Preparation method and application of heteropolyacid anchored nickel sulfide self-supporting electrode
By growing nickel hydroxide support on the surface of nickel foam and growing heteropolyacids in situ, a POM@Ni3S2/NF heterostructure was constructed, which solved the problem of weak adsorption capacity of nickel sulfide catalysts for OER intermediates and achieved efficient and stable electrocatalytic performance, suitable for industrial applications.
Patent Information
- Application Number
- CN202512045365.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-31
- Publication Date
- 2026-03-13
AI Technical Summary
Existing nickel sulfide catalysts have weak adsorption capacity for the key OER intermediate *OH under alkaline conditions, resulting in low water molecule activation efficiency, slow intermediate conversion, and limited catalytic activity and reaction kinetics.
Nickel hydroxide support was grown on the surface of nickel foam using a hydrothermal method, and heteropolyacids were grown in situ on the surface of nickel sulfide to form a heteropolyacid-anchored nickel sulfide self-supporting electrode, thus constructing a POM@Ni3S2/NF heterostructure. This achieved strong electrostatic anchoring of polyoxometalates and Ni3S2 nanosheet arrays, optimizing the electronic structure and catalytic active sites.
It significantly improves catalytic activity and stability, requiring only an overpotential lower than that of commercial IrO2, and operates stably for 50 hours at high current density. It solves the problems of weak *OH adsorption and easy dissolution of POM in traditional nickel-based sulfides, thus meeting the requirements for efficient and stable electrocatalysis.
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Figure CN121653703A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of energy materials technology, specifically to a method for preparing and applying a heteropolyacid-anchored nickel sulfide self-supporting electrode. Background Technology
[0002] Driven by accelerated industrialization, the development of green and low-carbon new energy sources has become a key direction. Hydrogen energy, as a new energy carrier with high calorific value and clean, pollution-free combustion, has attracted significant attention for its green production technology. Hydrogen production through water electrolysis involves two half-reactions: the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). The OER is a four-electron transfer process involving the adsorption and desorption of oxygen-containing intermediates such as *OH, *O, and *OOH, which suffers from inherently slow kinetics and high activation energy barriers, directly limiting the overall efficiency of water electrolysis. Therefore, developing efficient and stable OER electrocatalysts is a core requirement for promoting the industrialization of water electrolysis hydrogen production technology. Currently, noble metal oxides such as RuO2 and IrO2 are the best-performing OER electrocatalysts, exhibiting excellent catalytic activity under alkaline conditions. However, these materials are scarce, expensive, and lack durability, making it difficult to meet the needs of large-scale commercial applications. Therefore, developing low-cost, high-performance, and long-life non-noble metal OER electrocatalysts has become a core technical problem urgently needing to be solved in this field.
[0003] Nickel sulfide materials have attracted much attention due to their tunable electronic structure, good conductivity, low raw material cost, and inherent OER activity. However, single nickel sulfide catalysts have a key drawback: the active sites have weak adsorption capacity for the key OER intermediate *OH, resulting in low water molecule activation efficiency, slow intermediate conversion, and limited catalytic activity and reaction kinetics. Summary of the Invention
[0004] The purpose of this invention is to improve the alkaline oxygen evolution reaction performance of nickel sulfide and solve the problem that the active sites of nickel sulfide catalysts have weak adsorption capacity for the key OER intermediate *OH, resulting in low water molecule activation efficiency, slow intermediate conversion, and limited catalytic activity and reaction kinetics. Therefore, this invention provides a method for preparing and applying a heteropolyacid-anchored nickel sulfide self-supporting electrode.
[0005] This invention first grows a layer of nickel hydroxide support on the surface of nickel foam (NF) using a hydrothermal method, then immerses it in a solution of heteropoly acid, and further sulfides it using a hydrothermal method to grow the heteropoly acid in situ on the surface of nickel sulfide. After washing and drying, a self-supporting nickel sulfide electrode material (POM@Ni3S2 / NF) with excellent activity and stability and heteropoly acid anchoring is obtained, which can effectively improve the OER catalytic activity and stability of nickel sulfide electrode.
[0006] A method for preparing a heteropolyacid-anchored nickel sulfide self-supporting electrode is specifically carried out according to the following steps:
[0007] I. Preparation of polyacid FeMo6:
[0008] Under stirring conditions, ferric sulfate solution was added dropwise to boiling ammonium molybdate solution to obtain a mixed solution; the mixed solution was kept boiling and ultrasonic was applied until a crystal film appeared on the surface of the solution. Heating was stopped, and the solution was transferred to an ice-salt bath for stirring. After standing, the crystals precipitated and were placed at room temperature. The yellow crystals were then washed and dried to obtain polyacid FeMo6 crystal powder.
[0009] II. Pretreatment of Nickel Foam:
[0010] The nickel foam is cut and then cleaned to obtain pretreated nickel foam;
[0011] III. Preparation of Ni(OH)2 / NF:
[0012] The pretreated nickel foam was placed in a mixed solution containing nickel nitrate hexahydrate, ammonium fluoride and urea, and then placed in a hydrothermal reactor for hydrothermal reaction; after the reaction was completed, the nickel foam was removed, washed and dried to obtain the self-supporting electrode Ni(OH)2 / NF.
[0013] IV. POM grain aging:
[0014] ① Dissolve the polyacid FeMo6 crystal powder in water to obtain a FeMo6 solution;
[0015] ② Using the self-supporting electrode Ni(OH)2 / NF as the working electrode and a platinum sheet as the counter electrode, the two electrodes were immersed in FeMo6 solution in parallel and perpendicular positions. Electrophoresis was performed continuously under constant voltage to pre-adsorb FeMo6. After electrophoresis, the electrodes were removed, cleaned, and dried to obtain the self-supporting electrode POM@Ni(OH)2 / NF.
[0016] V. Preparation of POM@Ni3S2 / NF:
[0017] The self-supporting electrode POM@Ni(OH)2 / NF was placed in a hydrothermal reactor containing a sodium sulfide nonahydrate solution for hydrothermal reaction. After the reaction was completed, the electrode was removed, rinsed, and dried to obtain a heteropolyacid-anchored nickel sulfide self-supporting electrode.
[0018] The principle of this invention:
[0019] Polyoxometalates (POMs) are polyoxometalate clusters formed by the bonding of pre-transition metals such as Mo, W, and V with oxygen. They possess precise structures, controllable sizes, and tunable heteroatoms, and exist in anionic clusters. The high-valence metals in these POMs have high d-band centers, enabling strong interactions with OER intermediates and optimizing *OH adsorption energy. Simultaneously, when POMs are combined with transition metal supports, they can inhibit their own dissolution through strong interfacial interactions, enhancing catalyst stability.
[0020] Compared with the prior art, the present invention has the following beneficial effects:
[0021] I. Breakthrough Performance Enhancement: This invention constructs a POM@Ni3S2 / NF heterostructure catalyst through a two-step method (co-precipitation and hydrothermal sulfidation), achieving strong electrostatic anchoring between the polyoxometalate (FeMo6) and the Ni3S2 nanosheet array. This retains the excellent conductivity and inherent OER activity of Ni3S2 while precisely introducing Fe / Mo heteroatoms through FeMo6 to regulate the electronic structure. In 1M KOH electrolyte, an overpotential of only 230mV, 269mV, and 312mV is required to reach 10 mA·cm⁻¹. -2 100mA·cm -2 500mA·cm -2 The current density is far superior to that of commercial IrO2@NF (corresponding to overpotentials of 266mV, 355mV, and 505mV); and it is within 500mA·cm -2 It operates stably for 50 hours at high current density with an overpotential increase of only 1.23%, overcoming the dual defects of weak *OH adsorption and easy dissolution of POM in traditional nickel-based sulfides, thus meeting the requirements for efficient and stable electrocatalysis.
[0022] II. Precise Regulation of Activity Mechanism: Optimization of the electronic structure of Ni3S2 active sites was achieved through FeMo6 anchoring; XPS characterization confirmed the high valence Ni... 3+ The content increased from 22.01% in Ni3S2 / NF to 24.12%, and the binding energy of Ni and S elements underwent a negative shift, promoting electron transfer from Ni3S2 to POM. DFT calculations showed that the d-band center of the Mo active site in FeMo6 (3.24 eV) was significantly higher than that of the Ni site in Ni3S2 (-1.16 eV), which reduced the adsorption free energy of *OH from 1.59 eV to 1.14 eV and the OER rate-determining step (*O→*OOH) energy barrier from 1.77 eV to 1.53 eV, greatly accelerating the reaction kinetics. At the same time, the number of antibonding states below the Fermi level of the Mo-O bond decreased, improving the intermediate binding stability and providing a clear mechanism for the regulation of non-noble metal catalyst activity.
[0023] III. Highly efficient and economical preparation process: The preparation process does not require complex equipment. First, Ni(OH)2 nanosheet precursors are grown in situ on NF by co-precipitation. Then, they are mixed with FeMo6 and subjected to hydrothermal sulfidation to achieve uniform dispersion of FeMo6 and crystallization of Ni3S2. The finished product is obtained after washing with water and vacuum drying. The process parameters are easy to control. The performance can be optimized by adjusting the amount of FeMo6 and the hydrothermal parameters. The raw materials are low in cost and easy to obtain, avoiding dependence on precious metals. It is suitable for laboratory preparation and large-scale production, laying the foundation for industrial applications.
[0024] IV. Significantly Enhanced Structural Stability: The strong electrostatic interaction between FeMo6 and Ni3S2 effectively inhibits the dissolution of POM during the catalytic process. Furthermore, the 3D nanosheet array structure retains the high conductivity and porous characteristics of NF, which not only increases the specific surface area and exposes more active sites, but also facilitates electrolyte permeation and gas escape. Compared with the problems of easy agglomeration and easy POM loss of traditional nickel-based sulfides, the catalyst of this invention showed no significant changes in morphology and crystal structure after 50 hours of stability testing, and the elemental distribution was uniform. This solves the key problem of poor long-term stability of non-precious metal catalysts and broadens its application scenarios in fields such as water electrolysis for hydrogen production. Attached Figure Description
[0025] Figure 1 The image shows the XRD pattern of the polyacid FeMo6 crystal powder prepared in step one of Example 1.
[0026] Figure 2 XRD patterns of the POM@Ni3S2 / NF electrode prepared in Example 1 and the Ni3S2 / NF electrode prepared in Control Example 1;
[0027] Figure 3 Raman spectroscopy for the POM@Ni3S2 / NF electrode prepared in Example 1 and the Ni3S2 / NF electrode prepared in Control Example 1;
[0028] Figure 4 SEM image of the POM@Ni3S2 / NF electrode prepared in Example 1;
[0029] Figure 5 SEM image of the Ni3S2 / NF electrode prepared in Comparative Example 1;
[0030] Figure 6 The image shows a SEM image of the pretreated nickel foam NF prepared in step two of Example 1.
[0031] Figure 7 The image shows a SEM image of the self-supporting Ni(OH)2 / NF electrode prepared in step three of Example 1.
[0032] Figure 8 TEM image of the POM@Ni3S2 / NF electrode prepared in Example 1;
[0033] Figure 9 Linear sweep voltammetry curves of NF, Ni(OH)2 / NF, POM@Ni3S2 / NF prepared in Example 1, Ni3S2 / NF prepared in Control Example 1, and IrO2 / NF prepared in Control Example 2 in 1M KOH solution;
[0034] Figure 10 Chronopotential curve of the POM@Ni3S2 / NF electrode prepared in Example 1 in 1M KOH solution. Detailed Implementation
[0035] Specific Implementation Method 1: This implementation method is a method for preparing a heteropolyacid-anchored nickel sulfide self-supporting electrode, characterized in that the preparation method is specifically completed according to the following steps:
[0036] I. Preparation of polyacid FeMo6:
[0037] ① Add ammonium heptamolybdate tetrahydrate to boiling deionized water and stir until completely dissolved to obtain a clear and colorless ammonium molybdate solution;
[0038] ② Add ferric sulfate hexahydrate to deionized water and sonicate until completely dissolved to obtain a pale green ferric sulfate solution;
[0039] ③ Under stirring conditions, ferric sulfate solution is added dropwise to boiling ammonium molybdate solution to obtain a mixed solution; the mixed solution is kept boiling and ultrasonic is applied until a crystal film appears on the surface of the solution. Heating is stopped, and the solution is transferred to an ice-salt bath for stirring. After the crystals precipitate, the solution is transferred to room temperature and then the yellow crystals are washed and dried to obtain polyacid FeMo6 crystal powder.
[0040] II. Pretreatment of Nickel Foam:
[0041] The nickel foam is cut and then cleaned to obtain pretreated nickel foam;
[0042] III. Preparation of Ni(OH)2 / NF:
[0043] The pretreated nickel foam was placed in a mixed solution containing nickel nitrate hexahydrate, ammonium fluoride and urea, and then placed in a hydrothermal reactor for hydrothermal reaction; after the reaction was completed, the nickel foam was removed, washed and dried to obtain the self-supporting electrode Ni(OH)2 / NF.
[0044] IV. POM grain aging:
[0045] ① Dissolve the polyacid FeMo6 crystal powder in water to obtain a FeMo6 solution;
[0046] ② Using the self-supporting electrode Ni(OH)2 / NF as the working electrode and a platinum sheet as the counter electrode, the two electrodes were immersed in FeMo6 solution in parallel and perpendicular positions. Electrophoresis was performed continuously under constant voltage to pre-adsorb FeMo6. After electrophoresis, the electrodes were removed, cleaned, and dried to obtain the self-supporting electrode POM@Ni(OH)2 / NF.
[0047] V. Preparation of POM@Ni3S2 / NF:
[0048] The self-supporting electrode POM@Ni(OH)2 / NF was placed in a hydrothermal reactor containing a sodium sulfide nonahydrate solution for hydrothermal reaction. After the reaction was completed, the electrode was removed, rinsed, and dried to obtain a heteropolyacid-anchored nickel sulfide self-supporting electrode.
[0049] In step 1① of this embodiment, ammonium heptamolybdate tetrahydrate is added to boiling deionized water and stirred until completely dissolved to obtain a clear and colorless ammonium molybdate solution. This process of "boiling first and then adding" combined with steady-state micro-boiling and constant stirring helps to prevent the polymerization of molybdate ions caused by local overheating, ensures the uniformity of molybdate dispersion in the solution, and lays the foundation for the controllability of the morphology of the subsequent product.
[0050] In step 1③ of this embodiment, ferric sulfate solution is added dropwise to boiling ammonium molybdate solution under stirring conditions to obtain a mixed solution. This is to promote uniform mixing between ions, inhibit excessive grain growth, and achieve size control. The mixed solution is kept boiling and ultrasonic waves are applied until a crystalline film appears on the solution surface, at which point heating is stopped. This is because the ultrasonic cavitation effect can effectively break up the initially formed aggregates, reduce the crystal nucleus size, and provide sufficient micro-mixing for the system, thereby enhancing the coordination uniformity and nucleation density between metal ions. This step, by introducing an ultrasonic field to assist the reaction and concentration, aims to obtain finer, more uniformly dispersed precursor particles, ensuring the controllability of the subsequent crystallization process.
[0051] In step 1③ of this embodiment, rapid quenching is used to suppress grain growth and obtain smaller crystals. After heating is stopped, the crystals are transferred to an ice-salt bath at -10°C and stirred, then allowed to stand to complete the rapid and complete precipitation of crystals. After the crystals precipitate, they are transferred to room temperature, where a large number of fine, bright yellow crystals can be observed to precipitate. The suspension is then filtered using a vacuum filtration device with a microporous membrane with a pore size of 0.45 μm. The crystals are washed twice each with pre-cooled ice water and anhydrous ethanol to remove soluble impurities attached to the surface and maintain a low temperature. Finally, the crystals are dried in a vacuum drying oven at 60°C to obtain dry, loose, bright yellow polyacid FeMo6 crystal powder with a concentrated grain size distribution.
[0052] This embodiment utilizes the strong electrostatic anchoring of FeMo6 and Ni3S2 to optimize the electronic structure and enhance *OH adsorption capacity, effectively improving the catalytic activity and stability of the nickel sulfide electrode material. Its preparation process requires no complex equipment, has low raw material costs, and allows for easy parameter control, providing support for the large-scale application of non-precious metal OER electrocatalysts.
[0053] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the molar ratio of Fe ions to Mo ions in the mixed solution described in step one is 1:(4~6). The other steps are the same as in Specific Implementation Method One.
[0054] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that: in step 1, the mixture is transferred to an ice-salt bath and stirred for 5 to 10 minutes, then left to stand in the ice-salt bath for 10 to 20 minutes. After crystal precipitation, the mixture is transferred to room temperature and left for 5 to 10 minutes. The other steps are the same as in Specific Implementation Method 1 or 2.
[0055] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that: in step two, the nickel foam is cut, and then ultrasonically cleaned sequentially with acetone, 6 mol / L hydrochloric acid, and deionized water, with each ultrasonic cleaning lasting 10 to 20 minutes. Other steps are the same as in Specific Implementation Methods One to Three.
[0056] In this embodiment, hydrochloric acid is used for treatment to achieve controlled corrosion of the oxide layer (such as NiO, Ni(OH)2) on the surface of the nickel foam, which significantly increases the surface roughness, defect density and hydrophilicity, and exposes more highly active nickel sites, thereby greatly enhancing the adhesion strength and nucleation uniformity of subsequent functional materials on the substrate.
[0057] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the preparation method of the mixed solution containing nickel nitrate hexahydrate, ammonium fluoride, and urea in step three is as follows: 1 mmol of nickel nitrate hexahydrate, 6 mmol of ammonium fluoride, and 12 mmol of urea are dissolved in 30 mL to 40 mL of ultrapure water and stirred until homogeneous to obtain the mixed solution containing nickel nitrate hexahydrate, ammonium fluoride, and urea. Other steps are the same as in Specific Implementation Methods One to Four.
[0058] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the temperature of the hydrothermal reaction in step three is 110℃~130℃, and the reaction time is 10h~12h. The other steps are the same as in Specific Implementation Methods One to Five.
[0059] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that: the concentration of the FeMo6 solution mentioned in step four ① is 5 mmol / L to 15 mmol / L; and in step four ②, electrophoresis is performed continuously at a constant voltage of 1.0V for 2 to 3 hours. Other steps are the same as in Specific Implementation Methods One to Six.
[0060] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that: the concentration of the sodium sulfide nonahydrate solution in step five is 0.05 mol / L to 0.15 mol / L; the hydrothermal reaction temperature in step five is 120℃ to 180℃, and the hydrothermal reaction time is 6h to 12h. Other steps are the same as in Specific Implementation Methods One to Seven.
[0061] This embodiment utilizes a high-temperature and high-pressure environment to make S 2- The ions undergo an in-situ anion exchange reaction with Ni(OH)2, realizing the phase transformation from hydroxide to sulfide.
[0062] Specific Embodiment Nine: A heteropolyacid-anchored nickel sulfide self-supporting electrode prepared by any one of the preparation methods described in Specific Embodiments 1 to 8.
[0063] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One through Nine in that it involves the application of a heteropolyacid-anchored nickel sulfide self-supporting electrode in the oxygen evolution reaction in alkaline solution. The other steps are the same as in Specific Implementation Methods One through Nine.
[0064] The beneficial effects of the present invention are verified using the following embodiments:
[0065] Example 1: A method for preparing a heteropolyacid-anchored nickel sulfide self-supporting electrode (POM@Ni3S2 / NF), specifically completed according to the following steps:
[0066] I. Preparation of polyacid FeMo6:
[0067] ① Add 5.2g of ammonium heptamolybdate tetrahydrate to 80mL of boiling deionized water and stir until completely dissolved to obtain a clear and colorless ammonium molybdate solution;
[0068] ② Add 1.2g of ferric sulfate hexahydrate to 20mL of deionized water and sonicate at 100W until completely dissolved to obtain a light green ferric sulfate solution.
[0069] ③ Under stirring conditions, ferric sulfate solution was added dropwise to boiling ammonium molybdate solution at a constant rate of 2 mL / min to obtain a mixed solution. The mixed solution was kept boiling and ultrasonically treated (ultrasonic power of 100 W) for 30 min. A crystalline film appeared on the surface of the solution. Heating was stopped, and the solution was transferred to an ice-salt bath at -10°C and stirred for 5 min. Then it was kept still in the ice-salt bath for 10 min. After the crystals precipitated, the solution was transferred to room temperature (25°C) and left for 5 min. A large amount of fine, bright yellow crystals precipitated. The suspension was filtered using a vacuum filtration device with a microporous membrane with a pore size of 0.45 μm. The crystals were washed twice each with pre-cooled ice water and anhydrous ethanol. The filtered wet crystals were transferred to a petri dish and placed in a vacuum drying oven. The solution was dried at 60°C for 12 h to obtain dry, loose polyacid FeMo6 crystal powder with a concentrated crystal size distribution.
[0070] II. Pretreatment of Nickel Foam:
[0071] Commercially available nickel foam (area density approximately 320 g / m³) 2The nickel foam (with a porosity > 95%) was cut into pieces of 3cm × 4cm × 0.5mm. Then, the nickel foam was ultrasonically cleaned in sequence with acetone, 6mol / L hydrochloric acid, and deionized water for 15 minutes each time to obtain pretreated nickel foam (NF).
[0072] III. Preparation of Ni(OH)2 / NF:
[0073] The pretreated nickel foam was placed in a mixed solution containing nickel nitrate hexahydrate, ammonium fluoride and urea, and then placed in a hydrothermal reactor for hydrothermal reaction at a temperature of 120°C for 12 hours. After the reaction, the nickel foam was removed and washed three times each with ultrapure water and anhydrous ethanol, and then dried at 50°C for 12 hours to obtain the self-supporting electrode Ni(OH)2 / NF.
[0074] The preparation method of the mixed solution containing nickel nitrate hexahydrate, ammonium fluoride and urea in step three is as follows: dissolve 1 mmol nickel nitrate hexahydrate, 6 mmol ammonium fluoride and 12 mmol urea in 35 mL ultrapure water and stir evenly to obtain a mixed solution containing nickel nitrate hexahydrate, ammonium fluoride and urea.
[0075] IV. POM grain aging:
[0076] ① Dissolve the polyacid FeMo6 crystal powder in water to obtain a FeMo6 solution with a concentration of 10 mmol / L;
[0077] ② Using the self-supporting electrode Ni(OH)2 / NF as the working electrode and a platinum sheet as the counter electrode, the two electrodes were immersed in FeMo6 solution in parallel and perpendicular positions. A constant voltage of 1.0V was applied using an electrochemical workstation, and electrophoresis was performed continuously for 2 hours under constant voltage to pre-adsorb FeMo6. After electrophoresis, the electrodes were removed and washed in flowing ultrapure water and anhydrous ethanol for 30 seconds each. Finally, they were placed in a vacuum drying oven and dried at 40℃ and -0.1MPa for 1 hour to obtain the self-supporting electrode POM@Ni(OH)2 / NF.
[0078] V. Preparation of POM@Ni3S2 / NF:
[0079] The self-supporting electrode POM@Ni(OH)2 / NF was placed in a hydrothermal reactor containing sodium sulfide nonahydrate solution for hydrothermal reaction at 150℃ for 8 hours. After the reaction, the electrode was removed and ultrasonically rinsed three times in flowing deionized water and then in anhydrous ethanol for 1 minute each time. Finally, the electrode was transferred to a vacuum drying oven and dried at 50℃ and -0.1 MPa for 12 hours to obtain a heteropolyacid-anchored nickel sulfide self-supporting electrode (POM@Ni3S2 / NF electrode).
[0080] The concentration of the sodium sulfide nonahydrate solution mentioned in step five is 0.1 mol / L.
[0081] Comparing with Example 1: The preparation method of the Ni3S2 / NF electrode is specifically completed according to the following steps:
[0082] I. Pretreatment of Nickel Foam:
[0083] Commercially available nickel foam (area density approximately 320 g / m³) 2 The nickel foam (with a porosity > 95%) was cut into pieces of 3cm × 4cm × 0.5mm. Then, the nickel foam was ultrasonically cleaned in sequence with acetone, 6mol / L hydrochloric acid, and deionized water for 15 minutes each time to obtain the pretreated nickel foam.
[0084] II. Preparation of Ni(OH)2 / NF:
[0085] The pretreated nickel foam was placed in a mixed solution containing nickel nitrate hexahydrate, ammonium fluoride and urea, and then placed in a hydrothermal reactor for hydrothermal reaction at a temperature of 120°C for 12 hours. After the reaction, the nickel foam was removed and washed three times each with ultrapure water and anhydrous ethanol, and then dried at 50°C for 12 hours to obtain the self-supporting electrode Ni(OH)2 / NF.
[0086] The preparation method of the mixed solution containing nickel nitrate hexahydrate, ammonium fluoride and urea in step two is as follows: dissolve 1 mmol nickel nitrate hexahydrate, 6 mmol ammonium fluoride and 12 mmol urea in 35 mL of ultrapure water and stir evenly to obtain a mixed solution containing nickel nitrate hexahydrate, ammonium fluoride and urea.
[0087] III. Preparation of Ni3S2 / NF electrode:
[0088] The self-supported electrode Ni(OH)2 / NF was placed in a hydrothermal reactor containing sodium sulfide nonahydrate solution for hydrothermal reaction at a temperature of 150℃ for 8 hours. After the reaction, the electrode was removed and ultrasonically rinsed three times in flowing deionized water and anhydrous ethanol for 1 minute each time. Finally, the electrode was transferred to a vacuum drying oven and dried at 50℃ and a vacuum of -0.1MPa for 12 hours to obtain the Ni3S2 / NF electrode.
[0089] The concentration of the sodium sulfide nonahydrate solution mentioned in step three is 0.1 mol / L.
[0090] Comparative Example 2: The performance of the electrocatalytic oxygen evolution reaction was evaluated using a commercially available noble metal catalyst as a control sample. IrO2 catalyst was prepared and loaded onto NF: (1) 5 mg of IrO2 catalyst was added to a mixture of 950 μL anhydrous ethanol and 50 μL Nafion solution, and ultrasonically dispersed for 1 h to obtain a uniformly dispersed slurry; (2) 3 cm × 4 cm × 0.5 mm nickel foam (NF) was sequentially ultrasonically cleaned for 15 min each in acetone, 6 M HCl solution, and water, and then coated onto the NF with the slurry obtained in step (1), with a loading of 2.8 mg / cm³. -2 After vacuum drying, the sample IrO2 / NF is obtained.
[0091] Characterization tests:
[0092] like Figure 1 As shown, the polyacid FeMo6 crystal powder prepared in step one of Example 1 was tested using an X-ray diffractometer. The peaks completely corresponded to the theoretically fitted peaks, indicating the successful preparation of polyacid FeMo6.
[0093] like Figure 2 As shown, the POM@Ni3S2 / NF electrode prepared in Example 1 and the Ni3S2 / NF electrode prepared in Control Example 1 were tested using an X-ray diffractometer. All peaks were consistent with the PDF standard cards NF (No. 04-0850) and Ni3S2 (No. 44-1418), indicating the successful preparation of Ni3S2. No POM-related peaks were observed. The FeMo6 nanoparticles were highly dispersed and had a grain size of less than 1 nm. However, the detection limit of X-ray diffraction (XRD) technology is for grains larger than 3 nm, so the characteristic diffraction peaks of FeMo6 could not be identified.
[0094] like Figure 3 As shown, the POM@Ni3S2 / NF electrode prepared in Example 1 and the Ni3S2 / NF electrode prepared in Control Example 1 were tested using Raman spectroscopy at 200-400 cm⁻¹. -1 The wavenumber is the characteristic peak of Ni3S2, 700-1000 cm⁻¹. -1 The wavenumber is a characteristic peak of polyacid FeMo6, indicating successful loading of polyacid.
[0095] like Figure 4 , Figure 5 , Figure 6 and Figure 7 As shown, field emission scanning electron microscopy was used to examine the sample in Example 1.
[0096] Pretreated nickel foam (NF), self-supporting electrode Ni(OH)2 / NF, POM@Ni3S2 / NF electrode, and Ni3S2 / NF electrode prepared in Comparative Example 1 were tested. Scanning electron microscopy (SEM) images show that the pretreated nickel foam (NF) framework has a smooth surface; in the self-supporting electrode Ni(OH)2 / NF, nanosheet structures are vertically grown within the NF framework; the POM@Ni3S2 / NF electrode prepared in Example 1 and the Ni3S2 / NF electrode prepared in Comparative Example 1 retain the nanosheet structure, but the nanosheet surface becomes rougher.
[0097] like Figure 8 As shown, the POM@Ni3S2 / NF electrode prepared in Example 1 was tested using field emission transmission electron microscopy. The transmission electron microscopy images reveal that POM is uniformly distributed on the surface of the nanosheets.
[0098] Electrochemical performance testing:
[0099] All electrochemical tests were performed on a CHI 660E electrochemical workstation (Shanghai Chenhua Instrument Co., Ltd.). In a 1M KOH electrolyte, the pretreated nickel foam (NF) from Example 1, the self-supporting Ni(OH)2 / NF electrode, the POM@Ni3S2 / NF electrode, the Ni3S2 / NF electrode prepared in Control Example 1, and the IrO2 / NF electrode prepared in Control Example 2 were used as working electrodes, respectively. A graphite rod was used as the counter electrode, and a mercuric oxide (Hg / HgO, filled with 1 M KOH) electrode was used as the reference electrode. Oxygen evolution reaction (OER) performance was tested in a standard three-electrode system.
[0100] Figure 9 Linear sweep voltammetry curves of NF, Ni(OH)2 / NF, POM@Ni3S2 / NF prepared in Example 1, Ni3S2 / NF prepared in Control Example 1, and IrO2 / NF prepared in Control Example 2 in 1M KOH solution;
[0101] from Figure 9 As can be seen from this, to achieve 10, 100, and 500 mAcm -2 The overpotentials required for the POM@Ni3S2 / NF electrode prepared in Example 1 were 230, 269, and 312 mV, respectively, which were much lower than the overpotentials of Ni3S2 / NF (269, 373, 498 mV), Ni(OH)2 / NF (339, 430, 569 mV), and IrO2 / NF (approximately 266, 355, 505 mV) prepared in Comparative Example 1; while the maximum current density of NF did not reach 100 mAcm. -2 .
[0102] The OER stability of the POM@Ni3S2 / NF electrode, which exhibits the best OER performance, was tested under different current densities using a chronopotential-time method. The current density was set to 50 mA / cm². -2 and 500mAcm -2 .like Figure 10 As shown, the POM@Ni3S2 / NF electrode exhibits excellent OER stability at different current densities.
Claims
1. A method for preparing a heteropolyacid-anchored nickel sulfide self-supporting electrode, characterized in that... The preparation method is specifically carried out according to the following steps: I. Preparation of polyacid FeMo6: Under stirring conditions, ferric sulfate solution was added dropwise to boiling ammonium molybdate solution to obtain a mixed solution; the mixed solution was kept boiling and ultrasonic was applied until a crystal film appeared on the surface of the solution. Heating was stopped, and the solution was transferred to an ice-salt bath for stirring. After standing, the crystals precipitated and were placed at room temperature. The yellow crystals were then washed and dried to obtain polyacid FeMo6 crystal powder. II. Pretreatment of Nickel Foam: The nickel foam is cut and then cleaned to obtain pretreated nickel foam; III. Preparation of Ni(OH)2 / NF: The pretreated nickel foam was placed in a mixed solution containing nickel nitrate hexahydrate, ammonium fluoride and urea, and then placed in a hydrothermal reactor for hydrothermal reaction; after the reaction was completed, the nickel foam was removed, washed and dried to obtain the self-supporting electrode Ni(OH)2 / NF. IV. POM grain aging: ① Dissolve the polyacid FeMo6 crystal powder in water to obtain a FeMo6 solution; ② Using the self-supporting electrode Ni(OH)2 / NF as the working electrode and a platinum sheet as the counter electrode, the two electrodes were immersed in FeMo6 solution in parallel and perpendicular positions. Electrophoresis was performed continuously under constant voltage to pre-adsorb FeMo6. After electrophoresis, the electrodes were removed, cleaned, and dried to obtain the self-supporting electrode POM@Ni(OH)2 / NF. V. Preparation of POM@Ni3S2 / NF: The self-supporting electrode POM@Ni(OH)2 / NF was placed in a hydrothermal reactor containing a sodium sulfide nonahydrate solution for hydrothermal reaction. After the reaction was completed, the electrode was removed, rinsed, and dried to obtain a heteropolyacid-anchored nickel sulfide self-supporting electrode.
2. The method for preparing a heteropolyacid-anchored nickel sulfide self-supporting electrode according to claim 1, characterized in that... The molar ratio of Fe ions to Mo ions in the mixed solution described in step one is 1:(4~6).
3. The method for preparing a heteropolyacid-anchored nickel sulfide self-supporting electrode according to claim 1, characterized in that... In step one, transfer the mixture to an ice-salt bath and stir for 5 to 10 minutes, then let it stand in the ice-salt bath for 10 to 20 minutes. After the crystals precipitate, transfer it to room temperature and let it stand for 5 to 10 minutes.
4. The method for preparing a heteropolyacid-anchored nickel sulfide self-supporting electrode according to claim 1, characterized in that... In step two, the nickel foam is cut and then ultrasonically cleaned in sequence with acetone, 6 mol / L hydrochloric acid, and deionized water for 10 to 20 minutes each time.
5. The method for preparing a heteropolyacid-anchored nickel sulfide self-supporting electrode according to claim 1, characterized in that... The preparation method of the mixed solution containing nickel nitrate hexahydrate, ammonium fluoride and urea in step three is as follows: dissolve 1 mmol nickel nitrate hexahydrate, 6 mmol ammonium fluoride and 12 mmol urea in 30 mL to 40 mL of ultrapure water and stir evenly to obtain a mixed solution containing nickel nitrate hexahydrate, ammonium fluoride and urea.
6. The method for preparing a heteropolyacid-anchored nickel sulfide self-supporting electrode according to claim 1, characterized in that... The hydrothermal reaction in step three is carried out at a temperature of 110℃~130℃ for 10h~12h.
7. The method for preparing a heteropolyacid-anchored nickel sulfide self-supporting electrode according to claim 1, characterized in that... The concentration of the FeMo6 solution mentioned in step 4① is 5 mmol / L to 15 mmol / L; in step 4②, electrophoresis is performed continuously at a constant voltage of 1.0V for 2 to 3 hours.
8. The method for preparing a heteropolyacid-anchored nickel sulfide self-supporting electrode according to claim 1, characterized in that... The concentration of the sodium sulfide nonahydrate solution in step five is 0.05 mol / L to 0.15 mol / L; the temperature of the hydrothermal reaction in step five is 120℃ to 180℃, and the hydrothermal reaction time is 6h to 12h.
9. A heteropolyacid-anchored nickel sulfide self-supporting electrode prepared by the preparation method according to any one of claims 1 to 8.
10. The application of the heteropolyacid-anchored nickel sulfide self-supporting electrode according to claim 9, characterized in that... Application of heteropolyacid-anchored nickel sulfide self-supporting electrode in oxygen evolution reaction in alkaline solution.