Nano composite material as well as preparation method and application thereof

Abstract

The invention discloses a nano composite material and a preparation method and application thereof, the preparation method comprises the following steps: carrying out heating reaction on cobalt chloride hexahydrate, nickel chloride hexahydrate and urea to obtain NiCo2O4 solid powder; the preparation method comprises the following steps: grinding purple phosphorus, adding the ground purple phosphorus into absolute ethyl alcohol, carrying out ultrasonic crushing treatment, centrifugally collecting supernate, centrifugally collecting precipitate, drying and resuspending to obtain purple phosphorus nanosheet dispersion liquid; the preparation method comprises the following steps: adding rhenium disulfide nano-particles into pyrrolidone, carrying out ultrasonic crushing treatment, centrifuging, and collecting supernate, so as to obtain rhenium disulfide quantum dot dispersion liquid; niCo2O4 solid powder is added into absolute ethyl alcohol, the purple phosphorus nanosheet dispersion liquid and the rhenium disulfide quantum dot dispersion liquid are sequentially added, stirring continues for a period of time, and freeze drying is conducted; according to the nano composite material, VP NSs and ReS2 QDs are deposited on the surface of NiCo2O4, and under the synergistic effect of VP NSs and ReS2 QDs, the photocatalytic activity, the stability and the recycling performance of the composite material are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of composite materials technology, specifically to a nanocomposite material, its preparation method, and its applications. Background Technology

[0002] Today, the overexploitation and utilization of traditional fossil fuels has triggered severe environmental problems and an energy shortage crisis. Large amounts of water bodies polluted with highly toxic dyes pose a serious threat to the environment. Untreated wastewater discharged into natural water bodies not only disrupts the ecological balance but also severely impacts human health. Efficient wastewater treatment technologies are crucial for mitigating these risks and preventing further environmental and public health deterioration. Simultaneously, the world faces a severe and complex energy situation, and the development and utilization of clean and renewable energy are widely regarded as key pathways to overcoming this predicament. Hydrogen, with its advantages of light weight, zero pollution, high calorific value, wide application range, and abundant reserves, has become one of the most watched renewable energy sources. The sun, with its environmentally friendly and abundant resources, has become an important source of clean energy. Semiconductor-based photocatalysis technology has shown great potential in clean energy production and environmental remediation and is considered one of the ideal ways to achieve sustainable energy utilization in the future. The core of its practical application lies in developing low-cost, visible light-responsive, highly efficient, and stable semiconductor photocatalysts. Currently, studied photocatalytic materials include metal oxides, metal sulfides, metal phosphides, graphitic carbon nitride (g-C3N4), metal-organic frameworks (MOFs), and covalent organic frameworks (COFs). However, these materials still suffer from complex preparation processes, insufficient photocatalytic performance, and inadequate stability, which restricts their large-scale application. For example, while zinc sulfide (ZnS) and cadmium sulfide (CdS) exhibit high photocatalytic activity, their stability is often poor due to photocorrosion. Therefore, developing photocatalysts that combine excellent photocatalytic performance with high stability is of great significance for advancing this field.

[0003] Compared to traditional binary compounds such as cadmium sulfide (CdS) and zinc oxide (ZnO), ternary nickel-cobalt oxide (NiCo2O4) exhibits higher cation disorder, tunable electronic structure, and asymmetric bimetallic sites, showing great potential in the development of highly efficient visible-light-responsive photocatalysts. Nevertheless, pure-phase NiCo2O4 photocatalysts still face the problem of photogenerated carriers being confined to a single-phase system, increasing the probability of recombination. NiCo2O4 has a band gap (E9) of approximately 1.2–2.1 eV, capable of absorbing most visible light; however, its photocatalytic performance remains limited due to the severe recombination of photogenerated electron-hole pairs and their difficulty in effectively participating in surface reactions within a single-phase system.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a nanocomposite material, its preparation method, and its application. The nanocomposite material of this invention is synthesized using a hydrothermal method to obtain NiCo2O4, and VP NSs and ReS2QDs are deposited on its surface. VP NSs mainly provide mechanical support and stability, while ReS2QDs help improve conductivity. Through their synergistic effect, the photocatalytic activity, stability, and recyclability of the composite material are effectively improved. Furthermore, the composite material of this invention exhibits significantly enhanced activity in the photocatalytic degradation of organic matter and hydrogen production, and maintains excellent photostability even under prolonged illumination, providing a new approach for the design of efficient photocatalytic systems.

[0006] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0007] The first aspect of this invention provides a method for preparing a nanocomposite material, the method comprising the following steps:

[0008] (a) Cobalt chloride hexahydrate, nickel chloride hexahydrate and urea were dissolved in deionized water and heated to react. After solid-liquid separation and drying, NiCo2O4 solid powder was obtained.

[0009] (b) Grind the purple phosphorus, add it to anhydrous ethanol and sonicate it under ice bath conditions. Then centrifuge at 4500~5500 rpm, collect the supernatant, then centrifuge at 12000~14000 rpm, collect the precipitate, dry it, and resuspend it to obtain a dispersion of purple phosphorus nanosheets.

[0010] (c) Rhenium disulfide nanoparticles were added to pyrrolidone and subjected to ultrasonic disruption, followed by centrifugation. The supernatant was collected to obtain a rhenium disulfide quantum dot dispersion.

[0011] (d) NiCo2O4 solid powder was added to anhydrous ethanol and stirred until homogeneous. Then, purple phosphorus nanosheet dispersion and rhenium disulfide quantum dot dispersion were added sequentially under stirring conditions. The mixture was then stirred for a period of time under light-proof ice bath conditions and then freeze-dried to obtain the nanocomposite material.

[0012] Preferably, in step (a), the mass ratio of cobalt chloride hexahydrate, nickel chloride hexahydrate, and urea is (1.8~2.2):1:(3.5~4).

[0013] Preferably, in step (a), the heating reaction temperature is 95~105℃ and the time is 6~10h.

[0014] Preferably, in step (b), the ultrasonic power is 150~250W, the processing time is 10~15h, and the centrifugation time is 12~20min.

[0015] Preferably, in step (c), the ultrasonic power is 60~80W, the treatment time is 6~10h, the centrifugation speed is 5000~7000rpm, and the time is 12~18min.

[0016] Preferably, in step (d), the mass percentage of purple phosphorus nanosheets in the nanocomposite material is 1%~25%, and the mass percentage of rhenium disulfide quantum dots is 0.5%~2%; stirring is continued for 3~5 hours.

[0017] A second aspect of the present invention provides a nanocomposite material prepared by the above-described preparation method.

[0018] A third aspect of the present invention provides an application of the nanocomposite material prepared by the above preparation method in the photocatalytic degradation of organic matter.

[0019] The fourth aspect of this invention provides an application of the nanocomposite material prepared by the above-described method in wastewater treatment.

[0020] The fifth aspect of this invention provides an application of the nanocomposite material prepared by the above-described method in photocatalytic hydrogen production.

[0021] Compared with the prior art, the beneficial effects of the present invention include at least the following:

[0022] This invention utilizes a hydrothermal method to synthesize NiCo2O4 nanocomposite material and loads purple phosphorus nanosheets (VP ​​NSs) onto the surface of nickel-cobalt oxide to construct pn heterojunctions. This effectively promotes the separation of photogenerated electrons and holes and inhibits their recombination, while broadening the spectral absorption range and enhancing overall photocatalytic performance. Simultaneously, loading ReS2QDs onto the nickel-cobalt oxide surface helps improve conductivity. The synergistic effect of these two methods effectively improves the photocatalytic activity, stability, and recyclability of the composite material. Furthermore, this invention's composite material exhibits significantly enhanced activity in the photocatalytic degradation of organic matter and total water splitting for hydrogen production, and maintains excellent photostability even under prolonged illumination, providing a new approach for the design of highly efficient photocatalytic systems. Attached Figure Description

[0023] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0024] Figure 1The XRD patterns of NiCo2O4, ReS2QDs (1%)@NiCo2O4 and (VP NSs (7%) + ReS2QDs (1%))@NiCo2O4 and the NiCo2O4 standard card (PDF 02-1074) are shown in the experimental examples of this invention.

[0025] Figure 2 The images shown are SEM images, TEM images, EDS images, and elemental distribution maps of different materials used in the experimental examples of this invention.

[0026] Figure 3 The room temperature photoluminescence spectrum and ultraviolet-visible diffuse reflectance spectrum of NiCo2O4, ReS2QDs (1%) @ NiCo2O4 and (VP NSs (7%) + ReS2QDs (1%)) @ NiCo2O4 in the experimental examples of this invention;

[0027] Figure 4 The Raman spectra of NiCo2O4, VP NSs (7%)@ NiCo2O4 and (VP NSs (7%) + ReS2QDs (1%))@ NiCo2O4 in the experimental examples of this invention are shown below.

[0028] Figure 5 The results of a systematic analysis of the surface elemental composition and chemical valence state of (VP NSs (7%) + ReS2QDs (1%))@NiCo2O4 in the experimental example of this invention are as follows:

[0029] Figure 6 These are the results of transient photocurrent response tests and electrochemical impedance spectroscopy Nyquist plot analysis of different materials in the experimental examples of this invention;

[0030] Figure 7 The BET characterization spectra of NiCo2O4, ReS2QDs (1%)@NiCo2O4 and (VP NSs (7%) + ReS2QDs (1%))@NiCo2O4 in the experimental examples of this invention are shown below.

[0031] Figure 8 The results show the evaluation of the photocatalytic performance of different materials in the experimental examples of this invention.

[0032] Figure 9 These are the results of free radical capture experiments and carbon content testing experiments of different materials in the experimental examples of this invention;

[0033] Figure 10 These are the experimental results of the photocatalytic hydrogen production performance of different materials in the experimental examples of this invention;

[0034] Figure 11This invention relates to the photocatalytic mechanism and hydrogen production mechanism of (VP NSs (7%) + ReS2QDs (1%))@NiCo2O4 in the experimental example of this invention. Detailed Implementation

[0035] The embodiments of the technical solution of the present invention will be described in detail below with reference to the examples. The following embodiments are only used to illustrate the technical solution of the present invention more clearly, and are therefore only examples, and should not be used to limit the scope of protection of the present invention.

[0036] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0037] This invention provides a method for preparing a nanocomposite material, the method comprising the following steps:

[0038] (a) Cobalt chloride hexahydrate, nickel chloride hexahydrate and urea were dissolved in deionized water and heated to react. After solid-liquid separation and drying, NiCo2O4 solid powder was obtained.

[0039] (b) Grind the purple phosphorus, add it to anhydrous ethanol and sonicate it under ice bath conditions. Then centrifuge at 4500~5500 rpm, collect the supernatant, then centrifuge at 12000~14000 rpm, collect the precipitate, dry it, and resuspend it to obtain a dispersion of purple phosphorus nanosheets.

[0040] (c) Rhenium disulfide nanoparticles were added to pyrrolidone and subjected to ultrasonic disruption, followed by centrifugation. The supernatant was collected to obtain a rhenium disulfide quantum dot dispersion.

[0041] (d) NiCo2O4 solid powder was added to anhydrous ethanol and stirred until homogeneous. Then, purple phosphorus nanosheet dispersion and rhenium disulfide quantum dot dispersion were added sequentially under stirring conditions. The mixture was then stirred for a period of time under light-proof ice bath conditions and then freeze-dried to obtain the nanocomposite material.

[0042] In one embodiment, in step (a), the mass ratio of cobalt chloride hexahydrate, nickel chloride hexahydrate, and urea is (1.8~2.2):1:(3.5~4).

[0043] In one embodiment, in step (a), the heating reaction temperature is 95~105°C and the time is 6~10h.

[0044] In one embodiment, in step (b), the ultrasonic power is 150~250W, the processing time is 10~15h, and the centrifugation time is 12~20min.

[0045] In one embodiment, in step (c), the ultrasonic power is 60~80W, the treatment time is 6~10h, the centrifugation speed is 5000~7000rpm, and the time is 12~18min.

[0046] In one embodiment, in step (d), the mass percentage of purple phosphorus nanosheets in the nanocomposite material is 1%~25%, and the mass percentage of rhenium disulfide quantum dots is 0.5%~2%; stirring is continued for 3~5 hours.

[0047] Another embodiment of the present invention provides a nanocomposite material prepared by the above preparation method.

[0048] Another embodiment of the present invention provides an application of the nanocomposite material prepared by the above preparation method in the photocatalytic degradation of organic matter.

[0049] Another embodiment of the present invention provides an application of the nanocomposite material prepared by the above preparation method in wastewater treatment.

[0050] Another embodiment of the present invention provides an application of the nanocomposite material prepared by the above preparation method in photocatalytic hydrogen production.

[0051] The technical solution of the present invention will be further described in detail below through specific embodiments.

[0052] Example 1

[0053] This embodiment describes a method for preparing a nanocomposite material, which includes the following steps:

[0054] (a) 0.506 g of cobalt chloride hexahydrate (purchased from Wengjiang Reagent), 0.254 g of nickel chloride hexahydrate (purchased from Wengjiang Reagent) and 0.96 g of urea (purchased from Wengjiang Reagent) were dissolved in 40 ml of deionized water, stirred evenly, and then transferred to a high-pressure reactor and reacted at 100 °C for 8 h. After naturally cooling to room temperature, solid-liquid separation and drying were performed to obtain NiCo2O4 solid powder.

[0055] (b) Grind 500 mg of purple phosphorus for 45 min, then add it to 80 ml of anhydrous ethanol and sonicate (200 W) for 12 h under ice bath conditions. Then centrifuge at 5000 rpm for 15 min, collect the supernatant, then centrifuge at 13000 rpm for 15 min, collect the precipitate, dry it, and resuspend it to obtain a dispersion of purple phosphorus nanosheets (denoted as VP NSs).

[0056] (c) 0.005 g of rhenium disulfide nanoparticles were added to 10 ml of pyrrolidone and subjected to ultrasonic disruption (ultrasonic power 70 W). The mixture was then centrifuged at 6000 rpm for 15 min. The supernatant was collected to obtain a rhenium disulfide quantum dot (ReS2QDs) dispersion.

[0057] (d) 0.03 g NiCo2O4 solid powder was added to 5 ml anhydrous ethanol and stirred until homogeneous. Under stirring conditions, purple phosphorus nanosheet dispersion (1 mg / ml) and rhenium disulfide quantum dot dispersion were added sequentially. Then, the mixture was stirred for 4 h under light-protected water bath conditions and then freeze-dried to obtain the nanocomposite material (denoted as (VP ​​NSs (7%) + ReS2QDs (1%)) @ NiCo2O4).

[0058] Comparative Example 1

[0059] This comparative example illustrates a method for preparing a nanocomposite material, the method comprising the following steps:

[0060] (a) 0.506 g of cobalt chloride hexahydrate (purchased from Wengjiang Reagent), 0.254 g of nickel chloride hexahydrate (purchased from Wengjiang Reagent) and 0.96 g of urea (purchased from Wengjiang Reagent) were dissolved in 40 ml of deionized water, stirred evenly, and then transferred to a high-pressure reactor and reacted at 100 °C for 8 h. After naturally cooling to room temperature, solid-liquid separation and drying were performed to obtain NiCo2O4 solid powder.

[0061] (b) 0.005 g of rhenium disulfide nanoparticles were added to 10 ml of pyrrolidone and subjected to ultrasonic disruption (ultrasonic power 70 W). The mixture was then centrifuged at 6000 rpm for 15 min, and the supernatant was collected to obtain a rhenium disulfide quantum dot (ReS2QDs) dispersion.

[0062] (c) 0.03 g NiCo2O4 solid powder was added to 5 ml anhydrous ethanol and stirred until homogeneous. Rhenium disulfide quantum dot dispersion was added under stirring conditions. Then, stirring was continued for 4 h under light-protected water bath conditions. After freeze drying, the nanocomposite material (denoted as ReS2QDs(1%)@NiCo2O4) was obtained.

[0063] Comparative Example 2

[0064] This comparative example illustrates a method for preparing a nanocomposite material, the method comprising the following steps:

[0065] (a) 0.506 g of cobalt chloride hexahydrate (purchased from Wengjiang Reagent), 0.254 g of nickel chloride hexahydrate (purchased from Wengjiang Reagent) and 0.96 g of urea (purchased from Wengjiang Reagent) were dissolved in 40 ml of deionized water, stirred evenly, and then transferred to a high-pressure reactor and reacted at 100 °C for 8 h. After naturally cooling to room temperature, solid-liquid separation and drying were performed to obtain NiCo2O4 solid powder.

[0066] (b) Grind 500 mg of purple phosphorus for 45 min, then add it to 80 ml of anhydrous ethanol and sonicate (200 W) for 12 h under ice bath conditions. Then centrifuge at 5000 rpm for 15 min, collect the supernatant, then centrifuge at 13000 rpm for 15 min, collect the precipitate, dry it, and resuspend it to obtain a dispersion of purple phosphorus nanosheets (denoted as VP NSs).

[0067] (c) 0.03 g NiCo2O4 solid powder was added to 5 ml anhydrous ethanol and stirred until homogeneous. Purple phosphorus nanosheet dispersion was added sequentially under stirring conditions. Then, stirring was continued for 4 h under light-protected water bath conditions. After freeze drying, the nanocomposite material (denoted as VP NSs (7%) @ NiCo2O4) was obtained.

[0068] Experimental Example

[0069] According to the preparation methods of the examples and comparative examples, NiCo2O4, ReS2QDs (mass percentage X%)@NiCo2O4, (VP NSs (mass percentage Y%)@NiCo2O4, (VP NSs (mass percentage X%) + ReS2QDs (mass percentage Y%))@NiCo2O4 were obtained, wherein X is 1~25 and Y is 0.5~2;

[0070] 1. The crystal structure, lattice parameters, and phase composition of the prepared materials were characterized by X-ray diffraction (XRD). The crystallinity of the original NiCo2O4, ReS2QDs(1%)@NiCo2O4, and (VP NSs(7%) + ReS2QDs(1%))@NiCo2O4 were confirmed by analyzing the XRD patterns in the range of 15°–70° (2θ). Figure 1 The XRD patterns of pristine NiCo2O4 prepared by hydrothermal method and its doped ReS2QDs and VP NSs are shown.

[0071] In the spectrum, the diffraction peaks of NiCo2O4 appear at 18.906°, 31.148°, 36.696°, 44.622°, 55.439°, 59.094°, and 64.98°, corresponding to the (111), (220), (311), (400), (422), (511), and (440) crystal planes, respectively, which is consistent with the standard card (PDF02-1074), indicating that the sample has a typical spinel structure. The positions of the diffraction peaks of NiCo2O4 prepared under low-temperature conditions remain basically unchanged, with only slight shifts due to interfacial stress or bonding. These characteristic peaks confirm the successful synthesis of spiky NiCo2O4, consistent with previous research results.

[0072] Because the doping levels of ReS2QDs and VP NSs are relatively low, and the crystallinity of quantum dots and nanosheets is low, no obvious diffraction peaks were observed in the XRD pattern.

[0073] 2. The macroscopic morphology, microstructure, and elemental distribution characteristics of three materials—pure-phase NiCo2O4, VP NSs(7%)@NiCo2O4, and (VP NSs(7%) + ReS2QDs(1%))@NiCo2O4—were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) systems. This comprehensively verified the preparation effect of the composite materials. The characterization results are as follows: Figure 2 As shown; Figure 2 In the image: (a) Scanning electron microscope (SEM) image of pure-phase NiCo2O4; (b) Transmission electron microscope (TEM) image of VP NSs (7%)@NiCo2O4; (c) TEM image of (VP NSs (7%) + ReS2QDs (1%))@NiCo2O4 (scale bar 100 nm); (d) TEM image of (VP NSs (7%) + ReS2QDs (1%))@NiCo2O4 (scale bar 20 nm); (e) Schematic diagram of the lattice spacing of VP, ReS2 and NiCo2O4; (g) Energy dispersive X-ray spectroscopy (EDS) spectrum of (VP NSs (7%) + ReS2 QDs (1%))@NiCo2O4; (h) Overall elemental distribution of (VP NSs (7%) + ReS2QDs (1%))@NiCo2O4; (in) (VP NSs (7%) + ReS2QDs (1%))@NiCo2O4 Individual distribution spectra of Ni, Co, O, P, Re, and S elements in NiCo2O4 (NSs (7%) + ReS2QDs (1%))).

[0074] Figure 2Image (a) shows a SEM image of NiCo2O4, revealing a cubic phase nickel cobalt oxide nanosphere structure. This invention employs scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) to conduct in-depth research on the surface morphology and microstructure of the NiCo2O4 nanospheres. Figure 2 As shown in (a), the NiCo2O4 prepared in this invention exhibits a uniform, spiky, sea urchin-like structure, consistent with the scanning electron microscopy (SEM) characterization results. This indicates that the synthesized spiky, sea urchin-like NiCo2O4 has a large aspect ratio (LD = L / D, where L is the length of the nanoneedles and D is the diameter). This structure endows NiCo2O4 with a large specific surface area, providing more photocatalytic active sites; simultaneously, the migration distance of photogenerated carriers along a specific lattice direction is shortened, thereby increasing the probability of carrier diffusion to the material surface. Electrons tend to accumulate at the tips, thus enhancing photocatalytic performance.

[0075] Figure 2 (b) shows that VP NSs (7%) are uniformly dispersed on the surface of NiCo2O4 nanospheres. The introduction of VP NSs increases the number of active sites on the NiCo2O4 surface and provides new channels for charge transfer, thereby improving the decomposition ability of NiCo2O4.

[0076] Figure 2 Image (c) shows VP nanosheets and ReS2 quantum dots co-loaded on a NiCo2O4 substrate. Specifically, Figure 2 Image (d) clearly shows that VP nanosheets and ReS2 quantum dots are uniformly anchored on the NiCo2O4 surface. During the photocatalytic reaction, the surface electrons generated at the interface of VP nanosheets, ReS2 quantum dots, and NiCo2O4 enable efficient charge separation, enhancing material stability. Simultaneously, the interface forms an efficient electron transport channel, suppressing electron-hole recombination and ultimately improving photocatalytic efficiency.

[0077] Figure 2 In the middle (e), the lattice spacing of the NiCo2O4 sample is d=0.316 nm, which is consistent with the typical lattice parameters of spinel-type NiCo2O4 reported in the literature; Figure 2In Figure (f), for the composite material (VP nanosheets (7%) + ReS2 quantum dots (1%))@NiCo2O4, the lattice spacing d of the VP nanosheets is 0.23 nm, and the lattice spacing d of the ReS2 quantum dots is 0.26 nm. Clear lattice fringes in the dark field region confirm that a heterojunction has been formed between NiCo2O4 and ReS2 quantum dots. This structure can effectively coat NiCo2O4, improving its service life under high-temperature conditions. Simultaneously, the tight contact interface promotes charge migration and shortens carrier transport distance, indicating that a heterojunction has been successfully constructed between NiCo2O4 and VP nanosheets.

[0078] Figure 2 The middle (in) is the elemental distribution diagram of (VPNSs( 7%)+ReS2QDs(1%))@ NiCo2O4. The results show that cobalt (Co), oxygen (O), nickel (Ni), phosphorus (P) and sulfur (S) are uniformly distributed. Figure 2 The image (g) shows the EDS spectrum of (VP NSs (7%) + ReS2QDs (1%))@NiCo2O4. Characteristic peaks for Ni, Co, O, P, Re, and S were detected. The coexistence of these characteristic peaks confirms the presence of NiCo2O4, ReS2 quantum dots, and VP nanosheets in the composite material. These three components are in a chemical composite state, rather than a simple physical mixture or unreacted precursors. In conclusion, the (VP NSs (7%) + ReS2QDs (1%))@NiCo2O4 composite material has been successfully prepared.

[0079] 3. As is well known, the lifetime of photogenerated electron-hole pairs is closely related to photocatalytic activity. Photoluminescence (PL) spectroscopy analysis can directly reflect the recombination rate of photogenerated electron-hole pairs, thus revealing their influence on photocatalytic performance. PL spectroscopy analysis was performed on four samples: NiCo2O4, ReS2QDs(1%)@NiCo2O4, VP NSs(7%)@NiCo2O4, and (VP NSs(7%) + ReS2QDs(1%))@NiCo2O4. The results are as follows: Figure 3 As shown, Figure 3In the image, (a): room temperature photoluminescence (PL) spectra of four samples: NiCo2O4, ReS2QDs(1%)@NiCo2O4, VP NSs(7%)@NiCo2O4, and (VP NSs(7%)+ReS2QDs(1%))@NiCo2O4; (b): UV-Vis diffuse reflectance (UV-Vis DRS) spectra of NiCo2O4, ReS2QDs(1%)@NiCo2O4, VP NSs(7%)@NiCo2O4, and (VP NSs(7%)+ReS2QDs(1%))@NiCo2O4.

[0080] Figure 3 (a) Room temperature photoluminescence (PL) spectra of pure-phase NiCo2O4, ReS2 quantum dots (1%)@NiCo2O4, VP nanosheets (7%)@NiCo2O4, and (VP nanosheets (7%) + ReS2 quantum dots (1%))@NiCo2O4 samples at an excitation wavelength of 325 nm. As shown in the figure, the PL spectra of all samples exhibit similar characteristics, primarily consisting of two parts: the ultraviolet region and the visible light region. The emission peak in the ultraviolet region is centered around 398 nm, corresponding to the near-band edge emission (NBE) signal generated by free exciton recombination. Comparative analysis revealed that the (VP NSs (7%) + ReS2QDs (1%))@NiCo2O4 nanocomposite exhibited the lowest ultraviolet emission peak intensity. This phenomenon can be explained by the synergistic doping of VP NSs and ReS2QDs, which creates more photocatalytic active sites on the composite surface, thus more efficiently reducing the recombination probability of photogenerated electron-hole pairs. Therefore, the separation effect of photogenerated electron-hole pairs corresponding to the composite material is significantly enhanced. Ultraviolet-Vis diffuse reflectance spectroscopy (UV-Vis DRS) analysis was used to further analyze the results. Figure 3 (b) In this study, the light absorption properties and band structure of the composite material are investigated. Figure 3 As shown in (b), pure-phase NiCo2O4 (black curve) has a narrow indirect band gap (1.52 eV). Its valence band apex is typically highly positively charged, exhibiting strong oxidizing power, but its relatively large band gap limits its visible light absorption. This characteristic indicates that while the intrinsic light absorption range of pure-phase NiCo2O4 can extend into the near-infrared region, its photocatalytic degradation and hydrogen production performance are extremely limited. This implies that the photogenerated electron-hole recombination probability of this material is extremely high.

[0081] In contrast, the VP NSs (7%) + ReS2QDs (1%) @ NiCo2O4 composite material (blue curve) has a band gap of 2.13 eV, exhibiting light absorption capacity over a wider spectral range. Notably, although this composite material does not have the narrowest band gap, it exhibits the most superior photocatalytic activity. This phenomenon suggests that key factors influencing photocatalytic performance include not only the light capture range but also the separation and utilization efficiency of photogenerated carriers.

[0082] The above mechanism was further verified using photoluminescence (PL) spectroscopy. For example... Figure 3 As shown in (a), the emission peak intensity of the blue curve composite material is significantly lower than that of all other samples, including the ReS2 single-modified sample with a narrower band gap (green curve, band gap energy Eg = 1.59 eV). The green curve is close to the black curve, mainly for two reasons: first, the disulfide is doped into nickel cobalt oxide in the form of quantum dots, and its effect on the band gap is very limited; second, the band gap of the disulfide quantum dots themselves is close to that of NiCo2O4. The significant decrease in photoluminescence (PL) intensity directly confirms that VP nanosheets and ReS2 quantum dots have successfully constructed an efficient heterojunction structure in the NiCo2O4 matrix. This heterojunction can effectively suppress the nonradiative recombination of photogenerated electron-hole pairs, thereby significantly improving the charge separation efficiency.

[0083] Furthermore, the red curve represents the nickel cobalt oxide sample doped with purple phosphorus nanosheets, which exhibits a significantly larger band gap than the pure NiCo2O4. This result indicates that the introduction of purple phosphorus has a significant modulating effect on the band structure of the matrix material, and the optimized band gap is more conducive to the photocatalytic hydrogen evolution reaction.

[0084] Therefore, the core conclusion of this invention is as follows: the synergistic modification of VP and ReS2 does not primarily aim to infinitely broaden the photoresponse range of the material, but rather to construct an efficient charge separation pathway through precise bandgap modulation and interface engineering design. This optimized carrier dynamics process allows the composite material to maximize the utilization of absorbed light energy, driving the surface redox reaction.

[0085] In summary, the excellent bifunctional photocatalytic performance of the (VP nanosheets + ReS2 quantum dots)@NiCo2O4 composite material can be attributed to the synergistic effect of the introduction of VP and ReS2: while maintaining a broad spectral absorption capacity, the composite material significantly improves charge separation efficiency. This strategy not only successfully overcomes the intrinsic defect of severe carrier recombination in pure-phase NiCo2O4, but also makes it a highly efficient and stable photocatalyst with practical application potential.

[0086] 4. Raman spectroscopy has significant advantages in characterizing the conformational transformation, lattice strain, charge density, intrinsic stability, charged lattice coupling, magnetic coupling, and electromagnetic order of materials. Raman spectroscopy analysis of different materials yields the following results: Figure 4 As shown;

[0087] Depend on Figure 4 It can be seen that in the Raman spectrum of pure phase NiCo2O4, at 314 cm⁻¹... -1 512 cm -1 and 1078 cm -1 Three main characteristic peaks are clearly visible, with no interfering peaks. These peaks are symmetrical and have narrow half-widths, indicating that NiCo2O4 has high crystallinity and typical spinel structure characteristics. In the Raman spectrum of VP NSs (7%)@NiCo2O4, a new peak at 164 cm⁻¹ is observed. -1 With 269 cm -1 Two characteristic peaks correspond to the characteristic vibrations of PO or VO bonds in VP NSs; the NiCo2O4 peak at 512 cm⁻¹ is affected by the oxygen octahedral vibration confinement effect induced by VP nanosheet coating. -1 The characteristic peak at that location undergoes a redshift, shifting to 466 cm⁻¹. -1 And 1078 cm -1 The intensity of the characteristic peak decreased. In the spectrum of the VP NSs(7%)@NiCo2O4 sample, the intensity at 164 cm⁻¹ decreased. -1 With 269 cm -1 A characteristic peak appears at 512 cm⁻¹, corresponding to the characteristic vibrational signal of the VP nanosheets. Due to the confinement effect of oxygen octahedral vibration induced by the VP nanosheet coating, the characteristic peak of NiCo₂O₄ changes from 512 cm⁻¹. -1 Displaced to 466cm -1 ; and 1078cm -1 The decrease in characteristic peak intensity at 353 cm⁻¹ is attributed to the interfacial disordering effect caused by the introduction of VP nanosheets. This phenomenon indicates that VP nanosheets not only successfully loaded onto the NiCo₂O₄ matrix surface but also formed an interfacial coupling with the matrix. This interaction slightly altered the crystal vibrational modes of the material, ultimately contributing to the change in the intensity of the 353 cm⁻¹ peak. -1 With 368cm -1 A new characteristic peak appears at 466 cm⁻¹. In the Raman spectrum of (VP NSs (7%) + ReS₂QDs (1%))@NiCo₂O₄, the characteristic peak intensity is weak due to the low ReS₂QDs loading; however, the introduction of ReS₂QDs brings additional lattice stress, causing the original peak to shift to 466 cm⁻¹. -1 The main peak further shifted to a lower wavenumber to 460 cm⁻¹ -1Simultaneously, the synergistic effect of VP NSs and ReS2QDs leads to lattice distortion in NiCo2O4. Both jointly suppress the vibration of the oxygen octahedron, resulting not only in a sustained low-frequency shift of the main peak but also in a shift at the 1078 cm⁻¹. -1 The peak at that location almost completely disappeared; 466cm -1 The peak intensity at the point further decreased, which is related to the synergistic enhancement effect of ReS2QDs on the vibrational response of VP NSs. In summary, Raman spectroscopy analysis shows that ReS2QDs successfully formed a heterostructure with VPNSs and NiCo2O4, and the three components were successfully composited. The interfacial coupling and lattice interaction between the multiple components significantly changed the interfacial electronic environment of the composite material, which is consistent with the subsequent XPS analysis results.

[0088] 5. X-ray photoelectron spectroscopy (XPS) is a widely used characterization technique in materials science, which can be used to determine the elemental composition and chemical valence state of a sample surface. By analyzing the characteristic peaks of different elements, the surface chemical properties of the material can be understood in depth. To further investigate the interaction, surface chemical composition, and elemental valence state of the components in the (VP NSs (7%) + ReS2QDs (1%))@NiCo2O4 composite material, this invention performed XPS testing on the sample and peak fitting analysis on the high-resolution spectra of each element. The results are as follows: Figure 5 As shown, Figure 5 In the image, (a) is the full-spectrum scan; (b) is the Ni 2p high-resolution spectrum; (c) is the Co 2p high-resolution spectrum; (d) is the O 1s high-resolution spectrum; (e) is the P 2p high-resolution spectrum; (f) is the S 2p high-resolution spectrum; and (g) is the Re 4f high-resolution spectrum. This study systematically analyzed the surface elemental composition and chemical valence state of the (VP NSs (7%) + ReS2QDs (1%))@NiCo2O4 photocatalyst using X-ray photoelectron spectroscopy (XPS).

[0089] Figure 5 As shown in (b), the characteristic peaks of Ni 2p in NiCo2O4 correspond to two binding energies located at 874.01 eV (Ni2p1) and 856.50 eV (Ni 2p3); Figure 5 Image (c) shows that the two characteristic binding energies of Co 2p are located at 780.40 eV and 796.30 eV, respectively; from Figure 5 Two energy characteristic peaks of O 1s can be observed in (d), with binding energies of 530.78 eV and 532.60 eV, respectively; Figure 5As shown in (e), the orbital electron binding energies of the three energy characteristic peaks of phosphorus (P) are 132.50 eV (P 2p), 130.00 eV (P 2p1), and 129.50 eV (P 2p3), respectively. Figure 5 The sulfur (S) element in the middle (f) has two characteristic energy peaks in the S 2p orbital, with binding energies of 168.50 eV (S 2p1) and 169.70 eV (S 2p3), respectively. Figure 5 As shown in (g), the characteristic energy peak of Re 4f is located at 41.19 eV. In summary, the results of XPS full-spectrum scanning and high-resolution spectrum peak fitting jointly confirm that VP nanosheets (VP ​​NSs) and ReS2 quantum dots (ReS2QDs) have been successfully doped and loaded into the NiCo2O4 matrix.

[0090] 6. Photoelectrochemical behavior analysis:

[0091] To further clarify the role mechanism of VP NSs and ReS2QDs in the (VP NSs + ReS2QDs)@NiCo2O4 composite material, this invention investigates the mechanism through photogenerated electron-hole separation capability testing and photocurrent density-time response experiments. Electrochemical analysis was performed on all samples, including transient photocurrent response (IT) testing and electrochemical impedance spectroscopy (EIS) Nyquist plot analysis. The relevant results are as follows: Figure 6 As shown, Figure 6 In the figure, (a) transient photocurrent response of pure phase NiCo2O4, ReS2QDs (x%)@NiCo2O4 (x=0.5, 1, 1.5) and (VP NSs (y%) + ReS2QDs (1%))@NiCo2O4 (y=5, 7, 9) under light-on / off cycling conditions (once every 10 seconds); (b) electrochemical impedance spectroscopy of pure phase NiCo2O4, ReS2QDs (x%)@NiCo2O4 (x=0.5, 1, 1.5) and (VP NSs (y%) + ReS2QDs (1%))@NiCo2O4 (y=5, 7, 9) under visible light irradiation;

[0092] Figure 6Figure (a) shows the transient photocurrent (IT) response curves of all composite materials under visible light irradiation. Higher photocurrent density generally indicates better photocatalytic performance. Compared to pure-phase NiCo2O4, ReS2QDs(x%)@NiCo2O4 (x=0.5, 1, 1.5) and (VP NSs(y%) + ReS2QDs(1%))@NiCo2O4 (y=5, 7, 9) both exhibited stronger photocurrent signals. Among them, the photocurrent densities of pure-phase NiCo2O4 and ReS2QDs(x%)@NiCo2O4 were significantly lower than those of (VP NSs(y%) + ReS2QDs(1%))@NiCo2O4 (x=0.5, 1, 1.5; y=5, 7, 9), indicating that the former has relatively lower degradation efficiency. The reason for this phenomenon is that the interface region of (VP NSs(y%) + ReS2QDs(1%))@NiCo2O4 forms a special loading structure, which is more conducive to electron transport, thus enabling more efficient conversion of pollutants into harmless substances. The smaller the radius of the arc in the electrochemical impedance spectroscopy (EIS), the higher the interfacial charge mobility of the material and the lower the solid surface layer resistance. Figure 6 Figure (b) shows the impedance spectra of three composite materials under visible light irradiation: pure-phase NiCo2O4, ReS2QDs (x%)@NiCo2O4, and (VP NSs (y%) + ReS2QDs (1%))@NiCo2O4 (x=0.5, 1, 1.5; y=5, 7, 9). Figure 6 As shown in Figure (b), the impedance value of pure-phase NiCo2O4 is much greater than that of the two composite materials, ReS2QDs(x%)@NiCo2O4 and (VP NSs(y%) + ReS2QDs(1%))@NiCo2O4. Higher electron-hole pair separation and migration rates are observed in the electrochemical impedance spectroscopy (EIS) spectra. These results indicate that the light utilization and catalytic activity of both ReS2QDs(x%)@NiCo2O4 and (VP NSs(y%) + ReS2QDs(1%))@NiCo2O4 composite materials are superior to those of pure-phase NiCo2O4 (x = 0.5, 1, 1.5, y = 5, 7, 9). The VP NSs (7%) + ReS2QDs (1%) @ NiCo2O4 composite material exhibits the best photoelectric properties. The photoelectrochemical test results are in high agreement with the hydrogen production performance test data, which indirectly confirms that VP NSs and ReS2QDs loaded on the NiCo2O4 surface can serve as excellent electron acceptors, promoting electron migration and thus inhibiting electron-hole recombination.

[0093] 7. BET specific surface area and pore size analysis:

[0094] The nitrogen adsorption-desorption isotherm (BET), based on the theory proposed by Brunauer, Emmett, and Teller, is a classic method for determining the specific surface area of ​​solid materials. This invention systematically investigates the texture characteristics of four photocatalysts—pure-phase NiCo2O4, ReS2QDs(1%)@NiCo2O4, VPNSs(7%)@NiCo2O4, and (VP NSs(7%) + ReS2QDs(1%))@NiCo2O4—using nitrogen adsorption-desorption isotherms (BET) and pore size distribution curves. The final calculation results are shown in Table 1. Nitrogen adsorption-desorption tests were performed on the samples using a fully automated surface area and porosity analyzer (BET) at 77 K (liquid nitrogen temperature). The specific surface area of ​​spherical NiCo2O4 was 33.137 m² / g. In comparison, the specific surface area of ​​ReS2QDs (1%)@NiCo2O4 increased to 35.665 m² / g, and the specific surface area of ​​VP NSs (7%)@NiCo2O4 further increased to 42.443 m² / g. 2 / g; while the optimal composite material (VP NSs (7%) + ReS2QDs (1%))@NiCo2O4 has a specific surface area of ​​45.138 m². 2 / g. The results showed that the specific surface area and pore volume of the composite catalyst were significantly improved, which confirms that VP NSs and ReS2QDs have been successfully loaded onto the NiCo2O4 surface.

[0095] Figure 7The adsorption-desorption isotherms of different samples after calcination at 80℃ for 2 h are classified as Type III isotherms. In the low-pressure range (P / P0 = 0~0.1), the curve rises slowly, indicating low adsorption capacity. As the relative pressure increases, the pore filling capacity increases, and the number of hysteresis loops also increases, indicating a significant increase in adsorption capacity. In the low relative pressure region, the adsorption capacity is low, and the curve trend is flat, indicating weak interaction between the adsorbent and adsorbate. In the medium relative pressure region, the adsorption capacity gradually increases, and the curve shows an upward trend without a clear inflection point, indicating that the adsorption process is mainly driven by intermolecular forces of the adsorbate, forming multilayer adsorption. In the high relative pressure region, the adsorption capacity increases significantly, and the curve continues to climb, indicating that the adsorbate begins to fill the internal pores of the material, exhibiting mesoporous and macroporous filling characteristics. When the specific surface area is relatively constant, the pore size decreases with the increase of the number of pores. It is well known that photocatalysts with larger specific surface areas and pore volumes are more conducive to improving photocatalytic activity. This is because a larger specific surface area provides more active sites on the catalyst surface, which facilitates the adsorption of reactants and enhances light absorption efficiency. Therefore, increasing the specific surface area and pore volume has a positive effect on photocatalytic reactions. In addition, the experiment also found that pure phase NiCo2O4 has a structural collapse problem after nitrogen adsorption; while the structural stability of the (VP NSs (7%) + ReS2QDs (1%))@NiCo2O4 nanocomposite material after loading modification is significantly enhanced.

[0096] Table 1

[0097] sample <![CDATA[Specific surface area (m 2 / g)]]> <![CDATA[Pore volume (cm 3 / g)]]> Average pore size / nm <![CDATA[NiCo2O4]]> 33.137 0.16 22.6 <![CDATA[ReS2QDs (1%) @NiCo2O4]]> 35.665 0.17 22.0 <![CDATA[VP NSs (7%) @NiCo2O4]]> 42.443 0.19 20.3 <![CDATA[(VP NSs (7%) +ReS2QDs (1%)) @NiCo2O4]]> 45.138 0.20 18.9

[0098] 8. Evaluation of photocatalytic performance:

[0099] The photocatalytic performance of the samples was evaluated using a 20 mg·L⁻¹ Rhodamine B (Rh B) solution as the target pollutant. 20 mg of the nanocomposite material to be tested was weighed and added to 100 mL of a 20 mg·L⁻¹ solution at room temperature. -1 A suspension of RhB was prepared in an aqueous solution. This suspension was magnetically stirred in the dark for 30 min to establish an adsorption-desorption equilibrium system. A 300 W xenon lamp (equipped with a 420 nm cutoff filter) was used as the light source. Samples were taken at regular intervals during illumination, filtered through a 0.22 μm filter, and the concentration of RhB in the filtrate was determined using a TU-1810PC UV-Vis spectrophotometer at the characteristic absorption wavelength of 554 nm. The photocatalytic degradation efficiency was calculated using the formula C / C0×100% (where C is the RhB concentration after degradation and C0 is the initial concentration). (Instrument model: McMurray Tech ASAP 2020)

[0100] Photocatalytic degradation spectra of different nanocomposite materials, as follows Figure 8The degradation spectra shown include pure phase NiCo2O4, VP NSs (x%)@NiCo2O4 and (VP NSs (7%) + ReS2QDs (y%))@NiCo2O4 (y=0.5, 1, 1.5, 2) (x=1, 3, 5, 7, 9), as well as the degradation spectra of the blank control group. Figure 8 (a) Photocatalytic degradation curves of pure NiCo2O4, VP NSs (x%)@ NiCo2O4 (x=1, 3, 5, 7, 9) and blank control group; (b) Photocatalytic degradation curves of VP NSs (7%)@ NiCo2O4 and (VP NSs (7%) + ReS2QDs (y%))@ NiCo2O4 nanocomposite materials (y=0.5, 1, 1.5, 2); (c) Kinetic equation fitting diagram of the degradation curve corresponding to (b); (d) Cyclic stability test diagram of (VP NSs (7%) + ReS2QDs (1%))@ NiCo2O4 composite material;

[0101] Figure 8 No degradation was observed in the control group, indicating that the degradation process is closely related to light exposure. The photocatalytic activity of the material was evaluated by monitoring the degradation process of Rhodamine B (RhB) under visible light; the relevant results are as follows: Figure 8 As shown. The degradation curves of all Rhodamine B samples (with C / C0 as the ordinate and light exposure time as the abscissa) are as follows. Figure 8 As shown in (a) and (b). Figure 8The results in (a) and (b) show that all catalysts exhibit photocatalytic activity for the degradation of Rhodamine B. In (a), under 60 min of light irradiation, the photocatalytic degradation efficiency of Rhodamine B by each catalyst from low to high is as follows: pure-phase NiCo2O4 (52%) < VP NSs (1%)@NiCo2O4 (58%) < VP NSs (3%)@NiCo2O4 (60%) < VP NSs (5%)@NiCo2O4 (63%) < VP NSs (9%)@NiCo2O4 (72%) < VP NSs (7%)@NiCo2O4 (79%); in (b), the photocatalytic degradation efficiency of Rhodamine B by each catalyst from low to high is as follows: VP NSs (7%)@NiCo2O4 (79%) < (VP NSs (7%) + ReS2QDs (0.5%))@NiCo2O4 (81%) < (VP NSs (7%) + ReS2QDs (2%))@NiCo2O4 (84%) < (VP NSs (7%) + ReS2QDs (1.5%))@NiCo2O4 (88%). Among them, (VP NSs (7%) + ReS2QDs (1%))@NiCo2O4 has the best degradation effect, and the degradation rate is about 90.79% within 60 minutes of light irradiation. The pseudo-first-order kinetic model was used to plot ln(C / C0) against the light irradiation time to calculate the reaction rate constant (K), and the kinetic characteristics of the degradation reaction of Rhodamine B (Rh B) were determined. As Figure 8 shown in (c) in, the reaction rate constant K values of (VP NSs (7%) + ReS2QDs (y%))@NiCo2O4 (y = 0.5, 1, 1.5, 2) nanocomposites are 0.02166, 0.02277, 0.03167, 0.02934, 0.02482 min -1 . As Figure 8 shown in (c) in, the (VP NSs (7%) + ReS2QDs (1%))@NiCo2O4 composite photocatalyst exhibits the highest photocatalytic degradation rate. The stability of the composite photocatalyst with the best performance was evaluated by cyclic tests, and the results are as Figure 8 shown in (d) in: after five consecutive cyclic reactions, the photocatalytic activity of this composite material only decreased slightly, indicating its excellent stability and reusability.

[0102] 9. Free radical trapping experiment and carbon content test experiment:

[0103] The results of the free radical trapping experiment for Rh B degradation are as Figure 9 described, Figure 9In the figure, (a) shows the free radical capture experiment of Rhodamine B (Rh B) degradation: pure Rhodamine B solution, Rhodamine B solution + (VP NSs (7%) + ReS2QDs (1%)) @ NiCo2O4 catalyst Rh B system, Rhodamine B solution + (VP NSs (7%) + ReS2QDs (1%)) @ NiCo2O4 catalyst + benzoquinone (BQ) system, Rhodamine B solution + (VP NSs (7%) + ReS2QDs (1%)) @ NiCo2O4 catalyst + isopropanol (IPA) system; (b) shows the carbon (C) content determination: (A) Rh B blank control group under natural light, (B) carbon content change curve during dark adsorption, (C) carbon content change curve during photocatalytic degradation.

[0104] Figure 9 (a): Free radical capture experiment of RhB degradation. This figure analyzes the degradation law of RhB in different systems by plotting the ratio of residual pollutant concentration to initial concentration (C / C0) over time. It includes four curves:

[0105] Pure Rh B (black curve): Almost no degradation was observed, indicating that Rh B does not undergo self-degradation under given conditions.

[0106] RhB + (VP NSs (7%) + ReS2QDs (1%))@NiCo2O4 catalyst (red curve): The degradation rate reached 91.1% within 60 minutes, proving that the catalyst has a highly efficient promoting effect on the photocatalytic degradation of RhB.

[0107] Rh B+ catalyst + benzoquinone (BQ, blue curve): The degradation rate decreased to 64.1% within 60 minutes, indicating that superoxide radicals (O2) have reduced degradation. 2- (which can be cleared by BQ) participates in the Rh B degradation process.

[0108] Rhodamine B (Rh B) + catalyst + isopropanol (IPA, green curve): The degradation rate further decreased to 46% within 60 minutes, indicating that hydroxyl radicals (OH, which can be scavenged by IPA) also play a role in the degradation process.

[0109] In summary, this experiment confirms that in the (VP NSs (7%) + ReS2QDs (1%))@NiCo2O4 catalyst system, hydroxyl radicals (OH) and superoxide radicals (O) can effectively neutralize each other. 2- Both are key active species in the photocatalytic degradation of RhB, but the degradation of RhB is more dependent on O. 2- Free radicals.

[0110] Figure 9(b) Determination of carbon (C) content. This graph analyzes the behavioral characteristics of RhB at different stages by measuring changes in carbon content. The graph contains three curves:

[0111] (A) Blank control group of Rh B under natural light conditions: The carbon content did not change significantly, indicating that the carbon element in Rh B remained stable without external intervention.

[0112] (B) Carbon content curve under dark adsorption conditions: The carbon content changes slowly and tends to stabilize after 30 minutes, indicating that the adsorption process of Rh B under dark adsorption conditions has little effect on the carbon content and reaches adsorption equilibrium after 30 minutes.

[0113] (C) Carbon content curve during photocatalytic degradation: The carbon content decreased significantly by 84.4% within 60 minutes, confirming that the carbon element of Rh B was effectively decomposed during the photocatalytic process, further verifying the degradation efficiency of the photocatalytic system.

[0114] In summary, this experiment confirms from the perspective of carbon content that Rh B is decomposed through photocatalytic degradation.

[0115] 10. Photocatalytic hydrogen production performance:

[0116] The photocatalytic hydrogen production performance of the samples was evaluated using a fully automated online trace gas analysis system (Labsolar-6a) with a 300 W xenon lamp (PLS-SXE300+) as the light source. In a typical experiment, 20 mg of the prepared photocatalyst was added to 50 mL of an aqueous solution containing 5 mL of triethanolamine (sacrificial agent). The reaction system was evacuated to remove mixed air, and the system temperature was maintained at 279 K. The hydrogen produced was quantitatively detected by gas chromatography (GC-9790II).

[0117] A 300 W xenon lamp (Xe lamp) was used as a simulated solar source to mimic natural sunlight. In the photocatalytic hydrogen evolution test, 70 mg of pure-phase NiCo2O4, ReS2QDs (y%)@NiCo2O4 (y = 0.5, 1, 1.5), and (VPNSs (x%) + ReS2QDs (1%))@NiCo2O4 (x = 3, 5, 7, 9) samples were ultrasonically dispersed in a reaction solution consisting of 50 mL of ultrapure water and 200 mg of glucose (used as a sacrificial agent). Before the photoreaction began, dissolved oxygen in the aqueous solution was completely removed using a custom-designed photoreactor. Throughout the photocatalytic process, the system temperature was maintained at 6°C using a circulating condenser to ensure the reaction proceeded under isothermal conditions. Every hour, the volume of hydrogen (H2) produced was quantitatively analyzed using gas chromatography (GC) to obtain a curve showing the change in hydrogen production over time.

[0118] Experimental results are as follows Figure 10 As shown, Figure 10 In the figure, (a) the average hydrogen production rate of NiCo2O4 and VP NSs (x%) @ NiCo2O4 (x=5, 10, 15, 20, 25); (b) the average hydrogen production rate of VP NSs (20%) + ReS2QDs (y%) @ NiCo2O4 (y=0, 0.5, 1, 1.5); (c) the hourly hydrogen production of (VP NSs (20%) + ReS2QDs (1%)) @ NiCo2O4 after 5 photocatalytic hydrogen production cycles; (d) the light absorption curve and photon utilization efficiency graph of (VP NSs (20%) + ReS2QDs (1%)) @ NiCo2O4 composite material, where quantum efficiency (red curve) corresponds to the left axis and light absorption curve (blue curve) corresponds to the right axis.

[0119] Figure 10 (a) shows the average hydrogen evolution rate of pure-phase NiCo2O4 and ReS2QDs (y%)@NiCo2O4 nanocomposites. Notably, the hydrogen evolution rate of pure-phase NiCo2O4 is extremely low, only 13 μmol·g⁻¹. -1 ・h -1 However, studies have shown that even pure-phase NiCo2O4 can produce trace amounts of hydrogen, which can be attributed to its large specific surface area, providing abundant photocatalytic active sites and thus promoting the proton reduction reaction to some extent. For single-component modified (Pt) systems... Figure 10 [middle(a)] and the two-component synergistic system [Pt-(VP NSs (20%)+ReS2QDs (y%)@NiCo2O4] [ Figure 10 In [b], the introduction of rhenium disulfide (ReS2) resulted in an increase in hydrogen production rate (from 1100 μmol·g⁻¹). -1 ・h -1 Increased to 4362 μmol·g -1 ・h -1 This invention uses quantitative experiments to accurately measure performance, thereby eliminating the possibility that the performance improvement is due to accidental factors.

[0120] Figure 10Figure (b) shows that the introduction of Pt significantly improves hydrogen production efficiency and increases catalytic activity by nearly 4 times, highlighting the potential of Pt-based composite catalysts in efficient hydrogen evolution. The introduction of Pt into the "VP NSs (20%) + ReS2QDs (y%)" catalyst generally increases hydrogen production activity by 3-5 times (e.g., 700→2405, 890→3129, 1100→4362, 880→3320). The introduction of ReS2 (such as its inherent sulfur vacancies and the variable valence state of rhenium (Re)) promotes the separation and migration of photogenerated carriers. This kinetic optimization of the elementary reaction steps is the fundamental reason for the explosive growth in hydrogen production activity after Pt modification.

[0121] Figure 10 Figure (c) shows the hourly hydrogen production of (VP NSs (7%) + ReS2QDs (1%))@NiCo2O4 after 5 photocatalytic hydrogen production cycles. The almost completely overlapping and stable slope of the cycle curves in the figure indicate that the composite material has excellent cycling performance and structural stability. Furthermore, Figure 10 Figures (a) (hydrogen production versus time curve) and (b) (optical performance correlation curve) further confirm that both VP NSs and ReS2QDs can form tightly bonded heterojunctions with NiCo2O4. These heterojunctions not only improve charge separation efficiency but also significantly enhance the structural stability of NiCo2O4, as evidenced by the experimental phenomenon that "hydrogen production increases linearly over time without any significant decay." In a long-cycle reaction lasting up to 30 hours, the cumulative hydrogen production of both catalysts showed linear growth without decay (e.g., the cumulative hydrogen production of the Pt-based catalyst exceeded 25,000 μmol·g). -1 This fully demonstrates its structural stability and catalytic durability, providing crucial support for the practical application feasibility of this type of material.

[0122] Figure 10 In the middle (d) section, the light absorption characteristics and photoelectrochemical behavior of the (VP NSs (20%) + ReS2QDs (1%))@NiCo2O4 composite material were investigated by UV-Vis spectrophotometry and photocurrent response testing. UV-Vis spectroscopy showed that the composite material possesses a broad-spectrum light-harvesting capability in the visible light region; while the strong photocurrent response indicates excellent photogenerated charge separation efficiency. The synergistic optical effect of VP NSs, ReS2QDs, and NiCo2O4, by ensuring sufficient photon absorption, efficient charge generation, and rapid interfacial charge migration required for the proton reduction reaction, collectively endows the composite material with excellent photocatalytic hydrogen production performance. Figure 10The strong matching between the apparent quantum efficiency (AQY) curve and the light absorption spectrum in (d) directly correlates the "light absorption range (300~600 nm)" with the "photon-electron conversion efficiency (peak >12%)", explaining the kinetic origin of catalytic activity from the perspective of quantum efficiency.

[0123] Loading rhenium disulfide quantum dots (ReS2 QDs) onto the surface of NiCo2O4 significantly enhanced the hydrogen evolution activity of the material. Among the series of samples modified with VP nanosheets, VP NSs (20%)@NiCo2O4 exhibited the highest hydrogen evolution rate, reaching 700 μmol·g. -1 ・h -1 The hydrogen production rate is 46 times that of pure-phase nickel cobalt oxide. This significant increase in activity can be attributed to the multiple synergistic effects of ReS2QDs, including their excellent visible light absorption, high charge separation efficiency, and abundant proton adsorption and reduction active sites.

[0124] To further optimize photocatalytic performance, this invention prepared a (VP NSs (x%) + ReS2QDs (1%))@NiCo2O4 composite material by adjusting the loading ratio of rhenium disulfide quantum dots (ReS2QDs). Systematic analysis of the catalytic data showed that the hydrogen production rate of the material exhibited a volcanic-like trend with increasing ReS2QDs content. The hydrogen production rate of the Pt-(VP NSs (20%) + ReS2QDs (1%))@NiCo2O4 composite material reached 4362 μmol·g⁻¹. -1 ・h -1 The hydrogen production rate is 1.8 times that of Pt-VP NSs (20%)@NiCo2O4. This optimal doping ratio of VP NSs (20%) + ReS2QDs (1%) indicates that the rational combination of VP NSs, ReS2QDs and NiCo2O4 can accelerate interfacial electron migration in the photocatalytic process, thereby improving the kinetic efficiency of the proton reduction reaction.

[0125] 11. Photocatalytic mechanism:

[0126] Photocatalytic reactions on semiconductor materials mainly involve five processes: (i) absorption of photons by the semiconductor photocatalyst; (ii) photons excitation of semiconductor energy levels to generate electron-hole pairs; (iii) separation of electrons and holes in the semiconductor; (iv) migration of electrons and holes within the semiconductor; and (v) capture of electrons and holes by the reaction substrate. NiCo2O4 loaded with ReS2QDs and VP NSs can significantly enhance photocatalytic performance, making the above reactions easier to occur and accelerating the reaction rate.

[0127] The catalytic mechanism of the (VP NSs (7%) + ReS2QDs (1%))@NiCo2O4 composite material under visible light irradiation is as follows: Figure 11 As shown;

[0128] like Figure 11 As shown in (a), in the (VP NSs (7%) + ReS2QDs (1%))@NiCo2O4 composite structure, NiCo2O4, ReS2QDs, and VP NSs form a highly efficient heterojunction system, significantly improving the photocatalytic redox efficiency. The enhancement mechanism mainly relies on the following synergistic effects: First, bandgap modulation and charge separation: ReS2QDs conduction band electrons transfer to the NiCo2O4 valence band. This process enriches the NiCo2O4 conduction band with electrons of high reduction capacity, while the ReS2 valence band retains holes of high oxidation capacity, thus achieving effective spatial separation of photogenerated electron-hole pairs and significantly improving the system's redox capability. Second, built-in electric field and electron bridge: A built-in electric field is formed at the interface between VP NSs and NiCo2O4. This electric field drives directional charge migration, accelerating the separation of electron-hole pairs. Furthermore, the well-dispersed ReS2QDs act as a highly efficient electron "bridge," providing an optimized path for charge transport between composite materials and further reducing the carrier recombination probability. Third, vacancy-assisted catalysis: Oxygen vacancies (OVs) in NiCo2O4 can act as electron-capturing centers, effectively inhibiting electron-hole recombination; simultaneously, sulfur vacancies in ReS2QDs enhance the adsorption and activation of reactants such as O2 and H2O, promoting the growth of superoxide radicals (O2O2). 2- This process generates reactive oxygen species such as hydroxyl radicals (OH). Ultimately, these highly reactive free radicals can efficiently oxidize and degrade organic pollutants such as Rhodamine B (Rh B), completely mineralizing them into harmless substances such as water (H2O) and carbon dioxide (CO2).

[0129] like Figure 11As shown in (b), the hydrogen production mechanism of the (VP NSs (7%) + ReS2QDs (1%))@NiCo2O4 composite structure is as follows: First, quantum confinement effect and maximization of active sites: ReS2QDs exhibit a significant quantum confinement effect due to their extremely small size. This effect may change their band structure and further optimize hydrogen evolution activity. More importantly, the quantum dot morphology significantly increases the number of exposed edge active sites, providing abundant reaction sites for hydrogen production. Secondly, charge separation and migration are accelerated: the synergistic effect of the heterojunction (NiCo2O4 / VP NSs) and the co-catalyst modification (ReS2QDs) provides multiple high-speed channels for the separation and directional migration of photogenerated electron-hole pairs (as shown in the electron and hole diagram), greatly suppressing recombination probability and extending electron lifetime, which is the core of the efficiency improvement. Finally, stability is enhanced: ReS2QDs are firmly anchored on the NiCo2O4 substrate and stabilized by VP NSs, which can effectively prevent the aggregation and shedding of nanoparticles during the reaction, thereby improving the hydrogen production cycle stability of the catalyst.

[0130] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for preparing a nanocomposite material, characterized in that, The preparation method includes the following steps: (a) Cobalt chloride hexahydrate, nickel chloride hexahydrate and urea were dissolved in deionized water and heated to react. After solid-liquid separation and drying, NiCo2O4 solid powder was obtained. (b) Grind the purple phosphorus, add it to anhydrous ethanol and sonicate it under ice bath conditions. Then centrifuge at 4500~5500 rpm, collect the supernatant, then centrifuge at 12000~14000 rpm, collect the precipitate, dry it, and resuspend it to obtain a dispersion of purple phosphorus nanosheets. (c) Rhenium disulfide nanoparticles were added to pyrrolidone and subjected to ultrasonic disruption, followed by centrifugation. The supernatant was collected to obtain a rhenium disulfide quantum dot dispersion. (d) NiCo2O4 solid powder was added to anhydrous ethanol and stirred until homogeneous. Then, purple phosphorus nanosheet dispersion and rhenium disulfide quantum dot dispersion were added sequentially under stirring conditions. The mixture was then stirred for a period of time under light-proof ice bath conditions and then freeze-dried to obtain the nanocomposite material.

2. The preparation method according to claim 1, characterized in that, In step (a), the mass ratio of cobalt chloride hexahydrate, nickel chloride hexahydrate, and urea is (1.8~2.2):1:(3.5~4).

3. The preparation method according to claim 1, characterized in that, In step (a), the heating reaction temperature is 95~105℃ and the time is 6~10h.

4. The preparation method according to claim 1, characterized in that, In step (b), the ultrasonic power is 150~250W, the processing time is 10~15h, and the centrifugation time is 12~20min.

5. The preparation method according to claim 1, characterized in that, In step (c), the ultrasonic power is 60~80W, the treatment time is 6~10h, the centrifugation speed is 5000~7000rpm, and the time is 12~18min.

6. The preparation method according to claim 1, characterized in that, In step (d), the mass percentage of purple phosphorus nanosheets in the nanocomposite material is 1%~25%, and the mass percentage of rhenium disulfide quantum dots is 0.5%~2%; stirring is continued for 3~5 hours.

7. The nanocomposite material prepared by any one of claims 1 to 6.

8. The application of the nanocomposite material prepared by any one of claims 1 to 6 in the photocatalytic degradation of organic matter.

9. The application of the nanocomposite material prepared by any one of claims 1 to 6 in wastewater treatment.

10. The application of the nanocomposite material prepared by any one of claims 1 to 6 in photocatalytic hydrogen production.

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