Ni3Fe-LDH@NiCoP / NF heterojunction high-efficiency full water splitting electrocatalyst and its preparation method and application

Abstract

Ni3Fe-LDH@NiCoP / NF Heterojunction High-Efficiency Overall Water Splitting Electrocatalyst and Its Preparation Method and Application. The present invention belongs to the field of electrolytic water catalytic materials. The purpose of the present invention is to solve the technical problems that the Ni3Fe-LDH@NiCoP / NF heterojunction electrocatalyst synthesized by the current hydrothermal method is not conducive to electron transport, and at the same time the preparation process is complex, time-consuming, and toxic and harmful gases are generated during the phosphating treatment process. In the present invention, nickel salt, cobalt salt, phosphite, NH4Cl and CH3COONa are used as electrolytes, and the pretreated nickel-based material is used as the working electrode, and NiCoP-x is grown by constant current deposition; then nickel salt and iron salt are used as electrolytes, and the above product is used as the working electrode, and Ni3Fe-LDH is grown by constant voltage deposition to obtain a Ni3Fe-LDH@NiCoP / NF heterojunction high-efficiency overall water splitting electrocatalyst.

Description

Technical Field

[0001] The present invention belongs to the field of water electrolysis catalytic materials, and specifically relates to a Ni3Fe-LDH@NiCoP / NF heterojunction high-efficiency full water electrolysis catalyst, and a preparation method and application thereof. Background Art

[0002] As the depletion of fossil energy and environmental degradation become more and more serious, the development and utilization of renewable energy is imminent. Among many renewable energy sources, hydrogen energy has the advantages of high energy density and zero greenhouse gas emissions, and is considered to be one of the most promising energy sources to replace traditional fossil fuels. Electrocatalytic water decomposition to produce hydrogen is an effective method to achieve large-scale production of high-purity hydrogen, but the anodic oxygen evolution reaction (OER) in water electrolysis involves four proton-coupled electron transfers, which has slow kinetics and requires a high overpotential, resulting in low energy conversion efficiency, which is a bottleneck that urgently needs to be broken through in the field of water electrolysis to produce hydrogen. At present, the most effective electrocatalysts for OER electrocatalysis are RuO2 and IrO2, however, their high price and scarcity have seriously hindered their industrial application. Therefore, it is imperative to rationally design and low-cost preparation of economical, efficient and durable non-precious metal-based nanomaterials for OER electrocatalytic reactions.

[0003] In recent years, many non-precious metal-based OER catalysts have been widely studied. Among them, transition metal-based catalysts such as Fe, Co, and Ni, which are low-cost and abundant in reserves, are widely used in OER catalysts due to their tunable 3d electronic configuration and spin state. Metal hydroxides are widely used in photoelectrocatalysis and capacitors due to their excellent antioxidant properties in alkaline electrolytes. They are the best candidate catalysts for OER, but single-component hydroxides are difficult to simultaneously meet the excellent high activity, high conductivity, high specific surface area, and strong stability of efficient catalysts, and have certain limitations in practical applications. Multi-component synergistic strategies can enable catalytic materials to exert the strongest electrocatalytic performance. Studies have found that phosphides are considered to be potential catalytic materials for OER, but due to their poor intrinsic activity, they still need to be further improved. The organic combination of the two exposes more active sites, which greatly optimizes the overall electrocatalytic performance of the material and promotes its industrial production and large-scale application. Therefore, Ni3Fe-LDH@NiCoP / NF heterojunction efficient full water splitting electrocatalyst was born. However, at present, Ni3Fe-LDH@NiCoP / NF heterojunction efficient oxygen evolution electrocatalyst is mainly synthesized by hydrothermal method. This method is not only complex and time-consuming, but also produces PH3 toxic and harmful gas during the phosphating process. At the same time, Ni3Fe-LDH@NiCoP / NF prepared by hydrothermal-phosphating-rehydrothermal synthesis route usually presents nanowire shape, which is not conducive to mass transfer and electron transfer in electrocatalytic reaction. Summary of the invention

[0004] The purpose of the present invention is to solve the technical problems that the Ni3Fe-LDH@NiCoP / NF heterojunction electrocatalyst synthesized by the current hydrothermal method is not conducive to electron transmission, the preparation process is complicated, time-consuming, and toxic and harmful gases are generated during the phosphating process, and to provide a Ni3Fe-LDH@NiCoP / NF heterojunction high-efficiency full water splitting electrocatalyst and its preparation method and application.

[0005] One of the purposes of the present invention is to provide a method for preparing a Ni3Fe-LDH@NiCoP / NF heterojunction highly efficient full water splitting electrocatalyst, the preparation method being carried out according to the following steps:

[0006] S1: Using nickel salt, cobalt salt, phosphite, NH4Cl and CH3COONa as electrolytes and pretreated nickel-based materials as working electrodes, NiCoP-x was grown by constant current deposition in a two-electrode system with continuous stirring during the deposition process;

[0007] S2: Using nickel salt and iron salt as electrolyte and S1 product as working electrode, Ni3Fe-LDH was grown by constant voltage deposition in a three-electrode system. Continuous stirring was performed during the deposition process to obtain Ni3Fe-LDH@NiCoP / NF heterojunction efficient full water splitting electrocatalyst.

[0008] It is further defined that the nickel salt in S1 includes NiCl2, NiSO4, and Ni(NO3)2·6H2O.

[0009] It is further defined that the cobalt salt in S1 includes CoCl2, CoSO4, and Co(NO3)2·6H2O.

[0010] It is further defined that the phosphite in S1 includes one or a mixture of several of NaH2PO2, NH4H2PO2, and KH2PO2 in any ratio.

[0011] It is further defined that the concentration of nickel salt in S1 is 0.01-0.1 mol / L, the concentration of cobalt salt is 0.01-0.1 mol / L, the concentration of phosphite is 0.1-0.5 mol / L, the concentration of NH4Cl is 0.1-1.5 mol / L, and the concentration of CH3COONa is 0.001-0.01 mol / L.

[0012] Further, the parameters of the constant current deposition in S1 are: the current is 0.05-0.5A·cm -2 , time is 10 to 60 seconds, temperature is 25℃.

[0013] It is further defined that the electrode material in S1 is graphite, platinum carbon or titanium sheet.

[0014] It is further defined that the nickel-based material in S1 is nickel foam, nickel sheet or nickel mesh.

[0015] It is further defined that the pretreatment process in S1 is as follows: the nickel-based material is ultrasonically cleaned in acetone, HCl aqueous solution, ethanol, and deionized water in sequence, and then vacuum dried.

[0016] It is further defined that the nickel salt in S2 includes nickel sulfate, nickel nitrate, nickel carbonate, and nickel phosphate, and the iron salt includes iron sulfate and iron nitrate.

[0017] It is further defined that the electrolyte in S2 comprises at least one nitrate.

[0018] It is further defined that the nickel salt concentration in the electrolyte solution in S2 is 0.1 to 1.0 mol / L, and the iron salt concentration is 0.05 to 0.5 mol / L.

[0019] It is further defined that the parameters of the constant voltage deposition in S2 are: voltage of -0.9 to -1.5 V, time of 3 to 30 min, and temperature of 20 to 60°C.

[0020] The second object of the present invention is to provide a Ni3Fe-LDH@NiCoP / NF heterojunction high-efficiency oxygen evolution electrocatalyst prepared by the above method, wherein the morphology of the catalyst is nanospheres composed of two-dimensional nanosheets, and the nanospheres are interconnected by nanowires.

[0021] The third object of the present invention is to provide a Ni3Fe-LDH@NiCoP / NF heterojunction high-efficiency complete water splitting electrocatalyst prepared by the above method for use as an alkaline complete water splitting OER electrocatalyst.

[0022] The fourth object of the present invention is to provide a Ni3Fe-LDH@NiCoP / NF heterojunction high-efficiency complete water splitting electrocatalyst prepared by the above method for use as an alkaline complete water splitting HER electrocatalyst.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] The essential feature of the present invention is to provide a method for preparing a Ni3Fe-LDH@NiCoP / NF heterojunction full hydrolysis catalyst with simple preparation process, low price and excellent performance. The specific advantages are as follows:

[0025] 1) The present invention obtains a series of different electrocatalysts by regulating the current density in constant current deposition, so that a unique heterojunction interface is formed between Ni3Fe-LDH and NiCoP / NF. The microscopic morphology is a nanosphere composed of two-dimensional nanosheets, and each nanosphere is interconnected by nanowires. Compared with nanowires, this morphology can provide a good mass transfer and electron transfer channel for the catalytic reaction, resulting in a significant improvement in electrocatalytic performance. In addition, due to the strong conductivity of the foam metal carrier, the electron transfer is accelerated and the electrochemical active area is increased.

[0026] 2) The two-step electrodeposition method of the present invention has a short synthesis cycle, low energy consumption, and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Scanning electron microscope images of blank NF, NiCoP / NF-0.5 and Ni3Fe-LDH-8@NiCoP / NF-0.5 in Example 2; (a) blank NF, (b) NiCoP / NF-0.5; (c) Ni3Fe-LDH-8@NiCoP / NF-0.5;

[0028] Figure 2 is the XRD pattern of NiCoP / NF-0.5 in Example 2;

[0029] Figure 3 LSV curves of the electrocatalysts for complete water splitting OER of Examples 1-2 and Comparative Examples 1-2;

[0030] Figure 4 The Tafel slope diagram of the electrocatalysts for the complete water splitting OER of Examples 1-2 and Comparative Examples 1-2;

[0031] Figure 5 LSV curves of the electrocatalysts for complete water splitting HER of Examples 3-4 and Comparative Examples 2-3;

[0032] Figure 6 The Tafel slope diagram of the electrocatalysts for complete water splitting HER of Examples 3-4 and Comparative Examples 2-3;

[0033] Figure 7 This is the full water-lysis tank pressure diagram of the electrocatalysts of Example 2 and Comparative Examples 1 and 3. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0035] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art.

[0036] The terms "comprising," "including," "having," "containing," or any other variations thereof, as used in the following examples, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus comprising the listed elements is not necessarily limited to only those elements, but may include other elements not expressly listed or inherent to such composition, step, method, article, or apparatus.

[0037] Example 1: The preparation method of the Ni3Fe-LDH-8@NiCoP / NF heterojunction high-efficiency full water splitting electrocatalyst of this example is carried out according to the following steps:

[0038] S1:

[0039] First, an electrolyte aqueous solution containing 0.025 mol / L NiCl2, 0.025 mol / L CoCl2, 0.25 mol / L NaH2PO2, 1 mol / L NH4Cl and 0.003 mol / L CH3COONa was prepared;

[0040] Then, the nickel foam was ultrasonically cleaned in acetone for 15 minutes, then ultrasonically cleaned in a 2 mol / L HCl aqueous solution for 15 minutes, and finally ultrasonically cleaned in ethanol and deionized water for 10 minutes each, and then vacuum dried in a vacuum drying oven at 60° C. until completely dry, to obtain pretreated nickel foam;

[0041] Finally, the pretreated nickel foam was used as the working electrode and the titanium sheet electrode was used as the counter electrode at room temperature of 25 °C and 0.05 A·cm -2 The samples were deposited at a current density of 40 s under constant current for 40 s. Stirring was continued during the deposition process. The samples were taken out and rinsed with anhydrous ethanol and deionized water for 3 times, and then dried completely in a vacuum oven at 60 °C.

[0042] S2:

[0043] First, an electrolyte aqueous solution containing 0.3 mol / L Ni(NO3)2·6H2O and 0.1 mol / L Fe(NO3)3·9H2O was prepared as an electrolyte solution;

[0044] Then, using the S1 product as the working electrode, the platinum electrode as the counter electrode, and the Ag / AgCl electrode as the reference electrode, electrochemical deposition was carried out at a temperature of 25°C and a constant voltage of -1V for 8 minutes. Stirring was continued during the deposition process. After the deposition, it was repeatedly rinsed with ethanol and deionized water for 3 times, and then placed in a vacuum drying oven at 60°C for overnight to obtain the Ni3Fe-LDH-8@NiCoP / NF heterojunction high-efficiency full water splitting electrocatalyst, recorded as Ni3Fe-LDH-8@NiCoP / NF-0.05.

[0045] Example 2: The preparation method of the Ni3Fe-LDH-8@NiCoP / NF heterojunction high-efficiency full water splitting electrocatalyst of this example is carried out according to the following steps:

[0046] S1:

[0047] First, an electrolyte aqueous solution containing 0.025 mol / L NiCl2, 0.025 mol / L CoCl2, 0.25 mol / L NaH2PO2, 1 mol / L NH4Cl and 0.003 mol / L CH3COONa was prepared;

[0048] Then, the nickel foam was ultrasonically cleaned in acetone for 15 minutes, then ultrasonically cleaned in a 2 mol / L HCl aqueous solution for 15 minutes, and finally ultrasonically cleaned in ethanol and deionized water for 10 minutes each, and then vacuum dried in a vacuum drying oven at 60° C. until completely dry, to obtain pretreated nickel foam;

[0049] Finally, the pretreated nickel foam was used as the working electrode and the titanium sheet electrode was used as the counter electrode at room temperature of 25 °C and 0.5 A·cm -2 The samples were deposited at a current density of 40 s under constant current for 40 s. Stirring was continued during the deposition process. The samples were taken out and rinsed with anhydrous ethanol and deionized water for 3 times, and then dried completely in a vacuum oven at 60 °C.

[0050] S2:

[0051] First, an electrolyte aqueous solution containing 0.3 mol / L Ni(NO3)2·6H2O and 0.1 mol / L Fe(NO3)3·9H2O was prepared as an electrolyte solution;

[0052] Then, using the S1 product as the working electrode, the platinum electrode as the counter electrode, and the Ag / AgCl electrode as the reference electrode, electrochemical deposition was carried out at a temperature of 25°C and a constant voltage of -1V for 8 minutes. Stirring was continued during the deposition process. After the deposition, it was repeatedly rinsed with ethanol and deionized water for 3 times, and then placed in a vacuum drying oven at 60°C for overnight to obtain the Ni3Fe-LDH-8@NiCoP / NF heterojunction high-efficiency full water splitting electrocatalyst, recorded as Ni3Fe-LDH-8@NiCoP / NF-0.5.

[0053] The scanning electron microscopy images of blank NF, S1 product NiCoP / NF-0.5 and Ni3Fe-LDH-8@NiCoP / NF-0.5 in this example are shown in Figure 1 As shown in the figure, Figure (a) reveals the 3D porous structure of the blank NF substrate, which provides abundant sites for the growth of the catalyst, and has strong conductivity, which is conducive to electron transport and accelerates the occurrence of oxygen evolution reaction; Figure (b) shows that NiCoP / NF-0.5 is composed of nanosheets and nanospheres, and nanowires connect the nanospheres to each other, which provides a favorable channel for mass transfer and electron transfer; Figure (c) shows the composite morphology characteristics of Ni3Fe-LDH-8@NiCoP / NF-0.5.

[0054] The XRD pattern of NiCoP / NF-0.5 in this embodiment is as follows Figure 2 As shown in the figure, it can be seen that the peaks are at 40.9°, 45.6° and 54.4°, corresponding to the (111), (210) and (300) crystal planes of NiCoP, and the standard card is PDF#71-2336. It is confirmed that NiCoP can be successfully prepared by electrodeposition in a very short time.

[0055] Example 3: The preparation method of the Ni3Fe-LDH-8@NiCoP / NF heterojunction high-efficiency full water electrolysis catalyst of this example is carried out according to the following steps:

[0056] S1:

[0057] First, an electrolyte aqueous solution containing 0.025 mol / L NiCl2, 0.025 mol / L CoCl2, 0.25 mol / L NaH2PO2, 1 mol / L NH4Cl and 0.003 mol / L CH3COONa was prepared;

[0058] Then, the nickel foam was ultrasonically cleaned in acetone for 15 minutes, then ultrasonically cleaned in a 2 mol / L HCl aqueous solution for 15 minutes, and finally ultrasonically cleaned in ethanol and deionized water for 10 minutes each, and then vacuum dried in a vacuum drying oven at 60° C. until completely dry, to obtain pretreated nickel foam;

[0059] Finally, the pretreated nickel foam was used as the working electrode and the titanium sheet electrode was used as the counter electrode at room temperature of 25 °C and 0.2 A·cm -2 The samples were deposited at a current density of 40 s under constant current for 40 s. Stirring was continued during the deposition process. The samples were taken out and rinsed with anhydrous ethanol and deionized water for 3 times, and then dried completely in a vacuum oven at 60 °C.

[0060] S2:

[0061] First, an electrolyte aqueous solution containing 0.3 mol / L Ni(NO3)2·6H2O and 0.1 mol / L Fe(NO3)3·9H2O was prepared as an electrolyte solution;

[0062] Then, using the S1 product as the working electrode, the platinum electrode as the counter electrode, and the Ag / AgCl electrode as the reference electrode, electrochemical deposition was carried out at a temperature of 25°C and a constant voltage of -1V for 8 minutes. Stirring was continued during the deposition process. After the deposition, it was repeatedly rinsed with ethanol and deionized water for 3 times, and then placed in a vacuum drying oven at 60°C for overnight to obtain the Ni3Fe-LDH-8@NiCoP / NF heterojunction efficient full water splitting electrocatalyst, recorded as Ni3Fe-LDH-8@NiCoP / NF-0.2.

[0063] Example 4: The preparation method of the Ni3Fe-LDH-8@NiCoP / NF heterojunction high-efficiency full water splitting electrocatalyst of this example is carried out according to the following steps:

[0064] S1:

[0065] First, an electrolyte aqueous solution containing 0.025 mol / L NiCl2, 0.025 mol / L CoCl2, 0.25 mol / L NaH2PO2, 1 mol / L NH4Cl and 0.003 mol / L CH3COONa was prepared;

[0066] Then, the nickel foam was ultrasonically cleaned in acetone for 15 minutes, then ultrasonically cleaned in a 2 mol / L HCl aqueous solution for 15 minutes, and finally ultrasonically cleaned in ethanol and deionized water for 10 minutes each, and then vacuum dried in a vacuum drying oven at 60° C. until completely dry, to obtain pretreated nickel foam;

[0067] Finally, the pretreated nickel foam was used as the working electrode and the titanium sheet electrode was used as the counter electrode at room temperature of 25 °C and 0.4 A·cm -2 The samples were deposited at a current density of 40 s under constant current for 40 s. Stirring was continued during the deposition process. The samples were taken out and rinsed with anhydrous ethanol and deionized water for 3 times, and then dried completely in a vacuum oven at 60 °C.

[0068] S2:

[0069] First, an electrolyte aqueous solution containing 0.3 mol / L Ni(NO3)2·6H2O and 0.1 mol / L Fe(NO3)3·9H2O was prepared as an electrolyte solution;

[0070] Then, using the S1 product as the working electrode, the platinum electrode as the counter electrode, and the Ag / AgCl electrode as the reference electrode, electrochemical deposition was carried out at a temperature of 25°C and a constant voltage of -1V for 8 minutes. Stirring was continued during the deposition process. After the deposition, it was repeatedly rinsed with ethanol and deionized water for 3 times, and then placed in a vacuum drying oven at 60°C for overnight to obtain the Ni3Fe-LDH-8@NiCoP / NF heterojunction high-efficiency full water splitting electrocatalyst, recorded as Ni3Fe-LDH-8@NiCoP / NF-0.4.

[0071] Comparative Example 1: A method for preparing a RuO2 / NF oxygen evolution electrocatalyst comprises the following steps:

[0072] 6 mg of RuO2 powder and 32 μl of 5 wt.% Nafion solution were dissolved in 0.968 ml of a mixture of water and ethanol, wherein the volume ratio of water to ethanol was 4:1, and then ultrasonicated for at least 30 min to obtain a uniform mixture. Subsequently, 50 μl of the mixture was dropwise applied on a 1 cm*1 cm nickel foam and dried in a vacuum drying oven at 60°C to obtain a RuO2 / NF oxygen evolution electrocatalyst.

[0073] Comparative Example 2: Blank nickel foam as oxygen evolution electrocatalyst

[0074] The nickel foam was first ultrasonically cleaned in acetone for 15 min, then ultrasonically cleaned in a 2 mol / L HCl aqueous solution for 15 min, then ultrasonically cleaned in ethanol and deionized water for 10 min each, and finally placed in a vacuum drying oven at 60°C until completely dried.

[0075] Comparative Example 3: A method for preparing a Pt / C / NF oxygen evolution electrocatalyst comprises the following steps:

[0076] 10 mg of Pt / C powder and 32 microliters of 5 wt.% Nafion solution were dissolved in 0.968 ml of a mixture of water and ethanol, wherein the volume ratio of water to ethanol was 4:1, and then ultrasonicated for at least 30 minutes to obtain a uniform mixture. Subsequently, 50 microliters of the mixture was dropwise applied on a 1 cm*1 cm nickel foam and dried in a vacuum drying oven at 60°C to obtain a Pt / C / NF oxygen evolution electrocatalyst.

[0077] Application examples:

[0078] The electrocatalysts prepared in Examples 1-4 and Comparative Examples 1-3 were used as electrocatalysts for OER and HER to conduct a full water splitting test, and the electrolyte was 1 M KOH solution.

[0079] Detection test:

[0080] (I) The electrocatalytic oxygen production (OER) performance of the above catalyst materials was tested in a standard three-electrode electrolytic cell, wherein the cycle scan range was 0.1-1.1 V and the scan rate was 5 mV / s. The results are shown in Table 1 and Figure 3-4 It should be noted that all potentials obtained using Hg / HgO electrode as reference electrode in electrocatalytic tests are converted into reversible hydrogen electrode potentials in the property diagrams.

[0081] Table 1 Electrocatalytic oxygen production (OER) performance

[0082] Example 1 Example 2 Comparative Example 1 Comparative Example 2 <![CDATA[10mA·cm -2 Current density required overpotential (mV)]]> 175 126 287 355 <![CDATA[100mA·cm -2 Current density required overpotential (mV)]]> 255 182 384 -

[0083] The LSV curves of the electrocatalysts of Examples 1-2 and Comparative Examples 1-2 are as follows: Figure 3 As shown, the current density is 10mA / cm 2 When the overpotential of Ni3Fe-LDH-8@NiCoP / NF-0.05 prepared in Example 1 is 175mV, the overpotential of Ni3Fe-LDH-8@NiCoP / NF-0.5 prepared in Example 2 is only 126mV, the overpotential of RuO2 / NF prepared in Comparative Example 1 is 287mV, and the overpotential of blank NF prepared in Comparative Example 2 is 355mV. It can be seen that the overpotentials of Examples 1-2 of the present invention are greatly improved compared with Comparative Examples 1-2.

[0084] The Tafel slopes of the electrocatalysts of Examples 1-2 and Comparative Examples 1-2 are shown in FIG. Figure 4 As shown, the Tafel slope of Ni3Fe-LDH-8@NiCoP / NF-0.05 prepared in Example 1 is 84.93mV / dec, the Tafel slope of Ni3Fe-LDH-8@NiCoP / NF-0.5 prepared in Example 2 is 36.32mV / dec, the Tafel slope of RuO2 / NF prepared in Comparative Example 1 is 83.28mV / dec, and the Tafel slope of blank NF prepared in Comparative Example 2 is 87.34mV / dec. The magnitude of the Tafel slope value represents the speed of electron transfer kinetics. It can be seen that the electron transfer kinetics of the heterojunction material prepared in the present invention is faster.

[0085] (ii) The electrocatalytic hydrogen production (HER) performance of the above catalyst materials was tested in a standard three-electrode electrolytic cell, wherein the cycle scan range was -0.9 to -2 V and the scan rate was 5 mV / s. The results are shown in Figure 5-6 .

[0086] The LSV curves of the electrocatalysts of Examples 3-4 and Comparative Examples 2-3 are as follows: Figure 5As shown, it can be seen that the current density is 10mA / cm 2 The overpotential required for Ni3Fe-LDH-8@NiCoP / NF-0.2 prepared in Example 3 is 165mV, the overpotential required for Ni3Fe-LDH-8@NiCoP / NF-0.4 prepared in Example 4 is only 162mV, the overpotential of Pt / C / NF prepared in Comparative Example 3 is 151mV, and the overpotential of blank NF prepared in Comparative Example 2 is 168mV. However, it is worth noting that at high current density, the electrocatalytic performance of the material prepared in the present invention is significantly better than that of the commercial Pt / C catalyst. When it reaches 200mA / cm 2 At a current density of , the overpotential required for Ni3Fe-LDH-8@NiCoP / NF-0.2 prepared in Example 3 is 290 mV, the overpotential required for Ni3Fe-LDH-8@NiCoP / NF-0.4 prepared in Example 4 is only 283 mV, the overpotential of Pt / C / NF prepared in Comparative Example 3 is 329 mV, and the overpotential of blank NF prepared in Comparative Example 2 is 374 mV. The improvement in electrocatalytic performance is attributed to the strong coupling between Ni3Fe-LDH-8 and NiCoP.

[0087] The Tafel slopes of the electrocatalysts of Examples 3-4 and Comparative Examples 2-3 are shown in FIG. Figure 6 As shown, it can be seen that the Tafel slope of Ni3Fe-LDH-8@NiCoP / NF-0.2 prepared in Example 3 is 94.63mV / dec, the Tafel slope of Ni3Fe-LDH-8@NiCoP / NF-0.4 prepared in Example 4 is 94.67mV / dec, the Tafel slope of Pt / C / NF prepared in Comparative Example 3 is 128.86mV / dec, and the Tafel slope of blank NF prepared in Comparative Example 2 is 157.07mV / dec. The magnitude of the Tafel slope value represents the speed of electron transfer kinetics. It can be seen that the electron transfer kinetics of the heterojunction material prepared in the present invention is faster.

[0088] (III) The cell pressure of the above catalyst material in the overall water splitting reaction was tested. The results are as follows Figure 7 shown.

[0089] The pressure diagram of the complete water bath of the electrocatalysts of Example 2 and Comparative Examples 1 and 3 is as follows: Figure 7 As shown, from Figure 7 It can be seen that the Ni3Fe-LDH-8@NiCoP / NF-0.5 prepared in Example 2 can be used as an electrocatalyst for OER and HER to split water, and can reach 10 mA / cm at a lower cell voltage of 1.579 V. 2In comparison, the RuO2 / NF and Pt / C / NF electrocatalysts prepared in Comparative Examples 1 and 3 require 1.732V to reach 10mA / cm 2 This indicates that the heterojunction material prepared by the present invention can be used as a highly efficient water splitting electrocatalyst, providing great application prospects.

[0090] The above are only preferred specific embodiments of the present invention, which are all different implementations based on the overall concept of the present invention, and the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A Ni3Fe-LDH@NiCoP / NF heterojunction highly efficient overall water splitting electrocatalyst is used as an alkaline overall water splitting OER electrocatalyst, characterized in that: The preparation method of the Ni3Fe-LDH@NiCoP / NF heterojunction high-efficiency full water splitting electrocatalyst is carried out according to the following steps: S1: Using nickel salt, cobalt salt, phosphite, NH4Cl and CH3COONa as electrolytes and pretreated nickel-based materials as working electrodes, NiCoP-x was grown by constant current deposition in a two-electrode system with continuous stirring during the deposition process; the concentration of nickel salt was 0.01-0.1 mol / L, the concentration of cobalt salt was 0.01-0.1 mol / L, the concentration of phosphite was 0.1-0.5 mol / L, the concentration of NH4Cl was 0.1-1.5 mol / L, the concentration of CH3COONa was 0.001-0.01 mol / L, and the parameters of constant current deposition were: current was 0.05-0.5 A cm -2 , time is 10~60s, temperature is 25℃; S2: Using nickel salt and iron salt as electrolyte and S1 product as working electrode, Ni3Fe-LDH was grown by constant voltage deposition in a three-electrode system. Stirring was continued during the deposition process to obtain Ni3Fe-LDH@NiCoP / NF heterojunction high-efficiency full water electrocatalyst. The nickel salt concentration in the electrolyte solution was 0.1~1.0 mol / L, the iron salt concentration was 0.05~0.5 mol / L, there was at least one nitrate in the electrolyte, and the parameters of constant voltage deposition were: voltage of -0.9~-1.5 V, time of 3~30 min, and temperature of 20~60 °C.

2. The use according to claim 1, characterized in that: The nickel salts in S1 include NiCl2, NiSO4, Ni(NO3)2·6H2O, the cobalt salts include CoCl2, CoSO4, Co(NO3)2·6H2O, and the phosphite includes one or more of NaH2PO2, NH4H2PO2, and KH2PO2.

3. The use according to claim 1, characterized in that: The counter electrode material for constant current deposition in S1 is graphite, platinum carbon or titanium sheet.

4. The use according to claim 1, characterized in that: The nickel-based material in S1 is nickel foam, nickel sheet or nickel mesh. The pretreatment process is as follows: the nickel-based material is placed in acetone, HCl aqueous solution, ethanol, and deionized water for ultrasonic cleaning in sequence, and then vacuum dried.

5. The use according to claim 1, characterized in that: The nickel salts in S2 include nickel sulfate, nickel nitrate, nickel carbonate, and nickel phosphate, and the iron salts include iron sulfate and iron nitrate.

Images