A three-dimensional hierarchical NiCo2S4@NiMo3S4 / CT bifunctional electrocatalyst, its preparation method and application

Abstract

This invention discloses a three-dimensional hierarchical NiCo2S4@NiMo3S4 / CT bifunctional electrocatalyst, its preparation method, and its applications, belonging to the field of electrocatalytic materials technology in new energy technologies. This invention employs a combination of a two-stage hydrothermal method and an annealing method. A two-dimensional NiCo2O4 / CT precursor is grown on carbon cloth as a conductive substrate. After sulfidation, a framework NiCo2S4 nanotube array is obtained. A second hydrothermal method is then used to grow NiMo3S4 nanosheets on the NiCo2S4 / CT nanotubes. The ultrathin NiMo3S4 nanosheets provide more catalytic reaction sites, allowing the NiMo3S4 nanosheets to cover the surface of the NiCo2S4 nanotube array, thus forming a unique three-dimensional hierarchical NiCo2S4@NiMo3S4 / CT heterostructure bifunctional electrocatalyst. The three-dimensional hierarchical NiCo2S4@NiMo3S4 material obtained by this invention exhibits excellent catalytic performance, cycle stability, active sites, and a large specific surface area. The preparation method of this invention is simple, constructs a special interface, forms a rich defect and phase transition coupled electronic structure, and obtains a bimetallic sulfide with a heterostructure, which improves the electron transport rate and enhances the electrical properties of transition metal sulfides.

Description

Technical Field

[0001] This invention relates to the field of electrochemical catalytic materials and devices for new energy technologies, and particularly to a three-dimensional hierarchical NiCo2S4@NiMo3S4 / CT bifunctional electrocatalyst, its preparation method, and its application. Background Technology

[0002] The electrolysis process from water to hydrogen offers an effective solution for the conversion, storage, and release of intermittent renewable energy sources such as tidal, wind, and solar power. The water splitting process involves two reactions: the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). This splitting process requires highly efficient electrocatalysts; platinum is used for the HER, and RuO2 and IrO2 are used for the OER. Catalysts can lower the activation barrier, accelerate redox electron transport, and promote the reaction process. However, the scarcity and high cost of noble metal catalysts prevent their large-scale application, and they also exhibit weak bifunctionality and poor stability.

[0003] Transition metal sulfides (TMS) are a type of high-performance electrocatalyst, and TMSs, including MoS2, Ni3S2, and CoS2, have attracted much attention due to their excellent electrocatalytic performance. However, these TMSs suffer from several drawbacks, including poor electron / feedback transport kinetics separation, low electroactive sites, and relatively insufficient stability, all of which severely limit their ability to improve electrocatalytic activity. To enhance catalytic activity while ensuring material stability, bimetallic sulfides with unique structures have gradually become a research hotspot.

[0004] NiCo2S4 and NiMo3S4 are two of the most representative materials. The Mo-S and Co-S bonds doped with Ni exhibit metallic properties, which can improve electrical conductivity and increase the amount of Ni involved. 3+ While active sites are present, the instability and rapid degradation of single NiCo2S4 and NiMo3S4 in alkaline electrolytes significantly limit their catalytic performance. Therefore, developing electrocatalysts with high activity, long cycle life, and strong bifunctionality is crucial for advancing commercial water electrolysis. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art and provide a three-dimensional layered NiCo2S4@NiMo3S4 / CT bifunctional electrocatalyst, its preparation method and application. The NiCo2S4@NiMo3S4 / CT bifunctional electrocatalyst has high activity, long cycle life and strong bifunctionality.

[0006] A method for preparing a three-dimensional hierarchical NiCo2S4@NiMo3S4 / CT bifunctional electrocatalyst includes the following steps:

[0007] (1) Co(NO3)2·6H2O, Ni(NO3)2·6H2O and urea were added to a mixed solvent of ethanol and water and stirred to obtain a uniform mixed solution. Carbon cloth was added and dispersed evenly. The solution was heated, kept warm, washed and dried to obtain NiCo2O4 / CT precursor.

[0008] (2) Dissolve Na2S·9H2O in water, add the NiCo2O4 / CT precursor obtained in step (1), mix and heat and keep warm, wash and dry, and then calcine in an inert gas to sulfide NiCo2O4 to obtain NiCo2S4 nanotube array.

[0009] (3) Dissolve Na2MoO4·2H2O and NiSO4·6H2O in water, add CH4N2S, and continue stirring to obtain a mixed solution. Transfer the NiCo2S4 nanotube array into the mixed solution, heat and keep warm, wash and dry to obtain NiCo2S4@NiMo3S4 / CT bifunctional electrocatalyst.

[0010] As a preferred embodiment, the mass ratio of Co(NO3)2·6H2O, Ni(NO3)2·6H2O, and urea is 0.58:0.29:0.72, the volume ratio of ethanol to water is 1:1, and the Co content in the mixed solution is... 2+ and Ni 2+ The total concentration was 0.0057-0.0058 g / mL.

[0011] As a preferred embodiment, the mass of carbon cloth added is 90-95% of the theoretical weight of the NiCo2O4 / CT precursor.

[0012] As a preferred embodiment, the heating temperature in step (1) is 100-105℃, and the holding time is 8-8.1h.

[0013] As a preferred embodiment, in step (2), the mass ratio of Na2S·9H2O to NiCo2O4 / CT precursor is 3:11, wherein Na + The concentration was 0.00095 g / mL.

[0014] As a preferred embodiment, the process conditions for the heating and heat preservation reaction in step (2) are: heat preservation at 180-185℃ for 6-6.1h.

[0015] As a preferred embodiment, the calcination temperature in step (2) is 300-305℃ and the calcination time is 2-2.1h.

[0016] As a preferred embodiment, the drying temperature in steps (2) and (3) is 60-62℃ and the drying time is 12-12.1h.

[0017] As a preferred embodiment, in step (3), the mass ratio of Na2MoO4·2H2O, NiSO4·6H2O, and CH4N2S is 0.075:0.08125:0.2, wherein the Ni in the mixed solution... 2+ The concentration is 0.00045-0.000455 g / mL.

[0018] As a preferred embodiment, the process conditions for the heating and heat preservation reaction in step (3) are: heat preservation at 180-185℃ for 12-12.1h.

[0019] In the embodiments of the present invention, calcination mainly serves to improve the crystal quality and crystallinity of the NiCo2S4 nanotube array, thereby improving the conductivity and catalytic performance of the material to a certain extent. Annealing after the preparation of the NiCo2S4 nanotube array is performed to burn off excess impurities and ensure the smooth progress of the second hydrothermal reaction.

[0020] The carbon cloth described in this invention is a conductive carbon cloth with a flexible substrate. In the prepared NiCo2S4@NiMo3S4 / CT bifunctional electrocatalyst, the NiCo2S4 nanotube array serves as a framework support, and the NiMo3S4 nanosheet group covers the surface of the NiCo2S4 nanotube array.

[0021] The NiCo2S4 nanotubes in the NiCo2S4 nanotube array of the present invention have a diameter of 80-100 nm.

[0022] The NiMo3S4 nanosheet assembly of the present invention has a thickness of 20 nm and is composed of multiple layers of overlapping NiMo3S4 nanosheets.

[0023] This invention employs a three-dimensional hierarchical structure design, using flexible conductive carbon cloth as a substrate and NiCo2S4 nanotube array as a framework to support the outer ultrathin NiMo3S4 nanosheets, thereby forming a hierarchical structure of NiCo2S4@NiMo3S4 / CT. This not only increases the specific surface area of ​​the catalyst but also improves the catalytic activity and stability of the bifunctional electrocatalyst.

[0024] This invention uses conductive carbon cloth as a flexible substrate and grows NiCo2O4 nanoneedle arrays on the carbon cloth using a hydrothermal method as a precursor. The precursor is then sulfurized using a hydrothermal method to obtain NiCo2S4 nanotube arrays. High-temperature treatment in an inert gas Ar atmosphere ensures the stability of the NiCo2S4 nanotube arrays. Then, a secondary hydrothermal method is used to synthesize ultrathin NiMo3S4 nanosheets on the surface of the NiCo2S4 nanotube arrays, ultimately obtaining a three-dimensional layered NiCo2S4@NiMo3S4 / CT bifunctional electrocatalyst.

[0025] The three-dimensional layered NiCo2S4@NiMo3S4 / CT bifunctional electrocatalyst prepared by this invention exhibits good catalytic activity and stability in water electrolysis applications, serving both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) bifunctional electrocatalysts.

[0026] Compared with existing technologies, what are the advantages of this invention?

[0027] (1) The preparation method of the present invention is simple. A flexible bifunctional electrocatalytic material is designed with carbon cloth as the substrate. It can be bent and folded without the need for adhesive. Two-dimensional NiCo2O4 / CT precursor is grown with carbon cloth as the conductive base. After sulfidation, a framework NiCo2S4 nanotube array is obtained. NiMo3S4 nanosheets are grown on NiCo2S4 / CT nanotubes by secondary hydrothermal method. The ultrathin NiMo3S4 nanosheets provide catalytic reaction sites, and the NiMo3S4 nanosheet group covers the surface of NiCo2S4 nanotube array, thereby forming a unique three-dimensional layered NiCo2S4@NiMo3S4 / CT heterostructure bifunctional electrocatalyst.

[0028] (2) In this invention, the NiCo2O4 / CT precursor is sulfided and sintered to ensure that the sulfided NiCo2S4 and the NiMo3S4 epitaxially grown on its surface are combined in the form of nanotube array and ultrathin nanosheet, respectively, to construct a heterostructure. Compared with the NiCo2S4@NiMo3S4 / CT with a core-shell structure prepared by the all-hydrothermal method, the electron transport rate is improved, the electrical properties of transition metal sulfides are improved, and the catalyst performance is increased. At the same time, the NiCo2S4 nanotube array structure has good mechanical properties, and the ultrathin NiMo3S4 nanosheets as the skeleton material result in a catalyst with good stability.

[0029] (3) The ultrathin NiMo3S4 nanosheets prepared by this invention have a thickness of 20nm, which is beneficial to increase the specific surface area and provide more catalytic reaction sites. The synergistic effect between NiMo3S4 and NiCo2S4 improves the catalytic performance. Attached Figure Description

[0030] Figure 1 The images show scanning electron microscope (SEM) images of the three-dimensional layered NiCo2S4@NiMo3S4 / CT bifunctional electrocatalyst prepared in Example 1. (a) is the HTM (1 μm) of the three-dimensional layered NiCo2S4@NiMo3S4 / CT bifunctional electrocatalyst, and (b) is the TM (500 nm) of the three-dimensional layered NiCo2S4@NiMo3S4 / CT bifunctional electrocatalyst.

[0031] Figure 2 The image shows a scanning electron microscope (SEM) image of the NiCo2O4 / CT prepared for Comparative Example 1.

[0032] Figure 3 The image shows a scanning electron microscope (SEM) image of NiCo2S4 / CT prepared for Comparative Example 1.

[0033] Figure 4 Figure (a) shows the scanning electron microscope (SEM) images of NiCo2S4@NiMo3S4 / CT prepared in Comparative Example 3 (200 nm), and Figure (b) shows the scanning electron microscope (SEM) images of NiCo2S4@NiMo3S4 / CT prepared in Comparative Example 3 (100 nm).

[0034] Figure 5 The images show transmission electron microscopy (TEM) images of NiCo2S4 / CT prepared in Comparative Example 1 and NiCo2S4@NiMo3S4 / CT prepared in Example 1. Figure (a) is a TEM image of NiCo2S4 / CT prepared in Comparative Example 1, and Figure (b) is a TEM image of NiCo2S4@NiMo3S4 / CT prepared in Example 1.

[0035] Figure 6 The LSV and Tafel curves of HER and OER for NiCo2S4@NiMo3S4 / CT prepared in Example 1, NiCo2S4 / CT prepared in Comparative Example 1, and NiMo3S4 / CT prepared in Comparative Example 2 are shown. (a) LSV curves of HER for NiCo2S4@NiMo3S4 / CT prepared in Example 1, NiCo2S4 / CT prepared in Comparative Example 1, and NiMo3S4 / CT prepared in Comparative Example 2 are shown. (b) LSV curves of HER for NiCo2S4@NiMo3S4 / CT prepared in Example 1, NiCo2S4 / CT prepared in Comparative Example 1, and NiMo3S4 / CT prepared in Comparative Example 2 are shown. (c) LSV curves of OER for NiCo2S4@NiMo3S4 / CT prepared in Example 1, NiCo2S4 / CT prepared in Comparative Example 1, and NiMo3S4 / CT prepared in Comparative Example 2; (d) Tafel curves of OER for NiCo2S4@NiMo3S4 / CT prepared in Example 1, NiCo2S4 / CT prepared in Comparative Example 1, and NiMo3S4 / CT prepared in Comparative Example 2.

[0036] Figure 7 HER stability test curves of NiCo2S4@NiMo3S4 / CT prepared in Example 1, NiCo2S4 / CT prepared in Comparative Example 1, and NiMo3S4 / CT prepared in Comparative Example 2.

[0037] Figure 8OER stability test curves of NiCo2S4@NiMo3S4 / CT prepared in Example 1, NiCo2S4 / CT prepared in Comparative Example 1, and NiMo3S4 / CT prepared in Comparative Example 2.

[0038] Figure 9 The LSV test curve for the total water splitting of the NiCo2S4@NiMo3S4 / CT bifunctional electrocatalyst prepared in Example 1 is shown.

[0039] Figure 10 The total water splitting stability test curve of the NiCo2S4@NiMo3S4 / CT bifunctional electrocatalyst prepared in Example 1 is shown. Detailed Implementation

[0040] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0041] Example 1

[0042] A method for preparing a three-dimensional hierarchical NiCo2S4@NiMo3S4 / CT bifunctional electrocatalyst includes the following steps:

[0043] (1) Add 0.58g Co(NO3)2·6H2O, 0.29g Ni(NO3)2·6H2O and 0.72g urea to 40mL of ethanol / deionized water mixed solvent and stir to obtain a homogeneous mixed solution.

[0044] (2) Transfer the carbon cloth and the uniform mixed solution to a 50 mL reaction vessel, keep it at 100 °C for 8 h, cool to room temperature and dry after the reaction to obtain NiCo2O4 / CT precursor.

[0045] (3) Dissolve 0.24 g Na2S·9H2O in 30 mL of deionized water. Transfer the resulting clear solution and NiCo2O4 / CT precursor to a 50 mL reactor and keep it at 180 °C for 6 h. After the reaction, wash with deionized water and dry in air at 60 °C for 12 h. Then calcine at 300 °C for 2 h in an Ar atmosphere with a heating rate of 5 °C·min. -1 The gas flow rate was 30 sscm. After the reaction was completed, NiCo2S4 / CT was obtained.

[0046] (4) Dissolve 0.075g Na2MoO4·2H2O and 0.08125g NiSO4·6H2O in 40mL of deionized water, then add 0.2g CH4N2S and stir further. The resulting clear solution and the NiCo2S4 / CT carbon cloth sample obtained in (3) are transferred to a 50mL reaction vessel and kept at 180℃ for 12h. After the reaction, wash with deionized water and dry in air at 60℃ for 12h to finally obtain the product NiCo2S4@NiMo3S4 / CT. Scanning electron microscopy shows... Figure 1 As shown.

[0047] according to Figure 1 The scanning electron microscope (SEM) image of the NiCo2S4@NiMo3S4 / CT prepared in Example 1 shows that the surface of the NiCo2S4 nanotubes is covered with a layer of NiMo3S4 nanosheets, indicating that the NiCo2S4@NiMo3S4 / CT bifunctional electrocatalyst consists of a NiCo2S4 nanotube array supported by a conductive carbon cloth framework, and NiMo3S4 nanosheets covering the surface of the NiCo2S4 nanotube array; combined with Figure 5 (a) Transmission electron microscopy of the NiCo2S4 / CT prepared in Comparative Example 1 shows that the NiCo2S4 nanotube structure covering the NiMo3S4 layer is still clearly visible, indicating that the NiMo3S4 layer is extremely thin. Figure 5 (b) The high-resolution transmission electron microscopy image of NiCo2S4@NiMo3S4 / CT prepared in Example 1 confirms that NiMo3S4 and NiCo2S4 were successfully grown, with NiMo3S4 having a thickness of only 20 nm.

[0048] The NiCo2S4@NiMo3S4 / CT prepared in Example 1 was used as the working electrode, saturated calomel click as the reference electrode, and a stone-ground rod as the counter electrode. A 1M KOH solution was used as the electrolyte. Linear sweep voltammetry (LSV) and Tafel curve tests, as well as full hydrolysis LSV and full hydrolysis stability tests, were performed in the ranges of -2 to -1V and 0 to 1V. All tests were completed on the Donghua electrochemical workstation. Figure 6 As shown in (a) and (b), the result at 10 mA cm⁻¹ can be obtained. -2 The overpotentials for HER and OER are 59mV and 130mV, respectively; Figure 6 The Tafel curves obtained from fitting (c) and (d) also show that the Tafel slopes of NiCo2S4@NiMo3S4 / CT at OER and HER are 39.33 mV dec. -1 and 139.64mV dec -1 Subsequently, HER stability testing and OER stability testing were performed, such as... Figure 7 As shown, at 20mA / cm -2After 48 hours under alkaline conditions, the stability of HER remained at 86.67%, such as... Figure 8 As shown, at 100mA / cm -2 After 48 hours under alkaline conditions, the stability of OER remained at 96.6%, and it was able to maintain good performance even at higher current densities under alkaline conditions.

[0049] Furthermore, it improved the catalytic activity and stability of the bifunctional electrocatalyst, as demonstrated in LSV and stability tests for total water splitting. Figure 9 As shown, at 10 mA·cm -2 The overpotential required for complete water splitting is only 1.57V. Figure 10 As shown, after 24 hours, the stability of NiCo2S4@NiMo3S4 / CT remained at 98.32% under alkaline conditions.

[0050] Comparative Example 1

[0051] A method for preparing a NiCo2S4 / CT electrocatalyst includes the following steps:

[0052] (1) Add 0.58g Co(NO3)2·6H2O, 0.29g Ni(NO3)2·6H2O and 0.72g urea to 40mL of ethanol / deionized water mixed solvent and stir to obtain a homogeneous mixed solution.

[0053] (2) The carbon cloth and the homogeneous mixed solution were transferred to a 50 mL reaction vessel and kept at 100 °C for 8 h. After the reaction was completed, the mixture was cooled to room temperature and dried to obtain the NiCo2O4 / CT precursor. Scanning electron microscopy results are shown below. Figure 2 As shown.

[0054] (3) Dissolve 0.24 g Na2S·9H2O in 30 mL of deionized water. Transfer the resulting clear solution and NiCo2O4 / CT precursor to a 50 mL reactor and keep it at 180 °C for 6 h. After the reaction, wash with deionized water and dry in air at 60 °C for 12 h. Then calcine at 300 °C for 2 h in an Ar atmosphere with a heating rate of 5 °C·min. -1 The gas flow rate was 30 sscm. After the reaction was complete, NiCo2S4 / CT electrocatalyst was obtained. Scanning electron microscopy (SEM) results are shown below. Figure 3 As shown.

[0055] Depend on Figure 2 It can be seen that NiCo2O4 nanoneedles grow uniformly and vertically on the surface of each carbon fiber, with a maximum width of approximately 100 nm. Figure 3It can be seen that NiCo2O4 nanoneedles are sulfided into NiCo2S4 nanotubes, forming a nanotube array to obtain the NiCo2S4 / CT precursor. In this comparative example, the performance of the prepared NiCo2S4 / CT electrocatalyst was tested using the same method as in Example 1, and the results showed a performance at 10 mA / cm². -2 The overpotentials of NiCo2S4 / CT are 268mV and 275mV, respectively. Figure 6 In (c) and (d), the Tafel slopes of OER and HER in the Tafel curves are 175.9 mV dec. -1 and 187.04mV dec -1 At 20mA / cm -2 After 48 hours under alkaline conditions, the stability of HER remained at 88.57%, at 100 mA / cm². -2 The stability of OER remained at 91.33% after 48 hours under alkaline conditions, while no full hydrolysis test was performed on a single material.

[0056] Comparative Example 2

[0057] A method for preparing a NiMo3S4 / CT electrocatalyst includes the following steps:

[0058] 0.075 g Na2MoO4·2H2O and 0.08125 g NiSO4·6H2O were dissolved in 40 mL of deionized water. Then, 0.2 g CH4N2S was added and the mixture was stirred further to obtain a homogeneous solution. The carbon cloth and the homogeneous solution were transferred to a 50 mL reactor and kept at 180 °C for 12 h. After the reaction was completed, the mixture was washed with deionized water and dried in air at 60 °C for 12 h to obtain the product NiMo3S4 / CT.

[0059] The performance of the NiMo3S4 / CT electrocatalyst prepared in this comparative example was tested using the same method as in Example 1, and the results were obtained at 10 mA / cm². -2 The overpotentials of NiCo2S4 / CT are 228mV and 390mV, respectively. Figure 6 In (c) and (d), the Tafel slopes for OER and HER are 298.6 mV dec. -1 and 89.75mV dec -1 At 20mA / cm -2 After 48 hours under alkaline conditions, the stability of HER remained at 90.3%, at 100 mA / cm². -2 The stability of OER cannot be maintained after 48 hours under alkaline conditions, and a full hydrolysis test is not performed on a single material.

[0060] Compared with Example 1, the performance test results of the catalysts prepared in Comparative Examples 1 and 2 show that the catalytic materials formed by combining NiCo2S4 and NiMo3S4 with CT are unstable and rapidly degraded in alkaline electrolytes, which limits their catalytic performance.

[0061] Comparative Example 3

[0062] The method for preparing NiCo2S4@NiMo3S4 / CT catalyst using a fully hydrothermal process includes the following steps:

[0063] (1) 0.58g Co(NO3)2·6H2O, 0.29g Ni(NO3)2·6H2O and 0.72g urea were added to 40mL of ethanol / deionized water mixed solvent and stirred to obtain a uniform mixed solution. Carbon cloth was added and transferred to a 50mL reaction vessel. The mixture was kept at 100℃ for 8h. After the reaction was completed, the mixture was cooled to room temperature and dried to obtain NiCo2O4 / CT precursor.

[0064] (2) Dissolve 0.24 g Na2S·9H2O in 30 mL of deionized water. Transfer the resulting clear solution and NiCo2O4 / CT precursor to a 50 mL reactor and keep it at 180 °C for 6 h. After the reaction is complete, wash with deionized water and dry in air at 60 °C for 12 h to obtain NiCo2S4 / CT.

[0065] (3) Dissolve 0.075g Na2MoO4·2H2O and 0.08125g NiSO4·6H2O in 40mL of deionized water, then add 0.2g CH4N2S and stir further. The resulting clear solution and the NiCo2S4 / CT carbon cloth sample obtained in (3) are transferred to a 50mL reaction vessel and kept at 180℃ for 12h. After the reaction, wash with deionized water and dry in air at 60℃ for 12h to finally obtain the product NiCo2S4@NiMo3S4 / CT. Scanning electron microscopy results are as follows. Figure 4 As shown.

[0066] Scanning electron microscopy of the three-dimensional layered NiCo2S4@NiMo3S4 / CT bifunctional electrocatalyst prepared according to Example 1. Figure 1 Scanning electron microscopy of NiCo2S4@NiMo3S4 / CT catalyst prepared by the entire hydrothermal method in Comparative Example 3. Figure 4 This indicates that when the NiCo2O4 / CT precursor is sulfided but not sintered, and instead formed by a hydrothermal method, NiCo2S4@NiMo3S4 / CT cannot maintain the morphology of the nanotubes and nanosheets, but instead forms a core-shell-like structure, which also reduces the catalytic performance.

[0067] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a three-dimensional hierarchical NiCo2S4@NiMo3S4 / CT bifunctional electrocatalyst, characterized in that, Includes the following steps: (1) Co(NO3)2·6H2O, Ni(NO3)2·6H2O and urea were added to a mixed solvent of ethanol and water and stirred to obtain a mixed solution. Carbon cloth was added and dispersed evenly. After the reaction, the mixture was heated and kept warm, washed and dried to obtain NiCo2O4 / CT precursor. (2) Dissolve Na2S·9H2O in water and mix thoroughly. Add NiCo2O4 / CT precursor, mix and react, heat and keep warm, wash and dry, and then calcine in an inert gas to obtain NiCo2S4 nanotube array. (3) Dissolve Na2MoO4·2H2O and NiSO4·6H2O in water, add CH4N2S, and continue stirring to obtain a mixed solution. Transfer the NiCo2S4 nanotube array into the mixed solution, heat and keep warm, wash and dry to obtain the NiCo2S4@NiMo3S4 / CT bifunctional electrocatalyst.

2. The method for preparing the three-dimensional layered NiCo2S4@NiMo3S4 / CT bifunctional electrocatalyst according to claim 1, characterized in that, In step (1), the mass ratio of Co(NO3)2·6H2O, Ni(NO3)2·6H2O, and urea is 0.58:0.29:0.72, and the volume ratio of ethanol to water is 1:

1. The Co content in the mixed solution... 2+ and Ni 2+ The total concentration was 0.0057-0.0058 g / mL, and the mass of carbon cloth added was 90-95% of the theoretical weight of the NiCo2O4 / CT precursor.

3. The method for preparing the three-dimensional layered NiCo2S4@NiMo3S4 / CT bifunctional electrocatalyst according to claim 1, characterized in that, The heating temperature in step (1) is 100-105℃, and the holding time is 8-8.1h.

4. The method for preparing the three-dimensional layered NiCo2S4@NiMo3S4 / CT bifunctional electrocatalyst according to claim 1, characterized in that, In step (2), the mass ratio of Na2S·9H2O to NiCo2O4 / CT precursor is 3:11, where Na + The concentration was 0.00095 g / mL.

5. The method for preparing the three-dimensional layered NiCo2S4@NiMo3S4 / CT bifunctional electrocatalyst according to claim 1, characterized in that, The heating temperature in step (2) is 180-185℃, and the holding time is 6-6.1h.

6. The method for preparing the three-dimensional layered NiCo2S4@NiMo3S4 / CT bifunctional electrocatalyst according to claim 1, characterized in that, In step (2), the calcination temperature is 300-305℃ and the calcination time is 2-2.1h.

7. The method for preparing the three-dimensional layered NiCo2S4@NiMo3S4 / CT bifunctional electrocatalyst according to claim 1, characterized in that, In step (3), the mass ratio of Na₂MoO₄·2H₂O, NiSO₄·6H₂O, and CH₄N₂S is 0.075:0.08125:0.2, wherein the Ni in the mixed solution... 2+ The concentration is 0.00045-0.000455 g / mL.

8. The three-dimensional layered NiCo2S4@NiMo3S4 / CT prepared by the method according to any one of claims 1-7, characterized in that, It consists of conductive carbon cloth, a NiCo2S4 nanotube array as a framework support, and NiMo3S4 nanosheets covering the surface of the NiCo2S4 nanotube array.

9. The application of the three-dimensional layered NiCo2S4@NiMo3S4 / CT bifunctional electrocatalyst according to claim 8 in water electrolysis.

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