Catalyst and preparation method thereof

Abstract

A catalyst and a preparation method thereof belong to the technical field of precious metal catalysts. Ir particles are loaded on a porous metal oxide carrier, and the physical confinement of the porous metal oxide carrier is utilized to suppress the agglomeration of the Ir particles when reacting to generate IrO2 catalyst particles, thereby facilitating the control of the IrO2 catalyst particles to a smaller size. Furthermore, by controlling the atmosphere in a first annealing process to include a sulfur-containing gas, an iridium sulfide interface layer is formed on the surface of the Ir particles, and the interface layer can be dynamically maintained during the annealing process, thereby suppressing the surface migration of iridium atoms and reducing the possibility of agglomeration of the Ir particles and subsequent reactions to generate IrO2. Consequently, IrO2 catalyst particles with a smaller particle size can be produced, thereby improving the activity and durability of the catalyst.

Description

Technical Field

[0001] The present application relates to the technical field of precious metal catalysts, and in particular to a catalyst and a preparation method thereof. Background Art

[0002] Proton exchange membrane water electrolysis (PEMWE) is an efficient and clean water electrolysis hydrogen production technology with numerous advantages, including high current density, high product purity, rapid response, and compactness. PEMWE utilizes a proton exchange membrane (PEM) as an electrolyte, separating the anode and cathode. In a water electrolyzer, water undergoes the oxygen evolution reaction (OER) on the anode surface, generating oxygen and hydrogen ions. The hydrogen ions migrate through the PEM to the cathode, where they combine with electrons to generate hydrogen. In PEMWE, the oxygen evolution reaction (OER) at the anode is the rate-limiting step in the entire water electrolysis process. The activity and stability of the anode catalyst play a critical role in the OER rate. High-performance catalysts can reduce the reaction overpotential, increase the reaction rate, reduce energy loss, and extend the lifespan. Crystalline IrO2 is currently the most commonly used OER catalyst, offering advantages such as high activity and tolerance to strongly acidic environments. However, its current catalytic activity and durability still fall short of the requirements for large-scale application of PEMWE technology. Summary of the Invention

[0003] Without being bound by any theory, during the preparation of IrO2, high-temperature annealing can lead to the agglomeration of IrO2 particles, making the particle size of IrO2 particles larger than 10nm, or even reaching the micron level, which in turn leads to poor catalytic activity and durability of the catalyst.

[0004] The present application provides a catalyst and a preparation method thereof, which can produce IrO2 catalyst particles with smaller particle size, thereby improving the activity and durability of the catalyst.

[0005] In a first aspect, the present invention provides a method for preparing a catalyst, the method comprising:

[0006] obtaining a catalyst precursor, the catalyst precursor comprising Ir particles and a metal oxide porous support, wherein the Ir particles are supported on the metal oxide porous support;

[0007] The catalyst precursor is annealed and the metal oxide porous support is removed to obtain a catalyst. The annealing includes a first annealing and a second annealing. The atmosphere of the first annealing includes a first gas including a sulfur-containing gas; the atmosphere of the second annealing includes a second gas including an oxidizing gas.

[0008] In the technical solution of the embodiment of the present application, Ir particles are loaded onto a porous metal oxide carrier and the physical confinement of the porous metal oxide carrier is utilized to inhibit the agglomeration of Ir particles when reacting to generate IrO2 catalyst particles, which is beneficial for controlling the IrO2 catalyst particles to be smaller in size. In addition, by controlling the atmosphere in the first annealing process to include sulfur-containing gas, an iridium sulfide interface layer is formed on the surface of the Ir particles, and the interface layer can be dynamically maintained during the annealing process, which can inhibit the surface migration of iridium atoms and reduce the possibility of agglomeration of Ir particles and subsequent reactions to generate IrO2, thereby being able to produce IrO2 catalyst particles with smaller particle size, thereby improving the activity and durability of the catalyst.

[0009] In some embodiments, the average particle size of the Ir particles is 2 nm to 3 nm.

[0010] In the above implementation process, the size of the Ir particles is positively correlated to the size of the catalyst particles to a certain extent. Controlling the average particle size of the Ir particles to 2nm~3nm is conducive to making the average particle size of the final IrO2 catalyst particles below 5nm.

[0011] In some embodiments, the partial pressure of the sulfur-containing gas is 10 -4 atm~10 -2 atm.

[0012] In the above implementation process, the greater the partial pressure of the sulfur-containing gas, the thicker the iridium sulfide interface layer formed on the surface of the Ir particles, which is more conducive to inhibiting agglomeration and forming smaller particles of the catalyst; the smaller the partial pressure of the sulfur-containing gas, the thinner the iridium sulfide interface layer formed on the surface of the Ir particles, which is more conducive to maintaining the activity of the catalyst. By controlling the partial pressure of the sulfur-containing gas to 10 - 4 atm~10 -2 atm, which can take into account both the particle size and activity of the catalyst.

[0013] In some embodiments, the sulfur-containing gas includes H 2 S.

[0014] In some embodiments, the atmosphere of the first annealing further includes a third gas, and the third gas includes at least one of an inert gas or nitrogen.

[0015] In some embodiments, the endpoint temperature of the first annealing is 400° C. to 600° C.;

[0016] In some embodiments, the heating rate of the first annealing is 3°C / min to 7°C / min;

[0017] In some embodiments, the holding time of the first annealing is 0.5 h to 1.5 h.

[0018] In some embodiments, the metal oxide porous support contains at least five metal elements.

[0019] In the above embodiment, by controlling the metal elements in the metal oxide porous carrier to be at least five, a high-entropy metal oxide porous carrier is formed. The high-entropy metal oxide porous carrier has higher thermal structural stability and can better maintain the physical confinement effect on the particles therein during high-temperature annealing.

[0020] In some embodiments, the specific surface area of ​​the porous metal oxide support is ≥ 200 m 2 / g.

[0021] In some embodiments, the average pore size of the mesopores of the porous metal oxide support is 3 nm to 8 nm.

[0022] In some embodiments, the metal oxide porous support comprises a (FeCoNiCrMn) 3 O 4 porous support.

[0023] In some embodiments, obtaining a catalyst precursor comprises:

[0024] Obtaining a porous metal oxide support;

[0025] loading an Ir-containing compound onto a porous metal oxide support to obtain an intermediate;

[0026] The intermediate is reduced to form Ir particles from the Ir-containing compound, thereby obtaining a catalyst precursor.

[0027] In the above implementation process, by forming Ir particles from Ir-containing compounds on a porous metal oxide carrier, the physical confinement of the porous metal oxide carrier is utilized to avoid agglomeration of Ir particles during the generation process, which is conducive to the formation of smaller Ir particles and further conducive to the formation of smaller IrO2 catalyst particles.

[0028] In some embodiments, the Ir-containing compound includes one or more of iridium tetrachloride, iridium trichloride, chloroiridic acid, iridium acetate, and iridium acetylacetonate.

[0029] In some embodiments, the method of loading comprises impregnation.

[0030] In some embodiments, the reducing atmosphere includes hydrogen.

[0031] In some embodiments, obtaining a porous metal oxide support comprises:

[0032] obtaining a carrier precursor;

[0033] The carrier precursor is sintered to obtain a porous metal oxide carrier.

[0034] In some embodiments, the support precursor is synthesized using a sol-gel method.

[0035] In some embodiments, the sintering temperature is 400°C to 800°C.

[0036] In some embodiments, the removal method of the porous metal oxide support comprises acid etching.

[0037] In the above implementation process, the difference in solubility between the porous metal oxide support and the IrO2 catalyst particles under acidic conditions is utilized to achieve the removal of the porous metal oxide support.

[0038] In some embodiments, the acid solution for acid corrosion includes nitric acid, and the molar concentration of the nitric acid is 1 mol / L to 3 mol / L.

[0039] In the above implementation process, dilute nitric acid has a lower corrosion rate on IrO2 catalyst particles but a higher corrosion rate on metal oxide supports, and thus can better achieve the removal of the metal oxide porous support.

[0040] In some embodiments, the acid solution for acid corrosion further includes oxalic acid, and the molar concentration of oxalic acid is 0.1 mol / L to 0.5 mol / L.

[0041] In some embodiments, the acid etching process is accompanied by ultrasonic treatment.

[0042] In the above implementation process, by supplementing the acid solution corrosion process with ultrasonic treatment, the removal efficiency of the porous metal oxide support can be improved and the possibility of agglomeration of IrO2 catalyst particles can be reduced.

[0043] In some embodiments, the volume proportion of the oxidizing gas is 3% to 7%.

[0044] In some embodiments, the oxidizing gas includes oxygen.

[0045] In some embodiments, the atmosphere of the second annealing further includes a fourth gas, and the fourth gas includes at least one of an inert gas or nitrogen.

[0046] In some embodiments, the endpoint temperature of the second annealing is 800° C. to 1100° C.;

[0047] In some embodiments, the heating rate of the second annealing is 8°C / min to 12°C / min;

[0048] In some embodiments, the holding time of the second annealing is 0.2 h to 0.8 h.

[0049] In a second aspect, an embodiment of the present application provides a catalyst, which is prepared using the method provided in the first aspect.

[0050] In a third aspect, an embodiment of the present application provides a membrane electrode, which includes an anode catalyst layer, and the anode catalyst layer includes the catalyst provided in the second aspect.

[0051] In a fourth aspect, an embodiment of the present application provides a water electrolysis cell, which includes the membrane electrode provided in the third aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0053] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0054] Figure 1 A flowchart of the method provided in an embodiment of the present application;

[0055] Figure 2 The XRD pattern of the catalyst provided in Example 1 of the present application;

[0056] Figure 3 This is a TEM image of the catalyst provided in Example 1 of the present application. DETAILED DESCRIPTION

[0057] The embodiments of the present application will be described in detail below with reference to the examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, the conditions are carried out according to conventional conditions or manufacturer recommendations. The reagents or instruments used are not specified by the manufacturer and are conventional products that can be purchased commercially.

[0058] In the description of this application specification, the terms "including", "comprising", etc. mean "including but not limited to". In this document, relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. In this document, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "plurality" means two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b or c", or "at least one of a, b and c", can both mean: a, b, c, ab (i.e. a and b), ac, bc, or abc, where a, b and c can be single or multiple.

[0059] Without being bound by any theory, during the preparation of IrO2, high-temperature annealing can lead to the agglomeration of IrO2 particles, making the particle size of IrO2 particles larger than 10nm, or even reaching the micron level, which in turn leads to poor catalytic activity and durability of the catalyst.

[0060] The present application intends to provide a method for preparing a catalyst. During the preparation process of IrO2 catalyst particles, an iridium sulfide interface layer is first formed on the surface of the Ir particles to inhibit the surface migration of iridium atoms, reduce the possibility of agglomeration of Ir particles and subsequent reactions to generate IrO2, and thus produce IrO2 catalyst particles with smaller particle size, thereby improving the activity and durability of the catalyst.

[0061] Figure 1 For a flowchart of the method provided in the embodiment of this application, please refer to Figure 1 , the present application embodiment provides a method for preparing a catalyst, the method comprising:

[0062] S1. Obtaining a catalyst precursor, the catalyst precursor comprising Ir particles and a porous metal oxide support, wherein the Ir particles are supported on the porous metal oxide support;

[0063] S2. Annealing the catalyst precursor and removing the metal oxide porous support to obtain a catalyst, wherein the annealing includes a first annealing and a second annealing, wherein the atmosphere of the first annealing includes a first gas including a sulfur-containing gas; and the atmosphere of the second annealing includes a second gas including an oxidizing gas.

[0064] The method loads Ir particles on a porous metal oxide carrier and utilizes the physical confinement of the porous metal oxide carrier to suppress the agglomeration of Ir particles when reacting to generate IrO2 catalyst particles, thereby facilitating the control of the IrO2 catalyst particles to a smaller size. Furthermore, by controlling the atmosphere in the first annealing process to include a sulfur-containing gas, an iridium sulfide interface layer is formed on the surface of the Ir particles. The interface layer can be dynamically maintained during the annealing process, thereby suppressing the surface migration of iridium atoms and reducing the possibility of agglomeration of Ir particles and subsequent reactions to generate IrO2. Thus, IrO2 catalyst particles with a smaller particle size can be produced, thereby improving the activity and durability of the catalyst.

[0065] Specifically, the annealing process can be: first annealing: in N2 / H2S, the temperature is raised to 600°C at 5°C / min and kept at this temperature for 1 hour; by controlling the hydrogen sulfide partial pressure and the annealing temperature, a 1nm~2nm iridium sulfide interface layer is formed. This interface layer is dynamically maintained at high temperature, which can not only inhibit the surface migration of iridium atoms but also prevent the iridium particles from being completely converted into iridium sulfide, thereby maintaining the activity of subsequent catalysts; second annealing: the atmosphere is switched to Ar / O2 (5% O2 by volume), and then raised to 1000°C at 10°C / min, kept at this temperature for 30 minutes, and then rapidly cooled.

[0066] As an optional embodiment, the partial pressure of the sulfur-containing gas is 10 -4 atm~10 -2 Atm. The greater the partial pressure of the sulfur-containing gas, the thicker the iridium sulfide interface layer formed on the surface of the Ir particles, which is more conducive to inhibiting agglomeration and forming smaller particles of the catalyst; the smaller the partial pressure of the sulfur-containing gas, the thinner the iridium sulfide interface layer formed on the surface of the Ir particles, which is more conducive to maintaining the activity of the catalyst. By controlling the partial pressure of the sulfur-containing gas to 10 -4 atm~10 -2 atm, which can take into account both the particle size and activity of the catalyst.

[0067] For example, the partial pressure of the sulfur-containing gas may be 10 -4 atm, 10 -3 atm, 10 -2 atm, etc., which can also be 10 -4 atm~10 -2 Any value within the atm range.

[0068] As an optional embodiment, the sulfur-containing gas includes H 2 S. It should be noted that in other embodiments, the sulfur-containing gas may also be other gases, as long as it can react on the surface of the Ir particles to form an iridium sulfide interface layer.

[0069] As an optional embodiment, the first annealing atmosphere further includes a third gas, which includes at least one of an inert gas or nitrogen. The inert gas can be specifically selected from helium, argon, etc. The addition of the third gas can achieve regulation of the H2S partial pressure.

[0070] As an optional embodiment, the endpoint temperature of the first annealing is 400° C. to 600° C. For example, the endpoint temperature of the first annealing can be 400° C., 420° C., 440° C., 460° C., 480° C., 500° C., 520° C., 540° C., 560° C., 580° C., 600° C., etc., and can also be any value within the range of 400° C. to 600° C.

[0071] As an optional embodiment, the heating rate of the first annealing is 3°C / min to 7°C / min. For example, the heating rate of the first annealing can be 3°C / min, 3.5°C / min, 4°C / min, 4.5°C / min, 5°C / min, 5.5°C / min, 6°C / min, 6.5°C / min, 7°C / min, etc. It can also be any value in the range of 3°C / min to 7°C / min.

[0072] As an optional embodiment, the holding time of the first annealing is 0.5h~1.5h. Exemplarily, the holding time of the first annealing can be 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, 1h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, etc., and can also be any value within the range of 0.5h~1.5h.

[0073] It is understandable that the initial temperature of the first annealing is usually room temperature, that is, the first annealing process is to heat from room temperature at a heating rate of 3°C / min~7°C / min to an end temperature of 400°C~600°C, and keep at the end temperature for 0.5h~1.5h.

[0074] As an optional embodiment, the volume proportion of the oxidizing gas is 3% to 7%. For example, the volume proportion of the oxidizing gas can be 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, etc., and can also be any value within the range of 3% to 7%.

[0075] As an optional embodiment, the oxidizing gas includes oxygen. It should be noted that, in other embodiments, the oxidizing gas can be other oxidizing gases that only need to be able to react Ir into IrO2.

[0076] As an optional embodiment, the second annealing atmosphere further includes a fourth gas, which includes at least one of an inert gas or nitrogen. The fourth gas can adjust the proportion of the oxidizing gas in the entire atmosphere.

[0077] As an optional embodiment, the endpoint temperature of the second annealing is 800° C. to 1100° C. For example, the endpoint temperature of the second annealing can be 800° C., 850° C., 900° C., 950° C., 1000° C., 1050° C., 1100° C., etc., and can also be any value within the range of 800° C. to 1100° C.

[0078] As an optional embodiment, the heating rate of the second annealing is 8°C / min to 12°C / min. For example, the heating rate of the second annealing can be 8°C / min, 8.5°C / min, 9°C / min, 9.5°C / min, 10°C / min, 10.5°C / min, 11°C / min, 11.5°C / min, 12°C / min, etc. It can also be any value within the range of 8°C / min to 12°C / min.

[0079] As an optional embodiment, the holding time of the second annealing is 0.2h~0.8h. Exemplarily, the holding time of the second annealing can be 0.2h, 0.25h, 0.3h, 0.35h, 0.4h, 0.45h, 0.5h, 0.55h, 0.6h, 0.65h, 0.7h, 0.75h, 0.8h, etc., and can also be any value within the range of 0.2h~0.8h.

[0080] It can be understood that the initial temperature of the second annealing is usually the end temperature of the first annealing, that is, the process of the second annealing is to heat from the end temperature of the first annealing at a heating rate of 8°C / min~12°C / min to the end temperature of 800°C~1100°C, and keep it at the end temperature for 0.2h~0.8h.

[0081] During the entire second annealing process, the Ir inside the particles first reacts to form IrO2, and when the temperature reaches a certain level (around 1000°C), the iridium sulfide interface layer on the particle surface reacts to form a stable suboxidized state (IrO x , 0.5 <x<1.5)。

[0082] As an optional embodiment, the average particle size of the Ir particles is 2 nm to 3 nm. The size of the Ir particles is positively correlated to the size of the catalyst particles to a certain extent. Controlling the particle size of the Ir particles to 2 nm to 3 nm is conducive to ensuring that the average particle size of the final IrO2 catalyst particles is below 5 nm.

[0083] Illustratively, the average particle size of the Ir particles can be 2 nm, 2.1 nm, 2.2 nm, 2.3 nm, 2.4 nm, 2.5 nm, 2.6 nm, 2.7 nm, 2.8 nm, 2.9 nm, 3 nm, etc., and can also be any value within the range of 2 nm to 3 nm.

[0084] As an optional embodiment, the metal element in the porous metal oxide support is a transition metal, preferably at least five transition metals. Exemplarily, the metal element in the porous metal oxide support may be a transition metal element such as Fe, Co, Ni, Cr, Mn, etc. By controlling the number of metal elements in the porous metal oxide support to be at least five, a high-entropy porous metal oxide support is formed. The high-entropy porous metal oxide support has a high thermal structural stability and can better maintain the physical confinement effect on the particles therein during high-temperature annealing.

[0085] As an optional embodiment, the specific surface area of ​​the metal oxide porous carrier is ≥200m 2 / g. For example, the specific surface area of ​​the porous metal oxide carrier can be 200m 2 / g, 210m 2 / g, 220m 2 / g, 230m 2 / g, 240m 2 / g, 250m 2 / g, 260m 2 / g, 270m 2 / g, 280m 2 / g, 290m 2 / g、300m 2 / g, etc., which can also be ≥200m 2 Any value in the range of / g.

[0086] As an optional embodiment, the average pore size of the mesopores of the porous metal oxide support is 3 nm to 8 nm. For example, the average pore size of the mesopores of the porous metal oxide support can be 3 nm, 3.5 nm, 4 nm, 4.5 nm, 5 nm, 5.5 nm, 6 nm, 6.5 nm, 7 nm, 7.5 nm, 8 nm, etc., and can also be any value within the range of 3 nm to 8 nm.

[0087] As an optional embodiment, the average particle size of the porous metal oxide support is 50 nm to 300 nm. For example, the average particle size of the porous metal oxide support can be 50 nm, 70 nm, 100 nm, 120 nm, 150 nm, 170 nm, 200 nm, 220 nm, 250 nm, 270 nm, 300 nm, etc., and can also be any value within the range of 50 nm to 300 nm.

[0088] As an optional embodiment, the metal oxide porous support includes a (FeCoNiCrMn)3O4 porous support.

[0089] As an optional embodiment, obtaining the catalyst precursor includes:

[0090] S1.1. Obtain a porous metal oxide support;

[0091] S1.2. Loading the Ir-containing compound onto a porous metal oxide support to obtain an intermediate;

[0092] S1.3. Reduce the intermediate to form Ir particles from the Ir-containing compound to obtain a catalyst precursor.

[0093] By forming Ir particles from Ir-containing compounds on a porous metal oxide carrier, the physical confinement of the porous metal oxide carrier is utilized to avoid agglomeration of Ir particles during the generation process, which is conducive to the formation of smaller Ir particles and further conducive to the formation of smaller IrO2 catalyst particles.

[0094] Specifically, the loading process of the Ir-containing compound on the porous metal oxide support and the reduction process of the intermediate can be: IrCl3 solution is loaded into the pores of the porous metal oxide support by an impregnation method, and reduced under H2 to generate 2nm~3nm Ir particles.

[0095] As an optional embodiment, the Ir-containing compound includes one or more of iridium tetrachloride, iridium trichloride, chloroiridic acid, iridium acetate, and iridium acetylacetonate. In other embodiments, the Ir-containing compound may also be other soluble Ir-containing compounds so that they can be loaded onto the porous metal oxide support by an impregnation method.

[0096] As an optional embodiment, the loading method includes an impregnation method, which can easily load the Ir-containing compound on the metal oxide porous support and can load more Ir particles in the pores of the metal oxide porous support.

[0097] As an optional embodiment, the reducing atmosphere includes hydrogen.

[0098] As an optional embodiment, the loading amount of Ir particles is 10% to 30% of the total mass of the catalyst precursor. For example, the loading amount of Ir particles can be 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, etc., of the total mass of the catalyst precursor, and can also be any value within the range of 10% to 30%.

[0099] As an optional embodiment, obtaining the porous metal oxide support includes:

[0100] S1.1.1. Obtain a carrier precursor;

[0101] S1.1.2. Sinter the carrier precursor to obtain a porous metal oxide carrier.

[0102] Specifically, the process of obtaining the porous metal oxide support can be as follows: synthesizing the (FeCoNiCrMn)3O4 precursor by the sol-gel method, sintering it at 600 °C to form a porous framework structure with a specific surface area of ​​260 m 2 / g, the average pore size of the mesopores is about 5 nm, and the average particle size is about 120 nm.

[0103] It should be noted that, in other embodiments, the porous metal oxide carrier can be obtained not only by preparation but also by commercial purchase.

[0104] As an optional embodiment, the carrier precursor is synthesized by a sol-gel method.

[0105] As an optional embodiment, the sintering temperature is 400° C. to 800° C. For example, the sintering temperature may be 400° C., 420° C., 440° C., 460° C., 480° C., 500° C., 520° C., 540° C., 560° C., 580° C., 600° C., 620° C., 640° C., 660° C., 680° C., 700° C., 720° C., 740° C., 760° C., 780° C., 800° C., etc., and may also be any value within the range of 400° C. to 800° C.

[0106] As an optional embodiment, the method for removing the porous metal oxide support includes acid corrosion, which utilizes the difference in solubility between the porous metal oxide support and the IrO2 catalyst particles under acidic conditions to achieve removal of the porous metal oxide support.

[0107] As an optional embodiment, the acid solution for the acid corrosion includes nitric acid, and the molar concentration of the nitric acid is 1 mol / L to 3 mol / L. Dilute nitric acid has a low corrosion rate for IrO2 catalyst particles but a high corrosion rate for the metal oxide support, and thus is well suited for removing the porous metal oxide support.

[0108] Illustratively, the molar concentration of nitric acid can be 1 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L, 2 mol / L, 2.2 mol / L, 2.4 mol / L, 2.6 mol / L, 2.8 mol / L, 3 mol / L, etc., and it can also be any value within the range of 1 mol / L to 3 mol / L.

[0109] As an optional embodiment, the acid solution for acid corrosion further includes oxalic acid, and the molar concentration of oxalic acid is 0.1 mol / L to 0.5 mol / L. Exemplarily, the molar concentration of oxalic acid can be 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, 0.45 mol / L, 0.5 mol / L, etc., and can also be any value within the range of 0.1 mol / L to 0.5 mol / L.

[0110] As an optional embodiment, the acid etching process is accompanied by ultrasonic treatment. By supplementing the acid etching process with ultrasonic treatment, the removal efficiency of the porous metal oxide support can be improved and the possibility of agglomeration of IrO2 catalyst particles can be reduced.

[0111] Specifically, the removal process of the porous metal oxide support can be as follows: the annealed porous metal oxide support / IrO2 catalyst particle composite material is immersed in an acid solution (1.5 mol / L nitric acid and 0.3 mol / L oxalic acid are mixed in a volume ratio of 5:1. 1 g of catalyst requires 50 ml of mixed acid solution), placed in an ultrasonic reactor, and treated at 40 kHz for 3 h: the first ultrasonic stage (25°C, 1 h): dissolves loose oxides on the surface of the porous metal oxide support; the second ultrasonic stage (60°C, 2 h): strengthens the grain boundary corrosion of the porous metal oxide support, and at the same time suppresses the dissolution of the IrO2 catalyst particles at low temperature.

[0112] As an optional embodiment, the method further includes separating and purifying the IrO2 catalyst particles. The separation process may include centrifuging (8000 rpm, 10 minutes) the acid-washed solution to collect the IrO2 catalyst particles. The purification process includes washing the solution three times with deionized water to remove residual acid and metal complexes, followed by vacuum drying at 60°C for 12 hours to obtain the IrO2 catalyst particles.

[0113] Based on the same inventive concept, an embodiment of the present application further provides a catalyst, which is prepared using the method provided above.

[0114] The catalyst is prepared based on the above method. The specific steps of the method can refer to the above embodiments. Since the catalyst adopts part or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here.

[0115] Based on the same inventive concept, an embodiment of the present application further provides a membrane electrode, which includes an anode catalyst layer, and the anode catalyst layer includes the catalyst provided above.

[0116] The membrane electrode is realized based on the above-mentioned catalyst. The specific content of the catalyst can be referred to the above-mentioned embodiment. Since the membrane electrode adopts part or all of the technical solutions of the above-mentioned embodiment, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiment, which will not be repeated here.

[0117] As an optional embodiment, the membrane electrode further includes a gas diffusion layer and a proton exchange membrane, and the proton exchange membrane, the catalyst layer and the gas diffusion layer are arranged in sequence.

[0118] Based on the same inventive concept, an embodiment of the present application further provides a water electrolysis cell, which includes the membrane electrode provided above.

[0119] The water electrolysis cell is realized based on the above-mentioned membrane electrode. The specific content of the membrane electrode can be referred to the above-mentioned embodiment. Since the water electrolysis cell adopts part or all of the technical solutions of the above-mentioned embodiment, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiment, which will not be described one by one here.

[0120] The present application will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present application only and are not intended to limit the scope of the present application. The experimental methods in the following examples where specific conditions are not specified are usually measured in accordance with national standards. If there are no corresponding national standards, then the methods are carried out in accordance with general international standards, conventional conditions, or according to the conditions recommended by the manufacturer.

[0121] Example 1

[0122] A catalyst, the preparation process of which is as follows:

[0123] 1. Preparation of porous metal oxide supports: ① Weigh nitrates (Fe(NO₃)₃·9H₂O, Co(NO₃)₂·6H₂O, Ni(NO₃)₂·6H₂O, Cr(NO₃)₃·9H₂O, and Mn(NO₃)₂·4H₂O) at a metal ion molar ratio of 1:1:1:1:1 and dissolve in deionized water to a concentration of 0.3 mol / L. ② Dissolve dimethylimidazole in 100 ml of anhydrous ethanol at a molar ratio of 1:3 to the metal ion. Add the prepared dimethylimidazole ethanol solution dropwise to the solution prepared in ① and stir. Then, add triethylamine to adjust the pH to 9. Stir magnetically (600 rpm) until uniformly mixed. ③ Stir continuously at room temperature for 3 hours. The solution will gradually turn from transparent to turbid, eventually forming a viscous sol. Stop stirring and allow to stand for 24 hours to form a gel. ④. Dry the gel in an oven at 95°C for 18 hours to obtain a xerogel precursor. ⑤. Grind the dried precursor into a powder and calcine it in a muffle furnace under air: increase the temperature to 600°C at 2°C / min, hold for 3 hours, and cool naturally to room temperature to obtain a black (FeCoNiCrMn)3O4 nanocrystalline powder porous framework support.

[0124] 2. Preparation of catalyst precursor: ①. Grind the (FeCoNiCrMn)3O4 porous framework support to a particle size of 200 mesh and dry it in a vacuum oven at 120°C for 2 hours. ②. Slowly add 17mL of the prepared IrCl3 aqueous solution (concentration of 0.05 mol / L) to 1g of (FeCoNiCrMn)3O4 powder while ultrasonically oscillating (40kHz, 30min) to ensure that the solution fully penetrates the pores, so that the theoretical loading of Ir is 20.2% of the total mass of the catalyst precursor. ③. After impregnation, let the material stand at room temperature for 12 hours to age Ir. 3+ The precursor was uniformly adsorbed onto the inner wall of the pores and then transferred to an oven and dried at 80°C for 6 hours to evaporate the solvent, forming an IrCl3 / support precursor. ④ The precursor was placed in a tube furnace and introduced with a 5% H2 / Ar mixture (flow rate 50 mL / min). The temperature was increased from room temperature to 300°C at a rate of 2°C / min and maintained at 300°C for 2 hours (the H2 flow rate was reduced to 20 mL / min during the holding period to prevent Ir particle agglomeration). The precursor was then naturally cooled to room temperature to obtain a catalyst precursor in which Ir particles were supported within the pores of the (FeCoNiCrMn)3O4 porous framework support. The average particle size of the Ir particles was 2.5 nm (measured by XRD).

[0125] 3. Annealing the catalyst precursor: Place 1g of the catalyst precursor in a tube furnace for annealing. The annealing process includes the first annealing and the second annealing. The first annealing process is carried out in N2 / H2S (flow rate is 500ml / min), with the H2S partial pressure controlled at 10 -3 atm, raise the temperature to 600°C at 5°C / min, and keep it for 1h; second annealing: switch to Ar / O2 (5% O2) (flow rate of 500ml / min), raise the temperature to 1000°C at 10°C / min, keep it for 30 min, and then cool it quickly.

[0126] 4. Removal of the porous metal oxide support: The annealed porous metal oxide support / IrO2 composite material was immersed in an acid solution (mix 1.5 mol / L nitric acid and 0.3 mol / L oxalic acid in a volume ratio of 5:1. 1 g of the composite requires 50 ml of the mixed acid solution), placed in an ultrasonic reactor, and treated at 40 kHz for 3 h (first stage (25°C, 1 h), second stage (60°C, 2 h)).

[0127] 5. Collect the IrO2 particles from the acid-washed solution by centrifugation (8000 rpm, 10 min); wash with deionized water three times to remove residual acid and metal complexes; and dry under vacuum at 60°C for 12 h to obtain the IrO2 catalyst.

[0128] Figure 2 This is the XRD pattern of the catalyst provided in Example 1. It can be seen from the figure that the catalyst is a rutile phase iridium oxide catalyst.

[0129] Figure 3 This is a TEM image of the catalyst provided in Example 1. As can be seen from the image, the specific morphology of the catalyst is iridium oxide formed by the accumulation of small nanoparticles.

[0130] Example 2

[0131] This embodiment is the same as that of Example 1 except that ultrasonic treatment is not performed during the removal of the porous metal oxide support.

[0132] Example 3

[0133] In this embodiment, in addition to controlling the H2S partial pressure at 10 -5 atm, and the rest of the contents are the same as those in Example 1.

[0134] Example 4

[0135] In this embodiment, in addition to controlling the H2S partial pressure at 10 -4 atm, and the rest of the contents are the same as those in Example 1.

[0136] Example 5

[0137] In this embodiment, in addition to controlling the H2S partial pressure at 10 -2 atm, and the rest of the contents are the same as those in Example 1.

[0138] Example 6

[0139] In this embodiment, in addition to controlling the H2S partial pressure at 10 -1 atm, and the rest of the contents are the same as those in Example 1.

[0140] Example 7

[0141] In this embodiment, in addition to using MnO2 (with an average particle size of 160 nm and a specific surface area of ​​263 m 2 / g, with an average pore size of 5.5 nm) as the metal oxide porous support and the average particle size of the Ir particles being 2.8 nm, the rest of the contents are the same as in Example 1.

[0142] Comparative Example 1

[0143] The only difference between this embodiment and Example 1 is that hydrogen sulfide gas is not used in the first annealing.

[0144] Comparative Example 2

[0145] A catalyst, the preparation process of which is as follows:

[0146] ① The catalyst precursor was prepared by the preparation method of Example 1, but the annealing step was not performed on the catalyst precursor. Instead, the step of removing the metal oxide porous support was performed directly to obtain Ir particles with a particle size of 2.5 nm and not supported in the metal oxide porous support.

[0147] ② Annealing the Ir particles obtained in ①: Place 1g of Ir particles in a tube furnace for annealing. The annealing includes the first annealing and the second annealing. In the first annealing, the H2S partial pressure is controlled at 10 - 3 atm, raise the temperature to 600°C at 5°C / min, and keep it for 1h; second annealing: switch to Ar / O2 (5% O2) (flow rate of 500ml / min), raise the temperature to 1000°C at 10°C / min, keep it for 30 min, and then quickly cool it to obtain the catalyst.

[0148] The catalysts provided in each embodiment and comparative example were subjected to particle size test, electrical performance test and durability test. The specific test process is as follows:

[0149] Particle size test: The particle size is estimated by measuring the half-width at half maximum and the Bragg diffraction angle of the X-ray diffraction peak. The calculation formula is as follows:

[0150]

[0151] Where: D is the thickness along the direction perpendicular to the crystal plane, which can also be considered as the size of the grain.

[0152] K is the Scherrer constant, usually taken as 0.89. λ is the wavelength of the X-ray.

[0153] B 1 / 2 is the half-height width of the diffraction peak, in radians.

[0154] θ is the Bragg diffraction angle.

[0155] The particle size of the material is usually obtained by directly fitting from the XRD test data.

[0156] Electrical Performance Testing: Electrochemical tests were conducted using a Shanghai Chenhua CHI660E electrochemical station and a rotating disk electrode (Pine, USA). The catalysts were primarily tested using cyclic voltammetry (CV) and linear sweep voltage (LSV) techniques. All electrode potentials were normalized using a reversible hydrogen electrode (RHE).

[0157] (1) Preparation of working electrode

[0158] Using an electronic balance, 8 mg of each catalyst from each of the above examples and comparative examples was weighed and added to a 5 ml centrifuge tube. 2 ml of the prepared dispersion (300 ml of isopropanol, 100 ml of water, and 0.31 g of a 5 wt% Nafion solution) was then aspirated. The mixed solution was placed in a cell crusher and ultrasonically dispersed for 20 minutes to obtain a uniform catalyst ink. Using a 10 μL pipette, 10 μL of the catalyst ink was evenly dripped onto a pre-polished and cleaned gold electrode (0.196 cm in area). 2 ) on the electrode surface to prevent the ink from overflowing and to evenly spread it on the electrode surface. Wait for it to dry naturally to form a catalytic layer, and you have a working electrode.

[0159] (2) Electrochemical performance test

[0160] Cyclic voltammogram (CV) tests were performed over a potential range of 1.2–1.6 vs RHE (0.544–0.944 vs Hg₂SO₄) at a scan rate of 50 mVs⁻¹. Before each test, saturated N₂ was introduced for 60 min (in an oxygen-free environment) at a scan rate of 100 mVs⁻¹ until the CV curve stabilized, ensuring full catalyst activation.

[0161] Linear Sweep Voltammetry: To evaluate the OER electrocatalytic performance of the catalyst materials and their behavior during the reaction, anodic polarization measurements were performed, using linear sweep voltammetry (LSV) results as the basis for evaluation. The LSV scan rate was 50 mV·s⁻¹ over a range of 1.2–1.6 vs RHE, with a scan rate of 50 mV·s⁻¹ and a rotating disk electrode speed of 1600 rpm.

[0162] Durability Testing: To investigate the stability of the prepared catalyst in an acidic electrochemical environment, an accelerated durability test (ADT) was performed on the catalyst. The ADT scan rate was 100 mVs² for 3000 cycles between 1.2 and 1.6 vs RHE (0.544 to 0.944 vs Hg²SO²). CV and LSV data were collected before and after the cycles as described above. The electrochemical stability of the catalyst was evaluated by comparing the overpotential loss of the catalyst at different cycles.

[0163] The test results are shown in the following table:

[0164]

[0165] As can be seen from the above table, the catalyst prepared by the method provided in the examples of the present application has a better particle size, and thus has better activity and durability.

[0166] Comparison of the data in Example 1 and Example 2 shows that ultrasonic treatment is more conducive to producing a smaller catalyst when removing the porous metal oxide framework.

[0167] By comparing the data of Example 1 and Example 3 to Example 6, it can be seen that the lower the hydrogen sulfide content, the thinner the iridium sulfide layer on the surface, which causes the subsequent catalyst particle size to increase and the corresponding electrochemical performance to decrease; the higher the hydrogen sulfide content, the thicker the iridium sulfide layer on the surface, which causes the subsequent catalyst to have a significant decrease in corresponding electrochemical performance, which does not meet the requirements of high-activity iridium oxide.

[0168] By comparing the data of Example 1 and Example 7, it can be seen that using a high-entropy metal oxide as a porous carrier can be more conducive to preparing a smaller catalyst.

[0169] According to Example 1 and Comparative Examples 1 and 2, when there is no hydrogen sulfide gas or no oxide carrier, the catalyst particle size increases significantly and the electrochemical performance decreases sharply.

[0170] The above are merely specific embodiments of the present application to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but rather is intended to conform to the widest scope consistent with the principles and novel features of the present application.

Claims

1. A method for preparing a catalyst, characterized in that: The method comprises: A catalyst precursor is obtained, wherein the catalyst precursor includes Ir particles and a metal oxide porous support, wherein the Ir particles are supported on the metal oxide porous support; the metal elements in the metal oxide porous support include transition metals, and the metal elements in the metal oxide porous support include at least five kinds; The catalyst precursor is annealed, and then the metal oxide porous support is removed to obtain a catalyst, wherein the annealing includes a first annealing and a second annealing, and the atmosphere of the first annealing includes a first gas, the first gas includes a sulfur-containing gas, the sulfur-containing gas includes H2S, and the partial pressure of the sulfur-containing gas is 10 -4 atm~10 -2 atm, the endpoint temperature of the first annealing is 400° C. to 600° C.; the atmosphere of the second annealing includes a second gas, the second gas includes an oxidizing gas, and the catalyst is iridium oxide.

2. The method for preparing the catalyst according to claim 1, wherein The average particle size of the Ir particles is 2 nm to 3 nm; and / or The first annealing process satisfies at least one of the following (A1) to (A3): (A1) The first annealing atmosphere further includes a third gas, wherein the third gas includes at least one of an inert gas or nitrogen; (A2) The heating rate of the first annealing is 3°C / min to 7°C / min; (A3) The holding time of the first annealing is 0.5h~1.5h.

3. The method for preparing a catalyst according to any one of claims 1 to 2, characterized in that: The porous metal oxide support satisfies at least one of the following (B1) to (B3): (B1) The specific surface area of ​​the porous metal oxide carrier is ≥ 200 m 2 / g; (B2) The average pore size of the mesopores of the porous metal oxide support is 3 nm to 8 nm; (B3) The metal oxide porous support includes a (FeCoNiCrMn)3O4 porous support.

4. The method for preparing the catalyst according to claim 3, wherein The catalyst precursor is obtained by: Obtaining a porous metal oxide support; loading an Ir-containing compound onto the metal oxide porous support to obtain an intermediate; The intermediate is reduced to form Ir particles from the Ir-containing compound, thereby obtaining a catalyst precursor.

5. The method for preparing the catalyst according to claim 4, wherein The Ir-containing compound includes one or more of iridium tetrachloride, iridium trichloride, chloroiridic acid, iridium acetate and iridium acetylacetonate; and / or; The loading method includes an impregnation method; and / or The reducing atmosphere includes hydrogen.

6. The method for preparing the catalyst according to claim 4, wherein: The method of obtaining the porous metal oxide carrier comprises: obtaining a carrier precursor; The carrier precursor is sintered to obtain a porous metal oxide carrier.

7. The method for preparing the catalyst according to claim 6, characterized in that: The carrier precursor is synthesized by a sol-gel method; and / or The sintering temperature is 400°C to 800°C.

8. The method for preparing the catalyst according to claim 3, wherein: The method for removing the porous metal oxide support comprises acid corrosion.

9. The method for preparing the catalyst according to claim 8, wherein The acid solution for the acid corrosion includes nitric acid, and the molar concentration of the nitric acid is 1 mol / L to 3 mol / L.

10. The method for preparing a catalyst according to claim 9, characterized in that: The acid solution for acid corrosion further comprises oxalic acid, and the molar concentration of the oxalic acid is 0.1 mol / L to 0.5 mol / L.

11. The method for preparing a catalyst according to claim 8, wherein: The acid corrosion process is accompanied by ultrasonic treatment.

12. The method for preparing a catalyst according to claim 1, wherein: The second annealing process satisfies at least one of the following (C1) to (C6): (C1) The volume proportion of the oxidizing gas is 3% to 7%; (C2) the oxidizing gas includes oxygen; (C3) the atmosphere of the second annealing further includes a fourth gas, wherein the fourth gas includes at least one of an inert gas or nitrogen; (C4) The endpoint temperature of the second annealing is 800° C. to 1100° C.; (C5) The heating rate of the second annealing is 8°C / min to 12°C / min; (C6) The holding time of the second annealing is 0.2h~0.8h.

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