Ruthenium-copper alloy-loaded carbon-nitrogen ordered porous structure electrocatalyst as well as preparation and application thereof

Abstract

The invention discloses a ruthenium-copper alloy loaded carbon-nitrogen ordered porous structure electrocatalyst as well as preparation and application thereof. According to the invention, a polystyrene template etching method is adopted to thermally reduce and load the RuCu alloy, and the RuCu alloy load N-C ordered porous electrode material catalyst is obtained. According to the obtained ruthenium-copper alloy loaded carbon-nitrogen ordered porous structure electrocatalyst, a hydrogen substance (H *) overflows from Ru to a nitrogen-carbon doped ordered porous structure carrier, is well anchored on N-C, and is subjected to N-H combination with * NO captured by Cu. Besides, due to the porous structure, NO can be enriched, the electrochemical active area is high, most important parameters required by practical application can be met, the material has good catalytic performance when being used as an electrocatalyst for nitric oxide electroreduction, Faraday efficiency can be achieved, and nitric oxide can be stably catalyzed to generate ammonia.

Description

Technical Field

[0001] This invention belongs to the field of metal material preparation and application technology, and relates to a carbon-nitrogen ordered porous electrocatalyst supported on ruthenium-copper alloy and its preparation and application. Background Technology

[0002] NO is one of the major air pollutants, and its accumulation in the atmosphere severely damages the ecological environment. Traditional selective catalytic reduction (SCR) technology can effectively convert NO into harmless N2, but it requires the consumption of NH3 or H2. Furthermore, ammonia is considered an essential chemical in agriculture and is also an emerging hydrogen storage carrier. Its industrial synthesis relies on the energy-intensive and carbon-emitting Haber-Bosch process. In conclusion, the electroreduction of NO, a pollutant with a low fracture energy, to ammonia (NO→NH3) is a win-win approach for environmental remediation and pollutant remediation.

[0003] Copper-based catalysts have been reported as highly efficient cathode electrocatalysts for the NO reduction reaction (NORR), and experiments have demonstrated that at −0.9 V (vs. RHE), the yield of NH3 is 517.1 μmol cm⁻¹ compared to that using a Cu foam catalyst. -1 h-1, FE was 93.5%. Studies have shown that alloying copper with heteroatoms can regulate the electronic states of the alloy, thereby further improving the catalytic activity of the alloy catalyst. Copper and iron atoms are embedded in nitrogen-doped carbon nanosheets (O-Fe-N6-Cu) in a dual-site manner, forming atomically dispersed bimetallic active centers, with an FE of 90% in neutral electrolyte. The expansion strain interface formed by Co atoms embedded in the Cu lattice optimizes NO adsorption and activation; under low NO concentration (1% v / v) conditions, the NH3 yield is 627.20 μg h. -1 cm -1 The Faraday efficiency was 76.54%; these technologies have low Faraday efficiency and yield, and poor selectivity. Summary of the Invention

[0004] The first objective of this invention is to address the shortcomings of existing technologies by providing a method for preparing an electrocatalyst made of ruthenium-copper alloy supported carbon-nitrogen ordered porous electrode material. The electrocatalyst prepared by this method can enrich NO, has a high electrochemical active area, and can meet most of the important parameters required for practical applications. As an electrocatalyst, it has excellent catalytic performance for the electroreduction of nitric oxide.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a carbon-nitrogen ordered porous electrocatalyst supported on a ruthenium-copper alloy includes the following steps: Step S1: Synthesize polystyrene microspheres via emulsion method; Step S2: Immerse polystyrene microspheres in a precursor solution and dry them to obtain a porous precursor; mix methanol and ammonia to impregnate the porous precursor, and after filtration, drying and annealing, obtain a carbon-nitrogen ordered porous electrode material. Step S3: Add methanol, RuCl3·H2O and Cu(NO3)2·3H2O to the carbon-nitrogen ordered porous electrode material, disperse it ultrasonically, and then calcine it under a reducing atmosphere to obtain the carbon-nitrogen ordered porous structure (Ru:Cu is 1:9) electrocatalyst supported on ruthenium copper alloy.

[0006] As a preferred option, step S1 specifically involves: Styrene was pretreated with an alkaline solution, then polyvinylpyrrolidone (PVP) and water were added to remove oxygen. K2S2O8 was then added and stirred to carry out the styrene polymerization reaction. After cooling, polystyrene microspheres were obtained.

[0007] Preferably, the precursor solution in step S2 is prepared by dissolving Zn(NO3)2·6H2O and 2-methylimidazole in methanol solution at a molar ratio of (1-2):3 to obtain the precursor solution.

[0008] Preferably, the volume ratio of methanol to ammonia in step S2 is 1:(1-1.5), and more preferably 1:1.

[0009] Preferably, the annealing temperature in step S2 is 600-650 ℃, the annealing environment is argon atmosphere, and the annealing time is 2-4 h.

[0010] Preferably, the molar ratio of RuCl3·H2O to Cu(NO3)2·3H2O in step S3 is 1:(8-9), and more preferably 1:9.

[0011] Preferably, the reducing atmosphere in step S3 is hydrogen.

[0012] Preferably, the calcination temperature in step S3 is 300-350 ℃, and the calcination time is 2-4 h.

[0013] The second objective of this invention is to provide a carbon-nitrogen ordered porous electrocatalyst supported on a ruthenium-copper alloy, which is prepared using the above method.

[0014] A third objective of this invention is to provide the application of the above-mentioned carbon-nitrogen ordered porous electrocatalyst supported on ruthenium-copper alloy in the electroreduction of nitric oxide to ammonia.

[0015] Preferably, the application employs a three-electrode system, using carbon paper coated with a ruthenium-copper alloy and supported on a carbon-nitrogen ordered porous electrode material electrocatalyst as the working electrode, a platinum mesh as the counter electrode, and Ag / AgCl as the reference electrode. A closed electrolytic cell is used, with 0.1 M sodium sulfate as the electrolyte. Carbon dioxide is first bubbled continuously for 20-30 minutes to saturate the electrolyte, followed by the introduction of nitric oxide, and a voltage of -0.4 to -0.8 V vs. RHE is applied.

[0016] Compared with the prior art, the beneficial effects of the present invention are at least as follows: This invention employs a hydrogen overflow strategy, introducing highly reactive ruthenium (Ru) to allow hydrogen (H*) to overflow from Ru onto a nitrogen-carbon-doped, ordered porous support, where it is well anchored to NC and binds with *NO* captured by Cu to form NH3. Furthermore, the ordered porous curved structure used in this invention enhances the electric field, enriching NO within the pores and effectively addressing the poor mass transfer problem. Additionally, the curved structure has a larger specific surface area, providing more active sites for hydrogen overflow. The combination of these two factors further promotes the formation of the NH3 intermediate *NHO.

[0017] In summary, this invention achieves the effective binding of NH through the pathway of "bimetallic alloy synergistic adsorption - macroporous curvature diffusion - hydrogen overflow", realizing the capture of low-concentration NO. Under low-concentration NO conditions, it can stably catalyze the conversion of nitric oxide to ammonia. The micron-sized materials used are easy to prepare, and the overall method is low-cost and environmentally friendly. Attached Figure Description

[0018] Figure 1 This is a scanning electron microscope (SEM) image of the polyethylene microspheres obtained in Example 1 of the present invention.

[0019] Figure 2 This is a transmission electron microscope (TEM) image of the polyethylene microspheres obtained in Example 1 of the present invention.

[0020] Figure 3 This is the X-ray powder crystal diffraction (XRD) pattern of the electrocatalyst with NC ordered porous electrode material obtained in Example 2 of the present invention.

[0021] Figure 4 This is a scanning electron microscope (SEM) image of the electrocatalyst with NC ordered porous electrode material obtained in Example 2 of the present invention.

[0022] Figure 5 These are scanning electron microscope (SEM) images of the ruthenium copper alloy supported carbon-nitrogen ordered porous electrode material electrocatalyst obtained in Example 3 of the present invention, wherein (a) and (b) are scanning electron microscope (SEM) images at 200 nm and 100 nm sizes, respectively.

[0023] Figure 6 In the figures (a) and (b), respectively, are the linear sweep voltammetry (LSV) curves and Faraday efficiency (FE) plots of the carbon-nitrogen ordered porous electrocatalyst supported on ruthenium copper alloy obtained in this invention.

[0024] Figure 7 This is a persistent cycling test diagram of the carbon-nitrogen ordered porous electrocatalyst supported on ruthenium-copper alloy obtained in this invention for the electroreduction of nitric oxide. Detailed Implementation

[0025] As mentioned above, in view of the 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, which is mainly based on at least the following: This invention employs a ruthenium-copper alloy-supported carbon-nitrogen ordered porous electrode material for the coupled electrocatalytic conversion of nitrogen oxides. The invention utilizes a polystyrene template etching method to thermally reduce the supported RuCu alloy, obtaining the ruthenium-copper alloy-supported carbon-nitrogen ordered porous electrode material catalyst. Due to its porous structure, it can enrich NO and has a high electrochemical active surface area, sufficient to meet most of the important parameters required for practical applications. As an electrocatalyst for the electroreduction of nitric oxide, it exhibits excellent catalytic performance, achieving high atom utilization and precisely catalyzing the conversion of nitric oxide to ammonia.

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0027] In a first aspect, a method for preparing a carbon-nitrogen ordered porous electrocatalyst supported on a ruthenium-copper alloy is provided, specifically including the following steps: Step S1: Synthesis of polystyrene microspheres via emulsion method, specifically: First, pretreat 60-80 mL of styrene with 10-30 mL of NaOH solution and deionized water to remove stabilizers. Then, add the pretreated styrene to a 1 L round-bottom three-necked flask containing 2.5-4 g of PVP and 500 mL of water. After bubbling with nitrogen for 15 minutes, add 1 g of K2S2O8 to 50 mL of water and stir magnetically at 70 °C for 30-60 minutes. Quickly add this mixture to the three-necked flask to begin the styrene polymerization reaction. Continue stirring at this temperature for 12-24 hours and then cool to obtain an emulsion product of 330 nm monodisperse colloidal polystyrene microspheres (Polystyrene, PS). The product is then centrifuged and washed three times before use. Step S2: The polystyrene microspheres are assembled in an ordered manner, and then soaked and calcined to form an ordered macroporous structure, specifically as follows: First, Zn(NO3)2·6H2O and 2-methylimidazole were dissolved in methanol solution at a molar ratio of 1:3-2:3. Then, the PS monolithic template was immersed in the above solution for 45-90 min, and the impregnated composite monomer was transferred to a beaker and dried at 60 °C for several hours. At room temperature, the precursor was impregnated with a CH3OH / NH3·H2O (1:1-1.5 v / v) mixture. The obtained sample was filtered, dried in air, and then thermally annealed at 600-650 °C in an argon atmosphere for 2-4 hours to obtain a carbon-nitrogen ordered porous electrode material. Step S3: The structure obtained in step S2 is subjected to loading of RuCu alloy using a solution thermal reduction method; specifically: 10 mL of methanol solution, RuCl3·H2O, and Cu(NO3)2·3H2O in a metal molar ratio of 1:9 were added to the prepared carbon-nitrogen ordered porous electrode material, and the mixture was ultrasonically dispersed for 15-30 minutes. The mixture was then calcined under hydrogen at 300-350 °C for 2-4 hours to obtain the carbon-nitrogen ordered porous electrocatalyst supported on ruthenium-copper alloy.

[0028] Secondly, a carbon-nitrogen ordered porous electrocatalyst supported on a ruthenium-copper alloy is provided, which is prepared using the above method.

[0029] Thirdly, this invention provides the application of a carbon-nitrogen ordered porous electrocatalyst supported on ruthenium-copper alloy in the electroreduction of nitric oxide to ammonia.

[0030] The specific application employs a three-electrode system, using carbon paper coated with a carbon-nitrogen ordered porous electrocatalyst supported on ruthenium-copper alloy as the working electrode, a platinum mesh as the counter electrode, and Ag / AgCl as the reference electrode. A closed electrolytic cell is used, with 0.05-0.1 M sodium sulfate as the electrolyte. Nitric oxide is first bubbled continuously for 20-30 minutes to saturate the electrolyte, and then nitric oxide is introduced, with a voltage of -0.4 to -0.8 V vs. RHE applied.

[0031] Furthermore, it should be noted that the specific embodiments of the present invention described below do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

[0032] Example 1: Synthesis of polystyrene microspheres In a typical synthesis process, 60 mL of styrene is first pretreated with 10 mL of NaOH solution and deionized water to remove stabilizers. The pretreated styrene is then added to a 1 L round-bottom three-necked flask containing 2.5 g of PVP and 500 mL of water. After bubbling with nitrogen for 15 minutes, 1 g of K₂S₂O₈ is added to 50 mL of water, and the mixture is magnetically stirred at 70 °C for 30–60 minutes. This mixture is then rapidly added to the three-necked flask to initiate the styrene polymerization reaction. Stirring is continued at this temperature for 12–24 hours, followed by cooling. The resulting emulsion product is 330 nm monodisperse colloidal polystyrene microspheres (Polystyrene, PS). The product is centrifuged and washed three times before use.

[0033] The size, morphology, and microstructure of the obtained polystyrene microspheres were analyzed using SEM and TEM, such as... Figure 1 , Figure 2 As shown.

[0034] Example 2: Synthesis of carbon-nitrogen ordered porous electrode material electrocatalyst Zn(NO3)2·6H2O and 2-methylimidazole were first dissolved in methanol at a molar ratio of 1:3 to 2:3. The PS monolithic template was then immersed in the solution for 45-90 min. The impregnated composite monomer was then transferred to a beaker and dried at 60 °C for 12 h. The precursor was then impregnated with a CH3OH / NH3·H2O (1:1 v / v) mixture at room temperature. The resulting sample was filtered, dried in air, and then thermally annealed at 600 °C under argon for 2 h to obtain a carbon-nitrogen ordered porous electrode material.

[0035] The structure of the carbon-nitrogen ordered porous electrode material catalyst was analyzed by XRD, such as... Figure 3 As shown; The size, morphology, and microstructure of the carbon-nitrogen ordered porous electrode material catalyst were analyzed using SEM, such as... Figure 4 As shown; Example 3: Synthesis of a carbon-nitrogen ordered porous electrocatalyst supported on ruthenium-copper alloy The ruthenium-copper alloy-supported carbon-nitrogen ordered porous electrode material was prepared by thermal decomposition and reduction. 10 mL of methanol solution, RuCl3·H2O, and Cu(NO3)2·3H2O were added to the prepared carbon-nitrogen ordered porous electrode material, with a Ru:Cu molar ratio of 1:9, and the mixture was ultrasonically dispersed for 15-30 minutes. The material was then calcined at 300 °C under hydrogen for 2 hours. The final ruthenium-copper alloy-supported carbon-nitrogen ordered porous electrode material electrocatalyst exhibited the following size, morphology, and microstructure: [Figure showing details]. Figure 5 As shown.

[0036] Application Example 1: Application of carbon-nitrogen ordered porous electrocatalyst supported on ruthenium-copper alloy in the electroreduction of nitric oxide The carbon-nitrogen ordered porous electrocatalyst supported on ruthenium-copper alloy prepared in Example 3 above was applied to the electroreduction of nitric oxide: Electroreduction of nitric oxide was performed at room temperature using a standard three-electrode system. The electrochemical tests used a closed H-type electrolytic cell, with the two electrode chambers separated by a proton exchange membrane, allowing only protons to pass through. During the tests, a solution of 1 mg / cm³ was applied, similar to that used in Example 1. 2 The catalyst was used with carbon paper as the working electrode, a platinum mesh as the counter electrode, and Ag / AgCl as the reference electrode. The electrolyte was 0.05-0.1 M sodium sulfate. In the nitric oxide electroreduction experiment, nitric oxide was first saturated by bubbling for 20 min, followed by cyclic voltammetry activation, and then LSV testing at a scan rate of 5 mV / s. Subsequently, nitric oxide electroreduction tests were performed at different potentials (-0.4 to -0.8 V vs. RHE) to determine the reduction products and their Faradaic efficiency. The gaseous reduction products were detected by ultraviolet colorimetry.

[0037] The Faraday efficiency of the electroreduction products of nitric oxide is calculated using the following formula: Where F is the Faraday constant (96485 C mol) -1 ), It is the NH4 produced + The concentration is V, which is the volume of the cathode electrolyte (25 mL), t is the reduction time (1 hour), and Q is the total charge passing through the electrode.

[0038] The results are as follows Figure 6 , Figure 7 As shown, the Faraday efficiency of ammonia in the -0.4 to -0.8 V vs. RHE range reaches over 90%, and it can still maintain high performance after 100 h of continuous electrolysis, indicating that the ruthenium-copper alloy supported carbon-nitrogen ordered porous electrode material electrocatalyst has excellent catalytic efficiency in the electroreduction of nitric oxide.

[0039] The specific embodiments described above further illustrate the technical problems, technical solutions, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a carbon-nitrogen ordered porous electrocatalyst supported on a ruthenium-copper alloy, characterized in that, The preparation method includes the following steps: Step S1: Synthesize polystyrene microspheres via emulsion method; Step S2: Immerse polystyrene microspheres in a precursor solution and dry them to obtain a porous precursor; mix methanol and ammonia to impregnate the porous precursor, and after filtration, drying and annealing, obtain a carbon-nitrogen ordered porous electrode material. Step S3: Add methanol, RuCl3·H2O and Cu(NO3)2·3H2O to the carbon-nitrogen ordered porous electrode material, disperse it ultrasonically, and then calcine it under a reducing atmosphere to obtain the carbon-nitrogen ordered porous electrocatalyst supported on ruthenium copper alloy.

2. The preparation method according to claim 1, characterized in that, Step S1 is as follows: Styrene was pretreated with an alkaline solution, then polyvinylpyrrolidone and water were added to remove oxygen. K2S2O8 was then added and stirred to carry out the styrene polymerization reaction. After cooling, polystyrene microspheres were obtained.

3. The preparation method according to claim 1, characterized in that, The precursor solution in step S2 is prepared by dissolving Zn(NO3)2·6H2O and 2-methylimidazole in methanol solution at a molar ratio of (1-2):3 to obtain the precursor solution.

4. The preparation method according to claim 1, characterized in that, In step S2, the volume ratio of methanol to ammonia is 1:(1-1.5).

5. The preparation method according to claim 1, characterized in that, The annealing temperature in step S2 is 600-650℃, the annealing environment is argon atmosphere, and the annealing time is 2-4 h.

6. The preparation method according to claim 1, characterized in that, In step S3, the molar ratio of RuCl3·H2O to Cu(NO3)2·3H2O is 1:(8-9).

7. The preparation method according to claim 1, characterized in that, The reducing atmosphere described in step S3 is hydrogen.

8. A carbon-nitrogen ordered porous electrocatalyst supported on ruthenium-copper alloy, prepared by the method described in any one of claims 1-7.

9. The application of the carbon-nitrogen ordered porous electrocatalyst supported on ruthenium-copper alloy as described in claim 8 in the electroreduction of nitric oxide to ammonia.

10. The application according to claim 8, characterized in that, The specific application is as follows: a three-electrode system is adopted, with carbon paper coated with the carbon-nitrogen ordered porous structure electrocatalyst supported on ruthenium-copper alloy as the working electrode, a platinum mesh as the counter electrode, Ag / AgCl as the reference electrode, a closed electrolytic cell, and sodium sulfate solution as the electrolyte.

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