Electrolysis water self-supporting catalyst and preparation method and application thereof
By growing nitrogen-doped carbon nanotubes coated with metal nanoparticles in situ on carbonized wood, a self-supporting catalyst was constructed, which solved the problems of high overpotential and insufficient stability of existing electrocatalysts under high current density, and achieved efficient hydrogen production by water electrolysis.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZJU HANGZHOU GLOBAL SCI & TECH INNOVATION CENT
- Filing Date
- 2023-05-10
- Publication Date
- 2026-06-02
AI Technical Summary
Existing electrocatalysts have limited stability at low current densities and high overpotentials at industrial-grade current densities, resulting in insufficient catalytic activity and durability, making them unsuitable for large-scale water splitting to produce hydrogen.
Using carbonized wood as a substrate, nitrogen-doped carbon nanotubes are grown in situ on the carbonized wood and coated with metal nanoparticles through electrochemical deposition and co-pyrolysis methods to form a self-supporting catalyst, constructing a three-dimensional hierarchical porous structure to improve catalytic activity and stability.
Achieving high current density hydrogen production under low overvoltage conditions, the catalyst exhibits excellent stability and activity, reducing hydrogen production energy consumption and making it suitable for industrial-grade water electrolysis hydrogen production.
Smart Images
Figure CN116497397B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the technical field of catalysts, and particularly relates to a self-supporting catalyst for water electrolysis, its preparation method, and its application. Background Technology
[0002] With the rapid development of human society and the global economy, the consumption of traditional fossil fuels has caused serious global environmental problems and an energy crisis. Driven by the "dual carbon" goal, developing efficient, low-carbon, and sustainable clean energy and energy storage and conversion technologies is an effective way to solve these problems. Electrochemical water splitting driven by renewable electricity to produce high-purity hydrogen (H2) is a promising sustainable energy strategy. The slow kinetics of the hydrogen evolution reaction (HER) greatly hinder the energy efficiency and large-scale application of water splitting, thus requiring efficient and durable electrocatalysts.
[0003] Existing electrocatalysts operate at low current densities (≤100 mA / cm²). -2 While these catalysts perform well at low current densities (>500 mA / cm²), their stability is limited, making them unsuitable for large-scale water splitting for hydrogen production. Furthermore, these catalysts are typically in powder form, which, due to the cumbersome slurry electrode preparation process, limits their application at industrial-level current densities (>500 mA / cm²). -2 HER requires a high overpotential. Moreover, under extreme catalytic reaction environments such as industrial-grade current densities, strong acid and strong alkaline solutions, catalytic activity and durability are easily reduced. Summary of the Invention
[0004] The purpose of this invention is to solve the problems in the background art and to propose a self-supporting catalyst for water electrolysis, its preparation method, and its application.
[0005] To achieve the above objectives, this invention proposes a method for preparing a self-supporting catalyst for water electrolysis, comprising the following steps:
[0006] Carbonized wood was selected as the substrate and placed in a metal salt solution. Transition metals were then electrodeposited in situ on the carbonized wood using electrochemical deposition technology to obtain a precursor that is a hybrid of metal and carbonized wood.
[0007] The precursor and melamine were co-pyrolyzed to encapsulate metal nanoparticles in nitrogen-doped carbon nanotubes, which were then grown in situ on carbonized wood to obtain a self-supporting catalyst for water electrolysis.
[0008] Preferably, the carbonized wood is obtained by carbonizing natural wood at high temperatures, and the natural wood includes, but is not limited to, natural beech wood chips and bamboo.
[0009] Preferably, the carbonized wood is obtained by carbonizing natural wood at a carbonization temperature of 850–950°C and a carbonization time of 1–3 hours.
[0010] Preferably, the metal salt solution is at least one of nickel nitrate solution, cobalt nitrate solution, and ferric nitrate solution, and the solubility of the metal salt solution is 0.03 to 0.08 M.
[0011] Preferably, the metal is at least one of Fe, Co, and Ni, which corresponds to the metal contained in the metal salt solution.
[0012] Preferably, the co-pyrolysis is carried out under the conditions of a protective gas atmosphere, a pyrolysis temperature of 700-900℃, and a pyrolysis time of 1-3h. The protective gas includes, but is not limited to, nitrogen and argon. The pyrolysis temperature affects the diameter of the carbon nanotubes formed by co-pyrolysis, and the pyrolysis time affects the length or uniformity of the carbon nanotubes formed by co-pyrolysis.
[0013] Preferably, the amount of melamine added is 1 to 2.5 g. The amount of melamine added will affect the number of carbon nanotubes formed by co-pyrolysis, the uniformity of their morphology, and the number of tubular structures.
[0014] Preferably, the electrochemical deposition technology employs a three-electrode system with a voltage range of -0.6 to -1.2V. By adjusting electrochemical deposition parameters such as deposition voltage and deposition time, the metal loading in carbonized wood can be controlled, thereby achieving controllable preparation of the catalyst.
[0015] The technical principle of the preparation method of this invention is as follows: metal in metal salt solution is deposited onto the pores and surface of carbonized wood as a precursor by electrochemical deposition technology. Then, during co-pyrolysis, the precursor polymerizes with melamine to generate g-C3N4. The metal ions are reduced to metal seeds. As the temperature increases, g-C3N4 decomposes to provide carbon and nitrogen sources. The metal seeds catalyze the growth of nitrogen-doped carbon nanotubes from the decomposition products of g-C3N4, and finally form metal nanoparticles encapsulated in nitrogen-doped carbon nanotubes.
[0016] Ni metal nanoparticles are encapsulated in carbon nanotubes. The surrounding carbon layer can prevent the Ni metal nanoparticles from directly contacting the electrolyte, thereby improving corrosion resistance, slowing down the electrochemical leaching of Ni metal during the catalytic reaction, and improving stability. On the other hand, the carbon layer can also form a synergistic interface effect with the internal Ni metal, inducing charge redistribution and improving catalytic activity.
[0017] The present invention also proposes a self-supporting catalyst for water electrolysis prepared according to the above preparation method, wherein the self-supporting catalyst for water electrolysis has a three-dimensional hierarchical porous structure.
[0018] This invention also proposes the application of the above-mentioned self-supporting catalyst for water electrolysis in industrial-grade current density water electrolysis for hydrogen production.
[0019] The beneficial effects of this invention are:
[0020] 1. This invention uses carbonized wood as a carbon source and self-supporting substrate as a precursor. Through electrochemical deposition technology and co-pyrolysis, carbonized wood is converted into a self-supporting catalyst for water electrolysis with high conductivity and a three-dimensional hierarchical porous structure. The catalyst preparation process is simple and easy to control.
[0021] 2. During the preparation process, the nitrogen-doped carbon nanotubes formed by the co-pyrolysis of the precursor and melamine encapsulate the metal nanoparticles, achieving highly uniform dispersion of metal nanoparticles and avoiding agglomeration. On the one hand, this is conducive to the full exposure of catalytic active sites and the formation of a synergistic interface effect between the metal and carbon nanotubes, inducing charge redistribution and improving catalytic activity; on the other hand, it avoids direct contact between the metal nanoparticles and the electrolyte phase, thereby improving the corrosion resistance and stability of the metal nanoparticles.
[0022] 3. The self-supporting catalyst for water electrolysis of the present invention has a three-dimensional hierarchical porous structure of carbonized wood, which allows it to be used as a gas diffusion electrode for direct use in water electrolysis to produce hydrogen. It also avoids the use of binders required in traditional electrode preparation methods, and is conducive to enhancing mass transport and gas diffusion in electrocatalytic water splitting, thereby reducing hydrogen production energy consumption.
[0023] 4. The self-supporting catalyst for water electrolysis of the present invention achieves ≥500mA / cm under a low overvoltage of less than 0.5V. 2 It achieves industrial-grade current density for hydrogen production and has high efficiency in hydrogen production through water electrolysis.
[0024] The features and advantages of the present invention will be described in detail through embodiments and in conjunction with the accompanying drawings. Attached Figure Description
[0025] Figure 1 This is a SEM image of the self-supporting catalyst for water electrolysis prepared in the embodiments of the present invention.
[0026] Figure 2 This is a TEM image of the self-supporting catalyst for water electrolysis prepared in the embodiments of the present invention.
[0027] Figure 3 These are X-ray diffraction patterns of the self-supporting catalyst for water electrolysis and carbonized wood prepared in the embodiments of the present invention.
[0028] Figure 4 This is a comparison of the acidic catalytic hydrogen evolution activity of the self-supported water electrolysis catalyst and the Pt / c catalyst prepared in the embodiments of the present invention.
[0029] Figure 5 This is a stability test diagram of the self-supporting water electrolysis catalyst prepared in the embodiments of the present invention in acidic solution. Detailed Implementation
[0030] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. In the description of this application, it should be noted that the terms "inner," "outer," etc., indicating orientation or positional relationships are based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationships commonly used when the product of this application is in use. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first," "second," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.
[0031] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "setup" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.
[0032] The present invention will now be described in detail with reference to the accompanying drawings.
[0033] Example 1
[0034] This embodiment provides a method for preparing a self-supporting catalyst for water electrolysis, comprising the following steps:
[0035] The dimensions are 4×4×0.2cm. 3 Natural beech wood chips were rinsed with deionized water and ethanol, and then naturally dried for 12 hours. The dried natural beech wood chips were then placed in a tube furnace for high-temperature carbonization under an argon atmosphere. The furnace temperature was increased from room temperature to 300°C at a rate of 2°C / min and held for 1 hour. Subsequently, the temperature was increased to 900°C at a rate of 5°C / min and held for 2 hours. After the reaction was completed, the carbonized wood was washed several times in deionized water and ethanol solution and dried at 60°C for 12 hours to obtain carbonized wood, denoted as CW.
[0036] Ni(OH)₂ nanoparticles were electrochemically deposited on carbonized wood using a three-electrode system. Mercury / mercuric oxide was used as the reference electrode, a platinum sheet as the counter electrode, and the prepared carbonized wood as the working electrode. The electrolyte was a 0.05 M Ni(NO₃)₂·6H₂O solution. The carbonized wood was then cut into pieces with dimensions of 1×2×0.1 cm.3 The carbon sheet was first soaked in ethanol for 10 seconds, then clamped into a platinum electrode holder and partially immersed in Ni(NO3)2·6H2O electrolyte. Cyclic voltammetry (CV) was performed at room temperature on a CHI660E electrochemical workstation with a voltage range of -0.6V to -1.2V, a scan rate of 20mV / s, and 50 cycles. After electrodeposition, the carbon sheet was washed several times with deionized water and ethanol and dried at room temperature to obtain the precursor, denoted as Ni(OH)2 / CW.
[0037] The precursor Ni(OH)2 / CW and 2.0 g of melamine prepared above were placed in two separate ceramic boats and positioned in the center and upstream of a tube furnace, respectively. Under an Ar atmosphere in the tube furnace, the Ar flow rate was 150 ml / min, and the temperature was increased from room temperature to 500°C at a rate of 5°C / min, and held for 1 h. Subsequently, the temperature was increased to 800°C at the same rate and held for 2 h. After the co-pyrolysis reaction was completed, the temperature was lowered to room temperature. The obtained sample was washed several times with deionized water and ethanol and dried at room temperature to finally obtain the self-supported catalyst for water electrolysis, denoted as Ni@NCNT / CW-2.0.
[0038] This embodiment presents a self-supporting catalyst for water electrolysis, Ni@NCNT / CW-2.0, prepared according to the method described in this embodiment. This self-supporting catalyst has a three-dimensional hierarchical porous structure, which allows it to function as a gas diffusion electrode and can be directly used as an electrode for hydrogen production through water electrolysis. It also avoids the use of binders, such as Nafion solution, required in traditional electrode preparation methods, thereby reducing resistance, increasing electron transport rate, and improving gas diffusion.
[0039] This embodiment presents an application of the aforementioned self-supporting catalyst Ni@NCNT / CW-2.0 for water electrolysis in industrial-grade current density water electrolysis for hydrogen production.
[0040] Example 2
[0041] This embodiment provides a method for preparing a self-supporting catalyst for water electrolysis. Except for changing the amount of melamine added to 1.5g, and the resulting self-supporting catalyst for water electrolysis is denoted as Ni@NCNT / CW-1.5, the other steps are the same as in Example 1.
[0042] Example 3
[0043] This embodiment provides a method for preparing a self-supporting catalyst for water electrolysis. Except for changing the amount of melamine added to 1.0g and denoting the prepared self-supporting catalyst for water electrolysis as Ni@NCNT / CW-1.0, the other steps are the same as in Example 1.
[0044] Example 4
[0045] This embodiment provides a method for preparing a self-supporting catalyst for water electrolysis. Except that the metal salt solution used for electrochemical deposition is replaced with a 0.05M Co(NO3)2·6H2O solution, the prepared self-supporting catalyst for water electrolysis is denoted as Co@NCNT / CW. The remaining steps are the same as in Example 1.
[0046] Example 5
[0047] This embodiment provides a method for preparing a self-supporting catalyst for water electrolysis. Except that the metal salt solution used for electrochemical deposition is replaced with Fe(NO3)2·6H2O with a concentration of 0.05M, the prepared self-supporting catalyst for water electrolysis is denoted as Fe@NCNT / CW. The remaining steps are the same as in Example 1.
[0048] Example 6
[0049] This embodiment provides a method for preparing a self-supporting catalyst for water electrolysis. Except that the metal salt solution used for electrochemical deposition is replaced with a solution of 0.05M Co(NO3)2·6H2O solution and 0.05M Ni(NO3)2·6H2O solution mixed in a molar ratio of 1:1, the prepared self-supporting catalyst for water electrolysis is denoted as NiCo@NCNT / CW. The remaining steps are the same as in Example 1.
[0050] Example 7
[0051] This embodiment provides a method for preparing a self-supporting catalyst for water electrolysis. The only difference is that the metal salt solution used for electrochemical deposition is replaced with a solution of 0.05M Ni(NO3)2·6H2O solution, 0.05M Co(NO3)2·6H2O solution, and 0.05M Fe(NO3)2·6H2O solution mixed in a molar ratio of 3:1:1. The resulting self-supporting catalyst for water electrolysis is denoted as NiCoFe@NCNT / CW. The remaining steps are the same as in Example 1.
[0052] I. Performance Testing of Self-Supported Catalysts for Water Electrolysis
[0053] The self-supported water-splitting catalyst Ni@NCNT / CW-2.0 prepared according to the method in Example 1 was fabricated into scanning electron microscope (SEM) and transmission electron microscope (TEM) samples, respectively, and observed under SEM and TEM to obtain SEM images (SEN images) and TEM images (TEN images). The SEN images are shown below. Figure 1 As shown in the figure, the TEN diagram is as follows Figure 2 As shown.
[0054] Depend on Figure 1It can be seen that Ni metal nano-ions are encapsulated in carbon nanotubes and grown in situ in the pores and surface of carbonized wood. Each carbon nanotube is coated with Ni nanoparticles, which are located at the tip of the carbon nanotube and are highly dispersed. This is conducive to the full exposure of catalytic active sites and improves catalytic activity. The figure also shows that the self-supporting catalyst for water electrolysis has a three-dimensional hierarchical porous structure.
[0055] Depend on Figure 2 It can be seen that Ni metal nano-ions are coated in carbon nanotubes to form a core-shell structure.
[0056] II. Static Structural Analysis of Carbonized Wood and Self-Supported Catalysts for Water Electrolysis
[0057] Carbonized wood and self-supporting water electrolysis catalyst prepared according to the method in Example 1 were subjected to X-ray diffraction analysis to obtain the corresponding X-ray diffraction patterns, as shown below. Figure 3 As shown.
[0058] Figure 3 The XRD diffraction peaks at 44.5°, 51.8° and 76.4° correspond to the characteristic peaks of metallic Ni, while the XRD diffraction peaks at 24.8° and 43.6° correspond to the characteristic peaks of graphitic carbon, indicating that the Ni metal nanoparticles coated with nitrogen-doped carbon nanotubes have a crystal phase structure of metallic Ni rather than nitrides or carbides that form Ni.
[0059] III. Performance Testing of Self-Supported Catalysts for Water Electrolysis as Electrode Materials
[0060] The self-supported water electrolysis catalysts prepared according to Examples 1 to 3 were used as the experimental group, and the existing Pt / c catalyst was used as the control group. 0.5M H₂SO₄ solution was used as the electrolyte, Ag / AgCl as the reference electrode, and a Pt sheet as the counter electrode. The water electrolysis performance of the Ni@NCNT / CW catalyst and the Pt / c catalyst was tested on an electrochemical workstation. The linear sweep voltammetry (LSV) test voltage range was 0V to -1.2V (relative to the Ag / AgCl reference electrode); the current density for the constant current stability test was 500 mA / cm². 2 In this invention, the overpotential for hydrogen evolution testing is relative to the reversible hydrogen electrode. The electrocatalytic activity test results for the self-supporting water electrolysis catalyst and the Pt / C catalyst are as follows: Figure 4 As shown, the stability test results of the self-supporting catalyst for water electrolysis are as follows: Figure 5 As shown.
[0061] Depend on Figure 4 It can be seen that the self-supporting catalyst NiCo@NCNT / CW-2.0 for water electrolysis operates at an industrial-grade current density of 500 mA / cm². 2 and 1000mA / cm2 The overpotentials required for hydrogen production were 341 mV and 382 mV, respectively. The self-supporting catalyst Ni@NCNT / CW-1.5 for water electrolysis achieved 1000 mA / cm² at a low overpotential of less than 0.5 V. 2 Industrial-grade current density for hydrogen production, while Pt / C catalysts operate at current densities greater than 500 mA / cm². 2 The smaller overpotential required for hydrogen production indicates that the self-supporting water electrolysis catalyst of this invention exhibits superior catalytic activity at industrial-grade current densities.
[0062] Depend on Figure 5 It can be seen that at a constant current density of 500 mA / cm² 2 After 100 hours of continuous stability testing, the voltage of the self-supporting catalyst Ni@NCNT / CW for water electrolysis did not show significant decay, indicating that the Ni@NCNT / CW catalyst has excellent long-term durability.
[0063] The above embodiments are illustrative of the present invention and are not intended to limit the present invention. Any simple modifications to the present invention are within the scope of protection of the present invention.
Claims
1. A method for preparing a self-supporting catalyst for water electrolysis, characterized in that, It includes the following steps: Carbonized wood was selected as the substrate and placed in a metal salt solution. Transition metals were then electrodeposited in situ on the carbonized wood using electrochemical deposition technology to obtain a precursor that is a hybrid of metal and carbonized wood. The above precursor and melamine were co-pyrolyzed to encapsulate metal nanoparticles in nitrogen-doped carbon nanotubes and grow them in situ on carbonized wood to obtain a self-supporting catalyst for water electrolysis. The metal salt solution is at least one of nickel nitrate solution, cobalt nitrate solution and ferric nitrate solution, and the concentration of the metal salt solution is 0.03-0.08M; the co-pyrolysis is carried out at a pyrolysis temperature of 700-900℃ and the co-pyrolysis time is 1-3h.
2. The method for preparing the self-supporting catalyst for water electrolysis as described in claim 1, characterized in that: The carbonized wood is obtained by carbonizing natural wood at high temperatures.
3. The method for preparing the self-supporting catalyst for water electrolysis as described in claim 2, characterized in that: The carbonized wood is obtained by carbonizing natural wood at a carbonization temperature of 850-950℃ and a carbonization time of 1-3 hours.
4. The method for preparing the self-supporting catalyst for water electrolysis as described in claim 1, characterized in that: The metal is at least one of Fe, Co, and Ni.
5. The method for preparing the self-supporting catalyst for water electrolysis as described in claim 1, characterized in that: The co-pyrolysis is carried out under a protective gas atmosphere.
6. The method for preparing the self-supporting catalyst for water electrolysis as described in claim 1, characterized in that: The amount of melamine added is 1 to 2.5 g.
7. The method for preparing the self-supporting catalyst for water electrolysis as described in claim 1, characterized in that: The electrochemical deposition technique employs a three-electrode system with a voltage range of -0.6 to -1.2V.
8. A self-supporting catalyst for water electrolysis prepared by the method according to any one of claims 1 to 7, characterized in that: The self-supporting catalyst for water electrolysis has a three-dimensional hierarchical porous structure.
9. The application of the self-supporting catalyst for water electrolysis as described in claim 8 in industrial-grade current density water electrolysis for hydrogen production.