A supported oxygen evolution electrode with a nickel-iron buffer layer and a preparation method and application thereof

Abstract

The application provides a supported oxygen evolution electrode with a nickel-iron buffer layer and a preparation method and application thereof, and the preparation method comprises the following steps: electrochemically etching a metal substrate loaded with a nickel-iron-molybdenum precursor to obtain a metal substrate with a nickel-iron buffer layer; and then electrochemically depositing metal hydroxide to obtain the supported oxygen evolution electrode with the nickel-iron buffer layer. According to the application, the nickel-iron buffer layer with high nickel-iron capacity, high specific surface area and porous micropillar array structure is first constructed on the metal substrate, and then the electrochemical deposition of metal hydroxide is carried out, so that the defects of limited oxygen evolution reaction active sites, poor oxygen evolution activity and stability caused by the direct loading of the metal hydroxide on the metal substrate are avoided, and the obtained supported oxygen evolution electrode with the nickel-iron buffer layer has high oxygen evolution activity and stability.

Description

Technical Field

[0001] This invention belongs to the field of water electrolysis for hydrogen production technology, and relates to an oxygen evolution electrode, particularly a supported oxygen evolution electrode with a nickel-iron buffer layer, its preparation method, and its application. Background Technology

[0002] The oxygen evolution reaction (OER) is the anolyte reaction in water electrolysis for hydrogen production. Its overpotential and current density have a crucial impact on the energy consumption and hydrogen production rate. Noble metals Ru / Ir and their oxides exhibit good OER performance, but they are expensive and scarce, making them unsuitable for large-scale use. Industrially, nickel-based OER electrode materials such as nickel mesh, nickel foam, and Raney nickel are commonly used. However, due to the limited OER activity of nickel itself, these electrode materials cannot meet the demands of high-current-density water electrolysis for hydrogen production. Currently, non-noble metal composite hydroxides, such as nickel-iron hydroxide, cobalt-iron hydroxide, and nickel-cobalt-iron hydroxide, exhibit good OER activity and stability and are considered the next-generation OER anode materials for high-current-density alkaline water electrolysis for hydrogen production.

[0003] Currently, nickel-iron composite hydroxides are loaded onto metal substrates using hydrothermal methods, electrodeposition methods, and immersion etching methods. After loading the metal hydroxides, the OER activity of these electrodes is significantly improved. However, this method of directly loading metal hydroxides onto metal substrates has the following problems: (1) The specific surface area of ​​the metal substrate is low. Even if porous nickel foam is used as the metal substrate, its specific surface area is not high, resulting in limited active area and porous structure of the loaded metal hydroxide electrodes; (2) The loaded nickel-iron hydroxides only exist in the surface active layer. As the reaction proceeds, Fe elements will be lost, resulting in a gradual decrease in Fe content. Although nickel elements can be balanced and replenished from the substrate, the OER activity will gradually decrease over a long period of time until it drops to a level close to that of traditional nickel-based catalysts.

[0004] CN 111313041A discloses a method for preparing a nickel-iron hydroxide electrocatalyst. The method includes the following steps: dissolving iron salt, fluorine-containing compound, and urea in water and stirring to obtain a homogeneous solution; immersing nickel foam in the homogeneous solution, performing a hydrothermal reaction, cooling, and washing with a detergent to obtain the nickel-iron hydroxide electrocatalyst. The disclosed method relies on the reaction of iron salt solution with a nickel foam substrate to directly form nickel-iron hydroxide on a nickel foam substrate with limited surface area. However, the specific surface area and porous structure are limited, and the iron loading is limited, resulting in insufficient stability during long-term use. Furthermore, the subsequent high-potential oxygen evolution activation and low-potential hydrogen evolution activation times are as long as 8-12 hours.

[0005] CN 109201060A discloses a method for preparing a foamed nickel-nickel-iron oxide composite oxygen evolution catalyst. First, a mixed aqueous solution containing nickel salt, ferrous salt, and urea is provided. In the mixed aqueous solution, the concentration of nickel salt is 0.2 mol / L, the concentration of ferrous salt is 0.035–0.065 mol / L, and the concentration of urea is 1 mol / L. Then, the obtained mixed aqueous solution is subjected to a hydrothermal reaction with foamed nickel to grow nickel-iron hydroxide on the foamed nickel, obtaining a composite oxygen evolution catalyst precursor. The obtained composite oxygen evolution catalyst precursor is then calcined to obtain the foamed nickel-nickel-iron oxide composite oxygen evolution catalyst. The disclosed method also involves directly loading nickel-iron hydroxide onto a metal substrate, which similarly suffers from low specific surface area, limited porous structure, and poor oxygen evolution activity and stability.

[0006] Based on the above research, there is a need to provide an oxygen evolution electrode, wherein the oxygen evolution electrode is loaded with a buffer layer and a metal hydroxide layer. The buffer layer can increase the specific surface area of ​​the oxygen evolution electrode, improve the nickel-iron buffer capacity, facilitate the subsequent adsorption and loading of metal hydroxide, enhance the activity and stability of the oxygen evolution electrode, and solve the above-mentioned problems caused by the direct loading of metal hydroxide on the metal substrate. Summary of the Invention

[0007] The purpose of this invention is to provide a supported oxygen evolution electrode with a nickel-iron buffer layer, its preparation method, and its application. In traditional OER (oxygen evolution reaction) electrodes, metal hydroxides are directly deposited on a metal substrate. Due to the limited specific surface area of ​​the metal substrate, the supported metal hydroxides exist only in the surface active layer. As the reaction proceeds, the metal elements are gradually lost, leading to a gradual decrease in OER activity over a long period. This invention constructs a porous nickel-iron buffer layer with high specific surface area and high loading capacity before electrodepositing the metal hydroxides, thereby increasing the nickel-iron buffer capacity and thus improving the loading capacity of the metal hydroxides, as well as the oxygen evolution activity and stability.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a method for preparing a supported oxygen evolution electrode with a nickel-iron buffer layer, the method comprising the following steps:

[0010] Electrochemical etching is performed on a metal substrate loaded with a nickel-iron-molybdenum precursor to obtain a metal substrate with a nickel-iron buffer layer; then, metal hydroxide is electrochemically deposited to obtain the loaded oxygen evolution electrode with the nickel-iron buffer layer.

[0011] The metal substrate of the present invention is first loaded with a nickel-iron-molybdenum precursor NiFeMoO. xThe nickel-iron-molybdenum precursor layer is an intermediate layer of a micron-sized columnar array structure, and it also serves as the source of the nickel-iron buffer layer. Then, electrochemical etching is used to selectively etch Mo, constructing a nickel-iron buffer layer with high NiFe capacity, high specific surface area, and a porous micron-sized columnar array structure. This avoids the defects caused by direct loading of metal hydroxides onto the metal substrate, increases the specific surface area, facilitates electron transfer from the metal substrate to the reaction interface, and also facilitates bubble escape and solution contact during the oxygen evolution reaction. Simultaneously, a thin layer of nickel-iron hydroxide forms on the electrode surface during etching, improving the uniformity and strength of the subsequent metal hydroxide loading. The nickel-iron buffer layer not only facilitates metal hydroxide loading but also provides iron for the long-term oxygen evolution process.

[0012] Preferably, the loading of the nickel-iron buffer layer is 5–70 mg / cm³. 2 For example, it could be 5mg / cm³ 2 10mg / cm 2 15mg / cm 2 20mg / cm 2 25mg / cm 2 30mg / cm 2 35mg / cm 2 40mg / cm 2 45mg / cm 2 50mg / cm 2 55mg / cm 2 60mg / cm 2 65mg / cm 2 Or 70mg / cm 2 However, it is not limited to the listed values; other unlisted values ​​within the range are also applicable, with 5–50 mg / cm³ being the preferred value. 2 .

[0013] Preferably, in the nickel-iron buffer layer, the molar ratio of nickel to iron is 1:(0.05 to 0.5), for example, it can be 1:0.05, 1:0.1, 1:0.2, 1:0.3, 1:0.4 or 1:0.5, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0014] Preferably, the metal substrate supporting the nickel-iron-molybdenum precursor is obtained by hydrothermal treatment.

[0015] The hydrothermal treatment includes: hydrothermal reaction of the metal substrate in a mixture of nickel salt, iron salt and molybdenum salt, followed by cooling, cleaning and drying to obtain the metal substrate loaded with the nickel-iron-molybdenum precursor.

[0016] Preferably, the concentration ratio of the nickel salt, iron salt, and molybdenum salt is 1:(0.05~0.5):(0.2~0.5), for example, it can be 1:0.05:0.2, 1:0.1:0.3, 1:0.2:0.4, 1:0.3:0.5, 1:0.4:0.5, or 1:0.5:0.25, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0017] Preferably, the concentration of the nickel salt is 10 to 100 mM, for example, it can be 10 mM, 20 mM, 30 mM, 40 mM, 50 mM, 60 mM, 70 mM, 80 mM, 90 mM or 100 mM, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] Preferably, the temperature of the hydrothermal reaction is 120 to 180°C, for example, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C or 180°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] Preferably, the hydrothermal reaction time is 2 to 12 hours, for example, 2 hours, 4 hours, 6 hours, 8 hours, or 10 hours or 12 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] Preferably, the nickel salt comprises any one or a combination of at least two of nickel nitrate, nickel chloride, or nickel sulfate. Typical but non-limiting combinations include a combination of nickel nitrate and nickel chloride, a combination of nickel sulfate and nickel chloride, or a combination of nickel sulfate and nickel nitrate.

[0021] Preferably, the iron salt includes any one or a combination of at least two of ferric nitrate, ferric chloride, or ferric sulfate. Typical but non-limiting combinations include a combination of ferric nitrate and ferric chloride, a combination of ferric sulfate and ferric chloride, or a combination of ferric sulfate and ferric nitrate.

[0022] Preferably, the molybdenum salt comprises ammonium molybdate and / or sodium molybdate.

[0023] Preferably, the metal substrate comprises any one of nickel foam, nickel mesh, Raney nickel, nickel-plated stainless steel mesh, or nickel-plated iron mesh.

[0024] Preferably, the electrochemical etching includes: in an etching solution, using a metal substrate loaded with a nickel-iron-molybdenum precursor as the working electrode, with an auxiliary electrode, applying a periodic voltage for activation, to obtain the metal substrate with the nickel-iron buffer layer.

[0025] Preferably, the etching solution includes NaOH and / or KOH with a concentration of 0.2 to 8 M, for example, it can be 0.2 M, 1 M, 2 M, 3 M, 4 M, 5 M, 6 M, 7 M or 8 M, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] Preferably, the etching solution further includes 0.02 to 0.5 M of NaF and / or KF, for example, 0.02 M, 0.1 M, 0.2 M, 0.3 M, 0.4 M or 0.5 M, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] Preferably, the periodic voltage range is ±1 to ±8V, for example, it can be ±1V, ±2V, ±3V, ±4V, ±5V, ±6V, ±7V or ±8V, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0028] The range of the periodic voltage described in this invention refers to the variation range of the voltage over one period during the activation process.

[0029] Preferably, the period of the periodic voltage is 0.2 to 10 min, for example, it can be 0.2 min, 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min or 10 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] Preferably, the activation time is 10 to 60 minutes, for example, 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes or 60 minutes, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] Preferably, the activation temperature is 25 to 80°C, for example, it can be 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 65°C, 70°C, 75°C or 80°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] Preferably, the auxiliary electrode includes a titanium-ruthenium electrode or a graphite electrode.

[0033] Preferably, the electrochemical deposition includes: in a metal mixture, using a metal substrate with a nickel-iron buffer layer as the working electrode and an inert, non-soluble electrode as the counter electrode, performing electrodeposition to obtain the supported oxygen evolution electrode with the nickel-iron buffer layer.

[0034] Preferably, the metal salt in the metal mixture includes a combination of at least two of iron salts, nickel salts, or cobalt salts. Typical but not limited combinations include a combination of iron salts and nickel salts, a combination of iron salts and cobalt salts, or a combination of iron salts, nickel salts, and cobalt salts.

[0035] Preferably, the concentration of any one of the metal salts in the metal mixture is 0.02 to 0.2 M, for example, it can be 0.02 M, 0.05 M, 0.1 M, 0.15 M or 0.2 M, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] Preferably, the metal salt is any one or a combination of at least two of nitrates, chlorides, or sulfates. Typical but non-limiting combinations include combinations of nitrates and chlorides, combinations of sulfates and chlorides, or combinations of nitrates and sulfates.

[0037] Preferably, the current density of the electrodeposition is 10–250 mA·cm⁻¹. -2 For example, it could be 10 mA·cm -2 50mA·cm -2 100mA·cm -2 150mA·cm -2 200mA·cm -2 or 250mA·cm -2 However, this does not limit the listed values; other unlisted values ​​within the range are also applicable.

[0038] Preferably, the electrodeposition time is 10 to 600 s, for example, it can be 10 s, 50 s, 100 s, 150 s, 200 s, 250 s, 300 s, 350 s, 400 s, 450 s, 500 s, 550 s or 600 s, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0039] Preferably, the inert, non-soluble electrode includes a titanium-ruthenium electrode or a graphite electrode.

[0040] Preferably, the preparation method further includes pretreatment of the metal substrate before use.

[0041] Preferably, the pretreatment includes ultrasonic cleaning of the metal substrate sequentially with organic solvent, acid and ultrapure water, followed by air drying.

[0042] The metal substrate described in this invention undergoes a pre-cleaning process before use to remove oil and oxides from its surface, thereby facilitating the adhesion of subsequent carriers.

[0043] Preferably, the ultrasonic cleaning time using the organic solvent is 15 to 30 minutes, for example, 15 minutes, 20 minutes, 25 minutes or 30 minutes, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0044] Preferably, the organic solvent includes acetone and / or ethanol.

[0045] Preferably, the ultrasonic cleaning time using the acid solution is 5 to 30 minutes, for example, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes or 30 minutes, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0046] Preferably, the acid solution includes a 0.1 to 2 M hydrochloric acid solution, such as 0.1 M, 0.5 M, 1 M, 1.5 M or 2 M, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0047] Preferably, the ultrasonic cleaning time using the ultrapure water is 5 to 15 minutes, for example, 5 minutes, 8 minutes, 10 minutes, 12 minutes or 15 minutes, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0048] As a preferred embodiment of the preparation method of the present invention, the preparation method includes the following steps:

[0049] (1) The metal substrate was ultrasonically cleaned with organic solvent for 15-30 min, ultrasonically cleaned with acid for 5-30 min, and ultrasonically cleaned with ultrapure water for 5-15 min in sequence, and then dried to obtain the pretreated metal substrate.

[0050] (2) The metal substrate pretreated in step (1) is subjected to hydrothermal reaction at 120-180°C for 2-12 hours in a mixture of nickel salt, iron salt and molybdenum salt. After cooling, it is taken out, cleaned and dried to obtain the metal substrate loaded with nickel-iron-molybdenum precursor.

[0051] The concentration ratio of the nickel salt, iron salt, and molybdenum salt is 1:(0.05-0.5):(0.2-0.5), and the concentration of the nickel salt is 10-100 mM.

[0052] (3) In the etching solution, the metal substrate loaded with nickel-iron-molybdenum precursor described in step (2) is used as the working electrode, and an auxiliary electrode is added. A periodic voltage is applied, and the substrate is activated at 25-80°C for 10-60 min to obtain the metal substrate with nickel-iron buffer layer.

[0053] The range of the periodic voltage is ±1 to ±8V, and the period of the periodic voltage is 0.2 to 10 minutes.

[0054] The etching solution comprises MOH at a concentration of 0.2–8 M and MF at a concentration of 0.02–0.5 M, where M is Na and / or K;

[0055] The loading capacity of the nickel-iron buffer layer is 5–70 mg / cm³. 2 ;

[0056] (4) In the metal mixture, using the metal substrate with the nickel-iron buffer layer described in step (3) as the working electrode and the inert, non-soluble electrode as the counter electrode, at 10–250 mA·cm⁻¹ -2 Electrodeposition was performed at a current density for 10–600 s, followed by rinsing and drying to obtain the supported oxygen evolution electrode with a nickel-iron buffer layer.

[0057] In the metal mixture, the concentration of any one metal salt is 0.02 to 0.2 M, and the metal salt includes a combination of at least two of iron salt, nickel salt, or cobalt salt.

[0058] In a second aspect, the present invention provides a supported oxygen evolution electrode with a nickel-iron buffer layer, wherein the supported oxygen evolution electrode with the nickel-iron buffer layer is obtained by the preparation method described in the first aspect.

[0059] The supported oxygen evolution electrode comprises a metal substrate, and a nickel-iron buffer layer and a metal hydroxide layer loaded sequentially on the metal substrate.

[0060] Preferably, the nickel-iron buffer layer is a porous micron columnar array structure, with a corresponding specific capacitance of 200 mF·cm⁻¹. -2 The above, for example, could be 300 mF·cm -2 350mF·cm -2 400mF·cm -2 450mF·cm -2 500mF·cm -2 550mF·cm -2 600mF·cm -2 650mF·cm -2 700mF·cm -2 750mF·cm -2 800mF·cm -2 Or 850mF·cm -2 Preferably 200 mF·cm -2 ~1200mF·cm -2 .

[0061] The nickel-iron buffer layer of this invention has a high electrochemically active surface area. It is formed by the growth of numerous porous micropillars on a metal substrate, creating a buffer layer chemically assembled from nickel-iron porous micropillars. Each micropillar contains a large number of pores and has a rough surface. The specific capacitance corresponding to the electrochemically active surface area of ​​the nickel-iron buffer layer is 200 mF·cm⁻¹. -2 above.

[0062] Thirdly, the present invention provides an application of a supported oxygen evolution electrode having a nickel-iron buffer layer as described in the second aspect, the application including its use in water electrolysis for hydrogen production.

[0063] Compared with the prior art, the present invention has the following beneficial effects:

[0064] This invention constructs a nickel-iron buffer layer with high nickel-iron capacity, high specific surface area, and a porous micron columnar array structure by first loading a nickel-iron-molybdenum precursor using a hydrothermal method before depositing metal hydroxide on a metal substrate, and then selectively etching out Mo using an electrochemical etching method. This avoids the defects of limited active sites, poor oxygen evolution activity, and poor stability caused by directly loading metal hydroxide on a metal substrate. The construction of the buffer layer improves the specific surface area, oxygen evolution activity, and stability of the oxygen evolution electrode during long-term oxygen evolution. In addition, this invention does not require the use of expensive nickel-iron alloy substrates to construct a high-capacity, multi-level nickel-iron buffer layer. This invention can construct a nickel-iron buffer layer with a porous micron columnar array structure using an inexpensive substrate. Attached Figure Description

[0065] Figure 1 This is a scanning electron microscope image of the nickel foam containing the nickel-iron-molybdenum precursor described in Example 1 at 200x magnification;

[0066] Figure 2 This is a scanning electron microscope image of the nickel foam with nickel-iron-molybdenum precursor loaded as described in Example 1 at a magnification of 30,000.

[0067] Figure 3 This is a scanning electron microscope image of the nickel foam with the nickel-iron buffer layer described in Example 1 at 80,000x magnification;

[0068] Figure 4 This is a scanning electron microscope image of the oxygen evolution electrode with a nickel-iron buffer layer described in Example 1 at a magnification of 30,000. Detailed Implementation

[0069] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0070] Example 1

[0071] This embodiment provides a method for preparing a supported oxygen evolution electrode with a nickel-iron buffer layer, the method comprising the following steps:

[0072] (1) The foamed nickel was ultrasonically cleaned with acetone for 15 min, ultrasonically cleaned with 1M hydrochloric acid for 5 min, and ultrasonically cleaned with ultrapure water for 10 min in sequence, and then dried to obtain the pretreated foamed nickel.

[0073] (2) The foamed nickel pretreated in step (1) was hydrothermally reacted at 150°C for 8 hours in a mixture of nickel nitrate, ferric nitrate and ammonium molybdate. After cooling, it was taken out, washed and dried to obtain the foamed nickel loaded with nickel-iron-molybdenum precursor.

[0074] The concentration ratio of nickel nitrate, ferric nitrate, and ammonium molybdate is 1:0.25:0.25, and the concentration of nickel nitrate is 40 mM, the concentration of ferric nitrate is 10 mM, and the concentration of ammonium molybdate is 10 mM.

[0075] (3) In a 1M KOH solution, using the nickel foam with nickel-iron-molybdenum precursor loaded in step (2) as the working electrode and the titanium-ruthenium electrode as the auxiliary electrode, a periodic voltage is applied and activated at 25°C for 30 minutes to obtain the nickel foam with the nickel-iron buffer layer.

[0076] The periodic voltage range is ±3V, and the period of the periodic voltage is 1min;

[0077] The nickel-iron buffer layer has a porous micron-column array structure, and the loading capacity of the nickel-iron buffer layer is 31.2 mg / cm³. 2 The specific capacitance is 556 mF·cm. -2 ;

[0078] (4) In a mixture of ferrous sulfate and nickel nitrate, using the nickel foam with the nickel-iron buffer layer described in step (3) as the working electrode and the titanium-ruthenium electrode as the counter electrode, at 30 mA·cm -2 Electrodeposition was performed at a current density for 120 s, followed by rinsing with deionized water and drying to obtain the supported oxygen evolution electrode with a nickel-iron buffer layer.

[0079] The ferrous sulfate and nickel nitrate mixture has a concentration of 0.1 M and a concentration of 0.1 M, respectively.

[0080] The scanning electron microscope (SEM) image of the nickel foam containing the nickel-iron-molybdenum precursor described in this embodiment at 200x magnification is shown below. Figure 1 As shown, the scanning electron microscope image at 30,000x magnification is as follows: Figure 2 As shown, the scanning electron microscope image of the nickel foam with the nickel-iron buffer layer at 80,000x magnification is as follows. Figure 3As shown, the scanning electron microscope image of the supported oxygen evolution electrode with the nickel-iron buffer layer at 30,000x magnification is as follows. Figure 4 As shown.

[0081] Example 2

[0082] This embodiment provides a method for preparing a supported oxygen evolution electrode with a nickel-iron buffer layer, the method comprising the following steps:

[0083] (1) The foamed nickel was ultrasonically cleaned with acetone for 30 min, ultrasonically cleaned with 0.1M hydrochloric acid for 30 min, and ultrasonically cleaned with ultrapure water for 15 min in sequence, and then dried to obtain the pretreated foamed nickel.

[0084] (2) The foamed nickel pretreated in step (1) was hydrothermally reacted at 150°C for 8 hours in a mixture of nickel chloride, ferric chloride and sodium molybdate. After cooling, it was taken out, washed and dried to obtain the foamed nickel loaded with nickel-iron-molybdenum precursor.

[0085] The concentration ratio of nickel chloride, ferric chloride, and sodium molybdate is 1:0.1:0.5, the concentration of nickel chloride is 10 mM, the concentration of ferric chloride is 1 mM, and the concentration of sodium molybdate is 5 mM.

[0086] (3) In a 1M NaOH solution, using the nickel foam with nickel-iron-molybdenum precursor loaded in step (2) as the working electrode and the graphite electrode as the auxiliary electrode, a periodic voltage is applied and activated at 25°C for 30 minutes to obtain the nickel foam with the nickel-iron buffer layer.

[0087] The periodic voltage range is ±3V, and the period of the periodic voltage is 1min;

[0088] The nickel-iron buffer layer has a porous micron-column array structure, and the loading capacity of the nickel-iron buffer layer is 11.9 mg / cm³. 2 The specific capacitance is 232 mF·cm. -2 ;

[0089] (4) In a mixture of ferric nitrate and nickel chloride, using the nickel foam with the nickel-iron buffer layer described in step (3) as the working electrode and the titanium-ruthenium electrode as the counter electrode, at 30 mA·cm -2 Electrodeposition was performed at a current density for 120 s, followed by rinsing with deionized water and drying to obtain the supported oxygen evolution electrode with a nickel-iron buffer layer.

[0090] The concentration of ferric nitrate and nickel chloride in the mixture is 0.1M.

[0091] Example 3

[0092] This embodiment provides a method for preparing a supported oxygen evolution electrode with a nickel-iron buffer layer, the method comprising the following steps:

[0093] (1) The foamed nickel was ultrasonically cleaned with acetone for 15 min, ultrasonically cleaned with 2M hydrochloric acid for 5 min, and ultrasonically cleaned with ultrapure water for 5 min in sequence, and then dried to obtain pretreated foamed nickel.

[0094] (2) The foamed nickel pretreated in step (1) was hydrothermally reacted at 150°C for 8 hours in a mixture of nickel nitrate, ferric nitrate and ammonium molybdate. After cooling, it was taken out, washed and dried to obtain the foamed nickel loaded with nickel-iron-molybdenum precursor.

[0095] The concentration ratio of nickel nitrate, ferric nitrate, and ammonium molybdate is 1:0.3:0.25, the concentration of nickel nitrate is 100 mM, the concentration of ferric nitrate is 30 mM, and the concentration of ammonium molybdate is 25 mM.

[0096] (3) In a 1M KOH solution, using the nickel foam with nickel-iron-molybdenum precursor loaded in step (2) as the working electrode and the graphite electrode as the auxiliary electrode, a periodic voltage is applied and activated at 25°C for 30 minutes to obtain the nickel foam with the nickel-iron buffer layer.

[0097] The periodic voltage range is ±3V, and the period of the periodic voltage is 30min;

[0098] The nickel-iron buffer layer has a porous micron-column array structure, and the loading capacity of the nickel-iron buffer layer is 49.3 mg / cm³. 2 The specific capacitance is 821 mF·cm. -2 ;

[0099] (4) In a mixture of ferrous sulfate and nickel nitrate, using the nickel foam with the nickel-iron buffer layer described in step (3) as the working electrode and the titanium-ruthenium electrode as the counter electrode, at 30 mA·cm -2 Electrodeposition was performed at a current density for 120 s, followed by rinsing with deionized water and drying to obtain the supported oxygen evolution electrode with a nickel-iron buffer layer.

[0100] The ferrous sulfate and nickel nitrate mixture has a concentration of 0.1 M and a concentration of 0.1 M, respectively.

[0101] Example 4

[0102] This embodiment provides a method for preparing a supported oxygen evolution electrode with a nickel-iron buffer layer. The method, except that the hydrothermal reaction time in step (2) is 2 hours, ensures that the loading of the nickel-iron buffer layer in step (3) is 10.8 mg / cm³. 2 In addition, the specific capacitance is 217 mF·cm. -2Everything else is the same as in Example 1.

[0103] Example 5

[0104] This embodiment provides a method for preparing a supported oxygen evolution electrode with a nickel-iron buffer layer. The method, except that the hydrothermal reaction in step (2) is carried out at a temperature of 120°C for 12 hours, ensures that the loading of the nickel-iron buffer layer in step (3) is 23.6 mg / cm³. 2 The specific capacitance is 405 mF·cm. -2 Except for the above, everything else is the same as in Example 1.

[0105] Example 6

[0106] This embodiment provides a method for preparing a supported oxygen evolution electrode with a nickel-iron buffer layer. The method involves replacing the nickel foam with a nickel mesh of the same size, and in step (2), the hydrothermal reaction temperature is 160°C and the time is 5 hours, resulting in a nickel-iron buffer layer loading of 26.4 mg / cm³ in step (3). 2 The specific capacitance is 453 mF·cm. -2 Except for the above, everything else is the same as in Example 1.

[0107] Example 7

[0108] This embodiment provides a method for preparing a supported oxygen evolution electrode with a nickel-iron buffer layer. The method, except that the hydrothermal reaction in step (2) is carried out at a temperature of 180°C for 3 hours, ensures that the loading of the nickel-iron buffer layer in step (3) is 29.8 mg / cm³. 2 The specific capacitance is 504 mF·cm. -2 Except for the above, everything else is the same as in Example 6.

[0109] Example 8

[0110] This embodiment provides a method for preparing a supported oxygen evolution electrode with a nickel-iron buffer layer. The method differs in that the 1M KOH solution in step (3) is replaced with a mixed solution of 1M KOH and 0.5M KF, resulting in a nickel-iron buffer layer loading of 30.8 mg / cm³. 2 The specific capacitance is 489 mF·cm. -2 Except for the above, everything else is the same as in Example 6.

[0111] Example 9

[0112] This embodiment provides a method for preparing a supported oxygen evolution electrode with a nickel-iron buffer layer. The method differs from the previous one where the 1M KOH solution in step (3) is replaced with a mixed solution of 1M KOH and 0.02M KF, resulting in a nickel-iron buffer layer loading of 28.6 mg / cm³.2 The specific capacitance is 466 mF·cm. -2 Except for the above, everything else is the same as in Example 6.

[0113] Example 10

[0114] This embodiment provides a method for preparing a supported oxygen evolution electrode with a nickel-iron buffer layer. The method, except that step (3) involves a voltage range of ±1V, results in a nickel-iron buffer layer loading of 30.8 mg / cm³. 2 The specific capacitance is 529 mF·cm. -2 Except for the above, everything else is the same as in Example 9.

[0115] Example 11

[0116] This embodiment provides a method for preparing a supported oxygen evolution electrode with a nickel-iron buffer layer. The method, except that the voltage range in step (3) is ±8V, ensures that the loading of the nickel-iron buffer layer in step (3) is 27.7 mg / cm³. 2 The specific capacitance is 448 mF·cm. -2 Except for the above, everything else is the same as in Example 9.

[0117] Example 12

[0118] This embodiment provides a method for preparing a supported oxygen evolution electrode with a nickel-iron buffer layer. The method differs from the previous one in that the nickel nitrate concentration in step (4) is replaced with cobalt nitrate. (100 mA·cm⁻¹) -2 Except for electrodeposition at the current density for 60 seconds, everything else was the same as in Example 6.

[0119] Example 13

[0120] This embodiment provides a method for preparing a supported oxygen evolution electrode with a nickel-iron buffer layer. The preparation method, except that the mixture in step (4) is composed of 0.05M ferrous sulfate, 0.1M nickel nitrate, and 0.1M cobalt nitrate, at 200 mA·cm⁻¹ -2 Except for electrodeposition at the current density for 20 seconds, everything else was the same as in Example 6.

[0121] Example 14

[0122] This embodiment provides a method for preparing a supported oxygen evolution electrode with a nickel-iron buffer layer. The method, except that the hydrothermal reaction time in step (2) is 0.5 h, ensures that the loading of the nickel-iron buffer layer in step (3) is 3.8 mg / cm³. 2 The specific capacitance is only 85 mF·cm -2 Except for the above, everything else is the same as in Example 1.

[0123] Example 15

[0124] This embodiment provides a method for preparing a supported oxygen evolution electrode with a nickel-iron buffer layer. The method, except that the concentration of nickel nitrate in step (2) is 120 mM, ensures that the loading of the nickel-iron buffer layer in step (3) is 61 mg / cm³. 2 The specific capacitance is 915 mF·cm. -2 Except for the above, everything else is the same as in Example 1.

[0125] Comparative Example 1

[0126] This comparative example provides an oxygen evolution electrode, which is a nickel foam of the same size as in Example 1.

[0127] Comparative Example 2

[0128] This comparative example provides a method for preparing an oxygen evolution electrode, which is the same as that in Example 1 except that steps (2) and (3) are not performed.

[0129] The oxygen evolution electrode with a nickel-iron buffer layer provided in the above embodiments and the oxygen evolution electrode provided in the comparative example were respectively tested in 1M KOH electrolyte, with a salt bridge-saturated calomel as the reference electrode, at room temperature and 10 mA·cm⁻¹. -2 and 1000mA·cm -2 Under constant current density, the operating potential was tested;

[0130] The test results are shown in Table 1:

[0131] Table 1

[0132]

[0133]

[0134] The following points can be observed from Table 1:

[0135] (1) The oxygen evolution electrode obtained in Example 1 has excellent oxygen evolution performance. The scanning electron microscope image of the nickel foam loaded with nickel-iron-molybdenum precursor at 200x magnification is shown below. Figure 1 As shown, combined with Figure 1 It can be seen that a micron-sized columnar array of nickel-iron-molybdenum precursor layers grew in situ on the surface of the nickel foam, combined with Figure 2 and Figure 3 It can be seen that after etching, the surface of the micropillars becomes rough and has a porous structure, indicating the formation of a porous nickel-iron buffer layer with a high loading capacity. Figure 4It can be seen that after electrodeposition, the metal hydroxide forms a new level of porous structure by interweaving ultrathin nanosheets, making the entire oxygen evolution electrode a multi-level structure of metal substrate millimeter pores - nickel-iron buffer layer micron pores - metal hydroxide nanopores. Thus, it can be seen that the present invention first constructs a porous nickel-iron buffer layer with high specific surface area and high loading, and then performs metal hydroxide electrodeposition to prepare the oxygen evolution electrode with high metal hydroxide loading, thereby exhibiting excellent oxygen evolution activity and stability.

[0136] (2) As can be seen from Examples 1-7, the present invention controls the loading of the obtained nickel-iron buffer layer by controlling the conditions of the hydrothermal reaction in step (2), so that the loading of the nickel-iron buffer layer is between 5 and 50 mg / cm³. 2 Within the preferred range, the final oxygen evolution electrode with nickel-iron buffer layer has excellent oxygen evolution activity; as can be seen from Examples 8 to 11, the present invention controls the etching conditions in step (3) to regulate the loading amount of nickel-iron buffer layer, so that the loading amount of nickel-iron buffer layer is within the preferred range, so that the final oxygen evolution electrode with nickel-iron buffer layer also has excellent oxygen evolution activity.

[0137] (3) As can be seen from Examples 1 and 12-13, oxygen evolution electrodes with excellent performance can be obtained when different types of metal hydroxides are deposited. When trimetallic hydroxides are electrochemically deposited in Example 13, the oxygen evolution electrode obtained has better oxygen evolution activity than when bimetallic hydroxides are deposited in Examples 1 and 12.

[0138] (4) As can be seen from Examples 1 and 14-15, by controlling the reaction conditions, the loading of the nickel-iron buffer layer can be maintained at 5-50 mg / cm³. 2 Outside the preferred range, Example 14 has a smaller load, and Example 15 has a larger load, resulting in a higher specific capacitance and increased resistance. Therefore, the performance of the oxygen evolution electrode obtained in Examples 14 and 15 is lower than that obtained in Example 1. It can be seen that a reasonable buffer layer load can ensure that the oxygen evolution electrode has a high specific surface area and porous structure without affecting the performance of the oxygen evolution electrode.

[0139] (5) As can be seen from Example 1 and Comparative Examples 1 and 2, the performance of untreated foamed nickel as an oxygen evolution electrode or an oxygen evolution electrode without a nickel-iron buffer layer is lower than that of Example 1. This shows that the present invention first constructs a porous nickel-iron buffer layer with high specific surface area and high loading, and then prepares it by electrodepositing metal hydroxide. The resulting oxygen evolution electrode has excellent oxygen evolution activity and stability.

[0140] In summary, this invention provides a supported oxygen evolution electrode with a nickel-iron buffer layer, its preparation method, and its application. Before electrodepositing metal hydroxide, this invention first constructs a porous nickel-iron buffer layer with high specific surface area and high loading capacity, and then deposits the metal hydroxide layer, resulting in a supported oxygen evolution electrode with a multi-level structure of millimeter-micrometer-nanopores. This improves the nickel-iron buffer capacity, thereby enhancing the metal hydroxide loading capacity, as well as the oxygen evolution activity and stability of the oxygen evolution electrode.

[0141] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a supported oxygen evolution electrode with a nickel-iron buffer layer, characterized in that, The preparation method includes the following steps: Electrochemical etching is performed on a metal substrate loaded with a nickel-iron-molybdenum precursor to obtain a metal substrate with a nickel-iron buffer layer; then, metal hydroxide is electrochemically deposited to obtain the loaded oxygen evolution electrode with the nickel-iron buffer layer. The metal substrate supporting the nickel-iron-molybdenum precursor was obtained by hydrothermal treatment. The hydrothermal treatment includes: hydrothermal reaction of the metal substrate in a mixture of nickel salt, iron salt and molybdenum salt, followed by cooling, cleaning and drying to obtain the metal substrate loaded with the nickel-iron-molybdenum precursor; The hydrothermal reaction is carried out at a temperature of 120~180℃ for 2~12 hours. The loading capacity of the nickel-iron buffer layer is 5~50 mg / cm³. 2 ; The nickel-iron buffer layer has a porous micron columnar array structure, with a corresponding specific capacitance of 200 mF·cm. -2 above; The electrochemical deposition includes: in a metal mixture, using a metal substrate with a nickel-iron buffer layer as the working electrode and an inert, non-soluble electrode as the counter electrode, performing electrodeposition to obtain the supported oxygen evolution electrode with the nickel-iron buffer layer; The metal salts in the metal mixture are iron salts and nickel salts, or iron salts, nickel salts and cobalt salts.

2. The preparation method according to claim 1, characterized in that, In the nickel-iron buffer layer, the molar ratio of nickel to iron is 1:(0.05~0.5).

3. The preparation method according to claim 1, characterized in that, The metal substrate undergoes a hydrothermal reaction in a mixture of nickel salt, iron salt, and molybdenum salt, wherein the molar concentration ratio of the nickel salt, iron salt, and molybdenum salt is 1:(0.05~0.5):(0.2~0.5).

4. The preparation method according to claim 1, characterized in that, The metal substrate undergoes a hydrothermal reaction in a mixture of nickel salt, iron salt, and molybdenum salt, wherein the concentration of the nickel salt is 10-100 mM.

5. The preparation method according to claim 1, characterized in that, The metal substrate is hydrothermally reacted in a mixture of nickel salt, iron salt and molybdenum salt, wherein the nickel salt includes any one or a combination of at least two of nickel nitrate, nickel chloride or nickel sulfate.

6. The preparation method according to claim 1, characterized in that, The metal substrate is hydrothermally reacted in a mixture of nickel salt, iron salt and molybdenum salt, wherein the iron salt includes any one or a combination of at least two of ferric nitrate, ferric chloride or ferric sulfate.

7. The preparation method according to claim 1, characterized in that, The molybdenum salts include ammonium molybdate and / or sodium molybdate.

8. The preparation method according to claim 1, characterized in that, The metal substrate includes any one of nickel foam, nickel mesh, Raney nickel, nickel-plated stainless steel mesh, or nickel-plated iron mesh.

9. The preparation method according to claim 1, characterized in that, The electrochemical etching process includes: in an etching solution, using a metal substrate loaded with a nickel-iron-molybdenum precursor as the working electrode, with an auxiliary electrode, applying a periodic voltage for activation, to obtain the metal substrate with the nickel-iron buffer layer.

10. The preparation method according to claim 9, characterized in that, The etching solution includes NaOH and / or KOH with a concentration of 0.2~8M.

11. The preparation method according to claim 9, characterized in that, The etching solution also includes 0.02~0.5M of NaF and / or KF.

12. The preparation method according to claim 9, characterized in that, The range of the periodic voltage is ±1 to ±8V.

13. The preparation method according to claim 9, characterized in that, The period of the periodic voltage is 0.2 to 10 minutes.

14. The preparation method according to claim 9, characterized in that, The activation temperature is 25~80℃ and the time is 10~60min.

15. The preparation method according to claim 9, characterized in that, The auxiliary electrode includes a titanium-ruthenium electrode or a graphite electrode.

16. The preparation method according to claim 1, characterized in that, The concentration of any one metal salt in the metal mixture is 0.02~0.2M.

17. The preparation method according to claim 1, characterized in that, The current density of the electrodeposition is 10~250 mA·cm. -2 .

18. The preparation method according to claim 1, characterized in that, The electrodeposition time is 10~600s.

19. The preparation method according to claim 1, characterized in that, The inert, non-soluble electrode includes a titanium-ruthenium electrode or a graphite electrode.

20. The preparation method according to claim 1, characterized in that, The preparation method also includes pretreatment of the metal substrate before use: the metal substrate is ultrasonically cleaned sequentially with organic solvent, acid and ultrapure water, and then dried.

21. The preparation method according to claim 20, characterized in that, The ultrasonic cleaning time using the organic solvent is 15-30 minutes.

22. The preparation method according to claim 20, characterized in that, The organic solvents include acetone and / or ethanol.

23. The preparation method according to claim 20, characterized in that, The ultrasonic cleaning time using the acid solution is 5-30 minutes.

24. The preparation method according to claim 20, characterized in that, The acid solution includes a 0.1-2M hydrochloric acid solution.

25. The preparation method according to claim 20, characterized in that, The ultrasonic cleaning time using the ultrapure water is 5-15 minutes.

26. The preparation method according to claim 1, characterized in that, The preparation method includes the following steps: (1) The metal substrate was ultrasonically cleaned with organic solvent for 15-30 min, ultrasonically cleaned with acid for 5-30 min, and ultrasonically cleaned with ultrapure water for 5-15 min in sequence, and then dried to obtain the pretreated metal substrate. (2) The metal substrate pretreated in step (1) is subjected to hydrothermal reaction at 120~180℃ for 2~12h in a mixture of nickel salt, iron salt and molybdenum salt. After cooling, it is taken out, cleaned and dried to obtain the metal substrate loaded with nickel-iron-molybdenum precursor. The molar concentration ratio of the nickel salt, iron salt, and molybdenum salt is 1:(0.05~0.5):(0.2~0.5), and the concentration of the nickel salt is 10~100mM; (3) In the etching solution, the metal substrate loaded with nickel-iron-molybdenum precursor described in step (2) is used as the working electrode, and an auxiliary electrode is added. A periodic voltage is applied, and the substrate is activated at 25~80℃ for 10~60 min to obtain the metal substrate with nickel-iron buffer layer. The range of the periodic voltage is ±1 to ±8V, and the period of the periodic voltage is 0.2 to 10 minutes. The etching solution comprises 0.2-8M MOH and 0.02-0.5M MF, where M is Na and / or K; The loading capacity of the nickel-iron buffer layer is 5~50 mg / cm³. 2 ; (4) In the metal mixture, using the metal substrate with the nickel-iron buffer layer described in step (3) as the working electrode and the inert, non-soluble electrode as the counter electrode, at 10~250 mA·cm -2 Electrodeposition was performed at a current density for 10-600 s, followed by rinsing and drying to obtain the supported oxygen evolution electrode with a nickel-iron buffer layer. In the metal mixture, the concentration of any one metal salt is 0.02~0.2M, and the metal salt is an iron salt and a nickel salt, or an iron salt, a nickel salt and a cobalt salt.

27. A supported oxygen evolution electrode with a nickel-iron buffer layer, characterized in that, The loaded oxygen evolution electrode with a nickel-iron buffer layer is obtained by the preparation method described in any one of claims 1 to 26.

28. An application of the supported oxygen evolution electrode with a nickel-iron buffer layer as described in claim 27, characterized in that, The applications include hydrogen production via water electrolysis.

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