Preparation method and application of iridium-based nano high-entropy alloy for electrocatalyst of OER

Abstract

The invention belongs to the technical field of catalytic materials, and particularly relates to a preparation method and application of an iridium-based nano high-entropy alloy for an OER electrocatalyst. Five metal elements of iridium (Ir), ruthenium (Ru), iron (Fe), nickel (Ni) and tin (Sn) are mixed to serve as a parent material, and the parent material is mixed with an organic solvent aqueous solution which is specifically prepared to form powder turbid liquid or the parent material and the organic solvent aqueous solution are evenly mixed and pressed into a metal target material. And then the micro-nano powder or the metal target material in the turbid liquid is subjected to laser ablation treatment through a temperature field modulated laser liquid phase corrosion method, nano-particles are formed under the action of high-energy laser, and finally the iridium-based nano high-entropy alloy is prepared. The prepared iridium-based nano high-entropy alloy has excellent catalytic performance in the field of OER.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalytic materials, and particularly relates to a preparation method and application of an iridium-based nano-high entropy alloy for an electrocatalyst for OER. Background Art

[0002] In recent years, high-entropy nanoparticles have shown great application potential in the field of catalysis, which stems from their multi-element composition and unique high-entropy phase (complex atomic configurations generated by multi-element mixing). The former provides a huge component selection for the design and development of catalysts, and the latter endows these materials with diverse adsorption sites and a nearly continuous binding energy distribution pattern compared with traditional catalysts. These properties are particularly attractive for complex electrocatalytic reactions involving numerous intermediate steps and requiring versatility.

[0003] However, due to the large span of physicochemical properties (e.g., atomic size and electronic structure) between different constituent elements, it is difficult to synthesize high-entropy nanoparticles in a highly controllable manner. At the same time, phase separation and element segregation phenomena caused by the immiscibility characteristics of each constituent element bring considerable difficulties to the regulation of high-entropy nanocatalysts. Therefore, in order to overcome the immiscibility phenomenon caused by element differences and compositional complexity in high-entropy nanoparticles, new high-entropy alloy synthesis methods must be developed, relying on non-equilibrium methods in terms of temperature, force, pressure, energy field, etc. to achieve uniform mixing and small particle size preparation. For this reason, the present invention intends to rapidly heat the precursor to a high temperature to induce multi-element mixing to reach a solid solution state, and the short heating duration and subsequent rapid quenching help to retain a uniform structure and small particle size to achieve the controllable synthesis of high-entropy nanoparticles and improve their immiscibility phenomenon. Summary of the Invention

[0004] In order to overcome the above deficiencies of the prior art, the present invention proposes a method for synthesizing nano-iridium-based high entropy alloys based on temperature field modulation laser liquid-phase ablation technology. This method rapidly excites plasma through high-energy laser and quenches it in an extremely short time, thereby obtaining uniform miscibility in a non-equilibrium state, and thus preparing a single-phase high-entropy nanocatalyst. The prepared nano-iridium-based high entropy alloy is an OER catalyst with excellent performance, has excellent catalytic activity in the OER field, and significantly reduces the dosage of precious metal Ir (by more than 60%), and is expected to be applied in the field of electrochemistry.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] The first aspect of the present invention provides a preparation method for synthesizing nano iridium-based high-entropy alloy based on temperature-field modulated laser liquid-phase ablation technology, specifically: using a mixture of five metal elements, namely iridium (Ir), ruthenium (Ru), iron (Fe), nickel (Ni), and tin (Sn), as the parent material, mixing it with a specifically configured organic solvent aqueous solution to form a powder suspension, or uniformly mixing them and pressing them into a metal target, and then using the temperature-field modulated laser liquid-phase ablation method to perform laser ablation treatment on the micro-nano powder or metal target in the suspension under temperature-field modulation, so that a plasma plume is formed under the action of the temperature-field modulated high-energy laser, and the plasma plume rapidly condenses due to the rapid quenching effect, thereby preparing an iridium-based nano high-entropy alloy.

[0007] Preferably, the preparation method for synthesizing nano iridium-based high-entropy alloy based on temperature-field modulated laser liquid-phase ablation technology specifically includes the following steps:

[0008] S1. Dispersing five metal elements, namely iridium (Ir), ruthenium (Ru), iron (Fe), nickel (Ni), and tin (Sn), together in an organic solvent aqueous solution to form a powder suspension, and the organic solvent includes at least one of isopropanol, ethanol, or acetone; or pressing the five metal elements of iridium (Ir), ruthenium (Ru), iron (Fe), nickel (Ni), and tin (Sn) into a metal target and then fixing it in a solvent;

[0009] S2. Pre-cooling the powder suspension or metal target in S1 to cool it to 7 - 15 °C, and then using high-frequency high-energy laser to perform laser ablation treatment on the micro-nano powder or metal target in the suspension at this temperature, so that the mixed powder or metal target in the suspension forms high-entropy nanoparticles under the action of high-energy laser ablation.

[0010] More preferably, the molar ratio of the five metal elements of iridium, ruthenium, iron, nickel, and tin is 1 - 3:1 - 3:1 - 3:1 - 3:1 - 3.

[0011] More preferably, the organic solvent aqueous solution is prepared from isopropanol and water according to a volume ratio of 1 - 3:1.

[0012] More preferably, the laser ablation treatment uses a 355nm - 1064nm nanosecond laser and a 355nm - 1064nm laser light guiding system, or uses a 355nm - 1064nm picosecond laser and a 355nm - 1064nm laser light guiding system.

[0013] More preferably, the energy of the pulsed laser for the laser ablation treatment is 100 uJ - 1000 mJ, the frequency is 1 - 2000 Hz, and the action time is 10 min - 6 h.

[0014] More preferably, the device used for pre-cooling is integrated by a plurality of thermocouples and a temperature control device with an adjustable temperature range of 5 - 60 °C.

[0015] More preferably, after pre-cooling, the powder suspension or the metal target is cooled to 8 - 12 °C.

[0016] More preferably, the liquid ratio between the five metal elements and the aqueous solution of the organic solvent is 0.5 - 5 mg / mL.

[0017] More preferably, the five metal elements are dispersed in the aqueous solution of the organic solvent by a method of stirring + ultrasonic dispersion to be uniformly dispersed. The frequency of the ultrasonic wave is 30 - 50 kHz, and the ultrasonic time is 10 - 40 min.

[0018] The second aspect of the present invention provides a nano iridium-based high-entropy alloy prepared by using the preparation method described in the first aspect.

[0019] A nano iridium-based high-entropy alloy prepared by the method of the present invention is an efficient OER catalyst, and has excellent catalytic activity in the OER field, which can be comparable to commercial catalysts.

[0020] The third aspect of the present invention provides the application of the nano iridium-based high-entropy alloy described in the second aspect in the field of electrocatalysis.

[0021] Preferably, the electrocatalysis is electrocatalytic oxygen evolution.

[0022] The nano iridium-based high-entropy alloy prepared by using the method of the present invention is an OER electrocatalyst, has electrocatalytic oxygen evolution performance superior to commercial Ir black, and at the same time greatly reduces the dosage of the noble metal Ir, and can be applied to the anode catalyst of electrolyzed water.

[0023] More preferably, the electrocatalytic oxygen evolution is an electrocatalytic oxygen evolution reaction under alkaline conditions.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] The present invention discloses a preparation method of an iridium-based nano high-entropy alloy for an OER electrocatalyst. Five metal elements of iridium (Ir), ruthenium (Ru), iron (Fe), nickel (Ni), and tin (Sn) are mixed as the parent material, and are mixed with the aqueous solution of the organic solvent to form a powder suspension. Then, a method of laser liquid-phase ablation with temperature field modulation is used to perform laser ablation treatment on the micro-nano powder or the metal target in the suspension, so that nano-particles are formed under the action of high-energy laser, and finally an iridium-based nano high-entropy alloy is prepared. The prepared iridium-based nano high-entropy alloy has excellent catalytic performance in the OER field. Description of the Drawings

[0026] Figure 1TEM image of the nano-IrRuFeNiSn high-entropy alloy (IrRuFeNiSn-HEA) obtained by the reaction under the action of a temperature-field modulated laser;

[0027] Figure 2 TEM image of the nano-IrRuFeNiSn high-entropy alloy (c-IrRuFeNiSn-HEA) obtained by the reaction without the action of a temperature-field modulated laser;

[0028] Figure 3 TEM image of the nano-IrAgFeNiSn high-entropy alloy (IrAgFeNiSn-HEA) obtained by the reaction under the action of a temperature-field modulated laser;

[0029] Figure 4 EDS elemental distribution map (Ir, Ru, Fe, Ni, Sn) of the nano-IrRuFeNiSn high-entropy alloy (IrRuFeNiSn-HEA) obtained by the reaction under the action of a temperature-field modulated laser;

[0030] Figure 5 Electrochemical oxygen evolution performance diagram (compared with commercial Ir black) of the nano-IrRuFeNiSn high-entropy alloy (IrRuFeNiSn-HEA) obtained by the reaction under the action of a temperature-field modulated laser under alkaline conditions;

[0031] Figure 6 Electrochemical oxygen evolution performance diagram of the nano-IrRuFeNiSn high-entropy alloy obtained by the reaction under the action of a laser with or without temperature-field modulation under alkaline conditions. Detailed implementation manners

[0032] The following further describes the detailed implementation manners of the present invention. It should be noted here that the description of these implementation manners is used to help understand the present invention, but does not constitute a limitation to the present invention. In addition, the technical features involved in the various implementation manners of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0033] The experimental methods in the following examples are all conventional methods unless otherwise specified. The test materials used in the following examples are all available through conventional commercial channels unless otherwise specified.

[0034] Example 1: A method for fabricating a nano-IrRuFeNiSn high-entropy alloy (IrRuFeNiSn-HEA) by temperature-field modulated laser liquid-phase ablation

[0035] (1) Mix 50 mg of high-purity (99.9%) iridium, ruthenium, iron, nickel, and tin powders in a molar ratio of 1:1:1:1:1, and then use the method of stirring + ultrasonic to fully disperse them in an isopropanol aqueous solution (volume ratio of 1:1). The total volume of the solution is 50 mL, the ultrasonic frequency is 40 kHz, and the ultrasonic time is 30 min.

[0036] (2) Place the mixed solution in an open container device, and pre-cool the solution by using a cold water bath to cool it to 10 °C. After the temperature stabilizes, turn on the YAG high-energy laser (Spectra-Physics Laser), use nanosecond lasers with a wavelength of 532 nm and a laser light guiding system, set the focal length of the plano-convex lens to 500 mm, fix the lens 450 mm directly above the reaction container, and use the high-energy laser to perform laser ablation on the mixed solution in the container. The energy of the high-energy nanosecond laser is 600 mJ, the frequency is 50 Hz, and the irradiation time is 1 h. During the laser action process, monitor the solution temperature in real time, and always maintain the temperature rise and fall of the solution through a water cooling device (Shanghai Yushen Instrument Co., Ltd., model DFY-5) (that is, place the open container device in the water cooling device) so that the temperature always remains at 10 °C ± 0.2 °C. After the high-energy laser liquid-phase ablation, a nano-IrRuFeNiSn high-entropy alloy (IrRuFeNiSn-HEA) is obtained.

[0037] Comparative Example 1: A method for manufacturing a nano-IrRuFeNiSn high-entropy alloy (c-IrRuFeNiSn-HEA) by laser liquid-phase ablation

[0038] (1) Mix 50 mg of high-purity (99.9%) iridium, ruthenium, iron, nickel, and tin powders in a molar ratio of 1:1:1:1:1, and then use the method of stirring + ultrasonic to fully disperse them in an isopropyl alcohol aqueous solution (volume ratio of 1:1). The total volume of the solution is 50 mL, the ultrasonic frequency is 40 kHz, and the ultrasonic time is 30 min.

[0039] (2) Place the mixed solution in an open container device, turn on the YAG high-energy laser (Spectra-Physics Laser), use nanosecond lasers with a wavelength of 532 nm and a laser light guiding system, set the focal length of the plano-convex lens to 500 mm, fix the lens 450 mm directly above the reaction container, and use the high-energy laser to perform laser ablation on the mixed solution in the container. The energy of the high-energy nanosecond laser is 600 mJ, the frequency is 50 Hz, and the irradiation time is 1 h. After the high-energy laser liquid-phase ablation, a nano-IrRuFeNiSn high-entropy alloy (c-IrRuFeNiSn-HEA) is obtained.

[0040] Comparative Example 2: A method for manufacturing a nano-IrAgFeNiSn high-entropy alloy (c-IrAgFeNiSn-HEA) by temperature field modulation laser liquid-phase ablation

[0041] (1) Mix 50 mg of high-purity (99.9%) iridium, silver, iron, nickel, and tin powders in a molar ratio of 1:1:1:1:1, and then disperse them thoroughly in an isopropyl alcohol aqueous solution (volume ratio 1:1) by stirring + ultrasonic method. The total volume of the solution is 50 mL, the ultrasonic frequency is 40 kHz, and the ultrasonic time is 30 min.

[0042] (2) Place the mixed solution in an open container device, and pre-cool the solution by using a cold water bath to cool it to 10 °C. After the temperature stabilizes, turn on the YAG high-energy laser (Spectra-Physics Laser), use nanosecond lasers with a wavelength of 532 nm and a laser light guiding system, set the focal length of the plano-convex lens to 500 mm, fix the lens directly above the reaction container, and perform laser ablation on the mixed solution in the container with the high-energy laser. The energy of the high-energy nanosecond laser is 600 mJ, the frequency is 50 Hz, and the irradiation time is 1 h. During the laser action process, monitor the solution temperature in real time, and always maintain the temperature rise and fall of the solution through a water cooling device (Shanghai Yushen Instrument Co., Ltd., model DFY-5) (that is, place the open container device in the water cooling device) to keep the temperature always at 10 °C ± 0.2 °C. After the high-energy laser liquid-phase ablation, a nano iridium ruthenium iron nickel tin high-entropy alloy (c-IrAgFeNiSn-HEA) is obtained.

[0043] Experimental Example 1: Characterization and Performance Analysis of Nano Iridium Ruthenium Iron Nickel Tin High-Entropy Alloy (IrRuFeNiSn-HEA)

[0044] (1) Transmission Electron Microscopy (TEM) Analysis

[0045] Use the nano iridium-based high-entropy alloys prepared in Example 1 and Comparative Examples 1-2 as test samples, and perform TEM analysis on them with a 300 kV transmission electron microscope (FEI Tecnai G2 F30, FEI Company, USA). The obtained TEM images are as Figures 1-3 shown. It can be seen from Figure 1 that the nano iridium ruthenium iron nickel tin high-entropy alloy (IrRuFeNiSn-HEA) prepared by temperature field modulated laser liquid-phase ablation is spherical micro-nano particles with a uniform size distribution, and the particle size is about 30 nm ± 5 nm; while the TEM image of Comparative Example 1 is as Figure 2 shown. The iridium ruthenium iron nickel tin high-entropy alloy (c-IrRuFeNiSn-HEA) obtained by laser liquid-phase ablation without temperature field modulation is also spherical micro-nano particles, but the uniformity is poor, and the particle size ranges from 10 to 400 nm; Figure 3 The TEM image of Comparative Example 2 is shown. After replacing the element Ru with the Ag element in the same period, the obtained product (c-IrAgFeNiSn-HEA) has poor crystallinity, is difficult to maintain the alloy phase, and cannot form spherical micro-nano particles.

[0046] (2) EDS (Energy Dispersive Spectrometer) elemental distribution analysis

[0047] Taking the nano iridium-based high-entropy alloy prepared in Example 1 as the test sample, EDS elemental distribution analysis was carried out using the energy dispersive spectrometer equipped with a transmission electron microscope (FEI Tecnai G2 F30). Figure 4 is the EDS elemental distribution map of the nano iridium-based high-entropy alloy. It can be clearly seen from the figure that each element in the spherical-like nanoparticles is uniformly mixed to form an alloy. Metal atoms form a plasma plume under the action of intense laser. The growth time of the plasma plume is extremely short, and then the plasma plume rapidly condenses to form a nano high-entropy alloy due to the rapid quenching effect in the liquid environment.

[0048] (3) Electrochemical performance test

[0049] All electrochemical performance tests were carried out using a three-electrode system. The working electrode in the test was a glassy carbon electrode of nano iridium-based high-entropy alloy, the counter electrode was a graphite rod electrode, and the reference electrode was a mercury / mercuric oxide electrode. The electrolyte used was 1M potassium hydroxide solution. Among them, the preparation method of the working electrode is as follows:

[0050] Weigh 4 mg of the nano iridium-based high-entropy alloy or commercial Ir black catalyst in Example 1 or Comparative Example 1, add 780 μL of deionized water and 200 μL of isopropanol, and then add 20 μL of 5 wt% Nafion dispersion. After ultrasonic dispersion, take 4 μL of the prepared ink drop and place it on the surface of a polished glassy carbon electrode (diameter 3 mm), and dry it naturally at room temperature to obtain the working electrode.

[0051] The electrocatalytic oxygen evolution performance under alkaline conditions was carried out in 1M potassium hydroxide solution, and the test results are as Figures 5-6 shown, where the scanning rate of linear sweep voltammetry is 5 mV / s. From Figure 5 the electrochemical performance graph, it can be seen that under alkaline conditions, the overpotential corresponding to commercial iridium black at a current density of 10 mA·cm -2 is 280 mV, while the overpotential corresponding to the iridium-based high-entropy alloy (IrRuFeNiSn-HEA) in Example 1 at a current density of 10 mA·cm -2 is 250 mV, indicating that the iridium-based high-entropy alloy exhibits better catalytic activity than commercial iridium black. Figure 6 shows the comparison of the electrochemical performance of the iridium-based high-entropy alloy with or without temperature field modulation. The overpotential corresponding to Comparative Example 1 (c-IrRuFeNiSn-HEA) at a current density of 10 mA·cm -2 is 364 mV, which is much larger than that of the iridium-based high-entropy alloy (IrRuFeNiSn-HEA) obtained by applying temperature field modulation.

[0052] The above results prove that a uniformly distributed nano iridium-based high-entropy alloy is formed after the action of high-energy laser in a specific liquid and at a specific temperature. The synergistic effect of multiple elements endows it with a nearly continuous adsorption energy distribution, optimizes the elementary reaction kinetics of the electrocatalytic OER reaction, and promotes the catalytic activity. At the same time, due to the structural distortion caused by the miscibility of different elements, it is beneficial to optimize the internal stress of the nanoparticles and improve the structural reconstruction and selective dissolution during the long-term operation of the catalyst. Therefore, the iridium-based high-entropy alloy prepared by the method of the present invention is an OER catalyst superior to commercial Ir black.

[0053] The above detailed description of the embodiments of the present invention, but the present invention is not limited to the described embodiments. For those skilled in the art, without departing from the principle and spirit of the present invention, various changes, modifications, substitutions and variations of these embodiments still fall within the protection scope of the present invention.

Claims

1. A method for preparing nano-iridium-based high-entropy alloys based on temperature field modulated laser liquid phase ablation technology, characterized in that: A mixture of five metal elements, iridium, ruthenium, iron, nickel and tin, is used as the matrix material, which is mixed with a specially configured organic solvent aqueous solution to form a powder suspension or uniformly mixed and pressed into a metal target. Then, the temperature field modulated laser liquid phase ablation method is used to perform laser ablation on the micro-nano powder or metal target in the suspension under temperature field modulation, so that a plasma plume is formed under the action of a temperature field modulated high-energy laser. The plasma plume rapidly condenses due to the rapid quenching effect, thereby preparing an iridium-based nano high-entropy alloy.

2. The method for preparing nano-iridium-based high-entropy alloys based on temperature field modulated laser liquid phase ablation technology according to claim 1 is characterized in that: The following steps are involved: S1. Dispersing five metal elements, iridium, ruthenium, iron, nickel and tin, together in an organic solvent aqueous solution to prepare a powder suspension, wherein the organic solvent comprises at least one of isopropanol, ethanol or acetone; or pressing the five metal elements, iridium, ruthenium, iron, nickel and tin, into a metal target material, and then fixing it in a solvent; S2. Pre-cool the powder suspension or metal target of S1 to 7-15°C, and then use a high-frequency high-energy laser to perform laser ablation on the micro-nano powder or metal target in the suspension at this temperature, so that the mixed powder or metal target in the suspension forms high-entropy nanoparticles under the action of high-energy laser ablation.

3. The method for preparing nano-iridium-based high-entropy alloys based on temperature field modulated laser liquid phase ablation technology according to claim 2 is characterized in that: The molar ratio of the five metal elements, iridium, ruthenium, iron, nickel and tin, is 1-3:1-3:1-3:1-3:1-3.

4. The method for preparing nano-iridium-based high entropy alloys based on temperature field modulated laser liquid phase ablation technology according to claim 2 is characterized in that: The organic solvent aqueous solution is prepared by mixing isopropanol and water in a volume ratio of 1-3:

1.

5. The method for preparing nano-iridium-based high-entropy alloys based on temperature field modulated laser liquid phase ablation technology according to claim 2 is characterized in that: The laser ablation process uses a 355nm-1064nm nanosecond laser and a 355nm-1064nm laser light guide system, or uses a 355nm-1064nm picosecond laser and a 355nm-1064nm laser light guide system.

6. The method for preparing nano-iridium-based high entropy alloys based on temperature field modulated laser liquid phase ablation technology according to claim 2 is characterized in that: The energy of the pulse laser for the laser ablation treatment is 100uJ-1000mJ, the frequency is 1-2000Hz, and the action time is 10min-6h.

7. The method for preparing nano-iridium-based high entropy alloys based on temperature field modulated laser liquid phase ablation technology according to claim 2 is characterized in that: The solid-liquid ratio between the five metal elements and the organic solvent aqueous solution is 0.5-5 mg / mL.

8. The method for preparing nano-iridium-based high entropy alloys based on temperature field modulated laser liquid phase ablation technology according to claim 2 is characterized in that: After pre-cooling, the powder suspension or metal target is cooled to 8-12°C.

9. The nano-iridium-based high-entropy alloy prepared by the preparation method according to any one of claims 1 to 8.

10. Application of the nano-iridium-based high entropy alloy according to claim 9 in the field of electrocatalysis.

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