La-based fluorine-doped high-entropy perovskite oxide material and preparation method and application thereof

Abstract

The invention belongs to the technical field of composite electrode preparation, and discloses a La-based fluorine-doped high-entropy perovskite oxide material and a preparation method and application thereof, a nitrate hydrate solution is used as a raw material, and a nanoscale perovskite type high-entropy oxide is synthesized through a solution gel method. And then preparing the corresponding fluorine-doped high-entropy perovskite oxide electrode material through a simple and convenient fluorination method. And the obtained electrode material is high in quality, strong in stability and good in electrical transport performance. The fluorine-element-doped high-entropy perovskite oxide composite electrode is applied to an electrocatalytic water electrolysis oxygen evolution reaction system, and the water electrolysis oxygen evolution reaction can be effectively catalyzed and promoted. The invention shows that the fluorinated high-entropy oxide has good performance in the field of electrocatalysis, shows a good application prospect, provides a foundation for designing and improving an electrocatalyst with better catalytic performance, lays a foundation for mass production of subsequent catalysts, and has important significance. And moreover, the preparation process is simple, the preparation cost is low, the requirement on instruments is not high, and amplification experiments can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalytic materials, and in particular to a La-based fluorine-doped high-entropy perovskite oxide material and a preparation method and application thereof. A fluorine-doped nanoscale perovskite-type high-entropy oxide is prepared by using hydrated nitrate as a raw material through a solution gel method and a fluorination method, and is applied to the field of oxygen evolution electrocatalysis. Background Art

[0002] In recent years, high-entropy nanoparticles, which are composed of five or more elements in equal or nearly equal amounts, have attracted extensive attention from researchers at home and abroad due to their unique multi-element composition structure and significant performance advantages. In the field of materials science, high-entropy nanoparticles have broad development prospects. Through reasonable design, they can effectively optimize material properties and enhance their application potential in energy, environment, biomedicine and other fields. The origin of the concept of high entropy can be traced back to 2004, when Yeh proposed the formation of a single-phase solid solution and the configurational entropy of the mixture (S config ) and proposed the concept of "high entropy alloy" for the first time. Compared with traditional alloys, the content of each element in high entropy alloys is between 5% and 35% (atomic fraction), ensuring that each element is the main component. This unique configuration significantly increases the disorder of the alloy system, that is, the entropy value is higher, hence the name high entropy alloy. In the study of traditional alloy materials, the increase in the number of alloy components often leads to a decrease in alloy performance. Usually, an alloy system of n elements will form n+1 equilibrium phases. The phase composition of high entropy alloys is mainly simple body-centered cubic phase or face-centered cubic phase, rather than complex intermetallic compound phase, which reveals the unique advantages of high entropy alloys in performance.

[0003] The properties of high entropy alloys have triggered a wave of innovation in modern materials science. Initially, high entropy alloys were limited to combinations of five elements, but with the deepening of research, the types of elements have expanded to as many as fifteen, and the research field has also expanded from high entropy alloys to other types of materials such as high entropy carbides, high entropy fluorides, high entropy sulfides, and high entropy oxides. Although the research history of high entropy alloys is relatively short, high entropy nanoparticles have made significant progress in the research of energy and catalysis, especially in the field of catalysis. The flexibility of high entropy materials lies in their compositional diversity, which allows researchers to precisely control their catalytic activity and provide structural stability. For example, by designing non-precious metal nanoparticles (Co x Mo 0.7x )Fe 0.1 Ni 0.1 Cu 0.1 To overcome the immiscibility problem between Co and Mo, the ratio of Co and Mo and the related surface adsorption properties were successfully adjusted. x Mo0.7x )Fe 0.1 Ni 0.1 Cu 0.1 The nanoparticles, as catalysts, increased the efficiency of ammonia decomposition by four times, and worked stably for 50 hours at a high temperature of 500°C without significant performance degradation. This example fully demonstrates the advantages of high-entropy nanoparticles in catalytic performance and thermal stability, providing new opportunities for optimizing catalyst design.

[0004] In recent years, with the rapid development and widespread application of high entropy alloy technology, researchers have gradually extended the design strategy of multi-principal element high entropy to the field of ceramic materials, and successfully developed a series of multi-principal element high entropy ceramic materials. These materials are usually composed of 5 or more metal elements and non-metallic elements such as carbon, nitrogen, oxygen, and boron. Their properties and characteristics are highly consistent with those of typical high entropy alloys, and they also have the typical "four effects" of high entropy alloys: high entropy effect, slow diffusion effect, lattice distortion effect, and cocktail effect. The development of these multi-principal element high entropy ceramic materials not only enriches the theoretical system of materials science, but also provides a wider range of practical applications. They have shown great potential in the fields of energy, catalysis, electronics and information, biomedicine, etc., and have become an important driving force for the development of materials science and technology. With the deepening of research, multi-principal element high entropy ceramic materials will play a key role in more high-tech fields and provide innovative solutions to complex materials science problems.

[0005] Although the concept of high entropy alloys was proposed as early as 2004, the research that clearly proposed the concept of high entropy ceramics and demonstrated the effect of entropy stabilization did not attract people's attention until more than ten years later. In the field of high entropy ceramic materials research, the most leading and representative work is the research on single-phase high entropy oxide ceramics in the (CoCuMgNiZn)O system by Rost et al., which first revealed the key role of entropy stabilization in phase stability, marking the birth of a new material system called high entropy oxide ceramics (HEOs). This discovery has laid a solid foundation for the subsequent research on high entropy ceramic materials. HEOs not only inherit the excellent thermal and mechanical properties of traditional oxide materials, but also show unique polymorphic structures such as rock salt structure, fluorite structure, spinel structure, perovskite structure, etc., as well as a high degree of local chemical disorder due to the inclusion of multiple elements. These characteristics give HEOs rich functional properties, making them show significant application potential in many fields. For example, in high-temperature protective coatings, the stability and thermal stability of HEOs help provide long-lasting and effective protection; in energy storage applications, their specific polycrystalline structure and chemical properties promote more efficient energy conversion and storage; in the field of magnetic materials, the complex composition of HEOs produces unique magnetic properties, providing for the development of high-performance magnetic devices; in catalytic materials, the composite structure of HEOs and the synergistic effect of multivalent elements enhance catalytic activity and selectivity, providing a new approach for the development of environmentally friendly catalysts.

[0006] Through the above analysis, the problems and defects of the prior art are as follows:

[0007] There are many systems of high entropy oxides, among which the preparation and research of nanoscale perovskite-type high entropy oxides are relatively rare.

[0008] High entropy materials have multi-branch elements and distorted lattice properties and are potential candidates for preparing multi-active site catalysts. However, further efforts are needed to develop efficient, structurally reasonable, and compositionally rational high entropy catalysts. Summary of the invention

[0009] In view of the problems existing in the prior art, the present invention provides a La-based fluorine-doped high-entropy perovskite oxide material and a preparation method and application thereof.

[0010] The present invention is achieved by: a La-based fluorine-doped high-entropy perovskite oxide material and a preparation method and application thereof comprising:

[0011] Step 1: Preparation of La(Cr 0.2 Mn 0.2 Fe 0.2 Co 0.2 Ni 0.2)O3 mixed solution, abbreviated as LM5 mixed solution;

[0012] Lanthanum nitrate hexahydrate, chromium nitrate nonahydrate, manganese nitrate tetrahydrate, iron nitrate nonahydrate, cobalt nitrate hexahydrate and nickel nitrate hexahydrate are weighed according to the proportion of each element and dissolved in deionized water. The mixed solution is placed on a magnetic stirrer and stirred evenly.

[0013] Step 2, preparing a precursor solution;

[0014] Anhydrous citric acid was added to the mixed solution obtained in step 1, and the mixture was stirred evenly on a magnetic stirrer to form a precursor solution.

[0015] Step 3, preparing a precursor gel;

[0016] The precursor solution prepared in step 2 is placed on a magnetic heating stirrer for heating and stirring until the solution turns into a gel.

[0017] Step 4, preparing precursor powder;

[0018] The prepared gel was placed in a blast drying oven to dry. After all the water was evaporated, the obtained solid material was ground thoroughly in a mortar. The powder was put into a quartz crucible and then placed in a muffle furnace for high-temperature calcination. After the temperature was cooled to room temperature, LM5 precursor powder was obtained.

[0019] Step 5: Preparation of fluorine-doped La(Cr 0.2 Mn 0.2 Fe 0.2 Co 0.2 Ni 0.2 )O3 powder, abbreviated as FLM5;

[0020] The LM5 powder and ammonium fluoride (NH4F) powder obtained in step 4 are placed in a quartz crucible respectively, and placed in a tube furnace for heating treatment to obtain FLM5 powder.

[0021] Step six, preparing a composite electrode;

[0022] The FLM5 powder and acetylene black were mixed evenly and the mixture was dispersed in a mixed solution. The formed ink was ultrasonically dispersed in an ice bath, and the ink was dropped on the surface of a glassy carbon (GC) electrode and dried at room temperature.

[0023] Furthermore, the total amount of reagents used to prepare the mixed solution in step one is 2 mmol, and 0.8660 g of lanthanum nitrate hexahydrate, 0.1600 g of chromium nitrate nonahydrate, 0.1004 g of manganese nitrate tetrahydrate, 0.1616 g of ferric nitrate nonahydrate, 0.1164 g of cobalt nitrate hexahydrate, and 0.1163 g of nickel nitrate hexahydrate are weighed respectively according to a molar ratio of 5:1:1:1:1:1.

[0024] Further, in step 2, 0.7684 g of anhydrous citric acid is weighed according to a molar ratio of 2:1 between the anhydrous citric acid and the total amount of metal ions in the mixed solution.

[0025] Furthermore, in step three, the temperature of the magnetic heating stirrer is set to 70-90° C., and the stirring time is 8-12 h.

[0026] Furthermore, in step 4, the temperature of the blast drying oven is set to 130-150° C., and the drying time is 4-6 hours. The calcination temperature of the muffle furnace is 1000° C., and the calcination time is 7-9 hours.

[0027] Furthermore, in step five, the ratio of precursor powder to ammonium fluoride is 1:5, and 0.2 g of LM5 precursor powder and 1 g of ammonium fluoride are weighed according to the ratio. The temperature of the tube furnace is set to 300°C, and calcined for 2-3 h in an Ar or N2 atmosphere with a heating rate of 2°C / min.

[0028] Furthermore, in step six, 10 mg of FLM5 powder and 2 mg of acetylene black were weighed respectively.

[0029] Furthermore, in step six, the mixed solution contains 0.5 mL of deionized water, 0.47 mL of anhydrous ethanol and 0.03 mL of 5 wt % Nafion solution, and the ultrasonication time is 1-3 h.

[0030] Furthermore, in step six, the amount of ink dropped onto the surface of the glassy carbon (GC) electrode is 4 uL.

[0031] Furthermore, the electrochemical system includes a working electrode, an auxiliary electrode, a reference electrode and an electrolyte, wherein the working electrode includes the FLM5 composite electrode.

[0032] Furthermore, the auxiliary electrode is a platinum wire electrode, the reference electrode is a Hg / HgO electrode, and the electrolyte is 60 mL of a potassium hydroxide aqueous solution with a concentration of 0.1-1 mol / L.

[0033] In combination with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are as follows:

[0034] First, compared with the prior art, the present invention provides a high entropy perovskite oxide LM5 and a method for preparing a fluorinated high entropy perovskite oxide FLM5. The method adopts a solution gel method, first evaporating the corresponding nitrate precursor solution to form a gel, and then calcining it at high temperature in a muffle furnace to form a stable high entropy perovskite oxide. After that, a simple fluorination treatment is used to prepare a fluorine-doped high entropy perovskite oxide.

[0035] The fluorine-doped high-entropy perovskite oxide described in the present invention is used as a catalyst and exhibits very excellent performance in the field of electrocatalytic oxygen evolution reaction. The present invention synthesizes a stable and highly active fluorine-doped high-entropy perovskite oxide through an extremely simple solution gel method and fluorination treatment, which has low requirements for instruments and can realize scale-up experiments, laying a foundation for the subsequent mass production of catalysts, and is of great significance.

[0036] Second, the technical problems solved and the technological progress brought about:

[0037] Precise control of component ratio: By accurately weighing various reagents, the component ratio of the FLM5 high entropy oxide composite electrode is ensured to be accurate, thereby improving the performance and stability of the electrode.

[0038] Optimization of preparation process: By strictly controlling parameters such as heating temperature, stirring and drying time, the preparation process is optimized, so that the electrode material has better crystallinity and microstructure, thereby improving the electrochemical performance of the electrode.

[0039] Introducing ammonium fluoride treatment: Introducing ammonium fluoride treatment in step five further improves the performance of the electrode material and enhances the catalytic activity of the electrode by changing the surface properties of the material or introducing new active sites.

[0040] Innovative ink preparation: The innovative ink preparation method in step six enables the electrode materials to be better dispersed and fixed on the glassy carbon, improving the conductivity and stability of the electrode.

[0041] In summary, the present invention solves the problems of unstable electrode performance and insufficient catalytic activity in the prior art through precise control of component ratios, optimized preparation process and innovative subsequent processing steps, thus bringing about significant technological progress.

[0042] Third, the technical solution of the present invention solves the technical problems of the prior art.

[0043] 1) Uniformity and consistency issues in the preparation of high entropy oxide composite electrodes:

[0044] Existing technical problems: In the traditional preparation process of high entropy oxide composite electrodes, due to the uneven distribution of various metal elements during mixing and calcination, the performance of the final prepared composite electrode is unstable, affecting its effect in the electrocatalytic reaction.

[0045] The solution of the present invention: by strictly controlling the molar ratio of the mixed solution and the proportion of metal ions in the solution, and adopting precise temperature control and calcination process, the present invention effectively solves the problem of uneven element distribution, ensures the uniformity and consistency of the high entropy oxide composite electrode, and thus improves the performance stability of the electrode.

[0046] 2) Insufficient activity and catalytic performance of electrode materials:

[0047] Problems with existing technologies: In traditional preparation methods, due to internal defects in the materials and insufficient active sites, the catalytic performance of the electrodes is poor, especially in the electrocatalytic water decomposition reaction (OER), which exhibits a high overpotential and low catalytic efficiency.

[0048] Solution of the present invention: The present invention significantly improves the surface properties of the material and the exposure of active sites by introducing ammonium fluoride as an auxiliary agent during the preparation process and calcining at a specific temperature and atmosphere, thereby enhancing the catalytic performance of the high entropy oxide composite electrode in the OER reaction, showing a lower overpotential and higher catalytic efficiency.

[0049] 3) Durability and stability issues of electrodes in practical applications:

[0050] Problems with existing technologies: Many electrocatalytic electrodes are prone to performance degradation during long-term use, especially under alkaline conditions. The material's stability and corrosion resistance are insufficient, limiting its application in industry.

[0051] The solution of the present invention: By optimizing the calcination process and the composition ratio of the electrode material, the present invention improves the durability and chemical stability of the high entropy oxide composite electrode, so that it exhibits better corrosion resistance under alkaline conditions and can maintain efficient catalytic performance during long-term use.

[0052] The significant technical progress obtained by the present invention:

[0053] 1) Improved the uniformity of the electrode and the repeatability of the preparation process:

[0054] By strictly controlling the molar ratio of each element, temperature and stirring time, the preparation method of the present invention ensures the uniformity and consistency of the high entropy oxide composite electrode and significantly improves the repeatability of the preparation process. This improvement not only improves the performance stability of the electrode, but also makes large-scale production possible.

[0055] 2) Enhanced catalytic activity and efficiency of the electrode:

[0056] The present invention significantly increases the surface active sites of the electrode and improves the efficiency of the electrocatalytic reaction by introducing ammonium fluoride and treating the electrode material under specific calcination conditions. In the electrocatalytic water decomposition oxygen reaction, the electrode exhibits a lower overpotential and a higher catalytic efficiency, which greatly improves the overall performance of the reaction.

[0057] 3) Significantly improved the durability and chemical stability of the electrode:

[0058] By optimizing the composition of the electrode material and the calcination process, the present invention effectively improves the corrosion resistance of the electrode in an alkaline environment and the stability in long-term use. This makes the electrode have a longer service life and higher reliability in practical applications, and is suitable for industrial-scale electrocatalytic reaction systems.

[0059] 4) Promoted the application of high entropy oxide electrodes in the field of electrocatalysis:

[0060] The technical solution of the present invention not only solves the bottleneck of traditional electrodes in catalytic activity and stability, but also promotes the application of high entropy oxide materials in the field of electrocatalysis through significant technological progress, especially in electrocatalytic water decomposition, fuel cells and other new energy technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 1 is an X-ray diffraction (XRD) diagram of the LM5 and FLM5 high entropy perovskite oxide powders provided in the embodiments of the present invention, indicating the single-phase crystal structure of LM5 and FLM5.

[0062] Figure 2 The embodiments of the present invention provide scanning electron microscope (SEM) images of LM5 and FLM5 high entropy perovskite oxide powders, which reveal that LM5 and FLM5 have similar morphological structures.

[0063] Figure 3 The embodiment of the present invention provides an element distribution (EDS) diagram of LM5 and FLM5 high entropy perovskite oxide powders, which shows that each element in LM5 and FLM5 is uniformly distributed.

[0064] Figure 4 It is a comparison diagram of the linear voltammetric curves of the catalytic activity of the OER reaction of the LM5 and FLM5 high entropy perovskite oxide composite electrodes provided in the embodiments of the present invention, indicating that FLM5 has better OER catalytic performance than LM5, proving that fluorine doping improves the OER catalytic performance of the LM5 high entropy perovskite oxide.

[0065] Figure 5 It is a cyclic voltammogram of the double-layer capacitance of the LM5 and FLM5 high-entropy perovskite oxide composite electrodes provided in the embodiments of the present invention, indicating that FLM5 has a higher non-Faraday current response than LM5, proving that fluorine doping increases the electrochemically active surface area of ​​the LM5 high-entropy perovskite oxide.

[0066] Figure 6 It is a schematic diagram of double-layer capacitance of LM5 and FLM5 high-entropy perovskite oxide composite electrodes provided in an embodiment of the present invention, which directly indicates that FLM5 has a higher electrochemically active surface area than LM5.

[0067] Figure 7 It is the electrochemical impedance spectrum of the LM5 and FLM5 high entropy perovskite oxide composite electrodes provided in the embodiments of the present invention, revealing that the charge transfer resistance of FLM5 is 40.9Ω, which is smaller than the charge transfer resistance of LM5 (212.5Ω), indicating that FLM5 has faster OER kinetic characteristics. DETAILED DESCRIPTION

[0068] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0069] The method for preparing the FLM5 high entropy oxide composite electrode provided in the embodiment of the present invention and the application of the electrode in the electrocatalytic water decomposition oxygen reaction system. In order to enable those skilled in the art to fully understand how to implement the present invention, this section is an explanatory embodiment that expands the technical solution of the claims.

[0070] The method for preparing the La-based fluorine-doped high-entropy perovskite oxide material provided in the embodiment of the present invention comprises the following steps:

[0071] The first step is to prepare the LM5 mixed solution;

[0072] Lanthanum nitrate hexahydrate, chromium nitrate nonahydrate, manganese nitrate tetrahydrate, iron nitrate nonahydrate, cobalt nitrate hexahydrate and nickel nitrate hexahydrate reagents were weighed according to the proportion of each element and dissolved in deionized water. The mixed solution was placed on a magnetic stirrer and stirred evenly.

[0073] The second step is to prepare the precursor solution;

[0074] Anhydrous citric acid is added to the mixed solution prepared in the first step, and the mixture is placed on a magnetic stirrer and stirred evenly to form a precursor solution.

[0075] The third step is to prepare the precursor gel;

[0076] The prepared precursor solution is placed on a magnetic heating stirrer for heating and stirring until the solution turns into a gel.

[0077] Step 4: preparing precursor powder;

[0078] The prepared gel was placed in a blast drying oven to dry. After all the water was evaporated, the obtained solid material was placed in a mortar and ground thoroughly. The powder was put into a quartz crucible and then placed in a muffle furnace for high-temperature calcination. After the temperature was cooled to room temperature, LM5 precursor powder was obtained.

[0079] Step 5, preparing fluorinated high entropy perovskite oxide powder;

[0080] The LM5 precursor powder obtained in step 4 and ammonium fluoride are placed in a quartz crucible respectively, and placed in a tube furnace for heating treatment to obtain fluorine-doped high-entropy perovskite oxide FLM5 powder.

[0081] Step 6: preparing the composite electrode;

[0082] The FLM5 powder and the acetylene black powder were mixed evenly and the mixture was dispersed in the mixed solution. The formed ink was ultrasonically dispersed in an ice bath and the ink was dropped on the surface of the glassy carbon (GC) electrode at room temperature until it was completely dried.

[0083] The total amount of reagents used in the mixed solution prepared in the first step provided by the present invention is 2 mmol, and 0.8660 g of lanthanum nitrate hexahydrate, 0.1600 g of chromium nitrate nonahydrate, 0.1004 g of manganese nitrate tetrahydrate, 0.1616 g of ferric nitrate nonahydrate, 0.1164 g of cobalt nitrate hexahydrate, and 0.1163 g of nickel nitrate hexahydrate are weighed respectively according to a molar ratio of 5:1:1:1:1:1.

[0084] In the second step provided by the present invention, 0.7684 g of anhydrous citric acid is weighed according to a molar ratio of 2:1 between the anhydrous citric acid and the total amount of metal ions in the mixed solution.

[0085] In the third step provided by the present invention, the temperature of the heating magnetic heating stirrer is set to a constant 80° C., and the stirring time is 8-12 hours.

[0086] In the fourth step provided by the present invention, the temperature of the blast drying oven is set to be constant at 130° C., and the drying time is 4-6 hours. The calcination temperature of the muffle furnace is 1000° C., and the calcination time is 7 hours.

[0087] In the fifth step provided by the present invention, the ratio of precursor powder to ammonium fluoride is 1:5, 0.2g LM5 precursor powder and 1g ammonium fluoride powder are weighed respectively according to the ratio, the temperature of the tube furnace is set to 300°C, and calcined for 2h in Ar or N2 atmosphere, with a heating rate of 2°C / min.

[0088] In the sixth step provided by the present invention, 10 mg of FLM5 powder and 2 mg of acetylene black are weighed respectively.

[0089] In the sixth step provided by the present invention, the mixed solution contains 0.5 mL of deionized water, 0.47 mL of anhydrous ethanol and 0.03 mL of 5 wt % Nafion solution, and the ultrasonic time is 1 hour.

[0090] In the sixth step provided by the present invention, the amount of ink dropped on the glassy carbon is 4uL.

[0091] A La-based fluorine-doped high-entropy perovskite oxide composite electrode prepared according to the method.

[0092] An application of the La-based fluorine-doped high-entropy perovskite oxide composite electrode in an electrocatalytic water-oxygen decomposition reaction system, characterized in that the system comprises a working electrode, an auxiliary electrode, a reference electrode and an electrolyte, wherein the working electrode comprises the FLM5 composite electrode.

[0093] The auxiliary electrode provided by the present invention is a platinum wire electrode, the reference electrode is a Hg / HgO electrode, and the electrolyte is 60 mL of a potassium hydroxide aqueous solution with a concentration of 0.1-1 mol / L.

[0094] Example 1

[0095] A method for preparing a FLM5 composite electrode comprises the following steps:

[0096] (1) Preparation of LM5 mixed solution

[0097] According to the total amount of reagents 2 mmol and the molar ratio of each element 5:1:1:1:1:1, 0.8660 g of lanthanum nitrate hexahydrate, 0.1600 g of chromium nitrate nonahydrate, 0.1004 g of manganese nitrate tetrahydrate, 0.1616 g of iron nitrate nonahydrate, 0.1164 g of cobalt nitrate hexahydrate, and 0.1163 g of nickel nitrate hexahydrate were weighed respectively. The mixed reagents were poured into 80 mL of deionized water and placed on a magnetic stirrer until completely dissolved.

[0098] (2) Preparation of LM5 precursor solution

[0099] According to the molar ratio of the total amount of metal ions in the mixed solution to citric acid of 1:2, 4 mmol of citric acid with a total mass of 0.7684 g was weighed and added to the completely dissolved mixed solution to obtain a LM5 precursor solution.

[0100] (3) Preparation of LM5 precursor gel

[0101] The prepared LM5 precursor solution was placed on a magnetic heating stirrer at a constant temperature of 80° C. and heated and stirred for 12 h until the solution turned into a gel.

[0102] (4) Preparation of LM5 precursor powder

[0103] The prepared LM5 precursor gel was placed in a forced air drying oven and dried at a constant temperature of 130°C for 6 hours. After all the water was evaporated, the obtained solid material was placed in a ceramic mortar and fully ground. The ground powder was put into a quartz crucible and then placed in a muffle furnace. The temperature was set to 1000°C and high-temperature calcined for 7 hours with a heating rate of 5°C / min. After the temperature was cooled to room temperature, the prepared LM5 precursor powder was obtained.

[0104] (5) Preparation of FLM5 powder

[0105] According to the molar ratio of 1:5, 0.2 g of LM5 precursor powder and 1 g of ammonium fluoride were weighed on an electronic scale, placed in two quartz crucibles respectively, and then calcined in a tube furnace with a constant temperature of 300 °C, a calcination time of 2 h, and a heating rate of 2 °C / min to obtain FLM5 powder.

[0106] (6) Preparation of FLM5 composite electrode

[0107] Weigh 10 mg of FLM5 powder and 2 mg of acetylene black respectively, put them into a small glass bottle, and then add 0.5 mL of deionized water, 0.47 mL of anhydrous ethanol and 0.03 mL of 5 wt% Nafion solution into the glass bottle in sequence. After the formed ink is ultrasonically dispersed in an ice bath for 1 h, 4 uL of the ink is dropped on the surface of the glassy carbon (GC) electrode using a pipette and left at room temperature until it is completely dry.

[0108] The FLM5 composite electrode prepared in Example 1 is used to prepare an OER electrocatalytic system, and the preparation method thereof comprises the following steps:

[0109] The FLM5 composite electrode was used as the working electrode, and then the working electrode, the auxiliary electrode platinum wire electrode and the reference electrode Hg / HgO electrode were assembled and placed in an electrolyte. The electrolyte was 60 mL of a 1 mol / L potassium hydroxide aqueous solution and connected to an electrochemical workstation to obtain an OER electrocatalytic system.

[0110] Example 2

[0111] A method for preparing an LM5 composite electrode comprises the following steps:

[0112] (1) Preparation of LM5 mixed solution

[0113] According to the total amount of reagents 2 mmol and the molar ratio of each element 5:1:1:1:1:1, 0.8660 g of lanthanum nitrate hexahydrate, 0.1600 g of chromium nitrate nonahydrate, 0.1004 g of manganese nitrate tetrahydrate, 0.1616 g of iron nitrate nonahydrate, 0.1164 g of cobalt nitrate hexahydrate, and 0.1163 g of nickel nitrate hexahydrate were weighed respectively. The mixed reagents were poured into 80 mL of deionized water and placed on a magnetic stirrer until completely dissolved.

[0114] (2) Preparation of LM5 precursor solution

[0115] According to the molar ratio of the total amount of metal ions in the mixed solution to citric acid of 1:2, 4 mmol of citric acid with a total mass of 0.7684 g was weighed and added to the completely dissolved mixed solution to obtain a LM5 precursor solution.

[0116] (3) Preparation of LM5 precursor gel

[0117] The prepared LM5 precursor solution was placed on a heated magnetic stirrer at a constant temperature of 80° C. and heated and stirred for 12 h until the solution turned into a gel.

[0118] (4) Preparation of LM5 precursor powder

[0119] The prepared LM5 precursor gel was placed in a forced air drying oven and dried at a constant temperature of 130°C for 6 hours. After all the water was evaporated, the obtained solid material was placed in a ceramic mortar and fully ground. The ground powder was put into a quartz crucible and then placed in a muffle furnace. The temperature was set to 1000°C and high-temperature calcined for 7 hours with a heating rate of 5°C / min. After the temperature was cooled to room temperature, the prepared LM5 precursor powder was obtained.

[0120] (5) Preparation of LM5 composite electrode

[0121] Weigh 10 mg of LM5 precursor powder and 2 mg of acetylene black respectively, put them into a small glass bottle, and then add 0.5 mL of deionized water, 0.47 mL of anhydrous ethanol and 0.03 mL of 5 wt% Nafion solution into the glass bottle in sequence. After ultrasonically dispersing the formed ink in an ice bath for 1 hour, use a pipette to drop 4 uL of the ink on the surface of the glassy carbon (GC) electrode and leave it at room temperature until it is completely dry.

[0122] The LM5 composite electrode prepared in Example 2 is used to prepare an OER electrocatalytic system, and the preparation method thereof comprises the following steps:

[0123] The LM5 composite electrode was used as the working electrode, and then the working electrode, the auxiliary electrode platinum wire electrode and the reference electrode Hg / HgO electrode were assembled and placed in an electrolyte. The electrolyte was 60 mL of a 1 mol / L potassium hydroxide aqueous solution and connected to an electrochemical workstation to obtain an OER electrocatalytic system.

[0124] Test example

[0125] The FLM5 precursor powder prepared in Example 1 was physically characterized by X-ray diffraction. Figure 1 The FLM5 precursor powder prepared in Example 1 was characterized by scanning electron microscopy to determine its microscopic morphology. Figure 2 The elemental composition of the FLM5 precursor powder prepared in Example 1 was analyzed by energy spectrum, as shown in FIG. Figure 3 The FLM5 composite electrode prepared in Example 1 was subjected to linear voltammetric scanning and cyclic voltammetric scanning of double-layer capacitance through the OER catalytic system. The scanning results are shown as follows: Figure 4 , Figure 5As shown. The linear voltammetry curve is tested using the OER catalytic system at a reversible hydrogen electrode potential of 0.9 to 1.8 V, with a scan rate of 10 mV / s. For the cyclic voltammetry curve of the double-layer capacitor, it is tested at a reversible hydrogen electrode potential of 0.15 to 0.3 volts, with a scan rate from 50 mV / s to 500 mV / s. Figure 6 As shown in the figure, the current density at the potential of 1.15 volts in the cyclic voltammetry curve of the double-layer capacitor is selected for plotting, and its slope is the double-layer capacitor value. The electrochemical impedance spectrum is tested, and the equivalent circuit consisting of the electrolyte resistance (Rs), charge transfer resistance (Rct) and constant phase element (CPE) is used to fit the Nyquist plot. The results are shown in the figure. Figure 7 shown.

[0126] Figure 1 The X-ray diffraction (XRD) pattern of the obtained FLM5 powder sample is shown. Compared with the standard card PDF#500297, the sample has a single-phase orthorhombic perovskite structure without impurity phase. Figure 2 The microstructure of the obtained FLM5 precursor powder sample is granular. Figure 3 It can be seen that the elements of the FLM5 powder sample are evenly distributed. Figure 4 It can be concluded that the current density of the FLM5 composite electrode is the highest at a potential of 1.8 volts, reaching a maximum of 128.67 mA / cm 2 , with good OER performance. Figure 5 It can be seen that the electrochemically active surface area of ​​FLM5 is large, indicating that it has many surface active sites and high OER catalytic activity. Figure 6 As shown, the current density at a potential of 1.15 volts in the cyclic voltammetry curve of the double-layer capacitance is plotted, and its slope is the double-layer capacitance value of 1.33 mF. Figure 7 It can be found that the Rct of FLM5 is 40.9Ω.

[0127] Comparative Example 1

[0128] An OER electrocatalytic system includes an LM5 working electrode, an auxiliary electrode platinum wire electrode and a reference electrode Hg / HgO electrode, and the preparation method is consistent with the preparation method of the OER electrocatalytic system in Example 1. After testing by the method described in the test example in Example 1, the maximum current density of the LM5 composite electrode is 50.87 μA / cm 2 Compared with the OER electrocatalytic system prepared in Example 1, the current density is about 39.54% of that in Example 1, and the Rct of the LM5 composite electrode is 212.5Ω, which is much larger than the Rct value of 40.9Ω measured in Example 1. Therefore, the OER performance of the FLM5 composite electrode is much higher than that of the LM5 composite electrode, highlighting that the technology of the present invention has made significant progress.

[0129] The preparation method provided by the present invention has abundant raw material sources, and the preparation of FLM5 precursor powder is simple, fast, safe, and conducive to large-scale production. After fluorination treatment, the response current of the FLM5 composite electrode at the same potential is greatly improved. The electrochemical properties can be regulated by adjusting the molar ratio between the elements of FLM5 and the muffle furnace calcination temperature and duration, and the performance is stable and highly repeatable;

[0130] The FLM5 composite electrode prepared by the present invention can be directly used as a reaction electrode, has good conductivity, good stability in the oxygen evolution reaction of water electrolysis, and high electrocatalytic activity;

[0131] By applying the FLM5 composite electrode provided by the present invention to an electrocatalytic water-oxygen evolution reaction system, the electrolytic water-oxygen evolution reaction can be effectively catalyzed and promoted.

[0132] The present invention prepares FLM5 precursor powder by a solution-gel method, and the obtained material has stable performance and high repeatability, has low requirements on instruments, can realize scale-up experiments, and lays a foundation for subsequent mass production of catalysts, which is of great significance.

[0133] The present invention shows that the ohmic resistance of LM5 is small, which is attributed to the good conductivity of metal materials, the reasonable microstructure and the high oxidation state of transition metals that are good at adsorbing OER intermediates. After fluorination, the high electronegativity of F is conducive to the formation of electron clouds, and F is conducive to the migration of electron clouds, so the FLM5 electrode has durability and Rct is greatly reduced.

[0134] The following are two specific industrial application examples:

[0135] Example 1: Lithium-ion battery field

[0136] In the field of lithium-ion batteries, high entropy oxide composite electrode materials have broad application prospects. With the popularity of electric vehicles and mobile devices, the demand for high-performance, long-life lithium-ion batteries continues to increase. High entropy oxide composite electrodes have become key materials for improving the performance of lithium-ion batteries due to their excellent lithium storage and cycle performance.

[0137] 1. Material preparation: The preparation method of the FLM5 high entropy oxide composite electrode as claimed in the claim can be used to synthesize a composite electrode material with high performance. This method optimizes the structure and performance of the electrode material by precisely controlling the molar ratio of each element and utilizing technical means such as high temperature calcination and fluorination treatment.

[0138] 2. Performance improvement: Applying the prepared high entropy oxide composite electrodes to lithium-ion batteries can significantly improve the energy density and cycle life of the batteries. For example, in some experiments, lithium-ion batteries using high entropy oxide composite electrodes can still maintain a high capacity retention rate after hundreds of charge and discharge cycles, showing excellent cycle stability.

[0139] 3. Market application: This high-performance lithium-ion battery can be widely used in electric vehicles, smart phones, laptops and other fields to meet consumers' needs for long battery life, fast charging and stable performance.

[0140] Example 2: Zinc ion water battery field

[0141] In the field of zinc-ion aqueous batteries, high entropy oxides have also shown great application potential. As an environmentally friendly, safe and low-cost energy storage device, zinc-ion aqueous batteries have received widespread attention in recent years.

[0142] 1. Selection of electrode materials: High entropy oxides are used as positive electrode materials for zinc ion aqueous batteries by taking advantage of their multi-path electron transfer and remarkable structural stability. This material has high capacity, long cycle life and excellent rate performance, making it an ideal electrode material for zinc ion aqueous batteries.

[0143] 2. Improved battery performance: By applying high entropy oxides to zinc-ion aqueous batteries, the energy density and power density of the battery can be significantly improved. At the same time, due to the strong lattice strain field of high entropy oxides on high charge density Zn 2+ The battery has strong tolerance to electrostatic repulsion, so the cycle stability of the battery is also significantly improved.

[0144] 3. Application expansion: This high-performance zinc-ion water battery can be used in smart grids, energy storage power stations and other fields, providing an effective solution for the storage and utilization of renewable energy. At the same time, due to its environmental protection, safety and low cost, it is also suitable for distributed energy systems and microgrids.

[0145] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modification, equivalent substitution and improvement made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a FLM5 high entropy oxide composite electrode, characterized in that: The following steps are involved: Step 1, preparing LM5 mixed solution; Weigh the corresponding nitrates of lanthanum nitrate hexahydrate, chromium nitrate nonahydrate, manganese nitrate tetrahydrate, iron nitrate nonahydrate, cobalt nitrate hexahydrate and nickel nitrate hexahydrate according to the ratio of each element, and dissolve them in deionized water; place the mixed solution on a magnetic stirrer and stir it evenly; Step 2, preparing a precursor solution; Add anhydrous citric acid to the mixed solution obtained in step 1, place it on a magnetic stirrer and stir it evenly to form a precursor solution; Step 3, preparing a precursor gel; The prepared precursor solution is placed on a heated magnetic stirrer and heated and stirred until the solution turns into a gel; Step 4, preparing precursor powder; The obtained gel was placed in a blast drying oven to dry, and after all the water was evaporated, the obtained solid material was placed in a mortar and ground thoroughly, and the powder was placed in a quartz crucible and then placed in a muffle furnace for high-temperature calcination. After the temperature was cooled to room temperature, LM5 precursor powder was obtained; Step 5, preparing FLM5 powder; The LM5 precursor powder obtained in step 4 and ammonium fluoride are placed in a quartz crucible, respectively, and placed in a tube furnace for heating treatment to obtain FLM5 powder; Step six, preparing a composite electrode; FLM5 powder and acetylene black were mixed uniformly, and the mixture was dispersed in a mixed solution; the formed ink was ultrasonically dispersed in an ice bath, and the ink was dropped on a glassy carbon (GC) electrode until it was completely dried.

2. The method for preparing the FLM5 high entropy oxide composite electrode according to claim 1, characterized in that: The total amount of reagents used in the mixed solution prepared in step 1 is 2 mmol. According to the molar ratio of 5:1:1:1:1:1, 0.8660 g of lanthanum nitrate hexahydrate, 0.1600 g of chromium nitrate nonahydrate, 0.1004 g of manganese nitrate tetrahydrate, 0.1616 g of ferric nitrate nonahydrate, 0.1164 g of cobalt nitrate hexahydrate, and 0.1163 g of nickel nitrate hexahydrate were weighed respectively.

3. The method for preparing the FLM5 high entropy oxide composite electrode according to claim 1, characterized in that: In step 2, 0.7684 g of anhydrous citric acid is weighed according to the molar ratio of anhydrous citric acid to the total amount of metal ions in the mixed solution of 2:

1.

4. The method for preparing the FLM5 high entropy oxide composite electrode according to claim 1, characterized in that: In step 3, the temperature of the magnetic heating stirrer is set to 70-80°C, and the stirring time is 8-12h.

5. The method for preparing the FLM5 high entropy oxide composite electrode according to claim 1, characterized in that: In step 4, the temperature of the blast drying oven is set to 130-150° C., and the drying time is 4-6 hours. The calcination temperature of the muffle furnace is 1000° C., and the calcination time is 7-9 hours.

6. The method for preparing the FLM5 high entropy oxide composite electrode according to claim 1, characterized in that: In step five, the ratio of precursor powder to ammonium fluoride is 1:

5. 0.2g LM5 precursor powder and 1g ammonium fluoride are weighed according to the ratio. The temperature of the tube furnace is set to 300°C. Calcination is carried out in Ar or N2 atmosphere for 2-3h, and the heating rate is 2°C / min. In step six, 10mg FLM5 precursor powder and 2mg acetylene black are weighed respectively. The mixed solution in step six contains 0.5mL deionized water, 0.47mL anhydrous ethanol and 0.03mL 5wt% Nafion solution, and the ultrasonic time is 1-3h. The amount of ink dropped on the glassy carbon in step six is ​​4uL.

7. The FLM5 high entropy oxide composite electrode prepared according to the method according to any one of claims 1 to 6, characterized in that: The preparation steps include: Step 1: prepare a mixed solution, the total amount of reagents used is 2 mmol, and 0.8660 g of lanthanum nitrate hexahydrate, 0.1600 g of chromium nitrate nonahydrate, 0.1004 g of manganese nitrate tetrahydrate, 0.1616 g of ferric nitrate nonahydrate, 0.1164 g of cobalt nitrate hexahydrate, and 0.1163 g of nickel nitrate hexahydrate are weighed according to a molar ratio of 5:1:1:1:1:1; Step 2: Weigh 0.7684 g of anhydrous citric acid according to a molar ratio of 2:1 between anhydrous citric acid and the total amount of metal ions in the mixed solution; Step 3: The temperature of the magnetic heating stirrer is set to 70-80°C and the stirring time is 8-12h; Step 4: The temperature of the blast drying oven is set to 130-150°C, the drying time is 4-6 hours, the calcination temperature of the muffle furnace is 1000°C, and the calcination time is 7-9 hours; Step 5: The ratio of precursor powder to ammonium fluoride is 1:

5. Weigh 0.2g LM5 precursor powder and 1g ammonium fluoride respectively. Set the temperature of the tube furnace to 300℃. Calcinate for 2-3h in Ar or N2 atmosphere with a heating rate of 2℃ / min. Step 6: Weigh 10 mg of FLM5 powder and 2 mg of acetylene black, and mix the solution containing 0.5 mL of deionized water, 0.47 mL of anhydrous ethanol and 0.03 mL of 5 wt% Nafion solution. Ultrasonication time is 1-3 h, and the amount of ink dropped on the glassy carbon is 4 μL.

8. The electrocatalytic water-oxygen separation reaction system prepared by the FLM5 high entropy oxide composite electrode according to claim 7 is characterized in that: include: Working electrode: FLM5 high entropy oxide composite electrode; Auxiliary electrode: As part of the electrolytic cell, usually a platinum wire electrode; Reference electrode: usually Hg / HgO electrode; Electrolyte: 60mL of 0.1-1mol / L potassium hydroxide aqueous solution.

9. The electrocatalytic water-oxygen separation reaction system according to claim 8, characterized in that: The auxiliary electrode is a platinum wire electrode, the reference electrode is a Hg / HgO electrode, and the electrolyte is 60 mL of a potassium hydroxide aqueous solution with a concentration of 0.1-1 mol / L.

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