Electrode material for preparing Cu (II)-polymer from Cu (II)-EDTA (Ethylene Diamine Tetraacetic Acid) wastewater

Abstract

The invention discloses a method for preparing a Cu (II)-polymer electrode material by using Cu (II)-EDTA (Ethylene Diamine Tetraacetic Acid) wastewater. The core of the method is that the polymer material with high conductivity and low internal resistance is prepared from Cu (II)-EDTA wastewater through dopamine (DA) reconstruction and persulfate (PS) oxidative polymerization reaction. According to the method, DA is adopted as a competitive ligand under the alkaline condition, a non-free radical mechanism is initiated by activating PS through a metal-complex, so that DA and a Cu (II)-EDTA complex are subjected to complexing competition and are subjected to complexing reconstruction with Cu (II) to form a new complex, and then the Cu (II)-PDA material is obtained through oxidative polymerization. Cu (II)-PDA materials with different concentration gradients are designed through a complexing reconstruction-oxidative polymerization strategy, the electrochemical performance of Cu (II)-PDA is evaluated in combination with electrochemical testing, and the application potential of Cu (II)-PDA as a supercapacitor electrode material is explored. The conductivity and charge transfer performance of the material are far better than those of a traditional pure carbon material, and the material has excellent energy storage performance and low impedance characteristic. And meanwhile, the Cu (II)-PDA material is utilized in the supercapacitor electrode material, so that the supercapacitor electrode material has the advantages of high efficiency, environmental protection and economical efficiency.

Description

Technical Field

[0001] The present invention relates to a method for preparing a novel supercapacitor electrode material. This technology can be widely applied to the field of industrial wastewater resource utilization and energy storage devices, and is suitable for supercapacitors with high specific capacitance and long cycle life. Technical Background

[0002] At present, industrial wastewater contains a large amount of Cu(II)-organic complexes, which have high stability and are difficult to recycle resources using traditional methods. Existing technologies have tried to use oxidation polymerization or complex-breaking technologies to treat Cu(II)-wastewater, but they often consume a large amount of oxidants, have complex processes, and are difficult to achieve high-performance preparation of materials. Through the synergistic effect of dopamine and persulfate, Cu(II)-EDTA is removed while a polymerization product is produced for resource utilization. At the same time, with the rapid development of renewable energy, the demand for efficient energy storage systems is increasing day by day. Traditional supercapacitor electrodes mostly use materials such as activated carbon and conductive polymers, but they have problems such as limited specific capacitance, poor conductivity, and insufficient cycle life.

[0003] Supercapacitors have become a research hotspot in the energy storage field due to their advantages such as high power density, fast charge and discharge characteristics, and long cycle life. However, traditional carbon-based electrode materials have a relatively low specific capacitance (for example, the specific capacitance of activated carbon is usually less than 200 F g⁻¹), while polymer (such as polyaniline) conductive materials, although having pseudocapacitance characteristics, have poor cycle stability and are prone to structural collapse due to volume expansion. The Lee team was inspired by mussel biomimetics and used a porous carbon nanosheet (IPCN) electrode constructed by a composite of a polydopamine coating and Fe 3+ / tannic acid (TA). Its specific capacitance was increased by 40% compared with the unmodified material, and excellent cycle stability was demonstrated. In the prior art, Patent CN105914050B discloses the application of a chestnut shell-based nitrogen-doped carbon electrode material in supercapacitors. At a current density of 1 Ag -1 The highest specific capacitance reached 155 F g -1 However, it still cannot meet the high energy density requirements. The Lee team was inspired by mussel biomimetics and used a porous carbon nanosheet (IPCN) electrode constructed by a composite of a polydopamine coating and Fe 3+ / tannic acid (TA). Its specific capacitance was increased by 40% compared with the unmodified material and reached 244 F g -1 at a scan rate of 5 mV s -1 However, the metal loading is low and the conductivity improvement is limited. Therefore, it is of great significance to develop a new type of electrode material with both high specific capacitance and low cost. Summary of the Invention

[0004] The object of the present invention is to use the synergistic effect of DA-PS to produce Cu(II)-PDA as the oxidation product from Cu(II)-EDTA in wastewater. Subsequently, a supercapacitor electrode material based on copper-doped polydopamine is provided. Through the synergistic effect of copper and polydopamine, the specific capacitance and cycling stability are significantly improved, and at the same time, the recycling of heavy metals is realized.

[0005] To achieve the above object, the present invention adopts the following technical solutions: According to the first aspect of the present invention, there is provided a method for synthesizing a Cu(II)-PDA supercapacitor, comprising the following steps: S1. Prepare Cu(II)-organic complex wastewater, wherein the wastewater contains a Cu(II)-EDTA complex; S2. Under alkaline conditions, add a dopamine solution to the wastewater, so that dopamine undergoes a competitive complexation reaction with Cu(II)(II), and partially displace EDTA to form a Cu(II)-DA complex; S3. At the same time, add an appropriate amount of persulfate as an oxidant, and induce the Cu(II)-dopamine complex to undergo a C-C coupling polymerization reaction through a non-free radical activation mechanism to form a Cu(II)-polymer; S4. Heat-treat the obtained Cu(II)-polymer, and then mix Cu(II)-PDA with a binder and coat it on ITO conductive glass, and dry it to obtain an electrode.

[0006] Preferably, in step S1, the molar ratio of the copper salt to the ethylenediaminetetraacetate salt is 1:1; wherein, the copper salt is at least one of copper nitrate and copper sulfate, and the ethylenediaminetetraacetate salt is at least one of disodium ethylenediaminetetraacetate and ethylenediaminetetraacetic acid.

[0007] Preferably, in step S1, Cu(II)-EDTA is mixed evenly according to the molar ratio and stored for standby at a concentration of 1 mM - 5 mM.

[0008] Preferably, in step S2, the molar ratio of dopamine to Cu(II)-EDTA is 9:1 to 13:1, and the pH is maintained at a constant pH of 8.0 and the reaction temperature is 25 °C under a pH automatic titrator, and the stirring speed is 500 - 1000 r / min.

[0009] Preferably, in step S3, the persulfate is sodium persulfate or potassium persulfate. At the same time, the addition amounts of dopamine and persulfate in step S2 are 5 - 10 mM, and the pH is maintained at a constant pH of 8.0 and the reaction temperature is 25 °C under a pH automatic titrator, and the reaction time is 0.5 - 1 h.

[0010] Preferably, in step S3, the non-radical activation pathway induces the stretching of the O-O bond of persulfate through the Cu(II) coordination center to generate carbon-centered radicals (CCRs), driving the C-C bond coupling between DA molecules. After centrifuging the reaction, washing it three times with deionized water, and drying it in a vacuum drying oven at 80 °C for 12 h.

[0011] Preferably, in step S4, the binder is prepared by mixing ethanol:acetone:5% Nafion solution in a volume ratio of 10:10:1 to form a binder system. After mixing it with a magnetic stirrer at a speed of 800 rpm for 30 minutes, it is filtered through a 0.22 μm nylon filter membrane and stored in a sealed bottle (the effective use time limit does not exceed 6 hours).

[0012] Preferably, in step S4, 0.01 g of the Cu(II)-PDA polymer material is added to 525 μL of the binder solution and treated by ultrasound in an ice-water bath for 3 hours to obtain a homogeneous dispersion. Using a micropipette, 20 μL of the dispersion is precisely taken and evenly coated on the ITO conductive glass (controlling the coating area to be 1 × 1 cm), and after air-drying for 24 h, it is used for electrochemical testing.

[0013] Preferably, for the electrode prepared in step S4 in a three-electrode system, the cyclic voltage range is 0.4 - 1.0 V, and the potential scanning rate is 10 - 100 mV s -1 , the voltage range for the galvanostatic charge-discharge test is 0.3 - 1.0 V, and the current density is 1 - 10 A g -1 . The test frequency range for EIS testing is 0.01 Hz–100 kHz, and the amplitude of the AC perturbation is 5 mV. Description of the Drawings

[0014] Figure 1 : Cyclic performance comparison chart (Cu(II)-PDA vs. pure carbon electrode); Figure 2 : SEM image of the obtained electrode material.

[0015] Example 1: (1) Prepare Cu(II)-EDTA complex wastewater. 355.8 mg of Cu(II)(NO3)2•3H2O and 558.3 mg of C 10 H 14 N2O8Na2•2H2O are dissolved in deionized water in a 1:1 molar ratio and made up to 1 L to prepare 1.5 mM Cu(II)-EDTA complex simulated wastewater.

[0016] (2) Accurately weigh 569 mg of DA (C8H 11(NO2•HCl), dissolve them separately in deionized water and make up the volume to 0.1 L to obtain 30 mM stock solutions. Take 20 mL of Cu(II)-EDTA and 9 mL of DA in a 50 mL conical flask, and use a pH automatic potentiometric titrator to keep the pH constant under alkaline conditions, and stir magnetically.

[0017] (3) Add 1 mL of 150 mM PS as an oxidant, and induce the C-C coupling polymerization reaction of the Cu(II)-DA complex through a non-radical activation mechanism to form a Cu(II)-polymer. Keep the pH constant and stir magnetically for 30 min.

[0018] (4) Wash and dry the obtained Cu(II)-polymer. Then weigh 0.01 g of the Cu(II)-PDA polymer and add it to a binder system prepared according to a volume ratio of 1 mL of ethanol, 1 mL of acetone, and 0.1 mL of 5% Nafion solution. Treat it by ultrasound under ice-water bath conditions for 3 hours to obtain a homogeneous dispersion. Accurately take 20 μL of the dispersion and evenly coat it on the ITO conductive glass. After air-drying for 24 h, it is used for electrochemical testing. This supercapacitor shows a specific capacitance as high as 55.97 F / g at a current density of 1 A / g. -1 The specific capacitance at the current density is as high as 55.97 F / g. -1 The AC impedance (EIS): Re = 8.49 Ω.

[0019] Example 2: (1) Prepare Cu(II)-EDTA complex wastewater. Dissolve 711.6 mg of Cu(II)(NO3)2•3H2O and 1116.6 mg of C 10 H 14 N2O8Na2•2H2O in deionized water according to a 1:1 molar ratio and make up the volume to 1 L to obtain 3 mM Cu(II)-EDTA complex simulated wastewater.

[0020] (2) Accurately weigh 569 mg of DA (C8H 11 (NO2•HCl), dissolve them separately in deionized water and make up the volume to 0.1 L to obtain 30 mM stock solutions. Take 20 mL of Cu(II)-EDTA and 9 mL of DA in a 50 mL conical flask, and use a pH automatic potentiometric titrator to keep the pH constant under alkaline conditions, and stir magnetically.

[0021] (3) Add 1 mL of 150 mM PS as an oxidant, and induce the C-C coupling polymerization reaction of the Cu(II)-DA complex through a non-radical activation mechanism to form a Cu(II)-polymer. Keep the pH constant and stir magnetically for 30 min.

[0022] (4)The obtained Cu(II)-polymer was washed and dried. Subsequently, 0.01 g of the Cu(II)-PDA polymer was weighed and added to a binder system prepared by mixing 1 mL of ethanol, 1 mL of acetone, and 0.1 mL of 5% Nafion solution by volume. The mixture was treated by ultrasound in an ice-water bath for 3 hours to obtain a homogeneous dispersion. Exactly 20 μL of the dispersion was precisely taken and uniformly coated on an ITO conductive glass, and left to dry naturally for 24 h for electrochemical testing. The supercapacitor showed a specific capacitance as high as 284.04 Fg -1 at a current density of 1 A g -1 . The electrochemical impedance spectroscopy (EIS): Re = 8.14 Ω.

[0023] As described above, the above are only examples of the present invention and do not limit the present invention in other forms. Any person skilled in the art may use the disclosed technical content to make changes or modifications into equivalent embodiments with equivalent changes. However, any modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. An electrode material for preparing Cu(II)-polymer using Cu(II)-EDTA wastewater, the method comprising the following steps: S1. Prepare Cu(II)-EDTA wastewater, wherein the wastewater contains Cu(II)-EDTA complex; S2. Under alkaline conditions, add dopamine solution to the wastewater, so that dopamine undergoes a complexation competition reaction with Cu(II), and undergoes complexation reconstruction with Cu(II) to form a Cu(II)-DA complex; S3. At the same time, add an appropriate amount of persulfate as an oxidant, and induce the C-C coupling polymerization reaction of the Cu(II)-DA complex through the activation of PS by Cu(II)-DA / Cu(II)-EDTA to initiate a non-radical mechanism to form Cu(II)-PDA; S4. Filter, wash and dry the obtained Cu(II)-PDA, and then mix the Cu(II)-PDA with a binder and coat it on ITO conductive glass, and dry it to obtain an electrode.

2. The method according to claim 1, wherein: In step S1, the molar ratio of copper salt to ethylenediaminetetraacetate is 1:1; wherein, the copper salt is at least one of copper nitrate and copper sulfate, and the ethylenediaminetetraacetate is at least one of disodium ethylenediaminetetraacetate and ethylenediaminetetraacetic acid.

3. The method according to claim 1, characterized in that: In step S1, Cu(II)-EDTA is mixed evenly according to the molar ratio and stored for standby at a concentration of 1 mM - 5 mM.

4. The method according to claim 1, characterized in that: In step S2, the molar ratio of dopamine to Cu(II)-EDTA is 9:1 - 13:1, and the constant pH is maintained at 8.0 and the reaction temperature is 25 °C under a pH automatic titrator, and the stirring speed is 500 - 1000 r / min.

5. The method according to claim 1, wherein: In step S3, the persulfate is sodium persulfate or potassium persulfate. At the same time, the addition amounts of dopamine and persulfate in step S2 are 5 - 10 mM, and the constant pH is maintained at 8.0 and the reaction temperature is 25 °C under a pH automatic titrator, and the reaction time is 0.5 - 1 h.

6. The method according to claim 1, characterized in that: In step S3, the non-radical activation path induces the stretching of the O-O bond of persulfate through the Cu(II) coordination center to generate carbon-centered radicals (CCRs), driving the C-C bond coupling between DA molecules. The reaction is centrifuged, washed three times with deionized water, and then dried in a vacuum drying oven at 80 °C for 12 h.

7. The method according to claim 1, wherein: In step S4, the binder system is prepared according to the volume ratio of ethanol:acetone:5% Nafion solution = 10:10:

1. After mixing with a magnetic stirrer at a speed of 800 rpm for 30 minutes, it is filtered through a 0.22 μm nylon filter membrane and stored in a sealed bottle (the effective use time limit does not exceed 6 hours).

8. The method according to claim 1, characterized in that: In step S4, 0.01 g of Cu(II)-PDA polymer material is added to 525 μL of binder solution, and the mixture is treated by ultrasound in an ice-water bath for 3 hours to obtain a homogeneous dispersion. 20 μL of the dispersion is accurately taken with a micropipette and evenly coated on ITO conductive glass (the controlled coating area is 1 × 1 cm), and left to dry naturally for 24 h for electrochemical testing.

9. The method according to claim 1, wherein: The electrode prepared in step S4 is in a three-electrode system, with a cyclic voltage range of 0.4 - 1.0 V and a potential scanning rate of 10 - 100 mV s -1 , the voltage range for constant current charge-discharge test is 0.3 - 1.0 V, and the current density is 1 - 10 A g -1 , the test frequency range for EIS test is 0.01 Hz–100 kHz, and the amplitude of AC perturbation is 5 mV.

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