La-regulated crystalline / amorphous phase electrocatalytic oxygen evolution material and preparation method and application thereof

Abstract

The application relates to a La-regulated crystalline phase / amorphous phase electrocatalytic oxygen evolution material and a preparation method thereof. The material is formed through one-step microwave hydrothermal reaction of lanthanum nitrate hexahydrate, sodium molybdate dihydrate, iron nitrate nonahydrate, thioacetamide and water; the prepared high-activity electrode material (LaMoSFe@NF) with a crystalline phase / amorphous phase heterostructure more effectively utilizes the internal space of the nanomaterial by designing a unique catalyst structure, and the electrocatalytic oxygen evolution effect is improved.

Description

Technical Field

[0001] This invention relates to the field of electrochemical catalysis technology, specifically to a La-regulated crystalline / amorphous phase electrocatalytic oxygen evolution material, its preparation method, and its application in water electrolysis. Background Technology

[0002] With the increasing urgency of global energy structure transformation and the continued exacerbation of resource depletion and environmental problems caused by the overuse of fossil fuels, clean energy conversion technologies (such as water electrolysis for hydrogen production) have become a research focus. As one of the core reactions in the water electrolysis process, the oxygen evolution reaction (OER) has become a key bottleneck restricting overall energy efficiency due to its slow, multi-step electron transfer kinetics. Developing efficient electrocatalysts to reduce reaction overpotential is a core challenge for achieving the large-scale application of green hydrogen energy.

[0003] Currently, noble metal-based catalysts (such as Ir and Ru oxides) are considered benchmark materials for performance due to their unique electronic structure, exhibiting excellent catalytic activity and moderate intermediate adsorption capacity in OER processes. However, their scarcity leads to high costs, and structural instability under harsh reaction conditions severely limits their practical application prospects.

[0004] To overcome cost and stability limitations, researchers have turned to developing transition metal (Fe, Co, Ni, etc.)-based nanocatalysts. These materials, through multi-component compound systems such as oxides, phosphides, and sulfides, exhibit catalytic potential comparable to noble metals in alkaline media. However, existing materials generally face the contradiction of difficulty in synergistically improving activity and stability: highly active catalysts often suffer from decreased durability due to insufficient conductivity or chemical corrosion, while materials with excellent stability often have limited intrinsic activity. In addition, traditional synthesis methods usually rely on complex processes or extreme reaction conditions, which restricts the controllable preparation and large-scale application of these materials.

[0005] In recent years, the design of crystalline-amorphous heterostructures has provided a new direction for catalyst performance optimization. This structure achieves a synergistic improvement in catalytic activity and structural stability through the efficient charge transport of the crystalline phase and the abundant exposure of active sites in the amorphous phase. Theoretical studies have shown that electronic interactions at the two-phase interface can effectively regulate the adsorption behavior of reaction intermediates, thereby reducing the kinetic energy barrier. However, existing synthetic strategies are limited by the differences in nucleation and growth mechanisms between the crystalline and amorphous phases, making it difficult to achieve the controllable construction of high-density interfaces, resulting in the utilization rate of active sites falling far short of theoretical expectations.

[0006] Therefore, it is necessary to develop a simple and rapid synthesis method to prepare an efficient and stable oxygen evolution electrocatalyst for water electrolysis. Summary of the Invention

[0007] The purpose of this invention is to provide a highly efficient, highly active, and highly stable electrocatalytic oxygen evolution reaction (OER) material. This material's morphology is controlled by the element La, resulting in a unique layered stacked structure of a crystalline / amorphous heterojunction. This structure combines the high conductivity of the crystalline phase with the abundant unsaturated coordination of the amorphous phase. The crystalline phase promotes electron transfer, while the abundant unsaturated coordination of the amorphous phase provides rich OER active sites. Another objective of this invention is to provide a method for preparing the aforementioned crystalline / amorphous heterostructure electrocatalytic OER material. This method, through a low-energy synthesis process, a short-cycle reaction pathway, and controllable interface engineering, solves the problems of high energy consumption, cumbersome steps, and insufficient interface density in traditional heterostructure preparations, providing technical support for the large-scale production of highly active and stable OER catalysts.

[0008] The above-mentioned objective of this invention is achieved through the following technical solution:

[0009] A La-regulated crystalline / amorphous electrocatalytic oxygen evolution material is characterized by being formed by a one-step microwave hydrothermal reaction of lanthanum nitrate hexahydrate, sodium molybdate dihydrate, ferric nitrate nonahydrate, thioacetamide, and water.

[0010] To further clarify, the above-mentioned lanthanum nitrate hexahydrate 0.0052g, sodium molybdate dihydrate 0.0484g, ferric nitrate nonahydrate 0.0404g, thioacetamide 0.0152g, and water 15mL are present.

[0011] This invention uses the above-mentioned materials to synthesize a crystalline / amorphous phase electrocatalytic oxygen evolution material through a one-step microwave hydrothermal method. Specifically, it is a La-regulated crystalline / amorphous phase heterostructure electrode material (LaMoSFe@NF) with a layered stacked structure, which is used as a working electrode for the anodic electrocatalytic oxygen evolution reaction.

[0012] The preparation method of the above-mentioned crystalline / amorphous electrocatalytic oxygen evolution material is characterized by comprising the following preparation steps:

[0013] Take the above-mentioned amounts of lanthanum nitrate hexahydrate, sodium molybdate dihydrate, ferric nitrate nonahydrate, thioacetamide, and water, and carry out a one-step microwave hydrothermal reaction at 100°C for 5 minutes.

[0014] As a further optimization, the preparation method of the above-mentioned crystalline / amorphous electrocatalytic oxygen evolution material is characterized by including the following preparation steps:

[0015] (1) Pretreatment of nickel foam

[0016] Cut the nickel foam into pieces of 1cm×2cm×0.1cm, then soak them in 3mol / L hydrochloric acid solution for 1 hour, and then sonicate them in acetone, ethanol, and ultrapure water for 15 minutes each.

[0017] (2) Microwave hydrothermal reaction

[0018] Take the above-mentioned amounts of lanthanum nitrate hexahydrate, sodium molybdate dihydrate, ferric nitrate nonahydrate, and thioacetamide, respectively, and dissolve them in 15 mL of ultrapure water. Stir until completely dissolved to obtain a mixed solution. Transfer the obtained mixed solution and the pretreated nickel foam to a microwave reaction flask for microwave-assisted hydrothermal reaction at a reaction temperature of 100 °C for 5 min. After the reaction, cool to room temperature, rinse the material repeatedly with ethanol and deionized water, and finally dry it in a vacuum drying oven.

[0019] The present invention has the following beneficial effects:

[0020] 1. The La-regulated crystalline / amorphous electrocatalytic oxygen evolution material provided by this invention is specifically a La-regulated crystalline / amorphous heterostructure electrode material (LaMoSFe@NF) with high OER performance and a layered stacked structure. By regulating the catalyst morphology with La, this unique structure not only exposes more active sites and facilitates electron transfer, but also facilitates the removal of oxygen generated during the reaction, thereby improving the catalyst stability.

[0021] 2. The morphology of this crystalline / amorphous phase electrocatalytic oxygen evolution material is controlled by rare earth element La, and a heterostructure is formed by using inexpensive transition metals and molybdenum disulfide, with Fe existing in the amorphous phase, forming a unique heterostructure. This not only improves the activity of the catalyst, but also reduces the production cost of the oxygen evolution electrocatalyst.

[0022] 3. The synthesis method of the La-regulated crystalline / amorphous electrocatalytic oxygen evolution material provided by this invention has advantages such as low-energy synthesis process, short-cycle reaction path, and controllable interface engineering. It has few synthesis steps, requiring only one step, and exhibits an extremely fast reaction rate (5 min). Microwave radiation, as a non-traditional heat source, demonstrates significant advantages in the field of controllable synthesis of nanomaterials due to its instantaneous heating, uniform energy distribution, and green synthesis characteristics. Attached Figure Description

[0023] Figure 1The images are SEM images of LaMoSFe@NF prepared in Example 1 of this invention, and MoSFe@NF, LaSFe@NF, LaMoFe@NF and LaMoS@NF prepared in Comparative Examples 1 and 2, respectively, under a scanning electron microscope; wherein, (a) and (b) correspond to LaMoSFe@NF, (c) corresponds to MoSFe@NF, (d) corresponds to LaSFe@NF, (e) corresponds to LaMoFe@NF, and (f) corresponds to LaMoS@NF.

[0024] Figure 2 This is a TEM image of LaMoSFe@NF prepared in Example 1 of the present invention under a transmission electron microscope.

[0025] Figure 3 This is an HRTEM image of LaMoSFe@NF prepared in Example 1 of the present invention under a high-resolution transmission electron microscope.

[0026] Figure 4 The image shows the HAADF-STEM image and corresponding elemental mapping of LaMoSFe@NF prepared in Example 1 of this invention under a high-resolution transmission electron microscope.

[0027] Figure 5 The image shows the XRD pattern of LaMoSFe@NF prepared in Example 1 of this invention.

[0028] Figure 6 The polarization curves of LaMoSFe@NF prepared in Example 1 of the present invention, and LaMoSFe@NF, MoSFe@NF, LaSFe@NF, LaMoFe@NF and LaMoS@NF prepared in Comparative Examples 1 and 2, in alkaline media.

[0029] Figure 7 The cyclic voltammetry curves of LaMoSFe@NF prepared in Example 1 of this invention in alkaline medium at different scan rates (20, 40, 60, 80, 100 mV / s).

[0030] Figure 8 The current density-scan rate comparison graphs of LaMoSFe@NF prepared in Example 1 of the present invention, and LaMoSFe@NF, MoSFe@NF, LaSFe@NF, LaMoFe@NF and LaMoS@NF prepared in Comparative Examples 1 and 2 in alkaline media.

[0031] Figure 9 Impedance diagrams of LaMoSFe@NF prepared in Example 1 of the present invention, and LaMoSFe@NF, MoSFe@NF, LaSFe@NF, LaMoFe@NF and LaMoS@NF prepared in Comparative Examples 1 and 2 in alkaline media.

[0032] Figure 10 The current-time curve of LaMoSFe@NF prepared in Example 1 of this invention in an alkaline medium is shown. Detailed Implementation

[0033] The present invention will be specifically described below through embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above description.

[0034] Example 1

[0035] A method for preparing a La-regulated crystalline / amorphous electrocatalytic oxygen evolution material includes the following preparation steps:

[0036] Take 0.0052 g of lanthanum nitrate hexahydrate, 0.0484 g of sodium molybdate dihydrate, 0.0404 g of ferric nitrate nonahydrate, 0.0152 g of thioacetamide and 15 mL of water respectively, and carry out a one-step microwave hydrothermal reaction at 100 °C for 5 min.

[0037] This invention synthesizes a La-modulated electrode material (LaMoSFe@NF) with a crystalline / amorphous phase structure via a one-step microwave hydrothermal method, which can be used as a working electrode for efficient electrocatalytic oxygen evolution.

[0038] Example 2

[0039] A method for preparing a La-regulated crystalline / amorphous electrocatalytic oxygen evolution material includes the following preparation steps:

[0040] (1) Pretreatment of nickel foam

[0041] Cut the nickel foam into pieces of 1cm×2cm×0.1cm, then soak them in 3mol / L hydrochloric acid solution for 1 hour, and then sonicate them in acetone, ethanol, and ultrapure water for 15 minutes each.

[0042] (2) Microwave hydrothermal reaction

[0043] Take 0.0052 g of lanthanum nitrate hexahydrate, 0.0484 g of sodium molybdate dihydrate, 0.0404 g of ferric nitrate nonahydrate, and 0.0152 g of thioacetamide, respectively, and dissolve them in 15 mL of ultrapure water. Stir until completely dissolved to obtain a mixed solution. Transfer the obtained mixed solution and the pretreated nickel foam to a microwave reaction flask for microwave-assisted hydrothermal reaction at 100 °C for 5 min. After the reaction, cool to room temperature, rinse the material repeatedly with ethanol and deionized water, and finally dry it overnight in a vacuum drying oven.

[0044] Comparative Example 1

[0045] A method for preparing an electrocatalytic hydrogen evolution material (MoSFe@NF) includes the following preparation steps:

[0046] Nickel foam was cut into pieces measuring 1cm × 2cm × 0.1cm and then soaked in 3mol / L hydrochloric acid solution for 1 hour. It was then sonicated in acetone, ethanol, and ultrapure water for 15 minutes each. 0.0484g of sodium molybdate dihydrate, 0.0404g of ferric nitrate nonahydrate, and 0.0152g of thioacetamide were dissolved in 15mL of ultrapure water and stirred until completely dissolved. The resulting mixed solution and the treated nickel foam were transferred to a microwave-assisted hydrothermal reaction flask and subjected to a microwave-assisted hydrothermal reaction at 100℃ for 5 minutes. After the reaction, the mixture was cooled to room temperature and rinsed repeatedly with ethanol and deionized water, then dried overnight in a vacuum drying oven.

[0047] Comparative Example 2

[0048] A method for preparing an electrocatalytic oxygen evolution material (LaSFe@NF) includes the following preparation steps:

[0049] Nickel foam was cut into pieces measuring 1cm × 2cm × 0.1cm and then soaked in 3mol / L hydrochloric acid solution for 1 hour. It was then sonicated in acetone, ethanol, and ultrapure water for 15 minutes each. 0.0052g of lanthanum nitrate hexahydrate, 0.0404g of ferric nitrate nonahydrate, and 0.0152g of thioacetamide were dissolved in 15mL of ultrapure water and stirred until completely dissolved. The resulting mixed solution and the treated nickel foam were transferred to a microwave-assisted hydrothermal reaction flask and subjected to a microwave-assisted hydrothermal reaction at 100℃ for 5 minutes. After the reaction, the mixture was cooled to room temperature and rinsed repeatedly with ethanol and deionized water, then dried overnight in a vacuum drying oven.

[0050] Comparative Example 3

[0051] A method for preparing an electrocatalytic oxygen evolution material (LaMoFe@NF) includes the following preparation steps:

[0052] Nickel foam was cut into pieces measuring 1cm × 2cm × 0.1cm and then soaked in 3mol / L hydrochloric acid solution for 1 hour. It was then sonicated in acetone, ethanol, and ultrapure water for 15 minutes each. 0.0052g of lanthanum nitrate hexahydrate, 0.0484g of sodium molybdate dihydrate, and 0.0404g of ferric nitrate nonahydrate were dissolved in 15mL of ultrapure water and stirred until completely dissolved. The resulting mixed solution and the treated nickel foam were transferred to a microwave-assisted hydrothermal reaction flask and subjected to a microwave-assisted hydrothermal reaction at 100℃ for 5 minutes. After the reaction, the mixture was cooled to room temperature and rinsed repeatedly with ethanol and deionized water, then dried overnight in a vacuum drying oven.

[0053] Comparative Example 4

[0054] A method for preparing an electrocatalytic oxygen evolution material (LaMoS@NF) includes the following preparation steps:

[0055] Nickel foam was cut into pieces measuring 1cm × 2cm × 0.1cm and then soaked in 3mol / L hydrochloric acid solution for 1 hour. It was then sonicated in acetone, ethanol, and ultrapure water for 15 minutes each. 0.0052g of lanthanum nitrate hexahydrate, 0.0484g of sodium molybdate dihydrate, and 0.0152g of thioacetamide were dissolved in 15mL of ultrapure water and stirred until completely dissolved. The resulting mixed solution and the treated nickel foam were transferred to a microwave-assisted hydrothermal reaction flask and subjected to a microwave-assisted hydrothermal reaction at 100℃ for 5 minutes. After the reaction, the mixture was cooled to room temperature and rinsed repeatedly with ethanol and deionized water, then dried overnight in a vacuum drying oven.

[0056] The present invention also conducted the following oxygen evolution performance test experiments:

[0057] Preparation of alkaline electrocatalytic oxygen evolution using LaMoSFe@NF electrode material (all of which were prepared in Example 1) as the working electrode: The oxygen evolution performance in alkaline medium was tested using a three-electrode system consisting of 1 mol / L KOH as the electrolyte, a carbon rod as the counter electrode, a mercury / mercury oxide electrode as the reference electrode, and LaMoSFe@NF electrode material as the working electrode.

[0058] (1) The morphology of the synthesized LaMoSFe@NF, MoSFe@NF, LaSFe@NF, LaMoFe@NF and LaMoS@NF was characterized by scanning electron microscopy (SEM):

[0059] Depend on Figure 1SEM images a and b show that the LaMoSFe@NF catalyzed by La exhibits a "stepped" structure with obvious "gaps" between the structures. This structure is beneficial for promoting the electron transfer rate and improving the stability of the catalyst during the catalytic reaction. The "gaps" also facilitate the timely release of oxygen during the reaction, further enhancing the catalyst's stability. Figure 1 The SEM image of MoSFe@NF c shows that the catalyst without La regulation has a bud-like structure, with many active sites covered, leading to reduced catalytic activity. Figure 1 As can be seen from d, LaSFe@NF has a nanorod structure, while LaMoFe@NF ( Figure 1 e) then has no clear structure. Figure 1 As can be seen from f, the catalyst exhibits a nanosheet structure in the absence of an Fe source. Therefore, it can be concluded that the catalyst has a small specific surface area in the absence of Mo, S, and Fe sources, respectively, and that Mo, S, and Fe play indispensable roles in this catalyst.

[0060] (2) The obtained LaMoSFe@NF was characterized using transmission electron microscopy (TEM):

[0061] like Figure 2 As shown, LaMoSFe@NF exhibits a layered stacked structure.

[0062] (3) LaMoSFe@NF was characterized using high-resolution transmission electron microscopy (HRTEM):

[0063] Depend on Figure 3 As can be seen, the lattice spacing of 0.301 nm corresponds to the (0 0 6) crystal plane of MoS2, and the lattice spacing of 0.242 nm belongs to the (-3 1 7) crystal plane of NiSO4·6H2O. MoS2 and NiSO4·6H2O are adjacent and form a heterostructure interface. This can be determined by... Figure 3 The TEM image of b shows that the catalyst exhibits a crystalline / amorphous heterojunction. The formation of this heterojunction can induce abundant surface defects and coordinated unsaturated sites, thereby increasing the exposure of active sites. For example... Figure 4 As shown, the elemental mapping diagram clearly confirms that Fe, S, Mo, Ni, and O elements are uniformly distributed in LaMoSFe@NF, and the presence of La elements is not observed, proving that La only plays a role in regulating morphology.

[0064] (4) Characterization of the synthesized materials using X-ray diffraction (XRD):

[0065] like Figure 5As shown, the XDR characteristic diffraction peaks match very well with NiSO4·6H2O and Ni. 52.0° and 60.9° correspond to the (1 1 1) and (2 0 0) crystal planes of Ni:PDF#87-0712, respectively, while 17.6°, 18.9°, 20.9°, 23.5°, 25.8°, 28.5°, and 36.0° correspond to the (1 1 0), (-1 1 2), (-1 1 3), (-1 1 4), (11 4), (0 2 0), and (-2 2 2) crystal planes of NiSO4·6H2O:PDF#79-0189, respectively. No Fe-related peaks were observed, suggesting that the Fe phase may exist in an amorphous form. The MoS2 peak is not prominent, possibly due to its low content and amorphous characteristics.

[0066] (5) The polarization curves of the different prepared materials in alkaline medium were tested:

[0067] like Figure 6 As shown, polarization curves of different materials were tested in a 1 mol / L KOH electrolyte. Calculations revealed that LaMoSFe@NF exhibits the highest polarization at 10 mA / cm². -2 The overpotential of LaMoSFe@NF is 200mV, which is lower than that of MoSFe@NF (230mV), LaSFe@NF (290mV), LaMoFe@NF (240mV) and LaMoS@NF (330mV). LaMoSFe@NF has an overpotential of 100mA cm⁻¹. -2 The overpotential is only 310mV, demonstrating excellent OER performance.

[0068] (6) The cyclic voltammetry (CV) curves and current density-scan rate of the material were tested:

[0069] like Figure 7 The figure shows the cyclic voltammetry curves of the LaMoSFe@NF electrode material at scan rates of 20-100 mV / s, using 1 mol / L KOH as the electrolyte. Electrochemical double-layer capacitance (C0) is also applied. dl The electrochemically active surface area (ECSA) of these materials was studied. Figure 8 The current density-scan rate plot in the alkaline medium is shown in the figure. The Cdl value of LaMoSFe@NF is 36.8 mFcm. -2 Higher than MoSFe@NF (1.26mF cm) -2 ), LaSFe@NF(2.25mF cm -2 ), LaMoFe@NF(0.33mF cm -2 ) and LaMoS@NF(0.78mF cm -2This indicates that LaMoSFe@NF has more active sites and better catalytic activity.

[0070] (7) The electrochemical impedance of the different prepared materials was tested;

[0071] Figure 9 The figure shows the electrochemical impedance spectroscopy in an alkaline medium. It can be seen that LaMoSFe@NF has a small charge transfer resistance and a fast charge transfer kinetics.

[0072] (8) Stability testing of LaMoSFe@NF electrode material;

[0073] Figure 10 For LaMoSFe@NF in 1 mol L -1 In KOH solution at a current density of 100 mA cm⁻¹ -2 Under the specified conditions, the long-term electrocatalytic stability test curves of LaMoSFe@NF were obtained. The current density remained basically stable within 90 h, demonstrating that LaMoSFe@NF exhibits good stability in the electrocatalytic oxygen evolution process.

Claims

1. A La-modulated crystalline / amorphous phase electrocatalytic oxygen evolution material, characterized in that: It is formed by a one-step microwave hydrothermal reaction of lanthanum nitrate hexahydrate, sodium molybdate dihydrate, ferric nitrate nonahydrate, thioacetamide, and water.

2. The La-modulated crystalline / amorphous phase electrocatalytic oxygen evolution material as described in claim 1, characterized in that: The composition of the ingredients is as follows: 0.0052 g of lanthanum nitrate hexahydrate, 0.0484 g of sodium molybdate dihydrate, 0.0404 g of ferric nitrate nonahydrate, 0.0152 g of thioacetamide, and 15 mL of water.

3. The preparation method of the La-controlled crystalline / amorphous phase electrocatalytic oxygen evolution material as described in claim 1 or 2, characterized in that, The preparation steps include the following: taking the specified amounts of lanthanum nitrate hexahydrate, sodium molybdate dihydrate, ferric nitrate nonahydrate, thioacetamide, and water, and performing a one-step microwave hydrothermal reaction at 100°C for 5 minutes.

4. The preparation method of the La-controlled crystalline / amorphous phase electrocatalytic oxygen evolution material as described in claim 1 or 2, characterized in that, The preparation steps include the following: (1) Pretreatment of nickel foam Cut the nickel foam into pieces of 1cm×2cm×0.1cm, then soak them in 3mol / L hydrochloric acid solution for 1 hour, and then sonicate them in acetone, ethanol, and ultrapure water for 15 minutes each. (2) Microwave hydrothermal reaction The amounts of lanthanum nitrate hexahydrate, sodium molybdate dihydrate, ferric nitrate nonahydrate, and thioacetamide were respectively dissolved in 15 mL of ultrapure water and stirred until completely dissolved to obtain a mixed solution. The resulting mixed solution and the pretreated nickel foam were transferred to a microwave reaction flask for microwave-assisted hydrothermal reaction at 100 °C for 5 min. After the reaction, the mixture was cooled to room temperature and then rinsed repeatedly with ethanol and deionized water, and finally dried in a vacuum drying oven.

5. The application of the La-modulated crystalline / amorphous phase electrocatalytic oxygen evolution material as described in claim 1 or 2 in electrocatalytic oxygen evolution in alkaline media.

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