Method for recovering performance of seawater electrolysis device

Abstract

The application belongs to the technical field of electrolysis, and particularly relates to a seawater electrolysis device performance recovery method. The device comprises an anode material and a cathode material, a positive potential is applied to the anode material, a negative potential is applied to the cathode material, seawater is electrolyzed to produce hydrogen, the anode material comprises an anode self-supporting electrode and an anode catalyst, the cathode material comprises a cathode self-supporting electrode and a cathode catalyst, the anode catalyst and the cathode catalyst are the same, the anode self-supporting electrode and the cathode self-supporting electrode are the same, when the electrolysis device has performance attenuation, the electrolysis device stops power supply, a negative potential is applied to the anode material, and a positive potential is applied to the cathode, so that the performance of the electrolysis device is recovered. According to the application, the potentials on the two sides of the anode and the cathode are simply reversed, the online performance recovery of the electrolysis device can be realized in the continuous process of seawater electrolysis to produce hydrogen, the electrode material and other components do not need to be replaced, the operation is simple and fast, the recovery process cost is low, and the production efficiency of seawater electrolysis to produce hydrogen is almost not affected.

Description

Technical Field

[0001] This invention belongs to the field of electrolysis technology, specifically relating to a method for restoring the performance of a seawater electrolysis device. Background Technology

[0002] As the world's largest hydrogen producer, my country's hydrogen production exceeded 25 million tons in 2020. However, over 95% of this was produced from fossil fuels, failing to fundamentally address the carbon emission problem. In contrast, water electrolysis technology offers a significant advantage with zero carbon emissions. On the other hand, renewable energy sources such as wind and solar power are emerging. According to a report from the National New Energy Consumption Monitoring and Early Warning Center, in the first half of 2021 alone, my country's cumulative wind and solar power generation reached 500.8 billion kilowatt-hours, accounting for 12.9% of the country's total power generation. However, the total amount of wind and solar power curtailed nationwide was approximately 16 billion kilowatt-hours, indicating a serious energy waste problem. "Green hydrogen" technology, which combines renewable energy power generation with water electrolysis, is expected to be key to solving the problems of carbon emissions and renewable energy consumption. Offshore wind power and deep-sea beach photovoltaic power generation technologies are important components of "green hydrogen" technology.

[0003] Among water electrolysis technologies for hydrogen production, proton exchange membrane electrolysis and alkaline electrolysis are relatively mature and have been industrialized. However, both use pure water or alkaline-treated pure water as raw materials. Offshore wind power and deep-sea photovoltaic power generation systems operate in environments severely lacking freshwater resources. This situation directly limits the expansion of offshore wind and solar power generation, thus restricting the development of "green hydrogen" technology. On the other hand, freshwater is a scarce resource, and pure water electrolysis will be limited by raw material costs and resource reserves in the future. Seawater, on the other hand, accounts for 96.5% of the Earth's total water resources, making it a nearly unlimited resource. Furthermore, there has been a growing trend of research into high-performance electrode materials and process technologies for direct seawater electrolysis for hydrogen production.

[0004] The most critical factor currently hindering the development of seawater electrolysis technology is the inevitable accelerated deactivation of anode and cathode materials in caustic seawater electrolytes. Guo et al. (Nature Energy, 2023(8):264-272.) reported a bifunctional catalyst Cr2O3-CoO2 that can alleviate anode and cathode poisoning deactivation through local pH regulation. x It exhibits highly efficient and stable seawater electrolysis performance. However, due to the inability to completely avoid anodic corrosion and cathode blockage, after approximately 100 hours of operation, Cr2O3-CoO... xThe constructed seawater electrolysis device exhibited significant performance degradation. Sun et al. (Nature Communication, 2021, 12(1): 4182.) added hydrazine (N2H4) with a low redox equilibrium potential to the seawater electrolyte to prevent the anode material from being corroded by chloride ions and other halide ions at high potentials, but the deactivation problem of the cathode material was not effectively solved.

[0005] Despite the remarkable achievements in numerous studies on hydrogen production through seawater electrolysis, the complex electrochemical environment of seawater leads to the deactivation of anode and cathode materials in seawater electrolysis devices, making performance degradation of the anode and cathode in these devices unavoidable. Summary of the Invention

[0006] Based on the above background technology, the present invention provides a method for restoring the performance of a seawater electrolysis device. The seawater electrolysis process suffers from the following two problems: (1) High concentrations of halide ions (chloride, bromide, and iodide ions) in seawater cause the metal in the anode material to dissolve and its performance to degrade during electrolysis; (2) High concentrations of calcium and magnesium metal ions and positively charged colloidal insoluble impurities in seawater are deposited on the cathode surface under the influence of the cathode electric field and reduction potential, causing blockage and deactivation of the active sites on the cathode material surface. The present invention reverses the potential applied to the cathode and anode materials, i.e., applies a negative charge to the anode material, causing the metal cations dissolved from the anode during seawater electrolysis to be reconstructed on the electrode surface by the reduction potential in the form of electrophilic groups. Based on the regulatory effect of the re-deposited electrophilic groups, further corrosion by chloride ions during subsequent seawater electrolysis is avoided. Furthermore, a positive charge is applied to the cathode material, causing the harmful deposits covering the cathode surface to be decomposed by the oxidation potential, and the blockage at the active sites is cleared, thereby restoring the structure and performance of the anode and cathode materials.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] This invention provides a method for restoring the performance of a seawater electrolysis device. The device includes an anode material and a cathode material. A positive potential is applied to the anode material and a negative potential is applied to the cathode material to produce hydrogen through seawater electrolysis. The anode material includes a self-supporting anode electrode and an anode catalyst, and the cathode material includes a self-supporting cathode electrode and a cathode catalyst. The anode catalyst and the cathode catalyst are the same, and the anode self-supporting electrode and the cathode self-supporting electrode are the same. When the electrolysis device experiences performance degradation, the power supply to the electrolysis device is stopped, and a negative potential is applied to the anode material and a positive potential is applied to the cathode material to restore the performance of the electrolysis device.

[0009] The method for determining the performance degradation is as follows: under the same current, the voltage degradation rate exceeds 500μVh. -1 When this occurs, it is considered that performance degradation has occurred.

[0010] Based on the above technical solutions, preferably, the electrolyte solution of the seawater electrolysis device is seawater, which is natural seawater or simulated seawater.

[0011] Based on the above technical solutions, preferably, the seawater electrolysis device further includes a diaphragm; the diaphragm is a ZrO2 particle composite PPS porous diaphragm or a solid polymer electrolyte diaphragm.

[0012] Based on the above technical solutions, preferably, the anode catalyst and the cathode catalyst are bifunctional non-precious metal materials that simultaneously possess good hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities. Both the anode catalyst and the cathode catalyst are oxides, hydroxides, nitrides, phosphides, sulfides, or carbides of transition metals, wherein the transition metal is one or more of Cu, Ni, Fe, Co, Mn, Cr, V, Mo, and Nb; more preferably, NiFe hydroxide, NiMo nitride, NiCo sulfide, or CoFe phosphide.

[0013] Based on the above technical solutions, preferably, both the anode self-supporting electrode and the cathode self-supporting electrode are three-dimensional porous metal frameworks containing metal components with strong electrophilic properties, wherein the metal with strong electrophilic properties is one or more of Co, Fe, Mn, Cr, and V, and the three-dimensional porous metal framework is any one of foam metal, porous metal mesh, and metal fiber felt.

[0014] Based on the above technical solutions, a further preferred embodiment is that the metal with strong electrophilic properties is a nickel-cobalt bimetal; and the three-dimensional porous metal framework is a foamed nickel-iron.

[0015] Based on the above technical solution, preferably, a negative potential is applied to the anode material and a positive potential is applied to the cathode until the current density of the electrolysis device is 10–1000 mA / cm². -2 .

[0016] Based on the above technical solutions, preferably, the anode material is subjected to a negative potential and the cathode material is subjected to a positive potential in the electrolyte solution after seawater electrolysis to produce hydrogen, thereby recovering the dissolved transition metal ions in the electrolyte solution and constructing electrophilic groups.

[0017] Based on the above technical solutions, preferably, the simulated seawater is artificially prepared simulated seawater or a halide ion salt solution simulated seawater;

[0018] The seawater also includes natural seawater treated with alkaline substances or simulated seawater treated with alkaline substances; the alkaline substances are KOH, NaOH, KHCO3, NaHCO3, borate or phosphate buffers.

[0019] The seawater contains one or more of the following: high concentration of halide ions, high concentration of calcium and magnesium metal ions, or positively charged colloidal insoluble impurities.

[0020] The principle of this invention is as follows: The performance recovery method for a seawater electrolysis device involves applying a negative potential to the transition metal anode material in the post-electrolysis seawater solution. Utilizing the relatively active redox properties of transition metal ions, the strongly electrophilic transition metal ions dissolved from the self-supporting anode electrode are recovered by the reduction potential and reconstructed on the anode material surface as electrophilic groups, effectively restoring the surface structure and performance degradation of the anode material for seawater electrolysis hydrogen production. Because transition metal compounds possess strong redox properties, they can better exchange and couple with transition metal ions in the solution compared to other catalyst materials, thereby achieving strong electrophilic metal group doping. These electrophilic groups can regulate the coordination environment on the surface of the seawater electrolysis anode material, utilizing strong electrophilic properties to prevent further corrosion by chloride ions during subsequent seawater electrolysis operation, thus achieving performance recovery of the anode material during seawater electrolysis. Furthermore, because the self-supporting cathode electrode has a large specific surface area, applying a positive potential to the cathode material allows harmful deposits covering its surface to be decomposed by the oxidation potential, clearing blockages at active sites, thereby achieving performance recovery of the cathode material during seawater electrolysis. By combining the above two methods for restoring the structure of anode and cathode materials, the potential reversal performance can be restored. This process can be repeated multiple times during the continuous operation of seawater electrolysis, thereby achieving long-term stable operation of the seawater electrolysis device.

[0021] The beneficial effects of this invention are as follows:

[0022] (1) In this invention, the anode and cathode of the seawater electrolysis device are made of the same material. When performance is restored, a potential reversal is used: a positive potential is applied to the anode, and a negative potential is applied to the cathode. Utilizing the relatively active redox properties of transition metal ions, the negative potential allows the strongly electrophilic transition metals such as Co, Fe, Mn, Cr, and V dissolved in seawater to be recovered to the anode surface. Conversely, the positive potential oxidizes and decomposes insoluble impurities deposited on the cathode surface, thus restoring the surface structure of the anode and cathode of the seawater electrolysis device. After the anode and cathode are restored to their normal voltage operating conditions, the degraded performance of the electrolysis device is recovered, thereby achieving long-term stable operation of the high-efficiency seawater electrolysis device.

[0023] (2) The restoration method of this invention can oxidize and dissolve the harmful deposits covering the surface of the seawater electrolysis cathode material, effectively exposing the active structure on the cathode side blocked by impurities in seawater, thereby restoring electrolysis performance and avoiding deactivation of the cathode catalyst and self-supporting electrode. Therefore, this invention can use a three-dimensional porous structure as the supporting electrode, which can play a larger role in electrochemical active area while avoiding the blockage of the porous self-supporting electrode by a large amount of calcium and magnesium ions and other insoluble impurities in seawater, thus preventing performance degradation and solving the problem that porous structures are not suitable for seawater electrolysis devices.

[0024] (3) The catalyst composed of transition metal compounds in this invention has strong redox properties. Compared with other catalyst materials, it can better exchange and couple with transition metal ions in the solution, thereby achieving strong electrophilic metal group doping. This electrophilic group can regulate the coordination environment on the surface of the seawater electrolysis anode material. The strong electrophilic properties can be used to avoid further corrosion of chloride ions during the subsequent seawater electrolysis operation, thereby realizing the performance recovery of the anode material in the seawater electrolysis process.

[0025] (4) The present invention only requires a simple reversal of the potentials on both sides of the anode and cathode to realize the online performance recovery of the electrolysis device in the continuous process of seawater electrolysis to produce hydrogen. The electrode materials are all non-precious metals with low cost, and there is no need to replace the electrode materials and other components. The operation is simple and fast, the recovery process cost is low, and it has almost no impact on the production efficiency of seawater electrolysis to produce hydrogen. Attached Figure Description

[0026] Figure 1 The image shows a scanning electron microscope (SEM) image of NiCoS NAs / NFF in Example 1.

[0027] Figure 2 This is a scanning electron microscope energy dispersive spectroscopy (EDS) mapping image of NiCoS NAs / NFF in Example 1;

[0028] Figure 3 This is an EDS line scan of NiCoS Nas / NFF in Example 1;

[0029] Figure 4 This is a comparison of the voltage decay curves in Example 1 with and without performance recovery achieved through multiple potential reversals.

[0030] Figure 5 The image shows a SEM image of FeOOH-NiCoS NAs / NFF after the potential reversal performance was restored in Example 1.

[0031] Figure 6 This is the EDS mapping diagram of FeOOH-NiCoS NAs / NFF after the potential reversal performance was restored in Example 1;

[0032] Figure 7 This is an EDS line scan of FeOOH-NiCoS NAs / NFF after the potential reversal performance was restored in Example 1;

[0033] Figure 8 The figures show the potentiodynamic polarization curves of NiCoS NAs / NFF before and after potential reversal performance recovery in Example 1 in 1.0M KOH+2.0M NaCl. Detailed Implementation

[0034] The following examples are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way.

[0035] Unless otherwise specified, the materials used in the embodiments of the present invention can be obtained commercially or prepared according to conventional methods known to those skilled in the art.

[0036] Example 1

[0037] Using the synthesis method of Na et al. (Journal of Energy Chemistry, 2024, 91:370-382.; A metal sulfide electrode and its preparation method and application, 202310643496.3), a nickel-cobalt bimetallic sulfide nanorod array (NiCoS NAs) catalyst was prepared on the surface of a self-supporting nickel-iron foam (NiFe Foam, NFF) electrode and named NiCoS NAs / NFF. It has good HER and OER performance and was used as an anode and cathode material in seawater electrolysis cells.

[0038] like Figure 1 As shown in the SEM images, the NiCoS NAs catalyst is well dispersed on the NFF surface, and NiCoS NAs / NFF can be used as a HER / OER bifunctional electrode to achieve efficient seawater electrolysis.

[0039] like Figure 2 As shown, EDS mapping results indicate that Ni, Co, S, O, and Fe elements are uniformly distributed on the surface of the bifunctional electrode, with the following elemental proportions: Ni: 70.5 wt%, S: 23.9 wt%, O: 3.7 wt%, Co: 1.3 wt%, and Fe: 0.6 wt%.

[0040] like Figure 3 As shown, the EDS line scan results indicate that the NiCoS NAs catalyst on the self-supporting electrode NFF surface has a uniform nanorod structure.

[0041] Subsequently, NiCoS NAs / NFF was used as the anode and cathode materials to form a seawater electrolyzer, which was used to produce hydrogen through electrolysis in natural seawater alkalized with 1.0 M KOH.

[0042] like Figure 4 As shown, the seawater electrolysis cell operates at 600 mA / cm². 2 Hydrogen was produced by electrolysis at industrial-grade current densities. During this process, the electrolyzer experienced multiple performance degradations due to the harsh electrochemical environment of seawater, resulting in increased electrolysis voltage and reduced efficiency. However, with repeated potential reversals applied to the cathode and anode materials, the performance of the electrolyzer was restored and optimized multiple times, achieving stable hydrogen production for over 500 hours and exhibiting a negative decay rate. In the aforementioned seawater electrolyzer, if performance restoration was not performed, the electrode materials would rapidly deactivate, resulting in performance collapse within approximately 110 hours.

[0043] Seawater was electrolyzed for 24 hours using NiCoS NAs / NFF as the anode material, followed by performance recovery. Figure 5 As shown in the SEM images, in addition to the three-dimensional structure of NiCoS NAs, a well-dispersed metal oxide layer was deposited on the surface of the anode material after potential reversal performance restoration. This indicates that potential reversal can effectively recover the active metals dissolved from the anode material during seawater electrolysis, thereby restoring the anode material structure. Figure 6 As shown, EDS mapping results indicate that Ni, Co, S, O, and Fe elements still exhibit a uniform distribution on the surface of the anode material after potential reversal performance recovery, but their elemental proportions are as follows: Ni: 70.7 wt%, S: 21.7 wt%, O: 3.3 wt%, Co: 3.1 wt%, Fe: 1.2 wt%. The surface Fe element content is significantly increased, indicating that the Fe electrophilic metal component contained in the NFF substrate was corroded and dissolved by the seawater electrolyte during this process and recombined to the NiCoS NAs / NFF surface through negative potential. Figure 7 As shown, the EDS line scan results indicate that the NiCoSNAs nanorod structure on the anode material surface is coated with FeOOH after the potential reversal performance is restored, transforming it into a typical core-shell structure. NiCoSNAs forms the core structure, while the FeOOH introduced by negative potential recovery forms the shell structure. The anode material at this point can be named FeOOH-NiCoSNAs / NFF. This evidence suggests that while effectively restoring the structure of the anode material, the electrophilic metal contained in the self-supporting electrode component is successfully introduced to form a coating structure, further optimizing the performance of the seawater electrolyzer. The NiFe Foam self-supporting electrode contains a large amount of electrophilic Fe component, and its three-dimensional porous structure can prevent the large amount of calcium and magnesium ions and other insoluble impurities in seawater from clogging the porous self-supporting electrode and causing performance degradation.

[0044] like Figure 8 As shown in the potentiodynamic polarization curves, the FeOOH-NiCoS NAs / NFF reconstructed after potential reversal performance restoration exhibits a higher corrosion potential and lower corrosion current compared to the anolyte material without potential reversal under harsh anolyte conditions in simulated seawater using 1.0M KOH + 2.0M NaCl. This indicates that the FeOOH electrophilic groups introduced by this method can effectively regulate the coordination environment on the surface of the seawater electrolysis anolyte material, and utilize its strong electrophilic properties to avoid further corrosion by chloride ions during subsequent seawater electrolysis operations.

[0045] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the implementation. The scope of protection of the present invention should be determined by the scope defined in the claims. Other variations or modifications can be made based on the above description. Obvious variations or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A method for restoring the performance of a seawater electrolysis device, the device comprising an anode material and a cathode material, wherein a positive potential is applied to the anode material and a negative potential is applied to the cathode material to produce hydrogen through seawater electrolysis, characterized in that: The anode material includes a self-supporting anode electrode and an anode catalyst, and the cathode material includes a self-supporting cathode electrode and a cathode catalyst. The anode catalyst and the cathode catalyst are the same, and the anode self-supporting electrode and the cathode self-supporting electrode are the same. When the performance of the electrolysis device degrades, the electrolysis device stops supplying power, and a negative potential is applied to the anode material and a positive potential is applied to the cathode to restore the performance of the electrolysis device. Both the anode catalyst and the cathode catalyst are oxides, hydroxides, nitrides, phosphides, sulfides, or carbides of transition metals, wherein the transition metal is one or more selected from Cu, Ni, Fe, Co, Mn, Cr, V, Mo, and Nb. Both the anode self-supporting electrode and the cathode self-supporting electrode are three-dimensional porous metal frameworks containing a metal component with strong electrophilic properties, wherein the metal with strong electrophilic properties is Fe, and the three-dimensional porous metal framework is any one of foam metal, porous metal mesh, or metal fiber felt.

2. The method for restoring the performance of a seawater electrolysis device according to claim 1, characterized in that: The electrolyte solution in the seawater electrolysis device is seawater, which can be natural seawater or simulated seawater.

3. The method for restoring the performance of a seawater electrolysis device according to claim 1, characterized in that: The seawater electrolysis device also includes a diaphragm; the diaphragm is a solid polymer electrolyte diaphragm or a ZrO2 particle composite PPS porous diaphragm.

4. The method for restoring the performance of a seawater electrolysis device according to claim 1, characterized in that: A negative potential is applied to the anode material, and a positive potential is applied to the cathode material until the current density of the electrolysis device reaches 10~1000 mA cm⁻¹. -2 .

5. The method for restoring the performance of a seawater electrolysis device according to claim 1, characterized in that: The process involves applying a negative potential to the anode material and a positive potential to the cathode material in the electrolyte solution after hydrogen production via seawater electrolysis.

6. The method for restoring the performance of a seawater electrolysis device according to claim 2, characterized in that, The simulated seawater is artificially prepared simulated seawater or a halide ion salt solution that simulates seawater. The seawater also includes natural seawater or simulated seawater treated with alkaline substances, wherein the alkaline substances are KOH, NaOH, KHCO3, NaHCO3, borate or phosphate buffers.

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