A catalyst for electrolyzing seawater oxygen evolution suitable for industrial-grade electrolysis current density, as well as its preparation method and application

Abstract

The present invention relates to the technical field of electrolytic catalysts, and specifically to a catalyst for oxygen evolution from electrolytic seawater suitable for industrial-grade electrolytic current density, as well as a preparation method and application thereof. The present application discloses a method for preparing a catalyst for oxygen evolution from electrolytic seawater suitable for industrial-grade electrolytic current density, comprising the following steps: S1. substrate pretreatment, S2. preparation of electroplating solution, S3. preparation of precatalyst, S4. activation of the catalyst, using the precatalyst obtained in step S3 as a working electrode, a carbon rod as a counter electrode, and a mercury / mercuric oxide electrode as a reference electrode, and obtaining the catalyst by multiple cyclic voltammetric activations. The catalyst for oxygen evolution from electrolytic seawater prepared in the present application has excellent catalytic activity and can be stably used for a long time in alkaline real seawater at an industrial-grade electrolytic current density.

Description

Technical Field

[0001] The present invention relates to the technical field of electrolytic catalysts, and in particular to a seawater electrolysis oxygen evolution catalyst suitable for industrial-grade electrolysis current density, a preparation method thereof, and applications thereof. Background Art

[0002] Current water electrolysis technology requires high-quality water sources, typically using highly purified ultrapure water for hydrogen production. Large-scale application of pure water for hydrogen production remains challenging due to water resource distribution and cost. However, given that 96.5% of the Earth's water is seawater, which is abundant and requires no additional purification, seawater electrolysis is considered an effective approach for large-scale green hydrogen production.

[0003] Seawater contains a large amount of impurity ions and microorganisms, especially calcium ions, magnesium ions, chloride ions (Cl - ), which brings many challenges in the actual electrolysis of seawater. Specifically, seawater electrolysis involves the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode. Due to the presence of chloride ions on the anode side, there may be a competitive reaction of chloride ions during the oxidation process, especially when electrolysis is carried out at a high current density. - It consumes electrons to produce chlorine or other chlorine-containing byproducts, thereby significantly reducing the electrolysis efficiency and selectivity. Due to the presence of calcium ions and magnesium ions on the cathode side, H+ is rapidly consumed during the reduction process, and a local alkaline environment is generated around the active site. The calcium ions and magnesium ions are then converted into calcium hydroxide and magnesium hydroxide precipitation, blocking the active site. In addition, it is worth noting that Cl - The presence of ions can cause corrosion of the catalyst and / or conductive substrate, ultimately leading to electrode failure.

[0004] In the water electrolysis process, the OER reaction is more complex and has a higher reaction energy barrier than the HER reaction. Therefore, optimizing the OER catalytic activity is crucial to reducing the energy efficiency of hydrogen production from water electrolysis. How to design and develop seawater electrolysis oxygen evolution catalysts that can be used at industrial-grade electrolysis current densities remains a major challenge in the field of water electrolysis hydrogen production. To this end, this application provides a seawater electrolysis oxygen evolution catalyst suitable for industrial-grade electrolysis current densities, as well as its preparation method and application. Summary of the Invention

[0005] The present application discloses a catalyst for electrolyzing seawater oxygen evolution at an industrial-grade electrolysis current density, a preparation method thereof, and an application thereof. In the preparation method, large-sized rare earth elements are doped into transition metal alloys to adjust the electronic structure of the alloy elements and generate lattice strain, thereby improving the OER catalytic activity and stability. At the same time, the common ion effect of rare earth elements is utilized to reduce Cl -The adsorption of the catalyst enables efficient and stable electrolysis of seawater at industrial-grade electrolysis current densities. The resulting seawater electrolysis oxygen evolution catalyst exhibits excellent catalytic activity and can operate stably and long-term in alkaline real seawater at industrial-grade electrolysis current densities. This solves the numerous problems that impurity ions (such as calcium, magnesium, and chloride ions) in seawater can cause during the electrolysis process, such as competitive reactions with chloride ions that reduce electrolysis efficiency and selectivity, precipitation of calcium and magnesium ions that block active sites, and corrosion of the catalyst and conductive substrate caused by chloride ions.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] In a first aspect, the present application provides a method for preparing a catalyst for electrolyzing seawater oxygen evolution at an industrial-grade electrolysis current density, comprising the following steps:

[0008] S1. Substrate pretreatment

[0009] Ultrasonic cleaning of the substrate to be deposited to obtain a pre-treated substrate;

[0010] Ultrasonic cleaning was performed in ethanol, acetone, hydrochloric acid, and ethanol, respectively, with the concentration of hydrochloric acid being 1-5 mol / L;

[0011] S2. Preparation of electroplating solution

[0012] The plating solution includes the following raw materials:

[0013] 0.1-6 mol / L metal ions; H3BO3, NH4Cl, NaCl;

[0014] The molar ratio of metal ions, H3BO3; NH4Cl; NaCl is: 1:0.05-0.5:0.1-3.0:0.1-1.0;

[0015] S3. Preparation of precatalyst

[0016] The untreated substrate is used as the working anode and the previously treated substrate is used as the working cathode. The working anode and the working cathode are placed in the electroplating solution with adjusted pH for electrodeposition. After the electrodeposition is completed, the conductive substrate with the pre-catalyst deposited is taken out.

[0017] S4. Activation of Catalyst

[0018] The catalyst was obtained by cyclic voltammetry activation using the precatalyst obtained in step S3 as a working electrode, a carbon rod as a counter electrode, and a mercury / mercuric oxide electrode as a reference electrode.

[0019] In some specific embodiments, the substrate is any one of Ni foil, Ni mesh, Ti foil, Ti mesh, stainless steel sheet, stainless steel mesh, nickel foam, iron foam, copper foam, carbon felt, and nickel felt.

[0020] In some specific embodiments, in step S2, the metal ions include nickel salts, transition metal salts other than nickel, and salts of rare earth elements; wherein the transition metal salt other than nickel is any one of cobalt salts, iron salts, molybdates, and ruthenium salts.

[0021] In some specific embodiments, the nickel salt is any one or more of nickel chloride, nickel nitrate, nickel acetate, nickel sulfate, nickel oxalate, nickel perchlorate, nickel chlorate, and nickel bromide;

[0022] The cobalt salt is any one or more of cobalt chloride, cobalt nitrate, cobalt sulfate, cobalt oxalate, cobalt chlorate, cobalt perchlorate, and cobalt acetate; the iron salt is any one or more of ferric chloride, ferrous chloride, ferrous nitrate, ferrous sulfate, ferrous sulfate, ferrous oxalate, ferrous oxalate, ferrous acetate, ferric perchlorate, ferrous chlorate, ferrous acetate, and ferric bromide;

[0023] The molybdate is any one or more of ammonium molybdate, sodium molybdate, potassium molybdate, and lithium molybdate; the ruthenium salt is ruthenium chloride;

[0024] The salt of the rare earth element is any one or more of lanthanum nitrate, cerium nitrate, praseodymium nitrate, neodymium nitrate, samarium nitrate, europium nitrate, and yttrium nitrate.

[0025] In some embodiments, in step S3, the pH of the plating solution needs to be adjusted to 3.0-6.0.

[0026] In some embodiments, in step S3, the distance between the working anode and the working cathode is 1 cm, and the current density is 20-80 mA / cm 2 The electrochemical deposition is carried out with a direct current of 5-30min and the plating solution temperature is maintained at 30-80℃.

[0027] In some specific embodiments, in step S4, during the multiple cyclic voltammetric activations, the voltage window is scanned in the range of 0-1.0 V vs Hg / HgO, the scan rate is 50-100 mV / s, and the number of cycles is 50-300.

[0028] In a second aspect, the present application provides a seawater electrolysis oxygen evolution catalyst suitable for industrial-grade electrolysis current density, including one prepared by the preparation method described in the first aspect.

[0029] In some specific embodiments, the electrolysis of seawater oxygen evolution catalyst is composed of Ni, transition metals other than nickel, rare earth elements and O element; wherein Ni accounts for 65-80% of the total metal element molar ratio, transition metals other than nickel account for 10-25% of the total metal element molar ratio, and rare earth metals account for 1-10% of the total metal element molar ratio; the total metal elements refer to Ni, transition metals other than nickel, and rare earth metals.

[0030] In a third aspect, the present application provides an application of a catalyst, wherein the catalyst prepared by the preparation method described in the first aspect or the catalyst described in the second aspect is applied to the field of electrolysis of alkaline seawater.

[0031] The beneficial effects of this application are:

[0032] 1. In the preparation method described in the present application, the pretreatment of the substrate provides a favorable growth surface for the deposition of the precatalyst. The precatalyst is a rare earth element-doped transition metal alloy obtained on a conductive substrate by a one-step deposition method. The precatalyst is activated by cyclic voltammetry to convert the surface of the transition metal alloy into transition metal oxide / transition metal hydroxide, thereby achieving catalyst activation.

[0033] On the one hand, the unique 4f and 5d orbitals of rare earth elements can couple with the d orbitals of transition metals, so rare earth elements have an electronic buffering effect and thus adjust the electronic structure of transition metals, improving the kinetics of oxygen evolution reaction; on the other hand, rare earth elements exist in the form of oxides in the catalyst, which has excellent corrosion resistance and can greatly improve the stability of the catalyst in simulated seawater and real alkaline seawater. As a result, the catalyst can be used in simulated seawater and real alkaline seawater at an industrial-grade electrolysis current density (500mA / cm 2 ) Long-term stable operation.

[0034] 2. The seawater electrolysis oxygen evolution catalyst prepared in this application has the morphology of a uniformly sized nanosheet array, an alloy phase inside to achieve excellent charge transfer, and a transition metal oxide / hydroxide loaded with rare earth element oxides on the outside to improve surface conversion and achieve high catalytic activity. At the same time, the presence of rare earth element oxides ensures the stability of the catalyst in simulated seawater / real alkaline seawater.

[0035] 3. The seawater electrolysis oxygen evolution catalyst prepared in this application not only has excellent catalytic activity in alkaline pure water electrolyte, but also maintains excellent catalytic activity in simulated seawater / real alkaline seawater, and can serve stably for a long time at industrial-grade electrolysis current density, and can be applied in the field of industrial seawater electrolysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The present invention will be further described below with reference to the accompanying drawings and examples.

[0037] Figure 1 This is a morphology diagram of the sample prepared in Example 1 of the present invention;

[0038] Figure 2 is a morphology diagram of the sample prepared in Example 2 of the present invention;

[0039] Figure 3 is an X-ray powder diffraction (XRD) pattern of the precatalyst prepared in Example 2 of the present invention;

[0040] Figure 4-Figure 6 is the EDS graph of the sample prepared in Example 2 of the present invention;

[0041] Figure 7 Comparison of polarization curves (LSV) of the sample prepared in Example 2 of the present invention (rare earth element-doped catalyst), nickel foam, and undoped rare earth element catalyst in 1 mol / L KOH;

[0042] Figure 8 The LSV curves of the sample prepared in Example 2 of the present invention, nickel foam, and IrO2 in simulated seawater (1 mol / L KOH + 0.5 mol / L NaCl) are compared;

[0043] Figure 9 The LSV curves of the sample prepared in Example 2 of the present invention in alkaline pure water, simulated seawater and alkaline real seawater are compared;

[0044] Figure 10 The Tafel curves of the catalyst prepared in Example 2 of the present invention (a rare earth element-doped catalyst), foamed nickel, and an undoped rare earth element catalyst when corroded in simulated seawater are shown;

[0045] Figure 11 This is the IT curve of the stability test of the catalyst prepared in Example 2 of the present invention in alkaline real seawater. DETAILED DESCRIPTION

[0046] In order to facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the embodiments. The contents mentioned in the embodiments are not intended to limit the present invention.

[0047] As used herein, "and / or" includes the term of any and all combinations of one or more of the associated listed items. The terms used herein are only used to describe specific embodiments and are not intended to limit the invention. As used herein, the singular forms "a", "an", "an" and "the" are also intended to include the plural forms, unless the context clearly indicates otherwise. It is further understood that "including", when used in this specification, specifies the stated features, integers, steps, operations, elements and / or components, but does not preclude the existence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0048] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It is further understood that terms, such as those defined in commonly used dictionaries, are interpreted in accordance with their meanings in the context of the relevant art and are not idealized or overly formalized unless expressly defined otherwise herein.

[0049] The exemplary inventions described herein may suitably lack any one or more element limitations that are not specifically disclosed herein. Therefore, terms such as "comprises," "includes," "contains," and the like should be understood broadly and non-restrictively. In addition, the terminology used herein is used as a description, not a limitation, and the use of these terminology expressions that do not include any equivalent characteristics is unintentional, but only describes a portion of their characteristics, but various modifications are possible within the scope of the invention based on the disclosure of the present invention. Therefore, although the present invention has been specifically disclosed through preferred embodiments and optional features, the modifications disclosed herein to embody changes to the invention may be recorded by those skilled in the art, and such modifications and changes will be considered to be within the scope of the invention.

[0050] The raw material or reagent used in the embodiments of the present invention and the comparative example are all purchased from the market mainstream manufacturers, and the manufacturer or concentration are not specified. They are all the raw material or reagent of the analytical grade that can be conventionally obtained. As long as the desired effect can be achieved, there are no particular restrictions. The instrument and equipment used in the present embodiment are all purchased from the main manufacturers in the market. As long as the desired effect can be achieved, there are no particular restrictions. In the present embodiment, the specific technology or conditions are not specified. The technology or conditions described in the document in this area or the product specification are carried out.

[0051] Explanation of terms:

[0052] Oxygen evolution reaction (OER): The oxygen generation reaction that occurs at the anode during electrolysis. In water electrolysis, this process involves water molecules losing electrons to generate oxygen, hydrogen ions, and electrons. It is one of the key half-reactions in the electrolytic hydrogen production process. Its reaction kinetics are relatively complex and the reaction energy barrier is high. Therefore, optimizing its catalytic activity is crucial to reducing the energy efficiency of hydrogen production from water electrolysis.

[0053] The hydrogen evolution reaction (HER) is a hydrogen evolution reaction that occurs at the cathode during electrolysis, typically when hydrogen ions gain electrons on the electrode surface. In seawater electrolysis, the cathode HER can be affected by impurities such as calcium and magnesium ions in the seawater, altering the environment surrounding the active sites and affecting reaction efficiency.

[0054] Cyclic voltammetry: A commonly used electrochemical analysis method. In this application, it is used for catalyst activation. By repeatedly scanning the electrode surface at a specific scan rate within a certain voltage window, redox reactions occur, thereby changing the catalyst surface structure and promoting the conversion of the transition metal alloy surface into highly catalytically active transition metal oxides / hydroxides. The presence of rare earth elements also affects the redox potential and reaction rate of the transition metal, further optimizing catalyst performance.

[0055] Lattice strain: A stress state within a crystal caused by changes in the interatomic distances or distortion of the crystal structure. In this application, lattice strain is generated by doping a transition metal alloy with a large-sized rare earth element, which distorts the alloy lattice. This strain can modulate the electronic structure of the alloying elements, thereby affecting the catalytic activity and stability of the catalyst.

[0056] Common ion effect: In this application, this refers to the effect of the presence of rare earth elements on chloride ion adsorption. Due to certain properties of rare earth elements, chloride ion adsorption on the catalyst surface is reduced, thereby reducing the adverse effects of chloride ions during electrolysis, such as competitive reactions and corrosion of the catalyst and conductive substrate, and improving the catalyst's electrolytic performance in seawater.

[0057] Transition metals are metallic elements located in the d-zone of the periodic table, such as iron, cobalt, and nickel. Transition metal alloys possess excellent physical and chemical properties, such as high strength, high hardness, good electrical conductivity, and catalytic activity, and are widely used in many industrial fields.

[0058] Rare earth elements: The lanthanides (La to Lu) in the periodic table, as well as scandium (Sc) and yttrium (Y), have unique 4f and 5d orbital electron structures that can adjust the electronic properties of other metals, enhance catalytic performance and improve corrosion resistance.

[0059] Industrial electrolysis current density: refers to the high current density required in electrolysis processes used in industrial applications, typically hundreds to thousands of milliamperes per square centimeter (mA / cm²).

[0060] Currently, seawater electrolysis involves the cathode hydrogen evolution reaction (HER) and the anodic oxygen evolution reaction (OER). These complex reaction processes are affected by the large number of impurity ions and microorganisms in seawater. Chloride ions at the anode are prone to competitive reactions during oxidation, consuming electrons to produce chlorine gas or other chlorine-containing byproducts, which also corrode the catalyst and conductive substrate. During the reduction process, calcium and magnesium ions at the cathode rapidly consume H⁺, creating a localized alkaline environment. This in turn leads to the formation of calcium hydroxide and magnesium hydroxide precipitates that block active sites. These factors collectively lead to technical issues such as low electrolysis efficiency and poor catalyst stability when traditional water electrolysis technology is applied in seawater.

[0061] To this end, the present application provides a method for preparing a catalyst for electrolyzing seawater oxygen evolution at an industrial-grade electrolysis current density, comprising the following steps:

[0062] S1. Substrate pretreatment

[0063] Ultrasonic cleaning of the substrate to be deposited to obtain a pre-treated substrate;

[0064] Ultrasonic cleaning was performed in ethanol, acetone, hydrochloric acid, and ethanol, respectively, with the concentration of hydrochloric acid being 1-5 mol / L;

[0065] S2. Preparation of electroplating solution

[0066] The plating solution includes the following raw materials:

[0067] 0.1-6 mol / L metal ions; H3BO3, NH4Cl, NaCl;

[0068] The molar ratio of metal ions, H3BO3; NH4Cl; NaCl is: 1:0.05-0.5:0.1-3.0:0.1-1.0;

[0069] S3. Preparation of precatalyst

[0070] The untreated substrate is used as the working anode and the previously treated substrate is used as the working cathode. The working anode and the working cathode are placed in the electroplating solution with adjusted pH for electrodeposition. After the electrodeposition is completed, the conductive substrate with the pre-catalyst deposited is taken out.

[0071] S4. Activation of Catalyst

[0072] The catalyst was obtained by cyclic voltammetry activation using the precatalyst obtained in step S3 as a working electrode, a carbon rod as a counter electrode, and a mercury / mercuric oxide electrode as a reference electrode.

[0073] Specifically, in step S1, the substrate is any one of Ni foil, Ni mesh, Ti foil, Ti mesh, stainless steel sheet, stainless steel mesh, foamed nickel, foamed iron, foamed copper, carbon felt, and nickel felt.

[0074] In this application, in step S1, the solubility of ethanol and acetone is used to remove organic impurities such as oil on the substrate surface, while hydrochloric acid dissolves inorganic impurities such as metal oxides on the substrate surface. Ultrasonic cleaning of the substrate to be deposited in different solvents can effectively remove various types of dirt, leaving the substrate surface clean, facilitating uniform deposition and adhesion of the precatalyst during subsequent electrodeposition, thereby ensuring catalyst quality and performance.

[0075] Specifically, in step S2, the metal ions include nickel salts, transition metal salts other than nickel, and salts of rare earth elements; among them, transition metal salts other than nickel include cobalt salts (such as cobalt chloride, cobalt nitrate, etc.), iron salts (such as ferric chloride, ferric nitrate, etc.), molybdates (such as ammonium molybdate, sodium molybdate, etc.), ruthenium salts (such as ruthenium chloride), etc.

[0076] The nickel salt is any one or more of nickel chloride, nickel nitrate, nickel acetate, nickel sulfate, nickel oxalate, nickel perchlorate, nickel chlorate, and nickel bromide;

[0077] The cobalt salt is any one or more of cobalt chloride, cobalt nitrate, cobalt sulfate, cobalt oxalate, cobalt chlorate, cobalt perchlorate, and cobalt acetate; the iron salt is any one or more of ferric chloride, ferrous chloride, ferrous nitrate, ferrous sulfate, ferrous sulfate, ferrous oxalate, ferrous oxalate, ferrous acetate, ferric perchlorate, ferrous chlorate, ferrous acetate, and ferric bromide;

[0078] The molybdate is any one or more of ammonium molybdate, sodium molybdate, potassium molybdate, and lithium molybdate; the ruthenium salt is ruthenium chloride;

[0079] The salt of the rare earth element is any one or more of lanthanum nitrate, cerium nitrate, praseodymium nitrate, neodymium nitrate, samarium nitrate, europium nitrate, and yttrium nitrate.

[0080] In step S2, by precisely preparing an electroplating solution containing specific concentrations of metal ions (such as nickel salts, cobalt salts, etc. and rare earth element salts), H3BO3, NH4Cl, NaCl and having a certain pH value, it is ensured that during electrodeposition, the metal ions can be deposited on the substrate in a predetermined proportion to form the required catalyst precursor composed of Ni, specific transition metals, rare earth elements and O elements in a proportion that meets the requirements (such as Ni accounting for 65-80% of the total metal elements by mole ratio).

[0081] Specifically, in step S3, the pH of the plating solution needs to be adjusted to 3.0-6.0. The distance between the working anode and the working cathode is 1 cm, and the current density is 20-80 mA / cm 2 The electrochemical deposition is carried out with a direct current of 5-30min and the plating solution temperature is maintained at 30-80℃.

[0082] In this application, the principle of electrochemical deposition is utilized, with the untreated substrate serving as the working anode and the pre-treated substrate serving as the working cathode, and direct current is applied to a plating solution containing a variety of metal ions. Under the action of the electric field, the metal ions in the plating solution move toward the cathode and obtain electrons on its surface, undergoing a reduction reaction and deposition. Transition metal ions such as Ni²⁺ and Co²⁺, as well as rare earth element ions, will deposit on the cathode substrate in a certain proportion to form an alloy. By controlling parameters such as current density, deposition time, and plating solution temperature, the deposition rate and the alloy growth process can be precisely adjusted, thereby affecting the composition, crystal structure, and morphology of the pre-catalyst, ultimately determining the performance of the catalyst.

[0083] Therefore, a rare earth element-doped transition metal alloy precatalyst is formed on the treated substrate through electrodeposition, laying the foundation for subsequent activation to produce the final catalyst with excellent performance. This step enables the orderly deposition of metal ions on the substrate surface, initially building the basic framework of the catalyst and enabling preliminary control of the catalyst composition and microstructure, thereby affecting its catalytic performance.

[0084] Specifically, in step S4, during the multiple cyclic voltammetry activations, the voltage window is scanned in the range of 0-1.0 V vs Hg / HgO, the scan rate is 50-100 mV / s, and the number of cycles is 50-300 times.

[0085] In this application, during a cyclic voltammetry scan, the precatalyst serves as the working electrode, and a series of redox reactions occur on the electrode surface within a specific voltage window (0-1.0V vs Hg / HgO) and scan rate (50-100mV / s). As the number of cycles (50-300 times) increases, the metal atoms on the surface of the transition metal alloy gradually react with OH⁻ and other substances in the electrolyte, converting into the corresponding oxides or hydroxides. The presence of rare earth elements may affect the redox potential and reaction rate of the transition metal, promoting the surface conversion process and forming a structure with abundant active sites and good electron transfer ability on the catalyst surface, thereby improving the catalyst's oxygen evolution catalytic activity and stability in simulated seawater and real alkaline seawater.

[0086] Therefore, the pre-catalyst is treated by cyclic voltammetry to transform the surface of the pre-catalyst to form transition metal oxides / transition metal hydroxides with high catalytic activity, thereby activating the pre-catalyst into a catalyst that can efficiently and stably electrolyze seawater at industrial-grade electrolysis current density.

[0087] The electrolytic seawater oxygen evolution catalyst obtained by the above preparation method is composed of Ni, transition metals other than nickel, rare earth elements and O element; wherein Ni accounts for 65%-80% of the total metal element molar ratio, transition metals other than nickel account for 10%-25% of the total metal element molar ratio, and rare earth metals account for 1%-10% of the total metal element molar ratio; the total metal elements refer to Ni, transition metals other than nickel, and rare earth metals.

[0088] Specifically, the following aspects are used to ensure that the element composition ratio of the catalyst meets the requirements:

[0089] Raw material ratio control: When preparing the electroplating solution in step S2, the concentration and ratio of metal ions are precisely controlled. The molar ratio of metal ions, H₃BO₃, NH₄Cl, and NaCl is 1:0.05-0.5:0.1-3.0:0.1-1.0. The metal ions include nickel salts, transition metal salts other than nickel (such as cobalt salts, iron salts, molybdates, and ruthenium salts), and salts of rare earth elements (such as lanthanum nitrate and cerium nitrate), with their respective concentrations within the range of 0.1-6 mol / L. By accurately weighing and blending these raw materials, the ratio of each element in the electroplating solution is determined from the source, providing a foundation for the subsequent deposition of a catalyst that meets the composition requirements. For example, to prepare a catalyst with a molar ratio of 70% nickel, 20% cobalt, and 10% la, the specific amounts of nickel salt, cobalt salt, and lanthanum nitrate in the electroplating solution are calculated based on their molar masses and the target ratio.

[0090] Electrodeposition parameter control: During the preparation of the pre-catalyst in step S3, the conditions of the electrodeposition have a significant impact on the catalyst composition. The distance between the working anode and the working cathode is fixed at 1 cm, and the current density is 20-80 mA / cm 2 The electroplating solution is maintained in a water bath at 30°C-80°C, with a DC current of 5-30 minutes. These parameters work together to determine the deposition rate and amount of metal ions deposited on the substrate. The deposition rates of different metal ions vary depending on their properties and electrodeposition conditions. By optimizing these parameters, the metal ions can be deposited on the substrate in a predetermined proportion to form an alloy. For example, appropriately reducing the current density and extending the deposition time may facilitate the deposition of relatively difficult-to-deposit metal ions, such as rare earth elements, thereby ensuring their proportion in the alloy meets the requirements.

[0091] After preparation, the catalyst's composition can be verified through various analytical methods, such as X-ray powder diffraction (XRD). Taking Example 2 as an example, the characteristic peaks in the XRD pattern of the precatalyst prepared therein substantially match the Ni characteristic peaks of PDF04-0850 and are shifted toward lower angles, confirming an increase in the Ni lattice spacing. This is presumably due to the doping of another transition metal and rare earth element into the Ni lattice. This confirms the successful doping of the elements and their impact on the Ni lattice, ensuring that the catalyst composition actually prepared meets the design requirements.

[0092] The following is a further description of the catalyst for electrolyzing seawater oxygen evolution and its preparation method and application according to the present invention with reference to specific embodiments:

[0093] Example 1

[0094] A method for preparing a catalyst for electrolyzing seawater oxygen evolution at an industrial-grade electrolysis current density comprises the following steps:

[0095] (1) Substrate pretreatment

[0096] The substrate to be deposited was ultrasonically cleaned in ethanol, acetone, hydrochloric acid, and ethanol in sequence to remove surface dirt. The concentration of hydrochloric acid was 3 mol / L. The substrate was then rinsed with deionized water to obtain a spare substrate.

[0097] (2) Prepare metal electroplating solution

[0098] A metal electroplating mother solution containing 3 mol / L NiCl2·6H2O, 3 mol / L CoCl2·6H2O, 0.5 mol / L La(NO3)3·6H2O, 0.5 mol / L H3BO3, 1.2 mol / L NH4Cl, and 0.1 mol / L NaCl was prepared; and after adjusting the pH to 4.5, a metal electroplating mother solution was obtained.

[0099] (3) Preparation of precatalyst

[0100] The untreated substrate was used as the working anode and the pre-treated substrate was used as the working cathode. They were placed in the metal plating solution (2). The distance between the working anode and the working cathode was 1 cm, and the current density was 40 mA / cm 2 The electroplating was carried out with a direct current of 10 min and the plating solution temperature was maintained at 60 °C.

[0101] (4) Catalyst activation

[0102] The precatalyst obtained in step S3 was activated using cyclic voltammetry. The precatalyst obtained in step S3 was used as the working electrode, a carbon rod as the counter electrode, a mercury / mercuric oxide electrode as the reference electrode, and a 1 mol / L KOH solution as the electrolyte. Cyclic voltammetry was performed 100 times in the range of 0-1.0 V vs. Hg / HgO at a scan rate of 50 mV / s to obtain the catalyst. After activation, the catalyst was further used as a catalytic electrode for electrolysis of alkaline seawater for seawater electrolysis testing.

[0103] Among them, the morphology of the electrolytic seawater oxygen evolution catalyst suitable for industrial-grade electrolysis current density is as follows: Figure 1 As shown in the figure, it can be seen that the main body of the material appears as a nanoflower cluster, and a large number of spherical particles are loaded on the surface.

[0104] The electrochemical tests of the seawater electrolysis oxygen evolution catalyst with an industrial-grade electrolysis current density were carried out as follows:

[0105] Electrochemical testing of the electrodes was performed at room temperature using a CHI 660E electrochemical workstation. The electrolytic cell used a standard three-electrode system. The seawater electrolysis oxygen evolution catalyst suitable for industrial-grade electrolysis current density obtained in this example was clamped with a platinum electrode holder as the working electrode, a graphite rod as the counter electrode, and Hg / HgO as the reference electrode. The electrolytes were simulated seawater (1 mol / L KOH + 0.5 mol / L NaCl) and real alkaline seawater (seawater obtained from Shenzhen Qianhai Bay, with 1 mol / L KOH added). The linear sweep voltammogram (LSV) scan rate was 5 mV / s, the voltage was manually compensated using 93% iR, and the potential scan range was 0.9 to -1.83 V. According to the formula: overpotential = actual measured potential + 0.059 × pH + 0.095 V - 1.23 V.

[0106] Example 2

[0107] A method for preparing a catalyst for electrolyzing seawater oxygen evolution at an industrial-grade electrolysis current density comprises the following steps:

[0108] The difference from Example 1 is that in step (2), a metal plating mother solution of 1 mol / L NiNO3·6H2O, 1 mol / L CoNO3·6H2O, 0.2 mol / L La(NO3)3·6H2O, 0.2 mol / L H3BO3, 0.5 mol / L NH4Cl, and 0.05 mol / L NaCl is used, and the pH is adjusted to 4. In step (3), the current density is 50 mA / cm 2 The electrodeposition time was 15 min, and the remaining steps were the same as in Example 1. The catalyst morphology was obtained as follows Figure 2As shown in the figure, it can be seen that the main body of the material presents a nanosheet array morphology, and the surface is loaded with spherical particles.

[0109] Figure 3 This is the XRD pattern of the precatalyst prepared in this example. The characteristic peaks of the precatalyst closely match those of Ni in PDF04-0850. The shift of the characteristic peaks toward lower angles confirms an increase in the Ni lattice spacing, presumably due to doping of another transition metal and rare earth element into the Ni lattice. Further characterization of the catalytic activity of the oxygen evolution catalyst prepared in this example demonstrates that this method can successfully prepare a range of rare earth element-doped catalysts.

[0110] Figure 7 Prepare the sample for Example 2 ( Figure 4-6 The EDS graph of the sample prepared in Example 1 shows the comparison of LSV curves of the rare earth element-doped catalyst, nickel foam, and undoped rare earth element catalyst in 1M KOH. The rare earth element-doped catalyst can achieve 1000 mA / cm at 1.55V. 2 The current density of the catalyst without rare earth doping is only 286 mA / cm at the same voltage. 2 Current density: nickel foam current density does not exceed 10mA / cm 2 , proving that doping with rare earth elements optimizes OER catalytic activity. The performance of the catalyst prepared in this example was compared with that of nickel foam and IrO2 in simulated seawater (1 mol / L KOH + 0.5 mol / L NaCl). The catalyst prepared in this example showed the best catalytic activity in simulated seawater, such as the catalyst and IrO2 achieved 100 mA / cm 2 The current density required voltages of 1.52V and 1.70V, respectively, confirming that the catalyst performs better than IrO2 in simulated seawater. Furthermore, the catalyst prepared in this example was subjected to LSV tests in alkaline pure water, simulated seawater, and alkaline real seawater (1 mol / L KOH, 1 mol / L KOH + 0.5 mol / L NaCl, 20 wt.% KOH + seawater). The results are as follows: Figure 9 The catalytic performance of the catalyst in pure water, simulated seawater and alkaline real seawater is basically the same, which proves that the quality of water has little effect on the catalytic activity, and the catalyst also has excellent catalytic activity in alkaline seawater. Figure 10 The Tafel curves of the catalyst (doped rare earth element catalyst) prepared in this example, nickel foam, and undoped rare earth element catalyst were respectively corroded in simulated seawater. The corrosion potentials of nickel foam, undoped rare earth element catalyst, and doped rare earth element catalyst in simulated seawater were 0.898 V, 0.610 V, and 0.952 V, respectively, and the corrosion current density was 0.0132 mA / cm 2 , 0.0123mA / cm2 , 0.00698mA / cm 2 , confirming that rare earth element-doped catalysts have the best corrosion resistance. Figure 11 The stability test curve of the catalyst prepared in this example in alkaline real seawater (20wt.% KOH + seawater) is shown. The catalyst can react with 500mA / cm 2 The catalyst ran stably at a current density of 100 nm for nearly 400 h and has the potential to operate stably for a longer period of time, confirming that the catalyst can serve stably for a long time at an industrial-grade electrolysis current density in alkaline real seawater.

[0111] Example 3

[0112] A method for preparing a catalyst for electrolyzing seawater oxygen evolution at an industrial-grade electrolysis current density comprises the following steps:

[0113] The difference from Example 1 is that in step (2), a metal plating mother solution of 3 mol / L NiCl2·6H2O, 3 mol / L (NH4)2MoO4·4H2O, 0.5 mol / L Ce(NO3)3·6H2O, 0.5 mol / L H3BO3, 1.2 mol / L NH4Cl, and 0.1 mol / L NaCl is used, and the pH is adjusted to 4. In step (3), the current density is 50 mA / cm 2 , the electrodeposition time was 10 min, and the remaining steps were the same as in Example 1.

[0114] Example 4

[0115] A method for preparing a catalyst for electrolyzing seawater oxygen evolution at an industrial-grade electrolysis current density comprises the following steps:

[0116] The difference from Example 1 is that in step (2), a metal plating mother solution of 1 mol / L NiCl2·6H2O, 1 mol / L RuCl3·4H2O, 0.2 mol / L Ce(NO3)3·6H2O, 0.5 mol / L H3BO3, 1.2 mol / L NH4Cl, and 0.1 mol / L NaCl is used, and the pH is adjusted to 4.5. In step (3), the current density is 25 mA / cm 2 , the electrodeposition time was 20 min, and the remaining steps were the same as in Example 1.

[0117] Example 5

[0118] A method for preparing a catalyst for electrolyzing seawater oxygen evolution at an industrial-grade electrolysis current density comprises the following steps:

[0119] The difference from Example 1 is that: step (2) uses a metal plating mother solution of 3 mol / L NiCl2·6H2O, 3 mol / L FeCl2·4H2O, 0.5 mol / L Ce(NO3)3·6H2O, 0.5 mol / L H3BO3, 1.2 mol / L NH4Cl, and 0.1 mol / L NaCl; in step (3), the current density is 50 mA / cm 2 , the electrodeposition time was 15 min, and the remaining steps were the same as in Example 1.

[0120] Example 6

[0121] A method for preparing a catalyst for electrolyzing seawater oxygen evolution at an industrial-grade electrolysis current density comprises the following steps:

[0122] The difference from Example 1 is that in step (2), a metal plating mother solution of 1 mol / L NiNO3·6H2O, 1 mol / L FeCl2, 0.2 mol / L La(NO3)3·6H2O, 0.2 mol / L H3BO3, 0.5 mol / L NH4Cl, and 0.05 mol / L NaCl is used, and the pH is adjusted to 4. In step (3), the current density is 50 mA / cm 2 , the electrodeposition time was 15 min, and the remaining steps were the same as in Example 1.

[0123] Example 7

[0124] A method for preparing a catalyst for electrolyzing seawater oxygen evolution at an industrial-grade electrolysis current density comprises the following steps:

[0125] The difference from Example 1 is that in step (2), a metal plating mother solution of 1 mol / L NiNO3·6H2O, 1 mol / L CoNO3·6H2O, 0.2 mol / L Ce(NO3)3·6H2O, 0.2 mol / L H3BO3, 0.5 mol / L NH4Cl, and 0.05 mol / L NaCl is used, and the pH is adjusted to 4.5. In step (3), the current density is 50 mA / cm 2 , the electrodeposition time was 15 min, and the remaining steps were the same as in Example 1.

[0126] Example 8

[0127] A method for preparing a catalyst for electrolyzing seawater oxygen evolution at an industrial-grade electrolysis current density comprises the following steps:

[0128] The difference from Example 1 is that in step (2), a metal plating mother solution of 1 mol / L NiNO3·6H2O, 1 mol / L Fe(NO3)2, 0.2 mol / L Ce(NO3)3·6H2O, 0.2 mol / L H3BO3, 0.5 mol / L NH4Cl, and 0.05 mol / L NaCl is used, and the pH is adjusted to 4.5. In step (3), the current density is 50 mA / cm 2 , the electrodeposition time was 15 min, and the remaining steps were the same as in Example 1.

[0129] As can be seen from the various parameters in the above embodiments, the preparation method of this specific embodiment can control the growth and morphology of the rare earth element-doped transition metal alloy catalyst by adjusting the type and concentration of metal ions, electrodeposition current density, electrodeposition time and reaction temperature. In this embodiment, the conductive substrate is pre-treated to obtain a clean conductive substrate, and a rare earth element-doped transition metal alloy is prepared on the conductive substrate by a cathode plating method, and the final catalyst is further obtained by cyclic voltammetry activation; the catalyst morphology is a nanoflower cluster or a nanosheet array, and spherical particles are loaded on the substrate / nanosheet. The catalyst has good conductivity, good corrosion resistance, and excellent catalytic activity for oxygen evolution in electrolysis of alkaline seawater. The composition and morphology of the rare earth element-doped transition metal alloy catalyst have a crucial influence on the catalytic activity and stability. Different elements have different reaction intermediate adsorption capacities and different atomic radii of different elements during the catalytic reaction process, which leads to different effects on the catalytic activity and stability of the design of rare earth element-doped transition metal alloy catalysts. Rare earth doped NiCo / Fe / Ru / Mo exhibits excellent oxygen evolution catalytic activity. For example, in 1M simulated seawater, the catalysts prepared in Examples 3, 4, 5, 6, 7, and 8 reach 100 mA / cm 2 The current density required is 1.62V, 1.51V, 1.64V, 1.55V, 1.58V, and 1.53V, respectively. However, since the catalyst is composed of three elements, the difference in atomic radius will affect the structural stability and corrosion resistance of the catalyst. For example, Examples 3 and 4 can only operate for 105 hours and 82 hours at a current density of 500 mA / cm² in alkaline real seawater. This is mainly due to the large difference in atomic radius, which makes it easy for elements with larger radius to precipitate during long-term operation and thus the catalyst fails. Therefore, by rationally regulating the types of rare earth elements and transition metal elements and the structure and morphology of the alloy catalyst, excellent catalytic activity and corrosion resistance can be achieved, which can be applied to the field of electrolysis of alkaline seawater.

[0130] The above embodiments are preferred implementation schemes of the present invention. In addition, the present invention can also be implemented in other ways. Any obvious replacement without departing from the concept of the present invention is within the scope of protection of the present invention.

Claims

1. A method for preparing a catalyst for electrolyzing seawater oxygen evolution at an industrial-grade electrolysis current density, characterized in that: The following steps are involved: S1. Substrate pretreatment Ultrasonic cleaning of the substrate to be deposited to obtain a pre-treated substrate; Ultrasonic cleaning was performed in ethanol, acetone, hydrochloric acid, and ethanol, respectively, with the concentration of hydrochloric acid being 1-5 mol / L; S2. Preparation of electroplating solution The plating solution includes the following raw materials: 0.1-6 mol / L metal ions; H3BO3, NH4Cl, NaCl; The molar ratio of metal ions, H3BO3; NH4Cl; NaCl is: 1:0.05-0.5:0.1-3.0:0.1-1.0; The metal ions are nickel salts, transition metal salts other than nickel, and salts of rare earth elements; wherein the transition metal salts other than nickel are any one of cobalt salts and iron salts; and the salts of rare earth elements are any one of lanthanum nitrate and cerium nitrate; S3. Preparation of precatalyst The untreated substrate is used as the working anode and the previously treated substrate is used as the working cathode. The working anode and the working cathode are placed in a plating solution with a well-adjusted pH value for electrodeposition. After the electrodeposition is completed, the conductive substrate with the pre-catalyst deposited is removed. The pH value of the plating solution needs to be adjusted to 3.0-6.

0. The current density is 20-80 mA / cm 2 Direct current is used for electrodeposition, the electrodeposition time is 5-30 min, and the plating solution temperature is maintained at 30℃-80℃; S4. Activation of Catalyst The catalyst is obtained by cyclic voltammetry activation using the precatalyst obtained in step S3 as a working electrode, a carbon rod as a counter electrode, and a mercury / mercuric oxide electrode as a reference electrode; The electrolytic seawater oxygen evolution catalyst is composed of Ni, transition metals other than nickel, rare earth elements and O element; wherein Ni accounts for 65%-80% of the total metal elements by molar ratio, transition metals other than nickel account for 10%-25% of the total metal elements by molar ratio, and rare earth metals account for 1%-10% of the total metal elements by molar ratio; the total metal elements refer to Ni, transition metals other than nickel and rare earth metals.

2. The preparation method according to claim 1, characterized in that The substrate is any one of Ni foil, Ni mesh, Ti foil, Ti mesh, stainless steel sheet, stainless steel mesh, foam nickel, foam iron, foam copper, carbon felt, and nickel felt.

3. The preparation method according to claim 1, characterized in that The nickel salt is any one or more of nickel chloride, nickel nitrate, nickel acetate, nickel sulfate, nickel oxalate, nickel perchlorate, nickel chlorate, and nickel bromide; The cobalt salt is any one or more of cobalt chloride, cobalt nitrate, cobalt sulfate, cobalt oxalate, cobalt chlorate, cobalt perchlorate, and cobalt acetate; the iron salt is any one or more of ferric chloride, ferrous chloride, ferrous nitrate, ferrous sulfate, ferrous sulfate, ferrous oxalate, ferrous oxalate, ferrous acetate, ferric perchlorate, ferrous chlorate, ferrous acetate, and ferric bromide.

4. The preparation method according to claim 1, characterized in that In step S3, the distance between the working anode and the working cathode is 1 cm.

5. The preparation method according to claim 1, characterized in that In step S4, during multiple cyclic voltammetry activations, the voltage window is scanned in the range of 0-1.0 V vs Hg / HgO, the scan rate is 50-100 mV / s, and the number of cycles is 50-300.

6. A catalyst for electrolyzing seawater oxygen evolution suitable for industrial-grade electrolysis current density, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 5.

7. Application of a catalyst, characterized in that The catalyst prepared by the preparation method according to any one of claims 1 to 5 or the catalyst according to claim 6 is applied to the field of electrolysis of alkaline seawater.

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