A ruthenium dioxide fiber supported on cobalt tetroxide, its preparation method and application

Abstract

The present invention discloses a cobalt tetroxide supported ruthenium dioxide fiber, its preparation method and application, which relate to the technical field of electrolytic water. In the present invention, calcium alginate fiber is prepared by wet spinning of sodium alginate and calcium chloride, and then the calcium alginate fiber is successively reacted with hydrochloric acid and cobalt chloride and then calcined to obtain cobalt tetroxide fiber, and then it is reacted with ruthenium trichloride and carbonized to obtain cobalt tetroxide supported ruthenium dioxide fiber. The present invention utilizes the electron transfer from Co<subgt;3< / subgt;O<subgt;4< / subgt> to RuO<subgt;2< / subgt>, which reduces the valence state of ruthenium, can not only inhibit the dissolution of high-valent ruthenium during the acidic OER process, thereby improving the OER activity in acidic media, but also improve the stability. Specifically, in a 0.1 M HClO<subgt;4 electrolyte and at a current density of 10 mA / cm<supgt;2, the overpotential is 220 mV and the voltage remains basically unchanged after continuous testing for 100 h.

Description

Technical Field

[0001] The present invention relates to the technical field of electrolyzed water, and particularly to a ruthenium dioxide-loaded cobalt tetroxide fiber, a preparation method thereof, and an application thereof. Background Art

[0002] Hydrogen is regarded as an ideal energy carrier due to its advantages of being clean, pollution-free, efficient, and storable. Hydrogen production by electrolyzing water is currently the most efficient and convenient method for producing hydrogen. According to the types of electrolytes and transfer ions, electrolyzed water is divided into alkaline electrolyzed water, proton exchange membrane electrolyzed water, and solid oxide electrolyzed water. Among them, although the alkaline electrolyzed water technology is mature, the use of alkaline electrolytes will cause corrosion, and the generated gas contains alkali mist that needs to be purified. In addition, the use of porous diaphragms also limits the working current density and electrolysis efficiency. Although solid oxide electrolyzed water can avoid the use of precious metals, the durability problems of ceramic materials at high temperatures and during long-term operation limit its application. Proton exchange membrane electrolyzed water has the advantages of low ohmic resistance, high current density, and good compatibility with sustainable energy, and is considered to be the most promising electrolyzed water method at present.

[0003] Currently, due to the lack of effective and stable electrocatalysts, the development of proton exchange membrane electrolyzed water is restricted by the anodic oxygen evolution reaction (OER). For example, noble metal ruthenium-based materials, as commonly used electrocatalysts, have unsatisfactory stability and will form soluble substances such as RuO4 during the acidic OER process, resulting in performance degradation. At the same time, the content of Ru noble metal in noble metal ruthenium-based materials usually exceeds 80 wt%, and Ru has a high cost and scarce resources. Therefore, developing high-performance and high-stability catalysts for proton exchange membrane electrolyzed water is currently a research and development hotspot.

[0004] In the prior art, "Preparation of RuO2 / Co3O4@NC Composite Material and Its Electrocatalytic Performance for Overall Water Splitting" (Li Xiao et al., Acta Compositae Sinica, December 2024) discloses that ZIF-L-Co is first calcined in an inert gas to obtain Co3O4 coated with a graphite carbon layer, that is, Co@CN, and then an RuCl3 solution is dropped onto the surface of Co@CN and calcined in air, so that RuO2 is loaded on the surface of Co3O4@NC nanoparticles to obtain an RuO2 / Co3O4@NC composite material. Although the prepared composite material has good OER and HER catalytic activities under alkaline medium conditions, its inner core Co3O4 will adjust the electronic structure of the surface RuO2 to make it in a high valence state, and the increase in the Ru valence state will bring the problem of poor stability. In addition, when it is used for the OER process in a strong acidic medium, the high-valence Ru is extremely easy to react with H + to generate soluble Ru ions, resulting in the loss of active components and further causing irreversible attenuation of OER activity.

[0005] Therefore, it is particularly necessary to develop electrocatalysts with high performance and high stability to improve their OER activity and stability when used in proton exchange membrane water electrolysis. Summary of the Invention

[0006] In view of the above-mentioned prior art, the object of the present invention is to provide a ruthenium dioxide fiber supported on cobalt tetroxide, its preparation method and application. The present invention uses sodium alginate and calcium chloride to prepare calcium alginate fibers by wet spinning, and then the calcium alginate fibers are successively reacted with hydrochloric acid and cobalt chloride and then calcined to obtain cobalt tetroxide fibers, and then reacted with ruthenium trichloride and carbonized to obtain ruthenium dioxide fibers supported on cobalt tetroxide. The present invention utilizes the electron transfer from Co3O4 to RuO2, resulting in the reduction of the valence state of ruthenium, which can not only inhibit the dissolution of high-valent ruthenium during the acidic OER process, thereby improving the OER activity in acidic media, but also improve the stability. Specifically, in a 0.1 M HClO4 electrolyte and a current density of 10 mA / cm 2 the overpotential is 220 mV, and the voltage remains basically unchanged after continuous testing for 100 h.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] In the first aspect of the present invention, a preparation method of a ruthenium dioxide fiber supported on cobalt tetroxide is provided, including the following steps:

[0009] (1) Using sodium alginate and calcium chloride solutions as raw materials, wet spinning is carried out to obtain calcium alginate fibers; the calcium alginate fibers are mixed with hydrochloric acid and reacted to obtain hydrogen alginate fibers; the hydrogen alginate fibers are mixed and reacted with cobalt chloride solution to obtain cobalt alginate fibers; the cobalt alginate fibers are calcined to obtain cobalt tetroxide fibers;

[0010] (2) The cobalt tetroxide fibers and ruthenium trichloride solution are mixed for hydrothermal reaction to obtain cobalt tetroxide fibers loaded with ruthenium precursors; the cobalt tetroxide fibers loaded with ruthenium precursors are carbonized to obtain ruthenium dioxide fibers supported on cobalt tetroxide.

[0011] Preferably, in step (1), the mass fraction of the sodium alginate solution is 0.8%-1.2%; the mass fraction of the calcium chloride solution is 3.5%-4.5%.

[0012] Preferably, in step (1), the specific steps of wet spinning are: the sodium alginate solution is extruded through a spinneret and enters a coagulation bath containing calcium chloride solution for solidification and molding to obtain nascent fibers; the nascent fibers are washed with water, stretched and dried to obtain calcium alginate fibers.

[0013] Furthermore, the residence time of the sodium alginate solution in the coagulation bath after extrusion through the spinneret is 15 - 25 s, and the temperature of the coagulation bath is 25 - 35 °C; the linear velocity of the sodium alginate solution after extrusion through the spinneret is 10 - 15 m / min; the draw ratio is 0.90 - 0.92%.

[0014] Preferably, in step (1), the concentration of hydrochloric acid is 0.8 - 1.2 mol / L.

[0015] Preferably, in step (1), the addition ratio of calcium alginate fiber, hydrochloric acid, and cobalt chloride in the cobalt chloride solution is (0.8 - 1.2) g : 100 mL : 500 mg.

[0016] Preferably, in step (1), the cobalt chloride solution is prepared by mixing cobalt chloride, water, and ethanol at a material liquid ratio of (450 - 550) mg : 50 mL : 50 mL.

[0017] Preferably, in step (1), the reaction time between calcium alginate fiber and hydrochloric acid is 150 - 200 min; the reaction time between calcium hydrogen alginate fiber and cobalt chloride solution is 250 - 350 min.

[0018] Preferably, in step (1), the specific calcination operation is as follows: Place the cobalt alginate fiber in an air atmosphere and heat it to 450 - 550 °C at a heating rate of 1 - 3 °C / min, then keep it calcined for 1.5 - 2.5 h.

[0019] Preferably, in step (2), the mass fraction of the ruthenium trichloride solution is 0.08% - 0.10%.

[0020] Preferably, in step (2), the addition amount of cobalt tetroxide fiber and ruthenium trichloride solution is (0.08 - 0.12) g : 50 mL.

[0021] Preferably, in step (2), the hydrothermal reaction temperature is 110 - 130 °C, and the hydrothermal reaction time is 2.5 - 3.5 h.

[0022] Preferably, in step (2), the specific carbonization operation is as follows: Place the cobalt tetroxide fiber loaded with ruthenium precursor in an air atmosphere, heat it to 250 - 350 °C at a heating rate of 3 - 6 °C / min, and keep it heat - treated for 2.5 - 3.5 h to obtain cobalt tetroxide - supported ruthenium dioxide fiber.

[0023] In the second aspect of the present invention, cobalt tetroxide - supported ruthenium dioxide fiber prepared by the above - mentioned preparation method is provided.

[0024] In the third aspect of the present invention, the application of the above - mentioned cobalt tetroxide - supported ruthenium dioxide fiber in electrolyzing water or seawater in an acidic medium is provided.

[0025] Preferably, the acidic medium is a HClO4 solution with a concentration of 0.05 - 0.15 M.

[0026] Advantages of the present invention:

[0027] 1. In the present invention, sodium alginate solution and calcium chloride solution are subjected to wet spinning to obtain calcium alginate fibers. Then, the calcium alginate fibers are reacted with hydrochloric acid and cobalt chloride solution in sequence to obtain cobalt alginate fibers. The cobalt alginate fibers are calcined to obtain cobalt ferrite fibers; the cobalt ferrite fibers and ruthenium trichloride solution are subjected to hydrothermal reaction and then carbonized to obtain ruthenium dioxide supported on cobalt ferrite fibers. The ruthenium dioxide supported on cobalt ferrite fibers prepared in the present invention has high catalytic activity and good stability as an electrocatalyst. Specifically, its overpotential at a current density of 10 mA / cm² in 0.1 M HClO4 electrolyte is 220 mV, and after testing in 0.1 M HClO4 electrolyte for 100 h, its voltage remains basically unchanged, showing excellent catalytic stability. 2 The overpotential at a current density of 10 mA / cm² in 0.1 M HClO4 electrolyte is 220 mV, and after testing in 0.1 M HClO4 electrolyte for 100 h, its voltage remains basically unchanged, showing excellent catalytic stability.

[0028] 2. For the ruthenium dioxide supported on cobalt ferrite fibers prepared in the present invention, cobalt ferrite serves as an electron donor, transferring electrons from Co to Ru, which reduces the oxidation state of Ru. This electron transfer changes the local electronic structure of Ru, thereby reducing the valence state of Ru and making it exist in a stable medium or low valence state. At the same time, by reducing the valence state of Ru, the dissolution of high-valent ruthenium during the acidic OER process is inhibited.

[0029] Therefore, in the present invention, the valence state of Ru is reduced by the electron donor action of Co3O4, effectively inhibiting the generation and dissolution of high-valent Ru during the acidic OER process. This mechanism not only improves the stability of the catalyst but also enhances its intrinsic catalytic activity by optimizing the electronic state of Ru, thus achieving efficient and durable OER performance in acidic media.

[0030] 3. The ruthenium dioxide supported on cobalt ferrite fibers prepared in the present invention has an obvious one-dimensional structure and abundant pores. This structure increases the contact area between the ruthenium dioxide supported on cobalt ferrite fiber catalyst and the electrolyte, promoting the transport of the electrolyte and the release of O2.

[0031] 4. Using sodium alginate as a raw material, it has a wide source, is environmentally friendly, safe, and is a huge renewable resource, making it an ideal raw material for preparing hollow fiber materials. The method of the present invention can be used to prepare a large amount of ruthenium dioxide supported on cobalt ferrite fibers without expensive equipment and can be widely used in the electrolysis of seawater. Description of the Drawings

[0032] Figure 1: SEM images of ruthenium dioxide - loaded cobalt tetroxide fibers prepared in Example 1; among them, (a) is the SEM image at a scale of 4 μm, and (b) is the SEM image at a scale of 10 μm;

[0033] Figure 2 : XRD pattern of ruthenium dioxide - loaded cobalt tetroxide fibers prepared in Example 1;

[0034] Figure 3 : Transmission electron microscope image of ruthenium dioxide - loaded cobalt tetroxide fibers prepared in Example 1;

[0035] Figure 4 : Energy spectrum diagram of ruthenium dioxide - loaded cobalt tetroxide fibers prepared in Example 1;

[0036] Figure 5 : OER performance diagrams of different electrocatalysts in acidic electrolyte in Test Example 1;

[0037] Figure 6 : OER stability diagrams of different electrocatalysts in acidic electrolyte in Test Example 1;

[0038] Figure 7 : Performance diagrams of ruthenium dioxide - loaded cobalt tetroxide fibers in acidic electrolytic simulated seawater in Test Example 2;

[0039] Figure 8 : Performance diagrams of ruthenium dioxide - loaded cobalt tetroxide fibers in acidic electrolytic seawater in Test Example 2. Detailed implementation manners

[0040] It should be noted that the following detailed descriptions are all illustrative and are intended to provide further explanations for this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs.

[0041] Currently, proton - exchange membrane electrolysis of water is considered the most promising method for water electrolysis at present due to its advantages such as low ohmic resistance, high current density, and good compatibility with sustainable energy. However, since a strong acidic medium is required for proton - exchange membrane electrolysis of water, developing an electrocatalyst with high OER activity and high stability for proton - exchange membrane electrolysis of water is a current research hotspot.

[0042] Although the prior art discloses that RuO2 / Co3O4@NC composites can be used as electrocatalysts for water electrolysis, in the above - mentioned electrocatalysts, the inner - core Co3O4 will adjust the electronic structure of the surface RuO2 to make it in a high - valence state, and the increase in the Ru valence state will lead to the problem of poor stability. In addition, when it is used in a strong acidic medium for the OER process, the high - valence Ru is extremely easy to react with H +The reaction generates soluble Ru ions, resulting in the loss of active components and then causing irreversible decay of the OER activity. In addition, the above electrocatalyst is applicable to water electrolysis in an alkaline medium.

[0043] For the electrode reactions occurring in acidic medium water electrolysis and alkaline medium water electrolysis, the roles played by the electrocatalyst are completely different, and the electrocatalysts used for water electrolysis in alkaline medium and acidic medium usually cannot be directly transferred. Specifically,

[0044] [[ID=⑥]]During alkaline medium water electrolysis, after the electrolytic cell is powered on, the positive electrode gains electrons, releases hydrogen, and generates hydroxide ions (OH - ), and the 0H - ions migrate from the positive electrode to the negative electrode through the electrolyte, release electrons at the negative electrode, and generate oxygen and water.

[0045] The electrolysis reaction is as follows:

[0046] Positive electrode reaction: 2H2O + 4e - →2H2 + 4OH - ; In this process, the catalyst needs to have both water dissociation and H adsorption;

[0047] Negative electrode reaction: 4OH - →O2 + H2O + 4e - ; In this process, the catalyst is used to optimize the OH⁻ adsorption and deprotonation processes.

[0048] During acidic medium water electrolysis, protons (H + ) are generated from water at the positive electrode, oxygen and electrons are released, and the protons reach the negative electrode through the proton exchange membrane from the positive electrode and become hydrogen after obtaining electrons at the negative electrode.

[0049] The electrolysis reaction is as follows:

[0050] Positive electrode reaction: 2H2O → 4H + + 4e - + O2; In this process, the catalyst is used for surface promoting H2O dissociation and O - O bond formation;

[0051] Negative electrode reaction: 4H + + 4e - →2H2; In this process, the catalyst needs to efficiently adsorb H⁺ and promote H - H bond binding.

[0052] Based on this, the present invention provides an electrocatalyst for water electrolysis in a strong acidic medium - ruthenium dioxide - loaded cobalt ferrite fibers. The present invention uses sodium alginate and calcium chloride to prepare calcium alginate fibers by wet spinning, then reacts the calcium alginate fibers with hydrochloric acid and cobalt chloride in sequence and calcines them to obtain cobalt ferrite fibers, and then reacts them with ruthenium trichloride and carbonizes them to obtain ruthenium dioxide - loaded cobalt ferrite fibers.

[0053] During the acidic OER process, the surface of Ru-based catalysts (such as RuO2) will be further oxidized to Ru in higher valence states (such as +5 and +6) at high potentials. These Ru species in higher valence states are prone to dissolve into the electrolyte in a strong acidic environment (such as H2SO4 or HClO4 electrolyte), resulting in irreversible loss of the active sites of the catalyst, thus leading to poor stability and low activity of the catalyst. In the present invention, cobalt tetroxide is used as an electron donor, and electrons are transferred from Co to Ru to reduce the oxidation state of Ru. Through this electron transfer, the local electronic structure of Ru is changed, and it exists in stable intermediate and lower valence states. Thereby, the prepared ruthenium dioxide supported on cobalt tetroxide not only improves the stability of the catalyst, but also enhances its intrinsic catalytic activity by optimizing the electronic state of Ru, thus achieving efficient and durable OER performance in acidic media.

[0054] In addition, the prepared ruthenium dioxide supported on cobalt tetroxide fibers has an obvious one-dimensional structure and abundant pores. This structure increases the contact area between the ruthenium dioxide supported on cobalt tetroxide fiber catalyst and the electrolyte, and promotes the transport of the electrolyte and the release of O2.

[0055] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0056] The experimental materials used in the embodiments of the present invention are all conventional experimental materials in the art and can be obtained through commercial channels.

[0057] Example 1: Ruthenium dioxide supported on cobalt tetroxide fibers

[0058] (1) After extruding a sodium alginate solution with a mass fraction of 1.0% through a spinneret, it enters a coagulation bath containing calcium chloride solution at a temperature of 30 °C and stays for 20 s to solidify and form a primary fiber; after washing the primary fiber with deionized water, it is stretched and dried to obtain a calcium alginate fiber; wherein, the mass fraction of the calcium chloride solution is 4%, the linear velocity after extrusion is 12 m / min, and the draw ratio is 0.91%;

[0059] Mix cobalt chloride, deionized water and ethanol according to a liquid ratio of 500 mg: 50 mL: 50 mL to obtain a cobalt chloride solution; after mixing the calcium alginate fiber with hydrochloric acid with a concentration of 1 mol / L, react under ultrasonic treatment for 180 min, wash with water and then dry to obtain a hydrogen alginate fiber; after mixing the hydrogen alginate fiber with the cobalt chloride solution, react under ultrasonic treatment for 300 min, wash with water and then dry to obtain a cobalt alginate fiber; wherein, the addition amount of cobalt chloride in the calcium alginate fiber, hydrochloric acid and cobalt chloride solution is 1 g: 100 mL: 500 mg;

[0060] Place cobalt alginate fibers in a tubular furnace. Under an air atmosphere, heat them at a heating rate of 2 °C / min to 500 °C and keep them calcined for 2 h to obtain cobalt cobaltite fibers;

[0061] (2) Mix cobalt cobaltite fibers with a ruthenium trichloride solution with a mass fraction of 0.08% at a material-liquid ratio of 0.1 g:50 mL, and then carry out a hydrothermal reaction at 120 °C for 3 h. After washing and drying, obtain cobalt cobaltite fibers loaded with ruthenium precursors;

[0062] Place the cobalt cobaltite fibers loaded with ruthenium precursors in a tubular furnace. Under an air atmosphere, heat them at a heating rate of 5 °C / min to 300 °C and keep them treated for 3 h to obtain cobalt cobaltite fibers loaded with ruthenium dioxide.

[0063] Perform structural characterization on the cobalt cobaltite fibers loaded with ruthenium dioxide prepared in this example, and the results are as Figures 1-4 shown.

[0064] Through Figure 1 it can be seen that the diameter of the cobalt cobaltite fibers loaded with ruthenium dioxide prepared in this example is about 12 μm and has obvious one-dimensional structures and abundant pores. From Figure 2 it can be seen that the XRD pattern of the cobalt cobaltite fibers loaded with ruthenium dioxide prepared in this example contains Co3O4 (PDF#97-003-6256). Since the Ru content in the cobalt cobaltite fibers loaded with ruthenium dioxide is very small, there is no peak related to Ru in the XRD pattern. Through Figure 3 the HRTEM image can prove that the prepared cobalt cobaltite fibers loaded with ruthenium dioxide contain RuO2. Through Figure 4 it can be seen that electrons are transferred from Co to Ru, effectively inhibiting the generation and dissolution of high-valent Ru during the acidic OER process. This mechanism not only improves the stability of the catalyst, but also enhances its intrinsic catalytic activity by optimizing the electronic state of Ru, thus achieving efficient and durable OER performance in acidic media.

[0065] Example 2: Cobalt cobaltite fibers loaded with ruthenium dioxide

[0066] (1) Extrude a sodium alginate solution with a mass fraction of 0.8% through a spinneret and enter a coagulation bath containing calcium chloride solution at a temperature of 25 °C and stay for 15 s to solidify and form, obtaining primary fibers; after washing the primary fibers with deionized water, carry out stretching and drying to obtain calcium alginate fibers; among them, the mass fraction of the calcium chloride solution is 3.5%, the linear velocity after extrusion is 10 m / min, and the draw ratio is 0.90%;

[0067] Mix cobalt chloride, deionized water, and ethanol according to a material-liquid ratio of 450 mg: 50 mL: 50 mL to obtain a cobalt chloride solution; mix calcium alginate fiber with hydrochloric acid at a concentration of 0.8 mol / L, react under ultrasonic treatment for 150 min, wash with water and dry to obtain hydrogen alginate fiber; mix hydrogen alginate fiber with the cobalt chloride solution, react under ultrasonic treatment for 250 min, wash with water and dry to obtain cobalt alginate fiber; wherein, the addition amounts of calcium alginate fiber, hydrochloric acid, and cobalt chloride in the cobalt chloride solution are 0.8 g: 100 mL: 500 mg;

[0068] Place the cobalt alginate fiber in a tubular furnace, under an air atmosphere, heat it to 450 °C at a heating rate of 1 °C / min, and keep it calcined for 2.5 h to obtain cobalt tetroxide fiber;

[0069] (2) Mix the cobalt tetroxide fiber and ruthenium trichloride solution with a mass fraction of 0.05% according to a material-liquid ratio of 0.08 g: 50 mL, carry out a hydrothermal reaction at 110 °C for 3.5 h, wash and dry to obtain a cobalt tetroxide fiber supported ruthenium precursor;

[0070] Place the cobalt tetroxide fiber supported ruthenium precursor in a tubular furnace, under an air atmosphere, heat it to 250 °C at a heating rate of 3 °C / min, and keep it treated for 3.5 h to obtain a cobalt tetroxide supported ruthenium dioxide fiber.

[0071] Example 3: Cobalt tetroxide supported ruthenium dioxide fiber

[0072] (1) Extrude the sodium alginate solution with a mass fraction of 1.2% through a spinneret, enter a coagulation bath containing calcium chloride solution at a temperature of 35 °C and stay for 25 s to solidify and form a primary fiber; wash the primary fiber with deionized water, stretch and dry to obtain calcium alginate fiber; wherein, the mass fraction of the calcium chloride solution is 4.5%, the linear velocity after extrusion is 15 m / min, and the draw ratio is 0.92%;

[0073] Mix cobalt chloride, deionized water, and ethanol according to a material-liquid ratio of 550 mg: 50 mL: 50 mL to obtain a cobalt chloride solution; mix calcium alginate fiber with hydrochloric acid at a concentration of 1.2 mol / L, react under ultrasonic treatment for 200 min, wash with water and dry to obtain hydrogen alginate fiber; mix hydrogen alginate fiber with the cobalt chloride solution, react under ultrasonic treatment for 350 min, wash with water and dry to obtain cobalt alginate fiber; wherein, the addition amounts of calcium alginate fiber, hydrochloric acid, and cobalt chloride in the cobalt chloride solution are 1.2 g: 100 mL: 500 mg;

[0074] Place the cobalt alginate fiber in a tubular furnace, under an air atmosphere, heat it to 550 °C at a heating rate of 3 °C / min, and keep it calcined for 1.5 h to obtain cobalt tetroxide fiber;

[0075] (2) Mix cobalt cobaltite fibers with a ruthenium(III) chloride solution with a mass fraction of 0.10% at a material ratio of 0.12 g:50 mL, then carry out hydrothermal reaction at 130 °C for 2.5 h. After washing and drying, ruthenium precursor-supported cobalt cobaltite fibers are obtained.

[0076] Place the ruthenium precursor-supported cobalt cobaltite fibers in a tube furnace. Under an air atmosphere, heat them to 350 °C at a heating rate of 6 °C / min, and keep them at this temperature for 2.5 h to obtain cobalt cobaltite-supported ruthenium dioxide fibers.

[0077] Comparative Example 1: Ruthenium dioxide electrocatalyst

[0078] Place a ruthenium(III) chloride solution with a mass fraction of 0.08% in a tube furnace. Under an air atmosphere, heat it to 300 °C at a heating rate of 5 °C / min, and keep it at this temperature for 3 h to obtain a ruthenium dioxide electrocatalyst.

[0079] Comparative Example 2: Cobalt cobaltite fiber electrocatalyst

[0080] Extrude a sodium alginate solution with a mass fraction of 1.0% through a spinneret and then enter a coagulation bath containing calcium chloride solution at 30 °C and stay for 20 s to solidify and form primary fibers. Wash the primary fibers with deionized water, then stretch and dry them to obtain calcium alginate fibers. Among them, the mass fraction of the calcium chloride solution is 4%, the linear velocity after extrusion is 12 m / min, and the draw ratio is 0.91%.

[0081] Mix cobalt chloride, deionized water and ethanol at a material ratio of 500 mg:50 mL:50 mL to obtain a cobalt chloride solution. Mix the calcium alginate fibers with hydrochloric acid with a concentration of 1 mol / L, and react under ultrasonic treatment for 180 min. After washing with water and drying, hydrogen alginate fibers are obtained. Mix the hydrogen alginate fibers with the cobalt chloride solution, and react under ultrasonic treatment for 300 min. After washing with water and drying, cobalt alginate fibers are obtained. Among them, the addition amounts of cobalt chloride in the calcium alginate fibers, hydrochloric acid and cobalt chloride solution are 1 g:100 mL:500 mg.

[0082] Place the cobalt alginate fibers in a tube furnace. Under an air atmosphere, heat them to 500 °C at a heating rate of 2 °C / min, and keep them calcined at this temperature for 2 h to obtain a cobalt cobaltite fiber electrocatalyst.

[0083] Test Example 1: Electrochemical performance test

[0084] Detect the electrochemical performances of the materials prepared in Example 1, Comparative Examples 1-2 and commercial RuO2. The specific steps are as follows:

[0085] Weigh 3 mg of the catalysts prepared in Example 1 and Comparative Examples 1-2 separately, disperse them in 330 μL of Nafion / ethanol mixed solution, and ultrasonically treat for 30 min to obtain a catalyst suspension; polish and grind the glassy carbon electrode and dry it naturally. Take 8 μL of the catalyst suspension and drop it onto a glassy carbon electrode with an area of 0.196 cm² and dry it at room temperature;

[0086] Place the prepared catalyst in a standard three-electrode system to test its electrochemical performance. Among them, the electrolyte is 0.1 M HClO4, a platinum wire, a glassy carbon electrode, and a standard hydrogen electrode are used as the counter electrode, working electrode, and reference electrode respectively. The OER activity of the catalyst is tested by the LSV method, and the results are as Figure 5 shown. Among them, the scanning rate of the LSV polarization curve is 5 mV / s, and the loading amount of the catalyst is 0.417 mg / cm²; then, the stability of the ruthenium dioxide-coated cobalt tetroxide fiber prepared in Example 1 as a catalyst is tested by a 100 h v-t test, and the results are as Figure 6 shown; during the test process, for the OER performance detection, the potential range is above 1.1 V vs RHE, and the LSV scanning direction is positive.

[0087] It can be seen from Figure 5 that in 0.1 M HClO4 electrolyte at a current density of 10 mA / cm 2 the overpotential of the ruthenium dioxide-coated cobalt tetroxide fiber prepared by the present invention is 220 mV. The overpotential of the reference catalyst commercial RuO2 is 320 mV, and the overpotential of the cobalt tetroxide fiber prepared in Comparative Example 2 is 400 mV. Thus, it can be seen that the ruthenium dioxide-coated cobalt tetroxide fiber prepared by the present invention has good OER activity as a catalyst.

[0088] It can be seen from Figure 6 that after testing the ruthenium dioxide-coated cobalt tetroxide fiber prepared by the present invention in 0.1 M HClO4 electrolyte for 100 h, its voltage remains basically unchanged. Thus, it can be seen that the ruthenium dioxide-coated cobalt tetroxide fiber has excellent catalytic stability.

[0089] Test Example 2: Water electrolysis test

[0090] Detect the water electrolysis performance of the ruthenium dioxide-coated cobalt tetroxide electrocatalyst prepared in Example 1. The specific steps are as follows:

[0091] The OER performance of the electrolyzed simulated seawater and seawater for preparing the catalyst in Experimental Example 1 was tested in a three-electrode system, and the electrolytes were simulated seawater and seawater respectively. Among them, the simulated seawater was prepared by mixing 0.01 M HClO4 and 0.58 M NaCl in a volume ratio of 2:1; the seawater was prepared by mixing 0.01 M HClO4 and natural seawater in a volume ratio of 1:1.

[0092] A platinum wire, a glassy carbon electrode, and a standard hydrogen electrode were used as the counter electrode, working electrode, and reference electrode respectively, and the LSV method was used to test the OER activity of the catalyst. Among them, the scanning rate of the LSV polarization curve was 5 mV / s, and the loading amount of the catalyst was 0.417 mg / cm². During the test process, for the OER performance detection, the potential range was above 1.1 V vs RHE, and the LSV scanning direction was positive. The detection results are as Figures 7-8 shown.

[0093] It can be seen from Figure 7 that the voltage of the ruthenium dioxide fiber supported cobalt ferrite electrolyzing simulated seawater in this example at a current density of 10 mA / cm 2 was 1.43 V. It can be seen from Figure 8 that the voltage of the ruthenium dioxide fiber supported cobalt ferrite electrolyzing seawater in this example at a current density of 10 mA / cm 2 was 1.44 V.

[0094] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. Application of ruthenium dioxide-loaded cobalt tetroxide fiber in electrolyzing water or seawater in acidic medium, characterized in that, The preparation method of the cobalt tetroxide supported ruthenium dioxide fiber is as follows: (1) Using sodium alginate and calcium chloride solution as raw materials, through wet spinning, calcium alginate fiber is obtained; after mixing the calcium alginate fiber with hydrochloric acid, a reaction is carried out to obtain hydrogen alginate fiber; after mixing the hydrogen alginate fiber with cobalt chloride solution, a reaction is carried out to obtain cobalt alginate fiber; the cobalt alginate fiber is calcined to obtain cobalt tetroxide fiber; (2) Mix the cobalt tetroxide fiber and ruthenium trichloride solution and carry out a hydrothermal reaction to obtain cobalt tetroxide fiber supported ruthenium precursor; Carry out carbonization treatment on the cobalt tetroxide fiber supported ruthenium precursor to obtain the cobalt tetroxide supported ruthenium dioxide fiber; When the cobalt tetroxide supported ruthenium dioxide fiber electrolyzes water or seawater in an acidic medium, the acidic medium is a 0.05 - 0.15M HClO4 solution.

2. The application according to claim 1, characterized in that In step (1), the mass fraction of the sodium alginate solution is 0.8% - 1.2%; the mass fraction of the calcium chloride solution is 3.5% - 4.5%, the concentration of hydrochloric acid is 0.8 - 1.2 mol / L, and the cobalt chloride solution is prepared by mixing cobalt chloride, water and ethanol according to the material ratio of (450 - 550) mg: 50 mL: 50 mL.

3. The application according to claim 1, characterized in that, The specific steps of wet spinning are as follows: extrude the sodium alginate solution through a spinneret and enter the coagulation bath containing calcium chloride solution for solidification and forming to obtain a nascent fiber; wash the nascent fiber with water, stretch and dry it to obtain calcium alginate fiber; The residence time of the sodium alginate solution in the coagulation bath after extrusion through the spinneret is 15 - 25 s, and the temperature of the coagulation bath is 25 - 35 °C; the linear velocity of the sodium alginate solution after extrusion through the spinneret is 10 - 15 m / min; the draw ratio is 0.90 - 0.92%.

4. The application according to claim 1, characterized in that In step (1), the addition ratio of calcium alginate fiber, hydrochloric acid and cobalt chloride in the cobalt chloride solution is (0.8 - 1.2) g: 100 mL: 500 mg; the reaction time of calcium alginate fiber and hydrochloric acid is 150 - 200 min, and the reaction time of hydrogen alginate fiber and cobalt chloride solution is 250 - 350 min.

5. The application according to claim 1, wherein In step (1), the specific operation of calcination is as follows: place the cobalt alginate fiber in an air atmosphere, heat it to 450 - 550 °C at a heating rate of 1 - 3 °C / min, and then keep it for calcination for 1.5 - 2.5 h.

6. The application according to claim 1, characterized in that, In step (2), the mass fraction of the ruthenium trichloride solution is 0.08% - 0.10%; the addition amount of cobalt tetroxide fiber and ruthenium trichloride solution is (0.08 - 0.12) g: 50 mL.

7. The application according to claim 1, characterized in that, In step (2), the hydrothermal reaction temperature is 110 - 130 °C, and the hydrothermal reaction time is 2.5 - 3.5 h; the specific operation of carbonization is as follows: place the cobalt tetroxide fiber supported ruthenium precursor in an air atmosphere, heat it to 250 - 350 °C at a heating rate of 3 - 6 °C / min, and keep it for treatment for 2.5 - 3.5 h.

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