A cobalt-iron bimetallic selenide composite material with one-dimensional morphology and a preparation method and application thereof

Abstract

The application relates to a cobalt-iron bimetallic selenide composite material with one-dimensional morphology and a preparation method and application thereof. The application prepares a spinnable precursor sol by taking cobalt nitrate, iron nitrate and polyvinylpyrrolidone as reaction raw materials, obtains cobalt ferrite nanofibers through electrospinning and calcination, then takes the prepared cobalt ferrite nanofibers, hydrazine hydrate and selenium powder as raw materials to carry out in-situ selenization through a hydrothermal method, and thus forms an electrocatalyst cobalt-iron bimetallic selenide composite material with one-dimensional morphology. The composite material electrocatalyst prepared by the application has good oxygen evolution properties, and the overpotential under a current density of 10 mA cm ‑2 is only 283 mV, the Tafel slope is extremely small, meanwhile, small electrochemical impedance is beneficial to electron transmission; after 1000 cycles of CV circulation, the polarization curve does not obviously attenuate, indicating that the stability is good; the preparation method of the application has simple steps and has the potential for large-scale production.

Description

Technical Field

[0001] This invention relates to a cobalt-iron bimetallic selenide composite material with a one-dimensional morphology, its preparation method and application, belonging to the fields of new energy materials and electrochemical catalysis. Background Technology

[0002] The current energy shortage and increasingly severe environmental pollution have prompted the search for new clean and renewable resources to achieve the sustainable use of natural resources. In recent years, environmentally friendly and renewable new energy sources such as ocean energy, geothermal energy, and biomass energy have been explored; however, their instability, low efficiency, and high cost limit their wider application. Hydrogen energy, as a clean, sustainable, green, and efficient energy carrier, is considered one of the potential alternatives to fossil fuels in the future. Among various hydrogen production strategies, water electrolysis is considered the most environmentally friendly and effective method for the sustainable production of high-purity hydrogen. The oxygen evolution reaction (OER) is the anodic reaction in water electrolysis, and its reaction rate is much lower than that of the cathodic hydrogen evolution reaction (HER). To improve the reaction rate of the anodic half-reaction, extensive research is currently focused on exploring high-performance OER catalysts.

[0003] Ideal oxygen evolution catalysts are noble metal-based materials, but their limited reserves and high costs make them unsuitable for large-scale applications. Therefore, the research and utilization of inexpensive, abundant, and highly efficient and stable non-noble metal catalysts has become a current research hotspot.

[0004] Current research indicates that transition metal selenides possess advantages such as high conductivity and excellent chemical stability, making them promising for research and application in the field of electrocatalysis and attracting significant attention and investment from researchers. Various transition metal selenide materials for electrocatalytic hydrolysis have already been prepared.

[0005] Chinese patent CN112054217A discloses a method for preparing a CoSe2 / C composite electrocatalyst, using carbon material as a support, and loading CoSe2 onto the support through high-temperature selenization to avoid the aggregation of CoSe2. However, its performance at 10 mA / cm² is limited. -2 The overpotential at current density is as high as 350mV, while the limiting current density is only 50mA cm⁻¹. -2 A large overpotential requires additional energy to facilitate the normal electrolysis of water.

[0006] Chinese patent CN107475744A discloses a method for preparing a FeSe2 composite electrocatalyst. This composite material involves loading iron diselenide nanoparticles onto a conductive substrate. The conductive substrate is required as the matrix to load the iron diselenide nanoparticles. The method operates at 10 mA cm⁻¹. -2At the current density, the overpotential reaches 218 mV, and the Tafel slope is 86 mV dec. -1 Its charge transfer kinetics are slow, requiring more energy to be provided when a higher current density is needed.

[0007] Studies have shown that polymetallic selenides, due to the modulation of their electronic structure and conductivity, possess a richer number of redox reaction sites, thus exhibiting better catalytic activity than monometallic selenides. For example, Co synthesized from nickel foam via electrodeposition... 0.9 Fe 0.1 Se / NF (see Journal of Energy Chemistry, 2021, 60, 194-201) possesses excellent catalytic activity and stability; however, the electrodeposition method is cumbersome and requires stringent conditions, making it unsuitable for industrial production. Therefore, preparing nanoscale bimetallic selenides using green and convenient methods presents a significant challenge. Electrospinning, due to its controllable morphology, high efficiency, environmental friendliness, and economy, has proven to be the most promising strategy for fabricating one-dimensional nanostructures. One-dimensional nanocatalysts possess abundant catalytic active sites and high conductivity, showing great promise in the field of electrocatalysis. However, there are currently no reports on one-dimensional cobalt-iron bimetallic selenides.

[0008] In summary, there is an urgent need to find a one-dimensional cobalt-iron bimetallic selenide composite material that is easy to prepare, has abundant active sites, and exhibits superior electrocatalytic performance. Summary of the Invention

[0009] To overcome the shortcomings of existing technologies, this invention provides a cobalt-iron bimetallic selenide composite material that is simple to prepare, has a one-dimensional morphology, exhibits excellent electrocatalytic oxygen evolution performance under alkaline electrolyte conditions, has a high current density at low overpotentials, low charge transfer resistance, and low cost, and can be widely used in water electrolysis.

[0010] Terminology Explanation:

[0011] Spinning receiving distance: The distance from the electrospinning needle to the receiving device.

[0012] Room temperature: has a meaning known to those skilled in the art, and generally refers to 25±2℃.

[0013] The technical solution of the present invention is as follows:

[0014] This invention constructs a one-dimensional cobalt-iron bimetallic selenide composite material, thereby preparing an electrocatalytic material with abundant active sites, high electrical conductivity, and high electrocatalytic activity. The cobalt-iron bimetallic selenide composite material is obtained through a combination of electrospinning and hydrothermal methods.

[0015] This invention provides a specific method for preparing one-dimensional cobalt-iron bimetallic selenide composite materials.

[0016] A cobalt-iron bimetallic selenide composite material with a one-dimensional morphology, the specific steps of which are as follows:

[0017] (1) Dissolve cobalt nitrate hexahydrate and ferric nitrate nonahydrate in a mixed solution of ethanol and N,N-dimethylformamide at room temperature, and stir for 10-30 min until completely dissolved to obtain a mixed clear solution;

[0018] (2) Add polyvinylpyrrolidone (PVP) to the mixed solution in step (1) and stir until the solution is mixed evenly to obtain a sol of cobalt nitrate and ferric nitrate.

[0019] (3) The sol obtained in step (2) is electrospun at room temperature to obtain precursor fibers;

[0020] (4) After drying the precursor fibers obtained in step (3), calcine them in a muffle furnace at 400-600℃ and keep warm for 60-180 min to obtain cobalt ferrite nanofibers.

[0021] (5) Add the cobalt ferrite nanofibers obtained in step (4) to the hydrothermal reactor, dissolve them in water, and sonicate for 10-30 minutes; the purpose of sonication is to make the prepared cobalt ferrite fibers disperse evenly and ensure that the hydrothermal selenization reaction in the next step is more complete.

[0022] (6) Add selenium powder to hydrazine hydrate solution (N2H4·H2O), stir until completely dissolved, then add to the hydrothermal reactor in step (5), and stir for 10-30 min.

[0023] (7) Transfer the hydrothermal reactor from step (6) to an oven at 180°C and heat for 12-24 hours;

[0024] (8) Centrifuge the solution after the reaction is completed, and wash the resulting substance with ethanol and deionized water to obtain the electrocatalyst cobalt iron bimetallic selenide composite material.

[0025] Preferably, in step (1), the volume ratio of anhydrous ethanol to N,N-dimethylformamide is 4:1.

[0026] Preferably, in step (1), the molar ratio of cobalt nitrate hexahydrate to ferric nitrate nonahydrate is 1:2.

[0027] Preferably, in step (2), the mass ratio of polyvinylpyrrolidone (PVP) to anhydrous ethanol is 1:(7.9-8).

[0028] Preferably, in step (3), the electrospinning voltage is 15-25kV, the humidity is 20-30%, the receiving distance is 10-30cm, and the feeding speed is 0.5-1.5mL / h. -1 .

[0029] Preferably, the drying time in step (4) is 8-12 hours.

[0030] Preferably, the heating rate in step (4) is 2-5℃ / min. -1 .

[0031] Preferably, the mass fraction of hydrazine hydrate in step 6 is 50%.

[0032] Preferably, in step (6), the mass ratio of cobalt ferrite to selenium powder is 1:2.

[0033] This invention employs a two-step process combining electrospinning and hydrothermal methods to prepare cobalt-iron bimetallic selenide composite materials. After preparing cobalt ferrite nanofibers by electrospinning, the cobalt ferrite nanofibers are then selenized in situ using a hydrothermal method to generate the cobalt-iron bimetallic selenide composite material.

[0034] The aforementioned cobalt-iron bimetallic selenide composite nanomaterials are used for electrocatalytic oxygen evolution reaction under alkaline electrolyte conditions.

[0035] The beneficial effects of this invention are:

[0036] (1) The present invention uses cobalt ferrite prepared by electrospinning technology as the matrix for subsequent selenization, which provides the morphology of nanofibers. The nanofibers are used as the matrix for in-situ selenization reaction, which maintains the morphology of cobalt ferrite. The preparation conditions are simple, the cost is low, and it has abundant active sites.

[0037] (2) The cobalt-iron bimetallic selenide composite material prepared in this invention is a composite material of iron diselenide and cobalt diselenide, possessing high electronic conductivity and electrochemical activity. In 1 mol L... -1 KOH solution, 10 mA cm -2 The overpotential at that time was 283mV, and the Tafel slope was only 34mV dec. -1 It has low charge transfer resistance, faster electron transport, and lower energy barrier. Compared with noble metal catalysts, this catalyst has low preparation cost and lower overpotential than commercially available ruthenium dioxide, making it widely applicable in the field of oxygen evolution through water electrolysis. Attached Figure Description

[0038] Figure 1 The X-ray diffraction patterns of the cobalt-iron bimetallic selenide composite materials prepared in Examples 1-4 of this invention and the comparative examples 1-3 are shown.

[0039] Figure 2The image shows the microstructure of the cobalt-iron bimetallic selenide composite material prepared in Example 1 of this invention; where a and b are scanning electron microscope (SEM) images; and c is a transmission electron microscope (TEM) image.

[0040] Figure 3 The LSV curves of the cobalt-iron bimetallic selenide composite materials prepared in Examples 1-4 of this invention and Comparative Examples 1-3 are shown.

[0041] Figure 4 Tafel slope diagrams of the cobalt-iron bimetallic selenide composite materials prepared in Examples 1-4 and Comparative Examples 1-3 of this invention;

[0042] Figure 5 Electrochemical impedance spectroscopy (EIS) diagrams of the cobalt-iron bimetallic selenide composite materials prepared in Examples 1-4 and Comparative Examples 1-3 of the present invention;

[0043] Figure 6 The LSV curve of the cobalt-iron bimetallic selenide composite material prepared in Example 1 of this invention after 1000 CV cycles is shown.

[0044] Figure 7 The current density-time curve of the cobalt-iron bimetallic selenide composite material prepared in Example 1 of this invention at a constant potential of 1.513V (vsRHE). Detailed Implementation

[0045] The present invention will be further described below with reference to specific embodiments, and the advantages and features of the present invention will become clearer with the description. However, the embodiments are merely exemplary and do not constitute any limitation on the scope of the present invention. Those skilled in the art should understand that modifications or substitutions can be made to the details and form of the technical solutions of the present invention without departing from the spirit and scope of the present invention, but all such modifications and substitutions fall within the protection scope of the present invention.

[0046] Example 1: A cobalt-iron bimetallic selenide composite material with one-dimensional morphology and its preparation method. The steps of the preparation method are as follows:

[0047] (1) Weigh 0.5 mmol of cobalt nitrate hexahydrate and 1 mmol of ferric nitrate nonahydrate and dissolve them in 8 mL of anhydrous ethanol and 2 mL of N,N-dimethylformamide. Stir for 30 min until completely dissolved to obtain a clear red solution.

[0048] (2) Add 0.8g of polyvinylpyrrolidone (PVP) to the cobalt nitrate and ferric nitrate mixed solution obtained in step (1) and stir until the solution is mixed evenly to obtain a cobalt nitrate and ferric nitrate mixed sol.

[0049] (3) The cobalt nitrate and ferric nitrate sol obtained in step (2) is placed under a voltage of 20 kV, a humidity of 25%, a receiving distance of 20 cm, and a propulsion speed of 0.5 mL / h. -1 Precursor fibers were obtained by electrospinning at room temperature.

[0050] (4) Place the precursor fiber obtained in step (3) in a muffle furnace at 2°C for 2 min. -1 Cobalt ferrite nanofibers were obtained by heating to 500℃ and holding for 120 minutes.

[0051] (5) Weigh 0.05g of cobalt ferrite obtained in step (4) and add it to a hydrothermal reactor. Add 24mL of water and sonicate for 30min.

[0052] (6) Add 0.1g of selenium powder to 6mL of hydrazine hydrate (N2H4·H2O), stir until completely dissolved, then add to the hydrothermal reactor of step (5), and stir for 30min.

[0053] (7) Transfer the hydrothermal reactor from step (6) to an oven at 180°C and heat for 24 hours.

[0054] (8) After centrifuging the solution after the reaction is completed, the resulting substance is washed three times with ethanol and deionized water to obtain the electrocatalyst cobalt iron bimetallic selenide composite material.

[0055] Figure 1 The image shows the X-ray diffraction (XRD) pattern of the cobalt-iron bimetallic selenide composite material prepared in this embodiment. The diffraction peaks match those of the standard PDF cards CoSe2 (89-2003) and FeSe2 (79-1982), indicating that the cobalt-iron bimetallic selenide composite material was successfully synthesized.

[0056] Figure 2 a and 2b are SEM images of this embodiment. It can be seen that the prepared composite material has a one-dimensional nano-morphology and the fibers are continuous and uniform. Figure 2 c is a TEM image of this embodiment, which also shows that it is formed by two substances with different morphologies, and is a one-dimensional nanocomposite material. Therefore, a cobalt-iron bimetallic selenide composite material was successfully prepared.

[0057] Example 2: A cobalt-iron bimetallic selenide composite material with one-dimensional morphology and its preparation method

[0058] The preparation method involves the following steps:

[0059] (1) Weigh 0.5 mmol of cobalt nitrate hexahydrate and 1 mmol of ferric nitrate nonahydrate and dissolve them in 8 mL of anhydrous ethanol and 2 mL of N,N-dimethylformamide. Stir for 20 min until completely dissolved to obtain a clear red solution.

[0060] (2) Add 0.8g of polyvinylpyrrolidone (PVP) to the cobalt nitrate and ferric nitrate mixed solution obtained in step (1) and stir until the solution is evenly mixed to obtain a cobalt nitrate and ferric nitrate mixed sol.

[0061] (3) The cobalt nitrate and ferric nitrate sol obtained in step (2) is placed under a voltage of 20 kV, a humidity of 20%, a receiving distance of 20 cm, and a propulsion speed of 1 mL / h. -1 Precursor fibers were obtained by electrospinning at room temperature.

[0062] (4) Place the precursor fiber obtained in step (3) in a muffle furnace at 2°C for 2 min. -1 Cobalt ferrite nanofibers were obtained by heating to 500℃ and holding for 120 minutes.

[0063] (5) Weigh 0.05g of cobalt ferrite obtained in step (4) and add it to a hydrothermal reactor. Add 24mL of water and sonicate for 30min.

[0064] (6) Add 0.1g of selenium powder to 6mL of hydrazine hydrate (N2H4·H2O), stir until completely dissolved, then add to the hydrothermal reactor of step (5), and stir for 30min.

[0065] (7) Transfer the hydrothermal reactor from step (6) to an oven at 180°C and heat for 20 hours.

[0066] (8) After centrifuging the solution after the reaction is complete, the resulting substance is washed three times with ethanol and deionized water to obtain the electrocatalyst cobalt iron bimetallic selenide composite material.

[0067] Example 3: A cobalt-iron bimetallic selenide composite material with one-dimensional morphology and its preparation method. The steps of the preparation method are as follows:

[0068] (1) Weigh 0.5 mmol of cobalt nitrate hexahydrate and 1 mmol of ferric nitrate nonahydrate and dissolve them in 8 mL of anhydrous ethanol and 2 mL of N,N-dimethylformamide. Stir for 30 min until completely dissolved to obtain a clear red solution.

[0069] (2) Add 0.8g of polyvinylpyrrolidone (PVP) to the cobalt nitrate and ferric nitrate mixed solution obtained in step (1) and stir until the solution is mixed evenly to obtain a cobalt nitrate and ferric nitrate mixed sol.

[0070] (3) The cobalt nitrate and ferric nitrate sol obtained in step (2) is placed under a voltage of 20 kV, a humidity of 25%, a receiving distance of 20 cm, and a propulsion speed of 1 mL / h. -1 Precursor fibers were obtained by electrospinning at room temperature.

[0071] (4) Place the precursor fiber obtained in step (3) in a muffle furnace and heat it at 5°C for 5 minutes. -1 Cobalt ferrite nanofibers were obtained by heating to 500℃ and holding for 120 minutes.

[0072] (5) Weigh 0.05g of cobalt ferrite obtained in step (4) and add it to a hydrothermal reactor. Add 24mL of water and sonicate for 20min.

[0073] (6) Add 0.1g of selenium powder to 6mL of hydrazine hydrate (N2H4·H2O), stir until completely dissolved, then add to the hydrothermal reactor of step (5), and stir for 30min.

[0074] (7) Transfer the hydrothermal reactor from step (6) to an oven at 180°C and heat for 16 hours.

[0075] (8) After the reaction is completed, the solution is centrifuged multiple times, and the resulting substance is washed three times with ethanol and deionized water to obtain the electrocatalyst cobalt iron bimetallic selenide composite material.

[0076] Example 4: A cobalt-iron bimetallic selenide composite material with one-dimensional morphology and its preparation method. The steps of the preparation method are as follows:

[0077] (1) Weigh 0.5 mmol of cobalt nitrate hexahydrate and 1 mmol of ferric nitrate nonahydrate and dissolve them in 8 mL of anhydrous ethanol and 2 mL of N,N-dimethylformamide. Stir for 30 min until completely dissolved to obtain a clear red solution.

[0078] (2) Add 0.8g of polyvinylpyrrolidone (PVP) to the cobalt nitrate and ferric nitrate mixed solution obtained in step (1) and stir until the solution is mixed evenly to obtain a cobalt nitrate and ferric nitrate mixed sol.

[0079] (3) The cobalt nitrate and ferric nitrate sol obtained in step (2) is placed under a voltage of 20 kV, a humidity of 25%, a receiving distance of 20 cm, and a propulsion speed of 1.2 mL / h. -1 Precursor fibers were obtained by electrospinning at room temperature.

[0080] (4) Place the precursor fiber obtained in step (3) in a muffle furnace at 2°C for 2 min. -1 Cobalt ferrite nanofibers were obtained by heating to 500℃ and holding for 120 minutes.

[0081] (5) Weigh 0.05g of cobalt ferrite obtained in step (4) and add it to a hydrothermal reactor. Add 24mL of water and sonicate for 30min.

[0082] (6) Add 0.1g of selenium powder to 6mL of hydrazine hydrate (N2H4·H2O), stir until completely dissolved, then add to the hydrothermal reactor of step (5), and stir for 30min.

[0083] (7) Transfer the hydrothermal reactor from step (6) to an oven at 180°C and heat for 12 hours.

[0084] (8) After centrifuging the solution after the reaction is completed, the resulting substance is washed three times with ethanol and deionized water to obtain the electrocatalyst cobalt iron bimetallic selenide composite material.

[0085] Comparative Example 1

[0086] A method for preparing cobalt selenide electrocatalytic material, comprising the following steps:

[0087] (1) Weigh 1 mmol of cobalt nitrate hexahydrate and dissolve it in 8 mL of anhydrous ethanol and 2 mL of N,N-dimethylformamide. Stir for 30 min until completely dissolved to obtain a pink and clear solution.

[0088] (2) Add 0.8g of polyvinylpyrrolidone (PVP) to the cobalt nitrate solution obtained in step (1) and stir until the solution is mixed evenly to obtain cobalt nitrate sol.

[0089] (3) The cobalt nitrate sol obtained in step (2) is placed under a voltage of 20 kV, a humidity of 25%, a receiving distance of 20 cm, and a propulsion speed of 0.5 mL / h. -1 Precursor fibers were obtained by electrospinning at room temperature.

[0090] (4) Place the precursor fiber obtained in step (3) in a muffle furnace at 2°C for 2 min. -1 Cobalt tetroxide nanofibers were obtained by heating to 500℃ and holding for 120 minutes.

[0091] (5) Weigh 0.05g of cobalt nitrate obtained in step (4) and add it to a hydrothermal reactor. Add 24mL of water and sonicate for 30min.

[0092] (6) Add 0.1g of selenium powder to 6mL of hydrazine hydrate (N2H4·H2O), stir until completely dissolved, then add to the hydrothermal reactor of step (5), and stir for 30min.

[0093] (7) Transfer the hydrothermal reactor from step (6) to an oven at 180°C and heat for 20 hours.

[0094] (8) After centrifuging the solution after the reaction is completed, the resulting substance is washed three times with ethanol and deionized water to obtain the electrocatalyst of cobalt selenide material.

[0095] Comparative Example 2

[0096] A method for preparing an iron selenide electrocatalytic material, comprising the following steps:

[0097] (1) Weigh 1 mmol of ferric nitrate nonahydrate and dissolve it in 8 mL of anhydrous ethanol and 2 mL of N,N-dimethylformamide. Stir for 30 min until completely dissolved to obtain a clear red solution.

[0098] (2) Add 0.8g of polyvinylpyrrolidone (PVP) to the ferric nitrate solution obtained in step (1) and stir until the solution is mixed evenly to obtain ferric nitrate sol.

[0099] (3) The ferric nitrate sol obtained in step (2) is placed under a voltage of 20 kV, a humidity of 25%, a receiving distance of 20 cm, and a propulsion speed of 0.5 mL / h. -1 Precursor fibers were obtained by electrospinning at room temperature.

[0100] (4) Place the precursor fiber obtained in step (3) in a muffle furnace at 2°C for 2 min. -1 The temperature was raised to 500℃ and held for 120 minutes to obtain ferric oxide nanofibers.

[0101] (5) Weigh 0.05g of ferric oxide obtained in step (4) and add it to a hydrothermal reactor. Add 24mL of water and sonicate for 30min.

[0102] (6) Add 0.1g of selenium powder to 6mL of hydrazine hydrate (N2H4·H2O), stir until completely dissolved, then add to the hydrothermal reactor of step (5), and stir for 30min.

[0103] (7) Transfer the hydrothermal reactor from step (6) to an oven at 180°C and heat for 24 hours.

[0104] (8) After centrifuging the solution after the reaction is complete, the resulting substance is washed three times with ethanol and deionized water to obtain the electrocatalyst of iron selenide material.

[0105] Comparative Example 3

[0106] A method for preparing a cobalt ferrite electrocatalytic material, comprising the following steps:

[0107] (1) Weigh 0.5 mmol of cobalt nitrate hexahydrate and 1 mmol of ferric nitrate nonahydrate and dissolve them in 8 mL of anhydrous ethanol and 2 mL of N,N-dimethylformamide. Stir for 30 min until completely dissolved to obtain a clear red solution.

[0108] (2) Add 0.8g of polyvinylpyrrolidone (PVP) to the cobalt nitrate and ferric nitrate mixed solution obtained in step (1) and stir until the solution is mixed evenly to obtain a cobalt nitrate and ferric nitrate mixed sol.

[0109] (3) The cobalt nitrate and ferric nitrate sol obtained in step (2) is placed under a voltage of 20 kV, a humidity of 25%, a receiving distance of 20 cm, and a propulsion speed of 0.5 mL / h. -1 Precursor fibers were obtained by electrospinning at room temperature.

[0110] (4) Place the precursor fiber obtained in step (3) in a muffle furnace at 2°C for 2 min. -1 Cobalt ferrite nanofibers were obtained by heating to 500℃ and holding for 120 minutes.

[0111] Application examples

[0112] This invention is applied to the field of hydrogen production technology through water electrolysis, specifically to the field of electrocatalytic oxygen evolution. Therefore, electrochemical oxygen evolution tests were performed on Examples 1-4 and Comparative Examples 1-3. The specific implementation method is as follows: A three-electrode system controlled by an electrochemical workstation was used for the determination. The working electrode was controlled by a commercial rotating disk electrode system, and the electrode was kept rotating at 1600 rpm during the test to remove bubbles generated on the catalyst surface. In the test, a glassy carbon electrode was used as the working electrode, a graphite rod electrode as the counter electrode, and a Hg / HgO electrode as the reference electrode. The polarization curve (linear voltammetry scan, LSV) was measured in a 1 M KOH solution saturated with N2, with a catalyst loading of approximately 0.3 mg / cm³. -2 The polarization curves were all subjected to 90% IR compensation, and the scan rate was 5 mV / s. -1 Electrochemical impedance spectroscopy (EIS) measurements from 10 5 The frequency is 0.1 Hz, and the amplitude is 5 mV at 1.47 V relative to RHE.

[0113] Depend on Figure 3 It can be seen that the electrocatalyst cobalt-iron bimetallic selenide composite materials prepared in Examples 1-4 have a larger limiting current density compared with Comparative Examples 1, 2, and 3, and the limiting current density of Example 1 can reach 140 mA cm⁻¹. -2 Meanwhile, Examples 1-4 were performed at 10 mA cm -2 The overpotential at current density is lower, and the performance is significantly improved compared to single metal cobalt and iron selenides and cobalt ferrite. Figure 5 The figure shows the Tafel slopes for Examples 1-4 and Comparative Examples 1, 2, and 3. It can be seen from the figure that Example 1 has the lowest Tafel slope, while the Tafel slopes for Examples 1-4 show no significant difference. Meanwhile, from... Figure 6 The electrochemical impedance spectroscopy shows that Examples 1-4 have low charge transfer resistance and fast electron transport, and Example 1 has the lowest electrochemical impedance. In summary, the prepared cobalt-iron bimetallic selenide composite material has good electrocatalytic activity. Figure 6The CV curve of Example 1 after 1000 cycles shows that the polarization curve has no obvious decay, indicating that this electrocatalyst has good stability. Figure 7 This demonstrates the durability of the cobalt-iron bimetallic selenide electrocatalyst composite material obtained in Example 1. Under a constant potential of 1.513V (vs RHE), the current density of Example 1 can remain relatively stable after 20 hours of continuous electrolysis.

Claims

1. A cobalt-iron bimetallic selenide composite material with a one-dimensional morphology, characterized in that, The main components of the composite material are cobalt diselenide and iron diselenide, which are converted into a cobalt-iron bimetallic selenide composite material through in-situ selenization. The preparation method of the cobalt-iron bimetallic selenide composite material with one-dimensional morphology includes the following specific steps: (1) Dissolve cobalt nitrate hexahydrate and ferric nitrate nonahydrate in a mixed solution of ethanol and N,N-dimethylformamide at room temperature, and stir for 10-30 min until completely dissolved to obtain a mixed clear solution; (2) Add polyvinylpyrrolidone to the mixed solution in step (1) and stir until the solution is evenly mixed to obtain a sol of cobalt nitrate and ferric nitrate; (3) The sol obtained in step (2) is electrospun at room temperature to obtain precursor fibers; (4) After drying the precursor fibers obtained in step (3), calcine them in a muffle furnace at 400-600℃ for 60-180 min to obtain cobalt ferrite nanofibers. (5) Add the cobalt ferrite nanofibers obtained in step (4) to a hydrothermal reactor, dissolve them in water, and sonicate for 10-30 minutes; (6) Add selenium powder to hydrazine hydrate solution, stir until completely dissolved, then add to the hydrothermal reactor in step (5), and stir for 10-30 min. (7) Transfer the hydrothermal reactor from step (6) to an oven at 180°C and heat for 12-24 hours; (8) Centrifuge the solution after the reaction is completed, and wash the obtained substance with ethanol and deionized water to obtain the electrocatalyst cobalt iron bimetallic selenide composite material. In step (3), the electrospinning voltage is 15-25 kV, the humidity is 20-30%, the receiving distance is 10-30 cm, and the advancing speed is 0.5-1.5 ml / h. -1 ; The heating rate in step (4) is 2-5℃ min. -1 ; In step (6), the hydrazine hydrate solution contains 50% hydrazine hydrate by mass; the mass ratio of cobalt ferrite to selenium powder is 1:

2.

2. The cobalt-iron bimetallic selenide composite material with one-dimensional morphology according to claim 1, characterized in that, In step (1), the volume ratio of anhydrous ethanol to N,N-dimethylformamide is 4:

1.

3. The cobalt-iron bimetallic selenide composite material with one-dimensional morphology according to claim 1, characterized in that, In step (1), the molar ratio of cobalt nitrate hexahydrate to ferric nitrate nonahydrate is 1:

2.

4. The cobalt-iron bimetallic selenide composite material with a one-dimensional morphology according to claim 1, characterized in that, The drying time in step (4) is 8-12 h.

5. The application of the cobalt-iron bimetallic selenide composite material with one-dimensional morphology as described in any one of claims 1-4 in electrocatalytic oxygen evolution.

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