CN113562766A - Modified metal chalcogenide nanosheet and preparation method and application thereof - Google Patents

Modified metal chalcogenide nanosheet and preparation method and application thereof Download PDF

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CN113562766A
CN113562766A CN202010350643.4A CN202010350643A CN113562766A CN 113562766 A CN113562766 A CN 113562766A CN 202010350643 A CN202010350643 A CN 202010350643A CN 113562766 A CN113562766 A CN 113562766A
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metal chalcogenide
electrochemical
nanosheet
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CN113562766B (en
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李立宏
俞晓夏
宋延林
邢献然
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Institute of Chemistry CAS
University of Science and Technology Beijing USTB
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Institute of Chemistry CAS
University of Science and Technology Beijing USTB
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Abstract

The invention relates to the technical field of electrocatalysis, and discloses a modified metal chalcogenide nanosheet and a preparation method and application thereof. The method comprises the steps of sequentially carrying out electrochemical intercalation treatment and electrochemical etching treatment on the metal chalcogenide; wherein the metal in the metal chalcogenide is a transition metal and/or a group IV metal; the intercalation agent used in the electrochemical intercalation treatment is alkyl ammonium halide. The preparation method is simple and environment-friendly, and the prepared catalyst is high in activity and suitable for large-scale production.

Description

Modified metal chalcogenide nanosheet and preparation method and application thereof
Technical Field
The invention relates to the technical field of electrocatalysis, in particular to a modified metal chalcogenide nanosheet and a preparation method and application thereof.
Background
Under the large background of rapid development of economy, the increasingly serious problems of energy shortage and environmental pollution caused by fossil fuel consumption become great obstacles for the harmonious development of human beings and nature. In order to meet the increasing energy demand of human beings, reduce the emission of carbon dioxide and pollutants, reduce energy consumption, and develop sustainable clean energy, it becomes vital. Hydrogen is regarded as one of the future energy development directions as a clean energy source with no pollution and high energy density. Hydrogen is currently produced from natural gas primarily by steam methane reforming (i.e., the reaction of methane and water to produce hydrogen and carbon dioxide), and greenhouse gas emissions from this process are large and neither renewable nor carbon neutral. Compared with the steam reformed hydrogen widely used at present, the hydrogen production by electrocatalysis water cracking has the advantages of regeneration, environmental protection and the like.
In recent years, metal sulfide/selenide nanosheets have attracted much attention in the field of catalysts as a metal sulfide having a two-dimensional structure. The catalyst has the advantages of abundant earth resources, good electrochemical stability, high activity and the like, and is generally considered to be a substitute of a noble metal catalyst with great potential. The existing preparation method for preparing the metal sulfide/selenide with high catalytic activity mainly comprises the following steps: (1) the method of atom substitution is used, and has the disadvantages that atom doping is not uniform, doping defects are difficult to control, high-temperature treatment is required, and energy consumption is high; (2) the surface is loaded with noble metals such as platinum and the like, and the method has the defects of complex preparation process and greatly increased preparation cost; (3) the hydrogen is used for high-temperature annealing, and the method has the defects that high-temperature treatment is needed, and energy consumption is high; (4) plasma bombardment, and the method has the disadvantages of higher preparation cost and difficult large-scale application; (5) the method of heating at high temperature by using steam has the disadvantages of high temperature treatment and high energy consumption. The methods have the problems of complex preparation conditions, high cost, high reaction conditions, high energy consumption, environmental protection and difficult batch production, and the problems limit the large-scale commercial application of the metal sulfide/selenide nanosheets. Therefore, the preparation of a modified metal sulfide/selenide nanosheet catalyst with high catalytic activity is still a very challenging task.
Disclosure of Invention
The invention aims to overcome the problems in the prior art and provides a preparation method of a modified metal chalcogenide nanosheet, which is simple and environment-friendly in preparation process, high in activity of the prepared catalyst and suitable for large-scale production.
In order to solve the above technical problems, the inventors of the present invention have found through research that the layered metal chalcogenide has poor electrochemical hydrogen evolution performance because basal planes of the layered metal chalcogenide are substantially inert during hydrogen evolution, only active sites located at edges have catalytic activity, and transition efficiency of electrons between nanosheets of the metal chalcogenide is low.
In view of the above problems, the inventors of the present invention have originally created a large number of sulfur/selenium vacancies on the basal plane of a metal chalcogenide nanosheet by two steps of electrochemical intercalation and electrochemical etching, resulting in defect-rich modified metal chalcogenide (modified metal sulfide/selenide) nanosheets directly from the bulk metal chalcogenide crystal. The creation of the sulfur/selenium vacancy greatly increases the number of active sites of the metal chalcogenide nanosheet and improves the electrocatalytic hydrogen evolution performance of the metal chalcogenide nanosheet catalyst. In addition, the preparation method is simple and environment-friendly because high-temperature and high-pressure treatment is not needed, and the preparation method has the condition of large-scale commercial preparation.
Specifically, the invention provides a preparation method of a modified metal chalcogenide nanosheet, which is characterized by comprising the steps of sequentially carrying out electrochemical intercalation treatment and electrochemical etching treatment on a metal chalcogenide; wherein the metal element in the metal chalcogenide is a transition metal element and/or a group IV metal element; the intercalation agent used in the electrochemical intercalation treatment is alkyl ammonium halide.
Preferably, the chalcogen in the metal chalcogenide is sulfur and/or selenium.
More preferably, the metal chalcogenide is one or more selected from the group consisting of molybdenum disulfide, tungsten disulfide, rhenium disulfide, niobium disulfide, tin disulfide, molybdenum diselenide, tungsten diselenide, rhenium diselenide, niobium diselenide, and tin diselenide.
Preferably, the alkylammonium halide is a tetraalkylammonium halide.
More preferably, the alkyl ammonium halide is one or more of tetramethyl ammonium bromide, tetraethyl ammonium bromide, tetrapropyl ammonium bromide, tetrabutyl ammonium bromide, tetraheptyl ammonium bromide, tetramethyl ammonium chloride, tetraethyl ammonium chloride, tetrapropyl ammonium chloride, tetrabutyl ammonium chloride and tetraheptyl ammonium chloride.
Preferably, in the electrochemical intercalation process, a metal chalcogenide is used as the cathode and an inert electrode is used as the anode.
Preferably, the conditions of the electrochemical intercalation process include: the applied voltage is 0.01-100V, preferably 1-50V, and the intercalation time is 1 min-72 h.
Preferably, the electrolyte used in the electrochemical intercalation treatment is one or more selected from alcohol solvents, nitrile solvents and halogenated hydrocarbon solvents, and more preferably one or more selected from ethanol, propanol, butanol, acetonitrile, propionitrile and carbon tetrachloride.
Preferably, in the electrochemical etching treatment, a product obtained by the electrochemical intercalation treatment is used as a cathode, and an inert electrode is used as an anode.
Preferably, the conditions of the electrochemical etching treatment include: the etching voltage is 0.01-100V, preferably 1-50V, and the etching time is 1 min-72 h.
Preferably, the electrolyte used in the electrochemical etching treatment is one or more selected from a sulfuric acid solution, a perchloric acid solution, and a hypochlorous acid solution.
Preferably, the concentration of the electrolyte used in the electrochemical etching treatment is 0.01-15M.
Preferably, the modified metal chalcogenide nanosheets have a thickness of 1-100nm and a lateral dimension of 1nm-100 μm;
preferably, the thickness of the metal chalcogenide material used is 1 μm or more, preferably 1mm or more, and the lateral dimension is 1cm or more, preferably 1 to 10 cm.
Preferably, the starting material of the metal chalcogenide used is a metal chalcogenide crystal.
Preferably, after the electrochemical intercalation treatment, a cleaning treatment is performed, and then the electrochemical etching treatment is performed.
Preferably, after the electrochemical etching treatment, ultrasonic treatment and solid-liquid separation are sequentially performed to obtain the modified metal chalcogenide nanosheet.
The second aspect of the present invention provides a modified metal chalcogenide nanosheet prepared according to the preparation method of the present invention described above.
A third aspect of the present invention provides the use of the above-described modified metal chalcogenide nanosheet of the present invention for a hydrogen evolution electrocatalyst.
Through the technical scheme, compared with the prior art, the invention has the beneficial effects that: after the electrochemical two-step method disclosed by the invention is used for processing, a vacancy is generated on a relatively inert basal plane, the number of active sites of the modified metal chalcogenide nanosheet is greatly increased by creating the vacancy, and the electro-catalytic hydrogen evolution performance of the modified metal chalcogenide nanosheet catalyst is improved.
The modified metal chalcogenide nanosheet prepared by the method has high catalytic activity, can be prepared at normal temperature and normal pressure, saves energy, is simple in equipment, safe and environment-friendly, wide in raw material source and low in cost, can be prepared in large scale, is beneficial to large-scale industrial production, and has considerable technical transformation prospect.
Drawings
Fig. 1 is a schematic flow diagram of a method of preparing a modified metal chalcogenide nanoplate of the present invention.
Figure 2 shows the raw material molybdenum disulfide crystals used in example 1 (left) and the electrochemically intercalated molybdenum disulfide material (right).
Fig. 3 is a TEM spectrum of the modified molybdenum disulfide nanosheet prepared in example 1.
FIG. 4 is an AFM spectrum of the modified molybdenum disulfide nanosheet prepared in example 1.
Fig. 5 is a catalytic performance diagram of an electrocatalytic hydrogen evolution reaction of the modified molybdenum disulfide nanosheet prepared in example 1.
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
The invention provides a preparation method of a modified metal chalcogenide nanosheet, which comprises the steps of sequentially carrying out electrochemical intercalation treatment and electrochemical etching treatment on a metal chalcogenide; wherein the metal element in the metal chalcogenide is a transition metal element and/or a group IV metal element; the intercalation agent used in the electrochemical intercalation treatment is alkyl ammonium halide.
In the preparation method of the present invention, the chalcogen in the metal chalcogenide may be sulfur and/or selenium, that is, the metal chalcogenide is a sulfide and/or selenide of a metal. The metal element in the metal chalcogenide may be a transition metal element such as molybdenum, tungsten, rhenium, niobium, palladium, rhodium, and/or a group IV metal element such as tin, germanium, lead, and preferably tin. As a specific metal chalcogenide, one or more selected from molybdenum disulfide, tungsten disulfide, rhenium disulfide, niobium disulfide, tin disulfide, molybdenum diselenide, tungsten diselenide, rhenium diselenide, niobium diselenide, and tin diselenide may be preferably used.
According to the preparation method, the interlayer spacing of the metal chalcogenide with larger size is increased by electrochemical intercalation treatment, so that the expanded metal chalcogenide is formed, and the lamellar modified metal chalcogenide nanosheet is convenient to obtain.
As a method of electrochemical intercalation treatment, it is necessary to use alkylammonium halide as an intercalating agent. As a specific alkyl ammonium halide, one or more of alkyl ammonium chloride, alkyl ammonium bromide, and alkyl ammonium iodide may be mentioned. The alkyl ammonium halide is preferably tetraalkyl ammonium halide, wherein the alkyl group can be one or more of methyl, ethyl, propyl, butyl, pentyl and hexyl. Preferably, the alkyl ammonium halide is one or more of tetramethyl ammonium bromide, tetraethyl ammonium bromide, tetrapropyl ammonium bromide, tetrabutyl ammonium bromide, tetraheptyl ammonium bromide, tetramethyl ammonium chloride, tetraethyl ammonium chloride, tetrapropyl ammonium chloride, tetrabutyl ammonium chloride and tetraheptyl ammonium chloride.
In the electrochemical intercalation process, a metal chalcogenide is used as the cathode and an inert electrode is used as the anode. The inert electrode may be, for example, a Pt electrode, a graphite electrode, a platinum carbon electrode, a gold electrode, or the like. The electrolyte used in the electrochemical intercalation treatment can be one or more selected from alcohol solvents, nitrile solvents and halogenated hydrocarbon solvents, such as alcohols of C1-C6, nitriles of C1-C4 and/or halogenated hydrocarbons of C1-C4, and specifically can be one or more selected from ethanol, propanol, butanol, acetonitrile, propionitrile and carbon tetrachloride. In order to improve the effect and efficiency of the electrochemical intercalation process, the conditions of the electrochemical intercalation process may include: the applied voltage is 0.01-100V, preferably 1-50V, more preferably 5-10V, and the intercalation time is 1 min-72 h, preferably 10 min-10 h, more preferably 20 min-2 h. Specifically, the applied voltage may be 0.01V, 0.5V, 1V, 2V, 4V, 5V, 8V, 10V, 16V, 20V, 32V, 50V, 64V, or 100V; the intercalation time may be 1min, 30min, 60min, 1h, 2h, 3h, 6h, 10h, 24h, 50h or 72 h.
According to the preparation method of the invention, after the electrochemical intercalation treatment, a cleaning treatment is preferably carried out, and then the electrochemical etching treatment is carried out. The intercalation agent in the product can be removed through the cleaning treatment, thereby being beneficial to the implementation of the electrochemical etching treatment. The washing treatment may be performed using absolute ethanol, absolute propanol, acetone, isopropanol, or the like. The washing treatment may be carried out once or more, preferably 3 to 5 times, for securing washing.
According to the preparation method of the invention, the product obtained by electrochemical intercalation treatment is subjected to electrochemical etching treatment so as to form etching defects, namely chalcogen vacancies (such as sulfur vacancies and selenium vacancies).
In the electrochemical etching treatment, a product obtained by the electrochemical intercalation treatment is used as a cathode, and an inert electrode is used as an anode. The inert electrode may be, for example, a Pt electrode, a graphite electrode, a platinum carbon electrode, a gold electrode, or the like. The electrolyte used in the electrochemical etching treatment may be one or more selected from a sulfuric acid solution, a perchloric acid solution and hypochlorous acid in a hypochlorous acid solution, and preferably, the electrolyte used in the electrochemical etching treatment has a concentration of 0.01 to 15M, more preferably, a sulfuric acid solution has a concentration of 0.01 to 10M, more preferably, a perchloric acid solution has a concentration of 0.01 to 10M, and more preferably, a hypochloric acid solution has a concentration of 0.01 to 5M.
In order to improve the effect and efficiency of the electrochemical etching treatment, preferably, the conditions of the electrochemical etching treatment include: the etching voltage is 0.01-100V, preferably 1-50V, more preferably 1-2.5V; the etching time is 1min to 72h, preferably 10min to 10h, and more preferably 20min to 2 h. Specifically, the etching voltage may be 0.01V, 0.5V, 1V, 2V, 4V, 5V, 8V, 10V, 16V, 20V, 32V, 50V, 64V, or 100V; the etching time can be 1min, 30min, 60min, 1h, 2h, 3h, 6h, 10h, 24h, 50h or 72 h. By appropriate adjustment of the voltage in the electrochemical etching process, a maximum concentration of chalcogen vacancies (e.g., sulfur vacancies, selenium vacancies) of up to 30%, preferably 5-15%, can be achieved.
According to the preparation method, after the electrochemical etching treatment, ultrasonic treatment and solid-liquid separation are sequentially carried out, so that the modified metal chalcogenide nanosheet is obtained. The conditions of the sonication may include: the power is 100-. The method of solid-liquid separation may be centrifugation, filtration, or the like, as long as the obtained modified metal chalcogenide nanosheet can be separated. Wherein centrifugation is preferable, and the centrifugation conditions may be, for example, 2000-. By matching ultrasonic treatment and solid-liquid separation, impurities in the prepared modified metal chalcogenide nanosheet can be further removed, and the modified metal chalcogenide nanosheet with higher purity can be obtained.
In the present invention, the electrochemical intercalation process and the electrochemical etching process may be performed using an electrolytic cell.
The modified metal chalcogenide prepared by the preparation method is lamellar, namely the modified metal chalcogenide nanosheet. Preferably, the nanoplatelets have a thickness of 1-100nm, preferably 2-10nm, and a lateral dimension of 1nm-100 μm, preferably 500nm-2 μm. By forming the nanosheets having an atomic-scale thickness and a relatively large lateral dimension, the prepared modified metal chalcogenide nanosheets can be more advantageously applied.
In the production method of the present invention, the metal chalcogenide material used is preferably a metal chalcogenide crystal, and specifically may be a natural metal chalcogenide crystal or an artificially synthesized metal chalcogenide crystal. In order to obtain a modified metal chalcogenide nanosheet of the above-described size, the thickness of the starting material of the metal chalcogenide used is preferably 1 μm or more, more preferably 1mm or more, for example 1 to 10mm, and the lateral dimension is preferably 1cm or more, more preferably 1 to 10 cm.
In the present invention, "lateral dimension" refers to the largest dimension perpendicular to the thickness direction.
The second aspect of the present invention provides a modified metal chalcogenide nanosheet prepared according to the preparation method of the present invention described above. In the modified metal chalcogenide nanosheets, the maximum concentration of chalcogen vacancies (e.g., sulfur vacancies, selenium vacancies) can be up to 30%, preferably 5-15%.
In a third aspect, the present invention provides the use of the modified metal chalcogenide nanosheets described above in the present invention for a hydrogen evolution electrocatalyst. The modified metal chalcogenide nanosheets prepared by the method of the invention increase the number of active sites thereof, thereby improving the electrocatalytic hydrogen evolution performance thereof.
The present invention will be described in detail below by way of examples. In the following examples, the TEM used was JEM-1011 type from Japan Electron corporation, and the AFM was MM8 type from Bruker corporation.
Example 1
A large piece of flaky molybdenum disulfide crystal (about 1mm in thickness, about 1cm in transverse dimension, same in size as shown in the left diagram in fig. 2) was fixed at the cathode of a two-electrode electrolytic cell, and electrochemical intercalation treatment of step 1 shown in fig. 1 was performed using a graphite rod as the anode and an acetonitrile solution of tetramethylammonium bromide as the electrolyte. The applied voltage was set at 5V and the reaction time lasted 60 min. During the intercalation reaction, tetramethylammonium bromide cation enters the gaps of the molybdenum disulfide crystals under the driving of negative potential, which causes the spacing between the molybdenum disulfide crystal layers to be enlarged and the volume to be expanded violently (as shown in the right diagram in fig. 2). After the treatment was completed, the expanded molybdenum disulfide crystals were washed 3 times with anhydrous ethanol to remove residual tetramethylammonium bromide.
The expanded molybdenum disulfide crystals were fixed to the cathode of a two-electrode electrolytic cell, using a graphite rod as the anode and a 0.5M sulfuric acid solution as the electrolyte for the desulfurization reaction, and subjected to electrochemical etching treatment as shown in step 2 in fig. 1. Setting the applied voltage to be 1.0V, keeping the reaction time for 60min, and after the reaction is finished, carrying out ultrasonic treatment (400W, 60min, the same below) and centrifugal treatment (3000rpm, 3min, the same below) to obtain the modified molybdenum disulfide nanosheet A1.
A high-resolution projection electron microscope image of the modified molybdenum disulfide nanosheet a1 prepared in this example is shown in fig. 3, and as can be clearly seen from fig. 3, after molybdenum disulfide is electrochemically desulfurized, a large number of sulfur vacancy defects are introduced on a basal plane of molybdenum disulfide, and these defects can be used as active sites in an electrocatalytic hydrogen evolution reaction of molybdenum disulfide; the electrocatalytic hydrogen evolution performance is shown in fig. 4, and it can be seen from fig. 4 that the catalytic performance of the molybdenum disulfide is greatly improved after the molybdenum disulfide is modified.
Example 2
The large flaky molybdenum disulfide crystal is fixed on the cathode of the double-electrode electrolytic cell, and the graphite rod is used as the anode. And (3) performing electrochemical intercalation treatment by using acetonitrile solution of tetramethyl ammonium bromide as electrolyte. The applied voltage was set at 10V and the reaction time lasted 60 min. In the intercalation reaction process, the spacing of the molybdenum disulfide crystal layers is increased, and the volume is expanded violently. After the treatment was completed, the expanded molybdenum disulfide crystals were washed 3 times with anhydrous ethanol.
And fixing the expanded molybdenum disulfide crystal on the cathode of a double-electrode electrolytic cell, using a graphite rod as an anode, and using 2M sulfuric acid solution as electrolyte to perform electrochemical etching treatment. Setting the applied voltage to be 2.5V, keeping the reaction time for 60min, and after the reaction is finished, carrying out ultrasonic treatment and centrifugal treatment to obtain the modified molybdenum disulfide nanosheet A2.
The TEM spectrogram and the AFM spectrogram of the modified molybdenum disulfide nanosheet A2 show similar characteristics to those of example 1, and a large number of sulfur vacancy defects are formed on the basal plane of molybdenum disulfide and serve as active sites in the electrocatalytic hydrogen evolution reaction, so that the modified molybdenum disulfide nanosheet has good electrocatalytic hydrogen evolution performance.
Example 3
The large flaky tungsten disulfide crystal is fixed on the cathode of the double-electrode electrolytic cell, and the graphite rod is used as the anode. Electrochemical intercalation treatment is carried out by using propionitrile solution of tetramethyl ammonium bromide as electrolyte. The applied voltage was set at 5V and the reaction time lasted 60 min. In the intercalation reaction process, the spacing between tungsten disulfide crystal layers is increased, and the volume is expanded violently. After the treatment was completed, the expanded tungsten disulfide crystals were washed 3 times with anhydrous ethanol.
The expanded tungsten disulfide crystal is fixed on the cathode of a double-electrode electrolytic cell, a graphite rod is used as an anode, and 0.5M sulfuric acid solution is used as electrolyte to carry out electrochemical etching treatment. Setting the applied voltage to be 1.0V, keeping the reaction time for 60min, and after the reaction is finished, carrying out ultrasonic treatment and centrifugal treatment to obtain the modified tungsten disulfide nanosheet A3.
The TEM spectrogram and the AFM spectrogram of the modified tungsten disulfide nanosheet A3 show similar characteristics to those of example 1, and a large number of sulfur vacancy defects are formed on the basal plane of tungsten disulfide and serve as active sites in the electrocatalytic hydrogen evolution reaction, so that the modified tungsten disulfide nanosheet has good electrocatalytic hydrogen evolution performance.
Example 4
The bulk flaky tungsten disulfide crystal is fixed at the cathode of a double-electrode electrolytic cell, a graphite rod is used as an anode, and propionitrile solution of tetramethyl ammonium bromide is used as electrolyte to carry out electrochemical intercalation treatment. The applied voltage was set at 10V and the reaction time lasted 60 min. In the intercalation reaction process, the spacing between tungsten disulfide crystal layers is increased, and the volume is expanded violently. After the treatment was completed, the expanded tungsten disulfide crystals were washed 3 times with anhydrous ethanol.
The expanded tungsten disulfide crystal is fixed on the cathode of a double-electrode electrolytic cell, a graphite rod is used as an anode, and 0.5M sulfuric acid solution is used as electrolyte to carry out electrochemical etching treatment. Setting the applied voltage to be 2.5V, keeping the reaction time for 60min, and after the reaction is finished, carrying out ultrasonic treatment and centrifugal treatment to obtain the modified tungsten disulfide nanosheet A4.
The TEM spectrogram and the AFM spectrogram of the modified tungsten disulfide nanosheet A4 show similar characteristics to those of example 1, and a large number of sulfur vacancy defects are formed on the basal plane of tungsten disulfide and serve as active sites in the electrocatalytic hydrogen evolution reaction, so that the modified tungsten disulfide nanosheet has good electrocatalytic hydrogen evolution performance.
Example 5
The bulk flaky molybdenum diselenide crystal is fixed at the cathode of a double-electrode electrolytic cell, a graphite rod is used as an anode, and a carbon tetrachloride solution of tetramethyl ammonium bromide is used as an electrolyte to carry out electrochemical intercalation treatment. The applied voltage was set at 5V and the reaction time lasted 60 min. In the intercalation process, the spacing between the molybdenum diselenide crystal layers is increased, and the volume is expanded violently. After the treatment, the expanded molybdenum diselenide crystals were washed 3 times with anhydrous ethanol.
The expanded molybdenum diselenide crystal is fixed on the cathode of a double-electrode electrolytic cell, a graphite rod is used as an anode, and 0.5M sulfuric acid solution is used as electrolyte to carry out electrochemical etching treatment. Setting the applied voltage to be 1.0V, keeping the reaction time for 60min, and after the reaction is finished, carrying out ultrasonic treatment and centrifugal treatment to obtain the modified molybdenum diselenide nanosheet A5.
The TEM spectrogram and the AFM spectrogram of the modified molybdenum diselenide nanosheet A5 show the characteristics similar to those of example 1, and a large number of selenium vacancy defects are formed on the basal plane of molybdenum diselenide and serve as active sites in the electrocatalytic hydrogen evolution reaction, so that the modified molybdenum diselenide nanosheet has good electrocatalytic hydrogen evolution performance.
Example 6
The bulk flaky molybdenum diselenide crystal is fixed at the cathode of a double-electrode electrolytic cell, a graphite rod is used as an anode, and propanol solution of tetramethyl ammonium bromide is used as electrolyte to carry out electrochemical intercalation treatment. The applied voltage was set at 10V and the reaction time lasted 60 min. In the intercalation process, the spacing between the molybdenum diselenide crystal layers is increased, and the volume is expanded violently. After the treatment, the expanded molybdenum diselenide crystals were washed 3 times with anhydrous ethanol.
The expanded molybdenum diselenide crystal is fixed on the cathode of a double-electrode electrolytic cell, a graphite rod is used as an anode, and 0.5M sulfuric acid solution is used as electrolyte to carry out electrochemical etching treatment. Setting the applied voltage to be 2.5V, keeping the reaction time for 60min, and after the reaction is finished, carrying out ultrasonic treatment and centrifugal treatment to obtain the modified molybdenum diselenide nanosheet A6.
The TEM spectrogram and the AFM spectrogram of the modified molybdenum diselenide nanosheet A6 show the characteristics similar to those of example 1, and a large number of selenium vacancy defects are formed on the basal plane of molybdenum diselenide and serve as active sites in the electrocatalytic hydrogen evolution reaction, so that the modified molybdenum diselenide nanosheet has good electrocatalytic hydrogen evolution performance.
Example 7
The bulk flaky tungsten diselenide crystal is fixed at the cathode of a double-electrode electrolytic cell, a graphite rod is used as an anode, and butanol solution of tetramethyl ammonium bromide is used as electrolyte to carry out electrochemical intercalation treatment. The applied voltage was set at 5V and the reaction time lasted 60 min. In the intercalation reaction process, the spacing of the tungsten diselenide crystal layers is increased, and the volume is expanded violently. After the treatment, the expanded tungsten diselenide crystal was washed 3 times with anhydrous ethanol.
The expanded tungsten diselenide crystal is fixed on the cathode of a double-electrode electrolytic cell, a graphite rod is used as an anode, and 0.5M sulfuric acid solution is used as electrolyte to carry out electrochemical etching treatment. Setting the applied voltage to be 1.0V, keeping the reaction time for 60min, and after the reaction is finished, carrying out ultrasonic treatment and centrifugal treatment to obtain the modified tungsten diselenide nanosheet A7.
The TEM spectrogram and the AFM spectrogram of the modified tungsten diselenide nanosheet A7 show the characteristics similar to those of example 1, and a large number of selenium vacancy defects are formed on the basal plane of tungsten diselenide and serve as active sites in the electrocatalytic hydrogen evolution reaction, so that the modified tungsten diselenide nanosheet has good electrocatalytic hydrogen evolution performance.
Example 8
The bulk flaky tungsten diselenide crystal is fixed at the cathode of a double-electrode electrolytic cell, a graphite rod is used as an anode, and acetonitrile solution of tetramethyl ammonium bromide is used as electrolyte to carry out electrochemical intercalation treatment. The applied voltage was set at 10V and the reaction time lasted 60 min. In the intercalation reaction process, the spacing of the tungsten diselenide crystal layers is increased, and the volume is expanded violently. After the treatment, the expanded tungsten diselenide crystal was washed 3 times with anhydrous ethanol.
The expanded tungsten diselenide crystal is fixed on the cathode of a double-electrode electrolytic cell, a graphite rod is used as an anode, and 0.5M sulfuric acid solution is used as electrolyte to carry out electrochemical etching treatment. Setting the applied voltage to be 2.5V, keeping the reaction time for 60min, and after the reaction is finished, carrying out ultrasonic treatment and centrifugal treatment to obtain the modified tungsten diselenide nanosheet A8.
The TEM spectrogram and the AFM spectrogram of the modified tungsten diselenide nanosheet A8 show the characteristics similar to those of example 1, and a large number of selenium vacancy defects are formed on the basal plane of tungsten diselenide and serve as active sites in the electrocatalytic hydrogen evolution reaction, so that the modified tungsten diselenide nanosheet has good electrocatalytic hydrogen evolution performance.
Example 9
The bulk flaky rhenium disulfide crystal is fixed on the cathode of a double-electrode electrolytic cell, a graphite rod is used as an anode, and an acetonitrile solution of tetraethylammonium bromide is used as an electrolyte to carry out electrochemical intercalation treatment. The applied voltage was set at 5V and the reaction time lasted 60 min. During the intercalation reaction, the spacing between the crystal layers of the rhenium disulfide is enlarged, and the volume is expanded violently. After the treatment is completed, the expanded rhenium disulfide crystals are washed 3 times with anhydrous ethanol.
The expanded rhenium disulfide crystal was fixed to the cathode of a two-electrode electrolytic cell, using a graphite rod as the anode, and 0.5M sulfuric acid solution as the electrolyte for electrochemical etching treatment. Setting the applied voltage to be 1.0V, keeping the reaction time for 60min, and after the reaction is finished, carrying out ultrasonic treatment and centrifugal treatment to obtain the modified rhenium disulfide nanosheet A9.
The TEM spectrogram and the AFM spectrogram of the modified rhenium disulfide nanosheet A9 show similar characteristics to those of example 1, and a large number of sulfur vacancy defects are formed on the basal plane of rhenium disulfide and serve as active sites in the electrocatalytic hydrogen evolution reaction, so that the modified rhenium disulfide nanosheet has good electrocatalytic hydrogen evolution performance.
Example 10
The bulk flaky niobium disulfide crystal is fixed at the cathode of a double-electrode electrolytic cell, a graphite rod is used as an anode, and acetonitrile solution of tetrapropyl ammonium bromide is used as electrolyte to carry out electrochemical intercalation treatment. The applied voltage was set at 10V and the reaction time lasted 60 min. In the intercalation reaction process, the spacing of the niobium disulfide crystal layer is increased, and the volume is expanded violently. After the treatment is completed, the expanded niobium disulfide crystals are washed 3 times with absolute ethanol.
The expanded niobium disulfide crystal is fixed on the cathode of a double-electrode electrolytic cell, a graphite rod is used as an anode, and 0.5M sulfuric acid solution is used as electrolyte to carry out electrochemical etching treatment. Setting the applied voltage to be 2.5V, keeping the reaction time for 60min, and after the reaction is finished, carrying out ultrasonic treatment and centrifugal treatment to obtain the modified niobium disulfide nanosheet A10.
The TEM spectrogram and the AFM spectrogram of the modified niobium disulfide nanosheet A10 show similar characteristics to those of example 1, and a large number of sulfur vacancy defects are formed on the basal plane of the niobium disulfide as active sites in the electrocatalytic hydrogen evolution reaction, so that the modified niobium disulfide nanosheet has good electrocatalytic hydrogen evolution performance.
Example 11
The bulk flaky tin disulfide crystal is fixed at the cathode of a double-electrode electrolytic cell, a graphite rod is used as an anode, and acetonitrile solution of tetrabutylammonium bromide is used as electrolyte to carry out electrochemical intercalation treatment. The applied voltage was set at 5V and the reaction time lasted 60 min. In the intercalation reaction process, the spacing between the tin disulfide crystal layers is increased, and the volume is expanded violently. After the treatment is completed, the expanded tin disulfide crystals are washed 3 times with absolute ethanol.
The expanded tin disulfide crystal was fixed to the cathode of a two-electrode electrolytic cell, using a graphite rod as the anode, and 0.5M sulfuric acid solution as the electrolyte for electrochemical etching treatment. Setting the applied voltage to be 1.0V, keeping the reaction time for 60min, and after the reaction is finished, carrying out ultrasonic treatment and centrifugal treatment to obtain the modified tin disulfide nanosheet A11.
The TEM spectrum and the AFM spectrum of the modified tin disulfide nanosheet A11 show similar characteristics to those of example 1, and a large number of sulfur vacancy defects are formed on the basal plane of the tin disulfide and serve as active sites in the electrocatalytic hydrogen evolution reaction, so that the modified tin disulfide nanosheet has good electrocatalytic hydrogen evolution performance.
Example 12
The bulk flaky tin disulfide crystal is fixed at the cathode of a double-electrode electrolytic cell, a graphite rod is used as an anode, and acetonitrile solution of tetraheptyl ammonium bromide is used as electrolyte to carry out electrochemical intercalation treatment. The applied voltage was set at 10V and the reaction time lasted 60 min. In the intercalation reaction process, the spacing between the tin disulfide crystal layers is increased, and the volume is expanded violently. After the treatment is completed, the expanded tin disulfide crystals are washed 3 times with absolute ethanol.
The expanded tin disulfide crystal was fixed to the cathode of a two-electrode electrolytic cell, using a graphite rod as the anode, and 0.5M sulfuric acid solution as the electrolyte for electrochemical etching treatment. Setting the applied voltage to be 2.5V, keeping the reaction time for 60min, and after the reaction is finished, carrying out ultrasonic treatment and centrifugal treatment to obtain the modified tin disulfide nanosheet A12.
The TEM spectrum and the AFM spectrum of the modified tin disulfide nanosheet A12 show similar characteristics to those of example 1, and a large number of sulfur vacancy defects are formed on the basal plane of the tin disulfide and serve as active sites in the electrocatalytic hydrogen evolution reaction, so that the modified tin disulfide nanosheet has good electrocatalytic hydrogen evolution performance.
Example 13
The bulk flaky tungsten diselenide crystal is fixed at the cathode of a double-electrode electrolytic cell, a graphite rod is used as an anode, and acetonitrile solution of tetramethyl ammonium bromide is used as electrolyte to carry out electrochemical intercalation treatment. The applied voltage was set at 5V and the reaction time lasted 60 min. In the intercalation reaction process, the spacing of the tungsten diselenide crystal layers is increased, and the volume is expanded violently. After the treatment, the expanded tungsten diselenide crystal was washed 3 times with anhydrous ethanol.
The expanded tungsten diselenide crystal is fixed on the cathode of a double-electrode electrolytic cell, a graphite rod is used as an anode, and 0.05M perchloric acid solution is used as electrolyte to carry out electrochemical etching treatment. Setting the applied voltage to be 1.0V, keeping the reaction time for 60min, and after the reaction is finished, carrying out ultrasonic treatment and centrifugal treatment to obtain the modified tungsten diselenide nanosheet A13.
The TEM spectrogram and the AFM spectrogram of the modified tungsten diselenide nanosheet A13 show the characteristics similar to those of example 1, and a large number of selenium vacancy defects are formed on the basal plane of tungsten diselenide and serve as active sites in the electrocatalytic hydrogen evolution reaction, so that the modified tungsten diselenide nanosheet has good electrocatalytic hydrogen evolution performance.
Example 14
The bulk flaky rhenium diselenide crystal is fixed at the cathode of a double-electrode electrolytic cell, a graphite rod is used as an anode, and acetonitrile solution of tetramethyl ammonium bromide is used as electrolyte to carry out electrochemical intercalation treatment. The applied voltage was set at 10V and the reaction time lasted 60 min. During the intercalation reaction, the spacing between the rhenium diselenide crystal layers is increased, and the volume is expanded violently. After the treatment was completed, the expanded rhenium diselenide crystals were washed 3 times with anhydrous ethanol.
The expanded rhenium diselenide crystal is fixed on the cathode of a double-electrode electrolytic cell, a graphite rod is used as an anode, and 5M perchloric acid solution is used as electrolyte to carry out electrochemical etching treatment. Setting the applied voltage to be 2.5V, keeping the reaction time for 60min, and after the reaction is finished, carrying out ultrasonic treatment and centrifugal treatment to obtain the modified rhenium diselenide nanosheet A14.
The TEM spectrogram and the AFM spectrogram of the modified rhenium diselenide nanosheet A14 show similar characteristics to those of example 1, and a large number of selenium vacancy defects are formed on the basal plane of rhenium diselenide and serve as active sites in the electrocatalytic hydrogen evolution reaction, so that the modified rhenium diselenide nanosheet has good electrocatalytic hydrogen evolution performance.
Example 15
The bulk flaky tin diselenide crystal is fixed at the cathode of a double-electrode electrolytic cell, a graphite rod is used as an anode, and acetonitrile solution of tetramethyl ammonium bromide is used as electrolyte to carry out electrochemical intercalation treatment. The applied voltage was set at 5V and the reaction time lasted 120 min. In the intercalation reaction process, the spacing between tin diselenide crystal layers is increased, and the volume is expanded violently. After the treatment was completed, the expanded tin diselenide crystals were washed 3 times with anhydrous ethanol.
The expanded tin diselenide crystal is fixed on the cathode of a double-electrode electrolytic cell, a graphite rod is used as an anode, and 0.2M hypochlorous acid solution is used as electrolyte to carry out electrochemical etching treatment. Setting the applied voltage to be 1.0V, keeping the reaction time for 30min, and after the reaction is finished, carrying out ultrasonic treatment (500W, 40min) and centrifugal treatment (2000rpm, 8min) to obtain the modified tin diselenide nanosheet A15.
The TEM spectrogram and the AFM spectrogram of the modified tin diselenide nanosheet A15 show similar characteristics to those of example 1, and a large number of selenium vacancy defects are formed on the basal plane of tin diselenide and serve as active sites in the electrocatalytic hydrogen evolution reaction, so that the modified tin diselenide nanosheet has good electrocatalytic hydrogen evolution performance.
Example 16
The bulk flaky niobium diselenide crystal is fixed at the cathode of a double-electrode electrolytic cell, a graphite rod is used as an anode, and acetonitrile solution of tetramethyl ammonium bromide is used as electrolyte to carry out electrochemical intercalation treatment. The applied voltage was set at 10V and the reaction time lasted 30 min. In the intercalation reaction process, the spacing of the niobium diselenide crystal layers is increased, and the volume is expanded violently. After the treatment, the expanded niobium diselenide crystal was washed with anhydrous ethanol 3 times.
The expanded niobium diselenide crystal is fixed on the cathode of a double-electrode electrolytic cell, a graphite rod is used as an anode, and 1M hypochlorous acid solution is used as electrolyte to carry out electrochemical etching treatment. Setting the applied voltage to be 2.5V, keeping the reaction time for 120min, and after the reaction is finished, carrying out ultrasonic treatment (600W, 30min) and centrifugal treatment (5000rpm, 2min) to obtain the modified niobium diselenide nanosheet A16.
The TEM spectrogram and the AFM spectrogram of the modified niobium diselenide nanosheet A16 show similar characteristics to those of example 1, and a large number of selenium vacancy defects are formed on the basal plane of the niobium diselenide to serve as active sites in the electrocatalytic hydrogen evolution reaction, so that the niobium diselenide nanosheet has good electrocatalytic hydrogen evolution performance.
Comparative example 1
Modified molybdenum disulfide nanosheets prepared according to the method of example 1, except that instead of electrochemical intercalation, flaking of the molybdenum disulfide was carried out by ultrasonic exfoliation (600W, 60 min).
The TEM spectrogram and the AFM spectrogram of the modified molybdenum disulfide nanosheet show that the modified molybdenum disulfide nanosheet is large in thickness, large in layer number, small in layer spacing of molybdenum disulfide, poor in electrochemical etching effect and small in number of sulfur vacancies, and therefore the electro-catalytic hydrogen evolution performance of the modified molybdenum disulfide nanosheet is poor.
Comparative example 2
Modified molybdenum disulfide nanoplates prepared according to the method of example 1, except that no electrochemical etching treatment was performed.
The TEM spectrogram and the AFM spectrogram of the modified molybdenum disulfide nanosheet show that the thickness and the number of layers of the modified molybdenum disulfide nanosheet are basically the same as those of the modified molybdenum disulfide nanosheet prepared by the method in example 1, but the existence of sulfur vacancies is difficult to observe, which indicates that the electrocatalytic hydrogen evolution performance of the modified molybdenum disulfide nanosheet is poor.
Test example
An electrochemical functional test of the modified molybdenum disulfide nanosheet catalyst prepared in example 1 was performed by using an electrochemical workstation (Autolab PGSTAT302N), and the test result is shown in fig. 5.
And (3) testing the performance of the catalyst: with 0.5M sulfuric acid solution (H)2SO4) As an electrolyte, a three-electrode EC cell was used. The graphite electrode and the Ag/AgCl electrode are respectively used as a counter electrode and a reference electrode. A working electrode was prepared by depositing a catalyst on a Glassy Carbon Electrode (GCE). First, 1mg of catalyst, 10. mu.L of Nafion solution was dissolved in 990. mu.L of water-isopropanol mixture (1: 3 volume ratio), and then 20. mu.L of catalyst ink was deposited on GCE and slowly dried at room temperature.
According to the modified molybdenum disulfide nanosheet, quaternary bromoammonium salt cations are inserted into molybdenum disulfide crystals through an electrochemical method, so that the interlayer spacing of the molybdenum disulfide crystals is increased, the volume of the molybdenum disulfide crystals is expanded, fluffy molybdenum disulfide crystals are obtained, then the fluffy molybdenum disulfide crystals are desulfurized through an electrochemical reduction method, and the modified molybdenum disulfide nanosheets which are uniform in size and rich in defects are obtained through ultrasonic stripping and centrifugal separation. By appropriate control of the voltage in the electrochemical etch, a maximum concentration of 30% sulfur vacancies can be achieved. As can be seen from FIG. 5, the catalytic activity of the desulfurized molybdenum disulfide nanosheet on the hydrogen evolution reaction is improved, the current density of the desulfurized molybdenum disulfide nanosheet at-1.0V (under-0.3V VS reversible hydrogen electrode) is 169% of that of the molybdenum disulfide nanosheet before desulfurization, and the Tafel slope is from 300mV dec-1Reduced to 136mV dec-1. The modified molybdenum disulfide nanosheet prepared by the method is proved to have greatly improved catalytic performance compared with the traditional molybdenum disulfide.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims (10)

1. A preparation method of a modified metal chalcogenide nanosheet is characterized by comprising the steps of sequentially carrying out electrochemical intercalation treatment and electrochemical etching treatment on a metal chalcogenide;
wherein the metal element in the metal chalcogenide is a transition metal element and/or a group IV metal element;
the intercalation agent used in the electrochemical intercalation treatment is alkyl ammonium halide.
2. The production method according to claim 1, wherein a chalcogen in the metal chalcogenide is sulfur and/or selenium;
preferably, the metal chalcogenide is one or more selected from the group consisting of molybdenum disulfide, tungsten disulfide, rhenium disulfide, niobium disulfide, tin disulfide, molybdenum diselenide, tungsten diselenide, rhenium diselenide, niobium diselenide, and tin diselenide.
3. The production method according to claim 1, wherein the alkylammonium halide is a tetraalkylammonium halide;
preferably, the alkyl ammonium halide is one or more of tetramethyl ammonium bromide, tetraethyl ammonium bromide, tetrapropyl ammonium bromide, tetrabutyl ammonium bromide, tetraheptyl ammonium bromide, tetramethyl ammonium chloride, tetraethyl ammonium chloride, tetrapropyl ammonium chloride, tetrabutyl ammonium chloride and tetraheptyl ammonium chloride.
4. The production method according to any one of claims 1 to 3, wherein in the electrochemical intercalation treatment, a metal chalcogenide is used as a cathode, and an inert electrode is used as an anode;
preferably, the conditions of the electrochemical intercalation process include: the applied voltage is 0.01-100V, preferably 1-50V, and the intercalation time is 1 min-72 h;
preferably, the electrolyte used in the electrochemical intercalation treatment is one or more selected from alcohol solvents, nitrile solvents and halogenated hydrocarbon solvents, and more preferably one or more selected from ethanol, propanol, butanol, acetonitrile, propionitrile and carbon tetrachloride.
5. The production method according to any one of claims 1 to 4, wherein in the electrochemical etching treatment, a product obtained by electrochemical intercalation treatment is used as a cathode, and an inert electrode is used as an anode;
preferably, the conditions of the electrochemical etching treatment include: the etching voltage is 0.01-100V, preferably 1-50V, and the etching time is 1 min-72 h.
6. The production method according to any one of claims 1 to 5, wherein the electrolytic solution used in the electrochemical etching treatment is one or more selected from a sulfuric acid solution, a perchloric acid solution, and a hypochlorous acid solution;
preferably, the concentration of the electrolyte used in the electrochemical etching treatment is 0.01-15M.
7. The production method according to any one of claims 1 to 6, wherein the modified metal chalcogenide nanosheet has a thickness of 1 to 100nm and a lateral dimension of 1nm to 100 μm;
preferably, the thickness of the starting material of the metal chalcogenide used is 1 μm or more, preferably 1mm or more, and the lateral dimension is 1cm or more, preferably 1 to 10 cm;
preferably, the starting material of the metal chalcogenide used is a metal chalcogenide crystal.
8. The preparation method according to any one of claims 1 to 7, wherein after the electrochemical intercalation treatment, a cleaning treatment is performed, and then the electrochemical etching treatment is performed;
preferably, after the electrochemical etching treatment, ultrasonic treatment and solid-liquid separation are sequentially performed to obtain the modified metal chalcogenide nanosheet.
9. Modified metal chalcogenide nanoplatelets prepared according to the preparation process of any one of claims 1 to 8.
10. Use of modified metal chalcogenide nanoplates as defined in claim 9 for hydrogen evolution electrocatalysts.
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