Preparation method and electro-catalysis application of iron-based spinel / MXene / NF composite material

Abstract

The invention discloses an iron-based spinel / MXene / NF composite material constructed based on coordination and an application of the iron-based spinel / MXene / NF composite material in an electro-catalytic oxygen evolution reaction. According to the composite material, iron-based spinel nanoparticles are uniformly anchored on the surface of MXene through a multi-step hydrothermal and physical mixing strategy and are loaded on a nickel foam (NF) substrate. In an electrocatalytic oxygen evolution reaction, transition metal of iron-based spinel provides abundant active sites, and electron transfer and electrolyte permeation are accelerated due to high conductivity and large specific surface area of MXene. Besides, a stable heterogeneous interface structure is formed through the strong coordination effect of metal cations with d holes in the iron-based spinel and oxygen / hydroxyl functional groups on the surface of MXene, the agglomeration phenomenon of the iron-based spinel is effectively reduced, the high activity of the material is ensured, and the cycling stability of the material is remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the field of nanomaterial preparation technology and electrocatalysis, and specifically relates to the preparation of a nanoparticle structure uniformly distributed on a two-dimensional nanosheet and its catalytic application in the field of electrochemical oxygen evolution. Background Art

[0002] As the global energy structure accelerates its transition to renewable energy, electrocatalytic water splitting technology for hydrogen production has become one of the core paths to achieve carbon neutrality because it can convert intermittent wind / solar energy into storable hydrogen energy. However, the large-scale application of this technology is limited by the slow four-electron transfer kinetics of the anodic oxygen evolution reaction (OER), whose overpotential is significantly higher than that of the cathode hydrogen evolution reaction (HER), resulting in high overall energy consumption. To address this bottleneck, iron-based spinel materials (MFe2O4) have been developed with their low cost, strong corrosion resistance and flexible and adjustable electronic structure (such as regulating the Fe 3+ / Fe 2+ ratio), has been proven in recent years to be effective in improving OER catalytic activity. It is worth noting that unlike the traditional adsorbate evolution mechanism (AEM) that relies on surface metal sites, the latest research shows that by activating the lattice oxygen in the spinel to participate in the reaction, a more efficient lattice oxygen oxidation mechanism (LOM) can be triggered, directly utilizing the lattice oxygen-oxygen coupling (OO bond formation) pathway to significantly reduce the reaction energy barrier, thereby improving the OER kinetics by 2-3 orders of magnitude. However, this breakthrough mechanism has given rise to a new technical contradiction: while the LOM pathway accelerates oxygen evolution, it will induce the irreversible accumulation of lattice oxygen vacancies (V0), greatly shortening the life of the catalyst. How to crack the seesaw effect of "high activity-low stability" is an important challenge in the current technical field.

[0003] MXene, a novel two-dimensional layered structure, not only possesses excellent mechanical properties and a large specific surface area, but its electrical conductivity and abundant active sites on the basal surface also play a crucial role in promoting sustainable energy development. Thanks to the controllable functional groups on the MXene surface, spinel oxides can be fixed through electrostatic attraction and coordination, resulting in uniform dispersion of the spinel, thereby increasing the utilization of the catalyst's active sites and boosting catalytic efficiency.

[0004] The present invention uses the electrode material prepared by rationally and uniformly loading iron-based spinel on MXene nanosheets for electrocatalytic OER, which provides a feasible way to improve the catalytic activity and structural stability of iron-based spinel oxides. Summary of the Invention

[0005] The present invention provides a method for preparing an iron-based spinel / MXene / NF composite material, which aims to prepare the composite material by loading nano-particles of iron-based spinel on the surface of MXene, and reacting the -OH and -F groups on the surface of MXene with the metal ions (such as Co 2+ 、Mn 2+ Through coordination bonds (e.g., ligands), strong interfacial interactions are formed, allowing the iron-based spinel to be evenly dispersed on the MXene, preventing accumulation and thus improving its application in energy storage and catalytic reactions. This method is simple to operate, highly adaptable, and improves the structural stability of the iron-based spinel without altering its original catalytic activity.

[0006] The technical solution of the present invention is as follows: an iron-based spinel / MXene / NF composite material is used as an OER electrode material, and the material is prepared by loading different iron-based spinel oxides on MXene.

[0007] A method for preparing an iron-based spinel / MXene / NF composite material comprises the following steps: (1) Add ultrathin MXene nanosheets into anhydrous ethanol and stir at room temperature to form a uniform dispersion A; (2) transferring the dispersion A from step (1) to a polytetrafluoroethylene liner; (3) placing the treated nickel foam in the polytetrafluoroethylene liner of step (2) and performing ultrasonic-assisted treatment to obtain a mixed solution B; (4) Transition metal salt and ferric chloride were added to the mixed solution B for microwave-assisted solvent thermal reaction. After cooling, the nickel foam was washed with ethanol and deionized water to obtain an iron-based spinel / MXene / NF composite material.

[0008] In some embodiments, the MXene is first etched with a mixed solution of NaF and concentrated HCl, and the etched MXene is dispersed in dimethyl sulfoxide, and then nitrogen is introduced for deoxygenation. The MXene is ultrasonically dispersed into a single layer at room temperature, and then filtered and dried in a vacuum drying oven to obtain MXene nanosheets.

[0009] As an embodiment of the present invention, the MXene in step (1) includes Ti3C2T x 、V2CT x 、Mo2TiC2T x 、Nb2CT x At least one of them.

[0010] As an embodiment of the present invention, the concentration of MXene in the dispersion A in step (1) is 0.1 to 10 mg / ml.

[0011] As an embodiment of the present invention, the frequency of the ultrasonic-assisted treatment in step (3) is 30 to 60 kHz, and the treatment time is 0.5 to 24 h.

[0012] As an embodiment of the present invention, the transition metal salt in step (4) is at least one of cobalt acetate, cobalt chloride, nickel acetate, nickel chloride, copper acetate, copper chloride, manganese acetate and manganese chloride.

[0013] As an embodiment of the present invention, the concentration of the transition metal salt in the mixed solution B in step (4) is 0.005-0.02 mM; preferably, the concentration of the transition metal salt is 0.011 mM.

[0014] As an embodiment of the present invention, the concentration of ferric chloride in the mixed solution B in step (4) is 0.01-0.04 mM; preferably, the concentration of ferric chloride is 0.022 mM.

[0015] As an embodiment of the present invention, the temperature of the microwave-assisted solvothermal reaction in step (4) is 50-250° C., the power is 300-600 W, and the reaction time is 1-24 h.

[0016] The iron-based spinel / MXene / NF composite material prepared by the preparation method has a structure in which nanoparticles are uniformly loaded on layered MXene.

[0017] Application of the iron-based spinel / MXene / NF composite material prepared by the preparation method in the preparation of electrocatalytic alkaline oxygen evolution.

[0018] After basic characterization of the iron-based spinel / MXene / NF composite material of the present invention, its electrocatalytic alkaline oxygen evolution performance was tested. The specific method is as follows: The resulting nickel foam-based iron-based spinel / MXene / NF composite material was used as the working electrode in a three-electrode system, with a mercury / mercuric oxide electrode as the reference electrode and a platinum sheet as the counter electrode. Electrocatalytic alkaline oxygen evolution performance was tested in a 1M KOH solution. The results showed that the iron-based spinel / MXene / NF composite material had a lower overpotential than both iron-based spinel / NF and MXene / NF under the same test conditions and exhibited excellent catalytic stability.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) The material synthesis method involved in the present invention is simple to operate and low-cost. The raw materials for preparation are not only affordable but also easy to obtain, and have significant potential for industrial application.

[0020] (2) In terms of specific process, the present invention adopts a step-by-step synthesis strategy, first mixing MXene with a NF (nickel foam) substrate and applying ultrasonic treatment. The cavitation effect generated by ultrasound can effectively prevent the self-stacking phenomenon of MXene due to weak interlayer van der Waals forces, promote the full dispersion of MXene nanosheets on the surface of the NF substrate, and achieve the maximum loading of MXene on the NF substrate. Compared with the traditional one-pot method, in which MXene fails to be effectively loaded on the NF substrate, resulting in disordered stacking and uneven dispersion, this method significantly improves the bonding efficiency of MXene and NF substrate by precisely controlling the pretreatment steps, laying a solid foundation for subsequent material performance optimization.

[0021] (3) The composite material constructed by this strategy can not only retain the MXene ultra-thin nanosheet structure in terms of morphology, but also uniformly load the iron-based spinel with nanoparticle morphology on the two-dimensional nanosheet to avoid the agglomeration of nanoparticles. This structure can not only improve the utilization rate of active sites, but also enhance the electrical conductivity of the material.

[0022] (4) Thanks to the advantages of structure and composition, the composite electrode exhibits excellent electrochemical performance, CuFe2O4 / V2CT x / NF at 10.0 mA cm −2 It has a low overpotential of 318 mV and a stability of up to 80 hours.

[0023] (5) The introduction of MXene into the composite material can significantly optimize the electronic structure, promote charge redistribution at the interface, and provide kinetic advantages for redox reactions.

[0024] (6) The method of the present invention is easy to operate and has low equipment requirements. The grown target sample has excellent catalytic activity and stability and can be widely used in the field of electrocatalysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 CuFe2O4 / V2CT synthesized in Example 1 x / NF scanning electron micrograph.

[0026] Figure 2 CuFe2O4 / V2CT synthesized in Example 1 x Transmission electron microscopy image of / NF.

[0027] Figure 3 CuFe2O4 / V2CT synthesized in Example 1 x LSV comparison chart of / NF. DETAILED DESCRIPTION

[0028] The present invention is described in detail below with reference to the accompanying drawings and embodiments. The following examples are implemented under the premise of the technical solution of the present invention, provide detailed implementation methods and specific operating procedures, and will help those skilled in the art to further understand the present invention. It should be pointed out that the scope of protection of the present invention is not limited to the following embodiments, and several adjustments and improvements made under the premise of the concept of the present invention all fall within the scope of protection of the present invention.

[0029] Example 1 Step 1: Transfer 40ml of 37% hydrochloric acid to a 100ml PTFE-lined container. Weigh 1g of sodium fluoride and 1g of V2AlC2 (500 mesh) and slowly add them to the hydrochloric acid solution. Place the PTFE-lined container in an oil bath and heat for 72 hours. After stirring, dilute the solution with deionized water and centrifuge at 9000 rpm. After each centrifugation, slowly pour the supernatant into the waste stream. Disperse the precipitate evenly with deionized water and continue centrifuging until the pH of the suspension reaches 6. Finally, collect the precipitate by vacuum filtration and dry it in a vacuum oven at 60°C.

[0030] 0.2 g of MXene was added to 200 ml of dimethyl sulfoxide (DMSO) solution and sonicated for 24 hours under inert gas reflux. After sonication, the solution was allowed to stand for half an hour, which helped to precipitate the bulk MXene to the bottom, while the MXene nanosheets remained in the upper black layer of the solution. The upper layer solution was then vacuum filtered, washed several times with ethanol and deionized water, and finally the resulting black solid was placed in a vacuum drying oven at 60 ° C for 12 hours. The black powder obtained is MXene nanosheets. Among them, MXene is V2CT x .

[0031] Step 2: Add an appropriate amount of MXene to a small amount of anhydrous ethanol and stir at room temperature to form dispersion A, where the concentration of dispersion A is 2.2 mg / mL.

[0032] Step 3: Transfer the dispersion A to the polytetrafluoroethylene liner of the microwave-assisted reactor and place the nickel foam treated with hydrochloric acid therein.

[0033] Step 4: Place the polytetrafluoroethylene liner in an ultrasonic machine with an ultrasonic frequency of 40 kHz and an ultrasonic time of 18 h to form a mixed solution B.

[0034] Step 5: Place 0.11 mM CuCl2 and 0.22 mM FeCl3 in mixed solution B, place in a microwave reactor, adjust the power to 400W, temperature to 160℃, and time to 2h. After the reaction is completed, place the CuFe2O4 / V2CT xAfter washing the nickel foam of / NF with ethanol and deionized water, it was placed in a vacuum drying oven at 60℃ and dried overnight to obtain the target sample CuFe2O4 / V2CT. x / NF. (CuFe2O4 / V2CT x / NF at 10.0 mA cm -2 The overpotential at this current density is 300 mV. Attachment Figure 1 CuFe2O4 / V2CT synthesized in Example 1 x SEM images of the / NF sample. The image shows many V2CT x Nanosheets are uniformly deposited on nickel foam, and CoFe2O4 nanoparticles are randomly deposited on V2CT x The surface is thinned, and the size of the CoFe2O4 nanoparticles becomes smaller without aggregation. The unique hybrid structure widens the interlayer spacing, increases the surface area, and is beneficial to the electron charge carrying capacity.

[0035] Attachment Figure 2 CuFe2O4 / V2CT synthesized in Example 1 x TEM image of the / NF sample. It verifies that CoFe2O4 is uniformly distributed in the V2CT x The nanosheets are made of nanomaterials, and the nanostructures present an ultra-thin morphology.

[0036] Attachment Figure 3 CuFe2O4 / V2CT synthesized in Example 1 x LSV curves of CoFe2O4 / V2CT x / NF sample at 10.0 mA cm -2 It has a minimum OER overpotential of 300 mV.

[0037] Example 2 The microwave reaction power in the fifth step of Example 1 was changed to 200W, and the other experimental conditions were the same as those in Example 1, and CuFe2O4 / V2CT was obtained. x / NF. The CuFe2O4 / V2CT prepared in this example x / NF at 10.0 mA cm -2 The overpotential at this current density is 371 mV.

[0038] Example 3 The microwave reaction power in the fifth step of Example 1 was changed to 700W, and the other experimental conditions were the same as those in Example 1, and CuFe2O4 / V2CT was obtained. x / NF. The CuFe2O4 / V2CT prepared in this example x / NF at 10.0 mA cm-2 The overpotential at this current density is 369 mV.

[0039] Example 4 The microwave reaction power in the fifth step of Example 1 was changed to 800W, and the other experimental conditions were the same as those in Example 1, and CuFe2O4 / V2CT was obtained. x / NF. The CuFe2O4 / V2CT prepared in this example x / NF at 10.0 mA cm -2 The overpotential at this current density is 376 mV.

[0040] Example 5 The microwave reaction in the fifth step of Example 1 was changed to a solvent thermal reaction. Other experimental conditions were the same as those in Example 1. CuFe2O4 / V2CT x / NF. The CuFe2O4 / V2CT prepared in this example x / NF at 10.0 mA cm -2 The overpotential at this current density is 338 mV.

[0041] Example 6 The multi-step process in Example 1 was changed to a one-pot process, i.e., 2.2 mg / mL V2CT x , 0.11 mM CuCl2 and 0.22 mM FeCl3 were placed in anhydrous ethanol, stirred at room temperature and placed in a polytetrafluoroethylene-lined microwave-assisted reactor, and nickel foam was placed therein. Other experimental conditions were the same as in Example 1 to obtain CuFe2O4 / V2CT x / NF. The CuFe2O4 / V2CT prepared in this example x / NF at 10.0 mA cm -2 The overpotential at this current density is 342 mV.

[0042] Example 7 The concentration of the dispersion A in the second step of Example 1 was changed to 15 mg / mL. Other experimental conditions were the same as those in Example 1. CuFe2O4 / V2CT was obtained. x / NF. The CuFe2O4 / V2CT prepared in this example x / NF at 10.0 mA cm -2 The overpotential at this current density is 365 mV.

[0043] Example 8 The concentrations of CuCl2 and FeCl3 in the fifth step of Example 1 were changed to 0.03 mM and 0.06 mM respectively. Other experimental conditions were the same as those in Example 1. CuFe2O4 / V2CT x / NF. The CuFe2O4 / V2CT prepared in this example x / NF at 10.0 mA cm -2 The overpotential at this current density is 349 mV.

[0044] This study proposes an innovative synthetic strategy, utilizing coordination, ultrasound-assisted, and microwave-assisted solvothermal methods to successfully prepare an iron-based spinel / MXene / NF composite material as a high-performance electrode material for the electrocatalytic oxygen evolution reaction (EOR). The abundant functional groups on the MXene surface form coordination bonds with the metal ions in the iron-based spinel, driving the uniform dispersion of the iron-based spinel nanoparticles on the MXene nanosheets at the molecular level. This ensures that more catalytically active sites are exposed on the composite surface, significantly improving catalytic efficiency. The preparation process utilizes a step-by-step approach to optimize the loading effect. MXene is first mixed with nickel foam. Ultrasound-induced cavitation is then used to break up MXene aggregates, promoting the full spread of MXene nanosheets on the NF surface, achieving efficient MXene loading on the conductive substrate. Subsequently, a microwave-assisted solvothermal method is introduced. Leveraging the rapid and uniform heating properties of microwaves, the nucleation and growth of the iron-based spinel nanoparticles are precisely controlled, resulting in a nanoparticle structure with uniform particle size and high crystallinity. Experimental results show that the iron-based spinel / MXene / NF electrode material prepared by this strategy exhibits excellent electrocatalytic performance: not only is the oxygen evolution reaction activity significantly improved, but it also maintains ultra-high stability during long-term cycle tests.

[0045] The above embodiments are merely preferred technical solutions of the present invention and should not be construed as limiting the present invention. The embodiments and features in the embodiments of this application may be arbitrarily combined with each other unless they conflict. The scope of protection of the present invention shall be the technical solutions described in the claims, including equivalent alternatives to the technical features of the technical solutions described in the claims. Equivalent alternatives and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A method for preparing an iron-based spinel / MXene / NF composite material, characterized in that: The method comprises the following preparation steps: (1) Add ultrathin MXene nanosheets into anhydrous ethanol and stir at room temperature to form a uniform dispersion A; (2) transferring the dispersion A from step (1) to a polytetrafluoroethylene liner; (3) placing the treated nickel foam in the polytetrafluoroethylene liner of step (2) and performing ultrasonic-assisted treatment to obtain a mixed solution B; (4) Transition metal salt and ferric chloride were added to the mixed solution B for microwave-assisted solvent thermal reaction. After cooling, the nickel foam was washed with ethanol and deionized water to obtain an iron-based spinel / MXene / NF composite material.

2. The method for preparing the iron-based spinel / MXene / NF composite material according to claim 1, wherein: The MXene in step (1) includes Ti3C2T x 、V2CT x 、Mo2TiC2T x 、Nb2CT x At least one of them.

3. The method for preparing the iron-based spinel / MXene / NF composite material according to claim 1, wherein: The concentration of MXene in the dispersion A described in step (1) is 0.1 to 10 mg / ml.

4. The method for preparing the iron-based spinel / MXene / NF composite material according to claim 1, wherein: The frequency of the ultrasound-assisted treatment in step (3) is 30 to 60 kHz, and the treatment time is 0.5 to 24 h.

5. The method for preparing the iron-based spinel / MXene / NF composite material according to claim 1, wherein: The transition metal salt in step (4) is at least one of cobalt acetate, cobalt chloride, nickel acetate, nickel chloride, copper acetate, copper chloride, manganese acetate and manganese chloride.

6. The method for preparing the iron-based spinel / MXene / NF composite material according to claim 1, wherein: The concentration of the transition metal salt in the mixed solution B in step (4) is 0.005-0.02 mM; preferably, the concentration of the transition metal salt is 0.011 mM.

7. The method for preparing the iron-based spinel / MXene / NF composite material according to claim 1, wherein: The concentration of ferric chloride in the mixed solution B in step (4) is 0.01-0.04 mM; preferably, the concentration of ferric chloride is 0.022 mM.

8. The method for preparing the iron-based spinel / MXene / NF composite material according to claim 1, wherein: The temperature of the microwave-assisted solvothermal reaction in step (4) is 50 to 250°C, the power is 300 to 600 W, and the reaction time is 1 to 24 h.

9. The iron-based spinel / MXene / NF composite material prepared by the preparation method according to any one of claims 1 to 9, wherein the composite material is composed of different types of iron-based spinels and layered MXene, and has a structure in which nanoparticles are uniformly distributed in ultrathin nanosheets.

10. Use of the iron-based spinel / MXene / NF composite material prepared by the preparation method according to any one of claims 1 to 9 in the preparation of electrocatalytic oxygen evolution.

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