A method for preparing a high-catalytic-performance nickel foam-supported Ru-Ni(OH)2 electrode and its application

Abstract

This invention provides a method for preparing a nickel foam-supported Ru-Ni(OH)2 electrode with good catalytic performance and its application. The preparation method is as follows: (1) The initial nickel foam support is immersed in a 3 mol / L hydrochloric acid solution for ultrasonic etching, and then removed and ultrasonicated with ethanol and deionized water respectively; (2) The nickel foam from step (1) is placed in a homogeneous solution of nickel nitrate, ammonium fluoride and urea for hydrothermal reaction. After the reaction, it is removed, washed with ethanol and deionized water, and dried to obtain nickel foam loaded with nickel hydroxide; (3) The nickel foam loaded with nickel hydroxide from step (2) is immersed in a ruthenium trichloride solution for ion exchange. After the reaction, the electrode is removed, washed with water, and dried to obtain a nickel foam-supported Ru-Ni(OH)2 electrode. The nickel foam-supported Ru-Ni(OH)2 electrode prepared by the method of this invention exhibits excellent removal effect on bromate in wastewater, and the prepared electrode has high stability.

Description

Technical Field

[0001] This invention relates to the field of electrocatalysis technology, specifically to a method for preparing a nickel foam-supported Ru-Ni(OH)2 electrode and its application. Background Technology

[0002] Bromate is a common disinfection byproduct in drinking water. Due to its potential carcinogenicity and nephrotoxicity, it has been classified as a Group 2B carcinogen by the International Agency for Research on Cancer. With the widespread application of ozone pre-oxidation and ozone-bioactivated carbon combined processes in water treatment and remediation, bromate emissions are gradually increasing, and bromate pollution should be given sufficient attention. Bromate is highly stable in water, making the exploration of an efficient method for its removal a significant research endeavor.

[0003] The World Health Organization stipulates that the bromate content in drinking water should not exceed 10 μg / L. To meet this standard, methods including filtration, chemical reduction, and biodegradation have been explored. However, these methods often have limitations such as high operating costs, secondary pollution, and complex operating procedures. Electrochemical reduction of bromate to bromide is an effective method for treating bromate-containing water, with advantages such as simple maintenance, fast reaction rate, and no secondary pollution. In electrochemical reduction of bromate, it mainly utilizes electrode materials to promote the direct or indirect reduction of bromate. Direct reduction involves bromate gaining electrons on the electrode surface and being reduced to bromide; while indirect reduction is achieved through the Volmer reaction (H₂O + e⁻). - =H ad +OH - The generated atomic hydrogen (H*) serves as a key mediator. Nickel foam's excellent electrical conductivity, porous structure, and high mechanical strength promote electron transport and catalyst loading. Simultaneously, atomic hydrogen (H*), as an important medium, is generated very slowly in the Volmer reaction; however, composite materials based on noble metals can improve the adsorption and desorption processes of atomic hydrogen through optimized electronic structures. Platinum is one of the most effective catalysts for the Volmer reaction, but its high cost and limited reserves necessitate the development of more cost-effective, high-efficiency electrodes to address bromate contamination issues. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a method for preparing a high-catalytic-performance nickel foam-supported Ru-Ni(OH)₂ electrode to achieve efficient bromate removal. This method uses nickel foam as a substrate and nickel hydroxide as a precursor, employing a simple ion exchange method to load ruthenium, thereby preparing a nickel foam-supported Ru-Ni(OH)₂ electrode. To solve the above technical problem, this invention provides a method for preparing a high-catalytic-performance nickel foam-supported Ru-Ni(OH)₂ electrode, comprising the following steps:

[0005] (1) Place the initial nickel foam carrier in a hydrochloric acid solution with a molar concentration of 3 mol / L and ultrasonically etch it for 10-20 minutes. Then take it out and ultrasonically etch it with ethanol and deionized water for 10-15 minutes respectively.

[0006] (2) The nickel foam from step (1) is placed in a homogeneous solution of nickel nitrate, ammonium fluoride and urea in a mass ratio of 0.466~1.454:0.178~0.556:0.481~1.502 and subjected to a hydrothermal reaction at 90-120℃ for 4-8 hours. After the reaction, the foam is removed and washed with ethanol and deionized water, and dried at 70℃ for 2-4 hours to obtain nickel foam loaded with nickel hydroxide.

[0007] (3) Immerse the nickel foam loaded with nickel hydroxide in step (2) into a 0.05-0.60 g / L ruthenium trichloride solution for ion exchange for 2-6 hours. After completion, remove the electrode, wash it with water, and dry it at 70°C for 3-5 hours to obtain a nickel foam loaded Ru-Ni(OH)2 electrode.

[0008] As a preferred embodiment, in step (1), the etching time of the nickel foam carrier in the hydrochloric acid solution is 15-20 minutes.

[0009] In step (2), the preferred mass ratio of nickel nitrate hexahydrate, ammonium fluoride, and urea is 0.582–1.454: 0.223–0.556: 0.601–1.502, and the hydrothermal reaction time is 6–8 hours.

[0010] Preferably, in step (3), the concentration of ruthenium trichloride is 0.15–0.60 g / L, and the ion exchange time is 3–6 hours.

[0011] The present invention also provides an application of a nickel foam-loaded Ru-Ni(OH)2 electrode, which can be used for the treatment of bromate-containing wastewater by the above preparation method.

[0012] The present invention has the following beneficial effects:

[0013] 1. The raw materials used are simple and the synthesis method is easy.

[0014] 2. By loading Ru-Ni(OH)2 onto nickel foam, electron transfer is enhanced, and the generation and utilization efficiency of H* are improved, which greatly accelerates the removal of bromate. Attached Figure Description

[0015] Figure 1 This is the SEM image of Example 4.

[0016] Figure 2 This is the HRTEM spectrum of Example 4.

[0017] Figure 3 The XRD patterns are for Example 4 and the comparative example.

[0018] Figure 4 The cyclic voltammetry curves are for Example 4 and the comparative example. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] I. Examples and Comparative Examples

[0021] Example 1

[0022] (1) Place a 1cm*5cm nickel foam into a 3mol / L hydrochloric acid solution and ultrasonically etch it for 20 minutes. Then take it out and ultrasonically etch it for 15 minutes each with ethanol and deionized water.

[0023] (2) Weigh 1.454g of nickel nitrate hexahydrate, 0.556g of ammonium fluoride and 1.502g of urea, dissolve them in 60mL of deionized water and stir for 30 minutes. Add the foamed nickel treated in (1) and react in a 100mL reactor at 100℃ for 6 hours. After natural cooling, take it out, wash it with ethanol and deionized water, and dry it at 70℃ for 3 hours.

[0024] (3) Cut the product obtained in (2) into 1cm*1.5cm pieces and place them in a transparent sample bottle containing 20mL of ruthenium trichloride trihydrate aqueous solution with a concentration of 0.15g / L. Shake at 270r / min for 6 hours at 25℃ to carry out ion exchange. Take it out, wash it with deionized water, and then dry it at 70℃ for 4 hours.

[0025] Example 2

[0026] (1) Place a 1cm*5cm nickel foam into a 3mol / L hydrochloric acid solution and ultrasonically etch it for 20 minutes. Then take it out and ultrasonically etch it for 15 minutes each with ethanol and deionized water.

[0027] (2) Weigh 1.454g of nickel nitrate hexahydrate, 0.556g of ammonium fluoride and 1.502g of urea, dissolve them in 60mL of deionized water and stir for 30 minutes. Add the foamed nickel treated in (1) and react in a 100mL reactor at 100℃ for 6 hours. After natural cooling, take it out, wash it with ethanol and deionized water, and dry it at 70℃ for 3 hours.

[0028] (3) Cut the product obtained in (2) into 1cm*1.5cm pieces and place them in a transparent sample bottle containing 20mL of ruthenium trichloride trihydrate aqueous solution with a concentration of 0.30g / L. Shake at 270r / min for 6 hours at 25℃ to carry out ion exchange. Take it out, wash it with deionized water, and then dry it at 70℃ for 4 hours.

[0029] Example 3

[0030] (1) Place a 1cm*5cm nickel foam into a 3mol / L hydrochloric acid solution and ultrasonically etch it for 20 minutes. Then take it out and ultrasonically etch it for 15 minutes each with ethanol and deionized water.

[0031] (2) Weigh 1.454g of nickel nitrate hexahydrate, 0.556g of ammonium fluoride and 1.502g of urea, dissolve them in 60mL of deionized water and stir for 30 minutes. Add the foamed nickel treated in (1) and react in a 100mL reactor at 100℃ for 6 hours. After natural cooling, take it out, wash it with ethanol and deionized water, and dry it at 70℃ for 3 hours.

[0032] (3) Cut the product obtained in (2) into 1cm*1.5cm pieces and place them in a transparent sample bottle containing 20mL of ruthenium trichloride trihydrate aqueous solution with a concentration of 0.45g / L. Shake at 270r / min for 6 hours at 25℃ to carry out ion exchange. Take it out, wash it with deionized water, and then dry it at 70℃ for 4 hours.

[0033] Example 4

[0034] (1) Place a 1cm*5cm piece of nickel foam into a 3mol / L hydrochloric acid solution for etching for 20 minutes, then take it out and sonicate it with ethanol and deionized water for 15 minutes respectively.

[0035] (2) Weigh 1.454g of nickel nitrate hexahydrate, 0.556g of ammonium fluoride and 1.502g of urea, dissolve them in 60mL of deionized water and stir for 30 minutes. Add the foamed nickel treated in (1) and react in a 100mL reactor at 100℃ for 6 hours. After natural cooling, take it out, wash it with ethanol and deionized water, and dry it at 70℃ for 3 hours.

[0036] (3) Cut the product obtained in (2) into 1cm*1.5cm pieces and place them in a transparent sample bottle containing 20mL of ruthenium trichloride trihydrate aqueous solution with a concentration of 0.60g / L. Shake at 270r / min for 6 hours at 25℃ to carry out ion exchange. Take it out, wash it with deionized water, and then dry it at 70℃ for 4 hours.

[0037] Comparative Example

[0038] (1) Place a 1cm*5cm piece of nickel foam into a 3mol / L hydrochloric acid solution for etching for 20 minutes, then take it out and sonicate it with ethanol and deionized water for 15 minutes respectively.

[0039] (2) Weigh 1.454g of nickel nitrate hexahydrate, 0.556g of ammonium fluoride and 1.502g of urea, dissolve them in 60mL of deionized water and stir for 30 minutes. Add the foamed nickel treated in (1) and react in a 100mL reactor at 100℃ for 6 hours. After natural cooling, take it out, wash it with ethanol and deionized water, dry it at 70℃ for 3 hours, and then cut it into 1cm*1.5cm pieces.

[0040] II. Research on Bromate Removal

[0041] (1) The foamed nickel-supported Ru-Ni(OH)2 electrodes prepared in Examples 1-4 and the comparative examples were used for the treatment of bromate-containing wastewater. The specific steps are as follows:

[0042] A simulated water sample consisting of 50 μmol / L sodium bromate and 10 mmol / L sodium sulfate, with the pH adjusted to 5.0, was used to investigate the bromate removal performance of electrodes prepared in Examples 1-4 and the comparative example. 40 mL of the prepared sodium bromate solution was added to a 50 mL electrolytic cell, and the magnetic stirring speed was 300 r / min. The cathodes were the nickel foam-loaded Ru-Ni(OH)₂ electrodes prepared in Examples 1-4 and the nickel foam-loaded nickel hydroxide electrode of the comparative example. The anode was a 1.0 cm × 1.0 cm platinum sheet electrode. The distance between the cathode and anode was set to 1.8 cm, and the current density was 10 mA·cm⁻¹. -2 The reaction was carried out at 298.15 K for 90 minutes, and samples were taken at required time intervals. The bromate concentration was determined using potassium iodide as a reducing agent and a UV spectrophotometer.

[0043] Table 1 Comparison of the removal effects of different ruthenium loadings on bromate.

[0044] Example 1 Example 2 Example 3 Example 4 Comparative Example Time (minutes) Removal rate Removal rate Removal rate Removal rate Removal rate 0 0.00％ 0.00％ 0.00％ 0.00％ 0.00％ 5 14.40％ 18.51％ 19.53％ 23.98％ 4.08％ 10 23.99％ 30.48％ 33.74％ 34.91％ 5.78％ 15 33.60％ 41.73％ 43.68％ 44.08％ 7.13％ 20 42.86％ 51.16％ 50.78％ 55.36％ 8.49％ 30 52.80％ 64.22％ 67.47％ 69.82％ 9.85％ 45 65.84％ 73.29％ 79.55％ 82.51％ 11.89％ 60 72.35％ 79.10％ 84.52％ 88.86％ 16.30％ 90 80.59％ 83.45％ 88.78％ 91.33％ 20.03％

[0045] As shown in Table 1, the removal rate of bromate by the nickel foam-supported Ru-Ni(OH)2 electrodes prepared in Examples 1-4 and the nickel foam-supported nickel hydroxide electrode in the comparative example was greatly improved with the participation of ruthenium. With the increase of the initial ruthenium concentration during electrode preparation, the promoting effect of the prepared nickel foam-supported Ru-Ni(OH)2 electrodes on bromate removal also showed an upward trend, but the upward trend became increasingly slow. Considering cost, when the initial ruthenium concentration during electrode preparation was 0.6 g / L, the removal rate of bromate reached 91.33% within 90 minutes, which was significantly improved compared to the 20.03% removal rate of the comparative example.

[0046] III. Study on bromate removal under different current densities

[0047] The nickel-fed Ru-Ni(OH)2 electrode prepared in Example 4 was used to treat bromate-containing wastewater at different current densities to explore the effect of current density on bromate removal performance. The specific steps are as follows:

[0048] A simulated water sample was prepared by mixing 50 μmol / L sodium bromate and 10 mmol / L sodium sulfate, with the pH adjusted to 5.0. 40 mL of the prepared sodium bromate solution was added to a 50 mL electrolytic cell, and the magnetic stirring speed was 300 r / min. Different current densities were set, and the reaction was carried out at 298.15 K for 90 minutes. Samples were taken at the required time intervals.

[0049] Table 2 Comparison of bromate removal effects of different current densities

[0050] <![CDATA[1mA / cm 2 ]]> <![CDATA[2mA / cm 2 ]]> <![CDATA[5mA / cm 2 ]]> <![CDATA[10mA / cm 2 ]]> <![CDATA[15mA / cm 2 ]]> Time (minutes) Removal rate Removal rate Removal rate Removal rate Removal rate 0 0.00％ 0.00％ 0.00％ 0.00％ 0.00％ 5 2.85％ 16.57％ 23.37％ 24.77％ 20.45％ 10 5.34％ 32.44％ 35.24％ 34.19％ 34.56％ 15 8.56％ 41.96％ 46.05％ 45.35％ 43.02％ 20 10.69％ 53.60％ 58.26％ 57.92％ 55.01％ 30 18.89％ 70.17％ 74.32％ 69.78％ 66.29％ 45 28.52％ 83.22％ 82.00％ 80.25％ 77.22％ 60 38.49％ 90.62％ 88.97％ 86.18％ 83.22％ 90 55.59％ 96.61％ 93.51％ 90.72％ 87.09％

[0051] Table 2 shows that the nickel foam-supported Ru-Ni(OH)2 electrode prepared in Example 4 is significantly affected by current density. With increasing current density, the promoting effect of the prepared nickel foam-supported Ru-Ni(OH)2 electrode on bromate removal first increases and then decreases. This is because with increasing current density, the formation rate of H* accelerates, electron transfer is enhanced, and bromate removal is promoted. With further increases in current density, excessive H* accumulation may promote hydrogen formation and release (Heyrovsky and Tafel reactions), which is detrimental to bromate removal. The current density was 2 mA / cm². 2 At that time, the removal rate of bromate reached a maximum of 96.61% within 90 minutes, demonstrating a significant removal effect.

[0052] IV. Study on bromate removal under different pH conditions

[0053] The nickel foam-supported Ru-Ni(OH)2 electrode prepared in Example 4 was used to treat bromate-containing wastewater under different pH conditions to explore the effect of pH conditions on bromate removal performance. The specific steps are as follows:

[0054] Simulated water samples were prepared using 50 μmol / L sodium bromate and 10 mmol / L sodium sulfate, adjusted to different pH values. 40 mL of the prepared sodium bromate solution was added to a 50 mL electrolytic cell. The magnetic stirring speed was 300 r / min, and the current density was set to 2 mA·cm⁻¹. -2 The reaction was carried out at 298.15 K for 90 minutes, and samples were taken at the required time intervals.

[0055] Table 3 Comparison of bromate removal effects at different pH values

[0056] pH = 5.0 pH = 7.0 pH = 9.0 Time (minutes) Removal rate Removal rate Removal rate 0 0.00％ 0.00％ 0.00％ 5 16.57％ 14.66％ 7.70％ 10 32.44％ 24.32％ 11.91％ 15 41.96％ 33.62％ 18.56％ 20 53.60％ 42.20％ 23.81％ 30 70.17％ 58.30％ 34.33％ 45 83.22％ 74.39％ 50.43％ 60 90.62％ 82.98％ 63.03％ 90 96.61％ 93.35％ 76.33％

[0057] As shown in Table 3, the nickel foam-supported Ru-Ni(OH)₂ electrode prepared in Example 4 is significantly affected by pH. With increasing pH, the promoting effect of the prepared nickel foam-supported Ru-Ni(OH)₂ electrode on bromate removal decreases. This is because increasing pH inhibits the formation of H*, and simultaneously, increasing the pH increases the energy barrier for Br-O bond breaking, thereby reducing electrocatalytic performance. At pH 5, the highest bromate removal rate reached 96.61% within 90 minutes, demonstrating excellent removal performance.

[0058] V. Study on bromate removal under different initial bromate concentrations

[0059] Under different initial bromate concentrations, the nickel foam-supported Ru-Ni(OH)2 electrode prepared in Example 4 was used to treat bromate-containing wastewater to explore the effect of initial bromate concentration on bromate removal performance. The specific steps are as follows:

[0060] Simulated water samples were prepared using sodium bromate at concentrations of 10 μmol / L, 20 μmol / L, and 50 μmol / L, and sodium sulfate at 10 mmol / L, respectively, with the pH adjusted to 5.0. 40 mL of the prepared sodium bromate solution was added to a 50 mL electrolytic cell, and the mixture was magnetically stirred at 300 rpm with a current density of 2 mA·cm⁻¹. -2 The reaction was carried out at 298.15 K for 90 minutes, and samples were taken at the required time intervals.

[0061] Table 4 Comparison of the effects of different initial bromate concentrations on bromate removal

[0062]

[0063]

[0064] As shown in Table 4, the nickel foam-supported Ru-Ni(OH)₂ electrode prepared in Example 4 was less affected by the initial bromate concentration. With decreasing initial bromate concentration, the promoting effect of the prepared nickel foam-supported Ru-Ni(OH)₂ electrode on bromate removal showed a slight decreasing trend. This may be because the utilization rate of the reducing agent (electrons and H*) during bromate reduction is reduced, thus decreasing the electrocatalytic performance. However, at all initial concentrations, the bromate removal rate reached over 90%, indicating significant potential for practical application.

[0065] VI. Electrode Stability Study

[0066] Electrode stability is a key indicator for formal use. In the electrocatalytic reduction of bromate, the electrode was reused five times, and the bromate removal efficiency was compared to evaluate the stability of the nickel foam-supported Ru-Ni(OH)2 electrode. The specific steps are as follows:

[0067] A simulated water sample consisting of 50 μmol / L sodium bromate and 10 mmol / L sodium sulfate, with the pH adjusted to 5.0, was used to investigate the bromate removal performance of the nickel-fed Ru-Ni(OH)₂ electrode prepared in Example 4. 40 mL of the prepared sodium bromate solution was added to a 50 mL electrolytic cell, and the magnetic stirring speed was 300 r / min, with a current density of 2 mA·cm⁻¹. -2 The reaction was carried out at 298.15 K for 90 minutes, with samples taken at required time intervals. After the experiment, the electrodes were washed with water, dried at 60 °C, and then used for repeated experiments.

[0068] Table 5 Comparison of bromate removal effects with different repetition cycles

[0069] Period 1 Period 2 Period 3 Period 4 Period 5 Removal rate 93.42％ 88.94％ 87.45％ 85.96％ 85.21％

[0070] As can be seen from Table 5, the removal efficiency of the nickel foam-supported Ru-Ni(OH)2 electrode prepared in Example 4 for bromate decreased slowly with the increase of the repetition cycle, from the initial 93.42% to 85.21% in the fifth cycle. This is mainly because the electrode loses some active material as the usage time increases, resulting in a decrease in removal performance.

Claims

1. A method for preparing a high-catalytic-performance nickel foam-supported Ru-Ni(OH)2 electrode, wherein the nickel foam-supported Ru-Ni(OH)2 electrode is applied to the treatment of bromate-containing wastewater, characterized in that, Includes the following steps: (1) The initial nickel foam carrier was placed in a hydrochloric acid / sulfuric acid / nitric acid solution with a molar concentration of 3 mol / L and ultrasonically etched to remove impurities and oxide film on the surface of the nickel foam. Then, it was ultrasonically etched with ethanol and deionized water for 10-15 minutes respectively. (2) The foamed nickel in step (1) is placed in a homogeneous solution of nickel nitrate hexahydrate, ammonium fluoride and urea, and undergoes a hydrothermal reaction at 90-120℃. Nickel nitrate hexahydrate serves as the nickel source, while ammonium fluoride and urea provide an alkaline environment for the reaction and promote the formation of a specific crystal structure. After the reaction is completed, the foamed nickel is removed, washed with ethanol and deionized water, and dried at 70℃ for 2-4 hours to obtain nickel foam loaded with nickel hydroxide. (3) Immerse the nickel foam loaded with nickel hydroxide in step (2) into a ruthenium trichloride solution to allow ruthenium ions to exchange with nickel hydroxide. After completion, remove the electrode, wash it with water, and dry it at 70°C for 3-5 hours to obtain a nickel foam loaded Ru-Ni(OH)2 electrode.

2. The method for preparing a high-catalytic-performance nickel foam-supported Ru-Ni(OH)2 electrode according to claim 1, characterized in that: In step (1), the etching time of the nickel foam carrier in hydrochloric acid solution is 10-20 minutes.

3. The method for preparing a high-catalytic-performance nickel foam-supported Ru-Ni(OH)2 electrode according to claim 1, characterized in that: In step (2), the mass ratio of nickel nitrate hexahydrate, ammonium fluoride and urea is 0.466~1.454:0.178~0.556:0.481~1.

502.

4. The method for preparing a high-catalytic-performance nickel foam-supported Ru-Ni(OH)2 electrode according to claim 1, characterized in that: In step (2), the hydrothermal reaction time is 4-8 hours.

5. The method for preparing a high-catalytic-performance nickel foam-supported Ru-Ni(OH)2 electrode according to claim 1, characterized in that: In step (3), the concentration of the ruthenium trichloride solution is 0.05~0.60 g / L.

6. The method for preparing a high-catalytic-performance nickel foam-supported Ru-Ni(OH)2 electrode according to claim 1, characterized in that: In step (3), the ion exchange time is 2-6 hours.

7. The application of the nickel foam-supported Ru-Ni(OH)2 electrode prepared by any one of claims 1-6 in the treatment of bromate-containing wastewater.

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