NiCo-LDH / Ni6S7 composite bifunctional catalytic electrode material with self-supporting nano-array structure and preparation method of NiCo-LDH / Ni6S7 composite bifunctional catalytic electrode material

Abstract

The invention discloses a NiCo-LDH / Ni6S7 composite bifunctional catalytic electrode material with a self-supporting nano array structure and a preparation method thereof.The preparation method comprises the steps that urea is added into a first solvent, and heating and stirring are conducted till the urea is completely dissolved to obtain a solution A; sequentially adding nickel salt and cobalt salt into the solution A, and stirring until the nickel salt and the cobalt salt are completely dissolved to obtain a solution B; adding ammonium salt into the solution B, and stirring until the ammonium salt is completely dissolved to obtain a solution C; putting the cleaned and dried foamed nickel into the solution C for hydrothermal reaction, and washing and drying to obtain a NiCo-LDH material with a self-supporting nano array structure; and adding a vulcanizing agent into a second solvent, heating and stirring until the vulcanizing agent is completely dissolved to obtain a solution D, putting the NiCo-LDH material with the self-supporting nano array structure into the solution D for hydrothermal reaction, and washing and drying to obtain the NiCo-LDH / / Ni6S7 composite material with the self-supporting nano array structure. The problems that an existing LDH material is prone to agglomeration and curling and poor in conductivity, and catalytic performance is reduced due to the fact that a polymer adhesive is used are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalysis, and particularly relates to a self-supporting nanoarray-structured NiCo-LDH / Ni6S7 composite bifunctional catalytic electrode material and a preparation method thereof. Background Art

[0002] With the rapid development of society, humans' dependence on traditional fossil fuels (such as coal, oil, and natural gas) has been increasing. However, the overuse of non-renewable energy has exacerbated the global energy crisis. In view of this, it is crucial to develop and utilize renewable and eco-friendly energy to replace fossil fuels. As a clean and green renewable energy, hydrogen energy has an energy density about three times that of oil and natural gas and is an important component of the future low-carbon energy system. An important means of hydrogen production is water electrolysis, which includes hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Compared with traditional hydrogen production technologies, water electrolysis for hydrogen production has the characteristics of high efficiency, no pollution, and high purity of hydrogen, and has received extensive attention in recent years. To reduce the energy consumption during water electrolysis and improve the efficiency of water electrolysis, the design and development of efficient HER / OER electrocatalysts are the key. The noble metal catalysts Pt and IrO2 / RuO2 are respectively the best catalysts for HER and OER, but their reserves are scarce and the prices are high, which also greatly hinders their industrial development to a large extent. Therefore, it is of great significance to prepare non-noble metal bifunctional catalysts with excellent activity and long durability.

[0003] Among non-noble metal catalysts, transition metal compounds including oxides, carbides, nitrides, sulfides, and hydroxides of Fe, Co, Ni, Mn, etc. all have the advantages of wide sources, low prices, and adjustable structures. Among them, LDH (layered double metal hydroxide) has attracted extensive attention from many scientific researchers in the field of electrocatalytic water splitting due to its unique layered structure, exchangeability of interlayer anions, adjustable composition structure of the lamellae, and good thermal stability.

[0004] However, the nano-sheet-structured LDH material is extremely prone to agglomeration and curling, which will cause a decrease in the specific surface area of LDH, resulting in a reduction of its active sites and a decrease in catalytic performance; in addition, the inherently poor conductivity of the LDH material affects its intrinsic activity. Moreover, most powdered LDH catalysts need to be coated on a conductive substrate with polymers such as polyvinylidene fluoride (PVDF) and Nafion for electrochemical performance testing and applications. The use of such binders usually produces adverse factors such as shielding of active sites and poor conductivity, reducing the catalytic performance of the catalyst. Summary of the Invention

[0005] To overcome the above-mentioned drawbacks of the prior art, the object of the present invention is to provide a self-supporting nanoarray-structured NiCo-LDH / Ni6S7 composite bifunctional catalytic electrode material and its preparation method, which solves the problem of reduced catalytic performance of existing LDH materials due to easy agglomeration and curling of the materials, poor conductivity, and the use of polymer binders.

[0006] The present invention is achieved through the following technical solutions:

[0007] A preparation method of a self-supporting nanoarray-structured NiCo-LDH / Ni6S7 composite bifunctional catalytic electrode material, comprising the following steps:

[0008] Step 1, adding urea to a first solvent, heating and stirring until completely dissolved to obtain solution A, and the concentration of solution A is 0.15 mol / L to 0.3 mol / L;

[0009] Step 2, successively adding a nickel salt and a cobalt salt to solution A, and stirring until completely dissolved to obtain solution B;

[0010] Wherein, the molar ratio of urea to the nickel salt is (6:1) to (1:1), and the molar ratio of the nickel salt to the cobalt salt is (6:1) to (1:6);

[0011] Step 3, adding an ammonium salt to solution B, and stirring until completely dissolved to obtain solution C; the molar ratio of the ammonium salt to the nickel salt is (3:1) to (1:3);

[0012] Step 4, putting the cleaned and dried nickel foam into solution C, carrying out a hydrothermal reaction at a temperature of 120 - 200 °C for 4 - 24 h, washing and drying to obtain a NiCo-LDH material with a self-supporting nanoarray structure;

[0013] Step 5, adding a sulfurizing agent to a second solvent, heating and stirring until completely dissolved to obtain solution D, the molar ratio of the sulfurizing agent to the nickel salt is (10:1) to (1:3), and the concentration of solution D is 0.075 mol / L to 0.15 mol / L;

[0014] Step 6, putting the NiCo-LDH material with a self-supporting nanoarray structure into solution D, carrying out a hydrothermal reaction at a temperature of 120 - 200 °C for 2 - 24 h, washing and drying to obtain a NiCo-LDH / / Ni6S7 composite material with a self-supporting nanoarray structure.

[0015] Further, in step 1, the first solvent is one or a mixture of water, methanol, ethanol, ethylene glycol, and glycerol, and the heating and stirring temperature is 20 - 60 °C.

[0016] Further, in the step 2, the nickel salt is one or a mixture of more than one of NiCl2·6H2O, NiSO4·6H2O, Ni(NO3)2·6H2O, Ni(OH)2, and NiCO3·2Ni(OH)2·4H2O, and the cobalt salt is one or a mixture of more than one of CoCl2·6H2O, CoF2, CoCO3, Co(NO3)2·6H2O, and CoSO4·7H2O.

[0017] Further, in the step 3, the ammonium salt is one of NH4Cl, NH4F, (NH4)2CO3, NH4HCO3, (NH4)2SO4, and NH4NO3.

[0018] Further, in the step 4, the hydrothermal reaction is any one of conventional hydrothermal, microwave hydrothermal, and homogeneous hydrothermal, and the drying method is any one of freeze drying, vacuum drying, and air drying.

[0019] Further, in the step 5, the sulfurizing agent is one or a mixture of more than one of Na2S·5H2O, NaHS, Na2S2O8, Na2S2O3, and CH3CSNH2.

[0020] Further, in the step 5, the second solvent is one or a mixture of more than one of water, methanol, ethanol, ethylene glycol, and glycerol, and the temperature of heating and stirring is 20 - 60 °C.

[0021] Further, in the step 6, the hydrothermal reaction is any one of conventional hydrothermal, microwave hydrothermal, and homogeneous hydrothermal, and the drying method is any one of freeze drying, vacuum drying, and air drying.

[0022] A self - supported nano - array - structured NiCo - LDH / Ni6S7 composite bifunctional catalytic electrode material obtained according to the described preparation method.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1. The introduction of the Ni6S7 phase in the present invention greatly changes the electron distribution of NiCo - LDH. Ni7S6 has abundant Ni - Ni and Ni - S bonds, which can promote the generation of OER intermediates (OOH*) and also help convert the adsorbed hydrogen radicals (H*) into H2, improving the adsorption performance of H* and OOH*, thereby improving the reaction performance of HER and OER.

[0025] 2. By introducing the Ni6S7 phase into the material in the present invention, a NiCo - LDH / Ni6S7 / NF heterojunction interface is formed, providing abundant active sites, fast charge and mass transfer for the reaction, and synergistically promoting the HER and OER performances.

[0026] 3. The preparation method of the present invention has the characteristics of low cost, simple operation and high repeatability.

[0027] In summary, the present invention selects nickel foam with a wide source, low price and excellent conductivity as the substrate material. On the nickel foam substrate, NiCo-LDH nanoarrays with abundant active sites are in-situ grown to improve the electrocatalytic activity of the material. Under the condition of maintaining the relatively excellent electrocatalytic activity of NiCo-LDH with a self-supporting nanoarray structure, a sulfidation modification treatment is carried out on it, introducing nickel sulfide (Ni7S6) phase into the NiCo-LDH nanoarray. The introduction of the Ni7S6 phase can not only increase the defects in the material and improve the catalytic activity; at the same time, the self-supporting nanoarray structure NiCo-LDH / Ni7S6 composite bifunctional electrode prepared by the present invention has the characteristics of good economic benefits, wide source of raw materials, green pollution-free and simple operation of the preparation method. Brief Description of the Drawings

[0028] Figure 1 XRD pattern of the NiCo-LDH / Ni6S7 composite material with a self-supporting nanoarray structure prepared in Example 1 of the present invention.

[0029] Figure 2 SEM image of the NiCo-LDH / Ni6S7 composite material with a self-supporting nanoarray structure prepared in Example 2 of the present invention.

[0030] Figure 3 Hydrogen evolution reaction (HER) polarization curve of the NiCo-LDH / Ni6S7 composite material with a self-supporting nanoarray structure prepared in Example 3 of the present invention and the existing NiCo-LDH. Detailed Description of the Invention

[0031] The following further elaborates on the present invention with specific embodiments, which are explanations rather than limitations of the present invention.

[0032] A preparation method of a self-supporting nanoarray structure NiCo-LDH / Ni6S7 composite bifunctional catalytic electrode material includes the following steps:

[0033] Step 1, dissolve urea in a first solvent, heat and stir until completely dissolved, and label it as solution A; the first solvent is one or a mixture of water, methanol, ethanol, ethylene glycol, and glycerol, and the temperature of heating and stirring is 20-60°C;

[0034] Step 2: Add nickel salts and cobalt salts to the above A solution in sequence, stir until completely dissolved, and label it as B solution; the added nickel salt is one or a mixture of more than one of NiCl2·6H2O, NiSO4·6H2O, Ni(NO3)2·6H2O, Ni(OH)2, NiCO3·2Ni(OH)2·4H2O, and the cobalt salt is one or a mixture of more than one of CoCl2·6H2O, CoF2, CoCO3, Co(NO3)2·6H2O, CoSO4·7H2O;

[0035] Among them, the molar ratio of the urea to the nickel salt is 6﹕1 to 1﹕1, and the molar ratio of the nickel salt to the cobalt salt is 6﹕1 to 1﹕6;

[0036] Step 3: Add an appropriate amount of ammonium salt to the above B solution. The hydrolysis of the ammonium salt can provide hydroxide ions for the precipitation reaction of metal ions and hydroxide ions to obtain C solution; the ammonium salt is one of NH4Cl, NH4F, (NH4)2CO3, NH4HCO3, (NH4)2SO4, NH4NO3;

[0037] Among them, the molar ratio of the ammonium salt to the nickel salt is 3﹕1 to 1﹕3;

[0038] Step 4: Transfer the C solution to a reaction kettle with a polytetrafluoroethylene lining, and then place the cleaned and dried nickel foam into the reaction kettle. Carry out hydrothermal reaction at a temperature of 120 - 200 °C for 4 - 24 h, wash and dry to obtain a self-supporting NiCo-LDH material with a nanoarray structure;

[0039] Step 5: Add a sulfurizing agent to the second solvent, heat and stir until completely dissolved to obtain D solution. The molar ratio of the sulfurizing agent to the nickel salt is (10﹕1) to (1﹕3);

[0040] The added sulfurizing agent is one or a mixture of more than one of Na2S·5H2O, NaHS, Na2S2O8, Na2S2O3, CH3CSNH2;

[0041] The second solvent is one or a mixture of water, methanol, ethanol, ethylene glycol, and glycerol, and the heating and stirring temperature is 20 - 60 °C.

[0042] Step 6: Put the self-supporting NiCo-LDH material with a nanoarray structure into the D solution, carry out hydrothermal reaction at a temperature of 120 - 200 °C for 2 - 24 h, wash and dry to obtain a NiCo-LDH / / Ni6S7 composite material with a self-supporting nanoarray structure.

[0043] The hydrothermal reactions in Step 4 and Step 6 are any one of traditional hydrothermal, microwave hydrothermal, and homogeneous hydrothermal, and the filling ratio of the reaction kettle is 40%-80%. The drying method is any one of freeze drying, vacuum drying, and air drying.

[0044] Example 1:

[0045] Step 1: Dissolve 6 mmol of urea in 40 mL of solvent. The solvent is water. After heating to 60 °C, stir until completely dissolved, and mark it as Solution A;

[0046] Step 2: Add 6 mmol of NiCl2·6H2O and 1 mmol of CoCl2·6H2O to the above Solution A in sequence, and stir until completely dissolved, and mark it as Solution B;

[0047] Step 3: Add 2 mmol of gNH4Cl to the above Solution B. The hydrolysis of ammonium salt can provide hydroxide ions for the precipitation reaction of metal ions and hydroxide ions to obtain Solution C;

[0048] Step 4: Transfer Solution C to a 50 ml polytetrafluoroethylene reaction kettle, and then place the cleaned and dried nickel foam into the reaction kettle. React at a hydrothermal temperature of 200 °C for 4 h. After washing and drying, a self-supporting NiCo-LDH material with a nanoarray structure is obtained;

[0049] Step 5: Dissolve 3 mmol of Na2S·5H2O in 40 ml of water. After heating to 60 °C, stir until completely dissolved to obtain Solution D;

[0050] Step 6: Transfer Solution D to a 50 ml polytetrafluoroethylene reaction kettle, put the self-supporting NiCo-LDH material with a nanoarray structure into it, react at a hydrothermal temperature of 200 °C for 2 h. After washing and drying, a self-supporting NiCo-LDH / / Ni6S7 composite material with a nanoarray structure is obtained.

[0051] The filling ratio of the reaction kettle in Step 4 and Step 6 is 80%, and the traditional hydrothermal method is adopted.

[0052] As Figure 1 shown, the abscissa is the 2θ angle, and the ordinate is the intensity. It can be seen from the figure that the diffraction peaks at 2θ angles of 44.6° and 51.9° correspond to the (111) and (220) crystal planes of nickel in the nickel foam. The diffraction peaks at 2θ angles of 14.7°, 28.9°, 33.8°, 35.4°, 36.5°, 47.3°, 56.0°, 59.0°, and 62.2° correspond to NiCo-LDH. The diffraction peaks at 2θ angles of 30.6°, 36.8°, 42.7°, and 53.7° correspond to Ni6S7.

[0053] Example 2:

[0054] Step 1: Dissolve 6 mmol of urea in a mixed solvent of 35 mL of water and ethylene glycol with a volume ratio of 1:1. After heating to 50 °C, stir until completely dissolved, and label it as Solution A;

[0055] Step 2: Add 3 mmol of NiSO4·6H2O and 1 mmol of CoF2 to the above Solution A in sequence, and stir until completely dissolved, and label it as Solution B;

[0056] Step 3: Add 1.5 mmol of NH4F to the above Solution B. The hydrolysis of ammonium salt can provide hydroxide ions for the precipitation reaction of metal ions and hydroxide ions to obtain Solution C;

[0057] Step 4: Transfer Solution C to a 50 ml polytetrafluoroethylene reaction kettle, and then place the cleaned and dried nickel foam into the reaction kettle. React at a solvothermal temperature of 180 °C for 8 h. After washing and drying, a self-supporting NiCo-LDH material with a nanoarray structure is obtained;

[0058] Step 5: Dissolve 3 mmol of NaHS in a mixed solvent of 35 ml of water and ethylene glycol with a volume ratio of 1:1. After heating to 50 °C, stir until completely dissolved to obtain Solution D;

[0059] Step 6: Transfer Solution D to a 50 ml polytetrafluoroethylene reaction kettle, put the self-supporting NiCo-LDH material with a nanoarray structure into it, and react at a solvothermal temperature of 180 °C for 6 h. After washing and drying, a self-supporting NiCo-LDH / / Ni6S7 composite material with a nanoarray structure is obtained.

[0060] The filling ratio of the reaction kettle in Steps 4 and 6 is 70%, and the traditional hydrothermal method is adopted.

[0061] As Figure 2 shown, it can be seen from the figure that the composite material is composed of nanorods and hexagonal nanosheets. Among them, the nanorods correspond to NiCo-LDH, and the hexagonal nanosheets correspond to Ni6S7. In the nanorod-structured NiCo-LDH, Ni is identified as the active site. Compared with the pure nanorod-structured NiCo-LDH, the hexagonal nanosheet structure of Ni6S7 generated after sulfidation not only provides a larger specific surface area, which can provide more active sites for the electrocatalytic hydrogen evolution reaction, but also the S site in this structure has good adsorption ability, which can reduce the energy barrier of water electrolysis, realize the inversion of active sites, and thus exhibit excellent catalytic activity.

[0062] Example 3:

[0063] Step 1: Dissolve 6 mmol of urea in a mixed solvent of 30 mL of water and ethanol with a volume ratio of 1:1. After heating to 40 °C, stir until completely dissolved, and label it as Solution A.

[0064] Step 2: Add 1 mmol of Ni(NO3)2·6H2O and 1 mmol of CoCO3 to the above Solution A in sequence, and stir until completely dissolved, and label it as Solution B.

[0065] Step 3: Add 1 mmol of (NH4)2CO3 to the above Solution B. The hydrolysis of ammonium salt can provide hydroxide ions for the precipitation reaction of metal ions and hydroxide ions to obtain Solution C.

[0066] Step 4: Transfer Solution C to a 50 ml polytetrafluoroethylene reaction kettle, and then place the cleaned and dried nickel foam into the reaction kettle. React at a solvothermal temperature of 160 °C for 14 h. After washing and drying, a self-supporting NiCo-LDH material with a nanoarray structure is obtained.

[0067] Step 5: Dissolve 3 mmol of Na2S2O8 in a mixed solvent of 30 ml of water and ethanol with a volume ratio of 1:1. After heating to 40 °C, stir until completely dissolved to obtain Solution D.

[0068] Step 6: Transfer Solution D to a 50 ml polytetrafluoroethylene reaction kettle, put the self-supporting NiCo-LDH material with a nanoarray structure into it, and react at a solvothermal temperature of 160 °C for 12 h. After washing and drying, a self-supporting NiCo-LDH / / Ni6S7 composite material with a nanoarray structure is obtained.

[0069] In Steps 4 and 6, the filling ratio of the reaction kettle is 60%, and the microwave hydrothermal method is adopted.

[0070] As Figure 3 shown, it can be seen from the figure that the self-supporting NiCo-LDH / / Ni6S7 composite material with a nanoarray structure exhibits excellent catalytic activity for the hydrogen evolution reaction (HER). Only a low overpotential of 179 mV is required to easily reach a current density of 10 mA cm -2 ; while to reach a current density of 10 mA cm -2 , the un-sulfurized NiCo-LDH requires an overpotential of 240 mV.

[0071] Example 4:

[0072] Step 1: Dissolve 6 mmol of urea in 25 mL of ethanol. After heating to 30 °C, stir until completely dissolved, and label it as Solution A.

[0073] Step 2: Add 1 mmol of Ni(OH)2 and 3 mmol of Co(NO3)2·6H2O to the above A solution in sequence, and stir until completely dissolved, marked as B solution;

[0074] Step 3: Add 2 mmol of NH4HCO3 to the above B solution. The hydrolysis of ammonium salt can provide hydroxide ions for the precipitation reaction of metal ions and hydroxide ions, obtaining C solution;

[0075] Step 4: Transfer the C solution to a 50 ml polytetrafluoroethylene reaction kettle, and then place the cleaned and dried nickel foam into the reaction kettle. React at a solvothermal temperature of 140 °C for 18 h. After washing and drying, a self-supporting NiCo-LDH material with a nanoarray structure is obtained;

[0076] Step 5: Dissolve 3 mmol of Na2S2O3 in 25 ml of ethanol. After heating to 30 °C, stir until completely dissolved to obtain D solution;

[0077] Step 6: Transfer the D solution to a 50 ml polytetrafluoroethylene reaction kettle, put the self-supporting NiCo-LDH material with a nanoarray structure into it, react at a solvothermal temperature of 140 °C for 18 h. After washing and drying, a self-supporting NiCo-LDH / / Ni6S7 composite material with a nanoarray structure is obtained.

[0078] In Steps 4 and 6, the filling ratio of the reaction kettle is 50%, and microwave hydrothermal is adopted.

[0079] Example 5:

[0080] Step 1: Dissolve 6 mmol of urea in 20 mL of glycerol. After heating to 20 °C, stir until completely dissolved, marked as A solution;

[0081] Step 2: Add 1 mmol of NiCO3·2Ni(OH)2·4H2O and 6 mmol of CoSO4·7H2O to the above A solution in sequence, and stir until completely dissolved, marked as B solution;

[0082] Step 3: Add 3 mmol of (NH4)2SO4 to the above B solution. The hydrolysis of ammonium salt can provide hydroxide ions for the precipitation reaction of metal ions and hydroxide ions, obtaining C solution;

[0083] Step 4: Transfer the C solution to a 50 ml polytetrafluoroethylene reaction kettle, and then place the cleaned and dried nickel foam into the reaction kettle. React at a solvothermal temperature of 120 °C for 24 h. After washing and drying, a self-supporting NiCo-LDH material with a nanoarray structure is obtained;

[0084] Step 5: Dissolve 3 mmol of CH3CSNH2 in 20 ml of glycerol. After heating to 20 °C, stir until completely dissolved to obtain Solution D.

[0085] Step 6: Transfer Solution D to a 50-ml polytetrafluoroethylene reaction kettle, put the self-supporting NiCo-LDH material with a nanoarray structure into it, and react at a solvothermal temperature of 120 °C for 24 h. After washing and drying, a self-supporting NiCo-LDH / / Ni6S7 composite material with a nanoarray structure is obtained.

[0086] The filling ratio of the reaction kettle in Steps 4 and 6 is 40%, and homogeneous hydrothermal method is adopted.

[0087] Example 6:

[0088] Step 1: Dissolve 6 mmol of urea in 20 mL of methanol. After heating to 35 °C, stir until completely dissolved and label it as Solution A.

[0089] Step 2: Sequentially add 2 mmol of NiCO3·2Ni(OH)2·4H2O and NiCl2·6H2O, and 3 mmol of CoSO4·7H2O to the above Solution A, and stir until completely dissolved, then label it as Solution B.

[0090] Step 3: Add 1 mmol of NH4NO3 to the above Solution B. The hydrolysis of ammonium salt can provide hydroxide ions for the precipitation reaction of metal ions and hydroxide ions to obtain Solution C.

[0091] Step 4: Transfer Solution C to a 50-ml polytetrafluoroethylene reaction kettle, and then place the cleaned and dried nickel foam into the reaction kettle. React at a solvothermal temperature of 150 °C for 19 h. After washing and drying, a self-supporting NiCo-LDH material with a nanoarray structure is obtained.

[0092] Step 5: Dissolve 20 mmol of Na2S·5H2O and NaHS in 133 ml of methanol. After heating to 35 °C, stir until completely dissolved to obtain Solution D.

[0093] Step 6: Transfer Solution D to a 200-ml polytetrafluoroethylene reaction kettle, put the self-supporting NiCo-LDH material with a nanoarray structure into it, and react at a solvothermal temperature of 150 °C for 19 h. After washing and drying, a self-supporting NiCo-LDH / / Ni6S7 composite material with a nanoarray structure is obtained.

[0094] Example 7:

[0095] Step 1: Dissolve 12 mmol of urea in 40 mL of glycerol. After heating to 25 °C, stir until completely dissolved, and label it as Solution A.

[0096] Step 2: Sequentially add 3 mmol of NiCl₂·6H₂O and 4 mmol of CoF₂ and CoCO₃ to the above Solution A, and stir until completely dissolved, then label it as Solution B.

[0097] Step 3: Add 6 mmol of NH₄NO₃ to the above Solution B. The hydrolysis of ammonium salt can provide hydroxide ions for the precipitation reaction of metal ions and hydroxide ions to obtain Solution C.

[0098] Step 4: Transfer Solution C to a 100 ml polytetrafluoroethylene reaction kettle, and then place the cleaned and dried nickel foam into the reaction kettle. React at a solvothermal temperature of 170 °C for 17 h. After washing and drying, a self-supporting NiCo-LDH material with a nanoarray structure is obtained.

[0099] Step 5: Dissolve 1 mmol of NaHS and Na₂S₂O₈ in 20 ml of glycerol. After heating to 25 °C, stir until completely dissolved to obtain Solution D.

[0100] Step 6: Transfer Solution D to a 50 ml polytetrafluoroethylene reaction kettle, put the self-supporting NiCo-LDH material with a nanoarray structure into it, and react at a solvothermal temperature of 170 °C for 17 h. After washing and drying, a self-supporting NiCo-LDH / / Ni₆S₇ composite material with a nanoarray structure is obtained.

[0101] Example 8:

[0102] Step 1: Dissolve 25 mmol of urea in 83 mL of ethylene glycol. After heating to 45 °C, stir until completely dissolved, and label it as Solution A.

[0103] Step 2: Sequentially add 5 mmol of NiSO₄·6H₂O and 4 mmol of CoCl₂·6H₂O to the above Solution A, and stir until completely dissolved, then label it as Solution B.

[0104] Step 3: Add 5 mmol of NH₄NO₃ to the above Solution B. The hydrolysis of ammonium salt can provide hydroxide ions for the precipitation reaction of metal ions and hydroxide ions to obtain Solution C.

[0105] Step 4: Transfer Solution C to a 200 ml polytetrafluoroethylene reaction kettle, and then place the cleaned and dried nickel foam into the reaction kettle. React at a solvothermal temperature of 190 °C for 15 h. After washing and drying, a self-supporting NiCo-LDH material with a nanoarray structure is obtained.

[0106] Step 5: Dissolve 25 mmol of CH2CSNH2 in 166 ml of ethylene glycol. After heating to 45 °C, stir until completely dissolved to obtain Solution D;

[0107] Step 6: Transfer Solution D to a 200-ml polytetrafluoroethylene reaction kettle, put the self-supporting NiCo-LDH material with a nanoarray structure into it, react at a solvothermal temperature of 190 °C for 15 h, and after washing and drying, a self-supporting NiCo-LDH / / Ni6S7 composite material with a nanoarray structure is obtained.

Claims

1. A preparation method of a NiCo-LDH / Ni6S7 composite bifunctional catalytic electrode material with a self-supporting nanoarray structure, characterized in that, It includes the following steps: Step 1: Add urea into the first solvent, heat and stir until it is completely dissolved to obtain solution A, and the concentration of solution A is 0.15 mol / L to 0.3 mol / L; Step 2: Sequentially add nickel salt and cobalt salt into solution A, and stir until it is completely dissolved to obtain solution B; Among them, the molar ratio of urea to nickel salt is (6:1) to (1:1), and the molar ratio of nickel salt to cobalt salt is (6:1) to (1:6); Step 3: Add ammonium salt into solution B, and stir until it is completely dissolved to obtain solution C; the molar ratio of ammonium salt to nickel salt is (3:1) to (1:3); Step 4: Put the cleaned and dried nickel foam into solution C, carry out hydrothermal reaction at a temperature of 120 - 200 °C for 4 - 24 h, wash and dry it to obtain a NiCo-LDH material with a self-supporting nanoarray structure; Step 5: Add a sulfurizing agent into the second solvent, heat and stir until it is completely dissolved to obtain solution D, the molar ratio of the sulfurizing agent to nickel salt is (10:1) to (1:3), and the concentration of solution D is 0.075 mol / L to 0.15 mol / L; Step 6: Put the NiCo-LDH material with a self-supporting nanoarray structure into solution D, carry out hydrothermal reaction at a temperature of 120 - 200 °C for 2 - 24 h, wash and dry it, and then a NiCo-LDH / / Ni6S7 composite material with a self-supporting nanoarray structure is obtained.

2. The preparation method of a self-supporting nanoarray-structured NiCo-LDH / Ni6S7 composite bifunctional catalytic electrode material according to claim 1, characterized in that, In step 1, the first solvent is one or a mixture of water, methanol, ethanol, ethylene glycol, and glycerol, and the temperature of heating and stirring is 20 - 60 °C.

3. The preparation method of a self-supporting nanoarray-structured NiCo-LDH / Ni6S7 composite bifunctional catalytic electrode material according to claim 1, characterized in that, In step 2, the nickel salt is one or a mixture of NiCl2·6H2O, NiSO4·6H2O, Ni(NO3)2·6H2O, Ni(OH)2, and NiCO3·2Ni(OH)2·4H2O, and the cobalt salt is one or a mixture of CoCl2·6H2O, CoF2, CoCO3, Co(NO3)2·6H2O, and CoSO4·7H2O.

4. The preparation method of a self-supporting nanoarray-structured NiCo-LDH / Ni6S7 composite bifunctional catalytic electrode material according to claim 1, characterized in that, In step 3, the ammonium salt is one of NH4Cl, NH4F, (NH4)2CO3, NH4HCO3, (NH4)2SO4, and NH4NO3.

5. The preparation method of a self-supporting nanoarray-structured NiCo-LDH / Ni6S7 composite bifunctional catalytic electrode material according to claim 1, characterized in that, In step 4, the hydrothermal reaction is any one of traditional hydrothermal, microwave hydrothermal, and homogeneous hydrothermal, and the drying method is any one of freeze drying, vacuum drying, and air drying.

6. The preparation method of a self-supporting nanoarray structure NiCo-LDH / Ni6S7 composite bifunctional catalytic electrode material according to claim 1, characterized in that, In step 5, the sulfurizing agent is one or a mixture of Na2S·5H2O, NaHS, Na2S2O8, Na2S2O3, and CH3CSNH2.

7. The preparation method of a self-supporting nanoarray-structured NiCo-LDH / Ni6S7 composite bifunctional catalytic electrode material according to claim 1, characterized in that, In step 5, the second solvent is one or a mixture of water, methanol, ethanol, ethylene glycol, and glycerol, and the temperature of heating and stirring is 20 - 60 °C.

8. The preparation method of a self-supporting nanoarray-structured NiCo-LDH / Ni6S7 composite bifunctional catalytic electrode material according to claim 1, characterized in that, In step 6, the hydrothermal reaction is any one of traditional hydrothermal, microwave hydrothermal, and homogeneous hydrothermal, and the drying method is any one of freeze drying, vacuum drying, and air drying.

9. A self-supporting nanoarray-structured NiCo-LDH / Ni6S7 composite bifunctional catalytic electrode material obtained by the preparation method according to any one of the above claims 1-8.

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