阅读说明：本技术 一种zif-8/石墨烯复合气凝胶及其制备方法与应用 (ZIF-8/graphene composite aerogel and preparation method and application thereof ) 是由 王建芝 左训行 郭自依 于 2021-08-19 设计创作，主要内容包括：本发明提供了一种ZIF-8/石墨烯复合气凝胶及其制备方法与应用,制备方法包括步骤：将石墨粉与硝酸钠混合,缓慢滴入酸溶液,然后加入锰源,搅拌反应,洗涤、离心后得到氧化石墨烯溶液；向所述氧化石墨烯溶液内加入锌源、二甲基咪唑水溶液,超声搅拌均匀,置于高压反应釜内进行水热反应,反应结束后将产物冷冻干燥,得到气凝胶；将所述气凝胶置于马弗炉内进行煅烧,得到ZIF-8/石墨烯复合气凝胶。本发明涉及的制备方法简单,反应条件温和,制得的ZIF-8/石墨烯复合气凝胶结构稳定、活性位点数量多,有利于提高电催化析氢的效率。(The invention provides a ZIF-8/graphene composite aerogel and a preparation method and application thereof, wherein the preparation method comprises the following steps: mixing graphite powder and sodium nitrate, slowly dropping an acid solution, then adding a manganese source, stirring for reaction, washing, and centrifuging to obtain a graphene oxide solution; adding a zinc source and a dimethyl imidazole aqueous solution into the graphene oxide solution, ultrasonically stirring uniformly, placing the graphene oxide solution into a high-pressure reaction kettle for hydrothermal reaction, and freeze-drying a product after the reaction is finished to obtain aerogel; and placing the aerogel in a muffle furnace for calcining to obtain the ZIF-8/graphene composite aerogel. The preparation method provided by the invention is simple, the reaction conditions are mild, and the prepared ZIF-8/graphene composite aerogel is stable in structure and large in active site number, and is beneficial to improving the efficiency of electrocatalytic hydrogen evolution.)

1. A preparation method of ZIF-8/graphene composite aerogel is characterized by comprising the following steps:

s1, mixing graphite powder and sodium nitrate, slowly dripping an acid solution, adding a manganese source, stirring for reaction, washing, and centrifuging to obtain a graphene oxide solution;

s2, adding a zinc source and a dimethyl imidazole aqueous solution into the graphene oxide solution, ultrasonically stirring uniformly, placing the mixture into a high-pressure reaction kettle for hydrothermal reaction, and freeze-drying a product after the reaction is finished to obtain aerogel;

and S3, calcining the aerogel in a muffle furnace to obtain the ZIF-8/graphene composite aerogel.

2. The method of claim 1, wherein the manganese source of step S1 includes one of manganese dioxide, potassium manganate, manganese sulfate and potassium permanganate, and the acid solution includes one of concentrated sulfuric acid, concentrated hydrochloric acid and concentrated nitric acid.

3. The method as claimed in claim 2, wherein the graphite powder of step S1 is used in a ratio of (0.2g-0.7g) to (0.3g-0.9g) to (15ml-50ml) to (1.2g-4.9g) with respect to the sodium nitrate, the acid solution and the manganese source.

4. The method of claim 3, wherein the stirring reaction time of step S1 is in the range of 10min to 2 h.

5. The method of any one of claims 1 to 4, wherein the zinc source of step S2 includes one of zinc chloride, zinc nitrate, and zinc sulfate.

6. The method as claimed in claim 5, wherein the hydrothermal reaction conditions of step S2 include a reaction temperature in the range of 100 ℃ to 300 ℃ and a reaction time in the range of 6h to 19 h.

7. The method according to claim 5, wherein the concentration of the zinc source is 40 mg-L^-1To 100 mg.L^-1The concentration of the dimethyl imidazole aqueous solution is within the range of 30 mg.L^-1To 80 mg.L^-1In the range, the volume ratio of the zinc source to the aqueous dimethyl imidazole solution is in the range of 2:1 to 6: 5.

8. The method according to claim 1, wherein the calcining conditions of step S3 include hydrogen atmosphere, calcining temperature in the range of 300 ℃ to 900 ℃, and calcining time in the range of 1h to 6 h.

9. A ZIF-8/graphene composite aerogel, characterized by being prepared by the preparation method of the ZIF-8/graphene composite aerogel according to any one of claims 1 to 8.

10. Use of the ZIF-8/graphene composite aerogel of claim 9 in electrolysis of water for hydrogen evolution.

Technical Field

The invention relates to the technical field of new materials, and particularly relates to a ZIF-8/graphene composite aerogel and a preparation method and application thereof.

Background

Among the numerous new energy sources, hydrogen energy has a high combustion heat value and produces no pollution, and belongs to a very popular clean energy source in recent years. The hydrogen production by water electrolysis is the most mature hydrogen production process in the prior art, water is used as a raw material, protons are reduced into hydrogen, namely, the reduction half reaction of water decomposition is carried out, however, the reaction needs to be carried out under the action of certain catalysts. The high-efficiency catalyst can reduce the overpotential of hydrogen evolution or improve the current density of the catalyst in the hydrogen evolution process, and the application research of the transition metal compound in the hydrogen evolution reaction is concerned.

The metal organic framework compound (MOFs) is used as a crystalline nano porous material with the advantages of high specific surface area, large pore volume and the like, ZIF-8 (one type of MOFs) takes imidazole and derivatives thereof as organic ligands, and divalent transition metal ions (Zn) are used^{2 +}、Co²⁺Etc.) is a coordination site, and the nano porous material with a zeolite structure formed by self-assembly is considered to be an electrocatalytic material with high research value due to the advantages of imidazole groups, abundant nitrogen atoms, high specific surface area, high porosity and the like. However, ZIF-8 is prone to agglomeration during the preparation process and is difficult to control.

Due to the special monoatomic structure of graphene, graphene has a series of excellent performances such as good heat conduction and electrical conductivity, high specific surface area, good chemical stability and the like, and is one of the hottest materials in current research.

Therefore, how to show the synergistic effect of the 3D graphene network and the ZIFs, improve the application of the metal organic framework compound and the graphene in the aspect of electrochemical hydrogen evolution, and research and development of the ZIF-8/GO and ZIF-8/graphene composite material have high research value.

Disclosure of Invention

In view of the above, the invention provides a ZIF-8/graphene composite aerogel, and a preparation method and an application thereof, so that effective compounding of a metal organic framework compound and graphene is realized, and the electrocatalytic performance of the composite aerogel is improved.

In order to achieve the purpose, the technical scheme of the invention is realized as follows:

a preparation method of ZIF-8/graphene composite aerogel comprises the following steps:

s1, mixing graphite powder and sodium nitrate, slowly dripping an acid solution, adding a manganese source, stirring for reaction, washing, and centrifuging to obtain a graphene oxide solution;

s2, adding a zinc source and a dimethyl imidazole aqueous solution into the graphene oxide solution, ultrasonically stirring uniformly, placing the mixture into a high-pressure reaction kettle for hydrothermal reaction, and freeze-drying a product after the reaction is finished to obtain aerogel;

and S3, calcining the aerogel in a muffle furnace to obtain the ZIF-8/graphene composite aerogel.

Optionally, the manganese source of step S1 includes one of manganese dioxide, potassium manganate, manganese sulfate and potassium permanganate, and the acid solution includes one of concentrated sulfuric acid, concentrated hydrochloric acid and concentrated nitric acid.

Optionally, in step S1, the ratio of the graphite powder to the sodium nitrate, the acid solution and the manganese source is in the range of (0.2g-0.7g): 0.3g-0.9g): 15ml-50ml): 1.2g-4.9 g.

Optionally, the stirring reaction time of step S1 is in the range of 10min to 2 h.

Optionally, the zinc source of step S2 includes one of zinc chloride, zinc nitrate, and zinc sulfate.

Alternatively, the hydrothermal reaction conditions of step S2 include a reaction temperature in the range of 100 ℃ to 300 ℃ and a reaction time in the range of 6h to 19 h.

Optionally, the concentration of the zinc source is 40 mg-L^-1To 100 mg.L^-1The concentration of the dimethyl imidazole aqueous solution is within the range of 30 mg.L^-1To 80 mg.L^-1In the range, the volume ratio of the zinc source to the aqueous dimethyl imidazole solution is in the range of 2:1 to 6: 5.

Alternatively, the calcination conditions of step S3 include a hydrogen atmosphere, a calcination temperature in the range of 300 ℃ to 900 ℃, and a calcination time in the range of 1h to 6 h.

The invention also aims to provide the ZIF-8/graphene composite aerogel which is prepared by the preparation method of the ZIF-8/graphene composite aerogel.

The third purpose of the invention is to provide an application of the ZIF-8/graphene composite aerogel in electrolysis of water for hydrogen evolution.

Compared with the prior art, the ZIF-8/graphene composite aerogel and the preparation method and application thereof provided by the invention have the following advantages:

(1) according to the method, a metal organic framework structure which is directionally grown on the surface of graphene in situ is used as a precursor, and the precursor is calcined and reduced to obtain a carbon-coated metal nano compound, wherein the metal nano compound has good micro-morphology and pore channel structure; in addition, the organic ligand dimethyl imidazole in the metal organic framework is supported, and the graphene sheets can be assembled into a three-dimensional aerogel structure in a cross-linking manner in a hydrothermal reaction, so that the prepared ZIF-8/graphene composite aerogel has a stable structure and a large number of active sites, and the electrocatalytic hydrogen evolution efficiency is improved.

(2) The preparation method provided by the invention is simple, raw materials are simple and easy to obtain, reaction conditions are mild, the component content of the composite aerogel can be regulated and controlled, and the method is suitable for industrial production.

Drawings

In order to more clearly illustrate the technical solutions of the present invention or the prior art, the drawings needed for the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and those skilled in the art can also obtain other drawings according to the drawings without creative efforts.

FIG. 1 is a SEM image and elemental analysis of ZG-HA (co) according to example 1 of the present invention;

FIGS. 2 a-2 e are TEM images of N-G, Zn-G, ZG-HA (pa) and ZG-HA (co) according to example 1 of the present invention; FIG. 2f is a graph showing the particle size distribution of ZG-HA (co) in example 1 of the present invention;

FIG. 3 shows the N of Zn-G, N-G, ZG-HA (pa) and ZG-HA (co) according to the present invention₂-sorption-desorption attached figure;

FIG. 4 is an X-ray diffraction pattern of Zn-G, N-G, ZG-HA (pa) and ZG-HA (co) according to an embodiment of the present invention;

FIG. 5 is a Raman spectrum of Zn-G, N-G, ZG-HA (pa) and ZG-HA (co) according to the present invention;

FIG. 6 is a linear scan polarization curve of Zn-G, N-G, ZG-HA (pa) and ZG-HA (co) according to the present invention;

FIG. 7 is a graph of the stability test characterization of ZG-HA (co) according to the present invention.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.

It should be noted that in the description of the embodiments herein, the description of the term "some embodiments" means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. Throughout this specification, the schematic representations of the terms used above do not necessarily refer to the same implementation or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The term "in.. range" as used herein includes both ends, such as "in the range of 1 to 100" including both ends of 1 and 100.

The embodiment of the invention provides a preparation method of a ZIF-8/graphene composite aerogel, which comprises the following steps:

s1, mixing graphite powder with NaNO₃Mixing, slowly dripping an acid solution, adding a manganese source, stirring for reaction, washing, and centrifuging to obtain a graphene oxide solution;

s2, adding a zinc source and a dimethyl imidazole aqueous solution into the graphene oxide solution, ultrasonically stirring uniformly, placing the mixture into a high-pressure reaction kettle for hydrothermal reaction, and freeze-drying a product after the reaction is finished to obtain aerogel;

and S3, placing the aerogel in a muffle furnace to be calcined to obtain the ZIF-8/graphene composite aerogel.

According to the method, a metal organic framework structure which is directionally grown on the surface of graphene in situ is used as a precursor, and the precursor is calcined and reduced to obtain a carbon-coated metal nano compound, wherein the metal nano compound has good micro-morphology and pore channel structure; in addition, the organic ligand dimethyl imidazole in the metal organic framework is supported, and the graphene sheets can be assembled into a three-dimensional aerogel structure in a cross-linking manner in a hydrothermal reaction, so that the prepared ZIF-8/graphene composite aerogel has a stable structure and a large number of active sites, and the electrocatalytic hydrogen evolution efficiency is improved.

Specifically, in step S1, the manganese source includes one of manganese dioxide, potassium manganate, manganese sulfate, and potassium permanganate, and the acid solution includes one of concentrated sulfuric acid, concentrated hydrochloric acid, and concentrated nitric acid. And graphite powder and sodium nitrate NaNO₃The ratio of the amount of the acid solution to the amount of the manganese source is within the range of (0.2g-0.7g) to (0.3g-0.9g) to (15ml-50ml) to (1.2g-4.9 g). Preferably, the amount of graphite powder is 0.45g, NaNO₃The amount of the manganese source was 0.6g, the amount of the manganese source was 3g, and the amount of the acid solution was 30 mL.

The graphite powder and sodium nitrate are mixed and then dripped into the acid solution, and the stirring reaction time after the manganese source is added is within the range of 10min to 2 h.

It is understood that aerogels are a class of monolithic materials with a developed pore structure that has the advantages of low density, low thermal conductivity, developed pores, etc. The prepared graphene aerogel not only has the advantages of the conventional aerogel, but also has the conductive characteristic of carbon aerogel and a unique three-dimensional pore structure, and the unique structure enables the graphene aerogel to have more electrochemical reaction active sites than graphene, so that the electrical performance of the graphene aerogel is greatly improved.

Specifically, in step S2, the zinc source includes one of zinc chloride, zinc nitrate, and zinc sulfate. Wherein the concentration of the zinc source is 40 mg.L^-1To 100 mg.L^-1The concentration of the aqueous solution of dimethylimidazole is within the range of 30 mg.L^-1To 80 mg.L^-1In the range, the volume ratio of the zinc source to the aqueous dimethyl imidazole solution is in the range of 2:1 to 6: 5.

The conditions of the hydrothermal reaction in the high-pressure reaction kettle comprise that the reaction temperature is in the range of 100 ℃ to 300 ℃ and the reaction time is in the range of 6h to 19 h.

The metal organic framework structure can be directionally grown on the surface of the graphene in situ through a hydrothermal reaction, and due to the support of an organic ligand dimethyl imidazole in the metal organic framework structure, the graphene sheet layer can be cross-linked and assembled into a three-dimensional aerogel structure in the hydrothermal reaction.

Specifically, in step S3, the freeze-dried aerogel is calcined in a muffle furnace under conditions including a hydrogen atmosphere, a calcination temperature in the range of 300 ℃ to 900 ℃, and a calcination time in the range of 1h to 6 h.

The carbon-coated metal nano compound can be obtained after calcination and reduction, a series of metal nano compounds are synthesized, the metal nano compounds have good micro-morphology and pore junctions, and the metal compounds with uniform size are well prepared.

The preparation method provided by the invention is simple, raw materials are simple and easy to obtain, reaction conditions are mild, the component content of the composite aerogel can be regulated and controlled, and the method is suitable for industrial production.

The invention further provides a ZIF-8/graphene composite aerogel which is prepared by the preparation method of the ZIF-8/graphene composite aerogel.

The ZIF-8/graphene composite aerogel is prepared by taking ZIF-8 as a precursor and compounding the precursor with graphene, and the ZIF-8 has a large specific surface area and a regular nanostructure, so that the prepared composite aerogel has the advantages of controllable appearance and good porosity; the graphene has ultrahigh conductivity and large specific surface area, and can improve the specific surface area of the ZIF-8/graphene composite aerogel, so that the electrocatalytic active sites are increased, and the conductivity of the composite aerogel is increased when the composite aerogel is used for electrocatalytic hydrogen evolution.

The invention further provides application of the ZIF-8/graphene composite aerogel in water electrolysis and hydrogen evolution.

On the basis of the above embodiment, the following specific examples of the preparation method of the ZIF-8/graphene composite aerogel are given, and the invention is further illustrated. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. The following examples are examples of experimental procedures not specified under specific conditions, generally according to the conditions recommended by the manufacturer. Unless otherwise indicated, percentages and parts are by mass.

Example 1

The embodiment provides a preparation method of a ZIF-8/graphene composite aerogel, which comprises the following steps:

1) 0.5g of graphite powder and 0.3g of NaNO are mixed₃Placing the mixture into a 50mL three-neck flask, carrying out ice bath, mechanically stirring, and adding 25mL H in the stirring process₂SO₄(98%) was slowly added dropwise thereto, followed by addition of 2g of KMnO₄Slowly adding the mixture in 5 times, reacting for 50min, removing ice bath, and mechanically stirring at 15 ℃ for 24 h. Then adding 25mL of water, and continuing stirring for 30 min; then 30% H₂O₂Slowly adding the mixture into the reaction until no bubbles are generated; and after the reaction is finished, taking out the mixture, washing the mixture for 3 times by using a 10 wt% HCI aqueous solution, carrying out centrifugal separation, repeatedly washing the precipitate for several times by using water until the precipitate is neutral, carrying out centrifugal separation, dispersing a certain amount of precipitate in deionized water again, and carrying out ultrasonic treatment for 30min to obtain a brown graphene oxide solution.

2) The preparation concentration is 40 mg.L^-180mL of zinc nitrate aqueous solution and a concentration of 60 mg.L^-1Then 50. mu.l of the prepared zinc nitrate aqueous solution was added to 10mL of a graphene oxide solution (2 mg. mL) in a 20mL vial^-1) Performing ultrasonic treatment for 30min to obtain a uniform mixed solution; then slowly dripping 50 mul of dimethyl imidazole water solution into the mixture, carrying out ultrasonic treatment for 30min after dripping is finished, then putting a small medicine bottle into a 50mL high-pressure reaction kettle, and keeping the temperature at 140 ℃ for reaction for 24 h; and after the high-pressure reaction kettle is cooled to room temperature, freezing and drying the formed product to obtain the aerogel.

3) The aerogel was placed in a muffle furnace at 5% H₂Calcining for 1h at 500 ℃ in the atmosphere to obtain the ZIF-8/graphene composite aerogel, which is recorded as ZG-HA (co).

The structure of ZG-HA (co) prepared in example 1 was characterized by Scanning Electron Microscopy (SEM) and elemental analysis, and the result chart shown in FIG. 1 was obtained. As shown in fig. 1, the sample is in a net structure, and anisotropic lamellar bonding is provided at the cross-linking position, which illustrates a three-dimensional porous structure of the sample, and the pore structures are from micron to submicron, which provides a good channel for the transfer of a solution medium, on the other hand, we test the element distribution area of the sample by EDS mapping, and find that each element is well dispersed on the graphene lamellar layer, which illustrates that the metal organic framework is well bonded with graphene, and the dispersion is very uniform, so that the active site can be better displayed during the electrocatalytic reaction, thereby improving the performance.

Performing structural characterization on the nitrogen-doped graphene aerogel (N-G) of the single ligand composite, the zinc oxide-graphene aerogel (Zn-G), the ZIF-8 particle mixed composite ZG-HA (pa) and the ZG-HA (co), and obtaining result graphs shown in FIGS. 2 to 6. Comparing the structural characteristics of Zn-G, N-G, ZG-HA (pa) and ZG-HA (co), it can prove the advantages of our structural design on microstructure, the aerogel obtained by crosslinking with inorganic ligand shows good specific surface area and pore structure side surface, which illustrates the feasibility of this in situ growth method, i.e. in ZG-HA (co), the inorganic ligand not only plays the role of supporting skeleton crosslinking agent, but also plays the role of the limited domain framework of metal particles. Meanwhile, a new idea is provided for designing a novel carbon-based metal compound.

FIGS. 2 a-2 e are TEM images of N-G, Zn-G, ZG-HA (pa) and ZG-HA (co) according to the present invention. Fig. 2a is a transmission electron microscope image of a comparative sample N-G, which shows that the graphene surface is smooth, no particle recombination is found, and the abundant wrinkle stripes illustrate the cross-linked network structure, which also conforms to the condition that the inorganic ligand in the metal organic framework is used as a cross-linking agent to modify the graphene sheet layer. Fig. 2b is a transmission electron microscope image of a comparative sample Zn-G, which shows that due to the intervention of metal ions, the graphene sheet layer is seriously agglomerated in the self-assembly process, and zinc ions are adsorbed on the surface thereof due to electrostatic effect, but as shown in the figure, the metal particles are seriously agglomerated, which is probably due to the nucleation and growth phenomenon of the metal particles, i.e. the metal particles tend to grow in clusters on the graphene surface during hydrothermal reaction. FIG. 2c is a transmission electron micrograph of a comparative sample ZG-HA (pa), and it can be seen that the distribution of ZIF-8 particles among graphene sheets is not uniform, the agglomeration phenomenon is severe, which may cause the blocking of graphene channels, and the pore structure of the ZIF-8 particles is limited. As expected, the ZIF-8 in-situ growth method on the graphene sheet layer enables the metal particles to be well dispersed, as shown in fig. 2d-e, zinc oxide nanoparticles are uniformly distributed on the surface of graphene, and the graphene sheet layer is clear and does not undergo a severe agglomeration phenomenon, because zinc ions are firstly adsorbed on the surface of graphene, and then inorganic ligand molecules intervene to fill in vacant orbitals of the metal ions, so that the metal ions are limited during hydrothermal reaction, and the highly dispersed particles are obtained. FIG. 2f is a graph showing the distribution of ZG-HA (co) particle size distribution, as seen in FIG. 2, between 2 and 6nm, which is a size that allows better exposure of the active sites of the particles.

FIG. 3 shows N of Zn-G, N-G, ZG-HA (pa) and ZG-HA (co)₂The attached drawings of adsorption and desorption, as can be seen from fig. 3, Zn-G exhibits a type iii isotherm, and the adsorption effect is weak in a low-pressure region, which indicates that a single metal ion can cause severe agglomeration of graphene, which not only occupies an active site of graphene, but also does not have a pore structure by itself, and affects the specific surface and pore structure of the composite, which is also similar to that exhibited by a transmission electron microscope. N of N-G, ZG-HA (pa) and ZG-HA (co)₂The adsorption-desorption curve shows a curve having H₃Type IV isotherms for type hysteresis, indicating that these samples have a porous structure.

FIG. 4 is an X-ray diffraction pattern of Zn-G, N-G, ZG-HA (pa) and ZG-HA (co), and as can be seen from FIG. 4, Zn-G, N-G, ZG-HA (pa) and ZG-HA (co) both show 25.3 DEG diffraction peaks centered on the (001) crystal plane, which illustrates the composition of graphene amorphous carbon. In addition, the characteristic peaks of the (100) (002) (101) crystal face of ZnO appear in both ZG-HA (pa) and ZG-HA (co), which indicates that the obtained ZnO particles are ZnO, however, the characteristic peaks of ZIF-8 appear probably due to incomplete high-temperature reduction, but also indicates that the crystal structure of ZIF-8 is not influenced by both methods.

FIG. 5 shows the Raman spectra of Zn-G, N-G, ZG-HA (pa) and ZG-HA (co), and from FIG. 5, the Raman spectrum of the mixed aerogel is similar to the characteristic bands of GA reported in the literature, and it can be clearly seen that the Raman spectrum of GA is 1350cm^-1And 1590cm^-1There are two strong bands corresponding to the D and G bands of the carbon material, respectively. D and G bands (I)_D/I_G) Strength ratio of (A) generally indicates a composite materialThe degree of defect of (a). Zn-G, ZG-HA (pa) and I of ZG-HA (co)_D/I_GThe intensity ratios were 1.51, 1.42 and 1.45, respectively, all higher than N-G (1.36). I of ZG-HA (pa) and ZG-HA (co)_D/I_GThe slight increase in value is attributed to the doping of ZIF-8 grains and wrinkles in the interconnect frame, while Zn-G exhibits the highest I due to its disordered structure, and agglomeration_D/I_GIntensity ratio, which is correlated with the adsorption curve of BET. Further, I of ZG-HA (co)_D/I_GThe slight increase in value may be due to the fact that aerogels are not merely physical mixtures, but involve structural changes, and defect structures can provide a large number of active sites for binding to other molecules, which also explains the method of in situ growth.

Fig. 6 is a linear scanning polarization curve of Zn-G, N-G, ZG-ha (pa) and ZG-ha (co) according to an embodiment of the present invention, as can be seen from fig. 6, where Zn-G is a product obtained by hydrothermal reaction of zinc ions and graphene, N-G is a graphene aerogel modified by dimethylimidazole, ZG-ha (pa) is a zinc oxide graphene aerogel prepared by using ZIF-8 particles as a precursor, and ZG-ha (co) is a zinc oxide graphene aerogel prepared by using ZIF-8 particles grown in situ on a surface of graphene as a precursor. The test method is a linear voltammetry scanning method, the potential window of the scanning is-1.5V-1V, and the speed is 2mV^-1The base solution is 1mol L^-1Potassium hydroxide solution of (2). As can be seen from the figure, the hydrogen evolution initial overpotential of Pt/C is about 30mV, which is taken as a reference of a material with excellent hydrogen evolution performance and is not discussed. Generally, 10mA · cm is used^-2The overpotential (. eta.10) of the current density was used as a measure of the activity of the catalyst, and the hydrogen evolution starting potentials of the study subjects Zn-G, N-G, ZG-HA (pa) and ZG-HA (co) were about 203mV, 201mV, 177mV, and 154mV, respectively, indicating that ZG-HA (pa) has the best catalytic hydrogen evolution performance, ZG-HA (pa) has the second highest performance, and the ligand control group is relatively poor.

Example 2

The embodiment provides a preparation method of a ZIF-8/graphene composite aerogel, which comprises the following steps:

1) 0.5g of graphite powder and 0.45g of NaNO are mixed₃Placing the mixture into a 50mL three-neck flask, carrying out ice bath, mechanically stirring the mixture, and stirring the mixtureIn the process 15mLH₂SO₄(98%) was slowly added dropwise thereto, and then 3g of KMnO was added₄Slowly adding the mixture in 5 times, reacting for 45min, removing ice bath, and mechanically stirring at 15 ℃ for 48 h. Then adding 50mL of water, and continuing stirring for 30 min; then 30% H₂O₂Slowly adding the mixture into the reaction until no bubbles are generated; and after the reaction is finished, taking out the mixture, washing the mixture for 3 times by using a 15 wt% HCI aqueous solution, carrying out centrifugal separation, repeatedly washing the precipitate for several times by using water until the precipitate is neutral, carrying out centrifugal separation, dispersing a certain amount of precipitate in deionized water again, and carrying out ultrasonic treatment for 30min to obtain a brown graphene oxide solution.

2) The preparation concentration is 40 mg.L^-180mL of zinc nitrate aqueous solution and a concentration of 60 mg.L^-1Then 50. mu.l of the prepared zinc nitrate aqueous solution was added to 10mL of a graphene oxide solution (2 mg. mL) in a 20mL vial^-1) Performing ultrasonic treatment for 30min to obtain a uniform mixed solution; then slowly dripping 100 mul of dimethyl imidazole aqueous solution into the mixture, carrying out ultrasonic treatment for 30min after dripping is finished, then putting a small medicine bottle into a 50mL high-pressure reaction kettle, and keeping the temperature at 160 ℃ for reaction for 24 h; and after the high-pressure reaction kettle is cooled to room temperature, freezing and drying the formed product to obtain the aerogel.

3) The aerogel was placed in a muffle furnace at 5% H₂Calcining for 2 hours at the temperature of 400 ℃ in the atmosphere to obtain the ZIF-8/graphene composite aerogel ZG-HA (co).

The stability test was performed on ZG-HA (co) prepared in example 2, and the result graph shown in FIG. 7 was obtained. As can be seen from fig. 7, the hydrogen evolution performance of the catalyst did not decrease significantly before and after 1000 CV scans, which indicates that ZG-ha (co) has higher stability as a hydrogen evolution catalyst, probably because the stability of the nanomaterial structure is enhanced by the synergistic effect between the graphene sheet layer and the zinc oxide and the supporting skeleton effect of the inorganic ligand.

Example 3

The embodiment provides a preparation method of a ZIF-8/graphene composite aerogel, which comprises the following steps:

1) 0.3g of graphite powder and 0.45g of NaNO are mixed₃Put into a 50mL three-neck flaskIn the process of ice-bath, mechanical stirring, 25mLH in the stirring process₂SO₄(98%) was slowly added dropwise thereto, followed by addition of 2g of KMnO₄Slowly adding the mixture in 6 times, reacting for 30min, removing ice bath, and mechanically stirring at 35 ℃ for 48 h. Then adding 35mL of water, and continuing stirring for 30 min; then 30% H₂O₂Slowly adding the mixture into the reaction until no bubbles are generated; and after the reaction is finished, taking out the mixture, washing the mixture for 3 times by using a 5 wt% HCI aqueous solution, carrying out centrifugal separation, repeatedly washing the precipitate for several times by using water until the precipitate is neutral, carrying out centrifugal separation, dispersing a certain amount of precipitate in deionized water again, and carrying out ultrasonic treatment for 30min to obtain a brown graphene oxide solution.

2) The preparation concentration is 80 mg.L^-140mL of zinc nitrate aqueous solution and a concentration of 30 mg.L^-180mL of the aqueous solution of dimethylimidazole, and then 50. mu.l of the prepared aqueous solution of zinc nitrate was added to 10mL of the graphene oxide solution (2 mg. mL) placed in a 20mL vial^-1) Performing ultrasonic treatment for 30min to obtain a uniform mixed solution; then slowly dripping 50 mul of dimethyl imidazole water solution into the mixture, carrying out ultrasonic treatment for 30min after dripping is finished, then putting a small medicine bottle into a 50mL high-pressure reaction kettle, and keeping the temperature at 180 ℃ for reaction for 12 h; and after the high-pressure reaction kettle is cooled to room temperature, freezing and drying the formed product to obtain the aerogel.

3) The aerogel was placed in a muffle furnace at 5% H₂Calcining for 1h at the temperature of 600 ℃ in the atmosphere to obtain the ZIF-8/graphene composite aerogel ZG-HA (co).

Example 4

The embodiment provides a preparation method of a ZIF-8/graphene composite aerogel, which comprises the following steps:

1) 0.3g of graphite powder and 0.3g of NaNO are mixed₃Placing the mixture into a 50mL three-neck flask, carrying out ice bath, mechanically stirring, and adding 15mL H during stirring₂SO₄(98%) was slowly added dropwise thereto, and then 3g of KMnO was added₄Slowly adding the mixture in 6 times, reacting for 20min, removing ice bath, and mechanically stirring at 35 ℃ for 24 h. Then adding 45mL of water, and continuing stirring for 30 min; then 30% H₂O₂Slowly adding the mixture into the reaction until no bubbles are generated; after the reaction was completed, the mixture was taken out and dissolved in 5 wt% HCI waterWashing the solution for 3 times, performing centrifugal separation, repeatedly washing the precipitate for several times until the precipitate is neutral, performing centrifugal separation, taking a certain amount of precipitate, dispersing the precipitate in deionized water again, and performing ultrasonic treatment for 30min to obtain a brown graphene oxide solution.

2) The preparation concentration is 80 mg.L^-140mL of zinc nitrate aqueous solution and a concentration of 30 mg.L^-180mL of the aqueous solution of dimethylimidazole, and then 50. mu.l of the prepared aqueous solution of zinc nitrate was added to 10mL of the graphene oxide solution (2 mg. mL) placed in a 20mL vial^-1) Performing ultrasonic treatment for 30min to obtain a uniform mixed solution; then slowly dripping 50 mul of dimethyl imidazole water solution into the mixture, carrying out ultrasonic treatment for 30min after dripping is finished, then putting a small medicine bottle into a 50mL high-pressure reaction kettle, and keeping the temperature at 200 ℃ for reaction for 12 h; and after the high-pressure reaction kettle is cooled to room temperature, freezing and drying the formed product to obtain the aerogel.

3) The aerogel was placed in a muffle furnace at 10% H₂Calcining for 2 hours at the temperature of 300 ℃ in the atmosphere to obtain the ZIF-8/graphene composite aerogel ZG-HA (co).

Although the present disclosure has been described above, the scope of the present disclosure is not limited thereto. Various changes and modifications may be effected therein by one of ordinary skill in the pertinent art without departing from the spirit and scope of the present disclosure, and these changes and modifications are intended to be within the scope of the present disclosure.