Preparation method, product and application of self-supporting cobalt and cobalt oxide core-shell nanodisk material

Abstract

The invention discloses a preparation method of a self-supporting cobalt and cobalt oxide core-shell nanodisk material. The preparation method comprises the following steps: (1) soaking a substrate material in a cobalt salt solution; (2) calcining the soaked substrate material to obtain a cobalt oxide-loaded substrate material; and (3) calcining and reducing the substrate material loaded with the cobalt oxide in an H2 atmosphere to obtain the cobalt (at) cobalt oxide core-shell nanodisk material, which is recorded as Co (at) CoOX. The invention further discloses the cobalt (at) cobalt oxide core-shell nanodisk material obtained through the preparation method and application of the cobalt (at) cobalt oxide core-shell nanodisk material serving as an HER catalyst. The cobalt and cobalt oxide core-shell nanodisk material is prepared by a simple preparation method; and the material, as an electrocatalyst, shows excellent performance when being applied to hydrogen production through hydrolysis.

Description

Technical Field

[0001] The present invention belongs to the field of electrocatalysis, and particularly relates to a preparation method, product and application of a self-supporting cobalt@cobalt oxide core-shell nanodisk material. Background Art

[0002] The rapid development of the global economy has led to the overuse of traditional energy sources, and the demand for renewable clean energy is increasing day by day. Hydrogen energy is one of the most promising clean energy sources due to its high energy density, low-carbon cleanliness and other advantages. Among various hydrogen production methods, water electrolysis for hydrogen production (HER) is the simplest and most environmentally friendly method. However, current alkaline water electrolysis is mainly limited by problems such as slow reaction kinetics and poor stability, and its reaction rate is two to three orders of magnitude lower than that of acidic HER. In addition, although some studies have developed some efficient HER catalysts that can work well at low current densities (such as 10 mA cm -2 ). However, their activity and stability still cannot meet the expectations under high current conditions. This may be because more gas is formed during the HER process at high current density, and diffusion polarization control is stronger. In practical applications, the current density of contemporary chlor-alkali electrolyzers is usually between 200 and 500 mA cm -2 , and sometimes even reaches 1000 mA cm -2 . Therefore, the performance of electrocatalysts at high current density is more important, and the design of low-cost, highly active and stable electrode materials for HER at high current density remains a great challenge.

[0003] Transition metal Co has multiple oxidation states and can be converted between multiple oxidation states. In addition, Co atoms have 3 unfilled d orbitals, which can interact with reactants and intermediates to adsorb reactants and desorb products. Therefore, Co-based catalysts have excellent performance in electrocatalytic reactions. At the same time, cobalt-based catalysts have the advantages of low cost, high catalytic activity and rich resource reserves, and are one of the promising alternatives to precious metals. In addition, efficient HER catalysts at high current density should also have some characteristics: high intrinsic activity, a large number of active sites, a porous structure, and high tolerance to gases and electrolytes. Previous studies have shown that interface engineering by coupling multiple active components can effectively promote HER (for example, Chinese Patent No. CN118345429A discloses a self-supporting La-doped Co modified with nitrogen-doped carbon 3 O 4Oxygen evolution catalyst, which can promote the transfer of surface electrons and the mass transfer of intermediates. At the same time, the nanoarray structure can also expose a large number of active sites, making it a high-performance electrolytic water oxygen evolution catalyst. Heterostructure electrocatalysts can increase the catalytic sites at the active interface and improve the interfacial charge transfer kinetics, thus enabling higher catalytic activity than single-component catalysts. In addition, constructing a core-shell structure catalyst can effectively protect the unstable core layer components and prevent the loss of metals, thereby improving the stability of the catalyst (for example, Chinese Patent Publication No. CN119186650A discloses a bifunctional heterojunction catalyst, which is Co 3 O 4 nanowire@NiMoO 4 nanosheet array, whose overall shape is a porous and multi-folded paper hydrangea shape. Its heterojunction structure enables the catalyst to have excellent OER / HER bifunctional catalytic activity under alkaline conditions.).

[0004] Therefore, how to construct a cobalt-based catalyst with a heterostructure core-shell structure by a simple method is expected to improve the catalytic efficiency and stability of HER at high current density, which is of great significance for the development of the electrolytic water hydrogen production industry. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method of a self-supporting cobalt@cobalt oxide core-shell nanodisk material. The prepared cobalt@cobalt oxide core-shell nanodisk exhibits excellent performance as an electrocatalyst in water hydrolysis for hydrogen production.

[0006] The present invention provides the following technical solutions:

[0007] A preparation method of a cobalt@cobalt oxide core-shell nanodisk, the preparation method comprising:

[0008] (1) Immerse the substrate material in a cobalt salt solution;

[0009] (2) Calcinate the immersed substrate material to obtain a substrate material loaded with cobalt oxide;

[0010] (3) Calcinate and reduce the substrate material loaded with cobalt oxide in an H 2 atmosphere to obtain a cobalt@cobalt oxide (Co@CoO X ) core-shell nanodisk material, denoted as Co@CoO X .

[0011] The technical concept or principle of this application lies in that: the heterostructure electrocatalyst can increase the catalytic sites at the active interface and improve the interfacial charge transfer kinetics, thereby enabling higher catalytic activity than single-component materials; in addition, constructing a core-shell structure catalyst can effectively protect the unstable core-layer components and prevent the loss of metals, thus improving the stability of the catalyst; therefore, the present invention provides a simple impregnation-calcination-thermal reduction strategy to prepare a self-supported cobalt@cobalt oxide core-shell nanodisk catalyst for HER.

[0012] Preferably, in step (1), the concentration of the cobalt salt solution is 0.1 - 0.5 M.

[0013] Preferably, in step (1), the raw materials for the cobalt salt solution are various organic cobalt salts or inorganic cobalt salts, and the cobalt salt in the cobalt salt solution is selected from one or a combination of at least two of cobalt nitrate, cobalt nitrate hexahydrate, cobalt chloride, or cobalt sulfate.

[0014] Preferably, in step (1), the substrate material is selected from copper foam, nickel foam, or nickel-iron foam. The working area of the substrate material is 1 - 100 cm 2 .

[0015] Preferably, in step (2), the calcination temperature is 100 - 600 °C. Preferably, the calcination heating rate is 2 - 8 °C min -1 , and the holding time is 2 hours. Preferably, in step (3), the calcination reduction temperature is 100 - 300 °C, and the heating rate is 2 - 8 °C min -1 , and the holding time is 1 - 2 hours.

[0016] The present invention regulates the type of cobalt oxide and the content of cobalt and cobalt oxide by controlling the type of cobalt salt solution and the calcination temperature in step (2) and the calcination reduction temperature in step (3), so as to obtain a self-supported nanodisk structure morphology and excellent electrocatalytic performance at the same time.

[0017] The present invention also provides a cobalt@cobalt oxide (Co@CoO X ) core-shell nanodisk material obtained by the above preparation method.

[0018] Preferably, the cobalt oxide CoO X is one of CoO, Co 2 O 3 or Co 3 O 4 .

[0019] Preferably, the morphology of the prepared cobalt@cobalt oxide core-shell material is a self-supported nanodisk structure.

[0020] The present invention also provides an application of the above-mentioned Co@CoO X core-shell nanodisc material as a HER catalyst.

[0021] Compared with the prior art, the technical effect of the present invention is that: the self-supporting Co@CoO X core-shell nanodisc material is obtained by a simple preparation method, which can be used as an electrocatalyst and exhibits excellent performance for HER. At a current density of 200 mA cm -2 , its performance is comparable to that of commercial 20% Pt / C catalyst, and only 248 mV is required at the optimum; at a current density of 1000 mA cm -2 , its performance far exceeds that of commercial 20% Pt / C, and single Co and CoO x catalysts; moreover, the Co@CoO X core-shell nanodisc exhibits excellent stability, reaching 120 h at the optimum, exceeding the current HER catalysts. Description of the Drawings

[0022] Figure 1 SEM image of Co@Co 3 O 4 -NF prepared in Example 1.

[0023] Figure 2 HRTEM image of Co@Co 3 O 4 -NF prepared in Example 1.

[0024] Figure 3 LSV curve of Co@Co 3 O 4 -NF in 1 M KOH prepared in Example 1.

[0025] Figure 4 Stability test of Co@Co 3 O 4 -NF in 1 M KOH prepared in Example 1.

[0026] Figure 5 SEM image of Co@Co 2 O 3 -NF prepared in Example 2.

[0027] Figure 6 HRTEM image of Co@Co 2 O 3 -NF prepared in Example 2.

[0028] Figure 7 LSV curve of Co@Co 2 O 3LSV curve of -NF in 1 M KOH.

[0029] Figure 8 SEM image of Co@CoO-NF prepared in Example 3.

[0030] Figure 9 HRTEM image of Co@CoO-NF prepared in Example 3.

[0031] Figure 10 LSV curve of Co@CoO-NF prepared in Example 3 in 1 M KOH.

[0032] Figure 11 Co@Co prepared in Example 1 3 O 4 LSV curve of -NF-3 in 1 M KOH.

[0033] Figure 12 Co prepared in Comparative Example 2 3 O 4 SEM image of -NF.

[0034] Figure 13 Co prepared in Comparative Example 2 3 O 4 XRD pattern of -NF.

[0035] Figure 14 Co prepared in Comparative Example 2 3 O 4 LSV curve of -NF in 1 M KOH.

[0036] Figure 15 SEM image of Co-NF prepared in Comparative Example 3.

[0037] Figure 16 XRD pattern of Co-NF prepared in Comparative Example 3.

[0038] Figure 17 LSV curve of Co-NF prepared in Comparative Example 3 in 1 M KOH. Detailed implementation manners

[0039] To better understand the present invention, the content of the present invention will be further clarified below in conjunction with examples, but the content of the present invention is not limited to the following examples only.

[0040] Example 1

[0041] Preparation of Co@Co 3 O 4 -NF

[0042] First, cut nickel foam and ultrasonically clean it with hydrochloric acid, deionized water, and ethanol for 20 minutes in sequence; prepare a 0.34 M Co(NO 3 ) 2 ·6H 2 O solution, ultrasonicate for 30 minutes, immerse the cleaned nickel foam into the above Co solution, and dry it in an infrared dryer; repeat this step 3 times. Calcinate the prepared material in an air furnace at 500 °C for 2 hours, and then cool it to room temperature; then calcinate the prepared material in a tubular furnace under a hydrogen atmosphere at 100 °C for 1 hour to obtain Co@Co 3 O 4 -NF.

[0043] The SEM image of the Co@Co 3 O 4 -NF prepared in this example is shown in Figure 1 , indicating that the catalyst is a nanoplate structure assembled by particles. The HRTEM image shows that Co is coated with Co 3 O 4 to form a Co@Co 3 O 4 heterogeneous core-shell structure ( Figure 2 ). The LSV test shows that the performance of this catalyst at a current density of 200 mA cm -2 in 1 M KOH is comparable to that of commercial 20% Pt / C catalyst, and the overpotential only needs 248 mV ( Figure 3 ). At a current density of 1000 mA cm -2 , the performance far exceeds that of commercial 20% Pt / C and single Co and CoO x catalysts. The stability test shows that the catalyst has excellent stability for 120 h ( Figure 4 ).

[0044] Example 2

[0045] Preparation of Co@Co 2 O 3 -NF

[0046] First, cut nickel foam and ultrasonically clean it with hydrochloric acid, deionized water, and ethanol for 20 minutes in sequence; prepare a 0.34 M Co(NO 3 ) 2 ·6H 2 O solution, ultrasonicate for 30 minutes, immerse the cleaned nickel foam into the above Co solution, and dry it in an infrared dryer; repeat this step 3 times. Calcinate the prepared material in an air furnace at 300 °C for 2 hours, and then cool it to room temperature; then calcinate the prepared Co 3 O 4 -NF in a tubular furnace under a hydrogen atmosphere at 100 °C for 1 hour to obtain Co@Co2 O 3 -NF.

[0047] The Co@Co 2 O 3 -NF prepared in this example is shown in Figure 5 , indicating that the catalyst is a nanodisk structure. The HRTEM image shows that Co is coated with Co 2 O 3 to form a Co@Co 2 O 3 heterogeneous core-shell structure ( Figure 6 ). LSV tests show that the performance of this catalyst at a current density of 200 mA cm -2 in 1 M KOH is comparable to that of commercial 20% Pt / C catalyst, with an overpotential of 264 mV ( Figure 7 ).

[0048] Example 3

[0049] Preparation of Co@CoO-NF

[0050] First, cut nickel foam and ultrasonically clean it with hydrochloric acid, deionized water, and ethanol for 20 minutes in sequence; prepare a 0.34 M CoCl 2 solution, ultrasonicate it for 30 minutes, immerse the cleaned nickel foam into the above Co solution, and dry it in an infrared dryer; repeat this step 3 times. Calcinate the prepared material in an air furnace at 300 °C for 2 hours, then cool it to room temperature; then calcinate it in a tube furnace under a hydrogen atmosphere at 300 °C for 1 hour to obtain Co@CoO-NF.

[0051] The SEM image of the Co@CoO-NF prepared in this example is shown in Figure 8 , indicating that the catalyst is a nanodisk structure. The HRTEM image shows that Co is coated with CoO to form a Co@CoO heterogeneous core-shell structure ( Figure 9 ). LSV tests show that the overpotential of this catalyst at a current density of 200 mA cm -2 in 1 M KOH is only 252 mV ( Figure 10 ).

[0052] Comparative Example 1

[0053] Co@Co 3 O 4 -NF Preparation

[0054] First, cut nickel foam and ultrasonically clean it with hydrochloric acid, deionized water, and ethanol for 20 minutes in sequence; prepare a 0.34 M Co(NO 3 ) 2 ·6H 2O solution, ultrasonic for 30 minutes, soak the cleaned nickel foam into the above Co solution, and dry it in an infrared dryer; this step is repeated 3 times. Calcinate the prepared material in an air furnace at 500 °C for 2 hours, and then cool it to room temperature; then calcinate the prepared material in a tubular furnace under a hydrogen atmosphere at 100 °C for 3 hours to obtain Co@Co 3 O 4 -NF-3.

[0055] LSV test shows that the overpotential of this catalyst in 1 M KOH at a current density of 200 mA cm -2 is only 387 mV ( Figure 11 ).

[0056] Comparative Example 2

[0057] Co 3 O 4 -NF preparation

[0058] First, cut nickel foam, and ultrasonically clean it with hydrochloric acid, deionized water, and ethanol for 20 minutes in sequence; prepare 0.34 M Co(NO 3 ) 2 ·6H 2 O solution, ultrasonic for 30 minutes, soak the cleaned nickel foam into the above Co solution, and dry it in an infrared dryer; this step is repeated 3 times. Calcinate the prepared material in an air furnace at 500 °C for 2 hours, and then cool it to room temperature to obtain Co 3 O 4 -NF.

[0059] SEM images show that this catalyst has a particulate structure ( Figure 12 ). XRD shows that the catalyst is pure Co 3 O 4 ( Figure 13 ). LSV test shows that the overpotential of this catalyst in 1 M KOH at a current density of 200 mA cm -2 is 322 mV ( Figure 14 ).

[0060] Comparative Example 3

[0061] Co-NF preparation

[0062] First, cut nickel foam, and ultrasonically clean it with hydrochloric acid, deionized water, and ethanol for 20 minutes in sequence; prepare 0.34 M Co(NO 3 ) 2 ·6H 2O solution, ultrasonic for 30 minutes, the cleaned nickel foam is immersed in the above Co solution and dried in an infrared dryer; this step is repeated 3 times. The prepared material is calcined at 500°C for 2 hours in an air furnace and then cooled to room temperature to obtain Co 3 O 4 Then, the Co-NF was calcined in a tube furnace at 400°C for 4 hours under a hydrogen atmosphere to obtain Co-NF.

[0063] SEM images show that the catalyst is a nanoflower structure assembled from nanodisks ( Figure 15 ). XRD showed that the catalyst was pure Co ( Figure 16 ). LSV test shows that the catalyst has a conductivity of 200 mA cm in 1 M KOH. -2 The overpotential at the current density is 326mV ( Figure 17 ).

[0064] The specific implementation methods described above provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above is only the most preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, supplements and equivalent substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a self-supporting cobalt@cobalt oxide core-shell nanodisk material, characterized in that: The preparation method comprises: (1) Soaking the substrate material in a cobalt salt solution; (2) calcining the soaked base material to obtain a base material loaded with cobalt oxide; (3) The cobalt oxide-loaded substrate material is calcined and reduced in a H2 atmosphere to obtain a cobalt@cobalt oxide core-shell nanodisk material, denoted as Co@CoO X .

2. The method for preparing the self-supporting cobalt@cobalt oxide core-shell nanodisk material according to claim 1, characterized in that: In step (1), the concentration of the cobalt salt solution is 0.1-0.5M.

3. The method for preparing the self-supporting cobalt@cobalt oxide core-shell nanodisk material according to claim 1, characterized in that: In step (1), the cobalt salt in the cobalt salt solution is selected from one or a combination of at least two of cobalt nitrate, cobalt nitrate hexahydrate, cobalt chloride or cobalt sulfate.

4. The method for preparing the self-supporting cobalt@cobalt oxide core-shell nanodisk material according to claim 1, characterized in that: In step (1), the substrate material is selected from foamed copper, foamed nickel or foamed nickel-iron.

5. The method for preparing the cobalt@cobalt oxide core-shell nanodisk material according to claim 1, characterized in that: In step (2), the calcination temperature is 100-600°C.

6. The method for preparing the cobalt@cobalt oxide core-shell nanodisk material according to claim 1, characterized in that: In step (3), the calcination reduction temperature is 100-300° C., and the insulation time is 1 to 2 hours.

7. A self-supporting cobalt@cobalt oxide core-shell nanodisk material obtained by the preparation method according to any one of claims 1 to 6.

8. The self-supporting cobalt@cobalt oxide core-shell nanodisk material according to claim 7, characterized in that: The cobalt oxide is CoO, Co2O3 or Co3O4, and the morphology of the cobalt@cobalt oxide core-shell material is a self-supporting nano-disk structure.

9. Use of the self-supporting cobalt@cobalt oxide core-shell nanodisk as claimed in claim 8 as a HER catalyst.

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