CN114875445B - Amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene hydrogen evolution reaction catalyst and preparation and application thereof - Google Patents

Amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene hydrogen evolution reaction catalyst and preparation and application thereof Download PDF

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CN114875445B
CN114875445B CN202210501579.4A CN202210501579A CN114875445B CN 114875445 B CN114875445 B CN 114875445B CN 202210501579 A CN202210501579 A CN 202210501579A CN 114875445 B CN114875445 B CN 114875445B
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sulfide
hydrogen evolution
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graphene oxide
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CN114875445A (en
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区琼荣
张树宇
张岱
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Fudan University
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    • C25B11/091—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
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    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
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    • Y02P20/133—Renewable energy sources, e.g. sunlight

Abstract

The invention relates to an amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene hydrogen evolution reaction catalyst and preparation and application thereof, wherein the preparation process of the catalyst specifically comprises the following steps: (1) Firstly carrying out ultraviolet ozone treatment on graphene oxide, then carrying out heating reaction on the graphene oxide and nickel sulfate in water, and then carrying out freeze-drying to obtain three-dimensional graphene oxide; (2) Uniformly dispersing ammonium tetrathiomolybdate, ammonium tetrathiotungstate and three-dimensional graphene oxide into a solvent, and freeze-drying the dispersion liquid to obtain precursor powder, or coating the dispersion liquid on the surface of a load electrode and volatilizing the solvent to obtain a precursor electrode; (3) And placing the obtained precursor powder or precursor electrode in a vacuum cavity, and performing plasma treatment to obtain a target product. According to the invention, the catalytic activity of the catalyst is regulated and controlled by changing the mass ratio of the ammonium tetrathiomolybdate to the ammonium tetrathiotungstate and the like, so that the catalyst which does not contain noble metal and can efficiently catalyze industrial-grade current density hydrogen evolution reaction is obtained.

Description

Amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene hydrogen evolution reaction catalyst and preparation and application thereof
Technical Field
The invention belongs to the technical field of catalysts, and relates to an amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene hydrogen evolution reaction catalyst, and preparation and application thereof.
Background
The world today, the massive consumption of fossil energy inevitably causes worldwide energy crisis and environmental pollution, and the development of green energy technology is critical for the sustainable development of human society. Hydrogen is an ideal energy carrier, has high energy density and does not generate greenhouse gases when burned. Hydrogen belongs to a secondary energy source, which does not naturally exist in nature and must be produced manually. The current industrial hydrogen production method mainly comprises methane steam reforming and coal gasification, and the method still depends on fossil energy sources to produce hydrogen, and does not meet the requirement of sustainable development. The hydrogen prepared by electrolyzing water can get rid of the dependence on fossil energy and realize the storage and transportation of electric energy generated by renewable energy sources such as solar energy, wind energy and the like. The hydrogen gas is prepared by electrolysis of water, and the overpotential applied by the hydrogen gas during cathode precipitation (namely, the electric energy consumption is reduced) is reduced by using a catalyst, however, the hydrogen gas precipitation reaction catalyst used in the industry at present is platinum-based noble metal, and the material has lower content in the nature and high price. Therefore, developing a high-performance hydrogen evolution reaction catalyst is important to developing renewable energy hydrogen production.
With molybdenum disulfide (MoS) 2 ) The transition metal sulfide is a potential hydrogen evolution reaction catalyst for replacing platinum-based noble metals. Crystalline state MoS 2 Only the edge position is an active site for catalyzing hydrogen gas precipitation reaction, so that the catalytic performance is far from that of platinum-based noble metals; molybdenum sulphide in the amorphous state has higher catalytic properties but is less stable because it is in the amorphous state. Commercial hydrogen gas evolution reaction catalyst is required to be in 500mA cm -2 The above current density works stably, and no amorphous transition metal sulfide catalyst satisfying the above condition has been reported.
Disclosure of Invention
The invention aims to provide an amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene hydrogen evolution reaction catalyst, and preparation and application thereof, wherein the catalyst has high catalytic activity and high stability in the water electrolysis process under industrial current density. In addition, the invention can realize the regulation and control of the catalyst performance by controlling the mass ratio of the ammonium tetrathiomolybdate and the ammonium tetrathiotungstate in the precursor and the plasma treatment process, thereby obtaining the hydrogen evolution reaction catalyst with optimal performance.
The aim of the invention can be achieved by the following technical scheme:
one of the technical schemes of the invention provides a preparation method of an amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene hydrogen evolution reaction catalyst, which comprises the following steps:
(1) Firstly carrying out ultraviolet ozone treatment on graphene oxide, then carrying out heating reaction on the graphene oxide and nickel sulfate in water, and then carrying out freeze-drying to obtain three-dimensional graphene oxide;
(2) Uniformly dispersing ammonium tetrathiomolybdate, ammonium tetrathiotungstate and three-dimensional graphene oxide into a solvent to obtain a dispersion liquid, and freeze-drying the dispersion liquid to obtain precursor powder, or coating the dispersion liquid on the surface of a reloaded electrode and volatilizing the solvent to obtain a precursor electrode;
(3) And placing the obtained precursor powder or precursor electrode in a vacuum cavity, and performing plasma treatment to obtain the target product catalyst or the target product catalyst covered on the surface of the load electrode.
Further, in the step (1), the time of the ultraviolet ozone treatment is 30-180min. The purpose of the ultraviolet ozone treatment is to increase oxygen-containing functional groups on the graphene oxide, and the oxygen-containing functional groups can have coordination action and electrostatic action with transition metal ions under hydrothermal conditions, namely, cross-linking is carried out under the action of the metal ions, so that the separated two-dimensional graphene oxide sheets are assembled into the three-dimensional graphene oxide. The invention discovers that the time of the ultraviolet ozone treatment has no obvious influence on the morphology of the three-dimensional graphene oxide, and the overlong time of the ultraviolet ozone treatment can lead to the reduction of the conductivity of the three-dimensional graphene oxide and reduce the catalytic performance of the amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene. Therefore, the invention limits the time of the ultraviolet ozone treatment to 30-180min. The ultraviolet ozone treatment in the invention uses 185nm ultraviolet lamp with the ultraviolet radiation intensity of 50-1000 mu W cm -2 The distance between the sample table and the ultraviolet lamp tube is 5-10 cm, and the working environment is air or oxygen atmosphere.
Further, in the step (1), the temperature of the heating reaction is 40-90 ℃ and the time is 2-10h.
Further, in the step (1), the mass ratio of graphene oxide to nickel sulfate after being treated by ultraviolet ozone is 1:1 to 1:5.
further, in the step (2), the mass ratio of the total mass of the ammonium tetrathiomolybdate and the ammonium tetrathiotungstate to the three-dimensional graphene oxide is 1:1 to 5:1, the mass ratio of the ammonium tetrathiomolybdate to the ammonium tetrathiotungstate is 1: 5-5: 1.
further, in the step (2), the solvent is dimethylformamide.
Further, in the step (3), the plasma used in the plasma treatment process is non-thermal equilibrium plasma, the discharge atmosphere is mixed gas of argon and ammonia, and the background vacuum degree is 0.5X10 -3 ～1.5×10 -3 Pa。
Further, in the step (3), the total flow of argon and ammonia is 80-150 standard milliliters per minute, and the flow ratio of argon to ammonia is 7:3 to 9:1.
further, in the step (3), the discharge air pressure is 1-10 Pa, the discharge power is 50-200W, and the plasma treatment time is 2-20 min.
Still further, the plasma includes, but is not limited to, inductively coupled plasma, capacitively coupled plasma, microwave plasma, dielectric barrier discharge plasma, and the like.
The second technical scheme of the invention provides an amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene hydrogen evolution reaction catalyst which is prepared by adopting any one of the preparation methods.
The third technical scheme of the invention provides application of the amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene hydrogen evolution reaction catalyst, which is used for catalyzing hydrogen evolution reaction. In particular, when it is used to catalyze a hydrogen evolution reaction, it is measured at 1000mA cm -2 The overpotential under the current density is less than 350mV, and the performance is superior to that of the commercial platinum carbon (Pt/C) catalyst on the market.
According to the invention, the graphene oxide is treated by ultraviolet ozone, so that the oxygen-containing functional groups on the surface of the graphene oxide are increased: the ultraviolet ozone can oxidize the original hydroxyl in the graphene oxide into carboxyl while introducing epoxy groups on the surface of the graphene oxide. These oxygen-containing functional groups can provide a riveting site for metal ions: the metal ions can connect the separated graphene oxide sheets through electrostatic action and coordination action between the metal ions and the epoxy functional groups to form the three-dimensional graphene oxide. According to the invention, the three-dimensional graphene oxide is prepared by heating graphene oxide and nickel sulfate subjected to ultraviolet ozone treatment in water. The invention discovers that three-dimensional graphene oxide can be finally obtained by changing the ultraviolet ozone treatment time, the mass ratio of graphene oxide to nickel sulfate and the heating reaction temperature and time within a certain range. The plasma used in the present invention is a non-thermal equilibrium plasma including, but not limited to, inductively coupled plasma, capacitively coupled plasmaThe plasma, microwave plasma and dielectric barrier discharge plasma have high reactivity at low temperature, so that the invention can simultaneously reduce the ammonium tetrathiomolybdate and the ammonium tetrathiotungstate into amorphous molybdenum sulfide/tungsten sulfide at normal temperature. The non-thermal balance plasma hardly generates heating effect on the sample in the treatment process, so that the crystallization of molybdenum sulfide and tungsten sulfide caused by the temperature rise of the sample can be avoided, and the amorphous state of a target product is ensured. Dimethylformamide is only used as a solvent for uniformly mixing the raw materials and does not play a role in the reaction process. Ammonia gas is introduced in the discharge atmosphere in order to achieve nitrogen doping while reducing graphene oxide. The ammonia gas can be ionized in the plasma to generate active groups such as electrons, amino ions, free radicals and the like, and the reactive activity of the groups is very high, so that nitrogen doping can be introduced into the graphene. However, the amount of ammonia in the discharge atmosphere should not be too much, otherwise, the discharge power of the plasma is difficult to maintain stable, so the flow ratio of argon to ammonia in the invention is 7:3 to 9:1. the theoretical calculation of the density functional shows that the disulfide ions (2S 2- ) The catalyst is a main reason for excellent catalytic activity of hydrogen gas precipitation reaction under high current density: the adsorption energy of hydrogen atoms on disulfide ions at high current densities can be kept comparable to that at thermodynamic equilibrium. The density functional theory calculation also shows that: proper degree of tungsten doping can promote the stability of amorphous molybdenum sulfide/tungsten sulfide clusters, and too high concentration of tungsten doping can lead to unstable amorphous clusters, which is important for preparing a catalyst capable of stably working in the process of electrolyzing water with high current density. Therefore, after the influence of the mass ratio of the ammonium tetrathiomolybdate to the ammonium tetrathiotungstate in the precursor on the catalyst performance is explored, the mass ratio of the ammonium tetrathiomolybdate to the ammonium tetrathiotungstate in the precursor is preferably set to be 1:1. the type of plasma must be a non-thermal equilibrium plasma, while species include, but are not limited to, inductively coupled plasma, capacitively coupled plasma, microwave plasma, and dielectric barrier discharge plasma, since the non-thermal equilibrium plasma is highly reactive at low temperatures and has no heating effect on the sample, thus ensuring non-product molybdenum sulfide/tungsten sulfideCrystalline nature. If a thermal equilibrium plasma is used, the sample will be in a high temperature state during the preparation process, and the molybdenum sulfide/tungsten sulfide will crystallize, so that the amorphous product will not be obtained. The embodiment of the invention uses inductively coupled plasma, other types of non-thermal equilibrium plasmas can be used, but the corresponding plasma power, discharge pressure and optimal processing time can all be changed. It is intended that all types of plasma devices be covered by the claims. The argon gas in the discharge atmosphere acts to sustain the discharge and reduce, and the ammonia gas acts to reduce and provide a source of doped nitrogen. If other reducing gases are used in the discharge atmosphere, the corresponding optimum treatment time will vary. The plasma power determines the rate at which the precursor is reduced, i.e., the processing time. If the plasma power is low, longer processing times are required to achieve the same reduction level, which only reduces efficiency. The power used by the inductively coupled plasma equipment is 50-200W used in the invention. The discharge pressure must be matched to the discharge power to develop the maximum power of the inductively coupled plasma apparatus. The discharge pressure is too low or too high to reduce the plasma power and prolong the treatment time, and the maximum discharge power can be achieved only when the discharge pressure is 1-10 Pa.
Compared with the prior art, the invention has the following advantages:
1. the amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene hydrogen evolution reaction catalyst with high catalytic activity and high stability in the water electrolysis process under the industrial current density and the preparation method thereof are simple and convenient to operate, free of pollution and free of high temperature, and can promote the development of large-scale preparation of the high-current density hydrogen evolution reaction catalyst.
2. According to the invention, the regulation and optimization of the amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene catalytic performance are realized by controlling the mass ratio of the ammonium tetrathiomolybdate to the ammonium tetrathiotungstate in the precursor and the plasma treatment time. At a suitable mass ratio of ammonium tetrathiomolybdate to ammonium tetrathiotungstate and a suitable treatment time, we obtained a current density of 1000mA cm -2 When needed over-powerAnd the catalyst has excellent performance, is less than 350mV, and can stably work for 24 hours at the current density without obvious attenuation of activity. At present, no report is made on the same purpose by using other preparation methods, and no report is made on the fact that the method can be used at 1000mA cm -2 Reports of amorphous transition metal sulfide catalysts that work stably at current densities.
3. The technical route provided by the invention can be applied to preparing other transition metal sulfides.
Drawings
Fig. 1 is a field emission Scanning Electron Microscope (SEM) topography of a three-dimensional graphene oxide.
FIG. 2 is a-MoWS prepared in example 1 x A field emission Transmission Electron Microscope (TEM) topography of/3D N-RGO@1:2-10 min.
FIG. 3 is a-MoWS prepared in example 2 x TEM topography of 1-10min at 3D N-RGO@1.
FIG. 4 is a-MoWS prepared in example 3 x TEM topography of 1-10min at 3D N-RGO@2.
FIG. 5 is a graph showing the performance of a Linear Sweep Voltammogram (LSV) of the amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen-doped graphene catalyzed hydrogen evolution reaction prepared in examples 1-3, wherein 1 is a-MoWS prepared in example 1 x LSV curve of/3 DN-RGO@1:2-10min, 2 is a-MoWS prepared in example 2 x LSV curve of/3 DN-RGO@1:1-10min, 3 is a-MoWS prepared in example 3 x LSV curve of 1-10 min/3 DN-RGO@2.
FIG. 6 is a-MoWS prepared in example 4 x 3D N-RGO@1:1-5min, a-MoWS prepared in example 2 x 1-10 min/3D N-RGO@1, a-MoWS prepared in example 5 x 3D N-RGO@1:1-15min, and catalytic hydrogen evolution reaction performance of commercial platinum carbon catalyst (20% Pt/C).
FIG. 7 is a-MoWS prepared in example 2 x Stability test results of/3D N-RGO@1:1-10 min.
Detailed Description
The invention will now be described in detail with reference to the drawings and specific examples. The present embodiment is implemented on the premise of the technical scheme of the present invention, and a detailed implementation manner and a specific operation process are given, but the protection scope of the present invention is not limited to the following examples.
In the following examples, graphene oxide powder was purchased from Nanj Xianfeng nanomaterial technologies Inc. under the product designation XF002-2. In addition, the ultraviolet ozone treatment process comprises the following steps: an ultraviolet lamp of 185nm was used, and the ultraviolet radiation intensity was 500. Mu.W cm -2 About (50 to 1000. Mu.W cm as required) -2 The distance between the sample table and the ultraviolet lamp tube is about 8cm (can be adjusted within the range of 5-10 cm according to the requirement), and the working environment is air (can be replaced by oxygen atmosphere).
The remainder, unless specifically stated, is indicative of a conventional commercially available feedstock or conventional processing technique in the art.
Example 1:
an amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene hydrogen gas precipitation reaction catalyst comprises the following specific synthesis process:
(1) 20mg of graphene oxide was taken and treated with ultraviolet ozone for 60 minutes. 20mg of graphene oxide subjected to ultraviolet ozone treatment and 80mg of nickel sulfate hexahydrate were added to water, and heated at 80℃for 5 hours, to obtain a black hydrogel. And carrying out freeze-drying treatment on the obtained hydrogel to obtain the three-dimensional graphene oxide.
(2) 10mg of ammonium tetrathiomolybdate, 20mg of ammonium tetrathiotungstate and 10mg of three-dimensional graphene oxide are weighed and dispersed in 10ml of DMF solvent in an ultrasonic manner to obtain fully dispersed precursor solution, and a sample prepared according to the proportion is named as a-MoWS x /3D N-RGO@1:2-10min。
(3) Lyophilizing the precursor solution to obtain precursor powder; or 5 μl of the precursor solution is coated on the surface of the commercial glassy carbon electrode, and the precursor electrode is obtained after the solvent volatilizes.
(4) And (3) placing the precursor powder or the precursor electrode obtained in the step (2) into a vacuum cavity, and treating by using inductively coupled plasma. The plasma parameters were: background vacuum was 1.0X10 -3 Pa, the total flow of argon and ammonia is 100 standard milliliters per minute, and the flow ratio of the argon to the ammonia is 9:1,the discharge pressure was 4Pa, the discharge power was 100W, and the treatment time was 10 minutes.
The Transmission Electron Microscope (TEM) morphology of the sample prepared in example 1 above is shown in fig. 2, and the catalytic hydrogen evolution reaction performance is shown in fig. 5, 1.
Example 2:
an amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene hydrogen gas precipitation reaction catalyst comprises the following specific synthesis process:
the difference between this embodiment and the embodiment of embodiment 1 is that: the solid powder weighed in the step (2) is 15mg of ammonium tetrathiomolybdate, 15mg of ammonium tetrathiotungstate and 10mg of three-dimensional graphene oxide, and the obtained product is named as a-MoWS x 3D N-RGO@1:1-10min, the other steps are the same as those of embodiment (1) to (4) of example 1.
The TEM morphology of the sample prepared in example 2 above is shown in fig. 3, and the catalytic hydrogen evolution reaction performance is shown in fig. 5, 2.
Example 3:
an amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene hydrogen gas precipitation reaction catalyst comprises the following specific synthesis process:
the difference between this embodiment and the embodiment of embodiment 1 is that: the solid powder weighed in the step (2) is 20mg of ammonium tetrathiomolybdate, 10mg of ammonium tetrathiotungstate and 10mg of three-dimensional graphene oxide, and the obtained product is named as a-MoWS x 3D N-RGO@2:1-10min, the other steps are the same as those of embodiment (1) to (4) of example 1.
The TEM morphology of the sample prepared in example 3 above is shown in fig. 4, and the catalytic hydrogen evolution reaction performance is shown in fig. 5, 3.
From a scanning electron microscope morphology graph (figure 1) of the three-dimensional graphene oxide, the original planar flaky graphene oxide is subjected to ultraviolet ozone treatment, and a three-dimensional network structure is formed under the crosslinking action of nickel ions. Comparing the TEM topography of the samples prepared in examples 1-3 above (fig. 2-4), it was found that changing the mass ratio of ammonium tetrathiomolybdate to ammonium tetrathiotungstate in the precursor did not change the amorphous structure of the product: no regular lattice fringes were observed in the TEM topography of the samples prepared in examples 1-3, indicating that all 3 samples were completely amorphous.
The activity of the amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen-doped graphene prepared in the above examples 1-3 in catalyzing hydrogen evolution reaction was studied, as shown in FIG. 4, at a current density of 500mA cm -2 The overpotential was 329mV, 277mV and 297mV in this order. With the increase of the proportion of the ammonium tetrathiotungstate in the precursor, the catalytic performance of the hydrogen precipitation reaction of the final product is firstly improved and then reduced. The theoretical calculation of density functional shows that the reason for improving the catalytic performance of the hydrogen gas precipitation reaction is that the introduction of tungsten doping with proper degree into amorphous molybdenum sulfide can optimize the hydrogen atoms in disulfide ions (2S) 2- ) The adsorption energy is maintained at a value which is not greatly different from that of the thermodynamic equilibrium state under the condition of high current density. The reason for the decrease is that too high a concentration of tungsten doping will cause unstable amorphous clusters, 2S 2- Will evolve into S with poor catalytic activity 2- . The meaning of introducing tungsten doping in the invention is that a proper amount of tungsten doping can enhance the catalytic activity of amorphous molybdenum sulfide, and the catalytic activity of the amorphous molybdenum sulfide can be reduced once the tungsten doping degree is too high.
The effect of plasma treatment time on the catalytic performance of the hydrogen evolution reaction of amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene was investigated using the optimal precursor ratio (i.e., optimal tungsten doping concentration) in example 2, see in particular the following examples.
Example 4:
an amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene hydrogen gas precipitation reaction catalyst comprises the following specific synthesis process:
the difference between this embodiment and the embodiment of embodiment 2 is that: the plasma treatment time was 5min and the resulting product was designated a-MoWS x 3D N-RGO@1:1-5min, the other steps are the same as those of embodiment (1) to (3) of example 2.
The performance of the amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen-doped graphene prepared in example 4 described above in catalyzing the hydrogen evolution reaction is shown as 1 in fig. 6.
Example 5:
an amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene hydrogen gas precipitation reaction catalyst comprises the following specific synthesis process:
the difference between this embodiment and the embodiment of embodiment 2 is that: the plasma treatment time was 15min and the resulting product was designated a-MoWS x 3D N-RGO@1:1-15min, the other steps are the same as those of embodiment (1) to (3) of example 2.
The performance of the amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene prepared in example 5 above in catalyzing the hydrogen evolution reaction is shown as 3 in fig. 6.
The catalytic performance of the hydrogen gas evolution reaction of the amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene prepared in examples 2, 4 and 5 was studied for different times by plasma treatment at the optimal precursor ratios, as shown in fig. 6, and the catalytic performance of the hydrogen gas evolution reaction of the catalyst prepared in example 2 was 2 in fig. 6. It was found that as the plasma treatment time was extended, a-MoWS x The catalytic performance of/RGO@1:1 is improved and then reduced. The theoretical calculation of the density functional shows that the disulfide ions (2S 2- ) The main catalytic active species in amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene can cause 2S when the plasma treatment time is too short or too long 2- The content is reduced, and therefore, proper plasma treatment time is critical to obtain optimal catalytic performance of the hydrogen evolution reaction. For inductively coupled plasma and power used in the embodiments of the invention, the optimal processing time is 10min. The optimal process time may vary if other types of plasmas and powers are used.
Amorphous molybdenum sulfide/tungsten sulfide/three-dimensional Nitrogen-doped graphene (a-MoWS) prepared in example 2 x 3DN-RGO@1:1-10 min) as working electrode (cathode) for hydrogen gas evolution reaction, saturated silver chloride as reference electrode, carbon rod counter electrode (anode), catalytic hydrogen gas evolution reaction, a-MoWS x The hydrogen evolution initial overpotential of/3D N-RGO@1 is 60mV for 1-10 min; 500mA cm 2 And 1000mA cm 2 The overpotential at the current density is 277mV and 348mV respectively, and shows excellent electrochemical hydrogen evolution catalytic performance. The catalytic performance of the commercial platinum carbon catalyst (20% Pt/C) for the hydrogen evolution reaction is shown in FIG. 6, 4, and it can be seen that the catalyst of the present inventionThe prepared amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene catalyst material has performance lower than that of a commercial platinum carbon catalyst in a low current density range, but when the current density exceeds 850mA cm -2 After that, the overpotential of the amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene is lower than that of commercial platinum carbon, which shows that the hydrogen precipitation reaction catalytic performance of the amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene prepared by the invention is superior to that of commercial glass carbon electrode under the condition of high current density. Study of stability of amorphous molybdenum sulfide/tungsten sulfide/three-dimensional Nitrogen doped graphene prepared in example 2 in catalytic Hydrogen evolution reaction under Industrial-grade Current Density, using the catalyst as working electrode (cathode), saturated silver chloride as reference electrode, platinum mesh counter electrode (anode), at 1000mA cm -2 To avoid anode-dissolved platinum ions from depositing on the cathode, which would affect the stability of the catalyst being evaluated, an H-type cell was used and Nafion 177 membrane was used to separate the cathode and anode regions. The results of the stability test are shown in FIG. 7, where a-MoWS was used during 24 hours of catalytic electrolysis of water by applying a resistance-compensated constant overpotential of 349mV at the cathode x The current density of the cathode where the anode is positioned at the temperature of/3D N-RGO@1:1-10min can be stably maintained at 1000mA cm -2 About, it was shown that the catalytic activity did not decay. Therefore, the invention provides a preparation method of the amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene hydrogen evolution reaction catalyst with high catalytic activity and high stability in the water electrolysis process under the industrial current density.
In addition, the present invention has been studied to find that if low plasma power is used, a longer process time is required to achieve the same reduction degree and doping degree, and efficiency is lowered. As for the discharge gas pressure, for the inductively coupled plasma apparatus used in the embodiment of the present invention, the maximum discharge power can be obtained only when the gas pressure is 1 to 10Pa, and too low or too high gas pressure may cause the plasma power to decrease, and the processing time to be prolonged. As for the flow ratio of argon to ammonia, ammonia provides a nitrogen source for doped graphene, so the flow is not too low, but the flow is also not too high, otherwise the discharge power of plasma is difficult to maintain stable.
Comparative example 1:
most of them are the same as in example 1, except that the step of pre-treating graphene oxide with ultraviolet ozone is omitted. Here, it was found that the final lyophilization of step 1 does not give complete three-dimensional graphene, but rather loose graphene oxide powder, because the coordination and electrostatic interactions of graphene oxide with nickel ions, which are not uv-ozone treated, are not sufficient in number, and the system collapses during lyophilization, failing to give a three-dimensional structure.
Comparative example 2:
most of the same as in example 1, except that the process of treating the precursor powder or the precursor electrode with plasma was omitted. It was found that the precursor powder or precursor electrode could not be converted to amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene without plasma treatment, but instead the original ammonium tetrathiomolybdate, ammonium tetrathiotungstate, and three-dimensional graphene oxide. The precursor powder or precursor electrode which is not treated by the plasma cannot catalyze hydrogen evolution reaction, and has no catalytic activity.
Comparative example 3
Most of the same as in example 1 except that the mixed gas of argon and ammonia was adjusted to a single argon gas at an equal flow rate. It was found that if the plasma treatment is performed using pure argon without introducing ammonia gas in the discharge atmosphere, nitrogen doping cannot be introduced into the three-dimensional graphene, and the nitrogen doping contributes to enhancing the catalytic activity of the hydrogen evolution reaction of the graphene, so that the catalytic activity of the hydrogen evolution reaction of the final product may be deteriorated.
Example 6:
compared to example 1, the vast majority are identical, except in this example: the time of the ultraviolet ozone treatment was adjusted to 30min.
Example 7:
compared to example 1, the vast majority are identical, except in this example: the time of the ultraviolet ozone treatment is adjusted to 180min.
Example 8:
compared to example 1, the vast majority are identical, except in this example: the temperature for introducing the heating reaction of the nickel sulfate hexahydrate is 40 ℃ and the time is 10 hours.
Example 9:
compared to example 1, the vast majority are identical, except in this example: the temperature for introducing the heating reaction of the nickel sulfate hexahydrate is 90 ℃ and the time is 2 hours.
Example 10:
compared to example 1, the vast majority are identical, except in this example: the mass ratio of graphene oxide to nickel sulfate after ultraviolet ozone treatment is 1:5.
example 11:
compared to example 1, the vast majority are identical, except in this example: the mass ratio of graphene oxide to nickel sulfate after ultraviolet ozone treatment is 1:1.
example 12:
compared to example 1, the vast majority are identical, except in this example: the mass of the ammonium tetrathiomolybdate is kept unchanged, and the mass ratio of the total mass of the ammonium tetrathiomolybdate and the ammonium tetrathiotungstate to the three-dimensional graphene oxide is adjusted to be 1:1, the mass ratio of the ammonium tetrathiomolybdate to the ammonium tetrathiotungstate is 1: 5-5: 1.
example 13:
compared to example 1, the vast majority are identical, except in this example: the mass of the ammonium tetrathiomolybdate is kept unchanged, and the mass ratio of the total mass of the ammonium tetrathiomolybdate and the ammonium tetrathiotungstate to the three-dimensional graphene oxide is adjusted to be 5:1, the mass ratio of the ammonium tetrathiomolybdate to the ammonium tetrathiotungstate is 1: 5-5: 1.
example 14:
compared to example 1, the vast majority are identical, except in this example: background vacuum degree in plasma treatment process is 0.5×10 -3 。
Example 15:
compared to example 1, the vast majority are identical, except in this example: background vacuum degree in plasma treatment process is 1.5X10 -3 Pa。
Example 16:
compared to example 1, the vast majority are identical, except in this example: the total flow of argon and ammonia is 80 standard milliliters per minute, and the flow ratio of argon to ammonia is 7:3.
example 17:
compared to example 1, the vast majority are identical, except in this example: the total flow of argon and ammonia is 150 standard milliliters per minute, and the flow ratio of argon to ammonia is 8:2.
example 18:
compared to example 1, the vast majority are identical, except in this example: the discharge pressure was 1Pa, the discharge power was 50W, and the plasma treatment time was 20 minutes.
Example 19:
compared to example 1, the vast majority are identical, except in this example: the discharge pressure was 10Pa, the discharge power was 200W, and the plasma treatment time was 2 minutes.
The previous description of the embodiments is provided to facilitate a person of ordinary skill in the art in order to make and use the present invention. It will be apparent to those skilled in the art that various modifications can be readily made to these embodiments and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above-described embodiments, and those skilled in the art, based on the present disclosure, should make improvements and modifications without departing from the scope of the present invention.

Claims (9)

1. The preparation method of the amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene hydrogen evolution reaction catalyst is characterized by comprising the following steps of:
(1) Firstly carrying out ultraviolet ozone treatment on graphene oxide, then carrying out heating reaction on the graphene oxide and nickel sulfate in water, and then carrying out freeze-drying to obtain three-dimensional graphene oxide;
(2) Uniformly dispersing ammonium tetrathiomolybdate, ammonium tetrathiotungstate and three-dimensional graphene oxide into a solvent to obtain a dispersion liquid, and freeze-drying the dispersion liquid to obtain precursor powder, or coating the dispersion liquid on the surface of a reloaded electrode and volatilizing the solvent to obtain a precursor electrode;
(3) Placing the obtained precursor powder or precursor electrode in a vacuum cavity, and performing plasma treatment to obtain a target product catalyst or a target product catalyst covered on the surface of a load electrode;
in the step (2), the mass ratio of the total mass of the ammonium tetrathiomolybdate and the ammonium tetrathiotungstate to the three-dimensional graphene oxide is 1: 1-5: 1, the mass ratio of the ammonium tetrathiomolybdate to the ammonium tetrathiotungstate is 1: 5-5: 1, a step of;
in the step (3), the plasma used in the plasma treatment process is non-thermal equilibrium plasma, and the discharge atmosphere is mixed gas of argon and ammonia.
2. The method for preparing the amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene hydrogen evolution reaction catalyst according to claim 1, wherein in the step (1), the ultraviolet ozone treatment time is 30-180min;
the temperature of the heating reaction is 40-90 ℃ and the time is 2-10h.
3. The method for preparing the amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene hydrogen evolution reaction catalyst according to claim 1, wherein in the step (1), the mass ratio of graphene oxide to nickel sulfate after ultraviolet ozone treatment is 1: 1-1: 5.
4. the method for preparing the amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene hydrogen evolution reaction catalyst according to claim 1, wherein in the step (2), the solvent is dimethylformamide.
5. The method for preparing the amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene hydrogen evolution reaction catalyst according to claim 1, wherein in the step (3), the background vacuum degree is 0.5' 10 -3 ~1.5´10 -3 Pa。
6. The method for preparing the amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene hydrogen evolution reaction catalyst according to claim 5, wherein in the step (3), the total flow of argon and ammonia is 80-150 standard milliliters per minute, and the flow ratio of argon to ammonia is 7: 3-9: 1.
7. the method for preparing the amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene hydrogen evolution reaction catalyst according to claim 5, wherein in the step (3), the discharge pressure is 1-10 Pa, the discharge power is 50-200W, and the plasma treatment time is 2-20 min.
8. An amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene hydrogen evolution reaction catalyst prepared by the preparation method according to any one of claims 1 to 7.
9. The use of an amorphous molybdenum sulfide/tungsten sulfide/three-dimensional nitrogen doped graphene hydrogen evolution reaction catalyst according to claim 8, wherein the catalyst is used for catalyzing hydrogen evolution reactions.
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CN108896621A (en) * 2018-04-08 2018-11-27 山东大学 A kind of ammonia gas sensor and preparation method thereof loading platinum grain
CN113529126A (en) * 2021-06-18 2021-10-22 复旦大学 Amorphous molybdenum sulfide/graphene catalyst with controllable catalytic active species content and preparation and application thereof

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Publication number Priority date Publication date Assignee Title
CN108896621A (en) * 2018-04-08 2018-11-27 山东大学 A kind of ammonia gas sensor and preparation method thereof loading platinum grain
CN113529126A (en) * 2021-06-18 2021-10-22 复旦大学 Amorphous molybdenum sulfide/graphene catalyst with controllable catalytic active species content and preparation and application thereof

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