A bismuth-modified wrinkled two-dimensional tin oxide composite material, a preparation method and application thereof

Abstract

The present application relates to a kind of bismuth modified wrinkle two-dimensional tin oxide composite material and its preparation method and application, the preparation method includes the following steps: (1) tin powder and bismuth powder are mixed, by first heat treatment, obtain alloy powder;(2) the alloy powder obtained in step (1) and first solvent are mixed, inert gas is introduced into the reaction system, by second heat treatment, obtain liquid metal;(3) the liquid metal obtained in step (2) and second solvent are mixed, oxygen is introduced into the reaction system, by third heat treatment, obtain precipitate;(4) the precipitate obtained in step (3) and third solution are mixed, after centrifugation, take supernatant and drop to heat shrinkage piece, by fourth heat treatment, obtain the bismuth modified wrinkle two-dimensional tin oxide composite material.The present application utilizes the characteristics of heat shrinkage piece heating and shrinkage to make two-dimensional material produce wrinkle morphology, and wrinkle morphology has positive influence on the catalytic performance of tin oxide composite material electrocatalytic reduction CO2.

Description

Technical Field

[0001] This invention relates to the field of electrochemical catalyst preparation technology, and in particular to a bismuth-modified wrinkled two-dimensional tin oxide composite material, its preparation method, and its application. Background Technology

[0002] Developing carbon dioxide conversion strategies to produce low-carbon chemicals and fuels is considered one of the most important and effective solutions for reducing global carbon emissions. Among the many technologies for reducing carbon dioxide, electrocatalysis stands out due to its advantages such as mild reaction conditions, controllable reaction processes, and the ability to utilize intermittent electricity generated from renewable energy sources. However, exploring low-cost, high-conversion-rate, and highly selective electrocatalysts to convert carbon dioxide into target products remains a challenge.

[0003] Two-dimensional materials possess unique electronic and structural properties, excellent electrical conductivity, high atomic utilization, high specific surface area, and easily tunable structures, making them highly promising for the electrocatalytic reduction of carbon dioxide. Exploring low-cost, non-precious metal 2D nanosheets to convert carbon dioxide into the target product with sufficiently high reaction rates and efficiencies remains a key research focus.

[0004] Binary metal catalysts offer an effective method for tuning the selectivity and activity of carbon dioxide catalytic conversion, such as Pd-Sn alloys, Pd-Pt bimetallic nanoparticles, and Ag-Sn core-shell structures. However, the industrial application of this process depends on inexpensive catalysts, gradually increasing local current density, and long-term stability.

[0005] Currently, metal-based electrocatalysts used in CO2RR (CO2 Electroreduction Reaction) mainly include Sn, Bi, In, Pb, Hg, Cd, and Tl. Although noble metals such as gold (Au), silver (Ag), and palladium (Pd) with nanostructures exhibit excellent catalytic activity and high selectivity, their high cost hinders large-scale applications. While Pb, Hg, Cd, and Tl possess selectivity, they are highly toxic and environmentally harmful, and In is relatively expensive. Therefore, among numerous metal catalysts, Sn or Bi are the most ideal catalysts. Sn-based catalysts have attracted considerable attention in the field of electrocatalytic CO2RR research in recent years due to their excellent catalytic performance, abundant reserves, and low cost.

[0006] The size, morphology, and structure of Sn-based catalysts significantly influence their catalytic performance. Two-dimensional materials, by altering their dimensions (thickness and lateral dimensions), can have their electronic properties modified, thereby improving electron transfer and carbon dioxide reduction efficiency. This represents a promising research area for electrocatalytic carbon dioxide reduction. In recent years, numerous studies have focused on identifying new materials for electrocatalytic CO2RR or comparing the effects of different elemental modifications on the catalytic performance of existing materials. However, few studies have focused on the impact of strain resulting from changes in the morphology of two-dimensional nanosheets on their catalytic effects.

[0007] Given the shortcomings of existing technologies, how to provide a two-dimensional tin-based composite material and a method for preparing the nanosheets by inducing strain on the nanosheets themselves, so as to conduct in-depth research on the influence of strain caused by the morphology of the two-dimensional composite material on the electrocatalytic carbon dioxide reduction performance, has become an urgent problem to be solved. Summary of the Invention

[0008] To address the aforementioned technical problems, the present invention aims to provide a bismuth-modified wrinkled two-dimensional tin oxide composite material, its preparation method, and its applications. The preparation method of the bismuth-modified wrinkled two-dimensional tin oxide composite material of the present invention involves using oxygen injection and solvent dispersion to peel off the oxide layer formed on the surface of a liquid tin-bismuth metal alloy, resulting in an amorphous SnO mainly modified by two-dimensional metal elements. x (x=2-4) Materials composed of nanosheets. The thermal shrinkage properties of the heat-shrinkable sheets were used to induce a wrinkled morphology in the nanosheets, thereby inducing strain in the material. Within a specific potential window (-0.87~-1.17V vs. RHE), the wrinkled morphology significantly improved the Faraday efficiency of the electrocatalytic reduction of carbon dioxide to C1 products and suppressed the competing hydrogen evolution reaction, while maintaining excellent stability.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing a bismuth-modified wrinkled two-dimensional tin oxide composite material, the method comprising the following steps:

[0011] (1) Mix tin powder and bismuth powder, and then perform a first heat treatment to obtain alloy powder;

[0012] (2) Mix the alloy powder obtained in step (1) and the first solvent, introduce an inert gas into the reaction system, and after a second heat treatment, obtain liquid metal;

[0013] (3) The liquid metal and the second solvent obtained in step (2) are mixed, oxygen is introduced into the reaction system, and after a third heat treatment, a precipitate is obtained;

[0014] (4) Mix the precipitate obtained in step (3) with the third solution, centrifuge, take the supernatant and drop it onto the heat shrink sheet, and after the fourth heat treatment, obtain the bismuth-modified wrinkled two-dimensional tin oxide composite material.

[0015] This invention employs an oxygen injection and solvent dispersion method. During the process of oxygen being bubbled into the solvent through the bottom of a V-shaped tube containing tin-bismuth liquid metal, the surface oxidation of the tin-bismuth liquid metal is completed and then stripped into the solvent, resulting in an amorphous SnO primarily modified by two-dimensional metal elements. x (x=2-4) Materials composed of nanosheets. In tin-bismuth (Sn-Bi) liquid metal alloys, Sn preferentially undergoes selective oxidation on the liquid metal surface due to its much higher affinity for oxygen than Bi, according to the principle of minimizing Gibbs free energy. When oxygen enters the liquid metal through the bottom of a V-tube, the bubbles generate strong shear forces as they pass through the liquid-gas interface. This shear force peels off the newly formed two-dimensional oxide layer on the surface and carries it into the solvent, achieving a continuous process of "oxidation, peeling, and dispersion simultaneously." The rapid peeling process causes the oxide to cool quickly and stabilize in the solvent after leaving the liquid metal matrix, lacking sufficient time for long-range lattice ordering, thus forming an amorphous structure with high surface energy and abundant defect sites. Although Sn is preferentially oxidized, during the peeling process, trace amounts of Bi atoms are embedded into SnO due to atomic exchange or physical encapsulation at the interface. x In the lattice. This modification with metallic elements can adjust the band structure of the material and enhance its conductivity.

[0016] Unlike traditional research, this invention further utilizes the thermal shrinkage properties of heat-shrinkable sheets to create a wrinkled morphology in the nanosheets. The curvature of the wrinkles leads to SnO x The lattice of the nanosheets undergoes tensile or compressive strain. This microscopic strain alters the d-band centers of the atoms, thereby optimizing the adsorption energy for carbon dioxide intermediates. The strain effect from wrinkles, combined with the defect effect of the amorphous state, lowers the activation energy barrier required for CO2 molecule activation.

[0017] This invention increases the overpotential of the hydrogen evolution reaction through Bi modification and specific surface strain modulation. At the catalytic active sites, [the following is observed / improved / adjusted]... The reduced competitive adsorption of intermediates makes electrons more inclined to participate in the CO2 reduction pathway. This invention is not a simple material stacking, but rather a solution to the contradiction between activity and selectivity in chemical catalysis by using physical and mechanical means through a clever combination of "dynamic interface stripping" and "post-treatment strain induction".

[0018] The heat shrink sheet used in this invention is the commonly used heat shrink sheet in the prior art, as long as it can achieve the function of heat shrinkage. For example, the heat shrink sheet used in this invention is heat shrink sheet purchased from Taobao (Changsha Green New Materials, Fanyi Heat CraftArt), which is a 0.2mm thick, fully transparent, unpolished heat shrink sheet with a heat shrink ratio of 2.5:1 after complete heat shrinkage. Each time it is used, it is cut into 4×4cm sheets.

[0019] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0020] In some embodiments, the molar ratio of tin powder and bismuth powder in step (1) is 1:(0.7-0.8), for example, it can be 1:0.7, 1:0.72, 1:0.75, 1:0.78 or 1:0.8, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] In some embodiments, the total mass of tin powder and bismuth powder in step (1) is 10g-15g, for example, it can be 10g, 12g or 15g, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] In some embodiments, the temperature of the first heat treatment in step (1) is 300℃-380℃, for example, it can be 300℃, 310℃, 320℃, 330℃, 340℃, 350℃, 360℃, 370℃ or 380℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0023] In some embodiments, the first heat treatment time is 10 min to 30 min, for example, it can be 10 min, 15 min, 20 min, 25 min or 30 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] In some embodiments, the inert gas in step (2) includes any one or a combination of at least two of nitrogen, argon, or helium.

[0025] In some embodiments, the inert gas introduction rate in step (2) is 100 sccm-200 sccm, for example, it can be 100 sccm, 150 sccm, 180 sccm or 200 sccm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] In this invention, if the rate of inert gas introduction is too low, it is impossible to cool quickly enough to form liquid metal.

[0027] In some embodiments, step (2) of the second heat treatment is an oil bath.

[0028] In some embodiments, step (2) the second heat treatment is performed in an inert gas atmosphere.

[0029] In some embodiments, the temperature of the second heat treatment in step (2) is 165℃-200℃, for example, it can be 165℃, 170℃, 175℃, 180℃, 185℃, 190℃, 195℃ or 200℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 170℃-180℃.

[0030] In this invention, if the temperature of the second heat treatment is too low, the melting point of the liquid metal cannot be reached.

[0031] In some embodiments, the second heat treatment time is 10 min to 60 min, for example, it can be 10 min, 20 min, 30 min, 40 min, 50 min or 60 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] In some embodiments, the boiling points of the first solvent and the second solvent are ≥180°C.

[0033] In some embodiments, the first solvent and the second solvent each independently comprise any one or a combination of at least two of ethylene glycol, diethylene glycol, triethylene glycol, 1,3-propanediol, 1,4-butanediol, or 1,2-pentanediol. Typical but non-limiting combinations include combinations of ethylene glycol and diethylene glycol, combinations of diethylene glycol and triethylene glycol, combinations of 1,3-propanediol and 1,4-butanediol, combinations of 1,4-butanediol and 1,2-pentanediol, combinations of ethylene glycol, diethylene glycol, and triethylene glycol, and combinations of triethylene glycol, 1,3-propanediol, and 1,4-butanediol.

[0034] In some embodiments, the oxygen inlet rate in step (3) is 10 sccm-200 sccm, for example, it can be 10 sccm, 20 sccm, 50 sccm, 80 sccm, 100 sccm, 120 sccm, 150 sccm, 180 sccm or 200 sccm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] This invention further controls the oxygen flow rate to 10 sccm-200 sccm. The oxygen flow rate is related to the purity of the nanosheets and the sample preparation speed. If the oxygen flow rate is too low, the oxidation and peeling of the liquid metal surface formed by tin-bismuth and the collection rate into the solution are slow, making it difficult to achieve a fast sample preparation speed per unit time. If the oxygen flow rate is too high, the liquid metal cools too quickly, resulting in more alloy adhering to the surface of the two-dimensional nanosheets, affecting the purity of the nanosheets in the sample. This invention aims to prepare nanosheets with high purity per unit time to facilitate comparison of the effect of wrinkle morphology on the catalytic performance of two-dimensional nanosheets. The optimal experimental conditions were determined by scanning electron microscopy, with an oxygen flow rate of 100 sccm-200 sccm.

[0036] In some embodiments, the third heat treatment in step (3) is an oil bath.

[0037] In some embodiments, the third heat treatment in step (2) is performed in an oxygen atmosphere.

[0038] In some embodiments, the temperature of the third heat treatment in step (3) is 165℃-200℃, for example, it can be 165℃, 170℃, 175℃, 180℃, 185℃, 190℃, 195℃ or 200℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 170℃-180℃.

[0039] In some embodiments, the third heat treatment time is 10 min to 60 min, for example, it can be 10 min, 20 min, 30 min, 40 min, 50 min or 60 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] In some embodiments, the third solution in step (3) includes ethanol.

[0041] In some embodiments, centrifugation and washing are included after the third heat treatment in step (3) and before the precipitate is obtained.

[0042] In some embodiments, the centrifugation speed in step (3) is 8000rpm-10000rpm, for example, it can be 8000rpm, 9000rpm or 10000rpm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 9000rpm-10000rpm.

[0043] In some embodiments, the centrifugation time in step (3) is 10 min to 20 min, for example, it can be 10 min, 12 min, 15 min, 18 min or 20 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0044] The detergent used in the washing process is ethanol.

[0045] In some embodiments, the third solution in step (4) comprises ethanol.

[0046] In some embodiments, the centrifugation speed in step (4) is 100 rpm to 10000 rpm, for example, it can be 100 rpm, 500 rpm, 1000 rpm, 1500 rpm, 2000 rpm, 2500 rpm, 3000 rpm, 3500 rpm, 4000 rpm, 5000 rpm, 6000 rpm, 7000 rpm, 8000 rpm, 9000 rpm or 10000 rpm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 2000 rpm to 3500 rpm.

[0047] In step (4) of this invention, the centrifugation speed is further controlled to be 100 rpm-10000 rpm. The centrifugation speed is related to the sample yield and the purity of the nanosheets. If the centrifugation speed is too high, the sample yield will be low; if the centrifugation speed is too low, the purity of the nanosheets in the sample will be too low.

[0048] In some embodiments, the centrifugation time in step (4) is 0.5 min to 2 min, for example, it can be 0.5 min, 1 min, 1.5 min or 2 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0049] In some embodiments, the temperature of the fourth heat treatment in step (4) is 100℃-150℃, for example, it can be 100℃, 110℃, 120℃, 130℃, 140℃ or 150℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 115℃-125℃.

[0050] This invention further controls the temperature of the fourth heat treatment to 100℃-150℃. The temperature of the fourth heat treatment affects the degree of shrinkage of the heat-shrink sheet. If the temperature of the fourth heat treatment is too low, the heat-shrink sheet will not shrink completely, and the nanosheet will not obtain sufficient compressive strain to induce instability wrinkles. The surface will remain flat or have only slight undulations. Without the band structure optimization brought about by strain engineering, the selectivity of the catalyst cannot be significantly improved, and the Faraday efficiency will be at a low level. If the temperature of the fourth heat treatment is too high, even if the complete crystallization temperature is not reached, the excessive heat energy will induce amorphous SnO. xLocal atomic rearrangement occurs, leading to the thermal elimination or annihilation of highly active defect sites (such as oxygen vacancies). The diffusion rate of two-dimensional metal elements (such as Bi) modified on the surface is accelerated at high temperatures, which may cause aggregation or migration into the bulk phase, thus disrupting the originally uniform distribution of surface active sites. Consequently, it becomes impossible to determine the impact of wrinkled morphology on the catalytic performance of two-dimensional nanosheets.

[0051] In some embodiments, the time for the fourth heat treatment is 1 min to 10 min, for example, it can be 1 min, 3 min, 5 min, 8 min or 10 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 5 min to 10 min.

[0052] This invention further controls the fourth heat treatment time to 5-10 minutes to regulate the shrinkage degree of the heat-shrinkable sheet, thereby affecting the wrinkle morphology of the two-dimensional nanosheet composite material. Different wrinkle morphologies introduce different strains, and strain is closely related to the catalytic performance of the material, thus affecting its catalytic activity. If the fourth heat treatment time is too long, the heat-shrinkable sheet will shrink completely, and the wrinkle morphology will no longer change significantly with time; therefore, the catalytic activity will not change significantly with time either. If the time is too short, the shrinkage will be incomplete, and the two-dimensional nanosheets will not form continuous, ordered wrinkles, but rather exhibit local stacking or large flat areas. The interlayer overlap of the nanosheets shields the active sites, resulting in an electrochemically active area that is far lower than expected.

[0053] As a preferred embodiment of the preparation method of the present invention, the preparation method includes the following steps:

[0054] (1) Mix tin powder and bismuth powder in a molar ratio of 1:(0.7-0.8) with a total mass of 10g-15g. Perform a first heat treatment in a muffle furnace at 300℃-380℃ for 10min-30min. After natural cooling, obtain alloy powder.

[0055] (2) Mix the alloy powder obtained in step (1) with 10ml-20ml of the first solvent, bubble in the reaction system to introduce inert gas, and perform a second heat treatment at 170℃-180℃ for 10min-60min in an oil bath under an inert gas atmosphere to obtain liquid metal.

[0056] (3) Mix the liquid metal obtained in step (2) with 10 ml-20 ml of the second solvent, introduce oxygen into the reaction system at a flow rate of 10 sccm-200 sccm, and simultaneously perform a third heat treatment at 170℃-180℃ for 10 min-60 min in an oil bath under an oxygen atmosphere, centrifuge at 8000 rpm-10000 rpm for 10 min-20 min, and wash the product with ethanol 3-5 times to obtain the precipitate;

[0057] (4) Mix the precipitate obtained in step (3) with 30ml-50ml of ethanol, centrifuge at 2000rpm-3500rpm for 0.5min-2min to obtain the non-wrinkled two-dimensional tin oxide composite material in the supernatant, drop the supernatant onto the heat shrink sheet, and perform a fourth heat treatment in a muffle furnace at 115℃-125℃ for 1min-10min. Scrape off the product from the surface of the heat shrink sheet to obtain the bismuth-modified wrinkled two-dimensional tin oxide composite material.

[0058] In a second aspect, the present invention provides a bismuth-modified two-dimensional tin oxide composite material as described in the first aspect, wherein the bismuth-modified bismuth-modified two-dimensional tin oxide composite material is prepared according to the preparation method described in the first aspect.

[0059] The bismuth-modified wrinkled two-dimensional tin oxide composite material provided by this invention consists mainly of amorphous SnO with a thickness of about 3 nm and a lateral dimension exceeding 2 μm, modified with a metal oxide. x (x=2-4) Nanosheets, whose large size and low thickness endow them with extremely high flexibility. This "flexibility" not only makes them easy to undergo controllable deformation (such as wrinkling), but more importantly, the local strain introduced by deformation can effectively regulate the electronic structure and surface activity of the material, thus providing an ideal structural platform for studying the structure-activity relationship between wrinkled morphology and catalytic performance. Compared with the crystalline, planar tin oxide materials commonly used in the prior art, the amorphous substrate used in this material has more coordination unsaturated sites and defects, which can serve as active centers for catalytic reactions. The coexistence of surface metal oxide modification and a small amount of tin-bismuth alloy at the edge of the nanosheet further produces a synergistic catalytic effect, which is beneficial to improving the catalytic activity and stability of the material.

[0060] Thirdly, the present invention provides an application of the bismuth-modified two-dimensional tin oxide composite material as described in the second aspect, wherein the bismuth-modified bismuth-modified two-dimensional tin oxide composite material is used for the electrocatalytic reduction of carbon dioxide to formic acid.

[0061] The wrinkled two-dimensional tin oxide composite material provided by this invention is used in the working electrode for the electrocatalytic reduction of carbon dioxide to formic acid. The working electrode can be prepared by existing methods. This composite material exhibits significant advantages in the electrocatalytic reduction of carbon dioxide. In the voltage range of -0.87 to -1.17 V vs. RHE, its C1 product Faradaic efficiency is significantly improved compared with the unstrained material. At -1.07 V vs. RHE, the Faradaic efficiency can reach more than 90%, which is about 17% higher. At the same time, it effectively suppresses the hydrogen evolution side reaction and exhibits excellent catalytic selectivity and stability.

[0062] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0063] Compared with the prior art, the present invention has at least the following beneficial effects:

[0064] (1) The present invention removes the oxide layer formed on the surface of liquid tin-bismuth alloy by means of oxygen injection and solvent dispersion, and obtains an amorphous SnO mainly modified by two-dimensional metal elements. x (x=2-4) Materials composed of nanosheets. Unlike traditional research, this invention further utilizes the thermal shrinkage properties of heat-shrinkable sheets to induce a wrinkled morphology in the nanosheets, thereby inducing strain in the material. The wrinkled morphology significantly improves the Faraday efficiency of the electrocatalytic reduction of carbon dioxide to C1 products and suppresses the competing hydrogen evolution reaction, while maintaining excellent stability.

[0065] (2) The bismuth-modified wrinkled two-dimensional tin oxide composite material provided by the present invention is mainly composed of bismuth-modified amorphous SnO with a thickness of about 3 nm and a lateral dimension of more than 2 μm. x (x=2-4) Nanosheets: The large size and low thickness of the nanosheets give them great flexibility. Small amounts of tin-bismuth alloys can be found at the edges of some nanosheets. This is because, during the process of liquid metal forming an oxide layer and rising into the dispersion solvent driven by oxygen bubbles, some of the liquid metal is carried into the solvent along with the exfoliated nanosheets. Although centrifugation removes most of the large particles, some particles remain encapsulated within the nanosheets and cannot be completely removed.

[0066] (3) The wrinkled two-dimensional tin oxide composite material provided by the present invention is used in the working electrode for the electrocatalytic reduction of carbon dioxide to formic acid. The working electrode can be prepared by the methods in the prior art. The composite material shows significant advantages in the electrocatalytic reduction of carbon dioxide. In the voltage range of -0.87~-1.17V vs. RHE, its C1 product Faradaic efficiency is greatly improved compared with the unstrained material. At -1.07V vs. RHE, the Faradaic efficiency can reach more than 90%, which is about 17% higher. At the same time, it effectively suppresses the hydrogen evolution side reaction and shows excellent catalytic selectivity and stability. Attached Figure Description

[0067] Figure 1 This is a scanning electron microscope (SEM) image of the bismuth-modified wrinkled two-dimensional tin oxide composite material obtained in Example 1 of the present invention;

[0068] Figure 2This is a high-resolution transmission electron microscope (HRTEM) image of the bismuth-modified wrinkled two-dimensional tin oxide composite material obtained in Example 1 of the present invention;

[0069] Figure 3 This is an atomic force microscope (AFM) image of the bismuth-modified two-dimensional tin oxide composite material obtained in Comparative Example 1 of this invention;

[0070] Figure 4 This is a transmission electron microscope (TEM) image of the bismuth-modified two-dimensional tin oxide composite material obtained in Comparative Example 1 of this invention;

[0071] Figure 5 These are TEM images and corresponding elemental distribution diagrams of the bismuth-modified two-dimensional tin oxide composite material obtained in Comparative Example 1 of this invention.

[0072] Figure 6 This is the X-ray photoelectron spectroscopy (XPS) spectrum of Sn element in the bismuth-modified two-dimensional tin oxide composite material obtained in Comparative Example 1 of this invention;

[0073] Figure 7 This is an XPS image of the Bi element in the bismuth-modified two-dimensional tin oxide composite material obtained in Comparative Example 1 of this invention.

[0074] Figure 8 This is an HRTEM image of the bismuth-modified two-dimensional tin oxide composite material obtained in Comparative Example 1 of this invention;

[0075] Figure 9 This is a local current density diagram of the electrodes used in Application Example 1 and Comparative Application Example 1 of the present invention for electrocatalytic carbon dioxide reduction testing.

[0076] Figure 10 This is a Faraday efficiency diagram of the electrodes used in Application Example 1 and Comparative Application Example 1 of the present invention for electrocatalytic carbon dioxide reduction testing;

[0077] Figure 11 This is the it curve of the electrode of Application Example 1 of the present invention under a voltage of -1.07V vs. RHE for 12 hours. Detailed Implementation

[0078] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0079] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0080] Unless otherwise specified, all reagents and consumables used in the following examples and comparative examples were purchased from conventional reagent manufacturers in the art; unless otherwise specified, the experimental methods and techniques used were conventional methods and techniques in the art.

[0081] Example 1

[0082] This embodiment provides a bismuth-modified wrinkled two-dimensional tin oxide composite material, wherein the thickness of the bismuth-modified wrinkled two-dimensional tin oxide composite material is 3 nm and the lateral dimension is 2 μm;

[0083] The method for preparing the bismuth-modified wrinkled two-dimensional tin oxide composite material provided in this embodiment includes the following steps:

[0084] (1) Tin powder and bismuth powder were mixed in a molar ratio of 1:0.75, with a total mass of 10g. The mixture was subjected to a first heat treatment at 350°C for 20min in a muffle furnace and then naturally cooled to obtain alloy powder.

[0085] (2) Mix the alloy powder obtained in step (1) with 15 ml of diethylene glycol, bubble inert gas into the reaction system, and perform a second heat treatment at 180°C for 30 min in an inert gas atmosphere and oil bath to obtain Sn-Bi liquid metal.

[0086] (3) Mix the liquid metal obtained in step (2) with 15 ml of diethylene glycol, introduce oxygen into the reaction system at a flow rate of 100 sccm, and simultaneously perform a third heat treatment at 180°C for 30 min in an oil bath under an oxygen atmosphere. Centrifuge at 10000 rpm for 15 min, wash the product three times with ethanol to obtain the precipitate.

[0087] (4) Mix the precipitate obtained in step (3) with 40 ml of ethanol, centrifuge at 3000 rpm for 1 min, take the supernatant and drop it onto the heat shrink sheet (Changsha Green New Materials, Fanyi Heat Craft Art), perform a fourth heat treatment in a muffle furnace at 120℃ for 5 min, scrape the product off the surface of the heat shrink sheet, and obtain the bismuth-modified wrinkled two-dimensional tin oxide composite material.

[0088] Example 2

[0089] This embodiment provides a bismuth-modified wrinkled two-dimensional tin oxide composite material, wherein the thickness of the bismuth-modified wrinkled two-dimensional tin oxide composite material is 2.8 nm and the lateral dimension is 2 μm;

[0090] The method for preparing the bismuth-modified wrinkled two-dimensional tin oxide composite material provided in this embodiment includes the following steps:

[0091] (1) Tin powder and bismuth powder were mixed in a molar ratio of 1:0.75, with a total mass of 12g. The mixture was subjected to a first heat treatment at 300℃ for 30min in a muffle furnace and then naturally cooled to obtain alloy powder.

[0092] (2) Mix the alloy powder obtained in step (1) with 15 ml of diethylene glycol, bubble inert gas into the reaction system, and perform a second heat treatment at 175 °C for 30 min in an inert gas atmosphere and oil bath to obtain Sn-Bi liquid metal.

[0093] (3) Mix the liquid metal obtained in step (2) with 15 ml of diethylene glycol, introduce oxygen into the reaction system at a flow rate of 100 sccm, and simultaneously perform a third heat treatment at 175°C for 30 min in an oil bath under an oxygen atmosphere. Centrifuge at 9000 rpm for 20 min, wash the product with ethanol 4 times, and obtain the precipitate.

[0094] (4) Mix the precipitate obtained in step (3) with 35 ml of ethanol, centrifuge at 2000 rpm for 2 min, take the supernatant and drop it onto the heat shrink sheet, perform a fourth heat treatment in a muffle furnace at 120 °C for 10 min, scrape the product off the surface of the heat shrink sheet, and obtain the bismuth-modified wrinkled two-dimensional tin oxide composite material.

[0095] Example 3

[0096] This embodiment provides a bismuth-modified wrinkled two-dimensional tin oxide composite material, wherein the thickness of the bismuth-modified wrinkled two-dimensional tin oxide composite material is 2.8 nm and the lateral dimension is 2 μm;

[0097] The method for preparing the bismuth-modified wrinkled two-dimensional tin oxide composite material provided in this embodiment includes the following steps:

[0098] (1) Tin powder and bismuth powder were mixed in a molar ratio of 1:0.78, with a total mass of 15g. The mixture was subjected to a first heat treatment at 380°C for 15min in a muffle furnace and then naturally cooled to obtain alloy powder.

[0099] (2) Mix the alloy powder obtained in step (1) with 20 ml of diethylene glycol, bubble inert gas into the reaction system, and perform a second heat treatment at 180 °C for 40 min in an inert gas atmosphere and oil bath to obtain Sn-Bi liquid metal.

[0100] (3) Mix the liquid metal obtained in step (2) with 20 ml of diethylene glycol, introduce oxygen into the reaction system at a flow rate of 150 sccm, and simultaneously perform a third heat treatment at 180°C for 40 min in an oil bath under an oxygen atmosphere. Centrifuge at 10000 rpm for 10 min, wash the product with ethanol 5 times, and obtain the precipitate.

[0101] (4) Mix the precipitate obtained in step (3) with 50 ml of ethanol, centrifuge at 2500 rpm for 1.5 min, take the supernatant and drop it onto the heat shrink sheet, perform a fourth heat treatment in a muffle furnace at 125 °C for 5 min, scrape the product off the surface of the heat shrink sheet, and obtain the bismuth-modified wrinkled two-dimensional tin oxide composite material.

[0102] Example 4

[0103] This embodiment provides a bismuth-modified wrinkled two-dimensional tin oxide composite material. The only difference from Example 1 is that when preparing the bismuth-modified wrinkled two-dimensional tin oxide composite material, the oxygen flow rate in step (3) is 300 sccm, and the other steps remain unchanged.

[0104] Example 5

[0105] This embodiment provides a bismuth-modified wrinkled two-dimensional tin oxide composite material. The only difference from Example 1 is that when preparing the bismuth-modified wrinkled two-dimensional tin oxide composite material, the oxygen flow rate in step (3) is 8 sccm, and the other steps remain unchanged.

[0106] Example 6

[0107] This embodiment provides a bismuth-modified wrinkled two-dimensional tin oxide composite material. The only difference from Example 1 is that when preparing the bismuth-modified wrinkled two-dimensional tin oxide composite material, the time for the fourth heat treatment in step (4) is 1 min, and the other steps remain unchanged.

[0108] Example 7

[0109] This embodiment provides a bismuth-modified wrinkled two-dimensional tin oxide composite material. The only difference from Example 1 is that when preparing the bismuth-modified wrinkled two-dimensional tin oxide composite material, the temperature of the fourth heat treatment in step (4) is 90°C, and the other steps remain unchanged.

[0110] Comparative Example 1

[0111] This comparative example provides a bismuth-modified two-dimensional tin oxide composite material, which differs from Example 1 only in that step (4) was not performed when preparing the bismuth-modified two-dimensional tin oxide composite material.

[0112] Application Example 1

[0113] This application example provides an electrode for the electrocatalytic reduction of carbon dioxide to formic acid, which is prepared by the following method:

[0114] Weigh 1 mg of the bismuth-modified wrinkled two-dimensional tin oxide composite material prepared in Example 1, and add it to a sample tube along with 0.4 mg of carbon black. Add 150 μL of ethanol and 5 μL of Nafion solution, and sonicate for 30 min. Shake for 3 min to ensure thorough mixing. Use a pipette to evenly coat the prepared sample slurry onto a cut carbon paper, and dry it using an infrared lamp or by air drying to obtain an electrode for the electrocatalytic reduction of carbon dioxide to formic acid. The catalyst loading on the carbon paper is 1 mg / cm³. 2 .

[0115] Application Examples 2-7

[0116] Application Examples 2-7 each provide an electrode for the electrocatalytic reduction of carbon dioxide to formic acid. The only difference between the preparation method of the electrode and that of Application Example 1 is that the bismuth-modified wrinkled two-dimensional tin oxide composite material obtained in Example 1 is replaced with the bismuth-modified wrinkled two-dimensional tin oxide composite material obtained in Examples 2-7, while the rest of the method remains unchanged.

[0117] Comparative Application Example 1

[0118] Comparative Application Example 1 provides an electrode for the electrocatalytic reduction of carbon dioxide to formic acid. The only difference between the preparation method of the electrode and that of Application Example 1 is that the bismuth-modified wrinkled two-dimensional tin oxide composite material obtained in Example 1 is replaced with the tin oxide composite material obtained in Comparative Example 1, while the rest of the methods remain unchanged.

[0119] test:

[0120] (1) Phase analysis of the materials obtained in Example 1 and Comparative Example 1:

[0121] The SEM image of the bismuth-modified wrinkled two-dimensional tin oxide composite material prepared in Example 1 is shown below. Figure 1 As shown, from Figure 1 It can be seen that the material surface has obvious wrinkled morphology. High-resolution transmission electron microscopy (HRTEM) of the tin oxide composite material prepared in Comparative Example 1 shows... Figure 8 It can be seen that the bismuth element modified on the surface of the nanosheets has lattice fringes, while the nanosheet body itself does not. Therefore, the nanosheets prepared in Comparative Example 1 are amorphous SnO modified with Bi₂O₃. x (x=2-4) nanosheets, with a lattice spacing of 0.33 nm for Bi2O3 on the nanosheets.

[0122] High-resolution transmission electron microscopy (HRTEM) of the bismuth-modified wrinkled two-dimensional tin oxide composite material prepared in Example 1 is shown below. Figure 2 As shown, from Figure 2 It is known that the lattice spacing of Bi2O3 on the nanosheet is 0.32~0.36 nm. This variation is attributed to the change in local strain level during the shrinkage process of the heat-shrink sheet. Although the macroscopic shrinkage rate remains consistent, there are local strain differences. The strain generated by the heat shrinkage process leads to an increase rather than a decrease in the lattice spacing. This is because when the heat-shrinked sample is scraped off the heat-shrink sheet, the sample on the surface is mainly generated by bending deformation.

[0123] The atomic force microscope (AFM) image of the tin oxide composite material obtained in Comparative Example 1 is shown below. Figure 3 As shown, from Figure 3 It can be seen that the main body of the material prepared in Comparative Example 1 is a nanosheet with a thickness of about 2.8 nm and a lateral dimension of more than 2 μm. The large size and low thickness give the nanosheet great flexibility.

[0124] The transmission electron microscope (TEM) image and elemental distribution map of the tin oxide composite material obtained in Comparative Example 1 are shown below. Figure 4 and Figure 5 As shown in the figure, the nanosheets in Comparative Example 1 have relatively uniformly distributed spots on their surface. Figure 5 Further elemental analysis revealed that the nanosheets were mainly composed of Sn and O elements, while the relatively uniformly dispersed spots were composed of Bi elements.

[0125] Further analysis of the composition and valence state of the nanosheets was conducted, and the X-ray photoelectron spectroscopy (XPS) of the tin oxide composite material obtained in Comparative Example 1 was performed. Figure 6 As shown, by Figure 6 The Sn3d spectrum shows that Sn 3d values ​​at 486.79 / 495.19 eV and 484.86 / 493.26 eV correspond to Sn 3d 5 / 2 and Sn 3d 3 / 2 The two band structures clearly show that Sn(4+ / 2+) has a large proportion, while Sn(0) has a very small proportion. The proportion of Sn(0) indicates that the alloy content in the sample is very small, and the main body of the material is nanosheets.

[0126] XPS analysis of bismuth in the tin oxide composite material obtained in Comparative Example 1 is as follows: Figure 7 As shown, by Figure 7 The Bi 4f spectrum shows that bismuth is mainly composed of Bi. 3+ and Bi 0 Two valence states exist, corresponding to the spectral peak in Bi 4f 5 / 2 and Bi 4f 7 / 2Both have a considerable proportion, which is due to the bismuth modification on the nanosheets. Compared with elemental bismuth in the alloy (156.65 / 161.92 eV), bismuth in the sample is more predominantly in the form of oxides (159.52 / 164.84 eV).

[0127] (2) Test the electrodes prepared in the corresponding application example 1-application example 7 and comparison application example 1.

[0128] Test conditions: Electrocatalytic CO2 reduction reaction tests were conducted in an H-type electrolytic cell. The cathode and anode cells of the electrolytic cell were separated by a Nafion 117 membrane, and each end of the electrolytic cell contained 30 ml of 0.5 M KHCO3. A three-electrode system was used, with carbon paper supporting the material as the working electrode, saturated Ag / AgCl as the reference electrode, and a platinum mesh electrode as the counter electrode. All electrocatalytic CO2 reduction tests were performed at room temperature and pressure using an electrochemical workstation (CHI660).

[0129] The electrolytic cell was first saturated with CO2 at 20 sccm for 15 min to ensure electrolyte saturation (pH 7.35) and to eliminate air interference. Cyclic voltammetry (CV) was first performed in the range of -0.17 to -1.37 V (vs. RHE) at a scan rate of 100 mV / s. Then, linear sweep voltammetry (LSV) was performed within the same voltage range at a scan rate of 10 mV / s. Constant voltage testing was then performed, and time-current (it) curves were obtained. The gaseous products were directly measured by gas chromatography. 550 μL of electrolyte, 10 μL of LDM, and 100 μL of L2O were added to an NMR tube, and the liquid phase products were analyzed by NMR (AVANCE III 400). 1 The H-spectrum was tested using a pressure water peak procedure.

[0130] Depend on Figure 9 It can be seen that within the voltage range of -0.87 to -1.17 V vs. RHE, the bismuth-modified two-dimensional tin oxide composite material with wrinkled morphology described in Example 1 is used to electrocatalyze the reduction of CO2 to HCOO. - The local current density increases significantly, and when the voltage exceeds -1.27V vs. RHE, HCOO - The local current density of H2 was lower than that of Comparative Application Example 1; while in Application Example 1, the local current density of H2 was significantly reduced in the range of -0.87 to -1.17 V vs. RHE; the local current density of CO was significantly increased at -1.07 V vs. RHE, and the changes were not significant at other test voltages compared to before strain.

[0131] Depend on Figure 10It can be seen that, within the range of -0.87 to -1.37 V vs. RHE, the Faraday efficiency comparison analysis of the products at different voltages shows that the main products are gaseous CO and liquid HCOO. - The C1 product and the gaseous H2 generated in the competing reaction. Compared with Comparative Application Example 1, in the range of -0.87 to -1.17 V vs. RHE, the Faradaic efficiency of the C1 product of the electrode in Application Example 1 increases with increasing voltage, exhibiting higher selectivity. At -1.07 V vs. RHE, the catalyst in Application Example 1 electrocatalyzes the reduction of FE from CO2. C1 The maximum efficiency reached 91.8%, which was more than 17% higher than that of the material in Comparative Application Example 1, while greatly suppressing the competing hydrogen evolution reaction.

[0132] Depend on Figure 11 It can be seen that, during the catalytic cycling test at a constant voltage of -1.07V vs. RHE for 12 hours, the current density of the electrode in Application Example 1 remained consistently at 35 mA·cm⁻¹. -2 This indicates that the bismuth-modified wrinkled two-dimensional tin oxide composite material prepared in Example 1 has excellent electrochemical stability.

[0133] The Faraday efficiency of the electrocatalytic CO2 reduction test is shown in Table 1 below. The data in Table 1 are the average values ​​calculated from multiple tests to make the results more accurate.

[0134] Table 1

[0135]

[0136] The test results show that:

[0137] (1) As can be seen from Application Examples 1-3, the present invention prepares bismuth-modified wrinkled two-dimensional tin oxide composite material by oxygen injection and solvent dispersion, and then uses the heat shrinkage property of heat shrink sheet to generate wrinkled morphology in two-dimensional material. Through electrocatalytic carbon dioxide reduction test, it is proved that the wrinkled morphology has a positive influence on the catalytic performance of bismuth-modified two-dimensional tin oxide composite material for electrocatalytic reduction of CO2 in the range of -0.87~-1.17V vs. RHE.

[0138] (2) By comparing Application Example 1 with Application Examples 4-5, it can be seen that the present invention further controls the oxygen flow rate to 100sccm-200sccm. The oxygen flow rate is related to the purity of the nanosheets and the sample preparation speed. If the oxygen flow rate is too low, the oxidation and stripping speed of the tin-bismuth liquid metal surface and the collection speed into the solution will be slow, making it difficult to achieve a fast sample preparation speed per unit time. If the oxygen flow rate is too high, the liquid metal will cool down too quickly, and more alloys will adhere to the surface of the two-dimensional nanosheets, affecting the purity of the nanosheets in the sample and thus affecting the catalytic performance.

[0139] (3) By comparing Application Example 1 and Application Example 6, it can be seen that the present invention further controls the time of the fourth heat treatment to 5-10 min. The time of the fourth heat treatment affects the degree of shrinkage of the heat-shrinkable sheet, thereby affecting the wrinkle morphology of the two-dimensional nanosheet composite material. Different wrinkle morphologies will introduce different strains, and strain is closely related to the catalytic performance of the material, thus affecting its catalytic activity. If the fourth heat treatment time is too long, the heat-shrinkable sheet will shrink completely, and the wrinkle morphology will no longer change significantly with time, so the catalytic activity will not change significantly with time; if the time is too short, the shrinkage will be incomplete, and the two-dimensional nanosheets will not form continuous and orderly wrinkles, but will have local stacking or large flat areas. The interlayer overlap of the nanosheets shields the active sites, resulting in an electrochemical active area that is much lower than expected.

[0140] (4) By comparing Application Example 1 and Application Example 7, it can be seen that the present invention further controls the temperature of the fourth heat treatment to 100℃-150℃. The temperature of the fourth heat treatment affects the degree of shrinkage of the heat-shrinkable sheet. If the temperature of the fourth heat treatment is too low, the heat-shrinkable sheet will not shrink completely, and the nanosheet will not be able to obtain sufficient compressive strain to induce unstable wrinkles. The surface will remain flat or have only slight undulations. The band structure optimization brought about by strain engineering is lacking, the selectivity of the catalyst cannot be qualitatively improved, and the Faraday efficiency will be at a low level. If the temperature of the fourth heat treatment is too high, even if the complete crystallization temperature is not reached, the excessive heat energy will induce amorphous SnO. x Local atomic rearrangement occurs, leading to thermal elimination or annihilation of highly active defect sites. The diffusion rate of Bi metal elements modified on the surface accelerates at high temperatures, which may cause aggregation or migration into the bulk phase, thus disrupting the originally uniform distribution of surface active sites.

[0141] (5) As can be seen from Application Example 1 and Comparative Application Example 1, when step (4) is not performed, that is, when the composite material is not treated with heat shrink sheet, the material cannot obtain the performance gain brought by strain engineering due to the lack of wrinkle morphology. This strongly proves that the wrinkle generation by heat shrink sheet is the core mechanism for improving the electrocatalytic carbon dioxide reduction performance of bismuth modified two-dimensional tin oxide composite material, and is the key to the substantial technical progress of this invention.

[0142] In summary, this invention prepares bismuth-modified wrinkled two-dimensional tin oxide composite materials by oxygen injection and solvent dispersion. Then, the wrinkled morphology is generated in the two-dimensional material by utilizing the shrinkage property of heat-shrink sheets. Electrocatalytic carbon dioxide reduction tests demonstrate that the wrinkled morphology has a positive impact on the electrocatalytic reduction performance of bismuth-modified two-dimensional tin oxide composite materials in the range of -0.87 to -1.17 V vs. RHE.

[0143] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a bismuth-modified wrinkled two-dimensional tin oxide composite material, characterized in that, The preparation method includes the following steps: (1) Mix tin powder and bismuth powder, and then perform a first heat treatment to obtain alloy powder; (2) Mix the alloy powder obtained in step (1) and the first solvent, introduce an inert gas into the reaction system, and after a second heat treatment, obtain liquid metal; (3) The liquid metal and the second solvent obtained in step (2) are mixed, oxygen is introduced into the reaction system, and after a third heat treatment, a precipitate is obtained; (4) Mix the precipitate obtained in step (3) with the third solution, centrifuge, take the supernatant and drop it onto the heat shrink sheet, and after the fourth heat treatment, obtain the bismuth-modified wrinkled two-dimensional tin oxide composite material.

2. The preparation method according to claim 1, characterized in that, The molar ratio of tin powder and bismuth powder in step (1) is 1:(0.7-0.8).

3. The preparation method according to claim 1, characterized in that, Step (1) The temperature of the first heat treatment is 300℃-380℃; And / or, the duration of the first heat treatment is 10 min to 30 min.

4. The preparation method according to claim 1, characterized in that, The inert gas is introduced at a rate of 100 sccm-200 sccm in step (2); And / or, in step (2), the second heat treatment is performed in an inert gas atmosphere; And / or, in step (2), the temperature of the second heat treatment is 165℃-200℃; And / or, the duration of the second heat treatment is 10 min to 60 min; And / or, the first solvent and the second solvent each independently comprise any one or a combination of at least two of ethylene glycol, diethylene glycol, triethylene glycol, 1,3-propanediol, 1,4-butanediol or 1,2-pentanediol.

5. The preparation method according to claim 1, characterized in that, The oxygen introduction rate in step (3) is 10 sccm-200 sccm; And / or, the third heat treatment in step (2) is performed in an oxygen atmosphere; And / or, the temperature of the third heat treatment in step (3) is 165℃-200℃; And / or, the duration of the third heat treatment is 10 min to 60 min; And / or, the third solution in step (3) includes ethanol; And / or, after the third heat treatment described in step (3) and before obtaining the precipitate, centrifugation and washing are also included.

6. The preparation method according to claim 1, characterized in that, The third solution in step (4) includes ethanol; And / or, the centrifugation speed in step (4) is 100 rpm to 10000 rpm, and the centrifugation time is 0.5 min to 2 min.

7. The preparation method according to claim 1, characterized in that, The temperature of the fourth heat treatment in step (4) is 100℃-150℃; And / or, the duration of the fourth heat treatment is 1 min to 10 min.

8. The preparation method according to claim 1, characterized in that, The preparation method includes the following steps: (1) Tin powder and bismuth powder are mixed in a molar ratio of 1:(0.7-0.8), and subjected to a first heat treatment at 300℃-380℃ for 10min-30min in a muffle furnace. After natural cooling, alloy powder is obtained. (2) Mix the alloy powder obtained in step (1) and the first solvent, bubble in the reaction system with inert gas, and perform a second heat treatment at 170℃-180℃ for 10min-60min in an inert gas atmosphere and oil bath to obtain liquid metal. (3) Mix the liquid metal and the second solvent obtained in step (2), introduce oxygen into the reaction system at a flow rate of 10 sccm-200 sccm, and simultaneously perform a third heat treatment at 170℃-180℃ for 10 min-60 min in an oil bath under an oxygen atmosphere, centrifuge at 8000rpm-10000rpm for 10 min-20 min, and wash the product with ethanol 3-5 times to obtain the precipitate; (4) Mix the precipitate obtained in step (3) with ethanol, centrifuge at 2000rpm-3500rpm for 0.5min-2min to obtain the non-wrinkled two-dimensional tin oxide composite material in the supernatant, take the supernatant and drop it onto the heat shrink sheet, and perform a fourth heat treatment in a muffle furnace at 115℃-125℃ for 1min-10min. Scrape off the product from the surface of the heat shrink sheet to obtain the bismuth-modified wrinkled two-dimensional tin oxide composite material.

9. A bismuth-modified wrinkled two-dimensional tin oxide composite material, characterized in that, The bismuth-modified wrinkled two-dimensional tin oxide composite material is prepared by the preparation method according to any one of claims 1-8.

10. An application of the bismuth-modified wrinkled two-dimensional tin oxide composite material as described in claim 9, characterized in that, The bismuth-modified wrinkled two-dimensional tin oxide composite material is used for the electrocatalytic reduction of carbon dioxide to formic acid.

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