Two-dimensional porous nanosheet multi-element metal oxide as well as preparation method and application thereof

Abstract

The invention relates to the technical field of electrochemical water electrolysis, in particular to a two-dimensional porous nanosheet multi-element metal oxide as well as a preparation method and application thereof. According to the invention, a two-dimensional porous nanosheet structure is formed by three times of heat treatment of a template salt, an iridium source, an auxiliary metal salt, a heteroatom doping auxiliary agent, a microstructure control auxiliary agent and a solvent. The performance of the low-Ir-content catalyst is improved from the aspects of multi-metal alloying effect, heteroatom doping, catalyst structure adjustment and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical electrolyzed water, and particularly relates to a two-dimensional porous nanosheet multi-metal oxide, a preparation method thereof, and an application thereof. Background Art

[0002] Disclosing the information of this background art section is only intended to increase the understanding of the overall background of the present invention, and it is not necessarily regarded as an admission or an implication in any form that this information constitutes the prior art already known to those of ordinary skill in the art.

[0003] The increasing global energy demand and ecological problems have forced us to develop green and renewable energy conversion and storage technologies. Among them, the proton exchange membrane electrolyzed water (PEMWE) hydrogen production technology, as an efficient energy storage and conversion device, has received wide attention for its high energy conversion efficiency and environmental friendliness. The hydrogen evolution reaction occurs at the cathode of the proton exchange membrane electrolyzed water, and the oxygen evolution reaction occurs at the anode. Compared with the hydrogen evolution reaction, the oxygen evolution reaction has slow kinetics and requires highly active catalytic sites. At the same time, under the strong acidic and strong oxidizing conditions on the anode side, the oxygen evolution reaction catalyst faces the tests of stability and durability.

[0004] At present, IrO2 has been found to be able to efficiently and stably catalyze the acidic oxygen evolution reaction. However, the scarcity and high price of the precious metal Ir resources severely limit the large-scale application of the proton exchange membrane electrolyzed water technology. Therefore, it is imperative to develop low-Ir content catalysts with excellent properties similar to IrO2. Summary of the Invention

[0005] In order to overcome the above problems, the present invention provides a two-dimensional porous nanosheet multi-metal oxide, a preparation method thereof, and an application thereof.

[0006] To achieve the above technical objectives, the present invention adopts the following technical solutions:

[0007] In the first aspect of the present invention, there is provided a two-dimensional porous nanosheet multi-metal oxide, the oxide being an iridium-based multi-metal oxide, and:

[0008] doped with at least one heteroatom C selected from nitrogen and phosphorus;

[0009] containing at least one metal element B selected from ruthenium, iron, cobalt, nickel, manganese, and copper;

[0010] and having a two-dimensional porous nanosheet structure.

[0011] In the second aspect of the present invention, there is provided a preparation method of the two-dimensional porous nanosheet multi-metal oxide according to the first aspect, including the following steps:

[0012] (1) Add an iridium source, an auxiliary metal salt, a heteroatom doping promoter, and a microstructure control promoter to a solvent. After mixing evenly, a first precursor material is formed.

[0013] (2) Add a template salt to the first precursor material. After mixing evenly, a second precursor material is formed.

[0014] (3) Perform a first heat treatment on the second precursor material under an inert gas. After removing the solvent, perform a second heat treatment to form a third precursor material.

[0015] (4) Perform a third heat treatment on the third precursor material in an atmosphere containing oxygen to obtain a two-dimensional porous nanosheet multi-metal oxide.

[0016] In the third aspect of the present invention, there is provided an application of the two-dimensional porous nanosheet multi-metal oxide described in the first aspect as an electrocatalytic oxygen evolution catalyst.

[0017] The beneficial effects of the present invention are as follows:

[0018] (1) The present invention relates to the technical field of electrochemical water electrolysis, and specifically relates to a two-dimensional porous nanosheet multi-metal oxide and its preparation method and application. In the present invention, a two-dimensional porous nanosheet structure Ir a B b C x O y (such as Ir a Ru b N x O y ) is formed by three heat treatments using a template salt, an iridium source, an auxiliary metal salt, a heteroatom doping promoter, a microstructure control promoter, and a solvent. In the present invention, the performance of the low-Ir content catalyst is improved from aspects such as the multi-metal alloying effect, heteroatom doping, and adjustment of the catalyst structure; specifically, in the present invention, the structure of the iridium-based catalyst is modified by introducing one or several auxiliary metals to form a multi-metal alloying effect, which can improve the catalytic performance of the iridium-based catalyst. At the same time, under the doping of the heteroatom doping promoter, the heteroatom will coordinate with the metal, further adjusting the structure of the iridium-based catalyst and improving the catalytic performance of the iridium-based catalyst. In addition, under the control of the microstructure control promoter, a two-dimensional nanosheet structure is formed. In order to increase the active sites of the reaction and the specific surface area, the template salt has a low solubility in the limited solvent. When the salt template becomes a molten state, it will etch the two-dimensional nanosheet to form a two-dimensional porous nanosheet structure. The two-dimensional porous nanosheet structure has a nanoscale thickness and a high electrochemically active surface area (ECSA). Its reactive phase interface is almost completely exposed, which can greatly increase the mass-charge transfer rate and accelerate the reaction; at the same time, due to its unique two-dimensional nanoscale size effect and alloyed electronic structure, the two-dimensional porous nanosheet structure can effectively reduce the reaction energy barrier and improve the reaction activity of the catalyst.

[0019] (2) The template salt in the present invention can be recycled and reused, reducing the preparation cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0021] Figure 1 is the preparation process of the two-dimensional porous nanosheet multi-metal oxide in the present invention;

[0022] Figure 2 is the SEM image of the ground template salt in Example 1;

[0023] Figure 3 is the SEM image of the two-dimensional porous nanosheet catalyst in Example 1;

[0024] Figure 4 is the nitrogen adsorption curve of the two-dimensional porous nanosheet catalyst in Example 1;

[0025] Figure 5 is the half-cell OER performance diagram of the two-dimensional porous nanosheet catalyst in Example 1;

[0026] Figure 6 is the single-cell performance diagram of the two-dimensional porous nanosheet catalyst in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0027] It should be noted that the following detailed description is exemplary and is intended to provide further illustration of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0028] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular forms are also intended to include the plural forms. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0029] The first typical embodiment of the present invention provides a two-dimensional porous nanosheet multi-metal oxide, wherein the oxide is an iridium-based multi-metal oxide, and:

[0030] doped with at least one heteroatom C selected from nitrogen and phosphorus;

[0031] comprising at least one metal element B selected from ruthenium, iron, cobalt, nickel, manganese, and copper;

[0032] and having a two-dimensional porous nanosheet structure.

[0033] A second typical embodiment of the present invention provides a method for preparing the two-dimensional porous nanosheet multi-metal oxide described in the first aspect, comprising the following steps:

[0034] (1) Adding an iridium source, an auxiliary metal salt, a heteroatom doping assistant, and a microstructure control assistant to a solvent, and forming a first precursor material after mixing evenly;

[0035] (2) Adding a template salt to the first precursor material, and forming a second precursor material after mixing evenly;

[0036] (3) Performing a first heat treatment on the second precursor material under an inert gas, removing the solvent, and then performing a second heat treatment to form a third precursor material;

[0037] (4) Performing a third heat treatment on the third precursor material in an atmosphere containing oxygen to obtain the two-dimensional porous nanosheet multi-metal oxide.

[0038] In one or more embodiments, in step (1), the iridium source is selected from one or more of chloroiridic acid, iridium acetylacetonate, iridium chloride, potassium chloroiridate, sodium chloroiridate, and iridium acetate.

[0039] In one or more embodiments, in step (1), the auxiliary metal salt is selected from one or more of nitrates, halides, sulfates, and acetates of ruthenium, iron, cobalt, nickel, manganese, or copper.

[0040] Preferably, the mass ratio of the auxiliary metal salt to the iridium source is 0.1 - 4:1.

[0041] In one or more embodiments, in step (1), the heteroatom doping assistant is selected from soluble organic and inorganic compounds containing N or P; preferably one or more of ammonium chloride, ammonia water, ammonium nitrate, ammonium bicarbonate, ammonium acetate, cyanamide, urea, phosphonic acid, sodium phosphate, and sodium hydrogen phosphate.

[0042] Preferably, the mass ratio of the heteroatom doping assistant to the iridium source is 0.5 - 4:1.

[0043] In one or more embodiments, in step (1), the microstructure control assistant is selected from surfactants, preferably one or more of polyvinylpyrrolidone (PVP), cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and cetyltrimethylammonium chloride (CTMAC).

[0044] Preferably, the mass ratio of the microstructure control additive to the iridium source is 0.5 to 10:1.

[0045] In one or more embodiments, in step (1), the solvent is selected from one or more of N-methylpyrrolidone (NMP), petroleum ether, n-heptane, and xylene. The template salt is insoluble or slightly soluble in the solvent.

[0046] Preferably, the mass ratio of the solvent to the iridium source is 1 to 10:1.

[0047] In one or more embodiments, in step (2), the template salt is selected from one or more of nitrates, halides, sulfates, acetates, carbonates, and bicarbonates of sodium or potassium.

[0048] Preferably, the mass ratio of the template salt to the iridium source is 5 to 100:1.

[0049] In one or more embodiments, in step (2), the template salt is ground to a defined particle size before use.

[0050] Preferably, the particle size of the template salt is 100 to 10,000 nm.

[0051] In one or more embodiments, in step (3), the temperature of the first heat treatment is 150 to 500 °C, the heat treatment time is 1 to 3 h, and the heating rate is 3 to 10 °C / min.

[0052] In one or more embodiments, in step (3), the temperature of the second heat treatment is 500 to 900 °C, the heat treatment time is 1.5 to 3 h, and the heating rate is 3 to 10 °C / min.

[0053] In one or more embodiments, in step (4), the oxygen-containing atmosphere includes one of air or oxygen;

[0054] The oxygen-containing atmosphere may further include one or two of ammonia and phosphine gas.

[0055] In one or more embodiments, in step (4), the temperature of the third heat treatment is 250 to 600 °C, the heat treatment time is 0.5 to 2 h, and the heating rate is 3 to 10 °C / min.

[0056] A third typical embodiment of the present invention provides the use of the two-dimensional porous nanosheet multi-metal oxide described in the first aspect as an electrocatalytic oxygen evolution catalyst.

[0057] In one or more embodiments, the two-dimensional porous nanosheet multi-metal oxide is used as an anode catalyst in a proton exchange membrane electrolyzer.

[0058] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0059] Example 1

[0060] (1) Weigh 5 g each of sodium chloride and sodium nitrate, and then mix and grind them in a ball mill for 3 h to make them fully mixed and reduce their particle size. The particle size after grinding is 1000 nm, and it is used as the template salt. The ground template salt is as Figure 2 shown.

[0061] (2) Weigh 0.4 g of iridium chloride, 1.2 g of ruthenium chloride, 1.2 g of urea, and 0.5 g of polyvinylpyrrolidone (PVP) and place them in a beaker. Then add 100 mL of N-methylpyrrolidone (NMP), stir (300 rpm) for 30 min and ultrasonicate (200 w) for 30 min to make them evenly mixed, forming the first precursor material.

[0062] (3) Add 10 g of the ground template salt obtained in step (1) to the first precursor material, stir (300 rpm) for 1 h and ultrasonicate (200 w) for 1 h to make them evenly mixed, forming the second precursor material.

[0063] (3) Heat the second precursor material to 180 °C in an argon atmosphere at a heating rate of 5 °C / min, keep it at a constant temperature for 2 h to remove the liquid solvent; heat the solid mixture to 820 °C at a heating rate of 10 °C / min in a nitrogen atmosphere and keep it for 2 h. After cooling to room temperature, wash the product with water to remove the soluble template salt, and then freeze-dry it to obtain the two-dimensional nanosheets, that is, the third precursor material;

[0064] Heat the third precursor material to 400 °C at a heating rate of 5 °C / min in an air atmosphere and keep it for 1 h to obtain the final product, the two-dimensional porous nanosheet catalyst. Its SEM image is as Figure 3 shown.

[0065] Example 2

[0066] (1) Weigh 5 g each of sodium chloride and sodium nitrate, and then mix and grind them in a ball mill for 3 h to make them fully mixed and reduce their particle size. The particle size after grinding is 200 nm, and it is used as the template salt.

[0067] (2) Weigh 0.4 g of iridium chloride, 1.2 g of nickel chloride, 1.2 g of urea, and 0.5 g of polyvinylpyrrolidone (PVP) and place them in a beaker. Then add 100 mL of N-methylpyrrolidone (NMP), stir (300 rpm) for 30 min and ultrasonicate (200 w) for 30 min to make them evenly mixed, forming the first precursor material.

[0068] (3) Add 10 g of the ground template salt obtained in step (1) to the first precursor material, stir (300 rpm) for 1 h and sonicate (200 w) for 1 h to mix them evenly, forming the second precursor material.

[0069] (3) Heat the second precursor material to 180 °C in an argon atmosphere at a heating rate of 5 °C / min, hold at a constant temperature for 2 h to remove the liquid solvent; heat the solid mixture to 820 °C at a heating rate of 10 °C / min in a nitrogen atmosphere and hold for 2 h, cool to room temperature, wash the product with water to remove the soluble template salt, and then freeze-dry to obtain the two-dimensional nanosheets, i.e., the third precursor material.

[0070] Heat the third precursor material to 400 °C at a heating rate of 5 °C / min in an air atmosphere and hold for 1 h to obtain the final product, the two-dimensional porous nanosheet catalyst.

[0071] Example 3

[0072] (1) Weigh 5 g each of sodium chloride and sodium nitrate, then mix and grind them in a ball mill for 3 h to mix them thoroughly and reduce their particle size. The particle size after grinding is 2000 nm. Use this as the template salt. The ground template salt is as Figure 2 shown.

[0073] (2) Weigh 0.4 g of iridium chloride, 1.2 g of ruthenium chloride, 1.2 g of urea, and 0.5 g of polyvinylpyrrolidone (PVP) and place them in a beaker. Then add 100 mL of N-methylpyrrolidone (NMP), stir (300 rpm) for 30 min and sonicate (200 w) for 30 min to mix them evenly, forming the first precursor material.

[0074] (3) Add 10 g of the ground template salt obtained in step (1) to the first precursor material, stir (300 rpm) for 1 h and sonicate (200 w) for 1 h to mix them evenly, forming the second precursor material.

[0075] (3) Heat the second precursor material to 300 °C in an argon atmosphere at a heating rate of 5 °C / min, hold at a constant temperature for 2 h to remove the liquid solvent; heat the solid mixture to 600 °C at a heating rate of 10 °C / min in a nitrogen atmosphere and hold for 3 h, cool to room temperature, wash the product with water to remove the soluble template salt, and then freeze-dry to obtain the two-dimensional nanosheets, i.e., the third precursor material.

[0076] Heat the third precursor material to 500 °C at a heating rate of 5 °C / min in an air atmosphere and hold for 1 h to obtain the final product, the two-dimensional porous nanosheet catalyst.

[0077] Example 4

[0078] (1) Weigh 5 g each of sodium chloride and sodium nitrate, and then mix and grind them in a ball milling jar for 3 h to make them fully mixed and reduce their particle size. The particle size after grinding is 8000 nm, which is used as the template salt. The ground template salt is as shown in Figure 2 .

[0079] (2) Weigh 0.4 g of iridium chloride, 1.2 g of ruthenium chloride, 1.2 g of urea, and 0.5 g of polyvinylpyrrolidone (PVP) and place them in a beaker. Then add 100 mL of N-methylpyrrolidone (NMP), stir (300 rpm) for 30 min and sonicate (200 w) for 30 min to make them evenly mixed, forming the first precursor material.

[0080] (3) Add 10 g of the ground template salt obtained in step (1) to the first precursor material, stir (300 rpm) for 1 h and sonicate (200 w) for 1 h to make them evenly mixed, forming the second precursor material.

[0081] (3) Heat the second precursor material to 300 °C in an argon atmosphere at a heating rate of 5 °C / min, keep it at a constant temperature for 2 h to remove the liquid solvent; heat the solid mixture to 600 °C at a heating rate of 10 °C / min in a nitrogen atmosphere and keep it for 3 h. After cooling to room temperature, wash the product with water to remove the soluble template salt, and then freeze-dry it to obtain the two-dimensional nanosheets, that is, the third precursor material;

[0082] Heat the third precursor material to 500 °C at a heating rate of 5 °C / min in an atmosphere of a mixed gas of oxygen and ammonia (volume ratio 3:1) and keep it for 1 h to obtain the final product, the two-dimensional porous nanosheet catalyst.

[0083] Example 5

[0084] Perform nitrogen adsorption tests on the two-dimensional porous nanosheet material prepared in Example 1 to determine its specific surface area. The test results are as shown in Figure 4 , Table 1: It can be seen from Figure 4 that the two-dimensional porous nanosheet material has a specific surface area as high as 284.7 m 2 / g due to its two-dimensional porous nanosheet structure, which is higher than that of other competing catalysts, showing the characteristic of high specific surface area of two-dimensional nanosheet materials, which can greatly increase the reaction active area and expose more reaction active sites.

[0085] Table 1 Comparison of specific surface areas of catalyst materials

[0086]

[0087] The proton exchange membrane water electrolysis hydrogen production electrolytic cell was assembled using the two-dimensional porous nanosheet material prepared in Example 1, and the performance of the cell was characterized. The results are as Figures 4 to 6 shown.

[0088] As can be seen from Figures 4 to 6 , the two-dimensional porous nanosheet material has better half-cell performance, single-cell performance and durability than the catalyst of the comparative example at an extremely low Ir loading of 0.40 mg Ir / cm 2 . It exhibits excellent electrochemical activity and is expected to further reduce the Ir loading in PEM water electrolysis for hydrogen production.

[0089] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A two-dimensional porous nanosheet-shaped multi-metal oxide, characterized in that: The oxide is an iridium-based multinary metal oxide, and: doped with at least one heteroatom C selected from nitrogen and phosphorus; Containing at least one metal element B selected from ruthenium, iron, cobalt, nickel, manganese and copper; And has a two-dimensional porous nanosheet structure.

2. The method for preparing the two-dimensional porous nanosheet-like multi-metal oxide according to claim 1, characterized in that: The steps include: (1) adding an iridium source, an auxiliary metal salt, a heteroatom doping agent, and a microstructure control agent into a solvent and mixing them uniformly to form a first precursor material; (2) adding a template salt to the first precursor material and mixing them evenly to form a second precursor material; (3) subjecting the second precursor material to a first heat treatment under an inert gas, removing the solvent, and then subjecting the second heat treatment to a second heat treatment to form a third precursor material; (4) subjecting the third precursor material to a third heat treatment in an atmosphere containing oxygen to obtain a two-dimensional porous nanosheet-shaped multi-metal oxide.

3. The preparation method according to claim 2, characterized in that: In step (1), the iridium source is selected from one or more of chloroiridic acid, iridium acetylacetonate, iridium chloride, potassium chloroiridate, sodium chloroiridate and iridium acetate; Or, in step (1), the auxiliary metal salt is selected from one or more of nitrates, halides, sulfates and acetates of ruthenium, iron, cobalt, nickel, manganese or copper; Preferably, the mass ratio of the auxiliary metal salt to the iridium source is 0.1 to 4:

1.

4. The preparation method according to claim 2, characterized in that: In step (1), the heteroatom doping aid is selected from soluble organic and inorganic compounds containing N or P; preferably one or more of ammonium chloride, ammonia water, ammonium nitrate, ammonium bicarbonate, ammonium acetate, cyanamide, urea, phosphonic acid, sodium phosphate and sodium hydrogen phosphate; Preferably, the mass ratio of the heteroatom doping auxiliary agent to the iridium source is 0.5 to 4:1; Or, in step (1), the microstructure control aid is selected from a surfactant, preferably one or more of polyvinyl pyrrolidone, hexadecyltrimethylammonium bromide, sodium dodecylsulfonate, and hexadecyltrimethylammonium chloride; Preferably, the mass ratio of the microstructure control additive to the iridium source is 0.5 to 10:

1.

5. The preparation method according to claim 2, characterized in that: In step (1), the solvent is selected from one or more of N-methylpyrrolidone, petroleum ether, n-heptane and xylene; Preferably, the mass ratio of the solvent to the iridium source is 1 to 10:

1.

6. The preparation method according to claim 2, characterized in that: In step (2), the template salt is selected from one or more of sodium or potassium nitrates, halides, sulfates, acetates, carbonates and bicarbonates; Preferably, the mass ratio of the template salt to the iridium source is 5 to 100:

1.

7. The preparation method according to claim 2, characterized in that: In step (2), the template salt is ground to a specified particle size before use; preferably, the particle size of the template salt is 100 to 10000 nm.

8. The preparation method according to claim 2, characterized in that: In step (3), the temperature of the first heat treatment is 150-500° C., the heat treatment time is 1-3 h, and the heating rate is 3-10° C. / min; Or, in step (3), the temperature of the second heat treatment is 500-900°C, the heat treatment time is 1.5-3h, and the heating rate is 3-10°C / min; Or, in step (4), the atmosphere containing oxygen includes one of air or oxygen; The oxygen-containing atmosphere may also include one or both of ammonia and phosphine gases; Alternatively, in step (4), the temperature of the third heat treatment is 250-600° C., the heat treatment time is 0.5-2 h, and the heating rate is 3-10° C. / min.

9. Use of the two-dimensional porous nanosheet-shaped multi-metal oxide according to claim 1 as an electrocatalytic oxygen production catalyst.

10. The use according to claim 9, characterized in that The two-dimensional porous nanosheet-shaped multi-metal oxide is used as an anode catalyst in a proton exchange membrane electrolyzer.

Images