An electrolytic seawater oxygen evolution catalyst and its preparation method

Abstract

The present application discloses an electrolytic seawater oxygen evolution catalyst and a preparation method thereof. The electrolytic seawater oxygen evolution catalyst is a transition metal and polypyrrole composite deposited in situ electrochemically on a metal substrate by an anodic oxidation method, effectively solving the problems that existing OER catalysts based on transition metal-based materials have poor long-term service effects under amperometric large currents and cannot meet the application requirements of industrial electrolyzed water and electrolyzed seawater.

Description

Technical Field

[0001] The present disclosure relates to the technical field of catalysts, and specifically to an electrocatalytic seawater oxygen evolution catalyst and a preparation method thereof. Background Art

[0002] The statements in this section only provide background information related to the present disclosure and do not constitute prior art.

[0003] Electrocatalytic materials and technologies, including hydrogen evolution reaction (HER) of water electrolysis, CO2 / CO reduction to chemicals and fuels (CO2 / CORR), oxygen reduction to H2O2 reaction (ORR), etc., are one of the most promising new energy technologies recognized worldwide. These cathodic reactions all require coupling with oxygen evolution reaction (OER) as the anodic reaction to provide protons and balance charges.

[0004] The oxygen evolution reaction usually uses water as a raw material. Compared with fresh water resources, seawater accounts for 95% of the total water resources on the earth and is the most suitable raw material for electrolysis. However, compared with pure water electrolysis, there are high concentrations of chloride ions in seawater, which will cause chlorine evolution reaction (ClER) and compete with the oxygen evolution reaction. This requires the prepared OER catalyst to have high activity. At the same time, the corrosion of the catalyst by chloride ions will cause the catalyst to dissolve and the structure to collapse, resulting in poor durability of the catalyst, which is another key challenge that needs to be solved for long-term seawater electrolysis.

[0005] Transition metal-based OER materials have good catalytic activity, and the preparation cost is hundreds of times lower than that of noble metal catalysts. Therefore, OER catalysts based on transition metal-based materials have received extensive attention; such as transition metal organic framework compounds modified by organic ligands, transition metal oxides and hydroxides doped with elements such as P, S, and B. Most of these catalysts are obtained by mixing with a binder and sticking to the surface of the metal substrate or by conventional methods such as solvothermal reaction, chemical vapor deposition, and coprecipitation to cause the reaction of external metal reagents and other reagents on the surface of the metal substrate, rather than growing from the original metal substrate elements, belonging to a physical deposition layer. Therefore, there is a poor interfacial bond between such catalysts and the metal substrate, and they can usually only operate stably for no more than 300 hours at a relatively low current density and in an electrolyte without chloride ions, far lower than the requirements of industrial water electrolysis and seawater electrolysis applications.

[0006] In addition, in order to improve the catalytic activity, most of the current seawater electrolysis OER catalysts pursue large specific surface area and ultra-thin sheet structure during preparation, but this structure makes the catalyst easy to collapse during service and cannot resist the corrosion of corrosive chloride ions. At present, some work designs to construct various insoluble protective layers on the catalyst surface, but these protective layers cover the active sites and also slightly reduce the catalytic activity. Moreover, although the operating stability of the catalyst has been slightly improved, its service life still cannot meet the requirements of industrial applications.

[0007] Therefore, most of the current OER catalysts for seawater electrolysis still have the problem of not being able to simultaneously achieve high catalytic activity and stable structure.

[0008] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may contain information that does not constitute prior art. Summary of the invention

[0009] In view of this, the present disclosure provides a seawater electrolysis oxygen evolution catalyst to solve the problem that the existing transition metal-based OER catalysts have poor long-term service effect under ampere-level large currents and cannot meet the application requirements of industrial water electrolysis and seawater electrolysis.

[0010] On the other hand, the present disclosure also provides a method for preparing the seawater electrolysis oxygen evolution catalyst.

[0011] In a first aspect, the electrolytic seawater oxygen evolution catalyst is:

[0012] Transition metal and polypyrrole composites deposited in situ electrochemically on metal substrates by anodic oxidation.

[0013] In some embodiments of the present disclosure, the metal substrate is selected from the group consisting of nickel foam, nickel sheet, iron foam, iron sheet, stainless steel mesh, and stainless steel sheet.

[0014] In a second aspect, the method for preparing the catalyst for oxygen evolution by electrolysis of seawater described in the first aspect comprises:

[0015] An electrolytic cell is formed using the metal substrate as a working electrode and a counter electrode;

[0016] The pyrrole monomer and the metal salt are mixed into a deionized water solution to obtain a deposition electrolyte;

[0017] The catalyst for oxygen evolution by electrolysis of seawater is obtained by electro-deposition using a constant current method.

[0018] In some embodiments of the present disclosure, the electrolytic cell is a two-electrode H-type electrolytic cell separated by a proton exchange membrane.

[0019] In some embodiments of the present disclosure, the deposition electrolyte further includes a main dopant and an auxiliary dopant;

[0020] The main dopant is sodium nitrate, and the auxiliary dopant is sodium molybdate.

[0021] In some embodiments of the present disclosure, the concentration of the sodium nitrate is 0.1-0.4 mol / L, and the concentration of the sodium molybdate is 0.02-0.05 mol / L.

[0022] In some embodiments of the present disclosure, the metal salt is one or more of nickel sulfate, ferrous sulfate, or cobalt sulfate.

[0023] In some embodiments of the present disclosure, the concentration of the pyrrole monomer is 0.2-0.5 mol / L, and the concentration of the metal salt is 0.01-0.05 mol / L.

[0024] In some embodiments of the present disclosure, the deposition current of the electrodeposition is 10-30 mA cm -2 , and the deposition time is 200-600 s; and / or,

[0025] The counter electrode is a graphite electrode or a platinum electrode.

[0026] The present disclosure has the following beneficial effects:

[0027] The electrolytic seawater oxygen evolution catalyst of the present disclosure is a composite of a transition metal / polypyrrole (representing the transition metal and polypyrrole) electrochemically deposited in-situ on a metal substrate by an anodic oxidation method. Compared with the existing electrolytic seawater oxygen evolution catalysts, the following performance improvements are achieved:

[0028] 1. The interfacial bonding force between the catalyst and the metal substrate is improved

[0029] Because under the anodic oxidation current, the oxidation of the metal substrate will generate metal ions with empty orbitals, which have a coordination effect with the nitrogen atoms with lone pair electrons in the polypyrrole, and a metal-nitrogen (M-N) bond can be formed, enabling the in-situ polymerization growth of the polymer on the metal substrate and enhancing the interfacial bonding force between the deposition layer and the metal substrate. Therefore, the metal substrate can simultaneously serve as a conductive carrier and a metal ion source, reducing the catalyst preparation cost;

[0030] 2. The structural stability of the catalyst is improved

[0031] Polypyrrole has good mechanical stability, and there is a coordination bond between the nitrogen atoms with lone pair electrons on the polypyrrole and the metal ions with empty orbitals generated by the dissolution of the metal substrate and the externally added metal ions with empty orbitals, resulting in the excellent mechanical stability and high structural stability of the finally formed transition metal / polypyrrole composite oxygen evolution catalyst. Therefore, it is not easy to dissolve or collapse during service.

[0032] 3. The catalytic activity of the catalyst is improved.

[0033] The catalyst has hydrophilicity. Due to the π-d electron effect between polypyrrole and metal ions, the catalyst has good oxygen evolution catalytic activity. Therefore, the overpotential of the catalyst of the present disclosure can be 235 mV at 10 mA cm -2 , which is superior to the nickel foam catalyst modified with commercial ruthenium dioxide (RuO2).

[0034] 4. The corrosion resistance of the catalyst is improved.

[0035] Anions have a certain repulsive effect on chloride ions. Therefore, to a certain extent, they can inhibit the erosion of chloride ions on the catalyst. At present, anions in the oxygen evolution catalyst for electrolyzing seawater mainly come from two aspects. One is to add a large amount of anions to the electrolyte. Although this method has a certain effect, steps such as seawater treatment and anion addition are required before use, and seawater cannot be directly electrolyzed. The process is complicated, and the additional addition of a large amount of anions will increase the cost. The other is generated by the structural evolution of the material itself, such as the evolution of selenide into selenate and the evolution of phosphide into phosphate. Although the anions generated by the oxidative dissolution of these catalysts can repel chloride ions, they also make the catalyst structure loose and easy to collapse, and are prone to fall off from the metal substrate surface due to bubble impact during long-term service.

[0036] For the catalyst of the present disclosure, anions are directly introduced during the preparation process, without the need to be additionally added to the electrolyte or for the catalyst itself to undergo structural evolution. It has no impact on the structural stability of the material. At the same time, the polymer material polypyrrole itself has a certain density, and its density has not changed after being compounded with transition metals. In addition, the introduction of a small amount of molybdate can promote the polymerization of the polymer and improve its density. Moreover, by adjusting and optimizing conditions such as the concentration of each component in the electrolyte, deposition current, and deposition time, the deposited transition metal / polypyrrole composite catalyst is made more dense. Therefore, the catalyst of the present disclosure has a dense and stable structure, so it has a good barrier effect on corrosive media. Therefore, under the combined action of the repulsive effect of anions on chloride ions and the barrier effect of the catalyst itself on corrosive media, the corrosion resistance of the catalyst is improved.

[0037] 5. The long-term operation stability at an ampere-level large current density is improved.

[0038] Under the synergistic effect of the above excellent interfacial binding force, structural stability, oxygen evolution catalytic activity, corrosion resistance, etc., the catalyst of the present disclosure can stably operate for about 2170 h, 1945 h, and 1400 h respectively in 1 mol / L KOH solution, 1 mol / L KOH + 0.5 mol / L NaCl simulated seawater solution, and 1 mol / L KOH + real seawater solution at an amperometric large current density, and the long-term operation stability is greatly improved. Description of the Drawings

[0039] Through the description of the embodiments of the present disclosure with reference to the following drawings, the above and other objects, features, and advantages of the present disclosure will become clearer. In the drawings:

[0040] Figure 1 Process flow for preparing the electrolytic seawater oxygen evolution catalyst of the present disclosure;

[0041] Figure 2 Surface scanning electron microscope (SEM) images of Examples 1-4 of the present disclosure;

[0042] Figure 3 Cross-sectional SEM image of Example 1 of the present disclosure;

[0043] Figure 4 Linear sweep voltammetry (LSV) curves of Examples 1-4 and Comparative Example 1 of the present disclosure;

[0044] Figure 5 Operating curve of Example 1 of the present disclosure in 1 mol / L KOH solution at 25 °C under a current of 500 mA cm -2 ;

[0045] Figure 6 Operating curve of Example 1 of the present disclosure in 1 mol / L KOH solution at 25 °C under a current of 500 mA cm -2 after operating for 1100 h;

[0046] Figure 7 Operating curve of Example 1 of the present disclosure in 1 mol / L KOH + 0.5 mol / L NaCl solution at 40 °C under a current of 500 mA cm -2 ;

[0047] Figure 8 Operating curve of Example 1 of the present disclosure in 1 mol / L KOH + seawater solution at 25 °C under a current of 500 mA cm -2 ;

[0048] Figure 9 Surface scanning electron microscope (SEM) image of Comparative Example 1 of the present disclosure;

[0049] Figure 10 For Comparative Example 1 of the present disclosure at 500 mA cm -2 current, 25 °C, 1 mol / L

[0050] Operating curve in KOH solution;

[0051] Figure 11 For Comparative Example 1 of the present disclosure at 500 mA cm -2 Surface SEM image after operating in 1 mol / L KOH solution at 25 °C and 500 mA cm current for about 13 h. Specific embodiments

[0052] The following describes the present disclosure based on embodiments. However, it should be noted that the present disclosure is not limited to these embodiments. In the following detailed description of the present disclosure, some specific details are described in detail. However, those skilled in the art can also fully understand the present disclosure for the parts not described in detail.

[0053] In addition, those of ordinary skill in the art should understand that the provided drawings are only for illustrating the purpose, features, and advantages of the present disclosure, and the drawings are not actually drawn to scale.

[0054] At the same time, unless the context clearly requires otherwise, the words "including", "comprising", and similar words throughout the specification and claims should be interpreted as having an inclusive meaning rather than an exclusive or exhaustive meaning; that is, it is the meaning of "including but not limited to".

[0055] The inventors of the present application found through research that most of the catalysts in the publicly available literature and patents are formed by bonding with a binder on the surface of a metal substrate or by reacting an external metal reagent and other reagents on the surface of the metal substrate, rather than "primitively grown" from the metal substrate elements, and belong to a physical deposition layer. Therefore, the metal substrate-catalyst layer interface is only physically bonded, presenting problems such as poor bonding strength. During use, there are also problems such as a large interface resistance between the metal and the catalyst, which is not conducive to electron transfer, and the catalyst is prone to falling off from the metal substrate due to bubble impact. In addition, in order to improve the catalyst activity, most current catalysts pursue a large specific surface area, an ultrathin sheet-like structure, etc. during preparation, which makes the structure of the catalyst prone to collapse and unable to resist the erosion of corrosive chloride ions during service. Therefore, the poor metal-catalyst interface bonding and poor structural stability ultimately lead to the catalyst being unable to withstand an ampere-level large current and having a poor long-term service effect, far lower than the requirements of industrial electrolysis of water and electrolysis of seawater applications.

[0056] Based on the above findings, the catalysts of the present disclosure improve the actual service stability of the catalysts under ampere-level large current from aspects such as improving the catalyst activity, the interfacial bonding force with the metal substrate, the structural stability, and the corrosion resistance.

[0057] The specific technical concept adopted by the catalyst of the present disclosure is: an anodic oxidation method is used to electrochemically deposit a transition metal / polypyrrole composite in-situ on a metal substrate as an oxygen evolution catalyst for electrolyzing seawater.

[0058] For the above technical concept of the present disclosure, because under anodic oxidation current, metal ions with empty orbitals generated by the oxidation of the metal substrate can coordinate with nitrogen atoms with empty orbitals on the polymer to form M-N bonds, enabling the catalyst to grow in-situ on the surface of the metal substrate and enhancing the interfacial bonding force between the deposited layer and the metal substrate. Therefore, the metal substrate can serve as both a conductive carrier and a metal ion source simultaneously. The polypyrrole material itself is dense and has good mechanical stability, and the metal ions can form coordination bonds with nitrogen atoms on the polypyrrole, with π-d electron interactions existing. Therefore, the transition metal / polypyrrole composite oxygen evolution catalyst has excellent structural stability and oxygen evolution catalytic activity. Additionally, for the oxygen evolution reaction catalyst for electrolyzing seawater of the present disclosure, anions are directly introduced during the preparation process, without the need to be added separately to the electrolyte or for the structure of the catalyst itself to evolve, which has no impact on the structural stability of the material. Therefore, the catalyst of the present disclosure has a dense and stable structure, has a good barrier effect on corrosive media, and the corrosion resistance of the catalyst is improved.

[0059] Example 1

[0060] I. Preparation of the transition metal / polypyrrole composite oxygen evolution catalyst

[0061] The preparation process of the transition metal / polypyrrole composite oxygen evolution catalyst in Example 1 of the present disclosure is as Figure 1 shown, and specifically includes the following steps:

[0062] 1. Metal substrate treatment and electrolyte preparation

[0063] S1. Cleaning of the nickel foam substrate: The nickel foam substrate is cleaned with hydrochloric acid, water, etc., and set aside;

[0064] S2. Preparation of the deposition electrolyte: 0.2 mol / L pyrrole monomer, 0.03 mol / L ferrous sulfate, 0.2 mol / L sodium nitrate, and 0.04 mol / L sodium molybdate are added to water, and stirred to obtain the deposition electrolyte, which is set aside;

[0065] 2. Electrochemical oxidation in-situ polymerization growth

[0066] S3. Preparation of the electrolytic cell: A two-electrode H-type electrolytic cell separated by a proton exchange membrane (Nafion-117) is used, and the metal substrate treated in the first step and a graphite rod are used as the working electrode and the counter electrode respectively;

[0067] S4. Electrodeposition: At 20 mA cm -2Perform constant current deposition for 400 s, and then dry in an oven to obtain the target catalyst.

[0068] In the process of in-situ polymerization growth by electrochemical oxidation, on the one hand, the metal substrate A (A is nickel foam in Example 1 of this embodiment) is oxidized, and metal ions A (metal ions A are Ni 2+ ions in Example 1 of this embodiment) are dissolved out. The nitrogen atom on the pyrrole monomer coordinates with metal ions A and metal ions B in the externally added metal salt B (metal salt B is FeSO4 in Example 1 of this embodiment, and metal ions B are Fe 2+ / Fe 3+ ions) to grow in-situ polymerization on the metal substrate A, enhancing the interfacial bonding force between the deposition layer and the metal substrate. At this time, the metal substrate serves as both a conductive carrier and a metal ion source; moreover, the metal ions form coordination bonds with the nitrogen atoms on the polypyrrole, and there is π-d electron interaction. Therefore, the metal / polypyrrole composite catalyst has excellent structural stability and oxygen evolution catalytic activity. On the other hand, the anions in the metal salt B (the anions in the metal salt B are SO4 2- ions in Example 1 of this embodiment) and the anions in the dopants C and D (the dopants C and D are NaNO3 and Na2MoO4 respectively in Example 1 of this embodiment, and the anions in C and D are NO3 - and MoO4 2- ions respectively) are doped into the polymer. Because the organic monomer becomes a cation radical during the anodic oxidation process and needs anions to provide electrons and balance the charge, SO4 2- , NO3 - and MoO4 2- ions can participate in the polymerization process to form a multi-anion doped metal / polypyrrole composite catalyst. Because the structure of the transition metal / polypyrrole composite catalyst has a barrier effect on the corrosive medium, and the doped anions have a repulsive effect on the corrosive chloride ions, the corrosion resistance of the catalyst described in Example 1 of this disclosure is enhanced. On the third aspect, the polypyrrole material itself is relatively stable and dense, and the introduction of molybdate can promote the polymerization of polypyrrole, making its structure more stable and dense. Therefore, the structure of the catalyst is stable, so that the catalyst of this disclosure is not easy to collapse during service and can better resist the erosion of corrosive chloride ions.

[0069] It can be seen that the above-mentioned oxygen evolution catalyst prepared by in-situ electrochemical deposition of transition metal / polypyrrole composite on a metal substrate has excellent oxygen evolution catalytic activity, interfacial binding force, structural stability, corrosion resistance, etc., which can greatly improve the problems of limited activity of traditional catalysts, easy structural collapse during service, easy detachment from the metal substrate surface, and inability to resist the erosion of corrosive chloride ions. Therefore, the transition metal / polypyrrole composite oxygen evolution catalyst prepared in Example 1 of the present disclosure can be used as an oxygen evolution electrode for the anode of electrolyzed water and electrolyzed seawater, and can operate stably for a long time at an amperometric large current density.

[0070] II. Morphology and Performance Testing of Transition Metal / Polypyrrole Composite Oxygen Evolution Catalyst

[0071] 1. Perform surface SEM testing ( Figure 2 ) and cross-section SEM testing ( Figure 3 ) on the transition metal / polypyrrole composite oxygen evolution catalyst of Example 1. The test results show that the structure of this transition metal / polypyrrole composite oxygen evolution catalyst is dense, with a thickness between 300 - 500 nm, and has good interfacial binding with NF.

[0072] 2. Perform electrochemical testing on the transition metal / polypyrrole composite oxygen evolution catalyst of Example 1. The electrochemical testing system is a three-electrode system, where the transition metal / polypyrrole composite oxygen evolution catalyst of Example 1 is the working electrode, the mercury / mercuric oxide electrode is the reference electrode, and the platinum sheet electrode is the counter electrode.

[0073] To evaluate its oxygen evolution activity, perform LSV curve testing with a scanning rate of 10 mV s -1 . The test results are as Figure 4 . The overpotential of the transition metal / polypyrrole composite oxygen evolution catalyst of Example 1 is 235 mV at 10 mA cm 2 , and the Tafel slope is only 38 mV dec -1 .

[0074] To evaluate its operation stability, perform chronopotentiometry stability testing. As Figure 5 shown, the metal / polypyrrole composite oxygen evolution catalyst of Example 1 can operate stably for about 2170 h under the conditions of a temperature of 25 °C, an electrolyte of 1 mol / L KOH, and a working current of 500 mA cm -2 . As Figure 6 shown, at a current of 500 mA cm -2 , after operating in a 1 mol / L KOH solution at 25 °C for 1100 h, it still adheres firmly to the metal substrate surface and its structure has not collapsed. As Figure 7As shown, at a temperature of 40 °C, an electrolyte of 1 mol / L KOH + 0.5 mol / L NaCl, and a working current of 500 mA cm -2 , it can also operate stably for about 1945 h. As Figure 8 shown, at a temperature of 25 °C, an electrolyte of 1 mol / L KOH + seawater, and a working current of 500 mA cm -2 , it can also operate stably for about 1400 h.

[0075] Example 2

[0076] I. Preparation of transition metal / polypyrrole composite oxygen evolution catalyst

[0077] 1. Metal substrate treatment and electrolyte preparation

[0078] S1. Cleaning of nickel sheet substrate: Clean the nickel sheet substrate with hydrochloric acid, water, etc., and set aside;

[0079] S2. Preparation of deposition electrolyte: Add 0.2 mol / L pyrrole monomer, 0.03 mol / L ferrous sulfate, 0.2 mol / L sodium nitrate, and 0.04 mol / L sodium molybdate into an aqueous solution, stir to obtain the deposition electrolyte, and set aside;

[0080] 2. Electrochemical oxidation in-situ polymerization growth

[0081] S3. Preparation of electrolytic cell: Use a two-electrode H-type electrolytic cell separated by a proton exchange membrane (Nafion-117), and use the metal substrate treated in the first step and a graphite rod as the working electrode and the counter electrode respectively;

[0082] S4. Electrodeposition: Deposit at a constant current of 20 mA cm -2 for 400 s, and then dry in an oven to obtain the target catalyst.

[0083] II. Morphology and performance testing of transition metal / polypyrrole composite oxygen evolution catalyst

[0084] 1. Perform surface SEM testing ( Figure 2 ) on the transition metal / polypyrrole composite oxygen evolution catalyst of this Example 2. The test results show that the structure of the transition metal / polypyrrole composite oxygen evolution catalyst is dense.

[0085] 2. Perform electrochemical testing on the transition metal / polypyrrole composite oxygen evolution catalyst of this Example 2. The electrochemical testing system is a three-electrode system, where the transition metal / polypyrrole composite oxygen evolution catalyst of this Example 2 is the working electrode, the mercury / mercuric oxide electrode is the reference electrode, and the platinum sheet electrode is the counter electrode.

[0086] To evaluate its oxygen evolution activity, an LSV curve test was conducted with a scanning rate of 10 mV s -1 . The test results are as follows Figure 4 shown. The overpotential of the transition metal / polypyrrole composite oxygen evolution catalyst of Example 2 was 300 mV at 10 mA cm -2 .

[0087] Example 3

[0088] I. Preparation of the transition metal / polypyrrole composite oxygen evolution catalyst

[0089] 1. Treatment of the metal substrate and preparation of the electrolyte

[0090] S1. Cleaning of the iron foam substrate: The iron foam substrate was cleaned with hydrochloric acid, water, etc. and reserved;

[0091] S2. Preparation of the deposition electrolyte: 0.2 mol / L pyrrole monomer, 0.03 mol / L nickel sulfate, 0.2 mol / L sodium nitrate, and 0.04 mol / L sodium molybdate were added to water, and stirred to obtain the deposition electrolyte and reserved;

[0092] 2. Electrochemical oxidation in-situ polymerization growth

[0093] S3. Preparation of the electrolytic cell: A two-electrode H-type electrolytic cell separated by a proton exchange membrane (Nafion-117) was used, and the metal substrate treated in the first step and the graphite rod were used as the working electrode and the counter electrode respectively;

[0094] S4. Electrochemical deposition: Constant current deposition was carried out at 20 mA cm -2 for 400 s, and then dried in an oven to obtain the target catalyst.

[0095] II. Morphology and performance testing of the transition metal / polypyrrole composite oxygen evolution catalyst

[0096] 1. Surface SEM testing was carried out on the transition metal / polypyrrole composite oxygen evolution catalyst of Example 3 ( Figure 2 ), and the test results showed that the structure of the transition metal / polypyrrole composite oxygen evolution catalyst was dense.

[0097] 2. Electrochemical testing was carried out on the transition metal / polypyrrole composite oxygen evolution catalyst of Example 3. The electrochemical testing system was a three-electrode system, in which the transition metal / polypyrrole composite oxygen evolution catalyst of Example 3 was the working electrode, the mercury / mercuric oxide electrode was the reference electrode, and the platinum sheet electrode was the counter electrode.

[0098] To evaluate its oxygen evolution activity, an LSV curve test was conducted with a scanning rate of 10 mV s -1 . The test results are as follows Figure 4As shown, the overpotential of the transition metal / polypyrrole composite oxygen evolution catalyst of Example 3 is 278 mV at 10 mA cm -2 -2.

[0099] Example 4

[0100] I. Preparation of Transition Metal / Polypyrrole Composite Oxygen Evolution Catalyst

[0101] 1. Treatment of Metal Substrate and Preparation of Electrolyte

[0102] S1. Cleaning of stainless steel mesh substrate: Clean the stainless steel mesh substrate with hydrochloric acid, acetone, water, etc., and set aside;

[0103] S2. Preparation of deposition electrolyte: Add 0.2 mol / L pyrrole monomer, 0.03 mol / L cobalt sulfate, 0.2 mol / L sodium nitrate, and 0.04 mol / L sodium molybdate to water, stir to obtain the deposition electrolyte, and set aside;

[0104] 2. Electrochemical Oxidation In-situ Polymerization Growth

[0105] S3. Preparation of electrolytic cell: Use a two-electrode H-type electrolytic cell separated by a proton exchange membrane (Nafion-117), and use the metal substrate treated in the first step and a graphite rod as the working electrode and the counter electrode respectively;

[0106] S4. Electrodeposition: Deposit at a constant current of 20 mA cm -2 -2 for 400 s, and then dry in an oven to obtain the target catalyst.

[0107] II. Morphology and Performance Testing of Transition Metal / Polypyrrole Composite Oxygen Evolution Catalyst

[0108] 1. Perform surface SEM testing ( Figure 2 ) on the transition metal / polypyrrole composite oxygen evolution catalyst of Example 4. The test results show that the structure of the transition metal / polypyrrole composite oxygen evolution catalyst is dense.

[0109] 2. Perform electrochemical testing on the transition metal / polypyrrole composite oxygen evolution catalyst of Example 4. The electrochemical testing system is a three-electrode system, where the transition metal / polypyrrole composite oxygen evolution catalyst of Example 4 is the working electrode, the mercury / mercuric oxide electrode is the reference electrode, and the platinum sheet electrode is the counter electrode.

[0110] To evaluate its oxygen evolution activity, perform LSV curve testing with a scanning rate of 10 mV s -1 . The test results are as Figure 4 shown. The overpotential of the transition metal / polypyrrole composite oxygen evolution catalyst of Example 4 is 302 mV at 10 mA cm -2 -2.

[0111] Comparative Example 1

[0112] I. Preparation of a commercial ruthenium dioxide (RuO₂)-modified nickel foam catalyst, which specifically includes the following steps:

[0113] S1. Cleaning of the nickel foam substrate: The nickel foam substrate is cleaned with hydrochloric acid, acetone, water, etc., and reserved for use;

[0114] S2. Catalyst dispersion process: Weigh 10 mg of the purchased commercial RuO₂ catalyst powder, and disperse it in a mixed solvent prepared from 0.1 mL of 5 wt% Nafion and 1.9 mL of isopropanol;

[0115] S3. Use a pipette to suck 0.3 mL of the uniformly dispersed solution in step S2 and drop it onto the surface of the treated nickel foam, and then dry it in an oven to obtain the target catalyst.

[0116] II. Morphology and performance testing of the commercial RuO₂-modified nickel foam oxygen evolution catalyst

[0117] 1. Perform surface SEM testing on the commercial RuO₂-modified nickel foam oxygen evolution catalyst of this Comparative Example 1 ( Figure 9 ), and the test results show that the structure of the commercial RuO₂-modified nickel foam oxygen evolution catalyst is loose.

[0118] 2. Perform electrochemical testing on the commercial RuO₂-modified nickel foam oxygen evolution catalyst of this Comparative Example 1. The electrochemical testing system is a three-electrode system, where the commercial RuO₂-modified nickel foam oxygen evolution catalyst of this Comparative Example 1 is the working electrode, the mercury / mercuric oxide electrode is the reference electrode, and the platinum plate electrode is the counter electrode.

[0119] To evaluate its oxygen evolution activity, perform an LSV curve test with a scanning rate of 10 mV s -1 . The test results are as Figure 5 shown. The overpotential of the transition metal / polypyrrole composite oxygen evolution catalyst of this Comparative Example 1 is 351 mV at 10 mA cm -2 .

[0120] To evaluate its operating stability, perform a chronopotentiometry stability test. As Figure 10 shown, the commercial RuO₂-modified nickel foam oxygen evolution catalyst of this Comparative Example 1 cannot operate stably under the conditions of a temperature of 25

[0121] °C, an electrolyte of 1 mol / L KOH, and a working current of 500 mA cm -2 , and it cannot be used after only 13 h of operation. As Figure 11 shown, at 500 mA cm -2Under the current, after running for about 13 h in 1 mol / L KOH solution at 25 °C, the catalyst peeled off from the surface of the metal substrate in a large area.

[0122] The above-described embodiments are only for expressing the implementation manners of the present disclosure. The description is relatively specific and detailed, but it should not be construed as a limitation on the patent scope of the present disclosure. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present disclosure, several deformations, equivalent substitutions, improvements, etc. can be made, and these all belong to the protection scope of the present disclosure. Therefore, the protection scope of the patent of the present disclosure shall be subject to the appended claims.

Claims

1. An electrolytic seawater oxygen evolution catalyst, characterized in that, The catalyst is as follows: A multi-anion doped transition metal and polypyrrole composite electrochemically deposited in-situ on a metal substrate by anodic oxidation; The metal substrate serves as both a conductive carrier and a metal ion source.

2. The electrolytic seawater oxygen evolution catalyst according to claim 1, wherein: The metal substrate is selected from nickel foam, nickel sheet, iron foam, iron sheet, stainless steel mesh, and stainless steel sheet.

3. The preparation method of the electrolytic seawater oxygen evolution catalyst according to claim 1 or 2, characterized in that, It includes: Using the metal substrate as the working electrode and the counter electrode to form an electrolytic cell; Mixing pyrrole monomer and metal salt into deionized aqueous solution to obtain a deposition electrolyte; Using the constant current method for electrodeposition to obtain the electrolytic seawater oxygen evolution catalyst.

4. The preparation method of the electrolytic seawater oxygen evolution catalyst according to claim 3, wherein: The electrolytic cell is a dual-electrode H-type electrolytic cell separated by a proton exchange membrane.

5. The preparation method of the electrolytic seawater oxygen evolution catalyst according to claim 4, wherein: The deposition electrolyte further includes a main dopant and an auxiliary dopant; The main dopant is sodium nitrate, and the auxiliary dopant is sodium molybdate.

6. The preparation method of the electrolytic seawater oxygen evolution catalyst according to claim 5, wherein: The concentration of sodium nitrate is 0.1 - 0.4 mol / L, and the concentration of sodium molybdate is 0.02 - 0.05 mol / L.

7. The preparation method of the electrolytic seawater oxygen evolution catalyst according to claim 6, wherein: The metal salt is one or more of nickel sulfate, ferrous sulfate, or cobalt sulfate.

8. The preparation method of the electrolytic seawater oxygen evolution catalyst according to claim 7, wherein: The concentration of the pyrrole monomer is 0.2 - 0.5 mol / L, and the concentration of the metal salt is 0.01 - 0.05 mol / L.

9. The preparation method of the electrolytic seawater oxygen evolution catalyst according to any one of claims 3 - 8, wherein: The deposition current of the electro-deposition is 10 - 30 mA cm -2 , and the deposition time is 200 - 600 s.

10. The preparation method of the electrolytic seawater oxygen evolution catalyst according to claim 9, wherein: The counter electrode is a graphite electrode or a platinum electrode.

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