Iridium / cobaltosic oxide mesoporous single crystal oxygen evolution catalyst and preparation method thereof

Abstract

The invention provides an iridium / cobaltosic oxide mesoporous monocrystal oxygen evolution catalyst and a preparation method thereof, and relates to the technical field of catalyst preparation, and the preparation method comprises the following steps: S1, preparing a mesoporous monocrystal cobalt hydroxide sheet; s2, dispersing mesoporous monocrystal cobalt hydroxide and an iridium-containing compound in an ethanol-water mixed solution, heating to a certain temperature, stirring to react for a period of time, and then washing and drying a reaction product; and S3, roasting the dried reaction product in an air atmosphere for a period of time to obtain the catalyst. The catalyst disclosed by the invention has high Ir load, extremely low overpotential and ultrahigh stability, and has huge potential in practical application of electrolyzed water.

Description

Technical Field

[0001] The invention relates to the technical field of catalyst preparation, in particular to an iridium / cobalt tetroxide mesoporous single crystal oxygen evolution catalyst and a preparation method thereof. Background Art

[0002] Hydrogen is considered an ideal alternative to fossil fuels due to its high energy density and clean properties. Among various hydrogen production technologies, the use of renewable energy to generate electricity and produce hydrogen through water electrolysis is considered a sustainable approach. Among them, proton exchange membrane (PEM) water electrolysis technology has shown significant technical advantages due to its efficient operation at high current density, good adaptability to intermittent power sources such as wind and solar energy, few side reactions, and high hydrogen purity. However, the widespread application of PEM electrolyzers still faces a key challenge: the oxygen evolution reaction (OER) at the anode involves multi-electron proton transfer, which has slow kinetics and requires high overpotential driving, and most catalysts are easily decomposed in acidic environments and have poor stability. Therefore, the development of OER catalysts with both high activity and high stability under acidic conditions is crucial to improve the overall hydrogen production efficiency. At present, IrO2 is the only material that can maintain high catalytic activity under the harsh acidic conditions of PEM electrolyzers, but it is expensive due to the scarcity of iridium resources. Therefore, designing highly active and highly stable acidic OER catalysts to reduce dependence on precious metal Ir has become an urgent need to improve the economic and sustainability of catalysts.

[0003] How to achieve high Ir loading while achieving high activity and stability remains a major challenge that needs to be solved. Mesoporous single crystal materials have become a potential solution to this challenge because they have both mesoporous structure and single crystal characteristics. The mesoporous structure significantly increases the number of active sites or catalyst loading sites, and compared with nanocrystals, the single crystal structure can accelerate electron transfer during electrocatalysis and reduce the risk of metal leaching. These characteristics make mesoporous single crystal materials show great potential in breaking the balance between activity and stability in acidic OER catalysis. Therefore, the rational design and optimization of mesoporous single crystal materials is expected to provide a new direction for the development of the next generation of efficient and durable acidic OER catalysts. Summary of the invention

[0004] The present invention proposes a two-step method for preparing an iridium-loaded mesoporous single-crystalline cobalt oxide oxygen evolution catalyst for efficient and stable OER catalysis. First, a coprecipitation method coupled with a template method is used to prepare a mesoporous single-crystalline cobalt hydroxide, and then an Ir species is loaded on the cobalt hydroxide by an ethanol thermal method, and an iridium-loaded mesoporous single-crystalline cobalt oxide is obtained by heat treatment. Specifically:

[0005] A method for preparing an iridium / cobalt tetroxide mesoporous single crystal oxygen evolution catalyst comprises:

[0006] Step S1: Prepare mesoporous single-crystalline cobalt hydroxide flakes;

[0007] Step S2: Disperse mesoporous single-crystalline cobalt hydroxide and an Ir-containing compound in a mixed solution of ethanol and water, heat to a certain temperature, stir and react for a period of time, and then wash and dry the reaction product;

[0008] Step S3: Calcinate the dried reaction product in an air atmosphere for a period of time to obtain an iridium / cobalt tetroxide mesoporous single-crystalline oxygen evolution catalyst.

[0009] Furthermore, step S1 includes:

[0010] Step S11: Dissolve P123 in deionized water to obtain a P123 aqueous solution with a concentration of 0.005 - 0.5 g / mL;

[0011] Step S12: Dissolve a soluble metal salt of Co in the P123 aqueous solution to obtain a reaction solution with a Co element concentration of 0.01 - 0.5 mol / L;

[0012] Step S13: Stir and heat the reaction solution at a rotation speed of 50 - 1000 r / min to 50 - 100 °C, add ammonia water with a molar amount 0.5 - 10 times that of the Co metal salt, and react for 0.1 - 96 h;

[0013] Step S14: After the reaction, wash repeatedly to obtain mesoporous single-crystalline cobalt hydroxide flakes.

[0014] Furthermore, in step S2, the mass ratio of mesoporous single-crystalline cobalt hydroxide to the Ir salt is 0.5 - 10.

[0015] Furthermore, in step S2, the Ir-containing compound is one or more of potassium hexachloroiridate(III), ammonium hexachloroiridate(III), iridium(III) chloride, and chloroiridic acid.

[0016] Furthermore, in step S2, in the mixed solution of ethanol and water, the volume ratio of ethanol to water is 0.01 - 100.

[0017] Furthermore, in step S2, the heating temperature is 20 - 100 °C, the stirring rotation speed is 50 - 1000 r / min; the reaction time is 0.1 - 48 h.

[0018] Furthermore, in step S3, the calcination temperature is 200 - 800 °C, and the calcination time is 0.1 - 10 h.

[0019] Furthermore, the present invention also provides an iridium / cobalt oxide mesoporous single crystal oxygen evolution catalyst, with a spinel-phase cobalt oxide mesoporous single crystal as the carrier. The carrier particle size is between 30 nanometers and 50 micrometers, and the carrier mesopores are between 2 and 50 nanometers; the Ir active phase is loaded on the carrier, and the Ir active phase includes Ir single atoms, oxidized Ir nanoclusters or oxidized Ir nanoparticles.

[0020] Furthermore, for the catalyst of the present invention, the loading amount of Ir is 13.8 wt%; and it can provide an overpotential of η 10 of 248 mV under acidic conditions.

[0021] Furthermore, the present invention also provides the application of the catalyst in the field of water electrolysis.

[0022] The beneficial effects brought by the technical solutions provided by the embodiments of the present invention at least include:

[0023] The mesoporous single crystal structure of the present invention provides additional OER active sites, and the mesoporous structure provides more Ir loading sites, thus achieving a high Ir loading amount. Using transition metal oxides as the matrix material, compared with noble metal oxides and alloys, the amount of Ir used is greatly reduced. The catalyst prepared by the present invention provides an ultra-low overpotential of 248 mV under acidic conditions. As an acidic OER catalyst, it ranks among the most advanced acidic OER catalysts at present and can stably catalyze for more than 100 h. In the PEM water electrolysis test, the catalyst achieved current densities of 200 and 300 mA cm -2 at voltages of 1.54 V and 1.59 V respectively, and stably operated for 330 hours at a current density of 200 mA cm -2 . BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0025] Figure 1 It is the TEM image of the iridium / cobalt oxide mesoporous single crystal oxygen evolution catalyst of Embodiment 1 of the present invention.

[0026] Figure 2 It is the spherical aberration electron microscope image of the iridium / cobalt oxide mesoporous single crystal oxygen evolution catalyst of Embodiment 1 of the present invention.

[0027] Figure 3EDS surface scan image of the iridium / cobalt oxide mesoporous single crystal catalyst of Example 1 of the present invention, where (a) is its dark field TEM image, (b) is the EDS surface scan distribution map of its Ir element, (c) is the EDS surface scan distribution map of its Co element, and (d) is the EDS surface scan distribution map of its Co and Ir elements.

[0028] Figure 4 OER polarization curve of the iridium / cobalt oxide mesoporous single crystal oxygen evolution catalyst of Example 1 of the present invention in 0.5 M H2SO4.

[0029] Figure 5 For the iridium / cobalt oxide mesoporous single crystal oxygen evolution catalyst of Example 1 of the present invention in a PEM electrolyzer cell at 200 mA cm -2 Stability test at current density. Detailed implementation manners

[0030] The technical solutions in the present invention will be described below.

[0031] In the embodiments of the present invention, words such as "exemplarily" and "for example" are used to represent examples, illustrations or explanations. Any embodiment or design solution described as an "example" in the present invention should not be construed as being more preferred or having more advantages than other embodiments or design solutions. Rather, the use of the word "example" is intended to present concepts in a specific manner. In addition, in the embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one of the two.

[0032] In the embodiments of the present invention, "image" and "picture" can sometimes be used interchangeably. It should be noted that when the difference is not emphasized, the meanings they express are the same. "Of", "corresponding" and "corresponding to" can sometimes be used interchangeably. It should be noted that when the difference is not emphasized, the meanings they express are the same.

[0033] In the embodiments of the present invention, sometimes subscripts such as W1 may be miswritten as non-subscript forms such as W1. When the difference is not emphasized, the meanings they express are the same.

[0034] To make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in detail with specific embodiments.

[0035] Example 1

[0036] Dissolve 1 g of P123 in 50 ml of deionized water to prepare an aqueous P123 solution. Add 0.25 g of cobalt nitrate hexahydrate, stir and heat it to 80 °C at a speed of 600 r / min on a magnetic stirrer, add 0.75 mL of ammonia water, react for a period of time to obtain a precipitate, wash it and dry it to obtain mesoporous single-crystalline cobalt hydroxide. Take 50 mg of the dried mesoporous single-crystalline cobalt hydroxide and 30 mg of potassium chloroiridate, add them to a mixed solution of 10 mL of deionized water and 10 ml of ethanol, react at 80 °C for 2 h, wash it and dry it, and then calcine it at 450 °C for 2 h in an air atmosphere to obtain iridium-loaded mesoporous single-crystalline cobalt tetroxide. TEM image ( Figure 1 ) shows that the prepared iridium-loaded mesoporous single-crystalline cobalt tetroxide has a size of about 1 μm and the mesopore size is about 18 - 20 nm. The spherical aberration electron microscope photograph shows that Ir is uniformly distributed on the Co3O4 nanosheets, and the EDS surface scan shows that Co and Ir are uniformly distributed in the whole material, and Ir is enriched inside the mesopores. The space confinement effect of the mesoporous structure can prevent the loss of Ir element during the reaction. LSV curve ( Figure 4 ) shows that it can reach a low overpotential of 248 mV (10 mA cm -2 ), and it can be stable for 330 hours in the PEM water electrolysis test at 200 mA cm -2 ( Figure 5 ).

[0037] Example 2

[0038] Dissolve 0.8 g of P123 in 50 ml of deionized water to prepare an aqueous P123 solution. Add 0.25 g of cobalt nitrate hexahydrate, stir and heat it to 75 °C at a speed of 800 r / min on a magnetic stirrer, add 0.8 mL of ammonia water, react for a period of time to obtain a precipitate, wash it and dry it to obtain mesoporous single-crystalline cobalt hydroxide. Take 50 mg of the dried mesoporous single-crystalline cobalt hydroxide and 15 mg of potassium chloroiridate, add them to a mixed solution of 10 mL of deionized water and 10 ml of ethanol, react at 80 °C for 2 h, wash it and dry it, and then calcine it at 400 °C for 2 h in an air atmosphere to obtain iridium-loaded mesoporous single-crystalline cobalt tetroxide. The prepared iridium-loaded mesoporous single-crystalline cobalt tetroxide has a size of about 1 μm and the mesopore size is about 20 nm.

[0039] Example 3

[0040] Dissolve 1.2 g of P123 in 50 mL of deionized water to prepare an aqueous P123 solution. Add 0.3 g of cobalt nitrate hexahydrate, stir and heat it to 80 °C at a speed of 500 r / min on a magnetic stirrer, add 1 mL of ammonia water, react for a period of time to obtain a precipitate, wash it and dry it to obtain mesoporous single-crystalline cobalt hydroxide. Take 50 mg of the dried mesoporous single-crystalline cobalt hydroxide and 20 mg of ammonium chloroiridate, add them to a mixed solution of 10 mL of deionized water and 10 mL of ethanol, react at 70 °C for 2 h, wash and dry it, and then calcine it at 500 °C for 2 h in an air atmosphere to obtain iridium-loaded mesoporous single-crystalline cobalt tetroxide. The prepared iridium-loaded mesoporous single-crystalline cobalt tetroxide has a size of about 1 μm and a mesoporous size of about 20 nm.

[0041] As described above, it is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A method for preparing an iridium / cobalt oxide mesoporous single crystal oxygen evolution catalyst, characterized in that: include: Step S1, preparing mesoporous single crystal cobalt hydroxide; Step S2, dispersing the mesoporous single crystal cobalt hydroxide and the iridium-containing compound in a mixed solution of ethanol and water, heating to a certain temperature and stirring to react for a period of time, and then washing and drying the reaction product; Step S3, calcining the dried reaction product in an air atmosphere for a period of time to obtain an iridium / cobalt tetroxide mesoporous single crystal oxygen evolution catalyst.

2. The method according to claim 1, characterized in that Step S1 includes: Step S11, dissolving P123 in deionized water to obtain a P123 aqueous solution with a concentration of 0.005-0.5 g / mL; Step S12, dissolving a soluble metal salt of Co in a P123 aqueous solution to obtain a reaction solution having a Co element concentration of 0.01-0.5 mol / L; Step S13, stirring the reaction solution at a speed of 50-1000 r / min and heating it to 50-100° C., adding ammonia water in an amount of 0.5-10 times the molar number of the Co metal salt, and reacting for 0.1-96 h; Step S14: After the reaction is completed, the mixture is washed repeatedly to obtain a mesoporous single crystal cobalt hydroxide.

3. The method according to claim 1, characterized in that In step S2, the mass ratio of the mesoporous single crystal cobalt hydroxide to the iridium-containing compound is 0.5-10.

4. The method according to claim 1, characterized in that: In step S2, the iridium-containing compound is one or more of potassium chloroiridate, ammonium chloroiridate, iridium chloride, and chloroiridic acid.

5. The method according to claim 1, characterized in that In step S2, in the ethanol-water mixed solution, the volume ratio of ethanol to water is 0.01-100.

6. The method according to claim 1, characterized in that In step S2, the heating temperature is 20-100°C, the stirring speed is 50-1000 r / min; and the reaction time is 0.1-48 h.

7. The method according to claim 1, characterized in that In step S3, the calcination temperature is 200-800°C, and the calcination time is 0.1-10 h.

8. A catalyst prepared according to the method according to any one of claims 1 to 7, characterized in that: The carrier is a spinel phase cobalt oxide mesoporous single crystal, the carrier particle size is between 30 nanometers and 50 micrometers, and the carrier mesopores are between 2 and 50 nanometers; the carrier is loaded with an Ir active phase, and the Ir active phase includes Ir single atoms, oxidized Ir nanoclusters or oxidized Ir nanoparticles.

9. The catalyst according to claim 8, characterized in that The loading amount of Ir is 13.8wt%; and it can provide η 10 The overpotential is 248mV.

10. Use of the catalyst prepared by the method according to any one of claims 1 to 7, or the catalyst according to any one of claims 8 to 9, in the field of water electrolysis.

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