Ni-fe-based bifunctional water-splitting electrocatalyst, preparation method and application

Abstract

The application belongs to the technical field of water electrolysis catalysts, and discloses a NiFe-based bifunctional water decomposition electrocatalyst, a preparation method and application thereof, the catalyst is a core-shell heterostructure, a three-dimensional self-supporting NiFe-based OER / HER bifunctional electrocatalyst, specifically, a coral spherical NiFe-LDH coated basic cobalt carbonate nanowire nanomaterial NiFe-LDH@Co-CH / NF with a three-dimensional hierarchical porous core-shell heterostructure; the catalyst is prepared by a two-step method of hydrothermal and solvothermal, and the foam nickel is used as a conductive substrate, the inner layer is the basic cobalt carbonate nanowire, and the outer layer is the NiFe-LDH nanosheet. The catalyst has excellent OER and HER performance, significantly accelerates the diffusion and transfer of the electrolyte solution, excites the synergistic effect and electron transfer, and improves the catalytic activity of the catalyst. The water electrolysis system assembled by the catalyst has excellent water electrolysis performance, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of water electrolysis catalyst technology, specifically to NiFe-based bifunctional water splitting electrocatalysts, their preparation methods, and applications. Background Technology

[0002] Against the backdrop of the global clean energy transition, hydrogen energy, as a highly efficient clean energy carrier, is receiving increasing attention. Especially in the process of producing hydrogen through water electrolysis using electricity generated from renewable energy sources such as solar and wind power, hydrogen, as a zero-emission energy source, is of great significance for building a sustainable energy system. However, water electrolysis technology currently faces two key challenges: high overpotential due to low electrode reactivity and insufficient stability of electrode materials. Traditionally, noble metal catalysts such as RuO2 and Pt are often used in water electrolysis to catalyze the oxygen evolution reaction (OER) at the anolysus and the hydrogen evolution reaction (HER) at the cathodicly, respectively, due to their excellent catalytic performance. However, their high cost and limited natural resources restrict their large-scale commercial application. Therefore, the development of efficient, stable, and low-cost non-noble metal-based electrocatalysts has become a current research hotspot, aiming to reduce electrode overpotential and enhance catalytic performance. However, the optimal catalytic environments for OER and HER differ significantly; neutral and alkaline electrolytes favor OER, while acidic electrolytes favor HER. This mismatch in catalytic environments can affect the operating efficiency of the entire water electrolysis system, and existing catalysts are difficult to match between the two catalytic environments to achieve bifunctional electrocatalysis.

[0003] Existing water electrolysis catalysts suffer from high costs, low catalytic activity, and poor stability. The design and synthesis of bifunctional, high-performance electrocatalysts involves a wide range of influencing factors, including product composition, formulation, microstructure, and preparation processes. In particular, it requires comprehensive consideration of various factors and the construction of unique, efficient microstructures to overcome the constraints of catalytic environment mismatch through multi-faceted coordination. Due to numerous technical challenges, current technologies cannot yet solve these problems and synthesize bifunctional, high-performance electrocatalysts.

[0004] Therefore, adopting new technological concepts and overcoming problems such as catalytic environment mismatch from multiple aspects, and designing and synthesizing OER / HER bifunctional electrocatalysts with high cost performance, high activity and stability are of great significance for improving the overall efficiency of water electrolysis systems, reducing costs and promoting the development of the hydrogen economy. Summary of the Invention

[0005] The purpose of this invention is to address the problems of insurmountable catalytic environment mismatch, high cost, low catalytic activity, and low stability of existing bifunctional water electrolysis catalysts. This invention employs a novel technical concept to provide a NiFe-based bifunctional water splitting electrocatalyst, its preparation method, and its application. Through the combination of components, proportions, and processes, a unique microstructure is designed and synthesized, resulting in a high-performance, high-activity, and stable OER / HER electrocatalyst. This bifunctional electrocatalyst is a NiFe-LDH@Co-CH / NF core-shell heterostructure supported by coral-spherical three-dimensional self-supporting nickel foam. It exhibits excellent OER / HER catalytic activity and high stability in alkaline water electrolysis systems and can be applied to the OER and HER processes of catalytic water electrolysis, improving the overall efficiency of the water electrolysis system and reducing costs.

[0006] To achieve the above objectives, the technical solution provided by this invention is as follows:

[0007] A NiFe-based bifunctional water splitting electrocatalyst, characterized in that it is a core-shell heterostructure, three-dimensional self-supporting NiFe-based OER / HER bifunctional electrocatalyst, specifically a basic cobalt carbonate nanowire nanomaterial NiFe-LDH@Co-CH / NF coated with coral-shaped NiFe-LDH having a three-dimensional hierarchical porous core-shell heterostructure.

[0008] The NiFe-based bifunctional water splitting electrocatalyst has a coral-spherical layered heterogeneous structure, with nickel foam as the conductive substrate, Co-CH nanowires as the inner layer with a diameter of 230-250 nm, which are uniformly distributed on the nickel foam substrate; and NiFe-LDH nanosheets as the outer layer with a width of 170-190 nm. The coral-spherical NiFe-LDH-coated basic cobalt carbonate nanowire nanomaterial NiFe-LDH@Co-CH / NF is grown in situ on the nickel foam conductive substrate.

[0009] A method for preparing a NiFe-based bifunctional water splitting electrocatalyst, using nickel foam as a conductive substrate, involves a two-step hydrothermal and solvothermal process to prepare the bifunctional electrocatalyst NiFe-LDH@Co-CH / NF. First, a basic cobalt carbonate nanowire precursor is grown in situ via hydrothermal methods. Then, a layer of NiFe-LDH nanosheets is composited onto the outer layer of the basic cobalt carbonate nanowires via a solvothermal method. This gives the catalyst a self-supporting, layered, core-shell heterostructure and a unique hierarchical porous structure. The hierarchical porous structure increases the surface area and the number of active sites, optimizes the electron transport pathway, promotes mass transfer and product release, and enhances the OER / HER bifunctional electrocatalytic performance. The method includes the following steps:

[0010] S1: Substrate pretreatment: Nickel foam (NF, 2×3cm) was treated with hydrochloric acid solution and ethanol.2 The block-shaped substrate is pretreated to ensure a clean surface, serving as a conductive NF substrate.

[0011] S2: Preparation of NF-supported basic cobalt carbonate nanowire precursor: The pretreated conductive NF substrate was immersed in a pink transparent aqueous solution containing appropriate amounts of ammonium fluoride, cobalt salt, and urea for 10 minutes, and then transferred to a reaction vessel and heated to 120°C for 5 hours. After the reaction, the conductive NF substrate was removed, washed with ultrapure water to remove surface impurities, and dried to obtain the basic cobalt carbonate nanowire precursor Co-CH / NF.

[0012] S3: Catalyst preparation: The cleaned Co-CH / NF was placed in a yellowish-brown ethanol dispersion containing appropriate amounts of urea, iron salt, and nickel salt, and then transferred to a reaction vessel. The mixture was heated to 90°C and reacted for 10 hours. After the reaction was completed and cooled to room temperature, the product was washed with ultrapure water and dried to obtain NiFe-LDH@Co-CH / NF.

[0013] The cobalt salt in steps S2 and S3 is Co(NO3)2·6H2O, the nickel salt is Ni(NO3)2·6H2O, and the iron salt is Fe(NO3)3·6H2O.

[0014] An application of a NiFe-based bifunctional water splitting electrocatalyst in the oxygen evolution and hydrogen evolution reactions of water electrolysis, serving as a bifunctional catalyst for both OER and HER; specifically, a coral-spherical NiFe-based core-shell heterostructure bifunctional electrocatalyst is used as the anode and cathode active materials in a complete water splitting battery. The aforementioned core-shell heterostructure electrocatalyst NiFe-LDH@Co-CH / NF achieves 100 mA / cm² in the alkaline oxygen evolution reaction. -2 The overpotential required for high current density is only 240mV, and in the alkaline hydrogen evolution reaction, only 91mV of overpotential is needed to reach 10mAcm. -2 The current density. When the core-shell heterostructure electrocatalyst NiFe-LDH@Co-CH / NF was used as both anode and cathode in the same alkaline electrolytic cell for water electrolysis performance testing, the current density was [value missing]. -2 The battery voltage is 1.60V at the specified current density and can operate stably for more than 90 hours.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects:

[0016] 1. The NiFe-based bifunctional water splitting electrocatalyst, its preparation method, and its applications provided by this invention employ a novel technical concept. Through simultaneous improvement and integration of components, ratios, and processes, a unique hierarchical porous microstructure is designed and synthesized, resulting in a high-performance, cost-effective, highly active, and stable OER / HER electrocatalyst, NiFe-LDH@Co-CH / NF. Furthermore, this bifunctional electrocatalyst possesses a core-shell heterostructure supported by coral-spherical three-dimensional self-supporting nickel foam, solving the problem of catalytic environment mismatch that bifunctional catalysts cannot overcome. This allows it to exhibit excellent OER / HER catalytic activity and high stability in alkaline water electrolysis systems. Applying this catalyst to the OER and HER processes of catalytic water electrolysis simplifies the overall structure of the water electrolysis system, improves its overall efficiency, and reduces costs. It demonstrates broad potential and application prospects in promoting the development of efficient and economical water electrolysis technology and facilitating the construction of a green hydrogen economy.

[0017] 2. This invention successfully synthesizes a three-dimensional self-supporting coral-shaped spherical core-shell heterostructure bifunctional electrocatalyst. During the synthesis process, by controlling the process conditions of the hydrothermal and solvothermal two-step preparation method, coral-shaped NiFe-LDH-coated basic cobalt carbonate nanowires (NiFe-LDH@Co-CH / NF) were grown in situ on a nickel foam substrate. This gives the NiFe-LDH@Co-CH / NF electrocatalyst a unique coral-shaped, hierarchical porous, and layered heterostructure. The hierarchical porous structure increases the surface area and the number of active sites, promoting mass transfer and product release. As a result, the catalyst exhibits excellent electrocatalytic performance, simultaneously improving the catalyst's catalytic activity, stability, and cost-effectiveness. This solves the problems of high cost, low catalytic activity, and low stability of existing bifunctional water electrolysis catalysts.

[0018] 3. The preparation method provided by the present invention is a self-supporting electrocatalyst. Using nickel foam as a conductive substrate, a basic cobalt carbonate nanowire precursor is grown in situ by hydrothermal method. Furthermore, a NiFe-LDH nanosheet is composited on the outer layer of the basic cobalt carbonate nanowire by solvothermal method. This layered heterogeneous structure exposes more active sites in the catalyst, accelerates the diffusion and transfer of electrolyte solution, and thus improves the catalytic activity of the catalyst.

[0019] 4. The bifunctional catalyst provided by this invention has an inner layer of basic cobalt carbonate nanowires grown on porous nickel foam and an outer layer of NiFe-LDH nanosheets. The heterogeneous interface between the inner and outer layers not only increases the surface area but also optimizes the electron transport path and reduces the interfacial barrier for mass transfer kinetics and charge transfer, thereby improving the electrocatalytic performance of OER and HER.

[0020] 5. The core-shell heterostructure bifunctional electrocatalyst synthesized in this invention also possesses excellent alkaline OER / HER catalytic activity, which is of great significance for the further development and assembly of efficient and stable bifunctional electrocatalytic water electrolysis systems.

[0021] 6. The core-shell heterostructure electrocatalyst and its preparation method provided by the present invention use transition metals as raw materials, which reduces production costs. The synthesis method is simple and easy to operate, with few operation steps, high preparation efficiency, and environmental friendliness, which is conducive to industrial production. Attached Figure Description

[0022] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0023] Figure 1 This is a scanning electron microscope (SEM) image of NiFe-LDH@Co-CH / NF prepared in Example 1.

[0024] Figure 2 (a) is a transmission electron microscope (TEM) image of NiFe-LDH@Co-CH / NF prepared in Example 1;

[0025] Figure 2 (b) is a high-resolution transmission electron microscope (HRTEM) image of NiFe-LDH@Co-CH / NF prepared in Example 1.

[0026] Figure 3 This is the energy dispersive spectroscopy (EDS) spectrum of NiFe-LDH@Co-CH / NF prepared in Example 1.

[0027] Figure 4 (a) shows the OER polarization curves of NiFe-LDH@Co-CH / NF prepared in Example 1, Co-CH / NF prepared in Comparative Example 1, NiFe-LDH / NF prepared in Comparative Example 2, and nickel foam in a 1.0 M KOH alkaline environment.

[0028] Figure 4 (b) shows the HER polarization curves of NiFe-LDH@Co-CH / NF prepared in Example 1, Co-CH / NF prepared in Comparative Example 1, NiFe-LDH / NF prepared in Comparative Example 2, and nickel foam in a 1.0 M KOH alkaline environment.

[0029] Figure 5 The figures (a) and (b) are the water electrolysis polarization curves and stability test results of the water electrolysis device (NiFe-LDH@Co-CH / NF(-,+)) assembled using NiFe-LDH@Co-CH / NF as both anode and cathode in Example 1. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments, so that those skilled in the art can implement it based on the description.

[0031] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0032] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0033] Basic Implementation

[0034] A NiFe-based bifunctional water splitting electrocatalyst is a core-shell heterostructure, three-dimensional self-supporting NiFe-based OER / HER bifunctional electrocatalyst. Specifically, it is a basic cobalt carbonate nanowire nanomaterial NiFe-LDH@Co-CH / NF coated with coral-shaped NiFe-LDH with a three-dimensional hierarchical porous core-shell heterostructure.

[0035] The NiFe-based bifunctional water splitting electrocatalyst has a coral-spherical layered heterogeneous structure, with nickel foam as the conductive substrate, Co-CH nanowires as the inner layer with a diameter of 230-250 nm, which are uniformly distributed on the nickel foam substrate; and NiFe-LDH nanosheets as the outer layer with a width of 170-190 nm. The coral-spherical NiFe-LDH-coated basic cobalt carbonate nanowire nanomaterial NiFe-LDH@Co-CH / NF is grown in situ on the nickel foam conductive substrate.

[0036] A method for preparing a NiFe-based bifunctional water splitting electrocatalyst, using nickel foam as a conductive substrate, involves a two-step hydrothermal and solvothermal process to prepare the bifunctional electrocatalyst NiFe-LDH@Co-CH / NF. First, a basic cobalt carbonate nanowire precursor is grown in situ via hydrothermal methods. Then, a layer of NiFe-LDH nanosheets is composited onto the outer layer of the basic cobalt carbonate nanowires via a solvothermal method. This gives the catalyst a self-supporting, layered, core-shell heterostructure and a unique hierarchical porous structure. The hierarchical porous structure increases the surface area and the number of active sites, optimizes the electron transport pathway, promotes mass transfer and product release, and enhances the OER / HER bifunctional electrocatalytic performance. The method includes the following steps:

[0037] S1: Substrate pretreatment: Nickel foam (NF, 2×3cm) was treated with hydrochloric acid solution and ethanol. 2 The block-shaped substrate is pretreated to ensure a clean surface, serving as a conductive NF substrate.

[0038] S2: Preparation of NF-supported basic cobalt carbonate nanowire precursor: The pretreated conductive NF substrate was immersed in a pink transparent aqueous solution containing appropriate amounts of ammonium fluoride, cobalt salt, and urea for 10 minutes, and then transferred to a reaction vessel and heated to 120°C for 5 hours. After the reaction, the conductive NF substrate was removed, washed with ultrapure water to remove surface impurities, and dried to obtain the basic cobalt carbonate nanowire precursor Co-CH / NF.

[0039] S3: Catalyst preparation: The cleaned Co-CH / NF was placed in a yellowish-brown ethanol dispersion containing appropriate amounts of urea, iron salt, and nickel salt, and then transferred to a reaction vessel. The mixture was heated to 90°C and reacted for 10 hours. After the reaction was completed and cooled to room temperature, the product was washed with ultrapure water and dried to obtain NiFe-LDH@Co-CH / NF.

[0040] The cobalt salt in steps S2 and S3 is Co(NO3)2·6H2O, the nickel salt is Ni(NO3)2·6H2O, and the iron salt is Fe(NO3)3·6H2O.

[0041] An application of a NiFe-based bifunctional water splitting electrocatalyst in the oxygen evolution and hydrogen evolution reactions of water electrolysis, serving as a bifunctional catalyst for both OER and HER; specifically, a coral-spherical NiFe-based core-shell heterostructure bifunctional electrocatalyst is used as the anode and cathode active materials in a complete water splitting battery. The aforementioned core-shell heterostructure electrocatalyst NiFe-LDH@Co-CH / NF achieves 100 mA / cm² in the alkaline oxygen evolution reaction. -2 The overpotential required for high current density is only 240mV, and in the alkaline hydrogen evolution reaction, only 91mV of overpotential is needed to reach 10mA cm⁻¹. -2 The current density. When the core-shell heterostructure electrocatalyst NiFe-LDH@Co-CH / NF was used as both anode and cathode in the same alkaline electrolytic cell for water electrolysis performance testing, the current density was [value missing]. -2 The battery voltage is 1.60V at the specified current density and can operate stably for more than 90 hours.

[0042] This embodiment fully utilizes the unique chemical properties and structural advantages of NiFe layered double hydroxides (NiFe-LDH) in the design of bifunctional electrocatalysts, combining preparation processes and the construction of microstructures through composition and ratio. The special layered structure of NiFe-LDH can accelerate the release and transfer of gaseous products in solution by increasing the diffusion and transfer rates of water molecules, while the synergistic effect between different components can improve electrocatalytic performance. The NiFe-LDH prepared in this embodiment not only has advantages such as flexible chemical composition, resistance to degradation, and excellent OER catalytic activity and durability in alkaline media. This invention overcomes the problem of slow HER kinetics caused by the high energy barrier of the Volmer step, which reduces HER performance. Furthermore, this invention also overcomes the problem of requiring high electrode overpotentials to drive the HER and OER processes due to relatively slow electrokinetic characteristics. In summary, this invention, through comprehensive selection of catalyst components, ratios, and processes, designs and synthesizes a high-performance, highly efficient microstructure-based bifunctional electrocatalyst based on NiFe-LDH, which is of great significance for the industrialization of water electrolysis.

[0043] Example 1

[0044] This embodiment is a further refinement based on the basic embodiment.

[0045] See appendix Figure 1-5 This embodiment provides a NiFe-based bifunctional water splitting electrocatalyst and its preparation method. The catalyst is obtained by in-situ growth of NiFe-LDH-coated basic cobalt carbonate nanowires on a nickel foam substrate using hydrothermal and solvothermal methods. The catalyst has a coral spherical shape and a layered heterogeneous microstructure. It has a porous structure inside the coral spherical skeleton, which is also similar to the shape of carnation petals. It is a nanoscale layered porous bifunctional electrocatalyst with a core-shell heterostructure.

[0046] In the preparation process, the catalyst adopts a self-supporting design, using nickel foam as a conductive substrate. First, a basic cobalt carbonate nanowire precursor is grown in situ on the nickel foam using a hydrothermal method. Then, a layer of NiFe-LDH nanosheets is composited on the outer layer of the basic cobalt carbonate nanowires using a solvothermal method. This layered heterogeneous structure can effectively expose more active sites while increasing the surface area and accelerating the diffusion and transfer of electrolyte solution, thereby significantly improving the catalytic activity of the catalyst.

[0047] The preparation method of the NiFe-based bifunctional water splitting electrocatalyst (core-shell heterostructure bifunctional electrocatalyst) specifically includes the following steps:

[0048] Step S1: Treat nickel foam (NF) with 1.0M hydrochloric acid solution and ethanol to ensure surface cleanliness and serve as a conductive substrate layer; specifically, place the nickel foam in 1.0M HCl solution, sonicate for 15 minutes, then rinse with deionized water 2-3 times, place the rinsed nickel foam in ethanol, sonicate for 15 minutes, and obtain the treated nickel foam as a conductive NF substrate.

[0049] Step S2: Disperse appropriate amounts of ammonium fluoride, cobalt nitrate, and urea in an appropriate amount of ultrapure water to obtain a transparent and uniformly dispersed pink aqueous solution; specifically: dissolve 0.873g Co(NO3)2·6H2O, 0.3704g NH4F, and 1.5015g Co(NH2)2 in 35ml of ultrapure water, and sonicate until the solution is uniformly dispersed to obtain a transparent pink aqueous solution; in the pink aqueous solution, the amount of ammonium fluoride is 0.3704g, the amount of cobalt nitrate is 0.873g, and the amount of urea is 1.5015g;

[0050] The resulting pink aqueous solution and a clean piece of NF (pre-cut 2cm x 3cm) 2 The sample was transferred to a 50 ml hydrothermal reactor. The reactor was placed in an oven and heated to 120 °C for 5 hours. After the reaction was completed, the sample was cooled to room temperature. The obtained Co-CH / NF sample was washed with ultrapure water and ethanol and then dried. The basic cobalt carbonate nanowire precursor Co-CH / NF was collected.

[0051] Step S3: Disperse an appropriate amount of urea, ferric nitrate, and nickel nitrate into an appropriate amount of ethanol to obtain a uniformly dispersed, transparent, yellowish-brown solution. Specifically, dissolve 0.0967g Ni(NO3)2·6H2O, 0.1345g Fe(NO3)3·9H2O, and 0.06g Co(NH2)2 in 35ml of ethanol, and sonicate until the solution is uniformly dispersed to obtain a transparent, yellowish-brown solution.

[0052] The above transparent yellowish-brown solution was transferred to a 50 ml hydrothermal reactor, and the Co-CH / NF precursor obtained above was added. The reactor was placed in an oven and heated to 90 °C for 10 h. After the reaction was completed, it was cooled to room temperature. The obtained product was washed with deionized water and ethanol, and then dried. The target product NiFe-LDH@Co-CH / NF sample was obtained after drying.

[0053] The electrocatalyst prepared by the above method has a core-shell heterostructure, which is a basic cobalt carbonate nanowire nanomaterial NiFe-LDH@Co-CH / NF with an overall coral spherical shape. The Co-CH nanowires serve as the inner layer with a diameter of 230-250 nm and are uniformly distributed on the nickel foam conductive substrate; the NiFe-LDH nanosheets serve as the outer layer with a width of 170-190 nm.

[0054] The catalyst prepared by the above method is a heterostructure NiFe-LDH@Co-CH / NF catalyst, which has a three-dimensional self-supporting hierarchical porous structure and heterogeneous interface. It can improve the electron transport rate and mass transfer resistance while increasing the surface area and the number of active sites, thus significantly improving the catalytic effect and stability of OER and HER.

[0055] The core-shell heterostructure electrocatalyst NiFe-LDH@Co-CH / NF exhibits excellent OER performance at 100 mA / cm². -2 It exhibits an overpotential of 240mV at a current density of 10mAcm and also demonstrates excellent HER performance. -2 The overpotential at the current density is 91mV.

[0056] The core-shell heterostructure electrocatalyst NiFe-LDH@Co-CH / NF exhibits excellent water electrolysis performance. When this catalyst was used as both the anode and cathode in an alkaline electrolysis cell, its water electrolysis performance was tested at 10 mA / cm². -2 The battery voltage is 1.60V at the specified current density.

[0057] The synthesis method of the core-shell heterostructure electrocatalyst NiFe-LDH@Co-CH / NF provided in this embodiment is simple, easy to operate, requires low equipment, and has low production cost. It also provides corresponding technical guidance for the preparation of other self-supporting bifunctional electrocatalysts.

[0058] Comparative Example 1

[0059] Dissolve 0.873g Co(NO3)2·6H2O, 0.3704g NH4F, and 1.5015g Co(NH2)2 in 35ml of ultrapure water, and sonicate until the solution is evenly dispersed to obtain a transparent pink solution.

[0060] The above transparent pink solution was transferred to a 50ml hydrothermal reactor, and a piece of treated nickel foam (2cm×3cm) was added. The reactor was placed in an oven and heated to 120℃ for 5 hours. After the reaction was completed, the mixture was cooled to room temperature. The product was cleaned with deionized water and ethanol and dried to obtain Co-CH / NF.

[0061] Comparative Example 2

[0062] Dissolve 0.0967g Ni(NO3)2·6H2O, 0.1345g Fe(NO3)3·9H2O, and 0.06g Co(NH2)2 in 35ml of ethanol, and sonicate until the solution is evenly dispersed to obtain a transparent yellowish-brown solution.

[0063] The above transparent yellowish-brown solution was transferred to a 50ml hydrothermal reactor, and a piece of treated nickel foam (2cm×3cm) was added. The reactor was placed in an oven and heated to 90℃ for 10h. After the reaction was completed, it was cooled to room temperature. The product was cleaned with deionized water and ethanol and dried to obtain NiFe-LDH / NF.

[0064] The core-shell heterostructure bifunctional electrocatalyst NiFe-LDH@Co-CH / NF prepared in the above embodiments of the present invention was obtained by constructing the microstructure through a two-step method involving hydrothermal and solvothermal processes. Figure 1 and attached Figure 2 The images show the SEM and TEM images of the NiFe-LDH@Co-CH / NF catalyst, respectively. The successful preparation of the catalyst can be seen from the images. The catalyst has an overall coral spherical shape, with an inner layer of basic cobalt carbonate nanowires and an outer layer of NiFe-LDH nanosheets.

[0065] EDS for NiFe-LDH@Co-CH / NF is attached. Figure 3 As shown, Co, Ni, Fe, and O coexist, and the Co / (Ni+Fe) ratio is 1:1.1. Composed of inner basic cobalt carbonate nanowires and outer NiFe-LDH nanosheets, this catalyst possesses a unique multilayer heterogeneous structure, which is beneficial for increasing the specific surface area of ​​the catalyst. It also effectively exposes more active sites and accelerates the diffusion and transfer of the electrolyte solution, thereby significantly enhancing the catalytic activity of the catalyst.

[0066] As attached Figure 4 As shown in a, compared with Co-CH / NF(η) in Comparative Example 1 100 =330mV,η 500 =390mV) and NiFe-LDH / NF in Comparative Example 2 (η 100 =270mV,η 500 Compared to (η = 330mV), the NiFe-LDH@Co-CH / NF catalyst exhibits superior OER performance (η = 330mV). 100 =240mV,η 500 =290mV).

[0067] As attached Figure 4 As shown in b, compared with Co-CH / NF(η) in Comparative Example 1 10=124mV) and NiFe-LDH / NF in Comparative Example 2 (η 10 Compared to (η = 149 mV), the NiFe-LDH@Co-CH / NF catalyst exhibits superior HER performance (η = 149 mV). 10 =91mV). It is worth noting that the water electrolysis system assembled with this catalyst as the anode and cathode respectively also exhibited excellent water electrolysis performance.

[0068] As attached Figure 5 As shown in Figure a, the NiFe-LDH@Co-CH / NF(-,+) water electrolysis device operates at 10 mA / cm². -2 At this current density, the battery voltage is only 1.60V, indicating excellent water electrolysis performance. Furthermore, after a 90-hour stability test, the battery voltage still retains 99.4% (see attached image). Figure 5 b) indicates that it has excellent stability.

[0069] The bifunctional electrocatalyst NiFe-LDH@Co-CH / NF prepared by the above embodiments of the present invention through a two-step hydrothermal and solvothermal method has a core-shell heterostructure and a unique hierarchical porous structure. The hierarchical porous structure increases the surface area and the number of active sites, optimizes the electron transport path, and promotes mass transfer and product release, thereby enabling the catalyst to exhibit excellent electrocatalytic performance.

[0070] This invention provides a method for preparing bifunctional electrocatalysts, which uses few components, has a simple and easy-to-operate process, and low production cost. It also has certain reference value for the preparation of other self-supporting bifunctional electrocatalysts.

[0071] The NiFe-based bifunctional water splitting electrocatalyst, its preparation method, and its application provided in the above embodiments of the present invention are core-shell heterostructure, three-dimensional self-supporting NiFe-based OER / HER bifunctional electrocatalysts. Specifically, they are coral-spherical NiFe-LDH-coated basic cobalt carbonate nanowire nanomaterials (NiFe-LDH@Co-CH / NF) with a three-dimensional hierarchical porous core-shell heterostructure. Using nickel foam as a conductive substrate, the inner layer is basic cobalt carbonate nanowires, and the outer layer is NiFe-LDH nanosheets. This microstructure is constructed through a two-step process of hydrothermal and solvothermal treatment. Due to its unique hierarchical heterostructure, the catalyst has a significantly richer number of active sites on its surface, greatly accelerating the diffusion and transfer of electrolyte solutions. The strong electronic interaction at the interface between the outer layer of the NiFe-LDH nanosheets and the Co-CH nanowires excites a synergistic effect and electron transfer, thereby improving the catalytic activity of the catalyst. This catalyst exhibits excellent OER and HER performance, and the water electrolysis system assembled with this catalyst also exhibits excellent water electrolysis performance. The core-shell heterostructure bifunctional electrocatalyst provided by this invention has broad potential and application prospects in promoting the development of efficient and economical water electrolysis technology and facilitating the construction of a green hydrogen economy.

[0072] It should be particularly noted that other technical solutions obtained by specific selection within the range of components, proportions, and process parameters described in this invention can all achieve the technical effects of this invention, and therefore will not be listed one by one. Furthermore, other catalyst technical solutions obtained by using equivalent components, proportions, preparation methods, and applications as described in this invention are all included within the protection scope of this invention.

[0073] In the description of this invention, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this invention, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0074] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A NiFe-based bifunctional water splitting electrocatalyst, characterized in that, It is a core-shell heterostructure, three-dimensional self-supporting NiFe-based OER / HER bifunctional electrocatalyst, specifically a basic cobalt carbonate nanowire nanomaterial NiFe-LDH@Co-CH / NF coated with coral spherical NiFe-LDH with a three-dimensional hierarchical porous core-shell heterostructure; The electrocatalyst has a coral-spherical layered heterogeneous structure, with nickel foam as the conductive substrate and uncalcined Co-CH nanowires as the inner layer, the inner layer having a diameter of 230-250 nm and being uniformly distributed on the nickel foam substrate; and a single-phase NiFe-LDH nanosheet as the outer layer, the outer layer having a width of 170-190 nm. The electrocatalyst is prepared via a two-step hydrothermal and solvothermal method. When used as a bifunctional catalyst in an alkaline electrolytic cell, it exhibits performance at 100 mA / cm². 2 The overpotential of OER at high current density is 240mV, and at 10mA / cm 2 The HER overpotential at the specified current density is 91 mV. When the water electrolysis performance was tested in the same alkaline electrolytic cell as both anode and cathode, at a current density of 10 mA / cm², the HER overpotential was [missing value]. 2 The battery voltage is 1.60V at the specified current density and can operate stably for more than 90 hours.

2. A method for preparing the NiFe-based bifunctional water splitting electrocatalyst according to claim 1, characterized in that, Using nickel foam as a conductive substrate, it is prepared via a two-step method involving hydrothermal and solvothermal processes, including the following steps: (1) Preparation of Co-CH / NF by hydrothermal method: 0.873g Co(NO3)2・6H2O, 0.3704g NH4F and 1.5015g CO(NH2)2 were dissolved in 35ml of ultrapure water and sonicated until the solution was evenly dispersed to obtain a transparent pink aqueous solution; clean nickel foam treated with 1.0M hydrochloric acid solution and ethanol was immersed in the pink aqueous solution and hydrothermally reacted at 120℃ for 5h; after the reaction was completed, the product was taken out, washed with ultrapure water and ethanol and dried to obtain Co-CH / NF; (2) Solvothermal growth of NiFe-LDH on Co-CH / NF surface: 0.0967g Ni(NO3)2・6H2O, 0.1345g Fe(NO3)3・9H2O, and 0.06g CO(NH2)2 were dissolved in 35ml ethanol and sonicated until the solution was evenly dispersed to obtain a transparent yellowish-brown solution; Co-CH / NF was immersed in the yellowish-brown solution and solvothermal reaction was carried out at 90℃ for 10h; after the reaction was completed, the product was taken out, washed with deionized water and ethanol, and dried to obtain NiFe-LDH@Co-CH / NF electrocatalyst.

3. The preparation method according to claim 2, characterized in that, The processing method of the nickel foam in step (1) is as follows: place the nickel foam in a 1.0M HCl solution and sonicate for 15 minutes, then rinse with deionized water 2-3 times, then clean with ethanol and dry.

4. The application of the NiFe-based bifunctional water splitting electrocatalyst of claim 1 in the oxygen evolution and hydrogen evolution reactions of water electrolysis, characterized in that, The NiFe-based bifunctional water splitting electrocatalyst was used as the anode and cathode active materials in a 1M KOH alkaline electrolyte solution for OER and HER dual catalysis.

5. The application according to claim 4, characterized in that, At 10mA / cm 2 At a given current density, the voltage of the fully hydrolytic battery is 1.60V, and it can operate stably for more than 90 hours.

6. The application according to claim 4, characterized in that, The electrocatalyst operates at 100 mA / cm 2 The overpotential of OER at high current density is 240mV, and at 10mA / cm 2 The HER overpotential at the current density is 91mV.

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