Preparation method, product and application of an iron spinel nanomaterial

Abstract

The present invention discloses a preparation method, product and application of an iron spinel nanomaterial. Fe3O4 nanoparticles with a diameter less than 10 nm are prepared by a colloid synthesis method as seeds, and a Fe3O4-MOx heterogeneous nanostructure is formed by adding a transition metal perchlorate M(ClO4) solution (M = Mn, Co, Ni) to grow on the outer edge by a seed-regulated growth method. High-temperature calcination drives the diffusion of metal ions to form a uniform iron spinel MFe2O4 nanomaterial. The present invention can effectively regulate the elemental composition, morphology and particle size of the iron spinel nanostructure, and obtain a nanoelectrocatalyst with a large specific surface area, many active sites and stable reaction activity. The method of the present invention is simple, easy to operate and has good repeatability. Using the MFe2O4 nanomaterial as an electrolytic water hydrogen evolution catalyst, the design and production of a cheap HER catalyst with low cost, high activity and stability can be realized, and it has broad application prospects.

Description

Technical Field

[0001] The present invention belongs to the field of electrocatalytic hydrogen evolution catalysts for electrolyzed water, and particularly relates to a preparation method, product and application of an iron spinel nanomaterial. Background Art

[0002] As a new type of clean energy, hydrogen energy has a high energy density, rich sources, can be directly burned for energy supply or provide raw materials for fuel cells, and has broad application prospects.

[0003] However, the current mainstream industrial hydrogen production technology has high energy consumption and high carbon emissions during the production process, which is not suitable for the current development and utilization trend of hydrogen energy research. At the same time, the electrolyzed water hydrogen production equipment is simple and easy to operate, has high flexibility, uses water as a raw material, and high-purity hydrogen can be obtained by passing electricity, and has high development and utilization value. In order to improve the disadvantage of low electric energy conversion rate in the electrolyzed water hydrogen production process, designing and preparing high-performance catalysts to improve the electrolyzed water hydrogen production efficiency is a very effective development path.

[0004] The chemical composition of spinel materials is AB2O4 (where A and B are metal ions), with rich and inexpensive constituent elements, stable chemical properties, environmental friendliness, and electrocatalytic activity. By controlling the structure, composition, valence state, morphology and defects of spinel nanomaterials, their electrocatalytic activity can be adjusted, and it is expected to show electrocatalytic hydrogen evolution activity comparable to that of noble metals.

[0005] However, spinel itself has poor conductivity, and the products obtained by traditional preparation methods have a relatively high content of impurities. The cumbersome preparation process easily leads to agglomeration and sintering of product nanoparticles, seriously affecting the catalytic performance of the product. Summary of the Invention

[0006] The purpose of this part is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this part, as well as in the abstract and title of the present application, to avoid obscuring the purpose of this part, the abstract and the title, and such simplifications or omissions shall not be used to limit the scope of the present invention.

[0007] In view of the above and / or problems existing in the prior art, the present invention is proposed.

[0008] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a preparation method of an iron spinel nanomaterial.

[0009] To solve the above technical problems, the present invention provides the following technical solution: A preparation method of an iron spinel nanomaterial, comprising,

[0010] The high-boiling organic solvent and the ligand are purified by vacuum ventilation circulation and then heated up. The iron precursor solution is injected thermally for reaction. After the reaction is completed, it is washed with polar and non-polar solvents, and the Fe3O4 nanoparticles are collected by centrifugation, namely the Fe3O4 nanoseeds;

[0011] The Fe3O4 nanoseeds are heated and dispersed in an organic mixed solvent containing a ligand. The transition metal precursor solution is injected under heating conditions, and the reaction is stirred. After the reaction is completed, it is washed with polar and non-polar solvents, and the Fe3O4-MOx heterostructure nanoparticles are collected by centrifugation;

[0012] The Fe3O4-MOx heterostructure nanoparticles are calcined after being heated up uniformly in a tube furnace to achieve the in-material thermal diffusion of metal ions, and the MFe2O4 nanomaterials are obtained, where M = Mn, Co or Ni.

[0013] As a preferred embodiment of the preparation method of the iron spinel nanomaterials described in the present invention, wherein: the iron precursor solution is a pyridine solution of Fe2(CO)9, the high-boiling organic solvent includes octadecene, and the ligand includes oleylamine.

[0014] As a preferred embodiment of the preparation method of the iron spinel nanomaterials described in the present invention, wherein: the organic mixed solvent containing a ligand includes a mixed solvent composed of xylene, oleylamine and oleic acid.

[0015] As a preferred embodiment of the preparation method of the iron spinel nanomaterials described in the present invention, wherein: in the reaction of thermally injecting the iron precursor solution, the temperature is 120-180 °C and the reaction time is 1-2 h.

[0016] As a preferred embodiment of the preparation method of the iron spinel nanomaterials described in the present invention, wherein: the transition metal precursor solution includes Mn(ClO4)2, Co(ClO4)2 and Ni(ClO4)2 solutions.

[0017] As a preferred embodiment of the preparation method of the iron spinel nanomaterials described in the present invention, wherein: the preparation of the Fe3O4-MOx heterostructure is regulated by the oil phase-water phase interface, the reaction temperature is 60-80 °C, and the reaction time is 1-2 h.

[0018] As a preferred embodiment of the preparation method of the iron spinel nanomaterials described in the present invention, wherein: the Fe3O4-MOx heterostructure nanoparticles are calcined after being heated up uniformly in a tube furnace, wherein the heating rate is 5 °C / min, the calcination temperature is 400-500 °C, and the calcination time is 1-2 h.

[0019] Another object of the present invention is to overcome the deficiencies in the prior art and provide a product prepared by a method for preparing an iron spinel nanomaterial, wherein the product is spinel nanoparticles of MFe2O4 (M = Mn, Co, Ni), with a uniform ellipsoidal morphology, an outer carbon layer, and a size within 20 nm.

[0020] Another object of the present invention is to overcome the deficiencies in the prior art and provide an application of a product prepared by a method for preparing an iron spinel nanomaterial in an electrolytic water hydrogen evolution catalyst.

[0021] Advantages of the present invention:

[0022] (1) The present invention uses a step-by-step synthesis method of nanocrystal seed-regulated growth to prepare a heterostructure, which has highly controllable morphology for small-sized nanoparticles, a wide range of selectable transition metals, low cost, mild reaction conditions, and short time consumption.

[0023] (2) The present invention realizes the homogeneous transformation of the heterostructure into spinel through subsequent high-temperature calcination, can largely maintain the size and morphology of the nanoparticles, and effectively carbonizes the surface organic ligands to obtain a homogeneous iron spinel series of nanomaterials with a large specific surface area and high reaction activity as an electrolytic water hydrogen evolution catalyst; the controllable preparation of the bimetallic oxide heterostructure realizes the selective combination of different types of transition metal elements, reduces the agglomeration and sintering of the nanoparticles, fully exposes the active sites, and the small amount of carbonized ligands on the surface also play a role in enhancing conductivity and stabilizing the catalyst. The preparation process of the entire homogeneous iron spinel series of nanocatalysts ensures the stability of its own composition, structure, crystal phase, and surface, and shows high activity and stability in the electrocatalytic hydrogen evolution reaction. Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings. Among them:

[0025] Figure 1 XRD patterns of Fe3O4, Fe3O4-Mn3O4, and MnFe2O4 prepared in Example 1 of the present invention.

[0026] Figure 2 EDS element distribution spectrum of Fe3O4-Mn3O4 prepared in Example 1 of the present invention.

[0027] Figure 3 XRD patterns of Fe3O4-Co3O4 and CoFe2O4 prepared in Example 2 of the present invention.

[0028] Figure 4 XRD patterns of Fe3O4-NiO2 and NiFe2O4 prepared in Example 3 of the present invention.

[0029] Figure 5 Hydrogen evolution catalytic performance graphs of Fe3O4-Mn3O4 and MnFe2O4 prepared in Example 1 of the present invention for water electrolysis.

[0030] Figure 6 Hydrogen evolution catalytic performance graphs of Fe3O4-Co3O4 and CoFe2O4 prepared in Example 2 of the present invention for water electrolysis.

[0031] Figure 7 Hydrogen evolution catalytic performance graphs of Fe3O4-NiO2 and NiFe2O4 prepared in Example 3 of the present invention for water electrolysis. Detailed implementation manners

[0032] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following describes the detailed implementation manners of the present invention in conjunction with the embodiments of the specification.

[0033] Many specific details are set forth in the following description to facilitate a thorough understanding of the present invention. However, the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0034] Secondly, the so-called "one embodiment" or "embodiment" refers to a specific feature, structure, or characteristic that can be included in at least one implementation manner of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it an individual or alternative embodiment that excludes other embodiments.

[0035] Example 1

[0036] (1) Synthesis of Fe3O4 nanoseeds:

[0037] Add a small amount of oleylamine (225 μL) to the octadecene (20 mL) solvent, and remove low-boiling impurities through vacuum heating and nitrogen circulation;

[0038] Under a nitrogen atmosphere, heat up to 180 °C, and thermally inject the iron precursor solution: dissolve Fe2(CO)9 (0.2 g) in pyridine (3 mL), and after reacting for 1 hour, naturally cool to room temperature;

[0039] Wash with ethanol and n-hexane, and dry to obtain small-sized Fe3O4 nanoseeds.

[0040] Figure 1The XRD pattern of the Fe3O4 nanoseeds has strong diffraction peaks, and the characteristic peaks correspond to the Fe3O4 standard spectrum Figure 1 one by one, indicating the pure phase and high crystallinity of the Fe3O4 nanoseeds.

[0041] (2) Preparation of Fe3O4-Mn3O4 heterostructured nanoparticles:

[0042] Disperse 20 mg of Fe3O4 nanoparticles in a mixed solvent of xylene (10 mL), oleylamine (820 μL), and oleic acid (80 μL), heat to 80 °C, inject 1 mL of an aqueous Mn(ClO4)2 solution (0.2 mol / L), and stir for 1 hour.

[0043] When the heating temperature is 60 °C, the reaction is not as complete as at 80 °C, and there are a small amount of reaction precursors remaining in the reaction solution; extending the reaction time to 2 h cannot effectively improve the yield of Fe3O4-Mn3O4.

[0044] Wash with absolute ethanol and n-hexane, and dry to obtain Fe3O4-Mn3O4.

[0045] Figure 1 The XRD pattern of Fe3O4-Mn3O4 clearly shows that the crystal diffraction peaks correspond to the magnetite Fe3O4 standard spectrum, and the shoulder peaks at 29°, 32°, and 60° indicate the presence of the Mn3O4 crystal phase.

[0046] Calcine Fe3O4-Mn3O4 in a tubular furnace at a heating rate of 5 °C / min at 500 °C for 2 h, and cool naturally to obtain MnFe2O4 spinel nanomaterials.

[0047] When the calcination temperature is 400 °C, the sample composition is mainly MnFe2O4 and contains a small amount of Fe3O4-Mn3O4 impurities, indicating that the ideal conversion temperature for homogeneous iron spinel is 500 °C.

[0048] Figure 1 The XRD spectrum proves the pure spinel crystal phase of the obtained MnFe2O4 crystals.

[0049] Figure 2 This is the element distribution map of the EDS element distribution spectrum of Fe3O4-Mn3O4 prepared in this example, indicating the uniform distribution of Fe, Mn, and O elements

[0050] Electrolytic water hydrogen evolution reaction performance evaluation:

[0051] Adopt a three-electrode system: the working electrode is a glassy carbon electrode connected to the RDE, the counter electrode is a carbon rod, the reference electrode is a saturated Ag / AgCl electrode, and the electrolyte is 1 M KOH.

[0052] The voltage range of the CV test curve is 0.2 to -0.6 V, and the scanning rate is 50 mV / s.

[0053] For the LSV test, the RDE rotation speed is 1600 rpm, the test voltage range is -1 to 0 V, and the scanning speed is 5 mV / s. Read the initial overpotential (η1), the overpotential (η10) at a current density of 10 mA / cm2, and the overpotential (η100) at a current density of 100 mA / cm2.

[0054] The overpotentials of Fe3O4-Mn3O4 and MnFe2O4 in this example at η1, η10, and η100 are shown in Table 1, and the LSV curves are shown in Figure 5 . The lower the overpotential, the better the performance.

[0055] The electrocatalytic hydrogen evolution activity of MnFe2O4 is higher than that of Fe3O4-Mn3O4.

[0056] Table 1

[0057]

[0058] Example 2

[0059] Preparation of CoFe2O4 spinel nanomaterials:

[0060] Disperse small-sized Fe3O4 nanoseeds (20 mg) in a mixed solvent of xylene (10 mL), oleylamine (820 μL), and oleic acid (80 μL), heat to 80 °C, inject 1 mL of Co(ClO4)2 aqueous solution (0.2 mol / L), and stir and react for 1 hour.

[0061] Wash with absolute ethanol and n-hexane, and dry to obtain Fe3O4-Co3O4.

[0062] Calcine Fe3O4-Co3O4 in a tubular furnace at a heating rate of 5 °C / min at 500 °C for 2 h, and naturally cool to obtain CoFe2O4 spinel nanomaterials.

[0063] Figure 3 The XRD pattern in

[0064] Evaluation of the performance of the electrolytic water hydrogen evolution reaction:

[0065] The overpotentials of Fe3O4-Co3O4 and CoFe2O4 in this example at η1, η10, and η100 are shown in Table 2, and the LSV curves are shown in Figure 6 . The lower the overpotential, the better the performance.

[0066] The electrocatalytic hydrogen evolution activity of CoFe2O4 is higher than that of Fe3O4-Co3O4.

[0067] Table 2

[0068]

[0069]

[0070] Example 3

[0071] Preparation of NiFe2O4 spinel nanomaterials:

[0072] Disperse small-sized Fe3O4 nanoseeds (20 mg) in a mixed solvent of xylene (10 mL), oleylamine (820 μL), and oleic acid (80 μL), heat to 80 °C, inject 1 mL of Ni(ClO4)2 aqueous solution (0.2 mol / L), and stir and react for 1 hour.

[0073] Wash with absolute ethanol and n-hexane, and obtain Fe3O4-NiO2 after drying.

[0074] Calcine Fe3O4-NiO2 in a tubular furnace at a heating rate of 5 °C / min at 500 °C for 2 h, and naturally cool to obtain NiFe2O4 spinel nanomaterials.

[0075] Figure 4 The XRD pattern in... proves the pure spinel crystal phase of the obtained NiFe2O4 nanomaterials.

[0076] Evaluation of electrocatalytic hydrogen evolution reaction performance:

[0077] The overpotentials of Fe3O4-NiO2 and NiFe2O4 in this example at η1, η10, and η100 are shown in Table 2, and the LSV curves are shown in Figure 7 . The lower the overpotential, the better the performance.

[0078] The electrocatalytic hydrogen evolution activity of NiFe2O4 is higher than that of Fe3O4-NiO2.

[0079] Table 3

[0080]

[0081] The electrocatalytic hydrogen evolution performance of spinel-structured MnFe2O4, CoFe2O4, and NiFe2O4 after high-temperature calcination is higher than that of the oxide heterostructures Fe3O4-Mn3O4, Fe3O4-Co3O4, and Fe3O4-NiO2 of the corresponding elements. The possible reason is that the spinel-structured nanoparticles maintain small-sized particles and regular and uniform morphologies, have a large specific surface area, a carbonized thin layer coating on the surface, and more active sites.

[0082] The present invention prepares iron oxide nanoseeds and mixed oxide heterostructures step by step at the oil phase and the oil phase-water phase interface, which can effectively regulate the composition and morphology of the target nanomaterials, laying a foundation for the subsequent uniform diffusion of thermally driven metal ions within the heterostructures. This method ensures the diverse adjustability of the selected metals, ensures the retention of the morphology and size of the prepared nanomaterials during high-temperature calcination, and the prepared homogeneous iron spinel series nanomaterials have regular and uniform morphologies, large specific surface areas, and many active sites, meeting the requirements of hydrogen evolution catalysts for reaction conductivity and catalytic stability, and can be used as effective electrocatalytic hydrogen evolution materials for practical research.

[0083] The present invention prepares Fe3O4 nanoparticles with a diameter of less than 10 nm as seeds by colloidal synthesis, and uses the seed-regulated growth method to grow on the outer edge of the transition metal perchlorate M(ClO4) solution (M = Mn, Co, Ni) to form Fe3O4-MOx heteronanostructures. High-temperature calcination drives the diffusion of metal ions to form uniform iron spinel MFe2O4 nanomaterials; the present invention can effectively regulate the elemental composition, morphology and particle size of the iron spinel nanostructures, and obtain nanocatalysts with a large specific surface area, many active sites and stable reaction activity. The method of the present invention is simple and easy to operate, and has good repeatability. Using the MFe2O4 nanomaterials as electrolytic water hydrogen evolution catalysts can realize the design and production of low-cost, highly active and stable inexpensive HER catalysts, and has broad application prospects.

[0084] Traditional commonly used spinel preparation process methods include solid-phase sintering method, melting method, high-temperature atomization method, dry washing method, co-precipitation method, etc. Among them, high-temperature solid-phase synthesis is the most mature method for industrial production of spinel materials. The composite oxide formed by the contact reaction between solid interfaces nucleates and grows, and the target spinel product is obtained after repeated calcination. The main disadvantage is that the calcination temperature is usually as high as 1500 °C and the time is more than dozens of hours. The entire preparation process consumes energy and time, and the grain morphology, size and specific surface area of the prepared spinel materials are greatly affected by the synthesis conditions, and it is difficult to generate small-sized particles with a uniform morphology reaching the nanoscale, and the electrocatalytic activity is not high. The present invention is applicable to the controllable preparation of iron spinels with different elements. Through a multi-step synthesis and transformation method at low temperature and short time, it can accurately control nanoscale small-sized particles, effectively prevent the agglomeration and sintering of iron spinel nanomaterials, and maintain a good surface specific surface area and electrocatalytic activity.

[0085] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A preparation method of an iron spinel nanomaterial, characterized in that: including The high-boiling organic solvent and the ligand are purified by reduced-pressure ventilation circulation and then heated. A thermal injection of an iron precursor solution is carried out for reaction. After the reaction is completed, it is washed with polar and non-polar solvents, and Fe3O4 nanoparticles, namely Fe3O4 nanoseeds, are collected by centrifugation. The Fe3O4 nanoseeds are heated and dispersed in an organic mixed solvent containing a ligand. A transition metal precursor solution is injected under heating conditions, and the reaction is stirred. After the reaction is completed, it is washed with polar and non-polar solvents, and Fe3O4-MOx heterostructure nanoparticles are collected by centrifugation. The Fe3O4-MOx heterostructure nanoparticles are calcined after being heated at a constant rate in a tube furnace to achieve in-material thermal diffusion of metal ions, and an MFe2O4 nanomaterial is obtained, where M = Mn, Co or Ni. Among them, the high-boiling organic solvent includes octadecene, and the ligand includes oleylamine. The organic mixed solvent containing a ligand includes a mixed solvent composed of xylene, oleylamine and oleic acid. The transition metal precursor solution includes Mn(ClO4)2, Co(ClO4)2 and Ni(ClO4)2 solutions. Preparation of Fe3O4-MOx heterostructures by regulating the oil phase-water phase interface, with the reaction temperature being 60-80 °C. The calcination temperature is 400-500 °C.

2. The preparation method of the iron spinel nanomaterial according to claim 1, characterized in that: For the reaction with the thermal injection of the iron precursor solution, the temperature is 120-180 °C and the reaction time is 1-2 h.

3. The preparation method of the iron spinel nanomaterial according to claim 1, wherein: Preparation of Fe3O4-MOx heterostructures by regulating the oil phase-water phase interface, with the reaction time being 1-2 h.

4. The preparation method of the iron spinel nanomaterial according to claim 1, wherein: The Fe3O4-MOx heterostructure nanoparticles are calcined after being heated at a constant rate in a tube furnace. Among them, the heating rate is 5 °C / min and the calcination time is 1-2 h.

5. A product prepared by the preparation method of the iron spinel nanomaterial according to any one of claims 1 to 4.

6. The product according to claim 5, characterized in that: The product is MFe2O4 (M = Mn, Co, Ni) spinel nanoparticles with a uniform ellipsoidal morphology, an outer carbon layer, and a size within 20 nm.

7. Application of the product according to claim 5 in an electrolytic water hydrogen evolution catalyst.

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