A self-supporting ruthenium-copper alloy nanomaterial and application thereof to electrocatalytic preparation of amino compounds

Abstract

The application provides a self-supporting ruthenium-copper alloy nanomaterial, wherein the foam copper cleaned by hydrochloric acid is placed in an ammonium persulfate and potassium hydroxide solution for soaking, then cleaned by deionized water, placed in a ruthenium chloride solution for soaking, cleaned, heated to 200 DEG C under inert gas protection for 2 hours, then cooled to room temperature, and finally reduced in a 1 M KOH solution for 6 hours at a current density of-100 mA•cm ‑2 The application adopts an ultrafast and simple ion exchange method to synthesize a self-supporting RuCu catalyst, which can efficiently reduce nitroaromatics to arylamines, and can realize ultra-high yield, Faraday efficiency and selectivity in a very wide potential range. The high performance can be maintained in a wide range of pH value solutions and a wide range of nitrate concentrations, and the self-supporting RuCu catalyst shows good application potential.

Description

Technical Field

[0001] This invention relates to an electrocatalytic catalyst, specifically to a self-supported ruthenium-copper alloy nanomaterial and its application in the electroreduction of nitroaromatic hydrocarbons to arylamines. Background Technology

[0002] Aromatic amines are used in the manufacture of dyes, pharmaceuticals, resins, and intermediates, and are among the world's most produced chemicals, with an estimated production of 7.85 million metric tons (aniline) in 2023. The traditional industrial synthesis of aromatic amines generally involves the chemical reduction and catalytic hydrogenation reduction of nitroaromatics. Traditional chemical reduction methods utilize metal reducing agents (such as iron, zinc, or tin), requiring the addition of large amounts of metal, resulting in high reaction costs and generating significant sludge and pollution. Catalytic hydrogenation utilizes precious metal catalysts and strong reducing agents (such as N₂H₄, NaBH₄, CO, or H₂) under high temperature and pressure. This process is inefficient, produces large amounts of carbon dioxide, and the use of hydrogen poses a potential explosion risk. Therefore, there is an urgent need for a more efficient strategy driven by renewable energy to meet the production requirements of sustainable development and chemical compatibility.

[0003] Electrochemical selective reduction methods can utilize renewable electricity to produce the required chemicals, thus offering a compelling alternative to the traditional method of reducing nitrobenzene to aniline. Its unique advantages include mild reaction conditions, excellent energy efficiency, and the ability to use water as a green hydrogen source. Although extensive research and promising results have been achieved in the electrocatalysis of nitroaromatics, it suffers from poor stability (<200 h) and low reaction rates (current density <100 mA-cm). -2 The low tolerance to reaction conditions (potential or pH) and poor matrix scalability severely limit its industrial application. Furthermore, current catalyst systems for the production of aniline from nitrobenzene rarely consider practical production efficiency and usability; the main research focus is on improving the performance of one-pot reactions, without extending to the stability of the catalytic system, scale-up reactions, and the reactivity with various nitro compounds. Summary of the Invention

[0004] Purpose of the invention: The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a self-supporting ruthenium-copper alloy nanomaterial and its application in the electrocatalytic preparation of amino compounds.

[0005] To address the aforementioned technical problems, this invention discloses a self-supporting ruthenium-copper alloy nanomaterial, prepared through the following steps: Foamed copper, cleaned with hydrochloric acid, is immersed in a persulfate and alkaline solution for 0.5–2 hours, then washed with deionized water, and immersed in a ruthenium chloride solution. After cleaning, under inert gas protection, the temperature is raised to 100–300°C and maintained for 0.5–4 hours, followed by cooling to room temperature. Finally, it is immersed in an alkaline solution at -50 to -500 mA·cm⁻¹. -2 The current density is reduced for 2 to 6 hours.

[0006] The foamed copper was cleaned with hydrochloric acid.

[0007] The persulfate is any one of ammonium persulfate, potassium persulfate, or sodium persulfate, with a concentration of 0.05–0.5 M; the alkaline solution is potassium hydroxide or sodium hydroxide, with a concentration of 0.1–2 M.

[0008] Preferably, the persulfate is ammonium persulfate with a concentration of 0.1M, and the alkaline solution is potassium hydroxide with a concentration of 1M.

[0009] The concentration of the ruthenium chloride solution is 0.05–0.5 mM, and the soaking time is 2–20 h.

[0010] The alkaline solution is a 0.1M to 2M KOH or NaOH solution.

[0011] The inert gas is nitrogen or argon.

[0012] Preferably, the heating rate is 5-20℃ / min.

[0013] This invention further proposes the application of the above-mentioned self-supporting ruthenium-copper alloy nanomaterials in the electrocatalytic preparation of amino compounds from nitro compounds.

[0014] Specifically, in application, the reaction conditions are: aqueous solution with pH = 0 to 14, substrate concentration of 0.01 to 0.25 M, reaction voltage range of 0 to -0.7 V, and reaction pH of 0 to 1.

[0015] Beneficial Effects: This application utilizes an ultrafast and simple ion exchange method to synthesize a self-supported RuCu catalyst (named RuCu NSs) that can efficiently electroreduce nitroaromatics to arylamines. Using p-nitrophenol as a model substrate, the RuCu alloy achieves ultra-high yields (>99.9%), Faradaic efficiencies (>99.9%), and selectivity (>99.9%) over a wide potential range. It maintains high performance across a wide pH range (including 1M KOH, 0.5M K₂SO₄, and 0.5M H₂SO₄) and a wide concentration range of p-nitrophenol (12.5-250 mM), demonstrating excellent application potential. Furthermore, in a scaled-up flow electrochemical reactor, it maintains high performance and operates stably for 1,060 hours at a cell voltage of only 2.5V (current of -1.38A) to obtain kilogram-level products (0.501 kg p-aminophenol). Furthermore, the same electrocatalytic strategy appears to be effective for a variety of nitroaromatics as well. In summary, the successful widespread reduction of nitroaromatics using electricity as a renewable energy source and water as a green hydrogen source paves the way for safer, more sustainable, and more economical chemical / material manufacturing. Attached Figure Description

[0016] Figure 1 A schematic diagram of the synthesis steps of RuCu NSs;

[0017] Figure 2 XRD patterns of copper foam, Cu NSs, and RuCu NSs;

[0018] Figure 3 High-resolution transmission electron microscopy lattice diffraction patterns of Cu NSs and RuCu NSs;

[0019] Figure 4 Transmission electron microscope images of Cu NSs(1) and RuCu NSs(2);

[0020] Figure 5 Atomic force microscopy images of Cu NSs(1) and RuCu NSs(2);

[0021] Figure 6 The left image shows the Cu 2p XPS plots of Cu NSs and RuCu NSs, and the right image shows the Ru 3d XPS plots of RuCu NSs and RuCuO.

[0022] Figure 7 Linear sweep voltammetry and potentiostatic electrolysis tests were performed on Cu NSs and RuCu NSs in 1M KOH solution;

[0023] Figure 8Linear sweep voltammetry and potentiostatic electrolysis tests were performed on Cu NSs and RuCu NSs in 0.5M K2SO4 solution.

[0024] Figure 9 Linear sweep voltammetry and potentiostatic electrolysis tests were performed on Cu NSs and RuCu NSs in 0.5M H2SO4 solution.

[0025] Figure 10 This represents a portion of the current density obtained based on LSV and constant potential electrolysis.

[0026] Figure 11 The reduction performance of p-nitrophenol on RuCu NS / CF at different concentrations;

[0027] Figure 12 Polarization curves of RuCu NSs reducing p-nitrophenol in a flowing electrolytic cell;

[0028] Figure 13 The long-term electrocatalytic stability of RuCu NSs / CF was tested using a continuous flow system at Ecell = 2.5V (125mM p-nitrophenol + 1M KOH).

[0029] Figure 14 The results of performance tests of RuCu NSs in a flow reactor and in a single reaction, and the comparison of stability and Faraday efficiency with other works;

[0030] Figure 15 The catalytic effect of RuCu NSs on various types of nitroaromatic hydrocarbons as substrate molecules. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0032] Example 1: Preparation of self-supporting RuCu catalysts (RuCu NSs).

[0033] Figure 1 This is a schematic diagram of the RuCu catalyst synthesis. Copper foam, washed with hydrochloric acid, was immersed in a 0.1M ammonium persulfate and 1M potassium hydroxide solution for 1 hour, then washed with deionized water and immersed in a 10mM ruthenium chloride solution for 12 hours. After washing, the solution was heated to 200℃ at a rate of 10℃ / min under nitrogen protection and maintained for 2 hours, then cooled to room temperature. Finally, it was dissolved in 1M KOH solution at -100mA·cm⁻¹. -2 The current density was reduced for 6 hours to obtain RuCu NSs.

[0034] Meanwhile, a Ru-free catalyst control sample was prepared using the same method, with the treatment method being similar to that described above, except that the ruthenium chloride solution was replaced with a pure aqueous solution to obtain Cu NSs.

[0035] Figures 2-6 The image shows the characterization results of the synthesized RuCu NSs. This application employs an ultrafast and simple ion exchange method to synthesize a self-supporting RuCu catalyst. This strategy not only allows for the large-scale and simple synthesis of the catalyst but also has a short synthesis time, showing potential for large-scale production. The crystal structures of RuCu NSs and Cu NSs were determined by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM).

[0036] like Figure 2 As shown, Cu NSs and RuCu NSs exhibit characteristic diffraction peaks of tetragonal Cu (PDF NO.). The interplanar spacing of RuCu NSs measured by HRTEM is 0.207 nm. Figure 3 The RuCu nanosheet structure corresponds to the (111) plane of Cu. Low-magnification transmission electron microscopy (TEM) further reveals the RuCu nanosheet structure. Figure 4 ),in Figure 4 (1) is Cu NSs, (2) is RuCu NSs. Atomic force microscopy (AFM) images of RuCu NSs further show that the nanosheets are approximately 80 nm thick. Figure 5 ).

[0037] The electronic structures of RuCu NSs and Cu NSs were investigated using XPS. In the high-resolution Cu 2p² / ³ XPS spectrum of RuCu NSs, the 2p² / ³ binding peaks at approximately 933.5 eV, 935.1 eV, and 942.5 eV were attributed to Cu, respectively. 2+ Cu + / Cu 0 And satellite peaks. Compared with Cu NSs, the binding energy of Cu in RuCu NSs decreased by 0.4 eV, indicating that Ru doping reduced the valence state of Cu. After electrochemical reduction, the characteristic peak of Ru 3d5 / 2 decreased from 281.3 eV to 280.5 eV, and Ru existed in the form of Ru0. Figure 6 In summary, we have successfully synthesized RuCu alloy nanosheets on a copper foam substrate.

[0038] Example 2: Application of RuCu alloy nanosheets in the electrocatalytic preparation of amino compounds.

[0039] p-Aminophenol is a widely used fine organic chemical intermediate. For the model reaction of p-nitrophenol (p-NP) to p-aminophenol (p-AP), the reduction performance of RuCu NSs and Cu NSs in 1M KOH, 0.5M K2SO4, and 0.5M H2SO4 was first evaluated using linear sweep voltammetry (LSV). The results are as follows: Figures 7-9 The addition of Ru significantly improved the hydrogen evolution reaction (HER) performance in various solutions. The addition of 25 mM p-NP increased the reduction current in all solutions, indicating effective p-NP reduction. Furthermore, the reduction current of RuCu for p-NP increased significantly more than that of Cu as the pH decreased. The electrocatalytic p-NP reduction performance of RuCu NSs and Cu NSs in different solutions was further investigated under different potential conditions. Specifically, during electrolysis, the amount of electricity required for the theoretical complete conversion of the substrate (579.9 C, yield numerically equal to Faraday efficiency) was injected at different potentials, and the products were quantified by high-performance liquid chromatography (HPLC). Figures 7-9 As shown. In 1M KOH, the initial potential of RuCu NSs is 0.4V. RHE The reaction yield, FE, and selectivity remained around 99% between 0.1V and -0.3V, significantly higher than Cu NSs. Similar to alkaline solutions, RuCu NSs exhibited a higher onset potential and greater reducibility at lower potentials compared to Cu NSs. In summary, RuCu NSs can reduce p-nitrophenol to p-aminophenol over a wide potential range in solutions with varying pH values.

[0040] To further compare the reaction characteristics, partial current densities were calculated. For example... Figure 10 As shown, the current density is highest in alkaline solutions, followed by acidic and neutral solutions.

[0041] To further investigate the potential for industrial production, we conducted a series of experiments on RuCu NSs.

[0042] The reaction conditions were: 40 mL of 1 M KOH solution, and an electrode area of ​​4 cm². 2 The prepared RuCu electrode was used as the working electrode, the Pt sheet as the counter electrode, and mercury oxide as the reference electrode. The reaction potential was 0 V relative to RHE, and the charge passing through each 1 mmol of substrate was 580 C. The results indicate that the prepared RuCu catalyst can maintain high performance over a wide range. Figure 11 ).

[0043] Stability under prolonged high current density is a prerequisite for application. RuCu NSs was tested in a flow reactor. The reaction conditions were: 100 mM p-nitrophenol in 1 M KOH solution (400 mL), and an electrode area of ​​4 cm². 2 The prepared RuCu electrode was used as the working electrode, and the RuIr titanium mesh was used as the counter electrode. The reaction potential was 0 V relative to RHE, and the charge passing through each 1 mmol of substrate was 600 C. After the reaction was complete, the solution was replaced and the reaction continued. Figure 12 As shown, the polarization curves indicate that the reaction begins to drive at a cell potential of 1.11 V, with a total current of -1.38 A and a current density of -0.34 A at an electrolysis voltage of 2.5 V. The electrolysis voltage can be reduced by further optimizing the structure of the electrolysis device (e.g., using a membrane electrode or increasing the temperature) and replacing the anodic oxygen evolution reaction (e.g., various types of alcohol oxidation). After 1060 hours of potentiostatic polarization, the current density of RuCu remained stable. Figure 13 The Faraday efficiency remained at 90%, and the selectivity at 94%, while yielding 0.511 kg of crude p-aminophenol. Compared to previously reported catalysts, both single-cell reaction and 1060 hours of flow electrolysis showed strong competitiveness. Figure 14 (As shown in Table 1). This further confirms the excellent effect of electrocatalysis in practical applications.

[0044] Table 1

[0045]

[0046]

[0047] Furthermore, to investigate the substrate scope of RuCu NSs, we used various types of nitroaromatic hydrocarbons as substrate molecules, with the prepared RuCu NSs as the cathode and a platinum sheet as the anode. 1 mmol of reactant was added, and the reaction solution consisted of 35 mL of 1M KOH solution and 5 mL of dioxane (to increase substrate solubility). Figure 15 As shown, RuCu NSs exhibit high yields and selectivity for common electron-donating and electron-taking groups (2b-2g), and also maintain good performance for molecules containing other easily reducible groups (2h-2o) (such as halogens, carbon-carbon double bonds, and carbon-carbon triple bonds), as well as non-aromatic nitrobenzenes (2s), nitrobenzenes containing N-heterocyclic groups (2t), and nitrobenzenes containing multiple nitro groups (2u). Aromatic nitrobenzene compounds (2p-2r) containing groups unstable in acidic and alkaline solutions (such as cyano, carbonyl, and aldehyde groups) still show high activity because RuCu NSs function in solutions with varying pH values. For drugs (2x, 2y) and drug derivatives (2v, 2w), RuCu NSs ensure the stability of functional groups in the substrate molecule.

[0048] This invention provides a self-supported ruthenium-copper alloy nanomaterial and its application in the electrocatalytic preparation of amino compounds. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. The use of a self-supporting ruthenium-copper alloy nanomaterial in the electrocatalytic preparation of arylamines from nitroaromatic compounds, characterized in that, The self-supporting ruthenium-copper alloy nanomaterial is prepared by the following steps: placing the foam copper cleaned with hydrochloric acid in a persulfate and alkaline solution for 0.5-2 hours, then washing with deionized water, placing in a 10 mM ruthenium chloride solution for 2-20 hours, washing, then heating to 200°C under inert gas protection for 2 hours, then cooling to room temperature, and finally reducing in an alkaline solution at a current density of-50 to-500 mA•cm -2 for 2-6 hours.

2. Use according to claim 1, characterized in that, The persulfate salt is any one of ammonium persulfate, potassium persulfate or sodium persulfate, and the concentration is 0.05-0.5 M; The alkaline solution is potassium hydroxide or sodium hydroxide, and the concentration is 0.1-2 M.

3. Use according to claim 1, characterized in that, The persulfate salt is ammonium persulfate, and the concentration is 0.1 M; the alkaline solution is potassium hydroxide, and the concentration is 1 M.

4. Use according to claim 1, characterized in that, The alkaline solution is 0.1 M-2 M KOH or NaOH solution.

5. The use according to claim 1, characterized in that, The inert gas is nitrogen or argon.

6. Use according to claim 1, characterized in that, The temperature rising rate is 5-20 ℃ / min.

7. The use according to claim 1, characterized in that, In application, the reaction condition is that the reaction substrate concentration is 0.01-0.25 M in an aqueous solution with pH=0-14, and the reaction voltage range is 0- -0.7 V.

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