Application of fullerol-supported palladium nanowire composites in the electrocatalytic dechlorination of 2,4-dichlorophenol

Abstract

This invention discloses the application of a fullerol-supported palladium nanowire composite material in the electrocatalytic dechlorination of 2,4-dichlorophenol. The fullerol-supported palladium nanowire composite material is loaded onto a conductive substrate to form a working electrode. This working electrode is used as the cathode of an electrochemical reactor to perform an electrocatalytic dechlorination reaction on wastewater containing 2,4-dichlorophenol. This invention, by modifying fullerol-modified palladium nanowires, yields a highly promising electrocatalyst for the dechlorination of 2,4-dichlorophenol, which enhances the adsorption and activation capacity for 2,4-dichlorophenol, thereby improving catalytic selectivity and reaction rate.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical technology, specifically relating to the application of a fullerol-supported palladium nanowire composite material in the electrocatalytic dechlorination of 2,4-dichlorophenol. Background Technology

[0002] With the rapid development of modern industry and agriculture, various organic pollutants are continuously being released into the natural environment, posing an increasingly serious threat to ecosystems and human health. In recent years, organic compounds such as antibiotics, pesticides, and their metabolites have gradually been listed as emerging pollutants due to their persistence, biotoxicity, and potential ecological risks, attracting widespread attention from researchers. Among them, 2,4-dichlorophenol (2,4-DCP), as an important chemical intermediate and pesticide degradation product, is widely present in water bodies, soil, and sediments, and has become one of the typical halogenated aromatic pollutants that urgently need attention in the environmental field.

[0003] 2,4-DCP is an important precursor in the synthesis of many pesticides (such as 2,4-D herbicides), pharmaceuticals, dyes, and fungicides. It is also an intermediate in the degradation of some chlorinated organic compounds in the environment. Due to its extensive use and incomplete treatment in industrial production, 2,4-DCP enters the aquatic environment through industrial wastewater, agricultural runoff, and domestic sewage. This compound exhibits strong chemical stability, some lipid solubility, and poor biodegradability. In particular, the presence of two chlorine atoms in its molecular structure makes it difficult to decompose effectively under natural conditions, leading to long-term persistence in the environment and potential bioaccumulation through the food chain, thus posing potential ecotoxicity and health risks.

[0004] Currently, common treatment methods for typical halogenated aromatic pollutants include physical, biological, and chemical methods. Among them, chemical methods, including chemical catalytic oxidation, electrochemical catalysis, photocatalysis, and advanced oxidation technologies, have been widely used for the degradation of antibiotics in water due to their advantages such as simple operation, high efficiency, mild reaction conditions, and low risk of secondary pollution.

[0005] Electrochemical catalysis, which utilizes continuous electrons provided by the cathode to achieve selective hydrodechlorination of 2,4-DCP, has attracted considerable attention in recent years. The selection of the cathode catalyst is crucial for improving the dechlorination efficiency of 2,4-DCP. Among numerous cathode catalyst materials, palladium (Pd)-based materials are widely recognized as one of the most active noble metal catalysts in electrochemical hydrodechlorination (EHDC) reactions due to their unique electronic structure and physicochemical properties. Their advantages are mainly reflected in several aspects: First, their excellent catalytic activity; Pd has extremely strong adsorption and activation capabilities for hydrogen, enabling efficient dissociation of water molecules or protons to produce atomic hydrogen (H*, the key active species in hydrodechlorination reactions); second, Pd exhibits dechlorination selectivity for halogenated aromatic compounds such as 2,4-DCP, significantly reducing the activation energy for C-Cl bond breaking and achieving efficient dechlorination conversion; furthermore, Pd possesses good conductivity and stability, facilitating rapid electron transfer on the electrode surface. Simultaneously, under the negative potential environment of electrochemical reduction, the Pd metallic state is relatively stable, not easily oxidized or corroded, ensuring the sustained progress of the catalytic reaction.

[0006] However, single Pd catalysts still have significant limitations in practical applications: First, as a precious metal, Pd is scarce in the Earth's crust and expensive, which greatly limits its large-scale industrial application. How to maintain high activity while reducing the amount of Pd used through other means is a current research challenge. Second, catalyst poisoning and deactivation are significant issues. During the electrochemical degradation of 2,4-DCP, intermediate products (such as phenol and cyclohexanone) or byproducts are easily strongly adsorbed onto the active sites of Pd, leading to the occupation of active sites and a decrease in catalytic efficiency over time. Third, the competing hydrogen evolution reaction (HER) is also a major challenge. In aqueous systems, the HER is the main competing reaction for hydrodechlorination. If the electronic structure of the Pd surface is not properly controlled, a large number of electrons will be consumed to generate hydrogen gas instead of being used for the dechlorination of pollutants, which will greatly reduce the degradation rate and current efficiency of the target pollutants. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide an application of fullerol-supported palladium nanowire composite material in the electrocatalytic dechlorination of 2,4-dichlorophenol, which can significantly improve the reaction efficiency and current efficiency of Pd and promote its practical application in the treatment of 2,4-dichlorophenol pollution.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: Application of a fullerol-supported palladium nanowire composite material in the electrocatalytic hydrodechlorination of 2,4-dichlorophenol; The preparation method of the fullerol-supported palladium nanowire composite material is as follows: a palladium precursor solution is mixed with fullerol, then a reducing agent is added, the mixture is stirred and reacted, and then centrifuged to obtain the fullerol-supported palladium nanowire composite material; the fullerol-supported palladium nanowire composite material is loaded onto a conductive substrate to form a working electrode; the working electrode is used as the cathode of an electrochemical reaction device to perform an electrocatalytic hydrogen dechlorination reaction on wastewater containing 2,4-dichlorophenol.

[0009] As a preferred technical solution, the chemical formula of the fullerol is C0. 60 (OH) x x = 24 - 48.

[0010] As a preferred technical solution, the palladium precursor is one or more of palladium chloride, potassium chloride palladiumate, sodium chloride palladiumate, and palladium nitrate.

[0011] As a preferred technical solution, the molar ratio of the palladium precursor to fullerol is 1:0.01-0.03.

[0012] As a preferred technical solution, the reducing agent is one or more of sodium borohydride, hydrazine hydrate, ascorbic acid, or citric acid.

[0013] As a preferred technical solution, when performing electrocatalytic hydrogen dechlorination reaction on wastewater containing 2,4-dichlorophenol, the operating voltage is -0.8 to -0.9V.

[0014] As a preferred technical solution, when performing electrocatalytic hydrogen dechlorination on wastewater containing 2,4-dichlorophenol, the initial concentration of 2,4-dichlorophenol in the wastewater is 5-100 mg / L.

[0015] The beneficial effects of this invention are as follows: This invention loads fullerol onto palladium nanowires to obtain a highly promising and efficient catalytic system. In the electrocatalytic dechlorination reaction of 2,4-dichlorophenol, it can enhance the adsorption and activation of 2,4-dichlorophenol, thereby improving catalytic selectivity and reaction rate.

[0016] First, fullerols, as functionalized carbon materials, possess abundant electronic structures and hydrophilic hydroxyl groups. Through π-π interactions and polar interactions, they can effectively adsorb 2,4-dichlorophenol molecules from water, achieving contaminant enrichment on the catalyst surface and significantly increasing the local concentration of reactants, laying the foundation for subsequent efficient degradation. Palladium nanowires, with their high specific surface area and specific crystal facet exposure characteristics, can provide a large number of active sites, promoting hydrogen activation and transfer. In the hydrodechlorination reaction, the active hydrogen (H*) generated on the Pd surface can efficiently attack the C-Cl bonds of 2,4-dichlorophenol molecules, achieving rapid dechlorination and generating low-toxicity or non-toxic products.

[0017] Secondly, fullerol and palladium nanowires have a synergistic effect, specifically manifested in the following ways: (1) The strong interfacial electronic interaction between fullerol and palladium nanowires can regulate the electronic structure of Pd, forming an electron-deficient Pd state, enhancing its adsorption and activation ability for 2,4-dichlorophenol, and improving catalytic selectivity and reaction rate. (2) In practical applications of electrocatalytic dechlorination, palladium catalysts are easily poisoned and deactivated by the adsorption of chloride ions, dechlorination products, natural organic matter (NOM), etc. generated during dechlorination. The uniform coating of fullerol on the surface of palladium nanowires can form a physical isolation layer, effectively preventing direct contact between poisoned species and Pd active sites. (3) The abundant hydrophilic hydroxyl groups on the surface of fullerol can form an ordered hydrogen bond network at the catalyst-water interface: On the one hand, this hydrogen bond network can effectively capture and enrich 2,4-dichlorophenol molecules in water through hydrogen bonding, significantly increasing the local concentration of reactants on the catalyst surface; on the other hand, it can promote the efficient transfer of protons along the hydrogen bond network, accelerate the transfer of H* on the Pd surface, and reduce the energy barrier of the hydrodechlorination reaction. Attached Figure Description

[0018] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the following figures are provided for illustration: Figure 1 shows the SEM image of Pd prepared in Comparative Example 1; Figure 2 shows the Pd / C prepared in Example 1. 60 SEM image of -OH; Figure 3 shows Pd and Pd / C. 60 Comparison of X-ray photoelectron spectra of -OH materials; Figure 4 shows Pd and Pd / C. 60 Liquid phase peak area of ​​2,4-DCP after 180 min of electrocatalytic reaction in the -OH system; Figure 5 shows the Pd and Pd / C ratio in the electrocatalytic reaction. 60 The degradation efficiency of -OH on 2,4-DCP varies over time; Figure 6 shows the Pd / C ratio at different initial concentrations. 60 The liquid phase peak area of ​​2,4-DCP after 180 min of electrocatalytic reaction in the -OH system; Figure 7 shows the Pd / C ratio in the electrocatalytic reaction. 60 The degradation efficiency of -OH on different concentrations of 2,4-DCP varies over time; Figure 8 shows the Pd / C ratio at different voltages in the electrocatalytic reaction. 60 The degradation efficiency of -OH on 2,4-DCP varies over time; Figure 9 shows Pd and Pd / C. 60 Comparison of cyclic voltammetry curves of -OH in electrolytes containing and without 2,4-DCP. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0020] The fullerols used in the following examples are C 60 -OH indicates that its chemical formula is C 60 (OH) 26 Purchased from Suzhou Dade Carbon Nanotechnology Co., Ltd.

[0021] Example 1: Preparation of Pd / C 60 -OH working electrode (1) Dissolve 0.1g PdCl2 in 100 µL of concentrated hydrochloric acid, then dilute with deionized water to 10 mL; transfer the solution to a glass container, heat in an oil bath at 60℃ for 1 hour, cool and store at 4℃. (2) Take 315µL dCl2 stock solution and 1m CLC 60 Mix -OH (0.1 mg / mL) and sonicate for 10 min; (3) Prepare 0.24 mg mL -1 17 mL of NaBH4 solution; slowly add the above mixed solution dropwise into the NaBH4 solution and place it on a magnetic stirrer, stirring continuously at 500 rpm for 1 h; (4) After stirring stopped, the black solid was collected by centrifugation at 5000 rpm for 4 min, and washed three times with deionized water and ethanol by centrifugation to obtain Pd / C. 60 -OH composite materials; (5) To Pd / C 60 In the -OH composite material, ethanol and isopropanol (4:1) and 5 μL Nafion binder are added, and the mixture is sonicated for 10 min to form a uniform catalyst ink. This catalyst ink is then drop-coated onto pretreated carbon paper to prepare Pd / C composite material. 60 -OH working electrode.

[0022] Comparative Example 1: Preparation of Pd Working Electrode (1) Dissolve 0.1g PdCl2 in 100 µL of concentrated hydrochloric acid, then dilute with deionized water to 10mL; transfer the solution to a glass container, heat in an oil bath at 60℃ for 1 hour, cool and store at 4℃; (2) Take 315µL dCl2 stock solution and add deionized water to a total volume of 2mL, and sonicate for 5min; (3) Prepare 0.24 mg mL -117 mL of NaBH4 solution; slowly add the above solution dropwise into the NaBH4 solution and place it on a magnetic stirrer, stirring continuously at 500 rpm for 1 h; (4) After stirring stopped, the black solid was collected by centrifugation at 5000 rpm for 4 min and washed three times with deionized water and ethanol to obtain Pd nanowire material. (5) Add ethanol and isopropanol (4:1) and 5 uL Nafion binder to Pd nanowire material, sonicate for 10 min to form a uniform catalyst ink liquid, and then drop the catalyst ink liquid onto the pretreated carbon paper to prepare the Pd working electrode.

[0023] Figure 1 and Figure 2 The results showed that the Pd nanowires exhibited a unique "chain-like" three-dimensional network morphology, which is a chain-like structure formed by Pd self-assembly. The Pd nanoparticles (approximately 3-8 nm in diameter) were uniformly distributed and possessed an extremely high aspect ratio. This structure achieved high dispersion of the active components, resulting in a high specific surface area and abundant surface active sites. In contrast, the Pd nanowires exhibited a unique "chain-like" three-dimensional network morphology, which is a chain-like structure formed by Pd self-assembly. The Pd nanoparticles (approximately 3-8 nm in diameter) were uniformly distributed and possessed an extremely high aspect ratio. This structure enabled high dispersion of the active components, resulting in a high specific surface area and abundant surface active sites. 60 Even after -OH binding, Pd nanowires can still maintain their unique morphology, with only a thin coating layer observed on their surface.

[0024] Figure 3 XPS results showed that both materials exhibited obvious Pd peaks, and Pd could be observed. 2+ The presence of this component indicates a certain degree of oxidation on the Pd surface. And the Pd / C... 60 Compared to pure Pd, -OH groups in Pd 0 The relative strength of Pd is significantly enhanced. 2+ The proportion of the peaks decreased accordingly, and the peaks as a whole shifted towards the higher binding energy line, confirming that Pd is in an electron-deficient state, which indicates that C 60 The introduction of the -OH support alters the electronic structure of Pd, which can improve its adsorption and activation behavior for 2,4-DCP.

[0025] Test 1: Testing Pd and Pd / C 60 The effect of the -OH working electrode on the electrocatalytic dechlorination of 2,4-DCP (1) Activation of working electrode: The working electrode, platinum electrode and reference electrode are placed in the prepared 50mM Na2SO4 electrode activation solution and CV is scanned to achieve the purpose of activating the working electrode; (2) A double-chamber H-type electrolytic cell was used. 40 mL of Na2SO4 electrolyte was added to the cathode and anode chambers respectively, and N2 was used to exhaust air for 5 min to remove air from the electrolyte. (3) Add 0.32 mL of 5 g / L 2,4-DCP stock solution to the cathode chamber and stir for 5 min to make the pollutants uniformly dispersed. The concentration of 2,4-DCP is 40 mg / L. (4) Take about 0.5 mL of sample using a glass sampler; connect the workstation and set the working voltage to -0.8V to start the test; (5) Take approximately 0.5 mL of sample at predetermined times (0, 30, 60, ..., 180 min); (6) After the electrochemical reaction, the obtained sample is placed in a high performance liquid chromatograph for analysis. Based on the established standard curve, the concentration of 2,4-DCP at different reaction times is calculated. (7) Calculate the degradation rate (η) = (C0 - C t ) / C0*100%, where C0 is the initial concentration of 2,4-DCP in mg / L, C t It represents the concentration of 2,4-DCP at time t (mg / L). The results show (e.g.) Figure 4 and Figure 5 As shown in the figure, at -0.8V, after electrochemical catalytic hydrogenolysis and dechlorination, the removal rate of 2,4-DCP increased with time. At 180 min, the degradation rate of 2,4-DCP by the Pd working electrode was 66.7%, while the Pd / C ratio was... 60 The degradation rate of -OH at the working electrode reached 99.9%. This demonstrates that Pd / C 60 -OH exhibits higher electrocatalytic activity for the electrocatalytic dechlorination of 2,4-DCP.

[0026] Test 2: Testing Pd / C 60 Electrocatalytic dechlorination effect of the -OH working electrode at different concentrations of 2,4-DCP (1) Activation of working electrode: The working electrode, platinum electrode and reference electrode are placed in the prepared 50mM Na2SO4 electrode activation solution and CV is scanned to achieve the purpose of activating the working electrode; (2) A double-chamber H-type electrolytic cell was used. 40 mL of Na2SO4 electrolyte was added to the cathode and anode chambers respectively, and N2 was used to exhaust air for 5 min to remove air from the electrolyte. (3) Add 0.32 mL, 0.40 mL, 0.64 mL and 0.80 mL of 2,4-DCP stock solution with a concentration of 5 g / L to the cathode chamber respectively, stir for 5 min to make the pollutants uniformly dispersed, and the concentrations of 2,4-DCP are 40 mg / L, 50 mg / L, 80 mg / L and 100 mg / L respectively; (4) Take about 0.5 mL of sample using a glass sampler; connect the workstation and set the working voltage to -0.8V to start the test; (5) Take approximately 0.5 mL of sample at predetermined times (0, 30, 60, ..., 180 min); (6) After the electrochemical reaction, the obtained sample is placed in a high performance liquid chromatograph for analysis. Based on the established standard curve, the concentration of 2,4-DCP at different reaction times is calculated. (7) Calculate the degradation rate (η) = (C0 - C t ) / C0*100%, where C0 is the initial concentration of 2,4-DCP in mg / L, C t It represents the concentration of 2,4-DCP at time t (mg / L). The results show (e.g.) Figure 6 and Figure 7 As shown), for 2,4-DCP with an initial concentration of 40-100 mg / L, Pd / C 60 The degradation efficiency of the -OH working electrode remained at a high level, indicating that the Pd / C 60 -OH electrodes can withstand high levels of contamination, which is beneficial for their practical application.

[0027] Test 3: Testing Pd / C 60 Electrocatalytic dechlorination effect of the -OH working electrode on 2,4-DCP at different voltages (1) Activation of working electrode: The working electrode, platinum electrode and reference electrode are placed in the prepared 50mM Na2SO4 electrode activation solution and CV is scanned to achieve the purpose of activating the working electrode; (2) A double-chamber H-type electrolytic cell was used. 40 mL of Na2SO4 electrolyte was added to the cathode and anode chambers respectively, and N2 was used to exhaust air for 5 min to remove air from the electrolyte. (3) Add 0.32 mL of 5 g / L 2,4-DCP stock solution to the cathode chamber and stir for 5 min to make the pollutants uniformly dispersed. The concentration of 2,4-DCP is 40 mg / L. (4) Take about 0.5 mL of sample using a glass sampler; connect to the workstation and set the working voltage to -0.7V, 0.8V, -0.9V, and -1.0V respectively to start the test; (5) Take approximately 0.5 mL of sample at predetermined times (0, 30, 60, ..., 180 min); (6) After the electrochemical reaction, the obtained sample is placed in a high performance liquid chromatograph for analysis. Based on the established standard curve, the concentration of 2,4-DCP at different reaction times is calculated. (7) Calculate the degradation rate (η) = (C0 - C t ) / C0*100%, where C0 is the initial concentration of 2,4-DCP in mg / L, Ct It represents the concentration of 2,4-DCP at time t (mg / L). The results show (e.g.) Figure 8 (As shown), voltage versus Pd / C 60 The electrocatalytic dechlorination reaction of -OH has a significant impact. Specifically, at an operating voltage of -0.8 to -0.9 V, the Pd / C... 60 The -OH working electrode can maintain a relatively good degradation effect, but both excessively high and low voltages limit the removal of 2,4-DCP. This is because when the voltage is too low, the kinetics of the cathode hydrogen evolution reaction are limited, resulting in insufficient generation rate of active hydrogen atoms (H), which cannot meet the requirements of the dechlorination reaction; while when the voltage is too high (e.g., -1.0 V), the violent hydrogen evolution side reaction will dominate, which not only reduces the current efficiency, but also the large number of hydrogen bubbles generated will hinder the mass transfer and diffusion of reactants to the electrode surface, thereby inhibiting the degradation effect.

[0028] Test 4: Testing Pd and Pd / C 60 Comparison of anti-poisoning properties of -OH working electrodes Activating the working electrode: Immerse the working electrode, platinum electrode, and reference electrode in a prepared 50mM Na2SO4 electrode activation solution and scan the LSV to achieve the purpose of activating the working electrode. Add 100 mL of Na2SO4 electrolyte to the electrolytic cell and purge with nitrogen (N2) for 5 min to remove air from the electrolyte. Add 0.8 mL of 5 g / L 2,4-DCP stock solution to the electrolyte and stir for 5 min to ensure uniform dispersion of the contaminants, resulting in a 2,4-DCP concentration of 40 mg / L. Connect the workstation and set the upper / lower scan limits, scan rate, and number of cycles to begin the test. After the test, the optimal number of laps was selected for analysis.

[0029] The results show (e.g.) Figure 9 As shown in the figure, both electrodes exhibited obvious redox peaks, indicating that an electrochemical reaction of 2,4-DCP occurred on the electrode surface. It is noteworthy that, compared to the pure Pd electrode, the Pd / C… 60 The -OH-modified electrode exhibited significant hydrogen production suppression in the negative potential region (approximately -0.2 V to -0.6 V vs. RHE), indicating that the hydrogen evolution side reaction was mitigated in this system. This is consistent with the experimentally obtained difference in dechlorination current efficiency between the two methods (pure Pd: 11% vs. Pd / C). 60 -OH: 29.8%. In electrolytes containing 2,4-DCP, the oxidation peak current during positive potential scanning also showed significant differences between the two: in the pure Pd system, the H oxidation peak showed a significant decrease compared to the system without 2,4-DCP, while in the Pd / C...60 In the -OH system, the decrease is smaller, indicating that the degree of poisoning is also weaker. Pd / C 60 The unique electrochemical characteristics exhibited by the -OH electrode indicate that it possesses superior electrocatalytic activity and responsiveness to target pollutants.

[0030] The above-described embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. The application of a fullerol-supported palladium nanowire composite material in the electrocatalytic dechlorination of 2,4-dichlorophenol, characterized in that: The preparation method of the fullerol-supported palladium nanowire composite material is as follows: a palladium precursor solution is mixed with fullerol, then a reducing agent is added, the mixture is stirred and reacted, and then centrifuged to obtain the fullerol-supported palladium nanowire composite material. Fullerol-supported palladium nanowire composites were loaded onto a conductive substrate to form a working electrode. The working electrode was used as the cathode of an electrochemical reaction device to perform an electrocatalytic hydrogen dechlorination reaction on wastewater containing 2,4-dichlorophenol.

2. The application of the fullerol-supported palladium nanowire composite material according to claim 1 in the electrocatalytic dechlorination of 2,4-dichlorophenol, characterized in that: The chemical formula of the fullerol is C 60 (OH) x x = 24 - 48.

3. The application of the fullerol-supported palladium nanowire composite material according to claim 1 in the electrocatalytic dechlorination of 2,4-dichlorophenol, characterized in that: The palladium precursor is one or more of palladium chloride, potassium chloride palladiumate, sodium chloride palladiumate, and palladium nitrate.

4. The application of the fullerol-supported palladium nanowire composite material according to claim 1 in the electrocatalytic dechlorination of 2,4-dichlorophenol, characterized in that: The molar ratio of the palladium precursor to fullerol is 1:0.01-0.

03.

5. The application of the fullerol-supported palladium nanowire composite material according to claim 1 in the electrocatalytic dechlorination of 2,4-dichlorophenol, characterized in that: The reducing agent is one or more of sodium borohydride, hydrazine hydrate, ascorbic acid, or citric acid.

6. The application of the fullerol-supported palladium nanowire composite material according to claim 1 in the electrocatalytic dechlorination of 2,4-dichlorophenol, characterized in that: When performing electrocatalytic hydrogen dechlorination reaction on wastewater containing 2,4-dichlorophenol, the operating voltage is -0.8 to -0.9 V.

7. The application of the fullerol-supported palladium nanowire composite material according to claim 1 in the electrocatalytic dechlorination of 2,4-dichlorophenol, characterized in that: When performing electrocatalytic hydrogen dechlorination on wastewater containing 2,4-dichlorophenol, the initial concentration of 2,4-dichlorophenol in the wastewater is 5-100 mg / L.

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