CoS / CuCo2S4 photocatalyst and its preparation method and application

Abstract

The present application belongs to the field of catalyst technology, and specifically relates to a CoS / CuCo2S4 photocatalyst, a preparation method thereof, and an application thereof. Co(NO3)2·6H2O and Cu(NO3)2·3H2O are dissolved in ethylene glycol to obtain a first solution and a second solution, respectively; the second solution is then added dropwise to the first solution while stirring to obtain a third solution; stirring is continued, and then sodium dimethyldithiocarbamate is added to obtain a suspension, which is subjected to a hydrothermal reaction, washed, and dried to obtain the CoS / CuCo2S4 photocatalyst. The present invention constructs a CS / CCS hollow spherical type II heterostructure with rich sulfur vacancies and interfacial Co‑S bonding by a one-step hydrothermal method. The interfacial Co‑S bond acts as an atomic-level channel to effectively promote the separation and transmission of photogenerated carriers, so that a large number of photogenerated electrons are enriched on the CCS surface and stably exist in the active site, thereby enhancing the CO2 photoreduction activity.

Description

Technical Field

[0001] The present application belongs to the field of catalyst technology, and specifically relates to a CoS / CuCo2S4 photocatalyst and its preparation method and application. Background Art

[0002] Solar-driven photocatalytic CO2 reduction technology can convert it into high-value chemicals. In the CO2 photoreduction product system, C1 products (such as CH4 and especially CO) have become a research hotspot due to their low kinetic energy barriers. However, how to generate high-value-added C through CC coupling to meet the specific needs of the energy field and industry is still a hot topic. 2+ Products (such as C2H2, C2H4, and C2H6) still face significant challenges. As a key raw material in the chemical, biological, and pharmaceutical industries, ethylene (C2H4) synthesis research has both scientific exploration and industrial application value.

[0003] Currently, photocatalysts such as ZnSe-CsSnCl3, Mn3O4 / FeNbO4, TiO2 / In2O3, and BiOIO3 / Bi-MOF have demonstrated enhanced CO2 reduction activity. However, most reported type II heterojunctions rely solely on weak physical adsorption and stacking forces, resulting in loose interfacial contact. This creates significant charge transfer resistance, hindering the high-throughput transport of photogenerated carriers at the interface between the components, thereby limiting their CO2 reduction performance. Summary of the Invention

[0004] The purpose of the present invention is to address the deficiencies of the prior art and provide a CoS / CuCo2S4 photocatalyst and its preparation method and application, specifically adopting the following technical solutions:

[0005] In a first aspect, the present invention provides a method for preparing a CoS / CuCo2S4 photocatalyst, comprising the following steps:

[0006] Dissolving Co(NO3)2·6H2O and Cu(NO3)2·3H2O in ethylene glycol to obtain a first solution and a second solution, respectively; then dropping the second solution into the first solution while stirring to obtain a third solution;

[0007] The third solution was continued to be stirred, and then sodium dimethyldithiocarbamate was added to obtain a suspension;

[0008] The suspension is subjected to a hydrothermal reaction, and after completion of the reaction, centrifuged, washed, and dried to obtain the CoS / CuCo2S4 photocatalyst.

[0009] The present invention successfully constructed sulfur-rich vacancies (V S), CoS / CuCo2S4 (CS / CCS) hollow spherical type II heterostructure with Co-S bonding at the interface. In the above preparation process, the ternary copper cobalt sulfide (CuCo2S4) presents a cubic spinel structure (space group Fd-3m), with Cu and Co atoms occupying tetrahedral and octahedral sites respectively. In addition, CoS (CS) has unique advantages. Its conduction band and valence band potentials are lower than those of CCS, and its work function is higher than that of CCS. Moreover, the coupling of CS and CCS can not only form a chemically bonded heterojunction by sharing S atoms at the heterojunction interface (enhancing interface compatibility), but also generate rich V in the heterojunction based on the atom sharing mechanism. S .

[0010] As a further preferred embodiment, the molar ratio of Cu(NO3)2·3H2O to Co(NO3)2·6H2O is 1-3:20. It can be seen from the present examples and comparative examples that when the amount of Cu(NO3)2·3H2O is too large, only CuCo2S4 nanosheets can be obtained, but no CoS / CuCo2S4 catalyst can be obtained.

[0011] As a further preferred embodiment, the molar ratio of Co(NO3)2·6H2O to sodium dimethyldithiocarbamate is 1:2.5-3.

[0012] As a further preferred embodiment, the dripping speed is 1 drop / 6 seconds to 1 drop / 8 seconds.

[0013] As a further preferred embodiment, the third solution is stirred for 0.3 h to 1 h.

[0014] As a further preferred embodiment, the temperature of the hydrothermal reaction is 160°C.

[0015] As a further preferred embodiment, the hydrothermal reaction time is 16 h.

[0016] In a second aspect, the present invention provides a CoS / CuCo2S4 photocatalyst, which is prepared by the above-mentioned preparation method.

[0017] In a third aspect, the present invention provides the use of the above-mentioned CoS / CuCo2S4 photocatalyst in photocatalytic CO2 reduction.

[0018] As a further preferred embodiment, the above-mentioned CoS / CuCo2S4 photocatalyst is used for photocatalytic conversion of CO2 to C2H4.

[0019] The beneficial effects of the present invention are:

[0020] The present invention provides a V-rich S, a method for preparing a CoS / CuCo2S4 hollow spherical type II heterostructure photocatalyst with interfacial Co-S bonding. The synthesis method has mild reaction conditions and is simple and easy to operate. Among them, the interfacial Co-S bond acts as an atomic-level channel to effectively promote the separation and transmission of photogenerated carriers, so that a large number of photogenerated electrons are enriched on the CCS surface and stably exist in the active site, thereby enhancing the CO2 photoreduction activity. V S The introduction of induced highly delocalized electron distribution and shortened the distance between adjacent Cu-Co atoms, resulting in local metallization of Cu and Co atoms and the formation of Cu-Co double sites connected by metallic bonds. These sites not only transformed the endothermic rate-determining step of single CCS (*CO dimerization to *COCO) into an exothermic process (promoting CC coupling), but also reduced the overall activation energy barrier, synergistically promoting the generation of C2H4. The optimized photocatalyst used H2O vapor as a hydrogen source and hole scavenger, and showed excellent performance in the photocatalytic reduction of CO2 to C2H4: the C2H4 yield and electron selectivity reached 28.79 μmol g, respectively. -1 h -1 and 93.95%, and the product selectivity was 72.14%. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 Shown are transmission electron microscopy (TEM) images and high-resolution transmission electron microscopy (HRTEM) images; among them, (a) and (b) in the figure are TEM images of CS HNs; (c) in the figure is a high-resolution transmission electron microscopy (HRTEM) image of CS HNs; (d) and (e) in the figure are TEM images of CCS NSs; (f) in the figure is a high-resolution transmission electron microscopy (HRTEM) image of CCS NSs; (g) in the figure is an HRTEM image of CS / CCS-10; (h) in the figure is an HRTEM image of CS / CCS-10; (i) in the figure is an element distribution map of CS / CCS-10; (j) in the figure is a Cu element distribution map; (k) in the figure is a Co element distribution map; (l) in the figure is an S element distribution map.

[0023] Figure 2Shown are electron paramagnetic resonance (EPR) spectra, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) spectra and Raman spectra; among them, (a) in the figure is the EPR spectra of CS / CCS-10 and CS HNs; (b) in the figure is the XRD spectra of CS / CCS-5, CS / CCS-10, CS / CCS-15, CS HNs and CCS NSs; (c) in the figure is the FTIR spectra of CS / CCS-10, CS HNs and CCS NSs; (d) in the figure is the Raman spectra of CS / CCS-10, CS HNs and CCS NSs.

[0024] Figure 3 The photocatalytic CO2 reduction performance test diagram is shown; among them, (a) and (b) in the figure are the photocatalytic CO2 reduction performance test diagrams of CS / CCS-5, CS / CCS-10, CS / CCS-15, CS HNs, and CCS NSs, and (c) in the figure is the photocatalytic CO2 reduction cycle test diagram of CS / CCS-10; (d) in the figure is the photocatalytic CO2 reduction cycle test diagram of CS / CCS-10. 13 CO2 production 13 C2H4 and 13 Mass spectrum of CO.

[0025] Figure 4 Shown are the energy band diagrams before and after contact with the catalyst provided in the comparative example and the schematic diagram of the mechanism of photocatalytic CO2 reduction; (a) and (b) in the figure are the energy band diagrams before and after contact with CCS NSs and CSHNs, respectively; (c) in the figure is a schematic diagram of the mechanism of photocatalytic CO2 reduction of the heterostructure constructed by CCSNSs and CSHNs.

[0026] Figure 5 The surface potential images before and after illumination are shown; (a) and (b) are the surface potential images of CSHNs in the dark and after illumination, respectively; (d) and (e) are the surface potential images of CS / CCS-10 in the dark and after illumination, respectively; (c) and (f) are the line scan surface potential differences of CS HNs and CS / CCS-10, respectively, where ΔCPD = CPD 光照 - CPD 暗处 .

[0027] Figure 6Shown are UV-visible absorption spectra, transient photocurrent response spectra, electrochemical impedance spectra, and photoluminescence spectra; among them, (a) in the figure is the UV-visible absorption spectra of CS / CCS-5, CS / CCS-10, CS / CCS-15, CS HNs, and CCS NSs; (b) in the figure is the transient photocurrent response spectra of CS / CCS-10, CS HNs, CCS NSs, and CS / CCS-M; (c) in the figure is the electrochemical impedance spectra of CS / CCS-10, CS HNs, CCS NSs, and CS / CCS-M; (d) in the figure is the photoluminescence spectra of CS / CCS-10, CS HNs, and CCS NSs.

[0028] Figure 7 Shown are the CO2 temperature-programmed desorption curve, the in situ FTIR graph of CO2 photoreduction, the adsorption energy of CO on different active sites, the Bader charge of the surface cobalt and copper sites in the absence and presence of Vs, and the electron localization function graph in the absence and presence of Vs; among them, (a) in the figure is the CO2 temperature-programmed desorption curve of CS / CCS-10 and CCS NSs, CS HNs; (b) in the figure is the in situ FTIR graph of CO2 photoreduction on CS / CCS-10; (c) in the figure and (d) in the figure are the adsorption energies of CO on different active sites of CCS NSs and CS / CCS-10, respectively; (e) in the figure and (f) in the figure are the Bader charges of the surface cobalt and copper sites in CS / CCS-10 in the absence and presence of Vs, respectively; (g) in the figure and (h) in the figure are the electron localization function graphs in CS / CCS-10 in the absence and presence of Vs, respectively. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0030] Example 1

[0031] A method for preparing a CoS / CuCo2S4 hollow spherical type II heterostructure photocatalyst rich in sulfur vacancies and interfacial Co-S bonding, which specifically comprises the following steps:

[0032] (1) Dissolve 0.6 mmol of Co(NO3)2·6H2O in 20 mL of ethylene glycol (EG) to form solution A;

[0033] (2) Dissolve 0.03 mmol of Cu(NO3)2·3H2O in 20 mL of EG to prepare solution B;

[0034] (3) Add solution B dropwise (1 drop / 7 seconds) to solution A under vigorous stirring to obtain solution C;

[0035] (4) After continuing stirring for 0.5 h, 1.5 mmol of sodium dimethyldithiocarbamate was added to solution C to obtain suspension D;

[0036] (5) The suspension D was transferred to a 100 mL hydrothermal reactor and subjected to hydrothermal reaction at 160 °C for 16 h to obtain a black precipitate, which was separated by high-speed centrifugation at 10,000 rpm for 5 min, washed three times with deionized water, and finally dried in a freeze dryer for 12 h. A CoS / CuCo2S4 hollow spherical type II heterostructure photocatalyst with rich sulfur vacancies and interfacial Co-S bonding was obtained.

[0037] The molar ratio of Cu(NO3)2·3H2O to Co(NO3)2·6H2O used in the CoS / CuCo2S4 heterostructure photocatalyst of this embodiment is 1:20, and the CoS / CuCo2S4 heterostructure photocatalyst is marked as CS / CCS-5.

[0038] Example 2

[0039] A method for preparing a CoS / CuCo2S4 hollow spherical type II heterostructure photocatalyst rich in sulfur vacancies and interfacial Co-S bonding, which specifically comprises the following steps:

[0040] (1) Dissolve 0.6 mmol of Co(NO3)2·6H2O in 20 mL of ethylene glycol (EG) to form solution A;

[0041] (2) Dissolve 0.06 mmol of Cu(NO3)2·3H2O in 20 mL of EG to prepare solution B;

[0042] (3) Add solution B dropwise (1 drop / 7 seconds) to solution A under vigorous stirring to obtain solution C;

[0043] (4) After continuing stirring for 0.5 h, 1.5 mmol of sodium dimethyldithiocarbamate was added to solution C to obtain suspension D;

[0044] (5) The suspension D was transferred to a 100 mL hydrothermal reactor and subjected to hydrothermal reaction at 160 °C for 16 h to obtain a black precipitate, which was separated by high-speed centrifugation at 10,000 rpm for 5 min, washed three times with deionized water, and finally dried in a freeze dryer for 12 h. A CoS / CuCo2S4 hollow spherical heterostructure photocatalyst with rich sulfur vacancies and interfacial Co-S bonding was obtained.

[0045] The molar ratio of Cu(NO3)2·3H2O to Co(NO3)2·6H2O used in the CoS / CuCo2S4 heterostructure photocatalyst of this embodiment is 2:20, and the CoS / CuCo2S4 heterostructure photocatalyst is marked as CS / CCS-10.

[0046] Example 3

[0047] A method for preparing a CoS / CuCo2S4 hollow spherical type II heterostructure photocatalyst rich in sulfur vacancies and interfacial Co-S bonding, which specifically comprises the following steps:

[0048] (1) Dissolve 0.6 mmol of Co(NO3)2·6H2O in 20 mL of ethylene glycol (EG) to form solution A;

[0049] (2) Dissolve 0.09 mmol of Cu(NO3)2·3H2O in 20 mL of EG to prepare solution B;

[0050] (3) Add solution B dropwise (1 drop / 7 seconds) to solution A under vigorous stirring to obtain solution C;

[0051] (4) After continuing stirring for 0.5 h, 1.5 mmol of sodium dimethyldithiocarbamate was added to solution C to obtain suspension D;

[0052] (5) The suspension D was transferred to a 100 mL hydrothermal reactor and subjected to hydrothermal reaction at 160 °C for 16 h to obtain a black precipitate, which was separated by high-speed centrifugation at 10,000 rpm for 5 min, washed three times with deionized water, and finally dried in a freeze dryer for 12 h. A CoS / CuCo2S4 hollow spherical heterostructure photocatalyst with rich sulfur vacancies and interfacial Co-S bonding was obtained.

[0053] The molar ratio of Cu(NO3)2·3H2O to Co(NO3)2·6H2O used in the CoS / CuCo2S4 heterostructure photocatalyst of this embodiment is 3:20, and the CoS / CuCo2S4 heterostructure photocatalyst is marked as CS / CCS-15.

[0054] Comparative Example 1

[0055] A method for preparing a CoS hollow spherical structure photocatalyst comprises the following steps:

[0056] (1) Dissolve 0.6 mmol of Co(NO3)2·6H2O in 20 mL of ethylene glycol (EG) to form solution A.

[0057] (2) After continuing stirring for 0.5 h, 1.5 mmol of sodium dimethyldithiocarbamate was added to solution A to obtain suspension B;

[0058] (3) The suspension B was transferred to a 100 mL hydrothermal reactor and subjected to hydrothermal reaction at 160 °C for 16 h to obtain a black precipitate, which was centrifuged at 10,000 rpm for 5 min, washed three times with deionized water, and finally dried in a freeze dryer for 12 h to obtain a CoS hollow spherical structure photocatalyst (labeled as CS HNs).

[0059] Comparative Example 2

[0060] A method for preparing a CuCo2S4 nanosheet photocatalyst comprises the following steps:

[0061] (1) Dissolve 0.6 mmol of Co(NO3)2·6H2O in 20 mL of ethylene glycol (EG) to form solution A;

[0062] (2) Dissolve 0.3 mmol of Cu(NO3)2·3H2O in 20 mL of EG to prepare solution B;

[0063] (3) Add solution B dropwise (1 drop / 7 seconds) to solution A under vigorous stirring to obtain solution C;

[0064] (4) After continuing stirring for 0.5 h, 1.5 mmol of sodium dimethyldithiocarbamate was added to solution C to obtain suspension D;

[0065] (5) The suspension D was transferred to a 100 mL hydrothermal reactor and subjected to hydrothermal reaction at 160 °C for 16 h to obtain a black precipitate, which was centrifuged at 10,000 rpm for 5 min, washed three times with deionized water, and finally dried in a freeze dryer for 12 h to obtain a CuCo2S4 nanosheet structured photocatalyst.

[0066] The molar ratio of Cu(NO3)2·3H2O to Co(NO3)2·6H2O used in the CuCo2S4 nanosheet photocatalyst of this comparative example is 10:20, and the CuCo2S4 nanosheet photocatalyst is marked as CCS NSs.

[0067] Comparative Example 3

[0068] A method for preparing a physically mixed photocatalyst of CoS hollow spherical structures and CuCo2S4 nanosheets, which specifically comprises the following steps:

[0069] 0.6 mmol of CS HNs (Comparative Example 1) and 0.06 mmol of CCS NSs (Comparative Example 2) were transferred to an agate mortar and vigorously ground for 30 min to obtain a mixed black powder, which was labeled as CS / CCS-M.

[0070] Example 4

[0071] The samples of Examples 1 to 3 and Comparative Examples 1 to 3 were analyzed by TEM, XRD, EPR, FTIR, UV-visible absorption spectroscopy, photoelectrochemical testing, CO2 temperature-programmed desorption curves, and in-situ diffuse reflectance Fourier transform infrared spectroscopy of CO2 photoreduction.

[0072] The results are as follows Figure 1-Figure 2 and Figure 4-Figure 7 As shown, Figure 1 (a) Figure 1 (b) is the TEM image of Comparative Example 1 (CS HNs) of the present invention. Figure 1 (c) is the HRTEM image of Comparative Example 1 (CS HNs) of the present invention, which shows that CS HNs have a hollow spherical structure; Figure 1 (d) Figure 1 (e) is a TEM image of Comparative Example 2 (CCS NSs) of the present invention. Figure 1 (f) HRTEM image of Comparative Example 2 (CCS NSs) of the present invention, showing that CCS NSs has a nanosheet structure. Figure 1 (g) is the TEM image of Example 2 (CS / CCS-10) of the present invention. Figure 1 (h) is the HRTEM image of Example 2 (CS / CCS-10) of the present invention, which shows that CS / CCS-10 inherits the hollow spherical structure of CS HNs. Figure 1 (i) is the element distribution diagram of Example 2 (CS / CCS-10) of the present invention, which shows that the catalyst (CS / CCS-10) prepared in Example 2 is composed of three elements: Cu, Co, and S.

[0073] Figure 2 (a) is the electron paramagnetic resonance (EPR) spectra of Example 2 (CS / CCS-10) of the present invention and Comparative Example 1 (CS HNs), which shows that Vs is almost absent in CS HNs, while Vs is abundant in CS / CCS-10. Figure 2(b) is the XRD pattern of Examples 1 to 3 (CS / CCS-5, CS / CCS-10, CS / CCS-15) of the present invention and Comparative Examples 1 to 2 (CS HNs, CCS NSs), which shows that the main characteristic diffraction peaks of CS HNs appear at 30.61°, 35.32°, 46.97° and 54.41°, corresponding to the (100), (101), (102), and (110) planes of the hexagonal phase CS (JCPDS no. 65-8977). The main characteristic diffraction peaks of CCS NSs appear at 26.59°, 31.27°, 37.94°, 46.99°, 49.99° and 54.79°, corresponding to the (022), (113), (004), (224), (115) and (044) planes of cubic phase CCS (JCPDS no.42-1450). It is worth noting that the diffraction peaks of CS / CCS-5, CS / CCS-10 and CS / CCS-15 all have the characteristic diffraction peaks of CS and CCS, and there are no other characteristic peaks of impurities, which proves that CS / CCS-5, CS / CCS-10 and CS / CCS-15 are all composed of CS and CCS. Figure 2 (c) is the Fourier transform infrared spectrum (FTIR) of Example 2 (CS / CCS-10) of the present invention and Comparative Examples 1-2 (CS HNs, CCS NSs). Figure 2 (d) is the Raman spectra of Example 2 (CS / CCS-10) of the present invention and Comparative Examples 1-2 (CS HNs, CCS NSs), proving the existence of interfacial Co-S bonds in CS / CCS-10.

[0074] Figure 4 (a) Figure 4 (b) shows the energy band diagrams of comparative example 2 (CCS NSs) and comparative example 1 (CS HNs) before and after contact; Figure 4 (c) is a schematic diagram of the mechanism of photocatalytic CO2 reduction of CS / CCS-10, indicating that after coupling of CCS NSs and CS HNs, a type II heterostructure is constructed. Under light conditions, it is beneficial for photogenerated electrons and holes to flow to CCS NSs and CSHNs respectively, thereby facilitating the photocatalytic CO2 reduction performance.

[0075] Figure 5 (a) Figure 5 (b) shows the surface potential images of the comparative example (CS HNs) before and after illumination, respectively, indicating that under dark conditions, the surface potential (SP) of CS HNs is 198.3 mV ~ -30.0 mV, and under visible light irradiation, its SP is 276.5 mV ~ 90.7 mV; Figure 5 (d) Figure 5 (e) in the figure shows the surface potential images of Example (CS / CCS-10) before and after illumination, respectively. It shows that for CS / CCS-10, the SP value under illumination (101.7 mV ~ -191.4 mV) is lower than the SP value under dark conditions (111.3 mV ~ -154.8 mV), indicating that under illumination conditions, the photogenerated electrons of CS are transferred to CCS. Figure 5 (c) Figure 5 (f) Line scan surface potential difference (ΔCPD) of comparative example (CS HNs) and example (CS / CCS-10), where ΔCPD = CPD 光照 - CPD 暗处 , indicating that the surface potential difference of CS / CCS-10 is 48.7 mV, significantly higher than that of CS HNs (28.7 mV). This confirms that the enhanced separation kinetics of photogenerated carriers promotes the accumulation of photogenerated electrons on the CCS surface, thereby creating an electron-rich environment, which is crucial for the reduction of carbon dioxide to C2 products.

[0076] Figure 6 (a) is the UV-visible absorption spectra of Examples 1 to 3 (CS / CCS-5, CS / CCS-10, CS / CCS-15) and Comparative Examples 1 and 2 (CS HNs, CCS NSs) of the present invention. Figure 6 (b) is the transient photocurrent response spectrum of Example 2 (CS / CCS-10) of the present invention and Comparative Examples 1 to 3 (CS HNs, CCS NSs, CS / CCS-M). Figure 6 (c) is the electrochemical impedance spectroscopy of Example 2 (CS / CCS-10) of the present invention and Comparative Examples 1 to 3 (CS HNs, CCS NSs, CS / CCS-M). Figure 6 (d) is the photoluminescence spectra of Example 2 (CS / CCS-10) and Comparative Examples 1-2 (CS HNs, CCS NSs), all of which prove that CS / CCS-10 is conducive to the separation and transfer of photogenerated charges.

[0077] Figure 7 Panel (a) shows the CO2 temperature-programmed desorption curves for CS / CCS-10 (Example 2) and Comparative Examples 1 and 2 (CCS NSs and CS HNs). CCS NSs exhibit two desorption peaks (200°C-350°C and 350°C-500°C), while CSHNs exhibit only one desorption peak (200°C-350°C). In contrast, CS / CCS-10 exhibits a significant increase in peak area between 200°C and 350°C, with a new peak appearing between 500°C and 600°C, indicating enhanced CO2 adsorption capacity. Figure 7 (b) is the in-situ FTIR image of CO2 photoreduction on Example 2 (CS / CCS-10) of the present invention, showing that at 1261 cm -1 、1558 cm -1 、1580 cm -1 The characteristic peak at 1072 cm is attributed to *COOH. -1 The characteristic peak at 1750 cm-1 belongs to *CHO, which proves that CO2 adsorption and activation do occur on the surface of the photocatalyst, and it is a continuous proton-electron coupling process. -1 The characteristic peak at 1716 cm is attributed to CO chemical adsorption (*CO). Due to the presence of Vs, the Cu-Co bond distance is shortened, and coupling can form *COCO. -1 The characteristic peak at 1342 cm is attributed to the vibration of the *COCO intermediate. -1 The peak at 1445 cm is attributed to *CH2. -1 The peak at 1680 cm is attributed to the vibration of C=C, indicating that CS / CCS-10 is indeed beneficial to the formation of C2H4 by shortening the distance of Co-Cu bonds. -1 The *CH2=CH2 intermediate that was finally desorbed from the surface was detected at , indicating that C2H4 was formed instantaneously during the photocatalytic CO2 reduction process. Figure 7 (c) Figure 7 Figure (d) shows the adsorption energies of CO at different active sites in Comparative Example 2 (CCS NSs) and Example 2 (CS / CCS-10). The adsorption energies of CCS NSs at the Cu and Co sites are -2.87 eV and -3.12 eV, respectively, significantly higher than the adsorption energy at the S site (-2.01 eV). This indicates a strong adsorption tendency of *CO at the Cu and CO sites. The adsorption strengths for CS / CCS-10 are in the order: Co (-1.17 eV) > Cu (-0.85 eV) > Vs (-0.83 eV) > S (0.17 eV), indicating that the Cu and Co atoms adjacent to Vs are the primary active sites for Co adsorption. Figure 7 (e) in Figure 7 (f) in the figure shows the Bader charges of the surface cobalt and copper sites in Example 2 (CS / CCS-10) of the present invention, with and without Vs, respectively. The Bader charges of Cu and Co sites on the CS / CCS-10 surface are 10.58 e and 8.46 e, respectively. After the introduction of Vs, the calculated Bader charges of Cu and Co surfaces increase to 10.64 e and 8.62 e, respectively. This result suggests that the presence of Vs in CS / CCS-10 can enrich the Cu and Ga atoms near Vs with more electrons. Figure 7(g) in Figure 7 Figures (h) show the electron localization function plots for Example 2 (CS / CCS-10) of the present invention, with and without Vs. These plots demonstrate that Vs can lead to a highly delocalized electron distribution in the original region of the S atom, shortening the distance between the two active sites from 3.3 Å to 2.7 Å. This promotes the localized metallization of Cu and Co near Vs, forming a Cu-Co metallic bond. The Cu-Co bimetallic active site likely lowers the energy barrier for *COCO coupling, thereby promoting the formation of C2H4.

[0078] Example 5

[0079] The five products CS / CCS-5, CS / CCS-10, CS / CCS-15, CCS NSs and CS HNs obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were used as photocatalysts and applied to CO2 reduction. The specific steps were as follows:

[0080] 50 mg of photocatalyst was placed in a sealed glass reactor with an area of ​​4.2 cm 2 A 250 W xenon lamp was used as the light source for the photocatalytic reaction. Before irradiation, the reactor was vacuumed using a vacuum pump, and then high-purity CO2 gas was introduced into the reaction device to reach ambient pressure; 0.4 mL of deionized water was injected into the reactor, and the prepared photocatalyst was equilibrated in the CO2 atmosphere for several hours. The temperature of the reaction system was always maintained at 25°C by circulating cooling water; during the irradiation process, 0.5 mL of gas was extracted from the reaction bottle every hour and subsequently analyzed using a gas chromatograph (GC9790 IIA, Zhejiang Fuli Analytical Instrument Co., Ltd., China), which was equipped with FID and TCD detectors.

[0081] The results are as follows Figure 3 As shown, Figure 3 (a) and Figure 3 (b) is a photocatalytic CO2 reduction performance test diagram of Examples 1 to 3 (CS / CCS-5, CS / CCS-10, CS / CCS-15) of the present invention and Comparative Examples 1 to 2 (CS HNs, CCS NSs). The results show that Example CS / CCS-10 has the best photocatalytic CO2 reduction to C2H4 performance (C2H4 production rate and electron selectivity are 28.79 μmol -1 h -1The product selectivity was 72.14%, significantly higher than that of the comparative examples (CS HNs and CCS NSs). The electron selectivity was calculated according to the following formula: (C2H4) = 12n(C2H4) / [12n(C2H4) + 2n(CO)] × 100%. The ethylene product selectivity was calculated according to the following formula: (C2H4) = n(C2H4) / [n(C2H4) + n(CO)] × 100%. Here, n(C2H4) and n(CO) represent the amounts of C2H4 and CO produced, respectively.

[0082] Figure 3 (c) is a photocatalytic CO2 reduction cycle test diagram of Example 2 (CS / CCS-10) of the present invention, which shows that Example CS / CCS-10 has excellent cycle stability. Figure 3 (d) is the photocatalytic reaction of Example 2 (CS / CCS-10) of the present invention. 13 CO2 production 13 C2H4 and 13 The mass spectrum of CO confirmed the occurrence of photocatalytic CO2 reduction reaction.

[0083] The embodiments of the present application are described above in conjunction with the accompanying drawings. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the core idea of ​​the present application, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present application, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present application and the claims, all of which are within the protection of the present application.

Claims

1. A method for preparing a CoS / CuCo2S4 photocatalyst, characterized in that: The following steps are involved: Dissolving Co(NO3)2·6H2O and Cu(NO3)2·3H2O in ethylene glycol to obtain a first solution and a second solution, respectively; then dropping the second solution into the first solution while stirring to obtain a third solution; The third solution was continued to be stirred, and then sodium dimethyldithiocarbamate was added to obtain a suspension; The suspension is subjected to a hydrothermal reaction, and after completion of the reaction, the suspension is centrifuged, washed, and dried to obtain the CoS / CuCo2S4 photocatalyst; The molar ratio of Cu(NO3)2·3H2O and Co(NO3)2·6H2O is 1-3:

20.

2. The preparation method according to claim 1, characterized in that The molar ratio of Co(NO3)2·6H2O to sodium dimethyldithiocarbamate is 1:2.5-3.

3. The preparation method according to claim 1, characterized in that The dripping speed is 1 drop / 6 seconds to 1 drop / 8 seconds.

4. The preparation method according to claim 1, characterized in that The third solution is stirred for 0.3 h to 1 h.

5. The preparation method according to claim 1, characterized in that The temperature of the hydrothermal reaction is 160°C.

6. The preparation method according to claim 5, characterized in that The hydrothermal reaction time is 16 h.

7. A CoS / CuCo2S4 photocatalyst, characterized in that The invention is prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the CoS / CuCo2S4 photocatalyst according to claim 7 in photocatalytic CO2 reduction.

9. The use according to claim 8, characterized in that The CoS / CuCo2S4 photocatalyst is used for photocatalytically producing C2H4 from CO2.

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