Oxygen-containing functional group modified cobalt-based carbon nanotube as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of water treatment, and discloses an oxygen-containing functional group modified cobalt-based carbon nanotube as well as a preparation method and application thereof. The preparation method comprises the following steps: mixing and stirring functionalized carbon nanotubes, cobalt salt, cyanuric acid, melamine and a solvent, and then performing centrifugal separation, washing and drying to obtain a precursor; calcining the precursor in a protective atmosphere, and then pickling to obtain the oxygen-containing functional group modified cobalt-based carbon nanotube. Cobalt nitrate is used as a cobalt source, cobalt exists in the form of ions, in the calcining process, cobalt is embedded into a carbon nano tube by means of nitrogen of melamine, cobalt monoatoms exist, cobalt clusters are generated, oxygen-containing functional groups and the cobalt clusters have a regulation and control effect on a charge structure of an active center of the cobalt monoatoms, and the oxygen-containing functional groups and the cobalt clusters have a regulation and control effect on the active center of the cobalt monoatoms. The electric charge density of a cobalt monatomic active center is weakened together, and the binding energy to an intermediate OOH is regulated and controlled, so that the material is a 2e--ORR electrocatalyst with high activity and high selectivity.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, and in particular to a cobalt-based carbon nanotube modified with an oxygen-containing functional group, and a preparation method and application thereof. Background Art

[0002] As a valuable oxidant, hydrogen peroxide (H2O2) has been widely used in wastewater treatment, chemical synthesis, papermaking, disinfection, etc. The industrial production of H2O2 mainly relies on the large-scale anthraquinone method, which not only requires a large amount of energy input, but also continuously produces organic waste. The electrochemical oxygen reduction reaction (ORR) is a selective two-electron pathway (O2+2H + +2e - →H2O2, E0 = 0.68V) to generate H2O2, which has the advantages of sustainable operation, mild conditions, and on-site green synthesis. However, how to speed up 2e - -ORR to drive the electrochemical process by slow kinetics while suppressing the competing 4e - Pathway (O2+4H + +4e - →2H2O, E0=1.23V), which poses a huge challenge to the design of efficient and highly selective electrocatalysts and has scientific significance and application value. Summary of the invention

[0003] The purpose of the present invention is to provide a cobalt-based carbon nanotube modified with an oxygen-containing functional group and a preparation method and application thereof, so as to solve the problems of low efficiency and poor selectivity of the existing catalyst in catalyzing the generation of H2O2.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides a method for preparing cobalt-based carbon nanotubes modified with oxygen-containing functional groups, comprising the following steps:

[0006] Functionalized carbon nanotubes, cobalt salt, cyanuric acid, melamine and solvent are mixed to obtain a precursor solution; the precursor solution is stirred, centrifuged, washed and dried to obtain a precursor; the precursor is calcined under a protective atmosphere to obtain cobalt-based carbon nanotubes modified with oxygen-containing functional groups;

[0007] Wherein, the functionalized carbon nanotube is one of carboxylated carbon nanotube, hydroxylated carbon nanotube and carboxylated carbon nanotube treated with strong acid.

[0008] Preferably, in the above method for preparing cobalt-based carbon nanotubes modified with oxygen-containing functional groups, the method for preparing the carboxylated carbon nanotubes treated with strong acid comprises: subjecting the carboxylated carbon nanotubes to a heat treatment with a mixed strong acid.

[0009] Preferably, in the above method for preparing cobalt-based carbon nanotubes modified with oxygen-containing functional groups, in the method for preparing acid-treated carboxylated carbon nanotubes, the mixed acid solution is a mixture of concentrated nitric acid and concentrated sulfuric acid.

[0010] Preferably, in the above method for preparing cobalt-based carbon nanotubes modified with oxygen-containing functional groups, the mass ratio of the functionalized carbon nanotubes, cobalt salt, cyanuric acid and melamine is 0.1-0.3: 0.4-0.6: 0.8-1.3: 0.8-1.2.

[0011] Preferably, in the above method for preparing cobalt-based carbon nanotubes modified with oxygen-containing functional groups, the solvent is a mixture of ethanol and water.

[0012] Preferably, in the above method for preparing cobalt-based carbon nanotubes modified with oxygen-containing functional groups, the stirring time is 20 to 30 hours.

[0013] Preferably, in the above method for preparing cobalt-based carbon nanotubes modified with oxygen-containing functional groups, the calcination temperature is 750-850° C.; and the calcination time is 3-4 hours.

[0014] Preferably, in the above method for preparing cobalt-based carbon nanotubes modified with oxygen-containing functional groups, acid washing is further performed after the calcination.

[0015] The invention also provides a method for preparing a cobalt-based carbon nanotube modified with an oxygen-containing functional group, and obtains a cobalt-based carbon nanotube modified with an oxygen-containing functional group.

[0016] The present invention also provides a cobalt-based carbon nanotube modified with oxygen-containing functional groups in catalysis 2e - -Application of ORR in producing H2O2 or treating organic pollutants in wastewater.

[0017] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) In the cobalt-based carbon nanotubes modified with oxygen-containing functional groups of the present invention, cobalt nitrate is used as the cobalt source, and cobalt exists in the form of ions. During the calcination process, cobalt is embedded into the carbon nanotubes with the help of nitrogen from melamine, and both cobalt single atoms and cobalt clusters are generated. In the prior art, the cobalt element synthesized using cobalt phthalocyanine as the cobalt source exists only in the form of single atoms. In the present invention, the oxygen-containing functional groups and cobalt clusters have a regulating effect on the charge structure of the cobalt single atom active center, jointly weakening the charge density of the cobalt single atom active center, regulating the binding energy to the intermediate OOH, and making the material a 2e with high activity and high selectivity. - -ORR electrocatalyst.

[0019] (2) The cobalt-based carbon nanotubes modified with oxygen-containing functional groups of the present invention have high stability and can be used for long-term stable electroproduction of H2O2 experiments. Moreover, the electrocatalyst of the present invention can be used for in-situ degradation of pollutants after producing H2O2. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the description of the embodiments or the prior art are briefly introduced below.

[0021] Figure 1 EDS maps of Co@CNT (COC) prepared in Example 1;

[0022] Figure 2 XPS O1s peaks of Co@CNT(COC), Co@CNT(C-OH), and Co@CNT(C=O) prepared in Examples 1 to 3;

[0023] Figure 3 AC-TEM scanning image of Co@CNT (COC) prepared in Example 1;

[0024] Figure 4 Graph showing the 1-hour production of H2O2 in a flow cell using Co@CNT(COC) prepared in Example 1 and Co@CNT(CH) prepared in Comparative Example 1 as cathode electrodes;

[0025] Figure 5 This is a stability test diagram of the Co@CNT (COC) prepared in Example 1 as a cathode electrode in a flow cell to produce H2O2 for 100 hours;

[0026] Figure 6 The in-situ degradation diagram of nine common pollutants in the flow cell using Co@CNT (COC) prepared in Example 1 as the cathode electrode; MB represents methylene blue, RhB represents rhodamine B, MO represents methyl orange, CBZ represents carbamazepine, CIP represents ciprofloxacin, Ph represents phenol, TC represents tetracycline, SMZ represents sulfamethoxazole, and SDZ represents sulfadiazine;

[0027] Figure 7 The 1-hour production graph of H2O2 in a flow cell using Co@CNT(C-OH) prepared in Example 2 and Co@CNT(CH) prepared in Comparative Example 1 as cathode electrodes;

[0028] Figure 8 Graph showing the 1 h production of H2O2 in a flow cell using Co@CNT (C=O) prepared in Example 3 and Co@CNT (CH) prepared in Comparative Example 1 as cathode electrodes. DETAILED DESCRIPTION

[0029] The present invention provides a method for preparing cobalt-based carbon nanotubes modified with oxygen-containing functional groups, comprising the following steps:

[0030] Functionalized carbon nanotubes, cobalt salt, cyanuric acid, melamine and solvent are mixed to obtain a precursor solution; the precursor solution is stirred, centrifuged, washed and dried to obtain a precursor; the precursor is calcined under a protective atmosphere to obtain cobalt-based carbon nanotubes modified with oxygen-containing functional groups.

[0031] In the present invention, the functionalized carbon nanotubes are preferably one of carboxylated carbon nanotubes, hydroxylated carbon nanotubes, and carboxylated carbon nanotubes treated with strong acid, and are further preferably carboxylated carbon nanotubes treated with strong acid. The carboxylated carbon nanotubes and hydroxylated carbon nanotubes used in the embodiments of the present invention were purchased from Beijing Boyu High-Tech New Materials Technology Co., Ltd., and the models are M3-CH and M3-OH, respectively.

[0032] In the present invention, the cobalt salt is preferably cobalt nitrate hexahydrate.

[0033] In the present invention, the preparation method of the strong acid treated carboxylated carbon nanotubes is preferably: heat treating the carboxylated carbon nanotubes with a mixed strong acid; the dosage ratio of the carboxylated carbon nanotubes and the mixed strong acid is preferably 1g:100mL; the heating temperature is preferably 80°C; the heating time is preferably 1h; and the heating treatment also includes cooling, ethanol centrifugal washing, and drying.

[0034] In the present invention, in the preparation method of the strong acid treated carboxylated carbon nanotubes, the mixed strong acid is preferably a mixture of concentrated nitric acid and concentrated sulfuric acid; the mass fraction of the concentrated nitric acid is preferably 65-68%; the concentration of the concentrated sulfuric acid is preferably 18.4M; the volume ratio of the concentrated nitric acid to the concentrated sulfuric acid is preferably 1:3.

[0035] In the present invention, the mass ratio of the functionalized carbon nanotubes, cobalt salt, cyanuric acid and melamine is preferably 0.1-0.3:0.4-0.6:0.8-1.3:0.8-1.2, and more preferably 0.2:0.582:1.02:1.

[0036] In the present invention, the usage ratio of the functionalized carbon nanotubes to the solvent is preferably 0.1-0.3 g:50-100 mL, and more preferably 0.2 g:90 mL.

[0037] In the present invention, the solvent is preferably a mixture of ethanol and water, and more preferably a mixture of ethanol and water in a volume ratio of 1:1.

[0038] In the present invention, the method for mixing the functionalized carbon nanotubes, cobalt salt, cyanuric acid, melamine and solvent is preferably as follows: dissolving the cobalt salt, cyanuric acid and melamine in one-third volume of the solvent respectively to obtain a cobalt salt solution, a cyanuric acid solution and a melamine solution respectively; then mixing the cobalt salt solution and the melamine solution, adding the functionalized carbon nanotubes, stirring at room temperature at 250 rpm for 20 min, and then adding the cyanuric acid solution.

[0039] In the present invention, the stirring time is preferably 20 to 30 hours, more preferably 22 to 25 hours, and more preferably 24 hours; the stirring speed is preferably 200 to 500 rpm, more preferably 250 to 400 rpm, and more preferably 300 rpm; the stirring temperature is preferably 25°C.

[0040] In the present invention, the rotation speed of the centrifugal separation is preferably 5000-8000 rpm, more preferably 5200-7500 rpm, and more preferably 6000 rpm; the time of the centrifugal separation is preferably 5-10 min, more preferably 5-6 min, and more preferably 5 min.

[0041] In the present invention, the washing is preferably performed using ethanol.

[0042] In the present invention, the drying temperature is preferably 60-80°C, more preferably 60-70°C, and more preferably 60°C; the drying time is preferably 8-16h, more preferably 10-13h, and more preferably 12h.

[0043] In the present invention, the calcination temperature is preferably 750-850°C, more preferably 780-830°C, and more preferably 800°C; the calcination time is preferably 3-4h, and more preferably 3.5h; the calcination heating rate is preferably 1-5°C / min, more preferably 2-5°C / min, and more preferably 3°C / min.

[0044] In the present invention, the protective atmosphere is preferably nitrogen.

[0045] In the present invention, the calcination further includes acid washing.

[0046] In the present invention, the pickling method is preferably: pickling the calcined product with a sulfuric acid solution; the concentration of the sulfuric acid solution is preferably 0.1-2 mol / L, more preferably 0.3-1 mol / L, more preferably 0.5 mol / L; the pickling temperature is preferably 70-80°C, more preferably 75-80°C, more preferably 80°C; the pickling time is preferably 10-14h, more preferably 11-13h, more preferably 12h; the stirring speed of the pickling is preferably 200-400rpm, more preferably 230-300rpm, more preferably 250rpm.

[0047] In the present invention, the acid washing further includes centrifugation, water washing and drying.

[0048] In the present invention, the centrifugal speed is preferably 5000-8000 rpm, more preferably 5500-7000 rpm, and more preferably 6000 rpm; the centrifugal time is preferably 5-10 min, more preferably 5-8 min, and more preferably 5 min.

[0049] In the present invention, the drying temperature is preferably 60 to 80° C., more preferably 60 to 70° C., and more preferably 60° C.; the drying time is preferably 10 to 16 h, more preferably 11 to 14 h, and more preferably 12 h.

[0050] The invention also provides a method for preparing a cobalt-based carbon nanotube modified with an oxygen-containing functional group, and obtains a cobalt-based carbon nanotube modified with an oxygen-containing functional group.

[0051] The present invention also provides a cobalt-based carbon nanotube modified with oxygen-containing functional groups in catalysis 2e - -Application of ORR in producing H2O2 or treating organic pollutants in wastewater.

[0052] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] Example 1

[0054] This embodiment provides a cobalt-based carbon nanotube modified with an oxygen-containing functional group, and the preparation method thereof comprises the following steps:

[0055] (1) Weigh 1 g of carboxylated carbon nanotubes, place them in a mixed acid (25 mL of concentrated nitric acid + 75 mL of concentrated sulfuric acid) and ultrasonicate for 30 min, then heat and stir at 80° C. and reflux through a condenser. After treatment for 1 h, cool to room temperature, wash with ethanol by centrifugation, and dry in an oven at 60° C. to obtain strongly acid-treated carboxylated carbon nanotubes;

[0056] (2) Weigh 0.582 g of cobalt nitrate hexahydrate, 1.02 g of cyanuric acid and 1.00 g of melamine, and dissolve them in a mixture of 30 mL of ethanol and deionized water (the volume ratio of ethanol to deionized water is 1:1) to obtain a cobalt nitrate solution, a cyanuric acid mixture and a melamine mixture; then mix the cobalt nitrate solution with the melamine mixture, add 200 mg of carboxylated carbon nanotubes treated with strong acid, and continue stirring at room temperature at 250 rpm for 20 min to obtain 60 mL of a mixture; add the cyanuric acid mixture to the mixture to obtain 90 mL of a dark gray mixture, and then stir at room temperature at 300 rpm for 24 h to mix it evenly. During the stirring process, seal the beaker with a sealing film to prevent ethanol from volatilizing; after stirring, centrifuge the mixture at 6000 rpm for 5 min using a centrifuge, wash it three times with ethanol, and then dry it in an oven at 60°C for 12 h. After drying, grind it finely with a mortar to obtain a precursor;

[0057] (3) The precursor was transferred into a ceramic boat and calcined at 800°C for 3.5 h in a tube furnace under a nitrogen atmosphere with a heating rate of 3°C / min. After calcination, the precursor was naturally cooled to room temperature under a nitrogen atmosphere, and then the obtained black powder was immersed in a 0.5 mol / L dilute sulfuric acid solution and acid-treated at 80°C and a stirring rate of 250 rpm for 12 h to remove excess impurities and cobalt nanoparticles. After the acid treatment, the precursor was centrifuged at 6000 rpm and then washed with deionized water for 3 times until neutral. The precipitate was collected and dried in an oven at 60°C for 12 h to obtain epoxy group-modified cobalt-based carbon nanotubes, denoted as Co@CNT(COC).

[0058] Comparative Example 1

[0059] This comparative example provides a cobalt-based carbon nanotube, which is specifically referred to in Example 1, except that the carboxylated carbon nanotube is replaced by carbon nanotube, and the carbon nanotube is not subjected to the strong acid treatment of step (1), thereby obtaining a cobalt-based carbon nanotube without oxygen functional group, which is recorded as Co@CNT(CH).

[0060] The EDS image of Co@CNT (COC) prepared in Example 1 is as follows: Figure 1 As shown. Figure 1 It can be seen that oxygen and cobalt are evenly dispersed on the carbon nanotubes, exposing more reactive sites, which is conducive to the occurrence of efficient 2e- -ORR reaction.

[0061] The XPS test of Co@CNT (COC) prepared in Example 1 is as follows Figure 2 As shown. Figure 2 It can be seen that the types of oxygen functional groups on carbon nanotubes are mainly epoxy (COC), and the epoxy group has an excellent regulatory effect on the cobalt active sites coordinated by nitrogen, which is the reason why Co@CNT (COC) can be used as a cathode material to produce high activity and high selectivity 2e - -The important reason for ORR reaction.

[0062] The spherical aberration corrected transmission electron microscope (AC-TEM) scanning results of Co@CNT (COC) prepared in Example 1 are as follows: Figure 3 As shown. Figure 3 It can be seen that single cobalt atoms and cobalt clusters coexist on the surface of carbon nanotubes. Single cobalt atoms are circled by red dashed circles, and cobalt clusters are circled by green dashed circles.

[0063] The method for preparing the cathode electrode with Co@CNT(COC) prepared in Example 1 is as follows: weigh 5 mg of Co@CNT(COC), dissolve it in a mixture of 0.98 mL of deionized water and 0.02 mL of naphthol, and ultrasonically treat it at a frequency of 25 kHz for 1 hour to obtain a dispersion, and apply 100 uL of the dispersion to a gas diffusion electrode (GDE) of 2 cm×2 cm to prepare a cathode electrode. The cathode electrode is prepared by the same method with Co@CNT(CH) prepared in Comparative Example 1, except that Co@CNT(COC) is replaced by Co@CNT(CH).

[0064] The cathode electrodes prepared from Co@CNT (COC) of Example 1 and Co@CNT (CH) of Comparative Example 1 were used as cathodes of the flow cell for H2O2 electroproduction. The electrochemical H2O2 production performance test was carried out in constant current mode (CP) at a test current density of 50 mA / cm 2 , 50mL 0.5mol / L H2SO4 was used for both the cathode and anode liquids, the cathode and anode in the flow cell were separated by a proton exchange membrane (PEM), the electrolyte flow rate was 3.637mL / min, and the 1h production of H2O2 was as follows Figure 4 As shown. Figure 4 It can be seen that the 1hH2O2 concentration of Co@CNT(COC) reaches 800mg / L, which is higher than 140mg / L of Co@CNT(CH), and 5.71 times that of Co@CNT(CH).

[0065] The cathode electrode prepared from Co@CNT (COC) of Example 1 was used as the cathode of the flow cell for H2O2 electroproduction; the electrochemical stability test was carried out in constant current mode (CP) with a test current density of 50 mA / cm 2 , 0.5 mol / L H2SO4 was used for both the cathode liquid and the anode liquid, the cathode and the anode in the flow cell were separated by a proton exchange membrane (PEM), the electrolyte flow rate was 5 mL / h, the test time was 100 h, and the stability test results were as follows Figure 5 As shown. Figure 5 It can be seen that in the 120-h long-term experiment, the flow cell voltage remained basically constant, and continuously and stably produced about 4800 ppm of H2O2.

[0066] The cathode electrode prepared by Co@CNT (COC) in Example 1 was used as the cathode of the flow cell to perform in-situ degradation of pollutants in constant current mode (CP) at a current density of 50 mA / cm 2 , 50mL 0.5mol / L H2SO4 was used for both the cathode liquid and the anode liquid. The cathode and anode in the circulation cell were separated by a proton exchange membrane (PEM). The electrolyte flow rate was 3.637mL / min. Pollutants were added to the cathode liquid for circulation. Broad-spectrum dyes (methylene blue, rhodamine B, methyl orange) were added at a concentration of 10mg / L, drugs (carbamazepine, ciprofloxacin, phenol) and antibiotics (tetracycline, sulfamethoxazole, sulfadiazine) were added at a concentration of 1mg / L, and Fe 2+ The addition amount was 1mmol / L; the degradation results were as follows Figure 6 As shown. Figure 6 It can be seen that after 30 to 50 minutes of degradation, a relatively high removal rate was achieved.

[0067] Example 2

[0068] This embodiment provides a cobalt-based carbon nanotube modified with an oxygen-containing functional group, and the preparation method thereof comprises the following steps:

[0069] (1) Weigh 0.582 g of cobalt nitrate hexahydrate, 1.02 g of cyanuric acid and 1.00 g of melamine, and dissolve them in a mixture of 30 mL of ethanol and deionized water (the volume ratio of ethanol to deionized water is 1:1) to obtain a cobalt nitrate solution, a cyanuric acid mixture and a melamine mixture; then mix the cobalt nitrate solution with the melamine mixture, add 200 mg of hydroxylated carbon nanotubes, and continue stirring at room temperature at 250 rpm for 20 min to obtain 60 mL of a mixture; add the cyanuric acid mixture to the mixture to obtain 90 mL of a dark gray mixture, and then stir at room temperature at 300 rpm for 24 h to mix it evenly. During the stirring process, seal the beaker with a sealing film to prevent ethanol from volatilizing; after the stirring is completed, use a centrifuge to centrifuge the mixture at 6000 rpm for 5 min, wash it with ethanol three times, and then dry it in an oven at 60°C for 12 h. After drying, use a mortar to grind it finely to obtain a precursor;

[0070] (2) The precursor was transferred into a ceramic boat and calcined at 800°C for 3.5 h in a tube furnace under a nitrogen atmosphere with a heating rate of 3°C / min. After calcination, the precursor was naturally cooled to room temperature under a nitrogen atmosphere, and then the obtained black powder was immersed in a 0.5 mol / L dilute sulfuric acid solution and acid-treated at 80°C and a stirring rate of 250 rpm for 12 h to remove excess impurities and cobalt nanoparticles. After the acid treatment, the precursor was centrifuged at 6000 rpm and then washed with deionized water for 3 times until neutral. The precipitate was collected and dried in an oven at 60°C for 12 h to obtain cobalt-based carbon nanotubes modified with hydroxyl groups, which were recorded as Co@CNT(C-OH).

[0071] The XPS test of Co@CNT(C-OH) prepared in Example 2 is as follows Figure 2 As shown. Figure 2 It can be seen that the oxygen functional groups on the carbon nanotubes are mainly hydroxyl groups (C-OH).

[0072] The Co@CNT(C-OH) prepared in Example 2 was used as a cathode electrode in a flow cell for H2O2 electroproduction. The electrochemical H2O2 production performance test was carried out in constant current mode (CP) at a current density of 50 mA / cm 2 , 50mL 0.5mol / L H2SO4 was used for both the cathode and anode liquids, the cathode and anode in the flow cell were separated by a proton exchange membrane (PEM), the electrolyte flow rate was 3.637mL / min, and the 1h production of H2O2 was as follows Figure 7 As shown. Figure 7 It can be seen that the 1h H2O2 concentration of Co@CNT(C-OH) reaches 270mg / L, which is 1.93 times that of Co@CNT(CH).

[0073] Example 3

[0074] This embodiment provides a cobalt-based carbon nanotube modified with an oxygen-containing functional group, and the preparation method thereof comprises the following steps:

[0075] (1) Weigh 0.582 g of cobalt nitrate hexahydrate, 1.02 g of cyanuric acid and 1.00 g of melamine, and dissolve them in a mixture of 30 mL of ethanol and deionized water (the volume ratio of ethanol to deionized water is 1:1) to obtain a cobalt nitrate solution, a cyanuric acid mixture and a melamine mixture; then mix the cobalt nitrate solution with the melamine mixture, add 200 mg of carboxylated carbon nanotubes, and continue stirring at room temperature at 250 rpm for 20 min to obtain 60 mL of a mixture; add the cyanuric acid mixture to the mixture to obtain 90 mL of a dark gray mixture, and then stir at room temperature at 300 rpm for 24 h to mix it evenly. During the stirring process, seal the beaker with a sealing film to prevent ethanol from volatilizing; after stirring, centrifuge the mixture at 6000 rpm for 5 min using a centrifuge, wash it three times with ethanol, and then dry it in an oven at 60°C for 12 h. After drying, grind it finely with a mortar to obtain a precursor;

[0076] (2) The precursor was transferred into a ceramic boat and calcined at 800°C for 3.5 h in a tube furnace under a nitrogen atmosphere with a heating rate of 3°C / min. After calcination, the precursor was naturally cooled to room temperature under a nitrogen atmosphere, and then the obtained black powder was immersed in a 0.5 mol / L dilute sulfuric acid solution and acid-treated at 80°C and a stirring rate of 250 rpm for 12 h to remove excess impurities and cobalt nanoparticles. After the acid treatment, the precursor was centrifuged at 6000 rpm and then washed with deionized water for 3 times until neutral. The precipitate was collected and dried in an oven at 60°C for 12 h to obtain cobalt-based carbon nanotubes modified with carbonyl oxygen groups, which were recorded as Co@CNT (C=O).

[0077] The XPS detection of Co@CNTC=O) prepared in Example 3 is as follows Figure 2 As shown. Figure 2 It can be seen that the oxygen functional groups on the carbon nanotubes are mainly carbonyl (C=O).

[0078] The Co@CNT (C=O) prepared in Example 3 was used as a cathode electrode in a flow cell for H2O2 electroproduction. The electrochemical H2O2 production performance test was carried out in constant current mode (CP) at a current density of 50 mA / cm 2 , 50mL 0.5mol / L H2SO4 was used for both the cathode and anode liquids, the cathode and anode in the flow cell were separated by a proton exchange membrane (PEM), the electrolyte flow rate was 3.637mL / min, and the 1h production of H2O2 was as follows Figure 8 As shown. Figure 8 It can be seen that the 1h H2O2 concentration of Co@CNT(C=O) reaches 200mg / L, which is 1.42 times that of Co@CNT(CH).

[0079] In summary, the present invention provides a cobalt-based carbon nanotube modified with an oxygen-containing group. In the catalyst, cobalt metal exists as an active site. The incorporation of oxygen functional groups as a second coordination environment cooperates with cobalt clusters to weaken the charge density of the active site. Different oxygen functional groups have different weakening degrees, which optimizes the 2e - -ORR performance, and its ability to degrade pollutants in situ demonstrates its great potential for practical applications.

[0080] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing cobalt-based carbon nanotubes modified with oxygen-containing functional groups, characterized in that: The following steps are involved: Functionalized carbon nanotubes, cobalt salt, cyanuric acid, melamine and solvent are mixed to obtain a precursor solution; the precursor solution is stirred, centrifuged, washed and dried to obtain a precursor; the precursor is calcined under a protective atmosphere to obtain cobalt-based carbon nanotubes modified with oxygen-containing functional groups; Wherein, the functionalized carbon nanotube is one of carboxylated carbon nanotube, hydroxylated carbon nanotube and carboxylated carbon nanotube treated with strong acid.

2. The method for preparing cobalt-based carbon nanotubes modified with oxygen-containing functional groups according to claim 1, characterized in that: The method for preparing the carboxylated carbon nanotubes treated with strong acid comprises: subjecting the carboxylated carbon nanotubes to a heating treatment with a mixed strong acid.

3. The method for preparing cobalt-based carbon nanotubes modified with oxygen-containing functional groups according to claim 2, characterized in that: In the method for preparing acid-treated carboxylated carbon nanotubes, the mixed strong acid is a mixture of concentrated nitric acid and concentrated sulfuric acid.

4. The method for preparing a cobalt-based carbon nanotube modified with an oxygen-containing functional group according to claim 1 or 2, characterized in that: The mass ratio of the functionalized carbon nanotubes, cobalt salt, cyanuric acid and melamine is 0.1-0.3: 0.4-0.6: 0.8-1.3: 0.8-1.

2.

5. The method for preparing cobalt-based carbon nanotubes modified with oxygen-containing functional groups according to claim 4, characterized in that: The solvent is a mixture of ethanol and water.

6. The method for preparing cobalt-based carbon nanotubes modified with oxygen-containing functional groups according to any one of claims 1 to 3, characterized in that: The stirring time is 20 to 30 hours.

7. The method for preparing cobalt-based carbon nanotubes modified with oxygen-containing functional groups according to claim 6, characterized in that: The calcination temperature is 750-850° C. and the calcination time is 3-4 hours.

8. The method for preparing cobalt-based carbon nanotubes modified with oxygen-containing functional groups according to claim 7, characterized in that: The calcination is followed by acid washing.

9. A cobalt-based carbon nanotube modified with an oxygen-containing functional group obtained by the method for preparing a cobalt-based carbon nanotube modified with an oxygen-containing functional group as claimed in any one of claims 1 to 8.

10. The cobalt-based carbon nanotube modified with oxygen-containing functional groups as claimed in claim 9 is used for catalysis of 2e - -Application of ORR in producing H2O2 or treating organic pollutants in wastewater.

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