Porous spinel type nickel cobaltate as well as preparation method and application thereof

Abstract

The invention discloses porous spinel nickel cobaltate as well as a preparation method and application thereof, and belongs to the technical field of hydrogen storage materials. The porous spinel type nickel cobaltate is of a three-dimensional communicated porous structure, and the preparation method of the porous spinel type nickel cobaltate comprises the following steps that firstly, nickel, cobalt and aluminum metal elementary substances are smelted into a nickel-cobalt-aluminum ternary alloy through a smelting method, and the alloy is mechanically smashed; then, the alloy powder is poured into a sodium hydroxide solution to be subjected to dealloying treatment, a treated solid product is washed and dried, and porous nickel-cobalt solid solution powder is obtained; and finally, the porous nickel-cobalt solid solution powder is placed in a muffle furnace in an air atmosphere for oxidation treatment, and a target product can be obtained. According to the preparation method of the porous spinel nickel cobaltate, non-precious nickel, cobalt and aluminum metal are used as initial raw materials, the source is wide, the cost is low, the process is simple, safety and reliability are achieved, and large-scale production is easy. The porous spinel nickel cobaltate prepared by the method can be applied to hydrogen storage of sodium aluminum hydride, the hydrogen desorption temperature of the sodium aluminum hydride can be remarkably reduced, and the porous spinel nickel cobaltate has high hydrogen desorption amount.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrogen storage materials, and in particular relates to a porous spinel-type nickel cobalt oxide and a preparation method thereof, and application thereof in sodium aluminohydride hydrogen storage. Background Art

[0002] Hydrogen is considered to be an ideal secondary energy source for mankind in the future. Its safe and efficient storage and transportation are the key to realizing large-scale application of hydrogen and hydrogen economy. Compared with high-pressure gaseous and deep-cold liquid hydrogen storage, solid-state hydrogen storage has the advantages of safety, reliability and high hydrogen storage density. Among them, as a representative of coordinated hydride hydrogen storage materials, sodium aluminum hydride (NaAlH4) has the advantages of high hydrogen storage capacity and low cost, and is an important solid-state hydrogen storage material. However, NaAlH4 has high thermodynamic stability and activation energy of hydrogen desorption reaction, and requires higher temperature for effective hydrogen desorption, which greatly limits its practical application. Catalyst doping is one of the main methods to reduce the desorption temperature of NaAlH4 and improve its reversibility, among which transition metal oxide catalysts are typical representatives.

[0003] Spinel nickel cobalt oxide (NiCo2O4) has the advantages of good conductivity, high electrochemical activity, abundant resources and environmental friendliness, and is widely used in the field of energy storage and conversion such as hydrogen / electricity. Porous spinel NiCo2O4 has a three-dimensional interconnected porous structure, a larger specific surface area, and more active sites, thus showing better catalytic performance. At present, the preparation methods of porous spinel NiCo2O4 mainly include hydrothermal method, solvothermal method, microwave-assisted method, template method, sol-gel method, etc. For example, Kim et al. used cobalt chloride hexahydrate and nickel chloride hexahydrate as raw materials and synthesized porous flower-like NiCo2O4 on nickel foam by hydrothermal method, but the process is cumbersome, the production efficiency is low, and nickel foam needs to be used as a substrate or base [Tae Hyun Kim, Ganesh Kumar Veerasubramani, Sang Jae Kim, Journal of Industrial and Engineering Chemistry, 2018, 61: 181-187]. Li et al. synthesized three-dimensional multi-level NiCo2O4 by solvent thermal method combined with calcination, but it is difficult to mass produce and has safety risks [Li Qun, Zhang Kuo, Li Yanhua, et al., Journal of Composite Materials, 2024, 41 (1)? 281-292]. Lei et al. synthesized three-dimensional layered NiCo2O4 microspheres by microwave assisted method, but the operation is complicated and difficult to scale production [Ying Lei, Jing Li, Yanyan Wang, et al, ACS Applied Materials Interfaces, 2014, 6 (3)? 1773-1780]. Bai et al. used silica sol as a template to prepare a three-dimensional porous NiCo2O4 composite material, but the preparation process is cumbersome, time-consuming, and the material morphology and structure are single [Yang Bai, Ranran Wang, Xiaoyu Lu, et al, Journal of Colloid and Interface Science, 2016, 468: 1-9].

[0004] In summary, although good progress has been made in the preparation of porous spinel NiCo2O4 catalysts at home and abroad, it still cannot meet the requirements of practical applications for high performance, low cost and easy large-scale production. At the same time, for hydrogen storage applications, the dehydrogenation temperature of NaAlH4 is still relatively high. Summary of the invention

[0005] In view of the shortcomings of the existing porous NiCo2O4 preparation technology and NaAlH4 hydrogen storage technology, the present invention provides a porous spinel NiCo2O4 and a preparation method with simple preparation process, low cost, safety and reliability, in order to apply it to NaAlH4 hydrogen storage and significantly reduce the dehydrogenation temperature of NaAlH4.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] The porous spinel NiCo2O4 provided by the present invention has a three-dimensional interconnected porous structure, and its preparation comprises the following steps:

[0008] (1) using a smelting method to smelt nickel, cobalt and aluminum metal elements in a molar ratio of 1:2:13-20 into a nickel-cobalt-aluminum ternary alloy, and mechanically crushing the alloy into a powder with a particle size of less than 200 mesh;

[0009] (2) pouring the alloy powder obtained in step (1) into a sodium hydroxide solution for dealloying treatment, and washing and drying the treated solid product to obtain a porous nickel-cobalt solid solution powder;

[0010] (3) The porous nickel-cobalt solid solution powder obtained in step (2) is placed in a muffle furnace in an air atmosphere for oxidation treatment to obtain porous spinel NiCo2O4.

[0011] As an optimization, the concentration of the sodium hydroxide solution in the preparation step (2) is 2-3 mol / L, the temperature is 25-30° C., and the dealloying time is 8-12 h.

[0012] As an optimization, the temperature of the oxidation treatment in the preparation step (3) is 400-500° C. and the time is 4-8 hours.

[0013] The present invention also provides the use of the porous spinel NiCo2O4 obtained by the above preparation method in NaAlH4 hydrogen storage materials, specifically, the porous spinel NiCo2O4 is mechanically mixed with NaAlH4, wherein the addition amount of NiCo2O4 is 10-40wt.%.

[0014] As an optimization, the added amount of NiCo2O4 is 20wt.%.

[0015] The innovations of the present invention are as follows:

[0016] The present invention uses nickel-cobalt-aluminum ternary alloy as a precursor, and obtains a porous NiCo2O4 catalyst through a two-step process of dealloying + oxidation. In the dealloying process, with the release of aluminum elements and the rearrangement of nickel and cobalt atoms, a nickel-cobalt solid solution is obtained, which not only realizes the uniform distribution of components at the atomic scale, but also forms fine and loose porous particle characteristics; then through a simple controllable oxidation treatment, it is ensured that oxide phase separation does not occur during the oxidation process, and porous spinel NiCo2O4 is obtained. In terms of the application of NaAlH4 hydrogen storage materials, spinel NiCo2O4 can promote the charge migration between sodium ions and [AlH4] ion groups, reduce the binding energy of Al-H bonds, and thus reduce the dehydrogenation temperature of NaAlH4; at the same time, porous NiCo2O4 has a larger specific surface area and more active sites, so it can exert a stronger catalytic effect.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The method for preparing porous spinel NiCo2O4 provided is simple in process, safe and reliable, and easy to mass produce.

[0019] (2) The method for preparing the porous spinel NiCo2O4 uses non-precious nickel, cobalt and aluminum metals as initial raw materials, which are widely available and low in cost.

[0020] (3) The provided porous spinel NiCo2O4 is used as a catalyst for NaAlH4 hydrogen storage material, which can reduce the initial dehydrogenation temperature of NaAlH4 to 86°C and has a high dehydrogenation capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the X-ray diffraction pattern of the porous nickel-cobalt solid solution in Example 1 of the present invention.

[0022] Figure 2 This is the X-ray diffraction pattern of the porous spinel NiCo2O4 in Example 1 of the present invention.

[0023] Figure 3 This is a scanning electron microscope photograph of the porous spinel NiCo2O4 in Example 1 of the present invention.

[0024] Figure 4 1 is the temperature-increasing hydrogen release curve of the NaAlH4-based hydrogen storage material and pure NaAlH4 in Example 1 of the present invention.

[0025] Figure 5 This is the temperature increase hydrogen release curve of the NaAlH4-based hydrogen storage material in Example 2 of the present invention. DETAILED DESCRIPTION

[0026] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments, but the present invention is not limited to the following embodiments.

[0027] Example 1

[0028] A nickel-cobalt-aluminum ternary alloy was prepared by vacuum induction melting method using nickel flakes, cobalt particles and aluminum flakes with a molar ratio of 1:2:17, and the alloy was mechanically crushed into a powder with a particle size of less than 200 meshes; the alloy powder was poured into a 3 mol / L sodium hydroxide solution at 25°C for 8 hours of dealloying treatment; the dealloyed solid product was washed with distilled water and alcohol in succession, and then vacuum dried to obtain a porous nickel-cobalt solid solution powder (whose X-ray diffraction pattern is shown in FIG. Figure 1 As shown); placing the porous nickel-cobalt solid solution powder in a muffle furnace and performing oxidation treatment in an air atmosphere (temperature of 500°C for 4 hours) to obtain the porous spinel NiCo2O4. Figure 2 and Figure 3 It can be seen that the porous spinel NiCo2O4 is composed of a single NiCo2O4 phase and has a three-dimensional interconnected porous structure. 20wt.% of porous spinel NiCo2O4 and NaAlH4 were mixed by mechanical ball milling. Figure 4 It can be seen that the obtained NaAlH4-based hydrogen storage material starts to release hydrogen at 86°C and basically ends at 230°C, with a hydrogen release amount of about 4.4wt.%; in comparison, the initial dehydrogenation temperature of pure NaAlH4 is as high as 175°C, and the end dehydrogenation temperature is higher than 300°C.

[0029] Example 2

[0030] The nickel sheet, cobalt particles and aluminum sheet with a molar ratio of 1:2:17 are melted into a nickel-cobalt-aluminum ternary alloy by vacuum induction melting, and the alloy is mechanically crushed into a powder with a particle size less than 200 mesh; the alloy powder is poured into a 3 mol / L sodium hydroxide solution at 25°C for dealloying treatment for 8 hours; the dealloyed solid product is washed with distilled water and alcohol successively, and then vacuum dried to obtain a porous nickel-cobalt solid solution powder; the porous nickel-cobalt solid solution powder is placed in a muffle furnace and oxidized in an air atmosphere (temperature of 450°C, time of 8 hours) to obtain the porous spinel NiCo2O4. 15wt.% of porous spinel NiCo2O4 is mixed with NaAlH4 by mechanical ball milling. Figure 5 It can be seen that the obtained NaAlH4-based hydrogen storage material starts to release hydrogen at 95°C and basically ends at 250°C, with a hydrogen release amount of about 4.7wt.%.

[0031] Example 3

[0032] The nickel sheet, cobalt granules and aluminum sheet with a molar ratio of 1:2:13 are melted into a nickel-cobalt-aluminum ternary alloy by vacuum induction melting method, and the alloy is mechanically crushed into a powder with a particle size less than 200 mesh; the alloy powder is poured into a 2mol / L sodium hydroxide solution at 25°C for 10 hours of dealloying treatment; the solid product after dealloying is washed with distilled water and alcohol successively, and then vacuum dried to obtain a porous nickel-cobalt solid solution powder; the porous nickel-cobalt solid solution powder is placed in a muffle furnace and oxidized in an air atmosphere (temperature 400°C, time 8 hours) to obtain the porous spinel NiCo2O4. Mechanical mixing of 10wt.% porous spinel NiCo2O4 with NaAlH4 can significantly reduce the dehydrogenation temperature of NaAlH4.

[0033] Example 4

[0034] The nickel sheet, cobalt particles and aluminum sheet with a molar ratio of 1:2:20 are melted into a nickel-cobalt-aluminum ternary alloy by vacuum induction melting method, and the alloy is mechanically crushed into a powder with a particle size less than 200 mesh; the alloy powder is poured into a 3mol / L sodium hydroxide solution at 30°C for 12 hours of dealloying treatment; the solid product after dealloying is washed with distilled water and alcohol successively, and then vacuum dried to obtain a porous nickel-cobalt solid solution powder; the porous nickel-cobalt solid solution powder is placed in a muffle furnace and oxidized in an air atmosphere (temperature is 450°C, time is 6 hours) to obtain the porous spinel NiCo2O4. Mechanically mixing 40wt.% of the porous spinel NiCo2O4 with NaAlH4 can significantly reduce the dehydrogenation temperature of NaAlH4.

Claims

1. A porous spinel nickel cobalt oxide, characterized in that: The spinel-type nickel cobalt oxide has a three-dimensional interconnected porous structure, and the preparation method thereof comprises the following steps: (1) using a smelting method to smelt nickel, cobalt and aluminum metal elements in a molar ratio of 1:2:13 to 20 into a nickel-cobalt-aluminum ternary alloy, and mechanically crushing the alloy into a powder with a particle size of less than 200 mesh; (2) pouring the alloy powder obtained in step (1) into a sodium hydroxide solution for dealloying treatment, and washing and drying the treated solid product to obtain a porous nickel-cobalt solid solution powder; (3) The porous nickel-cobalt solid solution powder obtained in step (2) is placed in a muffle furnace in an air atmosphere for oxidation treatment to obtain spinel nickel cobalt oxide.

2. The porous spinel nickel cobalt oxide according to claim 1, characterized in that: In the preparation step (2), the concentration of the sodium hydroxide solution is 2-3 mol / L, the temperature is 25-30° C., and the dealloying time is 8-12 h.

3. The porous spinel nickel cobalt oxide according to claim 1, characterized in that: The temperature of the oxidation treatment in the preparation step (3) is 400-500° C. and the time is 4-8 hours.

4. Use of the porous spinel nickel cobalt oxide as claimed in claim 1 in sodium aluminohydride hydrogen storage material.

5. The use of the porous spinel nickel cobalt oxide in sodium aluminohydride hydrogen storage material according to claim 4, characterized in that: The porous spinel nickel cobaltate and sodium aluminum hydride are mechanically mixed, wherein the addition amount of the nickel cobaltate is 10-40wt.%.

6. The use of the porous spinel nickel cobalt oxide in sodium aluminohydride hydrogen storage material according to claim 5, characterized in that: The added amount of the nickel cobaltate is 20 wt.%.

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