Preparation method and application of MOF-derived bimetallic NiCo-C difunctional electrocatalyst
By preparing MOF-derived NiCo@C electrocatalysts, the problems of high price, poor stability and high OER thermodynamic energy barrier of precious metal-based catalysts were solved, and an electrocatalytic effect with low overpotential and high stability was achieved, which promoted the diffusion and transport of electrolytes and ions and improved the catalytic activity.
Patent Information
- Application Number
- CN202510820080.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-18
- Publication Date
- 2025-09-23
AI Technical Summary
Existing precious metal-based catalysts have problems of high price, poor stability and scarcity in electrochemical water splitting. The anodic oxygen evolution reaction (OER) has a high thermodynamic energy barrier and slow kinetics, and the H2/O2 mixture produced by electrolysis has an explosion risk. The traditional OER process reduces the water splitting efficiency.
A MOF-derived bimetallic NiCo@C bifunctional electrocatalyst was used to synthesize surface-exposed NiCo alloy nanoparticles by heat-treating the MOF precursor. The preparation method is simple and low-cost, and it can serve as an electrocatalyst for both alkaline cathode HER and anodic MOR reactions.
It achieves low overpotential and high stability in HER and MOR, improves catalytic activity, and provides a hybrid water electrolysis system for electrocatalytic production of hydrogen and high-value-added chemicals to replace traditional high-energy-consuming chemical technologies.
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Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of electrocatalytic materials, and specifically to a preparation method and application of a MOF-derived bimetallic NiCo@C bifunctional electrocatalyst. Background Art
[0002] Electrochemical water splitting is a highly efficient method for producing high-purity hydrogen, with a theoretical voltage of 1.23 V. However, the anodic oxygen evolution reaction (OER) involves a four-electron transfer process, a high thermodynamic barrier, slow kinetics, and the H2 / O2 mixture produced by electrolysis poses an explosion risk. To overcome these drawbacks, alternative oxidation reactions have been proposed, such as the oxidation of methanol to formate, which has a low thermodynamic potential (0.103 V). Furthermore, formate is an important chemical that avoids CO2 formation, potentially allowing for the indirect release of H2 from methanol.
[0003] Currently, noble metal (e.g., platinum, IrO2)-based catalysts have high catalytic efficiency for electrochemical water splitting, but their high price, poor stability, and scarcity limit their large-scale application. Due to the high energy barrier of OH bond rupture and O=O bond formation, the OER process severely reduces the efficiency of water splitting. For Ni-based catalysts, doping with other metals (e.g., Co, Fe, Mn, etc.) to form a multi-element alloy can adjust the electronic structure of the catalyst and optimize its surface adsorption and activation ability for reactants. Co is cheaper than Ni, and the addition of a Co source to form NiCo alloy nanoparticles can adjust the electronic structure of the alloy and improve the catalytic activity. At the same time, the cathode hydrogen evolution reaction (HER) is innovatively coupled with the anode methanol oxidation reaction (MOR) to construct a methanol-water co-electrolysis system. Summary of the Invention
[0004] The present invention aims to provide a method for preparing a MOF-derived bimetallic NiCo@C bifunctional electrocatalyst, which adopts a "heat treatment of MOF precursor" strategy to synthesize a spherical bifunctional electrocatalyst (NiCo@C) with surface-exposed NiCo alloy nanoparticles. The preparation method is simple, low-cost, and has high reaction catalytic activity.
[0005] The purpose of the present invention is achieved through the following technical solutions:
[0006] A preparation method and application of a MOF-derived bimetallic NiCo@C bifunctional electrocatalyst. The preparation method is as follows:
[0007] (1) Preparation of NiCo-MOF precursor: A certain amount of Ni(NO3)2·6H2O and Co(NO3)2·6H2O were dissolved in DMF and methanol, and ultrasonicated to form a pale purple homogeneous solution. The solution was transferred to a 50 mL hydrothermal reactor for solvothermal reaction. The solid-liquid mixture after the reaction was centrifuged, washed with ethanol, and then vacuum dried to obtain a green NiCo-MOF powder.
[0008] (2) Preparation of NiCo@C: The NiCo-MOF powder obtained in step (1) was placed in the middle of a tube furnace and heat-treated under an argon atmosphere for 2 h. After cooling to room temperature, the powder was ground to obtain a spherical NiCo@C bifunctional catalyst.
[0009] The NiCo@C bifunctional catalyst prepared by this method inherits the spherical structure of the precursor, with nickel-cobalt alloy nanoparticles exposed on the MOF surface, approximately 70-100 nm in diameter. The NiCo@C bifunctional catalyst can serve as an electrocatalyst for both the alkaline cathode HER and anodic MOR reactions, exhibiting low overpotential and high stability in both HER and MOR reactions.
[0010] Compared with the prior art, the present invention has the following beneficial effects:
[0011] 1. The NiCo@C bifunctional catalyst of "pyrolysis MOF precursor" prepared by the present invention adopts the "pyrolysis MOF precursor" strategy to synthesize small and uniformly dispersed NiCo@C catalyst with a size of 70-100nm using MOF as a precursor.
[0012] 2. In the NiCo@C bifunctional catalyst of the "pyrolysis MOF precursor" prepared by the present invention, NiCo gradually precipitates on the surface during the high-temperature carbonization process to form NiCo alloy nanoparticles, which are directly exposed on the catalyst surface, increasing the active sites and specific surface area. At the same time, there are a large number of gaps between the nanoparticles, and a porous hollow structure exists. This may be caused by the carbonization of organic ligands to generate gas during the heat treatment process, which is beneficial to the diffusion and transmission of electrolytes and ions, and can greatly promote the catalytic reaction.
[0013] 3. The preparation method of the NiCo@C bifunctional electrocatalyst developed by the present invention can be obtained by heat treating the MOF-derived bimetallic NiCo-MOF precursor, which exhibits low overpotential in the cathode hydrogen evolution reaction of alkaline water electrolysis and the anode methanol oxidation, and the HER activity (η 10 =88mV), MOR activity (η 50=1.58V). The introduction of a cobalt source exposes the NiCo alloy nanoparticles, significantly enhancing the catalytic activity. This system exhibits excellent hydrogen production and methanol oxidation performance, providing a promising approach for designing hybrid water electrolysis systems that can replace traditional energy-intensive chemical technologies and simultaneously produce hydrogen and high-value-added chemicals. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Figure 1 Scanning electron microscope images of the catalysts prepared in Examples 1-3:
[0015] (a)Ni@C, (b)Co@C, (c)NiCo@C
[0016] Figure 2 is the XRD spectrum of each sample synthesized in Examples 1-3;
[0017] Figure 3 Performance comparison chart of NiCo@C prepared in Example 1 and other catalysts:
[0018] (a) HER performance, (b) OER and MOR performance DETAILED DESCRIPTION
[0019] The present invention is described in detail below through examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above-mentioned contents of the present invention.
[0020] Example 1
[0021] A method for preparing a MOF-derived bimetallic NiCo@C bifunctional electrocatalyst is carried out as follows:
[0022] (1) Preparation of NiCo-MOF precursor: Weigh 0.75mmol Ni(NO3)2·6H2O and 0.25mmol Co(NO3)2·6H2O and place them in 15mL methanol, then weigh 1mmol 1,3,5-benzenetricarboxylic acid (H3BTC) and place them in 15mL N,N-dimethylformamide (DMF). After mixing evenly at room temperature, ultrasonic oscillation technology is used to promote dissolution until a clear, transparent and lavender homogeneous solution is formed. The solution is transferred to a 50mL hydrothermal reactor and reacted at 150℃ for 12h. After cooling naturally to room temperature, the solid-liquid mixture after reaction is centrifuged at a speed of 9000rpm for 5min, washed three times with ethanol, and then vacuum dried at 60℃ for 12h to obtain green NiCo-MOF powder;
[0023] (2) Preparation of NiCo@C: Ni obtained in step (1) 0.75 Co 0.25 -MOF powder was placed in the middle of a tube furnace and heated to 800°C at a heating rate of 5°C / min under an argon atmosphere. The temperature was maintained for 2 hours and then naturally cooled to room temperature to obtain a NiCo@C bifunctional catalyst.
[0024] Example 2
[0025] A preparation method of a comparative sample C catalyst Ni@C, the specific steps are as follows:
[0026] (1) Preparation of Ni-MOF precursor: Weigh 1mmol Ni(NO3)2·6H2O and place it in 15mL methanol, then weigh 1mM 1,3,5-benzenetricarboxylic acid (H3BTC) and place it in 15mL N,N-dimethylformamide (DMF). After mixing evenly at room temperature, ultrasonic oscillation technology is used to promote dissolution until a clear, transparent, and pale purple homogeneous solution is formed. The solution is transferred to a 50mL hydrothermal reactor and reacted at 150℃ for 12h. After cooling naturally to room temperature, the solid-liquid mixture after reaction is centrifuged at a speed of 9000rpm for 5min, washed three times with ethanol, and then vacuum dried at 60℃ for 12h to obtain green Ni-MOF powder;
[0027] (2) Preparation of Ni@C: The Ni-MOF powder obtained in step (1) was placed in the middle of a tube furnace and heated to 800°C at a heating rate of 5°C / min under an argon atmosphere. The mixture was kept at this temperature for 2 h. The mixture was then cooled naturally to room temperature to obtain a Ni@C bifunctional catalyst.
[0028] Example 3
[0029] A preparation method of a comparative sample C catalyst Co@C, the specific steps are as follows:
[0030] (1) Preparation of Co-MOF precursor: Weigh 1 mmol Co(NO3)2·6H2O and place it in 15 mL methanol, then weigh 1 mM 1,3,5-benzenetricarboxylic acid (H3BTC) and place it in 15 mL N,N-dimethylformamide (DMF). After mixing evenly at room temperature, ultrasonic oscillation technology is used to promote dissolution until a clear, transparent, and pale purple homogeneous solution is formed. The solution is transferred to a 50 mL hydrothermal autoclave and reacted at 150 ° C for 12 hours. After cooling naturally to room temperature, the solid-liquid mixture after reaction is centrifuged at a speed of 9000 rpm for 5 minutes, washed three times with ethanol, and then vacuum dried at 60 ° C for 12 hours to obtain purple Co-MOF powder;
[0031] (2) Preparation of Co@C: The Co-MOF powder obtained in step (1) was placed in the middle of a tube furnace and heated to 800°C at a heating rate of 5°C / min under an argon atmosphere. The mixture was kept at this temperature for 2 h. The mixture was then cooled naturally to room temperature to obtain a Co@C bifunctional catalyst.
[0032] Related performance tests:
[0033] This section only tests samples provided in some embodiments, and other samples also have the same or similar physical and chemical properties.
[0034] (1) Half-reaction (HER / MOR) performance test
[0035] Three-electrode system: To prepare the working electrode, 10 mg of catalyst was weighed and mixed with 30 μL of a 5 wt% Nafion solution in 400 μL of isopropanol and 600 μL of deionized water. The mixture was ultrasonicated for 3 hours. 5 μL of the evenly dispersed catalyst solution was then loaded onto a 3 mm diameter glassy carbon electrode and allowed to dry naturally, serving as the working electrode. A Hg / HgO electrode served as the reference electrode, and a graphite sheet served as the counter electrode. The electrolyte for the HER reaction was a 1 M KOH solution, while the electrolyte for the MOR reaction was a 1 M KOH + 1 M CHOH solution.
[0036] HER test: Under normal temperature and pressure conditions, N2 gas flow was introduced for 30 minutes to remove other gases in the solution. Cyclic voltammetry was performed for 30 cycles to activate the catalyst, and then LSV test was performed at a scan rate of 100 mV / s to determine the HER reaction overpotential.
[0037] MOR test: Under normal temperature and pressure conditions, N2 gas flow was introduced for 30 minutes to remove other gases in the solution. Cyclic voltammetry was performed for 30 cycles to activate the catalyst, and then an LSV test was performed at a scan rate of 100 mV / s to determine the reaction overpotential of MOR.
[0038] In the two-electrode system, the catalyst dispersion was prepared in the same way as the working electrode and dropped on a 1×2 cm 2 The catalyst loading on nickel foam (NF) was 0.707 mg cm -2 After drying, the electrochemical tests were performed as working and counter electrodes. The electrolyte was a 1M KOH + 1M CH3OH solution. At room temperature and pressure, a nitrogen gas flow was introduced for 30 minutes to remove other gases from the solution. Cyclic voltammetry was performed for 30 cycles to activate the catalyst, followed by LSV testing at a scan rate of 100 mV / s to determine the cell's reaction overpotential.
[0039] Figure 1The morphology of the catalysts prepared in Examples 1-3 is analyzed. a is an electron microscope image of NiCo@C, b is an electron microscope image of Ni@C, and c is an electron microscope image of Co@C. By comparing the electron microscope images of the three, it can be found that the Ni@C structure is spherical, and small metal particles are distributed on the surface. For the NiCo@C catalyst, after the Co source is added, the metal particles on the surface of the sphere increase and become larger. After observing Co@C, the surface structure of Co@C is relatively rough, and a large number of lumps are attached to the surface, which may be due to the low crystallinity of Co on its surface. This shows that the metal particles on the surface of NiCo@C may be Co attached to the surface of the catalyst to form an alloy with Ni. It is confirmed that the added cobalt ions are conducive to exposing more active centers.
[0040] Figure 2 The catalysts prepared in Examples 1-3 were subjected to XRD crystal structure analysis. Analysis of the XRD spectrum revealed that Ni@C exhibited (111) and (200) diffraction peaks at 2θ≈44.5° and 51.8°, which matched those of the Ni standard card (PDF#04-0850), indicating a face-centered cubic (fcc) structure. Co@C exhibited peaks at 2θ≈44.2° and 51.5° corresponding to those of the Co standard card (PDF#15-0806), suggesting a possible fcc or hexagonal close-packed (hcp) structure, requiring further confirmation in conjunction with other peak positions. The diffraction peaks of NiCo@C were located between those of Ni@C and Co@C, with a slight shift toward lower angles (relative to Ni), indicating that Co incorporation resulted in lattice expansion. After Co doping, the fcc structure of Ni is maintained, but the lattice parameter increases due to the introduction of Co, and there is no obvious single Ni or Co phase peak, indicating that a uniform Ni-Co alloy phase is formed rather than a simple mixture. This structural change optimizes the electronic structure of the catalyst, thereby affecting its catalytic performance.
[0041] Figure 3 The performance test is performed on the half reaction of the catalyst. (a) The HER performance test is performed on the catalysts of Examples 1-3. With the introduction of cobalt, the catalyst performance is significantly affected. However, the prepared C material does not show obvious hydrogen evolution activity. This shows that the larger specific surface area and the smaller and more evenly dispersed NiCo nanoparticles together improve the activity of the catalyst. (b) The MOR performance test is performed on the catalysts of Examples 1-3. After the introduction of methanol, the oxidation potential on the catalyst is significantly reduced, and the catalyst shows a higher static bending strength response. This shows that the MOR reaction is easier to occur than the OER reaction and has a higher energy conversion efficiency.
Claims
1. A preparation method and application of a MOF-derived bimetallic NiCo@C bifunctional electrocatalyst. Characterized by: (1) dissolving a nickel source, a cobalt source, and an organic ligand in an organic solvent by a solvothermal method, sonicating to form a clear, transparent, and pale purple homogeneous solution, and adding the solution into a reactor for a solvothermal reaction; (2) centrifuging the solid-liquid mixture obtained in step (1), washing with ethanol, and drying to obtain a MOF precursor; (3) High-temperature argon atmosphere annealing: The MOF precursor obtained in step (2) is placed in the middle of a tube furnace and carbonized at high temperature under an argon atmosphere. After natural cooling, a carbonized spherical NiCo@C catalyst is finally obtained.
2. The method for preparing a MOF-derived bimetallic NiCo@C bifunctional electrocatalyst according to claim 1, characterized in that: In step (1), the nickel salt is a soluble nickel salt nickel nitrate hexahydrate, and the cobalt source is a soluble cobalt source cobalt nitrate hexahydrate.
3. The method for preparing a MOF-derived bimetallic NiCo@C bifunctional electrocatalyst according to claim 1, characterized in that: In step (1), the organic ligand is, and the organic solvent is methanol and N,N-dimethylformamide (DMF).
4. The method for preparing a MOF-derived bimetallic NiCo@C bifunctional electrocatalyst according to claim 1, characterized in that: In step (1), the amounts of the nickel source and the cobalt source are 0.75 mmol and 0.25 mmol respectively.
5. The method for preparing NiCox@C bifunctional electrocatalyst from a MOF-derived bimetallic NiCo-MOF precursor according to claim 1, characterized in that: The hydrothermal conditions in step (1) are heating to 120-180° C. and the reaction time is 10-14 h.
6. The method for preparing a MOF-derived bimetallic NiCo@C bifunctional electrocatalyst according to claim 1, characterized in that: In step (2), vacuum drying is used for drying, the temperature range is 50-80° C., and the drying time is 8-14 h.
7. The method for preparing a MOF-derived bimetallic NiCo@C bifunctional electrocatalyst according to claim 1, characterized in that: In step (3), under an argon atmosphere, the temperature is raised to 700-900°C at a heating rate of 2-5°C / min and kept at this temperature for 2-4 hours.
8. A NiCo@C bifunctional electrocatalyst prepared from a MOF-derived bimetallic NiCo-MOF precursor prepared by the method of any one of claims 1-7. The bifunctional catalyst inherits the spherical structure of the precursor, but due to the addition of a cobalt source, numerous NiCo alloy nanoparticles are formed on its surface.
9. The MOF-derived bimetallic NiCo-MOF precursor of claim 8 is used to prepare a NiCo@C bifunctional electrocatalyst for electrochemical hydrogen production and methanol oxidation, characterized in that The specific application method is: NiCo@C bifunctional electrocatalyst is made into a working electrode, and methanol is electrocatalytically converted into formate under alkaline conditions and hydrogen is produced simultaneously.