NiFe-based catalyst, oxygen evolution electrode, preparation method of NiFe-based catalyst and oxygen evolution electrode, and application of NiFe-based catalyst and oxygen evolution electrode in water electrolysis oxygen evolution

Abstract

The invention relates to a NiFe-based catalyst, an oxygen evolution electrode, a preparation method of the NiFe-based catalyst and an application of the NiFe-based catalyst and the oxygen evolution electrode in water electrolysis oxygen evolution. Before electrochemical activation, the NiFe-based catalyst provided by the invention comprises the following components: 10-40 at% of Mo; the content of Ni is 20 at%-80 at%; the content of Fe is 10 at%-40 at%; after the NiFe-based catalyst is subjected to electrochemical activation, at least part of Mo ions are dissolved out. The Mo-doped NiFe-based catalyst is synthesized by adopting a one-step hydrothermal method, Mo ions can be dissolved out in the electrochemical activation process, more oxygen vacancies are manufactured by utilizing the continuous dissolution process of the Mo element, the conductivity and intrinsic activity of the NiFe-based catalytic material can be remarkably improved, and the material shows better oxygen evolution performance.

Description

Technical Field

[0001] This invention relates to the technical field of anion exchange membrane electrolysis water production catalysts, and more specifically, to NiFe-based catalysts, oxygen evolution electrodes, their preparation methods, and their applications in oxygen evolution during water electrolysis. Background Technology

[0002] Anion exchange membrane (AEM) water electrolysis for hydrogen production can reduce the internal resistance of the electrolyzer, increase the current density and adaptability to fluctuations in energy, and outperform alkaline aqueous solution water electrolysis for hydrogen production. At the same time, it does not use precious metal catalysts, which significantly reduces costs and overcomes the problems of expensive equipment and limited resources caused by the use of precious metal catalysts in proton exchange membrane water electrolysis for hydrogen production. Therefore, it has become an important direction for future large-scale green hydrogen production technology.

[0003] The water electrolysis process consists of two half-reactions: hydrogen evolution at the cathode and oxygen evolution at the anode. The oxygen evolution reaction (OER) involves a four-electron transfer process, making it more complex and kineticly slower, often becoming the rate-determining step in the process. Currently, commercially available OER catalysts are noble metal Ir-based catalysts, which are expensive and have limited reserves. Therefore, there is an urgent need to develop efficient and stable non-noble metal OER catalysts and electrodes.

[0004] Transition metals such as NiFe alloys have attracted widespread attention due to their low cost and good oxygen evolution reaction (OER) activity. However, in the initial stage of the electrolysis process, these transition metal catalysts undergo remodeling into oxides or hydroxides, which serve as active sites on the catalyst surface. Since OER occurs on the catalyst surface, the surface electronic structure is crucial to both the activity and stability of the catalyst. However, the activity and stability of existing NiFe alloy catalysts still require further improvement. Summary of the Invention

[0005] To address the problems in existing technologies, this invention proposes a NiFe-based catalyst, an oxygen evolution electrode, its preparation method, and its application in oxygen evolution through water electrolysis. This invention prepares a Mo-doped NiFe-based catalyst and optimizes its adsorption energy and electrocatalytic performance by adjusting the catalyst's surface chemistry through defect engineering strategies. Specifically, this invention synthesizes a Mo-doped NiFe-based composite oxygen evolution catalyst using a one-step hydrothermal method and selectively etches Mo ions based on an electrochemical activation process, promoting catalyst structural reconstruction while simultaneously introducing cation vacancy defects in situ. Results show that the leaching of Mo ions triggers the reconstruction of the NiFe-based catalyst and simultaneously brings the metal active sites to an unsaturated coordination state, thereby improving the catalyst's activity.

[0006] One objective of this invention is to provide a NiFe-based catalyst, which comprises the following components before electrochemical activation:

[0007] The Mo content is 10 at% to 40 at%; for example, 10 at%, 15 at%, 20 at%, 25 at%, 30 at%, 35 at% and 40 at%;

[0008] The Ni content is 20 at% to 80 at%; for example, 20 at%, 30 at%, 40 at%, 50 at%, 60 at%, 70 at% and 80 at%;

[0009] The Fe content is 10 at% to 40 at%; for example, 10 at%, 15 at%, 20 at%, 25 at%, 30 at%, 35 at% and 40 at%;

[0010] The NiFe-based catalyst dissolves at least some Mo ions after electrochemical activation.

[0011] In the NiFe-based catalyst of the present invention, preferably, the NiFe-based catalyst comprises the following components before electrochemical activation:

[0012] The Mo content is 20 at% to 30 at%;

[0013] The Ni content is 40 at% to 60 at%;

[0014] The Fe content is 20 at% to 30 at%; and / or,

[0015] The NiFe-based catalyst has a particulate or two-dimensional nanosheet structure; preferably, the thickness of the two-dimensional nanosheet is 10–70 nm; for example, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, or 70 nm; and / or, the average particle size of the particulate is 90–110 nm; for example, 90 nm, 95 nm, 100 nm, 105 nm, or 110 nm; more preferably, the thickness of the two-dimensional nanosheet is 20–70 nm, more preferably 20–50 nm; and / or,

[0016] The NiFe-based catalyst was electrochemically activated by cyclic voltammetry.

[0017] Preferably, the NiFe-based catalyst is electrochemically activated in an alkaline solution by cyclic voltammetry.

[0018] More preferably, the voltage for the electrochemical activation process is set at 1.2–2.0 V vs. RHE (reversible hydrogen reference electrode), preferably 1.2–1.8 V vs. RHE (reversible hydrogen reference electrode), and a CV scan is performed at a scan rate of 50–100 mV / s for 20–100 cycles; and / or,

[0019] The alkali in the alkaline solution is selected from alkali metal hydroxides; preferably KOH; and / or...

[0020] The concentration of the alkaline solution is 1–2 mol / L.

[0021] In this invention, the Mo ions dissolved after electrochemical activation of the NiFe-based catalyst account for more than 80% of the total Mo ions, preferably 80% to 95%.

[0022] The NiFe-based catalyst prepared by this invention has low crystallinity, and the addition of Fe weakens the interaction between Mo and Ni, leading to the rapid dissolution of Mo in alkaline solution under electrochemical conditions. The defect sites formed promote the structural reconstruction of the NiFe catalyst and reduce the free energy for the formation of surface active sites, thereby improving the catalyst activity.

[0023] The second objective of this invention is to provide a method for preparing a NiFe-based catalyst, comprising the following steps:

[0024] (1) A catalyst precursor solution containing nickel source, iron source and molybdenum source is added dropwise to an alkaline solution and mixed to obtain a mixed solution;

[0025] (2) After the mixture is subjected to a hydrothermal reaction, the solid is separated from the liquid and then freeze-dried to obtain an intermediate sample;

[0026] (3) The intermediate sample is reduced to obtain the NiFe-based catalyst;

[0027] The NiFe-based catalyst described in this invention is preferably prepared using the method described above.

[0028] In the preparation method of the NiFe-based catalyst described in this invention, preferably,

[0029] Step (1),

[0030] The nickel source is selected from water-soluble nickel salts, preferably nickel sulfate; and / or,

[0031] The iron source is selected from water-soluble iron salts, preferably ferrous sulfate; and / or,

[0032] The molybdenum source is selected from water-soluble molybdenum salts, preferably ammonium molybdate; and / or,

[0033] The alkali in the alkaline solution is selected from at least one of KOH, NaOH, or ammonia water; and / or,

[0034] In the catalyst precursor solution, the molar ratio of nickel source to iron source is 1–3:1; preferably 1.5–2.5:1; for example, 1:1, 1.5:1, 2:1, 2.5:1, 3:1; and / or,

[0035] In the catalyst precursor solution, the molar ratio of nickel source to molybdenum source is 1–5:1; preferably 2–4:1; for example, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1; and / or,

[0036] In the catalyst precursor solution, the molar volume ratio of nickel source to solvent water is 0.1–1 mol / L; preferably 0.4–0.8 mol / L; for example, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L; and / or,

[0037] The concentration of the alkaline solution is 1–4 mol / L, preferably 2–3 mol / L; for example, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L; and / or,

[0038] The molar ratio of nickel source to alkali in the alkaline solution is 0.1–1:1; preferably 0.4–0.8:1; for example, 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1; and / or,

[0039] The mixing temperature is room temperature; and / or,

[0040] The mixing time is 10 to 60 minutes, preferably 15 to 25 minutes; for example, 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, or 60 minutes.

[0041] In the preparation method of the NiFe-based catalyst described in this invention, preferably,

[0042] Step (2),

[0043] The temperature of the hydrothermal reaction is 80–250°C; preferably 100–200°C; for example, 80°C, 100°C, 120°C, 140°C, 160°C, 180°C, 200°C, 220°C, 240°C, 250°C; and / or,

[0044] The hydrothermal reaction time is 6–36 hours; preferably 12–30 hours; for example, 6 hours, 12 hours, 18 hours, 24 hours, 30 hours, or 36 hours; and / or,

[0045] The solid-liquid separation method is vacuum filtration; and / or,

[0046] The freeze-drying temperature is -10 to -60°C; preferably -40 to -45°C; for example, -10°C, -20°C, -30°C, -40°C, -50°C, -60°C; and / or,

[0047] The freeze-drying time is 6 to 36 hours, preferably 20 to 30 hours; for example, 6 hours, 12 hours, 18 hours, 24 hours, 30 hours, or 36 hours.

[0048] In the preparation method of the NiFe-based catalyst described in this invention, preferably,

[0049] Step (3),

[0050] The atmosphere for the reduction treatment is a mixture of H2 and a protective gas, preferably in which the volume content of hydrogen is 5-15%; for example, 5%, 7.5%, 10%, 12.5%, or 15%; and / or, the flow rate of the mixture is 50-100 mL / min; for example, 50 mL / min, 60 mL / min, 70 mL / min, 80 mL / min, 90 mL / min, or 100 mL / min.

[0051] The reduction treatment is heated to 300℃~550℃ and held for 1~4h; preferably, the reduction treatment is heated to 350℃~400℃ and held for 2-3h; for example, the reduction treatment is heated to 300℃, 350℃, 400℃, 450℃, 500℃, 550℃ and held for 1h, 2h, 3h, 4h respectively; more preferably, the heating rate is 1℃ / min~10℃ / min; for example, 1℃ / min, 3℃ / min, 5℃ / min, 8℃ / min, 10℃ / min.

[0052] This invention synthesizes a Mo-doped NiFe-based catalyst by introducing Mo element during the hydrothermal process. The Mo-doped NiFe-based catalyst of this invention can dissolve Mo ions during the electrochemical activation process, and the defect vacancy density of the material is increased, the activation energy is reduced, and the oxygen evolution performance is improved based on the dissolution process of Mo during activation.

[0053] A third objective of this invention is to provide an application of a NiFe-based catalyst as described in one objective of this invention, or a NiFe-based catalyst prepared by the method described in one objective of this invention, in oxygen evolution through water electrolysis.

[0054] The fourth objective of this invention is to provide an oxygen evolution electrode, wherein the oxygen evolution electrode includes a catalyst, the catalyst being a NiFe-based catalyst as described in one objective of this invention or a NiFe-based catalyst prepared by the method described in another objective of this invention.

[0055] In the oxygen evolution electrode described in this invention, preferably,

[0056] The oxygen evolution electrode includes a gas diffusion layer and a catalyst layer supported on the gas diffusion layer, the catalyst layer including a catalyst and an optional anionic polymer;

[0057] Preferably,

[0058] The catalyst loading is 1-2.5 mg cm⁻¹ -2 Preferably 2-2.5 mg cm -2 ; and / or, the gas diffusion layer is selected from at least one of carbon paper, nickel foam, nickel felt, or nickel-iron foam; and / or,

[0059] When an anionic polymer is included, the anionic polymer is selected from anionic polymers that have adhesive and anionic conduction properties; preferably, the anionic polymer is selected from anionic polymer A5-HCO3.

[0060] In this invention, anionic polymers can be selectively added according to the needs of the oxygen evolution electrode. The anionic polymers are commonly used in existing oxygen evolution electrodes, and the loading amount of the anionic polymer is the conventional loading amount for existing oxygen evolution electrodes; preferably, the loading amount of the anionic polymer is 0.15-0.75 mg / cm³. -2 .

[0061] The fifth objective of this invention is to provide a method for preparing an oxygen evolution electrode, comprising the following steps:

[0062] The oxygen evolution electrode is obtained by loading an organic solution containing a catalyst and an optional anionic polymer onto a gas diffusion layer.

[0063] The oxygen evolution electrode described in the fourth objective of this invention is preferably prepared using the method described above.

[0064] In the method for preparing the oxygen evolution electrode according to the present invention, preferably,

[0065] In the organic solution, the catalyst concentration is 5–20 mg / mL, for example, 5 mg / mL, 7.5 mg / mL, 10 mg / mL, 12.5 mg / mL, 15 mg / mL, 17.5 mg / mL, or 20 mg / mL; and / or,

[0066] When anionic polymers are included, the organic solution contains anionic polymers at a mass concentration of 10%-30%; for example, 10%, 15%, 20%, 25%, or 30%; and / or,

[0067] The organic solvent in the organic solution is an alcohol solvent; preferably selected from at least one of methanol, ethanol, n-propanol, or isopropanol; and / or,

[0068] The loading method is at least one of spraying or scraping transfer.

[0069] The sixth objective of this invention is to provide an application of an oxygen evolution electrode as described in the fourth objective of this invention or an oxygen evolution electrode prepared by the method described in the fifth objective of this invention in the electrolysis of water for oxygen evolution.

[0070] The substances and parameters not limited in this invention can be selected according to existing technology, which is a conventional technical means in this field.

[0071] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values; these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In the following, various technical solutions can, in principle, be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0072] The beneficial effects of this invention are:

[0073] This invention employs a one-step hydrothermal method to synthesize a Mo-doped NiFe-based catalyst. During electrochemical activation, Mo ions are dissolved, and the continuous dissolution of Mo creates more oxygen vacancies, significantly improving the conductivity and intrinsic activity of the NiFe-based catalyst. The material exhibits excellent oxygen evolution performance. (The last sentence appears to be incomplete and possibly refers to a specific catalyst, "At a current density of 10 mA / cm²", which is not directly related to the preceding text.) 2 At that time, the oxygen evolution overpotential was 258 mV, significantly better than that of IrO2, RuO2, and NiFe catalysts. Furthermore, when the catalyst of this invention was used as the oxygen evolution anode and assembled with a Pt / C cathode into an AEM electrolytic cell, a current density of 1 A / cm² was achieved under 1 M KOH and 80 °C conditions. 2 The time slot voltage is 1.71V, 0.5A cm. -2 Under these conditions, the NiFe-based catalyst exhibited excellent stability during a 1000-hour durability test. Therefore, the NiFe-based catalyst of this invention has the advantages of low cost, high catalytic performance, and high stability. Attached Figure Description

[0074] Figure 1 SEM image of the sample in Example 1;

[0075] Figure 2 The energy dispersive spectroscopy (EDS) results for the sample in Example 1;

[0076] Figure 3 The LSV polarization curve of the sample in Example 1;

[0077] Figure 4 The Tafel slope of the sample in Example 1;

[0078] Figure 5 The AC impedance spectrum of the sample in Example 1;

[0079] Figure 6 The capacitance current density of the sample in Example 1;

[0080] Figure 7 The stability of the three-electrode performance of the sample in Example 1;

[0081] Figure 8 The polarization curve of the membrane electrode in Application Example 1;

[0082] Figure 9 To demonstrate the long-cycle stability of the membrane electrode in Application Example 1;

[0083] Figure 10 The polarization curve of the membrane electrode in Application Example 2;

[0084] Figure 11 To improve the long-cycle stability of the membrane electrode in Application Example 2;

[0085] Figure 12 SEM image of the sample in Example 2;

[0086] Figure 13 SEM image of the sample in Example 3;

[0087] Figure 14 XPS spectra of the sample in Example 1 before and after electrochemical activation;

[0088] Figure 15 The images show the EPR spectra of the sample before and after electrochemical activation in Example 1. Detailed Implementation

[0089] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0090] It should also be noted that the various specific technical features described in the following embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the various possible combinations will not be described separately in this invention.

[0091] Furthermore, various embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention. The resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0092] Unless otherwise specified, the raw materials used in the examples and comparative examples are all publicly available in the prior art, such as those that can be directly purchased or prepared according to publicly available methods. For example, the anionic polymer A5-HCO3 of this invention was purchased from Shengerno Company.

[0093] Example 1

[0094] Preparation of NiFe-based catalysts (i.e., Mo-NiFe catalysts):

[0095] Solution 1: Nickel sulfate (AR, 16 mmol), ferrous sulfate heptahydrate (AR, 8 mmol), and ammonium molybdate (AR, 8 mmol) were dissolved in 40 mL of distilled water.

[0096] Solution 2: KOH (AR, 40 mmol) dissolved in 20 mL of distilled water.

[0097] Solution 2 was added dropwise to solution 1. After the addition was complete, the mixture was stirred for 20 minutes. Once the reaction was complete, the mixture was transferred to a 100 mL reactor and reacted at 150 °C for 24 hours. After the reactor cooled down, the sample was filtered and then freeze-dried at -45 °C for 24 hours (cold trap temperature -80 °C, sample plate temperature -45 °C) to obtain an intermediate sample.

[0098] The above intermediate sample was placed in a vacuum tube furnace for reduction treatment. Under the condition of a mixed gas of H2 / Ar (with a hydrogen volume content of 10%) at a flow rate of 80 mL / min, the temperature was increased to 370℃ at a rate of 5℃ / min and held for 2 h; thus, a NiFe-based catalyst (i.e., Mo-NiFe catalyst) was obtained. The NiFe-based catalyst of this invention exhibits a two-dimensional nanostructure, with the thickness of its nanosheet structure being 10-50 nm, such as... Figure 1 As shown. By Figure 2 The EDS mapping results show that Ni, Fe, and Mo are uniformly distributed in the two-dimensional structure.

[0099] Electrochemical activation and performance testing of NiFe-based catalysts:

[0100] Weigh 10 mg of the catalyst and add it to 1.5 mL of isopropanol and 0.5 mL of water, then sonicate for 60 min. Next, add 80 μL of Nafion and sonicate for 10 min. Take 5 μL of the dispersion three times and add it dropwise to a rotating disk electrode for electrochemical activation of the NiFe-based catalyst and to test its oxygen evolution performance in water electrolysis.

[0101] A three-electrode system was constructed using a rotating disk electrode loaded with the catalyst as the working electrode, a graphite rod as the counter electrode, a standard hydrogen electrode as the reference electrode, and 1M KOH solution as the electrolyte. The catalyst was activated and stabilized using cyclic voltammetry, and its OER performance was evaluated using linear sweep voltammetry (LSV). Electrochemical testing was conducted using a Shanghai Chenhua 760E electrochemical workstation. Before testing, N2 was passed through the electrolyte for approximately 30 minutes to saturate it. The three-electrode system was then assembled, with the voltage range set at 1.2–1.8 V (vs. RHE). A CV scan of 50 mV / s was performed for 20 cycles to ensure complete sample activation and exposure of active sites. Linear sweep voltammetry (LSV) was then performed at 1.2–1.8 V.

[0102] The results of the sample before and after activation are as follows Figure 14 , Figure 15 As shown, a significant dissolution process of Mo occurred on the electrode surface before and after activation, with almost no Mo present on the surface. However, the oxygen vacancy density was significantly increased, which in turn improved charge conductivity. Specifically, the Mo ions dissolved from the NiFe-based catalyst after electrochemical activation accounted for more than 80% of the total Mo ions.

[0103] The results of the linear sweep voltammetry (LSV) test are as follows: Figure 3 As shown. At a current density of 100 mA / cm² 2 At that time, the oxygen evolution overpotential was 258 mV, significantly better than IrO2, RuO2, and the NiFe catalyst in Comparative Example 3. Its Tafel slope was 44.2 mV / dec. Figure 4 As shown, the smaller the Tafel slope, the faster the current density increases, indicating faster catalyst kinetics and better catalytic activity.

[0104] The kinetic activity of the catalyst was tested using alternating current impedance spectroscopy. Test conditions: a 10mV perturbation near the test voltage, and a frequency range of 100kHz to 1Hz. The alternating current impedance spectroscopy reveals the resistivity of the material, allowing for analysis and comparison of the kinetic activities of different materials. The Rct of the catalyst obtained in this example was measured to be 1.7Ω. Figure 5 As shown, the catalyst of the present invention has the lowest resistance value.

[0105] CV scanning of the electrodes was performed using different scan rates, such as Figure 6 As shown, the calculated C dl The double-layer capacitance is 1.37 mF cm. -2 The value of Cdl can reflect the charge storage capacity of the electrode surface. Compared with the NiFe catalyst of Comparative Example 3 without Mo, the Mo-NiFe catalyst of the present invention has more electrochemical active sites.

[0106] The electrochemical stability of the catalyst obtained in this example was evaluated using a time-potential assay. Figure 7 As shown in the figure, the catalyst obtained in this embodiment shows a small increase in potential after 300 hours, indicating that the catalyst has good stability.

[0107] Application Example 1

[0108] A method for preparing an oxygen evolution electrode:

[0109] The catalyst sample from Example 1 was sprayed onto the surface of a gas diffusion layer to obtain a gas diffusion electrode for the oxygen evolution reaction. The oxygen evolution electrode was prepared using the CCS method. The Mo-NiFe catalyst was formulated into a spraying ink using isopropanol as the solvent and a small amount of anionic polymer A5-HCO3 was added. The catalyst concentration in the spraying ink was 10 mg / mL, and the mass concentration of the anionic polymer was 20%. The prepared solution was ultrasonically dispersed for 1 hour. The spraying ink was then sprayed onto the surface of the gas diffusion layer (carbon paper) using a spraying method, with a catalyst loading of 2 mg / mL. -2 The electrode area is 4 cm². 2 .

[0110] The sample prepared above was used as an oxygen evolution electrode in an alkaline membrane electrolyzer. The effective area of ​​a single cell was 4 cm². 2 The electrode consists of an anode (the oxygen evolution electrode prepared above), a cathode, an anion exchange membrane (AEM, PiperION, 40 μm), and two stainless steel current collectors. The cathode was prepared using the CCS method, and a 150 μm thick layer of 20 wt% Pt / C (Johnson Matthey) commercial catalyst was sprayed onto Toray carbon paper 060, with a Pt loading of 0.4 mg / cm³. -2 The AEM was placed between the oxygen evolution electrode and the hydrogen evolution electrode. After the electrodes were assembled, activation was performed using cyclic voltammetry (1.2–2.0 V (vs. RHE), with 20 CV scans at a scan rate of 50 mV / s). The polarization curves of the electrodes were measured using LSV at 1.2–2.2 V and a current density of 0.5 A / cm². -2Under these conditions, the durability of AEMWE (Anion Exchange Membrane Water Electrolysis) was evaluated using the time-potential method. Performance testing was conducted using an IPS 100A electrochemical workstation. AEMWE was tested at 60°C using 1M KOH as the electrolyte. Polarization curves are shown below. Figure 8 As shown, by Figure 8 The current density is 1.0 Acm. -2 At that time, the electrolyzer voltage using the NiFe catalyst of this invention as the anode was 1.71 V, which significantly outperformed the electrolyzer using IrO2 as the anode and the electrolyzer using the NiFe catalyst of Comparative Example 3 as the anode. Durability is as follows... Figure 9 As shown, 0.5Acm -2 Under these conditions, the 1000-hour durability test showed good stability.

[0111] Application Example 2

[0112] The catalyst sample prepared in Example 1 was used as the anode, and the method was basically the same as in Application Example 1, except that the polarization curves of the electrolyzer were tested at temperatures of 70°C and 80°C. Figure 10 As shown, the current density is 1 A cm⁻¹. -2 The electrolytic cell voltage is only 1.63V (80℃) and only 1.66V (70℃); and at a current density of 1A cm⁻¹ -2 The durability of the electrolytic cell was tested at 80℃. Figure 11 As shown, the performance of the electrolyzer remained stable after 300 hours.

[0113] Example 2

[0114] Preparation of NiFe-based catalysts (i.e., Mo-NiFe catalysts):

[0115] The procedure was carried out according to Example 1, except that the hydrothermal temperature was 100°C. Scanning electron microscopy was performed as follows: Figure 12 As shown, the catalyst has an overall morphology of particles with an average particle size of approximately 100 nm.

[0116] Linear sweep voltammetry (LSV) testing was performed using the same method as in Example 1, at a current density of 100 mA / cm². 2 At that time, the oxygen evolution overpotential was 288mV.

[0117] Example 3

[0118] Preparation of NiFe-based catalysts (i.e., Mo-NiFe catalysts):

[0119] The procedure was carried out according to Example 1, except that the hydrothermal temperature was 200°C. Scanning electron microscopy was performed as follows: Figure 13 As shown, the catalyst has an overall morphology of nanosheet structure. When magnified, it is a nanosheet structure composed of particulate materials. It is relatively large and thick, with a thickness of 30-70 nm.

[0120] Linear sweep voltammetry (LSV) testing was performed using the same method as in Example 1, at a current density of 100 mA / cm². 2 At that time, the oxygen evolution overpotential was 280mV.

[0121] Example 4

[0122] Preparation of NiFe-based catalysts (i.e., Mo-NiFe catalysts):

[0123] The procedure was carried out according to Example 1, except that nickel sulfate (AR, 16 mmol), ferrous sulfate heptahydrate (AR, 8 mmol), and ammonium molybdate (AR, 16 mmol) were used.

[0124] Linear sweep voltammetry (LSV) testing was performed using the same method as in Example 1, at a current density of 100 mA / cm². 2 At that time, the oxygen evolution overpotential was 260mV.

[0125] Example 5

[0126] Preparation of NiFe-based catalysts (i.e., Mo-NiFe catalysts):

[0127] The procedure was carried out according to Example 1, except that nickel sulfate (AR, 16 mmol), ferrous sulfate heptahydrate (AR, 8 mmol), and ammonium molybdate (AR, 4 mmol) were used.

[0128] Linear sweep voltammetry (LSV) testing was performed using the same method as in Example 1, at a current density of 100 mA / cm². 2 At that time, the oxygen evolution overpotential was 265mV.

[0129] Example 6

[0130] Preparation of NiFe-based catalysts (i.e., Mo-NiFe catalysts):

[0131] The method was carried out according to Example 1, except that the high-temperature calcination temperature was 550°C.

[0132] Linear sweep voltammetry (LSV) testing was performed using the same method as in Example 1, at a current density of 100 mA / cm². 2 At that time, the oxygen evolution overpotential was 268mV.

[0133] Comparative Example 1

[0134] Commercial RuO2 was used as the oxygen evolution catalyst. Electrode solutions were prepared using the same method and coated onto the surface of a disk electrode for electrochemical performance testing. The test results are as follows: Figure 3 As shown, at 100mA / cm 2 At the current density, the oxygen evolution overpotential of RuO2 is approximately 385mV.

[0135] Comparative Example 2

[0136] Commercially available IrO2 was used as the oxygen evolution catalyst. Electrode solutions were prepared using the same method and coated onto the surface of a disk electrode for electrochemical performance testing. The test results are as follows: Figure 3 As shown, at 10mA / cm 2 At the current density, the oxygen evolution overpotential of IrO2 is approximately 410 mV.

[0137] Comparative Example 3

[0138] Unlike Example 1, ammonium molybdate was not added; instead, nickel sulfate (AR, 16 mmol) and ferrous sulfate heptahydrate (AR, 8 mmol) were added to prepare the NiFe catalyst. Electrode solutions were prepared using the same method and coated onto the surface of a disk electrode for electrochemical performance testing. The test results are as follows: Figure 3 As shown, at 100mA / cm 2 At the current density, the oxygen evolution overpotential is approximately 450mV.

[0139] The results above show that Example 1 exhibits the lowest oxygen evolution overpotential at 258 mV, indicating good catalytic activity. The oxygen evolution overpotentials of Examples 2, 3, 4, 5, and 6 are all higher than that of Example 1, but still lower than those of Comparative Examples 1 and 2. Comparative Example 3 shows the highest oxygen evolution overpotential at 450 mV. These data indicate that the NiFe-based catalyst of this invention (i.e., the Mo-NiFe catalyst) has better performance than the NiFe-based catalyst without molybdenum.

[0140] In summary, this invention synthesizes a NiFeMo-based two-dimensional nanostructured oxygen evolution catalyst using a one-step hydrothermal method. Furthermore, electrochemical activation allows for the dissolution of Mo from the catalyst, creating more oxygen vacancies and significantly improving the conductivity and intrinsic activity of the catalytic material, resulting in superior oxygen evolution performance. In particular, the catalyst exhibits excellent performance at a current density of 100 mA / cm². 2 At that time, the oxygen evolution overpotential was 258 mV, which was significantly better than the IrO2 catalyst of Comparative Example 2, RuO2 catalyst of Comparative Example 1, and NiFe catalyst of Comparative Example 3.

[0141] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

[0142] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0143] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0144] In the context of this specification, except where expressly stated otherwise, any matters or issues not mentioned shall apply directly to those known in the art without any modification.

Claims

1. A NiFe-based catalyst, characterized in that: The NiFe-based catalyst comprises the following components before electrochemical activation: Mo content is 10 at% to 40 at%; Ni content is 20 at% to 80 at%; The Fe content is 10 at% to 40 at%; The NiFe-based catalyst dissolves at least some Mo ions after electrochemical activation.

2. The NiFe-based catalyst according to claim 1, characterized in that: The NiFe-based catalyst comprises the following components before electrochemical activation: The Mo content is 20 at% to 30 at%; The Ni content is 40 at% to 60 at%; The Fe content is 20 at% to 30 at%; and / or, The NiFe-based catalyst has a particulate or two-dimensional nanosheet structure; preferably, the thickness of the two-dimensional nanosheet is 10–70 nm; and / or, the average particle size of the particulate is 90–110 nm; more preferably, the thickness of the two-dimensional nanosheet is 20–70 nm, more preferably 20–50 nm; and / or, The NiFe-based catalyst was electrochemically activated by cyclic voltammetry. Preferably, the NiFe-based catalyst is electrochemically activated in an alkaline solution by cyclic voltammetry. More preferably, the voltage for the electrochemical activation process is set at 1.2–2.0 V vs. RHE, and a CV scan is performed at a scan rate of 50–100 mV / s for 20–100 cycles; and / or, The alkali in the alkaline solution is selected from alkali metal hydroxides; and / or, The concentration of the alkaline solution is 1–2 mol / L.

3. A method for preparing a NiFe-based catalyst, characterized in that, Includes the following steps: (1) A catalyst precursor solution containing nickel source, iron source and molybdenum source is added dropwise to an alkaline solution and mixed to obtain a mixed solution; (2) After the mixture is subjected to a hydrothermal reaction, the solid is separated from the liquid and the solid is freeze-dried to obtain an intermediate sample; (3) The intermediate sample is reduced to obtain the NiFe-based catalyst; The NiFe-based catalyst according to any one of claims 1-2 is preferably prepared using the method described above.

4. The method for preparing the NiFe-based catalyst according to claim 3, characterized in that: Step (1), The nickel source is selected from water-soluble nickel salts, preferably nickel sulfate; and / or, The iron source is selected from water-soluble iron salts, preferably ferrous sulfate; and / or, The molybdenum source is selected from water-soluble molybdenum salts, preferably ammonium molybdate; and / or, The alkali in the alkaline solution is selected from at least one of KOH, NaOH, or ammonia water; and / or, In the catalyst precursor solution, the molar ratio of nickel source to iron source is 1–3:1; preferably 1.5–2.5:1; and / or, In the catalyst precursor solution, the molar ratio of nickel source to molybdenum source is 1–5:1; preferably 2–4:1; and / or, In the catalyst precursor solution, the molar volume ratio of nickel source to solvent water is 0.1–1 mol / L; preferably 0.4–0.8 mol / L; and / or, The concentration of the alkaline solution is 1–4 mol / L; preferably 2–3 mol / L; and / or, The molar ratio of nickel source to alkali in the alkaline solution is 0.1–1:1; preferably 0.4–0.8:1; and / or, The mixing temperature is room temperature; and / or, The mixing time is 10 to 60 minutes, preferably 15 to 25 minutes.

5. The method for preparing the NiFe-based catalyst according to claim 3, characterized in that: Step (2), The temperature of the hydrothermal reaction is 80–250°C; preferably 100–200°C; and / or, The hydrothermal reaction time is 6–36 h; preferably 12–30 h; and / or, The solid-liquid separation method is vacuum filtration; and / or, The freeze-drying temperature is -10 to -60°C; preferably -40 to -45°C; and / or, The freeze-drying time is 6 to 36 hours, preferably 20 to 30 hours.

6. The method for preparing the NiFe-based catalyst according to claim 3, characterized in that: Step (3), The atmosphere for the reduction treatment is a mixture of H2 and a protective gas, preferably in which the volume content of hydrogen is 5-15%; and / or, the flow rate of the mixture is 50-100 mL / min; The reduction treatment is heated to 300℃~550℃ and held for 1~4h; preferably, the reduction treatment is heated to 350℃~400℃ and held for 2~3h; more preferably, the heating rate is 1℃ / min~10℃ / min.

7. The application of a NiFe-based catalyst as described in any one of claims 1-2 or a NiFe-based catalyst prepared by the method as described in any one of claims 3-6 in oxygen evolution by water electrolysis.

8. An oxygen evolution electrode, characterized in that: The oxygen evolution electrode includes a catalyst, which is the NiFe-based catalyst according to any one of claims 1-2 or the NiFe-based catalyst prepared by the method according to any one of claims 3-6.

9. The oxygen evolution electrode according to claim 8, characterized in that: The oxygen evolution electrode includes a gas diffusion layer and a catalyst layer supported on the gas diffusion layer, the catalyst layer including the catalyst and an optional anionic polymer; Preferably, The catalyst loading is 1–2.5 mg cm⁻¹. -2 Preferably 2–2.5 mg cm -2 ; and / or, The gas diffusion layer is selected from at least one of carbon paper, nickel foam, nickel felt, or nickel-iron foam; and / or, When an anionic polymer is included, the anionic polymer is selected from anionic polymers that have adhesive and anionic conduction properties; preferably, the anionic polymer is selected from anionic polymer A5-HCO3.

10. A method for preparing an oxygen evolution electrode, characterized in that, Includes the following steps: The oxygen evolution electrode is obtained by loading an organic solution containing a catalyst and an optional anionic polymer onto a gas diffusion layer. The oxygen evolution electrode according to any one of claims 8-9 is preferably prepared by the method described above.

11. The method for preparing the oxygen evolution electrode according to claim 10, characterized in that: In the organic solution, the catalyst concentration is 5–20 mg / mL, and / or, When anionic polymers are included, the organic solution contains anionic polymers at a mass concentration of 10% to 30%; and / or, The organic solvent in the organic solution is an alcohol solvent; preferably selected from at least one of methanol, ethanol, n-propanol, or isopropanol; and / or, The loading method is at least one of spraying or scraping transfer.

12. The application of an oxygen evolution electrode as described in any one of claims 8-9 or an oxygen evolution electrode prepared by the method as described in any one of claims 10-11 in oxygen evolution during water electrolysis.

Images