In-situ growth of nanocomposite electrode and preparation method and application thereof

Abstract

This invention proposes an in-situ grown nanocomposite electrode, its preparation method, and its application. The method includes the following steps: 1) Immersing pretreated carbon paper in a methanol solution of cobalt nitrate hexahydrate, followed by adding a methanol solution of 2-methylimidazole and stirring; 2) Adding potassium tetrachloropalladate to the above solution and stirring at room temperature, then adding sodium borohydride solution for reduction, and drying the catalyst-coated carbon paper in a vacuum oven at 60°C overnight; 3) Pyrolyzing the dried carbon paper in a nitrogen atmosphere to obtain a PdCo / carbon paper electrode material. This method is easy to operate, and the prepared composite electrode has a stable catalytic effect and a significant degradation effect on pollutants in wastewater.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical water treatment technology, and particularly relates to an in-situ grown PdCo / carbon paper electrode material, its preparation method, and its application. Background Technology

[0002] Electrochemical water treatment technology is a method that uses electrochemical reactions to remove or transform pollutants in water. It achieves purification by applying an electric current to electrodes, causing oxidation-reduction reactions in the pollutants. This technology offers advantages such as high efficiency, environmental friendliness, and low energy consumption, and is suitable for treating pollutants such as heavy metals, organic matter, and microorganisms. Electrochemical methods include electrolysis, electrodialysis, and electroflotation, and are widely used in industrial wastewater treatment and drinking water purification. With technological advancements, electrochemical water treatment is developing towards lower costs and wider applications.

[0003] In electrocatalytic hydrodechlorination, atomic hydrogen (H*) is generated by water electrolysis on the catalyst surface. This has been proven to remove halogens from many difficult-to-oxidize halogenated pollutants. H* attacks the C-Cl bond, converting it to a C-H bond, thereby significantly reducing the molecular toxicity and stability of the halogenated pollutants and increasing the biodegradability of wastewater. Electrocatalytic hydrodehalogenation can typically be achieved through direct electron transfer (DET) and indirect electron transfer (IET) processes. However, both DET and IET have competing side reactions, thus requiring ideal catalyst materials to overcome side reactions such as hydrogen evolution reaction and improve the efficiency of electrocatalytic hydrodehalogenation.

[0004] Zeolite imidazole ester framework material (ZIF-67) is a class of materials composed of Co 2+ The center and 2-Mim ligand are assembled

[0005] Metal-organic frameworks (MOFs) possess high thermal and chemical stability and can be prepared using simple and environmentally friendly organic synthesis methods. The nanostructure and average particle size of ZIF-67 can be tuned by controlling experimental conditions, allowing for precise control of the material's pore size. Thanks to its strong binding sites, conductive MOFs can serve as ideal interlayers, simultaneously immobilizing and modulating the electronic structure of Pd particles. ZIF-67 has found wide application in various scenarios such as catalysis, gas separation and storage, sensing and energy storage, air filtration, wastewater treatment, and drug delivery. ZIF-67-derived carbon is a porous carbon material obtained by high-temperature carbonization of ZIF-67. Inheriting the porous structure of ZIF-67, ZIF-67-derived carbon provides numerous active sites and a high specific surface area for its applications in electrocatalysis, gas adsorption, and energy storage. This high specific surface area helps improve the adsorption capacity and catalytic reaction efficiency. During carbonization, the metal components in ZIF-67 form nanoparticles, which enhance the material's conductivity. Due to the excellent thermal stability of ZIF-67 itself, ZIF-67-derived carbon also typically exhibits high thermal stability, making it suitable for high-temperature applications. Because of its unique physicochemical properties, ZIF-67-derived carbon shows broad application potential in numerous fields, including supercapacitors, lithium-ion batteries, fuel cells, electrocatalytic water splitting, gas adsorption, and storage. Pd catalysts can absorb protons at low overpotentials to generate highly reduced H* species, which are then adsorbed onto the Pd surface (H*ads), thus achieving an indirect H*ads-mediated dehalogenation pathway for target pollutants. Summary of the Invention

[0006] This invention proposes an in-situ grown composite electrode, its preparation method, and its application. The in-situ grown composite electrode is obtained by using an impregnation method and controlling conditions such as the precursor ratio. It is then used to prepare immobilized three-dimensional electrodes and to remove pollutants from wastewater, exhibiting superior catalytic performance.

[0007] In a first aspect, the present invention provides a method for preparing an in-situ grown composite electrode material, comprising the following steps:

[0008] 1) Add hydrophilically pretreated carbon paper to a methanol solution of cobalt nitrate, stir for the first time, then add a methanol solution of 2-methylimidazole, and stir for the second time.

[0009] 2) Add potassium tetrachloropalladium to the solution obtained in step 1) and stir for the first time, then add sodium borohydride solution and stir for the second time; take out the carbon paper, wash it with ethanol, and dry it to obtain carbon paper material with Pd / ZIF-67 grown in situ.

[0010] 3) The Pd / ZIF-67 carbon paper material obtained in step 2) is pyrolyzed in a nitrogen atmosphere to obtain PdCo / carbon paper electrode material.

[0011] Furthermore, the hydrophilic pretreated carbon paper is prepared by the following steps: the carbon paper is cut and then soaked in concentrated nitric acid, the acid adhering to the surface is washed off with deionized water and then dried. The size of the cut carbon paper is 2×2cm; the drying temperature is 60℃ and the time is 12h.

[0012] Furthermore, the molar ratio of cobalt nitrate to 2-methylimidazole is 1:8.6.

[0013] Furthermore, in step 1), the stirring speed is 300 rpm, the first stirring time is at least 1 hour, and the second stirring time is at least 12 hours.

[0014] Furthermore, the molar ratio of potassium tetrachloropalladium to cobalt nitrate is 1:0.1 to 2, and the molar ratio of sodium borohydride to potassium tetrachloropalladium is 5:1.

[0015] Furthermore, in step 2), the stirring speed is 300 rpm, the first stirring time is at least 12 hours, the second stirring time is at least 15 minutes, the drying temperature is 60℃, and the time is 12 hours.

[0016] Furthermore, in step 3), the mixture is pyrolyzed at 800°C for 3 hours in a nitrogen atmosphere at a heating rate of 5°C / min.

[0017] Secondly, the present invention proposes an in-situ grown composite electrode material prepared by the method described in the first aspect.

[0018] Thirdly, the present invention proposes the application of an in-situ grown composite electrode material prepared by the method described in the first aspect in the removal of pollutants from wastewater.

[0019] Furthermore, the contaminants include 2,4,6-trichlorophenol, 2,4,-dichlorophenol, p-chlorophenol, diclofenac sodium, and atrazine.

[0020] Furthermore, the pH of the wastewater to be treated is 4-7.

[0021] Fourthly, the present invention proposes a through-type electrode reactor comprising the in-situ grown composite electrode material prepared by the method described in the first aspect.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] This invention aims to enhance the production of H* in water electrolysis for dehalogenation of pollutants. It proposes a method for preparing an in-situ grown nanocomposite electrode. By controlling the molar ratio of Co to Pd, a PdCo / carbon paper electrode material with a 1:1 PdCo molar ratio is obtained, which significantly improves the efficiency of hydrodehalogenation. This material is filled into a through-hole electrode reactor, and through an electrocatalytic reduction process, the generation and utilization of H* are enhanced with the aid of a microfluidic field. This improves the reaction interface between the pollutants and the electrode. H* attacks the C-Cl bonds on the pollutants, transforming halogenated pollutants that are difficult to directly degrade by oxidation into easily removable organic pollutants, reducing their biotoxicity and thus achieving the degradation goal.

[0024] The electrode material preparation and application methods proposed in this invention are simple and reasonable, with stable effects. The immobilized electrode can be reused. It has significant effects in the electrocatalytic hydrogenation dehalogenation degradation of pollutants such as 2,4,6-trichlorophenol, 2,4-dichlorophenol, p-chlorophenol, diclofenac sodium, and atrazine, and has good application prospects in the field of water treatment. Attached Figure Description

[0025] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0026] Figure 1 This is a scanning electron microscope image of the in-situ grown nanocomposite electrode material prepared in Example 1 of the present invention.

[0027] Figure 2 This is a diagram showing the electrochemical degradation effect of 2,4,6-trichlorophenol in wastewater in Example 2 of the present invention.

[0028] Figure 3 This is a cyclic voltammetry diagram of the process for removing contaminant 2,4,6-trichlorophenol in Example 2 of the present invention.

[0029] Figure 4 This is a diagram showing the degradation effect of some common halogenated pollutants in Example 2 of the present invention. Detailed Implementation

[0030] The present application will be further described below with reference to specific embodiments.

[0031] It should be noted that terms such as "upper", "lower", "left", "right", and "middle" used in this specification are only for clarity of description and are not intended to limit the scope of implementation. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered as within the scope of this application.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the term “and / or” as used herein includes any and all combinations of one or more of the associated listed items.

[0033] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0034] As used herein, the term “about” is used to provide for the flexibility and imprecision associated with a given term, measure, or value. Those skilled in the art can readily determine the degree of flexibility for a particular variable.

[0035] As used herein, the term “at least one of…” is intended to be synonymous with “one or more of…”. For example, “at least one of A, B, and C” explicitly includes only A, only B, only C, and combinations thereof.

[0036] Concentration, amount, and other numerical data may be presented in range format herein. It should be understood that such range format is used solely for convenience and brevity and should be flexibly interpreted to include not only the values ​​explicitly stated as the limits of the range, but also all individual values ​​or subranges encompassed within the range, as if each value and subrange were explicitly stated. For example, a range of values ​​from about 1 to about 4.5 should be interpreted to include not only the explicitly stated limits of 1 to 4.5, but also individual numbers (such as 2, 3, 4) and subranges (such as 1 to 3, 2 to 4, etc.). The same principle applies to ranges that describe only a single value, such as “less than about 4.5,” which should be interpreted to include all the aforementioned values ​​and ranges. Furthermore, this interpretation should apply regardless of the breadth of the range or characteristic described.

[0037] In one embodiment of the present invention, electrospun nanocomposite electrode material is filled into a through-type electrode reactor, and wastewater to be treated is continuously pumped into the reactor for pollutant degradation.

[0038] Example 1

[0039] The preparation method of the in-situ grown nanocomposite electrode material of the present invention includes the following steps:

[0040] (1) Cut the carbon paper into 2×2cm pieces and soak it in concentrated nitric acid for 24h. After washing off the acid adhering to the surface with deionized water, dry it at 60℃ for 12h.

[0041] (2) Dissolve 1.16g of cobalt nitrohydrate hexahydrate in 40ml of methanol to obtain solution one, add the obtained pre-treated carbon paper and stir at 300rpm for 1h, dissolve 3.3g of 2-methylimidazole in 40ml of methanol to obtain solution two, pour solution two into solution one and mix and continue stirring for 12h.

[0042] (3) Add 1.3g of potassium tetrachloropalladium to the obtained solution and continue stirring for 12h; add 20ml of sodium borohydride solution (1mmol / L) and continue stirring for 15min; take out the carbon paper, wash it with ethanol, and dry it at 60℃ for 12h to obtain carbon paper material with Pd / ZIF-67 grown in situ.

[0043] (4) The obtained in-situ grown Pd / ZIF-67 carbon paper material was pyrolyzed at 800℃ for 3h in a nitrogen atmosphere at a heating rate of 5℃ / min to obtain a PdCo / carbon paper electrode material with a Co:Pd molar ratio of 1:1. This material was named the Co:Pd=1:1 sample and characterized by scanning electron microscopy. The results are as follows: Figure 1 .

[0044] Example 2

[0045] The process is the same as in Example 1, except that the molar ratio of CoPd is changed to 1:0.1, 1:0.2, 1:0.5, 1:1, and 1:2, respectively, to obtain PdCo / carbon paper electrode materials with different CoPd ratios, which are named Co:Pd=1:0.1 sample, Co:Pd=1:0.2 sample, Co:Pd=1:0.5 sample, Co:Pd=1:1.0 sample, and Co:Pd=1:2.0 sample, respectively.

[0046] Application Example 1

[0047] Experiment on the removal of pollutants from water using in-situ grown nanocomposite electrode materials

[0048] Different molar amounts of PdCo / carbon paper electrode materials obtained in Examples 1 and 2 were filled into a through-type electrode reactor, which mainly consisted of two electrode plates and a filter membrane in between. During the experiment, water was pumped in through a hole on one side of the electrode plate and flowed out through a hole on the other side of the electrode plate, returning to the beaker, thus achieving the removal of pollutants. A degradation experiment was conducted using 2,4,6-trichlorophenol as an example, and the specific process is as follows:

[0049] Prepare 100 mL of an aqueous solution containing 10 ppm of the contaminant 2,4,6-trichlorophenol (2,4,6-TCP) and 50 mmol of Na₂SO₄, and adjust the pH of the solution to 4.0 ± 0.1. Before the electrocatalytic process, purge the beaker with nitrogen gas for 30 min. During the electrocatalytic process, after turning on the peristaltic pump, the solution in the beaker is continuously pumped into the cathode chamber of the through-hole electrode reactor. After entering the anode chamber, the solution is circulated back to the beaker. Timing begins when the first drop of liquid flows out of the peristaltic tube returning to the beaker. Samples are taken at intervals to detect the concentration of 2,4,6-TCP. The results are as follows: Figure 2 As shown.

[0050] Depend on Figure 2 It can be seen that, compared with in-situ grown nanocomposite electrode materials with different Co:Pd ratios, the in-situ grown PdCo / carbon paper electrode of the Co:Pd=1:1 sample (Example 1) can achieve a degradation of 2,4,6-trichlorophenol of more than 92%.

[0051] During the degradation experiment, cyclic voltammetry (CV) using a three-electrode system showed a significant H* response in the reaction, as shown in the attached figure. Figure 3 As shown. By Figure 3 It can be seen that the Co:Pd=1:1 sample electrode (Example 1) has a significant enhancing effect on the generation of H*.

[0052] In addition, during the degradation experiment, the pH was adjusted, and it was found that the Co:Pd=1:1 sample (Example 1) had a good degradation effect on 2,4,6-trichlorophenol in the pH range of 4-7, indicating that it has a relatively broad range of applications in water treatment.

[0053] Application Example 2

[0054] The Co:Pd = 1:1 sample obtained in Example 1 was filled into a through-hole electrode reactor, and the dehalogenation effect of several other common halogenated contaminants was tested. The procedure was the same as in Example 1, and the test results are as follows. Figure 4 As shown. By Figure 4 It can be seen that it has a good degradation effect on a variety of pollutants.

[0055] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing in-situ grown composite electrode material, characterized in that, Includes the following steps: 1) Add hydrophilically pretreated carbon paper to a methanol solution of cobalt nitrate, stir for the first time, then add a methanol solution of 2-methylimidazole, and stir for the second time. 2) Add potassium tetrachloropalladium to the solution obtained in step 1) and stir for the first time, then add sodium borohydride solution and stir for the second time; take out the carbon paper, wash it with ethanol, and dry it to obtain carbon paper material with Pd / ZIF-67 grown in situ. 3) The Pd / ZIF-67 carbon paper material obtained in step 2) is pyrolyzed in a nitrogen atmosphere to obtain PdCo / carbon paper electrode material. The molar ratio of cobalt nitrate to 2-methylimidazole is 1:8.

6. The molar ratio of potassium tetrachloropalladium to cobalt nitrate is 1:0.1~2, and the molar ratio of sodium borohydride to potassium tetrachloropalladium is 5:

1.

2. The method of claim 1, wherein, In step 1), the stirring speed is 300 rpm, the first stirring time is at least 1 hour, and the second stirring time is at least 12 hours.

3. The method as described in claim 1, characterized in that, In step 2), the stirring speed is 300 rpm, the first stirring time is at least 12 h, the second stirring time is at least 15 min, the drying temperature is 60 ℃, and the time is 12 h.

4. The method as described in claim 1, characterized in that, In step 3), the mixture is pyrolyzed at 800 °C for 3 h in a nitrogen atmosphere at a heating rate of 5 °C / min.

5. An in-situ grown composite electrode material prepared by the method according to any one of claims 1-4.

6. The application of an in-situ grown composite electrode material prepared by the method according to any one of claims 1-4 in the removal of pollutants from wastewater.

7. The application as described in claim 6, characterized in that, The contaminants include one or more of 2,4,6-trichlorophenol, 2,4,2-dichlorophenol, p-chlorophenol, diclofenac sodium, and atrazine.

8. A through-type electrode reactor, characterized in that, It comprises in-situ grown composite electrode material prepared by the method as described in any one of claims 1-4.

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