Electrolytic seawater oxygen evolution catalyst suitable for industrial-grade electrolytic current density as well as preparation method and application of electrolytic seawater oxygen evolution catalyst

Abstract

The invention relates to the technical field of electrolytic catalysts, in particular to an electrolytic seawater oxygen evolution catalyst suitable for industrial-grade electrolytic current density and a preparation method and application of the electrolytic seawater oxygen evolution catalyst. The invention discloses a preparation method of an electrolytic seawater oxygen evolution catalyst suitable for industrial-grade electrolytic current density, which comprises the following steps: S1, substrate pretreatment, S2, electroplating liquid preparation, S3, pre-catalyst preparation, S4, catalyst activation, taking the pre-catalyst obtained in the S3 as a working electrode, taking a carbon rod as a counter electrode, and taking the electroplating liquid as an electroplating liquid. A mercury / mercuric oxide electrode is used as a reference electrode, and the catalyst is obtained through repeated cyclic voltammetry activation. The seawater electrolysis oxygen evolution catalyst prepared in the invention has excellent catalytic activity, and can stably serve in alkaline real seawater for a long time with industrial-grade electrolysis current density.

Description

Technical Field

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

[0002] At present, water electrolysis technology has high requirements on the quality of water supply sources, and usually requires the use of highly purified ultrapure water for electrolysis to produce hydrogen. From the perspective of water resource distribution and cost, the use of pure water for electrolysis to produce hydrogen is still challenging in large-scale applications. Considering that 96.5% of the water on Earth is seawater, which has abundant reserves and does not require additional purification, electrolysis of seawater is therefore considered to be one of the effective ways to achieve 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 electrolyzing at a high current density. - It consumes electrons to produce chlorine or other chlorine-containing byproducts, which significantly reduces the efficiency and selectivity of electrolysis. 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 can cause corrosion of the catalyst and / or conductive substrate, ultimately leading to electrode failure.

[0004] In the process of water electrolysis, OER is more complex and has a higher reaction energy barrier than HER reaction, so optimizing OER catalytic activity is crucial to reducing the energy efficiency of hydrogen production by water electrolysis. How to design and develop seawater electrolysis oxygen evolution catalysts that can be suitable for industrial-grade electrolysis current density is still a major challenge in the field of water electrolysis hydrogen production. To this end, the present application provides a seawater electrolysis oxygen evolution catalyst suitable for industrial-grade electrolysis current density and 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 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, and at the same time utilizing the common ion effect of rare earth elements to reduce Cl -The catalyst is adsorbed, and then the electrolysis of seawater is achieved efficiently and stably at an industrial-grade electrolysis current density; the prepared seawater electrolysis oxygen evolution catalyst has excellent catalytic activity and can be used stably for a long time in alkaline real seawater at an industrial-grade electrolysis current density. It solves many problems caused by impurity ions (such as calcium ions, magnesium ions, and chloride ions) in the electrolysis process, such as the competitive reaction of chloride ions reducing the electrolysis efficiency and selectivity, the precipitation of calcium ions and magnesium ions blocking the active sites, and the corrosion of catalysts and conductive substrates caused by chloride ions.

[0006] The purpose of the present invention is achieved through the following technical solutions: 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: 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, and the concentration of hydrochloric acid was 1-5 mol / L; S2. Preparation of plating solution The electroplating solution includes the following raw materials: 0.1-6mol / L metal ions; H3BO3, NH4Cl, NaCl; Wherein, the molar ratio of metal ion, H3BO3; NH4Cl; NaCl is: 1: 0.05-0.5: 0.1-3.0: 0.1-1.0; 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 the electroplating solution with adjusted pH to perform electrodeposition. After the electrodeposition is completed, the conductive substrate with the pre-catalyst deposited is taken out. S4. Activation of Catalyst The catalyst is obtained by using the precatalyst obtained in step S3 as a working electrode, a carbon rod as a counter electrode, and a mercury / mercury oxide electrode as a reference electrode through multiple cyclic voltammetric activations.

[0007] In some specific embodiments, 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.

[0008] 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.

[0009] 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; 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; The molybdate is any one or more of ammonium molybdate, sodium molybdate, potassium molybdate, and lithium molybdate; the ruthenium salt is ruthenium chloride; 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.

[0010] In some specific embodiments, in step S3, the pH of the plating solution needs to be adjusted to 3.0-6.0.

[0011] In some specific 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 Direct current is applied for electrochemical deposition, the deposition time is 5-30 minutes, and the plating solution temperature is maintained at 30-80°C.

[0012] 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 scanning speed is 50-100 mV / s, and the number of cycles is 50-300 times.

[0013] In a second aspect, the present application provides a catalyst for oxygen evolution by electrolysis of seawater suitable for industrial-grade electrolysis current density, including one prepared by the preparation method described in the first aspect.

[0014] 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 molar ratio, and rare earth metals account for 1-10% of the total metal molar ratio; the total metal elements refer to Ni, transition metals other than nickel, and rare earth metals.

[0015] 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.

[0016] The beneficial effects of this application are: 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 transition metal alloy doped with a rare earth element 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 a transition metal oxide / transition metal hydroxide, thereby achieving activation of the catalyst.

[0017] 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 and improve the kinetics of oxygen evolution reaction; on the other hand, rare earth elements exist in the catalyst in the form of oxides, which have 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.

[0018] 2. The catalyst for oxygen evolution by electrolysis of seawater prepared in the present application has the morphology of a nanosheet array of uniform size, 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.

[0019] 3. The seawater electrolysis oxygen evolution catalyst prepared in the present 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 be stably served for a long time under industrial-grade electrolysis current density, and can be applied to the field of industrial seawater electrolysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0021] Figure 1 This is a morphology diagram of a sample prepared in Example 1 of the present invention; Figure 2 is a morphology diagram of a sample prepared in Example 2 of the present invention; Figure 3 is an X-ray powder diffraction (XRD) pattern of the precatalyst prepared in Example 2 of the present invention; Figure 4-Figure 6 is the EDS image of the sample prepared in Example 2 of the present invention; Figure 7 The polarization curves (LSV) of the sample prepared in Example 2 of the present invention (doped rare earth element catalyst) are compared with those of nickel foam and undoped rare earth element catalyst in 1 mol / L KOH; Figure 8The 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; Fig. 9 The LSV curves of the samples prepared in Example 2 of the present invention in alkaline pure water, simulated seawater and alkaline real seawater are compared; Fig.10 The Tafel curves of the catalyst (rare earth element-doped catalyst) prepared in Example 2 of the present invention, the nickel foam, and the catalyst not doped with rare earth elements in simulated seawater; Fig.11 It is the stability test curve of the catalyst prepared in Example 2 of the present invention in alkaline real seawater. DETAILED DESCRIPTION

[0022] In order to facilitate the understanding of those skilled in the art, the present invention is further described below in conjunction with embodiments, and the contents mentioned in the implementation modes are not intended to limit the present invention.

[0023] As used herein, "and / or" includes the term of any and all combinations of one or more associated listed items. The terms used herein are only used to describe specific embodiments and are not intended to limit the present 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 compositions, but does not exclude the existence or addition of one or more other features, integers, steps, operations, elements, compositions and / or combinations thereof.

[0024] 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 the invention belongs. It is further understood that terms, such as 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 formal meanings unless explicitly defined as such herein.

[0025] The exemplary invention described herein may appropriately lack any one or more element limitations, which are not specifically disclosed herein. Therefore, the terms "comprise", "include", "contain", etc. should be understood broadly and non-restrictively. In addition, the terminology used herein is used as a description, not a limitation, and it is unintentional to use these terminology expressions that do not include any equivalent characteristics, but only describe some of their characteristics, but according to the description of the present invention, various modifications are possible within the scope 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 the changes of the present 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 present invention.

[0026] The raw materials or reagents used in the embodiments of the present invention and the comparative examples are all purchased from mainstream manufacturers in the market. The manufacturer or concentration is not specified, and they are all analytically pure raw materials or reagents that can be routinely obtained. As long as the expected effect can be achieved, there is no particular restriction. The instruments and equipment used in the present embodiment are all purchased from major manufacturers in the market. As long as the expected effect can be achieved, there is no particular restriction. If specific techniques or conditions are not specified in the present embodiment, the techniques or conditions described in the literature in this area or according to the product specification are carried out.

[0027] Terminology explanation: Oxygen evolution reaction (OER): The oxygen generation reaction that occurs at the anode during the electrolysis process. In the electrolysis of water, it involves the process in which water molecules lose electrons to generate oxygen, hydrogen ions and electrons. It is one of the important half-reactions in the process of hydrogen production by electrolysis of water. 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 by electrolysis of water.

[0028] Hydrogen evolution reaction (HER): The hydrogen generation reaction that occurs at the cathode during electrolysis, usually when hydrogen ions gain electrons on the electrode surface to generate hydrogen. In seawater electrolysis, the cathode hydrogen evolution reaction will be affected by impurity ions such as calcium ions and magnesium ions in seawater, causing changes in the environment around the active site and affecting the reaction efficiency.

[0029] Cyclic voltammetry: A commonly used electrochemical analysis method. In this application, it is used for the activation process of the catalyst. By scanning repeatedly at a specific scanning speed within a certain voltage window, a redox reaction occurs on the electrode surface, thereby changing the catalyst surface structure and promoting the conversion of the transition metal alloy surface into a transition metal oxide / hydroxide with high catalytic activity. At the same time, the presence of rare earth elements will affect the redox potential and reaction rate of the transition metal, further optimizing the catalyst performance.

[0030] Lattice strain: A stress state generated inside a crystal due to a change in the interatomic distance or a distortion of the crystal structure. In this application, by doping a large-sized rare earth element into a transition metal alloy, the alloy lattice is distorted to produce lattice strain, which can adjust the electronic structure of the alloy element and thus affect the catalytic activity and stability of the catalyst.

[0031] Common ion effect: In this application, it refers to the effect of the presence of rare earth elements on the adsorption of chloride ions. Due to certain characteristics of rare earth elements, the adsorption of chloride ions on the catalyst surface is reduced, thereby reducing the adverse effects of chloride ions in the electrolysis process, such as competitive reactions, corrosion of catalysts and conductive substrates, and improving the electrolysis performance of the catalyst in seawater.

[0032] Transition metals: refers to metal elements located in the d zone of the periodic table, such as iron, cobalt, nickel, etc. Transition metal alloys have good physical and chemical properties, such as high strength, high hardness, good electrical conductivity and catalytic activity, and are widely used in many industrial fields.

[0033] Rare earth elements: Lanthanides (La to Lu) in the periodic table, as well as scandium (Sc) and yttrium (Y), which have unique 4f and 5d orbital electron structures that can adjust the electronic properties of other metals, enhance catalytic performance and improve corrosion resistance.

[0034] 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).

[0035] Currently, seawater electrolysis involves the cathode hydrogen evolution reaction (HER) and the anode oxygen evolution reaction (OER), and its complex reaction process is affected by a large number of impurity ions and microorganisms in seawater. Chloride ions at the anode are prone to competitive reactions during the oxidation process, consuming electrons to produce chlorine or other chlorine-containing byproducts, while corroding the catalyst and the conductive substrate. During the reduction process, calcium ions and magnesium ions at the cathode produce a local alkaline environment due to the rapid consumption of H⁺, which in turn forms calcium hydroxide and magnesium hydroxide precipitation to block the active sites. These factors together lead to technical problems such as low electrolysis efficiency and poor catalyst stability when traditional water electrolysis technology is applied in seawater.

[0036] 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: 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, and the concentration of hydrochloric acid was 1-5 mol / L; S2. Preparation of plating solution The electroplating solution includes the following raw materials: 0.1-6mol / L metal ions; H3BO3, NH4Cl, NaCl; Wherein, the molar ratio of metal ion, H3BO3; NH4Cl; NaCl is: 1: 0.05-0.5: 0.1-3.0: 0.1-1.0; 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 the electroplating solution with adjusted pH to perform electrodeposition. After the electrodeposition is completed, the conductive substrate with the pre-catalyst deposited is taken out. S4. Activation of Catalyst The catalyst is obtained by using the precatalyst obtained in step S3 as a working electrode, a carbon rod as a counter electrode, and a mercury / mercury oxide electrode as a reference electrode through multiple cyclic voltammetric activations.

[0037] 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.

[0038] In the present application, in step S1, the solubility of ethanol and acetone is used to remove organic impurities such as oil on the substrate surface, and hydrochloric acid can dissolve inorganic impurities such as metal oxides on the substrate surface. If the substrate to be deposited is ultrasonically cleaned in different solvents in sequence, various types of dirt can be effectively removed, making the substrate surface clean, which is conducive to the uniform deposition and attachment of the pre-catalyst during subsequent electrodeposition, and ensuring the quality and performance of the catalyst.

[0039] 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.

[0040] 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; The molybdate is any one or more of ammonium molybdate, sodium molybdate, potassium molybdate, and lithium molybdate; the ruthenium salt is ruthenium chloride; 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.

[0041] In step S2, by accurately preparing an electroplating solution containing metal ions of specific concentration (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, each metal ion 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 and the proportion meets the requirements (Ni accounts for 65-80% of the total metal elements by molar ratio, etc.).

[0042] 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 Direct current is applied for electrochemical deposition, the deposition time is 5-30 minutes, and the plating solution temperature is maintained at 30-80°C.

[0043] In this application, the principle of electrochemical deposition is used, with the untreated substrate as the working anode and the pre-treated substrate as the working cathode, and direct current is applied to the 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 to undergo a reduction reaction and deposit. Transition metal ions such as Ni²⁺ and Co²⁺ and rare earth element ions will be deposited 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 growth process of the alloy can be accurately adjusted, thereby affecting the composition, crystal structure, and morphology of the pre-catalyst, and ultimately determining the performance of the catalyst.

[0044] Therefore, a rare earth element-doped transition metal alloy precatalyst is formed on the treated substrate by electrodeposition, laying the foundation for the subsequent activation to generate a catalyst with good performance. This step enables the metal ions to be deposited in an orderly manner on the substrate surface, initially constructing the basic structure of the catalyst, and achieving preliminary regulation of the catalyst composition and microstructure, thereby affecting its catalytic performance.

[0045] Specifically, 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 scanning speed is 50-100 mV / s, and the number of cycles is 50-300 times.

[0046] In this application, during the cyclic voltammetry scan, the precatalyst is used as the working electrode, and a series of redox reactions occur on the electrode surface at 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 will gradually react with OH⁻ in the electrolyte and convert into corresponding oxides or hydroxides. The presence of rare earth elements may affect the redox potential and reaction rate of transition metals, promote the surface conversion process, and form a structure with rich active sites and good electron transfer ability on the catalyst surface, thereby improving the oxygen evolution catalytic activity of the catalyst and its stability in simulated seawater and real alkaline seawater.

[0047] Therefore, the pre-catalyst is treated by cyclic voltammetry to transform the surface of the pre-catalyst to form a transition metal oxide / transition metal hydroxide with high catalytic activity, thereby activating the pre-catalyst into a catalyst that can efficiently and stably electrolyze seawater at an industrial-grade electrolysis current density.

[0048] The seawater electrolysis 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 molar ratio, and rare earth metals account for 1%-10% of the total metal molar ratio; the total metal elements refer to Ni, transition metals other than nickel, and rare earth metals.

[0049] Specifically, the following aspects are used to ensure that the element composition ratio of the catalyst meets the requirements: 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, wherein the metal ions include nickel salts, transition metal salts other than nickel (such as cobalt salts, iron salts, molybdates, ruthenium salts, etc.) and salts of rare earth elements (such as lanthanum nitrate, cerium nitrate, etc.), and the concentration of each is within the range of 0.1-6 mol / L. By accurately weighing and blending these raw materials, the proportion of each element in the electroplating solution is determined from the source, providing a basis for the subsequent deposition of a catalyst that meets the composition requirements. For example, if a catalyst with a molar ratio of 70% of Ni, 20% of Co, and 10% of La in the total metal elements is to be prepared, the specific amount of the corresponding nickel salt, cobalt salt, and lanthanum nitrate in the electroplating solution will be calculated based on their molar mass and target ratio.

[0050] Electrodeposition parameter control: In the process of preparing the pre-catalyst in step S3, the conditions of the electrodeposition have an important influence 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 direct current is 5-30 minutes, the deposition time is 30-80 minutes, and the electroplating solution is kept in a water bath at 30℃-80℃. These parameters work together to determine the deposition rate and amount of metal ions on the substrate. The deposition rates of different metal ions will vary depending on their own properties and electrodeposition conditions. By optimizing these parameters, each metal ion 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 be conducive to better deposition of relatively difficult-to-deposit metal ions such as rare earth elements, thereby ensuring that their proportion in the alloy meets the requirements.

[0051] After the preparation is completed, the components of the catalyst can be tested and verified by a variety of analytical methods, such as X-ray powder diffraction (XRD) and other technologies. Taking Example 2 as an example, the characteristic peaks of the XRD pattern of the pre-catalyst prepared therein are basically consistent with the Ni characteristic peaks of PDF04-0850 and shifted to a low angle, confirming that the Ni lattice spacing has increased. It is speculated that another transition metal and rare earth element are doped into the Ni lattice, thereby verifying the successful doping of the elements and the impact on the Ni lattice, ensuring that the catalyst components actually prepared meet the design requirements.

[0052] The following is a further description of the catalyst for oxygen evolution by electrolysis of seawater and its preparation method and application according to the present invention in conjunction with specific embodiments: Example 1 A method for preparing a catalyst for electrolyzing seawater oxygen evolution at an industrial-grade electrolysis current density comprises the following steps: (1) Substrate pretreatment 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, and then rinsed with deionized water to obtain a spare substrate.

[0053] (2) Prepare metal electroplating solution 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; after adjusting the pH to 4.5, the metal electroplating mother solution was obtained.

[0054] (3) Preparation of pre-catalyst 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 temperature of the electroplating solution was maintained at 60 °C.

[0055] (4) Catalyst activation The precatalyst obtained in step S3 is activated by cyclic voltammetry, with the precatalyst obtained in step S3 as the working electrode, the carbon rod as the counter electrode, the mercury / mercuric oxide electrode as the reference electrode, and a 1 mol / L KOH solution as the electrolyte. The catalyst is activated by cyclic voltammetry 100 times at a scan rate of 50 mV / s in the range of 0-1.0 V vs Hg / HgO. After the activation is completed, it can be further used as a catalytic electrode for electrolysis of alkaline seawater to perform electrolysis of seawater testing.

[0056] Among them, the morphology of the oxygen evolution catalyst for electrolysis of seawater 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.

[0057] The obtained seawater electrolysis oxygen evolution catalyst suitable for industrial-grade electrolysis current density was subjected to the following electrochemical tests: Electrochemical tests were performed on the electrodes at room temperature using a CHI 660E electrochemical workstation. The electrolytic cell was a standard three-electrode system. The electrolytic seawater oxygen evolution catalyst suitable for industrial-grade electrolysis current density obtained in this embodiment was clamped with a platinum electrode clip as a working electrode, a graphite rod as a counter electrode, and Hg / HgO as a reference electrode. The electrolyte was divided into simulated seawater (1 mol / L KOH+0.5 mol / L NaCl) and real alkaline seawater (seawater was taken from Qianhai Bay, Shenzhen, and 1 mol / L KOH was added to the seawater). The scan rate of the linear sweep voltammogram (LSV) was 5 mV / s, the voltage was manually compensated by 93% iR, and the potential scanning range was 0.9~-1.83 V. According to the formula: overpotential = actual measured potential + 0.059×pH + 0.095V-1.23V.

[0058] Example 2 A method for preparing a catalyst for electrolyzing seawater oxygen evolution at an industrial-grade electrolysis current density comprises the following steps: 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 2 As 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.

[0059] Figure 3 This is the XRD diagram of the precatalyst prepared in this example. The characteristic peak of the precatalyst is basically consistent with the Ni characteristic peak of PDF04-0850. The characteristic peak shifts to a low angle, confirming that the Ni lattice spacing increases. It is speculated that another transition metal and rare earth element are doped into the Ni lattice. The catalytic activity of the oxygen evolution catalyst in this example is further characterized, indicating that this method can successfully prepare a series of catalysts doped with rare earth elements.

[0060] 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 the LSV curves of the rare earth element-doped catalyst, the nickel foam, and the undoped rare earth element catalyst in 1M KOH. The rare earth element-doped catalyst can achieve 1000 mA / cm at 1.55 V. 2 The current density is only 286 mA / cm at the same voltage for the catalyst not doped with rare earth elements. 2 Current density: the current density of nickel foam should not exceed 10mA / cm 2 , proving that doping with rare earth elements optimizes the 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 exhibited the best catalytic activity in simulated seawater, such as the catalyst and IrO2 achieved 100mA / cm 2 The current density required 1.52V and 1.70V voltages, respectively, confirming that the catalyst performs better than IrO2 in simulated seawater. Further, 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: Fig. 9The 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. Fig.10 The Tafel curves of the catalyst (doped rare earth element catalyst) prepared in this example, the nickel foam, and the undoped rare earth element catalyst were respectively corroded in simulated seawater. The corrosion potentials of the nickel foam, the undoped rare earth element catalyst, and the 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 / cm 2 , 0.00698mA / cm 2 , confirming that rare earth element-doped catalysts have the best corrosion resistance. Fig.11 The stability test curve of the catalyst prepared in this example in alkaline real seawater (20wt.% KOH + seawater) is shown in Figure 1. The catalyst can react with 500mA / cm 2 The catalyst was able to operate stably at an industrial-grade electrolysis current density for a long time in alkaline real seawater, and has the potential to operate stably for nearly 400 h.

[0061] Example 3 A method for preparing a catalyst for electrolyzing seawater oxygen evolution at an industrial-grade electrolysis current density comprises the following steps: 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.

[0062] Example 4 A method for preparing a catalyst for electrolyzing seawater oxygen evolution at an industrial-grade electrolysis current density comprises the following steps: 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 / cm2 The electrodeposition time was 20 min, and the remaining steps were the same as in Example 1.

[0063] Example 5 A method for preparing a catalyst for electrolyzing seawater oxygen evolution at an industrial-grade electrolysis current density comprises the following steps: 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 consistent with implementation 1.

[0064] Example 6 A method for preparing a catalyst for electrolyzing seawater oxygen evolution at an industrial-grade electrolysis current density comprises the following steps: 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 consistent with implementation 1.

[0065] Example 7 A method for preparing a catalyst for electrolyzing seawater oxygen evolution at an industrial-grade electrolysis current density comprises the following steps: 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 consistent with implementation 1.

[0066] Example 8 A method for preparing a catalyst for electrolyzing seawater oxygen evolution at an industrial-grade electrolysis current density comprises the following steps: 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 consistent with implementation 1.

[0067] From the various parameters in the above embodiments, it can be seen that the preparation method of this specific embodiment can control the growth and morphology of rare earth element-doped transition metal alloy catalysts 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 cathode electroplating, and the final catalyst is further obtained by cyclic voltammetry activation; the catalyst morphology is a nano flower cluster or a nano sheet array, and spherical particles are loaded on the substrate / nano sheet. The catalyst has good conductivity, good corrosion resistance, and excellent electrolytic alkaline seawater oxygen evolution catalytic activity. The composition and morphology of rare earth element-doped transition metal alloy catalysts have a crucial influence on catalytic activity and stability. Different elements have different reaction intermediate adsorption capacities and different atomic radius differences of different elements during the catalytic reaction, 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 1 M simulated seawater, the catalysts prepared in Examples 3, 4, 5, 6, 7, and 8 reach 100 mA / cm 2 The current density needs to be 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 run for 105 hours and 82 hours at a current density of 500 mA / cm² in alkaline real seawater. This is mainly attributed to the large difference in atomic radius, which makes it easy for elements with larger radius to precipitate during long-term operation and thus cause the catalyst to fail. Therefore, by rationally regulating the types of rare earth elements, transition metal elements, and the structure and morphology of alloy catalysts, excellent catalytic activity and corrosion resistance can be achieved, which can be applied to the field of electrolysis of alkaline seawater.

[0068] The above embodiments are preferred implementation schemes of the present invention. In addition, the present invention may also be implemented in other ways. Any obvious replacement without departing from the concept of the present invention is within the protection scope of the present invention.

Claims

1. A method for preparing a catalyst for electrolyzing seawater oxygen evolution suitable for 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 plating solution The electroplating solution includes the following raw materials: 0.1-6 mol / L metal ions; H3BO3, NH4Cl, NaCl; Wherein, the molar ratio of metal ion, H3BO3; NH4Cl; NaCl is: 1: 0.05-0.5: 0.1-3.0: 0.1-1.0; 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 the electroplating solution with adjusted pH to perform electrodeposition. After the electrodeposition is completed, the conductive substrate with the pre-catalyst deposited is taken out. S4. Activation of Catalyst The catalyst is obtained by using the precatalyst obtained in step S3 as a working electrode, a carbon rod as a counter electrode, and a mercury / mercury oxide electrode as a reference electrode through multiple cyclic voltammetric activations.

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, foamed nickel, foamed iron, foamed copper, carbon felt, and nickel felt.

3. The preparation method according to claim 1, characterized in that: 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.

4. The preparation method according to claim 3, 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; The molybdate is any one or more of ammonium molybdate, sodium molybdate, potassium molybdate, and lithium molybdate; the ruthenium salt is ruthenium chloride; 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.

5. The preparation method according to claim 1, characterized in that: In step S3, the pH of the plating solution needs to be adjusted to 3.0-6.

0.

6. 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, and the current density is 20-80 mA / cm 2 Direct current is applied for electrochemical deposition, the deposition time is 5-30 minutes, and the plating solution temperature is maintained at 30℃-80℃.

7. The preparation method according to claim 1, characterized in that: 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.

8. A catalyst for oxygen evolution by electrolysis of seawater 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 7.

9. The catalyst for oxygen evolution by electrolysis of seawater according to claim 8, characterized in that: 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 element molar ratio, transition metals other than nickel account for 10%-25% of the total metal molar ratio, and rare earth metals account for 1%-10% of the total metal molar ratio; the total metal elements refer to Ni, transition metals other than nickel, and rare earth metals.

10. Use of a catalyst, characterized in that: The catalyst prepared by the preparation method according to any one of claims 1 to 7 or the catalyst according to any one of claims 8 to 9 is applied in the field of electrolysis of alkaline seawater.

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