A sulfur-oxygen co-coordinated Cu single-atom supported WO3 composite material, its preparation method and application

Abstract

This invention relates to a sulfur-oxygen co-coordinated Cu single-atom supported WO3 composite material, its preparation method, and its application. The preparation method includes the following steps: dissolving tungsten salt, sulfur source, copper salt, and reducing agent in water and stirring thoroughly to obtain a homogeneous precursor solution; transferring the precursor solution to a sealed microwave reaction vessel and performing a high-pressure microwave reaction under protective gas pressure to obtain a Cu-modified S-WO3 precursor; and annealing the Cu-modified S-WO3 precursor in a reducing atmosphere to finally obtain the sulfur-oxygen co-coordinated Cu single-atom supported WO3 composite material. Compared with existing technologies, the preparation process of this invention is simple, has high reaction efficiency, and low energy consumption. The obtained composite material exhibits excellent catalytic activity and stability in the photoelectrocatalytic reduction of NO to ammonia.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic materials technology, and in particular to a sulfur-oxygen co-coordinated Cu single-atom supported WO3 composite material, its preparation method and application. Background Technology

[0002] With the acceleration of industrialization and urbanization, air pollution problems caused by industrial emissions and transportation activities have become increasingly prominent, among which nitrogen oxides (NOxides) are a major contributor. x Nitrogen oxides (NOx), as a typical pollutant, pose significant threats to both the ecological environment and human health. They mainly include NO, NO2, and N2O, with NO being the most abundant. x NO accounts for over 90% of emissions, primarily from fuel combustion, especially vehicle exhaust. Therefore, developing efficient and green NO conversion and treatment technologies is of significant environmental and social importance.

[0003] Against the backdrop of increasing demands for clean energy and sustainable development, photoelectrocatalysis, as a green technology capable of driving chemical reactions under mild conditions, has attracted widespread attention. This technology, through the synergistic effect of light and electrical energy, promotes the generation and migration of photogenerated charge carriers and has shown promising application prospects in fields such as water splitting and carbon dioxide reduction. In recent years, the conversion of NO into harmless or high-value-added products (such as N2, NH3, or NH2OH) using photoelectrocatalysis under ambient temperature and pressure conditions has been considered a pollution control approach with potential applications.

[0004] Tungsten oxide (WO3) is a common n-type semiconductor material with good chemical stability and visible light response, attracting widespread attention in photocatalysis and photoelectrocatalysis. However, existing WO3-based materials still suffer from problems such as rapid photogenerated carrier recombination rate, slow reaction kinetics, and limited number of active sites in the photoelectrocatalytic NO conversion process, resulting in the need for further improvement in their overall catalytic performance.

[0005] Introducing metal active components is considered a feasible modification approach to improve the photoelectrocatalytic activity of WO3-based materials. However, conventional metal loading methods often suffer from problems such as easy aggregation of metal particles, low utilization efficiency, and insufficient stability under reaction conditions. In particular, in photoelectrocatalytic multi-electron reaction systems, the structural stability of metal active centers is difficult to maintain over a long period of time.

[0006] Single-atom catalysts exhibit significant advantages in heterogeneous catalysis due to their highly dispersed metal atoms and high atom utilization. CN114899435A discloses a method for preparing metal single-atom-anchored binary heterostructure catalysts. This method uses an ultrasonic-assisted photochemical reduction process to form indium single-atom anchors in the binary heterostructure, achieving efficient and uniform indium single-atom dispersion and high loading, thus improving catalyst performance and applicability. However, this method mainly relies on defect sites in a specific sulfide system for anchoring, resulting in an uncontrollable coordination environment. Furthermore, single-atom migration and aggregation risks still exist during the reduction process. Additionally, the lack of effective control over the electronic structure of the metal-support interface hinders further improvement in reaction selectivity and stability. Therefore, achieving stable single-atom anchoring and synergistic electronic structure control on semiconductor supports remains challenging, especially in achieving a balance between high activity and high stability without compromising the photoelectric properties of the support. An effective strategy for this is still lacking.

[0007] Besides constructing metal active centers, the modulation of semiconductor supports using non-metallic elements is also considered an important approach to improve photoelectrocatalytic performance. Sulfur, due to its similar chemical valence state to oxygen but different electronegativity and atomic radius, can modulate the local electronic structure and band structure of WO3 materials by partially substituting the O sites, thereby improving visible light absorption and promoting the separation and migration of photogenerated carriers. Simultaneously, the introduction of S helps induce the formation of defect states or oxygen vacancies, enhancing electron transport capabilities and increasing surface reactivity. Furthermore, the strong coordination ability of S atoms can provide stable anchoring sites for transition metal single atoms, enhancing the interaction between the active center and the support through the formation of metal-S coordination structures, and inhibiting the migration and aggregation of metal atoms during the reaction process. However, how to effectively regulate S and synergistically construct stable single-atom active structures while ensuring the stability of the WO3 crystal structure still requires further exploration.

[0008] Therefore, how to achieve the synergistic unity of carrier electronic structure optimization and active center stable anchoring in WO3-based semiconductor systems by combining non-metallic element regulation with metal single-atom construction remains an urgent technical problem to be solved. Summary of the Invention

[0009] The purpose of this invention is to overcome the defects of the prior art by providing a sulfur-oxygen co-coordinated Cu single-atom supported WO3 composite material, its preparation method and application.

[0010] This invention can simultaneously improve carrier separation efficiency, interfacial reaction kinetics, and active site stability without weakening the photoelectric performance of semiconductors, thereby constructing a photoelectrocatalytic system with both high activity and high stability, and realizing the efficient conversion and resource utilization of atmospheric pollutant NO.

[0011] The objective of this invention can be achieved through the following technical solutions: This invention first provides a method for preparing a Cu single-atom-supported WO3 composite material with sulfur-oxygen co-coordination, the method comprising the following steps: S1: Dissolve tungsten salt, sulfur source, copper salt and reducing agent in water and stir thoroughly to obtain a homogeneous precursor solution; S2: The precursor solution is transferred to a closed microwave reaction vessel and subjected to high-pressure microwave reaction under protective gas pressure to obtain Cu-modified S-WO3 precursor; S3: The Cu-modified S-WO3 precursor was annealed in a reducing atmosphere to obtain a Cu single-atom-supported WO3 composite material with sulfur-oxygen co-coordination.

[0012] Further, in step S1, the molar ratio of the tungsten salt, sulfur source and copper salt is 1:(4-8):(0.01-0.5), preferably 1:(4-8):(0.01-0.2).

[0013] Further, in step S1, the tungsten salt is any one or a combination of sodium tungstate, potassium tungstate, ammonium tungstate, lithium tungstate, and ammonium paratungstate.

[0014] Further, in step S1, the sulfur source is any one or a combination of thiourea and thioacetamide.

[0015] Further, in step S1, the copper salt is any one or a combination of copper nitrate, copper chloride, copper sulfate, and copper acetate.

[0016] Further, in step S1, the molar ratio of the reducing agent to the tungsten salt is (1.5-2.5):1.

[0017] Further, in step S1, the reducing agent is any one or a combination of hydroxylamine hydrochloride and sodium sulfite, preferably hydroxylamine hydrochloride.

[0018] Furthermore, in step S2, the heating rate of the high-pressure microwave reaction is 10-20 °C / min, preferably 15 °C / min.

[0019] Furthermore, in step S2, the temperature of the high-voltage microwave reaction is 160-210 ℃, preferably 200 ℃.

[0020] Furthermore, in step S2, the heat preservation time of the high-pressure microwave reaction is 40-80 min, preferably 60 min.

[0021] Furthermore, in step S2, the initial pressure of the high-pressure microwave reaction is 30-40 bar, preferably 35 bar.

[0022] Furthermore, in step S2, the protective gas is either nitrogen or helium, preferably nitrogen.

[0023] Furthermore, in step S3, the annealing temperature is 300-500 ℃, preferably 400 ℃.

[0024] Furthermore, in step S3, the annealing process takes 1-4 hours, preferably 2 hours.

[0025] Furthermore, in step S3, the annealing process is carried out in a hydrogen or hydrogen / inert gas mixed atmosphere. During the annealing process, copper species undergo in-situ reconstruction, anchoring themselves as single atoms on the surface of the WO3 framework via sulfur atoms.

[0026] The present invention also provides a sulfur-oxygen co-coordinated Cu single-atom supported WO3 composite material, which is prepared by any of the above preparation methods.

[0027] Furthermore, the composite material has an overall nanorod structure with a length of 200-600 nm and a diameter of 20-100 nm.

[0028] Furthermore, the composite material comprises a sulfur-oxygen co-coordinated S-WO3 matrix and Cu single atoms uniformly dispersed and stably anchored on the S-WO3 matrix.

[0029] Furthermore, the Cu single atoms are uniformly dispersed in single-atom form, without forming metal particles or clusters.

[0030] Furthermore, some of the O in the S-WO3 body is replaced by S.

[0031] Furthermore, the Cu single atoms are loaded on the surface of the S-WO3 host in a four-coordinate structure, wherein the Cu single atoms are coordinated with three sulfur atoms and one oxygen atom respectively to form a Cu-S3-O1 coordination structure.

[0032] This invention also provides the application of a sulfur-oxygen co-coordinated Cu single-atom supported WO3 composite material in the photoelectrocatalytic reduction of nitric oxide to ammonia.

[0033] Compared with the prior art, the present invention has the following technical advantages: (1) The present invention innovatively prepared a sulfur-oxygen co-coordinated Cu single-atom supported WO3 composite material. The introduction of Cu single atoms in the WO3-based semiconductor constructs atomically dispersed high-efficiency reactive sites, while effectively controlling the electronic structure and charge transport characteristics of the material, thereby significantly improving the photoelectrocatalytic activity of the material, which can be used to achieve efficient reduction of NO to ammonia under mild conditions.

[0034] (2) By controlling the composition of the carrier anion, the present invention introduces sulfur to partially replace oxygen and constructs a defect-state sulfur tungsten oxide structure in the tungsten oxide lattice, providing a stable anchoring point for copper single atoms, effectively inhibiting the migration and aggregation of copper species in the preparation and reaction process, and significantly improving the dispersion stability and catalytic durability of copper single atoms.

[0035] (3) In the Cu SAs@S-WO3 composite material of the present invention, S-WO3 serves as a photoelectrocatalytic carrier, possessing both good photoresponse capability and electron transport performance. The defect states introduced by sulfur substitution help promote the separation and migration of photogenerated carriers. The uniformly dispersed Cu single atoms serve as reactive centers, which can stably adsorb and activate NO molecules, thereby effectively promoting the selective reduction reaction of NO to NH3.

[0036] (4) Under the synergistic effect of light and applied bias voltage, the photogenerated electrons generated in S-WO3 can continuously participate in the NO reduction reaction under a low driving voltage condition. The Cu single-atom active sites further reduce the reaction energy barrier, thereby realizing an efficient and stable photoelectric synergistic NO reduction to ammonia synthesis process.

[0037] (5) The present invention uses microwave method combined with annealing to prepare composite materials. Microwave reaction has the advantages of uniform heating, short reaction time and high energy utilization efficiency. Annealing is beneficial to promote atomic-level reconstruction and stabilize the dispersion state of copper single atoms. The method is simple, low energy consumption and good repeatability, and has the potential for large-scale preparation and practical application. Attached Figure Description

[0038] Figure 1 The images show transmission electron microscopy (TEM) images and selected area electron diffraction (SED) images of the Cu SAs@S-WO3 composite material prepared in Example 1 of this invention.

[0039] Figure 2 The X-ray diffraction patterns are those of the composite material prepared in Example 1 of the present invention, WO3 in Comparative Example 1, and S-WO3 in Comparative Example 2.

[0040] Figure 3 The images show the normalized X-ray absorption near-edge structure (XANES) spectrum and extended X-ray absorption fine structure (EXAFS) spectrum of the Cu-K composite material prepared in Example 1 of this invention.

[0041] Figure 4 The results are synchrotron radiation fitting results of the composite material prepared in Example 1 of this invention.

[0042] Figure 5 The linear voltammetric scan curves of the composite material prepared in Example 1 of this invention under light and dark conditions in an argon- and NO-saturated electrolyte.

[0043] Figure 6 This is the standard curve for NH3 in the photoelectrocatalytic performance test.

[0044] Figure 7 The NH3 yield and Faraday efficiency of the composite material prepared in Example 1 of the present invention, and Comparative Examples 1 and 2 are shown under illumination and under a bias voltage of -0.4V.

[0045] Figure 8 The NH3 yield and Faraday efficiency of the composite material prepared in Example 1 of this invention under different potential conditions are shown.

[0046] Figure 9 The NH3 yield and Faraday efficiency of the composite material prepared in Example 1 of this invention under three conditions: photoelectric, pure electric, and pure light.

[0047] Figure 10 The current density and NH3 Faraday efficiency of the composite material prepared in Example 1 of this invention were measured during a 200-hour stability test. Detailed Implementation

[0048] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0049] Unless otherwise specified, the reagents, methods, instruments, and equipment used in this invention are conventional in the art. Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0050] In the following embodiments, the sulfur-oxygen co-coordinated Cu single-atom supported WO3 composite material of the present invention is denoted as Cu SAs@S-WO3.

[0051] The microwave reactor used to prepare Cu SAs@S-WO3 composite material was an Ultra Wave reactor manufactured by Milestone; transmission electron microscopy (TEM) characterization was performed using a JEM-2100 TEM from Japan; XRD characterization of the composite material was performed using a BRUKER D8 ADVANCE X-ray diffractometer; and the electrochemical workstation used in the photoelectrocatalytic NO reduction test was a Chenhua CHI 760.

[0052] Example 1: This embodiment provides a sulfur-oxygen co-coordinated Cu single-atom-supported WO3 composite material, the specific preparation method of which is as follows: Weigh out 0.005 mol of sodium tungstate, 0.02 mol of thiourea, 0.001 mol of copper nitrate and 0.01 mol of hydroxylamine hydrochloride, add them to 30 mL of deionized water, and stir magnetically for 1 hour at room temperature to fully dissolve them and form a homogeneous precursor solution.

[0053] Subsequently, the homogeneous liquid mixture of the above substances was placed in a microwave tube to obtain a precursor solution, and the microwave tube was placed in a microwave reactor. Under nitrogen protection, the initial pressure was adjusted to 35 bar. The reaction system was carried out at 10 °C / min. -1 The temperature was increased from room temperature to 200 °C and maintained at this temperature for 1 hour. After the reaction, the system was allowed to cool naturally to room temperature, and the resulting product was washed repeatedly with deionized water and anhydrous ethanol to remove residual impurities. The washed sample was dried at 80 °C for 12 hours to obtain the precursor.

[0054] Subsequently, an appropriate amount of the aforementioned precursor was placed in the center of a tubular furnace, and under a continuously purged hydrogen atmosphere, it was heated at 5°C / min. -1 The temperature was increased to 400 °C at a rising rate and held at that temperature for 2 hours. After the reaction was completed, the system was allowed to cool naturally to room temperature in the furnace, finally yielding Cu SAs@S-WO3 material.

[0055] Example 2: This embodiment provides a Cu single-atom-loaded WO3 composite material with sulfur-oxygen co-coordination.

[0056] The difference from Example 1 is that the microwave reaction temperature in this example is 160 °C. All other steps and parameters are the same as in Example 1.

[0057] Example 3: This embodiment provides a Cu single-atom-loaded WO3 composite material with sulfur-oxygen co-coordination.

[0058] The difference from Example 1 is that the microwave reaction temperature in this example is 170 °C. All other steps and parameters are the same as in Example 1.

[0059] Example 4: This embodiment provides a Cu single-atom-loaded WO3 composite material with sulfur-oxygen co-coordination.

[0060] The difference from Example 1 is that the microwave reaction temperature in this example is 180 °C. All other steps and parameters are the same as in Example 1.

[0061] Example 5: This embodiment provides a Cu single-atom-loaded WO3 composite material with sulfur-oxygen co-coordination.

[0062] The difference from Example 1 is that the microwave reaction temperature in this example is 190 °C. All other steps and parameters are the same as in Example 1.

[0063] Example 6: This embodiment provides a Cu single-atom-loaded WO3 composite material with sulfur-oxygen co-coordination.

[0064] The difference from Example 1 is that the microwave reaction temperature in this example is 210 °C. All other steps and parameters are the same as in Example 1.

[0065] Example 7: This embodiment provides a Cu single-atom-loaded WO3 composite material with sulfur-oxygen co-coordination.

[0066] The difference from Example 1 is that the amount of copper nitrate used in this example is 0.0005 mol. All other steps and parameters are the same as in Example 1.

[0067] Example 8: This embodiment provides a Cu single-atom-loaded WO3 composite material with sulfur-oxygen co-coordination.

[0068] The difference from Example 1 is that the amount of copper nitrate used in this example is 0.0015 mol. All other steps and parameters are the same as in Example 1.

[0069] Example 9: This embodiment provides a Cu single-atom-loaded WO3 composite material with sulfur-oxygen co-coordination.

[0070] The difference from Example 1 is that the copper source in this example is 0.0015 mol of copper sulfate. All other steps and parameters are the same as in Example 1.

[0071] Example 10: This embodiment provides a Cu single-atom-loaded WO3 composite material with sulfur-oxygen co-coordination.

[0072] The difference from Example 1 is that the copper source in this example is 0.0015 mol of copper acetate. All other steps and parameters are the same as in Example 1.

[0073] Example 11: This embodiment provides a Cu single-atom-loaded WO3 composite material with sulfur-oxygen co-coordination.

[0074] The difference from Example 1 is that the copper source in this example is 0.0015 mol of copper chloride. All other steps and parameters are the same as in Example 1.

[0075] Example 12: This embodiment provides a Cu single-atom-loaded WO3 composite material with sulfur-oxygen co-coordination.

[0076] The difference from Example 1 is that the copper sulfur source in this example is 0.02 mol of thioacetamide, and the amount of copper nitrate used is 0.0015 mol. Other steps and parameters are the same as in Example 1.

[0077] Comparative Example 1: This comparative example uses pure WO3 material, and the specific preparation method is as follows: Add 3 mL of concentrated nitric acid (65%) and 25 mL of deionized water to a beaker and stir for 10 minutes under magnetic stirring to obtain solution A. Then, dissolve 0.4948 g of Na₂WO₄·2H₂O in 10 mL of deionized water and stir for 5 minutes to obtain solution B. Slowly add solution B to solution A and continue stirring for 30 minutes to obtain a homogeneous mixture. Then, place the homogeneous mixture in a microwave tube to obtain a precursor solution, and place the microwave tube in a microwave reactor. Incubate at 35 bar and 10 °C / min. -1 The temperature was increased to 150 °C at a rising rate and maintained at this temperature for 72 minutes. After the reaction, the mixture was cooled to room temperature, and the product was washed three times with deionized water and ethanol, respectively, and centrifuged at 10,000 rpm. The obtained product was then vacuum-dried at 80 °C for 12 hours. Subsequently, the dried sample was placed in the center of a tube furnace and heated at 5 °C·min under a continuous hydrogen atmosphere. -1 The temperature was increased to 400 °C at a rising rate and held at that temperature for 2 hours. After the reaction was complete, the system was allowed to cool naturally to room temperature in the furnace, finally yielding pure WO3.

[0078] Comparative Example 2: This comparative example uses S-WO3 material, and the specific preparation method is as follows: 0.005 mol of sodium tungstate, 0.02 mol of thiourea, and 0.01 mol of hydroxylamine hydrochloride were weighed and added to 30 mL of deionized water. The mixture was magnetically stirred at room temperature for 1 hour to ensure complete dissolution and form a homogeneous precursor solution. The homogeneous liquid mixture was then placed in a microwave tube to obtain the precursor solution. The microwave tube was placed in a microwave reactor, and the initial pressure was adjusted to 35 bar under nitrogen protection. The reaction system was accelerated at 10 °C / min. -1The temperature was increased from room temperature to 200 °C and maintained at this temperature for 1 hour. After the reaction, the system was allowed to cool naturally to room temperature, and the resulting product was washed repeatedly with deionized water and anhydrous ethanol to remove residual impurities. The washed sample was dried at 80 °C for 12 hours to obtain the precursor S-WO3. Subsequently, an appropriate amount of the above S-WO3 precursor was placed in the center of a tube furnace and heated at 5 °C·min under a continuous hydrogen atmosphere. -1 The temperature was increased to 400 °C at a rising rate and held at that temperature for 2 hours. After the reaction was completed, the system was allowed to cool naturally to room temperature in the furnace, finally yielding S-WO3 material.

[0079] The materials obtained in Example 1 and Comparative Examples 1-2 were tested as follows: (1) Morphological characterization: Surface morphology was observed using a transmission electron microscope.

[0080] (2) Composition characterization: X-ray diffraction patterns were used to characterize the samples prepared in Example 1, Comparative Example 1 and Comparative Example 2, and XANES and EXAFS spectra were used to test the composite material of Example 1.

[0081] (3) Photoelectrocatalytic performance testing: All photoelectrocatalytic tests in this invention were conducted in an H-type electrolytic cell. The cathode chamber was illuminated through a quartz glass window, with the working electrode directly opposite the window. The testing conditions were ambient temperature and pressure. The electrolyte was a 0.5 M Na2SO4 solution. The working electrode was a carbon paper supported on the catalyst. The reference electrode and counter electrode were Ag / AgCl electrodes and foils (1×1 cm). 2 75 mL of electrolyte was added to each of the two reaction chambers of the electrolytic cell. Before the photoelectrocatalytic reaction, the cathode chamber was purged with pure Ar to remove any remaining air from the reaction cell. The gas flow rate was controlled by a flow meter (60 SCCM). Then, NO / Ar (10 vol.% NO) gas was bubbled into the cathode reaction cell at 60 SCCM for 30 min before the photoelectrocatalytic reduction reaction began. The exhaust gas was removed using a 4 M saturated KOH solution. The NH3 Faraday efficiency and yield in this study were calculated after 1 h of reaction.

[0082] ①Detection of NH3: The presence of NH3 was detected using the indophenol blue colorimetric method, and the NH3 concentration in the cathode electrolyte after photoelectrocatalytic reduction was quantitatively analyzed by visible spectrophotometry (UV-Vis). The colorant consisted of 5 wt% salicylic acid, 5 wt% sodium citrate, and 1 M NaOH aqueous solution, which were mixed thoroughly to obtain colorimetric reagent A. The oxidant solution B was 0.05 M NaClO aqueous solution. The catalyst was 1 wt% sodium nitroprusside aqueous solution, which was used as solution C. The procedure involved pipetting 100 μL of the electrolyte after 1 h of reaction, diluting it to 1 mL with 0.5 M Na2SO4 electrolyte, and then adding 1 mL of solution A, 0.5 mL of solution B, and 100 μL of solution C to the test liquid and mixing thoroughly. The entire colorimetric process was carried out at room temperature in the dark for 2 h. After color development, the absorbance of the colored liquid was measured at 655 nm using UV-Vis, and the concentration of NH3 was calculated from a standard curve.

[0083] ②Standard curve of NH3: First, prepare a 100 ppm NH4Cl solution as the stock solution. Then, dilute the stock solution to a series of NH4Cl solutions with the same concentration gradient (1, 2, 4, 6, 8, 10 ppm). After indophenol blue staining, measure the absorbance at 655 nm using UV-Vis (e.g., ...). Figure 6 As shown in a), the results are plotted with absorbance as the ordinate, NH4 + A standard curve of NH3 was plotted with concentration on the x-axis, as shown below. Figure 6 As shown in b.

[0084] Depend on Figure 1 As can be seen from Example 1, during the preparation process, highly dispersed copper species were achieved on the surface of the defective S-WO3 support through microwave reaction and subsequent annealing. The resulting material exhibits a regular one-dimensional nanorod structure with a uniform overall morphology. No obvious metallic copper particles or agglomeration were observed on the surface, indicating that the copper species did not exist in the form of metallic or oxide particles. Figure 1 As can be seen from b, the corresponding selected area electron diffraction pattern shows clear and regularly arranged diffraction spots, reflecting that the nanorod is a single crystal structure.

[0085] Depend on Figure 2 It can be seen that the diffraction peaks of the composite material obtained in Example 1 mainly correspond to the crystal structure of WO3. No characteristic diffraction peaks of metallic copper or copper compounds were observed, indicating that the introduction of copper did not form a detectable crystalline phase, further indicating that copper species exist in a highly dispersed state in the material.

[0086] Depend on Figure 3 It can be seen that, Figure 3a presents the Cu-K edge X-ray absorption near-edge structure spectra of Cu SAs@S-WO3, Cu foil, Cu2O, and CuO from Example 1. The absorption edge position of Cu SAs@S-WO3 is between Cu2O and CuO, indicating that the average valence state of copper in the material is between +1 and +2. Figure 3 In the b-Fourier transform EXAFS spectrum, Cu SAs@S-WO3 exhibits a distinct coordination peak at approximately 1.7 Å, which can be attributed to the Cu-S (and partly Cu-O) coordination structure. No Cu-Cu coordination signal was observed, indicating the absence of copper metal or copper clusters in the material. Further wavelet transform EXAFS analysis in k-space and R-space further validated the single-atom dispersion characteristics of copper atoms on the S-WO3 support.

[0087] Figure 4 The results of synchrotron radiation fitting show that copper single atoms are coordinated with three sulfur atoms and one oxygen atom to form a Cu-S3-O1 coordination structure.

[0088] Figure 5 Linear sweep voltammetry (LSV) curves of the Cu SAs@S-WO3 catalyst in Example 1 under Ar and NO atmospheres, respectively, under light and dark conditions. It can be seen that under Ar atmosphere, the LSV curves under light and dark conditions show little difference; while under NO atmosphere, the current density under light conditions increases significantly, indicating that under photoelectric synergy, this material can participate more effectively in the NO reduction reaction, suggesting that the introduction of copper single atoms provides stable and uniformly dispersed active sites for the reaction.

[0089] Depend on Figure 7 The results show that, under illumination and a bias voltage of -0.4 V, the NH3 yield and Faradaic efficiency of Cu SAs@S-WO3 in Example 1, as well as Comparative Examples 1 and 2, are compared. It can be seen that Example 1 exhibits a higher NH3 yield and Faradaic efficiency under photoelectrocatalytic conditions, indicating a synergistic promoting effect between the copper single atom and the S-WO3 support, which is beneficial to improving the overall performance of NO reduction to ammonia synthesis.

[0090] Depend on Figure 8 It can be seen that the NH3 yield and Faradaic efficiency of Cu SAs@S-WO3 in Example 1 change with potential during the photoelectrocatalytic reduction of NO at different applied potentials. Among them, the material exhibits higher NH3 generation performance at -0.4 V.

[0091] Depend on Figure 9As can be seen from the reaction results of Example 1 under photoelectrocatalysis (PEC), pure photocatalysis (PC), and pure electrocatalysis (EC) conditions, Example 1 exhibits the highest NH3 yield and Faradaic efficiency under photoelectrocatalysis conditions. However, under conditions of only light irradiation or only applied bias voltage, its reaction performance is lower than that under photoelectrocatalysis conditions. These results indicate that in Example 1, the simultaneous action of light irradiation and applied bias voltage has a synergistic promoting effect on the NO reduction reaction.

[0092] Depend on Figure 10 It can be seen that the Cu SAs@S-WO3 prepared in Example 1 exhibited good stability during the 200-hour cycle test.

[0093] In summary, this invention utilizes a convenient and rapid high-pressure microwave and annealing process to obtain Cu SAs@S-WO3 nanorod composite materials, and confirms that the copper in the material exists in a single-atom structure. This composite material was then used to prepare a semiconductor photocathode and applied to the photoelectrocatalytic reduction of NO to ammonia, achieving excellent ammonia yield and Faraday efficiency. This demonstrates the unique application prospects and value of this invention in the field of photoelectrocatalytic reduction of NO to ammonia.

[0094] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a sulfur-oxygen co-coordinated Cu single-atom supported WO3 composite material, characterized in that, The preparation method includes the following steps: S1: Dissolve tungsten salt, sulfur source, copper salt and reducing agent in water and stir thoroughly to obtain a homogeneous precursor solution; S2: The precursor solution is transferred to a closed microwave reaction vessel and subjected to high-pressure microwave reaction under protective gas pressure to obtain Cu-modified S-WO3 precursor; S3: The Cu-modified S-WO3 precursor was annealed in a reducing atmosphere to obtain a Cu single-atom-supported WO3 composite material with sulfur-oxygen co-coordination.

2. The method for preparing a sulfur-oxygen co-coordinated Cu single-atom supported WO3 composite material according to claim 1, characterized in that, In step S1, the molar ratio of the tungsten salt, sulfur source, and copper salt is 1:(4-8):(0.01-0.5).

3. The method for preparing a sulfur-oxygen co-coordinated Cu single-atom supported WO3 composite material according to claim 1, characterized in that, In step S1, the tungsten salt is any one or a combination of sodium tungstate, potassium tungstate, ammonium tungstate, lithium tungstate, and ammonium paratungstate. The sulfur source is any one or a combination of thiourea and thioacetamide; The copper salt is any one or a combination of copper nitrate, copper chloride, copper sulfate, and copper acetate.

4. The method for preparing a sulfur-oxygen co-coordinated Cu single-atom supported WO3 composite material according to claim 1, characterized in that, In step S2, the molar ratio of the reducing agent to the tungsten salt is (1.5-2.5):1; The reducing agent is hydroxylamine hydrochloride, sodium sulfite, or any one or a combination thereof.

5. The method for preparing a sulfur-oxygen co-coordinated Cu single-atom supported WO3 composite material according to claim 1, characterized in that, In step S2, the heating rate of the high-pressure microwave reaction is 10-20 °C / min; The temperature of the high-voltage microwave reaction is 160-210 ℃; The heat preservation time for the high-pressure microwave reaction is 40-80 min; The initial pressure of the high-pressure microwave reaction is 30-40 bar; The protective gas is either nitrogen or helium.

6. The method for preparing a sulfur-oxygen co-coordinated Cu single-atom supported WO3 composite material according to claim 1, characterized in that, In step S3, the annealing temperature is 300-500 ℃; The annealing process takes 1-4 hours.

7. The method for preparing a sulfur-oxygen co-coordinated Cu single-atom supported WO3 composite material according to claim 1, characterized in that, In step S3, the annealing process is carried out in a hydrogen atmosphere or a hydrogen / inert gas mixture.

8. A Cu single-atom-supported WO3 composite material with sulfur-oxygen co-coordination, characterized in that, Prepared by the preparation method according to any one of claims 1-7; The composite material comprises a sulfur-oxygen co-coordinated S-WO3 matrix and Cu single atoms uniformly dispersed and stably anchored on the S-WO3 matrix.

9. The sulfur-oxygen co-coordinated Cu single-atom supported WO3 composite material according to claim 8, characterized in that, In the S-WO3 body, some of the O is replaced by S; The Cu single atoms are loaded on the surface of the S-WO3 host in a four-coordinate structure, wherein the Cu single atoms are coordinated with three sulfur atoms and one oxygen atom respectively.

10. The application of the sulfur-oxygen co-coordinated Cu single-atom supported WO3 composite material as described in claim 8 in the photoelectrocatalytic reduction of nitric oxide to ammonia.

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