A ruthenium complex modified nickel-based metal organic framework material, a preparation method thereof and application thereof in electrocatalytic reduction of nitrate to produce ammonia
By introducing ruthenium complexes into nickel-based metal framework materials, altering the local electron density and optimizing the catalytic center, a Ni-Ru synergistic catalytic pathway was constructed, solving the kinetic and selectivity problems in the electrocatalytic nitrate reduction process and achieving high ammonia yield and selectivity.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- LIAONING UNIVERSITY
- Filing Date
- 2026-05-14
- Publication Date
- 2026-06-26
AI Technical Summary
In existing technologies, the electrocatalytic reduction of nitrate to ammonia is constrained by factors such as slow kinetics, harmful byproducts, competitive hydrogen evolution reaction, and low water dissociation efficiency under neutral conditions, resulting in poor ammonia selectivity and yield. This limits the performance and applications of pure Ni-BDC materials.
By introducing ruthenium complexes to modify nickel-based metal framework materials, the local electron density of Ni-BDC is altered, a Ni-Ru synergistic catalytic pathway is constructed, the microenvironment of the catalytic center is optimized, and the exposure of active sites and interfacial charge transfer processes are improved.
It significantly improves the activity and Faraday efficiency of the electrocatalytic nitrate reduction reaction, enhances the yield and selectivity of ammonia, and exhibits superior structural stability and catalytic performance.
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Figure CN122279675A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of catalyst materials technology, specifically relating to a ruthenium complex-modified nickel-based metal framework material, its preparation method, and its application in electrocatalytic nitrate reduction to ammonia. Background Technology
[0002] Ammonia is an important industrial chemical widely used in the synthesis of fertilizers, pharmaceuticals, plastics, and dyes. Due to its high hydrogen content (17.6% by mass), it is also considered a carbon-free energy carrier. Currently, the Haber-Bosch process, characterized by high energy consumption and high carbon emissions, remains the mainstream process for industrial ammonia synthesis. Therefore, there is an urgent need to develop efficient and green new technologies to partially or completely replace it. Electrochemical nitrate reduction for ammonia synthesis, with its advantages of high current density, mild conditions, and abundant raw material sources, has become a promising alternative to the Haber-Bosch process.
[0003] The electrocatalytic reduction of nitrate to ammonia is constrained by multiple factors, including slow kinetics, harmful byproducts, competitive hydrogen evolution reaction, low water dissociation efficiency under neutral conditions, and electrostatic repulsion, resulting in poor ammonia selectivity and yield. Therefore, developing high-performance electrocatalysts to meet industrial needs is crucial. Metal-organic frameworks (MOFs), crystalline materials with clear structures composed of metal nodes and organic linkers, show broad application prospects in catalysis. Pure Ni-BDC, due to its simple structure, composition, and morphology, limits its performance and application improvements. The introduction of ruthenium complexes can not only significantly increase the exposure of electrocatalytic active sites but also optimize the interfacial charge transfer process.
[0004] Currently, no metal-organic framework composite materials based on ruthenium complexes have been found. Summary of the Invention
[0005] To address the aforementioned technical problems, one objective of this invention is to provide a nickel-based metal framework material modified with ruthenium complexes. By introducing ruthenium complexes, the local electron density of Ni-BDC is altered, optimizing the d-band center of Ni sites. This transforms the reaction pathway from simple Ni catalysis to Ni-Ru co-catalysis, significantly reducing the energy barrier of the rate-determining step.
[0006] The second objective of this invention is to provide the application of ruthenium complex-modified nickel-based metal framework materials in the electrocatalytic reduction of nitrate to ammonia. The method of this invention significantly improves the activity of the electrocatalytic nitrate reduction reaction.
[0007] To achieve the above-mentioned objectives, the technical solution adopted by this invention is: a ruthenium complex-modified nickel-based metal framework material, the preparation method of which includes: slowly adding a solution of N,N-dimethylacetamide (DMAC) in terephthalic acid to an aqueous solution of nickel chloride, mixing evenly, adding a ruthenium complex, continuing to stir, transferring the resulting mixed solution to an autoclave and sealing it for solvothermal treatment, cooling to room temperature, centrifuging, immersing the resulting precipitate in an aqueous solution of ammonium hexafluorophosphate, stirring at room temperature, centrifuging, washing, and drying to obtain the ruthenium complex-modified nickel-based metal framework material RuNi-BDC.
[0008] Furthermore, the ruthenium complex is an organorurus complex.
[0009] Furthermore, the organorruthenium complex is terpyridine ruthenium [Ru(bpy)3]Cl2, dichlorobispyridine ruthenium [Ru(bpy)2]Cl2, or derivatives of these two complexes.
[0010] Furthermore, in molar ratio, nickel chloride: terephthalic acid: ruthenium complex = (1 mmol - 3 mmol): (0.5 mmol - 1.5 mmol): (0.01 mmol - 0.02 mmol).
[0011] Furthermore, the N,N-dimethylacetamide solution of terephthalic acid is prepared in a material-to-liquid ratio of terephthalic acid:N,N-dimethylacetamide = (10 mg - 12 mg):1 mL.
[0012] Furthermore, the nickel chloride aqueous solution is prepared in a feed-to-liquid ratio of nickel chloride to water of (16 mg - 18 mg): 1 mL.
[0013] Furthermore, the solvothermal treatment is performed at 150 °C - 200 °C for 10 h - 12 h.
[0014] This invention provides the application of a ruthenium complex-modified nickel-based metal framework material as an electrode material in the electrocatalytic reduction of nitrate to ammonia.
[0015] Further, the method is as follows: a three-electrode system is constructed using a nickel-based metal framework material RuNi-BDC modified with ruthenium complex as the working electrode, an Hg / HgO electrode as the reference electrode, a carbon rod as the counter electrode, Nafion 117 as the proton exchange membrane, and 1 M KOH and 0.1 M KNO3 solution as the electrolyte. Electrocatalytic reduction of nitrate to ammonia is carried out in an H-type electrolytic cell.
[0016] Furthermore, the preparation method of the working electrode includes: adding RuNi-BDC to a mixed solution of ultrapure water, ethanol and Nafion, ultrasonically dispersing until uniformly mixed, dropping it onto the substrate surface, and vacuum drying to obtain the working electrode.
[0017] The beneficial effects of this invention are:
[0018] 1. The RuNi-BDC composite material provided by this invention is prepared by a one-pot solvothermal reaction using a nickel source, an organic ligand, and a ruthenium-based complex as precursors. In this system, [Ru(bpy)3] 2+ The ruthenium inlay not only acts as a modulator of electronic structure, optimizing the adsorption energy of the Ni center for reaction intermediates, but more importantly, it constructs a Ni-Ru dual-center synergistic catalytic pathway. This pathway alters the kinetics of nitrate reduction. By changing the introduction ratio and ligand structure of the ruthenium complex, the microenvironment of the catalytic center can be effectively optimized, thereby significantly improving the Faraday efficiency and yield of nitrate to ammonia conversion.
[0019] 2. The RuNi-BDC composite material provided by this invention effectively promotes the synergistic catalytic effect between active centers. Its organic ligands can interact with the Ni-BDC framework, ensuring high dispersion of ruthenium species in the MOF matrix, thereby enhancing the structural stability of the composite material. During the electrocatalytic reduction of nitrate, the interfacial interaction between the ruthenium complex ligands and the MOF ligands can effectively modulate the electron transfer behavior between catalytic centers, thus regulating catalytic activity and reaction kinetics. Compared with materials prepared using inorganic ruthenium salts (such as ruthenium chloride) as the ruthenium source, the RuNi-BDC composite material based on organic ruthenium complexes exhibits superior structural stability and catalytic performance.
[0020] 3. The RuNi-BDC composite material provided by this invention involves adding ruthenium tripyridine [Ru(bpy)3]Cl2 to a mixed solution of anhydrous nickel chloride and terephthalic acid. The introduction of the ruthenium complex in the resulting RuNi-BDC alters the local electron density of the Ni-BDC, optimizes the d-band center of the Ni site, and transforms the reaction pathway from simple Ni catalysis to Ni-Ru synergistic catalysis. This significantly reduces the energy barrier of the rate-determining step and improves the activity of the electrocatalytic nitrate reduction reaction.
[0021] 4. The RuNi-BDC provided by this invention is used for the electrocatalytic reduction of nitrate to ammonia. By controlling the amount of ruthenium complex introduced, the coordination environment of the active site, the local electron density, and the conductivity of the MOF framework can be effectively modulated. Furthermore, by controlling the ligand structure of the ruthenium complex (such as introducing electron-withdrawing or electron-donating substituents), the electronic structure of the catalytic active center and its interfacial interaction with the MOF framework can be precisely controlled, thereby optimizing the catalytic performance. Attached Figure Description
[0022] Figure 1 These are the X-ray diffraction (XRD) patterns of Ni-BDC and RuNi-BDC prepared in Example 1.
[0023] Figure 2 This is a scanning electron microscope (SEM) image of the RuNi-BDC prepared in Example 1.
[0024] Figure 3 This is a graph showing the ammonia yield and Faraday efficiency of RuNi-BDC prepared in Example 1 for the electrocatalytic reduction of nitrate to ammonia. Detailed Implementation
[0025] Example 1: A ruthenium complex-modified nickel-based metal framework material (RuNi-BDC)
[0026] (a) Preparation method:
[0027] Anhydrous nickel chloride (259.2 mg, 2 mmol) was added to 15 mL of ultrapure water and magnetically stirred until completely dissolved to obtain an aqueous solution of nickel chloride.
[0028] Add 166.3 mg, 1 mmol of terephthalic acid to 15 mL of DMAC and stir magnetically until completely dissolved to obtain a DMAC solution of terephthalic acid.
[0029] Dissolve 2 g of ammonium hexafluorophosphate in 35 mL of water and stir magnetically until completely dissolved to obtain an aqueous solution of ammonium hexafluorophosphate.
[0030] A DMAC solution of terephthalic acid was slowly added dropwise to an aqueous solution of nickel chloride. After mixing thoroughly, ruthenium tripyridine [Ru(bpy)3]Cl2 (10.8 mg, 0.015 mmol) was added, and stirring was continued for 10 min. The resulting mixture was then transferred to an autoclave and sealed. Solvent heat treatment was performed at 150 °C for 10 h. After cooling to room temperature, the mixture was centrifuged, the supernatant was discarded, and the resulting precipitate was soaked in an aqueous solution of ammonium hexafluorophosphate and stirred at room temperature for 12 h. After the precipitate was removed, it was washed by centrifugation with deionized water and ethanol, respectively, and dried to obtain a ruthenium complex-modified nickel-based metal framework material (RuNi-BDC) with a purity of 98%.
[0031] (ii) Characterization
[0032] Figure 1 These are the X-ray diffraction (XRD) patterns of Ni-BDC and RuNi-BDC. Figure 1 The results show that the diffraction peaks of the synthesized product RuNi-BDC are basically consistent with the characteristic peaks of Ni-BDC, indicating that the one-pot solvothermal method successfully preserved the main framework structure of MOF.
[0033] Figure 2 This is a scanning electron microscope (SEM) image of RuNi-BDC. Figure 2 This indicates that RuNi-BDC is a stacked nanosheet structure.
[0034] Table 1 shows the elemental composition of RuNi-BDC. Table 1 indicates that Ru was successfully doped into Ni-BDC.
[0035]
[0036] Example 2: Application of ruthenium complex-modified nickel-based metal framework materials in electrocatalytic nitrate reduction for ammonia production.
[0037] (I) Application of RuNi-BDC as an electrode material in electrocatalytic reduction of nitrate to ammonia
[0038] 1. Preparation of working electrode
[0039] 10 mg of RuNi-BDC prepared in Example 1 was weighed and dispersed in a mixture of 500 μL ultrapure water, 480 μL ethanol and 20 μL Nafion (5 wt%). The mixture was sonicated for 30 min to obtain a catalyst solution. Subsequently, 20 μL of the catalyst solution was drop-coated onto the surface of a 1 cm × 1 cm carbon cloth and dried in a vacuum environment at 60 ℃ for 12 h to obtain the working electrode.
[0040] 2. Ammonia production performance test
[0041] The electrocatalytic nitrate reduction performance was tested using an H-type electrolytic cell, with a Nafion 117 proton exchange membrane separating the anode and cathode. The electrolyte was a mixed solution of 1 M KOH and 0.1 M KNO3. A three-electrode system was constructed, using the RuNi-BDC-coated carbon cloth as the working electrode, an Hg / HgO electrode as the reference electrode, and a carbon rod as the counter electrode. Argon gas was continuously introduced into the cathode during the test to maintain an inert atmosphere. Electrocatalytic nitrate reduction was then carried out at different potentials. The cathode electrolyte was sampled every 1 hour, and the ammonia content was determined using the indophenol blue colorimetric method. The results are shown below. Figure 3 .
[0042] Figure 3 The ammonia yield and Faradaic efficiency of RuNi-BDC in 1 M KOH and 0.1 M KNO3 solutions at different potentials are shown. Figure 3 As shown, the material exhibits the best Faraday efficiency of 99% at -0.9 V (relative to the reversible hydrogen electrode), with an optimal ammonia yield of 220 mg·h⁻¹. -1 mg cat -1 .
[0043] (II) Effect of different amounts of [Ru(bpy)3]Cl2 added on RuNi-BDC on electrocatalytic nitrate reduction to ammonia production
[0044] The method is the same as in Example 1, except that the amount of [Ru(bpy)3]Cl2 added is changed to 0.010 mmol and 0.020 mmol to obtain RuNi-BDC prepared with different amounts of [Ru(bpy)3]Cl2 added.
[0045] Working electrodes were prepared from RuNi-BDC with different amounts of [Ru(bpy)3]Cl2 added, and the ammonia production performance was tested according to (I). The results are shown in Table 2.
[0046]
[0047] As shown in Table 2, RuNi-BDC with an optimal addition of 0.015 mmol [Ru(bpy)3]Cl2 at an optimal potential of -0.9 V exhibits the best FE and ammonia yield.
[0048] (III) Effects of different working electrodes on electrocatalytic nitrate reduction to ammonia production
[0049] Working electrodes were prepared according to the method in (I) using RuNi-BDC (prepared in Example 1) with the organic ruthenium source [Ru(bpy)3]Cl2, RuNi-BDC (prepared using the same method as Example 1, but with a different ruthenium source) with the inorganic ruthenium source RuCl3·xH2O, Ni-BDC, pure nickel sheet, nickel oxide, amorphous nickel boride, and ordinary nickel-based MOF as catalyst materials. Then, ammonia production performance was tested according to (I), and the results are shown in Table 3.
[0050]
[0051] As shown in Table 3, compared with RuNi-BDC prepared using inorganic ruthenium salt RuCl3·xH2O as the ruthenium source, as well as pure Ni-BDC, pure nickel sheet, nickel oxide, amorphous nickel boride, and ordinary nickel-based MOF, RuNi-BDC prepared by the present invention using the organic ruthenium complex [Ru(bpy)3]Cl2 has the best FE and ammonia yield at the optimal potential. This indicates that the nickel-based metal framework material modified by the ruthenium complex of the present invention has excellent electrocatalytic nitrate reduction performance.
Claims
1. A nickel-based metal framework material modified with a ruthenium complex, characterized in that, The preparation method includes: slowly adding a solution of N,N-dimethylacetamide in terephthalic acid to an aqueous solution of nickel chloride, mixing thoroughly, adding a ruthenium complex, continuing stirring, transferring the resulting mixed solution to an autoclave and sealing it for solvothermal treatment, cooling to room temperature, centrifuging, immersing the resulting precipitate in an aqueous solution of ammonium hexafluorophosphate, stirring at room temperature, centrifuging, washing, and drying to obtain a ruthenium complex-modified nickel-based metal framework material RuNi-BDC.
2. The ruthenium complex-modified nickel-based metal framework material according to claim 1, characterized in that, The ruthenium complex is an organorruthenium complex.
3. The ruthenium complex-modified nickel-based metal framework material according to claim 2, characterized in that, The organorruthenium complex is terpyridineruthenium[Ru(bpy)3]Cl2, dichlorobispyridineruthenium[Ru(bpy)2]Cl2, or derivatives of these two complexes.
4. A ruthenium complex-modified nickel-based metal framework material according to claim 1, 2, or 3, characterized in that, In molar ratio, nickel chloride: terephthalic acid: ruthenium complex = (1 mmol - 3 mmol): (0.5 mmol - 1.5 mmol): (0.01 mmol - 0.02 mmol).
5. A ruthenium complex-modified nickel-based metal framework material according to claim 1, 2, or 3, characterized in that, The N,N-dimethylacetamide solution of terephthalic acid is prepared with a material-to-liquid ratio of terephthalic acid:N,N-dimethylacetamide = (10 mg - 12 mg):1 mL.
6. A ruthenium complex-modified nickel-based metal framework material according to claim 1, 2, or 3, characterized in that, The nickel chloride aqueous solution is prepared with a feed-to-liquid ratio of nickel chloride to water of (16 mg - 18 mg): 1 mL.
7. A ruthenium complex-modified nickel-based metal framework material according to claim 1, 2, or 3, characterized in that, The solvothermal treatment is a reaction at 150 ℃ - 200 ℃ for 10 h - 12 h.
8. The application of a ruthenium complex-modified nickel-based metal framework material as described in any one of claims 1-7 as an electrode material in the electrocatalytic reduction of nitrate to ammonia.
9. The application according to claim 8, characterized in that, The method is as follows: a three-electrode system was constructed using a nickel-based metal framework material RuNi-BDC modified with ruthenium complex as the working electrode, an Hg / HgO electrode as the reference electrode, a carbon rod as the counter electrode, Nafion 117 as the proton exchange membrane, and 1 M KOH and 0.1 M KNO3 solution as the electrolyte. Electrocatalytic reduction of nitrate to ammonia was carried out in an H-type electrolytic cell.
10. The application according to claim 9, characterized in that, The preparation method of the working electrode includes: adding RuNi-BDC to a mixed solution of ultrapure water, ethanol and Nafion, ultrasonically dispersing until uniformly mixed, dropping it onto the substrate surface, and vacuum drying to obtain the working electrode.