A ruthenium-iridium alloy material and its preparation method and application

Abstract

The present invention discloses a ruthenium-iridium alloy material, its preparation method, and application. The ruthenium-iridium alloy material is prepared by the following method: iridium chloride and ruthenium chloride are added as metal sources to a mixed solution of N-methylpyrrolidone and formic acid, and the mixture is thoroughly stirred; then the temperature is raised to synthesize a ruthenium-iridium alloy composed of ultrasmall nanoparticles through a solvothermal method. This method uses iridium chloride and ruthenium chloride as metal sources, N-methylpyrrolidone as a solvent, and solvothermal method under the reducing action of formic acid to synthesize a ruthenium-iridium alloy having a "fingerprint-like" structure. Due to its unique morphology and optimized electronic structure, the alloy material has excellent catalytic activity and excellent stability in the acidic electrocatalytic oxygen evolution reaction, and can be used as an anode catalyst for proton exchange membrane water electrolysis to produce hydrogen.

Description

Technical Field

[0001] The present invention relates to the technical field of acidic electrochemical oxygen evolution, and in particular to a ruthenium-iridium alloy material and a preparation method and application thereof. Background Art

[0002] Since the Industrial Revolution, fossil fuels such as oil and coal have become the primary energy sources. However, their overuse has led to serious environmental problems, including the greenhouse effect. Consequently, efforts to reduce carbon emissions and pursue clean energy have garnered widespread attention. Hydrogen, as a zero-carbon, green energy source, has emerged as a promising energy source. Consequently, hydrogen energy technology has been extensively researched in recent decades.

[0003] Acidic electrochemical oxygen evolution technology is an important component of electrocatalytic water splitting to produce hydrogen. Despite decades of research, many technical challenges remain. As the anode reaction for electrocatalytic water splitting to produce hydrogen, electrochemical oxygen evolution is kinetically inert due to the four-electron transfer reaction. Therefore, the preparation of acidic electrochemical oxygen evolution catalysts has become one of the bottlenecks in the development of electrocatalytic water splitting to produce hydrogen. Due to the high requirements for catalyst stability under acidic conditions, the currently preferred catalysts are mainly iridium-based catalysts. However, the intrinsic activity of iridium-based catalysts is insufficient, making it difficult to meet the requirements of industrial water electrolysis to produce hydrogen. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is how to prepare a new catalyst material to improve the intrinsic activity and electrochemical stability of the acidic electrochemical oxygen evolution catalyst.

[0005] In order to solve the above technical problems, the first aspect of the present invention provides a method for preparing a ruthenium-iridium alloy material, comprising the following steps:

[0006] S1. Adding iridium chloride and ruthenium chloride as metal sources to a mixed solution of N-methylpyrrolidone and formic acid, and stirring the mixed solution thoroughly;

[0007] S2. Raise the temperature to synthesize a ruthenium-iridium alloy composed of ultrasmall nanoparticles through a solvothermal method.

[0008] Furthermore, in step S1, the concentration of iridium chloride after mixing is less than or equal to 1.5 mg / mL.

[0009] Furthermore, in step S1, the concentration of ruthenium chloride after mixing is less than or equal to 1.5 mg / mL.

[0010] Furthermore, in step S1, the volume ratio of N-methylpyrrolidone to formic acid is 2:1 to 4:1.

[0011] Furthermore, in step S2, the heating temperature is 100-120°C.

[0012] A second aspect of the present invention provides a ruthenium-iridium alloy material prepared by the above-mentioned preparation method.

[0013] A second aspect of the present invention provides an application of the above-mentioned ruthenium-iridium alloy material as a catalyst in an acidic electrocatalytic oxygen evolution reaction.

[0014] Furthermore, when the ruthenium-iridium alloy material is used as a catalyst, the ruthenium-iridium alloy material is first dispersed in a solvent to obtain a catalyst solution, and the catalyst solution is coated on the working electrode.

[0015] Furthermore, when the ruthenium-iridium alloy material is used as a catalyst, the working potential of the acidic electrocatalytic oxygen evolution reaction is 1.3-2.0V.

[0016] Furthermore, when the ruthenium-iridium alloy material is used as a catalyst, the current density in a 0.5 mol / L sulfuric acid aqueous solution is 10 mA / cm 2 When the overpotential is less than 250mV, the potential drop rate is less than 5% after 150 hours of constant current operation.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The preparation method of the present invention is simple and easy. Iridium chloride and ruthenium chloride are used as metal sources, N-methylpyrrolidone is used as solvent, and a "fingerprint-like" ruthenium-iridium alloy composed of ultrasmall nanoparticles is synthesized in one step by a solvothermal method under the reducing action of formic acid.

[0019] (2) The present invention forms a ruthenium-iridium alloy by replacing the iridium on the surface with ruthenium. The structure of the metal iridium and the charge distribution on its surface can be adjusted through synthesis, so that the ruthenium-iridium alloy has a special morphology and an optimized electronic structure, thereby improving its intrinsic activity and stability.

[0020] (3) The ruthenium-iridium alloy of the present invention has excellent catalytic activity and excellent stability in the acidic electrocatalytic oxygen evolution reaction, and has good application prospects as an anode catalyst for proton exchange membrane water electrolysis to produce hydrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is an X-ray diffraction pattern of the ruthenium-iridium alloy prepared in Example 1 of the present invention;

[0022] Figure 2 is a transmission electron microscope image of the ruthenium-iridium alloy prepared in Example 1 of the present invention;

[0023] Figure 3 This is a high-resolution transmission electron microscope image of the ruthenium-iridium alloy prepared in Example 1 of the present invention;

[0024] Figure 4 1 is an element distribution diagram of the ruthenium-iridium alloy prepared in Example 1 of the present invention;

[0025] Figure 5 This is a linear scanning curve diagram of the materials of Example 1, Comparative Example 1 and Comparative Example 2 of the present invention used as catalysts in the acidic electrocatalytic oxygen evolution reaction;

[0026] Figure 6 It is a stability test curve diagram of the materials of Example 1 of the present invention and Comparative Example 1 as catalysts. DETAILED DESCRIPTION

[0027] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0028] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0029] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The present description and examples are intended to be illustrative only.

[0030] A specific embodiment of the present invention provides a method for preparing a ruthenium-iridium alloy material. Using iridium chloride and ruthenium chloride as metal sources and N-methylpyrrolidone as solvent, a "fingerprint-like" ruthenium-iridium alloy composed of ultrasmall nanoparticles is synthesized via a solvothermal method under the reducing action of formic acid. Ruthenium doping enhances the intrinsic activity and stability of the iridium catalyst. The preparation method is simple and easy, utilizing a one-step solvothermal synthesis method.

[0031] In a specific embodiment, the concentration of iridium chloride in the reaction system is less than or equal to 1.5 mg / mL, the concentration of ruthenium chloride is less than or equal to 1.5 mg / mL, and the volume ratio of N-methylpyrrolidone to formic acid is 2:1 to 4:1. After the iridium chloride and ruthenium chloride are thoroughly mixed, the temperature is raised to 100-120°C for reaction. Under the reducing effect of formic acid, ruthenium replaces the iridium on the surface to form a ruthenium-iridium alloy, which adjusts the structure of the metallic iridium and its surface charge distribution to enhance its intrinsic activity and stability.

[0032] The ruthenium-iridium alloy material can be used as a catalyst in the acidic electrocatalytic oxygen evolution reaction. As one implementation method, the "fingerprint-like" ruthenium-iridium alloy material composed of ultra-small nanoparticles is dispersed in a solvent to obtain a catalyst solution, which is then applied to a working electrode. The operating potential of the acidic electrocatalytic oxygen evolution reaction is 1.3-2.0V. The solvent used is not limited. As one implementation method, the solvent consists of deionized water, ethanol, and a binder.

[0033] Ruthenium-iridium alloy has high efficiency in acidic electrocatalytic oxygen evolution reaction and high stability. The current density is 10mA / cm in 0.5mol / L sulfuric acid aqueous solution. 2 When the overpotential is less than 250mV, the potential drop rate is less than 5% after 150 hours of constant current operation.

[0034] The technical effects of the present invention are described below with reference to specific embodiments.

[0035] Example 1

[0036] In this embodiment, a ruthenium-iridium alloy is prepared, and the specific process is as follows:

[0037] Dissolve 5 mg of iridium chloride and 5 mg of ruthenium chloride in 5 ml of a mixed solution of N-methylpyrrolidone and formic acid (volume ratio of 3:1) and stir evenly. Heat the solution to 100°C and maintain this temperature for 5 hours. Wash and centrifuge three times, then place in an oven and dry at 70°C for 12 hours to obtain a ruthenium-iridium alloy powder.

[0038] The ruthenium-iridium alloy powder prepared in this example was subjected to X-ray diffraction analysis, and the results were as follows: Figure 1 As shown, from Figure 1 The characteristic peaks of metallic ruthenium and iridium can be seen in the figure, proving that the ruthenium-iridium alloy was synthesized by the above method.

[0039] The ruthenium-iridium alloy powder prepared in this embodiment was analyzed by transmission electron microscopy, and the test results are as follows: Figure 2 and Figure 3 As shown, it can be observed that the material is ruthenium-iridium nanoparticles smaller than 1 nm, with a "fingerprint-like" morphology.

[0040] The ruthenium-iridium alloy material prepared in this example is used as an electrocatalyst for acidic electrocatalytic oxygen evolution, and the process is as follows:

[0041] (1) Preparation of catalyst ink

[0042] 4 mg of the ruthenium-iridium alloy powder prepared above and 4 mg of carbon paste powder were weighed, added to 735 μL of deionized water and 235 μL of ethanol, and 30 μL of 5% Nafion 117 solution was added, and ultrasonic dispersion was performed for half an hour to obtain catalyst ink.

[0043] (2) Linear scan test

[0044] The electrocatalytic performance of the catalyst was characterized using a Shanghai Chenhua CHI760E electrochemical workstation with a three-electrode system. A 0.5 mol / L sulfuric acid solution was used as the electrolyte, a platinum mesh electrode was used as the counter electrode, and 250 μL of the catalytic ink was drop-coated on a hydrophilic carbon paper as the working electrode.

[0045] During the test, a linear sweep test was performed in the potential range of 1.23-1.8V for the reversible hydrogen electrode. The results are as follows: Figure 3 As shown in the figure, the ruthenium-iridium alloy catalyst of this embodiment is 2 The overpotential is 237 mV, indicating that the catalyst has high catalytic activity.

[0046] (3) Stability test

[0047] The stability test was carried out using the test system described in (2) above. The results were as follows: Figure 4 As shown in the figure, the ruthenium-iridium alloy catalyst of this embodiment is subjected to a current density of 10 mA / cm 2 After 150 h of operation, there was no obvious decrease in potential, indicating that the catalyst has excellent stability.

[0048] Example 2

[0049] In this embodiment, a ruthenium-iridium alloy is prepared, and the specific process is as follows:

[0050] Dissolve 1 mg of iridium chloride and 5 mg of ruthenium chloride in 5 ml of a mixed solution of N-methylpyrrolidone and formic acid (volume ratio of 3:1) and stir evenly. Heat the solution to 110°C and maintain this temperature for 5 hours. Wash and centrifuge three times, then place in an oven and dry at 70°C for 12 hours to obtain a ruthenium-iridium alloy powder.

[0051] The ruthenium-iridium alloy material prepared in this example was used as an electrocatalyst for acidic electrocatalytic oxygen evolution, and the process was the same as in Example 1. In a 0.5 mol / L sulfuric acid aqueous solution, the current density was 10 mA / cm 2 The overpotential is 243 mV when the device is operated at constant current for 150 hours, and the potential does not drop significantly.

[0052] Example 3

[0053] In this embodiment, a ruthenium-iridium alloy is prepared, and the specific process is as follows:

[0054] Dissolve 3.5 mg of iridium chloride and 2 mg of ruthenium chloride in 5 ml of a mixed solution of N-methylpyrrolidone and formic acid (volume ratio of 3:1) and stir evenly. Heat the solution to 120°C and maintain this temperature for 5 hours. Wash and centrifuge three times, then place in an oven and dry at 70°C for 12 hours to obtain a ruthenium-iridium alloy powder.

[0055] The ruthenium-iridium alloy material prepared in this example was used as an electrocatalyst for acidic electrocatalytic oxygen evolution, and the process was the same as in Example 1. In a 0.5 mol / L sulfuric acid aqueous solution, the current density was 10 mA / cm 2 The overpotential is 246 mV when the device is operated at constant current for 150 hours, and the overpotential does not drop significantly.

[0056] Comparative Example 1

[0057] In this comparative example, commercial iridium dioxide was used as an electrocatalyst for acidic electrocatalytic oxygen evolution, and the process was the same as in Example 1. The test results are shown in FIG. Figure 3 and Figure 4 As shown, the catalyst of Comparative Example 1 is 2 When subjected to constant current operation for 4 hours, the catalyst rapidly deactivated, indicating that its stability was poor.

[0058] Comparative Example 2

[0059] In this embodiment, the preparation process of the material is as follows:

[0060] Dissolve 5 mg of iridium chloride in 5 ml of a mixed solution of N-methylpyrrolidone and formic acid (volume ratio of 3:1) and stir evenly. Heat the solution to 100°C and maintain this temperature for 5 hours. Wash and centrifuge three times, then place in an oven and dry at 70°C for 12 hours to obtain a metal powder.

[0061] The material prepared in this example was used as an electrocatalyst for acidic electrocatalytic oxygen evolution, and the process was the same as steps (1) and (2) in Example 1. The test results are shown in FIG. Figure 3 As shown, the catalyst of Comparative Example 2 is 2 When , the overpotential is greater than that of the catalyst in Example 1, indicating lower activity.

[0062] Comparative Example 3

[0063] In this embodiment, the preparation process of the material is as follows:

[0064] 5 mg of ruthenium chloride was dissolved in 5 ml of a mixture of N-methylpyrrolidone and formic acid (3:1 by volume) and stirred thoroughly. The solution was heated to 100°C and maintained at that temperature for 5 hours. The solution was washed and centrifuged three times, and finally dried in an oven at 70°C for 12 hours. No product was obtained. This indicates that no metal nanoparticles were formed when only ruthenium chloride was added as the metal source.

[0065] Although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A method for preparing a ruthenium-iridium alloy material, characterized in that: The following steps are involved: S1. Adding iridium chloride and ruthenium chloride as metal sources to a mixed solution of N-methylpyrrolidone and formic acid, wherein the volume ratio of N-methylpyrrolidone to formic acid is 2:1 to 4:1, and stirring them thoroughly. After mixing, the concentration of iridium chloride is less than or equal to 1.5 mg / mL, and the concentration of ruthenium chloride is less than or equal to 1.5 mg / mL; S2. Raise the temperature to synthesize a ruthenium-iridium alloy composed of ultra-small nanoparticles by a solvent thermal method. The heating temperature is 100-120°C. The obtained material is ruthenium-iridium nanoparticles less than 1nm, and the morphology is fingerprint-like.

2. A ruthenium-iridium alloy material, characterized in that: Prepared by the preparation method as claimed in claim 1.

3. An application of the ruthenium-iridium alloy material according to claim 2, characterized in that: The ruthenium-iridium alloy material is used as a catalyst in an acidic electrocatalytic oxygen evolution reaction.

4. The use according to claim 3, characterized in that The ruthenium-iridium alloy material is dispersed in a solvent to obtain a catalyst solution, and the catalyst solution is coated on a working electrode.

5. The use according to claim 4, characterized in that The working potential of the acidic electrocatalytic oxygen evolution reaction is 1.3-2.0V.

6. The use according to claim 5, characterized in that The current density is 10 mA / cm in 0.5 mol / L sulfuric acid aqueous solution. 2 When the overpotential is less than 250mV, the potential drop rate is less than 5% after 150 hours of constant current operation.

Images