Performance recovery method for seawater electrolysis device

Abstract

The invention 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, positive potential is applied to the anode material, negative potential is applied to the cathode material for seawater electrolysis hydrogen production, 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 is the same as the cathode catalyst, and the cathode catalyst is the same as the cathode catalyst. The anode self-supporting electrode and the cathode self-supporting electrode are the same, when the electrolysis device is subjected to performance degradation, the electrolysis device stops supplying power, negative potential is applied to the anode material, positive potential is applied to the cathode, and performance recovery of the electrolysis device is achieved. On-line performance recovery of the electrolysis device can be achieved in the continuous process of seawater electrolysis hydrogen production only by simply reversing the potentials on the two sides of the cathode and the anode, electrode materials and other parts do not need to be replaced, operation is easy, convenient and rapid, the recovery process cost is low, and the production benefits of seawater electrolysis hydrogen production are almost not affected.

Description

Technical Field

[0001] The invention belongs to the technical field of electrolysis, and in particular relates to a method for restoring the performance of a seawater electrolysis device. Background Art

[0002] As the largest hydrogen producer, my country's hydrogen production in 2020 has exceeded 25 million tons, but more than 95% of it comes from fossil energy hydrogen production, which cannot fundamentally solve the problem of carbon emissions. Compared with fossil energy hydrogen production, water electrolysis hydrogen production technology has the significant advantage of zero carbon emissions. On the other hand, renewable energy represented by wind power and photovoltaics has emerged. According to a report released by the National New Energy Absorption Detection and Early Warning Center, in the first half of 2021 alone, my country's cumulative wind power and photovoltaic power generation was 500.8 billion kWh, accounting for 12.9% of the country's total power generation, but the total amount of wind and photovoltaic power abandoned nationwide was about 16 billion kWh, and the problem of energy waste was serious. The "green hydrogen" technology that combines renewable energy power generation with water electrolysis hydrogen production technology is expected to become the key to solving the problems of "carbon emissions" and "renewable energy absorption". Among them, offshore wind power and offshore beach photovoltaic power generation technology are important components of "green hydrogen" technology.

[0003] Among the technologies for producing hydrogen by electrolysis of water, proton exchange membrane electrolysis of water and alkaline electrolysis of water are relatively mature and have been industrialized. However, both use pure water or pure water treated with alkaline as raw materials, and there is a serious lack of fresh water resources in the working environment of offshore wind power and offshore beach photovoltaic power generation devices. This situation will directly limit the expansion of offshore wind power and solar power generation, and limit the development of "green hydrogen" technology. On the other hand, fresh water is actually a scarce resource, and pure water electrolysis will be limited by raw material costs and resource reserves in the future; seawater accounts for 96.5% of the total water reserves on the earth, which is a nearly unlimited resource. In addition, there has been a trend of increasing research on high-performance electrode materials and process technologies for direct seawater electrolysis to produce hydrogen.

[0004] At present, the most critical factor restricting 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 Cr that can alleviate the deactivation of anode and cathode toxicity by local pH regulation. 2 O 3 -CoO x , and showed efficient and stable seawater electrolysis performance. However, since it is impossible to completely avoid the problems of anode corrosion and cathode clogging, after about 100 hours of operation, Cr 2 O 3 -CoO xThe seawater electrolysis device showed obvious performance degradation. Sun et al. (Nature Communication, 2021, 12(1): 4182.) added hydrazine (N) with low redox equilibrium potential to the seawater electrolyte. 2 H 4 ) is used to prevent the anode material from being corroded by halogen ions such as chloride ions at high potential, but the deactivation problem of the cathode material has not been effectively solved.

[0005] Although many studies on hydrogen production by seawater electrolysis have achieved remarkable results, the electrochemical environment of seawater is relatively complex, which will lead to the deactivation of the anode and cathode materials of the seawater electrolysis device, and the performance degradation of the anode and cathode of the seawater electrolysis device is always difficult to avoid. 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. There are two problems in the process of seawater electrolysis: (1) high concentration of halogen ions (halogen ions are chloride ions, bromide ions, and iodide ions) in seawater causes the metal of the anode material to dissolve and the performance to decay during the electrolysis process; (2) high concentration of calcium and magnesium metal ions and positively charged colloidal insoluble impurities in seawater are deposited on the cathode surface under the action of the cathode electric field and reduction potential, causing the blockage and inactivation of the active sites on the surface of the cathode material. The present invention reverses the potential applied to the cathode material and the anode material, that is, applies a negative charge to the anode material, so that the metal cations dissolved from the anode during the seawater electrolysis process are reconstructed to the electrode surface in the form of electrophilic groups by the reduction potential, and based on the regulatory effect of the re-deposited electrophilic groups, further corrosion of chloride ions during the subsequent seawater electrolysis operation is avoided; and a positive charge is applied to the cathode material, so that the harmful sediments covering the cathode surface are decomposed by the oxidation potential, and the blockage at the active site is cleared, thereby realizing the recovery of the structure and performance of the anode and cathode materials.

[0007] In order to achieve the above object, the technical solution of the present invention is as follows:

[0008] The present invention provides a method for recovering the performance of a seawater electrolysis device. The device comprises 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 electrolyze seawater 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 is the same as the cathode catalyst. The anode self-supporting electrode is the same as the cathode self-supporting electrode. When the performance of the electrolysis device decays, the power supply to the electrolysis device is stopped, a negative potential is applied to the anode material and a positive potential is applied to the cathode material, so as to realize performance recovery of the electrolysis device.

[0009] The performance degradation is determined by: when the current is the same, the voltage decay rate exceeds 500μVh -1When , it is considered that performance degradation has occurred.

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

[0011] Based on the above technical solution, preferably, the seawater electrolysis device further includes a diaphragm; the diaphragm is ZrO 2 Particle composite PPS porous diaphragm or solid polymer electrolyte diaphragm.

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

[0013] Based on the above technical scheme, preferably, the anode self-supporting electrode and the cathode self-supporting electrode are both three-dimensional porous structure metal frames 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 structure metal frame is any one of foam metal, porous metal mesh, and metal fiber felt.

[0014] Based on the above technical solution, it is further preferred that the metal with strong electrophilic properties is a nickel-cobalt bimetal; and the three-dimensional porous structure metal framework is 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 to 1000 mA cm -2 .

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

[0017] Based on the above technical solution, preferably, the simulated seawater is artificially prepared simulated seawater or halogen 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, KHCO 3 、NaHCO 3, borate or phosphate buffers.

[0019] The above seawater contains one or more of high concentrations of halogen ions, high concentrations of calcium and magnesium metal ions, or positively charged colloidal insoluble impurities.

[0020] The principle of the present invention is: the performance recovery method of the seawater electrolysis device of the present invention applies a negative potential to the transition metal anode material in the seawater solution after electrolysis, and utilizes the relatively active redox characteristics of the transition metal ions to make the strong electrophilic transition metal ions dissolved by the anode self-supporting electrode be recovered by the reduction potential, and reconstructed to the surface of the anode material in the form of electrophilic groups, effectively restoring the surface structure and performance attenuation of the anode material for hydrogen production by seawater electrolysis. Because the transition metal compound has a strong redox characteristic, it can better complete the exchange and coupling with the transition metal ions in the solution compared with other catalyst materials, thereby realizing the doping of metal groups with strong electrophilic characteristics. The above-mentioned electrophilic group can regulate the coordination environment of the surface of the seawater electrolysis anode material, and utilize the strong electrophilic characteristics 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; because the cathode self-supporting electrode has a large specific surface area structure, by applying a positive potential to the cathode material, the harmful sediments covering its surface can be decomposed by the oxidation potential, and the blockage at the active site is cleared, thereby realizing the performance recovery of the cathode material in the seawater electrolysis process. The recovery means of the above two anode materials and cathode material structures are combined to complete the potential reversal performance recovery, and the above operation can be repeated many times to perform performance recovery many times during the continuous operation of seawater electrolysis, thereby realizing long-term stable operation of the seawater electrolysis device.

[0021] The beneficial effects of the present invention are:

[0022] (1) The anode and cathode of the seawater electrolysis device of the present invention are made of the same material. When the performance is restored, the potential is reversed, a positive potential is applied to the anode, and a negative potential is applied to the cathode. By utilizing the relatively active redox characteristics of transition metal ions, the transition metals such as Co, Fe, Mn, Cr, and V dissolved in seawater with strong electrophilic characteristics are recovered to the anode surface through the negative potential, and the insoluble impurities deposited on the cathode surface are oxidized and decomposed through the positive potential, so that the surface structure of the positive and negative electrodes of the seawater electrolysis device can be restored. After the positive and negative electrodes of the seawater electrolysis are restored to the normal voltage working conditions again, the attenuated performance of the electrolysis device is restored, thereby realizing the long-term stable operation of the efficient seawater electrolysis device.

[0023] (2) The recovery method of the present invention can oxidize and dissolve harmful sediments covering the surface of the cathode material for seawater electrolysis, effectively expose the active structure on the cathode side blocked by impurities in seawater, thereby restoring the electrolysis performance and avoiding the deactivation of the cathode catalyst and the self-supporting electrode. Therefore, the present invention can select a three-dimensional porous structure as a supporting electrode, which can play a role of a larger electrochemical active area while avoiding the blocking of the porous structure self-supporting electrode by more calcium, magnesium ions and other insoluble impurities in seawater, causing performance degradation, and solving the problem that the porous structure is not suitable for seawater electrolysis devices.

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

[0025] (4) The present invention can realize the online performance recovery of the electrolysis device in the continuous process of seawater electrolysis to produce hydrogen by simply reversing the potential on both sides of the anode and cathode. 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 there is almost no impact on the production efficiency of seawater electrolysis to produce hydrogen. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0029] Figure 4 Comparison of voltage decay curves of performance recovery by multiple potential reversals and without performance recovery in Example 1;

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

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

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

[0033] Figure 8 Potentiodynamic polarization curves of NiCoS NAs / NFF before potential reversal performance recovery and FeOOH-NiCoS NAs after potential reversal performance recovery in 1.0 M KOH + 2.0 M NaCl in Example 1. DETAILED DESCRIPTION

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

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

[0036] Example 1

[0037] 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) was used to prepare a nickel-cobalt bimetallic sulfide nanorod array (NiCoS NAs) catalyst on the surface of a nickel-iron foam (NiFe Foam, NFF) self-supporting electrode. It was named NiCoS NAs / NFF, which has good HER and OER performance and is used as anode and cathode materials in seawater electrolysis cells.

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

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

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

[0041] Subsequently, NiCoS NAs / NFF was used as anode material and cathode material to form a seawater electrolysis cell, and hydrogen was produced by electrolysis in natural seawater alkalized with 1.0 M KOH.

[0042] like Figure 4 As shown, the seawater electrolysis cell is at 600mA / cm 2 Hydrogen was produced by electrolysis at an industrial-grade current density of . During the period, due to the harsh electrochemical environment of seawater, the electrolytic cell experienced performance decay many times, resulting in an increase in electrolysis voltage and a decrease in efficiency. However, with repeated potential reversals applied to the cathode and anode materials, the performance of the electrolytic cell was restored and optimized many times, stably producing hydrogen by electrolysis for more than 500 hours and showing a negative decay rate. In the above-mentioned seawater electrolytic cell, if performance recovery is not performed, the electrode material will deactivate rapidly, and performance collapse will occur in about 110 hours.

[0043] NiCoS NAs / NFF was used as anode material to electrolyze seawater for 24 h, and then the performance was restored. Figure 5 As shown in the figure, the SEM image shows that after the potential reversal performance recovery, in addition to the three-dimensional structure of NiCoS NAs, a layer of well-dispersed metal oxide layer is deposited on the surface of the anode material, indicating that potential reversal can effectively recover the active metals dissolved from the anode material in seawater electrolysis, thereby restoring the structure of the anode material. Figure 6 As shown in the figure, the EDS mapping results show that the Ni, Co, S, O and Fe elements are still evenly distributed on the surface of the anode material after the potential reversal performance is restored, but the element proportions are: Ni: 70.7wt%, S: 21.7wt%, O: 3.3wt%, Co: 3.1wt%, Fe: 1.2wt%, and the surface Fe content is significantly increased, indicating that the Fe electrophilic metal component contained in the NFF substrate is corroded and dissolved by the seawater electrolyte during this process, and recombined to the NiCoS NAs / NFF surface through the negative potential. Figure 7 As shown in the figure, the EDS line scan results show that the NiCoSNAs nanorod structure on the surface of the anode material is coated with FeOOH after the potential reversal performance is restored, and is converted into a typical core-shell structure, in which NiCoSNAs is the core structure and FeOOH introduced by negative potential recovery is the shell structure. The anode material at this time can be named FeOOH-NiCoSNAs / NFF. The above evidence shows that while effectively realizing the structural recovery 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 electrolysis cell. The NiFe Foam self-supporting electrode contains a large amount of electrophilic metal Fe components, and its three-dimensional porous structure can prevent the large amount of calcium, magnesium ions and other insoluble impurities in seawater from clogging the porous structure self-supporting electrode and causing performance degradation.

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

[0045] The above embodiments are only preferred embodiments of the present invention and are not intended to limit the implementation methods. The protection scope of the present invention shall be subject to the scope defined in the claims. Other different forms of changes or modifications may be made based on the above description. Obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for restoring the performance of a seawater electrolysis device, wherein the device comprises 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 electrolyze seawater to produce hydrogen, characterized in that: The anode material includes an anode self-supporting electrode and an anode catalyst, and the cathode material includes a cathode self-supporting electrode and a cathode catalyst. The anode catalyst is the same as the cathode catalyst, and the anode self-supporting electrode is the same as the cathode self-supporting electrode. When the performance of the electrolysis device decays, the electrolysis device stops supplying power, a negative potential is applied to the anode material and a positive potential is applied to the cathode to achieve performance recovery of the electrolysis device.

2. The method for restoring the performance of a seawater electrolysis device according to claim 1, characterized in that: The electrolyte solution of the seawater electrolysis device is seawater, and the seawater is 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: The anode catalyst and the cathode catalyst are both oxides, hydroxides, nitrides, phosphides, sulfides or carbides of transition metals, and the transition metals are one or more of Cu, Ni, Fe, Co, Mn, Cr, V, Mo and Nb.

5. The method for restoring the performance of a seawater electrolysis device according to claim 1, characterized in that: The anode self-supporting electrode and the cathode self-supporting electrode are both three-dimensional porous structure metal frames containing strong electrophilic metal components, wherein the strong electrophilic metal is one or more of Co, Fe, Mn, Cr, and V, and the three-dimensional porous structure metal frame is any one of foam metal, porous metal mesh, and metal fiber felt.

6. 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 to 1000 mA cm -2 .

7. 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 in an electrolyte solution after hydrogen production by seawater electrolysis.

8. 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 halogen ion salt solution simulated seawater; 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 buffer.

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