CN115161691A

CN115161691A - Oxygen evolution catalyst of FeCoNiMg high-entropy amorphous alloy powder and preparation method thereof

Info

Publication number: CN115161691A
Application number: CN202210899079.0A
Authority: CN
Inventors: 苗芳; 闫志杰; 武伟; 李大赵; 王睿; 康燕
Original assignee: North University of China
Current assignee: North University of China
Priority date: 2022-07-28
Filing date: 2022-07-28
Publication date: 2022-10-11

Abstract

The invention discloses a FeCoNiMg high-entropy amorphous alloy powder oxygen evolution catalyst and a preparation method thereof. The molecular formula of the catalyst is Fe _4‑x Co _4‑x Ni _4‑x Mg _x And X =1 to 2. The preparation method of the FeCoNiMg catalyst mainly comprises the steps of uniformly mixing ferrous salt, cobalt salt, nickel salt and magnesium salt, adding the mixture into water to obtain precursor solution, and introducing protective gas to remove oxygen in the solution; slowly dripping a sodium borohydride solution into the front-driving solution, fully reacting, keeping strong mechanical stirring in the dripping and reacting processes, and continuously introducing protective gas; and finally, carrying out suction filtration, cleaning and vacuum drying to obtain the FeCoNiMg high-entropy amorphous alloy catalyst. The invention obtains the high entropy with low cost, excellent catalytic effect and good stability, which is suitable for batch production and is obtained by regulating and controlling the alloy componentsAmorphous alloy oxygen evolution catalyst. The preparation method has the advantages of low cost, high efficiency, uniform components and simple and convenient operation, and the prepared FeCoNiMg high-entropy amorphous alloy particles show excellent electrocatalysis performance, and have the advantages of low over-potential, low Tafel slope, high stability and the like.

Description

Oxygen evolution catalyst of FeCoNiMg high-entropy amorphous alloy powder and preparation method thereof

Technical Field

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

Background

In the world, people all face two global problems of energy shortage and environmental pollution, and people are engaged in developing and utilizing green clean energy such as hydrogen in order to relieve the two problems. Reviewing the energy form consumed by human, the changes of the energy carriers reflect the trends of carbon reduction and hydrogenation and the reduction of the carbon-hydrogen ratio in wood-drilling and fire-taking in ancient times, coal used in the farming times and petroleum and natural gas applied in large scale in the industrial times. At present, the carbon peak reaching and carbon neutralization development targets are provided in China, and the carbon reduction process is further accelerated. Hydrogen is gaining increasing attention as a zero-carbon energy carrier: 20% of CO in the world in 2050 ₂ Emission reduction can be accomplished by hydrogen energy substitution, which will account for 18% of the world's energy market. Paris agreement is accelerating the transformation of global energy system from fossil fuel to efficient and renewable low-carbon energy system. The hydrogen source is wide, the heat value is high, the hydrogen-rich solar energy generating device is clean and carbon-free, can store energy, generate electricity and heat, is flexible and efficient, has rich application scenes, is considered as an ideal energy carrier for promoting the clean and efficient utilization of the traditional fossil energy and supporting the large-scale development of renewable energy, and is favored by various countries. Hydrogen energy is an ideal secondary energy source, and has a high hydrogen calorific value and an energy density (140 MJ/kg) more than twice as high as that of a solid fuel (50 MJ/kg) compared with other energy sources. And the combustion product is water, which is the most environment-friendly energy source, and can be stored in a high-pressure tank in a gas-liquid phase mode, and can also be stored in a hydrogen storage material in a solid-phase mode, such as metal hydride, coordination hydride, porous material and the like. Therefore, hydrogen is considered to be the most promising energy carrier to replace traditional fossil fuels.

The utilization of hydrogen energy needs to start with hydrogen production, which is rarely present in elemental form in nature and needs to be produced by industrial processes. The sources of hydrogen are divided into the ways of industrial by-product hydrogen production, fossil fuel hydrogen production, water electrolysis hydrogen production and the like, and the difference lies in the regeneration of raw materials and CO ₂ And the cost of emission and hydrogen production. At present, more than 95% of the world's hydrogen production is derived from fossil fuel reforming, and the production process necessarily emits CO ₂ (ii) a About 4% to 5% of the hydrogen is derived from the electrolysis of water and the process is CO free ₂ And (4) discharging. The hydrogen production process is divided into ash hydrogen (coal hydrogen production), blue hydrogen (natural gas hydrogen production) and green hydrogen (water electrolysis hydrogen production and renewable energy) according to the carbon emission intensity. The development of the hydrogen energy industry is originally designed to be zero-carbon or low-carbon emission, so that the grey hydrogen and the blue hydrogen are gradually replaced by green hydrogen based on renewable energy sources, and the green hydrogen is the development direction of the future energy industry.

At present, one of the more important methods for producing hydrogen is to obtain a large amount of high-purity hydrogen by electrolyzing water, and the hydrogen production by electrolyzing water becomes a promising hydrogen production mode due to simple operation, low cost, zero greenhouse gas emission and high energy conversion efficiency. The hydrogen obtained by water electrolysis has high purity which can reach more than 99.9 percent, and can be directly applied to the manufacturing industry of precise electronic devices with high requirements on the hydrogen purity. The hydrogen production by water electrolysis is that under the action of direct current, water molecules are dissociated into hydrogen and oxygen through an electrochemical process, and the hydrogen and oxygen are separated out at the cathode and the anode respectively. According to different diaphragms, the method can be divided into alkaline water electrolysis, proton exchange membrane water electrolysis and solid oxide water electrolysis. The industrial application of the industrial water electrolysis technology begins in the 20 th century, and the alkaline liquid electrolytic cell water electrolysis technology has realized the industrial-scale hydrogen production and is applied to the industrial demands of ammonia production, petroleum refining and the like. After the 70's of the 20 th century, the development of proton exchange membrane water electrolysis technology was driven by the demand of energy shortage, environmental pollution and space exploration. Meanwhile, the high-pressure compact alkaline water electrolysis technology required by the development of special fields is also correspondingly developed. The water electrolysis hydrogen production technology which can be practically applied at present mainly comprises two technologies of alkaline liquid water electrolysis and solid polymer water electrolysis. The water electrolysis technology of alkaline liquid is carried out by using KOH,The NaOH aqueous solution is used as electrolyte, such as asbestos cloth or the like is used as a diaphragm, and water is electrolyzed under the action of direct current to generate hydrogen and oxygen. The produced gas needs dealkalization fog treatment. The electrolysis of alkaline liquid water has been industrialized in the middle of the 20 th century. However, in liquid electrolyte systems, the alkaline electrolyte (e.g., KOH) used will react with CO in the air ₂ Reacting to form a carbonate, such as K, insoluble under alkaline conditions ₂ CO ₃ . These insoluble carbonates can block the porous catalytic layers, hindering the transfer of products and reactants, greatly reducing the performance of the cell. On the other hand, alkaline liquid electrolyte cells are also difficult to shut down or start up quickly, and the rate of hydrogen production is also difficult to adjust quickly because the pressure must be constantly maintained balanced across the anode and cathode of the cell to prevent the mixing of oxyhydrogen gas across the porous asbestos membrane, which can cause an explosion.

Since alkaline liquid electrolyte electrolyzers still have many problems to be improved, the rapid development of Solid Polymer Electrolyte (SPE) water electrolysis technology is promoted. The first practical SPE was a Proton Exchange Membrane (PEM), hence also known as PEM electrolysis. The proton exchange membrane is used for replacing an asbestos membrane, conducting protons and isolating gas on two sides of the electrode, so that the defect caused by using strong alkaline liquid electrolyte in an alkaline liquid electrolyte electrolytic cell is avoided. The operating current density of PEM electrolyzers is generally higher than 1A/cm ² At least four times of alkaline water electrolytic cell, has the advantages of high efficiency, high gas purity, environmental protection, low energy consumption, no alkaline liquid, small volume, safety, reliability, capability of realizing higher gas pressure and the like, and is known as one of electrolytic hydrogen production technologies with great development prospects in the hydrogen production field. The main components of a typical PEM water electrolysis cell comprise a cathode and an anode end plate, an anode and cathode gas diffusion layer, an anode and cathode catalyst layer, a proton exchange membrane and the like. Wherein, the end plate plays the roles of fixing the electrolytic cell assembly, guiding the transmission of electricity, distributing water and gas and the like; the diffusion layer plays a role in collecting flow, promoting the transfer of gas and liquid and the like; the core of the catalyst layer is a three-phase interface composed of a catalyst, an electron conductive medium, and a proton conductive medium, and is a core site where electrochemical reactions occur.

Reaction of electrolyzed waterThe method mainly comprises two reactions, one is an oxygen production reaction, and the other is a hydrogen production reaction. In order to make the water electrolysis reaction proceed, at least 1.23V of voltage is needed to drive the reaction to proceed normally. Therefore, there is a need to provide electrocatalysts with sufficiently high activity, and among many, noble metal electrocatalysts are electrolytic water catalysts that currently have high activity. The hydrogen and oxygen evolution electro-catalyst is very important for the whole water electrolysis hydrogen production reaction. The ideal electrocatalyst should have characteristics of corrosion resistance, good specific surface area, porosity, catalytic activity, electronic conductivity, electrochemical stability, low cost, environmental friendliness, and the like. The hydrogen evolution electro-catalyst of the cathode is in a strong acid working environment and is easy to corrode, agglomerate, run off and the like, and in order to ensure the performance and the service life of the electrolytic cell, the hydrogen evolution catalyst material mainly selects the corrosion-resistant Pt and Pd noble metals and the alloys thereof. Compared with a cathode, the anode polarization is more prominent and is an important factor influencing the hydrogen production efficiency of PEM water electrolysis. The anode oxygen evolution electrocatalyst can only select a few of oxidation-resistant and corrosion-resistant Ir, ru and other noble metals or oxides thereof as catalyst materials under the harsh strong oxidizing environment, wherein RuO ₂ And IrO ₂ The catalytic activity for oxygen evolution reaction is best. Compare RuO ₂ ，IrO ₂ The catalytic activity is slightly weak, but the stability is better, the price is cheaper than that of Pt, the catalyst becomes a main material of an oxygen evolution catalyst, the catalyst is similar to a hydrogen evolution catalyst, a non-noble metal material with corrosion resistance and high catalytic activity under acidic and high oxygen evolution potentials is developed, and the reduction of noble metal loading is a research focus. Composite oxide catalysts, alloy catalysts and carrier-supported catalysts are the hot spots for the study of oxygen evolution catalysts.

It follows that the noble metal catalysts are very expensive and relatively low in inventory, which greatly limits their large scale production applications. Therefore, in order to produce hydrogen by electrolysis with high efficiency and to enable industrialization, it is necessary to find a hydrogen evolution catalyst material having good hydrogen evolution performance and low cost. Most of the electrolytic water catalysts with excellent performance reported at present belong to the category of single metal or bimetal, but most of the single metal or bimetal electrolytic water catalysts still require a large overpotential to achieve the ideal current density in the alkaline electrolyte, which may be due to the problems of the electrochemical active sites and the electrode structure, particularly due to the lack of the electrochemical active sites for water dissociation, the improper hydrogen binding energy causes the slow adsorption and binding of H, and the electrode made of the insulating polymer binder has poor electron transfer and mass transfer properties, and the purpose is to maintain the low dimensional nano structure of the synthetic catalyst.

There is therefore an urgent need to explore new and versatile catalysts for electrolysis of water, where high-entropy alloys (HEA) naturally enter the public view due to their complex functional properties. The high-entropy material is a novel multi-principal-element material consisting of multiple elements in an equimolar ratio or a nearly equimolar ratio, and breaks through the traditional material design concept. High entropy materials exhibit many structural and performance characteristics that are different from conventional materials due to their unique crystal structure characteristics. At present, various high-entropy materials have been developed at home and abroad, have unique advantages in the aspects of mechanical, physical and chemical properties and the like, have great application potential in many fields, and become one of important research hotspots in the international material academia.

High entropy alloys have a controllable electronic structure, an optimizable d-band center, and outstanding structural stability, thus highly meeting the requirements necessary to become advanced catalysts. Research shows that in the high-entropy alloy, atoms of various elements are randomly distributed on lattice positions in a disordered mode, so that the high-entropy alloy thermodynamically shows a high-entropy effect, the slow diffusion effect kinetically shows, and the lattice distortion effect structurally shows. The specific strength of some high-entropy alloys is much better than that of the traditional alloys, and the fracture resistance, the tensile strength, the corrosion resistance and the oxidation resistance of the high-entropy alloys are better than those of the traditional alloys. The high-entropy alloy material is expected to provide a wide platform for the development of an electrolytic water catalyst, and the catalyst with excellent performance and stability is found from the high-entropy alloy, so that the high-entropy alloy material has an extremely wide composition space. The multi-element metal nano material catalyst has a cocktail effect of high-entropy alloy on performance, different combination modes of various metal elements and combination of different catalyst modification methods provide infinite possibility for preparing an excellent multifunctional full-hydrolysis catalyst, so that the high-entropy alloy nano material catalyst has great potential in the field of hydrogen production by water electrolysis.

Currently, some research on the High-Entropy Alloy material in the aspect of electrolytic water catalyst has been gradually started, for example, the teaching team of the university of Beijing Xia Ding cooperates with the Standby assistant researchers of the university of Chinese science and technology, named Sub-2nm Ultrasmall High-entry Nanoparticles for expression Superior or electrochemical Hydrogen Evolution, published by the Journal of the American Chemical Society, which reports ultra-small High-Entropy Alloy (us-HEA) (NiCoFePtRh) Nanoparticles (NPs) with higher Hydrogen Evolution (HER) performance, and which reveals the real reaction process and catalytic mechanism of the High-Entropy Alloy in the electrolytic water Hydrogen Evolution catalytic reaction through in-situ characterization means and theoretical calculation, which provides strong support for the High-Entropy Alloy as a sufficiently advanced electrocatalyst. In addition, the Fangshan professor research group at the university of southeast south China published on Applied Catalysis B: environmental research on a research result entitled "Efficient FeCoNiCuPd thin-film electrochemical system for alkaline oxidation and hydrogen evolution reactions" reported that a FeCoNiCuPd high-entropy alloy film with good crystallinity is prepared on a conductive substrate by magnetron sputtering, and the film has excellent HER and OER electrocatalytic performance in an alkaline medium. For bulk water splitting, only 1.52V of low voltage is needed in 1M KOH to achieve 10mA cm ^-2 And can be used under a large current (800 mA cm) ^-2 ) The continuous catalytic water electrolysis lasts for more than 100 hours, and the efficient and stable hydrogen production by alkaline water electrolysis can be realized. In addition, patent CN113522308B also discloses a high-entropy alloy catalyst, a preparation method and an application thereof, and the preparation method of the high-entropy alloy catalyst related thereto mainly comprises preparing a noble metal precursor solution; preparing a non-noble metal precursor solution; preparing a reducing agent solution; and mixing the noble metal precursor solution and the non-noble metal precursor solution, adding a reducing agent solution, and reducing under a reducing gas to prepare the high-entropy alloy catalyst. The prepared high-entropy alloy catalyst is extremely active in HER and OER in an acid environment, can well reduce the cell voltage for hydrogen production by water electrolysis in the acid environment, and has excellent stability.Furthermore, patent CN111621808B also discloses a quaternary high-entropy foam for high-activity electrolyzed water and a preparation method thereof, wherein the preparation method mainly comprises the step of placing a 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 Mixing the solution; and carrying out constant-current electrochemical deposition. The surface oxygen evolution overpotential of the NiCuCoFe high-entropy alloy foam prepared by the method can be as low as 250mV, which is lower than the level of a common high-entropy alloy strip, a film and the surface. However, in the overall view of the preparation and the effect of the water electrolysis catalyst, the water electrolysis catalyst still contains more precious metal components, the price is still higher, and the cost can not be effectively controlled; or the preparation method is complex and is not suitable for industrial popularization and application; or the catalytic activity is still to be improved, and better catalytic activity is not achieved. Therefore, how to prepare the high-entropy alloy electrocatalyst with high catalytic activity, controllable cost and large-scale industrialized popularization and production still remains a technical problem which needs to be solved at present.

Disclosure of Invention

In one aspect of the invention, the invention provides a FeCoNiMg high-entropy alloy powder electrocatalyst which has high catalytic activity and low cost and can be produced in large scale, and the electrocatalyst is used as an oxygen evolution catalyst in the water electrolysis process. The oxygen evolution catalyst is FeCoNiMg high-entropy amorphous alloy particles, and the chemical molecular formula of the catalyst is Fe _4-x Co _4-x Ni _4-x Mg _x And X = 1-2, the high-entropy amorphous alloy particle powder is in a nanometer flower-shaped structure, and the particle size distribution of the nanometer powder is 10nm-100nm.

In another aspect of the invention, the invention also provides a preparation method which is simple in process and can be industrially popularized in a large scale for preparing the high-entropy alloy nanoparticles with high catalytic activity.

Further, the invention discloses a preparation method of the FeCoNiMg high-entropy amorphous alloy nanoparticle oxygen evolution catalyst, which is characterized by comprising the following steps:

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

(2) Weighing sodium borohydride to prepare a sodium borohydride solution;

(3) Then introducing protective gas to remove oxygen in the precursor solution, and slowly dropwise adding a sodium borohydride solution into the precursor solution under the protection of the protective gas under the strong mechanical stirring until the dropwise adding is complete;

(4) And (3) carrying out suction filtration on the solution after reaction, cleaning the powder obtained by suction filtration, and then carrying out vacuum drying to obtain FeCoNiMg high-entropy amorphous alloy nanoparticles.

Further, in the step (1), the metal salt preferably includes nitrate, acetate, acetylacetonate, chloride, and the like.

Further, in the step (1), the water-soluble ferrous salt, cobalt salt, nickel salt and magnesium salt are preferably obtained in a molar ratio of 1; further preferred ratios are 1; the most preferred ratio is 1.

Further, in the above step (1), the uniform mixing is preferably carried out in a round-bottomed flask;

further, in the 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, most preferably 1:2.

Further, in the step (2), the concentration of the prepared aqueous solution of sodium borohydride is preferably 0.3 to 0.6mol/L, and most preferably 0.4mol/L.

Further, in the step (3), the protective gas in the step (3) is N ₂ Ar or He;

further, in the step (3) above, naBH is added to the precursor solution at a fixed dropping rate using a peristaltic pump ₄ The solution is added dropwise into the precursor solution until NaBH is added ₄ After the solution is completely added dropwise, strong stirring and gas protection are continuously kept for 1 hour until no bubbles are generated, and then sufficient reaction is indicated.

Further, onIn the step (3), the dropping rate of the sodium borohydride aqueous solution is preferably 5-12 m L/min; mechanical agitation and N aeration ₂ The gas time is generally from 0.5 to 1.5h, preferably 1h.

Furthermore, in the step (3), the reaction can be made uniform by adopting strong mechanical stirring, and the stirring speed is 200-1000rpm.

Further, in the step (4), the precipitate obtained by suction filtration is repeatedly washed with deionized water and ethanol to remove impurities in the particles, and preferably, deionized water and ethanol are respectively washed for 3 times.

Further, in the step (4), the vacuum drying is carried out at 25 to 70 ℃, preferably at room temperature of 25 ℃; the vacuum drying is carried out by adopting a drying oven, and the drying time is 24-72 h.

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

The invention has the beneficial effects that:

(1) The invention adopts a simple method to combine metal components with greatly different melting points to prepare the high-efficiency long-term stable high-entropy alloy nanoparticle electrolytic water catalyst, the whole preparation process can be carried out without heating or pH adjustment, the process is simple, the operation is simple and convenient, the preparation cost is low, and the final product is single and is convenient to collect.

(2) The FeCoNiMg high-entropy alloy nanoparticles prepared by the method show excellent water electrolysis performance when used as an oxygen evolution catalyst for water electrolysis, not only reduce the cost of the catalyst, but also improve the catalytic performance, and Mg and FeCoNi are combined to generate an (FeCoNiMg) active substance which can change the adsorption energy with an intermediate, reduce the adsorption strength and optimize the catalytic activity.

Drawings

The technical solution of the present invention will be further described in detail with reference to the accompanying drawings.

FIG. 1 is a Scanning Electron Microscope (SEM) photograph and an energy spectrum (EDS) of FeCoNiMg high-entropy amorphous alloy nanoparticles prepared in example;

FIG. 2 is an X-ray diffraction (XRD) pattern of FeCoNiMg nanoparticles prepared in example;

FIG. 3 is a Linear Sweep Voltammetry (LSV) curve for the use of nanoparticle alloys prepared with FeCoNiMg prepared in the examples and FeCoNi, feCoMg, feNiMg, coNiMg prepared in comparative examples as electrolytic water oxygen evolution catalysts;

FIG. 4 is a Tafel plot of FeCoNiMg prepared in examples and nanoparticles prepared in comparative examples FeCoNi, feCoMg, feNiMg, coNiMg used as oxygen evolution catalysts for electrolysis of water;

FIG. 5 is an ECSA plot of nanoparticles made with FeCoNiMg prepared in the examples and FeCoNi, feCoMg, feNiMg, coNiMg comparative examples;

FIG. 6 shows that FeCoNiMg high-entropy amorphous nanoparticles prepared in the example are 10m A/cm when used as the catalyst for oxygen evolution by electrolysis of water ² I-t plot at constant current density;

FIG. 7 is a graph comparing the LSV curves of the example FeCoNiMg initial sample and the sample after undergoing a 72h oxygen evolution reaction.

Detailed Description

The present invention will be further described below for better understanding the objects, technical solutions and advantages thereof, without limiting the scope of the present invention to the following examples, which are only intended to illustrate the present invention in detail and are not intended to limit the scope of the present invention in any way. The instruments and devices referred to in the following examples are conventional instruments and devices unless otherwise specified; the raw materials are all conventional commercial industrial raw materials if not specifically indicated; the processing and manufacturing methods are conventional methods unless otherwise specified. It should be understood that the description is intended to be exemplary only, and is not intended to limit the scope of the present invention. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present invention.

Further, in the embodiment of the invention, the invention provides a FeCoNiMg high-entropy alloy powder electrocatalyst which has high catalytic activity and low cost and can be produced in large scale, and the FeCoNiMg high-entropy alloy powder electrocatalyst is used as an oxygen evolution catalyst in the water electrolysis process.

Further, in the embodiment of the invention, the oxygen evolution catalyst is FeCoNiMg high-entropy amorphous alloy particles,

further, in the embodiment of the invention, the chemical formula of the catalyst is Fe _4-x Co _4-x Ni _4-x Mg _x X =1 to 2, wherein X =2 is preferable. The magnesium content in the range can ensure that the prepared high-entropy amorphous alloy nano-particles have relatively better oxygen evolution catalysis effect. Since (FeCoNiMg) OOH active species are generated during the high entropy alloy catalytic reaction, the species may promote electrocatalytic activity. And if X is less than 1 or greater than 2, such (FeCoNiMg) OOH active species will be reduced during the high entropy alloy catalytic reaction, thus affecting the electrocatalytic activity during the catalytic reaction.

Further, in the embodiment of the invention, the high-entropy amorphous alloy particle powder has a nano flower-like structure, the structure has a large specific surface area, more active sites can be provided for catalysis, and the loose structure can promote substance and electron transport. Therefore, the nano flower-shaped structure provided by the invention can ensure that the prepared high-entropy amorphous alloy nano particles have relatively better oxygen evolution catalysis effect.

Further, in the embodiment of the invention, the particle size distribution of the nano powder is 10nm-100nm, and if the particle size is too small, the particles can agglomerate; if the particle size is too large, the specific surface area is reduced and the catalytic activity is lowered. Therefore, the high-entropy amorphous alloy nano-particles within the particle size distribution range have relatively better oxygen evolution catalysis effect.

Further, in the embodiment of the invention, the invention also provides a preparation method which is simple in process and can be industrially popularized in a large scale for preparing the high-entropy alloy nanoparticles with high catalytic activity.

Further, in the embodiment of the invention, the invention discloses a preparation method of the FeCoNiMg high-entropy amorphous alloy nanoparticle oxygen evolution catalyst, which is characterized by comprising the following steps of:

(2) Weighing sodium borohydride to prepare a sodium borohydride solution;

Further, in the embodiment of the present invention, in the above step (1), the metal salt preferably includes a water-soluble nitrate, acetate, acetylacetonate, chloride, or the like. However, the metal salt used in the present invention is not particularly limited, and commercially available metal salt materials such as water-soluble nitrates, acetates, acetylacetonates, and chlorides known to those skilled in the art may be used.

Further, in the embodiment of the present invention, in the step (1), the water-soluble ferrous salt, cobalt salt, nickel salt and magnesium salt preferably obtain a molar ratio of 1; further preferred ratios are 1; the most preferred ratio is 1.

Further, in the present embodiment, in the above step (1), the uniform mixing is preferably performed in a round-bottom flask; however, in the present invention, the round-bottom flask is not particularly limited, and a commercially available round-bottom flask known to those skilled in the art may be used as the reaction apparatus.

Further, in the embodiment of the present invention, in the step (2), sodium borohydride is used as a reducing agent, and sodium borohydride is a strong reducing agent, so that the metal chloride salt is easily reduced, and reduced impurities are few.

Further, in the embodiment of the present invention, in the step (2), sodium borohydride may 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, most preferably 1:2.

Further, in the embodiment of the present invention, the concentration of the prepared sodium borohydride aqueous solution is preferably 0.3 to 0.6mol/L, and most preferably 0.4mol/L. However, the sodium borohydride in the present invention is not limited to any more specific one, and commercially available sodium borohydride known to those skilled in the art may be used as the reaction material.

Further, in the embodiment of the present invention, in the step (3), the protective gas in the step (3) is selected to be N ₂ Ar or He;

further, in an embodiment of the present invention, in step (3) above, naBH is added to the precursor solution using a peristaltic pump at a fixed drop rate ₄ The solution was added drop wise to the precursor solution. However, the peristaltic pump for sodium borohydride is not limited to any more specific one, and a commercially available peristaltic pump known to those skilled in the art may be used as the reaction apparatus.

Further, in the embodiment of the present invention, in the step (3), the dropping rate of the aqueous solution of sodium borohydride is preferably 5 to 12m L/min. The inventor researches and finds that in the reasonable dropping speed range, the high-entropy amorphous alloy nanoparticle oxygen evolution catalyst disclosed by the invention is easier to prepare, the sample reaction is incomplete due to too low dropping speed, and the impurity content in the powder is high due to too high dropping speed.

Further, in the embodiment of the present invention, in the step (3) above, naBH is waited ₄ After the solution is completely dripped, strong stirring and gas protection are continuously kept for 1h until no bubbles are generated, which indicates that the reaction is complete; mechanical agitation and N aeration ₂ The gas time is generally from 0.5 to 1.5h, preferably 1h.

Further, in the embodiment of the present invention, the reaction can be made uniform by strong mechanical stirring in step (3) at a stirring speed of 200-1000rpm. However, the present invention is not limited to any particular means for the strong mechanical stirring, and may be any commercially available strong mechanical stirring apparatus known to those skilled in the art.

Further, in the embodiment of the present invention, in the step (4), the precipitate obtained by suction filtration is repeatedly washed with deionized water and ethanol to remove impurities in the particles, and preferably, deionized water and ethanol are respectively washed for 3 times; however, the present invention is not limited to any particular examples, and commercially available deionized water and ethanol known to those skilled in the art may be used as the reaction raw materials.

Further, in the embodiment of the present invention, the vacuum drying is performed at 25 to 70 ℃, preferably at room temperature of 25 ℃; the vacuum drying is carried out by adopting a vacuum drying oven, and the drying time is 24-72 h. However, the present invention is not limited to any particular vacuum drying oven, and a commercially available vacuum drying oven known to those skilled in the art may be used as the reaction apparatus.

Further, in the embodiment of the invention, the invention also provides an application of the high-entropy amorphous alloy nanoparticle oxygen evolution catalyst in an OER reaction, wherein the high-entropy amorphous alloy nanoparticle is selected from alloy nanoparticles prepared by the method. The high-entropy amorphous alloy nanoparticles are FeCoNiMg alloy powder, the oxygen evolution performance of the high-entropy amorphous alloy nanoparticles is tested, an electrochemical workstation is used for testing the electrolytic water oxygen evolution catalytic performance of a prepared electrode, a three-electrode system is adopted, a counter electrode is a platinum sheet electrode, a reference electrode is an Hg/HgO electrode, and an electrolyte is preferably KOH aqueous solution with the concentration of 0.1-1 mol/L.

The invention will now be described with reference to specific examples, which are intended to be illustrative only and not to be limiting in any way. In addition, the percentages recited in the examples are by mass unless otherwise specified.

Example 1

The FeCoNiMg high-entropy amorphous alloy nano-particles are prepared by the following preparation processes:

step 1, weighing metal salt (FeCl in the metal salt) with the total molar weight of 0.004mol ₂ ·4H ₂ O：CoCl ₂ ·6H ₂ O：NiCl ₂ ·6H ₂ O：MgCl ₂ ·6H ₂ And (3) dissolving the following components in 50mL of deionized water, and stirring the solution uniformly to obtain a reaction precursor solution, wherein the components are O = 1.

Step 2, transferring the reaction precursor solution into a clean three-neck flask, and continuously introducing a protective gas N in the whole reaction process to avoid oxidizing the product by oxygen in the air ₂ To prevent oxidation of the product.

Step 3, weighing 0.008mol of NaBH ₄ And is configured to be 0.4mol/L NaBH ₄ An aqueous solution;

step 4, naBH was added at a fixed drop rate of 5mL/min using a peristaltic pump ₄ Adding aqueous solution dropwise into the precursor solution until NaBH is added ₄ After the solution is completely dripped, strong stirring and gas protection are continuously kept for 1h until no bubbles are generated, which indicates that the reaction is complete.

Step 5, collecting reacted powder by using a suction filter, repeatedly washing the powder for three times by using absolute ethyl alcohol and deionized water, and removing impurities adsorbed on a product;

and 6, finally, placing the cleaned black product in a vacuum drying oven, and performing vacuum drying for 20 hours at room temperature to obtain FeCoNiMg powder, wherein the molecular formula of the FeCoNiMg is Fe ₁ Co ₁ Ni ₁ Mg ₁ 。

Comparative example 1

The FeCoNi alloy nanoparticles are prepared by the following steps:

step 1, weighing metal salt with total molar quantity of 0.003mol (wherein the metal salt quantity selected by FeCoNi alloy is FeCl) ₂ ·4H ₂ O：CoCl ₂ ·6H ₂ O：NiCl ₂ ·6H ₂ Dissolving the raw materials in 50mL of deionized water, and fully dissolving and uniformly stirring to obtain a reaction precursor solution;

Step 3, weighing 0.006mol of NaBH ₄ And is configured to be 0.4mol/L NaBH ₄ An aqueous solution;

and 6, finally, placing the cleaned black product in a vacuum drying oven, and carrying out vacuum drying for 20 hours at room temperature to obtain FeCoNi alloy nano powder.

Comparative example 2

The FeCoMg alloy nanoparticles are prepared by the following preparation process:

step 1, weighing metal salt with total molar quantity of 0.003mol (wherein the metal salt quantity selected by FeCoMg alloy is FeCl) ₂ ·4H ₂ O：CoCl ₂ ·6H ₂ O：MgCl ₂ ·6H ₂ Dissolving the raw materials in 50mL of deionized water, and stirring uniformly to obtain a reaction precursor solution, wherein the O = 1;

step 4, naBH was added at a fixed drop rate of 5mL/min using a peristaltic pump ₄ Adding the aqueous solution dropwise into the precursor solution until NaBH is required ₄ After the solution is completely dripped, strong stirring and gas protection are continuously kept for 1h until no bubbles are generated, which indicates that the reaction is complete.

and 6, finally, placing the cleaned black product in a vacuum drying oven, and carrying out vacuum drying for 20 hours at room temperature to obtain FeCoMg alloy nano powder.

Comparative example 3

The preparation method of the FeNiMg alloy nano-particles comprises the following steps:

step 1, weighing metal salt with the total molar weight of 0.003mol (wherein the metal salt selected by the FeNiMg alloy is FeCl ₂ ·4H ₂ O：NiCl ₂ ·6H ₂ O：MgCl ₂ ·6H ₂ Dissolving the raw materials in 50mL of deionized water, and stirring uniformly to obtain a reaction precursor solution, wherein the O = 1;

Step 3, weighing 0.006mol of NaBH ₄ And prepared into NaBH of 0.4mol/L ₄ An aqueous solution;

and step 6, finally, placing the cleaned black product in a vacuum drying oven, and carrying out vacuum drying for 20 hours at room temperature to obtain FeNiMg alloy nano powder.

Comparative example 4

CoNiMg alloy nanoparticles are prepared by the following steps:

step 1, weighing the metal salt with the total molar quantity of 0.003mol (wherein the metal salt is selected by CoNiMg alloyIs CoCl ₂ ·6H ₂ O：NiCl ₂ ·6H ₂ O：MgCl ₂ ·6H ₂ Dissolving the raw materials in 50mL of deionized water, and stirring uniformly to obtain a reaction precursor solution, wherein the O = 1;

and 6, finally, placing the cleaned black product in a vacuum drying oven, and carrying out vacuum drying for 20 hours at room temperature to obtain the CoNiMg alloy nano powder.

And (3) performance testing:

FeCoNiMg, feCoNi, feCoMg, feNiMg and CoNiMg alloy nanoparticles prepared in the examples and the comparative examples of the invention are used as electrolytic water oxygen evolution catalysts to test the oxygen evolution performance of the catalysts, an electrochemical workstation is used to test the electrolytic water oxygen evolution catalytic performance of prepared electrodes, a three-electrode system is adopted, wherein a counter electrode is a platinum sheet electrode, a reference electrode is a Hg/HgO electrode, and an electrolyte is a KOH aqueous solution with the concentration of 1 mol/L.

As shown in fig. 1, an SEM photograph and an energy spectrum of the FeCoNiMg high-entropy amorphous alloy nanoparticles prepared in this embodiment are shown, and it can be seen from the SEM photograph that the size of the prepared powder is about 50nm, the powder is in a nano flower-like structure, the powder is loosely distributed, and the loose nano flower structure can provide a transmission channel for the electrolyte, thereby promoting the performance of the catalytic performance. The EDS picture shows that the elements of the FeCoNiMg high-entropy amorphous alloy particles are uniformly distributed.

Fig. 2 shows XRD results for example FeCoNiMg nanoparticles. The XRD curve of the powder has a steamed bread peak near 2 theta =45 degrees, has no obvious crystal diffraction peak, is consistent with a typical amorphous structure, and shows that the prepared FeCoNiMg alloy nano-particles have a complete amorphous structure, thereby successfully preparing the FeCoNiMg high-entropy amorphous alloy nano-particles.

FIG. 3 is a Linear Sweep Voltammetry (LSV) curve for example FeCoNiMg and comparative example FeCoNi, feCoMg, feNiMg, coNiMg alloy nanoparticles used as an electrolytic water oxygen evolution catalyst at a current density of 10m A/cm ² The overpotential is 280mV, 326mV, 330mV, 340mV, 320mV respectively. The overpotential of FeCoNiMg is the lowest, and the electrocatalytic performance of FeCoNiMg is obviously superior to that of commercial IrO ₂ (340 mV) and RuO ₂ (327mV)。

FIG. 4 shows Taffel slopes of 42.9mV/dec, 50.6mV/dec, 51.6mV/dec, 72.1mV/dec, and 47.6mV/dec for example FeCoNiMg and comparative example FeCoNi, feCoMg, feNiMg, coNiMg alloy nanoparticles, respectively, when used as an electrolytic water oxygen evolution catalyst. Among them, the FeCoNiMg high-entropy amorphous alloy nanoparticles prepared in example 1 showed the most excellent oxygen evolution catalytic performance.

FIG. 5 is an ECSA diagram of FeCoNiMg and FeCoNi, feCoMg, feNiMg, coNiMg nanoalloys, from which it can be seen that C of FeCoNiMg and FeCoNi, feCoMg, feNiMg, coNiMg nanoparticles _dl Are respectively 1.22, 0.48, 0.45, 0.53 and 0.73MF/cm ² In which C of FeCoNiMg _dl At the maximum, it is proved that the electrochemical active surface area is the largest, namely the active sites are increased, and the optimal catalytic oxygen evolution performance is consistent.

The FeCoNiMg high-entropy amorphous alloy nanoparticles prepared in example 1 are loaded on conductive carbon paper to serve as working electrodes, the stability of the working electrodes is tested by a chronopotentiometry method, as shown in FIG. 6, after 72 hours of continuous circulation, the curve is stable, the current attenuation is less than 20%, which indicates that the stability of the working electrodes is good, and after 72 hours of continuous circulation, the LSV curve of the working electrodes is tested, as shown in FIG. 7, the LSV curve of the working electrodes is basically overlapped with the initial LSV curve, which indicates that the working electrodes have good stability.

The foregoing examples are merely illustrative of and explain the present invention and are not to be construed as limiting the scope of the invention. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention.

Claims

1. The high-entropy amorphous alloy nanoparticle oxygen evolution catalyst is characterized in that the oxygen evolution catalyst is FeCoNiMg high-entropy amorphous alloy particles, the high-entropy amorphous alloy particle powder is in a nanometer flower-shaped structure, and the particle size distribution of the nanometer powder is 10nm-100nm.

2. The high-entropy amorphous alloy nanoparticle oxygen evolution catalyst according to claim 1, wherein the process for preparing the high-entropy amorphous alloy particles comprises: preparing high-entropy amorphous alloy powder by a one-time reduction method through mixing iron salt, cobalt salt, nickel salt and magnesium salt for metal salt hydrolysis, wherein the molar weight of the iron salt, the cobalt salt, the nickel salt and the magnesium salt is 1.

3. A preparation method of a high-entropy amorphous alloy nanoparticle oxygen evolution catalyst is characterized by comprising the following steps:

(2) Weighing sodium borohydride to prepare a sodium borohydride solution;

(3) Under the mechanical stirring, introducing protective gas, and slowly dropwise adding a sodium borohydride solution into the precursor solution until the dropwise adding is complete;

4. The preparation method according to claim 3, wherein the ferrous salt, the cobalt salt, the nickel salt and the magnesium salt are mixed in the step (1) according to a molar ratio of 1.

5. The preparation method according to claim 3, wherein in the step (2), sodium borohydride is weighed according to the following ratio: the molar ratio of the total metal ions in the mixed metal salt to the sodium borohydride is 1:1-1.5, and the concentration of the sodium borohydride solution is 0.3-0.6 mol/L.

6. The preparation method according to claim 3, wherein the stirring speed in step (3) is 200 to 1000rpm, and the dropping rate of the aqueous solution of sodium borohydride is 5 to 12mL/min.

7. The method according to claim 3, wherein the protective gas in the step (3) is N ₂ And Ar or He, after the dropwise addition is finished, the mechanical stirring and ventilation time is 0.5-1.5 h, and the step is carried out in a fume hood.

8. The preparation method according to claim 3, wherein in the step (4), the precipitate obtained by suction filtration is repeatedly washed by deionized water and ethanol to remove impurities in the particles, and vacuum drying is carried out at room temperature for 24-72 hours.

9. The application of the high-entropy amorphous alloy nanoparticle oxygen evolution catalyst in OER reaction is characterized in that the high-entropy amorphous alloy nanoparticles are selected from the alloy nanoparticles of any one of claims 1-2 or the alloy nanoparticles prepared by the method of any one of claims 3-8.

10. The use according to claim 9, wherein the high entropy amorphous alloy nanoparticle FeCoNiMg alloy powder and the electrolyte is 0.1-1M KOH solution.