Bismuth nanotube rich in atom defects and preparation method thereof

Abstract

The invention belongs to but not limited to the technical field of synthesis of nano materials, and discloses a bismuth nanotube rich in atom defects and a preparation method thereof.The preparation method comprises the steps that Bi metal soluble salt and potassium halide salt are dissolved in deionized water, ethyl alcohol or ethylene glycol solvent in sequence, and after uniform dispersion, the mixture is transferred into a hydrothermal reaction kettle for a reaction; and under the action of a surfactant, reducing the obtained precursor by using a sodium borohydride aqueous solution to obtain the bismuth nanotube. The crystal face index of the main exposed crystal face of the synthesized bismuth nanotube crystal phase is (202), and the bismuth nanotube crystal phase is uniform in size, hollow in structure, rich in metal atom defects and capable of being widely applied to the fields of thermoelectric materials, electronic devices, photoelectric devices, biological medicine, catalysis, batteries and the like, and the preparation method is simple in process, safe, low in cost and suitable for large-scale production.

Description

Technical Field

[0001] The present invention belongs to but is not limited to the technical field of nano material synthesis, and in particular relates to a bismuth nanotube rich in atomic defects and a preparation method thereof. Background Art

[0002] Nanomaterials are an important foundation for the development of nanotechnology. Their unique properties, including electron ballistic transport effect and Coulomb blockade, have broad application prospects in optics, electricity, magnetism, catalysis and sensors. Nanomaterials refer to materials that have at least one dimension in the nanometer range in three-dimensional space or are composed of them as basic units. The basic units of nanomaterials can be divided into three categories according to the number of dimensions: (1) Zero-dimensional: refers to the three dimensions of the space are all in the nanometer range, such as nanoparticles, atomic clusters, etc.; (2) One-dimensional: refers to the space with two dimensions in the nanometer range, such as nanowires, nanorods, nanotubes, etc.; (3) Two-dimensional: refers to the three dimensions of the space at the nanometer scale, such as ultra-thin films, multilayer films, superlattices, etc. Since scientist Lijiama discovered carbon nanotube materials in 1991, this neat and consistent surface structure and many characteristics have not only stimulated the rapid development of nanotechnology, but also greatly promoted the fields of physics, chemistry, materials science, etc. Nanotubes generally include inorganic nanotubes of metals, oxides, and semiconductors, organic nanotubes, and composite nanotube-shaped materials. The outstanding electrochemical properties of nanotubes make them very important in the fields of nanoscale electronic devices, sensitive devices, biological devices, nanomedical capsules, nanochemistry, electrode materials and hydrogen storage energy materials. In addition, one-dimensional tubular nanomaterials are not only the basis for studying other low-dimensional materials, but also closely related to nanoelectronic devices and microsensors. Therefore, it is of great theoretical significance and academic value to design and synthesize nanotubes with regular size, controllable morphology and stable structure and to study their related physical and chemical properties.

[0003] As a chemical element, bismuth is located in a special area between the metal area and the semiconductor area in the periodic table, and has typical semi-metallic characteristics. Over the past century, researchers have conducted extensive research on the physical and chemical properties of bismuth. Bismuth has extremely strong anti-magnetism, significant de Haas-van Alphen effect, cyclotron resonance phenomenon, unique electromagnetic effect, piezoresistance, low thermal conductivity, unique electrical transport and other physical properties. In recent years, with the development of nanotechnology and thin film technology, the research on bismuth has focused more on the influence of special structures on its performance, and it has also been found that bismuth with different configurations has a large number of peculiar physical properties. On the other hand, bismuth has the advantages of abundant reserves, non-toxicity and low price, and can be widely used in thermoelectric materials, electronic devices, optoelectronic devices, biomedicine, catalysis and batteries.

[0004] In existing research, the most reported morphologies of bismuth single-element materials are nanosheets, nanoplates, nanotubes and nanowires. Among these morphologies, the synthesis technology of bismuth nanotubes still faces major challenges. At present, the preparation methods of bismuth nanotube materials are mostly limited to electrochemical reduction methods, which mainly involve in-situ electrochemical reduction of bismuth oxides or aqueous solutions of bismuth compounds and deposition on working electrodes. The disadvantage of this method is that during the electrochemical process, the morphological changes of the material are uncontrollable, the size is uneven, and it depends on the accidental nature of the experiment. In addition, the preparation process is cumbersome and cannot be used for large-scale synthesis, making the synthesis of the material very difficult. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a bismuth nanotube rich in atomic defects and a preparation method thereof. Bismuth oxyhalide is used as a precursor, and the synthesized Bi nanotube is small in size and rich in metal defects.

[0006] The present invention is achieved by a method for preparing bismuth nanotubes rich in atomic defects, comprising the following steps:

[0007] Step 1, dissolving a soluble Bi metal salt in a conventional solvent to obtain a soluble Bi metal salt solution as a mixed solution A;

[0008] Step 2, adding potassium halide to mixed solution A under vigorous stirring to obtain mixed solution B;

[0009] Step 3, transferring the obtained mixed solution B into the inner tank of the reaction kettle, heating it to a certain temperature and then keeping it warm, then cooling it to room temperature with the furnace, taking it out and centrifuging it to obtain a precursor material;

[0010] Step 4, mixing polyvinyl pyrrolidone and deionized water at a mass ratio of 1:100-200, and stirring until completely dissolved to obtain a mixed solution C;

[0011] Step 5, adding the obtained precursor powder to the mixed solution C under vigorous stirring conditions to obtain a mixed solution D;

[0012] Step 6, dissolving NaBH4 in deionized water, stirring until completely dissolved, to obtain a mixed solution E;

[0013] Step seven, under vigorous stirring, the mixed solution D and the mixed solution E are mixed in a mass ratio of 3:10 and then reduced to obtain a porous Bi nanotube material.

[0014] Furthermore, the soluble Bi metal salt described in step 1 is any one of bismuth nitrate hydrate, bismuth sulfate hydrate or bismuth trichloride hydrate, and the conventional solvent is any one of deionized water, ethanol or ethylene glycol.

[0015] Furthermore, the concentration of the Bi metal soluble salt solution described in step 1 is 0.01 to 0.06 mol / L.

[0016] Furthermore, the potassium halide salt described in step 2 is any one of potassium chloride, potassium bromide or potassium iodide, and the added molar mass ratio is Bi:Cl=1:1~2, Bi:Br=1:1~2, Bi:I=1:1~2.

[0017] Furthermore, the temperature in step three is 800° C. to 200° C., and the insulation time is 3 h to 24 h.

[0018] Furthermore, the molecular weight of the polyvinyl pyrrolidone described in step 4 is any one of 5800, 40000, 58000 or 1300000.

[0019] Furthermore, the molar mass of the precursor added in step five is 0.5 to 2 mol.

[0020] Furthermore, the concentration of the NaBH4 solution described in step six is ​​0.05-0.5 mol / L.

[0021] Furthermore, in step seven, when reducing with NaBH4 solution, the reaction time is 2 to 24 hours.

[0022] Another object of the present invention is to provide a method for preparing bismuth nanotubes rich in atomic defects and to prepare bismuth nanotubes rich in atomic defects.

[0023] In combination with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are as follows:

[0024] First, based on the common problems of complex operation, high synthesis cost and inability to mass produce in current preparation methods of bismuth nanotubes, the present invention provides a bismuth nanotube rich in atomic defects and a preparation method thereof. Bismuth nanotubes of uniform size are prepared by reducing a bismuth oxyhalide precursor with a strong reducing agent. The preparation method is simple and easy to mass produce. The synthesized bismuth nanotubes are rich in atomic defects, which are crucial to the application of bismuth single-substance materials in various fields.

[0025] Through the simple synthesis method of bismuth nanotubes rich in atomic defects provided by the present invention, the synthesized nanotubes have uniform size, large specific surface area, and an average diameter of about 5nm, providing access to three different but interconnected regions - the inner surface, the outer surface and the tube end. In addition, the nanotubes are rich in atomic defects and can play different roles in many fields, which has important guiding significance for the preparation research of nanomaterials and the application of bismuth single-substance materials in various fields.

[0026] Second, as auxiliary evidence of the inventiveness of the claims of the present invention, it is also reflected in the following important aspects:

[0027] (1) The expected benefits and commercial value of the technical solution of the present invention after transformation are:

[0028] Studies have shown that bismuth has a wide range of applications in the field of science and technology. For example, bismuth and its alloys have good thermoelectric properties, and nanostructures can significantly improve their thermoelectric properties. In particular, bismuth nanotubes, due to their unique size effect and quantum confinement effect, can show better performance in thermoelectric conversion efficiency and are widely studied for use in thermoelectric materials. Bismuth nanotubes can be used in field effect transistors, nanoelectronic devices and other fields because of their excellent electron transport performance and large specific surface area, which helps to improve the sensitivity of the device. At the same time, bismuth nanotubes have good biocompatibility and low toxicity, and can be used in drug delivery, cancer treatment (such as photothermal therapy) and biosensors. In the field of catalysis and batteries, bismuth nanotubes also show good activity and can be used in the fields of water electrolysis to produce hydrogen, carbon dioxide reduction and redox flow batteries. In particular, bismuth is also quite advantageous in the field of electrocatalytic carbon dioxide reduction for the production of liquid fuels with high commercial value, formic acid. Formic acid is a product with a clear market demand. When bismuth nanotubes are used as catalysts in the field of electrocatalytic carbon dioxide reduction, the catalyst preparation process is simple, and the electrocatalytic CO2 reduction has high selectivity and activity, which is expected to achieve industrial-grade mass production of formic acid. In addition, PV cells can be used to supply power for power input to reduce power consumption. Solid electrolytes or distillation separation can be used to achieve industrial-grade formic acid preparation and separation and purification for application in leather, pesticides, medicines, dyes, rubber and other industries. In summary, bismuth nanotubes are widely used in various fields. The present invention provides a bismuth nanotube rich in atomic defects and a preparation method thereof. The preparation method is simple and easy to operate. From the perspective of market demand, material, manufacturing and separation cost analysis, the commercial value and economic efficiency of bismuth nanotubes are very high.

[0029] (2) The technical solution of the present invention fills the technical gap in the industry at home and abroad:

[0030] The technical solution of the present invention fills the technical gap in the convenient and efficient preparation of defect-rich, stable, uniform-sized bismuth nanotubes in the domestic and foreign industries, and studies the application of bismuth nanotubes in various industries. At present, the research on the preparation method mainly focuses on the uncontrollable electrochemical reduction method, which has the disadvantages of uneven morphology of synthesized nanotubes and low success rate. In addition, the bismuth element itself is very easy to disintegrate and has unstable characteristics. How to stably prepare bismuth nanotubes of uniform size has always been a technical problem. The present invention uses a simple hydrothermal method and a chemical reduction method to prepare uniform bismuth nanotubes with high defect concentrations, achieving a technological breakthrough. Taking the application of bismuth nanotubes in electrocatalytic carbon dioxide reduction as an example, the atomic defects constructed on its surface play a key role in improving the performance of electrocatalytic CO2 reduction, which is specifically manifested in the selective adsorption and activation of reactants and intermediates, the dissociation of products, the transmission of charges, etc., improving the selectivity and activity of electrocatalytic CO2 reduction to produce formic acid, and is expected to achieve industrial-grade formic acid production. In addition, the excellent properties of bismuth nanotubes can also enhance their application in thermoelectric materials, electronic devices, optoelectronic devices, and biomedicine. It can be seen that the defect-rich, stable, and uniformly sized bismuth nanotubes prepared by the present invention can be widely used in various fields, filling the technical gaps in the domestic and foreign industries, promoting the development of various fields, and also providing a theoretical reference for its subsequent research, which has good guidance and application significance.

[0031] (3) The technical solution of the present invention solves the technical problems that people have been eager to solve but have never been able to solve successfully:

[0032] The technical solution of the present invention provides theoretical guidance for defect-rich bismuth nanotubes. Previously, most of the research on the morphology control of bismuth materials focused on nanosheets, nanoflowers, etc. How to stably prepare bismuth nanotubes of uniform size has always been a technical problem. The basic research on the application of bismuth nanotubes in thermoelectric materials, electronic devices, optoelectronic devices, biomedicine, catalysis, and batteries is a blank area and a technical problem that has not been successfully achieved. Through the technical solution of the present invention, the preparation method of bismuth nanotubes and their application in the field of electrocatalytic carbon dioxide reduction are studied, and even extended to other application fields, providing technical support for the application research of bismuth nanotubes. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a flow chart of a method for preparing bismuth nanotubes rich in atomic defects provided by an embodiment of the present invention;

[0034] Figure 2 is an XRD (X-ray diffraction) diagram of the bismuth oxychloride precursor provided in Example 1 of the present invention;

[0035] Figure 3This is a TEM (transmission electron microscope) image of the bismuth oxychloride precursor provided in Example 1 of the present invention converted into bismuth nanotubes;

[0036] Figure 4 is an XRD diagram of the bismuth oxychloride precursor converted into bismuth nanotubes provided in Example 1 of the present invention;

[0037] Figure 5 is the XRD pattern of the bismuth oxybromide precursor provided in Example 3 of the present invention;

[0038] Figure 6 This is a SEM (scanning electron microscope) image of the bismuth oxybromide precursor converted into bismuth nanotubes provided in Example 3 of the present invention;

[0039] Figure 7 is an XRD diagram of the bismuth oxybromide precursor converted into bismuth nanotubes provided in Example 3 of the present invention;

[0040] Figure 8 is the XRD pattern of the bismuth oxyiodide precursor provided in Example 3 of the present invention;

[0041] Fig. 9 is a SEM image of the bismuth iodide precursor converted into bismuth nanotubes provided in Example 5 of the present invention;

[0042] Fig.10 is an XRD diagram of the bismuth oxyiodide precursor converted into bismuth nanotubes provided in Example 5 of the present invention;

[0043] Fig.11 The bismuth oxychloride precursor converted into bismuth nanotubes, the bismuth oxybromide precursor converted into bismuth nanotubes and the bismuth oxyiodide precursor converted into bismuth nanotubes provided in Examples 1, 3 and 5 of the present invention are subjected to a 5 mV s -1 Linear sweep voltammetry (LSV) curve test diagram of scanning rate;

[0044] Fig.12 is a Faraday efficiency (FE) diagram of methane, carbon monoxide and formic acid at different potentials for converting the bismuth oxychloride precursor provided in Example 1 of the present invention into bismuth nanotubes;

[0045] Fig.13 FE diagrams of hydrogen gas at different potentials when the bismuth oxychloride precursor provided in Example 1 of the present invention is converted into bismuth nanotubes;

[0046] Fig.14 FE diagrams of methane, carbon monoxide and formic acid at different potentials when the bismuth oxybromide precursor provided in Example 3 of the present invention is converted into bismuth nanotubes;

[0047] Fig.15FE diagrams of hydrogen gas at different potentials when the bismuth oxybromide precursor provided in Example 3 of the present invention is converted into bismuth nanotubes;

[0048] Fig.16 FE diagrams of methane, carbon monoxide and formic acid at different potentials for the conversion of the bismuth iodide precursor provided in Example 5 of the present invention into bismuth nanotubes;

[0049] Fig.17 It is the FE diagram of hydrogen at different potentials when the iodine bismuth precursor provided in Example 5 of the present invention is converted into bismuth nanotubes. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0051] like Figure 1 As shown, the method for preparing bismuth nanotubes rich in atomic defects provided by an embodiment of the present invention comprises the following steps:

[0052] Step 1, dissolving a soluble salt of bismuth metal in a conventional solvent to obtain a soluble salt solution of bismuth metal as a mixed solution A;

[0053] Step 2, adding potassium halide to mixed solution A under vigorous stirring to obtain mixed solution B;

[0054] Step 3, transferring the obtained mixed solution B into the inner tank of the reaction kettle, heating it to a certain temperature and then keeping it warm, then cooling it to room temperature with the furnace, taking it out and centrifuging it to obtain a precursor material;

[0055] Step 4, mixing polyvinyl pyrrolidone and deionized water at a mass ratio of 1:100-200, and stirring until completely dissolved to obtain a mixed solution C;

[0056] Step 5, adding the obtained precursor powder to the mixed solution C under vigorous stirring conditions to obtain a mixed solution D;

[0057] Step 6, dissolving sodium borohydride in deionized water, stirring until completely dissolved, to obtain a mixed solution E;

[0058] Step seven, under vigorous stirring, the mixed solution D and the mixed solution E are mixed in a mass ratio of 3:10 and then reduced to obtain a porous bismuth nanotube material.

[0059] Example 1

[0060] A method for preparing bismuth oxychloride precursor into bismuth nanotubes comprises the following steps:

[0061] (1) Dissolve 2 mmol of bismuth nitrate pentahydrate in 30 mL of deionized water;

[0062] (2) Add 2 mmol potassium chloride until fully dissolved;

[0063] (3) The mixed solution was transferred to a hydrothermal reactor and reacted at 160° C. for 12 h. The obtained sample was centrifuged and dried at 60° C. to obtain a bismuth oxychloride precursor;

[0064] (4) adding 0.2 g of polyvinyl pyrrolidone and 0.10 g of bismuth oxychloride precursor into 20 mL of deionized water;

[0065] (5) Add 7.5 mL of 50 mM / L sodium borohydride solution, stir for 2 h, and then centrifuge and dry the resulting solution to obtain bismuth nanotubes rich in metal defects.

[0066] The bismuth oxychloride precursor in step (3) of Example 1 was subjected to XRD characterization test. Figure 2 The results show that the bismuth oxychloride precursor was successfully synthesized. The metal defect-rich bismuth nanotubes synthesized in Example 1 were characterized by TEM. Figure 3 As shown. The results show that in TEM, the sample is a double-layer nanotube morphology with a diameter of about 5nm. Further, the synthesized bismuth nanotubes were characterized by XRD test. Figure 4 In the figure, the peak corresponding to bismuth can be clearly seen.

[0067] Example 2

[0068] A method for preparing bismuth oxychloride precursor into bismuth nanotubes comprises the following steps:

[0069] (1) Dissolve 2 mmol of bismuth nitrate pentahydrate in 30 mL of deionized water;

[0070] (2) Add 2 mmol potassium chloride until fully dissolved;

[0071] (3) The mixed solution was transferred to a hydrothermal reactor and reacted at 160° C. for 12 h. The obtained sample was centrifuged and dried at 60° C. to obtain a bismuth oxychloride precursor;

[0072] (4) adding 0.2 g of polyvinyl pyrrolidone and 0.10 g of bismuth oxychloride precursor into 20 mL of deionized water;

[0073] (5) Add 7.5 mL of 50 mM / L sodium borohydride solution, stir for 4 h, and then centrifuge and dry the resulting solution to obtain bismuth nanotubes rich in metal defects.

[0074] Example 3

[0075] A method for preparing bismuth nanotubes by converting a bismuth oxybromide precursor into bismuth nanotubes comprises the following steps:

[0076] (1) Dissolve 1 mmol of bismuth nitrate pentahydrate in 30 mL of ethylene glycol;

[0077] (2) Add 1 mmol potassium bromide until fully dissolved;

[0078] (3) The mixed solution was transferred to a hydrothermal reactor and reacted at 120°C for 18 hours. The obtained sample was centrifuged and dried at 60°C to obtain a bismuth oxybromide precursor;

[0079] (4) adding 0.2 g of polyvinyl pyrrolidone and 0.13 g of bismuth oxybromide precursor to 20 mL of deionized water;

[0080] (5) Add 7.5 mL of 50 mM / L sodium borohydride solution, stir for 2 h, and then centrifuge and dry the resulting solution to obtain bismuth nanotubes rich in metal defects.

[0081] The bismuth oxychloride precursor in step (3) of Example 3 was subjected to XRD characterization test. Figure 5 The results show that the bismuth oxychloride precursor was successfully synthesized. The metal defect-rich bismuth nanotubes synthesized in Example 3 were characterized by SEM. Figure 6 As shown. The results show that in SEM, the sample is a double-layer nanotube morphology with a diameter of about 5nm. Further, the synthesized bismuth nanotubes were characterized by XRD test. Figure 7 In the figure, the peak corresponding to bismuth can be clearly seen.

[0082] Example 4

[0083] A method for preparing bismuth nanotubes by converting a bismuth oxybromide precursor comprises the following steps:

[0084] (1) Dissolve 1 mmol of bismuth nitrate pentahydrate in 30 mL of ethylene glycol;

[0085] (2) Add 1 mmol potassium bromide until fully dissolved;

[0086] (3) The mixed solution was transferred to a hydrothermal reactor and reacted at 120°C for 18 hours. The obtained sample was centrifuged and dried at 60°C to obtain a bismuth oxybromide precursor;

[0087] (4) adding 0.2 g of polyvinyl pyrrolidone and 0.13 g of bismuth oxybromide precursor to 20 mL of deionized water;

[0088] (5) Add 7.5 mL of 50 mM / L sodium borohydride solution, stir for 4 h, and then centrifuge and dry the resulting solution to obtain bismuth nanotubes rich in metal defects.

[0089] Example 5

[0090] A method for preparing bismuth nanotubes by converting a bismuth iodide precursor comprises the following steps:

[0091] (1) Dissolve 2 mmol of bismuth nitrate pentahydrate in 30 mL of ethylene glycol;

[0092] (2) Add 2 mmol potassium bromide until fully dissolved;

[0093] (3) The mixed solution was transferred to a hydrothermal reactor and reacted at 80°C for 3 hours. The obtained sample was centrifuged and dried at 60°C to obtain a bismuth iodide precursor;

[0094] (4) adding 0.2 g of polyvinyl pyrrolidone and 0.14 g of bismuth iodide precursor to 20 mL of deionized water;

[0095] (5) Add 7.5 mL of 50 mM / L sodium borohydride solution, stir for 2 h, and then centrifuge and dry the resulting solution to obtain bismuth nanotubes rich in metal defects.

[0096] The bismuth oxychloride precursor in step (3) of Example 5 was subjected to XRD characterization test. Figure 8 The results show that the bismuth oxychloride precursor was successfully synthesized. The metal defect-rich bismuth nanotubes synthesized in Example 5 were characterized by SEM. Fig. 9 As shown. The results show that in SEM, the sample is a double-layer nanotube morphology with a diameter of about 5nm. Further, the synthesized bismuth nanotubes were characterized by XRD test. Fig.10 In the figure, the peak corresponding to bismuth can be clearly seen.

[0097] Example 6

[0098] A method for preparing bismuth nanotubes by converting a bismuth iodide precursor comprises the following steps:

[0099] (1) Dissolve 2 mmol of bismuth nitrate pentahydrate in 30 mL of ethylene glycol;

[0100] (2) Add 2 mmol potassium bromide until fully dissolved;

[0101] (3) The mixed solution was transferred to a hydrothermal reactor and reacted at 80°C for 3 hours. The obtained sample was centrifuged and dried at 60°C to obtain a bismuth iodide precursor;

[0102] (4) adding 0.2 g of polyvinyl pyrrolidone and 0.14 g of bismuth iodide precursor to 20 mL of deionized water;

[0103] (5) Add 7.5 mL of 50 mM / L sodium borohydride solution, stir for 4 h, and then centrifuge and dry the resulting solution to obtain bismuth nanotubes rich in metal defects.

[0104] 1. Specific application fields or related products of the present invention.

[0105] The defect-rich bismuth nanotube material prepared by the present invention can be widely used in the fields of thermoelectric materials, electronic devices, optoelectronic devices, biomedicine, catalysis, batteries, etc. The application of the material in the field of electrocatalytic carbon dioxide reduction is described in detail below.

[0106] Electrocatalytic carbon dioxide reduction has attracted wide attention due to its mild operating conditions (ambient temperature and pressure), the wide distribution of reduction products and the ability to adjust by changing various parameters, the reduction reaction driven by electrical energy and the electrical energy can be converted from some renewable energy sources, such as light energy, tidal energy, wind energy, and even chemical energy in waste. Studies have shown that among the many products of electrocatalytic carbon dioxide reduction, formic acid, as a safe and convenient liquid fuel, has attracted wide attention due to its most economic benefits, and has potential industrial application prospects in the production of fuel cells, hydrogen storage and other chemicals. The atomic defects of the bismuth nanotube electrocatalyst provided in the embodiment of the present invention are active sites, which promote the transmission of electrons, are conducive to the adsorption and activation of CO2 molecules to generate *HCOO intermediates, can effectively improve the activity of bismuth-based electrocatalysts, promote the catalytic activity and selectivity of electrocatalytic CO2 reduction to produce formic acid, can not only realize the industrial application of electrocatalytic carbon dioxide reduction to produce formic acid, but also have theoretical significance in research, so that the atomic defect state bismuth nanotube electrocatalytic material has a wide range of application prospects.

[0107] 2. Relevant evidence of the technical effects obtained by the embodiments of the present invention.

[0108] The embodiments of the present invention have achieved some positive effects during the research and development or use process, and do have great advantages compared with the prior art. Taking the application of bismuth nanotubes in the field of electrocatalytic carbon dioxide reduction as an example, the following content is described in combination with data, charts, etc. of the experimental process.

[0109] In order to evaluate the performance of the above-mentioned defect-rich bismuth nanotubes in the electrocatalytic reduction of carbon dioxide to produce formic acid, a Shimadzu GC-2030 chromatograph with a dielectric barrier discharge plasma detector (BID) detector was used for online gas phase product detection, and liquid phase products were detected by ion chromatography. All electrochemical tests were performed on a Chenhua electrochemical workstation. 10 mg of electrocatalyst was ultrasonically mixed with 1000 μL of isopropanol and 50 uL of naphthol solution (5%, D520, DuPont) for 30 min to form a uniform catalyst ink. Then 30 μL of catalyst ink was dropped on the surface of hydrophobic carbon paper (Toray TGP-H-060) and dried at 45 ° C for 3 h to prepare a working electrode. In an H-type electrolytic cell, 0.1 M KHCO3 was used as the electrolyte, a platinum sheet (1.5 cm × 1.5 cm) was used as the counter electrode, and an Ag / AgCl electrode was used as the reference electrode. Carbon dioxide gas was introduced into the electrolytic cell for electrocatalytic carbon dioxide reduction testing.

[0110] The bismuth nanotubes synthesized in Example 1 with bismuth oxychloride as a precursor, the bismuth nanotubes synthesized in Example 3 with bismuth oxybromide as a precursor, and the bismuth nanotubes synthesized in Example 5 with bismuth oxyiodine as a precursor were subjected to electrocatalytic carbon dioxide reduction experiments. Fig.11 The linear sweep voltammetry (LSV) curves of the three catalysts were tested in a 0.1M KHCO3 solution saturated with carbon dioxide. The results showed that compared with the previously reported bismuth-based catalysts, the atomic defect-rich bismuth nanotube electrocatalyst exhibited a higher current density and a smaller initial potential in a carbon dioxide atmosphere, indicating that it has good electrocatalytic carbon dioxide reduction performance.

[0111] Fig.12 The Faradaic efficiency of the bismuth nanotubes with bismuth oxychloride as a precursor synthesized in Example 1 for electrocatalytic reduction of carbon dioxide to produce formic acid at different potentials is shown. The Faradaic efficiency of formic acid in the potential range of -1.07 to -1.34 V vs. standard hydrogen electrode (RHE) exceeds 90%. In particular, at -1.25 V, the Faradaic efficiency of formic acid reaches 94%, containing only a small amount of methane and carbon monoxide products, which shows the excellent formic acid selectivity of the bismuth nanotube catalyst with bismuth oxychloride as a precursor. Fig.13 The competitive hydrogen evolution reaction analysis of the electrocatalytic carbon dioxide reduction reaction of the bismuth nanotubes synthesized in Example 1 with bismuth oxychloride as a precursor at different potentials is shown. The results show that the Faraday efficiency of hydrogen at the potential of -1.01 to -1.34 V vs. RHE is less than 10%, indicating that the bismuth nanotubes with bismuth oxychloride as a precursor have good performance in electrocatalytic carbon dioxide reduction to produce formic acid, and the hydrogen evolution reaction is relatively small.

[0112] Fig.14 The Faraday efficiency of the bismuth nanotubes with bismuth oxybromide as a precursor for electrocatalytic reduction of carbon dioxide to produce formic acid at different potentials is shown. The Faraday efficiency of formic acid in the potential range of -1.01 to -1.34 V vs. standard hydrogen electrode (RHE) exceeds 90%. In particular, at -1.19 V, the Faraday efficiency of formic acid reaches 92.8%, containing only a small amount of methane and carbon monoxide products, which shows the excellent formic acid selectivity of the bismuth nanotube catalyst with bismuth oxybromide as a precursor. Fig.15 The competitive hydrogen evolution reaction analysis of the electrocatalytic carbon dioxide reduction reaction of the bismuth nanotubes synthesized in Example 3 with bismuth oxybromide as a precursor at different potentials is shown. The results show that the Faraday efficiency of hydrogen at the potential of -0.94 to -1.34 V vs. RHE is less than 10%, indicating that the bismuth nanotubes with bismuth oxybromide as a precursor have good performance in electrocatalytic carbon dioxide reduction to produce formic acid, and the hydrogen evolution reaction is relatively small.

[0113] Fig.16The Faradaic efficiency of the bismuth nanotubes with bismuth iodide as a precursor synthesized in Example 5 for electrocatalytic reduction of carbon dioxide to produce formic acid at different potentials is shown. The Faradaic efficiency of formic acid in the potential range of -1.07 to -1.34 V vs. standard hydrogen electrode (RHE) exceeds 90%. In particular, at -1.25 V, the Faradaic efficiency of formic acid reaches 94.1%, containing only a small amount of methane and carbon monoxide products, which shows the excellent formic acid selectivity of the bismuth nanotube catalyst with bismuth iodide as a precursor. Fig.17 The competitive hydrogen evolution reaction analysis of the electrocatalytic carbon dioxide reduction reaction of the bismuth nanotubes synthesized in Example 5 with bismuth iodide as a precursor at different potentials is shown. The results show that the Faraday efficiency of hydrogen at potentials of -0.94 to -1.34 V vs. RHE is less than 10%, indicating that the bismuth nanotubes with bismuth iodide as a precursor have good performance in electrocatalytic carbon dioxide reduction to produce formic acid, and the hydrogen evolution reaction is relatively small.

[0114] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for preparing bismuth nanotubes rich in atomic defects, characterized in that: The following steps are involved: Step 1, dissolving a soluble Bi metal salt in a conventional solvent to obtain a soluble Bi metal salt solution as a mixed solution A; Step 2, adding potassium halide to mixed solution A under vigorous stirring to obtain mixed solution B; Step 3, transferring the obtained mixed solution B into the inner tank of the reaction kettle, heating it to a certain temperature and then keeping it warm, then cooling it to room temperature with the furnace, taking it out and centrifuging it to obtain a precursor material; Step 4, mixing polyvinyl pyrrolidone and deionized water at a mass ratio of 1:100-200, and stirring until completely dissolved to obtain a mixed solution C; Step 5, adding the obtained precursor powder to the mixed solution C under vigorous stirring conditions to obtain a mixed solution D; Step 6, dissolving NaBH4 in deionized water, stirring until completely dissolved, to obtain a mixed solution E; Step seven, under vigorous stirring, the mixed solution D and the mixed solution E are mixed in a mass ratio of 3:10 and then reduced to obtain a porous Bi nanotube material.

2. The method for preparing atomic defect-rich bismuth nanotubes according to claim 1, characterized in that: The soluble Bi metal salt described in step 1 is any one of bismuth nitrate hydrate, bismuth sulfate hydrate or bismuth trichloride hydrate, and the conventional solvent is any one of deionized water, ethanol or ethylene glycol.

3. The method for preparing atomic defect-rich bismuth nanotubes according to claim 1, characterized in that: The concentration of the Bi metal soluble salt solution described in step 1 is 0.01-0.06 mol / L.

4. The method for preparing bismuth nanotubes rich in atomic defects according to claim 1, characterized in that: The potassium halide salt described in step 2 is any one of potassium chloride, potassium bromide or potassium iodide, and the added molar mass ratio is Bi:Cl=1:1~2, Bi:Br=1:1~2, Bi:I=1:1~2.

5. The method for preparing bismuth nanotubes rich in atomic defects according to claim 1, characterized in that: The temperature described in step 3 is 800° C. to 200° C., and the insulation time is 3 h to 24 h.

6. The method for preparing atomic defect-rich bismuth nanotubes according to claim 1, characterized in that: The molecular weight of the polyvinyl pyrrolidone described in step 4 is any one of 5800, 40000, 58000 or 1300000.

7. The method for preparing atomic defect-rich bismuth nanotubes according to claim 1, characterized in that: The molar mass of the precursor added in step 5 is 0.5 to 2 mol.

8. The method for preparing bismuth nanotubes rich in atomic defects according to claim 1, characterized in that: The concentration of the NaBH4 solution described in step six is ​​0.05-0.5 mol / L.

9. The method for preparing bismuth nanotubes rich in atomic defects according to claim 1, characterized in that: In step 7, when reducing with NaBH4 solution, the reaction time is 2 to 24 hours.

10. A bismuth nanotube rich in atomic defects prepared by the method for preparing a bismuth nanotube rich in atomic defects as claimed in any one of claims 1 to 9.

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