A Cu-anchored Bi4O5I2 heterostructure photocatalyst, its preparation method and application

Abstract

The present invention relates to the field of photocatalysis, and provides a Cu-anchored Bi4O5I2 heterostructure photocatalyst, a preparation method thereof and an application thereof. The method comprises the following steps: mixing Bi4O5I2 microflowers with water to obtain a suspension of type I; mixing triethanolamine with the suspension of type I to obtain a suspension of type II; mixing a copper salt with the suspension of type II to obtain a turbid liquid; irradiating the turbid liquid with light having a wavelength of 350 nm to 780 nm, separating out a solid product, washing and drying to obtain the Cu-anchored Bi4O5I2 heterostructure photocatalyst. Compared with single Bi4O5I2, the Cu-anchored Bi4O5I2 heterostructure photocatalyst has significantly enhanced performance in catalyzing CO2 reduction.

Description

Technical Field

[0001] The present invention relates to the field of photocatalysis, and particularly to a heterostructure photocatalyst, a preparation method thereof, and an application thereof. Background Art

[0002] Photocatalytic reduction of CO2 to hydrocarbon fuels is a promising strategy to simultaneously address the energy crisis and the greenhouse effect. A typical photocatalytic CO2 reduction process sequentially includes three key steps: (1) light absorption; (2) separation and transfer of photo-generated carriers; (3) reduction of CO2 and oxidation of H2O by electrons and holes on the photocatalyst surface, which is the most important part of the photocatalytic process. Therefore, the development of an efficient CO2 reduction photocatalyst requires meeting the above three requirements simultaneously. So far, a variety of inorganic and organic photocatalysts, such as TiO2, CeO2, Bi4O5I2, polymers (g-C3N4 and COFs), have been used to achieve CO2 photoreduction.

[0003] Bismuth-rich bismuth oxyiodide (Bi4O5I2) is a novel narrow-bandgap (~2.4 eV) photocatalyst, which has received increasing attention due to its good visible light absorption ability, relatively negative conduction band (CB) potential, layered structure, and excellent optoelectronic properties. Previous studies have shown that the morphology has a great influence on the photocatalytic performance of Bi4O5I2. Hierarchical microflowers assembled from nanosheets can provide more active sites due to their high surface area, thus accelerating the surface photocatalytic reaction kinetics. However, due to its limited light energy absorption, the solar energy utilization rate of the original Bi4O5I2 microflowers (Bi4O5I2MFs) is still very poor. In addition, the original Bi4O5I2MFs usually suffer from severe recombination of photo-generated carriers. These disadvantages lead to an unsatisfactory CO2 conversion efficiency, limiting its practical application. Therefore, improving solar energy absorption and suppressing carrier recombination are the keys to improving the photocatalytic CO2 reduction performance of Bi4O5I2.

[0004] To improve the solar energy utilization rate of photocatalysts, various methods have been adopted, such as element doping, vacancy engineering, constructing heterostructures, etc. In addition, modifying n-type semiconductor photocatalysts with plasmonic metal nanoparticles (NPs) can also improve the solar energy utilization rate due to their surface plasmon resonance (SPR) absorption and SPR-induced hot electron injection. For example, noble metal nanoparticles (such as Au, Ag NPs) are usually used to modify semiconductors to prepare plasmonic semiconductor-based photocatalysts, including Cd / Au, Au@ZnO, Ag / Bi3TaO7, Ag / In2O3, and Ag@CeO2. However, these noble metals are expensive and scarce, limiting the practical application of plasmonic photocatalysts. Summary of the Invention

[0005] In view of this, the present invention provides a Cu-anchored Bi4O5I2 heterostructure photocatalyst, a preparation method thereof, and an application thereof, which solve at least one problem existing in the prior art.

[0006] A preparation method of a Cu-anchored Bi4O5I2 heterostructure photocatalyst provided by the present invention comprises the following steps:

[0007] Mix Bi4O5I2 microflowers with water to obtain a suspension of type I;

[0008] Mix triethanolamine with the suspension of type I to obtain a suspension of type II;

[0009] Mix a copper salt with the suspension of type II to obtain a turbid liquid;

[0010] Irradiate the turbid liquid with light having a wavelength of 350 nm to 780 nm, separate out the solid product, wash and dry it to obtain the Cu-anchored Bi4O5I2 heterostructure photocatalyst (labeled as Bi4O5I2@Cu).

[0011] Through the above technical solution, non-noble metal Cu nanoparticles (Cu NPs) are photodeposited on Bi4O5I2 microflowers, so that the surface plasmon resonance (SPR) effect of Cu NPs is combined with the Bi4O5I2 / Cu Schottky junction, thereby obtaining a product with excellent photocatalytic performance.

[0012] The Cu-anchored Bi4O5I2 heterostructure photocatalyst is obtained by using the above method, that is, the present invention provides a Cu-anchored Bi4O5I2 heterostructure photocatalyst.

[0013] The Cu-anchored Bi4O5I2 heterostructure photocatalyst can catalyze CO2 reduction. Therefore, the present invention also provides an application of the Cu-anchored Bi4O5I2 heterostructure photocatalyst, which is used for catalyzing CO2 reduction.

[0014] Due to the above technical solutions, the embodiments of the present invention have the following beneficial effects: The preparation method of Bi4O5I2@Cu has mild reaction conditions, is simple and easy to operate, and avoids the use of precious metals; the SPR effect of Cu NPs in Bi4O5I2@Cu is combined with the Bi4O5I2 / Cu Schottky junction. The SPR effect of Cu NPs can enhance the light absorption of Bi4O5I2 in a wide spectral range and induce the hot electrons of Cu NPs to be injected into the CB of Bi4O5I2; the Bi4O5I2 / Cu Schottky junction can significantly promote the separation and transfer of photogenerated carriers; compared with Bi4O5I2 microflowers, the synergistic effect of the SPR effect of Cu NPs and the Bi4O5I2 / Cu Schottky junction significantly enhances its photocatalytic CO2 reduction performance. Description of the Drawings

[0015] Figure 1 It is the X-ray diffraction (XRD) pattern of the products of Examples 1-3 of the present invention (Bi4O5I2@Cu-0.25, Bi4O5I2@Cu-0.5, Bi4O5I2@Cu-0.75) and the product of Comparative Example 1 (Bi4O5I2MFs).

[0016] Figure 2(a) is the scanning electron microscope (SEM) image of the product of Example 2 of the present invention (Bi4O5I2@Cu-0.5).

[0017] Figure 2(b) is the scanning electron microscope (SEM) image of the product of Example 2 of the present invention (Bi4O5I2@Cu-0.5).

[0018] Figure 2(c) is the transmission electron microscope (TEM) image of the product of Example 2 of the present invention (Bi4O5I2@Cu-0.5).

[0019] Figure 2(d) is the high-resolution transmission electron microscope (HRTEM) image of the product of Example 2 of the present invention (Bi4O5I2@Cu-0.5).

[0020] Figure 2(e) is the elemental distribution map of the product of Example 2 of the present invention (Bi4O5I2@Cu-0.5).

[0021] Figure 3 It is the X-ray photoelectron spectroscopy (XPS) pattern of the product of Example 2 of the present invention (Bi4O5I2@Cu-0.5), the products of Comparative Examples 1-2 (Bi4O5I2MFs and CuNPs).

[0022] Figure 4(a) is the UV-Vis absorption spectra of the products of Examples 1-3 of the present invention (Bi4O5I2@Cu-0.25, Bi4O5I2@Cu-0.5, Bi4O5I2@Cu-0.75) and the products of Comparative Examples 1-2 (Bi4O5I2 MFs and Cu NPs).

[0023] Figure 4(b) is the N2 adsorption-desorption isotherm diagrams of the product of Example 2 of the present invention (Bi4O5I2@Cu-0.5) and the product of Comparative Example 1 (Bi4O5I2 MFs).

[0024] Figure 4(c) is the CO2 adsorption isotherm test diagrams of the product of Example 2 of the present invention (Bi4O5I2@Cu-0.5) and the product of Comparative Example 1 (Bi4O5I2 MFs).

[0025] Figure 4(d) is the CO2 temperature-programmed desorption curve diagrams of the product of Example 2 of the present invention (Bi4O5I2@Cu-0.5) and the product of Comparative Example 1 (Bi4O5I2 MFs).

[0026] Figure 4(e) is the in-situ diffuse reflectance infrared Fourier transform spectroscopy diagrams of the photocatalytic CO2 reduction of the product of Example 2 of the present invention (Bi4O5I2@Cu-0.5).

[0027] Figure 5(a) is the photocatalytic CO2 reduction performance test diagrams of the products of Examples 1-3 of the present invention (Bi4O5I2@Cu-0.25, Bi4O5I2@Cu-0.5, Bi4O5I2@Cu-0.75) and the product of Comparative Example 1 (Bi4O5I2 MFs).

[0028] Figure 5(b) is the photocatalytic CO2 reduction performance test diagrams of the products of Examples 1-3 of the present invention (Bi4O5I2@Cu-0.25, Bi4O5I2@Cu-0.5, Bi4O5I2@Cu-0.75) and the product of Comparative Example 1 (Bi4O5I2 MFs).

[0029] Figure 5(c) is the photocatalytic CO2 reduction cycle test diagrams of the product of Example 2 of the present invention (Bi4O5I2@Cu-0.5).

[0030] Figure 5(d) is the photocatalytic CO2 reduction performance test diagrams of the product of Example 2 of the present invention (Bi4O5I2@Cu-0.5) under different conditions.

[0031] Figure 6(a) is the Mott-Schottky diagrams of the products of Comparative Examples 1-2 of the present invention (Bi4O5I2 MFs and Cu NPs).

[0032] Figure 6(b) is the transient photocurrent response spectra of the products of Examples 1-3 of the present invention (Bi4O5I2@Cu-0.25, Bi4O5I2@Cu-0.5, Bi4O5I2@Cu-0.75) and the product of Comparative Example 1 (Bi4O5I2 MFs).

[0033] Figure 6(c) is the electrochemical impedance spectra of the products of Examples 1-3 of the present invention (Bi4O5I2@Cu-0.25, Bi4O5I2@Cu-0.5, Bi4O5I2@Cu-0.75) and the product of Comparative Example 1 (Bi4O5I2 MFs).

[0034] Figure 6(d) is the photoluminescence spectra of the product of Example 2 of the present invention (Bi4O5I2@Cu-0.5) and the product of Comparative Example 1 (Bi4O5I2 MFs).

[0035] Figure 6(e) is the time-resolved fluorescence spectra of the product of Example 2 of the present invention (Bi4O5I2@Cu-0.5) and the product of Comparative Example 1 (Bi4O5I2 MFs).

[0036] Figure 6(f) is the transient photocurrent response curves (λ>700nm) of the product of Example 2 of the present invention (Bi4O5I2@Cu-0.5) and the products of Comparative Examples 1-2 (Bi4O5I2 MFs and Cu NPs). Detailed implementation manners

[0037] The following will clearly and completely describe the concept of the present invention and the technical effects produced in combination with the examples and the drawings to fully elaborate the purpose, scheme and effects of the present invention.

[0038] The coupling of metal and semiconductor can construct a Schottky junction at their interface, thereby effectively separating carriers by generating an internal built-in electric field. The inventors found that anchoring plasmonic non-noble metal nanoparticles on Bi4O5I2 to form a plasmonic photocatalyst, enabling the synergistic effect of the plasmonic effect and the Schottky junction, can improve the photocatalytic CO2 reduction activity, which is a new approach to preparing excellent photocatalysts. The inventors successfully prepared a heterostructure photocatalyst (labeled Bi4O5I2@Cu) by photodepositing non-noble metal Cu NPs on self-assembled Bi4O5I2 microflowers. Experimental results show that the constructed Bi4O5I2@Cu combines the SPR effect of Cu NPs with the Bi4O5I2 / Cu Schottky junction. The SPR effect of Cu NPs can enhance the light absorption of Bi4O5I2 in a wide spectral range and induce the hot electrons of Cu NPs to inject into the CB of Bi4O5I2. In addition, the Bi4O5I2 / Cu Schottky junction can significantly promote the separation and transfer of photogenerated carriers. Thus, the inventors summarized the technical solution of the present invention.

[0039] The present invention provides a preparation method of a Cu-anchored Bi4O5I2 heterostructure photocatalyst, and the method comprises the following steps:

[0040] S1. Mix Bi4O5I2 microflowers with water to obtain a suspension of type I;

[0041] S2. Mix triethanolamine with the suspension of type I to obtain a suspension of type II;

[0042] S3. Mix a copper salt with the suspension of type II to obtain a turbid liquid;

[0043] S4. Irradiate the turbid liquid with light having a wavelength of 350 nm to 780 nm, separate out the solid product, wash and dry it to obtain the Cu-anchored Bi4O5I2 heterostructure photocatalyst.

[0044] In some preferred embodiments, the Bi4O5I2 microflowers in step S1 can be synthesized according to the following steps:

[0045] S101. Add bismuth nitrate pentahydrate to ethylene glycol, and wait for it to completely dissolve to obtain solution A;

[0046] S102. Add potassium iodide to ethylene glycol, and wait for it to completely dissolve to obtain solution B;

[0047] S103. Dropwise add solution B into solution A, carry out a hydrothermal reaction to obtain a yellow precipitate, perform high-speed centrifugal separation on the precipitate, wash it with deionized water, and finally dry it in a freeze dryer to obtain a yellow powder;

[0048] S104. Place the yellow powder in a muffle furnace and carry out calcination to obtain Bi4O5I2 microflowers.

[0049] In some preferred embodiments, the molar mass ratio of the bismuth nitrate pentahydrate in step S101 to the potassium iodide in step S102 is 1:1; the dropping speed in step S103 is 1 drop / second to 2 drops / second; the temperature of the hydrothermal reaction in step S103 is 160 °C, and the reaction time is 10 h.

[0050] In some preferred embodiments, the temperature of the calcination in step S104 is 400 °C, and the calcination time is 3 h.

[0051] In some preferred embodiments, the water in step S1 is deionized water.

[0052] In some preferred embodiments, the copper salt in step S3 is copper chloride dihydrate, copper sulfate pentahydrate or copper nitrate trihydrate. Among them, the copper salt in step S3 is most preferably copper chloride dihydrate.

[0053] In some preferred embodiments, the mass ratio of copper chloride dihydrate in step S3 to the Bi4O5I2 microflowers in step S1 is 0.25% to 0.75%:1. Among them, the most preferred mass ratio of copper chloride dihydrate in step S3 to the Bi4O5I2 microflowers in step S1 is 0.5%:1.

[0054] In some preferred embodiments, the volume ratio of water in step S1 to triethanolamine in step S2 is 95:5.

[0055] In some preferred embodiments, the light with a wavelength of 350 nm to 780 nm in step S4 is the light generated by a xenon lamp, the intensity of the xenon lamp is 250 W, and the irradiation time is 1 h.

[0056] Using the above method, a Cu-anchored Bi4O5I2 heterostructure photocatalyst is obtained, that is, the present invention provides a Cu-anchored Bi4O5I2 heterostructure photocatalyst.

[0057] The Cu-anchored Bi4O5I2 heterostructure photocatalyst can catalyze CO2 reduction. Therefore, the present invention also provides the application of the Cu-anchored Bi4O5I2 heterostructure photocatalyst, and uses it to catalyze CO2 reduction.

[0058] Several typical examples are introduced below.

[0059] In the following examples, the Bi4O5I2 microflowers were synthesized according to the following steps:

[0060] (1) Add 1 mmol of bismuth nitrate pentahydrate to 20 mL of ethylene glycol, ultrasonicate it for 10 min, and wait for it to completely dissolve to obtain solution A;

[0061] (2) Add 1 mmol of potassium iodide to 20 mL of ethylene glycol, ultrasonicate it for 10 min, and wait for it to completely dissolve to obtain solution B;

[0062] (3) Drop solution B into solution A drop by drop, stir magnetically for 0.5 h, then transfer the mixture to a 100 mL hydrothermal reactor; carry out a hydrothermal reaction at 160 °C for 10 h to obtain a yellow precipitate, centrifuge it at a high speed of 10000 rpm for 5 min, wash it 3 times with deionized water, and finally dry it in a freeze dryer for 12 hours;

[0063] (5) Place the product in a muffle furnace for calcination, the reaction temperature is 400 °C, and the reaction time is 3 h, thereby obtaining Bi4O5I2 microflowers.

[0064] Example 1

[0065] Prepare the Cu-anchored Bi4O5I2 heterostructure photocatalyst according to the following steps:

[0066] (1) Add 0.3 g of Bi4O5I2 microflowers into 95 mL of deionized water, and ultrasonically stir until completely dispersed to form a suspension of type I;

[0067] (2) Add 5 mL of triethanolamine into the suspension of type I, and ultrasonically stir until completely dispersed to form a suspension of type II;

[0068] (3) Add 0.002 g of copper chloride dihydrate into the suspension of type II, and magnetically stir for 0.5 h to obtain a turbid liquid;

[0069] (4) Irradiate the turbid liquid under the irradiation of a 250 W xenon lamp and under vigorous stirring conditions for 1 h. The product is centrifuged, washed and then dried to obtain the Cu-anchored Bi4O5I2 heterostructure photocatalyst.

[0070] In this example, the mass ratio of Cu to Bi4O5I2 is 0.25% respectively. Mark the Cu-anchored Bi4O5I2 heterostructure photocatalyst obtained in this example as Bi4O5I2@Cu-0.25.

[0071] Example 2

[0072] Prepare the Cu-anchored Bi4O5I2 heterostructure photocatalyst according to the following steps:

[0073] (1) Add 0.3 g of Bi4O5I2 microflowers into 95 mL of deionized water, and ultrasonically stir until completely dispersed to form a suspension of type I;

[0074] (2) Add 5 mL of triethanolamine into the suspension of type I, and ultrasonically stir until completely dispersed to form a suspension of type II;

[0075] (3) Add 0.004 g of copper chloride dihydrate into the suspension of type II, and magnetically stir for 0.5 h to obtain a turbid liquid;

[0076] (4) Irradiate the turbid liquid under the irradiation of a 250W xenon lamp and under vigorous stirring conditions for 1 h. The product is centrifuged, washed and then dried to obtain the Cu-anchored Bi4O5I2 heterostructure photocatalyst.

[0077] In this example, the mass ratio of Cu to Bi4O5I2 is 0.5% respectively. Mark the Cu-anchored Bi4O5I2 heterostructure photocatalyst obtained in this example as Bi4O5I2@Cu-0.5. Bi4O5I2@Cu-0.5 can efficiently photoreduce CO2 to CO without any sacrificial agent.

[0078] Example 3

[0079] Prepare the Cu-anchored Bi4O5I2 heterostructure photocatalyst according to the following steps:

[0080] (1) Add 0.3 g of Bi4O5I2 microflowers into 95 mL of deionized water, and ultrasonically stir until completely dispersed to form a suspension of type I;

[0081] (2) Add 5 mL of triethanolamine into the suspension of type I, and ultrasonically stir until completely dispersed to form a suspension of type II;

[0082] (3) Add 0.006 g of copper chloride dihydrate into the suspension of type II, and magnetically stir for 0.5 h to obtain a turbid liquid;

[0083] (4) Irradiate the turbid liquid under irradiation of a 250 W xenon lamp and under vigorous stirring conditions for 1 h. The product is centrifuged, washed and then dried to obtain the Cu-anchored Bi4O5I2 heterostructure photocatalyst.

[0084] In this example, the mass ratio of Cu to Bi4O5I2 is 0.75% respectively. Mark the obtained Cu-anchored Bi4O5I2 heterostructure photocatalyst as Bi4O5I2@Cu-0.75.

[0085] Comparative Example 1

[0086] Prepare Bi4O5I2 microflowers according to the following steps:

[0087] (1) Add 1 mmol of bismuth nitrate pentahydrate into 20 mL of ethylene glycol, ultrasonically stir it for 10 min until completely dissolved to obtain solution A;

[0088] (2) Add 1 mmol of potassium iodide into 20 mL of ethylene glycol, ultrasonically stir it for 10 min until completely dissolved to obtain solution B;

[0089] (3) Dropwise add solution B into solution A, magnetically stir for 0.5 h, then transfer the mixture to a 100 mL hydrothermal autoclave; carry out hydrothermal reaction at 160 °C for 10 h to obtain a yellow precipitate, centrifuge and separate it at a high speed of 10000 rpm for 5 min, wash it 3 times with deionized water, and finally dry it in a freeze dryer for 12 hours;

[0090] (4) Place the product in a muffle furnace for calcination, the reaction temperature is 400 °C, and the reaction time is 3 h to obtain Bi4O5I2 microflowers (marked as Bi4O5I2MFs).

[0091] Comparative Example 2

[0092] Prepare Cu NPs according to the following steps:

[0093] (1) Add 1.133 g of Cu(NO)3·3H2O to 50 mL of deionized water, stir ultrasonically until completely dispersed, and then evacuate with N2 for 0.5 h to remove O2;

[0094] (2) Rapidly add 10 mL of the prepared NaBH4 solution (the molar ratio of Cu to NaBH4 is 1:10) to the above solution under a N2 atmosphere;

[0095] (3) After reacting for 0.5 h, the product is centrifuged, washed, and dried to obtain Cu NPs.

[0096] X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible absorption spectroscopy, N2 adsorption-desorption isotherm, CO2 adsorption isotherm, CO2 temperature-programmed desorption curve, and in-situ diffuse reflectance infrared Fourier transform spectroscopy of CO2 photoreduction are used to analyze the product.

[0097] Figure 1 XRD patterns of Bi4O5I2@Cu-0.25, Bi4O5I2@Cu-0.5, Bi4O5I2@Cu-0.75, and Bi4O5I2 MFs. It can be seen from Figure 1 that there are no impurity phases in Bi4O5I2@Cu-0.25, Bi4O5I2@Cu-0.5, Bi4O5I2@Cu-0.75, and Bi4O5I2 MFs. The XRD pattern of Bi4O5I2 MFs is consistent with the simulated pattern of monoclinic Bi4O5I2 reported previously; after photo-depositing Cu NPs, the relative intensity of the diffraction peaks of Bi4O5I2 in the Bi4O5I2@Cu composite decreases; while the characteristic peaks of Cu cannot be observed, which may be due to the good dispersion and extremely low content of Cu NPs.

[0098] Figures 2(a) and 2(b) are SEM images of Bi4O5I2@Cu-0.5. Figure 2(c) is a TEM image of Bi4O5I2@Cu-0.5. Figure 2(d) is a HRTEM image of Bi4O5I2@Cu-0.5, indicating that Cu NPs are anchored on the Bi4O5I2 microflowers assembled by nanosheets. Figure 2(e) is an elemental distribution map of Bi4O5I2@Cu-0.5, indicating that Bi4O5I2@Cu-0.5 is composed of four elements: Bi, I, O, and Cu.

[0099] Figure 3XPS spectra of Bi4O5I2@Cu-0.5, Bi4O5I2 MFs, and Cu NPs are shown. It can be seen from the figure that the binding energy of Bi4O5I2@Cu-0.5 has shifted, indicating a strong electronic interaction between Bi4O5I2 MFs and Cu NPs, which generates a built-in electric field and greatly promotes the separation of carriers.

[0100] Figure 4(a) shows the UV-visible absorption spectra of Bi4O5I2@Cu-0.25, Bi4O5I2@Cu-0.5, Bi4O5I2@Cu-0.75, Bi4O5I2 MFs, and Cu NPs, indicating that the light absorption range of Bi4O5I2@Cu-0.25, Bi4O5I2@Cu-0.5, and Bi4O5I2@Cu-0.75 has broadened. Figure 4(b) shows the N2 adsorption-desorption isotherms of Bi4O5I2@Cu-0.5 and Bi4O5I2 MFs, excluding the increase in surface area of Bi4O5I2@Cu-0.5 as the main reason for the improvement of its photocatalytic activity. Figure 4(c) shows the CO2 adsorption isotherm test diagrams of Bi4O5I2@Cu-0.5 and Bi4O5I2 MFs, indicating that: compared with Bi4O5I2 MFs, the CO2 adsorption capacity of Bi4O5I2@Cu-0.5 is significantly enhanced (3.1 cm 3 / g), which is beneficial to CO2 reduction. Figure 4(d) shows the CO2 temperature-programmed desorption curves of Bi4O5I2@Cu-0.5 and Bi4O5I2 MFs. In the desorption temperature range of 310 °C to 550 °C, it is detected that the peak area of Bi4O5I2@Cu-0.5 is significantly larger than that of Bi4O5I2 MFs, indicating that the CO2 adsorption capacity of Bi4O5I2@Cu-0.5 is significantly improved, which is beneficial to accelerating the photocatalytic CO2 reduction. Figure 4(e) is the in-situ diffuse reflectance infrared Fourier transform spectrum of the photocatalytic CO2 reduction of Bi4O5I2@Cu-0.5. As the irradiation time increases, the peak intensity representing the intermediate formed during the photocatalytic process gradually increases. Bi4O5I2@Cu-0.5 shows two obvious characteristic peaks at 1557 and 1540 cm -1 −1, which are attributed to the key intermediate COOH* for the reduction of CO2 to CO and CH4. This indicates that the photocatalytic CO2 reduction of Bi4O5I2@Cu-0.5 is a continuous proton-coupled electron transfer process.

[0101] Figure 6(a) is the Mott - Schottky plot of Bi4O5I2 MFs and Cu NPs, indicating that the Fermi levels of Bi4O5I2 MFs and Cu NPs are -0.4 and 0.1 V (vs. RHE), respectively. Figures 6(b) and 6(c) are the transient photocurrent response curves and electrochemical impedance spectra of Bi4O5I2@Cu - 0.25, Bi4O5I2@Cu - 0.5, Bi4O5I2@Cu - 0.75, and Bi4O5I2 MFs, respectively; Figures 6(d) and 6(e) are the photoluminescence spectra and time - resolved fluorescence spectra of Bi4O5I2@Cu - 0.5 and Bi4O5I2 MFs, respectively, all confirming the enhanced carrier separation and migration efficiency of Bi4O5I2@Cu - 0.25, Bi4O5I2@Cu - 0.5, and Bi4O5I2@Cu - 0.75. Figure 6(f) is the transient photocurrent response curve of Bi4O5I2@Cu - 0.5, Bi4O5I2 MFs, and Cu NPs under a light source with a wavelength greater than 700 nm. A relatively obvious photocurrent was only detected on Bi4O5I2@Cu - 0.5, indicating that a part of the hot electrons of Cu NPs transferred to the CB of Bi4O5I2.

[0102] Application Example 1

[0103] Using the five products Bi4O5I2 MFs, Bi4O5I2@Cu - 0.25, Bi4O5I2@Cu - 0.5, Bi4O5I2@Cu - 0.75, and Cu NPs obtained in Examples 1 - 3 and Comparative Examples 1 - 2 as photocatalysts for CO2 reduction, specifically: 50 mg of each photocatalyst was respectively placed in a sealed glass reactor with an area of 4.2 cm 2 . A 250 W xenon lamp was used as the light source for the photocatalytic reaction. Before irradiation, the reactor was evacuated using a vacuum pump, and then high - purity CO2 gas was introduced into the reaction device to reach ambient pressure. 0.4 mL of deionized water was injected into the reactor. The prepared photocatalyst was equilibrated in a CO2 atmosphere for several hours. The temperature of the reaction system was always maintained at 25 °C by circulating cooling water. During irradiation, 0.5 mL of gas was withdrawn from the reaction flask every hour and analyzed subsequently using a gas chromatograph (GC9790 IIA, Fuli Analytical Instruments Co., Ltd., Zhejiang, China), which was equipped with FID and TCD detectors.

[0104] Figures 5(a) and 5(b) are the test diagrams of the photocatalytic CO2 reduction performance of Bi4O5I2@Cu - 0.25, Bi4O5I2@Cu - 0.5, Bi4O5I2@Cu - 0.75, and Bi4O5I2 MFs. Bi4O5I2@Cu - 0.5 has the optimal performance for photocatalytic reduction of CO2 to CO (the average CO yield is 2.73 μmol g-1 h -1 ), about 4.9 times that of Bi4O5I2MFs (0.56 μmol g -1 h -1 ). Figure 5(c) is the photocatalytic CO2 reduction cycle test chart of Bi4O5I2@Cu-0.5, indicating that Bi4O5I2@Cu-0.5 has excellent cycle stability. Figure 5(d) is the photocatalytic CO2 reduction performance test chart of Bi4O5I2@Cu-0.5 under different conditions, showing that the CO2 photoreduction reaction in Bi4O5I2@Cu-0.5 is driven by light in the presence of the photocatalyst, and the carbon source of the product only comes from the injected CO2.

[0105] As described above, it is only the preferred embodiment of the present invention. The present invention is not limited to the above embodiments. As long as it achieves the technical effects of the present invention by the same means, it shall fall within the protection scope of the present invention. Within the protection scope of the present invention, various different modifications and changes can be made to its technical solutions and / or implementation manners.

Claims

1. A preparation method of a Cu-anchored Bi4O5I2 heterostructure photocatalyst for catalytic CO2 reduction, comprising the following steps: Mix Bi4O5I2 microflowers with water to obtain a suspension of Class I; Mix triethanolamine with the suspension of Class I to obtain a suspension of Class II; Mix copper salt with the suspension of Class II to obtain a turbid solution; Irradiate the turbid solution with light having a wavelength of 350 nm to 780 nm, separate the solid product, wash and dry it to obtain the Cu-anchored Bi4O5I2 heterostructure photocatalyst; Among them, the heterostructure in the Cu-anchored Bi4O5I2 heterostructure photocatalyst is a Bi4O5I2 / Cu Schottky junction; the copper salt is copper chloride dihydrate, and the mass ratio of Cu to Bi4O5I2 in the copper chloride dihydrate is 0.25%:1, 0.5%:1 or 0.75%:1; the volume ratio of water to triethanolamine is 95:5; the light having a wavelength of 350 nm to 780 nm is the light generated by a xenon lamp, the power of the xenon lamp is 250 W, and the irradiation time is 1 h; The Bi4O5I2 microflowers are synthesized according to the following steps: Add bismuth nitrate pentahydrate to ethylene glycol and wait for it to completely dissolve to obtain Solution A; Add potassium iodide to ethylene glycol and wait for it to completely dissolve to obtain Solution B; Drop Solution B into Solution A drop by drop, carry out a hydrothermal reaction to obtain a yellow precipitate, perform high-speed centrifugation separation on the precipitate, wash it with deionized water, and finally dry it in a freeze dryer to obtain a yellow powder; Place the yellow powder in a muffle furnace and calcine it to obtain Bi4O5I2 microflowers.

2. The method according to claim 1, wherein: The water is deionized water.

3. A Cu-anchored Bi4O5I2 heterostructure photocatalyst obtained by the method according to any one of claims 1 to 2.

4. The application of the Cu-anchored Bi4O5I2 heterostructure photocatalyst according to claim 3, wherein: The Cu-anchored Bi4O5I2 heterostructure photocatalyst is used for catalyzing CO2 reduction.

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