Preparation method of porous carbonized wood-supported ruthenium-based hydrotalcite nanosheets oxygen evolution electrocatalyst

Abstract

The present invention belongs to the technical field of electrocatalysts, and specifically relates to a method for preparing a porous carbonized wood-supported ruthenium-based hydrotalcite nanosheet oxygen evolution electrocatalyst, comprising the following steps: (1) cutting basswood into wood chips, sequentially ultrasonically treating with deionized water and ethanol, and then vacuum drying; (2) pre-carbonizing the dried wood chips, and then calcining them under the protection of an inert gas to obtain a carbonized wood substrate; (3) dissolving nickel nitrate hexahydrate, ferric nitrate nonahydrate, ruthenium trichloride, and urea in deionized water to obtain a precursor solution; (4) mixing the carbonized wood substrate and the precursor solution and placing them in a high-pressure reactor for hydrothermal reaction, cooling to room temperature, collecting the product, repeatedly washing with deionized water and ethanol, and drying to obtain a porous carbonized wood-supported ruthenium-based hydrotalcite nanosheet oxygen evolution electrocatalyst. The electrocatalyst prepared by the present invention has excellent catalytic activity and stability.

Description

Technical Field

[0001] The invention belongs to the technical field of electrocatalysts, and in particular relates to a method for preparing a porous carbonized wood-supported ruthenium-based hydrotalcite nanosheet oxygen evolution electrocatalyst. Background Art

[0002] In water electrolysis, the additional potential required for the anodic oxygen evolution reaction (OER) is a key factor limiting energy conversion efficiency, as it involves complex proton-coupled electron transfer processes and unfavorable thermodynamic conditions. Therefore, the present invention aims to reduce the OER overpotential to improve overall energy efficiency. Ruthenium-based electrocatalysts are considered benchmark materials for OER due to their excellent electrocatalytic performance, but their stability under operating conditions is particularly poor. The preparation processes of currently mainstream catalysts, such as metallic ruthenium (elemental ruthenium and ruthenium alloys), ruthenium-based oxides, and ruthenium-based phosphides / chalcogenides, are quite cumbersome and often involve necessary high-temperature annealing steps. Furthermore, these catalysts are typically powdered catalysts that require the use of binders during use, resulting in increased interfacial resistance, low active material utilization, and stability issues. Summary of the Invention

[0003] The present invention aims to solve the above technical problems and provides a method for preparing a porous carbonized wood-supported ruthenium-based hydrotalcite nanosheet oxygen evolution electrocatalyst. The method is simple and the prepared oxygen evolution electrocatalyst has strong catalytic activity and stability.

[0004] The technical solution of the present invention is:

[0005] A method for preparing porous carbonized wood-supported ruthenium-based hydrotalcite nanosheets oxygen evolution electrocatalyst comprises the following steps:

[0006] (1) Pretreatment: Basswood was cut into wood chips, which were ultrasonically treated with deionized water and ethanol in sequence and then vacuum dried to obtain dry wood chips;

[0007] (2) Preparation of carbonized wood: pre-carbonize the dried wood chips and then calcine them under inert gas protection to obtain a carbonized wood substrate;

[0008] (3) Preparation of precursor solution: nickel nitrate hexahydrate, ferric nitrate nonahydrate, ruthenium trichloride and urea are dissolved in deionized water to obtain a precursor solution;

[0009] (4) Hydrothermal reaction: The carbonized wood substrate in step (2) and the precursor solution in step (3) are mixed and placed in a high-pressure reactor for hydrothermal reaction. After cooling to room temperature, the product is collected, repeatedly washed with deionized water and ethanol, and dried to obtain a porous carbonized wood-supported ruthenium-based hydrotalcite nanosheet oxygen evolution electrocatalyst.

[0010] In order to remove impurities in the basswood and avoid affecting the subsequent carbonization quality, it is washed with deionized water and ethanol in sequence. Preferably, in step (1) of the present invention, the material-liquid ratio of basswood to deionized water or ethanol is 1:20-30 g / ml; in order to better remove impurities in the product and prevent teamwork, it is necessary to wash with deionized water and ethanol in sequence. Preferably, in step (4), the material-liquid ratio of the product to deionized water or ethanol is 1:20-30 g / ml; each ultrasonic treatment time is 20-30 min.

[0011] To achieve better catalytic activity and stability, preferably, in step (1) of the present invention, the wood chips have a length of 200-300 mm, a width of 150-200 mm, and a thickness of 1-2 mm. If the wood chips are too large, the pores of the support after carbonization will also be relatively long, affecting the diffusion rate of the subsequent catalyst and reducing the performance of the catalyst. If the wood chips are too small, the hydrotalcite nanosheets may easily agglomerate and may also break or deactivate during the reaction, resulting in reduced catalytic activity.

[0012] To improve the carbonization effect, the wood chips need to be pre-carbonized before carbonization. Preferably, in step (2) of the present invention, the dried wood chips are pre-carbonized in air at 200-300°C for 5-6 hours. Pre-carbonization can remove aliphatic structures, moisture, and volatile components, providing more favorable conditions for the subsequent formation of carbonized voids.

[0013] In order to improve the hardness and oxidation resistance of carbonized wood and obtain a better carbon carrier, the present invention adds silicon carbide to modify the wood chips during the carbonization process. Preferably, in step (2) of the present invention, after pre-carbonization, 0.5-1.1% of the weight of the dry wood chips is mixed with the pre-carbonized wood chips, and then calcined under the protection of inert gas. By adding silicon carbide, the hardness of the carbonized wood and the oxidation resistance during carbonization at high temperature can be improved, the structure and activity of the carbonized wood can be effectively protected, and the foundation for the stability of the subsequent catalyst can be laid. However, the amount of silicon carbide added should be moderate. If the amount added is too high, it will interfere with the interaction force of the molecular chains inside the pre-carbonized basswood chips. Excessive silicon carbide may form stress concentration points inside the pre-carbonized basswood chips, causing stress cracking, reducing the mechanical strength and stiffness of the basswood after carbonization, thereby affecting the subsequent loading performance and stability of the catalyst; if the amount of silicon carbide added is insufficient, the modification effect on the pre-carbonized basswood chips is not obvious, and the effect of the present invention cannot be achieved.

[0014] In order to obtain a better carbonization effect and improve the mechanical strength and performance of carbonized wood, preferably, in step (2) of the present invention, the temperature is 900-1100°C and the argon gas rate is 0.8-1.0 L min -1 Calcination under the conditions of 5~7 h.

[0015] In order to improve the catalytic activity of the electrocatalyst, it is necessary to rationally prepare the precursor solution. Preferably, step (3) of the present invention is specifically as follows: 0.4-0.8 mmol nickel nitrate hexahydrate, 0.1-0.4 mmol ferric nitrate nonahydrate, 0.04-0.06 mmol ruthenium trichloride and 4-6 mmol urea are dissolved in 30 mL deionized water and stirred for 20-35 min to obtain a precursor solution.

[0016] In order to improve the performance of the electrocatalyst, preferably, the carbonized wood substrate in step (4) of the present invention and the precursor liquid in step (3) are in a ratio of 0.1:20-30 g / ml. If the ratio of the carbonized wood substrate is too high, the active sites of the catalyst will be reduced, thereby reducing the catalytic efficiency and reaction rate of the catalyst; if the ratio of the carbonized wood substrate is too low, the metal nanoparticles cannot be fully dispersed on the carrier, and may agglomerate, reducing the effective surface area of the catalyst, reducing the number of active sites of the catalyst, and reducing the catalytic activity of the catalyst. In addition, the carbonized wood substrate not only provides support but also helps stabilize the metal nanoparticles. If the ratio of the carbonized wood substrate is too low, it may cause the loss of active components, affecting the stability of the catalyst.

[0017] In order to improve the catalytic activity and stability of the electrocatalyst, preferably, in step (4) of the present invention, the hydrothermal conditions are: reaction at 100-200°C for 10-14 hours. The mild hydrothermal conditions of the present invention allow the active components to be evenly deposited in the pores and on the surface of the carbonized wood substrate, thereby obtaining a highly dense porous carbonized wood-supported ruthenium-based hydrotalcite nanosheet oxygen evolution electrocatalyst.

[0018] Preferably, in step (4) of the present invention, before the precursor solution is mixed with the carbonized wood substrate in step (2), 0.3-0.8% of mannitol by weight of the precursor solution is added and mixed evenly with the precursor solution. During the hydrothermal reaction, as the temperature rises, water may partially evaporate to form bubbles. When the active components are loaded onto the carbonized wood substrate, the bubbles may cause cavities or cracks in the catalyst layer, and may also interfere with the uniform distribution of the active components, thereby affecting the mechanical strength and stability of the catalyst, easily causing catalyst deactivation, increasing dead materials, and affecting the activity of the electrocatalyst. When mannitol is added to the precursor solution, due to its strong permeability, when bubbles appear, it can penetrate into the bubbles, which can reduce the accumulation of bubbles and even eliminate the bubbles, so that the bubbles quickly leave the precursor solution, thereby enhancing the adhesion of the hydrotalcite nanosheets on the carbonized wood substrate, making the catalytic activity more evenly attached, ensuring the structural integrity of the catalyst, and improving the catalytic activity and stability of the catalyst.

[0019] Due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0020] 1. The electrocatalyst prepared by the method of the present invention is used as an anode catalyst in the electrolysis of water and has good catalytic activity. The OER reaction requires a low overpotential, which can reach 100 mA cm -2 , and has good stability.

[0021] 2. In the method of the present invention, a carbonized wood substrate with a three-dimensional ordered porous network is used as a catalyst carrier. A simple one-step hydrothermal method is used to obtain a hydrotalcite nanosheet array catalyst grown on the carbonized wood substrate skeleton. The method of the present invention has mild reaction conditions, which not only can retain the three-dimensional ordered porous structure of the wood itself, providing a favorable channel for electrolyte penetration and gas transmission, but also provides a large number of nucleation sites for the growth of hydrotalcite nanosheets after modification with silicon carbide during carbonization, avoiding the occurrence of agglomeration during the nucleation and growth process of nanoparticles, and achieving uniform and dense growth of nanosheets.

[0022] 3. When preparing the electrocatalyst by the method of the present invention, adding silicon carbide during the carbonization process of the wood chips can improve the hardness and oxidation resistance of the wood chips, prevent the structure of the wood chips from being destroyed or deformed during the carbonization process, and obtain a stable, three-dimensional ordered porous structure with uniform voids, especially obtaining smoother microchannels, so that highly active hydrotalcite nanosheets grow evenly and densely on the carbonized wood skeleton, reducing the generation of dead materials and better approaching the active sites. In addition, the three-dimensional ordered porous structure is conducive to exposing more active sites, which can achieve good electrolyte ion penetration / accessibility and abundant gas transmission channels, thereby further improving the catalytic activity and stability of the electrocatalyst.

[0023] 4. In the method of the present invention, mannitol is added to the precursor solution and mixed with the carbonized wood substrate. During the reaction, due to the strong permeability of mannitol, when bubbles appear, it can penetrate into the bubbles, which can reduce the accumulation of bubbles and even eliminate the bubbles, so that the bubbles quickly leave the precursor solution, thereby enhancing the adhesion of the hydrotalcite nanosheets on the carbonized wood substrate. At the same time, under the combination of hydrothermal conditions, the synergistic effect with mannitol prevents the agglomeration of ions in the solution, allowing the hydrotalcite to be more evenly and densely attached to the carbonized wood substrate, thereby obtaining an electrocatalyst with high stability and high catalytic activity.

[0024] 5. The method of the present invention is simple and easy to operate, does not require annealing operation, and does not require the use of a binder during use, but still obtains an electrocatalyst with high catalytic activity and good stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a transverse scanning electron microscope image of the electrode prepared in Example 1 of the present invention;

[0026] Figure 2 This is a longitudinal scanning electron microscope image of the electrode prepared in Example 1 of the present invention;

[0027] Figure 3 The oxygen evolution polarization curves of the electrodes prepared in Example 1 and Comparative Examples 1-3 of the present invention are shown;

[0028] Figure 4 This is a stability curve diagram of the electrode prepared in Example 1 of the present invention.

[0029] Figure 5 This is a stability curve diagram of different electrodes in Experimental Example 2 of the present invention.

[0030] Figure 6 This is a stability curve diagram of different electrodes in Experimental Example 3 of the present invention. DETAILED DESCRIPTION

[0031] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention. Example 1

[0032] A method for preparing porous carbonized wood-supported ruthenium-based hydrotalcite nanosheets oxygen evolution electrocatalyst comprises the following steps:

[0033] (1) Pretreatment: Basswood was cut into 200-300 mm × 150-200 mm × 1-2 mm basswood chips along the vertical direction of the tree growth. The chips were ultrasonically cleaned at 50 kHz using ethanol and deionized water at a material-liquid ratio of 1:25 g / ml for 25 min each time. The chips were then dried in a vacuum drying oven at 60 °C for 8 h to obtain dry chips.

[0034] (2) Preparation of carbonized wood: Dry wood chips were heated to 200°C at a rate of 5°C / min under air conditions and pre-carbonized at this temperature for 6 hours. Silicon carbide (0.5% by weight of the dry wood chips) was then mixed evenly with the pre-carbonized wood chips. The mixture was then heated to 900°C at an argon rate of 1.0 L / min and kept warm for 7 hours. After cooling to room temperature, the wood chips were ultrasonically cleaned at 50 kHz using ethanol and deionized water at a material-liquid ratio of 1:25 g / ml for 25 minutes each time. The wood chips were then dried in a vacuum drying oven at 60°C for 24 hours to obtain a carbonized wood substrate.

[0035] (3) Preparation of precursor solution: Dissolve 0.4 mmol nickel nitrate hexahydrate (Ni(NO3)2·6H2O), 0.4 mmol iron nitrate nonahydrate (Fe(NO3)3·9H2O), 0.06 mmol ruthenium trichloride (RuCl3) and 6 mmol urea (CH4N2O) in 30 mL of deionized water and stir for 30 min to obtain a precursor solution;

[0036] (4) Hydrothermal reaction: Take 0.8% of the weight of the precursor solution and mix it evenly with the precursor solution, then add the carbonized wood substrate according to the material-liquid ratio of the carbonized wood substrate and the precursor solution of 0.1:25g / ml, and then put them together in a 50mL high-pressure reactor, react at 100℃ for 14h, collect the product, and use ethanol and deionized water in turn according to the material-liquid ratio of 1:25g / ml at 50kHz for ultrasonic cleaning, each ultrasonic cleaning for 20min, repeat the cleaning 3 times, put it in a vacuum drying oven at a drying temperature of 60℃, and dry it for 24h to obtain porous carbonized wood-supported ruthenium-based hydrotalcite nanosheets oxygen evolution electrocatalyst, its lateral scanning electron microscope image is as shown below. Figure 1 The longitudinal scanning electron microscope image is shown in Figure 2 shown.

[0037] The porous carbonized wood supported ruthenium-based hydrotalcite nanosheet oxygen evolution electrocatalyst in Example 1 was directly used as the anode working electrode and immersed in 1.0 M KOH solution to perform a linear sweep voltammetry test of hydrogen evolution to characterize its electrocatalytic activity for hydrogen evolution reaction. Figure 3 As shown, at 100 mA cm -2 Under the current density, the overpotential of the porous carbonized wood supported ruthenium-based hydrotalcite nanosheets for oxygen evolution catalysis is only 300 mV, showing excellent electrocatalytic activity. In addition, the porous carbonized wood supported ruthenium-based hydrotalcite nanosheets oxygen evolution catalyst in Example 1 was directly used as the anode working electrode and immersed in a 1.0M KOH solution for 50 hours for chronopotentiometry test to determine its long-term stability. Figure 4 As shown in the figure, the voltage only increased by about 2.3% after 50h stability test, which shows the excellent stability of the catalyst. Example 2

[0038] A method for preparing porous carbonized wood-supported ruthenium-based hydrotalcite nanosheets oxygen evolution electrocatalyst comprises the following steps:

[0039] (1) Pretreatment: Basswood was cut into 200-300 mm × 150-200 mm × 1-2 mm basswood chips along the vertical direction of the tree growth. The chips were ultrasonically cleaned at 50 kHz using ethanol and deionized water at a material-liquid ratio of 1:30 g / ml for 20 min each time. The chips were then dried in a vacuum drying oven at 60 °C for 8 h to obtain dry chips.

[0040] (2) Preparation of carbonized wood: Dry wood chips were heated to 260°C at a rate of 5°C / min under air conditions and pre-carbonized at this temperature for 6 hours. Silicon carbide (0.8% by weight of the dry wood chips) was then mixed evenly with the pre-carbonized wood chips. The mixture was then heated to 1000°C at an argon rate of 0.8 L / min and kept warm for 6 hours. After cooling to room temperature, the wood chips were ultrasonically cleaned at 50 kHz using ethanol and deionized water at a material-liquid ratio of 1:20-30 g / ml for 20 minutes each time. The wood chips were then placed in a vacuum drying oven at 60°C and dried for 24 hours to obtain a carbonized wood substrate.

[0041] (3) Preparation of precursor solution: Dissolve 0.6 mmol nickel nitrate hexahydrate (Ni(NO3)2·6H2O), 0.3 mmol iron nitrate nonahydrate (Fe(NO3)3·9H2O), 0.05 mmol ruthenium trichloride (RuCl3) and 5 mmol urea (CH4N2O) in 30 mL deionized water and stir for 35 min to obtain a precursor solution;

[0042] (4) Hydrothermal reaction: Take 0.5% mannitol by weight of the precursor solution and mix it evenly with the precursor solution, then add the carbonized wood substrate according to the material-liquid ratio of carbonized wood substrate to precursor solution of 0.1:20 g / ml, and then put them into a 50 mL high-pressure reactor, react at 120 ° C for 12 h, collect the product, and use ethanol and deionized water in turn according to the material-liquid ratio of 1:20 g / ml for ultrasonic cleaning at 50 kHz, each ultrasonic cleaning for 25 minutes, repeat the cleaning 3 times, put it into a vacuum drying oven at a drying temperature of 60 ° C, and dry it for 24 h to obtain porous carbonized wood-supported ruthenium-based hydrotalcite nanosheets oxygen evolution electrocatalyst. Example 3

[0043] A method for preparing porous carbonized wood-supported ruthenium-based hydrotalcite nanosheets oxygen evolution electrocatalyst comprises the following steps:

[0044] (1) Pretreatment: Basswood was cut into 200-300 mm × 150-200 mm × 1-2 mm basswood chips along the vertical direction of tree growth, and ultrasonically cleaned at 50 kHz using ethanol and deionized water at a material-liquid ratio of 1:20 g / ml for 30 min each time, and then dried in a vacuum drying oven at 60 °C for 8 h to obtain dry wood chips;

[0045] (2) Preparation of carbonized wood: Dry wood chips were heated to 300°C at a rate of 5°C / min under air conditions and pre-carbonized at this temperature for 5 h. Silicon carbide (1.1% by weight of the dry wood chips) was then mixed evenly with the pre-carbonized wood chips. The mixture was then heated to 1100°C at an argon rate of 0.8 L / min and kept warm for 5 h. After cooling to room temperature, the wood chips were ultrasonically cleaned at 50 kHz using ethanol and deionized water at a material-liquid ratio of 1:20 g / ml for 30 min each time. The wood chips were then dried in a vacuum drying oven at 60°C for 24 h to obtain a carbonized wood substrate.

[0046] (3) Preparation of precursor solution: Dissolve 0.8 mmol nickel nitrate hexahydrate (Ni(NO3)2·6H2O), 0.1 mmol iron nitrate nonahydrate (Fe(NO3)3·9H2O), 0.04 mmol ruthenium trichloride (RuCl3) and 4 mmol urea (CH4N2O) in 30 mL of deionized water and stir for 20 min to obtain a precursor solution;

[0047] (4) Hydrothermal reaction: Take 0.3% mannitol by weight of the precursor solution and mix it evenly with the precursor solution, then add the carbonized wood substrate according to the material-liquid ratio of carbonized wood substrate to precursor solution of 0.1:30 g / ml, and then put them together in a 50 mL high-pressure reactor, react at 200 ° C for 10 hours, collect the product, and use ethanol and deionized water in turn according to the material-liquid ratio of 1:30 g / ml at 50 kHz for ultrasonic cleaning, each ultrasonic cleaning for 30 minutes, repeat the cleaning 3 times, put it in a vacuum drying oven at a drying temperature of 60 ° C, and dry it for 24 hours to obtain porous carbonized wood-supported ruthenium-based hydrotalcite nanosheets oxygen evolution electrocatalyst.

[0048] Comparative Example 1

[0049] A method for preparing a foamed nickel-based hydrotalcite nanosheet oxygen evolution electrocatalyst comprises the following steps:

[0050] (1) Pretreatment: First, the nickel foam was cut into a size of 200-300 mm × 150-200 mm × 1-2 mm, and ultrasonically cleaned in 3M hydrochloric acid, acetone, ethanol, and deionized water in sequence, with each ultrasonic cleaning time being 20 min. Then, the nickel foam was dried in a vacuum drying oven at 60 °C for 8 h to obtain dry nickel foam.

[0051] (2) Preparation of precursor solution: Dissolve 0.4 mmol nickel nitrate hexahydrate (Ni(NO3)2·6H2O), 0.4 mmol iron nitrate nonahydrate (Fe(NO3)3·9H2O), 0.06 mmol ruthenium trichloride (RuCl3) and 6 mmol urea (CH4N2O) in 30 mL of deionized water and stir for 30 min to obtain a precursor solution;

[0052] (3) Hydrothermal reaction: The dried nickel foam obtained in step (1) and the precursor solution in step (2) were placed in a 50 mL high-pressure reactor at a material-liquid ratio of 0.1:25 g / ml, and reacted at 120°C for 12 h. The product was collected and ultrasonically cleaned at 50 kHz using ethanol and deionized water at a material-liquid ratio of 1:20-30 g / ml. The cleaning was repeated 3 times, and the product was placed in a vacuum drying oven at a drying temperature of 60°C for 24 h to obtain a foamed nickel-based hydrotalcite nanosheet oxygen evolution electrocatalyst.

[0053] Comparative Example 2

[0054] A method for preparing a carbon paper-based hydrotalcite nanosheet oxygen evolution electrocatalyst comprises the following steps:

[0055] (1) Pretreatment: First, cut the hydrophilic carbon paper into a size of 200-300 mm × 150-200 mm, and ultrasonically clean it in acetone, ethanol, and deionized water in sequence. Each ultrasonic cleaning time is 20 min. Then, put it in a vacuum drying oven at 60 °C for 8 h to obtain dry carbon paper.

[0056] (2) Preparation of precursor solution: Dissolve 0.4 mmol nickel nitrate hexahydrate (Ni(NO3)2·6H2O), 0.4 mmol iron nitrate nonahydrate (Fe(NO3)3·9H2O), 0.06 mmol ruthenium trichloride (RuCl3) and 6 mmol urea (CH4N2O) in 30 mL of deionized water and stir for 30 min to obtain a precursor solution;

[0057] (3) Hydrothermal reaction: The dried carbon paper obtained in step (1) and the precursor solution in step (2) were placed in a 50 mL high-pressure reactor at a material-liquid ratio of 0.1:25 g / ml, and reacted at 120°C for 12 h. The product was collected and ultrasonically cleaned at 50 kHz using ethanol and deionized water at a material-liquid ratio of 1:20-30 g / ml. The cleaning was repeated three times, and the product was placed in a vacuum drying oven at a drying temperature of 60°C for 24 h to obtain a carbon paper-based hydrotalcite nanosheet oxygen evolution electrocatalyst.

[0058] Comparative Example 3

[0059] A method for preparing a carbon cloth-based hydrotalcite nanosheet oxygen evolution electrocatalyst comprises the following steps:

[0060] (1) Pretreatment: First, the carbon cloth was cut into a size of 200-300 mm × 150-200 mm, and ultrasonically cleaned in acetone, ethanol, and deionized water in sequence, with each ultrasonic cleaning time being 20 min. Then, it was placed in a vacuum drying oven at 60 °C and dried for 8 h to obtain dry carbon cloth;

[0061] (2) Preparation of precursor solution: Dissolve 0.4 mmol nickel nitrate hexahydrate (Ni(NO3)2·6H2O), 0.4 mmol iron nitrate nonahydrate (Fe(NO3)3·9H2O), 0.06 mmol ruthenium trichloride (RuCl3) and 6 mmol urea (CH4N2O) in 30 mL of deionized water and stir for 30 min to obtain a precursor solution;

[0062] (3) Hydrothermal reaction: The dry carbon cloth obtained in step (1) and the precursor solution in step (2) were placed in a 50 mL high-pressure reactor at a material-liquid ratio of 0.1:25 g / ml, and reacted at 120°C for 12 h. The product was collected and ultrasonically cleaned at 50 kHz using ethanol and deionized water at a material-liquid ratio of 1:20-30 g / ml. The cleaning was repeated 3 times, and the product was placed in a vacuum drying oven at a drying temperature of 60°C for 24 h to obtain a carbon cloth-based hydrotalcite nanosheet oxygen evolution electrocatalyst.

[0063] Test Example 1

[0064] In order to verify the effect of different supports on the performance of electrocatalysts, the following different groups of experiments were set up:

[0065] (1) Example 1;

[0066] (2) Comparative Example 1;

[0067] (3) Comparative Example 2;

[0068] (4) Comparative Example 3.

[0069] The electrocatalysts of the above groups were directly used as anode working electrodes and immersed in 1.0 M KOH solution to conduct hydrogen evolution linear sweep voltammetry test. The results are shown in Figure 3 .

[0070] like Figure 3 As shown, from Figure 3 It can be seen that at 100mA cm -2 Under the current density, the overpotential of the electrocatalyst of Example 1 is only 300 mV, showing excellent electrocatalytic activity; while Comparative Examples 1-3 use different carriers and have a high electrocatalytic activity when obtaining 100 mA cm -2 At a current density, a higher overpotential is required. Therefore, it is shown that the carbonized wood substrate used in the present invention as a carrier of the catalytically active component to prepare the electrocatalyst has a higher electrocatalytic activity.

[0071] Test Example 2

[0072] In order to verify the effect of carbonized wood modified with different silicon carbide contents on the final performance of the electrocatalyst, the following different groups were set up:

[0073] Table 1 Silicon carbide content corresponding to different groups

[0074] Group Silicon carbide as a percentage of dry wood chips weight Comparative Example 4 0% Example 1 group 0.5% Example 4 Group 0.8% Example 5 Group 1.1% Comparative Example 5 1.4%

[0075] Note: Except for the percentage of silicon carbide in the weight of the dried wood chips in each group, the other steps and parameters are the same as those in Example 1.

[0076] (1) The electrocatalysts of each group were directly used as anode working electrodes and immersed in 1.0 M KOH solution to conduct hydrogen evolution linear sweep voltammetry test. The analysis results are shown in Table 2.

[0077] Table 2 Overpotential of different groups at different current densities in Table 1

[0078] Group <![CDATA[50 mA cm -2 Overpotential / mV]]> <![CDATA[100 mA cm -2 Overpotential / mV]]> Comparative Example 4 368 479 Example 1 group 273 298 Example 4 Group 286 311 Example 5 Group 281 306 Comparative Example 5 301 374

[0079] As can be seen from Table 2, as the percentage of silicon carbide in the weight of the dry wood chips increases, the required overpotential at different current densities first decreases and then increases, indicating that the best catalytic activity can be obtained within the range of the percentage of silicon carbide in the weight of the dry wood chips of the present invention. Too low or too high an amount of silicon carbide added will affect the final catalytic activity of the electrocatalyst.

[0080] (2) The different porous carbonized wood-supported ruthenium-based hydrotalcite nanosheet oxygen evolution catalysts in Table 1 were directly used as anode working electrodes and immersed in 1.0 M KOH solution for 50 h of chronopotentiometry test to determine their long-term stability. The results are shown in Figure 1. Figure 5 shown.

[0081] from Figure 5 It can be seen that the voltage of Example 1, Example 4 and Example 5 groups was stable after 50 hours of stability testing, and only increased by 2.3-2.9%, indicating that when the amount of silicon carbide added was within the scope of the present invention, the prepared electrocatalyst had excellent stability. However, when the amount of silicon carbide added exceeded the scope of the present invention, the voltage increased by 25%-30% after 50 hours of stability testing, indicating that the amount of silicon carbide added in the present invention significantly affected the stability of the final electrocatalyst.

[0082] Test Example 3

[0083] In order to verify the effect of different mannitol addition amounts on the final performance of the electrocatalyst, the following different groups were set up:

[0084] Table 3 Precursor treatment conditions of different groups

[0085] Group Precursor liquid treatment Comparative Example 5 No mannitol Example 6 Mannitol accounts for 0.3% of the precursor solution weight Example 1 group Mannitol accounts for 0.8% of the precursor solution weight Comparative Example 6 Mannitol accounts for 1.1% of the precursor solution weight Comparative Example 7 Mannitol replaced with pentaerythritol

[0086] Note: Except for the different precursor solution treatment conditions, the other steps and parameters of each group are the same as those of Example 1.

[0087] (1) The above-mentioned electrocatalysts were directly used as anode working electrodes and immersed in 1.0 M KOH solution to conduct hydrogen evolution linear sweep voltammetry tests. The analysis results are shown in Table 4.

[0088] Table 4 Overpotential at fixed current density for different groups in Table 3

[0089] Group <![CDATA[100 mA cm -2 Overpotential / mV]]> Comparative Example 5 515 Example 6 301 Example 1 group 295 Comparative Example 6 442 Comparative Example 7 474

[0090] From Table 4, we can see that different precursor solution treatment conditions ultimately affect the catalytic performance of the electrocatalyst. In Comparative Example 5, which does not contain mannitol, the electrocatalytic performance of the electrocatalyst is significantly improved when the electrocatalytic performance reaches 100 mA cm -2 When the current density is high, a higher overpotential is required because, in the hydrothermal reaction, as the temperature rises, water may partially evaporate and form bubbles. When the speed at which the bubbles are discharged from the precursor liquid is lower than the speed at which the active components are loaded on the carbonized wood substrate, the bubbles are easily accumulated, resulting in cavities or cracks in the catalyst layer, which also interferes with the uniform distribution of the active components, easily causing the electrocatalyst to deactivate during the catalytic process, increasing dead materials, and thus reducing the activity of the electrocatalyst. When the mannitol content is increased beyond the scope of the present invention, during the hydrothermal reaction, it may cause local crystal growth to be too fast, reducing the integrity of the electrocatalyst and thus reducing the catalytic activity of the electrocatalyst. When mannitol is replaced with pentaerythritol, due to the poor permeability of pentaerythritol, when the speed at which the bubbles are discharged from the precursor liquid is lower than the speed at which the active components are loaded on the carbonized wood substrate, the bubbles are easily accumulated, resulting in cavities or cracks in the catalyst layer, which also interferes with the uniform distribution of the active components, easily causing the electrocatalyst to deactivate during the catalytic process, increasing dead materials, and thus reducing the activity of the electrocatalyst. In the method of the present invention, adding a certain amount of mannitol during the hydrothermal reaction can improve the activity of the electrocatalyst.

[0091] (2) The different porous carbonized wood-supported ruthenium-based hydrotalcite nanosheet oxygen evolution catalysts in Table 3 were directly used as anode working electrodes and immersed in 1.0 M KOH solution for 50 h of chronopotentiometry test to determine their long-term stability. The results are shown in Figure 3. Figure 6 shown.

[0092] from Figure 6 It can be seen that the voltage of Example 1 and Example 6 groups was stable after 50h stability test, and only increased by 2.3-2.7%, indicating that the amount of mannitol added was within the scope of the present invention, and the prepared electrocatalyst had excellent stability. However, when the amount of mannitol added exceeded the scope of the present invention or no mannitol was added or mannitol was replaced with pentaerythritol, the voltage increased by 40%-50% after 50h stability test, indicating that the amount of mannitol added and whether it was added significantly affected the stability of the final electrocatalyst.

[0093] The above description is a detailed description of the preferred embodiments of the present invention, but the embodiments are not intended to limit the scope of the patent application of the present invention. Any equivalent changes or modifications completed under the technical spirit suggested by the present invention should fall within the patent scope covered by the present invention.

Claims

1. A method for preparing porous carbonized wood-supported ruthenium-based hydrotalcite nanosheets for oxygen evolution electrocatalyst, characterized by: The following steps are involved: (1) Pretreatment: Basswood was cut into wood chips, which were ultrasonically treated with deionized water and ethanol in sequence and then vacuum dried to obtain dry wood chips; (2) Preparation of carbonized wood: pre-carbonize the dried wood chips, calcine them under inert gas protection, ultrasonically treat them with deionized water and ethanol, and then vacuum dry them to obtain a carbonized wood substrate; (3) Preparation of precursor solution: dissolve nickel nitrate hexahydrate, ferric nitrate nonahydrate, ruthenium trichloride and urea in deionized water and stir to obtain a precursor solution; (4) Hydrothermal reaction: the carbonized wood substrate in step (2) and the precursor solution in step (3) are mixed and placed in a high-pressure reactor for hydrothermal reaction. After cooling to room temperature, the product is collected, and ultrasonically cleaned repeatedly with deionized water and ethanol, and dried to obtain a porous carbonized wood-supported ruthenium-based hydrotalcite nanosheet oxygen evolution electrocatalyst; In step (2), the dried wood chips are pre-carbonized in air at 200-300°C for 5-6 hours; In the step (2), after pre-carbonization, 0.5-1.1% of the weight of the dry wood chips is mixed with silicon carbide and the pre-carbonized wood chips, and then calcined under the protection of inert gas; In the step (4), before the precursor liquid is mixed with the carbonized wood substrate in the step (2), 0.3-0.8% of the weight of the precursor liquid is added to the precursor liquid and mixed evenly.

2. The method for preparing the porous carbonized wood-supported ruthenium-based hydrotalcite nanosheet oxygen evolution electrocatalyst according to claim 1, characterized in that: In the step (1), the material-liquid ratio of basswood to deionized water or ethanol is 1:20-30 g / ml; in the step (2), the material-liquid ratio of calcined wood chips to deionized water or ethanol is 1:20-30 g / ml; in the step (4), the material-liquid ratio of the product to deionized water or ethanol is 1:20-30 g / ml; in the steps (1), (2) and (4), each ultrasonic cleaning time is 20-30 min.

3. The method for preparing the porous carbonized wood-supported ruthenium-based hydrotalcite nanosheet oxygen evolution electrocatalyst according to claim 1, characterized in that: In the step (1), the wood chips have a length of 200-300 mm, a width of 150-200 mm, and a thickness of 1-2 mm.

4. The method for preparing the porous carbonized wood-supported ruthenium-based hydrotalcite nanosheet oxygen evolution electrocatalyst according to claim 1, characterized in that: In the step (2), the calcination is carried out at a temperature of 900-1100° C. and an argon gas flow rate of 0.8-1.0 L / min for 5-7 h.

5. The method for preparing the porous carbonized wood-supported ruthenium-based hydrotalcite nanosheet oxygen evolution electrocatalyst according to claim 1, characterized in that: The step (3) is specifically as follows: 0.4-0.8 mmol nickel nitrate hexahydrate, 0.1-0.4 mmol ferric nitrate nonahydrate, 0.04-0.06 mmol ruthenium trichloride and 4-6 mmol urea are dissolved in 30 mL deionized water, and stirred for 20-35 min to obtain a precursor solution.

6. The method for preparing the porous carbonized wood-supported ruthenium-based hydrotalcite nanosheet oxygen evolution electrocatalyst according to claim 1, characterized in that: The material-liquid ratio of the carbonized wood substrate in step (4) to the precursor liquid in step (3) is 0.1:20-30 g / ml.

7. The method for preparing the porous carbonized wood-supported ruthenium-based hydrotalcite nanosheet oxygen evolution electrocatalyst according to claim 1, characterized in that: In step (4), the hydrothermal conditions are: reacting at 100-200° C. for 10-14 hours.

Images