Preparation and Application of an Angstrom-Confined Electrocatalyst for Selectively Activating Molecular Oxygen to Produce Hydroxyl Radicals

Abstract

The present invention belongs to the technical field of electrocatalyst preparation, and specifically relates to the preparation and application of an angstrom-confined electrocatalyst for selectively activating molecular oxygen to produce hydroxyl radicals. The present invention uses 2H-phase MoS₂ as a precursor, loads metal single atoms on the surface of the precursor, and intercalates alkali metal cations; the angstrom-confined catalyst is 1T-phase MoS₂ loaded with metal single atoms. The angstrom-confined catalyst provided by the present invention has high three-electron selectivity, can significantly expose catalytic active sites, accelerate the mass transfer of reactants, generate reactive oxygen species in a through-flow reactor, and achieve a high hydroxyl radical generation rate and utilization efficiency in angstrom channels. The preparation method is simple and has good electrochemical stability. The present invention lays a foundation for angstrom-confined catalysis and reflects the importance of the angstrom-confined strategy in the design of highly efficient catalysts for water pollution control.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalysts, and particularly to the preparation and application of an angstrom-confined electrocatalyst for selectively activating molecular oxygen to produce hydroxyl radicals. Background Art

[0002] The confinement effect of using the nanoconfinement effect to confine the reaction in a nanoreactor (such as an interface, channel, cavity, and pore) has attracted great attention because it can significantly improve the intrinsic properties of the catalytic system (such as: electronic structure, mass transfer, electron transfer, phase state, and reaction rate, etc.). From a thermodynamic perspective, according to Le Chatelier's principle, by enriching and concentrating reactants or removing products, the reaction equilibrium can be changed, thereby accelerating the reaction rate. Therefore, the nanoconfinement effect can regulate the electron distribution on the catalyst surface, thereby improving the activity, selectivity, and stability of the catalytic system. In recent years, significant progress has been made in the applied research of the nanoconfinement effect in the environmental field (including adsorption and membrane technology). Theoretical predictions show that angstrom-scale confined catalysts have better catalytic performance than traditional nanoconfinement due to stronger electron interactions, more precise spatial localization, and more efficient diffusion and reaction processes. Although angstrom-confined catalysis (ACC) is extremely attractive in fields such as water treatment, its practical application still faces many challenges. For example, the precise construction of angstrom-scale channels, the uniform distribution of catalytic active centers at the angstrom scale, and the balance between stability and activity limit the further promotion of ACC technology.

[0003] Two-dimensional (2D) structures are considered ideal materials for enhancing the reactant diffusion path due to their high-exposed specific surface area and abundant active sites. Due to the inherent van der Waals interaction in the interlayer space, layered two-dimensional structures are the best angstrom-confined reactors for fixing various active sites, such as metals, small organic molecules, and polymers. In addition, the huge capillary action (>50 bar) in the nanochannels of two-dimensional materials can significantly accelerate the molecular transport process. Therefore, the layered structure assembled by two-dimensional materials can be used as an angstrom-confined space for water pollution treatment. Especially in recent years, molybdenum disulfide (MoS2) nanosheets have attracted extensive attention due to their unique electrical, physicochemical, biological, and mechanical properties. MoS2 nanosheets have been widely used in electronic devices, catalysis, biomedicine, and energy-related fields, and will also show important potential in the environmental field. Usually, 2H-phase MoS2 has semiconductor properties, and its bandgap range is 1.3-1.9 eV, depending on the interlayer thickness; in contrast, 1T-phase MoS2 exhibits obvious metallic properties, and its electronic conductivity is about 10 times that of the 2H-phase 7times. The unique structure and electronic properties of MoS2 make it possible to precisely regulate catalytic reactions, laying a solid foundation for the breakthrough of environmental catalysis technology and being of great significance for selectively activating molecular oxygen to generate reactive oxygen species (ROS) within the angstrom scale range.

[0004] Water pollution poses a serious threat to human health and aquatic ecosystems. Therefore, the development and implementation of efficient wastewater treatment technologies are crucial for eliminating pollutants. Although antibiotics have played an important role in improving human health, their potential harmful effects on aquatic ecosystems and human health, as well as the risk of the spread of antibiotic resistance in ecosystems, bring more severe challenges to environmental remediation. The electro-Fenton technology has received extensive attention due to its unique advantages. This technology undergoes a two-electron oxygen reduction reaction with O2 as the reactant, and further activates the in-situ generated hydrogen peroxide to obtain ROS (including: hydroxyl radical (HO · ), superoxide radical (O2 ·- ), singlet oxygen, etc. 1 O2)), showing great potential in the degradation of organic pollutants. It is worth noting that the hydroxyl radical, with its strong oxidizing property (oxidation potential up to 2.80 V), has become an ideal oxidant for degrading organic pollutants in the environmental field. However, the short lifetime of free radicals (10 -6 ~10 -9 s) limits their mass transfer efficiency from the catalyst surface to the solution where the target pollutants are located, severely restricting the actual utilization rate of free radicals in heterogeneous reactions. In addition, free radicals inevitably react with dissolved organic matter and coexisting inorganic ions in the water matrix, thus significantly reducing their reaction ability with target pollutants. These problems indicate that the intervention of angstrom confinement technology is urgently needed. By designing and optimizing a heterogeneous catalytic system similar to Fenton, the effective utilization rate of free radicals can be significantly improved, providing an innovative solution for water pollution treatment. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a preparation and application of an angstrom-confined electrocatalyst for selectively activating molecular oxygen to produce hydroxyl radicals. The angstrom-confined catalyst provided by the present invention has high three-electron selectivity, can significantly expose catalytic active sites, accelerate the mass transfer of reactants, generate reactive oxygen species in a through-flow reactor, achieve a high hydroxyl radical generation rate and utilization efficiency within angstrom channels, has a simple preparation method, and has good electrochemical stability. The present invention lays a foundation for angstrom-confined catalysis, reflecting the importance of the angstrom confinement strategy in the design of highly efficient catalysts for water pollution control.

[0006] The first object of the present invention is to provide an angstrom-confined catalyst for selectively activating molecular oxygen to produce hydroxyl radicals, with 2H-phase MoS2 as the precursor, and the surface of the precursor is loaded with metal single atoms and intercalated with alkali metal cations; the angstrom-confined catalyst is 1T-phase MoS2 loaded with metal single atoms.

[0007] In some embodiments of the present invention, the metal single atoms are one or more of iron, cobalt, nickel, and copper; further preferably, they are iron single atoms; the definition of metal single atoms in the present invention can be generalized as: the active metals in the catalyst are uniformly dispersed on the carrier in the form of single atoms, and there is no interaction of any form between each individual atom. The single atoms formed on the surface of the precursor prepared in the present invention are, for example, single atoms such as Fe, Co, Ni, and Cu, and the metal single atoms are loaded on the MoS2 carrier.

[0008] The alkali metal cations include one or more of lithium ions, sodium ions, and potassium ions.

[0009] In some embodiments of the present invention, the loading amount of the metal single atoms is 0.5 - 3.0 wt%, and exemplarily, it can be 0.5 wt%, 1.0 wt%, 1.5 wt%, 2.0 wt%, 2.5 wt%, 3.0 wt%, etc.; the loading amount of the alkali metal cations is 0.5 - 3.0 wt%, and exemplarily, it can be 0.5 wt%, 1.0 wt%, 1.5 wt%, 2.0 wt%, 2.5 wt%, 3.0 wt%, etc.

[0010] The second object of the present invention is to provide a preparation method of the angstrom-confined catalyst for selectively activating molecular oxygen to produce hydroxyl radicals, comprising the following steps:

[0011] (1) Mix and heat-react a soluble molybdenum precursor, a sulfur source, and a metal source in a solvent to obtain an angstrom-confined catalyst precursor;

[0012] (2) Mix the angstrom-confined catalyst precursor obtained in step (1) with an alkali metal source, and heat and calcine it in a reducing atmosphere to obtain the angstrom-confined catalyst.

[0013] In some embodiments of the present invention, in step (1), the soluble molybdenum precursor is selected from one or more of ammonium molybdate, ammonium tetrathiomolybdate, or sodium molybdate;

[0014] The metal source is selected from one or more of an iron source, a copper source, a nickel source, and a cobalt source.

[0015] In some embodiments of the present invention, the sulfur source is selected from one or more of thiourea, sodium sulfide, and sulfur powder.

[0016] In some embodiments of the present invention, in step (1), the temperature of the mixed heating is 180 - 220 °C, and the reaction time is 8 - 36 h; the solvent is water.

[0017] The mass ratio of the soluble molybdenum precursor, sulfur source, and metal source is (35 - 45):(35 - 45):(2 - 8).

[0018] Further, step (1) further includes drying the product, the drying time is 6 - 48 h, and the drying temperature is 60 - 90 °C.

[0019] In some embodiments of the present invention, in step (2), the alkali metal source is selected from one or more of sodium source, potassium source, or lithium salt;

[0020] The gas of the reducing atmosphere includes hydrogen and an inert gas;

[0021] The volume content of the hydrogen is 2 - 10%, and exemplarily, it can be 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, etc.

[0022] Further, the inert gas is selected from argon and / or nitrogen.

[0023] Further, the alkali metal source is selected from one or more of sodium hydroxide, potassium hydroxide, and lithium hydroxide.

[0024] In some embodiments of the present invention, in step (2), the temperature of the heating and calcination is 700 - 1000 °C, and the time is 1 - 4 h;

[0025] The mass ratio of the angstrom-confined catalyst precursor to the alkali metal source is 1:(0.075 - 2.0).

[0026] Further, the mass ratio of the soluble molybdenum precursor, sulfur source, metal source, and alkali metal source is (35 - 45):(35 - 45):(2 - 8):(12 - 23).

[0027] Further, in step (2), it further includes ultrasonic treatment, centrifugation, dialysis, and drying of the product;

[0028] The time of the ultrasonic treatment is 4 - 12 h;

[0029] The centrifugation time is 5 min, and the rotation speed is 8000 rpm;

[0030] The drying method is vacuum drying, and the drying time is 6 - 48 h.

[0031] The third object of the present invention is to provide an application of an angstrom-confined catalyst in wastewater treatment and environmental remediation. The angstrom-confined catalyst includes the angstrom-confined catalyst for selectively activating molecular oxygen to produce hydroxyl radicals; the range value of the angstrom confinement interval is 9-13 angstroms.

[0032] In some embodiments of the present invention, an application of an angstrom-confined catalyst in degrading organic pollutants, where the organic pollutants include sulfonamides (such as sulfamethoxazole), tetracyclines (such as oxytetracycline), and endocrine disruptors (such as bisphenol A, etc.).

[0033] In the present invention, by embedding alkali metal cations into the 2H-phase MoS2 of the prepared supported single-atom catalyst, 1T-phase MoS2 with different interlayer spacings is obtained, and angstrom-scale channels are formed through the interface between MoS2 layers, thereby successfully constructing an angstrom-confined space.

[0034] The above technical solutions of the present invention have the following advantages compared with the prior art:

[0035] 1. The present invention provides an angstrom-confined catalyst, where the mass fraction of metal single atoms (such as single-atom iron) in the angstrom-confined catalyst is 0.5-3.0%, and the mass fraction of alkali metals is 0.5-3.0%. The angstrom-confined catalyst provided by the present invention has a high HO· yield, high catalytic activity, a simple preparation method, and good electrochemical stability.

[0036] 2. Compared with non-angstrom-confined catalysts, the angstrom-confined catalyst provided by the present invention realizes the transformation from a four-electron to a three-electron oxygen reduction process and can selectively generate hydroxyl radicals.

[0037] 3. The angstrom-confined catalyst provided by the present invention can achieve the enrichment of HO· in the confined space, thereby achieving the efficient removal of target pollutants. Through the construction of the angstrom-confined space, the rapid generation of HO· in the confined space can be promoted, and the yield of HO· is as high as 121 μM·L -1 .

[0038] 4. The present invention provides a preparation method of the above angstrom-confined catalyst, including the following steps: (1) mixing, reacting, washing, and drying a soluble molybdenum precursor, a sulfur source, a metal source, and water to obtain an angstrom-confined catalyst precursor; (2) grinding, calcining, ultrasonicating, centrifuging, dialyzing, and drying the angstrom-confined catalyst precursor with an alkali metal source to obtain an angstrom-confined catalyst. By using dialysis treatment, residual alkali metal cations can be removed, thereby improving the three-electron selectivity during the oxygen reduction process.

[0039] 5. The Ångström-confined catalyst provided by the present invention can be used for electrochemical reactions after being loaded on carbon paper, carbon cloth, carbon felt or other conductive current collectors.

[0040] 6. The present invention also provides an application of an Ångström-confined catalyst or an Ångström-confined catalyst prepared by this preparation method in wastewater treatment and environmental remediation. The catalyst provided by the present invention can efficiently degrade new pollutants, meeting the economic, flexible and sustainable water purification requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to make the content of the present invention easier to be clearly understood, the following further describes the present invention in detail according to specific embodiments of the present invention in combination with the drawings, wherein,

[0042] Figure 1 is the transmission electron microscope of the Ångström-confined catalyst prepared in Example 1 of the present invention;

[0043] Figure 2 is the aberration-corrected electron microscope image of the Ångström-confined catalyst obtained in Example 1 of the present invention;

[0044] Figure 3 is Fe-MoS2 in 0.05 M Na2SO4 with O2 saturation and pH = 3 in Test Example 1 of the present invention

[0045] (Comparative Example 1), Li-Fe-MoS2 (Example 3), K-Fe-MoS2 (Example 2) and Na-Fe-MoS2

[0046] (Example 1) Quantitative analysis of HO· generated at the cathode;

[0047] Figure 4 is the R-space data obtained from the Fourier transform (FT) curve of the synchrotron radiation X-ray absorption spectrum of the Ångström-confined catalysts obtained in Example 1 and Comparative Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0048] The following further describes the present invention in combination with the drawings and specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it, but the embodiments cited are not intended to limit the present invention.

[0049] Example 1

[0050] This example provides an Ångström-confined catalyst, in which the mass fraction of iron is 1.8% and the mass fraction of sodium is 1.5%.

[0051] This example also provides a preparation method of an Ångström-confined catalyst, including the following steps:

[0052] (1) Preparation of angstrom-confined catalyst precursor: 1.248 g (NH4)2MoO4 and 1.142 g CH4N2S were dissolved in 60 mL deionized water. Ultrasonic dispersion was performed at room temperature for 10 minutes to make it a uniform and transparent reddish-brown solution. Then 0.123 g Fe(NO3)3·9H2O was added to the reddish-brown solution. After stirring and dissolving, the mixed solution was transferred to a 100 mL polytetrafluoroethylene-lined autoclave. The autoclave was then sealed and kept in an oven at 200°C for 24 hours. After the reactor was cooled to room temperature, the Fe-MoS2 was washed with deionized water and ethanol respectively to remove the unreacted precursor, and then the Fe-MoS2 sample was dried at 80°C for 24 hours to obtain 2H phase MoS2 powder (i.e., angstrom-confined catalyst precursor).

[0053] (2) Preparation of angstrom-confined catalyst: The 2H phase MoS2 powder obtained in step (1) was ground and mixed with a certain amount of NaOH (mass ratio of 2:1) to obtain a mixture. The mixture was then calcined in an Ar / H2 (H2 volume content of 5%) atmosphere at 800°C for 2 hours. The calcined product was treated with ultrasound for 8 hours. The obtained product was centrifuged at 8000 rpm for 5 minutes to separate the suspension, and then dialyzed using a dialysis membrane to remove residual cations, finally obtaining a 1T phase Na-Fe-MoS2 angstrom-confined catalyst. The obtained product was structurally characterized, and the results are shown in FIG. Figure 1 、 Figure 2 and Figure 4 ,Depend on Figure 1 and Figure 2 It can be seen that after the insertion of alkali metal cations, MoS2 transforms from the 2H phase to the 1T phase, forming an angstrom confined space (about 10.3 angstroms). Figure 4 As shown in the R space data obtained from the Fourier transform (FT) curve of the synchrotron radiation X-ray absorption spectrum of the Angstrom confined catalyst obtained in Example 1 of the present invention, the standard sample iron foil is There are obvious Fe-Fe bonds at There are obvious Fe-Fe bonds at There are Fe-S bonds at the sites, but no Fe-Fe or Fe-O bonds, indicating that the prepared catalyst is a single-atom catalyst rather than a catalyst loaded with a single metal or metal oxide.

[0054] Example 2 (Compared with Example 1, different alkali metal doping is used)

[0055] This embodiment provides an angstrom-confined catalyst, in which the mass fraction of iron is 1.7% and the mass fraction of potassium is 2.0%.

[0056] This embodiment also provides a preparation method of an angstrom-confined catalyst, comprising the following steps:

[0057] (1) Prepare the angstrom-confined catalyst precursor: Dissolve 1.248 g of (NH4)2MoO4 and 1.142 g of CH4N2S in 60 mL of deionized water. With the aid of ultrasonic dispersion for 10 minutes at room temperature, make it into a uniform and transparent reddish-brown solution. Then add 0.123 g of Fe(NO3)3·9H2O to the reddish-brown solution. After stirring and dissolving, transfer the mixed solution to a 100 mL polytetrafluoroethylene-lined autoclave. Then seal the autoclave and keep it in an oven at 200 °C for 24 hours. After the reactor is cooled to room temperature, wash the Fe-MoS2 with deionized water and ethanol respectively to remove the unreacted precursors, and then dry the Fe-MoS2 sample at 80 °C for 24 hours to obtain 2H-phase MoS2 powder (i.e., the angstrom-confined catalyst precursor).

[0058] (2) Prepare the angstrom-confined catalyst: Grind and mix the 2H-phase MoS2 powder obtained in step (1) with a certain amount of KOH (mass ratio is 1.4:1) to obtain a mixture. Then calcine the mixture in an Ar / H2 (volume content of H2 is 5%) atmosphere at 800 °C for 2 hours. The calcined product is treated in ultrasonic for 8 h. After the obtained product is centrifuged at a speed of 8000 rpm for 5 minutes to separate the suspension, then dialysis treatment is carried out using a dialysis membrane to remove the residual cations, and finally obtain 1T-phase K-Fe-MoS2 angstrom-confined catalyst (angstrom-confined space is about 13 angstroms).

[0059] Example 3 (compared with Example 1, different alkali metal doping is adopted)

[0060] This embodiment provides an angstrom-confined catalyst, in which the mass fraction of iron is 1.8% and the mass fraction of lithium is 1.0%.

[0061] This embodiment also provides a preparation method of an angstrom-confined catalyst, comprising the following steps:

[0062] (1) Preparation of the angstrom-confined catalyst precursor: Dissolve 1.248 g of (NH4)2MoO4 and 1.142 g of CH4N2S in 60 mL of deionized water. With the aid of ultrasonic dispersion for 10 minutes at room temperature, make it into a homogeneous and transparent reddish-brown solution. Then add 0.123 g of Fe(NO3)3·9H2O to the reddish-brown solution. After stirring and dissolving, transfer the mixed solution to a 100 mL polytetrafluoroethylene-lined autoclave. Then seal the autoclave and keep it in an oven at 200 °C for 24 hours. After the reactor is cooled to room temperature, wash the Fe-MoS2 with deionized water and ethanol respectively to remove the unreacted precursors, and then dry the Fe-MoS2 sample at 80 °C for 24 hours to obtain 2H-phase MoS2 powder (i.e., the angstrom-confined catalyst precursor).

[0063] (2) Preparation of the angstrom-confined catalyst: Grind and mix the 2H-phase MoS2 powder obtained in step (1) with a certain amount of LiOH (mass ratio is 3.3:1). Then calcine the mixture in an Ar / H2 (volume content of H2 is 5%) atmosphere at 800 °C for 2 hours. The calcined product is treated in ultrasonic for 8 h. After the obtained product is centrifuged for 5 minutes at a rotational speed of 8000 rpm to separate the suspension, then dialysis treatment is carried out using a dialysis membrane to remove the residual cations, and finally 1T-phase Li-Fe-MoS2 angstrom-confined catalyst (angstrom-confined space is about 9 angstroms) is obtained.

[0064] Example 4

[0065] This example provides an angstrom-confined catalyst, in which the mass fraction of iron is 1.5% and the mass fraction of sodium is 1.5%.

[0066] This example also provides a preparation method of an angstrom-confined catalyst, including the following steps:

[0067] (1) Preparation of the angstrom-confined catalyst precursor: Dissolve 1.248 g of (NH4)2MoS4 and 1.142 g of CH4N2S in 60 mL of deionized water. With the aid of ultrasonic dispersion for 10 minutes at room temperature, make it into a homogeneous and transparent reddish-brown solution. Then add 0.123 g of Fe(NO3)3·9H2O to the reddish-brown solution. After stirring and dissolving, transfer the mixed solution to a 100 mL polytetrafluoroethylene-lined autoclave. Then seal the autoclave and keep it in an oven at 200 °C for 24 hours. After the reactor is cooled to room temperature, wash the Fe-MoS2 with deionized water and ethanol respectively to remove the unreacted precursors, and then dry the Fe-MoS2 sample at 80 °C for 24 hours to obtain 2H-phase MoS2 powder (i.e., the angstrom-confined catalyst precursor).

[0068] (2) Preparation of the angstrom-confined catalyst: Grind and mix the obtained 2H-phase MoS2 powder from step (1) with a certain amount of NaOH (mass ratio 2:1). Then calcine the mixture in an Ar / H2 atmosphere (volume content of H2 is 5%) at 800 °C for 2 hours. Treat the calcined product by ultrasound for 8 h. Centrifuge the obtained product at a rotation speed of 8000 rpm for 5 minutes to separate the suspension, and then perform dialysis treatment using a dialysis membrane to remove residual cations, finally obtaining the 1T-phase Na-Fe-MoS2 angstrom-confined catalyst.

[0069] Example 5

[0070] This example provides an angstrom-confined catalyst, in which the mass fraction of iron is 1.6% and the mass fraction of sodium is 2.1%.

[0071] This example also provides a preparation method of an angstrom-confined catalyst, including the following steps:

[0072] (1) Preparation of the angstrom-confined catalyst precursor: Dissolve 1.248 g of Na2MoO4 and 1.142 g of CH4N2S in 60 mL of deionized water. Disperse it by ultrasound for 10 minutes at room temperature to make it a uniform transparent reddish-brown solution. Then add 0.123 g of Fe(NO3)3·9H2O to the reddish-brown solution. After stirring and dissolving, transfer the mixed solution to a 100 mL autoclave with a polytetrafluoroethylene inner liner. Then seal the autoclave and keep it in an oven at 200 °C for 24 hours. After the reactor cools to room temperature, wash the Fe-MoS2 with deionized water and ethanol respectively to remove unreacted precursors, and then dry the Fe-MoS2 sample at 80 °C for 24 hours to obtain 2H-phase MoS2 powder (i.e., the angstrom-confined catalyst precursor).

[0073] (2) Preparation of the angstrom-confined catalyst: Grind and mix the obtained 2H-phase MoS2 powder from step (1) with a certain amount of NaOH (mass ratio 2:1). Then calcine the mixture in an Ar / H2 atmosphere (volume content of H2 is 5%) at 800 °C for 2 hours. Treat the calcined product by ultrasound for 8 h. Centrifuge the obtained product at a rotation speed of 8000 rpm for 5 minutes to separate the suspension, and then perform dialysis treatment using a dialysis membrane to remove residual cations, finally obtaining the 1T-phase Na-Fe-MoS angstrom-confined catalyst.

[0074] Example 6

[0075] This example provides an angstrom-confined catalyst, in which the mass fraction of iron is 2.5% and the mass fraction of sodium is 1.4%.

[0076] This embodiment also provides a method for preparing an angstrom-confined catalyst, which includes the following steps:

[0077] (1) Preparation of the angstrom-confined catalyst precursor: Dissolve 1.248 g of (NH4)2MoO4 and 1.142 g of CH4N2S in 60 mL of deionized water. With the aid of ultrasonic dispersion for 10 minutes at room temperature, make it into a uniform and transparent reddish-brown solution. Then add 0.246 g of Fe(NO3)3·9H2O to the reddish-brown solution. After stirring and dissolving, transfer the mixed solution to a 100 mL polytetrafluoroethylene-lined autoclave. Then seal the autoclave and keep it in an oven at 200 °C for 24 hours. After the reactor is cooled to room temperature, wash the Fe-MoS2 with deionized water and ethanol respectively to remove the unreacted precursors, and then dry the Fe-MoS2 sample at 80 °C for 24 hours to obtain 2H-phase MoS2 powder (i.e., the angstrom-confined catalyst precursor).

[0078] (2) Preparation of the angstrom-confined catalyst: Grind and mix the 2H-phase MoS2 powder obtained in step (1) with a certain amount of NaOH (mass ratio is 2:1). Then calcine the mixture in an Ar / H2 (volume content of H2 is 5%) atmosphere at 800 °C for 2 hours. The calcined product is treated in ultrasonic for 8 h, and the obtained product is centrifuged for 5 minutes at a rotation speed of 8000 rpm to separate the suspension, and then dialysis treatment is carried out using a dialysis membrane to remove the residual cations, and finally 1T-phase Na-Fe-MoS2 angstrom-confined catalyst is obtained.

[0079] Example 7

[0080] This embodiment provides an angstrom-confined catalyst, in which the mass fraction of iron is 1.5% and the mass fraction of sodium is 2.1%.

[0081] This embodiment also provides a method for preparing an angstrom-confined catalyst, which includes the following steps:

[0082] (1) Preparation of the angstrom-confined catalyst precursor: Dissolve 1.248 g of (NH4)2MoO4 and 1.142 g of CH4N2S in 60 mL of deionized water. With the aid of ultrasonic dispersion for 10 minutes at room temperature, make it into a uniform and transparent reddish-brown solution. Then add 0.123 g of Fe(NO3)3·9H2O to the reddish-brown solution. After stirring and dissolving, transfer the mixed solution to a 100 mL polytetrafluoroethylene-lined autoclave. Then seal the autoclave and keep it in an oven at 200 °C for 24 hours. After the reactor is cooled to room temperature, wash the Fe-MoS2 with deionized water and ethanol respectively to remove the unreacted precursors, and then dry the Fe-MoS2 sample at 80 °C for 24 hours to obtain 2H-phase MoS2 powder (i.e., the angstrom-confined catalyst precursor).

[0083] (2) Preparation of the angstrom-confined catalyst: Grind and mix the obtained 2H-phase MoS2 powder in step (1) with a certain amount of NaOH (mass ratio is 1.3:1). Then calcine the mixture in an Ar / H2 (volume content of H2 is 5%) atmosphere at 800 °C for 2 hours. The calcined product is treated in ultrasonic for 8 h. The obtained product is centrifuged at a speed of 8000 rpm for 5 minutes to separate the suspension, and then dialysis treatment is carried out using a dialysis membrane to remove the residual cations, and finally the 1T-phase Na-Fe-MoS2 angstrom-confined catalyst is obtained.

[0084] Example 8

[0085] This example provides an angstrom-confined catalyst, in which the mass fraction of copper is 0.7% and the mass fraction of sodium is 1.5%.

[0086] This example also provides a preparation method of the angstrom-confined catalyst, including the following steps:

[0087] (1) Preparation of the angstrom-confined catalyst precursor: Dissolve 1.248 g of (NH4)2MoO4 and 1.142 g of CH4N2S in 60 mL of deionized water. Disperse it by ultrasonic for 10 minutes at room temperature to make it a uniform transparent blue solution. Then add 0.0561 g of Cu(NO3)2·9H2O to the red-brown solution. After stirring and dissolving, transfer the mixed solution to a 100 mL polytetrafluoroethylene-lined autoclave. Then seal the autoclave and keep it in an oven at 200 °C for 24 hours. After the reactor cools to room temperature, wash the Cu-MoS2 with deionized water and ethanol respectively to remove the unreacted precursors, and then dry the Cu-MoS2 sample at 80 °C for 24 hours to obtain the 2H-phase MoS2 powder (i.e., the angstrom-confined catalyst precursor).

[0088] (2) Preparation of the angstrom-confined catalyst: Grind and mix the obtained 2H-phase MoS2 powder in step (1) with a certain amount of NaOH (mass ratio is 2:1). Then calcine the mixture in an Ar / H2 (volume content of H2 is 5%) atmosphere at 800 °C for 2 hours. The calcined product is treated in ultrasonic for 8 h. The obtained product is centrifuged at a speed of 8000 rpm for 5 minutes to separate the suspension, and then dialysis treatment is carried out using a dialysis membrane to remove the residual cations, and finally the 1T-phase Na-Cu-MoS2 angstrom-confined catalyst is obtained.

[0089] Example 9

[0090] This example provides an angstrom-confined catalyst, in which the mass fraction of nickel is 0.5% and the mass fraction of sodium is 1.5%.

[0091] This embodiment also provides a method for preparing an angstrom-confined catalyst, comprising the following steps:

[0092] (1) Preparation of the angstrom-confined catalyst precursor: Dissolve 1.248 g of (NH4)2MoO4 and 1.142 g of CH4N2S in 60 mL of deionized water. With the aid of ultrasonic dispersion at room temperature for 10 minutes, make it into a uniform and transparent green solution. Then add 0.087 g of NiNO3·6H2O to the reddish-brown solution. After stirring and dissolving, transfer the mixed solution to a 100 mL polytetrafluoroethylene-lined autoclave. Then seal the autoclave and keep it in an oven at 200 °C for 24 hours. After the reactor is cooled to room temperature, wash the Ni-MoS2 with deionized water and ethanol respectively to remove the unreacted precursors, and then dry the Ni-MoS2 sample at 80 °C for 24 hours to obtain 2H-phase MoS2 powder (i.e., the angstrom-confined catalyst precursor).

[0093] (2) Preparation of the angstrom-confined catalyst: Grind and mix the 2H-phase MoS2 powder obtained in step (1) with a certain amount of NaOH (mass ratio is 2:1). Then calcine the mixture in an Ar / H2 (volume content of H2 is 5%) atmosphere at 800 °C for 2 hours. Treat the calcined product by ultrasonic treatment for 8 h. After centrifuging the product at a speed of 8000 rpm for 5 minutes to separate the suspension, then carry out dialysis treatment using a dialysis membrane to remove the residual cations, and finally obtain 1T-phase Na-Ni-MoS2 angstrom-confined catalyst.

[0094] Example 10

[0095] This embodiment provides an angstrom-confined catalyst, in which the mass fraction of cobalt is 0.6% and the mass fraction of sodium is 1.4%.

[0096] This embodiment also provides a method for preparing an angstrom-confined catalyst, comprising the following steps:

[0097] (1) Preparation of the angstrom-confined catalyst precursor: Dissolve 1.248 g of (NH4)2MoO4 and 1.142 g of CH4N2S in 60 mL of deionized water. With the aid of ultrasonic dispersion at room temperature for 10 minutes, make it into a uniform and transparent red solution. Then add 0.087 g of Co(NO3)2·6H2O to the reddish-brown solution. After stirring and dissolving, transfer the mixed solution to a 100 mL polytetrafluoroethylene-lined autoclave. Then seal the autoclave and keep it in an oven at 200 °C for 24 hours. After the reactor is cooled to room temperature, wash the Co-MoS2 with deionized water and ethanol respectively to remove the unreacted precursors, and then dry the Co-MoS2 sample at 80 °C for 24 hours to obtain 2H-phase MoS2 powder (i.e., the angstrom-confined catalyst precursor).

[0098] (2) Preparation of an angstrom-confined catalyst: The 2H phase MoS2 powder obtained in step (1) was ground and mixed with a certain amount of NaOH (mass ratio of 2:1). The mixture was then calcined at 800°C in an Ar / H2 atmosphere (H2 volume content of 5%) for 2 hours. The calcined product was ultrasonically treated for 8 hours. The obtained product was centrifuged at 8000 rpm for 5 minutes to separate the suspension, and then dialyzed to remove residual cations, thereby obtaining a 1T phase Na-Co-MoS2 angstrom-confined catalyst.

[0099] Comparative Example 1 (Compared with Example 1, without alkali metal cation intercalation treatment)

[0100] This comparative example also provides a method for preparing an Angstrom-confined catalyst, comprising the following steps:

[0101] Preparation of angstrom-confined catalyst precursor: 1.248g (NH4)2MoO4 and 1.142g CH4N2S were dissolved in 60mL deionized water. Ultrasonic dispersion was carried out at room temperature for 10 minutes to make it a uniform and transparent reddish-brown solution. Then 0.123g Fe(NO3)3·9H2O was added to the reddish-brown solution. After stirring and dissolving, the mixed solution was transferred to a 100mL polytetrafluoroethylene-lined autoclave. The autoclave was then sealed and kept in an oven at 200°C for 24 hours. After the reactor was cooled to room temperature, Fe-MoS2 was washed with deionized water and ethanol respectively to remove the unreacted precursor, and then the Fe-MoS2 sample was dried at 80°C for 24 hours to obtain a non-angstrom-confined catalyst. The obtained non-angstrom-confined catalyst was structurally characterized, see Figure 4 . Figure 4 As shown in the R space data obtained from the Fourier transform (FT) curve of the synchrotron radiation X-ray absorption spectrum of the Angstrom confined catalyst obtained in Example 1 of the present invention and the non-Angstrom confined catalyst obtained in Comparative Example 1, the standard sample iron foil is There are obvious Fe-Fe bonds at There are obvious Fe-Fe bonds at There are Fe-S bonds at the sites, but no Fe-Fe or Fe-O bonds, indicating that the prepared catalyst is a single-atom catalyst rather than a catalyst loaded with a single metal or metal oxide.

[0102] Comparative Example 2 (Compared with Example 1, hydrogen was not used during calcination)

[0103] This comparative example also provides a method for preparing an Angstrom-confined catalyst, comprising the following steps:

[0104] (1) Preparation of the angstrom-confined catalyst precursor: Dissolve 1.248 g of (NH4)2MoO4 and 1.142 g of CH4N2S in 60 mL of deionized water. With the aid of ultrasonic dispersion for 10 minutes at room temperature, make it into a uniform and transparent reddish-brown solution. Then add 0.123 g of Fe(NO3)3·9H2O to the reddish-brown solution. After stirring and dissolving, transfer the mixed solution to a 100 mL polytetrafluoroethylene-lined autoclave. Then seal the autoclave and keep it in an oven at 200 °C for 24 hours. After the reactor is cooled to room temperature, wash the Fe-MoS2 with deionized water and ethanol respectively to remove the unreacted precursors, and then dry the Fe-MoS2 sample at 80 °C for 24 hours to obtain 2H-phase MoS2 powder (i.e., the angstrom-confined catalyst precursor).

[0105] (2) Preparation of the angstrom-confined catalyst: Grind and mix the 2H-phase MoS2 powder obtained in step (1) with a certain amount of NaOH (mass ratio is 2:1). Then calcine the mixture in an Ar atmosphere at 800 °C for 2 hours. After the obtained product is centrifuged at a speed of 8000 rpm for 5 minutes to separate the suspension, then carry out dialysis treatment to remove the residual cations, and finally obtain the nanoparticle catalyst NP-Fe-MoS2.

[0106] Test Example 1

[0107] Perform performance tests on the catalysts prepared in Examples 1-10 and Comparative Examples 1-2. The content of the performance test is the yield of ·OH. The specific test method is as follows:

[0108] Test method for the yield of ·OH: Grind the catalysts prepared in Examples 1-10 and Comparative Examples 1-2. Add 0.01 mol of dimethyl sulfoxide (DMSO) and 0.05 mol of anhydrous sodium sulfate (Na2SO4) to 1 L of water, and adjust the pH of the solution to 3 using dilute sulfuric acid. Take 100 mL of the prepared solution and apply a constant current of 30 mA on a potentiostat for reaction. The experiment uses a two-electrode system. The working electrode is the carbon paper electrode (2.5 cm × 5 cm) loaded with the prepared catalyst, and the counter electrode is a platinum sheet. The electrodes are placed in parallel with a spacing of 2 cm, and oxygen is introduced in advance for 30 minutes. During the reaction, take 1 mL of the sample every 5 minutes and add 1 mM of 2,4-dinitrophenylhydrazine solution. After the mixed solution is kept in a water bath at 60 °C for 30 minutes, take it out. Next, perform concentration determination by high-performance liquid chromatography. The detection conditions are that the ratio of water to methanol is 40:60, the detection wavelength is 355 nm, and the flow rate is set at 0.8 mL min -1 , and the peak emergence time is 5.2 minutes.

[0109] The test results are shown in Table 1 below:

[0110] Table 1

[0111] <![CDATA[Yield of HO· (μM·L -1 )]]> Example 1 121.0 Example 2 59 Example 3 87.7 Example 4 101.2 Example 5 98.4 Example 6 73.2 Example 7 80.7 Example 8 77.2 Example 9 75.1 Example 10 65.6 Comparative Example 1 11.2 Comparative Example 2 36.0

[0112] Conclusion: The catalysts prepared in Examples 1 - 10 and Comparative Examples 1 - 2 were respectively subjected to rotating disk catalyst tests, and then the calculated hydroxyl radical yields reached between 11.2 - 121.0, and the yield of the optimal sample, Example 1, reached 121.0 μM·L -1 , and the hydroxyl radical yields of all of them were much higher than those of other catalysts.

[0113] Test Example 2

[0114] The catalysts prepared in Examples 1 - 10 and Comparative Examples 1 - 2 were applied to the simulated polluted wastewater treatment process. The specific test method was as follows:

[0115] The indexes of the wastewater inlet were: 10 mg / L sulfamethoxazole, pH = 3, 0.05 M sodium sulfate solution.

[0116] The test method was as follows: The catalysts prepared in Examples 1 - 10 and Comparative Examples 1 - 2 were used as the cathode, and a platinum sheet was used as the anode. A potentiostat was used to conduct a degradation test at a constant current of 30 mA. Aeration was carried out for 30 min before the degradation reaction, and the oxygen flow rate was 200 mL / min, and the aeration rate was kept constant during the degradation process. Sampling was carried out after 30 minutes of degradation, and the content of sulfamethoxazole was tested by liquid chromatography.

[0117] The test results are shown in Table 2 below:

[0118] Table 2

[0119] Sulfamethoxazole removal rate % Example 1 100 Example 2 55 Example 3 68 Example 4 83 Example 5 88 Example 6 74 Example 7 91 Example 8 65.2 Example 9 57.1 Example 10 51.4 Comparative Example 1 17 Comparative Example 2 23

[0120] Conclusion: The catalysts prepared in Examples 1 - 10 and Comparative Examples 1 - 2 were respectively subjected to sulfamethoxazole degradation tests. The sulfamethoxazole removal rates were between 100% - 51.4%, and the removal rate of the optimal sample, Example 1, reached 100%. The sulfamethoxazole removal rates of all of them were much higher than those of the catalysts obtained in Comparative Example 1 and Comparative Example 2.

[0121] Obviously, the above examples are only for clearly illustrating the examples and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of this invention.

Claims

1. An angstrom-confined catalyst for selectively activating molecular oxygen to produce hydroxyl radicals for the electrocatalytic degradation of organic pollutants, wherein the organic pollutants include sulfonamides, tetracyclines, or endocrine disruptors. The angstrom-confined catalyst uses a 2H-phase MoS2 precursor, the surface of which is loaded with metal single atoms and intercalated with alkali metal cations. The angstrom-confined catalyst is a 1T-phase MoS2 loaded with metal single atoms; the metal single atoms are one or more of iron, cobalt, nickel, and copper; and the angstrom range of the angstrom in the angstrom-confined catalyst is 9-13 angstroms. The preparation method of the angstrom confined catalyst comprises the following steps: (1) A soluble molybdenum precursor, a sulfur source, and a metal source are mixed and heated in a solvent to obtain an angstrom-confined catalyst precursor; the mixing and heating temperature is 180-220°C, and the reaction time is 8-36 hours; (2) The angstrom-confined catalyst precursor obtained in step (1) is mixed with an alkali metal source, heated and calcined under a reducing atmosphere, dialyzed, and dried to obtain the angstrom-confined catalyst.

2. The use according to claim 1, characterized in that The alkali metal cations include one or more of lithium ions, sodium ions, and potassium ions.

3. The use according to claim 1, characterized in that The loading amount of the metal single atom is 0.5-3.0 wt%; the loading amount of the alkali metal cation is 0.5-3.0 wt%.

4. The use according to claim 1, characterized in that In step (1), the soluble molybdenum precursor is selected from one or more of ammonium molybdate, ammonium tetrathiomolybdate or sodium molybdate; The metal source is selected from one or more of an iron source, a copper source, a nickel source, and a cobalt source.

5. The use according to claim 1, characterized in that The sulfur source is selected from one or more of thiourea, sodium sulfide, and sulfur powder.

6. The use according to claim 1, characterized in that In step (1), the mass ratio of the soluble molybdenum precursor, the sulfur source, and the metal source is (35-45): (35-45): (2-8).

7. The use according to claim 1, characterized in that In step (2), the alkali metal source is selected from one or more of a sodium source, a potassium source or a lithium salt; The reducing atmosphere includes hydrogen and inactive gases. The volume content of the hydrogen is 2-10%.

8. The use according to claim 1, characterized in that In step (2), the heating and calcining temperature is 700-1000°C and the time is 1-4 hours; The molar ratio of the angstrom-confined catalyst precursor to the alkali metal source is 1:(0.5-5).

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