Method for synthesizing heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst under assistance of magnetic field

Abstract

The invention provides a method for synthesizing a heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst under the assistance of a magnetic field, and belongs to the technical field of preparation of electrolyzed water hydrogen evolution catalysts.The method comprises the steps that a foamy copper substrate is subjected to ultrasonic treatment in hydrochloric acid, absolute ethyl alcohol and deionized water in sequence, then vacuum drying is conducted, and pretreated foamy copper is obtained; dissolving nickel salt and molybdenum salt in deionized water, then adding a complexing agent, a buffering agent and conducting salt, and uniformly mixing to obtain an electro-deposition solution; transferring the electro-deposition solution into an electrolytic tank, and adjusting the pH value of the electro-deposition solution to be alkaline; the electrolytic tank is transferred into a magnetic field, and electro-deposition treatment is prepared; the pretreated foamy copper is used as a working electrode, a graphite sheet is used as a counter electrode, Hg / HgO is used as a reference electrode, and constant-current electro-deposition treatment is carried out on the electro-deposition solution to obtain the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst. The method for synthesizing the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst under the assistance of the magnetic field, provided by the invention, is simple in process, low in cost, low in energy consumption and high in yield.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation of hydrogen evolution catalysts by electrolysis of water, and in particular to a method for synthesizing a heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst with the assistance of a magnetic field. Background Art

[0002] Since the Industrial Revolution, the burning of large amounts of fossil energy has emitted large amounts of CO2, SO x 、NO x Gases such as carbon monoxide and hydrogen are seriously threatening the environment on which we depend. As the most promising clean energy carrier, hydrogen is considered a promising alternative to fossil fuels due to its high energy density and zero carbon emissions from combustion products. Hydrogen production through water electrolysis has become the mainstream technology for large-scale green hydrogen production due to its sophisticated process and high H2 purity. However, fresh water only accounts for 2.5% of total water resources globally. Over-reliance on fresh water for hydrogen production will exacerbate the freshwater resource crisis.

[0003] The use of seawater electrolysis to produce hydrogen can overcome the limitation of fresh water resources. However, the slow reaction kinetics in the process of seawater electrolysis limits the progress of hydrogen evolution reaction. At the same time, the complex ion environment in seawater (i.e. high concentration of Cl - and various dissolved metal cations) can easily lead to corrosion and poisoning of the catalyst, reducing the activity of the electrode and accelerating deactivation and decomposition.

[0004] Although precious metal catalysts such as platinum have high HER activity, their high cost and insufficient durability in seawater severely limit their application in seawater catalytic hydrogen production. Therefore, the development of industrial-grade current density (>400mAcm -2 ) Non-precious metal catalysts with high activity and durability are crucial for accelerating the development of alkaline seawater electrolysis for hydrogen production.

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

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

[0007] Preparation of Ni4Mo / MoO in the prior art x There are two main methods for preparing heterogeneous hydrogen evolution catalysts: hydrothermal method and electrodeposition method.

[0008] Among them, the hydrothermal method is to synthesize NiMoO4 precursor by hydrothermal method, and the precursor is calcined at high temperature (usually 400-800℃) in a reducing atmosphere (usually Ar / H2 mixed gas) to obtain Ni4Mo / MoO x However, the preparation process involves high-temperature calcination, which consumes additional energy. Furthermore, the process is complex, time-consuming, and has low yields, making it difficult to achieve mass production in industrial production.

[0009] Although the electrodeposition method can solve the problems of complex process, long time and low yield in the hydrothermal preparation process, the concentration polarization during the deposition process will lead to reduced mass transfer efficiency, resulting in insufficient exposure of active sites and agglomeration of alloy particles in the prepared catalyst, making it 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 for preparing a heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst with simple process, low cost, low energy consumption and high yield. Summary of the Invention

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

[0012] To solve the above technical problems, the present invention provides a method for magnetic field-assisted synthesis of a heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst, comprising the following steps:

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

[0014] Dissolving nickel salt and molybdenum salt in deionized water, then adding a complexing agent, a buffer and a conductive salt and mixing them to obtain an electrodeposition solution;

[0015] transferring the electrodeposition solution to an electrolytic cell and adjusting the pH of the electrodeposition solution to alkaline;

[0016] Transferring the electrolytic cell to a magnetic field in preparation for electrodeposition treatment;

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

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

[0019] Furthermore, the vacuum drying temperature is 40 to 90° C., and the vacuum drying time is 1 to 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, the step of adjusting the pH of the electrodeposition solution to alkaline is to adjust the pH of the electrodeposition solution to 8-11 using NH3·H2O.

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

[0025] Furthermore, the current during the constant current electroplating treatment of the electroplating solution is -0.5 to -1 A, and the electroplating time is 5 to 60 minutes.

[0026] The present invention provides a method for magnetic field-assisted synthesis of heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts. A magnetic field is applied to the electrodeposition solution during the electrodeposition process, which can improve the concentration polarization phenomenon generated during the electrodeposition process. Since the charged ions are affected by the Lorentz force in the magnetic field, and the metal ions in the electrodeposition process are affected by the electric field and the magnetic field, the electrodeposition solution can generate macroscopic convection, that is, the magnetohydrodynamic (MHD) effect. The electrodeposition reaction consumes the metal ions on the surface of the substrate, and the macroscopic convection generated by the MHD effect can accelerate the replenishment of metal ions in the bulk phase, suppress the concentration polarization phenomenon, keep the reaction within the preset metal ion concentration condition range, and enhance the material transfer on the electrode surface. In addition, the introduction of the magnetic field can reduce the boundary layer thickness, enhance nucleation, and thus suppress the agglomeration of metal particles. At the same time, the introduction of the magnetic field can also refine the Ni4Mo grain size, so that the catalyst has a larger specific surface area, which is beneficial to the exposure of active sites and promotes its 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 the electrodeposition process by introducing a magnetic field of appropriate strength.

[0028] In addition, the present invention provides a method for magnetic field-assisted synthesis of heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts. The heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts can be prepared by a one-step electrodeposition method under the assistance of a magnetic field. 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 lower cost.

[0029] At the same time, the present invention provides a method for magnetic field-assisted synthesis of heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts. The prepared heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst is used for seawater electrolysis and has excellent catalytic activity and stability for hydrogen evolution reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A flow chart of a method for magnetic field-assisted synthesis of a heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst provided by an embodiment of the present invention;

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

[0032] Figure 3 Ni4Mo / MoO prepared in the comparative example of the present invention x TEM image of nickel-molybdenum-based hydrogen evolution catalyst, where Figure 3 (a) and Figure 3 (c) is a low-magnification TEM image. Figure 3 (b) Figure 3 (a) High-magnification TEM image of the corresponding area, Figure 3 (d) Figure 3 (c) High-magnification TEM image of the corresponding area;

[0033] Figure 4 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) Figure 4 (a) High-magnification TEM image of the corresponding area, Figure 4 (d) Figure 4 (c) High-magnification TEM image of the corresponding area;

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

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

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

[0037] Figure 8 Ni4Mo / MoO prepared in the comparative example of the present invention x Comparison of stability test curves of the nickel-molybdenum-based hydrogen evolution catalyst prepared in Example 1 and the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst in alkaline seawater solution at ampere-level current density;

[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 an alkaline solution. DETAILED DESCRIPTION

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

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

[0041] The oil stains and oxide layer on the surface of the copper foam can be removed by placing the copper foam in hydrochloric acid, anhydrous ethanol and deionized water in sequence for ultrasonic treatment.

[0042] The copper foam after ultrasonic cleaning is then vacuum dried to remove residual liquid on the surface. The pretreated copper foam obtained by the above pretreatment is used as a working electrode in the subsequent electrodeposition process, which is beneficial to the electrodeposition process.

[0043] Wherein, the molar concentration of hydrochloric acid is 1 to 5M.

[0044] The vacuum drying temperature is 40 to 90° C., and the vacuum drying time is 1 to 6 hours.

[0045] Step 2) dissolving a nickel salt and a molybdenum salt in deionized water to obtain a mixed solution of the nickel salt and molybdenum salt, and then adding a complexing agent, a buffer, and a conductive salt to the mixed solution of the nickel salt and molybdenum salt and mixing them uniformly to obtain an electrodeposition solution. By adding the complexing agent, the buffer, and the conductive salt to the mixed solution of the nickel salt and molybdenum salt, the conductivity of the electrodeposition solution can be enhanced, and the nickel and molybdenum elements can also be simultaneously precipitated during the subsequent electrodeposition process.

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

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

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

[0049] Step 3) transferring the electrodeposition solution to an electrolytic cell and adjusting the pH of the electrodeposition solution to alkaline.

[0050] In order to adjust the pH of the electrodeposition solution, NH 3 ·H 2 O is added to the electrodeposition solution to adjust the pH of the electrodeposition solution to 8-11.

[0051] Step 4) The electrolytic cell is transferred to the magnetic field of an electromagnet to prepare for electrodeposition treatment.

[0052] The electromagnet can generate a uniform magnetic field, and in order to achieve an ideal electrodeposition effect, the magnetic field strength of the electromagnet is controlled at 0 to 2T.

[0053] Step 5) Using the pretreated copper foam as the working electrode, the 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 expected electrodeposition effect, when the electrodeposition solution is subjected to constant current electrodeposition treatment, the current is controlled to be -0.5 to -1A, and the electrodeposition time is 5 to 60 minutes.

[0055] The present 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. Since charged ions are acted upon by the Lorentz force in the magnetic field, and metal ions in the electrodeposition process are acted upon by the electric and magnetic fields, the electrodeposition solution can generate macroscopic convection, i.e., magnetohydrodynamic (MHD) effect. The electrodeposition reaction consumes metal ions on the surface of the substrate, and the macroscopic convection generated by the MHD effect can accelerate the replenishment of metal ions in the bulk phase, thereby suppressing the concentration polarization phenomenon generated during the electrodeposition process, so that the reaction is always kept within the preset metal ion concentration condition range, and enhancing the material transfer on the electrode surface. In addition, the introduction of the magnetic field can reduce the boundary layer thickness, enhance nucleation, and thus suppress the agglomeration of metal particles. At the same time, the introduction of the magnetic field can also refine the Ni4Mo grain size, so that the catalyst has a larger specific surface area, which is conducive to the exposure of active sites and promotes its participation in the catalytic reaction. Therefore, the present invention effectively solves the problems of particle agglomeration and insufficient exposure of active sites caused by concentration polarization during the electrodeposition process by introducing a magnetic field of appropriate intensity.

[0056] Furthermore, the present invention provides a method for the magnetic field-assisted synthesis of a heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst. This method, which can be prepared through a one-step electrodeposition process with the assistance of a magnetic field, offers a simpler process, easier operation, lower energy consumption, and lower costs compared to traditional hydrothermal methods for preparing heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts. The resulting heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst exhibits excellent catalytic activity and stability in the hydrogen evolution reaction, when used in seawater electrolysis.

[0057] The following is a detailed description of the method for synthesizing a heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst provided by the present invention through comparative examples and examples.

[0058] Comparative Example 1

[0059] This comparative example provides a traditional electrodeposition method for preparing Ni4Mo / MoO x The method for preparing a nickel-molybdenum-based hydrogen evolution catalyst comprises 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 h to remove the residual liquid on the surface to prepare the pretreated copper foam.

[0061] S2: An electrodeposition solution was prepared by using a molar ratio of nickel sulfate: sodium molybdate: sodium chloride: sodium citrate = 5:1:10:10 and a mass ratio of sodium molybdate: deionized water = 0.1:30.

[0062] S3: The electrodeposition solution was transferred to an electrolytic cell and the pH of the solution was adjusted to 10 using NH3·H2O.

[0063] S4: Using an electrochemical workstation, pretreated copper foam was used as the working electrode, graphite sheet as the counter electrode, and Hg / HgO as the reference electrode. Each electrode was placed in an electroplating solution and subjected to constant current electroplating treatment at a current of -0.5A for 5 minutes to prepare a Ni4Mo / MoO x Type 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 in Figure 2. 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 in Figure 1. Figure 3 shown.

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

[0067] Depend on Figure 3 (a) and Figure 3 (b) It can be shown that the Ni4Mo / MoO prepared by the conventional electrodeposition method in this comparative example x The material distribution in the nickel-molybdenum-based hydrogen evolution catalyst is uneven.

[0068] in, Figure 3 (c) is a low-magnification TEM image. Figure 3 The dark spherical particles in (c) are agglomerates of super-large metal particles. Figure 3 (d) Figure 3 (c) High-magnification TEM image of the corresponding area, Figure 3 The yellow dotted line in (d) is the crystal Ni4Mo and amorphous MoO x The junction of.

[0069] Figure 3 (c) and Figure 3 (d) It can be shown that the Ni4Mo / MoO prepared by the conventional electrodeposition method in this comparative example x The nickel-molybdenum-based hydrogen evolution catalyst has the phenomenon of insufficient exposure of active sites and agglomeration of alloy particles. Therefore, this comparative example adopts the Ni4Mo / MoO prepared by traditional electrodeposition method. x It is difficult for nickel-molybdenum-based hydrogen evolution catalysts to achieve high activity and stable hydrogen evolution at high current density.

[0070] In order to detect the Ni4Mo / MoO x The phase composition of the nickel-molybdenum-based hydrogen evolution catalyst is as follows: Ni4Mo / MoO x The XRD pattern of the nickel-molybdenum-based hydrogen evolution catalyst is shown in Figure 2. Figure 5 This comparative example does not use a magnetic field to assist the synthesis of the catalyst, that is, the magnetic field strength of this comparative example is 0T, that is, this comparative example is Figure 5 The curve corresponding to NiMo-0T in .

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

[0072] In order to characterize the activity of the prepared catalyst, the Ni4Mo / MoO x The polarization curve of hydrogen evolution reaction of nickel-molybdenum-based hydrogen evolution catalyst is shown in Figure 7 This comparative example does not use a magnetic field to assist the synthesis of the catalyst, that is, the magnetic field strength of this comparative example is 0T, that is, this comparative example is Figure 7 The curve corresponding to NiMo-0T in .

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

[0074] Example 1

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

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

[0077] S2: An electrodeposition solution was prepared by using a molar ratio of nickel sulfate: sodium molybdate: sodium chloride: sodium citrate = 5:1:10:10 and a mass ratio of sodium molybdate: deionized water = 0.1:30.

[0078] S3: The electrodeposition solution was transferred to an electrolytic cell and the pH of the solution was adjusted to 10 using NH3·H2O.

[0079] S4: The electrolytic cell is transferred to a 2T magnetic field and is ready to start the electrodeposition process.

[0080] S5: Using an electrochemical workstation, pretreated copper foam was used 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 -0.5 A for 5 min to produce a highly active and stable heterojunction nickel-molybdenum-based hydrogen evolution catalyst.

[0081] The SEM image of the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared in the embodiment of the present invention is as follows: Figure 1 (b) shown.

[0082] from Figure 2From the comparison between (a) and (b), it can be seen 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 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] The TEM image of the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared in the embodiment of the present invention is as follows: Figure 4 shown.

[0084] in, Figure 4 (a) and Figure 4 (c) is a low-magnification TEM image. Figure 4 (b) Figure 4 (a) High-magnification TEM image of the corresponding area, Figure 4 (d) Figure 4 (c) High-magnification TEM image of the corresponding area. The dark spherical particles are crystalline Ni4Mo, and the light amorphous film is amorphous MoO X , Figure 4 (b) and Figure 3 The yellow dotted line in (d) is the crystal Ni4Mo and amorphous MoO x The junction of.

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

[0086] In order to detect the phase composition of the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared in Example 1 of the present invention, the XRD pattern of the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared in Example 1 of the present invention is as follows: Figure 5 The magnetic field strength used in Example 1 of the present invention to assist in the synthesis of the catalyst is 2T, that is, Example 1 of the present invention is Figure 5 The curve corresponding to NiMo-2T.

[0087] from Figure 5 Comparison shows that compared with the catalyst prepared in the comparative example, Ni4Mo crystals are present in the catalyst prepared in Example 1 of the present invention; and, at the peak position corresponding to the (121) plane, the peak intensity decreases and the peak broadens after the magnetic field is applied, indicating that the catalyst prepared in Example 1 of the present invention has 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] In order to test the specific surface area of ​​the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared in Example 1 of the present invention, the N2 adsorption / desorption curve of the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared in Example 1 of the present invention is as follows: Figure 6 The magnetic field strength used in Example 1 of the present invention to assist in the synthesis of the catalyst is 2T, that is, Example 1 of the present invention is Figure 6 The curve corresponding to NiMo-2T.

[0089] from Figure 6 By comparison, it can be seen that 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] In order to characterize the activity of the prepared catalyst, the polarization curve of the hydrogen evolution reaction of the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared in Example 1 of the present invention is as follows: Figure 7 The magnetic field strength used in Example 1 of the present invention to assist in the synthesis of the catalyst is 2T, that is, Example 1 of the present invention is Figure 7 The curve corresponding to NiMo-2T.

[0091] from Figure 7 From the comparison, it can be seen that the catalyst prepared in Example 1 of the present invention has a smaller overpotential than the catalyst prepared in the comparative example at the same current density, which indicates that the catalyst prepared in Example 1 of the present invention with the assistance of a magnetic field has a better catalytic activity.

[0092] In order to characterize the stability of the catalyst in alkaline seawater solution at ampere-level current density, the stability test curve of the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared in Example 1 of the present invention in alkaline seawater solution at ampere-level current density is shown as follows: Figure 8 The magnetic field strength used in Example 1 of the present invention to assist in the synthesis of the catalyst is 2T, that is, Example 1 of the present invention is Figure 8 The curve corresponding to NiMo-2T.

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

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

[0095] from Figure 9It can be seen that the overpotential of the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst prepared in Example 1 of the present invention has almost no change after the test lasts for 100 hours, 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] An embodiment of the present invention provides a method for magnetic field-assisted synthesis of a heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst, 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 minutes respectively, and then vacuum dried at 50°C for 4 hours to remove the residual liquid on the surface to prepare the pretreated copper foam.

[0099] S2: An electrodeposition solution was prepared by using a molar ratio of nickel sulfate: sodium molybdate: sodium chloride: sodium citrate of 16:1:24:24 and a mass ratio of sodium molybdate: deionized water of 0.0775:50.

[0100] S3: The electrodeposition solution was transferred to an electrolytic cell and the pH of the solution was adjusted to 9 using NH3·H2O.

[0101] S4: The electrolytic cell is transferred to a 1 T uniform magnetic field and is ready to start the electrodeposition process.

[0102] S5: Using an electrochemical workstation, pretreated copper foam was used 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 -0.6 A for 10 min to produce a highly active and stable heterojunction nickel-molybdenum-based hydrogen evolution catalyst.

[0103] Example 3

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

[0105] S1: The copper foam was sequentially placed in 5 M hydrochloric acid, anhydrous ethanol and deionized water and ultrasonically treated for 8 min respectively, and then vacuum dried at 70 °C for 2 h to remove the residual liquid on the surface to prepare the pretreated copper foam.

[0106] S2: An electrodeposition solution was prepared by using a molar ratio of nickel sulfate: sodium molybdate: sodium chloride: sodium citrate = 1:1:1.5:1.5 and a mass ratio of sodium molybdate: deionized water = 2.48:50.

[0107] S3: The electrodeposition solution was transferred to an electrolytic cell and the pH of the solution was adjusted to 8 using NH3·H2O.

[0108] S4: The electrolytic cell is transferred to a uniform magnetic field of 1.5 T and is ready to start the electrodeposition experiment.

[0109] S5: Using an electrochemical workstation, pretreated copper foam was used 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 -0.7 A for 15 min to produce a highly active and stable heterojunction nickel-molybdenum-based hydrogen evolution catalyst.

[0110] The methods for synthesizing a heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst assisted by a magnetic field in Examples 2 and 3 of the present invention are as follows. The electroplating treatment of the electroplating solution is performed under magnetic field conditions of 1 T and 1.5 T, respectively. Therefore, as in Example 1, the obtained heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst has a rich Ni4Mo / MoO x The heterogeneous structure (i.e., rich heterojunction) and the grain refinement phenomenon occurred in the prepared heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst, which avoided the agglomeration of grain particles, formed smaller grains and more uniform material distribution. The smaller grain size means that the prepared heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst has a larger specific surface area and more active sites are exposed, which will have better catalytic performance and is conducive to the efficient progress of subsequent catalytic reactions.

[0111] In order to further illustrate the method for synthesizing a heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst assisted by a magnetic field provided in Examples 1-3 of the present invention, the prepared heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst has relatively superior performance. The heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts prepared in Examples 1-3 of the present invention and the Ni4Mo / MoO prepared in the comparative example were compared. x The performance tests of catalyst activity and catalyst stability of the nickel-molybdenum-based hydrogen evolution catalyst were carried out respectively. The specific test methods are as follows:

[0112] 1. Catalyst activity test method: A three-electrode system was composed of the catalysts prepared in Examples 1-3 and the comparative example as the working electrode, a graphite sheet as the counter electrode, and a Hg / HgO electrode as the reference electrode. The electrolyte was 1 M KOH solution. Linear sweep voltammetry (LSV) was used for measurement using an electrochemical workstation (VSP, Bio-Logic).

[0113] 2. Catalyst stability test method: A three-electrode system was composed of the catalysts prepared in Examples 1-3 and the comparative example as the working electrode, a graphite sheet as the counter electrode, and a Hg / HgO electrode as the reference electrode. The electrolyte was alkaline (1M KOH) or alkaline seawater (1M KOH+seawater) solution. Chronopotentiometry (CP) was used for measurement using an electrochemical workstation (VSP, Bio-Logic).

[0114] The heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts prepared in Examples 1-3 of the present 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] Example Comparative Example Example 1 Example 2 Example 3 <![CDATA[Overpotential / mV (@ 10 mA cm -2 )]]> 26 17 20 25 <![CDATA[Stability / hour (@ 1A cm -2 )]]> 296 1500 698 502

[0117] According to the performance evaluation standards recognized in the field of electrocatalysis, the -2 The smaller the overpotential under current density, the better the catalytic activity. -2 The longer the test time at the ampere-level current density is and the performance does not decay, the better the stability is. As can be seen from the comparison in Table 1, the 10mA cm -2 The overpotential at the current density is less than 10 mA cm-3 of the comparative example. -2 The overpotential at current density is 1A cm for Examples 1-3 of the present invention. -2 The test time at the ampere-level current density is higher than that of the comparative example at 1A cm -2 Therefore, it can be seen that the heterojunction-rich nickel-molybdenum-based hydrogen evolution catalysts prepared in Examples 1-3 of the present invention are better than the Ni4Mo / MoO prepared in the comparative example. x The nickel-molybdenum-based hydrogen evolution catalyst has good catalytic activity and high stability.

[0118] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for synthesizing a heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst assisted by a magnetic field, characterized in that: The steps include: The copper foam was sequentially ultrasonically treated in hydrochloric acid, anhydrous ethanol and deionized water, and then vacuum dried to obtain the pretreated copper foam. Dissolving nickel salt and molybdenum salt in deionized water, then adding a complexing agent, a buffer and a conductive salt and mixing them to obtain an electrodeposition solution; Transferring the electrodeposition solution to an electrolytic cell and adjusting the pH of the electrodeposition solution to alkaline; Transferring the electrolytic cell to a magnetic field in preparation for electrodeposition treatment; A heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst was obtained by constant current electrodeposition treatment of the electrodeposition solution using pretreated copper foam as the working electrode, graphite sheet as the counter electrode, and Hg / HgO as the reference electrode.

2. The method for synthesizing a nickel-molybdenum-based hydrogen evolution catalyst assisted by a magnetic field according to claim 1, wherein: The molar concentration of the hydrochloric acid is 1-5M.

3. The method for synthesizing a nickel-molybdenum-based hydrogen evolution catalyst assisted by a magnetic field according to claim 1, wherein: The vacuum drying temperature is 40-90° C., and the vacuum drying time is 1-6 hours.

4. The method for synthesizing a heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst assisted by a magnetic field according to claim 1, characterized in that: The nickel salt is nickel sulfate hexahydrate, and the molybdenum salt is sodium molybdate dihydrate.

5. The method for synthesizing a nickel-molybdenum-based hydrogen evolution catalyst assisted by a magnetic field according to claim 1, characterized in that: The molar ratio of the nickel salt to the molybdenum salt is 1:1 to 1:

32.

6. The method for synthesizing a nickel-molybdenum-based hydrogen evolution catalyst assisted by a magnetic field according to claim 1, characterized in that: The complexing agent and buffer are sodium citrate, and the conductive salt is sodium chloride.

7. The method for synthesizing a nickel-molybdenum-based hydrogen evolution catalyst assisted by a magnetic field according to claim 1, characterized in that: The step of adjusting the pH of the electrodeposition solution to alkaline is to adjust the pH of the electrodeposition solution to 8-11 using NH 3 ·H 2 O.

8. The method for synthesizing a heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst assisted by a magnetic field according to claim 1, characterized in that: The magnetic field strength is 0-2T.

9. The method for synthesizing a heterojunction-rich nickel-molybdenum-based hydrogen evolution catalyst assisted by a magnetic field according to claim 1, characterized in that: The current of the constant current electroplating treatment on the electroplating solution is -0.5 to -1A, and the electroplating time is 5 to 60 minutes.

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