Porous copper electrode with surface modified with hydrophobic ionic liquid and application of porous copper electrode
By modifying the surface of a porous copper electrode with a hydrophobic ionic liquid, the problems of low nitrogen solubility and competing hydrogen evolution reactions in electrocatalytic nitrogen fixation were solved, achieving efficient green ammonia synthesis and improving catalytic performance and selectivity.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-27
- Publication Date
- 2026-04-14
AI Technical Summary
In existing electrocatalytic nitrogen fixation technologies, nitrogen has extremely low solubility in water, resulting in insufficient nitrogen source supply. Furthermore, water, as a proton carrier, easily triggers hydrogen evolution competition reactions, limiting the catalytic rate and selectivity.
A porous copper electrode with a surface-modified hydrophobic ionic liquid was used. The porous copper electrode was prepared by electrodeposition and the surface of the electrode was modified with a hydrophobic ionic liquid to improve the solubility of nitrogen and reduce the interfacial water content, thereby suppressing the hydrogen evolution side reaction.
It significantly improves the solubility and activation efficiency of nitrogen, enhances nitrogen fixation performance, increases ammonia production rate and Faraday efficiency, while reducing energy consumption and carbon emissions, meeting the needs of green chemical development.
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Figure CN121852972A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of electrochemical catalysis technology, specifically to a porous copper electrode with a surface-modified hydrophobic ionic liquid and its application. Background Technology
[0002] Ammonia is one of the most widely produced and used chemicals globally, primarily in agricultural fertilizers, and in recent years has been expanding into the energy sector. Traditional ammonia synthesis uses the Haber-Bosch process, employing nitrogen and hydrogen as raw materials and requiring catalytic reactions under high temperature and pressure. This process is not only energy-intensive but also generates significant carbon emissions, contradicting the demands of green development. Electrocatalytic nitrogen fixation technology, as an ideal green ammonia synthesis route, uses water instead of hydrogen as the proton source. It enables nitrogen reduction at ambient temperature and pressure through green electrocatalysis, reducing energy consumption and carbon emissions at the source, and possesses broad application potential.
[0003] However, electrocatalytic nitrogen fixation technology faces two fundamental bottlenecks in aqueous systems, severely limiting its catalytic rate and Faraday efficiency. Firstly, nitrogen has extremely low solubility in water (approximately 0.66 mM), leading to insufficient nitrogen supply and difficulty in meeting reaction requirements. Secondly, water, as a proton carrier, easily triggers hydrogen evolution competition reactions, vying for reaction sites and electron resources, thus reducing the selectivity of the target product. Current research largely focuses on catalyst design and modification, optimizing catalyst surface composition and electronic structure through various regulatory strategies. While this can improve catalytic activity and selectivity to some extent, it cannot fundamentally solve the core problems of low nitrogen solubility and high proton activity in aqueous solutions, making it difficult to achieve a breakthrough improvement in nitrogen fixation performance.
[0004] To address the aforementioned technical bottlenecks and break through the traditional approach of optimizing a single catalyst, this study proposes a porous copper electrode with a surface-modified hydrophobic ionic liquid and its application scheme from the perspective of microenvironment regulation in the reaction system. This scheme aims to simultaneously improve nitrogen source supply efficiency and suppress hydrogen evolution competition reactions, overcoming the performance limitations of electrocatalytic nitrogen fixation in aqueous solutions by regulating the reaction microenvironment, thus providing a new path for the industrialization of green ammonia synthesis technology. Summary of the Invention
[0005] In view of this, the technical problem to be solved by this invention is to propose a porous copper electrode with a surface-modified hydrophobic ionic liquid and its application. Since copper is a metal material with poor hydrogen evolution performance and has been widely used in electrocatalytic small molecule reduction reactions such as carbon dioxide reduction, it is a potential candidate catalyst for electrocatalytic nitrogen fixation. Furthermore, related research on ionic liquids has found that ionic liquids with fluorine-containing anions exhibit higher nitrogen solubility and stronger hydrophobicity. The strong interaction forces (such as dispersion forces and electrostatic forces) between fluorine-containing groups and nitrogen gas are beneficial for dissolving and activating nitrogen molecules, while fluorine-containing ionic liquids generally exhibit strong hydrophobicity. Using this type of ionic liquid in surface-modified copper electrode materials, its higher nitrogen solubility and stronger hydrophobicity can effectively enrich nitrogen gas and reduce interfacial water content, thereby enhancing nitrogen fixation performance and suppressing hydrogen evolution side reactions.
[0006] 1. The technical problems in the existing technology that this solution aims to solve; This design aims to solve the following technical problems in existing technologies: (1) When the existing electrocatalytic nitrogen fixation technology uses water as the proton source, the solubility of nitrogen in water is extremely low (only about 0.66 mM), resulting in insufficient nitrogen supply in the reaction system, making it difficult to fully participate in the catalytic reaction. This essentially limits the reaction rate of electrocatalytic nitrogen fixation and cannot meet the demand for efficient ammonia production.
[0007] (2) Water as a proton carrier is prone to triggering hydrogen evolution competition side reactions. These side reactions compete with the nitrogen fixation reaction for protons and reaction sites, which not only reduces the selectivity of the nitrogen fixation reaction, but also significantly affects the nitrogen fixation Faraday efficiency. Even by optimizing the intrinsic properties of the catalyst, it is difficult to fundamentally solve this problem, which restricts the practical application of electrocatalytic nitrogen fixation technology.
[0008] 2. Technical Solution To achieve the above objectives, the present invention provides the following technical solution: a porous copper electrode with a surface-modified hydrophobic ionic liquid and its application, the specific steps of which are as follows: S1, copper sulfate is dissolved in an aqueous sulfuric acid solution as an electrolyte, and copper-based conductive materials are used as the working electrode and counter electrode, respectively, to prepare a porous copper electrode by electrodeposition. S2, a hydrophobic ionic liquid is dissolved in anhydrous ethanol, and the mixed solution is drop-coated onto the surface of a porous copper electrode. After drying, a porous copper electrode with a surface-modified hydrophobic ionic liquid is obtained.
[0009] Preferably, the molar concentrations of copper sulfate and sulfuric acid in S1 are 0.01~0.5 M and 0.1~3 M, respectively.
[0010] Preferably, the electrodeposition current density in S1 is 0.1~5 A cm⁻¹. -2The electrodeposition time is 0.5~10 min.
[0011] Preferably, the hydrophobic ionic liquid anion described in S2 is a fluorine-containing anion selected from bis(trifluoromethanesulfonyl)imide (NTf2) - ), trifluoromethanesulfonate (OTf) - ), hexafluorophosphate (PF6) - One or more of the following, with a loading of 0.1~2 mg cm -2 The drying conditions described in S2 are vacuum drying, with a drying temperature of 15~30 ℃ and a drying time of 1~4 h. The concentration of the hydrophobic ionic liquid in the mixed solution is 0.2~0.5 g mL. -1 .
[0012] A second aspect of the present invention provides a porous copper electrode with a surface-modified hydrophobic ionic liquid obtained by the above preparation method.
[0013] The third aspect of the present invention provides the application of the porous copper electrode with the above-mentioned surface-modified hydrophobic ionic liquid as a catalytic electrode in the electrocatalytic reduction of nitrogen to ammonia in an aqueous electrolyte (selected from sulfuric acid aqueous solution, hydrochloric acid aqueous solution, and phosphoric acid aqueous solution).
[0014] Compared with the prior art, the porous copper electrode with surface-modified hydrophobic ionic liquid and its application provided by the present invention have the following beneficial effects: (1) Core improvement of nitrogen fixation performance: Hydrophobic ionic liquid (fluorine-containing anionic type) can significantly improve nitrogen solubility and enhance the interface enrichment effect, while reducing the water content near the active site to the ppm level. This not only strengthens the nitrogen activation and reduction reaction, but also effectively inhibits the hydrogen evolution side reaction, greatly improving the ammonia production rate and nitrogen fixation Faraday efficiency, thus fundamentally breaking through the performance bottleneck of low nitrogen solubility and high proton activity in aqueous solution.
[0015] (2) Significant advantages of electrode structure: The porous copper electrode prepared by one-step electrodeposition method has a three-dimensional sparse porous morphology, which can expose rich catalytic active sites and facilitate electrolyte penetration and product mass transfer and diffusion. Copper itself has poor hydrogen evolution performance and is a high-quality substrate for electrocatalytic nitrogen fixation. After being modified with ionic liquid, the interfacial environment of the catalytic reaction is further optimized.
[0016] (3) The preparation process is simple and controllable: the electrode is prepared by a combination of electrodeposition and drop coating. There is no need for complex equipment and harsh reaction conditions. The process steps are simple and easy to operate. The key parameters (such as electrolyte concentration, electrodeposition current density and ionic liquid loading) can be precisely controlled. The repeatability is good, which is convenient for large-scale preparation and practical application.
[0017] (4) Broad prospects for green applications: When applied to the electrocatalytic reduction of nitrogen to produce ammonia, water is used as the proton source. Green ammonia can be synthesized at room temperature and pressure using green electricity. Compared with the traditional Haber-Bosch method, it does not require high temperature and high pressure conditions, has lower energy consumption and less carbon emissions, which meets the needs of green chemical development. At the same time, it expands the application scenarios of copper-based materials and ionic liquids in the field of electrocatalytic nitrogen fixation. Attached Figure Description
[0018] Figure 1 This is a SEM image of the porous copper electrode prepared in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the water droplet contact angle of the porous copper electrode prepared in Embodiment 1 of the present invention; Figure 3 The ionic liquid [P] used in Example 1 of this invention 6,6,6,14 A schematic diagram of the chemical structure of [NTf2]; Figure 4 This is a SEM image of the porous copper electrode with surface-modified hydrophobic ionic liquid prepared in Example 1 of the present invention. Figure 5 This is a schematic diagram of the water droplet contact angle of the porous copper electrode with surface-modified hydrophobic ionic liquid prepared in Example 1 of the present invention; Figure 6 This is a schematic diagram comparing the ammonia production rates in 0.05 M sulfuric acid aqueous solution when the porous copper electrode prepared in Example 1 of the present invention and the porous copper electrode with surface-modified hydrophobic ionic liquid are applied to electrocatalytic nitrogen fixation and ammonia production. Figure 7 This is a schematic diagram comparing the Faraday efficiency of the porous copper electrode prepared in Example 1 of the present invention and the porous copper electrode with surface-modified hydrophobic ionic liquid in 0.05 M sulfuric acid aqueous solution when applied to electrocatalytic nitrogen fixation and ammonia production. Figure 8 This is a schematic diagram of the process for preparing a porous copper electrode with a surface-modified hydrophobic ionic liquid according to the present invention. Detailed Implementation
[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0020] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.
[0021] Example 1; please refer to Figures 1 to 8 As shown: To address the problems mentioned in the technical solutions, this application provides a method for preparing a porous copper electrode with a surface-modified hydrophobic ionic liquid. The specific preparation steps are as follows: Preparation steps: Step 1: Dissolve copper sulfate in an aqueous sulfuric acid solution to prepare a 1.5 M sulfuric acid aqueous solution containing 0.1 M copper sulfate. Use this solution as the electrolyte and a copper sheet (0.5 cm × 2.5 cm) as both the working and counter electrodes to fabricate a porous copper electrode via electrodeposition. The electrodeposition parameters are set as follows: current density 2 A / cm². -2 The electrodeposition time was 2 minutes. After electrodeposition, the sample was carefully rinsed with deionized water and anhydrous ethanol, and then subjected to a 20°C test. o Vacuum drying in a C oven yields a porous copper electrode. The morphology of the porous copper electrode is characterized, and its SEM image is shown below. Figure 1 The diagram shows a three-dimensional porous structure. The regular pore structure formed on its surface is formed by hydrogen bubbles generated in situ during the electrodeposition process as templates. This porous structure is beneficial for exposing abundant catalytic active sites, and also facilitates the mass transfer and diffusion of electrolyte and products. Figure 2 The diagram shows the water droplet contact angle of the porous copper electrode. It can be observed that the water droplet contact angle of the porous copper electrode is 0°. o It has excellent hydrophilicity.
[0022] Step 2, add 1 mL of hydrophobic ionic liquid [P] 6,6,6,14 [NTf2] was dissolved in 9 mL of anhydrous ethanol. 0.5 mL of the mixed solution was drop-coated onto the surface of a porous copper electrode and incubated at 20°C. o A porous copper electrode with a surface-modified hydrophobic ionic liquid was obtained after vacuum drying in a C oven. The ionic liquid loading was calculated to be 1 mg / cm³ by weighing. -2 Ionic liquids [P] 6,6,6,14 The chemical structure of [NTf2] is as follows: Figure 3 As shown, the fluorinated anionic group imparts excellent nitrogen solubility and hydrophobicity, and the long alkyl chain also contributes to improving its nitrogen solubility and hydrophobicity. For example... Figure 4 SEM images show that the ionic liquid was successfully and uniformly loaded onto the surface of the porous copper electrode. Contact angle experiments indicate that the porous copper electrode modified with the ionic liquid exhibits strong hydrophobicity, with a water droplet contact angle as high as 142.6°. o ( Figure 5 ).
[0023] Example 2; The porous copper electrode with surface-modified hydrophobic ionic liquid prepared in Example 1 was used as a catalytic electrode in the electrocatalytic reduction of nitrogen to ammonia. The specific steps are as follows: Electrocatalytic nitrogen fixation performance was tested in a standard three-electrode cell. A porous copper electrode modified with a hydrophobic ionic liquid was used as the working electrode, a carbon rod as the counter electrode, and a saturated calomel electrode as the reference electrode. The electrocatalytic nitrogen fixation performance was tested in a nitrogen-saturated 0.05 M sulfuric acid aqueous solution. For comparison, an unmodified porous copper electrode was used as the control electrode for the same performance test. Electrolysis was performed for 2 h at different electrolysis potentials (-0.1, -0.2, -0.3, -0.4, and -0.5 V vs. RHE, the reversible hydrogen electrode potential). After the reaction, the ammonia production rate and Faraday efficiency were measured and calculated by UV-Vis spectroscopy. Specific results are shown in [link to results]. Figure 6 and Figure 7 .
[0024] Depend on Figure 6 The results show that, at the same potential, the porous copper electrode modified with hydrophobic ionic liquid exhibits a faster ammonia production rate than the unmodified porous copper electrode. Specifically, at a potential of -0.3 V vs. RHE, the porous copper electrode modified with hydrophobic ionic liquid achieves the highest ammonia production rate of 8.1 × 10⁻⁶. 10 mol s 1 cm 2 The highest ammonia production rate (4 × 10⁻⁶) is achieved by an unmodified porous copper electrode. 10 mol s 1 cm 2 2 times; Depend on Figure 7 The results show that, at the same potential, the porous copper electrode with surface-modified hydrophobic ionic liquid has a higher nitrogen fixation Faraday efficiency than the unmodified porous copper electrode. Specifically, at a potential of -0.3 V vs. RHE, the porous copper electrode with surface-modified hydrophobic ionic liquid achieved the highest nitrogen fixation Faraday efficiency of 31.2%, which is 2.5 times the highest ammonia production rate of 12.5% of the unmodified porous copper electrode.
[0025] The above results demonstrate that the electrocatalytic nitrogen fixation performance of the porous copper electrode is significantly improved by modification with a hydrophobic ionic liquid. The porous copper electrode with surface-modified hydrophobic ionic liquid provided by this invention can be used as a high-performance catalytic electrode in electrocatalytic nitrogen fixation for ammonia production. It should be noted that the term "comprising" or any other variation thereof is intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0026] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A method for preparing a porous copper electrode with a surface-modified hydrophobic ionic liquid, characterized in that, Includes the following steps: S1, copper sulfate is dissolved in an aqueous sulfuric acid solution as an electrolyte, and copper-based conductive materials are used as the working electrode and counter electrode, respectively, to prepare a porous copper electrode by electrodeposition. S2, a hydrophobic ionic liquid is dissolved in anhydrous ethanol, and the mixed solution is drop-coated onto the surface of a porous copper electrode. After drying, a porous copper electrode with a surface-modified hydrophobic ionic liquid is obtained.
2. The method for preparing a porous copper electrode with a surface-modified hydrophobic ionic liquid according to claim 1, characterized in that, The molar concentrations of copper sulfate and sulfuric acid in S1 are 0.01~0.5 M and 0.1~3 M, respectively.
3. The method for preparing a porous copper electrode with a surface-modified hydrophobic ionic liquid according to claim 1, characterized in that, The electrodeposition current density described in S1 is 0.1~5 A cm⁻¹. -2 The electrodeposition time is 0.5~10 min.
4. The method for preparing a porous copper electrode with a surface-modified hydrophobic ionic liquid according to claim 1, characterized in that, The hydrophobic ionic liquid anion mentioned in S2 is a fluorine-containing anion, which is selected from bis(trifluoromethanesulfonyl)imide (NTf2) - ), trifluoromethanesulfonate (OTf) - ), hexafluorophosphate (PF6) - One or more of the following, with a loading of 0.1~2 mg cm -2 The drying conditions described in S2 are vacuum drying, with a drying temperature of 15~30 ℃ and a drying time of 1~4 h. The concentration of the hydrophobic ionic liquid in the mixed solution is 0.2~0.5 g mL. -1 .
5. A porous copper electrode with a surface-modified hydrophobic ionic liquid prepared by the preparation method according to any one of claims 1-4.
6. The application of a porous copper electrode with a surface-modified hydrophobic ionic liquid as a catalyst in the electrocatalytic reduction of nitrogen to ammonia in an aqueous electrolyte, as described in claim 5, wherein the aqueous electrolyte is one of sulfuric acid aqueous solution, hydrochloric acid aqueous solution, and phosphoric acid aqueous solution.