High-performance iron oxide-nitrogen doped carbon-single-walled carbon nanohorn ternary composite electrode material and preparation method thereof

Abstract

The invention provides a high-performance iron oxide-nitrogen doped carbon-single-walled carbon nanohorn (Fe2O3 (at) NC / SWCNHs) ternary composite electrode material and a preparation method of the high-performance iron oxide-nitrogen doped carbon-single-walled carbon nanohorn ternary composite electrode material. The preparation method comprises the following steps: preparing a hybrid of an iron-based metal organic framework material (Fe-MOFs) and SWCNHs by adopting a solvothermal method; and preparing the Fe2O3 (at) NC / SWCNHs ternary composite electrode material through a high-temperature roasting method by taking the formed Fe-MOFs as a precursor and a self-sacrifice template. The obtained ternary composite electrode material has unique fusiform morphology, rich mesoporous structures and appropriate nitrogen content, shows high specific capacitance and excellent cycle stability, and has practical application and popularization values in the field of supercapacitors.

Description

Technical Field

[0001] The present invention belongs to the technical field of supercapacitor electrode materials and relates to a high-performance iron oxide-nitrogen doped carbon-single-walled carbon nanohorn (Fe 2 O 3 @NC / SWCNHs) ternary composite electrode material and its preparation method. Background Art

[0002] In order to solve the energy crisis and environmental pollution caused by the rapid consumption of traditional fossil fuels, it is urgent to develop new and efficient energy storage / conversion devices. Supercapacitors have the advantages of fast charging and discharging speed, high power density, and long cycle life, and are the most promising energy storage devices. However, in some emerging high-tech fields, the practical application of supercapacitors is still limited, mainly due to their low energy density. The development of new high-performance electrode materials is the key to improving the energy density of supercapacitors. So far, researchers have developed a variety of functional electrode materials, mainly including three types of electrode materials: carbon materials, conductive polymers, and transition metal oxides.

[0003] Among the many transition metal oxides, iron oxide (Fe 2 O 3 ) is an attractive pseudocapacitive electrode material due to its high theoretical specific capacitance, variable oxidation state, abundant sources, and low price. However, similar to other transition metal oxides, Fe 2 O 3 It inevitably has the disadvantages of poor conductivity and easy agglomeration. In addition, the large volume change during the charge and discharge process easily leads to structural collapse, resulting in a decrease in specific capacitance and poor rate performance. These disadvantages make Fe 2 O 3 The actual specific capacitance of the electrode material is much smaller than the theoretical specific capacitance, which limits the Fe 2 O 3 Practical applications of electrode materials in the field of supercapacitors.

[0004] Carbon materials, such as carbon nanofibers, carbon nanotubes, graphene, etc., have the advantages of large specific surface area, good conductivity, and high electrochemical stability. They are a common type of supercapacitor electrode material. Carbon materials mainly exhibit double-layer capacitance (EDLC) performance, thus having high power density, excellent rate performance, and long cycle life. Therefore, carbon materials are combined with Fe 2 O 3 Combined with Fe 2 O 3 / C composite electrode materials can improve Fe 2 O 3Electrochemical properties such as conductivity, rate performance and cycle stability of electrode materials. On this basis, further introducing heteroatoms, such as nitrogen (N), sulfur (S), phosphorus (P), etc., can adjust the electronic properties and surface chemical properties of the composite material, introduce more defects and active sites, and enhance the interaction between metal oxides and carbon materials, thereby further improving Fe 2 O 3 Electrochemical properties of C / C composite electrode materials. Summary of the invention

[0005] In order to meet the urgent demand for high-performance electrode materials in the field of supercapacitors, the present invention aims to provide a high-performance iron oxide-nitrogen-doped carbon-single-walled carbon nanohorn (Fe 2 O 3 @NC / SWCNHs) ternary composite electrode materials.

[0006] In order to achieve the above-mentioned purpose, the present invention adopts solvent thermal combined with high temperature calcination method to prepare Fe 2 O 3 @NC / SWCNHs ternary composite electrode material. Among them, Fe 2 O 3 @NC is prepared by using metal organic framework (MOFs) materials as precursors and self-sacrificial templates. MOFs are a new type of crystalline porous material composed of metal ions and organic ligands. SWCNHs is a new type of carbon nanomaterial with a unique dahlia-like spherical morphology, rich porous structure, and rich edge defects and active sites. The present invention comprehensively utilizes nano-Fe 2 O 3 The synergistic advantages of the pseudocapacitance of SWCNHs and the double-layer capacitance of SWCNHs, as well as the effect of nitrogen doping, lead to the high-performance Fe 2 O 3 @NC / SWCNHs ternary composite electrode materials.

[0007] Specifically, the purpose of the present invention is to provide a method for preparing a high-performance iron oxide-nitrogen-doped carbon-single-walled carbon nanohorn ternary composite electrode material, characterized in that it comprises the following steps:

[0008] S1. Preparation of Fe-MOFs / SWCNHs hybrids by solvothermal method:

[0009] Ferrous chloride (FeCl 3 6H 2 O), 2-aminoterephthalic acid (NH 2 -BDC), triethylamine dispersed in N,N-dimethylformamide (DMF) solvent;

[0010] SWCNHs were dispersed in DMF solvent;

[0011] The two mixtures are uniformly mixed and then subjected to a solvothermal reaction to obtain a Fe-MOFs / SWCNHs hybrid;

[0012] S2. The product Fe-MOFs / SWCNHs obtained in step S1 was used as a precursor and a self-sacrificial template to prepare Fe 2 O 3 @NC / SWCNHs ternary composite electrode materials.

[0013] It is worth noting that in this step, the Fe-MOFs / SWCNHs hybrid is placed in a high temperature environment for calcination, and the Fe-MOFs are converted into Fe 2 O 3 The core-shell structure is composed of nanoparticles as the core and the in-situ formed nitrogen-doped carbon layer as the shell. 2 O 3 @NC is uniformly dispersed in the carbon nanohorn matrix, thereby obtaining Fe 2 O 3 @NC / SWCNHs ternary composite electrode materials.

[0014] Further, the ratio of raw materials in step S1 is:

[0015]

[0016] Furthermore, the hydrothermal reaction temperature in step S1 is 120 to 200° C., and the reaction time is 5 to 36 hours.

[0017] Furthermore, the vacuum drying temperature in step S1 is 40 to 100° C., and the drying time is 3 to 48 hours.

[0018] Furthermore, the calcination temperature in step S2 is 300 to 450° C., and the reaction time is 1.5 to 6 hours.

[0019] Beneficial technical effects of the present invention:

[0020] 1. Fe of the present invention 2 O 3 The preparation method of @NC / SWCNHs ternary composite electrode material is the common solvent thermal and high-temperature calcination method, which has the advantages of simple process flow, mild reaction conditions, strong controllability and good repeatability. It is suitable for large-scale industrial production and practical application promotion.

[0021] 2. The present invention uses Fe-MOFs as a precursor and a self-sacrificial template, and the synthesized ternary composite electrode material has a multi-level pore structure, a high specific surface area, controllable morphological characteristics, and excellent electrochemical properties.

[0022] 3. Fe of the present invention 2 O 3 @NC presents a spindle structure, inheriting the unique morphology of Fe-MOFs. 2 O 3 @NC spindle consists of a large amount of Fe 2 O 3 Nanoparticle composition, Fe 2 O 3 The nanoparticles are tightly wrapped by the in-situ formed nitrogen-doped carbon layer and SWCNHs. This effective protection can prevent Fe 2 O 3 The agglomeration of nanoparticles can effectively prevent Fe 2 O 3 The electrode material undergoes structural collapse during high-temperature calcination and charge-discharge cycles.

[0023] 4. Fe of the present invention 2 O 3 The @NC / SWCNHs ternary composite electrode material is rich in a large number of mesoporous structures, which not only effectively promote the ion diffusion dynamics, but also provide sufficient free space for mechanical relaxation and volume expansion during the charge and discharge cycle, thereby effectively protecting the stability of the electrode active materials.

[0024] 5. Fe of the present invention 2 O 3 @NC / SWCNHs ternary composite electrode materials have a suitable nitrogen content. Nitrogen doping can adjust the electronic properties and surface chemical properties of the composite materials, introduce more defects and active sites, and enhance the interaction between metal oxides and carbon materials, thereby further improving the electrochemical performance of the composite electrode materials.

[0025] 6. The present invention comprehensively utilizes nano-Fe 2 O 3 The synergistic advantages of the pseudocapacitance of SWCNHs and the double-layer capacitance of SWCNHs, as well as the nitrogen doping effect, lead to the development of a new type of high-performance Fe 2 O 3 @NC / SWCNHs ternary composite electrode material has broad application prospects in the field of supercapacitors. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Fe 2 O 3 Schematic diagram of the synthesis process of @NC / SWCNHs ternary composite electrode materials.

[0027] Figure 2 Fe obtained in Example 1 2 O 3Scanning electron microscope (SEM) image of @NC / SWCNHs ternary composite electrode material.

[0028] Figure 3 Fe obtained in Example 1 2 O 3 Transmission electron microscopy (TEM) image of @NC / SWCNHs ternary composite electrode material.

[0029] Figure 4 Fe obtained in Example 1 2 O 3 @NC / SWCNHs ternary composite electrode material cycling stability curve after 1000 charge and discharge cycles. DETAILED DESCRIPTION

[0030] The present invention is further described below in conjunction with the embodiments, but it should not be understood that the above subject matter of the present invention is limited to the following embodiments. Without departing from the above technical ideas of the present invention, various substitutions and changes are made according to the common technical knowledge and customary means in the art, which should all be included in the protection scope of the present invention.

[0031] Example 1

[0032] Step 1: 0.4 g FeCl 3 6H 2 O, 1.1 g NH 2 -BDC, and 0.74g triethylamine were added to 30mL DMF solvent and stirred for 1 hour. At the same time, 20mg SWCNHs were added to 20mL DMF solvent and ultrasonically dispersed for 30 minutes. The above two solutions were evenly mixed, transferred to a hydrothermal reactor, and reacted at 150°C for 24 hours. After the reaction was completed, it was naturally cooled to room temperature, the product was collected by filtration, repeatedly rinsed with DMF and ethanol, and then vacuum dried at 70°C for 12h to obtain Fe-MOFs / SWCNHs hybrids.

[0033] Step 2: The Fe-MOFs / SWCNHs hybrid obtained in step 1 was placed in a muffle furnace and calcined at 350 °C for 3 hours. The obtained product was Fe 2 O 3 @NC / SWCNHs ternary composite electrode materials.

[0034] Scanning electron microscopy (SEM) was used to characterize Fe 2 O 3 The structure and morphology of @NC / SWCNHs ternary composite electrode materials, the obtained SEM images are shown in Figure 2 As shown. It can be seen that Fe 2 O 3@NC presents a spindle-shaped structure, inheriting the unique morphology of Fe-MOFs. 2 O 3 The @NCs are uniformly dispersed in the spherical SWCNHs matrix.

[0035] Transmission electron microscopy (TEM) was used to characterize Fe 2 O 3 The microstructure of the @NC / SWCNHs ternary composite electrode material, the TEM image obtained is as follows Figure 3 As shown in the figure, it can be seen that the spindle structure formed by Fe-MOFs after high temperature calcination is composed of a large amount of Fe 2 O 3 Nanoparticle composition. Fe 2 O 3 The nanoparticles are tightly wrapped by the in-situ formed nitrogen-doped carbon layer and SWCNHs. This effective protection can prevent Fe 2 O 3 The agglomeration of nanoparticles can effectively prevent Fe 2 O 3 The electrode material undergoes structural collapse during high-temperature calcination and charge-discharge cycling. In addition, the thermal decomposition of organic ligands during high-temperature calcination produces a large number of mesoporous structures, which not only effectively promote the ion diffusion dynamics, but also provide sufficient free space for mechanical relaxation and volume expansion during charge-discharge cycling, thereby effectively protecting the stability of the electrode active material.

[0036] After electrochemical performance testing, at a current density of 1A / g, Fe 2 O 3 The specific capacitance of @NC / SWCNHs ternary composite electrode material is 288F / g. After 1000 charge and discharge cycles, the specific capacitance retention rate is 83.7%, showing excellent long-term cycle stability.

[0037] Example 2

[0038] Step 1: 0.3 g FeCl 3 6H 2 O,0.8g NH 2 -BDC, and 0.5g triethylamine were added to 20mL DMF solvent and stirred for 2 hours. At the same time, 10mg SWCNHs were added to 10mL DMF solvent and ultrasonically dispersed for 50 minutes. The above two solutions were evenly mixed, transferred to a hydrothermal reactor, and reacted at 180°C for 15 hours. After the reaction was completed, it was naturally cooled to room temperature, the product was collected by filtration, repeatedly rinsed with DMF and ethanol, and then vacuum dried at 50°C for 24 hours to obtain Fe-MOFs / SWCNHs hybrids.

[0039] Step 2: The Fe-MOFs / SWCNHs hybrid obtained in step 1 was placed in a muffle furnace and calcined at 400 °C for 2 hours. The obtained product was Fe 2 O 3 @NC / SWCNHs ternary composite electrode materials.

[0040] Fe 2 O 3 The electrochemical performance of @NC / SWCNHs ternary composite electrode material was tested. At a current density of 1A / g, the specific capacitance was 273F / g. After 1000 charge and discharge cycles, the specific capacitance retention rate was 83.1%, showing excellent long-term cycle stability.

[0041] Example 3

[0042] Step 1: 0.3 g FeCl 3 6H 2 O, 0.6 g NH 2 -BDC, and 0.6g triethylamine were added to 30mL DMF solvent and stirred for 1 hour. At the same time, 30mg SWCNHs were added to 30mL DMF solvent and ultrasonically dispersed for 45 minutes. The above two solutions were evenly mixed, transferred to a hydrothermal reactor, and reacted at 200°C for 5 hours. After the reaction was completed, it was naturally cooled to room temperature, the product was collected by filtration, repeatedly rinsed with DMF and ethanol, and then vacuum dried at 40°C for 48h to obtain Fe-MOFs / SWCNHs hybrids.

[0043] Step 2: The Fe-MOFs / SWCNHs hybrid obtained in step 1 was placed in a muffle furnace and calcined at 300 °C for 6 hours. The obtained product was Fe 2 O 3 @NC / SWCNHs ternary composite electrode materials.

[0044] Fe 2 O 3 The electrochemical performance of the @NC / SWCNHs ternary composite electrode material was tested. At a current density of 1A / g, the specific capacitance was 266F / g. After 1000 charge and discharge cycles, the specific capacitance retention rate was 82.9%, showing excellent long-term cycle stability.

[0045] Example 4

[0046] Step 1: 0.4 g FeCl 3 6H 2 O,1g NH 2-BDC, and 0.6g triethylamine were added to 30mL DMF solvent and stirred for 0.5 hours. At the same time, 10mg SWCNHs were added to 15mL DMF solvent and ultrasonically dispersed for 20 minutes. The above two solutions were evenly mixed, transferred to a hydrothermal reactor, and reacted at 120°C for 36 hours. After the reaction was completed, it was naturally cooled to room temperature, the product was collected by filtration, repeatedly rinsed with DMF and ethanol, and then vacuum dried at 100°C for 3 hours to obtain Fe-MOFs / SWCNHs hybrids.

[0047] Step 2: The Fe-MOFs / SWCNHs hybrid obtained in step 1 was placed in a muffle furnace and calcined at 450 °C for 1.5 hours. The obtained product was Fe 2 O 3 @NC / SWCNHs ternary composite electrode materials.

[0048] Fe 2 O 3 The electrochemical performance of @NC / SWCNHs ternary composite electrode material was tested. At a current density of 1A / g, the specific capacitance was 257F / g. After 1000 charge and discharge cycles, the specific capacitance retention rate was 80.8%, showing excellent long-term cycle stability.

Claims

1. A method for preparing a high-performance iron oxide-nitrogen-doped carbon-single-walled carbon nanohorn ternary composite electrode material, characterized in that: The following steps are involved: S1. Preparation of Fe-MOFs / SWCNHs hybrids by the solvothermal method: Ferric chloride (FeCl3·6H2O), 2-aminoterephthalic acid (NH2-BDC), and triethylamine were dispersed in N,N-dimethylformamide (DMF) solvent; SWCNHs were dispersed in DMF solvent; The two mixtures are uniformly mixed and then subjected to a solvothermal reaction to obtain a Fe-MOFs / SWCNHs hybrid; S2. The product Fe-MOFs / SWCNHs obtained in step S1 is used as a precursor and a self-sacrificial template to prepare a Fe2O3@NC / SWCNHs ternary composite electrode material by a high temperature calcination method.

2. The method for preparing a high-performance iron oxide-nitrogen doped carbon-single-walled carbon nanohorn ternary composite electrode material according to claim 1, characterized in that: The ratio of raw materials in step S1 is:

3. The method for preparing a high-performance iron oxide-nitrogen doped carbon-single-walled carbon nanohorn ternary composite electrode material according to claim 1, characterized in that: The hydrothermal reaction temperature in step S1 is 120 to 200° C., and the reaction time is 5 to 36 hours.

4. The method for preparing a high-performance iron oxide-nitrogen doped carbon-single-walled carbon nanohorn ternary composite electrode material according to claim 1, characterized in that: The vacuum drying temperature in step S1 is 40 to 100° C., and the drying time is 3 to 48 hours.

5. The method for preparing a high-performance iron oxide-nitrogen doped carbon-single-walled carbon nanohorn ternary composite electrode material according to claim 1, characterized in that: The calcination temperature in step S2 is 300-450° C., and the reaction time is 1.5-6 hours.

6. A high-performance iron oxide-nitrogen-doped carbon-single-walled carbon nanohorn ternary composite electrode material obtained according to the method described in any one of claims 1 to 5.

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