MoS2 / MoO x Heterogeneous nanosheets, their preparation methods and applications

Abstract

This invention discloses a MoS2 / MoO x Heterogeneous nanosheets, their preparation methods, and applications belong to the field of nanocatalyst technology. The preparation method of this invention includes two steps: (1) hydrothermal synthesis to prepare bulk MoS2; (2) oxidation reaction of the bulk MoS2 with hydrogen peroxide solution. The product prepared by this invention contains three-dimensional MoO. x The presence of [something] can improve the conductivity of MoS2, while MoO [something] can [something]. x It is also an active material, thus its catalytic activity can be improved. Furthermore, MoS2 also possesses the advantage of acid tolerance, making it suitable for use with MoO. x They provide protection. The two complement and reinforce each other. This invention prepares this heterogeneous compound MoS2 / MoO. x Good interfacial contact can improve charge transport and regulate the intrinsic activity of catalyst active sites, thus exhibiting good catalytic performance.

Description

Technical Field

[0001] This invention belongs to the field of nanocatalyst technology, specifically relating to a MoS2 / MoO2 catalyst. x Heterogeneous nanosheets, their preparation methods, and applications. Background Technology

[0002] Water electrolysis, as one of the industrial methods for producing hydrogen, is gradually replacing steam reforming, eliminating dependence on natural gas and reducing costs. Water electrolysis involves the electrolysis of water into hydrogen and oxygen under the influence of direct current. During the reaction, multiple electron transfers are involved, creating a kinetic energy barrier, commonly known as activation energy. This generates overpotential, negatively impacting the reaction. Furthermore, numerous side reactions occur, reducing Faraday efficiency and producing certain byproducts. These are issues that need to be addressed for the industrialization of water electrolysis.

[0003] In the process of producing hydrogen through water electrolysis, the key issue is the catalyst. A catalyst can lower the activation energy of water electrolysis, thereby reducing the overpotential and increasing the reaction rate and efficiency. Based on the different anode and cathode, catalysts can be categorized into hydrogen evolution catalysts and oxygen evolution catalysts.

[0004] Among transition metal alloys used in hydrogen evolution catalysts, noble Pt group elements exhibit excellent electrocatalytic activity. They also possess the advantage of low hydrogen overpotential; however, their high cost limits large-scale production. Observing hydrogen volcanoes reveals that MoS2 is an alternative, consisting of hexagonally arranged Mo and S atoms forming a graphene-like two-dimensional layered structure. The Mo planes are covalently bonded to two adjacent hexagonally arranged S atoms, resulting in S-Mo-S coupling. Weak van der Waals forces exist between the layers of MoS2. Simultaneously, the d-shell orbitals of the central Mo atom are not fully filled, giving it unique electron transport properties. These characteristics of molybdenum disulfide contribute to its good electrochemical catalytic performance. However, the low conductivity of MoS2 leads to poor charge transport and instability during electrochemical cycling, resulting in decreased catalytic performance.

[0005] Based on the above reasons, this application is hereby submitted. Summary of the Invention

[0006] Based on the above reasons, and in view of the problems or defects existing in the prior art, the purpose of this invention is to provide a MoS2 / MoO x Heterogeneous nanosheets, their preparation methods, and applications address or at least partially address the aforementioned technical deficiencies in the prior art.

[0007] To achieve one of the above-mentioned objectives of the present invention, the technical solution adopted by the present invention is as follows:

[0008] A MoS2 / MoO x A method for preparing heterogeneous nanosheets, the method specifically including the following steps:

[0009] (1) Thiourea, ammonium molybdate and ultrapure water are mixed according to the ratio and stirred to dissolve to obtain a mixed reaction solution; then the mixed reaction solution is transferred to a clean reaction vessel and heated to 120-180℃ for hydrothermal reaction for 20-30h; after the reaction is completed, it is naturally cooled to a lower temperature, the obtained product is filtered and dried to obtain blocky MoS2.

[0010] (2) At room temperature, the blocky MoS2 prepared in step (1) is mixed with hydrogen peroxide solution according to the specified ratio, and the mixture is stirred for 2-6 hours. After the reaction is completed, the mixture is filtered and dried to obtain the MoS2 / MoO2 / MoO2 / MoO2 / MoS ...S2 / MoO2 / MoS2 / MoS2 / x Heterogeneous nanosheets.

[0011] Furthermore, in the above technical solution, the ammonium molybdate mentioned in step (1) is ammonium molybdate or its hydrate, for example, it can be any one of ammonium molybdate trihydrate, ammonium molybdate tetrahydrate, etc.

[0012] Further, in the above technical solution, the molar ratio of thiourea to ammonium molybdate in step (1) is (10-20):1. If the thiourea content is too low, the reaction of ammonium molybdate cannot be guaranteed to be complete; if the thiourea content is too high, the molybdenum disulfide will be rich in defects, leading to sample instability, thicker nanosheets, and poorer conductivity. In a preferred embodiment of the present invention, the molar ratio of thiourea to ammonium molybdate tetrahydrate is 14:1.

[0013] Furthermore, in the above technical solution, the ratio of thiourea to ultrapure water in step (1) is 1 part by mass : (25-50) parts by volume, wherein the part by mass and the parts by volume are based on g:mL.

[0014] Furthermore, in the above technical solution, the temperature of the hydrothermal reaction in step (1) is preferably 150°C.

[0015] Furthermore, in the above technical solution, the hydrothermal reaction time in step (1) is preferably 24 hours.

[0016] Furthermore, in the above technical solution, the drying in step (1) is preferably carried out in an oven at 60°C for 10 hours.

[0017] Specifically, in the above technical solution, the normal temperature mentioned in step (2) refers to the natural room temperature conditions in all four seasons, without any additional cooling or heating treatment. The normal temperature is generally controlled at 10-30℃, preferably 15-25℃.

[0018] Furthermore, in the above technical solution, the concentration of the hydrogen peroxide solution in step (2) can be 0.1-1.0%, more preferably 0.2-0.4%, and more preferably 0.3%.

[0019] Furthermore, in the above technical solution, the ratio of the amount of blocky MoS2 to hydrogen peroxide solution in step (2) is 100 parts by mass: (10-30) parts by volume, wherein the ratio of parts by mass to parts by volume is based on mg:mL.

[0020] Furthermore, in the above technical solution, the stirring reaction time in step (2) is preferably 4 hours.

[0021] A second object of the present invention is to provide a MoS2 / MoO prepared by the method described above. x Heterogeneous nanosheets.

[0022] A third object of the present invention is to provide a MoS2 / MoO prepared by the method described above. x Application of heterogeneous nanosheets as catalysts in electrochemical hydrogen evolution reaction.

[0023] An electrochemical hydrogen evolution catalyst comprising MoS2 / MoO prepared by the method described above. x Heterogeneous nanosheets.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] This invention proposes a controlled oxidation method using hydrogen peroxide to prepare a MoS2 / MoO2 mixture. x Heterogeneous nanosheets are used for electrochemical hydrogen evolution. The original MoS2 exhibits poor catalytic performance due to its self-packing caused by weak interlayer interactions, high exposure of inactive substrate surfaces, and interfacial defects, leading to a decline in catalytic performance during cycling. In contrast, the three-dimensional MoO2 of this invention… x The presence of [something] can improve the conductivity of MoS2, while MoO [something] can [something]. x It is also an active material, thus its catalytic activity can be improved. Furthermore, MoS2 also possesses the advantage of acid tolerance, making it suitable for use with MoO. x They provide protection. The two complement and reinforce each other. This invention prepares this heterogeneous compound MoS2 / MoO. x Good interfacial contact can improve charge transport and regulate the intrinsic activity of catalyst active sites, thus exhibiting good catalytic performance. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This invention is for preparing MoS2 / MoO x Process flow diagram of heterogeneous nanosheets;

[0028] Figure 2 This is the MoS2 / MoO prepared in Example 1 of the present invention. x SEM image of the catalyst at -0.30;

[0029] Figure 3 The MoS2 / MoO prepared in Examples 1-4 of this invention x XRD pattern of heterogeneous nanosheet catalyst;

[0030] Figure 4 The following are the electrochemical characterization results of Pt / C catalysts modified with different hydrogen peroxide concentrations: (a) Polarization curves of Pt / C catalysts modified with different hydrogen peroxide concentrations; (b) Tafel plots of the polarization curves in Figure (a) after IR correction; (c) Electric double layer capacitance curves of catalysts modified with different hydrogen peroxide concentrations; (d) Impedance curves of catalysts modified with different hydrogen peroxide concentrations.

[0031] Figure 5 This is the MoS2 / MoO prepared in Example 1 of the present invention. x CA curve of the catalyst -0.30;

[0032] Figure 6 This is the MoS2 / MoO prepared in Example 1 of the present invention. x Cyclic stability curve of the catalyst -0.30 Detailed Implementation

[0033] The present invention will be further described in detail below through implementation examples. These implementation examples are carried out based on the technology of the present invention. Detailed implementation methods and specific operating procedures are provided to illustrate the inventiveness of the present invention, but the scope of protection of the present invention is not limited to the following implementation examples.

[0034] Based on the information contained in this application, various modifications to the precise description of the invention can be readily made by those skilled in the art. It should be understood that the scope of the invention is not limited to the defined processes, properties, or components, as these embodiments and other descriptions are merely illustrative of specific aspects of the invention.

[0035] To better understand the invention and not to limit its scope, all figures indicating amounts, percentages, and other numerical values ​​used in this application should, in all cases, be understood to be modified by the word "approximately." Therefore, unless otherwise stated, the numerical parameters listed in the specification are approximate values ​​and may vary depending on the desired properties being sought. Each numerical parameter should at least be considered as obtained based on reported significant figures and through conventional rounding methods.

[0036] The equipment and raw materials used in this invention are all commercially available or commonly used in the field. Unless otherwise specified, the methods in the following embodiments are conventional methods in the field.

[0037] Example 1

[0038] This embodiment describes a MoS2 / MoO2 x Heterogeneous nanosheets (MoS2 / MoO) x A method for preparing a 0.30 catalyst, the method specifically comprising the following steps:

[0039] (1) Take 1.0657g thiourea, 1.2359g ammonium molybdate, and 30mL ultrapure water into a clean 50ml beaker and dissolve them by ultrasonic stirring. After the solid is fully dissolved into a solution, transfer the solution into a clean reaction vessel (the reaction vessel needs to be washed with nitric acid before use). Set the oven temperature to 150℃ and the time to 24h for hydrothermal synthesis of molybdenum disulfide. After the reaction is completed, let the reaction vessel cool naturally to room temperature. Take out the product and filter it to obtain a black solid. Put it into a clean petri dish, seal it with plastic wrap, and dry it in a 60℃ oven for 10h to obtain blocky MoS2. Carefully transfer it into a mortar with a spatula and grind it into powder. Put it into a sample tube and label it for later use.

[0040] (2) Take a 100mL volumetric flask and prepare a 0.30% hydrogen peroxide deionized water solution. Take a clean 50mL beaker and add 200mg of the blocky MoS2 prepared in step (1) above and 30mL of the 0.30% hydrogen peroxide deionized water solution prepared above. Stir the resulting mixture for 4h. After stirring, filter the resulting product, dry it at 60℃ for 12h, label it and pack it for testing.

[0041] Example 2

[0042] This embodiment describes a MoS2 / MoO2 x Heterogeneous nanosheets (MoS2 / MoO) x The preparation method of the catalyst (-0.0) is basically the same as that in Example 1, except that the mass concentration of the hydrogen peroxide aqueous solution used in step (2) of this example is 0%.

[0043] Example 3

[0044] This embodiment describes a MoS2 / MoO2 x Heterogeneous nanosheets (MoS2 / MoO) x The preparation method of the catalyst (-0.20) is basically the same as that in Example 1, except that the mass concentration of the hydrogen peroxide aqueous solution used in step (2) of this example is 0.20%.

[0045] Example 4

[0046] This embodiment describes a MoS2 / MoO2 x Heterogeneous nanosheets (MoS2 / MoO) x The preparation method of the catalyst (-0.40) is basically the same as that in Example 1, except that the mass concentration of the hydrogen peroxide aqueous solution used in step (2) of this example is 0.40%.

[0047] Example 5

[0048] This embodiment describes a MoS2 / MoO2 x Heterogeneous nanosheets (MoS2 / MoO) x The preparation method of the catalyst (-120℃) is basically the same as that in Example 1, except that the temperature of the oven is set to 120℃ in step (1) of this example.

[0049] Example 6

[0050] This embodiment describes a MoS2 / MoO2 x Heterogeneous nanosheets (MoS2 / MoO) x The preparation method of the catalyst (-180℃) is basically the same as that in Example 1, except that the temperature of the oven is set to 180℃ in step (1) of this example.

[0051] Structural testing:

[0052] Figure 2 This is the MoS2 / MoO prepared in Example 1 of the present invention. x SEM image of the -0.30 catalyst. From Figure 2As we can see, the catalyst exhibits the morphological characteristics of nanoflower particles, which are formed by the tight stacking of multiple layers of nanosheets. Its edge wrinkles are clearly visible, and these wrinkles are discontinuous, providing a high edge exposure rate and reducing the proportion of inert basal surface exposure. Simultaneously, due to the corrosive effect of hydrogen peroxide, corrosion occurs on the catalyst surface, which also enhances the exposure of the catalyst's active sites and improves catalytic performance.

[0053] Figure 3 The MoS2 / MoO prepared in Examples 1-4 of this invention x XRD pattern of heterogeneous nanosheet catalyst. Figure 3 The figure provides detailed crystal information for catalysts with different oxidation concentrations. From the figure, we can see that the peak of molybdenum disulfide overlaps with the standard MoS2 (JCPDS 02-0132) XRD pattern. 2θ at 14.4, 33.0, 35.6, 44.4, and 58.4 corresponds to the crystal plane diffraction of the (002), (100), (102), (104), and (110) crystal planes of molybdenum disulfide, respectively. This indicates that we successfully prepared molybdenum disulfide material. The low diffraction intensity is due to the poor crystallinity produced by the hydrothermal method. However, the molybdenum oxide peak is difficult to observe. This may be because the prepared molybdenum oxide has low crystallinity and exists in a highly dispersed or amorphous state on the support surface; it may also be because oxygen and sulfur belong to the same group, and the reaction results in substitution, causing a change in crystal phase that is not easily reflected in the XRD pattern. Furthermore, since the oxidation of molybdenum disulfide by peroxide in this invention is carried out at room temperature, the oxidation ratio of molybdenum disulfide is relatively low, which may also be the reason why the molybdenum oxide peak is difficult to detect. Furthermore, we can observe a shift in the peaks of the molybdenum disulfide catalysts after oxidation with 0.30 and 0.40 mol / L hydrogen peroxide. The peak corresponding to the (002) plane of the catalyst oxidized with 0.30 mol / L hydrogen peroxide shows a significant shift. This is because the oxidation by hydrogen peroxide increases the interlayer spacing at the edges of the molybdenum disulfide, causing a shift in the XRD pattern. The increased interlayer spacing exposes more defects and active sites, leading to a corresponding increase in the catalyst's hydrogen evolution catalytic performance, which is consistent with our previous LSV test results.

[0054] Electrochemical performance testing of the catalyst for hydrogen evolution:

[0055] (I) Preparatory work before the test

[0056] The working electrode was polished and cleaned on deerskin using Al2O3 polishing powder, and the electrolytic cell was ultrasonically dried in an ultrasonic machine. The graphite rod was ultrasonically cleaned in ultrapure water, and the reference electrode was wiped clean. Ink preparation: 2 mg of catalyst with different hydrogen peroxide concentrations, 2 mg of XC72 carbon powder, 0.2 ml of anhydrous ethanol, 0.78 ml of ultrapure water, and 0.02 ml of Nafion solution (5%) were added to four clean ink bottles respectively. The prepared ink solutions were sealed and ultrasonicated for at least half an hour until the catalyst dispersion was good.

[0057] Once the ink is prepared, begin preparing the electrode. Use a pipette to transfer 5 μL of the dispersed ink solution and drop it onto the smooth mirror surface in the center of the electrode. After the first drop dries, drop the second drop, repeating this process four times for a total of 20 μL.

[0058] (II) Electrochemical Performance Testing

[0059] Insert the working electrode, calomel reference electrode, and graphite rod into the 0.5M sulfuric acid electrolyte and fix them in place. Connect them to the electrochemical workstation, turn on the nitrogen gas, and start the test after checking that everything is correct.

[0060] Polarization curves: The polarization curve LSV is a crucial parameter for evaluating catalyst activity. Using a 0.5M sulfuric acid electrolyte, a potential window of 0V to -0.6V was set, with a scan rate of 5mV / s. After setting the parameters, the test was started. After each test, the working electrode was removed and surface air bubbles were blown off before the next test, until the two polarization curves coincided. The current density was 10mA / cm². 2 The overpotential at the electrode is used to evaluate the hydrogen evolution performance of the catalyst; the lower the value, the better the performance. If the curves do not overlap, activation treatment is required. Stirring is performed throughout the test. In data processing, the measured overpotential is usually converted to the potential relative to the reversible hydrogen electrode (RHE) and IR compensation is performed.

[0061]

[0062] Where E (measured) is the actual measured potential. The electrode potential of the selected reference electrode is given by , pH is the acidity or alkalinity of the electrolyte, and IR compensation is used to counteract the influence of the internal resistance of the test system on the catalyst performance. It is generally provided by the series impedance Rs of the electrochemical impedance spectroscopy (EIS) or directly compensated by the test system.

[0063] Tafel curves: Tafel curves can be used to determine the reaction characteristics of an electrode and the controlling steps affecting catalytic efficiency. They can also be used to determine fundamental kinetic parameters of the catalyst, such as exchange current density and the Tafel slope, derived from the LSV polarization curve via the Tafel equation. The Tafel equation is: η = b * log j + a, where j is the current density and b is the Tafel slope.

[0064] Cyclic voltammetry (CV) testing: In hydrogen electrolysis, CV is generally used to evaluate the cyclic stability of catalyst materials, perform surface activation treatment on the catalyst material, and measure the electric double layer capacitance. When measuring cyclic stability, a scan range can be given, and three scans of 1000 cycles at a scan rate of 100 mV / s are performed. Then, the LSV is measured, and the polarization curves before and after the test are compared to observe the potential changes and compare the cyclic stability. When activating the electrode, the potential window is set to -0.241 V to 0.259 V. The voltage should not be set too high to avoid catalyst oxidation and deactivation. When measuring the electric double layer capacitance, a series of CV plots are obtained in the capacitance region at a scan rate increasing by 10 mV / s to 100 mV / s, with the window set to -0.081 V to 0.019 V. The test should not be stirred. The slope of the difference between the positive and negative current densities corresponding to the centrosymmetric voltage, ΔJ, is taken as the Y-axis, and the slope of this slope relative to the scan rate X-axis is the electric double layer capacitance.

[0065] Electrochemical impedance spectroscopy (EIS) is used in HER to measure resistance. The principle is to treat the entire test system as a resistor while applying an external excitation signal. The corresponding response signal is then used to determine the charge transport and mass transport processes. In HER, we are primarily concerned with charge transport, mainly in the mid-to-high frequency range; therefore, measuring the semi-circular shape is sufficient. The electrode must be activated before each EIS measurement.

[0066] Potentiostatic Calibration (CA): Potentiostatic calibration is also a method used to evaluate catalyst stability. It involves applying a specific voltage to the working electrode and observing the change in current over time. Generally, the smaller the change in current, the more stable the performance. A typical voltage applied in LSV is 10 mA / cm. 2 The corresponding voltage at that time. Before testing CA, the best performing catalyst ink needs to be prepared. Take 2 mg of the best performing catalyst, 2 mg of XC72 carbon powder, 0.98 ml of anhydrous ethanol, and 0.02 ml of Nafion solution and add them to the ink bottle. Sonicate for at least 30 minutes. Prepare a 1×1.5 cm 2 The carbon paper was sprayed with the catalyst to a depth of 1×1 cm using a spray gun. 2 Within the carbon paper area. Electrode clamps hold the carbon paper for testing. Stirring is required throughout the test.

[0067] (II) Analysis of Electrochemical Performance Test Results:

[0068] Figure 4 a represents the obtained LSV polarization curve, from Figure 4 As shown in Figure a, through experimental comparison, the MoS2 catalyst synthesized at a hydrothermal temperature of 150℃ exhibits higher HER performance. (At 10 mA / cm²) 2 The overpotential at the exchange current density was 216 mV, significantly lower than that of MoS2 at 120℃ (253 mV) and 180℃ (228 mV). Therefore, we selected the MoS2 catalyst synthesized at 150℃ hydrothermal temperature as the precursor for controlled oxidation. Under acidic conditions, the Pt / C catalyst at 10 mA / cm²... 2 The overpotential at the exchange current density was 24.3 mV. This was achieved by oxidizing the molybdenum sulfide catalyst with 0.20 mol / L peroxide at 10 mA / cm². 2 The overpotential at the exchange current density was 199 mV. This was achieved by oxidizing the molybdenum sulfide catalyst with 0.30 mol / L peroxide at 10 mA / cm². 2 The overpotential at the exchange current density was 160 mV. This was achieved using a molybdenum sulfide catalyst oxidized with 0.40 mol / L peroxide at a current density of 10 mA / cm². 2 The overpotential at the exchange current density is 191 mV. It can be seen that the optimal oxidation concentration is 0.30 mol / L. After modification, the catalyst overpotential decreased by approximately 50 mV, and its activity was significantly improved.

[0069] After correcting the potential for ohmic potential drop (IR) loss caused by the resistance between the electrolyte and the electrode, the Tafel curve is extracted from the polarization curve data. The linear portion of the Tafel curve (…) Figure 4 (b) The equation is fitted to the Tafel equation (η = b * log j + a, where j is the current density and b is the Tafel slope). The graph shows that the Tafel slope for the Pt / C catalyst is 27.6 mV / dec, for the original molybdenum disulfide catalyst it is 54.7 mV / dec, for the molybdenum disulfide catalyst after oxidation with 0.20 mol / L peroxide it is 52.1 mV / dec, for the catalyst after oxidation with 0.30 mol / L peroxide it is 47.9 mV / dec, and for the catalyst after oxidation with 0.40 mol / L peroxide it is 51.9 mV / dec. Except for the Pt / C catalyst, the molybdenum disulfide catalyst after oxidation with 0.30 mol / L peroxide has a lower Tafel slope compared to other catalysts. With increasing overpotential, the current density increases at a faster rate, exhibiting faster hydrogen evolution kinetics and higher reaction kinetic efficiency.

[0070] To clarify MoS2 / MoOx The mechanism of excellent HER activity at heterogeneous interfaces was investigated, and the electro-double-layer capacitance of the catalysts under different hydrogen peroxide concentrations was measured. Figure 4 c) The density of active sites in the molybdenum sulfide catalyst after hydrogen peroxide oxidation was evaluated. Due to its larger specific surface area, the study found that the bilayer capacitance of the original molybdenum sulfide catalyst was 55.2 mF / cm². 2 The bilayer capacitance of the molybdenum sulfide catalyst after oxidation with 0.20 mol / L peroxide was 96.2 mF / cm. 2 The bilayer capacitance of the molybdenum sulfide catalyst after oxidation with 0.30 mol / L peroxide was 118.7 mF / cm. 2 The bilayer capacitance of the molybdenum sulfide catalyst after oxidation with 0.40 mol / L peroxide was 88.8 mF / cm. 2 The molybdenum sulfide catalyst oxidized with 0.30 mol / L peroxide showed a relatively higher bilayer capacitance, indicating that it has a larger surface area and can expose more active sites.

[0071] EIS electrochemical impedance spectroscopy provides us with some information about electron transfer kinetics, from Figure 4 As can be seen from d, the molybdenum sulfide catalyst oxidized by 0.30 mol / L peroxide also exhibits a smaller charge transfer resistance compared to other catalysts. This indicates that the catalyst has a faster electron transfer rate, which is beneficial for improving the HER kinetics at the catalyst interface.

[0072] Meanwhile, this invention also shows the CA response results of the molybdenum sulfide catalyst after oxidation with 0.30 mol / L peroxide under acidic conditions. Figure 5 During 20 hours of operation, the catalytic current density remained at 10 mA / cm² at an overpotential of 160 mV. 2 The value of around 100 indicates that this catalyst possesses good stability.

[0073] Maintaining catalyst stability in acidic electrolytes is essential for the long-term use of batteries. To measure the long-term stability of the electrocatalyst, we continuously monitored cyclic voltammetry for 3000 cycles. Figure 6 A slight deterioration in the cathode current was observed after 1000 cycles, with the deterioration lessening at the subsequent 2000 and 3000 cycles. After 3000 cycles, the cathode current remained at 10 mA / cm². 2 At the given current density, the potential increased by only 12 mV. This indicates that the catalyst possesses good acid tolerance and cycling stability.

[0074] In summary:

[0075] This invention first prepares a molybdenum disulfide catalyst by hydrothermal synthesis at 150℃ for 24 hours, and then performs controlled oxidation modification with hydrogen peroxide to synthesize MoS2 / MoO. x Heterogeneous nanosheets. By varying the hydrogen peroxide concentration, the electrochemical hydrogen evolution performance of a series of catalysts with different oxidation concentrations was tested, and the optimal oxidation concentration for hydrogen evolution performance was determined. Furthermore, through physical characterization of the catalyst with the best performance, the following conclusions were drawn:

[0076] (1) When the concentration of hydrogen peroxide is 0.30 mol / L, at 10 mA / cm 2 At a current density of 160 mV, the catalyst exhibits an overpotential of 160 mV and a Tafel slope of 47.9 mV / dec. It is a catalyst with excellent hydrogen evolution performance, and the optimal oxidation concentration of 0.30 mol / L hydrogen peroxide was determined by this invention. This invention also compares the original molybdenum sulfide with MoS2 / MoO modified with 0.30 mol / L hydrogen peroxide. x Comparison of heterogeneous nanosheets revealed that at 10 mA / cm 2 At the same current density, the overpotential of the latter was reduced by approximately 50 mV compared to the former. The modified catalyst showed a significant improvement in hydrogen evolution performance. It has broad development prospects in the field of hydrogen evolution catalysts for water electrolysis.

[0077] (2) The present invention modifies MoS2 / MoO2 with a hydrogen peroxide concentration of 0.30 mol / L. x Physical characterization of heterogeneous nanosheets was performed. The nanosheets we prepared exhibited the morphological characteristics of nanoflower particles. The edge wrinkles of the nanoflower particles and the corrosion phenomena caused by hydrogen peroxide corrosion provided a large number of edge active sites, which are beneficial to improving hydrogen evolution performance.

[0078] (3) Regarding the modification mechanism of molybdenum disulfide catalyst by controlled oxidation of hydrogen peroxide, this invention, through experimental research, yielded the following reasons: First, the oxidation effect of hydrogen peroxide alters the insufficient exposure of active sites caused by the self-stacking effect of weak interlayer interactions in layered molybdenum disulfide. Oxidation increases the interlayer spacing at the edges of molybdenum disulfide, correspondingly increasing the number of active sites, catalyst conductivity, and electron transport speed, all of which affect the catalyst's hydrogen evolution performance. Second, hydrogen peroxide itself is corrosive, producing a corrosive effect during the oxidation of molybdenum disulfide, affecting its morphology. The nanopores generated by corrosion increase the exposure of active sites, thereby improving the hydrogen evolution performance. In summary, this invention, through the construction of MoS2 / MoO... x Heterogeneous nanosheets, through their interfacial synergistic effect and electronic modulation, enhance the hydrogen evolution performance of molybdenum disulfide catalysts.

Claims

1. A MoS2 / MoO x A method for preparing heterogeneous nanosheets, characterized in that: The method specifically includes the following steps: (1) Thiourea, ammonium molybdate and ultrapure water are mixed according to the ratio and stirred to dissolve to obtain a mixed reaction solution; then the mixed reaction solution is transferred to a clean reaction vessel and heated to 150℃ for hydrothermal reaction for 20-30h; after the reaction is completed, it is naturally cooled to a lower temperature, the obtained product is filtered and dried to obtain blocky MoS2; (2) At room temperature, the blocky MoS2 prepared in step (1) is mixed with a 0.3% hydrogen peroxide solution according to the specified ratio, and the mixture is stirred for 2-6 hours. After the reaction is completed, the mixture is filtered and dried to obtain the MoS2 / MoO2. x Heterogeneous nanosheets.

2. The method according to claim 1, characterized in that: The molar ratio of thiourea to ammonium molybdate in step (1) is 14:

1.

3. The method according to claim 1, characterized in that: The hydrothermal reaction time in step (1) is 24 hours.

4. The method according to claim 1, characterized in that: The stirring reaction time in step (2) is 4 hours.

5. The MoS2 / MoO prepared by the method according to any one of claims 1-4 x Heterogeneous nanosheets.

6. The MoS2 / MoO prepared by the method according to any one of claims 1-4 x Application of heterogeneous nanosheets as catalysts in electrochemical hydrogen evolution reaction.

7. An electrochemical hydrogen evolution catalyst, characterized in that: Including MoS2 / MoO prepared by the method according to any one of claims 1-4 x Heterogeneous nanosheets.

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