A nickel-molybdenum sulfur electrocatalyst and a preparation method thereof

Abstract

The present application relates to a kind of nickel-molybdenum sulfur electrocatalyst and its preparation method, comprising, obtaining hydrothermal reaction liquid, including according to (1.08~1.68):(0.52~1.12):(1.0~1.4):100 weight ratio obtainable soluble nickel salt, ammonium molybdate, ammonium fluoride, first solvent, and configuration hydrothermal reaction liquid;Obtain electrocatalyst precursor, including the foam nickel is placed in the hydrothermal reaction liquid carries out hydrothermal reaction, to make the foam nickel grow electrocatalyst precursor;Obtain nickel-molybdenum sulfur electrocatalyst, including the sulfidation reaction of the electrocatalyst precursor, to generate nickel-molybdenum sulfur electrocatalyst, with the advantage of improving electrocatalyst catalytic performance.

Description

Technical Field

[0001] This invention relates to the field of electrocatalysis technology, and in particular to a nickel-molybdenum-sulfur electrocatalyst and its preparation method. Background Technology

[0002] With the depletion of fossil fuels and rapid environmental degradation, the development of clean fuels for sustainable human use has become an urgent priority. Hydrogen (H2), due to its environmental friendliness and high combustion value, has gradually become a potential candidate for future energy supply. However, currently, the vast majority of hydrogen comes from coal and natural gas, causing severe energy shortages and environmental pollution. To achieve efficient and clean hydrogen production, water electrolysis technology is widely used. It can produce high-quality hydrogen from abundant water resources and is considered a simple way to achieve green hydrogen production.

[0003] Electrocatalysts are typically used in the process of producing hydrogen through water electrolysis. Because Pt group noble metals have high intrinsic activity, low catalytic barriers and excellent stability, they have become ideal electrocatalysts for the hydrogen evolution reaction (hydrogen production through water electrolysis). However, their scarcity and high price limit their widespread application.

[0004] Among the many hydrogen evolution catalysts, transition metal sulfides (such as MoS2, NiS and Ni3S2) are considered to be promising hydrogen evolution electrocatalysts due to their high conductivity and unique electronic structure. However, single-metal electrocatalysts often fail to achieve satisfactory results in the hydrogen evolution reaction. Therefore, developing bimetallic electrocatalysts with suitable morphologies to improve the hydrogen evolution effect of electrocatalysts is worthy of our research. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the defects in the prior art, thereby providing a method for preparing a nickel-molybdenum-sulfur electrocatalyst.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing a nickel-molybdenum-sulfur electrocatalyst includes: obtaining a hydrothermal reaction solution, comprising obtaining a soluble nickel salt, ammonium molybdate, ammonium fluoride, and a first solvent in a weight ratio of (1.08–1.68):(0.52–1.12):(1.0–1.4):100, and preparing the hydrothermal reaction solution; obtaining an electrocatalyst precursor, comprising placing nickel foam in the hydrothermal reaction solution for a hydrothermal reaction to grow the electrocatalyst precursor on the nickel foam; and obtaining the nickel-molybdenum-sulfur electrocatalyst, comprising performing a sulfidation reaction on the electrocatalyst precursor to generate the nickel-molybdenum-sulfur electrocatalyst.

[0008] Preferably, the preparation of the hydrothermal reaction solution includes dissolving the soluble nickel salt, the ammonium molybdate, and the ammonium fluoride in the first solvent and stirring continuously for 4 to 6 minutes.

[0009] Preferably, the reaction temperature of the hydrothermal reaction is in the range of 120–180°C; and the reaction time of the hydrothermal reaction is in the range of 7–17 hours.

[0010] Preferably, the sulfidation reaction of the electrocatalyst precursor includes obtaining sodium thiosulfate and a second solvent at a weight ratio of 1:50 and preparing a sulfidation reaction solution; and placing the electrocatalyst precursor in the sulfidation reaction solution to carry out the sulfidation reaction.

[0011] Preferably, the reaction temperature of the vulcanization reaction is in the range of 90 to 110°C; and the reaction time of the vulcanization reaction is in the range of 5 to 11 hours.

[0012] Preferably, the hydrothermal reaction is carried out in a reactor with a polytetrafluoroethylene liner; and / or, the vulcanization reaction is carried out in a reactor with a polytetrafluoroethylene liner.

[0013] Preferably, the method further includes cleaning the nickel foam sequentially with ethanol, 1 mol / L hydrochloric acid, and deionized water for cleaning.

[0014] Preferably, the method further includes rinsing the electrocatalyst precursor with deionized water for cleaning.

[0015] Preferably, the process further includes vacuum drying of the nickel-molybdenum-sulfur electrocatalyst, wherein the drying time ranges from 9 to 15 hours and the drying temperature ranges from 50 to 70°C.

[0016] A nickel-molybdenum-sulfur electrocatalyst is prepared by the above-described preparation method.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: The preparation method of the nickel-molybdenum-sulfur electrocatalyst provided in the above technical solution involves obtaining soluble nickel salt, ammonium molybdate, ammonium fluoride, and a first solvent in a weight ratio of (1.08~1.68):(0.52~1.12):(1.0~1.4):100, preparing a hydrothermal reaction solution, and placing nickel foam in the hydrothermal reaction solution to grow an electrocatalyst precursor. The electrocatalyst precursor is then subjected to a sulfidation reaction, resulting in a final nickel-molybdenum-sulfur electrocatalyst exhibiting an interlaced sheet-like structure with a thickness of approximately 0.1 μm. Multiple thin sheets form a mesh-like sphere, and the stacking of these spheres creates a porous material to increase the specific surface area, expose more active sites, and improve the catalyst's activity. The nickel-molybdenum-sulfur electrocatalyst prepared by this method effectively reduces preparation costs compared to Pt group noble metal electrocatalysts. Compared to monometallic electrocatalysts, it effectively improves the hydrogen evolution efficiency. Furthermore, by adding an appropriate amount of ammonium fluoride, the morphology of the bimetallic electrocatalyst can be controlled, thereby regulating the configuration and coordination of atoms on the crystal surface, lowering the adsorption and desorption barriers of hydrogen species, and further improving the reaction rate and hydrogen evolution efficiency. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the preparation method of the present invention.

[0020] Figure 2 for Figure 1 A schematic diagram illustrating the specific steps of one example of step S3.2.

[0021] Figure 3 The XRD patterns of the electrocatalysts prepared for the examples and comparative examples are shown.

[0022] Figure 4 XRD patterns of the electrocatalysts prepared for the examples and comparative examples at 32.2°.

[0023] Figure 5 SEM images of nickel-molybdenum-sulfur electrocatalysts prepared by adding ammonium fluoride in different proportions according to the present invention.

[0024] Figure 6 SEM images of the monometallic and bimetallic electrocatalysts prepared in this invention.

[0025] Figure 7This is a SEM image of the nickel foam used in this invention.

[0026] Figure 8 SEM image of NiMoO4·xH2O-F0 prepared according to the present invention.

[0027] Figure 9 The linear sweep voltammetry curve is shown for the nickel-molybdenum-sulfur electrocatalyst prepared in this invention.

[0028] Figure 10 The image shows the Tafel curve of the nickel-molybdenum-sulfur electrocatalyst prepared in this invention.

[0029] Figure 11 The C of the nickel-molybdenum-sulfur electrocatalyst prepared in this invention is... dl picture.

[0030] Figure 12 The image shows the Nyquist plot of the nickel-molybdenum-sulfur electrocatalyst prepared in this invention.

[0031] Figure 13 Mo-NiS-F prepared for this invention 1.2 Chronopotential diagram of an electrocatalyst. Detailed Implementation

[0032] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0034] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0035] See Figures 1 to 13 This invention provides a method for preparing a nickel-molybdenum-sulfur electrocatalyst, comprising:

[0036] S1: Obtaining the hydrothermal reaction solution, specifically including:

[0037] S1.1: Obtain soluble nickel salt, ammonium molybdate, ammonium fluoride, and first solvent according to the weight ratio of (1.08~1.68):(0.52~1.12):(1.0~1.4):100.

[0038] The soluble nickel salt can be nickel acetate, nickel chloride, nickel nitrate, or nickel sulfate, and the ammonium molybdate can be monoammonium molybdate, diammonium molybdate, tetraammonium molybdate, heptaammonium molybdate, octaammonium molybdate, or dodecaammonium molybdate. The first solvent can be deionized water, ethanol, etc. In this embodiment, the soluble nickel salt can be nickel sulfate, the ammonium molybdate can be monoammonium molybdate, and in order to save costs, the first solvent is deionized water.

[0039] Mo is a common n-type dopant among various metal cation dopants, which can increase the free electron concentration of electrocatalysts. Its doping can effectively improve the conductivity and stability of the substrate material. In this embodiment, by adding an appropriate amount of ammonium molybdate, a bimetallic electrocatalyst can be prepared. Compared with monometallic electrocatalysts, it can effectively improve the hydrogen evolution effect of the electrocatalyst. In addition, an appropriate amount of ammonium fluoride is added in this embodiment, which can control the morphology of the bimetallic electrocatalyst, thereby regulating the configuration and coordination of atoms on the crystal surface, reducing the adsorption and desorption barrier of hydrogen species, and further improving the hydrogen evolution reaction rate and hydrogen evolution effect.

[0040] S1.2: Dissolve the obtained soluble nickel salt, ammonium molybdate, and ammonium fluoride in the first solvent and stir continuously for 4 to 6 minutes to prepare a hydrothermal reaction solution.

[0041] Continuous stirring allows each substance to dissolve more quickly, ensuring complete dissolution in the first solvent. Insufficient stirring time leads to incomplete dissolution, affecting the elemental composition of the electrocatalyst and consequently its electrocatalytic activity. Conversely, excessive stirring causes ammonium fluoride to gradually hydrolyze, resulting in premature nickel hydroxide precipitate formation, which affects the composition and structure of the electrocatalyst. Therefore, to ensure complete dissolution of each substance while avoiding premature nickel hydroxide precipitate formation, the stirring time in this embodiment can be set to 4 minutes, 5 minutes, or 6 minutes, with 5 minutes being preferred.

[0042] S2: Obtaining electrocatalyst precursors, specifically including:

[0043] S2.1: Clean the nickel foam sequentially with ethanol, 1 mol / L hydrochloric acid, and deionized water for cleaning.

[0044] Ethanol can remove oil stains from the surface of the foam cotton; hydrochloric acid can remove the oxide layer on the surface of the foam cotton; and deionized water for cleaning can remove residual ethanol and hydrochloric acid. Specifically, the cleaning time can be set to 15 minutes, and the cleaning step is carried out before the nickel foam is added to the hydrothermal reaction solution, thereby removing impurities or foreign matter from the surface of the nickel foam in advance to avoid affecting the formation of the electrocatalyst precursor.

[0045] Furthermore, ultrasonic cleaning can be used to enhance the cleaning effect. Alternatively, in other embodiments, deionized water, ethanol, or 1 mol / L hydrochloric acid can be used to clean the nickel foam. Other cleaning agents, such as acetone, ether, or methanol, can also be used. Of course, stored clean nickel foam can also be used directly without prior cleaning.

[0046] S2.2: Place the nickel foam in a hydrothermal reaction solution to carry out a hydrothermal reaction, so that an electrocatalyst precursor can be grown on the nickel foam.

[0047] Specifically, during operation, in order to increase the contact area between the nickel foam and the hydrothermal reaction liquid, and thus facilitate the growth of electrocatalyst precursors on the nickel foam, in this embodiment, the nickel foam can be placed vertically in a reaction vessel of a certain capacity. For example, when 100 mL of plasma water is taken, the reaction vessel can be 150 mL in capacity. The reaction vessel can be a stainless steel reaction vessel with a polytetrafluoroethylene liner, thereby avoiding the influence of the reaction vessel on the hydrothermal reaction. Furthermore, since the temperature of the hydrothermal reaction affects the reaction rate and product selectivity, when the temperature is too low, the hydrothermal reaction rate is slow, the reaction is incomplete, and a single-component precursor cannot be obtained. When the temperature is too high, the reaction rate increases, but at the same time, the uncertainty of the product and the occurrence of side reactions also increase, and a single-component precursor cannot be obtained. In order to improve the reaction rate and avoid the occurrence of side reactions, in this embodiment, the reaction temperature of the hydrothermal reaction is in the range of 120-180℃, specifically 120℃, 140℃, 160℃ or 180℃, preferably 140℃, so that the hydrothermal reaction proceeds smoothly while generating fewer by-products, thus ensuring the purity of the precursor.

[0048] Furthermore, since the hydrothermal reaction time determines the degree of grain growth, when the reaction time is short, the grain growth is incomplete and a uniform morphology cannot be obtained. When the reaction time is long, the grains will grow excessively and may form larger particles, which also affects the uniformity of the morphology. In order to ensure that the precursor grains can grow stably and obtain a regular and uniform morphology, in this embodiment, the reaction time of the hydrothermal reaction is in the range of 7 to 17 hours, specifically set to 7 hours, 12 hours or 17 hours, preferably 12 hours.

[0049] S3: Obtaining nickel-molybdenum-sulfur electrocatalysts, specifically including:

[0050] S3.1: The electrocatalyst precursor obtained in step S2 is rinsed with deionized water for cleaning, thereby cleaning its surface and preventing impurities or foreign matter from affecting its sulfidation reaction. It is worth noting that the cleaning step itself is not mandatory and may be omitted in other embodiments; the cleaning agent does not necessarily have to be deionized water for cleaning, and other cleaning agents with cleaning effect that do not affect the sulfidation reaction may be used, such as ethanol, diethyl ether, etc.

[0051] S3.2: Sulfidation reaction of the electrocatalyst precursor to generate a nickel-molybdenum-sulfur electrocatalyst. Specifically, this includes:

[0052] S3.2.1: Obtain sodium thiosulfate and a second solvent at a weight ratio of 1:50, and prepare the sulfidation reaction solution. Of course, in other embodiments, sodium thiosulfate can also be sodium sulfide nonahydrate, thioacetamide, or thiourea. Compared to other embodiments where sodium sulfide nonahydrate, thioacetamide, or thiourea cause varying degrees of damage to the precursor morphology during the sulfidation reaction, leading to a decrease in electrocatalyst performance, sodium thiosulfate has a slower decomposition rate, allowing for gradual sulfidation of the precursor without damaging its morphology. In this embodiment, using sodium thiosulfate facilitates a gentle and thorough sulfidation of the precursor.

[0053] S3.2.2: The electrocatalyst precursor is placed in the sulfidation reaction solution for sulfidation reaction to generate a nickel-molybdenum-sulfur electrocatalyst. Similarly, during operation, in order to increase the contact area between the electrocatalyst precursor and the sulfidation reaction solution, and thus facilitate the growth of the nickel-molybdenum-sulfur electrocatalyst on the electrocatalyst precursor, in this embodiment, the electrocatalyst precursor can be vertically placed in a reaction vessel of a certain capacity. The reaction vessel can be a stainless steel reaction vessel with a polytetrafluoroethylene liner, thereby avoiding the influence of the reaction vessel on the sulfidation reaction. Furthermore, in order to decompose sodium thiosulfate and initiate the sulfidation reaction, in this embodiment, the reaction temperature of the sulfidation reaction is in the range of 90–110°C, specifically 90°C, 100°C, or 110°C, preferably 100°C, so that sodium thiosulfate can lose its water of crystallization and decompose, thereby allowing the sulfidation reaction to proceed smoothly. The reaction time of the sulfidation reaction is in the range of 5–11 hours, specifically 5 hours, 8 hours, or 11 hours, preferably 8 hours, so that sodium thiosulfate can be fully decomposed, the precursor can be thoroughly sulfided, and the increase of by-products caused by over-sulfidation can be prevented.

[0054] S3.2.3: Vacuum drying of the nickel-molybdenum-sulfur electrocatalyst. The drying time can be 9 hours, 12 hours, or 15 hours, preferably 12 hours. The drying temperature can be 50℃, 60℃, or 70℃, preferably 60℃. This ensures the electrocatalyst is thoroughly dried without decomposition, modification, or structural collapse. Furthermore, vacuum drying helps prevent oxidation of the electrocatalyst, ensuring the uniformity of its composition and structure.

[0055] Nickel-molybdenum-sulfur electrocatalysts were prepared based on the above method, with nickel sulfate as the soluble nickel salt, first deionized water as the first solvent, and second deionized water as the second solvent as an example. In step S1.1, different nickel-molybdenum-sulfur electrocatalysts can be obtained by changing the weight ratio of each raw material component. To obtain the optimal nickel-molybdenum-sulfur electrocatalyst, multiple sets of experiments were conducted, and the specific data are shown in Table 1 below, with Mo-NiS-F... x NiS-F xThe term "X" is used to characterize the electrocatalysts generated with different masses of ammonium fluoride and different types of metals added, where X represents the mass of ammonium fluoride added. For example, when ammonium fluoride is added in a ratio of 1.2, the corresponding nickel-molybdenum-sulfur electrocatalyst can be represented as Mo-NiS-F. 1.2 .

[0056]

[0057] Table 1

[0058] See Figures 3 to 13 To verify the catalytic performance of bimetallic nickel-molybdenum-sulfur electrocatalysts, monometallic nickel-based catalysts, monometallic molybdenum-based catalysts, and bimetallic nickel-molybdenum-sulfur electrocatalysts with different amounts of ammonium fluoride added, XRD pattern analysis, SEM image analysis, and electrocatalytic performance testing were conducted based on the above examples. Specifically, the performance of various electrocatalysts was tested in a three-electrode system, using the prepared nickel-molybdenum-sulfur electrocatalyst as the working electrode, a graphite rod as the counter electrode, and an Hg / HgO electrode as the reference electrode, with a 1 mol / L KOH solution as the electrolyte; PARSTAT4000 was used for testing. + The electrocatalytic performance of the nickel-molybdenum-sulfur electrocatalyst was tested on an electrochemical workstation. Furthermore, referring to Table 1 above, to compare the performance of the generated nickel-molybdenum-sulfur electrocatalyst, foamed nickel (NF; Comparative Example 6) cleaned in step S2.1, the washed electrocatalyst precursor obtained in step S3.1 (NiMoO4·xH2O-F0; Comparative Example 7), and the existing high-performance Pt / C (Comparative Example 8) were also added for comparison.

[0059] For details, see Figure 3 and Figure 4 XRD analysis was performed on the electrocatalysts prepared according to the proportions in Table 1 above, showing that NiS-F 1.2 and MoS2-F 1.2 The samples exhibited NiS (JCPDS No. 86-2281) and MoS2 (JCPDS No. 37-1492) phases, respectively. The precursor was NiMoO4·xH2O. After sulfidation, the electrocatalysts all exhibited the NiS (JCPDS No. 86-2281) phase. The peak values ​​at 18.4°, 30.3°, 32.2°, 35.7°, 40.4°, 48.8°, and 52.6° corresponded to (110), (101), (300), (021), (211), (131), and (401), respectively. The low number of impurity peaks indicates that the prepared samples have high purity.

[0060] Notably, no Mo-related diffraction peaks were found in the XRD pattern after sulfidation, suggesting that Mo and Ni may have undergone isomorphous substitution during the reaction, forming Mo-doped NiS. See also Figure 4 The diffraction peak of Mo-NiS-Fx at 32.2° is different from that of NiS-F. 1.2 The leftward shift of the diffraction peak at 32.2° is due to the introduction of Mo heteroatoms, which are larger than the host Ni atom. Furthermore, the amount of ammonium fluoride added does not alter the crystal structure of the sample, indicating that ammonium fluoride does not have any other impact on morphology control.

[0061] See 5 to Figure 8 The optimal ammonium fluoride ratio can be determined by observing the effect of adding different proportions of ammonium fluoride on the morphology of nickel-molybdenum-sulfur electrocatalysts. Furthermore, the morphological characteristics of monometallic and bimetallic electrocatalysts under the optimal ammonium fluoride ratio can be observed to determine their electrocatalytic performance. Even further, the morphology of nickel foam (NF) and NiMoO4·xH2O-FO can be observed to determine the electrocatalytic performance of different electrocatalysts.

[0062] Specifically, see Figure 5 ,in Figure 5 a, Figure 5 b、 Figure 5 c. Figure 5 d、 Figure 5 e Figure 5 f represents Mo-NiS-F0 and Mo-NiS-F respectively. 0.6 Mo-NiS-F 1.0 Mo-NiS-F 1.2 Mo-NiS-F 1.4 Mo-NiS-F 1.8 The morphology of the nickel-molybdenum-sulfur electrocatalyst shows that when the mass of ammonium fluoride is 0.6 g, the morphology is a uniformly distributed cone shape with a smooth surface and a sharp tip. When the mass of ammonium fluoride is 1.8 g, the morphology is large granular particles. When the mass of ammonium fluoride is 1.0 g, 1.2 g, or 1.4 g, the morphology is uniformly distributed in flakes. That is, when the mass of ammonium fluoride is 1.0 g, 1.2 g, or 1.4 g (with a ratio range of 1.0–1.4), the morphology is regular and uniform, which is beneficial to improving its electrocatalytic performance. Furthermore, when the mass of ammonium fluoride is 1.2 g, the flake structure is three-dimensional, thin, and interwoven, which is beneficial to increasing the specific surface area. However, when the mass of ammonium fluoride is less than 1.0 g or greater than 1.4 g, the nickel-molybdenum-sulfur electrocatalyst no longer has a regular morphology and contains large particles with a large specific surface area, which is not conducive to the formation of active sites.

[0063] Further, see Figure 6 ,in Figure 6 g、 Figure 6 h、 Figure 6 i respectively displays NiS-F 1.2MoS2-F 1.2 Mo-NiS-F 1.2 From the morphology, it can be known that NiS-F 1.2 The morphology exhibits a disordered appearance, with large particles present. (MoS2-F) 1.2 The morphology is a disordered and dense thin layer, while Mo-NiS-F 1.2 The morphology exhibits an interlaced, sheet-like structure with a thickness of approximately 0.1 μm. Multiple sheets form a network sphere, and the accumulation of these network spheres creates a porous material, namely Mo-NiS-F. 1.2 Compared to NiS-F 1.2 and MoS2-F 1.2 In contrast, the morphology is more three-dimensional, the specific surface area is increased, and more active sites are exposed, namely the bimetallic Mo-NiS-F 1.2 It exhibits superior catalytic performance.

[0064] Furthermore, see Figure 7 The morphology of nickel foam (NF) can be observed; the surface is smooth and free of loaded material, similar to Mo-NiS-F. 1.2 In comparison, Mo-NiS-F 1.2 A plate-like electrocatalyst structure was grown on the NF surface, completely covering the NF surface, indicating that the electrocatalyst growth was very successful; see also Figure 8 The morphology of NiMoO4·xH2O-F0 can be observed, showing a columnar structure, but with severe clustering. NF surface can also be observed in some locations. It is similar to Mo-NiS-F... 1.2 In comparison, Mo-NiS-F 1.2 It exhibits a uniform sheet-like structure with few clusters and completely covers the NF surface.

[0065] Specifically, the linear sweep voltammetry (LSV) method was used for testing, with a scan rate of 5 mV·s. -1 The results were displayed using LVS curves. It's worth noting that the LVS curve is an overpotential-current density curve. Overpotential reflects the additional energy required to overcome the reaction energy barrier during the reaction process. Under the same current density conditions, a smaller overpotential indicates higher catalytic activity of the electrocatalyst. (See also...) Figure 9 From Mo-NiS-F 1.2 Mo-NiS-F 1.0 Mo-NiS-F 1.4 NiS-F 1.2 MoS2-F 1.2 Mo-NiS-F0, Mo-NiS-F 0.6 Mo-NiS-F 1.8The LVS curves of NF, NiMoO4·xH2O-F0, and Pt / C show that, with a current density of 10 mA·cm⁻¹, -2 The overpotential at that time was used as comparative data, and the results are shown in Table 2 below:

[0066] <![CDATA[Mo-NiS-F 1.2 ]]> 79 <![CDATA[Mo-NiS-F 1.0 ]]> 85 <![CDATA[Mo-NiS-F 1.4 ]]> 83 <![CDATA[NiS-F 1.2 ]]> 143 <![CDATA[MoS2-F 1.2 ]]> 176 <![CDATA[Mo-NiS-F0]]> 123 <![CDATA[Mo-NiS-F 0.6 ]]> 94 <![CDATA[Mo-NiS-F 1.8 ]]> 111 NF 236 <![CDATA[NiMoO4·xH2O-F0]]> 202 Pt / C 77

[0067] Table 2

[0068] The current density is equal to the measuring current divided by the total area of ​​NF (nickel foam). According to the Nernst equation E(RHE) = E(Hg / HgO) + 0.098V + 0.059 × pH, the electrode potential of Hg / HgO is calibrated as RHE.

[0069] As shown in Table 2 above, NiS-F 1.2 and MoS2-F 1.2 At a current density of 10 mA·cm -2 The overpotentials at these times were 143 mV and 176 mV, respectively, while those at Mo-NiS-F... 1.2 At a current density of 10 mA·cm -2 The overpotential at that time was 79mV, which is the overpotential of the bimetallic Mo-NiS-F. 1.2 Compared to NiS-F 1.2 and MoS2-F 1.2 It exhibits superior catalytic performance compared to Mo-NiS-FO and Mo-NiS-F. 0.6 Mo-NiS-F 1.0 Mo-NiS-F 1.2 Mo-NiS-F 1.4 Mo-NiS-F 1.8 At a current density of 10 mA·cm -2 The overpotential at which ammonium fluoride is measured, specifically when the amount of ammonium fluoride is 1.0 g, 1.2 g, or 1.4 g, is lower than in the other cases. Furthermore, when the amount of ammonium fluoride is 1.2 g, the overpotential is only 79 mV, which is comparable to the overpotential of the noble metal Pt / C. The platy structure of Mo-NiS-F is evident. 1.2 Due to its high specific surface area, it generates more active sites, resulting in optimal electrocatalytic performance.

[0070] Specifically, the logarithm of current density [log(j)] versus overpotential can be plotted using the LSV curve to obtain the Tafel curve, and the results are presented as a Tafel curve graph. It is worth noting that the Tafel slope can be obtained from the Tafel curve graph of the nickel-molybdenum-sulfur electrocatalyst. The smaller the Tafel slope, the faster the current density increases and the smaller the change in overpotential, indicating better electrocatalyst performance. See also... Figure 10 From Mo-NiS-F1.2 Mo-NiS-F 1.0 Mo-NiS-F 1.4 NiS-F 1.2 MoS2-F 1.2 Mo-NiS-F0, Mo-NiS-F 0.6 Mo-NiS-F 1.8 The Tafel curves for NF, NiMoO4·xH2O-F0, and Pt / C show the corresponding Tafel slopes as shown in Table 3 below:

[0071] <![CDATA[Mo-NiS-F 1.2 ]]> 50.7 <![CDATA[Mo-NiS-F 1.0 ]]> 55.6 <![CDATA[Mo-NiS-F 1.4 ]]> 53.9 <![CDATA[NiS-F 1.2 ]]> 97.8 <![CDATA[MoS2-F 1.2 ]]> 118.5 <![CDATA[Mo-NiS-F0]]> 80.1 <![CDATA[Mo-NiS-F 0.6 ]]> 57.1 <![CDATA[Mo-NiS-F 1.8 ]]> 72.2 NF 189.9 <![CDATA[NiMoO4·xH2O-F0]]> 136.1 Pt / C 49.8

[0072] Table 3

[0073] As shown in Table 3 above, NiS-F 1.2 and MoS2-F 1.2 The Tafel slopes are 97.8 mV·dec. -1 and 118.5mV·dec -1 And Mo-NiS-F 1.2 The Tafel slope is 50.7 mV·dec -1 That is, the bimetallic Mo-NiS-F 1.2 Compared to NiS-F 1.2 and MoS2-F 1.2 It exhibits superior catalytic performance compared to Mo-NiS-FO and Mo-NiS-F. 0.6 Mo-NiS-F 1.0 Mo-NiS-F 1.2 Mo-NiS-F 1.4 Mo-NiS-F 1.8 The Tafel slope, specifically, in the bimetallic electrocatalyst, is lower when ammonium fluoride is used at concentrations of 1.0 g, 1.2 g, or 1.4 g compared to the other cases. Furthermore, when ammonium fluoride is used at 1.2 g, the Tafel slope is only 50.7 mV·dec. -1 This is almost comparable to the Tafel slope of the noble metal Pt / C, indicating that adding ammonium fluoride to control the catalyst morphology during the preparation of bimetallic electrocatalysts can significantly reduce the Tafel slope. The Tafel slope suggests that the HER kinetics of Mo-NiS-F1.2 include the Heyrovsky reaction and the Volmer reaction, with the rate-determining step being the Heyrovsky reaction.

[0074] Specifically, cyclic voltammetry (CV) curves are tested at different scan rates. The charging current at different scan rates can be obtained from the CV curves. The slope of the straight line between the charging current and the scan rate represents the double-layer capacitance (C).dl ), from the C of nickel-molybdenum-sulfur electrocatalyst dl The graph can be used to assess the effective surface area of ​​the electrode, C. dl A larger value indicates a higher electrochemical active surface area of ​​the electrocatalyst. See also Figure 11 From Mo-NiS-F 1.2 Mo-NiS-F 1.0 Mo-NiS-F 1.4 NiS-F 1.2 MoS2-F 1.2 Mo-NiS-F0, Mo-NiS-F 0.6 Mo-NiS-F 1.8 The CV curves of NF, NiMoO4·xH2O-F0, and Pt / C show that their corresponding double-layer capacitance (C) dl As shown in Table 4 below:

[0075] <![CDATA[Mo-NiS-F 1.2 ]]> 43.9 <![CDATA[Mo-NiS-F 1.0 ]]> 41.4 <![CDATA[Mo-NiS-F 1.4 ]]> 39.4 <![CDATA[NiS-F 1.2 ]]> 23.7 <![CDATA[MoS2-F 1.2 ]]> 9.1 <![CDATA[Mo-NiS-F0]]> 29.5 <![CDATA[Mo-NiS-F 0.6 ]]> 33.1 <![CDATA[Mo-NiS-F 1.8 ]]> 27.5 NF 14.8 <![CDATA[NiMoO4·xH2O-F0]]> 15.8 Pt / C 41.7

[0076] And Mo-NiS-F 1.2 C dl It is 43.9 mF·cm -2 That is, the bimetallic Mo-NiS-F 1.2 Compared to NiS-F 1.2 and MoS2-F 1.2 It exhibits a higher electrochemical active area compared to Mo-NiS-F0 and Mo-NiS-F. 0.6 Mo-NiS-F 1.0 Mo-NiS-F 1.2 Mo-NiS-F 1.4 Mo-NiS-F 1.8 C dl That is, when ammonium fluoride is taken as 1.0g, 1.2g, or 1.4g, C dl It is higher than the other cases, and when the ammonium fluoride content is 1.2g, its C dl Reaching 43.9 mF·cm -2 This exceeds the C of the precious metal Pt / C. dl The visible sheet-like structure of Mo-NiS-F 1.2 It possesses the highest electrochemical active area, which is related to its plate-like morphology and high specific surface area, providing more pathways for close contact with the electrolyte solution.

[0077] Specifically, electrochemical impedance spectroscopy (EIS) was performed at -0.75 V (vs Hg / HgO) in the frequency range of 100 kHz to 0.1 Hz to obtain the Nyquist plot of the electrocatalyst. It is worth noting that the diameter of the semicircle in the Nyquist plot represents the electron transfer resistance (Rct), which reflects the transfer efficiency between the electrocatalyst surface and the electrolyte; a lower value is better. Figure 12 From Mo-NiS-F 1.2 Mo-NiS-F 1.0 Mo-NiS-F 1.4 NiS-F 1.2 MoS2-F 1.2 Mo-NiS-F0, Mo-NiS-F 0.6 Mo-NiS-F 1.8 The Nyquist plots of NF, NiMoO4·xH2O-F0, and Pt / C show that their corresponding electron transfer resistances (Rct) are shown in Table 5 below:

[0078]

[0079]

[0080] Table 5

[0081] As shown in Table 5 above, NiS-F 1.2 and MoS2-F 1.2 The Rct values ​​are 10.0 Ω and 16.5 Ω, respectively, while those of Mo-NiS-F... 1.2 The Rct is 2.1Ω, which is the value of the bimetallic Mo-NiS-F. 1.2 Compared to NiS-F 1.2 and MoS2-F 1.2 It exhibits a lower electron transfer resistance compared to Mo-NiS-FO and Mo-NiS-F. 0.6 Mo-NiS-F 1.0 Mo-NiS-F 1.2 Mo-NiS-F 1.4 Mo-NiS-F 1.8 The Rct of the ammonium fluoride, specifically when the ammonium fluoride content is 1.0 g, 1.2 g, or 1.4 g, is lower than in the other cases. Furthermore, when the ammonium fluoride content is 1.2 g, its Rct is only 2.1 Ω, lower than the 2.3 Ω of the noble metal Pt / C. This is evident in the plate-like structure of Mo-NiS-F. 1.2 It has the highest electron transport rate.

[0082] Specifically, chronopotential testing was performed under constant current conditions to study the stability of the catalyst. The stability of electrocatalysts is a prerequisite for their large-scale application. Chronopotential analysis was used to test the stability of Mo-NiS-F... 1.2 For catalyst stability, see the results. Figure 13 Mo-NiS-F 1.2 Even at a current density of 10 mA·cm -2 Even after working continuously for 20 hours, it still exhibited excellent electrochemical durability.

[0083] In summary, compared with the monometallic NiS-F electrocatalyst, the bimetallic nickel-molybdenum-sulfur electrocatalyst exhibits superior performance. 1.2 and MoS2-F 1.2 It exhibits superior catalytic performance for the hydrogen evolution reaction. This is especially true for the plate-structured nickel-molybdenum-sulfur electrocatalyst (Mo-NiS-F). 1.2 The sheet-like nickel-molybdenum-sulfur electrocatalyst (Mo-NiS-F) exhibits excellent performance in electron transfer, bubble release rate, and electrochemical active area. 1.2 Compared to other amorphous nickel-molybdenum-sulfur electrocatalysts (Mo-NiS-FO, Mo-NiS-F...),... 0.6 Mo-NiS-F 1.8 It is easier to obtain high electrocatalytic activity.

[0084] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a nickel-molybdenum-sulfur electrocatalyst, characterized in that, include, Obtaining a hydrothermal reaction solution includes preparing a soluble nickel salt, ammonium molybdate, ammonium fluoride, and a first solvent in a weight ratio of (1.08–1.68):(0.52–1.12):(1.0–1.4):100, and then preparing the hydrothermal reaction solution, wherein the soluble nickel salt is nickel sulfate; Obtaining an electrocatalyst precursor includes placing nickel foam in the hydrothermal reaction solution to carry out a hydrothermal reaction, so that an electrocatalyst precursor grows on the nickel foam. Obtaining a nickel-molybdenum-sulfur electrocatalyst includes subjecting the electrocatalyst precursor to a sulfidation reaction to generate the nickel-molybdenum-sulfur electrocatalyst, wherein the sulfidation reaction uses sodium thiosulfate to prepare the sulfidation reaction solution.

2. The method for preparing a nickel-molybdenum-sulfur electrocatalyst according to claim 1, characterized in that, The prepared hydrothermal reaction solution includes, The soluble nickel salt, the ammonium molybdate, and the ammonium fluoride are dissolved in the first solvent and stirred continuously for 4 to 6 minutes.

3. The method for preparing a nickel-molybdenum-sulfur electrocatalyst according to claim 1, characterized in that, The reaction temperature of the hydrothermal reaction ranges from 120 to 180°C. The reaction time of the hydrothermal reaction ranges from 7 to 17 hours.

4. The method for preparing a nickel-molybdenum-sulfur electrocatalyst according to claim 1, characterized in that, The sulfidation reaction of the electrocatalyst precursor includes, Sodium thiosulfate and a second solvent were prepared according to a weight ratio of 1:50, and a sulfidation reaction solution was prepared. The electrocatalyst precursor is placed in the sulfidation reaction solution for sulfidation reaction.

5. The method for preparing a nickel-molybdenum-sulfur electrocatalyst according to claim 1, characterized in that, The reaction temperature of the sulfidation reaction is in the range of 90 to 110°C; The reaction time for the vulcanization reaction ranges from 5 to 11 hours.

6. The method for preparing a nickel-molybdenum-sulfur electrocatalyst according to claim 1, characterized in that, The hydrothermal reaction is carried out in a reactor with a polytetrafluoroethylene liner. And / or, The vulcanization reaction is carried out in a reaction vessel with a polytetrafluoroethylene liner.

7. The method for preparing a nickel-molybdenum-sulfur electrocatalyst according to claim 1, characterized in that, It also includes, The nickel foam was cleaned sequentially with ethanol, 1 mol / L hydrochloric acid, and deionized water for cleaning.

8. The method for preparing a nickel-molybdenum-sulfur electrocatalyst according to claim 1, characterized in that, It also includes, The electrocatalyst precursor was rinsed with deionized water for cleaning.

9. The method for preparing a nickel-molybdenum-sulfur electrocatalyst according to claim 1, characterized in that, It also includes, The nickel-molybdenum-sulfur electrocatalyst is subjected to vacuum drying, wherein the drying time ranges from 9 to 15 hours and the drying temperature ranges from 50 to 70°C.

10. A nickel-molybdenum-sulfur electrocatalyst, characterized in that, Prepared by the preparation method according to any one of claims 1 to 9.

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