Palladium-nickel phosphide copper-foam nickel composite electrode and preparation method and application thereof

Abstract

This invention discloses a palladium-nickel phosphide copper-foam nickel composite electrode, its preparation method, and its application. The preparation method includes: step one, NF substrate pretreatment; step two, preparing an intermediate layer using a constant current deposition method to obtain Ni-Cu-P / NF; and step three, preparing a catalyst layer using a pulse electrodeposition method to obtain Pd / Ni-Cu-P / NF. The Pd / Ni-Cu-P / NF electrode designed in this invention improves the deposition environment of the Pd catalyst layer on a three-dimensional scale through the Ni-Cu-P intermediate layer, thereby increasing the dispersion of Pd nanoparticles, increasing active sites, and reducing the amount of Pd required. Furthermore, under the action of Ni-Cu-P, the generation of active hydrogen can be accelerated, while simultaneously increasing the Pd content in the Pd catalyst layer. 2+ The content of Pd promotes the activation of C-Cl bonds, thereby further improving the dechlorination efficiency and solving the problems of poor Pd dispersion, low activity, large dosage, and high electrode preparation cost of existing dechlorination electrodes.

Description

Technical Field

[0001] This invention relates to the field of electrochemical technology, specifically to a palladium-nickel phosphide copper-foam nickel composite electrode, its preparation method, and its application. Background Technology

[0002] Chlorophenols are widely used as intermediates in the synthesis of industrial products such as dyes and pesticides, and frequently appear in the aquatic environment due to the discharge of chemical wastewater and the use of chlorinated products. Chlorophenols are a typical class of globally prevalent chlorinated organic pollutants, possessing extremely high biotoxicity and unable to completely degrade in the natural environment. This persistence and bioaccumulation increase the environmental risks after exposure, posing a serious threat to human health and the ecological environment, making chlorophenol pollution a global concern. Therefore, researching efficient and green degradation technologies for chlorophenols is of great significance for protecting human health and aquatic safety. Currently, the main methods for treating chlorophenols in water include biological methods, physical methods, and chemical oxidation-reduction methods. While biological methods are low-cost and large-scale, they have stringent requirements for water quality and environmental conditions, can only treat low-concentration chlorophenol wastewater, and have long cycles and slow degradation rates, limiting their practical application. Physical methods mainly involve phase transfer of chlorophenols in water, generally failing to achieve complete removal, and are often used as pretreatment methods for other approaches. Chemical oxidation-reduction methods require the addition of strong oxidizing or reducing substances to degrade chlorophenols, increasing processing costs and resulting in high costs. Furthermore, the reaction conditions are generally quite harsh.

[0003] Compared to the methods mentioned above, electrocatalytic hydrodechlorination (EHDC) technology is increasingly considered a more promising method for dechlorinating chlorinated organic compounds due to its advantages such as high efficiency, mild reaction conditions, simple operation, and no secondary pollution. The development of high-performance dechlorination electrodes is a key research focus in this field. Among common electrode materials, nickel foam (NF) is widely used as an electrode substrate material due to its large specific surface area, porous structure, and good conductivity. The noble metal palladium (Pd) exhibits good EHDC activity due to its excellent active hydrogen catalytic generation and storage capabilities, making it the most frequently used catalyst layer material for dechlorination electrodes. However, in existing technologies, Pd is directly loaded onto the substrate, such as in Pd / NF electrodes. The large size of Pd particles and limited exposure of active sites result in limited EHDC activity and low dechlorination efficiency. Furthermore, the tendency of Pd particles to aggregate leads to a large amount of Pd used, increasing the electrode preparation cost. Studies have shown that depositing a Pd catalyst layer on an intermediate layer and then loading it onto a substrate can improve the catalytic activity of the electrode, such as Pd / polypyrrole / NF and Pd / graphene-polypyrrole / NF. However, Pd particles still exhibit aggregation, and the dechlorination performance needs further improvement. Summary of the Invention

[0004] The purpose of this invention is to provide a palladium-nickel phosphide copper-foamed nickel composite electrode, its preparation method, and its application, so as to solve the problems mentioned in the background art, such as poor Pd dispersion, low activity, large dosage, and high electrode preparation cost of existing dechlorination electrodes.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a palladium-nickel phosphide copper-foam nickel composite electrode, comprising an NF substrate, a Ni-Cu-P intermediate layer and a Pd catalyst layer, wherein the Ni-Cu-P intermediate layer is disposed on the outer wall of the NF substrate and the Pd catalyst layer is disposed on the outer wall of the Ni-Cu-P intermediate layer.

[0006] The preparation method of palladium-nickel copper phosphide-nickel foam composite electrode includes step one, NF substrate pretreatment; step two, preparation of intermediate layer by constant current deposition to obtain Ni-Cu-P / NF; and step three, preparation of catalyst layer by pulse electrodeposition to obtain Pd / Ni-Cu-P / NF.

[0007] In step one above, the nickel foam is ultrasonically cleaned in 3M hydrochloric acid solution for 10-20 minutes to remove the surface oxide layer, then rinsed with deionized water, ultrasonically cleaned in anhydrous ethanol solution for 5-10 minutes, rinsed with deionized water, and then dried with high-purity nitrogen gas to obtain the NF substrate.

[0008] In step two above, the NF substrate obtained in step one is used as the cathode and the platinum sheet is used as the anode. A Ni-Cu-P intermediate layer is prepared by constant current deposition to obtain Ni-Cu-P / NF.

[0009] In step three above, using the Ni-Cu-P / NF obtained in step two as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode (SCE) as the reference electrode, a Pd catalyst layer is loaded on Ni-Cu-P / NF using pulse electrodeposition to obtain a Pd / Ni-Cu-P / NF composite electrode.

[0010] Preferably, in step one, the size of the nickel foam is 25mm × 25mm × 0.5mm.

[0011] Preferably, in step two, the conditions for preparing the Ni-Cu-P intermediate layer using the constant current deposition method are: a current density of 8-12 mA / cm². 2 Electrolytic deposition time is 10-20 minutes, electrolyte is 40 mL, composition includes NH4Cl (0.2-0.3 M), CuCl2·2H2O (0.01-0.04 M), NiCl2·6H2O (0.15-0.25 M), NaH2PO2·H2O (0.15-0.25 M), maintain the molar ratio of NiCl2·6H2O to NaH2PO2·H2O at 1:1.

[0012] Preferably, in step three, the conditions for preparing the Pd catalyst layer using the pulse electrodeposition method are: 7500 dual-potential steps (high potential 0V vs. SCE, pulse width 0.2s; low potential -1.4 to -1.6V vs. SCE, pulse width 0.2s), 100mL electrolyte, comprising 0.2-1.0mM PdCl2 and 12-60mM NaCl, maintaining a PdCl2 to NaCl molar ratio of 1:60.

[0013] The application of the palladium-nickel phosphide copper-foamed nickel composite electrode includes the following steps: Step 1, constructing the electrode system; Step 2, electrolytic dechlorination; and Step 3, detecting the dechlorination effect.

[0014] In step one above, the anode and cathode chambers of the H-type electrolytic cell are separated by a Nafion-117 proton exchange membrane. A Pd / Ni-Cu-P / NF electrode is used as the working electrode and placed in the cathode chamber; a platinum sheet is used as the counter electrode and placed in the anode chamber; catholyte is injected into the cathode chamber and anolyte is injected into the anode chamber; thus completing the construction of the electrode system.

[0015] In step two above, high-purity nitrogen gas is introduced into the anode and cathode chambers for 10 minutes, and then constant current electrolytic dechlorination is performed. During this period, the cathode chamber is kept magnetically stirred to eliminate the effect of concentration polarization.

[0016] In step three above, 0.8 mL of the catholyte is sampled at a set time, and the concentrations of 2,4-dichlorophenol, 2-chlorophenol, 4-chlorophenol, and phenol are detected by high performance liquid chromatography over time to assess the dechlorination performance of the Pd / Ni-Cu-P / NF electrode.

[0017] Preferably, in step one, the platinum sheet has a size of 25mm × 25mm.

[0018] Preferably, in step one, the catholyte volume is 80 mL, the 2,4-dichlorophenol concentration is 25-150 mg / L, the Na2SO4 concentration is 0.01-0.1 M, and the pH value is 1.5-6.2; the anolyte volume is 80 mL, and the Na2SO4 concentration is 0.05 M.

[0019] Preferably, in step two, the current density is 0.24-0.64 mA / cm². 2 .

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: The Pd / Ni-Cu-P / NF electrode designed in this invention improves the deposition environment of the Pd catalyst layer on a three-dimensional scale through the Ni-Cu-P intermediate layer, enhances the dispersibility of Pd nanoparticles, increases active sites, and reduces the amount of Pd used; in addition, under the action of Ni-Cu-P, the generation of active hydrogen can be accelerated, while increasing the amount of Pd in ​​the Pd catalyst layer. 2+The content of Pd promotes the activation of C-Cl bonds, thereby further improving the dechlorination efficiency and solving the problems of poor Pd dispersion, low activity, large dosage, and high electrode preparation cost of existing dechlorination electrodes. Attached Figure Description

[0021] Figure 1 This is a front sectional view of the composite electrode structure of the present invention;

[0022] Figure 2 This is a flowchart of the preparation method of the present invention;

[0023] Figure 3 This is an application flowchart of the present invention;

[0024] Figure 4 Scanning electron microscope image of Ni-Cu-P / NF;

[0025] Figure 5 Scanning electron microscope image of Pd / Ni-Cu-P / NF;

[0026] Figure 6 For Pd / NF, Pd 4.0 A graph comparing the EHDC performance of / NF and Pd / Ni-Cu-P / NF electrodes on 2,4-dichlorophenol.

[0027] Figure 7 The graph shows the product selectivity and mass balance during the EHDC process of 2,4-dichlorophenol.

[0028] Figure 8 The graph shows the effect of Pd / Ni-Cu-P / NF electrode on 2,4-dichlorophenol in five consecutive EHDC cycles.

[0029] In the figure: 1. NF substrate; 2. Ni-Cu-P interlayer; 3. Pd catalyst layer. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Please see Figure 1 An embodiment of the present invention provides a palladium-nickel phosphide copper-foam nickel composite electrode, comprising an NF substrate 1, a Ni-Cu-P intermediate layer 2 and a Pd catalyst layer 3, wherein the Ni-Cu-P intermediate layer 2 is disposed on the outer wall of the NF substrate 1 and the Pd catalyst layer 3 is disposed on the outer wall of the Ni-Cu-P intermediate layer 2.

[0032] Please see Figure 2 , Figure 4 and Figure 5 The present invention provides an embodiment of a method for preparing a palladium-nickel phosphide copper-foam nickel composite electrode, comprising: step one, NF substrate pretreatment; step two, preparing an intermediate layer to obtain Ni-Cu-P / NF by constant current deposition; and step three, preparing a catalyst layer to obtain Pd / Ni-Cu-P / NF by pulse electrodeposition.

[0033] In step one above, a nickel foam with dimensions of 25mm×25mm×0.5mm is ultrasonically cleaned in 3M hydrochloric acid solution for 15 minutes to remove the surface oxide layer. Then it is rinsed with deionized water, ultrasonically cleaned in anhydrous ethanol solution for 5 minutes, rinsed with deionized water, and then dried with high-purity nitrogen gas to obtain NF substrate 1.

[0034] In step two above, using the NF substrate 1 obtained in step one as the cathode and a platinum sheet as the anode, a Ni-Cu-P intermediate layer 2 is prepared by constant current deposition to obtain Ni-Cu-P / NF; the conditions are: current density of 10 mA / cm². 2 The electrolytic deposition time was 10 minutes, and the electrolyte was 40 mL, consisting of NiCl2·6H2O (0.2 M), CuCl2·2H2O (0.03 M), NaH2PO2·H2O (0.2 M), and NH4Cl (0.25 M).

[0035] In step three above, the Ni-Cu-P / NF obtained in step two is used as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode (SCE) as the reference electrode. A Pd catalyst layer 3 is loaded on the Ni-Cu-P / NF using pulse electrodeposition to obtain a Pd / Ni-Cu-P / NF composite electrode. The conditions are: 7500 dual potential steps (high potential 0V vs. SCE, pulse width 0.2s; low potential -1.5V vs. SCE, pulse width 0.2s), and 100mL of electrolyte consisting of 0.5mM MPdCl2 and 30mM NaCl.

[0036] Please see Figure 3 The present invention provides an embodiment of the application of a palladium-nickel phosphide copper-foam nickel composite electrode, comprising: step one, constructing an electrode system; step two, electrolytic dechlorination; and step three, detecting the dechlorination effect.

[0037] In step one above, the anode and cathode chambers of the H-type electrolytic cell are separated by a Nafion-117 proton exchange membrane. A Pd / Ni-Cu-P / NF electrode is used as the working electrode and placed in the cathode chamber; a 25mm×25mm platinum sheet is used as the counter electrode and placed in the anode chamber; catholyte is injected into the cathode chamber, and anolyte is injected into the anode chamber; thus completing the construction of the electrode system; wherein the catholyte volume is 80mL, the 2,4-dichlorophenol concentration is 50mg / L, the Na2SO4 concentration is 0.05M, and the pH value is 2.3; the anolyte volume is 80mL, and the Na2SO4 concentration is 0.05M.

[0038] In step two above, high-purity nitrogen gas is introduced into the anode and cathode chambers for 10 minutes, followed by constant-current electrolytic dechlorination at a current density of 0.40 mA / cm². 2 During this period, the cathode chamber is kept magnetically stirred to eliminate the effects of concentration polarization;

[0039] In step three above, 0.8 mL of the catholyte is sampled at a set time, and the concentrations of 2,4-dichlorophenol, 2-chlorophenol, 4-chlorophenol, and phenol are detected by high performance liquid chromatography over time to assess the dechlorination performance of the Pd / Ni-Cu-P / NF electrode.

[0040] Comparative Example 1:

[0041] The preparation method of palladium-nickel copper phosphide-nickel foam composite electrode is the same as that in the example, except that in step three, Ni-Cu-P / NF is used as the working electrode instead of NF. Other preparation conditions remain unchanged, and Pd / NF electrodes with the same Pd loading can be prepared.

[0042] Comparative Example 2:

[0043] The preparation method of the palladium-nickel phosphide copper-foamed nickel composite electrode is the same as that in the example, except that in step three, the working electrode is changed from Ni-Cu-P / NF to NF, and the electrolyte composition is changed to 2.0 mM MPdCl2 and 120 mM NaCl. Other preparation conditions remain unchanged, and Pd with a 4-fold Pd loading can be obtained. 4.0 / NF electrode.

[0044] Based on the above, such as Figure 4 As shown, the Ni-Cu-P microstructure exhibits a micro-nano dendritic structure, which can provide abundant porosity and a large specific surface area for depositing the Pd catalyst layer; for example... Figure 5 As shown, on the Pd / Ni-Cu-P / NF electrode, Pd nanoparticles are uniformly loaded on the Ni-Cu-P interlayer. From the morphology, they still maintain the micro-nano dendritic structure, thus providing more reactive sites; for example... Figure 6As shown, the Pd / NF electrode exhibited a dechlorination efficiency of only 52.7% within 150 minutes, while the Pd / Ni-Cu-P / NF electrode showed significantly enhanced dechlorination performance, reaching 100% efficiency after 150 minutes. This indicates that the introduction of the Ni-Cu-P interlayer significantly improved the EHDC activity of the composite electrode. When the Pd loading was increased fourfold, the dechlorination performance also improved significantly, reaching 90% efficiency after 150 minutes, approaching that of the Pd / Ni-Cu-P / NF electrode; however, it was still lower than that of the Pd / Ni-Cu-P / NF electrode. 4.0 Compared to the / NF electrode, the Pd / Ni-Cu-P / NF electrode reduces the amount of Pd by 75% and exhibits higher EHDC performance. Figure 7 The changes in 2,4-dichlorophenol, 2-chlorophenol, 4-chlorophenol, and phenol with reaction time and the sum of all products were shown. The results indicated that as the concentration of 2,4-dichlorophenol decreased, the concentration of phenol increased rapidly. Only trace amounts of 2-chlorophenol were detected in the first 80 minutes of the reaction, while 4-chlorophenol remained undetectable throughout the reaction. After 150 minutes of reaction, the dechlorination efficiency of 2,4-dichlorophenol was 100%, and neither 2-chlorophenol nor 4-chlorophenol was detected. The conversion rate of phenol reached 96.5%, indicating that the Pd / Ni-Cu-P / NF electrode prepared in this invention has good dechlorination performance and high selectivity. Figure 8 As shown, after five cycles of use, the dechlorination efficiency of the Pd / Ni-Cu-P / NF electrode still reached 95.1%, indicating that the electrode has good stability. This high stability can be attributed to the in-situ growth of the Pd and Ni-Cu-P catalyst layers on the conductive substrate, which provides good contact and high mechanical strength between the surface layer, the intermediate layer, and the substrate. The composite electrode designed in this invention uses NF as the substrate, dendritic Ni-Cu-P as the intermediate layer, and Pd nanoparticles as the catalyst layer. Ni-Cu-P can break H-OH bonds, providing a rich hydrogen source for the Pd catalyst, accelerating the generation of active hydrogen, and simultaneously increasing the Pd content in the Pd catalyst layer. 2+ The content of Pd promotes the activation of C-Cl bonds, thereby improving the dechlorination performance of the composite electrode. In addition, the dendritic micro-nano structure of Ni-Cu-P can provide a huge specific surface area for the supported palladium, which is beneficial to increase the dispersibility and active sites of Pd particles, thereby reducing the amount of Pd used. The preparation methods of each step in this invention are all electrochemical methods, which are simple, mild in synthesis conditions, and easy to operate. The Pd / Ni-Cu-P / NF electrode has high dechlorination efficiency and good selectivity for chlorophenol compounds (specifically 2,4-dichlorophenol), with few by-products, which facilitates the subsequent treatment of chlorophenol wastewater. The Pd particles in the catalyst layer of the Pd / Ni-Cu-P / NF electrode have good dispersibility and low Pd usage. Compared with the Pd / NF electrode without the Ni-Cu-P intermediate layer, the amount of Pd used can be reduced by 75% under the premise of the same dechlorination efficiency, which greatly reduces the preparation cost of the electrode.

[0045] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A palladium-nickel phosphide copper-foam nickel composite electrode, comprising an NF substrate (1), a Ni-Cu-P interlayer (2), and a Pd catalyst layer (3), characterized in that: A Ni-Cu-P intermediate layer (2) is provided on the outer wall of the NF substrate (1), and a Pd catalyst layer (3) is provided on the outer wall of the Ni-Cu-P intermediate layer (2).

2. A method for preparing a palladium-nickel phosphide copper-nickel foam composite electrode, comprising: step one, pretreatment of the NF substrate; step two, preparation of an intermediate layer to obtain Ni-Cu-P / NF by constant current deposition; and step three, preparation of a catalyst layer to obtain Pd / Ni-Cu-P / NF by pulse electrodeposition; characterized in that: In step one above, the nickel foam is ultrasonically cleaned in 3M hydrochloric acid solution for 10-20 minutes to remove the surface oxide layer, then rinsed with deionized water, ultrasonically cleaned in anhydrous ethanol solution for 5-10 minutes, rinsed with deionized water, and then dried with high-purity nitrogen gas to obtain NF substrate (1). In step two above, the NF substrate (1) obtained in step one is used as the cathode and the platinum sheet is used as the anode. The Ni-Cu-P intermediate layer (2) is prepared by constant current deposition to obtain Ni-Cu-P / NF. In step three above, the Ni-Cu-P / NF obtained in step two is used as the working electrode, the platinum sheet is used as the counter electrode, and the saturated calomel electrode (SCE) is used as the reference electrode. A Pd catalyst layer is loaded on Ni-Cu-P / NF using pulse electrodeposition (3) to obtain a Pd / Ni-Cu-P / NF composite electrode.

3. The method for preparing the palladium-nickel phosphide copper-foam nickel composite electrode according to claim 2, characterized in that: In step one, the size of the nickel foam is 25mm × 25mm × 0.5mm.

4. The method for preparing the palladium-nickel phosphide copper-foam nickel composite electrode according to claim 2, characterized in that: In step two, the conditions for preparing the Ni-Cu-P intermediate layer (2) using the constant current deposition method are: current density of 8-12 mA / cm². 2 Electrolytic deposition time is 10-20 minutes, electrolyte is 40 mL, composition includes NH4Cl, CuCl2·2H2O, NiCl2·6H2O, NaH2PO2·H2O, maintain the molar ratio of NiCl2·6H2O to NaH2PO2·H2O at 1:

1.

5. The method for preparing the palladium-nickel phosphide copper-foam nickel composite electrode according to claim 2, characterized in that: In step three, the conditions for preparing the Pd catalyst layer (3) by pulse electrodeposition are: 7500 potential steps, 100 mL electrolyte, and the composition includes 0.2-1.0 mM PdCl2 and 12-60 mM NaCl, maintaining a PdCl2 to NaCl molar ratio of 1:

60.

6. The application of a palladium-nickel phosphide copper-foamed nickel composite electrode, comprising step one, constructing the electrode system; step two, electrolytic dechlorination; and step three, detecting the dechlorination effect; characterized in that: In step one above, the anode and cathode chambers of the H-type electrolytic cell are separated by a Nafion-117 proton exchange membrane. A Pd / Ni-Cu-P / NF electrode is used as the working electrode and placed in the cathode chamber; a platinum sheet is used as the counter electrode and placed in the anode chamber; catholyte is injected into the cathode chamber and anolyte is injected into the anode chamber; thus completing the construction of the electrode system. In step two above, high-purity nitrogen gas is introduced into the anode and cathode chambers for 10 minutes, and then constant current electrolytic dechlorination is performed. During this period, the cathode chamber is kept magnetically stirred to eliminate the effect of concentration polarization. In step three above, 0.8 mL of the catholyte is sampled at a set time, and the concentrations of 2,4-dichlorophenol, 2-chlorophenol, 4-chlorophenol, and phenol are detected by high performance liquid chromatography over time to assess the dechlorination performance of the Pd / Ni-Cu-P / NF electrode.

7. The application of the palladium-nickel phosphide copper-foam nickel composite electrode according to claim 6, characterized in that: In step one, the platinum sheet has a size of 25mm × 25mm.

8. The application of the palladium-nickel phosphide copper-foam nickel composite electrode according to claim 6, characterized in that: In step one, the catholyte volume is 80 mL, the 2,4-dichlorophenol concentration is 25-150 mg / L, the Na2SO4 concentration is 0.01-0.1 M, and the pH value is 1.5-6.2; the anolyte volume is 80 mL, and the Na2SO4 concentration is 0.05 M.

9. The application of the palladium-nickel phosphide copper-foam nickel composite electrode according to claim 6, characterized in that: In step two, the current density is 0.24-0.64 mA / cm². 2 .

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