High-stability ruthenium-based catalyst and preparation method thereof

Abstract

The invention is suitable for the technical field of catalyst preparation, and provides a high-stability ruthenium-based catalyst and a preparation method thereof.The preparation method comprises the following steps that ruthenium salt, doped salt and molten salt are ground to be evenly mixed, poured into a porcelain boat, subjected to heat preservation at 550 DEG C for 3-5 h, taken out after being naturally cooled, heated in a water bath and then washed with water, then soaked with 0.5 mol / L sulfuric acid for 24 h and subjected to ultrasonic treatment for 2 h, and the high-stability ruthenium-based catalyst is obtained; and continuously washing with water, washing with absolute ethyl alcohol once, and drying to obtain the product. The performance of the catalyst is improved by replacing part of Ru atoms with Ge atoms; by adopting the improved molten salt method, the operation steps are simplified, and the reaction temperature is reduced. After the catalyst is subjected to water bath heating, acid soaking and ultrasonic treatment, uniform dispersion is realized, and salt residues are reduced. The method is simple and safe to operate, the adopted molten salt is low in price and has the potential of large-scale production, and the activity, dispersity and stability of the catalyst are further improved.

Description

Technical Field

[0001] The invention belongs to the technical field of catalyst preparation, and in particular relates to a high-stability ruthenium-based catalyst and a preparation method thereof. Background Art

[0002] With the gradual reduction of traditional energy reserves and the serious environmental pollution caused by combustion products, finding green and clean energy has become a top priority. As a green and clean energy with great potential, hydrogen energy has attracted much attention in its production methods, such as water electrolysis. Among them, proton exchange membrane (PEM) water electrolysis technology is highly praised for its advantages such as high current density, high energy conversion efficiency and high hydrogen purity.

[0003] At present, commercial acidic oxygen evolution reaction (OER) catalysts are mainly iridium-based catalysts, but their high prices limit their widespread application. Therefore, ruthenium-based catalysts are regarded as the most promising materials to replace iridium-based catalysts. However, there are some problems with the preparation methods of ruthenium-based catalysts, such as impregnation, sol-gel, microemulsion, chemical vapor deposition and in-situ preparation technology. During the drying process, the impregnation method may cause the concentration of active substances on the inner surface to decrease due to the movement of catalytic active substances to the outer surface, thereby making the distribution of active components on the carrier uneven. The sol-gel method has a complex reaction process, which requires precise control of the conditions of each reaction step, and the long drying time affects the preparation efficiency. The chemical vapor deposition method has high requirements for equipment and harsh reaction conditions. The in-situ preparation technology is difficult and the reaction device is complex. In addition, the existing technology usually heats ruthenium powder at 800-900°C to obtain ruthenium dioxide, and the synthesized ruthenium dioxide has extremely poor stability. The above problems therefore limit the further improvement of the performance of ruthenium-based catalysts and their large-scale application.

[0004] As a new preparation technology, the molten salt method has the advantages of achieving high dispersibility, adjustable morphology and structure, etc., but the relevant preparation methods still need to be further improved and optimized. To this end, the present invention proposes a high-stability ruthenium-based catalyst and a preparation method thereof. Summary of the invention

[0005] The purpose of the present invention is to provide a high-stability ruthenium-based catalyst and a preparation method thereof, aiming to solve the problems raised in the above-mentioned background technology.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A method for preparing a high-stability ruthenium-based catalyst comprises the following steps:

[0008] Prepare ruthenium salt and doping salt, select molten salt, grind ruthenium salt, doping salt and molten salt in a mortar until mixed evenly, pour into a porcelain boat, keep warm at 550°C for 3-5h, take out after natural cooling, then heat in a water bath at 80°C for 5min, then wash with water, soak in 0.5mol / L sulfuric acid for 24h, ultrasonicate for 2h, continue washing with water, wash once with anhydrous ethanol, and finally dry to obtain the final product.

[0009] Furthermore, the ruthenium salt is anhydrous ruthenium chloride, hydrated ruthenium chloride or ruthenium acetylacetonate.

[0010] Furthermore, the molten salt is sodium carbonate, sodium nitrate, potassium nitrate, sodium sulfate or potassium sulfate.

[0011] Furthermore, when the ruthenium salt is anhydrous ruthenium chloride and the molten salt is sodium carbonate, the preparation method of the ruthenium-based catalyst is as follows:

[0012] 0.5mmol anhydrous RuCl3 powder, 0.02mmol Ge2O3(CH2CH2COOH)2 and 2gNa2CO3 were ground in a mortar until they were evenly mixed, poured into a porcelain boat, placed in a muffle furnace, heated to 550℃ at a heating rate of 3℃ / min, and kept at 550℃ for 5h. After natural cooling, the sample was taken out of the muffle furnace; first the sample was placed in a beaker, 50mL deionized water was added, and then the beaker was placed in a water bath, heated in a water bath at 80℃ for 5min, washed three times with water to remove the molten salt, and after washing, soaked in 0.5mol / L sulfuric acid for 24h, and ultrasonicated in an ultrasonic machine for 2h, then washed three times with deionized water, and then washed once with anhydrous ethanol, and finally dried to obtain the final product.

[0013] A high-stability ruthenium-based catalyst prepared according to the above-mentioned method for preparing a high-stability ruthenium-based catalyst.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] The present invention successfully doped germanium in the ruthenium dioxide catalyst by replacing some Ru atoms with Ge atoms, thereby significantly improving the activity and stability of the catalyst. The present invention adopts an improved molten salt method to prepare the catalyst, simplifying the operation steps and reducing the reaction temperature. After the catalyst is heated in a water bath, acid-bubbled and ultrasonically treated, the dispersibility is improved, the dissolution process is accelerated, uniform dispersion is achieved, and salt residue is effectively reduced. The method is not only simple and safe to operate, but also uses a low-priced molten salt, has the potential for large-scale production, and further improves the activity, dispersibility and stability of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The LSV curves were tested for the linear voltammetric curves of three catalysts: germanium-doped ruthenium dioxide, RuO2, and commercial RuO2.

[0017] Figure 2 These are the XRD patterns of three catalysts: germanium-doped ruthenium dioxide, RuO2, and commercial RuO2.

[0018] Figure 3 This is a constant current test of three catalysts: germanium-doped ruthenium dioxide, RuO2, and commercial RuO2.

[0019] Figure 4 These are the EIS graphs of three catalysts: germanium-doped ruthenium dioxide, RuO2, and commercial RuO2.

[0020] Figure 5 SEM image of germanium-doped ruthenium dioxide. DETAILED DESCRIPTION

[0021] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be understood as limiting the scope of the present invention. The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials can be obtained from commercial sources unless otherwise specified.

[0022] The specific implementation of the present invention is described in detail below in conjunction with specific embodiments.

[0023] Embodiment 1, 0.5mmol anhydrous RuCl3 powder, 0.02mmol Ge2O3(CH2CH2COOH)2 (organic germanium, Ge-132), 2g Na2CO3 are mixed and ground, poured into a porcelain boat, placed in a muffle furnace, heated to 550℃ at a heating rate of 3℃ / min, kept warm for 5h, and then cooled naturally. After taking out the sample from the muffle furnace, the sample is first placed in a beaker, 50mL deionized water is added, and then the beaker is placed in a water bath, heated in a water bath at 80℃ for 5min, washed three times, the molten salt is removed, and then soaked in 0.5mol / L sulfuric acid for 24h, and ultrasonicated in an ultrasonic machine for 2h, then washed three times with deionized water, and then cleaned once with anhydrous ethanol, and can be tested after drying. What is obtained is ruthenium dioxide doped with germanium, which is abbreviated as Ge.

[0024] Comparative Example 1: 0.5mmol of anhydrous RuCl3 powder and 2g of Na2CO3 were mixed and ground, poured into a porcelain boat, and placed in a muffle furnace. The temperature was raised to 550°C at a heating rate of 3°C / min, kept warm for 5h, and then cooled naturally. After taking out the sample from the muffle furnace, the sample was first placed in a beaker, 50mL of deionized water was added, and then the beaker was placed in a water bath, heated at 80°C for 5min, washed three times with water to remove the molten salt, and then soaked in 0.5mol / L sulfuric acid for 24h, and ultrasonicated in an ultrasonic machine for 2h, and then washed three times with deionized water, and then washed once with anhydrous ethanol, and then dried before testing. It is recorded as RuO2.

[0025] Comparative Example 2: Commercial RuO2 was used for testing, denoted as c-RuO2.

[0026] The test results of the catalysts obtained in Example 1, Comparative Example 1 and Comparative Example 2 are as follows:

[0027] Figure 1 The LSV curves of the linear voltammetry curves of the three catalysts were tested. It can be seen from the figure that the overpotential of ruthenium dioxide doped with germanium is the smallest, which is 203mv, indicating that its catalytic performance is the best.

[0028] Figure 2 Figure 2 shows the XRD patterns of the three catalysts. The characteristic peaks of the samples are consistent with the PDF card PDF#40-1290, proving that the samples are indeed RuO2.

[0029] Figure 3 From the constant current test of the three catalysts, it can be seen that the stability of germanium-doped ruthenium dioxide is as high as more than 120 hours, which is significantly improved compared with commercial RuO2.

[0030] Figure 4 The EIS graphs of the three catalysts show that the semicircle radius of germanium-doped ruthenium dioxide is the smallest, that is, the impedance is the smallest, indicating that its charge transfer at the interface is the fastest, which also confirms its faster reaction kinetics.

[0031] Figure 5 This is the SEM image of a germanium-doped ruthenium dioxide sample. It can be seen that the sample is granular with a small diameter.

[0032] Conclusion: The present invention successfully doped germanium elements into the ruthenium dioxide catalyst by replacing some Ru atoms with Ge atoms (other elements can also be introduced to dope ruthenium dioxide), thereby significantly improving the activity and stability of the catalyst. The present invention adopts an improved molten salt method to prepare the catalyst, which simplifies the operation steps and reduces the reaction temperature. After the catalyst is heated in a water bath, acid-soaked and ultrasonically treated, the dispersibility is improved, the dissolution process is accelerated, uniform dispersion is achieved, and salt residue is effectively reduced. This method is not only simple and safe to operate, but also uses low-priced molten salts, has the potential for large-scale production, and further improves the activity, dispersibility and stability of the catalyst.

[0033] The above are only preferred embodiments of the present invention. It should be pointed out that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention. These should also be regarded as the protection scope of the present invention. These will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A method for preparing a highly stable ruthenium-based catalyst, characterized in that: The following steps are involved: Prepare ruthenium salt and doping salt, select molten salt, grind ruthenium salt, doping salt and molten salt in a mortar until mixed evenly, pour into a porcelain boat, keep warm at 550°C for 3-5h, take out after natural cooling, then heat in a water bath at 80°C for 5min, then wash with water, soak in 0.5mol / L sulfuric acid for 24h, ultrasonicate for 2h, continue washing with water, wash once with anhydrous ethanol, and finally dry to obtain the final product.

2. The method for preparing a highly stable ruthenium-based catalyst according to claim 1, characterized in that: The ruthenium salt is anhydrous ruthenium chloride, hydrated ruthenium chloride or ruthenium acetylacetonate.

3. The method for preparing a highly stable ruthenium-based catalyst according to claim 2, characterized in that: The molten salt is sodium carbonate, sodium nitrate, potassium nitrate, sodium sulfate or potassium sulfate.

4. The method for preparing a highly stable ruthenium-based catalyst according to claim 3, characterized in that: When the ruthenium salt is anhydrous ruthenium chloride and the molten salt is sodium carbonate, the preparation method of the ruthenium-based catalyst is specifically as follows: 0.5mmol anhydrous RuCl3 powder, 0.02mmol Ge2O3(CH2CH2COOH)2, and 2g Na2CO3 were ground in a mortar until they were evenly mixed, poured into a porcelain boat, placed in a muffle furnace, heated to 550℃ at a heating rate of 3℃ / min, and kept at 550℃ for 5h. After natural cooling, the sample was taken out of the muffle furnace; first the sample was placed in a beaker, 50mL deionized water was added, and then the beaker was placed in a water bath, heated in a water bath at 80℃ for 5min, washed three times with water to remove the molten salt, and after washing, soaked in 0.5mol / L sulfuric acid for 24h, and ultrasonicated in an ultrasonic machine for 2h, then washed three times with deionized water, and then washed once with anhydrous ethanol, and finally dried to obtain the final product.

5. A high-stability ruthenium-based catalyst prepared according to the method for preparing a high-stability ruthenium-based catalyst according to any one of claims 1 to 4.

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