Iron cobalt nickel chromium oxide nanomaterial, preparation method and application thereof

Abstract

The application discloses a preparation method, device and application of an iron-cobalt-nickel-chromium oxide catalyst. The preparation method of the iron-cobalt-nickel-chromium oxide material comprises the following steps: preparing an iron-cobalt-nickel layered hydroxide intermediate through electrodeposition under a certain current density condition, further passivating through a chromium nitrate solution and high-temperature treatment, and obtaining the iron-cobalt-nickel-chromium oxide catalyst material. The iron-cobalt-nickel-chromium oxide material can be applied to an electrocatalytic process as an anode catalyst and a cathode catalyst respectively, the Faraday efficiencies of anode oxygen evolution and cathode hydrogen evolution reactions can both reach and maintain above 90%, the device constructed by the application can maintain a stable cell voltage within 600 hours, and the high-efficiency effects of cathode hydrogen evolution and anode oxidation can be used in multiple fields such as removal of organic pollutants in water through anode oxidation and hydrogen production from seawater through cathodes, and have a relatively wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of new energy, specifically to an iron-cobalt-nickel-chromium oxide nanomaterial, its preparation method, and its application. Background Technology

[0002] Seawater resources are abundant and possess high ionic conductivity, eliminating the need for additional ions when used for hydrogen production via seawater electrolysis, thus saving costs. However, because the redox potential of the chlorine evolution reaction (chlorine: 1.36V) is close to that of the oxygen evolution reaction (1.23V vs RHE), the chlorine evolution reaction present in seawater can compete with the oxygen evolution reaction to produce chlorine gas, leading to corrosion of the anode and causing unstable operation of seawater electrolysis for hydrogen production. Therefore, using suitable spacer materials to limit the oxidation reaction of chloride ions at the anode is crucial for improving the direct seawater electrolysis hydrogen production. Currently, various spacer materials are available for use in direct seawater electrolysis hydrogen production. For example, a Chinese patent titled "A System and Method for Hydrogen Production from Seawater Using Alkali and Proton Exchange Membrane Hybridization" uses a proton exchange membrane to separate the anode and cathode liquids; a Chinese patent titled "A Direct Hydrogen Production Device with a Conductive Hydrophobic Membrane and a Method for Hydrogen Production from Seawater Using the Same" uses an integrated conductive hydrophobic membrane, combining seawater desalination and water electrolysis hydrogen production technologies; a Chinese patent titled "A PBI Proton Exchange Membrane Electrolysis Module and a Hydrogen Production Device for Hydrogen Production from Seawater Electrolysis" modularizes the anode and cathode catalysts and the membrane to achieve hydrogen production from seawater electrolysis, but the aforementioned spacer materials have not yet been applied on a large scale and are still in the laboratory research stage.

[0003] A bipolar membrane is a composite membrane of anions and cations. While preventing the passage of any ions, it enables highly efficient dissociation of water. As a spacer material, it effectively isolates the solutions in the cathode and anode chambers of seawater directly electrolyzed for hydrogen production, thereby eliminating the side reaction of chloride ions at the anode and improving the efficiency of seawater electrolysis. A properly designed bipolar membrane seawater electrolysis device, combined with asymmetric electrolyte feeding, can not only limit chloride ion diffusion to the anode but also provide an alkaline environment at the anode and an acidic environment at the cathode, inhibiting seawater precipitation in the cathode chamber and thus achieving stable hydrogen evolution. However, the rate of water dissociation in the bipolar membrane is much greater than the rate of water electrolysis. Therefore, excess hydrogen ions and hydroxide ions generated by water dissociation migrate to the cathode and anode chambers respectively, causing drastic pH changes in the anode and cathode solutions, which in turn affects the operational stability of the bipolar membrane seawater hydrogen production device.

[0004] Therefore, considering the synergistic effect of anode and cathode catalysts with bipolar membrane water dissociation, catalysts that can operate efficiently and stably over a wide pH range are more suitable for bipolar membrane seawater electrolysis devices. Currently, the catalysts used in bipolar membrane seawater electrolysis devices are mainly noble metal-based catalysts, with IrOx as the anode catalyst and Pt as the cathode catalyst. Noble metal-based catalysts suffer from high cost, low natural abundance, and poor stability. While non-noble metal catalysts have been reported in other seawater electrolysis hydrogen production systems, research on non-noble metal catalysts specifically for bipolar membrane seawater electrolysis hydrogen production devices is limited.

[0005] Iron-cobalt-nickel layered hydroxide materials exhibit excellent water electrolysis activity over a wide pH range, and their adaptability to a broad range of electrolytes makes them potential candidates for bipolar membranes. However, the activity of iron-cobalt-nickel layered hydroxides as cathode catalysts in seawater electrolysis for hydrogen production remains poor and requires further improvement.

[0006] The purpose of this invention is to propose a bipolar membrane-based seawater electrolysis hydrogen production device and to develop a novel bifunctional catalyst adapted to it for cathode hydrogen evolution and anode oxygen evolution. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the problems of easy precipitation and poor operational stability of the electrodes in seawater electrolysis. Based on the ion transport characteristics of bipolar membranes, the present invention provides a device for seawater electrolysis based on bipolar membranes and a method for preparing iron-cobalt-nickel-chromium oxide nanomaterials.

[0008] The iron-cobalt-nickel-chromium oxide nanomaterials are characterized by their adaptability to a wide pH range. The bipolar membrane completely prevents chloride ions from permeating into the anode chamber, and the hydrogen ions generated by water dissociation within the membrane inhibit the precipitation of calcium and magnesium ions in seawater. The synergistic effect of the iron-cobalt-nickel-chromium oxide nanomaterials and the bipolar membrane ensures stable operation of the seawater electrolysis hydrogen production process. Furthermore, the iron-cobalt-nickel-chromium oxide nanomaterials used in the seawater electrolysis device are prepared by electrodeposition and calcination methods, which are simple and efficient. The resulting material can efficiently generate oxygen under alkaline conditions and efficiently generate hydrogen in simulated seawater. It can adapt to pH changes in the electrolyte in the bipolar membrane-based seawater electrolysis device, thus achieving long-term stable operation of the reactor. In addition, since no precious metals are used, the cost is also lower.

[0009] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0010] A further object of the present invention is to provide a bipolar membrane-based seawater electrolysis device.

[0011] A further objective of this invention is to provide a method for preparing iron-cobalt-nickel-chromium oxide nanomaterials.

[0012] A further objective of this invention is to provide the application of the aforementioned iron-cobalt-nickel-chromium oxide nanomaterials as anode and cathode materials in seawater electrolysis devices.

[0013] The above-mentioned objective of the present invention is achieved through the following technical solution:

[0014] A method for preparing iron-cobalt-nickel-chromium oxide nanomaterials includes the following steps:

[0015] S1. Prepare a mixed solution containing iron, cobalt and nickel salts to obtain a precursor solution;

[0016] S2. The precursor solution is used as the electrolyte to carry out an electrochemical deposition reaction to obtain iron-cobalt-nickel layered hydroxide. Before electrodeposition, the nickel foam is cleaned.

[0017] S3. Immerse the iron-cobalt-nickel layered hydroxide material in a chromium salt solution, dry it, and then calcine it to obtain iron-cobalt-nickel-chromium oxide nanomaterials.

[0018] Preferably, the cleaning process in step S2 is as follows: first, ultrasonically clean the nickel foam with hydrochloric acid for 10-25 minutes; then, ultrasonically clean the nickel foam with an inorganic solvent for 10-25 minutes; then, ultrasonically clean the nickel foam with deionized water for 10-25 minutes; and finally, dry it overnight.

[0019] Preferably, the inorganic solvent is acetone or ethanol, and the concentration of the hydrochloric acid is 1–3 mol / L.

[0020] More preferably, the drying temperature is 60–80°C.

[0021] Preferably, the size of the nickel foam in step S2 is 2×2cm.

[0022] Preferably, the average pore size of the nickel foam in step S2 is 0.1 to 0.15 mm, and the porosity is 96% to 97%.

[0023] Preferably, the solvent is water.

[0024] More preferably, the drying temperature is 60–80°C.

[0025] Preferably, the molar ratio of cobalt to nickel in the electrolyte for electrodeposition in step S2 is 1:1:2.

[0026] Preferably, in the electrolyte, the sum of the masses of iron, cobalt and nickel sources to the volume ratio of solvent is (4-5) g: 50 mL.

[0027] More preferably, the iron source is ferrous sulfate.

[0028] More preferably, the cobalt source is cobalt nitrate.

[0029] More preferably, the nickel source is nickel nitrate.

[0030] More preferably, the electrodeposition reaction is carried out in a three-electrode system.

[0031] More preferably, in the three-electrode system, the nickel foam described in step S2 is the working electrode, the platinum wire electrode is the counter electrode, and the saturated calomel electrode is the reference electrode.

[0032] More preferably, the voltage used in the electrodeposition reaction is -1.0V.

[0033] More preferably, the electrodeposition reaction time is 10 to 25 minutes.

[0034] More preferably, the electrolyte for electrodeposition can undergo 1 to 6 electrodeposition reactions.

[0035] Preferably, the electrodeposition reaction in step S2 includes a cleaning and drying step.

[0036] More preferably, the drying temperature is 60–80°C.

[0037] Preferably, the concentration of chromium in the chromium-containing solution in step S3 is 0.05–0.2 mol / L.

[0038] More preferably, the chromium-containing solution is a chromium nitrate solution.

[0039] Preferably, the soaking time in step S3 is 5 to 30 minutes.

[0040] Preferably, the soaking process in step S3 includes washing and drying steps.

[0041] More preferably, the drying temperature is 30–50°C.

[0042] Preferably, the calcination temperature in step S3 is 300–500°C.

[0043] Preferably, the calcination time in step S3 is 2 to 4 hours.

[0044] A nanomaterial of iron-cobalt-nickel-cobalt oxide was prepared by the above-described preparation method.

[0045] The application of the aforementioned iron-cobalt-nickel-cobalt oxide nanomaterials as cathodes and anodes in the preparation of bipolar membrane-based seawater electrolysis devices is also within the scope of protection of this invention.

[0046] A bipolar membrane-based seawater electrolysis device includes a bipolar membrane, an anode, an anolyte, a cathode, and a catholyte; the anode and cathode are made of the aforementioned iron-cobalt-nickel-cobalt oxide nanomaterials, the anolyte is 1M potassium hydroxide, and the catholyte is simulated seawater.

[0047] Using the iron-cobalt-nickel-chromium oxide nanomaterials of this invention as both anode and cathode materials, potassium hydroxide as the anolyte, simulated seawater as the cathode solution, and a bipolar membrane as the diaphragm, a bipolar membrane-based seawater electrolysis device was constructed. The Faraday efficiency of this seawater electrolysis device for hydrogen and oxygen evolution exceeds 90%. The bipolar membrane seawater electrolysis device with reverse configuration exhibits better stability, while the seawater electrolysis device with forward configuration requires a lower voltage.

[0048] Preferably, the concentration of the anolyte is 1M.

[0049] Preferably, the concentration of the catholyte is 33.1 g / L.

[0050] Preferably, the ion concentration of the simulated seawater is: Na + 0.9±0.2g·L -1 ,K + 0.35±0.03g·L -1 Ca 2+ 0.4±0.04g·L -1 Mg 2+ 1.2±0.12g·L -1 ,Cl - 1.8±0.9g·L -1 SO4 2- 2.2±0.2g·L -1 .

[0051] Preferably, the distance between the anode and the cathode is 0.5 to 1.0 cm.

[0052] Preferably, the forward configuration is such that, when constructing a seawater electrolysis device, the anion exchange layer of the bipolar membrane faces the cathode and the cation exchange layer faces the anode.

[0053] Preferably, the reverse configuration is such that the anion exchange layer of the bipolar membrane faces the anode and the cation exchange layer faces the cathode.

[0054] Preferably, the hydrogen produced in the cathode chamber and the oxygen produced in the anode chamber of the seawater electrolysis device are collected by a gas sampling bag.

[0055] Preferably, the catholyte and anolyte are circulated by a peristaltic pump.

[0056] More preferably, the flow rate of the peristaltic pump is 10–60 mL / min.

[0057] Preferably, the applied voltage is provided by a DC power supply.

[0058] More preferably, the current density provided by the DC power supply is 10–600 mA / cm². 2 .

[0059] Compared with the prior art, the beneficial effects of the present invention are:

[0060] (1) This invention utilizes a specific electrodeposition reaction to form iron-cobalt-nickel layered hydroxide nanosheets on nickel foam, where iron, nickel, and cobalt sources react. These nanosheets are then calcined to obtain iron-cobalt-nickel-chromium oxide nanomaterials. The resulting material can undergo oxygen evolution reaction in an alkaline environment and also exhibits good hydrogen evolution performance in simulated seawater. Therefore, these iron-cobalt-nickel-chromium oxide nanomaterials are suitable for bipolar membrane-based seawater electrolysis devices where the electrolyte pH and conductivity vary significantly, facilitating long-term stable operation. Furthermore, this method does not use precious metals such as platinum, ruthenium, and iridium, resulting in a simple preparation process and low cost.

[0061] (2) The iron-cobalt-nickel-chromium oxide nanomaterial of the present invention, as an electrode material for a bipolar membrane-based seawater electrolysis device, not only enables the seawater electrolysis device to achieve a Faraday efficiency of over 90% for hydrogen and oxygen evolution, but also, because the iron-cobalt-nickel-chromium oxide nanomaterial can adapt to a wide range of pH values, and because the bipolar membrane not only completely prevents chloride ions from permeating into the anode chamber, but also inhibits the precipitation of calcium and magnesium ions in seawater by the hydrogen ions generated by water dissociation within the membrane, the synergistic effect of the catalyst and the bipolar membrane enables the reactor to operate stably for a long period of time. Attached Figure Description

[0062] Figure 1 This is a schematic diagram of the bipolar membrane-based seawater electrolysis device in Example 2.

[0063] Figure 2 The images are scanning electron microscope images of the iron-cobalt-nickel-chromium oxide nanomaterials of Example 1 at different magnifications.

[0064] Figure 3 The image shows the XRD pattern of the iron-cobalt-nickel-chromium oxide nanomaterial from Example 1.

[0065] Figure 4 The images show transmission electron microscopy (TEM) images and selected area electron diffraction (SID) patterns of the iron-cobalt-nickel-chromium oxide nanomaterials of Example 1.

[0066] Figure 5 The figure shows the test results of the iron-cobalt-nickel-chromium oxide nanomaterials of Example 1 in simulated seawater electrolyte hydrogen evolution and alkaline electrolyte oxygen evolution.

[0067] Figure 6 The voltage-current density curves of the bipolar membrane-based seawater electrolysis devices in Examples 2-3 under different bipolar membrane configuration modes are shown.

[0068] Figure 7 The voltage-current density curves are for the bipolar membrane-based seawater electrolysis devices in Examples 4-12.

[0069] Figure 8 The graph shows the hydrogen evolution rate results of the bipolar membrane-based seawater electrolysis devices in Examples 4-12.

[0070] Figure 9 The graph shows the oxygen evolution rate results of the bipolar membrane-based seawater electrolysis devices in Examples 4-12.

[0071] Figure 10 The graph shows the cell voltage variation of the bipolar membrane-based seawater electrolysis devices in Examples 3 and 4 after 600 hours of operation. Detailed Implementation

[0072] The present invention will now be described in further detail with reference to the accompanying drawings.

[0073] Example 1

[0074] This embodiment provides a method for preparing iron-cobalt-nickel-chromium oxide nanomaterials, including the following steps:

[0075] 1. First, pre-treat the 2×2cm nickel foam to remove grease and oxides from its surface: ultrasonically clean the nickel foam with inorganic solvent, then ultrasonically clean it with hydrochloric acid, and finally ultrasonically clean it with deionized water before use.

[0076] The inorganic solvent was ethanol, and the concentration of hydrochloric acid was 1 mol / L; the ultrasonic cleaning time was 20 min.

[0077] 2. Preparation of iron-cobalt-nickel layered hydroxide nanomaterials by electrodeposition: Ferrous sulfate, nickel nitrate hexahydrate, and cobalt nitrate hexahydrate were dissolved in 50 mL of deionized water and stirred for 10 min to obtain the electrolyte for electrodeposition. A three-electrode system was then constructed using pretreated nickel foam as the working electrode, platinum wire as the counter electrode, and a saturated calomel electrode as the reference electrode. The reaction was carried out at -1.0 V for 20 min. After the reaction, the nanomaterials were repeatedly rinsed with deionized water and dried to obtain the iron-cobalt-nickel layered hydroxide.

[0078] 3. Preparation of iron-cobalt-nickel-chromium oxide nanomaterials by calcination: Iron-cobalt-nickel layered hydroxide was immersed in chromium nitrate solution for 10 min, dried, and then calcined in a muffle furnace at 400℃ for 3 h to obtain iron-cobalt-nickel-chromium oxide nanomaterials.

[0079] The molar ratio of ferrous sulfate, cobalt nitrate hexahydrate, and nickel nitrate hexahydrate was 1:1:2; the ratio of the sum of the masses of ferrous sulfate, cobalt nitrate hexahydrate, and nickel nitrate hexahydrate to the volume of deionized water was 4.74 g: 50 mL; the concentration of the chromium nitrate solution was 0.1 mol / L; the drying temperature was 60℃; and the drying time was 12 h.

[0080] Example 2

[0081] This embodiment provides a bipolar membrane-based seawater electrolysis device, which includes: an anode chamber, a cathode chamber, a bipolar membrane, anolyte and catholyte contained in the anode chamber and cathode chamber, and a cathode disposed opposite to the anode in the anode chamber and the cathode chamber.

[0082] The materials forming the main bodies of the anode and cathode chambers are silicone gaskets and plexiglass, and the materials for the anode and cathode are iron-cobalt-nickel-chromium oxide nanomaterials prepared in Example 1; the anolyte is a 1M potassium hydroxide solution, and the catholyte is a simulated seawater solution.

[0083] The structure of the bipolar membrane-based seawater electrolysis device is as follows: Figure 1 As shown, the anode is in direct contact with the anolyte, and the cathode is in direct contact with the catholyte. The anode and cathode chambers are separated by a bipolar membrane. The anion exchange layer of the bipolar membrane faces the anode, and the cation exchange layer faces the cathode. The anode and cathode are connected to a DC power supply via titanium wires. Both the anode and cathode chambers are cylinders with a diameter of 3 cm and a volume of approximately 9.8 mL. The effective area of ​​both the anode and cathode is 4 cm². 2 The distance between the two electrodes is 1 cm. The volumes of the catholy and anolyte are both 100 mL, and the electrolyte is circulated by a peristaltic pump. The DC power supply current is set to 0.08 A, and the current density on the electrodes is 20 mA / cm². 2 The peristaltic pump flow rate was set to 20 mL / min. The generated gas was collected by a gas sampling bag.

[0084] Example 3

[0085] This embodiment provides a seawater electrolysis device based on a bipolar membrane. This seawater electrolysis device is basically the same as the device in Embodiment 2, except that the anion exchange layer of the bipolar membrane faces the cathode and the cation exchange layer faces the anode.

[0086] Example 4

[0087] This embodiment provides a bipolar membrane-based seawater electrolysis device, which is basically the same as the seawater electrolysis device in Embodiment 2, except that the anode material is a titanium mesh and the cathode material is a titanium mesh.

[0088] Example 5

[0089] This embodiment provides a bipolar membrane-based seawater electrolysis device, which is basically the same as the seawater electrolysis device in Embodiment 2, except that the anode material is a titanium mesh and the cathode material is an iron-cobalt-nickel-chromium oxide nanomaterial.

[0090] Example 6

[0091] This embodiment provides a bipolar membrane-based seawater electrolysis device, which has a basically the same configuration as the seawater electrolysis device in Embodiment 4, except that the current density is set to 100 mA / cm². 2 .

[0092] Example 7

[0093] This embodiment provides a bipolar membrane-based seawater electrolysis device, which has a basically the same configuration as the seawater electrolysis device in Embodiment 5, except that the current density is set to 100 mA / cm². 2 .

[0094] Example 8

[0095] This embodiment provides a bipolar membrane-based seawater electrolysis device, which has a basically the same configuration as the seawater electrolysis device in Embodiment 6, except that the current density is set to 100 mA / cm². 2 .

[0096] Example 9

[0097] This embodiment provides a bipolar membrane-based seawater electrolysis device, which has a basically the same configuration as the seawater electrolysis device in Embodiment 4, except that the current density is set to 500 mA / cm². 2 .

[0098] Example 10

[0099] This embodiment provides a bipolar membrane-based seawater electrolysis device, which has a basically the same configuration as the seawater electrolysis device in Embodiment 5, except that the current density is set to 500 mA / cm². 2 .

[0100] Example 11

[0101] This embodiment provides a bipolar membrane-based seawater electrolysis device, which has a basically the same configuration as the seawater electrolysis device in Embodiment 6, except that the current density is set to 500 mA / cm². 2 .

[0102] Performance testing

[0103] 1. Characterization of morphology and material composition

[0104] The iron-cobalt-nickel-chromium oxide nanomaterials obtained in Example 1 were scanned using an electron microscope, and the results are as follows: Figure 2 As shown, Figure 2 (A) and (B) are scanning electron microscope (SEM) images of iron-cobalt-nickel-chromium oxide nanomaterials at different magnifications. Figure 2 (A) indicates that the iron-cobalt-nickel-chromium oxide material appears as uniform microspheres distributed on a nickel foam substrate; from Figure 2 (B) It can be seen that the iron-cobalt-nickel-chromium oxide nanomaterials exhibit a nanosheet structure. X-ray diffraction (XRD) analysis was performed on the iron-cobalt-nickel-chromium oxide nanomaterials from Example 1, and the results are as follows... Figure 3 As shown. From Figure 3 As can be seen from the XRD pattern of the iron-cobalt-nickel-chromium oxide material, the crystal planes (003), (006), (012), and (0015) are displayed (JCPDS No. 51-0463). The crystal planes (111), (220), (311), (222), (400), (422), (511), and (440) correspond to the diffraction peaks of the iron-cobalt-nickel-chromium oxide nanomaterial.

[0105] The iron-cobalt-nickel-chromium oxide nanomaterials obtained in Example 1 were characterized by transmission electron microscopy, and the results are as follows: Figure 4 As shown. Consistent with the scanning electron microscope images, the transmission electron microscope images also reveal the two-dimensional nanostructure of iron-cobalt-nickel-chromium oxide. Figure 4 (A)). The lattice fringe spacings are 0.246 nm and 0.204 nm, respectively, corresponding to the (311) and (400) crystal planes of iron-cobalt-nickel-chromium oxide. Figure 4 (B) Selected area electron diffraction pattern ( Figure 4 (C) shows the diffraction rings of the (220), (222), and (400) crystal planes of the iron-cobalt-nickel-chromium oxide nanomaterial, which is consistent with the XRD results, indicating that the material was successfully synthesized. The two-dimensional nanosheet structure of the iron-cobalt-nickel-chromium oxide nanomaterial has a large specific surface area, which can increase the contact area between the catalyst and the electrolyte, thereby accelerating the interfacial reaction.

[0106] 2. Electrochemical performance testing

[0107] The iron-cobalt-nickel-chromium oxide nanomaterials obtained in Example 1 were placed in a three-electrode system to test their hydrogen evolution and oxygen evolution performance. The results are as follows: Figure 5 As shown. Figure 5 This is a graph showing the results of a linear voltammetric scan. From... Figure 5 (A) It can be seen that in simulated seawater, iron-cobalt-nickel-chromium oxide nanomaterials can achieve 10 mA·cm⁻¹ at a voltage of -0.11V (vs. RHE). -2 The current density is around 10 mA·cm⁻¹, while nickel foam requires 0.25 V (vs. RHE). For the oxygen evolution reaction, when 1 M potassium hydroxide is used as the electrolyte, the iron-cobalt-nickel-chromium oxide nanomaterials achieve a current density of around 10 mA·cm⁻¹. -2 The oxygen evolution overpotential is 78 mV. Figure 5 (B) Therefore, iron-cobalt-nickel-chromium oxide nanomaterials have good hydrogen and oxygen evolution properties.

[0108] Examples 2 and 3, which use the iron-cobalt-nickel-chromium oxide nanomaterials obtained in Example 1 as the cathode and anode, are bipolar membrane-based seawater electrolysis devices with different bipolar membrane configurations at 20 mA·cm⁻¹. -2 Stability tests such as Figure 6 As shown. The bipolar membrane seawater electrolysis device in the reverse configuration mode of Example 2 aims to achieve 20 mA·cm⁻¹. -2 The required current density is 2.82V, while the device with the forward-configured bipolar membrane only requires 2.11V. This indicates that both bipolar membrane configurations can perform seawater electrolysis. The forward-configured bipolar membrane reduces the applied voltage, but the electrolyzer voltage increases over time. This may be because, in the forward mode, the pH of the cathode solution gradually rises, causing calcium and magnesium ions in the simulated seawater to precipitate on the electrode surface, clogging the active sites and increasing the electrolyzer voltage. In the reverse mode, hydrogen ions generated by water dissociation in the bipolar membrane migrate to the cathode chamber, maintaining the pH of the cathode solution and preventing it from rising, thus ensuring stable reactor operation. Therefore, Examples 3-12 all adopted the reverse configuration mode. Figures 5-10 ).

[0109] When both the anode and cathode are titanium mesh (Examples 2, 4, and 5), at 20 mA·cm -2 At the given current density, the cell voltage was 2.66 V, and the hydrogen evolution rate was 1.44 mmol·h⁻¹. -1 The oxygen evolution rate was 0.76 mmol·h. -1 ; at 100mA·cm -2 At the given current density, the cell voltage was 3.49 V, and the hydrogen evolution rate was 8.32 mmol·h⁻¹. -1 The oxygen evolution rate was 3.67 mmol·h. -1 At 500mA·cm -2 At the given current density, the cell voltage was 7.56 V, and the hydrogen evolution rate was 36.39 mmol·h⁻¹. -1 The oxygen evolution rate was 18.17 mmol·h. -1 .

[0110] When both the anode and cathode are iron-cobalt-nickel-chromium oxide nanomaterials (Examples 6-8), at 20 mA·cm -2 At the given current density, the cell voltage was 2.7 V, and the hydrogen evolution rate was 1.48 mmol·h⁻¹. -1 The oxygen evolution rate was 0.74 mmol·h. -1 ; at 100mA·cm -2 At the given current density, the cell voltage was 3.72 V, and the hydrogen evolution rate was 7.42 mmol·h⁻¹. -1 The oxygen evolution rate was 3.66 mmol·h. -1 At 500mA·cm -2At the given current density, the cell voltage was 7.3 V, and the hydrogen evolution rate was 37.22 mmol·h⁻¹. -1 The oxygen evolution rate was 19.29 mmol·h. -1 .

[0111] When the anode is a titanium mesh and the cathode is an iron-cobalt-nickel-chromium oxide nanomaterial (Examples 9-11), at 20 mA·cm -2 At the given current density, the cell voltage was 2.7 V, and the hydrogen evolution rate was 1.48 mmol·h⁻¹. -1 The oxygen evolution rate was 0.74 mmol·h. -1 ; at 100mA·cm -2 At the given current density, the cell voltage was 4.14 V, and the hydrogen evolution rate was 7.24 mmol·h⁻¹. -1 The oxygen evolution rate was 3.71 mmol·h. -1 At 500mA·cm -2 At the given current density, the cell voltage was 8.95 V, and the hydrogen evolution rate was 36.93 mmol·h⁻¹. -1 The oxygen evolution rate was 18.42 mmol·h. -1 .

[0112] The seawater electrolysis devices of Examples 2 and 4 were subjected to a 600-hour stability test. Figure 10 The results show that reverse assembly of the bipolar film at 20 mA·cm -2 At the specified current densities, both electrodes operated stably, with cell voltages stabilizing at 2.49V and 2.82V, respectively. Furthermore, the bipolar membrane seawater electrolysis device using iron-cobalt-nickel-chromium oxide nanomaterials as electrodes exhibited a lower cell voltage than the titanium mesh during long-term operation. The average hydrogen evolution and oxygen evolution rates during 600 hours of operation in Examples 2 and 4 were 1.43 and 1.46 mmol·h, respectively. -1 and 0.72, 0.73 mmol·h -1 .

[0113] In summary, iron-cobalt-nickel-chromium oxide nanomaterials can be applied to bipolar membrane-based seawater electrolysis devices, achieving low cell voltage and stable operation.

[0114] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A method for preparing iron-cobalt-nickel-chromium oxide nanomaterials, characterized in that: Includes the following steps: S1. Prepare a mixed solution containing iron, cobalt and nickel salts to obtain a precursor solution; S2. Using the precursor solution as an electrolyte, an electrochemical deposition reaction is carried out to obtain iron-cobalt-nickel layered hydroxide; S3. Immerse the iron-cobalt-nickel layered hydroxide material in a chromium salt solution, dry it, and then calcine it to obtain iron-cobalt-nickel-chromium oxide nanomaterials.

2. The method for preparing an iron-cobalt-nickel-chromium oxide nanomaterial according to claim 1, characterized in that: In S1, the nickel salt is nickel nitrate, the cobalt salt is cobalt nitrate, and the iron salt is ferrous sulfate; in the mixed solution, the molar ratio of iron, cobalt, and nickel is 1:1:2, and the electrolyte volume is 50 mL. The sum of the masses of iron, cobalt and nickel sources and the volume ratio of solvent are (4-5) g: 50 mL, and the electrolyte is used 1-6 times.

3. The method for preparing an iron-cobalt-nickel-chromium oxide nanomaterial according to claim 1, characterized in that: In S2, the working electrode for the electrochemical deposition reaction is nickel foam, the counter electrode is a platinum wire electrode, and the reference electrode is a saturated calomel electrode. The electrodeposition voltage is -1.0V, and the deposition time is 10–25 min. The nickel foam is cleaned before electrodeposition. The nickel foam has a size of 2×2cm, an average pore size of 0.1 to 0.15mm, and a porosity of 96% to 97%.

4. The method for preparing an iron-cobalt-nickel-chromium oxide nanomaterial according to claim 3, characterized in that: The pre-cleaning of the nickel foam in S2 includes: The nickel foam was ultrasonically cleaned with hydrochloric acid for 10-25 minutes, then ultrasonically cleaned with an inorganic solvent for 10-25 minutes, and finally ultrasonically cleaned with deionized water for 10-25 minutes. It was then dried overnight. The inorganic solvent is acetone or ethanol, the hydrochloric acid concentration is 1-3 mol / L, and the drying temperature is 60-80℃.

5. The method for preparing an iron-cobalt-nickel-chromium oxide nanomaterial according to claim 1, characterized in that: The chromium salt in S3 is chromium nitrate with a concentration of 0.05–0.2 mol / L, a solution volume of 50 mL, and a soaking time of 5–30 min. After soaking, the solution is washed and dried.

6. A method for preparing an iron-cobalt-nickel-chromium oxide nanomaterial according to claim 1 or 5, characterized in that: The calcination temperature in S3 is 300–500℃, and the calcination time is 2–4 hours.

7. A nanomaterial of iron-cobalt-nickel-chromium oxide, characterized in that, It is prepared by any of the preparation methods described in claims 1 to 5.

8. The application of the iron-cobalt-nickel-chromium oxide nanomaterial according to claim 7 as a cathode and anode in the preparation of an electrolytic seawater device.

9. A seawater electrolysis device based on a bipolar membrane, characterized in that: It includes an anode, a bipolar membrane, a cathode, and an electrolyte; the anode and cathode are made of the iron-cobalt-nickel-chromium oxide nanomaterial as described in claim 7, the distance between the anode and cathode is 0.5 to 1.0 cm, and the electrolyte is potassium hydroxide and simulated seawater.

10. The seawater electrolysis apparatus according to claim 9, characterized in that: The potassium hydroxide concentration is 0.5–3 mol / L, and the simulated seawater is prepared from 33.1 g / L sea salt.

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