Method for synthesizing noble metal-semiconductor heterostructure and photocatalytic system for reducing carbon dioxide comprising noble metal-semiconductor heterostructure

Abstract

The invention provides a method for synthesizing a noble metal-semiconductor heterostructure. The method comprises the following steps: S1, forming a noble metal seed; s2, mixing at least one metal precursor comprising a first metal and a first solvent to obtain a first solution comprising a first mixture; s3, heating the first solution in a first heating process to obtain a transparent solution; s4, mixing noble metal seeds, the transparent solution and a second solvent to obtain a second solution; and S5, heating the second solution by using a second heating process to grow a semiconductor structure containing the first metal on the noble metal seed so as to form a noble metal-semiconductor heterostructure therein. In addition, the invention also provides a photocatalytic system which comprises the noble metal-semiconductor heterostructure and is used for reducing carbon dioxide.

Description

Technical Field

[0001] The present invention generally relates to a method for synthesizing a heterostructure and a photocatalytic system. More specifically, the present invention relates to a method for synthesizing a noble metal-semiconductor heterostructure and a photocatalytic system comprising the synthesized noble metal-semiconductor heterostructure. Background Art

[0002] Heterostructures have attracted great attention due to their physicochemical properties arising from the morphology, interfaces and spatial arrangement of different components. Precise control of their nanoscale structure is crucial to understand the structure-property correlation and improve their performance in various applications such as electronics, catalysis, and solar energy conversion. So far, seed / template epitaxial growth is the most commonly used strategy to precisely control hierarchical heterostructures. The epitaxial growth of secondary materials on specific crystal planes of the seed / template allows them to grow epitaxially following the crystal direction of the seed / template. Combined with the exquisite control of the exposed crystal planes and crystal phases of the seed / template, this strategy has successfully prepared various hierarchical heterostructures with well-defined spatial structures, interfaces, crystal phases and editable components.

[0003] However, since epitaxial growth generally requires components to have similar structures (typically lattice mismatch less than 5%), the aforementioned seed / template epitaxial growth is mainly used to prepare heterostructures composed of components with similar lattice structures and / or chemical bonding, such as metal-metal, metal oxide-metal oxide, metal sulfide-metal sulfide, perovskite-perovskite and metal-organic framework (MOF)-MOF heterostructures. For heterostructures made of significantly different materials, where the two materials may have a large lattice mismatch (typically greater than 20%) and different chemical bonding, the epitaxial growth of noble metal-semiconductor heterostructures in particular remains a huge challenge. Generally, the preparation of noble metal-semiconductor heterostructures relies on traditional non-epitaxial strategies including chemical deposition, non-epitaxial growth promoted by cation exchange, phase transfer, photochemical deposition, chemical extraction, sol-gel method, etc. Although the obtained non-epitaxial noble metal-semiconductor heterostructures have shown great potential in many fields such as catalysis, photovoltaic devices and sensors, their widespread application is hindered by the difficulty in accurately defining their structure and interface. Therefore, a reliable epitaxial growth method is urgently needed to rationally construct hierarchical noble metal-semiconductor heterostructures with precisely controlled architectures and well-defined interfaces, especially to meet the needs of epitaxially growing semiconductors on noble metals with 4H phase or 4H / fcc phase or 2H / fcc phase. Summary of the invention

[0004] The object of the present invention is to provide a method for synthesizing a noble metal-semiconductor heterostructure and a photocatalytic system comprising the synthesized noble metal-semiconductor heterostructure in order to solve the above-mentioned technical problems.

[0005] According to a first aspect of the present invention, a method for synthesizing a noble metal-semiconductor heterostructure comprises the following steps S1 to S6. Step S1: forming a noble metal seed. Step S2: mixing at least one metal precursor comprising a first metal and a first solvent to obtain a first solution comprising a first mixture. Step S3: heating the first solution through a first heating process to obtain a transparent solution. Step S4: mixing the noble metal seed, the transparent solution and the second solvent to obtain a second solution. Step S5: heating the second solution through a second heating process to grow a semiconductor structure comprising the first metal on the noble metal seed, thereby forming a noble metal-semiconductor heterostructure.

[0006] According to one embodiment of the present invention, step S1 further includes steps S11 to S13. Step S11: Mixing the noble metal salt and the third solvent in the reaction chamber to obtain a third solution. Step S12: Heating the reaction chamber containing the third solution through a third heating process to form noble metal seeds in the third solution. Step S13: After the third heating process, collecting the noble metal seeds from the reaction chamber.

[0007] According to one embodiment of the present invention, in step S11, the noble metal salt includes a noble metal. In step S12, the third heating process includes subjecting the sealed reaction chamber to an oil bath treatment, treating the third solvent at a constant temperature for a certain period of time. In step S13, the reaction chamber with the third solution is centrifuged, and then the reaction chamber is cleaned with toluene multiple times to disperse the noble metal seeds therein.

[0008] According to one embodiment of the present invention, in step S12, the third solvent is selected from one of the following two combinations 1 and 2: combination 1: oleylamine, N-ethylcyclohexylamine, hexane and 1,2-dichloropropane; and combination 2: 4-tert-butylpyridine, oleylamine and heptane.

[0009] According to one embodiment of the present invention, the noble metal salt comprises HAuCl 4 ·xH 2 O.

[0010] According to one embodiment of the present invention, the noble metal seed has a 4H phase, a 4H / fcc phase or a 2H / fcc phase.

[0011] According to one embodiment of the present invention, the metal precursor includes at least one of a metal oxide containing a first metal and a metal halide containing a first metal.

[0012] According to one embodiment of the present invention, the metal halide includes chlorine (Cl).

[0013] According to one embodiment of the present invention, the first metal includes cadmium (Cd), nickel (Ni), iron (Fe), cobalt (Co) or platinum (Pt).

[0014] According to one embodiment of the present invention, the metal precursor includes a metal oleate containing a first metal.

[0015] According to one embodiment of the present invention, the mixing process of step S4 further includes mixing an inorganic salt having the same element as the semiconductor structure.

[0016] According to one embodiment of the present invention, the inorganic salt includes NH 4 SCN, while the same element in the inorganic salt and semiconductor structure is sulfur (S).

[0017] According to one embodiment of the present invention, the second solvent comprises oleylamine.

[0018] According to one embodiment of the present invention, the second heating process includes a sub-step of heating the second solution to a temperature range within a certain period of time.

[0019] According to one embodiment of the present invention, the second heating process includes a sub-step of heating the second solution at a constant heating rate within a certain period of time.

[0020] According to one embodiment of the present invention, the method further comprises step S6: collecting the noble metal-semiconductor heterostructure.

[0021] According to a second aspect of the present invention, there is provided a method for photocatalytic reduction of carbon dioxide (CO 2 ). The photocatalytic system comprises a container, a strong base substance, a photocatalyst and a light hole sacrificial reagent. The container contains water. The strong base substance is dissolved in the water in the container. The photocatalyst comprises the above-mentioned noble metal-semiconductor heterostructure, wherein the noble metal-semiconductor heterostructure comprises a noble metal seed and a semiconductor structure formed thereon. The photocatalyst is dissolved in the water in the container. The light hole sacrificial reagent is placed in the water in the container.

[0022] According to one embodiment of the present invention, the strong base substance includes potassium hydroxide (KOH). The noble metal-semiconductor heterostructure includes 4H Au-CdS, 4H Au-NiS, 4H Au-Pd 4S, 4H Au-Fe 3 O4, 4H Au-NiO, 4H Au-CoO, 4H / fcc Au-CdS or 2H / fcc Au-CdS. The photohole sacrificial agent includes polyethylene (PE), polyvinyl chloride (PVC) or polyethylene terephthalate (PET).

[0023] According to one embodiment of the present invention, the noble metal-semiconductor heterostructure is a 1D-1D heterostructure or a 2D-1D heterostructure.

[0024] According to the above, in an embodiment of the present invention, a novel wet chemical method is provided for precisely controlling the synthesis of a series of noble metal-semiconductor heterostructures with microstructures of epitaxial interfaces. By performing the steps of the above synthesis method, a series of epitaxial growth of semiconductor nanomaterials can be achieved on Au nanomaterials with 4H phase, 4H / fcc phase and 2H / fcc heterophase. The synthesized noble metal-semiconductor heterostructures can have a high quantum yield of plasmon-induced charge transfer, indicating the advantages of epitaxial noble metal-semiconductor interfaces. In addition, in some cases, the synthesized noble metal-semiconductor heterostructures can be used for the CO 2+ / - 2H / fcc heterostructures of the present invention. 2 The photocatalytic system of the reduction reaction. The synthesized noble metal-semiconductor heterostructure has excellent stability. The photocatalytic system of the invention can achieve a high carbon monoxide (CO) generation rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The embodiments of the present invention will be described in detail below with reference to the following drawings.

[0026] Figure 1a A flowchart showing the main steps of synthesizing a noble metal-semiconductor heterostructure according to a first embodiment of the present invention;

[0027] Figure 1b Shows Figure 1a Flow chart of the main sub-steps of step S1;

[0028] Figure 2a Scanning electron microscope (SEM) images of 4H Au-CdS noble metal-semiconductor heterostructures (nanomaterials) are shown;

[0029] Figure 2b High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images of one-dimensional (1D) multibranched structures of epitaxial 4H Au-CdS noble metal-semiconductor heterostructures are shown;

[0030] Figure 2cA magnified high-angle annular bright-field scanning transmission electron microscopy (HAABF-STEM) image of an epitaxial 4H Au-CdS noble metal-semiconductor heterostructure is shown;

[0031] Figure 2d Energy dispersive X-ray spectroscopy (EDS) mapping of epitaxial 4H Au-CdS noble metal-semiconductor heterostructure is shown;

[0032] Figure 3a Cs-HAADF-STEM image of an epitaxial 4H Au-CdS noble metal-semiconductor heterostructure is shown.

[0033] Figure 3b Fast Fourier transform (FFT) patterns of epitaxial 4H Au-CdS noble metal-semiconductor heterostructures are shown.

[0034] Figure 4a The X-ray diffraction (XRD) pattern of the epitaxial 4H Au-CdS noble metal-semiconductor heterostructure is shown.

[0035] Figure 4b High-resolution X-ray photoelectron spectroscopy (XPS) spectra of epitaxial 4H Au-CdS noble metal-semiconductor heterostructures are shown.

[0036] Figure 5a and Figure 5b SEM images of epitaxial 2H / fcc Au-CdS noble metal-semiconductor heterostructures (nanomaterials) at different magnifications are shown.

[0037] Figure 6a An ABF-STEM image of an epitaxial 2H / fcc Au-CdS noble metal-semiconductor heterostructure is shown.

[0038] Figure 6b Shown is the EDS mapping of an epitaxial 2H / fcc Au-CdS noble metal-semiconductor heterostructure.

[0039] Figure 7a Cs-HAADF-STEM image of an epitaxial 2H / fcc Au-CdS noble metal-semiconductor heterostructure is shown.

[0040] Figure 7b The FFT pattern of the epitaxial 2H / fcc Au-CdS noble metal-semiconductor heterostructure is shown.

[0041] Figure 8 Shown is the selected area electron diffraction (SAED) pattern of the epitaxial 2H / fcc Au-CdS metal-semiconductor heterostructure.

[0042] Figure 9aShows 4H Au-Ni 2 S 3 Transmission electron microscopy (TEM) image of a noble metal-semiconductor heterostructure.

[0043] Figure 9b Shows epitaxial 4H Au-Ni at different magnifications 2 S 3 High-resolution transmission electron microscopy (HRTEM) image of a noble metal-semiconductor heterostructure.

[0044] Fig.10a The epitaxial 4H Au-Ni 2 S 3 Cs-HAADF-STEM image of a noble metal-semiconductor heterostructure.

[0045] Fig.10b The epitaxial 4H Au-Ni 2 S 3 EDS mapping of noble metal-semiconductor heterostructures.

[0046] Fig.11a The epitaxial 4H Au-Ni 2 S 3 Cs-HAADF-STEM image of a noble metal-semiconductor heterostructure.

[0047] Fig.11b The epitaxial 4H Au-Ni 2 S 3 FFT patterns of noble metal-semiconductor heterostructures.

[0048] Fig.12 shows the epitaxial 4H Au-Pd 4 EDS mapping of noble metal-semiconductor heterostructures.

[0049] Fig.13a shows the epitaxial 4H Au-Pd 4 Cs-HAADF-STEM image of S metal-semiconductor heterostructure.

[0050] Fig.13b shows the epitaxial 4H Au-Pd 4 S FFT pattern of metal-semiconductor heterostructure.

[0051] Fig.14a shows the epitaxial 4H Au-Co 3 O 4 TEM image of a metal-semiconductor heterostructure.

[0052] Fig.14b and Fig.14cshows the epitaxial 4H Au-Co 3 O 4 HRTEM image of a metal-semiconductor heterostructure.

[0053] Fig.14d shows the epitaxial 4H Au-Co 3 O 4 FFT patterns of metal-semiconductor heterostructures.

[0054] Fig.15 shows the epitaxial 4H Au-Co 3 O 4 EDS line scan results of metal-semiconductor heterostructures.

[0055] Fig.16 shows the epitaxial 4H Au-Co 3 O 4 Raman spectroscopy of metal-semiconductor heterostructures.

[0056] Fig.17a shows the epitaxial 4H Au-Co 3 O 4 High-resolution XPS spectrum of Au 4f in metal-semiconductor heterostructures.

[0057] Fig.17b shows the epitaxial 4H Au-Co 3 O 4 High-resolution XPS spectrum of Co 2p in metal-semiconductor heterostructures.

[0058] Fig.17c shows the epitaxial 4H Au-Co 3 O 4 High-resolution XPS spectrum of O 1s in metal-semiconductor heterostructures.

[0059] Fig.18 shows the epitaxial 4H Au-Co 3 O 4 XRD patterns of metal-semiconductor heterostructures.

[0060] Fig.19a TEM image of epitaxial 4H Au-NiO metal-semiconductor heterostructure is shown.

[0061] Fig.19b HRTEM image of epitaxial 4H Au-NiO metal-semiconductor heterostructure is shown.

[0062] Fig.19c The FFT pattern of the epitaxial 4H Au-NiO metal-semiconductor heterostructure is shown.

[0063] Fig.20a The epitaxial 4H Au-Fe 3 O 4 TEM image of a metal-semiconductor heterostructure.

[0064] Fig.20b The epitaxial 4H Au-Fe 3 O 4 HRTEM image of metal-semiconductor heterostructure;

[0065] Fig.20c The epitaxial 4H Au-Fe 3 O 4 FFT patterns of metal-semiconductor heterostructures;

[0066] Fig.21a Displays Cd 3 P 2 Mid-infrared femtosecond transient absorption spectroscopy;

[0067] Figure 21b shows the mid-infrared femtosecond transient absorption spectrum of the CdS noble metal-semiconductor heterostructure;

[0068] Fig.21c The mid-infrared femtosecond transient absorption spectrum of the 4H Au-CdS noble metal-semiconductor heterostructure is shown.

[0069] Fig. 22 The synchronous photocatalytic CO catalysis using epitaxial 4H Au-CdS noble metal-semiconductor heterostructures was demonstrated. 2 Schematic diagram of reduction and microplastic modification;

[0070] Fig.23 We demonstrate simultaneous photocatalytic CO catalysis using epitaxial 4H Au-CdS noble metal-semiconductor heterostructures. 2 Gas chromatography (GC) spectra of products in reduction and microplastic modification reactions;

[0071] Fig.24a The photocatalytic CO conversion of epitaxial 4H Au-CdS noble metal-semiconductor heterostructures mixed with polyethylene (PE) plastics was demonstrated. 2 GC spectrum of the product during reduction;

[0072] Figure 24b The photocatalytic CO catalysis using a blank epitaxial 4H Au-CdS noble metal-semiconductor heterostructure was demonstrated. 2 GC spectrum of the product upon reduction.

[0073] Fig.24c The photocatalytic CO 2 GC spectrum of C1 product during reduction;

[0074] Fig.25a Simultaneous photocatalytic CO catalysis using different plastics and photocatalysts was demonstrated. 2 CO generation rate in reduction and microplastic modification reactions;

[0075] Fig.25b The epitaxial 4H Au-CdS noble metal-semiconductor heterostructure was shown to be effective in simultaneous photocatalytic CO 2 Stability testing in reduction and microplastic modification reactions;

[0076] Fig.26 We demonstrate simultaneous photocatalytic CO catalysis using epitaxial 4H Au-CdS noble metal-semiconductor heterostructures. 2 Nuclear magnetic resonance (NMR) spectra of liquid products in reduction and polyethylene (PE) microplastic modification reactions;

[0077] Fig. 27 The simultaneous photocatalytic CO 2 TEM image of epitaxial 4H Au-CdS noble metal-semiconductor heterostructure after reduction and plastic modification reactions;

[0078] Fig.28 The simultaneous photocatalytic CO 2 TEM image of epitaxial 4H Au-CdS noble metal-semiconductor heterostructure after reduction and plastic modification reactions.

[0079] Fig.29 Synchronous photocatalytic CO catalysis using epitaxial 4H Au-CdS 1D-1D noble metal-semiconductor heterostructures was demonstrated. 2 NMR spectra of liquid products in reduction and modification reactions of polyvinyl chloride (PVC) microplastics;

[0080] Fig.30 Synchronous photocatalytic CO catalysis using epitaxial 4H Au-CdS 1D-1D noble metal-semiconductor heterostructures was demonstrated. 2 NMR spectra of liquid products from reduction and modification reactions of polyethylene terephthalate (PET) microplastics. DETAILED DESCRIPTION

[0081] In the following description, methods for synthesizing noble metal-semiconductor heterostructures, photocatalytic systems, etc. are provided as preferred examples. For those of ordinary skill in the art, the present invention may be modified, including additions and / or substitutions, without departing from the scope and spirit of the present invention. Specific details may be omitted to avoid obscuring the invention; however, the present disclosure is intended to enable those of ordinary skill in the art to practice the teachings herein without undue experimentation.

[0082] Figure 1a A flow chart showing the main steps S1 to S6 of synthesizing a noble metal-semiconductor heterostructure according to a first embodiment of the present invention is shown. Figure 1b A flow chart showing the main sub-steps S11 to S13 in step S1 is shown.

[0083] refer to Figure 1a The method 100 provided is a wet chemical method for synthesizing a noble metal-semiconductor heterostructure. In step S1, the crystalline phase of the noble metal seed is selected from a 4H phase, a 4H / fcc phase, or a 2H / fcc phase. In an embodiment of the present invention, the material of the noble metal seed is a noble metal. The noble metal may be gold (Au), but the present invention is not limited thereto. On the other hand, in an embodiment of the present invention, the formed or synthesized noble metal-semiconductor heterostructure may have a 4H phase, a 4H / fcc phase, or a 2H / fcc phase. Reference Figure 1b , the step S1 of forming the noble metal seed also includes a plurality of main sub-steps S11 to S13. According to different crystal phases, the detailed manufacturing process of forming the noble metal seed with different phases is slightly different, which will be described in detail in the following paragraphs.

[0084] Synthesis process of noble metal seeds in 4H phase, 4H / fcc phase or 2H / fcc phase

[0085] Synthesis process of 4H phase gold (Au) seeds

[0086] refer to Figure 1b In step S11, a noble metal salt and a solvent are mixed in a reaction chamber to obtain a solution. In detail, in an embodiment, the noble metal salt may include a noble metal, such as gold (Au). Specifically, 100 mg of HAuCl is used in step S11. 4 ·3H 2 O as a noble metal salt, the composition of the solvent includes, for example, 20 ml of oleylamine (98%), 4 ml of N-ethylcyclohexylamine, 184 ml of hexane and 4 ml of 1,2-dichloropropane. It should be noted that the weight and type of the noble metal salt in step S11 and the volume and type of the composition of the solvent in step S11 can be appropriately changed according to the requirements of ordinary technicians. The reaction chamber can be, for example, a 500 ml glass bottle, but the present invention is not limited thereto.

[0087] Before proceeding to the next step, in order to prevent a negative influence caused by external air, the opening of the reaction chamber may be selectively sealed using a sealing member such as a polytetrafluoroethylene (PTFE) tape and a Bala film, but the present invention is not limited thereto.

[0088] refer to Figure 1bIn step S12, the reaction chamber containing the solution in step S11 is heated by a heating process to form a noble metal seed in the solution. The heating process in step S12 includes subjecting the sealed reaction chamber containing the solvent in step S11 to an oil bath treatment at a constant temperature for a given period of time. More specifically, the reaction chamber may be heated in an oil bath at 58° C. for 48 hours.

[0089] refer to Figure 1b In step S13, after the above-mentioned heating process in step S12, the precious metal seeds are collected from the reaction chamber. The collection process can be achieved by centrifuging in the reaction chamber containing the above-mentioned solution, for example, at a centrifugal rate of 4000 rpm for 3 minutes. Subsequently, the reaction chamber is cleaned multiple times (for example, three times) with toluene to disperse the precious metal seeds therein. Thus, after completing steps S11 to S13, 4H phase gold (Au) seeds can be formed.

[0090] Synthesis process of 4H / fcc phase gold (Au) seeds

[0091] The process of synthesizing the Au seeds with 4H / fcc phase is basically similar to the method of synthesizing the Au seeds with 4H phase, with the main difference being that the temperature of the heating process in step S12 is different, for example, 80°C. The detailed synthesis process of the Au seeds with 4H / fcc phase is described below. 100 mg of HAuCl 4 ·3H 2 O, 20 ml of oleylamine (98%), 4 ml of N-ethylcyclohexylamine, 184 ml of hexane and 4 ml of 1,2-dichloropropane were fully mixed in a 500 ml glass bottle. After sealing the glass bottle with polytetrafluoroethylene (PTFE) tape and parafilm, the glass bottle was heated in an oil bath preset at 80° C. for 48 hours. The product (i.e., Au seeds with 4H / fcc phase) was collected by centrifugation at 4000 rpm for 3 minutes, and then the collected product was washed three times with toluene, and finally the product was redispersed in 10 ml of toluene.

[0092] Synthesis process of 2H / fcc phase gold (Au) seeds

[0093] The process of synthesizing 2H / fcc phase Au seeds is basically similar to the method of synthesizing 4H / fcc phase Au seeds, with the main difference being that the solvent composition used in step S11 is different, for example, 30 ml of 4-tert-butylpyridine, 40 ml of oleylamine (98%) and 50 ml of heptane. The detailed synthesis process of 2H / fcc phase Au seeds is described below. 100 mg of HAuCl 4 ·3H 2O, 30 ml of 4-tert-butylpyridine, 40 ml of oleylamine (98%) and 50 ml of heptane were thoroughly mixed in a 500 ml glass bottle. Then, after sealing the glass bottle with polytetrafluoroethylene (PTFE) tape and parafilm, it was heated in an oil bath preset at 80° C. for 4 hours. The product (e.g., Au seeds of 2H / fcc phase) was collected by centrifugation at 5000 rpm for 3 minutes, and then the product was washed three times with toluene, and finally the product was redispersed in 10 ml of toluene.

[0094] Next, the other steps S2 to S6 of the synthesis method 100 will be described in the following paragraphs. Since the synthesis processes of different noble metal-semiconductor heterostructures are slightly different, the detailed synthesis process of a single noble metal-semiconductor heterojunction (e.g., 4H Au-CdS) will be described first in combination with steps S2 to S6.

[0095] Synthesis process of noble metal-semiconductor heterostructures

[0096] Synthesis process of noble metal-semiconductor heterostructure (4HAu-CdS)

[0097] review Figure 1a In step S2, at least one metal precursor, including a metal and a solvent, is mixed in a reactor chamber to obtain a solution containing a mixture. In detail, two types of metal precursors are used in step S2, namely metal oxides and metal halides. The metal halide may include chlorine (Cl). The metal in the metal precursor serves as a metal element of the semiconductor (e.g., CdS) to be formed. The metal precursor used may be, for example, 1 to 10 mg of CdO (metal oxide) and 1 to 5 mg of CdCl 2 (metal halide), they all contain metal cadmium (Cd). The components of the solvent in step S2 include, for example, 1 to 5 ml of oleic acid and 5 to 20 ml of 1-octadecene. It is worth noting that the weight and type of metal oxides and metal halides, as well as the type of solvent in step S2 can be appropriately changed according to the requirements of ordinary technicians. The reaction chamber can be, for example, a 50 ml three-necked flask, but the present invention is not limited thereto.

[0098] Before proceeding to the next step, a preheating and prestirring process can be selected, which can ensure uniform heating of the solution in step S2 and facilitate the complete chemical reaction of its components. In detail, the solution in a 50 ml three-necked flask is degassed at 80 to 120° C. for 5 to 30 minutes under strong magnetic stirring at 750 rpm.

[0099] In step S3, the solution obtained in step S2 is heated and stirred to obtain a transparent solution. Specifically, the solution in step S2 is heated and stirred at N 2The mixture was heated to 250°C to 280°C under a nitrogen atmosphere until the solution became transparent. The transparent solution was then cooled to 190°C to 260°C.

[0100] In step S4, a noble metal seed (e.g., the product collected from step S13, 4H Au seed), a transparent solution, and a solvent are mixed to obtain a solution. In detail, the mixing process of step S4 further mixes an inorganic salt having the same element (e.g., sulfur (S)) as the semiconductor structure to be formed (e.g., CdS), such as NH 4 SCN. The solvent used in step S4 may be oleylamine. More specifically, 1 to 6 mg of 4H Au seeds, a transparent solution, 3 to 12 mg of NH 4 A mixture of SCN and 1 to 2 ml of oleylamine.

[0101] In step S5, the solution (obtained from step S3) is heated by a heating process to grow a semiconductor structure (e.g., CdS) containing a metal (e.g., Cd in a metal precursor) on a noble metal seed (e.g., 4HAu seed), thereby forming a noble metal-semiconductor heterostructure (e.g., 4H Au-CdS) therein. The heating process in step S5 includes a sub-step of heating the solution within a certain time range. In detail, the solution is heated for 2 to 6 minutes within a temperature range of 190 to 260° C. by a heating device (e.g., a heating jacket). After step S5, the heating device is removed to stop the chemical reaction of synthesizing the noble metal-semiconductor heterostructure.

[0102] In step S6, the noble metal-semiconductor heterostructure is collected. More specifically, after the solution in step S5 is cooled to 50 to 100° C. by removing the heating device, 5 to 10 milliliters of toluene are injected into the reaction flask. Then, 5 to 10 milliliters of ethanol are added to the solution, and the product (i.e., the noble metal-semiconductor heterostructure) is collected by performing a centrifugation process on the reaction flask containing the solution obtained in step S5, for example, at a rate of 8000 revolutions per minute for 3 minutes. The obtained precipitate can be washed with a mixture of toluene and ethanol (volume ratio: 1 / 1) and then dispersed into 10 milliliters of toluene. At this point, the synthesis method of the noble metal-semiconductor heterostructure of the present invention has been completed.

[0103] Noble metal-semiconductor heterostructure (2H / f c c Synthesis process of Au-CdS

[0104] The synthesis method of 2H / fcc Au-CdS is basically similar to the synthesis method of 4H Au-CdS, with the main difference being that the noble metal seed (Au seed) used in step S4 has a 2H / fcc phase.

[0105] The detailed synthesis of the noble metal-semiconductor heterostructure (2H / fcc Au-CdS) is described below. 1 to 10 mg of CdO, 1 to 5 mg of CdCl 2 , 1 to 5 ml of oleic acid, and 5 to 20 ml of 1-octadecenylamine were added to a 50 ml three-necked flask and degassed at 80 to 120 °C for 5 to 30 min under strong magnetic stirring at 750 rpm. 2 Heat to 250 to 280 °C under a CO atmosphere until the solution becomes transparent. Cool the transparent solution to 190 to 260 °C and inject 1 to 6 mg of 2H / fcc Au seeds, 3 to 12 mg of NH 4 A mixture of SCN and 1 to 2 ml of oleic acid amine was added, and the temperature of the flask was maintained at 190 to 260°C for 2 to 6 minutes. Then, the heating jacket was removed to stop the reaction. After the solution was cooled to 50 to 100°C, 5 to 10 ml of toluene was injected into the reaction flask. Then, 5 to 10 ml of ethanol was added to the solution, and the product (i.e., 2H / fcc Au-CdS) was collected by centrifugation at a rate of 8000 rpm for 3 minutes. The resulting precipitate was washed with a mixture of toluene and ethanol (volume ratio: 1 / 1) and then dispersed in 10 ml of toluene.

[0106] Noble metal-semiconductor heterostructure (4H Au-Ni 2 S 3 )

[0107] 4H Au-Ni 2 S 3 The synthesis method of 4H Au-CdS is basically similar to that of 4H Au-CdS, with the main differences being: 1) the metal precursor used in step S2 includes only one type, for example, metal halide (e.g. NiCl 2 ). 2) The processing temperatures in some steps are slightly different.

[0108] The following describes 4H Au-Ni 2 S 3 Detailed synthesis process. 1 to 10 mg of NiCl 2 , 1 to 5 ml of oleylamine and 5 to 20 ml of 1-octadecenylamine were added to a 50 ml three-necked flask and degassed at 80 to 120 °C for 5 to 30 minutes under strong magnetic stirring at 750 rpm. 2 Heat to 160 to 180 °C under a CO atmosphere until the solution becomes transparent. Inject 1 to 6 mg of 4H Au seeds, 3 to 12 mg of NH 4SCN and 1 to 2 ml of oleylamine mixture, keep the flask temperature at 160 to 180 ° C for 2 to 6 minutes. Then, remove the heating mantle to stop the reaction. After the solution is cooled to 50 to 100 ° C, inject 5 to 10 ml of toluene into the reaction flask. Then, add 5 to 10 ml of ethanol to the solution and collect the product (e.g., 4H Au-Ni 2 S 3 The collected precipitate (product) was washed with a mixture of toluene and ethanol (volume ratio: 1 / 1) and then dispersed in 10 ml of toluene.

[0109] Noble metal-semiconductor heterostructures (4H Au-P d 4 S) Synthesis process

[0110] 4H Au-Pd 4 The synthesis method of S is basically similar to that of 4H Au-CdS, with the main differences being: 1) the metal precursor used in step S2 only includes one type, such as metal halide (e.g. PdCl 2 ). 2) The processing temperature in some steps is slightly different from 4H Au-CdS.

[0111] The following describes 4H Au-Pd 4 Detailed synthesis of S. 2 , 1 to 5 ml of oleylamine and 5 to 20 ml of 1-octadecenylamine were added to a 50 ml three-necked flask and degassed at 80 to 120 °C for 5 to 30 minutes under strong magnetic stirring at 750 rpm. 2 Heat to 160 to 180 °C under a CO atmosphere until the solution becomes transparent. Inject 1 to 6 mg of 4H Au seeds, 3 to 12 mg of NH 4 SCN and 1 to 2 ml of oleylamine mixture, keep the flask temperature at 160 to 180 ° C for 2 to 6 minutes. Then remove the heating mantle to stop the reaction. After the solution is cooled to 50 to 100 ° C, inject 5 to 10 ml of toluene into the reaction flask. Then, add 5 to 10 ml of ethanol to the solution and collect the product (e.g., 4HAu-Pd 4 S). The collected precipitate (product) was washed with a mixture of toluene and ethanol (volume ratio: 1 / 1) and then dispersed in 10 ml of toluene.

[0112] Noble metal-semiconductor heterostructure (4H Au-Fe 3 O 4 )

[0113] 4H Au-Fe 3 O 4The synthesis method of is similar to that of 4H Au-CdS, with the main differences being: 1) the metal precursor used in step S2 includes metal oleate, such as iron oleate. 2) the volume of the solvent component used in step S2 is different from that of 4H Au-CdS. 3) the weight of the noble metal seed used is different from that of 4H Au-CdS. 4) 4H Au-Fe 3 O 4 The processing temperature of some steps in the synthesis process is different from that of 4H Au-CdS. 5) In step S4, the inorganic salt NH 4 SCN is not used. 6) The heating process of step S5 includes a sub-step with a constant heating rate, which lasts for a period of time.

[0114] The following describes 4H Au-Fe 3 O 4 Detailed synthesis process. 100 to 200 mg of iron oleate, 0.1 to 0.5 ml of oleic acid, 5 to 20 ml of 1-octadecylamine and 100 to 500 mg of octadecylamine were added to a 50 ml three-necked flask and degassed at 80 to 120 ° C for 5 to 30 minutes under strong magnetic stirring at 750 rpm. After all solid materials were dissolved, the reaction flask was heated to 150 to 200 ° C, and then 1 to 10 mg of 4H Au seeds and 0.5 to 1 ml of oleylamine mixture were quickly injected into the flask. After injection, the temperature was raised to 250 to 300 ° C at a rate of 5 ° C per minute and maintained for 1 to 2 hours. Finally, the heating mantle was removed to stop the reaction. When the solution cooled to 100 to 120 ° C, 3 to 5 ml of toluene and 3 to 5 ml of ethanol (volume ratio: 1 / 1) mixed solution was injected into the reaction flask. The final product (e.g., 4H Au-Fe) was collected by centrifugation at 7,000 rpm for 5 min. 3 O 4 The obtained precipitate was washed 3 to 5 times with a mixture of toluene and ethanol (volume ratio: 1 / 1), and then dispersed in 10 ml of toluene.

[0115] 4H Au-Co 3 O 4 The synthesis process of 4H Au-NiO is similar to that of 4H Au-Fe 3 O 4 The synthesis process of is similar, the main difference is that the metal oleate used is changed to cobalt oleate or nickel oleate.

[0116] It should be noted that the formed 4H Au-CdS, 4H Au-NiS, 4H Au-Pd 4 S, 4H Au-Fe 3 O 4, 4H Au-NiO, 4H Au-CoO and 4H / fcc Au-CdS are all 1D-1D noble metal-semiconductor heterostructures, while the formed 2H / fcc Au-CdS is a 2D-1D noble metal-semiconductor heterostructure.

[0117] refer to Figures 2a to 2d , the 4H Au-CdS metal-semiconductor heterostructures formed by the above synthesis method were characterized by high-resolution transmission electron microscopy (HRTEM), Cs high-angle annular dark-field scanning transmission electron microscopy (Cs-HAADF-STEM), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Figure 2a and 2b The 1D multi-branched structure of the epitaxial 4HAu-CdS metal-semiconductor heterostructure (nanoscale material) is shown. The length of the 4HAu seeds is about 1000 to 3000 nanometers, and the length of the CdS nanorods is about 20 to 25 nanometers. Figure 2c It shows that CdS nanorods grow vertically on 4H Au seeds, and the structure of 4H Au seeds can be nanowires. Figure 2d It is shown that Cd and S elements construct uniform branches on 4H Au nanowires. Figure 3a The abrupt interface between 4H Au seeds and CdS is shown. Figure 3b Aligned spots in the fast Fourier transform (FFT) pattern are shown and indicate that the CdS nanomaterials are epitaxially grown along the 4H Au seeds with an epitaxial relationship of 4H Au(110)||CdS(101) and 4H Au(004)||CdS(002).

[0118] refer to Figure 4a In the XRD pattern of the epitaxial 4H Au-CdS metal-semiconductor heterostructure, the peaks located at 24.9°, 26.5°, 28.2°, 36.6°, 43.7°, 47.8°, and 51.9° match well with the (100), (002), (101), (102), (110), (103), and (112) crystal planes of wurtzite CdS. It is noteworthy that peaks located at 36.2° and 42.1° are observed, which are characteristic peaks of 4H Au seeds, indicating that the 4H phase of Au is maintained after CdS growth. Figure 3b The high-resolution XPS spectrum of Pd 3d shows peaks at 87.6 and 84.0 eV, which can be attributed to the Au4f 5 / 2 and Au 4f 7 / 2 It can be seen that after the growth of CdS, Pd is not sulfided and remains in the metallic state.

[0119] refer to Figures 5a to 8The 2H / fcc Au-CdS metal-semiconductor heterostructures formed by the above synthesis method were characterized by HRTEM, Cs-HAADF-STEM, XPS and SEM. Figure 5a SEM images of epitaxial 2H / fcc Au-CdS metal-semiconductor heterostructures are shown, demonstrating that CdS nanorods grow vertically on 2H / fcc Au nanosheets. Figure 5b , the thickness of the epitaxial 2H / fcc Au-CdS noble metal-semiconductor heterostructure is about 30 nanometers. Figure 6b , Figure 6b Shows the homogeneous branches constructed by Cd and S elements on 2H / fcc Au nanosheets. Figure 7a , Figure 7a Shows the abrupt interface between 2H / fccAu nanosheets and CdS. Figure 7b , Figure 7b Aligned spots in the FFT pattern are shown, demonstrating the epitaxial growth of CdS on 2H / fcc Au nanosheets. Figure 8 , Figure 8 The SAED patterns in show the epitaxial relationship of 2H Au(110)||CdS(101) and the epitaxial relationship of 2H Au(10-11)||CdS(001).

[0120] Semiconductor Pd 4 S and Ni 2 S 3 It can be grown on 4H Au seeds with a core-shell structure. 2 S 3 For example, refer to Figures 9a to 10b , Ni and S elements build a homogeneous shell on 4HAu seeds (nanowires). Fig.11a , Fig.11a 4HAu and Ni 2 S 3 The mutation interface between Fig.11b , the aligned spots in the FFT pattern indicate that Ni 2 S 3 The shell layer is epitaxially grown on 4H Au seeds. Fig.12 As shown, Pd and S elements construct a homogeneous shell layer on 4H Au nanowires. Fig.13a , Fig.13a The 4H Au seeds and Ni 2 S 3 On the other hand, the mutation interface between Fig.13b , the aligned spots in the FFT pattern indicate that Pd 4 The S shell was epitaxially grown on 4H Au seeds.

[0121] Au oxides (e.g., Co 3 O 4 , Fe 3 O 4 and NiO) can also be grown epitaxially on Au (e.g. in 4H phase) as mentioned in the previous paragraph. 3 O 4 For example, refer to Fig.14a ,Co 3 O 4 Can be grown on 4H Au to form a core-shell structure. Fig.14b and 14c , Fig.14b and 14c The 4H Au seeds and Co 3 O 4 The mutation interface between Fig.14d , the aligned spots in the FFT pattern indicate that Co 3 O 4 The shell layer is epitaxially grown on 4H Au seeds. Fig.15 The EDS line scan results shown in Figure 2 demonstrate that Co and O elements construct a homogeneous shell on the 4H Au nanowires. Figures 16 to 18 , Raman Fig.16 ), XPS (Figure 17) and XRD ( Fig.18 ) spectrum confirmed that in Co 3 O 4 After growth Co 3 O 4 The presence of and the 4H phase of the 4H Au seeds can be maintained.

[0122] For 4H Au-NiO metal semiconductor heterostructures and 4H Au-Fe 3 O 4 Metal-semiconductor heterostructures, all of which have an epitaxial 1D-1D structure. Fig.19a , Fig.19a It was shown that NiO can be grown on 4H Au seeds. Fig.19b , Fig.19b The abrupt interface between the 4H Au seeds and NiO is shown. Fig.19c , Fig.19c The aligned spots in the displayed FFT patterns indicate the epitaxial growth of the NiO shell on the 4H Au seeds. Fig.20a , Fig.20a Display Fe 3 O 4 Can be grown on 4H Au seeds. Fig.20b , Fig.20b The 4H Au seeds and Fe3 O 4 The mutation interface between Fig.20c , Fig.20c The aligned spots in the displayed FFT pattern indicate the Fe 3 O 4 The shell layer was epitaxially grown on 4H Au seeds.

[0123] Subsequently, the quantum yield (QY) of the noble metal-semiconductor heterostructure synthesized in the present invention is measured, wherein the 4H Au-CdS noble metal-semiconductor heterostructure is taken as an example. In an embodiment of the present invention, the measurement of QY can be performed by a mid-infrared pump-probe transient absorption (TA) spectrometer. The specific measurement principle is described as follows.

[0124] QY Measurement of Plasmon-Induced Hot Electron Transfer in 4H Au-CdS Noble Metal-Semiconductor Heterostructures

[0125] The QY of the plasmon-induced hot electrons transferred from 4H Au to CdS under 600 nm excitation can be determined by the CdS conduction band (CB) electrons at about 3340 cm -1 The CB electrons in CdS produce a broad infrared absorption that can be attributed to transitions from 1∑ to higher energy levels (such as 1π). To determine the QY of plasma-induced hot electron transfer, the IR signal amplitude of each CB electron in CdS is quantified and expressed as S 0 Therefore, S 0 It can be calculated by the following equation (1). Where ΔA is the maximum signal amplitude obtained from the dynamics and N(CdS CB electrons) is the number of electrons in the conduction band of CdS, which can be determined from the number of photons absorbed by CdS (under 400 nm excitation, each photon generates one electron in the CB band of CdS). Therefore, N(CdS CB electrons) is equal to the pump photon flux in the pump / probe overlap region multiplied by the sample absorption Where hv is the photon energy.

[0126] The QY is calculated based on the number of hot electrons generated in Au-CdS by absorbed photons under 550 nm excitation, as shown in equation (2).

[0127] In equation (2), beam size (600 nm) and beam size (400 nm) represent the overlap area of ​​the pump and probe beams under 550 nm and 400 nm pump laser excitation, respectively. The ratio of these two ratios can be obtained by calculating the overlap area of ​​the pump and probe beams under the same conditions on the calibration sample (Cd3 P 2 The calibration sample is excited at two wavelengths and is expected to have the same QY in terms of producing CB electrons. Then, It can be described as follows:

[0128]

[0129] Therefore, the quantum yield of plasma-induced hot electrons is given by equation (4).

[0130]

[0131] Here, ΔS is defined as the following equation, i.e., ΔS = ΔA / (power). ΔS represents the quantity to be obtained from the transient IR measurement. In order to improve the measurement accuracy and check the linearity of the signal, ΔA as a function of excitation power was measured for all samples. The TA signal amplitude increases linearly with the excitation power. ΔS can be obtained from the slope of the fitted linear curve. The optical density (OD) of all samples was controlled between approximately 0.2 and 0.8. It should be noted that since the CdS nanorods were grown directly on 4HAu seeds, the diameter of the CdS nanorods in the control sample may be slightly different compared to the diameter of the nanorods in the heterostructure. This may affect the quantum yield because the optical properties of the nanorods depend on their size (absorption cross section); therefore, independently synthesized CdS nanorods were used to calculate the quantum yield of each sample.

[0132] Referring to FIG. 21 , the mid-infrared pump-probe TA spectroscopy measurement results reveal that in the 4H Au-CdS 1D-1D heterostructure, the plasma-induced charge transfer from 4H Au to CdS has a high quantum yield (about 2.64%). This result breaks the existing rule that only small plasma noble metals (<10 nanometers) can achieve high quantum yields. For example, in the CdS nanorods at the Au tip, when the diameter of the Au nanoparticles is greater than 6 nanometers, the quantum yield will be less than 1%. However, in the 4HAu-CdS noble metal-semiconductor heterostructure of the present invention, a higher quantum yield (about 2.64%) has been achieved, and the size of the Au is larger (for example, the size of the Au is about 1000 to 3000 nanometers), indicating the superiority and importance of the epitaxial interface of the noble metal-semiconductor heterostructure of the present invention.

[0133] As we all know, due to the huge consumption of fossil fuels, the atmospheric CO 2 The concentration of carbon dioxide is increasing, and the world is facing a serious energy and environmental crisis. Carbon neutrality has become the goal of the entire human society. 2 Conversion into fuel chemicals is considered to utilize CO 2The ideal strategy is to store solar energy in chemicals, which is also called artificial photosynthesis. However, artificial photosynthesis faces several problems. First, CO 2 The solubility in water is low, and excess H + The competitive hydrogen evolution reaction is promoted, which is thermodynamically and kinetically more efficient than CO 2 Reduction reaction has more advantages. Secondly, the conventional photocatalysts used in artificial photosynthesis have low quantum efficiency because the light-induced holes are difficult to consume, and usually require the addition of sacrificial agents, which greatly limits the practical application of artificial photosynthesis. Thirdly, the conventional photocatalysts have low stability because the holes induced in artificial photosynthesis may oxidize and cause self-corrosion.

[0134] Due to the effective separation of photoinduced electrons and holes in the epitaxial 4H Au-CdS 1D-1D heterostructure of the present invention, coupled with the superior CO 2 Therefore, the epitaxial 4H Au-CdS 1D-1D heterostructure of the present invention can be used as an efficient photocatalyst for photocatalytic CO 2 In the embodiment of the present invention, other noble metal-semiconductor heterostructures (e.g., 4H Au-NiS, 4H Au-Pd 4 S, 4H Au-Fe 3 O 4 , 4H Au-NiO, 4H Au-CoO, 4H / fcc Au-CdS or 2H / fcc Au-CdS) also exhibit excellent photoinduced electron and hole separation ability, so they can also be used as photocatalytic CO 2 In an embodiment of the present invention, a photocatalytic system comprising a noble metal-semiconductor heterostructure is also provided for reducing carbon dioxide (CO 2 The detailed structure of the photocatalytic system, including the 4H Au-CdS noble metal-semiconductor heterostructure and its effect, will be described as an example in the following paragraphs.

[0135] Specifically, the photocatalytic system includes a container, a strong base substance, a photocatalyst and a light hole sacrificial reagent. The container includes water. The strong base substance is dissolved in the water in the container, thereby forming a strong base solution in the container. The photocatalyst includes the above-mentioned noble metal-semiconductor heterostructure and is dissolved in the water in the container. The light hole sacrificial reagent is placed in the water in the container.

[0136] More specifically, the strong base substance may be, for example, potassium hydroxide (KOH), and the strong base solution may be an aqueous potassium hydroxide solution (i.e., a 10 M potassium hydroxide aqueous solution), which can greatly increase the CO2 Solubility in water. The material of the light hole sacrificial reagent can be, for example, microplastics. The material of the microplastic can be, for example, polyethylene (PE), polyvinyl chloride (PVC) or polyethylene terephthalate (PET). The function of the light hole sacrificial reagent is to reduce the negative impact of light-induced holes on the photocatalyst, thereby improving the photocatalytic CO 2 The quantum efficiency of the reduction reaction, such as Fig. 22 The detailed preparation process of the photocatalytic system of the present invention will be described as follows.

[0137] 10 mg of the 4H Au-CdS noble metal-semiconductor heterostructure of the present invention was dissolved in 5 ml of chloroform and 1 ml of N,N-dimethylformamide. Then, 1 ml of 1.0M solution of triethyl sodium tetrafluoroborate in methyl chloride was added to the 4H Au-CdS noble metal-semiconductor heterostructure under an argon atmosphere. Next, the formed solution was stirred for 1 hour, and the 4H Au-CdS noble metal-semiconductor heterostructure was collected by centrifugation at 4000 to 10000 revolutions per minute for 1 to 5 minutes. The collected product was washed 3 times with acetonitrile and dried under vacuum. Finally, the dried Au-CdS noble metal-semiconductor heterostructure was dispersed in 10 ml of 10M KOH solution.

[0138] Next, 10 mg of the 4H Au-CdS noble metal-semiconductor heterostructure was mixed with 10 mL of 10 M KOH solution and pumped with CO along with 100 mg of microplastics (e.g., PE). 2 To saturation. Place the above solution into a 80kPa CO 2 The quartz photocatalytic reactor is placed in a quartz photocatalytic reactor and stirred slightly, and the reactor is irradiated with a 300W Xe lamp (e.g., Microsolar 300, Perfect Light) equipped with a solar simulator filter. The light intensity is measured with a power meter (PM100D, THORLABS). The gas produced by the gas chromatograph (Agilent, 8890) with a thermal conductivity detector and a flame ionization detector is sampled regularly. The solution product is identified by a gas chromatograph mass spectrometer (GC, Agilent 7890A-5975C, equipped with a DB-Waxetr column).

[0139] refer to Fig.23 As shown in the gas chromatogram, the photocatalytic CO 2 In the reduction reaction, the gas product is pure CO, indicating that the competing hydrogen evolution reaction is greatly suppressed. The gas product is almost pure CO without any H 2 This solves the problem that the presence of excess H+ in water promotes competition (thermodynamically and kinetically more than CO2 It is found that adding photo-hole sacrificial reagents (such as microplastics) can efficiently consume light-induced holes and greatly improve the photocatalytic CO 2 For example, compared with Case 2, which uses a blank epitaxial 4H Au-CdS noble metal-semiconductor heterostructure instead of microplastics, the CO yield in Case 1 increased by more than 1000 times (e.g. Fig.24a and 24b shown).

[0140] Compared with Case 3 using blank CdS nanorods, Case 1 showed a significant improvement in photocatalytic CO 2 The reduction reaction showed higher selectivity. Specifically, the gas product of Case 1 was 100% CO, but the gas product of Case 3 was about 65% CO, 25% CH4 and 10% H 2 (like Fig.24c shown).

[0141] In other embodiments, the microplastic may be PVC or PET. Fig.25a and 25b , photocatalytic CO can also be increased in the case of PVC microplastics and PET microplastics 2 Quantum efficiency of reduction reaction. Fig.25b , using the photocatalytic system of the present invention to photocatalyze CO 2 During the reduction reaction, the epitaxial 4H Au-CdS noble metal-semiconductor heterostructure is very stable and can produce CO at a rate of 1.5 L / g per hour for more than 24 hours without any reduction, solving the self-corrosion problem of the photocatalyst.

[0142] At the same time, microplastics with photo-hole sacrificial reagents are used in photocatalytic CO 2 The reduction reaction will degrade the metal into liquid fuel (i.e., formic acid and acetic acid), which means that the synthetic noble metal-semiconductor heterostructure of the present invention can solve the problem of CO in the atmosphere. 2 and the problem of increasing microplastics. Fig.26 As shown, epitaxial 4H Au-CdS noble metal-semiconductor heterostructures were used for simultaneous photocatalytic CO 2 The NMR spectra of the liquid products of the reduction and PE microplastic reforming reactions showed signals of formic acid, acetic acid, and isopropanol, indicating that the carbon chains had been degraded.

[0143] refer to Fig.26, SEM images of PE microplastics after photocatalysis show the serious corrosion of PE microplastics after the reaction. The unique 1D-1D multi-branched structure of the epitaxial 4H Au-CdS 1D-1D heterostructure enables 4H Au-CdS to be firmly attached to PE microplastics, greatly increasing the photocatalytic efficiency.

[0144] refer to Fig. 27 , the HRTEM image of the epitaxial 4H Au-CdS noble metal-semiconductor heterostructure after photocatalysis shows that the 1D-1D multi-branched structure of 4H Au-CdS is maintained, proving the high stability of the 4H Au-CdS photocatalyst. Similarly, reference Fig.28 and 29 , when using PVC (see Fig.28 ) and PET (see Fig.29 ) of photocatalytic CO 2 The NMR spectrum of the reduced liquid product showed signals of short-chain organic matter, indicating that the microplastics had been degraded into liquid fuel.

[0145] The embodiments of the present disclosure provide a robust and novel wet chemical method for synthesizing noble metal-semiconductor heterostructures. By performing the steps of the above-mentioned synthesis method, epitaxial growth of semiconductor nanomaterials can be achieved on Au nanomaterials having 4H phase, 4H / fcc phase and 2H / fcc heterophase. The formed noble metal-semiconductor heterostructure has excellent stability and quantum efficiency, and is very suitable for use as a CO 2 Photocatalyst for reduction reactions.

[0146] For example, in some cases, the formed 4H Au-CdS noble metal-semiconductor heterostructure can be used for CO in the photocatalytic system of the present invention. 2 The photocatalytic reduction of CO was greatly improved by using a strong alkaline aqueous solution in the photocatalytic system. 2 In addition, due to the superior CO solubility of 4H Au in the 4H Au-CdS noble metal-semiconductor heterostructure 2 Reduction performance, competitive H 2 The gas product of the photocatalytic reaction is almost pure CO without any H 2 In addition, it was found that the addition of photohole sacrificial reagents (e.g., microplastics) could efficiently consume light-induced holes and greatly improve the photocatalytic CO 2 The quantum efficiency of the reduction reaction. For example, after adding polyethylene (PE) microplastics, the yield of CO increased by more than 1,000 times. At the same time, it was found that microplastics degraded into liquid fuels (i.e., formic acid and acetic acid), which means that the noble metal-semiconductor heterostructure of the present invention can simultaneously solve the problem of CO in the atmosphere. 2and microplastics. In some cases, the noble metal-semiconductor heterostructure of the present invention is very stable and can produce CO at a rate of 1.5 liters per gram per hour for more than 24 hours without any reduction. That is, the invention can simultaneously produce CO 2 photocatalytic conversion of microplastics into fuels (e.g. CO).

[0147] It should be noted that in the above examples, the noble metal-semiconductor heterostructure is applied in a photocatalytic system. In other embodiments, the noble metal-semiconductor heterostructure can also be used in other devices in other fields.

[0148] The embodiment was chosen and described in order to best explain the principles of the invention and the practical application, thereby enabling others skilled in the art to understand the invention for various embodiments and with various modifications as are suited to the particular use contemplated.

[0149] As used herein and not otherwise defined, the terms "substantially," "approximately," and "about" are used to describe and explain small variations. When used in connection with an event or circumstance, these terms can encompass situations where the event or circumstance occurs precisely, as well as situations where the event or circumstance occurs approximately. For example, when used in connection with a numerical value, these terms can encompass variations within a range of less than or equal to ±10% of the numerical value, for example, less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. The term "substantially coplanar" can mean that two surfaces are nearly in the same plane within microns, for example, within 40 μm, within 30 μm, within 20 μm, within 10 μm, or within 1 μm.

[0150] The singular terms "a", "an", and "the" used herein may include plural referents unless the context clearly indicates otherwise. In the description of certain embodiments, providing a component "on" another component may cover the case where the aforementioned component is directly on (e.g., with) the latter component (e.g., in physical contact with the latter component), as well as the case where one or more components are interposed between the aforementioned component and the latter component.

[0151] Although the present disclosure has described and illustrated specific embodiments, these descriptions and illustrations are not limiting. Those skilled in the art will appreciate that various changes may be made to accommodate specific circumstances, materials, compositions of matter, methods or process objectives, and that equivalents may be substituted without departing from the true spirit and scope of the present disclosure as defined in the appended claims. The drawings may not necessarily be drawn to scale. Due to manufacturing processes and tolerances, there may be differences between the renderings of the present disclosure and the actual device. Although the methods disclosed herein have been described as specific operations performed in a specific order, it should be understood that these operations may be combined, subdivided or reordered to form equivalent methods without departing from the teachings of the present disclosure. Therefore, unless expressly indicated, the order and grouping of operations described do not constitute limitations.

Claims

1. A method for synthesizing a noble metal-semiconductor heterostructure, comprising: Step S1: forming a noble metal seed; Step S2: mixing at least one metal precursor including a first metal and a first solvent to obtain a first solution containing a first mixture; Step S3: heating the first solution through a first heating process to obtain a transparent solution; Step S4: mixing the noble metal seed, the transparent solution and the second solvent to obtain a second solution; as well as Step S5: heating the second solution through a second heating process to grow a semiconductor structure containing the first metal on the noble metal seed, thereby forming a noble metal-semiconductor heterostructure.

2. The method according to claim 1, further comprising: Step S11: mixing the noble metal salt and the third solvent in the reaction chamber to obtain a third solution; Step S12: heating the reaction chamber containing the third solution through a third heating process, so that the noble metal seeds are formed in the third solution; as well as Step S13: After the third heating process, collecting the noble metal seeds from the reaction chamber.

3. The method according to claim 2, wherein: In step S11, the noble metal salt includes a noble metal; In step S12, the third heating process includes sealing the third solvent in the reaction chamber and then performing an oil bath treatment at a constant temperature for a certain period of time; as well as In step S13, the reaction chamber containing the third solution is centrifuged, and then the reaction chamber is cleaned with toluene for multiple times to disperse the noble metal seeds therein.

4. The method according to claim 3, wherein: In step S12, the third solvent is selected from the following two combinations 1 and 2: Combination 1: oleylamine, N-ethylcyclohexylamine, hexane, and 1,2-dichloropropane; and Combination 2: 4-tert-butylpyridine, oleylamine, and heptane.

5. The method according to claim 3, wherein: The noble metal salt includes HAuCl4·xH2O. The method according to claim 1 , wherein the noble metal seed has a 4H phase, a 4H / fcc phase, or a 2H / fcc phase. 7 . The method of claim 1 , wherein the metal precursor comprises at least one of a metal oxide containing a first metal and a metal halide containing a first metal. The method of claim 7 , wherein the metal halide comprises chlorine (Cl). 9 . The method of claim 1 , wherein the first metal comprises cadmium (Cd), nickel (Ni), iron (Fe), cobalt (Co), or platinum (Pt).

10. The method of claim 1, wherein the metal precursor comprises a metal oleate comprising the first metal. The method of claim 10 , wherein the first metal comprises iron (Fe), nickel (Ni), or cobalt (Co). 12 . The method according to claim 1 , wherein the mixing process of step S4 further comprises mixing an inorganic salt having the same element as the semiconductor structure.

13. The method of claim 1, wherein the inorganic salt comprises NH4SCN, and the same element of the inorganic salt and the semiconductor structure is sulfur (S).

14. The method of claim 1, wherein the second solvent comprises oleylamine.

15. The method according to claim 1, wherein the second heating process comprises a sub-step of heating the second solution to a temperature range within a certain time.

16. The method according to claim 1, wherein the second heating process comprises a sub-step of heating the second solution at a constant temperature increasing rate within a certain period of time. 17 . The method according to claim 1 , further comprising step S6 : collecting the noble metal-semiconductor heterostructure.

18. A photocatalytic system for reducing carbon dioxide comprising a noble metal-semiconductor heterostructure, comprising: a container containing water; a strong alkaline substance dissolved in the water in the container; a photocatalyst dissolved in water in the container, the photocatalyst comprising a noble metal-semiconductor heterostructure comprising a noble metal seed and a semiconductor structure formed thereon; and A light hole sacrificial reagent is placed in the water in the container.

19. The photocatalytic system according to claim 18, wherein The strong alkaline substance includes potassium hydroxide (KOH); The noble metal-semiconductor heterostructure includes 4H Au-CdS, 4H Au-NiS, 4H Au-Pd4S, 4H Au-Fe3O4, 4HAu-NiO, 4H Au-CoO, 4H / fcc Au-CdS or 2H / fcc Au-CdS; and The photohole sacrificial agent includes polyethylene (PE), polyvinyl chloride (PVC) or polyethylene terephthalate (PET).

20. The photocatalytic system of claim 18, wherein the noble metal-semiconductor heterostructure is a 1D-1D heterostructure or a 2D-1D heterostructure.

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