Preparation method of low-cost high-entropy alloy aerogel electrocatalytic material

Abstract

The application belongs to the technical field of preparation of nanoporous materials, and relates to a preparation method of low-cost high-entropy alloy aerogel electrocatalytic materials. Five kinds of metal salt solutions are uniformly mixed by stirring, a reducing agent is added, and then the freezing and thawing technology is used, followed by solvent replacement and combination of the freeze-drying method, so that the low-cost high-activity and multifunctional high-entropy alloy aerogel material is finally obtained. The application has the advantages of low material cost and convenient process, and has the advantages of low energy consumption, lower cost, multifunctional integration, higher stability and easy scale production.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of preparation process of aerogel materials, and particularly relates to a preparation method of a low-cost high-entropy alloy aerogel electrocatalytic material by using a self-assembly technology combined with a freeze-drying process. BACKGROUND

[0002] Fuel cells have the advantages of high theoretical energy density, environmental friendliness and low cost, and have become one of the best replacement options for traditional energy. Among the reaction processes involved in various fuel cells, oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) both occupy an important position, and their reaction efficiency dominates the performance of the battery charging and discharging process. ORR is a four-electron proton coupling process, which is complex and difficult to control, and has slow kinetics, so it is necessary to use an efficient ORR catalyst to promote the reaction process. However, the current commercial catalyst mainly uses Pt / C, and this catalyst has defects such as resource scarcity, poor stability and insufficient catalytic activity, which limit its wide application. Therefore, it is of great significance to develop an electrocatalyst that simultaneously has high catalytic activity, high stability and low cost.

[0003] Aerogel is a nanoporous material composed of nanoparticles, which has unique properties such as high specific surface area, high porosity and ultra-low bulk density, and has received extensive attention in the fields of thermal insulation, adsorption, catalysis and sensing. The high specific surface area and highly interconnected pores of aerogel material can expose more reaction active sites, and at the same time facilitate the full contact of the catalyst with the electrolyte, thereby improving the reaction efficiency. Therefore, aerogel is an ideal electrocatalytic carrier.

[0004] High-entropy alloys (HEAs) are composed of five or more elements with similar atomic ratios (5%-35%) and have attracted widespread attention due to their excellent mechanical and chemical properties. In addition, the cocktail effect of HEAs can effectively provide multiple sites to adsorb different intermediates, and the electronic structure of the active site can be finely adjusted by the surrounding atoms, thereby obtaining superior catalytic performance. He (Energy Storage Materials, 2023, 58, 287-298.) synthesized CrMnFeCoNi HEAs based on a low-temperature solution method. Due to the presence of twin defects, the occurrence of large lattice distortion and the electronic synergy between different components, the energy barrier of the OER rate-determining step is reduced, making it 10mA / cm 2at a current density of 10 mA / cm2, the overpotential is 265 mV, and the Tafel slope is 37.9 mV / dec, which is much higher than the characteristics of the standard commercial catalyst based on RuO2. However, the HEAs electrocatalysts reported so far are mainly low-dimensional, and it is of great significance to realize HEAs with unique three-dimensional structure in order to further expose more active sites. HEAs aerogel has a hierarchical layered porous structure, allowing effective mass transport in the pores and having smaller diffusion resistance and easier access to active sites (crystal face defects and crystal face active species, etc.). The HEAs aerogel network skeleton is mainly composed of interconnected noble metal nanounits with a size of several nanometers, which is the optimal range of catalyst size selected for electrochemical catalytic processes such as ORR, methanol oxidation reaction (MOR), and OER. Ju (Chemical Engineering Journal, 2023, 473, 145347) et al. synthesized PtBi 1.5 Ni 0.2 Co 0.2 Cu 0.2 HEAs aerogel shows an aerogel structure with large specific surface area and high porosity. In MOR, PtBi 1.5 Ni 0.2 Co 0.2 Cu 0.2 The mass activity of HEAs is 4.19 A·mg Pt -1 , and the long-term stability (>0.33 A·mg Pt -1 after 10 times of 3600 s stability test) is better than that of binary Pt-based alloy and commercial Pt / C. However, the above research only has a certain degree of breakthrough in single function, and the content of noble metal is high, so it is still a great challenge to realize single-phase high-entropy alloy aerogel electrocatalysis with the advantages of low cost, high catalytic activity, multifunctionality, and high stability. SUMMARY

[0005] The purpose of the present application is to provide a preparation method of a low-cost high-entropy alloy aerogel electrocatalytic material for improving the existing electrocatalytic materials which are expensive, poor in stability, single in performance, and insufficient in activity. A low-noble metal loading, high-activity, and multifunctional HEAs aerogel electrocatalyst is prepared by using freeze-thaw technology combined with freeze-drying method. The method has simple raw materials and process, low energy consumption, and controllable structure, and the prepared aerogel material has the characteristics of low density, high specific surface area, and high porosity, which has a positive significance for realizing the application of HEAs aerogel in the field of electrocatalysis.

[0006] The application aims to realize the preparation method of a low-cost high-entropy alloy aerogel catalytic material through the following steps.

[0007] (1) Five kinds of metal salts with equal amounts of substances are dissolved in deionized water, and stirred at 20-40℃ to make them uniformly mixed, and then a weighed reducing agent is added and stirred for 10-30 min to prepare a co-precursor solution;

[0008] (2) The co-precursor solution obtained in step (1) is frozen in liquid nitrogen for 2-20 min, and then thawed in a water bath at 10-40℃;

[0009] (3) The sample after thawing in step (2) is stirred for 0.1-2 h to form a whole gel;

[0010] (4) The wet gel obtained in step (3) is subjected to impurity removal, and deionized water is used for washing 3-8 times, with an interval of 6-18 h each time;

[0011] (5) The HEAs wet gel after washing in step (4) is frozen in liquid nitrogen for 2-15 min, and then subjected to freeze-drying treatment, and finally the HEAs aerogel is obtained;

[0012] In step (1), the molar concentration of the five metals after the metal salt is dissolved in deionized water is 0.005-0.015 mmol / mL; the metal salt is any four kinds of metal salt mixed with palladium chloride among platinum salt, copper salt, nickel salt, cobalt salt, manganese salt or iron salt; in step (2), the molar ratio of the five kinds of metal salt and the reducing agent is 1:(1-5).

[0013] Preferably, in step (1), the platinum salt is one of chloroplatinic acid, platinum nitrate or platinum sulfate; the copper salt is one of copper chloride trihydrate, copper nitrate pentahydrate, copper sulfate or copper carbonate; the nickel salt is one of nickel chloride hexahydrate, nickel nitrate, nickel sulfate or nickel nitrite; the cobalt salt is one of cobalt chloride hexahydrate, cobalt acetate, cobalt sulfate or cobalt nitrate; the iron salt is one of iron chloride hexahydrate, iron nitrate, iron sulfate, ferrous sulfate or iron hydroxide; and the manganese salt is one of manganese chloride, manganese sulfate, manganese chromate or manganese carbonate.

[0014] Preferably, in step (1), the reducing agent is one or a mixture of two or more of sodium borohydride, potassium borohydride, lithium borohydride or lithium aluminum hydride.

[0015] Preferably, in step (1), the stirring speed of adding the reducing agent is 200-1300 r / min.

[0016] Preferably, in step (3), the stirring speed is 200-1500 r / min.

[0017] Preferably, the freeze-drying temperature in step (5) is -60 to -5 DEG C, and the drying time is 8 to 40 hours.

[0018] Advantages:

[0019] The method and the low-cost HEAs for electrocatalysis prepared by the method have the following characteristics:

[0020] (1) The process is simple, low-cost and low-energy consumption. The freeze-thaw technology is used, and the low-cost and safe freeze-drying method is used to obtain the HEAs aerogel with low noble metal loading.

[0021] (2) The material has low noble metal loading density, low cost, high catalytic activity, high stability and multifunctionalization.

[0022] (3) The HEAs aerogel prepared by the method exhibits excellent electrocatalytic activity and stability in various electrocatalytic fields, which has a positive significance for the industrialization and practical application of the HEAs aerogel in the electrocatalytic field. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is the XRD spectrum of the HEAs aerogel prepared in Example 1;

[0024] Figure 2 is the application of the HEAs aerogel prepared in Example 2 in the field of zinc-air battery, wherein (a) is the open-circuit voltage of the HEAs aerogel cathode zinc-air battery, (b) is the power density test, (c) is the real object picture of the zinc-air battery charging the mobile phone, and (d) is the charge-discharge cycle test of the zinc-air battery. DETAILED DESCRIPTION

[0025] Example 1

[0026] Take equal molar ratio of palladium chloride, chloroplatinic acid, copper chloride trihydrate, nickel chloride hexahydrate and iron chloride hexahydrate 0.075 mmol, dissolved in 15 mL of deionized water, stirred at 20 ℃ to make it uniform, add reducing agent sodium borohydride, the molar ratio of metal salt to sodium borohydride is 1:1, stir at 20 ℃ for 30 min to prepare co-precursor solution, the stirring speed is 200 r / min; The co-precursor solution obtained is frozen in liquid nitrogen for 2 min, and then thawed in a 10 ℃ water bath; The sample after thawing is stirred at a speed of 200 r / min for 2 h to form a whole gel; Then the wet gel obtained above is subjected to solvent replacement, deionized water is used for solvent replacement for 3 times, and the interval time is 18 h each time; The HEAs wet gel after replacement is frozen in liquid nitrogen for 2 min, and then the frozen wet gel is subjected to freeze-drying treatment, the drying temperature is-60 ℃, and the drying time is 8 h, finally the low-cost, high catalytic activity and multi-functional PdPtCuNiFe HEAs aerogel is obtained, which is black block. Figure 1 The XRD spectrum of the prepared PdPtCuNiFe HEAs aerogel is shown in the figure, and the diffraction peak is a Pd-dominant face-centered cubic crystal type.

[0027] Example 2

[0028] Take equal molar ratio of palladium chloride, platinum nitrate, copper nitrate pentahydrate, nickel nitrate and cobalt chloride hexahydrate 0.227 mmol, dissolved in 25 mL of deionized water, stirred at 26 ℃ to make it uniform, add potassium borohydride, the molar ratio of metal precursor to potassium borohydride is 1:2.3, stir at 26 ℃ for 23 min to prepare co-precursor solution, the stirring speed is 500 r / min; The co-precursor solution obtained is frozen in liquid nitrogen for 6 min, and then thawed in a 22 ℃ water bath; The sample after thawing is stirred at a speed of 500 r / min for 1.6 h to form a whole gel; Then the wet gel obtained above is subjected to solvent replacement, deionized water is used for solvent replacement for 4 times, and the interval time is 14 h each time; The HEAs wet gel after replacement is frozen in liquid nitrogen for 6 min, and then the frozen wet gel is subjected to freeze-drying treatment, the drying temperature is-38 ℃, and the drying time is 18 h, finally the low-cost, high catalytic activity and multi-functional PdPtCuNiCo HEAs aerogel is obtained. The prepared PdPtCuNiCo HEAs aerogel is black block. Through testing, it is found that the half-wave potential can reach 0.88 V vs. RHE, the OER overpotential is 307 mV, and the HER overpotential is 37 mV. Figure 2For the performance test of PdPtCuNiCo HEAs aerogel applied in zinc-air battery, (a) the open-circuit voltage can reach 1.48V, (b) the power density is 199mW·cm -2 , (c) is the photo of the zinc-air battery powering the mobile phone, and the efficiency only decreases by 2.7% ((d)) after 600h continuous charge-discharge cycle, compared with the commercial Pt / C+RuO2 electrocatalyst, each index has great improvement.

[0029] Example 3

[0030] Take 0.455mmol of equimolar ratio of palladium chloride, platinum sulfate, copper sulfate, cobalt nitrate and iron nitrate and dissolve them in 37mL of deionized water, stir at 33℃ to make them uniform, add lithium borohydride, the molar ratio of metal precursor to lithium borohydride is 1:3.3, stir at 33℃ for 14min to prepare the co-precursor solution, the stirring speed is 890r / min; quickly freeze the obtained co-precursor solution in liquid nitrogen for 13min, then wait for thawing in a 31℃ water bath; stir the thawed sample at a speed of 730r / min for 1.1h to form a whole gel; then perform solvent replacement on the obtained wet gel, use deionized water for solvent replacement for 5 times, with an interval of 10h each time; freeze the replaced HEAs wet gel in liquid nitrogen for 11min, then perform freeze-drying treatment on the frozen wet gel, the drying temperature is-20℃, the drying time is 28h, finally obtain the low-cost, high-catalytic activity and multi-functional PdPtCuFeCo HEAs aerogel, which is black block. It is found through testing that the half-wave potential can reach 0.89V vs.RHE, the OER overpotential is 382mV, and the HER overpotential is 22mV.

[0031] Example 4

[0032] 0.6 mmol of palladium chloride, chloroplatinic acid, copper carbonate, manganese chloride and iron sulfate were taken in equal molar ratio and dissolved in 50 mL of deionized water, and stirred at 40°C to make them uniformly mixed, lithium aluminum hydride was added, the molar ratio of metal precursor to lithium aluminum hydride was 1:5, and stirred at 40°C for 10 min to prepare a co-precursor solution, the stirring speed was 1300 r / min; the obtained co-precursor solution was quickly frozen in liquid nitrogen for 20 min, and then thawed in a 40°C water bath; the thawed sample was stirred at a speed of 1500 r / min for 0.2 h to form a whole gel; then the obtained wet gel was subjected to solvent replacement, and deionized water was used for solvent replacement for 8 times, and the interval time was 6 h each time; the replaced HEAs wet gel was quickly frozen in liquid nitrogen for 15 min, and then the frozen wet gel was subjected to freeze-drying treatment, the drying temperature was-5°C, and the drying time was 40 h, finally a low-cost, high-catalytic activity and multi-functional PdPtCuFeMn HEAs aerogel was obtained, which was black and blocky. It was found through testing that the half-wave potential could reach 0.88 V vs. RHE, the OER overpotential was 386 mV, and the HER overpotential was 31.7 mV.

Claims

1. The application of a low-cost, high-entropy alloy aerogel catalytic material in the oxygen evolution reaction, hydrogen evolution reaction, and zinc-air battery cathode, wherein the specific steps of the preparation method of the catalytic material are as follows: (1) Dissolve five metal salts of equal amounts in deionized water, stir at 20-40 °C to mix them evenly, add the weighed reducing agent and stir for 10-30 min to prepare a co-precursor solution. (2) Freeze the co-precursor solution obtained in step (1) in liquid nitrogen for 2-20 min, and then wait for it to thaw in a water bath at 10-40 °C; (3) Stir the thawed sample from step (2) for 0.1 to 2 h to form a complete gel; (4) Remove impurities from the wet gel obtained in step (3), washing it with deionized water 3 to 8 times, with an interval of 6 to 18 hours between each wash; (5) The HEAs wet gel washed in step (4) is frozen in liquid nitrogen for 2-15 min, and then freeze-dried to obtain HEAs aerogel; this material is used in zinc-air batteries, with an open-circuit voltage of 1.48 V and a power density of 199 mW·cm. -2 After 600 hours of continuous charge-discharge cycles, the efficiency decreased by only 2.7%; in: In step (1), the molar concentration of the five metals after the metal salt is dissolved in deionized water is 0.005~0.015 mmol / mL; the metal salt is a mixture of platinum salt, copper salt, nickel salt, cobalt salt and palladium chloride; in step (2), the molar ratio of the five metal salts and the reducing agent is 1:(1~5).

2. The application according to claim 1, characterized in that... The platinum salt mentioned in step (1) is one of chloroplatinic acid, platinum nitrate or platinum sulfate; the copper salt is one of copper chloride trihydrate, copper nitrate pentahydrate, copper sulfate or copper carbonate; the nickel salt is one of nickel chloride hexahydrate, nickel nitrate, nickel sulfate or nickel nitrite; the cobalt salt is one of cobalt chloride hexahydrate, cobalt acetate, cobalt sulfate or cobalt nitrate.

3. The application according to claim 1, characterized in that... The reducing agent mentioned in step (1) is one or a mixture of two or more of sodium borohydride, potassium borohydride, lithium borohydride or lithium aluminum hydride.

4. The application according to claim 1, characterized in that... In step (1), the stirring speed when adding the reducing agent is 200~1300 r / min.

5. The application according to claim 1, characterized in that... In step (3), the stirring speed is 200~1500 r / min.

6. The application according to claim 1, characterized in that... In step (5), the freeze-drying temperature is -60 to -5 ℃ and the drying time is 8 to 40 h.

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