Iridium-based nanowire, its iridium-based catalyst, and methods for their production

Abstract

An iridium-based nanowire and a preparation method therefor, and an iridium-based catalyst containing same and a preparation method therefor. The iridium-based nanowire comprises a twin of iridium and at least one transition metal selected from iron, cobalt, and nickel. Preferably, the diameter d of the nanowire is 0.5-6 nm, and further preferably, the grain size of the twin is (0.8-1.1)·d nm.

Description

Iridium-based nanowires, iridium-based catalysts containing the same, and preparation methods thereof Technical Field

[0001] The present invention belongs to the field of electrocatalysis, and in particular relates to an iridium-based nanowire, an iridium-based catalyst containing the same, and a preparation method thereof. Background Art

[0002] By converting CO2 into valuable chemicals and fuels, CO2 electrolysis can effectively reduce greenhouse gas emissions, mitigate climate change, and contribute to the achievement of carbon neutrality. This technology converts electrical energy into chemical energy, promoting energy storage and recycling, reducing dependence on fossil fuels, and providing a key solution for building a sustainable energy system.

[0003] Iridium is a commonly used catalyst for the oxygen evolution reaction (OER) at the anode of carbon dioxide electrolysis. However, the extremely low abundance of iridium in the Earth's crust limits its large-scale application. To further improve the efficiency of iridium catalysts and reduce the amount of precious metals used, alloying is a viable approach. This can improve the stability and activity of the catalyst and reduce the amount of precious metals used.

[0004] Iridium-based alloy catalysts have achieved some success. CN110453256B discloses a polyhedral cobalt-iridium nanoparticle catalyst prepared by electrochemical deposition; CN112475314A discloses an iridium-based nanowire prepared by a mixed solvent chemical synthesis method. The nanowires have a diameter of 20 to 100 nm. Both of these catalysts exhibit better oxygen evolution reaction performance than iridium nanocatalysts. However, these synthesis processes are generally not conducive to scale-up. Nanowires with large particle sizes and large cross-sections often have a low electrochemically active surface area, and the catalyst performance needs to be improved.

[0005] Summary of the Invention

[0006] The present invention aims to provide an iridium-based catalyst, a preparation method and an application thereof. The catalyst has the advantages of a large electrochemically active surface area, high catalytic activity for oxygen evolution reaction and good stability, and is suitable for oxygen evolution reaction under acidic conditions.

[0007] The first aspect of the present invention provides an iridium-based nanowire; it comprises twins of iridium and at least one transition metal selected from iron, cobalt, and nickel. Preferably, the nanowire has a diameter d of 0.5 to 6 nm, more preferably 0.5 to 5 nm, and further preferably, the twin grain size is (0.8 to 1.1)·d nm.

[0008] A second aspect of the present invention provides a method for preparing iridium-based nanowires, comprising the steps of:

[0009] A1. dissolving the capping agent, iridium source and crystal face coordination agent in the first alcohol to obtain an iridium source solution,

[0010] A2. dissolving the transition metal source in the second alcohol to obtain a transition metal source solution,

[0011] A3. The solution of step A1 is mixed with the solution of step A2 to obtain a mixture;

[0012] A4. reacting the mixture from step A3 under heating conditions to obtain iridium-based nanowires.

[0013] Preferably, the crystal plane coordination agent comprises an inorganic iodide; and

[0014] The capping agent is polyvinyl pyrrolidone with a weight average molecular weight of 8,000 to 40,000.

[0015] A third aspect of the present invention provides an iridium-based catalyst, comprising the iridium-based nanowires according to the first aspect, which are located on a nitrogen-doped carbon material as a support.

[0016] A fourth aspect of the present invention provides a method for preparing the iridium-based catalyst, comprising the following steps:

[0017] B1. Providing an iridium-based nanowire according to the first aspect, or providing an iridium-based nanowire obtained by the method according to the second aspect;

[0018] B2. mixing the nitrogen-doped carbon material with the iridium-based nanowires,

[0019] B3. heat-treating the mixture obtained in step B2,

[0020] An iridium-based catalyst containing iridium-based nanowires as active components and nitrogen-doped carbon materials as carriers is obtained.

[0021] The fifth aspect of the present invention is the use of the above-mentioned iridium-based nanowires or iridium-based catalysts in oxygen evolution reaction.

[0022] The present invention includes the following beneficial effects:

[0023] The iridium-based catalyst of the present invention comprises twinned nanowires as the active component, which have a large electrochemical surface area. This active component not only significantly reduces the amount of precious metal iridium required, but also exhibits excellent catalytic activity and stability in the oxygen evolution reaction. In the twinned nanowires of the present invention, iridium is concentrated on the surface of the twinned nanowires, with at least a portion of the iridium on the surface being in an oxidized state, maximizing the catalytic effect of iridium. Furthermore, the preparation method provided by the present invention is simple and has minimal environmental impact. The prepared iridium-based catalyst is uniform in size, making it suitable for large-scale production.

[0024] Other features and advantages of the present application will be described in detail in the following description of the drawings and the detailed description of the embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings are used to provide further understanding of the present application and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present application, but do not constitute a limitation to the present application.

[0026] FIG1 is a TEM image of iridium-based nanowires, an active component of Example 1, and a diffraction image obtained by fast Fourier transform (FFT);

[0027] FIG2 is a high-resolution TEM image of iridium-based nanowires, an active component of Example 1;

[0028] FIG3 is an X-ray diffraction image of iridium-based nanowires, an active component of Example 1;

[0029] FIG4 is an XPS image of the Ir 4f region of the iridium-based catalyst before atmosphere heat treatment in Example 1, where the dotted line represents metallic iridium;

[0030] FIG5 is an XPS image of the Ir 4f region of the iridium-based catalyst after atmosphere heat treatment in Example 1, where the dotted line portion represents metallic iridium.

[0031] FIG6 is a TEM image of the iridium-based nanowires as the active component in Comparative Example 2. DETAILED DESCRIPTION

[0032] The following is a detailed description of the specific embodiments of the present application. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present application and are not intended to limit the present application.

[0033] Any specific numerical value disclosed herein (including the endpoints of a numerical range) is not limited to the exact value of the numerical value, but should be understood to also include values ​​close to the exact value, such as all possible values ​​within ±5% of the exact value. Moreover, for a disclosed numerical range, any combination of the endpoints of the range, between the endpoints and the specific points in the range, and between the specific points can be used to generate one or more new numerical ranges, and these new numerical ranges should also be considered to be specifically disclosed herein.

[0034] Unless otherwise specified, the terms used herein have the same meaning as commonly understood by those skilled in the art. If a term is defined herein and its definition is different from the commonly understood meaning in the art, the definition herein shall prevail.

[0035] When a component, element, or layer is referred to as being "on," "connected," "connected," or "coupled" to another element or layer, it may be directly on, connected, connected, or coupled to the other component, element, or layer, or there may be intervening elements or layers. Conversely, when an element is referred to as being directly on, "directly connected," "directly connected," or "directly coupled" to another element or layer, there may be no intervening elements or layers. Other words used to describe the relationship between elements should be interpreted in a similar manner (e.g., "between" vs. "directly between," "adjacent" vs. "directly adjacent," etc.). As used herein, the term "and / or" includes any and all combinations of one or more of the associated enumerated items.

[0036] Any method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as a certain order of performance. It is also to be understood that additional or alternative steps may be used unless otherwise specified.

[0037] Unless the context clearly indicates otherwise, as used herein, the singular forms "a," "an," and "the" may be intended to include the plural forms as well. The terms "comprising," "including," "containing," and "having" are inclusive and thus specify the presence of stated features, elements, compositions, steps, integers, operations, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or collections thereof. Although the open-ended term "comprising" should be understood as a non-limiting term for describing and claiming the various embodiments described herein, in certain aspects, the term may instead be understood as a more restrictive and limited term, such as "consisting of" or "consisting essentially of." Thus, for any given embodiment reciting compositions, materials, components, elements, features, integers, operations, and / or process steps, the present disclosure also specifically includes embodiments consisting of or consisting essentially of such stated compositions, materials, components, elements, features, integers, operations, and / or process steps. In the case of "consisting of," alternative embodiments exclude any additional compositions, materials, components, elements, features, integers, operations and / or process steps, while in the case of "consisting essentially of," any additional compositions, materials, components, elements, features, integers, operations and / or process steps that materially affect the basic and novel characteristics are excluded from such embodiments, but any compositions, materials, components, elements, features, integers, operations and / or process steps that do not materially affect the basic and novel characteristics may be included in such embodiments.

[0038] In the context of this invention, twins are defined as regular, non-parallel intergrowths of two or more crystals of the same mineral. Twins are a symmetrical intergrowth between two or more adjacent crystals of the same mineral. At the microscopic level, twin boundaries are characterized by two grain orientations sharing a set of atomic positions in the crystal lattice.

[0039] In the context of the present invention, twinned nanowires / catalysts refer to nanowires / catalytic materials having a twinned structure.

[0040] In the context of the present invention, a crystal plane coordination agent is an agent that achieves control over the morphology of nanocrystals through a specific coordination effect.

[0041] In the context of the present invention, an iridium source and a transition metal source serve as raw materials for providing iridium and transition metal, respectively.

[0042] In the context of the present invention, percentages are by weight unless otherwise specified.

[0043] In the context of the present invention, unless otherwise specified, pressure refers to absolute pressure.

[0044] Unless otherwise specified, the terms used herein have the same meaning as commonly understood by those skilled in the art. If a term is defined herein and its definition is different from the commonly understood meaning in the art, the definition herein shall prevail.

[0045] Iridium-based nanowires

[0046] The first aspect of the present invention provides an iridium-based nanowire; it comprises twins of iridium and at least one transition metal selected from iron, cobalt, and nickel. Preferably, the nanowire diameter d is 0.5 to 6 nm, more preferably 0.5 to 5 nm, and further preferably, the twins have a grain size of (0.8 to 1.1) d nm. The nanowire diameter d is, for example, 0.5 nm, 0.6 nm, 0.7 nm, 0.8 nm, 0.9 nm, 1 nm, 1.5 nm, 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm, 5 nm, 5.5 nm, and 6 nm. The twin grain size is, for example, 0.8 d nm, 0.85 d nm, 0.9 d nm, 0.95 d nm, 1 d nm, 1.05 d nm, and 1.1 d nm. The twin grain size is expressed as the product of a constant and the nanowire diameter, that is, for example, 0.8·d nm represents 0.8 times the nanowire diameter. In the case of d=5 nm, this means that the twin grain size is 4 nm.

[0047] Nanowires are nanometer-scale wires. In other words, nanowires are one-dimensional structures with nanometer-scale lengths in the horizontal direction. There is no limit to the length of a nanowire in the vertical direction.

[0048] When the nanowire diameter is less than 0.5 nm, the nanowire structure is unstable due to the small size of the twin grains. When the nanowire diameter is greater than 6 nm, the electrochemical surface area of ​​the material is small due to the reduction in geometric surface area.

[0049] According to some embodiments of the present invention, the twinned nanowires are dendritic and formed by nanocrystals connected by orientation. According to other embodiments of the present invention, the twinned nanowires are linear or mesh-like.

[0050] Compared to traditional catalysts, the surface and interface properties of twinned nanowire catalysts can be finely tuned, forming specialized electronic structures at the nanowire interfaces that provide more active sites, thereby increasing catalytic activity. The twin interfaces can alter the stress distribution of the catalyst at the nanoscale, helping to resist lattice distortion at high temperatures and improving the catalyst's thermal stability and durability.

[0051] Furthermore, the atomic ratio of iridium to transition metal in the active component is 1:(0.1-5), preferably 1:(0.2-3).

[0052] Preferably, the atomic % concentration of iridium on the surface of the iridium-based nanowire is at least 1% higher, preferably at least 2% higher, more preferably at least 5% higher than the atomic % concentration of iridium in the bulk of the iridium-based nanowire.

[0053] Preferably, the iridium in an oxidized state on the surface of the iridium-based nanowire accounts for at least 20 atomic %, preferably at least 30 atomic %, more preferably at least 40 atomic %, based on 100% of all iridium atoms on the surface.

[0054] Although not limiting the present invention, it is believed that iridium and the transition metal form alloys, such as iridium-cobalt alloys, iridium-nickel alloys, and iridium-iron alloys, which further grow to form twinned nanowires.

[0055] Preparation of iridium-based nanowires

[0056] A second aspect of the present invention provides a method for preparing iridium-based nanowires, comprising the steps of:

[0057] A1. The capping agent, the iridium source and the crystal face coordinating agent are dissolved in a first alcohol to obtain an iridium source solution, preferably, the capping agent is dissolved in a first alcohol, to which an iridium source and a crystal face coordinating agent are added and dissolved to obtain an iridium source solution;

[0058] A2. dissolving the transition metal source in the second alcohol to obtain a transition metal source solution,

[0059] A3. The solution of step A1 is mixed with the solution of step A2 to obtain a mixture;

[0060] A4. reacting the mixture from step A3 under heating conditions to obtain iridium-based nanowires.

[0061] Preferably, the crystal face coordination agent comprises an inorganic iodide. According to a preferred embodiment, the crystal face coordination agent is a mixture of an inorganic iodide and a quaternary ammonium bromide salt with a relative molecular weight less than 360.

[0062] The capping agent stabilizes the nanoparticles during their growth, reducing their surface energy and ensuring their stable existence. Preferably, the capping agent is polyvinyl pyrrolidone with a weight-average molecular weight of 8,000 to 40,000. Furthermore, the capping agent is polyvinyl pyrrolidone with a weight-average molecular weight of 8,000 to 60,000; preferably, the weight-average molecular weight of the polyvinyl pyrrolidone is 12,000 to 45,000, and more preferably, the weight-average molecular weight of the polyvinyl pyrrolidone is 15,000 to 30,000.

[0063] Furthermore, the iridium source is selected from soluble salts of iridium, preferably at least one selected from iridium chloride, iridium acetylacetonate, carbonyl iridium, hexachloroiridic acid, sodium hexachloroiridate, ammonium hexachloroiridate, tetrairidium dodecacarbonyl, etc.

[0064] Furthermore, the transition metal source is selected from soluble salts of transition metals iron, cobalt, and nickel, preferably at least one of soluble chlorides, bromides, nitrates, sulfates, carbonates, acetates, and acetylacetonates of iron, cobalt, and nickel.

[0065] Furthermore, the crystal face coordination agent is a mixture of crystal face coordination agent a and crystal face coordination agent b. Crystal face coordination agent a is used to improve the crystallization degree of the nanocrystals, and crystal face coordination agent b is used to promote the orientation and connection of the nanocrystals to form twin nanowires. Preferably, crystal face coordination agent a is a quaternary ammonium bromide salt with a relative molecular weight of less than 360. Preferably, crystal face coordination agent b is an inorganic iodide;

[0066] More preferably, the quaternary ammonium bromide salt is a compound selected from the general formula R4NBr, wherein R independently represents a C1-C4 alkyl group, an aryl group, a C1-C4 alkyl-substituted aryl group, and is preferably selected from at least one of tetramethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, tetrabutylammonium bromide, benzyltrimethylammonium bromide, benzyltriethylammonium bromide, etc.

[0067] More preferably, the inorganic iodide is at least one selected from alkali metal iodides (such as lithium iodide, sodium iodide, potassium iodide) or ammonium iodide.

[0068] Furthermore, the first alcohol and the second alcohol are the same or different, preferably the same. The first alcohol and the second alcohol are, independently of each other, preferably a polyol, preferably a C2-C5 polyol, and preferably a diol and / or a triol. Preferably, the polyol is at least one selected from ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, glycerol, diethylene glycol, triethylene glycol, and the like.

[0069] Furthermore, the mixing order is to dissolve the capping agent in the first alcohol, add the iridium source and the crystal plane coordination agent in sequence and fully dissolve them, and then add the transition metal source dissolved in the second alcohol and stir until fully mixed.

[0070] Furthermore, the molar ratio of the iridium source, the transition metal source, and the crystal face coordination agent is 1:(0.5-15):(5.1-32), preferably 1:(0.5-10):(5.1-32); preferably, the molar ratio of the iridium source, the quaternary ammonium bromide salt, and the inorganic iodide in the crystal face coordination agent in step (1) is 1:(5-30):(0.1-1.2), preferably 1:(8-20):(0.3-1). When there are multiple moles of iridium in 1 mole of iridium source, the calculation is based on the molar number of iridium. For example, in the case of tetrairidium dodecacarbonyl, 1 mole of tetrairidium dodecacarbonyl corresponds to 4 moles of iridium source. For example, in the case of dicobalt octacarbonyl, 1 mole of dicobalt octacarbonyl corresponds to 2 moles of cobalt source. The crystal face coordination agent is based on the sum of the molar numbers of the crystal face coordination agents used, that is, the sum of the molar numbers of crystal face coordination agent a and crystal face coordination agent b.

[0071] Furthermore, the mass ratio of the iridium source (converted into the mass of hydrated iridium chloride with an equal molar amount of iridium), the capping agent and the alcohol is 1:(8-12):(1500-1800), preferably 1:(8-10):(1500-1800).

[0072] Furthermore, the heating is preferably carried out in a sealed state, such as in an autoclave; optionally, a polyol solvent thermal reaction is carried out under heating conditions; optionally, the heating temperature is 130 to 230°C, preferably 160 to 190°C; and the heating time is 4 to 60 hours, preferably 24 to 48 hours. The pressure is generally the pressure generated by the reaction system under heating. The pressure can be, for example, 0.8 to 1.5 bar. (abs) , preferably 1.0~1.2bar (abs) .

[0073] Furthermore, the iridium-based nanowires obtained after the heating reaction can be post-treated using conventional post-treatment steps in the art (e.g., centrifugation, washing, drying, etc.) to produce purified iridium-based nanowires. The centrifugation step includes, but is not limited to, adding acetone to the obtained product after the heating reaction and centrifuging it; the washing and drying steps include, but are not limited to, ultrasonically dispersing the black precipitate after centrifugation with ethanol, adding acetone to wash it, and centrifuging it, repeating these steps several times, and drying to obtain the purified iridium-based nanowires.

[0074] Optionally, the method further comprises:

[0075] A5: After step A4, heat-treating the iridium-based nanowires.

[0076] Preferably, the heat treatment comprises the following steps:

[0077] A5.1 Under nitrogen and / or inert gas protection, heat from room temperature to 80-120°C at a rate of 5-10°C / min and maintain at this temperature for 0.5-1h;

[0078] A5.2 introduce an oxidizing atmosphere, further raise the temperature to 200-350°C at a heating rate of 2-5°C / min, and treat in the oxidizing atmosphere for 0.5-4h; optionally, the oxygen content in the oxidizing atmosphere in step (2) is 5vol%-20vol%.

[0079] Surprisingly, it was found that in step B2.1, water and other small molecules adsorbed on the surfaces of the active component and the carrier were removed; in step B2.2, the composition of the active component changed from a surface transition metal-rich structure to a surface iridium-rich structure, and the proportion of iridium atoms in a high-valence state on the surface increased.

[0080] Iridium-based catalysts

[0081] The third aspect of the present invention provides an iridium-based catalyst, comprising the iridium-based nanowires according to the first aspect, wherein the iridium-based nanowires are located on a nitrogen-doped carbon material as a carrier.

[0082] The iridium-based nanowires as active components include iridium and at least one transition metal selected from iron, cobalt, and nickel; and the carrier is a nitrogen-doped carbon material.

[0083] The carbon material is, for example, at least one of carbon black, graphene, carbon nanotubes, activated carbon, and graphite. Furthermore, the nitrogen-doped carbon material is selected from at least one of nitrogen-doped carbon black, nitrogen-doped graphene, nitrogen-doped carbon nanotubes, nitrogen-doped activated carbon, and nitrogen-doped graphite.

[0084] Furthermore, the molar content of nitrogen in the nitrogen-doped carbon material is 0.5% to 5%, preferably 0.5% to 3%, for example 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% and 5%.

[0085] Furthermore, in parts by weight, the catalyst comprises 10 to 95 parts by weight of iridium-based nanowires as an active component and 5 to 90 parts by weight of a nitrogen-doped carbon material carrier, preferably 20 to 90 parts by weight of the active component and 10 to 80 parts by weight of the nitrogen-doped carbon material carrier.

[0086] Furthermore, the electrochemical surface area of ​​the catalyst is 36 to 78 cm 2 , for example, it can be 40cm 2 , 45cm 2 , 50cm 2 , 55cm 2 、60cm 2 、65cm 2 , 70cm 2 , 75cm 2 The electrochemical surface area of ​​the catalyst is preferably 38 to 78 cm 2 .

[0087] Preparation method of iridium-based catalyst

[0088] A fourth aspect of the present invention provides a method for preparing the iridium-based catalyst, comprising the following steps:

[0089] B1. Providing an iridium-based nanowire according to the first aspect, or providing an iridium-based nanowire obtained by the method according to the second aspect;

[0090] B2. mixing the nitrogen-doped carbon material with the iridium-based nanowires;

[0091] B3. heat-treating the mixture obtained in step B2,

[0092] An iridium-based catalyst containing iridium-based nanowires as active components and nitrogen-doped carbon materials as carriers is obtained.

[0093] In the preparation method, the order of step B2 and step B3 can be reversed, that is, the heat treatment of the iridium-based nanowires can be performed first, and then the nitrogen-doped carbon material is mixed with the iridium-based nanowires.

[0094] Before heat treatment, the nanowires have a surface composition characterized by transition metal segregation. After heat treatment, the surface iridium atom content increases, while the transition metal atom content decreases, resulting in a surface composition characterized by iridium segregation, and an increased proportion of oxidized iridium atoms on the surface. This heat treatment is also referred to as temperature-programmed heat treatment.

[0095] Furthermore, the nitrogen-doped carbon material in step B2 is nitrogen-doped with a nitrogen source via solid-phase or liquid-phase reaction with a carbon support, preferably using a solid-phase doping method. The solid-phase doping method comprises thoroughly mixing the carbon material and nitrogen source powder, and heating under oxidizing conditions to obtain a nitrogen-doped carbon support powder. The mass ratio of the carbon support to the nitrogen source powder is 1:0.2-5.

[0096] Furthermore, the nitrogen source in the nitrogen doping can be selected from conventional nitrogen sources disclosed in the art, such as but not limited to at least one of urea, biuret, ammonium nitrate, ammonium bicarbonate, melamine, etc.

[0097] Furthermore, the carbon material in the nitrogen-doped carbon material is at least one of carbon black, graphene, carbon nanotubes, activated carbon, and graphite. Optionally, the carbon material may be pre-treated with oxidation. Compared to conventional carbon materials, nitrogen-doped carbon materials help strengthen the anchoring effect between the iridium-based nanowires and the support, thereby improving the stability of the catalyst.

[0098] Furthermore, the nitrogen doping atmosphere is an oxygen atmosphere having an oxygen content of 5 vol% to 20 vol%. In the oxidizing atmosphere, excluding oxygen, the remainder is nitrogen and / or at least one of an inert gas, wherein the inert gas is selected from at least one of argon and helium. The heating temperature is 150 to 350°C, preferably 200 to 350°C, and the heating time is 0.5 to 6 hours, preferably 0.5 to 4 hours.

[0099] Furthermore, in step B2, a dispersion containing the iridium-based nanowires prepared in step B1 is first prepared and then mixed with the nitrogen-doped carbon material. Optionally, after mixing, the mixture is ultrasonicated, centrifuged, and dried to obtain a solid powder.

[0100] Furthermore, the dispersion in step B2 is ethanol and / or isopropanol containing iridium-based nanowires, and the mass fraction of the iridium-based nanowires in the iridium-based nanowire dispersion is 0.2% to 2%.

[0101] Furthermore, in step B2, the mass ratio of the iridium-based nanowires as the active component to the nitrogen-doped carbon material as the support is 10-95:5-90, preferably 20-90:10-80.

[0102] Furthermore, the ultrasonication time in step B2 is 8 to 24 hours; the drying temperature is 60 to 120° C., and the drying time is 4 to 12 hours.

[0103] Furthermore, the heat treatment in step B3 includes the following steps:

[0104] B3.1. Under nitrogen and / or inert gas protection, raise the temperature from room temperature to 80-120°C at a rate of 5-10°C / min and maintain at this temperature for 0.5-1 h.

[0105] B3.2. Pass an oxidizing atmosphere and further increase the temperature to 200-350°C at a heating rate of 2-5°C / min. Treat in the oxidizing atmosphere for 0.5-4 hours.

[0106] In step B3.1, water and other molecules adsorbed on the surfaces of the active component and the support are removed; in step B3.2, the composition of the active component changes from a surface transition metal-rich structure to a surface iridium-rich structure, and the surface is in an oxidized state, that is, the proportion of iridium atoms with higher valence states increases.

[0107] Furthermore, the oxygen content in the oxidizing atmosphere in step B3.2 is 5 vol% to 20 vol%.

[0108] Furthermore, in the oxidizing atmosphere described in step B3.2, except for oxygen, the remaining is nitrogen and / or at least one of an inert gas, wherein the inert gas is selected from at least one of argon, helium, and neon.

[0109] Application in oxygen evolution reaction

[0110] The fifth aspect of the present invention is the use of the above-mentioned iridium-based nanowires or iridium-based catalysts in oxygen evolution reaction.

[0111] Furthermore, the iridium-based nanowires or iridium-based catalysts described above are preferably used in the oxygen evolution reaction under acidic conditions.

[0112] Furthermore, the oxygen evolution reaction under acidic conditions may be an anodic oxygen evolution reaction carried out by combining electrolysis of carbon dioxide with any cathode reaction under acidic conditions.

[0113] Furthermore, the acidic oxygen evolution reaction includes an oxygen evolution reaction occurring on the surface of the polymer electrolyte membrane and in the acidic solution.

[0114] Furthermore, the polymer electrolyte membrane includes at least one of a perfluorosulfonic acid proton membrane, a partially fluorinated polymer proton membrane, a non-fluorinated polymer proton membrane, and a composite membrane.

[0115] Furthermore, the acidic solution is selected from at least one of perchloric acid and sulfuric acid, and the concentration of the acidic solution is 0.01 to 2 mol / L.

[0116] Furthermore, the acidic solution is an acidic solution saturated with oxygen at a temperature of 20 to 80°C.

[0117] It should be noted that the iridium-based nanowires or iridium-based catalysts of the present invention are not limited to the above-mentioned oxygen evolution reaction, but can also be used in fields such as automobile exhaust purification, electrochemistry, petroleum refining, and environmental protection.

[0118] The content of the present invention includes the following aspects

[0119] 1. An iridium-based catalyst comprising an active component and a carrier;

[0120] The active component is a twin nanowire comprising iridium and at least one transition metal selected from iron, cobalt and nickel; the diameter d of the nanowire is 0.5 to 6 nm, and the size of the twin crystal grains constituting the nanowire is (0.8 to 1.1)·d nm.

[0121] 2. According to the iridium-based catalyst described in aspect 1, the carrier is a nitrogen-doped carbon material.

[0122] 3. According to the iridium-based catalyst described in aspect 2, the catalyst comprises 10 to 95 parts of active components and 5 to 90 parts of nitrogen-doped carbon material carriers, in parts by weight; optionally, the atomic ratio of iridium to transition metal in the active component is 1:(0.1 to 5).

[0123] 4. According to the iridium-based catalyst described in aspect 1, the nitrogen-doped carbon material is selected from at least one of nitrogen-doped carbon black, nitrogen-doped graphene, and nitrogen-doped carbon nanotubes; optionally, the molar content of nitrogen in the nitrogen-doped carbon material is 0.5% to 5%.

[0124] 5. The iridium-based catalyst according to aspect 1, wherein the electrochemical surface area of ​​the catalyst is 36 to 78 cm 2 .

[0125] 6. The method for preparing the iridium-based catalyst according to any one of aspects 1 to 5 comprises the following steps:

[0126] (1) mixing an iridium source and a transition metal source, a capping agent, a crystal plane coordination agent, and an organic alcohol in a certain order, and heating the mixture to react to obtain an iridium-based nanowire active component;

[0127] (2) The nitrogen-doped carbon material is mixed with the iridium-based nanowire active component, and then subjected to a programmed temperature-raising atmosphere heat treatment to obtain the iridium-based catalyst.

[0128] 7. The preparation method according to aspect 6, wherein the mixing in the certain order in step (1) is to dissolve the capping agent in an organic alcohol, add the iridium source and the crystal face coordination agent in sequence and fully dissolve them, and then add the transition metal source dissolved in the organic alcohol and stir until fully mixed;

[0129] The iridium source in step (1) is selected from at least one of iridium chloride, iridium acetylacetonate, iridium carbonyl, hexachloroiridic acid, sodium hexachloroiridate, and ammonium hexachloroiridate; optionally, the transition metal source in step (1) is selected from at least one of soluble chlorides, bromides, nitrates, sulfates, carbonates, acetates, and acetylacetonates corresponding to transition metals iron, cobalt, and nickel.

[0130] 8. According to the preparation method described in aspect 6, the crystal plane coordination reagent in step (1) is a mixture of an organic quaternary ammonium bromide salt and an inorganic iodide with a relative molecular weight of less than 360; optionally, the capping agent in step (1) is polyvinyl pyrrolidone with a weight-average molecular weight of 8,000 to 40,000; optionally, the organic alcohol in step (1) is preferably a polyol.

[0131] 9. According to the preparation method described in aspect 6, the molar ratio of the iridium source, transition metal source, and crystal plane coordination agent in step (1) is 1:(0.5-15):(5.1-32), preferably 1:(0.5-10):(5.1-32).

[0132] 10. According to the preparation method described in aspect 8, the molar ratio of the iridium source and the organic quaternary ammonium bromide salt to the inorganic iodide in the crystal face coordination reagent in step (1) is 1:(5-30):(0.1-1.2).

[0133] 11. According to the preparation method described in aspect 6, the iridium source in step (1) is based on iridium chloride hydrate and the mass ratio of the capping agent to the organic alcohol is 1:(8-12):(1500-1800).

[0134] 12. According to the preparation method described in aspect 6, the heating temperature in step (1) is 130-230°C; the heating time is 4-60 hours; and the pressure is 0.8-1.5 bar.

[0135] 13. According to the preparation method described in aspect 6, the carbon carrier in the nitrogen-doped carbon material in step (2) is at least one of carbon black, graphene, carbon nanotubes, and activated carbon; optionally; the mass ratio of the iridium-based nanowire active component to the nitrogen-doped carbon carrier in step (2) is 10-95:5-90.

[0136] 14. According to the preparation method of aspect 6, the temperature-programmed atmosphere heat treatment in step (2) comprises the following steps:

[0137] (1) Under nitrogen and / or inert gas protection, heat from room temperature to 80-120°C at a rate of 5-10°C / min, and maintain at this temperature for 0.5-1h;

[0138] (2) introducing an oxidizing atmosphere, further heating to 200-350° C., at a heating rate of 2-5° C. / min, and treating in the oxidizing atmosphere for 0.5-4 h; optionally, the oxygen content in the oxidizing atmosphere in step (2) is 5 vol% to 20 vol% oxygen.

[0139] 15. Use of the iridium-based catalyst described in any one of aspects 1 to 6 in an oxygen evolution reaction under acidic conditions.

[0140] Example

[0141] The following examples will further illustrate the technical solutions provided by the present invention, but the protection scope of the present invention is not limited to these examples.

[0142] In the following examples, the oxygen saturation temperature was 0.5 mol·L at 25°C. -1 In sulfuric acid solution, a three-electrode system was tested using an Ag / AgCl electrode as the reference electrode, a platinum electrode as the counter electrode, and a rotating disk electrode at 1600 rpm as the working electrode. The catalyst and perfluorosulfonic acid polymer Nafion solution were dispersed in water / ethanol / isopropanol and ultrasonically dispersed to obtain a catalyst slurry. The catalyst slurry was then dropped onto the surface of the rotating disk electrode and dried to obtain a thin film electrode. The oxygen evolution reaction current at a reaction overpotential of 0.25 V was used as a reference to compare the oxygen evolution reaction activity of the catalyst. The catalyst was tested at a reaction overpotential of 10 mA cm -2 The time of stable operation at a current density of 100 nm was used as the evaluation criterion for the stability of the catalyst.

[0143] The electrochemically active surface area of ​​the catalyst is obtained by the electrochemical (double layer) capacitance in the solution, where the electrochemical capacitance is determined by the non-Faradaic capacitance current during the double layer charging process of cyclic voltammetry scans at different scan rates. The electrochemically active surface area of ​​the catalyst is the ratio of the electrochemical capacitance to the characteristic capacitance of the electrolyte, at 0.5 mol·L -1 In H2SO4 solution, the characteristic capacitance of the electrolyte is 0.035mF·cm -2 The specific activity of the catalyst is based on the oxygen evolution reaction current per unit electrochemical active surface area and the reaction overpotential of 0.25V, and is calculated according to the following formula:

[0144] Where A represents the specific activity of the catalyst, I 0.25V It represents the oxygen evolution reaction current at a reaction overpotential of 0.25 V measured in the aforementioned three-electrode system, and ECSA represents the electrochemically active surface area per unit area.

[0145] The carbon dioxide electrolysis test was carried out using a membrane electrode (MEA) electrolysis cell with a double-layer membrane. The proton exchange membrane was from Chemours, USA. N117 membrane and anion exchange membrane are from Dioxide Materials of the United States X37-50 membrane, deionized water as electrolyte, temperature 80°C, current density 0.5A / cm 2 .

[0146] In the present invention, the diameter of the nanowire is measured by transmission electron microscopy (TEM) images, with a TEM acceleration voltage of 200 to 300 kV and a magnification of 200 to 1500 k×. Nano Measurer software is used to measure the length perpendicular to the axial direction of the nanowire in the TEM image. 200 measurement results at different positions are counted, and the average and standard deviation are calculated to obtain the diameter of the nanowire. The size of the twin crystals constituting the nanowire is calculated from the powder X-ray diffraction (XRD) results using the Scherrer formula. The incident light Cu K α The line wavelength is The slit width was 1 / 2° and the 2θ scanning rate was 4°·min -1 The elemental composition of the nanowire surface and the valence state of iridium were obtained by X-ray photoelectron spectroscopy (XPS) using monochromatic Al K α The X-ray source and element binding energy were calibrated using the C1s line at 284.6 eV.

[0147] Example 1

[0148] 2.5g of polyvinylpyrrolidone (PVP) with a weight-average molecular weight of 29,000 was dissolved in 350g of ethylene glycol, and then 1mmol of iridium chloride hydrate, 12mmol of tetraethylammonium bromide, and 0.5mmol of potassium iodide were added and stirred for 0.5h to obtain a clear solution A1. 2mmol of cobalt chloride hexahydrate (the molar ratio of iridium source to cobalt source was 1:2) was dissolved in 125g of ethylene glycol to obtain solution B1. Solution B1 was added to A1 and stirred until fully mixed. The solution was then added to an 800mL hydrothermal autoclave and reacted at 190°C and 1 bar for 48h. The resulting product was added with acetone and centrifuged to obtain a black precipitate. It was ultrasonically dispersed with ethanol, washed with acetone, and the above steps were repeated several times. The purified iridium-cobalt nanowires were dried. The ratio of iridium atoms to cobalt atoms was 1:0.6. The TEM image of the iridium-cobalt nanowires is shown in Figure 1. As can be seen from Figure 1, the size distribution of the nanowires is narrow, and obvious diffraction rings appear in the fast Fourier transform diffraction pattern, indicating that the nanowires have a twin structure. The nanowire diameter d is 3.5±0.3nm, and the twin grain size of the nanowire is 3.4nm. The high-resolution TEM image in Figure 2 shows that the nanowire mainly exposes the (111) and (200) faces. The XRD pattern of the iridium-cobalt nanowire is shown in Figure 3. The diffraction peak position of the iridium-cobalt nanowire in the figure is between that of metallic iridium and cobalt, and no other impurity peaks appear, indicating that the nanowire has an alloy structure.

[0149] The step of nitrogen-doping graphene is to fully grind and mix 1g of graphene oxide and 4g of urea, heat them at 250°C for 2h in an oxidizing atmosphere containing 10vol% oxygen and 90vol% helium, and cool them to obtain nitrogen-doped graphene powder.

[0150] 46 mg of iridium-cobalt nanowires were dispersed in 50 mL of ethanol, and 85 mg of nitrogen-doped graphene was added. The mixture was ultrasonically treated for 12 hours and centrifuged to obtain a black precipitate. The resulting solid powder was then dried in an 80°C oven for 8 hours to obtain a black solid powder. Under a helium atmosphere, the solid powder was heated from room temperature to 100°C at a rate of 5°C / min and maintained at this temperature for 1 hour. An oxidizing atmosphere containing 10 vol% oxygen and 90 vol% helium was then introduced, and the temperature was further increased to 250°C at a rate of 5°C / min. The mixture was treated in this oxidizing atmosphere for 2.5 hours to obtain the supported iridium-cobalt nanowire catalyst.

[0151] The surface composition of the iridium-cobalt nanowires was determined by XPS. The XPS spectrum of the iridium-cobalt nanowires before loading is shown in Figure 4. Before loading, the surface iridium atoms accounted for 57% of the total metal atoms, and the proportion of surface oxidized iridium was 36%. The XPS spectrum of the iridium-cobalt nanowires after loading is shown in Figure 5. After loading, the surface iridium atoms accounted for 63% of the total metal atoms (iridium and cobalt), and the proportion of surface oxidized iridium atoms was 49%.

[0152] At 25°C, oxygen saturation is 0.5 mol·L -1 In sulfuric acid solution, a three-electrode system using an Ag / AgCl electrode as a reference electrode, a platinum electrode as a counter electrode, and a rotating disk electrode at 1600 rpm as a working electrode has an electrochemically active surface area of ​​54.4 cm at a reaction overpotential of 0.25 V. 2 , catalyst specific activity 113.0μA / cm 2 , at 10 mA·cm -2 The system can run stably for 32 hours at a current density of 100 nm.

[0153] 8 mg of iridium cobalt nanowire catalyst was ultrasonically dispersed in a mixed solvent consisting of 2.6 mL of isopropanol, 1.2 mL of ethanol and 0.2 mL of water, and sprayed evenly on a 4 cm 2 Metal loading 2 mg / cm on the hydrophilic side of SGL 28BC carbon paper 2 , as the anode gas diffusion electrode (GDE) for carbon dioxide electrolysis. 4 mg of 80% silver catalyst (from Fuel Cell Store, USA) was ultrasonically dispersed in a mixed solvent consisting of 3.2 mL of isopropanol, 0.6 mL of ethanol, and 0.2 mL of water, and sprayed evenly on a 4 cm 2 Metal loading 1 mg / cm on the hydrophilic side of SGL 28BC carbon paper 2, as the cathode GDE for carbon dioxide electrolysis. The electrolysis voltage of the MEA electrolysis cell in constant current mode is 2.4V.

[0154] Example 2

[0155] 3.5g of polyvinyl pyrrolidone (PVP) with a weight average molecular weight of 25000 was dissolved in 350g of ethylene glycol, and then 1mmol of iridium acetylacetonate and 5mmol of tetramethylammonium bromide and 0.3mmol of sodium iodide were added and stirred for 0.5h to obtain a clear solution A2. 4mmol of ferrous sulfate heptahydrate (the molar ratio of iridium source to iron source was 1:4) was dissolved in 150g of ethylene glycol to obtain solution B2. Solution B2 was added to A2 and stirred until fully mixed and added to an 800mL hydrothermal kettle. The reaction was carried out at 180°C and 0.8bar for 36h. The resulting product was added with acetone and centrifuged to obtain a black precipitate. It was ultrasonically dispersed with ethanol, centrifuged and washed with acetone, and the above steps were repeated several times. The purified iridium iron nanowires were dried. The ratio of iridium atoms to iron atoms was 1:1.2. The TEM image of the iridium iron nanowires is similar to Figure 1. It can be seen that the size distribution of the nanowires is narrow, and obvious diffraction rings appear in the fast Fourier transform diffraction pattern, indicating that the nanowires have a twin structure. The diameter d of the nanowire is 3.7±0.3nm, and the size of the twin grains constituting the nanowire is 3.5nm.

[0156] The steps of nitrogen-doping graphene are as follows: 1g of graphene oxide and 3g of melamine are fully ground and mixed, heated at 350°C for 4h in an oxidizing atmosphere containing 20vol% oxygen and 80vol% helium, and cooled to obtain nitrogen-doped graphene powder.

[0157] 57 mg of iridium iron nanowires were dispersed in 50 mL of isopropanol, and 85 mg of nitrogen-doped graphene was added. The mixture was ultrasonically treated for 10 hours and centrifuged to obtain a black precipitate. The resulting solid powder was then dried in an oven at 70°C for 6 hours to obtain a black solid powder. Under an argon atmosphere, the solid powder was heated from room temperature to 80°C at a rate of 6°C / min and maintained at this temperature for 0.9 hours. An oxidizing atmosphere containing 15 vol% oxygen and 85 vol% nitrogen was then introduced, and the temperature was further increased to 220°C at a rate of 4°C / min. The oxidizing atmosphere was then maintained for 1.5 hours to obtain the iridium iron nanowire catalyst.

[0158] At 25°C, oxygen saturation is 0.5 mol·L -1 In sulfuric acid solution, a three-electrode system using an Ag / AgCl electrode as a reference electrode, a platinum electrode as a counter electrode, and a rotating disk electrode at 1600 rpm as a working electrode has an electrochemically active surface area of ​​51.4 cm at a reaction overpotential of 0.25 V. 2 , catalyst specific activity 125.4μA / cm 2 , at 10 mA·cm -2The system can be operated stably for 25 h at a current density of 100 nm.

[0159] Example 3

[0160] 3 g of polyvinylpyrrolidone (PVP) with a weight-average molecular weight of 55,000 was dissolved in 375 g of glycerol. 0.25 mmol of tetrairidium dodecacarbonyl, 8 mmol of tetraethylammonium bromide, and 0.1 mmol of ammonium iodide were added and stirred for 0.5 h to obtain a clear solution A3. 0.5 mmol of hydrated nickel bromide (the molar ratio of iridium source to nickel source was 1:0.5, based on the molar number of iridium) was dissolved in 150 g of glycerol to obtain solution B3. Solution B3 was added to solution A3 and stirred until thoroughly mixed. The solution was then added to an 800 mL hydrothermal autoclave and reacted at 170°C and 0.9 bar for 30 h. The resulting product was added to acetone and centrifuged to obtain a black precipitate. This was ultrasonically dispersed with ethanol, washed by centrifugation with acetone, and the above steps were repeated several times before drying to obtain purified iridium-nickel nanowires. The ratio of iridium atoms to nickel atoms was 1:0.2. The TEM image of the iridium-nickel nanowires is similar to Figure 1, showing a narrow size distribution of the nanowires and distinct diffraction rings in the fast Fourier transform diffraction pattern, indicating a twinned structure. The nanowire diameter, d, is 1.4 ± 0.2 nm, and the twinned grains comprising the nanowires are 1.2 nm in size.

[0161] The steps of nitrogen-doping carbon nanotubes are as follows: 1g of oxidized carbon nanotubes and 2g of ammonium bicarbonate are fully ground and mixed, heated at 320°C for 3h in an oxidizing atmosphere containing 20vol% oxygen and 80vol% helium, and cooled to obtain nitrogen-doped carbon nanotube powder.

[0162] 21 mg of iridium-nickel nanowires were dispersed in 50 mL of isopropanol, and 85 mg of nitrogen-doped carbon nanotubes were added. The mixture was ultrasonically treated for 20 hours and centrifuged to obtain a black precipitate. The resulting solid powder was then dried in a 120°C oven for 12 hours to obtain a black solid powder. The solid powder was then heated from room temperature to 110°C under a nitrogen atmosphere at a rate of 7°C / min and maintained at this temperature for 0.5 hours. An oxidizing atmosphere containing 20 vol% oxygen and 80 vol% argon was then introduced, and the temperature was further increased to 240°C at a rate of 3°C / min. The mixture was treated in this oxidizing atmosphere for 2 hours to obtain the iridium-nickel nanowire catalyst.

[0163] At 25°C, oxygen saturation is 0.5 mol·L -1 In sulfuric acid solution, a three-electrode system using an Ag / AgCl electrode as a reference electrode, a platinum electrode as a counter electrode, and a rotating disk electrode at 1600 rpm as a working electrode has an electrochemically active surface area of ​​67.1 cm at a reaction overpotential of 0.25 V. 2 , catalyst specific activity 97.1μA / cm 2 , at 10 mA·cm -2The system ran stably for 29 h at a current density of 1.5 GHz.

[0164] Example 4

[0165] 3g of polyvinylpyrrolidone (PVP) with a weight average molecular weight of 15000 was dissolved in 350g of glycerol, and then 1mmol of iridium acetylacetonate, 15mmol of tetrabutylammonium bromide, and 0.7mmol of potassium iodide were added and stirred for 0.5h to obtain a clear solution A4. 1mmol of basic nickel carbonate (the molar ratio of iridium source to nickel source was 1:1) was dissolved in 200g of glycerol to obtain solution B4. Solution B4 was added to A4 and stirred until fully mixed. The solution was then added to an 800mL hydrothermal reactor and reacted at 160°C and 1.1bar for 24h. The resulting product was added with acetone and centrifuged to obtain a black precipitate. It was ultrasonically dispersed with ethanol, washed with acetone, and the above steps were repeated several times. The purified iridium nickel nanowires were dried. The ratio of iridium atoms to nickel atoms was 1:0.3. The TEM image of the iridium nickel nanowires is similar to Figure 1. It can be seen that the size distribution of the nanowires is narrow and obvious diffraction rings appear in the fast Fourier transform diffraction pattern, indicating that the nanowires have a twin structure. The diameter d of the nanowire is 2.2±0.2nm, and the size of the twin grains constituting the nanowire is 2.2nm.

[0166] The steps of nitrogen-doping carbon black are as follows: 1g of carbon black and 1g of biuret are fully ground and mixed, heated at 300°C for 2h in an oxidizing atmosphere containing 15vol% oxygen and 85vol% helium, and cooled to obtain nitrogen-doped carbon black powder.

[0167] 26 mg of iridium nickel nanowires were dispersed in 50 mL of ethanol, and 85 mg of nitrogen-doped carbon black was added. The mixture was ultrasonically treated for 15 hours and centrifuged to obtain a black precipitate. The resulting solid powder was then dried in a 100°C oven for 10 hours to obtain a black solid powder. The solid powder was then heated from room temperature to 90°C under a helium atmosphere at a rate of 8°C / min and maintained at this temperature for 0.8 hours. An oxidizing atmosphere containing 10 vol% oxygen and 90 vol% argon was then introduced, and the temperature was further increased to 300°C at a rate of 2°C / min. The oxidizing atmosphere was then maintained for 4 hours to obtain the iridium nickel nanowire catalyst.

[0168] At 25°C, oxygen saturation is 0.5 mol·L -1 In sulfuric acid solution, a three-electrode system using an Ag / AgCl electrode as a reference electrode, a platinum electrode as a counter electrode, and a rotating disk electrode at 1600 rpm as a working electrode has an electrochemically active surface area of ​​60.5 cm at a reaction overpotential of 0.25 V. 2 , catalyst specific activity 102.9μA / cm 2 , at 10 mA·cm -2 The system ran stably for 37 h at a current density of 1.5 GHz.

[0169] Example 5

[0170] 3.8 g of polyvinylpyrrolidone (PVP) with a weight-average molecular weight of 20,000 was dissolved in 400 g of 1,2-propylene glycol. 1 mmol of hydrated iridium chloride, 20 mmol of tetramethylammonium bromide, and 0.9 mmol of sodium iodide were added and stirred for 0.5 h to obtain a clear solution A5. 10 mmol of ferric acetylacetonate (a molar ratio of iridium source to iron source of 1:10) was dissolved in 160 g of 1,2-propylene glycol to obtain solution B5. Solution B5 was added to A5 and stirred until thoroughly mixed. The solution was then added to an 800 mL hydrothermal autoclave and reacted at 170°C and 1 bar for 36 h. The resulting product was centrifuged in acetone to obtain a black precipitate, which was ultrasonically dispersed in ethanol, washed by centrifugation in acetone, and repeated several times before drying to obtain purified iridium-iron nanowires. The ratio of iridium atoms to iron atoms was 1:3. The TEM image of the iridium iron nanowires is similar to Figure 1, showing a narrow size distribution of the nanowires and distinct diffraction rings in the fast Fourier transform diffraction pattern, indicating a twinned structure. The nanowire diameter, d, is 4.6±0.5nm, and the twinned grain size of the nanowires is 4.9nm.

[0171] The steps of nitrogen-doping carbon black are as follows: 1 g of carbon black and 0.5 g of biuret are fully ground and mixed, heated at 200° C. for 0.5 h in an oxidizing atmosphere containing 5 vol% oxygen and 95 vol% helium, and cooled to obtain nitrogen-doped carbon black powder.

[0172] 340 mg of iridium iron nanowires were dispersed in 50 mL of ethanol, and 85 mg of nitrogen-doped carbon black was added. The mixture was ultrasonically treated for 18 hours and centrifuged to obtain a black precipitate. The resulting solid powder was then dried in an oven at 110°C for 10 hours to obtain a black solid powder. Under an argon atmosphere, the solid powder was heated from room temperature to 100°C at a rate of 9°C / min and maintained at this temperature for 0.7 hours. An oxidizing atmosphere containing 15 vol% oxygen and 85 vol% helium was then introduced, and the temperature was further increased to 270°C at a rate of 3°C / min. The oxidizing atmosphere was then maintained for 3 hours to obtain the iridium iron nanowire catalyst.

[0173] At 25°C, oxygen saturation is 0.5 mol·L -1 In sulfuric acid solution, a three-electrode system using an Ag / AgCl electrode as a reference electrode, a platinum electrode as a counter electrode, and a rotating disk electrode at 1600 rpm as a working electrode has an electrochemically active surface area of ​​42.7 cm at a reaction overpotential of 0.25 V. 2 , catalyst specific activity 109.6μA / cm 2 , at 10 mA·cm -2 The system ran stably for 41 h at a current density of 1.5 GHz.

[0174] Example 6

[0175] 2.75 g of polyvinylpyrrolidone (PVP) with a weight-average molecular weight of 25,000 was dissolved in 400 g of 1,2-propylene glycol. 1 mmol of iridium acetylacetonate, 30 mmol of tetrabutylammonium bromide, and 1.1 mmol of ammonium iodide were added and stirred for 0.5 h to obtain a clear solution A6. 3 mmol of dicobalt octacarbonyl (the molar ratio of iridium source to cobalt source was 1:6, based on the moles of cobalt) was dissolved in 170 g of 1,2-propylene glycol to obtain solution B6. Solution B6 was added to solution A6 and stirred until thoroughly mixed. The solution was then added to an 800 mL hydrothermal autoclave and reacted at 180°C and 1 bar for 30 h. The resulting product was centrifuged in acetone to obtain a black precipitate, which was ultrasonically dispersed in ethanol, washed by centrifugation in acetone, and repeated several times before drying to obtain purified iridium-cobalt nanowires. The ratio of iridium atoms to cobalt atoms was 1:2. The TEM image of the iridium-cobalt nanowires is similar to Figure 1, showing a narrow size distribution of the nanowires. The fast Fourier transform diffraction pattern shows distinct diffraction rings, indicating a twinned structure. The nanowire diameter, d, is 4.1 ± 0.4 nm, and the twinned grains comprising the nanowires are 4.5 nm in size.

[0176] The steps of nitrogen-doping carbon nanotubes are as follows: 1g of carbon black and 2.5g of urea are fully ground and mixed, heated at 270°C for 1h in an oxidizing atmosphere containing 15vol% oxygen and 85vol% helium, and cooled to obtain nitrogen-doped carbon nanotubes.

[0177] 128 mg of iridium-cobalt nanowires were dispersed in 50 mL of ethanol, and 85 mg of nitrogen-doped carbon nanotubes were added. The mixture was ultrasonically treated for 22 hours and centrifuged to obtain a black precipitate. The resulting solid powder was then dried in a 60°C oven for 4 hours to obtain a black solid powder. The solid powder was then heated from room temperature to 110°C under a nitrogen atmosphere at a rate of 8°C / min and maintained at this temperature for 0.6 hours. An oxidizing atmosphere containing 20 vol% oxygen and 80 vol% nitrogen was then introduced, and the temperature was further increased to 210°C at a rate of 5°C / min. The mixture was treated in this oxidizing atmosphere for 3.5 hours to obtain the iridium-cobalt nanowire catalyst.

[0178] At 25°C, oxygen saturation is 0.5 mol·L -1 In sulfuric acid solution, a three-electrode system using an Ag / AgCl electrode as a reference electrode, a platinum electrode as a counter electrode, and a rotating disk electrode at 1600 rpm as a working electrode has an electrochemically active surface area of ​​48.3 cm at a reaction overpotential of 0.25 V. 2 , catalyst specific activity 108.3μA / cm 2 , at 10 mA·cm -2 The device ran stably for 44 h at a current density of 1.5 GHz.

[0179] Example 7

[0180] 2.75 g of polyvinylpyrrolidone (PVP) with a weight-average molecular weight of 8000 was dissolved in 320 g of ethylene glycol. 0.25 mmol of tetrairidium dodecacarbonyl, 24 mmol of benzyltriethylammonium bromide, and 1.2 mmol of potassium iodide were added and stirred for 0.5 h to obtain a clear solution A7. 8 mmol of nickel chloride hexahydrate (the molar ratio of iridium source to nickel source was 1:8, based on the moles of iridium) was dissolved in 160 g of ethylene glycol to obtain solution B7. Solution B7 was added to A7 and stirred until thoroughly mixed. The solution was then added to an 800 mL hydrothermal autoclave and reacted at 160°C and 1.2 bar for 48 h. The resulting product was dried, added to acetone, and centrifuged to obtain a black precipitate. The precipitate was ultrasonically dispersed with ethanol, washed with acetone, and centrifuged several times to obtain purified iridium-nickel nanowires. The ratio of iridium atoms to nickel atoms was 1:2.5. The TEM image of the iridium-nickel nanowires is similar to Figure 1, showing a narrow size distribution of the nanowires and distinct diffraction rings in the fast Fourier transform diffraction pattern, indicating a twinned structure. The nanowire diameter, d, is 4.3 ± 0.5 nm, and the twinned grain size of the nanowires is 4.7 nm.

[0181] The steps of nitrogen-doping carbon nanotubes are as follows: 1g of oxidized carbon nanotubes and 0.2g of urea are fully ground and mixed, heated at 240°C for 1.5h in an oxidizing atmosphere containing 5vol% oxygen and 95vol% helium, and cooled to obtain nitrogen-doped carbon nanotubes.

[0182] 198 mg of iridium-nickel nanowires were dispersed in 50 mL of ethanol, and 85 mg of nitrogen-doped carbon nanotubes were added. The mixture was ultrasonically treated for 24 hours and centrifuged to obtain a black precipitate. The precipitate was then dried in a 90°C oven for 12 hours to obtain a black solid powder. The solid powder was then heated from room temperature to 90°C under argon at a rate of 7°C / min and maintained at this temperature for 0.6 hours. An oxidizing atmosphere containing 20 vol% oxygen and 80 vol% nitrogen was then introduced, and the temperature was further increased to 200°C at a rate of 4°C / min. The oxidizing atmosphere was then maintained for 1 hour to obtain the iridium-nickel nanowire catalyst.

[0183] At 25°C, oxygen saturation is 0.5 mol·L -1 In sulfuric acid solution, a three-electrode system using an Ag / AgCl electrode as a reference electrode, a platinum electrode as a counter electrode, and a rotating disk electrode at 1600 rpm as a working electrode has an electrochemically active surface area of ​​46.0 cm at a reaction overpotential of 0.25 V. 2 , catalyst specific activity 87.5μA / cm 2 , at 10 mA·cm -2 The device ran stably for 42 h at a current density of 1.5 GHz.

[0184] Example 8

[0185] 3.5g of polyvinylpyrrolidone (PVP) with a weight average molecular weight of 29000 was dissolved in 300g of glycerol, and then 1mmol of hydrated iridium chloride, 26mmol of benzyltriethylammonium bromide and 0.5mmol of sodium iodide were added and stirred for 0.5h to obtain a clear solution A8. 5mmol of cobalt acetate (the molar ratio of iridium source to cobalt source was 1:5) was dissolved in 200g of glycerol to obtain solution B8. Solution B8 was added to A8 and stirred until fully mixed and then added to an 800mL hydrothermal autoclave. The reaction was carried out at 190°C and 1.5bar for 24h. The resulting product was added with acetone and centrifuged to obtain a black precipitate. It was ultrasonically dispersed with ethanol, washed with acetone and centrifuged. The above steps were repeated several times and dried to obtain purified iridium cobalt nanowires. The ratio of iridium atoms to cobalt atoms was 1:1.5. The TEM image of the iridium cobalt nanowires is similar to Figure 1. It can be seen that the size distribution of the nanowires is narrow and obvious diffraction rings appear in the fast Fourier transform diffraction pattern, indicating that the nanowires have a twin structure. The diameter d of the nanowire is 3.9±0.4nm, and the size of the twin grains constituting the nanowire is 3.7nm.

[0186] The steps of nitrogen-doping graphene are as follows: 1g of graphene oxide and 5g of melamine are fully ground and mixed, heated at 220°C for 3h in an oxidizing atmosphere containing 5vol% oxygen and 95vol% helium, and cooled to obtain nitrogen-doped graphene.

[0187] 85 mg of iridium-cobalt nanowires were dispersed in 50 mL of ethanol, and 85 mg of nitrogen-doped graphene was added. The mixture was ultrasonically treated for 8 hours and centrifuged to obtain a black precipitate. The resulting solid powder was then dried in an 80°C oven for 8 hours to obtain a black solid powder. Under a nitrogen atmosphere, the solid powder was heated from room temperature to 120°C at a rate of 10°C / min and held at this temperature for 0.8 hours. An oxidizing atmosphere containing 10 vol% oxygen and 90 vol% helium was then introduced, and the temperature was further increased to 280°C at a rate of 5°C / min. The oxidizing atmosphere was then maintained for 3 hours to obtain the iridium-cobalt nanowire catalyst.

[0188] At 25°C, oxygen saturation is 0.5 mol·L -1 In sulfuric acid solution, a three-electrode system using an Ag / AgCl electrode as a reference electrode, a platinum electrode as a counter electrode, and a rotating disk electrode at 1600 rpm as a working electrode has an electrochemically active surface area of ​​49.8 cm at a reaction overpotential of 0.25 V. 2 , catalyst specific activity 116.5μA / cm 2 , at 10 mA·cm -2 The device ran stably for 42 h at a current density of 1.5 GHz.

[0189] Example 9

[0190] 2.5g of polyvinylpyrrolidone (PVP) with a weight average molecular weight of 29000 was dissolved in 350g of ethylene glycol, and then 1mmol of iridium chloride hydrate, 12mmol of tetraethylammonium bromide and 0.5mmol of potassium iodide were added and stirred for 0.5h to obtain a clear solution A1. 0.3mmol of cobalt chloride hexahydrate (the molar ratio of iridium source to cobalt source was 1:0.3) was dissolved in 125g of ethylene glycol to obtain solution B9. Solution B9 was added to A1 and stirred until fully mixed and then added to an 800mL hydrothermal autoclave. The reaction was carried out at 190°C and 1 bar for 48h. The resulting product was added with acetone and centrifuged to obtain a black precipitate. It was ultrasonically dispersed with ethanol, washed with acetone and centrifuged. The above steps were repeated several times and dried to obtain purified iridium cobalt nanowires. The ratio of iridium atoms to cobalt atoms was 1:0.1. The TEM image of the iridium cobalt nanowires is similar to Figure 1. It can be seen that the size distribution of the nanowires is narrow and obvious diffraction rings appear in the fast Fourier transform diffraction pattern, indicating that the nanowires have a twin structure. The diameter d of the nanowire is 0.5±0.1nm, and the size of the twin grains constituting the nanowire is 0.4nm.

[0191] The step of nitrogen-doping graphene is to fully grind and mix 1g of graphene oxide and 4g of urea, heat them at 250°C for 2h in an oxidizing atmosphere containing 10vol% oxygen and 90vol% helium, and cool them to obtain nitrogen-doped graphene powder.

[0192] 9.5 mg of iridium-cobalt nanowires were dispersed in 50 mL of ethanol, and 85 mg of nitrogen-doped graphene was added. The mixture was ultrasonically treated for 12 hours and centrifuged to obtain a black precipitate. The resulting solid powder was then dried in an 80°C oven for 8 hours to obtain a black solid powder. The solid powder was then heated from room temperature to 100°C at a rate of 5°C / min under a helium atmosphere and maintained at this temperature for 1 hour. An oxidizing atmosphere containing 10 vol% oxygen and 90 vol% helium was then introduced, and the temperature was further increased to 250°C at a rate of 5°C / min. The oxidizing atmosphere was then maintained for 2.5 hours to obtain the iridium-cobalt nanowire catalyst.

[0193] At 25°C, oxygen saturation is 0.5 mol·L -1 In sulfuric acid solution, a three-electrode system using an Ag / AgCl electrode as a reference electrode, a platinum electrode as a counter electrode, and a rotating disk electrode at 1600 rpm as a working electrode has an electrochemically active surface area of ​​77.9 cm at a reaction overpotential of 0.25 V. 2 , catalyst specific activity 71.7μA / cm 2 , at 10 mA·cm -2 The system can run stably for 35h at a current density of 1000 nm.

[0194] Example 10

[0195] 2.5g of polyvinylpyrrolidone (PVP) with a weight average molecular weight of 29000 was dissolved in 350g of ethylene glycol, and then 1mmol of iridium chloride hydrate, 12mmol of tetraethylammonium bromide, and 0.5mmol of potassium iodide were added and stirred for 0.5h to obtain a clear solution A1. 15mmol of cobalt chloride hexahydrate (the molar ratio of iridium source to cobalt source was 1:15) was dissolved in 125g of ethylene glycol to obtain solution B10. Solution B10 was added to A1 and stirred until fully mixed. The solution was then added to an 800mL hydrothermal autoclave and reacted at 190°C and 1 bar for 48h. The resulting product was added with acetone and centrifuged to obtain a black precipitate. It was ultrasonically dispersed with ethanol, washed with acetone, and the above steps were repeated several times. The purified iridium cobalt nanowires were dried. The ratio of iridium atoms to cobalt atoms was 1:5. The TEM image of the iridium cobalt nanowires is similar to Figure 1. It can be seen that the size distribution of the nanowires is narrow and obvious diffraction rings appear in the fast Fourier transform diffraction pattern, indicating that the nanowires have a twin structure. The diameter d of the nanowire is 5.0±0.7nm, and the size of the twin grains constituting the nanowire is 4.4nm.

[0196] The step of nitrogen-doping graphene is to fully grind and mix 1g of graphene oxide and 4g of urea, heat them at 250°C for 2h in an oxidizing atmosphere containing 10vol% oxygen and 90vol% helium, and cool them to obtain nitrogen-doped graphene powder.

[0197] 1.6g of iridium-cobalt nanowires were dispersed in 50mL of ethanol, and 85mg of nitrogen-doped graphene was added. The mixture was ultrasonically treated for 12h and centrifuged to obtain a black precipitate. The precipitate was then dried in an 80°C oven for 8h to obtain a black solid powder. The solid powder was then heated from room temperature to 100°C under a helium atmosphere at a rate of 5°C / min and held at this temperature for 1h. An oxidizing atmosphere containing 10vol% oxygen and 90vol% helium was then introduced, and the temperature was further increased to 250°C at a rate of 5°C / min. The oxidizing atmosphere was then maintained for 2.5h to obtain the iridium-cobalt nanowire catalyst.

[0198] At 25°C, oxygen saturation is 0.5 mol·L -1 In sulfuric acid solution, a three-electrode system using an Ag / AgCl electrode as a reference electrode, a platinum electrode as a counter electrode, and a rotating disk electrode at 1600 rpm as a working electrode has an electrochemically active surface area of ​​36.2 cm at a reaction overpotential of 0.25 V. 2 , catalyst specific activity 57.2μA / cm 2 , at 10 mA·cm -2 The system ran stably for 27 h at a current density of 1.5 GHz.

[0199] Example 11

[0200] 2.5 g of polyvinylpyrrolidone (PVP) with a weight-average molecular weight of 29,000 was dissolved in 350 g of ethylene glycol. 1 mmol of iridium chloride hydrate, 12 mmol of tetraethylammonium bromide, and 0.5 mmol of potassium iodide were added and stirred for 0.5 h to obtain a clear solution A1. 2 mmol of cobalt chloride hexahydrate (the molar ratio of iridium source to nickel source was 1:2) was dissolved in 125 g of ethylene glycol to obtain solution B1. Solution B1 was added to solution A1 and stirred until thoroughly mixed. The solution was then added to an 800 mL hydrothermal autoclave and reacted at 190°C and 1 bar for 48 h. The resulting product was added to acetone and centrifuged to obtain a black precipitate. This was ultrasonically dispersed in ethanol, washed by centrifugation in acetone, and the above steps were repeated several times before drying to obtain purified iridium-cobalt nanowires. The ratio of iridium atoms to cobalt atoms was 1:0.6. The nanowire diameter d was 3.5±0.3 nm, and the twin crystals comprising the nanowires had a grain size of 3.4 nm.

[0201] Under a helium atmosphere, the iridium-based nanowires were heated from room temperature to 100°C at a rate of 5°C / min and held at this temperature for 1 hour. An oxidizing atmosphere containing 10 vol% oxygen and 90 vol% helium was then introduced, and the temperature was further raised to 250°C at a rate of 5°C / min. The oxidizing atmosphere was maintained for 2.5 hours, yielding temperature-programmed iridium-cobalt nanowires.

[0202] The surface composition of iridium cobalt nanowires was determined by XPS. Before the programmed temperature heat treatment, the surface iridium atoms accounted for 57% of the total metal atoms, and the proportion of iridium in the surface oxidized state was 36%. After the programmed temperature heat treatment, the surface iridium atoms accounted for 64% of the total metal atoms before loading, and the proportion of iridium in the surface oxidized state was 53%. After loading, the surface iridium atoms accounted for 64% of the total metal atoms, and the proportion of iridium in the surface oxidized state was 53%.

[0203] At 25°C, oxygen saturation is 0.5 mol·L -1 In sulfuric acid solution, a three-electrode system using an Ag / AgCl electrode as a reference electrode, a platinum electrode as a counter electrode, and a rotating disk electrode at 1600 rpm as a working electrode was used. At a reaction overpotential of 0.25 V, the electrochemically active surface area of ​​the catalyst without temperature-programmed atmosphere heat treatment was 40.8 cm 2 , catalyst specific activity 65.5μA / cm 2 , at 10 mA·cm -2 The electrochemically active surface area of ​​the catalyst after the programmed temperature atmosphere heat treatment was 53.2 cm 2 , catalyst specific activity 117.5μA / cm 2 , at 10 mA·cm -2 The system can be operated stably for 30 h at a current density of 100 nm.

[0204] Example 12

[0205] 2.5g of polyvinyl pyrrolidone (PVP) with a weight average molecular weight of 29000 was dissolved in 350g of ethylene glycol, and then 1mmol of iridium chloride hydrate and 0.5mmol of potassium iodide were added and stirred for 0.5h to obtain a clear solution C1. 2mmol of cobalt chloride hexahydrate (the molar ratio of iridium source to cobalt source was 1:2) was dissolved in 125g of ethylene glycol to obtain solution B1. Solution B1 was added to C1 and stirred until fully mixed and then added to an 800mL hydrothermal autoclave. The reaction was carried out at 190°C and 1 bar for 48h. The resulting product was added with acetone and centrifuged to obtain a black precipitate. It was ultrasonically dispersed with ethanol, centrifuged and washed with acetone, and the above steps were repeated several times. The purified iridium cobalt nanowires were dried. The ratio of iridium atoms to cobalt atoms was 1:0.6. The TEM image of the iridium cobalt nanowires is similar to Figure 1. It can be seen that the size distribution of the nanowires is narrow and obvious diffraction rings appear in the fast Fourier transform diffraction pattern, indicating that the nanowires have a twin structure. The diameter d of the nanowire is 4.9±0.6nm, and the size of the twin grains constituting the nanowire is 4.1nm.

[0206] The step of nitrogen-doping graphene is to fully grind and mix 1g of graphene oxide and 4g of urea, heat them at 250°C for 2h in an oxidizing atmosphere containing 10vol% oxygen and 90vol% helium, and cool them to obtain nitrogen-doped graphene powder.

[0207] 46 mg of iridium-cobalt nanowires were dispersed in 50 mL of ethanol, and 85 mg of nitrogen-doped graphene was added. The mixture was ultrasonically treated for 12 hours and centrifuged to obtain a black precipitate. The resulting solid powder was then dried in an 80°C oven for 8 hours to obtain a black solid powder. Under a helium atmosphere, the solid powder was heated from room temperature to 100°C at a rate of 5°C / min and maintained at this temperature for 1 hour. An oxidizing atmosphere containing 10 vol% oxygen and 90 vol% helium was then introduced, and the temperature was further increased to 250°C at a rate of 5°C / min. The oxidizing atmosphere was then maintained for 2.5 hours to obtain the iridium-cobalt nanowire catalyst.

[0208] At 25°C, oxygen saturation is 0.5 mol·L -1 In sulfuric acid solution, a three-electrode system using an Ag / AgCl electrode as a reference electrode, a platinum electrode as a counter electrode, and a rotating disk electrode at 1600 rpm as a working electrode has an electrochemically active surface area of ​​37.7 cm at a reaction overpotential of 0.25 V. 2 , the catalyst specific activity is 74.9μA / cm 2 , at 10 mA·cm -2 The system ran stably for 16 h at a current density of 1.5 GHz.

[0209] Example 13

[0210] 2.5g of polyvinylpyrrolidone (PVP) with a weight average molecular weight of 29000 was dissolved in 350g of ethylene glycol, and then 1mmol of iridium chloride hydrate, 12mmol of tetraethylammonium bromide and 0.5mmol of potassium iodide were added and stirred for 0.5h to obtain a clear solution A1. 2mmol of cobalt chloride hexahydrate (the molar ratio of iridium source to cobalt source was 1:2) was dissolved in 125g of ethylene glycol to obtain solution B1. Solution B1 was added to A1 and stirred until fully mixed. The solution was then added to an 800mL hydrothermal reactor and reacted at 190°C and 1 bar for 48h. The resulting product was added with acetone and centrifuged to obtain a black precipitate. It was ultrasonically dispersed with ethanol, washed with acetone, and the above steps were repeated several times. The purified iridium cobalt nanowires were dried. The ratio of iridium atoms to cobalt atoms was 1:0.6. The TEM image of the iridium cobalt nanowires is similar to Figure 1. It can be seen that the size distribution of the nanowires is narrow and obvious diffraction rings appear in the fast Fourier transform diffraction pattern, indicating that the nanowires have a twin structure. The diameter d of the nanowire is 3.5±0.3 nm, and the size of the twin grains constituting the nanowire is 3.4 nm.

[0211] 46 mg of iridium-cobalt nanowires were dispersed in 50 mL of ethanol, and 85 mg of graphene was added. The mixture was ultrasonically treated for 12 hours and centrifuged to obtain a black precipitate. The resulting solid powder was then dried in an 80°C oven for 8 hours to obtain a black solid powder. The solid powder was then heated from room temperature to 100°C under a helium atmosphere at a rate of 5°C / min and maintained at this temperature for 1 hour. An oxidizing atmosphere containing 10 vol% oxygen and 90 vol% helium was then introduced, and the temperature was further increased to 250°C at a rate of 5°C / min. The oxidizing atmosphere was then maintained for 2.5 hours to obtain the iridium-cobalt nanowire catalyst.

[0212] At 25°C, oxygen saturation is 0.5 mol·L -1 In sulfuric acid solution, a three-electrode system using an Ag / AgCl electrode as a reference electrode, a platinum electrode as a counter electrode, and a rotating disk electrode at 1600 rpm as a working electrode has an electrochemically active surface area of ​​53.6 cm at a reaction overpotential of 0.25 V. 2 , catalyst specific activity 48.4μA / cm 2 , at 10 mA·cm -2 The system ran stably for 18 h at a current density of 1.5 GHz.

[0213] Example 14

[0214] 2.5 g of polyvinylpyrrolidone (PVP) with a weight-average molecular weight of 29,000, 1 mmol of hydrated iridium chloride, 2 mmol of cobalt chloride hexahydrate (the molar ratio of iridium source to cobalt source was 1:2), 12 mmol of tetraethylammonium bromide, and 0.5 mmol of potassium iodide were added to 475 g of ethylene glycol and stirred for 0.5 h to obtain a clear solution. This solution was then added to an 800 mL hydrothermal autoclave and reacted at 190°C and 1 bar for 48 h. The resulting product was then added to acetone and centrifuged to obtain a black precipitate. This was ultrasonically dispersed in ethanol, washed by centrifugation in acetone, and the above steps were repeated several times before drying to obtain purified iridium-cobalt nanowires. The ratio of iridium atoms to cobalt atoms was 1:0.6. The nanowire diameter d was 3.6±0.3 nm, and the twin crystals comprising the nanowires had a grain size of 3.3 nm.

[0215] The step of nitrogen-doping graphene is to fully grind and mix 1g of graphene oxide and 4g of urea, heat them at 250°C for 2h in an oxidizing atmosphere containing 10vol% oxygen and 90vol% helium, and cool them to obtain nitrogen-doped graphene powder.

[0216] 46 mg of iridium-cobalt nanowires were dispersed in 50 mL of ethanol, and 85 mg of nitrogen-doped graphene was added. The mixture was ultrasonically treated for 12 hours and centrifuged to obtain a black precipitate. The resulting solid powder was then dried in an 80°C oven for 8 hours to obtain a black solid powder. Under a helium atmosphere, the solid powder was heated from room temperature to 100°C at a rate of 5°C / min and maintained at this temperature for 1 hour. An oxidizing atmosphere containing 10 vol% oxygen and 90 vol% helium was then introduced, and the temperature was further increased to 250°C at a rate of 5°C / min. The oxidizing atmosphere was then maintained for 2.5 hours to obtain the iridium-cobalt nanowire catalyst.

[0217] At 25°C, oxygen saturation is 0.5 mol·L -1 In sulfuric acid solution, a three-electrode system using an Ag / AgCl electrode as a reference electrode, a platinum electrode as a counter electrode, and a rotating disk electrode at 1600 rpm as a working electrode has an electrochemically active surface area of ​​46.8 cm at a reaction overpotential of 0.25 V. 2 , catalyst specific activity 52.1μA / cm 2 , at 10 mA·cm -2 The system can be operated stably for 20 h at a current density of 100 nm.

[0218] Example 15

[0219] 2.5 g of polyvinylpyrrolidone (PVP) with a weight-average molecular weight of 29,000 was dissolved in 350 g of ethylene glycol. 1 mmol of iridium chloride hydrate was added and stirred for 0.5 h to obtain a clear solution C5. 2 mmol of cobalt chloride hexahydrate (the molar ratio of iridium source to cobalt source was 1:2), 12 mmol of tetraethylammonium bromide, and 0.5 mmol of potassium iodide were dissolved in 125 g of ethylene glycol to obtain solution D1. Solution D1 was added to C5 and stirred until thoroughly mixed. The solution was then added to an 800 mL hydrothermal autoclave and reacted at 190°C and 1 bar for 48 h. The resulting product was added to acetone and centrifuged to obtain a black precipitate. This was ultrasonically dispersed in ethanol, washed by centrifugation in acetone, and the above steps were repeated several times before drying to obtain purified iridium-cobalt nanowires. The ratio of iridium atoms to cobalt atoms was 1:0.2. The nanowire diameter d was 0.8±0.2 nm, and the twin crystals comprising the nanowires had a grain size of 0.8 nm.

[0220] The step of nitrogen-doping graphene is to fully grind and mix 1g of graphene oxide and 4g of urea, heat them at 250°C for 2h in an oxidizing atmosphere containing 10vol% oxygen and 90vol% helium, and cool them to obtain nitrogen-doped graphene powder.

[0221] 46 mg of iridium-cobalt nanowires were dispersed in 50 mL of ethanol, and 85 mg of nitrogen-doped graphene was added. The mixture was ultrasonically treated for 12 hours and centrifuged to obtain a black precipitate. The resulting solid powder was then dried in an 80°C oven for 8 hours to obtain a black solid powder. Under a helium atmosphere, the solid powder was heated from room temperature to 100°C at a rate of 5°C / min and maintained at this temperature for 1 hour. An oxidizing atmosphere containing 10 vol% oxygen and 90 vol% helium was then introduced, and the temperature was further increased to 250°C at a rate of 5°C / min. The oxidizing atmosphere was then maintained for 2.5 hours to obtain the iridium-cobalt nanowire catalyst.

[0222] At 25°C, oxygen saturation is 0.5 mol·L -1 In sulfuric acid solution, a three-electrode system using an Ag / AgCl electrode as a reference electrode, a platinum electrode as a counter electrode, and a rotating disk electrode at 1600 rpm as a working electrode has an electrochemically active surface area of ​​63.2 cm at a reaction overpotential of 0.25 V. 2 , catalyst specific activity 40.9μA / cm 2 , at 10 mA·cm -2 The system ran stably for 18 h at a current density of 1.5 GHz.

[0223] Example 16

[0224] 2.5 g of polyvinylpyrrolidone (PVP) with a weight-average molecular weight of 29,000 was dissolved in 350 g of ethylene glycol. 1 mmol of iridium chloride hydrate, 12 mmol of tetraethylammonium bromide, and 0.5 mmol of potassium iodide were added and stirred for 0.5 h to obtain a clear solution A1. 2 mmol of cobalt chloride hexahydrate (iridium source: cobalt source molar ratio of 1:2) was dissolved in 125 g of ethylene glycol to obtain solution B1. Solution B1 was added to solution A1 and stirred until thoroughly mixed. The solution was then added to an 800 mL hydrothermal autoclave and reacted at 190°C and 1 bar for 48 h. The resulting product was centrifuged in acetone to obtain a black precipitate, which was ultrasonically dispersed in ethanol. The product was then washed by centrifugation in acetone. This process was repeated several times and dried to obtain purified iridium-cobalt nanowires. The nanowire diameter d was 3.5 ± 0.3 nm, and the twin crystals comprising the nanowires had a grain size of 3.4 nm.

[0225] The step of nitrogen-doping graphene is to fully grind and mix 1g of graphene oxide and 4g of urea, heat them at 250°C for 2h in an oxidizing atmosphere containing 10vol% oxygen and 90vol% helium, and cool them to obtain nitrogen-doped graphene powder.

[0226] 46 mg of iridium cobalt nanowires were dispersed in 50 mL of ethanol, 85 mg of nitrogen-doped graphene was added, and the mixture was ultrasonically treated for 12 h. The mixture was centrifuged to obtain a black precipitate, which was then dried in an oven at 80°C for 8 h to obtain a black solid powder. The solid powder was heated from room temperature to 250°C in an oxidizing atmosphere containing 10 vol% oxygen and 90 vol% helium at a heating rate of 5°C / min and treated in an oxidizing atmosphere for 2.5 h to obtain an iridium cobalt nanowire catalyst.

[0227] At 25°C, oxygen saturation is 0.5 mol·L -1 In sulfuric acid solution, a three-electrode system using an Ag / AgCl electrode as a reference electrode, a platinum electrode as a counter electrode, and a rotating disk electrode at 1600 rpm as a working electrode has an electrochemically active surface area of ​​57.5 cm at a reaction overpotential of 0.25 V. 2 , catalyst specific activity 37μA / cm 2 , at 10 mA·cm -2 The system ran stably for 17 h at a current density of 1.5 GHz.

[0228] Comparative Example 1

[0229] A commercial iridium carbon catalyst with a loading of 40% was saturated with 0.5 mol·L oxygen at 25°C. -1 In sulfuric acid solution, using a three-electrode system at a reaction overpotential of 0.25 V, the electrochemically active surface area of ​​the catalyst was 28.6 cm 2 , catalyst specific activity 36.6μA / cm 2 , at 10 mA·cm -2The system ran stably for 13 h at a current density of 1.5 GHz.

[0230] 8 mg of commercial iridium carbon catalyst was ultrasonically dispersed in a mixed solvent consisting of 2.6 mL of isopropanol, 1.2 mL of ethanol and 0.2 mL of water, and sprayed evenly on a 4 cm 2 Metal loading 2 mg / cm on the hydrophilic side of SGL 28BC carbon paper 2 , as the anode gas diffusion electrode (GDE) for carbon dioxide electrolysis, and the cathode GDE for carbon dioxide electrolysis are the same as those in Example 1. The electrolysis voltage of the MEA electrolysis cell in constant current mode is 3.3V.

[0231] Comparative Example 2

[0232] 2.5 g of polyvinylpyrrolidone (PVP) with a weight-average molecular weight of 29,000 was dissolved in 350 g of ethylene glycol. 1 mmol of iridium chloride hydrate and 12 mmol of tetraethylammonium bromide were added and stirred for 0.5 h to obtain a clear solution C2. 2 mmol of cobalt chloride hexahydrate (the molar ratio of iridium source to cobalt source was 1:2) was dissolved in 125 g of ethylene glycol to obtain solution B1. Solution B1 was added to C2 and stirred until thoroughly mixed. The solution was then added to an 800 mL hydrothermal autoclave and reacted at 190°C and 1 bar for 48 h. The resulting product was added to acetone and centrifuged to obtain a black precipitate. This was ultrasonically dispersed in ethanol, washed by centrifugation in acetone, and the above steps were repeated several times before drying to obtain purified iridium-cobalt nanocrystals. The ratio of iridium atoms to cobalt atoms was 1:0.6. TEM images of the iridium-cobalt nanocrystals are shown in Figure 6, showing no twin formation. The nanocrystal diameter d was 3.5±0.2 nm.

[0233] The step of nitrogen-doping graphene is to fully grind and mix 1g of graphene oxide and 4g of urea, heat them at 250°C for 2h in an oxidizing atmosphere containing 10vol% oxygen and 90vol% helium, and cool them to obtain nitrogen-doped graphene powder.

[0234] 46 mg of iridium-cobalt nanocrystals were dispersed in 50 mL of ethanol, and 85 mg of nitrogen-doped graphene was added. The mixture was ultrasonically treated for 12 hours and centrifuged to obtain a black precipitate. The precipitate was then dried in an 80°C oven for 8 hours to obtain a black solid powder. The solid powder was then heated from room temperature to 100°C at a rate of 5°C / min under a helium atmosphere and maintained at this temperature for 1 hour. An oxidizing atmosphere containing 10 vol% oxygen and 90 vol% helium was then introduced, and the temperature was further increased to 250°C at a rate of 5°C / min. The mixture was treated in the oxidizing atmosphere for 2.5 hours to obtain the iridium-cobalt nanocrystal catalyst.

[0235] At 25°C, oxygen saturation is 0.5 mol·L -1In sulfuric acid solution, a three-electrode system using an Ag / AgCl electrode as a reference electrode, a platinum electrode as a counter electrode, and a rotating disk electrode at 1600 rpm as a working electrode has an electrochemically active surface area of ​​53.5 cm at a reaction overpotential of 0.25 V. 2 , catalyst specific activity 47.8μA / cm 2 , at 10 mA·cm -2 The system ran stably for 27 h at a current density of 1.5 GHz.

[0236] Comparative Example 3

[0237] 1 mmol of iridium chloride hydrate, 12 mmol of tetraethylammonium bromide, and 0.5 mmol of potassium iodide were added to 475 g of ethylene glycol and stirred for 0.5 h to obtain a clear solution C3. 2 mmol of cobalt chloride hexahydrate (iridium source: cobalt source molar ratio of 1:2) was dissolved in 125 g of ethylene glycol to obtain solution B1. Solution B1 was added to C3 and stirred until thoroughly mixed. The mixture was then added to an 800 mL hydrothermal autoclave and reacted at 190°C and 1 bar for 48 h. The resulting product was added to acetone and centrifuged to obtain a black precipitate. This was ultrasonically dispersed in ethanol, washed by centrifugation in acetone, and the above steps were repeated several times before drying to obtain purified iridium-cobalt nanocrystals. The ratio of iridium atoms to cobalt atoms was 1:0.3. The diameter d of the iridium-cobalt nanocrystals was 243±57 nm.

[0238] The step of nitrogen-doping graphene is to fully grind and mix 1g of graphene oxide and 4g of urea, heat them at 250°C for 2h in an oxidizing atmosphere containing 10vol% oxygen and 90vol% helium, and cool them to obtain nitrogen-doped graphene powder.

[0239] 46 mg of iridium-cobalt nanocrystals were dispersed in 50 mL of ethanol, and 85 mg of nitrogen-doped graphene was added. The mixture was ultrasonically treated for 12 hours and centrifuged to obtain a black precipitate. The precipitate was then dried in an 80°C oven for 8 hours to obtain a black solid powder. The solid powder was then heated from room temperature to 100°C at a rate of 5°C / min under a helium atmosphere and maintained at this temperature for 1 hour. An oxidizing atmosphere containing 10 vol% oxygen and 90 vol% helium was then introduced, and the temperature was further increased to 250°C at a rate of 5°C / min. The mixture was treated in the oxidizing atmosphere for 2.5 hours to obtain the iridium-cobalt nanocrystal catalyst.

[0240] At 25°C, oxygen saturation is 0.5 mol·L -1 In sulfuric acid solution, a three-electrode system using an Ag / AgCl electrode as a reference electrode, a platinum electrode as a counter electrode, and a rotating disk electrode at 1600 rpm as a working electrode has an electrochemically active surface area of ​​5.9 cm at a reaction overpotential of 0.25 V. 2 , catalyst specific activity 12.5μA / cm 2 , at 10 mA·cm-2 The system ran stably for 12 h at a current density of 1.

[0241] Comparative Example 4

[0242] 2.5g of polyvinylpyrrolidone (PVP) with a weight-average molecular weight of 29,000 was dissolved in 475g of ethylene glycol. 1mmol of hydrated iridium chloride, 12mmol of tetraethylammonium bromide, and 0.5mmol of potassium iodide were added. The mixture was stirred for 0.5h to obtain a clear solution C4, which was then added to an 800mL hydrothermal reactor and reacted at 190°C and 1 bar for 48h. The resulting product was added to acetone and centrifuged to obtain a black precipitate. This was ultrasonically dispersed in ethanol, washed by centrifugation in acetone, and the above steps were repeated several times before drying to obtain purified iridium nanowires. The TEM image of the iridium nanowires is similar to Figure 1, showing a narrow size distribution and a twinned structure. The nanowire diameter d is 2.7±0.3nm, and the twinned grain size of the nanowires is 2.6nm.

[0243] The step of nitrogen-doping graphene is to fully grind and mix 1g of graphene oxide and 4g of urea, heat them at 250°C for 2h in an oxidizing atmosphere containing 10vol% oxygen and 90vol% helium, and cool them to obtain nitrogen-doped graphene powder.

[0244] 46 mg of iridium nanowires were dispersed in 50 mL of ethanol, and 85 mg of nitrogen-doped graphene was added. The mixture was ultrasonically treated for 12 hours and centrifuged to obtain a black precipitate. The precipitate was then dried in an 80°C oven for 8 hours to obtain a black solid powder. The solid powder was then heated from room temperature to 100°C under a helium atmosphere at a rate of 5°C / min and maintained at this temperature for 1 hour. An oxidizing atmosphere containing 10 vol% oxygen and 90 vol% helium was then introduced, and the temperature was further increased to 250°C at a rate of 5°C / min. The oxidizing atmosphere was then maintained for 2.5 hours to obtain the iridium nanowire catalyst.

[0245] At 25°C, oxygen saturation is 0.5 mol·L -1 In sulfuric acid solution, a three-electrode system using an Ag / AgCl electrode as a reference electrode, a platinum electrode as a counter electrode, and a rotating disk electrode at 1600 rpm as a working electrode has an electrochemically active surface area of ​​58.3 cm at a reaction overpotential of 0.25 V. 2 , catalyst specific activity 45.1μA / cm 2 , at 10 mA·cm -2 The system ran stably for 22 h at a current density of 1.5 GHz.

[0246] Comparative Example 5

[0247] 2.5 g of polyvinylpyrrolidone (PVP) with a weight-average molecular weight of 29,000 was dissolved in 350 g of ethylene glycol. 1 mmol of iridium chloride hydrate, 12 mmol of hexadecyltrimethylammonium bromide, and 0.5 mmol of potassium iodide were added and stirred for 0.5 h to obtain a clear solution C6. 2 mmol of cobalt chloride hexahydrate (a molar ratio of iridium source to cobalt source of 1:2) was dissolved in 125 g of ethylene glycol to obtain solution B1. Solution B1 was added to C6 and stirred until thoroughly mixed. The solution was then added to an 800 mL hydrothermal autoclave and reacted at 190°C and 1 bar for 48 h. The resulting product was centrifuged in acetone to obtain a black precipitate. This was ultrasonically dispersed in ethanol, washed by centrifugation in acetone, and the above steps were repeated several times before drying to obtain purified iridium-cobalt nanocrystals. The ratio of iridium atoms to cobalt atoms was 1:0.5. The nanocrystal diameter d was 152±34 nm.

[0248] The step of nitrogen-doping graphene is to fully grind and mix 1g of graphene oxide and 4g of urea, heat them at 250°C for 2h in an oxidizing atmosphere containing 10vol% oxygen and 90vol% helium, and cool them to obtain nitrogen-doped graphene powder.

[0249] 46 mg of iridium-cobalt nanocrystals were dispersed in 50 mL of ethanol, and 85 mg of nitrogen-doped graphene was added. The mixture was ultrasonically treated for 12 hours and centrifuged to obtain a black precipitate. The precipitate was then dried in an 80°C oven for 8 hours to obtain a black solid powder. The solid powder was then heated from room temperature to 100°C at a rate of 5°C / min under a helium atmosphere and maintained at this temperature for 1 hour. An oxidizing atmosphere containing 10 vol% oxygen and 90 vol% helium was then introduced, and the temperature was further increased to 250°C at a rate of 5°C / min. The mixture was treated in the oxidizing atmosphere for 2.5 hours to obtain the iridium-cobalt nanocrystal catalyst.

[0250] At 25°C, oxygen saturation is 0.5 mol·L -1 In sulfuric acid solution, a three-electrode system using an Ag / AgCl electrode as a reference electrode, a platinum electrode as a counter electrode, and a rotating disk electrode at 1600 rpm as a working electrode has an electrochemically active surface area of ​​16.2 cm at a reaction overpotential of 0.25 V. 2 , catalyst specific activity 21.7μA / cm 2 , at 10 mA·cm -2 The system can run stably for 15 h at a current density of 1.

[0251] Comparative Example 6

[0252] 2.5 g of polyvinylpyrrolidone (PVP) with a weight-average molecular weight of 360,000 was dissolved in 350 g of ethylene glycol. 1 mmol of iridium chloride hydrate, 12 mmol of tetraethylammonium bromide, and 0.5 mmol of potassium iodide were added and stirred for 0.5 h to obtain a clear solution C7. 2 mmol of cobalt chloride hexahydrate (a molar ratio of iridium source to cobalt source of 1:2) was dissolved in 125 g of ethylene glycol to obtain solution B1. Solution B1 was added to C7 and stirred until thoroughly mixed. The solution was then added to an 800 mL hydrothermal autoclave and reacted at 190°C and 1 bar for 48 h. The resulting product was centrifuged in acetone to obtain a black precipitate. This was ultrasonically dispersed in ethanol, washed by centrifugation in acetone, and the above steps were repeated several times before drying to obtain purified iridium-cobalt nanocrystals with a diameter d of 0.5 nm.

[0253] The step of nitrogen-doping graphene is to fully grind and mix 1g of graphene oxide and 4g of urea, heat them at 250°C for 2h in an oxidizing atmosphere containing 10vol% oxygen and 90vol% helium, and cool them to obtain nitrogen-doped graphene powder.

[0254] 46 mg of iridium cobalt nanocrystals were dispersed in 50 mL of ethanol, 85 mg of nitrogen-doped graphene was added, and the mixture was ultrasonically treated for 12 h. The mixture was centrifuged to obtain a black precipitate, which was then dried in an oven at 80°C for 8 h to obtain a black solid powder. The solid powder was heated from room temperature to 250°C in an oxidizing atmosphere containing 10 vol% oxygen and 90 vol% helium at a heating rate of 5°C / min, and treated in an oxidizing atmosphere for 2.5 h to obtain an iridium cobalt nanocrystal catalyst.

[0255] At 25°C, oxygen saturation is 0.5 mol·L -1 In sulfuric acid solution, a three-electrode system using an Ag / AgCl electrode as a reference electrode, a platinum electrode as a counter electrode, and a rotating disk electrode at 1600 rpm as a working electrode has an electrochemically active surface area of ​​23.7 cm at a reaction overpotential of 0.25 V. 2 , catalyst specific activity 5.5μA / cm 2 , at 10 mA·cm -2 The system can be operated stably for 10 h at a current density of 1.

[0256] Table 1 Physicochemical properties and catalytic performance of various examples and comparative examples

[0257] The embodiments described above are intended only to illustrate the present invention and do not constitute any limitation thereto. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory rather than restrictive. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the invention described therein relates to specific methods, materials and embodiments, it does not mean that the invention is limited to the specific examples disclosed therein. On the contrary, the invention may be extended to all other methods and applications having the same function.

Claims

1. An iridium-based nanowire containing a twin crystal made up of iridium and at least one transition metal selected from iron, cobalt and nickel, preferably the diameter d of the nanowire is from 0.5 to 6 nm, and more preferably the grain size of the twin crystals is (0.8-1.1) d nm.

2. An iridium-based nanowire according to claim 1, wherein the atomic ratio of iridium to the transition metal is 1: (0.1-5), preferably 1: (0.2-3); and / or at least one form from tree-like, linear and mesh-like forms is selected as the form of the iridium-based nanowire.

3. The iridium-based nanowire of claim 1, wherein the percentage concentration of iridium on the surface of the iridium-based nanowire is at least 1% higher, preferably at least 2% higher, and more preferably at least 5% higher than the percentage concentration of iridium in the entire iridium-based nanowire; and / or iridium in the oxidized state on the surface of the iridium-based nanowire is at least 20%, preferably at least 30%, and more preferably at least 40%.

4. A method for producing an iridium-based nanowire according to any one of paragraphs 1-3, comprising the following steps: A1. The protective substance, the iridium parent compound and the crystal face coordinating substance are dissolved in the first alcohol to obtain a solution of the iridium parent compound; A2. The starting transition metal compound is dissolved in the second alcohol to yield a solution of the starting transition metal compound; A3. the solution obtained in step A1 is mixed with the solution obtained in step A2 to obtain a mixture; A4. The mixture obtained in step A3 is reacted under heating conditions to produce an iridium-based nanowire; wherein the crystal face coordinating substance contains inorganic iodide; and The protective substance is polyvinylpyrrolidone, which has an average molecular weight of 8,000 to 60,000.

5. The manufacturing method according to paragraph 4, having one or more of the following features: soluble iridium salts are selected as the starting iridium compound, preferably at least one of the following compounds: iridium chloride, iridium acetylacetonate, iridium carbonyl, hexachloroiridic acid, sodium hexachloroiridate, ammonium hexachloroiridate, and tetrairidium dodecacarbonyl; soluble salts of iron, cobalt and nickel are selected as the starting compound of the transition metal, and at least one of the following salts is preferably selected: chlorides, bromides, nitrates, sulfates, carbonates, acetates and acetylacetonates of iron, cobalt and nickel; the first alcohol and the second alcohol are the same or different, and in this capacity, independently of each other, polyhydric alcohols are selected, preferably polyhydric alcohols containing from 2 to 5 carbon atoms, more preferably, at least one of the following compounds is selected as the polyhydric alcohol: ethylene glycol, 1,2-propanediol, 1,3-propanediol, glycerol, diethylene glycol, triethylene glycol, dipropylene glycol, etc.; at least one of the alkali metal iodides, such as lithium iodide, sodium iodide, potassium iodide, ammonium iodide, etc., is selected as the inorganic iodide; The crystal face coordinating substance is a mixture of inorganic iodide and quaternary ammonium bromide, which has a relative molecular weight of less than 360, and quaternary ammonium bromide is selected from compounds with the general formula R4NBr, where the radicals R, independently of one another, are C1-C4 alkyl, aryl, or C1-C4 alkyl-substituted aryl, which is preferably at least one of the following compounds: tetramethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, tetrabutylammonium bromide, benzyltrimethylammonium bromide and benzyltriethylammonium bromide.

6. The manufacturing method according to claim 4 or 5, characterized in that the molar ratio of the starting iridium compound, the starting transition metal compound, and the crystal face coordinating substance is 1: (0.5-15): (5.1-32), preferably 1: (0.5-10): (5.1-32).

7. The manufacturing method according to any one of paragraphs 4-6, characterized in that the molar ratio of the starting iridium compound, quaternary ammonium bromide in the crystal face coordinating substance and inorganic iodide in the crystal face coordinating substance is 1: (5-30): (0.1-1.2), preferably 1: (8-20): (0.3-1), more preferably 1: (12-20): (0.3-1) and even more preferably 1: (12-20): (0.5-0.9).

8. The manufacturing method according to any one of paragraphs 4-7, characterized in that the mass ratio of the initial iridium compound, the protective substance and the alcohol is 1: (8-12): (1000-2000), preferably 1: (8-10): (1000-2000), preferably 1: (8-10): (1500-1800) and preferably 1: (8-10): (1700-1800).

9. The manufacturing method according to any one of claims 4 to 8, characterized in that the reaction temperature in step A4 is 130-230°C; the absolute pressure is 0.8-1.5 bar; and the reaction duration is 4-60 hours, preferably the reaction temperature is 150-200°C; the absolute pressure is 1.0-1.2 bar; and the reaction duration is 24-48 hours.

10. A manufacturing method according to any one of paragraphs 4-9, characterized in that the method additionally includes the following steps: A5. After step A4, the iridium-based nanowire is subjected to heat treatment; Preferably, the heat treatment includes the following steps: A5.

1. in a protective atmosphere of nitrogen and / or inert gas, the temperature is increased from room temperature to 80-120°C at a heating rate of 5-10°C / min, and this temperature is maintained for 30-60 minutes; A5.

2. With the introduction of an oxidizing atmosphere, the temperature is further increased to 200-350°C at a heating rate of 2-5°C / min, and the iridium-based nanowire is treated in the oxidizing atmosphere for 0.5-4 hours; optionally, the oxygen content in the oxidizing atmosphere in step A5.2 is 5-20 vol%.

11. An iridium-based catalyst comprising an iridium-based nanowire according to any one of claims 1-3, characterized in that the iridium-based nanowire is located on a nitrogen-doped carbon material which is a support.

12. An iridium-based catalyst according to claim 11, characterized in that, in terms of parts by weight, the catalyst contains from 10 to 95 parts by weight of an iridium-based nanowire, which is an active component, and from 5 to 90 parts by weight of a nitrogen-doped carbon material, which is a support.

13. An iridium-based catalyst according to claim 11 or 12, characterized in that at least one of the following materials is selected as a support for the nitrogen-doped carbon material: carbon black, graphene, carbon nanotubes, activated carbon and graphite; optionally, the molar fraction of nitrogen in the nitrogen-doped carbon material is from 0.5% to 5% and preferably from 0.5% to 3%.

14. An iridium-based catalyst according to any one of paragraphs 11-13, characterized in that the electrochemically active surface area of ​​the catalyst is 36-78 cm 2 .

15. A method for producing an iridium-based catalyst according to any one of paragraphs 11-14, comprising the following steps: B1. obtaining an iridium-based nanowire according to any one of claims 1-3, or obtaining an iridium-based nanowire by the method according to any one of claims 4-10; B2. iridium-based nanowire is mixed with nitrogen-doped carbon material; B3. the mixture obtained in stage B2 is subjected to heat treatment, to obtain an iridium-based catalyst in which the iridium-based nanowire is an active component and the nitrogen-doped carbon material is a support.

16. The manufacturing method according to paragraph 15, characterized in that it has one or more of the following features: the carbon material in the nitrogen-doped carbon material in step B2 is at least one of the following materials: carbon black, graphene, carbon nanotubes, activated carbon, and graphite; the carbon material in stage B2 may be subjected to oxidative pretreatment; the nitrogen-doped carbon material in step B2 is obtained by doping a carbon carrier with nitrogen using a nitrogen starting compound in a solid-phase or liquid-phase reaction; preferably, at least one of the following compounds is selected as the nitrogen starting compound: urea, biuret, ammonium nitrate, ammonium bicarbonate and melamine; preferably, the weight ratio of the carbon carrier and the powdered nitrogen starting compound is 1: (0.2-5); preferably, the oxygen content in the oxidizing atmosphere is 5-20 vol.%, wherein the remaining gas is at least one gas comprising nitrogen and / or an inert gas; the heating temperature is from 150 to 350°C, and preferably from 200 to 350°C, and the heating duration is from 0.5 to 6 hours, preferably 0.5 to 4 hours; and the mass ratio of the iridium-based nanowire, which is the active component, and the nitrogen-doped carbon material, which is the carrier, in step B2 is 10-95:5-90.

17. The manufacturing method according to paragraph 16, characterized in that the heat treatment at stage B3 includes the following stages: B3.

1. in a protective atmosphere of nitrogen and / or inert gas, the temperature is increased from room temperature to 80-120°C at a heating rate of 5-10°C / min, and this temperature is maintained for 30-60 minutes; B3.

2. with the introduction of an oxidizing atmosphere, the temperature is further increased to 200-350°C at a heating rate of 2-5°C / min, and the mixture is treated in an oxidizing atmosphere for 0.5-4 hours; optionally, the oxygen content in the oxidizing atmosphere in step (2) is 5-20 vol.%.

18. Use of an iridium-based nanowire according to any one of claims 1-3 or an iridium-based catalyst according to any one of claims 11-14 in an oxygen-evolving reaction.