Three-dimensional layered NiCo2S4-coated NiMo3S4 / CT difunctional electrocatalyst as well as preparation method and application of three-dimensional layered NiCo2S4-coated NiMo3S4 / CT difunctional electrocatalyst

Abstract

The invention discloses a three-dimensional layered NiCo2S4-coated NiMo3S4 / CT bifunctional electrocatalyst as well as a preparation method and application thereof, and belongs to the technical field of new energy technology electrocatalytic materials. A two-time hydrothermal method and an annealing method are combined, carbon cloth is used as a conductive substrate to grow a two-dimensional NiCo2O4 / CT precursor, a framework NiCo2S4 nanotube array is obtained through vulcanization, NiMo3S4 nanosheets are grown on NiCo2S4 / CT nanotubes through a two-time hydrothermal method, the ultrathin NiMo3S4 nanosheets are used for providing more catalytic reaction sites, a NiMo3S4 nanosheet group covers the surface of the NiCo2S4 nanotube array, and the surface of the NiCo2S4 nanotube array is coated with the NiMo3S4 nanosheets. And thus, the bifunctional electrocatalyst with a unique three-dimensional layered NiCo < 2 > S < 4 >-NiMo < 3 > S < 4 > / CT heterostructure is formed. The three-dimensional layered NiCo < 2 > S < 4 >-coated NiMo < 3 > S < 4 > material obtained by the invention has excellent catalytic performance and cycling stability, active sites and large specific surface area. The preparation method is simple, a special interface is constructed, abundant defects and a phase change coupling electronic structure are formed, the bimetallic sulfide with a heterostructure is obtained, the electron transmission rate is increased, and the electrical property of the transition metal sulfide is improved.

Description

Technical Field

[0001] The present invention relates to the field of electrochemical catalytic materials and devices in new energy technologies, and particularly to a three-dimensional hierarchical NiCo 2 S 4 @NiMo 3 S 4 / CT bifunctional electrocatalyst and its preparation method and application. Background Art

[0002] The electrolysis process from water to hydrogen provides an effective solution for the conversion, storage, and release of intermittent renewable energy such as tidal energy, wind energy, and solar energy. The water splitting process includes 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 hydrogen evolution reaction, and RuO 2 , IrO 2 are used for the oxygen evolution reaction. Catalysts can lower the activation barrier, accelerate the redox electron transfer, and promote the reaction process. However, the scarcity and high cost of noble metal catalysts prevent large-scale applications, and the catalysts have weak bifunctionality and poor stability.

[0003] Transition metal sulfides are one of the high-performance electrocatalysts, including MoS 2 , Ni 3 S 2 , and CoS 2 among others. Transition metal sulfides (TMS) have attracted much attention due to their excellent electrocatalytic performance. However, these TMS have some drawbacks, including poor separation of ion / electron transport kinetics, low electroactive sites, and relatively insufficient stability, which will seriously limit the improvement of their electrocatalytic activity. In order to ensure the stability of the material while improving the catalytic activity, bimetallic sulfides with special structures have gradually become a research hotspot.

[0004] NiCo 2 S 4 and NiMo 3 S 4 are two of the most representative materials. The Mo-S and Co-S bonds doped with Ni have metallic properties, which can improve the electrical conductivity and increase a large number of Ni 3+ active sites. However, the instability and rapid degradation of single NiCo 2 S 4 and NiMo 3 S 4 in alkaline electrolytes greatly limit their catalytic performance. Therefore, the development of electrocatalytic materials with high activity, long cycle life, and strong bifunctionality is the key to promoting commercial water electrolysis. Summary of the Invention

[0005] The object of the present invention is to overcome the defects existing in the above-mentioned prior art, and provide a three-dimensional hierarchical NiCo 2 S 4 @NiMo 3 S 4 / CT bifunctional electrocatalyst and its preparation method and application. The NiCo 2 S 4 @NiMo 3 S 4 / CT bifunctional electrocatalyst has properties such as high activity, long cycle life and strong bifunctionality.

[0006] A preparation method of a three-dimensional hierarchical NiCo 2 S 4 @NiMo 3 S 4 / CT bifunctional electrocatalyst comprises the following steps:

[0007] (1) Co(NO 3 ) 2 ·6H 2 O, Ni(NO 3 ) 2 ·6H 2 O and urea are added to a mixed solvent of ethanol and water, stirred to obtain a uniform mixed solution, carbon cloth is added and dispersed evenly, heated and kept warm, washed and dried to obtain a NiCo 2 O 4 / CT precursor;

[0008] (2) Na 2 S·9H 2 O is dissolved in water, the NiCo 2 O 4 / CT precursor obtained in step (1) is added, and after mixing, it is heated and kept warm, washed and dried, and then calcined in an inert gas to sulfide NiCo 2 O 4 to obtain a NiCo 2 S 4 nanotube array;

[0009] (3) Na 2 MoO 4 ·2H 2 O and NiSO 4 ·6H 2 O are dissolved in water, CH 4 N 2 S is added, and stirring is continued to obtain a mixed solution. The NiCo 2 S 4 nanotube array is transferred and added to the mixed solution, heated and kept warm, washed and dried to obtain NiCo2 S 4 @NiMo 3 S 4 / CT bifunctional electrocatalyst.

[0010] As a preferred embodiment, the mass ratio of Co(NO 3 ) 2 ·6H 2 O, Ni(NO 3 ) 2 ·6H 2 O and urea is 0.58:0.29:0.72, the volume ratio of ethanol and water is 1:1, and the total concentration of Co 2+ and Ni 2+ in the mixed solution is 0.0057 - 0.0058 g / mL.

[0011] As a preferred embodiment, the mass of the carbon cloth added is 90 - 95% of the theoretical weight of the NiCo 2 O 4 / CT precursor.

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

[0013] As a preferred embodiment, in step (2), the mass ratio of Na 2 S·9H 2 O to the NiCo 2 O 4 / CT precursor is 3:11, and the concentration of Na + is 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 °C for 6 - 6.1 h.

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

[0016] As a preferred embodiment, the drying temperatures in both step (2) and step (3) are 60 - 62 °C, and the drying time is 12 - 12.1 h.

[0017] As a preferred embodiment, in step (3), Na 2 MoO 4 ·2H 2 O, NiSO 4 ·6H 2 O and CH 4 N 2The mass ratio of S is 0.075:0.08125:0.2, and the concentration of Ni in the mixed solution 2+ 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 °C for 12 - 12.1 h.

[0019] In the embodiment of the present invention, the main function of calcination is to improve the crystal quality and crystallinity of the NiCo 2 S 4 nanotube array crystals, thereby improving the electrical conductivity and catalytic performance of the material to a certain extent. After the NiCo 2 S 4 nanotube array is prepared, annealing is carried out to burn off excess impurities and ensure the smooth progress of the second hydrothermal reaction.

[0020] The carbon cloth described in the present invention is a conductive carbon cloth with a flexible substrate. The prepared NiCo 2 S 4 @NiMo 3 S 4 / CT bifunctional electrocatalyst, the NiCo 2 S 4 nanotube array serves as a skeleton support, and the NiMo 3 S 4 nanosheet group covers the surface of the NiCo 2 S 4 nanotube array.

[0021] The NiCo 2 S 4 nanotube array in the present invention, the diameter of the NiCo 2 S 4 nanotubes is 80 - 100 nm.

[0022] The NiMo 3 S 4 nanosheet group described in the present invention has a thickness of 20 nm and is composed of multiple layers of NiMo 3 S 4 nanosheets overlapping each other.

[0023] The present invention adopts a three-dimensional hierarchical structure design, using a flexible conductive carbon cloth as the substrate, and the NiCo 2 S 4 nanotube array as a skeleton to support the outer ultra-thin NiMo 3 S 4 nanosheets, thereby forming NiCo 2 S 4 @NiMo 3 S4 The hierarchical structure of / CT not only improves the specific surface area of the catalyst but also enhances the catalytic activity and stability of the bifunctional electrocatalyst.

[0024] In this invention, a conductive carbon cloth material is selected as the flexible substrate, and NiCo is grown on the carbon cloth by hydrothermal method 2 O 4 nanoneedle arrays as precursors, and the precursors are sulfided by hydrothermal method to obtain NiCo 2 S 4 nanotube arrays. High-temperature treatment in an inert gas Ar atmosphere enables the stable existence of NiCo 2 S 4 nanotube arrays, and then secondary hydrothermal method is carried out to synthesize ultrathin NiMo 2 S 4 nanosheets on the surface of NiCo 3 S 4 nanotube arrays, and finally a three-dimensional hierarchical NiCo 2 S 4 @NiMo 3 S 4 / CT bifunctional electrocatalyst is obtained.

[0025] In the application of the three-dimensional hierarchical NiCo 2 S 4 @NiMo 3 S 4 / CT bifunctional electrocatalyst in water electrolysis, it has good catalytic activity and stability for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) bifunctional electrocatalysts.

[0026] Compared with the prior art, what are the advantages of this invention:

[0027] (1) The preparation method of this invention is simple. A flexible bifunctional electrocatalytic material is designed with a carbon cloth material as the substrate, which can be bent and folded without adhesives. Two-dimensional NiCo is grown on the carbon cloth as the conductive base 2 O 4 / CT precursor, and after sulfidation, a framework NiCo 2 S 4 nanotube array is obtained. Secondary hydrothermal method enables NiCo 2 S 4 / CT nanotubes to grow NiMo 3 S 4 nanosheets. The ultrathin NiMo 3 S 4 nanosheets are used to provide catalytic reaction sites, and the NiMo 3 S 4 nanosheet groups cover NiCo 2 S4 on the surface of the nanotube array, thus forming a unique three-dimensional layered NiCo 2 S 4 @NiMo 3 S 4 / CT heterostructure bifunctional electrocatalyst.

[0028] (2) In the present invention, NiCo 2 O 4 / CT precursor is vulcanized and sintered to ensure that after vulcanization, NiCo 2 S 4 and NiMo 3 S 4 grown epitaxially on its surface are combined in the form of nanotube arrays and ultrathin nanosheets respectively to construct a heterostructure. Compared with the NiCo 2 S 4 @NiMo 3 S 4 / CT prepared by the all-hydrothermal method and presented in a core-shell structure, the electron transfer rate is increased, the electrical properties of the transition metal sulfide are improved, the catalyst performance is enhanced, and at the same time, the NiCo 2 S 4 nanotube array structure has good mechanical properties. As the framework material, the ultrathin NiMo 3 S 4 nanosheets endow the obtained catalyst with good stability.

[0029] (3) The thickness of the ultrathin NiMo 3 S 4 nanosheets prepared in the present invention is 20 nm, which is beneficial to increasing the specific surface area and providing more catalytic reaction sites. The synergistic effect between NiMo 3 S 4 and NiCo 2 S 4 together improves the catalytic performance. Description of the Drawings

[0030] Figure 1 Figure 61 shows the scanning electron microscope image of the three-dimensional layered NiCo 2 S 4 @NiMo 3 S 4 / CT bifunctional electrocatalyst prepared in Example 1. (a) shows the HTM (1 μm) of the three-dimensional layered NiCo 2 S 4 @NiMo 3 S 4 / CT bifunctional electrocatalyst. (b) shows the HTM (1 μm) of the three-dimensional layered NiCo 2 S 4 @NiMo3 S 4 TM (500 nm) of the S / CT bifunctional electrocatalyst.

[0031] Figure 2 NiCo prepared for Comparative Example 1 2 O 4 Scanning electron micrograph of NiCo / O / CT.

[0032] Figure 3 NiCo prepared for Comparative Example 1 2 S 4 Scanning electron micrograph of NiCo / S / CT.

[0033] Figure 4 NiCo prepared for Comparative Example 3 2 S 4 @NiMo 3 S 4 Scanning electron micrograph of NiCo@NiMoS / CT. Figure (a) shows NiCoS@NiMoS / CT prepared for Comparative Example 3 2 S 4 @NiMo 3 S 4 Scanning electron micrograph of NiCo@NiMoS / CT (200 nm). Figure (b) shows NiCoS@NiMoS / CT prepared for Comparative Example 3 2 S 4 @NiMo 3 S 4 Scanning electron micrograph of NiCo@NiMoS / CT (100 nm).

[0034] Figure 5 NiCo prepared for Comparative Example 1 2 S 4 / CT and NiCoS@NiMoS / CT prepared for Example 1 2 S 4 @NiMo 3 S 4 Transmission electron micrograph of NiCoS / CT. Figure (a) shows NiCoS / CT prepared for Comparative Example 1 2 S 4 Transmission electron micrograph of NiCoS@NiMoS / CT. Figure (b) shows NiCoS@NiMoS / CT prepared for Example 1 2 S 4 @NiMo 3 S 4 Transmission electron micrograph of NiCoS@NiMoS / CT.

[0035] Figure 6 NiCoS@NiMoS / CT prepared for Example 1 2 S 4 @NiMo 3 S 4 / CT, NiCoS / CT prepared for Comparative Example 1 2 S 4 / CT and NiMoS / CT prepared for Comparative Example 2 3 S4 LSV and Tafel curves of HER and OER of / CT, (a) is NiCo 2 S 4 @NiMo 3 S 4 / CT prepared in Comparative Example 1, NiCo 2 S 4 / CT and NiMo prepared in Comparative Example 2 3 S 4 LSV curve of HER of / CT; (b) is NiCo 2 S 4 @NiMo 3 S 4 / CT prepared in Example 1, NiCo 2 S 4 / CT and NiMo prepared in Comparative Example 2 3 S 4 LSV curve of OER of / CT; (c) is NiCo 2 S 4 @NiMo 3 S 4 / CT prepared in Example 1, NiCo 2 S 4 / CT and NiMo prepared in Comparative Example 2 3 S 4 Tafel curve of OER of / CT; (d) is NiCo 2 S 4 @NiMo 3 S 4 / CT prepared in Example 1, NiCo 2 S 4 / CT and NiMo prepared in Comparative Example 2 3 S 4 Tafel curve of HER of / CT.

[0036] Figure 7 For NiCo prepared in Example 1 2 S 4 @NiMo 3 S 4 / CT prepared in Example 1, NiCo 2 S 4 / CT and NiMo prepared in Comparative Example 2 3 S 4 HER stability test curve of / CT.

[0037] Figure 8 For NiCo prepared in Example 1 2S 4 @NiMo 3 S 4 / CT, NiCo prepared in Comparative Example 1 2 S 4 / CT and NiMo prepared in Comparative Example 2 3 S 4 OER stability test curves of / CT.

[0038] Figure 9 NiCo prepared for Example 1 2 S 4 @NiMo 3 S 4 LSV test curves of the overall water splitting of the / CT bifunctional electrocatalyst.

[0039] Figure 10 NiCo prepared for Example 1 2 S 4 @NiMo 3 S 4 Stability test curves of the overall water splitting of the / CT bifunctional electrocatalyst. Detailed implementation manners

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

[0041] Example 1

[0042] A three-dimensional hierarchical NiCo 2 S 4 @NiMo 3 S 4 Preparation method of / CT bifunctional electrocatalyst, comprising the following steps:

[0043] (1) 0.58 g of Co(NO 3 ) 2 ·6H 2 O, 0.29 g of Ni(NO 3 ) 2 ·6H 2 O and 0.72 g of urea are added to 40 mL of a mixed solvent of ethanol / deionized water and stirred to obtain a uniformly mixed solution.

[0044] (2) The carbon cloth and the uniformly mixed solution are transferred to a 50 mL autoclave, kept at 100 °C for 8 h, cooled to room temperature and dried after the reaction to obtain the NiCo 2 O 4 / CT precursor.

[0045] (3) 0.24 g of Na 2 S·9H2 O is dissolved in 30 mL of deionized water, and the resulting clear solution and NiCo 2 O 4 / CT precursor are transferred to a 50 mL reaction kettle, kept at 180 °C for 6 h. After the reaction is completed, it is washed with deionized water and dried in air at 60 °C for 12 h, and then calcined at 300 °C for 2 h in an Ar atmosphere with a heating rate of 5 °C·min -1 , and the gas flow is 30 sscm. After the reaction is completed, NiCo 2 S 4 / CT is obtained.

[0046] (4) Dissolve 0.075 g of Na 2 MoO 4 ·2H 2 O and 0.08125 g of NiSO 4 ·6H 2 O in 40 mL of deionized water, then add 0.2 g of CH 4 N 2 S and stir further. The resulting clear solution and the NiCo 2 S 4 / CT carbon cloth sample obtained in (3) are transferred to a 50 mL reaction kettle, kept at 180 °C for 12 h. After the reaction is completed, it is washed with deionized water and dried in air at 60 °C for 12 h. Finally, the product NiCo 2 S 4 @NiMo 3 S 4 / CT is obtained, and the scanning electron microscope is as Figure 1 shown.

[0047] According to Figure 1 the NiCo prepared in Example 1 2 S 4 @NiMo 3 S 4 / CT scanning electron micrograph shows that the surface of the NiCo 2 S 4 nanotubes is covered with a layer of NiMo 3 S 4 nanosheets, indicating that the NiCo 2 S 4 @NiMo 3 S 4 / CT bifunctional electrocatalysis is composed of a NiCo 2 S 4 nanotube array supported by a conductive carbon cloth as a framework, and NiMo 2 S 4 nanosheets covering the surface of the NiCo 3 S 4 nanotube array; combinedFigure 5 (a) NiCo prepared in Comparative Example 1 2 S 4 The transmission electron microscopy of S / CT shows that the NiCo under the NiMo layer 3 S 4 nanotube structure is still clearly visible, indicating that NiMo 2 S 4 is extremely thin, and 3 S 4 and Figure 5 (b) NiCo prepared in Example 1 2 S 4 @NiMo 3 S 4 The high-resolution transmission electron microscopy image of S@NiMoS / CT confirms that NiMo 3 S 4 and NiCo 2 S 4 are successfully grown, and the thickness of NiMo 3 S 4 is only 20 nm.

[0048] Using NiCo 2 S 4 @NiMo 3 S 4 / CT as the working electrode, saturated calomel electrode as the reference electrode, graphite rod as the counter electrode, and 1 M KOH solution as the electrolyte, linear sweep voltammetry LSV and Tafel curve tests and overall water splitting LSV test curves and overall water splitting stability tests were carried out in the range of -2 to -1 V and 0 to 1 V. All tests were completed on the Donghua Electrochemical Workstation. As shown in Figure 6 (a) and (b), the overpotentials of HER and OER at 10 mA cm -2 are 59 mV and 130 mV respectively; as shown in Figure 6 (c) and (d), the Tafel curves obtained by fitting also show that NiCo 2 S 4 @NiMo 3 S 4 / CT has Tafel slopes of 39.33 mV dec -1 and 139.64 mV dec -1 for OER and HER respectively. After that, HER stability test and OER stability test were carried out respectively. As shown in Figure 7 , the stability of HER remains at 86.67% after 48 hours under alkaline conditions at 20 mA / cm -2 ; as shown in Figure 8 , at 100 mA / cm -2The stability of OER remains at 96.6% after 48 hours under alkaline conditions, and good performance can still be maintained at a relatively high current density under alkaline conditions.

[0049] In addition, the catalytic activity and stability of the bifunctional electrocatalyst were also improved. During the overall water splitting LSV test and the overall water splitting stability test, as Figure 9 shown, the overpotential required for overall water splitting at 10 mA·cm -2 is only 1.57 V. Figure 10 As shown, after 24 hours, the stability of NiCo 2 S 4 @NiMo 3 S 4 / CT under alkaline conditions still remains at 98.32%.

[0050] Comparative Example 1

[0051] A preparation method of a NiCo 2 S 4 / CT electrocatalyst includes the following steps:

[0052] (1) 0.58 g of Co(NO 3 ) 2 ·6H 2 O, 0.29 g of Ni(NO 3 ) 2 ·6H 2 O and 0.72 g of urea were added to 40 mL of a mixed solvent of ethanol / deionized water and stirred to obtain a homogeneous mixed solution.

[0053] (2) The carbon cloth and the homogeneous mixed solution were transferred to a 50 mL autoclave, kept at 100 °C for 8 h, cooled to room temperature and dried after the reaction to obtain a NiCo 2 O 4 / CT precursor, and the scanning electron microscope is as Figure 2 shown.

[0054] (3) 0.24 g of Na 2 S·9H 2 O was dissolved in 30 mL of deionized water, and the obtained clear solution and the NiCo 2 O 4 / CT precursor were transferred to a 50 mL autoclave, kept at 180 °C for 6 h, washed with deionized water after the reaction, dried in air at 60 °C for 12 h, and then calcined at 300 °C for 2 h in an Ar atmosphere with a heating rate of 5 °C·min -1 , and the gas flow was 30 sscm. After the reaction, a NiCo 2 S 4 / CT electrocatalyst was obtained, and the scanning electron microscope is asFigure 3 as shown

[0055] From Figure 2 it can be seen that NiCo 2 O 4 nanoneedles grow vertically and uniformly on the surface of each carbon fiber. The width at the widest part is about 100 nm. From Figure 3 it can be seen that NiCo 2 O 4 nanoneedles are sulfided into NiCo 2 S 4 nanotubes, forming a nanotube array, to obtain NiCo 2 S 4 / CT precursor; In this comparative example, the prepared NiCo 2 S 4 / CT electrocatalyst was tested for performance in the same manner as in Example 1, and the overpotentials of NiCo -2 under 10 mA cm 2 S 4 / CT were 268 mV and 275 mV respectively, and Figure 6 (c) and (d) The Tafel slopes of OER and HER in the Tafel curves were 175.9 mV dec -1 and 187.04 mV dec -1 , respectively. The stability of HER remained at 88.57% after 48 hours under 20 mA / cm -2 in alkaline conditions, and the stability of OER remained at 91.33% after 48 hours under 100 mA / cm -2 in alkaline conditions. For single materials, full hydrolysis tests were not conducted.

[0056] Comparative Example 2

[0057] A preparation method of a NiMo 3 S 4 / CT electrocatalyst, comprising the following steps:

[0058] Dissolve 0.075 g of Na 2 MoO 4 ·2H 2 O and 0.08125 g of NiSO 4 ·6H 2 O in 40 mL of deionized water, then add 0.2 g of CH 4 N 2 S and stir further to obtain a uniformly mixed solution. Transfer the carbon cloth and the uniformly mixed solution to a 50 mL reaction kettle, keep it at 180 °C for 12 h. After the reaction, wash it with deionized water and dry it at 60 °C in air for 12 h to obtain the product NiMo 3 S4 / CT.

[0059] The NiMo prepared in this comparative example was subjected to performance testing in the same manner as in Example 1 3 S 4 / CT electrocatalyst, and the overpotentials of NiCo -2 at 10 mA cm 2 S 4 / CT were 228 mV and 390 mV respectively, and Figure 6 (c) and (d) the Tafel slopes of OER and HER in the Tafel curves were 298.6 mV dec -1 and 89.75 mV dec -1 , and the stability of HER remained at 90.3% after 48 hours under alkaline conditions at 20 mA / cm -2 . After 48 hours under alkaline conditions at 100 mA / cm -2 , the stability of OER could not be maintained, and full hydrolysis testing was not performed on the single material.

[0060] Compared with the catalyst prepared in Examples 1, the performance test results of the catalysts prepared in Comparative Examples 1 and 2 showed that the single NiCo 2 S 4 and NiMo 3 S 4 composite with CT to form a catalytic material was unstable and rapidly degraded in alkaline electrolyte, limiting its catalytic performance.

[0061] Comparative Example 3

[0062] A method for preparing NiCo 2 S 4 @NiMo 3 S 4 / CT catalyst by a one-step hydrothermal method, comprising the following steps:

[0063] (1) 0.58 g of Co(NO 3 ) 2 ·6H 2 O, 0.29 g of Ni(NO 3 ) 2 ·6H 2 O and 0.72 g of urea were added to 40 mL of a mixed solvent of ethanol / deionized water and stirred to obtain a homogeneous mixed solution. The carbon cloth was added and transferred to a 50 mL autoclave, and kept at 100 °C for 8 h. After the reaction, it was cooled to room temperature and dried to obtain a NiCo 2 O 4 / CT precursor.

[0064] (2) 0.24 g of Na 2S·9H 2 O is dissolved in 30 mL of deionized water, and the resulting clear solution and NiCo 2 O 4 / CT precursor are transferred to a 50 mL autoclave, kept at 180 °C for 6 h. After the reaction is completed, it is washed with deionized water and dried in air at 60 °C for 12 h to obtain NiCo 2 S 4 / CT.

[0065] (3) Dissolve 0.075 g of Na 2 MoO 4 ·2H 2 O and 0.08125 g of NiSO 4 ·6H 2 O in 40 mL of deionized water, then add 0.2 g of CH 4 N 2 S and stir further. The resulting clear solution and the NiCo 2 S 4 / CT carbon cloth sample obtained in (3) are transferred to a 50 mL autoclave, kept at 180 °C for 12 h. After the reaction is completed, it is washed with deionized water and dried in air at 60 °C for 12 h. Finally, the product NiCo 2 S 4 @NiMo 3 S 4 / CT is obtained, and the scanning electron microscope is as Figure 4 shown.

[0066] Prepare the scanning electron microscope of the three-dimensional hierarchical NiCo 2 S 4 @NiMo 3 S4 / CT bifunctional electrocatalyst according to Example 1 Figure 1 and Comparative Example 3 prepare NiCo 2 S 4 @NiMo 3 S 4 / CT catalyst scanning electron microscope Figure 4 This shows that when the NiCo 2 O 4 / CT precursor is sulfided without sintering, but the NiCo 2 S 4 @NiMo 3 S 4 / CT formed by the all-hydrothermal method cannot maintain the combined morphology of nanotubes and nanosheets, but forms a similar core-shell structure, and the catalytic performance will also decline.

[0067] The above description of the embodiments is provided to enable those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a three-dimensional layered NiCo2S4@NiMo3S4 / CT bifunctional electrocatalyst, characterized in that: The steps include: (1) adding Co(NO3)2·6H2O, Ni(NO3)2·6H2O and urea to a mixed solvent of ethanol and water and stirring to obtain a mixture solution, adding carbon cloth to disperse evenly, heating and heat preservation, washing and drying after the reaction, and obtaining a NiCo2O4 / CT precursor; (2) dissolving Na2S·9H2O in water and mixing thoroughly, adding NiCo2O4 / CT precursor, heating and keeping warm after mixing and reacting, washing, drying, and then calcining in an inert gas to obtain a NiCo2S4 nanotube array; (3) Na2MoO4·2H2O and NiSO4·6H2O were dissolved in water, CH4N2S was added, and the mixture was stirred continuously to obtain a mixed solution. The NiCo2S4 nanotube array was transferred into the mixed solution, heated and kept warm, washed, and dried to obtain a 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: The mass ratio of Co(NO3)2·6H2O, Ni(NO3)2·6H2O and urea in step (1) is 0.58:0.29:0.72, the volume of ethanol and water is 1:1, and the Co in the mixed solution is 2+ and Ni 2+ The total concentration is 0.0057-0.0058 g / mL, and the mass of carbon cloth added is 90-95% of the theoretical weight of 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° C., and the insulation time is 8-8.1 h.

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, wherein Na + The concentration is 0.00095g / 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° C., and the insulation time is 6-6.1 h.

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° C., and the calcination time is 2-2.1 h.

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 Ni in the mixed solution is 2+ The concentration is 0.00045-0.000455g / mL.

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

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

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