Sheet-shaped Ni7P3 / bicrystal phase Ni composite material prepared based on tetrabutylphosphonium chloride and preparation method and application of sheet-shaped Ni7P3 / bicrystal phase Ni composite material

Abstract

The invention discloses a lamellar Ni7P3 / bicrystal phase Ni composite material prepared based on tetrabutylphosphonium chloride as well as a preparation method and application thereof, and relates to the technical field of electro-catalytic materials. The invention relates to a lamellar Ni7P3 / bicrystal phase Ni composite material prepared on the basis of tetrabutylphosphonium chloride. The lamellar Ni7P3 / bicrystal phase Ni composite material consists of a Ni7P3 compound and a Ni elementary substance, wherein the Ni elementary substance comprises a face-centered cubic structure crystal form and a hexagonal close packing structure crystal form; and the whole Ni7P3 / bicrystal phase Ni composite material is in a sheet shape. According to the lamellar Ni7P3 / bicrystal phase Ni composite material prepared by the method, stable coexistence of bicrystal phase Ni and lamellar morphology regulation and control are realized by virtue of multiple effects of a solvent of tetrabutyl phosphonium chloride, a phosphorus source and a template; according to the present invention, the overpotential at the current density of 10 mAcm <-2 > is as low as 250 mV, the electrocatalytic oxygen evolution performance is significantly improved through the synergistic effect of the Ni7P3 intrinsic activity, the heterojunction electron optimization, the bicrystal Ni function complementation and the sheet specific surface area increasing, the preparation method is controllable, the material cost is low, the material is suitable for being used as the OER working electrode, and the support is provided for the efficient hydrogen production through water decomposition.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic materials technology, specifically to a sheet-like Ni7P3 / bicrystalline Ni composite material prepared based on tetrabutylphosphine chloride, its preparation method, and its application. Background Technology

[0002] As the global energy structure shifts towards cleaner and more sustainable energy sources, electrocatalytic water splitting for hydrogen production, a technology that can directly utilize renewable electricity to produce high-purity hydrogen, has become a crucial approach to addressing the shortage of traditional fossil fuels and environmental pollution. In electrocatalytic water splitting systems, the oxygen evolution reaction (OER) is the core bottleneck restricting overall hydrogen production efficiency due to its high energy barrier and slow kinetics. Therefore, developing highly active, stable, and low-cost OER catalysts has become a key research focus and critical requirement in this field.

[0003] Nickel-phosphorus compounds (such as Ni7P3) have shown significant application potential in electrocatalysis due to their unique crystal structure and electronic properties, making them one of the important candidate materials to replace noble metal catalysts. Specifically, phosphorus and nickel atoms in Ni7P3 are bonded together by special chemical bonds, giving it both metallic and non-metallic properties. In the electrocatalytic water splitting process, Ni7P3, with its optimized electronic structure, can provide sufficient and highly efficient catalytic active sites for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), effectively improving the efficiency of hydrogen production from water splitting by reducing the reaction overpotential and accelerating the reaction kinetics. However, current research on Ni7P3 has mostly focused on single-phase materials, and its composite systems with other functional components (such as metallic nickel) have not been fully explored, resulting in the incomplete release of Ni7P3's catalytic potential.

[0004] Nickel (Ni), as a low-cost and highly stable transition metal, is also a research hotspot in the field of electrocatalytic oxygen evolution. On the one hand, Ni has a high melting point and good corrosion resistance, making it suitable for the harsh environments of common reaction systems such as alkaline water electrolysis. On the other hand, Ni's 3d orbitals contain unpaired electrons, which can form stable bonds with OER reaction intermediates, providing necessary adsorption and activation sites for the reaction. At the same time, in alkaline systems, a thin and stable oxide film can form on the Ni surface, further enhancing catalytic stability.

[0005] In optimizing the catalytic performance of nickel metal, crystal form regulation has become a key direction: single crystal forms often suffer from insufficient electronic structure adaptability or limited surface active sites. However, the two typical crystal forms of nickel metal—Ni (JCPDS04-0850) and Ni (JCPDS45-1027), namely face-centered cubic (fcc) and hexagonal close-packed (hcp)—can form an effective complement. The former is usually a face-centered cubic structure with high atomic packing density and excellent conductivity, while the latter is mostly a hexagonal close-packed structure with surface energy and active site characteristics that are more adapted to specific reaction requirements. The synergistic existence of the two can significantly alleviate the shortcomings of single crystal forms in catalytic efficiency or stability, and further expand the application potential of nickel metal in the field of oxygen evolution in water electrolysis.

[0006] Therefore, this invention aims to explore a synthesis method for a Ni7P3 / Ni (including bicrystalline Ni) mixture in order to obtain a catalyst with excellent oxygen evolution performance in water electrolysis. The above are the technical problems that urgently need to be solved by those skilled in the art.

[0007] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention provides a sheet-like Ni7P3 / bicrystalline Ni composite material prepared based on tetrabutylphosphine chloride, its preparation method, and its application, thereby resolving the issues raised in the background section.

[0009] A sheet-like Ni7P3 / bicrystalline Ni composite material prepared based on tetrabutylphosphine chloride, wherein the Ni7P3 / bicrystalline Ni composite material is composed of Ni7P3 compound and elemental Ni; Among them, elemental Ni contains two crystal forms, namely face-centered cubic structure and hexagonal close-packed structure; and the Ni7P3 / bicrystalline Ni composite material has a thin sheet-like morphology.

[0010] Preferably, the XRD diffraction peaks of the face-centered cubic crystal form match JCPDS standard card number 04-0850, and the XRD diffraction peaks of the hexagonal close-packed crystal form match JCPDS standard card number 45-1027.

[0011] A method for preparing a sheet-like Ni7P3 / bicrystalline Ni composite material based on tetrabutylphosphine chloride as described above includes the following steps: Using tetrabutylphosphine chloride as a solvent and phosphorus source, the tetrabutylphosphine chloride was heated and subjected to ultrasonic treatment until a homogeneous system was formed. Then, a nickel-containing precursor was added to the system, and ultrasonic treatment was continued to dissolve the nickel-containing precursor, resulting in a homogeneous mixed solution. The homogeneous mixed solution obtained in step (1) is transferred to a reaction vessel and placed in a heating device. It is then heated under an inert gas protective atmosphere and kept at a certain temperature for a period of time to allow the system to react and generate a Ni7P3 / Ni mixture. After the reaction in step (2) is completed and the system is naturally cooled to room temperature, the obtained product is washed and centrifuged in sequence, and then the separated solid product is vacuum dried to obtain the Ni7P3 / Ni mixture. In step (1), tetrabutylphosphine chloride also serves as a template agent, guiding the generated Ni7P3 / Ni mixture to form a sheet-like morphology.

[0012] Preferably, the nickel-containing precursor is nickel nitrate hexahydrate.

[0013] Preferably, the ultrasonic treatment of tetrabutylphosphine chloride in step (1) is performed by water-isolated ultrasonic treatment, and the ultrasonic treatment temperature is 60-120℃.

[0014] Preferably, the heating device in step (2) is a tube furnace and the reaction vessel is a crucible.

[0015] Preferably, the heating rate of the heating treatment in step (2) is 2-15℃ / min, and the calcination temperature is 300-450℃.

[0016] Preferably, the washing reagent used in step (3) is a combination of ethanol and water, and the washing method is alternating washing or mixed washing.

[0017] Preferably, the vacuum drying temperature in step (3) is room temperature, and the drying time is 10-30 hours.

[0018] An application of a sheet-like Ni7P3 / bicrystalline Ni composite material prepared based on tetrabutylphosphine chloride as described above in the electrocatalytic oxygen evolution reaction, wherein the Ni7P3 / bicrystalline Ni composite material is used to prepare a working electrode.

[0019] The present invention provides a sheet-like Ni7P3 / bicrystalline Ni composite material based on tetrabutylphosphine chloride, its preparation method, and its application, which have the following beneficial effects: (1) The sheet-like Ni7P3 / bicrystalline Ni composite material prepared by the present invention achieves stable coexistence of bicrystalline Ni and control of sheet morphology by means of the solvent, phosphorus source and template of tetrabutylphosphine chloride.

[0020] (2) The sheet-like Ni7P3 / bicrystalline Ni composite material prepared in this invention, at 10 mA / cm², -2 With an overpotential as low as 250mV at current density, the electrocatalytic oxygen evolution performance is significantly improved through the synergistic effects of the intrinsic activity of Ni7P3, the electronic optimization of the heterojunction, the functional complementarity of bicrystalline Ni, and the increased specific surface area of ​​the thin film.

[0021] (3) At the same time, the preparation method of the present invention is controllable and the material cost is low, making it suitable as an OER working electrode and providing support for efficient water splitting to produce hydrogen. Attached Figure Description

[0022] Figure 1 The image shows the X-ray diffraction (XRD) pattern of the Ni7P3 / bicrystalline Ni composite material prepared in Example 1. Figure 2 Transmission electron microscopy (TEM) image of the Ni7P3 / bicrystalline Ni composite material prepared in Example 1; Figure 3 Linear sweep voltammetry (LSV) plot of the Ni7P3 / bicrystalline Ni composite material prepared in Example 1 in 1.0 M KOH electrolyte. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] To address the aforementioned technical problems, this invention provides a sheet-like Ni7P3 / bicrystalline Ni composite material prepared based on tetrabutylphosphine chloride, its preparation method, and its application, thereby resolving the issues raised in the background section.

[0025] I. Preparation steps and structural and morphological characterization experiments of sheet-like Ni7P3 / bicrystalline Ni composite materials Example 1: Weigh 5g of tetrabutylphosphine chloride and place it in a beaker. Sonicate the solution in a water bath at 80℃ to obtain liquid tetrabutylphosphine chloride. Then, add 0.5mmol of nickel nitrate hexahydrate to the tetrabutylphosphine chloride. Sonicate for 10min to obtain a homogeneous solution.

[0026] The solutions were transferred to crucibles and heated in a tube furnace under a nitrogen atmosphere at a heating rate of 10 °C / min. -1 Maintain at 350℃ for 3 hours.

[0027] After the reaction was complete, the mixture was allowed to cool naturally to room temperature. The product was washed several times with ethanol and water to remove organic impurities and byproducts. After centrifugation at 10,000 rpm, a black precipitate was obtained and dried under vacuum at room temperature for one day.

[0028] XRD ( Figure 1 This demonstrates the successful acquisition of a Ni7P3 / bicrystalline Ni composite material. It contains two Ni crystal phases: hexagonal nickel (JCPDS45-1027) and cubic nickel (JCPDS04-0850). TEM ( Figure 2 This indicates that the Ni7P3 / bicrystalline Ni composite material mixture is a sheet-like material.

[0029] It should be noted that the preparation method of the sheet-like Ni7P3 / bicrystalline Ni composite material based on tetrabutylphosphine chloride provided in Example 1 of this invention can be divided into two steps, the functions of which are explained below: The first step involves adding nickel nitrate hexahydrate to tetrabutylphosphine chloride and sonicating for 10 minutes to obtain a homogeneous solution. This process promotes more uniform nucleation. Water-isolated sonication accelerates the dissolution of nickel nitrate and utilizes the ultrasonic cavitation effect to generate localized high temperatures, high pressures, and strong microjets, breaking down solute aggregation forces and allowing Ni to dissolve more readily. 2+ Uniform dispersion in tetrabutylphosphine chloride eliminates concentration differences. Uniformly dispersed Ni 2+ The formation of a "supersaturated homogeneous phase" with consistent nucleation free energy barriers in each region, and the reduction of nucleation activation energy by ultrasound, promotes synchronous nucleation within the system, ultimately forming initial crystal nuclei of uniform size and distribution, laying the foundation for subsequent crystal growth.

[0030] The second step is to transfer the obtained homogeneous solution into a crucible and heat it in a tube furnace.

[0031] 1. Formation of Ni7P3 / bicrystalline Ni composite material: Tetrabutylphosphine chloride can be decomposed by heating at high temperatures into tributylphosphine (TBP). Simultaneously, due to the negative charge of phosphorus (P), it possesses certain reducing properties, enabling it to react with Ni. 2+ The phosphorus and nickel are reduced to Ni nanoparticles. TBP, which has a strong coordination ability, is adsorbed on the Ni nanoparticles, and phosphorus and nickel diffuse in all directions, eventually reaching equilibrium to form Ni7P3; the uncoordinated Ni is converted into elemental nickel.

[0032] 2. Formation of bicrystalline Ni: Tributylphosphine (TBP) produced by the decomposition of tetrabutylphosphine chloride at high temperature has strong coordination ability and can be selectively adsorbed on different crystal faces of Ni nanoparticles (such as the (111) face of fcc and the (0001) face of hcp). Its steric hindrance effect will inhibit the growth rate of some crystal faces, while the unadsorbed crystal faces will continue to grow, resulting in crystal branching during crystal growth. Some particles extend along the close packing direction of fcc and some along the packing direction of hcp, laying the foundation for bicrystalline coexistence. Meanwhile, a suitable heating rate provides a key kinetic window for the formation of bicrystalline Ni: when the heating rate is slow, Ni atoms have enough time to adjust their atomic packing mode, thus enabling the simultaneous formation of face-centered cubic (fcc) and hexagonal close-packed (hcp) phases; when the heating rate is fast, tributylphosphine (TBP) produced by the decomposition of tetrabutylphosphine chloride can lock the initially generated hcp nuclei with strong coordination, preventing them from completely transforming into the fcc phase.

[0033] Subsequent heat treatment within a specific temperature range ensures that both the fcc and hcp phases complete crystal growth while preventing the complete transformation of the metastable hcp phase. Furthermore, during the process of P atoms generated from the decomposition of tetrabutylphosphine chloride combining with Ni to form Ni7P3, an electron density reconstruction occurs at the interface. This interfacial electronic effect alters the crystal field stabilization energy of Ni, reducing the thermodynamic stability difference between the fcc and hcp phases, ultimately enabling the two crystal forms to coexist stably in the same system, forming a bicrystalline Ni structure.

[0034] 3. Formation of thin-film morphology: The "soft template" effect of tetrabutylphosphine chloride lays the foundation for the thin-film morphology: in the molten state, it exhibits a layered molecular stacking structure (similar to a liquid crystal phase), with long-chain butyl groups arranged in parallel to form "two-dimensional channels," and the dissolved Ni... 2+ Confined within it, it can only diffuse along the plane of the channel, while diffusion in the vertical direction is suppressed, thus determining the two-dimensional orientation of crystal growth from the source; The TBP molecules produced by the decomposition of tetrabutylphosphine chloride at high temperature have a planar triangular coordination structure, which makes them more likely to be adsorbed on the high surface energy crystal surfaces of Ni or Ni7P3 crystals (such as the (100) surface of fcc-Ni and the (10-10) surface of hcp-Ni). The growth rate of the covered crystal surfaces is slowed down due to the reduced surface energy, while the low surface energy crystal surfaces that are not adsorbed (such as the (111) surface of fcc-Ni and the (0001) surface of hcp-Ni) grow rapidly. Through "selective growth", the crystal is promoted to extend along the planar direction of the low surface energy crystal surface.

[0035] II. Optimization Experiment of Preparation Parameters for Thin-Layer Ni7P3 / Dual-Phase Ni Composite Material The parameters in the preparation process of the sheet-like Ni7P3 / bicrystalline Ni composite material were adjusted successively, and a total of 13 examples (including the previous example 1) were designed to prepare the sheet-like Ni7P3 / bicrystalline Ni composite material. The prepared sheet-like Ni7P3 / bicrystalline Ni composite material was then applied to the electrolysis of water to perform hydrogen evolution performance tests.

[0036] To clearly present the parameter differences in the preparation process of sheet-like Ni7P3 / bicrystalline Ni composite materials in Examples 1-13, the specific values ​​of the key preparation parameters (including ultrasonic temperature, mass of tetrabutylphosphine chloride, amount of nickel nitrate hexahydrate, heating rate, calcination temperature, and holding time) involved in these 13 examples are summarized in Table 1 below. In Examples 2-13, the steps for preparing sheet-like Ni7P3 / bicrystalline Ni composite materials were identical except for the differences in the key preparation parameters mentioned above.

[0037] Table 1 Electrochemical measurements were performed using an electrochemical workstation (Shanghai Chenhua CHI 760E). A standard three-electrode system was employed, with a saturated calomel electrode as the reference electrode, graphite as the counter electrode, and glassy carbon electrode as the working electrode.

[0038] The obtained Ni7P3 / bicrystalline Ni was used to modify a glassy carbon electrode. After vacuum drying at room temperature, 5 μL of 0.2% Nafion was added to prevent the metallic nickel from detaching. All data were obtained at room temperature in 1.0 M KOH (electrolyte), and all electrode potentials were converted to the standard hydrogen electrode potential (RHE).

[0039] In all embodiments of the present invention, the Ni7P3 / bicrystalline Ni composite material prepared in Example 1 exhibits the best performance in water electrolysis and oxygen evolution applications: such as Figure 3 As shown, the composite material prepared in Example 1 has a performance of 10 mA / cm². -2 The overpotential at the current density is as low as 250mV. Its excellent performance is due to the synergistic enhancement of catalysis by multiple components and structures. The specific mechanism can be broken down into the following aspects: First, Ni7P3 itself is an excellent electrocatalytic oxygen evolution catalyst. Its unique crystal structure and electronic properties provide ample active sites for OER. The phosphorus element in Ni7P3 can modify and regulate the d-band center of Ni, further adapting it to the four-electron transfer kinetics requirements of OER. Furthermore, its strong corrosion resistance lays the foundation for efficient catalysis. Second, Ni7P3 forms a heterojunction with Ni, resulting in electron rearrangement at the interface. This electronic effect precisely optimizes the adsorption energy barrier of OER reaction intermediates (*OH / *O / *OOH), accelerating the reaction process. Third, the bimorphic Ni exhibits complementary advantages: one crystal form enhances electron transport efficiency through high conductivity, while the other relies on high surface activity to enhance intermediate adsorption capacity, effectively alleviating the performance limitations of a single crystal form. Simultaneously, the thin-film structure increases the specific surface area and improves structural stability. These multiple factors synergistically contribute to achieving highly efficient oxygen evolution catalysis.

[0040] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications to the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the invention. All variations and improvements should fall within the protection scope defined by the claims of this invention.

Claims

1. A flaky Ni7P3 / twin-phase Ni composite material prepared based on tetrabutylphosphonium chloride, characterized in that, Ni7P3 / bicrystalline Ni composite material is composed of Ni7P3 compound and elemental Ni. Among them, elemental Ni contains two crystal forms, namely face-centered cubic structure and hexagonal close-packed structure; and the Ni7P3 / bicrystalline Ni composite material has a thin sheet-like morphology.

2. A thin flake-like Ni7P3 / twin-phase Ni composite material prepared based on tetrabutylphosphonium chloride according to claim 1, characterized in that, The XRD diffraction peaks of the face-centered cubic crystal form match JCPDS standard card number 04-0850, and the XRD diffraction peaks of the hexagonal close-packed crystal form match JCPDS standard card number 45-1027.

3. A method for preparing a flaky Ni7P3 / twin-phase Ni composite material based on tetrabutylphosphonium chloride according to claim 1, characterized by, Includes the following steps: Using tetrabutylphosphine chloride as a solvent and phosphorus source, the tetrabutylphosphine chloride was heated and subjected to ultrasonic treatment until a homogeneous system was formed. Then, a nickel-containing precursor was added to the system, and ultrasonic treatment was continued to dissolve the nickel-containing precursor, resulting in a homogeneous mixed solution. The homogeneous mixed solution obtained in step (1) is transferred to a reaction vessel and placed in a heating device. It is then heated under an inert gas protective atmosphere and kept at a certain temperature for a period of time to allow the system to react and generate a Ni7P3 / Ni mixture. After the reaction in step (2) is completed and the system is naturally cooled to room temperature, the obtained product is washed and centrifuged in sequence, and then the separated solid product is vacuum dried to obtain the Ni7P3 / Ni mixture. In step (1), tetrabutylphosphine chloride also serves as a template agent, guiding the generated Ni7P3 / Ni mixture to form a sheet-like morphology.

4. The method for preparing a flaky Ni7P3 / bi-crystal phase Ni composite material based on tetrabutylphosphonium chloride according to claim 3, characterized in that, The nickel-containing precursor is nickel nitrate hexahydrate.

5. The method for preparing the thin-plate-like Ni7P3 / bi-crystal phase Ni composite material based on tetrabutylphosphonium chloride according to claim 3, characterized in that, In step (1), the ultrasonic treatment of tetrabutylphosphine chloride is carried out by water-isolated ultrasonic treatment, and the ultrasonic treatment temperature is 60-120℃.

6. The method for preparing the thin-platelet shaped Ni7P3 / bi-crystal phase Ni composite material based on tetrabutylphosphonium chloride according to claim 3, characterized in that, The heating device in step (2) is a tube furnace, and the reaction vessel is a crucible.

7. The method for preparing the thin-platelet-shaped Ni7P3 / bi-crystal phase Ni composite material based on tetrabutylphosphonium chloride according to claim 3, characterized in that, The heating rate in step (2) is 2-15℃ / min, and the calcination temperature is 300-450℃.

8. The method for preparing the sheet-like Ni7P3 / bicrystalline Ni composite material based on tetrabutylphosphine chloride according to claim 3, characterized in that, The washing reagent used in step (3) is a combination of ethanol and water, and the washing method is alternating washing or mixed washing.

9. The method for preparing the sheet-like Ni7P3 / bicrystalline Ni composite material based on tetrabutylphosphine chloride according to claim 3, characterized in that, The vacuum drying temperature in step (3) is room temperature, and the drying time is 10-30 hours.

10. The application of the sheet-like Ni7P3 / bicrystalline Ni composite material prepared based on tetrabutylphosphine chloride according to claim 1 in the electrocatalytic oxygen evolution reaction, wherein the Ni7P3 / bicrystalline Ni composite material is used to prepare the working electrode.

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