A kind of iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material and preparation method thereof

Abstract

The present invention proposes an iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material and a preparation method thereof, which belongs to the technical field of electrocatalysis and is used to solve the technical problems of complex preparation process and low catalytic activity of the current Fe-Co-NiLDH-based electrocatalyst. The preparation method comprises the following steps: soaking the nickel foam in a cobalt salt aqueous solution, then adding a 2-methylimidazole aqueous solution, continuing to soak, and finally soaking the MOF precursor in a mixed aqueous solution containing Fe salt, Ni salt and urea; the present invention obtains a three-dimensional self-supporting hierarchical iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material through a simple one-step double cation exchange strategy, which can provide more exposed active sites and enhanced electron transfer capacity, and accelerate the mass transfer process; in addition, the three-metal active sites further improve their catalytic activity through strong coupling synergy.

Description

Technical Field

[0001] The invention belongs to the technical field of electrocatalysis, and in particular relates to an iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material and a preparation method thereof. Background Art

[0002] The oxygen evolution reaction (OER) is important in various energy storage and conversion systems, such as water splitting devices and metal-air batteries. However, the sluggish kinetics caused by its inherent four-step proton-coupled electron transfer process is considered to be a bottleneck for the development of these technologies. Although Ir- and Ru-based catalysts are the most efficient OER electrocatalysts, their high cost and scarcity have greatly limited their large-scale application. Therefore, exploring low-cost, efficient, operationally feasible, highly active and stable non-precious metal OER catalysts is particularly important for the development of energy conversion technologies.

[0003] Given the earth's abundance and high catalytic activity, first-row transition metal oxides, hydroxides, sulfides, nitrides, and phosphides show great potential for OER. Hollow nanostructures have structure-dependent characteristics, such as large surface area, multiple interfaces, and short charge transfer distances, showing obvious advantages as OER catalysts. Compared with hollow structures with smooth surfaces, nanocages composed of ultrathin nanosheets have larger surface areas and shorter mass transfer diffusion distances, showing obvious advantages in catalysis. For example, patent publication number CN109652822A discloses the use of LDH as a template to prepare a layered metal organic framework material nanoarray water oxidation electrocatalyst, using nickel nitrate hexahydrate as a nickel source, iron nitrate nonahydrate as an iron source, ammonium fluoride as a fluorine source and urea to jointly regulate the pH value of the precursor solution, nickel foam as a conductive substrate, and a hydrothermal method to prepare a NiFe-LDH / NF precursor template, and then using nickel nitrate hexahydrate and iron nitrate nonahydrate as auxiliary complexing agents, terephthalic acid as an organic ligand, nitrogen, nitrogen dimethylformamide as an organic solvent, anhydrous ethanol and deionized water as weak ligand solvents and strong ligand solvents to regulate the coordination form of the metal center and the organic ligand, and a solvent thermal method to convert the NiFe-LDH / NF precursor template into a highly regularly arranged three-dimensional layered structure Fe0.1-Ni-MOF nanoarray, which has high activity as a water oxidation electrocatalyst. However, due to the cumbersome and complex synthesis process, it is not conducive to the practical application of complex hollow catalysts. Recently, the cation exchange synthesis method is a self-template method that can adjust the dimension and morphology of the material. It provides an easily controllable method for preparing well-defined hollow structures. For example, application publication number CN113897635A discloses a MOFs-derived nickel-cobalt double hydroxide array electrocatalytic oxygen evolution material and its preparation method, wherein the nickel foam is soaked in 2-methylimidazole, and then Co salt is added, and the three-dimensional array precursor formed by in-situ growth of Co-MOFs nanosheets is obtained by continuing to soak; the three-dimensional array precursor is soaked in Ni salt and allowed to react, which has the characteristics of a simple preparation method.

[0004] In addition to bimetallic LDH-based nanocage electrocatalysts, trimetallic LDH-based nanocage electrocatalysts are also a research hotspot. For example, Fe-Ni-Co layered double hydroxide (LDH) has a significantly enhanced catalytic activity due to the synergistic effect between the three substances Ni, Co and Fe, and is considered to be the most promising OER catalyst in alkaline solution. However, the preparation of trimetallic LDH-based nanocage electrocatalysts mostly adopts the hydrothermal method, which has inherent limitations such as high cost and long time consumption. In addition, the active sites mainly located on the catalyst surface during the OER catalytic process have a positive effect on the catalytic performance of the material. Therefore, it is of great significance to finely design the nanostructure of Fe-Co-Ni LDH-based electrocatalysts by increasing the number of exposed active sites to improve their OER performance. Summary of the invention

[0005] In view of the technical problems of complex preparation process and low catalytic activity of current Fe-Co-NiLDH-based electrocatalysts, the present invention proposes an iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material and a preparation method thereof, which can provide more exposed active sites and enhanced electron transport capacity, and accelerate the mass transfer process; in addition, the tri-metal active sites further improve their catalytic activity through strong coupling synergy.

[0006] In order to achieve the above object, the technical solution of the present invention is achieved as follows:

[0007] A method for preparing an iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material comprises the following steps:

[0008] Preparation of three-dimensional nanosheet array precursors formed by in-situ growth of Co-MOFs nanosheets

[0009] The clean nickel foam is soaked in a certain amount of cobalt salt solution for 10-30 minutes. After the cobalt salt is uniformly adsorbed on the surface of the nickel foam, a certain amount of 2-methylimidazole aqueous solution is added to the above solution, and the solution is soaked for 4-6 hours. The solution is washed and dried to obtain a three-dimensional array precursor formed by in-situ growth of purple Co-MOFs nanosheets. Preferably, the molar ratio of 2-methylimidazole to Co salt is 8:0.5-2. Preferably, Co salt is Co(NO3)2·6H2O. Preferably, the concentration of 2-methylimidazole aqueous solution is 0.08-0.8 mol·L -1 Preferably, the concentration of the Co salt solution is 0.01-0.1 mol·L -1 ;

[0010] Preparation of Fe-Ni-Co double hydroxide nanocages for electrocatalytic oxygen evolution

[0011] The three-dimensional array precursor is immersed in a mixed aqueous solution of Fe and Ni salts in an oil bath at 70-90° C., urea is added, and the mixture is allowed to react for 20-60 minutes to obtain an Fe-Ni-Co double hydroxide nanocage array electrocatalytic material;

[0012] The molar ratio of Fe in the Fe salt, Ni in the Ni salt, and Co in the Co salt is (1-8):(4-8):12. Preferably, the Fe salt is FeSO4; preferably, the concentration of the Fe salt in the mixed aqueous solution is 0.008-0.08 mol·L -1 Preferably, the Ni salt is Ni(NO3)2·6H2O; Preferably, the concentration of the Ni salt in the mixed aqueous solution is 0.02-0.08 mol·L -1 The content of urea in the mixed aqueous solution is 1-10 mg·mL -1; Preferably, the content of urea in the mixed aqueous solution is 5 mg·mL -1

[0013] The iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material prepared by the above method.

[0014] Beneficial effects of the present invention:

[0015] (1) The present invention uses a simple one-step double cation exchange strategy to use Co-MOFs array as a precursor to obtain a three-dimensional self-supporting hierarchical iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material, which can provide more exposed active sites and enhanced electron transport capacity, and accelerate the mass transfer process; in addition, the three-metal active sites further improve their catalytic activity through strong coupling synergy. Due to the synergistic effect of this series of factors, the prepared iron-cobalt-nickel double hydroxide nanocage exhibits significant oxygen evolution activity in alkaline electrolytes, achieving 100mAcm at a low overpotential of 272mV. -2 The current density is high and has good stability.

[0016] (2) The double cation etching process adopted in the present invention only takes 20 minutes and the reaction temperature is only 70-90°C, realizing the transformation of MOF materials into multi-metal double hydroxide nanocage materials. It not only provides a new strategy for ultra-fast and simple preparation of low-cost, efficient and stable OER electrocatalysts, but also provides a new method for preparing multi-metal hydroxide nanocages with good electronic structure and morphology. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 This is a scanning electron microscope (SEM) image of the iron-cobalt-nickel double hydroxide material prepared in Example 2;

[0019] Figure 2 The X-ray diffraction (XRD) pattern of the iron-cobalt-nickel double hydroxide material prepared in Example 2;

[0020] Figure 3 The X-ray photoelectron spectroscopy (XPS) spectrum of Fe2p, Ni2p and Co2p orbitals in the iron-cobalt-nickel double hydroxide material prepared in Example 2;

[0021] Figure 4 is the electrocatalytic performance data diagram;

[0022] Figure 5 The impedance spectrum. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Example 1

[0025] A method for preparing an iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material comprises the following steps:

[0026] Preparation of three-dimensional array precursors formed by in-situ growth of Co-MOFs nanosheets

[0027] Place clean nickel foam in 20 mL of 0.05 mol·L -1 The nickel foam was immersed in a Co(NO3)2 aqueous solution for 20 min. After the cobalt salt was evenly adsorbed on the surface of the nickel foam, 20 mL of 0.4 mol·L -1 The 2-methylimidazole aqueous solution was soaked for 6 hours, and then the nickel foam was washed and dried to obtain a three-dimensional array precursor formed by in-situ growth of purple Co-MOFs nanosheets;

[0028] Preparation of Fe-Co-Ni Double Hydroxide Nanocages for Electrocatalytic Oxygen Evolution

[0029] The three-dimensional array precursor formed by in-situ growth of Co-MOFs nanosheets was immersed in 20 mL of 0.0082 mol·L -1 FeSO4 and 0.026mol·L -1 100 mg of urea was added to a mixed aqueous solution of Ni(NO3)2 and allowed to react for 60 minutes to obtain an iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material.

[0030] Example 2

[0031] A method for preparing an iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material comprises the following steps:

[0032] Preparation of three-dimensional array precursors formed by in-situ growth of Co-MOFs nanosheets

[0033] Place clean nickel foam in 20 mL of 0.05 mol·L -1The nickel foam was immersed in a Co(NO3)2 aqueous solution for 20 min. After the cobalt salt was evenly adsorbed on the surface of the nickel foam, 20 mL of 0.4 mol·L -1 The 2-methylimidazole aqueous solution was soaked for 4 hours, and then the nickel foam was washed and dried to obtain a three-dimensional array precursor formed by in-situ growth of purple Co-MOFs nanosheets;

[0034] Preparation of Fe-Co-Ni Double Hydroxide Nanocages for Electrocatalytic Oxygen Evolution

[0035] The three-dimensional array precursor formed by in-situ growth of Co-MOFs nanosheets was immersed in 20 mL of 0.0164 mol·L -1 FeSO4 and 0.026mol·L -1 2 mixed aqueous solution, and 100 mg of urea was added, and the reaction was allowed to stand for 20 minutes to obtain iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material (Fe-Co-Ni-LDH).

[0036] The morphology of the samples prepared in this example was verified by SEM. Figure 1 As shown. Since the Co-MOF sheet array serves as a sacrificial template for the in situ growth of Fe-Co-Ni-LDH, the sample also inherits a similar sheet array after transformation in the presence of FeSO4 and Ni(NO3)2 ( Figure 1 ). In addition, it can be observed that the Co-MOF precursor skeleton is well preserved, and the interlocking nanosheets stand vertically and evenly throughout the hollow skeleton, forming abundant straight paths and passages ( Figure 1 ), which is obviously different from the Fe-Co-LDH single nanosheet structure. The XRD spectrum of Fe-Co-Ni-LDH nanocage ( Figure 2 ) can be determined as a typical amorphous LDH phase, indicating that the Co-MOF precursor is completely consumed during the reaction. The surface elemental composition and chemical properties of Fe-Co-Ni-LDH nanocages were studied by X-ray photoelectron spectroscopy (XPS), such as Figure 3 The measured spectrum shows that the Fe-Co-Ni-LDH sample is mainly composed of Fe, Co, Ni and O elements. The binding energy of Co 2p at 780.8 and 796.9 eV and the satellite peaks at 785.9 and 802.6 eV in the Fe-Co-Ni-LDH nanocage can be attributed to Co 2+ Species. The XPS spectrum of Ni 2p spectrum shows that 2p 3 / 2 (855.8eV) and 2p 1 / 2 The peaks in the (873.5 eV) region and the peaks at 861.5 eV and 879.6 eV are similar to those of Ni 2+The presence of Fe species is related to the presence of Fe 2p. The high-resolution XPS spectrum of Fe 2p shows that most of the Fe species in the sample are in the +3 oxidation state. The above results prove the introduction of Fe element.

[0037] Example 3

[0038] A method for preparing an iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material comprises the following steps:

[0039] Preparation of three-dimensional array precursors formed by in-situ growth of Co-MOFs nanosheets

[0040] Place clean nickel foam in 20 mL of 0.05 mol·L -1 The nickel foam was immersed in a Co(NO3)2 aqueous solution for 20 min. After the cobalt salt was evenly adsorbed on the surface of the nickel foam, 20 mL of 0.4 mol·L -1 The 2-methylimidazole aqueous solution was soaked for 5 hours, and then the nickel foam was washed and dried to obtain a three-dimensional array precursor formed by in-situ growth of purple Co-MOFs nanosheets;

[0041] Preparation of Fe-Co-Ni Double Hydroxide Nanocages for Electrocatalytic Oxygen Evolution

[0042] The three-dimensional array precursor formed by in-situ growth of Co-MOFs nanosheets was immersed in 20 mL of 0.0246 mol·L -1 FeSO4 and 0.026mol·L -1 100 mg of urea was added to a mixed aqueous solution of Ni(NO3)2 and allowed to react for 20 minutes to obtain an iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material.

[0043] Example 4

[0044] A method for preparing an iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material comprises the following steps:

[0045] Preparation of three-dimensional array precursors formed by in-situ growth of Co-MOFs nanosheets

[0046] Place clean nickel foam in 20 mL of 0.05 mol·L -1 The nickel foam was immersed in a Co(NO3)2 aqueous solution for 20 min. After the cobalt salt was evenly adsorbed on the surface of the nickel foam, 20 mL of 0.4 mol·L -1 The 2-methylimidazole aqueous solution was soaked for 5 hours, and then the nickel foam was washed and dried to obtain a three-dimensional array precursor formed by in-situ growth of purple Co-MOFs nanosheets;

[0047] Preparation of Fe-Co-Ni Double Hydroxide Nanocages for Electrocatalytic Oxygen Evolution

[0048] The three-dimensional array precursor formed by in-situ growth of Co-MOFs nanosheets was immersed in 20 mL of 0.0328 mol·L -1 FeSO4 and 0.026mol·L -1 100 mg of urea was added to a mixed aqueous solution of Ni(NO3)2 and allowed to react for 50 minutes to obtain an iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material.

[0049] Example 5

[0050] A method for preparing an iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material comprises the following steps:

[0051] Preparation of three-dimensional array precursors formed by in-situ growth of Co-MOFs nanosheets

[0052] Place clean nickel foam in 20 mL of 0.05 mol·L -1 The nickel foam was immersed in a Co(NO3)2 aqueous solution for 20 min. After the cobalt salt was evenly adsorbed on the surface of the nickel foam, 20 mL of 0.4 mol·L -1 The 2-methylimidazole aqueous solution was soaked for 4 hours, and then the nickel foam was washed and dried to obtain a three-dimensional array precursor formed by in-situ growth of purple Co-MOFs nanosheets;

[0053] Preparation of Fe-Co-Ni Double Hydroxide Nanocages for Electrocatalytic Oxygen Evolution

[0054] The three-dimensional array precursor formed by in-situ growth of Co-MOFs nanosheets was immersed in 20 mL of 0.0492 mol·L -1 FeSO4 and 0.026mol·L -1 100 mg of urea was added to a mixed aqueous solution of Ni(NO3)2 and allowed to react for 60 minutes to obtain an iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material.

[0055] Example 6

[0056] A method for preparing an iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material comprises the following steps:

[0057] Preparation of three-dimensional array precursors formed by in-situ growth of Co-MOFs nanosheets

[0058] Place clean nickel foam in 20 mL of 0.05 mol·L -1Soak in Co(NO3)2 aqueous solution for 20 min, wait for the cobalt salt to be evenly adsorbed on the surface of nickel foam, and then add 20 mL of 0.4 mol·L -1 The 2-methylimidazole aqueous solution was soaked for 6 hours, and then the nickel foam was washed and dried to obtain a three-dimensional array precursor formed by in-situ growth of purple Co-MOFs nanosheets;

[0059] Preparation of Fe-Co-Ni Double Hydroxide Nanocages for Electrocatalytic Oxygen Evolution

[0060] The three-dimensional array precursor formed by in-situ growth of Co-MOFs nanosheets was immersed in 20 mL of 0.0164 mol·L -1 FeSO4 and 0.026mol·L -1 100 mg of urea was added to a mixed aqueous solution of Ni(NO3)2 and allowed to react for 30 minutes to obtain an iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material.

[0061] Example 7

[0062] A method for preparing an iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material comprises the following steps:

[0063] Preparation of three-dimensional array precursors formed by in-situ growth of Co-MOFs nanosheets

[0064] Place clean nickel foam in 20 mL of 0.05 mol·L -1 The nickel foam was immersed in a Co(NO3)2 aqueous solution for 20 min. After the cobalt salt was evenly adsorbed on the surface of the nickel foam, 20 mL of 0.4 mol·L -1 The 2-methylimidazole aqueous solution was soaked for 6 hours, and then the nickel foam was washed and dried to obtain a three-dimensional array precursor formed by in-situ growth of purple Co-MOFs nanosheets;

[0065] Preparation of Fe-Co-Ni Double Hydroxide Nanocages for Electrocatalytic Oxygen Evolution

[0066] The three-dimensional array precursor formed by in-situ growth of Co-MOFs nanosheets was immersed in 20 mL of 0.0164 mol·L -1 FeSO4 and 0.026mol·L -1 100 mg of urea was added to a mixed aqueous solution of Ni(NO3)2 and allowed to react for 20 minutes to obtain an iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material.

[0067] Example 8

[0068] A method for preparing an iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material comprises the following steps:

[0069] Preparation of three-dimensional array precursors formed by in-situ growth of Co-MOFs nanosheets

[0070] Place clean nickel foam in 20 mL of 0.1 mol·L -1 The nickel foam was immersed in a Co(NO3)2 aqueous solution for 30 min. After the cobalt salt was evenly adsorbed on the surface of the nickel foam, 20 mL of 0.8 mol·L -1 The 2-methylimidazole aqueous solution was soaked for 6 hours, and then the nickel foam was washed and dried to obtain a three-dimensional array precursor formed by in-situ growth of purple Co-MOFs nanosheets;

[0071] Preparation of Fe-Co-Ni Double Hydroxide Nanocages for Electrocatalytic Oxygen Evolution

[0072] The three-dimensional array precursor formed by in-situ growth of Co-MOFs nanosheets was immersed in 20 mL of 0.0738 mol·L -1 FeSO4 and 0.078 mol·L -1 100 mg of urea was added to a mixed aqueous solution of Ni(NO3)2 and allowed to react for 20 minutes to obtain an iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material.

[0073] Example 9

[0074] A method for preparing an iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material comprises the following steps:

[0075] Preparation of three-dimensional array precursors formed by in-situ growth of Co-MOFs nanosheets

[0076] Place clean nickel foam in 20 mL of 0.01 mol·L -1 The nickel foam was immersed in a Co(NO3)2 aqueous solution for 10 min. After the cobalt salt was evenly adsorbed on the surface of the nickel foam, 20 mL of 0.16 mol·L -1 The 2-methylimidazole aqueous solution was soaked for 4 hours, and then the nickel foam was washed and dried to obtain a three-dimensional array precursor formed by in-situ growth of purple Co-MOFs nanosheets;

[0077] Preparation of Fe-Co-Ni Double Hydroxide Nanocages for Electrocatalytic Oxygen Evolution

[0078] The three-dimensional array precursor formed by in-situ growth of Co-MOFs nanosheets was immersed in 20 mL of 0.0082 mol·L -1 FeSO4 and 0.033 mol·L-1 100 mg of urea was added to a mixed aqueous solution of Ni(NO3)2 and allowed to react for 20 minutes to obtain an iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material.

[0079] Comparative Example 1

[0080] A method for preparing a nickel-cobalt double hydroxide nanocage electrocatalytic oxygen evolution material comprises the following steps:

[0081] Preparation of three-dimensional array precursors formed by in-situ growth of Co-MOFs nanosheets

[0082] Place clean nickel foam in 20 mL of 0.05 mol·L -1 The nickel foam was immersed in a Co(NO3)2 aqueous solution for 20 min. After the cobalt salt was evenly adsorbed on the surface of the nickel foam, 20 mL of 0.4 mol·L -1 The 2-methylimidazole aqueous solution was soaked for 4 hours, and then the nickel foam was washed and dried to obtain a three-dimensional array precursor formed by in-situ growth of purple Co-MOFs nanosheets;

[0083] Preparation of NiCo Double Hydroxide Nanocages for Electrocatalytic Oxygen Evolution

[0084] The three-dimensional array precursor formed by in-situ growth of Co-MOFs nanosheets was immersed in 20 mL of 0.026 mol·L -1 The Ni(NO3)2 aqueous solution was added with 100 mg of urea and allowed to react for 20 min to obtain a nickel cobalt double hydroxide nanocage electrocatalytic oxygen evolution material (Ni-Co LDH).

[0085] Comparative Example 2

[0086] A method for preparing an iron-cobalt double hydroxide nanocage electrocatalytic oxygen evolution material comprises the following steps:

[0087] Preparation of three-dimensional array precursors formed by in-situ growth of Co-MOFs nanosheets

[0088] Place clean nickel foam in 20 mL of 0.05 mol·L -1 The nickel foam was immersed in a Co(NO3)2 aqueous solution for 20 min. After the cobalt salt was evenly adsorbed on the surface of the nickel foam, 20 mL of 0.4 mol·L -1 The 2-methylimidazole aqueous solution was soaked for 4 hours, and then the nickel foam was washed and dried to obtain a three-dimensional array precursor formed by in-situ growth of purple Co-MOFs nanosheets;

[0089] Preparation of Fe-Co-Ni Double Hydroxide Nanocages for Electrocatalytic Oxygen Evolution

[0090] The three-dimensional array precursor formed by in-situ growth of Co-MOFs nanosheets was immersed in 20 mL of 0.0164 mol·L -1 The FeSO4 aqueous solution was added with 100 mg of urea and allowed to react for 20 min to obtain an iron-cobalt double hydroxide nanocage electrocatalytic oxygen evolution material (Fe-Co LDH).

[0091] Test Case

[0092] In order to illustrate the effect of optimization on catalytic performance, the present invention was conducted in an alkaline solution (1.0 M KOH) at 2 mV s -1 The OER activity of Fe-Co-Ni-LDH nanocages was studied using a three-electrode system at a scan rate of . The electrocatalytic performance of Fe-Co-Ni-LDH, Ni-Co LDH, Fe-Co LDH, Ir / C and NF was studied. Figure 4 Figure 3 is the IR compensated cyclic voltammetry (CV) curve. It can be seen that when the contents of Ni-Co LDH, Fe-Co LDH, Ir / C and NF are the same, the current density of Fe-Co-Ni-LDH nanocage catalyst is significantly higher than that of Ni-Co LDH catalyst. When it reaches 50 mA cm -2 The current density of Fe-Co-Ni-LDH nanocage catalyst is only 246mV, which is 122mV lower than that of Ni-Co LDH. In addition, the OER kinetics of Fe-Co-Ni-LDH is much faster than that of Ni-Co LDH. The current density of Fe-Co-Ni-LDH can reach 100mA cm at η272mV. -2 , which is 133 mV lower than that of Ni-Co LDH (Figure 4). In order to understand the reason for the enhanced activity, electrochemical impedance spectroscopy was used to characterize the Figure 5 As shown, Fe-Co-Ni-LDH has a smaller semicircle compared with Fe-Co LDH and Ni-Co LDH, indicating its lower resistance and faster charge transfer kinetics. The above results show that Fe-Co-Ni-LDH has a good electrochemical active surface area and high charge transfer capacity. Thanks to these characteristics, Fe-Co-Ni-LDH has excellent oxygen evolution reaction ability.

[0093] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing an iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material, characterized in that: The following steps are involved: (1) Preparation of three-dimensional nanosheet array precursors formed by in-situ growth of Co-MOFs nanosheets The nickel foam is immersed in a cobalt salt aqueous solution, and then a 2-methylimidazole aqueous solution is added and the immersion is continued to obtain a three-dimensional array precursor formed by in-situ growth of Co-MOFs nanosheets; (2) Preparation of Fe-Co-Ni double hydroxide nanocages for electrocatalytic oxygen evolution The three-dimensional array precursor obtained in step (1) is immersed in a mixed aqueous solution containing iron salt and nickel salt, and urea is added, and allowed to react to obtain an iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material; The concentration of the iron salt in the mixed aqueous solution in step (2) is 0.008-0.08 mol·L -1 , the concentration of nickel salt is 0.02-0.08 mol·L -1 ; The iron salt is FeSO4; the nickel salt is Ni(NO3)2·6H2O.

2. The method for preparing the iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material according to claim 1, characterized in that: The molar ratio of the iron element in the iron salt, the nickel element in the nickel salt and the cobalt element in the cobalt salt is (1-8):(4-8):

12.

3. The method for preparing the iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material according to claim 1 or 2, characterized in that: The cobalt salt in step (1) is Co(NO3)2·6H2O; the concentration of the cobalt salt aqueous solution is 0.01-0.1 mol·L -1 ; The concentration of 2-methylimidazole aqueous solution is 0.08-0.8 mol·L -1 .

4. The method for preparing the iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material according to claim 3, characterized in that: In the step (1), the molar ratio of 2-methylimidazole to cobalt salt is 8:(0.5-2).

5. The method for preparing the iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material according to claim 4, characterized in that: In the step (1), after the cobalt salt is uniformly adsorbed on the surface of the nickel foam, the 2-methylimidazole aqueous solution is added; the soaking time is continued for 4-6 hours.

6. The method for preparing the iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material according to claim 5, characterized in that: The standing reaction time in step (2) is 20-60 minutes and the temperature is 70-90°C.

7. An iron-cobalt-nickel double hydroxide nanocage electrocatalytic oxygen evolution material prepared by the method according to any one of claims 1 to 6.

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