Se-doped CuCo2S4 composite material, all-solid-state sodium ion selective electrode, its preparation method and application

Abstract

This invention discloses a Se-doped CuCo2S4 composite material, an all-solid-state sodium ion selective electrode, its preparation method, and its application. In the composite material, Se atoms replace some S sites in the CuCo2S4 lattice, forming a lattice-doped structure; the Se doping amount, calculated as the amount of SeO2 added, is 0.1–0.3 mmol. The preparation method includes dissolving a copper source and a cobalt source in anhydrous methanol, adding a sulfur source and SeO2, and then performing a solvothermal reaction. This invention also discloses an all-solid-state sodium ion selective electrode, comprising an electrode substrate, a transduction layer, and a sodium ion selective film disposed on the surface of the transduction layer, wherein the transduction layer is made of the aforementioned Se-doped CuCo2S4 composite material. This electrode exhibits a near-Nernst response to sodium ions, with a detection limit of 10. ‑5.2 M. This invention significantly improves the capacitance and hydrophobicity of materials by inducing lattice expansion and sulfur vacancy formation through Se doping, achieving stable detection of sodium ions. Furthermore, the preparation process is simple and has promising prospects for industrial application.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical analysis sensor materials, specifically involving Se-doped CuCo2S4 composite materials, all-solid-state sodium ion selective electrodes, their preparation methods, and applications. Background Technology

[0002] All-solid-state ion-selective electrodes, due to their simple structure and ease of miniaturization, show significant promise for accurate detection of electrolyte ions in complex environments. Their typical configuration is a sandwich structure, consisting of a conductive substrate at the bottom, a solid transducer layer in the middle, and an ion-selective membrane at the top. The solid transducer layer acts as an ion-electron transducer, responsible for converting the input ionic chemical signal into a stable potential signal that can be read by external circuitry. Given the differences in conduction mechanisms between the ion-selective membrane (ion conductor) and the conductive substrate (electron conductor), constructing a clear and efficient ion-electron transduction path is crucial for ensuring the long-term potential stability and measurement repeatability of all-solid-state ion-selective electrodes.

[0003] Currently, research on transduction layer materials mainly focuses on two categories: conductive polymers and carbon nanomaterials. When conductive polymers (such as polyaniline, polypyrrole, and poly-3-octylthiophene) are used as transduction layers, they are prone to redox side reactions and are sensitive to environmental factors such as light, oxygen, and carbon dioxide, leading to electrode potential drift and limiting their stability in practical applications. While carbon nanomaterials (such as graphene, carbon nanotubes, and fullerenes) possess good conductivity and chemical stability, their ion-electron transduction capability primarily relies on double-layer capacitance. However, the limited double-layer capacitance makes it difficult to meet the capacitance performance requirements of highly stable electrodes.

[0004] In recent years, transition metal sulfides have gradually attracted researchers' attention due to their high theoretical specific capacitance, abundant redox active sites, and tunable microstructure. For example, Chinese patent application CN202110393835.8 further prepared a NiCo2S4 transconducting layer with a nanoporous structure using electrodeposition, utilizing its redox capacitance to stabilize the interface potential. Chinese patent application CN202411152847.1 discloses a Ni3S4-MoS2 heterojunction material as the transconducting layer of an all-solid-state sodium ion selective electrode, which enhances the capacitance and hydrophobicity of the material through the heterojunction effect, achieving the detection of sodium ions.

[0005] However, the aforementioned multi-metal sulfide transconducting layer materials still face challenges in practical applications. On the one hand, although morphology control or heterostructures can improve material performance to some extent, the preparation process of heterostructured materials involves the composite of different components, resulting in difficulties in controlling interface uniformity and poor reproducibility. Furthermore, the heterostructure interface may deteriorate over long-term use. On the other hand, the intrinsic conductivity and number of active sites in existing multi-metal sulfide materials still need further improvement, making it difficult to meet the dual requirements of high capacitance and high stability for all-solid-state ion-selective electrodes. Therefore, how to provide a novel transconducting layer material with both high capacitance and good hydrophobicity to achieve stable detection of sodium ions is a pressing technical problem to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a Se-doped CuCo2S4 composite material, an all-solid-state sodium ion selective electrode, its preparation method and application.

[0007] The specific technical solution of the present invention is as follows: In a first aspect, the present invention provides a Se-doped CuCo2S4 composite material, wherein Se atoms replace some S sites in the CuCo2S4 lattice to form a lattice-doped structure; the amount of Se doping in the composite material is 0.1 to 0.3 mmol, relative to a 2 mmol copper source, based on the amount of SeO2 added.

[0008] Secondly, the present invention provides a method for preparing a Se-doped CuCo2S4 composite material, comprising the following steps: S1. Dissolve the copper source and cobalt source in anhydrous methanol, then add the sulfur source and disperse by ultrasonication to obtain mixed solution A; S2. Add SeO2 to the mixed solution A from step S1 and stir to obtain mixed solution B; S3. Heat the mixed solution B to carry out a solvothermal reaction. After the reaction is completed, cool to room temperature to obtain a precipitate. Wash the precipitate and dry it to obtain the Se-doped CuCo2S4 composite material.

[0009] Preferably, in step S1, the copper source is CuCl2·2H2O, the cobalt source is CoCl2·6H2O, and the sulfur source is thiourea; the molar ratio of the copper source, cobalt source, and sulfur source is 1:2:4.

[0010] Preferably, the amount of SeO2 added in step S2 is 0.1 to 0.3 mmol, relative to 2 mmol of copper source; the solvothermal reaction temperature in step S3 is 150 to 180°C, and the reaction time is 16 to 24 hours.

[0011] Thirdly, the present invention provides an all-solid-state sodium ion selective electrode, comprising an electrode substrate, a transduction layer coated on the surface of the electrode substrate, and a sodium ion selective film disposed on the surface of the transduction layer, wherein the transduction layer is made of the Se-doped CuCo2S4 composite material described in the first aspect above.

[0012] Preferably, the loading amount of the transconducting layer on the electrode substrate surface is 0.15 to 0.25 mg.

[0013] Preferably, the electrode substrate is any one of glassy carbon electrode, gold electrode, platinum electrode and screen-printed electrode.

[0014] Fourthly, the present invention provides a method for preparing an all-solid-state sodium ion selective electrode, comprising the following steps: (1) The electrode substrate is pretreated to make its surface clean and have a mirror gloss; (2) The Se-doped CuCo2S4 composite material obtained by the preparation method according to any one of claims 2-4 is ultrasonically dispersed in a solvent to obtain a dispersion, and the dispersion is drop-coated onto the surface of the electrode substrate after the pretreatment in step (1), and dried to form a transconducting layer; (3) The sodium ion selective membrane solution is drop-coated onto the surface of the transconducting layer formed in step (2) and dried to obtain the all-solid sodium ion selective electrode.

[0015] Preferably, the concentration of the dispersion in step (2) is 10–30 mg / mL.

[0016] Preferably, the sodium ion selective membrane solution in step (3) is prepared by dissolving sodium ion carrier, sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, di-n-octyl sebacate and polyvinyl chloride in tetrahydrofuran.

[0017] Fifthly, the present invention provides an application of the Se-doped CuCo2S4 composite material described in the first aspect or the all-solid-state sodium ion selective electrode described in the third aspect above, for detecting the sodium ion concentration in a solution.

[0018] This invention modulates the lattice structure and electronic properties of CuCo2S4 through Se atom doping. Since the atomic radius of Se (1.98 Å) is larger than that of S (1.84 Å), Se atoms, after replacing some S sites in the CuCo2S4 lattice, cause lattice expansion and local distortion, thereby inducing the formation of sulfur vacancies. With increasing Se doping concentration, the sulfur vacancy concentration increases. These sulfur vacancies, acting as redox active sites, provide more reactive centers, significantly improving the material's capacitance. Simultaneously, Se doping induces the formation of a unique three-dimensional flower-like nanosheet structure. When the Se doping concentration reaches 0.3 mmol, abundant nanoparticles appear on the flower-like surface, forming a multi-level structure, increasing the specific surface area of ​​the material, and effectively improving its capacitance. Based on these effects, this invention constructs an all-solid-state sodium-ion selective electrode using Se-doped CuCo2S4 as the transconducting layer, achieving highly sensitive and stable detection of sodium ions.

[0019] Compared with the prior art, the beneficial technical effects of this invention are reflected in: 1. This invention uses Se-doped CuCo2S4 as the transconducting layer material for an all-solid-state sodium-ion selective electrode. By substituting S sites with Se atoms, lattice expansion and sulfur vacancies are induced, thereby improving capacitance. This invention achieves homogeneous modification through atomic doping, resulting in a uniform structure. This avoids the risk of interface degradation during long-term use at heterogeneous interfaces, leading to superior structural stability.

[0020] 2. Significantly Improved Capacitance Performance. This invention effectively controls the sulfur vacancy concentration in CuCo2S4 through Se doping. Sulfur vacancies, as redox active sites, provide more reactive centers, thereby significantly improving the material's capacitance performance. EPR characterization confirms that the sulfur vacancy concentration increases with increasing Se doping amount, and the capacitance performance is enhanced accordingly, achieving controllable regulation of the material's capacitance performance.

[0021] 3. Excellent hydrophobic properties. The Se-CuCo2S4 material prepared in this invention exhibits a three-dimensional flower-like nanosheet structure. With the increase of Se doping concentration, abundant nanoparticles gradually appear on the surface of the flower sheets, forming a unique multi-level structure, which effectively increases the specific surface area of ​​the material. Contact angle tests show that the water contact angle of the materials at all doping ratios is above 108°, exhibiting excellent hydrophobicity, which is beneficial for suppressing the formation of a water layer at the interface between the transconductance layer and the ion-selective membrane.

[0022] 4. Excellent sodium ion detection performance. An all-solid-state sodium ion selective electrode constructed based on Se0.3-CuCo2S4 as the transconducting layer exhibits excellent sodium ion detection performance at 10... - ¹~10 -5 M Na +It exhibits a good linear response across the concentration range, with a Nernst slope of 58.52 mV / dec, close to the theoretical Nernst response (59.2 mV / dec), and a detection limit of 10. -5.2 M.

[0023] 5. This invention uses a one-step solvothermal method to prepare Se-CuCo2S4 material, which is simple, mild, easy to scale up, and has good prospects for industrial application. Attached Figure Description

[0024] Figure 1 ad is CuCo2S4, Se 0.1 -CuCo2S4, Se 0.2 -CuCo2S4, Se 0.3 Scanning electron microscope image of CuCo2S4.

[0025] Figure 2 CuCo2S4, Se 0.1 -CuCo2S4, Se 0.2 -CuCo2S4, Se 0.3 X-ray diffraction pattern of CuCo2S4.

[0026] Figure 3 CuCo2S4, Se 0.1 -CuCo2S4, Se 0.2 -CuCo2S4, Se 0.3 EPR sulfur vacancy characterization of various CuCo2S4 materials.

[0027] Figure 4 CuCo2S4, Se 0.1 -CuCo2S4, Se 0.2 -CuCo2S4, Se 0.3 Cyclic voltammetry curves of various CuCo2S4 materials.

[0028] Figure 5 For Se with different loads 0.3 Cyclic voltammetry curves of CuCo2S4 material on the electrode surface.

[0029] Figure 6 ab are based on Se 0.3 Potential response diagram and calibration curve of all-solid-state sodium ion selective electrode of CuCo2S4.

[0030] Figure 7 CuCo2S4, Se 0.1 -CuCo2S4, Se 0.2 -CuCo2S4, Se 0.3Water contact angle diagrams for various CuCo2S4 materials. Detailed Implementation

[0031] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0032] The following description sets forth many specific details to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0033] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0034] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0035] All reagents used in the examples were commercially available analytical grade reagents. Among them, sodium ion carrier X, 4-tert-butylcalix[4] aryl-tetraacetic acid tetraethyl ester (CAS No.: 97600-39-0) was purchased from Sigma-Aldrich, product number 71747. Sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaTFPB), (CAS No.: 79060-88-1) was purchased from Sigma-Aldrich, product code 72017; Di-n-octyl sebacate (DOS), (CAS No.: 122-62-3), was purchased from Sigma-Aldrich, product code 84818; Polyvinyl chloride (PVC), (CAS No.: 9002-86-2) was purchased from Sigma-Aldrich, product number 81387; Tetrahydrofuran (THF), (CAS No.: 109-99-9), was purchased from Sigma-Aldrich, product code 34865; Copper chloride dihydrate (CuCl2·2H2O) (CAS No.: 10125-13-0) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., product code C431252; Cobalt chloride hexahydrate (CoCl2·6H2O), (CAS No.: 7791-13-1), was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., product code C118625; Thiourea (CH4N2S), (CAS No.: 62-56-6) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., product code T112514; Selenium dioxide (SeO2) (CAS No.: 7446-08-4) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., product code S110873; Anhydrous methanol (CAS No.: 67-56-1) was purchased from Sinopharm Chemical Reagent Co., Ltd., product code 800804190.

[0036] Preparation Example 1: Preparation of Se-CuCo2S4 Transduction Layer Material The specific steps for preparing Se-CuCo2S4 materials with different Se doping amounts are as follows: (1) Dissolve 1 mmol CuCl2·2H2O and 2 mmol CoCl2·6H2O in 40 mL of anhydrous methanol, then add 4 mmol thiourea (CH4N2S), and stir vigorously for 10 minutes at room temperature to obtain a mixed solution.

[0037] (2) Add 0 mmol, 0.1 mmol, 0.2 mmol and 0.3 mmol of SeO2 to the above mixed solution respectively, and continue stirring for 10 minutes to obtain a homogeneous mixed solution.

[0038] (3) The mixed solution was transferred to a 100 mL Teflon-lined high-pressure reactor and heated at 160 °C for 20 hours. After naturally cooling to room temperature, the resulting black solid product was washed repeatedly with ethanol and deionized water and dried under vacuum to obtain the Se-doped CuCo2S4 transconducting layer material.

[0039] Depending on the amount of SeO2 added, they were labeled as CuCo2S4 (0 mmol), Se0.1-CuCo2S4 (0.1 mmol), Se0.2-CuCo2S4 (0.2 mmol) and Se0.3-CuCo2S4 (0.3 mmol).

[0040] Preparation Example 2: Preparation of Sodium Ion Selective Membrane Solution Mix 2.5 mg of sodium ion carrier X, 1 mg of sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaTFPB), 164.3 mg of di-n-octyl sebacate (DOS), and 82.25 mg of polyvinyl chloride (PVC), add 2.5 mL of tetrahydrofuran (THF), and stir at room temperature for 3 hours until completely dissolved to form a transparent solution, thus obtaining the sodium ion selective membrane solution.

[0041] In the above components, the mass percentages of sodium ion carrier, NaTFPB, DOS, and PVC are 1% wt, 0.4% wt, 65.7% wt, and 32.9% wt, respectively.

[0042] Example 1: Construction of an all-solid-state sodium ion selective electrode based on Se0.3-CuCo2S4 Pretreatment of glassy carbon electrode: A 3 mm diameter glassy carbon electrode was polished on a polishing cloth with 0.3 μm and 0.05 μm alumina dispersions until the electrode surface achieved a mirror-like finish. Subsequently, it was ultrasonically cleaned for 3 minutes each in a 1:5 HNO3:H2O mixture, anhydrous ethanol, and deionized water, and then dried under an argon atmosphere for later use.

[0043] Transduction layer modification: The Se0.3-CuCo2S4 material prepared in Preparation Example 1 was ultrasonically dispersed in deionized water to prepare a dispersion with a concentration of 20 mg / mL. 10 μL of the dispersion was drop-coated onto the surface of the pretreated glassy carbon electrode (loading amount of 0.20 mg) using a pipette and dried at room temperature in a fume hood for 6 hours to form a transduction layer, labeled as GC / Se0.3-CuCo2S4.

[0044] Ion-selective membrane coating: Using a pipette, 10 μL of the sodium ion-selective membrane solution prepared in Example 2 was dropped onto the top of the GC / Se0.3-CuCo2S4 electrode in 10 separate applications, for a total coating volume of 100 μL. After coating, the electrode was placed in a fume hood and dried at room temperature for 12 hours to obtain an all-solid-state sodium ion-selective electrode based on Se0.3-CuCo2S4 as the transconducting layer, labeled as GC / Se0.3-CuCo2S4 / Na + -ISM.

[0045] Example 2: Construction of an all-solid-state sodium ion selective electrode based on Se0.2-CuCo2S4 The method is the same as in Example 1, except that the Se0.2-CuCo2S4 material prepared in Preparation Example 1 is used instead of Se0.3-CuCo2S4 to construct an all-solid-state sodium ion selective electrode, labeled as GC / Se0.2-CuCo2S4 / Na. + -ISM.

[0046] Example 3: Construction of an all-solid-state sodium ion selective electrode based on Se0.1-CuCo2S4 The method is the same as in Example 1, except that the Se0.1-CuCo2S4 material prepared in Preparation Example 1 is used instead of Se0.3-CuCo2S4 to construct an all-solid-state sodium ion selective electrode, labeled as GC / Se0.1-CuCo2S4 / Na. + -ISM.

[0047] Comparative Example 1: Construction of an all-solid-state sodium ion-selective electrode based on undoped CuCo2S4 The method is the same as in Example 1, except that undoped CuCo2S4 material prepared in Preparation Example 1 is used instead of Se0.3-CuCo2S4 to construct an all-solid-state sodium ion selective electrode, labeled as GC / CuCo2S4 / Na. + -ISM.

[0048] Material structure characterization The morphology of the four materials prepared in Preparation Example 1 was characterized using a scanning electron microscope (SEM, model: Sirion200, FEI).

[0049] like Figure 1 As shown in figure a, CuCo2S4 exhibits a three-dimensional flower-like structure assembled from nanosheets. The nanosheets have uniform thickness, and the flower-like structure has a size of approximately 4 μm. Figure 1 As shown in b, when the Se doping concentration is 0.1 mmol, Se0.1-CuCo2S4 basically maintains its flower-like structure, but slight roughening begins to appear on the surface of the nanosheets. Figure 1 As shown in Figure c, the surface roughness of Se0.2-CuCo2S4 nanosheets further increases when the Se doping concentration increases to 0.2 mmol. Figure 1 As shown in d, when the Se doping amount reaches 0.3 mmol, a large number of uniformly distributed nanoparticles begin to appear on the surface of Se0.3-CuCo2S4 flower-shaped flakes, forming a multi-level structure with a nanoparticle size of about 40 nm.

[0050] The above results indicate that the variation in Se doping amount significantly affects the microstructure of the material. In particular, when the Se doping amount reaches 0.3 mmol, the material exhibits a multi-level structure that is different from that of undoped CuCo2S4.

[0051] The four materials prepared in Example 1 were subjected to crystal phase analysis using an X-ray diffractometer (XRD, model: Philips X' Pert Pro Cu Kα radiation, λ=1.5406 Å, scanning range 10°~80°).

[0052] like Figure 2As shown, the diffraction peaks of all samples are consistent with the standard CuCo2S4 spectrum (JCPDS #42-1450), indicating that Se doping did not change the main crystal phase structure of the material. Notably, with the increase of Se doping amount, the diffraction peak of the (113) crystal plane gradually shifted from 31.5° to a lower angle of 31.1°, and the diffraction peak of the (044) crystal plane gradually shifted from 54.8° to a lower angle of 54.4°. This shift of the crystal planes to lower angles is due to the fact that the ionic radius of Se (1.98 Å) is greater than that of S (1.84 Å). After the Se atoms replace the S sites, the CuCo2S4 lattice expands, which conforms to the Bragg equation 2d sinθ = λ. The increase in interplanar spacing d leads to a decrease in diffraction angle θ.

[0053] The sulfur vacancy concentrations of the four materials prepared in Example 1 were characterized using an electron paramagnetic resonance spectrometer (EPR, model: Bruker A300 X-band CW, test conditions: microwave frequency 9.4 GHz, modulation frequency 100 kHz, temperature 298 K).

[0054] like Figure 3 As shown, all samples exhibited an EPR characteristic signal at g=2.003, which is attributed to sulfur vacancy defects in the material. The EPR signal intensity increased sequentially with increasing Se doping concentration, indicating an increasing trend in sulfur vacancy concentration. These results demonstrate that Se doping can effectively regulate the sulfur vacancy concentration in CuCo2S4, and the sulfur vacancy concentration is positively correlated with the Se doping concentration. This phenomenon can be attributed to the fact that when larger-radius Se atoms replace smaller-radius S atoms in the lattice, the local lattice around the Se atoms is expanded and distorted, thereby promoting the formation of sulfur vacancies.

[0055] Capacitive performance testing of transconductance layer materials 1. Comparison of capacitive properties of materials with different Se doping levels Weigh 20 mg of each material prepared in Preparation Example 1 and disperse them in 1 mL of deionized water. Sonicate the solution for 30 minutes to obtain a dispersion with a concentration of 20 mg / mL. Drop 10 μL of the dispersion onto the surface of a glassy carbon electrode (3 mm in diameter) and dry it in a fume hood for 12 hours to obtain electrodes modified with different materials (labeled as GC / CuCo2S4, GC / Se0.1-CuCo2S4, GC / Se0.2-CuCo2S4, and GC / Se0.3-CuCo2S4, respectively).

[0056] A three-electrode system was constructed using a modified glassy carbon electrode as the working electrode, a platinum wire as the counter electrode, and Ag / AgCl (3 mol / L KCl) as the reference electrode. The electrochemical performance of each electrode was tested using cyclic voltammetry (CV) in 0.1 M KCl solution using a CHI760E electrochemical workstation at a scan rate of 100 mV / s and a potential window of -0.3 V to 0.7 V. The test results are shown in Table 1.

[0057] Table 1 Comparison of capacitive properties of materials with different Se doping concentrations

[0058] like Figure 4 As shown in Table 1, the integrated area of ​​the CV curve gradually increases with increasing Se doping concentration. Compared to the integrated area of ​​CuCo2S4, the integrated area of ​​Se0.1-CuCo2S4 increases by 1.31 times, Se0.2-CuCo2S4 by 1.83 times, and Se0.3-CuCo2S4 by 2.20 times. This result is consistent with the trend of sulfur vacancy concentration variation characterized by EPR, confirming that the increase in sulfur vacancies provides more redox active sites, thereby increasing the capacitance of the material. The capacitance of the Se0.3-CuCo2S4 material of this invention is significantly better than that of undoped CuCo2S4.

[0059] 2. Capacitive performance of Se0.3-CuCo2S4 The capacitance performance of the Se0.3-CuCo2S4 modified electrode was quantitatively determined using the cyclic voltammetry test conditions described above. Based on the integral area calculation of the cyclic voltammetry curves, the integral area of ​​the Se0.3-CuCo2S4 material's capacitance is 2.2 times that of CuCo2S4, which is a significant improvement compared to undoped CuCo2S4 (capacitance values ​​are based on an integral area of ​​1.00 in Table 1, with actual capacitance values ​​being lower). This indicates that the present invention effectively improves the capacitance performance of the material through Se doping.

[0060] 3. Optimization of transduction layer load Weigh out 4 mg, 8 mg, 12 mg, 16 mg, 20 mg, 24 mg, and 28 mg of Se0.3-CuCo2S4 material prepared in Preparation Example 1, and disperse each in 1 mL of deionized water. Sonicate for 30 minutes to prepare dispersions with concentrations of 4 mg / mL, 8 mg / mL, 12 mg / mL, 16 mg / mL, 20 mg / mL, 24 mg / mL, and 28 mg / mL, respectively. Drop 10 μL of each dispersion onto the surface of a glassy carbon electrode and dry in a fume hood for 12 h to obtain GC / Se0.3-CuCo2S4 electrodes with different mass loadings of 0.04 mg, 0.08 mg, 0.12 mg, 0.16 mg, 0.20 mg, 0.24 mg, and 0.28 mg, respectively.

[0061] Cyclic voltammetry tests were performed on each electrode according to method 1, and the test results are shown in Table 2.

[0062] Table 2. Different load values ​​Se 0.3 Cyclic voltammetry results of CuCo2S4 electrode

[0063] As shown in Table 2 and Figure 5 As shown, with increasing mass loading, the integral area of ​​the CV curve first increases and then slightly decreases. When the loading is from 0.04 mg to 0.20 mg, the integral area gradually increases; it reaches its maximum value at 0.20 mg. When the loading continues to increase to 0.24 mg and 0.28 mg, the integral area decreases slightly, possibly due to excessively thick transconducting layers hindering ion transport. The integral area of ​​the cyclic voltammetry curve directly reflects the capacitance performance of the electrode; a larger integral area indicates a stronger charge storage capacity and higher ion-electron transduction efficiency. This result shows that an appropriate transconducting layer loading can fully utilize the high capacitance characteristics of the material, while an excessively thick transconducting layer will hinder ion transport and reduce electrode performance. Subsequent experiments were conducted with a 0.20 mg loading of Se0.3-CuCo2S4 to ensure optimal electrode capacitance performance.

[0064] Electrode performance testing Before use, the constructed all-solid-state sodium ion selective electrode should be subjected to 10 - Activated in ³ M NaCl solution for 24 hours, then in 10 -9 Activated in M ​​NaCl solution for 48 hours.

[0065] Potential response performance testing: The potential response was tested using the open-circuit potential testing method. The all-solid-state sodium ion-selective electrode constructed in Example 5 was used as the working electrode, the Ag / AgCl electrode as the reference electrode, and the platinum electrode as the counter electrode. Using a CHI760E electrochemical workstation, 10... -7 M, 10 -6 M, 10 -5 M, 10 -4 M, 10 - ³ M, 10 - ² M, 10 - The potential response of a NaCl solution of concentration M was tested, and the potential response was recorded for each concentration until it stabilized. The Nernst slope and detection limit were calculated based on the calibration curve.

[0066] Hydrophobicity testing: The contact angle (°) of the materials was measured using the seated drop method to evaluate their hydrophobic properties. The testing instrument was a contact angle meter. Testing conditions: room temperature, droplet volume 2 μL, and measurements were taken at 5 different locations for each sample, with the average value recorded. The test samples were the CuCo₂S₄, Se₀.₁-CuCo₂S₄, Se₀.₂-CuCo₂S₄, and Se₀.₃-CuCo₂S₄ materials prepared in Preparation Example 1. Figure 7 As shown, the water contact angle of undoped CuCo2S4 is 138.05°, while those of Se0.1-CuCo2S4, Se0.2-CuCo2S4, and Se0.3-CuCo2S4 are 131.26°, 124.04°, and 108.42°, respectively. All samples have a water contact angle greater than 90°, indicating that the Se-CuCo2S4 material prepared in this invention has good hydrophobic properties, which is beneficial for suppressing the formation of a water layer at the interface between the transconducting layer and the ion-selective membrane.

[0067] like Figure 6 As shown in Figure a, the electrode exhibits a stable potential response in NaCl solutions of different concentrations. Figure 6 The calibration curve of b shows that the all-solid-state sodium ion selective electrode based on Se0.3-CuCo2S4 as the transduction layer is effective at 10... - ¹~10 -5 M Na + It exhibits a good linear response within the concentration range, and the linear regression equation is E = 0.4434 + 0.05852 log[Na] + The correlation coefficient R² = 0.999, the Nernst slope is 58.52 mV / dec, and the detection limit reaches 10. -5.2 M.

[0068] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included within the scope of the technical solution of the present invention.

[0069] It should be particularly noted that the various embodiments listed in this specification and accompanying drawings are intended to illustrate the technical solutions and advantages of the present invention, and not to limit the scope of protection of the present invention. Without departing from the core ideas and technical effects of the present invention, those skilled in the art can make any form of improvement, substitution, combination, or modification to the structural arrangement, process parameters, material selection, control logic, etc., of the described embodiments; any obvious changes based on the same concept should be considered equivalent solutions of the present invention and should be included within the scope of protection defined by the claims of the present invention. The actual scope of protection of the present invention is determined by the appended claims and should be correctly understood in conjunction with the specification and accompanying drawings.

Claims

1. A Se-doped CuCo2S4 composite material, characterized in that: In the composite material, Se atoms replace some S sites in the CuCo2S4 lattice to form a lattice-doped structure; the amount of Se doping in the composite material, based on the amount of SeO2 added, is 0.1 to 0.3 mmol, relative to a 2 mmol copper source.

2. A method for preparing the Se-doped CuCo2S4 composite material as described in claim 1, characterized in that, Includes the following steps: S1. Dissolve the copper source and cobalt source in anhydrous methanol, then add the sulfur source and disperse by ultrasonication to obtain mixed solution A; S2. Add SeO2 to the mixed solution A from step S1 and stir to obtain mixed solution B; S3. Heat the mixed solution B to carry out a solvothermal reaction. After the reaction is completed, cool to room temperature to obtain a precipitate. Wash the precipitate and dry it to obtain the Se-doped CuCo2S4 composite material.

3. The preparation method according to claim 2, characterized in that: In step S1, the copper source is CuCl2·2H2O, the cobalt source is CoCl2·6H2O, and the sulfur source is thiourea; the molar ratio of the copper source, cobalt source, and sulfur source is 1:2:

4.

4. The preparation method according to claim 2, characterized in that: The amount of SeO2 added in step S2 is 0.1 to 0.3 mmol, relative to 2 mmol of copper source; the solvothermal reaction temperature in step S3 is 150 to 180°C, and the reaction time is 16 to 24 hours.

5. A fully solid-state sodium-ion selective electrode, comprising an electrode substrate, a transconducting layer coated on the surface of the electrode substrate, and a sodium-ion selective film disposed on the surface of the transconducting layer, characterized in that: The transduction layer is made of the Se-doped CuCo2S4 composite material as described in claim 1.

6. The all-solid-state sodium ion selective electrode according to claim 5, characterized in that: The transconducting layer has a loading of 0.15–0.25 mg on the electrode substrate surface.

7. The all-solid-state sodium ion selective electrode according to claim 5, characterized in that: The electrode substrate is any one of glassy carbon electrode, gold electrode, platinum electrode, and screen-printed electrode.

8. A method for preparing an all-solid-state sodium ion selective electrode as described in any one of claims 5-7, characterized in that, Includes the following steps: (1) The electrode substrate is pretreated to make its surface clean and have a mirror gloss; (2) The Se-doped CuCo2S4 composite material obtained by the preparation method according to any one of claims 2-4 is ultrasonically dispersed in a solvent to obtain a dispersion, and the dispersion is drop-coated onto the surface of the electrode substrate after the pretreatment in step (1), and dried to form a transconducting layer; (3) The sodium ion selective membrane solution is drop-coated onto the surface of the transconducting layer formed in step (2) and dried to obtain the all-solid sodium ion selective electrode.

9. The preparation method according to claim 8, characterized in that: The concentration of the dispersion in step (2) is 10-30 mg / mL, and the sodium ion selective membrane solution in step (3) is prepared by dissolving sodium ion carrier, sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, di-n-octyl sebacate and polyvinyl chloride in tetrahydrofuran.

10. The application of the Se-doped CuCo2S4 composite material of claim 1 or the all-solid-state sodium ion selective electrode of any one of claims 5-7, characterized in that: Used to detect the concentration of sodium ions in a solution.

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