Difunctional carbon-based powder monatomic catalyst as well as preparation method and application thereof

Abstract

The invention relates to a difunctional carbon-based powder monatomic catalyst as well as a preparation method and application thereof, the catalyst is prepared by taking carbon-based powder as a conductive substrate, firstly coating the surface of the carbon-based powder with an atomic-scale metal oxide by utilizing an atomic layer deposition technology, and then loading noble metal monatomic. The bifunctional catalyst provided by the invention has excellent OER / ORR performance under a strong alkaline condition, and when the bifunctional catalyst is used as a positive electrode of a zinc-air battery, the whole battery device shows good cycle performance.

Description

Technical Field

[0001] The invention belongs to the technical field of zinc-air batteries, and particularly relates to a bifunctional carbon-based powder single-atom catalyst and a preparation method and application thereof. Background Art

[0002] Zinc-air battery is a new type of metal-air battery with a capacity of 1086Wh kg -1 The high theoretical energy density of Zn / air batteries. Due to its advantages such as high safety and high energy density, it has attracted extensive attention from researchers in recent years. The main electrochemical reactions involved in the positive electrode of zinc-air batteries include oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). The kinetics of these reactions are slow, which seriously limits the operating efficiency of battery devices. Therefore, in order to reduce the reaction overpotential and improve the energy storage / conversion efficiency of the device, it is necessary to further study bifunctional catalyst materials with high OER / ORR activity.

[0003] At present, the main methods for loading nanocatalysts on powder substrate materials include impregnation, hydrothermal, electrochemical, chemical vapor deposition, etc. The impregnation method has poor controllability and it is difficult to control the loading amount; the hydrothermal and electrochemical deposition methods are difficult to control the size of the loaded metal particles; the chemical vapor deposition method has a long process cycle and high preparation cost, which limits its practical application.

[0004] CN111111658B mentions a method of adding a platinum-containing solution to a prepared powder substrate solution, and preparing a Pt single-atom catalyst through a series of methods such as filtering, washing, drying, and reducing atmosphere calcination. The prepared catalyst has high activity and stability. However, the preparation method is complicated, making it difficult to mass produce. CN113996312A discloses a method for preparing an iron-doped magnesium-aluminum spinel-loaded bimetallic catalyst using ALD technology, and the powder material is placed in a planar chamber of the ALD deposition system for deposition, but is limited by the chamber structure design, and it is difficult to uniformly load the metal catalyst on the powder material. Therefore, it is crucial to develop a preparation method for uniformly loading noble metal single atoms on the surface of a carbon-based powder material. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a bifunctional carbon-based powder single-atom catalyst and a preparation method and application thereof. The catalyst has excellent OER / ORR bifunctional catalytic activity under strong alkaline conditions and can be used as a positive electrode material in the field of zinc-air batteries.

[0006] The present invention provides a bifunctional carbon-based powder single-atom catalyst. The catalyst uses carbon-based powder as a conductive substrate, and utilizes atomic layer deposition technology to first coat atomic-level metal oxides on the surface of the carbon-based powder, and then loads noble metal single atoms.

[0007] Preferably, the carbon-based powder material is one or more of carbon nanotubes, graphene, and carbon-nitrogen skeleton materials.

[0008] Preferably, the metal oxide is TiO2.

[0009] Preferably, the noble metal single atom is a platinum atom.

[0010] The present invention also provides a method for preparing a bifunctional carbon-based powder single-atom catalyst, comprising the following steps:

[0011] (1) placing the carbon-based powder into a rotary chamber, rotating and heating it under nitrogen protection, and performing a deposition step after the chamber temperature and pressure reach the set values;

[0012] (2) Pulsing a titanium-containing organic precursor into a rotating chamber to complete atomic-level TiO2 coating by deposition to obtain TiO2 / carbon-based powder;

[0013] (3) Pulsing a platinum-containing organic precursor into a rotating chamber, and completing the loading of platinum atoms by deposition to obtain the bifunctional carbon-based powder single atom catalyst.

[0014] Preferably, the chamber temperature in step (1) is set to 120-250° C., and the chamber pressure is set to 0.01 torr-0.05 torr.

[0015] Preferably, the carrier gas in step (1) is high-purity N2 with a flow rate of 100 to 500 sccm.

[0016] Preferably, the cavity rotation speed in step (1) is 1 to 10 rpm.

[0017] Preferably, the titanium-containing organic precursor in step (2) is tetrakis(dimethylamino)titanium, and the temperature of the precursor cylinder is set to 60-110°C.

[0018] Preferably, the titanium-containing organic precursor in step (2) is pulsed into the chamber until the chamber pressure is 0.5 to 2 torr (preferably 0.5 to 1 torr), and the holding time is 1 to 10 minutes (preferably 1.5 to 4.5 minutes). After the adsorption is completed, high-purity nitrogen is introduced for purging for 1 to 3 minutes.

[0019] Preferably, O3 gas pulses enter the chamber, the chamber pressure is 1 to 3 torr (preferably 1 to 2 torr), the duration is 1 to 10 minutes (preferably 2 to 5 minutes), and high-purity nitrogen is introduced for purging for 1 to 3 minutes.

[0020] Preferably, the platinum-containing organic precursor in step (3) is trimethyl(methylcyclopentadienyl)platinum, and the temperature of the precursor cylinder is set to 70-120° C. (preferably 75-95° C.).

[0021] Preferably, the platinum-containing organic precursor in step (3) is pulsed into the chamber until the chamber pressure is 0.1 to 2 torr (preferably 0.3 to 0.8 torr), the holding time is 1 to 10 minutes (preferably 2 to 6 minutes), and after the adsorption is completed, high-purity nitrogen is introduced for 1 to 3 minutes;

[0022] Preferably, O3 gas pulses enter the chamber, the chamber pressure is 1 to 4 torr (preferably 1.5 to 2.5 torr), and the duration is 1 to 10 minutes (preferably 3 to 8 minutes).

[0023] Preferably, the number of depositions in step (2) is 1-10 cycles; and the number of depositions in step (3) is 1-3 cycles.

[0024] The present invention also provides an application of a bifunctional carbon-based powder single-atom catalyst in lithium-ion batteries, gas catalysis, photoelectrocatalytic hydrogen production or zinc-air batteries.

[0025] Beneficial Effects

[0026] The present invention coats metal oxides on the surface of carbon-based powders, which can effectively reduce the corrosion of alkaline electrolytes on catalysts; the preparation steps are all completed in the chamber of the atomic layer deposition system, the preparation process is controllable and has the potential for large-scale production; the prepared bifunctional catalyst has excellent OER / ORR performance under strong alkaline conditions, and when it is used as the positive electrode of a zinc-air battery, the overall battery device exhibits good cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the SEM image of the bifunctional carbon-based powder single atom catalyst prepared in Example 1.

[0028] Figure 2 This is the mapping diagram of the bifunctional carbon-based powder single atom catalyst prepared in Example 1.

[0029] Figure 3 TEM image and mapping scan image of the bifunctional carbon-based powder single atom catalyst prepared in Example 1.

[0030] Figure 4 ORR performance diagram of the bifunctional carbon-based powder single atom catalyst prepared in Examples 1-4.

[0031] Figure 5This is the OER performance diagram of the bifunctional carbon-based powder single atom catalyst prepared in Example 1.

[0032] Figure 6 This is the power density curve of the bifunctional carbon-based powder single-atom catalyst prepared in Example 5 as the positive electrode material. Test conditions: catalyst loading is 0.2 mg cm -2 The electrolyte is a mixed solution of 6 mol potassium hydroxide and 0.2 mol zinc acetate.

[0033] Figure 7 The charge / discharge cycle diagram of the bifunctional carbon-based powder single-atom catalyst prepared in Example 5 as the positive electrode material. Test conditions: catalyst loading is 0.1 mg cm -2 The electrolyte is a mixed solution of 6 mol potassium hydroxide and 0.2 mol zinc acetate, and the current density during charge / discharge is 5 mA cm -2 . DETAILED DESCRIPTION

[0034] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0035] Example 1

[0036] (1) Preparation of carbon-based powder: ZIF-8 powder was placed in a tubular furnace and annealed at 800°C for 10 h to obtain a carbon-nitrogen skeleton with an octahedral structure as a carbon-based powder; 300 mg of the carbon-based powder was placed in a rotary chamber, and the chamber temperature and pressure were rotated and heated under nitrogen protection. After the chamber temperature and pressure reached the set values, the deposition step was performed. The chamber temperature was set to 180°C and the chamber pressure was 0.05 torr; the carrier gas was high-purity N2 with a flow rate of 300 sccm; and the chamber rotation speed was 5 rpm.

[0037] (2) Powder coating of TiO2: Pulse tetrakis(dimethylamino)titanium (the temperature of the precursor cylinder is set to 80°C) into a rotary chamber, and complete the atomic-level coating of TiO2 by deposition to obtain TiO2 / carbon-based powder; the chamber pressure is 0.5 torr, the holding time is 3 minutes, and high-purity nitrogen is passed through for 3 minutes after adsorption; O3 gas pulses into the chamber, the chamber pressure is 1 torr, the duration is 3 minutes, and high-purity nitrogen is passed through for 3 minutes. Repeat the above steps to complete 2 cycles of TiO2 coating and obtain TiO2 / carbon-based material catalyst powder.

[0038] (3) Preparation of Pt single atom: Trimethyl (methylcyclopentadienyl) platinum (the temperature of the precursor cylinder is set to 80°C) is pulsed into the rotary chamber, and the loading of platinum atoms is completed by deposition to obtain the bifunctional carbon-based powder single atom catalyst; the chamber pressure is 0.5 torr, and the holding time is 4 minutes. After the adsorption is completed, high-purity nitrogen is passed through for 3 minutes; O3 gas pulses enter the chamber, and O3 gas pulses enter the chamber. The chamber pressure is 2 torr and the duration is 5 minutes. The above steps are repeated for 1 cycle to obtain Pt / TiO2 / carbon-based material single atom catalyst powder.

[0039] Depend on Figure 1 As shown, the scanning electron microscope photo shows that the ZIF-8 powder still retains the original carbon-nitrogen skeleton after high-temperature carbonization.

[0040] Depend on Figure 2 As shown, by testing the mapping spectrum of the scanning electron microscope, it is proved that the carbon-nitrogen skeleton powder material is successfully coated with TiO2 and Pt.

[0041] Depend on Figure 3 As shown, by testing the mapping spectrum of the transmission electron microscope, it was further confirmed that the carbon-nitrogen skeleton powder material successfully coated TiO2 and Pt.

[0042] Depend on Figure 5 As shown, on the surface of the prepared carbon-nitrogen skeleton, 2 circles of TiO2 and then 1 circle of Pt were deposited. The powder was loaded on carbon paper and tested. The results showed that it had good OER performance.

[0043] Example 2

[0044] The carbon-nitrogen skeleton powder of the same mass as that in Example 1 was placed in the chamber of the atomic layer deposition system, and five cycles of TiO2 deposition were performed. After completion, one cycle of Pt single atom deposition was performed.

[0045] Example 3

[0046] The carbon-nitrogen skeleton powder of the same mass as that in Example 1 was placed in the chamber of the atomic layer deposition system, and 10 cycles of TiO2 deposition were performed. After completion, 1 cycle of Pt single atom deposition was performed.

[0047] Example 4

[0048] The carbon-nitrogen skeleton powder of the same mass as that in Example 1 was placed in the chamber of the atomic layer deposition system, and 20 cycles of TiO2 deposition were performed. After completion, 1 cycle of Pt single atom deposition was performed.

[0049] Depend on Figure 4As shown in the figure, the ORR performance of powders coated with different numbers of TiO2 circles was tested, and it was found that on the surface of the prepared carbon-nitrogen skeleton, the ORR performance of the powder material first deposited 20 circles of TiO2 and then 1 circle of Pt was relatively poor, indicating that a too thick TiO2 layer would hinder charge transfer.

[0050] Example 5

[0051] 300 mg of carbon nanotube powder was taken and placed in a solution of concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 1:3, and the reaction was continued at 70°C for 1 hour. The powder was washed, filtered, and dried to obtain carbon nanotubes with hydroxyl groups. The carbon nanotube powder with hydroxyl groups was placed in the chamber of the atomic layer deposition system, and three cycles of TiO2 deposition were performed as in Example 1. After completion, one cycle of Pt single atom deposition was performed.

[0052] Depend on Figure 6 As shown in the figure, the prepared catalyst powder was used as the positive electrode material of the zinc-air battery, and the assembled device had a power of 165 mWcm -2 power density.

[0053] Depend on Figure 7 As shown in the figure, the prepared catalyst powder was used as the positive electrode material of the zinc-air battery, and the assembled device was -2 At a current density of 15 minutes each, the battery can be stably cycled for 200 cycles.

Claims

1. A bifunctional carbon-based powder single-atom catalyst, characterized in that: The catalyst uses carbon-based powder as a conductive substrate, and utilizes atomic layer deposition technology to first coat atomic-level metal oxides on the surface of the carbon-based powder, and then loads single atoms of precious metals to obtain the catalyst.

2. The bifunctional carbon-based powder single-atom catalyst according to claim 1, characterized in that: The carbon-based powder material is one or more of carbon nanotubes, graphene, and carbon-nitrogen skeleton materials.

3. The bifunctional carbon-based powder single-atom catalyst according to claim 1, characterized in that: The metal oxide is TiO2.

4. The bifunctional carbon-based powder single-atom catalyst according to claim 1, characterized in that: The noble metal single atom is a platinum atom.

5. A method for preparing a bifunctional carbon-based powder single-atom catalyst as claimed in any one of claims 1 to 4, comprising the following steps: (1) placing the carbon-based powder into a rotary chamber, rotating and heating it under nitrogen protection, and performing a deposition step after the chamber temperature and pressure reach the set values; (2) Pulsing a titanium-containing organic precursor into a rotating chamber to complete atomic-level TiO2 coating by deposition to obtain TiO2 / carbon-based powder; (3) Pulsing a platinum-containing organic precursor into a rotating chamber, and completing the loading of platinum atoms by deposition to obtain the bifunctional carbon-based powder single atom catalyst.

6. The preparation method according to claim 5, characterized in that: The chamber temperature in step (1) is set to 100-300° C., and the chamber pressure is set to 0.01 torr-0.1 torr.

7. The preparation method according to claim 5, characterized in that: The titanium-containing organic precursor in step (2) is tetrakis(dimethylamino)titanium.

8. The preparation method according to claim 5, characterized in that: The platinum-containing organic precursor in step (3) is trimethyl(methylcyclopentadienyl)platinum.

9. The preparation method according to claim 5, characterized in that: The number of depositions in step (2) is 1-10 cycles; the number of depositions in step (3) is 1-3 cycles.

10. Use of the bifunctional carbon-based powder single-atom catalyst according to any one of claims 1 to 4 in lithium-ion batteries, gas catalysis, photoelectrocatalytic hydrogen production or zinc-air batteries.

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