NiMo-based crystalline / amorphous heterostructure composite material, its preparation method and application

Abstract

This application belongs to the technical field of electrocatalytic hydrogen evolution, and specifically relates to a NiMo-based crystalline / amorphous heterostructure composite material, its preparation method and application. The method is as follows: First, a pair of nickel wires are immersed in a NaOH solution and electrochemically exfoliated under an alternating current voltage, centrifuged and washed, and ultrasonicated to obtain a dispersion of Ni element nanosheets. Then, it is dropped into an ethanol solution containing MoCl5, stirred, and then a sodium borohydride solution is dropped, stirred and reacted, centrifuged, washed, and dried to obtain a precursor powder of the composite material; finally, it is placed in a tube furnace to maintain a flowing hydrogen / argon mixed atmosphere and subjected to high-temperature annealing treatment to obtain. The present invention proposes an electron modulation strategy for the NiMo-based crystalline / amorphous heterostructure, enabling crystalline Ni to promote the efficient electron transfer of the amorphous NiMoB structure, thereby increasing the number of active sites and enhancing the site activity; it can reduce the potential barrier during the HER process, accelerate the HER kinetics, and exhibit excellent HER performance.

Description

Technical Field

[0001] This application belongs to the technical field of electrocatalytic hydrogen evolution, and particularly relates to a NiMo-based crystalline / amorphous heterostructure composite material, a preparation method thereof, and an application thereof. Background Art

[0002] As an environmentally friendly strategy, water electrolysis for hydrogen production can use electrical energy generated from renewable energy sources such as solar energy and wind energy to produce zero-carbon hydrogen fuel on a large scale. However, the high dissociation energy of water molecules leads to a high overpotential, thus making the kinetic process of the hydrogen evolution reaction (HER) slow. Although platinum-based materials are considered ideal electrocatalysts due to their excellent HER performance, their insufficient durability, scarce resources, and high cost limit their large-scale commercial applications. Therefore, developing efficient, low-cost, and stable electrocatalysts to improve the alkaline HER kinetics is crucial for promoting the commercialization process of water electrolysis for hydrogen production technology. These catalysts will help reduce the cost of hydrogen production, improve system stability, and ultimately achieve large-scale, economical, and sustainable production of hydrogen energy. Summary of the Invention

[0003] The object of the present invention is to solve the deficiencies of the prior art and provide a NiMo-based crystalline / amorphous heterostructure composite material, a preparation method thereof, and an application thereof. The following specific technical solutions are adopted:

[0004] In a first aspect, an embodiment of the present application provides a preparation method of a NiMo-based crystalline / amorphous heterostructure composite material, including the following steps:

[0005] S1: Immerse a pair of nickel wires in an NaOH solution, perform electrochemical stripping under an alternating current voltage, centrifuge and wash, and ultrasonicate to obtain a dispersion of Ni element nanosheets;

[0006] S2: Drop the dispersion of Ni element nanosheets into an ethanol solution containing MoCl5, stir, then dropwise add a sodium borohydride solution, stir and react, centrifuge, wash, and dry to obtain a precursor powder of the composite material;

[0007] S3: Place the precursor powder of the composite material in a tubular furnace and maintain a flowing hydrogen / argon mixed atmosphere for high-temperature annealing treatment to obtain the NiMo-based crystalline / amorphous heterostructure composite material.

[0008] By adopting the electron modulation strategy of the crystalline (Ni) / amorphous (NiMoB) alloy heterostructure, the present invention can utilize crystalline transition metals to promote efficient electron transfer in the amorphous alloy structure. Among them, the introduction of boron element can induce the formation of lattice defects and amorphous structure, thereby regulating the electronic structure of the host material, generating electrocatalytic unsaturated coordination active sites, which not only increases the number of active sites but also enhances the activity of the sites. It can perfectly improve the problem that a large number of defects in the existing amorphous electrocatalysts increase the complexity of electron transport and lead to a high charge transfer resistance. In addition, due to its ideal hydrogen adsorption activity, the Ni-based alloy in the present invention shows excellent effects in the alkaline HER process, and exhibits more superior electrocatalytic properties due to its rich surface dangling bonds and unsaturated coordination sites.

[0009] As a further preferred embodiment, the NiMo-based crystalline / amorphous heterostructure composite material is formed by a heterostructure of crystalline Ni and amorphous NiMoB; the lattice distance in the NiMo-based crystalline / amorphous heterostructure composite material corresponds to Ni(111).

[0010] As a further preferred embodiment, the content of Ni in the NiMo-based crystalline / amorphous heterostructure composite material is 10 wt%-20 wt%, and the content of Mo is 50 wt%-70 wt%.

[0011] As a further preferred embodiment, the volume ratio of the Ni element-containing nanosheet dispersion liquid, the ethanol solution containing MoCl5, and the sodium borohydride solution is 10:5:2. In the preparation process of the present invention, too low a Ni / Mo ratio is not conducive to the precipitation of crystalline Ni; too high a Ni / Mo ratio will cause Mo and Ni to precipitate in an alloy crystalline form. Therefore, too high or too low a Ni / Mo ratio is not conducive to the formation of the NiMo-based crystalline / amorphous heterostructure composite material with high-performance hydrogen evolution activity.

[0012] As a further preferred embodiment, the mass concentration of the Ni element-containing nanosheet dispersion liquid is 1 mg·mL -1 ~ 3 mg·mL -1 ; the mass concentration of the ethanol solution containing MoCl5 is 20 mg·mL -1 ~25 mg·mL -1 ; the mass concentration of the sodium borohydride solution is 30 mg·mL -1 ~ 50 mg·mL -1 .

[0013] As a further preferred embodiment, the voltage of the alternating current is 7 V~ 9 V; the time of electrochemical stripping is 80 min~120 min.

[0014] As a further preferred embodiment, the specific parameters for maintaining the flowing hydrogen / argon mixed atmosphere are as follows: at a gas flow rate of 50 mL·min -1 ~ 70 mL·min -1 of a 10% hydrogen / 90% argon mixed atmosphere is introduced.

[0015] As a further preferred embodiment, the specific parameters of the high-temperature annealing treatment are as follows:

[0016] at a heating rate of 5 ℃·min -1 from room temperature to 400 ℃~600 ℃, then held for 0.5 h~2 h, and finally naturally cooled to room temperature.

[0017] In a second aspect, the present invention provides a NiMo-based crystalline / amorphous heterostructure composite material prepared by the above preparation method.

[0018] In a third aspect, the present invention provides the use of the above NiMo-based crystalline / amorphous heterostructure composite material as an electrocatalyst in the hydrogen evolution reaction of electrocatalytic water splitting.

[0019] The beneficial effects of the present invention are as follows:

[0020] (1) The preparation method of the present invention is simple in operation and strong in repeatability. An electron modulation strategy for NiMo-based crystalline / amorphous heterostructures is proposed, enabling crystalline Ni to promote efficient electron transfer in the amorphous NiMoB structure, thereby increasing the number of active sites and enhancing the site activity;

[0021] (2) The composite material prepared by the present invention can lower the potential barrier of the HER process, accelerate HER kinetics, and exhibit excellent HER performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0023] Figure 1 Shown is the XRD pattern of the NiMo-based crystalline / amorphous heterostructure composite material;

[0024] Figure 2 is the EDX-Mapping pattern of the NiMo-based crystalline / amorphous heterostructure composite material provided by some embodiments of the present application;

[0025] Figure 3The SEM image of the NiMo-based crystalline / amorphous heterostructure composite material is shown;

[0026] Figure 4 The TEM image of the NiMo-based crystalline / amorphous heterostructure composite material is shown;

[0027] Figure 5 The linear sweep voltammetry polarization curve of the NiMo-based crystalline / amorphous heterostructure composite material as an electrocatalyst in 1 M KOH is shown;

[0028] Figure 6 The Tafel curve of the NiMo-based crystalline / amorphous heterostructure composite material as an electrocatalyst is shown;

[0029] Figure 7 The continuous chronopotentiometry curve of the NiMo-based crystalline / amorphous heterostructure composite material as an electrocatalyst at different current densities is shown. Detailed implementation manners

[0030] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.

[0031] The surface, interface morphology and structure of the products of the present invention are determined by a field emission scanning electron microscope (SEM) and a transmission electron microscope (TEM); the crystal phases contained in the products are determined using an X-ray diffractometer (XRD); the element distribution and composition are determined by energy-dispersive X-ray spectroscopy imaging (EDX-mapping) supported by TEM; the electrocatalytic hydrogen evolution reaction performance of the products is measured on a Shanghai Chenhua electrochemical workstation.

[0032] Example 1

[0033] A NiMo-based crystalline / amorphous heterostructure composite material, and its specific preparation method is as follows:

[0034] (1) Immerse a pair of nickel wires (diameter 0.5 mm) in 20 mL of 4 M NaOH solution. The immersion depth of the nickel wires in the solution is 1.5 cm, and the spacing is kept at 1.5 cm. Adopt a two-electrode system, set the voltage of the alternating current to 8 V, and perform electrochemical exfoliation treatment for 100 min. After centrifugally washing the product with deionized water, add 40 mL of deionized water and ultrasonically mix evenly to form a dispersion liquid of Ni element nanosheets; Transfer 20 mL of the dispersion liquid, and gradually add 10 mL of 21.9 mg·mL -1An ethanol solution of MoCl5 with a mass concentration was stirred for 30 min, and then 4 mL of an aqueous solution of sodium borohydride with a mass concentration was added dropwise again. -1 Stirring was continued for 30 min. The product was centrifuged, washed, and freeze-dried to obtain the composite precursor powder.

[0035] (2)The precursor powder was spread flat in a porcelain boat and placed in the central heating zone of a tube furnace. It was heated from room temperature to 500 °C at a heating rate of 5 °C·min ‒1 and held for 1 h for high-temperature heat treatment. Finally, it was naturally cooled to obtain the NiMo-based crystalline / amorphous heterostructure composite material (i.e., c-Ni / a-NiMoB, where c represents crystalline and a represents amorphous).

[0036] The prepared NiMo-based crystalline / amorphous heterostructure composite material was subjected to characterization performance tests (XRD, EDX-Mapping, SEM, TEM). The specific results are as Figures 1-4 shown:

[0037] Figure 1 This is the XRD pattern of the NiMo-based crystalline / amorphous heterostructure composite material. By comparing with the standard card, it can be confirmed that the obtained composite material contains the crystalline phase of metallic nickel, and the amorphous species cannot be detected by the XRD instrument.

[0038] Figure 2 This is the EDX-Mapping pattern of the NiMo-based crystalline / amorphous heterostructure composite material. This analysis reveals the uniform distribution of elements such as Ni, Mo, and B in the composite material.

[0039] Figure 3 This is the SEM image of the NiMo-based crystalline / amorphous heterostructure composite material. This material presents a two-dimensional structure with a rough surface.

[0040] Figure 4 This is the TEM image of the NiMo-based crystalline / amorphous heterostructure composite material. Among them, Figure 4 a shows that the flaky two-dimensional structure can be clearly observed, and its surface is in the shape of irregular particles; Figure 4 b reveals the heterointerfaces between the metal crystalline phase and the amorphous structure. Among them, the 10-fold lattice distance (10d) of 2.06 nm in the lattice fringe region corresponds to the (111) plane of crystalline metal Ni; and the structures surrounded by the dotted lines are all amorphous regions. The above structural characterizations all indicate that the crystalline / amorphous heterostructure composite material has been prepared.

[0041] Example 2

[0042] The performance test of the obtained NiMo-based crystalline / amorphous heterostructure composite material as an electrocatalyst for hydrogen evolution reaction in electrolyzed water is carried out as follows:

[0043] (1) Preparation of the working electrode of the electrocatalyst:

[0044] First, weigh 5 mg of the NiMo-based crystalline / amorphous heterostructure composite material powder, 40 μL of 5 wt% nafion solution, and 960 μL of ethanol, and add them to a centrifuge tube. Secondly, suspend the centrifuge tube in an ultrasonic cleaner and ultrasonically treat it for more than 60 minutes to form a relatively uniform ink-like catalyst dispersion liquid in the centrifuge tube. Finally, use a pipette to drop 8 μL of the catalyst ink on the surface of the 3 mm diameter glassy carbon electrode disk, and wait for it to dry naturally to form a film before performing electrochemical performance tests.

[0045] (2) Electrochemical performance research:

[0046] The electrochemical performance test is carried out on a Shanghai Chenhua electrochemical workstation (model CHI760E). The electrolyte used is 1 mol·L –1 aqueous KOH solution; the three-electrode system configuration used is: that is, the glassy carbon electrode modified with the electrocatalyst is used as the working electrode, the graphite rod is used as the auxiliary electrode, and the saturated calomel electrode (SCE) is used as the reference electrode. According to the Nernst equation, the potential in the test is converted into the reversible hydrogen electrode potential ( E RHE ); subtract E RHE from 0 V, and that is the HER overpotential η .

[0047] After immersing the three-electrode configuration in the electrolyte and connecting it to the workstation, perform the following operations: (i) Perform a linear voltammetry scan test at a rate of 2 mV·s –1 to obtain a polarization curve; (ii) According to the data obtained from the polarization curve (potential E RHE and current density j ), establish a linear regression between E RHE and log|current density ( j , mA cm –2 ), and the Tafel slope of the HER process of the electrocatalyst working electrode can be calculated; (iii) Perform continuous chronopotentiometry tests at different current densities to obtain the stability test results of the prepared electrocatalyst working electrode, and the results are as shown in Figures 5-7 :

[0048] Figure 5Linear sweep voltammetry polarization curves of NiMo-based crystalline / amorphous heterostructure composites as electrocatalysts in 1 M KOH. The test results show that the crystalline Ni / amorphous NiMoB heterostructure composite exhibits excellent alkaline HER electrocatalytic activity, and only requires an overpotential of 55 mV to generate a reference current density (equivalent to the current density generated by a solar device with an efficiency of 12.3 %). –2 The reference current density (equivalent to the current density generated by a solar device with an efficiency of 12.3 %) only requires an overpotential of 55 mV.

[0049] Figure 6 Tafel curves of NiMo-based crystalline / amorphous heterostructure composites as electrocatalysts. The figure shows that the Tafel slope of the NiMo-based crystalline / amorphous heterostructure composite is only 44.7 mV·dec –1 , and its extremely low Tafel slope value indicates that the composite has fast alkaline hydrogen evolution reaction kinetics.

[0050] Figure 7 Chronopotentiometry curves of NiMo-based crystalline / amorphous heterostructure composites as electrocatalysts at different current densities. The test shows that the composite has outstanding durability, obtains stable potential curves at different current densities, and there is no obvious attenuation in the potential of 50 mA·cm -2 after 25 h of testing.

[0051] The embodiments of the present application have been described above in conjunction with the accompanying drawings. Specific examples are used in this article to elaborate on the principles and implementation manners of the present application. The description of the above embodiments is only used to help understand the core idea of the present application. However, the present application is not limited to the above specific implementation manners. The above specific implementation manners are only illustrative and not restrictive. Under the inspiration of the present application, those of ordinary skill in the art can also make many forms without departing from the purpose of the present application and the scope protected by the claims, and all belong to the protection scope of the present application.

Claims

1. A preparation method of a NiMo-based crystalline / amorphous heterostructure composite material, characterized in that, It includes the following steps: S1: Immerse a pair of nickel wires in a NaOH solution, perform electrochemical stripping under the voltage of alternating current, centrifuge and wash, and ultrasonicate to obtain a dispersion of Ni element nanosheets; S2: Drop the dispersion of Ni element nanosheets into an ethanol solution containing MoCl5, stir, then dropwise add a sodium borohydride solution, stir and react, centrifuge, wash, and dry to obtain a precursor powder of the composite material; S3: Place the precursor powder of the composite material in a tube furnace to maintain a flowing hydrogen / argon mixed atmosphere, and perform high-temperature annealing treatment to obtain the NiMo-based crystalline / amorphous heterostructure composite material; The NiMo-based crystalline / amorphous heterostructure composite material forms a heterostructure composed of crystalline Ni and amorphous NiMoB; The lattice distance in the NiMo-based crystalline / amorphous heterostructure composite material corresponds to Ni(111); 2. The preparation method according to claim 1, characterized in that, In the NiMo-based crystalline / amorphous heterostructure composite material, the content of Ni is 10 wt%-20 wt%, and the content of Mo is 50 wt%-70 wt%; 3. The preparation method according to claim 1, characterized in that, The volume ratio of the usage amounts of the dispersion of Ni element nanosheets, the ethanol solution containing MoCl5, and the sodium borohydride solution is 10:5:2; 4. The preparation method according to claim 3, wherein The mass concentration of the Ni element-containing nanosheet dispersion is 1 mg·mL -1 ~ 3 mg·mL -1 ; the mass concentration of the ethanol solution containing MoCl5 is 20 mg·mL -1 ~25 mg·mL -1 ; the mass concentration of the sodium borohydride solution is 30 mg·mL -1 ~ 50 mg·mL -1 .

5. The preparation method according to claim 1, wherein The voltage of the alternating current is 7 V to 9 V; the time of the electrochemical stripping is 80 min to 120 min; 6. The preparation method according to claim 1, wherein, The specific parameters for maintaining the flowing hydrogen / argon mixed atmosphere are as follows: a gas flow rate of 50 mL·min -1 ~ 70 mL·min -1 is introduced into a 10% hydrogen / 90% argon mixed atmosphere.

7. The preparation method according to claim 1, characterized in that, The specific parameters of the high-temperature annealing treatment are as follows: At a heating rate of 5 °C·min -1 heat from room temperature to 400 °C - 600 °C, then hold for 0.5 h - 2 h, and finally cool naturally to room temperature.

8. A NiMo-based crystalline / amorphous heterostructure composite material, characterized in that, Prepared by the preparation method according to any one of claims 1-7; 9. Use of the NiMo-based crystalline / amorphous heterostructure composite material according to claim 8 as an electrocatalyst, characterized in that, The NiMo-based crystalline / amorphous heterostructure composite material is used as an electrocatalyst for electrocatalytic water splitting to produce hydrogen.

Images