solution, its implementation process, and its principles. However, it should be understood that within the scope of this invention, the above-mentioned technical features of this invention and the technical features specifically described below (exemplary embodiments) can be combined with each other to constitute new or preferred technical solutions.

[0015] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0016] Example 1 Preparation method of ruthenium-doped copper nanowire composite nanocatalyst 1) The dimensions are 2 × 4 cm 2 The foamed copper was ultrasonically cleaned for 10 minutes each in ethanol, 0.1 M hydrochloric acid aqueous solution and deionized water to remove surface oil and natural oxide layer.

[0017] 2) Subsequently, the treated copper foam was immersed in a mixed solution containing 0.1 M ammonium persulfate and 1.0 M sodium hydroxide, and allowed to stand at room temperature for 1 h to grow a uniform and dense array of copper hydroxide nanowires in situ on the surface of the copper foam. After the reaction was completed, the sample was removed and thoroughly rinsed with deionized water until neutral to obtain a copper hydroxide nanowire / copper foam electrode.

[0018] 3) The above-mentioned copper hydroxide nanowire / copper foam electrode was immersed in a solution containing 10 mM ruthenium chloride and allowed to stand for 12 h at room temperature and pressure for ion exchange. After the reaction was completed, the sample was taken out and rinsed thoroughly with deionized water to remove unbound ruthenium salts, thus obtaining the ruthenium-doped copper hydroxide nanowire / copper foam electrode.

[0019] 4) The above-mentioned ruthenium-doped copper hydroxide nanowires / foamed copper electrode was placed in an argon protective atmosphere and heated at 200 °C for 2 h to cause the copper hydroxide nanowires to undergo dehydration transformation, forming a ruthenium-doped copper oxide nanowire structure, while maintaining the nanowire array morphology without significant collapse, thus obtaining the ruthenium-doped copper oxide / foamed copper electrode.

[0020] 5) Using the above-mentioned ruthenium-doped copper oxide / foamed copper electrode as the working electrode, electrochemical reduction was performed in a 0.5 M potassium bicarbonate aqueous solution under constant current mode, with an applied current density of 500 mA cm⁻¹. -2 The processing time was 10 hours. During the electrochemical reduction process, copper oxide nanowires were reduced to metallic copper nanowires, while ruthenium species were transformed into highly dispersed ruthenium nanoclusters and stably loaded onto the surface of copper nanowires, ultimately obtaining a ruthenium-doped copper nanowire / foam copper electrode.

[0021] Example 2 Preparation method of ruthenium-doped copper nanowire composite nanocatalyst 1) The dimensions are 2 × 4 cm 2 The foamed copper was ultrasonically cleaned for 10 minutes each in ethanol, 0.1 M hydrochloric acid aqueous solution and deionized water to remove surface oil and natural oxide layer.

[0022] 2) Subsequently, the treated copper foam was immersed in a mixed solution containing 0.05 M ammonium persulfate and 0.5 M sodium hydroxide, and allowed to stand at room temperature for 2 h to grow a uniform and dense copper hydroxide nanowire array in situ on the surface of the copper foam. After the reaction was completed, the sample was removed and thoroughly rinsed with deionized water until neutral to obtain a copper hydroxide nanowire / copper foam electrode.

[0023] 3) The above-mentioned copper hydroxide nanowire / copper foam electrode was immersed in a solution containing 5 mM ruthenium chloride and allowed to stand for 24 h at room temperature and pressure for ion exchange. After the reaction was completed, the sample was removed and thoroughly rinsed with deionized water to remove unbound ruthenium salts, thus obtaining the ruthenium-doped copper hydroxide nanowire / copper foam electrode.

[0024] 4) The above-mentioned ruthenium-doped copper hydroxide nanowires / copper foam electrode was placed in an argon protective atmosphere and heated at 150 °C for 5 h to cause the copper hydroxide nanowires to undergo dehydration transformation, forming a ruthenium-doped copper oxide nanowire structure, while maintaining the nanowire array morphology without significant collapse, thus obtaining the ruthenium-doped copper oxide / copper foam electrode.

[0025] 5) Using the above-mentioned ruthenium-doped copper oxide / foamed copper electrode as the working electrode, electrochemical reduction was performed in a 0.25 M potassium bicarbonate aqueous solution under constant current mode at an applied current density of 300 mA cm⁻¹. -2 The treatment time was 24 h. During the electrochemical reduction process, copper oxide nanowires were reduced to metallic copper nanowires, while ruthenium species were transformed into highly dispersed ruthenium nanoclusters and stably loaded on the surface of copper nanowires, ultimately obtaining a ruthenium-doped copper nanowire / foam copper electrode.

[0026] Example 3 Preparation method of ruthenium-doped copper nanowire composite nanocatalyst 1) The dimensions are 2 × 4 cm 2 The foamed copper was ultrasonically cleaned for 10 minutes each in ethanol, 0.1 M hydrochloric acid aqueous solution and deionized water to remove surface oil and natural oxide layer.

[0027] 2) Subsequently, the treated copper foam was immersed in a mixed solution containing 0.2 M ammonium persulfate and 2 M sodium hydroxide, and allowed to stand at room temperature for 0.5 h to grow a uniform and dense array of copper hydroxide nanowires in situ on the surface of the copper foam. After the reaction was completed, the sample was removed and thoroughly rinsed with deionized water until neutral to obtain a copper hydroxide nanowire / copper foam electrode.

[0028] 3) The above-mentioned copper hydroxide nanowire / copper foam electrode was immersed in a solution containing 60 mM ruthenium chloride and allowed to stand for 2 h at room temperature and pressure for ion exchange. After the reaction was completed, the sample was removed and thoroughly rinsed with deionized water to remove unbound ruthenium salts, thus obtaining the ruthenium-doped copper hydroxide nanowire / copper foam electrode.

[0029] 4) The above-mentioned ruthenium-doped copper hydroxide nanowire / foam copper electrode was placed in an argon protective atmosphere and heated at 400 °C for 1 h to cause the copper hydroxide nanowire to undergo dehydration transformation, forming a ruthenium-doped copper oxide nanowire structure, while maintaining the nanowire array morphology without significant collapse, thus obtaining the ruthenium-doped copper oxide / foam copper electrode.

[0030] 5) Using the above-mentioned ruthenium-doped copper oxide / foamed copper electrode as the working electrode, electrochemical reduction was performed in a 1 M potassium bicarbonate aqueous solution under constant current mode, with an applied current density of 800 mA cm⁻¹. -2 The processing time was 3 hours. During the electrochemical reduction process, copper oxide nanowires were reduced to metallic copper nanowires, while ruthenium species were transformed into highly dispersed ruthenium nanoclusters and stably loaded onto the surface of copper nanowires, ultimately obtaining a ruthenium-doped copper nanowire / foam copper electrode.

[0031] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for synthesizing a catalyst for hydrogen production from seawater based on a ruthenium-doped copper nanowire composite structure, characterized in that, The synthesis method includes the following steps: The first step is to use ultrasonic cleaning to remove organic contaminants and oxide layers from the surface of the foamed copper. The second step involves immersing copper foam in an alkaline oxidation solution containing ammonium persulfate and sodium hydroxide, and reacting it at room temperature to generate an in-situ copper hydroxide nanowire array on the surface of the copper foam, which serves as a self-supporting electrode for the copper hydroxide nanowires. The third step involves immersing the copper hydroxide nanowire self-supporting electrode obtained in the second step into an aqueous solution containing ruthenium salt for ion exchange reaction. The reaction is allowed to proceed under normal temperature and pressure to uniformly introduce ruthenium species onto the surface of the copper-based nanostructure, thereby obtaining a ruthenium-doped copper hydroxide nanowire electrode. The fourth step involves subjecting the ruthenium-doped copper hydroxide nanowire electrode obtained in the third step to low-temperature heat treatment under inert gas protection, transforming it into an oxide nanowire structure to obtain a ruthenium-doped copper oxide nanowire electrode. In the fifth step, the copper oxide nanowire electrode obtained in the fourth step is immersed in potassium bicarbonate electrolyte. Through constant current electrochemical reduction, the oxide nanowire is converted into metallic copper nanowire, and ruthenium clusters are formed on its surface, thus obtaining a ruthenium-doped copper nanowire composite electrode.

2. The method for synthesizing a seawater electrolysis hydrogen production catalyst based on a ruthenium-doped copper nanowire composite structure according to claim 1, characterized in that, In the first step, the foamed copper is ultrasonically cleaned in sequence with ethanol, dilute hydrochloric acid solution and deionized water.

3. The method for synthesizing a seawater electrolysis hydrogen production catalyst based on a ruthenium-doped copper nanowire composite structure according to claim 1, characterized in that, In the second step, the concentration of ammonium persulfate in the alkaline oxidizing solution is 0.05–0.2 M, and the concentration of sodium hydroxide is 0.5–2 M.

4. The method for synthesizing a seawater electrolysis hydrogen production catalyst based on a ruthenium-doped copper nanowire composite structure according to claim 1, characterized in that, In the second step, the molar ratio of ammonium persulfate to sodium hydroxide in the alkaline oxidizing solution is 1:

10.

5. The method for synthesizing a seawater electrolysis hydrogen production catalyst based on a ruthenium-doped copper nanowire composite structure according to claim 1, characterized in that, The reaction time for the second step is 0.5–2 h.

6. The method for synthesizing a seawater electrolysis hydrogen production catalyst based on a ruthenium-doped copper nanowire composite structure according to claim 1, characterized in that, In the third step: The reaction time is 2–24 h; The concentration of ruthenium salt in the aqueous solution containing ruthenium salt is 5–60 mM. The ruthenium salt is ruthenium chloride.

7. The method for synthesizing a seawater electrolysis hydrogen production catalyst based on a ruthenium-doped copper nanowire composite structure according to claim 1, characterized in that, In the fourth step, the low-temperature heat treatment is carried out under an argon atmosphere at a temperature of 150–400 °C for a duration of 1–5 h.

8. The method for synthesizing a seawater electrolysis hydrogen production catalyst based on a ruthenium-doped copper nanowire composite structure according to claim 1, characterized in that, In the fifth step: The concentration of the potassium bicarbonate electrolyte is 0.25–1 M; The current density of the constant current treatment is 300–800 mA cm⁻¹ -2 The constant current treatment time is 3–24 h.

9. A catalyst for hydrogen production from seawater based on a ruthenium-doped copper nanowire composite structure, characterized in that, The seawater electrolysis hydrogen production catalyst comprises a foamed copper current collector and an in-situ grown copper nanowire array on its surface, wherein the surface of the copper nanowires is uniformly loaded with ruthenium metal or ruthenium-based nanoclusters; wherein: The copper nanowires are constructed in situ from copper foam through chemical oxidation, thermal conversion and electrochemical reduction processes. The ruthenium is distributed on the surface or near the surface of the copper nanowires in the form of metallic ruthenium or clusters. The catalyst for producing hydrogen through seawater electrolysis has an integral self-supporting electrode structure and requires no binder.

10. The seawater electrolysis hydrogen production catalyst based on a ruthenium-doped copper nanowire composite structure according to claim 9, characterized in that, In the aforementioned seawater electrolysis hydrogen production catalyst: The copper nanowires have a diameter of 40–100 nm and a length greater than 500 nm. The size of the clusters is 2–5 nm; The ruthenium mass loading is 0.05–0.8 mg cm⁻¹. -2 .

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