阅读说明：本技术 还原氧化石墨烯负载金属单原子催化剂的制备方法 (Preparation method of reduced graphene oxide loaded metal monatomic catalyst ) 是由 刘珍珍 张侃 张胜利 董超然 于 2021-01-15 设计创作，主要内容包括：本发明公开了一种还原氧化石墨烯负载金属单原子催化剂的制备方法。所述方法以氧化石墨烯为基底,金属氯化物为前驱体、二甲基亚砜为溶剂,混合搅拌均匀后置于磁力搅拌釜中,采用一步溶剂热法,将金属单原子铆钉在还原氧化石墨烯的表面制得还原氧化石墨烯负载金属单原子催化剂,本发明在电催化合成氨领域具有良好的催化性能和稳定性。(The invention discloses a preparation method of a reduced graphene oxide loaded metal monatomic catalyst. According to the method, graphene oxide is used as a substrate, metal chloride is used as a precursor, dimethyl sulfoxide is used as a solvent, the mixture is uniformly stirred and then placed in a magnetic stirring kettle, and a one-step solvothermal method is adopted to prepare the reduced graphene oxide loaded metal monatomic catalyst on the surface of the reduced graphene oxide by using a metal monatomic rivet.)

1. The preparation method of the reduced graphene oxide loaded metal monatomic catalyst is characterized by comprising the following steps of:

(1) ultrasonically dispersing graphene oxide in a dimethyl sulfoxide organic solvent to obtain a graphene oxide dispersion liquid;

(2) dissolving a metal precursor in dimethyl sulfoxide to prepare a metal precursor solution;

(3) and mixing the graphene oxide dispersion liquid and the metal precursor solution, stirring until the mixture is uniformly mixed, placing the mixture in a magnetic stirring reaction kettle, carrying out solvothermal reaction at the temperature of 130-150 ℃, washing a product for several times by using ethanol and deionized water after the reaction is finished, and then carrying out freeze drying to obtain the reduced graphene oxide loaded metal monatomic catalyst.

2. The method according to claim 1, wherein in the step (2), the metal precursor is MoCl₅、NbCl₅Or WCl₅。

3. The preparation method according to claim 1, wherein in the step (3), the solvothermal reaction time is 10-12 h.

4. The production method according to claim 1, wherein in the step (3), the stirring speed is 700 rpm.

5. The preparation method according to claim 1, wherein in the step (3), the mass ratio of the graphene oxide to the metal precursor is 100: 1-5: 1.

Technical Field

The invention relates to a preparation method of a reduced graphene oxide loaded metal monatomic catalyst, belonging to the field of metal catalysts.

Background

As an important chemical raw material, ammonia has wide application in the aspects of chemical production, agriculture, energy conversion and the like. At present, the industrial synthesis of ammonia mainly adopts a Haber-Bosch process technology with high temperature and high pressure. In view of this, it is very necessary to develop a new route for synthesizing ammonia under mild conditions for energy saving and environmental protection. The electrocatalytic nitrogen reduction can be theoretically carried out at normal temperature and normal pressure, and the sources of raw materials (water and nitrogen) are wide, which brings a chance for realizing green synthesis of ammonia under mild conditions. However, due to the problems of extremely difficult activation and breakage of N-N triple bond, low solubility of nitrogen and the like, the electroreduction reaction of nitrogen is extremely difficult to perform in thermodynamics and kinetics, and the existence of hydrogen evolution competition reaction causes that the efficiency and the selectivity of the electrocatalytic nitrogen synthesis of ammonia are extremely low. Therefore, how to improve the selectivity of the electrocatalytic nitrogen reduction reaction and further improve the efficiency of electrocatalytic ammonia synthesis is a difficult problem in the research of electrochemical ammonia synthesis under normal temperature and pressure.

The monatomic catalyst with the active metal center dispersed by atoms has great potential in improving the electrochemical synthesis of ammonia. Firstly, different from the traditional metal nano catalyst, the single metal atom catalyst can effectively inhibit HER activity, namely the Faraday efficiency of electrocatalytic synthesis of ammonia is improved to a great extent; second, near 100% atomic utilization of the monatomic catalyst can increase NH₃The synthesis efficiency of (2).

However, due to the high surface energy of the monoatomic species, the synthesis of a high dispersion density monoatomic catalyst remains a great challenge. At present, various methods for preparing metal monoatomic atoms have been reported. Professor grandschool uses atomic deposition technology to realize the deposition of Platinum monoatomic atoms on graphene (Cheng N, Stambula S, Wang D, et al. ARTICLE Platinum single-atom and cluster catalyst of the hydrogen evolution reaction [ J ]. Nature Communications,2016,7.), and the catalyst has excellent catalytic performance. But the atomic deposition technology has high cost and needs to use metal organic salt, so the application and popularization of the method are limited. The paragraph peak teaches that graphene oxide, metal precursor and hydrogen peroxide are subjected to hydrothermal assembly, and then high-temperature (900 ℃) annealing is carried out in an ammonia atmosphere, so as to effectively prepare a series of metal monatomic catalysts (Fei H, Dong J, Feng Y, et al. general synthesis and defined structural identification of MN4C4 single-atom catalysts [ J ] Nature catalysts, 2018,1(1): 63-72.). However, the method involves ammonia gas and high-temperature treatment, and the conditions are harsh, so that large-scale preparation is difficult to realize.

Disclosure of Invention

The invention aims to provide a preparation method of a reduced graphene oxide loaded metal monatomic catalyst, which is efficient, simple to operate, free of precise and complicated equipment and suitable for large-scale production.

The technical scheme for realizing the aim of the invention is as follows:

the preparation method of the reduced graphene oxide loaded metal monatomic catalyst comprises the following steps:

(1) ultrasonically dispersing Graphene Oxide (GO) in a dimethyl sulfoxide (DMSO) organic solvent to obtain a graphene oxide dispersion liquid;

(2) dissolving a metal precursor in DMSO (dimethyl sulfoxide), and preparing a metal precursor solution;

(3) and mixing the graphene oxide dispersion liquid and the metal precursor solution, stirring until the mixture is uniformly mixed, placing the mixture in a magnetic stirring reaction kettle, carrying out solvothermal reaction at the temperature of 130-150 ℃, washing a product for several times by using ethanol and deionized water after the reaction is finished, and then carrying out freeze drying to obtain the reduced graphene oxide loaded metal monatomic catalyst.

Preferably, in the step (2), the metal precursor is MoCl₅、NbCl₅Or WCl₅。

Preferably, in the step (3), the solvothermal reaction time is 10-12 h.

Preferably, in step (3), the stirring speed is 700 rpm.

Preferably, in the step (3), the mass ratio of the graphene oxide to the metal precursor is 100: 1-5: 1.

in the present invention, MoCl₅、NbCl₅And WCl₅And when the graphene oxide is solid, the graphene oxide is a dimer, the graphene oxide is decomposed into a monomer in a dimethyl sulfoxide solvent, a metal center with positive electricity is exposed, a large number of oxygen-containing functional groups with negative electricity are arranged on the surface of the graphene oxide, the graphene oxide and the graphene oxide attract each other, and a monatomic rivet is arranged on the reduced graphene oxide by a one-step hot solvent method to prepare the reduced graphene oxide supported monatomic catalyst.

Compared with the prior art, the invention has the advantages that:

(1) the method can realize the control of loading metal monoatomic species on the reduced graphene oxide by adjusting the species of the precursor metal salt;

(2) the invention can regulate the load capacity of metal single atoms by regulating the addition of the precursor metal salt;

(3) the invention has simple and safe operation process and low cost, and is suitable for large-scale preparation.

Drawings

Fig. 1 is an SEM image of a reduced graphene oxide-supported Nb monoatomic catalyst prepared in example 1.

Fig. 2 is a TEM image of the reduced graphene oxide-supported Nb monoatomic catalyst prepared in example 1.

Fig. 3 is a diagram of a reduced graphene oxide supported Nb monatomic catalyst prepared in example 1 under a high angle annular dark field scanning transmission electron microscope.

Fig. 4 is an I-t curve of the reduced graphene oxide-supported Nb monoatomic catalyst prepared in example 1.

FIG. 5 is the yield R per given potential of the reduced graphene oxide-supported Nb monatomic catalyst prepared in example 1_NH3And a faraday efficiency FE.

Fig. 6 is a view of a reduced graphene oxide supported W monatomic catalyst prepared in example 2 under a high angle annular dark field scanning transmission electron microscope.

Fig. 7 is a view of a reduced graphene oxide supported Mo monatomic catalyst prepared in example 3 under a high angle annular dark field scanning transmission electron microscope.

Fig. 8 is a view of a reduced graphene oxide-supported Nb cluster catalyst prepared in comparative example 1 under a high-angle annular dark-field scanning transmission electron microscope.

Fig. 9 is a view under a transmission electron microscope of the reduced graphene oxide-supported Sb particle catalyst prepared in comparative example 2.

FIG. 10 is a graph showing the yield R per given potential of the reduced graphene oxide catalyst prepared in comparative example 3_NH3And a faraday efficiency FE.

Detailed Description

The present invention will be described in further detail with reference to the following examples and the accompanying drawings.

Example 1

Preparing a reduced graphene oxide loaded Nb monatomic catalyst:

step 1, adding graphene oxide into dimethyl sulfoxide, and performing ultrasonic dispersion to obtain a uniform graphene oxide dispersion liquid (GO/DMSO) with the concentration of 4 mg/mL;

step 2, preparing 2mg/mL NbCl in a glove box₅DMSO solution;

step 3, taking 4mL of GO/DMSO solution in the step 1 and NbCl in the step 2₅The DMSO solution was mixed with 150. mu.L/17 mL of DMSO solution under stirring, and then transferred to a reaction vessel to react at 140 ℃ for 12 hours. And after the reaction is finished, centrifugally collecting the product, sequentially washing the product with absolute ethyl alcohol and deionized water, removing the residual DMSO solution, and freeze-drying to obtain a sample, namely the reduced graphene oxide loaded Nb monatomic catalyst.

Fig. 1 is an SEM image of a reduced graphene oxide-Nb monoatomic catalyst, fig. 2 is a TEM image of a reduced graphene oxide-Nb monoatomic catalyst, and fig. 3 is a high-angle annular dark field-scanning transmission electron microscope (HAADF-STEM) image of a reduced graphene oxide-Nb monoatomic catalyst, in which bright Nb monoatomic atoms are uniformly dispersed on the surface of reduced graphene oxide and the metal loading concentration is high. Fig. 4 is an I-t curve of the catalyst at each given potential, indicating that the reduced graphene oxide supported Nb monatomic catalyst has excellent stability. FIG. 5 shows the productivity R of the catalyst at each given potential_NH3And Faraday efficiency FE, which shows that the reduced graphene oxide loaded Nb monatomic catalyst has excellent activity for synthesizing ammonia by electrocatalysis, and the excellent performance is superior to most reported electrocatalysis ammonia synthesis catalysts.

Example 2

Preparing a reduced graphene oxide loaded W monatomic catalyst:

step 1, adding graphene oxide into dimethyl sulfoxide, and performing ultrasonic dispersion to obtain a uniform graphene oxide dispersion liquid (GO/DMSO) with the concentration of 4 mg/mL;

step 2, in a glove box, preparing WCl of 2mg/mL₅DMSO solution;

step 3, taking 4mL of GO/DMSO solution in step 1 and WCl in step 2₅200 mu L of DMSO solution and 17mL of DMSO solution are stirred and mixed uniformly, then transferred to a reaction kettle and reacted for 11h at 140 ℃. And after the reaction is finished, centrifugally collecting the product, sequentially washing the product with absolute ethyl alcohol and deionized water, removing the residual DMSO solution, and freeze-drying to obtain a sample, namely the reduced graphene oxide loaded W monatomic catalyst.

Fig. 4 is a high angle annular dark field-scanning transmission electron microscope (HAADF-STEM) image of a reduced graphene oxide supported W monatomic catalyst, with bright W monatomics uniformly dispersed on the reduced graphene oxide surface.

Example 3

Preparing a reduced graphene oxide loaded Mo monatomic catalyst:

step 1, adding graphene oxide into dimethyl sulfoxide, and performing ultrasonic dispersion to obtain a uniform graphene oxide dispersion liquid (GO/DMSO) with the concentration of 4 mg/mL;

step 2, in a glove box, preparing 2mg/mL MoCl₅DMSO solution;

step 3, taking 4mL of GO/DMSO solution in step 1 and MoCl in step 2₅200 mu L of DMSO solution and 17mL of DMSO solution are stirred and mixed uniformly, then transferred to a reaction kettle and reacted for 12h at 140 ℃. And after the reaction is finished, centrifugally collecting the product, sequentially cleaning the product with absolute ethyl alcohol and deionized water to remove the residual DMSO solution, and freeze-drying the product to obtain a sample, namely the reduced graphene oxide loaded Mo monatomic catalyst.

Fig. 4 is a high angle annular dark field-scanning transmission electron microscope (HAADF-STEM) image of a reduced graphene oxide supported Mo monatomic catalyst, with bright Mo monatomic uniformly dispersed on the reduced graphene oxide surface.

Comparative example 1

Preparing a reduced graphene oxide loaded Nb monatomic catalyst:

step 1, adding graphene oxide into dimethyl sulfoxide, and performing ultrasonic dispersion to obtain a uniform graphene oxide dispersion liquid (GO/DMSO) with the concentration of 4 mg/mL;

step 2, inIn a glove box, NbCl of 2mg/mL is prepared₅DMSO solution;

step 3, taking 4mL of GO/DMSO solution in step 1 and NbCl in step 2₅The mixture was stirred and mixed uniformly in 1mL of DMSO solution and 17mL of DMSO solution, and then transferred to a reaction vessel to react at 140 ℃ for 12 hours. And after the reaction is finished, centrifugally collecting the product, sequentially cleaning the product with absolute ethyl alcohol and deionized water, removing the residual DMSO solution, and freeze-drying to obtain a sample, namely the reduced graphene oxide supported Nb cluster catalyst.

Fig. 8 is an image of a high angle annular dark field-scanning transmission electron microscope (HAADF-STEM) of the catalyst, and it is known that, since the amount of the metal precursor added is too large, the single atoms are agglomerated on the surface of the reduced graphene oxide to form clusters.

Comparative example 2

Preparing a reduced graphene oxide supported Sb particle catalyst:

step 1, adding graphene oxide into dimethyl sulfoxide, and performing ultrasonic dispersion to obtain a uniform graphene oxide dispersion liquid (GO/DMSO) with the concentration of 4 mg/mL;

step 2, in a glove box, preparing 2mg/mL SbCl₃DMSO solution;

step 3, taking 4mL of GO/DMSO solution in the step 1 and SbCl in the step 2₃1mL of DMSO solution and 17mL of DMSO solution were mixed with stirring, transferred to a reaction vessel, and reacted at 140 ℃ for 12 hours. And after the reaction is finished, centrifugally collecting the product, sequentially cleaning the product with absolute ethyl alcohol and deionized water to remove the residual DMSO solution, and freeze-drying the product to obtain a sample, namely the reduced graphene oxide supported Sb particle catalyst.

Fig. 9 is a Transmission Electron Microscope (TEM) image of the catalyst, and it can be seen that Sb particles are supported on reduced graphene oxide. Due to the precursor SbCl₃Non-dimeric form cannot be decomposed into a monomer in a dimethylsulfoxide solvent, and thus cannot form a monoatomic form.

Comparative example 3

Preparing a reduced graphene oxide catalyst:

step 1, adding graphene oxide into dimethyl sulfoxide, and performing ultrasonic dispersion to obtain a uniform graphene oxide dispersion liquid (GO/DMSO) with the concentration of 4 mg/mL;

and 2, taking 4mL of GO/DMSO solution and 18mL of DMSO solution in the step 1, stirring and mixing uniformly, transferring to a reaction kettle, and reacting for 12h at 140 ℃. And after the reaction is finished, centrifugally collecting the product, sequentially washing the product with absolute ethyl alcohol and deionized water, removing the residual DMSO solution, and freeze-drying to obtain a sample, namely the reduced graphene oxide catalyst.

And 3, taking 4mg of reduced graphene oxide catalyst, 730 mu L of ethanol and 70 mu L of deionized water 200 mu L, nafion membrane solution, carrying out ultrasonic treatment for 30min to obtain uniformly dispersed catalyst ink, taking 50 mu L of catalyst ink, dropwise coating the catalyst ink on carbon paper, drying at room temperature to obtain a reduced graphene oxide/carbon paper working electrode, and carrying out an electro-catalytic synthesis ammonia test.

FIG. 10 is the yield R of reduced graphene oxide at each given potential_NH3And faraday efficiency FE, it is known that the performance of the reduced graphene oxide supported Nb monatomic catalyst is superior to that of the reduced graphene oxide catalyst.