CN114540873A - Palladium/gamma-manganese dioxide/foamed nickel composite electrode and preparation method and application thereof - Google Patents

Palladium/gamma-manganese dioxide/foamed nickel composite electrode and preparation method and application thereof Download PDF

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CN114540873A
CN114540873A CN202210437901.1A CN202210437901A CN114540873A CN 114540873 A CN114540873 A CN 114540873A CN 202210437901 A CN202210437901 A CN 202210437901A CN 114540873 A CN114540873 A CN 114540873A
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陈吕军
徐冉云
李菲菲
田金平
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Tsinghua University
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Abstract

The invention discloses a palladium/gamma-manganese dioxide/foamed nickel composite electrode and a preparation method and application thereof, belonging to the technical field of electrochemical water treatment2An intermediate layer prepared by chemical deposition of Pd nanoparticles; wherein, gamma-MnO2The loading capacity of the middle layer on the foamed nickel is 0.30-0.35 mg/cm2(ii) a The deposition amount of the Pd nano-particles is 0.68-0.72 mg/cm2. The invention also provides a preparation method of the composite electrode. Book (I)Pd/gamma-MnO prepared by invention2the/Ni foam composite electrode has the advantages of large specific surface area, high catalytic activity and good circulation stability, can quickly and efficiently electro-catalytically treat chlorophenol pollutants in wastewater, and has wide application prospect.

Description

Palladium/gamma-manganese dioxide/foamed nickel composite electrode and preparation method and application thereof
Technical Field
The invention belongs to electrochemistryThe invention belongs to the technical field of water treatment, and particularly relates to Pd/gamma-MnO2a/Ni foam composite electrode and a preparation method and application thereof.
Background
Chlorinated aromatic compounds discharged in industrial and agricultural production activities are pollutants widely existing in soil and underground water, have the characteristics of high toxicity and high durability, and are difficult to degrade in natural environment. The electrocatalytic reduction dechlorination technology has the advantages of high reaction activity, mild reaction conditions, convenient operation, no secondary pollution and the like, and can be used for degrading and removing chlorinated aromatic pollutants.
The direct electrochemical dechlorination of the inert material needs higher overpotential and higher energy consumption, so that the search for the material capable of efficiently catalyzing the dehalogenation reaction has important economic value in the aspect of electrode preparation. The transition metal palladium has lower hydrogen evolution potential and higher atomic hydrogen adsorption and storage capacity, has the catalytic characteristic of decomposing hydrogen into active hydrogen atoms, and is considered to be an ideal catalyst for electrochemical reduction and dehalogenation. Although the electrode prepared by directly electrodepositing palladium on a substrate has high dehalogenation efficiency, the problems of low current efficiency, large load capacity, high cost and the like exist. Therefore, there is a need to develop a highly efficient modified composite electrode with a small catalyst loading, a high degree of dispersion, a low degree of agglomeration, and high catalytic activity and stability.
Disclosure of Invention
The invention aims to provide Pd/gamma-MnO2The composite electrode has the advantages of high catalytic activity, large specific surface area, long service life, low cost and the like, and the intermediate layer contained in the composite electrode is gamma crystal form MnO with a regular hexagonal structure2More active sites can be provided, and the adsorption and decomposition of the pollutants are more favorable.
The technical scheme of the invention is as follows:
the embodiment of the invention provides Pd/gamma-MnO2The composite electrode is prepared by taking foam nickel as a matrix and forming gamma-MnO on the surface of the foam nickel through a hydrothermal reaction2Intermediate layer by chemical depositionPd nanoparticles.
In some embodiments, γ -MnO2The loading capacity of the middle layer on the foamed nickel is 0.30-0.35 mg/cm2(ii) a The deposition amount of the Pd nano-particles is 0.68-0.72 mg/cm2。
The embodiment of the invention provides Pd/gamma-MnO2the/Ni foam composite electrode has the following advantages: the embodiment of the invention provides Pd/gamma-MnO2the/Ni foam composite electrode has large specific surface area, high catalytic activity and good circulation stability, and can quickly and efficiently electro-catalyze and treat chlorophenol pollutants in wastewater; and MnO in the composite electrode2The middle layer is MnO of gamma crystal form with a regular hexagonal structure2Can provide more active sites, is more beneficial to the adsorption and decomposition of pollutants, and only needs to load a small amount of gamma-MnO2A better catalytic effect can be achieved; in addition, MnO with gamma crystal form is loaded on the foamed nickel substrate2And then, the roughness of the surface of the electrode is obviously improved, the specific surface area is increased, and the problem that metal palladium is easy to agglomerate when chemical deposition is directly carried out on the surface of the foam nickel base can be further improved.
The embodiment of the invention also provides Pd/gamma-MnO2The preparation method of the/Ni foam composite electrode comprises the following steps:
(1) foam nickel pretreatment: firstly, ultrasonically treating the foamed nickel with acetone for 15-20 min to remove organic matters on the surface of the foamed nickel; then 10% hydrochloric acid is used for ultrasonic treatment for 10-15 min to remove the surface oxide layer; finally, repeatedly cleaning the nickel foam with distilled water for 2-5 times, and then airing the nickel foam in the air to obtain pretreated foamed nickel;
（2）γ-MnO2preparation of the intermediate layer: mixing MnSO4And KMnO4Dissolving in water to prepare a reaction solution A; then placing the pretreated foamed nickel into the reaction solution A for hydrothermal reaction; naturally cooling to room temperature after the reaction is finished, taking out the reacted foam nickel, sequentially cleaning the foam nickel by using ethanol and deionized water, and airing to obtain gamma-MnO2a/Ni foam electrode;
(3) chemical deposition of Pd nanoparticles: PdCl2Dissolving NaCl and NaCl in water to prepare a solution B; then the gamma-MnO obtained in the step (2) is added2Putting the/Ni foam electrode in the solution B, oscillating on a constant temperature shaking table until the color of the solution B is changed from yellow to colorless to obtain Pd/gamma-MnO2the/Ni foam composite electrode.
In some embodiments, MnSO4And KMnO4In a molar ratio of 3: 2; MnSO in reaction liquid A4The concentration of (B) is 0.5 to 2.0 mM, preferably 1.5 mM.
In some embodiments, the temperature of the hydrothermal reaction is 120-140 ℃, preferably 140 ℃; the reaction time is 20-24 h, preferably 24 h.
In some embodiments, the PdCl is a complex of two or more compounds2The mol ratio of NaCl to NaCl is 1: 3; PdCl in solution B2The concentration of (B) is 4 to 12 mM.
In some embodiments, the temperature of shaking in step (3) is 30 to 35 ℃, preferably 30 ℃.
Pd/gamma-MnO in the examples of the present invention2The preparation method of the/Ni foam composite electrode comprises the following two steps: the first step is to prepare gamma-MnO on the pretreated foam nickel by using hydrothermal reaction2An intermediate layer; the second step is to load the Pd nano-particles to gamma-MnO by using a chemical deposition method2Compared with a Pd/Ni foam electrode with the same dechlorination effect, the preparation method can save about 75% of noble metal palladium loading capacity, and is simple to operate, mild in synthesis conditions and convenient to manage.
The embodiment of the invention also provides a method for performing electrocatalysis reduction and dechlorination on chlorinated organic matters in water, which comprises the following steps: with the above Pd/gamma-MnO2The method comprises the following steps of taking a/Ni foam composite electrode as a working electrode, taking a Pt sheet as a counter electrode, taking a saturated calomel electrode as a reference electrode, carrying out electro-reduction dechlorination on chlorinated organic pollutants in an H-shaped reactor in a constant current mode, and adopting Na as an anode electrolyte and a cathode electrolyte2SO4And (3) solution.
In some embodiments, Na2SO4The concentration of the solution is 25 to 50 mM, preferably 50 mM.
In some embodiments, the constant current range is-8 to-10 mA, preferably-10 mA.
Compared with the prior art, the technical scheme provided by the invention has the following advantages:
1. Pd/gamma-MnO of the present invention2the/Ni foam composite electrode has the advantages of high catalytic activity, large specific surface area, long service life, good circulation stability, low cost and the like, can quickly and efficiently electro-catalytically treat chlorophenol pollutants in wastewater, and can effectively relieve Cl-、HCO3-、NO3-The electrode poisoning problem caused by anions can still have better dechlorination effect under the condition of complex water quality, and the method has wide social and economic benefits.
2. Pd/gamma-MnO of the present invention2MnO in/Ni foam composite electrode2The middle layer is MnO of gamma crystal form with a regular hexagonal structure2Can provide more active sites, is more beneficial to the adsorption and decomposition of pollutants, and only needs to load a small amount of gamma-MnO2Better catalytic effect can be achieved, and the cost of wastewater treatment is saved.
3. Pd/gamma-MnO of the present invention2Gamma-MnO in/Ni foam composite electrode2The middle layer is of a nano-sheet microstructure and is vertically arranged on the foamed nickel substrate, and micropores are formed among the sheets, so that the transfer and diffusion of electrons/protons are accelerated, the overpotential is reduced, and the electrocatalytic reduction reaction is facilitated; in addition, when the foam nickel is loaded with gamma-MnO2And then, the roughness of the surface of the foam nickel is increased, the specific surface area is increased, and the problem that the metal palladium is easy to agglomerate when chemical deposition is directly carried out on the surface of the foam nickel can be further improved.
4. The preparation method has the advantages of simple process, mild synthesis conditions, easy operation and convenient management; in addition, compared with a Pd/Ni foam electrode with the same dechlorination effect, the preparation method can save about 75 percent of the noble metal palladium loading capacity, thereby greatly reducing the dechlorination cost of chlorinated organic pollutants.
Drawings
FIG. 1 is an X-ray diffraction pattern of different electrodes, wherein (a) is an X-ray diffraction pattern of a Pd/Ni foam electrode prepared in comparative example 1; (b) Gamma-MnO prepared for example 1 of the present invention2X-ray diffraction of/Ni foam electrodeA drawing; (c) Pd/gamma-MnO prepared for example 1 of the present invention2X-ray diffraction pattern of the/Ni foam composite electrode.
FIG. 2 shows the preparation of gamma-MnO according to the hydrothermal method2X-ray diffraction pattern of the powder.
FIG. 3 is a scanning electron micrograph of different electrodes, wherein (a) is a scanning electron micrograph of Ni foam pretreated in example 1 of the present invention; (b) scanning electron micrograph of Pd/Ni foam electrode prepared in comparative example 1; (c) Gamma-MnO obtained in example 1 of the present invention2Scanning electron micrographs of the/Ni foam electrode; (d) Pd/gamma-MnO obtained in example 1 of the present invention2Scanning electron microscope images of the/Ni foam composite electrode.
FIG. 4 shows γ -MnO obtained in example 1 of the present invention2Scanning electron microscope images of the porous nanostructure on the surface of the/Ni foam electrode.
FIG. 5 is a schematic diagram showing the construction of an apparatus for performing electro-catalytic reduction dechlorination according to the present invention, in which FIG. 1 is an electrochemical workstation; 2 is a reference electrode; 3 is working electrode Pd/gamma-MnO2/Ni foam (cathode); 4 is a counter electrode Pt (anode); 5 is a magnetic rotor; 6 is a cation exchange membrane.
FIG. 6 shows various gamma-MnO prepared in examples 1-4 of the present invention2Supported Pd/gamma-MnO2And the dechlorination efficiency chart of the 2,4, 6-trichlorophenol-containing wastewater after being electrocatalytic treated by the/Ni foam composite electrode for 2 hours.
FIG. 7 shows Pd/gamma-MnO prepared in example 1 of the present invention2And dechlorination effect graphs of the/Ni foam composite electrode and the Pd/Ni foam electrodes with different palladium loading amounts prepared in the comparative examples 1 and 2 after being subjected to electrocatalysis treatment for 2 h.
FIG. 8 shows Pd/gamma-MnO prepared in example 1 of the present invention2A graph showing the relationship between the number of times of use of the/Ni foam composite electrode and the dechlorination effect.
FIG. 9 shows Pd/gamma-MnO prepared in example 2 of the present invention2Dechlorination effect of the/Ni foam composite electrode and the Pd/Ni foam electrode prepared in the comparative example 2 after 4h of electrocatalytic treatment in the presence of different anions.
Detailed Description
The following detailed description of embodiments of the invention is intended to be illustrative, and not to be construed as limiting the invention.
The embodiment of the invention provides Pd/gamma-MnO2The composite electrode is prepared by taking foam nickel as a matrix and forming gamma-MnO on the surface of the foam nickel through a hydrothermal reaction2The middle layer is prepared by chemical deposition of Pd nano-particles.
In some embodiments, γ -MnO2The loading capacity of the middle layer on the foamed nickel is 0.30-0.35 mg/cm2(ii) a The deposition amount of the Pd nano-particles is 0.68-0.72 mg/cm2。
The embodiment of the invention provides Pd/gamma-MnO2the/Ni foam composite electrode has the following advantages: the embodiment of the invention provides Pd/gamma-MnO2the/Ni foam composite electrode has large specific surface area, high catalytic activity and good circulation stability, and can quickly and efficiently electro-catalyze and treat chlorophenol pollutants in wastewater; and gamma-MnO in the composite electrode2Has a regular hexagonal structure, can provide more active sites, is more beneficial to the adsorption and decomposition of pollutants, and only needs to load a small amount of gamma-MnO2A better catalytic effect can be achieved.
The embodiment of the invention also provides Pd/gamma-MnO2The preparation method of the/Ni foam composite electrode comprises the following steps:
(1) foam nickel pretreatment: firstly, ultrasonically treating the foamed nickel with acetone for 15-20 min to remove organic matters on the surface of the foamed nickel; then 10% hydrochloric acid is used for ultrasonic treatment for 10-15 min to remove an oxide layer on the surface of the film; finally, repeatedly cleaning the nickel foam by using distilled water for 2-5 times, and then airing the nickel foam in the air to obtain pretreated nickel foam;
（2）γ-MnO2preparation of the intermediate layer: mixing MnSO4And KMnO4Dissolving in water to prepare a reaction solution A; then placing the pretreated foamed nickel in the reaction solution A for hydrothermal reaction; naturally cooling to room temperature after the reaction is finished, taking out the reacted foam nickel, sequentially cleaning the foam nickel by using ethanol and deionized water, and airing to obtain gamma-MnO2a/Ni foam electrode;
(3) chemical deposition of Pd nanoparticles: PdCl2Dissolving NaCl and NaCl in water to prepare a solution B; then the gamma-MnO obtained in the step (2) is added2Putting the/Ni foam electrode in the solution B, oscillating on a constant temperature shaking table until the color of the solution B is changed from yellow to colorless to obtain Pd/gamma-MnO2the/Ni foam composite electrode.
In some embodiments, MnSO4And KMnO4In a molar ratio of 3: 2; MnSO in the reaction liquid A4The concentration of (B) is 0.5 to 2.0 mM, preferably 1.5 mM.
In some embodiments, the temperature of the hydrothermal reaction is 120-140 ℃, preferably 140 ℃; the reaction time is 20-24 h, preferably 24 h.
In some embodiments, the PdCl is a complex of two or more compounds2The mol ratio of NaCl to NaCl is 1: 3; PdCl in solution B2The concentration of (b) is 4-12 mM.
In some embodiments, the temperature of shaking in step (3) is 30 to 35 ℃, preferably 30 ℃.
Pd/gamma-MnO of the present invention2The preparation method of the/Ni foam composite electrode comprises the steps of firstly preparing gamma-MnO on a foam nickel matrix through a hydrothermal reaction2The middle layer is further subjected to chemical deposition of Pd nano-particles to prepare Pd/gamma-MnO2The preparation method of the/Ni foam composite electrode is simple, the synthesis condition is mild, and compared with the Pd/Ni foam electrode with the same dechlorination effect, the preparation method can save about 75% of the noble metal palladium loading capacity and save the wastewater treatment cost.
The embodiment of the invention also provides a method for dechlorinating chlorinated organic compounds in water by electrocatalysis, which comprises the following steps: with the above Pd/gamma-MnO2the/Ni foam composite electrode is used as a working electrode (cathode), the Pt sheet is used as a counter electrode (anode), the saturated calomel electrode is used as a reference electrode, the chlorinated organic pollutants are subjected to electro-reduction dechlorination treatment in an H-shaped reactor under a constant current mode, and Na is adopted as an anode electrolyte and a cathode electrolyte2SO4And (3) solution.
In some embodiments, Na2SO4The concentration of the solution is 25 to 50 mM, preferably 50 mM.
In some embodiments, the constant current range is-8 to-10 mA, preferably-10 mA.
The present invention is described in further detail below by way of specific examples.
Example 1
This example provides a Pd/γ -MnO2The Ni foam composite electrode takes foam nickel as a matrix, and gamma-MnO is formed on the surface of the foam nickel through a hydrothermal reaction2An intermediate layer prepared by chemical deposition of Pd nanoparticles; the obtained Pd/gamma-MnO2In the/Ni foam composite electrode, gamma-MnO2The supporting amount of the intermediate layer was 0.33 mg/cm2The deposition amount of the Pd nanoparticles was 0.7 mg/cm2。
The Pd/gamma-MnO2The preparation method of the/Ni foam composite electrode comprises the following steps:
(1) foam nickel pretreatment: firstly, performing ultrasonic treatment on foamed nickel (30 mm multiplied by 20 mm) with acetone for 15 min to remove organic matters on the surface of the foamed nickel; then 10% hydrochloric acid is used for ultrasonic treatment for 15 min to remove the surface oxide layer; finally, repeatedly washing the nickel foam with distilled water for 3 times, and then airing the nickel foam in the air to obtain pretreated nickel foam, wherein a scanning electron microscope image of the pretreated nickel foam is shown as (a) in fig. 3;
（2）γ-MnO2preparation of the intermediate layer: mixing MnSO4And KMnO4Dissolving in water at a molar ratio of 3:2, wherein MnSO4The concentration of the reaction solution in water is 1.5 mM, and a reaction solution A is prepared; then 20mL of the reaction solution A is put into a reaction kettle, and the pretreated nickel foam is put into the reaction solution A for hydrothermal reaction at the temperature of 140 ℃ for 24 hours; naturally cooling to room temperature after the reaction is finished, taking out the reacted foam nickel, sequentially cleaning the foam nickel by using ethanol and deionized water, and airing in the air to obtain gamma-MnO2a/Ni foam electrode;
the obtained gamma-MnO2The X-ray diffraction pattern of the/Ni foam electrode is shown in FIG. 1 (b) and the scanning electron micrograph is shown in FIG. 3 (c), and it can be seen that when γ -MnO is supported on the surface of the foam nickel substrate2The surface roughness is obviously increased, and the specific surface area is improved; further, FIG. 4 is a partially enlarged view of (c) in FIG. 3, and γ -MnO can be observed2Table of/Ni foam electrodeThe surface is a porous nano structure, wherein, the gamma-MnO is in a nano sheet shape2Nano-sheet gamma-MnO vertically arranged on the surface of foam nickel base2The micropores with the size of 50-300 nm exist between the sheets, the formed nano porous structure film greatly reduces bubble adhesion, and the high-reactivity edge can be exposed in electrolyte, so that the transfer and diffusion of electrons/protons are accelerated, the overpotential is reduced, and the electrocatalytic reduction reaction is facilitated.
(3) Chemical deposition of Pd nanoparticles: PdCl2And NaCl in a molar ratio of 1:3 in water, wherein PdCl2The concentration of NaCl in water is 12 mM, and solution B is prepared; then the gamma-MnO obtained in the step (2) is added2Putting the/Ni foam electrode into 20mL of solution B, putting the solution B into a sealed conical flask, putting the conical flask into a constant-temperature shaking table at the temperature of 30 ℃, and oscillating until the color of the solution B is changed from yellow to colorless to prepare Pd/gamma-MnO2the/Ni foam composite electrode.
Finally prepared Pd/gamma-MnO2In the/Ni foam composite electrode, gamma-MnO2The supporting amount of the intermediate layer was 0.33 mg/cm2The deposition amount of the Pd nanoparticles was 0.7 mg/cm2。
The obtained Pd/gamma-MnO2An X-ray diffraction pattern of the/Ni foam composite electrode is shown in (c) of FIG. 1, and a scanning electron microscope pattern is shown in (d) of FIG. 3. FIG. 2 shows γ -MnO prepared by hydrothermal reaction under the same hydrothermal conditions as in step (2) of this example2X-ray diffraction patterns of the powders from which we can see that the examples of the invention use MnSO4And KMnO4MnO is prepared by controlling the proportion of the reaction raw materials and hydrothermal reaction conditions2MnO of gamma crystal form with regular hexagonal structure2The nano-sheet can provide more active sites, and is more beneficial to adsorption and decomposition of pollutants.
Example 2
In this example, Pd/γ -MnO2The preparation process of the/Ni foam composite electrode is the same as that of the example 1, except that: ' in step (2), MnSO4Concentration in water was 0.5 mM ", final preparationObtained Pd/gamma-MnO2In the/Ni foam composite electrode, gamma-MnO2The loading amount of the middle layer is 0.15 mg/cm2The deposition amount of the Pd nanoparticles was 0.7 mg/cm2。
Example 3
In this example, Pd/γ -MnO2The preparation process of the/Ni foam composite electrode is the same as that of the example 1, except that: ' MnSO in step (2)4Concentration in water 1 mM ", Pd/gamma-MnO prepared finally2In the/Ni foam composite electrode, gamma-MnO2The supporting amount of the intermediate layer was 0.21 mg/cm2The deposition amount of the Pd nanoparticles was 0.7 mg/cm2。
Example 4
In this example, Pd/γ -MnO2The preparation process of the/Ni foam composite electrode is the same as that of the example 1, except that: ' MnSO in step (2)4Concentration in water 2 mM ", Pd/gamma-MnO prepared finally2In the/Ni foam composite electrode, gamma-MnO2The supporting amount of the intermediate layer was 0.42 mg/cm2The deposition amount of the Pd nanoparticles was 0.7 mg/cm2。
Comparative example 1
The present comparative example provides a Pd/Ni foam electrode, the method of making the Pd/Ni foam electrode comprising the steps of:
(1) foam nickel pretreatment: firstly, performing ultrasonic treatment on foamed nickel (30 mm multiplied by 20 mm) with acetone for 15 min to remove organic matters on the surface of the foamed nickel; then 10% hydrochloric acid is used for ultrasonic treatment for 15 min to remove the surface oxide layer; finally, repeatedly cleaning the nickel foam by using distilled water for 3 times, and then airing the nickel foam in the air to obtain pretreated nickel foam;
(2) chemical deposition of Pd nanoparticles: PdCl2And NaCl in a molar ratio of 1:3 in water, wherein PdCl2The concentration of (A) is 4 mM, the concentration of NaCl is 12 mM, and solution B is prepared; and placing the pretreated foamed nickel into 20mL of solution B, placing the solution B into a sealed conical flask, and placing the conical flask into a constant-temperature shaking table at the temperature of 30 ℃ for shaking until the color of the solution B is changed from yellow to colorless, thereby preparing the Pd/Ni foam electrode.
In the obtained Pd/Ni foam electrode, the loading amount of Pd was 0.7 mg/cm2。
The X-ray diffraction pattern and the scanning electron micrograph of the obtained Pd/Ni foam electrode are shown in fig. 1 (a) and fig. 3 (b), respectively. By comparing (b) Pd/Ni foam electrode in FIG. 3 with (d) Pd/γ -MnO in FIG. 32According to a scanning electron microscope image of the/Ni foam composite electrode, the Pd metal is directly deposited on the foamed nickel substrate by using a chemical deposition method, and the palladium metal on the surface of the prepared Pd/Ni foam electrode is easy to aggregate to form larger particles; and by loading gamma-MnO on the foamed nickel matrix2After the intermediate layer, Pd metal is deposited chemically to obtain Pd/gamma-MnO2the/Ni foam composite electrode can enable Pd particles on the surface of the electrode to be more dispersed, and the particle size is obviously reduced.
Comparative example 2
The present comparative example provides a Pd/Ni foam electrode, the method of making the Pd/Ni foam electrode comprising the steps of:
(1) foam nickel pretreatment: firstly, performing ultrasonic treatment on foamed nickel (30 mm multiplied by 20 mm) with acetone for 15 min to remove organic matters on the surface of the foamed nickel; then 10% hydrochloric acid is used for ultrasonic treatment for 15 min to remove the surface oxide layer; finally, repeatedly cleaning the nickel foam by using distilled water for 3 times, and then airing the nickel foam in the air to obtain pretreated nickel foam;
(2) chemical deposition of Pd nanoparticles: PdCl2And NaCl in a molar ratio of 1:3 in water, wherein PdCl2With the concentration of 16 mM and the concentration of NaCl of 48 mM, to prepare a solution B; and placing the pretreated foamed nickel into 20mL of solution B, placing the solution B into a sealed conical flask, and placing the conical flask into a constant-temperature shaking table at the temperature of 30 ℃ for shaking until the color of the solution B is changed from yellow to colorless, thereby preparing the Pd/Ni foam electrode.
In the obtained Pd/Ni foam electrode, the loading amount of Pd is 2.8 mg/cm2。
Application example 1
Having different gamma-MnO levels, obtained respectively in examples 1-4 of the present invention2Supported Pd/gamma-MnO2the/Ni foam composite electrode is used as a working electrode, a platinum sheet is used as a counter electrode, a saturated calomel electrode is used as a reference electrode, a cathode chamber and an anode chamber are separated by a cation exchange membrane, and the electrolyte adopts 50 mM Na2SO4And (3) carrying out reduction dechlorination on the solution under the current of-10 mA for 2h, wherein the treatment time is 100 mL of wastewater containing 25 mg/L of 2,4, 6-trichlorophenol.
As shown in FIG. 6, different γ -MnO prepared in examples 1-4 of the present invention2Supported Pd/gamma-MnO2The dechlorination efficiency chart of 2,4, 6-trichlorophenol-containing wastewater after electrocatalysis treatment by the/Ni foam composite electrode for 2 hours can be seen from the chart, and after 2 hours of electrocatalysis is carried out on the 2,4, 6-trichlorophenol-containing wastewater, gamma-MnO is added2The loading amount is 0.33 mg/cm2Pd/gamma-MnO of2The dechlorination efficiency of the/Ni foam composite electrode to the 2,4, 6-trichlorophenol is the highest and can reach 98.5 percent.
Application example 2
Pd/gamma-MnO prepared in example 1 of the present invention, respectively2the/Ni foam composite electrode and the Pd/Ni foam electrodes prepared in comparative example 1 and comparative example 2 are used as working electrodes, platinum sheets are used as counter electrodes, saturated calomel electrodes are used as reference electrodes, a cathode chamber and an anode chamber are separated by a cation exchange membrane, and 50 mM Na is used as electrolyte2SO4And (3) carrying out reduction dechlorination on the solution under the current of-10 mA to treat 100 mL of wastewater containing 50 mg/L of o-chlorophenol, wherein the treatment time is 2 h.
FIG. 7 shows Pd/gamma-MnO prepared in example 1 of the present invention2Dechlorination effect diagram of o-chlorophenol-containing wastewater after electrocatalytic treatment for 2h by using/Ni foam composite electrode and Pd/Ni foam electrodes with different Pd loading amounts prepared in comparative example 1 and comparative example 2, wherein Pd (0.7)/gamma-MnO2Ni is Pd/gamma-MnO prepared in example 1 of the present invention2the/Ni foam composite electrode has a Pd loading of 0.7 mg/cm2(ii) a Pd (0.7)/Ni was the Pd/Ni foam electrode obtained in comparative example 1, and the Pd loading was 0.7 mg/cm2(ii) a Pd (2.8)/Ni was the Pd/Ni foam electrode obtained in comparative example 2, and the Pd loading was 2.8 mg/cm2. As can be seen from the figure, the Pd/γ -MnO obtained in example 1 after electrocatalysis for 2h2The degradation rate of the/Ni foam composite electrode to the o-chlorophenol is about 98.5%, compared with the Pd/Ni foam electrode with the same Pd loading amount, the catalytic activity of the electrode is obviously improved, and the dechlorination effect is obviously improved; in addition, through the Pd (2.8)/Ni foam electrode and Pd (0.7)/gamma-MnO in FIG. 72The dechlorination effect of the/Ni foam composite electrode can be seen, and the two electrodesThe dechlorination effect is similar, but Pd/gamma-MnO2the/Ni foam composite electrode can achieve dechlorination effect equivalent to that of a Pd/Ni foam electrode only by using a smaller amount of Pd metal, and about 75% of noble metal Pd is saved.
FIG. 8 shows Pd/gamma-MnO prepared in example 1 of the present invention2FIG. 1 is a graph showing the relationship between the number of times of use of the/Ni foam composite electrode and dechlorination effect, and Pd/gamma-MnO obtained by using example 1 of the present invention2the/Ni foam composite electrode is used for carrying out electrocatalytic reduction dechlorination on the waste water containing the o-chlorophenol, and when the electrode is repeatedly used for the 6 th time, the removal rate of the o-chlorophenol in the waste water still reaches more than 95 percent, so that the composite electrode is proved to have high catalytic activity and good stability.
Application example 3
Pd/gamma-MnO prepared in example 22the/Ni foam composite electrode and the Pd/Ni foam electrode prepared in the comparative example 2 are respectively used as a working electrode, a platinum sheet is used as a counter electrode, a saturated calomel electrode is used as a reference electrode, a cathode chamber and an anode chamber are separated by a cation exchange membrane, and the electrolyte adopts 50 mM Na2SO4The solutions were each dosed with 10 mM Cl at-10 mA-，HCO3 -，NO3 -Waiting for different anions (adding 10 mM Na)2SO4As a blank control) was subjected to electro-reductive dechlorination for 4 hours in a 50 mg/L o-chlorophenol solution.
FIG. 9 shows Pd/gamma-MnO prepared in example 2 of the present invention2Dechlorination effect of the/Ni foam composite electrode and the Pd/Ni foam electrode prepared in the comparative example 2 after 4h of electrocatalytic treatment in the presence of different anions, and Cl can be seen from the figure-，HCO3 -，NO3 -The existence of different anions causes negative influence on the electrocatalytic degradation of the o-chlorophenol; however, the Pd/gamma-MnO prepared in example 2 of the present invention was compared with the Pd/Ni foam electrode having 4 times Pd loading amount2The influence of anions on the/Ni foam composite electrode is obviously smaller, and the catalytic activity of the electrode is higher.
In the present disclosure, the terms "one embodiment," "some embodiments," "an example," "a specific example," or "some examples" and the like mean that a specific feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. In this specification, the schematic representations of the terms used above are not necessarily intended to refer 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, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are exemplary and not to be construed as limiting the present invention, and that changes, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.

Claims (10)

1. Pd/gamma-MnO2The composite electrode is characterized in that foam nickel is used as a matrix, and gamma-MnO is formed on the surface of the foam nickel through a hydrothermal reaction2An intermediate layer prepared by chemical deposition of Pd nanoparticles.
2. The Pd/γ -MnO of claim 12the/Ni foam composite electrode is characterized in that the gamma-MnO is2The loading capacity of the middle layer on the foamed nickel is 0.30-0.35 mg/cm2(ii) a The deposition amount of the Pd nano-particles is 0.68-0.72 mg/cm2。
3. A Pd/γ -MnO as defined in claim 1 or 22The preparation method of the/Ni foam composite electrode is characterized by comprising the following steps of:
(1) pretreating foamed nickel;
(2) mixing MnSO4And KMnO4Dissolving in water to prepare a reaction solution A; then placing the pretreated foamed nickel into the reaction solution A to make hydrothermal reactionThe preparation method comprises the following steps of; finally, the reacted foam nickel is sequentially washed by ethanol and deionized water and dried to obtain the gamma-MnO2a/Ni foam electrode;
(3) PdCl2Dissolving NaCl and NaCl in water to prepare a solution B; then adding gamma-MnO2Putting the/Ni foam electrode in the solution B, oscillating on a constant temperature shaking table until the color of the solution B is changed from yellow to colorless to obtain Pd/gamma-MnO2the/Ni foam composite electrode.
4. A Pd/γ -MnO according to claim 32The preparation method of the/Ni foam composite electrode is characterized by comprising the following pretreatment steps: firstly, performing ultrasonic treatment on the foamed nickel for 15-20 min by using acetone; then carrying out ultrasonic treatment for 10-15 min by using 10% hydrochloric acid; and finally, washing with distilled water, and airing to obtain the pretreated foamed nickel.
5. A Pd/γ -MnO according to claim 32The preparation method of the/Ni foam composite electrode is characterized in that the MnSO4And said KMnO4Is 3: 2.
6. A Pd/γ -MnO according to claim 32The preparation method of the/Ni foam composite electrode is characterized in that the temperature of the hydrothermal reaction is 120-140 ℃; the reaction time is 20-24 h.
7. A Pd/γ -MnO according to claim 32The preparation method of the/Ni foam composite electrode is characterized in that the PdCl is prepared from PdCl2And the molar ratio of the NaCl is 1: 3.
8. A method for treating chlorinated organic matters in water through electrocatalytic reduction and dechlorination is characterized by comprising the following steps: Pd/gamma-MnO as defined in claim 1 or 22The method comprises the following steps of taking a/Ni foam composite electrode as a working electrode, taking a Pt sheet as a counter electrode, taking a saturated calomel electrode as a reference electrode, carrying out electro-reduction dechlorination on chlorinated organic pollutants in an H-shaped reactor in a constant current mode, and adopting Na as an anode electrolyte and a cathode electrolyte2SO4And (3) solution.
9. The method for the electro-catalytic reduction dechlorination of chlorinated organic compounds in water according to claim 8, wherein the Na is2SO4The concentration of the solution is 25-50 mM.
10. The method for electro-catalytic reduction dechlorination of chlorinated organic compounds in water according to claim 8, wherein the constant current range is-8 to-10 mA.
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