Cobalt monatomic electrocatalyst and preparation and application thereof

Abstract

The invention discloses a cobalt monatomic electrocatalyst as well as preparation and application thereof. According to the catalyst, raw powder mesoporous silica with a template agent is used as a carrier, an active component cobalt salt metal precursor is introduced through solid-phase grinding, carbon and active metal atoms are coordinated in the high-temperature activation process, and active sites are anchored on the carrier. The monatomic catalyst provided by the invention has highly dispersed active sites, and the utilization efficiency and catalytic activity of metal sites are greatly improved. In electro-catalysis OER, the catalyst shows excellent catalytic activity and stability. The research opens up a new way for simply and efficiently synthesizing a monatomic functional material, and provides guidance for manufacturing a high-performance OER catalyst by using non-noble metal.

Description

Technical Field

[0001] The present invention relates to an electrocatalyst and its preparation and application, in particular to a cobalt-containing single-atom electrocatalyst with highly dispersed active sites and its preparation and application, belonging to the technical field of industrial catalysis. Background Art

[0002] The electrocatalytic oxygen evolution reaction (OER) is a key step in hydrogen production from water electrolysis and is of great significance for the production and storage of clean energy. The electrocatalytic decomposition of water involves the oxygen evolution reaction (OER) at the anode and the hydrogen evolution reaction (HER) at the cathode. Because the anodic OER in water electrolysis is a hysteretic chemical process involving four-electron transfer, a high overpotential is typically required to drive the reaction, resulting in significant energy loss. To improve the catalytic activity and stability of the OER, researchers have developed a variety of catalysts, among which single-atom catalysts have attracted widespread attention due to their unique electronic structure and high atomic utilization. Currently, the most promising OER catalysts are the precious metals iridium and ruthenium, but their high cost and material scarcity preclude their large-scale application. Cobalt (Co), an inexpensive and abundant transition metal, has been shown to exhibit excellent catalytic performance in the OER. However, conventional Co-based catalysts often suffer from issues such as uneven active sites and poor stability. Therefore, the development of efficient Co single-atom catalysts has become a research hotspot. Summary of the Invention

[0003] The present invention aims to address the deficiencies of the prior art by providing a method for preparing a cobalt single-atom electrocatalyst with high oxygen evolution performance. Another object of the present invention is to provide a catalyst produced by the above-mentioned preparation method. Yet another object of the present invention is to provide applications of the above-mentioned catalyst. First, a mesoporous silica support containing a template is synthesized. Then, an active component precursor is introduced into the confined space between the mesoporous silica template and the silicon wall through solid grinding. During a high-temperature treatment process, the template is converted to form a carbon layer, which interacts with the metal, ultimately yielding a cobalt single-atom catalyst. This catalyst exhibits high activity and stability in the electrocatalytic oxygen evolution reaction.

[0004] The technical solution of the present invention is as follows: the precious metal catalysts (such as iridium and ruthenium) currently used in OER are expensive and have limited resources, making it difficult to meet the needs of large-scale applications; the stability is poor during long-term operation, which easily leads to performance degradation; the environmental impact is large, and the mining and processing processes have a significant negative impact on the environment. The present invention designs a cobalt-containing single-atom electrocatalyst with highly dispersed active sites. The limited threshold space between the mesoporous silica wall and the template and the carbon layer formed in situ at high temperature form a strong interaction with the metal, enhancing the interaction between the cobalt site and the carrier, thereby stabilizing the dispersed state of the single atom in the carrier, preventing the migration and agglomeration of the active sites, and reducing the loss of active sites during recycling.

[0005] The specific technical solution of the present invention is: a method for preparing a cobalt single-atom electrocatalyst, the specific steps of which are as follows:

[0006] First, the carrier raw powder mesoporous silica and the active component metal precursor cobalt salt are weighed and placed in a mortar, and fully ground at room temperature to allow the metal precursor to enter the pores of the raw powder mesoporous silica; then heat treated in a protective atmosphere, and after cooling, a cobalt single atom catalyst is obtained.

[0007] The preferred raw powder mesoporous silica SBA-15 carrier is prepared according to patent CN202011552071.4.

[0008] Preferably, the metal precursor cobalt salt is cobalt nitrate or cobalt acetate; wherein the mass content of the active component in the carrier is 5% to 10%.

[0009] Preferably, the grinding time is 0.5-0.8h, grinding to 200-300 mesh; the heat treatment temperature is 650-900°C, the heat treatment time is 2-5h; and cooling to 20-30°C.

[0010] Preferably, the protective atmosphere is argon.

[0011] The present invention also provides a single-atom cobalt catalyst prepared by the above-mentioned method. Using mesoporous silica in the presence of a template as a carrier, an active component precursor is introduced into the confined space between the silicon wall and the template through solid-phase grinding. High-temperature treatment forms an in-situ carbon layer while simultaneously anchoring the metal, resulting in a cobalt single-atom electrocatalyst with high oxygen evolution performance, wherein the active component is a single cobalt atom.

[0012] The present invention also provides the use of the above-mentioned single-atom cobalt catalyst in the electrocatalytic oxygen evolution reaction. The specific steps are as follows: dispersing the catalyst into a uniform slurry solution, taking the catalyst slurry solution and dripping it onto the carbon cloth, with the catalyst loading amount being 0.4 to 1.1 mg / cm 2 After the slurry is completely dried, it is used as a working electrode, a platinum electrode is selected as a counter electrode, a mercury / mercuric oxide electrode is selected as a reference electrode, and the electrolyte is a 1-3 mol / L potassium hydroxide KOH solution for electrocatalytic oxygen evolution reaction.

[0013] The preferred method for preparing the slurry solution is as follows: take the prepared cobalt single-atom catalyst, add a mixed solution of ethanol and Nafion (5wt%), the volume ratio of the two being 6 to 10:1, and obtain a catalyst slurry solution after uniform dispersion by ultrasonication; wherein the concentration of the catalyst in the slurry solution is 20 to 55 mg / mL.

[0014] The activity of the catalysts was evaluated by linear sweep voltammetry (LSV), and the stability of the catalysts was evaluated by the relationship between current and time (it) at a constant voltage.

[0015] Beneficial Effects: The cobalt single-atom electrocatalyst described in this invention is a novel single-atom catalyst that is highly dispersed and exhibits excellent cyclic stability. By solid-phase grinding, the active component precursor is introduced into the threshold space between the template and the silicon wall. While the carbon layer is formed in situ at high temperatures, it also anchors the metal, resulting in a cobalt single-atom electrocatalyst with high oxygen evolution performance. This has the following advantages:

[0016] (1) High activity: Cobalt single atoms are uniformly dispersed on the mesoporous silica support with a carbon layer, forming abundant active sites and significantly improving the catalytic activity of OER.

[0017] (2) High stability: The mesoporous silica carrier with a carbon layer has good electrical conductivity and chemical stability. Its limited threshold space effectively prevents the aggregation and loss of cobalt atoms, ensuring the long-term stability of the catalyst.

[0018] (3) Low cost: Cobalt is a low-cost, abundant transition metal that has a lower cost advantage than precious metal catalysts.

[0019] (4) Simple preparation: The preparation method is simple, easy to produce on a large scale, and suitable for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 (A) and (B) are respectively a transmission electron microscope image and a spherical aberration-corrected high-angle annular dark-field scanning electron microscope image of the sample of Example 1 of the present invention. DETAILED DESCRIPTION

[0021] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with specific embodiments.

[0022] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0023] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0024] Example 1:

[0025] (1) A method for obtaining a raw powder mesoporous silica SBA-15 carrier, referring to Example 1 in patent CN112791693B, raw powder SBA-15, denoted as TOS.

[0026] (2) Weigh 0.01 g of Co(NO3)2·6H2O and 0.2 g of TOS into a mortar and grind them into 200 mesh at room temperature for 0.5 h to allow the Co(NO3)2·6H2O precursor salt to enter the pores of SBA-15. Then, heat treat at 650 °C in an argon atmosphere for 2 h to obtain a single-atom catalyst (sample 1-1). Figure 1 (A) is a transmission electron micrograph of the sample, in which no aggregation of nanoparticles is observed. Figure 1 (B) is an electron micrograph of the sample with spherical aberration. The bright spots circled in red represent individual iron atoms, visually demonstrating the successful synthesis of the single-atom catalyst. For comparison purposes, Co(NO₃)₂·6H₂O and TFS were ground and calcined using the same procedure to produce Comparative Samples 1-2.

[0027] (3) Take 0.01g of the catalyst prepared above and add it to a mixed solution of 0.45mL of ethanol and 50μL of Nafion (5wt%). After ultrasonic dispersion for 1h, a uniform catalyst slurry solution is obtained. Take 5μL of the slurry and drop it into a 0.25cm 2 After the slurry was completely dried, it was used as a working electrode with a catalyst loading of 0.4 mg / cm 2 A platinum electrode was selected as the counter electrode, a mercury / mercuric oxide electrode was selected as the reference electrode, and a 1 mol / L potassium hydroxide (KOH) solution was used as the electrolyte. An electrochemical workstation was used to record the linear polarization curve of the working electrode obtained at a scan rate of 10 mV / s in a three-electrode electrolytic cell. In this example, the electrocatalyst sample 1-1 was tested at a scan rate of 10 mA / cm 2 The overpotential required for the working current density is 260mV. 2 The current of sample 1-2 electrocatalyst can maintain 97% of the initial working current when tested at the actual working potential of 10mA / cm 2 The overpotential required for the working current density is 460mV. 2 After testing for 24 hours at the actual working potential, the current can maintain 67% of the initial working current.

[0028] Example 2:

[0029] (1) TOS was prepared according to the preparation method of Example 1.

[0030] (2) 0.02 g of Co(CH3COO)2 and 0.2 g of TOS were weighed and placed in a mortar. Solid-phase grinding was performed at room temperature for 0.6 h to a 250-mesh size, allowing the Co(CH3COO)2 precursor salt to enter the pores of SBA-15. The catalyst was then heat-treated at 700°C for 3 h in an argon atmosphere to obtain a single-atom catalyst (Sample 2-1). For comparison purposes, Co(CH3COO)2 and TFS were ground and calcined using the same procedure to obtain Comparative Sample 2-2.

[0031] (3) Take 0.01g of the catalyst prepared above and add it to a mixed solution of 0.3mL of ethanol and 50μL of Nafion (5wt%). After ultrasonic dispersion for 1h, a uniform catalyst slurry solution is obtained. Take 5μL of the slurry and drop it into a 0.25cm 2 After the slurry was completely dried, it was used as a working electrode with a catalyst loading of 0.55 mg / cm 2 A platinum electrode was selected as the counter electrode, a mercury / mercuric oxide electrode was selected as the reference electrode, and a 1 mol / L potassium hydroxide (KOH) solution was used as the electrolyte. An electrochemical workstation was used to record the linear polarization curve of the working electrode obtained at a scan rate of 10 mV / s in a three-electrode electrolytic cell. In this example, the electrocatalyst sample 2-1 was tested at a scan rate of 10 mA / cm 2 The overpotential required for the working current density is 290mV. 2 The current of sample 2-2 electrocatalyst can maintain 95% of the initial working current when tested at the actual working potential of 10mA / cm 2 The overpotential required for the working current density is 360mV. 2 When tested at the actual working potential for 24 hours, the current can maintain 55% of the initial working current.

[0032] Example 3:

[0033] (1) TOS was prepared according to the preparation method of Example 1.

[0034] (2) 0.015 g of Co(NO₃)₂·6H₂O and 0.2 g of TOS were weighed and placed in a mortar. Solid-phase grinding was performed at room temperature for 0.7 h to a 280-mesh size, allowing the Co(NO₃)₂·6H₂O precursor salt to enter the pores of SBA-15. The catalyst was then heat-treated at 800°C for 4 h in an argon atmosphere to obtain a single-atom catalyst (Sample 3-1). For comparison purposes, Co(NO₃)₂·6H₂O and TFS were ground and calcined using the same procedure to obtain Comparative Sample 3-2.

[0035] (3) Take 0.02g of the catalyst prepared above and add it to a mixed solution of 0.35mL of ethanol and 50μL of Nafion (5wt%). After ultrasonic dispersion for 1h, a uniform catalyst slurry solution is obtained. Take 5μL of the slurry and drop it into a 0.25cm 2 After the slurry is completely dried, it is used as a working electrode with a catalyst loading of 1 mg / cm 2 A platinum electrode was selected as the counter electrode, a mercury / mercuric oxide electrode was selected as the reference electrode, and a 2 mol / L potassium hydroxide (KOH) solution was used as the electrolyte. An electrochemical workstation was used to record the linear polarization curve of the working electrode obtained at a scan rate of 10 mV / s in a three-electrode electrolytic cell. In this example, the electrocatalyst sample 3-1 was tested at a scan rate of 10 mA / cm 2 The overpotential required for the working current density is 300mV. 2 The current of sample 3-2 electrocatalyst can maintain 93% of the initial working current at the actual working potential of 10 minutes. 2 The overpotential required for the working current density is 470mV. 2 After testing for 24 hours at the actual working potential, the current can maintain 57% of the initial working current.

[0036] Example 4:

[0037] (1) TOS was prepared according to the preparation method of Example 1.

[0038] (2) 0.01 g of Co(CH3COO)2 and 0.2 g of TOS were weighed and placed in a mortar. Solid-phase grinding was performed at room temperature for 0.8 h to a 300-mesh size, allowing the Co(CH3COO)2 precursor salt to enter the pores of SBA-15. The catalyst was then heat-treated at 900°C in an argon atmosphere for 5 h to obtain a single-atom catalyst (Sample 4-1). For comparison purposes, Co(CH3COO)2 and TFS were ground and calcined using the same procedure to obtain Comparative Sample 4-2.

[0039] (3) Take 0.03g of the catalyst prepared above and add it to a mixed solution of 0.50mL of ethanol and 50μL of Nafion (5wt%). After ultrasonic dispersion for 1h, a uniform catalyst slurry solution is obtained. Take 5μL of the slurry and drop it into a 0.25cm 2 After the slurry was completely dried, it was used as a working electrode with a catalyst loading of 1.08 mg / cm 2A platinum electrode was selected as the counter electrode, a mercury / mercuric oxide electrode was selected as the reference electrode, and a 3 mol / L potassium hydroxide (KOH) solution was used as the electrolyte. An electrochemical workstation was used to record the linear polarization curve of the working electrode obtained at a scan rate of 10 mV / s in a three-electrode electrolytic cell. In this example, the electrocatalyst sample 4-1 was tested at a scan rate of 10 mA / cm 2 The overpotential required for the working current density is 320mV. 2 The current of sample 4-2 electrocatalyst can maintain 90% of the initial working current when tested at the actual working potential of 10mA / cm 2 The overpotential required for the working current density is 450mV. 2 When tested at the actual working potential for 24 hours, the current can maintain 50% of the initial working current.

Claims

1. A method for preparing a cobalt single-atom electrocatalyst, the specific steps of which are as follows: First, the carrier raw powder mesoporous silica and the active component metal precursor cobalt salt are weighed and placed in a mortar and ground to allow the metal precursor to enter the pores of the raw powder mesoporous silica; then heat treated in a protective atmosphere and cooled to obtain a cobalt single atom catalyst.

2. The preparation method according to claim 1, wherein The metal precursor cobalt salt is cobalt nitrate or cobalt acetate; the mass content of the active component metal precursor cobalt salt in the carrier is 5% to 10%.

3. The preparation method according to claim 1, wherein The grinding time is 0.5-0.8h, grinding to 200-300 mesh; the heat treatment temperature is 650-900°C, the heat treatment time is 2-5h; and cooling to 20-30°C.

4. The preparation method according to claim 1, characterized in that The protective atmosphere is argon.

5. A single-atom cobalt catalyst prepared by the method according to claims 1 to 4.

6. Use of the single-atom cobalt catalyst as claimed in claim 5 in an electrocatalytic oxygen evolution reaction.

7. The use according to claim 6, wherein the specific steps are as follows: dispersing the catalyst into a uniform slurry solution, taking the catalyst slurry solution and dropping it onto the carbon cloth, wherein the catalyst loading amount is 0.4 to 1.1 mg / cm 2 After the slurry is completely dried, it is used as a working electrode, a platinum electrode is selected as a counter electrode, a mercury / mercuric oxide electrode is selected as a reference electrode, and the electrolyte is a 1-3 mol / L potassium hydroxide KOH solution for electrocatalytic oxygen evolution reaction.

8. The use according to claim 7, characterized in that The slurry solution is prepared as follows: the prepared cobalt single-atom catalyst is added to a mixed solution of ethanol and Nafion at a volume ratio of 6 to 10:1, and the catalyst slurry solution is obtained after uniform dispersion by ultrasonication; The concentration of the catalyst in the slurry solution is 20-55 mg / mL.

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