Method of making a ni-fe-l dh carbonate and oxalate hybrid electrocatalyst, product and use

Abstract

This invention discloses a method for preparing a NiFe-LDH carbonate and oxalate hybrid electrocatalyst, comprising the following steps: S1, preparing NiFe-LDH carbonate and oxalate hybrid electrocatalyst. 2+ Salt and Fe 3+ The salt is dissolved in water, and then carbonate and oxalate are added to obtain solution A; Ni 2+ The molar ratio of salt to Fe³⁺ salt is 2–4:1, and the molar ratio of carbonate salt to oxalate salt is 1:0.5–2. S2: At room temperature, a noble metal precursor solution is added dropwise to solution A, with a noble metal loading of 0.05–0.5 wt%, to obtain solution B. S3: An alkaline solution is added dropwise to solution B to adjust the pH to 9.5–11.0, and the co-precipitation reaction is carried out at room temperature for 2–6 h. The precipitate C is obtained by filtration. S4: Precipitate C is powdered to obtain the electrocatalyst. This method effectively solves the problems of difficult morphology control, easy agglomeration of single-atom loading, insufficient amorphous phase ratio, and high production cost.

Description

Technical Field

[0001] This invention relates to a method for preparing an electrocatalyst, and more particularly to a method, product, and application of a NiFe-LDH carbonate-oxalate hybrid electrocatalyst. Background Technology

[0002] The oxygen evolution reaction (OER), a key anodic half-reaction in the water electrolysis hydrogen production process, involves a complex four-electron-to-four-proton transfer process. Its extremely slow kinetics necessitate a high overpotential, making it a significant bottleneck hindering the efficient and low-cost commercialization of alkaline / neutral / acidic water splitting technologies. Traditionally, noble metal oxides such as IrO2 and RuO2 have been considered benchmarks for OER performance; however, they suffer from fatal drawbacks such as extremely low abundance of precious metals in the Earth's crust, high cost, limited resources, and poor economics for large-scale production, severely restricting their widespread application in GW-scale green hydrogen industries.

[0003] Against this backdrop, the development of non-precious metal-based OER catalysts has become a core focus for both academia and industry. Among them, NiFe layered double hydroxides (NiFe-LDH), with their unique layered structure, tunable metal composition ratios, relatively abundant reserves on Earth, and high intrinsic activity in alkaline media, have rapidly emerged as one of the most promising non-precious metal OER catalyst platforms. 3+ The introduction of this substance triggers a unique dd-electron coupling effect and partial charge transfer between Ni and Fe, leading to an increase in the oxidation state of Ni and a rearrangement of its electronic structure, which significantly optimizes the key intermediate for OER ( OH、 O、 The adsorption energy of OOH) gives NiFe-LDH an OER performance far superior to that of similar materials such as pure Ni(OH)2, Co(OH)2, NiAl-LDH, or NiCo-LDH. Studies have shown that in alkaline media, NiFe-LDH can achieve an OER of ≤200 mV at 10 mA·cm⁻¹. -2 Overpotential, Tafel slope can be as low as 30-40 mV·dec -1 It has approached or even surpassed the performance level of noble metal benchmark catalysts under certain conditions.

[0004] However, the current mainstream NiFe-LDH preparation still heavily relies on hydrothermal / solvothermal methods, which typically require reactions at high temperatures of 120-200℃ and autogenous pressure in an autoclave for several to tens of hours. This traditional method has several significant drawbacks: (1) Difficulty in morphological control: The hydrothermal process is highly sensitive to parameters such as temperature, pH, precursor concentration, and solvent polarity, making it difficult to accurately and reproducibly prepare ultrathin nanosheet array structures with high exposure and high specific surface area. Actual products often exhibit random orientation, severe stacking, or uneven size distribution, significantly limiting the effective specific surface area and mass transport efficiency. 3+ with Ni 2+ The synergistic effect was not fully realized.

[0005] (2) Single-atom loading is prone to aggregation: When attempting to load extremely low amounts of Ir or Ru single atoms to achieve synergistic enhancement of noble metals, the highly crystalline surface generated by the hydrothermal method lacks sufficient anchoring sites. Noble metal atoms are prone to surface migration, aggregation into clusters or nanoparticles under thermodynamic drive, resulting in a sharp decrease in single-atom utilization and making it impossible to achieve efficient synergistic catalysis under ultra-low loading.

[0006] (3) Insufficient proportion of amorphous phase: Hydrothermal high temperature and high pressure conditions naturally promote the formation of highly crystalline products, which is not conducive to the retention of amorphous / low crystalline phases. Numerous studies have shown that amorphous NiFe-LDH has a much better intrinsic OER activity than its highly crystalline counterpart due to its abundant coordination unsaturated sites, large number of oxygen vacancies, and grain boundary defects. Traditional hydrothermal methods are difficult to achieve a high proportion of amorphization while maintaining the high activity of NiFe.

[0007] (4) High energy and equipment costs: The high temperature and high pressure process consumes a lot of energy, has a long cycle, and requires stringent equipment, which is seriously inconsistent with the development goals of the green, low carbon and rapid hydrogen energy industry. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing, a product of, and an application of a NiFe-LDH carbonate-oxalate hybrid electrocatalyst, so as to effectively solve the above-mentioned technical problems.

[0009] The technical solution of this invention: A method for preparing a NiFe-LDH carbonate and oxalate hybrid electrocatalyst, comprising the following steps: S1, Ni 2+ Salt and Fe 3+ The salt is dissolved in water, and then carbonate and oxalate are added to obtain solution A; Ni 2+ The molar ratio of salt to Fe³⁺ salt is 2–4:1, and the molar ratio of carbonate salt to oxalate salt is 1:0.5–2. S2. At room temperature, a noble metal precursor solution is added dropwise to solution A, wherein the loading of noble metal in the noble metal precursor solution is 0.05-0.5 wt%, to obtain solution B. S3. Add alkaline solution to solution B to adjust the pH to 9.5-11.0, and co-precipitate at room temperature for 2-6 hours. Filter to obtain precipitate C. S4. The precipitate C is prepared into powder to obtain an electrocatalyst.

[0010] In the aforementioned method for preparing NiFe-LDH carbonate and oxalate hybrid electrocatalyst, step S4 involves the following steps: aging, centrifuging, and washing the precipitate C, followed by vacuum drying at 40-65°C for 8-15 hours to obtain the electrocatalyst.

[0011] In the aforementioned method for preparing the NiFe-LDH carbonate and oxalate hybrid electrocatalyst, the oxalate salt is at least one of sodium oxalate, potassium oxalate, and ammonium oxalate.

[0012] In the aforementioned method for preparing NiFe-LDH carbonate and oxalate hybrid electrocatalysts, the carbonate salt is Na2CO3 or (NH4)2CO3.

[0013] In the aforementioned method for preparing the NiFe-LDH carbonate and oxalate hybrid electrocatalyst, the molar ratio of carbonate salt to oxalate salt is 1:0.6–1.5; Ni 2+ Salt and Fe 3+ The molar ratio of salts is 2.5 to 3.5:1.

[0014] In the aforementioned method for preparing NiFe-LDH carbonate and oxalate hybrid electrocatalysts, Ni 2+ The salt is Ni(NO3)2·6H2O, Fe 3+ The salt is Fe(NO3)3·9H2O.

[0015] In the aforementioned method for preparing a NiFe-LDH carbonate and oxalate hybrid electrocatalyst, or in step S3, nickel foam, carbon cloth, titanium mesh, and stainless steel mesh are placed in a solution, impregnated in situ, and co-precipitated to obtain an integrated electrode with an electrocatalyst.

[0016] An electrocatalyst, prepared by the aforementioned method for preparing electrocatalysts based on NiFe-LDH carbonate and oxalate hybridization; the electrocatalyst exhibits a nanosheet array morphology with a specific surface area ≥300 m². 2 / g.

[0017] In one of the aforementioned electrocatalysts, the amorphous region accounts for 55% to 68%.

[0018] The application of electrocatalysts in alkaline / neutral water electrolysis hydrogen production devices, electrolyzer membrane electrode assemblies, industrial alkaline electrolyzer electrodes, or regenerative fuel cells, wherein the electrocatalyst is one of the aforementioned electrocatalysts.

[0019] Carbonate provides a rigid lamellar framework, maintaining the integrity of the basic layered structure of LDH; oxalate (C2O4) 2-As a planar bidentate ligand, its two carboxyl groups can form a bridging coordination mode between LDH layers, creating a stable cooperative electronic environment with carbonate hybrid intercalation. The bidentate chelating ability of oxalate precisely captures and guides noble metal ions to nucleate and grow, forming a highly exposed ultrathin nanosheet array; the hybrid anion simultaneously constructs an auxiliary electron trap, synergistically enhancing Fe... 3+ The unique d-band modulation effect optimizes the adsorption energy of OER intermediates; room temperature conditions significantly inhibit crystal growth, resulting in an amorphous phase ratio of 55%–68%, exposing a large number of edge and crystal-amorphous interface active sites. NiFe electronic synergy and carbonate / oxalate hybridization modulation achieve a breakthrough improvement in OER performance.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Achieve precise morphology control of ultrathin nanosheet arrays: Obtain highly exposed ultrathin nanosheet arrays in one step, with a specific surface area ≥310 m² / g, significantly improved exposure rate of edge active sites, and abundant electrolyte and bubble transport channels; 2. Compared with the traditional hydrothermal method, the present invention is completed at room temperature and atmospheric pressure throughout the process, without the need for high temperature and high pressure, additional templates or surfactants, reducing energy consumption by more than 80% and process complexity by 70%. It can be directly grown in situ on conductive current collectors such as nickel foam, carbon cloth, and titanium mesh, eliminating the coating and binder steps, and is particularly suitable for industrial large-area electrode preparation. 3. Amorphous phase ratio 55%–68% (XRD shows significant broadening peaks, crystallinity reduced by 45%–65% compared to hydrothermal method), combined with oxalate / carbonate hybrid electron traps and Fe 3+ Its unique electronic regulation increases the density of active sites by 2 to 3 times, and the utilization rate of noble metal atoms is close to 100%. 4. Achieving 10mA·cm under ultra-low load conditions -2 Overpotential ≤195 mV, Tafel slope ≤38 mV·dec -1 The stability decay is less than 4% after 1000 h. The intrinsic high activity of NiFe, the synergistic electronic regulation of hybridization, and the synergistic gain of ultra-low precious metals result in comprehensive OER performance that surpasses existing NiFe-LDH-based catalyst systems, giving it a significant competitive advantage in the field of water electrolysis for hydrogen production. Attached Figure Description

[0021] Figure 1 XRD patterns (comparison of room temperature preparation in Example 1 and hydrothermal method at 180°C in Comparative Example 4).

[0022] Figure 2 FTIR spectrum (Example 1); Figure 3 Polarization curve diagram; Figure 4 Overpotential comparison diagram; Figure 5 Tafel curve; Figure 6 Stability test graph; Figure 7 SEM image of Example 1; Figure 8 SEM image of Comparative Example 4. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0024] To address the series of technical challenges faced by traditional hydrothermal methods for NiFe-LDH preparation, such as uncontrollable morphology, unstable single-atom anchoring, insufficient amorphous phase ratio, high energy density, and high cost, this invention proposes a novel room-temperature one-step co-precipitation strategy. This process, under mild conditions of room temperature and pressure, without the need for heating or high-pressure equipment, introduces carbonate ions (CO3-)... 2- ) and oxalate (C2O4) 2— Hybrid anion systems enable synergistic regulation across multiple scales and functions: Morphology guidance of ultrathin nanosheet arrays: carbonate ions provide stable interlayer support and pH buffering, while the bidentate coordination mode of oxalate ions regulates the nucleation rate and crystal facet selectivity, inducing the formation of highly exposed ultrathin nanosheet array structures, which significantly improves the exposure of active sites, electrolyte wettability and electron / ion transport efficiency.

[0025] Strong anchoring and stable dispersion of single atoms: The two adjacent carboxyl oxygen atoms of oxalate can form a five-membered chelate ring, which can accurately capture noble metal ions. Combined with the abundant defects induced by carbonate (oxygen vacancies, coordination unsaturated sites, low crystallinity regions), high affinity anchoring sites are constructed in situ at room temperature, which can effectively capture and stabilize Ir / Ru single atoms, significantly inhibit agglomeration, and achieve atomic-level high dispersion and high utilization.

[0026] Amorphous phase enrichment and electronic structure optimization: Room temperature rapid precipitation process "freezes" a high proportion of amorphous / low-crystallinity phases (55%-68%), significantly increasing grain boundaries, defect density, and localized electron traps. Fe 3+ The d-band modulation combined with the synergistic electronic effect of hybrid anions further optimizes the adsorption energy of key OER intermediates and reduces overpotential.

[0027] Meanwhile, this room-temperature hybrid anion-induced strategy completely breaks through the energy and equipment barriers of traditional methods, significantly simplifies the process, reduces costs, and improves scalability. It provides a green and efficient technical path for achieving ultimate OER performance under ultra-low noble metal loading conditions based on the NiFe-LDH platform, and has outstanding academic innovation significance and broad industrial application prospects.

[0028] Example. A method for preparing a NiFe-LDH carbonate and oxalate hybrid electrocatalyst, characterized by comprising the following steps: S1, Ni 2+ Salt and Fe 3+ The salt is dissolved in water, and then carbonate and oxalate are added to obtain solution A; Ni 2+ The molar ratio of salt to Fe³⁺ salt is 2–4:1, and the molar ratio of carbonate salt to oxalate salt is 1:0.5–2. S2. At room temperature, a noble metal precursor solution is added dropwise to solution A, wherein the loading of noble metal in the noble metal precursor solution is 0.05-0.5 wt%, to obtain solution B. S3. Add alkaline solution to solution B to adjust the pH to 9.5-11.0, and co-precipitate at room temperature for 2-6 hours. Filter to obtain precipitate C. S4. The precipitate C is prepared into powder to obtain an electrocatalyst.

[0029] In step S4, the powder preparation process is as follows: the precipitate C is aged, centrifuged and washed, and then vacuum dried at 40-65℃ for 8-15 hours to obtain the electrocatalyst.

[0030] Oxalate salts are at least one of sodium oxalate, potassium oxalate, and ammonium oxalate.

[0031] The carbonate is Na2CO3 or (NH4)2CO3.

[0032] The molar ratio of carbonate to oxalate is 1:0.6–1.5; Ni 2+ Salt and Fe 3+ The molar ratio of salts is 2.5 to 3.5:1.

[0033] Ni 2+ The salt is Ni(NO3)2·6H2O, Fe 3+ The salt is Fe(NO3)3·9H2O.

[0034] Alternatively, in step S3, nickel foam, carbon cloth, titanium mesh, and stainless steel mesh are placed in the solution, impregnated in situ, and co-precipitated to obtain an integrated electrode with an electrocatalyst.

[0035] An electrocatalyst was prepared using the aforementioned method for preparing electrocatalysts based on NiFe-LDH carbonate and oxalate hybridization; the electrocatalyst exhibits a nanosheet array morphology with a specific surface area ≥300 m². 2 / g.

[0036] The amorphous region of the electrocatalyst accounts for 55% to 68%.

[0037] In a 1 M KOH solution, the current density is 10 mA·cm⁻¹ -2 The overpotential at that time is ≤195 mV.

[0038] In 1 M KOH @ 10 mA·cm -2 After 1000 hours of constant current testing, the overpotential decay is ≤4%.

[0039] The application of electrocatalysts in alkaline / neutral water electrolysis hydrogen production devices, electrolyzer membrane electrode assemblies, industrial alkaline electrolyzer electrodes, or regenerative fuel cells, wherein the electrocatalyst is one of the aforementioned electrocatalysts.

[0040] Example 1. (NiFe + CO3) 2- (+oxalate system, ultrathin nanosheet array morphology) Ni(NO3)2·6H2O, 2.908 g; Fe(NO3)3·9H2O, 2.020 g; Na2CO3, 0.530 g; Na2C2O4, 0.670 g; dissolved in 100 mL of deionized water. 0.6 mL of 0.01 mol / L H2IrCl6 solution (theoretical Ir loading 0.25 wt%) was added dropwise with stirring at room temperature. 1M NaOH solution was slowly added until pH=10.0, and the reaction was allowed to proceed for 3.5 h at room temperature. After aging for 12 h, the mixture was centrifuged, washed, and vacuum dried at 60℃ for 12 h to obtain an IrSA@CO3 / C2O4-NiFe-LDH ultrathin nanosheet array.

[0041] SEM revealed a highly ordered array of ultrathin nanosheets. Figure 7 As shown, a is the view at 5 μm magnification, and b is the view at 2 μm magnification), with a specific surface area of ​​322 m² / g; the XRD (003) peak is significantly broadened ( Figure 1 As shown), the amorphous region accounts for approximately 62%. In 1 MKOH, 10 mA·cm -2 Overpotential 191 mV, Tafel slope 33 mV·dec -1 The decay rate is 3.2% over 1000 hours.

[0042] Example 2 (Ru system).

[0043] The noble metal precursor in Example 1 was replaced with RuCl3 (Ru loading 0.20 wt%), with all other conditions remaining the same. The resulting catalyst had a specific surface area of ​​318 m² / g, an overpotential of 193 mV, and a Tafel slope of 36 mV·dec. -1 The decay rate is 3.5% over 1000 hours.

[0044] Example 3 (direct in-situ growth on nickel foam).

[0045] The powder preparation process in Example 1 was modified by in-situ impregnation-co-precipitation on pretreated nickel foam, while all other conditions remained the same. The resulting integrated electrode had a specific surface area of ​​315 m² / g, an overpotential of 189 mV, and a decay of 3.0% over 1000 h. The electrode / catalyst interface showed strong bonding with no detachment.

[0046] Comparative Example 4 (Hydrothermal method control example).

[0047] Ir / NiFe-LDH of the same composition (without oxalate / carbonate) was prepared by hydrothermal treatment at 180℃ for 12 h. The morphology consisted of severely stacked thick lamellar layers, with no observable amorphous components with rough edges. Figure 8 As shown, c is a view of the SEM of Comparative Example 4 at a magnification of 5 μm (specific surface area < 145 m²). 2 / g, overpotential 258 mV, Tafel slope 52 mV·dec -1 The decay rate is 28% over 200 hours.

[0048] Comparative Example 5 (Oxalate-free room temperature control).

[0049] Using only Na2CO3, the rest is the same as in Example 1. The nanosheet array has an irregular morphology and a specific surface area of ​​185 m². 2 / g, amorphous phase only about 42%, overpotential 228 mV, Tafel slope 45 mV·dec -1 .

[0050] Comparative Example 6 (Bis carbonate-free room temperature control) Only Na2C2O4 was used; everything else was the same as in Example 1. The LDH layered structure was incomplete, its morphology was out of control, and its specific surface area was <130 m². 2 / g, overpotential 247 mV, poor stability (42% decay in 200 h).

Claims

1. A method for preparing a NiFe-LDH carbonate and oxalate hybrid electrocatalyst, characterized in that, Includes the following steps: S1, Ni 2+ Salt and Fe 3+ The salt is dissolved in water, and then carbonate and oxalate are added to obtain solution A; Ni 2+ The molar ratio of salt to Fe³⁺ salt is 2–4:1, and the molar ratio of carbonate salt to oxalate salt is 1:0.5–2. S2. At room temperature, a noble metal precursor solution is added dropwise to solution A, wherein the loading of noble metal in the noble metal precursor solution is 0.05-0.5 wt%, to obtain solution B. S3. Add alkaline solution to solution B to adjust the pH to 9.5-11.0, and co-precipitate at room temperature for 2-6 hours. Filter to obtain precipitate C. S4. The precipitate C is prepared into powder to obtain an electrocatalyst.

2. The method for preparing the NiFe-LDH carbonate and oxalate hybrid electrocatalyst according to claim 1, characterized in that, In step S4, the powder preparation process is as follows: the precipitate C is aged, centrifuged and washed, and then vacuum dried at 40-65℃ for 8-15 hours to obtain the electrocatalyst.

3. The method for preparing the NiFe-LDH carbonate and oxalate hybrid electrocatalyst according to claim 1, characterized in that, Oxalate salts are at least one of sodium oxalate, potassium oxalate, and ammonium oxalate.

4. The method for preparing the NiFe-LDH carbonate and oxalate hybrid electrocatalyst according to claim 1, characterized in that: The carbonate is Na2CO3 or (NH4)2CO3.

5. The method for preparing the NiFe-LDH carbonate and oxalate hybrid electrocatalyst according to claim 1, characterized in that, The molar ratio of carbonate to oxalate is 1:0.6–1.5; Ni 2+ Salt and Fe 3+ The molar ratio of salts is 2.5 to 3.5:

1.

6. The method for preparing the NiFe-LDH carbonate and oxalate hybrid electrocatalyst according to claim 1, characterized in that, Ni 2+ The salt is Ni(NO3)2·6H2O, Fe 3+ The salt is Fe(NO3)3·9H2O.

7. The method for preparing the NiFe-LDH carbonate and oxalate hybrid electrocatalyst according to claim 1, characterized in that: Alternatively, in step S3, nickel foam, carbon cloth, titanium mesh, and stainless steel mesh are placed in the solution, impregnated in situ, and co-precipitated to obtain an integrated electrode with an electrocatalyst.

8. An electrocatalyst, characterized in that, The electrocatalyst is prepared by any one of the methods described in claims 1-6, which involves the hybridization of NiFe-LDH carbonate and oxalate ions; the electrocatalyst exhibits a nanosheet array morphology with a specific surface area ≥300 m². 2 / g.

9. An electrocatalyst according to claim 1, characterized in that, The amorphous region of the electrocatalyst accounts for 55% to 68%.

10. The application of electrocatalysts in alkaline / neutral water electrolysis hydrogen production devices, electrolyzer membrane electrode assemblies, industrial alkaline electrolyzer electrodes, or regenerative fuel cells, characterized in that, The electrocatalyst is one of the electrocatalysts described in claim 8 or 9.

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