Method of making an electrode, electrode and use thereof

Abstract

The application provides a preparation method of an electrode, the electrode and application thereof, and relates to the technical field of electrochemistry. The preparation method of the electrode comprises the following steps: submerging nickel material in water for 20-30 hours to obtain etching material; soaking the etching material in a ferric salt solution for 0.5-1.5 hours to obtain ion exchange material; and performing phosphating treatment on the ion exchange material. The preparation method of the electrode provided by the application is simple in operation, low in cost and environmentally friendly, and the electrode prepared by the aforementioned preparation method has excellent performance, a long service life and high practicability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrochemistry, in particular to a preparation method of an electrode, the electrode and application thereof. BACKGROUND

[0002] With the development of human society, population explosion and resource depletion lead to the rapid increase of demand for new energy. Among various clean and renewable new energy, solar power generation and wind power generation have lower requirements for geographical conditions and can be popularized in many places in China. However, the power generation of these two power generation methods is greatly affected by weather, so it is urgent to have an efficient energy storage method to store the energy at the power generation peak. Among many technologies, the power generated by solar power generation and wind power generation is used to electrolyze water to produce hydrogen, so that the electrical energy of clean energy is stored in the form of chemical energy hydrogen energy, which has obvious advantages in energy storage. 1kg of hydrogen can store 1.4x10 5 kJ of energy, and the energy density is more than 130 times that of lithium ion batteries.

[0003] Currently, the water electrolysis equipment for industrialization uses noble metals such as platinum (Pt), palladium (Pd), ruthenium (Ru), iridium (Ir), and rhodium (Rh) and their oxides as hydrogen and oxygen production electrodes. The material is too expensive and the cost is high. Moreover, in the preparation method of the existing electrode, fluorides (hydrofluoric acid or ammonium fluoride, etc.) are often used for hydrothermal treatment, so as to obtain a nano structure with a large specific surface area. However, these processes will discharge a large amount of fluorine-containing wastewater which is difficult to treat, causing damage to the ecological environment. Based on this, how to environmentally prepare high-efficiency, long-life and low-cost water electrolysis catalytic electrodes is a hot spot for research by the academic and industrial circles at home and abroad. SUMMARY

[0004] The purpose of the present application is to provide a preparation method of an electrode, which is simple to operate, low in cost and environmentally friendly.

[0005] Another purpose of the present application is to provide an electrode prepared by the above method, which has excellent performance, long service life and high practicability.

[0006] Still another purpose of the present application is to provide the application of the above electrode.

[0007] The technical problem of the present application is solved by using the following technical scheme:

[0008] A preparation method of an electrode, comprising:

[0009] immersing a nickel material in water for 20-30h to obtain an etching material;

[0010] immersing the etching material in a ferric salt solution for 0.5-1.5h to obtain an ion exchange material;

[0011] The ion exchange material is subjected to phosphating treatment.

[0012] Optionally, in some embodiments of the present application, after the phosphating treatment, further comprising: forming a titanium dioxide film on the surface of the material subjected to the phosphating treatment.

[0013] Optionally, in some embodiments of the present application, the method of forming the titanium dioxide film comprises: immersing the material subjected to the phosphating treatment in a titanium tetrachloride solution for 3-5 s.

[0014] Optionally, in some embodiments of the present application, the concentration of the titanium tetrachloride solution is 0.005-0.015 mol / L.

[0015] Optionally, in some embodiments of the present application, before immersing the nickel material in water, further comprising: immersing the nickel material in a hydrochloric acid solution for 1-2 h.

[0016] Optionally, in some embodiments of the present application, the water is selected from one or more of deionized water, distilled water, pure water, and ultrapure water.

[0017] Optionally, in some embodiments of the present application, the solute in the ferric salt solution is selected from one or more of ferric nitrate, ferric sulfate, a hydrate of ferric nitrate, and a hydrate of ferric sulfate; and / or

[0018] The concentration of the trivalent iron ions in the ferric salt solution is 0.05-0.2 mol / L.

[0019] Optionally, in some embodiments of the present application, the phosphating treatment comprises: treating the ion exchange material in a phosphorus-containing atmosphere for 2-6 h to form a phosphide on the surface of the ion exchange material.

[0020] In addition, an electrode is prepared by the above-mentioned electrode preparation method.

[0021] In addition, the above-mentioned electrode is applied in electrolysis of water.

[0022] Compared with the prior art, the present application has the following beneficial effects: the present scheme uses a nickel material as a substrate, forms nickel-iron hydroxide in situ on the surface of the nickel material, and then performs phosphating treatment to form a phosphide with catalytic activity. In this process:

[0023] 1. Since the raw materials used are mainly iron and nickel, the cost is low compared with noble metals; the cost of auxiliary materials such as water used in the preparation process is also low, and the preparation process has low requirements for the environment, so the entire preparation method has very high cost performance;

[0024] 2. The present scheme uses water to etch the nickel material to form a nanosheet structure on the surface of the nickel material, and the etching method is energy-saving and environmentally friendly;

[0025] 3. The etching and ion exchange step-by-step process can effectively avoid the combined processing solution being slightly acidic and unable to form nanosheet structures;

[0026] 4. Since the nanosheet structure is formed by etching on a nickel material substrate, the nickel phosphide and iron phosphide generated on the surface of the nickel material after ion exchange and phosphating treatment can be anchored on the surface of the nickel material and tightly combined with the substrate, and is not easy to fall off during use, and the resistance of the two-phase interface is also small;

[0027] 5. The nickel phosphide-iron phosphide on the surface of the electrode prepared by the scheme has high hydrogen evolution activity, oxygen evolution activity and corrosion resistance, and the nanosheet structure formed increases the surface area of the electrode, thereby increasing the number of active sites, which is beneficial to improve the overall water electrolysis performance;

[0028] The preparation method of the electrode provided by the scheme is simple in operation, energy-saving and environmentally friendly, the electrode prepared can be used as a hydrogen evolution cathode and an oxygen evolution anode at the same time in water electrolysis application, has a long service life and high catalytic activity, is low in cost, high in practicality, and suitable for wide promotion. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0030] Figure 1 is a scanning electron microscope image (200 times) of the electrode provided by the embodiment 1 of the present application;

[0031] Figure 2 is a scanning electron microscope image (50000 times) of the electrode provided by the embodiment 1 of the present application;

[0032] Figure 3 is an X-ray diffraction pattern of the electrode provided by the embodiment 1 of the present application;

[0033] Figure 4 is the polarization curve of the electrode provided by the embodiment 1 of the present application for electrocatalytic hydrogen evolution and oxygen evolution test;

[0034] Figure 5 is the polarization curve of the electrode provided by the embodiment of the present application for hydrogen evolution and oxygen evolution in 1M KOH solution;

[0035] Figure 6 is the polarization curve of the electrode provided by the embodiment of the present application for hydrogen evolution and oxygen evolution in 1M KOH solution;

[0036] Figure 7 is the full water splitting polarization curve of the electrode provided in Embodiment 1 of the present application before testing and after 700 hours of constant current testing;

[0037] Figure 8 is the current change curve of the electrode provided in Embodiment 1 of the present application in the 2V constant voltage stability test; 2 voltage change curve in the constant current stability test;

[0038] Figure 9 is the current change curve of the electrode provided in Embodiment of the present application in the 2V constant voltage stability test;

[0039] Figure 10 is the polarization curve of the electrode provided in Embodiment of the present application before and after the long-term test of electrocatalytic hydrogen evolution and oxygen evolution test. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present application will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0041] The technical solutions provided by the present application will be described in detail below. It should be noted that the description order of the following embodiments is not intended to limit the preferred order of the embodiments. In addition, in the description of the present application, the term "comprising" means "including but not limited to". Various embodiments of the present application can exist in the form of a range; it should be understood that the description in the form of a range is only for the convenience and brevity, and should not be understood as a hard limit on the scope of the present application; therefore, it should be considered that the described range has been specifically disclosed all possible sub-ranges and single values within the range.

[0042] The embodiment of the present application provides a preparation method of an electrode, comprising:

[0043] immersing the nickel material in water for 20-30h to obtain an etching material;

[0044] immersing the etching material in a ferric salt solution for 0.5-1.5h to obtain an ion exchange material;

[0045] phosphating the ion exchange material.

[0046] In this scheme, nickel material is immersed in water to complete the etching, forming a nickel hydroxide nanosheet structure on the surface of the nickel material, increasing the surface area of ​​the electrode. Using an iron salt solution, and based on the similar radius of iron ions and nickel ions, ion exchange between the nickel material with the nanosheet structure and the iron salt solution is achieved through spontaneous diffusion. The obtained ion exchange material is then phosphated to form phosphides on the surface of the ion exchange material.

[0047] The raw materials used in this scheme are mainly iron and nickel, which are inexpensive. Compared with materials containing precious metal elements such as ruthenium chloride (RuCl3) (80-700 yuan / g), the raw materials used in this scheme, such as ferric nitrate nonahydrate (Fe(NO3)3·9H2O), are much cheaper, costing only 0.05-0.5 yuan / g. Therefore, the electrode preparation method provided in this scheme has significant advantages in industrial production.

[0048] Phosphating is a chemical reaction that forms a chemical conversion film. Phosphating can form metal phosphides, which have high conductivity and can also serve as active materials. In this scheme, phosphating mainly involves forming phosphides on the surface of the ion exchange material.

[0049] In some embodiments, nickel foam can be selected as the nickel material. Nickel foam is one of the most inexpensive foam metals, thereby further reducing the cost of electrode fabrication. After immersion for 20–30 hours, the nickel material can be removed and allowed to air dry or dried. The preferred immersion time is 24 hours. The amount of nickel and water used is limited to ensure that the nickel material is completely submerged in the water.

[0050] In some embodiments, the etching material can be removed and dried after immersion in the iron salt solution. The immersion time of the etching material in the iron salt solution is preferably 1 hour. The amount of etching material and iron salt solution used is limited to ensure that the etching material is completely submerged in the iron salt solution.

[0051] In some embodiments, after phosphating, the process further includes forming a titanium dioxide film on the surface of the phosphated material. The formed titanium dioxide film serves as a protective layer, effectively inhibiting corrosion of the electrode during use and thus extending its service life. Simultaneously, the longer electrode lifespan further reduces the cost of the electrode in application.

[0052] Furthermore, the method for forming a titanium dioxide thin film includes immersing the phosphated material in a titanium tetrachloride solution for 3–5 seconds. After sufficient immersion, the material can be removed and air-dried to obtain an electrode with a structure of nickel-iron bimetallic phosphide / titanium dioxide / nickel foam. The solvent for the titanium tetrachloride solution can be fully dehydrated anhydrous ethanol or anhydrous methanol.

[0053] Furthermore, the concentration of the titanium tetrachloride solution can be 0.005–0.015 mol / L, preferably 0.01 mol / L. An appropriate concentration of titanium tetrachloride solution promotes the formation of titanium dioxide thin films. mol / L can also be represented by M.

[0054] In some embodiments, before immersing the nickel material in water, the process further includes soaking the nickel material in a hydrochloric acid solution for 1-2 hours. The soaking time is preferably 1.5 hours. Hydrochloric acid pretreatment of the nickel material removes any stable and dense oxide layer that may form on its surface, providing a good foundation for subsequent etching. Furthermore, the solution used to etch the nickel oxide layer is hydrochloric acid, which is environmentally friendly. The concentration of the hydrochloric acid solution can be 3M, and the solvent can be water.

[0055] In addition, before immersing the nickel material in hydrochloric acid solution, it can be pre-cleaned with water and solvent to remove water-soluble impurities and grease from its surface. The water mentioned here can be selected from one or more of deionized water, distilled water, pure water, and ultrapure water, preferably pure water; the solvent mentioned here can be a non-polar solvent or a weakly polar solvent, preferably ethanol. The order in which water and solvent are used to clean the nickel material is not limited, but it is preferable to use pure water first, followed by ethanol.

[0056] After soaking the nickel material in hydrochloric acid solution, it can be removed and cleaned. After cleaning, the nickel material can be soaked in water for 20 to 30 hours.

[0057] In some embodiments, the water used for soaking the nickel material for 20-30 hours is selected from one or more of deionized water, distilled water, pure water, and ultrapure water. This avoids the introduction of impurities.

[0058] In some embodiments, the solute in the iron salt solution may be selected from one or more of ferric nitrate (Fe(NO3)3), ferric sulfate (Fe2(SO4)3), ferric nitrate hydrate, and ferric sulfate hydrate.

[0059] In some embodiments, the concentration of ferric ions in the iron salt solution is 0.05–0.2 mol / L, preferably 0.1 mol / L. The solvent for the iron salt solution is water.

[0060] In some embodiments, the phosphating treatment includes treating the ion exchange material in a phosphorus-containing atmosphere for 2–6 hours to form a phosphide on the surface of the ion exchange material. Further, the phosphorus-containing atmosphere can be provided in various ways:

[0061] Using sodium hypophosphite: Sodium hypophosphite and ion exchange material are placed separately in a ceramic boat and then placed in a tube furnace. Phosphating is performed under a protective gas atmosphere to obtain nickel-iron bimetallic phosphide / nickel foam. The protective gas can be selected from one or more of nitrogen and inert gases (e.g., argon). Sodium hypophosphite hydrate (NaH₂PO₂·H₂O) can be used, and the amount of sodium hypophosphite used is determined by the size of the tube furnace—per 1 cm³. 3 The tubular furnace volume corresponds to 1.2–2 mg of NaH₂PO₂·H₂O, preferably 2 mg, to ensure a consistent concentration of phosphine (PH₃) gas generated within the furnace chamber. In the tubular furnace, a ceramic boat containing sodium hypophosphite can be placed upstream of the gas flow, while a ceramic boat containing ion exchange material can be placed downstream. This allows the phosphine produced by the decomposition of sodium hypophosphite to flow downstream with the protective gas flow, ensuring a consistent phosphine concentration around the ion exchange material. The temperature program in the tubular furnace is as follows: 1–4 °C / min (preferably 2 °C / min), heating to 300–400 °C (preferably 350 °C) and holding for 1.5–2.5 h (preferably 2 h), followed by natural cooling. Oxygen must be prevented from entering the furnace tubes throughout the process, and the generated exhaust gas can be absorbed with copper sulfate solution. The slower heating rate prevents the sodium hypophosphite from boiling violently after melting and contaminating the equipment. Cooling is not subject to excessive restrictions; natural cooling is sufficient. During the process, sodium hypophosphite decomposes upon heating, producing phosphine gas. The phosphine then reacts with nickel-iron hydroxide on the surface of the ion exchange material to form phosphide.

[0062] Using red phosphorus: Red phosphorus is used instead of sodium hypophosphite, and the temperature program is 2-5℃ / min, heating to 400-500℃ (preferably 450℃) and holding for 1-2 hours (preferably 1.5 hours).

[0063] Using phosphine gas: Place the ion exchange material in a tube furnace and directly introduce phosphine gas into the tube furnace. The temperature program is 5-10℃ / min, heating to 300-400℃ (preferably 350℃) and holding at that temperature for 1.5-2.5h (preferably 2h).

[0064] Considering environmental protection, safety, and storage, sodium hypophosphite is preferred for providing a phosphorus-containing atmosphere and for phosphating the ion exchange material. Furthermore, by controlling the phosphating conditions (sodium hypophosphite dosage and temperature program), it is possible to ensure thorough phosphating of the ion exchange material surface to achieve high electrocatalytic activity, while also ensuring that phosphine reacts only on the electrode surface, thus maintaining the strength, toughness, and conductivity of the internal nickel substrate.

[0065] An embodiment of the present invention also provides an electrode, which is prepared by the electrode preparation method described above. The entire surface of the electrode is formed with a phosphide layer including nickel phosphide and iron phosphide, while the internal body still retains a nickel substrate with strong toughness and conductivity.

[0066] Embodiments of the present invention also provide the application of the above-described electrode in water electrolysis. Further, it can be used in electrocatalytic hydrogen evolution, electrocatalytic oxygen evolution, or electrocatalytic total water electrolysis. In application, the electrode can be cut to the target size, one end can be ground until the silvery-white nickel substrate is exposed, then a wire can be soldered to the ground area, and the terminal can be sealed with epoxy resin to form a spare electrode (working electrode).

[0067] When using a three-electrode system, the electrolyte can be a potassium hydroxide solution or a sodium hydroxide solution with a concentration of 0.1–12 M, the operating temperature is room temperature, the above-mentioned spare electrode is used as the working electrode, the platinum wire is used as the counter electrode, and the Hg / HgO electrode is used as the reference electrode; when using a two-electrode system, the electrolyte can be a potassium hydroxide solution or a sodium hydroxide solution with a concentration of 0.01–12 M, and the above-mentioned spare electrode is used as both the working electrode and the counter electrode.

[0068] Example 1

[0069] This embodiment provides a method for preparing a nickel-iron bimetallic phosphide / nickel foam electrode:

[0070] (1) Cut the nickel foam into appropriate sizes, ultrasonically clean it in pure water for 5 minutes, then ultrasonically clean it in anhydrous ethanol for 5 minutes, and then soak it in a 3M hydrochloric acid solution for 1.5 hours. After soaking, remove the nickel foam from the hydrochloric acid solution, rinse off the residual acid with pure water, and then completely immerse it in pure water for 24 hours. After that, take it out and dry it in a 60℃ oven.

[0071] (2) Using 0.1M Fe(NO3)3 as the target, 4.04g Fe(NO3)3·9H2O was dissolved in 100mL of pure water to obtain an iron salt solution. Then, the material obtained in step (1) was immersed in the iron salt solution to carry out an ion exchange reaction. After soaking for 1 hour, the material was taken out and dried in an oven at 60℃.

[0072] (3) Phosphating is performed using a tubular furnace, wherein the inner diameter of the furnace tube is 4cm and the length is 20cm, with each 1cm... 3The target volume of the tubular furnace corresponds to 2 mg of NaH2PO2·H2O. Calculations show that 0.5 g of NaH2PO2·H2O should be used. Place the NaH2PO2·H2O and the ion exchange material obtained in step (2) into two ceramic boats respectively. Place the ceramic boat containing NaH2PO2·H2O upstream of the gas flow and the ceramic boat containing the ion exchange material downstream of the gas flow. After sealing the furnace tube, alternately evacuate and then fill with nitrogen. Repeat this three times to ensure that there is no oxygen in the tube. Then control the nitrogen to flow slowly through the furnace tube and set the temperature program (heat up to 350℃ at 2℃ / min, hold at 350℃ for 2 hours, and then cool naturally) to start the phosphating treatment. After the reaction is completed, take out the material to obtain nickel-iron bimetallic phosphide / foamed nickel electrode.

[0073] This embodiment also provides an electrode prepared using the above method, and performs electrocatalytic performance testing after electrode treatment, including:

[0074] (1) Cut the electrode material into 5mm×5mm size and leave a small section of the terminal. Grind the terminal until the silver-white metal foam nickel base is exposed. Then, use solder to connect the wire to the ground area and encapsulate the terminal with epoxy resin to make a spare electrode.

[0075] (2) Electrocatalytic hydrogen evolution and oxygen evolution test: A three-electrode system was used, with 1M KOH solution as the electrolyte, the above-mentioned spare electrode as the working electrode, platinum wire as the counter electrode, and Hg / HgO electrode as the reference electrode.

[0076] (3) Complete water splitting test: A two-electrode system was adopted, and the working electrode and the counter electrode were both selected from the above-mentioned spare electrodes.

[0077] Example 2

[0078] This embodiment provides a method for preparing a nickel-iron bimetallic phosphide / titanium dioxide / nickel foam electrode:

[0079] (1) Cut the nickel foam into appropriate sizes, ultrasonically clean it in pure water for 5 minutes, then ultrasonically clean it in anhydrous ethanol for 5 minutes, and then soak it in a 3M hydrochloric acid solution for 1.5 hours. After soaking, remove the nickel foam from the hydrochloric acid solution, rinse off the residual acid with pure water, and then completely immerse it in pure water for 24 hours. After that, take it out and dry it in a 60℃ oven.

[0080] (2) Using 0.1M Fe(NO3)3 as the target, 4.04g Fe(NO3)3·9H2O was dissolved in 100mL of pure water to obtain an iron salt solution. Then, the material obtained in step (1) was immersed in the iron salt solution to carry out an ion exchange reaction. After soaking for 1 hour, the material was taken out and dried in an oven at 60℃.

[0081] (3) Phosphating is performed using a tubular furnace, wherein the inner diameter of the furnace tube is 4cm and the length is 20cm, with each 1cm... 3 The target volume of the tubular furnace corresponds to 2 mg of NaH2PO2·H2O. Calculations show that 0.5 g of NaH2PO2·H2O should be used. Place the NaH2PO2·H2O and the ion exchange material obtained in step (2) into two ceramic boats respectively. Place the ceramic boat containing NaH2PO2·H2O upstream of the gas flow and the ceramic boat containing the ion exchange material downstream of the gas flow. After sealing the furnace tube, alternately evacuate and then fill with nitrogen. Repeat this three times to ensure that there is no oxygen in the tube. Then control the nitrogen to flow slowly through the furnace tube and set the temperature program (heat up to 350℃ at 2℃ / min, hold at 350℃ for 2 hours, and then cool naturally) to start the phosphating treatment. After the reaction is completed, take out the material to obtain nickel-iron bimetallic phosphide / foamed nickel electrode.

[0082] (4) Immerse the material obtained in step (3) in 0.01M TiCl4 solution (where the solvent is anhydrous methanol) for 4s, take out the material and air dry it to obtain nickel-iron bimetallic phosphide / titanium dioxide / nickel foam electrode.

[0083] This embodiment also provides an electrode prepared using the above method, and performs electrocatalytic performance testing after electrode treatment, including:

[0084] (1) Cut the electrode material into 5m×5mm size and leave a small section of the terminal. Grind the terminal until the silver-white metal foam nickel base is exposed. Then, use solder to connect the wire to the ground area and encapsulate the terminal with epoxy resin to make a spare electrode.

[0085] (2) Electrocatalytic hydrogen evolution and oxygen evolution test: A three-electrode system was used, with 1M KOH solution as the electrolyte, the above-mentioned spare electrode as the working electrode, platinum wire as the counter electrode, and Hg / HgO electrode as the reference electrode.

[0086] (3) Complete water splitting test: A two-electrode system was adopted, and the working electrode and the counter electrode were both selected from the above-mentioned spare electrodes.

[0087] Example 3

[0088] This embodiment provides a method for preparing a nickel-iron bimetallic phosphide / nickel foam electrode:

[0089] (1) Cut the nickel foam into appropriate sizes, ultrasonically clean it in pure water for 5 minutes, then ultrasonically clean it in anhydrous ethanol for 5 minutes, and then soak it in a 3M hydrochloric acid solution for 1.5 hours. After soaking, remove the nickel foam from the hydrochloric acid solution, rinse off the residual acid with pure water, and then completely immerse it in pure water for 24 hours. After that, take it out and dry it in a 60℃ oven.

[0090] (2) Using 0.05M Fe(NO3)3 as the target, 2.02g Fe(NO3)3·9H2O was dissolved in 100mL of pure water to obtain an iron salt solution. Then, the material obtained in step (1) was immersed in the iron salt solution to carry out an ion exchange reaction. After soaking for 1 hour, the material was taken out and dried in an oven at 60℃.

[0091] (3) Phosphating is performed using a tubular furnace, wherein the inner diameter of the furnace tube is 4cm and the length is 20cm, with each 1cm... 3 The target volume of the tubular furnace corresponds to 2 mg of NaH2PO2·H2O. Calculations show that 0.5 g of NaH2PO2·H2O should be used. Place the NaH2PO2·H2O and the ion exchange material obtained in step (2) into two ceramic boats respectively. Place the ceramic boat containing NaH2PO2·H2O upstream of the gas flow and the ceramic boat containing the ion exchange material downstream of the gas flow. After sealing the furnace tube, alternately evacuate and then fill with nitrogen. Repeat this three times to ensure that there is no oxygen in the tube. Then control the nitrogen to flow slowly through the furnace tube and set the temperature program (heat up to 350℃ at 2℃ / min, hold at 350℃ for 2 hours, and then cool naturally) to start the phosphating treatment. After the reaction is completed, take out the material to obtain nickel-iron bimetallic phosphide / foamed nickel electrode.

[0092] This embodiment also provides an electrode prepared using the above preparation method. After treating the electrode, its electrocatalytic performance is tested. The electrode treatment and electrocatalytic performance testing methods are the same as those in Example 1.

[0093] Example 4

[0094] This embodiment provides a method for preparing a nickel-iron bimetallic phosphide / nickel foam electrode:

[0095] (1) Cut the nickel foam into appropriate sizes, ultrasonically clean it in pure water for 5 minutes, then ultrasonically clean it in anhydrous ethanol for 5 minutes, and then soak it in a 3M hydrochloric acid solution for 1.5 hours. After soaking, remove the nickel foam from the hydrochloric acid solution, rinse off the residual acid with pure water, and then completely immerse it in pure water for 24 hours. After that, take it out and dry it in a 60℃ oven.

[0096] (2) Using 0.2M Fe(NO3)3 as the target, 8.08g Fe(NO3)3·9H2O was dissolved in 100mL of pure water to obtain an iron salt solution. Then, the material obtained in step (1) was immersed in the iron salt solution to carry out an ion exchange reaction. After soaking for 1 hour, the material was taken out and dried in an oven at 60℃.

[0097] (3) Phosphating is performed using a tubular furnace, wherein the inner diameter of the furnace tube is 4cm and the length is 20cm, with each 1cm... 3The target volume of the tubular furnace corresponds to 2 mg of NaH2PO2·H2O. Calculations show that 0.5 g of NaH2PO2·H2O should be used. Place the NaH2PO2·H2O and the ion exchange material obtained in step (2) into two ceramic boats respectively. Place the ceramic boat containing NaH2PO2·H2O upstream of the gas flow and the ceramic boat containing the ion exchange material downstream of the gas flow. After sealing the furnace tube, alternately evacuate and then fill with nitrogen. Repeat this three times to ensure that there is no oxygen in the tube. Then control the nitrogen to flow slowly through the furnace tube and set the temperature program (heat up to 350℃ at 2℃ / min, hold at 350℃ for 2 hours, and then cool naturally) to start the phosphating treatment. After the reaction is completed, take out the material to obtain nickel-iron bimetallic phosphide / foamed nickel electrode.

[0098] This embodiment also provides an electrode prepared using the above preparation method. After treating the electrode, its electrocatalytic performance is tested. The electrode treatment and electrocatalytic performance testing methods are the same as those in Example 1.

[0099] Example 5

[0100] This embodiment provides a method for preparing a nickel-iron bimetallic phosphide / nickel foam electrode:

[0101] (1) Cut the nickel foam into appropriate sizes, ultrasonically clean it in pure water for 5 minutes, then ultrasonically clean it in anhydrous ethanol for 5 minutes, and then soak it in a 3M hydrochloric acid solution for 1.5 hours. After soaking, remove the nickel foam from the hydrochloric acid solution, rinse off the residual acid with pure water, and then completely immerse it in pure water for 24 hours. After that, take it out and dry it in a 60℃ oven.

[0102] (2) Using 0.1M Fe(NO3)3 as the target, 4.04g Fe(NO3)3·9H2O was dissolved in 100mL of pure water to obtain an iron salt solution. Then, the material obtained in step (1) was immersed in the iron salt solution to carry out an ion exchange reaction. After soaking for 1 hour, the material was taken out and dried in an oven at 60℃.

[0103] (3) Phosphating is performed using a tubular furnace, wherein the inner diameter of the furnace tube is 4cm and the length is 20cm, with each 1cm... 3The target volume of the tubular furnace corresponds to 1.6 mg of NaH2PO2·H2O. Calculations show that 0.4 g of NaH2PO2·H2O should be used. Place the NaH2PO2·H2O and the ion exchange material obtained in step (2) into two ceramic boats respectively. Place the ceramic boat containing NaH2PO2·H2O upstream of the gas flow and the ceramic boat containing the ion exchange material downstream of the gas flow. After sealing the furnace tube, alternately evacuate and then fill with nitrogen. Repeat this three times to ensure that there is no oxygen in the tube. Then control the nitrogen to flow slowly through the furnace tube and set the temperature program (heat up to 350℃ at 2℃ / min, hold at 350℃ for 2 hours, and then cool naturally) to start the phosphating treatment. After the reaction is completed, take out the material to obtain nickel-iron bimetallic phosphide / foamed nickel electrode.

[0104] This embodiment also provides an electrode prepared using the above preparation method. After treating the electrode, its electrocatalytic performance is tested. The electrode treatment and electrocatalytic performance testing methods are the same as those in Example 1.

[0105] Example 6

[0106] This embodiment provides a method for preparing a nickel-iron bimetallic phosphide / nickel foam electrode:

[0107] (1) Cut the nickel foam into appropriate sizes, ultrasonically clean it in pure water for 5 minutes, then ultrasonically clean it in anhydrous ethanol for 5 minutes, and then soak it in a 3M hydrochloric acid solution for 1.5 hours. After soaking, remove the nickel foam from the hydrochloric acid solution, rinse off the residual acid with pure water, and then completely immerse it in pure water for 24 hours. After that, take it out and dry it in a 60℃ oven.

[0108] (2) Using 0.1M Fe(NO3)3 as the target, 4.04g Fe(NO3)3·9H2O was dissolved in 100mL of pure water to obtain an iron salt solution. Then, the material obtained in step (1) was immersed in the iron salt solution to carry out an ion exchange reaction. After soaking for 1 hour, the material was taken out and dried in an oven at 60℃.

[0109] (3) Phosphating is performed using a tubular furnace, wherein the inner diameter of the furnace tube is 4cm and the length is 20cm, with each 1cm... 3The target volume of the tubular furnace corresponds to 1.2 mg of NaH2PO2·H2O. Calculations show that 0.3 g of NaH2PO2·H2O should be used. Place the NaH2PO2·H2O and the ion exchange material obtained in step (2) into two ceramic boats respectively. Place the ceramic boat containing NaH2PO2·H2O upstream of the gas flow and the ceramic boat containing the ion exchange material downstream of the gas flow. After sealing the furnace tube, alternately evacuate and then fill with nitrogen. Repeat this three times to ensure that there is no oxygen in the tube. Then control the nitrogen to flow slowly through the furnace tube and set the temperature program (heat up to 350℃ at 2℃ / min, hold at 350℃ for 2 hours, and then cool naturally) to start the phosphating treatment. After the reaction is completed, take out the material to obtain nickel-iron bimetallic phosphide / foamed nickel electrode.

[0110] This embodiment also provides an electrode prepared using the above preparation method. After treating the electrode, its electrocatalytic performance is tested. The electrode treatment and electrocatalytic performance testing methods are the same as those in Example 1.

[0111] Composition and structure characterization:

[0112] (1) Scanning electron microscopy characterization

[0113] Figure 1 , Figure 2 The images shown are scanning electron microscope (SEM) images of the electrode provided in Example 1 at 200x and 50,000x magnification, respectively. Figure 1 It can be seen that the three-dimensional network structure of the nickel foam substrate is preserved, which is beneficial for ion transport in the water electrolysis process and enables the electrode to have a large number of active sites; Figure 2 It can be seen that there are a large number of dispersed nanosheets on the electrode surface. These nanosheets are firmly attached to the nickel foam substrate, which further increases the number of active sites.

[0114] (2) X-ray diffraction characterization

[0115] Figure 3 The X-ray diffraction pattern of the electrode provided in Example 1 shows that the three highest peaks marked by squares are diffraction peaks of metallic Ni. Their intensity is much higher than that of other peaks, indicating that most of Ni has not been converted into nickel phosphide. The triangles and circles mark Fe2P and Ni5P4, respectively, indicating that the electrode preparation method provided in this example has successfully prepared nickel-iron bimetallic phosphide.

[0116] (3) Electrocatalytic test results

[0117] 3.1) Hydrogen evolution and oxygen evolution tests

[0118] Figure 4 The figure shows the polarization curves for hydrogen evolution and oxygen evolution tests of the electrode provided in Example 1. As can be seen from the figure, the electrode can achieve 1000 mA / cm² in both hydrogen evolution and oxygen evolution tests.2 The above current density is 100 mA / cm². 2 The overpotential does not exceed 400mV, indicating that the electrode provided in Example 1 has high hydrogen evolution and oxygen evolution performance under both high and low current conditions.

[0119] Figure 5 The polarization curves of the electrodes prepared in Examples 1, 3, and 4 are shown in 1M KOH solution for hydrogen evolution and oxygen evolution. The three electrodes used different concentrations of ferric nitrate in the ion exchange step during preparation (target ferric nitrate concentrations were 0.1M, 0.05M, and 0.2M, respectively). The comparison shows that the electrode prepared with 0.1M Fe(NO3)3 as the target ion exchange concentration (Example 1) exhibits better hydrogen evolution and oxygen evolution performance.

[0120] Figure 6 The polarization curves of the electrodes prepared in Examples 1, 5, and 6 in 1M KOH solution are shown. The amount of sodium hypophosphite used in the phosphating step of the preparation process of the three electrodes is different (0.5 g, 0.4 g, and 0.3 g, respectively). It can be seen that the electrode prepared by phosphating with 0.5 g NaH2PO2·H2O (Example 1) has better hydrogen and oxygen evolution performance. This is because the higher phosphorus source content helps to facilitate the full reaction on the surface of the ion exchange material.

[0121] 3.2) Complete water lysis test

[0122] Figure 7 The figure shows the polarization curve of the electrode provided in Example 1 for complete water splitting. As can be seen from the figure, the electrode exhibits excellent complete water splitting performance, consistent with the results of hydrogen evolution and oxygen evolution tests. After 700 hours of testing, the electrode's complete water splitting performance showed only limited attenuation, indicating that the electrode has a long service life.

[0123] Figure 8 The figure shows the voltage change curve of the electrode provided in Example 1 during the constant current stability test. As can be seen from the figure, the voltage between the two electrodes slowly increases from an initial value of approximately 1.9V at the start of the test, indicating that the total water splitting efficiency is slowly decreasing. After 450 hours of reaction, the electrolyte was replaced, and the voltage dropped back to 1.9V, only rising to 2.2V after 700 hours. This indicates that the activity of the electrode itself did not decrease significantly, which is consistent with the results shown in the polarization curve of the electrode's total water splitting.

[0124] Figure 9Figure 10 shows the current change curves of the electrodes prepared in Examples 1 and 2 during the 2V constant voltage stability test (curve I for the electrode of Example 1 and curve II for the electrode of Example 2). The electrode provided in Example 2 has a TiO2 thin film, which improves the electrode's stability, and its current decay is significantly slower. Figure 10 shows the polarization curves of the electrode before and after long-term testing for electrocatalytic hydrogen evolution and oxygen evolution. The electrode with the TiO2 thin film provided in Example 2 initially showed a slight decrease in performance, but its performance decay was minimal after long-term testing, further demonstrating that the formed TiO2 thin film can improve the electrode's stability.

[0125] The technical solutions provided by the embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for preparing an electrode, characterized in that, include: The nickel material is immersed in water for 20-30 hours to obtain the etching material; The etching material is immersed in an iron salt solution for 0.5 to 1.5 hours to obtain an ion exchange material; The ion exchange material is subjected to phosphating treatment; Following the phosphating treatment, the process further includes: forming a titanium dioxide film on the surface of the phosphating material; The method for forming a titanium dioxide film includes immersing the phosphated material in a titanium tetrachloride solution for 3-5 seconds, and then removing it and air-drying it.

2. The method for preparing the electrode according to claim 1, characterized in that, The concentration of the titanium tetrachloride solution is 0.005~0.015 mol / L.

3. The method for preparing the electrode according to claim 1, characterized in that, Before immersing the nickel material in water, the process also includes soaking the nickel material in a hydrochloric acid solution for 1-2 hours.

4. The method for preparing the electrode according to claim 1, characterized in that, The water is selected from one or more of deionized water, distilled water, pure water, and ultrapure water.

5. The method for preparing the electrode according to claim 1, characterized in that, The solute in the iron salt solution is selected from one or more of ferric nitrate, ferric sulfate, ferric nitrate hydrate, and ferric sulfate hydrate; and / or The concentration of ferric ions in the iron salt solution is 0.05~0.2 mol / L.

6. The method for preparing the electrode according to claim 1, characterized in that, The phosphating treatment includes treating the ion exchange material under a phosphorus-containing atmosphere for 2-6 hours to form phosphides on the surface of the ion exchange material.

Images