Nickel phthalocyanine / carbon nanotube monatomic catalyst as well as preparation method and application thereof

Abstract

The invention discloses a nickel phthalocyanine / carbon nanotube monatomic catalyst as well as a preparation method and application thereof. The nickel phthalocyanine / carbon nanotube monatomic catalyst comprises a multi-walled carbon nanotube and nickel phthalocyanine loaded on the surface of the multi-walled carbon nanotube. The nickel phthalocyanine / carbon nanotube monatomic catalyst is mainly used for degrading sulfamethoxazole through electron activation of PMS, the degradation rate of the nickel phthalocyanine / carbon nanotube monatomic catalyst reaches up to 93.70% and reaches 90% or above within 15 min, and meanwhile the nickel phthalocyanine / carbon nanotube monatomic catalyst has the good degradation rate for various organic pollutants. The method is suitable for being applied to actual water bodies, and has stability and recyclability.

Description

Technical Field

[0001] The present invention belongs to the technical field of water treatment technology and environmental functional materials, and in particular relates to a nickel phthalocyanine / carbon nanotube single-atom catalyst and a preparation method and application thereof. Background Art

[0002] Sulfonamide antibiotics, a class of highly effective, broad-spectrum antimicrobial drugs, are widely used in pharmaceuticals and personal care products. However, due to their high chemical stability, they are not easily degraded under natural conditions, resulting in large amounts of residues in water, posing potential ecological risks. Furthermore, numerous organic pollutants are also prevalent in various water bodies, further complicating water environmental management. Therefore, efficient, advanced, and novel antibiotic wastewater treatment technologies are urgently needed to address the increasingly severe water safety challenges.

[0003] Advanced oxidation processes (AOPs) are pollutant degradation technologies based on the activation of peroxymonosulfate (PMS) to produce a variety of highly oxidizing substances. They are favored for their simplicity, high efficiency, minimal secondary pollution, and recyclability. In AOPs, single-atom catalysts are often used to activate peroxymonosulfate (PMS) due to their unique catalytic properties in numerous energy conversion reactions, such as oxygen reduction, oxygen evolution, and carbon dioxide reduction. However, single-atom catalysts often suffer from poor electron transfer efficiency, low atom utilization, and weak catalytic selectivity. To optimize catalytic performance, researchers generally modify and increase reactive sites through multi-metal doping strategies or calcination to enhance catalytic activity. However, these methods suffer from atom economy deficiencies and the easy dissolution of metal active sites. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the present invention aims to provide a nickel phthalocyanine / carbon nanotube single-atom catalyst.

[0005] Another object of the present invention is to provide a method for preparing nickel phthalocyanine / carbon nanotube single-atom catalyst.

[0006] Another object of the present invention is to provide an application of nickel phthalocyanine / carbon nanotube single-atom catalyst in activating peroxymonosulfate to degrade pollutants.

[0007] The purpose of the present invention is achieved through the following technical solutions.

[0008] A nickel phthalocyanine / carbon nanotube single-atom catalyst comprises a multi-walled carbon nanotube and nickel phthalocyanine loaded on the surface of the multi-walled carbon nanotube.

[0009] A method for preparing a nickel phthalocyanine / carbon nanotube single-atom catalyst comprises the following steps:

[0010] Multi-walled carbon nanotubes, nickel phthalocyanine, a first solvent and a second solvent are uniformly mixed, and stirred at room temperature of 20-25°C for 24-36 hours to obtain a mixed solution. The mixed solution is sequentially centrifuged, washed, and vacuum-dried to obtain a nickel phthalocyanine / carbon nanotube single-atom catalyst, wherein the ratio of multi-walled carbon nanotubes to nickel phthalocyanine is (0.1-0.5):(0.1-0.5) by mass, and the diameter of the multi-walled carbon nanotubes is 4-20 nm.

[0011] In the above technical solution, the diameter of the multi-walled carbon nanotubes is preferably 8 to 15 nm.

[0012] In the above technical solution, multi-walled carbon nanotubes are dispersed in a first solvent and mixed evenly by ultrasound for 30 to 40 minutes to obtain a nanotube solution; nickel phthalocyanine is dispersed in a second solvent and mixed evenly by ultrasound for 30 to 40 minutes to obtain a nickel phthalocyanine solution; all the nanotube solution is added to the nickel phthalocyanine solution, and stirred at 20 to 25° C. for 24 to 36 hours to obtain a mixed solution.

[0013] In the above technical solution, the first solvent is methanol; the second solvent is methanol.

[0014] In the above technical solution, the mass fraction of the multi-walled carbon nanotubes and the volume fraction of the first solvent is (0.1-0.5):(80-100), the unit of the mass fraction is g, and the unit of the volume fraction is mL.

[0015] In the above technical solution, the mass fraction of nickel phthalocyanine and the volume fraction of the second solvent is (0.1-0.5):(1-5), the unit of the mass fraction is g, and the unit of the volume fraction is mL.

[0016] In the above technical solution, the centrifugal speed is 8000-11000 r / s, and the centrifugal time is 3-5 min.

[0017] In the above technical solution, the washing operation includes: flushing with methanol at least 3 times.

[0018] In the above technical solution, the vacuum drying temperature is 50 to 80° C., and the vacuum drying time is 12 to 24 hours.

[0019] Application of the above nickel phthalocyanine / carbon nanotube single-atom catalyst in activating peroxymonosulfate to degrade pollutants.

[0020] In the above technical solution, the nickel phthalocyanine / carbon nanotube single-atom catalyst activates peroxymonosulfate to produce high-valent metals and singlet oxygen.

[0021] In the above technical solution, the electron transfer process mediated by nickel phthalocyanine / carbon nanotube single-atom catalyst plays a leading role in activating peroxymonosulfate to degrade pollutants.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The nickel phthalocyanine / carbon nanotube single-atom catalyst of the present invention degrades sulfamethoxazole mainly by electron-activated PMS, with a degradation rate of up to 93.70%, and a degradation rate of more than 90% is achieved within 15 minutes. At the same time, the nickel phthalocyanine / carbon nanotube single-atom catalyst has a good degradation rate for various organic pollutants.

[0024] (2) The nickel phthalocyanine / carbon nanotube single-atom catalyst of the present invention is not affected by coexisting ions, is suitable for application in actual water bodies, and has stability and recyclability.

[0025] (3) The preparation method of the present invention utilizes multi-walled carbon nanotubes of different diameters to regulate nickel phthalocyanine, thereby enhancing its ability to activate PMS to degrade pollutants. The preparation method is simple, efficient, and low-cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 X-ray diffraction patterns of the nickel phthalocyanine / carbon nanotube single-atom catalysts prepared in Examples 1 to 4 and the carbon nanotube single-atom catalyst prepared in Comparative Example 1;

[0027] Figure 2 The element distribution on the surface of the nickel phthalocyanine / carbon nanotube single-atom catalyst prepared in Example 3;

[0028] Figure 3 TEM image of nickel phthalocyanine / carbon nanotube single atom catalyst prepared in Example 3;

[0029] Figure 4 Degradation curves of SMX by the nickel phthalocyanine / carbon nanotube single-atom catalysts prepared in Examples 1 to 4 and the carbon nanotube single-atom catalyst prepared in Comparative Example 1;

[0030] Figure 5 Degradation curves of PMS, nickel phthalocyanine / carbon nanotube single atom catalyst prepared in Example 3, and nickel phthalocyanine / carbon nanotube single atom catalyst activated PMS to SMX;

[0031] Figure 6 This is the degradation curve of SMX at different pH values ​​for the nickel phthalocyanine / carbon nanotube single-atom catalyst prepared in Example 3;

[0032] Figure 7 This is the degradation curve of SMX by the nickel phthalocyanine / carbon nanotube single-atom catalyst prepared in Example 3 under different coexisting ions;

[0033] Figure 8 This is the degradation curve of SMX in different water bodies by the nickel phthalocyanine / carbon nanotube single-atom catalyst prepared in Example 3;

[0034] Figure 9 This is the degradation curve of SMX under different cycle times of the nickel phthalocyanine / carbon nanotube single-atom catalyst prepared in Example 3;

[0035] Figure 10 The degradation curves of nickel phthalocyanine / carbon nanotube single-atom catalyst prepared in Example 3 for different pollutants;

[0036] Figure 11 The degradation curves of nickel phthalocyanine / carbon nanotube single-atom catalyst prepared in Example 3 to SMX under different quenching agents;

[0037] Figure 12 This is the electron paramagnetic resonance spectrum of the nickel phthalocyanine / carbon nanotube single atom catalyst prepared in Example 3, where (a) is O2 - Electron paramagnetic resonance spectrum, (b) 1 O2 electron paramagnetic resonance spectrum;

[0038] Figure 13 The chronoamperometric curves of a standard three-electrode system using the nickel phthalocyanine / carbon nanotube single-atom catalysts prepared in Examples 1 to 4 and the carbon nanotube single-atom catalyst prepared in Comparative Example 1;

[0039] Figure 14 The electrochemical impedance spectroscopy diagrams of the standard three-electrode system are shown using the nickel phthalocyanine / carbon nanotube single-atom catalysts prepared in Examples 1 to 4 and the carbon nanotube single-atom catalyst prepared in Comparative Example 1. DETAILED DESCRIPTION

[0040] The technical solution of the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0041] In the following examples, nickel phthalocyanine (NiPc) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0042] Multi-walled carbon nanotubes (MWCNTs) with diameters of 2-4 nm, 4-8 nm, 8-15 nm, and 15-20 nm were purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.

[0043] In the following examples, before preparing nickel phthalocyanine / carbon nanotube single-atom catalyst, multi-walled carbon nanotubes need to be pretreated. The pretreatment operation includes: placing the multi-walled carbon nanotubes in 6 mol·L -1The precipitated carbon nanotubes were soaked in HCl aqueous solution for 12 h to remove metal impurities, filtered after soaking, washed with deionized water three times, and freeze-dried at -78 °C for 24 h.

[0044] Examples 1 to 4

[0045] A method for preparing a nickel phthalocyanine / carbon nanotube single-atom catalyst comprises the following steps:

[0046] Multi-walled carbon nanotubes were dispersed in a first solvent (methanol) by ultrasonic treatment for 30 minutes and mixed uniformly to obtain a nanotube solution; nickel phthalocyanine was dispersed in a second solvent (methanol) by ultrasonic treatment for 30 minutes and mixed uniformly to obtain a nickel phthalocyanine solution; all the nanotube solution was added to the nickel phthalocyanine solution, stirred at room temperature of 20-25°C for 24 hours to obtain a mixed solution, and the mixed solution was centrifuged at a speed of 11000 r / s for 5 minutes, rinsed with methanol three times, and vacuum dried at 60°C for 12 hours to obtain a nickel phthalocyanine / carbon nanotube single atom catalyst, wherein the ratio of multi-walled carbon nanotubes to nickel phthalocyanine was 0.5:0.1 by mass; the ratio of the mass fraction of multi-walled carbon nanotubes to the volume fraction of the first solvent was 0.5:80, and the ratio of the mass fraction of nickel phthalocyanine to the volume fraction of the second solvent was 0.1:1, the unit of mass fraction was g, and the unit of volume fraction was mL.

[0047] The serial numbers of the nickel phthalocyanine / carbon nanotube single-atom catalysts prepared in Examples 1 to 4 and the diameters of the multi-walled carbon nanotubes used are shown in Table 1.

[0048] Table 1

[0049] Example Diameter of multi-walled carbon nanotubes serial number Example 1 2~4nm NiPc / CNT-1 Example 2 4~8nm NiPc / CNT-2 Example 3 8~15nm NiPc / CNT-3 Example 4 15~20nm NiPc / CNT-4

[0050] Comparative Example 1

[0051] A carbon nanotube single-atom catalyst (numbered CNT-3) is the multi-walled carbon nanotube used in Example 3.

[0052] X-ray diffraction was performed on the nickel phthalocyanine / carbon nanotube single atom catalysts prepared in Examples 1 to 4 and the carbon nanotube single atom catalyst prepared in Comparative Example 1. The X-ray diffraction patterns are as follows: Figure 1 As shown by Figure 1 It can be seen that the diffraction peaks of the nickel phthalocyanine / carbon nanotube single-atom catalysts prepared in Examples 1 to 4 all correspond well to the diffraction peaks of the multi-walled carbon nanotubes (Comparative Example 1). In addition, no characteristic peaks related to Ni were found in the X-ray diffraction pattern, which is mainly because the Ni doping amount is too low.

[0053] The surface of the nickel phthalocyanine / carbon nanotube single atom catalyst prepared in Example 3 was subjected to elemental analysis. Figure 2 As shown by Figure 2It can be seen that the C, N and Ni elements are evenly distributed on the surface of the nickel phthalocyanine / carbon nanotube single atom catalyst prepared in Example 3, indicating that the nickel phthalocyanine / carbon nanotube single atom catalyst was successfully prepared.

[0054] The nickel phthalocyanine / carbon nanotube single atom catalyst prepared in Example 3 was subjected to transmission electron microscopy (TEM). Figure 3 As shown, combined Figure 2 and Figure 3 It can be seen that nickel phthalocyanine in the nickel phthalocyanine / carbon nanotube single-atom catalyst is loaded on the surface of multi-walled carbon nanotubes.

[0055] Example 5

[0056] Degradation experiment: At 25°C, the catalyst was dispersed in a 100 mL beaker containing 50 mL of pollutant aqueous solution and stirred for 30 min to reach adsorption-desorption equilibrium. After adsorption-desorption equilibrium, PMS was added to obtain a test solution. The test solution was stirred for 30 min for degradation. 2 mL of the test solution was taken every 5 min and filtered with a 0.22 μm filter membrane. The concentration (C) of sulfamethoxazole was obtained by high performance liquid chromatography. The catalyst was one of the nickel phthalocyanine / carbon nanotube single atom catalysts prepared in Examples 1 to 4 and the carbon nanotube single atom catalyst prepared in Comparative Example 1. The PMS dosage was 20 mg. The initial concentration of the catalyst in the pollutant aqueous solution was 0.4 g·L -1 The pollutant aqueous solution is a mixture of pollutants and deionized water. The initial concentration of the pollutant in the pollutant aqueous solution (C0) is 20 ppm. The pH of the pollutant aqueous solution is 7.2. The pollutant is sulfamethoxazole (SMX). The degradation curves of the pollutant by different catalysts are shown in FIG. Figure 4 As shown, according to the degradation rate formula The degradation rate at 30 minutes of degradation was calculated, as shown in Table 2.

[0057] Table 2

[0058] Example / Comparative Example Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Degradation rate 75.39％ 90.01％ 93.70％ 86.83％ 57.01％

[0059] Depend on Figure 4As can be seen from Table 2, the degradation rates of the nickel phthalocyanine / carbon nanotube single-atom catalysts prepared in Examples 2 to 4 are much higher than those of the multi-walled carbon nanotubes (Comparative Example 1), and as the diameter of the multi-walled carbon nanotubes used increases, the catalytic performance of the nickel phthalocyanine / carbon nanotube single-atom catalysts presents a trend similar to a volcano curve, which first increases and then decreases. Among them, the nickel phthalocyanine / carbon nanotube single-atom catalyst prepared in Example 3 using multi-walled carbon nanotubes with a diameter of 8 to 15 nm has the best degradation effect, with a degradation rate of up to 93.70%, and a degradation rate of more than 90% is reached in 15 minutes. This shows that the key factor in controlling catalytic activity is the diameter of the carbon nanotubes (i.e., the diameter), which can efficiently activate PMS to produce more and faster active species, thereby promoting the removal of difficult-to-degrade pollutants.

[0060] Example 6

[0061] Referring to the “degradation experiment” in Example 5, the nickel phthalocyanine / carbon nanotube single-atom catalyst prepared in Example 3 was used as a “catalyst” to degrade the pollutant aqueous solution (the pollutant was sulfamethoxazole) for 30 min. The pH of the pollutant aqueous solution was 7.2. Different dosages of the catalyst were set: the initial concentration of the catalyst in the pollutant aqueous solution was 0 g·L -1 , 0.1g·L -1 , 0.2g·L -1 , 0.3g·L -1 , 0.4g·L -1 and 0.5 g·L -1 The degradation rates of sulfamethoxazole at 30 minutes after the catalyst addition were shown in Table 3. As shown in Table 3, the degradation rate increased with the increase of catalyst concentration (dosage). When the initial catalyst concentration was 0.4 g·L -1 When sulfamethoxazole was added, 93.70% of the degradation was achieved, showing a high efficiency degradation ability at a low dosage.

[0062] Table 3

[0063]

[0064] In the following examples, unless otherwise specified, the initial concentration of the catalyst in the pollutant aqueous solution was 0.4 g·L -1 .

[0065] Example 7

[0066] Referring to the "Degradation Experiment" in Example 5, the nickel phthalocyanine / carbon nanotube single-atom catalyst prepared in Example 3 was used as the "catalyst" to degrade an aqueous pollutant solution (the pollutant being sulfamethoxazole) for 30 minutes. The pH of the aqueous pollutant solution was 7.2, and the PMS dosages were 0 mg, 8 mg, 10 mg, 15 mg, 20 mg, and 25 mg, respectively. The degradation rates of sulfamethoxazole by the catalyst at different PMS dosages at the 30th minute of degradation are shown in Table 4. As can be seen from Table 4, 93.70% degradation of sulfamethoxazole was achieved at a PMS dosage of 20 mg. Therefore, 20 mg was selected as the PMS dosage for the following experiments.

[0067] Table 4

[0068]

[0069] Figure 5 The degradation curves of PMS, nickel phthalocyanine / carbon nanotube single atom catalyst prepared in Example 3, and nickel phthalocyanine / carbon nanotube single atom catalyst prepared in Example 3 activated PMS to SMX, wherein: Figure 5 The "PMS" in Example 6 is the catalyst dosage of "0g·L -1 "The degradation curve of Figure 5 The “catalyst” in the figure is the degradation curve of the PMS dosage of “0 mg” in Example 7. Figure 5 The “catalyst + PMS” is the degradation curve of the nickel phthalocyanine / carbon nanotube single atom catalyst prepared in Example 3 of Example 5 as the “catalyst”. Figure 5 It can be seen that the catalyst dosage is "0g·L -1 In the degradation curve of ", the ability of PMS to remove sulfamethoxazole alone is very weak, with only 35.10% of sulfamethoxazole removed within 30 minutes. The degradation rate of sulfamethoxazole by the nickel phthalocyanine / carbon nanotube single-atom catalyst prepared in Example 3 alone within 30 minutes was only 7%, which is significantly lower than the catalytic performance of the nickel phthalocyanine / carbon nanotube single-atom catalyst prepared in Example 3 activated by PMS.

[0070] Example 8

[0071] Referring to the "degradation experiment" in Example 5, the nickel phthalocyanine / carbon nanotube single-atom catalyst prepared in Example 3 was used as a "catalyst" to degrade the pollutant aqueous solution (the pollutant was sulfamethoxazole) for 30 minutes. The pH of the pollutant aqueous solution was 3, 5, 7, 9 and 11, respectively. The pH was adjusted by adjusting the acidity with 0.1 mol / L hydrochloric acid or the alkalinity with 0.1 mol / L sodium hydroxide aqueous solution. The pH was measured using a pH meter. The degradation curves of the catalyst for sulfamethoxazole at different pH values ​​are shown in FIG. Figure 6 The degradation rates at 30 min are shown in Table 5.

[0072] Table 5

[0073] pH 3 5 7 9 11 Degradation rate 90.43％ 92.81％ 93.69％ 70.50％ 68.16％

[0074] Depend on Figure 6 As shown in Table 5, the nickel phthalocyanine / carbon nanotube single-atom catalyst exhibits excellent degradation performance under neutral and even acidic conditions. Although the degradation rate decreases under alkaline conditions of pH 9-11, it remains above 68%. Furthermore, actual wastewater is typically in the neutral to weakly alkaline range (pH 7-8). Therefore, the nickel phthalocyanine / carbon nanotube single-atom catalyst prepared in Example 3 is environmentally stable.

[0075] Example 9

[0076] Blank experiment: The degradation of the pollutant aqueous solution (the pollutant is sulfamethoxazole) is consistent with that in Example 5 "Degradation Experiment" using the nickel phthalocyanine / carbon nanotube single atom catalyst prepared in Example 3 as the "catalyst". The degradation curve is as follows: Figure 7 Indicated by "blank"

[0077] Coexistence experiment: The coexistence experiment is basically the same as the blank experiment. The difference is that in the coexistence experiment, an interfering substance is added to the pollutant aqueous solution at the same time as the catalyst. The interfering substance is NaCl (free Cl in the test solution). - As coexisting ions), NaNO3 (NO3 is released in the test solution - As coexisting ions), Na2CO3 (free CO3 in the test solution 2- As coexisting ions), NaHCO3 (free HCO3 in the test solution - As coexisting ions), Na2SO4 (free SO4 in the test solution 2- As a coexisting ion) and one of HA, the concentration of the interfering substance in the test solution is 10mmol / L. The degradation curves of sulfamethoxazole by the catalyst under different coexisting ions are shown in Figure 2. Figure 7 The degradation rate at 30 minutes is shown in Table 6. Figure 7 As shown in Table 6, compared with the blank experiment (degradation rate is 93.70%), the nickel phthalocyanine / carbon nanotube single-atom catalyst prepared in Example 3 can maintain a high catalytic activity and pollutant degradation rate in the presence of different coexisting ions.

[0078] Table 6

[0079] Coexisting ions <![CDATA[Cl - ]]> <![CDATA[NO3 - ]]> <![CDATA[CO3 2- ]]> <![CDATA[HCO3 - ]]> <![CDATA[SO4 2- ]]> HA Degradation rate 92.71％ 92.67％ 92.60％ 90.25％ 97.90％ 92.26％

[0080] Example 10

[0081] Referring to the "degradation experiment" in Example 5, the nickel phthalocyanine / carbon nanotube single-atom catalyst prepared in Example 3 was used as a "catalyst" to degrade the pollutant aqueous solution (the pollutant was sulfamethoxazole) for 30 minutes. The pH of the pollutant aqueous solution was 7.2. The deionized water in the pollutant aqueous solution was replaced with ultrapure water (UP water), tap water, river water, lake water (from Horseshoe Lake) and secondary effluent. The degradation curves of the catalyst for sulfamethoxazole under different water bodies are shown as follows. Figure 8 The degradation rates at 30 min are shown in Table 7. Figure 8 As shown in Table 7, the degradation rate of sulfamethoxazole by the nickel phthalocyanine / carbon nanotube single-atom catalyst prepared in Example 3 in different water bodies is more than 88%.

[0082] Table 7

[0083] water bodies Ultrapure water Tap water river water Secondary water lake water Degradation rate 93.69％ 90.28％ 88.97％ 91.42％ 90.64％

[0084] Example 11

[0085] To investigate the stability of the nickel phthalocyanine / carbon nanotube single-atom catalyst, the following steps were repeated four times: Referring to the "degradation experiment" in Example 5, the nickel phthalocyanine / carbon nanotube single-atom catalyst prepared in Example 3 was used as a "catalyst" to degrade the pollutant aqueous solution (the pollutant was sulfamethoxazole) for 30 minutes, and the pH of the pollutant aqueous solution was 7.2.

[0086] After each cycle, the catalyst was centrifuged using a desktop high-speed centrifuge, then washed alternately with deionized water and anhydrous ethanol three times, and dried in vacuum at 60°C for 12 h.

[0087] The degradation curve of sulfamethoxazole by the catalyst in each cycle operation is as follows: Figure 9 As shown. Figure 9 It can be seen that after the fourth cycle, the degradation rate of sulfamethoxazole by the nickel phthalocyanine / carbon nanotube single-atom catalyst prepared in Example 3 still reached more than 80%. The nickel phthalocyanine / carbon nanotube single-atom catalyst has good stability and feasibility.

[0088] Example 12

[0089] Referring to the "degradation experiment" in Example 5, the nickel phthalocyanine / carbon nanotube single-atom catalyst prepared in Example 3 was used as a "catalyst" to degrade the pollutant aqueous solution for 30 minutes. The pH of the pollutant aqueous solution was 7.2, and the pollutant was one of phenol, p-chlorophenol, sulfamethoxazole, p-nitrophenol and benzoic acid. The degradation curves of the catalyst for different pollutants are shown in FIG. Figure 10 As shown in Table 8, the degradation rate at 30 min is shown in Table 8. Figure 10It can be seen that the nickel phthalocyanine / carbon nanotube single-atom catalyst prepared in Example 3 has a good degradation effect on different types of pollutants.

[0090] Table 8

[0091] pollutants phenol p-Chlorophenol Sulfamethoxazole p-Nitrophenol benzoic acid Degradation rate 75.58％ 79.01％ 93.70％ 81.11％ 88.02％

[0092] Example 13

[0093] Quencher experiment: The degradation of the pollutant aqueous solution (the pollutant is sulfamethoxazole) by using the nickel phthalocyanine / carbon nanotube single atom catalyst prepared in Example 3 as the "catalyst" is basically the same as that in Example 5 "degradation experiment". The difference is that in the quencher experiment, a quencher is added to the pollutant aqueous solution at the same time as the catalyst. The quenchers are DMSO (for quenching high-valent metals), β-carotene (for quenching singlet oxygen), tert-butanol (for quenching hydroxyl radicals), methanol (for quenching sulfate radicals), superoxide One of DMSO (used to quench superoxide free radicals) and potassium dichromate (used to quench electrons), wherein the dosage of DMSO in the pollutant aqueous solution is 100uL, the dosage of β-carotene in the pollutant aqueous solution is 0.005g, the dosage of SOD in the pollutant aqueous solution is 1g, the dosage of tert-butanol in the pollutant aqueous solution is 0.488mL, the dosage of methanol in the pollutant aqueous solution is 500uL, and the dosage of potassium dichromate in the pollutant aqueous solution is 1.46mg. The degradation curves of sulfamethoxazole by the catalyst under different quenching agents are shown in Figure 2. Figure 11 As shown in Table 9, the degradation rate at 30 minutes is shown in Table 9. Figure 11 It can be seen that free radicals do not play a dominant role in the degradation of SMX in the activation of PMS by nickel phthalocyanine / carbon nanotube single-atom catalysts. Although high-valent metals and singlet oxygen in the non-radical pathway are active species produced by the activation of PMS by nickel phthalocyanine / carbon nanotube single-atom catalysts prepared in Example 3, the dominant role should be played by the electron transfer process mediated by nickel phthalocyanine / carbon nanotube single-atom catalysts.

[0094] Table 9

[0095] Quencher DMSO beta-carotene tert-Butanol Methanol SOD Potassium dichromate Degradation rate 67.66％ 78.96％ 91.72％ 92.23％ 88.08％ 12.79％

[0096] The electron paramagnetic resonance spectrum of the oxygen active species generated by the nickel phthalocyanine / carbon nanotube single atom catalyst prepared in Example 3 was detected.

[0097] Detection of singlet oxygen: 2 mg of nickel phthalocyanine / carbon nanotube single atom catalyst prepared in Example 3, 2 mg of PMS and 1 mL of pure water were mixed, 10 μL of 2,2,6,6-tetramethylpiperidine (TEMP) was added and stirred for 5 min, and the singlet oxygen signal was detected. The results were as follows: Figure 12 As shown in a;

[0098] Detection of superoxide radicals: 2 mg of nickel phthalocyanine / carbon nanotube single atom catalyst prepared in Example 3, 2 mg of PMS and 1 mL of methanol were mixed, 10 μL of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) was added and stirred for 5 min, and the superoxide radical signal was detected. The results were as follows: Figure 12 As shown in b;

[0099] Depend on Figure 12 It can be seen that the electron paramagnetic resonance spectrum verifies that the nickel phthalocyanine / carbon nanotube single atom catalyst prepared in Example 3 activates PMS to produce singlet oxygen.

[0100] Example 14

[0101] In order to further verify the electron transfer process (ETP) mediated by nickel phthalocyanine / carbon nanotube single-atom catalyst, a standard three-electrode system was set up. The standard three-electrode system includes: working electrode, reference electrode and counter electrode. The electrolyte is Na2SO4 aqueous solution (50 mL), the concentration of Na2SO4 in the aqueous solution is 0.5 mol / L, the pH of the electrolyte is 7, the reference electrode is saturated calomel electrode (Ag / AgCl), and the counter electrode is platinum sheet.

[0102] The method for obtaining the above-mentioned working electrode comprises: placing 2 mg of catalyst, 1 mL of anhydrous ethanol and 20 μL of Nafion perfluorinated resin solution (manufacturer: Yanshen (Tianjin) Technology Co., Ltd.) in a centrifuge tube, ultrasonicating for 30 min to obtain a slurry, and evenly applying the slurry on a single surface of 4 cm 2 One side of the FTO conductive glass (manufacturer: South China Xiangcheng Technology Co., Ltd.) was naturally dried at room temperature of 20-25° C., and then dried at 60° C. for 8 h to obtain a working electrode, wherein the catalyst was one of the nickel phthalocyanine / carbon nanotube single atom catalysts prepared in Examples 1-4 and the carbon nanotube single atom catalyst prepared in Comparative Example 1;

[0103] At a voltage of 0.5 V, a standard three-electrode system of nickel phthalocyanine / carbon nanotube single-atom catalysts prepared in Examples 1 to 4 and the carbon nanotube single-atom catalyst prepared in Comparative Example 1 was subjected to a 1200 s chronoamperometry (CA) test using a CHI760E electrochemical workstation. During the test, 5 mL of PMS aqueous solution and 5 mL of SMX solution were added at the 400th s and the 800th s, respectively, to obtain the following: Figure 13 The chronoamperometric curve is shown in FIG. 3 , wherein the SMX content in the SMX solution is 60 ppm, and the PMS aqueous solution is a mixture of 500 mL of deionized water and 16 mg of PMS.

[0104] Depend on Figure 13It can be seen that after adding PMS, the working electrode quickly generates a small positive current, indicating that a small amount of electrons are rapidly transferred from the surface of the nickel phthalocyanine / carbon nanotube single-atom catalyst to the PMS for activation. When SMX is added, the working electrode also quickly generates a positive current. Among them, the working electrode of the nickel phthalocyanine / carbon nanotube single-atom catalyst prepared in Example 3 generates the largest positive current peak, indicating that SMX is continuously consuming PMS, causing a large number of electrons to continuously transfer from the surface of the nickel phthalocyanine / carbon nanotube single-atom catalyst to PMS. Therefore, the nickel phthalocyanine / carbon nanotube single-atom catalyst prepared in Example 3 activates PMS to achieve 93.70% degradation of SMX, which is mainly controlled by ETP.

[0105] In summary, the nickel phthalocyanine / carbon nanotube single-atom catalyst prepared in Example 3 activates PMS to produce high-valent metals and singlet oxygen, but the electron transfer process (ETP) mediated by the nickel phthalocyanine / carbon nanotube single-atom catalyst is the main reason for the removal of SMX.

[0106] Example 14

[0107] In the range of 0.05~10 5 Hz frequency range, electrochemical impedance spectroscopy (EIS) tests were performed on the standard three-electrode system of the nickel phthalocyanine / carbon nanotube single-atom catalysts prepared in Examples 1 to 4 and the carbon nanotube single-atom catalyst prepared in Comparative Example 1 using a CHI760E electrochemical workstation. The EIS spectra were as follows: Figure 14 As shown,

[0108] Depend on Figure 14 As can be seen, the semicircle radius corresponding to the standard three-electrode system using the nickel phthalocyanine / carbon nanotube single-atom catalyst prepared in Example 3 is larger than that of Examples 1-2, and smaller than that of Example 4 and Comparative Example 1. This indicates that the nickel phthalocyanine / carbon nanotube single-atom catalyst prepared in Example 3 has suitable interfacial charge transfer resistance and excellent internal electron transfer efficiency, further verifying that the nickel phthalocyanine / carbon nanotube single-atom catalyst prepared in Example 3 greatly improves the efficiency of PMS activation. These results also indicate that excessively large or small multi-walled carbon nanotube diameters affect charge transfer between metal active sites and N coordination bonds. Only an appropriate diameter can maximize charge transfer and optimize catalytic performance.

[0109] The above is an exemplary description of the present invention. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by other skilled in the art without expending creative labor falls within the scope of protection of the present invention.

Claims

1. A nickel phthalocyanine / carbon nanotube single-atom catalyst, characterized in that: include: Multi-walled carbon nanotubes and nickel phthalocyanine loaded on the surface of the multi-walled carbon nanotubes.

2. A method for preparing nickel phthalocyanine / carbon nanotube single-atom catalyst, characterized in that: The following steps are involved: Multi-walled carbon nanotubes, nickel phthalocyanine, a first solvent and a second solvent are uniformly mixed, and stirred at room temperature of 20-25°C for 24-36 hours to obtain a mixed solution. The mixed solution is sequentially centrifuged, washed, and vacuum-dried to obtain a nickel phthalocyanine / carbon nanotube single-atom catalyst, wherein the ratio of multi-walled carbon nanotubes to nickel phthalocyanine is (0.1-0.5):(0.1-0.5) by mass, and the diameter of the multi-walled carbon nanotubes is 4-20 nm.

3. The preparation method according to claim 2, characterized in that The diameter of multi-walled carbon nanotubes is 8 to 15 nm.

4. The preparation method according to claim 2, characterized in that The multi-walled carbon nanotubes are dispersed in the first solvent and mixed evenly by ultrasonication for 30 to 40 minutes to obtain a nanotube solution; nickel phthalocyanine is dispersed in the second solvent and mixed evenly by ultrasonication for 30 to 40 minutes to obtain a nickel phthalocyanine solution; all the nanotube solution is added to the nickel phthalocyanine solution, and stirred at 20 to 25° C. for 24 to 36 hours to obtain a mixed solution.

5. The preparation method according to claim 2, characterized in that The first solvent is methanol; the second solvent is methanol.

6. The preparation method according to claim 2, characterized in that The mass fraction ratio of the multi-walled carbon nanotubes to the volume fraction ratio of the first solvent is (0.1-0.5): (80-100), the unit of the mass fraction ratio is g, and the unit of the volume fraction ratio is mL.

7. The preparation method according to claim 2, characterized in that The mass fraction ratio of nickel phthalocyanine to the volume fraction ratio of the second solvent is (0.1-0.5):(1-5), the unit of the mass fraction ratio is g, and the unit of the volume fraction ratio is mL.

8. Use of the nickel phthalocyanine / carbon nanotube single-atom catalyst according to claim 1 in activating peroxymonosulfate to degrade pollutants.

9. The use according to claim 8, characterized in that The nickel phthalocyanine / carbon nanotube single-atom catalyst activates peroxymonosulfate to generate high-valent metals and singlet oxygen.

10. The use according to claim 8, characterized in that The dominant role in the degradation of pollutants by activated peroxymonosulfate is the electron transfer process mediated by nickel phthalocyanine / carbon nanotube single-atom catalysts.

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