CN114540873B - 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 PDFInfo
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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 treatment 2 An intermediate layer prepared by chemical deposition of Pd nanoparticles; wherein, gamma-MnO 2 The loading capacity of the middle layer on the foamed nickel is 0.30-0.35 mg/cm 2 (ii) a The deposition amount of the Pd nano-particles is 0.68-0.72 mg/cm 2 . The invention also provides a preparation method of the composite electrode. Pd/gamma-MnO prepared by the invention 2 the/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
Technical Field
The invention belongs to the technical field of electrochemical water treatment, and particularly relates to Pd/gamma-MnO 2 a/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-MnO 2 The 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 structure 2 More 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-MnO 2 The composite electrode is prepared by taking foamed nickel as a matrix and forming gamma-MnO on the surface of the foamed nickel through hydrothermal reaction 2 The middle layer is prepared by chemical deposition of Pd nano-particles.
In some embodiments, γ -MnO 2 The loading capacity of the middle layer on the foamed nickel is 0.30-0.35 mg/cm 2 (ii) a The deposition amount of the Pd nano-particles is 0.68-0.72 mg/cm 2 。
The embodiment of the invention provides Pd/gamma-MnO 2 the/Ni foam composite electrode has the following advantages: Pd/gamma-MnO provided by the embodiment of the invention 2 the/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 electrode 2 The middle layer is MnO of gamma crystal form with a regular hexagonal structure 2 More active sites can be provided, the adsorption and decomposition of pollutants are more favorable, and only a small amount of gamma-MnO is loaded 2 A better catalytic effect can be achieved; in addition, MnO with gamma crystal form is loaded on the foamed nickel substrate 2 Then, electricityThe roughness of the surface of the electrode is obviously improved, 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 base can be further improved.
The embodiment of the invention also provides Pd/gamma-MnO 2 The 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 by using distilled water for 2-5 times, and then airing the nickel foam in the air to obtain pretreated nickel foam;
(2)γ-MnO 2 preparation of the intermediate layer: mixing MnSO 4 And KMnO 4 Dissolving 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-MnO 2 a/Ni foam electrode;
(3) chemical deposition of Pd nanoparticles: PdCl 2 Dissolving NaCl and NaCl in water to prepare a solution B; then the gamma-MnO obtained in the step (2) is added 2 Putting 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-MnO 2 the/Ni foam composite electrode.
In some embodiments, MnSO 4 And KMnO 4 In a molar ratio of 3: 2; MnSO in reaction liquid A 4 The concentration of (B) is 0.5 to 2.0mM, 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 compounds 2 The mol ratio of NaCl to NaCl is 1: 3; PdCl in solution B 2 The 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 invention 2 /Ni foam compositionThe preparation method of the electrode comprises the following two steps: the first step is to prepare gamma-MnO on the pretreated foam nickel by using hydrothermal reaction 2 An intermediate layer; the second step is to load the Pd nano-particles to gamma-MnO by using a chemical deposition method 2 Compared with a Pd/Ni foam electrode with the same dechlorination effect, the preparation method can save about 75% of precious 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-MnO 2 The 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 electrolyte 2 SO 4 And (3) solution.
In some embodiments, Na 2 SO 4 The concentration of the solution is 25 to 50mM, 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 invention 2 the/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 - 、HCO 3 - 、NO 3 - 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 invention 2 MnO in/Ni foam composite electrode 2 The middle layer is MnO of gamma crystal form with a regular hexagonal structure 2 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-MnO 2 A better catalytic effect can be achieved,the cost of wastewater treatment is saved.
3. Pd/gamma-MnO of the present invention 2 Gamma-MnO in/Ni foam composite electrode 2 The middle layer is of a nano-sheet microstructure and is vertically arranged on the foamed nickel matrix, and micropores are formed between 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-MnO 2 And 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 invention 2 X-ray diffraction pattern of/Ni foam electrode; (c) Pd/gamma-MnO prepared for the inventive example 1 2 X-ray diffraction pattern of the/Ni foam composite electrode.
FIG. 2 shows the preparation of gamma-MnO according to the hydrothermal method 2 X-ray diffraction pattern of the powder.
FIG. 3 is a SEM image of different electrodes, wherein (a) is a SEM image of a pretreated Ni foam 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 invention 2 Scanning electron micrographs of the/Ni foam electrode; (d) Pd/gamma-MnO obtained in example 1 of the present invention 2 Scanning electron microscope images of the/Ni foam composite electrode.
FIG. 4 shows γ -MnO obtained in example 1 of the present invention 2 Scanning electron microscope images of the porous nanostructure on the surface of the/Ni foam electrode.
FIG. 5 is a schematic diagram of an electrocatalytic reduction dechlorination apparatus according to the present inventionFor purposes of illustration, FIG. 1 is an electrochemical workstation; 2 is a reference electrode; 3 is working electrode Pd/gamma-MnO 2 /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 invention 2 Supported Pd/gamma-MnO 2 And 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 invention 2 And 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 invention 2 A 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 invention 2 Dechlorination 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 describes embodiments of the invention, which are exemplary and intended to be illustrative of the invention and are not to be construed as limiting the invention.
The embodiment of the invention provides Pd/gamma-MnO 2 The 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 reaction 2 The middle layer is prepared by chemical deposition of Pd nano-particles.
In some embodiments, γ -MnO 2 The loading capacity of the middle layer on the foamed nickel is 0.30-0.35 mg/cm 2 (ii) a The deposition amount of the Pd nano-particles is 0.68-0.72 mg/cm 2 。
The embodiment of the invention provides Pd/gamma-MnO 2 the/Ni foam composite electrode has the following advantages: the embodiment of the invention provides Pd/gamma-MnO 2 the/Ni foam composite electrode has large specific surface area, high catalytic activity and good circulation stability, and can quickly and efficiently treat wastewater through electrocatalysisChlorophenol-type contaminants; and gamma-MnO in the composite electrode 2 Has 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-MnO 2 A better catalytic effect can be achieved.
The embodiment of the invention also provides Pd/gamma-MnO 2 The 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 by using distilled water for 2-5 times, and then airing the nickel foam in the air to obtain pretreated nickel foam;
(2)γ-MnO 2 preparation of the intermediate layer: mixing MnSO 4 And KMnO 4 Dissolving 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-MnO 2 a/Ni foam electrode;
(3) chemical deposition of Pd nanoparticles: PdCl 2 Dissolving NaCl in water to prepare a solution B; then the gamma-MnO obtained in the step (2) is added 2 Putting 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-MnO 2 the/Ni foam composite electrode.
In some embodiments, MnSO 4 And KMnO 4 In a molar ratio of 3: 2; MnSO in reaction liquid A 4 The concentration of (B) is 0.5 to 2.0mM, 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 compounds 2 The mol ratio of NaCl to NaCl is 1: 3; PdCl in solution B 2 The 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 of the present invention 2 The preparation method of the/Ni foam composite electrode comprises the steps of firstly preparing gamma-MnO on a foam nickel matrix through a hydrothermal reaction 2 The middle layer is further subjected to chemical deposition of Pd nano-particles to prepare Pd/gamma-MnO 2 The 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 performing electrocatalysis reduction and dechlorination on chlorinated organic matters in water, which comprises the following steps: with the above Pd/gamma-MnO 2 the/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 electrolyte 2 SO 4 And (3) solution.
In some embodiments, Na 2 SO 4 The concentration of the solution is 25 to 50mM, 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 -MnO 2 The 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 reaction 2 An intermediate layer prepared by chemical deposition of Pd nanoparticles; the obtained Pd/gamma-MnO 2 In the/Ni foam composite electrode, gamma-MnO 2 The supporting amount of the intermediate layer was 0.33mg/cm 2 The deposition amount of the Pd nanoparticles was 0.7mg/cm 2 。
The Pd/gamma-MnO 2 The preparation method of the/Ni foam composite electrode comprises the following steps:
(1) foam nickel pretreatment: firstly, performing ultrasonic treatment on foamed nickel (30mm multiplied by 20mm) with acetone for 15min to remove organic matters on the surface of the foamed nickel; then 10% hydrochloric acid is used for ultrasonic treatment for 15min 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-MnO 2 preparation of the intermediate layer: mixing MnSO 4 And KMnO 4 Dissolving in water at a molar ratio of 3:2, wherein MnSO 4 The concentration of the reaction solution in water is 1.5mM, 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-MnO 2 a/Ni foam electrode;
the obtained gamma-MnO 2 The 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 substrate 2 The 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 observed 2 The surface of the/Ni foam electrode is of a porous nano structure, wherein the surface of the/Ni foam electrode is of nano flaky gamma-MnO 2 Nano-sheet gamma-MnO vertically arranged on the surface of foam nickel base 2 The 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: PdCl 2 And NaCl in a molar ratio of 1:3 in water, wherein PdCl 2 The concentration of NaCl in water is 12mM, and solution B is prepared; then the gamma-MnO obtained in the step (2) is added 2 Putting 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-MnO 2 the/Ni foam composite electrode.
Finally prepared Pd/gamma-MnO 2 In the/Ni foam composite electrode, gamma-MnO 2 The supporting amount of the intermediate layer was 0.33mg/cm 2 The deposition amount of the Pd nanoparticles was 0.7mg/cm 2 。
The obtained Pd/gamma-MnO 2 An 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 example 2 X-ray diffraction patterns of the powders from which we can see that the examples of the invention use MnSO 4 And KMnO 4 MnO is prepared by controlling the proportion of the reaction raw materials and hydrothermal reaction conditions 2 MnO of gamma crystal form with regular hexagonal structure 2 The nano-sheet can provide more active sites, and is more beneficial to adsorption and decomposition of pollutants.
Example 2
In this example, Pd/γ -MnO 2 The preparation process of the/Ni foam composite electrode is the same as that of the example 1, except that: ' MnSO in step (2) 4 Concentration in water was 0.5mM ", Pd/gamma-MnO was finally prepared 2 In the/Ni foam composite electrode, gamma-MnO 2 The supporting amount of the intermediate layer is 0.15mg/cm 2 The deposition amount of the Pd nanoparticles was 0.7mg/cm 2 。
Example 3
In this example, Pd/γ -MnO 2 The preparation process of the/Ni foam composite electrode is the same as that of the example 1, except that: ' MnSO in step (2) 4 Concentration in water 1mM ", Pd/gamma-MnO prepared finally 2 In the/Ni foam composite electrode, gamma-MnO 2 The supporting amount of the intermediate layer was 0.21mg/cm 2 The deposition amount of the Pd nanoparticles was 0.7mg/cm 2 。
Example 4
In this example, Pd/γ -MnO 2 The preparation process of the/Ni foam composite electrode is the same as that of the example 1, except that: ' MnSO in step (2) 4 Concentration in water 2mM ", Pd/gamma-MnO prepared finally 2 In the/Ni foam composite electrode, gamma-MnO 2 The supporting amount of the intermediate layer was 0.42mg/cm 2 The deposition amount of the Pd nanoparticles was 0.7mg/cm 2 。
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 (30mm multiplied by 20mm) with acetone for 15min to remove organic matters on the surface of the foamed nickel; then 10% hydrochloric acid is used for ultrasonic treatment for 15min 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: PdCl 2 And NaCl in a molar ratio of 1:3 in water, wherein PdCl 2 The concentration of (A) is 4mM, the concentration of NaCl is 12mM, 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 0.7mg/cm 2 。
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. 3 2 According 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 matrix 2 After the intermediate layer, Pd metal is deposited chemically to obtain Pd/gamma-MnO 2 the/Ni foam composite electrode can enable Pd particles on the surface of the electrode to be more dispersed, and the particle size to be 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 (30mm multiplied by 20mm) with acetone for 15min to remove organic matters on the surface of the foamed nickel; then 10% hydrochloric acid is used for ultrasonic treatment for 15min 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: PdCl 2 And NaCl in a molar ratio of 1:3 in water, wherein PdCl 2 With the concentration of 16mM and the concentration of NaCl of 48mM, 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 2.8mg/cm 2 。
Application example 1
Having different gamma-MnO levels, obtained respectively in examples 1-4 of the present invention 2 Supported Pd/gamma-MnO 2 the/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 50mM Na 2 SO 4 The solution is subjected to electro-reduction dechlorination treatment under the current of-10 mA for 2 hours on 100mL of wastewater containing 25mg/L of 2,4, 6-trichlorophenol.
As shown in FIG. 6, different γ -MnO prepared in examples 1-4 of the present invention 2 Supported Pd/gamma-MnO 2 The 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 added 2 The loading amount is 0.33mg/cm 2 Pd/gamma-MnO of 2 The 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, respectively 2 The Pd/Ni foam electrode prepared in comparative example 1 and comparative example 2 and the/Ni foam composite electrode are used as working electrodes, platinum sheets are used as counter electrodes, 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 50mM Na is adopted as electrolyte 2 SO 4 And (3) carrying out electro-reduction dechlorination on 100mL of wastewater containing 50mg/L o-chlorophenol under the current of-10 mA for 2 h.
FIG. 7 shows Pd/gamma-MnO prepared in example 1 of the present invention 2 Dechlorination 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-MnO 2 Ni is Pd/gamma-MnO prepared in example 1 of the present invention 2 the/Ni foam composite electrode has a Pd loading of 0.7mg/cm 2 (ii) a Pd (0.7)/Ni was the Pd/Ni foam electrode obtained in comparative example 1, and the Pd loading was 0.7mg/cm 2 (ii) a Pd (2.8)/Ni was the Pd/Ni foam electrode obtained in comparative example 2, and the Pd loading was 2.8mg/cm 2 . As can be seen from the figure, the Pd/gamma-MnO obtained in example 1 after electrocatalysis for 2h 2 The 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. 7 2 The dechlorination effect of the/Ni foam composite electrode is similar to that of the/Ni foam composite electrode, but Pd/gamma-MnO 2 the/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 invention 2 FIG. 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 invention 2 the/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 2 2 the/Ni foam composite electrode and the Pd/Ni foam electrode prepared in comparative example 2 were used as working electrodes, a platinum sheet was used as a counter electrode, a saturated calomel electrode was used as a reference electrode, and a cathode chamber and an anode chamber were exchanged with cationsThe electrolyte is 50mM Na 2 SO 4 The solution is respectively added with 10mM Cl under the current of-10 mA - ，HCO 3 - ，NO 3 - Waiting for different anions (adding 10mM Na) 2 SO 4 As a blank control) was subjected to electro-reductive dechlorination for 4 hours in a 50mg/L o-chlorophenol solution.
FIG. 9 shows Pd/gamma-MnO prepared in example 2 of the present invention 2 Dechlorination 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 - ，HCO 3 - ，NO 3 - 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 amount 2 The 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 is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, 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-MnO 2 The 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 reaction 2 An intermediate layer prepared by chemical deposition of Pd nanoparticles; the gamma-MnO 2 The middle layer is MnO of gamma crystal form with a regular hexagonal structure 2 The γ -MnO 2 The middle layer is of a nano-sheet microstructure and is vertically arranged on the foamed nickel, and micropores are formed between the sheets.
2. The Pd/γ -MnO of claim 1 2 the/Ni foam composite electrode is characterized in that the gamma-MnO is 2 The loading capacity of the middle layer on the foamed nickel is 0.30-0.35 mg/cm 2 (ii) a The deposition amount of the Pd nano-particles is 0.68-0.72 mg/cm 2 。
3. A Pd/γ -MnO as defined in claim 1 or 2 2 The preparation method of the/Ni foam composite electrode is characterized by comprising the following steps of:
(1) pretreating foamed nickel;
(2) mixing MnSO 4 And KMnO 4 Dissolving in water to prepare a reaction solution A; then placing the pretreated foamed nickel into the reaction solution A for hydrothermal reaction; finally, the reacted foam nickel is sequentially washed by ethanol and deionized water and dried to obtain the gamma-MnO 2 a/Ni foam electrode;
(3) PdCl 2 Dissolving NaCl in water to prepare a solution B; then adding gamma-MnO 2 Putting 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-MnO 2 the/Ni foam composite electrode.
4. A Pd/γ -MnO according to claim 3 2 The preparation method of the/Ni foam composite electrode is characterized by comprising the following pretreatment steps: firstly, ultrasonically treating the foamed nickel for 15-20 min by using acetone; then carrying out ultrasonic treatment for 10-15 min by using 10% hydrochloric acid; finally washing with distilled water, and drying in the airDrying to obtain the pretreated foamed nickel.
5. A Pd/γ -MnO according to claim 3 2 The preparation method of the/Ni foam composite electrode is characterized in that the MnSO 4 And said KMnO 4 Is 3: 2.
6. A Pd/γ -MnO according to claim 3 2 The 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 3 2 The preparation method of the/Ni foam composite electrode is characterized in that the PdCl is prepared from PdCl 2 And 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 2 2 The 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 electrolyte 2 SO 4 And (3) solution.
9. The method for the electro-catalytic reduction dechlorination of chlorinated organic compounds in water according to claim 8, wherein the Na is 2 SO 4 The concentration of the solution is 25-50 mM.
10. The method for the electro-catalytic reduction and dechlorination of chlorinated organic compounds in water as claimed in claim 8, wherein the constant current range is-8 to-10 mA.
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