Metal-organic framework derived Fe-CoF2 / MXene catalyst and preparation method and application thereof

Abstract

The application discloses a metal-organic framework derived Fe-CoF2 / MXene catalyst and a preparation method and application thereof, and belongs to the technical field of medicines. The preparation method comprises the following steps: S101, loading MXene solution on a nickel foam through an electrochemical deposition method in a three-electrode system; S102, adding the nickel foam loaded with MXene into a mixed solution of Co(NO3)2.6H2O and 2-methyl imidazole to perform room temperature co-precipitation; S103, after the co-precipitated nickel foam is washed clean and dried, the nickel foam is continuously transferred into a K3[Fe(CN)6] solution to perform a ligand exchange reaction; the nickel foam is continuously washed clean and dried, and then is transferred into a tube furnace and is annealed under an inert gas atmosphere to obtain a final product. The application further provides the Fe-CoF2 / MXene catalyst and application thereof. According to the application, a three-dimensional porous cubic structure Fe-CoF2 / MXene catalyst is in-situ grown on the MXene under mild conditions, and the structure is favorable for exposing more active sites and enhancing the transmission rate of substances between the catalyst and an electrolyte.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of medicines, in particular to a metal-organic framework derived Fe-CoF2 / MXene catalyst and a preparation method and application thereof. BACKGROUND

[0002] Hydrogen energy is considered as a pollution-free and environmentally friendly energy source and will eventually replace existing fossil fuels. Electrochemical water splitting is an important hydrogen production system, including anode oxygen evolution reaction (OER) and cathode hydrogen evolution reaction (HER). However, due to the complex four-electron transfer process, OER must overcome a high reaction energy barrier. Noble metal-based electrocatalysts (such as RuO2 and IrO2) promote the development of low overpotential OER. However, their practical application is hindered by resource scarcity and high cost. Therefore, finding a resource-rich and efficient OER electrocatalyst is the most important work at present.

[0003] In recent years, transition metal-based electrocatalysts have attracted much attention, and transition metal oxides / hydroxides, sulfides, phosphides, nitrides and carbides have all made important contributions. Since the ionic bond between metal and fluorine is easy to dissociate during the reaction process, because fluorine has the largest electronegativity among non-metal elements, it is beneficial for water splitting to proceed. At the same time, the coexistence of metal-oxygen bond and metal-fluorine bond promotes surface reconstruction, improving the electrical conductivity of the catalyst. More importantly, hydrogen fluoride gas can etch the surface of the material, thereby increasing the number of active sites. Therefore, transition metal fluorides are considered to be one of the main materials for improving OER activity.

[0004] In recent years, through continuous research on electrocatalyst materials, although the inherent structure of metal fluorides makes them excellent electrocatalysts, their stability and efficiency still face some challenges, so currently transition metal fluorides are rarely applied in the field of water splitting. Prussian blue analogues (PBA) as a representative of metal-organic framework materials are widely used in the synthesis of hollow or porous template materials due to their unique advantages of adjustable pore size, large specific surface area and diverse composition. However, the development of pure PBA materials for OER is hindered by their inert intrinsic action and poor electronic conductivity. Atomic doping or modification has been proven to be a beneficial method to further improve the inherent activity of metal fluorides by adjusting the electronic structure and accelerating the reaction kinetics.

[0005] As a booming family of two-dimensional materials, MXenes have shown excellent performance in the field of electrochemistry. Due to its excellent electrical conductivity and metal conductivity (the conductivity of Ti3C2 can reach 9880 S / cm), surface hydrophobicity, good mechanical stability, high active surface and easily adjustable structure, etc. Intriguing properties, and increasingly attracting people's attention, and has become one of the hotspots in the field of electrochemical energy storage and conversion. The general chemical formula of MXenes is Mn +1 X n T x , wherein M is one or more early transition metals, X is one or more of C, N, B, T x is the rich functional groups on the surface of MXenes, usually one or more of -OH, -O and halogen elements. A large number of functional groups make MXenes have rich surface chemistry, high hydrophilicity and adjustable properties, which in turn provide the possibility of high-performance structure for hybridization with other materials.

[0006] In recent years, with the development of science and technology, cobalt-based catalysts are increasingly widely used in the field of electrocatalytic decomposition of water, etc. The existing technology discloses a fluorinated cobalt nanomaterial as an electrochemical, electrocatalytic and related field. Through the related application of the heterojunction composed of two substances, it is shown that low-cost and high-efficiency electrocatalysts can be expanded. In the Chinese patent application with the application number 202410462264.2, a hydroxyl fluorinated nickel / hydroxyl fluorinated cobalt heterojunction nanomaterial is disclosed, and the preparation method thereof is specifically disclosed as follows: the mixture of hydrated fluorinated nickel / hydrated fluorinated cobalt heterojunction material or fluorinated nickel / fluorinated cobalt heterojunction material and alcohol, water is placed in a reaction kettle for hydrothermal / solvothermal reaction; the temperature of the solvothermal reaction is 80-350℃; the holding time of the solvothermal reaction is 0.1-24 hours; the ratio of alcohol to water in the solvent is 100%-0%. However, the size of the nanometer heterojunction nanoparticles prepared by the patent is uneven, and it is difficult to ensure the consistency of product quality in large-scale production. Although there are many heterojunction studies in the existing technology, there is no research on the composite of cobalt difluoride and conductive matrix. MXene material has more outstanding characteristics than CoF2 in conductivity, and metal element doping is also beneficial to change the coordination environment of the catalyst, thereby enhancing the electrocatalytic properties, so this method of metal-doped and conductive material-combined is worth further studying. SUMMARY

[0007] The purpose of the present application is to provide a metal-organic framework derived Fe-CoF2 / MXene catalyst and its preparation method and application, in order to solve the problems in the background art.

[0008] To achieve the above object, the application provides a preparation method of a metal-organic framework derived Fe-CoF2 / MXene catalyst, comprising the following steps:

[0009] S101, transferring the prepared MXene suspension into a three-electrode electrolytic cell, using a foamed nickel as a working electrode, a graphite rod as a counter electrode, and Ag / AgCl as a reference electrode, and performing electrodeposition under a constant voltage to load the MXene on the foamed nickel (NF) to obtain MXene / NF;

[0010] S102, adding the MXene / NF into a mixed solution of Co(NO3)2.6H2O and 2-methyl imidazole to perform room temperature co-precipitation to obtain ZIF-67 / MXene / NF, and washing and drying the co-precipitated ZIF-67 / MXene / NF;

[0011] S103, transferring the dried ZIF-67 / MXene / NF into a K3[Fe(CN)6] solution to perform a ligand exchange reaction to obtain CoFe-PBA / MXene / NF, washing and drying the obtained CoFe-PBA / MXene / NF, and transferring the CoFe-PBA / MXene / NF and NH4F into a tube furnace and annealing under an inert gas atmosphere to obtain a final product Fe-CoF2 / MXene catalyst.

[0012] Preferably, in S101, the concentration of the MXene suspension is 2mg·mL -1 .

[0013] Preferably, in S101, the electrodeposition is performed for 30s under a constant voltage of 5V.

[0014] Preferably, in S102, the amount of substance of Co(NO3)2.6H2O in the mixed solution of Co(NO3)2.6H2O and 2-methyl imidazole is 2.5mmol, and the amount of substance of 2-methyl imidazole is 0.3mmol.

[0015] Preferably, in S103, the concentration of the K3[Fe(CN)6] solution is 40mg·mL -1 .

[0016] Preferably, in S103, the annealing treatment is performed in the tube furnace under an N2 atmosphere at a heating rate of 2℃·min -1 to 350℃, and the annealing is performed for 2h after the annealing is completed.

[0017] The application further provides a metal-organic framework derived Fe-CoF2 / MXene catalyst prepared by the above preparation method, and the Fe-CoF2 / MXene catalyst has a porous nanocube structure.

[0018] The application also provides application of the metal-organic framework derived Fe-CoF2 / MXene catalyst in an electrochemical reaction of catalytic decomposition of water to produce oxygen.

[0019] The application utilizes metal-organic frameworks to obtain Fe-CoF2 / MXene porous nanocube electrocatalysts with controllable morphology, uniform size and high specific surface area through coordination exchange and in-situ fluorination, which is expected to play an important role in a wider range of emerging fields, such as electrocatalysis.

[0020] The application is a method of electrochemical deposition, coprecipitation and ligand exchange at room temperature to grow CoFe-PBA on MXene in-situ, and through in-situ fluorination in an inert gas, the final product, i.e., Fe-CoF2 / MXene porous nanocube electrocatalyst, is obtained. The Fe-CoF2 / MXene electrocatalyst obtained by relatively mild conditions has a hollow porous nanocube structure, contains a large number of nanoparticles, increases the electrochemical surface area, exposes more active sites, ensures rapid transmission of electrons and ions, and rapid release of generated oxygen bubbles, and is low in cost and simple in operation.

[0021] The technical solutions of the application will be further described in detail below with the aid of drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a preparation method flowchart of the Fe-CoF2 / MXene porous nanocube electrocatalyst of the application;

[0023] Figure 2 is a scanning electron microscope (SEM) spectrum of the Fe-CoF2 / MXene porous nanocube electrocatalyst prepared in Example 1 of the application, and the sample is in the form of nanocubes;

[0024] Figure 3 is a transmission electron microscope (TEM) spectrum of the Fe-CoF2 / MXene porous nanocube electrocatalyst prepared in Example 1 of the application, and the sample is in the form of porous nanocubes;

[0025] Figure 4 is a comparison chart of electrochemical performance of the Fe-CoF2 / MXene porous nanocube electrocatalyst prepared in Example 1 of the application, the CoF2 / MXene catalyst prepared in Example 2 and the Fe-CoF2 catalyst prepared in Example 3;

[0026] Figure 5is a Tafel slope comparison chart of the Fe-CoF2 / MXene porous nanocube electrocatalyst prepared in Embodiment 1 of the present application, the CoF2 / MXene catalyst prepared in Embodiment 2, and the Fe-CoF2 catalyst prepared in Embodiment 3.

[0027] Figure 6 is an electrochemical impedance (EIS) comparison chart of the Fe-CoF2 / MXene porous nanocube electrocatalyst prepared in Embodiment 1 of the present application, the CoF2 / MXene catalyst prepared in Embodiment 2, and the Fe-CoF2 catalyst prepared in Embodiment 3. DETAILED DESCRIPTION

[0028] As shown in Figure 1 , the present application provides a preparation method of a Fe-CoF2 / MXene porous nanocube electrocatalyst, which specifically comprises the following steps:

[0029] S101, transferring the prepared MXene suspension into a three-electrode electrolytic cell, using foamed nickel as a working electrode, a graphite rod as a counter electrode, and Ag / AgCl as a reference electrode, and performing electrodeposition under a constant voltage to load the MXene on the foamed nickel (NF) to obtain MXene / NF.

[0030] S102, adding the MXene / NF into a mixed solution of Co(NO3)2·6H2O and 2-methylimidazole for room temperature co-precipitation to obtain ZIF-67 / MXene / NF, and washing and drying the co-precipitated ZIF-67 / MXene / NF.

[0031] S103, transferring the dried ZIF-67 / MXene / NF into a K3[Fe(CN)6] solution for ligand exchange reaction to obtain CoFe-PBA / MXene / NF; washing and drying the obtained CoFe-PBA / MXene / NF, and transferring it and NH4F into a tube furnace and annealing under an inert gas atmosphere to obtain the final product Fe-CoF2 / MXene catalyst.

[0032] In a preferred embodiment of the present application, the concentration of the MXene suspension is 2mg·mL -1 .

[0033] In a preferred embodiment of the present application, the mass concentration of the K3[Fe(CN)6] solution is 40mg·mL -1 .

[0034] The technical solutions of the present application are further described below by means of the drawings and examples. It should be understood that these examples are only used to illustrate the present application and not to limit the scope of the present application, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application shall be equivalent replacements and shall be included in the protection scope of the present application. In addition, it should be understood that after reading the content of the present application, those skilled in the art can make various modifications or modifications to the present application, and these equivalent forms also fall within the scope defined by the claims attached to the present application and are within the protection scope of the present application.

[0035] Reference to "embodiment" in this text means that the specific features, structures or properties described in connection with the embodiment can be included in at least one embodiment of the present application. The word "embodiment" appearing at various places in the specification does not necessarily refer to the same embodiment, nor does it particularly limit its independence or association with other embodiments. In principle, in the present application, as long as there is no technical contradiction or conflict, the technical features mentioned in each embodiment can be combined in any way to form a corresponding implementable technical solution.

[0036] Unless otherwise defined, the meanings of the technical terms used herein are the same as those commonly understood by those skilled in the art to which the present application belongs; the use of related terms herein is only for the purpose of describing specific embodiments and is not intended to limit the present application.

[0037] Unless otherwise specified, the reagents, instruments, equipment, etc. used in the present application are reagents, instruments and equipment commonly used by those skilled in the art.

[0038] Example 1

[0039] The present embodiment provides a preparation method of Fe-CoF2 / MXene porous nanocubic electrocatalyst, which specifically comprises the following steps:

[0040] (1) Preparation of MXene suspension (Ti3C2T x Suspension): 1 g of Ti3AlC2 was dispersed in 9M HCl and 1 g of LiF, dispersed in a polytetrafluoroethylene beaker and stirred at 35℃ for 24h. Then centrifuged with deionized water and ethanol at 4500rpm for several times to make it into a neutral solution. Finally, ultrasonic treatment in ice water bath under Ar environment for 6h, centrifuged at 3500rpm to take the supernatant.

[0041] (2) Ti3C2T x Suspension) was obtained by 30s constant voltage (5V) electrophoresis deposition process with NF and graphite rod as anode and cathode, and Ag / AgCl as reference electrode. x(MXene) modified NF (denoted as MXene / NF).

[0042] (3) 2.5 mmol of Co(NO3)2·6H2O was dissolved in 40 mL of aqueous solution to obtain a light pink solution, 0.3 mmol of 2-methylimidazole aqueous solution was quickly poured into the Co(NO3)2·6H2O solution, and continuous stirring was carried out for 10 min to obtain a mixed solution of Co(NO3)2·6H2O and 2-methylimidazole, then the MXene / NF was immersed in the above mixed solution for 12 h for room temperature co-precipitation to obtain ZIF-67 / MXene / NF, and then washed with distilled water and alcohol, and finally dried at 60°C for 8 h.

[0043] (4) The dried ZIF-67 / MXene / NF was transferred into 40 mol·L -1 of K3[Fe(CN)6] solution for ligand exchange reaction for 8 h to obtain a CoFe-PBA / MXene / NF precursor, and then washed with distilled water and alcohol, and finally dried at 60°C for 8 h, then the CoFe-PBA / MXene precursor and NH4F were loaded into a tube furnace, and then the furnace was heated to 350°C at a heating rate of 2°C·min -1 in N2 atmosphere for annealing treatment, and then annealed for 2 h to obtain a final product Fe-CoF2 / MXene catalyst.

[0044] The properties of the obtained final product were observed, and the results are shown in FIGS. Figure 2 and Figure 3 .

[0045] Figure 2 FIG. 1 is a scanning electron microscope (SEM) image of a Fe-CoF2 / MXene porous nanocube electrocatalyst prepared in Example 1, and the sample is in the form of nanocubes.

[0046] Figure 3 FIG. 2 is a transmission electron microscope (TEM) image of a Fe-CoF2 / MXene porous nanocube electrocatalyst prepared in Example 1, and the sample is in the form of porous nanocubes. This hollow nanocube structure contains a large number of nanoparticles, increases the electrochemical surface area, and exposes more active sites.

[0047] Example 2

[0048] The present embodiment provides a preparation method of a CoF2 / MXene catalyst, which specifically comprises the following steps:

[0049] (1) Preparation of MXene suspension: 1 g of Ti3AlC2 was dispersed in 9 M HCl and 1 g of LiF, dispersed in a polytetrafluoroethylene beaker and stirred at 35℃ for 24 h. Then centrifuged multiple times with deionized water and ethanol at 4500 rpm to make it a neutral solution. Finally, ice water bath ultrasonic treatment for 6 h under Ar atmosphere, centrifugation at 3500 rpm to take the supernatant.

[0050] (2) NF and graphite rod as anode and cathode, Ag / AgCl as reference electrode, Ti3C2T x suspension by 30 s constant voltage (5 V) electrophoresis deposition process to obtain Ti3C2T x (MXene) modified NF (denoted as MXene / NF).

[0051] (3) 2.5 mmol of Co(NO3)2·6H2O was dissolved in 40 mL of aqueous solution to obtain a light pink solution, 0.3 mmol of 2-methylimidazole aqueous solution was quickly poured into the Co(NO3)2·6H2O solution, and continuous stirring was carried out for 10 min to obtain a mixed solution of Co(NO3)2·6H2O and 2-methylimidazole. Subsequently, the MXene / NF was immersed in the above mixed solution for 12 h for room temperature co-precipitation to obtain ZIF-67 / MXene / NF, which was then washed with distilled water and alcohol, and finally dried at 60℃ for 8 h.

[0052] (4) The dried ZIF-67 / MXene / NF and NH4F were loaded into a tube furnace, and then the furnace was heated to 350℃ at a heating rate of 2℃·min -1 -1, and the final product CoF2 / MXene catalyst was obtained after annealing for 2 h.

[0053] Example 3

[0054] The present embodiment provides a preparation method of Fe-CoF2 catalyst, which specifically comprises the following steps:

[0055] (1) 2.5 mmol of Co(NO3)2·6H2O was dissolved in 40 mL of aqueous solution to obtain a light pink solution, 0.3 mmol of 2-methylimidazole aqueous solution was quickly poured into the Co(NO3)2·6H2O solution, and continuous stirring was carried out for 10 min to obtain a mixed solution of Co(NO3)2·6H2O and 2-methylimidazole. Subsequently, a piece of NF was immersed in the above mixed solution for 12 h for room temperature co-precipitation to obtain ZIF-67 / NF, which was then washed with distilled water and alcohol, and finally dried at 60℃ for 8 h.

[0056] (4) The dried ZIF-67 / NF was transferred into 40 mol·L -1 of K3[Fe(CN)6] solution for ligand exchange reaction for 8 h to obtain a CoFe-PBA / NF precursor, the CoFe-PBA / NF precursor and NH4F were loaded into a tube furnace, and then the furnace was heated to 350℃ at a heating rate of 2℃·min -1

[0057] Performance test

[0058] The performance test includes: at room temperature, electrochemical tests of all samples were performed in 1.0 M KOH using an electrochemical workstation with a standard three-electrode system. The working electrode on the nickel foam (NF) was made of Fe-CoF2 / MXene prepared by the examples. The reference was calibrated and converted to a reversible hydrogen electrode (RHE) by the formula.

[0059] E RHE = E(Hg / HgO) + 0.89

[0060] Before each OER test, the three-electrode system was bubbled with high-purity nitrogen for 30 minutes. To explore the OER activity, linear sweep voltammetry tests were performed at a scan rate of 0V to 1.8V at a speed of 5mV / s. Electrochemical impedance spectroscopy (EIS) measurements were obtained in the frequency range of 0.01 to 10 5 Hz, and were fitted by ZView software. The Hg / HgO electrode in 1M KOH aqueous solution was used as the reference electrode.

[0061] The performance of the heterojunction catalysts prepared in Examples 1-3 was tested according to the above method, and the specific performance test results are shown in Figures 4-6

[0062] Figure 4 is the electrochemical performance comparison chart of the Fe-CoF2 / MXene porous nanocube electrocatalyst prepared in Example 1, the CoF2 / MXene catalyst prepared in Example 2, and the Fe-CoF2 catalyst prepared in Example 3. It is found through comparison that at the same current density, the overpotential of Fe-CoF2 / MXene is the smallest, and the performance is the best.

[0063] Figure 5 ​​is a Tafel slope comparison chart of the Fe-CoF2 / MXene porous nanocube electrocatalyst prepared in Example 1, the CoF2 / MXene catalyst prepared in Example 2, and the Fe-CoF2 catalyst prepared in Example 3 provided by the embodiment of the present application. It is found through comparison that the Fe-CoF2 / MXene Tafel slope is the lowest, indicating that the reaction can be driven at a lower energy, so that the reaction rate is significantly improved at low voltage.

[0064] Figure 6 is an electrochemical impedance (EIS) comparison chart of the Fe-CoF2 / MXene porous nanocube electrocatalyst prepared in Example 1, the CoF2 / MXene catalyst prepared in Example 2, and the Fe-CoF2 catalyst prepared in Example 3 provided by the embodiment of the present application. It is found through comparison that the Fe-CoF2 / MXene electrochemical impedance is the lowest.

[0065] Therefore, compared with the prior art, the present application is a method of electrochemical deposition, coprecipitation and ligand exchange at room temperature, and Fe-CoF2 / MXene porous nanocube electrocatalyst is obtained by in-situ fluorination in an inert gas. The results introduced in the present application may provide new opportunities for finding effective and low-cost oxygen evolution reaction electrocatalyst materials.

[0066] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application but not to limit it, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that: it can still modify or equivalently replace the technical solutions of the present application, and these modifications or equivalent replacements also cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A method for preparing a metal-organic framework derived Fe-CoF2 / MXene catalyst, characterized in that, The method comprises the following steps: S101, transferring the prepared MXene suspension into a three-electrode electrolytic cell, using a foamed nickel as a working electrode, a graphite rod as a counter electrode, and Ag / AgCl as a reference electrode, and performing electrodeposition under a constant voltage to load the MXene on the foamed nickel to obtain MXene / NF; S102, adding the MXene / NF into a mixed solution of Co(NO3)2·6H2O and 2-methylimidazole to perform room-temperature co-precipitation to obtain ZIF-67 / MXene / NF, washing and drying the co-precipitated ZIF-67 / MXene / NF; S103, transferring the dried ZIF-67 / MXene / NF into a K3[Fe(CN)6] solution to perform a ligand exchange reaction to obtain CoFe-PBA / MXene / NF; washing and drying the obtained CoFe-PBA / MXene / NF, and transferring the CoFe-PBA / MXene / NF and NH4F into a tube furnace and annealing under an inert gas atmosphere to obtain a final product Fe-CoF2 / MXene catalyst.

2. The method of claim 1, wherein the method is characterized by: The concentration of the MXene suspension in S101 is 2 mg·mL -1 .

3. The method of claim 1, wherein the method is characterized by: In the S101, the electrodeposition is performed at 5V for 30s.

4. The method of claim 1, wherein the method is characterized by: In the S102, the amount-of-substance of Co(NO3)2·6H2O in the mixed solution of Co(NO3)2·6H2O and 2-methylimidazole is 2.5mmol, and the amount-of-substance of 2-methylimidazole is 0.3mmol.

5. The method of claim 1, wherein the method is characterized by: The concentration of the K3[Fe(CN)6] solution in S103 is 40 mg·mL -1 .

6. The method of claim 1, wherein the method is characterized by: In S103, annealing treatment is performed by heating in a tube furnace to 350℃ at a heating rate of 2℃·min -1 in a N2 atmosphere, and holding for 2h after the annealing is completed.

7. A metal-organic framework derived Fe-CoF2 / MXene catalyst, characterized in that: The Fe-CoF2 / MXene catalyst is prepared by the preparation method in any one of claims 1-6, and the Fe-CoF2 / MXene catalyst has a porous nanocube structure.

8. Use of a metal-organic framework derived Fe-CoF2 / MXene catalyst according to claim 7, characterized in that: The Fe-CoF2 / MXene catalyst is applied to an electrochemical reaction of catalytic decomposition of water for oxygen evolution.

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