A bimetallic nanomaterial modified carbon felt electrode and methods of making and using the same

Abstract

The application belongs to the field of nanomaterials and electrochemistry, and particularly relates to a bimetallic nanomaterial modified carbon felt electrode and a preparation and use method thereof. The specific technology comprises: a bimetallic nanomaterial modified carbon felt electrode, the modified carbon felt electrode comprises a carbon felt substrate, and the surface of the carbon felt substrate is coated with a modified slurry layer; the material of the modified slurry layer comprises elemental zero-valent iron-cerium dioxide nanocomposite, carbon black and a binder. The application utilizes the electron transfer capacity of elemental zero-valent iron, the reversible oxidation-reduction characteristics and enrichment adsorption performance of cerium dioxide, and the interface synergistic effect of the bimetallic catalytic components to realize high-sensitivity electrochemical detection of trace chloroacetic acid disinfection by-products in water.

Description

Technical Field

[0001] This invention belongs to the fields of nanomaterials and electrochemistry, specifically relating to a bimetallic nanomaterial modified carbon felt electrode and its preparation and use methods. Background Technology

[0002] Chlorination disinfection is a mainstream process in the water treatment field. During chlorination disinfection, chlorine agents undergo electrophilic substitution, oxidation, and addition reactions with natural organic matter and inorganic precursors in the raw water, generating chloroacetic acid disinfection byproducts (DBPs) that are teratogenic, carcinogenic, and mutagenic. Among them, trichloroacetic acid (TCAA), dichloroacetic acid (DCAA), and monochloroacetic acid (MCAA) are disinfection byproducts with high detection rates and wide distribution in tap water supply systems.

[0003] Currently, routine monitoring of chloroacetic acid disinfection byproducts in water bodies mainly relies on offline detection methods using large instruments such as gas chromatography, liquid chromatography, and ion chromatography. While these methods offer high separation efficiency and low detection limits, they suffer from drawbacks such as bulky equipment, high purchase and maintenance costs, complex and time-consuming processes, and the need for multiple sample pretreatment steps including extraction, derivatization, and purification, making it difficult to meet the demands for rapid, real-time, on-site detection.

[0004] Electrochemical detection methods offer advantages such as ease of operation, rapid response, wide dynamic linear range, low cost, and portability, making them promising for trace pollutant detection. However, for the detection of chloroacetic acid disinfection byproducts, existing electrochemical biosensors using hemoglobin as the recognition element are susceptible to external conditions such as temperature, humidity, and pH, resulting in insufficient long-term stability. Conventional single-metal oxide-based electrode materials exhibit high overpotentials and slow reaction kinetics, with detection limits typically only reaching the micromolar level, which is insufficient to meet the detection requirements of nanomolar-level trace disinfection byproducts in real water bodies.

[0005] Therefore, developing novel nanocomposite modified electrodes with high conductivity, abundant catalytic active sites, and stable chemical structure to achieve highly sensitive electrochemical quantitative detection of trace chloroacetic acid disinfection byproducts in water is a technical problem that needs to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to provide a bimetallic nanomaterial modified carbon felt electrode and its preparation and use methods.

[0007] To achieve the above-mentioned objectives, the technical solution adopted by this invention is: a bimetallic nanomaterial-modified carbon felt electrode, wherein the modified carbon felt electrode comprises a carbon felt substrate, and the surface of the carbon felt substrate is coated with a modified slurry layer; the material of the modified slurry layer comprises elemental zero-valent iron-cerium dioxide nanocomposite material, carbon black, and a binder. Preferably, in the elemental zero-valent iron-cerium dioxide nanocomposite material, by mass ratio, Fe... 0 CeO2 = (0.5-2):1; the adhesive is polyvinylidene fluoride. Preferably, the modified slurry layer is coated on both sides of the carbon felt substrate, and the loading of the modified slurry layer is 10 mg / cm³. 2 .

[0008] Accordingly, the preparation method of the bimetallic nanomaterial-modified carbon felt electrode includes the following steps:

[0009] (1) Preparation of elemental zero-valent iron-cerium dioxide nanocomposite material: under the protection of inert gas, CeO2 powder was mixed with FeSO4•7H2O solution to obtain a mixture; NaBH4 solution was slowly added dropwise to the mixture as a reducing agent and the reaction was continuously stirred. After the reaction was completed, the product was filtered, washed and vacuum dried to obtain the elemental zero-valent iron-cerium dioxide nanocomposite material.

[0010] (2) Preparation of modified slurry: Dissolve the elemental zero-valent iron-cerium dioxide nanocomposite material, binder and conductive carbon black in an organic solvent, mix thoroughly to obtain a uniformly dispersed modified slurry;

[0011] (3) Coating and drying: The modified slurry is uniformly coated on the surface of the carbon felt substrate and dried under vacuum to form a modified slurry layer, thereby obtaining the bimetallic nanomaterial modified carbon felt electrode.

[0012] Preferably, the steps for preparing the CeO2 powder include: dissolving cerium nitrate hexahydrate in deionized water to obtain solution A, slowly adding NaOH solution dropwise to solution A until a precipitate appears, then performing a microwave hydrothermal reaction, and after the reaction is terminated, centrifuging, washing, drying, and calcining the obtained precipitate to obtain CeO2 powder.

[0013] Accordingly, an electrochemical detection sensor includes a carbon felt electrode modified with the bimetallic nanomaterial, or a carbon felt electrode modified with the bimetallic nanomaterial prepared by the preparation method.

[0014] Preferably, the sensor uses the bimetallic nanomaterial-modified carbon felt electrode as the working electrode, Ag / AgCl as the reference electrode, and a platinum sheet as the counter electrode.

[0015] Correspondingly, the bimetallic nanomaterial-modified carbon felt electrode, or the bimetallic nanomaterial-modified carbon felt electrode prepared by the preparation method, or the electrochemical detection sensor is used in the detection of trace chloroacetic acid disinfection byproducts in water.

[0016] Accordingly, a method for detecting trace amounts of chloroacetic acid disinfection byproducts in water, the method comprising the following steps:

[0017] (1) Constructing an electrochemical detection sensor: The bimetallic nanomaterial-modified carbon felt electrode is used as the working electrode, Ag / AgCl is used as the reference electrode, and a platinum sheet is used as the counter electrode;

[0018] (2) The electrochemical detection sensor is placed in an electrolyte system containing the target analyte, and cyclic voltammetry is performed using an electrochemical workstation;

[0019] (3) Based on the change in electrochemical reduction peak current output by cyclic voltammetry scanning test, establish a current-concentration linear calibration curve to complete the quantitative detection of chloroacetic acid substances in water.

[0020] This invention offers the following advantages: It utilizes the electron transport capacity of elemental zero-valent iron and the reversible redox properties and enrichment adsorption performance of cerium dioxide, achieving highly sensitive electrochemical detection of trace chloroacetic acid disinfection byproducts in water through the interfacial synergistic effect of the bimetallic catalytic components. Compared with existing technologies, this invention has at least the following advantages:

[0021] (1) This invention uses elemental Fe 0 Fe is combined with CeO2 to construct a modified interface. 0 The introduction of [a specific substance] altered the electronic structure of the CeO2 surface, lowering the interfacial reaction energy barrier. Electrochemical impedance spectroscopy results showed that, compared to a pure carbon felt electrode (R...), [the following is a possible interpretation of the original text, which is incomplete and requires further context]. ct =15.82Ω) and a single CeO2 modified electrode (R ct =11.72Ω), the charge transfer resistance R of the composite electrode of the present invention ct Reduced to 8.392Ω, ohmic resistance R s The impedance was reduced to 1.183Ω, which lowered the electron transport and ion diffusion resistance at the sensing interface.

[0022] (2) This invention utilizes Fe 0 Fe is formed as an electron donor under voltammetric scanning. 0 →Fe 2+ →Fe 3+ Continuous electron transport pathway; CeO2 achieves interfacial enrichment and adsorption of target molecules through its high specific surface area, and through Ce... 4+ / Ce 3+The redox cycle is involved in charge-mediated processes. The two combine to form a synergistic catalytic network on the electrode surface, which has the ability to electrocatalytically break the C-Cl bonds in chlorine-containing disinfection byproduct molecules.

[0023] (3) Extremely high detection sensitivity. Within the trace detection range of 4–20 μg / L, the detection limits of the electrode sensor of this invention for TCAA, DCAA, and MCAA in water are 3.15 nM, 5.67 nM, and 12.03 nM (S / N=3), respectively, and the sensitivities are 60.39 μA / (μg·L). -1 ), 42.62 μA / (μg·L) -1 ) and 27.42 μA / (μg·L -1 ).

[0024] (4) At the same concentration level, the sensor of the present invention has a reduction current response intensity of TCAA that is 1.6 times higher than that of MCAA, more than 5 times higher than that of TBAA, and more than 40 times higher than that of interfering organic acids such as citric acid and acetic acid, demonstrating selective recognition ability of chloroacetic acid disinfection byproducts.

[0025] (5) This detection method does not require pretreatment steps such as extraction, esterification and derivatization. The test process is carried out in a buffer system of diluted water sample. In the spiked test of real tap water and Shahe surface water, the recovery rate is 100.0% to 106.84%, and the precision RSD can be controlled within 2.0%. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the fabrication process of the electrochemical sensor of the present invention;

[0027] Figure 2 Fe prepared in Example 1 of this invention 0 SEM image and elemental mapping diagram of the -CeO2@CF electrode; Figure 2 a is the SEM image of CeO2@CF; Figure 2 b is Fe 0 SEM image of @CF; Figure 2 c represents Fe at 100μm 0 SEM images of -CeO2@CF Figure 2 d is Fe at 200μm 0 SEM images of -CeO2@CF; Figure 2 e is Fe 0 -CeO2@CF nanomaterial C mapping image of a specific selected region. Figure 2 f is Fe 0 Ce mapping image of a specific selected region of the -CeO2@CF nanomaterial. Figure 2 g is Fe 0Fe mapping image of a specific selected region in the -CeO2@CF nanomaterial. Figure 2 h is Fe 0 -O mapping image of a specific selected region of CeO2@CF nanomaterial. Figure 2 i represents the EDS energy spectrum of CeO2@CF. Figure 2 j is Fe 0 EDS energy spectrum of -CeO2@CF;

[0028] Figure 3 The XRD patterns, FT-IR patterns, and elemental XPS patterns are included; among them, Figure 3 a is the XRD pattern; Figure 3 b is the FT-IR spectrum; Figure 3 c is the Ce 3d XPS plot; Figure 3 d is the Fe 2p XPS spectrum;

[0029] Figure 4 For different Fe 0 Comparison of the effects of CeO2 doping mass ratio on the electrochemical reduction peak current response;

[0030] Figure 5 Fe prepared in Example 1 of this invention 0 Cyclic voltammetry curves and linear relationships between peak current and scan rate for the CeO2@CF electrode at different scan rates; among them, Figure 5 a is the cyclic voltammetry curve at different scan rates; Figure 5 b is a graph showing the relationship between peak current and scan rate;

[0031] Figure 6 The graph shows the effect of different pH electrolyte systems on the peak current response intensity of the sensor.

[0032] Figure 7 Pure carbon felt electrode (CF), CeO2@CF, Fe 0 @CF and Fe 0 Comparison of cyclic voltammetric scan curves for -CeO2@CF electrodes;

[0033] Figure 8 Pure carbon felt electrode (CF), CeO2@CF, Fe 0 @CF and the Fe of this invention 0 Comparison of Bode phase angles in the electrochemical impedance spectroscopy of the -CeO2@CF electrode;

[0034] Figure 9 Pure carbon felt electrode (CF), CeO2@CF, Fe 0 @CF and the Fe of this invention 0Nyquist comparison diagram of -CeO2@CF electrode after equivalent circuit fitting;

[0035] Figure 10 Fe 0 Electrochemical CV response and linear relationship of the CeO2@CF sensor for 20–100 µg / L TCAA, DCAA, and MCAA; among which, Figure 10 a is Fe 0 -CeO2@CF sensor electrochemical CV response to 20–100 μg / L TCAA; Figure 10 b represents the linear relationship between the CV peak current change and concentration of TCAA; Figure 10 c is Fe 0 -CeO2@CF sensor electrochemical CV response to 20–100 μg / L DCAA; Figure 10 d represents the linear relationship between the change in peak current (CV) of DCAA and its concentration; Figure 10 e is Fe 0 -CeO2@CF sensor electrochemical CV response to 20–100 μg / L MCAA; Figure 10 f represents the linear relationship between the CV peak current change and concentration of MCAA;

[0036] Figure 11 For Fe 0 Electrochemical CV response and linear relationship of the CeO2@CF sensor for 4–20 µg / L DCAA and MCAA; among which, Figure 11 a is Fe 0 -CeO2@CF sensor electrochemical CV response to 4–20 μg / L DCAA; Figure 11 b represents the linear relationship between the change in peak current (CV) of DCAA and its concentration; Figure 11 c is Fe 0 -CeO2@CF sensor electrochemical CV response to 4–20 μg / L MCAA; Figure 11 d represents the linear relationship between the change in peak current (CV) of DCAA and its concentration;

[0037] Figure 12 Fe 0 -Electrochemical voltammetric response and linear calibration curve of CeO2@CF sensor for trace concentration range of 4-20 μg / L TCAA; Figure 12 a is Fe 0 -CeO2@CF sensor electrochemical CV response to 4–20 μg / L TCAA; Figure 12 b represents the linear relationship between the change in CV peak current of TCAA and its concentration;

[0038] Figure 13 Fe 0 Cyclic stability, long-term storage stability and selectivity test graphs for -CeO2@CF; Figure 13 a is Fe 0 Scan plot of peak current variation over 8 CV cycles for -CeO2@CF; Figure 13 b represents the same Fe 0 - Peak current histogram of each cyclic voltammetric scan of the CeO2@CF electrode; Figure 13 c is Fe 0 A schematic diagram of the peak current response of the -CeO2@CF electrode after continuous measurement for 5 days at room temperature; Figure 13 d is Fe 0 Response diagram of -CeO2@CF to TCAA, DCAA, MCAA, TCAcAm, TBAA, DCM, CA, HAc, and Trichloroacetaldehyde. Detailed Implementation

[0039] This invention provides a bimetallic nanomaterial-modified carbon felt electrode for detecting chloroacetic acid disinfection byproducts in water. The bimetal refers to iron and cerium, and the nanomaterial refers to elemental zero-valent iron-cerium dioxide nanocomposite material. The modified carbon felt electrode includes a carbon felt substrate, the surface of which is coated with a modified slurry layer. The modified slurry layer comprises elemental zero-valent iron-cerium dioxide nanocomposite material, carbon black (conductive), and a binder. The binder is a carbon-based conductive material, optionally polyvinylidene fluoride, carbon nanotubes, or graphene.

[0040] In the aforementioned elemental zero-valent iron-cerium dioxide nanocomposite material, by mass ratio, Fe 0 CeO2 = (0.5-2):1, more preferably 1:1. In the modified slurry layer, the mass ratio of elemental zero-valent iron-cerium dioxide nanocomposite material: binder: conductive carbon black is 8:1:1.

[0041] The size of the carbon felt substrate is determined according to the actual application, for example, it can be 2×2cm. The modified slurry layer is coated on both sides of the carbon felt substrate, and the loading of the modified slurry layer is 10mg / cm³. 2 .

[0042] This invention also provides a method for preparing the bimetallic nanomaterial-modified carbon felt electrode, specifically including the following steps:

[0043] 1. Preparation of cerium dioxide powder: Cerium nitrate hexahydrate was dissolved in deionized water to obtain solution A, in which the concentration of cerium nitrate hexahydrate was 151.99 g / L to 911.91 g / L. 1–10 mol / L NaOH solution was slowly added dropwise to solution A until a precipitate appeared, obtaining a mixed solution. The mixed solution was transferred to a polytetrafluoroethylene microwave reactor for microwave hydrothermal reaction (power P = 100–500 W) for 30–60 min. After the reaction was terminated, the resulting precipitate was centrifuged (centrifugation conditions: 5000–10000 rpm, centrifugation for 30–60 min), washed and dried alternately with anhydrous ethanol and distilled water, and then dried in a vacuum drying oven at 60°C for 12–18 h. Finally, it was calcined (microwave calcination conditions: P = 100–500 W, microwave calcination for 5–10 min) to obtain CeO2 powder.

[0044] 2. Preparation of elemental zero-valent iron-cerium dioxide nanocomposite material: Under the protection of an inert gas such as nitrogen, the CeO2 powder and FeSO4·7H2O solution are mixed in a reaction vessel to obtain a mixture. The mass ratio of CeO2:FeSO4·7H2O is 1:0.5 to 1:2; the concentration of FeSO4·7H2O is 0.04 to 0.08 mol / L.

[0045] A 0.2–0.8 mol / L NaBH4 solution was slowly added dropwise to the mixture while stirring continuously for 1.2–2.5 h. After the reaction was completed, the product was washed alternately with water and ethanol. Once the flowing washing liquid was clear, the filtration and washing were stopped. Subsequently, the product was vacuum dried at 25–35 °C for 1–2 h to obtain elemental zero-valent iron-cerium dioxide nanocomposite material.

[0046] 3. Preparation of modified slurry: The elemental zero-valent iron-cerium dioxide nanocomposite material, binder and conductive carbon black are dissolved in an organic solvent (N-methylpyrrolidone), and after stirring and ultrasonic treatment, a uniformly dispersed modified slurry is obtained.

[0047] 4. Coating and drying: The modified slurry is uniformly coated on the surface of the carbon felt substrate and dried under vacuum to form a modified slurry layer, thus obtaining the bimetallic nanomaterial modified carbon felt electrode.

[0048] This invention also provides a method for detecting chloroacetic acid-like substances in water using a carbon felt electrode modified with the aforementioned bimetallic nanomaterial, specifically comprising the following steps:

[0049] 1. Construct an electrochemical three-electrode working system: The bimetallic nanomaterial-modified carbon felt electrode is used as the working electrode, Ag / AgCl is used as the reference electrode, and a platinum sheet is used as the counter electrode.

[0050] 2. Place the three-electrode working system in an electrolyte system containing the target analyte and perform cyclic voltammetry scanning using an electrochemical workstation. The electrolyte can be a phosphorus buffered solution (PBS) with pH=6, prepared by mixing 0.42 g NaH2PO4•2H2O, 1.23 g Na2HPO4, and 8.0 g NaCl with 1 L of ultrapure water. The concentration of the target analyte depends on the concentration of TCAA, DCAA, and MCAA to be detected. For real water sample testing, the electrodes can be directly placed in the actual water sample. Considering that the content of disinfection byproducts in the actual water sample may be low, a stock solution of a specific concentration of the target pollutant can be prepared in advance. The stock solution is added to the actual water sample, and then the electrodes are placed in for detection. Finally, the detected concentration is compared with the concentration of the pollutant in the added stock solution to obtain the concentration of the target pollutant in the actual water sample.

[0051] 3. Based on the change in electrochemical reduction peak current output from the cyclic voltammetric scan test, establish a current-concentration linear calibration curve to complete the quantitative detection of chloroacetic acid substances in water.

[0052] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art, and the data obtained are all average values ​​obtained after at least three repetitions, and each repetition yields valid data.

[0053] Example 1: Preparation of bimetallic nanomaterial-modified carbon felt electrode

[0054] The overall fabrication process of bimetallic nanomaterial-modified carbon felt electrodes is as follows: Figure 1 As shown, the specific steps include the following:

[0055] 1. Synthesis of cerium dioxide powder

[0056] Weigh 3.0397 g of Ce(NO3)3·6H2O and dissolve it in 10 mL of deionized water to obtain a clear solution A. Under constant temperature and magnetic stirring, slowly add 10 mol / L NaOH aqueous solution to solution A at a rate of 1 drop / s until a white precipitate forms. Transfer the mixture containing the precipitate to a polytetrafluoroethylene microwave reaction vessel, seal it, and place it in a microwave oven for a microwave hydrothermal reaction. The microwave hydrothermal reaction conditions are: P (power) = 100 W, and the microwave hydrothermal time is 30 min. After the reaction is terminated, allow it to cool naturally to room temperature. Collect the obtained precipitate by centrifugation in a benchtop centrifuge, wash it alternately with deionized water and anhydrous ethanol 3–5 times, and then dry it in a vacuum drying oven at 60 °C. Place the dried powder into a high-temperature resistant crucible and calcine it in a microwave oven at 100 W for 5 min to obtain pale yellow CeO2 nanoparticles with a face-centered cubic fluorite structure.

[0057] 2. Synthesis of elemental zero-valent iron-cerium dioxide nanocomposites

[0058] High-purity argon gas was introduced into a sealed three-necked flask to purge oxygen. 0.22 g of the CeO2 powder prepared in step 1 was weighed and added to 100 mL of a 0.04 M FeSO4·7H2O solution. The solution was magnetically stirred to ensure uniform dispersion, yielding a mixture. 0.2 M NaBH4 solution was slowly added dropwise to the mixture using a burette, and the reaction was continuously stirred at room temperature for 1.5 h. After the reaction was complete, the product was vacuum filtered, washed with oxygen-free ultrapure water and anhydrous ethanol, and vacuum dried at room temperature for 12 h to obtain Fe. 0 Fe with a mass ratio of 1:1 to CeO2 0 -CeO2 nanocomposite materials.

[0059] The SEM morphology and elemental mapping of the prepared composite material coated on the carbon felt substrate are as follows: Figure 2 As shown. Figure 2 a is a SEM image of CeO2@CF, which shows an irregular plate-like aggregate morphology; Figure 2 b is Fe 0 The SEM image of @CF shows clusters and chain-like structures composed of spherical particles ranging from 100 to 250 nm. Figure 2 c~d are Fe 0 SEM images of -CeO2@CF show Fe... 0 -CeO2@CF nanomaterial particles are uniformly coated on carbon fibers, and Fe3O4 nanometers are 300-400 nm thick. 0 Spherical particles are dispersed on a cerium oxide matrix; Figures e to h show Fe 0-Mapping images of C, Ce, Fe, and O in selected regions of the CeO2@CF nanomaterial show the uniform distribution of C, O, Fe, and Ce in the composite material; Figures i and j show CeO2@CF and Fe 0 EDS energy dispersive spectroscopy of CeO2@CF, showing the difference between the CeO2@CF material before and after composite Fe. 0 -Elemental distribution differences in CeO2@CF materials. Results show that CeO2@CF exhibits an irregular plate-like aggregate morphology, with Fe... 0 @CF consists of clusters and chain structures composed of spherical particles ranging from 100 to 250 nm, Fe 0 -CeO2@CF nanomaterial particles are uniformly coated on carbon fibers, effectively inhibiting nanoparticle aggregation, fully exposing the heterogeneous interface, and constructing Fe 0 The synergistic battery system with CeO2 accelerates interfacial electron transfer, significantly improving the enrichment efficiency and reaction kinetics of TCAA, DCAA, and MCAA at the electrode interface. The prepared electrochemical sensor exhibits a detection limit in the nM range and high sensitivity, providing support for the portable, high-precision detection of trace DBPs in drinking water.

[0060] 3. Coating and molding of modified working electrodes

[0061] Weigh the Fe prepared in step 2 according to a mass ratio of 8:1:1. 0 CeO2 nanocomposite materials, polyvinylidene fluoride (PVDF), and conductive carbon black were placed together in a beaker containing 5 mL of N-methylpyrrolidone (NMP). The mixture was first stirred on a magnetic stirrer for 1 hour, and then transferred to an ultrasonic cleaner and ultrasonically treated at 540 W and 40 kHz for 4 hours to prepare a uniformly dispersed modified slurry.

[0062] The carbon felt is acid-washed and activated: first soaked in acetone for 24 hours, then in hydrochloric acid for 1 hour, and then in sodium hydroxide for 1 hour. During the process of changing the soaking solution, it is rinsed several times with distilled water. Finally, the soaked carbon felt is dried at room temperature of 25°C.

[0063] A carbon felt measuring 2×2 cm, after acid washing and activation treatment, was selected as the substrate. The modified slurry was uniformly coated on both sides of the carbon felt, with a coating load of 10 mg / cm². After coating, the substrate was transferred to a vacuum drying oven and dried at 60°C for 12 hours to obtain Fe. 0 -CeO2@CF working electrode. Prepared Fe 0 The XRD, FT-IR, and XPS characterization results of the -CeO2@CF electrode are as follows: Figure 3 As shown. The results show that XRD confirms Fe 0The presence of Fe in the CeO2 crystalline phase and the emergence of new Fe-O and Ce-O chemical bond vibration peaks in FT-IR indicate that Fe and Ce form a tight interfacial bond, effectively accelerating interfacial electron transport. XPS results show the presence of Fe on the material surface. 0 Fe 2+ Fe 3+ Multiple valence states of iron species are present while retaining the redox system of Ce. The multivalent metals construct a continuous and reversible redox cycle, forming a Fe-Ce synergistic catalytic closed loop, accelerating interfacial electron transfer, and significantly improving the enrichment efficiency and reaction kinetics of TCAA, DCAA, and MCAA at the electrode interface.

[0064] Following steps 1-3, with all other conditions identical, except that the amount of CeO2 powder added in step 2 was adjusted to 0.44g, 0.147g, and 0.11g respectively, to prepare Fe... 0 Comparative working electrodes with CeO2 mass ratios of 0.5:1, 1.5:1, and 2:1.

[0065] Example 2: Optimization of Sensing and Detection Conditions

[0066] 1. Fe 0 The Influence of CeO2 Bimetallic Component Doping Ratio on Detection Results

[0067] A standard three-electrode testing system based on a CHI760E electrochemical workstation was constructed, and four Fe44 Fe444 Fe34 ... 0 Modified carbon felt electrodes with different mass ratios to CeO2 were used as working electrodes, Ag / AgCl electrodes as reference electrodes, and Pt sheets as counter electrodes. Cyclic voltammetry was performed in phosphate buffer solution (PBS) at pH 6 containing 100 μg / L TCAA (trichloroacetic acid) (scan rate 30 mV / s), and the change in reduction peak current (ΔIp) of each working electrode was recorded.

[0068] The results are as follows Figure 4 As shown, the results indicate that when Fe 0 The sensor exhibits the largest change in reduction peak current when the mass ratio of Fe to CeO2 is 1:1. This is likely because at this ratio, Fe... 0 The dispersion of Fe reaches its optimal level on the CeO2 fluorite structure surface, with a match between the number of adsorption sites and electron transport sites, resulting in the highest synergistic efficiency between the bimetals. 0 When the content is too low (0.5:1), there are insufficient electron transport sites; when Fe 0 When the content is too high (1.5:1 and 2:1), the high surface energy nanoparticles are prone to magnetization and agglomeration, covering the active adsorption sites of CeO2. Therefore, 1:1 was determined to be the optimal doping ratio.

[0069] 2. The impact of scanning rate ratio on detection results

[0070] Fe prepared using Example 1 0 Fe with a mass ratio of 1:1 to CeO2 0 Cyclic voltammetry was performed on a CeO2@CF electrode in a PBS system at pH 6 at scan rates of 15, 30, 40, 50, 60, 70, and 80 mV / s. The results are as follows: Figure 5 As shown. Figure 5 a represents the effect of different scan rates; the scan rate in electrochemical testing also affects the electrochemical response of the electrode material. When the scan rate is 30 mV / s, the CV curve is stable, complete, and the peak current variation reaches its maximum. Figure 5 b is the graph showing the relationship between peak current and scan rate, confirming the effectiveness of TCAA in Fe... 0 The reaction on the CeO2@CF electrode is a typical adsorption-controlled process. The results show that the reproducibility of the seven CV curves obtained at different scan rates is good, and the reduction peak current increases regularly with increasing scan rate. The linear fit of the peak current (Ip) to the scan rate (ν) is Ip(mA) = -0.0400ν - 0.7149 (i.e., ... Figure 5 In step b, Ip = -0.0400x - 0.7149), and R² = 0.9911, indicating that the reaction of the target analyte at the electrode interface is an adsorption-controlled surface process. The CV baseline is most stable and the peak current differentiation is largest at 30 mV / s. Therefore, 30 mV / s is determined to be the optimal scan rate.

[0071] 3. The effect of electrolyte pH on test results

[0072] Fe prepared using Example 1 0 Fe with a mass ratio of 1:1 to CeO2 0 -CeO2@CF electrode, PBS buffer solutions with pH values ​​of 4.0, 5.0, 6.0, 7.0, and 8.0 were prepared, and 100 μg / L TCAA was added to each system. Voltammetric scanning was performed at 30 mV / s. The results are as follows. Figure 6 As shown, the results indicate that the current response reaches its maximum at pH=6.0. This may be because, under weakly acidic conditions, Fe... 0 Fe produced by oxidation 2+ It is not easily hydrolyzed, maintaining a continuous electron transport path; the hydroxyl groups on the CeO2 surface have the strongest adsorption capacity for TCAA through hydrogen bonding and electrostatic interactions. 4+ / Ce 3+ High valence state cycling efficiency; under strongly acidic conditions (pH=4.0), excess protons overprotonate the CeO2 surface and accelerate Fe... 0Acid etching depletes protons; under alkaline conditions (pH ≥ 7.0), the proton supply required for C-Cl bond breaking is suppressed. Therefore, pH = 6.0 was determined to be the optimal reaction system.

[0073] Example 3: Performance Testing

[0074] In this embodiment, unless otherwise specified, the Fe prepared in Example 1 was used under the preferred conditions of Example 2 (scan rate 30 mV / s, pH=6.0). 0 -CeO2@CF electrode (Fe 0 The detection was performed using a CeO2 ratio of 1:1.

[0075] 1. Electrochemical Impedance Spectroscopy (EIS) Test

[0076] Under the preferred conditions of Example 2 (scan rate 30 mV / s, pH=6.0), pure carbon felt electrode (CF), CeO2@CF, Fe 0 @CF and Fe prepared in Example 1 0 -CeO2@CF electrode (Fe 0 A comparative EIS test was conducted using CeO2 (1:1 ratio). Among the components, CeO2@CF and Fe... 0 The preparation method of @CF is the same as in Example 1, except that the corresponding other metal material is not added. The test frequency is 0.01Hz to 100000Hz, and the AC signal amplitude is 0.01V. The R of each electrode is obtained by fitting the Nyquist curve through the Randles equivalent circuit model. s With R ct The values ​​are shown in Table 1.

[0077] Table 1. Fitting parameters of Rs and Rct for different modified electrodes

[0078]

[0079] Table 1 shows that the pure CF electrode lacks active transition metal components, resulting in an interfacial charge transfer resistance as high as 15.82 Ω. CeO2@CF utilizes the electrochemical activity of CeO2 to slightly reduce the impedance to 11.72 Ω, but this is limited by its semiconductor conductivity. Fe 0 @CF enables R through a metallic conductive network ct It decreased to 9.266Ω. Fe 0 -CeO2@CF's R ct The impedance dropped to 8.392Ω and Rs dropped to 1.183Ω, exhibiting the lowest phase angle across the entire frequency domain. This indicates that the interfacial coupling between the electron transport network of elemental iron and the reversible valence cycle of rare earth oxides reduced the sensing interface impedance.

[0080] 2. Electrochemical performance (CV, EIS, capacitance measurement) testing

[0081] Construct a 2×2cm Fe 0 A three-electrode system was established using CeO2@CF nanomaterials modified carbon felt (CF) as the working electrode, Ag / AgCl as the reference electrode, and a Pt sheet as the counter electrode. Electrochemical measurements were performed using a Shanghai Chenhua CHI760E electrochemical workstation. Impedance spectra (Nyquist and Bode plots) were obtained to analyze the charge transfer characteristics and impedance changes at the electrode interfaces. Test conditions: frequency scan range of 0.01 Hz to 100,000 Hz, AC signal amplitude of 0.01 V, settling time of 2 s, and single-frequency measurement mode.

[0082] Pure carbon felt electrode (CF), CeO2@CF, Fe 0 @CF and the Fe of this invention 0 Cyclic voltammetric scan curves of the -CeO2@CF electrode, for example... Figure 7 As shown in the figure, the Bode phase angle comparison diagram of the electrochemical impedance spectroscopy is as follows: Figure 8 As shown, the Nyquist comparison diagram after equivalent circuit fitting is as follows: Figure 9 As shown. The results show: Fe 0 -CeO2@CF exhibits a pair of distinct redox peaks between 0.2V and 0.8V, showing the strongest peak current response compared to other materials. Simultaneously, it exhibits the lowest interfacial charge transfer impedance and the highest capacitance, indicating that Fe... 0 -CeO2@CF possesses the most abundant electrochemical active sites and the strongest charge transfer capability, mainly attributed to the synergistic redox reaction between Fe and Ce (e.g., FeO2@CF). 0 / Fe 2+ / Fe 3+ With Ce 3+ / Ce 4+ Electron transfer coupling significantly improves the electron transfer efficiency of the electrodes.

[0083] 3. Performance test for quantitative detection of trace disinfection byproducts

[0084] Under the preferred conditions of Example 2, the Fe prepared in Example 1 was used 0 -CeO2@CF electrode (Fe 0 The concentration ratio of TCAA, DCAA, and MCAA standard solutions was 1:1 (CeO2 = 1:1), and gradient tests were performed on the solutions in both the high concentration range (20–100 μg / L) and the low trace concentration range (4–20 μg / L). The test results in the high concentration range (20–100 μg / L) are shown below. Figure 10 As shown, Figure 10 a is Fe 0- The electrochemical CV response diagram of the CeO2@CF sensor to 20–100 μg / L TCAA shows that as the concentration of TCAA increases from 20 to 100 μg / L, the peak current of the reduction peak increases with the increase of its concentration, and the maximum current change can be as high as 2.93 mA. Figure 10 b represents the linear relationship between the CV peak current change and concentration of TCAA, showing a good linear relationship between TCAA concentration and peak current change in the range of 20–100 μg / L. 2 It is 0.9797; Figure 10 c is Fe 0 -CeO2@CF sensor electrochemical CV response diagram for 20~100μg / LDCAA. The results show that the CV curve trend of DCAA is consistent with that of TCAA, but the absolute value of current of DCAA is lower than that of TCAA at the same concentration. Figure 10 d represents the linear relationship between the peak current change and concentration for DCAA. The linearity between concentration and peak current change is slightly lower than that for TCAA. 2 It is 0.9699; Figure 10 e is Fe 0 The electrochemical CV response plots of the -CeO2@CF sensor to 20–100 μg / L MCAA show that Fe 0 -CeO2@CF showed the lowest electrochemical response to 20–100 μg / L MCAA; Figure 10 f represents the linear relationship between the peak current change and concentration of MCAA, and the linearity R between concentration and peak current change is given by [formula missing]. 2 It is 0.9984.

[0085] The test results in the low trace concentration range (4–20 μg / L) are as follows: Figure 11 As shown, Figure 11 a is Fe 0 The electrochemical CV response plots of the -CeO2@CF sensor to 4–20 μg / L DCAA show that the peak current response increases with increasing DCAA concentration. Figure 11 b represents the linear relationship between the peak current change of DCAA and concentration. At the same concentration, Fe... 0 The electrochemical response of the CeO2@CF electrode to DCAA (0.74 mA) is significantly lower than that to TCAA (1.06 mA). Calculations based on experimental data show that Fe... 0 The sensitivity of the -CeO2@CF electrode for DCAA detection is 42.62 μA / μg·L. -1 (LOD=5.67 nM (S / N=3)); Figure 11 c is Fe 0Electrochemical CV response plots of the -CeO2@CF sensor for 4–20 μg / L MCAA show that the peak current response increases with increasing MCAA concentration. Figure 11 d represents the linear relationship between the peak current change (CV) of DCAA and the concentration. At the same concentration, Fe... 0 The electrochemical response of the CeO2@CF electrode to MCAA (0.60 mA) was significantly lower than that to TCAA (1.06 mA). Calculations based on experimental data revealed that Fe... 0 The sensitivity of the -CeO2@CF electrode for MCAA detection is 27.42 μA / μg·L. -1 (LOD=12.03nM (S / N=3)).

[0086] The results showed that, within the same range of 4–20 μg / L, the order of the electrochemical response of the sensor was TCAA > DCAA > MCAA, which is consistent with the rule that the activation energy of the dechlorination reaction decreases as the number of chlorine atoms in the molecule increases.

[0087] The electrochemical voltammetric response and linear calibration curves of TCAA in the trace concentration range of 4–20 μg / L are shown in the figure below. Figure 12 As shown. Figure 12 a is Fe 0 Electrochemical CV response of the -CeO2@CF sensor to 4–20 μg / L TCAA. As the TCAA concentration increases from 4 to 20 μg / L, Fe... 0 The reduction peak current of the -CeO2@CF electrode increases with increasing concentration; Figure 12 b represents the linear relationship between the CV peak current change and concentration of TCAA, showing the relationship between TCAA concentration and peak current. The fitted curve exhibits a good linear relationship in the range of 4–20 μg / L (R0). 2 =0.9986). Based on the linear fitting equation, the sensor's sensitivity to TCAA detection is calculated to be 60.39 μA / μg·L. -1 (LOD=3.15 nM (S / N=3))

[0088] The results showed that: Fe 0 The -CeO2@CF sensor exhibits strong electrochemical response signals to three DBPs ranging from 4 to 20 μg / L, and the peak current shows a good linear relationship with the pollutant concentration. Among them, Fe... 0 The -CeO2@CF electrode exhibited the strongest electrochemical response and highest sensitivity to TCAA (60.39 μA / μg·L). -1 And the detection limit is the lowest (LOD=3.15 nM (S / N=3)). Fe 0The -CeO2@CF electrode showed significantly lower electrochemical responses to DCAA and MCAA than to TCAA, with a sensitivity and detection limit of 42.62 μA / μg·L for both. -1 (LOD=5.67 nM (S / N=3)), 27.42 μA / μg·L -1 (LOD=12.03 nM (S / N=3)). Therefore, Fe 0 The electrochemical sensor constructed with -CeO2@CF exhibited superior detection performance for TCAA with higher chlorine substitution numbers.

[0089] Within the range of 20–100 μg / L, the absolute value of the reduction peak current increases systematically with increasing TCAA concentration, reaching a maximum change of 1.06 mA. A linear fit was performed with concentration on the x-axis and peak current change on the y-axis, yielding an R² of 0.9996. Based on the 3x signal-to-noise ratio formula (LOD = 3Sb / k), the sensor's sensitivity to TCAA is 60.39 μA / (μg·L). -1 The detection limit was 3.15 nM (S / N=3).

[0090] 3. Selectivity and stability assessment

[0091] The test results for selectivity, cyclic stability, and long-term storage stability are as follows: Figure 13 As shown.

[0092] (1) Cyclic stability: When the same Fe 0 The -CeO2@CF electrode was continuously scanned for 8 to 10 cycles at a potential window of -0.2 to 1.2 V and a scan rate of 30 mV / s. Figure 13 a is Fe 0 The peak current variation scan of -CeO2@CF over 8 CV cycles shows that the CV peak shapes are basically overlapping in the eight scans, and the peak current fluctuations are minimal. Figure 13 b represents the same Fe 0 The peak current histograms of the CeO2@CF electrode after each cycle of cyclic voltammetry scanning show that the sensor degradation is minimal, even negligible. After 10 consecutive scans, the CV curve profiles from the 1st to the 10th cycle are essentially identical, with peak current fluctuations less than 1.5%. These results indicate that the sensor exhibits excellent stability and good electrode cyclic stability.

[0093] (2) Long-term storage stability: Fe 0 -CeO2@CF electrode is placed in a normal room temperature atmospheric environment, such as Figure 13 As shown in Figure c, after 5 consecutive days of storage, 82.3% of the initial current signal was retained, indicating good long-term storage stability. In practical applications, storing the sensing electrodes in an inert gas-sealed environment and unsealing them only before use will further improve storage stability.

[0094] (3) Selective recognition: At a concentration level of 20 μg / L, voltammetric scans were performed on TCAA and eight interfering substances (TBAA, DCM, TCAcAm, trichloroacetaldehyde, MCAA, DCAA, citrate (CA), and acetic acid (HAc)). Figure 13 As shown in d, Fe 0 The -CeO2@CF sensor showed a reduction peak current intensity for TCAA that was more than 1.6 times that of MCAA, more than 5 times that of TBAA, and more than 40 times that of citric acid and acetic acid, indicating that Fe 0 The -CeO2@CF sensor responds significantly more to chloroacetic acid DBPs than to other substances, indicating that the sensing interface has a targeted catalytic breakage pathway for C-Cl bonds, which can avoid interference from coexisting organic compounds.

[0095] Example 4: Spiking Analysis of Real Environmental Water Samples and Comparison with GC-MS Method

[0096] Laboratory tap water was selected as the actual research medium. After filtration through a 0.45 μm filter membrane, the water sample was directly injected into PBS electrolyte at pH 6.0 without extraction or derivatization. Two spiking concentrations (50 μg / L and 5 μg / L) were set up, and the results were measured in triplicate (n=3). GC-MS was used for comparative analysis simultaneously, with three replicates, and the average value was taken. The results are shown in Table 2.

[0097] Table 2 Fe 0 Comparison table of water sample detection results using CeO2@CF and GC-MS methods

[0098]

[0099] The results showed that the recovery rate of DBPs in tap water by conventional gas chromatography-tandem mass spectrometry was in the range of 101.7% to 111.6%. The Fe prepared in Example 1 of this invention... 0 -CeO2@CF (Fe 0 The spiked recoveries of the sensor (CeO2=1:1) ranged from 100.8% to 104.3%, all meeting the national standard requirement of 80% to 120% recovery. The overall RSD of the method of this invention was less than 2.0%, which is superior to the 1.59% to 4.99% fluctuation range of the GC-MS method, indicating that this invention has good accuracy and reliability for the detection of TCAA, DCAA, and MCAA in complex matrices.

[0100] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any modifications, alterations, alterations, or substitutions made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A bimetallic nanomaterial-modified carbon felt electrode, characterized in that: The modified carbon felt electrode includes a carbon felt substrate, the surface of which is coated with a modified slurry layer; the modified slurry layer is made of elemental zero-valent iron-cerium dioxide nanocomposite material, carbon black and binder.

2. The bimetallic nanomaterial-modified carbon felt electrode according to claim 1, characterized in that: In the aforementioned elemental zero-valent iron-cerium dioxide nanocomposite material, by mass ratio, Fe 0 CeO2 = (0.5~2):

1.

3. The bimetallic nanomaterial-modified carbon felt electrode according to claim 1, characterized in that: The adhesive is polyvinylidene fluoride.

4. The bimetallic nanomaterial-modified carbon felt electrode according to claim 1, characterized in that: The modified slurry layer is coated on both sides of the carbon felt substrate, and the loading of the modified slurry layer is 10 mg / cm³. 2 .

5. The method for preparing the bimetallic nanomaterial-modified carbon felt electrode according to any one of claims 1 to 4, characterized in that: The preparation method includes the following steps: (1) Preparation of elemental zero-valent iron-cerium dioxide nanocomposite material: under the protection of inert gas, CeO2 powder was mixed with FeSO4•7H2O solution to obtain a mixture; NaBH4 solution was slowly added dropwise to the mixture as a reducing agent and the reaction was continuously stirred. After the reaction was completed, the product was filtered, washed and vacuum dried to obtain the elemental zero-valent iron-cerium dioxide nanocomposite material. (2) Preparation of modified slurry: Dissolve the elemental zero-valent iron-cerium dioxide nanocomposite material, binder and carbon black in an organic solvent, mix thoroughly to obtain a uniformly dispersed modified slurry; (3) Coating and drying: The modified slurry is uniformly coated on the surface of the carbon felt substrate and dried under vacuum to form a modified slurry layer, thereby obtaining the bimetallic nanomaterial modified carbon felt electrode.

6. The preparation method according to claim 5, characterized in that: The steps for preparing the CeO2 powder include: dissolving cerium nitrate hexahydrate in deionized water to obtain solution A; slowly adding NaOH solution to solution A until a precipitate appears; then performing a microwave hydrothermal reaction; after the reaction is terminated, centrifuging, washing, drying, and calcining the obtained precipitate to obtain CeO2 powder.

7. An electrochemical detection sensor, characterized in that: The sensor includes a carbon felt electrode modified with bimetallic nanomaterials according to any one of claims 1 to 4, or a carbon felt electrode modified with bimetallic nanomaterials according to the preparation method of claim 5 or 6.

8. The sensor according to claim 7, characterized in that: The sensor uses a bimetallic nanomaterial-modified carbon felt electrode as the working electrode, Ag / AgCl as the reference electrode, and a platinum sheet as the counter electrode.

9. The application of the bimetallic nanomaterial modified carbon felt electrode according to any one of claims 1 to 4, or the bimetallic nanomaterial modified carbon felt electrode prepared by the preparation method according to claim 5 or 6, or the electrochemical detection sensor according to claim 7 or 8 in the detection of trace chloroacetic acid disinfection byproducts in water.

10. A method for detecting trace amounts of chloroacetic acid disinfection byproducts in water, characterized in that: The method includes the following steps: (1) Constructing an electrochemical detection sensor: using a carbon felt electrode modified with bimetallic nanomaterials as described in any one of claims 1 to 4 as the working electrode, using Ag / AgCl as the reference electrode, and using a platinum sheet as the counter electrode; (2) The electrochemical detection sensor is placed in an electrolyte system containing the target analyte, and cyclic voltammetry is performed using an electrochemical workstation; (3) Based on the change in electrochemical reduction peak current output by cyclic voltammetry scanning test, establish a current-concentration linear calibration curve to complete the quantitative detection of chloroacetic acid substances in water.

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