In-situ electrochemical reconfiguration of cobalt-ruthenium based catalytic electrode and its preparation method and application in electrocatalytic reduction of nitrate

Abstract

The application provides an in-situ electrochemical restructuring cobalt-ruthenium-based catalytic electrode and a preparation method and application thereof in electrocatalytic nitrate reduction. The in-situ electrochemical restructuring cobalt-ruthenium-based catalytic electrode prepared by the application can continuously expose more active sites, realizes the dissolution of Co during NO3RR and causes in-situ electrochemical restructuring, and therefore exhibits excellent ammonia Faraday efficiency at a low overpotential, the Faraday efficiency is more than 90% when the applied voltage is 0 to -0.2 V, the ammonia yield is increased from 7 mg h ‑1 cm ‑2 to 16 mg h ‑1 cm ‑2 .

Description

Technical Field

[0001] This invention belongs to the field of electrocatalysis technology, specifically relating to an in-situ electrochemically reconstructed cobalt-ruthenium-based catalytic electrode, its preparation method, and its application in electrocatalytic nitrate reduction. Background Technology

[0002] Ammonia (NH3) is one of the most important chemicals in modern society, widely used in fertilizers, pharmaceuticals, and many other industrial sectors. However, over 96% of NH3 production relies on the Haber-Bosch process, using H2 from fossil fuels, accounting for approximately 1% to 2% of global energy consumption and contributing about 1.5% of global CO2 emissions. With the NH3 market projected to expand significantly, and given its potential as a clean, carbon-free fuel or for hydrogen storage, alternative green NH3 synthesis pathways need to be considered to achieve the goal of climate neutrality by 2050.

[0003] Electrosynthesis of NH3, produced from nitrogen-containing feedstocks, appears more feasible than the energy- and carbon-intensive Haber-Bosch process due to its milder process conditions and compatibility with renewable energy sources. Among these technologies, the nitric acid reduction reaction (NO3RR) is thermodynamically more favorable for NH3 production than the direct N2 reduction reaction because of its lower N=O bond breaking energy (204 kJ / mol). -1 In addition, wastewater from the fertilizer industry, metal smelting, and nuclear power plants contains ≥0.1 mol L. -1 The nitrate concentration is suitable for industrial-scale NH3 electrosynthesis. Therefore, NO3RR also represents a waste-to-value strategy that helps alleviate the global nitrogen cycle imbalance. However, the slow 8-electron transfer process involved in the nitrate reduction reaction makes the conversion of NO3... - The efficient conversion to NH3 presents significant challenges. Therefore, developing efficient electrocatalysts is a prerequisite for further promoting the application of NO3RR.

[0004] Over the past five years, NO3RR catalysts based on transition metals (e.g., Fe, Co, Ni, Cu, and Zn) have been rapidly developed under alkaline conditions, exhibiting ammonia faradaic efficiencies exceeding 75%. However, these catalysts often require relatively negative operating potentials (-0.5 to -0.95 V vs. RHE) to achieve 1–5 mg h⁻¹. -1 cm -2 The considerable ammonia yield results in high energy consumption. This is mainly attributed to the proton-coupled electron transfer properties of electrochemical NH3 production, where adsorbed hydrogen (*H) plays a crucial role in each electron transfer step.

[0005] Most transition metal-based catalysts can only provide sufficient hydrogen at extremely negative potentials to maintain significant surface hydrogenation rates, especially under alkaline conditions. Recent studies have found that noble metal catalysts containing platinum group metals (e.g., Ru, Rh, Pd) can enhance the hydrogenation step at more positive potentials (≥-0.4 V vs. RHE) and significantly reduce the overpotential of NO3RR due to their excellent hydrogen adsorption and desorption capabilities. However, another challenge with platinum group metals is the need for better suppression of the hydrogen evolution reaction, as high hydrogen coverage tends to be kinetically favorable for hydrogen evolution rather than NO3RR. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide an in-situ electrochemically reconstructed cobalt-ruthenium-based catalytic electrode, its preparation method, and its application in electrocatalytic nitrate reduction.

[0007] To achieve the above objectives, the solution adopted by the present invention is as follows:

[0008] In a first aspect, the present invention provides a method for preparing an in-situ electrochemically reconstructed cobalt-ruthenium-based catalytic electrode, comprising the following steps:

[0009] Step (1), preparation of bimetallic Co-Ru alloy catalyst particles: The mixed solution of cobalt salt and ruthenium salt is kept at 0°C in an ice bath. The reducing agent solution is slowly added dropwise to the mixed solution to form a dark precipitate. The precipitate is collected by centrifugation, and repeatedly washed and dried with deionized water and ethanol to obtain bimetallic Co-Ru alloy catalyst particles.

[0010] Step (2), preparation of carbon nanotube microelectrodes: multiple hollow quartz capillaries are wound and drawn to form a microelectrode array support. Then, in a protective gas atmosphere, carbon source gas or carbon source mixed gas is passed countercurrently for pyrolysis to deposit carbon in the quartz capillaries, forming a carbon nanotube microelectrode array with a micro-ring cross-section. Then, the carbon nanotube microelectrode array is placed in a scanning electron microscope (SEM) and its tip is processed by focused ion beam (FIB) to obtain a carbon nanotube microelectrode with a disk-shaped plane tip and controlled size.

[0011] Step (3): The bimetallic Co-Ru catalyst particles obtained in step (1) are uniformly dispersed on an ultra-flat gold-coated silicon wafer, and then placed flat on the SEM stage. The carbon nanotube microelectrode in the SEM is vertically aligned with the probe tip, ensuring that its tip disk-shaped plane is collinear with it. The micromanipulator robotic arm inside the SEM is driven by the controller to select and precisely transfer a single Co-Ru alloy particle from the wafer surface through the probe tip to the target position of the disk-shaped tip plane of the carbon nanotube microelectrode processed by FIB, thus obtaining a catalytic electrode on carbon paper with a single bimetallic Co-Ru alloy catalyst particle reconstructed.

[0012] Preferably, in step (1), the cobalt salt and ruthenium salt are chlorides, sulfates, or nitrates of Co and Ru, and / or their hydrates; preferably, the cobalt salt is CoCl2, and the ruthenium salt is RuCl3; in the mixed solution, the molar ratio Co:Ru = (0.1-10):1, preferably, the molar ratio Co:Ru = (0.1-5):1, and the molar concentrations of the CoCl2 solution and the RuCl3 solution are 0.02-0.08 mol / L; The reducing agent is selected from one or more of potassium borohydride (KBH4), sodium borohydride (NaBH4), lithium borohydride (LiBH4), lithium aluminum hydride (LiAlH4), sodium thioborohydride (NaBH2S3), and tri-sec-butyllithium borohydride (LiBH(CH3CH2CH(CH3))3), preferably sodium borohydride (NaBH4). The molar concentration of the reducing agent solution is 0.1-0.5 mol / L, and the solvent of the reducing agent solution is NaOH.

[0013] Preferably, in step (2), the carbon source gas or carbon source mixture is acetylene gas or a mixture of propane and n-butane; the protective gas is selected from one or two of argon and nitrogen, preferably argon; the flow rate of the protective gas is 50-70 mL / min.

[0014] Preferably, in step (3), the micromanipulator is equipped with a robotic arm capable of precise three-dimensional movement along the three axes of x, y and z, which enables fine control.

[0015] Secondly, the present invention also provides an in-situ electrochemically reconstructed cobalt-ruthenium-based catalytic electrode prepared by the preparation method described above, which is a catalytic electrode in which a single particle of a bimetallic Co-Ru alloy catalyst is reconstructed and supported on carbon paper.

[0016] Preferably, the loading rate of the bimetallic Co-Ru alloy catalyst single particles on carbon paper is 0.1-10 mg / cm³. 2 Preferably, it is 0.1-5 mg / cm³. 2 More preferably 0.1-1 mg / cm³ 2 The mass ratio of Co to Ru is (1-10):1.

[0017] Thirdly, the present invention also provides the application of the in-situ electrochemically reconstructed cobalt-ruthenium-based catalytic electrode as described above in the electrocatalytic reduction of nitrates.

[0018] Preferably, a three-electrode system is constructed using the in-situ electrochemically reconstructed cobalt-ruthenium-based catalytic electrode as the working electrode, a platinum mesh as the auxiliary electrode, and an Ag / AgCl / 3M KCl electrode as the reference electrode. This three-electrode system is placed in a nitrate-containing dual-chamber H-type electrolytic cell. The anode and cathode chambers of the H-type electrolytic cell are pretreated with... The 117 membrane was used to separate the nitrates and the electrocatalytic conversion of nitrates to high-value ammonia was carried out using an Autolab electrochemical workstation.

[0019] Preferably, the electrolyte is a NaOH solution with a concentration of 0.06-0.2 mol / L, with 0.1-1 mol / L NaNO3 added, and used after being left to stand overnight at room temperature.

[0020] Preferably, when the applied voltage is 0 to -0.2V, the Faraday efficiency exceeds 90%, and the ammonia yield increases from 7 mg / h. -1 cm -2 Increased to 16mg h -1 cm -2 When the nitrate concentration varies from 0.1 to 1 mol / L, the Faraday efficiency can be maintained above 60% when the applied voltage is 0 to -0.1 V.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] The in-situ electrochemically reconstructed cobalt-ruthenium-based catalytic electrode prepared in this invention is used to load bimetallic Co-Ru alloy catalyst single particles onto carbon nanotube microelectrodes using a combination of SEM-FIB techniques. This Co-Ru-based catalytic electrode is then used for the electrocatalytic reduction of nitrate to ammonia. The obtained Co-Ru-based catalytic electrode can continuously expose more active sites, achieving in-situ electrochemical reconstruction caused by the dissolution of Co during NO3RR. Therefore, it exhibits excellent ammonia Faradaic efficiency at low overpotentials, exceeding 90% with an applied voltage of 0 to -0.2 V, and ammonia yield increasing from 7 mg / h. -1 cm -2 Increased to 16mg h -1 cm -2 . Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the FIB-SEM dual-beam electron microscope involved in this invention.

[0024] Figure 2 This is a schematic diagram of the SEM-FIB process for the in-situ electrochemical reconstruction of the cobalt-ruthenium-based catalytic electrode involved in this invention.

[0025] Figure 3This is a schematic diagram of an example of a carbon nanotube microelectrode array for in-situ electrochemical reconstruction of a cobalt-ruthenium-based catalytic electrode, as per the present invention.

[0026] Figure 4 This is a transmission electron microscope (TEM) image of the in-situ electrochemically reconstructed cobalt-ruthenium-based catalytic electrode involved in this invention.

[0027] Figure 5 Faraday efficiency charts for the Co-Ru alloy catalytic electrode, Co catalytic electrode, and Ru catalytic electrode prepared in Examples 1-3 of this invention.

[0028] Figure 6 Ammonia yield charts for the Co-Ru alloy catalytic electrode, Co catalytic electrode, and Ru catalytic electrode prepared in Examples 1-3 of this invention.

[0029] Figure 7 The chart shows the cycle stability of the in-situ electrochemically reconstructed cobalt-ruthenium-based catalytic electrode prepared in Example 4 of this invention for the Faraday efficiency. Detailed Implementation

[0030] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0031] This invention provides a method for preparing an in-situ electrochemically reconstructed cobalt-ruthenium-based catalytic electrode, comprising the following steps:

[0032] Step (1), preparation of bimetallic Co-Ru alloy catalyst particles: The mixed solution of cobalt salt and ruthenium salt is kept at 0°C in an ice bath. The reducing agent solution is slowly added dropwise to the mixed solution to form a dark precipitate. The precipitate is collected by centrifugation, and repeatedly washed and dried with deionized water and ethanol to obtain bimetallic Co-Ru alloy catalyst particles.

[0033] In this step, the present invention uses a composite material of transition metal Co and noble metal Ru as the electrocatalytic electrode. The embodiments of the present invention have confirmed that using a bimetallic Co-Ru alloy as the electrocatalytic electrode can effectively solve the problem that a single Co-based electrode requires a relatively negative operating potential (-0.5 to -0.95V vs. RHE) to achieve 1-5 mg / h in the electrocatalytic nitrate reduction reaction (NO3RR). -1 cm -2The present invention addresses the challenges of achieving a considerable ammonia yield and high Faradaic efficiency. Compared to single Co-based or single Ru-based electrodes, Co-Ru alloy materials exhibit higher electrocatalytic activity and better selectivity for single products. The mechanism may lie in the fact that transition metal catalysts containing platinum group metals (Ru, Rh, Pd) optimize the reaction kinetics of NO3RR due to their excellent hydrogen adsorption and desorption capabilities. This allows for improved hydrogenation at more positive potentials (≥-0.4V vs. RHE) and a significant reduction in the overpotential of NO3RR. However, another challenge with platinum group metals is the need to better suppress hydrogen evolution reactions, as high hydrogen coverage tends to be kinetically favorable for hydrogen evolution rather than NO3RR ammonia production. Transition metals (e.g., Fe, Co, Ni, Cu, and Zn) can suppress water dissociation and regulate the coverage of adsorbed hydrogen (*H), thereby suppressing undesirable hydrogen evolution reactions. Therefore, this invention precisely controls the appropriate amount of adsorbed hydrogen through a combination of transition metals and noble metals to meet the specific hydrogenation requirements of NO3RR, thereby achieving high ammonia Faradaic efficiency.

[0034] In this step, for example, a reducing agent solution can be slowly added dropwise to a mixed solution of cobalt and ruthenium salts in a round-bottom flask to carry out a reduction precipitation reaction. The cobalt and ruthenium salts used can be chlorides, sulfates, or nitrates of Co and Ru, and / or their hydrates. In this embodiment of the invention, CoCl2 is used as the cobalt salt and RuCl3 as the ruthenium salt to illustrate the technical solution of the invention. In the mixed solution containing cobalt and ruthenium salts, the molar ratio Co:Ru = (0.1-10):1, preferably Co:Ru = (0.1-5):1, and the molar concentrations of the CoCl2 solution and the RuCl3 solution are, for example, both 0.02-0.08 mol / L. The reducing agent used can be potassium borohydride (KBH4), sodium borohydride (NaBH4), lithium borohydride (LiBH4), lithium aluminum hydride (LiAlH4), sodium thioborohydride (NaBH2S3), or tri-sec-butyllithium borohydride (LiBH(CH3CH2CH(CH3))3). In this embodiment of the invention, sodium borohydride (NaBH4) is used as an example to illustrate the technical solution of the invention. In the reducing agent solution, the molar concentration of the reducing agent solution is 0.1-0.5 mol / L, and the solvent of the reducing agent solution is NaOH.

[0035] In this step, the reduction precipitation reaction is carried out by placing the reaction system in an ice bath at around 0°C. After reacting for 20-40 minutes, a dark precipitate is formed. These precipitates are then collected by centrifugation, repeatedly washed with deionized water and ethanol, and dried to finally obtain bimetallic Co-Ru alloy catalyst particles.

[0036] Step (2), preparation of carbon nanotube microelectrodes: multiple hollow quartz capillaries are wound and drawn to form a microelectrode array support. Then, in a protective gas atmosphere, carbon source gas or carbon source mixed gas is passed countercurrently for pyrolysis to deposit carbon in the quartz capillaries, forming a carbon nanotube microelectrode array with a micro-ring cross-section. Then, the carbon nanotube microelectrode array is placed in a scanning electron microscope (SEM) and its tip is processed by focused ion beam (FIB) to obtain a carbon nanotube microelectrode with a disk-shaped plane tip and controlled size.

[0037] In this step, the carbon source gas or carbon source gas mixture used can be acetylene gas or a mixture of propane and n-butane. The protective gas used can be argon and / or nitrogen, preferably argon; the flow rate of the protective gas is 50-70 mL / min, for example, 60 mL / min.

[0038] In this step, multiple hollow quartz capillaries are wound and drawn to form a microelectrode array support. Then, in a protective gas atmosphere such as argon, acetylene gas or a mixture of propane and n-butane is passed countercurrently for pyrolysis, depositing carbon within the quartz capillaries to form a microelectrode array support. Figure 2 The image shows a single carbon nanotube microelectrode array with a cross-section resembling a microring and a diameter of approximately 10-50 μm. This carbon nanotube microelectrode array is then placed in a... Figure 1 In the FIB-SEM dual-beam electron microscope shown, the tip is processed using the focused ion beam (FIB) to obtain the following result: Figure 2 The carbon nanoelectrode shown has a disc-shaped planar tip and controlled dimensions.

[0039] Typically, in a FIB-SEM dual-beam electron microscope, there is a certain angle between the ion beam of the FIB and the electron beam of the SEM. The electron beam of the SEM is perpendicular to the sample stage. During the FIB sample processing, the sample stage needs to be rotated by a certain angle to make the sample stage perpendicular to the ion beam of the FIB.

[0040] Step (3): The bimetallic Co-Ru catalyst particles obtained in step (1) are uniformly dispersed on an ultra-flat gold-coated silicon wafer, and then placed flat on an SEM stage. The carbon nanotube microelectrode in the SEM is vertically aligned with the probe tip, ensuring that its tip disk-shaped plane is collinear with it. The micromanipulator robotic arm inside the SEM (such as...) is driven by a controller. Figure 2 As shown, a single Co-Ru alloy particle is selected from the wafer surface and precisely transferred through the probe tip to the target position on the disk-shaped tip plane of the carbon nanoelectrode processed by FIB, thereby obtaining a bimetallic Co-Ru alloy catalyst single particle reconstructed and loaded on carbon paper as a catalytic electrode.

[0041] In this step, the micromanipulator is equipped with a robotic arm capable of precise three-dimensional movement along the x, y, and z axes, enabling fine control.

[0042] The present invention also provides an in-situ electrochemically reconstructed cobalt-ruthenium-based catalytic electrode prepared by the preparation method described above.

[0043] According to the preparation method of the present invention, a bimetallic Co-Ru alloy catalyst single particle reconstructed and supported on carbon paper is prepared to form a catalytic electrode as described above. Figure 3 Taking the 15 carbon nanotube microelectrode array shown as an example, bimetallic Co-Ru alloy catalyst single particles were loaded on 8 of the carbon nanotube microelectrodes using FIB-SEM technology.

[0044] Using the preparation method of this invention, the loading rate of bimetallic Co-Ru alloy catalyst single particles supported on carbon paper is 0.1-10 mg / cm³. 2 Preferably, it is 0.1-5 mg / cm³. 2 More preferably 0.1-1 mg / cm³ 2 (e.g., 0.2 mg / cm) 2 0.3 mg / cm 2 0.4 mg / cm 2 0.5 mg / cm 2 0.6 mg / cm 2 0.7 mg / cm 2 0.8 mg / cm 2 0.9 mg / cm 2 The mass ratio of Co to Ru is (1-10):1 (e.g., 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, preferably 5:1).

[0045] Figure 4 Transmission electron microscopy (TEM) images of the in-situ electrochemically reconstructed cobalt-ruthenium-based catalytic electrode obtained by the preparation method of the present invention are presented.

[0046] The present invention also provides the application of the in-situ electrochemically reconstructed cobalt-ruthenium-based catalytic electrode as described above in the electrocatalytic reduction of nitrates.

[0047] Furthermore, the present invention also provides an electrochemical system for the electrocatalytic reduction of nitrates. In this electrochemical system, the in-situ electrochemically reconstructed cobalt-ruthenium-based catalytic electrode of the present invention is used as the working electrode, a platinum mesh is used as the auxiliary electrode, and an Ag / AgCl / 3M KCl electrode is used as the reference electrode, forming a three-electrode system. This three-electrode system is placed in a nitrate-containing dual-chamber H-type electrolytic cell, wherein the anode and cathode chambers of the H-type electrolytic cell are pretreated with... The 117 membrane was used to separate the nitrates and the electrocatalytic conversion of nitrates to high-value ammonia was carried out using an Autolab electrochemical workstation.

[0048] In the electrochemical system for electrocatalytic nitrate reduction provided by this invention, the electrolyte is a NaOH solution with a concentration of 0.06-0.2 mol / L, with 0.1-1 mol / L NaNO3 added, and used after being left overnight at room temperature.

[0049] As demonstrated by the embodiments of the present invention, the electrochemical system for electrocatalytic nitrate reduction using the in-situ electrochemical reconstruction of the cobalt-ruthenium-based catalytic electrode of the present invention, for example using a electrode loaded with 0.5 mg / cm³, is effective. 2 The bimetallic Co-Ru alloy catalyst has a single particle size of 0.25 cm. 2 Geometric area carbon paper can achieve a Faraday efficiency exceeding 90% with an applied voltage of 0 to -0.2V, and an ammonia yield increasing from 7 mg / h. -1 cm -2 Increased to 16mg h -1 cm -2 When the nitrate concentration varies from 0.1 to 1 mol / L, the Faraday efficiency can be maintained above 60% when the applied voltage is 0 to -0.1 V.

[0050] The present invention provides an in-situ electrochemical reconstruction of a cobalt-ruthenium-based catalytic electrode and an electrochemical system for electrocatalytic nitrate reduction. By using a combination of SEM-FIB technology, a single particle of a bimetallic Co-Ru alloy catalyst is loaded onto a carbon nanotube microelectrode to obtain a Co-Ru-based catalytic electrode for the electrochemical reaction of nitrate reduction to ammonia. The obtained Co-Ru-based catalytic electrode can continuously expose more active sites, realizing in-situ electrochemical reconstruction caused by the dissolution of Co during NO3RR. Therefore, it exhibits excellent ammonia Faraday efficiency at low overpotentials.

[0051] The present invention will be further illustrated below with reference to specific embodiments. The purpose of these embodiments is to provide a better understanding of the invention and to demonstrate its essential characteristics. Therefore, the examples given should not be considered as limitations on the scope of protection of the present invention. It is also specifically noted that, unless otherwise specified, the specific experimental methods and equipment involved in the embodiments are conventional methods or implemented according to the conditions recommended in the manufacturer's instructions, and the reagents involved are all commercially available unless otherwise specified.

[0052] Example 1:

[0053] A method for preparing an in-situ electrochemically reconstructed cobalt-ruthenium-based catalytic electrode includes the following steps:

[0054] Step S1: In a round-bottom flask, 20 mL of a mixed solution of 0.04 mol / L CoCl2 and 20 mL of 0.05 mol / L RuCl3 was rinsed with argon gas at 60 mL / min and kept at 0 °C in an ice bath; 20 mL of 0.3 mol / L NaBH4 solution (with 0.1 mol / L NaOH as solvent) was slowly added dropwise to the mixed solution, and a dark precipitate was immediately observed to form; after 30 minutes, the precipitate was collected by centrifugation, washed repeatedly with deionized water and ethanol, and then dried at 70 °C to obtain bimetallic Co-Ru catalyst particles;

[0055] Step S2: Multiple hollow quartz capillaries are wound and drawn to form a microelectrode array support. Then, a mixture of propane and n-butane is passed countercurrently in argon gas for pyrolysis, depositing carbon inside the quartz capillaries to form a carbon nanotube microelectrode array with a micro-ring cross-section. The carbon nanotube microelectrode array is then placed in a scanning electron microscope (SEM) and its tip is processed by focused ion beam (FIB) to obtain a carbon nanotube microelectrode with a disk-shaped plane tip and controlled size.

[0056] Step S3: The bimetallic Co-Ru catalyst particles obtained in step (1) are uniformly dispersed on an ultra-flat gold-coated silicon wafer, and then placed flat on the SEM stage. The carbon nanotube microelectrode in the SEM is vertically aligned with the probe tip, ensuring that its tip disk-shaped plane is collinear with it. The micromanipulator robotic arm inside the SEM is driven by the controller to select and precisely transfer a single Co-Ru alloy particle from the wafer surface through the probe tip to the target position of the disk-shaped tip plane of the carbon nanotube microelectrode processed by FIB, thus obtaining a catalytic electrode on carbon paper with a single bimetallic Co-Ru alloy catalyst particle reconstructed.

[0057] Transmission electron microscopy (TEM) image of the prepared in-situ electrochemically reconstructed cobalt-ruthenium-based catalytic electrode is shown below. Figure 4 As shown.

[0058] Electrochemical tests were conducted in an H-type electrolytic cell using a three-electrode configuration and an Autolab electrochemical workstation. The anode and cathode chambers of the H-type electrolytic cell were pretreated with... A 117 membrane separates the electrodes. The working electrode is the in-situ electrochemically reconstructed cobalt-ruthenium-based catalytic electrode prepared in this embodiment (loaded with 0.5 mg / cm³). 2 The bimetallic Co-Ru alloy catalyst has a single particle size of 0.25 cm. 2(Geometric area carbon paper). The reference electrode was a dual-compartment Ag / AgCl / 3M KCl electrode, and the auxiliary electrode was a Pt mesh. The electrolyte was a 0.1M NaOH solution with 0.1M NaNO3 added, incubated overnight at room temperature before use. Potentiostatic tests were performed for 1 hour, and the electrolyte was collected and refrigerated for analysis. Further 15 cycles of 2-hour potentiostatic tests (vs. RHE-0.1V) were conducted to evaluate the long-term performance of the Co-Ru alloy catalyst, with fresh electrolyte replaced after each test.

[0059] Example 2:

[0060] The preparation of electrode materials and the method for catalytic reduction of nitrates are as in Example 1, except that in step S1, only 20 mL of 0.04 mol / L CoCl2 is used to obtain a metal Co catalyst particle.

[0061] Example 3:

[0062] The preparation of electrode materials and the method for catalytic reduction of nitrates are as in Example 1, except that in step S1, only 20 mL of RuCl3 with a concentration of 0.05 mol / L is used to obtain a metal Ru catalyst particle.

[0063] Figure 5 and Figure 6 The Faraday efficiency and ammonia yield graphs of the Co-Ru alloy catalytic electrode, Co catalytic electrode, and Ru catalytic electrode prepared in Examples 1-3 of this invention are given respectively. Figure 5 and Figure 6 As can be seen, compared with Co and Ru catalytic electrodes, the Co-Ru alloy catalytic electrode prepared in this invention has higher Faradaic efficiency and ammonia yield. At an applied voltage of 0 to -0.2 V, the Faradaic efficiency exceeds 90%, and the ammonia yield increases from 7 mg / h. -1 cm -2 Increased to 16mg h -1 cm -2 .

[0064] Example 4:

[0065] The preparation of electrode materials and the method of catalytic reduction of nitrate are the same as in Example 1, except that the nitrate concentration of the Co-Ru alloy catalytic electrode prepared in Example 1 is from 0.1 to 1 M when performing NO3RR.

[0066] Figure 7 A graph showing the Faraday efficiency of the Co-Ru alloy catalytic electrode prepared in Example 4 of this invention during NO3RR at nitrate concentrations ranging from 0.1 to 1 M is provided. Figure 7It can be seen that the Co-Ru alloy catalytic electrode prepared in this invention exhibits high Faraday efficiency when performing NO3RR at nitrate concentrations ranging from 0.1 to 1 M, indicating that the Co-Ru alloy catalytic electrode prepared in this invention has high cycle stability in terms of Faraday efficiency.

[0067] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an in-situ electrochemically reconstructed cobalt-ruthenium-based catalytic electrode, characterized in that, Includes the following steps: Step (1), preparation of bimetallic Co-Ru alloy catalyst particles: The mixed solution of cobalt salt and ruthenium salt is kept at 0°C in an ice bath. The reducing agent solution is slowly added dropwise to the mixed solution to form a dark precipitate. The precipitate is collected by centrifugation, and repeatedly washed and dried with deionized water and ethanol to obtain bimetallic Co-Ru alloy catalyst particles; wherein, in the mixed solution of cobalt salt and ruthenium salt, the molar ratio Co:Ru = (0.1-10):1; Step (2), preparation of carbon nanotube microelectrodes: multiple hollow quartz capillaries are wound and drawn to form a microelectrode array support. Then, in a protective gas atmosphere, carbon source gas or carbon source mixed gas is passed countercurrently for pyrolysis to deposit carbon in the quartz capillaries, forming a carbon nanotube microelectrode array with a micro-ring cross-section. Then, the carbon nanotube microelectrode array is placed in a scanning electron microscope (SEM) and its tip is processed by focused ion beam (FIB) to obtain a carbon nanotube microelectrode with a disk-shaped plane tip and controlled size. Step (3): The bimetallic Co-Ru catalyst particles obtained in step (1) are uniformly dispersed on an ultra-flat gold-coated silicon wafer, and then placed flat on the SEM stage. The carbon nanotube microelectrode in the SEM is vertically aligned with the probe tip, ensuring that its tip disk-shaped plane is collinear with it. The micromanipulator robotic arm inside the SEM is driven by the controller to select and precisely transfer a single Co-Ru alloy particle from the wafer surface through the probe tip to the target position of the disk-shaped tip plane of the carbon nanotube microelectrode processed by FIB, thus obtaining a catalytic electrode on carbon paper with a single bimetallic Co-Ru alloy catalyst particle reconstructed.

2. The preparation method according to claim 1, characterized in that, In step (1), the cobalt salt and ruthenium salt are chlorides, sulfates or nitrates of Co and Ru, and / or their hydrates; in the mixed solution, the molar concentration of the CoCl2 solution and the RuCl3 solution is 0.02-0.08 mol / L; the reducing agent is selected from one or more of potassium borohydride (KBH4), sodium borohydride (NaBH4), lithium borohydride (LiBH4), lithium aluminum hydride (LiAlH4), sodium thioborohydride (NaBH2S3), and trisec-butyl borohydride (LiBH(CH3CH2CH(CH3))3), the molar concentration of the reducing agent solution is 0.1-0.5 mol / L, and the solvent of the reducing agent solution is NaOH.

3. The preparation method according to claim 1, characterized in that, In step (2), the carbon source gas or carbon source mixture is acetylene gas or a mixture of propane and n-butane; the protective gas is selected from one or two of argon and nitrogen; the flow rate of the protective gas is 50-70 mL / min.

4. The preparation method according to claim 1, characterized in that, In step (3), the micromanipulator is equipped with a robotic arm that can make precise three-dimensional movements along the three axes of x, y and z, which can achieve fine control.

5. An in-situ electrochemically reconstructed cobalt-ruthenium-based catalytic electrode prepared by the preparation method according to any one of claims 1-4, characterized in that, A catalytic electrode supported on carbon paper was reconstructed from a single particle of a bimetallic Co-Ru alloy catalyst.

6. The in-situ electrochemical reconstruction of the cobalt-ruthenium-based catalytic electrode according to claim 5, characterized in that, The loading rate of bimetallic Co-Ru alloy catalyst single particles on carbon paper is 0.1-10 mg / cm³. 2 The mass ratio of Co to Ru is (1-10):

1.

7. The application of an in-situ electrochemically reconstructed cobalt-ruthenium-based catalytic electrode as described in claim 5 or 6 in the electrocatalytic reduction of nitrates.

8. The application according to claim 7, characterized in that, Using the aforementioned in-situ electrochemically reconstructed cobalt-ruthenium-based catalytic electrode as the working electrode, a platinum mesh as the auxiliary electrode, and an Ag / AgCl / 3M KCl electrode as the reference electrode, a three-electrode system was constructed. This three-electrode system was placed in a nitrate-containing dual-chamber H-type electrolytic cell, with the anode and cathode chambers of the H-type electrolytic cell separated by a pretreated Nafion® 117 membrane. The electrocatalytic conversion of nitrate to high-value-added ammonia was carried out using an Autolab electrochemical workstation.

9. The application according to claim 8, characterized in that, The electrolyte is a 0.06-0.2 mol / L NaOH solution with 0.1-1 mol / L NaNO3 added, and used after being left to stand overnight at room temperature.

10. The application according to claim 8 or 9, characterized in that, With an applied voltage of 0 to -0.2V, the Faraday efficiency exceeds 90%, and the ammonia yield increases from 7 mg / h. -1 cm -2 Increased to 16 mg h -1 cm -2 When the nitrate concentration varies from 0.1 to 1 mol / L, the Faraday efficiency can be maintained above 60% when the applied voltage is 0 to -0.1 V.

Images