Iridium-ruthenium-based high-entropy metal oxide electrocatalysts, methods of preparation, and applications

Abstract

The application belongs to the technical field of electrocatalyst synthesis, and relates to an iridium-ruthenium-based high-entropy metal oxide electrocatalyst, a preparation method and application. The application comprises the following steps: (1) grinding heavy metal salts and base salts to obtain a metal salt mixture, wherein the heavy metal salts are a combination of ruthenium salts, iridium salts, manganese salts, tin salts and chromium salts, and the base salts are sodium chloride; after ball milling the metal salt mixture for 1 hour, sodium hydroxide solution is added, and ball milling is continued for 1 hour to obtain a tin-doped iridium-ruthenium solid solution oxide precursor; (3) heat treating the tin-doped iridium-ruthenium solid solution oxide precursor to obtain an iridium-ruthenium-based high-entropy metal oxide containing sodium chloride; and (4) water washing the iridium-ruthenium-based high-entropy metal oxide containing sodium chloride to obtain an iridium-ruthenium-based high-entropy metal oxide electrocatalyst. The application significantly improves the durability and service life of the material.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalyst synthesis technology, specifically relating to an iridium-ruthenium-based high-entropy metal oxide electrocatalyst, its preparation method, and its application. Background Technology

[0002] Currently, anode materials for the oxygen evolution reaction (OER) in acidic media have been widely used in many fields, including proton exchange membrane electrolyzers (PEMWE), organic synthesis processes, hydrometallurgy, and wastewater treatment. During electrochemical water splitting, the OER reaction at the anode faces thermodynamic challenges, and the kinetic reaction is relatively slow, requiring a relatively high overpotential to sustain the reaction.

[0003] Iridium-based oxides, ruthenium-based oxides, and their derivatives possess sufficient corrosion resistance to remain stable in the harsh acidic and oxidizing environment of OER reactions. However, iridium-based electrocatalysts are scarce, making it difficult to meet the demands of large-scale industrial applications. Furthermore, during the OER reaction, ruthenium metal is prone to over-oxidation, leading to the formation of soluble Ru. n>+4 This process accelerates the degradation of ruthenium catalysts, leading to poor stability. Therefore, developing a novel OER electrocatalyst with excellent electrocatalytic activity, high long-term stability, and low cost in acidic media has become an urgent problem to be solved.

[0004] In recent years, with the rapid development of materials science, high-entropy metal oxides have gradually become a research focus in the field of energy catalysis due to their unique synergistic effect of multi-metal element composition and excellent physicochemical stability. High-entropy metal oxides, through the combination of multiple metal oxides, form a single solid solution structure by leveraging the entropy stabilization effect, thus exhibiting excellent thermal stability, chemical corrosion resistance, and mechanical strength. These properties give high-entropy metal oxides significant advantages in extreme environments, especially in the anodic catalytic reaction of acidic PEMWE electrolyzers, where their application potential is widely recognized.

[0005] In recent years, researchers have been actively exploring various preparation methods to improve the activity and stability of high-entropy metal oxide catalysts. For example, Chinese patent document CN119976995A discloses a two-dimensional high-entropy metal oxide, its preparation method, and its applications. This high-entropy metal oxide has a hydrotalcite macroscopic morphology, is composed of five or more metals selected from iron, cobalt, nickel, copper, zinc, aluminum, and manganese, and exhibits a typical hexagonal structure with the maximum opposite side length of approximately 100-150 nm. Additionally, Chinese patent document CN119841623A discloses a high-entropy metal oxide material and its preparation method in the field of supercapacitor materials. This method uses nitrates corresponding to Cr, Fe, Co, and Ni, and ammonium paramolybdate as raw materials, prepared through a simple solution synthesis method. By controlling the proportions of various metal elements and the synthesis conditions, the specific surface area of ​​the material can be increased by utilizing the high entropy effect of multiple metal elements. The high entropy metal oxides obtained can still maintain structural stability and electrochemical activity under high temperature or extreme electrochemical conditions, and are not prone to phase separation or degradation, thereby effectively improving the durability and service life of the material.

[0006] Because the OER (Optical Emission Reduction) reaction in water electrolysis is always carried out under strong acidity and high voltage conditions, the catalyst surface is inevitably exposed to an acidic environment. Therefore, mitigating the corrosion of catalyst materials by the strong acid environment during the reaction is of great significance for realizing large-scale proton exchange membrane (PEMWE) water electrolysis for hydrogen production. Summary of the Invention

[0007] The purpose of this invention is to address the above-mentioned problems by providing an iridium-ruthenium-based high-entropy metal oxide electrocatalyst.

[0008] Another object of the present invention is to provide a method for preparing an iridium-ruthenium-based high-entropy metal oxide electrocatalyst.

[0009] Another object of the present invention is to provide an application of an iridium-ruthenium-based high-entropy metal oxide electrocatalyst as a working electrode in the oxygen evolution reaction of water electrolysis in acidic solution.

[0010] Another objective of this invention is to provide an application of an iridium-ruthenium-based high-entropy metal oxide electrocatalyst as an anode in a proton exchange membrane water electrolysis reaction to produce hydrogen.

[0011] To achieve the above objectives, the present invention provides the following technical solution:

[0012] An iridium-ruthenium-based high-entropy metal oxide electrocatalyst, with the chemical formula Mn 0.13 Sn 0.13 Cr 0.13 Ru 0.3 Ir 0.3O2.

[0013] A method for preparing an iridium-ruthenium-based high-entropy metal oxide electrocatalyst includes the following steps:

[0014] (1) Grind the heavy metal salt and the matrix salt to obtain a metal salt mixture.

[0015] The heavy metal salts are combinations of ruthenium, iridium, manganese, tin, and chromium salts, with sodium chloride as the matrix salt;

[0016] (2) After ball milling the metal salt mixture for 1 hour, sodium hydroxide solution was added, and ball milling was continued for 1 hour to obtain the tin-doped iridium-ruthenium solid solution oxide precursor;

[0017] (3) Heat-treat the tin-doped iridium-ruthenium solid solution oxide precursor to obtain iridium-ruthenium-based high-entropy metal oxide containing sodium chloride;

[0018] (4) The iridium-ruthenium-based high-entropy metal oxide containing sodium chloride is washed with water to obtain the iridium-ruthenium-based high-entropy metal oxide electrocatalyst.

[0019] In the above-mentioned method for preparing iridium-ruthenium-based high-entropy metal oxide electrocatalysts, in step (1), the molar ratio is ruthenium salt: iridium salt: manganese salt: tin salt: chromium salt = 30:30:13:13:13, and matrix salt: heavy metal salt = 8.5:1.

[0020] In the above-mentioned method for preparing iridium-ruthenium-based high-entropy metal oxide electrocatalysts, in step (1), the ruthenium salt is ruthenium chloride, the iridium salt is iridium chloride trihydrate, the manganese salt is manganese chloride, the tin salt is tin dichloride dihydrate, and the chromium salt is chromium chloride hexahydrate.

[0021] In the above-mentioned method for preparing iridium-ruthenium-based high-entropy metal oxide electrocatalyst, in step (2), the concentration of the sodium hydroxide solution is 5 mmol / L, and 0.5 mL of sodium hydroxide solution is added to each millimole of metal salt mixture.

[0022] In the above-mentioned method for preparing iridium-ruthenium-based high-entropy metal oxide electrocatalyst, in step (3), the tin-doped iridium-ruthenium solid solution oxide precursor is calcined at 400°C for 6 hours.

[0023] An application of the above-mentioned iridium-ruthenium-based high-entropy metal oxide electrocatalyst as the working electrode in the oxygen evolution reaction of water electrolysis in acidic solution.

[0024] In the above-mentioned application of iridium-ruthenium-based high-entropy metal oxide electrocatalyst as working electrode in the electrolysis of water and oxygen evolution reaction in acidic solution, a three-electrode system is adopted, with Hg / Hg2SO4 electrode as reference electrode, carbon rod as counter electrode, glassy carbon electrode supported on iridium-ruthenium-based high-entropy metal oxide electrocatalyst as working electrode, and 0.5 M sulfuric acid solution as electrolyte.

[0025] An application of the above-mentioned iridium-ruthenium-based high-entropy metal oxide electrocatalyst as an anode in the proton exchange membrane water electrolysis reaction to produce hydrogen.

[0026] In the above-mentioned application of ruthenium-based high-entropy metal oxide electrocatalyst as the anode in the proton exchange membrane water electrolysis hydrogen production reaction, Pt / C catalyst is used as the cathode, iridium-ruthenium-based high-entropy metal oxide electrocatalyst is used as the anode, 0.5M sulfuric acid solution is used as the electrolyte, and N212 proton exchange membrane is used as the proton conduction membrane.

[0027] Compared with existing technologies, the advantages of this invention are:

[0028] 1. The iridium-ruthenium-based high-entropy metal oxide electrocatalyst provided by the present invention increases the specific surface area of ​​the material through the high-entropy effect of multiple metal elements. The high-entropy oxide can still maintain structural stability and electrochemical activity under acidic conditions, which significantly improves the durability and service life of the material.

[0029] 2. The iridium-ruthenium-based high-entropy metal oxide electrocatalyst provided by this invention exhibits both high catalytic activity and good stability in the electrolysis of water to produce oxygen in acidic electrolytes: for example, at a current density of 10 mA / cm². 2 At that time, the overpotential was 257 mV.

[0030] 3. The iridium-ruthenium-based high-entropy metal oxide electrocatalyst provided by this invention exhibits excellent activity and stability in water electrolysis for hydrogen production: for example, it can achieve 2 A / cm² at an electrolyzer voltage of 1.74 V. 2 The current density. Attached Figure Description

[0031] Figure 1 The catalyst Mn prepared in Example 1 0.13 Sn 0.13 Cr 0.13 Ru 0.3 Ir 0.3 Scanning electron microscope image of O2;

[0032] Figure 2 The catalyst Mn prepared in Example 1 0.13 Sn 0.13 Cr 0.13 Ru 0.3 Ir 0.3Energy dispersive X-ray spectrum of O2;

[0033] Figure 3 The catalyst Mn prepared in Example 1 0.13 Sn 0.13 Cr 0.13 Ru 0.3 Ir 0.3 X-ray diffraction (XRD) pattern of O2;

[0034] Figure 4 Polarization curves of the oxygen evolution reaction in water electrolysis in an application example, using the catalyst prepared in Example 1, ruthenium oxide, and iridium oxide as the anode;

[0035] Figure 5 The catalyst prepared in Example 1 was used as the anode in an application example. The electrochemical surface area (CV) of the oxygen evolution reaction in water electrolysis was measured.

[0036] Figure 6 Comparison of the electrochemical area of ​​the oxygen evolution reaction in water electrolysis in an application example using the catalyst prepared in Example 1, ruthenium oxide, and iridium oxide as anodes.

[0037] Figure 7 Using the catalyst prepared in Example 1, ruthenium oxide, and iridium oxide as the anode, and 20% Pt / C catalyst as the cathode, at 80°C... o Polarization curves of proton exchange membrane electrolysis for hydrogen production under condition C. Detailed Implementation

[0038] The present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0039] Example 1:

[0040] This embodiment provides a method for preparing an iridium-ruthenium-based high-entropy metal oxide electrocatalyst, characterized by comprising the following steps:

[0041] (1) Weigh 0.633 g of ruthenium chloride, 0.911 g of iridium chloride trihydrate, 0.166 g of manganese chloride, 0.298 g of tin dihydrate, 0.352 g of chromium chloride hexahydrate and 5 g of sodium chloride, place them in a mortar and grind for 5 min to mix them thoroughly;

[0042] (2) Pour the ground mixed solid into a ball mill jar, add an appropriate amount of agate grinding media balls of different sizes, and ball mill for 1 h at 500 rpm;

[0043] (3) Add 5 mL of 5 mmol / L sodium hydroxide solution to the ball mill jar and continue ball milling for 1 h at 500 rpm;

[0044] (4) The ball-milled tin-doped iridium-ruthenium solid solution oxide precursor was dried at 400 °C. o Calcination was carried out for 6 hours in air atmosphere at C.

[0045] (5) The iridium-ruthenium-based high-entropy metal oxide containing sodium chloride obtained in step (4) is washed with pure water to obtain an iridium-ruthenium-based high-entropy metal oxide catalyst, denoted as Mn. 0.13 Sn 0.13 Cr 0.13 Ru 0.3 Ir 0.3 O2.

[0046] The preparation principle of the iridium-ruthenium-based high-entropy metal oxide electrocatalyst provided by this invention is as follows: a solid solution of sodium chloride and metal precursor is formed through ball milling, followed by calcination to form an iridium-ruthenium-based high-entropy metal oxide. Through the high-entropy effect of multiple metal elements, the specific surface area of ​​the material is increased. This high-entropy oxide electrocatalyst maintains structural stability and electrochemical activity under acidic conditions, is not prone to phase separation or degradation, stabilizes the active sites of ruthenium and iridium, and improves the durability and service life of the material.

[0047] The iridium and ruthenium salts constitute the main metal salt, with a molar ratio of iridium to ruthenium of 1:1. The molar ratio of manganese, tin, and chromium salts to the main metal salt is approximately 2:3. When the content of manganese, tin, and chromium salts is too low, high-entropy metal oxides cannot be formed to break the immiscibility gaps between metal elements through internal synergistic effects, resulting in little impact on the electronic structure of the ruthenium and iridium sites in the electrocatalyst, leading to minimal improvement in its electrocatalytic activity and stability. Conversely, when the content of manganese, tin, and chromium salts is too high, complexes of manganese dioxide, tin dioxide, chromium dioxide, and ruthenium-iridium solid solution oxides are easily formed, leading to a decrease in its electrocatalytic activity.

[0048] In step (1), when the sodium chloride content is too low, the precursor will be unevenly dispersed, and the yield of the catalyst will be low. Therefore, it is necessary to control the supply of sodium chloride to be sufficient.

[0049] When the calcination temperature is too low, a mixed structure of amorphous and microcrystalline materials will be formed, reducing the conductivity of the catalyst.

[0050] The macroscopic morphology and elemental distribution of the prepared iridium-ruthenium-based high-entropy metal oxide catalyst were observed using scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM). The SEM results are shown below. Figure 1 As shown, the catalyst exhibits a compacted, fine-particle morphology with a uniform particle size distribution; scanning transmission electron microscopy combined with energy-dispersive X-ray spectroscopy is shown in the figure. Figure 2As shown, it can be clearly seen that each metal is uniformly dispersed in the iridium-ruthenium-based high-entropy metal oxide. The X-ray diffraction (XRD) pattern of the iridium-ruthenium-based high-entropy metal oxide electrocatalyst prepared in this embodiment is shown below. Figure 3 As shown, the iridium-ruthenium-based high-entropy metal oxides still retain the characteristic peaks of rutile phase metal oxides, proving the successful synthesis of high-entropy metal oxides.

[0051] Application Example 1

[0052] This application example provides an application of the iridium-ruthenium-based high-entropy metal oxide electrocatalyst prepared in Example 1 as the working electrode in the oxygen evolution reaction of water electrolysis in acidic solution, specifically including the following steps.

[0053] (1) A three-electrode system was used, with the glassy carbon electrode supported on the catalyst prepared in the example as the working electrode, a carbon rod as the counter electrode, Hg / Hg2SO4 as the reference electrode, and 0.5 M sulfuric acid solution as the electrolyte;

[0054] (2) Cyclic voltammetry (CV) activation: A Shanghai Chenhua CHI 760E electrochemical workstation was used. The CV program was employed, with a test range of 0.4–1.1 V vs. RHE and a scan rate of 50 mV s. -1 After 40 CV cyclic scans, the electrode reached a stable state.

[0055] After CV activation of the catalysts in Example 1, ruthenium oxide, and iridium oxide, the program was switched to linear sweep voltammetry (LSV) with a test range of 0.6–1.2 V vs. RHE, a scan rate of 5 mV / s, and overpotentials of 0 V and 10 mA cm⁻¹ relative to the reversible hydrogen electrode. -2 The potential difference measured below. Figure 4 The Mn provided in this embodiment 0.13 Sn 0.13 Cr 0.13 Ru 0.3 Ir 0.3 Polarization curves of the oxygen evolution reaction in water electrolysis using O2 catalyst, ruthenium oxide, and iridium oxide in 0.5 M H2SO4 solution, from... Figure 4 As can be seen from this, in acidic electrolytes, Mn 0.13 Sn 0.13 Cr 0.13 Ru 0.3 Ir 0.3 O2 catalyst at 10 mA cm -2 The overpotential at current density is only 257 mV, which is superior to that of ruthenium oxide catalysts. Figure 5 The Mn provided in this embodiment 0.13 Sn 0.13 Cr 0.13 Ru0.3 Ir 0.3 Electrochemical surface area (CV) curves of the oxygen evolution reaction in water electrolysis in 0.5 M H2SO4 solution using O2 catalyst. Figure 6 A comparison of the electrochemical areas of the oxygen evolution reaction in water electrolysis in the examples, using the catalysts prepared in the examples, ruthenium oxide, and iridium oxide as anodes, from the perspective of application examples. Figure 6 As can be seen from this, in acidic electrolytes, Mn 0.13 Sn 0.13 Cr 0.13 Ru 0.3 Ir 0.3 O2 catalysts have the largest electrochemical surface area compared to ruthenium oxide and iridium oxide.

[0056] Application Example 2

[0057] This application example provides an example of using the iridium-ruthenium-based high-entropy metal oxide electrocatalyst prepared in Example 1 as an anode in a proton exchange membrane water electrolysis reaction to produce hydrogen.

[0058] Specifically, the catalyst Mn prepared in Example 1 0.13 Sn 0.13 Cr 0.13 Ru 0.3 Ir 0.3 Using O2, ruthenium oxide, or iridium oxide as the anode, a 20% Pt / C catalyst as the cathode, 0.5 M sulfuric acid solution as the electrolyte, and a N212 proton exchange membrane as the proton conduction membrane, at 80°C... o Under C conditions, the LSV program was used to test the range of 1.2~2.1 V at a scan rate of 5 mV / s. The catalyst Mn provided in Example 1 was used... 0.13 Sn 0.13 Cr 0.13 Ru 0.3 Ir 0.3 The polarization curves for hydrogen production via proton exchange membrane (PEM) electrolysis of water using O2, ruthenium oxide, or iridium oxide as the anode are shown in the figure. Figure 7 As shown, it can be seen that in acidic electrolytes, Mn 0.13 Sn 0.13 Cr 0.13 Ru 0.3 Ir 0.3 The O2 catalyst only requires an electrolyzer voltage of 1.74 V to achieve 2 A / cm². 2 It has a higher current density and better performance than ruthenium oxide and iridium oxide catalysts.

[0059] The specific embodiments described herein are merely illustrative examples of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention.

Claims

1. An iridium-ruthenium-based high-entropy metal oxide electrocatalyst, characterized in that, The chemical formula is Mn 0.13 Sn 0.13 Cr 0.13 Ru 0.3 Ir 0.3 O2.

2. The method for preparing the iridium-ruthenium-based high-entropy metal oxide electrocatalyst according to claim 1, characterized in that, Includes the following steps: (1) Grind the heavy metal salt and the matrix salt to obtain a metal salt mixture. The heavy metal salts are combinations of ruthenium, iridium, manganese, tin, and chromium salts, with sodium chloride as the matrix salt; (2) After ball milling the metal salt mixture for 1 hour, sodium hydroxide solution was added, and ball milling was continued for 1 hour to obtain the tin-doped iridium-ruthenium solid solution oxide precursor; (3) Heat-treat the tin-doped iridium-ruthenium solid solution oxide precursor to obtain iridium-ruthenium-based high-entropy metal oxide containing sodium chloride; (4) The iridium-ruthenium-based high-entropy metal oxide containing sodium chloride is washed with water to obtain the iridium-ruthenium-based high-entropy metal oxide electrocatalyst.

3. The method for preparing the iridium-ruthenium-based high-entropy metal oxide electrocatalyst according to claim 1, characterized in that, In step (1), the molar ratio is ruthenium salt: iridium salt: manganese salt: tin salt: chromium salt = 30:30:13:13:13, and the matrix salt: heavy metal salt = 8.5:

1.

4. The method for preparing the iridium-ruthenium-based high-entropy metal oxide electrocatalyst according to claim 1, characterized in that, In step (1), the ruthenium salt is ruthenium chloride, the iridium salt is iridium chloride trihydrate, the manganese salt is manganese chloride, the tin salt is tin dichloride dihydrate, and the chromium salt is chromium chloride hexahydrate.

5. The method for preparing the iridium-ruthenium-based high-entropy metal oxide electrocatalyst according to claim 1, characterized in that, In step (2), the concentration of the sodium hydroxide solution is 5 mmol / L, and 0.5 mL of sodium hydroxide solution is added to each millimole of the metal salt mixture.

6. The method for preparing the iridium-ruthenium-based high-entropy metal oxide electrocatalyst according to claim 1, characterized in that, In step (3), the tin-doped iridium-ruthenium solid solution oxide precursor is calcined at 400°C for 6 hours.

7. The application of the iridium-ruthenium-based high-entropy metal oxide electrocatalyst according to claim 1 as a working electrode in the oxygen evolution reaction of water electrolysis in acidic solution.

8. The application of the iridium-ruthenium-based high-entropy metal oxide electrocatalyst according to claim 7 as a working electrode in the oxygen evolution reaction of water electrolysis in acidic solution, characterized in that, A three-electrode system was adopted, with an Hg / Hg2SO4 electrode as the reference electrode, a carbon rod as the counter electrode, a glassy carbon electrode supported on an iridium-ruthenium-based high-entropy metal oxide electrocatalyst as the working electrode, and a 0.5 M sulfuric acid solution as the electrolyte.

9. The application of the iridium-ruthenium-based high-entropy metal oxide electrocatalyst according to claim 1 as an anode in the proton exchange membrane water electrolysis reaction for hydrogen production.

10. The application of the ruthenium-based high-entropy metal oxide electrocatalyst according to claim 9 as an anode in the proton exchange membrane water electrolysis to produce hydrogen, characterized in that, A Pt / C catalyst was used as the cathode, an iridium-ruthenium-based high-entropy metal oxide electrocatalyst was used as the anode, a 0.5 M sulfuric acid solution was used as the electrolyte, and a N212 proton exchange membrane was used as the proton conduction membrane.

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