A ruthenium-based catalyst with high stability and a preparation method thereof

Abstract

The application 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: grinding ruthenium salt, doping salt and molten salt until they are uniformly mixed, pouring into a porcelain boat, keeping at 550 DEG C for 3-5 h, taking out after natural cooling, water washing after water bath heating, soaking in 0.5 mol / L sulfuric acid for 24 h, ultrasonic treatment for 2 h, continuing water washing, cleaning once with anhydrous ethanol, and drying to obtain the product.The application improves the catalyst performance by replacing part of Ru atoms with Ge atoms; the improved molten salt method simplifies the operation steps and reduces the reaction temperature.The catalyst is uniformly dispersed after water bath heating, acid soaking and ultrasonic treatment, and the salt residue is reduced.The method is not only simple and safe, but also has the potential for large-scale production by using low-cost molten salt, and further improves the activity, dispersity and stability of the catalyst.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalyst preparation, and particularly relates to a high-stability ruthenium-based catalyst and a preparation method thereof. BACKGROUND

[0002] With the gradual decrease of traditional energy reserves and the serious pollution of combustion products to the environment, it has become an urgent task to find green and clean energy. Hydrogen energy, as a kind of green and clean energy with great potential, has attracted much attention in the method of its preparation. Among them, the proton exchange membrane (PEM) water electrolysis technology is highly praised because of its high current density, high energy conversion efficiency and high hydrogen purity.

[0003] At present, the commercial acid oxygen evolution reaction (OER) catalyst is mainly iridium-based catalyst, but its high price limits its wide application. Therefore, the ruthenium-based catalyst is considered as the most promising material to replace the iridium-based catalyst. However, the preparation methods of the ruthenium-based catalyst, such as impregnation method, sol-gel method, microemulsion method, chemical vapor deposition method and in-situ preparation technology, all have some problems. In the impregnation method, the active material may move to the outer surface during the drying process, resulting in a decrease in the concentration of the inner surface active material, and thus the active component is not uniformly distributed on the carrier. The sol-gel method has a complex reaction process, and the conditions of each reaction step need to be accurately controlled, and the drying time is long, which 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. And the existing technology usually heats the ruthenium powder at 800-900 DEG C to prepare ruthenium dioxide, and the synthesized ruthenium dioxide has poor stability. The above problems therefore limit the further improvement and large-scale application of the performance of the ruthenium-based catalyst.

[0004] As a new type of preparation technology, the molten salt method has the advantages of high dispersibility, controllable morphology and structure, etc., but the related preparation methods still need to be further improved and optimized. Therefore, the present application provides a high-stability ruthenium-based catalyst and a preparation method thereof. SUMMARY

[0005] The purpose of the present application is to provide a high-stability ruthenium-based catalyst and a preparation method thereof, which aims to solve the problems raised in the background art.

[0006] The purpose of the present application is achieved by the following technical solutions:

[0007] A preparation method of a high-stability ruthenium-based catalyst, comprising the following steps:

[0008] The ruthenium salt and the doping salt are prepared, and after the molten salt is selected, the ruthenium salt, the doping salt and the molten salt are ground in a mortar to be uniformly mixed, poured into a porcelain boat, and then kept at 550 DEG C for 3-5 h, and after natural cooling, the sample is taken out, then heated in a water bath at 80 DEG C for 5 min, and then washed with water, after washing with water, soaked in 0.5 mol / L sulfuric acid for 24 h, ultrasonic treatment for 2 h, continue to wash with water, and then washed once with anhydrous ethanol, and finally dried to obtain the final product.

[0009] Further, the ruthenium salt is anhydrous ruthenium chloride, hydrated ruthenium chloride or ruthenium acetylacetone.

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

[0011] Further, 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:

[0012] The 0.5 mmol of anhydrous RuCl3 powder, 0.02 mmol of Ge2O3(CH2CH2COOH)2 and 2 g of Na2CO3 are ground in a mortar to be uniformly mixed, poured into a porcelain boat, placed in a muffle furnace, heated to 550 DEG C at a heating rate of 3 DEG C / min, and kept at 550 DEG C for 5 h, and after natural cooling, the sample is taken out from the muffle furnace; first, the sample is placed in a beaker, 50 mL of deionized water is added, and then the beaker is placed in a water bath, heated in a water bath at 80 DEG C for 5 min, washed with water three times to remove the molten salt, after washing with water, soaked in 0.5 mol / L sulfuric acid for 24 h, and ultrasonic treatment for 2 h in an ultrasonic machine, then washed with deionized water three times, washed once with anhydrous ethanol, and finally dried to obtain the final product.

[0013] A high-stability ruthenium-based catalyst prepared by the preparation method of the high-stability ruthenium-based catalyst.

[0014] Compared with the prior art, the beneficial effects of the present application are:

[0015] The present application successfully dopes germanium element in the ruthenium dioxide catalyst by replacing part of the Ru atoms with Ge atoms, thereby significantly improving the activity and stability of the catalyst. The improved molten salt method is used to prepare the catalyst, which simplifies the operation steps and reduces the reaction temperature. After water bath heating, acid soaking and ultrasonic treatment, the dispersibility of the catalyst is improved, the dissolution process is accelerated, uniform dispersion is achieved, and salt residues are effectively reduced. The method is not only simple and safe to operate, but also uses low-cost molten salt, which has the potential for large-scale production, and further improves the activity, dispersibility and stability of the catalyst. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 Linear voltammetry curves LSV curves of three catalysts of doped germanium ruthenium dioxide, RuO2, commercial RuO2.

[0017] Figure 2 XRD patterns of three catalysts of doped germanium ruthenium dioxide, RuO2, commercial RuO2.

[0018] Figure 3 Constant current tests of three catalysts of doped germanium ruthenium dioxide, RuO2, commercial RuO2.

[0019] Figure 4 EIS diagrams of three catalysts of doped germanium ruthenium dioxide, RuO2, commercial RuO2.

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

[0021] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present application, the technical solutions of the present application are described in detail as follows, but cannot be understood as limiting the implementable scope of the present application. In the following examples, the experimental methods are conventional methods unless otherwise specified; and the reagents and materials can be obtained from commercial channels unless otherwise specified.

[0022] The specific implementation of the present application is described in detail in combination with specific examples.

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

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

[0025] Comparative Example 2, commercial RuO2 was tested, denoted as c-RuO2.

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

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

[0028] Figure 2 The XRD patterns of the three catalysts are shown in the figure. The characteristic peaks of the sample are consistent with the PDF card PDF#40-1290, which can prove that the sample is indeed RuO2.

[0029] Figure 3 The constant current test of the three catalysts can be seen. The stability of the germanium-doped ruthenium dioxide is as high as 120 h or more, and the stability is significantly improved compared with the commercial RuO2.

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

[0031] Figure 5 The SEM image of the germanium-doped ruthenium dioxide sample can be seen. The sample is in the form of particles with small diameters.

[0032] Conclusion: The Ge element is successfully doped in the ruthenium dioxide catalyst by replacing part of Ru atoms with Ge atoms (other elements can also be introduced to dope the ruthenium dioxide), so that the activity and stability of the catalyst are significantly improved. The improved molten salt method is used to prepare the catalyst, so that the operation steps are simplified and the reaction temperature is reduced. After water bath heating, acid bubbling and ultrasonic treatment, the dispersibility of the catalyst is improved, the dissolution process is accelerated, uniform dispersion is realized, and salt residues are effectively reduced. The method is simple and safe, the price of the molten salt used is low, and it has the potential for large-scale production, further improving the activity, dispersibility and stability of the catalyst.

[0033] The above is only the preferred embodiment of the present application, and it should be pointed out that for those skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, which should be considered as the protection scope of the present application, and these will not affect the effect and practicality of the patent.

Claims

1. A method for preparing a high stability ruthenium-based catalyst, characterized by, The method comprises the following steps: The ruthenium salt and the doping salt are prepared, and after the molten salt is selected, the ruthenium salt, the doping salt and the molten salt are ground in a mortar until they are uniformly mixed, are poured into a porcelain boat, are kept at 550 DEG C for 3-5 h, are taken out after being naturally cooled, are heated in a water bath at 80 DEG C for 5 min, are then washed with water, are soaked in 0.5 mol / L sulfuric acid for 24 h after the water washing is completed, are ultrasonically treated for 2 h, are continuously washed with water, are washed once with anhydrous ethanol, and are finally dried to obtain the final product; The ruthenium salt is anhydrous ruthenium chloride, hydrated ruthenium chloride or ruthenium acetylacetone; The doping salt is organic germanium Ge-132; The molten salt is sodium carbonate, sodium nitrate, potassium nitrate, sodium sulfate or potassium sulfate.

2. The method for preparing the highly stable ruthenium-based catalyst according to claim 1, 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: 0.5 mmol of RuCl3 powder, 0.02 mmol of (CH2CH2COOHGe)2O3 and 2 g of Na2CO3 are ground in a mortar until they are uniformly mixed, are poured into a porcelain boat, are placed in a muffle furnace, are heated to 550 DEG C at a heating rate of 3 DEG C / min, are kept at 550 DEG C for 5 h, are taken out from the muffle furnace after being naturally cooled, are first placed in a beaker, 50 mL of deionized water is added, the beaker is then placed in a water bath, is heated in a water bath at 80 DEG C for 5 min, is washed with water for three times to remove the molten salt, is soaked in 0.5 mol / L sulfuric acid for 24 h after the water washing is completed, is ultrasonically treated for 2 h in an ultrasonic machine, is then washed with deionized water for three times, is washed once with anhydrous ethanol, and is finally dried to obtain the final product.

3. A high-stability ruthenium-based catalyst prepared by the preparation method of the high-stability ruthenium-based catalyst according to any one of claims 1-2.

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