An oxygen evolution catalyst of FeCoNiMg high entropy amorphous alloy powder and preparation method thereof

Abstract

The present invention discloses an oxygen evolution catalyst of FeCoNiMg high-entropy amorphous alloy powder and a preparation method thereof. The molecular formula of the catalyst is Fe 4‑x Co 4‑x Ni 4‑x Mg x , where X = 1-2. The preparation method of the FeCoNiMg catalyst mainly includes uniformly mixing ferrous salt, cobalt salt, nickel salt and magnesium salt and adding them into water to obtain a precursor solution, and introducing a protective gas to remove oxygen in the solution; slowly dropping a sodium borohydride solution into the precursor solution, fully reacting, and maintaining strong mechanical stirring and continuous introduction of the protective gas during the dropping and reaction processes; finally, performing suction filtration, washing and vacuum drying to obtain the FeCoNiMg high-entropy amorphous alloy catalyst. The present invention obtains a high-entropy amorphous alloy oxygen evolution catalyst with low cost, suitable for batch production, excellent catalytic effect and good stability by regulating the alloy composition. The preparation method of the present invention has low cost, high efficiency, uniform composition, simple operation, and the prepared FeCoNiMg high-entropy amorphous alloy particles exhibit excellent electrocatalytic performance, with advantages such as low overpotential potential, low Tafel slope and high stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of oxygen evolution catalysts, and particularly relates to an oxygen evolution catalyst of FeCoNiMg high-entropy amorphous alloy powder and a preparation method thereof. Background Art

[0002] In today's world, all mankind is facing two global problems of energy shortage and environmental pollution. In order to alleviate these two problems, people are making efforts to develop and utilize green clean energies such as hydrogen. Looking back at the forms of energy consumed by humans, from drilling wood to make fire in ancient times, coal used since the agricultural era, and large-scale application of oil and natural gas in the industrial era, the changes in these energy carriers reflect the trend of carbon reduction and hydrogen addition, and the decrease in the carbon-hydrogen ratio. Currently, the proposal of China's carbon peak and carbon neutrality development goals will further speed up the process of carbon reduction. As a zero-carbon energy carrier, hydrogen is receiving more and more attention: 20% of the world's CO 2 emissions can be replaced by hydrogen energy, and hydrogen energy consumption will account for 18% of the world energy market. The Paris Agreement is accelerating the transformation of the global energy system from being dominated by fossil fuels to an efficient and renewable low-carbon energy system. Hydrogen has a wide range of sources, high calorific value, is clean and carbon-free, can be used for energy storage, power generation, and heating, is flexible and efficient, and has rich application scenarios. It is considered an ideal energy carrier to promote the clean and efficient utilization of traditional fossil fuels and support the large-scale development of renewable energy, and is favored by various countries. Hydrogen energy is an ideal secondary energy source. Compared with other energy sources, hydrogen has a high calorific value, and its energy density (140 MJ / kg) is more than twice that of solid fuels (50 MJ / kg). And the combustion product is water, which is the most environmentally friendly energy. It can be stored in high-pressure tanks in the form of gas and liquid phases, and can also be stored in hydrogen storage materials in the form of solid phases, such as metal hydrides, coordination hydrides, porous materials, etc. Therefore, hydrogen is considered the most promising energy carrier to replace traditional fossil fuels.

[0003] The utilization of hydrogen energy needs to start from hydrogen production. Since hydrogen rarely exists in the form of a simple substance in nature, it needs to be produced through industrial processes. The sources of hydrogen are divided into industrial by-product hydrogen, fossil fuel hydrogen production, electrolytic water hydrogen production and other ways, and the differences lie in the regenerability of raw materials, CO 2 emissions, and hydrogen production costs. Currently, more than 95% of hydrogen production in the world comes from fossil fuel reforming, and CO 2 emissions are inevitable in the production process; about 4% - 5% of hydrogen comes from electrolytic water, and there is no CO 2 emission in the production process. Hydrogen production processes are divided into gray hydrogen (hydrogen production from coal), blue hydrogen (hydrogen production from natural gas), and green hydrogen (electrolytic water hydrogen production, renewable energy) according to the carbon emission intensity. The original intention of the development of the hydrogen energy industry is zero-carbon or low-carbon emissions. Therefore, gray hydrogen and blue hydrogen will gradually be replaced by green hydrogen based on renewable energy, and green hydrogen is the development direction of the future energy industry.

[0004] Currently, one of the more important methods for producing hydrogen is to obtain a large amount of high-purity hydrogen through electrolysis of water. Hydrogen production by electrolysis of water has become a promising hydrogen production method due to its simple operation, low cost, zero greenhouse gas emissions, and high energy conversion efficiency. The hydrogen obtained by electrolysis of water has a relatively high purity, reaching over 99.9%, and can be directly applied to the manufacturing industry of precision electronic devices with high requirements for hydrogen purity. Electrolysis of water to produce hydrogen is to dissociate water molecules into hydrogen and oxygen through an electrochemical process under the action of direct current, and they are respectively precipitated at the cathode and anode. According to different diaphragms, it can be divided into alkaline water electrolysis, proton exchange membrane water electrolysis, and solid oxide water electrolysis. The industrial application of industrialized water electrolysis technology began in the 1920s. The alkaline liquid electrolytic cell water electrolysis technology has realized industrial-scale hydrogen production and is applied to industrial demands such as ammonia production and oil refining. After the 1970s, the development of proton exchange membrane water electrolysis technology was driven by energy shortages, environmental pollution, and the needs in space exploration. At the same time, the high-pressure compact alkaline water electrolysis technology required for the development of special fields has also been correspondingly developed. Currently, the practically applicable hydrogen production technologies by electrolysis of water mainly include two types: alkaline liquid water electrolysis and solid polymer water electrolysis. The alkaline liquid water electrolysis technology uses aqueous solutions of KOH and NaOH as electrolytes. For example, asbestos cloth is used as a diaphragm. Under the action of direct current, water is electrolyzed to generate hydrogen and oxygen. The produced gas needs to be treated to remove alkali mist. Alkaline liquid water electrolysis achieved industrialization in the mid-20th century. However, in the liquid electrolyte system, the alkaline electrolyte used (such as KOH) will react with CO 2 in the air to form carbonates that are insoluble under alkaline conditions, such as K 2 CO 3 . These insoluble carbonates will block the porous catalytic layer, hinder the transfer of products and reactants, and greatly reduce the performance of the electrolytic cell. On the other hand, it is also difficult for the alkaline liquid electrolyte electrolytic cell to be quickly shut down or started, and the hydrogen production rate is also difficult to quickly adjust because the pressure balance on both sides of the anode and cathode of the electrolytic cell must be maintained at all times to prevent the mixing of hydrogen and oxygen gases through the porous asbestos membrane, which may cause an explosion.

[0005] Due to the many problems that still need to be improved in the alkaline liquid electrolyte electrolytic cell, it has promoted the rapid development of solid polymer electrolyte (SPE) water electrolysis technology. The first SPE actually applied is the proton exchange membrane (PEM), so it is also called PEM electrolysis. Replacing the asbestos membrane with a proton exchange membrane to conduct protons and isolate the gases on both sides of the electrodes avoids the disadvantages brought by using strong alkaline liquid electrolytes in the alkaline liquid electrolyte electrolytic cell. The operating current density of the PEM electrolytic cell is usually higher than 1 A / cm 2, at least four times that of an alkaline water electrolyzer, has the advantages of high efficiency, high gas purity, environmental friendliness, low energy consumption, no lye, small volume, safety and reliability, and can achieve higher gas production pressure. It is recognized as one of the electrolytic hydrogen production technologies with great development prospects in the field of hydrogen production. The main components of a typical PEM water electrolyzer include the anode and cathode end plates, the anode and cathode gas diffusion layers, the anode and cathode catalyst layers, and the proton exchange membrane, etc. Among them, the end plate plays a role in fixing the electrolyzer components, guiding the transfer of electricity, and distributing water and gas; the diffusion layer plays a role in current collection and promoting the transfer of gas and liquid; the core of the catalyst layer is the three-phase interface composed of a catalyst, an electron conduction medium, and a proton conduction medium, which is the core place where the electrochemical reaction occurs.

[0006] The reaction of electrolyzing water mainly includes two reactions, one is the oxygen evolution reaction, and the other is the hydrogen evolution reaction. To enable the electrolysis of water reaction to proceed, at least 1.23V of voltage needs to be provided to drive this reaction to proceed normally. Therefore, an electrocatalyst with sufficiently high activity needs to be provided. Among many catalysts, noble metal electrocatalysts are currently electrolytic water catalysts with high activity. Hydrogen evolution and oxygen evolution electrocatalysts are very important for the entire electrolytic hydrogen production reaction of water electrolysis. An ideal electrocatalyst should have characteristics such as corrosion resistance, good specific surface area, porosity, catalytic activity, electronic conductivity, electrochemical stability, low cost, and environmental friendliness. The cathode hydrogen evolution electrocatalyst is in a strongly acidic working environment and is prone to problems such as corrosion, agglomeration, and loss. To ensure the performance and lifespan of the electrolyzer, the hydrogen evolution catalyst material is mainly selected from corrosion-resistant noble metals such as Pt and Pd and their alloys. Compared with the cathode, the anode polarization is more prominent, which is an important factor affecting the efficiency of PEM electrolytic hydrogen production. The harsh strongly oxidizing environment makes the anode oxygen evolution electrocatalyst can only select a few noble metals such as Ir and Ru or their oxides with antioxidant and corrosion-resistant properties as catalyst materials, among which RuO 2 and IrO 2 have the best catalytic activity for the oxygen evolution reaction. Compared with RuO 2 , IrO 2 has slightly weaker catalytic activity but better stability and is cheaper than Pt, becoming the main material of the oxygen evolution catalyst. Similar to the hydrogen evolution catalyst, developing non-noble metal materials with corrosion resistance and high catalytic activity under acidic and high oxygen evolution potential conditions and reducing the noble metal loading are the research focuses. Composite oxide catalysts, alloy catalysts, and supported catalysts are the research hotspots of oxygen evolution catalysts.

[0007] It can be seen that due to the high price and relatively small reserves of noble metal catalysts, their large-scale production and application are greatly restricted. Therefore, to make hydrogen production by electrolyzing water efficient and industrializable, it is necessary to find a hydrogen evolution catalytic material with good hydrogen evolution performance and low price. Most of the reported excellent electrolyzed water catalysts belong to the category of single-metal or double-metal, but most single-metal or double-metal electrolyzed water catalysts still require a large overpotential to achieve an ideal current density in alkaline electrolytes, which may be due to the problems of electrochemical active sites and electrode structure. Specifically, there are no electrochemical active sites for water dissociation, and inappropriate hydrogen binding energy leads to slow adsorption and binding of H. At the same time, the electron transferability and mass transferability of the electrodes made of insulating polymer adhesives are poor, aiming to maintain the low-dimensional nanostructure of the synthesized catalyst.

[0008] Therefore, there is an urgent need to explore novel and multifunctional electrolyzed water catalysts. At this time, high-entropy alloys (HEAs) naturally come into the public eye due to their complex functional characteristics. High-entropy materials are a new type of multi-principal element material composed of multiple elements in equimolar or near-equimolar ratios, breaking the traditional material design concept. With their unique crystal structure characteristics, high-entropy materials exhibit many organizational and performance characteristics different from traditional materials. Currently, a variety of high-entropy materials have been developed at home and abroad, with unique advantages in mechanical, physical, and chemical properties, and great application potential in many fields, and have become one of the important research hotspots in the international material academic community.

[0009] High-entropy alloys have a tunable electronic structure, an optimizable d-band center, and outstanding structural stability, thus highly meeting the necessary requirements to become advanced catalysts. Research has found that in high-entropy alloys, the atoms of various elements are disorderly and randomly distributed at lattice positions. Therefore, they exhibit a high-entropy effect thermodynamically, a slow diffusion effect kinetically, and a lattice distortion effect structurally. The specific strength of some high-entropy alloys is much better than that of traditional alloys, and their fracture resistance, tensile strength, corrosion resistance, and oxidation resistance are all better than those of traditional alloys. High-entropy alloy materials are expected to provide a broad platform for the development of electrolyzed water catalysts. Discovering catalysts with excellent performance and stability from high-entropy alloys has an extremely broad compositional space. Multimetallic nanomaterial catalysts have the "cocktail effect" of high-entropy alloys in terms of performance. The different combination methods of multiple metal elements and the combination of different catalyst modification methods provide infinite possibilities for the preparation of excellent multifunctional overall water splitting catalysts. Therefore, high-entropy alloy nanomaterial catalysts have great potential in the field of hydrogen production by electrolyzing water.

[0010] At present, some research has gradually begun on high-entropy alloy materials in electrolytic water catalysts. For example, the research team of Professor Xiadingguo Xia from Peking University and Associate Researcher Wangsheng Chu from the University of Science and Technology of China published an article titled "Sub-2nm Ultrasmall High-Entropy Alloy Nanoparticles for Extremely Superior Electrocatalytic Hydrogen Evolution" in the Journal of the American Chemical Society. It reported ultrasmall high-entropy alloy (us-HEA) (NiCoFePtRh) nanoparticles (NPs) with high hydrogen evolution reaction (HER) performance, and through in-situ characterization methods and theoretical calculations, it revealed the real reaction process and catalytic mechanism of high-entropy alloys in the electrolytic water hydrogen evolution catalytic reaction. This research provides strong support for high-entropy alloys as sufficiently advanced electrocatalysts. In addition, the research group of Professor Feng Fang from Southeast University published a research result titled "Efficient FeCoNiCuPd thin-film electrocatalyst for alkaline oxygen and hydrogen evolution reactions" in Applied Catalysis B: Environmental. It reported the preparation of a well-crystallized FeCoNiCuPd high-entropy alloy thin film on a conductive substrate by magnetron sputtering. This thin film has excellent HER and OER electrocatalytic performance in alkaline media. For overall water splitting, a low voltage of only 1.52 V in 1 M KOH can achieve a current density of 10 mA cm -2 , and can continuously catalyze the electrolysis of water for more than 100 hours at a large current (800 mA cm -2 ), enabling efficient and stable hydrogen production by alkaline electrolytic water. In addition, Patent CN113522308B also discloses a high-entropy alloy catalyst and its preparation method and application. The preparation method of the high-entropy alloy catalyst involved mainly includes preparing a noble metal precursor solution; preparing a non-noble metal precursor solution; preparing a reducing agent solution; mixing the noble metal precursor solution and the non-noble metal precursor solution, adding the reducing agent solution, and then reducing under a reducing gas to obtain the high-entropy alloy catalyst. The prepared high-entropy alloy catalyst is extremely active in HER and OER in an acidic environment, can well reduce the cell voltage of hydrogen production by electrolytic water in an acidic environment, and has excellent stability. Furthermore, Patent CN111621808B also discloses a quaternary high-entropy foam for highly active electrolytic water and its preparation method. The preparation method mainly includes placing the working electrode in CuSO 4 , NiSO 4、CoSO 4 、Fe 2 (SO 4 ) 3 、(NH 4 ) 2 SO 4 、Na 3 C 6 H 5 O 7 and H 3 BO 3 In the mixed solution; constant current electrochemical deposition is carried out. The surface oxygen evolution overpotential of the NiCuCoFe high entropy alloy foam prepared by this method can be as low as 250mV, which is lower than the level of ordinary high entropy alloy strips, films and surfaces. However, looking at the preparation and effects of the above-mentioned water electrolysis catalysts, either they still contain a large amount of precious metal components, the price is still high, and the cost cannot be effectively controlled; or the preparation method is relatively complicated and not suitable for industrial promotion and application; or the catalytic activity still needs to be improved and has not achieved better catalytic activity. Therefore, how to prepare a high-entropy alloy electrocatalyst with high catalytic activity, controllable cost and large-scale industrial promotion and production is still a technical problem that needs to be solved urgently. SUMMARY OF THE INVENTION

[0011] In one aspect of the present invention, the present invention provides a FeCoNiMg high entropy alloy powder electrocatalyst which has high catalytic activity and low cost and can be mass-produced, and is used as an oxygen evolution catalyst in the electrolysis of water. The oxygen evolution catalyst is FeCoNiMg high entropy amorphous alloy particles, and the chemical formula of the catalyst is Fe 4-x Co 4-x Ni 4-x Mg x , X=1-2, the high entropy amorphous alloy particle powder has a nano flower structure, and the nano powder particle size distribution is 10nm-100nm.

[0012] In another aspect of the present invention, the present invention also provides a preparation method for preparing high-entropy alloy nanoparticles with high catalytic activity, which has a simple process and can be industrialized and promoted on a large scale.

[0013] Furthermore, the present invention discloses a method for preparing a FeCoNiMg high entropy amorphous alloy nanoparticle oxygen evolution catalyst, characterized in that the preparation method comprises the following steps:

[0014] (1) uniformly mixing water-soluble ferrous salt, cobalt salt, nickel salt and magnesium salt, adding water to the obtained mixed metal salt, and stirring until completely dissolved to obtain a reaction precursor solution;

[0015] (2) Weigh sodium borohydride to prepare a sodium borohydride solution;

[0016] (3) Then introduce a protective gas to remove oxygen in the precursor solution. Under strong mechanical stirring and the protection of the protective gas, slowly dropwise add a sodium borohydride solution to the precursor solution until the addition is complete.

[0017] (4) Filter the reaction solution by suction filtration, wash the powder obtained by suction filtration, and then dry it under vacuum to obtain FeCoNiMg high-entropy amorphous alloy nanoparticles.

[0018] Furthermore, in the above step (1), the metal salts are preferably nitrates, acetates, acetylacetonates, chlorides, etc.

[0019] Furthermore, in the above step (1), the molar ratio of the water-soluble ferrous salt, cobalt salt, nickel salt, and magnesium salt is preferably 1:1:1:1 to 3:3:3:1; a further preferred ratio is 1:1:1:1 to 2:2:2:1; the most preferred ratio is 1:1:1:1.

[0020] Furthermore, in the above step (1), the uniform mixing is preferably carried out in a round-bottom flask.

[0021] Furthermore, in the above step (2), the sodium borohydride can be weighed according to the following ratio: the molar ratio of the total amount of metal ions in the mixed metal salts to sodium borohydride is preferably 1:1 to 1:3, and the most preferred is 1:2.

[0022] Furthermore, in the above step (2), the concentration of the prepared aqueous sodium borohydride solution is preferably 0.3 - 0.6 mol / L, and the most preferred is 0.4 mol / L.

[0023] Furthermore, in the above step (3), the protective gas selected in step (3) is N 2 , Ar or He;

[0024] Furthermore, in the above step (3), use a peristaltic pump to add the NaBH 4 solution drop by drop into the precursor solution at a fixed dropping rate. After the NaBH 4 solution is completely added, continuously maintain strong stirring and gas protection for 1 h until no bubbles are generated, indicating that the reaction is complete.

[0025] Furthermore, in the above step (3), the dropping rate of the aqueous sodium borohydride solution is preferably 5 - 12 mL / min; the mechanical stirring and N 2 gas passing time is generally 0.5 - 1.5 h, preferably 1 h.

[0026] Furthermore, in the above step (3), strong mechanical stirring can make the reaction uniform, and the stirring speed is 200 - 1000 rpm.

[0027] Further, in the above step (4), the precipitate obtained by suction filtration is repeatedly washed with deionized water and ethanol to remove impurities in the particles. Preferably, it is washed 3 times with deionized water and alcohol respectively.

[0028] Further, in the above step (4), vacuum drying is carried out at 25°C to 70°C, preferably at room temperature of 25°C; vacuum drying is carried out using a drying oven, and the drying time is 24 to 72 h.

[0029] Further, in another aspect of the present invention, the present invention also provides an application of a high-entropy amorphous alloy nanoparticle oxygen evolution catalyst in the OER reaction. The high-entropy amorphous alloy nanoparticles are selected from the alloy nanoparticles prepared by the above method. The high-entropy amorphous alloy nanoparticles are FeCoNiMg alloy powder, and the electrolyte is 0.1 to 1 M KOH solution.

[0030] Advantages of the present invention:

[0031] (1) The present invention uses a simple method to combine metal components with greatly different melting points to prepare an efficient, long-stable high-entropy alloy nanoparticle electrolyzed water catalyst. The entire preparation process can be carried out without heating and without adjusting the pH. The process is simple, the operation is convenient, the preparation cost is low, and the final product is single and convenient to collect.

[0032] (2) The FeCoNiMg high-entropy alloy nanoparticles prepared by the present invention show excellent electrolyzed water performance when used as an electrolyzed water oxygen evolution catalyst, which not only reduces the catalyst cost but also improves its catalytic performance. Mg and FeCoNi can combine to form an active substance (FeCoNiMg), which can change the adsorption energy with the intermediate, reduce the adsorption intensity, and optimize the catalytic activity. Description of the drawings

[0033] The technical solutions of the present invention will be further described in detail below with reference to the drawings.

[0034] Figure 1 It is a scanning electron microscope (SEM) photograph and energy dispersive spectroscopy (EDS) of the FeCoNiMg high-entropy amorphous alloy nanoparticles prepared in the examples;

[0035] Figure 2 It is an X-ray diffraction (XRD) pattern of the FeCoNiMg nanoparticles prepared in the examples;

[0036] Figure 3 It is a linear sweep voltammetry (LSV) curve when the nanoparticles alloys of FeCoNiMg prepared in the examples and the comparative examples FeCoNi, FeCoMg, FeNiMg, and CoNiMg are used as electrolyzed water oxygen evolution catalysts;

[0037] Figure 4 Tafel curves of the nano - particles prepared for the examples of FeCoNiMg and the comparative examples of FeCoNi, FeCoMg, FeNiMg, and CoNiMg when used as oxygen evolution catalysts for electrolytic water;

[0038] Figure 5 ECSA diagrams of the nano - particles prepared for the examples of FeCoNiMg and the comparative examples of FeCoNi, FeCoMg, FeNiMg, and CoNiMg;

[0039] Figure 6 i - t diagram of the FeCoNiMg high - entropy amorphous nano - particles prepared for the examples when used as an oxygen evolution catalyst for electrolytic water at a constant current density of 10 mA / cm 2 ;

[0040] Figure 7 Comparison diagram of LSV curves of the initial sample of FeCoNiMg in the examples and the sample after 72 h of oxygen evolution reaction; Detailed implementation mode

[0041] To more clearly understand the purpose, technical solution, and beneficial effects of the present invention, the following further explains the present invention. However, the protection scope of the present invention is not limited to the following examples. The following examples are only used to illustrate the present invention in detail and do not limit the scope of the present invention in any way. In the following examples, the instrument equipment involved, unless otherwise specified, are all conventional instrument equipment; the raw materials involved, unless otherwise specified, are all commercially available conventional industrial raw materials; the processing and manufacturing methods involved, unless otherwise specified, are all conventional methods. It should be understood that these descriptions are only exemplary and do not intend to limit the scope of the present invention. In addition, in the following description, the description of well - known structures and technologies is omitted to avoid unnecessarily confusing the concept of the present invention.

[0042] Furthermore, in the embodiments of the present invention, the present invention provides an FeCoNiMg high - entropy alloy powder electro - catalyst with both high catalytic activity and low cost and can be mass - produced, which is used as an oxygen evolution catalyst in the electrolytic water process.

[0043] Furthermore, in the embodiments of the present invention, the oxygen evolution catalyst is an FeCoNiMg high - entropy amorphous alloy particle,

[0044] Furthermore, in the embodiments of the present invention, the chemical formula of the catalyst is Fe 4-x Co 4-x Ni 4-x Mg x, X = 1 - 2, preferably X = 2. Using the magnesium content within the above range of the present invention can ensure that the prepared high-entropy amorphous alloy nanoparticles have relatively better oxygen evolution catalytic effect. Since (FeCoNiMg)OOH active substance will be generated during the high-entropy alloy catalytic reaction process, this substance can promote the electrocatalytic activity. If X is less than 1 or greater than 2, then the amount of this (FeCoNiMg)OOH active substance will be reduced during the high-entropy alloy catalytic reaction process, thus affecting the electrocatalytic activity during the catalytic reaction process.

[0045] Furthermore, in the embodiments of the present invention, the high-entropy amorphous alloy particle powder has a nanoflower-like structure. This structure has a large specific surface area, which can provide more active sites for catalysis, and this structure is loose, which can promote the transport of substances and electrons. Therefore, using the nanoflower-like structure of the present invention can ensure that the prepared high-entropy amorphous alloy nanoparticles have relatively better oxygen evolution catalytic effect.

[0046] Furthermore, in the embodiments of the present invention, the particle size distribution of the nano powder is 10nm - 100nm. If the particle size is too small, the particles will agglomerate; if the particle size is too large, the specific surface area will decrease and the catalytic activity will decrease. Therefore, using the high-entropy amorphous alloy nanoparticles within the above particle size distribution range of the present invention has relatively better oxygen evolution catalytic effect.

[0047] Furthermore, in the embodiments of the present invention, the present invention also provides a preparation method with simple process and can be industrially promoted on a large scale for preparing high-entropy alloy nanoparticles with high catalytic activity.

[0048] Furthermore, in the embodiments of the present invention, the present invention discloses a preparation method of an FeCoNiMg high-entropy amorphous alloy nanoparticle oxygen evolution catalyst, which is characterized in that the preparation method includes the following steps:

[0049] (1) Uniformly mix water-soluble ferrous salt, cobalt salt, nickel salt and magnesium salt, add water to the obtained mixed metal salt, and stir until completely dissolved to obtain a reaction precursor solution;

[0050] (2) Weigh sodium borohydride and prepare it into a sodium borohydride solution;

[0051] (3) Then introduce a protective gas to remove oxygen in the precursor solution. Under strong mechanical stirring and the protection of the protective gas, slowly dropwise add the sodium borohydride solution to the precursor solution until the addition is complete;

[0052] (4) Perform suction filtration on the reaction solution, wash the powder obtained by suction filtration, and then dry it in vacuum to obtain FeCoNiMg high-entropy amorphous alloy nanoparticles.

[0053] Further, in the embodiments of the present invention, in the above step (1), the metal salt is preferably selected from water-soluble nitrates, acetates, acetylacetonates, chlorides, etc. However, the present invention does not have any other more specific limitations on the metal salt, and commercially available water-soluble nitrates, acetates, acetylacetonates, chlorides and other metal salt raw materials well-known to those skilled in the art can be used.

[0054] Further, in the embodiments of the present invention, in the above step (1), the molar ratio of the water-soluble ferrous salt, cobalt salt, nickel salt and magnesium salt is preferably 1:1:1:1 to 3:3:3:1; a further preferred ratio is 1:1:1:1 to 2:2:2:1; the most preferred ratio is 1:1:1:1.

[0055] Further, in the embodiments of the present invention, in the above step (1), the uniform mixing is preferably carried out in a round-bottom flask; however, the present invention does not have any other more specific limitations on the round-bottom flask, and a commercially available round-bottom flask well-known to those skilled in the art can be used as the reaction device.

[0056] Further, in the embodiments of the present invention, in the above step (2), sodium borohydride is used as the reducing agent. Sodium borohydride is a strong reducing agent that can easily reduce metal chloride salts with fewer reduction impurities.

[0057] Further, in the embodiments of the present invention, in the above step (2), sodium borohydride can be weighed according to the following ratio: the molar ratio of the total amount of metal ions in the mixed metal salt to sodium borohydride is preferably 1:1 to 1:3, and the most preferred is 1:2.

[0058] Further, in the embodiments of the present invention, the concentration of the prepared aqueous sodium borohydride solution is preferably 0.3 - 0.6 mol / L, and the most preferred is 0.4 mol / L. However, the present invention does not have any other more specific limitations on the sodium borohydride, and commercially available sodium borohydride well-known to those skilled in the art can be used as the reaction raw material.

[0059] Further, in the embodiments of the present invention, in the above step (3), the protective gas in step (3) is selected as N 2 , Ar or He;

[0060] Further, in the embodiments of the present invention, in the above step (3), the NaBH 4 solution is added dropwise to the precursor solution at a fixed dropping rate using a peristaltic pump. However, the present invention does not have any other more specific limitations on the sodium borohydride peristaltic pump, and a commercially available peristaltic pump well-known to those skilled in the art can be used as the reaction device.

[0061] Further, in the embodiments of the present invention, in the above step (3), the dropping rate of the sodium borohydride aqueous solution is preferably 5-12 mL / min. The inventors have found through research that within the above reasonable dropping rate range, it is easier to prepare the oxygen evolution catalyst of the high-entropy amorphous alloy nanoparticles described in the present invention. If the dropping rate is too slow, the sample reaction will be incomplete, and if the dropping rate is too fast, the impurity content in the powder will be relatively high.

[0062] Further, in the embodiments of the present invention, in the above step (3), after the NaBH 4 solution is completely dropped, strong stirring and gas protection are continuously maintained for 1 h until no bubbles are generated, indicating that the reaction is complete; the mechanical stirring and nitrogen 2 purging time is generally 0.5-1.5 h, preferably 1 h.

[0063] Further, in the embodiments of the present invention, in step (3), strong mechanical stirring can make the reaction uniform, and the stirring speed is 200-1000 rpm. However, the present invention does not have other more specific limitations on the strong mechanical stirring, and a commercially available strong mechanical stirring device well-known to those skilled in the art can be used.

[0064] Further, in the embodiments of the present invention, in step (4), the precipitate obtained by suction filtration is repeatedly washed with deionized water and ethanol to remove impurities in the particles. Preferably, it is washed 3 times with deionized water and alcohol respectively; however, the present invention does not have other more specific limitations on the deionized water and ethanol, and commercially available deionized water and ethanol well-known to those skilled in the art can be used as reaction raw materials.

[0065] Further, in the embodiments of the present invention, vacuum drying is carried out at 25°C to 70°C, preferably at room temperature of 25°C; vacuum drying is carried out using a vacuum drying oven, and the drying time is 24-72 h. However, the present invention does not have other more specific limitations on the vacuum drying oven, and a commercially available vacuum drying oven well-known to those skilled in the art can be used as the reaction device.

[0066] Further, in the embodiments of the present invention, the present invention also provides an application of the high-entropy amorphous alloy nanoparticle oxygen evolution catalyst in the OER reaction. The high-entropy amorphous alloy nanoparticles are selected from the alloy nanoparticles prepared by the above method. The high-entropy amorphous alloy nanoparticles are FeCoNiMg alloy powders, and their oxygen evolution performance is tested. The electrocatalytic performance of the prepared electrode for water electrolysis oxygen evolution is tested using an electrochemical workstation, and a three-electrode system is adopted, where the counter electrode is a platinum sheet electrode, the reference electrode is a Hg / HgO electrode, and the electrolyte is preferably a KOH aqueous solution with a concentration of 0.1-1 mol / L.

[0067] The present invention will be described below with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way. In addition, the percentage content described in the embodiments generally refers to the mass percentage content unless otherwise specified.

[0068] Example 1

[0069] Prepare FeCoNiMg high-entropy amorphous alloy nanoparticles, and the preparation process is as follows:

[0070] Step 1, weigh metal salts with a total molar amount of 0.004 mol (where FeCl 2 ·4H 2 O: CoCl 2 ·6H 2 O: NiCl 2 ·6H 2 O: MgCl 2 ·6H 2 O = 1:1:1:1), dissolve them in 50 mL of deionized water, fully dissolve and stir evenly to obtain a reaction precursor solution.

[0071] Step 2, transfer the reaction precursor solution to a clean three-necked flask. To avoid oxidation of the product by oxygen in the air, a protective gas N 2 needs to be continuously introduced throughout the reaction process to prevent the product from being oxidized.

[0072] Step 3, weigh 0.008 mol of NaBH 4 , and configure it into a 0.4 mol / L aqueous solution of NaBH 4 ;

[0073] Step 4, use a peristaltic pump to dropwise add the aqueous solution of NaBH 4 to the precursor solution at a fixed dropping rate of 5 mL / min. After the addition of the NaBH 4 solution is complete, continue to maintain strong stirring and gas protection for 1 h until no bubbles are generated, indicating that the reaction is complete.

[0074] Step 5, use a suction filter to collect the reaction powder, and wash it three times repeatedly with absolute ethanol and deionized water to remove the impurities adsorbed on the product;

[0075] Step 6, finally place the washed black product in a vacuum drying oven and vacuum dry it at room temperature for 20 h to obtain FeCoNiMg powder, where the molecular formula of FeCoNiMg is Fe 1 Co 1 Ni 1 Mg 1 .

[0076] Comparative Example 1

[0077] Prepare FeCoNi alloy nanoparticles, and the preparation process is as follows:

[0078] Step 1, Weigh metal salts with a total molar amount of 0.003 mol (where the amounts of metal salts selected for the FeCoNi alloy are FeCl 2 ·4H 2 O: CoCl 2 ·6H 2 O: NiCl 2 ·6H 2 O = 1:1:1. Dissolve them in 50 mL of deionized water, fully dissolve and stir evenly to obtain a reaction precursor solution;

[0079] Step 2, Transfer the reaction precursor solution to a clean three-necked flask. To avoid oxidation of the product by oxygen in the air, a protective gas N 2 needs to be continuously introduced during the whole reaction process to prevent the product from being oxidized.

[0080] Step 3, Weigh 0.006 mol of NaBH 4 , and configure it into a 0.4 mol / L NaBH 4 aqueous solution;

[0081] Step 4, Use a peristaltic pump to dropwise add the NaBH 4 aqueous solution into the precursor solution at a fixed dropping rate of 5 mL / min. After the NaBH 4 solution is completely dropped, continuously maintain strong stirring and gas protection for 1 h until no bubbles are generated, indicating that the reaction is complete.

[0082] Step 5, Use a suction filter to collect the reaction powder, and repeatedly wash it three times with absolute ethanol and deionized water to remove impurities adsorbed on the product;

[0083] Step 6, Finally, place the washed black product in a vacuum drying oven and vacuum dry it at room temperature for 20 hours to obtain FeCoNi alloy nano powder.

[0084] Comparative Example 2

[0085] Prepare FeCoMg alloy nanoparticles, and the preparation process is as follows:

[0086] Step 1, Weigh metal salts with a total molar amount of 0.003 mol (where the amounts of metal salts selected for the FeCoMg alloy are FeCl 2 ·4H 2 O: CoCl 2 ·6H 2 O: MgCl 2·6H 2 O = 1:1:1, dissolve them in 50 mL of deionized water, fully dissolve and stir evenly to obtain the reaction precursor solution;

[0087] Step 2, transfer the reaction precursor solution to a clean three-necked flask. To avoid oxidation of the product by oxygen in the air, a protective gas N needs to be continuously introduced throughout the reaction process 2 to prevent the product from being oxidized.

[0088] Step 3, weigh 0.006 mol of NaBH 4 , and configure it into a 0.4 mol / L aqueous solution of NaBH 4 ;

[0089] Step 4, use a peristaltic pump to dropwise add the aqueous solution of NaBH 4 to the precursor solution at a fixed dropping rate of 5 mL / min. After the addition of the NaBH 4 solution is complete, continue to maintain strong stirring and gas protection for 1 h until no bubbles are generated, indicating that the reaction is complete.

[0090] Step 5, use a suction filter to collect the reaction powder, and wash it three times with absolute ethanol and deionized water to remove impurities adsorbed on the product;

[0091] Step 6, finally place the washed black product in a vacuum drying oven and vacuum dry it at room temperature for 20 hours to obtain FeCoMg alloy nano-powder.

[0092] Comparative Example 3

[0093] Prepare FeNiMg alloy nanoparticles, and the preparation process is as follows:

[0094] Step 1, weigh a total molar amount of 0.003 mol of metal salts (where the amounts of metal salts selected for the FeNiMg alloy are FeCl 2 ·4H 2 O: NiCl 2 ·6H 2 O: MgCl 2 ·6H 2 O = 1:1:1, dissolve them in 50 mL of deionized water, fully dissolve and stir evenly to obtain the reaction precursor solution;

[0095] Step 2, transfer the reaction precursor solution to a clean three-necked flask. To avoid oxidation of the product by oxygen in the air, a protective gas N needs to be continuously introduced throughout the reaction process 2 to prevent the product from being oxidized.

[0096] Step 3, weigh 0.006 mol of NaBH 4 , and prepare it into an aqueous solution of NaBH 4 with a concentration of 0.4 mol / L;

[0097] Step 4, use a peristaltic pump to dropwise add the aqueous solution of NaBH 4 into the precursor solution at a fixed dropping rate of 5 mL / min. After the addition of the NaBH 4 solution is complete, continue to maintain strong stirring and gas protection for 1 h until no bubbles are generated, indicating that the reaction is complete.

[0098] Step 5, use a suction filter to collect the reacted powder, and wash it three times repeatedly with absolute ethanol and deionized water to remove the impurities adsorbed on the product;

[0099] Step 6, finally place the washed black product in a vacuum drying oven and vacuum dry it at room temperature for 20 hours to obtain FeNiMg alloy nano-powder.

[0100] Comparative Example 4

[0101] Prepare CoNiMg alloy nanoparticles, and the preparation process is as follows:

[0102] Step 1, weigh metal salts with a total molar amount of 0.003 mol (where the amounts of metal salts selected for the CoNiMg alloy are CoCl 2 ·6H 2 O: NiCl 2 ·6H 2 O: MgCl 2 ·6H 2 O = 1:1:1), dissolve them in 50 mL of deionized water, fully dissolve and stir evenly to obtain the reaction precursor solution;

[0103] Step 2, transfer the reaction precursor solution to a clean three-necked flask. To avoid oxidation of the product by oxygen in the air, it is necessary to continuously introduce a protective gas N 2 during the whole reaction process to prevent the product from being oxidized.

[0104] Step 3, weigh 0.006 mol of NaBH 4 , and prepare it into an aqueous solution of NaBH 4 with a concentration of 0.4 mol / L;

[0105] Step 4, use a peristaltic pump to dropwise add the aqueous solution of NaBH 4 into the precursor solution at a fixed dropping rate of 5 mL / min. After the addition of the NaBH 4 solution is complete, continue to maintain strong stirring and gas protection for 1 h until no bubbles are generated, indicating that the reaction is complete.

[0106] Step 5: Use a suction filter to collect the reacted powder, and repeatedly wash it three times with absolute ethanol and deionized water to remove the impurities adsorbed on the product.

[0107] Step 6: Finally, place the washed black product in a vacuum drying oven and vacuum dry it at room temperature for 20 hours to obtain CoNiMg alloy nano-powders.

[0108] Performance test:

[0109] Use the FeCoNiMg, FeCoNi, FeCoMg, FeNiMg, and CoNiMg alloy nano-particles prepared in the examples and comparative examples of the present invention as the oxygen evolution catalyst for electrolytic water, test their oxygen evolution performance, use an electrochemical workstation to test the oxygen evolution catalytic performance of the prepared electrode, adopt a three-electrode system, where the counter electrode is a platinum sheet electrode, the reference electrode is a Hg / HgO electrode, and the electrolyte is a 1 mol / L KOH aqueous solution.

[0110] As Figure 1 shown are the SEM photograph and energy spectrum diagram of the FeCoNiMg high-entropy amorphous alloy nano-particles prepared in this example. It can be seen from the SEM photograph that the size of the prepared powder is about 50 nm, the powder has a nano-flower structure, the powder distribution is loose, and the loose nano-flower structure can provide a transmission channel for the electrolyte and promote the catalytic performance. It can be seen from the EDS diagram that the prepared FeCoNiMg high-entropy amorphous alloy particles have a uniform element distribution.

[0111] Figure 2 Shows the XRD results of the FeCoNiMg nano-particles in the example. The XRD curve of this powder has a broad peak near 2θ = 45° and no obvious crystal diffraction peaks, which is consistent with the typical amorphous structure, indicating that the prepared FeCoNiMg alloy nano-particles have a completely amorphous structure, demonstrating the successful preparation of FeCoNiMg high-entropy amorphous alloy nano-particles.

[0112] Figure 3 Are the linear sweep voltammetry (LSV) curves of the FeCoNiMg in the example and the FeCoNi, FeCoMg, FeNiMg, and CoNiMg alloy nano-particles in the comparative examples when used as the oxygen evolution catalyst for electrolytic water. When the current density is 10 mA / cm 2 , the overpotentials are 280 mV, 326 mV, 330 mV, 340 mV, and 320 mV respectively. The overpotential of FeCoNiMg is the lowest, and its electrocatalytic performance is significantly better than that of commercial IrO 2 (340 mV) and RuO 2 (327 mV).

[0113] Figure 4 For the alloy nanoparticles of FeCoNiMg in the examples and FeCoNi, FeCoMg, FeNiMg, and CoNiMg in the comparative examples, when used as the oxygen evolution catalyst for electrolytic water, the Tafel slopes are 42.9 mV / dec, 50.6 mV / dec, 51.6 mV / dec, 72.1 mV / dec, and 47.6 mV / dec respectively. Among them, the FeCoNiMg high-entropy amorphous alloy nanoparticles prepared in Example 1 exhibit the most excellent oxygen evolution catalytic performance.

[0114] Figure 5 The ECSA diagrams of FeCoNiMg and FeCoNi, FeCoMg, FeNiMg, and CoNiMg nanoalloys are shown. It can be seen from the figure that the C of FeCoNiMg and FeCoNi, FeCoMg, FeNiMg, and CoNiMg nanoparticles dl are 1.22, 0.48, 0.45, 0.53, and 0.73 mF / cm respectively 2 , among which the C of FeCoNiMg dl is the largest, proving that its electrochemically active surface area is the largest, that is, the number of active sites increases, which is consistent with its best catalytic oxygen evolution performance.

[0115] The FeCoNiMg high-entropy amorphous alloy nanoparticles prepared in Example 1 are loaded on the conductive carbon paper as the working electrode, and its stability is tested by chronopotentiometry. As Figure 6 shown, after continuous cycling for 72 hours, the curve is stable and the current decay is less than 20%, indicating its good stability. And after continuous cycling for 72 hours, its LSV curve is tested. As Figure 7 shown, its LSV curve basically coincides with the initial LSV curve, indicating its good stability.

[0116] The above examples are only used to illustrate and explain the present invention exemplarily, and should not be construed as limiting the protection scope of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

Claims

1. A high entropy amorphous alloy nanoparticle oxygen evolution catalyst, characterized in that: The oxygen evolution catalyst is FeCoNiMg high entropy amorphous alloy particles. The high entropy amorphous alloy particle powder has a nano flower structure. The nano powder particle size distribution is 10nm-100nm. The chemical molecular formula of the catalyst is Fe 4-x Co 4-x Ni 4-x Mg x , X = 1 to 2; The method for preparing high entropy amorphous alloy particles comprises the following steps: (1) uniformly mixing water-soluble ferrous salt, cobalt salt, nickel salt and magnesium salt, adding water to the obtained mixed metal salt, stirring until the mixed metal salt is completely dissolved, and obtaining a reaction precursor solution; (2) weighing sodium borohydride to prepare a sodium borohydride solution; (3) introducing a protective gas under mechanical stirring, and slowly dropping the sodium borohydride solution into the precursor solution until the addition is complete; (4) filtering the post-reaction solution, washing the powder obtained by the filtration, and then vacuum drying, so as to obtain FeCoNiMg high entropy amorphous alloy nanoparticles; In step (1), the ferrous salt, the cobalt salt, the nickel salt and the magnesium salt are mixed in a molar ratio of 1:1:1:1 to 3:3:3:1; In step (2), sodium borohydride is weighed according to the following ratio: the molar ratio of the total amount of metal ions in the mixed metal salt to sodium borohydride is 1:1 to 1:1.5, and the concentration of the sodium borohydride solution is 0.3 to 0.6 mol / L; In step (3), the stirring speed is 200 to 1000 rpm, and the dropping rate of the sodium borohydride aqueous solution is 5 to 12 mL / min.

2. The high entropy amorphous alloy nanoparticle oxygen evolution catalyst according to claim 1, characterized in that: In step (1), the ferrous salt, cobalt salt, nickel salt and magnesium salt are selected as corresponding nitrates, acetates, acetylacetonates or chlorides.

3. The high entropy amorphous alloy nanoparticle oxygen evolution catalyst according to claim 1, characterized in that: In step (3), the protective gas is N2, Ar or He. After the dropwise addition is completed, the mechanical stirring and ventilation time is 0.5 to 1.5 hours. This step is carried out in a fume hood.

4. The high entropy amorphous alloy nanoparticle oxygen evolution catalyst according to claim 1, characterized in that: In step (4), the precipitate obtained by suction filtration is repeatedly washed with deionized water and ethanol to remove impurities in the particles, and vacuum drying is performed at room temperature for 24 to 72 hours.

5. A high entropy amorphous alloy nanoparticle oxygen evolution catalyst is used in an OER reaction, characterized in that: The high entropy amorphous alloy nanoparticles are selected from the alloy nanoparticles described in any one of claims 1-4.

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