CN114540873B - A kind of palladium/γ-manganese dioxide/foam nickel composite electrode and preparation method and application thereof - Google Patents

Abstract

The invention discloses a palladium/γ-manganese dioxide/foamed nickel composite electrode, a preparation method and application thereof, and belongs to the technical field of electrochemical water treatment. A MnO ₂ intermediate layer of γ-crystal form is formed on the nickel surface, and is prepared by chemically depositing Pd nanoparticles; wherein, the loading amount of the γ-MnO ₂ intermediate layer on the nickel foam is 0.30-0.35 mg/cm ² ; The deposition amount of the particles was 0.68-0.72 mg/cm ² . The present invention also provides a preparation method of the above-mentioned composite electrode. The Pd/γ-MnO ₂ /Ni foam composite electrode prepared by the invention has large specific surface area, high catalytic activity and good cycle stability, can electrocatalytically treat chlorophenol pollutants in wastewater quickly and efficiently, and has broad application prospects.

Description

A kind of palladium/γ-manganese dioxide/foam nickel composite electrode and preparation method and application thereof

technical field

The invention belongs to the technical field of electrochemical water treatment, and in particular, the invention relates to a Pd/γ-MnO ₂ /Nifoam composite electrode and a preparation method and application thereof.

Background technique

Chlorinated aromatic compounds discharged from industrial and agricultural production activities are widespread pollutants in soil and groundwater. They are highly toxic and persistent, and are difficult to degrade in the natural environment. Electrocatalytic reduction dechlorination technology has the advantages of high reactivity, mild reaction conditions, convenient operation, and no secondary pollution, and can be used to degrade and remove chlorinated aromatic pollutants.

The direct electrochemical dechlorination of inert materials requires high overpotential and high energy consumption. Therefore, it is of great economic value in electrode preparation to find materials that can catalyze the dehalogenation reaction efficiently. The transition metal palladium has low hydrogen evolution potential and high atomic hydrogen adsorption and storage capacity, and has catalytic properties to decompose hydrogen into active hydrogen atoms, and is considered to be an ideal catalyst for electrochemical reductive dehalogenation. Although the electrode prepared by electrodepositing palladium directly on the substrate has high dehalogenation efficiency, it has the problems of low current efficiency, large loading and high cost. Therefore, there is an urgent need to develop high-efficiency modified composite electrodes with small catalyst loading, high dispersion, low aggregation, and high catalytic activity and stability.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a Pd/γ-MnO ₂ /Ni foam composite electrode and its preparation method and application. The composite electrode has the advantages of high catalytic activity, large specific surface area, long service life and low cost. The intermediate layer contained in the MnO 2 is γ-crystal MnO ₂ with a regular hexagonal structure, which can provide more active sites and is more favorable for the adsorption and decomposition of pollutants.

The technical scheme of the present invention is as follows:

The embodiment of the present invention provides a Pd/γ-MnO ₂ /Ni foam composite electrode. The composite electrode is based on foamed nickel. First, a γ-MnO ₂ intermediate layer is formed on the surface of the foamed nickel through a hydrothermal reaction, and then chemically prepared by depositing Pd nanoparticles.

In some embodiments, the loading amount of the γ-MnO ₂ intermediate layer on the nickel foam is 0.30-0.35 mg/cm ² ; the deposition amount of Pd nanoparticles is 0.68-0.72 mg/cm ² .

The Pd/γ-MnO ₂ /Ni foam composite electrode provided by the embodiment of the present invention has the following advantages: the Pd/γ-MnO ₂ /Ni foam composite electrode provided by the embodiment of the present invention has a large specific surface area, high catalytic activity, and good cycle stability , which can quickly and efficiently treat chlorophenol pollutants in wastewater; and the MnO ₂ intermediate layer in the composite electrode is γ-crystal MnO ₂ with a regular hexagonal structure, which can provide more active sites, It is more favorable for the adsorption and decomposition of pollutants, and only a small amount of γ-MnO ₂ can be loaded to achieve a good catalytic effect; in addition, when the γ-crystalline MnO ₂ is loaded on the nickel foam substrate, the roughness of the electrode surface increases significantly , the specific surface area is increased, which can improve the problem that metal palladium is prone to agglomeration when chemical deposition is performed directly on the surface of the foamed nickel substrate.

The embodiment of the present invention also provides a preparation method of a Pd/γ-MnO ₂ /Ni foam composite electrode, comprising the following steps:

(1) Pretreatment of nickel foam: First, ultrasonicate the nickel foam with acetone for 15 to 20 minutes to remove organic matter on the surface; then ultrasonicate it with 10% hydrochloric acid for 10 to 15 minutes to remove the oxide layer on the surface; finally, rinse it repeatedly with distilled water for 2 to 5 times. after drying in the air to obtain pretreated nickel foam;

(2) Preparation of γ-MnO ₂ intermediate layer: MnSO ₄ and KMnO ₄ are dissolved in water to prepare reaction solution A; then the pretreated nickel foam is placed in reaction solution A to carry out hydrothermal reaction; the reaction ends After cooling to room temperature naturally, the reacted nickel foam was taken out, washed with ethanol and deionized water in turn, and dried to obtain a γ-MnO ₂ /Ni foam electrode;

(3) Electroless deposition of Pd nanoparticles: Dissolve PdCl ₂ and NaCl in water to prepare solution B; then place the γ-MnO ₂ /Ni foam electrode obtained in step (2) in solution B and shake on a constant temperature shaker , until the color of solution B changed from yellow to colorless, and the Pd/γ-MnO ₂ /Ni foam composite electrode was obtained.

In some embodiments, the molar ratio of MnSO ₄ and KMnO ₄ is 3:2; the concentration of MnSO ₄ in the reaction solution A is 0.5-2.0 mM, preferably 1.5 mM.

In some embodiments, the temperature of the hydrothermal reaction is 120-140° C., preferably 140° C.; the reaction time is 20-24 h, preferably 24 h.

In some embodiments, the molar ratio of PdCl ₂ and NaCl is 1:3; the concentration of PdCl ₂ in solution B is 4-12 mM.

In some embodiments, the temperature of shaking in step (3) is 30-35°C, preferably 30°C.

The preparation method of the Pd/γ-MnO ₂ /Ni foam composite electrode in the embodiment of the present invention is generally divided into two steps: the first step is to use hydrothermal reaction to prepare a γ-MnO ₂ intermediate layer on the pretreated nickel foam The second step is to use chemical deposition method to load Pd nanoparticles on the surface of γ-MnO _2. Compared with the Pd/Ni foam electrode with the same dechlorination effect, the preparation method of the present invention can save about 75% of the precious metal palladium The preparation method has the advantages of simple operation, mild synthesis conditions and convenient management.

The embodiment of the present invention also provides a method for electrocatalytic reduction and dechlorination treatment of chlorinated organic matter in water, comprising the following steps: using the above Pd/γ-MnO ₂ /Ni foam composite electrode as a working electrode, a Pt sheet as a counter electrode, saturated The calomel electrode was used as the reference electrode. In the H-type reactor, the chlorinated organic pollutants were treated by electroreduction and dechlorination under the galvanostatic mode. The anolyte and catholyte were Na ₂ SO ₄ solution.

In some embodiments, the concentration of the Na ₂ SO ₄ solution is 25-50 mM, preferably 50 mM.

In some embodiments, the galvanostatic range is -8 to -10 mA, preferably 10 mA.

Compared with the prior art, the technical solution provided by the present invention has the following advantages:

1. The Pd/γ-MnO ₂ /Ni foam composite electrode of the present invention has the advantages of high catalytic activity, large specific surface area, long service life, good cycle stability, low cost, etc., and can electrocatalytically treat chlorophenols in wastewater quickly and efficiently. It can effectively alleviate the electrode poisoning problem caused by anions such as Cl ^- , HCO ₃ ^- , NO ₃ ^- , etc., and can still have a good dechlorination effect under complex water quality conditions, and has a wide range of social and economic benefits.

2. The MnO ₂ intermediate layer in the Pd/γ-MnO ₂ /Ni foam composite electrode of the present invention is MnO ₂ in the γ crystal form with a regular hexagonal structure, which can provide more active sites and can adsorb and decompose pollutants. More advantageously, only a small amount of γ-MnO ₂ can be loaded to achieve a better catalytic effect, which saves the cost of wastewater treatment.

3. The γ-MnO ₂ intermediate layer in the Pd/γ-MnO ₂ /Ni foam composite electrode of the present invention has a nano-sheet-like microstructure, and is vertically arranged on the foamed nickel substrate. The transfer and diffusion of electrons/protons reduces the overpotential and facilitates the electrocatalytic reduction reaction; in addition, when the nickel foam is loaded with γ-MnO ₂ , the surface roughness of the nickel foam increases and the specific surface area increases, which can improve the performance of the foam. The problem of metal palladium agglomeration easily occurs when the nickel surface is directly chemically deposited.

4. The preparation method of the present invention has simple process, mild synthesis conditions, easy operation and convenient management; in addition, compared with the Pd/Ni foam electrode with the same dechlorination effect, the preparation method of the present invention can save about 75% of The precious metal palladium loading greatly reduces the cost of dechlorination of chlorinated organic pollutants.

Description of drawings

Figure 1 is the X-ray diffraction pattern of different electrodes, wherein (a) is the X-ray diffraction pattern of the Pd/Ni foam electrode prepared in Comparative Example 1; (b) is the γ-MnO ₂ prepared in Example 1 of the present invention The X-ray diffraction pattern of the /Ni foam electrode; (c) is the X-ray diffraction pattern of the Pd/γ-MnO ₂ /Ni foam composite electrode prepared in Example 1 of the present invention.

Figure 2 is the X-ray diffraction pattern of the γ-MnO ₂ powder prepared by the hydrothermal method.

Fig. 3 is the scanning electron microscope image of different electrodes, wherein (a) is the scanning electron microscope image of the pretreated Ni foam in Example 1 of the present invention; (b) is the scanning electron microscope image of the Pd/Ni foam electrode prepared in Comparative Example 1 Electron microscope image; (c) is the scanning electron microscope image of the γ-MnO ₂ /Ni foam electrode obtained in Example 1 of the present invention; (d) is the scanning electron microscope image of the Pd/γ-MnO ₂ /Nifoam composite electrode obtained in Example 1 of the present invention Electron micrograph.

4 is a scanning electron microscope image of the porous nanostructure on the surface of the γ-MnO ₂ /Ni foam electrode obtained in Example 1 of the present invention.

5 is a schematic structural diagram of the electrocatalytic reduction and dechlorination device of the present invention, in which 1 is an electrochemical workstation; 2 is a reference electrode; 3 is a working electrode Pd/γ-MnO ₂ /Ni foam (cathode); 4 is a pair of Electrode Pt (anode); 5 is a magnetic rotor; 6 is a cation exchange membrane.

Figure 6 is the electrocatalytic treatment of 2,4,6-trichlorophenol-containing wastewater with Pd/γ-MnO ₂ /Ni foam composite electrodes with different γ-MnO ₂ loadings prepared in Examples 1-4 of the present invention after 2h Dechlorination efficiency diagram.

Figure 7 is the Pd/γ-MnO ₂ /Ni foam composite electrode prepared in Example 1 of the present invention and the Pd/Ni foam electrodes with different palladium loadings prepared in Comparative Example 1 and Comparative Example 2 after electrocatalytic treatment for 2h Dechlorination effect diagram of wastewater containing o-chlorophenol.

FIG. 8 is a graph showing the relationship between the times of use and the dechlorination effect of the Pd/γ-MnO ₂ /Ni foam composite electrode prepared in Example 1 of the present invention.

Figure 9 shows the dechlorination of the Pd/γ-MnO ₂ /Ni foam composite electrode prepared in Example 2 of the present invention and the Pd/Ni foam electrode prepared in Comparative Example 2 after electrocatalytic treatment for 4 hours in the presence of different anions renderings.

Detailed ways

The embodiments of the present invention are described in detail below, and the embodiments are exemplary and intended to explain the present invention, but should not be construed as a limitation of the present invention.

The embodiment of the present invention provides a Pd/γ-MnO ₂ /Ni foam composite electrode. The composite electrode is based on foamed nickel. First, a γ-MnO ₂ intermediate layer is formed on the surface of the foamed nickel through a hydrothermal reaction, and then chemically prepared by depositing Pd nanoparticles.

In some embodiments, the loading amount of the γ-MnO ₂ intermediate layer on the nickel foam is 0.30-0.35 mg/cm ² ; the deposition amount of Pd nanoparticles is 0.68-0.72 mg/cm ² .

The Pd/γ-MnO ₂ /Ni foam composite electrode provided by the embodiment of the present invention has the following advantages: the Pd/γ-MnO ₂ /Ni foam composite electrode provided by the embodiment of the present invention has a large specific surface area, high catalytic activity, and good cycle stability , which can electrocatalytically treat chlorophenol pollutants in wastewater quickly and efficiently; and the γ-MnO ₂ in the composite electrode has a regular hexagonal structure, which can provide more active sites and is more favorable for the adsorption and decomposition of pollutants. , only a small amount of γ-MnO ₂ can be loaded to achieve good catalytic effect.

The embodiment of the present invention also provides a preparation method of a Pd/γ-MnO ₂ /Ni foam composite electrode, comprising the following steps:

(1) Pretreatment of nickel foam: First, ultrasonicate the nickel foam with acetone for 15 to 20 minutes to remove organic matter on the surface; then ultrasonicate it with 10% hydrochloric acid for 10 to 15 minutes to remove the oxide layer on the surface; finally, rinse it repeatedly with distilled water for 2 to 5 times. after drying in the air to obtain pretreated nickel foam;

(2) Preparation of γ-MnO ₂ intermediate layer: MnSO ₄ and KMnO ₄ are dissolved in water to prepare reaction solution A; then the pretreated nickel foam is placed in reaction solution A to carry out hydrothermal reaction; the reaction ends After cooling to room temperature naturally, the reacted nickel foam was taken out, washed with ethanol and deionized water in turn, and dried to obtain a γ-MnO ₂ /Ni foam electrode;

(3) Electroless deposition of Pd nanoparticles: Dissolve PdCl ₂ and NaCl in water to prepare solution B; then place the γ-MnO ₂ /Ni foam electrode obtained in step (2) in solution B and shake on a constant temperature shaker , until the color of solution B changed from yellow to colorless, and the Pd/γ-MnO ₂ /Ni foam composite electrode was obtained.

In some embodiments, the molar ratio of MnSO ₄ and KMnO ₄ is 3:2; the concentration of MnSO ₄ in the reaction solution A is 0.5-2.0 mM, preferably 1.5 mM.

In some embodiments, the temperature of the hydrothermal reaction is 120-140° C., preferably 140° C.; the reaction time is 20-24 h, preferably 24 h.

In some embodiments, the molar ratio of PdCl ₂ and NaCl is 1:3; the concentration of PdCl ₂ in solution B is 4-12 mM.

In some embodiments, the temperature of shaking in step (3) is 30-35°C, preferably 30°C.

The preparation method of the Pd/γ-MnO ₂ /Ni foam composite electrode of the present invention firstly prepares a γ-MnO ₂ intermediate layer on a nickel foam substrate by hydrothermal reaction, and then chemically deposits Pd nanoparticles to prepare Pd/γ-MnO ₂ /Ni foam composite electrode, the preparation method is simple, the synthesis conditions are mild, and compared with the Pd/Ni foam electrode with the same dechlorination effect, the preparation method of the present invention can save about 75% of the precious metal palladium loading and waste water processing costs.

The embodiment of the present invention also provides a method for electrocatalytic reduction and dechlorination treatment of chlorinated organic matter in water, comprising the following steps: using the above Pd/γ-MnO ₂ /Ni foam composite electrode as a working electrode (cathode), and a Pt sheet as a counter electrode Electrode (anode), saturated calomel electrode as reference electrode, in H-type reactor, electroreduction dechlorination treatment of chlorinated organic pollutants in galvanostatic mode, anolyte and catholyte using Na ₂ SO ₄ solution.

In some embodiments, the concentration of the Na ₂ SO ₄ solution is 25-50 mM, preferably 50 mM.

In some embodiments, the galvanostatic range is -8 to -10 mA, preferably 10 mA.

The present invention will be described in further detail below through specific embodiments.

Example 1

This embodiment provides a Pd/γ-MnO ₂ /Ni foam composite electrode, which uses nickel foam as a matrix, firstly forms a γ-MnO ₂ intermediate layer on the surface of the nickel foam through hydrothermal reaction, and then chemically deposits Pd nanoparticles In the obtained Pd/γ-MnO ₂ /Ni foam composite electrode, the loading amount of the γ-MnO ₂ intermediate layer was 0.33 mg/cm ² , and the deposition amount of Pd nanoparticles was 0.7 mg/cm ² .

The preparation method of the Pd/γ-MnO ₂ /Ni foam composite electrode includes the following steps:

(1) Pretreatment of nickel foam: First, ultrasonicate the nickel foam (30mm×20mm) with acetone for 15 minutes to remove the surface organics; then ultrasonicate with 10% hydrochloric acid for 15 minutes to remove the oxide layer on the surface; Finally, after repeated cleaning with distilled water for 3 times , dried in the air to obtain pretreated nickel foam, and the scanning electron microscope image of the pretreated nickel foam is shown in Figure 3 (a);

(2) Preparation of γ-MnO ₂ intermediate layer: MnSO ₄ and KMnO ₄ were dissolved in water at a molar ratio of 3:2, wherein the concentration of MnSO ₄ in water was 1.5 mM, and the reaction solution A was prepared; Liquid A is put into the reaction kettle, and the pretreated nickel foam is placed in the reaction liquid A, and the hydrothermal reaction is carried out. The temperature of the hydrothermal reaction is 140 ° C, and the reaction time is 24 h; after the reaction is completed, the temperature is naturally cooled to room temperature. , take out the reacted nickel foam, wash it with ethanol and deionized water in turn, and dry it in the air to obtain a γ-MnO ₂ /Ni foam electrode;

The X-ray diffraction pattern of the obtained γ-MnO ₂ /Ni foam electrode is shown in Fig. 1(b), and the scanning electron microscope image is shown in Fig. 3(c). It can be seen that when the surface of the nickel foam substrate is loaded with γ- After MnO ₂ , the surface roughness increases significantly, which increases the specific surface area; in addition, Fig. 4 is a partial enlarged view of (c) in Fig. 3, it can be observed that the surface of the γ-MnO ₂ /Ni foam electrode is a porous nanostructure, Among them, the nano-sheet γ-MnO ₂ is vertically arranged on the surface of the foamed nickel substrate, and the nano-sheet γ-MnO ₂ has micropores of 50-300 nm between the sheets, which form a nanoporous structure film. The bubble adhesion is greatly reduced, and the highly reactive edges can be exposed to the electrolyte, thereby accelerating the transfer and diffusion of electrons/protons, reducing the overpotential, and facilitating the electrocatalytic reduction reaction.

(3) Chemical deposition of Pd nanoparticles: Dissolve PdCl ₂ and NaCl in water at a molar ratio of 1:3, wherein the concentration of PdCl ₂ in water is 4 mM, and the concentration of NaCl in water is 12 mM to prepare solution B; The γ-MnO ₂ /Ni foam electrode obtained in step (2) was placed in 20 mL of solution B, placed in a sealed conical The color changed from yellow to colorless, and the Pd/γ-MnO ₂ /Ni foam composite electrode was prepared.

In the final Pd/γ-MnO ₂ /Ni foam composite electrode, the loading amount of the γ-MnO ₂ intermediate layer was 0.33 mg/cm ² , and the deposition amount of Pd nanoparticles was 0.7 mg/cm ² .

The X-ray diffraction pattern of the obtained Pd/γ-MnO ₂ /Ni foam composite electrode is shown in Fig. 1(c), and the scanning electron microscope image is shown in Fig. 3(d). Fig. 2 is the X-ray diffractogram of the γ- _MnO powder obtained by carrying out the hydrothermal reaction under the same hydrothermal conditions as in step (2) of the present embodiment, we can see from the figure that the embodiment of the present invention Using MnSO ₄ and KMnO ₄ as the reaction raw materials, by controlling the ratio of the reaction raw materials and the hydrothermal reaction conditions, the prepared MnO ₂ is a γ-crystal MnO ₂ nanosheet with a regular hexagonal structure, which can provide more active sites It is more favorable for the adsorption and decomposition of pollutants.

Example 2

In this example, the preparation process of the Pd/γ-MnO ₂ /Ni foam composite electrode is the same as that in Example 1, the difference is: "the concentration of MnSO ₄ in water in step (2) is 0.5mM", the final prepared In the Pd/γ-MnO ₂ /Ni foam composite electrode, the loading amount of the γ-MnO ₂ intermediate layer was 0.15 mg/cm ² , and the deposition amount of Pd nanoparticles was 0.7 mg/cm ² .

Example 3

In this example, the preparation process of the Pd/γ-MnO ₂ /Ni foam composite electrode is the same as that in Example 1, the difference is: "the concentration of MnSO ₄ in water in step (2) is 1 mM", the final Pd In the /γ-MnO ₂ /Ni foam composite electrode, the loading amount of the γ-MnO ₂ intermediate layer was 0.21 mg/cm ² , and the deposition amount of Pd nanoparticles was 0.7 mg/cm ² .

Example 4

In this example, the preparation process of the Pd/γ-MnO ₂ /Ni foam composite electrode is the same as that in Example 1, the difference is: "the concentration of MnSO ₄ in water in step (2) is 2mM", the final Pd In the /γ-MnO ₂ /Ni foam composite electrode, the loading amount of the γ-MnO ₂ intermediate layer was 0.42 mg/cm ² , and the deposition amount of Pd nanoparticles was 0.7 mg/cm ² .

Comparative Example 1

This comparative example provides a Pd/Ni foam electrode, and the preparation method of the Pd/Ni foam electrode includes the following steps:

(1) Pretreatment of nickel foam: First, ultrasonicate the nickel foam (30mm×20mm) with acetone for 15 minutes to remove the surface organics; then ultrasonicate with 10% hydrochloric acid for 15 minutes to remove the oxide layer on the surface; Finally, after repeated cleaning with distilled water for 3 times , dried in the air to obtain pretreated nickel foam;

(2) Chemical deposition of Pd nanoparticles: Dissolve PdCl ₂ and NaCl in water at a molar ratio of 1:3, wherein the concentration of PdCl ₂ is 4 mM, and the concentration of NaCl is 12 mM to prepare solution B; The nickel foam was placed in 20 mL of solution B, placed in a sealed conical flask, and placed in a constant temperature shaker with a temperature of 30 °C to shake until the color of solution B changed from yellow to colorless, and Pd/ Ni foam electrodes.

In the obtained Pd/Ni foam electrode, the loading amount of Pd was 0.7 mg/cm ² .

The X-ray diffraction pattern of the obtained Pd/Ni foam electrode is shown in Fig. 1(a), and the scanning electron microscope image is shown in Fig. 3(b). By comparing the SEM images of (b) Pd/Ni foam electrode in Figure 3 and (d) Pd/γ-MnO ₂ /Ni foam composite electrode in Figure 3, it can be found that Pd metal is directly deposited on the foam by simply using chemical deposition method. On the nickel substrate, the palladium metal on the surface of the prepared Pd/Nifoam electrode is easy to agglomerate and form larger particles; while the γ-MnO ₂ intermediate layer is loaded on the foamed nickel substrate, and then Pd metal is chemically deposited. The Pd/γ-MnO ₂ /Ni foam composite electrode can be obtained, which can make the Pd particles on the electrode surface more dispersed, and the particle size is obviously reduced.

Comparative Example 2

This comparative example provides a Pd/Ni foam electrode, and the preparation method of the Pd/Ni foam electrode includes the following steps:

(1) Pretreatment of nickel foam: First, ultrasonicate the nickel foam (30mm×20mm) with acetone for 15 minutes to remove the surface organics; then ultrasonicate with 10% hydrochloric acid for 15 minutes to remove the oxide layer on the surface; Finally, after repeated cleaning with distilled water for 3 times , dried in the air to obtain pretreated nickel foam;

(2) Chemical deposition of Pd nanoparticles: Dissolve PdCl ₂ and NaCl in water at a molar ratio of 1:3, wherein the concentration of PdCl ₂ is 16 mM, and the concentration of NaCl is 48 mM to prepare solution B; The nickel foam was placed in 20 mL of solution B, placed in a sealed conical flask, and placed in a constant temperature shaker with a temperature of 30 °C to shake until the color of solution B changed from yellow to colorless, and Pd/ Ni foam electrodes.

In the obtained Pd/Ni foam electrode, the loading amount of Pd was 2.8 mg/cm ² .

Application example 1

The Pd/γ-MnO ₂ /Ni foam composite electrodes with different γ-MnO ₂ loadings prepared in Examples 1-4 of the present invention were used as the working electrode, the platinum sheet was used as the counter electrode, and the saturated calomel electrode was used as the reference. Electrode, the cathode and anode compartments are separated by a cation exchange membrane, the electrolyte is a 50mM _Na2SO4 solution, and 100mL wastewater containing 25mg/L 2,4,6 _- trichlorophenol is treated by electroreductive dechlorination at a current of -10mA , the processing time is 2h.

As shown in Figure 6, the electrocatalytic treatment of 2,4,6-trichlorophenol-containing wastewater by Pd/γ-MnO ₂ /Nifoam composite electrodes with different γ-MnO ₂ loadings prepared in Examples 1-4 of the present invention Dechlorination efficiency diagram after 2h, from the figure we can see that after electrocatalysis of 2,4,6-trichlorophenol-containing wastewater for 2h, the loading of γ- _MnO2 is 0.33 mg/ ^cm2 of Pd/γ -MnO ₂ /Ni foam composite electrode has the highest dechlorination efficiency of 2,4,6-trichlorophenol, which can reach 98.5%.

Application example 2

The Pd/γ-MnO ₂ /Ni foam composite electrode prepared in Example 1 of the present invention and the Pd/Ni foam electrodes prepared in Comparative Example 1 and Comparative Example 2 were used as the working electrode, the platinum sheet was used as the counter electrode, and the saturated Gan The mercury electrode was used as the reference electrode, the cathode and anode compartments were separated by a cation exchange membrane, the electrolyte was a 50mM _Na2SO4 solution, and 100mL of wastewater containing 50mg/L o-chlorophenol was treated by electroreduction and dechlorination at a current of -10mA _. The processing time is 2h.

Figure 7 shows the Pd/γ-MnO ₂ /Ni foam composite electrode prepared in Example 1 of the present invention and the Pd/Ni foam electrodes with different Pd loadings prepared in Comparative Example 1 and Comparative Example 2 after electrocatalytic treatment for 2h. Dechlorination effect diagram of o-chlorophenol wastewater, wherein Pd(0.7)/γ-MnO ₂ /Ni is the Pd/γ-MnO ₂ /Ni foam composite electrode prepared in Example 1 of the present invention, and its Pd loading is 0.7 mg/cm ² ; Pd(0.7)/Ni is the Pd/Ni foam electrode prepared in Comparative Example 1, and its Pd loading is 0.7 mg/cm ² ; Pd(2.8)/Ni is the Pd/Ni foam electrode prepared in Comparative Example 2 The prepared Pd/Ni foam electrode had a Pd loading of 2.8 mg/cm ² . It can be seen from the figure that after electrocatalysis for 2 hours, the degradation rate of o-chlorophenol by the Pd/γ-MnO ₂ /Ni foam composite electrode obtained in Example 1 is about 98.5%, compared with the Pd/Ni foam electrode with the same Pd loading. , the catalytic activity is significantly improved, and the dechlorination effect is significantly improved; in addition, the dechlorination effect of the Pd(2.8)/Ni foam electrode and the Pd(0.7)/γ-MnO ₂ /Ni foam composite electrode in Figure 7 can be seen. The dechlorination effect of the two is similar, but the Pd/γ-MnO ₂ /Ni foam composite electrode only needs to use a smaller amount of Pd metal to achieve the same dechlorination effect as the Pd/Ni foam electrode, saving about 75% precious metal Pd.

8 is a graph showing the relationship between the number of times of use and the dechlorination effect of the Pd/γ-MnO ₂ /Ni foam composite electrode prepared in Example 1 of the present invention. The /γ-MnO ₂ /Ni foam composite electrode was used for electrocatalytic reduction and dechlorination of wastewater containing o-chlorophenol, and the removal rate of o-chlorophenol in wastewater was still more than 95% after repeated use for the sixth time, which proved that the composite electrode The electrode has high catalytic activity and good stability.

Application example 3

The Pd/γ-MnO ₂ /Ni foam composite electrode prepared in Example 2 and the Pd/Nifoam electrode prepared in Comparative Example 2 were used as the working electrode, the platinum sheet was used as the counter electrode, and the saturated calomel electrode was used as the reference electrode. , the cathode and anode compartments are separated by cation exchange membrane, the electrolyte adopts 50mM Na ₂ SO ₄ solution, and under the current of -10mA, 10mM Cl ^- , HCO ₃ ^- , NO ₃ ^- and other different anions ( Electroreduction dechlorination was carried out by adding 10 mM Na ₂ SO ₄ as blank control) 50 mg/L o-chlorophenol solution, and the treatment time was 4 h.

Figure 9 shows the dechlorination of the Pd/γ-MnO ₂ /Ni foam composite electrode prepared in Example 2 of the present invention and the Pd/Ni foam electrode prepared in Comparative Example 2 after electrocatalytic treatment for 4 hours in the presence of different anions It can be seen from the figure that the presence of different anions such as Cl ^- , HCO ₃ ^- , NO ₃ ^- has a negative impact on the electrocatalytic degradation of o-chlorophenol; Compared with the electrode, the Pd/γ-MnO ₂ /Ni foam composite electrode prepared in Example 2 of the present invention is significantly less affected by anions, and the electrode catalytic activity is higher.

In this disclosure, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples" and the like mean a specific feature, structure, material, or description described in connection with the embodiment or example. Features are included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, those skilled in the art may combine and combine the different embodiments or examples described in this specification, as well as the features of the different embodiments or examples, without conflicting each other.

Although the embodiments of the present invention have been shown and described above, it should be understood that the above-mentioned embodiments are exemplary and should not be construed as limiting the present invention. Embodiments are subject to variations, modifications, substitutions and variations.

Claims (10)

1. a Pd/γ-MnO ₂ /Ni foam composite electrode, is characterized in that, the composite electrode is based on nickel foam, first by hydrothermal reaction on the surface of nickel foam to form γ-MnO ₂ intermediate layer, then by It is prepared by chemically depositing Pd nanoparticles; the γ-MnO ₂ intermediate layer is a γ-crystal MnO ₂ with a regular hexagonal structure, and the γ-MnO ₂ intermediate layer has a nano-sheet-like microstructure and is vertical Arranged on nickel foam, there are micropores between the sheets. 2. A Pd/γ-MnO ₂ /Ni foam composite electrode according to claim 1, wherein the loading of the γ-MnO ₂ intermediate layer on the nickel foam is 0.30-0.35 mg/cm ² ; The deposition amount of the Pd nanoparticles is 0.68-0.72 mg/cm ² . 3. the preparation method of a kind of Pd/γ-MnO ₂ /Ni foam composite electrode described in claim 1 or 2, is characterized in that, comprises the following steps: (1) Pretreatment of nickel foam; (2) Dissolve MnSO ₄ and KMnO ₄ in water to prepare reaction solution A; then place the pretreated nickel foam in reaction solution A for hydrothermal reaction; finally wash the reaction with ethanol and deionized water in sequence The resulting nickel foam is dried to obtain a γ-MnO ₂ /Ni foam electrode; (3) Dissolve PdCl ₂ and NaCl in water to prepare solution B; then place the γ-MnO ₂ /Ni foam electrode in solution B and shake on a constant temperature shaker until the color of solution B changes from yellow to colorless , the Pd/γ-MnO ₂ /Ni foam composite electrode was obtained. 4. The preparation method of a Pd/γ-MnO ₂ /Ni foam composite electrode according to claim 3, characterized in that, the step of the pretreatment is: ultrasonicating the nickel foam with acetone for 15-20 min first; Then ultrasonicated with 10% hydrochloric acid for 10-15 min; finally washed with distilled water, and dried to obtain pretreated nickel foam. 5 . The method for preparing a Pd/γ-MnO ₂ /Ni foam composite electrode according to claim 3 , wherein the molar ratio of the MnSO ₄ to the KMnO ₄ is 3:2. 6 . 6. The preparation method of a Pd/γ-MnO ₂ /Ni foam composite electrode according to claim 3, wherein the temperature of the hydrothermal reaction is 120-140 °C; the reaction time is 20-24 h . 7 . The method for preparing a Pd/γ-MnO ₂ /Ni foam composite electrode according to claim 3 , wherein the molar ratio of the PdCl ₂ to the NaCl is 1:3. 8 . 8. A method for electrocatalytic reduction and dechlorination treatment of chlorinated organic matter in water, comprising the steps of: using the Pd/γ-MnO ₂ /Ni foam composite electrode according to claim 1 or 2 as a working electrode, a Pt The sheet was used as the counter electrode, and the saturated calomel electrode was used as the reference electrode. In the H-type reactor, the chlorinated organic pollutants were treated by electroreduction and dechlorination under the galvanostatic mode, and _Na2SO4 solution was used as the anolyte and catholyte _. 9 . The method for treating chlorinated organics in water by electrocatalytic reduction and dechlorination according to claim 8 , wherein the concentration of the Na ₂ SO ₄ solution is 25-50 mM. 10 . 10. The method for treating chlorinated organics in water by electrocatalytic reduction and dechlorination according to claim 8, wherein the constant current range is -8～-10 mA.

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