Cobalt-based high-density monatomic catalyst for acidic electrolyzed water as well as preparation method and application of cobalt-based high-density monatomic catalyst

Abstract

The invention discloses a cobalt-based high-density monatomic catalyst for acidic electrolyzed water as well as a preparation method and application of the cobalt-based high-density monatomic catalyst, and belongs to the technical field of catalysts. The cobalt-based high-density monatomic catalyst comprises a nano cobaltosic oxide carrier and monodispersed iridium monatomic loaded on the carrier, the loading capacity of the iridium single atoms is more than 6wt%, and the density of the iridium single atoms is more than 4 / nm < 2 >. The invention discloses an application of the monatomic catalyst in an electrocatalytic water decomposition reaction. By improving the utilization rate and the loading density of single atoms, the catalyst has high activity and high stability in an electro-catalytic water decomposition reaction. In addition, the cobalt-based high-density monatomic catalyst is convenient to synthesize and low in cost, and has huge potential in industrial application.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalysts, in particular to a cobalt-based high-density single-atom catalyst and a preparation method and application thereof, in particular to an Ir1 / Co3O4 ultra-high-density single-atom catalyst for acidic water electrolysis and a preparation method and application thereof. BACKGROUND

[0002] An acidic proton exchange membrane water electrolyzer mainly comprises an anode, a cathode and a proton exchange membrane. It has outstanding advantages such as compact structure and excellent hydrogen production purity, and has become a green hydrogen production technology route with great development potential. In this technology system, the oxygen evolution reaction (OER) as a core link, due to the slow kinetics process, causes a large overpotential in the reaction process, which is the key bottleneck restricting the performance improvement of the electrolyzer. At the same time, the acidic electrolysis environment can cause the activity decline and structure instability of the anode catalyst. This negative effect greatly hinders the large-scale promotion and application of the acidic proton exchange membrane water electrolyzer. Among the existing commonly used catalysts, iridium-based oxides exhibit high OER activity in acidic environments and should be the ideal choice. However, the high cost and scarcity of the noble metal iridium (Ir) act as an insurmountable gap, making it difficult for such catalysts to achieve large-scale application. Therefore, developing an acidic proton exchange membrane water electrolyzer catalyst with high activity and low noble metal content has become a key to promoting the practicality and scalability of this technology.

[0003] Single-atom catalysts are a kind of anode catalysts with great potential and have attracted much attention in the field of electrocatalysis. In the single-atom catalyst system, isolated atoms usually act as single active sites to catalyze the oxygen evolution reaction (OER). However, due to the limitation of this "unit point" catalytic mode, the activity of the oxygen evolution reaction is often difficult to break through the established proportionality limit, resulting in an obvious upper limit of its catalytic performance. Therefore, constructing near-neighbor sites by adjusting the density of single atoms has become an innovative strategy to improve the oxygen evolution performance of single-atom catalysts. In the near-neighbor site system, each site can act as an active center for adsorbing oxygen evolution reaction intermediates. This unique structural characteristic promotes a fundamental change in the reaction mechanism - from the traditional adsorption evolution mechanism (AEM) to the oxide path mechanism (OPM), thereby successfully breaking through the proportionality limit and significantly improving the catalytic performance of the oxygen evolution reaction. However, how to change the density of single atoms, optimize the structural design of near-neighbor sites, and maximize the synergistic effect between sites has become the key to further improving the oxygen evolution performance of single-atom catalysts. SUMMARY

[0004] Based on the development of the background art and existing problems, the present application provides a cobalt-based high-density single-atom catalyst and a preparation method and application thereof. The cobalt-based single-atom catalyst is applied in an electrochemical oxygen evolution reaction, has high activity, and good catalytic stability.

[0005] The present application provides a cobalt-based high-density monatomic catalyst, comprising a nano-cobalt tetroxide carrier and monodispersed iridium monatomic atoms loaded on the carrier; the loading amount of the iridium monatomic atoms is more than 6wt%, and the density of the iridium monatomic atoms is 4 / nm 2 The above.

[0006] Preferably, the loading amount of the iridium monatomic atoms is 10-20wt%, preferably 15-18wt%; and the density of the iridium monatomic atoms is 5-10 / nm 2 .

[0007] The present application provides a preparation method of a cobalt-based high-density monatomic catalyst, comprising the following steps:

[0008] Dissolving ZIF-67 in a mixed solution of methanol and water to obtain a ZIF-67 solution;

[0009] Injecting an iridium source aqueous solution into the ZIF-67 solution in proportion, and performing an ion exchange reaction under stirring to obtain a reaction sample; the mass ratio of the ZIF-67 to the iridium source is 99-101: 18-37;

[0010] The reaction sample is sequentially subjected to sample washing, separation, drying and calcination to obtain a cobalt-based high-density monatomic catalyst loaded with monodispersed iridium.

[0011] Preferably, the mass-volume ratio of the ZIF-67 to water is 4-5mg: 1-2mL, and the volume ratio of the water to methanol is 3.5-4: 0.5-1.

[0012] Preferably, the mass ratio of the ZIF-67 to the iridium source is 99-101: 36-37, and the iridium source is selected from chloroiridic acid.

[0013] Preferably, the speed of injecting the iridium source aqueous solution into the ZIF-67 solution is 5-6mL / h.

[0014] Preferably, the ion exchange reaction is performed at room temperature, and the reaction time under stirring is 3-5 days.

[0015] Preferably, the sample washing and separation comprise: washing the reaction sample with ethanol for 3-5 times, and centrifuging at a rotation speed of 10000-11000r / min for 3-5min.

[0016] Preferably, the drying is freeze-drying; the calcination is performed in air, the temperature of the calcination is 340-360℃, the heating rate is 5-10℃ / min, and the time is 2-3h.

[0017] The application provides application of a monatomic catalyst in an electrocatalytic water decomposition reaction, the monatomic catalyst being a cobalt-based high-density monatomic catalyst or a cobalt-based high-density monatomic catalyst obtained by the preparation method.

[0018] The application can load iridium monatomic atoms on a nano cobalt tetroxide (nano Co3O4) carrier uniformly, monodispersely and highly densely, thereby constructing a novel cobalt-based high-density monatomic catalyst, which can be expressed as Ir1 / Co3O4. The catalyst enhances the synergistic efficiency between adjacent sites and combines the high atomic utilization rate advantage of monatomic atoms on a substrate, so that the cobalt-based high-density monatomic catalyst exhibits excellent catalytic activity and stability in the electrocatalytic water decomposition reaction. At the same time, the catalyst not only significantly improves the atomic utilization rate, but also optimizes the spatial structure of adjacent sites. Therefore, the Ir1 / Co3O4 high-density monatomic catalyst and the preparation method thereof have far-reaching scientific significance and practical application value for promoting the efficient electrocatalytic water decomposition reaction. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a transmission electron microscope image of the Ir1 / Co3O4 high-density monatomic catalyst obtained in Example 1 of the application;

[0020] Figure 2 It is an X-ray electron diffraction image of the Ir1 / Co3O4 high-density monatomic catalyst obtained in Example 1 of the application;

[0021] Figure 3 It is a scanning transmission electron microscope high-angle annular dark field image and element distribution given by an energy spectrum of the Ir1 / Co3O4 high-density monatomic catalyst obtained in Example 1 of the application, including: (a) a scanning transmission electron microscope high-angle annular dark field image and (b) an element distribution of the Ir1 / Co3O4 high-density monatomic catalyst;

[0022] Figure 4 It is a transmission electron microscope image of the high-density monatomic catalyst of Examples 1-2 of the application;

[0023] Figure 5 It is a polarization curve of the electrocatalytic water decomposition reaction of the Ir1 / Co3O4 high-density monatomic catalyst obtained in Examples 1-2 of the application and a comparison with Co3O4 catalyst and the like;

[0024] Figure 6 It is a constant current mode stability comparison curve of the electrocatalytic water decomposition reaction of the Ir1 / Co3O4 high-density monatomic catalyst obtained in Example 1 of the application. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0026] The present application provides a cobalt-based high-density single-atom catalyst, comprising a nano-tricobalt tetraoxide carrier and single-atom iridium loaded on the carrier; the loading amount of the single-atom iridium is more than 6wt%, and the density of the single-atom iridium is 4 / nm 2 The present application provides a cobalt-based high-density single-atom catalyst, comprising a nano-tricobalt tetraoxide carrier and single-atom iridium loaded on the carrier; the loading amount of the single-atom iridium is more than 6wt%, and the density of the single-atom iridium is 4 / nm

[0027] The cobalt-based single-atom catalyst provided by the present application has high activity and good catalytic stability when applied in an electrochemical oxygen evolution reaction.

[0028] The cobalt-based single-atom catalyst provided by the present application has high activity and good catalytic stability when applied in an electrochemical oxygen evolution reaction.

[0029] The loading amount of the single-atom iridium in the nano-Co3O4 carrier is more than 6wt%, which can be 10-20wt%, and is preferably 15-18wt%. The density of the single-atom iridium is 4 / nm 2 The present application provides a cobalt-based high-density single-atom catalyst, comprising a nano-tricobalt tetraoxide carrier and single-atom iridium loaded on the carrier; the loading amount of the single-atom iridium is more than 6wt%, and the density of the single-atom iridium is 4 / nm 2 .

[0030] The loading amount of the single-atom iridium in the nano-Co3O4 carrier is more than 6wt%, which can be 10-20wt%, and is preferably 15-18wt%. The density of the single-atom iridium is 4 / nm 2 ; the catalyst can be referred to as an Ir1 / Co3O4 ultra-high-density single-atom catalyst, or an ultra-high-density single-atom catalyst for electrocatalytic water splitting, etc.

[0031] The single-atom density in the traditional single-atom catalyst is low, and the catalyst reaction synergistic effect is mainly achieved through the interaction between the single atom and the carrier (for example, the interaction between the Ir-Co pairs in 4.6%-Ir1 / Co3O4 when the single-atom density is low; the loading amount of the Ir single atom in the Co3O4 carrier is generally 3.5-5.0wt%, and the density of the Ir single atom is 2.0-3.0 / nm 2 ).

[0032] In some embodiments, the Ir single-atom density of the cobalt-based high-density single-atom catalyst is 6.0-7.0 / nm 2The loading of Ir single atoms in the support is 10.5~12.0 wt%. In some preferred embodiments of this application, the ultra-high density single-atom catalyst can be represented as 17.4%-Ir1 / Co3O4. By controlling the loading of single-atom Ir, an ultra-high density distribution of Ir single atoms (e.g., 9.7 atoms / nm) is achieved. 2 This exceeds the single-atom loading of most existing single-atom catalysts. Simultaneously, it forms numerous Ir-Ir adjacent pairs, which is beneficial for synergistic catalysis and improves catalyst activity, primarily targeting applications in acidic water electrolysis.

[0033] Accordingly, the present invention provides a method for preparing a cobalt-based high-density single-atom catalyst, comprising the following steps:

[0034] ZIF-67 was dissolved in a mixture of methanol and water to obtain a ZIF-67 solution.

[0035] An aqueous solution of iridium source was injected into the ZIF-67 solution in a certain proportion, and an ion exchange reaction was carried out under stirring to obtain a reaction sample; the mass ratio of ZIF-67 to iridium source was 99~101:18~37.

[0036] The reaction sample was sequentially washed, separated, dried, and calcined to obtain a cobalt-based high-density single-atom catalyst supported on monodisperse iridium.

[0037] In this embodiment of the invention, a certain proportion of ZIF-67 can be dissolved in a mixed solution of methanol and water to obtain a ZIF-67 solution. ZIF-67 is a cobalt-based zeolite imidazole ester framework material composed of cobalt ions (Co... 2+ It coordinates with 2-methylimidazole ligands to form a three-dimensional network structure, belonging to the cubic crystal system; its molecular weight is approximately 223.14. ZIF-67 described in this application can be a commercially available product; its preparation can be carried out according to methods well known to those skilled in the art, for example, dissolving cobalt nitrate hexahydrate and hexadecyltrimethylammonium bromide in deionized water, then pouring the solution into deionized water containing dimethylimidazole, stirring thoroughly for 12 hours, washing the resulting sample five times by centrifugation with ethanol, and vacuum drying for 24 hours to obtain ZIF-67.

[0038] In a preferred embodiment of the present invention, the mass-to-volume ratio of ZIF-67 to water is 4~5 mg: 1~2 mL, and the volume ratio of water to methanol is 3.5~4: 0.5~1. The water is generally deionized water.

[0039] In this embodiment of the invention, an aqueous solution of iridium source is also prepared: the iridium source can be dissolved in deionized water; the iridium source is preferably chloroiridium acid, and its mass-to-volume ratio with deionized water can be 36~37 mg: 15 mL.

[0040] In a specific embodiment of the present invention, the iridium source aqueous solution can be injected into the ZIF-67 solution above for reaction; after thorough stirring and reaction, the resulting sample is washed, separated, dried and calcined to obtain the Ir1 / Co3O4 ultra-high density single-atom catalyst.

[0041] Preferably, the mass ratio of ZIF-67 to the iridium source is 99~101:36~37. The injection is performed by pushing the solution into the ZIF-67 solution using a syringe, with the iridium source aqueous solution being injected into the ZIF-67 solution at a rate of 5~6 mL / h, more preferably 5~5.5 mL / h. The reaction is an ion exchange reaction, generally carried out at room temperature, and the reaction time can be 3~5 days with stirring.

[0042] After obtaining the reaction sample, the embodiments of the present invention perform washing and separation. Specifically, the sample can be washed with ethanol 3-5 times and centrifuged at 10,000-11,000 rpm for 3-5 minutes. More preferably, the obtained reaction sample is washed with ethanol five times and centrifuged at 11,000 rpm for 4 minutes.

[0043] In a preferred embodiment of the present invention, the sample obtained by centrifugation is vacuum freeze-dried. After drying for 24 hours, it can be calcined in air for 2 to 3 hours. The calcination temperature is preferably 340 to 360°C, and more preferably 350 to 360°C. The heating rate is preferably 5 to 10°C / min, and more preferably 5 to 6°C / min, thereby obtaining the cobalt-based high-density single-atom catalyst.

[0044] In traditional techniques, isolated single atoms often possess high surface energy, making them prone to aggregation on the support surface. To avoid aggregation, the density of single atoms on the metal oxide surface is typically low, and the distance between neighboring single atoms is relatively large. As the density of single atoms increases, the distance between neighboring single atoms decreases, and the probability of atomic migration and aggregation during the preparation process increases accordingly.

[0045] This invention presents a strategy for ion exchange-assisted structural transformation of metal-organic frameworks (MOFs), successfully achieving the precise construction of ultra-high-density single-atom catalysts. The core of this strategy lies in cleverly utilizing the inherent structural instability of MOFs in aqueous solutions. Through slow ion exchange between target metal Ir ions and MOF (ZIF-67) framework ions, a gradual structural transformation of the MOF framework is induced. This ion exchange-assisted structural transformation process enables the layer-by-layer, controllable embedding of target metal atoms into the support. This "conversion-while-embedding" approach effectively suppresses the migration and aggregation of metal atoms during introduction and transformation, thereby achieving the controllable preparation of ultra-high-density single-atom catalysts.

[0046] The present invention also provides an application of a single-atom catalyst in the electrocatalytic water splitting reaction, wherein the single-atom catalyst is the cobalt-based high-density single-atom catalyst described above, or the cobalt-based high-density single-atom catalyst obtained by the preparation method described above.

[0047] In this invention, the cobalt-based high-density single-atom catalyst can be prepared into a catalyst solution, then applied to a substrate, and subsequently assembled into an electrocatalytic water splitting device. Some embodiments involve electrocatalytic measurements using a standard three-electrode system at room temperature. A titanium felt loaded with the prepared catalyst is used as the working electrode, and the mass loading of the catalyst on the titanium felt can be 1-2 mg·cm³. -2 A platinum wire was used as the counter electrode, and a mercury / mercuric sulfate electrode was used as the reference electrode. Specifically, in a 0.1 M perchloric acid (HClO4) electrolyte, linear sweep voltammetry was used within a potential range of 1.1 to 1.7 V, at a rate of 5 mV·s. -1 The polarization curves of the oxygen evolution reaction (OER) were obtained at a scan rate of 50 mA·cm⁻¹. -2 Durability tests were conducted.

[0048] In an acidic environment, the Ir1 / Co3O4 ultra-high density single-atom catalyst of some embodiments of the present invention electrocatalytically splits water at 10 mA·cm⁻¹. -2 The operating voltage under current density conditions is only 0.25V, and the required overpotential is reduced by 140mV compared to the Co3O4 catalyst. In particular, this Ir1 / Co3O4 ultra-high density single-atom catalyst operates at 50mA·cm⁻¹. -2 Under the specified current density conditions, stability was achieved for continuous operation for 2200 hours. This invention, by improving the utilization rate and loading density of specific single atoms, exhibits high activity and stability in the electrocatalytic water splitting reaction. It is convenient to synthesize, low in cost, and has great potential for industrial application.

[0049] To better understand the technical content of this invention, specific embodiments are provided below to further illustrate the invention. The substances used in these embodiments can be purchased commercially or prepared; specifically, cobalt nitrate hexahydrate and hexadecyltrimethylammonium bromide are dissolved in deionized water, then poured into deionized water containing dimethylimidazole, and stirred thoroughly for 12 hours. The resulting sample is washed five times by centrifugation with ethanol and vacuum dried for 24 hours to obtain ZIF-67.

[0050] Comparative Example 1

[0051] This comparative example presents a method for preparing two-dimensional Co3O4 nanosheets, comprising the following steps: dissolving 100 mg ZIF-67 in a mixed solution of 10 ml methanol and 40 ml deionized water, stirring thoroughly for 4 days, washing the resulting sample 5 times with ethanol, centrifuging at 11000 rpm for 4 minutes, vacuum drying the centrifuged sample for 24 hours, and then calcining it in air at 350 °C for 2 hours to obtain two-dimensional Co3O4 nanosheets.

[0052] Comparative Example 2

[0053] This comparative example presents a method for preparing an Ir1 / Co3O4 single-atom catalyst, comprising the following steps: dissolving 100 mg of ZIF-67 in a mixed solution of 10 ml methanol and 40 ml deionized water to obtain a ZIF-67 solution; dissolving 50 μl of 0.45 M chloroiridium acid in 20 ml deionized water, and injecting 15 ml of the solution into the above ZIF-67 methanol-water solution at a rate of 5 ml / h, and stirring thoroughly for 4 days. The resulting sample was washed 5 times with ethanol, centrifuged at 11000 rpm for 4 minutes, and then vacuum-dried for 24 hours, followed by calcination in air at 350 °C for 2 hours to obtain a 4.6%-Ir1 / Co3O4 single-atom catalyst with a low single-atom density.

[0054] Testing revealed that the mass fraction of Ir atoms in the obtained 4.6%-Ir1 / Co3O4 single-atom catalyst was 4.6%, and the density of Ir single atoms was 2.7 atoms / nm. 2 .

[0055] Example 1

[0056] This embodiment proposes a method for preparing an Ir1 / Co3O4 ultra-high density single-atom catalyst, including the following steps:

[0057] 100 mg of ZIF-67 was dissolved in a mixture of 10 ml of methanol and 40 ml of deionized water to obtain a ZIF-67 methanol-water solution. 200 μl of 0.45 M chloroiridium acid was dissolved in 20 ml of deionized water, and 15 ml of this solution was added to the ZIF-67 methanol-water solution at a rate of 5 ml / hour. The mixture was stirred thoroughly and reacted for 4 days. The resulting sample was washed five times with ethanol, centrifuged at 11000 rpm for 4 minutes, and then vacuum-dried for 24 hours. Finally, it was calcined in air at 350 °C for 2 hours to obtain the Ir1 / Co3O4 ultra-high density single-atom catalyst.

[0058] Testing revealed that the Ir1 / Co3O4 ultra-high density single-atom catalyst contained 17.4% Ir atoms by mass, with a density of 9.7 Ir atoms / nm. 2 .

[0059] The transmission electron microscope image of the Ir1 / Co3O4 ultra-high density single-atom catalyst prepared in this embodiment is as follows: Figure 1 As shown, the X-ray electron diffraction image is as follows: Figure 2 As shown, the elemental distribution given by the high-angle annular dark-field image and its energy spectrum from a scanning transmission electron microscope is as follows: Figure 3 As shown in the figure, the characteristic peaks of the 17.4%-Ir1 / Co3O4 sample are consistent with the structure of Co3O4 (PDF card number #25-0270), indicating that no iridium (Ir)-based metals or metal oxides were detected. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images of the 17.4%-Ir1 / Co3O4 sample show numerous isolated bright spots against the Co3O4 support background, confirming that iridium species exist in an atomically dispersed form. Furthermore, energy-dispersive X-ray (EDX) elemental mapping results indicate that Co, O, and Ir species are uniformly distributed in the 17.4%-Ir1 / Co3O4 sample.

[0060] Example 2

[0061] Preparation of 11.4%-Ir1 / Co3O4 single-atom catalyst:

[0062] 100 mg of ZIF-67 was dissolved in a mixture of 10 ml of methanol and 40 ml of deionized water to obtain a ZIF-67 methanol-water solution. 100 μl of 0.45 M chloroiridium acid was dissolved in 20 ml of deionized water, and 15 ml of this solution was added to the ZIF-67 methanol-water solution at a rate of 5 ml / hour. The mixture was stirred thoroughly and reacted for 4 days. The resulting sample was washed five times with ethanol, centrifuged at 11,000 rpm for 4 minutes, and then vacuum-dried for 24 hours. Afterward, it was calcined in air at 350 °C for 2 hours to obtain an 11.4%-Ir1 / Co3O4 single-atom catalyst.

[0063] Testing revealed that the mass fraction of Ir atoms in the obtained 11.4%-Ir1 / Co3O4 single-atom catalyst was 11.4%, and the density of Ir single atoms was 6.5 atoms / nm. 2 Furthermore, the transmission electron microscope image of the single-atom catalyst prepared in this embodiment is shown below. Figure 4 .

[0064] Figure 4 Transmission electron microscopy (TEM) images showed that the prepared low-density 4.6%-Ir1 / Co3O4, 11.4%-Ir1 / Co3O4 and ultra-high-density 17.4%-Ir1 / Co3O4 samples all exhibited morphological characteristics similar to those of the Co3O4 support, and all had the morphology of nanosheets.

[0065] Experimental test case

[0066] Performance evaluation of Ir1 / Co3O4 ultra-high density single-atom catalyst at room temperature:

[0067] 5 mg of the Ir1 / Co3O4 high-density single-atom catalyst obtained in Examples 1 and 2, and 20 μl of Nafion solution were dispersed in a mixed solution of 0.5 ml ethanol and 0.5 ml deionized water, and sonicated for 2 hours to obtain a homogeneous solution. Then, the above solution was dropped onto a 2 cm² titanium felt, and 0.5 cm² of the above titanium felt was used as the working electrode, the mercurous sulfate electrode as the reference electrode, and the platinum wire electrode as the counter electrode. The electrolyte solution was a 0.1 M perchloric acid solution.

[0068] Within the potential range of 1.1~1.7V, at a rate of 5mV·s -1 Linear voltammetric scans were performed at a scanning speed to obtain polarization curves, with a solution ohmic drop compensation of 5.5 Ω; similarly, in the same system, 50 mA·cm⁻¹ was applied in constant current mode. -2 Current density was measured, and the change in operating voltage over time was recorded. The test duration was 2200 hours, and the solution ohmic drop compensation was 5.5Ω.

[0069] The polarization curves of the Ir1 / Co3O4 high-density single-atom catalyst in the electrocatalytic water splitting reaction, and comparisons with the Co3O4 catalyst of Comparative Example 1 and the 4.6%-Ir1 / Co3O4 catalyst of Comparative Example 2, are shown below. Figure 5 As shown, the stability test curve of the electrocatalytic water splitting reaction of this ultra-high density single-atom catalyst is also shown. Figure 6 As shown. (Refer to...) Figure 5 and Figure 6 17.4% -Ir1 / Co3O4 at 10 mA·cm -2 The overpotential required is only 250 mV, which is 90 mV lower than that of the low-density 4.6%-Ir1 / Co3O4 and 30 mV lower than that of 11.4%-Ir1 / Co3O4; this indicates that the ultra-high density single-atom catalyst of this invention has excellent acidic OER activity. It also exhibits excellent stability; the 17.4%-Ir1 / Co3O4 exhibits good stability at 50 mA·cm⁻¹. -2 It operated stably for 2200 hours. This demonstrates that, in terms of both activity and stability, this cobalt-based high-density single-atom catalyst outperforms the vast majority of cobalt-based acidic OER catalysts currently in use.

[0070] As demonstrated by the above embodiments, the Ir1 / Co3O4 ultra-high-density single-atom catalyst obtained by this invention exhibits excellent catalytic activity and stability in the electrocatalytic water splitting reaction. Furthermore, this invention is convenient to synthesize, low in cost, and conducive to industrial application. By improving the utilization rate and loading density of single atoms, this invention achieves high activity and high stability in the electrocatalytic water splitting reaction. The cobalt-based high-density single-atom catalyst is convenient to synthesize, low in cost, and has great potential for industrial application.

[0071] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A cobalt-based high-density single-atom catalyst, characterized in that, The mixture includes a nano-cobalt tetroxide support and monodisperse iridium single atoms loaded on the support; the loading of the iridium single atoms is above 6 wt%, and the density of the iridium single atoms is 4 atoms / nm. 2 above.

2. The cobalt-based high-density single-atom catalyst according to claim 1, characterized in that, The loading of the iridium single atoms is 10-20 wt%, preferably 15-18 wt%; the density of the iridium single atoms is 5-10 atoms / nm. 2 .

3. A method for preparing a cobalt-based high-density single-atom catalyst, characterized in that, Includes the following steps: ZIF-67 was dissolved in a mixture of methanol and water to obtain a ZIF-67 solution. An aqueous solution of iridium source was injected into the ZIF-67 solution in a certain proportion, and an ion exchange reaction was carried out under stirring to obtain a reaction sample; the mass ratio of ZIF-67 to iridium source was 99~101:18~37. The reaction sample was sequentially washed, separated, dried, and calcined to obtain a cobalt-based high-density single-atom catalyst supported on monodisperse iridium.

4. The preparation method according to claim 3, characterized in that, The mass-to-volume ratio of ZIF-67 to water is 4~5 mg: 1~2 mL, and the volume ratio of water to methanol is 3.5~4: 0.5~1.

5. The preparation method according to claim 4, characterized in that, The mass ratio of ZIF-67 to the iridium source is 99~101:36~37, and the iridium source is selected from chloroiridium acid.

6. The preparation method according to any one of claims 3-5, characterized in that, The iridium source aqueous solution is injected into the ZIF-67 solution at a rate of 5~6 mL / h.

7. The preparation method according to claim 6, characterized in that, The ion exchange reaction is carried out at room temperature, and the reaction time is 3 to 5 days with stirring.

8. The preparation method according to claim 7, characterized in that, The washing and separation process includes: washing the reaction sample with ethanol 3-5 times, centrifuging at 10,000-11,000 rpm for 3-5 minutes.

9. The preparation method according to claim 8, characterized in that, The drying is freeze drying; the calcination is carried out in air at a temperature of 340~360℃, a heating rate of 5~10℃ / min, and a time of 2~3h.

10. The application of a single-atom catalyst in the electrocatalytic water splitting reaction, characterized in that, The single-atom catalyst is the cobalt-based high-density single-atom catalyst according to any one of claims 1-2, or the cobalt-based high-density single-atom catalyst obtained by the preparation method according to any one of claims 3-9.

Images