2D / 3D nanoflower-like CuCo2S4@Co3O4 catalyst, preparation method and application

Abstract

This invention discloses a method for preparing a 2D / 3D nanoflower-like CuCo2S4@Co3O4 catalyst, comprising: 1) dissolving CuCo-LDH and CH4N2S in ethanol by stirring to obtain solution A; 2) transferring solution A to a reaction vessel, heating and reacting, then centrifuging, washing, and drying to obtain product A; 3) calcining product A to obtain the catalyst CuCo2S4@Co3O. This invention relies on a layered double hydroxide topological transformation and in-situ sulfidation strategy to prepare a catalyst with a 2D / 3D hierarchical CuCo2S4@Co3O4 nanoflower structure. It possesses a unique 2D / 3D hierarchical structure, abundant interfacial active sites, and a tight heterojunction interface, successfully improving the catalyst's light absorption capacity, accelerating the separation of photogenerated electrons and holes, and greatly enhancing the catalyst's catalytic performance. This solves the problems of large interfacial defects and few interfacial sites in current catalysts.

Description

Technical Field

[0001] This invention relates to the technical field of catalyst preparation, and more particularly to a 2D / 3D nanoflower-like CuCo2S4@Co3O4 catalyst, its preparation method, and its application. Background Technology

[0002] Over the past decade, semiconductor heterojunction engineering has been considered a viable strategy. This involves coupling and bandgap matching of semiconductors with different functions, such as Cd. 0·7 Zn 0·3 Se / Cu2O@Cu, Co9S8-Fe@CNC-F@CCS@ZIF8 / 67-1 / 1, Co3O4 / TiO2, and CuCo2S4@CuCo2O4 have been successfully applied in carbon neutralization, water splitting, photocatalytic degradation of pollutants, and photoelectrochemical (PEC) detection. Copper-based and cobalt-based oxide or sulfide semiconductor heterojunctions exhibit excellent photocatalytic performance in environmental catalysis. The presence of heteroatoms (S, P, N, etc.) can adjust the electron distribution of adjacent atoms, thereby enhancing intrinsic catalytic activity. Well-designed heterojunctions can rely on an internal electric field to accelerate the separation and transfer of photogenerated charges, enhance light absorption, and improve photocatalytic efficiency. In particular, heterojunctions with layered 2D / 3D structures, such as ZnIn2S4 / CeO2, In2O3@ZnIn2S4, and Bi2S3 / CeVO4, show excellent photocatalytic and photoelectrochemical performance, indicating that the morphology of the catalyst affects its performance to a certain extent.

[0003] An unusual 2D / 3D hierarchical layered hydrogen hydroxides (LDHs) have been synthesized and applied to energy storage devices. The anisotropic structure possesses multiple open cavities, abundant transport channels, and more surface catalytic active sites. The 2D / 3D structure can also promote light absorption through multi-level light diffraction and scattering, thereby improving photoelectrocatalytic performance. Furthermore, the heterojunction interface directly affects the spatial separation efficiency of electron-hole pairs, as photogenerated carriers need to overcome the interface energy barrier during migration and transfer. The heterojunction interface with coordinated unsaturated atoms and defects is also considered a catalytic active site, which is beneficial for accelerating the catalytic reaction process and significantly improving photocatalytic efficiency. Yang et al. successfully prepared a BiVO4 / FeVO4@rGO photocatalyst with a 3D / 2D / 2D structure via a one-step hydrothermal method. This unique structure forms nanochannels at the interface contact, improving the photoinduced charge transport and migration efficiency. The removal rates of chloroform and hexavalent chromium reached 91.5% and 90.9% within 100 min and 90 min, respectively. It is significantly higher than that of pure BiVO4 and FeVO4. To date, these reported semiconductor heterojunctions are usually based on co-precipitation, electrodeposition or solvothermal synthesis. Due to the asynchronous nucleation and growth of the two heterophases, a loose interface with lattice mismatch is usually formed, and the interface sites are extremely sparse.

[0004] Layered double hydroxides (LDHs) are a class of 2D anionic clay materials, generally expressed as [M 1-x 2+ M x 3+ [(OH)2](A n– ) x / n ·mH2O], where M 2+ and M 3+ They are divalent and trivalent metals, respectively. n- LDHs are charge-balancing anions. LDHs possess an adjustable chemical composition, allowing for the adjustment of the molar ratio of metal cations and intercalated anions. In other words, the inherent characteristics of LDHs can be precisely tuned to meet the needs of a variety of applications. Furthermore, LDHs can be topologically transformed into mixed metal oxides (MMOs) through a simple calcination process. Because MMOs... 2+ and M 3+ Highly dispersed within LDH layers, MMOs possess highly distributed transition metal interfaces and abundant atomic-level interfacial active sites, thereby enhancing catalytic activity.

[0005] In summary, providing a catalyst with a 2D / 3D hierarchical structure and its preparation method to solve the problems of large interface defects and few interface sites in current catalysts is an urgent issue to be addressed. Summary of the Invention

[0006] In view of this, the present invention discloses a 2D / 3D nanoflower-like CuCo2S4@Co3O4 catalyst, its preparation method and its application, to solve the problems of poor separation efficiency of photogenerated electrons and holes due to large interfacial charge transfer resistance in existing photocatalysts and few interfacial active sites.

[0007] This invention provides a method for preparing a 2D / 3D nanoflower-like CuCo2S4@Co3O4 catalyst, comprising:

[0008] 1) Dissolve CuCo-LDH and CH4N2S in ethanol by stirring to obtain solution A;

[0009] 2) After transferring solution A to the reaction vessel and heating it, the product A is obtained by centrifugation, washing, and drying.

[0010] 3) After calcining product A, the catalyst CuCo2S4@Co3O was obtained.

[0011] Preferably, the CuCo-LDH is of the sea urchin type, and its preparation method is as follows: Co(NO3)2·6H2O, Cu(NO3)2·3H2O, urea and NH4F are dissolved in deionized water, and the mixture is stirred to form a homogeneous solution; then, the solution is sealed in a reaction vessel and reacted at high temperature; finally, the mixture in the high-pressure vessel is taken out, washed with deionized water and anhydrous ethanol, and dried to obtain CuCo-LDH.

[0012] Preferably, in step 1), the mass of CuCo-LDH is 0.25g, the mass of CH4N2S is 0.3, 0.5 or 0.7g, and the amount of ethanol used is 35ml.

[0013] Preferably, in step 2), the temperature of the reaction in the reactor is 180°C and the time is 8 hours.

[0014] Preferably, the calcination is performed by calcining at 400°C for 2 hours in a muffle furnace.

[0015] Secondly, the present invention also provides applications of the 2D / 3D nanoflower-like CuCo2S4@Co3O4 catalyst prepared by the above method, which can be used for photocatalytic degradation of DCF, photoelectric detection of diclofenac sodium, or as a working electrode to prepare a "signal on" PEC sensing platform for quantitative detection of DCF.

[0016] This invention provides a 2D / 3D nanoflower-like CuCo2S4@Co3O4 catalyst, its preparation method, and its application. By utilizing a strategy combining CuCo-LDH topological transformation and in-situ external sulfidation, a bifunctional CuCo2S4@Co3O4 heterojunction catalyst is constructed for photocatalytic degradation and photoelectrochemical detection of DCF.

[0017] During sulfidation and calcination, rod-shaped CuCo-LDH is miraculously transformed into 2D nanosheets and self-assembled 3D nanoflowers. Abundant ultrathin 2D nanosheets simultaneously nucleate and grow rapidly on the petals, forming layered 2D / 3D nanoflowers. This generates a highly distributed interface structure and extremely dense interface sites, increasing light absorption capacity, providing channels for ion / molecule diffusion in different directions, greatly reducing interfacial charge transfer resistance to accelerate electron-hole separation, and exposing abundant active sites to improve photocatalytic and photoelectrocatalytic activity.

[0018] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit the disclosure of this invention. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 XRD (a) and FT-IR (b) of LDH, CuCo2S4@Co3O4-3 and CuCo2O4 in the embodiments disclosed in this invention;

[0022] Figure 2 Comparison of XPS spectral data of LDH and CuCo2S4@Co3O4-3 in the embodiments disclosed in this invention: (a) Cu 2p, (b) Co 2p, (c) S2p and (d) O 1s;

[0023] Figure 3 SEM images of LDH (a, c, e) and CuCo2S4@Co3O4-3 (b, d, f) in the embodiments disclosed in this invention, and elemental mapping diagrams of LDH (g) and CuCo2S4@Co3O4-3 (h);

[0024] Figure 4 EDS spectra of LDH(a) and CuCo2S4@Co3O4-3(b) in the embodiments disclosed in this invention;

[0025] Figure 5The UV-vis DRS (a), PL spectrum (b), photocurrent response (c), and EIS Nyquist plot (d) of LDH and CuCo2S4@Co3O4-3 in the embodiments disclosed in this invention are shown.

[0026] Figure 6 The following are the degradation diagrams of DCF by different catalysts in the embodiments of the present invention (a), the UV-Vis absorption spectra at different time periods (b), the fitted first-order kinetic curves (c), and the pseudo-first-order reaction rate constants (d).

[0027] Figure 7 The TOC removal curves of CuCo2S4@Co3O4-3 for DCF degradation in the embodiments disclosed in this invention are shown in (a), the effect of catalyst dosage on DCF degradation is shown in (b), and the effect of different water samples on DCF degradation is shown in (c).

[0028] Figure 8 The figures show the experimental results of CuCo2S4@Co3O4-3 (a) after 5 cycles and the XRD patterns before and after the cycles (b) in the embodiments disclosed in this invention. The inset is the SEM image after the cycles.

[0029] Figure 9 The photocurrent response (a) and corresponding calibration curve (b) of CuCo2S4@Co3O4-3 at different DCF concentrations are shown in the embodiments disclosed in this invention. Detailed Implementation

[0030] The present invention will be further explained below with reference to specific implementation schemes, but this is not intended to limit the scope of protection of the present invention.

[0031] This implementation scheme constructs a tightly connected heterojunction interface through calcination and in-situ sulfidation, reducing the interfacial energy barrier, promoting the transfer of photogenerated electrons, and improving the separation efficiency of photogenerated carriers. Furthermore, leveraging the uniform elemental distribution in LDH, a catalyst with abundant heterojunction interfaces is formed through topological transformation. These heterojunction interfaces serve as catalytic reaction centers, significantly enhancing the catalyst's catalytic performance.

[0032] First, this embodiment provides a method for preparing a 2D / 3D nanoflower-like CuCo2S4@Co3O4 catalyst, wherein the CuCo-LDH is of the sea urchin type. The preparation method is as follows: Co(NO3)2·6H2O, Cu(NO3)2·3H2O, urea and NH4F are dissolved in deionized water and the mixture is stirred to form a homogeneous solution; then, the solution is sealed in a reaction vessel and kept at a certain temperature; finally, the mixture in the high-pressure vessel is taken out, washed three times with deionized water and anhydrous ethanol, and then dried overnight to obtain CuCo-LDH.

[0033] Preferably, the preparation method of sea urchin-type CuCo-LDH is as follows: 1.455g Co(NO3)2·6H2O, 0.121g Cu(NO3)2·3H2O, 1.2g urea, and 0.222g NH4F are dissolved in 35mL of deionized water, and the mixture is stirred for 30min to form a homogeneous solution. Then, the solution is sealed in a reaction vessel (50mL) and kept at 120℃ for 6h. Finally, the mixture in the autoclave is removed, washed three times with deionized water and anhydrous ethanol, and then dried overnight at 60℃ to obtain CuCo-LDH (named LDH).

[0034] CuCo-LDH and CH4N2S were then dissolved in ethanol and stirred. The resulting solution was transferred to a reaction vessel and heated. After the reaction was completed, the product was obtained by centrifugation, washing and drying. The product was then calcined in a muffle furnace to obtain the catalyst CuCo2S4@Co3O4.

[0035] Preferably, 0.25 g of the prepared LDH and certain amounts of CH4N2S (0.3, 0.5, and 0.7 g) were dissolved in 35 mL of ethanol and stirred for 30 min. The resulting solution was transferred to a reaction vessel and heated at 180 °C for 8 h. After the reaction was completed, the product was obtained by centrifugation, washing, and drying, and then calcined in a muffle furnace at 400 °C for 2 h. The obtained catalysts were named CuCo2S4@Co3O4-1, CuCo2S4@Co3O4-2, and CuCo2S4@Co3O4-3. For comparison, LDH was directly calcined at 400 °C to obtain a mixed metal oxide (CuCo2O4).

[0036] This implementation scheme constructs a tightly connected heterojunction interface through calcination and in-situ sulfidation, reducing the interfacial energy barrier, promoting the transfer of photogenerated electrons, and improving the separation efficiency of photogenerated carriers. Furthermore, leveraging the uniform elemental distribution in LDH, a catalyst with abundant heterojunction interfaces is formed through topological transformation. These heterojunction interfaces serve as catalytic reaction centers, significantly enhancing the catalyst's catalytic performance.

[0037] In this implementation scheme, the actual catalytic activity of the prepared CuCo2S4@Co3O4 nanoflower heterojunction catalyst for photocatalytic degradation of DCF was evaluated in laboratory, lake, Nüer River, and Bohai Bay water samples. Furthermore, a "signal-on" PEC sensing platform was prepared using CuCo2S4@Co3O4 nanoflowers as the working electrode. This platform exhibits high sensitivity, good reproducibility, and good stability.

[0038] Specifically, photocatalytic performance: DCF was degraded under a 300W mercury lamp to evaluate the photocatalytic performance of the CuCo2S4@Co3O4 composite material; typically, at 50 mL 20 mg·L⁻¹ -10.025 g of photocatalyst was added to the DCF solution, and the mixture was magnetically stirred in the dark for 30 min to reach adsorption-desorption equilibrium. The DCF solution was then irradiated under a 300 W mercury lamp. Every 5 min, 3.5 mL of the solution was taken to measure the DCF concentration, filtered through a 0.22 μm filter, and then the DCF concentration in the supernatant was measured at 275 nm using a UV-Vis spectrophotometer. In the free radical capture experiment, potassium iodide (KI), isopropanol (IPA), silver nitrate (AgNO3), and 4-hydroxy-2,2,6,6-tetramethyl-piperidinooxy (TEMPOL) were used to capture h, respectively. + ·OH, e - and O2 - The trapping agent.

[0039] Photoelectric detection process: 3 mg of CuCo2S4@Co3O4-3 was accurately weighed, ultrasonically dispersed in 2 mL of deionized water, and then uniformly drop-coated onto the conductive surface of FTO glass. The electrode was then dried in an oven at 60 °C to obtain a CuCo2S4@Co3O4-3 / FTO electrode. Using CuCo2S4@Co3O4-3 / FTO as the working electrode, a calomel electrode as the reference electrode, and a platinum sheet as the counter electrode, a photoelectrochemical sensor was constructed. The photoelectrochemical sensor was then tested at 0.1 mol·L⁻¹. -1 In Na2SO4 electrolyte solution, under a bias voltage of 0.8V (vs. SCE), the change in anodic photocurrent was recorded by the it method to perform quantitative analysis of DCF.

[0040] XRD and FT-IR spectroscopy characterized the crystal structure of the LDH and CuCo2S4@Co3O4-3 composite material. Figure 1As shown, the diffraction peaks at 24.16°, 33.55°, 34.89°, 39.42°, and 62.04° correspond to LDH. After calcination and in-situ sulfidation, the diffraction peaks of LDH disappeared, and new characteristic diffraction peaks appeared at 26.52°, 31.09°, 37.96°, 49.99°, 54.79° and 31.27°, 36.85°, 44.67°, corresponding to the (022), (113), (004), (115), and (044) crystal planes of CuCo2S4 (PDF#42-1450) and the (220), (311), and (400) crystal planes of Co3O4 (PDF#73-1701), respectively. This proves that the CuCo2S4@Co3O4 semiconductor heterojunction was successfully prepared. Furthermore, new characteristic diffraction peaks appeared at 24.53° and 34.38°, inferred to be CoSO4, possibly generated during calcination in air. The XRD pattern obtained from direct calcination at 400°C is as follows... Figure 1 As shown in Figure a, the (220), (311), (222), (400), (422), (511), and (440) crystal planes of CuCo2O4 at 31.27°, 36.74°, 38.47°, 44.69°, 55.41°, 59.08°, and 65.07° (PDF#25-0270) indicate that a mixed metal oxide was obtained by direct calcination.

[0041] Figure 1 Figure b shows the FT-IR spectrum of the LDH and CuCo2S4@Co3O4-3 composite material. For LDH, approximately 3400 cm⁻¹ -1 and 1640cm -1 The peaks at 1368 cm⁻¹ represent the stretching vibration of OH and the bending vibration of H₂O, respectively. -1 and 830cm -1 The peak at that point forms carbonate ions (CO3) with LDH. 2- The results suggest that CO3 was successfully synthesized due to its stretching vibrations. 2- Intercalated LDH. 400-800cm -1 The peaks within this range are attributed to vibrations of the MO and M-OH bonds, appearing at 693 cm⁻¹. -1 and 521cm -1 The peaks belong to the stretching vibrations of Co-O and Cu-O. However, after topological transformation and in-situ sulfidation, the unique carbonate peak of LDH disappears in the FT-IR spectrum of CuCo2S4@Co3O4-3, indicating that some S has replaced oxygen, and the stretching vibrations of Cu-S and Co-S (MS) are at 609 cm⁻¹. -1 and 1128cm -1The XRD results indicate that a CuCo2S4@Co3O4-3 heterojunction photocatalyst was successfully prepared through topological phase transformation and in-situ sulfidation of LDH.

[0042] The elemental composition and valence states of LDH and CuCo2S4@Co3O4-3 were determined using XPS technology. Cu, Co, O and Cu, Co, O, S were clearly observed in XPS, indicating the successful preparation of LDH and CuCo2S4@Co3O4. For LDH, a high-resolution Cu 2p spectrum was obtained. Figure 2 The two characteristic peaks at 936.69 eV, 943.15 eV, and 962.35 eV are characteristic satellite peaks of Cu. The peaks observed at 933.38.2 eV and 954.01 eV are similar to those of Cu. + Correspondingly, Cu 2p was observed at 935.33 eV and 955.22 eV. 3 / 2 and Cu 2p 1 / 2 The two peaks, with a distance of approximately 20 eV between them, are related to Cu. 2+ The eigenvalues ​​are consistent, indicating that Cu in LDH 2+ and Cu + Coexistence. Compared to LDH, the binding energy of CuCo2S4@Co3O4-3 shifts to a lower value, likely due to changes in electron density caused by electron migration. In LDH, the characteristic peaks at 786.64 eV and 802.64 eV in the Co 2p orbital belong to Co satellite peaks, while the two peaks observed at 780.94 and 798.26 eV belong to the Co 2p orbital. 1 / 2 and Co 2p 3 / 2 This indicates that Co in LDH 2+ and Co 3+ Coexistence. The S2p spectrum has two peaks at 168.60 eV and 168.90 eV, which belong to S2p. 3 / 2 and S2p 1 / 2 This confirms the formation of metal sulfide bonds. The O1s spectrum of LDH (…) Figure 3 In d), two distinct peaks are observed, attributed to the metal hydroxyl group (M-OH) (531.33 eV) and adsorbed water (532.02 eV), respectively. The O1s spectrum of CuCo2S4@Co3O4-3 shows a red shift of the peak at 531.33 eV after topological transformation and in-situ sulfidation of LDH, likely due to the formation of metal-sulfur bonds from the addition of sulfur.

[0043] The microstructure of the prepared LDH and CuCo2S4@Co3O4-3 was characterized using scanning electron microscopy. Figure 3 a and Figure 3In the initial hydrothermal environment, the LDH sample formed a rod-like structure, with NH4F acting as a structural medium to promote the formation of nanosheets. When the solution was placed under hydrothermal conditions at 120℃, urea initially hydrolyzed to NH4. + CO2 and OH - CO(NH2)2 + 3H2O → 2NH4 + +CO2↑+2OH - This increases the pH of the solution, providing an alkaline environment. Subsequently, LDH crystals form under the hydrolysis and aggregation of metal ions, and the surface gradually forms a sea urchin-like morphology composed of tightly packed irregular nanoneedles of 200-600 nm in size, providing more active sites. After the topological phase transition and in-situ sulfidation of LDH, and with the extension of hydrothermal time, it self-assembles into 3D nanoflowers. Figure 3 As shown in (b), a large number of irregular ultrathin nanosheets grow on the surface of the nanopetals, forming a 2D / 3D structure. Figure 3 LDH (d) has a large specific surface area and abundant pores, which is beneficial for multi-level diffraction and scattering of light, thus improving its light absorption capacity. EDS results show that LDH (d) Figure 3 In the catalysts Cu, Co, O and Cu, Co, O, S are uniformly distributed (g) and CuCo2S4@Co3O4-3. Figure 3 (h), which strongly confirms the successful combination of CuCo2S4 and Co3O4. Furthermore, the EDS plot shows (h). Figure 3 The oxygen content in CuCo2S4 decreased by 18.76%, indicating that S partially replaced the lattice during hydrothermal calcination. This further demonstrates the successful preparation of CuCo2S4 and Co3O4.

[0044] Photoelectrochemical properties of the catalyst CuCo2S4@Co3O4-3:

[0045] The light absorption properties of the material were analyzed using ultraviolet-visible diffuse reflectance spectroscopy, such as... Figure 6 As shown in Figure a, after topological transformation and in-situ sulfidation, the light absorption capacity of CuCo2S4@Co3O4-3 is significantly increased. To investigate the separation of photogenerated carriers, fluorescence photoluminescence spectroscopy was used to evaluate the separation efficiency of electron-hole pairs. Figure 5Figure 'a' shows the fluorescence spectrum. Since fluorescence is emitted during the recombination of photogenerated electrons and holes, the fluorescence intensity is directly proportional to the recombination rate of photogenerated carriers. The weaker the fluorescence intensity, the higher the electron-hole separation. Experimental results show that when the excitation wavelength is 357 nm, LDH has an emission peak at around 425 nm. After topological transformation and in-situ sulfidation, the fluorescence intensity of CuCo2S4@Co3O4-3 at 425 nm is significantly reduced, indicating that the recombination of photogenerated electrons and holes in CuCo2S4@Co3O4-3 is significantly suppressed. Figure 5 As shown in Figure c, the photocurrent intensity of CuCo2S4@Co3O4-3 is approximately twice that of LDH, indicating that CuCo2S4@Co3O4-3 possesses excellent electron-hole separation capabilities. Simultaneously, the Nyquist plot of CuCo2S4@Co3O4-3 shows a smaller radius of curvature than that of the original LDH. Figure 5 (d) indicates that it has low charge transfer resistance and high photogenerated electron-hole separation efficiency. These results demonstrate that the formation of CuCo2S4 and Co3O4 heterojunctions effectively promotes the separation and migration of photogenerated carriers.

[0046] Photocatalytic performance of the catalyst:

[0047] The photocatalytic activity of the prepared catalyst was evaluated using DCF, a common pharmaceutical compound, as the target. Figure 6 As shown in Figure a, under irradiation with a 300W mercury lamp, the degradation rate of DCF within 30 minutes was only 1.3%, indicating that DCF has inherent stability in nature and is difficult to photolyze. When LDH, CuCo2O4, CuCo2S4@Co3O4-1, CuCo2S4@Co3O4-2, and CuCo2S4@Co3O4-3 were added to the solution, and adsorption-desorption equilibrium was reached after 30 minutes of adsorption in the dark, the degradation rates of DCF after 30 minutes of light irradiation were 77.89%, 89.48%, 92.98%, 96.19%, and 100%, respectively. In particular, CuCo2S4@Co3O4-3 showed significantly better catalytic ability than LDH and CuCo2O4, with degradation rates 1.28 times and 1.45 times higher, respectively. CuCo2S4@Co3O4-3 exhibits excellent photocatalytic activity, indicating that the construction of the heterojunction improves the separation of photogenerated carriers, thereby enhancing the photocatalytic activity of the catalyst, which is consistent with previous electrochemical characterization. Furthermore, the kinetics of the DCF degradation reaction can be fitted using a pseudo-first-order kinetic model, such as... Figure 6 As shown in c.

[0048] Ln(C t / C0)=-kt

[0049] Where k(min) -1 Ct (mg·L -1 ) and CO (mg·L -1 The reaction rate constants and DCF concentrations at times t=0 and t are respectively. The reaction rate constants k for LDH, CuCo2O4, CuCo2S4@Co3O4-1, CuCo2S4@Co3O4-2, and CuCo2S4@Co3O4-3 are 42.68 × 10⁻⁶. -3 59.01×10 -3 74.53×10 -3 88.70×10 -3 and 129.66×10 -3 The reaction rate constants were 3.04 times and 2.20 times that of LDH and CuCo2O4, respectively. This indicates that the 2D / 3D hierarchical structure in the catalyst facilitates DCF contact with a large number of nanosheet edge active sites and a large number of interfacial active sites, thereby improving the catalytic reaction rate.

[0050] To further understand the evolution of DCF degradation by CuCo2S4@Co3O4-3, samples were collected at certain time intervals and analyzed using a UV-Vis spectrophotometer. The scanning results are as follows: Figure 6 As shown in Figure b, DCF has a maximum absorption peak near 275 nm. After 5 minutes of illumination, the structure of DCF itself is destroyed, producing other intermediates, which exhibit absorption bands at 240 nm and 330 nm. These byproducts are common persistent products formed during the photodegradation of DCF. The UV-Vis absorption peaks weaken with the extension of photoreaction time. This confirms that CuCo2S4@Co3O4-3 can decompose the aromatic groups in DCF molecules and can efficiently photodegrade DCF in aqueous media. TOC testing shows that... Figure 7 As shown in Figure a, when the illumination time is 30 to 60 minutes, the TOC removal rate is 90%. This directly indicates that most DCF molecules are mineralized into CO2 and H2O. In summary, the CuCo2S4@Co3O4-3 composite material exhibits excellent mineralization efficiency and degradation rate in the photodegradation of DCF. The above results show that CuCo2S4@Co3O4-3 demonstrates the best photocatalytic performance for the degradation of DCF.

[0051] Investigate the effect of catalyst dosage on it. For example Figure 7As shown in Figure b, the results indicate that the degradation efficiency gradually increases with the increase of catalyst dosage. When 25 mg of catalyst is added, the degradation rate of DCF by CuCo2S4@Co3O4-3 can reach 100% within 30 min. This is because the more catalyst is added, the more active sites it can provide. However, when 30 mg of catalyst is added, the degradation rate decreases. This is because when an excessive amount of catalyst is added, it will cause the photocatalyst particles to agglomerate, which may cover their active sites and reduce their photocatalytic ability.

[0052] Furthermore, to evaluate the potential of the CuCo2S4@Co3O4-3 catalyst in practical applications, we selected four typical water samples for study. For example... Figure 7 As shown in Figure c, the DCF degradation rates for tap water, river water (Nü'er River, Jinzhou, Liaoning), lake water (Bohai University Lake), and seawater (Bohai Bay) were 97.31%, 98.17%, 97.24%, and 83.36%, respectively, indicating good performance.

[0053] Catalyst stability: To verify the stability of the photocatalyst, CuCo2S4@Co3O4-3 was subjected to 5 cycles of catalytic reaction, such as... Figure 8 As shown, after five cycles of repeated use, CuCo2S4@Co3O4-3 still achieved a DCF removal rate of 81.14% through photocatalytic degradation, indicating that the catalyst has good stability. XRD and SEM analyses of the crystal form and morphology of the catalyst in the five-cycle samples showed no significant changes before and after photodegradation.

[0054] Photocatalytic mechanism: To investigate the transport pathway and main active components of photogenerated carriers, isopropanol (IPA), potassium iodide (KI), silver nitrate (AgNO3), and 4-hydroxy-2,2,6,6-tetramethylpiperidinoxy (TEMPOL) were added to the reaction system, respectively, with concentrations of ·OH and h⁻¹. + e - , and O2 - The trapping agent. The results are as follows: Figure 9 As shown, when the KI scavenger was added, the degradation rate changed from the original 100.00% to 71.96%, with the largest change in degradation rate, indicating that h + These are the main active species in the degradation reaction process; at the same time, the addition of IPA and TEMPOL significantly reduced the degradation rate, indicating that ·OH and ·O2 are the main active species in the degradation process. - It also played a crucial role in the degradation process; when the catalyst dosage was 15 mg, the degradation rate of DCF was 80.29%, and after adding AgNO3, the degradation rate of DCF increased to 85.8%. The main reason for this was that when AgNO3 was added, more e-elements were captured. - , promoted h+ and e - Separation promotes the photocatalytic reaction. Therefore, in summary, it can be deduced that h + e - ·OH, ·O2 - All participated in the catalytic reaction, and the order of their influence on the reaction is h. + O2 - >·OH>e - .

[0055] To further verify the type of free radicals generated in the system, we conducted electron spin resonance (ESR) experiments. DMPO-·O2 was not detected in the ESR spectra under dark reaction conditions. - The signal was similar to that of DMPO-·OH, but after 15 minutes of light irradiation, four peaks with intensities of approximately 1:2:2:1 could be accurately observed, indicating the formation of ·OH during this process. Similarly, for DMPO-·O2... - Four peaks with a typical intensity ratio of 1:1:1:1 can be observed. This indicates that ·O2 is formed during the reaction. - These results are consistent with those obtained from the trapping agent experiments. Photocatalytic performance is heavily influenced by the electronic structure of the photocatalyst. The band gaps (Eg) of CuCo2S4 and Co3O4 can be determined using the formula for absorbance spectra:

[0056] αhν=A(hν-E g ) n / 2

[0057] Where α, h, A, and Eg represent the absorption coefficient, photon energy, constant value, and band gap energy, respectively. The band gaps of CuCo₂S₄ and Co₃O₄ can be determined to be 1.59 eV and 3.01 eV, respectively. Figure 9 The valence and conduction bands of the photocatalysts were measured and calculated using a Mott-Schottky method. The figures show that the slopes of both CuCo₂S₄ and Co₃O₄ are negative, indicating that they are both p-type semiconductors. The flat band potentials of CuCo₂S₄ and Co₃O₄ are approximately +0.56V and +0.30V, respectively, corresponding to valence band values ​​of +0.76V and +0.50V. Furthermore, the valence band potentials (Et) of CuCo₂S₄ and Co₃O₄ are... VB The values ​​can be estimated as -0.83 eV and -2.51 eV using the following empirical formulas.

[0058] E CB =E VB -E g

[0059] Based on the above experimental conclusions and photocatalytic degradation results, combined with the above characterization analysis, it is believed that the degradation mechanism of DCF by the CuCo2S4@Co3O4-3 composite catalyst conforms to the type II heterojunction mechanism. When irradiated with ultraviolet light, CuCo2S4 and Co3O4 generate electron-hole pairs. Compared with CuCo2S4 (-0.83 eV), the conduction band potential of Co3O4 (-2.34 eV) is more negative. Therefore, photogenerated electrons on the conduction band of Co3O4 can easily transfer from the heterojunction formed at the interface to the conduction band of CuCo2S4, and the electrons on the conduction band of CuCo2S4... - O2 reacts with O2 on the surface of the catalyst, thereby producing ·O2. - Furthermore, holes will flow from the lower valence band of CuCo2S4 to Co3O4. The valence band potentials of CuCo2S4 and Co3O4 are insufficient to generate ·OH / OH. - (1.99V vs NHE) and ·OH / H2O (2.27V vs NHE). From this, it can be inferred that ·OH is not produced through direct oxidation of holes, but rather through electrons. - This is produced by the multi-step reduction of O2. Specifically, O2 reacts with H... + and e - H2O2 is produced by combination with O2. - They combine to form ·OH, or pollutant molecules are directly oxidized. Therefore, in the presence of ·OH and ·O2... - Under the synergistic effect of holes, DCF is rapidly mineralized and degraded. The formation of heterojunctions greatly promotes the separation of photogenerated carriers, providing more active materials for the catalytic reaction. Furthermore, the compact interface structure of the heterojunction formed by topological transformation reduces interfacial charge transfer resistance, and the abundant interfaces provide more reaction centers for the catalytic reaction. The hierarchical flower-like structure improves the catalyst's light utilization efficiency and provides more active sites at the lamellar edges. These characteristics work synergistically to give CuCo2S4@Co3O4-3 excellent catalytic performance. This process can be represented by the following equation:

[0060] CuCo2S4@Co3O4-3+hν→h + +e -

[0061] O2+e - →·O2 -

[0062] O2+2e - +2H + →H2O2

[0063] ·O2 - +H₂O₂→·OH⁺OH - +O2

[0064] h + +·OH+e - +·O2 - +DCF→CO2+H2O…

[0065] In addition, a PEC sensor based on CuCo2S4@Co3O4-3 / FTO as the working electrode was fabricated for quantitative detection of DCF. Figure 6 Figure a shows the CuCo2S4@Co3O4-3 / FTO electrode pair at 0.1 mol·L⁻¹. -1 Different concentrations of DCF in Na2SO4 exhibited a typical "signal on" response. For example... Figure 6 As shown in Figure b, the photocurrent is linear with the DCF concentration at 10 mol·L⁻¹. -1 and 500 μmol·L -1 Within the range, there is a good linear relationship, and two linear regression equations are shown:

[0066] ΔI=0.34c+18.99(r=0.9939, C DCF 10 nmol·L -1 ~10μmol·L -1 ),

[0067] ΔI=1.56c+0.55(r=0.9914, C DCF 10 μmol·L -1 ~500 μmol·L -1 ).

[0068] The limit of detection (LOD, 3S / N) and the limit of quantitation (LOQ, 10S / N) are 6.31 nmol·L⁻¹, respectively. -1 and 21.03 nmol·L -1 .

[0069] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the following claims.

[0070] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for preparing a 2D / 3D nanoflower-like CuCo2S4@Co3O4 catalyst, characterized in that, include: 1) CuCo-LDH and CH4N2S were dissolved in ethanol by stirring to obtain solution A; wherein the CuCo-LDH was of the sea urchin type; 2) After transferring solution A to the reaction vessel and heating it, the product A is obtained by centrifugation, washing, and drying. 3) After calcining product A, the catalyst CuCo2S4@Co3O4 was obtained.

2. The method for preparing a 2D / 3D nanoflower-like CuCo2S4@Co3O4 catalyst according to claim 1, characterized in that, The preparation method of CuCo-LDH is as follows: Co(NO3)2·6H2O, Cu(NO3)2·3H2O, urea and NH4F are dissolved in deionized water and the mixture is stirred to form a homogeneous solution; then, the solution is sealed in a reaction vessel and reacted at high temperature; finally, the mixture in the high-pressure vessel is taken out, washed with deionized water and anhydrous ethanol, and dried to obtain CuCo-LDH.

3. The method for preparing a 2D / 3D nanoflower-like CuCo2S4@Co3O4 catalyst according to claim 1, characterized in that, In step 1), the mass of CuCo-LDH is 0.25g, the mass of CH4N2S is 0.3, 0.5 or 0.7g, and the amount of ethanol used is 35mL.

4. The method for preparing a 2D / 3D nanoflower-like CuCo2S4@Co3O4 catalyst according to claim 1, characterized in that, In step 2), the temperature of the reaction in the reactor is 180℃ and the time is 8h.

5. The method for preparing a 2D / 3D nanoflower-like CuCo2S4@Co3O4 catalyst according to claim 1, characterized in that, The calcination process involves calcining at 400°C in a muffle furnace for 2 hours.

6. The 2D / 3D nanoflower-like CuCo2S4@Co3O4 catalyst obtained by any one of the preparation methods according to claims 1-5, characterized in that, The catalyst has a distinct 2D / 3D nanoflower-like structure.

7. The application of the 2D / 3D nanoflower-like CuCo2S4@Co3O4 catalyst prepared according to any one of claims 1-5, characterized in that, It can be applied to the photocatalytic degradation of diclofenac sodium DCF, or the photoelectric detection of diclofenac sodium, or as a working electrode to prepare a "signal on" PEC sensing platform for quantitative detection of diclofenac sodium DCF.

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