Carbon-based catalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of catalysts, in particular to a carbon-based catalyst and a preparation method and application thereof. The carbon-based catalyst comprises a carrier and ruthenium atoms loaded on the carrier, the carrier comprises a nitrogen-doped carbon-based material and metal single atoms loaded on the carbon-based material, and the ruthenium atoms are loaded on the carbon-based material; the carrier is configured to be obtained by carbonizing metal phthalocyanine, and the carrier comprises metal single atoms, carbon atoms and nitrogen atoms. According to the carbon-based catalyst, by optimizing the structure of the carrier, the stability and dispersity of ruthenium atoms loaded on the carrier are improved, meanwhile, the oxidation performance of the carbon-based catalyst is further adjusted, pollutants in wastewater are promoted to be converted into polymers, the separation and collection efficiency of pollutant conversion products is improved, and the water purification effect is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalysts, in particular to a carbon-based catalyst and a preparation method and application thereof. BACKGROUND

[0002] In a ruthenium-loaded carbon-based catalyst, the size, dispersity and loading amount of the ruthenium catalytic anchor point are not easy to control, and the stability of ruthenium is poor, which causes the dissolution of ruthenium from the catalyst, reduces the catalytic efficiency and stability of the catalyst. At the same time, when such a catalyst and an activated oxidizing agent are used to oxidize pollutants in wastewater, free radical oxidation often occurs, which causes the pollutants to be converted into small molecular products in a dissolved state, which brings great difficulty to the collection of the decomposition products of the pollutants and the purification of the water body. SUMMARY

[0003] The present application discloses a carbon-based catalyst and a preparation method and application thereof, to solve the problems of ruthenium dissolution in a ruthenium-loaded carbon-based catalyst and the difficulty in collecting the decomposition products of pollutants catalyzed by the catalyst.

[0004] To achieve the above-mentioned purpose, in a first aspect, the present application discloses a carbon-based catalyst, the carbon-based catalyst comprising a carrier and ruthenium atoms loaded on the carrier, the carrier comprising a nitrogen-doped carbon-based material and metal monatomic atoms loaded on the carbon-based material, and the ruthenium atoms being loaded on the carbon-based material. The carrier is configured to be obtained by carbonization of a metal phthalocyanine, and the carrier comprises the metal monatomic atoms, carbon atoms and nitrogen atoms.

[0005] Further, the carrier further comprises sulfur atoms.

[0006] Further, the molar ratio of the ruthenium atoms, the carbon atoms, the nitrogen atoms and the sulfur atoms is (0.4-0.9):(84.6-90.0):(6.5-10.6):(3.1-3.9).

[0007] Further, the ruthenium atoms are loaded on the carrier in the form of ruthenium clusters, and the particle size of the ruthenium clusters is 2 nm-20 nm; and / or, The metal phthalocyanine comprises at least one of cobalt phthalocyanine, iron phthalocyanine, copper phthalocyanine, nickel phthalocyanine, zinc phthalocyanine and manganese phthalocyanine.

[0008] In a second aspect, the present application provides a preparation method of a carbon-based catalyst, the carbon-based catalyst being the carbon-based catalyst of the first aspect, and the preparation method comprising the following steps: Calcination: calcining a metal precursor mixture in an atmosphere of a non-reactive gas at 650°C-1300°C for 0.5 h-3 h to obtain the carbon-based catalyst, the metal precursor mixture comprising the metal phthalocyanine and a ruthenium source.

[0009] Further, the non-reactive gas comprises at least one of nitrogen, argon or helium; and / or, The ruthenium source comprises at least one of ruthenium chloride, ruthenium acetylacetonate, ruthenium nitrate; and / or, In the step of calcining, the heating rate is 1℃ / min~15℃ / min.

[0010] Further, the preparation method of the metal precursor mixture comprises: adding the metal phthalocyanine and the ruthenium source into a first solvent, stirring at 50℃~100℃ until the first solvent volatilizes, to obtain the metal precursor mixture.

[0011] Further, the preparation method of the metal precursor mixture further comprises adding a nitrogen-sulfur source into the first solvent.

[0012] Further, the nitrogen-sulfur source comprises at least one of trithiocyanic acid, thiocyanic acid, thiourea, thioacetamide, melamine; and / or, The mass ratio of the metal phthalocyanine, the ruthenium source and the nitrogen-sulfur source is 1:1:1~1:1:20.

[0013] In a third aspect, the present application further provides an application of the carbon-based catalyst. The carbon-based catalyst is the carbon-based catalyst of the first aspect, or the carbon-based catalyst is prepared by the preparation method of the second aspect. The carbon-based catalyst is combined with an oxidant to be used for oxidizing and polymerizing organic pollutant wastewater.

[0014] Compared with the prior art, the present application has the following beneficial effects: In the carbon-based catalyst of the present application, by optimizing the carrier structure, the stability and dispersion of ruthenium atoms on the carrier are improved, and at the same time, the oxidation performance of the carbon-based catalyst is further adjusted, which promotes the conversion of pollutants in wastewater into polymers, improves the separation and collection efficiency of pollutant conversion products, and improves the water purification effect.

[0015] The carrier in the present application is prepared in-situ by carbonization of metal phthalocyanine, and the ruthenium atoms are loaded on the carrier through metal-carrier interaction with carbon atoms and nitrogen atoms in the carrier. Due to the structural characteristics of metal phthalocyanine, the density and dispersion of metal monatomic atoms formed in the carbonization process are improved; the metal monatomic atoms and the carbon atoms and nitrogen atoms in the carrier cooperatively produce a confinement effect, which strengthens the stability of the combination of ruthenium atoms and the carrier. Meanwhile, when the carbon-based catalyst in the present application and the oxidizing agent jointly participate in the oxidative decomposition of pollutants in wastewater, the oxidizing agent is adsorbed on the ruthenium atoms of the carbon-based catalyst through electrostatic interaction or hydrogen bonding, and under the confinement effect of the carrier, the carbon-based catalyst and the oxidizing agent form an adduct through metal-oxygen coordination under the electronic regulation of the carrier. The oxidation potential of the adduct tends to be mild, and the adduct does not decompose into free radicals, but participates in the reaction as a non-free radical active species, so that the pollutants in the wastewater undergo non-free radical oxidation reaction and form polymers through oxidative polymerization. The polymers are easy to precipitate from the water body, making the pollutant conversion products easier to collect and improving the purification effect of the water body. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings used in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0017] Figure 1 is a transmission electron microscope image of the carbon-based catalyst provided in Embodiment 1 of the present application; Figure 2 is a TEM Mapping image and a HAADF-STEM image of the carbon-based catalyst provided in Embodiment 1 of the present application; Figure 3 is an X-ray diffraction pattern of the carbon-based catalyst provided in Embodiment 1 of the present application; Figure 4 is an X-ray photoelectron spectrogram of the carbon-based catalyst provided in Embodiments 1-3 and Comparative Example 2 of the present application. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0019] Oxidative polymerization process utilizes active oxygen species (ROS) generated by Fenton-like reaction (e.g. activated persulfate PMS or periodate PI) to convert organic pollutants into solid polymers. Compared with AOPs, oxidative polymerization not only can remove total organic carbon (TOC) more efficiently, but also significantly reduce chemical consumption and carbon emissions. More importantly, the generated polymers can be separated and recovered by simple methods such as precipitation and filtration, providing a feasible direction for the resource utilization of organic pollutants, which has both environmental and economic values. The core prerequisite for realizing this process is to develop efficient catalytic materials that can precisely activate PMS, PI and other oxidants and meet the needs of oxidative polymerization.

[0020] Compared with other metal-supported carbon-based catalysts, ruthenium atoms have a unique electronic structure, so the ruthenium atoms and the carbon-based support have stronger orbital interaction, and the combination is stronger, which exhibits better stability and activity in the treatment of organic pollutants. However, the existing ruthenium-supported carbon-based catalysts still have some deficiencies. On the one hand, the size, dispersion and loading amount of the ruthenium anchor points cannot be accurately controlled, which easily leads to poor structural uniformity of the ruthenium-supported carbon-based catalysts, and further causes limited catalytic efficiency of the catalysts, serious ruthenium leaching, narrow pH adaptation range and weak anti-interference ability. On the other hand, the ruthenium in the catalysts exists in the form of high-valence ruthenium, which activates the oxidant to form free radicals. The activity of the free radicals causes the degradation reaction of pollutants in the wastewater, forming small molecule substances such as formic acid. These small molecule substances still exist in the wastewater, which makes it difficult to collect these decomposition products and increases the difficulty of purifying the wastewater.

[0021] Based on the above analysis, the embodiment of the present application provides a carbon-based catalyst, which comprises a carrier and ruthenium atoms supported on the carrier, the carrier comprises a nitrogen-doped carbon-based material and metal monatomic atoms supported on the carbon-based material, and the ruthenium atoms are supported on the carbon-based material. The carrier is configured to be obtained by carbonizing a metal phthalocyanine, and the carrier comprises metal monatomic atoms, carbon atoms and nitrogen atoms.

[0022] The structural formula of the metal phthalocyanine is shown as formula (1), wherein M is a central metal. In the carrier formed after carbonization of the metal phthalocyanine, the density and dispersion of the metal monatomic atoms are improved, and the metal monatomic atoms form coordination with the nitrogen atoms, so the density and dispersion of the metal monatomic atom-nitrogen-carbon anchor points are also improved. In the embodiment of the present application, the metal monatomic atom-nitrogen-carbon anchor points in the carrier structure can better capture the ruthenium atoms to form a “metal monatomic atom-ruthenium atom” interface, which has good thermodynamic stability, so the stability of the ruthenium atoms supported on the carrier is improved, and the stability of the carbon-based catalyst is improved.

[0023]

[0024] Formula (1) In the carbon-based catalyst of the present application, by optimizing the carrier structure, the stability and dispersion of ruthenium atoms on the carrier are improved, and at the same time, the oxidation performance of the carbon-based catalyst is further adjusted, which promotes the conversion of pollutants in wastewater into polymers, improves the separation and collection efficiency of pollutant conversion products, and improves the water purification effect.

[0025] The carrier in the present application is prepared in situ by carbonization of metal phthalocyanine, and the ruthenium atoms are loaded on the carrier through metal-carrier interaction with carbon atoms and nitrogen atoms in the carrier. Due to the structural characteristics of metal phthalocyanine, the density and dispersion of metal monatomic atoms formed during carbonization are improved; the metal monatomic atoms and the carbon atoms and nitrogen atoms in the carrier cooperatively produce a confinement effect, which strengthens the binding stability of ruthenium atoms and the carrier. At the same time, the metal monatomic atoms are cooperatively confined by carbon and nitrogen atoms in the carrier, thereby enhancing the binding stability between ruthenium atoms and the carrier. At the same time, significant electronic interaction occurs between monatomic ruthenium and its coordination environment, which regulates the electronic structure of ruthenium atoms through charge redistribution, further promotes the high dispersion of ruthenium atoms and improves the atomic utilization efficiency, thereby improving the overall catalytic performance of the catalyst.

[0026] When the carbon-based catalyst and the oxidant in the present application jointly participate in the oxidative decomposition of pollutants in wastewater, the oxidant is adsorbed on the ruthenium atoms of the carbon-based catalyst through electrostatic interaction or hydrogen bonding. The metal monatomic atom form in the carrier of the carbon-based catalyst has a discrete and unsaturated electronic structure compared to metal clusters or nanometal, and its catalytic behavior depends on metal-carrier interaction, which is more prone to mild activation of the oxidant in a metal-oxygen coordination manner under the electronic regulation of the carrier, thereby inhibiting the generation of free radicals and promoting the reaction system to mainly follow a non-radical oxidation path. Under the confinement of the carrier, the carbon-based catalyst and the oxidant form an adduct through metal-oxygen coordination. Under the electronic regulation of the carrier, the oxidation potential of the adduct tends to be mild, and the adduct does not decompose into free radicals but participates in the reaction as a non-radical active species, causing the pollutants in the wastewater to undergo non-radical oxidation reaction and form polymers. The polymers are easily precipitated from the water body, making the pollutant conversion products easier to collect, thereby improving the water purification effect.

[0027] Further, the metal phthalocyanine includes at least one of cobalt phthalocyanine, iron phthalocyanine, copper phthalocyanine, nickel phthalocyanine, zinc phthalocyanine, and manganese phthalocyanine. Preferably, the metal phthalocyanine is cobalt phthalocyanine. In the embodiments of the present application, when the metal phthalocyanine is cobalt phthalocyanine, the introduction of cobalt atoms helps the oxidation products of pollutants to form solution precipitates, improves the efficiency of the polymers precipitating from the water body, and reduces the phenomenon of the polymers covering the ruthenium atoms of the catalyst, so that the carbon-based catalyst has long-term stable catalytic performance, further improving the water purification effect.

[0028] Further, the carrier further comprises a sulfur atom. In the embodiments of the present application, the sulfur doping in the carrier can increase the defect density of the carrier, strengthen the interaction between ruthenium and carbon atoms and nitrogen atoms on the carrier, and the lone pair electrons on the sulfur atom can also form coordination with ruthenium, so that the anchoring of ruthenium and the carrier is further strengthened, the dissolution of ruthenium is reduced, and the catalytic efficiency and stability of the carbon-based catalyst of the present application are improved.

[0029] Further, the molar ratio of the ruthenium atom, the carbon atom, the nitrogen atom and the sulfur atom is (0.4-0.9):(84.6-90.0):(6.5-10.6):(3.1-3.9). The molar ratio of each atom is obtained by X-ray photoelectron spectroscopy. For example, the molar ratio of the ruthenium atom, the carbon atom, the nitrogen atom and the sulfur atom is 0.4:90.0:6.5:3.1, 0.5:88.4:7.8:3.3, 0.7:87.1:8.6:3.6 or 0.9:84.6:10.6:3.9. In the embodiments of the present application, when the mass ratio of each atom is in the above range, the dispersion and stability of the ruthenium atom loaded on the carrier are better. Preferably, the molar ratio of the ruthenium atom, the carbon atom, the nitrogen atom and the sulfur atom is 0.6:87.9:8.1:3.4.

[0030] Further, the ruthenium atom is loaded on the carrier in the form of a ruthenium cluster, and the particle size of the ruthenium cluster is 2 nm-20 nm.

[0031] The cluster refers to a sub-nanometer scale aggregate composed of several to millions of structural units (atoms or molecules). These aggregates can be formed by covalent bonds or metal bonds, or by hydrogen bonds and van der Waals forces. The particle size of the ruthenium cluster is obtained by transmission electron microscopy (TEM) and statistics. For example, the particle size of the ruthenium cluster is 2 nm, 5 nm, 9 nm, 13 nm, 17 nm or 20 nm. In the embodiments of the present application, the ruthenium cluster has more sites for metal-support interaction with the carrier, stronger force, better stability of ruthenium loading, more sites for adsorbing oxidants on the surface of the ruthenium cluster, and better catalytic activity. At the same time, the interface electron interaction between the metal single atom and the ruthenium cluster is stronger, the electron cloud density of the ruthenium anchor point is optimized through charge redistribution, the further agglomeration of the ruthenium cluster is reduced, the dispersion of ruthenium is promoted, the utilization rate of ruthenium atoms is improved, and finally the catalytic efficiency of the catalyst is improved. When the particle size of the ruthenium cluster is in the above range, both good stability and good utilization rate of ruthenium source can be maintained, and the catalytic activity of the catalyst is further improved. Preferably, the particle size of the ruthenium cluster is 2 nm-5 nm.

[0032] The application further provides a preparation method of the carbon-based catalyst. It can be understood that the preparation method is one method for obtaining the carbon-based catalyst, but is not limited to the only method. That is, the carbon-based catalyst of the application can also be prepared by other methods, which are not limited by the application, and therefore the preparation method provided by the application should not be understood as a limitation of the carbon-based catalyst.

[0033] The preparation method comprises the following steps: calcination: calcining the metal precursor mixture in a non-reactive gas atmosphere at 650-1300℃ for 0.5-3h to obtain the carbon-based catalyst, wherein the metal precursor mixture comprises metal phthalocyanine and a ruthenium source.

[0034] The non-reactive gas is at least one of nitrogen, argon or helium. The ruthenium source comprises at least one of ruthenium chloride, ruthenium acetylacetonate or ruthenium nitrate. The temperature of the calcination is 650℃, 800℃, 970℃, 1100℃, 1260℃ or 1300℃, and the time of the calcination is 0.5h, 1.5h, 2.5h or 3h.

[0035] In the application, when the calcination temperature and the calcination time are within the above ranges, the decomposition degree of the metal phthalocyanine can be ensured to form the metal monatomic-nitrogen-carbon anchor point, and the collapse of the formed metal monatomic-nitrogen-carbon anchor structure can be avoided to reduce the thermal migration and agglomeration of ruthenium atoms, thereby ensuring the catalytic activity of the carbon-based catalyst. Preferably, the ruthenium source is ruthenium acetylacetonate, the temperature of the calcination is 800-1000℃, and the time of the calcination is 1-2h.

[0036] Further, in the step of calcination, the temperature rising rate is 1-15℃ / min. The temperature rising rate is 1℃ / min, 4℃ / min, 7℃ / min, 10℃ / min, 13℃ / min or 15℃ / min. In the application, when the temperature rising rate is within the above range, the carbonization of the metal phthalocyanine in the metal precursor mixture is more complete, which is beneficial to increasing the specific surface area of the carbon-based catalyst and improving the catalytic effect. Preferably, the temperature rising rate is 3-5℃ / min.

[0037] Further, the method for preparing the metal precursor mixture comprises: adding the metal phthalocyanine and the ruthenium source into a first solvent, and stirring at 50-100°C until the first solvent volatilizes to obtain the metal precursor mixture. The first solvent comprises at least one of ethanol, water, methanol or acetone. The temperature of the stirring is exemplarily 50°C, 60°C, 70°C, 80°C, 90°C or 100°C. In the embodiments of the present application, the metal phthalocyanine and the ruthenium source are mixed in the liquid phase by using the pretreatment method of one-pot synthesis. This method does not need intermediate separation, and ensures that the metal single-atom-nitrogen-carbon anchor and the ruthenium source are more easily accessible in the pyrolysis process, thereby improving the stability and dispersity of the ruthenium atoms in the carbon-based catalyst. Preferably, the temperature of the stirring is 50-60°C.

[0038] Further, the method for preparing the metal precursor mixture further comprises adding a nitrogen-sulfur source into the first solvent. The nitrogen-sulfur source comprises at least one of thiocyanic acid, thiocyanic acid, thiourea, thioacetamide or melamine. In the embodiments of the present application, the nitrogen atoms in the nitrogen-sulfur source are doped into the carrier, thereby increasing the content of the nitrogen atoms in the carrier and further strengthening the metal-carrier interaction force between the ruthenium atoms and the carrier, and improving the stability of the ruthenium atoms. The sulfur atoms in the nitrogen-sulfur source are doped into the carrier, a part of which is used to form metal sulfides with the metal atoms, thereby further reducing the agglomeration of the ruthenium atoms from the steric hindrance, increasing the dispersion degree of the ruthenium atoms and improving the utilization rate of the ruthenium atoms, and finally improving the catalytic efficiency of the carbon-based catalyst; another part of the sulfur can increase the defect density of the carrier and strengthen the interaction between the ruthenium atoms and the nitrogen atoms. In addition, the lone pair electrons in the sulfur can form coordination with the ruthenium, thereby optimizing the electronic structure of the ruthenium, further strengthening the anchoring effect of the ruthenium clusters and the carrier, further limiting the migration and aggregation of the ruthenium atoms on the surface of the carrier, ensuring the high dispersion and uniformity of the ruthenium atoms and reducing the elution of the ruthenium atoms, and improving the catalytic efficiency and stability of the carbon-based catalyst.

[0039] Further, in the preparation step of the metal precursor mixture, the metal phthalocyanine, the ruthenium source and the nitrogen-sulfur source are dispersed in the first solvent by using the ultrasonic dispersion method. The ultrasonic dispersion time is 10-60 s, and exemplarily, the ultrasonic dispersion time is 20 s, 30 s or 60 s. In the embodiments of the present application, the ultrasonic dispersion promotes the more sufficient dispersion of the metal phthalocyanine, the ruthenium source and the nitrogen-sulfur source in the first solvent, thereby improving the uniformity of the carbon-based catalyst formed after calcination and improving the catalytic performance of the carbon-based catalyst. When the ultrasonic dispersion time is within the above range, the metal precursor mixture can be fully dispersed, while avoiding local overheating of the solvent or degradation of the metal precursor or the nuclear weapon. The well-dispersed metal precursor mixture helps to improve the good dispersion of the metal single-atom-nitrogen-carbon anchor in the carbon-based catalyst obtained after calcination, thereby improving the catalytic activity and reaction selectivity of the carbon-based catalyst.

[0040] Further, in the preparation step of the metal precursor mixture, the stirring speed is 300 rpm-700 rpm. Illustratively, the stirring speed is 300 rpm, 400 rpm, 500 rpm, 600 rpm or 700 rpm. In the embodiments of the present application, when the stirring speed is in the above range, the metal phthalocyanine, the ruthenium source and the nitrogen-sulfur source can be fully mixed in the first solvent, and at the same time, the first solvent can be more fully and quickly volatilized to obtain the metal precursor mixture.

[0041] Further, the mass ratio of the metal phthalocyanine, the ruthenium source and the nitrogen-sulfur source is 1:0.1:1-1:1:20. Illustratively, the mass ratio of the metal phthalocyanine, the ruthenium source and the nitrogen-sulfur source is 1:0.1:1, 1:0.1:6, 1:1:9, 1:1:12, 1:1:16, 1:1:19 or 1:1:20. In the embodiments of the present application, when the mass ratio of the metal phthalocyanine, the ruthenium source and the nitrogen-sulfur source is in the above range, the ruthenium cluster has good stability and dispersity on the carrier, so that the carbon-based catalyst has excellent catalytic activity and stability. Preferably, the mass ratio of the metal phthalocyanine, the ruthenium source and the nitrogen-sulfur source is 1:0.2:20.

[0042] Further, the mass of the metal phthalocyanine is 10 mg-400 mg, the mass of the ruthenium source is 10 mg-100 mg, and the mass of the nitrogen-sulfur source is 1 g-8 g. Illustratively, the mass of the metal phthalocyanine is 10 mg, 80 mg, 120 mg, 250 mg, 370 mg or 400 mg, the mass of the ruthenium source is 10 mg, 30 mg, 60 mg or 100 mg, and the mass of the nitrogen-sulfur source is 1 g, 3 g, 6 g or 8 g. Preferably, the mass of the metal phthalocyanine is 200 mg, the mass of the ruthenium source is 40 mg, and the mass of the nitrogen-sulfur source is 4 g.

[0043] Further, before the calcination step, the preparation method further comprises drying the metal precursor mixture. The drying temperature is 50°C-90°C, and the drying time is 1 h-24 h. Illustratively, the drying temperature is 50°C, 60°C, 70°C, 80°C or 90°C, and the drying time is 1 h, 5 h, 8 h, 13 h, 18 h, 21 h or 24 h. In the embodiments of the present application, when the metal precursor mixture is dried at the above temperature and time, the volatilization of the first solvent can be promoted and the uniformity of the metal precursor mixture can be improved, so that a carbon-based catalyst with well-dispersed metal single-atom-nitrogen-carbon anchor points can be formed in the subsequent calcination step, which is beneficial to improve the catalytic performance and stability of the carbon-based catalyst. Preferably, the drying temperature is 60°C, and the drying time is 12 h.

[0044] Further, before the step of calcining, the preparation method further comprises grinding the metal precursor mixture, and the particle size of the ground metal precursor mixture is 5-50 μm. The particle size is measured by a laser particle size analyzer or a microscope. In the embodiments of the present application, the step of grinding further improves the uniformity of each component in the metal precursor mixture, ensures the uniformity and stability of the subsequent calcination step, and ensures the performance of the carbon-based catalyst.

[0045] Further, after the step of calcining, the preparation method further comprises mixing and stirring the carbon-based catalyst with an acid solution for 1-12 h. For example, the carbon-based catalyst is mixed and stirred with the acid solution for 1 h, 3 h, 7 h, 9 h, 11 h, or 12 h. In the embodiments of the present application, the acid solution can remove the unreacted ruthenium source, and also remove the metal sulfide with a non-single-atom structure, thereby further improving the catalytic activity of the carbon-based catalyst. Preferably, the mixing and stirring time is 7 h.

[0046] Further, the acid solution comprises one or both of a sulfuric acid solution and a hydrochloric acid solution, the concentration of the acid solution is 0.5-2 mol / L, and the stirring speed is 300-700 rpm. For example, the concentration of the acid solution is 0.5 mol / L, 1 mol / L, 1.5 mol / L, or 2 mol / L, and the stirring speed is 300 rpm, 400 rpm, 500 rpm, 600 rpm, or 700 rpm. In the embodiments of the present application, when the concentration of the acid solution and the stirring speed are within the above ranges, the acid solution washing can remove the impurities on the surface of the carrier, improve the exposure degree of the surface active sites, and improve the catalytic performance of the carbon-based catalyst. Preferably, the acid solution is a sulfuric acid solution, the concentration of the acid solution is 1 mol / L, and the stirring speed is 600 rpm.

[0047] Preferably, the acid solution is a sulfuric acid solution with a concentration of 1 mol / L and a stirring speed of 600 rpm, which can achieve the best carrier surface activity and ruthenium cluster dispersion effect.

[0048] The present application also provides an application of a carbon-based catalyst. The carbon-based catalyst is the catalyst described above or prepared by the preparation method described above. The catalyst is combined with an oxidizing agent to oxidize and polymerize organic pollutants in wastewater.

[0049] The oxidizing agent comprises at least one of sodium periodate, peroxymonosulfate, and hydrogen peroxide. The organic matter comprises at least one of sulfamethoxazole, aniline, p-chlorophenol, phenol, rhodamine B, tetracycline, p-nitroaniline, and sulfonamide.

[0050] The pH of the organic pollutant wastewater is 2-14. Illustratively, the pH of the organic pollutant wastewater is 2, 4, 7, 9, 12, or 14. In the embodiments of the present application, for the organic pollutant wastewater with a pH of 2-14, the carbon-based catalyst of the present application can achieve good activation of the oxidizing agent, so that the organic pollutants can achieve oxidative polymerization (organic pollutant removal rate ≥98% in 15 min), and the conversion products can be recovered and the water body can be purified. Preferably, the pH of the organic pollutant wastewater is 3-7.

[0051] Further, the mass ratio of the carbon-based catalyst to the oxidizing agent is 10:300-100:300, and the molar ratio of the organic pollutant to the oxidizing agent is 0.1:1-10:1. Illustratively, the mass ratio of the carbon-based catalyst to the oxidizing agent is 10:300, 50:300, 70:300, or 100:300. Illustratively, the molar ratio of the organic pollutant to the oxidizing agent is 0.1:1, 1:1, 3:15, 5:1, or 10:1. In the present application, when the mass ratio of the carbon-based catalyst to the oxidizing agent is in the above range, and the molar ratio of the organic pollutant to the oxidizing agent is in the above range, the carbon-based catalyst has better oxidation effect on the oxidizing agent, the oxidizing agent catalyst adduct formed can react with the organic pollutants, the organic pollutants undergo oxidative polymerization, and the collection effect of the conversion products and the purification effect of the water body are better. Preferably, the mass ratio of the carbon-based catalyst to the oxidizing agent is 10:300-100:300, and the molar ratio of the organic pollutant to the oxidizing agent is 0.1:1-10:1.

[0052] The technical solutions of the present application will be further explained below in combination with more specific embodiments and experimental test results.

[0053] Embodiment 1 The present application discloses a carbon-based catalyst, and a preparation method of the carbon-based catalyst is as follows: Step 1: Preparation of metal precursor mixture 4 g of thiocyanic acid, 0.2 g of cobalt phthalocyanine, and 20 mg of ruthenium acetylacetonate were added to a 250 mL beaker. Then 40 mL of ethanol was added, and ultrasonic dispersion was performed for 30 s. The obtained suspension was stirred at 80°C until the solution volatilized, and a metal precursor mixture was obtained.

[0054] Step 2: The metal precursor mixture was dried at 70°C.

[0055] Step 3: The metal precursor mixture was ground into a powdered metal precursor mixture with a particle size of 5 μm-50 μm.

[0056] Step 4: The powdered metal precursor mixture was placed in a tube furnace under a nitrogen atmosphere, heated to 800°C at a heating rate of 5°C / min, and calcined for 2 h.

[0057] Step 5: Mix the carbon-based catalyst with 50 mL of 1 mol / L sulfuric acid solution, sonicate for 15 s, stir for 6 h, and then filter to separate the carbon-based catalyst.

[0058] Step 6: Wash the carbon-based catalyst 2-3 times with deionized water and freeze-dry it.

[0059] Example 2 The only difference between this embodiment and Embodiment 1 is that the amount of ruthenium acetylacetone used in step 1 is 40 mg.

[0060] Example 3 The only difference between this embodiment and Embodiment 1 is that the amount of ruthenium acetylacetone used in step 1 is 10 mg.

[0061] Example 4 The only difference between this embodiment and Embodiment 1 is that in step 1, cobalt phthalocyanine is replaced with an equimolar amount of iron phthalocyanine.

[0062] Example 5 The only difference between this embodiment and Embodiment 1 is that in step 1, cobalt phthalocyanine is replaced with an equimolar amount of copper phthalocyanine.

[0063] Example 6 The only difference between this embodiment and Embodiment 1 is that the amount of cobalt phthalocyanine used in step 1 is 0.1 g.

[0064] Example 7 The only difference between this embodiment and Embodiment 1 is that the amount of cobalt phthalocyanine used in step 1 is 0.05 g.

[0065] Comparative Example 1 The only difference between this comparative example and Example 1 is that ruthenium acetylacetone is not added in step 1.

[0066] Comparative Example 2 The only difference between this comparative example and Example 1 is that cobalt phthalocyanine is not added in step 1.

[0067] Performance testing: 1. Component analysis test Example 1 was tested using transmission electron microscopy (TEM) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). TEM images are shown below. Figure 1 As shown, Figure 1 (a) ~ Figure 1 (d) shows TEM images at different magnifications, illustrating the loading and dispersion of ruthenium clusters and the size of the ruthenium clusters in the carbon-based catalyst of Example 1. The HAADF-STEM image is shown in 2(a), and the transmission electron microscope mapping is shown in...Figure 2 (b) and Figure 2 As shown in (c), Figure 2 (b) shows the distribution of ruthenium atoms in the carbon-based catalyst of Example 1. Figure 2 (c) shows the distribution of ruthenium atoms, carbon atoms, single atoms, cobalt atoms, sulfur atoms, and oxygen atoms in the carbon-based catalyst of Example 1. The oxygen atoms are mainly due to the absorption of moisture and CO2 from the air by the carbon-based catalyst; the oxygen atom content is not strongly correlated with catalytic activity. Example 1 was tested using an X-ray diffractometer, and the test results are as follows: Figure 3 As shown. Examples 1-3 and Comparative Example 2 were tested using X-ray photoelectron spectroscopy, and the test results are as follows. Figure 4 As shown.

[0068] Depend on Figure 1 and Figure 2 (a) shows that ruthenium atoms loaded on the support have good dispersion. Figure 2 (b) and 2(c) show the distribution of atoms on the carbon-based catalyst. Cobalt, ruthenium, nitrogen and sulfur atoms are highly overlapping in the carbon-based catalyst, indicating the close spatial correlation between cobalt single atoms and ruthenium atoms at the nanoscale. Figure 3 In the diffraction pattern, only the (002) and (101) peaks of graphitic carbon were observed, and no characteristic diffraction peaks belonging to metal Ru or metal Co were found. This indicates that Co is dispersed at the atomic level (forming Co-NC anchor points), while ruthenium atoms exist in the form of highly dispersed amorphous or ultrafine nanoclusters, which is consistent with the observations of the HAADF-STEM image. Figure 4 In the figure, the peak of Co is around 778 eV, and the peak of Ru appears around 496 eV. It can be observed from the figure that the carbon-based catalyst also contains four atoms: S, N, C and O.

[0069] 2. Oxidation efficiency test A 1 L solution of 0.1 mmol / L rhodamine B was prepared. 3 mg of the carbon-based catalysts corresponding to Examples 1-7 and Comparative Examples 1-2 were added to 100 mL of the 25 μmol / L rhodamine B solution, followed by 15.4 mg of persulfate. Samples were taken at 1 min, 3 min, 5 min, 7 min, 10 min, and 15 min to calculate the remaining concentration and removal rate of rhodamine B. The remaining concentration of rhodamine B was measured using a UV-Vis spectrophotometer, and calculated based on the magnitude and value of absorbance, and the relationship between absorbance and concentration (Lamböller-Beer Law). The removal rate was the ratio of the remaining concentration of rhodamine B to the initial concentration of rhodamine B. The test results are shown in Table 1.

[0070] Rhodamine B was replaced by aniline, and the aniline removal rate was tested at 15 min sampling in Example 1, which was 99.4%. Persulfate was replaced by sodium periodate, and the Rhodamine B removal rate was tested at 15 min sampling, which was 99.2%. No persulfate was added, and the aniline removal rate was tested at 15 min sampling, which was 3.1%.

[0071] 3. Oxidative polymerization efficiency test To 100 mL of a sulfamethoxazole solution with a concentration of 1 mmol / L, 15 mg of the carbon-based catalysts corresponding to Examples 1-7 and Comparative Examples 1-2 was added, and ultrasonic treatment was performed for 15 s. Then, X mL of persulfate with a concentration of 2 mmol / L was added, and after reaction for 60 min, filtration was performed to obtain a reaction liquid from which the catalyst was removed. The reaction liquid was left to stand for 24 h to form a precipitate, and then the precipitate was collected by filtration, and the contaminants on the surface of the catalyst were also collected. The oxidative polymerization efficiency of the carbon-based catalyst was calculated. The test results are shown in Table 2.

[0072] Rhodamine B was replaced by aniline, and the results of the oxidative polymerization efficiency test of Example 1 were as follows: the catalyst surface recovery rate was 75.1%, the solution precipitate recovery rate was 23.6%, and the total recovery rate was 98.7%. Persulfate was replaced by sodium periodate, and the results of the oxidative polymerization efficiency test of Example 1 were as follows: the catalyst surface recovery rate was 80.2%, the solution precipitate recovery rate was 18.1%, and the total recovery rate was 98.3%. No persulfate was added, and the results of the oxidative polymerization efficiency test of Example 1 were as follows: the catalyst surface recovery rate was 3.1%, the solution precipitate recovery rate was 0%, and the total recovery rate was 3.1%.

[0073] 4. Carbon-based catalyst cycle stability test Example 1 was used for three cycles, and the results of the Rhodamine B removal rate test for the first and third times are shown in Table 3.

[0074] Table 1. Oxidation efficiency test results of Examples 1-7 and Comparative Examples 1-2

[0075] Table 2. Oxidative polymerization efficiency test results of Examples 1-7 and Comparative Examples 1-2

[0076] Table 3. Cycle stability test results of Examples 1-7 and Comparative Examples 1-2

[0077] As can be seen from the data in Table 1 and Table 2, the removal rates of rhodamine B of Examples 1-7 are higher than that of Comparative Example 1, and the catalytic oxidation effect is more excellent. The active substance in the examples is a ruthenium atom, while the active substance in Comparative Example 1 is a cobalt atom in phthalocyanine cobalt. The ruthenium atom has a unique electronic structure and a stronger bonding with the carrier, and exhibits more excellent stability and catalytic activity in the treatment of organic pollutants.

[0078] The carrier in the carbon-based catalyst of the examples is formed in situ by carbonization of metal phthalocyanine, and the ruthenium atom is loaded with the carrier by metal-carrier interaction. Due to the structural characteristics of metal phthalocyanine, the density and dispersion of metal monomers are improved. The metal monomers and carbon atoms and nitrogen atoms in the carrier cooperatively produce a confinement effect, which strengthens the stability of the combination of the ruthenium atom and the carrier. Under the confinement effect of the carrier, the carbon-based catalyst and the oxidizing agent form an adduct by metal-oxygen coordination. The adduct participates in the reaction as a non-radical active species, forms a polymer by oxidative polymerization, and precipitates in the solution. Compared with Comparative Example 2, the carbon-based catalyst in Example 1 contains a cobalt atom. In addition to the existing effect, the introduction of the cobalt atom helps the oxidation products of the pollutants to form a solution precipitate. Therefore, the catalytic efficiency of Example 1 is higher, and the removal rate of rhodamine B can still be maintained to increase after 10 min, indicating that the carbon-based catalyst of the present application has the effect of long-time catalysis.

[0079] The total recovery rate of Examples 1-7 is improved compared with Comparative Examples 1-2. In addition, the test results of the cycle stability of Example 1 are shown in Table 3. The retention rate of catalyst activity is 99.1% after 3 cycles, which also proves the improvement of the stability of the combination between the ruthenium atom and the carrier of the carbon-based catalyst.

[0080] Taking Example 1 of the present application as an example, the oxidation performance of different organic pollutants and different oxidizing agents is tested. The removal rate of the organic pollutants is greater than 99% in 15 min, and the total recovery rate of the organic pollutants is greater than 98%, which shows good catalytic effect. When the carbon-based catalyst of the example is not added, the removal rate of the organic pollutants is only 3.1%, and the total recovery rate of the organic pollutants is also only 3.1%, which indicates that the removal of the organic pollutants by the carbon-based catalyst of the present application is achieved by catalytic oxidation, rather than by physical adsorption.

[0081] The technical solutions disclosed in the examples of the present application are described in detail above, and specific examples are applied to explain the principles and implementation modes of the present application. The above description of the examples is only used to help understand the technical solutions and core invention points of the examples of the present application. Meanwhile, for those skilled in the art, according to the idea of the present application, the specific implementation modes and application ranges can be changed. In summary, the content of the specification should not be understood as a limitation of the present application.

Claims

1. A carbon-based catalyst, characterized in that, The carbon-based catalyst includes a support and ruthenium atoms supported on the support. The support includes a nitrogen-doped carbon-based material and metal single atoms supported on the carbon-based material. The ruthenium atoms are supported on the carbon-based material. The support is configured to be obtained by metal phthalocyanine carbonization, and the support comprises the metal single atom, carbon atom and nitrogen atom.

2. The carbon-based catalyst according to claim 1, characterized in that, The carrier also includes sulfur atoms.

3. The carbon-based catalyst according to claim 2, characterized in that, The molar ratio of the ruthenium atom, the carbon atom, the nitrogen atom, and the sulfur atom is (0.4~0.9):(84.6~90.0):(6.5~10.6):(3.1~3.9).

4. The carbon-based catalyst according to any one of claims 1-3, characterized in that, The ruthenium atoms are loaded onto the support in the form of ruthenium clusters, the particle size of which is 2 nm to 20 nm; and / or, The metal phthalocyanine includes at least one of cobalt phthalocyanine, iron phthalocyanine, copper phthalocyanine, nickel phthalocyanine, zinc phthalocyanine, and manganese phthalocyanine.

5. A method for preparing a carbon-based catalyst as described in any one of claims 1-4, characterized in that, The preparation method includes the following steps: Calcination: The metal precursor mixture is calcined for 0.5 h to 3 h in a non-reactive gas atmosphere at 650℃ to 1300℃ to obtain the carbon-based catalyst, wherein the metal precursor mixture includes the metal phthalocyanine and ruthenium source.

6. The preparation method according to claim 5, characterized in that, The non-reactive gas includes at least one of nitrogen, argon, or helium; and / or, The ruthenium source includes at least one of ruthenium chloride, ruthenium acetylacetone, and ruthenium nitrate; and / or, In the calcination step, the heating rate is 1℃ / min to 15℃ / min.

7. The preparation method according to claim 5, characterized in that, The preparation method of the metal precursor mixture includes: adding the metal phthalocyanine and the ruthenium source to a first solvent, stirring at 50°C to 100°C until the first solvent evaporates, to obtain the metal precursor mixture.

8. The preparation method according to claim 7, characterized in that, The method for preparing the metal precursor mixture further includes adding a nitrogen and sulfur source to the first solvent.

9. The preparation method according to claim 8, characterized in that, The nitrogen and sulfur source includes at least one of melamine, thiocyanate, thiourea, thioacetamide, and melamine; and / or, The mass ratio of the metal phthalocyanine, the ruthenium source, and the nitrogen-sulfur source is 1:1:1 to 1:1:

20.

10. The application of a carbon-based catalyst, characterized in that, The carbon-based catalyst is the carbon-based catalyst according to any one of claims 1-4, or the carbon-based catalyst is prepared by the preparation method according to any one of claims 5-9. The carbon-based catalyst is combined with an oxidant for oxidizing polymerized organic pollutant wastewater.

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