Co3O4 / Zn0. 5Cd0. 5S composite material, preparation method and application

Abstract

The invention belongs to the technical field of photocatalysis, and particularly relates to a Co3O4 / Zn0. 5Cd0. 5S composite material as well as a preparation method and application thereof. The Co3O4 / Zn0. 5Cd0. 5S composite photocatalyst is successfully prepared by adopting an in-situ photodeposition method, the performance of Zn0. 5Cd0. 5S photo-reforming PLA plastic is doubled through successful loading of Co3O4, and the excellent photo-reforming performance of the PLA plastic is shown. Co3O4 with excellent oxidation capacity is introduced, so that rapid separation of photo-induced electrons and holes in the semiconductor photocatalyst is promoted, the photo-induced electrons are enriched on Zn0. 5Cd0. 5S, meanwhile, the photo-induced holes are enriched on Co3O4, and surface oxidation-reduction reaction is facilitated. The research result has practical significance on the design of a redox photocatalyst and the production of fuels and chemicals through plastic reforming.

Description

Technical Field

[0001] This invention belongs to the field of photocatalysis technology, specifically relating to a Co3O4 / Zn 0.5 Cd 0.5 S composite materials, preparation methods and applications. Background Technology

[0002] Polylactic acid (PLA), as a biodegradable plastic, is widely used in many fields such as disposable products and packaging materials. However, the natural degradation process of PLA usually requires specific conditions and a long time, making its degradation problem in the environment increasingly prominent. Therefore, the recycling and reuse of waste PLA plastics is a complex and urgent problem to be solved. In the context of photo-reforming technology, designing efficient photocatalysts to achieve highly selective conversion of plastics and synergistic hydrogen production is particularly important. However, the key scientific problem in the photo-reforming reaction of plastics is how to improve the activity and selectivity of photocatalysts to achieve efficient plastic conversion. This involves multiple aspects such as the light absorption performance of photocatalysts, the separation efficiency of photogenerated carriers, and surface reactivity.

[0003] To improve the efficiency of photocatalytic plastic reforming reactions, traditional photocatalysts such as titanium dioxide (TiO2) and graphitic carbon nitride (g-C3N4) have been extensively studied in the field of photocatalysis. While these materials exhibit certain photocatalytic activity, they still have some shortcomings in processing waste plastics. First, these traditional photocatalysts have a narrow light absorption range, mainly concentrated in the ultraviolet region, which limits the effective utilization of solar energy. Second, the separation efficiency of photogenerated carriers is low, leading to a large number of photogenerated electrons and holes recombinating rapidly during the photocatalytic process, unable to participate in subsequent catalytic reactions, thus reducing photocatalytic efficiency. Furthermore, the number of reactive sites on the catalyst surface is limited, making it difficult to meet the complex chemical reaction requirements in plastic reforming reactions. To overcome these shortcomings, researchers have attempted to improve the performance of photocatalysts through composite strategies. For example, loading metal nanoparticles onto the surface of semiconductor photocatalysts can enhance light absorption and promote charge transfer. However, these composite materials often face problems such as complex processes, high costs, and insufficient stability during preparation, limiting their large-scale application. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings and deficiencies of the existing technology and to provide a Co3O4 / Zn 0.5 Cd 0.5 S composite materials, preparation methods and applications.

[0005] The technical solution adopted in this invention is as follows: a Co3O4 / Zn 0.5 Cd 0.5S composite material, which contains Co3O4 and Zn 0.5 Cd 0.5 S nanoparticles, wherein the Co3O4 is loaded with Zn 0.5 Cd 0.5 S nanoparticle surface.

[0006] Co3O4 / Zn as described above 0.5 Cd 0.5 The preparation method of S composite material includes the following steps: Zn 0.5 Cd 0.5 S nanoparticles and an aqueous solution containing cobalt salt were mixed and dispersed, and then reacted under visible light irradiation to obtain Co3O4 / Zn. 0.5 Cd 0.5 S composite material.

[0007] The Zn 0.5 Cd 0.5 S nanoparticles were synthesized via a one-step solvothermal method.

[0008] Cadmium acetate dihydrate and zinc acetate dihydrate were added to a mixed solution of H2O and DMF, stirred, and then thioacetamide was added to the solution. The mixture was reacted at 160-200℃ for 16-20 h. After the reaction was completed, the mixture was cooled to room temperature, the supernatant was discarded, and the precipitate was washed and dried to obtain Zn. 0.5 Cd 0.5 S nanoparticles.

[0009] Co3O4 / Zn as described above 0.5 Cd 0.5 Application of S composite material as a photocatalyst for photocatalytic plastic reforming reaction.

[0010] The plastic is polylactic acid.

[0011] A method for photo-reforming polylactic acid includes the following steps: (1) Pretreatment of PLA in an alkaline solution, stirring at 25-100℃ for 1-24h; (2) The pretreated solution and Zn 0.5 Cd 0.5 S nanoparticles and an aqueous solution containing cobalt salts are mixed and reacted under visible light irradiation.

[0012] In step (2), the reaction system temperature is maintained at 6 °C and the reaction is carried out under irradiation by a 300W Xe lamp.

[0013] The Zn 0.5 Cd 0.5 S nanoparticles were synthesized via a one-step solvothermal method.

[0014] The method for photo-reforming polylactic acid according to claim 9 is characterized by comprising the following steps: adding cadmium acetate dihydrate and zinc acetate dihydrate to a mixed solution of H2O and DMF, stirring, adding thioacetamide to the above solution, and reacting at 160-200℃ for 16-20 h; after the reaction is completed, cooling to room temperature, discarding the supernatant, and obtaining Zn by washing and drying the precipitate. 0.5 Cd 0.5 S nanoparticles.

[0015] The beneficial effects of this invention are as follows: This invention successfully prepared Co3O4 / Zn using in-situ photodeposition. 0.5 Cd 0.5 S composite photocatalyst, successful loading of Co3O4 enables Zn 0.5 Cd 0.5 S-light reforming doubled the properties of PLA plastic. Zn 0.5 Cd 0.5 The synergistic effect of S and Co3O4 can promote the effective separation of photogenerated electrons and holes, thereby improving its photocatalytic activity. Co3O4 / Zn 0.5 Cd 0.5 The S-composite photocatalyst exhibited excellent photoreforming properties in PLA plastic. The introduction of Co3O4, with its superior oxidizing power, promoted the rapid separation of photogenerated electrons and holes in the semiconductor photocatalyst, thereby enabling the photogenerated electrons to be generated in Zn. 0.5 Cd 0.5 S is enriched on S, while photogenerated holes are enriched on Co3O4, which is conducive to the surface redox reaction. Specifically, Zn is enriched on S. 0.5 Cd 0.5 Electrons on S participate in the proton reduction reaction to produce hydrogen gas, while holes enriched on Co3O4 are consumed by the pretreated PLA substrate and converted into organic acids. Optimized Co3O4 / Zn 0.5 Cd 0.5 S showed 34 mmol g within 4 hours. -1 h -1 The high hydrogen production rate also produced 3.2 mmol of pyruvate. During a continuous 12-hour reaction, 1.5% Co3O4 / Zn 0.5 Cd 0.5 The S photocatalyst also exhibited excellent stability. These findings have practical implications for the design of redox photocatalysts and the production of fuels and chemicals through plastic reforming. Attached Figure Description

[0016] 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, the drawings described below are only some embodiments of the present invention. For those skilled in the art, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0017] Figure 1 (a) is the SEM image of CZS, and (b) is the SEM image of 1.5% Co3O4 / CZS, (cd) is the TEM image, and (ej) is the elemental distribution map. (d) is the large image of the area within the red box in (c). Figure 2 In the image, (a) is an HR-TEM image of CZS; (b) is an HR-TEM image of 1.5% Co3O4 / CZS. Figure 3 In the image, (a) is the XRD pattern of the sample; (b) is the FT-IR spectrum of CZS, 1.5% Co3O4 / CZS and 5% Co3O4 / CZS; and (c) is the Raman spectrum of the sample. Figure 4 XPS spectra of (a) Zn 2p, (b) Cd 3d and (c) S 2p in CZS and 1.5% Co3O4 / CZS; XPS spectra of (d) O 1s and (e) Co 2p in 1.5% Co3O4 / CZS; Figure 5 In the figure, (a) hydrogen production rates of a series of CZS catalysts loaded with different Co3O4 contents after 4 hours of reaction; (b) 1H NMR spectra of pretreated PLA photo-reforming reaction after 4 hours (1.5% Co3O4 / CZS as catalyst). Figure 6 The hydrogen production of (a) 1.5% Co3O4 / CZS photocatalyst after 12 hours of continuous reaction and (b) 1H NMR spectrum of pretreated PLA photo-reforming reaction after 12 hours (1.5% Co3O4 / CZS as catalyst). Figure 7 13C NMR spectra of the liquid phase products after photoreforming of 1.5% Co3O4 / CZS, (a) after 4 hours of reaction, (b) after 12 hours of reaction; Figure 8 (a) UV-vis DRS spectra of CZS and 1.5% Co3O4 / CZS and (b) Tauc plots of (αhν)2 versus photon energy (hν) for CZS and 1.5% Co3O4 / CZS; Figure 9(a) Mott-Schottky plot of CZS, (b) TRPL spectrum of the sample, (c) transient photocurrent response and (d) electrochemical impedance (EIS) Nyquist plot; Figure 10 In the middle, (a) Co3O4 / Zn 0.5 Cd 0.5 (a) Photoreforming mechanism of S; (b) Possible oxidation reaction pathways for photoreforming of lactic acid. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0019] Example 1; (1) Zn was synthesized by a one-step solvothermal method 0.5 Cd 0.5 S (denoted as CZS). The specific process is as follows: 10 mmol of cadmium acetate dihydrate and 10 mmol of zinc acetate dihydrate are added to a mixed solution of 40 mL H2O and 20 mL DMF. After stirring for 30 min, 25 mmol of thioacetamide (TAA) is added to the above solution. Finally, the mixture is transferred to a 100 mL Teflon-lined steel high-pressure reactor and heated at 180 °C for 18 hours. During this process, the hydrolysis of TAA leads to the generation of negatively charged S ions, which then react with Cd in the solution. 2+ and Zn 2+ Metal ions react to form Zn0.5Cd0.5S nanoparticles. After the reaction is complete, the mixture is cooled to room temperature, the supernatant is discarded, and the bright yellow precipitate at the bottom of the reactor is washed sequentially with ultrapure water and ethanol, followed by centrifugation. Finally, it is dried in an oven at 60 °C for 12 hours.

[0020] (2) PLA pretreatment: PLA plastic was placed in an alkaline solution with a concentration of 5 M and then heated at 80 °C for 12 hours. Under the combined action of the alkaline solution and heating, the long chain structure of PLA gradually hydrolyzed, and over time, the long chain broke into small molecule lactic acid monomers. To determine the hydrolysis rate of PLA, proton nuclear magnetic resonance spectroscopy (NMR) was used. 1 Quantitative analysis was performed using ¹H NMR. Using 5 mg of maleic acid standard as an internal standard, the hydrolysis rate of PLA was calculated to be 84.4%.

[0021] (3) Co3O4 / Zn was prepared by in-situ photodeposition. 0.5 Cd 0.5 S. Before the experimental reaction, 20 mg of Zn was added. 0.5 Cd 0.5S was ultrasonically dispersed in 50 mL of PLA pretreated solution, and then a certain amount of 0.1 M cobalt nitrate hexahydrate was added. After ultrasonication for 30 minutes, it was transferred to a photocatalytic reaction vessel, and the reaction system temperature was maintained at 6 °C. Photodeposition reaction was carried out under irradiation with 300W Xelamp visible light. By adjusting the amount of cobalt nitrate used, Co3O4 / Zn with different Co3O4 contents were synthesized. 0.5 Cd 0.5 S composite material (the theoretical contents of Co3O4 in the composite material are 0.5 wt%, 1 wt%, 1.5 wt%, and 2 wt%, respectively).

[0022] The morphology of CZS and 1.5% Co3O4 / CZS composite photocatalysts was characterized using scanning electron microscopy. Figure 1 As shown in figure a, the particle size of CZS is mostly in the range of 150~180 nm. After photodeposition of Co3O4, the surface of CZS becomes rough, but the size of CZS particles does not change significantly, such as... Figure 1 As shown in b and c. In Figure 1 In diagram d, Co3O4 particles (marked by red circles in the image) can be seen dispersed on CZS. Energy-dispersive X-ray spectroscopy (EDS) was used to analyze the elemental composition of the 1.5% Co3O4 / CZS photocatalyst (e.g., ...). Figure 1 (As shown in ej). The figure shows that Zn, Cd, Co, S and O elements are uniformly dispersed, which also confirms the distribution of Co3O4 on CZS.

[0023] like Figure 2 As shown in figure a, according to the high-resolution transmission electron microscopy (HR-TEM) results of CZS, the spacing between adjacent lattice fringes is 0.33 nm, which corresponds to the (002) crystal plane of CZS. After loading Co3O4, as shown in figure a... Figure 2 As shown in b, the lattice fringe spacing of CZS remained unchanged. In 1.5% Co3O4 / CZS, the lattice spacing of CZS was 0.33 nm. Furthermore, Figure 2 The black dashed line in b clearly marks the interface between Co3O4 and CZS. Below the black dashed line, a lattice fringe spacing of 0.195 nm can be observed, corresponding to the (400) crystal plane of Co3O4. This observation further confirms the successful loading of Co3O4 onto the CZS surface.

[0024] The phase structure of the prepared CZS sample was characterized by X-ray diffraction. Figure 3a). In the XRD pattern of the pure CZS sample, 25.39°, 27.14°, 28.58°, 44.78°, and 53.12° correspond to the (100), (002), (101), (110), and (200) crystal planes, respectively. The XRD pattern of CZS is consistent with the PDF card of hexagonal CdS (JCPDS No. 41-1049), indicating that the prepared CZS is hexagonal. The difference is that, compared to ZnS, the diffraction peaks of CZS shift towards the lower angle side; this phenomenon is attributed to the larger Cd content. 2+ It enters the ZnS lattice and replaces the smaller Zn atoms. 2+ This leads to an increase in the lattice spacing of ZnS (hexagonal ZnS JCPDS No. 36-1450), which also indicates the successful synthesis of CZS solid solution.

[0025] The successful preparation of Co3O4 was further confirmed by observing the characteristic vibrations in Co3O4 using FT-IR spectroscopy. In the FT-IR spectrum ( Figure 3 b), 664 cm −1 The peak at that location corresponds to Co in Co3O4. 3+ The stretching vibration of -O, 570 cm −1 The peak at that location corresponds to Co. 2+ The stretching vibration of -O. The characteristic peaks of Co3O4 in 1.5% Co3O4 / CZS are not obvious, possibly due to the low Co3O4 loading. In 5% Co3O4 / CZS (using the same method to photodeposit 5 wt% Co3O4 onto CZS), clear infrared characteristic vibrational peaks of Co3O4 indicate successful Co3O4 preparation. Furthermore, Raman spectroscopy shows... Figure 3 Presented in c. 1LO, 2LO phonon, and multiphonon processes can be clearly observed. 314 cm −1 and 621 cm −1 The peaks at this point can be attributed to the 1LO and 2LO longitudinal phonon vibration modes of the CZS, respectively. 247 cm⁻¹ -1 The peak at 686 cm corresponds to the A1(TO) vibrational mode of the CZS. -1 The peak at that location corresponds to the A of Co3O4. 1g Symmetric stretching vibrations also confirmed the presence of Co3O4, a result consistent with infrared spectroscopy results. Figure 3 b).

[0026] XPS testing was used to study the elemental composition and surface chemical state of the samples, such as... Figure 4 As shown, Zn, Cd, O, Co, and S elements are all present in the XPS spectrum of 1.5% Co3O4 / CZS, which is consistent with the EDS mapping results. In the Zn 2p spectrum of CZS, Zn 2p...3 / 2 and Zn2p 1 / 2 Located at 1021.99 and 1044.83 eV respectively ( Figure 4 a). Cd 3d of Cd 3d 5 / 2 and Cd 3d 3 / 2 Located at 405.04 eV and 411.76 eV respectively ( Figure 4 b). For example Figure 4 As shown in c, in the S 2p spectrum of CZS, the orbital peaks at 161.62 eV and 162.60 eV correspond to S 2p. 3 / 2 and S 2p 1 / 2 .like Figure 4 As shown in Figure d, in the O 1s spectrum of 1.5% Co3O4 / CZS, the characteristic peaks at 529.89 eV, 532.15 eV, and 533.70 eV correspond to lattice oxygen, hydroxyl oxygen, and water adsorbed on the sample surface, respectively. In the Co 2p spectrum of 1.5% Co3O4 / CZS, the peaks with binding energies of 780.59 eV and 782.17 eV correspond to Co 1s and 2s, respectively. 3+ 2p 3 / 2 Orbit and Co 2+ 2p 3 / 2 track( Figure 4 e). Co 2+ -O and Co 3+ The presence of -O indicates that Co3O4 was successfully loaded onto CZS. Furthermore, as... Figure 4 As shown in a and b, compared to the pure CZS sample, the Zn 2p of 1.5% Co3O4 / CZS... 3 / 2 and Cd 3d 5 / 2 The atomic orbital binding energies (1021.91 eV and 404.96 eV, respectively) both underwent a slight negative shift, S 2p 3 / 2 A negative shift also occurred. This result indicates that after Co3O4 is loaded onto CZS, free electrons flow to CZS.

[0027] During the 4-hour photo-reforming reaction, experimental detection and analysis revealed that the hydrogen production rate of the sample increased with the increase of Co3O4 loading. Figure 5 As shown in Figure a, the hydrogen production rate was highest at 34.00 mmol g when the Co3O4 loading was 1.5 wt%. -1 h -1 However, when the Co3O4 loading reached 2 wt%, the hydrogen production rate decreased significantly, becoming 20.00 mmol g. -1 h -1 This phenomenon can be attributed to the presence of Co3O4 particles in Zn. 0.5 Cd0.5 The aggregation of S on the surface leads to a surface shielding effect, which in turn affects the light absorption capacity of the catalyst. In addition, excess Co3O4 may also become a recombination center, reducing the utilization efficiency of photogenerated carriers.

[0028] When the liquid products were analyzed using 1H NMR spectroscopy, it was found that the product obtained after 4 hours of reaction was mainly pyruvate, with no carbonate formation observed. This result... Figure 5 The results are clearly presented in b. The conversion rate of the substrate was calculated using 1H NMR spectroscopy. After 4 hours of photoreforming with 1.5% Co3O4 / CZS, the conversion rate of the PLA-pretreated substrate was 26.8%, while 3.2 mmol of pyruvate was produced. This experimental result reveals that when using Co3O4 / Zn... 0.5 Cd 0.5 When S is used as a catalyst in the photo-reforming reaction of polylactic acid, lactic acid is mainly converted into pyruvate through oxidation in the initial stage of the reaction, indicating that the catalyst has high selectivity for pyruvate in the initial stage of the reaction.

[0029] To investigate the stability of the prepared photocatalyst, the reaction time was extended to 12 hours. Experimental results showed (e.g.) Figure 6 As shown in Figure a), during the 12-hour photo-reforming process, the hydrogen production performance of the catalyst maintained a linear increasing trend. The hydrogen production rate of the 1.5% Co3O4 / CZS sample in the 12-hour photo-reforming reaction was 31.62 mmol g. -1 h -1 This demonstrates the excellent stability of the semiconductor photocatalyst. Furthermore, analysis of the products after 12 hours of photo-irradiation revealed the presence of acetate (e.g., ...). Figure 6 (As shown in b). This indicates that after extending the reaction to 12 hours, pyruvate underwent further oxidation, generating acetate.

[0030] Adopted 13 ¹³C NMR analysis of the liquid phase products confirmed the formation of carbonates in the products. Figure 7 As shown in a and b, the reaction times are compared at 4 hours and 12 hours. 13 The C10 NMR spectrum revealed characteristic peaks of carbonates after 12 hours of reaction. For lactic acid, the peroxidation product under light is carbon dioxide. However, because the solution in the reaction system is alkaline, the carbon dioxide reacts with hydroxide ions in the solution, converting to carbonate. This result indicates that further oxidation of the product occurred with prolonged reaction time.

[0031] To evaluate the optical properties of the samples, ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS) was used for analysis. The absorption edge of the pure CZS sample is located at approximately 530 nm, such as... Figure 8 As shown in Figure a, when Co3O4 nanoparticles are loaded onto the surface of CZS, the light absorption capacity of the 1.5% Co3O4 / CZS composite material in the visible light region is significantly enhanced compared to CZS, which is mainly attributed to the light absorption characteristics of Co3O4 nanoparticles. The band gap of the material was determined using the Kubelka-Munk method, and ( αhν ) 2 With photon energy ( hν Plot the graph for CZS (direct bandgap semiconductor), such as... Figure 8 As shown in b. By ( αhν ) 2 Extrapolating to zero, we obtain the band gap of CZS ( E g The band gap value is 2.42 eV. Normally, the Kubelka-Munk method cannot be directly used to calculate the band gap of composite materials. However, due to the low loading of Co3O4 nanoparticles in the Co3O4 / CZS composite material and the absorption of Co3O4 across the entire spectral range (300-800 nm), the band gap of 1.5% Co3O4 / CZS can be determined to be 2.42 eV. The band gap values ​​of CZS and 1.5% Co3O4 / CZS indicate that the Co3O4 loaded by photodeposition maintains the intrinsic band gap characteristics of the substrate material.

[0032] The band structure of CZS is determined by the Mott-Schottky curve, such as... Figure 9 As shown in figure a, the slope of the Mott-Schottky curve for CZS is positive, indicating that CZS exhibits n-type semiconductor characteristics. The flat-band potential of CZS can be determined from the Mott-Schottky curve. E fb The voltage is -0.68 V (vs Ag / AgCl, pH=7). The conduction band position of the n-type semiconductor ( E CB )Compare E fb The value is approximately negative 0.1 - 0.2 V; we take an empirical value of 0.2 V. According to the Nernst formula... E NHE = E Ag / AgCl + 0.059×PH + 0.197 V, the calculated CZS E CB (vs NHE) is -0.27 V. (By) E VB =E CB + E g , E g Depend on Figure 9 b is obtained as 2.42 eV, therefore the valence band potential of CZS is... E VB (vs NHE) is 2.15 V. Time-resolved fluorescence spectroscopy was used to analyze the lifetime of photogenerated carriers, such as... Figure 10 As shown in b, the fluorescence decay curves of CZS and 1.5% Co3O4 / CZS were fitted using the double exponential method. Calculations showed that the average fluorescence lifetime of CZS was 4.21 ns, while that of 1.5% Co3O4 / CZS was 5.82 ns. Longer fluorescence lifetimes are generally associated with longer carrier lifetimes in the photoexcited state. This result indicates that Co3O4 loading prolongs the lifetime of photogenerated carriers, which is beneficial for photocatalytic reactions. To further investigate the kinetics of photoinduced electron-hole pairs, transient photocurrent and electrochemical impedance spectroscopy were used in a detailed study. Figure 9 In c, 1.5% Co3O4 / CZS exhibited the highest photocurrent intensity, indicating that the separation efficiency of photogenerated carriers was significantly improved after Co3O4 deposition, thereby enhancing the generation of photocurrent. Furthermore, in Figure 9 Although 2% Co3O4 / CZS has the smallest arc radius in d, the separation efficiency of photogenerated carriers is the result of comprehensive analysis. Compared with the arc radius of CZS, the smaller arc radius of 1.5% Co3O4 / CZS also proves the improvement of the carrier migration process.

[0033] Co3O4 / Zn 0.5 Cd 0.5 The rational mechanism of S-light reforming of polylactic acid plastics is as follows: Figure 10 As shown in a, Co3O4 is used as a co-catalyst supported on Zn. 0.5 Cd 0.5 When S is on the surface, Co3O4 itself has catalytic activity, and reacts with Zn. 0.5 Cd 0.5 The S-composite exhibits a synergistic catalytic effect, significantly enhancing the Zn content. 0.5 Cd 0.5 The catalytic performance of S. Furthermore, Co3O4 photodeposition on Zn 0.5 Cd 0.5 When the S surface is exposed, electrons flow towards Zn. 0.5 Cd 0.5 S favors the hydrogen evolution reaction. Specifically, Zn 0.5 Cd 0.5Electrons on the CB in S reduce protons to produce hydrogen gas, while holes migrate to Co3O4 and participate in the oxidation reaction of the substrate. According to 1 H-NMR and 13 The C-NMR results suggest a process for the photoreforming reaction of PLA, such as... Figure 10 As shown in b, the oxidation products of lactic acid over time are, in order: pyruvate, acetic acid, and carbon dioxide. Based on this, the proposed pathway for PLA photoreforming is: lactic acid—pyruvate—acetic acid, with carbon dioxide as the product of the peroxidation reaction. Specifically, lactic acid is produced by the reaction of Co3O4 / Zn... 0.5 Cd 0.5 S catalyst selectively oxidizes to pyruvate, which is then further oxidized to acetic acid. In addition, some peroxidation product carbon dioxide is produced. Since the reaction system is alkaline, it exists in the form of carbonate. This work not only reveals the transformation pathway of pretreated PLA in the photo-reforming process, but also contributes to understanding the Co3O4 / Zn ratio. 0.5 Cd 0.5 The catalytic mechanism of S composite materials provides a basis for this study.

[0034] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A Co3O4 / Zn 0.5 Cd 0.5 S composite material, characterized in that: It contains Co3O4 and Zn 0.5 Cd 0.5 S nanoparticles, wherein the Co3O4 is loaded with Zn 0.5 Cd 0.5 S nanoparticle surface.

2. The Co3O4 / Zn as described in claim 1 0.5 Cd 0.5 The preparation method of S composite material is characterized by: Includes the following steps: Zn 0.5 Cd 0.5 S nanoparticles and an aqueous solution containing cobalt salt were mixed and dispersed, and then reacted under visible light irradiation to obtain Co3O4 / Zn. 0.5 Cd 0.5 S composite material.

3. The Co3O4 / Zn according to claim 2 0.5 Cd 0.5 The method for preparing S composite material is characterized by: The Zn 0.5 Cd 0.5 S nanoparticles were synthesized via a one-step solvothermal method.

4. The Co3O4 / Zn according to claim 3 0.5 Cd 0.5 The preparation method of S composite material is characterized by: Includes the following steps: Cadmium acetate dihydrate and zinc acetate dihydrate were added to a mixed solution of H2O and DMF, stirred, and then thioacetamide was added to the solution. The mixture was reacted at 160-200℃ for 16-20 h. After the reaction was completed, the mixture was cooled to room temperature, the supernatant was discarded, and the precipitate was washed and dried to obtain Zn. 0.5 Cd 0.5 S nanoparticles.

5. The Co3O4 / Zn as described in claim 1 0.5 Cd 0.5 Application of S composite material as a photocatalyst for photocatalytic plastic reforming reaction.

6. The application according to claim 5, characterized in that: The plastic is polylactic acid.

7. A method for photo-reforming polylactic acid, characterized in that... Includes the following steps: (1) Pretreatment of PLA in an alkaline solution, stirring at 25-100℃ for 1-24h; (2) The pretreated solution and Zn 0.5 Cd 0.5 S nanoparticles and an aqueous solution containing cobalt salts are mixed and reacted under visible light irradiation.

8. The method for photo-reforming polylactic acid according to claim 7, characterized in that: In step (2), the reaction system temperature is maintained at 6 °C and the reaction is carried out under irradiation by a 300W Xe lamp.

9. The method for photo-reforming polylactic acid according to claim 7, characterized in that: The Zn 0.5 Cd 0.5 S nanoparticles were synthesized via a one-step solvothermal method.

10. The method for photo-reforming polylactic acid according to claim 9, characterized in that... Includes the following steps: Cadmium acetate dihydrate and zinc acetate dihydrate were added to a mixed solution of H2O and DMF, stirred, and then thioacetamide was added to the solution. The mixture was reacted at 160-200℃ for 16-20 h. After the reaction was completed, the mixture was cooled to room temperature, the supernatant was discarded, and the precipitate was washed and dried to obtain Zn. 0.5 Cd 0.5 S nanoparticles.

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