Palladium-loaded bismuth-based heterojunction photocatalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of photocatalysts, and particularly relates to a palladium-loaded bismuth-based heterojunction photocatalyst as well as a preparation method and application thereof. The palladium-loaded bismuth-based heterojunction photocatalyst provided by the invention comprises Pd nano-particle active sites and a heterojunction structure formed by CuBi2O4 and a BiOBr nanosheet, wherein the Pd nano-particle active sites and the CuBi2O4 and BiOBr nano-sheets are arranged in the heterojunction structure; the active sites of the Pd nanoparticles are loaded on the BiOBr nanosheets to form Pd-BiOBr; the Pd-BiOBr is loaded on the surface of the CuBi2O4; and the CuBi2O4 is in a rod-shaped array. The catalyst is applied to photocatalysis of CO2RR, and the selectivity and the yield of a C2 product can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalysts, and more particularly relates to a palladium-loaded bismuth-based heterojunction photocatalyst and a preparation method and application thereof. Background Art

[0002] Building a carbon-negative technology system centered on CO2 resource utilization based on CO2 emission reduction technologies, and reconstructing CO2 into high-value-added carbon-based compounds (such as methanol, formic acid, ethane, and ethylene) or chemical raw materials (such as urea) through chemical conversion, has become a cutting-edge approach to addressing the dual dilemma of "emission reduction and energy storage." Current CO2 conversion technologies primarily encompass heterogeneous catalysis, enzymatic catalysis, and photocatalytic synergistic catalysis. Among them, photocatalytic reduction technology offers unique advantages in artificial photosynthesis due to its room-temperature and atmospheric pressure operation and sustainable nature, directly utilizing solar energy. The production of C2 products requires two CO2 molecules via C-C coupling. Compared to the production of two independent C1 products, this theoretically reduces the energy consumption of the reaction steps and improves the efficiency of solar energy utilization. Furthermore, each mole of C2 product can fix more CO2 (2 mol CO2 → 1 mol C2H4), resulting in higher carbon atom utilization. C2 products (such as ethylene and ethanol) are important chemical raw materials and fuels, with a market value far exceeding that of C2 products (such as CO and CH4). For example, ethylene is the core raw material for synthesizing plastics, ethanol can be used as a clean fuel or solvent, and high C2 yield can directly improve the economic feasibility of photocatalytic technology.

[0003] Among the many semiconductor materials for photocatalytic CO2RR, Bi-based materials are considered to be one of the most promising photocatalysts for industrial-scale application due to their unique electronic structure, suitable band gap, stable photochemical properties and environmental friendliness. However, Bi-based materials have inherent defects such as inefficient charge separation and insufficient active sites, which make it impossible to achieve ideal C2 product generation. In recent years, many studies have overcome the inherent defects of Bi-based materials by using catalyst design methods such as defect engineering and heterostructure construction, or by introducing sacrificial agents in the photocatalytic process. However, in the photocatalytic reaction, sacrificial agents (such as methanol, triethanolamine, Na2S / Na2SO3, etc.) are often used to consume photogenerated holes (H +), inhibiting electron-hole recombination, thereby improving the efficiency of reduction reactions (such as CO2 reduction and hydrogen production). Sacrificial agents have some negative effects on the reaction system. First, the sacrificial agent itself may participate in the oxidation reaction and generate by-products (such as methanol oxidation to formaldehyde and formic acid), interfering with the selectivity of the target product. Secondly, the sacrificial agent artificially increases the apparent quantum efficiency by rapidly consuming holes, but it may mask the deficiencies in the intrinsic performance of the catalyst (such as charge separation ability). Finally, the sacrificial agent is irreversibly consumed in the reaction (such as methanol is oxidized to CO2) and needs to be continuously replenished, resulting in high operating costs. Under this circumstance, the laboratory results completed are difficult to generalize to actual application scenarios (such as the lack of sufficient sacrificial agent supply in the natural environment). Therefore, it is very necessary to design a sacrificial agent-free Bi-based photocatalytic system to efficiently convert CO2 into C2 products. Summary of the Invention

[0004] The purpose of the present invention is to provide a palladium-loaded bismuth-based heterojunction photocatalyst, its preparation method and application, and to solve the problems of inefficient photogenerated charge separation and insufficient active sites in Bi-based catalysts by constructing heterojunctions and active sites, thereby achieving highly selective photocatalytic reduction of carbon dioxide to C2 products in the absence of sacrificial agents.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] One of the technical solutions of the present invention is to provide a palladium-loaded bismuth-based heterojunction photocatalyst, wherein the catalyst comprises Pd nanoparticle active sites and a heterojunction structure formed by CuBi2O4 and BiOBr nanosheets;

[0007] The active sites of the Pd nanoparticles are loaded on the BiOBr nanosheets to form Pd-BiOBr;

[0008] The Pd-BiOBr is loaded on the surface of the CuBi2O4;

[0009] The CuBi2O4 is in a rod-shaped array.

[0010] Furthermore, the diameter of the CuBi2O4 is 100-150nm.

[0011] The second technical solution of the present invention is to provide a method for preparing the above-mentioned palladium-loaded bismuth-based heterojunction photocatalyst, comprising the following steps:

[0012] Taking a first bismuth source, a copper source and an alkaline reagent as reactants, CuBi2O4 is obtained through a hydrothermal reaction;

[0013] Using a second bismuth source and a bromine source as reactants, adjusting the pH to neutral, and undergoing a solvothermal reaction to obtain BiOBr nanosheets;

[0014] The BiOBr nanosheets and a palladium source are used as reactants, and in the presence of ethanol, a photoreduction reaction is carried out to obtain Pd-BiOBr;

[0015] Dispersing the CuBi2O4 in ethanol to obtain a CuBi2O4 suspension;

[0016] dispersing the Pd-BiOBr in isopropanol to obtain a Pd-BiOBr suspension;

[0017] The CuBi2O4 suspension and the Pd-BiOBr suspension are mixed to obtain a mixed system, and the mixed system is subjected to solvent thermal reflux treatment to obtain the palladium-loaded bismuth-based heterojunction photocatalyst.

[0018] Furthermore, the mass ratio of the first bismuth source, the copper source and the alkaline reagent is 2.42:0.60:0.87.

[0019] Furthermore, the temperature of the hydrothermal reaction is 180° C. and the time is 24 hours.

[0020] Furthermore, the first bismuth source includes at least one of Bi(NO3)3·5H2O, BiCl3 and Bi2(SO4)3.

[0021] Furthermore, the copper source includes at least one of Cu(NO3)2·2.5H2O, Cu(NO3)2·5H2O and CuCl2·2H2O.

[0022] Furthermore, the alkaline reagent includes NaOH and / or KOH.

[0023] Furthermore, the mass ratio of the second bismuth source to the bromine source is 1.36:0.3.

[0024] Furthermore, the temperature of the solvent thermal reaction is 140° C. and the time is 12 h.

[0025] Furthermore, the second bismuth source includes at least one of Bi(NO3)3·5H2O, BiCl3 and Bi2(SO4)3.

[0026] Furthermore, the bromine source includes NaBr and / or KBr.

[0027] Furthermore, the usage ratio of the BiOBr nanosheets, palladium source and ethanol is 300 mg:8.3 mg:10 mL.

[0028] Furthermore, the palladium source includes Na2PdCl4 and / or K2PdCl4.

[0029] Furthermore, the palladium source is added in the form of an aqueous solution with a concentration of 100 mg / mL.

[0030] Furthermore, the photoreduction reaction is carried out using 300W xenon lamp light for 30 minutes.

[0031] Furthermore, the dosage ratio of CuBi2O4 to ethanol in the CuBi2O4 suspension is 3-11 mg:50 mL.

[0032] Furthermore, the dosage ratio of Pd-BiOBr to isopropyl alcohol in the Pd-BiOBr suspension is 50 mg:50 mL.

[0033] Furthermore, the volume ratio of ethanol to isopropanol in the mixed system is 1:1.

[0034] Furthermore, the temperature of the solvent heat reflux treatment is 80° C. and the time is 1 hour.

[0035] The third technical solution of the present invention is to provide an application of the above-mentioned bismuth-based heterojunction photocatalyst in photocatalytic CO2RR.

[0036] Technical solution 4 of the present invention: Provide an application of the above-mentioned bismuth-based heterojunction photocatalyst in improving the selectivity and yield of C2 products in photocatalytic CO2RR

[0037] The fifth technical solution of the present invention: provides a method for preparing C2 products by photocatalytic CO2RR, wherein the catalyst used in the method is the above-mentioned loaded bismuth-based heterojunction photocatalyst.

[0038] Furthermore, the C2 product includes C2H4 and / or C2H6.

[0039] The present invention discloses the following technical effects:

[0040] The present invention utilizes two Bi-based semiconductor materials, CuBi2O4 and BiOBr, to form a heterojunction to improve the separation problem of photogenerated carriers, and loads Pd NPs on BiOBr to provide active sites. The synergistic effect of the two improves the efficiency of photocatalytic CO2RR and increases product selectivity and yield.

[0041] The present invention is based on the construction of Pd nanoparticle active sites and CuBi2O4 / BiOBr heterojunction design of Bi-based photocatalysts, which effectively improves the problems of low charge separation and insufficient active sites of Bi-based photocatalysts, enabling them to photocatalytically convert CO2 into CO, C2H4, and C2H6, with the C2H6 production rate reaching 29.03 μmol·g -1 ·h -1 , the gas selectivity reaches 74%, which is significantly better than that of a single material. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0043] Figure 1 Characterization images of BOB, CBO, Pd-BOB and Pd-BOB / CBO-4, where (a) is the SEM image of BOB, (b) is the SEM image of Pd-BOB, (c) is the SEM image of CBO, (d) is the SEM image of Pd-BOB / CBO-4, (e) is the TEM image of BOB, (f) is the TEM image of CBO, (g) is the TEM image of Pd-BOB, (h) is the TEM image of Pd-BOB / CBO-4, and (i) is the EDS energy spectrum and element distribution map of Pd-BOB / CBO-4.

[0044] Figure 2 The XRD patterns of the products obtained in Example 1 and Example 2 are shown in FIG.

[0045] Figure 3 The XRD patterns of the product obtained in Example 1 and BiOBr prepared under different pH conditions are shown.

[0046] Figure 4 The CO2RR product selectivity of the palladium-loaded bismuth-based heterojunction photocatalyst obtained in Example 1 and Example 2.

[0047] Figure 5 CO2RR yields of CBO, BOB, Pd-BOB, CBO / BOB, palladium-supported bismuth-based heterojunction photocatalysts obtained in Example 1 and Example 2. DETAILED DESCRIPTION

[0048] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0049] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0050] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0051] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0052] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0053] Example 1

[0054] The preparation steps of the palladium-supported bismuth-based heterojunction photocatalyst include:

[0055] S1. 2.42 g Bi(NO3)3·5H2O, 0.60 g Cu(NO3)2·2.5H2O and 0.87 g NaOH were stirred in 80 mL H2O for 3 h to fully dissolve, and then transferred to a polytetrafluoroethylene-lined autoclave and hydrothermally reacted at 180°C for 24 h. After cooling to room temperature, the precipitate was washed by centrifugation with ethanol and H2O, and the obtained precipitate was dried at 60°C overnight to obtain CuBi2O4, which was recorded as CBO.

[0056] S2, 1.36g Bi(NO3)3·5H2O was dissolved in 50mL ethylene glycol and stirred for 30min, then 0.3g NaBr was added and stirred for 30min. -1 The pH value of the solution was controlled at 7 by adding NaOH, and the mixture was transferred to a polytetrafluoroethylene-lined autoclave and heated at 140 °C for 12 h. After cooling to room temperature, the solid product was collected by centrifugation, washed with methanol three times, and dried at 60 °C for 12 h to obtain BiOBr, which was recorded as BOB.

[0057] S3. Weigh 300 mg of BOB and disperse it in 40 mL of H2O. Ultrasonicate for 15 min and stir for 2 h. Inject 83 μL of Na2PdCl4 (100 mg / mL) solution and stir for 30 min. Then add 10 mL of anhydrous ethanol and irradiate with xenon light for 30 min. Then, wash the mixed sample with water and ethanol by centrifugation and dry at 60°C overnight to obtain Pd-BiOBr, which is recorded as Pd-BOB.

[0058] S4. Disperse 9 mg of CBO in 50 mL of anhydrous ethanol and sonicate for 30 min to obtain a CBO suspension; add 50 mg of Pd-BOC to 50 mL of isopropanol and stir for 12 h to obtain a Pd-BOB suspension; inject the obtained CBO suspension into the Pd-BOB suspension, stir and reflux at 80° C. for 1 h, filter, wash with ethanol, and dry at 60° C. for 12 h to obtain a palladium-loaded bismuth-based heterojunction photocatalyst, denoted as Pd-BOB / CBO-4 (the loading amount of CBO relative to Pd-BOB is 18 wt %, the same below).

[0059] Example 2

[0060] Compared with Example 1, the only difference is that the amount of CBO used in step S4 is 3 mg, 5 mg, 7 mg or 11 mg.

[0061] When the amount of CBO was 3 mg, the product was recorded as Pd-BOB / CBO-1.

[0062] When the amount of CBO used was 5 mg, the product was recorded as Pd-BOB / CBO-2.

[0063] When the amount of CBO used was 7 mg, the product was recorded as Pd-BOB / CBO-3.

[0064] When the amount of CBO used was 11 mg, the product was recorded as Pd-BOB / CBO-5.

[0065] Comparative Example 1

[0066] The preparation steps of bismuth-based heterojunction photocatalyst include:

[0067] S1. 2.42 g Bi(NO3)3·5H2O, 0.60 g Cu(NO3)2·2.5H2O and 0.87 g NaOH were stirred in 80 mL H2O for 3 h to fully dissolve, and then transferred to a polytetrafluoroethylene-lined autoclave and hydrothermally reacted at 180°C for 24 h. After cooling to room temperature, the precipitate was washed by centrifugation with ethanol and H2O, and the obtained precipitate was dried at 60°C overnight to obtain CuBi2O4, which was recorded as CBO.

[0068] S2, 1.36g Bi(NO3)3·5H2O was dissolved in 50mL ethylene glycol and stirred for 30min, then 0.3g NaBr was added and stirred for 30min. -1 The pH value of the solution was controlled at 7 by adding NaOH, and the mixture was transferred to a polytetrafluoroethylene-lined autoclave and heated at 140 °C for 12 h. After cooling to room temperature, the solid product was collected by centrifugation, washed with methanol three times, and dried at 60 °C for 12 h to obtain BiOBr, which was recorded as BOB.

[0069] S4. Disperse 9 mg of CBO in 50 mL of anhydrous ethanol and sonicate for 30 min to obtain a CBO suspension. Add 50 mg of BOC to 50 mL of isopropanol and stir for 12 h to obtain a BOB suspension. Inject the obtained CBO suspension into the BOB suspension, stir and reflux at 80°C for 1 h, filter, wash with ethanol, and dry at 60°C for 12 h to obtain a palladium-supported bismuth-based heterojunction photocatalyst, which is recorded as CBO / BOB.

[0070] Comparative Example 2

[0071] The preparation steps of BiOBr include:

[0072] 1.36 g of Bi(NO3)3·5H2O was dissolved in 50 mL of ethylene glycol and stirred for 30 min. Subsequently, 0.3 g of NaBr was added and stirring was continued for 30 min. The pH value was controlled to 3 and the mixture was transferred to a polytetrafluoroethylene-lined autoclave. The mixture was heated at 140°C for 12 h. After cooling to room temperature, the solid product was collected by centrifugation, washed three times with methanol, and dried at 60°C for 12 h to obtain BiOBr, which was recorded as BOB-3.

[0073] Test example

[0074] Figure 1 Characterization images of BOB, CBO, Pd-BOB and Pd-BOB / CBO-4, where (a) is the SEM image of BOB, (b) is the SEM image of Pd-BOB, (c) is the SEM image of CBO, (d) is the SEM image of Pd-BOB / CBO-4, (e) is the TEM image of BOB, (f) is the TEM image of CBO, (g) is the TEM image of Pd-BOB, (h) is the TEM image of Pd-BOB / CBO-4, and (i) is the EDS energy spectrum and element distribution map of Pd-BOB / CBO-4.

[0075] Figure 2 The XRD patterns of the products obtained in Example 1 and Example 2 are shown in FIG.

[0076] Figure 3 The XRD patterns of the product obtained in Example 1 and BiOBr prepared under different pH conditions are shown.

[0077] Depend on Figure 3-Figure 4 It can be seen that the XRD diffraction pattern shows the successful preparation of BiOBr and CuBi2O4. In order to obtain BiOBr with better photocatalytic activity, the BiOBr prepared at pH = 7 showed a diffraction peak shift compared to the standard crystal prepared at pH = 3. When the pH value changes, more defects may be generated in the material during the synthesis process, such as vacancies or interstitial atoms, which will cause strain in the lattice, thereby changing the interplanar spacing and shifting the position of the diffraction peak. For example, under alkaline or acidic conditions, the material may dissolve or recrystallize, generating stress. pH adjustment will affect the shrinkage of the material during drying or calcination, resulting in residual stress, thereby changing the lattice constant. For example, during the drying process, different pH may lead to different interactions between particles, generating internal stress, which in turn affects the XRD diffraction peak position.

[0078] Photocatalytic CO2RR test:

[0079] The photocatalytic CO2 reduction performance test was carried out in a sealed flat-bottom flask (50 mL) using a xenon lamp (300 W) as the irradiation light source. 10 mg of the sample was weighed and fully ultrasonically dispersed in 1 mL of ethanol. The resulting suspension was coated on quartz glass, and the system was then dried at 60 ° C for 30 minutes to completely remove the solvent. Subsequently, the quartz glass and H2O (1 mL) were placed in a flat-bottom flask. The flask system was deoxygenated by blowing in high-purity CO2 gas and then sealed. After light irradiation, the generated gas was analyzed by a gas chromatography system with TCD and FID detectors, and the selective parts were Figure 4 , the yield is shown in Figure 5 .

[0080] Among them, the samples are CBO, BOB, BOB-3, Pd-BOB, Pd-BOB / CBO-1, Pd-BOB / CBO-2, Pd-BOB / CBO-3, Pd-BOB / CBO-4, Pd-BOB / CBO-5 and CBO / BOB.

[0081] Figure 4 The CO2RR product selectivity of the palladium-loaded bismuth-based heterojunction photocatalyst obtained in Example 1 and Example 2.

[0082] Figure 5 CO2RR yields of CBO, BOB, Pd-BOB, CBO / BOB, palladium-loaded bismuth-based heterojunction photocatalysts obtained in Example 1 and Example 2 (6, 10, 14, 18, and 22 in the figure correspond to the products with different Pd loadings in Example 1 and Example 2, respectively).

[0083] As can be seen from the figure, the photocatalytic performance of CBO, BOB, Pd-BOB, CBO / BOB, palladium-loaded bismuth-based heterojunction photocatalysts obtained in Example 1 and Example 2 was compared by photocatalytic reduction of CO2 performance test. Figure 5 It can be seen that the photocatalytic products and photocatalytic performance of the palladium-loaded bismuth-based heterojunction photocatalyst composite materials obtained by CBO, BOB, Pd-BOB, CBO / BOB, Example 1 and Example 2 are different. Among them, CBO and BOB monomer materials can only reduce CO2 to CH4 and CO, and do not have the ability to reduce CO2 to C2 products such as C2H4 or C2H6. After loading Pd nanoparticles on BiOBr (Pd-BOB), thanks to the construction of active sites, the photocatalytic activity increased significantly, C2H4 or C2H6 appeared in the product, and the production of CH4 and CO also increased significantly. BiOBr and CuBi2O4 form a heterojunction (CBO / BOB), which also slightly improves the photocatalytic activity, resulting in an increase in the production of CH4, a further reduction product compared to CO. Among them, the palladium-loaded bismuth-based heterojunction photocatalyst in Example 1, that is, CBO:Pd-BOB=18%, has the highest photocatalytic activity, with a C2H6 production rate of 29.03μmol·g-1·h-1 and a C2H4 production rate of 3.95μmol·g-1·h-1, indicating that the synergistic effect of the Pd active site and the heterojunction promotes charge separation and transfer, inhibits carrier recombination, and achieves the goal of CC coupling to form C2 products in the absence of a sacrificial agent. Figure 4It can be seen that after six hours of catalytic reduction of CO2 by the palladium-supported bismuth-based heterojunction photocatalysts obtained in Examples 1 and 2, the yields of CO, C2H4, and C2H6, as well as the selectivity of C2H4 and C2H6, can be converted into CO, C2H4, and C2H6. However, as the composite ratio changes, the yields of C2H4 and C2H6 continue to increase, while the yield of CO continues to decrease. When CBO:Pd-BOB=18%, the yields of C2H4 and C2H6 reach the highest, reaching 23.7μmol·g-1 and 174.18μmol·g-1, respectively. At the same time, the selectivity of C2H6 product also reaches the highest, i.e., 74%. It is worth noting that further increasing the CuBi2O4 content reduces the photocatalytic activity and C2H6 selectivity of the composite material. The reason may be that when the CuBi2O4 addition amount is 18%, the Pd-BiOBr particles bound to the CuBi2O4 nanorods are evenly dispersed, while when the CuBi2O4 content exceeds 18%, especially when it is close to 22%, CuBi2O4 is widely dispersed, the Pd-BiOBr content is relatively reduced, and the average loading amount of Pd-BiOB on CuBi2O4 will decrease, thereby reducing the CO2 concentration at the catalytic active site Pd and making it easier for photogenerated electrons and holes to recombine.

[0084] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0085] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A palladium-supported bismuth-based heterojunction photocatalyst, characterized in that: The catalyst includes Pd nanoparticle active sites and a heterojunction structure formed by CuBi2O4 and BiOBr nanosheets; The active sites of the Pd nanoparticles are loaded on the BiOBr nanosheets to form Pd-BiOBr; The Pd-BiOBr is loaded on the surface of the CuBi2O4; The CuBi2O4 is in a rod-shaped array.

2. The method for preparing a palladium-supported bismuth-based heterojunction photocatalyst according to claim 1, wherein the steps include: Taking a first bismuth source, a copper source and an alkaline reagent as reactants, CuBi2O4 is obtained through a hydrothermal reaction; A second bismuth source and a bromine source are used as reactants, the pH is adjusted to neutral, and BiOBr nanosheets are obtained through a solvothermal reaction; The BiOBr nanosheets and a palladium source are used as reactants, and in the presence of ethanol, a photoreduction reaction is carried out to obtain Pd-BiOBr; Dispersing the CuBi2O4 in ethanol to obtain a CuBi2O4 suspension; dispersing the Pd-BiOBr in isopropanol to obtain a Pd-BiOBr suspension; The CuBi2O4 suspension and the Pd-BiOBr suspension are mixed to obtain a mixed system, and the mixed system is subjected to solvent thermal reflux treatment to obtain the palladium-loaded bismuth-based heterojunction photocatalyst.

3. The preparation method according to claim 2, wherein The mass ratio of the first bismuth source, the copper source and the alkaline reagent is 2.42:0.60:0.87; And / or, the mass ratio of the second bismuth source to the bromine source is 1.36:0.3; and / or, the BiOBr nanosheets, palladium source, and ethanol are used in a ratio of 300 mg:8.3 mg:10 mL; and / or, the ratio of CuBi2O4 to ethanol in the CuBi2O4 suspension is 3-11 mg:50 mL; and / or, the ratio of Pd-BiOBr to isopropyl alcohol in the Pd-BiOBr suspension is 50 mg:50 mL; And / or, the volume ratio of ethanol to isopropanol in the mixed system is 1:

1.

4. The preparation method according to claim 2, wherein The temperature of the hydrothermal reaction is 180°C and the time is 24h; and / or, the solvothermal reaction temperature is 140° C. and the time is 12 h; And / or, the photoreduction reaction is performed using 300W xenon lamp irradiation for 30 minutes; And / or, the temperature of the solvent thermal reflux treatment is 80° C. and the time is 1 hour.

5. The preparation method according to claim 2, wherein The first bismuth source includes at least one of Bi(NO3)3·5H2O, BiCl3 and Bi2(SO4)3; and / or, the copper source comprises at least one of Cu(NO3)2·2.5H2O, Cu(NO3)2·5H2O and CuCl2·2H2O; And / or, the alkaline reagent includes NaOH and / or KOH.

6. The preparation method according to claim 2, wherein The second bismuth source includes at least one of Bi(NO3)3·5H2O, BiCl3 and Bi2(SO4)3; And / or, the bromine source comprises NaBr and / or KBr; And / or, the palladium source includes Na2PdCl4 and / or K2PdCl4.

7. The preparation method according to claim 6, wherein The palladium source was added in the form of an aqueous solution with a concentration of 100 mg / mL.

8. Use of the supported bismuth-based heterojunction photocatalyst according to claim 1 in photocatalytic CO2RR.

9. Use of the supported bismuth-based heterojunction photocatalyst according to claim 1 in improving the selectivity and yield of C2 products in photocatalytic CO2RR.

10. A method for preparing C2 products by photocatalytic CO2RR, characterized in that: The catalyst used in the method is the loaded bismuth-based heterojunction photocatalyst described in claim 1.

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