阅读说明：本技术 一种超小中空立方体纳米材料及其制备方法与电催化析氢中的应用 (Ultra-small hollow cubic nano material, preparation method thereof and application thereof in electrocatalytic hydrogen evolution ) 是由 周炎 罗佳冰 张军 王雪媛 王淑涛 脱永笑 贾翠萍 于 2020-06-08 设计创作，主要内容包括：本发明涉及一种超小中空立方体纳米材料及其制备方法与电催化析氢中的应用,属于纳米材料合成领域。本发明由ZIF-67前驱体通过简单的一步水热法200℃反应12h合成了超小Co<Sub>3</Sub>S<Sub>4</Sub>-MoS<Sub>2</Sub>中空立方体纳米复合材料。本发明合成的纳米材料具有超小的特殊结构,实验过程简单可行,对环境友好,且中空结构可提供较大比表面积,加快电子传输,具有优异的析氢性能和良好的稳定性,有较大潜在实用价值。(The invention relates to an ultra-small hollow cubic nano material, a preparation method thereof and application thereof in electrocatalytic hydrogen evolution, belonging to the field of nano material synthesis. The invention synthesizes the ultra-small Co from a ZIF-67 precursor through a simple one-step hydrothermal method at 200 ℃ for 12h 3 S 4 ‑MoS 2 Hollow cubic nanocomposites. The nano material synthesized by the method has an ultra-small special structure, the experimental process is simple and feasible, the environment is protected, the hollow structure can provide a larger specific surface area, the electron transmission is accelerated, and the nano material has excellent hydrogen evolution performance and is goodGood stability and great potential practical value.)

1. The ultra-small hollow cubic nano material is characterized in that the material is Co₃S₄-MoS₂The composite material is of a hollow cubic nanostructure, and the size of the composite material is 300-500 nm.

2. The ultrasmall hollow cubic nanomaterial of claim 1, wherein said Co is₃S₄-MoS₂Lattice distance in the composite material corresponds to Co₃S₄(440)、Co₃S₄(400)、Co₃S₄(311) And MoS₂(002)。

3. The ultra-small hollow cubic nanomaterial as claimed in claim 1, wherein the ultra-small hollow cubic nanomaterial has an X-ray photoelectron spectrum showing peaks containing five components of C1S, O1S, Mo3d, Co2p and S2p, and 781.84eV (Co2 p) in the Co region_3/2) And 798.03eV (Co2 p)_1/2) Corresponds to Co₃S₄Phase (1); in the Mo3d region, two satellite peaks appear at 803.49eV and 786.17eV, respectively, corresponding to Co²⁺And Co³⁺Two main peaks at 232.13eV and 228.89eV correspond to Mo3d_3/2And Mo3d_5/2Is Mo⁴⁺(ii) a In the region of S2p, there are two sets of peaks for the Co-S bond and Mo-S bond, one set at 161.56eV and 164.31eV, respectively, corresponding to the Co-S bond S2p_3/2And S2p_1/2A track; the other group, located at 161.83 and 162.94eV, corresponds to S2p in the Mo-S bond_3/2And S2p_1/2A track.

4. The method for preparing the ultra-small hollow cubic nanomaterial of claim 1, comprising the steps of:

and (3) dispersing ZIF-67 into an ethanol solution, adding sodium molybdate dihydrate and thioacetamide, and carrying out one-step hydrothermal reaction to obtain the hollow cubic nanomaterial consisting of the ultra-small structure.

5. The method for preparing the ultra-small hollow cubic nanomaterial as claimed in claim 4, wherein the ZIF-67 is synthesized from a 2-methylimidazole methanol solution and a cobalt nitrate hexahydrate methanol solution at room temperature.

6. The method for preparing ultra-small hollow cubic nanomaterial of claim 5, wherein the synthesis steps of ZIF-67 are as follows:

mixing the methanol solution of cobalt nitrate hexahydrate and the methanol solution of 2-methylimidazole, stirring, standing at room temperature for 24 hours for reaction, centrifuging the purple product obtained after the reaction is finished, and drying to obtain ZIF-67.

7. The preparation method of the ultra-small hollow cubic nanomaterial according to claim 4, wherein the mass ratio of ZIF-67, sodium molybdate dihydrate to thioacetamide is 1: (0.7-1): (2.4-2.8).

8. The method for preparing ultra-small hollow cubic nanomaterial as defined in claim 4, wherein the hydrothermal reaction temperature is 190-.

9. The method for preparing ultra-small hollow cubic nanomaterial according to claim 4, wherein the ultra-small hollow cubic nanomaterial is obtained by cooling to room temperature after the reaction is finished, and performing centrifugal cleaning and drying₃S₄-MoS₂A hollow composite material.

10. Use of the ultrasmall hollow cubic nanomaterial of claim 1 in electrocatalytic hydrogen evolution.

Technical Field

The invention relates to a preparation method of an ultra-small hollow cubic nano material, in particular to a hollow cubic nano composite material formed by an ultra-small structure, belonging to the field of nano material synthesis.

Background

Hydrogen energy has become a new type of energy source that prevents the energy and environmental crisis caused by the consumption of traditional fossil fuels. The electrolyzed water is also called electrochemical water cracking and is a high-efficiency direct hydrogen production method. Usually consisting of two half-reactions, hydrogen and oxygen evolution, and an electrocatalyst is usually required to lower the potential required to drive the electrolyzed water process. Although platinum is the most effective catalyst for hydrogen evolution reaction, the rarity and high price limit the application potential, and therefore, the development of an efficient, stable and low-cost electrocatalyst for hydrogen evolution reaction has become a major concern.

Transition metal compounds, such as transition metal carbides, sulfides, selenides, phosphides, and borides, exhibit excellent performance in promoting hydrogen evolution reactions, with transition metal sulfides exhibiting excellent catalytic performance due to their unique electronic structures. Molybdenum disulfide is considered an excellent electrocatalyst because of its good surface energy matched to the absorption of hydrogen species. And compared with binary metal compounds, ternary metal compounds have better catalytic activity due to more active centers, synergistic effects and tunable electronic structures.

Constructing hollow structures is another effective method to increase the activity of electrocatalysts. In recent years, metal organic frameworks have been used as an ideal precursor for the synthesis of transition metal compounds. For example: CN110681407A discloses a Fe-doped [email protected] NCNTFs nano composite material and a preparation method thereof. The method comprises the following steps: adding ferric nitrate into the ZIF-67 precursor, taking ethanol as a reaction solvent, and stirring at room temperature to obtain a Fe-doped ZIF-67 precursor; made of tellurium powderAnd calcining the Fe-doped ZIF-67 precursor as a tellurium source in an Ar/H2 mixed atmosphere to obtain the Fe-doped [email protected] NCNTFs nano composite material. CN110538662A discloses a preparation method of a cobalt-doped rhenium disulfide nanosheet array for electrocatalytic hydrogen evolution, which comprises the following steps: adding 2-methylimidazole aqueous solution into cobalt nitrate hexahydrate aqueous solution, and immersing an acid-treated carbon cloth into the mixed solution; after reacting for a period of time, taking a sample, and cleaning the sample with deionized water; and growing in the same solution for a period of time to obtain a ZIF-67 nano array sample named ZIF-67/CC, and finally, cleaning the sample and drying. Dissolving cobalt nitrate hexahydrate in a mixed solution of ultrapure water and ethanol, putting the prepared ZIF-67/CC into the mixed solution for hydrolysis to obtain a product cobalt hydroxide nano array Co (OH)₂(ii)/CC; obtaining the product Co-ReS₂and/CC. However, the preparation of the compound with a special structure still has certain difficulty, so that the invention is provided for synthesizing the nano material with the special structure by further using the metal organic framework as a precursor to be applied to electrocatalytic hydrogen evolution.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides the hollow cubic nanocomposite material formed by the ultra-small structure, the ultra-small special structure can accelerate the electron transmission rate, the hollow cubic structure provides larger specific surface area, and the high efficiency and high capacity of hydrogen gas precipitation in the electrocatalysis process can be realized, so the hollow cubic nanocomposite material has higher application value in the synthesis of hydrogen clean energy.

The invention also provides a preparation method of the hollow cubic nanocomposite material formed by the ultra-small structure and application of the hollow cubic nanocomposite material in the aspect of electrocatalytic hydrogen evolution.

The technical scheme of the invention is as follows:

an ultra-small hollow cubic nano material is Co₃S₄-MoS₂The composite material is of a hollow cubic nanostructure, and the size of the composite material is 300-500 nm.

According to the invention, preferably, said Co₃S₄-MoS₂Lattice distance in the composite material corresponds to Co₃S₄(440)、Co₃S₄(400)、Co₃S₄(311) And MoS₂(002). Under high resolution conditions, the cobaltosic sulfide and molybdenum disulfide are in a sticky state.

According to the invention, preferably, the X-ray photoelectron spectrum of the ultra-small hollow cubic nanomaterial shows that the peak contains five components of C1S, O1S, Mo3d, Co2p and S2p, and in the Co region, 781.84eV (Co2 p)_3/2) And 798.03eV (Co2 p)_1/2) Corresponds to Co₃S₄Phase (1); in the Mo3d region, two satellite peaks appear at 803.49eV and 786.17eV, respectively, corresponding to Co²⁺And Co³⁺Two main peaks at 232.13eV and 228.89eV correspond to Mo3d_3/2And Mo3d_5/2Is Mo⁴⁺(ii) a In the region of S2p, there are two sets of peaks for the Co-S bond and Mo-S bond, one set at 161.56eV and 164.31eV, respectively, corresponding to the Co-S bond S2p_3/2And S2p_1/2A track; the other group, located at 161.83 and 162.94eV, corresponds to S2p in the Mo-S bond_3/2And S2p_1/2A track.

According to the invention, the preparation method of the ultra-small hollow cubic nano material comprises the following steps:

and (3) dispersing ZIF-67 into an ethanol solution, adding sodium molybdate dihydrate and thioacetamide, and carrying out one-step hydrothermal reaction to obtain the hollow cubic nanomaterial consisting of the ultra-small structure.

According to the invention, preferably, the ZIF-67 is synthesized by a 2-methylimidazole methanol solution and a cobalt nitrate hexahydrate methanol solution at room temperature;

further preferably, the synthesis of ZIF-67 comprises the following steps:

mixing the methanol solution of cobalt nitrate hexahydrate and the methanol solution of 2-methylimidazole, stirring, standing at room temperature for 24 hours for reaction, centrifuging the purple product obtained after the reaction is finished, and drying to obtain ZIF-67. Preferably, the concentrations of cobalt nitrate hexahydrate and 2-methylimidazole are respectively 5mmol L^-1And 40mmol L^-1。

According to the invention, the preferred mass ratio of ZIF-67, sodium molybdate dihydrate and thioacetamide is 1: (0.7-1): (2.4-2.8), and more preferably 1:0.83: 2.57.

According to the invention, the hydrothermal reaction temperature is preferably 190-205 ℃, and the reaction time is 10-14 h; further preferably, the hydrothermal reaction temperature is 200 ℃ and the reaction time is 12 hours.

According to the present invention, it is preferable that the reaction is finished, then cooled to room temperature, centrifugally washed, and dried to obtain ultra-small Co₃S₄-MoS₂A hollow composite material.

The invention also provides application of the ultra-small hollow cubic nano material in electrocatalytic hydrogen evolution.

The invention takes ZIF-67 as a precursor, and synthesizes a hollow cube formed by a super-small structure through a simple one-step hydrothermal reaction, the super-small special structure can accelerate the electron transmission rate, the hollow cube structure provides a larger specific surface area, and hydrogen gas precipitation with high efficiency and high capacity in the electrocatalysis process can be realized, and the experimental flow is shown in figure 16.

The hydrogen evolution performance of the present invention was tested as follows: dispersing 5mg of catalyst sample into 500 mul of ethanol, adding 20 mul of Nafion solution to form uniform slurry, carrying out ultrasonic treatment for 1h, and then dropwise adding 100 mul of mixed solution into the pretreated carbon paper, wherein the loading concentration is 1mgcm^-2As the working electrode.

The polarization curve (LSV) and cyclic voltammetry Curve (CV) of the invention were tested in a 1.0MKOH solution using a CHI660E electrochemical workstation, using Ag/AgCl (3M KCl) as a reference electrode and a graphite electrode as a counter electrode, the electrolyte was deoxygenated by introducing nitrogen gas for 30min before each experiment, and the sweep rate was set at 5 mV. s^-1And a stable polarization curve was obtained after 20 scans.

In an alternating current impedance (EIS) test of the present invention, the open circuit potential parameter was set to-0.176V (versus an Ag/AgCl electrode) and the frequency was set from 100000Hz to 0.01 Hz.

The overpotential (eta) to log (j) of the method obtains a tafel curve, and then the tafel slope is calculated to evaluate the dynamic performance of the electro-catalytic hydrogen production of the catalyst.

All potential values in the experiment of the invention are corrected by the standard hydrogen electrode, and the electrode potential calibration equation is the equation:

E_RHE＝E_Ag/AgCl+0.059pH+E⁰ _Ag/AgCl(E⁰ _Ag/AgCl＝0.209V)

compared with the prior art, the invention has the following beneficial effects:

1. the invention synthesizes the hollow cubic nano composite material formed by the ultra-small special structure by taking ZIF-67 as a precursor for the first time, firstly, 2-methylimidazole methanol solution and cobalt nitrate hexahydrate methanol solution are used for synthesizing the ZIF-67 at room temperature, a synthesized sample is dispersed into ethanol solution, sodium molybdate dihydrate and thioacetamide are added, and the hollow cubic nano material formed by the ultra-small structure is obtained by one-step simple hydrothermal reaction. The nano material synthesized by the invention has an ultra-small special structure, the experimental process is simple and feasible, the environment is protected, the electron transmission rate can be accelerated by the ultra-small special structure, and the hollow cubic structure provides a larger specific surface area.

2. The invention finds that through the performance test of the linear scanning curve: the hollow cubic nano composite material formed by the ultra-small structure has excellent hydrogen evolution performance, and is particularly suitable for molybdenum disulfide (MoS)₂) Cobaltosic sulfide (Co)₃S₄) Compared with the prior art, the method can realize high efficiency and high capacity of hydrogen gas precipitation in the electrocatalysis process under the same current density, thereby having higher application value in the electrocatalysis hydrogen precipitation. Good stability, and current density of 10mA cm^-2The overpotential only needs 105 mV.

Drawings

FIG. 1 is a TEM photograph of 67 nm zeolite imidazole based framework material obtained in example 1;

FIG. 2 is a view showing a subminiature Co obtained in example 2₃S₄-MoS₂A transmission electron microscope photograph of the hollow nano material;

FIG. 3 is a view showing a subminiature Co obtained in example 2₃S₄-MoS₂High-resolution transmission electron microscope photos of the hollow nano materials;

FIG. 4 shows a subminiature Co obtained in example 2₃S₄-MoS₂X-ray diffraction patterns of the hollow nanomaterials compared to example 1, comparative examples 7, 8;

FIG. 5 shows a subminiature Co obtained in example 2₃S₄-MoS₂Hollow nano materials X-ray photoelectron spectrum (a) and high resolution energy spectrums of Co2p (b), Mo3d (c) and S2p (d);

FIG. 6 shows a subminiature Co obtained in example 2₃S₄-MoS₂The graph of the hydrogen evolution performance test of the hollow nano material is a linear scanning curve, (b) a cyclic voltammetry curve under different scanning speeds, (c) an alternating current impedance curve, (d) a tafel curve, (e) 100mA cm^-2Testing the stability of constant current under current density;

FIG. 7 shows a subminiature Co obtained in comparative example 1₃S₄-MoS₂A hollow nanomaterial transmission electron microscope picture;

FIG. 8 is a view showing that the ultra-small Co obtained in comparative example 2 is₃S₄-MoS₂A hollow nanomaterial transmission electron microscope picture;

FIG. 9 shows a subminiature Co obtained in comparative example 3₃S₄-MoS₂A hollow nanomaterial transmission electron microscope picture;

FIG. 10 shows the ultra-small Co obtained in comparative example 4₃S₄-MoS₂A hollow nanomaterial transmission electron microscope picture;

FIG. 11 shows a subminiature Co obtained in comparative example 5₃S₄-MoS₂A hollow nanomaterial transmission electron microscope picture;

FIG. 12 shows a subminiature Co obtained in comparative example 6₃S₄-MoS₂A hollow nanomaterial transmission electron microscope picture;

FIG. 13 shows Co obtained in comparative example 7₃S₄Scanning electron microscope pictures of the nano materials;

FIG. 14 shows MoS obtained in comparative example 8₂Scanning electron microscope pictures of the nano materials;

FIG. 15 is a graph showing ultra-small Co prepared in example 2 and comparative examples 1 to 6₃S₄-MoS₂Hollow nano material polarization curve contrast picture。

Fig. 16 shows a subminiature Co of embodiment 2₃S₄-MoS₂A flow chart for preparing the hollow nano material.

Detailed Description

The method for preparing the hollow cubic nanomaterial composed of ultra-small structures according to the present invention is described in detail with reference to the following embodiments and examples.

In the following examples, the main experimental reagents and instruments used are listed below:

cobalt nitrate hexahydrate (Co (NO)₃)₂·2H₂O), 2-methylimidazole (C)₄H₆N₂) Methanol, sodium molybdate dihydrate (Na)₂MoO₄·2H₂O), thioacetamide (CH)₃CSNH₂) Absolute ethanol, Nafion (5 wt%), 20% Pt/C, magnetic stirrer (Color liquid [ white ]]) A bench top high speed centrifuge (TG16-WS), an analytical electronic balance (BS210S), an electrothermal blowing dry box (DHG-9015A), an ultrasonic cleaner (KQ2200B type), an X-ray diffractometer (X' Pert PRO MPD), a transmission electron microscope (JEM-2100(UHR), an X-ray photoelectron spectroscopy (JEOL Ltd), an electrochemical workstation (CHI 660E).