Method for synthesizing a rich-heterojunction nickel-molybdenum-based hydrogen evolution catalyst with the aid of a magnetic field

Abstract

The application provides a method for synthesizing a nickel-molybdenum-based hydrogen evolution catalyst with rich heterojunctions under the assistance of a magnetic field, and belongs to the technical field of water electrolysis hydrogen evolution catalyst preparation. The steps of the method comprise the following: a foam copper substrate is sequentially subjected to ultrasonic treatment in hydrochloric acid, anhydrous ethanol and deionized water, and then vacuum drying is performed to obtain a pretreated foam copper; a nickel salt and a molybdenum salt are dissolved in deionized water, and then a complexing agent, a buffering agent and a conductive salt are added and uniformly mixed to obtain an electrodeposition solution; the electrodeposition solution is transferred to an electrolytic cell, and the pH of the electrodeposition solution is adjusted to be alkaline; the electrolytic cell is transferred to a magnetic field, and electrodeposition treatment is prepared; the pretreated foam copper is used as a working electrode, a graphite sheet is used as a counter electrode, and Hg / HgO is used as a reference electrode, and then constant current electrodeposition treatment is performed on the electrodeposition solution to obtain the nickel-molybdenum-based hydrogen evolution catalyst with rich heterojunctions. The method for synthesizing the nickel-molybdenum-based hydrogen evolution catalyst with rich heterojunctions under the assistance of a magnetic field is simple in process, low in cost, low in energy consumption and high in yield.

Description

Technical Field

[0001] This invention relates to the field of hydrogen evolution catalyst preparation technology for water electrolysis, and particularly to a method for magnetic field-assisted synthesis of heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts. Background Technology

[0002] Since the Industrial Revolution, the combustion of large quantities of fossil fuels has emitted significant amounts of CO2 and SO2. x NO x Gases such as hydrogen spores pose a serious threat to our environment. Hydrogen energy, as the most promising clean energy carrier, is considered a promising alternative to fossil fuels due to its high energy density and zero carbon emissions from combustion. Electrolysis of water to produce hydrogen has become the mainstream technology for large-scale green hydrogen production due to its well-developed process and high H2 purity. However, freshwater accounts for only 2.5% of global water resources. Over-reliance on freshwater for hydrogen production will exacerbate the freshwater resource crisis.

[0003] Hydrogen production via seawater electrolysis can overcome the limitations of freshwater resources. However, the slow reaction kinetics in seawater electrolysis restrict the hydrogen evolution reaction. Simultaneously, the complex ionic environment of seawater (i.e., high concentrations of Cl-) further complicates the process. - (And various dissolved metal cations) can easily lead to catalyst corrosion and poisoning, reduce electrode activity, and accelerate deactivation and decomposition.

[0004] Although noble metal catalysts, such as platinum, possess high HER activity, their high cost and insufficient durability in seawater severely limit their application in seawater catalytic hydrogen production. Therefore, the development of catalysts capable of operating at industrial-grade current densities (>400 mA / cm²) is crucial. -2 Highly active and durable non-precious metal catalysts are crucial for accelerating the development of alkaline seawater electrolysis for hydrogen production.

[0005] Among various types of non-precious metal catalysts, nickel-molybdenum alloys exhibit extremely high catalytic performance due to their tunable composition and modifiable electronic structure. However, the poor hydrogen desorption capacity of nickel-molybdenum alloys hinders hydrogen escape, resulting in a significant gap between their HER activity and that of commercial Pt / C catalysts.

[0006] Studies have shown that constructing Ni4Mo / MoO x Heterogeneous structures optimize the adsorption / desorption process of intermediates, thereby effectively improving the intrinsic activity of catalysts. This is currently an effective solution to enhance the ability of nickel-molybdenum alloys to catalyze hydrogen production from seawater.

[0007] Preparation of Ni4Mo / MoO in existing technologies x There are two main methods for developing heterogeneous hydrogen evolution catalysts: hydrothermal and electrodeposition.

[0008] The hydrothermal method involves the hydrothermal synthesis of NiMoO4 precursors, which are then calcined at high temperatures (typically 400-800℃) in a reducing atmosphere (usually an Ar / H2 mixture) to obtain Ni4Mo / MoO. x Heterogeneous hydrogen evolution catalysts. However, this preparation process involves high-temperature calcination, which consumes additional energy. At the same time, the process is complex, time-consuming, and has low yield, making it difficult to achieve mass production in industrial applications.

[0009] Although electrodeposition can solve the problems of complex process, long time and low yield in hydrothermal preparation, the concentration polarization during the deposition process will reduce the mass transfer efficiency, resulting in insufficient exposure of active sites and agglomeration of alloy particles in the prepared catalyst. As a result, it is difficult for the catalyst to achieve high activity and stable hydrogen evolution at high current density.

[0010] Therefore, there is an urgent need for a method to prepare a heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst that is simple in process, low in cost, low in energy consumption, and high in yield. Summary of the Invention

[0011] The technical problem to be solved by the present invention is to provide a method for magnetic field-assisted synthesis of heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts that is simple in process, low in cost, low in energy consumption and high in yield, so as to solve the problems of insufficient exposure of active sites and agglomeration of alloy particles in current catalysts.

[0012] To address the aforementioned technical problems, this invention provides a method for magnetic field-assisted synthesis of heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts, comprising the following steps:

[0013] Copper foam was ultrasonically treated sequentially with hydrochloric acid, anhydrous ethanol and deionized water, and then vacuum dried to obtain pretreated copper foam.

[0014] Nickel and molybdenum salts were dissolved in deionized water, and then complexing agent, buffer and conductive salt were added and mixed to obtain electrodeposition solution;

[0015] The electrodeposition solution was transferred to the electrolytic cell, and the pH of the electrodeposition solution was adjusted to alkaline.

[0016] The electrolytic cell is transferred into a magnetic field in preparation for electrodeposition.

[0017] Using pretreated copper foam as the working electrode, graphite sheet as the counter electrode, and Hg / HgO as the reference electrode, a heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst was obtained by constant current electrodeposition treatment of the electrodeposition solution.

[0018] Furthermore, the molar concentration of the hydrochloric acid is 1–5 M.

[0019] Furthermore, the vacuum drying temperature is 40–90°C, and the vacuum drying time is 1–6 hours.

[0020] Furthermore, the nickel salt is nickel sulfate hexahydrate, and the molybdenum salt is sodium molybdate dihydrate.

[0021] Furthermore, the molar ratio of the nickel salt to the molybdenum salt is 1:1 to 1:32.

[0022] Furthermore, the complexing agent and buffer are sodium citrate, and the conductive salt is sodium chloride.

[0023] Furthermore, adjusting the pH of the electrodeposition solution to alkaline is achieved by using NH3·H2O to adjust the pH of the electrodeposition solution to 8–11.

[0024] Furthermore, the magnetic field strength of the electromagnet is 0 to 2 T.

[0025] Furthermore, the current used for constant current electrodeposition treatment of the electrodeposition solution is -0.5 to -1 A, and the electrodeposition time is 5 min to 60 min.

[0026] This invention provides a method for magnetic field-assisted synthesis of heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts. Applying a magnetic field to the electrodeposition solution during the electrodeposition process can improve concentration polarization. Due to the Lorentz force acting on charged ions in the magnetic field, and the interaction of metal ions with the electric and magnetic fields during electrodeposition, macroscopic convection, i.e., magnetohydrodynamics (MHD), occurs in the electrodeposition solution. While the electrodeposition reaction consumes metal ions on the substrate surface, the macroscopic convection generated by the MHD effect accelerates the replenishment of metal ions in the bulk phase, suppressing concentration polarization and ensuring the reaction remains within a preset metal ion concentration range, thus enhancing mass transfer at the electrode surface. Furthermore, the introduction of the magnetic field reduces the boundary layer thickness, enhances nucleation, and suppresses metal particle aggregation. Simultaneously, the magnetic field also refines the Ni4Mo grain size, giving the catalyst a larger specific surface area, which is beneficial for exposing active sites and promoting their participation in the catalytic reaction.

[0027] Therefore, the present invention provides a method for magnetic field-assisted synthesis of heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts, which effectively solves the problems of particle agglomeration and insufficient exposure of active sites caused by concentration polarization during electrodeposition by introducing a magnetic field of appropriate strength.

[0028] Furthermore, the present invention provides a method for magnetic field-assisted synthesis of heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts. Under magnetic field assistance, the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts can be prepared by one-step electrodeposition. Compared with the traditional hydrothermal method for preparing heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts, the process is simple, easy to operate, consumes less energy, and has a lower cost.

[0029] Meanwhile, the present invention provides a method for magnetic field-assisted synthesis of heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts. The resulting heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts are used in seawater electrolysis and exhibit excellent catalytic activity and stability in the hydrogen evolution reaction. Attached Figure Description

[0030] Figure 1 This is a flowchart of a method for magnetic field-assisted synthesis of heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts according to an embodiment of the present invention;

[0031] Figure 2 The Ni4Mo / MoO prepared in the comparative example of this invention x Comparison of SEM images of the nickel-molybdenum-based hydrogen evolution catalyst and the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared in Example 1, wherein... Figure 2 (a) Ni4Mo / MoO prepared as a comparative example x SEM images of nickel-molybdenum based hydrogen evolution catalysts. Figure 2 (b) is a SEM image of the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared in Example 1;

[0032] Figure 3 The Ni4Mo / MoO prepared in the comparative example of this invention x TEM images of nickel-molybdenum based hydrogen evolution catalysts, in which Figure 3 (a) and Figure 3 (c) is a low-magnification TEM image. Figure 3 (b) is Figure 3 (a) High-magnification TEM image of the corresponding region. Figure 3 (d) is Figure 3 (c) High-magnification TEM image of the corresponding region;

[0033] Figure 4 This is a TEM image of the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared in Example 1 of the present invention, wherein... Figure 4 (a) and Figure 4 (c) is a low-magnification TEM image. Figure 4 (b) is Figure 4 (a) High-magnification TEM image of the corresponding region. Figure 4 (d) is Figure 4 (c) High-magnification TEM image of the corresponding region;

[0034] Figure 5 The Ni4Mo / MoO prepared in the comparative example of this invention x XRD comparison of the nickel-molybdenum-based hydrogen evolution catalyst and the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared in Example 1;

[0035] Figure 6 The Ni4Mo / MoO prepared in the comparative example of this invention xComparison of N2 adsorption / desorption curves of the nickel-molybdenum-based hydrogen evolution catalyst and the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared in Example 1;

[0036] Figure 7 The Ni4Mo / MoO prepared in the comparative example of this invention x Comparison of hydrogen evolution reaction polarization curves of the nickel-molybdenum-based hydrogen evolution catalyst and the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared in Example 1;

[0037] Figure 8 The Ni4Mo / MoO prepared in the comparative example of this invention x Comparison of stability test curves of the nickel-molybdenum-based hydrogen evolution catalyst and the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared in Example 1 in alkaline seawater solutions with ampere-level current densities.

[0038] Figure 9 This is a stability test curve of the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared in Example 1 of the present invention in alkaline solution. Detailed Implementation

[0039] See Figure 1 The present invention provides a method for magnetic field-assisted synthesis of heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts, comprising the following steps:

[0040] Step 1) The copper foam is ultrasonically treated in hydrochloric acid, anhydrous ethanol and deionized water in sequence, and then vacuum dried to obtain pretreated copper foam.

[0041] Oil and oxide layers on the surface of copper foam can be removed by ultrasonic treatment in hydrochloric acid, anhydrous ethanol and deionized water in sequence.

[0042] Then, vacuum drying is performed on the ultrasonically cleaned copper foam to remove residual liquid from the surface. The pretreated copper foam obtained through the above pretreatment is beneficial for electrodeposition as a working electrode in subsequent electrodeposition processes.

[0043] The molar concentration of hydrochloric acid is 1–5 M.

[0044] The vacuum drying temperature is 40–90℃, and the vacuum drying time is 1–6 hours.

[0045] Step 2) Dissolve nickel and molybdenum salts in deionized water to obtain a mixed solution of nickel and molybdenum salts. Then, add a complexing agent, a buffer, and a conductive salt to the mixed solution and mix thoroughly to obtain the electrodeposition solution. By adding a complexing agent, a buffer, and a conductive salt to the mixed solution of nickel and molybdenum salts, the conductivity of the electrodeposition solution can be enhanced, while also ensuring that nickel and molybdenum elements are deposited simultaneously during the subsequent electrodeposition process.

[0046] Among them, the nickel salt is nickel sulfate hexahydrate, and the molybdenum salt is sodium molybdate dihydrate.

[0047] Furthermore, the molar ratio of nickel salt to molybdenum salt is 1:1 to 1:32.

[0048] The complexing agent and buffer are both sodium citrate, and the conductive salt is sodium chloride.

[0049] Step 3) Transfer the electrodeposition solution to the electrolytic cell and adjust the pH of the electrodeposition solution to alkaline.

[0050] In order to adjust the pH of the electrodeposition solution, NH3·H2O was added to the electrodeposition solution to adjust the pH to 8-11.

[0051] Step 4) Transfer the electrolytic cell to the electromagnet magnetic field to prepare for electrodeposition treatment.

[0052] Among them, electromagnets can generate a uniform magnetic field, and in order to achieve the ideal electrodeposition effect, the magnetic field strength of electromagnets is controlled between 0 and 2T.

[0053] Step 5) Using pretreated copper foam as the working electrode, graphite sheet as the counter electrode, and Hg / HgO as the reference electrode, the electrodeposition solution is subjected to constant current electrodeposition treatment to obtain a heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst.

[0054] In order to achieve the desired electrodeposition effect, the current is controlled at -0.5 to -1A and the electrodeposition time is 5 min to 60 min during the constant current electrodeposition treatment of the electrodeposition solution.

[0055] This invention provides a method for magnetic field-assisted synthesis of heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts, in which a magnetic field is applied to the electrodeposition solution during the electrodeposition process. Due to the Lorentz force acting on charged ions in the magnetic field, and the interaction of metal ions during electrodeposition with both electric and magnetic fields, macroscopic convection, i.e., magnetohydrodynamic (MHD) effect, occurs in the electrodeposition solution. The electrodeposition reaction consumes metal ions on the substrate surface, while the macroscopic convection generated by the MHD effect accelerates the replenishment of metal ions in the bulk phase, thereby suppressing concentration polarization during electrodeposition and ensuring the reaction remains within a preset metal ion concentration range, enhancing mass transfer at the electrode surface. Furthermore, the introduction of the magnetic field reduces the boundary layer thickness, enhances nucleation, and thus suppresses metal particle agglomeration. Simultaneously, the magnetic field refines the Ni4Mo grain size, giving the catalyst a larger specific surface area, which is beneficial for the exposure of active sites and promotes their participation in the catalytic reaction. Therefore, this invention effectively solves the problems of particle agglomeration and insufficient exposure of active sites caused by concentration polarization during electrodeposition by introducing a magnetic field of appropriate intensity.

[0056] Furthermore, this invention provides a method for magnetic field-assisted synthesis of heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts. Under magnetic field assistance, the catalyst can be prepared via a one-step electrodeposition method. Compared to traditional hydrothermal methods for preparing heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts, this method is simpler, easier to operate, consumes less energy, and has lower costs. The resulting heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst exhibits excellent catalytic activity and stability in seawater electrolysis.

[0057] The following comparative examples and embodiments provide a detailed description of the method for magnetic field-assisted synthesis of heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts provided by the present invention.

[0058] Comparative Example 1

[0059] This comparative example provides a conventional electrodeposition method for preparing Ni4Mo / MoO. x A method for developing a nickel-molybdenum-based hydrogen evolution catalyst includes the following steps:

[0060] S1: The copper foam was placed in hydrochloric acid, anhydrous ethanol and deionized water in sequence for ultrasonic treatment, and then vacuum dried at 60°C for 3 hours to remove residual liquid on the surface, thus producing pretreated copper foam.

[0061] S2: Prepare an electrodeposition solution by mixing nickel sulfate:sodium molybdate:sodium chloride:sodium citrate in a molar ratio of 5:1:10:10 and sodium molybdate:deionized water in a mass ratio of 0.1:30.

[0062] S3: Transfer the electrodeposition solution to the electrolytic cell and adjust the pH of the solution to 10 using NH3·H2O.

[0063] S4: Using an electrochemical workstation, with pretreated copper foam as the working electrode, graphite sheet as the counter electrode, and Hg / HgO as the reference electrode, each electrode was placed in the electrodeposition solution and subjected to constant current electrodeposition treatment at a current of -0.5A for 5 minutes to prepare a Ni4Mo / MoO. x Nickel-molybdenum based hydrogen evolution catalyst.

[0064] The Ni4Mo / MoO prepared in this comparative example x SEM images of nickel-molybdenum based hydrogen evolution catalysts are shown below. Figure 2 As shown in (a).

[0065] The Ni4Mo / MoO prepared in this comparative example x TEM images of nickel-molybdenum based hydrogen evolution catalysts are shown below. Figure 3 As shown.

[0066] in, Figure 3 (a) is a low-magnification TEM image. Figure 3 (b) is Figure 3(a) High-magnification TEM image of the corresponding area, where the dark spherical particles are crystalline Ni4Mo and the light-colored amorphous film is amorphous MoO. X .

[0067] Depend on Figure 3 (a) and Figure 3 (b) This demonstrates that the Ni4Mo / MoO prepared in this comparative example using the traditional electrodeposition method... x The distribution of substances in the nickel-molybdenum-based hydrogen evolution catalyst is uneven.

[0068] in, Figure 3 (c) is a low-magnification TEM image. Figure 3 (c) The dark spherical particles are agglomerations of ultra-large metal particles. Figure 3 (d) is Figure 3 (c) High-magnification TEM image of the corresponding region Figure 3 (d) The yellow dashed lines represent crystalline Ni4Mo and amorphous MoO. x The boundary.

[0069] Figure 3 (c) and Figure 3 (d) This demonstrates that the Ni4Mo / MoO prepared in this comparative example using the traditional electrodeposition method... x Nickel-molybdenum based hydrogen evolution catalysts often exhibit insufficient exposure of active sites and agglomeration of alloy particles. Therefore, this comparative example uses a conventional electrodeposition method to prepare Ni4Mo / MoO4 catalysts. x Nickel-molybdenum based hydrogen evolution catalysts are difficult to achieve high activity and stable hydrogen evolution at high current densities.

[0070] To test the Ni4Mo / MoO prepared in this comparative example x Phase composition of the nickel-molybdenum-based hydrogen evolution catalyst, and the Ni4Mo / MoO prepared in this comparative example. x XRD images of nickel-molybdenum based hydrogen evolution catalysts are shown below. Figure 5 As shown. This comparative example did not use a magnetic field to assist in the synthesis of the catalyst; that is, the magnetic field strength of this comparative example is 0T. Figure 5 The curve corresponding to NiMo-0T.

[0071] To test the Ni4Mo / MoO prepared in this comparative example x The specific surface area of ​​the nickel-molybdenum-based hydrogen evolution catalyst, and the Ni4Mo / MoO prepared in this comparative example. x The N2 adsorption / desorption curves of the nickel-molybdenum-based hydrogen evolution catalyst are shown in the figure. Figure 6 As shown. This comparative example did not use a magnetic field to assist in the synthesis of the catalyst; that is, the magnetic field strength of this comparative example is 0T. Figure 6 The curve corresponding to NiMo-0T.

[0072] To characterize the activity of the prepared catalyst, the Ni4Mo / MoO4 catalyst prepared in this comparative example was used. x The polarization curves of the hydrogen evolution reaction of the nickel-molybdenum based hydrogen evolution catalyst are shown in the figure. Figure 7 As shown. This comparative example did not use a magnetic field to assist in the synthesis of the catalyst; that is, the magnetic field strength of this comparative example is 0T. Figure 7 The curve corresponding to NiMo-0T.

[0073] To characterize the stability of the catalyst in alkaline seawater solution at ampere-level current densities, this comparative example prepared Ni4Mo / MoO x The stability test curves of the nickel-molybdenum-based hydrogen evolution catalyst in alkaline seawater solutions at ampere-level current densities are shown in the figure below. Figure 8 As shown. This comparative example did not use a magnetic field to assist in the synthesis of the catalyst; that is, the magnetic field strength of this comparative example is 0T. Figure 8 The curve corresponding to NiMo-0T.

[0074] Example 1

[0075] This invention provides a method for magnetic field-assisted synthesis of heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts, comprising the following steps:

[0076] S1: The copper foam was subjected to ultrasonic treatment in 4M hydrochloric acid, anhydrous ethanol and deionized water respectively, and then vacuum dried at 60℃ for 3h to remove residual liquid on the surface, thus producing pretreated copper foam.

[0077] S2: Prepare an electrodeposition solution by mixing nickel sulfate:sodium molybdate:sodium chloride:sodium citrate in a molar ratio of 5:1:10:10 and sodium molybdate:deionized water in a mass ratio of 0.1:30.

[0078] S3: Transfer the electrodeposition solution to the electrolytic cell and adjust the pH of the solution to 10 using NH3·H2O.

[0079] S4: Transfer the electrolytic cell to a 2T magnetic field to prepare for the electrodeposition process.

[0080] S5: Using an electrochemical workstation, with pretreated copper foam as the working electrode, graphite sheet as the counter electrode, and Hg / HgO as the reference electrode, each electrode was placed in an electrodeposition solution and subjected to constant current electrodeposition treatment at a current of -0.5A for 5 minutes to prepare a highly active and stable heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst.

[0081] SEM images of the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared in the embodiments of the present invention are as follows: Figure 1 As shown in (b).

[0082] from Figure 2A comparison of (a) and (b) shows that the surface of the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared in Example 1 of the present invention is smoother, indicating that smaller grains and a more uniform material distribution are formed in the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared by electrodeposition under a magnetic field in Example 1 of the present invention.

[0083] TEM images of the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared in the embodiments of the present invention are as follows: Figure 4 As shown.

[0084] in, Figure 4 (a) and Figure 4 (c) is a low-magnification TEM image. Figure 4 (b) is Figure 4 (a) High-magnification TEM image of the corresponding region. Figure 4 (d) is Figure 4 (c) High-magnification TEM image of the corresponding region. The dark spherical particles are crystalline Ni₄Mo, and the light-colored amorphous film is amorphous MoO. X , Figure 4 (b) and Figure 3 (d) The yellow dashed lines represent crystalline Ni4Mo and amorphous MoO. x The boundary.

[0085] Depend on Figure 4 It can be seen that the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared by magnetic field-assisted electrodeposition in Example 1 of the present invention has a uniform material distribution and abundant Ni4Mo / MoO. x The structure is heterogeneous (i.e., rich in heterojunctions), and this distribution is present in different regions.

[0086] To determine the phase composition of the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared in Example 1 of this invention, the XRD image of the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared in Example 1 of this invention is shown below. Figure 5 As shown. In Example 1 of this invention, the magnetic field strength used for the magnetic field-assisted synthesis of the catalyst is 2T, that is, Example 1 of this invention is... Figure 5 The curve corresponding to NiMo-2T.

[0087] from Figure 5 The comparison shows that, compared with the catalyst prepared in the comparative example, the catalyst prepared in Example 1 of the present invention contains Ni4Mo crystals; and, at the peak position corresponding to the (121) plane, after applying a magnetic field, the peak intensity decreased and the peak broadened, indicating that the catalyst prepared in Example 1 of the present invention exhibited a grain refinement phenomenon. Smaller grain size means that more active sites are exposed, so the catalyst prepared in Example 1 of the present invention has better catalytic performance.

[0088] To test the specific surface area of ​​the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared in Example 1 of this invention, the N2 adsorption / desorption curves of the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared in Example 1 of this invention are shown in the figure below. Figure 6 As shown. In Example 1 of this invention, the magnetic field strength used for the magnetic field-assisted synthesis of the catalyst is 2T, that is, Example 1 of this invention is... Figure 6 The curve corresponding to NiMo-2T.

[0089] from Figure 6 As can be seen from the comparison, the catalyst prepared in Example 1 of the present invention has a larger specific surface area than the catalyst prepared in the comparative example, which is beneficial to the subsequent catalytic reaction.

[0090] To characterize the activity of the prepared catalyst, the hydrogen evolution reaction polarization curve of the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared in Example 1 of this invention is shown in the figure below. Figure 7 As shown. In Example 1 of this invention, the magnetic field strength used for the magnetic field-assisted synthesis of the catalyst is 2T, that is, Example 1 of this invention is... Figure 7 The curve corresponding to NiMo-2T.

[0091] from Figure 7 The comparison shows that the catalyst prepared in Example 1 of the present invention has a smaller overpotential than the catalyst prepared in the comparative example under the same current density, indicating that it has better catalytic activity.

[0092] To characterize the stability of the catalyst in alkaline seawater solution at ampere-level current densities, the stability test curve of the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared in Example 1 of this invention in alkaline seawater solution at ampere-level current densities is shown in the figure below. Figure 8 As shown. In Example 1 of this invention, the magnetic field strength used for the magnetic field-assisted synthesis of the catalyst is 2T, that is, Example 1 of this invention is... Figure 8 The curve corresponding to NiMo-2T.

[0093] from Figure 8 The comparison shows that the catalyst prepared in Example 1 of the present invention, under the assistance of a magnetic field, can continuously electrolyze seawater for more than 1500 hours, compared with the catalyst prepared by the conventional electrodeposition method in the comparative example without the assistance of a magnetic field, while the catalyst prepared by the conventional electrodeposition method in the comparative example is deactivated after 300 hours.

[0094] Furthermore, to characterize the stability of the catalyst prepared under magnetic field assistance in an alkaline environment according to Example 1 of the present invention, the stability test curve of the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared in Example 1 of the present invention in alkaline solution is shown in the figure below. Figure 9 As shown.

[0095] from Figure 9It can be seen that the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared in Example 1 of the present invention showed almost no change in overpotential after 100 hours of continuous testing, indicating that the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared in Example 1 of the present invention has excellent stability.

[0096] Example 2

[0097] This invention provides a method for magnetic field-assisted synthesis of heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts, comprising the following steps:

[0098] S1: The copper foam was placed in 3M hydrochloric acid, anhydrous ethanol and deionized water in sequence and ultrasonically treated for 20 min each. Then it was vacuum dried at 50℃ for 4 h to remove the residual liquid on the surface and prepare the pretreated copper foam.

[0099] S2: Prepare an electrodeposition solution by mixing nickel sulfate:sodium molybdate:sodium chloride:sodium citrate in a molar ratio of 16:1:24:24 and sodium molybdate:deionized water in a mass ratio of 0.0775:50.

[0100] S3: Transfer the electrodeposition solution to the electrolytic cell and adjust the pH of the solution to 9 using NH3·H2O.

[0101] S4: Transfer the electrolytic cell to a uniform magnetic field of 1T to prepare for electrodeposition.

[0102] S5: Using an electrochemical workstation, with pretreated copper foam as the working electrode, graphite sheet as the counter electrode, and Hg / HgO as the reference electrode, each electrode was placed in an electrodeposition solution and subjected to constant current electrodeposition treatment at a current of -0.6A for 10 minutes to prepare a highly active and stable heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst.

[0103] Example 3

[0104] This invention provides a method for magnetic field-assisted synthesis of heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts, comprising the following steps:

[0105] S1: The copper foam was placed in 5M hydrochloric acid, anhydrous ethanol and deionized water respectively for ultrasonic treatment for 8 minutes, and then vacuum dried at 70℃ for 2 hours to remove residual liquid on the surface, thus producing pretreated copper foam.

[0106] S2: Prepare an electrodeposition solution by mixing nickel sulfate:sodium molybdate:sodium chloride:sodium citrate in a molar ratio of 1:1:1.5:1.5 and sodium molybdate:deionized water in a mass ratio of 2.48:50.

[0107] S3: Transfer the electrodeposition solution to the electrolytic cell and adjust the pH of the solution to 8 using NH3·H2O.

[0108] S4: Transfer the electrolytic cell to a uniform magnetic field of 1.5T to prepare for the electrodeposition experiment.

[0109] S5: Using an electrochemical workstation, with pretreated copper foam as the working electrode, graphite sheet as the counter electrode, and Hg / HgO as the reference electrode, each electrode was placed in an electrodeposition solution and subjected to constant current electrodeposition treatment at a current of -0.7A for 15 minutes to prepare a highly active and stable heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst.

[0110] The present invention provides a method for magnetic field-assisted synthesis of a heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst in Examples 2 and 3. The electrodeposition of the electrodeposition solution is carried out under magnetic field conditions of 1T and 1.5T, respectively. Therefore, similar to Example 1, the obtained heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst possesses abundant Ni₄Mo / MoO₂. x The heterostructure (i.e., heterojunction-rich) and the resulting heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst exhibited grain refinement, which prevented grain agglomeration and resulted in smaller grains and a more uniform material distribution. The smaller grain size means that the resulting heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst has a larger specific surface area and more active sites exposed, resulting in better catalytic performance and facilitating the efficient conduction of subsequent catalytic reactions.

[0111] To further illustrate the method for magnetic field-assisted synthesis of heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts provided in Examples 1-3 of this invention, the prepared heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts exhibit superior performance. This is in contrast to the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts prepared in Examples 1-3 of this invention and the Ni4Mo / MoO4 catalyst prepared in the comparative example. x The nickel-molybdenum-based hydrogen evolution catalysts were subjected to performance tests for catalyst activity and catalyst stability, and the specific test methods are as follows:

[0112] 1. Test method for catalyst activity: The catalysts prepared in Examples 1-3 and the comparative example were used as working electrodes, graphite sheets as counter electrodes, and Hg / HgO electrodes as reference electrodes to form a three-electrode system. The electrolyte was 1M KOH solution. The linear sweep voltammetry (LSV) method was used to measure the activity using an electrochemical workstation (VSP, Bio-Logic).

[0113] 2. Test method for catalyst stability: The catalysts prepared in Examples 1-3 and the comparative example were used as working electrodes, graphite sheets as counter electrodes, and Hg / HgO electrodes as reference electrodes to form a three-electrode system. The electrolyte was an alkaline (1M KOH) or alkaline seawater (1M KOH + seawater) solution. The chronopotential method (CP) of an electrochemical workstation (VSP, Bio-Logic) was used for measurement.

[0114] The heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts prepared in Examples 1-3 of this invention and the Ni4Mo / MoO prepared in the comparative example x The performance test results of the nickel-molybdenum-based hydrogen evolution catalyst are shown in Table 1.

[0115] Table 1

[0116] <![CDATA[Overpotential / mV(@10mA cm -2 )]]> 26 17 20 25 <![CDATA[Stability / hour(@1A cm -2 )]]> 296 1500 698 502

[0117] According to the generally accepted performance evaluation standards in the field of electrocatalysis, at 10 mA cm⁻¹ -2 A smaller overpotential at current density indicates better catalytic activity, at 1 A cm⁻¹. -2 The longer the test time at ampere-level current densities and the absence of performance degradation, the better the stability. As can be seen from the comparison in Table 1, the 10mA cm⁻¹ of Examples 1-3 of this invention… -2 The overpotentials at the current density are all less than the 10 mA cm of the comparative example. -2 Overpotential at current density, 1A cm in Examples 1-3 of this invention -2 The test times at ampere-level current densities were all higher than those at 1 A cm⁻¹ in the comparative example. -2 The test time at ampere-level current densities also demonstrates that the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts prepared in Examples 1-3 of this invention are superior to the Ni4Mo / MoO catalysts prepared in the comparative example. x The nickel-molybdenum-based hydrogen evolution catalyst exhibits good catalytic activity and high stability.

[0118] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for magnetic field-assisted synthesis of heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts, characterized in that, Includes the following steps: Copper foam was ultrasonically treated sequentially with hydrochloric acid, anhydrous ethanol and deionized water, and then vacuum dried to obtain pretreated copper foam. Nickel and molybdenum salts were dissolved in deionized water, and then complexing agent, buffer and conductive salt were added and mixed to obtain electrodeposition solution; The electrodeposition solution was transferred to the electrolytic cell, and the pH of the electrodeposition solution was adjusted to alkaline. The electrolytic cell is transferred to a magnetic field with a strength of 1 to 2 T in preparation for electrodeposition. Using pretreated copper foam as the working electrode, graphite sheet as the counter electrode, and Hg / HgO as the reference electrode, the electrodeposition solution was subjected to constant current electrodeposition treatment for 5 min to 60 min at a current of -0.5 to -1 A to obtain a heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst. The nickel salt is nickel sulfate hexahydrate, and the molybdenum salt is sodium molybdate dihydrate; the molar ratio of the nickel salt to the molybdenum salt is 5:

1.

2. The method for magnetic field-assisted synthesis of heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts according to claim 1, characterized in that: The molar concentration of the hydrochloric acid is 1–5 M.

3. The method for magnetic field-assisted synthesis of heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts according to claim 1, characterized in that: The vacuum drying temperature is 40–90°C, and the vacuum drying time is 1–6 hours.

4. The method for magnetic field-assisted synthesis of heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts according to claim 1, characterized in that: The complexing agent and buffer are sodium citrate, and the conductive salt is sodium chloride.

5. The method for magnetic field-assisted synthesis of heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts according to claim 1, characterized in that: The process of adjusting the pH of the electrodeposition solution to alkaline is performed by using NH3•H2O to adjust the pH of the electrodeposition solution to 8-11.

Images