A self-supporting iron-zinc bimetallic selenide electrode and a preparation method and application thereof

Abstract

This invention relates to the field of supercapacitor technology, disclosing a self-supporting iron-zinc bimetallic selenide electrode, its preparation method, and its application. The method includes the following steps: Step 1, preparing an electrolyte by mixing iron and zinc salts, using a conductive substrate as the cathode and a graphite sheet or metal as the anode for electrodeposition; after deposition, removing the conductive substrate, cleaning, and drying to obtain a zinc-iron loaded electrode; Step 2, performing low-temperature selenization on the zinc-iron loaded electrode and selenium powder in a tube furnace; after completion, sequentially cleaning the zinc-iron loaded electrode with alkali, water, and ethanol, and drying to obtain the self-supporting iron-zinc bimetallic selenide electrode. This invention utilizes the combination of electrodeposition and low-temperature selenization, significantly shortening the time required, resulting in a controllable and reproducible electrode morphology and structure, and exhibiting high specific capacitance and good electrochemical activity at 2 mA·cm⁻¹. ‑2 At a current density, the area ratio capacitance reaches 1494.58 mF·cm. ‑2 .

Description

Technical Field

[0001] This invention relates to the field of supercapacitor technology, specifically to a self-supporting iron-zinc bimetallic selenide electrode, its preparation method, and its application. Background Technology

[0002] With the transformation and upgrading of my country's energy sector, there is an urgent need for an energy storage device to promote the development of the new energy industry. As a type of energy storage device, supercapacitors have advantages such as fast charging speed, high power density, long cycle life, high energy conversion efficiency, and good performance at ultra-low temperatures. With these advantages, supercapacitors have a wide range of applications in transportation, wind and solar power generation, network communication, and medical devices.

[0003] Supercapacitors can be classified into electric double-layer capacitors and pseudocapacitors based on their energy storage principles. Electric double-layer capacitors store charge by applying a voltage across the electrodes, causing ions in the electrolyte to move towards the electrodes and form an electric double layer. The electrode materials are often carbon materials with a large specific surface area, exhibiting good stability and reversibility, and high power density, but low energy density. Pseudocapacitors, on the other hand, store charge through redox reactions occurring on or near the electrode surface. The electrode materials are generally transition metal oxides, conductive polymers, and metal-organic frameworks. Compared to electric double-layer capacitors, pseudocapacitors have a higher energy density.

[0004] Metal compounds (metal oxides, metal sulfides, and metal hydroxides) are considered ideal electrode materials for pseudocapacitors due to their abundant oxidation states and active sites in redox reactions, resulting in large specific capacitance values. Transition metal selenides, compared to transition metal oxides and sulfides which are currently the mainstream electrode materials, have been studied less, especially bimetallic selenides. Compared to its oxygen and sulfur consortia, selenium's lower band gap and abundant chemical states lead to good electronic conductivity and high theoretical specific capacitance in its transition metal selenides. Furthermore, the better metallic and bimetallic synergistic effects of selenium contribute to its good electrochemical stability.

[0005] Currently, most bimetallic selenides are prepared using a solvothermal method similar to that used for bimetallic oxides. However, unlike the one-step solvothermal method for bimetallic oxides, bimetallic selenides require two or more steps. First, a bimetallic hydroxide precursor is prepared using the first solvothermal step. Then, the bimetallic hydroxide precursor is selenized using the second solvothermal step to finally prepare the bimetallic selenide. The entire preparation process is quite complicated and the growth rate of the active material is slow, requiring a long time.

[0006] Chinese patent document CN106783202A discloses a bimetallic selenide Cu x Mo ySe z The electrode material is prepared by placing nickel foam, which has been sequentially cleaned with acetone / hydrochloric acid / ethanol and deionized water, into a reaction vessel containing a copper / nickel precursor solution. A first-step hydrothermal reaction is carried out under sealed conditions at 120–200°C for 6–12 hours. After the reaction, the mixture is allowed to cool naturally to room temperature. The nickel foam is then removed, washed, and vacuum-dried to obtain a CuMo precursor loaded on the nickel foam. In the second step, the nickel foam loaded with the CuMo precursor is placed into a reaction vessel containing a small amount of selenium solution and subjected to a second-step hydrothermal reaction under sealed conditions at 160–200°C for 10–24 hours. The nickel foam is then removed, washed, and vacuum-dried to obtain nickel foam-like Cu. x Mo y Se z The bimetallic selenide electrode material contains a small amount of selenium solution, which is a hydrazine hydrate solution of selenium. The preparation method is to dissolve 0.3g of selenium powder in 30mL of hydrazine hydrate, mix them evenly, and let them stand for 24h.

[0007] However, this method has a long preparation time, low efficiency, poor repeatability of morphological structure design, and generates a lot of waste liquid during the preparation process. Summary of the Invention

[0008] This invention addresses the problems of long preparation time and low efficiency in bimetallic selenide electrodes by providing a rapid method for preparing self-supporting zinc-iron metal selenide electrodes. Utilizing a combination of electrodeposition and low-temperature selenization, the preparation time is significantly shortened. The resulting electrode exhibits controllable and reproducible morphology and structure, high specific capacitance, and excellent electrochemical activity at 2 mA·cm⁻¹. -2 At a current density, the area ratio capacitance reaches 1494.58 mF·cm. -2 .

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A method for preparing a self-supporting iron-zinc bimetallic selenide electrode includes the following steps:

[0011] Step 1: Prepare an electrolyte solution by mixing iron salt and zinc salt, perform electrodeposition using a conductive substrate as the cathode and a graphite sheet or metal as the anode, and after deposition, remove the conductive substrate, clean and dry it to obtain an electrode loaded with zinc and iron.

[0012] Step 2: The zinc-iron loaded electrode and selenium powder are subjected to low-temperature selenization in a tube furnace. After the process, the zinc-iron loaded electrode is washed with alkali, water and ethanol in sequence and dried to obtain the self-supporting iron-zinc bimetallic selenide electrode.

[0013] Current technologies for preparing bimetallic selenide electrodes primarily employ a two-step hydrothermal method, with each hydrothermal reaction lasting approximately 10 hours, resulting in a total preparation time of around 20 hours. This invention combines electrodeposition and low-temperature selenization, with electrodeposition taking approximately 10–30 minutes and low-temperature selenization approximately 7 hours, significantly reducing the preparation time to approximately 7–8 hours. The prepared zinc-iron bimetallic selenide benefits from the Zn content provided by the bimetallic system composed of different transition metals. 2+ Fe 3+ The use of two different metal ions and valence states, coupled with the lower band gap (0.37 eV) of FeSe2 compared to FeS2 (0.88 eV) and Fe2O3 (1.31 eV), leads to higher electrochemical efficiency. Therefore, zinc-iron bimetallic selenides (Zn-Fe-Se) exhibit higher energy and power densities. Furthermore, the use of a conductive substrate as a self-supporting matrix, such as carbon fiber, provides excellent mechanical strength and current collector performance. This combination ensures that the electrode material possesses both good mechanical strength and excellent electrochemical performance.

[0014] The conductive substrate includes any one of carbon fiber cloth, nickel foam, copper foam, ITO conductive glass, etc.

[0015] Preferably, the conductive substrate is carbon fiber cloth in use. Before use, the carbon fiber cloth is desizing, cleaning, and drying to obtain the carbon fiber cloth conductive substrate. As a self-supporting substrate, the carbon fiber cloth not only provides Faraday reaction space for the zinc-iron bimetallic selenide (Zn-Fe-Se) active material, but also gives the prepared electrode material excellent mechanical properties and conductivity, and can fully utilize the capacitive characteristics of the transition metal zinc-iron selenide.

[0016] More preferably, the carbon fiber cloth is made of T300; T300 has high electrical conductivity and excellent mechanical properties, including tensile strength and tensile modulus. During charging and discharging, it can act as a current collector to provide a faster electron transport rate, and at the same time, it can provide a high-strength load substrate for Zn-Fe-Se active materials.

[0017] Preferably, the carbon fiber cloth is desized by soaking in acetone, such as soaking at 20-30°C for 12-36 hours; more preferably soaking at 25°C for 24 hours.

[0018] Metals used for anodes include Zn or Fe, etc.

[0019] The zinc salt includes any one of zinc chloride, zinc sulfate, zinc nitrate, and their hydrates;

[0020] The iron salt includes any one of ferrous chloride, ferrous sulfate, ferric nitrate, and their hydrates.

[0021] Preferably, the zinc salt is zinc chloride, and the iron salt is ferrous chloride tetrahydrate. Chloride plating solution systems have good conductivity, fast deposition rate, low cost, minimal environmental pollution, and a large coating surface area, providing more reaction sites.

[0022] Preferably, the concentrations of iron salt and zinc salt in the electrolyte are each 0.01–0.1 mol / L; the molar ratio of zinc to iron in the zinc salt and iron salt is 2:1 to 1:3. Preferably, the molar ratio of zinc to iron in the zinc salt and iron salt is 2:1 to 1:2. At this zinc-iron ratio, the zinc-iron alloy coating deposited on the substrate bonds tightly to the carbon cloth substrate and is not easily detached during subsequent low-temperature selenization.

[0023] Preferably, the electrodeposition uses a deposition voltage of 2–5V and a deposition time of 5–30 min. A deposition voltage of 2.5–3.5V is preferred. Excessively high deposition voltage will lead to excessively rapid metal deposition, severe agglomeration, and a significant hydrogen evolution reaction. Longer deposition times do not necessarily result in higher capacitance, as the contribution of the double-layer capacitance is related to the specific surface area; a larger specific surface area results in a greater contribution. Pseudocapacitance, on the other hand, is related to rapid redox reactions on or near the electrode surface. Therefore, a thicker coating formed by long-term deposition does not contribute much to capacitance internally. Conversely, too short a deposition time will result in insufficient active material on the carbon cloth surface, directly reducing capacitance.

[0024] Preferably, in step 3, the total molar ratio of selenium powder to zinc and iron ions in the electrolyte is 2:1 or higher; more preferably 2 to 2.5:1.

[0025] Preferably, the low-temperature selenization is carried out at 50–450°C for 5–7 hours.

[0026] More preferably, the low-temperature selenization includes two stages: the first stage is to raise the temperature from 50°C to 350-450°C, and the time required for the temperature rise is 120-175 min; the second stage is to maintain the temperature at 350-450°C for 180-240 min.

[0027] Preferably, the cleaning of the conductive substrate in step 1 is water and / or ethanol cleaning;

[0028] In step 3, the alkali is 1-6M potassium hydroxide or sodium hydroxide; the purpose of alkali washing is to remove unreacted elemental selenium.

[0029] The above drying process involves drying at 50–70°C for 6–18 hours. For example, drying at 60°C for 12 hours.

[0030] This invention also provides a self-supporting iron-zinc bimetallic selenide electrode prepared according to the described method. This electrode exhibits excellent electrochemical performance, with the bimetallic selenide tightly bonded to the substrate, at 2 mA·cm⁻¹. ～2 At a current density, the area ratio capacitance reaches 1494.58 mF·cm. -2 It can be applied to the field of supercapacitors.

[0031] The present invention also provides a supercapacitor, including the self-supporting iron-zinc bimetallic selenide electrode, and further including an insulating glass fiber diaphragm and a potassium hydroxide electrolyte.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) The synthesis method of preparing self-supporting zinc-iron bimetallic selenide (Zn-Fe-Se) electrode of the present invention significantly shortens the preparation time compared with the commonly used two-step or multi-step solvothermal method for preparing bimetallic selenides, and the electrode material obtained has excellent mechanical properties and conductivity. Under the support of a conductive substrate, it can fully utilize the capacitance characteristics of transition metal zinc-iron selenide.

[0034] (2) In this invention, the morphology and structure of the coating on the substrate can be effectively controlled by adjusting the deposition voltage and the concentration of zinc and iron, thereby further realizing the regulation of the morphology and structure and composition of the bimetallic selenide. The structure and composition can be optimized in a simple and time-saving way, so that the electrode material has good electrochemical performance and can be directly applied to the field of supercapacitors. Attached Figure Description

[0035] Figure 1 The image shows a SEM image of a self-supporting zinc-iron bimetallic selenide (Zn-Fe-Se) electrode material prepared in Example 1 with a zinc-iron feed ratio of 2:1 and a deposition voltage of 3V.

[0036] Figure 2 The volt-ampere curves are for the self-supporting zinc-iron bimetallic selenide (Zn-Fe-Se) electrode material prepared in Example 1 with a zinc-iron feed ratio of 2:1 and a deposition voltage of 3V.

[0037] Figure 3 The constant current charge-discharge curve of the self-supporting zinc-iron bimetallic selenide (Zn-Fe-Se) electrode material prepared in Example 1 with a zinc-iron ratio of 2:1 and a deposition voltage of 3V is shown.

[0038] Figure 4 The image shows a SEM image of the self-supporting zinc-iron bimetallic selenide (Zn-Fe-Se) electrode material prepared in Example 2 with a zinc-iron ratio of 1:1 and a deposition voltage of 3V.

[0039] Figure 5The volt-ampere curves are for the self-supporting zinc-iron bimetallic selenide (Zn-Fe-Se) electrode material prepared in Example 2 with a zinc-iron ratio of 1:1 and a deposition voltage of 3V.

[0040] Figure 6 The constant current charge-discharge curve of the self-supporting zinc-iron bimetallic selenide (Zn-Fe-Se) electrode material prepared in Example 2 with a zinc-iron ratio of 1:1 and a deposition voltage of 3V is shown.

[0041] Figure 7 The image shows a SEM image of the self-supporting zinc-iron bimetallic selenide (Zn-Fe-Se) electrode material prepared in Example 3 with a zinc-iron ratio of 1:2 and a deposition voltage of 3V.

[0042] Figure 8 The volt-ampere curves are for the self-supporting zinc-iron bimetallic selenide (Zn-Fe-Se) electrode material prepared in Example 3 with a zinc-iron feed ratio of 1:2 and a deposition voltage of 3V.

[0043] Figure 9 The constant current charge-discharge curve of the self-supporting zinc-iron bimetallic selenide (Zn-Fe-Se) electrode material prepared in Example 3 with a zinc-iron ratio of 1:2 and a deposition voltage of 3V is shown.

[0044] Figure 10 For Comparative Example 1, a self-supporting zinc-iron bimetallic selenide (Zn-Fe-Se) electrode material was prepared with a zinc-iron feed ratio of 2:1 and a deposition voltage of 6V.

[0045] Figure 11 The image shows a SEM image of a self-supported zinc-iron bimetallic selenide (Zn-Fe-Se) electrode material prepared with a zinc-iron feed ratio of 2:1 and a deposition voltage of 9V, as shown in Comparative Example 2.

[0046] Figure 12 The image shows a SEM image of the self-supporting iron selenide (Fe-Se) electrode material prepared in Comparative Example 3 with a zinc-iron feed ratio of 0:1 and a deposition voltage of 3V.

[0047] Figure 13 The voltammetric curves of the self-supporting iron selenide (Fe-Se) electrode material prepared with a zinc-iron feed ratio of 0:1 and a deposition voltage of 3V are shown in Comparative Example 3.

[0048] Figure 14 The constant current charge-discharge curve of the self-supporting iron selenide (Fe-Se) electrode material prepared with a zinc-iron ratio of 0:1 and a deposition voltage of 3V is shown in Comparative Example 3. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Modifications or equivalent substitutions made by those skilled in the art based on their understanding of the technical solutions of this invention, without departing from the spirit and scope of the invention, should be covered within the protection scope of this invention.

[0050] All raw materials used in the following specific embodiments were purchased from the market.

[0051] Example 1

[0052] A method for preparing a self-supporting iron-zinc bimetallic selenide supercapacitor (Zn-Fe-Se) material involves loading iron-zinc bimetallic selenide onto the surface of carbon fiber cloth. The method for preparing this self-supporting iron-zinc bimetallic selenide electrode material includes the following steps:

[0053] (1) Cut T300 carbon fiber cloth into square pieces of 2cm×2cm, soak them in acetone at 25℃ for 24h to remove the sizing, then wash the desized carbon fiber cloth with deionized water and dry it in an oven at 60℃ to obtain pretreated carbon fiber cloth.

[0054] (2) Weigh 6.7 mmol of zinc chloride and 3.3 mmol of ferrous chloride tetrahydrate and dissolve them in 100 mL of deionized water. Stir thoroughly to obtain a mixed electrolyte with a concentration of 0.067 M zinc ions and 0.033 M iron ions (zinc ions: iron ions = 2:1). Use the pretreated carbon fiber cloth as the cathode and the graphite electrode as the electroplating anode. Use a dual-electrode electrolytic cell and set the deposition voltage to 3V, 6V and 9V respectively. The deposition time is 30 min. During the deposition process, sonication is performed to remove the bubbles generated by the hydrogen evolution side reaction. After the deposition is completed, wash with ethanol and deionized water in sequence and vacuum dry (60℃, 12 h) to obtain the precursor electrode of zinc-iron alloy loaded on carbon fiber cloth.

[0055] (3) Place the precursor electrode loaded with zinc and iron metal on the carbon fiber cloth obtained in step (2) in a crucible, and spread selenium powder evenly on the upper and lower surfaces of the electrode. The molar ratio of selenium powder to zinc and ferrous ions is 2:1. Place the entire crucible in a tube furnace and carry out low-temperature selenization in a nitrogen atmosphere. The selenization is divided into two stages. The first stage treatment temperature is raised from 50℃ to 400℃ at a rate of 2℃ / min and the treatment time is 175 minutes. The second stage treatment temperature is maintained at 400℃ for 4 hours.

[0056] (4) The electrode material obtained by selenization in step (3) is immersed in 6M KOH solution to clean it and remove the unreacted elemental selenium. Then it is cleaned with deionized water and ethanol in sequence and dried in a vacuum oven at 60°C for 12 hours to obtain a self-supporting iron-zinc bimetallic selenide (Zn-Fe-Se) electrode.

[0057] Figure 1 This is a scanning electron microscope image of the self-supporting zinc iron selenide (Zn-Fe-Se) electrode material prepared in this embodiment with a zinc-iron feed ratio of 2:1 and a deposition voltage of 3V. The scale bar is 5μm, and the average fiber diameter is 10.3μm. The zinc-iron bimetallic selenide (Zn-Fe-Se) active material is densely attached to the carbon fiber surface, showing a granular and short strip morphological structure with pores, no agglomeration, and no exposed carbon fiber surface, which is beneficial for charge storage.

[0058] Figure 2 The figure shows the CV (cyclic voltammetry) curves of the self-supported zinc-iron-selenide (Zn-Fe-Se) electrode material prepared in this embodiment with a zinc-iron feed ratio of 2:1, under different scan rates and with 6M KOH as the electrolyte. The figure shows the CV curves at different scan rates (5 / 10 / 20 / 50 / 100 mV·s). -1 The CV curves show obvious redox peaks, indicating that the electrochemical energy storage behavior of the self-supported zinc-iron bimetallic selenide (Zn-Fe-Se) is dominated by pseudocapacitance, accompanied by a small amount of double-layer capacitance. This is because when a voltage is applied across the electrode, ions in the solution inevitably move in a directional manner and adsorb onto the electrode surface to form a double layer.

[0059] Figure 3 The figure shows the GCD (Gas-Constant Charge-Discharge) curves of the self-supported zinc-iron selenide (Zn-Fe-Se) electrode material prepared in this embodiment with a zinc-iron feed ratio of 2:1, under different current densities and with 6M KOH as the electrolyte. The figures are displayed at different current densities (2 / 3 / 4 / 5 / 10 mA·cm⁻¹). -2 The GCD curve deviates from the isosceles triangle under these conditions, exhibiting significant redox reaction behavior, which is typical of Faraday pseudocapacitance characteristics, consistent with the CV test results. This electrode material exhibits performance at 2 mA·cm⁻¹. -2 It exhibits a current density of 1016.93 mF·cm⁻¹. -2 The area-to-capacitance ratio decreases with increasing current density, especially at 10 mA·cm². -2 It maintained 363.73 mF·cm at high current densities. -2 The area specific capacitance is due to the fact that the iron-zinc bimetallic selenide (Zn-Fe-Se) electrode material cannot completely undergo redox reactions under high current densities.

[0060] Example 2

[0061] The preparation method of the self-supporting zinc-iron bimetallic selenide (Zn-Fe-Se) electrode material in Example 2 is the same as that in Example 1, except that the molar ratio of zinc ions to ferrous ions in the electrolyte is 1:1 (0.05M zinc ions and 0.05M ferrous ions) during the metal co-deposition process.

[0062] Figure 4 This is a scanning electron microscope image of the self-supporting zinc-iron selenide (Zn-Fe-Se) electrode material prepared in Example 2 with a zinc-iron feeding ratio of 1:1. The scale bar is 5 μm, and the average fiber diameter is 8.7 μm. The zinc-iron bimetallic selenide (Zn-Fe-Se) active material is densely attached to the carbon fiber surface, showing a granular morphology and pore formation. Compared with Example 1, both the particles and pores are enlarged to a certain extent.

[0063] Figure 5 The figure shows the CV (cyclic voltammetry) curves of the self-supported zinc iron selenide (Zn-Fe-Se) electrode material prepared in Example 2 with a zinc-iron feed ratio of 1:1, under different scan rates and with 6M KOH as the electrolyte. The figure shows the CV curves at different scan rates (5 / 10 / 20 / 50 / 100 mV·s). -1 The CV curves show obvious redox peaks, indicating that the electrochemical energy storage behavior of the self-supported iron-zinc bimetallic selenide (Zn-Fe-Se) is dominated by pseudocapacitance, accompanied by a small amount of double-layer capacitance. This is because when a voltage is applied across the electrode, ions in the solution inevitably move in a directional manner and adsorb onto the electrode surface to form a double layer.

[0064] Figure 6 The figure shows the GCD (Gas-Constant Charge-Discharge) curves of the self-supported zinc-iron selenide (Zn-Fe-Se) electrode material prepared in Example 2 with a zinc-iron feed ratio of 1:1 under different current densities and with 6M KOH as the electrolyte. The figure shows the GCD curves (Gas-Constant Charge-Discharge) curves of the self-supported zinc-iron selenide (Zn-Fe-Se) electrode material prepared in Example 2 with a zinc-iron feed ratio of 1:1 under different current densities (2 / 3 / 4 / 5 / 10 mA·cm⁻¹). -2) The lower GCD curve deviates from the isosceles triangle, exhibiting a significant redox reaction, which is typical of Faraday pseudocapacitive characteristics, consistent with the CV test results. This electrode material exhibits performance at 2 mA·cm⁻¹. -2 It exhibits a current density of 1193.47 mF·cm⁻¹. -2 The area-to-capacitance ratio decreases with increasing current density, especially at 10 mA·cm². -2 It maintained 427.63 mF cm⁻¹ under high current density. -2The area specific capacitance is due to the fact that the iron-zinc bimetallic selenide (Zn-Fe-Se) electrode material cannot completely undergo redox reactions under high current densities.

[0065] Example 3

[0066] The preparation method of the self-supporting zinc-iron bimetallic selenide (Zn-Fe-Se) electrode material in Example 3 is the same as that in Example 1, except that the molar ratio of zinc ions to ferrous ions in the electrolyte is 1:2 (zinc ions 0.033M, ferrous ions 0.067M) during the metal co-deposition process.

[0067] Figure 7 This is a scanning electron microscope image of the self-supporting zinc-iron selenide (Zn-Fe-Se) electrode material prepared in Example 3 with a zinc-iron feeding ratio of 1:2. The scale bar is 10 μm, and the average fiber diameter is 12.4 μm. The zinc-iron bimetallic selenide active material is densely attached to the carbon fiber surface, showing a granular morphology and pore formation. Compared with Example 1, both the particles and pores are enlarged to a certain extent.

[0068] Figure 8 The figure shows the CV (cyclic voltammetry) curves of the self-supported zinc iron selenide (Zn-Fe-Se) electrode material prepared in Example 3 with a zinc-iron feed ratio of 1:2, under different scan rates and with 6M KOH as the electrolyte. The figure shows the CV curves at different scan rates (5 / 10 / 20 / 50 / 100 mV·s). -1 The CV curves show obvious redox peaks, indicating that the electrochemical energy storage behavior of the self-supported iron-zinc bimetallic selenide (Zn-Fe-Se) is dominated by pseudocapacitance, accompanied by a small amount of double-layer capacitance. This is because when a voltage is applied across the electrode, ions in the solution inevitably move in a directional manner and are adsorbed onto the electrode surface to form a double layer.

[0069] Figure 9 The figure shows the GCD (Gas Constant Current Charge-Discharge) curves of the self-supported zinc-iron selenide (Zn-Fe-Se) electrode material prepared in Example 3 with a zinc-iron feed ratio of 1:2 under different current densities and with 6M KOH as the electrolyte. The figure shows the GCD curves (Gas Constant Current Charge-Discharge) curves of the self-supported zinc-iron selenide (Zn-Fe-Se) electrode material prepared in Example 3 with a zinc-iron feed ratio of 1:2 under different current densities (2 / 3 / 4 / 5 / 10 mA·cm). -2 The GCD curve deviates from the isosceles triangle under these conditions, indicating a significant redox reaction, which is typical of Faraday pseudocapacitance characteristics, consistent with the CV test results. This electrode material exhibits performance at 2 mA·cm⁻¹. -2 It exhibits a current density of 1494.58 mF·cm⁻¹. -2 The area-to-capacitance ratio decreases with increasing current density, especially at 10 mA·cm². -2 It maintained 618.34 mF·cm at high current densities.-2 The area-to-capacitance ratio and electrochemical performance are superior to those of Examples 1 and 2.

[0070] Comparative Example 1

[0071] The preparation method of the self-supporting iron-zinc bimetallic selenide (Zn-Fe-Se) electrode material in Comparative Example 1 is the same as that in Example 1, except that the deposition voltage is 6V, and the self-supporting iron selenide (Fe-Se) electrode material is obtained.

[0072] Figure 10 The image shows a scanning electron microscope (SEM) image of the self-supporting zinc-iron selenide (Zn-Fe-Se) electrode material prepared in this embodiment with a zinc-iron feed ratio of 2:1 and a deposition voltage of 6V. The scale bar is 5μm and the average fiber diameter is 8.6μm. Compared with the coating prepared with a deposition voltage of 3V, the zinc-iron bimetallic selenide (Zn-Fe-Se) active material exhibits severe agglomeration and uneven distribution on the carbon fiber surface, with some areas exposed above the carbon fiber substrate. This may result in some "dead" volumes in electrochemical energy storage applications, which would be detrimental to charge storage.

[0073] Comparative Example 2

[0074] The preparation method of the self-supporting iron-zinc bimetallic selenide (Zn-Fe-Se) electrode material in Comparative Example 2 is the same as that in Example 1, except that the deposition voltage is 9V, and the self-supporting iron selenide (Fe-Se) electrode material is obtained.

[0075] Figure 11 The image shows a scanning electron microscope (SEM) image of the self-supporting zinc-iron selenide (Zn-Fe-Se) electrode material prepared in this embodiment with a zinc-iron feed ratio of 2:1 and a deposition voltage of 9V. The scale bar is 5μm, and the average fiber diameter is 9.1μm. Compared with the material prepared with a deposition voltage of 3V, the zinc-iron bimetallic selenide (Zn-Fe-Se) active material exhibits agglomeration, but the size of the agglomerates is reduced. At the same time, there are areas with loose coating, exposing the carbon fiber surface. Agglomeration is due to the larger electrodeposition nuclei under high voltage, and the severe hydrogen evolution reaction accompanied by high voltage, which leads to a loose coating. These are all unfavorable for charge storage.

[0076] Comparative Example 3

[0077] The preparation method of the self-supporting iron metal selenide (Fe-Se) electrode material is the same as that in Example 1, except that in the metal co-deposition process, the electrolyte contains only ferrous ions in a molar ratio of 0:1 (0.1M iron ions).

[0078] Figure 12The image shows a scanning electron microscope image of a self-supporting iron selenide (Fe-Se) electrode material prepared with a zinc-iron feed ratio of 0:1. The scale bar is 5 μm and the average fiber diameter is 6.2 μm. The iron selenide active material is exposed on the carbon fiber substrate surface in many places. This is because the hydrogen evolution reaction is severe during the electrodeposition process, resulting in a loose bond between the active material and the carbon fiber surface.

[0079] Figure 13 The figure shows the CV (cyclic voltammetry) curves of a self-supporting iron selenide (Fe-Se) electrode material prepared with a zinc-iron feed ratio of 0:1 at different current densities, using 6M KOH as the electrolyte. The figures are displayed at different scan rates (5 / 10 / 20 / 50 / 100 mV·s). -1 The CV curve also shows obvious redox peaks, indicating that the electrochemical energy storage behavior of self-supporting iron selenide (Zn-Fe-Se) is mainly pseudocapacitive, accompanied by a small amount of double-layer capacitance. This is because when a voltage is applied across the electrode, ions in the solution inevitably move in a directional manner and adsorb onto the electrode surface to form a double layer, thus providing double-layer capacitance.

[0080] Figure 14 The figure shows the GCD (galvanostatic charge-discharge curve) of a self-supporting iron selenide (Fe-Se) electrode material prepared with a zinc-to-iron ratio of 0:1 under different current densities and with 6M KOH as the electrolyte. The figures are displayed at different current densities (2 / 3 / 4 / 5 / 10 mA·cm⁻¹). -2 The GCD curve deviates from the isosceles triangle under these conditions, indicating a significant redox reaction, which is typical of Faraday pseudocapacitance characteristics, consistent with the CV test results. This electrode material exhibits performance at 2 mA·cm⁻¹. -2 It exhibits a current density of 546.23 mF·cm⁻¹. -2 The area-to-capacitance ratio decreases with increasing current density, especially at 10 mA·cm². -2 It maintained 280.33 mF·cm at high current densities. -2 The area specific capacitance and electrochemical performance of the sample were much lower than those of Examples 1-3, which was due to the shedding of surface active material during the electrochemical performance test.

[0081] The embodiments described above provide a detailed explanation of the technical solutions of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, or similar substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a self-supporting iron-zinc bimetallic selenide electrode, characterized in that, Including the following steps: Step 1: Prepare an electrolyte solution by mixing iron salt and zinc salt, perform electrodeposition using a conductive substrate as the cathode and a graphite sheet or metal as the anode, and after deposition, remove the conductive substrate, clean and dry it to obtain an electrode loaded with zinc and iron; the molar ratio of zinc to iron in the zinc salt and iron salt is 2:1 to 1:3; the electrodeposition uses a deposition voltage of 2 to 5V and a deposition time of 5 to 30 minutes; Step 2: The zinc-iron loaded electrode and selenium powder are subjected to low-temperature selenization in a tube furnace. After the process, the zinc-iron loaded electrode is washed with alkali, water and ethanol in sequence and dried to obtain the self-supporting iron-zinc bimetallic selenide electrode. The low-temperature selenization is carried out at 50~450℃ for 5~7 hours.

2. The method for preparing a self-supporting iron-zinc bimetallic selenide electrode according to claim 1, characterized in that, The zinc salt includes any one of zinc chloride, zinc sulfate, zinc nitrate and their hydrates; The iron salt includes any one of ferrous chloride, ferrous sulfate, ferric nitrate, and their hydrates.

3. The method for preparing a self-supporting iron-zinc bimetallic selenide electrode according to claim 1, characterized in that, The concentrations of iron salt and zinc salt in the electrolyte are each 0.01~0.1 mol / L.

4. The method for preparing a self-supporting iron-zinc bimetallic selenide electrode according to claim 1, characterized in that, The conductive substrate is carbon fiber cloth.

5. The method for preparing a self-supporting iron-zinc bimetallic selenide electrode according to claim 1, characterized in that, In step 2, the total molar ratio of selenium powder to zinc and iron in the electrolyte is greater than 2:

1.

6. The method for preparing a self-supporting iron-zinc bimetallic selenide electrode according to claim 1, characterized in that, The low-temperature selenization includes two stages: the first stage is to raise the temperature from 50°C to 350~450°C, and the time required for the temperature rise is 120~175 min; the second stage is to maintain the temperature at 350~450°C for 180~240 min.

7. A self-supporting iron-zinc bimetallic selenide electrode prepared by the preparation method according to any one of claims 1 to 6.

8. A supercapacitor, characterized in that, Includes the self-supporting iron-zinc bimetallic selenide electrode as described in claim 7.

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