Nitrogen-doped carbon nanotube hollow polyhedral material, difunctional electrode and application thereof

Abstract

The invention discloses a nitrogen-doped carbon nanotube hollow polyhedral material, a bifunctional electrode based on the material and application of the nitrogen-doped carbon nanotube hollow polyhedral material. The preparation method comprises the following steps: preparing a precursor material ZIF-8 (at) ZIF-67 with a core-shell structure by taking ZIF-8 with a dodecahedron structure as a template; wherein the dosage ratio of the ZIF-8 to the 2-methylimidazole to the cobalt salt is (0.2-0.5) g: (5-10) g: (1.7-34) mmol; and performing high-temperature pyrolysis on the precursor material in inert gas, and performing acid pickling and washing to be neutral to obtain the composite material. The difunctional electrode is an electrode for modifying the material, can be used for detecting H2O2 and glucose, or can be used as a cathode or an anode of an enzyme biological fuel cell. The difunctional electrode has the advantages of low detection limit, wide linear range and high sensitivity when being used for detecting H2O2 and glucose. The maximum open-circuit voltage of the constructed enzyme biological fuel cell is 0.423 V, and the maximum power density is 3.70 [mu] W / cm <-2 >. The electrode material disclosed by the invention has good performance and low cost, and has a wide prospect in application of electrochemical sensing and battery equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of biosensors and enzyme biofuel cells, and in particular to a nitrogen-doped carbon nanotube hollow polyhedron material, a bifunctional electrode and applications thereof. Background Art

[0002] Hydrogen peroxide (H2O2) is a hazardous chemical and one of the carcinogens announced by the World Health Organization. It is often used as a bleaching agent, disinfectant and preservative in the food industry. However, the transportation and storage of high-concentration H2O2 are very risky, which has caused major obstacles to its application. H2O2 can attack the central nervous system, interfere with the synthesis of genetic molecules DNA, and cause neuropsychiatric diseases. In biological systems, H2O2 belongs to a class of reactive oxygen species (ROS), which mainly comes from cell respiration, protein folding and various metabolic products, and is essential for maintaining normal cell function. However, high concentrations of ROS can cause oxidative stress, leading to organ and tissue function decline. Excessive H2O2 has extremely strong chemical activity and is a common marker for diseases related to oxidative stress. Therefore, it is of great significance to develop a simple, green and energy-saving high-performance catalyst for accurate, rapid and sensitive detection of H2O2. In addition, H2O2 is a byproduct of enzyme-catalyzed reactions such as glucose oxidase (GOx), lactate oxidase, urate oxidase and cholesterol oxidase. As we all know, human blood glucose concentration is an important indicator of human metabolic status and health, and hyperglycemia is one of the most typical characteristics of diabetic patients. Therefore, the development of a glucose sensor with high sensitivity, good selectivity and wide linear range is of practical significance for the diagnosis and prevention of related diseases.

[0003] At present, the research on enzyme biofuel cells mainly focuses on the preparation of new carrier materials and deep oxidation of fuels to improve the electron transfer efficiency between enzymes and electrodes and increase the energy density of batteries. Therefore, the rational design of carrier materials with high conductivity and three-dimensional porous structure is conducive to improving the electron transfer rate between enzymes and electrodes and increasing enzyme loading, which is the key to improving the power density of enzyme biofuel cells. At the same time, the porous structure is conducive to the capture of enzyme molecules, thereby improving the stability of enzyme biofuel cells.

[0004] At present, problems such as low charge transfer efficiency between enzymes and electrodes, small specific surface area of ​​electrodes, and difficulty in enzyme fixation are important factors hindering the development of electrochemical sensors and enzyme biofuel cells, which indirectly leads to problems such as poor stability, short life and high cost in traditional H2O2 and glucose sensors and enzyme biofuel cells. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a nitrogen-doped carbon nanotube hollow polyhedron material, a bifunctional electrode and its application, including detecting H2O2, glucose and constructing an enzyme biofuel cell. The bifunctional electrode based on the material has good detection limit, wide linear range and high sensitivity as a sensor, solving the problems of poor sensor stability and high cost; the constructed enzyme biofuel cell has good performance.

[0006] To achieve the above technical objectives, the technical solution of the present invention is as follows:

[0007] A nitrogen-doped carbon nanotube hollow polyhedron material, the material is prepared by the following method:

[0008] (1) uniformly mixing ZIF-8 having a dodecahedral structure and a cobalt salt in a solvent, and then slowly adding a 2-methylimidazole solution to react, to obtain a precursor material ZIF-8@ZIF-67 having a core-shell structure; the amount ratio of ZIF-8, 2-methylimidazole, and cobalt salt is 0.2-0.5 g: 5-10 g: 9-27 mmol; the most preferred ratio is 0.25 g: 5.634 g: 27 mmol;

[0009] (2) The precursor material ZIF-8@ZIF-67 is pyrolyzed at high temperature in an inert gas, and then acid-washed and then washed to neutrality to obtain the nitrogen-doped carbon nanotube hollow polyhedron material (NCNHP).

[0010] The nitrogen-doped carbon nanotube hollow polyhedron material used in the present invention has a core-shell structure as a precursor material, and retains the dodecahedral structure of the raw material ZIF-8, and has the characteristics of high symmetry, strong lattice and good structural stability, and the high porosity and multi-mesoporosis make NCNHP have good biocompatibility when combined with enzymes. At the same time, due to the use of a specific ligand 2-methylimidazole and cobalt element ratio, while maintaining the dodecahedral structure, more active sites are provided, so that more and longer nitrogen-doped carbon nanotubes are produced on the surface of the prepared nitrogen-doped carbon nanotube hollow polyhedron material, which is conducive to improving the electron transfer rate on the electrode surface and increasing the reaction active sites. At the same time, the hollow material and the large amount of nitrogen-doped carbon nanotubes improve the mass transfer efficiency. In addition, the nitrogen-doped carbon nanotubes distributed on the surface of the nitrogen-doped carbon nanotube hollow polyhedron material are also conducive to the loading of glucose oxidase. The nitrogen-doped carbon nanotubes as nanowires promote the electron transfer between the enzyme active center site and the electrode surface. Pyridine N, pyrrole N and Co-N x The presence of is conducive to promoting the adsorption of oxygen molecules and strengthening the oxygen reduction reaction of the non-enzymatic cathode. Therefore, the electrode constructed based on the nitrogen-doped carbon nanotube hollow polyhedron material of the present invention has unique advantages in detecting H2O2, glucose and constructing enzyme biofuel cells.

[0011] Preferably, the ZIF-8 having a dodecahedral structure described in step (1) is prepared by the following method:

[0012] (0) 2-Methylimidazole and zinc salt are uniformly mixed and reacted in a solvent to obtain ZIF-8.

[0013] Preferably, in step (0), the dosage ratio of 2-methylimidazole, zinc element and solvent is 50-100 mmol:5-50 mmol:80-100 mL; more preferably, the dosage ratio is 80 mmol:5 mmol:100 mL.

[0014] Preferably, the zinc salt in step (0) is zinc acetate.

[0015] Preferably, the solvent in step (0) is water.

[0016] Preferably, step (0) further comprises the steps of centrifuging and drying the reaction product at a drying temperature of 50 to 70°C.

[0017] Preferably, the solvent in step (1) is methanol.

[0018] Preferably, the solvent of the 2-methylimidazole solution in step (1) is methanol.

[0019] Preferably, the cobalt salt described in step (1) is cobalt nitrate.

[0020] Preferably, the uniform mixing method in step (1) is ultrasonic treatment, and the ultrasonic treatment time is preferably 3 to 6 minutes.

[0021] Preferably, the reaction temperature in step (1) is 20-30°C.

[0022] Preferably, step (1) further comprises the steps of centrifuging and drying the precursor material ZIF-8@ZIF-67.

[0023] Preferably, the inert gas in step (2) is nitrogen or argon.

[0024] Preferably, the high temperature pyrolysis in step (2) is:

[0025] The temperature is raised to 900-960°C at a heating rate of 2-10°C / min, and the pyrolysis is performed for 1.5-2.5 hours. More preferably, the high temperature pyrolysis is raised to 920°C at a heating rate of 5°C / min, and the pyrolysis is performed for 2 hours.

[0026] Preferably, the pickling in step (2) is performed by soaking in 1M H2SO4 for 1 to 5 hours. More preferably, the soaking time is 2 hours.

[0027] The second object of the present invention is to provide a bifunctional electrode, the surface of which is modified with the above-mentioned nitrogen-doped carbon nanotube hollow polyhedron material.

[0028] The bifunctional electrode is prepared by the following method:

[0029] (A) A nitrogen-doped carbon nanotube hollow polyhedron material (NCNHP) is prepared into a suspension in water, and then drop-coated on the surface of a clean and dry glassy carbon electrode (GCE). After drying, a Nafion solution is drop-coated on the electrode surface, and after drying, the bifunctional electrode (NCNHP / GCE) is obtained.

[0030] Preferably, the concentration of the Nafion solution is 0.5 wt %.

[0031] The third object of the present invention is to provide application of the bifunctional electrode in H2O2 detection.

[0032] The third object of the present invention is to provide a glucose sensor, which is an electrode whose surface is modified with the above-mentioned nitrogen-doped carbon nanotube hollow polyhedron material and glucose oxidase (GOx).

[0033] The glucose sensor is prepared by the following method:

[0034] (B) A nitrogen-doped carbon nanotube hollow polyhedron material (NCNHP) is prepared into a suspension in water, and then drop-coated on the surface of a clean and dry glassy carbon electrode (GCE). After drying, a glucose oxidase (GOx) solution is drop-coated on the electrode surface. After drying, a Nafion solution is drop-coated on the electrode surface. After drying, the glucose sensor (NCNHP / GOx / GCE) is obtained.

[0035] The fourth object of the present invention is to provide an enzyme biofuel cell, wherein the anode of the enzyme biofuel cell is a hydrophilic carbon material modified with the above-mentioned nitrogen-doped carbon nanotube hollow polyhedron material and glucose oxidase (GOx), or the cathode of the enzyme biofuel cell is a hydrophilic carbon material modified with the above-mentioned nitrogen-doped carbon nanotube hollow polyhedron material.

[0036] The anode is prepared by the following method:

[0037] (C) A nitrogen-doped carbon nanotube hollow polyhedron material (NCNHP) is prepared into a suspension in water, and then drop-coated on the surface of a clean, dry hydrophilic carbon material. After drying, a glucose oxidase (GOx) solution is drop-coated on the surface of the hydrophilic carbon material. After drying, a Nafion solution is drop-coated on the surface of the hydrophilic carbon material. After drying, the anode is obtained.

[0038] The cathode is prepared by the following method:

[0039] (D) A nitrogen-doped carbon nanotube hollow polyhedron material (NCNHP) is prepared into a suspension in water, and then drop-coated on the surface of a clean, dry hydrophilic carbon material. After drying, a Nafion solution is drop-coated on the surface of the hydrophilic carbon material, and the cathode is obtained after drying.

[0040] Preferably, the hydrophilic carbon material is hydrophilic carbon paper (CP). More preferably, the hydrophilic carbon paper is in a size of 1×1 cm.

[0041] Preferably, the anode and cathode chambers of the enzyme biofuel cell are separated by a Nafion 211 membrane, the anolyte is a buffer solution containing glucose saturated with N2, and the cathode solution is a buffer solution saturated with O2. The concentration of glucose in the anolyte is 100 mM.

[0042] Preferably, the buffer solution is 0.1M PBS buffer solution with a pH of 7.4.

[0043] Preferably, the concentration of NCNHP suspension is 4-6 mg / mL, and the modified volume of the electrode or hydrophilic carbon material surface is 10 μL; the modified volume of Nafion solution on the electrode or hydrophilic carbon material surface is 5 μL; the preferred NCNHP suspension concentration is 5 mg / mL.

[0044] Preferably, the concentration of the glucose oxidase (GOx) solution is 20 mg / mL, and the modified volume dripped on the surface of the electrode or hydrophilic carbon material is 4 to 10 μL; the preferred dripping volume of the glucose oxidase solution is 6 μL.

[0045] During the chronoamperometric test of the glucose sensor or enzyme biofuel cell, a 0.1 M PBS solution with a pH of 7.4 was used, the working potential was 0.6 V, the counter electrode was a platinum wire electrode, and the reference electrode was an Ag / AgCl electrode.

[0046] The linear sweep voltammetry method was used to test the performance of the enzyme biofuel cell at a sweep rate of 10 mV / s.

[0047] The detection range of the bifunctional electrode prepared by the present invention as a H2O2 sensor is 0.02-15.1 mM, and the sensitivity is 364.18 μAmM -1 cm -2 , the detection limit is 0.12μM; the detection range of the glucose sensor is 0.02~46.6mM, and the sensitivity is 95.64μAmM -1 cm -2 , the detection limit is 0.54μM; the maximum open circuit voltage of the enzyme biofuel cell is 0.423V, and the maximum power density is 3.70μW / cm -2 .

[0048] The present invention adopts high-temperature pyrolysis of ZIF-8@ZIF-67 core-shell structured precursor material to prepare NCNHP nanomaterials. A large number of carbon nanotubes are distributed on the surface of NCNHP, which is beneficial to improving the electron transfer rate of the electrode. NCNHP has the characteristics of large specific surface area, high porosity and abundant active sites, which plays an important role in improving the sensitivity and linear range of the sensor and building a high-performance enzyme biofuel cell.

[0049] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0050] The present invention uses ZIF-8@ZIF-67 with a core-shell structure as a precursor, which contains rich carbon and nitrogen ligands. During the high-temperature pyrolysis process, Co catalyzes and promotes the generation of carbon nanotubes to form N-doped carbon nanotube hollow polyhedrons (NCNHP). And NCNHP also has a certain oxygen reduction ability. Therefore, the MOF-derived carbon based on the core-shell structure constructs sensors and enzyme biofuel cells, which can largely solve the problems in the prior art.

[0051] (1) A large number of carbon nanotubes are distributed on the surface of the NCNHP nanomaterial prepared by the present invention, which greatly promotes the electron transfer rate while providing a large number of active sites.

[0052] (2) The H2O2 sensor and glucose sensor constructed based on NCNHP nanomaterials have a wide linear range of 0.02-15.1 mM and 1-54 mM, respectively.

[0053] (3) The H2O2 sensor constructed based on NCNHP nanomaterials has high sensitivity to H2O2 and glucose. The linear correlation equation between the current response and the H2O2 concentration is y = 25.49227C H2O2 +6.72505, R 2 =0.997, the detection limit is 0.12μM; the linear correlation equation between the current response and glucose concentration obtained by the glucose sensor is y=5.50038C glucose +2.05339, R 2 =0.999, and the detection limit is 0.54 μM.

[0054] (4) The NCNHP nanomaterials prepared by the present invention can be used as both cathode and anode materials to construct enzyme biofuel cells, and the maximum open circuit voltage obtained is 0.423 V and the maximum power density is 3.70 μW / cm -2 .

[0055] (5) Compared with other metal-doped MOF-based surface-modified carbon nanotube materials, the present invention obtains N-anchored dispersed single atoms by adjusting the ratio of single metal Co, and produces sufficient available single metal active sites. Compared with multi-metal, the single metal Co-doped material has pyridinic N, pyrrolic N and graphitic N, and also generates more Co-Nx, which is one of the most effective active sites for oxygen reduction reaction. In addition, it also has the advantages of simple synthesis, easy control and lower raw material cost.

[0056] (6) The present invention does not use expensive precious metal nanomaterials, has the advantages of low-cost raw materials, simple preparation and easy use, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 It is a schematic diagram of the preparation process of NCNHP, H2O2 sensor and glucose sensor in Example 1 of the present invention.

[0058] Figure 2 These are scanning electron microscope (SEM) images and transmission electron microscope (TEM) images of each ZIF-8@ZIF-67 prepared in Example 1, wherein a), c), e), g) and i) are SEM images of ZIF-8@ZIF-67-1, ZIF-8@ZIF-67-2, ZIF-8@ZIF-67-3, ZIF-8@ZIF-67-4 and ZIF-8@ZIF-67-5 materials, respectively; b), d), f), h) and j) are TEM images of ZIF-8@ZIF-67-1, ZIF-8@ZIF-67-2, ZIF-8@ZIF-67-3, ZIF-8@ZIF-67-4 and ZIF-8@ZIF-67-5 materials, respectively.

[0059] Figure 3 These are the SEM images and TEM images of each NCNHP prepared in Example 1, wherein a), c), e), g), and i) are the SEM images of NCNHP-1, NCNHP-2, NCNHP-3, NCNHP-4 and NCNHP-5 materials, respectively; b), d), f), h) and j) are the TEM images of NCNHP-1, NCNHP-2, NCNHP-3, NCNHP-4 and NCNHP-5 materials, respectively.

[0060] Figure 4 It is the X-ray diffraction pattern (XRD) of each NCNHP prepared in Example 1.

[0061] Figure 5 It is the N2 adsorption-desorption isotherm and pore size distribution curve of NCNHP-4 prepared in Example 1.

[0062] Figure 63 are the time-current curves of the sensors constructed by each NCNHP prepared in Example 1, wherein a) is the time-current curve of the H2O2 sensors constructed by NCNHP-1 / GCE, NCNHP-2 / GCE, NCNHP-3 / GCE, NCNHP-4 / GCE and NCNHP-5 / GCE when H2O2 is continuously added to the PBS buffer solution at a fixed potential of 0.6V; b) is the time-current curve of the glucose sensors constructed by NCNHP-1 / GOx / GCE, NCNHP-2 / GOx / GCE, NCNHP-3 / GOx / GCE, NCNHP-4 / GOx / GCE and NCNHP-5 / GOx / GCE when glucose is continuously added to the PBS buffer solution at a fixed potential of 0.6V.

[0063] Figure 7 These are the SEM images and TEM images of each NCNHP prepared in Example 2. a), c) and e) are the SEM images of NCNHP-900, NCNHP-920 and NCNHP-960 materials, respectively; b), d) and f) are the TEM images of NCNHP-900, NCNHP-920 and NCNHP-960 materials, respectively.

[0064] Figure 8 2 are the time-current curves of the sensors constructed by each NCNHP prepared in Example 2, wherein a) is the time-current curve of the H2O2 sensors constructed by NCNHP-900 / GCE, NCNHP-920 / GCE and NCNHP-960 / GCE when H2O2 is continuously added to the PBS buffer solution at a fixed potential of 0.6V; b) is the time-current curve of the glucose sensors constructed by NCNHP-900 / GOx / GCE, NCNHP-920 / GOx / GCE and NCNHP-960 / GOx / GCE when glucose is continuously added to the PBS buffer solution at a fixed potential of 0.6V.

[0065] Fig. 9 Graph showing the polarization curve and power density output curve of the enzyme biofuel cell constructed in Example 3. DETAILED DESCRIPTION

[0066] Below in conjunction with specific examples, the present invention is described in further detail.Should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0067] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0068] Example 1

[0069] (1) Take 80mmol 2-methylimidazole and 5mmol Zn(CH3COO)2·2H2O, dissolve them in 50mL pure water respectively, mix them and stir them at room temperature for 30min, collect the precipitate by centrifugation, wash it with pure water three times, and dry it in an oven at 60℃ for 8h. The white powder obtained is ZIF-8.

[0070] (2) 0.25 g ZIF-8, 5.634 g 2-methylimidazole and different amounts of Co(NO3)2·6H2O were dissolved in 50 mL methanol respectively. Then, the ZIF-8 solution and Co(NO3)2·6H2O were mixed and ultrasonicated for 3 min to form a uniform mixed solution. Then, the 2-methylimidazole solution was slowly poured into the mixed solution and stirred at room temperature for 24 h. The precipitate was collected by centrifugation and washed with methanol for 3 times. It was dried in an oven at 60 °C for 6 h. The purple powder obtained was ZIF-8@ZIF-67.

[0071] The amounts of Co(NO3)2·6H2O used were 0.530 g, 2.648 g, 5.292 g, 7.945 g and 10.593 g, and the obtained purple powders were named ZIF-8@ZIF-67-1, ZIF-8@ZIF-67-2, ZIF-8@ZIF-67-3, ZIF-8@ZIF-67-4 and ZIF-8@ZIF-67-5, respectively.

[0072] (3) The obtained purple powders ZIF-8@ZIF-67-1, ZIF-8@ZIF-67-2, ZIF-8@ZIF-67-3, ZIF-8@ZIF-67-4 and ZIF-8@ZIF-67-5 were placed in a tubular furnace in a nitrogen atmosphere, heated to 920°C at a heating rate of 5°C / min, and pyrolyzed for 2 h. The obtained black powders were acid-washed, washed with water to neutrality, and dried. The final products were recorded as NCNHP-1, NCNHP-2, NCNHP-3, NCNHP-4 and NCNHP-5.

[0073] (4) The five NCNHPs obtained above were dispersed in water to prepare a 5 mg / mL suspension; the glassy carbon electrode was polished into a mirror surface using alumina powder on a polishing cloth, and ultrasonically cleaned alternately with pure water and anhydrous ethanol, blown dry with nitrogen, 10 μL of NCNHP suspension was drop-coated on the surface of the glassy carbon electrode, and after drying at room temperature, 5 μL of 0.5% wt Nafion solution was drop-coated on the electrode surface and dried, and the electrode was slowly rinsed with pure water. The samples were recorded as NCNHP-1 / GCE, NCNHP-2 / GCE, NCNHP-3 / GCE, NCNHP-4 / GCE and NCNHP-5 / GCE, respectively.

[0074] (5) The glassy carbon electrode was polished into a mirror surface using alumina powder on a polishing cloth, and then ultrasonically cleaned with pure water and anhydrous ethanol alternately, dried with nitrogen gas, and 10 μL of 5 mg / mL NCNHP suspension was drop-coated on the surface of the glassy carbon electrode. After drying at room temperature, 6 μL of 20 mg / mL glucose oxidase solution was drop-coated on the electrode surface and dried at 4°C. Finally, 5 μL of 0.5% wt Nafion solution was drop-coated on the electrode surface and dried at 4°C. The electrode was slowly rinsed with pure water and recorded as NCNHP-1 / GOx / GCE, NCNHP-2 / GOx / GCE, NCNHP-3 / GOx / GCE, NCNHP-4 / GOx / GCE and NCNHP-5 / GOx / GCE, respectively.

[0075] (6) The obtained ZIF-8@ZIF-67 and NCNHP were physically characterized. The SEM and TEM images of ZIF-8@ZIF-67-1, ZIF-8@ZIF-67-2, ZIF-8@ZIF-67-3, ZIF-8@ZIF-67-4 and ZIF-8@ZIF-67-5 were obtained. Figure 2 ) shows that ZIF-8@ZIF-67 prepared with different ratios all present a dodecahedral structure with a size of about 500 nm. SEM and TEM images of NCNHP-1, NCNHP-2, NCNHP-3, NCNHP-4 and NCNHP-5 ( Figure 3 ) showed that NCNHP maintained the dodecahedral structure of the precursor ZIF-8@ZIF-67, but the inside was hollow and a large number of carbon nanotubes were distributed on the surface of the material; NCNHP-4( Figure 3 a) and Figure 3 b)) uniform morphology and large number of carbon nanotubes. The crystal phases of NCNHP-1, NCNHP-2, NCNHP-3, NCNHP-4 and NCNHP-5 catalysts were studied by XRD measurement ( Figure 4 ), the relatively sharp peak at 25.91° is attributed to the (002) plane of graphite carbon, and the two peaks at 44.4° and 51.5° correspond to the (111) and (200) planes of the crystal plane, respectively. The XRD spectrum shows that the diffraction peaks of the sample increase with the addition of the ligand Co 2+ The crystallinity of the material increases with the increase of Co 2+ The diffraction peak intensity of sample NCNHP-4 is the best.

[0076] From the N2 adsorption-desorption isotherm and pore size distribution curve ( Figure 5) It can be seen that the pore size distribution of the prepared NCNHP-4 is mainly between 10 and 50 nm. The larger number of mesopores is beneficial to improving the enzyme fixation efficiency and stability while maintaining good electrochemical properties; the dodecahedral material has a high degree of symmetry, a strong lattice and good chemical stability, the hollow structure improves the mass transfer efficiency, and the larger pore size has good biocompatibility for the enzyme.

[0077] The above characteristics provide the sensor with a large specific surface area and a good electron transfer rate, thereby effectively improving the performance of the sensor; among them, the H2O2 sensor and glucose sensor constructed by NCNHP-4 have the best performance. The performance of the sensors constructed by each material is shown in Table 1.

[0078] Table 1 Performance of H2O2 sensor and glucose sensor constructed by materials with different ratios

[0079]

[0080] The H2O2 sensor constructed by NCNHP-4 shows that the response current increases with the increase of H2O2 concentration, and shows a good linear relationship in the concentration range of 0.02-15.1 mM. The linear correlation equation is y=25.49227C H2O2 +6.72505, R 2 =0.997, sensitivity is 364.18μAmM -1 cm -2 The detection limit is 0.12μM. The glucose sensor constructed by NCNHP-4 shows that the response current increases with the increase of glucose concentration, and shows a good linear relationship in the concentration range of 0.02-46.6mM. The linear correlation equation is y=6.69473C glucose +8.23971, R 2 =0.996, sensitivity is 95.64μAmM -1 cm -2 , the detection limit was 0.54μM.

[0081] Example 2

[0082] (1) The ZIF-8@ZIF-67-4 precursor prepared according to the above Example 1 was placed in a tubular furnace in a nitrogen atmosphere and heated to 900°C, 920°C and 960°C at a heating rate of 5°C / min, respectively, and pyrolyzed for 2 h. The obtained black powder was acid-washed and then dried. The final products were NCNHP-900, NCNHP-920 and NCNHP-960.

[0083] (2) A H2O2 sensor and a glucose sensor were constructed according to steps (4) and (5) in the above Example 1; for the H2O2 sensor, the electrodes modified by NCNHP-900, NCNHP-920 and NCNHP-960 were denoted as NCNHP-900 / GCE, NCNHP-920 / GCE and NCNHP-960 / GCE, respectively; for the glucose sensor, they were denoted as NCNHP-900 / GOx / GCE, NCNHP-920 / GOx / GCE and NCNHP-960 / GOx / GCE, respectively.

[0084] The results are as follows Figure 6 As shown in Figure 2, the NCNHP prepared at different temperatures all present a dodecahedral structure with a hollow structure inside, a size of about 500 nm, and a large number of carbon nanotubes distributed on the surface; as shown in Table 2, the H2O2 sensor and glucose sensor constructed with NCNHP-920 have the best performance.

[0085] Table 2 Performance of H2O2 sensor and glucose sensor constructed by NCNHP prepared at different temperatures

[0086]

[0087] The H2O2 sensor constructed by NCNHP-920 shows that the response current increases with the increase of H2O2 concentration, and shows a good linear relationship in the concentration range of 0.02-15.1 mM. The linear correlation equation is y=25.49227C H2O2 +6.72505, R 2 =0.997, sensitivity is 364.18μAmM -1 cm -2 The detection limit is 0.12μM. The glucose sensor constructed by NCNHP-920 shows that the response current increases with the increase of glucose concentration, and shows a good linear relationship in the concentration range of 0.02-46.6mM. The linear correlation equation is y=6.69473C glucose +8.23971, R 2 =0.996, sensitivity is 95.64μAmM -1 cm -2 , the detection limit was 0.54μM.

[0088] Example 3

[0089] (1) NCNHP was prepared by the same method as that used in Example 2 to prepare NCNHP-920. (2) Construction of high-performance enzyme biofuel cell based on NCNHP: Cut hydrophilic carbon paper (CP) into 1×1 cm, connect them with titanium wire, wash them with anhydrous ethanol and pure water ultrasonically in turn, and dry them in an oven for use; for the preparation of the bioanode, drop the NCNHP suspension on the surface of the carbon paper and dry it at room temperature, then drop the glucose oxidase (GOx) solution on the electrode surface and dry it at 4°C, and finally drop the 0.5%wt Nafion solution on the electrode surface and dry it at 4°C, and slowly rinse the electrode with pure water, which is NCNHP / GOx / CP; for the preparation of the cathode, drop the NCNHP suspension on the surface of the carbon paper and dry it at room temperature, finally drop the 0.5%wt Nafion solution on the electrode surface at room temperature and dry it, and slowly rinse the electrode with pure water, which is NCNHP / CP; for the assembly of the battery, the anode and cathode chambers are separated by a Nafion 211 membrane, and the anode liquid is a 0.1M N2-saturated PBS buffer (pH=7.4, containing 100 mM glucose), the cathode liquid is O2-saturated 0.1 M PBS buffer (pH=7.4), and the anode and cathode electrode wires are connected to assemble a battery.

[0090] The results are as follows Figure 7 As shown in Figure 2, the high-performance enzyme biofuel cell constructed based on NCNHP has a maximum open circuit voltage of 0.423 V and a maximum power density of 3.70 μW / cm -2 .

Claims

1. A nitrogen-doped carbon nanotube hollow polyhedron material, characterized in that: The material is prepared by the following method: (1) ZIF-8 with a dodecahedral structure and a cobalt salt are uniformly mixed in a solvent, and then a 2-methylimidazole solution is slowly added to react to obtain a precursor material ZIF-8@ZIF-67 with a core-shell structure; the amount ratio of ZIF-8, 2-methylimidazole, and cobalt salt is 0.2-0.5 g: 5-10 g: 1.7-34 mmol; (2) The precursor material ZIF-8@ZIF-67 is pyrolyzed at high temperature in an inert gas, and then acid-washed and then washed to neutrality to obtain the nitrogen-doped carbon nanotube hollow polyhedron material.

2. The nitrogen-doped carbon nanotube hollow polyhedron material according to claim 1, characterized in that: The method for uniform mixing in step (1) is ultrasonic treatment.

3. The nitrogen-doped carbon nanotube hollow polyhedron material according to claim 1, characterized in that: The high temperature pyrolysis described in step (2) is: The temperature is raised to 900-960°C at a heating rate of 2-10°C / min, and the pyrolysis is performed for 1.5-2.5h. More preferably, the high-temperature pyrolysis is: the temperature is raised to 920°C at a heating rate of 5°C / min, and the pyrolysis is performed for 2h.

4. A bifunctional electrode, characterized in that: The bifunctional electrode is surface-modified with the nitrogen-doped carbon nanotube hollow polyhedron material described in claim 1.

5. Use of the bifunctional electrode according to claim 4 in H2O2 detection.

6. A glucose sensor, characterized in that: The glucose sensor is an electrode whose surface is modified with the nitrogen-doped carbon nanotube hollow polyhedron material according to claim 1 and glucose oxidase.

7. The glucose sensor according to claim 6, characterized in that The glucose sensor is prepared by the following method: (B) A nitrogen-doped carbon nanotube hollow polyhedron material is prepared into a suspension in water, and then drop-coated on the clean and dry surface of a glassy carbon electrode. After drying, a glucose oxidase solution is drop-coated on the electrode surface. After drying, a Nafion solution is drop-coated on the electrode surface. After drying, the glucose sensor is obtained.

8. An enzyme biofuel cell, characterized in that: The anode of the enzyme biofuel cell is a hydrophilic carbon material modified with the nitrogen-doped carbon nanotube hollow polyhedron material of claim 1 and glucose oxidase, or the cathode of the enzyme biofuel cell is a hydrophilic carbon material modified with the nitrogen-doped carbon nanotube hollow polyhedron material of claim 1.

9. The enzyme biofuel cell according to claim 8, characterized in that: The anode is prepared by the following method: (C) A nitrogen-doped carbon nanotube hollow polyhedron material is prepared into a suspension in water, and then drop-coated on the surface of a clean, dry hydrophilic carbon material. After drying, a glucose oxidase solution is drop-coated on the surface of the hydrophilic carbon material. After drying, a Nafion solution is drop-coated on the surface of the hydrophilic carbon material. After drying, the anode is obtained.

10. The enzyme biofuel cell according to claim 8, characterized in that: The cathode is prepared by the following method: (D) A nitrogen-doped carbon nanotube hollow polyhedron material is prepared into a suspension in water, and then drop-coated on the surface of a clean, dry hydrophilic carbon material. After drying, a Nafion solution is drop-coated on the surface of the hydrophilic carbon material, and the cathode is obtained after drying.

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