Quantum dot doped NiCo-LDH composite material and preparation method and application thereof

Abstract

The invention discloses a quantum dot doped NiCo-LDH composite material and a preparation method and application thereof, and belongs to the technical field of supercapacitor electrode materials. NiFe2O4 quantum dots are used as a doping agent, soluble Ni < 2 + > salt, soluble Co < 2 + > salt and trimesic acid are used as raw materials, a solvothermal reaction is performed to obtain an MOF loaded quantum dot precursor, and the MOF loaded quantum dot precursor is used for preparing the NiCo-LDH composite material. And triggering in-situ topological conversion of the MOF framework in the MOF-loaded quantum dot precursor to layered double hydroxides through alkali liquor, and synchronously realizing generation of an ultrathin nanosheet structure and uniform and firm doping of quantum dots. The quantum dot doped NiCo-LDH composite material disclosed by the invention is of a three-dimensional nano flower-shaped structure assembled by NiCo-LDH ultrathin nanosheets, and NiFe2O4 quantum dots are uniformly distributed on the nanosheets, so that the conductivity and the reaction activity of the composite material are effectively improved, and the composite material shows excellent pseudocapacitance performance and rapid ion diffusion capability.

Description

Technical Field

[0001] This invention belongs to the field of supercapacitor electrode material technology, specifically relating to a quantum dot-doped NiCo-LDH composite material, its preparation method, and its application. Background Technology

[0002] Supercapacitor technology is at a critical stage of development, with its rapid charge-discharge capability and cycle life of tens of thousands of cycles constituting unique advantages over traditional batteries. However, its relatively low energy density remains a core bottleneck restricting its expansion into wider energy storage applications. Therefore, designing novel electrode materials that can significantly improve energy storage capacity while maintaining high power density and long cycle life has become a key scientific issue and technological challenge in this field.

[0003] Against this backdrop, layered hydrogen hydroxides (LDHs) derived from metal-organic frameworks (MOFs) are considered highly promising pseudocapacitive electrode materials due to their tunable chemical composition, open layered structure, and abundant redox active sites. The inherent high specific surface area and regular pore structure of MOF precursors can be partially retained or reconstructed during the derivatization process, thus providing an ideal channel for the rapid transport of electrolyte ions.

[0004] To further overcome the limitations of such materials in terms of reaction kinetics and active site utilization, the introduction of quantum dots (QDs) to construct heterocomposite materials has become a cutting-edge strategy. As typical zero-dimensional nanomaterials, quantum dots typically have a size of less than 10 nanometers, thus exhibiting an extremely high surface atomic ratio and a significant quantum confinement effect. This not only exposes a wealth of electrochemical active sites but also greatly shortens the bulk diffusion distance of ions / electrons, potentially endowing the material with superior rate performance. However, quantum dots are prone to aggregation and deactivation during electrochemical processes due to their high surface energy. This not only leads to a sharp reduction in active sites, blockage of MOF channels, and deterioration of electrical contacts but also disrupts structural stability. Ultimately, this results in a comprehensive degradation of the electrode's core performance characteristics, including specific capacitance, rate performance, cycle life, and energy efficiency, completely negating the design advantages of heterocomposite structures. Patent application CN113555232A discloses a method for preparing a layered nickel-aluminum double hydroxide-carbon quantum dot composite material, as well as its application and testing methods. This material is prepared using a traditional co-precipitation method. Although the process is simple, the carbon quantum dots (CQDs) are introduced only through physical mixing, resulting in uneven distribution and weak interfacial bonding, leading to a low specific capacitance of the composite material (approximately 400 F·g). -1Furthermore, the structure is prone to stacking, resulting in poor rate capability and cycling performance. Patent application CN115360028A discloses a method for preparing and applying a CNTs@CuCo-LDH / BPQD composite electrode. This method obtains a hollow polyhedral structure by constructing and etching a ZIF-67 precursor. However, its key component, black phosphorus quantum dots (BPQD), is loaded via a post-immersion method, resulting in a weak interfacial physical composite. This leads to a specific capacitance of approximately 900 F·g for the composite electrode. -1 Furthermore, it is prone to detachment during long-term cycling. Patent application CN118942924A discloses a method for preparing PBA@NiCo-LDH-CQDs composite materials and their applications. It uses PBA as a hard template to construct a core-shell structure, although the performance is improved (specific capacitance is approximately 1309 F·g). -1 However, the synthesis route is extremely complicated, involving multiple centrifugation and washing processes, and carbon quantum dots (CQDs) are also post-composite, with both interface problems and process complexity. Summary of the Invention

[0005] This invention provides a quantum dot-doped NiCo-LDH composite material, its preparation method, and its application. It effectively solves the technical problem of low specific capacitance and poor long-cycle stability caused by weak interfacial bonding resulting from the simple physical mixing of quantum dots with MOFs when introducing quantum dots into MOFs. This invention uses NiFe2O4 as quantum dots, doping it into NiCo-LDH to obtain a three-dimensional nanoflower-like structure assembled from ultrathin nanosheets. The uniformly distributed NiFe2O4 quantum dots in the composite material effectively improve its conductivity and reactivity. This composite material also exhibits excellent pseudocapacitive properties and rapid ion diffusion capabilities, making it a promising candidate for supercapacitor electrode materials.

[0006] The first objective of this invention is to provide a method for preparing quantum dot-doped NiCo-LDH composite materials, comprising the following steps: Using NiFe2O4 quantum dots as dopants, and soluble Ni 2+ Salt, soluble Co 2+ Using salt and pyromellitic acid as raw materials, a MOF precursor is formed through a solvothermal reaction. At the same time, NiFe2O4 quantum dots are doped into the MOF precursor to obtain a MOF-loaded quantum dot precursor.

[0007] Under the triggering effect of alkali, the MOF framework in the MOF-loaded quantum dot precursor is transformed in situ into NiCo-LDH nanosheets, resulting in a quantum dot-doped NiCo-LDH composite material.

[0008] As a preferred embodiment, the soluble Ni 2+ Salt and soluble Co2+ The mass percentage of NiFe2O4 quantum dots, based on the total mass of the salt, is 1.7%–5.2%. When the mass percentage of NiFe2O4 quantum dots exceeds 5.2%, the electrochemical performance of the composite material significantly decreases; 5.2% serves as a critical value, and performance improvement beyond this value is limited. Similarly, when the mass percentage of NiFe2O4 quantum dots is less than 1.7%, the performance improvement is limited, similar to when it exceeds 5.2%. When the mass percentage of NiFe2O4 quantum dots is 1.7%, the electrochemical performance of the composite material begins to improve after loading, reaching its peak at 3.5%. Beyond 5.2%, the composite material performance significantly decreases; therefore, the mass percentage of NiFe2O4 quantum dots is limited to 1.7%–5.2%.

[0009] As a preferred embodiment, the preparation method of the quantum dot-doped NiCo-LDH composite material is as follows: the MOF-loaded quantum dot precursor is dispersed in an alkaline solution, and an in-situ topological transformation reaction is carried out at room temperature to obtain the quantum dot-doped NiCo-LDH composite material.

[0010] In a preferred embodiment, the alkaline solution is a KOH solution with a concentration of 0.5 mol / L to 1.5 mol / L, and the ratio of the MOF-loaded quantum dot precursor to the alkaline solution is 0.15 g: 10 mL. For the above KOH solution concentration, when the concentration is 1 mol / L, the in-situ topological transformation reaction is more stable, and the specific capacitance of the prepared quantum dot-doped NiCo-LDH composite material is optimal.

[0011] In a preferred embodiment, the solvothermal reaction specifically involves: reacting soluble Ni... 2+ Salt, soluble Co 2+ Salt, pyromellitic acid, and NiFe2O4 quantum dots were dissolved in N,N-dimethylformamide solvent and subjected to a solvothermal reaction at 140℃~170℃ for 11h~13h to obtain MOF-supported quantum dot precursors.

[0012] As a preferred embodiment, the soluble Ni 2+ Salt, soluble Co 2+ The molar ratio of salt to pyromellitic acid is 3:1:1.5.

[0013] As a preferred embodiment, the soluble Ni 2+ The salt is selected from Ni(NO3)2·6H2O; the soluble Co 2 + The salt is selected from Co(NO3)2·6H2O.

[0014] The second objective of this invention is to provide a quantum dot-doped NiCo-LDH composite material, which is prepared using the preparation method of the quantum dot-doped NiCo-LDH composite material described in any of the above-mentioned embodiments.

[0015] The third objective of this invention is to provide an application of the aforementioned quantum dot-doped NiCo-LDH composite material as a cathode material in supercapacitors.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for preparing quantum dot-doped NiCo-LDH composite materials, using NiFe2O4 quantum dots as dopants and soluble Ni... 2+ Salt, soluble Co 2+ Using salt and trimesic acid as raw materials, a MOF-loaded quantum dot precursor (NiCo-BTC@NiFe2O4) was obtained through a solvothermal reaction. Then, an in-situ topological transformation of the MOF framework in the precursor to a layered double hydroxide was triggered by alkali, simultaneously achieving the generation of an ultrathin nanosheet structure and uniform and robust doping of quantum dots. Finally, a loose and porous three-dimensional composite structure was obtained, namely, the quantum dot-doped NiCo-LDH composite material (NiCo-LDH@NiFe2O4). The quantum dot-doped NiCo-LDH composite material prepared in this invention exhibits a three-dimensional nanoflower-like structure assembled from NiCo-LDH ultrathin nanosheets, with NiFe2O4 quantum dots uniformly distributed on the nanosheets. This effectively improves the conductivity and reactivity of the composite material, effectively solving the problems of low specific capacitance and poor long-cycle stability caused by the weak interfacial bonding resulting from the simple physical mixing of quantum dots and MOF materials.

[0017] The quantum dot-doped NiCo-LDH composite material prepared by this invention exhibits excellent pseudocapacitive properties and rapid ion diffusion capability, and has broad application prospects as a supercapacitor electrode material.

[0018] This invention pre-confines NiFe2O4 quantum dots within a porous MOF framework, then transforms the MOF precursor into LDHs through an in-situ conversion strategy. This strategy cleverly utilizes the pores of the MOFs to spatially confine and disperse the quantum dots, while simultaneously constructing a highly interconnected conductive network of NiFe2O4 quantum dots on the derived LDH substrate. The derived NiCo-LDH possesses a three-dimensional porous, layered, and open framework, providing an ideal topological space for the conductive network. Furthermore, by simultaneously introducing NiFe2O4 quantum dots during the growth of NiCo-LDH, the components are tightly embedded in the interlayers, surface, and pores of NiCo-LDH. Through mutual entanglement, the NiFe2O4 quantum dots ultimately form a seamless, continuous, three-dimensional conductive architecture at the nanometer to micrometer scale, resulting in a hierarchical LDH@QDs structure. This achieves a synergistic enhancement between the high activity of quantum dots and the structural stability and high conductivity of NiCo-LDH, providing a new design concept and research path for developing next-generation supercapacitor electrode materials with both high energy density and high power density. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 The infrared spectrum of the quantum dot-doped NiCo-LDH composite material (NiCo-LDH@NiFe2O4) prepared in Example 1 of this invention.

[0021] Figure 2 Scanning electron microscope image of the MOF-loaded quantum dot precursor (NiCo-BTC@NiFe2O4) prepared in Example 1 of this invention.

[0022] Figure 3 Scanning electron microscope image of the quantum dot-doped NiCo-LDH composite material (NiCo-LDH@NiFe2O4) prepared in Example 1 of this invention.

[0023] Figure 4 The elemental distribution surface scan (EDS) image of the quantum dot-doped NiCo-LDH composite material (NiCo-LDH@NiFe2O4) prepared in Example 1 of this invention.

[0024] Figure 5X-ray powder diffraction pattern of the quantum dot-doped NiCo-LDH composite material (NiCo-LDH@NiFe2O4) prepared in Example 1 of this invention.

[0025] Figure 6 Cyclic voltammogram of the quantum dot-doped NiCo-LDH composite material (NiCo-LDH@NiFe2O4) prepared in Example 1 of this invention.

[0026] Figure 7 The discharge curve of the quantum dot-doped NiCo-LDH composite material (NiCo-LDH@NiFe2O4) prepared in Example 1 of this invention is shown in the constant current charge-discharge curve.

[0027] Figure 8 The discharge curve of the quantum dot-doped NiCo-LDH composite material (NiCo-LDH@NiFe2O4) prepared in Example 2 of this invention is a constant current charge-discharge curve.

[0028] Figure 9 The discharge curve of the quantum dot-doped NiCo-LDH composite material (NiCo-LDH@NiFe2O4) prepared in Example 3 of this invention is a constant current charge-discharge curve. Detailed Implementation

[0029] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific 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. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods, and the materials and reagents used in the following embodiments are commercially available unless otherwise specified.

[0030] Regarding existing methods for preparing composite electrode materials through quantum dot doping, firstly, invention patent application CN113555232A discloses a method for preparing a layered nickel-aluminum double hydroxide-carbon quantum dot composite material and its application and testing methods. This method uses a traditional co-precipitation method. Although the process is simple, the carbon quantum dots (CQDs) are only introduced through physical mixing, resulting in uneven distribution and weak interfacial bonding, leading to a low specific capacitance of the composite material (approximately 400 F·g). -1Furthermore, the structure is prone to stacking, resulting in poor rate capability and cycling performance. Secondly, the invention patent with publication number CN115360028A discloses a method for preparing and applying a CNTs@CuCo-LDH / BPQD composite electrode. This method obtains a hollow polyhedral structure by constructing and etching a ZIF-67 precursor. However, its key component, black phosphorus quantum dots (BPQD), is loaded via a post-immersion method, resulting in a weak interfacial physical composite. This leads to a specific capacitance of approximately 900 F·g for the composite electrode. -1 Furthermore, it is prone to detachment during long-term cycling. Third, the invention patent CN118942924A, after its application was published, discloses a method for preparing PBA@NiCo-LDH-CQDs composite materials and their applications. It uses PBA as a hard template to construct a core-shell structure, although the performance is improved (specific capacitance is approximately 1309 F·g). -1 However, the synthesis route is extremely cumbersome, involving multiple centrifugation and washing processes, and carbon quantum dots (CQDs) are also post-composite, presenting both interface problems and process complexity. Based on these technical issues, this invention provides a quantum dot-doped NiCo-LDH composite material, its preparation method, and its applications.

[0031] The technical concept of the present invention will be described below.

[0032] This invention provides a method for preparing quantum dot-doped NiCo-LDH composite materials, comprising the following steps: Using NiFe2O4 quantum dots as dopants, and soluble Ni 2+ Salt, soluble Co 2+ Using salt and pyromellitic acid as raw materials, a MOF precursor is formed through a solvothermal reaction. At the same time, NiFe2O4 quantum dots are doped into the MOF precursor to obtain a MOF-loaded quantum dot precursor.

[0033] Under the triggering effect of alkali, the MOF framework in the MOF-derived quantum dot precursor is transformed in situ into NiCo-LDH nanosheets, resulting in a quantum dot-doped NiCo-LDH composite material.

[0034] In the above technical solution, NiFe2O4 quantum dots are used as functional dopant to introduce soluble Ni 2+ Salt, soluble Co 2+In the MOF precursor constructed from salt and pyromellitic acid, NiFe₂O₄ quantum dots are introduced as structural seeds during the MOF construction stage. Subsequently, under base triggering, the MOF framework is transformed in situ into ultrathin NiCo-LDH nanosheets, with NiFe₂O₄ quantum dots firmly doped into the nanosheets. The composite material preparation method provided by this invention achieves atomic-level dispersion of NiFe₂O₄ quantum dots, strong interfacial coupling, and simultaneous construction of a three-dimensional porous structure in one step. Thanks to this, the NiCo-LDH@NiFe₂O₄ composite material prepared by this invention exhibits comprehensively leading electrochemical performance, achieving high efficiency at 1 A·g⁻¹. -1 At current density, the specific capacitance is as high as 2195 F·g -1 In summary, this invention not only achieves innovation in structural design through the "in-situ doping-conversion" mechanism in the synthesis path, but also achieves significant improvement in the key performance indicator of specific capacitance.

[0035] The technical effects of the present invention will be described below through specific embodiments and comparative examples.

[0036] Example 1 A method for preparing a quantum dot-doped NiCo-LDH composite material includes the following steps: S1. Nickel chloride hexahydrate (NiCl2·6H2O, 1.426 g) and ferric chloride hexahydrate (FeCl3·6H2O, 1.622 g) were dissolved together in 80 mL of deionized water and stirred at room temperature for 30 min. Then, concentrated ammonia was added dropwise to the mixed solution to adjust the pH to 8.0, and stirring was continued vigorously for 10 min. The resulting suspension was transferred to a hydrothermal reactor and reacted at 190 °C for 10 h. After the reaction was complete, the product was collected by centrifugation and washed three times successively with deionized water and anhydrous ethanol, and dried at 70 °C to obtain dark brown NiFe2O4 quantum dots, denoted as QDs.

[0037] In S2, nickel nitrate hexahydrate (Ni(NO3)2·6H2O, 0.655 g), cobalt nitrate hexahydrate (Co(NO3)2·6H2O, 0.218 g), and trimesic acid (H3BTC, 0.105 g) were dissolved together with the QDs prepared in S1 (0.030 g) in 60 mL of DMF and ultrasonically dispersed. The mixture was then transferred to a high-pressure reactor and reacted at 150 °C for 12 hours. After the reaction, the product was collected by centrifugation, washed three times with DMF and anhydrous ethanol, and dried at 70 °C to obtain the MOF-supported quantum dot precursor, denoted as NiCo-BTC@NiFe2O4.

[0038] In step S3, 0.15 g of the NiCo-BTC@NiFe2O4 prepared in step S2 was dispersed in 10 mL of a 1 M KOH solution and stirred continuously at room temperature for 6 hours. After the reaction was completed, the dark green product was collected by centrifugation and washed three times with deionized water and anhydrous ethanol, and dried at 70 °C to obtain the quantum dot-doped NiCo-LDH composite material, denoted as NiCo-LDH@NiFe2O4.

[0039] The electrochemical performance of the quantum dot-doped NiCo-LDH composite material prepared in Example 1 was tested. Specifically, a standard three-electrode system was used for electrochemical testing in a 6 mol / L KOH electrolyte. Using a 6 mol / L KOH solution as the electrolyte, the working electrode (a nickel foam sheet loaded with NiCo-LDH@QDs), the counter electrode (a platinum sheet), and the reference electrode (Hg / HgO, with the same concentration of KOH as the filling solution) were placed together in the electrolytic cell. Subsequently, the three electrodes were connected to the corresponding interfaces of the electrochemical workstation to form a complete test circuit for electrochemical testing.

[0040] The NiCo-LDH@NiFe2O4 material prepared in Example 1 above was tested at 1 A·g -1 ,2A·g -1 5A·g -1 8A·g -1 10A·g -1 The specific capacitance values ​​at the current density are 2195 F·g -1 2136F·g -1 1445F·g -1 1058F·g -1 856F·g -1 .

[0041] Example 2 A method for preparing a quantum dot-doped NiCo-LDH composite material includes the following steps: S1. Nickel chloride hexahydrate (NiCl2·6H2O, 1.426 g) and ferric chloride hexahydrate (FeCl3·6H2O, 1.622 g) were dissolved together in 80 mL of deionized water and stirred at room temperature for 30 min. Then, concentrated ammonia was added dropwise to the mixed solution to adjust the pH to 8.0, and stirring was continued vigorously for 10 min. The resulting suspension was transferred to a hydrothermal reactor and reacted at 190 °C for 10 h. After the reaction was complete, the product was collected by centrifugation and washed three times successively with deionized water and anhydrous ethanol, and dried at 70 °C to obtain dark brown NiFe2O4 quantum dots, denoted as QDs.

[0042] In S2, nickel nitrate hexahydrate (Ni(NO3)2·6H2O, 0.655 g), cobalt nitrate hexahydrate (Co(NO3)2·6H2O, 0.218 g), and trimesic acid (H3BTC, 0.105 g) were dissolved together with the QDs prepared in S1 (0.015 g) in 60 mL of DMF and ultrasonically dispersed. The mixture was then transferred to a high-pressure reactor and reacted at 150 °C for 12 hours. After the reaction, the product was collected by centrifugation, washed three times with DMF and anhydrous ethanol, and dried at 70 °C to obtain the MOF-supported quantum dot precursor, denoted as NiCo-BTC@NiFe2O4.

[0043] In step S3, the NiCo-BTC@NiFe2O4 (0.15 g) prepared in step S2 was dispersed in 10 mL of a 1 M KOH solution and stirred continuously at room temperature for 6 hours. After the reaction was completed, the dark green product was collected by centrifugation and washed three times with deionized water and anhydrous ethanol, and dried at 70 °C to obtain the quantum dot-doped NiCo-LDH composite material, denoted as NiCo-LDH@NiFe2O4.

[0044] Electrochemical tests were performed using the same three-electrode system as in Example 1 in a 6 mol / L KOH electrolyte. The electrochemical performance of the quantum dot-doped NiCo-LDH composite material prepared in Example 2 was also tested. The prepared NiCo-LDH@NiFe2O4 material exhibited good electrochemical performance at 1 A·g⁻¹. -1 2 A·g -1 5 A·g -1 8 A·g -1 10 A·g -1 The specific capacitance values ​​at the current densities are 1955 F·g -1 , 1945 F·g -1 1324 F·g -1 924 F·g -1 724F·g -1 .

[0045] Example 3 A method for preparing a quantum dot-doped NiCo-LDH composite material includes the following steps: S1. Nickel chloride hexahydrate (NiCl2·6H2O, 1.426 g) and ferric chloride hexahydrate (FeCl3·6H2O, 1.622 g) were dissolved together in 80 mL of deionized water and stirred at room temperature for 30 min. Then, concentrated ammonia was added dropwise to the mixed solution to adjust the pH to 8.0, and stirring was continued vigorously for 10 min. The resulting suspension was transferred to a hydrothermal reactor and reacted at 190 °C for 10 h. After the reaction was complete, the product was collected by centrifugation and washed three times successively with deionized water and anhydrous ethanol, and dried at 70 °C to obtain dark brown NiFe2O4 quantum dots, denoted as QDs.

[0046] In S2, nickel nitrate hexahydrate (Ni(NO3)2·6H2O, 0.655 g), cobalt nitrate hexahydrate (Co(NO3)2·6H2O, 0.218 g), and trimesic acid (H3BTC, 0.105 g) were dissolved together with the QDs prepared in S1 (0.045 g) in 60 mL of DMF and ultrasonically dispersed. The mixture was then transferred to a high-pressure reactor and reacted at 150 °C for 12 hours. After the reaction, the product was collected by centrifugation, washed three times with DMF and anhydrous ethanol, and dried at 70 °C to obtain the MOF-supported quantum dot precursor, denoted as NiCo-BTC@NiFe2O4.

[0047] In step S3, the NiCo-BTC@NiFe2O4 (0.15 g) prepared in step S2 was dispersed in 10 mL of a 1 M KOH solution and stirred continuously at room temperature for 6 hours. After the reaction was completed, the dark green product was collected by centrifugation and washed three times with deionized water and anhydrous ethanol, and dried at 70 °C to obtain the quantum dot-doped NiCo-LDH composite material, denoted as NiCo-LDH@NiFe2O4.

[0048] Electrochemical tests were performed using the same three-electrode system as in Example 1 in a 6 mol / L KOH electrolyte. The electrochemical performance of the quantum dot-doped NiCo-LDH composite material prepared in Example 3 was also tested. The prepared NiCo-LDH@NiFe2O4 material exhibited good electrochemical performance at 1 A·g⁻¹. -1 2 A·g -1 5 A·g -1 8 A·g -1 10 A·g -1 The specific capacitance values ​​at the current density are 1635 F·g -1 1409F·g -1 1013 F·g -1 793 F·g -1 689F·g -1 .

[0049] To further illustrate the technical effects of the present invention, a comparative example is also provided, as follows.

[0050] Comparative Example 1 The difference compared to Example 1 is that NiFe2O4 quantum dots were not added.

[0051] A method for preparing NiCo-LDH material includes the following steps: S1, nickel nitrate hexahydrate (Ni(NO3)2·6H2O, 0.655 g), cobalt nitrate hexahydrate (Co(NO3)2·6H2O, 0.218 g), and trimesic acid (H3BTC, 0.105 g) were dissolved together in 60 mL of DMF and ultrasonically dispersed. The mixture was then transferred to a high-pressure reactor and reacted at 150 °C for 12 hours. After the reaction, the product was collected by centrifugation, washed three times with DMF and anhydrous ethanol, and dried at 70 °C to obtain the MOF precursor, denoted as NiCo-BTC.

[0052] In step S2, the NiCo-BTC prepared in step S1 was dispersed in 10 mL of a 1 M KOH solution and stirred continuously at room temperature for 6 hours. After the reaction was completed, the dark green product was collected by centrifugation and washed thoroughly three times with deionized water and anhydrous ethanol, and dried at 70 °C to obtain NiCo-LDH material, denoted as NiCo-LDH.

[0053] Electrochemical tests were performed using the same three-electrode system as in Example 1 in a 6 mol / L KOH electrolyte. The electrochemical performance of the NiCo-LDH material prepared in Comparative Example 1 was tested. The prepared NiCo-LDH@NiFe2O4 material was tested at 1 A·g -1 2 A·g -1 5 A·g -1 8 A·g -1 10 A·g -1 The specific capacitance values ​​at the current density are 1380 F·g -1 1026F·g -1 707 F·g -1 449 F·g -1 342 F·g -1 .

[0054] The morphology and properties of the quantum dot-doped NiCo-LDH composite materials prepared in Examples 1 to 3 and the NiCo-LDH material prepared in Comparative Example 1 were characterized, and the results are as follows.

[0055] 1. FT-IR analysis: FT-IR analysis was performed on the NiCo-LDH@NiFe2O4 material prepared in Example 1 of this invention to verify the major functional groups in the NiCo-LDH@NiFe2O4 material. The results are as follows: Figure 1 As shown. From Figure 1 It can be concluded that the composite material underwent significant changes before and after alkaline solution treatment. For NiCo-BTC@NiFe2O4, the structure located at 1560 cm⁻¹... -1 and 1383cm -1 The characteristic peaks at this location are attributed to the -CoO- vibration. After alkali treatment, the intensity of these peaks significantly decreased, indicating that the organic ligands in the OH group... - It was gradually replaced under the influence of [other factors]. Meanwhile, at 3000cm... -1 ~3600cm -1 The broad bands observed within this range can be attributed to the stretching vibrations of the OH groups in adsorbed water molecules. At 644 cm⁻¹... -1 The newly appearing peaks nearby are attributed to the vibrations of the M-OH (M = Ni, Co) bond. The significant changes in these characteristic peaks confirm the successful transformation of NiCo-BTC@NiFe2O4 into NiCo-LDH@NiFe2O4 material.

[0056] 2. Microscopic morphology: The microstructure of the NiCo-LDH@NiFe2O4 material prepared in Example 1 was tested by scanning electron microscopy (SEM), and the results are as follows: Figure 2 , Figure 3 As shown in the SEM images, NiCo-BTC@NiFe2O4 appears as uniformly sized, densely structured nanospheres. After treatment with an alkaline solution, its morphology underwent a significant transformation, evolving into a three-dimensional nanoflower-like structure loosely assembled from ultrathin nanosheets. This morphological change directly confirms the presence of OH during the alkaline treatment process. - Through intercalation and exfoliation, the dense structure of the precursor undergoes dissociation and recombination, ultimately leading to the successful synthesis of NiCo-LDH@NiFe2O4 material with an open porous structure.

[0057] 3. EDS elemental analysis: The elemental distribution in selected regions of the NiCo-LDH@NiFe2O4 material prepared in Example 1 was analyzed by EDS, and the results are as follows: Figure 4 As shown. By Figure 4 It is evident that the NiCo-LDH@NiFe2O4 material mainly contains Ni, Co, Fe, and O, with Fe originating from NiFe2O4 quantum dots. Furthermore, these elements are uniformly distributed in the selected region, indicating a uniform distribution of elements within the functional material and a uniform distribution of NiFe2O4 quantum dots within NiCo-LDH.

[0058] 4. XRD analysis: XRD analysis was performed on the NiCo-LDH@NiFe2O4 material prepared in Example 1 to verify the crystal structure of the NiCo-LDH@NiFe2O4 material. The results are as follows: Figure 5 As shown. By Figure 5 It can be clearly seen that the peak values ​​correspond to the standard cards for Ni(OH)2 and Co(OH)2, proving the successful synthesis of the material. At the same time, the NiCo-LDH@NiFe2O4 material has good crystallinity.

[0059] 5. Cyclic Voltmeter-Ampere Test Analysis: Cyclic voltammetry (CV) tests were performed on the NiCo-LDH@NiFe2O4 material prepared in Example 1 to investigate its electrochemical energy storage behavior. The results are as follows: Figure 6 As shown in the figure, it is evident that within the potential window of 0V to 0.6V, the CV curve exhibits distinct redox peaks, the positions of which correspond to the characteristic electrochemical reactions of M(OH)2 / MOOH (M = Ni, Co), demonstrating that the composite material exhibits typical pseudocapacitive behavior in alkaline electrolytes. Simultaneously, the NiCo-LDH@NiFe2O4 material shows performance at 10mV·s⁻¹. -1 ~50mV·s -1 The ability to maintain a similar CV shape at different scan rates indicates that it has good reaction reversibility and rate performance.

[0060] 6. Constant current charge-discharge test analysis: The NiCo-LDH@NiFe2O4 materials prepared in Examples 1 to 3 were subjected to galvanostatic charge-discharge (GCD) tests to further evaluate their electrochemical performance. The results are as follows: Figures 7-9 As shown. By Figures 7-9 It is evident that, at a certain current density, the charge-discharge curve exhibits a distinct voltage plateau, corresponding to the reversible Faraday redox reaction occurring during the charge-discharge process, consistent with the characteristic peaks observed in the cyclic voltammetry test. Furthermore, the charge-discharge curve demonstrates good symmetry, indicating that the quantum dot-doped NiCo-LDH composite material prepared in this invention possesses high coulombic efficiency and excellent electrochemical reversibility. This result further confirms that NiCo-LDH@NiFe2O4, as a pseudocapacitive electrode material, exhibits stable and efficient electrochemical energy storage characteristics.

[0061] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the inventive concept of the present invention, can make other changes and modifications to these embodiments, all of which fall within the scope of the present invention.

[0062] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. If such modifications and variations fall within the scope of equivalents of this invention, then this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a quantum dot-doped NiCo-LDH composite material, characterized in that, Includes the following steps: Using NiFe2O4 quantum dots as dopants, and soluble Ni 2+ Salt, soluble Co 2+ Using salt and pyromellitic acid as raw materials, a MOF precursor is formed through a solvothermal reaction. At the same time, NiFe2O4 quantum dots are doped into the MOF precursor to obtain a MOF-loaded quantum dot precursor. Under the triggering effect of alkali, the MOF framework in the MOF-loaded quantum dot precursor is transformed in situ into NiCo-LDH nanosheets, resulting in a quantum dot-doped NiCo-LDH composite material.

2. The method for preparing quantum dot-doped NiCo-LDH composite material according to claim 1, characterized in that, With the soluble Ni 2+ Salt and soluble Co 2+ Based on the total mass of the salt, the mass percentage of the NiFe2O4 quantum dots is 1.7% to 5.2%.

3. The method for preparing quantum dot-doped NiCo-LDH composite material according to claim 1, characterized in that, The preparation method of the quantum dot-doped NiCo-LDH composite material is as follows: the MOF-loaded quantum dot precursor is dispersed in an alkaline solution, and an in-situ topological transformation reaction is carried out at room temperature to obtain the quantum dot-doped NiCo-LDH composite material.

4. The method for preparing quantum dot-doped NiCo-LDH composite material according to claim 3, characterized in that, The alkaline solution is a KOH solution with a concentration of 0.5 mol / L to 1.5 mol / L, and the ratio of the MOF-loaded quantum dot precursor to the alkaline solution is 0.15 g: 10 mL.

5. The method for preparing quantum dot-doped NiCo-LDH composite material according to claim 1, characterized in that, The solvothermal reaction specifically involves: reacting soluble Ni... 2+ Salt, soluble Co 2+ Salt, pyromellitic acid, and NiFe2O4 quantum dots were dissolved in N,N-dimethylformamide and subjected to a solvothermal reaction at 140℃~170℃ for 11h~13h to obtain MOF-supported quantum dot precursors.

6. The method for preparing quantum dot-doped NiCo-LDH composite material according to claim 1, characterized in that, The soluble Ni 2+ Salt, soluble Co 2+ The molar ratio of salt to pyromellitic acid is 3:1:1.

5.

7. The method for preparing quantum dot-doped NiCo-LDH composite material according to claim 1, characterized in that, The soluble Ni 2+ The salt is selected from Ni(NO3)2·6H2O; the soluble Co 2+ The salt is selected from Co(NO3)2·6H2O.

8. A quantum dot-doped NiCo-LDH composite material, characterized in that, The quantum dot-doped NiCo-LDH composite material was prepared using the preparation method described in any one of claims 1 to 7.

9. The application of the quantum dot-doped NiCo-LDH composite material of claim 8 as a positive electrode material in a supercapacitor.

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