High-stable self-forming monatomic ordered catalyst, preparation method and application thereof

Abstract

This invention relates to the field of electrocatalysis technology, specifically to a method for preparing and applying a highly stable self-forming single-atom ordered catalyst. The method includes the following steps: S1, taking an organometallic compound and a Pt precursor solution, dispersing them in an alcohol solvent, heating and mixing them in a water bath to obtain a mixture; S2, ultrasonically stirring the mixture obtained in S1, and simultaneously irradiating it with laser light while stirring to obtain a reactant solution; S3, centrifuging the reactant solution from S2, washing it with water, and then freeze-drying it under vacuum to finally obtain a Pt-X bimetallic single-atom catalyst. This invention prepares a highly stable self-forming single-atom ordered catalyst using laser irradiation, where platinum single atoms are confined within the pores of carbon nanotubes, and X metal is supported on the surface of the carbon nanotubes. This catalyst is suitable for the HOR and ORR reactions in fuel cells, exhibiting high activity and high stability, and showing significant effects on the HOR and ORR reactions.

Description

Technical Field

[0001] This invention relates to the field of electrocatalysis technology, specifically to a method for preparing and applying a highly stable self-forming single-atom ordered catalyst. Background Technology

[0002] Among renewable energy sources, hydrogen has become a key focus for researchers in development and utilization due to its diverse sources, high driving efficiency, and the fact that its emissions during operation are primarily water with no environmental pollution. Proton exchange membrane fuel cells, a novel energy conversion and storage electrochemical facility with wide applications in transportation, construction, industry, and more efficient energy storage, are devices that generate electricity through the chemical reaction of hydrogen and oxygen.

[0003] The concept of single-atom catalysis was first proposed in 2011, and single-atom Pt / FeOx catalysts were successfully prepared. In 2012, E. Charles H. Sykes's group at Tufts University in the United States achieved the dispersion of single-atom Pd on the Cu(111) surface. In 2014, Academician Bao Xinhe's group at the Dalian Institute of Chemical Physics prepared atomically dispersed Fe / SiO2, and made significant progress in the oxygen-free production of ethylene from methane and aromatization. In 2016, Zheng Nanfeng's group at Xiamen University synthesized a single-atom dispersed Pd / TiO2 catalyst using a simple photochemical method, which exhibited excellent activity in the C=C and C=O hydrogenation reactions.

[0004] However, when metals are formed at the single-atom level, the specific surface area increases dramatically, leading to a sharp increase in the surface free energy. This makes them highly susceptible to aggregation and coupling during preparation and reaction, forming large clusters and thus deactivating the catalyst. Therefore, it is necessary to design catalysts that prevent single-atom clustering. Furthermore, most current single-atom preparation methods suffer from drawbacks such as complex processes, high costs, and difficulty in industrial production. The earliest mass separation soft-landing method requires stringent experimental conditions, high costs, ultra-high vacuum preparation conditions, and demanding metal precursor selection. The deposition method is also incompatible with high specific surface area supports and mesoporous materials, making it unsuitable for large-scale production. Therefore, finding a simple method for preparing highly stable platinum-based single-atom dispersed catalysts is of great significance. Summary of the Invention

[0005] The purpose of this invention is to provide a highly stable self-forming single-atom ordered catalyst, its preparation method, and its application, in order to solve the problems of easy agglomeration of single-atom catalysts in the field of proton exchange membrane fuel cells, as well as the development limitations caused by the complexity and high cost of the preparation process.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] This invention provides a method for preparing a highly stable self-forming single-atom ordered catalyst, the method comprising the following steps:

[0008] S1. Disperse the organometallic compound X and the Pt precursor solution in an alcohol solvent, heat them in a water bath while mixing to obtain a mixed solution, wherein the X metal includes one or more of iron, tin and cobalt.

[0009] S2. The mixture obtained in step S1 is ultrasonicated and stirred, and laser light is applied simultaneously while stirring to obtain a reactant solution.

[0010] S3. Centrifuge the reactant solution obtained in step S2, wash with water, and then freeze-dry under vacuum to obtain the Pt-X bimetallic single-atom catalyst.

[0011] In the above technical solution, further, in step S1, the organometallic compound includes one or more of ferrocene, allyltributyltin, and octacarbonyldicobalt.

[0012] The Pt precursor in the Pt precursor solution includes one or more of the following: chloroplatinic acid (H2PtCl6), dichlorohexaaminoplatinum Pt(NH3)6Cl2, dichlorotetraaminoplatinum (Pt(NH3)4Cl2), and dinitrosodiaminoplatinum (Pt(NO2)2(NH3)2).

[0013] The alcohol solvents include one or more of ethanol, ethylene glycol, n-butanol, and isopropanol;

[0014] The mass ratio of the Pt precursor solution to the organometallic compound is 1:10-20, and the mass ratio of the organometallic compound to the alcohol solvent is 1:10-100.

[0015] The water bath heating temperature is 30–60°C.

[0016] In the above technical solution, further, in step S2, the ultrasonic time of the mixture is 0.5-1h, and the stirring time is 0.5-1h, so that the Pt precursor is adsorbed on the surface of the organometallic compound.

[0017] Under stirred conditions and laser irradiation at a stirring rate of 1000–1500 rpm / min, Pt ions in the Pt precursor are first reduced to platinum atoms. The organometallic compound then transforms into a carbon nanotube structure, with platinum atoms confined within the pores of the carbon nanotubes. Metal ions in the organometallic compound are reduced to X metal, which is then loaded onto the carbon nanotube surface. The laser power density is 100–110 W / cm². 2 The laser wavelength range covers the ultraviolet wavelength range of 248-337nm, the visible wavelength range of 590-630nm, and the infrared wavelength range of 890-905nm, with an illumination time of 10-30min.

[0018] In the above technical solution, further, in step S3, the number of water washing cycles is 3 to 6;

[0019] The pressure under the vacuum condition is -1.0 to 0 MPa;

[0020] The freeze-drying temperature is -80 to -60°C, and the freeze-drying time is 8 to 12 hours.

[0021] In another aspect, the present invention provides a catalyst prepared by the above-described method, wherein the catalyst has the following structure: platinum single atoms are confined within the pores of carbon nanotubes, and X metal is supported on the surface of the carbon nanotubes.

[0022] In another aspect, the present invention provides the application of the above-mentioned catalyst in a proton exchange membrane fuel cell.

[0023] The present invention has the following beneficial effects:

[0024] 1. This invention designs a single-atom bimetallic catalyst in which platinum single atoms are confined within the pores of carbon nanotubes, and metal X is supported on the surface of the carbon nanotubes. Compared with existing multi-metal systems, this catalyst structure has the advantage of enhanced synergistic catalytic effect of dual active sites. Firstly, it can achieve efficient utilization of precious metals. Secondly, the isolated distribution structure of platinum single atoms and metal X prevents aggregation between bimetallic single atoms. Moreover, compared with metal single atoms supported on the inner wall of carbon nanotubes, the metal atoms of this invention are confined within the pores, making it less likely for platinum single atoms to aggregate during catalyst preparation and use, thus greatly improving stability. Furthermore, in this invention, the Pt metal forms a highly stable single-atom structure due to the confinement of the carbon nanotube pores, making it less prone to agglomeration and the formation of large metal clusters during preparation and reaction. This structure can effectively block catalyst migration, CO poisoning, Oswald ripening, and desorption failure in later electrochemical applications, and greatly improves the activity compared to single-atom catalysts with disordered structures. The Pt-X single-atom catalyst provided by this invention is well-suited for HOR and ORR reactions in fuel cells, exhibiting high activity and high stability, and has a significant effect on HOR and ORR reactions.

[0025] 2. This invention provides a method for preparing a self-forming single-atom catalyst. Utilizing the metal-carbon coordination structure of organometallic compounds, this invention achieves a one-step transformation from organic ligands to a one-dimensional carbon nanotube structure through laser irradiation. The platinum precursor is reduced to generate Pt metal, and the platinum single atoms are confined and saturated within the pores of the carbon nanotubes, allowing X metal to deposit on the outer wall of the nanotubes to form an isolated distribution structure. This ultimately realizes a one-dimensional carbon nanotube-supported Pt-X bimetallic single-atom catalyst. This preparation method is low-cost, requires simple equipment, has a short preparation process, and uses mild preparation conditions. It overcomes the problems of harsh (ultra-high temperature, ultra-vacuum) or difficult-to-control (displacement method) preparation conditions of existing single-atom catalysts, demonstrating good practicality and economic efficiency, and excellent industrialization prospects.

[0026] 3. This invention provides a method for preparing a self-forming single-atom catalyst. The method uses laser irradiation under stirring conditions. Stirring accelerates fluidity and liquid-phase mixing. Simultaneously, carbon nanotubes are self-generated from organometallic compounds during stirring and laser treatment. Therefore, the simultaneous effect of these two preparation conditions facilitates sufficient contact between ions and carbon nanotubes, enabling ions to adsorb onto the carbon nanotubes and effectively improving the reduction efficiency of ions to single atoms on the carbon nanotube structure. Furthermore, the carbon nanotubes in this invention are self-generated from organometallic compounds during stirring and laser treatment. Compared to directly adding carbon nanotubes, this invention allows for control over the pore size and distribution of carbon nanotubes during the self-generation process through parameter regulation such as laser and stirring, thereby achieving confinement of single atoms and successfully preparing the catalyst structure required in this application. Attached Figure Description

[0027] Figure 1 HOR polarization curves of CO toxicity resistance for samples 1, 2, and 3;

[0028] Figure 2 The HOR polarization curves of the catalysts in Comparative Examples 1, 2, and 3 against CO poisoning are shown.

[0029] Figure 3 ORR polarization curves for Sample 1 and a commercial PtC catalyst. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention. Unless otherwise specified, the methods described are conventional methods. Unless otherwise specified, the raw materials can be obtained from publicly available commercial channels.

[0031] This invention features a simple preparation process, achieving a high yield of effective products in a single step. The prepared Pt-X bimetallic catalyst material exhibits superior electrocatalytic performance and stability in both hydroxide and oxygen reduction. The organometallic compound and a Pt precursor are dispersed in an alcohol solvent and ultrasonically stirred under specific temperature and pressure to form a homogeneous solution. The Pt precursor adsorbs onto the surface of the organometallic compound. Under a controlled stirring rate and with adjusted laser power density, wavelength, and irradiation time, Pt ions in the Pt precursor are first reduced to platinum atoms, and the organometallic compound transforms into a carbon nanotube structure, with platinum atoms confined within the pores of the carbon nanotubes. The completely reacted solution is washed several times with deionized water and then placed in a freeze-drying apparatus. Under vacuum conditions and with the freeze-drying apparatus set within a specific temperature range, the Pt-X bimetallic single-atom catalyst is finally obtained.

[0032] This invention solves the problem of low metal atom utilization in hydrogen hydroxide and platinum carbon oxygen reduction electrocatalysts, which are a limiting factor in the development of proton exchange membrane fuel cells. The method has advantages such as simple process steps, short process, and ordered structure. The prepared catalyst has a large specific surface area and significantly better catalytic activity and stability than commercial Pt / C catalysts. The entire synthesis route has low equipment requirements and good process stability, and has important value for industrial application.

[0033] Example 1

[0034] S1. Take 50 mg of organometallic compound ferrocene and 0.1 mol of chloroplatinic acid (H2PtCl6) solution, disperse them in 500 ml of ethanol solvent, heat in a water bath at 30 °C and mix them at the same time to obtain a mixed solution;

[0035] S2. The mixture described in S1 is sonicated for 0.5 hours, then stirred for 0.5 hours at a stirring rate of 1000 rpm / min. Simultaneously, it is irradiated with ultraviolet light in the wavelength range of 300 nm at a laser power density of 100 W / cm². 2 The light exposure time was 10 min, and a reactant solution was obtained.

[0036] S3. After centrifuging the reactant solution from S2 three times and washing it with water, freeze-dry it under vacuum at a pressure of -1.0 MPa at a temperature of -80°C for 8 hours to obtain the Pt-X bimetallic single-atom catalyst, which is designated as Sample 1.

[0037] The catalyst prepared in Example 1 was dispersed in anhydrous ethanol and sonicated for 30 min to obtain a homogeneous dispersion. 20 μL of this dispersion was pipetted onto a 5 mm diameter glassy carbon electrode and dried at 60 °C. Then, 1 μL of 0.5 wt.% Nafion solution was pipetted onto the catalyst layer and dried in air to obtain the working electrode. Cyclic voltammetry was performed in a high-purity N2-saturated 0.1 mol / L HClO4 solution at a scan rate of 50 mV / s and a scan range of 0.0–1.10 V (vs. RHE) for 30 cycles. Table 1 shows that the electrochemical active area is 66.4 m². 2 / g, after cyclic voltammetry scanning of the working electrode until the catalyst surface is clean and stable, it is removed for LSV testing. The HOR and ORR performance against CO poisoning are tested in H2-saturated and O2-saturated 0.1mol / L HClO4 solutions containing 5ppm CO, respectively. The scan rate is 10mV / s, the scan range is 0–0.5V, and the rotating disk electrode speed is 1600r / min. Figure 1 It can be seen that its HOR mass activity is 148 A / g, and the retention rate after 20,000 current cycles is 68%; from Figure 2 It can be seen that its ORR (Organic Ratio) activity is 920 A / g, which is much higher than that of commercial PtC (110 A / g).

[0038] Example 2

[0039] S1. Take 100 mg of organometallic compound propenyltributyltin and 0.1 mol of dichlorohexaaminoplatinum solution, disperse them in 1000 ml of ethanol solvent, heat in a water bath at 60 °C and mix them at the same time to obtain a mixed solution;

[0040] S2. The mixture described in S1 is sonicated for 1 hour, then stirred for 1 hour at a stirring rate of 1500 rpm. Simultaneously, it is irradiated with visible light at a wavelength of 630 nm and a laser power density of 110 W / cm². 2 The light exposure time was 30 minutes, and the reactant solution was obtained.

[0041] S3. After centrifuging the reactant solution from S2 six times and washing it with water, freeze-dry it under vacuum at a pressure of 0 MPa at a temperature of -60°C for 12 hours to finally obtain the Pt-X bimetallic single-atom catalyst.

[0042] The catalyst prepared in Example 2 was designated as Sample 2. Using the same testing methods and conditions as in Example 1, CV testing was performed. As shown in Table 1, its electrochemical active area was 68.2 m². 2 As shown in Table 1, the mass activity of the sample is 152 A / g, and the current retention rate after 20,000 cycles is 74%, as determined by LSV testing.

[0043] Example 3

[0044] S1. Take 75 mg of organometallic compound ferrocene and 0.1 mol of chloroplatinic acid (H2PtCl6) solution, disperse them in 750 ml of ethanol solvent, heat them in a water bath at 45 °C and mix them at the same time to obtain a mixed solution;

[0045] S2. The mixture described in S1 is sonicated for 0.75 hours, then stirred for another 0.75 hours at a stirring rate of 1250 rpm. Simultaneously, it is irradiated with infrared light with a wavelength range of 900 nm and a laser power density of 105 W / cm². 2 The light exposure time was 20 min, and a reactant solution was obtained.

[0046] S3. The reactant solution from S2 was centrifuged four times and washed with water. Then, it was freeze-dried under vacuum at a pressure of -0.5 MPa at a temperature of -70°C for 10 hours to finally obtain the Pt-X bimetallic single-atom catalyst.

[0047] The catalyst prepared in Example 3 is designated as Sample 3. Using the same testing methods and conditions as in Example 1, CV testing was performed. As shown in Table 1, its electrochemical active area is 64.3 m². 2 As shown in Table 1, the mass activity of the sample is 142 A / g, and the current retention rate after 20,000 cycles is 62%, as determined by LSV testing.

[0048] Comparative Example 1

[0049] S1. Take 50 mg of organometallic compound ferrocene and 0.1 mol of chloroplatinic acid (H2PtCl6) solution, disperse them in 500 ml of ethanol solvent, heat in a water bath at 30 °C and mix them at the same time to obtain a mixed solution;

[0050] S2. Sonicate the mixture described in S1 for 0.5 hours, then stir for 0.5 hours at a stirring rate of 1000 rpm. Simultaneously, irradiate the mixture with ultraviolet light in the wavelength range of 300 nm and a laser power density of 100 W / cm². 2 The light exposure time was 5 minutes, and a reactant solution was obtained.

[0051] S3. The reactant solution from S2 was centrifuged three times and washed with water. Then, it was freeze-dried under vacuum at a pressure of -1.0 MPa at a temperature of -80°C for 8 hours to finally obtain the Pt-X bimetallic single-atom catalyst.

[0052] Comparative Example 2

[0053] S1. Take 50 mg of organometallic compound ferrocene and 0.1 mol of chloroplatinic acid (H2PtCl6) solution, disperse them in 500 ml of ethanol solvent, heat in a water bath at 30 °C and mix them at the same time to obtain a mixed solution;

[0054] S2. Adjust the pH of the mixture from S1 to 10, sonicate the mixture from S1 for 0.5 h, and then stir for 0.5 h at a stirring rate of 1000 r to obtain the reactant solution.

[0055] S3. After centrifuging the reactant solution of S2 three times and washing it with water, the calcination temperature was 800 degrees Celsius, the reaction time was 8 hours, the pressure under vacuum was -1.0 MPa, and the freeze-drying temperature was -80 degrees Celsius for 8 hours, finally obtaining the Pt-X bimetallic single-atom catalyst.

[0056] Comparative Example 3

[0057] S1. Take 50 mg of organometallic compound ferrocene and 0.1 mol of chloroplatinic acid (H2PtCl6) solution, disperse them in 500 ml of ethanol solvent, heat in a water bath at 30 °C and mix them at the same time to obtain a mixed solution;

[0058] S2. The mixture described in S1 is sonicated for 0.5 hours, then stirred for 0.5 hours at a stirring rate of 1000 rpm. Simultaneously, it is irradiated with ultraviolet light with a wavelength range of 300 nm and a laser power density of 60 W / cm². 2 The light exposure time was 10 min, and a reactant solution was obtained.

[0059] S3. The reactant solution from S2 was centrifuged three times and washed with water. Then, it was freeze-dried under vacuum at a pressure of -1.0 MPa at a temperature of -80°C for 8 hours to finally obtain the Pt-X bimetallic single-atom catalyst.

[0060] Comparative Example 4

[0061] S1. Take 50 mg of organometallic compound ferrocene and 0.1 mol of chloroplatinic acid (H2PtCl6) solution, disperse them in 500 ml of ethanol solvent, heat in a water bath at 30 °C and mix them at the same time to obtain a mixed solution;

[0062] S2. Sonicate the mixture described in S1 for 0.5 hours, then irradiate it with ultraviolet light with a wavelength range of 300 nm and a laser power density of 100 W / cm². 2 The light exposure time was 10 min, and a reactant solution was obtained.

[0063] S3. The reactant solution from S2 was centrifuged three times and washed with water. Then, it was freeze-dried under vacuum at a pressure of -1.0 MPa at a temperature of -80°C for 8 hours to finally obtain the Pt-X bimetallic single-atom catalyst.

[0064] Comparative Example 5

[0065] S1. Take 50 mg of carbon nanotubes and 0.1 mol of chloroplatinic acid (H2PtCl6) solution, disperse them in 500 ml of ethanol solvent, heat them in a water bath at 30 °C while mixing to obtain a mixed solution;

[0066] S2. The mixture described in S1 is sonicated for 0.5 h and then stirred for 0.5 h. The stirring rate is 1000 r. At the same time, it is irradiated with ultraviolet light with a wavelength range of 300 nm, a laser power density of 100 W / cm2, and an irradiation time of 10 min to obtain the reactant solution.

[0067] S3. The reactant solution from S2 was centrifuged three times and washed with water. Then, under vacuum at a pressure of -1.0 MPa, it was freeze-dried at -80℃ for 8 hours to finally obtain the Pt-X bimetallic single-atom catalyst.

[0068] Using the same test methods and conditions as in Example 1, the catalysts prepared in Comparative Examples 1-5 were subjected to CV and LSV tests, and the relevant data are recorded in Table 1. As can be seen from Table 1, the active area and catalytic activity of the catalyst prepared in Comparative Example 1 are not as good as those in this application, and agglomeration is more likely to occur in Comparative Example 1.

[0069] Since the preparation method of Comparative Example 2 did not use laser method but the traditional coprecipitation method, the addition of precipitant in Comparative Example 2 will cause the local concentration to be too high, resulting in agglomeration or uneven composition, which leads to its low active area and activity.

[0070] As shown in Table 1, the catalyst prepared by Comparative Example 3 using a lower laser power has a lower active area and catalytic activity than that of this application.

[0071] As shown in Table 1, Comparative Example 4 did not employ simultaneous stirring and laser irradiation, resulting in a lower catalyst active area and catalytic activity compared to this application. This is because Comparative Example 4 did not use simultaneous stirring and laser irradiation, leading to a lower final conversion rate compared to this application.

[0072] Comparative Example 5 uses carbon nanotubes directly added to form a mixture, rather than using a self-generated method. As shown in Table 1, the active area and catalytic activity of the catalyst prepared by it are not as good as those of this application. Since the carbon nanotubes in this application are controllable, the pore size and pore distribution can be controlled, which is convenient for the confinement of single atoms.

[0073] Table 1

[0074] catalyst Electrochemical active area m2 / g HOR mass activity A / g 20,000-cycle current retention rate Example 1 66.4 148 68％ Example 2 68.2 152 74％ Example 3 64.3 142 62％ Comparative Example 1 42.5 112 52％ Comparative Example 2 55.3 126 56％ Comparative Example 3 46.8 116 54％ Comparative Example 4 52.5 123 54％ Comparative Example 5 48.5 118 56％

Claims

1. A method for preparing a highly stable self-forming monatomic ordered catalyst, characterized by: The method includes the following steps: S1. Disperse an organic compound containing metal X and a Pt precursor solution in an alcohol solvent, heat them in a water bath while mixing to obtain a mixed solution, wherein the metal X includes one or more of iron, tin, and cobalt. S2, ultrasonicating and stirring the mixed solution obtained in step S1, and irradiating the mixed solution with laser light under the stirring condition, the laser power density being 100-110 W / cm 2 , and the irradiation time being 10-30 min, to obtain a reactant solution; S3. Centrifuge the reactant solution obtained in step S2, wash with water, and then freeze-dry under vacuum to obtain the Pt-X bimetallic single-atom catalyst. The catalyst has the following structure: platinum single atoms are confined within the pores of carbon nanotubes, and X metal is supported on the surface of carbon nanotubes.

2. The preparation method according to claim 1, characterized in that: In step S1, the organic compound containing metal X includes one or more of ferrocene, allyltributyltin, and octacarbonyldicobalt. The Pt precursor in the Pt precursor solution includes one or more of the following: chloroplatinic acid (H2PtCl6), dichlorohexaaminoplatinum Pt(NH3)6Cl2, dichlorotetraaminoplatinum (Pt(NH3)4Cl2), and dinitrosodiaminoplatinum (Pt(NO2)2(NH3)2). The alcohol solvents include one or more of ethanol, ethylene glycol, n-butanol, and isopropanol; The mass ratio of the Pt precursor solution to the organometallic compound is 1:10~20, and the mass ratio of the organometallic compound to the alcohol solvent is 1:10~100; The water bath heating temperature is 30~60℃.

3. The preparation method according to claim 1, characterized in that: In step S2, the ultrasonic time of the mixture is 0.5~1h, and the stirring time is 0.5~1h; under stirring conditions, laser irradiation is performed at a stirring rate of 1000~1500rpm / min, and the laser wavelength range covers the ultraviolet wavelength range of 248-337nm, the visible wavelength range of 590-630nm, and the infrared wavelength range of 890-905nm.

4. The preparation method according to claim 1, characterized in that: In step S3, the number of water washes is 3 to 6; The pressure under the vacuum condition is -1.0~0 MPa; The freeze-drying temperature is -80~-60℃, and the freeze-drying time is 8~12h.

5. The application of a catalyst prepared by the method according to any one of claims 1-4 in a proton exchange membrane fuel cell.

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