Preparation method of single-atom coordinated composite photoelectric catalyst

Abstract

The present invention discloses a preparation method of a single-atom coordinated composite photoelectrocatalyst, which utilizes non-metal defects (sulfur / oxygen vacancies) and an amorphous substrate to synergistically anchor variable-valence single atoms and in-situ growth strategies and methods such as solvothermal method to achieve the coordination and composite of Bi2S3-S V and Co-N4-C. Through the liquid-phase sulfidation method, thioacetamide is used as a sulfur source to in-situ generate Bi2S3-S V , and by regulating the sulfur source ratio and reducing the concentration of thioacetamide, sulfur defects are directly introduced during the sulfidation process. Then, combined with the annealing process, Co single atoms are promoted to migrate to the Bi2S3-S V interface to form Co-S y coordination, while retaining the Co-N4 coordination within the N-C framework, constructing a unique Bi2S3-S V / Co-N4-C composite photoelectrocatalyst with the synergistic effect of sulfur vacancies and Co single-atom double coordination to achieve efficient photoelectrocatalytic hydrogen production and coupling reactions such as formaldehyde oxidation.

Description

Technical Field

[0001] The present invention relates to the technical field of photocatalysts, and particularly to a preparation method of a single-atom coordinated composite photocatalyst. Background Art

[0002] In the process of photocatalytic or photoelectrocatalytic water splitting for hydrogen production, the addition of sacrificial agents not only increases carbon emissions but also raises the cost of the reaction process. Constructing a catalyst that can achieve photocatalytic or photoelectrocatalytic water splitting for hydrogen production in an environment without sacrificial agents, or even in an electrolyte solution containing pollutants, while coupling an anodic oxidation reaction, is one of the important research directions in the field of catalysis. Summary of the Invention

[0003] The present invention provides a preparation method of a single-atom coordinated composite photocatalyst, which is used to solve problems such as the need to add sacrificial agents in the process of photocatalytic or photoelectrocatalytic material water splitting for hydrogen production, easy recombination of photogenerated electrons and holes, and lack of reactive sites.

[0004] The present invention adopts the following technical solutions:

[0005] A preparation method of a single-atom coordinated composite photocatalyst realizes the coordination and compounding of Bi2S3-S V and Co-N4-C by using non-metal defects (sulfur / oxygen vacancies) and an amorphous substrate to synergistically anchor variable-valence single atoms and an in-situ growth strategy and methods such as solvothermal method. Using thioacetamide as a sulfur source through a liquid-phase sulfidation method, Bi2S3-S is in-situ generated V and by regulating the sulfur source ratio and reducing the concentration of thioacetamide, sulfur defects are directly introduced during the sulfidation process. Then, combined with an annealing process, Co single atoms are promoted to migrate to the Bi2S3-S V interface to form Co-S y coordination, while retaining the Co-N4 coordination within the N-C framework. In addition, using formaldehyde and dyes to replace traditional hole sacrificial agents to consume a large number of holes, a unique Bi2S3-S V / Co-N4-C catalytic system with the synergistic effect of sulfur vacancies and Co single atoms double coordination to achieve efficient photoelectrocatalytic hydrogen production coupled with reactions such as formaldehyde oxidation is constructed. The steps of its preparation method are as follows:

[0006] (1) Take a certain amount of Co(NO3)2·6H2O and 2-MI and dissolve them in an appropriate amount of methanol solution. After fully stirring for 5 - 120 min, let it stand for 1 - 12 h, and collect the ZIF-67 crystals by centrifugation;

[0007] (2) Place a certain amount of the ZIF-67 crystals obtained in step (1) in an N2 atmosphere, heat to a certain temperature and keep it for 1 - 6 h, and then cool it to room temperature with the furnace to obtain Co-N4-C;

[0008] (3) Take a certain amount of Bi(NO3)3·5H2O and dissolve it in an appropriate amount of ethanol solution. After stirring until completely dissolved, add a certain amount of Co-N4-C and disperse it therein. After ultrasonic impregnation for 10 - 180 min, dry it to obtain Co-N4-C@Bi 3+ ;

[0009] (4) Take a certain amount of Co-N4-C@Bi 3+ and a certain amount of TAA and dissolve them in an appropriate amount of deionized water / ethylene glycol mixed solution, and stir well for 10 - 120 min;

[0010] (5) Transfer the solution stirred completely in step (4) into a solvothermal reaction kettle, react at a certain temperature for 6 - 24 h, and the obtained product is washed and dried in vacuum to obtain Co-N4-C@Bi2S3-S V ;

[0011] (6) Place a certain amount of Co-N4-C@Bi2S3-S V in an Ar atmosphere, heat it to a certain temperature and keep it for 30 - 240 min, and then cool it to room temperature with the furnace to obtain Bi2S3-S V / Co-N4-C composite photo - electrocatalyst.

[0012] Preferably, in step (1), the mass of Co(NO3)2·6H2O used is 0.1 - 10 g, the mass of 2 - MI is 0.1 - 10 g, and the volume of the methanol solution is 10 - 1000 mL.

[0013] Preferably, in step (2), the mass of ZIF - 67 used is 0.1 - 20 g, and the heating temperature is 600 - 1000 °C.

[0014] Preferably, in step (3), the mass of Bi(NO3)3·5H2O is 0.1 - 10 g, the volume of the ethanol solution is 10 - 1000 mL, the mass of Co-N4-C is 0.1 - 10 g, the drying temperature is 40 - 90 °C, and the time is 6 - 24 h.

[0015] Preferably, in step (4), the mass of Co-N4-C@Bi 3+ used is 0.1 - 20 g, the mass of TAA is 0.1 - 20 g, the volume fraction of the deionized water / ethylene glycol mixed solution is 5 - 95%, and the volume of the deionized water / ethylene glycol mixed solution is 10 - 1000 mL.

[0016] Preferably, in the step (5), the reaction temperature of the solvent thermal reaction kettle is 120 - 350 °C, the vacuum drying temperature is 40 - 90 °C, and the time is 6 - 24 h.

[0017] Preferably, in the step (6), the mass of Co - N4 - C@Bi2S3 - S V used is 0.1 - 20 g, and the heating temperature is 200 - 600 °C.

[0018] Compared with the prior art, the advantages of the present invention are as follows:

[0019] Through the synergistic anchoring of variable - valent single atoms by non - metallic defects (sulfur / oxygen vacancies) and amorphous substrates, and in - situ growth strategies and methods such as solvothermal method, Bi2S3 - S rich in defect states V is compounded with Co - N4 - C. The preparation process is simple and the production cost is low. Using formaldehyde or dye solution to replace the traditional hole sacrificial agent to consume a large number of holes, a unique single - atom synergistic coordination composite catalyst is constructed with the synergistic effect of sulfur vacancies and Co single - atom double coordination to achieve efficient photocatalytic hydrogen production coupled with reactions such as formaldehyde oxidation. The obtained Bi2S3 - S V / Co - N4 - C composite catalytic material significantly improves the light absorption range and ability of Bi2S3 and Co - N4 - C, and successfully improves the separation and migration ability of photogenerated electrons and holes. Among them, the Co - N4 site can stabilize Co atoms and regulate their d - band center, enhancing the adsorption and activation of formaldehyde, etc. The generated S - vacancy defects are combined with the amorphous substrate (Co - N4 - C) to form a Co - N / S composite coordination structure, which proves that the sulfur - vacancy - induced local electric - field polarization can adsorb single - atom precursors (Co 2+ ), and through the short - range ordered interface of the amorphous substrate, dynamic coordination is realized, inhibiting the migration and aggregation of Co single atoms, accelerating the transfer of holes to molecules such as formaldehyde, and at the same time, synergistically, sulfur vacancies act as electron - trapping centers, reducing the recombination of photogenerated electrons and holes, promoting the adsorption and dissociation of H2O molecules (H2O → H + + OH - ), providing the required H + for the photocatalytic hydrogen - production reaction (HER). In addition, sulfur vacancies can also optimize the surface electronic structure of Bi2S3, reduce the activation energy of formaldehyde oxidation, so as to realize the efficient photocatalytic hydrogen production coupled with anodic oxidation of formaldehyde, etc. by Bi2S3 - S V / Co - N4 - C, and is expected to be applied in the fields of photocatalysis or photoelectrocatalysis for CO2 reduction, pollutant degradation, and energy production, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the preparation flow chart of the sample in the preparation method of a single - atom synergistic coordination composite photocatalyst of the present invention.

[0021] Figure 2 is the aberration-corrected electron microscopy image of Bi2S3-S V / Co-N4-C composite material obtained in the preparation method of a single-atom coordinated composite photoelectrocatalyst of the present invention at different scales.

[0022] Figure 3 is the synchrotron radiation spectrum of Bi2S3-S V / Co-N4-C composite material obtained in the preparation method of a single-atom coordinated composite photoelectrocatalyst of the present invention.

[0023] Figure 4 is the photoelectrocatalytic performance diagram of the sample obtained in the example in the preparation method of a single-atom coordinated composite photoelectrocatalyst of the present invention. Detailed Embodiments

[0024] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making the protection scope of the present invention more clearly defined.

[0025] In the process of photocatalytic or photoelectrocatalytic water splitting for hydrogen production, the addition of sacrificial agents not only increases carbon emissions but also raises the cost of the reaction process. Constructing a catalyst that can achieve photocatalytic or photoelectrocatalytic water splitting for hydrogen production in an environment without sacrificial agents, or even in an electrolyte solution containing pollutants, while coupling an anodic oxidation reaction, is one of the important research directions in the field of catalysis.

[0026] In an electrolyte solution containing pollutants, the increase in the hydrogen evolution rate indicates that the pollutants act as hole sacrificial agents, consuming a large number of holes, thereby promoting the transport of carriers and ultimately improving the hydrogen evolution performance.

[0027] In Co-N4-C obtained by carbonizing ZIF-67, Co single atoms are anchored in the amorphous N-C support in the form of Co-N4 coordination, forming atomically dispersed active centers, and the N-C support can effectively prevent the aggregation of Co single atoms. This coordination structure stabilizes Co atoms through the bonding of nitrogen atoms with the carbon matrix, while endowing it with a unique electronic structure, enhancing the adsorption and activation ability of formaldehyde or other reaction intermediates. In addition, during the catalytic reaction process, the cycle of Co 2+ / Co 3+ can dynamically adjust the local electron density, promoting the formation of OOH or H intermediates and reducing the reaction energy barrier.

[0028] The sulfur vacancies introduce defect states in Bi2S3, extending the light response range to the visible and even near-infrared regions. At the same time, the sulfur vacancies serve as electron trapping centers, greatly reducing the recombination rate of photo-generated carriers and the activation energy for formaldehyde oxidation, etc., and effectively suppressing the photo-corrosion phenomenon of Bi2S3. In addition, the Bi sites exposed by the sulfur vacancies have strong adsorption ability for H2O or OH - and provide reaction sites for water splitting.

[0029] Therefore, to solve the problems such as the need to add sacrificial agents in the process of photocatalytic or photoelectrocatalytic water splitting for hydrogen production, the easy recombination of photo-generated electrons and holes, and the lack of reactive sites, this application creatively proposes to combine Bi2S3-S rich in defect states V with Co-N4-C to construct a trapezoidal heterojunction with a stable interface structure, high carrier separation efficiency, and strong redox activity. Among them, the built-in electric field drives photo-generated electrons to migrate from the conduction band of Bi2S3-S V to the Co single-atom sites of N-C. The Co-S coordination forms a strong coupling with the Bi2S3-S V interface, accelerating the transfer of holes to molecules such as formaldehyde. At the same time, the sulfur vacancies act as electron trapping centers in cooperation, reducing the recombination of photo-generated electrons and holes, promoting the adsorption and dissociation of H2O molecules, and providing the required H + for the photoelectrocatalytic hydrogen production reaction, and using Co single atoms as "electron channels" to further accelerate the interfacial charge transfer. Through synchrotron radiation results, it is found that the Co K-edge XANES curve of the Bi2S3-S V / Co-N4-C catalyst is located between CoPc and Co3O4, proving that the valence state of Co atoms in the catalyst is between +2 and +3. By fitting, the valence state of Co in the Bi2S3-S V / Co-N4-C catalyst is about +2.25. The R-space transformation of the EXAFS spectrum clarifies the coordination information of Co elements in the catalyst sample. Compared with Co Foil and Co3O4, no obvious Co-Co peak is observed in the Bi2S3-S V / Co-N4-C sample, proving that there is no bonding between Co elements, and obvious Co-N / S coordination bonds exist in the Bi2S3-S V / Co-N4-C sample, proving the VIn the / Co-N4-C sample, Co exists in the form of single atoms and forms a synergistic coordination structure of Co with N and S. In addition, adding formaldehyde or dyes to the electrolyte solution to replace the traditional hole sacrificial agent, consuming a large number of holes, and enabling more electrons to participate in the hydrogen evolution reaction on the platinum electrode, thereby realizing efficient photocatalytic hydrogen production coupled with reactions such as formaldehyde oxidation, is an effective strategy to improve the catalytic efficiency and reduce the cost of catalytic reactions. Using non-metallic defects (sulfur / oxygen vacancies) to synergistically anchor variable-valence single atoms with an amorphous substrate and in-situ growth strategies and methods such as solvothermal to prepare a single-atom synergistically coordinated Bi2S3-S V The process of using the / Co-N4-C composite catalytic material for photocatalytic hydrogen production coupled with anodic oxidation of formaldehyde, etc., has not been reported.

[0030] In view of this, the embodiments of the present application provide a preparation method of a single-atom synergistically coordinated composite photocatalyst, using non-metallic defects (sulfur / oxygen vacancies) to synergistically anchor variable-valence single atoms with an amorphous substrate and in-situ growth strategies and methods such as solvothermal to achieve the coordination and compounding of Bi2S3-S V and Co-N4-C. Using thioacetamide as a sulfur source through a liquid-phase sulfidation method, Bi2S3-S is in-situ generated V and by regulating the sulfur source ratio and reducing the concentration of thioacetamide, sulfur defects are directly introduced during the sulfidation process. Then, combined with an annealing process, it promotes the migration of Co single atoms to the Bi2S3-S V interface to form Co-S y coordination, while retaining the Co-N4 coordination within the N-C framework, constructing a unique dual coordination synergy of sulfur vacancies and Co single atoms to achieve efficient photocatalytic hydrogen production coupled with reactions such as formaldehyde oxidation of the Bi2S3-S V / Co-N4-C composite photocatalyst. Example 1

[0031] A preparation method of a single-atom synergistically coordinated composite photocatalyst.

[0032] (1) Add 0.378 g of Co(NO3)2·6H2O to 20 mL of methanol and stir well for 10 min; similarly, add 0.854 g of 2-MI to 20 mL of methanol and stir well for 20 min. Quickly drip the 2-MI solution into the Co(NO3)2·6H2O solution, stir vigorously for 10 min, then let it stand at room temperature for precipitation for 20 min. Separate the precipitate by centrifugation, wash it with anhydrous ethanol multiple times, and finally place the obtained product in a vacuum drying oven at 80 °C for drying for 12 h, and grind it to obtain ZIF-67 crystals;

[0033] (2) Place 1.0 g of ZIF-67 in an N2 atmosphere, heat it to 800 °C and hold for 2 h, and then cool it to room temperature in the furnace to obtain Co-N4-C; subsequently, dissolve 0.97 g of Bi(NO3)3·5H2O in 20 mL of ethanol solution. After stirring until completely dissolved, add 1.0 g of Co-N4-C and disperse it therein. After ultrasonic impregnation for 60 min, dry it at 60 °C for 24 h to obtain Co-N4-C@Bi 3+ ;

[0034] (3) Dissolve 1.0 g of Co-N4-C@Bi 3+ and 0.15 g of TAA in 200 mL of deionized water / ethylene glycol mixed solution, stir well for 60 min, then transfer the completely stirred solution into a solvothermal reaction kettle, react at 200 °C for 12 h, wash the obtained product with anhydrous ethanol for several times, and finally place the obtained product in a vacuum drying oven and dry it at 80 °C for 12 h to obtain Co-N4-C@Bi2S3-S V 。

[0035] (4) Place 1.0 g of Co-N4-C@Bi2S3-S V in an Ar atmosphere, heat it to 350 °C and hold for 60 min, and then cool it to room temperature in the furnace to obtain Bi2S3-S V / Co-N4-C composite photoelectrocatalyst. Example 2

[0036] A preparation method of a single-atom coordinated composite photoelectrocatalyst.

[0037] (1) Add 0.567 g of Co(NO3)2·6H2O to 30 mL of methanol and stir well for 15 min; similarly, add 1.281 g of 2-MI to 30 mL of methanol and stir well for 30 min. Quickly drip the 2-MI solution into the Co(NO3)2·6H2O solution, stir vigorously for 15 min, then let it stand at room temperature for precipitation for 30 min, separate the precipitate by centrifugation, wash it with anhydrous ethanol for several times, and finally place the obtained product in a vacuum drying oven and dry it at 60 °C for 18 h, and grind it to obtain ZIF-67 crystals;

[0038] (2) 1.5 g of ZIF-67 was placed in an N2 atmosphere and heated to 750 °C for 2.5 h. After cooling to room temperature in the furnace, Co-N4-C was obtained. Subsequently, 1.455 g of Bi(NO3)3·5H2O was dissolved in 30 mL of ethanol solution. After stirring until completely dissolved, 1.5 g of Co-N4-C was added and dispersed therein. After ultrasonic impregnation for 90 min, it was dried at 80 °C for 40 h to obtain Co-N4-C@Bi 3+ ;

[0039] (3) 1.5 g of Co-N4-C@Bi 3+ and 0.225 g of TAA were dissolved in 300 mL of deionized water / ethylene glycol mixed solution, and stirred thoroughly for 90 min. Subsequently, the stirred solution was transferred into a solvothermal reaction kettle and reacted at 180 °C for 14 h. The obtained product was washed with anhydrous ethanol multiple times, and finally the obtained product was placed in a vacuum drying oven and dried at 60 °C for 18 h to obtain Co-N4-C@Bi2S3-S V 。

[0040] (4) 1.5 g of Co-N4-C@Bi2S3-S V was placed in an Ar atmosphere and heated to 450 °C for 40 min. After cooling to room temperature in the furnace, Bi2S3-S V / Co-N4-C composite photoelectrocatalyst was obtained. Example 3

[0041] A preparation method of a single-atom coordinated composite photoelectrocatalyst.

[0042] (1) 0.756 g of Co(NO3)2·6H2O was added to 40 mL of methanol and stirred thoroughly for 20 min. Similarly, 1.708 g of 2-MI was added to 40 mL of methanol and stirred thoroughly for 40 min. The 2-MI solution was quickly dropped into the Co(NO3)2·6H2O solution, and stirred vigorously for 20 min. Then it was left to stand and precipitate at room temperature for 40 min. The precipitate was separated by centrifugation and washed with anhydrous ethanol multiple times. Finally, the obtained product was placed in a vacuum drying oven and dried at 70 °C for 14 h, and ground to obtain ZIF-67 crystals;

[0043] (2) Place 2.0 g of ZIF-67 in an N2 atmosphere, heat it to 700 °C and hold for 3 h, and then cool it to room temperature in the furnace to obtain Co-N4-C; subsequently, dissolve 1.94 g of Bi(NO3)3·5H2O in 40 mL of ethanol solution. After stirring until completely dissolved, add 2.0 g of Co-N4-C and disperse it therein. After ultrasonic impregnation for 120 min, dry it at 70 °C for 48 h to obtain Co-N4-C@Bi 3 + ;

[0044] (3) Dissolve 2.0 g of Co-N4-C@Bi 3+ and 0.30 g of TAA in 400 mL of deionized water / ethylene glycol mixed solution, stir well for 120 min, then transfer the completely stirred solution into a solvothermal reaction kettle, react at 220 °C for 10 h, wash the obtained product with anhydrous ethanol multiple times, and finally place the obtained product in a vacuum drying oven and dry it at 70 °C for 14 h to obtain Co-N4-C@Bi2S3-S V 。

[0045] (4) Place 2.0 g of Co-N4-C@Bi2S3-S V in an Ar atmosphere, heat it to 400 °C and hold for 50 min, and then cool it to room temperature in the furnace to obtain Bi2S3-S V / Co-N4-C composite photo-electrocatalyst.

[0046] In some embodiments of the present application, according to the above preparation method process, Figure 1 shows the preparation flow chart of the samples in the preparation methods provided in the above Examples 1 to 3.

[0047] In some embodiments of the present application, Figure 2 shows the aberration-corrected electron microscopy images of the Bi2S3-S V / Co-N4-C composite materials prepared in the above Examples 1 to 3 at different scales.

[0048] For example, in Figure 2 , the (a) region represents the aberration-corrected electron microscopy image with a scale of 5 nm, and the Co single atoms are represented inside the red dashed circle; the (b) region represents the aberration-corrected electron microscopy image with a scale of 2 nm, and the Co single atoms are represented inside the red dashed circle, and the position pointed by the yellow arrow is the sulfur vacancy S V 。

[0049] In some embodiments of the present application, Figure 3 shows the synchrotron radiation pattern of the Bi2S3-S V / Co-N4-C composite materials prepared in the above Examples 1 to 3, specifically includingFigure 3 The XANES spectra shown in region (a), and the EXAFS Fourier transform spectra shown in region (b).

[0050] In the XANES spectra, the abscissa Energy (eV) represents energy, with the unit of electron volt (eV); the ordinate Intensity (a.u.) represents intensity, with the unit of arbitrary unit (a.u.).

[0051] Specifically, Figure 3 Region (a) shows the XANES spectra of Co foil (cobalt foil), Co3O4 (cobalt tetroxide), CoPc (cobalt phthalocyanine), Bi2S3-S V / Co-N4-C.

[0052] In the EXAFS Fourier transform spectra, the abscissa R (Å) represents distance, with the unit of angstrom (Å); the ordinate FT(K 2 x(k))| (a.u.) represents the square of the amplitude modulus after Fourier transform, with the unit of arbitrary unit (a.u.).

[0053] Specifically, Figure 3 Region (b) shows the EXAFS Fourier transform spectra of Co foil, Co3O4, CoPc, Bi2S3-S V / Co-N4-C. Example 4

[0054] Perform a photoelectrocatalytic performance test. The electrolyte solution uses a mixed solution of 95 mL KOH (1 mol / L) and 5 mL formaldehyde solution (37 - 40 wt.%), that is, 100 mL of a formaldehyde / KOH mixed solution with a concentration of 0.6 mol / L. Use the carbon paper (1×1.5 cm V ) uniformly loaded with Bi2S3-S 2 / Co-N4-C composite as the working electrode, an Ag / AgCl electrode as the reference electrode, and a platinum sheet as the counter electrode. Add the pre-prepared 100 mL formaldehyde / KOH mixed solution into a quartz container, install a three-electrode device and an electrochemical analyzer, and conduct a photoelectrocatalytic experiment under a 300 W visible light source and a bias voltage of -0.4 V vs. RHE. Use high-performance liquid chromatography to determine the formaldehyde oxidation products and their oxidation rates at different time intervals, and use a gas chromatograph to measure the amount of H2 generated every half hour.

[0055] As an example, Figure 4 Shows the photoelectrocatalytic performance diagrams of the samples prepared in the above Examples 1 to 3, specifically including Figure 4Comparison chart of photocatalytic hydrogen production rates of the sample shown in region (a) with and without formaldehyde, and photocatalytic formaldehyde oxidation rate chart of the sample shown in region (b).

[0056] Figure 4 In the comparison chart of photocatalytic hydrogen production rates of the sample shown in region (a) with and without formaldehyde, the abscissa represents different samples, which are Bi2S3, Bi2S3-S V , Co-N4-C, Bi2S3 / Co-N4-C, Bi2S3-S V / Co-N4-C; the ordinate H2 generation rate (μmol⋅cm −2 ⋅h −1 ) represents the hydrogen generation rate, with the unit of μmol⋅cm −2 ⋅h −1 (micromoles per square centimeter per hour). Specifically, the hydrogen production rate increases sequentially from left to right, and the hydrogen production rate is faster in the presence of formaldehyde.

[0057] Figure 4 In the photocatalytic formaldehyde oxidation rate chart of the sample shown in region (b), the abscissa Time (h) represents time, with the unit of hour (h); the ordinate In(C0 / Ct) represents the natural logarithm of the ratio of the initial concentration of formaldehyde to the concentration at time t. Specifically, the order of photocatalytic formaldehyde oxidation rate from slow to fast is: Bi2S3, Bi2S3-S V , Co-N4-C, Bi2S3 / Co-N4-C, Bi2S3-S V / Co-N4-C, and their reaction rate constants k are equal to 0.026, 0.0426, 0.0984, 0.216, 0.296 in turn.

[0058] In summary, a preparation method of a single-atom coordinated composite photocatalyst provided by an embodiment of the present application uses a non-metal defect (sulfur / oxygen vacancy) and an amorphous substrate to synergistically anchor a variable-valence single atom and an in-situ growth strategy and methods such as solvothermal to prepare a Bi2S3-S V / Co-N4-C composite material. The technical method steps are as follows: Using Co(NO3)2·6H2O and 2-methylimidazole (hereinafter referred to as 2-MI) as raw materials and a methanol solution as a solvent to prepare ZIF-67; calcining ZIF-67 at high temperature in a N2 atmosphere to obtain a carbon nitride material with Co single atoms anchored in the form of Co-N4 coordination (hereinafter referred to as Co-N4-C); using Co-N4-C and Bi(NO3)3·5H2O as raw materials and an ethanol solution as a solvent, ultrasonic impregnation and then drying to obtain Co-N4-C with Bi 3+ loaded on the surface (hereinafter referred to as Co-N4-C@Bi 3+); with Co-N4-C@Bi 3+ , thioacetamide (hereinafter referred to as TAA) as raw materials, deionized water and ethylene glycol mixed solution as solvent, and Co-N4-C and sulfur vacancy-rich bismuth sulfide (hereinafter referred to as Bi2S3-S V ) composite (hereinafter referred to as Co-N4-C@Bi2S3-S V ); Finally, Co-N4-C@Bi2S3-S V Annealing in Ar atmosphere resulted in a Bi2S3-S V / Co-N4-C composite catalyst. Using carbon paper as substrate, Bi2S3-S V / Co-N4-C photoelectrode. The invention has the advantages of simple preparation process, low production cost, and the prepared Bi2S3-S V The Co-N4-C photoelectrode has a unique dual-coordination structure of Co single atoms, in which the Co-N4 site can stabilize the Co atom and regulate its d-band center, enhancing the adsorption and activation of formaldehyde (HCHO), while the Co-S coordination with Bi2S3-S V The interface forms a strong coupling, accelerating the transfer of holes to molecules such as formaldehyde, while cooperating with sulfur vacancies as electron capture centers to reduce the recombination of photogenerated electrons and holes, promote the adsorption and dissociation of H2O molecules, and promote the photoelectrocatalytic hydrogen evolution reaction (HER). In addition, sulfur vacancies can also optimize the electronic structure of the Bi2S3 surface, reduce the activation energy of oxidation of formaldehyde, and realize Bi2S3-S V / Co-N4-C highly efficient photocatalytic hydrogen production coupled with formaldehyde oxidation and other reactions. V / Co-N4-C also has the advantages of strong visible light response, tight interface bonding, stable structure and rich active sites, and is expected to be used in the fields of photoelectrocatalytic reduction of CO2, degradation of pollutants and production capacity.

[0059] Without limitation to this, any changes or substitutions that are not conceived through creative work should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope defined in the claims.

Claims

1. A method for preparing a single-atom cooperative coordination composite photoelectrocatalyst, characterized in that: include: (1) Dissolve a certain amount of Co(NO3)2·6H2O and 2-MI in an appropriate amount of methanol solution, stir thoroughly for 5-120 min, let stand for 1-12 h, and collect by centrifugation to obtain ZIF-67 crystals; (2) placing a certain amount of ZIF-67 crystals obtained in step (1) in a N2 atmosphere, heating to a certain temperature and maintaining for 1-6 hours, and cooling to room temperature in the furnace to obtain Co-N4-C; (3) Take a certain amount of Bi(NO3)3·5H2O and dissolve it in an appropriate amount of ethanol solution. After stirring until it is completely dissolved, add a certain amount of Co-N4-C and disperse it in it. After ultrasonic immersion for 10-180 minutes, dry it to obtain Co-N4-C@Bi 3+ ; (4) Take a certain amount of Co-N4-C@Bi 3+ Dissolve a certain amount of thioacetamide TAA in an appropriate amount of deionized water / ethylene glycol mixed solution and stir thoroughly for 10-120 minutes; (5) The solution stirred completely in step (4) was transferred into a solvent thermal reactor and reacted at a certain temperature for 6-24 hours. The obtained product was washed and vacuum dried to obtain Co-N4-C@Bi2S3-S V ; (6) A certain amount of Co-N4-C@Bi2S3-S V Place it in an Ar atmosphere, heat it to a certain temperature and keep it for 30-240 minutes, and then cool it to room temperature to obtain Bi2S3-S V / Co-N4-C composite photoelectrocatalyst.

2. The preparation method according to claim 1, characterized in that: The mass of Co(NO3)2·6H2O used in the step (1) is 0.1-10 g, the mass of 2-MI is 0.1-10 g, and the volume of the methanol solution is 10-1000 mL.

3. The preparation method according to claim 1, characterized in that: The mass of ZIF-67 used in the step (2) is 0.1-20 g, and the heating temperature is 600-1000° C.

4. The preparation method according to claim 1, characterized in that: In the step (3), the mass of Bi(NO3)3·5H2O is 0.1-10 g, the volume of the ethanol solution is 10-1000 mL, the mass of Co-N4-C is 0.1-10 g, the drying temperature is 40-90° C., and the drying time is 6-24 h.

5. The preparation method according to claim 1, characterized in that: The Co-N4-C@Bi used in step (4) 3+ The mass of is 0.1-20 g, the mass of TAA is 0.1-20 g, the volume fraction of the deionized water / ethylene glycol mixed solution is 5-95%, and the volume of the deionized water / ethylene glycol mixed solution is 10-1000 mL.

6. The preparation method according to claim 1, characterized in that: In the step (5), the reaction temperature of the solvent thermal reactor is 120-350° C., the vacuum drying temperature is 40-90° C., and the drying time is 6-24 h.

7. The preparation method according to claim 1, characterized in that: The Co-N4-C@Bi2S3-S used in step (6) V The mass is 0.1-20g and the heating temperature is 200-600℃.

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