CN113957478A - Sulfur and nitrogen co-doped graphene rich in edge defects and preparation method and application thereof - Google Patents

Sulfur and nitrogen co-doped graphene rich in edge defects and preparation method and application thereof Download PDF

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CN113957478A
CN113957478A CN202111331575.8A CN202111331575A CN113957478A CN 113957478 A CN113957478 A CN 113957478A CN 202111331575 A CN202111331575 A CN 202111331575A CN 113957478 A CN113957478 A CN 113957478A
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范修军
牟志星
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Abstract

The invention discloses sulfur and nitrogen co-doped graphene rich in edge defects and a preparation method and application thereof. The precursor is uniformly mixed in the suspension of graphene, and a rapid two-step synthesis method is utilized: the sulfur and nitrogen co-doped graphene with enriched edge defects can be prepared by hydrothermal and chemical vapor deposition, the inherent coordination structure of thiourea can be reserved in the two-step synthesis, the edge defects are induced to be generated, and a large number of active sites are provided. The preparation method has the advantages of simple synthesis, high repeatability, large-scale preparation and cheap and easily-obtained precursor.

Description

Sulfur and nitrogen co-doped graphene rich in edge defects and preparation method and application thereof
Technical Field
The invention belongs to the field of electrochemistry, and particularly relates to sulfur and nitrogen co-doped graphene rich in edge defects, and a preparation method and application thereof.
Background
Hydrogen peroxide (H)2O2) Is an important chemical and is widely applied in the fields of chemical industry, medicine, environmental protection and the like. At present, hydrogen peroxide is mainly prepared by a complicated and high-energy-consumption anthraquinone method, but needs an expensive palladium catalyst and generates a large amount of organic wastes. Thus, by electrocatalytic oxygen reductionThe formation of hydrogen peroxide (ORHP) is an economical and efficient process that can be used to replace the traditional anthraquinone process. For ORHP, instead of conventional four electron transfer oxygen reduction (4 e-ORR) to water, H is generated directly via a two electron transfer pathway (2 e-ORR)2O2. Platinum, palladium and alloys thereof have high ORHP activity due to unique electronic structures. But the cost for preparing the catalyst is too high, and the large-scale practical application is difficult. Therefore, the development of a catalyst material which is highly efficient, inexpensive and capable of suppressing 4e-ORR, for realizing green H production2O2It is of great importance.
Non-metallic nanocarbon materials such as graphene, carbon black, carbon nanotubes, and the like, have received wide attention. Among them, graphene is a good catalyst carrier because of its large specific surface area. But directly as a catalyst, the intrinsic activity is poor and the kinetics is slow. At present, transition metals or heteroatoms are introduced into graphene for modification, so that the chemical stability and catalytic activity of the material can be enhanced. The active functional group is constructed by doping atoms in a regulating material framework to form a coordination structure, which is a main strategy for designing the catalyst at present.
Disclosure of Invention
The invention aims to provide sulfur and nitrogen co-doped graphene rich in edge defects, and a preparation method and application thereof, and thiourea (CH) is utilized4N2S) as precursor and sulfur source, with ammonia (NH)3) As a nitrogen source, a hydrothermal method and a Chemical Vapor Deposition (CVD) method are adopted to synthesize sulfur and nitrogen co-doped graphene (SNC) rich in edge defects, and heteroatoms (N, S, O) can be covalently bonded with carbon atoms in the graphene to excite pi orbitals to provide a large number of electrons, accelerate local electron transfer, induce defect generation and provide more active sites to improve ORHP reaction kinetics. The nitrogen and sulfur codoping ensures the generation of externally introduced defects, and can regulate and control the coordination environment of active sites at an atomic scale to form active functional groups. The nitrogen atom with high electronegativity accelerates the charge transfer around the functional group, the sulfur atom with oxygen in the same family can enhance the adsorption of the functional group to oxygen molecules, and the SNC with unique coordination of nitrogen, sulfur and carbon has high electrocatalytic activity to ORHP and generates continuous catalysisTo H2O2Good selectivity and stability can be maintained in the process.
The invention provides sulfur and nitrogen co-doped graphene rich in edge defects, which is prepared by adsorbing thiourea precursor and graphene oxide and performing hydrothermal self-assembly through chemical vapor deposition, wherein the inherent coordination structure of thiourea can be chemically grafted on the edge of the graphene through hydrothermal self-assembly and is reserved in CVD synthesis to induce the generation of edge defects and provide a large number of active sites. The S-C-N coordination group inherent in thiourea is connected to graphene through a chemical covalent bond to finally form an S-C-N-C active functional group.
The preparation method of the sulfur and nitrogen co-doped graphene rich in the edge defects comprises the following steps:
(1) preparing graphene oxide, ultrasonically dispersing the graphene oxide in deionized water, and ultrasonically treating for 8 hours to obtain a uniform suspension liquid with the graphene oxide concentration of 2 mg/mL;
(2) hydrothermal reaction: will CH4N2S, adding the S into the graphene oxide suspension prepared in the step (1), stirring for 2 hours, then placing the mixture into a hydrothermal kettle for heating reaction at the temperature of 180-200 ℃ for 12-24 hours, cooling the hydrothermal kettle after the reaction is finished, taking out a columnar product, and placing the columnar product into a freeze dryer for drying for not less than 24 hours (-50 ℃ to-100 ℃), thus obtaining dry aerogel;
CH4N2the mass ratio of S in S to graphene oxide is 1-5: 95-99;
(3) chemical vapor deposition:
placing the aerogel prepared in the step (2) into the center of a tubular furnace, setting the furnace temperature at 800-900 ℃, setting the gas flow at 100 +/-5 sccm of Ar and NH 350 plus or minus 5 sccm, and the total air pressure is 2.8 plus or minus 0.1 Torr; and carrying out chemical vapor deposition reaction in a tubular furnace for 0.5-2 h to obtain the sulfur and nitrogen co-doped graphene rich in edge defects.
Further, the sulfur atom loading in the thiourea obtained in the step (2) is 1.5% of the mass percent of the graphene oxide.
Further, the reaction time of the chemical vapor deposition was 1 h, and the reaction temperature was 850 ℃.
The invention provides application of the sulfur and nitrogen codoped graphene rich in edge defects as a catalyst of electrocatalysis ORHP, wherein catalytic reaction is carried out on a rotating disc electric device, and the rotating speed is set at 1600 rpm; preparing electrode dispersion solution from 2 mg of catalyst, water, ethanol and Nafion (5 wt%) solution at volume ratio of 5:5:1, and uniformly dripping 5 μ L of the electrode dispersion solution on a ring disk electrode with loading amount of 0.1 mg/cm2(ii) a The catalytic process was carried out in a three-electrode system with an electrolyte of 0.1M KOH and saturated oxygen. Said catalyst being capable of catalyzing O2An electron-generating OOH intermediate is obtained and adsorbed on the active site, and then an electron is obtained to generate hydroperoxy radical HO2ˉ。
The invention has the beneficial effects that:
(1) the preparation method has the advantages of simple synthesis, high repeatability, large-scale preparation and cheap and easily-obtained precursor. The precursor is uniformly mixed in the suspension of graphene, and the sulfur and nitrogen co-doped graphene with enriched edge defects can be prepared by a rapid two-step synthesis method (hydrothermal and chemical vapor deposition).
(2) In the sulfur and nitrogen co-doped graphene prepared by the method, CH4N2The high electronegativity nitrogen and sulfur atoms provided by S can regulate and control the electronic structure on the graphene, and generate a large amount of in-plane edge defects, so that the intrinsic activity of the sulfur and nitrogen co-doped graphene is improved.
(4) In the sulfur and nitrogen co-doped graphene prepared by the method, CH4N2S and NH3A dinitrogen source is provided that forms a carbon-nitrogen covalent bond hydrothermally and is consolidated by high temperature nitridation during CVD.
(5) In the sulfur and nitrogen co-doped graphene prepared by the method, CH4N2The inherent coordination structure (S-C-N) of S can be reserved in the two-step synthesis process and is covalently connected in a graphene framework, an S-C-N-C functional group is further developed, the structural stability of sulfur and nitrogen co-doped graphene is improved, the rapid charge transfer is ensured, and the H is further promoted2O2Production and stability of.
(6) The sulfur and nitrogen co-doped graphene rich in edge defects, which is prepared by the invention, has ORHP performance and has the advantages of high activity, high selectivity, high current density, small Tafel slope, stable performance and the like.
Drawings
FIG. 1 is an XRD pattern of SNC @800 prepared in example 1 of the present invention;
FIG. 2 is a Raman spectrum of SNC @800 prepared in example 1 of the present invention;
FIG. 3 is a graph of the performance of SNC @800 prepared in example 1 of the present invention as a catalyst in electrocatalytic ORHP, wherein 3a is the polarization curve in 0.1M KOH electrolyte and 3b is the Tafel plot in 0.1M KOH electrolyte, with a scan rate of 5 mV/s;
FIG. 4 is H with SNC @800 as catalyst prepared in example 1 of the present invention2O2Selectivity curves calculated from the disk current density and the ring current density of fig. 3 a;
FIG. 5 is an XRD pattern of SNC @850 prepared in example 2 of the present invention;
FIG. 6 is a Raman spectrum of SNC @850 prepared in example 2 of the present invention;
FIG. 7 is an SEM image of SNC @850 prepared in example 2 of the present invention;
FIGS. 8a and 8b are TEM images of SNC @850 prepared in example 2 of the present invention at low power and high power, respectively;
FIG. 9 is an XPS plot of SNC @850 prepared in example 2 of the present invention, with the inset being the calculated element content from XPS;
FIGS. 10a, 10b and 10c are respectively XANES (X-ray absorption near edge structure) spectra for C K-edge, N K-edge and S K-edge for SNC @850, and 10d for SNC @85013C ssNMR (solid state nuclear magnetic resonance);
FIGS. 11a and 11b are transmission electron microscope (AC-TEM) images of the spherical aberration correction of SNC @850 prepared in example 2 of the present invention;
FIGS. 12a and 12b are the polarization curve and Tafel slope, respectively, for SNC @850 prepared in example 2 as a catalyst in 0.1 KOH electrolyte;
FIG. 13 is H with SNC @850 as catalyst, prepared in example 2 of the present invention2O2SelectingA linear curve calculated from the disk current density and the ring current density of FIG. 12 a;
FIG. 14 is an ORHP stability test curve for SNC @850 as a catalyst prepared in example 2 of the present invention;
FIG. 15 is an XRD pattern of SNC @900 prepared in example 3 of the present invention;
FIG. 16 is a Raman spectrum of SNC @900 prepared in example 3 of the present invention;
FIGS. 17a and 17b are the polarization curve and Tafel slope, respectively, for SNC @900 prepared in example 3 as the catalyst in 0.1 KOH electrolyte;
FIG. 18 is the H with SNC @900 as catalyst prepared in example 3 of the present invention2O2Selectivity curves, calculated from the disk current density and the ring current density of fig. 17 a.
Detailed Description
The present invention is further illustrated by, but is not limited to, the following examples.
Graphene oxide in the following examples is prepared by a Hummers improved method, and the specific preparation process is as follows: at 0oDispersing 3.0 g of graphite flakes in concentrated H with the volume ratio of 9:1 in ice water bath2SO4/H3PO4(360:40 mL), 18 g of KMnO was slowly added to the mixed solution4Stirring mechanically to oxidize thoroughly and release heat slowly, and raising the temperature of the water bath to 50 deg.CoC and keeping for 12 h. After the solution is cooled to room temperature, the solution is poured into 400 mL of crushed ice prepared in advance, the mixture is continuously stirred until the solution is completely dissolved, and H is slowly added2O2(30%) until the solution appeared bright yellow. And then repeatedly washing the graphene oxide by using HCl solution with the mass concentration of 30%, deionized water and diethyl ether in sequence through centrifugal separation to obtain the graphene oxide.
Example 1
(1) Preparing a graphene oxide suspension: ultrasonically dispersing 0.15 g of graphene oxide in 75 mL of deionized water, and ultrasonically treating for 8 hours to obtain a uniform suspension with the graphene oxide concentration of 2 mg/mL;
(2) hydrothermal reaction: taking CH with S accounting for 1.5% of graphene oxide by mass4N2S is put in step (1)Stirring and dispersing the prepared graphene oxide suspension for 2 hours, and then placing the reaction solution in a hydrothermal kettle to heat to 180 DEG oCContinuously reacting for 12 h, cooling the hydrothermal kettle after the reaction is finished, taking out the columnar product, and drying in a freeze dryer for 30 h to obtain a dried product;
(3) chemical vapor deposition: the furnace temperature was set to 800oC, gas flow rate Ar of 100 sccm and NH 350 sccm, and the total gas pressure is 2.85 Torr; and (3) putting the dried product prepared in the step (2) into the center of a tube furnace, carrying out chemical vapor deposition reaction in the tube furnace for 1 h, quickly removing a sample from the center of a hot zone of the tube furnace under the protection of continuous Ar flow, and cooling to room temperature to prepare the sulfur and nitrogen co-doped graphene SNC @800 rich in edge defects.
The application process comprises the following steps:
the sulfur and nitrogen co-doped graphene rich in edge defects prepared in the embodiment is applied to electrocatalysis ORHP as a catalyst:
the ORHP performance of the sulfur and nitrogen co-doped graphene rich in edge defects prepared by the present invention was tested on the upper chenhua electrochemical workstation (CHI 760E) us pine rotating disk electrical device (RRDE, AFE6R 2) using a three-electrode system. 2 mg of the sulfur and nitrogen co-doped graphene catalyst rich in edge defects and 40. mu.L of a 5 wt% Nafion solution were dispersed in 400. mu.L of v/v 1:1 water/ethanol (containing 200. mu.L of water and 200. mu.L of ethanol), followed by water bath sonication until a homogeneous suspension was formed. Then 5. mu.L of the catalyst suspension was loaded onto a rotating disk ring electrode (RRDE, AFE6R 2) having a disk area of 0.2376 cm2The area of the platinum ring is 0.2356 cm2The electrodes were dried at room temperature for 24 h before measurement. The loading of the catalyst is 0.1 mg/cm2。
All catalytic processes were carried out in a three-electrode system with an electrolyte of 0.1M KOH and saturated oxygen. Said catalyst being capable of catalyzing O2An electron-generating OOH intermediate is obtained and adsorbed on the active site, and then an electron is obtained to generate hydroperoxy radical HO2-a solvent. At O2Saturated 0.1M KOH electrolyte solution, platinum wire as pairThe electrode and an Ag/AgCl (saturated potassium chloride) electrode are used as reference electrodes, and the RRDE coated with the prepared sulfur and nitrogen co-doped graphene catalyst rich in edge defects is used as a working electrode to form a three-electrode system for testing ORHP performance. Pure nitrogen was bubbled for 30 minutes, air was removed, and a background current was collected by Linear Sweep Voltammetry (LSV) at a sweep rate of 5 mV/s for calculation of H2O2The yield was subtracted. The LSV test was then carried out by bubbling pure oxygen for 30 minutes to remove dissolved oxygen, the loop current collection voltage was set to 1.2V, the current collection voltage for the stability test was set to 0.40V, the RRDE rotation speed was 1600 rpm, and all potentials were switched to standard hydrogen electrodes (RHE): e (rhe) = E (Ag/AgCl) + 0.059 × pH + 0.1976. H2O2Yield = 200IR / IDN + IRIn which IRIs a ring current density, IDIs the disc current density and N is the RRDE collection efficiency of 0.37.
The applications in the following examples were all carried out under the process conditions described above.
The sulfur and nitrogen co-doped graphene SNC @800 rich in edge defects prepared in the embodiment can efficiently catalyze oxygen to generate hydrogen peroxide, and the H of the graphene SNC @800 is in an electrochemical window of 0-0.6V2O2The selectivity reaches more than 80 percent, and the good 2e-ORR performance is proved.
As shown in fig. 1, the XRD spectrum of SNC @800 has a strong diffraction of graphite (002) crystal plane, indicating a large crystal size in c-axis. (100) The exposure of crystal faces of (004), (110) and (004) shows that the prepared graphene has a coiled structure and can provide more ORHP active sites for the catalyst.
As shown in fig. 2, which is a raman spectrogram of SNC @800, the peak D representing the defect of a carbon atom is the strongest, indicating that the prepared graphene is enriched in defects. The appearance of the D + G peak indicates that the disorder degree of the graphene is large.
Shown in FIGS. 3a and 3b are the polarization curve and Tafel slope, respectively, for SNC @800 as a catalyst in 0.1 KOH electrolyte, where the Tafel slope is 117 mA dec-1And a loop current density of 0.58 mA cm at a voltage of 0.1V-2In the loop, the current density is 0.1 mA cm-2To get up ofThe initial potential was 0.77V, demonstrating that the catalyst has certain 2e-ORR properties.
As shown in FIG. 4, it is SNC @800 as the catalyst at 0-0.6V H2O2The selectivity curve, the selectivity is kept above 80%, shows that the catalyst has good ORHP activity.
Example 2 preparation of sulfur and nitrogen co-doped graphene rich in edge defects
(1) Preparing a graphene oxide suspension: ultrasonically dispersing 0.15 g of graphene oxide in 75 mL of deionized water, and ultrasonically treating for 8 hours to obtain a uniform suspension with the graphene oxide concentration of 2 mg/mL;
(2) hydrothermal reaction: taking CH with S accounting for 1.5% of graphene oxide by mass4N2S is placed in the graphene oxide suspension prepared in the step (1), stirred and dispersed for 2 hours, and then the reaction liquid is placed in a hydrothermal kettle and heated to 180 DEG oCContinuously reacting for 12 h, cooling the hydrothermal kettle after the reaction is finished, taking out the columnar product, and drying in a freeze dryer for 30 h to obtain a dried product;
(3) chemical vapor deposition: the furnace temperature was set to 850 deg.CoC, gas flow rate Ar of 100 sccm and NH 350 sccm, and the total gas pressure is 2.85 Torr; and (3) putting the dried product prepared in the step (2) into the center of a tubular furnace, carrying out chemical vapor deposition reaction in the tubular furnace for 1 h, quickly removing a sample from the center of a hot zone of the tubular furnace under the protection of continuous Ar flow, and cooling to room temperature to prepare the sulfur and nitrogen co-doped graphene SNC @850 rich in edge defects.
The doped graphene shows excellent catalytic activity and H in ORHP catalysis2O2Yield, high ring current density and initial potential, H at an electrochemical window of 0-0.6V2O2The selectivity reaches over 90 percent and reaches 99 percent at most, and the catalyst has good stability and cyclicity.
As shown in fig. 5, the XRD pattern for SNC @850 has a strong diffraction of graphite (002) crystal planes, indicating a large crystal size in the c-axis. (100) The exposure of crystal faces of (004), (110) and (004) shows that the prepared graphene has a coiled structure and can provide more ORHP active sites for the catalyst.
As shown in fig. 6, which is a raman spectrum of SNC @850, the peak D representing the defect of carbon atom is strongest, indicating that the prepared graphene is enriched in defects. The appearance of the D + G peak indicates that the disorder degree of the graphene is large.
As shown in fig. 7, which is an SEM image of SNC @850, it is shown that the prepared sulfur and nitrogen co-doped graphene has a loose dispersed layered structure.
As shown in fig. 8a and 8b, are TEM images of SNC @ 850. 8a shows that the prepared sulfur and nitrogen co-doped graphene has a curled appearance and a layered structure, is rich in wrinkles and ripples, and is beneficial to the surface electrochemical reaction. Where 8b is a high resolution TEM image, SNC @850 has a significant (002) graphite face stacking around 0.30 nm, which is smaller than the typical graphene layer spacing (0.34 nm), suggesting that thiourea as a precursor can induce the generation of a large number of defects, thus enhancing the interaction between graphite faces.
As shown in fig. 9, XPS survey spectrum and calculated elemental content for SNC @850 indicate successful doping of sulfur and nitrogen into graphene without the introduction of other transition metals and impurity elements.
10a, 10b and 10C, C K-edge, N K-edge and S K-edge XANES spectra of SNC @850, respectively, where 10a can be seen to have significant pi (C = C) and sigma (C-C) signals, which are typical graphene characteristic peaks, with a weak swell peak at 288 eV, which is between sp2Hybrid orbital sp3The intercrystalline state of graphene layers in hybrid orbital transition is caused by introducing covalent bonds such as C-N, C-S, C-O and the like into heteroatom doping. Fig. 10b reflects the presence of nitrogen in SNC @850 as pyridine-nitrogen, pyrrole-nitrogen, graphite-nitrogen, respectively, and fig. 10c shows that sulfur in thiourea eventually remains on the graphene framework as thiophene-sulfur, as well as the sulfur oxide phase and sulfonic acid groups left over from concentrated sulfuric acid oxidation during graphene preparation. It can be seen from FIG. 10d that SNC @850 has a typical sp around 125 ppm2NMR characteristic peaks for hybridized carbon atoms, C = S and S-C-N groups at 128.6 ppm and 164.3 ppm, respectively, indicate that the coordinated structure in thiourea can be retained in the two-step synthesis and eventually formedAn S-C-N-C reactive functional group.
As shown in fig. 11a and 11b, AC-TEM images of SNC @850 are shown, where 11a clearly observed graphene six-membered ring, non-six-membered ring, in-plane hole defects, and in the enlarged view of 11b it can be seen that the in-plane holes are large enough to be viewed as edges, which are distributed with the graphene six-membered ring and non-six-membered ring defects, indicating that the edge defect-rich sulfur and nitrogen co-doped graphene is successfully prepared.
Shown in FIGS. 12a and 12b are the polarization curve and Tafel slope, respectively, for SNC @850 as catalyst in 0.1 KOH electrolyte, where the Tafel slope is 87 mA dec-1And a loop current density of 0.74 mA cm at a voltage of 0.1V-2In the loop, the current density is 0.1 mA cm-2The initial potential at (A) was 0.81V, demonstrating excellent 2e-ORR performance of the catalyst.
As shown in FIG. 13, it is SNC @850 as a catalyst at 0-0.6V H2O2The selectivity curve, the selectivity is kept above 90%, shows that the catalyst has good ORHP activity.
As shown in FIG. 14, the ORHP stability test curve of SNC @850 as a catalyst still can maintain about 95% of H in the continuous polarization process of more than 50000 s2O2And selectivity shows that the catalyst has excellent cyclicity and stability.
Example 3 preparation of sulfur and nitrogen-codoped graphene rich in edge defects
(1) Preparing a graphene oxide suspension: ultrasonically dispersing 0.15 g of graphene oxide in 75 mL of deionized water, and ultrasonically treating for 8 hours to obtain a uniform suspension with the graphene oxide concentration of 2 mg/mL;
(2) hydrothermal reaction: taking CH with S accounting for 1.5% of graphene oxide by mass4N2S is placed in the graphene oxide suspension prepared in the step (1), stirred and dispersed for 2 hours, and then the reaction liquid is placed in a hydrothermal kettle and heated to 180 DEG oCContinuously reacting for 12 h, cooling the hydrothermal kettle after the reaction is finished, taking out the columnar product, and drying in a freeze dryer for 30 h to obtain a dried product;
(3) chemical vapor deposition: furnace temperature is set to900 oC, gas flow rate Ar of 100 sccm and NH 350 sccm, and the total gas pressure is 2.85 Torr; and (3) putting the dried product prepared in the step (2) into the center of a tubular furnace, carrying out chemical vapor deposition reaction in the tubular furnace for 1 h, quickly removing a sample from the center of a hot zone of the tubular furnace under the protection of continuous Ar flow, and cooling to room temperature to prepare the sulfur and nitrogen co-doped graphene SNC @900 rich in edge defects.
The doped graphene can efficiently catalyze oxygen to generate hydrogen peroxide, and the H of the doped graphene is within an electrochemical window of 0-0.6V2O2The selectivity reaches more than 80 percent, and the good 2e-ORR performance is proved.
As shown in fig. 15, the XRD spectrum for SNC @900 has a strong diffraction of graphite (002) crystal planes, indicating a large crystal size in the c-axis. (100) The exposure of crystal faces of (004), (110) and (004) shows that the prepared graphene has a coiled structure and can provide more ORHP active sites for the catalyst.
As shown in fig. 16, which is a raman spectrum of SNC @900, the peak D representing the defect of carbon atom is strongest, indicating that the prepared graphene is enriched in defects. The appearance of the D + G peak indicates that the disorder degree of the graphene is large.
Shown in FIGS. 17a and 17b are the polarization curve and Tafel slope, respectively, for SNC @900 as catalyst in 0.1 KOH electrolyte, where the Tafel slope is 128 mA dec-1And a loop current density of 0.64 mA cm at a voltage of 0.1V-2In the loop, the current density is 0.1 mA cm-2The initial potential at (b) was 0.75V, demonstrating that the catalyst has certain 2e-ORR properties.
As shown in FIG. 18, it is SNC @800 as the catalyst at 0-0.6V H2O2The selectivity curve, which remains at 80%, indicates that the catalyst has a certain ORHP activity.
Example 4 preparation of sulfur and nitrogen-codoped graphene rich in edge defects
(1) Preparing a graphene oxide suspension: ultrasonically dispersing 0.15 g of graphene oxide in 75 mL of deionized water, and ultrasonically treating for 8 hours to obtain a uniform suspension with the graphene oxide concentration of 2 mg/mL;
（2）hydrothermal reaction: taking CH with S accounting for 1.5% of graphene oxide by mass4N2S is placed in the graphene oxide suspension prepared in the step (1), stirred and dispersed for 2 hours, and then the reaction liquid is placed in a hydrothermal kettle and heated to 180 DEG oCContinuously reacting for 12 h, cooling the hydrothermal kettle after the reaction is finished, taking out the columnar product, and drying in a freeze dryer for 30 h to obtain a dried product;
(3) chemical vapor deposition: the furnace temperature was set to 850 deg.CoC, gas flow rate Ar of 100 sccm and NH 350 sccm, and the total gas pressure is 2.85 Torr; and (3) placing the dried product prepared in the step (2) into the center of a tube furnace, carrying out chemical vapor deposition reaction in the tube furnace for 0.5 h, quickly removing a sample from the center of a hot zone of the tube furnace under the protection of continuous Ar flow, and cooling to room temperature to prepare the sulfur and nitrogen co-doped graphene SNC rich in the edge defects.
Example 5 preparation of sulfur and nitrogen-codoped graphene rich in edge defects
(1) Preparing a graphene oxide suspension: ultrasonically dispersing 0.15 g of graphene oxide in 75 mL of deionized water, and ultrasonically treating for 8 hours to obtain a uniform suspension with the graphene oxide concentration of 2 mg/mL;
(2) hydrothermal reaction: taking CH with S accounting for 1.5% of graphene oxide by mass4N2S is placed in the graphene oxide suspension prepared in the step (1), stirred and dispersed for 2 hours, and then the reaction liquid is placed in a hydrothermal kettle and heated to 180 DEG oCContinuously reacting for 12 h, cooling the hydrothermal kettle after the reaction is finished, taking out the columnar product, and drying in a freeze dryer for 30 h to obtain a dried product;
(3) chemical vapor deposition: the furnace temperature was set to 850 deg.CoC, gas flow rate Ar of 100 sccm and NH 350 sccm, and the total gas pressure is 2.85 Torr; and (3) placing the dried product prepared in the step (2) into the center of a tubular furnace, carrying out chemical vapor deposition reaction in the tubular furnace for 2 h, quickly removing a sample from the center of a hot zone of the tubular furnace under the protection of continuous Ar flow, and cooling to room temperature to prepare the sulfur and nitrogen co-doped graphene SNC rich in the edge defects.

Claims (8)

1. A preparation method of sulfur and nitrogen co-doped graphene rich in edge defects is characterized by comprising the following steps: the thiourea precursor and graphene oxide are adsorbed and hydrothermally self-assembled, sulfur and nitrogen co-doped graphene is prepared through chemical vapor deposition, and the inherent coordination structure of thiourea can be grafted on the edge of the graphene through the hydrothermal self-assembly chemistry, so that edge defects are induced to be generated, and a large number of active sites are provided.
2. The preparation method of the sulfur and nitrogen co-doped graphene rich in edge defects according to claim 1, characterized by comprising the following steps:
(1) preparing graphene oxide, ultrasonically dispersing the graphene oxide in deionized water, and ultrasonically treating for 8 hours to obtain a uniform suspension liquid with the graphene oxide concentration of 2 mg/mL;
(2) hydrothermal reaction:
reacting thiourea with CH4N2S, adding the S into the graphene oxide suspension prepared in the step (1), stirring for 2 hours, then placing the graphene oxide suspension in a hydrothermal kettle for heating reaction at the temperature of 180-200 ℃ for 12-24 hours, cooling the hydrothermal kettle after the reaction is finished, taking out a columnar product, and placing the columnar product in a freeze dryer for drying for not less than 24 hours to obtain dry aerogel;
(3) chemical vapor deposition:
putting the aerogel prepared in the step (2) into the center of a tubular furnace, and setting the furnace temperature to be 800-900 DEG CoC, gas flow of Ar is 100 plus or minus 5 sccm and NH350 plus or minus 5 sccm, and the total air pressure is 2.8 plus or minus 0.1 Torr; and (3) performing high-temperature heat treatment reaction for 0.5-2 h to obtain the sulfur and nitrogen co-doped graphene rich in the edge defect.
3. The preparation method of the edge defect-rich sulfur-nitrogen co-doped graphene according to claim 2, characterized in that: and (3) the sulfur atom loading amount in the thiourea in the step (2) accounts for 1.5% of the mass percent of the graphene oxide.
4. The preparation method of the edge defect-rich sulfur-nitrogen co-doped graphene according to claim 2, characterized in that: CH (CH)4N2The mass ratio of S in S to graphene oxide is 1-5: 95-99.
5. The preparation method of the edge defect-rich sulfur-nitrogen co-doped graphene according to claim 2, characterized in that: the temperature of the freeze drying is-100 ℃ to-50 ℃.
6. The preparation method of the edge defect-rich sulfur-nitrogen co-doped graphene according to claim 2, characterized in that: the reaction time for the chemical vapor deposition in the tube furnace was 1 h and the reaction temperature was 850 ℃.
7. Application of the sulfur and nitrogen co-doped graphene rich in edge defects prepared by the preparation method of any one of claims 1-6 as a catalyst for electrocatalysis of ORHP.
8. Use according to claim 7, characterized in that: the catalytic reaction is carried out on a rotating disc electric device, and the rotating speed is set at 1600 rpm; preparing electrode dispersion solution from 2 mg of catalyst, water, ethanol and 5 wt% Nafion solution according to the volume ratio of 5:5:1, uniformly dripping 5 mu L of the electrode dispersion solution on a ring disk electrode, wherein the loading amount is 0.1 mg/cm2(ii) a The catalytic process was carried out in a three-electrode system with an electrolyte of 0.1M KOH and saturated oxygen.
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