NiFe-based catalyst resistant to chlorine corrosion, and preparation method and application thereof

Abstract

The application relates to the technical field of functional materials, and discloses a NiFe-based catalyst resistant to chlorine corrosion and a preparation method and application thereof, the preparation method comprising the following steps: dispersing a nickel source, a zinc source, an iron source and a precipitant in deionized water, uniformly stirring and then reacting, and preparing a precursor after cooling, washing and drying; and placing the precursor in a strong alkali solution, performing immersion etching, and obtaining the catalyst. The precursor with rich active sites is uniformly grown on the substrate through a hydrothermal method, and the Zn is partially etched through a normal-temperature immersion etching method, a large number of oxygen vacancies are introduced, the overpotential of OER is significantly reduced, and the OER activity in seawater splitting is promoted.

Description

Technical Field

[0001] This invention belongs to the field of functional materials technology, and specifically relates to an electrocatalytic material, namely a NiFe-based catalyst resistant to chlorine corrosion, its preparation method and application. Background Technology

[0002] Electrolysis of water to produce hydrogen is currently the most promising green hydrogen production technology. However, traditional freshwater electrolysis relies on scarce freshwater resources, creating a significant conflict with the increasingly severe global supply and demand imbalance for freshwater. Seawater, which accounts for 96.5% of the Earth's total water resources, offers a solution. Developing efficient and stable seawater electrolysis technology for hydrogen production can not only overcome freshwater resource limitations but also provide a sustainable raw material guarantee for the large-scale application of hydrogen energy, thus possessing significant strategic importance and application value.

[0003] The seawater electrolysis hydrogen production process mainly involves two half-reactions: the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode. The OER, due to its involvement of multiple electron transfers and complex intermediate formation processes, presents an extremely high kinetic energy barrier, making it a key bottleneck leading to excessive energy consumption in the electrolysis process. This has resulted in traditional seawater electrolysis technologies heavily relying on noble metal-based catalysts such as Ir and Ru to reduce reaction energy consumption. In recent years, significant progress has been made in the development of non-noble metal OER catalysts, attempting to replace expensive noble metal materials. However, most non-noble metal catalysts still face two major challenges in practical seawater electrolysis scenarios: First, it is difficult to meet the high current density required for industrial applications (typically ≥500 mA·cm). -2 Under the requirement of long-term stable operation, catalytic activity is prone to rapid decay; Second, the high concentration of chloride ions (Cl) in the seawater system - Not only does it cause anodic oxidation to generate chlorine gas during electrolysis, but it also causes severe corrosion to the active sites of the catalyst, resulting in a significant decrease in catalyst activity and a significant shortening of its service life.

[0004] The aforementioned issues have become the core obstacles restricting the industrialization of seawater electrolysis hydrogen production technology.

[0005] To address the aforementioned issues, developing non-precious metal catalysts that combine high OER activity with strong resistance to chlorine corrosion has become a research hotspot and challenge in this field. Among numerous non-precious metal materials, NiFe-based catalysts are widely regarded as ideal candidates for seawater electrolysis OER catalysts due to their excellent intrinsic OER activity, abundant reserves, and low cost.

[0006] In existing technologies, modified NiFe-based catalysts for alkaline seawater electrolysis primarily focus on introducing non-metallic elements such as nitrogen, sulfur, phosphorus, and boron through high-temperature processes such as hydrothermal methods and vapor deposition. The aim is to counteract the effects of Cl- by in-situ formation of oxygen-containing anionic species during electrolysis.- Corrosion. However, this type of high-temperature preparation process has significant drawbacks: On the one hand, high-temperature environments can cause irreversible damage to the framework structure of commonly used substrates such as nickel foam, affecting the mechanical stability of the electrodes; On the other hand, the violent impact of large-sized oxygen bubbles during electrolysis can exacerbate the shedding of the catalytic phase, leading to insufficient long-term operational stability of the catalyst.

[0007] Therefore, existing technologies still cannot fundamentally solve the core problems of chlorine corrosion and stability. Developing a NiFe-based catalyst with a mild preparation process, excellent resistance to chlorine corrosion, and high activity and long-term stability at high current densities has become a key technological bottleneck that urgently needs to be overcome in the industrialization process of seawater electrolysis hydrogen production technology. Summary of the Invention

[0008] To address the problems of existing non-precious metal catalysts used in seawater electrolysis for hydrogen production, such as difficulty in achieving stable operation at high current densities, rapid degradation, insufficient long-term stability, weak resistance to chlorine corrosion, and demanding preparation processes, this invention provides a chlorine-resistant NiFe-based catalyst, its preparation method, and its application.

[0009] This invention is achieved using the following technical solution: This invention provides a method for preparing a NiFe-based catalyst resistant to chlorine corrosion, comprising the following steps: S1, using a hydrothermal growth method, with nickel foam as the substrate, nickel source, zinc source, iron source and precipitant are dispersed in deionized water, the molar ratio of nickel source, zinc source, iron source and precipitant is (0.2~0.5):(0.5~1):(0.5~1):(4~6), preferably, the nickel source is nickel nitrate hexahydrate, the zinc source is zinc nitrate hexahydrate, the iron source is ferric chloride hexahydrate, and the precipitant is urea. After stirring evenly, it is transferred to a reaction vessel and reacted at 100~120℃ for 10~12h. After cooling, washing and drying, NiFeZn precursor is obtained. Specifically, the following steps are included: S11: Weigh 0.2-0.5 mmol nickel nitrate hexahydrate, 0.5-1 mmol zinc nitrate hexahydrate, 0.5-1 mmol ferric chloride hexahydrate, and 4-6 mmol urea, disperse them in 20-40 mL of deionized water, stir well, and prepare the precursor solution for the hydrothermal reaction. S12, the precursor solution is transferred to the reactor, and nickel foam is placed in the precursor solution. After sealing, it is reacted at 100~120℃ for 10~12h. S13, after the reaction is complete, cool naturally to room temperature, remove the substrate and rinse it alternately with deionized water and ethanol; S14 was rinsed and dried to obtain the NiFeZn precursor.

[0010] S2. Using room temperature immersion etching, the NiFeZn precursor obtained in step S1 is placed in a strong alkaline solution, which is a NaOH solution with a concentration of 4~8 mol / L. The strong alkaline environment passivates the Zn species. The immersion etching is carried out at room temperature for 12~24 h to obtain an oxygen-rich D-NiFeZn catalyst, where D represents a defect.

[0011] The present invention also provides a NiFe-based catalyst resistant to chlorine corrosion prepared by the above preparation method.

[0012] Specifically, the NiFe-based catalyst is a D-NiFeZn catalyst, which is supported on a nickel foam framework and forms a self-supporting structure; the surface of the NiFe-based catalyst contains Zn(OH)4. 2- Passivation layer, Zn(OH)4 2- The passivation layer effectively resists Cl in seawater - corrosion.

[0013] The present invention also provides the application of the above-mentioned chlorine-resistant NiFe-based catalyst in the electrolysis of seawater to produce hydrogen.

[0014] Specifically, NiFe-based catalysts are used as anodes and / or cathodes in alkaline anion exchange membrane electrolyzers.

[0015] Specifically, it is applied to current densities of 1 A·cm -2 Hydrogen production by electrolysis of seawater.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a NiFe-based catalyst resistant to chlorine corrosion, its preparation method, and its application. A nanosheet-like NiFeZn precursor is uniformly grown on a nickel foam substrate using a hydrothermal method, resulting in a NiFeZn precursor with abundant active sites. The Zn portion is then etched using a room-temperature immersion etching method, introducing a large number of oxygen vacancies (O2) during the etching process. v On the one hand, this process facilitates the formation of the highly active γ-NiOOH phase; on the other hand, it stimulates the lattice oxygen in the NiFe-based catalyst to participate in the OER (Organic Erosion Reactor). The synergistic effect of these two processes significantly reduces the overpotential of the OER, promoting its OER activity in seawater pyrolysis. Simultaneously, during the etching process, the strongly alkaline environment passivates the Zn species, allowing for the in-situ generation of stable Zn(OH)4 on the surface of the NiFeZn catalyst. 2- The passivation layer effectively repels Cl from seawater. - The adsorption of Cl in seawater allows the NiFeZn catalyst to effectively resist the adsorption of Cl. - To prevent corrosion and damage to active sites.

[0017] Compared to existing NiFe-based nickel foam self-supporting catalysts, this invention does not use traditional high-temperature non-metallic element doping processes, nor does it use non-metallic elements such as nitrogen, sulfur, phosphorus, and boron for modification, effectively reducing the damage to the nickel foam substrate caused by traditional weakly acidic preparation environments and high-temperature treatments.

[0018] The preparation method of this invention requires only two steps: hydrothermal treatment and room temperature impregnation. The steps are simple and the process is controllable. It does not require precious metals or complex precursors, resulting in low raw material costs. Experiments show that at 1 A·cm -2 Under the specified current density conditions, the prepared NiFeZn catalyst showed no significant morphological change after 1000 hours of stable pyrolysis of alkaline seawater in an alkaline anion exchange membrane electrolyzer, demonstrating significantly better performance than traditional non-precious metal catalysts. This catalyst exhibits excellent stability in alkaline seawater pyrolysis. The electrode application of this invention meets the objective requirements of industrial seawater pyrolysis equipment for long-term, high-efficiency catalytic materials and holds promise for large-scale production. Attached Figure Description

[0019] Figure 1 This shows the SEM image of the product obtained in Example 1 of the present invention.

[0020] Figure 2 This shows the SEM image of the product obtained in Example 2 of the present invention.

[0021] Figure 3 This is a SEM image of the product obtained in Example 3 of the present invention.

[0022] Figure 4 The image shows the XRD pattern of the product obtained in Example 1 of the present invention.

[0023] Figure 5 The diagram shows the electron paramagnetic (EPR) pattern of the product obtained in Example 1 of the present invention.

[0024] Figure 6 The image shows the Zn 2p XPS diagram of the product obtained in Example 1 of the present invention.

[0025] Figure 7 The OER polarization curves of the products obtained in Examples 1, 2, 3, Comparative Example 1 and Comparative Example 2 of the present invention are shown in alkaline electrolyte.

[0026] Figure 8 The image shows the Vt polarization curve of the product obtained in Example 1 of this invention after pyrolyzing alkaline natural seawater in an alkaline anion exchange membrane electrolyzer.

[0027] Figure 9 The figure shows the Vt polarization curve of the product obtained in Comparative Example 2 of the present invention during OER in alkaline natural seawater.

[0028] Figure 10This is a SEM image of the product obtained in Example 1 of the present invention after OER testing in alkaline natural seawater.

[0029] Figure 11 The OH groups of the products obtained in Example 1 and Comparative Example 2 of this invention represent the OH groups of the products obtained in Example 1 and Comparative Example 2 of this invention. and Cl Comparison chart of adsorption energy calculation results.

[0030] Figure 12 The images show Raman characterization diagrams of the product obtained in Example 1 of the present invention at different oxidation potentials.

[0031] Figure 13 The infrared characterization images of the product obtained in Example 1 of the present invention at different oxidation potentials are shown. Detailed Implementation

[0032] The specific embodiments of the present invention will be described in detail below.

[0033] Example 1 A method for preparing a NiFe-based catalyst resistant to chlorine corrosion includes the following steps: S1, using a hydrothermal growth method, a NiFeZn precursor was prepared using nickel foam as a substrate; Specifically, the following steps are included: S11: Weigh 0.25 mmol nickel nitrate hexahydrate, 0.75 mmol zinc nitrate hexahydrate, 0.5 mmol ferric chloride hexahydrate, and 5 mmol urea, disperse them in 20 mL of deionized water, stir well, and prepare the precursor solution for the hydrothermal reaction. S12, the precursor solution is transferred to the reactor, and a 1mm clean nickel foam is placed in the precursor solution. After sealing the package, it is reacted at 120°C for 12 hours. S13, after the reaction is complete, cool naturally to room temperature, remove the substrate and rinse it alternately with deionized water and ethanol; S14 was dried in a vacuum oven to obtain the NiFeZn precursor.

[0034] S2, 4.8 g of flake NaOH was dissolved in 20 mL of deionized water to prepare a 6 mol / L NaOH solution. The NiFeZn precursor obtained in step S1 was placed in the NaOH solution and immersed and etched at 25 °C for 12 h to obtain an oxygen-rich D-NiFeZn catalyst.

[0035] Example 2 A method for preparing a NiFe-based catalyst resistant to chlorine corrosion differs from Example 1 in that, in step S1, 0.25 mmol nickel nitrate hexahydrate, 0.75 mmol zinc nitrate hexahydrate, 0.8 mmol ferric chloride hexahydrate, and 5 mmol urea are weighed and dispersed in 20 mL of deionized water, while the rest is completely consistent with Example 1.

[0036] Example 3 A method for preparing a NiFe-based catalyst resistant to chlorine corrosion differs from Example 1 in that, in step S2, 6.4 g of flake NaOH is dissolved in 20 mL of deionized water to obtain an 8 mol / L NaOH solution; the rest is completely consistent with Example 1.

[0037] Comparative Example 1 A method for preparing a NiFe-based catalyst differs from Example 1 in that step S2 is omitted, while the rest is the same as in Example 1, resulting in a NiFeZn catalyst.

[0038] Comparative Example 2 A method for preparing a NiFe-based catalyst differs from Comparative Example 1 in that zinc nitrate hexahydrate is not added in step S11, while the rest is the same as Comparative Example 1, to obtain a NiFe-LDH catalyst.

[0039] The catalysts prepared in Example 1 and Comparative Example 1 were used as electrodes in a 1M KOH + seawater electrolyte for OER testing. A standard three-electrode system was used, with the Hg / HgO electrode as the reference electrode, the graphite electrode as the counter electrode, and the product prepared in Example 1 or Comparative Example 1 as the working electrode, with a geometric area of ​​1cm × 1cm.

[0040] Linear sweep voltammetry (LSV) was performed in an O2-saturated electrolyte at a scan rate of 5 mV / s. -1 The formula for converting electric potential is: E vs.RHE =E vs.Hg / HgO +0.059×pH+0.098; In the formula: E vs.RHE E represents the potential of the reversible hydrogen electrode (RHE). vs.Hg / HgO This represents the potential measured using Hg / HgO as the reference electrode.

[0041] The electrode of Example 1 was tested at 1 A·cm using a chronopotential profile in the same electrolyte. -2 OER stability under current density.

[0042] Structural characterization The morphology of the D-NiFeZn catalyst prepared in Example 1 was characterized by scanning electron microscopy (SEM), such as... Figure 1 As shown, the catalyst has a nanosheet structure.

[0043] The morphology of the D-NiFeZn catalyst prepared in Example 2 was characterized by scanning electron microscopy (SEM), such as... Figure 2 As shown, the catalyst has a nanosheet structure.

[0044] The morphology of the D-NiFeZn catalyst prepared in Example 3 was characterized by scanning electron microscopy (SEM), such as... Figure 3 As shown, the catalyst has a nanosheet structure.

[0045] The D-NiFeZn catalyst prepared in Example 1 was analyzed by X-ray diffraction (XRD). Figure 4 As shown, after comparison, the peak shape of the catalyst prepared in Example 1 is consistent with that of the NiFe-LDH standard card (JCPDS40-0215), indicating that the Zn species are amorphous or have low crystallinity.

[0046] The D-NiFeZn catalyst prepared in Example 1 was characterized by electron paramagnetic (EPR) characteristics, such as... Figure 5 As shown, alkaline etching promotes the generation of abundant oxygen vacancies in the D-NiFeZn catalyst.

[0047] The valence state of the D-NiFeZn catalyst prepared in Example 1 was analyzed by X-ray photoelectron spectroscopy (XPS), such as... Figure 6 As shown, after comparison, the Zn in the catalyst prepared in Example 1 is Zn(OH)4 2- It exists in form.

[0048] Performance testing like Figure 7 As shown, the OER polarization curves of the catalysts prepared in Example 1, Example 2, Example 3, Comparative Example 1, and Comparative Example 2 in alkaline electrolyte are compared. The D-NiFeZn catalyst prepared in Example 1 exhibits the best OER polarization at 100 mA·cm⁻¹. -2 At a current density, it exhibits an OER overpotential 60 mV lower than that of the NiFeZn catalyst prepared in Comparative Example 1, demonstrating its excellent OER catalytic activity. The OER overpotential of Example 1 is slightly lower than that of Examples 2 and 3, indicating that Example 1 represents the optimal preparation conditions.

[0049] The stability of the D-NiFeZn catalyst prepared in Example 1 was tested in an alkaline anion exchange membrane electrolyzer. Figure 8 The Vt polarization curve is shown in the figure, at 1 A·cm -2 Under current density conditions, the D-NiFeZn catalyst stably cracked alkaline seawater for 1000 hours, demonstrating its good stability when applied to the electrolysis of alkaline seawater under industrial current density conditions.

[0050] The OER stability of the NiFe-LDH catalyst prepared in Comparative Example 2 in a three-electrode system was tested. Figure 9 The Vt polarization curve is shown in the figure, at 1 A·cm -2 Under current density conditions, the NiFe-LDH catalyst exhibits poor stability in alkaline natural seawater, indicating that the Zn-free NiFe-LDH catalyst is susceptible to Cl-induced degradation. - Severe corrosion.

[0051] The catalyst electrode from Example 1, after stability testing, was removed, rinsed with deionized water, dried, and its morphology characterized using scanning electron microscopy (SEM). Figure 10 As shown, the catalyst retains its nanosheet shape, demonstrating an extremely stable structure.

[0052] Mechanism analysis Density functional theory (DFT) was used to analyze the OH groups of the products obtained in Example 1 and Comparative Example 2 of this invention. and Cl Adsorption energy is calculated. For example... Figure 11 As shown, compared to the Zn-free NiFe-LDH catalyst, the D-NiFeZn catalyst exhibits better performance for Cl... - To form an effective rejection.

[0053] The product obtained in Example 1 was subjected to Raman characterization tests at different oxidation potentials, such as... Figure 12 As shown, the D-NiFeZn catalyst forms a highly active γ-NiOOH phase during the OER process.

[0054] The product obtained in Example 1 was characterized by infrared spectroscopy at different oxidation potentials, such as... Figure 13 As shown, the D-NiFeZn catalyst excites lattice oxygen to participate in the reaction during the OER process.

[0055] In summary, this invention provides a highly active water electrolysis catalyst. The catalyst has a simple preparation process, is inexpensive and readily available, and exhibits good stability when applied to the electrocatalytic cracking of alkaline seawater, demonstrating promising prospects for industrial application.

[0056] The scope of protection claimed by this invention is not limited to the specific embodiments described above. Moreover, for those skilled in the art, this invention can have various modifications and alterations. Any modifications, improvements, and equivalent substitutions made within the concept and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for preparing a NiFe-based catalyst resistant to chlorine corrosion, characterized in that, Includes the following steps: S1, using a hydrothermal growth method, with nickel foam as the substrate, nickel source, zinc source, iron source and precipitant are dispersed in deionized water, the molar ratio of nickel source, zinc source, iron source and precipitant is (0.2~0.5):(0.5~1):(0.5~1):(4~6), after being stirred evenly, it is transferred to a reaction vessel and reacted at 100~120℃ for 10~12h. After cooling, washing and drying, NiFeZn precursor is obtained; S2. Using a room temperature immersion etching method, the NiFeZn precursor obtained in step S1 is placed in a strong alkaline solution and immersed and etched at room temperature for 12-24 hours to obtain an oxygen-rich D-NiFeZn catalyst.

2. The method for preparing a NiFe-based catalyst resistant to chlorine corrosion according to claim 1, characterized in that, In step S1, the nickel source is nickel nitrate hexahydrate, the zinc source is zinc nitrate hexahydrate, the iron source is ferric chloride hexahydrate, and the precipitant is urea.

3. The method for preparing a NiFe-based catalyst resistant to chlorine corrosion according to claim 2, characterized in that, Step S1 includes the following steps: S11: Weigh 0.2-0.5 mmol nickel nitrate hexahydrate, 0.5-1 mmol zinc nitrate hexahydrate, 0.5-1 mmol ferric chloride hexahydrate, and 4-6 mmol urea, disperse them in 20-40 mL of deionized water, stir well, and prepare the precursor solution for the hydrothermal reaction. S12, the precursor solution is transferred to the reactor, and nickel foam is placed in the precursor solution. After sealing, it is reacted at 100~120℃ for 10~12h. S13, after the reaction is complete, cool naturally to room temperature, remove the substrate and rinse it alternately with deionized water and ethanol; S14 was rinsed and dried to obtain the NiFeZn precursor.

4. The method for preparing a NiFe-based catalyst resistant to chlorine corrosion according to claim 1, characterized in that, In step S2, the strong alkali solution is a NaOH solution with a concentration of 4~8 mol / L.

5. The chlorine-resistant NiFe-based catalyst prepared by any one of claims 1 to 4.

6. The NiFe-based catalyst resistant to chlorine corrosion according to claim 5, characterized in that, The surface of the NiFe-based catalyst contains Zn(OH)4. 2- Passivation layer.

7. The application of the NiFe-based catalyst according to claim 6 in the electrolysis of seawater to produce hydrogen.

8. The application according to claim 7, characterized in that, The NiFe-based catalyst is used as an anode and / or cathode in an alkaline anion exchange membrane electrolyzer.

9. The application according to claim 7, characterized in that, Applied to a current density of 1 A·cm -2 Hydrogen production by electrolysis of seawater.

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