Nitrate chemical coordination transition metal-based material as well as preparation method and application thereof

Abstract

The invention discloses a nitrate radical chemical coordination transition metal-based material and a preparation method and application thereof, and belongs to the technical field of electrocatalysts.The preparation method comprises the following steps that a metal base material is placed in a heating container, and the temperature is increased to 200-400 DEG C; meanwhile, introducing the nitrogen-oxygen mixed gas into a plasma generator, and exciting to form a nitrogen-oxygen compound; and introducing the nitrogen oxide into the heating container, carrying out heat preservation treatment, and naturally cooling to obtain the nitrogen oxide composite material. In the catalyst, nitrate ions and a metal active center form a nitric acid type hydroxide through a strong chemical bond, the hydroxide has a relatively high reconstruction rate, and a reconstructed product has relatively good stability, so that the problems in the prior art can be effectively solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalysts, and in particular relates to a nitrate chemically coordinated transition metal-based material, a preparation method thereof, and an application thereof. Background Art

[0002] The oxygen evolution reaction (OER) is a core half-reaction in many clean energy technologies, including water electrolysis for hydrogen production and metal-air batteries. Its sluggish kinetics and the complexity of the multi-step electron transfer process severely restrict the energy conversion efficiency. Although noble metal-based catalysts such as iridium and ruthenium exhibit excellent activity, their scarcity and high cost greatly limit their large-scale application. Transition metal-based catalysts, represented by low-cost iron (Fe), cobalt (Co), nickel (Ni) and their compounds, have gradually been widely used in the OER field.

[0003] With advances in in situ characterization techniques, researchers have gradually confirmed that pre-catalysts (original electrocatalysts) generally undergo dynamic reconstruction of surface active sites during catalytic reactions. The rate of this reconstruction not only directly affects the density of active sites but also determines the structural integrity of the catalytic system. Because surface reconstruction behavior (such as the starting conditions, rate, and extent of reconstruction) determines the number and structure of catalytic species, researchers have developed various strategies such as morphology control and defect engineering to regulate the reconstruction process of pre-catalysts, in order to promote the directional and rapid formation of highly active phases, thereby improving OER performance.

[0004] Recently, the anion doping strategy has become an effective means to regulate the reconstructed behavior of transition metal-based electrocatalysts due to its simplicity of process. For example, Lim et al. successfully doped Cl into LiCoO2 by solid-phase reaction, and they found that Cl doping can effectively induce the LiCoO2 surface to convert into amorphous hydroxyhydroxide faster during the OER process, thereby improving the catalyst activity and stability. The Bourbaix potential-pH diagram further revealed that under alkaline OER conditions, the sulfur anion (S 2- 、Se 2- ) and nitrogen anions (P 3- 、N 3- ) will be preferentially oxidized to sulfate (SO4 2- ), selenate (SeO4 2- ), phosphate (PO4 3- ) and other oxygen-containing anions, whose dissolution and escape process triggers the hydroxylation reconstruction of metal cations. Compared with traditional single anions, oxygen-containing anions can effectively achieve precise control of the electronic structure and local coordination environment of catalysts by virtue of their strong electronegativity effect and thermodynamic regulation ability. Liao et al. modified SO4 on the surface of NiFe (hydroxy) hydroxide through a simple electrochemical anodic oxidation strategy. 2- Experimental and theoretical analysis revealed that SO4 2-Dual mechanisms for synergistically enhancing OER activity: SO4 2- Electrochemical leaching promotes the in situ reconstruction of the catalytically active phase NiFeOOH under OER conditions, while the surface adsorbed SO4 2- The residue stabilizes the OOH* intermediate species through electronic modulation to optimize the reaction kinetics, thereby synergistically improving the overall OER catalytic efficiency. Tang's team further found that the introduction of 0.1M SO4 into the 1M KOH electrolyte 2- , 0.1M CO3 2- and 0.1M NO3 - It can promote the reconstruction of the catalyst surface and enhance the OER activity. After in-depth analysis, it is shown that oxygen-containing anions can break the OH - The balance between adsorption and generation can also accelerate the release of OH-.

[0005] However, the weak physical adsorption (van der Waals force / hydrogen bond) between oxygen-containing anions and the catalyst surface mentioned in the above strategy leads to insufficient reconstruction stability under continuous electrochemical stress. Summary of the Invention

[0006] In response to the above-mentioned deficiencies in the prior art, the present invention provides a nitrate chemically coordinated transition metal-based material, a preparation method, and an application thereof. In the catalyst, nitrate ions and metal active centers form acidic hydroxides through strong chemical bonds. The hydroxides have a faster reconstruction rate and better stability, which can effectively solve the problems existing in the prior art.

[0007] To achieve the above-mentioned purpose, the technical solution adopted by the present invention to solve the technical problem is:

[0008] A method for preparing a nitrate chemically coordinated transition metal-based material comprises the following steps:

[0009] (1) Place the metal substrate in a heating container and heat it to 200-400°C;

[0010] (2) introducing nitrogen and oxygen mixed gas into a plasma generator to excite and form nitrogen oxides;

[0011] (3) The nitrogen oxide compound is introduced into a heating container, kept warm, and naturally cooled to obtain the product.

[0012] Furthermore, in step (1), the metal substrate includes Fe element, Ni element, Co element, NiFe alloy and NiCo alloy.

[0013] Furthermore, in step (1), the metal substrate is in the form of powder, film or foam.

[0014] Furthermore, the heating temperature rise rate in step (1) is 5-10°C / min.

[0015] Furthermore, in step (2), the volume ratio of nitrogen to oxygen in the nitrogen-oxygen mixed gas is 1-10:1-10.

[0016] Furthermore, the flow rate of the nitrogen-oxygen mixed gas in step (2) is 200-600 mL / min. -1 .

[0017] Furthermore, in step (2), the operating current of the plasma generator is 1-5A, and the operating voltage is 150-220V.

[0018] Furthermore, the heat preservation treatment time in step (3) is 0.2-3h.

[0019] A nitrate chemically coordinated transition metal-based material is prepared by the above method.

[0020] Application of the above-mentioned nitrate chemically coordinated transition metal-based material in the preparation of oxygen evolution electrocatalysts.

[0021] The beneficial effects produced by the present invention are:

[0022] 1. In the present invention, nitrogen and oxygen are ionized by a plasma generator to generate a mixture of highly reactive nitrogen ions and oxygen ions, which further generate nitrogen oxides (NO X ), nitrogen oxides react with metal substrates under high temperature conditions to form nitric acid-type oxides or hydroxides. Under the strong chemical coordination of nitrate ions, they can quickly reconstruct into real active centers in the oxygen evolution reaction, and the reconstructed catalytic materials have high stability. Taking nickel as an example, the prepared nitric acid-type nickel hydroxide (Ni2(NO3)(OH)2·2H2O) material has a high conductivity at 10mA cm -2 The overpotential is 230 mA cm -2 , and can work continuously for 600h at this current.

[0023] 2. The preparation method of the present invention has a simple operation process and is easy to produce. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the SEM photo of nickel foam;

[0025] Figure 2 This is a SEM photo of the nickel foam after treatment in Example 1;

[0026] Figure 3 This is the SEM picture of foam iron;

[0027] Figure 4 This is a SEM photo of the foamed iron after treatment in Example 2;

[0028] Figure 5 This is the SEM photo of cobalt foam;

[0029] Figure 6 This is a SEM photo of the cobalt foam after treatment in Example 3;

[0030] Figure 7 is the XRD pattern of the material obtained in Example 1;

[0031] Figure 8 is the Raman spectrum of the material obtained in Example 1;

[0032] Figure 9 This is the LSV curve of the material prepared in Example 1 when used in oxygen evolution reaction;

[0033] Figure 10 This is the stability curve of the material prepared in Example 1 when used in oxygen evolution reaction;

[0034] Figure 11 This is the LSV curve of the material prepared in Comparative Example 1 when used in oxygen evolution reaction;

[0035] Figure 12 This is the LSV curve of the material prepared in Comparative Example 2 when used for oxygen evolution reaction. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. That is, the embodiments described are only part of the embodiments of the present invention, rather than all embodiments.

[0037] Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the invention as claimed, but is merely intended to represent selected embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0038] It should be noted that relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or apparatus comprising the element.

[0039] The features and performance of the present invention are further described in detail below with reference to the embodiments and drawings.

[0040] Example 1

[0041] A nitrate chemically coordinated transition metal-based material, the preparation method of which comprises the following steps:

[0042] (1) A nickel foam substrate with a thickness of 1 mm, a length of 10 cm, and a width of 2 cm was placed in a quartz tube of a tube furnace and then heated to 350°C at a rate of 5°C / min;

[0043] (2) Nitrogen-oxygen mixed gas was heated at 200 mL / min. -1 The flow rate of nitrogen is introduced into the plasma generator, the volume ratio of nitrogen to oxygen is 10:1, the current of the plasma generator is 5A and the voltage is 220V when the plasma generator is working, and nitrogen oxides are formed under the excitation of the plasma generator;

[0044] (3) The nitrogen oxide compound is introduced into a heated quartz tube, kept warm for 0.5 h, and cooled naturally to obtain the product.

[0045] Example 2

[0046] A nitrate chemically coordinated transition metal-based material, the preparation method of which comprises the following steps:

[0047] (1) A foamed iron metal substrate with a thickness of 1 mm, a length of 10 cm, and a width of 2 cm was placed in a quartz tube of a tube furnace and then heated to 400 °C at a rate of 10 °C / min;

[0048] (2) Nitrogen-oxygen mixed gas was heated at 400 mL / min. -1The flow rate of nitrogen is introduced into the plasma generator, the volume ratio of nitrogen to oxygen is 5:1, the current of the plasma generator is 1A and the voltage is 180V when the plasma generator is working, and nitrogen oxides are formed under the excitation of the plasma generator;

[0049] (3) The nitrogen oxide compound is introduced into a heated quartz tube, kept warm for 0.5 h, and cooled naturally to obtain the product.

[0050] Example 3

[0051] A nitrate chemically coordinated transition metal-based material, the preparation method of which comprises the following steps:

[0052] (1) A foamed cobalt metal substrate with a thickness of 1 mm, a length of 10 cm, and a width of 2 cm was placed in a quartz tube of a tube furnace and then heated to 200 °C at a rate of 10 °C / min;

[0053] (2) Nitrogen-oxygen mixed gas was heated at 600 mL / min. -1 The flow rate of nitrogen is introduced into the plasma generator, the volume ratio of nitrogen to oxygen is 2:1, the current of the plasma generator is 5A and the voltage is 220V when the plasma generator is working, and nitrogen oxides are formed under the excitation of the plasma generator;

[0054] (3) The nitrogen oxide compound is passed into a heated quartz tube, kept warm for 1 hour, and cooled naturally to obtain the product.

[0055] Example 4

[0056] A nitrate chemically coordinated transition metal-based material, the preparation method of which comprises the following steps:

[0057] (1) A NiFe foam metal substrate with a thickness of 1 mm, a length of 10 cm, and a width of 2 cm was placed in a quartz tube of a tube furnace and then heated to 300 °C at a rate of 6 °C / min;

[0058] (2) Nitrogen-oxygen mixed gas was heated at 300 mL / min. -1 The flow rate of nitrogen is introduced into the plasma generator, the volume ratio of nitrogen to oxygen is 3:1, the current of the plasma generator is 4A and the voltage is 220V when the plasma generator is working, and nitrogen oxides are formed under the excitation of the plasma generator;

[0059] (3) The nitrogen oxide compound is introduced into a heated quartz tube, kept warm for 0.5 h, and cooled naturally to obtain the product.

[0060] Example 5

[0061] A nitrate chemically coordinated transition metal-based material, the preparation method of which comprises the following steps:

[0062] (1) 10 g of nickel powder was placed in a quartz tube of a tube furnace and then heated to 350 °C at a rate of 5 °C / min;

[0063] (2) Nitrogen-oxygen mixed gas was heated at 500 mL / min. -1 The flow rate of nitrogen is introduced into the plasma generator, the volume ratio of nitrogen to oxygen is 4:1, the current of the plasma generator is 5A and the voltage is 220V when the plasma generator is working, and nitrogen oxides are formed under the excitation of the plasma generator;

[0064] (3) The nitrogen oxide compound is introduced into a heated quartz tube, kept warm for 0.5 h, and cooled naturally to obtain the product.

[0065] Example 6

[0066] A nitrate chemically coordinated transition metal-based material, the preparation method of which comprises the following steps:

[0067] (1) Place 10 g of cobalt powder in a quartz tube of a tube furnace and heat it to 300 °C at a rate of 5 °C / min;

[0068] (2) Nitrogen-oxygen mixed gas was heated at 400 mL / min. -1 The flow rate of nitrogen is introduced into the plasma generator, the volume ratio of nitrogen to oxygen is 1:2, the current of the plasma generator is 5A and the voltage is 220V when the plasma generator is working, and nitrogen oxides are formed under the excitation of the plasma generator;

[0069] (3) The nitrogen oxide compound is introduced into a heated quartz tube, kept warm for 0.5 h, and cooled naturally to obtain the product.

[0070] Comparative Example 1

[0071] A nitrate chemically coordinated transition metal-based material, the preparation method of which comprises the following steps:

[0072] (1) A nickel foam substrate with a thickness of 1 mm, a length of 10 cm, and a width of 2 cm was placed in a quartz tube of a tube furnace and then heated to 150°C at a rate of 5°C / min;

[0073] (2) A nitrogen-oxygen mixture is introduced into a plasma generator at a flow rate of 200 mL / min-1, with a volume ratio of nitrogen to oxygen of 10:1. The plasma generator operates at a current of 5 A and a voltage of 220 V, and nitrogen oxides are formed under the excitation of the plasma generator;

[0074] (3) The nitrogen oxide compound is introduced into a heated quartz tube, kept warm for 0.5 h, and cooled naturally to obtain the product.

[0075] Comparative Example 2

[0076] A nitrate chemically coordinated transition metal-based material, the preparation method of which comprises the following steps:

[0077] (1) A nickel foam substrate with a thickness of 1 mm, a length of 10 cm, and a width of 2 cm was placed in a quartz tube of a tube furnace and then heated to 150°C at a rate of 5°C / min;

[0078] (2) Nitrogen-oxygen mixed gas was heated at 200 mL / min. -1 The flow rate of nitrogen is introduced into the plasma generator, the volume ratio of nitrogen to oxygen is 10:1, the current of the plasma generator is 5A and the voltage is 220V when the plasma generator is working, and nitrogen oxides are formed under the excitation of the plasma generator;

[0079] (3) The nitrogen oxide compound is introduced into a heated quartz tube, kept warm for 0.1 h, and cooled naturally to obtain the product.

[0080] Test example

[0081] Taking the materials prepared in Examples 1-3 and Comparative Examples 1-2 as examples, the performance and microstructure of the materials were measured, and they were used as electrocatalysts for oxygen evolution reaction to measure their working effects. Figure 1-12 .

[0082] Figure 1 This is the SEM photo of nickel foam. It can be seen that the surface of the untreated original nickel foam is smooth.

[0083] Figure 2 This is an SEM photo of the nickel foam after treatment in Example 1. It can be seen that the surface of the nickel foam is rough after treatment and is covered with new sheet materials, indicating that new materials are generated.

[0084] Figure 3 This is the SEM photo of foam iron. It can be seen that the surface of the untreated original foam iron is smooth.

[0085] Figure 4 This is a SEM photograph of the foamed iron after treatment in Example 2. It can be seen that the surface of the foamed iron is rough after treatment, which is conducive to increasing the specific surface area and further promoting the exposure of active sites.

[0086] Figure 5 This is an SEM photo of foamed cobalt. It can be seen that the surface of the foamed cobalt presents regular grooves after treatment.

[0087] Figure 6 This is the SEM photo of the cobalt foam after treatment in Example 3. It can be seen that the grooves have disappeared.

[0088] The increase in roughness and specific surface area is beneficial to the exposure of active sites.

[0089] Figure 7 This is the XRD pattern of the material obtained in Example 1. It can be seen that the nitric acid type nickel hydroxide phase appears in the sample obtained after treatment.

[0090] Figure 8 The Raman spectrum of the material obtained in Example 1 shows that the sample obtained after treatment has a Raman spectrum of 1000 cm -1 and 1030cm -1 A strong nitrate signal peak appeared.

[0091] Figure 9 The LSV curve of the material prepared in Example 1 when used for oxygen evolution reaction shows that the sample obtained after treatment has an LSV of 10 mA cm -2 The overpotential is 230mV.

[0092] Figure 10 The stability curve of the material prepared in Example 1 when used for oxygen evolution reaction shows that the sample obtained after treatment has a stability of 10 mA cm -2 It can run stably for 600h under the condition of

[0093] Figure 11 The LSV curve of the material prepared in Comparative Example 1 when used for oxygen evolution reaction shows that the sample obtained after treatment has an LSV of 10 mA cm -2 The overpotential is 330mV.

[0094] Figure 12 The LSV curve of the material prepared in Comparative Example 2 when used for oxygen evolution reaction shows that the sample obtained after treatment has an LSV of 10 mA cm -2 The overpotential is 302mV.

Claims

1. A method for preparing a nitrate chemically coordinated transition metal-based material, characterized in that: The following steps are involved: (1) Place the metal substrate in a heating container and heat it to 200-400°C; (2) introducing nitrogen and oxygen mixed gas into a plasma generator to excite and form nitrogen oxides; (3) The nitrogen oxide compound is introduced into a heating container, kept warm, and naturally cooled to obtain the product.

2. The method for preparing the nitrate chemically coordinated transition metal-based material according to claim 1, wherein: The metal substrate in step (1) includes Fe element, Ni element, Co element, NiFe alloy and NiCo alloy.

3. The method for preparing the nitrate chemically coordinated transition metal-based material according to claim 1, wherein: In step (1), the metal substrate is in the form of powder, film or foam.

4. The method for preparing the nitrate chemically coordinated transition metal-based material according to claim 1, wherein: The heating rate in step (1) is 5-10°C / min.

5. The method for preparing the nitrate chemically coordinated transition metal-based material according to claim 1, wherein: The volume ratio of nitrogen to oxygen in the nitrogen-oxygen mixed gas in step (2) is 1-10:1-10.

6. The method for preparing the nitrate chemically coordinated transition metal-based material according to claim 1, wherein: The flow rate of the nitrogen and oxygen mixed gas in step (2) is 200-600 mL / min -1 .

7. The method for preparing the nitrate chemically coordinated transition metal-based material according to claim 1, wherein: In step (2), the operating current of the plasma generator is 1-5A, and the operating voltage is 150-220V.

8. The method for preparing the nitrate chemically coordinated transition metal-based material according to claim 1, wherein: The heat preservation treatment time in step (3) is 0.2-3h.

9. A nitrate chemically coordinated transition metal-based material, characterized in that: Prepared by the method according to any one of claims 1 to 8.

10. Use of the nitrate chemically coordinated transition metal-based material according to claim 9 in the preparation of oxygen evolution electrocatalysts.

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