A supported boron-doped palladium oxide atomic cluster material, a preparation method and application thereof

Abstract

This invention discloses a supported boron-doped palladium oxide cluster catalyst, its preparation method, and its application. The preparation method includes optimizing the geometry and electronic structure of the Pd clusters through Pd precursor regulation and B atom doping. The B-doped Pd oxide cluster material substrate is carbon nitride, the Pd cluster loading is 0.5-2%, and B atoms are distributed in the Pd clusters. The molar ratio of B to Pd atoms is 0.01-0.2:1, and the average valence of Pd atoms is Pd₂. 1+ -Pd 4+ This catalyst can efficiently mineralize perfluorooctanoic acid and other carboxylic acid perfluorinated compounds in water through a chain reaction of decarboxylation coupled with hydroxylation and defluorination under normal temperature and pressure. The defluorination rate exceeds 95%, and its activity is not affected by environmental factors such as ions, dissolved organic matter, and pH in the water. The catalyst is suitable for the removal of perfluorocarboxylic acids from surface water, groundwater, or industrial wastewater, and has the advantages of simple operation, high efficiency, and good stability.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to a supported boron-doped titanium dioxide palladium cluster material, its preparation method, and its application. Background Technology

[0002] The carbon-fluorine (CF) bonds in perfluorinated and polyfluoroalkyl (PFAS) compounds have high bond energies, making them difficult to degrade naturally and causing them to accumulate in the environment, thus becoming typical persistent new pollutants. Perfluorooctanoic acid (PFOA, C7F) is an example. 15 PFOA (phosphoaminobutyric acid) is a representative PFAS with relatively high concentrations in the environment. It is highly biotoxic, has been classified as a Group 1 carcinogen, and poses multi-scale environmental risks. Therefore, there is an urgent need to develop materials and remediation technologies that can efficiently degrade PFOA to effectively solve the PFOA pollution problem.

[0003] The strong electronegativity (3.98) and small atomic radius (0.65 Å) of the F atom result in extremely short (1.35 Å) and extremely high (>485 kJ / mol) CF bonds in PFOA. This leads to excellent heat resistance in PFOA (decomposition temperature >400 °C). o C) PFOA exhibits resistance to acids and alkalis, photolysis, and microbial degradation, making it difficult for traditional chemical redox and biochemical treatments to effectively remove it. The activation and cleavage of the CF bond are crucial for the effective degradation of PFOA. Existing research attempts to attack the CF bond with reactive oxygen species (such as free radicals, singlet oxygen, and high-valence metal oxides) generated by Fenton / Fenton-like technologies. However, even the hydroxyl radical •OH (2.8 V vs NHE), with the strongest oxidation potential, struggles to effectively cleave the CF bond, resulting in limited degradation efficiency for PFOA using this type of technology. Overcoming the challenge of efficiently activating the CF bond is the core bottleneck currently facing this technology.

[0004] Pd atoms exhibit excellent performance in adsorbing and activating carbon-halogen (CX) bonds. According to existing theories, Pd can adsorb and activate CX bonds in halogenated organic compounds, forming C-Pd-X intermediates, thereby achieving dehalogenation reactions. Based on this, Pd-based catalysts are expected to promote the oxidative degradation of PFOA by •OH, achieving efficient removal of PFOA from water. However, currently used Pd nanoparticle (Pd NPs) catalysts in environmental remediation involve only surface atoms in the reaction. This results in low atom utilization, and the strong adsorption of F atoms by Pd atoms easily leads to the catalyst surface being covered by a large number of CF bonds, causing active site poisoning and further reducing its activity and atom utilization. Although Pd single-atom catalysts (SACs) can significantly improve atom utilization and regulate catalytic oxidation performance through coordination with the support, their single adsorption site may limit their adsorption capacity for CF bonds in PFOA and cause adsorption configuration changes (e.g., from adsorbing CF bonds to adsorbing carboxyl groups), preventing Pd atoms from effectively activating CF bonds and limiting their mass transfer and catalytic processes. In contrast, sub-nanometer Pd atom clusters are expected to achieve a balance between atom utilization, mass transfer performance and catalytic activity. By controlling the number and spatial arrangement of Pd atoms in the atom clusters, the adsorption and mass transfer process of PFOA with its special molecular structure can be optimized.

[0005] The electronic structure of Pd catalysts significantly affects their ability to activate CF bonds. For example, reduced PdNPs can catalyze the reduction of CF bonds in PFOA by atomic hydrogen, but the reaction is very slow; oxidized Pd-based catalysts can catalyze the generation of •OH from H₂O₂, and through ligand exchange and substitution reactions, react with CF bonds to rapidly generate hydroxylated or acetoxylated products. Given that PFOA has a pKa value of approximately 0, it readily dissociates in water into carboxyl anions (C₇F₂). 15 COO - Oxidized Pd atoms can also adsorb carboxyl groups from PFOA, forming C7F through catalytic decarboxylation. 15 - Free radicals. C7F formed after decarboxylation. 15 - The CF bonds on the carbon chain are more easily exposed, which facilitates the further adsorption and activation of CF bonds by the Pd catalyst, thereby catalyzing the hydroxylation substitution defluorination reaction. Therefore, we believe that oxidized Pd clusters with specific geometric and electronic structures have the potential to simultaneously optimize the mass transfer processes such as adsorption / activation / desorption with PFOA, and catalyze the coupled reactions of decarboxylation and hydroxylation substitution defluorination, thus achieving efficient oxidative degradation of PFOA. Constructing a degradation system based on oxidized Pd clusters / H2O2 is a feasible new pathway for efficient PFOA removal, and how to design and prepare oxidized Pd cluster catalysts with specific geometric and electronic structures is an important prerequisite for realizing this approach.

[0006] Carbon nitride (Cnitride) has a relatively fixed coordination structure and a large number of multi-scale coordination sites, making it a suitable support for the synthesis of geometrically controllable Pd cluster catalysts. Theoretically, doping Pd clusters with non-metallic elements (such as B) with different electronic properties can regulate the electronic structure of the Pd clusters, including the d-band centers and electronic states, thereby optimizing their adsorption / desorption performance and catalytic oxidation activity for reactants / intermediates. Based on this, we hypothesize that introducing B atoms into Pd clusters can induce charge distribution polarization within the cluster, causing electrons to shift from Pd atoms to B atoms, thus reducing the electron density of the Pd active center and increasing its oxidation state. Furthermore, B atoms may further influence the geometry and local coordination microenvironment of the Pd cluster through short-range coordination (e.g., increasing the interatomic distance of Pd atoms), thereby facilitating the synergistic adsorption and activation of carboxyl groups and CF bonds in PFOA molecules by different active sites, ultimately enhancing their catalytic oxidation activity. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by providing a supported boron-doped palladium oxide cluster material, its preparation method, and its applications.

[0008] The objective of this invention is achieved through the following technical solution: In a first aspect, the present invention provides a supported boron-doped palladium oxide cluster material CN / BPd. c The preparation methods include the following methods: S1: Add the organic palladium salt to acetic acid and stir magnetically for 0.5-1 h to obtain a Pd-acetic acid ligand solution; the molar ratio of the organic Pd salt to acetic acid is 0.001-0.05:1; S2: Dissolve the B dopant in ultrapure water, add the resulting solution to the Pd-acetic acid ligand solution obtained in step S1, and stir magnetically for 0.5-1 h to obtain a B-doped Pd atom cluster precursor solution; the molar ratio of the B dopant to Pd is 1-40:1. S3: Dissolve melamine in ultrapure water, and after complete dissolution, add the precursor solution obtained in step S2, and stir magnetically for 0.5-1 h to obtain a melamine-B-doped Pd atom cluster polymer solution; the molar ratio of melamine to Pd is 20-1000:1. S4: Dissolve cyanuric acid in ultrapure water. After complete dissolution, mix the resulting cyanuric acid solution with the polymer solution obtained in step S3, and stir continuously for 3-5 hours to allow it to self-assemble into CN / BPd. c Catalyst precursor; the molar ratio of melamine to cyanuric acid is 1:1; S5: The precursor obtained in step S4 is allowed to stand, filtered, dried, and ground into powder. Then, under inert gas protection, the powder is heated to 600°C using a calcination apparatus. o The material is kept at C for 3-5 hours to allow for complete pyrolysis, thereby obtaining the supported B-doped oxidized Pd atom cluster material.

[0009] Furthermore, the organic Pd salt is one or a mixture of several of palladium acetate, palladium acetylacetonate, and palladium diammonium nitrate.

[0010] Furthermore, the B dopant is one or a mixture of several of boric acid, ammonia borane, and dimethylaminoborane.

[0011] Furthermore, the inert gas is any one of nitrogen, argon, and helium, or a mixture of them in any proportion.

[0012] Furthermore, the calcination device is a tube furnace or an atmosphere furnace, with a heating rate of 5-15°C / min.

[0013] Secondly, the present invention provides a CN / BPd prepared by the method described in the first aspect above. c The material uses carbon nitride as a substrate, with palladium clusters dispersed on the substrate and boron doped into the palladium clusters. The palladium cluster loading is 0.5-2%, and the molar ratio of boron to palladium is 0.01-0.2:1. The coordination number of Pd-Pd bonds in the palladium clusters is 2.5-4, and the coordination number of Pd-B bonds is 0.1-3.2. The average valence of palladium atoms is Pd. 1+ To Pd 4+ By controlling the coordination and electronic structure of the palladium active center through boron doping, the palladium atoms are placed in an oxidized state.

[0014] Thirdly, the present invention provides the above-mentioned CN / BPd c The application of this material in the catalytic H2O2 oxidation degradation of carboxylic acid-containing perfluorinated compounds such as PFOA in water includes the following steps: CN / BPd c The material and H2O2 were added to water containing the target pollutant (perfluorocarboxylic acid) at a temperature of 10-25°C. o C, react for 24 to 48 hours to complete the oxidative degradation of perfluorocarboxylic acids in water. The perfluorocarboxylic acids are one or any combination of trifluoroacetic acid, pentafluoropropionic acid, heptafluorobutyric acid, nonafluoropentanoic acid, perfluorohexanoic acid, perfluoroheptanoic acid, and perfluorooctanoic acid.

[0015] Furthermore, the water body is surface water, groundwater, municipal sewage, or industrial wastewater, and the CN / BPd cThe material dosage is 0.5-2 g / L, the H2O2 dosage is 1-10 g / L, and the initial concentration of the perfluorocarboxylic acid pollutant is 0.1-1 mg / L.

[0016] The beneficial effects of this invention are as follows: This invention successfully prepares a CN / BPd precursor through a gradient coordination-high-temperature calcination method via hydrogen bonding between an organopalladium salt, a boron-containing ligand, and a carbon nitride support precursor. c Materials. The CN / BPd prepared in this invention c In this material, Pd is mainly dispersed on a carbon nitride support in the form of oxidized Pd atom clusters. The boron doping within these clusters effectively regulates the coordination and electronic structure of the Pd active centers, keeping the Pd atoms in an oxidized state. This material maintains high catalytic oxidation activity while improving palladium atom utilization. It exhibits high defluorination efficiency and good catalytic stability (retaining over 90% activity after more than 10 cycles) at room temperature and pressure, effectively catalyzing the oxidation and degradation of various difficult-to-remove perfluorocarboxylic acid pollutants in water using H₂O₂. The CN / BPd prepared in this invention... c The material solves the current technical bottleneck of the inability to degrade PFOA in a green and efficient manner, significantly improves the degradation effect of PFOA in water, and reduces the energy consumption of PFOA wastewater treatment technology. Attached Figure Description

[0017] Figure 1 For CN / BPd c Flowchart of the material preparation method.

[0018] Figure 2 The CN / BPd prepared in Example 1 c Scanning electron microscope image.

[0019] Figure 3 The CN / BPd prepared in Example 1 c Dark-field image of the material obtained by transmission electron microscopy.

[0020] Figure 4 To test the CN / BPd prepared in Example 1 c Carbon distribution map of the material after energy dispersive spectroscopy (EDS) scanning.

[0021] Figure 5 To test the CN / BPd prepared in Example 1 c Nitrogen distribution map after energy dispersive spectroscopy (EDS) of the material.

[0022] Figure 6 To test the CN / BPd prepared in Example 1 c Pd elemental distribution map after energy dispersive spectroscopy (EDS) of the material.

[0023] Figure 7To test the CN / BPd prepared in Example 1 c The distribution of B element after energy dispersive spectroscopy (EDS) of the material.

[0024] Figure 8 The CN / BPd prepared in Example 1 c Aberration-corrected scanning transmission electron microscope image of the material.

[0025] Figure 9 As a carbon nitride support (CN), a supported undoped boron Pd cluster (CN / Pd) c Materials and CN / BPd prepared in Example 1 c X-ray diffraction pattern of the material.

[0026] Figure 10 Commercially available elemental boron, commercially available boron nitride (h-BN) standard, and CN / BPd prepared in Example 1 were used. c Image of the near-edge absorption structure (XANES) of element B in the material.

[0027] Figure 11 CN / Pd c Materials and CN / BPd prepared in Example 1 c Comparison of Pd atomic valence states in materials.

[0028] Figure 12 The CN / BPd prepared in Example 1 c Performance evaluation diagram of material catalytic H2O2 oxidation degradation of PFOA.

[0029] Figure 13 The CN / BPd prepared in Example 1 c Performance evaluation diagram of the material in actual water treatment. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not represent all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0031] like Figure 1 As shown, a method for preparing a supported boron-doped palladium oxide cluster material includes the following steps: adding a boron dopant to a Pd-acetic acid solution for H-bond coordination, then adding melamine for further H-bond coordination, followed by the addition of cyanuric acid, and self-assembly followed by drying to obtain CN / BPd. cThe precursor, after calcination, yields the supported boron-doped palladium oxide cluster material CN / BPd. c .

[0032] Example 1

[0033] S1: Weigh 232.4 mg of palladium acetate powder and add it to 80 mL of acetic acid solution. Stir magnetically for 30 min to obtain Pd-acetic acid ligand solution. S2: Weigh 2.2g of boric acid and add it to 40 mL of ultrapure water and stir for 15 min to obtain a B dopant solution. Then add the solution to the Pd-acetic acid ligand solution obtained in step S1 and stir magnetically for 0.5 h to obtain a B-doped Pd atom cluster precursor solution. S3: Weigh 6.05 g of melamine powder and add it to 700 mL of ultrapure water. Heat and stir magnetically for 0.5 h. Then add the obtained melamine solution to the B-doped Pd atom cluster precursor solution obtained in step S2 and continue to stir magnetically for 1 h to obtain a melamine-coordinated B-doped oxidized Pd atom cluster precursor solution. S4: Weigh 6.19 g of cyanuric acid powder and add it to 700 mL of ultrapure water. Heat and stir magnetically for 0.5 h. Then add the resulting cyanuric acid solution to the solution obtained in step S3 and continue stirring magnetically for 5 h to allow it to fully self-assemble in the solution to form CN / BPd. c Precursor; S5: The precursor obtained in step S4 is made into powder through a settling-filtration-drying and grinding process. The powder is then placed in a tube furnace and heated at 10 mL / min under nitrogen protection. o The heating rate of C / min raised the furnace temperature to 600. o C, then calcined for 4 hours, yielding CN / BPd with approximately 3.3 Pd-Pd coordination bonds and approximately 3.2 Pd-B coordination bonds. c Material.

[0034] Example 2

[0035] S1: Weigh 315.2 mg of palladium acetylacetonate powder, add it to 80 mL of acetic acid solution, heat and stir magnetically for 30 min until palladium acetylacetonate is completely dissolved in acetic acid; S2: Weigh 2.1g of dimethylaminoborane and add it to 40 mL of ultrapure water and stir for 20 min to obtain a B dopant solution. Then add the solution to the Pd-acetic acid ligand solution obtained in step S1 and stir magnetically for 0.5 h to obtain a B-doped Pd atom cluster precursor solution. S3: Weigh 6.05 g of melamine powder and add it to 700 mL of ultrapure water. Heat and stir magnetically for 0.5 h. Then add the obtained melamine solution to the B-doped oxidized Pd atom cluster precursor solution obtained in step S2 and continue to stir magnetically for 1 h to obtain the melamine-coordinated B-doped oxidized Pd atom cluster precursor solution. S4: Weigh 6.19 g of cyanuric acid powder and add it to 700 mL of ultrapure water. Heat and stir magnetically for 0.5 h. Then add the resulting cyanuric acid solution to the solution obtained in step S3 and continue stirring magnetically for 5 h to allow it to fully self-assemble in the solution to form CN / BPd. c Precursor; S5: The precursor obtained in step S4 is made into powder through a settling-filtration-drying and grinding process. The powder is then placed in a tube furnace and heated at 15 mL / min under nitrogen protection. o The heating rate of C / min raised the furnace temperature to 600. o C, then calcined for 5 hours, yielding CN / BPd with approximately 2.5 Pd-Pd coordination bonds and approximately 2.0 Pd-B coordination bonds. c Material.

[0036] Example 3

[0037] S1: Weigh 238.5 mg of palladium diamine nitrate powder and add it to 80 mL of acetic acid solution. Heat to 40 °C. o C. Stir magnetically for 30 min until palladium diammine nitrate is completely dissolved in acetic acid; S2: Weigh 1.1g of boric acid and add it to 40 mL of ultrapure water and stir for 15 min to obtain a B dopant solution. Then add the solution to the Pd-acetic acid ligand solution obtained in step S1 and stir magnetically for 0.5 h to obtain a B-doped oxidized Pd atom cluster precursor solution. S3: Weigh 6.05 g of melamine powder and add it to 700 mL of ultrapure water. Heat and stir magnetically for 0.5 h. Then add the obtained melamine solution to the B-doped oxidized Pd atom cluster precursor solution obtained in step S2 and continue to stir magnetically for 1 h to obtain the melamine-coordinated B-doped oxidized Pd atom cluster precursor solution. S4: Weigh 6.19 g of cyanuric acid powder and add it to 700 mL of ultrapure water. Heat and stir magnetically for 0.5 h. Then add the resulting cyanuric acid solution to the solution obtained in step S3 and continue stirring magnetically for 5 h to allow it to fully self-assemble in the solution to form CN / BPd. c Precursor; S5: The precursor obtained in step S4 is made into powder through a settling-filtration-drying and grinding process. The powder is then placed in a tube furnace and heated under nitrogen protection at a flow rate of 5 mL / min. o The heating rate of C / min raised the furnace temperature to 600. o C, then calcined for 3 hours, yielding CN / BPd with approximately 2.6 Pd-Pd coordination bonds and approximately 1.2 Pd-B coordination bonds. c Material.

[0038] Figure 2 The image shows the CN / BPd prepared in Example 1. c Scanning electron microscope (SEM) image of the material, with a scale bar of 20 μm. CN / BPd is clearly visible in the image. c They exhibit a uniform tubular structure with a diameter of approximately 2-3 μm. Figure 3 The image shown is a dark-field transmission electron microscope (TEM) image of a local region of the same material, with a scale bar of 200 nm. Only local morphology of the support is observed in this image; no obvious bright spots are seen, indicating that no Pd nanoparticles with a distinct crystalline structure have formed in the material. Figures 4-7 The image shows the pair. Figure 3 CN / BPd in ​​the area shown c The energy spectrum scan of the material, in which Figure 4 The image shows the pair. Figure 3 CN / BPd shown c Carbon element distribution map after energy dispersive spectroscopy (EDS) of the material. Figure 5 As shown Figure 3 CN / BPd shown c Nitrogen distribution map after energy dispersive spectroscopy (EDS) of the material. Figure 6 for Figure 3 CN / BPd shown c Palladium elemental distribution map after energy dispersive spectroscopy (EDS) of the material. Figure 7 for Figure 3 CN / BPd shown c The distribution of B element after energy dispersive spectroscopy (EDS) of the material. Figures 4-7 The results show that the CN / BPd prepared in Example 1 c The main constituent elements of the support in the material are nitrogen and carbon, forming a carbon nitride support, while B and Pd elements are uniformly loaded on the support, confirming the successful synthesis of B-doped Pd atom cluster material.

[0039] Figure 8 The image shows the CN / BPd prepared in Example 1. c Aberration-corrected scanning transmission electron microscope image of the material. The scale bar shown in the image is 5 nm. Figure 8The image shows Pd particles with a diameter of approximately 2 nm uniformly loaded on a carbon nitride support. The atoms inside these particles are arranged irregularly, and no lattice fringes were observed, indicating that they are amorphous Pd atom cluster structures.

[0040] like Figure 9 The image shows a carbon nitride support (CN) and an undoped boron-supported Pd cluster (CN / Pd). c ) and CN / BPd c The X-ray diffraction pattern. CN is a material prepared by mixing and reacting the melamine solution prepared in step S3 of Example 1 with the cyanuric acid solution obtained in step S4 of Example 1 for 4 hours, followed by the treatment process of standing-filtering-drying-calcining for 4 hours in step S5 of Example 1; CN / Pd c The material was prepared by first mixing the Pd-acetic acid ligand solution obtained in step S1 of Example 1 with the melamine solution obtained in step S3 of Example 1 for 0.5 h, then mixing it with the cyanuric acid solution obtained in step S4 of Example 1 and reacting for 4 h, followed by the treatment process of standing, filtering, drying, and calcining for 4 h in step S5 of Example 1. Figure 9 It can be seen that diffraction peaks for carbon nitride appeared in all three materials, but no diffraction peaks corresponding to Pd nanocrystals were detected in either of the two materials with supported Pd atom clusters. Figure 8 Observations show that the prepared supported Pd cluster material mainly exists in the form of amorphous Pd clusters, and B doping does not change its basic morphology.

[0041] like Figure 10 The image shows elemental B, a commercially available h-BN standard, and CN / BPd. c XANES spectrum of element B in the material. Figure 10 It can be seen that CN / BPd c The absence of a characteristic peak at 194.2 eV for the boron (B) atoms in the material indicates that the B atoms are not coordinated with the nitrogen (N) atoms in the carbon nitride support, but are directly doped into the Pd atom clusters and directly coordinated with the Pd atoms. Additionally, CN / BPd... c The B atom in the material elutes at 190.6 eV, which is a negative shift compared to the B atom in elemental B. This indicates that the B atom gains electrons from the Pd atom, resulting in an increase in its own electron density and a decrease in its valence state. This, in turn, induces a decrease in the electron density of the Pd atom and an increase in its valence state.

[0042] like Figure 11 The figure shows CN / Pd c and CN / BPd c A comparison diagram of the oxidation states of Pd atoms in the material. Among them, CN / Pd... cThe material is prepared by first mixing the Pd-acetic acid ligand solution obtained in step S1 of Example 1 with the melamine solution obtained in step S3 of Example 1 for 0.5 h, then mixing it with the cyanuric acid solution obtained in step S4 of Example 1 for 4 h, and then undergoing the treatment process of standing-filtering-drying-calcining reaction for 4 h in step S5 of Example 1. Figure 11 'a' in the text represents CN / Pd. c Materials and CN / BPd prepared in Example 1 c X-ray photoelectron spectroscopy (XPS) of Pd atoms in the material; Figure 11 b in the text represents CN / Pd c Materials and CN / BPd prepared in Example 1 c XANES diagram of Pd atoms in the material. Figure 11 From 'a', we can see that CN / Pd without B doping... c In the material, Pd atoms are mainly in the zero valence state (Pd 0 ) and positive divalent presence (Pd 2+ Compared to CN / Pd c Materials, CN / BPd doped with B within atomic clusters c High valence state (Pd) in materials 4+ The proportion of Pd atoms increased significantly, and the valence of Pd atoms increased. Figure 11 From b, we can know that CN / Pd c The oxidation state of Pd atoms in the material is closer to zero valence in the Pd foil standard sample, while CN / BPd c The oxidation state of Pd atoms in the material is closer to that of palladium oxide (PdO) standard. This together confirms that B doping effectively modulates the electronic structure of Pd atom clusters, increasing their overall oxidation state.

[0043] Application Example 1 Weigh out 20 mg of CN support, CN-supported Pd single atoms (CN / Pd1), and CN / Pd, respectively. c and the CN / BPd prepared in Example 1 c Materials. The CN carrier was prepared by mixing the melamine solution prepared in step S3 of Example 1 with the cyanuric acid solution obtained in step S4 of Example 1 and reacting for 4 h, followed by the process of standing, filtering, drying, and calcining for 4 h in step S5 of Example 1; the CN / Pd1 material was prepared by mixing potassium tetrachloropalladate solution with 20 mL of acetic acid for 0.5 h, then mixing with the melamine solution obtained in step S3 of Example 1 for 0.5 h, then mixing with the cyanuric acid solution obtained in step S4 of Example 1 and reacting for 4 h, followed by the process of standing, filtering, drying, and calcining for 4 h in step S5 of Example 1; CN / Pd cThe material is prepared by first mixing the Pd-acetic acid ligand solution obtained in step S1 of Example 1 with the melamine solution obtained in step S3 of Example 1 for 0.5 h, then mixing and reacting it with the cyanuric acid solution obtained in step S4 of Example 1 for 4 h, and then undergoing the treatment process of standing-filtering-drying-calcining for 4 h in step S5 of Example 1. CN / Pd1, CN / Pd c and CN / BPd c The Pd loading in all materials was 1%. The four materials were added to polyethylene plastic serum bottles containing 20 mL of ultrapure water and ultrasonically dispersed for 10 min. Subsequently, 0.07 mL of 30% H2O2 solution and 0.1 mL of 0.48 mmol / L PFOA stock solution were injected into each reaction bottle, resulting in an initial PFOA concentration of 2.4 μmol / L in the reaction system.

[0044] The serum vials were sealed with rubber caps lined with polytetrafluoroethylene (PTFE) and thoroughly mixed. They were then placed on a rotary incubator at a rotation speed of 40 rpm to begin the reaction. At each preset reaction time point, 100 μL of the reaction solution was drawn and diluted to 1 mL, then filtered through a 0.22 μm filter membrane. The 100 μL filtered solution was analyzed using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS / MS) to determine the residual PFOA content. The PFOA content versus time curves in different reaction systems are shown below. Figure 12 As shown in a. From Figure 12 As can be seen from 'a', CN-supported materials and CN / Pd1 materials cannot effectively catalyze the degradation of PFOA. c The material's removal efficiency for PFOA was only about 40%, while CN / BPd c The material exhibits a significant removal effect on PFOA, achieving a removal rate exceeding 95% within 24 hours. Kinetic fitting of the PFOA degradation results yielded the reaction rate constants for the PFOA degradation catalyzed by H₂O₂ oxidation of each catalyst material, such as… Figure 12 As shown in b, from Figure 12 As can be seen from b, the reaction rate of conventional supported palladium single-atom materials is only 0.001 h⁻¹. -1 It exhibits almost no reactivity. The reaction rate of the undoped Pd cluster catalyst is only 0.005 h⁻¹. -1 The CN / BPd prepared in Example 1 c The reaction rate of PFOA degradation catalyzed by the material using H2O2 was 0.12 h. -1 They are CN / Pd1 and CN / Pd respectively. cThe results show that the oxidized Pd atom clusters doped with B significantly enhance the performance of Pd active sites in catalytic degradation of PFOA, by 120 times and 24 times respectively. This clearly demonstrates that B-doped oxidized Pd atom clusters greatly improve the performance of Pd active sites in catalytic degradation of PFOA.

[0045] At each preset reaction time point, a 1 mL sample was taken from each reaction system and diluted to 10 mL. The diluted solution was then filtered and pretreated sequentially using a 0.22 μm filter membrane, a C18 filter column, and an NA filter column, followed by ion chromatography to detect the content of fluoride ions generated in the reaction system. The generation of fluoride ions in the solution is as follows: Figure 12 As shown in c, Pd single-atom catalysts and conventional undoped Pd cluster catalysts have almost no degradation and defluorination effect on PFOA, while CN / BPd catalysts... c The H2O catalytic reaction system achieved a PFOA degradation and defluorination rate of over 95%, indicating that after B doping, oxidized Pd atom clusters can be completely degraded and converted into PFOA.

[0046] After the reaction proceeded for 12 hours, from CN / BPd c A 100 μL sample of the H₂O₂ catalytic system was diluted to 1 mL and filtered through a 0.22 μm filter membrane. The 100 μL filtered solution was then subjected to qualitative analysis using time-of-flight mass spectrometry (Q-TOF-MS) to identify intermediate products generated during the oxidative degradation of PFOA. The results are as follows: Figure 12 As shown in d, as the reaction proceeds, decarboxylation and defluorination intermediates with decreasing carbon chain lengths are generated sequentially in the reaction system. This indicates that PFOA achieves complete oxidative degradation under ambient temperature and pressure conditions through a sequential decarboxylation-coupled hydroxylation-defluorination reaction process on the surface of B-doped oxidized Pd atom clusters. Figure 12 The diagram in Figure 'e' further clarifies the reaction pathway.

[0047] comprehensive Figure 12 The results show that, compared with the low oxidative degradation performance of conventional Pd-based catalysts for PFOA, the B-doped oxidized Pd clusters prepared in Example 1 exhibit excellent catalytic activity and defluorination efficiency in the oxidative degradation of PFOA by H2O2. This material achieves the goal of green and efficient degradation of perfluorinated compounds such as PFOA in water under mild reaction conditions through a synergistic catalytic mechanism of catalytic decarboxylation coupled with hydroxylation defluorination.

[0048] Application Example 2 To facilitate efficient mass transfer in the reaction system and the separation and recovery of B-doped oxidized Pd clusters from the aqueous phase, the CN / BPd prepared in Example 1 was... cThe material was uniformly coated onto a polyvinylidene fluoride (PVDF) membrane to form a Pd cluster catalytic membrane. The fabricated Pd cluster catalytic membranes were then stacked in a column reactor to assemble a PFOA wastewater treatment membrane reactor. The effective volume of this reactor is 600 mL, and the CN / BPd ratio is [not specified in the original text]. c The effective loading capacity of the material is 2g / L. -1 A membrane treatment reactor for efficiently treating PFOA-containing wastewater was constructed by sequentially connecting the PFOA wastewater influent device, H2O2 dosing device, PFOA wastewater treatment membrane reactor, and effluent device using a quantitative sampling system and pipelines. The device is as follows: Figure 13 As shown in a, the concentration of H2O2 in this device is set to 1 g / L. -1 The hydraulic residence time of the membrane reactor is set to more than 24 hours to ensure the full catalytic degradation of PFOA by the B-doped oxidized Pd atom clusters.

[0049] To examine CN / BPd c The material's catalytic degradation versatility for different types of perfluorocarboxylic acids was assessed by preparing 1L solutions with a concentration of 1 mg / L. -1 Solutions of perfluoropropionic acid, perfluorobutyric acid, perfluorovalerate, perfluorohexanoic acid, and perfluoroheptanoic acid were added to the above reaction system. After the reaction was completed, 1 mL of the resulting solution was taken and filtered through a 0.22 μm filter membrane. 100 μL of the filtrate was then analyzed by HPLC-MS / MS to determine the remaining perfluorocarboxylic acid content in the solution. The results are shown below. Figure 13 As shown in b in the diagram. From Figure 13 As can be seen from b, CN / BPd c The material exhibits good catalytic degradation effects on various types of perfluorocarboxylic acids, indicating that CN / BPd c The material has good universality for compounds such as perfluorocarboxylic acids.

[0050] To verify the effect of environmental factors on CN / BPd c The effect of the material on the catalytic activity of H2O2 oxidation degradation of PFOA was investigated, with concentrations of 1 g / L. -1 NaCl - NaHCO3 - NaNO3 - NaSO4 2- CaCl2 was prepared in batch experiments, with 1 mL, 10 mL, and 100 mL of the above-mentioned CaCl2 solution added to simulated PFOA-contaminated wastewater, along with stock solutions containing dissolved organic matter (NOM) and PFOA at pH values ​​of 4, 7, and 10, respectively. - NaHCO3 - NaNO3 - NaSO4 2- The stock solution was prepared to make the PFOA concentration in the water 1 mg / L.-1 Cl - HCO3 - NO3 - SO4 2 The concentrations of ions and NOM were 1 mg / L. -1 10mg L -1 100 mg L -1 The simulated PFOA-contaminated wastewater with different ionic strengths was added to the following solutions: Figure 13 The degradation experiment was conducted in the reaction apparatus shown in Figure a. At preset time points, 100 μL samples were taken and diluted to 1 mL. After pretreatment, the PFOA content in the solution was detected by HPLC-MS / MS. Kinetic fitting was performed on the detection results to obtain the CN / BPd ratio under different ionic strength conditions. c The reaction rate constant of the material for the catalytic H2O2 oxidation degradation of PFOA is shown in the following results. Figure 13 As shown in c in Example 1. The results indicate that the CN / BPd prepared in Example 1... c The catalytic activity of the material for the H2O2 oxidation degradation of PFOA is not affected by various environmental factors, CN / BPd c The material exhibits excellent catalytic stability.

[0051] To verify CN / BPd c The material's recyclability was tested in 10 cyclic degradation experiments on the above-mentioned reaction device: 6 L of a solution with a concentration of 1 mg / L was prepared. -1 Simulated PFOA-contaminated wastewater was added in 10 batches to... Figure 13 In the reaction apparatus shown in Figure a, 100 μL of sample was taken every 24 h and diluted to 1 mL. After pretreatment, the PFOA content in the solution was detected by HPLC-MS / MS. The above experimental steps were repeated for 10 cycles. The PFOA removal rate in each cycle was calculated based on the detection results. The results are shown in Figure a. Figure 13 As shown by d in the diagram. Figure 13 As can be seen from d in Example 1, the CN / BPd prepared in Example 1... c The material consistently maintained excellent catalytic oxidation degradation effect on PFOA, with the removal rate of PFOA remaining above 90% in 10 cycles of degradation experiments.

[0052] Figure 13 The results show that CN / BPd c The material-catalyzed H2O2 reaction system not only exhibits excellent activity in the oxidative degradation of perfluorocarboxylic acids, but also maintains good versatility, catalytic stability, and reusability. It not only breaks through the technical bottleneck of the current difficulty in degrading PFOA-polluted wastewater, but also reduces treatment costs in practical PFOA-polluted wastewater treatment applications by recycling the catalyst.

[0053] Application Examples 1 and 2 show that CN / BPd c The material can be used to catalyze the oxidation and degradation of various carboxylic acid-containing perfluorinated compounds such as PFOA in water by H2O2 oxidation. Its characteristic feature is that it includes the following steps: CN / BPd... c The material and H2O2 are added to water containing carboxylic acid perfluorinated compounds such as PFOA, and the reaction is carried out for 24-48 hours to complete the oxidative degradation of PFOA and other carboxylic acid perfluorinated compounds in the water. The water body can be surface water, groundwater, municipal sewage, or industrial wastewater, and the dosage of the PFOA material is 0.1-2 g / L. -1 The amount of H2O2 added is 0.1−1 gL. -1 The concentration of the PFOA and other carboxylic acid-containing perfluorinated compounds is 0–2.4 μmol / L. -1 .

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. The application of a supported boron-doped palladium oxide cluster material in the catalytic oxidation and degradation of perfluorocarboxylic acids by H₂O₂, characterized in that, Includes the following steps: A supported boron-doped palladium atom cluster material and H2O2 solution were added to a water body containing perfluorocarboxylic acid, and the reaction was carried out continuously at normal pressure and room temperature to achieve the degradation of perfluorocarboxylic acid. Supported boron-doped palladium oxide clusters are constructed on a carbon nitride substrate. Palladium clusters are dispersed on the substrate, with boron doping integrated into the palladium clusters. The palladium cluster loading is 0.5-2%, and the molar ratio of boron to palladium is 0.01-0.2:

1. The coordination number of Pd-Pd bonds in the palladium clusters is 2.5-4, and the coordination number of Pd-B bonds is 0.1-3.

2. The valence of the palladium atom is Pd. 1+ To Pd 4+ By controlling the coordination and electronic structure of the palladium active center through boron doping, the palladium atoms are placed in an oxidized state.

2. The application according to claim 1, characterized in that, A method for preparing supported boron-doped palladium oxide cluster materials includes the following steps: S1: Add the organic palladium salt to acetic acid and stir magnetically to obtain a Pd-acetic acid ligand solution; S2: Dissolve the boron dopant in ultrapure water, then add the resulting boron dopant aqueous solution to the Pd-acetic acid ligand solution in step S1, and stir magnetically to obtain a boron-doped palladium cluster precursor solution. S3: Dissolve melamine in ultrapure water until it is completely dissolved, then add the boron-doped palladium cluster precursor solution obtained in step S2 to the melamine solution and stir magnetically to obtain a melamine-boron-doped palladium cluster polymerization solution. S4: Dissolve cyanuric acid in ultrapure water until it is completely dissolved, then mix the cyanuric acid solution with the melamine-boron-doped palladium cluster polymerization solution obtained in step S3, and continue stirring to allow it to self-assemble into a supported boron-doped palladium cluster catalyst precursor. S5: The catalyst precursor obtained in step S4 is allowed to stand, filtered, dried and ground into powder. Then, the powder is heated in a calcination device under inert gas protection to fully pyrolyze it, thus obtaining the supported boron-doped palladium atom cluster material.

3. The application according to claim 2, characterized in that, The organic palladium salt in step S1 is one or a mixture of several of palladium acetate, palladium acetylacetone, and palladium diammonium nitrate, and the molar ratio of the organic palladium salt to acetic acid is 0.0005–0.05:

1.

4. The application according to claim 2, characterized in that, The boron dopant in step S2 is one or a mixture of several of boric acid, ammonia borane, and dimethylaminoborane, and the molar ratio of boron dopant to palladium is 1-40:

1.

5. The application according to claim 2, characterized in that, In step S3, the molar ratio of melamine to palladium is 20-1000:

1.

6. The application according to claim 2, characterized in that, In step S4, the molar ratio of melamine to cyanuric acid is 1:

1.

7. The application according to claim 2, characterized in that, The inert gas in step S5 is any one of nitrogen, argon and helium or a mixture of them in any proportion. The calcination device is a tube furnace or an atmosphere furnace. The heating rate is set to 5-15°C / min, and the temperature is raised to 600°C for 3-5 hours.

8. The application according to claim 1, characterized in that, The water body is surface water, groundwater, or industrial wastewater. The perfluorocarboxylic acid is one or any combination of trifluoroacetic acid, pentafluoropropionic acid, heptafluorobutyric acid, nonafluoropentanoic acid, perfluorohexanoic acid, perfluoroheptanoic acid, and perfluorooctanoic acid. The concentration range of the perfluorocarboxylic acid in the water is 0.1-1 mg / L. The dosage of the supported boron-doped oxidized palladium cluster material in the water body is 0.5-2 g / L, and the dosage of H2O2 is 1-10 g / L.

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