A method for preparing a cross-shaped nanostructured PtCu alloy catalyst and its application

Abstract

This invention discloses a method for preparing a cross-shaped nanostructured PtCu alloy catalyst and its application, belonging to the field of electrocatalysis and fuel cell technology. The method involves sequentially adding an aqueous solution of chloroplatinic acid and a copper chloride solution to a reaction vessel, followed by the addition of a reducing agent and a dispersant. The mixture is then fully dissolved by ultrasound and stirring, and after homogenization, heated under an inert atmosphere. After the reaction, the catalyst is centrifuged, washed, and freeze-dried to obtain a PtCu alloy catalyst with a cross-shaped nanostructure. This invention uses an aqueous phase system, avoiding the use of macromolecular organic solvents, thus fundamentally solving the problems of the synthesized product being easily encapsulated by organic matter and the active sites being difficult to expose in traditional methods. Furthermore, the nanostructured catalyst obtained through aqueous phase synthesis has a clean surface, allowing for full exposure of the catalytic active centers and effective contact with the reactants, thereby significantly improving the electrocatalytic performance of the catalyst.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalysis and fuel cell technology, specifically relating to a method for preparing a cross-shaped nanostructured PtCu alloy catalyst and its application, particularly to a method for preparing a cross-shaped nanostructured PtCu alloy catalyst and its application in ethylene glycol fuel cells. Background Technology

[0002] Direct alcohol fuel cells (DFCs) use liquid alcohols as fuel and offer advantages such as environmental friendliness, high energy density, and high efficiency, potentially replacing traditional internal combustion engines. Anodic alcohol oxidation electrocatalysis is the core reaction of DFCs, and its catalytic activity, resistance to poisoning, and stability directly determine the output performance and lifespan of the fuel cell. Noble metal Pt nanostructure catalysts, due to their excellent catalytic performance and thermal stability, have become the core material for anodic catalysis in DFCs, widely used in the electro-oxidation processes of various alcohols such as methanol, ethanol, and ethylene glycol. However, Pt nanostructure catalysts face limitations in practical applications, such as susceptibility to poisoning, short lifespan, and high cost, hindering their further promotion and application. To address these issues, researchers often partially replace Pt with inexpensive 3d transition metal elements to form Pt-based binary / multi-component alloy catalysts, and investigate the relationship between their morphology, composition, and catalytic performance stability through condition control.

[0003] Currently, most methods for preparing Pt-based binary / multi-component alloy catalysts use organic solvent macromolecules as solvents. The resulting alloy nanocatalysts are mostly encapsulated by organic matter, preventing the active sites from being exposed and thus hindering contact with reactants, thereby reducing their electrocatalytic performance. Therefore, developing an aqueous solution-based method for preparing Pt-based alloy nanocatalysts is of great significance. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for preparing a cross-shaped nanostructured PtCu alloy catalyst and its application. Using chloroplatinic acid and copper chloride as raw materials, glycine as a reducing agent, and polyvinylpyrrolidone as a dispersant, this application prepares a highly selective cross-shaped nanostructured PtCu alloy catalyst under an inert atmosphere. The synthesized catalyst exhibits excellent electrocatalytic activity in electro-oxidation catalytic experiments of ethylene glycol fuel cells.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing a cross-shaped nanostructured PtCu alloy catalyst, comprising the following steps: In a reaction vessel, chloroplatinic acid aqueous solution and copper chloride solution were added sequentially, followed by a reducing agent and a dispersant. The mixture was fully dissolved by ultrasound and stirring. After being mixed evenly, the reaction was carried out under an inert atmosphere. After the reaction was completed, the catalyst was centrifuged, washed, and freeze-dried to obtain a PtCu alloy catalyst with a cross-shaped nanostructure. The molar ratio of chloroplatinic acid in the chloroplatinic acid aqueous solution to copper chloride in the copper chloride solution is 1.5:1 to 5:1. The mass ratio of the reducing agent, dispersant and chloroplatinic acid in the aqueous solution of chloroplatinic acid is (13~20):(6~14):1.

[0006] Furthermore, the reducing agent is glycine.

[0007] Furthermore, the dispersant is polyvinylpyrrolidone.

[0008] Furthermore, the power of the ultrasound is 400W~800W, and the duration of the ultrasound is 10min~30min.

[0009] Furthermore, the stirring speed is 400 rpm to 1000 rpm.

[0010] Furthermore, the temperature of the heating reaction is 160℃~200℃, and the heating reaction time is 4h~10h.

[0011] Furthermore, the freeze-drying temperature is -40℃ to 0℃, and the freeze-drying time is 6h to 12h.

[0012] Secondly, the present invention provides the application of the above-mentioned cross-shaped nanostructured PtCu alloy catalyst in ethylene glycol fuel cells.

[0013] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention uses chloroplatinic acid aqueous solution and copper chloride solution as raw materials, water as reaction medium, and a PtCu alloy catalyst with cross nanostructure is prepared under the action of reducing agent and dispersant. This method ensures that platinum and copper can grow according to a specific lattice matching mode during co-reduction by limiting the molar ratio of chloroplatinic acid to copper chloride to 1.5:1 to 5:1, thereby self-assembling to form a cross-shaped nanostructure. This structure has a high surface area and abundant edge / corner active sites, providing a structural basis for solving the problem of active site exposure. At the same time, by controlling the mass ratio of reducing agent, dispersant and chloroplatinic acid to (13~20):(6~14):1, the high concentration of reducing agent in the aqueous phase provides a strong chemical driving force, which allows crystal growth to be completed without macromolecular organic template agents. This achieves "surface cleanliness" of the product surface without firmly adsorbed long-chain organic molecules, directly solving the problem of difficult exposure of active sites in traditional methods. The appropriate amount of dispersant provides sufficient steric hindrance effect or electrostatic repulsion, allowing the cross structure to exist stably in the aqueous phase without fusion and aggregation. Moreover, because its amount is relatively low and it is in an aqueous environment, it is easy to be washed away in subsequent processing, avoiding the formation of a dense organic coating layer. In short, this invention uses an aqueous system, avoiding the use of macromolecular organic solvents, and fundamentally solves the problems of the synthesized products being easily encapsulated by organic matter and the active sites being difficult to expose in traditional methods. The surface-clean nanostructure catalyst obtained by aqueous synthesis can fully expose the catalytic active centers and effectively contact the reactants, thereby significantly improving the electrocatalytic performance of the catalyst.

[0014] (2) The entire preparation process of the present invention is green and environmentally friendly, easy to operate and low in cost, which is in line with the development direction of green chemistry and has good prospects for industrial application. Attached Figure Description

[0015] Figure 1 These are TEM images of the cross-shaped nanostructured PtCu alloy catalysts prepared in Examples 1-3 of this invention.

[0016] Figure 2 A comparison of cyclic voltammetry curves of the PtCu alloy catalyst prepared in Example 1 of this invention, the catalyst prepared in the comparative example, and the commercial Pt / C catalyst as ethylene glycol electro-oxidation catalysts.

[0017] Figure 3 This is a TEM image of the catalyst prepared in Comparative Example 1 of the present invention. Detailed Implementation

[0018] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments and accompanying drawings.

[0019] Unless otherwise specified, all reagents used in this invention are commercially available, and all methods used are conventional techniques in the art.

[0020] Example 1 A method for preparing a cross-shaped nanostructured PtCu alloy catalyst includes the following steps: 1.4 mL of 20 mmol / L chloroplatinic acid aqueous solution and 4.0 mL of 1.66 mmol / L copper chloride solution were measured into a 25 mL reaction vessel. Then, 200 mg of glycine and 110 mg of polyvinylpyrrolidone were added as reducing agent. The mixture was sonicated and stirred at a power of 600 W for 20 min and a stirring speed of 600 rpm until the glycine and polyvinylpyrrolidone were completely dissolved and mixed evenly. The mixture was then reacted at 200 °C for 8 h in an inert atmosphere. After the reaction was completed, the mixture was centrifuged with ethanol, washed, and freeze-dried at -40 °C for 12 h to obtain the cross-shaped nanostructured PtCu alloy catalyst.

[0021] The TEM image of the PtCu alloy catalyst prepared in this embodiment is shown below. Figure 1 As shown, by Figure 1 It can be seen that the catalyst exhibits a cross-shaped morphology, with relatively uniform size and high selectivity.

[0022] Example 2 A method for preparing a cross-shaped nanostructured PtCu alloy catalyst includes the following steps: 1.4 mL of 20 mmol / L chloroplatinic acid aqueous solution and 5.5 mL of 1.66 mmol / L copper chloride solution were measured into a 25 mL reaction vessel. Then, 220 mg of glycine and 130 mg of polyvinylpyrrolidone were added as reducing agent. The mixture was sonicated and stirred at 600 W for 20 min and 700 rpm until the glycine and polyvinylpyrrolidone were completely dissolved and mixed evenly. The mixture was then reacted at 200 °C for 10 h in an inert atmosphere. After the reaction was completed, the mixture was centrifuged with ethanol, washed, and freeze-dried at -40 °C for 12 h to obtain the cross-shaped nanostructured PtCu alloy catalyst.

[0023] The TEM image of the PtCu alloy catalyst prepared in this embodiment is shown below. Figure 1 As shown, by Figure 1 It can be seen that the catalyst exhibits a cross-shaped morphology, with relatively uniform size and high selectivity.

[0024] Example 3 A method for preparing a cross-shaped nanostructured PtCu alloy catalyst includes the following steps: 1.4 mL of 20 mmol / L chloroplatinic acid aqueous solution and 4.5 mL of 1.66 mmol / L copper chloride solution were measured into a 25 mL reaction vessel. Then, 205 mg of glycine and 120 mg of polyvinylpyrrolidone were added as reducing agent. The mixture was sonicated and stirred at a power of 600 W for 20 min and a stirring speed of 800 rpm until the glycine and polyvinylpyrrolidone were completely dissolved and mixed evenly. The mixture was then reacted at 200 °C for 9 h in an inert atmosphere. After the reaction was completed, the mixture was centrifuged with ethanol, washed, and freeze-dried at -40 °C for 12 h to obtain the cross-shaped nanostructured PtCu alloy catalyst.

[0025] The TEM image of the PtCu alloy catalyst prepared in this embodiment is shown below. Figure 1 As shown, by Figure 1 It can be seen that the catalyst exhibits a cross-shaped morphology, with relatively uniform size and high selectivity.

[0026] Comparative Example 1 1.4 mL of a 20 mmol / L chloroplatinic acid aqueous solution and 4.0 mL of a 1.66 mmol / L copper chloride solution were measured into a 25 mL reaction vessel. Then, 200 mg of glycine (reducing agent) and 110 mg of polyvinylpyrrolidone (dispersant) were added. Next, 10 mL of oleylamine solution was added to the solution. The mixture was sonicated and stirred at 600 W for 20 min at 600 rpm until the glycine and polyvinylpyrrolidone were completely dissolved and thoroughly mixed. The mixture was then reacted at 200 °C for 8 h under an inert atmosphere. After the reaction, the mixture was centrifuged with ethanol, washed, and freeze-dried at -40 °C for 12 h to obtain the PtCu alloy nanoparticle catalyst. The TEM image of the PtCu alloy nanoparticle catalyst prepared in this comparative example is shown below. Figure 3 As shown, by Figure 3 It can be seen that the addition of the organic macromolecule oleylamine during the reaction process causes the catalyst to form nanoparticles with a surface coated with a large amount of organic matter. Using the same test conditions as in Example 1, the highest current density of the PtCu alloy nanoparticle catalyst obtained in this comparative example during ethanol electro-oxidation was 0.22 mA / cm². 2 .

[0027] Performance testing: The cross-shaped nanostructured PtCu alloy catalyst prepared in Example 1, the PtCu alloy nanoparticle catalyst prepared in Comparative Example 1, and the commercial Pt / C catalyst were applied in the electro-oxidation of ethylene glycol fuel cells, as detailed below: The anodic electro-oxidation performance was tested using a conventional three-electrode system on a CHI760E electrochemical workstation. A saturated calomel electrode was used as the reference electrode, a carbon rod as the counter electrode, and a 3 mm diameter glassy carbon electrode as the working electrode. Suspensions of cross-shaped nanostructured PtCu alloy catalysts (6 μg catalyst content), catalyst suspensions prepared in Comparative Example 1, and commercially available Pt / C catalyst suspensions were dropped onto the surface of the glassy carbon electrode and dried under an infrared lamp. After the three catalyst suspensions formed thin films on the glassy carbon electrode, 2 μL of 0.05 wt% Nafio was then dropped onto the surface of the glassy carbon electrode. For the electrochemical activation area test of the three catalyst groups (catalyst content 6 μg), 0.1 M HClO4 solution was used as the electrolyte solution. Before the experiment, high-purity N2 was passed through the electrolyte solution for 10 min to remove oxygen. Then, cyclic voltammetry was performed at a rate of 50 mV / s, with the scan range set to -0.26 to 0.94 V. During the experiment, the atmosphere above the electrolytic cell solution was maintained as N2. The current density was expressed as the current per unit electrochemical activation area of ​​the catalyst on the working electrode. Stable cyclic voltammetry curves were obtained by cyclically scanning each working electrode at a rate of 50 mV / s for 50 cycles. Figure 2 As shown, compared with commercial Pt / C catalysts, the cross-shaped nanostructured PtCu alloy catalyst prepared in this invention exhibits a maximum current density of 0.44 mA / cm² in the ethanol electro-oxidation reaction. 2 This is far higher than that of commercial Pt / C catalysts (0.36 mA / cm). 2 The current density of the PtCu alloy nanoparticle catalyst prepared in Comparative Example 1 (0.22 mA / cm²) was compared with that of the catalyst prepared in Comparative Example 1. 2 This is mainly because when preparing PtCu alloy nanoparticle catalysts using macromolecular organic solvents, the product surface is easily coated with a large amount of organic matter, causing the active sites to be shielded and unable to be effectively exposed. This makes it difficult for the reactants to fully contact the active sites, ultimately resulting in low electrocatalytic performance. The cross-shaped nanostructured PtCu alloy catalyst prepared in this embodiment of the invention exposes more unsaturated sites compared to the PtCu alloy nanoparticle catalyst prepared in Comparative Example 1, thus exhibiting superior catalytic activity in the electro-oxidation reaction of ethylene glycol.

[0028] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described in this invention to avoid redundancy. Although preferred embodiments of this invention have been described, those skilled in the art, once they understand the inventive concept of this invention, can make other changes and modifications to these embodiments, and all such changes and modifications fall within the scope of this invention.

[0029] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. If such modifications and variations fall within the scope of equivalents of this invention, then this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a cross-nanostructured PtCu alloy catalyst, characterized in that, Includes the following steps: In a reaction vessel, chloroplatinic acid aqueous solution and copper chloride solution were added sequentially, followed by a reducing agent and a dispersant. The mixture was fully dissolved by ultrasound and stirring. After being mixed evenly, the reaction was carried out under an inert atmosphere. After the reaction was completed, the catalyst was centrifuged, washed, and freeze-dried to obtain a PtCu alloy catalyst with a cross-shaped nanostructure. The molar ratio of chloroplatinic acid in the chloroplatinic acid aqueous solution to copper chloride in the copper chloride solution is 1.5:1 to 5:

1. The mass ratio of the reducing agent, dispersant and chloroplatinic acid in the aqueous solution of chloroplatinic acid is (13~20):(6~14):

1.

2. The method of claim 1, wherein the cross-shaped nanostructured PtCu alloy catalyst is prepared by the following steps of: (a) preparing a PtCu alloy catalyst by a conventional method; (b) preparing a cross-shaped nanostructured PtCu alloy catalyst by a conventional method. The reducing agent is glycine.

3. The preparation method of the cross-shaped nanostructured PtCu alloy catalyst according to claim 1, characterized in that, The dispersant is polyvinylpyrrolidone.

4. The preparation method of the cross-shaped nanostructured PtCu alloy catalyst according to claim 1, characterized in that, The ultrasonic power is 400W~800W, and the ultrasonic time is 10min~30min.

5. The preparation method of the cross-shaped nanostructured PtCu alloy catalyst according to claim 1, characterized in that, The stirring speed is 400 rpm to 1000 rpm.

6. The preparation method of the cross-shaped nanostructured PtCu alloy catalyst according to claim 1, characterized in that, The heating reaction temperature is 160℃~200℃, and the heating reaction time is 4h~10h.

7. The preparation method of the cross-shaped nanostructured PtCu alloy catalyst according to claim 1, characterized in that, The freeze-drying temperature is -40℃ to 0℃, and the freeze-drying time is 6h to 12h.

8. The application of a cross-shaped nanostructured PtCu alloy catalyst prepared by the preparation method according to any one of claims 1 to 7 in an ethylene glycol fuel cell.

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