A composite phosphate seawater electrolyte, a preparation method and application thereof
By adding a composite phosphate buffer system to the seawater electrolyte, the microenvironment at the anode interface is regulated, solving the problems of anode passivation and corrosion, and improving the stability and efficiency of seawater electrolysis for hydrogen production. It is particularly suitable for nickel-containing substrates or active layer anodes.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HAINAN UNIV
- Filing Date
- 2026-05-09
- Publication Date
- 2026-07-07
AI Technical Summary
In the existing technology, the anode surface is prone to forming an inactive deposit layer and corrosion during seawater electrolysis, leading to passivation and increased energy consumption. In addition, the material cost is high and the process is complex, making it difficult to promote on a large scale.
A composite phosphate buffer system, including basic orthophosphate and acidic orthophosphate, is used to regulate the microenvironment at the interface near the anode, inhibit Cl- corrosion and capping layer formation, and improve charge transfer state.
It effectively inhibits anode passivation and corrosion, improves the stability and efficiency of seawater electrolysis hydrogen production system, reduces energy consumption, and is suitable for transition metal-based oxygen evolution anodes, especially nickel-containing substrates or active layer anodes.
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Figure CN122344731A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of seawater electrolysis for hydrogen production technology, and in particular to a composite phosphate seawater electrolyte, its preparation method, and its application. Background Technology
[0002] Hydrogen energy, as a clean, efficient, and sustainable secondary energy source, plays a crucial role in energy transition and the achievement of dual-carbon goals. Hydrogen production through water electrolysis has attracted widespread attention due to its high hydrogen purity and clean process. Compared to freshwater resources, seawater is abundant and widely distributed; directly utilizing seawater for hydrogen production through electrolysis can effectively alleviate freshwater resource depletion and has promising application prospects.
[0003] However, natural seawater has a complex composition, containing large amounts of sodium. + Cl - In addition, it also contains Mg 2+ Ca 2+ SO4 2+ HCO3 - Various ions, including Cl, are present. During seawater electrolysis, the anode is exposed to a high-potential, strongly oxidizing environment. The local pH, dissolved oxygen concentration, and ion distribution near the interface continuously change, easily inducing degradation of the anode surface structure and chemical state. On one hand, dense or semi-dense inactive deposition layers, oxide layers, or composite capping layers easily form on the anode surface during the reaction, obscuring active sites and increasing charge transfer resistance, thus manifesting as anode passivation. On the other hand, Cl... - Migration, enrichment, and competitive adsorption near the anode interface further exacerbate corrosion, local instability, and electrochemical performance degradation on the anode material surface. Anode passivation and corrosion problems are often coupled, ultimately leading to increased cell pressure, increased energy consumption, shortened electrode life, and reduced continuous system operation capability.
[0004] In existing technologies, to improve the stability of seawater electrolysis anodes, precious metal coatings, highly corrosion-resistant alloy substrates, complex pretreatment processes, or multi-stage seawater purification methods are commonly used. While these methods can delay performance degradation to some extent, they generally suffer from high material costs, complex processes, demanding equipment maintenance requirements, and limitations on large-scale application. Therefore, developing an electrolyte additive that can be directly applied to seawater electrolysis systems, has a simple addition method, low cost, and can effectively inhibit anode passivation has significant engineering value and industrial implications. Summary of the Invention
[0005] In view of this, this application provides a composite phosphate seawater electrolyte, its preparation method, and its application, which inhibits Cl- without significantly sacrificing oxygen evolution activity. -The corrosion of Ni-based anodes improves the long-term stability of alkaline seawater electrolysis, effectively overcoming the shortcomings of the existing technologies.
[0006] The first aspect of this application provides a composite phosphate seawater electrolyte, comprising seawater and an additive; the additive is a composite phosphate buffer system, which includes basic orthophosphate and acidic orthophosphate.
[0007] Phosphates possess excellent ion regulation, interface modulation, and buffering properties. Our research has found that adding an appropriate amount of phosphate to seawater can effectively regulate the microenvironment near the anode, inhibit the formation of unfavorable deposits and inactive capping layers, slow down the passivation process on the anode surface, and improve the charge transfer state at the electrode / electrolyte interface, thereby enhancing the operational stability of the seawater electrolysis hydrogen production system. Based on this, we submit this application.
[0008] Preferably, the pH of the composite phosphate seawater electrolyte is 6.0 to 8.0.
[0009] Preferably, the basic orthophosphate is selected from trisodium phosphate and / or tripotassium phosphate, and the acidic orthophosphate is selected from sodium dihydrogen phosphate and / or potassium dihydrogen phosphate. Specifically, the acidic orthophosphate is used to adjust the pH of the solution and does not introduce new impurity ions.
[0010] Preferably, the alkali metal ion in the basic orthophosphate is selected from Li. + Na + K + At least one of them. Considering Na + To avoid introducing new impurities, Na is preferred for high concentrations in seawater. + However, other alkali metal ions are also applicable to this application.
[0011] Preferably, the concentration of phosphate anions in the composite phosphate seawater electrolyte is 0.001~0.5 M.
[0012] Preferably, the concentration of phosphate anions in the composite phosphate seawater electrolyte is 0.01~0.1M.
[0013] Preferably, the seawater is natural seawater or simulated seawater that has been filtered.
[0014] A second aspect of this application also provides a method for preparing the above-mentioned composite phosphate seawater electrolyte, comprising the following steps:
[0015] Basic orthophosphate is dissolved in filtered seawater, stirred thoroughly, and sonicated to obtain a uniform suspension. Then, acidic orthophosphate is added to adjust the pH to 6.0-8.0 and fully dissolved to obtain a composite phosphate seawater electrolyte.
[0016] Specifically, the preparation method of the above-mentioned composite phosphate seawater electrolyte includes the following steps:
[0017] (1) Filter natural seawater to remove impurities;
[0018] (2) Weigh a certain mass of Na3PO4 and add it to about 100 mL of seawater and stir.
[0019] (3) Transfer the suspension to a volumetric flask and make up the volume with seawater to the target volume. The concentration of Na3PO4 is 0.01 M.
[0020] (4) Add a small amount of NaH2PO4 to adjust the pH of the solution to 6.0~8.0, dissolve it completely, and obtain the composite phosphate seawater electrolyte.
[0021] The third aspect of this application also provides the application of the aforementioned composite phosphate seawater electrolyte in suppressing passivation of seawater electrolysis anodes.
[0022] Preferably, the anode is an oxygen-evolving anode, which is a transition metal-based or compound-based oxygen-evolving anode; the transition metal-based oxygen-evolving anode is an oxygen-evolving anode with a nickel-containing substrate or a nickel-containing active layer.
[0023] Compared with the prior art, this application has the following advantages:
[0024] 1. To address the issue of Cl-containing compounds in natural or simulated seawater. - In this environment, Cl- easily forms at the oxygen evolution anode. - To address the problems of induced corrosion, formation of inactive coatings, and the resulting anode passivation and decreased long-term stability, this application provides a composite phosphate buffered seawater electrolyte system for seawater electrolytic oxygen evolution anodes. This system uses natural or simulated seawater as the medium and alkali metal phosphate as the core. By constructing a composite phosphate buffer system composed of acidic and basic phosphates, the pH window and buffer capacity of the seawater electrolyte are set, thereby enhancing the system's resistance to local acid-base disturbances and improving operational stability. The technical focus of this application is the interface between the seawater electrolyte and the oxygen evolution anode, particularly suitable for transition metal-based or compound-based oxygen evolution anodes, and preferably for nickel-containing substrates or nickel-containing active layers.
[0025] 2. The composite phosphate buffer system in this application can regulate the microenvironment at the interface near the anode in seawater electrolysis, reduce the accumulation and adsorption tendency of chloride ions on the anode surface, slow down the formation of inactive capping layers and unfavorable deposits, thereby helping to inhibit anode passivation and corrosion, and improve the operational stability of the seawater electrolysis system. The electrolyte in this application is suitable for natural seawater or simulated seawater, and is preferably used for transition metal-based oxygen evolution anodes, especially for oxygen evolution anodes with nickel-containing substrates or nickel-containing active layers. Attached Figure Description
[0026] To more clearly illustrate the technical solutions in this application or the prior art, the drawings used in the description of this application or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0027] Figure 1 A flowchart illustrating the preparation method of seawater electrolyte for seawater electrolysis;
[0028] Figure 2 This represents the hydrogen evolution potential of the electrolyte after the addition of phosphate. Detailed Implementation
[0029] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0030] Unless otherwise specified, the experimental methods used in the embodiments of this application are all conventional methods.
[0031] In the following examples and comparative examples, unless otherwise specified, all raw materials can be prepared by commercial purchase or conventional methods.
[0032] The composite phosphate buffer system used in this application has at least the following mechanism of action: phosphate can preferentially adsorb onto the anode surface to form a negatively charged interface layer, thereby inhibiting the absorption of Cl-. - The isohalides generate electrostatic repulsion, reducing their probability of approaching and adsorbing on the anode surface; simultaneously, they inhibit the electrostatic repulsion of OH groups. - The influence near the anode surface is relatively small, thus slowing down the anodic corrosion and passivation process without significantly sacrificing oxygen evolution reaction activity.
[0033] Example 1: Trisodium phosphate / Disodium phosphate buffer additive
[0034] like Figure 1 As shown, the preparation method of the composite phosphate seawater electrolyte includes the following steps:
[0035] (1) Take Na3PO4·12H2O and add it to deionized water and stir to dissolve it, so as to obtain a solution A1 with a concentration of 0.01 M;
[0036] (2) Add about 0.01 M~0.05 M NaH2PO4 to solution A1, adjust the ratio of the two to make the pH of the solution 6.0~8.0, and fully dissolve to obtain electrolyte A2, that is, composite phosphate seawater electrolyte;
[0037] Example 2:
[0038] This embodiment can be referred to in Embodiment 1, the difference being that the basic orthophosphate is tripotassium phosphate, and the specific amount of the substance added remains the same.
[0039] Comparative Example 1: Natural seawater was used directly as the electrolyte without any additives.
[0040] Comparative Example 2: Natural seawater was simply alkalized with NaOH to a pH equivalent to that of Example 1, without using a phosphate system.
[0041] Application Example: Electrolyte A obtained in Example 1 was used for hydrogen production by electrolysis of natural seawater. A nickel foam-supported NiFe-based oxygen evolution active layer was used as the anode, and a platinum sheet as the cathode. The electrolyte volume was 250 mL, and the electrolysis was carried out at room temperature at 100 mA / cm². 2 Constant current electrolysis is performed.
[0042] like Figure 2 As shown, compared to natural seawater, the addition of PO4... 3- / H2PO4 - Subsequently, the HER polarization curve of the zinc electrode shifted overall towards the negative potential direction, indicating that the overpotential required for hydrogen evolution reaction on the zinc surface increased, meaning its hydrogen evolution tendency was significantly reduced. This result demonstrates that phosphate additives can effectively weaken the hydrogen evolution side reaction on the zinc surface in seawater, thereby helping to mitigate zinc self-corrosion and interfacial instability.
[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.
Claims
1. A composite phosphate seawater electrolyte, characterized in that, It includes seawater and additives; the additives are a complex phosphate buffer system, which includes basic orthophosphate and acidic orthophosphate.
2. The composite phosphate seawater electrolyte according to claim 1, characterized in that, The pH of the composite phosphate seawater electrolyte is 6.0~8.
0.
3. The composite phosphate seawater electrolyte according to claim 1, characterized in that, The basic orthophosphate is selected from trisodium phosphate and / or tripotassium phosphate, and the acidic orthophosphate is selected from sodium dihydrogen phosphate and / or potassium dihydrogen phosphate.
4. The composite phosphate seawater electrolyte according to claim 3, characterized in that, The alkali metal ions in the basic orthophosphate are selected from Li + Na + K + At least one of them.
5. The composite phosphate seawater electrolyte according to claim 1, characterized in that, The concentration of phosphate anions in the composite phosphate seawater electrolyte is 0.001~0.5 M.
6. The composite phosphate seawater electrolyte according to claim 5, characterized in that, The concentration of phosphate anions in the composite phosphate seawater electrolyte is 0.01~0.1 M.
7. The composite phosphate seawater electrolyte according to claim 1, characterized in that, The seawater in question is either natural seawater or simulated seawater that has been filtered.
8. A method for preparing the composite phosphate seawater electrolyte according to any one of claims 1 to 7, characterized in that, Includes the following steps: Basic orthophosphate is dissolved in filtered seawater, stirred thoroughly, and sonicated to obtain a uniform suspension. Then, acidic orthophosphate is added to adjust the pH to 6.0-8.0 and fully dissolved to obtain a composite phosphate seawater electrolyte.
9. The application of the composite phosphate seawater electrolyte according to any one of claims 1 to 7 in suppressing the passivation of seawater electrolysis anodes.
10. The application according to claim 9, characterized in that, The anode is an oxygen-evolving anode, which is a transition metal-based or compound-based oxygen-evolving anode; the transition metal-based oxygen-evolving anode is an oxygen-evolving anode with a nickel-containing substrate or a nickel-containing active layer.