A carbon nanotube-encapsulated iron-nickel alloy wood carbon electrode and its preparation method and application

Abstract

The present invention discloses a carbon nanotube-encapsulated iron-nickel alloy wood carbon electrode and its preparation method and application. The method comprises the steps of carbonizing delignified wood in a protective gas flow to obtain a three-dimensional porous delignified carbonized wood; dispersing a metal source in a solvent and stirring to fully dissolve it to obtain a mixed solution; the metal source comprises a water-soluble nickel source and a water-soluble iron source; subjecting the three-dimensional porous delignified carbonized wood to a hydrothermal reaction in the mixed solution, cooling, washing, and drying to obtain a metal hydroxide-loaded delignified carbonized wood; and sequentially subjecting the carbon source and the metal hydroxide-loaded delignified carbonized wood to a protective gas flow and high-temperature annealing to obtain a carbon nanotube-encapsulated iron-nickel alloy wood carbon electrode. The present invention utilizes high-temperature annealing to synthesize a carbon nanotube-encapsulated iron-nickel alloy wood carbon electrode, constructing a chain-mail structure of carbon nanotube-encapsulated metal nanoparticles, thereby improving electrocatalytic activity and stability.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy catalytic electrode materials, and in particular to a carbon nanotube-encapsulated iron-nickel alloy wood carbon electrode and a preparation method and application thereof. Background Art

[0002] Fossil fuels support modern society's energy needs, but they also cause environmental pollution and resource depletion. Hydrogen energy, due to its clean and efficient properties, is key to energy transformation. Currently, hydrogen production relies on fossil fuels. Water electrolysis technology, which converts clean energy into hydrogen, offers environmental and high efficiency advantages and is expected to play a key role in the future energy mix.

[0003] The challenges facing water electrolysis hydrogen production technology primarily include high energy consumption, high manufacturing and maintenance costs, and issues with oxygen utilization. Currently, over 95% of global hydrogen production is gray hydrogen, produced from fossil fuels and emitting significant amounts of carbon dioxide. Green hydrogen, produced through water electrolysis using renewable energy, accounts for less than 1%. To reduce carbon dioxide emissions, green hydrogen production needs to increase significantly. It is expected that by 2030, the proportion of water electrolysis in the global hydrogen supply will increase to 33%. China's hydrogen energy industry is lacking in technological innovation, and the level of key technologies in various links of the industry chain lags significantly behind that of foreign countries, particularly in the field of renewable energy water electrolysis hydrogen production. Therefore, researchers are seeking to develop low-cost, highly stable three-dimensional porous electrode materials in order to improve the overall performance of water electrolysis hydrogen production by enhancing gas-liquid transport efficiency.

[0004] At present, three-dimensional porous materials such as nickel foam and copper foam are widely used as carriers for in-situ growth of electrode materials due to their excellent conductivity and pore structure. However, the high cost of these materials and the corrosion problems in the electrolysis environment limit their application. Therefore, researchers are seeking to develop low-cost, high-stability three-dimensional porous electrode materials in order to improve the overall performance of water electrolysis and hydrogen production by enhancing the gas-liquid transmission efficiency. Wood is a renewable resource with low-curvature pores and rich hierarchical pore structure. Wood-derived carbon materials maintain the three-dimensional structure of wood, which is conducive to the rapid penetration of electrolytes and the rapid transfer of ions and electrons (China Papermaking, 2022, 41(01): 106-117). Wood has good conductivity after high-temperature carbonization. Due to its low tortuosity and ordered conductive paths, it can simultaneously achieve better rapid ion diffusion and rapid charge conduction. The obtained overall carbon material can be directly used as a self-supporting electrode material (J. Mater. Chem. A, 2021, 9, 6172-6179). However, the chemical properties of the wood surface affect the infiltration of the electrolyte and the capture of active substances, and it is extremely challenging to develop surface properties that simultaneously meet all conditions. Summary of the Invention

[0005] In order to overcome the deficiencies of the prior art, the present invention aims to provide a carbon nanotube-encapsulated iron-nickel alloy wood carbon electrode and a preparation method and application thereof.

[0006] The primary purpose of the present invention is to provide a preparation method of a wood-carbon electrode of iron-nickel alloy encapsulated by carbon nanotubes through high-temperature annealing.

[0007] Another object of the present invention is to provide a wood-carbon electrode of carbon nanotube-encapsulated iron-nickel alloy prepared by the above preparation method.

[0008] Another object of the present invention is to provide the use of the above-mentioned carbon nanotube-encapsulated iron-nickel alloy wood carbon electrode in the electrolysis of water to produce hydrogen and / or oxygen.

[0009] The method comprises the following steps: slicing poplar wood, delignifying the wood, and freeze-drying the wood to obtain delignified wood; carbonizing the wood in a protective atmosphere to obtain three-dimensional porous delignified carbonized wood; dispersing a metal source in a solvent and stirring the solvent to obtain a mixed solution; reacting the three-dimensional porous delignified carbonized wood and the mixed solution in a high-pressure reactor, and then washing and drying the solvent to obtain delignified carbonized wood loaded with metal hydroxide; and sequentially annealing the carbon source and the metal hydroxide loaded delignified carbonized wood in a protective atmosphere at high temperature to obtain the carbon nanotube-encapsulated iron-nickel alloy wood-carbon electrode.

[0010] The present invention uses high-temperature annealing to synthesize a carbon nanotube-encapsulated iron-nickel alloy wood carbon electrode, constructing a chain armor structure of carbon nanotube-encapsulated metal nanoparticles to improve electrocatalytic activity and stability. The method is simple, efficient, low-cost, and suitable for large-scale promotion and application.

[0011] The purpose of the present invention is achieved by at least one of the following technical solutions.

[0012] The present invention provides a method for preparing a carbon nanotube-encapsulated iron-nickel alloy wood carbon electrode, comprising the following steps:

[0013] S1, delignifying the wood chips and then freeze-drying them to obtain delignified wood;

[0014] S2, placing the delignified wood obtained in step S1 in a protective gas flow for carbonization to obtain three-dimensional porous delignified carbonized wood;

[0015] S3, dispersing a metal source in a solvent and stirring to fully dissolve it to obtain a mixed solution; the metal source includes a water-soluble nickel source and a water-soluble iron source;

[0016] S4, placing the three-dimensional porous delignified carbonized wood obtained in step S2 in the mixed solution obtained in step S3 for hydrothermal reaction, cooling, washing, and drying to obtain delignified carbonized wood loaded with metal hydroxide;

[0017] S5. Placing the carbon source and the delignified carbonized wood loaded with metal hydroxide obtained in step S4 in a protective gas flow in sequence, and annealing at high temperature to obtain a carbon nanotube-encapsulated iron-nickel alloy wood-carbon electrode.

[0018] Furthermore, in step S1, the wood chips are obtained by slicing natural wood along a vertical growth direction; the natural wood is poplar; and the thickness of the wood chips is 0.1 to 0.3 cm;

[0019] Preferably, in step S1, the length*width*height of the wood chip is 4 cm×2 cm×(0.1-0.3) cm.

[0020] More preferably, in step S1 , the length*width*height of the wood chip is 4 cm×2 cm×0.1 cm.

[0021] Furthermore, in step S1, the wood chips are cleaned and dried;

[0022] Preferably, the drying temperature is 60 to 120°C and the drying time is 2 to 24 hours;

[0023] Further, in step S1, the treatment solution for delignification treatment is an aqueous solution of sodium chlorite and glacial acetic acid;

[0024] Preferably, the mass volume ratio of sodium chlorite, glacial acetic acid and water is 3.0-6.0 g:1.0-3.0 mL:300-600 mL.

[0025] Furthermore, in step S1, the delignification treatment temperature is 30°C to 120°C, and the time is 1h to 10h;

[0026] Furthermore, in step S1, the freeze-drying temperature is -20°C to -55°C, and the time is 12h to 72h.

[0027] Further, in step S2, the protective gas is at least one of Ar2 and N2;

[0028] Preferably, in step S2, the protective gas is N2.

[0029] Furthermore, in step S2, the flow rate of the protective gas flow is 20 to 120 mL / min;

[0030] Preferably, in step S2, the flow rate of the protective gas is 80 mL / min.

[0031] Furthermore, in step S2, the carbonization temperature is 200°C to 1200°C;

[0032] Preferably, in step S2, the carbonization temperature is 900°C.

[0033] Furthermore, in step S2, the carbonization heating rate is 1 to 20°C / min;

[0034] Preferably, in step S2, the heating rate of carbonization is 5°C / min.

[0035] Furthermore, in step S2, the carbonization time is 1 to 24 hours.

[0036] Preferably, in step S2, the carbonization time is 1 hour.

[0037] More preferably, the carbonization is first performed at 300° C. to 600° C. for 1 to 2 hours, and then at 800° C. to 1000° C. for 1 to 2 hours.

[0038] Furthermore, in step S3, the water-soluble nickel source is at least one of nickel sulfate, oxalate, nitrate, halide, acetate, and acetylacetonate; the water-soluble iron source is at least one of iron sulfate, oxalate, nitrate, halide, acetate, and acetylacetonate;

[0039] Preferably, in step S3, the water-soluble nickel source is nickel nitrate, and the water-soluble iron source is ferric nitrate.

[0040] Furthermore, in step S3, the solvent is water, or a mixed solvent of water and a water-soluble organic solvent;

[0041] Preferably, the water-soluble organic solvent is at least one of ethanolamine, diethanolamine, triethanolamine, N,N-dimethylformamide, and ethylenediamine;

[0042] Preferably, in step S3, the solvent is deionized water.

[0043] Furthermore, in step S3, urea is added to the mixed solution; the concentration of urea is 0.1 to 1 mol / L;

[0044] Furthermore, in step S3, the molar ratio of nickel to iron in the mixed solution is 0.1-4; and the total concentration of nickel and iron in the mixed solution is 0.01-0.3 mol / L.

[0045] Furthermore, in step S4, the temperature of the hydrothermal reaction is 100 to 300°C;

[0046] Preferably, in step S4, the temperature of the hydrothermal reaction is 120°C.

[0047] Furthermore, in step S4, the hydrothermal reaction time is 1 to 48 hours.

[0048] Preferably, in step S4, the hydrothermal reaction time is 12 hours.

[0049] Furthermore, in step S4, the drying temperature is 40 to 100°C and the drying time is 2 hours to 24 hours;

[0050] Furthermore, in step S5, the carbon source is at least one of urea and its derivatives, amines, amides, organic nitrogen heterocyclic compounds, and nitrogen-containing polymers;

[0051] Preferably, in step S5, the carbon source is amines.

[0052] More preferably, in step S5, the carbon source is melamine;

[0053] Further, in step S5, the protective gas is at least one of Ar2 and N2;

[0054] Preferably, in step S5, the protective atmosphere is Ar2.

[0055] Furthermore, in step S5, the flow rate of the protective gas flow is 1 to 100 mL / min;

[0056] Preferably, in step S5, the flow rate of the protective gas is 20 mL / min.

[0057] Furthermore, in step S5, the temperature of high temperature annealing is 400°C to 1200°C;

[0058] Preferably, in step S5 , the temperature of the high temperature annealing is 800° C.

[0059] Furthermore, in step S5, the heating rate of the high temperature annealing is 1 to 10°C / min;

[0060] Preferably, in step S5, the heating rate of the high temperature annealing is 5°C / min.

[0061] Furthermore, in step S5, the high temperature annealing time is 1 to 48 hours;

[0062] Preferably, in step S5, the high temperature annealing time is 2 hours.

[0063] More preferably, in step S5 , the high temperature annealing is first annealing at 400° C. to 600° C. for 1 to 12 hours, and then annealing at 700° C. to 900° C. for 1 to 24 hours.

[0064] Furthermore, in step S5, the mass volume ratio of the carbon source and the wood chips is 0.1-3 g: 0.8 cm 3 .

[0065] The present invention provides a wood carbon electrode of iron-nickel alloy encapsulated by carbon nanotubes prepared by the above preparation method.

[0066] The present invention also provides the use of the carbon nanotube-encapsulated iron-nickel alloy wood carbon electrode in the electrolysis of water to produce hydrogen and / or oxygen.

[0067] The carbon nanotube-encapsulated iron-nickel alloy wood carbon electrode of the present invention has the advantages of a wide source of raw materials, low preparation cost, strong universality of the preparation method, flexible and controllable preparation process, scalability, suitability for large-scale production, and adjustable components of the obtained alloy catalyst. The carbon nanotube-encapsulated iron-nickel alloy wood carbon electrode prepared under the preferred conditions of the present invention has excellent catalytic activity and stability for hydrogen production by electrolysis of water.

[0068] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0069] 1. The wood-carbon electrode provided by the present invention, which is constructed by high-temperature annealing of carbon nanotubes encapsulating iron-nickel alloy, is made of waste wood, which has the characteristics of wide source and low cost.

[0070] 2. The wood-carbon electrode provided by the present invention, which is constructed by high-temperature annealing of carbon nanotubes encapsulating iron-nickel alloy, has a mature and reliable preparation process, is suitable for large-scale manufacturing, and shows good commercial potential.

[0071] 3. The wood-carbon electrode provided by the present invention, which is constructed by high-temperature annealing of carbon nanotubes encapsulating iron-nickel alloy, has a unique three-dimensional hierarchical porous structure, low-curvature microchannels, adjustable hydrophilicity / hydrophobicity and good mechanical properties, and constructs an efficient gas-liquid-solid three-phase reaction interface for the electrolysis of water to produce hydrogen.

[0072] 4. The present invention provides a wood carbon electrode that is constructed by high-temperature annealing with carbon nanotubes encapsulating iron-nickel alloy. Its preparation method adopts a high-temperature annealing method to in situ grow a nanowire array of chain carbon nanotubes with an iron-nickel alloy encapsulated at the top on the wood carbon electrode. The resulting electrode greatly improves the catalytic activity and stability of the electrode due to the tip effect of the nanowire array and the protective effect of the top encapsulation.

[0073] 5. The wood carbon electrode provided by the present invention, which is constructed by high-temperature annealing of carbon nanotubes encapsulating iron-nickel alloy, is assembled as the anode and cathode into an anion exchange membrane electrolyzer for seawater electrolysis experiments. Only 1.86V is required to generate 2A / cm 2 The current can be stably operated for 1500h without obvious potential decay, indicating that the wood carbon electrode constructed by high-temperature annealing of carbon nanotubes encapsulating iron-nickel alloy has excellent catalytic activity and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Figure 1 This is a flow chart of the present invention for constructing a wood-carbon electrode of carbon nanotube-encapsulated iron-nickel alloy by high-temperature annealing.

[0075] Figure 2Scanning electron microscope (SEM) images of delignified carbonized wood and wood-carbon electrodes of carbon nanotube-encapsulated iron-nickel alloy constructed by high-temperature annealing in Example 1 of the present invention.

[0076] Figure 3 This is an energy dispersive X-ray spectroscopy (EDS) graph of the carbon nanotube-encapsulated iron-nickel alloy wood-carbon electrode constructed by high-temperature annealing in Example 1 of the present invention.

[0077] Figure 4 This is a high-resolution transmission electron microscopy (HRTEM) image of a wood-carbon electrode of carbon nanotube-encapsulated iron-nickel alloy constructed by high-temperature annealing in Example 1 of the present invention.

[0078] Figure 5 This is the X-ray diffraction (XRD) pattern of the wood-carbon electrode of carbon nanotube-encapsulated iron-nickel alloy constructed by high-temperature annealing in Example 1 of the present invention.

[0079] Figure 6 The linear sweep voltammograms of the carbon nanotube-encapsulated iron-nickel alloy wood carbon electrode constructed by high-temperature annealing in Examples 1 to 3 of the present invention for hydrogen evolution reaction and oxygen evolution reaction are shown.

[0080] Figure 7 The constant current density (100 mA / cm) of the wood carbon electrode of iron-nickel alloy encapsulated by carbon nanotubes constructed by high temperature annealing in Example 1 of the present invention for hydrogen evolution reaction is 2 ) under the stability curve.

[0081] Figure 8 The constant current density (100 mA / cm2) of the wood carbon electrode of iron-nickel alloy encapsulated by carbon nanotubes constructed by high temperature annealing in Example 1 of the present invention for oxygen evolution reaction is 2 ) under the stability curve.

[0082] Figure 9 The wood carbon electrode of carbon nanotube-encapsulated iron-nickel alloy constructed by high-temperature annealing in Example 1 of the present invention is used as both the anode and cathode in an anion exchange membrane electrolyzer, and a linear sweep voltammetry curve is obtained when used for electrolysis of alkaline seawater in comparison with a commercial electrode.

[0083] Figure 10 The wood carbon electrode of the iron-nickel alloy encapsulated by carbon nanotubes is constructed by high temperature annealing in Example 1 of the present invention and is used as the anode and cathode in the anion exchange membrane electrolyzer. The constant current density (2A / cm 2 ) under the stability curve.

[0084] Figure 11 The linear sweep voltammetry curves of the wood carbon electrodes used in comparative examples 1 to 3 of the present invention for hydrogen evolution reaction and oxygen evolution reaction are shown. DETAILED DESCRIPTION

[0085] The following examples further illustrate the specific implementation of the present invention, but the implementation and protection of the present invention are not limited thereto. It should be noted that if there are any processes not particularly described in detail below, they can be implemented or understood by those skilled in the art with reference to the prior art. Reagents or instruments used without the manufacturer indicated are considered to be conventional products that can be purchased commercially. The poplar wood used in the following examples and comparative examples was purchased and recycled from Yong'an He'an Industry and Trade Co., Ltd.

[0086] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments:

[0087] Example 1

[0088] A method for preparing a carbon nanotube-encapsulated iron-nickel alloy wood carbon electrode, such as Figure 1 As shown, the following steps are included:

[0089] 1) Preparation of delignified wood: Natural poplar wood was sliced ​​perpendicular to the growth direction to 4 cm × 2 cm × 0.1 cm in length, width, and height. These slices were then cleaned and dried overnight in an 80°C forced air oven. Four dried wood slices were then immersed in a mixture of 3.0 g of sodium chlorite, 1.0 ml of glacial acetic acid, and 300 ml of deionized water and heated in an oil bath at 110°C for 2 h. The treated wood was freeze-dried at -47°C for 24 h to obtain delignified wood.

[0090] 2) Preparation of delignified carbonized wood: Delignified wood was placed in a quartz tube furnace and purged with nitrogen (at a flow rate of 80 mL / min). The temperature was raised to 500°C at a rate of 5°C / min and carbonized for 1.5 h. It was then heated to 900°C and carbonized for another h to obtain a three-dimensional porous conductive delignified carbonized wood derived from wood charcoal.

[0091] 3) Prepare the metal source: Add 1.2 g of urea to 30 mL of a homogeneous aqueous solution (0.10 mmol / L nickel nitrate + 0.03 mmol / L iron nitrate) and stir until the solution is homogeneous and clear to obtain a mixed solution;

[0092] 4) Loading metal hydroxide on delignified carbonized wood: The mixed solution and a piece of delignified carbonized wood were transferred to a 50 mL polytetrafluoroethylene-lined stainless steel autoclave, which was then sealed and heated at 120°C for 12 h. After cooling to room temperature, the sample was removed, rinsed several times with deionized water, and then dried at 60°C for 12 h to obtain delignified carbonized wood loaded with metal hydroxide.

[0093] 5) In situ growth of carbon nanotubes encapsulating iron-nickel alloy: 0.6 g of melamine and a piece of delignified carbonized wood loaded with metal hydroxide were placed in a quartz tube furnace in sequence, and Ar2 (flow rate of 80 mL / min) was passed through. The temperature was raised to 500°C at a rate of 5°C / min and carbonized for 1 h. Then, it was heated to 800°C and carbonized for another 2 h to obtain a wood-carbon electrode of iron-nickel alloy encapsulated by carbon nanotubes.

[0094] The scanning electron microscope (SEM) images of the delignified carbonized wood obtained in Example 1 and the wood carbon electrode of carbon nanotubes encapsulated iron-nickel alloy constructed by high temperature annealing are as follows: Figure 2 As shown by Figure 2 It can be seen that compared with the smooth surface of delignified carbonized wood, the surface of the obtained carbon nanotube-encapsulated iron-nickel alloy wood carbon electrode presents a uniform and dense nanowire array.

[0095] The energy dispersive X-ray spectroscopy (EDS) of the carbon nanotube-encapsulated iron-nickel alloy wood carbon electrode obtained in Example 1 is shown in FIG. Figure 3 As shown by Figure 3 It can be seen that the Fe, Ni, C, and N elements are evenly distributed in the obtained carbon nanotube-encapsulated iron-nickel alloy wood carbon electrode.

[0096] The high resolution transmission electron microscopy (HRTEM) image of the carbon nanotube encapsulated iron-nickel alloy wood carbon electrode obtained in Example 1 is as follows: Figure 4 As shown by Figure 4 It can be seen that there are two lattice spacings of 0.20nm and 0.34nm in the obtained carbon nanotube-encapsulated iron-nickel alloy wood carbon electrode, which are attributed to the FeNi3 alloy (111) crystal plane and graphite carbon (002) crystal plane, respectively, which is consistent with the report in the literature (Applied Catalysis B: Environmental 268 (2020) 118729; Adv. Energy Mater., 1: 115-123).

[0097] The X-ray diffraction (XRD) pattern of the carbon nanotube-encapsulated iron-nickel alloy wood carbon electrode obtained in Example 1 is as follows: Figure 5 As shown by Figure 5 It can be seen that three characteristic diffraction peaks appear at 26.3°, 44.3° and 51.5° in the obtained carbon nanotube-encapsulated iron-nickel alloy wood carbon electrode, which are attributed to the graphite carbon (002) crystal plane, FeNi3 alloy (111) crystal plane and FeNi3 alloy (200) crystal plane, respectively, which is consistent with the report in the literature (Adv.Energy Mater., 1:115-123; Applied Catalysis B:Environmental 268 (2020) 118729).

[0098] The performance of hydrogen evolution reaction and oxygen evolution reaction was tested on the wood carbon electrode of iron-nickel alloy encapsulated by carbon nanotubes constructed by high temperature annealing in Example 1. The test conditions of hydrogen evolution reaction and oxygen evolution reaction were as follows: a standard three-electrode system was used as the test system, the obtained wood carbon electrode of iron-nickel alloy encapsulated by carbon nanotubes was used as the working electrode, Hg / HgO was used as the reference electrode, a graphite rod was used as the counter electrode, a 1 mol / L KOH solution (pH ≈ 13.8, the solvent was pure water) was used as the electrolyte, and the test instrument was Shanghai Chenhua CHI-660E electrochemical workstation. At room temperature of 25°C, its linear sweep voltammetry curve was tested, and the linear sweep voltammetry curve of the wood carbon electrode of iron-nickel alloy encapsulated by carbon nanotubes constructed by high temperature annealing was as shown in FIG. Figure 6 The solid line shows Figure 6 A in the figure is the linear sweep voltammetry curve of the hydrogen evolution reaction. Figure 6 B is the linear sweep voltammetry curve of the oxygen evolution reaction. At the same time, the wood carbon electrode constructed by high temperature annealing of carbon nanotubes encapsulating iron-nickel alloy was obtained, which was used for the hydrogen evolution reaction at a constant current density (100mA / cm 2 ) under the stability curve as shown in Figure 7 The solid line shows the constant current density (100 mA / cm 2 ) under the stability curve as shown in Figure 8 Shown by the solid line.

[0099] Mechanical strength tests were conducted on the carbon nanotube-encapsulated iron-nickel alloy wood-carbon electrode constructed through high-temperature annealing in Example 1. The electrode was placed under a weight 10,000 times its own weight and subjected to compression for one hour. The results showed that the material exhibited no visible cracks after the heavy compression, demonstrating adequate mechanical strength.

[0100] The electrolysis experiment of seawater was carried out on the wooden carbon electrode of iron-nickel alloy encapsulated by carbon nanotubes constructed by high-temperature annealing obtained in Example 1. The test conditions for electrolysis of seawater: an anion exchange membrane electrolyzer was used as the test device, and the wooden carbon electrode of iron-nickel alloy encapsulated by carbon nanotubes was used as the cathode and anode of the anion exchange membrane electrolyzer at the same time. 1 mol / L KOH solution (pH≈13.8, the solvent is natural seawater) was used as the electrolyte, and the test instrument was a Shanghai Chenhua CHI-660E electrochemical workstation coupled with a CHI-680D current amplifier. At room temperature of 25°C, its linear sweep voltammetry curve was tested, and the linear sweep voltammetry curve of the wooden carbon electrode of iron-nickel alloy encapsulated by carbon nanotubes constructed by high-temperature annealing was shown as follows: Figure 9 Indicated by the solid line. Figure 9 It can be seen that 2A / cm2 can be generated at a voltage of 1.86V. 2This performance far exceeds the performance of commercial electrodes Pt / C combined with RuO2 for water electrolysis and hydrogen production. At the same time, a wood carbon electrode constructed by high temperature annealing and encapsulating carbon nanotubes with iron-nickel alloy was obtained for the electrolysis of seawater with a constant current density (2A / cm 2 ) under the stability curve as shown in Figure 10 Indicated by the solid line. Figure 10 It can be seen that at 2A / cm 2 After 1500 hours of continuous electrolysis at the current density, the cell voltage only increased by 37mV.

[0101] Example 2

[0102] A method for preparing a carbon nanotube-encapsulated iron-nickel alloy wood carbon electrode comprises the following steps:

[0103] 1) Preparation of delignified wood: Natural poplar wood was sliced ​​perpendicular to the growth direction to 4 cm × 2 cm × 0.1 cm in length, width, and height. These slices were then cleaned and dried overnight in an 80°C forced air oven. Four dried wood slices were then immersed in a mixture of 3.0 g of sodium chlorite, 1.0 ml of glacial acetic acid, and 300 ml of deionized water and heated in an oil bath at 110°C for 2 h. The treated wood was freeze-dried at -47°C for 24 h to obtain delignified wood.

[0104] 2) Preparation of delignified carbonized wood: Delignified wood was placed in a quartz tube furnace and purged with nitrogen (at a flow rate of 80 mL / min). The temperature was raised to 500°C at a rate of 5°C / min and carbonized for 1.5 h. It was then heated to 900°C and carbonized for another h to obtain a three-dimensional porous conductive delignified carbonized wood derived from wood charcoal.

[0105] 3) Prepare the metal source: Add 1.2 g of urea to 30 mL of a homogenized solution of 0.10 mmol / L nickel nitrate and 0.03 mmol / L iron nitrate, and stir until the mixture is homogeneous and clear to obtain a mixed solution.

[0106] 4) Loading metal hydroxide on delignified carbonized wood: The mixed solution and a piece of delignified carbonized wood were transferred to a 50 mL polytetrafluoroethylene-lined stainless steel autoclave, which was then sealed and heated at 120°C for 12 h. After cooling to room temperature, the sample was removed, rinsed several times with deionized water, and then dried at 60°C for 12 h to obtain delignified carbonized wood loaded with metal hydroxide.

[0107] 5) In situ growth of carbon nanotubes encapsulating iron-nickel alloy: 0.3 g of melamine and a piece of delignified carbonized wood loaded with metal hydroxide were placed in a quartz tube furnace in sequence, and Ar2 (flow rate of 80 mL / min) was passed through. The temperature was raised to 500°C at a rate of 5°C / min and carbonized for 1 h. Then it was heated to 800°C and carbonized for another 2 h to obtain a wood-carbon electrode of iron-nickel alloy encapsulated by carbon nanotubes.

[0108] The performance of hydrogen evolution reaction and oxygen evolution reaction was tested on the wood carbon electrode of iron-nickel alloy encapsulated by carbon nanotubes constructed by high temperature annealing in Example 2. The test conditions of hydrogen evolution reaction and oxygen evolution reaction: a standard three-electrode system was used as the test system, with the obtained wood carbon electrode of iron-nickel alloy encapsulated by carbon nanotubes as the working electrode, Hg / HgO as the reference electrode, graphite rod as the counter electrode, 1 mol / L KOH solution (pH≈13.8, solvent is pure water) as the electrolyte, and the testing instrument was Shanghai Chenhua CHI-660E electrochemical workstation. At room temperature of 25°C, its linear sweep voltammetry curve was tested, and the linear sweep voltammetry curve of hydrogen evolution reaction and oxygen evolution reaction of the wood carbon electrode of iron-nickel alloy encapsulated by carbon nanotubes constructed by high temperature annealing was shown as follows. Figure 6 The solid line shows Figure 6 A in the figure is the linear sweep voltammetry curve of the hydrogen evolution reaction. Figure 6 B in FIG. 1 is the linear sweep voltammetry curve of the oxygen evolution reaction.

[0109] Example 3

[0110] A method for preparing a carbon nanotube-encapsulated iron-nickel alloy wood carbon electrode comprises the following steps:

[0111] 1) Preparation of delignified wood: Natural poplar wood was sliced ​​perpendicular to the growth direction to 4 cm × 2 cm × 0.1 cm in length, width, and height. These slices were then cleaned and dried overnight in an 80°C forced air oven. Four dried wood slices were then immersed in a mixture of 3.0 g of sodium chlorite, 1.0 ml of glacial acetic acid, and 300 ml of deionized water and heated in an oil bath at 110°C for 2 h. The treated wood was freeze-dried at -47°C for 24 h to obtain delignified wood.

[0112] 2) Preparation of delignified carbonized wood: Delignified wood was placed in a quartz tube furnace and purged with nitrogen (at a flow rate of 80 mL / min). The temperature was raised to 500°C at a rate of 5°C / min and carbonized for 1.5 h. It was then heated to 900°C and carbonized for another h to obtain a three-dimensional porous conductive delignified carbonized wood derived from wood charcoal.

[0113] 3) Prepare the metal source: Add 1.2 g of urea to 30 mL of a homogenized solution of 0.10 mmol / L nickel nitrate and 0.03 mmol / L iron nitrate, and stir until the mixture is homogeneous and clear to obtain a mixed solution.

[0114] 4) Loading metal hydroxide on delignified carbonized wood: The mixed solution and a piece of delignified carbonized wood were transferred to a 50 mL polytetrafluoroethylene-lined stainless steel autoclave, which was then sealed and heated at 120°C for 12 h. After cooling to room temperature, the sample was removed, rinsed several times with deionized water, and then dried at 60°C for 12 h to obtain delignified carbonized wood loaded with metal hydroxide.

[0115] 5) In situ growth of carbon nanotubes encapsulating iron-nickel alloy: 1.2 g of melamine and a piece of delignified carbonized wood loaded with metal hydroxide were placed in a quartz tube furnace in sequence, and Ar2 (flow rate of 80 mL / min) was passed through. The temperature was raised to 500°C at a rate of 5°C / min and carbonized for 1 h. Then, it was heated to 800°C and carbonized for another 2 h to obtain a wood-carbon electrode encapsulating iron-nickel alloy with carbon nanotubes.

[0116] The performance of hydrogen evolution reaction and oxygen evolution reaction was tested on the wood carbon electrode of iron-nickel alloy encapsulated by carbon nanotubes constructed by high temperature annealing in Example 3. The test conditions of hydrogen evolution reaction and oxygen evolution reaction: a standard three-electrode system was used as the test system, with the obtained wood carbon electrode of iron-nickel alloy encapsulated by carbon nanotubes as the working electrode, Hg / HgO as the reference electrode, graphite rod as the counter electrode, 1 mol / L KOH solution (pH≈13.8, the solvent is pure water) as the electrolyte, and the testing instrument was Shanghai Chenhua CHI-660E electrochemical workstation. At room temperature of 25°C, its linear sweep voltammetry curve was tested, and the linear sweep voltammetry curve of hydrogen evolution reaction and oxygen evolution reaction of the wood carbon electrode of iron-nickel alloy encapsulated by carbon nanotubes constructed by high temperature annealing was shown as follows. Figure 6 The solid line shows Figure 6 A in the figure is the linear sweep voltammetry curve of the hydrogen evolution reaction. Figure 6 B in FIG. 1 is the linear sweep voltammetry curve of the oxygen evolution reaction.

[0117] Comparative Example 1

[0118] The method for preparing a wood carbon electrode without high temperature annealing comprises the following steps:

[0119] 1) Preparation of delignified wood: Natural poplar wood was sliced ​​perpendicular to the growth direction to 4 cm × 2 cm × 0.1 cm in length, width, and height. These slices were then cleaned and dried overnight in an 80°C forced air oven. Four dried wood slices were then immersed in a mixture of 3.0 g of sodium chlorite, 1.0 ml of glacial acetic acid, and 300 ml of deionized water and heated in an oil bath at 110°C for 2 h. The treated wood was freeze-dried at -47°C for 24 h to obtain delignified wood.

[0120] 2) Preparation of delignified carbonized wood: Delignified wood was placed in a quartz tube furnace and purged with nitrogen (at a flow rate of 80 mL / min). The temperature was raised to 500°C at a rate of 5°C / min and carbonized for 1.5 h. It was then heated to 900°C and carbonized for another h to obtain a three-dimensional porous conductive delignified carbonized wood derived from wood charcoal.

[0121] 3) Prepare the metal source: Add 1.2 g of urea to 30 mL of a homogenized solution of 0.10 mmol / L nickel nitrate and 0.03 mmol / L iron nitrate, and stir until the mixture is homogeneous and clear to obtain a mixed solution.

[0122] 4) Loading metal hydroxides on delignified carbonized wood: The mixed solution and a piece of delignified carbonized wood were transferred to a stainless steel autoclave containing 50 mL of polytetrafluoroethylene, which was then sealed and heated at 120°C for 12 h. After cooling to room temperature, the sample was removed, rinsed several times with deionized water, and then dried at 60°C for 12 h to obtain a wood-carbon electrode without high-temperature annealing.

[0123] The performance of hydrogen evolution reaction and oxygen evolution reaction was tested on the wood carbon electrode of comparative example 1 which was not annealed at high temperature. The test conditions of hydrogen evolution reaction and oxygen evolution reaction were as follows: a standard three-electrode system was used as the test system, with the obtained wood carbon electrode which was not annealed at high temperature as the working electrode, Hg / HgO as the reference electrode, graphite rod as the counter electrode, 1 mol / L KOH solution (pH≈13.8, the solvent was pure water) as the electrolyte, and the test instrument was Shanghai Chenhua CHI-660E electrochemical workstation. At room temperature of 25°C, its linear sweep voltammetry curve was tested. The linear sweep voltammetry curve of the obtained wood carbon electrode which was not annealed at high temperature for hydrogen evolution reaction and oxygen evolution reaction is as shown below. Figure 11 The solid line shows Figure 11 A in the figure is the linear sweep voltammetry curve of the hydrogen evolution reaction. Figure 11 B in FIG. 1 is the linear sweep voltammetry curve of the oxygen evolution reaction.

[0124] Comparative Example 2

[0125] A method for preparing a non-delignified wood carbon electrode of iron-nickel alloy encapsulated by carbon nanotubes comprises the following steps:

[0126] 1) Preparation of dried wood: First, natural poplar wood was sliced ​​perpendicular to the growth direction to a length * width * height of 4 cm × 2 cm × 0.1 cm. These slices were then cleaned and dried overnight in a forced air drying oven at 80°C to obtain dried wood.

[0127] 2) Preparation of carbonized wood: Dry wood was placed in a quartz tube furnace and purged with nitrogen (at a flow rate of 80 mL / min). The temperature was raised to 500°C at a rate of 5°C / min and carbonized for 1.5 h. Then, it was heated to 900°C and carbonized for another h to obtain three-dimensional porous conductive non-delignified carbonized wood derived from wood charcoal.

[0128] 3) Prepare the metal source: Add 1.2 g of urea to 30 mL of a homogenized solution of 0.10 mmol / L nickel nitrate and 0.03 mmol / L iron nitrate, and stir until the mixture is homogeneous and clear to obtain a mixed solution.

[0129] 4) Loading metal hydroxide on carbonized wood: The mixed solution and a piece of non-delignified carbonized wood were transferred to a stainless steel autoclave containing 50 mL of polytetrafluoroethylene, which was then sealed and heated at 120°C for 12 h. After cooling to room temperature, the sample was removed, rinsed several times with deionized water, and then dried at 60°C for 12 h to obtain non-delignified carbonized wood loaded with metal hydroxide.

[0130] 5) In situ growth of carbon nanotubes encapsulating iron-nickel alloy: 0.6 g of melamine and a piece of non-delignified carbonized wood loaded with metal hydroxide were placed in a quartz tube furnace in sequence, and Ar2 (flow rate of 80 mL / min) was passed through. The temperature was raised to 500°C at a rate of 5°C / min and carbonized for 1 h. Then, it was heated to 800°C and carbonized for another 2 h to obtain a non-delignified wood carbon electrode of iron-nickel alloy encapsulated by carbon nanotubes.

[0131] The performance of hydrogen evolution reaction and oxygen evolution reaction was tested on the non-delignified wood carbon electrode of iron-nickel alloy encapsulated by carbon nanotubes constructed by high temperature annealing in comparative example 2. The test conditions of hydrogen evolution reaction and oxygen evolution reaction: a standard three-electrode system was used as the test system, the obtained non-delignified wood carbon electrode of iron-nickel alloy encapsulated by carbon nanotubes was used as the working electrode, Hg / HgO was used as the reference electrode, the graphite rod was used as the counter electrode, 1 mol / L KOH solution (pH≈13.8, the solvent was pure water) was used as the electrolyte, and the testing instrument was Shanghai Chenhua CHI-660E electrochemical workstation. At room temperature of 25°C, its linear sweep voltammetry curve was tested, and the linear sweep voltammetry curve of hydrogen evolution reaction and oxygen evolution reaction of the non-delignified wood carbon electrode of iron-nickel alloy encapsulated by carbon nanotubes constructed by high temperature annealing was shown as follows. Figure 11 The solid line shows Figure 11 A in the figure is the linear sweep voltammetry curve of the hydrogen evolution reaction. Figure 11B in FIG. 1 is the linear sweep voltammetry curve of the oxygen evolution reaction.

[0132] Comparative Example 3

[0133] A method for preparing a wood-carbon electrode loaded with an iron-nickel alloy comprises the following steps:

[0134] 1) Preparation of delignified wood: Natural poplar wood was sliced ​​perpendicular to the growth direction to 4 cm × 2 cm × 0.1 cm in length, width, and height. These slices were then cleaned and dried overnight in an 80°C forced air oven. Four dried wood slices were then immersed in a mixture of 3.0 g of sodium chlorite, 1.0 ml of glacial acetic acid, and 300 ml of deionized water and heated in an oil bath at 110°C for 2 h. The treated wood was freeze-dried at -47°C for 24 h to obtain delignified wood.

[0135] 2) Preparation of delignified carbonized wood: Delignified wood was placed in a quartz tube furnace and purged with nitrogen (at a flow rate of 80 mL / min). The temperature was raised to 500°C at a rate of 5°C / min and carbonized for 1.5 h. It was then heated to 900°C and carbonized for another h to obtain a three-dimensional porous conductive delignified carbonized wood derived from wood charcoal.

[0136] 3) Prepare the metal source: Add 1.2 g of urea to 30 mL of a homogenized solution of 0.10 mmol / L nickel nitrate and 0.03 mmol / L iron nitrate, and stir until the mixture is homogeneous and clear to obtain a mixed solution.

[0137] 4) Loading metal hydroxide on delignified carbonized wood: The mixed solution and a piece of delignified carbonized wood were transferred to a 50 mL polytetrafluoroethylene-lined stainless steel autoclave, which was then sealed and heated at 120°C for 12 h. After cooling to room temperature, the sample was removed, rinsed several times with deionized water, and then dried at 60°C for 12 h to obtain delignified carbonized wood loaded with metal hydroxide.

[0138] 5) In situ growth of iron-nickel alloy: A piece of delignified carbonized wood loaded with metal hydroxide was placed in a quartz tube furnace, and N2 / H2 (95:5, v / v) (flow rate of 80 mL / min) was passed through it. The temperature was raised to 500°C at a rate of 3°C / min and maintained for 2 h to obtain a wood-carbon electrode loaded with iron-nickel alloy.

[0139] The performance of hydrogen evolution reaction and oxygen evolution reaction was tested on the wood carbon electrode loaded with iron-nickel alloy in comparative example 3. Test conditions for hydrogen evolution reaction and oxygen evolution reaction: a standard three-electrode system was used as the test system, with the obtained wood carbon electrode loaded with iron-nickel alloy as the working electrode, Hg / HgO as the reference electrode, graphite rod as the counter electrode, 1 mol / L KOH solution (pH≈13.8, solvent is pure water) as the electrolyte, and the test instrument was Shanghai Chenhua CHI-660E electrochemical workstation. At room temperature of 25°C, its linear sweep voltammetry curve was tested, and the linear sweep voltammetry curve of the obtained wood carbon electrode loaded with iron-nickel alloy for hydrogen evolution reaction and oxygen evolution reaction is shown as follows: Figure 11 The solid line shows Figure 11 A in the figure is the linear sweep voltammetry curve of the hydrogen evolution reaction. Figure 11 B in FIG. 1 is the linear sweep voltammetry curve of the oxygen evolution reaction.

[0140] Data Analysis:

[0141] Combine Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 and Figure 5 The results show that the embodiment of the present invention can evenly and densely distribute the target carbon nanotube-encapsulated iron-nickel alloy nanowire array on the surface of delignified carbonized wood through the high-temperature annealing method, thereby preparing a carbon nanotube-encapsulated iron-nickel alloy wood carbon electrode.

[0142] Combine Figure 6 、 Figure 7 、 Figure 8 and Figure 11 The results show that the carbon nanotube-encapsulated iron-nickel alloy wood carbon electrode prepared in the embodiment of the present invention has excellent hydrogen evolution activity and oxygen evolution activity, and can efficiently produce oxygen and hydrogen by electrolysis of water under alkaline conditions. 2 The overpotentials of hydrogen evolution and oxygen evolution in Example 1 are 53 mV and 218 mV respectively, which are better than those in Example 2 (η HER =148mV,η OER =327mV), Example 3 (η HER =249mV,η OER =290mV), Comparative Example 1 (η HER =424mV,η OER =334mV), Comparative Example 2 (η HER =238mV,η OER =306mV) and Comparative Example 3 (η HER =289mV,η OER =303mV). At the same time, it can 2Stable electrolysis was carried out for 100 h at a current density of .

[0143] Combine Figure 9 、 Figure 10 The results show that the carbon nanotube-encapsulated iron-nickel alloy wood carbon electrode prepared in the embodiment of the present invention has excellent seawater electrolysis performance and can efficiently electrolyze seawater under alkaline conditions. 2 The cell voltage at the current density is only 1.86V, which is much better than the combination of commercial Pt / C and RuO2 (2A / cm 2 , 2.42V). It can also be used at 2A / cm 2 The electrolysis was stable for 1500 hours at the current density, showing excellent stability.

[0144] Combine Figure 6 Results show that the carbon nanotube-encapsulated iron-nickel alloy wood-carbon electrode prepared in this embodiment requires an appropriate amount of melamine. Compared to 0.3g and 1.2g melamine additions, the wood-carbon electrode annealed at high temperature with 0.6g melamine exhibits a more uniform and dense nanowire array arrangement, facilitating rapid mass transfer and degassing, resulting in superior hydrogen and oxygen evolution performance.

[0145] Combine Figure 6 and Figure 11 The results show that the wood-carbon electrode of carbon nanotube-encapsulated iron-nickel alloy constructed by high-temperature annealing in the embodiment of the present invention has completely improved hydrogen and oxygen evolution performance compared with Comparative Examples 1, 2 and 3. This is because the carbon nanotube-encapsulated iron-nickel alloy nanowire array produced by high-temperature annealing improves the catalytic microenvironment on the wood carbon surface, the delignified carbon substrate improves the conductivity, and the catalytic activity is greatly enhanced.

[0146] The above is only an embodiment of the present invention, and common knowledge such as the specific technical solutions or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect and practicality of the implementation of the present invention. The scope of protection required by the present invention shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing a water electrolysis electrode of carbon nanotube-encapsulated iron-nickel alloy, characterized in that: The following steps are involved: S1, delignifying the wood chips and then freeze-drying them to obtain delignified wood; S2, placing the delignified wood obtained in step S1 in a protective gas flow for carbonization to obtain three-dimensional porous delignified carbonized wood; S3, dispersing a metal source in a solvent and stirring to fully dissolve it to obtain a mixed solution; the metal source is a water-soluble nickel source and a water-soluble iron source; urea is further added to the mixed solution; the concentration of urea is 0.1 to 1 mol / L, the molar ratio of nickel element to iron element is 0.1 to 4, and the total concentration of nickel element and iron element is 0.01 to 0.3 mol / L; S4, placing the three-dimensional porous delignified carbonized wood obtained in step S2 in the mixed solution obtained in step S3 for hydrothermal reaction, cooling, washing, and drying to obtain delignified carbonized wood loaded with metal hydroxide; S5, placing the carbon source and the delignified carbonized wood loaded with metal hydroxide obtained in step S4 in a protective gas flow in sequence, and annealing at high temperature to obtain a carbon nanotube-encapsulated iron-nickel alloy wood carbon electrode; the mass volume ratio of the carbon source to the wood chip is 0.1-3 g:0.8 cm 3 ; The carbon source is melamine; the high temperature annealing is first annealing at 400℃~600℃ for 1~12 h, and then annealing at 700℃~900℃ for 1~24 h.

2. The method for preparing a water electrolysis electrode of carbon nanotube-encapsulated iron-nickel alloy according to claim 1, characterized in that: In step S1, the wood chips are obtained by slicing natural wood along a vertical growth direction; the natural wood is poplar; the thickness of the wood chips is 0.1 to 0.3 cm; In step S1, the treatment solution for delignification treatment is an aqueous solution of sodium chlorite and glacial acetic acid; the temperature of delignification treatment is 30° C. to 120° C., and the time is 1 hour to 10 hours; The freeze-drying temperature is -20°C to -55°C, and the time is 12h to 72h.

3. The method for preparing the carbon nanotube-encapsulated iron-nickel alloy water electrolysis electrode according to claim 1, characterized in that: In step S2, the protective gas is at least one of Ar2 and N2; the flow rate of the protective gas is 20 to 120 mL / min; the carbonization temperature is 200°C to 1200°C; the carbonization heating rate is 1 to 20°C / min; and the carbonization time is 1 to 24 h.

4. The method for preparing a water electrolysis electrode of carbon nanotube-encapsulated iron-nickel alloy according to claim 3, characterized in that: The carbonization is first carried out at 300°C to 600°C for 1 to 2 hours, and then at 800°C to 1000°C for 1 to 2 hours.

5. The method for preparing the carbon nanotube-encapsulated iron-nickel alloy water electrolysis electrode according to claim 1, characterized in that: In step S3, the water-soluble nickel source is at least one of nickel sulfate, oxalate, nitrate, halide, acetate, and acetylacetonate; the water-soluble iron source is at least one of iron sulfate, oxalate, nitrate, halide, acetate, and acetylacetonate; the solvent is water, or a mixed solvent of water and a water-soluble organic solvent; the water-soluble organic solvent is at least one of ethanolamine, diethanolamine, triethanolamine, N,N-dimethylformamide, and ethylenediamine.

6. The method for preparing the carbon nanotube-encapsulated iron-nickel alloy water electrolysis electrode according to claim 1, characterized in that: In step S4, the temperature of the hydrothermal reaction is 100 to 300° C.; and the time of the hydrothermal reaction is 1 to 48 hours.

7. The method for preparing the carbon nanotube-encapsulated iron-nickel alloy water electrolysis electrode according to claim 1, characterized in that: In step S5, the protective gas is at least one of Ar2 and N2; the flow rate of the protective gas is 1 to 100 mL / min; the heating rate of the high-temperature annealing is 1 to 10°C / min; and the time of the high-temperature annealing is 1 to 48 h.

8. A water electrolysis electrode of an iron-nickel alloy encapsulated by carbon nanotubes prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the carbon nanotube-encapsulated iron-nickel alloy water electrolysis electrode according to claim 8 in producing hydrogen and / or oxygen by electrolysis of water.

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