A chiral CuO / HgS heterojunction catalyst, its preparation method, and its application.

Abstract

This invention discloses a chiral CuO / HgS heterojunction catalyst, its preparation method, and its application, belonging to the field of inorganic chiral materials technology. The chiral CuO / HgS heterojunction includes D-CuO / D-HgS heterojunction, L-CuO / L-HgS heterojunction, D-CuO / L-HgS heterojunction, and L-CuO / D-HgS heterojunction. Its preparation method includes: (1) preparing chiral CuO powder using a liquid-phase synthesis method with chiral cysteine ​​and CuCl2; (2) obtaining chiral HgS crystal nuclei by reacting Hg(NO3)2 solution with chiral penicillamine and thioacetamide, and dispersing them in water to obtain chiral HgS seed colloids; (3) synthesizing chiral CuO / HgS heterojunctions using a seed-mediated epitaxial growth method. Using the prepared chiral material for photocatalytic CO2 reduction can yield high-value-added C2 and C3 products, achieving efficient energy utilization.

Description

Technical Field

[0001] This invention relates to the field of inorganic chiral materials technology, and in particular to a chiral CuO / HgS heterojunction, its preparation method and application, for photocatalytic reduction of CO2. Background Technology

[0002] Inorganic semiconductor photocatalytic reduction of CO2 is a green technology that uses sunlight to convert CO2 into high-value organic compounds such as CO and CH4 in the presence of a photocatalyst. This technology has attracted much attention due to its advantages such as economy, reproducibility, and safety. However, currently available photocatalysts suffer from the following problems: low visible light utilization, high carrier recombination rate, slow surface reaction kinetics, reduction products are mainly one-carbon products, and the yield and selectivity of catalytically reduced CO2 are low.

[0003] Chiral inorganic nanomaterials exhibit unique optical and catalytic properties, making their preparation not only of significant fundamental theoretical importance but also possessing immense potential application value. The literature Angew. Chem. Int. Ed. 2021, 60, 20036-20041 DOI:10.1002 / anie.202108142 (2021) reports the synthesis of a flower-like chiral metal oxide—Fe3O4—and its application in the photocatalytic reduction of CO2. This chiral Fe3O4 photocatalyst showed that the main product of CO2 reduction was CO, with a selectivity exceeding 85%, and its catalytic activity remained stable after five cycles, demonstrating excellent catalytic stability and durability. The literature Angew. Chem. Int. Ed. 2021, 60, 19024-19029 DOI: 10.1002 / anie.202105496 (2021) reported the synthesis of flower-like chiral BiOBr photocatalysts. Under visible light irradiation, the chiral BiOBr photocatalysts achieved highly efficient reduction of CO2 to CH4 with a product selectivity of 78%, which is nearly 3 times higher than that of non-chiral BiOBr catalysts.

[0004] Furthermore, single-component photocatalysts are limited by a single band gap, resulting in relatively fixed light utilization and carrier recombination rates. In the photocatalytic CO2 reduction reaction, they struggle to produce high-yield and high-value-added products, hindering further improvements in photocatalytic efficiency. In recent years, heterojunctions have been widely reported as an effective way to regulate electron transport between two materials. Among them, S-type heterojunctions, with their optimized band structure, exhibit unique photocatalytic advantages, simultaneously enhancing light-harvesting capabilities and improving charge separation performance. Summary of the Invention

[0005] To address the issues of low photocatalytic efficiency and low added value of single-component photocatalysts, this invention provides a chiral CuO / HgS heterojunction and applies it to the photocatalytic CO2 reduction reaction, aiming to improve photocatalysis and product added value.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a chiral CuO / HgS heterojunction, including a D-CuO / D-HgS heterojunction, an L-CuO / L-HgS heterojunction, a D-CuO / L-HgS heterojunction, and an L-CuO / D-HgS heterojunction.

[0007] Secondly, a method for preparing a chiral CuO / HgS heterojunction catalyst is provided, comprising the following steps: (1) Preparation of chiral CuO powder Chiral cysteine ​​was dissolved in water and sonicated. CuCl2 solution was added under high-speed stirring, and the pH was adjusted to 12 with NaOH solution. After heating and reaction, chiral CuO powder was obtained by centrifugation, washing and drying. (2) Preparation of chiral HgS seed colloid Hg(NO3)2 solution was mixed with chiral penicillamine solution, and NaOH solution was added first while stirring, followed by slow dropwise addition of thioacetamide solution. After the reaction was complete, the mixture was centrifuged and washed to obtain chiral HgS crystal nuclei, which were then dispersed in water to obtain chiral HgS seed colloids. (3) Preparation of chiral CuO / HgS heterojunction After adding water to the chiral HgS seed colloid, chiral CuO powder was added. Chiral penicillamine solution and NaOH solution were added sequentially under stirring. Then, Hg(NO3)2 solution and thioacetamide solution were slowly injected simultaneously using a syringe pump. After the reaction was completed, the mixture was centrifuged, washed, and dried to obtain a chiral CuO / HgS heterojunction.

[0008] Preferably, in step (1), the molar ratio of chiral cysteine ​​to CuCl2 is 0.5~1.5:1, the reaction temperature is 30~50℃, the time is 2~5h, the centrifugation speed is 5000~8000rpm, the time is 3~6min, and the washing medium is ultrapure water.

[0009] Preferably, in step (2), the molar ratio of Hg(NO3)2: chiral penicillamine: thioacetamide is 1:0.8~1:0.9~1.2, the thioacetamide solution is added uniformly over 3~6 min, the reaction temperature is 30~45℃, the reaction time is 10~20 h, the centrifugation speed is 5000~8000 rpm, the reaction time is 5~15 min, and the washing medium is isopropanol.

[0010] Preferably, in step (2), the concentration of chiral HgS seed colloid is 0.02~0.05 mol / L.

[0011] Preferably, in step (3), the volume molar ratio of chiral HgS seed colloid: CuO: chiral penicillamine: Hg(NO3)2: thioacetamide is 1L: 4~5mol: 1~3mol: 4~5mol: 4~6mol. Preferably, in step (3), Hg(NO3)2 and thioacetamide solution are injected at a constant rate within 4-8 hours. The reaction ends when the injection is completed. The reaction temperature is 35-45℃, the centrifugation speed is 5000-8000 rpm, and the time is 3-5 minutes.

[0012] In steps (2) and (3), the NaOH solution not only provides an alkaline environment but also acts as an OH group. - The source directly participates in the nucleation process of Cu(OH)2, while simultaneously regulating crystal growth kinetics, intermediate phase morphology, and the structural defects and crystallization characteristics of the final CuO.

[0013] Thirdly, an application of a chiral CuO / HgS heterojunction catalyst in photocatalytic CO2 reduction is provided.

[0014] Preferably, the resulting products include not only C2 products, but also C3 products in equivalent quantities.

[0015] Preferably, the C2 product is ethanol and the C3 product is acetone.

[0016] In the carbon dioxide reduction process, the coupling of C2 and C2 products via the dimerization of the primary reduction product CO is a crucial step in the synthesis of C2 products. The OCCO intermediate formed by CO dimerization is adsorbed onto the catalyst surface, forming chemisorption sites *OCCO, thereby initiating subsequent reactions. However, the OCCO intermediate will transition from the metastable triplet state OCCO (… 3 The OCCO transforms into an unstable singlet state (OCCO). The singlet OCCO will rapidly dissociate into two CO molecules, eventually terminating the CC coupling.

[0017] Chiral materials exhibit a unique chirality-induced spin selectivity (CISS) effect during electron transport, meaning that electrons undergo spin polarization during transport in a chiral medium. Chiral mesoporous inorganic materials can generate significant spin polarization through the CISS effect, promoting the formation of triplet OCCO (³OCCO) by adjusting their parallel electron spin alignment. Furthermore, the helical lattice distortion of the nanostructure can lower the reaction energy of *OCCO, thereby triggering C-C coupling and promoting subsequent *OCCO hydrogenation, which is beneficial for the formation of C2 products and thus significantly improves CO2 reduction efficiency.

[0018] Beneficial effects 1) The present invention performs chiral induction on the growth process of chiral CuO / HgS heterojunction. A chiral inducing agent is used to form a CuO / HgS heterojunction with a chiral structure through atomic-level arrangement. Furthermore, the chiral structure of the heterojunction can be retained even after the chiral inducing agent is removed. 2) The preparation method of the chiral CuO / HgS heterojunction of the present invention has the advantages of low cost, simple operation, small interference, accurate results and wide application; 3) The chiral CuO / HgS heterojunction of the present invention has high chiral optical activity, can be used as a catalyst for photocatalytic CO2 reduction reaction, and can improve product yield; 4) The chiral CuO / HgS heterojunction of the present invention photocatalytically reduces CO2 with a symmetrical structure to obtain high-value-added C2 and C3 products, including ethanol and acetone, thereby achieving efficient energy utilization.

[0019] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating the preparation process of the chiral CuO / HgS heterojunction of the present invention. Figure 2 Transmission electron microscopy (TEM) image and energy dispersive spectroscopy (EDS) scan of the chiral D-CuO / D-HgS heterojunction in Example 1; Figure 3 Transmission electron microscopy (TEM) image and energy dispersive spectroscopy (EDS) scan of the achiral A-CuO / A-HgS heterojunction in Comparative Example 1. Figure 4 The circular dichroisms are those of the CuO / HgS heterojunctions prepared in Examples 1-4 and Comparative Example 1. Figure 5 Band gap diagrams for CuO / HgS heterojunctions (a: A-CuO / HgO; b: D-CuO / D-HgS or L-CuO / L-HgS; c: D-CuO / L-HgS or L-CuO / D-HgS). Figure 6 Transient absorption spectra of CuO / HgS heterojunctions (e1, g1: D-CuO / D-HgS L-CP; e2, g2: D-CuO / D-HgS R-CP; f1, h1: D-CuO / L-HgS L-CP; f2, h2: D-CuO / L-HgS R-CP). Figure 7 The NMR spectrum of the photocatalytic CO2 reduction products of the chiral D-CuO / D-HgS heterojunction in Example 1 is shown. Figure 8Comparison of the content of photocatalytic CO2 reduction products of CuO / HgS heterojunctions prepared in Examples 1-4 and Comparative Example 1; Figure 9 Circular dichroisms of chiral CuO / HgS heterojunctions with different Cu / Hg ratios prepared in Examples 1-2 and Comparative Examples 2-3; Figure 10 The graph shows a comparison of product yields in the photocatalytic CO2 reduction reaction of chiral D-CuO / D-HgS heterojunctions with different Cu / Hg molar ratios prepared in Example 1 and Comparative Example 2. Detailed Implementation

[0021] The present invention will be further described below. It should be noted that this embodiment is based on the present technical solution and provides detailed implementation methods and specific operation processes, but the present invention is not limited to this embodiment.

[0022] Example 1 This embodiment provides a method for preparing a chiral D-CuO / D-HgS heterojunction, such as... Figure 1 As shown, it includes the following steps: (1) Preparation of D-CuO powder Dissolve 0.0136 g of D-cysteine ​​in 15.2 mL of ultrapure water. After sonication, add 1.6 mL of 0.25 M CuCl2 solution under high-speed stirring. Adjust the pH to 12 by slowly adding 1 M NaOH solution. Then stir the reaction at 40 °C for 3.5 hours. After that, centrifuge at 6000 rpm for 5 min and wash twice with ultrapure water. (2) Preparation of D-HgS crystal nuclei 70.0 mg Hg(NO3)2·H2O was mixed with 10.0 mL of deionized water in a 25 mL glass bottle. 2.0 mL of an aqueous solution containing 26.9 mg D-penicillamine was added. Then, under magnetic stirring, 0.6 mL of an aqueous solution containing 24.0 mg NaOH was added to the glass bottle. 2.0 mL of a 0.1 M thioacetamide solution was then slowly added dropwise at a rate of 0.4 mL / min. The mixed solution changed from colorless to dark brown. After stirring and reacting in a 38 °C water bath for 15 h, the mixture was collected by centrifugation at 6000 rpm for 10 min. The obtained product was D-HgS crystal nuclei, which were washed three times with isopropanol and dispersed in 5.0 mL of deionized water to obtain D-HgS seed colloids. (3) Preparation of D-HgS particles 50 μL of D-HgS seed colloidal solution and 5 mL of water were added to a three-necked round-bottom flask immersed in a 38℃ water bath. 18 mg of D-CuO powder was added. Under magnetic stirring, 1.0 mL of an aqueous solution containing 13.5 mg of D-penicillamine and 0.6 mL of an aqueous solution containing 24.0 mg of NaOH were added to the flask sequentially. Then, 6.0 mL of an aqueous solution containing 74.4 mg of Hg(NO3)2·H2O (mercury precursor solution) and 10 mL of an aqueous solution containing 19 mg of thioacetamide (sulfur precursor solution) were simultaneously injected into the flask using a syringe pump. The injection time was 4 h, and the reaction was carried out while being injected. An orange colloidal solution was obtained. The product was separated by centrifugation at 6000 rpm for 5 min, and a chiral D-CuO / D-HgS heterojunction with a Cu / Hg molar ratio of 1.04 was obtained.

[0023] Example 2 This embodiment provides a method for preparing a chiral D-CuO / L-HgS heterojunction. The difference from Example 1 is that the chiral molecules used are D-cysteine ​​and L-penicillamine, respectively. The amount of chiral CuO powder added in step (3) is 19 mg. The rest is the same as in Example 1, and a chiral D-CuO / L-HgS heterojunction with a Cu / Hg molar ratio of 1.10 is obtained.

[0024] Example 3 This embodiment provides a method for preparing a chiral L-CuO / L-HgS heterojunction. The difference from Example 1 is that the chiral molecules used are L-cysteine ​​and L-penicillamine, respectively. The rest is the same as in Example 1.

[0025] Example 4 This embodiment provides a method for preparing a chiral L-CuO / D-HgS heterojunction. The difference from Example 1 is that the chiral molecules used are L-cysteine ​​and D-penicillamine, respectively. The rest is the same as in Example 1.

[0026] Comparative Example 1 This comparative example provides a method for preparing a non-chiral A-CuO / A-HgS heterojunction, comprising the following steps: (1) Dissolve 3.24 mmol Hg(NO3)2·H2O, 5.32 mmol thioacetamide and 0.6 g PEG-2000 in 50 mL of deionized water and stir continuously at room temperature for 30 min. Then transfer to a polytetrafluoroethylene-lined autoclave and heat at 180 °C for 10 h. Then cool naturally to room temperature, centrifuge the obtained product, wash it several times with deionized water and ethanol, and dry it at 60 °C for 24 h to obtain achiral A-HgS particles. (2) Dissolve 0.0136 g of cysteine ​​in 15.2 mL of ultrapure water. After ultrasonic treatment, add 1.6 mL of 0.25 M CuCl2 solution under high-speed stirring. Adjust the pH value to 12 by slowly adding 1 M NaOH solution. Add 93 mg of achiral A-HgS particles. Then stir the reaction at 40 °C for 3.5 h. After that, centrifuge at 6000 rpm for 5 min. Wash twice with ultrapure water and dry to obtain achiral A-CuO / A-HgS heterojunction with a Cu / Hg molar ratio of 1.

[0027] Comparative Example 2 This comparative example provides a method for preparing chiral D-CuO / D-HgS. Following the preparation process in Example 1, chiral D-CuO / D-HgS heterojunctions with Cu / Hg molar ratios of 0.36, 2.86, and 4.55 were prepared respectively.

[0028] Comparative Example 3 This comparative example provides a method for preparing chiral D-CuO / L-HgS. Following the preparation process in Example 2, chiral D-CuO / L-HgS heterojunctions with Cu / Hg molar ratios of 0.36, 2.94, and 3.70 were prepared respectively.

[0029] Application examples This application example demonstrates the use of CuO / HgS heterojunctions in photocatalytic CO2 reduction reactions. The specific steps are as follows: Heterojunctions prepared in Examples 1-4 and Comparative Examples 1-3 are used as photocatalysts. 5 mg of the photocatalyst is placed in 40 mL of water, CO2 is introduced for 15-30 min to purge the air, the pressure is increased to 0.1 MPa, and the reaction is irradiated with a 300 W xenon lamp for 1 h.

[0030] Detection methods The chiral D-CuO / D-HgS heterojunction prepared in Example 1 and the achiral A-CuO / A-HgS heterojunction prepared in Comparative Example 1 were analyzed by electron microscopy and energy dispersive spectroscopy using a JEOL JSM-7800 transmission electron microscope. The results are as follows: Figures 2-3 As shown.

[0031] The chiral CuO / HgS heterojunctions prepared in Examples 1-4 and the achiral A-CuO / A-HgS heterojunctions prepared in Comparative Examples 2-3 were analyzed using a circular dichroism spectrometer of model XX. The obtained circular dichroism chromatograms are shown below. Figure 4 As shown.

[0032] The band gap diagrams of the chiral CuO / HgS heterojunctions prepared in Examples 1-4 and the achiral A-CuO / A-HgS heterojunction prepared in Comparative Example 1 were determined using a UV / Vis / NIR spectrophotometer (PerkinElmer, Lambda 750S). The transient absorption spectra of the chiral CuO / HgS heterojunctions prepared in Examples 1-2 and the achiral A-CuO / A-HgS heterojunction prepared in Comparative Example 1 were studied using a femtosecond transient absorption spectrometer (Ultrafastsystems, Helios).

[0033] After centrifugation, the solutions from each catalyst reaction in the application examples were collected as supernatants. Nuclear magnetic resonance spectroscopy was used to detect the products, with 50 μL of 20 ppm dimethyl sulfoxide (DMSO, 0.01405 μmol) as an internal standard. The product types were qualitatively determined, and the content of each product was quantitatively determined. The test results are as follows: Figures 5-6 As shown.

[0034] Results Analysis Figure 2 Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) images of the chiral D-CuO / D-HgS heterojunction prepared in Example 1. Figure 2 It can be seen that the morphology of the chiral D-CuO / D-Hg heterojunctions mainly exhibits the morphological characteristics of HgS, which may be attributed to the larger particle size of HgS compared to CuO. However, a more reasonable explanation is that CuO dissolves during the formation of HgS and subsequently deposits onto HgS, resulting in the co-deposition of the two and the formation of a large number of heterojunction structures. EDS analysis further confirms that the heterojunction construction methods include: (i) the coexistence of large-sized bipyramidal HgS nanoparticles and small-sized CuO particles at the interface to form heterojunctions; and (ii) uniform co-growth of CuO on the surface of bipyramidal HgS nanoparticles to form uniformly distributed heterostructures.

[0035] Figure 3 Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) images of the achiral A-CuO / A-HgS heterojunction prepared for Comparative Example 1 are shown. Figure 3 TEM images show that the achiral A-CuO / A-HgS heterojunction has an irregular morphology. EDS analysis confirms that CuO and HgS coexist within the same A-CuO / A-HgS heterojunction particles.

[0036] Figure 4 Circular dichroism chromatograms of the chiral CuO / HgS heterojunctions prepared in Examples 1-4 and the achiral CuO / HgS heterojunction prepared in Comparative Example 1. Figure 4It can be seen that the g-factors of the chiral CuO / HgS heterojunctions in Examples 1-4 exhibit similar trends to their DRCD spectra, showing a broad characteristic peak in the range of 400-360 nm. The g-factor of the CuO / HgS heterojunction reaches its maximum value at 540 nm, |g| ≈ (2.06-2.3) × 10⁻⁶. -4 This provides a quantitative characterization of the degree of chirality of the materials. The CD signal can be attributed to the helical distortion of the CuO and HgS lattices. As expected, due to the mutual cancellation of positive and negative signals and the lack of chiral structure, the achiral A-CuO / A-HgS in Comparative Example 1 exhibits a "silent" CD spectrum (no obvious signal).

[0037] Figure 5 The band gap diagram of the CuO / HgS heterojunction is shown below. Figure 5 As can be seen, in the achiral CuO / HgS heterostructure (composed of p-type CuO and n-type HgS semiconductors), after photoexcitation, the electrons occupying the conduction bands (CB) of CuO and HgS maintain a spin degenerate state, with an equal number of spin-up and spin-down electrons. Electrons in the CuO conduction band tend to follow the type II heterojunction charge transfer path, migrating from the CuO conduction band to the lower energy level of the HgS conduction band. Subsequently, electrons in the HgS conduction band can undergo two possible processes: one is direct recombination with holes in the HgS valence band (VB); the other is participation in a reduction reaction to reduce the substrate.

[0038] from Figure 5 As can be seen from b, in the isochiral CuO / HgS heterostructure, effective magnetic fields with the same chiral equivalent direction can be generated in CuO and HgS, and they possess the same chirality, leading to overlapping spin polarization. In this system, spin-polarized electrons in the CuO conduction band tend to migrate to the lower energy level of the HgS conduction band. Due to the spin-flipping effect, these electrons are prohibited from recombinating with valence band holes in CuO and HgS. Therefore, compared with the achiral A-CuO / A-HgS heterostructure, more electrons can accumulate in the HgS conduction band, exhibiting a longer carrier lifetime.

[0039] from Figure 5As shown in Figure c, in the heterochiral CuO / HgS heterostructure, CuO and HgS have opposite chirality, thus inducing effective magnetic fields with opposite directions and further leading to opposite spin polarization. Electrons in the HgS conduction band that undergo spin flipping can recombine with holes in the CuO valence band. Furthermore, electrons in the HgS conduction band cannot recombine with holes in their intrinsic valence band, but they can recombine with holes in the CuO valence band through a spin-orbit coupling mechanism. This process benefits from the antiparallel spin channels of CuO relative to HgS. This forms an S-scheme heterochiral CuO / HgS heterojunction, promoting the spatial separation of photogenerated electron-hole pairs and creating a new effective band gap compared to the achiral A-CuO / A-HgS heterostructure.

[0040] Figure 6 The transient absorption spectrum of the CuO / HgS heterojunction is shown. Circularly polarized transient absorption (TA) spectroscopy was used to investigate the different dynamic behaviors of photoexcited carriers and their spin states in the CuO / HgS heterojunction. Figure 6 It can be seen that, compared with D-CuO / D-HgS ( Figure 6 Compared to e1~e2, g1~g2), D-CuO / L-HgS ( Figure 6 The f1~f2 and h1~h2 signals exhibit significantly stronger stimulated emission (SE) intensity in the 500~550 nm range, which is attributed to photoluminescence generated by the recombination of holes in the CuO valence band and carriers in the HgS conduction band. This indicates the existence of a specific electron transport process in the D-CuO / L-HgS system, which is absent in L-CuO, D-CuO, L-HgS, D-HgS, and D-CuO / D-HgS alone. These results provide strong evidence that the enhanced S-scheme carrier-hole recombination / coupling behavior between HgS and CuO in D-CuO / L-HgS provides strong evidence for the operation of the heterochiral CuO / HgS heterojunction via the S-scheme mechanism.

[0041] Figure 7 The nuclear magnetic resonance spectrum of the product obtained from the photocatalytic CO2 reduction of the chiral D-CuO / D-HgS heterojunction prepared in Example 1. Figure 7 It can be seen that the products obtained by the photocatalytic reduction reaction of CO2 include ethanol and acetone.

[0042] Figure 8The graph shows a comparison of the product content of the chiral CuO / HgS heterojunctions prepared in Examples 1-4 and the achiral CuO / HgS heterojunction prepared in Comparative Example 1 when used as photocatalysts for CO2 reduction. Figure 8 It can be seen that the chiral CuO / HgS heterojunctions prepared in Examples 1-4 exhibit significantly higher product yields in the photocatalytic CO2 reduction reaction compared to Comparative Example 1. This demonstrates that the combined effect of chiral heterostructures can substantially improve both product yield and selectivity. The chiral D-CuO / D-HgS heterojunction prepared in Example 1 and the chiral L-CuO / L-HgS heterojunction prepared in Example 4 demonstrate high yields of ethanol and acetone in the photocatalytic CO2 reduction reaction. Specifically, the yields of ethanol (219 μmol / g·h) and acetone (108 μmol / g·h) obtained by photocatalytic CO2 reduction using the chiral D-CuO / D-HgS heterojunction prepared in Example 1 are as follows: ethanol 219 μmol / g·h and acetone 108 μmol / g·h. This indicates that heterojunction materials with the same chiral composition exhibit higher catalytic activity than those with opposite chiral compositions.

[0043] Figure 9 Circular dichroism chromatograms of chiral CuO / HgS heterojunctions with different Cu / Hg ratios prepared in Examples 1-2 and Comparative Examples 2-3. Figure 9 It can be seen that the g value of the sample gradually increases with the increase of the Hg / Cu atomic ratio. This trend indicates that HgS contributes more significantly to the circular dichroism intensity than CuO, because the g value of HgS is much higher than that of CuO.

[0044] Figure 10 This is a comparison chart of product yields in the photocatalytic CO2 reduction reaction of chiral D-CuO / D-HgS heterojunctions with different Cu / Hg ratios prepared in Example 1 and Comparative Example 2. Figure 10 It can be seen that as the Cu / Hg ratio decreases, the yield of ethanol gradually increases, with pure chiral D-HgS exhibiting the highest ethanol yield. The yield of acetone shows a trend of first increasing and then decreasing with decreasing Cu / Hg ratio, reaching its highest when the Cu / Hg molar ratio is 1.04. Therefore, it can be concluded that when the molar ratio of D-CuO / D-HgS in the chiral D-CuO / D-HgS heterojunction is approximately 1, both ethanol and acetone can be obtained simultaneously, and the yields of both products are relatively high.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A chiral CuO / HgS heterojunction catalyst characterized in that, Including D-CuO / D-HgS heterojunction, L-CuO / L-HgS heterojunction, D-CuO / L-HgS heterojunction, and L-CuO / D-HgS heterojunction.

2. The method for preparing a chiral CuO / HgS heterojunction catalyst as described in claim 1, characterized in that, Includes the following steps: (1) Preparation of chiral CuO powder Chiral cysteine ​​was dissolved in water and sonicated. CuCl2 solution was added under high-speed stirring, and the pH was adjusted to 12 with NaOH solution. After heating and reaction, chiral CuO powder was obtained by centrifugation, washing and drying. (2) Preparation of chiral HgS seed colloid Hg(NO3)2 solution was mixed with chiral penicillamine solution, and NaOH solution was added first while stirring, followed by slow dropwise addition of thioacetamide solution. After the reaction was complete, the mixture was centrifuged and washed to obtain chiral HgS crystal nuclei dispersed in water, thus obtaining chiral HgS seed colloids. (3) Preparation of chiral CuO / HgS heterojunction After adding water to the chiral HgS seed colloid, chiral CuO powder was added. Chiral penicillamine solution and NaOH solution were added sequentially under stirring. Then, Hg(NO3)2 solution and thioacetamide solution were slowly injected simultaneously using a syringe pump. After the reaction was completed, the mixture was centrifuged, washed, and dried to obtain a chiral CuO / HgS heterojunction.

3. The method for preparing a chiral CuO / HgS heterojunction catalyst according to claim 2, characterized in that, In step (1), the molar ratio of chiral cysteine ​​to CuCl2 is 0.5~1.5:1, the reaction temperature is 30~50℃, the reaction time is 2~5h, the centrifugation speed is 5000~8000rpm, the reaction time is 3~6min, and the washing medium is ultrapure water.

4. The method for preparing a chiral CuO / HgS heterojunction catalyst according to claim 2, characterized in that, In step (2), the molar ratio of Hg(NO3)2: chiral penicillamine: thioacetamide is 1:0.8~1:0.9~1.

2. The thioacetamide solution is added uniformly over 3~6 min. The reaction temperature is 30~50℃ and the reaction time is 10~20 h. The centrifugation speed is 5000~8000 rpm and the reaction time is 5~15 min. The washing medium is isopropanol.

5. The method for preparing a chiral CuO / HgS heterojunction catalyst according to claim 2, characterized in that, In step (2), the concentration of chiral HgS seed colloid is 0.02~0.05 mol / L.

6. The method for preparing a chiral CuO / HgS heterojunction catalyst according to claim 2, characterized in that, In step (3), the ratio of chiral HgS seed colloid: CuO: chiral penicillamine: Hg(NO3)2: thioacetamide is 1L: 4~5mol: 1~3mol: 4~5mol: 4~6mol.

7. The method for preparing a chiral CuO / HgS heterojunction catalyst according to claim 2, characterized in that, In step (3), Hg(NO3)2 and thioacetamide solution are injected at a constant rate over 4-8 hours. The reaction ends when the injection is complete. The reaction temperature is 35-45℃, the centrifugation speed is 5000-8000 rpm, and the time is 3-5 minutes.

8. The application of the chiral CuO / HgS heterojunction catalyst as described in claim 1 or the chiral CuO / HgS heterojunction catalyst obtained by the preparation methods of claims 2 to 7 in photocatalytic CO2 reduction.

9. Use according to claim 8, characterized in that, The resulting products include not only C2 products, but also C3 products in comparable quantities.

10. Use according to claim 9, characterized in that, The C2 product is ethanol, and the C3 product is acetone.

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