阅读说明：本技术 一种可高效电解水制氢制氧磁性木碳电极的制备方法 (Preparation method of magnetic wood-carbon electrode capable of efficiently electrolyzing water to prepare hydrogen and oxygen ) 是由 甘文涛 王耀星 尚莹 焦鹏 李雪琪 唐剑夫 于 2021-09-15 设计创作，主要内容包括：一种可高效电解水制氢制氧磁性木碳电极的制备方法,它涉及一种磁性木碳电极的制备方法。本发明要解决现有电催化剂多为非生物质原料,成本高,电解水性能较差,而木碳催化剂材料负载量低、电解水析氧反应与析氢反应的过电位较高的问题。制备方法：一、制备Ni/Fe离子混合溶液；二、真空浸渍；三、水热处理；四、冷冻干燥；五、碳化处理。本发明用于可高效电解水制氢制氧磁性木碳电极的制备。(A preparation method of a magnetic wood-carbon electrode capable of efficiently electrolyzing water to prepare hydrogen and oxygen relates to a preparation method of a magnetic wood-carbon electrode. The invention aims to solve the problems that the existing electrocatalysts are mostly non-biomass raw materials, the cost is high, the electrolytic water performance is poor, the wood carbon catalyst material has low load, and the overpotential of the electrolytic water oxygen evolution reaction and the hydrogen evolution reaction is high. The preparation method comprises the following steps: firstly, preparing a Ni/Fe ion mixed solution; secondly, vacuum impregnation; thirdly, carrying out hydrothermal treatment; fourthly, freeze drying; fifthly, carbonizing treatment. The invention is used for preparing the magnetic wood-carbon electrode capable of efficiently electrolyzing water to prepare hydrogen and oxygen.)

1. A preparation method of a magnetic wood-carbon electrode capable of efficiently electrolyzing water to prepare hydrogen and oxygen is characterized by comprising the following steps:

firstly, preparing a Ni/Fe ion mixed solution:

mixing an iron salt solution and a nickel salt solution to obtain a Ni/Fe ion mixed solution;

the total concentration of ferric salt and nickel salt in the Ni/Fe ion mixed solution is 0.05 mol/L-0.25 mol/L, and the molar ratio of ferric salt to nickel salt in the Ni/Fe ion mixed solution is 1 (1-4);

secondly, vacuum impregnation:

soaking wood in Ni/Fe ion mixed solution for 1-24 hr at room temperature and vacuum degree of 10 Pa-10 kPa;

secondly, repeating the second step for 2 to 5 times to obtain the impregnated wood;

thirdly, hydrothermal treatment:

soaking the impregnated wood in the Ni/Fe ion mixed solution again, standing for 4-6 h at room temperature to obtain a mixed solution impregnated with the wood, placing the mixed solution impregnated with the wood in a high-temperature high-pressure reaction kettle, and then reacting for 20-40 h at the temperature of 120-180 ℃ to obtain the wood after hydrothermal treatment;

fourthly, freeze drying:

cleaning the wood after the hydro-thermal treatment, freezing for 12-36 h at-15 to-25 ℃ to obtain frozen wood, and drying for 12-36 h in a vacuum environment at-40 to-50 ℃ and 5-10 Pa to obtain freeze-dried wood;

fifthly, carbonizing treatment:

and (3) putting the freeze-dried wood into a vacuum tube furnace, carbonizing for 2-8 h under the conditions that the temperature is 800-1200 ℃ and the argon rate is 0.8-1.0L/min, and cooling to room temperature to obtain the magnetic wood-carbon electrode capable of efficiently electrolyzing water to prepare hydrogen and oxygen.

2. The method for preparing the magnetic wood-carbon electrode capable of efficiently electrolyzing water to prepare hydrogen and oxygen according to claim 1, wherein the ferric salt solution in the step one is ferric nitrate solution, ferric chloride solution or ferric acetate solution.

3. The method for preparing the magnetic wood-carbon electrode capable of efficiently electrolyzing water to prepare hydrogen and oxygen according to claim 1, wherein the nickel salt solution in the step one is a nickel nitrate solution, a nickel chloride solution or a nickel acetate solution.

4. The method for preparing the magnetic wood-carbon electrode capable of efficiently electrolyzing water to prepare hydrogen and oxygen according to claim 1, wherein the wood in the second step is cleaned wood, and the method is specifically carried out according to the following steps: soaking the wood in distilled water or ethanol solution, ultrasonically cleaning for 20-30 min, and then drying for 1-24 h under vacuum at the temperature of 120-160 ℃ to obtain the cleaned wood.

5. The method for preparing the magnetic wood-carbon electrode capable of efficiently electrolyzing water to prepare hydrogen and oxygen according to claim 1, wherein the thickness of the wood in the second step is 0.5 mm-2.5 mm.

6. The method for preparing the magnetic wood-carbon electrode capable of efficiently electrolyzing water to prepare hydrogen and oxygen according to claim 1, wherein the wood in the second step is coniferous wood or broadleaf wood.

7. The preparation method of the magnetic wood-carbon electrode capable of efficiently electrolyzing water to prepare hydrogen and oxygen according to claim 1, wherein the step four is to wash the wood after the water heat treatment, and specifically comprises the following steps: soaking the wood after the hydro-thermal treatment in deionized water, and cleaning for 2-4 times, 20-50 min each time.

8. The method for preparing the magnetic wood-carbon electrode capable of efficiently electrolyzing water to prepare hydrogen and oxygen according to claim 1, wherein in the second step, wood is soaked in the Ni/Fe ion mixed solution and is soaked for 12-24 h in a vacuum environment with the room temperature and the vacuum degree of 10-50 Pa.

9. The preparation method of the magnetic wood-carbon electrode capable of efficiently electrolyzing water to prepare hydrogen and oxygen according to claim 1, wherein the reaction is carried out for 24-36 h at the temperature of 150-180 ℃ in the third step.

10. The method for preparing the magnetic wood-carbon electrode capable of efficiently electrolyzing water to prepare hydrogen and oxygen according to claim 1, wherein in the fifth step, the wood after freeze drying is placed in a vacuum tube furnace and is carbonized for 4 to 6 hours under the conditions that the temperature is 800 to 1000 ℃ and the argon gas velocity is 0.8 to 1.0L/min.

Technical Field

The invention relates to a preparation method of a magnetic wood-carbon electrode.

Background

The wood is the most abundant natural resource on the earth and is a green and environment-friendly renewable material. Wood, due to its cellulose framework and multi-layered structure, has been used as a biological substrate in a variety of applications, such as electrical and ionic conductors, optical devices, energy efficient construction, structural materials and environmental protection. Carbonized wood derived from natural wood is inexpensive, highly conductive, straight-channel, and has a layered porous structure, and is an optimal choice for manufacturing high-performance electrodes for various energy storage devices. Meanwhile, the inorganic nano material is effectively loaded in the carbonized wood pore canal to prepare the functional inorganic nano/wood composite novel material, and the method has important research value and practical significance for functional development and high added value utilization of wood.

Currently, energy shortages caused by rapid depletion of non-renewable fuel resources are one of the most pressing challenges worldwide. The production of clean hydrogen and oxygen from water by electrochemical water splitting is a promising solution due to the high energy density of hydrogen and zero carbon content release during processing. Among them, noble metal catalysts can effectively reduce overpotentials required for anodic Oxygen Evolution Reaction (OER) and cathodic Hydrogen Evolution Reaction (HER) in water decomposition process, but their high cost and scarcity severely limit their industrial applications. In recent years, much research has been devoted to the development of cost-effective HER and OER catalysts. Among them, transition metal compounds and their nitrides, phosphides and hydroxides, combined with a conductive matrix, have been used as bifunctional electrocatalysts for water splitting in electrochemical devices.

In recent years, researchers introduce defects and vacancies on the surface of the catalyst, or optimize the structure of the catalyst material by a template method, such as introducing heteroatoms, reconstructing the surface of the catalyst, and the like, but the methods are complex to operate and high in cost; substrates such as metal foam, carbon cloth, carbon paper and the like are widely used for synthesizing catalyst materials, but the substrates mostly have the phenomenon of falling off of the materials in the water electrolysis process due to weak binding force with the catalyst, so that the stability is low; although biomass raw materials, particularly derived carbon materials such as wood carbon and the like have lower cost, the problems of low catalyst material loading, higher overpotential of electrolytic water oxygen evolution reaction and hydrogen evolution reaction and the like still exist, and further excellent water electrolysis performance cannot be achieved.

In conclusion, the prior art cannot prepare the magnetic wood carbon catalyst for electrolyzing water with low cost and high efficiency.

Disclosure of Invention

The invention provides a preparation method of a magnetic wood-carbon electrode capable of efficiently electrolyzing water to produce hydrogen and oxygen, aiming at solving the problems that the existing electrocatalysts are mostly non-biological raw materials, the cost is high, the water electrolysis performance is poor, the wood-carbon catalyst material loading capacity is low, and the overpotential of the water electrolysis oxygen evolution reaction and the hydrogen evolution reaction is high.

A preparation method of a magnetic wood-carbon electrode capable of efficiently electrolyzing water to prepare hydrogen and oxygen is carried out according to the following steps:

firstly, preparing a Ni/Fe ion mixed solution:

mixing an iron salt solution and a nickel salt solution to obtain a Ni/Fe ion mixed solution;

the total concentration of ferric salt and nickel salt in the Ni/Fe ion mixed solution is 0.05 mol/L-0.25 mol/L, and the molar ratio of ferric salt to nickel salt in the Ni/Fe ion mixed solution is 1 (1-4);

secondly, vacuum impregnation:

soaking wood in Ni/Fe ion mixed solution for 1-24 hr at room temperature and vacuum degree of 10 Pa-10 kPa;

secondly, repeating the second step for 2 to 5 times to obtain the impregnated wood;

thirdly, hydrothermal treatment:

soaking the impregnated wood in the Ni/Fe ion mixed solution again, standing for 4-6 h at room temperature to obtain a mixed solution impregnated with the wood, placing the mixed solution impregnated with the wood in a high-temperature high-pressure reaction kettle, and then reacting for 20-40 h at the temperature of 120-180 ℃ to obtain the wood after hydrothermal treatment;

fourthly, freeze drying:

cleaning the wood after the hydro-thermal treatment, freezing for 12-36 h at-15 to-25 ℃ to obtain frozen wood, and drying for 12-36 h in a vacuum environment at-40 to-50 ℃ and 5-10 Pa to obtain freeze-dried wood;

fifthly, carbonizing treatment:

and (3) putting the freeze-dried wood into a vacuum tube furnace, carbonizing for 2-8 h under the conditions that the temperature is 800-1200 ℃ and the argon rate is 0.8-1.0L/min, and cooling to room temperature to obtain the magnetic wood-carbon electrode capable of efficiently electrolyzing water to prepare hydrogen and oxygen.

The invention has the beneficial effects that:

1. according to the invention, the Ni/Fe ion solution is fully immersed into the wood pore channels by adopting a vacuum impregnation method and a high-temperature hydrothermal method, the loading capacity on the original wood is increased, the Ni/Fe ions are chemically bonded with the hydroxyl on the surface of the wood, and the bonding force is strong, so that a modified wood precursor is prepared, and meanwhile, the chelation enables the catalyst material to be uniformly dispersed on the surface of the wood after high-temperature carbonization and simultaneously has high conductivity, so that the magnetic wood carbon catalyst with the natural wood 3D layered multi-stage structure is obtained by carbonization. The preparation process is simple, the wood raw material is low in price, and the wood is environment-friendly and renewable.

2. The prepared magnetic wood carbon catalyst has excellent magnetism, and shows excellent water electrolysis performance (at 10 mA/cm) under the action of an external magnetic field²At the current density of (2), the overpotential for the hydrogen evolution reaction reaches 76mV and the overpotential for the oxygen evolution reaction reaches 237mV) at 10mA/cm²The current density of (2) shows good stability when working for 50h, and the current density is only lost by 13%. The prepared wood carbon catalyst is low in price, excellent in magnetic property, renewable, capable of being produced in mass, and wide in application prospect in the field of energy storage and conversion.

The invention provides a preparation method of a magnetic wood-carbon electrode capable of efficiently electrolyzing water to prepare hydrogen and oxygen.

Drawings

FIG. 1 is a macroscopic photograph of wood as described in step two of the example;

FIG. 2 is a photomicrograph of the wood after hydrothermal treatment prepared in step three of the example;

FIG. 3 is a macroscopic photograph of the adsorption of the magnetic wood-carbon electrode and the permanent magnet for efficiently electrolyzing water to produce hydrogen and oxygen according to the first embodiment;

FIG. 4 is a VSM test, wherein 1 is the magnetic wood-carbon electrode prepared in the first example and used for efficiently electrolyzing water to prepare hydrogen and oxygen, and 2 is pure wood-carbon;

FIG. 5 is a scanning electron microscope image of 1000 times magnified magnetic wooden carbon electrode prepared by the first example and capable of efficiently electrolyzing water to produce hydrogen and oxygen;

FIG. 6 is a scanning electron microscope image of 8000 times magnification of the magnetic wood-carbon electrode prepared in the first embodiment and capable of efficiently electrolyzing water to produce hydrogen and oxygen;

FIG. 7 is an X-ray diffraction spectrum of a magnetic wood-carbon electrode prepared in the first embodiment and capable of efficiently electrolyzing water to produce hydrogen and oxygen;

FIG. 8 is a thermogravimetric curve, wherein 1 is the magnetic wood-carbon electrode capable of efficiently electrolyzing water to produce hydrogen and oxygen prepared by the first embodiment, and 2 is pure wood-carbon;

FIG. 9 is a polarization curve of oxygen evolution reaction of catalyst in the absence of magnetic field, wherein a is a magnetic wood-carbon electrode prepared in the first example and capable of efficiently electrolyzing water to produce hydrogen and oxygen, b is a Ni wood-carbon catalyst prepared in the first comparative experiment, and c is a Fe wood-carbon catalyst prepared in the second comparative experiment; d is pure wood carbon;

FIG. 10 is a polarization curve of hydrogen evolution reaction of catalyst in the absence of magnetic field, wherein a is a magnetic wood-carbon electrode prepared in the first example and capable of efficiently electrolyzing water to produce hydrogen and oxygen, b is a Ni wood-carbon catalyst prepared in the first comparative experiment, and c is a Fe wood-carbon catalyst prepared in the second comparative experiment; d is pure wood carbon;

FIG. 11 is a graph comparing the OER data before and after the application of the magnetic field for the magnetic wood-carbon electrode for efficiently electrolyzing water to produce hydrogen and oxygen as prepared in the first example, wherein a is the polarization curve of the OER after the application of the magnetic field, and b is the polarization curve of the OER before the application of the magnetic field;

fig. 12 is a graph comparing HER data before and after applying a magnetic field for the magnetic wood-carbon electrode for efficient hydrogen and oxygen production by electrolysis of water prepared in example one, where a is a polarization curve of HER after applying a magnetic field, and b is a polarization curve of HER before applying a magnetic field;

FIG. 13 is a polarization curve of water electrolysis before and after magnetic field application of the magnetic wood-carbon electrode for efficient hydrogen and oxygen production by water electrolysis prepared in the first example, wherein a is the polarization curve of water electrolysis after magnetic field application; b is the polarization curve of the electrolyzed water before the magnetic field is applied; c is a polarization curve of pure wood carbon electrolyzed water;

FIG. 14 shows that the external voltage of 1.557V is applied to the magnetic wood-carbon electrode capable of efficiently electrolyzing water to prepare hydrogen and oxygen prepared by the first embodiment at 10mA/cm²Stability curve at current density of (a).

Detailed Description

The first embodiment is as follows: the embodiment provides a preparation method of a magnetic wood-carbon electrode capable of efficiently electrolyzing water to prepare hydrogen and oxygen, which is carried out according to the following steps:

firstly, preparing a Ni/Fe ion mixed solution:

mixing an iron salt solution and a nickel salt solution to obtain a Ni/Fe ion mixed solution;

the total concentration of ferric salt and nickel salt in the Ni/Fe ion mixed solution is 0.05 mol/L-0.25 mol/L, and the molar ratio of ferric salt to nickel salt in the Ni/Fe ion mixed solution is 1 (1-4);

secondly, vacuum impregnation:

soaking wood in Ni/Fe ion mixed solution for 1-24 hr at room temperature and vacuum degree of 10 Pa-10 kPa;

secondly, repeating the second step for 2 to 5 times to obtain the impregnated wood;

thirdly, hydrothermal treatment:

soaking the impregnated wood in the Ni/Fe ion mixed solution again, standing for 4-6 h at room temperature to obtain a mixed solution impregnated with the wood, placing the mixed solution impregnated with the wood in a high-temperature high-pressure reaction kettle, and then reacting for 20-40 h at the temperature of 120-180 ℃ to obtain the wood after hydrothermal treatment;

fourthly, freeze drying:

cleaning the wood after the hydro-thermal treatment, freezing for 12-36 h at-15 to-25 ℃ to obtain frozen wood, and drying for 12-36 h in a vacuum environment at-40 to-50 ℃ and 5-10 Pa to obtain freeze-dried wood;

fifthly, carbonizing treatment:

and (3) putting the freeze-dried wood into a vacuum tube furnace, carbonizing for 2-8 h under the conditions that the temperature is 800-1200 ℃ and the argon rate is 0.8-1.0L/min, and cooling to room temperature to obtain the magnetic wood-carbon electrode capable of efficiently electrolyzing water to prepare hydrogen and oxygen.

The principle is as follows: the wood has a natural 3D layered multilevel structure and rich hydroxyl functional groups, and provides an excellent substrate for preparing a high-efficiency and low-cost catalyst; the high-temperature hydrothermal treatment accelerates the nickel iron ions to enter the pore channels of the wood, promotes the chemical bonding of the ions and the wood substrate, and improves the loading capacity of the nickel iron ions on the pore channels of the wood; the carbonization treatment can not only maintain the layered porous structure in the wood, but also endow the wood with excellent conductivity; the high-temperature treatment promotes the ferronickel nano particles to be synthesized in situ in the 3D pore channels of the wood, and the straight wood pore channels are favorable for the rapid transportation of electrolyte ions, thereby enhancing the activity of the catalyst.

The beneficial effects of the embodiment are as follows:

1. according to the embodiment, the Ni/Fe ion solution is fully immersed into the wood pore channels by adopting a vacuum impregnation method and a high-temperature hydrothermal method, the load capacity on the original wood is increased, Ni/Fe ions are chemically bonded with the hydroxyl on the surface of the wood, and the bonding force is strong, so that a modified wood precursor is prepared, and meanwhile, the chelation enables the catalyst material to be uniformly dispersed on the surface of the wood after high-temperature carbonization and has high conductivity, so that the magnetic wood-carbon catalyst with the natural wood 3D layered multi-stage structure is obtained through carbonization. The preparation process is simple, the wood raw material is low in price, and the wood is environment-friendly and renewable.

2. The prepared magnetic wood carbon catalyst has excellent magnetism, and shows excellent water electrolysis performance (at 10 mA/cm) under the action of an external magnetic field²At the current density of (2), the overpotential for the hydrogen evolution reaction reaches 76mV and the overpotential for the oxygen evolution reaction reaches 237mV) at 10mA/cm²Current density of (2) for 50hGood stability is shown, and the current density is only lost by 13%. The prepared wood carbon catalyst is low in price, excellent in magnetic property, renewable, capable of being produced in mass, and wide in application prospect in the field of energy storage and conversion.

The second embodiment is as follows: the first difference between the present embodiment and the specific embodiment is: the ferric salt solution in the step one is ferric nitrate solution, ferric chloride solution or ferric acetate solution. The rest is the same as the first embodiment.

The third concrete implementation mode: this embodiment is different from the first or second embodiment in that: the nickel salt solution in the first step is a nickel nitrate solution, a nickel chloride solution or a nickel acetate solution. The other is the same as in the first or second embodiment.

The fourth concrete implementation mode: the difference between this embodiment mode and one of the first to third embodiment modes is: the wood in the second step is cleaned wood, and the method specifically comprises the following steps: soaking the wood in distilled water or ethanol solution, ultrasonically cleaning for 20-30 min, and then drying for 1-24 h under vacuum at the temperature of 120-160 ℃ to obtain the cleaned wood. The other is the same as in the first or second embodiment.

The fifth concrete implementation mode: the difference between this embodiment and one of the first to fourth embodiments is: the thickness of the wood in the second step is 0.5 mm-2.5 mm. The rest is the same as the first to fourth embodiments.

The sixth specific implementation mode: the present embodiment is different from one or more of the first to fifth embodiments in that: and the wood in the second step is coniferous wood or broad-leaved wood. The rest is the same as the first to fifth embodiments.

The seventh embodiment: the difference between this embodiment and one of the first to sixth embodiments is: in the fourth step, the wood after the hydrothermal treatment is cleaned specifically according to the following steps: soaking the wood after the hydro-thermal treatment in deionized water, and cleaning for 2-4 times, 20-50 min each time. The others are the same as the first to sixth embodiments.

The specific implementation mode is eight: the present embodiment differs from one of the first to seventh embodiments in that: and secondly, soaking the wood in the Ni/Fe ion mixed solution for 12-24 hours in a vacuum environment with the room temperature and the vacuum degree of 10-50 Pa. The rest is the same as the first to seventh embodiments.

The specific implementation method nine: the present embodiment differs from the first to eighth embodiments in that: in the third step, the reaction is carried out for 24 to 36 hours at the temperature of between 150 and 180 ℃. The other points are the same as those in the first to eighth embodiments.

The detailed implementation mode is ten: the present embodiment differs from one of the first to ninth embodiments in that: and step five, putting the wood after freeze drying into a vacuum tube furnace, and carbonizing for 4-6 h under the conditions that the temperature is 800-1000 ℃ and the argon gas rate is 0.8-1.0L/min. The other points are the same as those in the first to ninth embodiments.

The following examples were used to demonstrate the beneficial effects of the present invention:

the first embodiment is as follows:

a preparation method of a magnetic wood-carbon electrode capable of efficiently electrolyzing water to prepare hydrogen and oxygen is carried out according to the following steps:

firstly, preparing a Ni/Fe ion mixed solution:

mixing an iron salt solution and a nickel salt solution to obtain a Ni/Fe ion mixed solution;

the total concentration of ferric salt and nickel salt in the Ni/Fe ion mixed solution is 0.2mol/L, and the molar ratio of ferric salt to nickel salt in the Ni/Fe ion mixed solution is 1: 3;

secondly, vacuum impregnation:

soaking wood in Ni/Fe ion mixed solution for 24h in a vacuum environment with room temperature and a vacuum degree of 15 Pa;

secondly, repeating the second step for 3 times to obtain impregnated wood;

thirdly, hydrothermal treatment:

soaking the impregnated wood in the Ni/Fe ion mixed solution again, standing for 4 hours at room temperature to obtain a mixed solution impregnated with the wood, placing the mixed solution impregnated with the wood in a high-temperature high-pressure reaction kettle, and then reacting for 24 hours at the temperature of 150 ℃ to obtain the wood subjected to hydrothermal treatment;

fourthly, freeze drying:

cleaning the wood subjected to the hydro-thermal treatment, freezing for 24 hours at the temperature of-20 ℃ to obtain frozen wood, and drying the frozen wood for 24 hours in a vacuum environment at the temperature of-50 ℃ and the vacuum degree of 5Pa to obtain freeze-dried wood;

fifthly, carbonizing treatment:

and (3) putting the freeze-dried wood into a vacuum tube furnace, carbonizing for 6 hours at the temperature of 800 ℃ and the argon rate of 0.8L/min, and cooling to room temperature to obtain the magnetic wood-carbon electrode capable of efficiently electrolyzing water to prepare hydrogen and oxygen.

The ferric salt solution in the step one is ferric nitrate solution.

The nickel salt solution in the first step is a nickel nitrate solution.

The wood in the second step is cleaned wood, and the method specifically comprises the following steps: soaking the wood in distilled water, ultrasonically cleaning for 25min, and then drying for 12h in vacuum at the temperature of 120 ℃ to obtain the cleaned wood.

The wood in the second step is basswood with the wood size of 20mm multiplied by 15mm multiplied by 2 mm.

In the fourth step, the wood after the hydrothermal treatment is cleaned specifically according to the following steps: and (3) soaking the wood subjected to the hydrothermal treatment in deionized water, and cleaning for 20min each time for 3 times.

Comparison experiment one: the comparative experiment differs from the first example in that: preparing Ni ion solution in the first step; the concentration of the nickel salt in the Ni ion solution is 0.15 mol/L. The rest is the same as the first embodiment.

Comparison experiment one: the comparative experiment differs from the first example in that: preparing Fe ion solution in the first step; the concentration of the ferric salt in the Fe ion solution is 0.05 mol/L. The rest is the same as the first embodiment.

FIG. 1 is a macroscopic photograph of wood as described in step two of the example. As can be seen from the figure, the surface of the cleaned wood is flat, smooth and free of impurities, and is beneficial to loading inorganic nano particles.

Fig. 2 is a macroscopic photograph of the wood after hydrothermal treatment prepared in example step three. As can be seen from the figure, the color of the wood changes from light to dark before and after the high-temperature hydrothermal treatment, which indicates that the Ni/Fe ion solution is successfully loaded on the wood pore channels.

Fig. 3 is a macroscopic photograph of the adsorption of the magnetic wood-carbon electrode and the permanent magnet capable of efficiently electrolyzing water to produce hydrogen and oxygen in the first embodiment. As can be seen from the figure, the permanent magnet can directly attract the wood carbon block, which shows that the calcined wood carbon has successfully loaded Ni/Fe nano particles, and simultaneously shows that the prepared Ni/Fe wood carbon catalyst has stronger magnetism.

Fig. 4 shows the VSM test, wherein 1 is the magnetic wood-carbon electrode prepared in the first embodiment and capable of efficiently electrolyzing water to produce hydrogen and oxygen, and 2 is pure wood-carbon. As can be seen from the figure, the magnetization intensity of the magnetic wood-carbon electrode capable of efficiently electrolyzing water to prepare hydrogen and oxygen is 12.9 emu/g.

FIG. 5 is a scanning electron microscope image of 1000 times magnified magnetic wooden carbon electrode prepared by the first example and capable of efficiently electrolyzing water to produce hydrogen and oxygen; FIG. 6 is a scanning electron microscope image of 8000 times magnification of the magnetic wood-carbon electrode prepared in the first example and capable of efficiently electrolyzing water to produce hydrogen and oxygen. As can be seen from the figure, the Ni/Fe nanoparticles are uniformly distributed around the pores and the grooves of the wood.

Fig. 7 is an X-ray diffraction spectrum, and 1 is the magnetic wood-carbon electrode capable of efficiently electrolyzing water to produce hydrogen and oxygen, prepared in the first embodiment. As can be seen, Ni was formed on the wood charcoal after the high-temperature carbonization₃Fe nanoparticles.

Fig. 8 is a thermogravimetric curve, wherein 1 is the magnetic wood-carbon electrode capable of efficiently electrolyzing water to produce hydrogen and oxygen prepared in the first embodiment, and 2 is pure wood-carbon. As can be seen, Ni is present on the wood carbon₃The loading of the Fe nanoparticles was 23%.

The catalysts prepared in the first embodiment and the first and second comparative experiments are tested in oxygen evolution reaction polarization curve, hydrogen evolution reaction polarization curve and electrolyzed water polarization curve under no magnetic field and magnetic field: the specific conditions of the magnetic field-free test are that the scanning speed is 5mV/s and the applied magnetic field intensity is 0 mT; the magnetic field test conditions were a scan rate of 5mV/s and an applied magnetic field strength of 300 mT.

FIG. 9 is a polarization curve of oxygen evolution reaction of catalyst in the absence of magnetic field, wherein a is a magnetic wood-carbon electrode prepared in the first example and capable of efficiently electrolyzing water to produce hydrogen and oxygen, b is a Ni wood-carbon catalyst prepared in the first comparative experiment, and c is a Fe wood-carbon catalyst prepared in the second comparative experiment; d is pure wood carbon. As can be seen, the synergistic effect of the nickel-iron alloy enhances the activity of the catalyst OER, wherein the OER over potential of the Ni/Fe wood carbon catalyst is 266 mV; the OER overpotential of the Ni wood carbon catalyst is 285 mV; the OER overpotential of the Fe wood carbon catalyst is 323 mV.

FIG. 10 is a polarization curve of hydrogen evolution reaction of catalyst in the absence of magnetic field, wherein a is a magnetic wood-carbon electrode prepared in the first example and capable of efficiently electrolyzing water to produce hydrogen and oxygen, b is a Ni wood-carbon catalyst prepared in the first comparative experiment, and c is a Fe wood-carbon catalyst prepared in the second comparative experiment; d is pure wood carbon. As can be seen from the figure, the synergistic effect of the nickel-iron alloy enhances the activity of the catalyst HER, wherein the HER overpotential of the Ni/Fe wood carbon catalyst is 102 mV; the HER overpotential of the Ni wood carbon catalyst is 138 mV; the HER overpotential for the Fe charcoal catalyst was 228 mV.

Fig. 11 is a graph comparing the OER data before and after the magnetic wood-carbon electrode for efficiently electrolyzing water to produce hydrogen and oxygen, prepared in example one, wherein a is the polarization curve of the OER after the magnetic field is applied, and b is the polarization curve of the OER before the magnetic field is applied. As can be seen, the overpotential of the OER of the electrolyzed water is 237mV under the action of the external magnetic field, and is reduced by 29mV compared with that of the electrolyzed water without the magnetic field, which shows that the magnetic Ni/Fe wood carbon catalyst enhances the activity of the OER under the driving of the magnetic field.

Fig. 12 is a graph comparing HER data before and after applying a magnetic field for the magnetic wood-carbon electrode for efficiently electrolyzing water to produce hydrogen and oxygen prepared in example one, where a is a polarization curve of HER after applying a magnetic field, and b is a polarization curve of HER before applying a magnetic field. As can be seen from the figure, under the action of an external magnetic field, the overpotential of HER of the electrolyzed water is 76mV, which is reduced by 26mV compared with that without the magnetic field, and the magnetic Ni/Fe wood carbon catalyst is shown to enhance the activity of HER under the driving of the magnetic field.

FIG. 13 is a polarization curve of water electrolysis before and after magnetic field application of the magnetic wood-carbon electrode for efficient hydrogen and oxygen production by water electrolysis prepared in the first example, wherein a is the polarization curve of water electrolysis after magnetic field application; b is the polarization curve of the electrolyzed water before the magnetic field is applied; and c is the polarization curve of the pure wood carbon electrolyzed water. As can be seen from the figure, the external voltage of the electrolyzed water needs 1.557V under the action of the external magnetic field, and is reduced by 27mV compared with the external voltage of 1.584V under no magnetic field, which shows that the magnetic Ni/Fe wood carbon catalyst enhances the activity of the electrolyzed water under the driving of the magnetic field.

FIG. 14 shows that the external voltage of 1.557V is applied to the magnetic wood-carbon electrode capable of efficiently electrolyzing water to prepare hydrogen and oxygen prepared by the first embodiment at 10mA/cm²Stability curve at current density of (a). As can be seen from the figure, the magnetic wood-carbon electrode capable of efficiently electrolyzing water to prepare hydrogen and oxygen is 10mA/cm²The current density of the high-voltage power supply is worked for 50 hours, and the stability is good, and the current density is only attenuated by 13%.