Nanorod-shaped nitrogen-doped ruthenium dioxide chlorine evolution catalyst and preparation method thereof

Abstract

The invention discloses a nanorod-shaped nitrogen-doped ruthenium dioxide chlorine evolution catalyst and a preparation method thereof. The nitrogen-doped ruthenium dioxide catalyst is obtained by mixing ruthenium trichloride and a nitrogen-containing precursor according to a certain proportion, dissolving the mixture in absolute ethyl alcohol, drying and calcining at a certain temperature. The microstructure of the nitrogen-doped ruthenium dioxide catalyst is in a nanorod shape, the nitrogen element is uniformly distributed in the nanorod, and the catalyst contains unsaturated coordinated Ru < 3 + >. A titanium sheet is coated with the prepared nitrogen-doped ruthenium dioxide catalyst by a spin-coating method for electrochemical testing and chlorine evolution activity testing. Compared with undoped ruthenium dioxide, the nitrogen-doped ruthenium dioxide has the advantages that the chlorine evolution potential is reduced, the electrochemical active area is increased, the electron transfer capability is improved, and the chlorine evolution activity is obviously improved. The nitrogen-doped ruthenium dioxide catalyst disclosed by the invention has the advantages of high chlorine evolution activity, simple preparation process and easiness in large-scale production.

Description

Technical Field

[0001] This invention relates to a nanorod-shaped nitrogen-doped ruthenium dioxide chlorine evolution catalyst and its preparation method, belonging to the field of inorganic materials technology. Background Technology

[0002] Electrochemical chlorine evolution reaction (ECER) can produce free chlorine (including Cl2, HClO, and ClO-) with strong oxidizing properties, which can be used in water treatment fields such as sterilization, disinfection, and oxidative degradation of pollutants in water. ECER can produce free chlorine on-site and on demand, avoiding the safety risks of transporting and storing liquid chlorine. It has been widely used in water treatment fields such as municipal drinking water disinfection, swimming pool and spa disinfection, and circulating cooling water treatment. The principle of ECER is to oxidize chloride ions (Cl-) in water to chlorine gas (Cl2) through electrolysis. The generated chlorine gas further reacts with water to produce hypochlorous acid (HClO) and its dissociated form, hypochlorite (ClO-). The anode material is the core of ECER, and the development of highly active anode materials is key to improving the performance of ECER.

[0003] Ruthenium dioxide (RuO2) possesses a unique electronic structure, metal-like conductivity, and excellent catalytic activity, making it widely used as an electrochemical anode material. The chlorine evolution catalytic performance of RuO2 is closely related to the valence state of RuO2 and the morphology of the catalyst. Researchers have improved the electrochemical chlorine evolution performance of RuO2 through doping modification [J. Environ. Chem. Eng., 2024, 12, 113622] and the construction of heterojunction catalysts [Appl. Catal. B-Environ. Energy, 2025, 366, 125043]. Current doping modifications (such as Pt-RuO2) offer limited morphological control over RuO2 catalysts, while specific morphologies, such as nanorod-shaped catalysts, typically possess higher specific surface areas and catalytic active sites, contributing to further improvements in catalytic performance. However, catalysts with specific morphologies (such as RuO2-Co3O4) require hydrothermal / solvothermal synthesis methods. Hydrothermal / solvothermal reactions are energy-intensive and difficult to scale up for production. Therefore, it is urgent to study simple and easy methods to simultaneously achieve doping modification and morphology control of ruthenium dioxide catalysts in order to improve the chlorine evolution performance of ruthenium dioxide. Summary of the Invention

[0004] This invention provides a nanorod-shaped nitrogen-doped ruthenium dioxide chlorine evolution catalyst and its preparation method. The preparation method is simple, easy to scale up for production, and the prepared catalyst has high chlorine evolution activity.

[0005] The technical solution of the present invention is as follows:

[0006] A nanorod-shaped nitrogen-doped ruthenium dioxide chlorine evolution catalyst and its preparation method are disclosed. The catalyst is characterized by being prepared by uniformly mixing ruthenium trichloride with a nitrogen-containing precursor in anhydrous ethanol, followed by drying and calcination. The preparation method is simple and easy to scale up for production. The prepared catalyst is nitrogen-doped ruthenium dioxide with a nanorod-shaped structure. The nanorods have a diameter of 15-40 nm and a length of 80-140 nm, with nitrogen uniformly distributed within the nanorods. The catalyst contains unsaturated coordinated Ru. 3+ Compared with undoped ruthenium dioxide prepared under the same conditions, the nitrogen-doped ruthenium dioxide prepared showed a lower chlorine evolution potential, a higher electrochemical active area, improved electron transfer performance, and significantly enhanced chlorine evolution activity.

[0007] A nanorod-shaped nitrogen-doped ruthenium dioxide chlorine evolution catalyst and its preparation method are detailed below:

[0008] (1) Take a certain amount of ruthenium trichloride and nitrogen-containing precursor and dissolve them in anhydrous ethanol, add a small amount of concentrated hydrochloric acid, stir evenly to obtain a precursor solution; place the precursor solution in a forced-air drying oven and dry it at 50-80℃. After the ethanol has completely evaporated, grind it evenly, then calcine it in a muffle furnace for 1-2 hours, cool it naturally to room temperature, and then grind it evenly to obtain nitrogen-doped ruthenium dioxide catalyst.

[0009] (2) The prepared nitrogen-doped ruthenium dioxide catalyst was coated onto a titanium sheet using a spin-coating method for electrochemical performance and chlorine evolution activity testing. The specific method is as follows:

[0010] Step ①: The titanium sheet is ultrasonically cleaned for 20 minutes using acetone, anhydrous ethanol, and deionized water, and then acid etched at 90°C for 2 hours using a 10% oxalic acid solution.

[0011] Step ②: Dissolve 3-7 mg of the nitrogen-doped ruthenium dioxide catalyst in 950 μL of isopropanol, and add 50 μL of 5% Nafion solution as a binder. Then, treat with ultrasound to form catalyst ink.

[0012] Step 3: The catalyst ink from step 2 is coated onto the titanium sheet from step 1 using spin coating. After natural drying, electrochemical and chlorine evolution performance tests are performed.

[0013] According to the method of the present invention, the preferred method is:

[0014] In step (1) above, the nitrogen-containing precursor is ammonium chloride.

[0015] In step (1) above, ruthenium trichloride and nitrogen-containing precursor are added to anhydrous ethanol according to the concentration of Ru being 20-30 g / L and the molar ratio of Ru to N being 7:(1-6).

[0016] In step (1) above, the calcination temperature of the muffle furnace can be selected as 500-800℃, and the calcination time is 1-2h.

[0017] In step (2) above, the electrochemical performance test includes chlorine evolution potential test, electrochemical active area test, and electron transfer performance test.

[0018] The technical features of this invention are as follows:

[0019] This invention achieves simultaneous nitrogen-doping modification and morphology control of ruthenium dioxide catalysts by adjusting the nitrogen source, nitrogen doping concentration, and calcination temperature. The preparation method is simple and easy to scale up for production. Ammonium chloride is used as the nitrogen source. During calcination, ammonium chloride induces the growth orientation of ruthenium dioxide, transforming it from particulate to nanorod-like structures. Simultaneously, ammonium chloride generates NH3 during calcination, which has reducing properties and can induce the formation of a certain amount of unsaturated Ru in the ruthenium dioxide catalyst. 3+ In nitrogen-doped ruthenium dioxide catalysts, nitrogen is uniformly distributed within the ruthenium dioxide nanorods. The incorporation of nitrogen into the tetragonal ruthenium dioxide lattice helps stabilize the unsaturated coordinated Ru. 3+ The nanorod structure is beneficial for increasing the specific surface area of ​​the catalyst, exposing more catalytic active sites; and for Ru with saturated coordination. 4+ In comparison, unsaturated coordinated Ru 3 + It exhibits higher chlorine evolution catalytic activity. Therefore, the prepared nitrogen-doped ruthenium dioxide catalyst has higher chlorine evolution activity. Attached Figure Description

[0020] Figure 1 This is a scanning electron microscope image of nitrogen-doped ruthenium dioxide from Example 1;

[0021] Figure 2 Here is a scanning electron microscope image of ruthenium dioxide in Comparative Example 1;

[0022] Figure 3 The XRD results are for nitrogen-doped ruthenium dioxide in Example 1;

[0023] Figure 4 The XPS results are for nitrogen-doped ruthenium dioxide in Example 1;

[0024] Figure 5 Linear voltammetric scan curves of nitrogen-doped ruthenium dioxide in Example 1, ruthenium dioxide in Comparative Example 1, and commercial ruthenium dioxide in Comparative Example 2;

[0025] Figure 6This is a graph showing the relationship between the current density difference (ΔJ / 2) and the scan rate for nitrogen-doped ruthenium dioxide in Example 1, ruthenium dioxide in Comparative Example 1, and commercial ruthenium dioxide in Comparative Example 2. The slope of the graph is equal to the double-layer capacitance (C). dl According to the formula, electrochemical active area = Cdl / Cs (Cs is the specific capacitance, with a value of 0.06 mF / cm). -2 ), calculate the electrochemical active area;

[0026] Figure 7 Electrochemical impedance spectroscopy (EIS) spectra of nitrogen-doped ruthenium dioxide in Example 1, ruthenium dioxide in Comparative Example 1, and commercial ruthenium dioxide in Comparative Example 2.

[0027] Figure 8 The graph shows the chlorine evolution yield of nitrogen-doped ruthenium dioxide in Example 1, ruthenium dioxide in Comparative Example 1, and commercial ruthenium dioxide in Comparative Example 2. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention. Unless otherwise specified, the materials and instruments used in the following embodiments are commercially available.

[0029] Example 1:

[0030] (1) 261.47 mg of RuCl3·xH2O and 22.93 mg of NH4Cl were added to 10 mL of anhydrous ethanol, and 300 μL of concentrated hydrochloric acid was added. The mixture was stirred until homogeneous to obtain a precursor solution with a Ru concentration of 26.15 g / L and a Ru:N molar ratio of 7:3. The precursor solution was dried in a forced-air drying oven at 60 °C. After the ethanol was completely evaporated, the solution was ground until homogeneous and then calcined in a muffle furnace at 500 °C for 1 h. After naturally cooling to room temperature, the solution was ground until homogeneous again to obtain a nitrogen-doped ruthenium dioxide catalyst. The prepared nitrogen-doped ruthenium dioxide catalyst has a nanorod structure with a diameter of 15-40 nm and a length of 80-140 nm. Nitrogen is uniformly distributed in the nanorods.

[0031] (2) The nitrogen-doped ruthenium dioxide catalyst was coated onto a titanium sheet using a spin-coating method for electrochemical testing and chlorine evolution activity testing. The specific method is as follows:

[0032] Step ①: The titanium sheet is ultrasonically cleaned for 20 minutes using acetone, anhydrous ethanol, and deionized water, and then acid etched at 90°C for 2 hours using a 10% oxalic acid solution.

[0033] Step ②: Dissolve 5 mg of the nitrogen-doped ruthenium dioxide catalyst in 950 μL of isopropanol, and add 50 μL of 5% Nafion solution as a binder. Then, treat with ultrasound to form catalyst ink.

[0034] Step 3: The catalyst ink from step 2 is coated onto the titanium sheet from step 1 using spin coating. After natural drying, electrochemical tests and chlorine evolution activity tests are performed.

[0035] The electrochemical test and chlorine evolution activity test results are shown in Table 1. The nitrogen-doped ruthenium dioxide catalyst exhibits good performance at 10 mA / cm². 2 The chlorine evolution potential is 1.455 V vs RHE, and the electrochemical active area is 141.7 cm². 2 The AC impedance was 7.35Ω, and the chlorine production at 15 min was 12.89 mg / L.

[0036] Example 2:

[0037] As described in Example 1, the difference is:

[0038] In step (1), 261.47 mg of RuCl3·xH2O and 15.28 mg of NH4Cl were added to 10 mL of anhydrous ethanol, and 300 μL of concentrated hydrochloric acid was added. The mixture was stirred until homogeneous to obtain a precursor solution with a Ru concentration of 26.15 g / L and a Ru:N molar ratio of 7:2.

[0039] In step (2), as shown in Table 1, the nitrogen-doped ruthenium dioxide catalyst at 10 mA / cm 2 The chlorine evolution potential is 1.457 V vs RHE, and the electrochemical active area is 138.2 cm². 2 The AC impedance was 7.42Ω, and the chlorine production at 15 min was 12.05 mg / L.

[0040] Example 3:

[0041] As described in Example 1, the difference is:

[0042] In step (1), the sample is calcined at 700°C for 1 hour in a muffle furnace.

[0043] In step (2), as shown in Table 1, the nitrogen-doped ruthenium dioxide catalyst at 10 mA / cm 2 The chlorine evolution potential is 1.385 V vs RHE, and the electrochemical active area is 147.2 cm². 2 The AC impedance was 2.63Ω, and the chlorine production at 15 min was 14.82 mg / L.

[0044] Comparative Example 1:

[0045] As described in Example 1, the difference is:

[0046] In step (1), only 261.47 mg of RuCl3·xH2O was added to 10 mL of anhydrous ethanol, without adding NH4Cl. The prepared ruthenium dioxide catalyst was not nitrogen-doped and had a nanoparticle structure with a diameter of 10-40 nm. The nanoparticles were densely arranged and exhibited agglomeration.

[0047] In step (2), as shown in Table 1, the undoped ruthenium dioxide catalyst at 10 mA / cm 2 The chlorine evolution potential is 1.481 V vs RHE, and the electrochemical active area is 86.5 cm². 2 The AC impedance was 12.26Ω, and the chlorine production at 15 min was 6.05 mg / L.

[0048] Comparative Example 2:

[0049] As described in Example 1, the difference is:

[0050] In step (1), the ruthenium dioxide catalyst is commercially available ruthenium dioxide (Sigma-Aldrich, CAS No.: 32740-79-7).

[0051] In step (2), as shown in Table 1, the commercial ruthenium dioxide catalyst at 10 mA / cm 2 The chlorine evolution potential is 1.610 V vs RHE, and the electrochemical active area is 19.5 cm². 2 The AC impedance was 14.21Ω, and the chlorine production at 15 min was 3.16 mg / L.

[0052] Table 1. Comparison of catalyst performance between different embodiments and comparative examples

[0053]

Claims

1. A nanorod-shaped nitrogen-doped ruthenium dioxide chlorine evolution catalyst and its preparation method, comprising the following steps: Step (1): Dissolve a certain amount of ruthenium trichloride and nitrogen-containing precursor in anhydrous ethanol, add a small amount of concentrated hydrochloric acid, stir evenly, and obtain a precursor solution; Step (2): Place the precursor solution from step (1) in a forced-air drying oven and dry it at 50-80℃. After the ethanol has completely evaporated, grind it evenly and then calcine it in a muffle furnace for 1-2 hours. After naturally cooling to room temperature, grind it evenly again to obtain nitrogen-doped ruthenium dioxide catalyst.

2. The preparation method according to claim 1, characterized in that, In step (1), the nitrogen-containing precursor is ammonium chloride.

3. The preparation method according to claim 1, characterized in that, In step (1), ruthenium trichloride and a nitrogen-containing precursor are added to anhydrous ethanol according to the concentration of Ru being 20-30 g / L and the molar ratio of Ru to N being 7:(1-6).

4. The preparation method according to claim 1, characterized in that, In step (2), the calcination temperature of the muffle furnace can be selected as 500-800℃, and the calcination time is 1-2h.

5. The preparation method according to claim 1, characterized in that, The nitrogen-doped ruthenium dioxide catalyst has a nanorod structure with a diameter of 15-40 nm and a length of 80-140 nm, and nitrogen is uniformly distributed in the nanorod.

6. The preparation method according to claim 1, characterized in that, The nitrogen-doped ruthenium dioxide catalyst contains unsaturated coordinated Ru. 3+ .

7. The preparation method according to claim 1, characterized in that, The nitrogen-doped ruthenium dioxide catalyst exhibits good chlorine evolution performance. Compared with undoped ruthenium dioxide under the same preparation conditions, nitrogen-doped ruthenium dioxide shows a lower chlorine evolution potential, a higher electrochemical active area, improved electron transfer performance, and significantly enhanced chlorine evolution activity.

8. As described in claim 7, characterized in that, The electrochemical tests for chlorine evolution potential, electrochemical active area, and electron transfer performance, as well as the chlorine evolution activity test, were performed by spin-coating the prepared catalyst onto a titanium sheet. The method is as follows: Step ①: The titanium sheet was ultrasonically cleaned for 20 minutes using acetone, anhydrous ethanol, and deionized water, and then acid etched at 90°C for 2 hours using a 10% oxalic acid solution. Step ②: Dissolve 3-7 mg of the nitrogen-doped ruthenium dioxide catalyst in 950 μL of isopropanol, and add 50 μL of 5% Nafion solution as a binder. Then, treat with ultrasound to form catalyst ink. Step 3: The catalyst ink from step 2 is coated onto the titanium sheet from step 1 using spin coating. After natural drying, electrochemical tests and chlorine evolution activity tests are performed.

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