Preparation method and application of rough nanosheet Co (OH) 2-WO3 / CC heterogeneous composite material

Abstract

The invention discloses a preparation method and application of a coarse nanosheet Co (OH) 2-WO3 / CC heterogeneous composite material, and relates to the technical field of electro-catalytic materials. The preparation method comprises the following steps: firstly, growing a ZIF-67 precursor on carbon cloth (CC) through an impregnation method to obtain ZIF-67 / CC; and soaking the ZIF-67 / CC in a Na2WO4 solution, and heating and etching the ZIF-67 / CC to obtain the Co (OH) 2-WO3 / CC heterogeneous composite material. The Co (OH) 2-WO3 / CC heterogeneous composite material has excellent electro-catalysis oxygen evolution performance and good full water decomposition performance under the alkaline condition, shows excellent conductivity and good stability, can be used as an excellent catalyst for electro-catalysis oxygen evolution reaction, and has certain practical application potential. The preparation method disclosed by the invention is very simple, short in preparation process and convenient for commercial popularization.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic materials technology, and in particular to a method for preparing and applying a rough nanosheet Co(OH)2-WO3 / CC heterocomposite material. Background Technology

[0002] With the continued growth of global energy demand and the increasing severity of environmental problems, the development of clean and efficient renewable energy technologies has become a current research hotspot. Hydrogen energy, due to its high energy density and zero carbon emissions, is considered an important component of the future energy system. Electrocatalytic water splitting technology can utilize electricity generated from renewable energy sources such as wind and solar power to achieve green hydrogen production and is considered one of the most promising hydrogen production methods. However, the oxygen evolution reaction (OER) is a four-electron transfer process. Due to its slow kinetics and high reaction overpotential, the overall efficiency of water splitting is severely reduced, limiting the large-scale application of this technology.

[0003] Currently, noble metal-based catalysts (such as IrO2 and RuO2) remain the most efficient OER electrocatalysts. However, these materials suffer from drawbacks such as resource scarcity, high cost, and insufficient stability, which greatly limit their industrial application. Therefore, developing efficient, stable, and inexpensive non-noble metal OER catalysts has become a key research focus.

[0004] Metal-organic frameworks (MOFs) have shown great potential in electrocatalysis due to their tunable pore structure and abundant active sites. ZIF-67, in particular, provides an ideal platform for constructing high-performance catalysts due to its unique self-templating properties. However, MOFs generally suffer from poor conductivity and insufficient stability. Therefore, it is essential to modify MOFs and develop MOF-like materials with better conductivity and OER catalytic activity. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing and applying a rough nanosheet Co(OH)2-WO3 / CC heterocomposite material, in order to solve the above-mentioned problems existing in the prior art.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] One of the technical solutions of the present invention: a method for preparing a rough nanosheet Co(OH)2-WO3 / CC heterocomposite material, comprising the following steps:

[0008] ZIF-67 precursor was first grown on carbon cloth (CC) by impregnation to obtain ZIF-67 / CC; then, ZIF-67 / CC was immersed in Na2WO4 solution and etched by heating to obtain the rough nanosheet Co(OH)2-WO3 / CC heterocomposite material.

[0009] This invention constructs a rough nanosheet Co(OH)2-WO3 heterocomposite material on carbon cloth in situ using impregnation and chemical etching methods, utilizing W 6+ The high-valence empty orbitals effectively modulate the electronic structure of the Co active center, significantly improving charge transfer efficiency and optimizing the adsorption energy of oxygen-containing intermediates. This composite material exhibits excellent OER and superior stability under alkaline conditions.

[0010] The advantage of using Na2WO4 solution for etching in this invention is that it selectively removes material through chemical means to construct the target structure, regulates the surface morphology of the material, and thus optimizes the physicochemical properties of the material, thereby significantly improving the specific surface area, conductivity, and catalytic activity of the catalyst.

[0011] Furthermore, the growth of ZIF-67 precursor on carbon cloth by impregnation method includes: impregnating pretreated carbon cloth in a precursor solution to grow ZIF-67 precursor on carbon cloth in situ, thereby obtaining ZIF-67 / CC.

[0012] Furthermore, the preparation steps of the precursor solution include: dissolving the cobalt source and the organic ligand in water respectively to obtain a cobalt source solution and an organic ligand solution; and adding the organic ligand solution dropwise into the Co source solution to obtain the precursor solution.

[0013] Furthermore, the cobalt source includes Co(NO3)2 or a hydrate of Co(NO3)2.

[0014] Furthermore, the organic ligand includes 2-methylimidazole.

[0015] Furthermore, the mass ratio of the cobalt source to the organic ligand is 0.6568:0.4656.

[0016] Furthermore, the ratio of the cobalt source to water is 0.6568g:20mL.

[0017] Furthermore, the ratio of the organic ligand to water is 0.4656 g: 20 mL.

[0018] Furthermore, the impregnation reaction is carried out at a temperature of 20-30°C (i.e., room temperature) for 6 hours.

[0019] Furthermore, the temperature of the impregnation reaction is preferably 25°C.

[0020] Preferably, the carbon cloth stands upright in the precursor solution.

[0021] Carbon cloth has good stretchability and flexibility, and is resistant to high temperatures. Its skeleton will not be destroyed under extreme conditions, making it suitable for use as a base for Co(OH)2-WO3.

[0022] Further, the pretreatment includes: heating the carbon arrangement in a nitric acid solution, followed by ultrasonic washing in water and anhydrous ethanol in sequence.

[0023] Optionally, the nitric acid solution is prepared by mixing concentrated nitric acid and water in a volume ratio of 3:5.

[0024] Optionally, the heat treatment is performed at a temperature of 100°C for 10 hours.

[0025] Furthermore, the etching temperature was 80°C and the etching time was 1 hour.

[0026] Furthermore, the Na2WO4 solution is prepared by mixing Na2WO4·2H2O with water at a ratio of 0.05-0.25g:10mL.

[0027] Preferably, the Na2WO4 solution is prepared by mixing Na2WO4·2H2O and water in a ratio of 0.15g:10mL.

[0028] The reason why this invention chose Na2WO4 solution as the etching solution is because it uses high-cost W 6+ Etching has the following advantages:

[0029] (1) Morphology controllability: The ZIF-67 framework is precisely etched through competitive coordination reaction to form staggered rough nanosheets, which significantly improves the specific surface area of ​​the catalyst; the nanosheets cross to form interconnected channels to accelerate electrolyte penetration and bubble release; (2) Interface synergy: WO4 2- With Co 2+ The reaction simultaneously generates WO3 and Co(OH)2, forming a tight interface. The synergistic effect significantly reduces the Tafel slope, lowers the charge transfer impedance, and improves the catalytic rate; (3): Electronic regulation: W 6+ The empty 5d orbital optimization of the Co site d band center reduces the adsorption energy barrier of *OOH and accelerates the reaction efficiency; (4): Availability: Sodium tungstate has abundant mineral reserves and mature industrial production technology. The supply chain is stable, and its cost-effectiveness and availability are significantly better than most rare metal compounds, making it economical and affordable.

[0030] This invention synthesizes rough nanosheet Co(OH)2-WO3 / CC heterocomposite materials by combining a room-temperature impregnation method with a mild chemical etching method. The preparation method has the following advantages:

[0031] (1) Cost-effective: Sodium tungstate is used to replace precious metals and low-temperature process is used instead of high-temperature annealing, which greatly reduces the cost; (2) Precise structure: Self-template is precisely etched to form interlaced rough nanosheets, which increases the specific surface area of ​​the catalyst and optimizes the catalytic performance; (3) Convenient application: The catalyst is directly grown on the surface of carbon cloth, avoiding the use of binders, and the mechanical strength and electrochemical durability of the catalyst are improved simultaneously.

[0032] The second technical solution of the present invention: a rough nanosheet Co(OH)2-WO3 / CC heterocomposite material prepared according to the above-mentioned preparation method of rough nanosheet Co(OH)2-WO3 / CC heterocomposite material.

[0033] The rough nanosheet Co(OH)2-WO3 / CC heterocomposite material of the present invention exhibits excellent electrocatalytic oxygen evolution performance and good total water splitting performance under alkaline conditions, and also shows excellent conductivity and good stability. It can be used as an excellent catalyst for electrocatalytic oxygen evolution reaction and has certain practical application potential.

[0034] The third technical solution of the present invention: the application of the above-mentioned rough nanosheet Co(OH)2-WO3 / CC heterocomposite material in the electrocatalytic oxygen evolution reaction.

[0035] Furthermore, the rough nanosheet Co(OH)2-WO3 / CC heterocomposite material is used as a catalyst for the electrocatalytic oxygen evolution reaction.

[0036] The fourth technical solution of the present invention: the application of the above-mentioned rough nanosheet Co(OH)2-WO3 / CC heterocomposite material in hydrogen production by total water splitting.

[0037] Furthermore, the rough nanosheet Co(OH)2-WO3 / CC heterocomposite material is used as an electrode (anode) in the electrocatalytic oxygen evolution reaction system.

[0038] The present invention discloses the following technical effects:

[0039] (1) This invention constructs a rough nanosheet Co(OH)2-WO3 heterocomposite material on carbon cloth in situ using impregnation and chemical etching methods, utilizing W 6+ The high-valence empty orbitals effectively modulate the electronic structure of the Co active center, significantly improving charge transfer efficiency and optimizing the adsorption energy of oxygen-containing intermediates. This composite material exhibits excellent OER and superior stability under alkaline conditions. In total water splitting, electrolyzers assembled with it as the anode also demonstrate excellent total water splitting performance and good stability, indicating that it can serve as a highly efficient and stable electrocatalytic catalyst for oxygen evolution and total water splitting, possessing practical application potential.

[0040] (2) The preparation method of this invention is simple and low-cost. This invention achieves morphology control and heterostructure construction in one step via hydrothermal treatment at 80℃ for 1 hour, realizing one-step etching and phase formation, avoiding the high-temperature annealing or multi-step reactions required by traditional methods. Simultaneously, it uses economical and efficient sodium tungstate to replace expensive precious metals, significantly reducing raw material costs. The self-supporting electrode prepared by this invention does not require a binder, significantly simplifying the device integration process. This method not only greatly shortens the preparation cycle but also has excellent potential for large-scale production, providing strong technical support for the commercialization and promotion of green hydrogen production technology. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 X-ray powder diffraction patterns of x Co(OH)2-WO3 / CC heterocomposites (b) prepared in Examples 2-6 and ZIF-67 / CC (a) prepared in Example 1.

[0043] Figure 2 Scanning electron microscope images of the x Co(OH)2-WO3 / CC heterocomposites prepared in Examples 2-6 and the ZIF-67 / CC prepared in Example 1, wherein (a) is the ZIF-67 / CC prepared in Example 1; (b) is the 0.05Co(OH)2-WO3 / CC prepared in Example 2; (c) is the 0.1Co(OH)2-WO3 / CC prepared in Example 3; (d) is the 0.15Co(OH)2-WO3 / CC prepared in Example 4; (e) is the 0.2Co(OH)2-WO3 / CC prepared in Example 5; and (f) is the 0.25Co(OH)2-WO3 / CC prepared in Example 6.

[0044] Figure 3 The microstructure and composition of the 0.15Co(OH)2-WO3 / CC heterocomposite material prepared in Example 4 are characterized, wherein (a) is a transmission electron microscope image; (b) is a high-resolution transmission electron microscope image; (c) is the corresponding lattice spacing distribution image of the dashed area in the high-resolution transmission electron microscope image; and (d)-(f) are the corresponding elemental mapping images.

[0045] Figure 4The contact angle test diagrams are of the ZIF-67 / CC heterocomposite material prepared in Example 1 and the 0.15Co(OH)2-WO3 / CC heterocomposite material prepared in Example 4, wherein (a) is the ZIF-67 / CC prepared in Example 1; and (b) is the 0.15Co(OH)2-WO3 / CC prepared in Example 4.

[0046] Figure 5 The images show various X-ray photoelectron spectra of the 0.15Co(OH)2-WO3 / CC heterocomposite material prepared in Example 4, where (a) is the full XPS spectrum; and (b)-(d) are high-resolution X-ray photoelectron spectra of the Co 2p, W 4f and O1s regions, respectively.

[0047] Figure 6 The electrochemical performance of the x Co(OH)2-WO3 / CC heterocomposites prepared in Examples 2-6, the ZIF-67 / CC prepared in Example 1, the RuO2 / CC prepared in Comparative Example 1, and other existing catalysts are compared in 1.0 M KOH. (a) shows the linear sweep curve of the electrocatalytic oxygen evolution reaction; (b) shows the Tafel slope plot; and (c) shows the electrochemical performance of the 0.15 Co(OH)2-WO3 / CC prepared in Example 4 compared to the catalyst reported in the prior art at a current density of 10 mA cm⁻¹. -2 Comparison of overpotential and Tafel slope at time; (d)-(g) are the electrochemical impedance spectra (d) and double-layer capacitance (C) of the xCo(OH)2-WO3 / CC heterocomposite materials prepared in Examples 2-6 and the ZIF-67 / CC prepared in Example 1, respectively. dl Figure (e), bar chart of electrochemical active area (f), curve of turnover frequency as a function of overpotential (g); (h) shows the 0.15Co(OH)2-WO3 / CC prepared in Example 4 at 10 mA cm⁻¹ -2 The timing potential test diagram below.

[0048] Figure 7 Cyclic voltammetry curves of x Co(OH)2-WO3 / CC heterocomposites prepared in Examples 2-6 and ZIF-67 / CC prepared in Example 1 in the non-Radida potential range are shown, where (a) is ZIF-67 / CC prepared in Example 1; (b)-(f) are x Co(OH)2-WO3 / CC prepared in Examples 2-6, respectively.

[0049] Figure 8 The diagram illustrates the complete water splitting process and results, where (a) is a schematic diagram of the complete water splitting in a two-electrode system; and (b) is a diagram of the two-electrode system Co(OH)2-WO3 / CC. (+) ||Pt / C / CC (-) and RuO2 / CC (+)||Pt / C / CC (-) Polarization curves in 1.0 M KOH; (c) shows the two-electrode system Co(OH)2-WO3 / CC. (+) ||Pt / C / CC (-) (i.e., This work) compares with existing reports of fully water-splitting batteries at 10 mA cm⁻¹. -2 Voltage comparison under current density; (d) is the two-electrode system Co(OH)2-WO3 / CC (+) ||Pt / C / CC (-) At 100mAcm -2 Stability test results under current density. Detailed Implementation

[0050] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0051] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0052] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0053] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0054] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0055] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0056] In specific embodiments of the present invention, room temperature or normal temperature refers to 20-30℃.

[0057] Unless otherwise specified, all raw materials used in the specific embodiments of this invention are commercially available products.

[0058] In the following examples, the Co(OH)2-WO3 / CC heterocomposite materials prepared are denoted as x Co(OH)2-WO3 / CC according to the different masses of Na2WO4·2H2O used during etching (where x represents the mass of Na2WO4·2H2O).

[0059] Example 1

[0060] ZIF-67 / CC was prepared by a room-temperature impregnation method, and the steps are as follows:

[0061] (1) Pretreatment of carbon cloth (CC): First, cut the CC into 1.0×1.5cm pieces. 2 Size. Then, place it in 24 mL of nitric acid solution (prepared by mixing 98 wt% concentrated nitric acid and deionized water in a 3:5 volume ratio) and heat at 100 °C for 10 h. After cooling, the treated CC is ultrasonically washed sequentially in deionized water and anhydrous ethanol for 15 min each, repeated three times. Finally, air dry for later use.

[0062] (2) Precursor synthesis: First, 0.6568 g of Co(NO3)2·6H2O was dissolved in 20 mL of deionized water to obtain a Co source solution. Simultaneously, 0.4656 g of C4H6N2 was weighed and dissolved in 20 mL of deionized water to obtain an organic ligand solution. Then, the organic ligand solution was slowly added dropwise to the Co source solution, causing the solution to change from transparent pink to purple. The mixture was then slowly stirred for 5 min to obtain the precursor solution. Finally, the pretreated CC was placed upright in the above precursor solution and allowed to stand at room temperature for 6 h to grow ZIF-67 nanosheet precursors in situ on the CC. After the reaction was complete, the product was removed and dried to obtain ZIF-67 / CC.

[0063] Example 2

[0064] Rough nanosheet Co(OH)2-WO3 / CC heterocomposite material was prepared by low-temperature heating etching, and the steps are as follows:

[0065] Weigh 0.05 g of Na2WO4·2H2O and dissolve it in 10 mL of deionized water to obtain a Na2WO4 solution. Place the ZIF-67 / CC composite material prepared in Example 1 into the above Na2WO4 solution and heat it at 80 °C for 1 h for etching. After the etching is completed, remove the product and air dry it to obtain a Co(OH)2-WO3 / CC heterocomposite material (denoted as 0.05Co(OH)2-WO3 / CC).

[0066] Example 3

[0067] Rough nanosheet Co(OH)2-WO3 / CC heterocomposite material was prepared by low-temperature heating etching, and the steps are as follows:

[0068] Weigh 0.10 g of Na2WO4·2H2O and dissolve it in 10 mL of deionized water to obtain a Na2WO4 solution. Place the ZIF-67 / CC composite material prepared in Example 1 into the above Na2WO4 solution and heat it at 80 °C for 1 h for etching. After the etching is completed, remove the product and air dry it to obtain a Co(OH)2-WO3 / CC heterocomposite material (denoted as 0.10Co(OH)2-WO3 / CC).

[0069] Example 4

[0070] Rough nanosheet Co(OH)2-WO3 / CC heterocomposite material was prepared by low-temperature heating etching, and the steps are as follows:

[0071] Weigh 0.15 g of Na2WO4·2H2O and dissolve it in 10 mL of deionized water to obtain a Na2WO4 solution. Place the ZIF-67 / CC composite material prepared in Example 1 into the above Na2WO4 solution and heat it at 80 °C for 1 h for etching. After the etching is completed, remove the product and air dry it to obtain a Co(OH)2-WO3 / CC heterocomposite material (denoted as 0.15Co(OH)2-WO3 / CC).

[0072] Example 5

[0073] The rough nanosheet Co(OH)2-WO3 / CC heterocomposite material was prepared by low-temperature etching, and the steps are as follows:

[0074] Weigh 0.20 g of Na2WO4·2H2O and dissolve it in 10 mL of deionized water to obtain a Na2WO4 solution. Place the ZIF-67 / CC composite material prepared in Example 1 into the above Na2WO4 solution and heat it at 80 °C for 1 h for etching. After the etching is completed, remove the product and air dry it to obtain a Co(OH)2-WO3 / CC heterocomposite material (denoted as 0.20Co(OH)2-WO3 / CC).

[0075] Example 6

[0076] Rough nanosheet Co(OH)2-WO3 / CC heterocomposite material was prepared by low-temperature heating etching, and the steps are as follows:

[0077] Weigh 0.25 g of Na2WO4·2H2O and dissolve it in 10 mL of deionized water to obtain a Na2WO4 solution. Place the ZIF-67 / CC composite material prepared in Example 1 into the above Na2WO4 solution and heat it at 80 °C for 1 h for etching. After the etching is completed, remove the product and air dry it to obtain a Co(OH)2-WO3 / CC heterocomposite material (denoted as 0.25Co(OH)2-WO3 / CC).

[0078] Comparative Example 1

[0079] Preparation of RuO2 electrode material

[0080] Add 2.0 mg RuO2 to 405 μL of a mixed solution (containing 200 μL deionized water, 200 μL anhydrous ethanol, and 5 μL 5 wt% Nafion) and sonicate for 30 min. Then, drop the slurry onto a CC (1 × 1 cm) plate. 2 The surface was pretreated using the same method as in Example 1) and then air-dried. The final electrode material is denoted as RuO2 / CC.

[0081] Comparative Example 2

[0082] Preparation of Pt / C electrode materials

[0083] 2.0 mg of Pt / C (containing 20 wt% Pt) was added to a 405 μL mixed solution (containing 200 μL deionized water, 200 μL anhydrous ethanol, and 5 μL 5 wt% Nafion) and ultrasonically dispersed for 30 min. Then, the slurry was drop-coated onto a pretreated CC (1 × 1 cm) substrate. 2 The surface was pretreated using the same method as in Example 1) and then air-dried. The final electrode material is denoted as Pt / C / CC.

[0084] Effect verification

[0085] 1. Structural characterization

[0086] (1) XRD characterization

[0087] Figure 1 X-ray powder diffraction patterns of the xCo(OH)2-WO3 / CC heterocomposite materials (b) prepared in Examples 2-6 and the ZIF-67 / CC (a) prepared in Example 1. Figure 1It can be seen that the main diffraction peaks exhibited by the synthesized ZIF-67 are consistent with those of the theoretically simulated ZIF-67, indicating that ZIF-67 / CC was successfully synthesized. Figure 1 (a)). After etching with Na2WO4 solution, the main components of the obtained x Co(OH)2-WO3 / CC heterocomposite material are α-Co(OH)2 (JCPDS: 46-0605) and WO3 (JCPDS: 54-0508). Figure 1 (b) It is worth noting that a series of Co(OH)2-WO3 / CC heterocomposites obtained by etching with different amounts of Na2WO4·2H2O (i.e., different concentrations of Na2WO4 solution) were analyzed, and it was found that their diffraction peak positions were roughly the same, but their intensities were different. This suggests that Na2WO4 etching may affect the crystal structure of the composite material (i.e., the catalyst).

[0088] (2) Microscopic morphology characterization

[0089] Figure 2 Scanning electron microscope (SEM) images of the xCo(OH)₂-WO₃ / CC heterocomposites prepared in Examples 2-6 and the ZIF-67 / CC prepared in Example 1 are shown, where (a) is ZIF-67 / CC and (b)-(f) are xCo(OH)₂-WO₃ / CC prepared in Examples 2-6, respectively. Figure 2 It is evident that ZIF-67 / CC exhibits a smooth two-dimensional (2D) nanosheet array structure with a thickness of approximately 150 nm. In contrast, xCo(OH)₂-WO₃ / CC displays an interlaced, rough 2D nanosheet structure with a relatively thinner thickness. This difference in nanosheet thickness may originate from the chemical reaction between Na₂WO₄ and the organic ligands or metal nodes of ZIF-67 during etching, leading to localized dissolution or decomposition of the material, thus reducing the nanosheet thickness. Furthermore, the network structure formed by the interlacing of rough nanosheets not only facilitates the exposure of more active sites but also accelerates mass transfer rates and bubble release. Notably, in the xCo(OH)₂-WO₃ / CC catalysts etched using different amounts of Na₂WO₄·2H₂O (i.e., different concentrations of Na₂WO₄ solution), the nanosheet thickness gradually decreases with increasing Na₂WO₄·2H₂O concentration. When the amount of Na2WO4·2H2O was 0.15g, the etching degree of the nanosheets reached the most uniform state. This structural optimization is beneficial to the rapid transport of electrolytes and the effective release of bubbles. Figure 2(d) However, when the amount of Na₂WO₄·2H₂O exceeds 0.15 g, the nanosheet structure begins to collapse, leading to a reduction in the overall framework structure and specific surface area, thus affecting the catalyst's performance. Therefore, when using 0.15 g of Na₂WO₄·2H₂O as the reactant (i.e., a solution concentration of 0.015 g / mL), the reaction is less suitable. -1 At this stage, it is possible to obtain the composite material (i.e., catalyst) with the best performance. The following section on electrocatalytic performance testing will further confirm this.

[0090] Figure 3 The microstructure and composition of the 0.15Co(OH)₂-WO₃ / CC heterocomposite material prepared in Example 4 are characterized. (a) is a transmission electron microscope (TEM) image; (b) is a high-resolution TEM image; (c) shows the lattice spacing distribution in the dashed area of ​​the high-resolution TEM image; (d)-(f) are the corresponding elemental mapping images. The microstructure of Co(OH)₂-WO₃ / CC was investigated in detail using TEM. The TEM images further confirmed that Co(OH)₂-WO₃ / CC possesses a rough nanosheet structure. Figure 3 The large-sized, rough nanostructure (a) has a size of approximately 2 μm. This large size facilitates a large active specific surface area, thus exposing abundant active sites. Furthermore, high-resolution TEM (HRTEM) images show lattice fringes of 0.26 and 0.23 nm, corresponding to the (002) and (105) crystal planes of WO3 and α-Co(OH)2, respectively. Figure 3 (b)-(c)). This result confirms the successful construction of the Co(OH)₂ and WO₃ heterointerface. The formation of the heterointerface facilitates the redistribution of electrons at the interface and optimizes the adsorption energy of reaction intermediates, thereby improving the catalytic activity of the catalyst. Corresponding elemental mapping images ( Figure 3 The figures (d)-(f) show that Co, W and O elements are present in Co(OH)2-WO3 / CC and that Co, W and O elements are uniformly distributed on the nanosheets.

[0091] (3)Surface characteristics

[0092] Figure 4 The contact angle test diagrams for ZIF-67 / CC (a) prepared in Example 1 and the 0.15Co(OH)2-WO3 / CC heterocomposite material (b) prepared in Example 4 are shown. The electrocatalytic activity of a catalyst largely depends on its mass transfer capacity, which can be evaluated by the wettability of the catalyst. Therefore, the contact angle (CA) test was used to investigate the ZIF-67 / CC (i.e., ...) heterocomposite material. Figure 4 The difference in wettability between ZIF-67 and Co(OH)2-WO3 / CC. For example... Figure 4 As shown, compared with ZIF-67 / CC (CA = 89.8°), Co(OH)2-WO3 / CC has a smaller contact angle (CA = 62.5°), indicating that Co(OH)2-WO3 / CC has enhanced hydrophilicity, which is beneficial for the rapid penetration and mass transfer of electrolyte in the Co(OH)2-WO3 / CC electrode. The enhanced hydrophilicity is mainly attributed to the increased surface roughness of ZIF-67 nanosheets after Na2WO4 treatment, thereby enhancing the interaction between the catalyst and water molecules.

[0093] (4) Element valence state analysis

[0094] Figure 5 The images show various X-ray photoelectron spectra of the 0.15Co(OH)₂-WO₃ / CC heterocomposite material prepared in Example 4. (a) is the full XPS spectrum; (b)-(d) are high-resolution X-ray photoelectron spectra of the Co 2p, W 4f, and O1s regions, respectively. Figure 5 It can be seen that Co(OH)2-WO3 / CC is mainly composed of Co, W and O elements, which is consistent with the above EDX energy dispersive spectroscopy analysis results. Figure 5 in (a)). Co 2p 3 / 2 The high-resolution XPS spectrum can be deconvolved into three peaks, corresponding to Co. 3+ (780.7eV), Co 2+ (782.5 eV) and satellite peak (786.5 eV) Figure 5 (b) Furthermore, the high-resolution W 4f spectrum of Co(OH)2-WO3 / CC exhibits a typical double peak (W 4f). 7 / 2 and W 4f 5 / 2 Their binding energies correspond to 35.2 and 37.4 eV, respectively. Figure 5 (c) indicates that W is present in Co(OH)2-WO3 / CC. 6+ Oxidation state. High-resolution O1s spectrum of Co(OH)2-WO3 / CC ( Figure 5 The middle (d) peaks can be fitted into three peaks, which belong to metal oxygen (MO) (529.9 eV), CO (531.1 eV) and adsorbed water (H2Oads) (532.2 eV).

[0095] 2. Electrochemical performance testing

[0096] Test Method: The electrocatalytic oxygen evolution test was performed on an electrochemical workstation (Bio-Logic VMP3, France) using a three-electrode system. The ZIF-67 / CC electrode material prepared in Example 1, the xCo(OH)2-WO3 / CC heterocomposite material prepared in Examples 2-6, and the RuO2 / CC electrode material prepared in Comparative Example 1 were used as working electrodes. A graphite plate was used as the counter electrode, a saturated calomel electrode as the reference electrode, and 1.0 M KOH solution as the electrolyte. The test temperature was 25 °C, and the scan rate was 1.0 mV / s. -1 The scanning range was 0-1.0V (vs SCE). Electrode potentials were obtained using a saturated calomel electrode and corrected using a reversible hydrogen electrode (RHE) and impedance compensation. All potentials in this invention were obtained according to the following Nernst equation:

[0097] E RHE =E SCE +0.241+0.059pH-iR

[0098] Where i is the test current and R is the solution impedance.

[0099] The test results are as follows:

[0100] Figure 6 The electrochemical performance of the x Co(OH)2-WO3 / CC heterocomposite materials prepared in Examples 2-6, ZIF-67 / CC prepared in Example 1, RuO2 / CC prepared in Comparative Example 1, and other catalysts reported in the prior art are compared in 1.0 M KOH. (a) is the linear scan curve of the electrocatalytic oxygen evolution reaction; (b) is the Tafel slope diagram; (c) compares the electrocatalytic performance of the 0.15 Co(OH)2-WO3 / CC prepared in Example 4 (i.e., This work) with the catalysts reported in the prior art [NiCo-N-CNTs-900 (Chemical Engineering Journal, 2023, 471:144378), NiCo2O4 (Chemical Engineering Journal, 2024, 482:148787), CMP-Py(Co)@Co (Advanced Materials 2023, 35:2309084), (Co,Ni)Se4@NiFe-LDH (Small)]. Science,2024,4:2300294), Co(OH)2 / VN@C(ChemicalEngineering Journal,2023,472:145076), Co 0.59 Fe 0.41-pydc (Dalton Transactions, 2024, 53: 1245-1252), CoP / Co(OH)2@NF (Inorganic Chemistry, 2023, 62: 18189-18197), Co@NC-A (Electrochimica Acta, 2024, 476: 143735), Fe-CoO / Co (Dalton Transactions, 2023, 52: 15928-15934)】 at a current density of 10 mA / cm -2 Comparison of overpotential and Tafel slope at time; (d)-(g) are the electrochemical impedance spectra (d) and double-layer capacitance (C) of the x Co(OH)2-WO3 / CC heterocomposite materials prepared in Examples 2-6 and the ZIF-67 / CC composite material prepared in Example 1, respectively. dl Figure (e), bar chart of electrochemical active area (f), curve of turnover frequency as a function of overpotential (g); (h) shows the 0.15Co(OH)2-WO3 / CC prepared in Example 4 at 10 mA cm⁻¹ -2 The following are images of the chronopotential test (the inset on the left is a schematic diagram of the chronopotential test apparatus, and the inset on the right is a scanning electron microscope (SEM) image of the 0.15·Co(OH)2-WO3 / CC after the test). Figure 6 As shown in Figure (a), the LSV polarization curves of a series of xCo(OH)2-WO3 / CC, ZIF-67 / CC, and RuO2 / CC obtained by etching with different amounts of Na2WO4·2H2O were compared. Compared with ZIF-67 / CC, the OER activity of xCo(OH)2-WO3 / CC obtained by Na2WO4 etching was significantly enhanced, among which the 0.15Co(OH)2-WO3 / CC catalyst showed the best OER performance at a current density of 10 mA cm⁻¹. -2 The overpotential was only 214 mV, which is better than RuO2 / CC (256 mV @ 10 mA cm). -2 ).like Figure 6 As shown in (b), compared to 0.05Co(OH)2-WO3 / CC (57.1mV dec) -1 ), 0.10Co(OH)2-WO3 / CC(56.6mV dec -1 ), 0.20Co(OH)2-WO3 / CC(56.5mV dec -1 ), 0.25Co(OH)2-WO3 / CC(58.1mV dec -1 ) and ZIF-67 / CC (59.8mV dec -1The Tafel slope is smallest for 0.15Co(OH)2-WO3 / CC (53.1 mV dec). -1 This indicates that it has faster OER reaction kinetics. Notably, the OER performance of 0.15Co(OH)₂-WO₃ / CC is also superior to most transition metal-based OER catalysts reported in the prior art. Figure 6 (c)). Electrochemical impedance spectroscopy (EIS) shows ( Figure 6 In the middle (d) sample, compared to other control samples, 0.15Co(OH)2-WO3 / CC exhibited the lowest charge transfer impedance (Rc). ct =0.7Ω), indicating a faster charge transfer rate, further demonstrating that the interfacial coupling between Co(OH)2 and WO3 can significantly accelerate charge transport. Furthermore, cyclic voltammetry (CV) was used to prepare xCo(OH)2-WO3 / CC heterocomposites in Examples 2-6 (…). Figure 7 (b)-(f)) and ZIF-67 / CC prepared in Example 1 Figure 7 (a) Cyclic voltammetry curves at different scan rates in the non-Radida potential range are shown in Figure [1]. Figure 7 The double-layer capacitance (C) of the catalyst was measured (as shown). dl ()( Figure 6 In the middle (e)), the electrochemical active surface area (ECSA) of the catalyst is calculated. Figure 6 (f)). For example Figure 6 As shown in (f), 0.15Co(OH)2-WO3 / CC has the highest ECSA (11020 cm⁻¹). 2 ), higher than ZIF-67 / CC (1955cm) 2 The results of etching with different amounts of Na₂WO₄·2H₂O yielded x Co(OH)₂-WO₃ / CC (x = 0.05, 0.1, 0.2, and 0.25), indicating that 0.15 Co(OH)₂-WO₃ / CC exposed more active sites, confirming the SEM analysis results. Furthermore, the conversion frequency (TOF) of the catalyst was calculated using ICP-MS results (Table 1) to assess its intrinsic activity. Figure 6 As shown in (g), compared to the control sample, 0.15Co(OH)₂-WO₃ / CC exhibits a higher TOF value, indicating that 0.15Co(OH)₂-WO₃ / CC possesses excellent intrinsic OER activity. Furthermore, the OER stability of 0.15Co(OH)₂-WO₃ / CC was investigated using chronopotential testing, as shown... Figure 6 As shown in (h), 0.15Co(OH)2-WO3 / CC can be used at 10 mA cm⁻¹. -2It can operate continuously for 100 hours at a current density with negligible overpotential fluctuations. Furthermore, through SEM images (such as...) Figure 6 As shown in the inset (h), a slight collapse in the morphology of the catalyst was observed after the stability test, but it still largely maintained its original rough nanosheet structure, indicating good structural stability. Therefore, the above results show that the heterostructure formed by the coupling of Co(OH)2 and WO3 can not only promote the charge transport rate, but also increase the number of active sites and enhance the intrinsic activity of OER, thereby improving OER performance.

[0101] Table 1. Metal content of different catalysts determined by ICP-MS

[0102]

[0103] 3. Full water splitting performance test

[0104] Test method: The overall water splitting performance was tested using a two-electrode system on an electrochemical workstation (Bio-Logic VMP3, France). The 0.15Co(OH)₂-WO₃ / CC electrode materials prepared in Example 4 and the Pt / C / CC electrode materials prepared in Comparative Example 2 were used as the anode and cathode, respectively, thus assembling a two-electrode system (denoted as Co(OH)₂-WO₃ / CC). (+) ||Pt / C / CC (-) To evaluate the feasibility of total water splitting using 0.15Co(OH)2-WO3 / CC, a 1.0M KOH solution was used as the electrolyte, and the test temperature was 25℃. Simultaneously, the RuO2 / CC electrode material prepared in Comparative Example 1 and the Pt / C / CC electrode material prepared in Comparative Example 2 were assembled into a two-electrode system for comparative study (the two-electrode system assembled from RuO2 / CC and Pt / C / CC is denoted as RuO2 / CC). (+) ||Pt / C / CC (-) The test results are as follows: Figure 8 As shown, (a) is a schematic diagram of total water splitting in a two-electrode system; (b) is a schematic diagram of the two-electrode system Co(OH)2-WO3 / CC. (+) ||Pt / C / CC (-) and RuO2 / CC (+) ||Pt / C / CC (-) Polarization curves in 1.0 M KOH; (c) shows the two-electrode system Co(OH)2-WO3 / CC. (+) ||Pt / C / CC (-)This work compares with existing technologies such as ZIF-Co2P / V3P@NF (Journal of Industrial and Engineering Chemistry, 2022, 110: 587-597), CoFeP@C (Advanced Energy Materials, 2022, 12: 2202394), Mo2C-CoO@N-CNFs (Chemical Engineering Journal, 2023, 451: 139025), Co(OH)F@CoFe-LDH (CrystEngComm, 2022, 24: 6018-6030), and Co... 5.47 N / MoN(Applied Surface Science,2023,623:156989), MoO2@CoN(Journal ofAlloys and Compounds,2023,968:172016), CoN-Gr-2(Journal ofEnergy Chemistry, 2021, 62: 440-450), Ni-CNFs / Ir-Co(OH)2 (Separation and Purification Technology, 2023, 324: 124638), CoN@VON (Applied Catalysis B: Environmental, 2019, 241: 521-527)] at 10mA cm -2 Voltage comparison under current density; (d) is the two-electrode system Co(OH)2-WO3 / CC (+) ||Pt / C / CC (-) The stability test results (with an inset showing a schematic diagram of the two-electrode system). (By...) Figure 8 It can be seen that Co(OH)2-WO3 / CC (+) ||Pt / C / CC (-) At 10mAcm -2 It can provide a battery voltage of 1.53V at a current density, which is consistent with RuO2 / CC. (+) ||Pt / C / CC (-) Its performance is comparable (1.53V@10mAcm). -2 More importantly, at 100mAcm -2 At current density, Co(OH)2-WO3 / CC (+) ||Pt / C / CC (-) It has a lower battery voltage (1.68V), which is superior to RuO2 / CC. (+)||Pt / C / CC (-) (1.73V@100mAcm -2 Furthermore, compared to existing all-water-splitting batteries, Co(OH)2-WO3 / CC exhibits significant competitiveness. Figure 8 (c)). For example Figure 8 As shown in (d), Co(OH)2-WO3 / CC (+) ||Pt / C / CC (-) It can be done at 100mAcm -2 The catalyst operated stably at the specified current density for 240 hours with almost no performance degradation, demonstrating excellent durability. Therefore, these results indicate that the Co(OH)₂-WO₃ / CC catalyst has promising commercial application prospects.

[0105] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a rough nanosheet Co(OH)₂-WO₃ / CC heterocomposite material, characterized in that, Includes the following steps: ZIF-67 precursor was first grown on carbon cloth by impregnation to obtain ZIF-67 / CC; then, ZIF-67 / CC was immersed in Na2WO4 solution and etched by heating to obtain the rough nanosheet Co(OH)2-WO3 / CC heterocomposite material.

2. The method for preparing the rough nanosheet Co(OH)₂-WO₃ / CC heterocomposite material as described in claim 1, characterized in that, The method of growing ZIF-67 precursor on carbon cloth by impregnation includes: impregnating pretreated carbon cloth in a precursor solution to grow ZIF-67 precursor in situ on carbon cloth.

3. The method for preparing the rough nanosheet Co(OH)₂-WO₃ / CC heterocomposite material as described in claim 2, characterized in that, The preparation steps of the precursor solution include: dissolving the cobalt source and the organic ligand in water respectively to obtain a cobalt source solution and an organic ligand solution; and adding the organic ligand solution dropwise into the Co source solution to obtain the precursor solution.

4. The method for preparing the rough nanosheet Co(OH)2-WO3 / CC heterocomposite material as described in claim 3, characterized in that, The cobalt source includes Co(NO3)2 or Co(NO3)2 hydrate; And / or, the organic ligand comprises 2-methylimidazole; And / or, the mass ratio of the cobalt source to the organic ligand is 0.6568:0.4656; And / or, the ratio of the cobalt source to water is 0.6568 g: 20 mL; And / or, the ratio of the organic ligand to water is 0.4656 g: 20 mL; And / or, the impregnation reaction is carried out at a temperature of 20-30°C for a time of 6 hours.

5. The method for preparing the rough nanosheet Co(OH)₂-WO₃ / CC heterocomposite material as described in claim 2, characterized in that, The pretreatment includes: heating the carbon arrangement in a nitric acid solution, followed by ultrasonic washing in water and anhydrous ethanol in sequence.

6. The method for preparing the rough nanosheet Co(OH)₂-WO₃ / CC heterocomposite material as described in claim 1, characterized in that, The temperature for the heating etching is 80°C, and the time is 1 hour.

7. The method for preparing the rough nanosheet Co(OH)₂-WO₃ / CC heterocomposite material as described in claim 1, characterized in that, The Na2WO4 solution is prepared by mixing Na2WO4·2H2O with water at a ratio of 0.05-0.25g:10mL.

8. A rough nanosheet Co(OH)2-WO3 / CC heterocomposite material prepared by a method according to any one of claims 1-7.

9. The application of the rough nanosheet Co(OH)2-WO3 / CC heterocomposite material as described in claim 8 in the electrocatalytic oxygen evolution reaction.

10. The application of the rough nanosheet Co(OH)2-WO3 / CC heterocomposite material as described in claim 8 in hydrogen production by total water splitting.

Images