Platinum-based electrocatalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of electrocatalysts, in particular to a platinum-based electrocatalyst and a preparation method and application thereof.The platinum-based electrocatalyst is a Pt active site loaded hollow carbon nanosphere (HCS), on the basis, the platinum-based electrocatalyst is coated with a graphene oxide layer, the coating layer induces compressive strain of a Pt (111) crystal face through thermal reduction shrinkage, and the Pt active site loaded hollow carbon nanosphere is obtained. And a composite structure with enhanced activity and stability protection is formed. The preparation method comprises the following steps: step 1, preparing microporous hollow carbon nanospheres (HCS); and step 2, preparation of the Pt-based electrocatalyst. Platinum nanoparticles are loaded on hollow carbon spheres to obtain a platinum-containing catalyst precursor with high catalytic activity, graphene oxide (GO) shrinks in the thermal reduction process to form a reduced graphene oxide (rGO) layer, lattices are induced on the surfaces of platinum active sites in the shrinkage process to generate compressive strain, so that the center of a d band of platinum is shifted upwards, and the platinum-containing catalyst is obtained. The adsorption energy of an oxygen reduction reaction (ORR) intermediate is improved, the reaction energy barrier is reduced, and the catalytic intrinsic activity is improved.

Description

Technical Field

[0001] This invention relates to the field of electrocatalyst technology, and in particular to a platinum-based electrocatalyst, its preparation method, and its application. Background Technology

[0002] Fuel cells and metal-air batteries are considered core technologies for achieving carbon neutrality due to their efficient and environmentally friendly energy conversion characteristics. However, the slow kinetics of the oxygen reduction reaction (ORR) at the cathode greatly limit the overall efficiency of fuel cells. Platinum group metals (PGMs) possess excellent intrinsic catalytic activity and remain among the few commercially viable catalytic materials for various catalytic applications. However, conventional platinum-based electrocatalysts are susceptible to performance degradation, such as activity poisoning and decreased stability during the reaction. The root cause lies in the direct exposure of the metal active sites in platinum-based catalysts to the electrolyte, which easily leads to the oxidation, migration, and aggregation of platinum, while strengthening structural stability typically results in a reduction of active sites.

[0003] Existing technologies (such as commercial platinum-carbon catalysts) exhibit a sharp decline in catalytic activity under low platinum loading and are susceptible to Ostwald ripening during long-term operation, leading to failure. Therefore, developing a catalyst that combines high activity, high stability, and low platinum loading has become a critical technological bottleneck that urgently needs to be overcome. Graphene oxide (GO) is an important variant of graphene, disrupting the π bonds between the original graphene layers and promoting flexibility and ductility. Reduced graphene oxide (rGO), formed under thermal reduction conditions, decomposes its internal oxygen-containing functional groups, reducing interlayer spacing. This shrinkage significantly improves conductivity and introduces mechanical stress. This shrinkage stress can be transferred to the nanoparticles supported on its surface, compressing the particle lattice and thus regulating the electronic structure. Currently, there is a lack of platinum-based electrocatalyst preparation schemes that systematically and controllably induce Pt lattice compressive strain while simultaneously achieving physical protection of Pt active sites using the thermal reduction shrinkage process of rGO. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a platinum-based electrocatalyst, its preparation method, and its application. By loading platinum active sites onto hollow carbon nanospheres and constructing a reduced graphene oxide protective layer on their surface to induce shrinkage strain on the Pt(111) crystal plane, the problem of balancing catalytic activity and stability of platinum-based catalysts is overcome.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A platinum-based electrocatalyst is a hollow carbon nanosphere (HCS) supported on Pt active sites, which is then coated with a graphene oxide layer. This coating layer induces compressive strain on the Pt(111) crystal plane through thermal reduction shrinkage, forming a composite structure that enhances activity and protects stability. This optimizes the electronic structure of the Pt catalytic active sites and reduces poisoning such as acid and alkali corrosion.

[0007] Preferably, the hollow carbon nanospheres are microporous nanospheres.

[0008] Preferably, the hollow carbon nanospheres have a diameter of 100~350nm and a carbon shell thickness of 5~30nm.

[0009] A method for preparing a platinum-based electrocatalyst includes the following steps:

[0010] Step 1: Preparation of microporous hollow carbon nanospheres (HCS)

[0011] 500 μL of polystyrene (PS) mother liquor was dispersed in 25 mL of deionized water, 35 μL of pyrrole was added, and 10 mL of aqueous solution containing 40 mg of ammonium persulfate was added dropwise while stirring. After stirring at room temperature for 4 h, the mixture was filtered, washed successively with deionized water and ethanol, and dried under vacuum at 60 °C for 12 h. After grinding, the mixture was carbonized at 800 °C for 2 h in a N2 atmosphere. The obtained product was acidified with nitric acid, washed, and dried to obtain the HCS precursor.

[0012] Step 2: Preparation of Pt-based electrocatalysts

[0013] 100 mg HCS was ultrasonically dispersed in 50 mL of ethylene glycol (EG) solution containing 32 mg potassium chloroplatinate (K2PtCl4), and the mixture was stirred in an oil bath at 120 °C for 12 h. The product was then filtered and dried to obtain HCS-Pt. Subsequently, HCS-Pt was reacted with a single-layer graphene oxide dispersion (1 mg / mL). -1 The mixture was sonicated for 20 min and stirred for 2 h; after centrifugation, washing, and freeze-drying, the resulting HCS-Pt@GO was placed in an H2 / Ar atmosphere and incubated at 2℃ for 2 min. -1 The temperature was raised to 270℃, held for 2 hours, and then allowed to cool naturally to obtain a platinum-based electrocatalyst (HCS-Pt@rGO) coated with a reduced graphene oxide layer.

[0014] Preferably, in step 2, the platinum content is 10-15 wt%, and the GO addition amount is 4 wt% of the precursor content.

[0015] The present invention also provides an application of the above-mentioned platinum-based electrocatalyst in fuel cells and metal-air battery catalyst materials.

[0016] By employing the above-mentioned technical solution, platinum nanoparticles are loaded onto hollow carbon spheres to obtain a platinum-containing catalyst precursor with high catalytic activity. Then, graphene oxide (GO) shrinks during thermal reduction to form a reduced graphene oxide (rGO) layer. This shrinkage process induces compressive strain in the lattice on the surface of the platinum active sites, thereby shifting the d-band center of platinum upward, increasing the adsorption energy of the oxygen reduction reaction (ORR) intermediate and lowering the reaction energy barrier, thus improving the intrinsic catalytic activity. At the same time, the rGO layer acts as a protective shell to prevent platinum crystals from being directly exposed to the electrolyte, significantly enhancing the durability and lifespan of the catalyst. It can be applied to the preparation of catalyst materials for fuel cells and metal-air batteries.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. This invention effectively optimizes the electronic structure of Pt and improves the intrinsic catalytic activity of ORR by in-situ inducing Pt lattice compressive strain through rGO thermal reduction shrinkage.

[0019] 2. This invention uses rGO thin layers to simultaneously achieve physical encapsulation of Pt active sites, effectively improving the structural stability of the catalyst during long-term electrochemical operation.

[0020] 3. This invention significantly reduces the amount of Pt used while maintaining high activity, and has good prospects for industrial application. Attached Figure Description

[0021] Figure 1 This is a comparison chart of the linear scanning voltammetric electrochemical performance of the embodiments of the present invention and Comparative Examples 1 and 2;

[0022] Figure 2 This is a comparison chart of the linear scanning voltammetric electrochemical performance of the embodiments of the present invention and comparative examples 3, 4, and 5;

[0023] Figure 3 This is a comparison chart of the linear scanning voltammetric electrochemical performance of the embodiments of the present invention and comparative examples 6, 7, and 8;

[0024] Figure 4 This is a comparison graph showing the linear cyclic voltammetric electrochemical performance of the embodiments of the present invention with that of Comparative Examples 1 and 2;

[0025] Figure 5 This is a comparison graph showing the linear cyclic voltammetric electrochemical performance of the embodiments of the present invention with that of Comparative Examples 3, 4, and 5;

[0026] Figure 6 This is a comparison chart of the linear cyclic voltammetric electrochemical performance of the embodiments of the present invention and comparative examples 6, 7, and 8;

[0027] Figure 7 This is a comparison chart of the cyclic voltammetric stability performance of the embodiments of the present invention and Comparative Examples 1 and 2;

[0028] Figure 8 This is a comparison diagram of the open circuit potentials of the assembled zinc-air battery devices in the embodiments of the present invention and Comparative Example 1.

[0029] Figure 9 This is a comparison chart of the charge-discharge cycle performance of the zinc-air battery devices assembled in the embodiments of the present invention and Comparative Example 1.

[0030] Figure 10 The image shows the morphology of the rGO layer under a 5nm scale in an embodiment of the present invention.

[0031] Figure 11 This is a high-resolution transmission electron microscope image of Comparative Example 1 of the present invention on a 1 nm scale, to demonstrate the original Pt(111) lattice spacing.

[0032] Figure 12 The image shown is a high-resolution transmission electron microscope image of an embodiment of the present invention on a 1 nm scale, to demonstrate that the Pt(111) lattice spacing is compressed.

[0033] Figure 13 This is a transmission electron microscopy (TEM) elemental energy spectrum of an embodiment of the present invention at a 10 nm scale.

[0034] Figure 14 This is a high-resolution X-ray photoelectron spectrum of embodiment C 1s of the present invention;

[0035] Figure 15 This is a high-resolution X-ray photoelectron spectrum of embodiment N 1s of the present invention;

[0036] Figure 16 This is a high-resolution X-ray photoelectron spectrum of Pt 4f according to an embodiment of the present invention;

[0037] Figure 17 The X-ray diffraction patterns of Pt element in the embodiments of the present invention and comparative examples 3, 4, and 5 are shown below.

[0038] Figure 18 The X-ray diffraction patterns of Pt element in the embodiments of the present invention and comparative examples 6, 7, and 8 are shown. Detailed Implementation

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings, so that those skilled in the art can better understand the advantages and features of the present invention, thereby making a clearer definition of the scope of protection of the present invention. The embodiments described in this invention are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0040] Note: There are no special restrictions on the source of any raw materials used in this invention. They can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0041] This invention provides a Pt-based catalyst, which is a hollow carbon nanosphere loaded with Pt active sites coated with a reduced graphene oxide layer. The active sites are Pt nanoparticles. The coating of the reduced graphene oxide layer induces the shrinkage strain of the Pt(111) crystal plane, which optimizes the adsorption of intermediates and reduces the theoretical overpotential, restricts the aggregation of Pt nanoparticles, and delays oxidation and dissolution. Due to the different pyrolysis temperatures, the shrinkage degree of the reduced graphene oxide layer changes, and the compressive strain degree of the Pt(111) crystal plane changes accordingly. The conductivity and intrinsic activity of the catalyst also change.

[0042] In this invention, the Pt content is 10-15 wt%, preferably 15 wt%. The loading of monolayer graphene oxide is 3-6 wt% of the precursor content, preferably 4 wt%. In this invention, hollow carbon nanospheres are the carriers of the metal active sites. Preferably, the hollow carbon nanospheres used are microporous nanospheres with a diameter of 100-350 nm and a shell thickness of 5-30 nm. Graphene oxide is the coating layer for the metal active sites and is also the key to inducing compressive strain on the Pt(111) crystal plane. Preferably, a monolayer graphene oxide aqueous dispersion with a sheet diameter of 100-500 nm is used.

[0043] This invention also provides a method for preparing a Pt-based electrocatalyst with lattice compressive strain induced by the above-mentioned thermally reduced graphene oxide layer, comprising the following steps:

[0044] 1) Preparation of microporous hollow carbon nanospheres (HCS)

[0045] 500 μL of polystyrene (PS) mother liquor was dispersed in 25 mL of deionized water, 35 μL of pyrrole was added, and 10 mL of aqueous solution containing 40 mg of ammonium persulfate was added dropwise while stirring. After stirring at room temperature for 4 h, the mixture was filtered, washed successively with deionized water and ethanol, and dried under vacuum at 60 °C for 12 h. After grinding, the mixture was carbonized at 800 °C for 2 h in a N2 atmosphere. The resulting product was acidified with nitric acid, washed, and dried to obtain the HCS precursor.

[0046] 2) Preparation of Pt-based electrocatalysts

[0047] 100 mg HCS was ultrasonically dispersed in 50 mL of ethylene glycol (EG) solution containing 32 mg potassium chloroplatinate (K₂PtCl₄), and the mixture was stirred in an oil bath at 120 °C for 12 h. The product was then filtered and dried to obtain HCS-Pt. Subsequently, HCS-Pt was reacted with a single-layer graphene oxide dispersion (1 mg / mL). -1The mixture was sonicated for 20 min and stirred for 2 h. After centrifugation, washing, and freeze-drying, the resulting HCS-Pt@GO was placed in an H2 / Ar atmosphere and incubated at 2 °C for 2 min. -1 The temperature was raised to 270℃, held for 2 hours, and then allowed to cool naturally to obtain a platinum-based electrocatalyst (HCS-Pt@rGO) coated with a reduced graphene oxide layer.

[0048] Example

[0049] This embodiment provides a Pt-based electrocatalyst with lattice compressive strain induced by thermal reduction of graphene oxide layers. The specific preparation method is as follows:

[0050] (1) Preparation of hollow carbon nanospheres (HCS): 500 μL of PS mother liquor was dispersed in 25 mL of deionized water under stirring. 35 μL of pyrrole was added, and 40 mg of ammonium persulfate solution dissolved in 10 mL of deionized water was slowly added dropwise under stirring. The mixture was stirred at room temperature for 4 h. The resulting suspension was filtered and washed with deionized water and ethanol. The resulting filter cake was placed in a vacuum drying oven and dried overnight at 60 °C. The dried filter cake was ground and placed in a crucible, which was then placed in a tube furnace and pyrolyzed at 800 °C for 2 h under a N2 atmosphere. The carbonized powder was ultrasonically dispersed in nitric acid and stirred overnight. After filtration, washing, and drying, the dried filter cake was ground and collected. The resulting powder was the hollow carbon nanospheres (HCS).

[0051] (2) 100 mg HCS was ultrasonically dispersed in 50 mL of ethylene glycol (EG) solution containing 32 mg potassium chloroplatinate (K2PtCl4), and the mixture was stirred in an oil bath at 120 °C for 12 h. The product after reaction was filtered and dried to obtain HCS-Pt. Subsequently, 10 mg HCS-Pt was reacted with 400 μL of monolayer graphene oxide dispersion (1 mg / mL). -1 The mixture was sonicated for 20 min and stirred for 2 h. After centrifugation, washing, and freeze-drying, HCS-Pt@GO was obtained. The obtained HCS-Pt@GO was then placed in an H2 / Ar atmosphere and incubated at 2℃ for 2 min. -1 The temperature was raised to 270℃, held for 2 hours, and then allowed to cool naturally to obtain a platinum-based electrocatalyst (HCS-Pt@rGO) coated with a reduced graphene oxide layer.

[0052] Comparative Example 1

[0053] The comparative example used in this invention is commercially available platinum carbon (JM, 20 wt%).

[0054] Comparative Example 2

[0055] The comparative example used in this invention is HCS-Pt without coating of reduced graphene oxide.

[0056] Comparative Example 3

[0057] The comparative example used in this invention is a platinum-based catalyst with a graphene oxide (GO) content of 3 wt%.

[0058] 100 mg HCS was ultrasonically dispersed in 50 mL of ethylene glycol (EG) solution containing 32 mg potassium chloroplatinate (K₂PtCl₄), and the mixture was stirred in an oil bath at 120 °C for 12 h. The product was then filtered and dried to obtain HCS-Pt. Subsequently, 10 mg HCS-Pt was reacted with 300 μL of monolayer graphene oxide dispersion (1 mg / mL). -1 The mixture was sonicated for 20 min and stirred for 2 h. After centrifugation, washing, and freeze-drying, HCS-Pt@GO was obtained. The obtained HCS-Pt@GO was then placed in an H2 / Ar atmosphere and incubated at 2℃ for 2 min. -1 The temperature was raised to 270℃, held for 2 hours, and then allowed to cool naturally to obtain a platinum-based electrocatalyst (HCS-Pt@rGO-3wt%) coated with a reduced graphene oxide layer.

[0059] Comparative Example 4

[0060] The comparative example used in this invention is a platinum-based catalyst with a graphene oxide (GO) content of 5 wt%.

[0061] 100 mg HCS was ultrasonically dispersed in 50 mL of ethylene glycol (EG) solution containing 32 mg potassium chloroplatinate (K₂PtCl₄), and the mixture was stirred in an oil bath at 120 °C for 12 h. The product was then filtered and dried to obtain HCS-Pt. Subsequently, 10 mg HCS-Pt was reacted with 500 μL of monolayer graphene oxide dispersion (1 mg / mL). -1 The mixture was sonicated for 20 min and stirred for 2 h. After centrifugation, washing, and freeze-drying, HCS-Pt@GO was obtained. The obtained HCS-Pt@GO was then placed in an H2 / Ar atmosphere and incubated at 2℃ for 2 min. -1 The temperature was raised to 270℃, held for 2 hours, and then naturally cooled to obtain a platinum-based electrocatalyst (HCS-Pt@rGO-5wt%) coated with a reduced graphene oxide layer.

[0062] Comparative Example 5

[0063] The comparative example used in this invention is a platinum-based catalyst with a graphene oxide (GO) content of 6 wt%.

[0064] 100 mg HCS was ultrasonically dispersed in 50 mL of ethylene glycol (EG) solution containing 32 mg potassium chloroplatinate (K₂PtCl₄), and the mixture was stirred in an oil bath at 120 °C for 12 h. The product was then filtered and dried to obtain HCS-Pt. Subsequently, 10 mg HCS-Pt was reacted with 400 μL of monolayer graphene oxide dispersion (1 mg / mL). -1The mixture was sonicated for 20 min and stirred for 2 h. After centrifugation, washing, and freeze-drying, HCS-Pt@GO was obtained. The obtained HCS-Pt@GO was then placed in an H2 / Ar atmosphere and incubated at 2℃ for 2 min. -1 The temperature was raised to 270℃, held for 2 hours, and then allowed to cool naturally to obtain a platinum-based electrocatalyst (HCS-Pt@rGO-6wt%) coated with a reduced graphene oxide layer.

[0065] Comparative Example 6

[0066] The comparative example used in this invention is a platinum-based catalyst with a thermal reduction temperature of 180°C.

[0067] 100 mg HCS was ultrasonically dispersed in 50 mL of ethylene glycol (EG) solution containing 32 mg potassium chloroplatinate (K₂PtCl₄), and the mixture was stirred in an oil bath at 120 °C for 12 h. The product was then filtered and dried to obtain HCS-Pt. Subsequently, 10 mg HCS-Pt was reacted with 400 μL of monolayer graphene oxide dispersion (1 mg / mL). -1 The mixture was sonicated for 20 min and stirred for 2 h. After centrifugation, washing, and freeze-drying, HCS-Pt@GO was obtained. The obtained HCS-Pt@GO was then placed in an H2 / Ar atmosphere and incubated at 2℃ for 2 min. -1 The temperature was raised to 180℃, held for 2 hours, and then allowed to cool naturally to obtain a platinum-based electrocatalyst (HCS-Pt@rGO T-180) coated with a reduced graphene oxide layer.

[0068] Comparative Example 7

[0069] The comparative example used in this invention is a platinum-based catalyst with a thermal reduction temperature of 240°C.

[0070] 100 mg HCS was ultrasonically dispersed in 50 mL of ethylene glycol (EG) solution containing 32 mg potassium chloroplatinate (K₂PtCl₄), and the mixture was stirred in an oil bath at 120 °C for 12 h. The product was then filtered and dried to obtain HCS-Pt. Subsequently, 10 mg HCS-Pt was reacted with 400 μL of monolayer graphene oxide dispersion (1 mg / mL). -1 The mixture was sonicated for 20 min and stirred for 2 h. After centrifugation, washing, and freeze-drying, HCS-Pt@GO was obtained. The obtained HCS-Pt@GO was then placed in an H2 / Ar atmosphere and incubated at 2℃ for 2 min. -1 The temperature was raised to 240℃, held for 2 hours, and then allowed to cool naturally to obtain a platinum-based electrocatalyst (HCS-Pt@rGO T-240) coated with a reduced graphene oxide layer.

[0071] Comparative Example 8

[0072] The comparative example used in this invention is a platinum-based catalyst with a thermal reduction temperature of 300°C.

[0073] 100 mg HCS was ultrasonically dispersed in 50 mL of ethylene glycol (EG) solution containing 32 mg potassium chloroplatinate (K₂PtCl₄), and the mixture was stirred in an oil bath at 120 °C for 12 h. The product was then filtered and dried to obtain HCS-Pt. Subsequently, 10 mg HCS-Pt was reacted with 400 μL of monolayer graphene oxide dispersion (1 mg / mL). -1 The mixture was sonicated for 20 min and stirred for 2 h. After centrifugation, washing, and freeze-drying, HCS-Pt@GO was obtained. The obtained HCS-Pt@GO was then placed in an H2 / Ar atmosphere and incubated at 2℃ for 2 min. -1 The temperature was raised to 270℃, held for 2 hours, and then allowed to cool naturally to obtain a platinum-based electrocatalyst (HCS-Pt@rGO T-300) coated with a reduced graphene oxide layer.

[0074] This invention first disperses PS mother liquor in deionized water, then adds pyrrole and ammonium persulfate solution, stirs the reaction, filters, washes with deionized water and anhydrous ethanol, vacuum dries the resulting powder, grinds it, places it in a crucible, and pyrolyzes it in a tube furnace. The resulting solid product is ground, collected, acid-washed with nitric acid, then filtered, washed, dried, and ground again to obtain hollow carbon nanospheres (HCS). The hollow carbon nanospheres (HCS) are ultrasonically dispersed in an ethylene glycol (EG) solution containing potassium chloroplatinate (K2PtCl4), and reacted in an oil bath at 120°C for 12 hours. The reacted product is filtered and dried to obtain HCS-Pt. Subsequently, 10 mg of HCS-Pt is reacted with a single-layer graphene oxide dispersion (1 mg / mL). -1 The mixture was sonicated for 20 min and stirred for 2 h. After centrifugation, washing, and freeze-drying, the resulting HCS-Pt@GO was placed in an H2 / Ar atmosphere and incubated at 2 °C for 2 min. -1 The temperature was raised to the target temperature, held for 2 hours, and then allowed to cool naturally to obtain a platinum-based electrocatalyst (HCS-Pt@rGO) coated with a reduced graphene oxide layer.

[0075] In this invention, a monolayer graphene oxide aqueous solution (1 mg / mL) is used to coat platinum nanoparticles. -1 The mass fraction of Pt is preferably 3-6 wt%, more preferably 4 wt%. The content of potassium chloroplatinate (K2PtCl4) is calculated based on the amount of Pt in the compound. In this invention, the preferred mass fraction of Pt is 10 wt% to 15 wt%, more preferably 15 wt%. The thermal reduction temperature of the catalyst in the H2 / Ar atmosphere is preferably 180-300℃, more preferably 270℃. The metal content in the catalyst is mainly affected by the content of the metal precursor potassium chloroplatinate (K2PtCl4), and the degree of shrinkage strain of the Pt(111) crystal plane is affected by the content of graphene oxide and the pyrolysis temperature in the H2 / Ar atmosphere.

[0076] The Pt-based electrocatalyst of the present invention, which uses the above-mentioned thermally reduced graphene oxide layer to induce lattice compressive strain, can be applied to the preparation of catalyst materials for fuel cells and metal-air batteries.

[0077] Test case

[0078] All embodiments and comparative examples of the present invention were subjected to linear cyclic voltammetry and linear scan voltammetry tests under the same test conditions.

[0079] This invention uses a rotating disk electrode device for electrochemical testing. The catalyst ink preparation formula is: 1 mg catalyst powder, 20 μL 5 wt% Nafion solution, 980 μL water and isopropanol dispersion (volume ratio 1:1). The catalyst drop volume is 10 μL. A glassy carbon electrode is used as the working electrode, a platinum mesh as the counter electrode, Hg / HgO as the reference electrode, and 0.1 M KOH as the electrolyte.

[0080] Figure 1 A comparison of the linear sweep voltammetric electrochemical performance of the above platinum-based catalyst with that of Comparative Examples 1 and 2 shows that the above platinum-based catalyst has a larger half-wave potential and limiting current density, a stronger affinity for oxygen, lower reaction barriers, and improved energy conversion efficiency.

[0081] Figure 2 A comparison of the linear sweep voltammetric electrochemical performance of the above catalyst with that of comparative examples 3, 4, and 5 shows that the above platinum-based catalyst has a larger half-wave potential and limiting current density, a stronger affinity for oxygen, lower reaction barriers, and improved energy conversion efficiency.

[0082] Figure 3 A comparison of the linear sweep voltammetric electrochemical performance of the above catalyst with that of comparative examples 6, 7, and 8 shows that the above platinum-based catalyst has a larger half-wave potential and limiting current density, a stronger affinity for oxygen, lower reaction barriers, and improved energy conversion efficiency.

[0083] Figure 4 The linear cyclic voltammetric electrochemical performance of the above catalyst was compared with that of Comparative Examples 1 and 2, and it can be seen that the examples have better catalytic activity.

[0084] Figure 5 A comparison of the linear cyclic voltammetric electrochemical performance of the above catalyst with that of Comparative Examples 3, 4, and 5 shows that the examples exhibit better catalytic activity.

[0085] Figure 6 A comparison of the linear cyclic voltammetric electrochemical performance of the above catalyst with that of Comparative Examples 6, 7, and 8 shows that the examples exhibit better catalytic activity.

[0086] Figure 7The linear scanning voltammetric electrochemical performance of the above catalyst compared with that of Comparative Examples 1 and 2 after 30,000 linear cyclic voltammetry cycles was compared, and the examples showed better catalytic stability.

[0087] Figure 8 , 9 The open-circuit potential and charge-discharge cycle performance of the catalyst tested after assembling the zinc-air battery device were superior to those of Comparative Example 1.

[0088] Figure 10 , 11 Figures 1 and 12 show the transmission electron microscopy (TEM) characterization images of the catalysts described above. The presence of the rGO layer and the shrinkage of the Pt nanoparticles were determined by measuring the morphology and lattice spacing.

[0089] Figure 13 The above catalyst is shown in the transmission electron microscopy (TEM) image. The elemental energy dispersive spectroscopy (EDS) confirmed the loading of Pt.

[0090] Figure 14 , 15 Figures 1 and 16 show the high-resolution X-ray energy dispersive spectra of C 1s, N 1s, and Pt 4f of the catalysts mentioned above.

[0091] Figure 17 , 18 The X-ray diffraction patterns of the above catalyst and Pt elements in Comparative Examples 3-8 are shown. By comparing the peak intensity and peak position, it is proved that the Pt element lattice is compressed.

[0092] In summary, this invention involves in-situ coating of GO onto the surface of Pt nanocrystals supported by hollow carbon spheres (HCS), and controlling the shrinkage of rGO by adjusting the thickness of the graphene oxide coating layer and the thermal reduction temperature. This shrinkage process induces compressive strain on the Pt(111) crystal plane, with the strain degree exhibiting a volcano-like relationship with the thermal reduction temperature. Simultaneously, the rGO layer effectively encapsulates the Pt crystals, preventing direct contact between them and the electrolyte and weakening the Ostwald ripening effect. Experimental results show that the shrinkage of the rGO coating layer induces compressive strain on the Pt(111) crystal plane, enhancing its electrocatalytic activity in the oxygen reduction reaction (ORR), significantly improving long-term stability, and demonstrating excellent cycle durability in zinc-air battery applications. This method overturns the traditional inverse relationship between activity and stability, achieving a synergistic improvement in both. This invention provides a new approach for improving the intrinsic activity of Pt-based catalysts and developing low-cost, high-durability ORR catalysts, possessing significant theoretical importance and application prospects.

[0093] The descriptions and practices disclosed in this invention are readily apparent and understandable to those skilled in the art, and various modifications and refinements can be made without departing from the principles of this invention. Therefore, any modifications or improvements made without departing from the spirit of this invention should also be considered within the scope of protection of this invention.

Claims

1. A platinum-based electrocatalyst, characterized in that, The platinum-based electrocatalyst is a hollow carbon nanosphere HCS supported on Pt active sites, which is then coated with a graphene oxide layer. This coating layer induces compressive strain on the Pt(111) crystal plane through thermal reduction shrinkage, forming a composite structure that enhances activity and protects stability.

2. The platinum-based electrocatalyst according to claim 1, characterized in that, The hollow carbon nanospheres are microporous nanospheres.

3. The platinum-based electrocatalyst according to claim 1, characterized in that, The hollow carbon nanospheres have a diameter of 100~350nm and a carbon shell thickness of 5~30nm.

4. A method for preparing a platinum-based electrocatalyst according to any one of claims 1-3, characterized in that, Includes the following steps: Step 1: Preparation of microporous hollow carbon nanospheres (HCS) 500 μL of polystyrene (PS) mother liquor was dispersed in 25 mL of deionized water, 35 μL of pyrrole was added, and 10 mL of aqueous solution containing 40 mg of ammonium persulfate was added dropwise while stirring. After stirring at room temperature for 4 h, the mixture was filtered, washed successively with deionized water and ethanol, and dried under vacuum at 60 °C for 12 h. After grinding, the mixture was carbonized at 800 °C for 2 h in a N2 atmosphere. The obtained product was acidified with nitric acid, washed, and dried to obtain the HCS precursor. Step 2: Preparation of Pt-based electrocatalysts 100 mg HCS was ultrasonically dispersed in 50 mL of ethylene glycol solution containing 32 mg potassium chloroplatinate, and the mixture was stirred in an oil bath at 120 °C for 12 h. The product was filtered and dried to obtain HCS-Pt. Subsequently, HCS-Pt was mixed with a monolayer graphene oxide dispersion and ultrasonicated for 20 min, then stirred for 2 h. After centrifugation, washing, and freeze-drying, the obtained HCS-Pt@GO was placed in an H2 / Ar atmosphere and incubated at 2 °C for 1 min. -1 The temperature was raised to 270℃, held for 2 hours, and then allowed to cool naturally to obtain a platinum-based electrocatalyst coated with a reduced graphene oxide layer.

5. The method for preparing a platinum-based electrocatalyst according to claim 4, characterized in that, In step 2, the platinum content is 10-15 wt%, and the GO addition amount is 4 wt% of the precursor content.

6. The application of the platinum-based electrocatalyst according to any one of claims 1-3 in fuel cells and metal-air battery catalyst materials.

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