Preparation method of nanotube array composite electrode, nanotube array composite electrode and application
By contacting iron salt and nickel salt on the conductive substrate of zinc oxide nanotube array, a modified Fe2O3 nanotube array composite electrode doped with nickel ions is formed, which solves the problem of poor stability of the iron oxide catalytic electrode and achieves efficient catalytic activity and stability in the electrolytic water process.
Patent Information
- Application Number
- CN202510484676.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-17
- Publication Date
- 2025-07-29
AI Technical Summary
The existing iron oxide (ferrous hydroxide) catalytic electrodes have problems such as poor stability and weakened catalytic activity during the electrolysis process, especially when they are easily peeled off during long-term use, resulting in a decrease in electrode stability and catalytic performance.
By reacting the conductive substrate of the zinc oxide nanotube array with contact with the iron salt and nickel salt in the presence of a solvent, a modified Fe2O3 nanotube array composite electrode doped with nickel ions is formed. The coordinated action between the iron ions and nickel ions is used to expose the surface reaction sites of the catalyst, and the structural stability and catalytic activity are improved.
The structural stability and catalytic activity stability of nanotube array composite electrodes during the electrolysis process are realized, and they can maintain efficient catalytic performance for a long time and reduce electrolytic costs.
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Figure CN120384304A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of catalytic electrolysis of water, and particularly to a preparation method of a nanotube array composite electrode, a nanotube array composite electrode and an application thereof. Background Art
[0002] As an effective and important means to address the current energy crisis in human society, water electrolysis for hydrogen production has received extensive attention and research. Previous related scientific studies have shown that efficient catalysts are the key to improving the efficiency of water electrolysis. Among various catalysts, although many composite catalysts exhibit very high catalytic performance, noble metal catalysts still occupy a very important position, and efforts to completely replace noble metal catalysts continue.
[0003] Among existing water electrolysis catalysts, iron oxides (iron hydroxides) are widely considered to be the most likely catalysts to replace noble metals because they have the following advantages: (1) They are extremely abundant on the earth (about 6.3 wt% of the total mass of the earth's crust), inexpensive, low in toxicity, and high in stability; (2) Their morphology is relatively easy to control, and the synthesis method is relatively simple; (3) Fe belongs to [Ar]3d 5-8 4s 2 electronic structure, has certain redox properties, and the oxide and hydroxide have relatively narrow bandwidths, and can absorb visible light for catalysis.
[0004] When existing iron oxides (iron hydroxides) are used as catalysts for electrolyzing water, there are problems such as difficult exposure of metal active sites, poor stability, short excited state lifetime, and short hole diffusion path (2 - 4 nm), and most of them are powder catalysts. When preparing electrodes with powder catalysts, a large amount of binder is required, and the active sites of the catalyst may be lost during the preparation process. In particular, the catalyst particles wrapped inside the binder are difficult to expose the surface active sites. Moreover, during the electrolysis of water, a large number of bubbles will be generated on the surface of the catalyst. Under the action of a large number of bubbles for a long time, there is a very high risk of peeling of the powder catalyst, which deteriorates the stability of the electrode and affects the catalytic performance of the catalyst and the effect of electrolyzing water. Summary of the Invention
[0005] The purpose of the present invention is to overcome the problems of poor stability of iron oxide (iron hydroxide) catalytic electrodes and weakened catalytic activity during the electrolysis process in the prior art, and to provide a preparation method of a nanotube array composite electrode, a nanotube array composite electrode and an application thereof. The composite electrode prepared by the preparation method of the nanotube array composite electrode has the advantages of stable structure and stable catalytic activity during catalytic electrolysis.
[0006] To achieve the above object, a first aspect of the present invention provides a method for preparing a nanotube array composite electrode, comprising: contacting a zinc oxide nanotube array conductive substrate with an iron salt and a nickel salt in the presence of a solvent.
[0007] Preferably, the iron salt is selected from at least one of ferric chloride, ferric nitrate, and ferric sulfate, preferably ferric chloride; the nickel salt is selected from at least one of nickel chloride, nickel nitrate, and nickel sulfate, preferably nickel chloride.
[0008] Preferably, relative to 1 g of the zinc oxide nanotube array conductive substrate, the amount of the iron salt in terms of iron is 0.001 - 0.1 mol / L, and the amount of the nickel salt in terms of nickel is 0.001 - 0.1 mol / L.
[0009] More preferably, the molar ratio of the iron salt to the nickel salt is 1:0.8 - 1.2.
[0010] Preferably, the conditions for the contact include: a temperature of 0 - 40°C and a time of 0.5 - 12 h.
[0011] More preferably, the method further includes calcining the product of the contact reaction, and the conditions for the calcination treatment include: an inert atmosphere, a temperature of 200 - 600°C, and a time of 2 - 4 h.
[0012] Preferably, the method for preparing the zinc oxide nanotube array conductive substrate includes the following steps:
[0013] S1. Mixing a zinc salt I, naphthol, an alcohol, and a solvent to obtain an adhesive;
[0014] S2. Coating the adhesive obtained in step S1 on the surface of the conductive substrate, and drying and calcining to obtain a conductive substrate with zinc oxide seeds covered on the surface;
[0015] S3. Reacting the conductive substrate with zinc oxide seeds covered on the surface in step S2 with a mixed solution containing hexamethylenetetramine and a zinc salt II.
[0016] Preferably, in step S2, the conductive substrate is selected from at least one of conductive glass, nickel foam, copper foam, carbon cloth, carbon paper, gold sheet, silver sheet, copper sheet, platinum sheet, iridium sheet, ruthenium sheet, and titanium sheet.
[0017] More preferably, the cross-sectional area of the conductive substrate is 1 - 10000 cm 2 , more preferably 100 - 1000 cm 2 .
[0018] More preferably, the zinc salt I and the zinc salt II are selected from at least one of zinc nitrate, zinc chloride, zinc sulfate, and zinc acetate.
[0019] Further preferably, in the step S1, the concentration of zinc salt I in the binder is 0.01 - 0.5 mol / L, more preferably 0.05 - 0.2 mol / L.
[0020] Further preferably, the alcohol is selected from at least one of methanol, ethylene glycol, propylene glycol, and isopropyl alcohol. Further preferably, in the step S3, the concentration of zinc salt II in the mixed solution is 0.05 - 0.2 mol / L.
[0021] Further preferably, in the step S3, the concentration of hexamethylenetetramine in the mixed solution is 0.01 - 0.5 mol / L.
[0022] Preferably, in the binder, the volume ratio of naphthol, alcohol, and solvent is 1:2 - 4:17 - 20.
[0023] Further preferably, in the step S2, the calcination conditions include: an inert atmosphere, a calcination temperature of 350 - 800 °C, and a time of 1 - 6 h.
[0024] Further preferably, in the step S3, the reaction conditions include: a temperature of 90 - 180 °C and a time of 2 - 24 h.
[0025] In the second aspect of the present invention, a nanotube array composite electrode prepared by the preparation method described in the first aspect above is provided.
[0026] Preferably, in the nanotube array composite electrode, the content of nickel ions is 2 - 27 wt%, and the content of iron ions is 73 - 98 wt%.
[0027] In the third aspect of the present invention, an application of the nanotube array composite electrode described in the second aspect above in water electrolysis is provided.
[0028] Through the above technical solution, the preparation method of the nanotube array composite electrode provided by the present invention contacts the zinc oxide nanotube array conductive substrate with a mixed solution containing iron salt and nickel salt, so that the process of the iron salt and nickel salt contacting the zinc oxide nanotube array replaces the zinc ions in the zinc oxide nanotube array to form a new nanotube array. This nanotube array is composed of extremely small particles, and the characteristics of these small particles are similar to flaky structures, which can expose the surface reaction sites of the catalyst to the greatest extent. Through the synergistic effect between iron ions and nickel ions, the structural stability and catalytic activity stability of the modified Fe2O3 nanotube array composite electrode doped with nickel ions during the electrode electrolysis process can be further improved. Description of the Drawings
[0029] Figure 1It is the front scanning electron microscope image of the modified Fe2O3 nanotube array composite electrode doped with nickel ions prepared on FTO;
[0030] Figure 2 It is the front scanning electron microscope image of the modified Fe2O3 nanotube array composite electrode doped with nickel ions prepared on nickel foam;
[0031] Figure 3 It is the side scanning electron microscope image of the modified Fe2O3 nanotube array composite electrode doped with nickel ions prepared on FTO;
[0032] Figure 4 It is the transmission electron microscope image of the modified Fe2O3 nanotube array composite electrode doped with nickel ions prepared on nickel foam;
[0033] Figure 5 It is the electrolysis performance test of the modified FeOOH nanotube array composite electrode doped with nickel ions prepared on nickel foam;
[0034] Figure 6 It is the water photolysis performance test of the modified Fe2O3 nanotube array composite electrode doped with nickel ions prepared on FTO. Detailed implementation mode
[0035] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.
[0036] The first aspect of the present invention provides a preparation method of a nanotube array composite electrode, including: in the presence of a solvent, bringing a zinc oxide nanotube array conductive substrate into contact reaction with an iron salt and a nickel salt.
[0037] The inventors unexpectedly found during the research on the nanotube array composite electrode that bringing the zinc oxide nanotube array conductive substrate into contact reaction with the iron salt and the nickel salt causes the iron salt and the nickel salt to replace the zinc ions in the zinc oxide nanotube array during the contact process to form a new nanotube array, and a modified Fe2O3 nanotube array composite electrode doped with nickel ions is prepared. This nanotube array is composed of extremely small particles, and these small particles have the characteristics similar to a flaky structure, which can expose the surface reaction sites of the catalyst to the greatest extent. Through the synergistic effect between iron ions and nickel ions, the structural stability and catalytic activity stability of the modified Fe2O3 nanotube array composite electrode doped with nickel ions during the electrode electrolysis process can be further improved.
[0038] The preparation method of the nanotube array composite electrode provided by the present invention contacts the zinc oxide nanotube array conductive substrate with a mixed solution containing iron salt and nickel salt, so that the process of contacting the iron salt and nickel salt with the zinc oxide nanotube array replaces the zinc ions in the zinc oxide nanotube array to form a new nanotube array. This nanotube array is composed of extremely small particles, and the characteristics of these small particles are similar to flaky structures, which can expose the surface reaction sites of the catalyst to the greatest extent. Through the synergistic effect with iron ions and nickel ions, the structural stability and catalytic activity stability of the modified Fe2O3 nanotube array composite electrode doped with nickel ions during the electrode electrolysis process can be further improved.
[0039] According to the present invention, preferably, the iron salt is selected from at least one of ferric chloride, ferric nitrate, and ferric sulfate, and preferably ferric chloride; the nickel salt is selected from at least one of nickel chloride, nickel nitrate, and nickel sulfate, and preferably nickel chloride. The inventors found that when the above preferred implementation mode is adopted, the structural stability of the nanotube array composite electrode prepared by this method and the stability of the catalytic activity during the catalytic electrolysis process can be further improved.
[0040] According to the present invention, preferably, relative to 1 g of the zinc oxide nanotube array conductive substrate, the dosage of the iron salt in terms of iron is 0.001 - 0.1 mol / L, specifically it can be 0.001 mol / L, 0.01 mol / L, 0.1 mol / L, or any value between the above two values; the dosage of the nickel salt in terms of nickel is 0.001 - 0.1 mol / L, specifically it can be 0.001 mol / L, 0.01 mol / L, 0.1 mol / L, or any value between the above two values. Further preferably, the molar ratio of the iron salt to the nickel salt is 1:0.8 - 1.2, specifically it can be 1:0.8, 1:1, 1:1.2, or any value between the above two values. The inventors found that when the above preferred implementation mode is adopted, the structural stability of the nanotube array composite electrode prepared by this method and the stability of the catalytic activity during the catalytic electrolysis process can be further improved.
[0041] According to the present invention, preferably, the conditions for the contact include: the temperature is 0 - 40 °C, specifically it can be 0 °C, 20 °C, 40 °C, or any value between the above two values; the time is 0.5 - 12 h, specifically it can be 0.5 h, 1 h, 2 h, 4 h, 8 h, 12 h, or any value between the above two values. The inventors found that when the above preferred implementation mode is adopted, the structural stability of the nanotube array composite electrode prepared by this method and the stability of the catalytic activity during the catalytic electrolysis process can be further improved.
[0042] According to the present invention, further preferably, the method further includes calcining the product of the contact reaction, and the conditions of the calcining treatment include: an inert atmosphere, a temperature of 200-600 °C, specifically 200 °C, 400 °C, 600 °C, or any value between the above two values; more preferably 200-400 °C, specifically 200 °C, 300 °C, 400 °C, or any value between the above two values; the time is 2-4 h, specifically 2 h, 3 h, 4 h, or any value between the above two values, and the heating rate during calcining is 5-8 °C / min, specifically 5 °C / min, 6 °C / min, 7 °C / min, 8 °C / min, or any value between the above two values. The inventors found that when the above preferred implementation mode is adopted, the structural stability of the nanotube array composite electrode prepared by this method and the stability of the catalytic activity during the catalytic electrolysis can be further improved.
[0043] According to the present invention, preferably, the method for preparing the zinc oxide nanotube array conductive substrate includes the following steps:
[0044] S1. Mix a zinc salt I, naphthol, an alcohol, and a solvent to obtain an adhesive;
[0045] S2. Coat the adhesive prepared in step S1 on the surface of the conductive substrate, and obtain a conductive substrate with zinc oxide seeds covered on the surface after drying and calcining;
[0046] S3. React the conductive substrate with zinc oxide seeds covered on the surface in step S2 with a mixed solution containing hexamethylenetetramine and a zinc salt II. The inventors found that the zinc oxide nanotube array conductive substrate prepared by the above method can further improve the structural stability of the nanotube array composite electrode prepared using this zinc oxide nanotube array conductive substrate and the stability of the catalytic activity during the catalytic electrolysis.
[0047] In the present invention, the solvent can be a commonly used solvent in the art, can be water, and further preferably distilled water.
[0048] According to the present invention, preferably, in the step S2, the conductive substrate is selected from at least one of conductive glass, nickel foam, copper foam, carbon cloth, carbon paper, gold sheet, silver sheet, copper sheet, platinum sheet, iridium sheet, ruthenium sheet and titanium sheet. Further preferably, the conductive substrate is selected from at least one of conductive glass, nickel foam, carbon paper, carbon cloth and copper foam. Specifically, the conductive substrate can be conductive glass, or nickel foam, or copper foam. Exemplarily, the conductive substrate can be FTO conductive glass. The inventors found that the zinc oxide nanotube array conductive substrate prepared by using the above conductive substrate can further improve the structural stability of the nanotube array composite electrode prepared by using the zinc oxide nanotube array conductive substrate and the stability of the catalytic activity during the catalytic electrolysis process.
[0049] According to the present invention, further preferably, before the adhesive is coated on the surface of the conductive substrate in the step S2, the conductive substrate is further subjected to cleaning and activation treatment. Specifically, there are no strict limitations on the methods of cleaning and activation treatment, and the common methods in the art can be used for cleaning and activation treatment. Exemplarily, taking the cleaning of the FTO glass substrate as an example, the FTO glass substrate is subjected to a comprehensive cleaning at least three times in acetone, distilled water and absolute ethanol in sequence, and then dried at a temperature of 25 - 60 °C for 0.5 - 4 h for standby. The dried FTO glass substrate is immersed in a 0.5 - 1 mol / L KMnO4 solution for 0.5 - 0.6 hours for activation. After activation, the FTO glass substrate is rinsed with clean water and then dried again at a temperature of 25 - 60 °C for 0.5 - 4 h for standby.
[0050] According to the present invention, further preferably, the cross-sectional area of the conductive substrate is 1 - 10000 cm 2 , specifically it can be 1 cm 2 , 100 cm 2 , 1000 cm 2 , 3000 cm 2 , 5000 cm 2 , 7000 cm 2 , 10000 cm 2 , or any value between the above two values; more preferably 100 - 1000 cm 2 , specifically it can be 100 cm 2 , 200 cm 2 , 300 cm 2 , 400 cm 2 , 500 cm 2 , 600 cm 2 , 700 cm 2 , 800 cm 2 , 900 cm 2 , 1000 cm2 or any value between the above two values. The inventors have found that the zinc oxide nanotube array conductive substrate prepared by the above preferred embodiment can further improve the structural stability of the nanotube array composite electrode prepared using the zinc oxide nanotube array conductive substrate and the stability of the catalytic activity during the catalytic electrolysis process.
[0051] According to the present invention, further preferably, the zinc salt I and the zinc salt II are selected from at least one of zinc nitrate, zinc chloride, zinc sulfate, and zinc acetate. Specifically, the zinc salt I and the zinc salt II can be zinc nitrate alone, or zinc chloride alone, or zinc sulfate alone, or zinc acetate alone, or a mixture of zinc nitrate and zinc chloride, or a mixture of zinc nitrate and zinc sulfate, or a mixture of zinc nitrate and zinc acetate. The inventors have found that the zinc oxide nanotube array conductive substrate prepared by the above preferred embodiment can further improve the structural stability of the nanotube array composite electrode prepared using the zinc oxide nanotube array conductive substrate and the stability of the catalytic activity during the catalytic electrolysis process.
[0052] According to the present invention, further preferably, in the step S1, the concentration of the zinc salt I in the binder is 0.01 - 0.5 mol / L, specifically it can be 0.01 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, or any value between the above two values; more preferably it is 0.05 - 0.2 mol / L, specifically it can be 0.05 mol / L, 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, or any value between the above two values. The inventors have found that the zinc oxide nanotube array conductive substrate prepared by the above preferred embodiment can further improve the structural stability of the nanotube array composite electrode prepared using the zinc oxide nanotube array conductive substrate and the stability of the catalytic activity during the catalytic electrolysis process.
[0053] According to the present invention, the alcohol is a volatile alcohol; further preferably, the alcohol is selected from at least one of methanol, ethylene glycol, propylene glycol, and isopropyl alcohol; specifically it can be methanol alone, or ethylene glycol alone, or propylene glycol alone, or isopropyl alcohol alone, or a mixture of methanol and ethylene glycol, or a mixed solution of propylene glycol and isopropyl alcohol. The inventors have found that the zinc oxide nanotube array conductive substrate prepared by the above preferred embodiment can further improve the structural stability of the nanotube array composite electrode prepared using the zinc oxide nanotube array conductive substrate and the stability of the catalytic activity during the catalytic electrolysis process.
[0054] According to the present invention, further preferably, in the step S3, the concentration of zinc salt II in the mixed solution is 0.05 - 0.2 mol / L, specifically, it can be 0.05 mol / L, 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, or any value between the above two values. The inventors have found that the zinc oxide nanotube array conductive substrate prepared by the above preferred embodiment can further improve the structural stability of the nanotube array composite electrode prepared using the zinc oxide nanotube array conductive substrate and the stability of the catalytic activity during the catalytic electrolysis process.
[0055] According to the present invention, further preferably, in the step S3, the concentration of hexamethylenetetramine in the mixed solution is 0.01 - 0.5 mol / L, specifically, it can be 0.05 mol / L, 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, or any value between the above two values. The inventors have found that the zinc oxide nanotube array conductive substrate prepared by the above preferred embodiment can further improve the structural stability of the nanotube array composite electrode prepared using the zinc oxide nanotube array conductive substrate and the stability of the catalytic activity during the catalytic electrolysis process.
[0056] According to the present invention, preferably, in the binder, the volume ratio of naphthol, alcohol and solvent is 1:2 - 4:17 - 20, specifically, it can be 1:2:17, 1:3:18, 1:4:20, or any value between the above ratios. The inventors have found that the zinc oxide nanotube array conductive substrate prepared by the above preferred embodiment can further improve the structural stability of the nanotube array composite electrode prepared using the zinc oxide nanotube array conductive substrate and the stability of the catalytic activity during the catalytic electrolysis process.
[0057] According to the present invention, further preferably, in the step S2, the conditions for calcination include: an inert atmosphere, specifically nitrogen, argon or air; the calcination temperature is 350 - 800 °C, specifically 350 °C, 400 °C, 500 °C, 600 °C, 700 °C, 800 °C, or any value between the above two values; the time is 1 - 6 h, specifically 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, or any value between the above two values; more preferably 2 - 4 h, specifically 2 h, 3 h, 4 h, or any value between the above two values; the heating rate during calcination is 5 - 8 °C / min, specifically 5 °C / min, 6 °C / min, 7 °C / min, 8 °C / min, or any value between the above two values. The inventors have found that the zinc oxide nanotube array conductive substrate prepared by the above preferred implementation method can further improve the structural stability of the nanotube array composite electrode prepared using the zinc oxide nanotube array conductive substrate and the stability of the catalytic activity during the catalytic electrolysis process.
[0058] According to the present invention, further preferably, in the step S3, the conditions for the reaction include: the temperature is 90 - 180 °C, specifically 90 °C, 110 °C, 130 °C, 150 °C, 180 °C, or any value between the above two values; the time is 2 - 24 h, specifically 2 h, 4 h, 6 h, 8 h, 10 h, 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, 24 h, or any value between the above two values. The inventors have found that the zinc oxide nanotube array conductive substrate prepared by the above preferred implementation method can further improve the structural stability of the nanotube array composite electrode prepared using the zinc oxide nanotube array conductive substrate and the stability of the catalytic activity during the catalytic electrolysis process.
[0059] According to the present invention, preferably, in the step S3, it also includes washing with water and drying after the reaction. After washing the zinc oxide nanotube array conductive substrate with water, the residual solvent and by-products on the surface can be removed. After rinsing 3 - 5 times with deionized water, it is vacuum dried at a temperature of 50 - 60 °C, specifically 50 °C, 55 °C, 60 °C, or any value between the above two values; the time is 1 - 2 h, specifically 1 h, 1.5 h, 2 h, or any value between the above two values. The inventors have found that the dried conductive substrate can better react with nickel ions and iron ions, improving the structural stability during the electrolysis of the nanotube array composite electrode and the stability of the catalytic activity during the catalytic electrolysis process.
[0060] As a relatively preferred implementation method of the present invention, taking the preparation method of the zinc oxide nanotube array conductive substrate using FTO glass as the conductive substrate as an example, the specific preparation process is as follows:
[0061] (1) Preparation of Zinc Oxide Nanotube Array Conductive Substrate
[0062] S1. Mix zinc salt I, naphthol, isopropanol and distilled water to obtain an adhesive. In the adhesive, the concentration of zinc salt I is 0.05 - 0.2 mol / L, and the volume ratio of naphthol, isopropanol and distilled water is 1:2 - 4:17 - 20;
[0063] S2. Coat the adhesive prepared in step S1 on the surface of the FTO glass conductive substrate with a cross-sectional area of 100 - 1000 cm 2 After natural drying, under the conditions of nitrogen and heating at a heating rate of 5 - 8 °C / min to a temperature of 350 - 800 °C, calcine for 2 - 4 h to obtain a conductive substrate with zinc oxide seed crystals covered on the surface;
[0064] S3. React the conductive substrate with zinc oxide seed crystals covered on the surface in step S2 and a mixed solution containing hexamethylenetetramine and zinc salt II at a temperature of 90 - 180 °C for 2 - 24 h. The concentration of zinc salt II in the mixed solution is 0.05 - 0.2 mol / L, and the concentration of hexamethylenetetramine is 0.01 - 0.5 mol / L. After the reaction, rinse the conductive substrate with grown zinc oxide nanotube array with deionized water for 3 - 5 times, and then dry it at a temperature of 50 - 60 °C for 1 - 2 h for standby.
[0065] (2) Preparation of Nanotube Array Composite Electrode
[0066] In the presence of a solvent, bring the zinc oxide nanotube array conductive substrate prepared in step (1) into contact with ferric chloride and nickel chloride, and react at a temperature of 0 - 40 °C for 0.5 - 12 h. Relative to 1 g of the zinc oxide nanotube array conductive substrate, the dosage of ferric chloride in terms of iron is 0.001 - 0.1 mol / L, and the dosage of nickel chloride in terms of nickel is 0.001 - 0.1 mol / L; after the reaction, rinse the surface of the conductive substrate with deionized water for 3 - 5 times, and dry it under vacuum to obtain a modified FeOOH nanotube array composite electrode doped with nickel ions; calcine the reaction product under the conditions of nitrogen and heating at a heating rate of 5 - 8 °C / min to a temperature of 200 - 400 °C for 2 - 4 h to obtain a modified Fe2O3 nanotube array composite electrode doped with nickel ions.
[0067] The above substances can be obtained through commercial purchase.
[0068] In a second aspect of the present invention, there is provided a nanotube array composite electrode prepared by the preparation method described in the first aspect above. The inventors have found that the nanotube array in the composite electrode is composed of extremely small particles, and these small particles combine to form a structure similar to a flake structure, which can expose the surface reaction sites of the catalyst to the greatest extent. Through the synergistic effect between iron ions and nickel ions, the structural stability during the electrolysis process of the nanotube array composite electrode and the catalytic activity stability during the catalytic electrolysis process are improved.
[0069] According to the present invention, preferably, in the nanotube array composite electrode, the content of nickel ions is 2 - 27 wt%, specifically it can be 2 wt%, 12 wt%, 27 wt%, or any value between the above two values; the content of iron ions is 73 - 98 wt%, specifically it can be 73 wt%, 82 wt%, 98 wt%, or any value between the above two values. The inventors have found that the structure of this nanotube array composite electrode is stable and can maintain the catalytic activity stability during a long-term catalytic electrolysis process.
[0070] In the present invention, in the nanotube array composite electrode, it also contains oxygen atoms, and the proportion of oxygen atoms during the preparation of the nanotube array composite electrode corresponds to the atomic ratio in Fe2O3.
[0071] In a third aspect of the present invention, there is provided the application of the nanotube array composite electrode described in the second aspect above in electrolyzing water. The inventors have found that when this nanotube array composite electrode is applied to electrolyze water, it has higher catalytic activity and stability, can meet the stability of long-term electrolytic catalysis, and reduce the electrolysis cost.
[0072] In the present invention, the device for electrolyzing water is not strictly limited, and a commonly used electrolyzing water device in the art can be used. Exemplarily, the oxygen evolution half-reaction electrochemical test system is carried out in a three-electrode electrolytic cell.
[0073] According to the present invention, preferably, the electrolyte is an aqueous solution of NaOH and / or an aqueous solution of KOH, and the concentration of the solute in the electrolyte is 0.1 - 1 mol / L, specifically it can be 0.1 mol / L, 0.5 mol / L, 1 mol / L, or any value between the above two values. Further preferably, the electrolysis conditions at least include: the irradiation power of the xenon lamp ≥ 300 W, specifically it can be 300 W, 400 W, 500 W, or any value greater than or equal to 500 W; the temperature is 10 - 50 °C, specifically it can be 10 °C, 25 °C, 50 °C, or any value between the above two values.
[0074] The present invention will be described in detail below through examples.
[0075] The FTO glass substrate was purchased from Foshan Shengrui Glass Products Co., Ltd., and the product number was 10125073916324. Without special instructions, the reagents or raw materials used were all conventional biochemical reagent grade products.
[0076] In the following examples, without special instructions, the room temperature was 25 ± 5 °C.
[0077] The conductive substrates used in the following examples were cleaned and activated by the following method;
[0078] (1) The conductive substrate was thoroughly cleaned three times successively in acetone, distilled water and absolute ethanol, and then dried at 60 °C for 3 h for standby;
[0079] (2) The cleaned conductive substrate in step (1) was immersed in a 0.5 mol / L KMnO4 solution for 0.5 h. After activating the surface of the FTO glass substrate, it was rinsed with water and then dried again at 60 °C for 3 h for standby.
[0080] Example 1
[0081] (1) Preparation of zinc oxide nanotube array conductive substrate
[0082] S1. 20 mg of zinc nitrate hexahydrate, 50 μL of naphthol, 100 μL of isopropanol and 850 μL of distilled water were mixed to obtain an adhesive. In the adhesive, the concentration of zinc nitrate was 0.2 mol / L, and the volume ratio of naphthol, isopropanol and distilled water was 1:2:17;
[0083] S2. 200 μL of the adhesive prepared in step S1 was coated on the surface of the activated and cleaned FTO glass conductive substrate with a cross-sectional area of 100 cm 2 . After natural air drying at room temperature, it was calcined at 400 °C for 2 h under the conditions of nitrogen and a heating rate of 5 °C / min to obtain a conductive substrate with zinc oxide seeds covered on the surface;
[0084] S3. The conductive substrate with zinc oxide seeds covered on the surface in step S2 and a mixed solution containing hexamethylenetetramine and zinc nitrate were reacted at 95 °C for 6 h. The concentration of zinc nitrate in the mixed solution was 0.05 mol / L, and the concentration of hexamethylenetetramine was 0.01 mol / L. After the reaction, the conductive substrate grown with zinc oxide nanotube arrays was rinsed with distilled water and dried at 100 °C for 2 h for standby.
[0085] (2) Preparation of nanotube array composite electrode
[0086] In the presence of solvent water, the zinc oxide nanotube array conductive substrate prepared in step (1) is mixed and contacted with ferric chloride and nickel chloride, and the reaction is carried out at a temperature of 40 °C for 0.5 h. Relative to 1 g of the zinc oxide nanotube array conductive substrate, the dosage of ferric chloride in terms of iron is 0.005 mol / L, the dosage of nickel chloride in terms of nickel is 0.005 mol / L, and the molar ratio of ferric chloride to nickel chloride is 1:1. After the reaction, the surface of the conductive substrate is rinsed three times with deionized water and dried in vacuum to obtain a modified FeOOH nanotube array composite electrode doped with nickel ions. The reaction product is calcined at a temperature of 400 °C for 2 h under nitrogen with a heating rate of 5 °C / min to obtain a nanotube array composite electrode of modified Fe2O3 doped with nickel ions.
[0087] By inductively coupled plasma (ICP) method, the content of iron ions in the modified Fe2O3 nanotube array doped with nickel ions is measured to be about 81 wt%, and the content of nickel ions is about 19%.
[0088] Example 2
[0089] (1) Preparation of zinc oxide nanotube array conductive substrate
[0090] S1. 20 mg of zinc acetate, 50 μL of naphthol, 200 μL of propylene glycol and 1000 μL of distilled water are mixed to obtain an adhesive. In the adhesive, the concentration of zinc acetate is 0.05 mol / L, and the volume ratio of naphthol, propylene glycol and distilled water is 1:4:20.
[0091] S2. 1250 μL of the adhesive prepared in step S1 is coated on the surface of the activated and cleaned nickel foam conductive substrate with a cross-sectional area of 500 cm 2 . After natural air drying at room temperature, it is calcined at a temperature of 800 °C for 4 h under nitrogen with a heating rate of 6 °C / min to obtain a conductive substrate with zinc oxide seeds covered on the surface.
[0092] S3. The conductive substrate with zinc oxide seeds covered on the surface in step S2 and a mixed solution containing hexamethylenetetramine and zinc acetate are reacted at a temperature of 120 °C for 24 h. The concentration of zinc acetate in the mixed solution is 0.2 mol / L, and the concentration of hexamethylenetetramine is 0.5 mol / L. After the reaction, the conductive substrate with zinc oxide nanotube array grown is rinsed with distilled water and dried at a temperature of 110 °C for 1 h for standby.
[0093] (2) Preparation of nanotube array composite electrode
[0094] In the presence of a solvent, the zinc oxide nanotube array conductive substrate prepared in step (1) is mixed and contacted with ferric chloride and nickel chloride, and the reaction is carried out at a temperature of 25 °C for 6 h. For 1 g of the zinc oxide nanotube array conductive substrate, the dosage of ferric chloride in terms of iron is 0.001 mol / L, the dosage of nickel chloride in terms of nickel is 0.001 mol / L, and the molar ratio of ferric chloride to nickel chloride is 1:1.2; after the reaction, the surface of the conductive substrate is rinsed three times with deionized water and vacuum dried to obtain a modified FeOOH nanotube array composite electrode doped with nickel ions; the reaction product is calcined at a temperature of 300 °C for 4 h under nitrogen with a heating rate of 6 °C / min to obtain a nanotube array composite electrode of modified Fe2O3 doped with nickel ions.
[0095] By means of inductively coupled plasma (ICP), it is determined that the content of iron ions in the modified Fe2O3 nanotube array doped with nickel ions is about 73 wt%, and the content of nickel ions is about 27 wt%.
[0096] Example 3
[0097] (1) Preparation of zinc oxide nanotube array conductive substrate
[0098] S1. 20 mg of zinc sulfate, 50 μL of naphthol, 150 μL of ethylene glycol and 1200 μL of distilled water are mixed to obtain an adhesive. In the adhesive, the concentration of zinc sulfate is 0.1 mol / L, and the volume ratio of naphthol, ethylene glycol and distilled water is 1:3:18;
[0099] S2. 1400 μL of the adhesive prepared in step S1 is coated on the surface of the activated and cleaned copper foam conductive substrate with a cross-sectional area of 1000 cm 2 . After natural air drying at room temperature, it is calcined at a temperature of 600 °C for 3 h under argon with a heating rate of 8 °C / min to obtain a conductive substrate with zinc oxide seeds covered on the surface;
[0100] S3. The conductive substrate with zinc oxide seeds covered on the surface in step S2 and a mixed solution containing hexamethylenetetramine and zinc sulfate are reacted at a temperature of 180 °C for 2 h. The concentration of zinc sulfate in the mixed solution is 0.1 mol / L, and the concentration of hexamethylenetetramine is 0.2 mol / L. After the reaction, the conductive substrate with zinc oxide nanotube arrays grown is rinsed with distilled water and dried at a temperature of 105 °C for 1.5 h for standby.
[0101] (2) Preparation of nanotube array composite electrode
[0102] In the presence of solvent water, the conductive substrate of zinc oxide nanotube array prepared in step (1) is mixed and contacted with ferric chloride and nickel chloride, and the reaction is carried out at a temperature of 0 °C for 12 h. Relative to 1 g of the conductive substrate of zinc oxide nanotube array, the dosage of ferric chloride in terms of iron is 0.1 mol / L, the dosage of nickel chloride in terms of nickel is 0.1 mol / L, and the molar ratio of ferric chloride to nickel chloride is 1:0.8; after the reaction, the surface of the conductive substrate is rinsed three times with deionized water and dried in vacuum to obtain a modified FeOOH nanotube array composite electrode doped with nickel ions; the reaction product is calcined at a temperature of 200 °C for 3 h under the conditions of nitrogen and a heating rate of 8 °C / min to obtain a modified Fe2O3 nanotube array composite electrode doped with nickel ions.
[0103] By inductively coupled plasma (ICP) method, it is determined that the content of iron ions in the modified Fe2O3 nanotube array doped with nickel ions is about 89 wt%, and the content of nickel ions is about 11 wt%.
[0104] Example 4
[0105] The modified Fe2O3 nanotube array composite electrode doped with nickel ions is prepared according to the method of Example 1, except that the mixing and contacting of the conductive substrate of zinc oxide nanotube array with ferric chloride and nickel chloride is replaced by the mixing and contacting of the conductive substrate of zinc oxide nanotube array with ferric nitrate and nickel nitrate.
[0106] By inductively coupled plasma (ICP) method, it is determined that the content of iron ions in the modified Fe2O3 nanotube array doped with nickel ions is about 78 wt%, and the content of nickel ions is about 22 wt%.
[0107] Example 5
[0108] The modified Fe2O3 nanotube array composite electrode doped with nickel ions is prepared according to the method of Example 1, except that the molar ratio of ferric chloride to nickel chloride of 1:1 is replaced by a molar ratio of ferric chloride to nickel chloride of 1:3.
[0109] By inductively coupled plasma (ICP) method, it is determined that the content of iron ions in the modified Fe2O3 nanotube array doped with nickel ions is about 69 wt%, and the content of nickel ions is about 31 wt%.
[0110] Example 6
[0111] The modified Fe2O3 nanotube array composite electrode doped with nickel ions is prepared according to the method of Example 1, except that the dosage of ferric chloride in terms of iron of 0.005 mol / L and the dosage of nickel chloride in terms of nickel of 0.005 mol / L are replaced by the dosage of ferric chloride in terms of iron of 0.5 mol / L and the dosage of nickel chloride in terms of nickel of 0.5 mol / L.
[0112] By inductively coupled plasma (ICP) method, the content of iron ions in the modified Fe2O3 nanotube array doped with nickel ions is about 82 wt%, and the content of nickel ions is about 18 wt%.
[0113] Example 7
[0114] Prepare the nanotube array composite electrode of modified Fe2O3 doped with nickel ions according to the method of Example 1. The difference is that in the preparation of the nanotube array composite electrode in step (2), the calcination at 400 °C for 2 h is replaced by the calcination at 600 °C for 1 h.
[0115] By inductively coupled plasma (ICP) method, the content of iron ions in the modified (Fe2O3)FeOOH nanotube array doped with nickel ions is about 81 wt%, and the content of nickel ions is about 19 wt%.
[0116] Example 8
[0117] Prepare the nanotube array composite electrode of modified Fe2O3 doped with nickel ions according to the method of Example 1. The difference is that in the preparation of the nanotube array composite electrode in step (2), the calcination at 400 °C for 2 h is replaced by the calcination at 1000 °C for 1 h.
[0118] By inductively coupled plasma (ICP) method, the content of iron ions in the modified (Fe2O3)FeOOH nanotube array doped with nickel ions is about 81%, and the content of nickel ions is about 19 wt%.
[0119] Example 9
[0120] Prepare the nanotube array composite electrode of modified Fe2O3 doped with nickel ions according to the method of Example 1. The difference is that in step (1), the ZnO nanotube array conductive substrate is prepared by the following method:
[0121] Ultrasonically clean the FTO conductive glass substrate successively in acetone, ethanol, and water. Using the cleaned FTO conductive glass substrate as the working electrode, a platinum sheet as the counter electrode, a saturated calomel electrode as the reference electrode, and an aqueous solution containing 0.2 mM Zn(Ac)2 and 0.1 M KCl, at a temperature of 85 °C, with continuous oxygen bubbles being introduced as the electrolyte; by applying a negative potential of -1 V (relative to the reference electrode) to the working electrode for 2 hours, a ZnO nanorod array is electrochemically deposited on the FTO conductive glass substrate.
[0122] By inductively coupled plasma (ICP) method, the content of iron ions in the modified Fe2O3 nanotube array doped with nickel ions is about 81 wt%, and the content of nickel ions is about 19 wt%.
[0123] Comparative Example 1
[0124] The FTO conductive glass substrate was ultrasonically cleaned successively in acetone, ethanol, and water. Using the cleaned FTO conductive glass substrate as the working electrode, a platinum sheet as the counter electrode, a saturated calomel electrode as the reference electrode, and an aqueous solution containing 0.2 mM Zn(Ac)2 and 0.1 M KCl, at a temperature of 85 °C, with oxygen bubbles continuously introduced as the electrolyte; by applying a negative potential of -1 V (relative to the reference electrode) to the working electrode for 2 hours, ZnO nanorod arrays were electrochemically deposited on the FTO conductive glass substrate.
[0125] Using the FTO conductive glass substrate carrying ZnO nanorod arrays as the working electrode, a platinum sheet as the counter electrode, a saturated calomel electrode as the reference electrode, and an aqueous solution containing 5 mM FeCl2, at a temperature of 50 °C as the electrolyte; by applying a positive potential of 0.95 V for 2 minutes to the working electrode (relative to the reference electrode), the Fe 2+ was oxidized to Fe 3+ and FeOOH precipitates were formed. The FeOOH precipitates were continuously deposited on the surface of the ZnO nanorods. At the same time, the ZnO nanorods gradually dissolved until completely disappeared due to the acidity of the electrolyte and the influence of the applied positive potential, forming FeOOH nanotube arrays, thus obtaining an FTO conductive glass substrate with FeOOH nanotube arrays grown on it; the FTO conductive glass substrate with FeOOH nanotube arrays grown on it was placed in a tube furnace and annealed at 500 °C for 2 hours to convert the FeOOH nanotube arrays into Fe2O3 nanotube arrays, and Fe2O3 nanotube arrays were obtained on the FTO conductive glass substrate.
[0126] By inductively coupled plasma (ICP) method, the iron content in the Fe2O3 nanotube array was determined to be about 100 wt%.
[0127] Comparative Example 2
[0128] The modified Fe2O3 nanotube array composite electrode doped with nickel ions was prepared according to the method of Example 1, except that nickel chloride was not added.
[0129] Comparative Example 3
[0130] The nanotube array composite electrode of modified Fe2O3 doped with nickel ions was prepared according to the method of Example 1, except that iron chloride was not added.
[0131] Comparative Example 4
[0132] Prepare a modified Fe2O3 nanotube array composite electrode doped with nickel ions according to the method of Example 1, except that nickel chloride is replaced with cobalt chloride.
[0133] Comparative Example 5
[0134] Prepare a modified Fe2O3 nanotube array composite electrode doped with nickel ions according to the method of Example 1, except that iron chloride is replaced with cobalt chloride.
[0135] Test Example 1
[0136] The nanotube array composite electrodes prepared in Examples 1 - 9 and Comparative Examples 1 - 5 were respectively subjected to electrolytic water tests. The oxygen evolution half - reaction electrochemical test system was carried out in a three - electrode electrolytic cell. The electrolyte was 1.0 mol / L KOH solution. The counter electrode was a Pt wire, and the reference electrode was an Ag / AgCl electrode. The nanotube array composite electrodes prepared in Examples 1 - 9 and Comparative Examples 1 - 5 were used as the working electrode. Before the oxygen evolution reaction test, the electrolyte was purged with oxygen for 30 minutes to saturate the solution with oxygen.
[0137] The photoelectrode test system was the same as the above - mentioned electrochemical test system, except that a 300W xenon lamp was added as the light source. The electro(photo)lytic water electrochemical performance test results are shown in Table 1.
[0138] Table 1
[0139]
[0140]
[0141] It can be seen from the results in Table 1 that the nickel - doped Examples 1 - 9 prepared by the preparation method of the present invention have significantly better effects than Comparative Examples 1 - 5 during the processes of electrolytic water and photolytic water, and better stability.
[0142] The preparation method of the nanotube array composite electrode provided by the present invention contacts the zinc oxide nanotube array conductive substrate with a mixed solution containing iron salt and nickel salt, so that the process of iron salt and nickel salt contacting the zinc oxide nanotube array replaces the zinc ions in the zinc oxide nanotube array to form a new nanotube array. This nanotube array is composed of extremely small particles, and these small particles are similar to the characteristics of a flaky structure, which can expose the surface reaction sites of the catalyst to the greatest extent. Through the synergistic effect with iron ions and nickel ions, it can further improve the structural stability and catalytic activity stability of the modified Fe2O3 nanotube array composite electrode doped with nickel ions during the electrode electrolysis process.
[0143] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.
Claims
1. A preparation method of a nanotube array composite electrode, characterized in that, Comprising: In the presence of a solvent, the zinc oxide nanotube array conductive substrate is brought into contact reaction with an iron salt and a nickel salt.
2. The preparation method according to claim 1, characterized in that, The iron salt is selected from at least one of ferric chloride, ferric nitrate and ferric sulfate, preferably ferric chloride; the nickel salt is selected from at least one of nickel chloride, nickel nitrate and nickel sulfate, preferably nickel chloride.
3. The preparation method according to claim 1, wherein, Relative to 1 g of the zinc oxide nanotube array conductive substrate, the dosage of the iron salt in terms of iron is 0.001 - 0.1 mol / L, and the dosage of the nickel salt in terms of nickel is 0.001 - 0.1 mol / L; Preferably, the molar ratio of the iron salt to the nickel salt is 1:0.8 - 1.
2.
4. The preparation method according to claim 1, characterized in that, The conditions for the contact include: the temperature is 0 - 40 °C, and the time is 0.5 - 12 h; Preferably, the method further includes calcining the product of the contact reaction, and the conditions for the calcining include: an inert atmosphere, the temperature is 200 - 600 °C, and the time is 2 - 4 h.
5. The preparation method according to any one of claims 1-4, characterized in that, The preparation method of the zinc oxide nanotube array conductive substrate includes the following steps: S1. Mix a zinc salt I, naphthol, an alcohol and a solvent to obtain an adhesive; S2. Coat the adhesive obtained in step S1 on the surface of the conductive substrate, and obtain a conductive substrate with zinc oxide seeds covered on the surface through drying and calcining; S3. React the conductive substrate with zinc oxide seeds covered on the surface in step S2 with a mixed solution containing hexamethylenetetramine and a zinc salt II.
6. The preparation method according to claim 5, wherein In step S2, the conductive substrate is selected from at least one of conductive glass, nickel foam, copper foam, carbon cloth, carbon paper, gold sheet, silver sheet, copper sheet, platinum sheet, iridium sheet, ruthenium sheet and titanium sheet; Preferably, the cross-sectional area of the conductive substrate is 1-10000 cm 2 , preferably 100-1000 cm 2 ; Preferably, the zinc salt I and the zinc salt II are selected from at least one of zinc nitrate, zinc chloride, zinc sulfate and zinc acetate; Preferably, in step S1, the concentration of the zinc salt I in the adhesive is 0.01 - 0.5 mol / L, more preferably 0.05 - 0.2 mol / L; Preferably, the alcohol is selected from at least one of methanol, ethylene glycol, propylene glycol and isopropyl alcohol; preferably, in step S3, the concentration of the zinc salt II in the mixed solution is 0.05 - 0.2 mol / L; Preferably, in step S3, the concentration of the hexamethylenetetramine in the mixed solution is 0.01 - 0.5 mol / L.
7. The preparation method according to claim 5, characterized in that, In the adhesive, the volume ratio of naphthol, alcohol and solvent is 1:2 - 4:17 - 20; Preferably, in step S2, the conditions for the calcining include: an inert atmosphere, the calcining temperature is 350 - 800 °C, and the time is 1 - 6 h; Preferably, in step S3, the conditions for the reaction include: the temperature is 90 - 180 °C, and the time is 2 - 24 h.
8. A nanotube array composite electrode prepared by the preparation method according to any one of claims 1 - 7.
9. The composite electrode according to claim 8, wherein, In the nanotube array composite electrode, the content of nickel ions is 2 - 27 wt%, and the content of iron ions is 73 - 98 wt%.
10. Application of the nanotube array composite electrode according to claim 8 or 9 in electrolyzing water.