Preparation method of nickel-based electrode with spin pinning effect and application of nickel-based electrode in chemical oxygen demand detection
By loading an antiferromagnetic metal oxide layer onto a nickel foam substrate, the spin pinning effect is used to enhance the binding force and electrocatalytic oxidation capability, thus solving the problems of insufficient stability and sensitivity of existing electrodes and achieving efficient COD detection.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-12
- Publication Date
- 2026-04-07
AI Technical Summary
Existing COD electrochemical detection electrodes are prone to catalytic activity decay after long-term operation, resulting in insufficient detection stability and sensitivity, especially for low-concentration samples.
A composite electrode is designed using ferromagnetic nickel foam as a substrate, with an antiferromagnetic or paramagnetic metal oxide layer loaded on the surface. The spin pinning effect is used to enhance the bonding force between the active layer and the substrate and the electrocatalytic oxidation capability.
The stability and sensitivity of the electrode were improved, enabling real-time, rapid, stable and sensitive detection of chemical oxygen demand in water.
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Figure CN121802503A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of environmental monitoring and relates to a method for preparing a composite electrode with a spin pinning effect, specifically for the detection of chemical oxygen demand (COD) concentration in environmental water bodies. Background Technology
[0002] Chemical oxygen demand (COD) quantifies the total amount of pollution by measuring the oxygen equivalent consumed by reducing substances (mainly organic matter) in water bodies that need to be oxidized. It is a key indicator in environmental monitoring for evaluating the degree of organic pollution in water bodies. COD measurement plays an important role in the assessment and management of aquatic ecological environment quality, effectively reflecting the load of organic pollutants in water bodies and providing important evidence for water environmental protection. For a long time, traditional COD measurement methods have relied on strong oxidants such as dichromates or permanganates, which have limitations such as complex and time-consuming processes, weak anti-interference ability, high cost, serious secondary pollution, use of toxic reagents such as mercuric sulfate, and poor reproducibility. Therefore, developing rapid and accurate new COD detection methods has become an important research direction in the field of environmental monitoring.
[0003] Currently, electrochemical oxidation detection of COD shows great application potential in water quality monitoring due to its advantages such as low cost, fast response, small size, and low pollution. According to a report by Cheng Xingyang et al., titled "Advances inrapid on-site detection of chemical oxygen demand: Insights into sensing mechanisms and practical applications," electrochemical oxidation detection is an electrocatalytic method based on the principle of electrocatalysis. It utilizes an electrochemically active electrode to rapidly oxidize organic matter. The key to electrochemical sensing detection of COD is the design of a stable and sensitive working electrode. Currently, widely studied working electrode materials (such as PbO2 electrodes and copper electrodes) still face challenges in practical applications: catalytic activity easily decays after long-term operation, detection stability decreases, and sensitivity is insufficient for low-concentration COD samples. Based on these problems, this invention designs and prepares a nickel-based electrode with a spin pinning effect, improving the stability and sensitivity of COD detection, and achieving real-time, rapid, stable, and sensitive detection of chemical oxygen demand in water. Summary of the Invention
[0004] To address the issues of insufficient stability and sensitivity of existing COD electrochemical detection electrodes, this invention provides a novel composite electrode preparation method and its application.
[0005] The core of this invention is the design and fabrication of a composite electrode with a special structure. This electrode uses ferromagnetic nickel foam (NF) as a substrate, with an antiferromagnetic or paramagnetic metal oxide layer loaded on its surface as a catalytic active layer. This unique "ferromagnetic / antiferromagnetic (paramagnetic)" structure can induce a spin pinning effect at the interface under an applied magnetic field. This effect brings a dual improvement to the electrode: first, it enhances the bonding force between the active layer and the substrate, enabling the electrode to withstand long-term water flow erosion and physical wear, thus improving stability; second, it enhances the electrocatalytic oxidation capacity of the active layer for organic matter, thereby generating a stronger detection current signal and improving sensitivity.
[0006] Based on this, the nickel-based electrode with spin pinning effect prepared in this invention can achieve real-time, rapid, stable and sensitive detection of chemical oxygen demand in water.
[0007] The technical solution of this invention:
[0008] A method for fabricating a nickel-based electrode with spin pinning effect, comprising the following steps:
[0009] 1) Pretreatment: The nickel substrate is ultrasonically treated with hydrochloric acid and organic solvent, then rinsed with deionized water and dried at room temperature;
[0010] The nickel substrate is ferromagnetic nickel foam, the hydrochloric acid concentration is 1~6 mol / L, and the organic solvent is anhydrous ethanol or acetone.
[0011] 2) Precursor loading: A precursor layer containing one of the metal elements copper, nickel, or cobalt is loaded onto the surface of the nickel substrate after the pretreatment in step 1) by electrodeposition, hydrothermal method or immersion method.
[0012] in,
[0013] The electrodeposition method uses a nickel substrate pretreated in step 1) as the working electrode, and deposits the electrode in an electrolyte containing the target metal salt at a constant potential of -1.0 V to -0.2 V for 5 to 30 min.
[0014] The hydrothermal method involves immersing the nickel substrate pretreated in step 1) into an aqueous solution containing metal salt and urea, and reacting it at 120~180 °C for 6~12 h; wherein the molar ratio of metal salt to urea is 1:(2~5).
[0015] The impregnation method involves immersing the nickel substrate pretreated in step 1) in a metal salt solution with a concentration of 0.1-0.5 mol / L at 60-80 °C for 0.5-2 h.
[0016] The metal oxide layer is one of copper oxide, nickel oxide, and cobalt oxide.
[0017] 3) Heat treatment: The nickel substrate loaded with precursor in step 2) is subjected to heat oxidation treatment to transform the precursor layer into an antiferromagnetic or paramagnetic metal oxide layer, thus obtaining a nickel-based electrode with spin pinning effect.
[0018] When the metal oxide layer is CuO or NiO, the nickel substrate treated in step 2) is placed in a muffle furnace and calcined in an air atmosphere; when the metal oxide layer is CoO, the nickel substrate treated in step 2) is placed in a tube furnace and calcined in an inert atmosphere (nitrogen or argon).
[0019] The thermal oxidation treatment is carried out at a temperature of 300-500 ℃, a heating rate of 3-5 ℃ / min, and a holding time of 1-3 h.
[0020] A method for detecting chemical oxygen demand (COD) in water using a nickel-based electrode with spin pinning effect as the detection electrode comprises the following steps:
[0021] A nickel-based electrode with spin pinning effect is used as the working electrode. A magnetic field is applied to both sides of the working electrode, and a three-electrode system is used for detection. The current value is detected at a constant working potential, and a standard curve between chemical oxygen demand and current response is constructed. The current value of the sample to be tested is obtained by detection, and the chemical oxygen demand of the sample to be tested is calculated by substituting it into the standard curve.
[0022] The strength of the magnetic field is 0.1~1 T, provided by a permanent magnet or electromagnet, and can be adjusted by changing the distance between the magnetic field source and the electrode or by the input current.
[0023] The three-electrode system uses a platinum sheet as the counter electrode and a saturated calomel electrode as the reference electrode. The current-time curve method is used as the detection method, and the applied working potential range is 0.4~0.9 V.
[0024] A standard curve was constructed in an alkaline electrolyte solution to correlate chemical oxygen demand (COD) with current. The steady-state current response to a series of organic compounds of different concentrations was recorded. The COD equivalent value corresponding to the organic compound concentration was used as the abscissa, and the measured current value was used as the ordinate. The standard curve was plotted by linear regression analysis, and its fitting equation was established. The COD of the sample was calculated by substituting the detected current value of the sample into the standard curve.
[0025] The organic matter includes one of glucose, glycine, fructose, ascorbic acid, sucrose, and potassium hydrogen phthalate, and the pH range of the alkaline electrolyte solution is 9-13.
[0026] The beneficial effects of this invention are:
[0027] 1. Good stability: The spin pinning effect at the ferromagnetic / antiferromagnetic (paramagnetic) interface enhances the bonding force between the antiferromagnetic or paramagnetic metal oxide layer and the ferromagnetic nickel substrate, reducing the shedding of the active layer and thus enhancing the stability of the electrode material.
[0028] 2. High sensitivity: The spin pinning effect can enhance the electrocatalytic oxidation ability of the metal oxide layer on organic matter, thereby generating a stronger detection current signal and improving sensitivity.
[0029] 3. Suitable for large-scale production: The method for preparing the nickel-based electrode with spin pinning effect of the present invention is simple and easy to operate, and is suitable for large-scale production. Attached Figure Description
[0030] Figure 1 This is a standard curve for detecting chemical oxygen demand in water using the NF / CuO electrode prepared in Example 1.
[0031] Figure 2 The image shows the test results of the NF / CuO electrode prepared in Example 1 for detecting different types of organic compounds.
[0032] Figure 3 The current-time graph for detecting chemical oxygen demand in water using the NF / CuO electrode prepared in Example 1 is shown.
[0033] Figure 4 The current-time graph for detecting chemical oxygen demand in water using the carbon cloth (CC) / CuO electrode prepared in Comparative Example 2 is shown.
[0034] Figure 5 The graph shows the continuous stability test results of the NF / CuO electrode prepared in Example 1 and the CC / CuO electrode prepared in Comparative Example 2 for detecting chemical oxygen demand in water.
[0035] Figure 6 The graphs show the test results of the electrodes prepared in Examples 1-4 and Comparative Examples 1-3 for detecting chemical oxygen demand in water. Detailed Implementation
[0036] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.
[0037] Example 1:
[0038] 1) Sonicate NF sequentially in 1 mol / L hydrochloric acid and anhydrous ethanol for 15 min, rinse thoroughly with deionized water, and dry at room temperature.
[0039] 2) The NF pretreated in step 1) was used as the working electrode, and a platinum sheet electrode and a saturated calomel electrode were used as the counter electrode and reference electrode, respectively. The NF was placed in a 0.05 mol / L copper sulfate pentahydrate solution and deposited at a constant potential of -0.4 V for 10 min. The NF was washed with deionized water and anhydrous ethanol and then vacuum dried at 60 °C for 12 h to obtain NF with copper precursor on the surface (the product is red on the surface of NF).
[0040] 3) The NF treated in step 2) is placed in a muffle furnace and annealed in air atmosphere. The temperature is increased to 300 ℃ at a heating rate of 5 ℃ / min and held for 2 h to obtain NF loaded with antiferromagnetic CuO (the product is black on the surface of NF), which is labeled as NF / CuO-1.
[0041] Example 2:
[0042] 1) Same as Example 1.
[0043] 2) The NF pretreated in step 1) was placed in a 0.1 mol / L copper nitrate trihydrate solution and immersed at 60 °C for 2 h. After being removed and cooled to room temperature, it was washed with deionized water and anhydrous ethanol and then vacuum dried at 60 °C for 12 h to obtain NF with copper precursor on surface (the product is red on the surface of NF).
[0044] 3) The NF treated in step 2) was placed in a muffle furnace and annealed in air atmosphere. The temperature was increased to 350 °C at a heating rate of 4 °C / min and held for 3 h to obtain NF loaded with antiferromagnetic CuO (the product is black on the surface of NF), which was labeled as NF / CuO-2.
[0045] Example 3:
[0046] 1) Same as Example 1.
[0047] 2) Dissolve 1 mmol nickel nitrate hexahydrate and 5 mmol urea in 20 ml deionized water and stir magnetically until clear. Transfer the mixed solution to a 50 ml Teflon-lined stainless steel high-pressure reactor. Immerse the NF pretreated in step 1) in the mixed solution and seal the reactor. Heat at 180 °C for 8 h. After cooling to room temperature, remove the NF and wash it with deionized water and anhydrous ethanol. Then, vacuum dry it at 60 °C for 12 h to obtain NF with surface-loaded nickel precursor (the product is green on the surface of NF).
[0048] 3) The NF treated in step 2) is placed in a muffle furnace and annealed in air atmosphere. The temperature is increased to 400 ℃ at a heating rate of 3 ℃ / min and held for 2 h to obtain NF loaded with antiferromagnetic NiO (the product is black on the surface of NF), which is labeled as NF / NiO.
[0049] Example 4:
[0050] 1) Same as Example 1.
[0051] 2) The NF pretreated in step 1) was placed in a 0.5 mol / L cobalt chloride hexahydrate solution and immersed at 80 °C for 0.5 h. After being taken out and cooled to room temperature, it was washed with deionized water and anhydrous ethanol and vacuum dried at 60 °C for 12 h to obtain NF with surface-loaded cobalt precursor (the product is pink on the surface of NF).
[0052] 3) The NF treated in step 2) was placed in a tube furnace and annealed in a nitrogen atmosphere. The temperature was increased to 500 °C at a rate of 4 °C / min and held for 1 h to obtain NF loaded with paramagnetic CoO (the product is black on the surface of NF), which was labeled as NF / CoO.
[0053] Comparative Example 1:
[0054] The NF that has undergone the pretreatment in step 1) of Example 1 is used as a blank control and labeled as NF.
[0055] Comparative Example 2:
[0056] Replace NF in Example 1 with carbon cloth (CC), and keep the other steps the same. This is labeled CC / CuO.
[0057] Comparative Example 3:
[0058] 1) Place NF in a muffle furnace and heat treat it in an air atmosphere. Heat it to 450°C at a heating rate of 5°C / min and hold it at that temperature for 0.5 h.
[0059] 2) Add 100 mg of nickel-zinc ferrite (NiZnFe4O) x The NF treated in step 1) was sonicated in 20 ml of ultrapure water for 20 min to obtain a homogeneous suspension. Then, the NF was immersed in the suspension and sonicated in an ultrasonic bath for 15 min, dried at room temperature, and labeled as NF / NiZnFe4O. x .
[0060] Implementation effect
[0061] Table 1 shows the electrochemical COD detection performance of the electrodes prepared in Examples 1-4 and Comparative Examples 1-3 as working electrodes, with an external magnetic field of 0.4T applied by a permanent magnet and a working potential of 0.6 V. A three-electrode system was used, with a platinum sheet electrode and a saturated calomel electrode as the counter electrode and reference electrode, respectively. The linear range, detection limit, sensitivity, and 12-h current retention rate are shown in Table 1.
[0062] Table 1
[0063]
[0064] As shown in Table 1, Examples 1-4 of the present invention outperformed Comparative Examples 1-3 in terms of linear range, detection limit, sensitivity, and 12-hour current retention rate. Among them, Example 1 (NF / CuO-1) achieved the best overall performance: it had a wide linear range (2-500 mg / L), a detection limit as low as 1.4 mg / L, and a sensitivity of 3.16 µA / mg L. -1 The COD is 5.18 times that of the blank NF, and it still maintains 93.6% current response after 12 hours of continuous testing, which is 27.9% higher than the blank NF, indicating good stability.
[0065] like Figure 3 and Figure 4 As shown, the electrodes of Example 1 (NF / CuO-1) and Comparative Example 2 (CC / CuO) were used to detect 500 mg / L COD under conditions of an applied magnetic field of 0.4 T using an electromagnet and without an applied magnetic field, respectively, with an operating potential of 0.6 V. The current response of NF / CuO under the applied magnetic field condition was increased by 0.608 mA compared to without an applied magnetic field, while the current response of CC / CuO remained almost unchanged with and without an applied magnetic field. Figure 5 As shown, NF / CuO maintained a current response of 93.8% after 12 hours of continuous testing, which is 21.7% higher than CC / CuO, indicating improved stability. This comparison demonstrates the spin pinning effect between the ferromagnetic nickel substrate and the antiferromagnetic / paramagnetic metal oxide layer, which is the intrinsic reason for the enhanced magnetic field performance of the electrode in this invention.
[0066] like Figure 6The figures show the current response values for detecting 500 mg / L COD in Examples 1-4 and Comparative Examples 1-3 under the condition of applying an external magnetic field of 0.3 T with an electromagnet and a working potential of 0.55 V. The current response values of Examples 1-4 are all higher than those of Comparative Examples 1-2, indicating that there is a spin pinning effect between the ferromagnetic nickel substrate and the antiferromagnetic / paramagnetic metal oxide layer (CuO, NiO, CoO). Although Comparative Example 3 is commonly used in OER reactions and has a spin pinning effect, its current response value is significantly lower than that of Examples 1-4, indicating that it cannot be directly and simply applied to the COD detection system. Furthermore, for the electrochemical oxidation process of COD detection, specific materials and structures need to be selected to fully utilize the synergistic enhancement effect of spin pinning on sensitivity and stability.
[0067] The preferred embodiments of the present invention have been described in detail above. However, this patent is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, other variations or modifications can be made. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the claims of the present invention.
Claims
1. A method for preparing a nickel-based electrode with spin pinning effect, characterized in that, The steps are as follows: 1) Pretreatment: The nickel substrate is ultrasonically treated with hydrochloric acid and organic solvent, then rinsed with deionized water and dried at room temperature; 2) Precursor loading: A precursor layer containing one of the metal elements copper, nickel, or cobalt is loaded onto the surface of the nickel substrate after the pretreatment in step 1) by electrodeposition, hydrothermal method or immersion method. 3) Heat treatment: The nickel substrate loaded with precursor in step 2) is subjected to heat oxidation treatment to transform the precursor layer into an antiferromagnetic or paramagnetic metal oxide layer, thus obtaining a nickel-based electrode with spin pinning effect.
2. The preparation method according to claim 1, characterized in that, In step 1), The nickel substrate is ferromagnetic nickel foam, the hydrochloric acid concentration is 1~6 mol / L, and the organic solvent is anhydrous ethanol or acetone.
3. The preparation method according to claim 1, characterized in that, In step 2), The electrodeposition method uses a nickel substrate pretreated in step 1) as the working electrode, and deposits the electrode in an electrolyte containing the target metal salt at a constant potential of -1.0 V to -0.2 V for 5 to 30 min. The hydrothermal method involves immersing the nickel substrate pretreated in step 1) into an aqueous solution containing metal salt and urea, and reacting it at 120~180 °C for 6~12 h; wherein the molar ratio of metal salt to urea is 1:(2~5). The impregnation method involves immersing the nickel substrate pretreated in step 1) in a metal salt solution with a concentration of 0.1-0.5 mol / L at 60-80 °C for 0.5-2 h. The metal oxide layer is one of copper oxide, nickel oxide, and cobalt oxide.
4. The preparation method according to claim 3, characterized in that, In step 3), When the metal oxide layer is CuO or NiO, the nickel substrate treated in step 2) is placed in a muffle furnace and calcined in an air atmosphere; when the metal oxide layer is CoO, the nickel substrate treated in step 2) is placed in a tube furnace and calcined in an inert atmosphere.
5. The preparation method according to claim 1, characterized in that, In step 3), The thermal oxidation treatment is carried out at a temperature of 300-500 ℃, a heating rate of 3-5 ℃ / min, and a holding time of 1-3 h.
6. An electrochemical detection method for chemical oxygen demand, characterized in that, Using a nickel-based electrode with spin pinning effect obtained by any one of claims 1-5 as the working electrode, a magnetic field is applied to both sides of the working electrode, and a three-electrode system is selected for detection. The current value is detected at a constant working potential, and a standard curve between chemical oxygen demand and current response is constructed. The current value of the sample to be tested is obtained by detection, and the chemical oxygen demand of the sample to be tested is calculated by substituting it into the standard curve.
7. The method for detecting chemical oxygen demand according to claim 6, characterized in that, The strength of the magnetic field is 0.1~1 T, provided by a permanent magnet or electromagnet, and can be adjusted by changing the distance between the magnetic field source and the electrode or by the input current.
8. The method for detecting chemical oxygen demand according to claim 6, characterized in that, The three-electrode system uses a platinum sheet as the counter electrode and a saturated calomel electrode as the reference electrode. The current-time curve method is used as the detection method, and the applied working potential range is 0.4~0.9 V.
9. The method for detecting chemical oxygen demand according to claim 6, characterized in that, A standard curve was constructed in an alkaline electrolyte solution to correlate chemical oxygen demand (COD) with current. The steady-state current response to a series of organic compounds of different concentrations was recorded. The COD equivalent value corresponding to the organic compound concentration was used as the abscissa, and the measured current value was used as the ordinate. The standard curve was plotted by linear regression analysis, and its fitting equation was established. The COD of the sample was calculated by substituting the detected current value of the sample into the standard curve.
10. The method for detecting chemical oxygen demand according to claim 9, characterized in that, The organic matter includes one of glucose, glycine, fructose, ascorbic acid, sucrose, and potassium hydrogen phthalate, and the pH range of the alkaline electrolyte solution is 9-13.