CN114235920A

CN114235920A - NiCo LDH/NiCoS @ C composite material and preparation method and application thereof

Info

Publication number: CN114235920A
Application number: CN202111560798.1A
Authority: CN
Inventors: 王丽丽; 李家慧; 尹振; 徐俊青; 何昊嘉; 赵旭
Original assignee: Tianjin Polytechnic University
Current assignee: Tianjin Polytechnic University
Priority date: 2021-12-20
Filing date: 2021-12-20
Publication date: 2022-03-25

Abstract

The invention belongs to a low-sulfur doped NiCo LDH/NiCoS @ C nanocomposite based on Co MOF, and particularly relates to a low-sulfur doped NiCo LDH/NiCoS @ C nanocomposite with simple steps, short time consumption and simple preparation methodCan be used for Oxygen Evolution Reaction (OER), enzyme-free glucose and hydrogen peroxide sensor. When the present invention is used as an OER catalyst, the current density is 10mA cm^‑2Only 207mV overpotential is needed, and the Tafel slope is as low as 48mV dec^‑1. When NiCo LDH/NiCoS @ C is used as an enzyme-free glucose sensor, the linear range of the response of the material to glucose is 1 mu M-3mM and 3-9mM, and the sensitivity is as high as 2167 mu AmM^‑1cm^‑2And 1417 μ AmM^‑ ¹cm^‑2The detection limit was as low as 208 nM. When the material is used as a catalytic material of an enzyme-free hydrogen peroxide sensor, the detection range is 10 mu M-12mM, and the sensitivity is as high as 285 mu AmM^‑1cm^‑2The detection limit was as low as 1.66. mu.M. The invention has the advantages of low cost, high electrocatalytic activity, simple and convenient operation, strong anti-interference capability, capability of quickly detecting glucose and hydrogen peroxide in human serum and excellent oxygen evolution performance.

Description

NiCo LDH/NiCoS @ C composite material and preparation method and application thereof

Technical Field

The invention belongs to the technical field of new energy materials and bioelectrochemical sensing, and particularly relates to a NiCo LDH/NiCoS @ C composite material and a preparation method and application thereof.

Background

With the rapid growth of the population and the continuous demand of people for good life, the development and innovation of modern science and technology are particularly important. From the perspective of energy technology, pollution caused by fossil energy combustion emission causes great harm to the environment and human bodies. Particularly, in recent years, strategic planning and strong fund support of China on new energy technologies promote low-carbon economic development mode to gradually replace traditional high-pollution development mode, and development of new energy is gradually the focus of research. Among them, hydrogen energy is one of the effective methods for hydrogen production by electrochemical decomposition of water due to its advantages of abundant source, high energy density, easily available raw materials, etc. However, the low rate of Oxygen Evolution Reaction (OER) as a key factor in the water electrolysis process limits the rate of water splitting. Therefore, the research on the efficient OER catalyst has great significance and value.

Since the 21 st century, diabetes has become one of the killers of human health and life. Regular blood sugar monitoring is of great help to prevent diabetes, especially for patients, the blood sugar content is monitored in time, and the complications can be reduced by reasonable medication, so that the life and health are saved. Hydrogen peroxide is widely used in industry, clinic, medicine, and is one of the most important molecules in biological systems. Hydrogen peroxide is a metabolic byproduct or intermediate product in cell growth. The excessive production and accumulation of hydrogen peroxide in cells may lead to various diseases such as alzheimer's disease, cardiovascular diseases and cancer, etc. Accurate detection and real-time monitoring of the concentration level of hydrogen peroxide are of great significance. However, the commonly used detection enzyme is expensive, has low stability and requires strict living environment. Therefore, it is necessary to design a sensor with high stability and low price, which can accurately and rapidly detect the blood sugar and the hydrogen peroxide content.

Metal Organic Frameworks (MOFs) are crystalline porous materials composed of coordination bonds between metal ions or clusters and organic ligands, with diverse framework and pore structures. These unique advantages enable MOFs to have good catalytic capabilities, and thus MOFs are a promising electrochemical sensing platform. However, the organic ligands that typically make up the MOFs are inert and the MOFs formed are bulky and thick, which are detrimental to the conductivity of the material.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides a NiCo LDH/NiCoS @ C composite material and a preparation method and application thereof, wherein the thickness of a nanosheet layer of the material is only 20-30nm, and the material further has the advantages of high electrocatalytic activity, high sensitivity, wide linear range, excellent selectivity and the like.

In order to achieve the purpose, the invention adopts the technical scheme that:

the invention provides a NiCo LDH/NiCoS @ C composite material, wherein a NiCo LDH/NiCoS nanosheet array is uniformly distributed on the surface of a carbon substrate, the NiCo LDH/NiCoS nanosheets are perpendicular to the surface of a carbon cloth fiber, the thickness of the NiCo LDH/NiCoS nanosheets is 20-30nm, and the surface wrinkle thickness of the nanosheets is about 3-6 nm. The formation of the ultrathin structure is beneficial to the rapid transmission of electrons/ions, and the resistance and the reaction energy barrier are effectively reduced, so that the improvement of the electrocatalysis performance is promoted.

The invention also provides a preparation method of the NiCo LDH/NiCoS @ C composite material, which comprises the following steps:

(1) preparation of Co MoF @ C: respectively dissolving cobalt nitrate hexahydrate and 2-methylimidazole in deionized water, uniformly stirring to prepare a cobalt nitrate hexahydrate aqueous solution and a 2-methylimidazole aqueous solution, then quickly pouring the 2-methylimidazole aqueous solution into the cobalt nitrate hexahydrate aqueous solution, soaking a carbon substrate in the mixed solution, standing at room temperature for reacting for 3-4 hours, washing and drying to obtain Co @ MOF C;

(2) preparation of NiCo LDH @ C: weighing nickel nitrate hexahydrate, dissolving the nickel nitrate hexahydrate in absolute ethyl alcohol, fully stirring, immersing Co MOF @ C in nickel nitrate hexahydrate ethanol solution, reacting for 1-3h at room temperature, washing and drying to obtain NiCo LDH @ C;

(3) dissolving thioacetamide in absolute ethyl alcohol to prepare a thioacetamide ethanol solution, transferring the thioacetamide ethanol solution and NiCo LDH @ C obtained in the step (2) into a high-pressure kettle, and heating for 2-6h at the temperature of 100-; and naturally cooling to room temperature, washing with deionized water and drying to obtain NiCo LDH/NiCoS @ C.

Further, in the step (1), the mass concentration of the cobalt nitrate hexahydrate aqueous solution is 0.005-0.05g/mL, and the mass concentration of the 2-methylimidazole aqueous solution is 0.02-0.2 g/mL. Preferably, the mass concentration of the cobalt nitrate hexahydrate aqueous solution is 0.01-0.02g/mL, and the mass concentration of the 2-methylimidazole aqueous solution is 0.03-0.05 g/mL.

Further, the mass concentration of the nickel nitrate hexahydrate ethanol solution in the step (2) is 0.003-0.03 g/mL. The mass concentration of the nickel nitrate hexahydrate ethanol solution is preferably 0.004-0.005 g/mL.

Further, the mass concentration of the ethanol solution of thioacetamide in the step (3) is 0.10-1 mg/mL. The preferred mass concentration of the thioacetamide ethanol solution is 0.1-0.2 mg/mL.

Further, the carbon substrate is a woven carbon substrate with high flexibility and high conductivity, such as carbon cloth, carbon felt, carbon paper, carbon fiber and the like.

The invention also provides application of the NiCo LDH/NiCoS @ C composite material as an OER catalyst in water electrolysis hydrogen production reaction.

The invention also provides application of the NiCo LDH/NiCoS @ C composite material as an enzyme-free glucose sensor.

The invention also provides application of the NiCo LDH/NiCoS @ C composite material as an enzyme-free hydrogen peroxide sensor.

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

1. according to the invention, a carbon substrate is used as a substrate, Co MOF grows at room temperature, MOF is used as a sacrificial template to etch and grow NiCo LDH, NiCo LDH/NiCoS @ C is generated by hydrothermal method, and the advantages of high electrocatalytic activity, high sensitivity, wide linear range, excellent selectivity and the like are shown in an oxygen evolution reaction, enzyme-free glucose and hydrogen peroxide sensor. When the material is used as a catalyst for OER, the material is at 10mAcm²Only 207mV overpotential is needed for the current density of (1); in addition, when the material is used as a catalytic material of an enzyme-free glucose sensor, the sensitivity of the material to glucose with the glucose detection ranges of 1 mu M-3mM and 3-9mM is as high as 2167 mu AmM^-1cm^-2And 1417 μ AmM^-1cm^-2Detection limit is as low as 208 nM; when the material is used as a catalytic material of an enzyme-free hydrogen peroxide sensor, the detection range is 10 mu M-12mM, and the sensitivity is as high as 285 mu AmM^-1cm^-2The detection limit was as low as 1.66. mu.M. In addition, as sensors, the sensor has good anti-interference performance on sodium chloride, ascorbic acid, fructose and the like.

2. The thickness of the nano-sheet layer is only 20-30nm, the thickness of the surface wrinkles of the nano-sheet is about 3-6nm, the transmission rate of electrons and ions is greatly enhanced, and the defect of poor conductivity of the MOF is overcome. The nano material grows on the carbon base in a self-supporting mode, and the electrode material can exert the best electrocatalytic performance based on a conductive network rich in the carbon base, the excellent pseudocapacitance characteristic of the transition metal sulfide and the unique MOF structure.

3. The transition metal sulfur compound of the present invention has excellent conductivity, redox activity and cycle stability. The electrochemical reaction of the transition metal sulfur compound occurs on the surface or interface of the electrode material, and the ultrathin structure of the material has a larger specific surface area, so that more active sites can be provided for the OER reaction.

Drawings

FIG. 1: example 1A SEM image of NiCo LDH/NiCoS @ C was prepared.

FIG. 2: example 1 TEM images of NiCo LDH/NiCoS @ C were prepared.

FIG. 3: EXAMPLE 1 preparation of NiCo LDH^1h@C、NiCo LDH^3h@C、NiCo LDH^1h/NiCoS @ C and NiCo LDH^3hSEM image of/NiCoS @ C.

FIG. 4: EXAMPLE 1 preparation of NiCo LDH^1h@C、NiCo LDH^3h@C、NiCo LDH^1h/NiCoS @ C and NiCo LDH^3hLSV profile of/NiCoS @ C in 1M KOH solution.

FIG. 5: the LSV profile of NiCo LDH/NiCoS @ C prepared in example 1 versus a control in 1M KOH solution.

FIG. 6: the Tafel slope plot of NiCo LDH/NiCoS @ C versus control prepared in example 1.

FIG. 7: an impedance plot of NiCo LDH/NiCoS @ C versus control was prepared as in example 1.

FIG. 8: CV profiles of NiCo LDH/NiCoS @ C prepared in example 1 with different concentrations of glucose were obtained.

FIG. 9: EXAMPLE 1 an amperometric current test plot for a NiCo LDH/NiCoS @ C enzyme-free glucose sensor was prepared.

FIG. 10: an anti-interference performance test chart of the enzyme-free glucose sensor of NiCo LDH/NiCoS @ C is prepared in example 1.

FIG. 11: example 1 a CV plot of NiCo LDH/NiCoS @ C with different concentrations of hydrogen peroxide was prepared.

FIG. 12: EXAMPLE 1 amperometric current measurements of enzyme-free hydrogen peroxide sensors prepared to produce NiCo LDH/NiCoS @ C.

FIG. 13: the anti-interference performance test chart of the enzyme-free hydrogen peroxide sensor of NiCo LDH/NiCoS @ C is prepared in the embodiment 1.

Detailed Description

In order to make the technical solutions of the present invention better understood by those skilled in the art, the present invention will be further described in detail with reference to the accompanying drawings and preferred embodiments.

Example 1: a preparation method of a NiCo LDH/NiCoS @ C composite material comprises the following steps: .

(1) Respectively dissolving 0.65g of cobalt nitrate hexahydrate and 1.2g of 2-methylimidazole in 40mL of deionized water, stirring for 10min, rapidly pouring the 2-methylimidazole aqueous solution into the cobalt nitrate hexahydrate aqueous solution under vigorous stirring, and adding 1 × 2cm²The carbon substrate (carbon cloth) is placed in the mixed solution which is fully and uniformly dissolved, and after standing for 3 hours at room temperature, the sample Co MOF @ C is obtained by washing and drying with deionized water.

(2) 0.2g of nickel nitrate hexahydrate is dissolved in 30mL of absolute ethanol, Co MOF @ C is immersed in an ethanol solution of the nickel nitrate hexahydrate after being uniformly stirred, and the mixture is kept stand at room temperature for 2 hours and then washed and dried by deionized water to obtain NiCo LDH @ C.

(3) 20mg of thioacetamide is dissolved in 40mL of absolute ethanol, after the thioacetamide is uniformly stirred, the ethanol solution of the thioacetamide and NiCo LDH @ C are transferred into a 100mL stainless steel autoclave with a polytetrafluoroethylene lining, and the autoclave is heated for 4 hours at the temperature of 100 ℃. And naturally cooling to room temperature, washing with deionized water and drying to obtain NiCo LDH/NiCoS @ C. FIGS. 1-2 are SEM and TEM images of NiCo LDH/NiCoS @ C, respectively. From SEM picture, it can be observed that NiCo LDH/NiCoS nanosheet array grows on the surface of the carbon cloth fiber uniformly, and the shape of the nanosheet is kept intact. The doping of the S element facilitates the reduction of the thickness of the nanosheets to 28 nm. In the TEM image, ultra-thin NiCo LDH/NiCoS nanosheets were grown vertically, with an upper pleat thickness of about 3-6nm observed. The formation of the ultrathin structure is beneficial to the rapid transmission of electrons/ions, and the resistance and the reaction energy barrier are effectively reduced, so that the improvement of the electrocatalysis performance is promoted.

Example 2: the Co MOF @ C is obtained by changing the room temperature standing time of the step (1) in the example 1 into 5h, and other conditions are the same as those of the examples 1 and 5h, so that the Co MOF grown on the carbon substrate grows densely and has thick and large sheet structure.

Example 3: changing the etching time (room temperature standing time) of step (2) in example 1 to 3h, and obtaining the NiCo LDH under the same other conditions as in example 1^3h@ C. Co MOF by comparing SEM images (FIG. 3 (a))The surface was intact and obvious lamellae could be observed; however, Co MOF was etched too thin, so that NiCo LDH was formed after further sulfidation process^3hthe/NiCoS @ C surface was cracked ((b) in FIG. 3), and there was clearly an over-etch phenomenon. The etching time (room temperature standing time) in the step (2) of the embodiment 1 is changed to 1h, and other conditions are the same as the embodiment 1. The obtained NiCo LDH^1hThe @ C sample surface was not visibly flaky ((C) in FIG. 3), and NiCo LDH after further sulfidation^3hthe/NiCoS @ C did not form an ultra-thin structure ((d) in FIG. 3). By the LSV test (fig. 4), the difference in etch time has an effect on the performance of the material. With increasing etching time, i.e. Ni²⁺The doping amount is increased, and the material is 10mAcm^-2The overpotential at the current density of (a) becomes small. However, the etching time is too long, which causes an increase in overpotential.

Example 4: the resulting NiCo LDH/NiCoS @ C composite prepared in example 1 was used as a catalyst for the OER reaction, and the main test procedures were as follows:

(1) a three-electrode system is selected for electrochemical test, and NiCo LDH/NiCoS @ C is respectively used as a working electrode, a platinum sheet is used as a counter electrode, and a mercury/mercury oxide electrode is used as a reference electrode in a 1M KOH solution.

(2) The catalyst was subjected to cyclic voltammetric scanning (CV) for 40 cycles prior to testing to better activate the catalyst. When Linear Sweep Voltammetry (LSV) is carried out, the voltage window is-0.3-0.7V, and the sweep rate is 5mV s^-1The LSV tests were all 90% IR compensated. Calculated at 10mAcm by testing the LSV of the different catalysts^-2The required overpotential for each catalyst at the current density of (c). The lower the overpotential, the better the performance of electrocatalytic OER reaction. FIG. 5 shows the current density of 10mAcm^-2Overpotential images of NiCo LDH/NiCoS @ C and control samples. From FIG. 5, it can be derived that passing Ni²⁺The electronic structure of NiCo LDH/NiCoS @ C is effectively adjusted, and a heterostructure can expose more active sites, so that the NiCo LDH/NiCoS @ C has the best catalytic activity.

(3) The tafel slope is a slope value calculated by linear transformation by combining an LSV curve through a formula eta ═ a + blgI. Tafel slope valueThe lower the oxygen evolution rate, the faster the reaction. FIG. 6 is a Tafel slope image of NiCo LDH/NiCoS @ C and control. It can be derived from FIG. 6 that the Tafel slope of NiCo LDH/NiCoS @ C is minimal (48mV dec) compared to the control^-1) Indicating that minimal reaction kinetics are present.

(4) The amplitude potential of the impedance test EIS is 0.05V, the frequency range is 0.01-100kHz, and the measured potential is consistent with the open-circuit voltage. FIG. 7 is an impedance image of NiCo LDH/NiCoS @ C and a control. It can be derived from FIG. 7 that the resistance of NiCo LDH/NiCoS @ C is the smallest, which indicates that the structure of NiCo LDH/NiCoS @ C is favorable for the rapid electron/ion transfer.

Example 5: the NiCo LDH/NiCoS @ C composite material prepared in example 1 is used as a catalytic material of an enzyme-free glucose sensor, and the main test steps are as follows:

(1) and respectively taking NiCo LDH/NiCoS @ C as a working electrode, a platinum sheet as a counter electrode, a mercury/mercury oxide electrode as a reference electrode and 0.5M NaOH solution as electrolyte, and carrying out electrochemical test under a three-electrode system.

(2) During cyclic voltammetry, the voltage window is selected to be-0.1-0.7V, and the sweep rate is 20mV s^-1To the 0.5M NaOH solution, 0 to 10mM of glucose was added, respectively. As the glucose concentration increased, the current density of the anodic peak increased and the potential also shifted towards high potential, indicating that the oxidation process of glucose is surface controlled. FIG. 8 is a graph of CV curves of NiCo LDH/NiCoS @ C versus glucose at different concentrations.

(3) When the amperometric current is tested, the voltage is 0.5V, the test time is 3000s, and glucose is added every 100 s. It can be seen that each addition of glucose caused a step-like current response to glucose by the electrode and stabilized within 2 s. As the glucose concentration increases, the current response increases. The glucose detection range is 1 mu M-3mM and 3-9mM, and the sensitivity is as high as 2167 mu AmM^-1cm^-2And 1417 μ AmM^-1cm^-2The detection limit was as low as 208nM (3 SNR). FIG. 9 is an amperometric assay image of NiCo LDH/NiCoS @ C as an enzyme-free glucose sensor.

(4) In the anti-interference performance test, the voltage is 0.5V, the test time is 1400s, and the obvious current response is shown only when glucose is added, and when 9 other interferents such as sodium chloride, ascorbic acid, fructose and the like are added, the current response is weak or basically zero. FIG. 10 is an image of the anti-interference performance test of NiCo LDH/NiCoS @ C as an enzyme-free glucose sensor.

Example 6: the NiCo LDH/NiCoS @ C composite material prepared in example 1 is used as a catalytic material of an enzyme-free hydrogen peroxide sensor, and the main test steps are as follows:

(2) During cyclic voltammetry, the voltage window is selected from-0.1-0.8V, and the sweep rate is 10-80mV s^-1To each 0.5M NaOH solution, 3mM of hydrogen peroxide was added. As the sweep rate increased, the current density of the cathode peak increased, indicating that the hydrogen peroxide reduction process was diffusion controlled. FIG. 11 is a graph of CV curves of NiCo LDH/NiCoS @ C vs 3mM hydrogen peroxide at different sweep rates.

(3) When the ampere-hour current is tested, the voltage is-0.35V, the test time is 3000s, and hydrogen peroxide is added every 100 s. It can be seen that each addition of hydrogen peroxide causes a step current response of the electrode to hydrogen peroxide and reaches a plateau within 5 s. As the hydrogen peroxide concentration increases, the current response increases. The detection range of the hydrogen peroxide is 10 mu M to 12mM and the sensitivity is as high as 285 mu AmM^-1cm^-2The detection limit was as low as 1.66. mu.M (signal-to-noise ratio of 3). FIG. 12 is an amperometric test image of NiCo LDH/NiCoS @ C as an enzyme-free hydrogen peroxide sensor.

(4) When the anti-interference performance is tested, the voltage is-0.35V, the test time is 1400s, and the obvious current response is shown only when the hydrogen peroxide is added, and when other interferents are added, the current response is weak or basically zero. FIG. 13 is an image of the anti-interference performance test of NiCo LDH/NiCoS @ C as an enzyme-free hydrogen peroxide sensor.

In conclusion, a NiCo LDH/NiCoS @ C composite material for oxygen evolution reaction, enzyme-free glucose and hydrogen peroxide sensors was prepared, which when used as a catalyst for OER, was at 10mAcm²Only 207mV overpotential is needed for the current density of (1); in addition, when the material is used as a catalytic material of an enzyme-free glucose sensor, the sensitivity of the material to glucose with the glucose detection ranges of 1 mu M-3mM and 3-9mM is as high as 2167 mu AmM^-1cm^-2And 1417 μ AmM^-1cm^-2Detection limit is as low as 208 nM; when the material is used as a catalytic material of an enzyme-free hydrogen peroxide sensor, the detection range is 10 mu M-12mM, and the sensitivity is as high as 285 mu AmM^-1cm^-2The detection limit was as low as 1.66. mu.M. In addition, as sensors, the sensor has good anti-interference performance on sodium chloride, ascorbic acid, fructose and the like.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims

1. A NiCoLDH/NiCoS @ C composite material is characterized in that: and a NiCoLDH/NiCoS nanosheet array is uniformly distributed on the surface of the carbon substrate, the NiCoLDH/NiCoS nanosheet is perpendicular to the surface of the carbon cloth fiber, the thickness of the NiCoLDH/NiCoS nanosheet is 20-30nm, and the thickness of the surface wrinkle of the nanosheet is about 3-6 nm.

2. A method of making the NiCoLDH/NiCoS @ C composite material of claim 1, wherein: the method comprises the following steps:

(1) preparation of comuf @ C: respectively dissolving cobalt nitrate hexahydrate and 2-methylimidazole in deionized water, uniformly stirring to prepare a cobalt nitrate hexahydrate aqueous solution and a 2-methylimidazole aqueous solution, then quickly pouring the 2-methylimidazole aqueous solution into the cobalt nitrate hexahydrate aqueous solution, soaking a carbon substrate in the mixed solution, standing at room temperature for reacting for 3-4 hours, washing, and drying to obtain CoMOF C;

(2) preparation of NiCoLDH @ C: weighing nickel nitrate hexahydrate, dissolving the nickel nitrate hexahydrate in absolute ethyl alcohol, fully stirring, immersing CoMOF @ C in nickel nitrate hexahydrate ethanol solution, reacting for 1-3h at room temperature, washing and drying to obtain NiCoLDH @ C;

(3) dissolving thioacetamide in absolute ethyl alcohol to prepare a thioacetamide ethanol solution, transferring the thioacetamide ethanol solution and the NiCoLDH @ C obtained in the step (2) into a high-pressure kettle, and heating for 2-6h at the temperature of 100-; and naturally cooling to room temperature, washing with deionized water and drying to obtain NiCoLDH/NiCoS @ C.

3. The method of preparing a NiCoLDH/NiCoS @ C composite material as set forth in claim 2, wherein: in the step (1), the mass concentration of the cobalt nitrate hexahydrate aqueous solution is 0.005-0.05g/mL, and the mass concentration of the 2-methylimidazole aqueous solution is 0.02-0.2 g/mL.

4. The method of preparing a NiCoLDH/NiCoS @ C composite material as set forth in claim 2, wherein: the mass concentration of the nickel nitrate hexahydrate ethanol solution in the step (2) is 0.003-0.03 g/mL.

5. The method of preparing a NiCoLDH/NiCoS @ C composite material as set forth in claim 2, wherein: the mass concentration of the ethanol solution of the thioacetamide in the step (3) is 0.10-1 mg/mL.

6. The method of preparing a NiCoLDH/NiCoS @ C composite material as set forth in claim 1, wherein: the carbon substrate is carbon cloth or carbon felt or carbon paper or carbon fiber.

7. Use of the NiCoLDH/NiCoS @ C composite material of claim 1 as an OER catalyst in a hydrogen production reaction by electrolysis of water.

8. Use of the NiCoLDH/NiCoS @ C composite material of claim 1 as an enzyme-free glucose sensor.

9. Use of the NiCoLDH/NiCoS @ C composite of claim 1 as an enzyme-free hydrogen peroxide sensor.