Sm diatomic electrocatalyst and preparation and oxysalt treatment method thereof

Abstract

The invention belongs to the technical field of electrochemical wastewater treatment, and relates to a Sm diatomic electrocatalyst, a preparation method thereof and a method for treating oxysalt wastewater. The catalyst takes nitrogen-doped carbon as a carrier, and Sm-Sm diatomic sites are anchored in a carbon skeleton in an atomic scale manner through Sm-N coordination. The preparation method comprises the following steps: self-assembling Sm2O3 and a nitrogen-containing organic matter in a buffer solution to obtain a precursor, carrying out high-temperature carbonization in an inert atmosphere, and then carrying out acid etching to remove redundant oxides so as to obtain the high-density Sm diatomic site. The catalyst is loaded on a conductive substrate as a cathode, and negative potential is applied to an aqueous solution containing nitrate, bromate and / or perchlorate, so that the nitrate can be efficiently reduced into nitrogen, the bromate and the perchlorate are reduced into corresponding halide ions, and the catalyst is prepared. The catalyst has the advantages of hydrogen evolution reaction inhibition, high oxysalt removal rate, good target product selectivity, excellent stability and the like.

Description

Technical Field

[0001] This invention relates to the field of electrochemical water treatment technology, specifically to an Sm diatomic electrocatalyst and its preparation method, as well as a method for treating oxyacid salts (including nitrates, bromates and perchlorates) in wastewater using the catalyst. Background Technology

[0002] With the increase in emissions from industry, agriculture, and urban life, a large amount of oxyacid pollutants, such as nitrates (NO3), are being produced. - ), bromate (BrO3) - ), perchlorate (ClO4) - These substances, such as pollutants, enter water bodies, posing a serious threat to the ecological environment and human health.

[0003] Existing technologies for treating oxyacid salts mainly include physical, chemical, and biological methods. Physical methods, such as reverse osmosis and ion exchange, can only achieve the transfer and enrichment of pollutants, resulting in secondary pollution such as high-salt concentrates. Chemical methods, such as catalytic hydrogenation, pose safety hazards in hydrogen production and transportation. Biological methods have limited efficiency under low temperature, low concentration, and fluctuating water quality conditions, and are prone to producing large amounts of sludge and potential pathogenic microorganisms.

[0004] Electrochemical catalysis utilizes electrons as a reducing agent to achieve the conversion of oxyacid salts at room temperature and pressure. It boasts advantages such as compact equipment, ease of automation, and compatibility with renewable energy sources, making it a promising strategy for pollutant removal. However, traditional oxyacid salt electroreduction systems generally suffer from several drawbacks: severe competitive hydrogen evolution reaction (HER), reduced Faraday efficiency, and difficulty in controlling selectivity; oxyacid salt processes involve multiple steps and electron transfers, easily forming hydrogenation byproducts such as NH3, causing secondary pollution; catalysts are prone to deactivation, require high overpotentials, and often rely on precious metals or complex structures, resulting in high costs and insufficient engineering feasibility; and there is a lack of effective utilization of the oxygen atom transfer (OAT) mechanism.

[0005] Taking nitrates as an example, a large amount of research has focused on NO3 - Electroreduction to NH3, achieving "green ammonia synthesis," often employs transition metal single-atom or diatomic catalysts such as Cu, Fe, and Co to enhance NO3 production. - →The Faraday efficiency and yield of NH3. However, in water treatment scenarios aimed at environmental harmlessness, NH3 itself is still a pollutant requiring further treatment; directly treating NO3... - It would be more ideal to convert it into harmless N2.

[0006] For BrO3 - ClO4 - Electrochemical reduction of BrO3 is currently largely based on noble metal catalytic systems such as Pd and Rh, although it can achieve...- / ClO4 - To Br - / Cl - However, it is costly, sensitive to water quality conditions, and has limited applicability to different types of oxyacid salts.

[0007] In nature, various reductases complete substrate deoxygenation-reduction processes through the OAT mechanism. Metal cofactors and organic ligands synergistically remove oxygen atoms from the substrate, ultimately generating water, thus achieving efficient deoxygenation-reduction. Rare earth metals, especially lanthanides, possess excellent oxygen affinity and variable valence states, theoretically making them suitable for constructing OAT-dominated catalytic cycles. Existing literature reports that Sm₂O₃ can serve as a catalyst for electrocatalytic N₂ reduction, and SmI₂ can participate as a chemical reducing agent in the N₂ / NO₃ cycle. x Reduction reactions have been observed, but the construction of rare-earth metal samarium (Sm) as diatomic sites and its loading onto N-doped carbon supports for NO3 reduction reactions has not yet been seen. - BrO3 - ClO4 - Reports on the electrochemical harmless reduction of oxyacid salts, etc.

[0008] Therefore, developing a novel electrocatalyst based on Sm diatomic sites that can efficiently, stably, and selectively remove various oxoacid salts via the OAT mechanism is of significant scientific importance and application value. Summary of the Invention

[0009] Purpose of the invention The purpose of this invention is to provide a Sm diatomic electrocatalyst and its preparation method, as well as a method for treating oxyacids in wastewater using the catalyst, in order to solve the problems of severe HER competition, difficulty in selectivity control, easy catalyst deactivation, high energy consumption, and difficulty in achieving efficient and harmless removal of multiple oxyacids in the electroreduction process of oxyacids in the prior art.

[0010] Specifically, the present invention aims to: 1. By constructing Sm diatomic / N-doped carbon (Sm2NC) catalysts, high-density and stable Sm diatomic active sites are provided, thereby improving the utilization rate of metal atoms; 2. Utilizing Sm's affinity for oxygen and wide valence range, NO3 is extracted via the OAT mechanism. - BrO3 - ClO4 - By gradually abstracting oxygen atoms from oxyacid salts, NO3 can be controlled. - To N2, BrO3 - / ClO4 - To Br - / Cl - Highly efficient electroreduction; 3. While inhibiting the formation of byproducts such as HER and NH3, it improves the removal rate of oxyacid salts and the selectivity of target products, making it suitable for the control of oxyacid salt pollution under low concentration or even near-drinking water standard conditions.

[0011] Technical solution To achieve the above objectives, the present invention provides a Sm diatomic electrocatalyst and its preparation method, and provides a method for treating oxyacid wastewater using the catalyst and a corresponding electrochemical treatment device.

[0012] First aspect: Sm diatomic electrocatalyst The electrocatalyst comprises an N-doped carbon support and samarium diatomic active sites supported on the surface of the N-doped carbon support. Each samarium atom forms an Sm-N coordination bond with the N-doped carbon support through at least three N coordinating atoms, and there are Sm-Sm coordination or metal-metal bonds between adjacent samarium atoms, resulting in atomically dispersed samarium diatomic active sites. The average valence state of samarium is +1.5 to +3.0, preferably about +2.1. In extended X-ray absorption fine structure (EXAFS) analysis, a main Sm-N coordination peak is observed in the R-space from 1.8 to 2.8 Å, and an Sm-Sm coordination peak is observed in the R-space from 3.0 to 4.0 Å. Preferably, the N-doped carbon support has a hollow porous structure and a bubble-like surface morphology, with a specific surface area greater than 100 m². 2 / g; More preferably, the loading of Sm in the electrocatalyst is 0.1 to 10 wt%.

[0013] The second aspect: Preparation method of Sm diatomic electrocatalysts The method includes: a precursor preparation step, in which a samarium-containing compound (preferably Sm2O3 nanorods) is dispersed in an aqueous solution containing a buffer, and a nitrogen-containing organic precursor (such as dopamine and urea) is added, and the mixture is stirred to form a samarium-organic composite precursor; a carbonization step, in which the samarium-organic composite precursor is heated to 600-1000℃ under an inert atmosphere and held at that temperature for 0.5-3h to carbonize the nitrogen-containing organic compound, thereby obtaining a samarium / oxide / N-doped carbon composite material; and an acid etching step, in which the composite material is contacted with an acid solution (such as 0.1-3 mol / L sulfuric acid) and treated at 50-100℃ for 2-12h to remove part of the oxide phase and expose the samarium diatomic sites, followed by washing and drying to obtain a Sm diatomic electrocatalyst.

[0014] Third aspect: Methods for treating oxyacid wastewater The method includes: setting up a cathode and an anode in an electrochemical reactor, using oxyacid salt wastewater as an electrolyte or part of the electrolyte, wherein the cathode comprises the aforementioned Sm diatomic electrocatalyst; and electrolyzing the oxyacid salt wastewater under the action of an external power source, causing the oxyacid salts therein to undergo an electrochemical reduction reaction. The oxyacid salts include at least one of nitrate, bromate, and perchlorate; nitrate is preferably reduced to nitrogen gas, and bromate and perchlorate are preferably reduced to bromide ions and chloride ions, respectively. Preferably, the electrolyte is a 0.01–1.0 mol / L sulfate solution, more preferably a 0.05 mol / L Na₂SO₄ solution; the cathode potential is -0.8–-1.6 V (relative to Ag / AgCl), preferably -1.0–-1.4 V; the initial concentration of nitrate is 1–500 mg / L, and the initial concentrations of bromate and perchlorate are 1–100 mg / L. Under typical conditions, after 12 hours of electrolysis, the removal rate of nitrate can reach about 95%, and the nitrogen selectivity is about 96%; the removal rates of bromate and perchlorate can reach about 99% and about 92%, respectively, and the bromide and chloride ion selectivity is close to 100%.

[0015] Fourth aspect: Electrochemical treatment device The device includes: an electrolytic cell having mutually isolated cathode and anode chambers; a cathode electrode disposed in the cathode chamber, the cathode electrode comprising a current collector and the aforementioned Sm diatomic electrocatalyst loaded on the current collector; an anode electrode disposed in the anode chamber; and a power source electrically connected to the cathode and anode electrodes. Preferably, the current collector is nickel foam, electrode carbon cloth, or titanium mesh; the electrolyte is a sulfate solution; and the electrolytic cell can be an H-type electrolytic cell or a membrane-separated electrolytic cell.

[0016] In brief, this invention involves the self-assembly of Sm₂O₃ nanorods with dopamine and urea in a Tris buffer solution to obtain a samarium-organic composite precursor. This precursor is then subjected to high-temperature carbonization under an inert atmosphere and subsequent acid etching to obtain an Sm₂-NC catalyst with Sm atoms uniformly dispersed on an N-doped hollow porous carbon support. This catalyst is then coated onto a conductive substrate (such as nickel foam) as a cathode, and subjected to NO₃⁻... - BrO3 - ClO4 - By applying a negative potential to an aqueous solution, efficient electrochemical reduction of oxyacid salts can be achieved.

[0017] Beneficial effects Compared with the prior art, the present invention has at least the following beneficial effects: 1. Highly efficient and harmless removal of nitrates. Under conditions of -1.3V (vsAg / AgCl) and 0.05mol / L Na2SO4 electrolyte, nitrates with an initial concentration of 100mg / L (as NO3) were effectively removed. -Electrolysis of a nitrate solution (calculated as N) for 12 hours produces NO3. - The removal rate was approximately 95.3%, with nitrogen (N2) as the main end product and an N2 selectivity of approximately 96.2%. NH3 and NO2 were also present. - The low generation rate helps avoid secondary pollution.

[0018] 2. Broad-spectrum oxyacid salt treatment capability. Under similar conditions, the catalyst of this invention exhibits good performance in treating BrO3 at an initial concentration of 25 mg / L. - and ClO4 - Removal rates of approximately 99.2% and 92.5% were achieved, respectively, for Br. - and Cl - With a selectivity approaching 100%, it demonstrates the general OAT deoxygenation capability for a variety of oxyacid salts.

[0019] 3. Suppressing HER to improve selectivity and energy efficiency. Thanks to the low HER activity and dual-atom site design of Sm, the hydrogen evolution reaction is significantly suppressed during electrolysis, and electrons are mainly used for the reduction of oxyacid salts, thereby improving Faraday efficiency and target product selectivity.

[0020] 4. High metal site utilization and structural stability. Sm is anchored in the N-doped carbon framework in a diatomic form, with a near 100% atomic utilization rate, which helps reduce metal usage and suppress agglomeration and dissolution; synchrotron radiation characterization shows that the Sm2N6 structure remains stable under operating conditions, which is beneficial for long-term operation.

[0021] 5. Low dependence on precious metals and cost advantage. Compared to BrO3, which relies on precious metals such as Pd and Rh. - / ClO4 - Compared to the reduction system, this invention uses rare earth samarium instead of precious metals, which is abundant in resources, has a lower cost, and is suitable for large-scale water treatment applications. Attached Figure Description

[0022] Figure 1 Here is a high-resolution transmission electron microscope (HRTEM) image of the Sm2-NC diatomic electrocatalyst of this invention, wherein: Figure 1 (a) is a low-magnification HRTEM image showing that the catalyst has a hollow porous carbon shell structure; Figure 1 (b) is a high-magnification HRTEM image showing regular striations of graphitized carbon layers on the surface of the carrier.

[0023] Figure 2 This is an aberration-corrected high-angle annular dark-field scanning electron microscope (HAADFSTEM) image of the Sm2-NC diatomic electrocatalyst of the present invention. The paired bright spots circled in yellow in the image are atomically dispersed Sm-Sm diatomic active sites.

[0024] Figure 3 The following are the synchrotron radiation X-ray absorption spectra analysis results of the Sm2-NC diatomic electrocatalyst of this invention, wherein: Figure 3 (a) shows the XANES spectrum of SmL3 edge, comparing the absorption edge position and peak shape of Sm foil, Sm2-NC and Sm2O3; Figure 3 (b) shows the corresponding EXAFSR spatial Fourier transform spectrum, displaying the positions and intensities of coordination peaks such as Sm-N and Sm-Sm; Figure 3 (c) is a comparison of the EXAFS fitting curve of the Sm2-NC catalyst with experimental data, used to determine the diatomic coordination structure of Sm2N6.

[0025] Figure 4 The figures show the performance curves of the Sm2-NC electrode of this invention in the electroreduction of different oxyacid salts, wherein: Figure 4 (a) Comparison curves of the removal rates of nitrate, bromate and perchlorate as a function of reaction time under the same electrolysis conditions; Figure 4 (b) shows the removal rates of the three oxoacid salts at the reaction endpoint and the corresponding N2 / Br ratios. - / Cl - Product selectivity bar chart comparison.

[0026] Figure 5 The photograph shows an actual electrochemical treatment device for treating oxyacid wastewater according to the present invention. It shows the structure of an H-type electrolytic cell with mutually isolated cathode and anode chambers and their connection method. An Sm2-NC cathode electrode is installed in the cathode chamber, and a counter electrode is installed in the anode chamber. The two chambers are connected by a central channel and an ion-conducting medium. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments, but the present invention is not limited to these embodiments. For those skilled in the art, any equivalent substitutions or modifications made without departing from the spirit and essence of the present invention should be considered to fall within the protection scope of the claims of the present invention.

[0028] Example 1: Preparation and Characterization of Sm2-NC Diatomic Electrocatalyst 1. Main reagents and raw materials The main reagents used in this embodiment are shown in Table 1.

[0029] Table 1. Main reagents used in the preparation of Sm2NC catalyst *The typical dosage is the dosage used in Example 1. Other examples may be adjusted accordingly.

[0030] Unless otherwise specified, all reagents listed in Table 1 are analytical grade or equivalent commercially available products, preferably purchased from Sinopharm Reagents or suppliers with equivalent quality assurance.

[0031] Sm2O3 nanorods serve as the samarium metal source; Tris buffer acts as both a Sm2O3 dispersant and a pH buffer; urea and dopamine hydrochloride act as nitrogen-containing organic precursors, jointly providing the C / N source and forming a polydopamine coating layer on the Sm2O3 surface; sulfuric acid is used for acid etching of the carbonization products; Nafion solution serves as a binder for the cathode electrode; and ethanol and deionized water are used as solvents and washing solutions.

[0032] 2. Main instruments and equipment The main equipment used in this embodiment is shown in Table 2.

[0033] Table 2 Main Instruments and Equipment As shown in Table 2, all instruments and equipment used in this embodiment are conventional laboratory instruments and equipment. A tube furnace and vacuum drying oven were used for precursor carbonization and drying; an ultrasonic cleaner was used for precursor dispersion and substrate pretreatment; HRTEM and HAADFSTEM were used for catalyst morphology and Sm two-atom site distribution characterization; and XRD was used for analyzing the carbon support and SmO. x The phase composition; the XAFS beamline of synchrotron radiation is used to obtain the valence state of Sm and the coordination structure of Sm-N / Sm-Sm.

[0034] 3. Catalyst preparation steps (1) Sm2O3 nanorod dispersion and precursor construction Add 100 mL of a 1 mol / L Tris buffer solution with a pH of 7.5 to a clean beaker. Weigh 400 mg of Sm2O3 nanorods and add them to the above solution. Sonicate the mixture in an ultrasonic cleaner for 60 min to obtain a uniform Sm2O3 dispersion A.

[0035] 120 mg of urea and 300 mg of dopamine hydrochloride were added to dispersion A and dissolved completely under magnetic stirring. Stirring was continued at room temperature (approximately 25 °C) for 24 h. Dopamine self-polymerized on the surface of Sm2O3 to form a polydopamine coating layer, yielding a polydopamine-modified Sm2O3 precursor, denoted as Sm2O3@DPA-urea.

[0036] After the reaction was complete, the sample was washed three times each with deionized water and ethanol until the supernatant was clear and colorless. The washed solid was then transferred to a petri dish and dried overnight in a vacuum drying oven at 60°C to obtain the dried precursor powder.

[0037] (2) Carbonization The dried Sm2O3@DPA-urea precursor was evenly spread in a quartz boat and placed in the center of a tube furnace. Argon gas (approximately 10 mL / min) was introduced as an inert atmosphere, and the temperature was increased to 800 °C at a rate of 5 °C / min, and held at this temperature for 2 h. The sample was then allowed to cool naturally to room temperature, and the carbonized product was obtained, denoted as Sm2O3@NC.

[0038] (3) Acid etching Prepare a 1 mol / L H₂SO₄ solution. Add the above carbonized product to the H₂SO₄ solution preheated to 80°C, with a solid-liquid ratio of approximately 1:10 (mass:volume). Etch with magnetic stirring at 80°C for 6 hours. After etching, filter while hot, and wash the filter cake three times each with deionized water and ethanol until the filtrate has a near-neutral pH and no metal ion residue. Dry the washed solid overnight in a vacuum drying oven at 60°C to obtain a black powdered Sm₂-NC catalyst.

[0039] (4) Electrode preparation Weigh 10 mg of Sm2-NC catalyst powder, add it to 1 mL of ethanol, add 80 μL (5 wt%) of Nafion solution, and disperse under ultrasonic conditions for 1 h to obtain a uniform catalyst ink.

[0040] A 25mm × 25mm nickel foam substrate was ultrasonically cleaned and dried using deionized water and ethanol. Catalyst ink was uniformly drop-coated onto the nickel foam surface and dried at room temperature to obtain an Sm2-NC / nickel foam cathode electrode for subsequent electrochemical testing.

[0041] 4. Structural and compositional characterization The main characterization conditions for the Sm2NC catalyst are summarized in Table 3.

[0042] Table 3. Structural and compositional characterization conditions of Sm2NC catalyst like Figure 1 As shown, HRTEM images indicate that the obtained Sm2NC catalyst has a hollow carbon shell structure with a bubble-like texture on the surface and no obvious agglomeration of metal nanoparticles.

[0043] like Figure 2 As shown, the HAADF-STEM image contains a large number of paired bright spots, which can be attributed to atomically dispersed Sm-Sm diatomic active sites.

[0044] like Figure 3As shown, synchrotron XANES / EXAFS analysis further revealed the valence state and local coordination environment of Sm. XANES fitting results showed that the average valence state of Sm was approximately +2.1; the EXAFSR spatial spectrum showed a main Sm-N coordination peak at approximately 1.91 Å and an Sm-Sm coordination peak at approximately 3.28 Å. EXAFS fitting showed that the coordination configuration of Sm in Sm2NC was Sm2N6, with an Sm-N coordination number of approximately 2.7 and an Sm-Sm coordination number of approximately 0.8 around each Sm atom, and average bond lengths of approximately 2.47 Å and 3.58 Å, respectively, thus proving the existence of stable Sm diatomic active sites in the catalyst.

[0045] Example 2 Nitrate (NO3) - Electrochemical treatment of wastewater This embodiment uses the Sm2-NC / nickel foam electrode prepared in Example 1 as the cathode to perform electrochemical reduction of simulated nitrate wastewater, in order to evaluate the catalyst's effect on NO3. - Its removal performance and nitrogen selectivity.

[0046] 1. Electrode and electrolytic cell configuration The configuration of electrodes and electrolytic cells is shown in Table 4.

[0047] Table 4NO3 - Electrode and electrolytic cell configuration for electroreduction experiments As shown in Table 4, this embodiment adopts an H-type three-electrode system, which has a simple structure and can effectively prevent the anodic products from interfering with the cathode reaction.

[0048] 2. NO3 - Preparation of simulated wastewater NO3 - The preparation conditions for the simulated wastewater are shown in Table 5.

[0049] Table 5 NO3 - Simulated wastewater preparation conditions The above conditions simulated a typical low- to medium-concentration nitrate wastewater environment, providing a reference for evaluating the suitability of the catalyst in practical applications.

[0050] 3. Electrolysis conditions and analytical methods Electrolysis conditions are listed in Table 6, and analytical items and methods are listed in Table 7.

[0051] Table 6 NO3 - Electrolysis conditions for electroreduction experiment Table 7 NO3 - Analytical methods for its reduction products The above analytical methods can achieve quantitative analysis of nitrogen species in the liquid phase and nitrogen balance calculation, providing a basis for evaluating reaction pathways and selectivity.

[0052] 4. NO3 - Electroreduction results NO3 - The concentrations of various nitrogen species and related performance indicators during the electroreduction process are shown in Table 8. The overall removal effect of the Sm2-NC electrode on the three oxoacids is shown in Table 8. Figure 4 .

[0053] Table 8NO3 - Electroreduction performance data Table 8 and Figure 4 It can be seen that as the electrolysis time increases, NO3... - The concentration decreased rapidly, and the removal rate reached approximately 95.3% after 12 hours; NO2 - The NH4⁺ concentration remained consistently low, total nitrogen was essentially conserved, and nitrogen selectivity was approximately 96.2%. These results indicate that the Sm2-NC cathode of this invention, while suppressing the formation of hydrogenation byproducts such as NH3, can efficiently remove NO3. - It is directly converted into N2, thus achieving the harmless removal of nitrates.

[0054] Example 3 BrO3 - and ClO4 - Electrochemical treatment of wastewater In this embodiment, the removal performance of the Sm2NC electrode for bromate and perchlorate was investigated under the same electrolysis system as in Example 2, in order to verify the broad-spectrum applicability of the catalyst.

[0055] (a) BrO3 - Electroreduction experiment 1. Simulated wastewater and equipment Except for replacing nitrate with bromate, the electrodes, electrolytic cell, and electrolysis conditions are the same as in Example 2, and will not be repeated here. BrO3 - The preparation conditions for the simulated wastewater are shown in Table 9.

[0056] Table 9 BrO3 - Simulated wastewater preparation conditions 2. Analytical Methods BrO3 - and its main reduction product Br - The analytical methods are shown in Table 10.

[0057] Table 10 BrO3- Electroreduction analysis items and methods 3.BrO3 - Electroreduction results BrO3 - The performance data for electroreduction are shown in Table 11.

[0058] Table 11 BrO3 - Electroreduction performance data From Table 11 and Figure 4 It can be seen that BrO3 - It was rapidly reduced on the Sm2NC electrode, and BrO3 was obtained after 12 hours. - Almost complete removal was achieved, with a removal rate of approximately 99.2%. Bromine ions were the main product, with selectivity approaching 100%, and no significant BrO2 was detected. - Intermediates, etc. Results show that the catalyst of this invention can purify highly toxic BrO3. - Efficient and selective conversion to low-toxicity Br - .

[0059] (ii) ClO4 - Electroreduction experiment 1. Simulated wastewater and equipment ClO4 - The simulated wastewater preparation conditions are shown in Table 12, and the rest of the equipment is the same as in Example 2.

[0060] Table 12ClO4 - Simulated wastewater preparation conditions 2. Analytical Methods ClO4 - The analytical methods for the reduction products are shown in Table 13.

[0061] Table 13 ClO4 - Electroreduction analysis items and methods 3.ClO4 - Electroreduction results ClO4 - The performance data for electroreduction are shown in Table 14.

[0062] Table 14 ClO4 - Electroreduction performance data From Table 14 and Figure 4 It can be known that ClO4 -It can be effectively reduced on the Sm2-NC electrode, with a removal rate of approximately 92.5% after 12 hours. - The selectivity is close to 100%. As the reaction proceeds, the intermediate ClO... x - First it is formed, then gradually decreases, and eventually almost all of it is converted into Cl. - This demonstrates that the catalyst of the present invention also exhibits excellent activity and selectivity in the electroreduction of perchlorate.

[0063] The above embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Various modifications, substitutions, and combinations made by those skilled in the art without departing from the spirit and essence of the invention should be considered to fall within the protection scope of the invention, as defined in the appended claims.

Claims

1. A Sm diatomic electrocatalyst characterized in that, The electrocatalyst comprises an N-doped carbon carrier and samarium diatomic active sites supported on the surface of the N-doped carbon carrier, wherein: (1) each samarium atom forms a Sm-N coordination bond with the N-doped carbon carrier through at least three N coordination atoms; (2) there is a Sm-Sm coordination or metal-metal bond between adjacent two samarium atoms, so that the samarium diatomic active sites are dispersed in an atomic level; (3) the average valence of samarium is +1.5 to +3.

0.

2. The Sm diatomic electrocatalyst of claim 1, wherein In the R space of an extended X-ray absorption fine structure spectrum, there is a Sm-N coordination main peak at 1.8-2.8 Å and a Sm-Sm coordination peak at 3.0-4.0 Å.

3. The Sm diatomic electrocatalyst of claim 1 or 2, wherein The N-doped carbon support has a hollow porous structure and a vesicular surface morphology, a specific surface area greater than 100 m 2 / g.

4. The Sm diatomic electrocatalyst of any of the preceding claims, wherein, The loading amount of samarium in the electrocatalyst is 0.1-10 wt%.

5. A method of preparing a Sm diatomic electrocatalyst, characterized in that, The method comprises the following steps: (1) a precursor preparation step: dispersing a samarium-containing compound in an aqueous solution containing a buffer, adding a nitrogen-containing organic precursor, stirring to react, and obtaining a samarium-organic composite precursor; (2) a carbonization step: heating the samarium-organic composite precursor to 600-1000 ℃ under an inert atmosphere and maintaining for 0.5-3 h, so that the nitrogen-containing organic precursor is carbonized to obtain a samarium / oxide / N-doped carbon composite material; (3) an acid etching step: contacting the composite material with an acid solution, treating at 50-100 ℃ for 2-12 h to remove part of the oxide phase and expose the samarium diatomic active sites, and then washing and drying to obtain the Sm diatomic electrocatalyst as claimed in claim 1.

6. The production method according to claim 5, wherein The samarium-containing compound is Sm2O3 nanorods, the nitrogen-containing organic precursor comprises dopamine and urea, the buffer is a tris(amino methane) solution, the carbonization temperature is 800 ℃, the heating rate is 5 ℃ / min, and the holding time is 2 h; the acid solution is a 1 mol / L sulfuric acid solution, and the treatment is carried out at 80 ℃ for 6 h.

7. A method of treating oxygen acid salt-containing wastewater, characterized by, The method comprises: providing a cathode and an anode in an electrochemical reactor, using an oxygen-containing acid salt wastewater as an electrolyte or part of an electrolyte, the cathode comprising the Sm diatomic electrocatalyst as claimed in any one of claims 1-4; and electrolyzing the oxygen-containing acid salt wastewater under the action of an external power source to cause an electrochemical reduction reaction of the oxygen-containing acid salt in the wastewater.

8. The method of claim 7, wherein, The oxygen-containing acid salt comprises at least one of nitrate, bromate and perchlorate; the electrolyte is a 0.01-1.0 mol / L sulfate solution, preferably a 0.05 mol / L Na2SO4 solution; and the cathode potential is -0.8 to -1.6 V (relative to Ag / AgCl).

9. The method of claim 7 or 8, wherein, After 12 h of electrolysis, the removal rate of nitrate is not less than 90%, the selectivity of nitrogen in the nitrate reduction product is not less than 90%; and / or the removal rate of bromate and / or perchlorate is not less than 90%, and the selectivity of bromide and / or chloride in the reduction product is not less than 90%.

10. An electrochemical treatment device for carrying out the method according to any one of claims 7 to 9, characterized in that The method comprises: providing an electrolytic cell having a cathode chamber and an anode chamber isolated from each other; A cathode electrode provided in the cathode chamber, the cathode electrode comprising a current collector and the Sm diatomic electrocatalyst according to any one of claims 1-4 supported on the current collector; an anode electrode provided in the anode chamber; and a power source electrically connected to the cathode electrode and the anode electrode.

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