Three-dimensional porous copper-palladium electrode material and preparation method and application thereof

Abstract

The application discloses a kind of three-dimensional porous copper palladium electrode materials and its preparation method and application, the preparation method includes the following steps: S1: preparation of foam copper sheet, and the foam copper sheet is pretreated;S2: palladium chloride powder is dissolved in salt solution to configure electrodeposition liquid;S3: the foam copper sheet after pretreatment is soaked in the electrodeposition liquid and carries out double potential electrodeposition;S4: electrode after double potential electrodeposition is taken out and is reduced;S5: the electrode after reduction is placed in alkali solution, and with 0.3~‑0.9V voltage is scanned, obtains the three-dimensional porous copper palladium electrode material.The preparation method of the application is simple, can control palladium particle size and loading, and the copper palladium electrode material prepared has the advantages of large specific surface area, good stability, high nitrogen selectivity and high denitrification performance, provides technical support for reduction of nitrate.

Description

Technical Field

[0001] This invention relates to the field of nitrate reduction and electrocatalytic materials technology, and particularly to a three-dimensional porous copper-palladium electrode material, its preparation method and application. Background Technology

[0002] Nitrogen, an essential element in nature, exists in water primarily as nitrite, nitrate, ammonium ions, and nitrogen gas. It is well known that nitrate concentrations in natural water bodies are harmless to humans. However, human activities, including fertilizer runoff from agricultural land, rainwater runoff from urban areas, and the discharge of untreated wastewater and sewage, have led to a sharp increase in nitrate concentrations in surface water and groundwater, causing nitrate pollution. Excessively high nitrate concentrations in water can seriously impact human safety and health. For example, high nitrate levels in drinking water can cause symptoms such as fatigue, shortness of breath, and cerebral hypoxia, leading to methemoglobinemia. Of particular concern is the potential toxicity of nitrates in infants and fetuses; long-term consumption of water with excessive nitrate levels can easily cause "blue baby syndrome," which in severe cases can lead to suffocation and death. Therefore, my country's "Standards for Drinking Water Quality" sets the maximum limit for nitrates at 10 mg / L, while the "Standards for Pollutant Discharge from Urban Wastewater Treatment Plants" sets the maximum discharge standards for total nitrogen and ammonia nitrogen at 20 mg / L and 25 mg / L, respectively. Furthermore, the International Agency for Research on Cancer (IARC) of the World Health Organization classified nitrates and nitrites as Group 2A carcinogens in October 2017. Therefore, nitrate-contaminated wastewater must be effectively treated before being discharged into the natural environment.

[0003] Currently reported methods for treating nitrate pollution include physicochemical denitrification, biological denitrification, chemical reduction denitrification, and electrocatalytic denitrification. Among these, electrocatalytic denitrification directly utilizes electrons as a reducing agent to convert nitrates into nitrites, and then into nitrogen gas. It exhibits excellent shock resistance, superior denitrification performance, and selectivity. Compared to the aforementioned methods, electrocatalytic denitrification is a promising treatment approach due to its high efficiency, environmental friendliness, mild reaction conditions, and low risk of secondary pollution.

[0004] The core of electrocatalytic denitrification lies in the electrocatalyst material. Copper-palladium catalysts are widely recognized as one of the most promising alloy catalysts due to their stability, low toxicity, high selectivity for nitrogen, and high nitrate removal efficiency. However, current methods for plating palladium onto copper surfaces are only suitable for smooth copper sheets. When used for plating palladium onto three-dimensional copper surfaces, palladium particles tend to detach and agglomerate. Summary of the Invention

[0005] To address the aforementioned problems, this invention aims to provide a three-dimensional porous copper-palladium electrode material, its preparation method, and its applications.

[0006] The technical solution of the present invention is as follows:

[0007] On the one hand, a method for preparing a three-dimensional porous copper-palladium electrode material is provided, comprising the following sub-steps:

[0008] S1: Prepare copper foam sheets and pre-treat the copper foam sheets;

[0009] S2: Dissolve palladium chloride powder in a salt solution to prepare an electrodeposition solution;

[0010] S3: Immerse the pretreated copper foam sheet in the electrodeposition solution for dual-potential electrodeposition;

[0011] S4: Remove the electrode after dual-potential electrodeposition and restore it;

[0012] S5: The reduced electrode is placed in an alkaline solution and scanned with a voltage of 0.3 to -0.9V to obtain the three-dimensional porous copper-palladium electrode material.

[0013] Preferably, step S1, the pretreatment of the foamed copper sheet specifically includes the following sub-steps: first, the foamed copper sheet is ultrasonically cleaned in acetone, and then the foamed copper sheet is ultrasonically cleaned in sulfuric acid solution.

[0014] Preferably, in step S2, the palladium concentration in the electrodeposition solution is 5–100 mg / L.

[0015] Preferably, in step S2, the salt solution is a sodium chloride solution or a potassium chloride solution.

[0016] Preferably, in step S3, dual-potential electrodeposition is performed with a low voltage of -0.95 to -1.50V, a high voltage of 0V, and an applied pulse length of 0.1 to 0.4s. The dual-potential electrodeposition time is 10 to 150 min.

[0017] Preferably, in step S4, reduction is carried out in a reducing atmosphere and at 100–200°C.

[0018] Preferably, the reducing atmosphere is a mixture of argon and hydrogen.

[0019] Preferably, in step S5, the concentration of the potassium hydroxide solution is 1–3 M.

[0020] On the other hand, a three-dimensional porous copper-palladium electrode material and its application in the reduction of nitrate are also provided. The three-dimensional porous copper-palladium electrode material is prepared by any one of the above-described methods for preparing three-dimensional porous copper-palladium electrode materials.

[0021] The beneficial effects of this invention are:

[0022] This invention uses a foamed copper sheet with a three-dimensional porous structure as the substrate to support the working electrode, and prepares a copper-palladium electrode material using a dual-potential deposition method. The preparation method is simple, and the prepared copper-palladium electrode material has a clear palladium / copper interface and good stability. Moreover, its structure contains a through-porous structure, which is conducive to molecular diffusion and transfer, and has a high nitrate removal rate. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 Here is a SEM image of the original foamed copper sheet in Example 1;

[0025] Figure 2 This is a TEM image of the three-dimensional porous copper-palladium electrode material in Example 1;

[0026] Figure 3 This is a schematic diagram showing the activity test results of the electrode materials in Example 1, Example 3, and Comparative Example 1;

[0027] Figure 4 This is a schematic diagram showing the stability test results of the three-dimensional porous copper-palladium electrode material in Example 3. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and technical features described in this application can be combined with each other. It should also be pointed out that, unless otherwise indicated, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terms "comprising" or "including" and similar words used in this invention refer to elements or objects preceding the word that encompass the elements or objects listed following the word and their equivalents, without excluding other elements or objects.

[0029] On one hand, the present invention provides a method for preparing a three-dimensional porous copper-palladium electrode material, comprising the following sub-steps:

[0030] S1: Prepare copper foam sheets and pre-treat the copper foam sheets.

[0031] In one specific embodiment, the pretreatment of the foamed copper sheet includes the following sub-steps: first, the foamed copper sheet is ultrasonically cleaned in acetone, and then the foamed copper sheet is ultrasonically cleaned in sulfuric acid solution.

[0032] In the above embodiments, ultrasonic cleaning with acetone can remove ester substances from the surface of the copper foam sheet, and ultrasonic cleaning with sulfuric acid solution can remove oxides from the surface of the copper foam sheet. It should be noted that the pretreatment methods in the above embodiments are conventional pretreatment methods for cleaning copper foam sheets, and other pretreatment methods for cleaning copper foam sheets in the prior art can also be applied to this invention.

[0033] S2: Dissolve palladium chloride powder in a salt solution to prepare an electrodeposition solution.

[0034] In one specific embodiment, the salt solution is a sodium chloride solution or a potassium chloride solution, and the palladium concentration in the electrodeposition solution is 5–100 mg / L.

[0035] S3: Immerse the pretreated copper foam sheet in the electrodeposition solution for dual-potential electrodeposition.

[0036] In one specific embodiment, dual-potential electrodeposition is performed with a low voltage of -0.95 to -1.50V, a high voltage of 0V, and an applied pulse length of 0.1 to 0.4s. The dual-potential electrodeposition time is 10 to 150 minutes.

[0037] S4: Remove the electrode after dual-potential electrodeposition and restore it.

[0038] In one specific embodiment, reduction is carried out in a reducing atmosphere and at 100–200°C, wherein the reducing atmosphere is a mixture of argon and hydrogen.

[0039] In the above embodiments, by performing a reduction treatment on the electrode after dual-potential electrodeposition, it can be ensured that the electrode is not over-oxidized during the subsequent drying process, and the oxygen-containing functional groups on the surface can be further removed to maintain the stability of the electrode surface.

[0040] S5: The reduced electrode is placed in an alkaline solution and scanned with a voltage of 0.3 to -0.9V to obtain the three-dimensional porous copper-palladium electrode material.

[0041] In the above embodiments, the reduced electrode is placed in an alkaline solution and scanned with a voltage of 0.3 to -0.9 V, which can improve the stability and electrochemical activity of the modified layer, and the scanning activation process can ensure the stability of the valence states of Cu and Pd elements on the electrode surface. In a specific embodiment, the concentration of the potassium hydroxide solution is 1 to 3 M.

[0042] This invention uses copper foam sheet as the substrate for supporting the working electrode. It has the characteristics of high specific surface area, excellent electrochemical performance, and a three-dimensional through-porous structure that is conducive to molecular diffusion and transfer. It can provide a high specific surface area for palladium attachment and can also serve as a copper source, thus saving costs.

[0043] This invention employs a dual-potential electrodeposition method, the entire process of which is essentially a cyclical process of alternating oxidation and reduction reactions. This process allows for the uniform dispersion of palladium on a copper foam sheet and effective control over the size of the generated palladium particles and their loading on the copper sheet. Furthermore, the preparation method of this invention is simple to operate, highly economical, and environmentally friendly. In addition, compared to copper-palladium electrode materials prepared by constant voltage electrodeposition on smooth copper sheets, the three-dimensional porous copper-palladium electrode material obtained by this invention has the advantages of controllable palladium particle size, loading, and uniformity of distribution (palladium cannot be deposited on copper foam sheets using constant voltage electrodeposition).

[0044] On the other hand, the present invention also provides a three-dimensional porous copper-palladium electrode material and its application in the reduction of nitrates, wherein the three-dimensional porous copper-palladium electrode material is prepared by any one of the above-described methods for preparing three-dimensional porous copper-palladium electrode materials.

[0045] Example 1

[0046] A three-dimensional porous copper-palladium electrode material is prepared by the following steps:

[0047] Cut the copper foam into 3cm x 3cm sheets. Then, attach a 4cm x 0.5cm piece of copper adhesive to one end of each sheet. Finally, apply acrylic structural adhesive to the area with the copper adhesive, ensuring that the exposed copper foam sheet area is 3cm x 2cm to serve as the substrate supporting the working electrode. Place the prepared copper foam sheet in acetone and sonicate for 10 minutes to remove surface esters, then place it in a 4M H₂SO₄ solution and sonicate for 10 minutes to remove surface oxides.

[0048] 8.34 mg of PdCl2 powder was dissolved in 100 mL of 65% KCl solution to prepare an electrodeposition solution with a palladium concentration of 5 mg / L. The cleaned copper foam sheet was immersed in the prepared palladium source electrodeposition solution. Electrodeposition was then performed for 20 min with an applied voltage of -0.95 V, a high voltage of 0 V, and a pulse length of 0.2 s. Afterward, the electrode was removed and placed in an argon-hydrogen atmosphere for reduction. Finally, the electrode was placed in a 1 M KOH solution and scanned with a voltage of 0.3–-0.9 V for approximately 5 min to obtain a three-dimensional porous copper-palladium electrode material.

[0049] Example 2

[0050] A three-dimensional porous copper-palladium electrode material is prepared by the following steps:

[0051] Cut the copper foam into 3cm x 3cm sheets. Then, attach a 4cm x 0.5cm piece of copper adhesive to one end of each sheet. Finally, apply acrylic structural adhesive to the area with the copper adhesive, ensuring that the exposed copper foam sheet area is 3cm x 2cm to serve as the substrate supporting the working electrode. Place the prepared copper foam sheet in acetone and sonicate for 10 minutes to remove surface esters, then place it in a 4M H₂SO₄ solution and sonicate for 10 minutes to remove surface oxides.

[0052] 25 mg of PdCl2 powder was dissolved in 100 mL of 65% KCl solution to prepare an electrodeposition solution with a palladium concentration of 15 mg / L. The cleaned copper foam sheet was immersed in the prepared palladium source electrodeposition solution. Electrodeposition was then performed for 60 min with an applied voltage of -1.25 V, a high voltage of 0 V, and a pulse length of 0.2 s. Afterward, the electrode was removed and placed in an argon-hydrogen atmosphere for reduction. Finally, the electrode was placed in a 1 M KOH solution and scanned with a voltage of 0.3–-0.9 V for approximately 5 min to obtain a three-dimensional porous copper-palladium electrode material.

[0053] Example 3

[0054] A three-dimensional porous copper-palladium electrode material is prepared by the following steps:

[0055] Cut the copper foam into 3cm x 3cm sheets. Then, attach a 4cm x 0.5cm piece of copper adhesive to one end of each sheet. Finally, apply acrylic structural adhesive to the area with the copper adhesive, ensuring that the exposed copper foam sheet area is 3cm x 2cm to serve as the substrate supporting the working electrode. Place the prepared copper foam sheet in acetone and sonicate for 10 minutes to remove surface esters, then place it in a 4M H₂SO₄ solution and sonicate for 10 minutes to remove surface oxides.

[0056] 41.68 mg of PdCl2 powder was dissolved in 100 mL of 65% KCl solution to prepare an electrodeposition solution with a palladium concentration of 25 mg / L. The cleaned copper foam sheet was immersed in the prepared palladium source electrodeposition solution. Electrodeposition was then performed for 120 min with an applied voltage of -1.50 V, a high voltage of 0 V, and a pulse length of 0.2 s. Afterward, the electrode was removed and placed in an argon-hydrogen atmosphere for reduction. Finally, the electrode was placed in a 1 M KOH solution and scanned with a voltage of 0.3–-0.9 V for approximately 5 min to obtain a three-dimensional porous copper-palladium electrode material.

[0057] Comparative Example 1

[0058] A planar copper-palladium electrode material is prepared by the following steps:

[0059] Cut a copper sheet into 3cm x 3cm pieces. Then, apply a 4cm x 0.5cm layer of copper adhesive to one end of each piece. Finally, apply acrylic structural adhesive to the area with the copper adhesive, ensuring that the exposed copper sheet area is 3cm x 2cm to serve as the substrate supporting the working electrode. Place the prepared copper sheet in acetone and sonicate for 10 minutes to remove surface esters, then place it in a 4M H₂SO₄ solution and sonicate for 10 minutes to remove surface oxides.

[0060] 8.34 mg of PdCl2 powder was dissolved in 100 mL of 65% KCl solution to prepare an electrodeposition solution with a palladium concentration of 5 mg / L. The cleaned copper sheet was immersed in the prepared palladium electrodeposition solution, and electrodeposition was performed for 20 min with a low voltage of -0.95 V, a high voltage of 0 V, and a pulse length of 0.2 s, to obtain a planar copper-palladium electrode material.

[0061] It should be noted that during the dual-potential electrodeposition of this invention, the electrodeposition solution changes from yellow to transparent, at which point all the substances in the electrodeposition solution are deposited on the foamed copper sheet. However, during the dual-potential electrodeposition of Comparative Example 1, the electrodeposition solution changes from yellow to black. This is because only a very small amount of palladium can be loaded on the smooth copper sheet used in Comparative Example 1. After the rest of the palladium is reduced, the electrodeposition solution turns black. Therefore, the reduction step of step S4 of this invention was not performed after electrodeposition in Comparative Example 1.

[0062] Test case

[0063] The microstructure of the electrode materials prepared in each embodiment was observed, with the original copper foam sheet microstructure of Example 1 as shown in the figure. Figure 1 As shown, the microstructure of the three-dimensional porous copper-palladium electrode material prepared in Example 1 is as follows. Figure 2 As shown. Comparison Figure 1 and Figure 2 It can be seen that the copper foam has a self-supporting three-dimensional porous network structure with hierarchical macroscopic porosity and a clean framework surface. After deposition, the network structure is retained, while the framework becomes coarser, with some uniform snowflake-like structures on the surface. Palladium did not exhibit agglomeration or detachment.

[0064] The electrode materials prepared in each example and Comparative Example 1 were tested under the conditions of -0.80V and Na2SO4 containing saturated Ar with 22.50 mg / L NO3-N for 8 hours. The nitrate removal results of each electrode material obtained by the test are as follows: Figure 3 As shown. From Figure 3 It can be seen that the three-dimensional porous copper-palladium electrode material prepared by this invention has a much greater activity for nitrate than the planar copper-palladium electrode material.

[0065] The three-dimensional porous copper-palladium electrode material prepared in Example 3 was subjected to cyclic testing, and the test results are as follows: Figure 4 As shown. From Figure 4 It can be seen that after four cycles, the activity of the three-dimensional porous copper-palladium electrode material did not decrease after 32 hours, demonstrating extremely high stability. This also shows that the three-dimensional porous copper-palladium electrode material prepared by this invention will not exhibit palladium shedding.

[0066] It should be noted that because the electrode material of Comparative Example 1 has very poor activity, its stability was not analyzed.

[0067] In addition, it should be noted that the above embodiments and comparative examples are only preferred embodiments and comparative examples of the present invention. The three-dimensional porous copper-palladium electrode material prepared by the inventors through orthogonal experiments and other methods also has extremely high activity and stability, and there will be no palladium agglomeration or palladium shedding.

[0068] In summary, this invention enables the preparation of copper-palladium electrode materials with higher activity towards nitrate ions. Compared with the prior art, this invention represents a significant advancement.

[0069] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a three-dimensional porous copper-palladium electrode material, characterized in that, Includes the following sub-steps: S1: Prepare copper foam sheets and pre-treat the copper foam sheets; S2: Dissolve palladium chloride powder in a salt solution to prepare an electrodeposition solution; S3: Immerse the pretreated copper foam sheet in the electrodeposition solution, and perform dual-potential electrodeposition with a low voltage of -0.95~-1.50V, a high voltage of 0V, and an applied pulse length of 0.1~0.4s. The dual-potential electrodeposition time is 10~150 min. S4: Remove the electrode after dual-potential electrodeposition and restore it; S5: The reduced electrode is placed in an alkaline solution and scanned with a voltage of 0.3~-0.9 V to obtain the three-dimensional porous copper-palladium electrode material.

2. The method for preparing the three-dimensional porous copper-palladium electrode material according to claim 1, characterized in that, In step S1, the pretreatment of the foamed copper sheet specifically includes the following sub-steps: first, the foamed copper sheet is ultrasonically cleaned in acetone, and then the foamed copper sheet is ultrasonically cleaned in sulfuric acid solution.

3. The method for preparing the three-dimensional porous copper-palladium electrode material according to claim 1, characterized in that, In step S2, the palladium concentration in the electrodeposition solution is 5~100 mg / L.

4. The method for preparing the three-dimensional porous copper-palladium electrode material according to claim 1 or 3, characterized in that, In step S2, the salt solution is a sodium chloride solution or a potassium chloride solution.

5. The method for preparing the three-dimensional porous copper-palladium electrode material according to claim 1, characterized in that, In step S4, reduction is carried out in a reducing atmosphere at 100~200 °C.

6. The method for preparing the three-dimensional porous copper-palladium electrode material according to claim 5, characterized in that, The reducing atmosphere is a mixture of argon and hydrogen.

7. The method for preparing the three-dimensional porous copper-palladium electrode material according to claim 1, characterized in that, In step S5, the alkaline solution is a potassium hydroxide solution with a concentration of 1~3 M.

8. A three-dimensional porous copper-palladium electrode material, characterized in that, It is prepared using the method for preparing the three-dimensional porous copper-palladium electrode material according to any one of claims 1-7.

9. The application of the three-dimensional porous copper-palladium electrode material as described in claim 8 in the reduction of nitrates.

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