Tellurium-based heterojunction nanomaterial, and preparation method and application thereof

Abstract

The application relates to the technical field of nanomaterial synthesis, in particular to a tellurium-based heterojunction nanomaterial and a preparation method and application thereof. The preparation method comprises the following steps: taking a first tellurium crystal and a second tellurium crystal as a working electrode and a counter electrode respectively, constructing a double-electrode electrochemical exfoliation system with water and an organic acid, and inputting an alternating current power source, obtaining the tellurium-based heterojunction nanomaterial through reaction. Under the action of an electric field, the organic acid is weakly ionized into hydrogen ions in water, the organic acid can be used as an intercalation reagent to intercalate the tellurium crystal, and the organic acid is changed into hydrogen gas under a reduction potential, so that the expansion and exfoliation of the tellurium are accelerated; the ionization degree of the organic acid is low, the movement of the hydrogen ions under the electric field is significantly constrained by the organic group anions, the exfoliation of the tellurium crystal by the hydrogen ions under the constraint is limited, and the hydrogen ions exist selectively in the intercalation gap in three-dimensional space, so that the edge part presents an amorphous atomic arrangement, the internal crystal presents crystallinity, and the tellurium-based heterojunction nanomaterial with amorphous phase-crystalline phase blending is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nanomaterial synthesis, and particularly relates to a tellurium-based heterojunction nanomaterial and a preparation method and application thereof. BACKGROUND

[0002] Semiconductor tellurium crystals have characteristics such as rich chemical valence, narrow band gap and tunable photoelectric performance, and have attracted wide attention. Generally, the van der Waals force between tellurium chains is weak, and the covalent bond within the chain is strong. The anisotropy of the two forces makes tellurium capable of being reduced in size by liquid phase exfoliation, thereby obtaining low-dimensional tellurium-based nanocomposites. For example, small-sized two-dimensional tellurium nanosheets or nanoparticles can be obtained by water bath ultrasonic in isopropyl alcohol as a solvent.

[0003] However, the surface phase structure of the nanomaterial obtained by the liquid phase exfoliation method is relatively single, the atomic arrangement is relatively regular, and only a small amount of atomic vacancies or local atomic arrangement deformations exist, the physical or chemical characteristics presented are relatively close, and specific functionalization such as rapid transmission of electrons, ions or photo-generated carriers in a gradient field is difficult to achieve.

[0004] Therefore, the prior art still needs to be improved and developed. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application aims to provide a tellurium-based heterojunction nanomaterial and a preparation method and application thereof, and aims to solve the problem that the surface phase structure of the tellurium nanomaterial prepared by the prior method is relatively single and the atomic arrangement is relatively regular.

[0006] The technical scheme of the present application is as follows:

[0007] A preparation method of a tellurium-based heterojunction nanomaterial, comprising the steps of:

[0008] A double-electrode electrochemical exfoliation system is constructed by taking a first tellurium crystal and a second tellurium crystal as a working electrode and a counter electrode respectively, taking water as a solvent, and taking an organic acid as an intercalation reagent;

[0009] An alternating current power supply is introduced into the double-electrode electrochemical exfoliation system, and a tellurium-based heterojunction nanomaterial is obtained after reaction.

[0010] The preparation method of the tellurium-based heterojunction nanomaterial, wherein the organic acid is a monobasic acid or a polybasic acid; and the organic acid contains one or more of an aromatic group, an alkyl group with at least three carbons, and an unsaturated double bond with at least three carbons.

[0011] The preparation method of the tellurium-based heterojunction nanomaterial, wherein the organic acid includes one or more of octanoic acid, succinic acid, adipic acid, linolenic acid, cinnamic acid, oleic acid, stearic acid, linoleic acid, palmitic acid and arachidonic acid.

[0012] The preparation method of the tellurium-based heterojunction nanomaterial, wherein the first tellurium crystal is a solid block or a powder; and the second tellurium crystal is a solid block or a powder.

[0013] Preferably, when the first tellurium crystal and / or the second tellurium crystal is a solid block, the tellurium crystal surface is wrapped with platinum wire to serve as the working electrode and the counter electrode.

[0014] Preferably, when the first tellurium crystal and / or the second tellurium crystal is a powder, the tellurium crystal is compounded with a binder and a conductive agent and then coated on a conductive support electrode to serve as the working electrode and the counter electrode.

[0015] The preparation method of the tellurium-based heterojunction nanomaterial, wherein the mass ratio of the organic acid to water is 1:(90-100).

[0016] The preparation method of the tellurium-based heterojunction nanomaterial, wherein the voltage of the alternating current power supply is ±(3-15) V, and the frequency of the alternating current power supply is 0.0001 Hz-1000 Hz.

[0017] The preparation method of the tellurium-based heterojunction nanomaterial, wherein the reaction time is 60-180 minutes, and the reaction is carried out at 25℃-80℃.

[0018] A tellurium-based heterojunction nanomaterial prepared by the preparation method.

[0019] The tellurium-based heterojunction nanomaterial, wherein the surface of the tellurium-based heterojunction nanomaterial simultaneously exists amorphous and crystalline structures.

[0020] Application of a tellurium-based heterojunction nanomaterial in semiconductors, energy or biomedicine.

[0021] Beneficial effects: the present application provides a tellurium-based heterojunction nanomaterial and its preparation method and application, the preparation method of the tellurium-based heterojunction nanomaterial comprises the following steps: taking a first tellurium crystal and a second tellurium crystal as a working electrode and a counter electrode respectively, taking water as a solvent, and taking an organic acid as an intercalation reagent to construct a double-electrode electrochemical exfoliation system; an alternating current power supply is introduced into the double-electrode electrochemical exfoliation system, and a tellurium-based heterojunction nanomaterial is obtained through reaction. The present application constructs a structure and functional material by an electrochemical in-situ modification method, and prepares a tellurium-based heterojunction nanomaterial with amorphous phase-crystalline phase blending; mainly through the weak ionization of hydrogen ions of the organic acid in water under the action of an electric field, the organic acid can be used as an intercalation reagent to intercalate the tellurium crystal, and become hydrogen gas under a reduction potential, which can accelerate the expansion and exfoliation of tellurium; since the ionization degree of the organic acid is low, the movement of hydrogen ions under the electric field is significantly constrained by the organic group anions, the exfoliation of the tellurium crystal by the hydrogen ions under the constraint is limited, the intercalation rate is relatively slow, and there is selectivity in the intercalation gap in three-dimensional space, so that the edge presents amorphous atomic arrangement, while the inside crystal presents crystallinity, and thus a tellurium-based heterojunction nanomaterial with amorphous phase-crystalline phase blending is obtained; and since the alternating current field voltage is switched rapidly, the two tellurium electrodes can both be exfoliated rapidly, and the exfoliation rate and the final yield of tellurium are improved. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is a process flow schematic diagram of the preparation method of the tellurium-based heterojunction nanomaterial of the present application.

[0023] Figure 2 It is an SEM characterization diagram of the tellurium-based heterojunction nanomaterial prepared in Example 1.

[0024] Figure 3 It is an SEM characterization diagram of the tellurium nanomaterial prepared in Comparative Example 1. DETAILED DESCRIPTION

[0025] The present application provides a tellurium-based heterojunction nanomaterial and its preparation method and application, in order to make the purpose, technical scheme and effect of the present application more clear and explicit, the present application is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application.

[0026] Those skilled in the art can understand that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as generally understood by those skilled in the art to which the present application belongs. It should also be understood that terms such as those defined in general dictionaries should be understood as having meanings consistent with those in the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined as such.

[0027] AsFigure 1 As shown, the present application provides a preparation method of tellurium-based heterojunction nanomaterial, comprising the steps of:

[0028] Step S10: taking the first tellurium crystal and the second tellurium crystal as the working electrode and the counter electrode respectively, taking water as the solvent, and taking the organic acid as the intercalation reagent to construct a two-electrode electrochemical exfoliation system;

[0029] Step S20: passing alternating current power into the two-electrode electrochemical exfoliation system to obtain the tellurium-based heterojunction nanomaterial through reaction.

[0030] In the present embodiment, the structure and functional material is constructed by the electrochemical in-situ modification method, and the amorphous-crystalline blended tellurium-based heterojunction nanomaterial is prepared; mainly through the weak ionization of hydrogen ions of the organic acid in water under the action of the electric field, the organic acid can be used as the intercalation reagent to intercalate the tellurium crystal, and become hydrogen gas under the reduction potential, which can accelerate the expansion and exfoliation of tellurium; since the ionization degree of the organic acid is low, the movement of hydrogen ions under the electric field is significantly constrained by the organic group anions, and the exfoliation of the tellurium crystal by the hydrogen ions under the constraint is limited, the intercalation rate is relatively slow, and there is selectivity in the intercalation gap in the three-dimensional space, so that the amorphous atoms are arranged at the edge, while the crystals are arranged in the interior, thereby obtaining the amorphous-crystalline blended tellurium-based heterojunction nanomaterial; and since the alternating current field voltage is switched rapidly, the two tellurium electrodes can be exfoliated rapidly, thereby improving the exfoliation rate and the final yield of tellurium.

[0031] Specifically, the tellurium-based heterojunction nanomaterial obtained by the preparation method has a special surface microstructure, i.e. the amorphous phase and the crystalline phase structures exist on the surface at the same time; the advantages of the amorphous phase mainly include:

[0032] 1) fast charge transfer can be achieved;

[0033] 2) sufficient active sites are provided for subsequent chemical or physical adsorption;

[0034] 3) the amorphous phase changes the electronic structure of the original crystalline phase, thereby changing the light absorption and photoelectric conversion behavior, such as narrowing the band gap, etc.

[0035] 4) the chemical potential at the interface of the amorphous phase and the crystalline phase is different, which induces a built-in electric field to promote carrier migration, etc.

[0036] In some embodiments, the organic acid is a monobasic acid (R-COOH) or a polybasic acid (R-(COOH) n); the organic acid contains one or more of an aromatic group, an alkyl group containing at least three carbons, and an unsaturated double bond containing at least three carbons. That is, R is one or more of an aromatic group, an alkyl group containing at least three carbons, and an unsaturated double bond containing at least three carbons. Under the action of an electric field, the organic acid weakly ionizes hydrogen ions in water, which can intercalate into tellurium crystals as an intercalation reagent and become hydrogen gas at a reduction potential, accelerating the expansion and exfoliation of tellurium; and, due to the low degree of ionization of the above-mentioned organic acid, the movement of hydrogen ions under an electric field is constrained by organic group anions, the exfoliation of tellurium crystals by hydrogen ions under constraint is limited, the intercalation rate is relatively slow, and there is selectivity in the intercalation gap in three-dimensional space, resulting in amorphous atomic arrangement at the edges and crystallinity in the interior of the crystal, thereby obtaining a tellurium-based heterojunction nanomaterial with amorphous-crystalline blending.

[0037] In a preferred embodiment, the organic acid includes, but is not limited to, one or more of octanoic acid, succinic acid, adipic acid, linolenic acid, cinnamic acid, oleic acid, stearic acid, linoleic acid, palmitic acid, and arachidonic acid.

[0038] In some embodiments, the first tellurium crystal and the second tellurium crystal are high-purity tellurium crystals with a purity of greater than or equal to 99% or 99.9%.

[0039] In some embodiments, the first tellurium crystal is a solid block or a powder; the second tellurium crystal is a solid block or a powder; both the solid block and the powder of the tellurium crystal can be used as the working electrode and the counter electrode; but the powder of the tellurium crystal needs to be compounded with a binder and a conductive agent before being coated on a conductive support electrode to be used as the working electrode and the counter electrode.

[0040] Preferably, when the first tellurium crystal and / or the second tellurium crystal is a solid block, the tellurium crystal surface is wrapped with a platinum wire to serve as the working electrode and the counter electrode; wrapping the platinum wire on the surface of the tellurium crystal can improve the conductivity of the electrode, and the solid block of the tellurium crystal without the platinum wire can also be directly used as the working electrode and the counter electrode.

[0041] Preferably, when the first tellurium crystal and / or the second tellurium crystal is a powder, the tellurium crystal is compounded with a binder and a conductive agent before being coated on a conductive support electrode to serve as the working electrode and the counter electrode.

[0042] In some embodiments, the binder includes, but is not limited to, polyvinylidene fluoride or its copolymer, nafion, etc.; the conductive agent includes, but is not limited to, common conductive solid powders such as conductive carbon black, carbon nanotubes, MXene, and graphene; and the conductive support electrode includes, but is not limited to, common highly conductive, porous, or dense conductive carriers such as copper foil, aluminum foil, foamed copper, foamed nickel, etc.

[0043] In some embodiments, the mass ratio of tellurium crystals to the binder and the conductive agent is 80:5-10:10-15; after mixing in the mass ratio, the mixture is coated on the conductive support electrode to obtain a working electrode and a counter electrode with good conductivity.

[0044] In a preferred embodiment, the mass ratio of tellurium crystals to the binder and the conductive agent is 80:10:10.

[0045] Specifically, the tellurium crystals, the binder and the conductive agent are mixed in N,N-dimethylformamide, and the solid content ratio is 0.5-1 mg / mL; after uniform dispersion, the mixture is coated on the conductive support electrode, and vacuum drying is performed at a temperature of 80-110°C for 24-48 h to obtain a tellurium-based electrode; the tellurium-based electrode can be used as a working electrode and a counter electrode.

[0046] In some embodiments, the mass ratio of the organic acid to water is 1:90-100; the volume ratio of the organic acid to water is controlled so that the organic acid weakly ionizes hydrogen ions in water under the action of an electric field, serves as an intercalation agent to intercalate tellurium crystals, and becomes hydrogen gas at a reduction potential to accelerate the expansion and exfoliation of tellurium.

[0047] In some embodiments, the voltage of the alternating current power supply is ±(3-15) V, and the frequency of the alternating current power supply is 0.0001-1000 Hz; by controlling the voltage and the frequency, the exfoliation speed of the tellurium electrode can be controlled to meet the actual production requirements; and the organic acid weakly ionizes hydrogen ions in water under the action of the voltage of ±(3-15) V, serves as an intercalation agent to intercalate tellurium crystals, and becomes hydrogen gas at a reduction potential to accelerate the expansion and exfoliation of tellurium.

[0048] In a preferred embodiment, the voltage of the alternating current power supply is ±12 V, and the frequency of the alternating current power supply is 0.1 Hz.

[0049] In some embodiments, the reaction time is 60-180 min, and the reaction is performed at 25-80°C; under the reaction time and temperature, the exfoliation of tellurium crystals is complete to obtain tellurium-based heterojunction nanomaterials with amorphous phase-crystalline phase blending.

[0050] In some embodiments, in the step S20, the mixed solution obtained after the reaction is subjected to vacuum filtration, solvent washing, and drying at room temperature to obtain tellurium-based heterojunction nanomaterials with amorphous phase-crystalline phase blending.

[0051] In addition, the application also provides a tellurium-based heterojunction nanomaterial prepared by the preparation method.

[0052] In the embodiment, the tellurium-based heterojunction nanomaterial obtained by the preparation method has a special surface microstructure, i.e., the surface simultaneously has amorphous phase and crystalline phase structures; the structure can realize rapid charge transfer and provide sufficient active sites for subsequent chemical or physical adsorption; and the amorphous phase changes the electronic structure of the original crystalline phase, thereby changing the light absorption and photoelectric conversion behavior, such as narrowing the band gap; at the same time, the chemical potentials at the amorphous phase-crystalline phase interface are different, which induces a built-in electric field to promote carrier migration, etc.

[0053] In some embodiments, the surface of the tellurium-based heterojunction nanomaterial simultaneously has amorphous phase and crystalline phase structures.

[0054] In addition, the application also provides an application of the tellurium-based heterojunction nanomaterial in semiconductors, energy or biomedicine.

[0055] The following examples are further provided to illustrate the application in detail. It should also be understood that the following examples are only used to further illustrate the application and cannot be understood as limiting the protection scope of the application. Some non-essential improvements and adjustments made by those skilled in the art according to the above content of the application all belong to the protection scope of the application.

[0056] Example 1

[0057] The embodiment provides a tellurium-based heterojunction nanomaterial with amorphous phase-crystalline phase blending, and the preparation steps are specifically as follows:

[0058] A high-purity platinum wire is wound on the surface of a solid block-shaped high-purity tellurium crystal and used as a working electrode and a counter electrode, water is used as a solvent, and octanoic acid is used as an intercalation reagent to construct a double-electrode electrochemical exfoliation system; an alternating current with a voltage amplitude of 12 V is introduced into the double-electrode electrochemical exfoliation system, the frequency is 0.1 Hz, the time is 120 minutes, the temperature is 50°C, and after the reaction, a mixed solution containing the tellurium-based heterojunction nanomaterial with amorphous phase-crystalline phase blending is obtained; the mixed solution is subjected to vacuum suction filtration and solvent (deionized water and anhydrous ethanol are used alternately) washing, and is dried at room temperature to obtain the tellurium-based heterojunction nanomaterial with amorphous phase-crystalline phase blending.

[0059] The tellurium-based heterojunction nanomaterial obtained in Example 1 is dispersed in a non-aqueous solvent for ultrasonic dispersion, and is dropped on a copper mesh for microstructure characterization, and the SEM characterization graph is as shown in Figure 2 .

[0060] It can be known that octanoic acid is used as an electrolyte, which forms a milky white oil-water mixed phase with water, and electrochemical exfoliation is carried out at the interface between the two. In the embodiment, the exfoliation rate of tellurium is slow, and the solution color gradually changes from milky white to dark brown. The product after exfoliation presents a two-dimensional sheet-like structure (as shown in Figure 2a) in FIG. 1; under further magnification detection, the surface of the tellurium-based heterojunction nanomaterial presents a mixed phase of atomically ordered arrangement of crystalline phase and amorphous arrangement of amorphous phase (as shown in b) in FIG. 1); and most of the amorphous component presents an atomic cluster structure (as shown in c) in FIG. 1). Figure 2 Figure 2

[0061] Comparative Example 1

[0062] This comparative example is substantially the same as Example 1, except that octanoic acid is replaced by hydrochloric acid to prepare the tellurium nanomaterial.

[0063] The tellurium nanomaterial obtained in Comparative Example 1 is dispersed in a non-aqueous solvent for ultrasonic dispersion, and dropped on a copper mesh for characterization of the microstructure, and the SEM characterization graph is shown in FIG. 2. Figure 3

[0064] It can be seen that, with hydrochloric acid as the electrolyte, it can form a homogeneous solution with water, and the stripping speed is faster. The surface of the product after stripping is mainly composed of crystalline components, and there are less amorphous phase, defect phase or other atomic arrangement deformities. In addition, it should be noted that other inorganic acids, including sulfuric acid, perchloric acid, phosphoric acid, carbonic acid or hydrogen diacid, or corresponding salts, etc. have similar stripping product structures. Such tellurium-based materials belong to traditional classical homogeneous materials.

[0065] In addition, under the irradiation of one standard sunlight, the photothermal temperature rise of the tellurium nanomaterial dispersion liquid obtained by stripping with hydrochloric acid in Comparative Example 1 is 15°C, and the photothermal temperature rise of the tellurium-based heterojunction nanomaterial dispersion liquid obtained by stripping with octanoic acid in Example 1 is 19°C. It can be seen that, under the same tellurium content, compared with the tellurium material stripped by inorganic acid, the tellurium nanomaterial stripped by organic acid has a higher photothermal temperature. In addition, the tellurium material dispersion liquid obtained by stripping with organic acid has higher chemical stability and dispersibility and is not easy to degrade in water.

[0066] ​​​In summary, the application provides a tellurium-based heterojunction nanomaterial, a preparation method and application thereof, the preparation method of the tellurium-based heterojunction nanomaterial comprising the following steps: constructing a double-electrode electrochemical exfoliation system by taking a tellurium crystal as a working electrode and a counter electrode, taking water as a solvent, and taking an organic acid as an intercalation reagent; introducing an alternating current power into the double-electrode electrochemical exfoliation system, and obtaining the tellurium-based heterojunction nanomaterial through reaction. The application constructs a structure and functional material by using an electrochemical in-situ modification method, and prepares a tellurium-based heterojunction nanomaterial with amorphous phase-crystalline phase blending. The organic acid is weakly ionized with hydrogen ions in water under the action of an electric field, and can be used as an intercalation reagent to intercalate the tellurium crystal and become hydrogen gas under a reduction potential, so as to accelerate the expansion and exfoliation of tellurium. Since the ionization degree of the organic acid is low, the movement of hydrogen ions under the electric field is significantly constrained by the organic group anions, and the exfoliation of the tellurium crystal by the hydrogen ions under constraint is limited, so the intercalation rate is relatively slow, and there is selectivity in the intercalation gap in three-dimensional space, so that the edge presents amorphous atomic arrangement, and the inside crystal presents crystallinity, thereby obtaining the tellurium-based heterojunction nanomaterial with amorphous phase-crystalline phase blending. In addition, due to the rapid switching of the alternating current electric field voltage, both tellurium electrodes can be rapidly exfoliated, so that the exfoliation rate and the final yield of tellurium are improved.

[0067] It should be understood that the application of the application is not limited to the above examples, and can be improved or changed according to the above description for those skilled in the art, and all these improvements and changes shall belong to the protection scope of the appended claims of the application.

Claims

1. A method for preparing a tellurium-based heterojunction nanomaterial, characterized in that, The method comprises the steps of: building a two-electrode electrochemical exfoliation system by taking a first tellurium crystal and a second tellurium crystal as a working electrode and a counter electrode respectively, taking water as a solvent, and taking an organic acid as an intercalation reagent; introducing an alternating current power supply into the two-electrode electrochemical exfoliation system, and obtaining a tellurium-based heterojunction nanomaterial through reaction. The organic acid comprises one or more of octanoic acid, succinic acid, adipic acid, linolenic acid, cinnamic acid, oleic acid, stearic acid, linoleic acid, palmitic acid, and arachidonic acid; the mass ratio of the organic acid to water is 1:(90-100); the voltage of the alternating current power supply is ±(3-15) V, and the frequency of the alternating current power supply is 0.0001 Hz-1000 Hz.

2. The method for preparing tellurium-based heterojunction nanomaterials according to claim 1, characterized in that, The first tellurium crystal is a solid block or a powder; and the second tellurium crystal is a solid block or a powder.

3. The method of claim 2, wherein the Te-based heterojunction nanomaterial is prepared by the following steps of: When the first tellurium crystal and / or the second tellurium crystal is a solid block, a platinum wire is wound around the surface of the tellurium crystal to serve as the working electrode and the counter electrode. ​ 4. The method for preparing tellurium-based heterojunction nanomaterials according to claim 2, characterized in that, When the first tellurium crystal and / or the second tellurium crystal is a powder, the tellurium crystal is compounded with a binder and a conductive agent, and then coated on a conductive support electrode to serve as the working electrode and the counter electrode.

5. The method for preparing tellurium-based heterojunction nanomaterials according to claim 1, characterized in that, The reaction time is 60-180 minutes, and the reaction is carried out at 25-80 °C.

6. A tellurium-based heterojunction nanomaterial, characterized in that, The tellurium-based heterojunction nanomaterial is prepared by the method of any one of claims 1-5, and the surface of the tellurium-based heterojunction nanomaterial simultaneously has amorphous and crystalline structures.

7. Use of the tellurium-based heterojunction nanomaterial of claim 6 in semiconductors, energy sources, or biomedicine.

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