CN114371202A

CN114371202A - Carbon fiber composite material and preparation method and application thereof

Info

Publication number: CN114371202A
Application number: CN202011095446.9A
Authority: CN
Inventors: 赵亚萍; 唐丽萍; 李明柳; 赵红; 苏丽访
Original assignee: Donghua University
Current assignee: Donghua University
Priority date: 2020-10-14
Filing date: 2020-10-14
Publication date: 2022-04-19
Anticipated expiration: 2040-10-14
Also published as: CN114371202B

Abstract

The invention relates to the technical field of carbon fiber composite materials, in particular to a carbon fiber composite material and a preparation method and application thereof. The carbon fiber composite material takes carbon fiber cloth as a substrate, and nickel cobalt sulfide grows in situ; the nickel cobalt sulfide is specifically a compound Co_xNi_3‑xS₄Or nano-particulate Ni₇S₆/CoNi₂S₄A composite material. The preparation method of the carbon fiber composite material comprises the steps of arranging the carbon fiber after pretreatment in a solvent, adding a sulfur source, a nickel source and a cobalt source, uniformly mixing, transferring into a reaction kettle, carrying out solvent thermal reaction, taking out, cleaning, drying and carrying out heat treatment in an inert atmosphere to obtain the carbon fiber composite material. The carbon fiber composite material prepared by the invention has excellent electrocatalytic performance when being used in an electrochemical catalyst, particularly in an enzyme-free glucose sensor, and the electrode has excellent sensitivity, linear range, selectivity and the like when being used for detecting glucoseAnd (4) stability.

Description

Carbon fiber composite material and preparation method and application thereof

Technical Field

The invention relates to the technical field of carbon fiber composite materials, in particular to a carbon fiber composite material and a preparation method and application thereof.

Background

Because the cost of isolating and purifying enzyme is high, the enzyme is easy to be inactivated by the influence of external environment such as pH, temperature and humidity, meanwhile, the problem of immobilization of the enzyme as an identification element is also very headache for researchers, the existence of a binder for immobilizing the enzyme is not beneficial to the contact of electrolyte ions and active substances in the electrochemical test process, and the enzyme glucose sensor has poor stability and short service life. To solve this problem, the development of non-enzymatic glucose sensors (also called fourth generation electrochemical glucose sensors) has become a hot spot of electrochemical biosensors, which overcome the problem of enzyme inactivation to some extent, exhibit good stability, reproducibility and long service life, and can be applied to actual human blood glucose monitoring.

The electrode material of the non-enzymatic glucose sensor is the key for influencing the non-enzymatic detection of glucose, and the nano material is a material with the size of nano scale, shows the effect superior to other materials, such as surface effect, macroscopic quantum tunneling effect, dielectric confinement effect and the like, and has the excellent properties of large specific surface area, more surface active centers, high reaction activity, high catalytic efficiency and the like. Due to the unique properties of the nano material, the sensitivity of the nano material to glucose detection by an enzyme-free glucose sensor is remarkably improved, and the development prospect in the sensing field is strong.

Disclosure of Invention

In order to solve the technical problems, the invention provides a carbon fiber composite material and a preparation method and application thereof. The carbon fiber cloth is used as a flexible substrate, and cobalt-nickel sulfide grows in situ on the surface of the fabric by a one-step solvothermal method and is used as a flexible electrode material for enzyme-free glucose sensing and energy storage respectively, and the electrode has excellent sensitivity, linear range, selectivity and stability in glucose detection.

One of the technical schemes of the invention is a carbon fiber composite material, which specifically comprises the steps of taking carbon fiber cloth as a substrate and growing nickel-cobalt sulfide in situ;

further, the nickel cobalt sulfide is specifically a compound Co_xNi_3-xS₄Or Ni₇S₆/CoNi₂S₄A nanocomposite material.

Further, the compound Co_xNi_3-xS₄Specifically CoNi₂S₄。

According to the second technical scheme, the preparation method of the carbon fiber composite material comprises the steps of arranging the pretreated carbon fibers in a solvent, adding a sulfur source, a nickel source and a cobalt source, uniformly mixing, transferring into a reaction kettle, carrying out solvent thermal reaction, taking out, cleaning, drying and carrying out heat treatment in an inert atmosphere to obtain the carbon fiber composite material.

Further, the pretreatment process of the carbon fiber cloth comprises the following steps: the carbon fiber after impurity removal treatment is arranged in a mixed acid solution of concentrated nitric acid and concentrated sulfuric acid with the volume ratio of 1:1, carbon fiber cloth is used as a working electrode, a three-electrode system is adopted to carry out electrochemical oxidation modification treatment on the carbon fiber cloth, and then the carbon fiber cloth is cleaned and dried.

Further, the thickness of the carbon fiber cloth is 0.33mm, and the pretreatment process of the carbon fiber cloth comprises the following steps: firstly, the carbon fiber cloth is respectively treated with ultrasonic treatment in acetone, ethanol and deionized water for 30min to remove impurities, and then dried at the temperature of 80 ℃ for standby. In order to improve the hydrophilicity of the carbon fiber cloth, before use, electrochemical oxidation modification treatment is carried out, mixed acid solution of concentrated nitric acid and concentrated sulfuric acid (the volume ratio is 1:1) is prepared to be used as electrolyte, an electrochemical workstation is used for adopting a three-electrode system, the carbon fiber cloth is respectively used as a working electrode, a platinum wire is used as a counter electrode, a saturated calomel electrode is used as a reference electrode, after the carbon fiber cloth is subjected to electrooxidation for 600s under the condition of 3V voltage, the carbon fiber cloth subjected to electrooxidation is ultrasonically cleaned to be neutral in deionized water, the carbon fiber cloth is dried at 80 ℃ for standby, and the resistance of the carbon cloth subjected to electrooxidation is 735 +/-60 m omega measured by using a four-probe.

Further, the sulfur source is CH₄N₂S, the cobalt source Co (NO)₃)₂·6H₂O, the nickel source is Ni (NO)₃)₂·6H₂O; the solvent is ethanol or ethanol water solution; the solvothermal reaction temperature is 120-180 ℃, the solvothermal reaction time is 6-20h, and the heat treatment is carried outComprises heating to 350 ℃ at a heating rate of 2 ℃/min, keeping the temperature for 2h, and then naturally cooling to room temperature.

Further, the nickel cobalt sulfide is specifically a compound Co_xNi_3-xS₄When in use, the molar ratio of nickel atoms to cobalt atoms to sulfur atoms is (2-4) to (1-2) to (5-10), and hexamethylenetetramine or polyethylene glycol-1000 is also added as an additive in the process of solvothermal reaction; the nickel cobalt sulfide is specifically Ni₇S₆/CoNi₂S₄In the case of the nano composite material, the molar ratio of nickel atoms to cobalt atoms to sulfur atoms is 2:1:5, and diphenylthiourea is also added as an additive in the solvothermal reaction process.

Further, the adding amount of the hexamethylenetetramine or the polyethylene glycol and the adding proportion of the sulfur atom are (0.2-1.0) g, (5-10) mmol; the addition amount of diphenylthiourea and the molar ratio of sulfur atoms added were (0.2-2.0): 5.

In the whole solvothermal preparation process, the addition of the hexamethylenetetramine can shorten the vulcanization process, avoid the formation of metal hydroxide and influence the distribution and the appearance of metal sulfides on the carbon fiber cloth. Therefore, the additive plays a critical role in the one-step solvothermal in-situ sulfide loading process. Polyethylene glycol is a water-soluble polymer, plays a role in dispersion in a vulcanization system, and is beneficial to the generation of nickel cobalt sulfide.

The large pi bond of the benzene ring is favorable for tight combination with the carbon fiber cloth, the conjugated pi bond can promote electron transfer, and CoNi is considered₂S₄The composite material of cobalt sulfide and nickel sulfide is more beneficial to improving the energy storage performance, diphenyl thiourea is selected as an additive, and on one hand, CoNi is promoted₂S₄The sulfur source is provided to create conditions for generating the composite material of sulfide/cobalt nickel sulfide at the same time of being tightly combined with the carbon cloth. The sulfur source being CH alone₄N₂S or diphenylthiourea can prevent cobalt nickel sulfide from uniformly growing on the surface of carbon fiber, CH₄N₂The mixture of S and diphenylthiourea can regulate and control the size of cobalt nickel sulfide particles to enable the cobalt nickel sulfide particles to grow uniformly.

In the third technical scheme of the invention, the carbon fiber composite material is applied to the aspect of electrochemical sensors.

Further, the carbon fiber composite material is used for the enzyme-free glucose sensor electrode.

Compared with the prior art, the invention has the following beneficial effects:

the invention takes carbon fiber cloth as a conductive flexible substrate and adopts a simple one-step solvothermal method to prepare Co with different structures_xNi_3-xS₄And Ni₇S₆/CoNi₂S₄The nano composite material fully utilizes the characteristics of the three-dimensional network structure of the carbon fiber cloth, so that the loading capacity of the active substance is increased, and the sensing and energy storage performances of the nano composite material are improved.

In-situ growth of Co on carbon fiber cloth by solvothermal method_xNi_3-xS₄Under optimized conditions, bean sprout-shaped CoNi is prepared₂S₄@ CFC material with a sensitivity to glucose of 3115 μ A mM^-1cm^-2The linear range of detectable glucose reaches 0.2 mu mol/L-3.041mmol/L, and the electrode material has almost no response to interference substances such as ascorbic acid, urea, lactose, fructose and the like, i.e. the electrode material has good selectivity to glucose.

Preparation of Ni by solvothermal method₇S₆/CoNi₂S₄When the system contains diphenylthiourea and the content is 0.6mmol, Ni is prepared₇S₆/CoNi₂S₄The nano particles are small in size and are uniformly distributed on the carbon fibers, and the existence of the diphenylthiourea in a solvothermal system regulates and controls Ni to a certain extent₇S₆/CoNi₂S₄The size of the particles. Meanwhile, when the solvothermal temperature is 160 ℃, the time is 10h, and the dosage of the diphenylthiourea is 0.6mmol, Ni is prepared₇S₆/CoNi₂S₄The nano composite material has the best performance when being applied to the non-enzyme glucose sensing and energy storage directions, and shows 2053 muA mM to glucose under the low working voltage of 0.52V for the catalytic oxidation of the glucose^-1cm^-2Sensitivity of, linear range of glucose detectable0.2 mu mol/L-7.081mmol/L, and the oxidation peak current response of the material at 100 th circle after the material is exposed in the air for 2 months at room temperature and 1mmol/L glucose is cycled for 100 times is maintained to be about 75.92 percent of the original value, which shows that the NS @ CNS CFC-0.6 electrode has good stability for detecting glucose and can be used for a long time. Applied to the direction of energy storage, the cyclic voltammetry curve shows the excellent reactivity and reversibility of the material, and the current density in discharge is respectively 1, 3, 5, 10 and 20mA cm^-2The NSCNS @ CFC-0.6 nanoparticles have charge levels as high as 1.561, 1.464, 1.401, 1.266, and 1.134C cm^-2NSCNS @ CFC-0.6 electrode at 30mA/cm²The retention rate of the charge quantity after 5000 cycles under the current density is 100 percent, and the excellent stability of the material is reflected.

Drawings

FIG. 1 is a cyclic voltammogram of an electrode of example 1 of the present invention under conditions of no glucose and 1mmol/L glucose;

FIG. 2 is a cyclic voltammogram of an electrode of example 1 of the present invention under conditions of no glucose and 1mmol/L glucose; wherein (a) NCS @ CFC-3 and CNS @ CFC-3', (b) CNS @ CFC and CNS @ CFC-HMT;

FIG. 3 is a graph of current-time response of an electrode to glucose in example 1 of the present invention; wherein (a) is CNS @ CFC-1 and CNS @ CFC-HMT, (b) is CNS @ CFC-X (X ═ 1,2, 3);

FIG. 4 is a SEM image of a composite of example 1 of the present invention wherein (a) and (b) are NCS @ CFC and (c) and (d) are NCS @ CFC-3;

FIG. 5 is a SEM photograph of the composite material of example 1 of the present invention, wherein (a), (b), (c) are CNS @ CFC-3, (d), (e), (f) are CNS @ CFC-HMT;

FIG. 6 is a plot of cyclic voltammograms at different scan rates for the CNS @ CFC-HMT electrode of example 1 in (a) glucose-free and (b) 0.1mol/L NaOH solution containing 1mmol/L glucose, respectively;

FIG. 7 is a cyclic voltammogram of different concentrations of glucose solution at the electrode of example 1;

FIG. 8 is a cyclic voltammogram of the electrode CNS @ CFC-HMT of example 1 against 1mM glucose;

fig. 9 is a plot of cyclic voltammetry (a) and charge and discharge (b) for CNS @ CFC-X (X ═ 1,2,3) electrode materials prepared under different HMT levels for example 1;

FIG. 10 is a graph of current versus time for glucose for electrodes prepared with different amounts of diphenylthiourea from example 2;

FIG. 11 is a graph of the current-time response of the NSCNS @ CFC prepared in example 2 to glucose at different solvothermal temperatures;

FIG. 12 is a graph of the current-time response of the NSCNS @ CFC prepared in example 2 to glucose at different solvothermal times;

FIG. 13 is an SEM image of the pure carbon fiber cloth of example 2 along with CNS @ CFC and NSCNS @ CFC materials at the same magnification;

FIG. 14 is a cyclic voltammogram of the NSCNS @ CFC-0.6 prepared in example 2;

FIG. 15 is a cyclic voltammogram of NSCNS @ CFC-0.6 prepared in example 2 versus 1mmol/L glucose;

FIG. 16 is a graph of (a) cyclic voltammogram, (b) charge and discharge curve, (c) cyclic voltammogram, (d) charge and discharge curve, (e) charge versus current density, (f) N cyclic stability for the NSCNS @ CFC-0.6 electrode prepared in example 2;

FIG. 17 is a graph of the cyclic voltammogram of NSCNS @ CFC prepared in example 2 at different solvothermal temperatures, (a), (b) charge and discharge curves;

FIG. 18 is a chart of the NSCNS @ CFC (a) cyclic voltammetry curves, (b) charge and discharge curves prepared under different solvothermal times for example 2.

Detailed Description

The following further illustrates embodiments of the invention, taken in conjunction with the accompanying drawings, which are not to be considered limiting of the invention, but are to be understood as more detailed descriptions of certain aspects, features and embodiments of the invention.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Further, for numerical ranges in this disclosure, it is understood that each intervening value, between the upper and lower limit of that range, is also specifically disclosed. Every smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference herein for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.

It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the present disclosure without departing from the scope or spirit of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification. The specification and examples are exemplary only.

As used herein, the terms "comprising," "including," "having," "containing," and the like are open-ended terms that mean including, but not limited to.

Pretreatment of the carbon fiber cloth used in the following examples of the invention: firstly, ultrasonic treatment is carried out on 0.33mm carbon fiber cloth in acetone, ethanol and deionized water for 30min to remove impurities, and then drying is carried out at the temperature of 80 ℃ for later use. In order to improve the hydrophilicity of the carbon fiber cloth, before use, electrochemical oxidation modification treatment is carried out, mixed acid solution of concentrated nitric acid and concentrated sulfuric acid (the volume ratio is 1:1) is prepared to be used as electrolyte, an electrochemical workstation is used for adopting a three-electrode system, the carbon fiber cloth is respectively used as a working electrode, a platinum wire is used as a counter electrode, a saturated calomel electrode is used as a reference electrode, after the carbon fiber cloth is subjected to electrooxidation for 600s under the condition of 3V voltage, the carbon fiber cloth subjected to electrooxidation is ultrasonically cleaned to be neutral in deionized water, the carbon fiber cloth is dried at 80 ℃ for standby, and the resistance of the carbon cloth subjected to electrooxidation is 735 +/-60 m omega measured by using a four-probe.

Method for verifying the properties of the materials prepared in the following examples:

1. morphology and structural characterization

Scanning Electron Microscope (SEM) used was a field emission scanning electron microscope of type S-4800 of Hitachi, Japan, in which the accelerating voltage was 5 kV.

2. Sensing performance

The CHI660E electrochemical workstation is used for carrying out sensing performance test on the prepared material by adopting a three-electrode system, and the prepared material is used as a working electrode (the active substance area of all electrode materials prepared in the invention is 1 cm)²) The sensing performance was performed in 0.1mol/L NaOH electrolyte with an Ag/AgCl (3mol/LKCl) electrode as reference electrode and a platinum wire as counter electrode.

3. Energy storage performance

The prepared material is used as a working electrode, a platinum wire is used as a counter electrode, a saturated calomel electrode is used as a reference electrode, and 2mol/L KOH is used as a test electrolyte.

Example 1

Co_xNi_3-xS₄The specific process of preparing the @ CFC electrode is as follows:

selecting a water/ethanol (v/v ═ 1:1) mixed solvent, adopting nickel nitrate hexahydrate as a nickel source, cobalt nitrate hexahydrate as a cobalt source, and adopting CH₄N₂S is used as a sulfur source and is polyethylene glycol-1000 (PEG-1000), Hexamethylenetetramine (HMT) and CH₄N₂O is an additive.

Mixed solvent thermal reaction: dissolving a certain amount of different additives in 60ml of solvent, adding the pretreated carbon fiber cloth, performing ultrasonic treatment for 30min, and then adding nickel nitrate hexahydrate, cobalt nitrate hexahydrate and CH one by one₄N₂S, performing ultrasonic treatment for 30min (the composition of each reaction system solution is shown in the following tables 1-3), transferring the mixed solution into a reaction kettle with a 100mL polytetrafluoroethylene inner container, continuously reacting for 10h at 160 ℃, naturally cooling after the reaction is finished, taking out the carbon fiber cloth with the cobalt-nickel sulfide precursor, ultrasonically cleaning the carbon fiber cloth with ethanol and deionized water for several times, and drying the carbon fiber cloth at 80 ℃ for later use.

And (3) heat treatment: and (3) horizontally placing the carbon fiber with the active substances in the ceramic crucible, heating the carbon fiber to 350 ℃ at a heating rate of 2 ℃/min in a tubular furnace under the protection of nitrogen atmosphere, calcining for 2h, naturally cooling to room temperature, and taking out a sample to obtain the carbon fiber cloth loaded cobalt-nickel sulfide.

TABLE 1 solution composition of different additive reaction systems

Sample (I)	Additive agent	Ni²⁺/mmol	Co²⁺/mmol	CH₄N₂S/mmol
					NCS@CFC	Is free of	2.0	4.0	10.0
NCS@CFC-1	CH₄N₂O	2.0	4.0	10.0
					NCS@CFC-2	CH₄N₂O+PEF-100	2.0	4.0	10.0
NCS@CFC-3	HMT	2.0	4.0	10.0
					NCS@CFC-4	HMT+CH₄N₂O	2.0	4.0	10.0

TABLE 2 solution composition for different reactant dosage systems

	Ni²⁺/mmol	Co²⁺/mmol	CH₄N₂S/mmol	HMT/g
					CNS@CFC-3’	4.0	2.0	10.0	0.2
CNS@CFC-HMT	2.0	1.0	5.0	0.2
					CNS@CFC	2.0	1.0	5.0	0.0

TABLE 3 solution composition of additive dosage system

	Ni²⁺/mmol	Co²⁺/mmol	CH₄N₂S/mmol	HMT/g
					CNS@CFC-1	2.0	1.0	10.0	0.2
CNS@CFC-2	2.0	1.0	10.0	0.5
					CNS@CFC-3	2.0	1.0	10.0	1.0

The results of the performance verification of the above prepared materials:

1. kind of additive

The cyclic voltammograms of the prepared NCS @ CFC, NCS @ CFC-1, NCS @ CFC-2, NCS @ CFC-3 and NCS @ CFC-4 electrodes in the absence and presence of 1mmol/L glucose are shown in FIG. 1 below.

As can be seen from FIG. 1, when no additive is added into the reaction system, the oxidation peak of the prepared NCS @ CFC is not obvious, and when 1mmol/L glucose is added, the oxidation peak of the electrode is obvious and has obvious current increase, which indicates that the NCS @ CFC electrode has electrocatalytic performance on glucose. Comparing the curves 2-6 shows that the NCS @ CFC-3 has the highest current response intensity value for glucose, and the electrode has the highest electrocatalytic oxidation characteristic for glucose. Wherein the oxidation peak currents of the NCS @ CFC-2 and NCS @ CFC-4 electrodes are similar to the NCS @ CFC electrode, indicating CH₄N₂O/PEG-1000 solution system and CH₄N₂In the O/HMT system, the catalytic performance of the electrode on glucose is not improved, probably due to CH₄N₂O, PEG-1000 and HMT have different functions in the process of growing nickel cobalt sulfide on the surface of carbon fiber cloth. Polyethylene glycol is a water-soluble polymer that acts as a dispersing agent in the vulcanization system. The minimum current response value is generated by combining NCS @ CFC-1, and CH in the reaction system can be obtained₄N₂The presence of O is detrimental to the formation of nickel cobalt sulphides, probably because the urea content in this experiment is too high and within a limited solvothermal timeCH₄N₂The hydrolysis reaction of O is dominant, and nickel cobalt hydroxide is more prone to be generated. And in the presence of PEG-1000, in favor of CH₄N₂O dispersibility in aqueous solution, OH produced by hydrolysis^-Under the dispersion action, the generation of a byproduct nickel cobalt hydroxide on the surface of the carbon fiber cloth is avoided, the generation of nickel cobalt sulfide is facilitated, and the comparison between the curve 3 and the curve 4 shows that the current response peak value of the curve 4 is stronger than that of the curve 3. Meanwhile, the NCS @ CFC-3 electrode is found to have the largest current response intensity value for glucose, which indicates that the electrocatalytic oxidation characteristic of the electrode for glucose is the highest, and the existence of HMT can improve the electrocatalytic oxidation characteristic of the electrode material.

Molar ratio of Ni/Co to the concentration of the main salt

The catalytic performance of the prepared CNS @ CFC-3, CNS @ CFC and CNS @ CFC-HMT on glucose at a scan rate of 3mV/s is shown in FIG. 2 below;

as can be seen from the observation of FIG. 2(a), when 1mmol/L glucose was added, the oxidation peak current of CNS @ CFC-3' became small, and in the theoretical presence of glucose, Ni was present²⁺Production of Ni in alkaline medium³⁺，Ni³⁺Catalytic oxidation of glucose would produce a higher current response than without glucose, but the opposite result is probably due to the structural instability of the CNS @ CFC-3 nanomaterial produced under this condition, which is presumably observed in subsequent morphological characterization. Meanwhile, it can be found that the oxidation peak current of CNS @ CFC-3(Ni/Co molar ratio is 2:1) in electrolytes containing no glucose and containing glucose is larger than that of NCS @ CFC-3, which is mainly caused by the difference of the structures of the products of the two, and the nickel-cobalt sulfide in the CNS @ CFC-3 is mainly CoNi₂S₄While the nickel cobalt sulfide in NCS @ CFC-3 is mainly NiCo₂S₄。

Under the premise of the same Ni/Co molar ratio (2:1), the total main salt concentration is changed, and the obtained products are also different, and the preparation conditions of CNS @ CFC-3 and CNS @ CFC-HMT are different in that the concentration of the main salt of the former is twice that of the latter, and the concentrations of the main salts of CNS @ CFC and CNS @ CFC-HMT are the same, and the difference is that HMT is not added, as can be seen in FIGS. 2(a) and (b). CNS @ CFC-HMT is especially pronounced in the test in its redox peak profile regardless of the presence or absence of glucose in the electrolyte, with the redox peak currents being higher than CNS @ CFC and CNS @ CFC-3, and with a significant increase in current in the presence of glucose. Indicating that CNS @ CFC-HMT has the greatest enhancement of current to glucose relative to other materials.

3. The amount of the additive

The current-time curve was plotted for CNS @ CFC-1, CNS @ CFC-2 and CNS @ CFC-3 electrodes using 0.54V as the operating voltage, 0.2mmol/L glucose was added to 0.1mmol/L NaOH electrolyte under continuous stirring, and the current response of the electrode to glucose was observed, and the cyclic voltammogram and the current-time curve are shown in FIG. 3 below.

From fig. 3(a), it can be seen that the CNS @ CFC-1 electrode has a very weak current response to glucose, which may be due to the fact that the addition of thiourea makes cobalt nickel sulfide grow in bulk on carbon fiber, the specific surface area is small, which is not favorable for ion transport, and the morphology can be observed from the subsequent SEM images. It is worth noting that the CV integrated area is almost doubled to facilitate the storage of charge. Meanwhile, as can be seen from FIG. 3(b), under the condition that 0.2mmol/L glucose exists in the CNS @ CFC-1 electrode, the cobalt-nickel sulfide catalyzes and oxidizes the glucose to generate a current increase of about 0.15mA, and as the content of HMT is increased to 0.5g, the current response of the cobalt-nickel sulfide to the glucose is obviously increased, the generated current response strength is about 0.42mA, and the response strength of CNS @ CFC-2 is almost doubled compared with the CNS @ CFC-1. It is evident from the figure that CNS @ CFC-3 has a higher catalytic effect on promoting the oxidation of glucose, catalyzing glucose in the presence of 0.2mmol/L glucose to produce a current response of 0.52 mA. Therefore, in the whole reaction system, when CH₄N₂The amount of S used was 10mmol, while the amount of HMT used was 1.0g, cobalt nickel sulfide grown on the carbon fiber cloth had higher catalytic performance for glucose.

4. Material morphology and structural characterization

SEM characterizations for NCS @ CFC (no additive) and NCS @ CFC-3(HMT as additive) are shown in FIGS. 4-5; comparing fig. 4(a) and (b), (c) and (d), when there is no additive in the solution, the carbon fiber surface only carries a small amount of particulate matter, and the addition of HMT is favorable for the growth of nickel cobalt sulfide on the carbon fiber cloth surface, and is connected with the nickel cobalt sulfideThe particles are continued to be in the shape of films. Notably, the particle size of NCS @ CFC-3 is significantly reduced. Viewing the SEM images of CNS @ CFC-3 and CNS @ CFC-HMT at different magnifications in FIG. 5, CNS @ CFC-3' formed a porous "folded stretched lantern-like" structure that could collapse during testing, leading to blockage of ion transport channels and thus affecting electrochemical test results. Comparing fig. 5(a-c) with fig. 4(c-d), when the molar ratio of Ni/Co is 2:1, the surface of the carbon fiber can form a regular morphology, the porous channel of CNS @ CFC-3 is more favorable for ion transport, and the electrocatalytic performance of NCS @ CFC-3 for glucose is higher and benefits from a more stable particle film-like structure in combination with the sensing test results. When the concentration of the main salt is reduced and the HMT content is unchanged, a three-dimensional sheet structure similar to a bean sprout shape is formed, and the CNS @ CFC-HMT is found to grow more densely and have a more stable structure than the CNS @ CFC-3, probably because the concentration of the main salt is reduced and OH generated by hydrolysis of the HMT is formed^-Compared with CNS @ CFC-3, the nickel salt and the cobalt salt are enough to react with each other to generate the nickel-cobalt hydroxide. Comparing the peak current intensities of oxidation for CNS @ CFC-3 and CNS @ CFC-HMT in FIG. 4(a-b), a more stable "bean sprout" -like morphology was obtained such that CNS @ CFC-HMT has a higher current response to glucose than CNS @ CFC-3.

5.TEM

By TEM analysis of the prepared material, the following conclusions were further verified:

the method is characterized in that HMT is used as an additive, nickel-cobalt sulfide on the carbon fiber cloth of NCS @ CFC-3 prepared under the condition that the ratio of nickel salt to cobalt salt is 1:2 grows in a particle form, and the prepared cobalt-nickel sulfide is in a polycrystalline structure;

for CNS @ CFC-HMT prepared under the conditions that the additive is HMT and the concentration of low main salt and the molar ratio of Ni to Co are 2:1, the cobalt-nickel sulfide on the carbon fiber cloth is CoNi grown in a sheet structure form₂S₄Cobalt nickel sulphide is a polycrystalline structure.

6. Sensing performance

The sensing performance of CNS @ CFC-HMT was tested by first examining the optimal scan rate for the enzyme-free detection of glucose in an electrochemical workstation using a three-electrode system, and examining the cyclic voltammetry profiles at scan rates of 1mV/s, 3mV/s, 5mV/s, 10mV/s, 20mV/s, 30mV/s, 50mV/s and 100mV/s in 0.1mol/L NaOH electrolyte and 1mol/L glucose-containing 0.1mol/L NaOH electrolyte, respectively, see FIG. 6. As can be seen from fig. 6, the current response intensity of CNS @ CFC-HMT in both electrolytes increases significantly with the increase of the scanning speed, regardless of the presence of glucose in the electrolyte, mainly because the process of electrocatalytic oxidation of glucose at the electrode surface belongs to the surface control process. Comparing fig. 6(a) and fig. 6(b), it can be seen that when the scan speed is smaller, the oxidation peak pattern is more obvious, but the experimental time is longer, and as the scan speed increases, the oxidation peak gradually weakens or even disappears, which may be caused by polarization, and it can be seen that when the scan speed is 10mV/s, the oxidation peaks in fig. 6(a) and (b) are all obvious, and when the scan speed continues to increase, the oxidation peak pattern becomes weak, so that 10mV/s is selected as the optimal scan speed for glucose test, which not only ensures the oxidation-reduction peak pattern to be obvious, but also prevents the experimental time from being too long.

Under the scanning speed of 10mV/s, adding 1mol/L, 2mol/L, 3mol/L and 4mol/L glucose solution into the uniformly stirred electrolyte respectively, and measuring the measured cyclic voltammetry curve as shown in the following figure 7; as can be seen from FIG. 7, as the glucose concentration in the electrolyte increased, the oxidation peak current and peak potential increased substantially linearly, while the reduction peak current and potential also decreased linearly, since there was always a linear decrease in the electrochemical test process

After addition of glucose, Ni³⁺Performing oxidation-reduction reaction with glucose to oxidize glucose into gluconolactone, which is reduced into Ni² ⁺This is an irreversible redox reaction, with increasing glucose concentration, Ni³⁺Is continuously consumed, so that

Proceeding to the right, so that the oxidation peak current is continuously increased, while the reduction peak current is continuously decreased;

the long-term stability of the CNS @ CFC-HMT electrode is researched by adopting cyclic voltammetry, the working voltage is set to be 0.50V, the scanning speed is 10mV/s, the CNS @ CFC-HMT electrode which completes the sensing test is exposed in the air for 70 days, then the electrode is circulated in electrolyte containing 1mmol/L glucose for 100 times, the 100 th circle of cyclic voltammetry curve is compared with the cyclic voltammetry curve for glucose at the beginning, as a result, as shown in FIG. 8, the oxidation peak current of the electrocatalytic glucose was 9.93mA at first, the oxidation peak current thereof was decreased to 6.81mA after the circulation for 100 cycles after 70 days, the retention rate of the response current was 68.6% of the original current response, the results indicate that after a long exposure of the flexible CNS @ CFC-HMT electrode, the high electrocatalytic activity of the electrode is still kept for detecting glucose, which indicates that the electrode has good long-term stability.

7. Hydrogen storage capability

The charge-discharge curve of the cyclic voltammetry curve of the electrode material of CNS @ CFC-X (X ═ 1,2,3) prepared under different HMT contents is shown in figure 9;

the electrode materials of CNS @ CFC-1 and CNS @ CFC-2 have a pair of symmetrical and obvious redox peaks, and the highly symmetrical redox peaks show that the electrode materials of CNS @ CFC-X (X ═ 1,2) have good reactivity and reversibility. According to observation, the integral area of the electrode material is increased along with the increase of the content of HMT, and when the content of HMT is 1.0g, namely CNS @ CFC-3 has the largest integral area, which is consistent with the result of detecting glucose, the electrode material is mainly closely related to the shape of the CNS @ CFC-X electrode, but the oxidation peak is not obvious, which shows that although the quantity of electric charge of the CNS @ CFC-3 is the largest, the reversibility of the material is poor. The constant current charge-discharge curve is consistent with the cyclic voltammetry curve, and FIG. 9(b) shows that when the HMT content is 1.0g, the charge-discharge time of the active material is longest, and the electrode materials of CNS @ CFC-1, CNS @ CFC-2 and CNS @ CFC-3 are calculated to be at 5mA/cm²The charge amount at the current density was 0.427C/cm, respectively²、0.631C/cm²And 1.349C/cm²It was found that the charge of cobalt nickel sulphide almost doubled with increasing HMT content. This is consistent with the intensity of the current signal generated by glucose detection with cobalt nickel sulfide, and is mainly benefited from cobalt nickel sulfideThe acicular crosslinking three-dimensional porous structure is beneficial to the rapid transfer of ions and the rapid occurrence of oxidation-reduction reaction.

Example 2

The difference from example 1 is that the system uses 30mL of ethanol as solvent and diphenylthiourea as additive. CNS @ CFC-0.2, CNS @ CFC-0.4 and NSCNS @ CFC-X (X ═ 0.6, 0.8, 1.0, 1.5, 2.0) electrodes were prepared solvothermally in one step according to table 4.

TABLE 4 solution composition of reaction systems with different amounts of diphenylthiourea

Sample (I)	Diphenylthiourea	Ni²⁺/mmol	Co²⁺/mmol	CH₄N₂S/mmol
					[email protected]	0.2	2.0	1.0	5.0
[email protected]	0.4	2.0	1.0	5.0
					[email protected]	0.6	2.0	1.0	5.0
[email protected]	0.8	2.0	1.0	5.0
					[email protected]	1.0	2.0	1.0	5.0
[email protected]	1.5	2.0	1.0	5.0
					[email protected]	2.0	2.0	1.0	5.0

In addition, NSCNS @ CFC grown under 10h conditions at 120 ℃, 140 ℃, 160 ℃ and 180 ℃ solvothermal temperatures were selected, respectively;

the solvothermal times of 6h, 8h, 10h, 15h and 20h were investigated for NSCNS @ CFC, respectively, at a solvothermal temperature of 160 ℃;

the following performance verifications were performed on the prepared material:

1. the amount of the additive

The influence of the dosage of the diphenylthiourea is considered, the CNS @ CFC electrode and the NSCNS @ CFC electrode are prepared by the next solvothermal method under the conditions that the dosage is 0.2mmol, 0.4mmol, 0.6mmol, 0.8mmol, 1.0mmol, 1.5mmol and 2.0mmol, the solvothermal time is 10h, and the solvothermal temperature is 160 ℃, and the current-time curve of 1mmol/L glucose under the working voltage of 0.52V is considered (figure 10). As shown in fig. 10, when the amount of diphenylthiourea is 0.6mmol and 1.0mmol, the prepared material has a large current response to glucose, the response at 1.0mmol increases and then decreases rapidly, the high current response cannot be maintained, and the 0.6mmol response strength is relatively high and stable, so that the electrocatalytic properties to glucose are better when the amount of diphenylthiourea is 0.6mmol in the solvothermal system.

2. Temperature of solvent heat

Under the condition of 10h, NSCNS @ CFC grows at the solvothermal temperatures of 120 ℃, 140 ℃, 160 ℃ and 180 ℃, the catalytic oxidation capacity of the 4 materials to glucose is considered, the oxidation potential of the catalytic glucose is set to be 0.54V, the catalytic response of the materials to 0.2mmol/L glucose is tested under continuous stirring, and the obtained current-time curve graph is shown in a graph shown in a figure 11; analysis of the current-time curve of fig. 11 shows that the current response of the electrode material to glucose is very weak and almost no response when the solvothermal temperature is 120 ℃, and the response current of the electrode to glucose gradually increases with the increase of the solvothermal temperature. The current response intensity of the CNS @ CFC electrode materials prepared at 140 ℃ and 180 ℃ is not greatly different, and the obvious discovery that the response current of the electrode to glucose is the maximum only when the solvothermal temperature is 160 ℃, and is far higher than the current response values of the electrode materials prepared at 120 ℃, 140 ℃ and 180 ℃.

3. Solvothermal time

The influence of the solvothermal times of 6h, 8h, 10h, 15h and 20h on the sensing performance of the NSCNS @ CFC electrode is examined at the solvothermal temperature of 160 ℃, and a current-time curve is shown in a figure 12; comparing the current curves of different solvothermal times in fig. 12, it can be seen that the response is the weakest at 20h, the performance of the catalytic oxidation of glucose is basically the same at 6h and 15h, the electrocatalytic performance is slightly higher at 8h, and when the solvothermal time is 10h, it can be seen that the cobalt nickel sulfide grown on the carbon fiber cloth under the condition has the highest electrocatalytic performance for the oxidation of glucose. The solvothermal time was increased from 6h to 10h, the catalytic activity of the active substance towards glucose was gradually increased, and as the solvothermal time was continued, the current response to glucose was significantly decreased. By combining the above discussion of the growth of the cobalt nickel sulfide active substance at different solvothermal temperatures on the catalytic performance of glucose, it can be found that the solvothermal temperatures have a more obvious influence on the catalytic performance of glucose, and the responses of the cobalt nickel sulfide prepared under different solvothermal temperatures are very different, and compared with the factor of different solvothermal times, the responses of the cobalt nickel sulfide prepared under different time conditions on glucose are generally higher than those of the active substance under different solvothermal temperature conditions.

In combination with the previous discussion of the solvothermal temperature, it can be seen that the prepared NSCNS @ CFC electrode is most excellent in the electrocatalytic oxidation performance of glucose in the solvothermal reaction system when the solvothermal temperature is 160 ℃ and the solvothermal time is 10 hours.

4. Characterization of material morphology and structure

The appearance of the self-supporting CNS @ CFC and NSCNS @ CFC materials was observed by SEM as shown in FIG. 13 below; when SEM images of the pure carbon fiber cloth only pretreated under the same magnification and the solvent-thermal preparation materials of diphenylthiourea with different dosages are analyzed, the surface of the pure carbon fiber cloth is not smooth, but gully stripes appear, and active groups such as hydroxyl, carboxyl and the like are introduced into the carbon fiber cloth after the electro-oxidation pretreatment. As can be seen from the whole SEM image, when the content of the diphenylthiourea is 0.6mmol, the cobalt nickel sulfide grows in the form of particles on the carbon fiber and the particle size is relatively uniform. When the content of the diphenylthiourea is 0.2mmol, the cobalt-nickel sulfide wraps the whole carbon fiber in a split bark shape, the size of the active substance nano particles is uneven, when the content is increased to 0.4mmol, cracks disappear, and the cobalt-nickel sulfide wraps the whole carbon fiber in a thick film shape, so that the ion transmission rate is slowed to a certain extent. When the content was increased to 0.8mmol, the cobalt nickel sulfide layer thickness increased, the surface became rough, the active material nanoparticles were not conspicuous, and the content continued to increase, and it was found that the cobalt nickel sulfide grew on the carbon fiber cloth or the thickness layer decreased, or grew in paste form, or grew unevenly and incompletely on the carbon fiber. Taken together, CNS growth on carbon fibers is advantageous when the diphenylthiourea content is 0.6mmol, so that the contact area of the electrolyte with the active species is maximized during electrochemical testing.

In addition, further research has found that in a solvothermal reaction system, when only CH is contained₄N₂During S, the cobalt-nickel sulfide does not grow densely along the whole carbon fiber, but has certain defects, and meanwhile, the particle size of the cobalt-nickel sulfide is not uniform and reaches hundreds of nanometers. When only diphenylthiourea is contained in the reaction system, cobalt nickel sulfide particles grow in a non-uniform stacking manner on the carbon fibers in a spherical shape. Compared with CH₄N₂Ni prepared by using system with S as sulfur source and 0.6mmol of diphenylthiourea as additive₇S₆/CoNi₂S₄Is singly CH₄N₂S or the single diphenylthiourea can prevent the cobalt-nickel sulfide from uniformly growing on the surface of the carbon fiber, so that the proper amount of diphenylthiourea can regulate and control the size of cobalt-nickel sulfide particles to uniformly grow. When cobalt nickel sulphide is grown at 120 c, only a very small amount of active material grows along the carbon fibre, and the growth is very non-uniform, both in the form of very small particles and in the form of lumpy agglomerates. Along with the rise of the solvothermal temperature, the cobalt-nickel sulfide grows along the whole carbon fiber, and the whole carbon fiber is tightly wrapped. When the solvothermal temperature is 140 ℃, cobalt nickel sulfide particles are larger and have different sizes, the temperature is continuously increased to 160 ℃, the cobalt nickel sulfide particles become uniform and the size of the cobalt nickel sulfide particles becomes smaller than 140 ℃, and when the solvothermal temperature is increased to 180 ℃, the cobalt nickel sulfide also exists in a particle form but occurs. The stacking phenomenon, like a paste, reduces the surface area of the active material to some extent. The active substance prepared at 160 ℃ has the largest specific surface area and larger electrocatalytic activity to glucoseAnd (4) performance is improved. Therefore, in the preparation of NSCNS @ CFC materials, it is appropriate to select 160 ℃ as the solvothermal reaction temperature. With the increase of the solvothermal time, the cobalt-nickel sulfide is etched by gas to generate a porous nanoparticle layer on the carbon fiber, when the solvothermal time is 15 hours, the cobalt-nickel sulfide grows thickly on the carbon fiber, the load capacity is improved compared with 6 hours and 8 hours, but the structure is not stable, and the cobalt-nickel sulfide on the surface of the carbon fiber may fall off in an electrochemical test. When the solvothermal time is 20 hours, the cobalt nickel sulfide is represented as a thin layer of porous sheet-shaped object and is also an unstable structure, compared with the NSCNS which is loaded and reacts for 10 hours at the solvothermal temperature of 160 ℃ and is a relatively stable structure, the electro-catalytic oxidation of glucose is more facilitated.

5. Sensing performance

Firstly, performing cyclic voltammetry test on NSCNS @ CFC-0.6, setting the potential interval to be 0-0.7V and the scanning speed to be 5mA/cm²Electrolyte is 0.1mol/L NaOH solution, the test condition is that 1mmol/L glucose is not added, and the test result is shown in figure 14; when no glucose was added to the electrolyte, a pair of redox peaks appeared at 0.349V and 0.510V, which was mainly the occurrence of Ni²⁺To Ni³⁺And Co²⁺To Co³⁺When glucose was added to the NaOH solution, the anodic peak current increased significantly from 2.677mA to 4.778mA, while the cathodic peak current decreased slightly, while the oxidation peak potential changed from 0.510V to 0.558V, while the reduction peak potential hardly changed in the presence of glucose, since the active sites on the electrode surface were covered with glucose and oxidation intermediates of glucose. The results show that NSCNS @ CFC-0.6 has effective electrocatalytic properties for glucose.

The potential interval of the glucose oxidation-reduction reaction is between 0.5V and 0.6V, so that four voltages of 0.50V, 0.52V, 0.54V and 0.56V are respectively taken in the potential interval to make a current response curve of NSCNS @ CFC-0.6 to glucose, 0.5 mmol/L glucose is continuously added into 0.1mol/L NaOH electrolyte under the stirring condition to make a current-time curve, and the result shows that when the voltage is 0.50V, after the glucose with the same concentration is continuously added, each time of electricity is carried outThe current response is the weakest, and the current response gradually increases with the increase of the reaction potential, particularly, the ampere response is the largest when the potential is 0.52V, and the background noise is weaker. Under the optimal working potential of 0.52V, glucose solutions with different concentrations are added into a continuously stirred 0.1mol/L NaOH electrolyte, and the current response when glucose with different concentrations is continuously added under the condition of 0.52V is tested, so that the result shows that the current response of NSCNS @ CFC-0.6 to glucose is increased in a step shape, and the step shape current response trend shows that NSCNS @ CFC-0.6 has good electrocatalytic oxidation characteristics to glucose. Fitting the response curves of the glucose with different concentrations to obtain a standard fitting curve of the response of the glucose concentration and the ampere current to obtain a linear regression equation: y (ma) 2.053x (mm) +4.401, wherein the linear correlation coefficient R²It is 0.9970, and the linear glucose concentration is in the range of 0.2. mu. mol/L-7.081 mmol/L. Thus, we can obtain a sensitivity of 2053. mu.A mM for glucose for NSCNS @ CFC-0.6^-1cm^-2The linear range of glucose detectable is 0.2. mu. mol/L-7.081mmol/L, compared to 3.4 glucose sensing performance (sensitivity 3115. mu.A mM)^-1cm^-2Linear range 0.2 μmo/L-3.041mmol/L), the linear range for detecting glucose is extended by as much as 1-fold although the sensitivity of NSCNS @ CFC-0.6 is decreased.

Further, the concentration of glucose is selected to be 100 mu mol/L, the concentration of other interfering substances is 10 mu mol/L, and the current-time curve test is carried out in 0.1mol/L NaOH electrolyte under the condition of continuous stirring at the optimal working potential of 0.52V, and the result shows that the active substance on the surface of the electrode rapidly catalyzes glucose to generate a larger current response after adding the glucose, in contrast, the current response hardly changes when adding the interfering substances such as lactose, fructose, sodium chloride, ascorbic acid and the like, and the current obviously responds after continuously adding the glucose, which shows that the electrode material only reacts with the glucose, and from another aspect, NSCNS CFC-0.6 electrode has good selectivity on non-enzymatic detection of the glucose, and is applied practically, the absence of a change in the current signal caused by the reaction of the electrode material with an interfering substance interferes with the enzyme-free glucose detection.

Further, the sensing properties of the materials prepared in the examples were compared, and the results are shown in table 5;

TABLE 5

The NSCNS @ CFC-0.6 has higher sensitivity, the linear range of the detected glucose is wider than that of other electrodes, the working potential of the detected glucose is at a medium level compared with that of other electrodes, and the low working potential prevents interference substances from reacting with active substances to generate current signals in the test process to influence the accuracy of the concentration of the detected glucose, which can be attributed to the fact that the nanoparticle form of the NSCNS @ CFC-0.6 electrode provides a shorter electron/ion transmission channel.

The degree of change in oxidation peak current of the CV curve was used to determine the long-term stability (fig. 15). FIG. 15 is a graph tested at a scan rate of 10mV/s in the presence of 1mmol/L glucose. Wherein, the 1 line is a CV curve of glucose before 2 months, the 2 line is a CV curve of the electrode taken at the 100 th circle after the electrode is exposed in the air for 2 months and circulated for 100 times at room temperature, and the calculation can obtain that the oxidation peak current response of the electrode material to 1mmol/L glucose after being exposed for 2 months and circulated for 100 times is maintained at about 75.92% of the original value, which indicates that the NSCNS @ CFC-0.6 electrode has good stability for detecting the glucose and can be used for a long time.

6. Energy storage performance

CV and GCD characterization of NSCNS @ CFC-0.6 using a three-electrode system is shown in FIGS. 16(a) and (b) for typical cyclic voltammograms of NSCNS @ CFC-0.6 at different scan rates of 1-20mV/s and GCD at different current densities, respectively. FIG. 16(a) shows that the CV curve for NSCNS @ CFC-0.6 exhibits nearly symmetrical redox peaks, primarily due to the nickel-cobalt rich Faraday redox reaction, with the anodic oxidation peak current and potential shifting positively and the cathodic reduction peak current and potential shifting negatively with increasing scan rate, due to electrolysis at small scan ratesOH in the substance^-Slowly wetting the whole electrode material, and fully mixing Ni in the active material²⁺And Co²⁺A redox reaction occurs. FIG. 16(b) is a charge and discharge curve of NSCNS @ CFC-0.6 at different current densities showing significant cell behavior. When the discharge current density is 1, 3, 5, 10 and 20mA/cm respectively²The NSCNS @ CFC-0.6 nanoparticle arrays have charge levels as high as 1.561, 1.464, 1.401, 1.266, and 1.134C/cm²As the discharge current density increases, the amount of charge gradually decreases. FIG. 16(c) is a CV curve of each nano-array electrode at a scanning rate of 10mV/s, with a potential window of-0.2-0.7V. As is apparent from fig. 16(c), the CV curves of all electrodes exhibited a pair of distinct redox peaks during cathodic and anodic scans, with the oxidation peak potential lying in the interval 0.4V to 0.6V and the reduction peak potential appearing in the interval 0 to 0.2V, which is significantly different from the electric double layer capacitance characterized by an approximately rectangular CV curve, indicating that the charges of the CNS @ CFC and the NSCNS @ CFC nanoarrays are determined by faradaic redox reactions. When the amounts of diphenylthiourea were 0.4, 0.8, 1.0 and 2.0mmol, respectively, the oxidation-reduction peak currents of the CV curves were close, which may be correlated with SEM images of the above samples, the integrated areas were slightly lower for the amounts of diphenylthiourea of 0.2 and 1.5mmol than for the other samples, whereas when the amount of diphenylthiourea was 0.6mmol, the oxidation-reduction peak currents were clearly seen to be much higher than for the other samples. FIG. 16(d) shows that each material was at 5mA/cm²The potential window of the constant current charge-discharge curve under the current density is 0-0.4V. The symmetrical shape of the GCD curve implies good electrochemical properties and good reversibility of the Faraday redox reaction, where the discharge time of NSCNS @ CFC-0.6 is higher than that of materials prepared under otherwise identical conditions. The rate capability of each material under different current densities can be obtained from FIG. 16(e), and it is evident that the charge amount of NSCNS @ CFC-0.6 is higher than that of other electrodes, 20mA/cm²The amount of charge at that time was 1mA/cm²72.6% of time, which shows good rate performance. The energy storage device needs to have good life at high current densities, and the NSCNS @ CFC-0.6 electrode material has a current density of 30mA/cm²The cycle stability test of (A) is shown in FIG. 16(f), after 5000 cycles, the charge retention rate of NSCNS @ CFC-0.6 is 100%, which shows the excellent cycle stability of NSCNS @ CFC-0.6.

The charge amounts of each material at different current densities are compared and shown in table 6;

TABLE 6

Sample (I)	1mA/cm²	3mA/cm²	5mA/cm²	10mA/cm²	20mA/cm²
						[email protected]	0.734	0.678	0.647	0.576	0.378
[email protected]	1.277	1.2	1.143	1.035	0.66
						[email protected]	1.561	1.464	1.401	1.266	1.134
[email protected]	1.237	1.179	1.138	1.062	0.914
						[email protected]	1.425	1.335	1.277	1.16	0.932
[email protected]	1.203	1.134	1.084	0.982	0.786
						[email protected]	1.235	1.194	1.162	1.081	0.944

Performing energy storage performance tests on each electrode prepared at different solvothermal temperatures, as shown in fig. 17; as can be seen from fig. 17(a), the electrode material prepared at 160 ℃ has a more distinct redox peak and a maximum integrated area at a sweep rate of 10mV/s compared to electrode materials prepared at other temperatures, and the symmetric redox peaks demonstrate that the material has excellent reversibility. From the charge and discharge curves of fig. 17(b), it can be calculated that the charge amounts of the electrode materials prepared under the conditions of 120 ℃, 140 ℃, 160 ℃ and 180 ℃ are respectively 0.277C/cm, 0.920C/cm, 1.401C/cm and 1.229C/cm, the solvothermal temperature is increased from 120 ℃ to 140 ℃, the charge amount is increased by 3 times, the solvothermal temperature is continuously increased, the charge amount increase rate is slowed, when the solvothermal temperature value is continuously increased to 180 ℃, the charge amount is reduced, which may be related to the morphology of the electrode material, the electrochemical test result is basically consistent with the catalytic performance of the glucose, comparing the charge amounts of the electrode materials prepared under the conditions of 140 ℃ and 180 ℃, the charge amount under 180 ℃ is found to be 0.3 times under the condition of 140 ℃ and slightly different from the catalytic oxidation performance of the glucose, which may be because only the active substance on the surface and the glucose are subjected to redox reaction when the glucose is catalyzed, when the charge and discharge test is carried out, the electrolyte ions have enough time to wet the active material and transmit to the inner surface of the active material, namely, more cobalt-nickel sulfide participates in the reaction. The electrode material is proved to have higher current response strength to glucose and more excellent electrochemical performance when the electrode preparation temperature is 160 ℃.

The energy storage performance of the NSCNS @ CFCs prepared at different solvothermal times was tested and is shown in figure 18; according to cyclic voltammetry curves of materials prepared under different solvent heating times at a scanning speed of 10mV/s, the electrode prepared within 6h has the largest integral area, but the redox peak type is not obvious, so that the catalysis on glucose is weak. The oxidation reduction peak at 15h has more obvious symmetry at the voltage of 0.1V and 0.4V, but the integral area is about half of that at 6 h. As can be seen from the observation in FIG. 18(a), the CV curves at 8h and 20h almost completely overlapped, and it is noted that the solvothermal time was 10hThe CV curve shows obvious symmetrical oxidation reduction peaks, which indicates that the material has the most excellent reaction activity and reversibility. While having a larger integration area than 15 h. As seen from the charge and discharge curves of fig. 18(b), the basic charge and discharge trend is consistent with the CV curve, and the charge amounts of the materials prepared at the solvothermal temperatures of 6h, 8h, 10h, 15h and 20h are respectively 2.494, 1.399, 1.401, 0.704 and 1.320C/cm at the same current density, i.e. 5mA/cm, as can be found from the data, the charge amounts at the solvothermal times of 8h, 10h and 20h are almost twice as large as that at the solvothermal time of 15h, and the charge amount at the time of 6h is the largest. It can be concluded that the maximum charge amount is present when the solvothermal time is 6 hours, and that the redox peak of the active material is most prominent and the redox peak current is maximum when the solvothermal time is 10 hours. In combination with the above discussion of solvothermal temperature, it was found that the temperature has a significant effect on its electrochemical performance, and relatively speaking, the solvothermal time has a small effect. The experimental discussion result of the solvothermal temperature and time factors shows that when the solvothermal temperature is 160 ℃, Ni grows on the carbon fiber cloth₇S₆/CoNi₂S₄The catalytic performance and the energy storage performance of the composite material to glucose are optimal, when the solvothermal time is 6 hours, the composite material has higher energy storage performance, only when the solvothermal time is 10 hours, the composite material has more sensitive current response and more excellent reaction activity to the glucose, and simultaneously the energy storage performance of the composite material is not much different from that of the composite material in 6 hours, comprehensive analysis shows that the solvothermal temperature is 160 ℃, and the solvothermal reaction time is 10 hours, so that the nano-particle Ni loaded on the carbon fiber cloth is subjected to solvothermal reaction₇S₆/CoNi₂S₄And has the best glucose sensing and energy storage performance.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included therein.

Claims

1. A carbon fiber composite material is characterized in that carbon fiber cloth is used as a substrate, and nickel cobalt sulfide grows in situ.

2. Carbon fiber composite material according to claim 1, wherein the nickel cobalt sulphide is in particular the compound Co_xNi_3-xS₄Or Ni₇S₆/CoNi₂S₄A nanocomposite material.

3. Carbon fiber composite material according to claim 2, characterized in that said compound Co_xNi_3-xS₄Specifically CoNi₂S₄。

4. A method for preparing a carbon fiber composite material according to any one of claims 1 to 3, characterized in that the carbon fiber composite material is obtained by placing the pretreated carbon fiber in a solvent, adding a sulfur source, a nickel source and a cobalt source, uniformly mixing, transferring into a reaction kettle for solvothermal reaction, taking out, cleaning and drying, and performing heat treatment in an inert atmosphere.

5. The method for preparing a carbon fiber composite material as claimed in claim 4, wherein the pretreatment process of the carbon fiber cloth comprises the steps of: the carbon fiber after impurity removal treatment is arranged in a mixed acid solution of concentrated nitric acid and concentrated sulfuric acid with the volume ratio of 1:1, carbon fiber cloth is used as a working electrode, a three-electrode system is adopted to carry out electrochemical oxidation modification treatment on the carbon fiber cloth, and then the carbon fiber cloth is cleaned and dried.

6. The method of producing a carbon fiber composite material as claimed in claim 4, wherein the sulfur source is CH₄N₂S, the cobalt source Co (NO)₃)₂·6H₂O, the nickel source is Ni (NO)₃)₂·6H₂O; the solvent is ethanol or ethanol water solution; the solvothermal reaction temperature is 120-180 ℃, the solvothermal reaction time is 6-20h, and the heat treatment comprises raising the temperature to 350 ℃ at a heating rate of 2 ℃/min, keeping the temperature for 2h, and then naturally cooling to room temperature.

7. Method for the production of a carbon fiber composite material according to claim 4, characterized in that the nickel cobalt sulphide is in particular the compound Co_xNi_3-xS₄When in use, the molar ratio of nickel atoms to cobalt atoms to sulfur atoms is (2-4) to (1-2) to (5-10), and hexamethylenetetramine or polyethylene glycol-1000 is also added as an additive in the process of solvothermal reaction; the nickel cobalt sulfide is specifically Ni₇S₆/CoNi₂S₄In the case of the nano composite material, the molar ratio of nickel atoms to cobalt atoms to sulfur atoms is 2:1:5, and diphenylthiourea is also added as an additive in the solvothermal reaction process.

8. The method for preparing the carbon fiber composite material according to claim 7, wherein the addition amount of the hexamethylenetetramine or polyethylene glycol and the addition ratio of the sulfur atom are (0.2-1.0) g (5-10) mmol; the addition amount of the diphenylthiourea and the addition molar ratio of the sulfur atom are (0.2-2.0): 5.

9. Use of a carbon fibre composite material according to any one of claims 1-3 in an electrochemical sensor.

10. Use of the carbon fiber composite material according to claim 9 in electrochemical sensors, characterized by being used for enzyme-free glucose sensor electrodes.