A Pd / Fe x Ni 1-x O / Nifoam composite electrode and its preparation method and application
By growing sheet iron-doped nickel oxide nanoarrays on the foam nickel substrate and uniformly anchoring the palladium nanoparticles, the Pd/FexNi1-xO/Nifom composite electrode was prepared, which solved the problem of easy agglomeration of precious metal Pd catalysts, and achieved an efficient and economical electrocatalytic reduction and dechlorination effect.
Patent Information
- Application Number
- CN202211223143.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-10-08
- Publication Date
- 2025-08-05
- Estimated Expiration
- 2042-10-08
AI Technical Summary
Existing precious metal Pd catalysts are prone to agglomeration in electrocatalytic reduction and dechlorination reactions, resulting in reduced catalytic activity and high cost, making it difficult to deal with chlorine-containing organic matter cost-effectively.
Using foam nickel as the substrate, a sheet-shaped iron-doped nickel oxide nanoarray was grown by hydrothermal-calcining method, and then uniformly anchored the palladium nanoparticles by chemical displacement method to prepare a Pd/FexNi1-xO/Nifom composite electrode to improve the dispersion and catalytic activity of the palladium nanoparticles.
It significantly improves the electrocatalytic reduction and dechlorination efficiency, reduces the use of precious metals, improves the stability and economicality of the electrode, and can be reused multiple times.
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Figure CN115679362B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of electrode material preparation, and specifically relates to a Pd / Fe x Ni 1-x The invention discloses a preparation method of an O / Nifoam composite electrode and an application of the electrode in an electrocatalytic reduction dechlorination reaction. Background Art
[0002] Chlorinated organic compounds are organic compounds in which hydrogen atoms in their molecular structures have been replaced by chlorine atoms. These primarily include chlorinated aliphatic hydrocarbons, chlorinated aromatic hydrocarbons, and their derivatives. Most of these organic compounds are toxic, harmful, and difficult to degrade, exhibiting carcinogenic and mutagenic properties. Chlorinated organic compounds are difficult to degrade in the natural environment and persist for extended periods. They can be transported through the atmosphere and water, impacting the regional and global environment, and posing a serious threat to human health and environmental safety.
[0003] Electrocatalytic reduction dechlorination (EDD) is attracting increasing attention due to its numerous advantages, including rapid reaction, minimal equipment requirements, mild operating conditions, and the production of biodegradable byproducts. A key step in the electrocatalytic treatment of chlorinated organic wastewater is the development of cost-effective and efficient catalysts. Rare metal catalysts are widely used to modify cathode materials due to their high reactivity and stability in EDD. Pd is the most effective catalyst for indirect EDD due to its ability to absorb protons at low overpotentials to generate H*, which is retained on the surface and subsequently attacks C-Cl bonds. However, precious metal Pd catalysts still face numerous limitations in wastewater treatment applications, including their high cost and scarcity. Conventional Pd-supported electrodes have large Pd nanoparticles and are prone to agglomeration during EDD, resulting in reduced catalytic activity and limiting their reusability. Therefore, reducing the size of Pd nanoparticles and improving their dispersion on the substrate electrode material are effective approaches to improve the activity, stability, and economic feasibility of EDD. Summary of the Invention
[0004] In order to solve the deficiencies of the prior art, the present invention aims to provide a Pd / Fe x Ni 1-x A method for preparing an O / Nifoam composite electrode is described, and the composite electrode is used for electrochemical dechlorination of chlorinated organic matter. This method significantly improves dechlorination efficiency, reduces precious metal input, and lowers economic costs. It can be used to simulate the dechlorination of chlorinated organic matter in natural water bodies.
[0005] The technical solution adopted in the present invention is as follows:
[0006] The Pd / Fe x Ni1-x The preparation method of the O / Nifoam composite electrode comprises the following steps:
[0007] Step 1, pre-treating the nickel foam substrate;
[0008] Step 2: Add nickel salt, iron salt, methanol and deionized water to a polytetrafluoroethylene liner to form a precursor solution, immerse the nickel foam obtained in step 1 in the precursor solution, and then transfer them to a reactor for hydrothermal reaction. After the reaction is completed and cooled, the nickel foam substrate is taken out, cleaned, dried, and then calcined in an air atmosphere to form an iron-doped nickel oxide layer on the surface of the nickel foam substrate to obtain Fe x Ni 1-x O / Nifoam electrode;
[0009] Step 3: Fe obtained in step 2 x Ni 1-x The O / Nifoam electrode was placed in a palladium source solution and placed in a constant temperature shaker. The solution was shaken at room temperature until it became colorless. After washing with distilled water and drying with high-purity nitrogen, the Pd / Fe x Ni 1-x O / Nifoam composite electrode.
[0010] Furthermore, in step one, the pretreatment includes placing the nickel foam substrate in a 2-5 mM hydrochloric acid solution, ultrasonically treating it for 10-40 minutes to remove the surface oxide layer, then rinsing it with deionized water and anhydrous ethanol several times in sequence, and finally blowing it dry with high-purity nitrogen for use.
[0011] Furthermore, in step 2, the feeding ratio of the nickel salt, iron salt, methanol and deionized water is 1~5 mmol:0.1~0.5 mmol:10~20 mL:20~30 mL, preferably 3 mmol:0.4 mmol:15 mL:25 mL.
[0012] Furthermore, in step 2, the temperature of the hydrothermal reaction is 100-150° C., preferably 120° C.; and the reaction time is 6-10 h, preferably 8 h.
[0013] Furthermore, in step 2, the cleaning and drying process is to wash the nickel foam substrate taken out after the hydrothermal reaction with deionized water and anhydrous ethanol several times in sequence, and then place it in a vacuum oven at 40-80°C for 3-10 hours; the nickel foam substrate has a flaky structure, and the molar amount of the nickel salt in the precursor solution is 0.005-0.01 mmol / mm2 to the surface area of one side of the nickel foam substrate. 2 .
[0014] Furthermore, in step 2, the calcination conditions include: calcining in a tubular furnace, heating from room temperature at a heating rate of 4-8°C / min to a calcination temperature of 300-400°C, preferably 350°C, then maintaining the constant temperature for 1-5 hours, preferably 2 hours, and then naturally cooling to room temperature.
[0015] Furthermore, in step 3, the concentration of the palladium source solution is 0.1-0.5 mM, preferably 0.33 mM; the nickel foam substrate is a sheet structure, and the ratio of the molar amount of the palladium source in the palladium source solution to the surface area of one side of the nickel foam substrate is (0.005-0.025)*10 -3 mmol / mm 2 The shaking speed is set to 120~180 rpm / min, preferably 150 rpm / min; the temperature is set to 20~35℃, and the time is 1~2.5 h, preferably 2 h.
[0016] The Pd / Fe x Ni 1-x Application of O / Nifoam composite electrode in electrocatalytic reduction dechlorination reaction, the prepared Pd / Fe x Ni 1-x O / Nifoam composite electrode is used as the working electrode to dechlorinate chlorinated organic matter by electrochemical dechlorination in an H-type three-electrode system. In the H-type three-electrode system, the prepared Pd / Fe x Ni 1-x The O / Nifoam composite electrode was used as the cathode working electrode, the platinum electrode was used as the anode counter electrode, and the saturated calomel electrode was used as the reference electrode. The cathode chamber and the anode chamber were separated by a cation exchange membrane. The cathode liquid was a mixture of Na2SO4 and chlorinated organic matter, where the concentration of the Na2SO4 solution was 1~3mM and the concentration of the chlorinated organic matter was below 50 mg / L. The anolyte was a 1~3mM Na2SO4 solution.
[0017] Furthermore, the electrochemical dechlorination method described in the application method is a constant potential dechlorination method, the cathode voltage is -0.5~-2V, the reaction temperature is room temperature, and the reaction time is 1~3 hours; the chlorine-containing organic pollutant is 2,4-dichlorophenoxyacetic acid.
[0018] Compared with the prior art, the present invention has the following beneficial effects:
[0019] 1. The present invention uses low-cost, highly conductive nickel foam as the base material, grows sheet-like iron-doped nickel oxide nanoarrays by hydrothermal-calcination method, and then uniformly anchors palladium nanoparticles by chemical replacement method to prepare Pd / Fe x Ni 1-xO / Nifoam composite electrode. This preparation method is simple and can effectively increase the dispersion of palladium nanoparticles on the electrode surface. The palladium loading on the 20 mm × 20 mm × 1.2 mm nickel foam substrate is only 0.68 mg. This significantly improves the electrode catalytic activity while reducing the use of precious metal Pd, effectively reducing economic costs.
[0020] 2. Pd / Fe of the present invention x Ni 1-x The O / Nifoam composite electrode exhibits excellent electrocatalytic performance in the electrocatalytic reduction dechlorination reaction, with a removal efficiency of 99% for 2,4-dichlorophenoxyacetic acid. It also has a long service life and can be reused many times, showing good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 TEM image of the composite electrode synthesized in Example 1.
[0022] Figure 2 This is a graph showing the degradation efficiency of the composite electrode prepared in Example 3 in six consecutive dechlorination experiments. DETAILED DESCRIPTION
[0023] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.
[0024] Example 1
[0025] A Pd / Fe x Ni 1-x Preparation of O / Nifoam composite electrode, the specific steps are as follows:
[0026] a. Pretreatment of nickel foam substrate: Place the nickel foam substrate (square sheet structure with a size of 20 mm × 20 mm × 1.2 mm) in a 3 mM dilute hydrochloric acid solution and ultrasonically wash it for 30 min to remove surface oxides. Then wash it three times with deionized water and anhydrous ethanol respectively, and finally blow it dry with high-purity nitrogen for later use.
[0027] b. Fe x Ni 1-xPreparation of O intermediate layer: 3 mmol nickel nitrate, 0.4 mmol ferric chloride, 15 mL methanol and 25 mL deionized water were added to a polytetrafluoroethylene liner and stirred for 30 min to form a precursor solution; the nickel foam substrate obtained by pretreatment in step a was immersed in the prepared precursor solution and transferred to a reactor for hydrothermal treatment at 120 ° C for 8 h; after the reaction was completed and cooled, the nickel foam substrate was taken out, washed three times with deionized water and anhydrous ethanol in sequence, and then placed in a vacuum oven at 50 ° C for 6 h; then, the dried nickel foam substrate was placed in a tube furnace, heated from room temperature to 350 ° C at a heating rate of 5 ° C / min, and maintained in an air atmosphere for 2 h to obtain Fe x Ni 1-x O / Nifoam composite electrode.
[0028] c. Palladium loading: Add 20 mL of 0.33 mM palladium chloride solution into a conical flask and add the Fe x Ni 1-x The O / Nifoam composite electrode was immersed in the above palladium chloride solution, sealed and placed in a 30°C constant temperature shaker, and shaken at a frequency of 150 rpm / min for 2 h until the solution was colorless. It was then taken out, rinsed with distilled water, and dried with high-purity nitrogen to obtain Pd / Fe x Ni 1-x O / Nifoam composite electrode. x Ni 1-x TEM image of O / Nifoam composite electrode Figure 1 As shown, it can be observed that Pd nanoparticles are uniformly dispersed in the Fe flakes. x Ni 1-x O on.
[0029] The Pd / Fe prepared in Example 1 x Ni 1-x O / Nifoam composite electrode is used for electrocatalytic reduction dechlorination of wastewater containing 2,4-dichlorophenoxyacetic acid. The dechlorination reaction is an H-type three-electrode system, with the Pd / Fe prepared in Example 1 x Ni 1-xAn O / Nifoam composite electrode served as the cathode working electrode, a platinum electrode (20 mm × 20 mm) served as the anode counter electrode, and the electrodes were spaced 8 cm apart. A saturated calomel electrode served as the reference electrode. The cathode and anode compartments were separated by a Nafion-117 cation exchange membrane. The catholyte consisted of 72 mL of a mixed solution of sodium sulfate and 2,4-DCPA (2 mM sodium sulfate and 10 mg / L 2,4-DCPA), and the anolyte was 36 mL of a 2 mM sodium sulfate solution. Potentiostatic dechlorination was employed, with the cathode voltage set at -1 V and the reaction temperature at 25°C. The experimental results, shown in Table 1, show a 99.9% removal efficiency of 2,4-DCPA after a 2-h reaction.
[0030] Example 2
[0031] In this embodiment 2, Pd / Fe x Ni 1-x The preparation process of the O / Nifoam composite electrode is the same as that in Example 1.
[0032] Pd / Fe prepared in Example 2 x Ni 1-x The O / Nifoam composite electrode was used for the electrocatalytic reduction dechlorination of 2,4-DCPA wastewater. This method differs from Example 1 in that the catholyte was replaced with Evian water instead of deionized water. The experimental results are shown in Table 1. After 4 hours of reaction, the removal efficiency of 2,4-DCPA reached 96.3%. The composition of the Evian water is shown in Table 2.
[0033] Table 2
[0034]
[0035] Example 3
[0036] In this embodiment 3, Pd / Fe x Ni 1-x The preparation process of the O / Nifoam composite electrode is the same as that in Example 1.
[0037] Pd / Fe prepared in Example 3 x Ni 1-xThe O / Nifoam composite electrode was applied to the electrocatalytic reduction dechlorination of wastewater containing 2,4-dichlorophenoxyacetic acid. This electrode differed from Example 1 in that 3 mM nitrate ions, 3 mM chloride ions, 3 mM carbonate ions, 3 mM bicarbonate ions (the cations bound to the anions were all sodium ions), and 2 mM calcium ions (the anions bound to the cations were chloride ions) were added to the cathode electrolyte to observe the effects of coexisting ions in natural water on the electrocatalytic reduction dechlorination process. The experimental results are shown in Table 1. After 2 h of reaction, the prepared composite electrode achieved a 2,4-dichlorophenoxyacetic acid removal rate of over 83%, indicating that the various coexisting ions in the water had little effect on the electrocatalytic reduction dechlorination performance of the composite electrode.
[0038]
[0039] Example 4
[0040] In this embodiment 4, Pd / Fe x Ni 1-x The preparation process of the O / Nifoam composite electrode is the same as that in Example 1.
[0041] Pd / Fe prepared in Example 4 x Ni 1-x O / Nifoam composite electrode is applied to the electrocatalytic reduction dechlorination reaction of wastewater containing 2,4-dichlorophenoxyacetic acid. The difference between it and Example 1 is that after each electrocatalytic reduction dechlorination reaction, Pd / Fe x Ni 1-x The O / Nifoam composite electrode was taken out and rinsed with deionized water, and then the next electrocatalytic reduction dechlorination experiment was started. Figure 2 As shown, Pd / Fe x Ni 1-x The O / Nifoam composite electrode can achieve a removal rate of 2,4-dichlorophenoxyacetic acid of about 99% during repeated use for 6 times, indicating that the composite electrode has good electrocatalytic performance stability and reusability.
[0042] Comparative Example 1:
[0043] In comparative example 1, the preparation process of the composite electrode is the same as that of example 1, except that the Fe x Ni 1-x O intermediate layer preparation steps", and finally the Pd / Nifoam composite electrode was prepared.
[0044] The Pd / Nifoam composite electrode of Control Example 1 was applied to the electrocatalytic reduction dechlorination reaction of wastewater containing 2,4-dichlorophenoxyacetic acid. The steps of the catalytic application reaction were the same as those of Example 1. The experimental results showed that the removal rate of 2,4-dichlorophenoxyacetic acid was 62.5% after reacting for 2 hours at a constant potential of -1 V at the cathode voltage.
[0045] The contents described in this specification are merely an enumeration of implementation forms of the inventive concept, and the protection scope of the present invention should not be considered as being limited to the specific forms described in the embodiments.
Claims
1. A Pd / Fe x Ni 1-x The preparation method of O / Nifoam composite electrode is characterized in that: The following steps are involved: Step 1: Pretreatment of nickel foam substrate: Place the nickel foam substrate in a 2-5 mM hydrochloric acid solution and ultrasonicate for 10-40 minutes to remove the surface oxide layer. Then rinse with deionized water and anhydrous ethanol several times, and finally blow dry with high-purity nitrogen gas for later use. Step 2, Fe x Ni 1-x Preparation of O intermediate layer: nickel salt, iron salt, methanol and deionized water are added to a polytetrafluoroethylene liner in a feed ratio of 1~5 mmol: 0.1~0.5mmol: 10~20 mL: 20~30 mL to form a precursor solution, the pretreated nickel foam is immersed in the precursor solution, transferred to a reactor and hydrothermally reacted at 100~150℃ for 6~10 hours; after the reaction, the nickel foam substrate is taken out, cleaned and dried, and then calcined in an air atmosphere in a tubular furnace, from room temperature at a heating rate of 4~8℃ / min to a calcination temperature of 300~400℃ for 1-2 hours to form an iron-doped nickel oxide layer Fe on the surface of the nickel foam substrate. x Ni 1-x O, and then cooled naturally to room temperature to obtain Fe x Ni 1-x O / Ni foam electrode; The nickel foam substrate is a sheet structure, and the ratio of the molar amount of nickel salt in the precursor solution to the surface area of one side of the nickel foam substrate is 0.005-0.01 mmol / mm 2 ; Step 3, Pd nanoparticle loading: Fe x Ni 1-x The O / Ni foam electrode was immersed in a 0.1-0.5 mM palladium source solution and shaken at 120-180 rpm in a constant temperature shaker at 20-35 °C for 1-2.5 hours until the solution was colorless. After removal, it was washed with deionized water and dried with high-purity nitrogen to obtain Pd / Fe x Ni 1-x O / Ni foam composite electrode.
2. A Pd / Fe according to claim 1 x Ni 1-x The preparation method of O / Nifoam composite electrode is characterized by: In step 2, the feed ratio of the nickel salt, iron salt, methanol and deionized water is 3 mmol:0.4 mmol:15 mL:25 mL; the temperature of the hydrothermal reaction is 120° C.; and the reaction time is 8 h.
3. A Pd / Fe according to claim 1 x Ni 1-x The preparation method of O / Nifoam composite electrode is characterized by: In step 2, the cleaning and drying process is to wash the nickel foam substrate taken out after the hydrothermal reaction with deionized water and anhydrous ethanol several times in sequence, and then put it into a vacuum oven at 40-80° C. and dry it for 3-10 hours.
4. A Pd / Fe according to claim 1 x Ni 1-x The preparation method of O / Nifoam composite electrode is characterized by: In step 2, the calcination temperature is 350° C. and the calcination time is 2 h.
5. A Pd / Fe according to claim 1 x Ni 1-x The preparation method of O / Nifoam composite electrode is characterized by: In step 3, the concentration of the palladium source solution is 0.33 mM; the nickel foam substrate is a sheet structure, and the ratio of the molar amount of the palladium source in the palladium source solution to the surface area of one side of the nickel foam substrate is (0.005-0.025)*10 -3 mmol / mm 2 The shaking speed was 150 rpm / min, the temperature was set at 20-35°C, and the time was 2 h.
6. A Pd / Fe prepared according to any one of claims 1 to 5 x Ni 1-x O / Nifoam composite electrode.
7. A Pd / Fe according to claim 6 x Ni 1-x Application of O / Nifoam composite electrode in electrocatalytic reduction dechlorination reaction.
8. A Pd / Fe according to claim 7 x Ni 1-x The application of O / Nifoam composite electrode in electrocatalytic reduction dechlorination reaction is characterized by: The prepared Pd / Fe x Ni 1-x O / Nifoam composite electrode is used as the working electrode to dechlorinate chlorinated organic matter by electrochemical dechlorination in an H-type three-electrode system. In the H-type three-electrode system, the prepared Pd / Fe x Ni 1-x The O / Nifoam composite electrode was used as the cathode working electrode, the platinum electrode was used as the anode counter electrode, and the saturated calomel electrode was used as the reference electrode. The cathode chamber and the anode chamber were separated by a cation exchange membrane. The cathode liquid was a mixture of Na2SO4 and chlorinated organic matter, where the concentration of the Na2SO4 solution was 1~3mM and the concentration of the chlorinated organic matter was below 50 mg / L. The anolyte was a 1~3mM Na2SO4 solution.
9. A Pd / Fe according to claim 8 x Ni 1-x The application of O / Nifoam composite electrode in electrocatalytic reduction dechlorination reaction is characterized by: The electrochemical dechlorination method is a constant potential dechlorination method, the cathode voltage is -0.5~-2V, the reaction temperature is room temperature, and the reaction time is 1~3 hours; the chlorine-containing organic pollutant is 2,4-dichlorophenoxyacetic acid.