One-dimensional zigzag ultrathin Pt-based nanoshell catalyst coated on carbon nanotube and having rich defects and preparation method of one-dimensional zigzag ultrathin Pt-based nanoshell catalyst

Abstract

The invention relates to the field of carbon-loaded nano-catalysts, in particular to a one-dimensional zigzag ultrathin Pt-based nano-shell catalyst which is coated on a carbon nanotube and has abundant defects and a preparation method of the one-dimensional zigzag ultrathin Pt-based nano-shell catalyst. According to the catalyst, a carbon nanotube film is used as a substrate, magnetron sputtering is carried out at room temperature, then rapid annealing is carried out, and finally a one-dimensional zigzag ultrathin Pt-based nano shell is formed and uniformly coats a carbon nanotube bundle. The ultrathin Pt-based nano shell has abundant surface structures (high-index edge steps) and a large number of crystal defects such as twin crystals and stacking faults, the electronic structure of surface atoms is adjusted, and the adsorption / desorption strength of an intermediate is optimized, so that the catalytic activity is influenced. According to the method, efficient and controllable preparation of the defect type Pt-based nanowire catalyst is achieved, the activity and stability of the catalyst are improved, the method can be suitable for various catalytic reactions related to fuel cells, and the method is expected to be a practical method for large-scale preparation and application of the catalyst.

Description

Technical Field

[0001] This invention relates to the field of carbon-supported nanocatalysts, specifically to a one-dimensional serrated ultrathin Pt-based nanoshell catalyst with abundant defects coated on carbon nanotubes and its preparation method. Background Technology

[0002] Direct alcohol fuel cells (DAFCs) are promising energy devices that convert the green chemical energy of methanol or ethanol into electrical energy, offering advantages such as high energy density, convenient storage, transportation, and environmental friendliness. However, the kinetics of the methanol oxidation and ethanol oxidation reactions at the anode are sluggish, several orders of magnitude slower than the hydrogen oxidation reaction, and the catalysts are prone to poisoning, which significantly limits the application of DAFCs. Pt nanomaterials are currently the most widely used catalysts for methanol and ethanol oxidation reactions, but they are expensive, have poor activity and stability, and pure Pt is particularly susceptible to deactivation due to the binding of CO intermediates. Therefore, efforts are being made to develop advanced Pt-based catalysts.

[0003] It is well known that the catalytic performance of a catalyst is closely related to its composition, size, shape, and geometry. For example, Pt combined with other transition metals to form Pt-M alloy catalysts (M = Fe, Co, Ni, Cu, Zn, Ru, Ir, etc.), and further processed into different shapes such as nanocubes, nanowires, nanoplates, nanoflowers, and nanosheets, improves catalytic activity due to ligand and strain effects. In fact, the atomic configuration of the surface is another key factor affecting catalyst performance, especially abundant surface structures (e.g., edges, corners) and crystal defects terminating at the surface (e.g., interstitial spaces, vacancies, dislocations, grain boundaries, twin boundaries, stacking faults, etc.). These optimize the intrinsic activity of the catalyst by regulating the surface geometry and electronic structure. Defect formation is a high-energy process, and traditional chemical strategies struggle to induce controllable defects in Pt-M nanocatalysts. Many synthetic methods have emerged, such as etching, dealloying, ion irradiation, and doping. However, these methods are insufficient to control and preserve these crystal defects during use.

[0004] Carbon nanotubes have been proven to significantly enhance the stability of nanocatalysts when used as carbon supports. A unique, strong symmetric periodic van der Waals (vdW) interaction exists between the supported nanocrystals and the single-walled carbon nanotube bundles, with an energy potential at the grooves. This leads to diffusion anisotropy of the nanocrystals and allows for relatively firm fixation of the nanocrystals. Therefore, from a defect engineering perspective, recrystallization of randomly distributed nanocrystals on single-walled carbon nanotube bundles can potentially lead to the generation of various crystal defects. Utilizing this property allows for the controllable preparation of defect catalysts and is beneficial for improving catalyst stability. Summary of the Invention

[0005] To improve catalyst activity and stability by designing stable and controllable surface structures and crystal defects, this invention aims to propose a one-dimensional serrated ultrathin Pt-based nanoshell catalyst with abundant defects coated on carbon nanotubes and its preparation method. Through magnetron sputtering and annealing, a catalyst with a defect-rich nanoshell structure was obtained. The thickness of this Pt-based (PtFe, PtCo, and PtNi) nanoshell is only 3–6 nm. The serrated edges of the nanoshell consist of high-index edge steps, exhibiting numerous crystal defects including {111} twin boundaries and stacking faults, as well as defect-induced strain, which significantly improves the catalytic activity for methanol and ethanol oxidation. Simultaneously, this Pt-based nanoshell catalyst exhibits good long-term durability, retaining edge steps, twins, and stacking faults even after stability testing. This invention provides a simple and efficient approach for synthesizing defect-type catalysts, and the prepared Pt-based nanoshell catalyst can be applied to various fuel cell-related catalytic reactions.

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

[0007] A one-dimensional serrated ultrathin Pt-based nanoshell catalyst with abundant defects coated on carbon nanotubes is obtained by depositing dense and uniformly distributed Pt-based catalyst nanoparticles of different compositions on a carbon nanotube film as a substrate through room temperature magnetron sputtering of a platinum target and other metal targets. The nanoparticles are then rapidly annealed to recrystallize, grow, and interconnect, ultimately yielding a one-dimensional serrated ultrathin Pt-based nanoshell catalyst with abundant defects completely coated on a carbon nanotube film.

[0008] The one-dimensional serrated ultrathin Pt-based nanoshell catalyst with abundant defects coated on carbon nanotubes uses a carbon nanotube film as the substrate. The carbon nanotube film is a self-supporting porous carbon nanotube film composed of overlapping single-walled carbon nanotube bundles. The pores are uniformly distributed, and the pore size varies with different thicknesses. The diameter of the single-walled carbon nanotube bundles in the carbon nanotube film used is 5–50 nm, the length of the single-walled carbon nanotubes is 5–50 μm, the thickness of the carbon nanotube film is 40–400 nm, and the average pore size is 10–50 nm.

[0009] The one-dimensional serrated ultrathin Pt-based nanoshell catalyst with abundant defects coated on carbon nanotubes is transferred to hollowed-out supports of various shapes and sizes for double-sided magnetron sputtering, which facilitates the uniform deposition of sputtering materials on each carbon nanotube bundle and is beneficial for large-area catalyst synthesis.

[0010] The aforementioned one-dimensional serrated ultrathin Pt-based nanoshell catalyst with abundant defects coated on carbon nanotubes is co-deposited with one or more of the following elements: Pt, Fe, Co, Ni, Cu, Zn, Ru, Rh, Ir, Sn, Au, and Ag. By changing the type of target material used in magnetron sputtering, Pt-based binary or ternary alloy nanoshell catalysts with different compositions can be prepared. This catalyst is suitable for various catalytic reactions related to fuel cells. Furthermore, by adjusting the sputtering power and sputtering time, the composition ratio and the deposition density of Pt-based nanoparticles on carbon nanotubes can be controlled.

[0011] The one-dimensional serrated ultrathin Pt-based nanoshell catalyst with abundant defects coated on carbon nanotubes is annealed after room temperature magnetron sputtering at a temperature of 270–300°C, a heating rate of 40°C ± 5°C / min, and a holding time of 1–1.5 h. This process ensures that the nanoparticles recrystallize but do not grow excessively, forming a one-dimensional serrated ultrathin Pt-based nanoshell coating the carbon nanotube film. During the annealing process, when adjacent nanoparticles undergo diffusion motion due to heating, they are subjected to strong anisotropic vdW interactions with the carbon nanotube bundles, resulting in crystal defects such as twins and stacking faults on the one-dimensional serrated ultrathin Pt-based nanoshell.

[0012] The one-dimensional serrated ultrathin Pt-based nanoshell catalyst with abundant defects coated on carbon nanotubes is described. The one-dimensional serrated ultrathin Pt-based nanoshell is a PtFe, PtCo, or PtNi nanoshell with a thickness of 3-6 nm. The serrated edge of the nanoshell is composed of high-index steps. The twin boundaries are all coherent {111} twin boundaries, as well as stacking faults terminating at {111} grain boundaries. The twin boundaries and stacking faults lead to different degrees of lattice strain, and the lattice strain distribution is non-uniform. The tensile or compressive strain is distributed in different regions, and the maximum strain is located at the twin boundaries and stacking faults.

[0013] The one-dimensional serrated ultrathin Pt-based nanoshell catalyst with abundant defects coated on carbon nanotubes has abundant active sites due to the lattice strain caused by edge steps and crystal defects. This results in a large electrochemical active surface area for the one-dimensional serrated ultrathin Pt-based nanoshell, enhancing the electrocatalytic activity of methanol oxidation and ethanol oxidation. The one-dimensional serrated ultrathin Pt-based nanoshell and the carbon nanotube film are in interlocked contact, anchoring the nanoparticles in the one-dimensional serrated ultrathin Pt-based nanoshell and stabilizing the defect structure of edge steps, twins and stacking faults.

[0014] The method for preparing the one-dimensional serrated ultrathin Pt-based nanoshell catalyst with abundant defects coated on carbon nanotubes involves first transferring a carbon nanotube film onto a hollowed-out metal scaffold, then depositing Pt-based nanoparticles by double-sided magnetron sputtering, followed by rapid annealing. The specific steps are as follows:

[0015] (1) Preparation of carbon nanotube thin films for magnetron sputtering:

[0016] First, use laser cutting to cut metal supports of different sizes and corresponding hollow sample trays. High-temperature resistant and high-thermal-conductivity metal materials are required, including molybdenum, tungsten, titanium, copper or 304 stainless steel alloys. Then, use acetone, anhydrous ethanol and deionized water to ultrasonically clean the metal supports in sequence to remove organic contaminants. Next, press the carbon nanotube film paper upside down on the metal supports, remove the carbon nanotube film paper, and obtain a suspended self-supporting carbon nanotube film.

[0017] (2) Install metal brackets:

[0018] The metal support carrying the self-supporting carbon nanotube film in step (1) is installed in the hole position on the corresponding hollow sample plate, connected and fixed by screws, and irradiated under infrared baking lamp for 1 hour to remove surface adsorbed water vapor.

[0019] (3) Magnetron sputtering deposition of Pt-based alloy nanoparticles:

[0020] Pt-based alloy nanoparticles were deposited by dual-target or triple-target co-sputtering in a magnetron sputtering deposition system. The deposition conditions were as follows: high-purity sputtering targets and a background vacuum of 5 × 10⁻⁶. -7 torr~1×10 -8 Torr, high-purity argon gas was used as the sputtering gas, the gas flow rate was 15-30 sccm, the deposition temperature was room temperature, the sample disk rotation speed was 20 rpm, the metal target deposition power was 50-200 W, and the deposition time was 20-80 s. After one side was deposited, the other side was deposited under the same deposition conditions, so that dense Pt-based nanoparticles were uniformly distributed on each carbon nanotube bundle.

[0021] (4) Rapid annealing:

[0022] The composite film with Pt-based nanoparticles deposited in step (3) is then annealed. The annealing conditions are: annealing temperature of 270-300℃, heating rate of 40℃ / min, holding time of 1-1.5h, and annealing atmosphere of argon containing 5 vol% hydrogen. This forms a nanoshell covering the carbon nanotubes and generates crystal defects such as twins and stacking faults in the nanoshell.

[0023] (5) Sample preparation for electrocatalytic performance testing:

[0024] Since the density of carbon nanotube bundles in the carbon nanotube film is not completely uniform, in order to more accurately control the Pt loading on the electrode, the serrated ultrathin nanoshell catalyst film with abundant defects coated on the carbon nanotubes prepared in step (4) was peeled off from the metal support, placed in anhydrous ethanol, and a high-precision cell disruptor was used with a power of 200W and a disruption time of 1h. Then, the volume was adjusted to 2mL to obtain a catalyst dispersion, which was directly drop-coated onto the rotating disk electrode. Then, 5μL of the dispersion was taken each time and drop-coated multiple times. The number of drop-coatings was determined based on the accurate Pt loading measured by inductively coupled plasma mass spectrometry (ICP). Finally, 10μL of a 1wt% perfluorosulfonic acid resin solution was drop-coated.

[0025] (6) Electrocatalytic performance test of methanol oxidation and ethanol oxidation.

[0026] The preparation method of the one-dimensional serrated ultrathin Pt-based nanoshell catalyst with abundant defects coated on carbon nanotubes, in step (6), uses the rotating disk after drop coating in step (5) as the working electrode, the platinum sheet as the counter electrode, and the saturated Ag / AgCl as the reference electrode. First, in a 0.1M HClO4 electrolyte saturated with N2, a CV scan is performed at a potential of 0.01–1.1 V vs RHE for 40 cycles to clean the catalyst electrode surface. The activity tests for methanol oxidation and ethanol oxidation are performed in N2-saturated 0.1M HClO4 + 0.5M CH3OH and 0.1M HClO4 + 0.5M CH3CH2OH electrolytes, respectively, at a scan rate of 50 mV / s. -1 The potential range was 0.1–1.2 V vs RHE. CV scans were performed, and the mass activity and specific activity were obtained by normalizing to the Pt loading and electrochemical active surface area, respectively. For the stability tests of methanol oxidation and ethanol oxidation, the CA curve was obtained by maintaining a fixed potential of 0.65 V vs RHE for 3000 s and recording the current decay. The CO dissolution curve was used to determine the catalyst's resistance to CO poisoning. CO was continuously passed into a 0.1 M HClO4 electrolyte for 10 min, while maintaining the working electrode potential constant at 0.1 V vs RHE. Then, high-purity nitrogen was passed into the electrolyte for 15 min to remove excess CO gas. Afterwards, the scan rate was 20 mV / s within the range of 0.05 V–0.1 V vs RHE.

[0027] In the preparation method of the one-dimensional serrated ultrathin Pt-based nanoshell catalyst with abundant defects coated on carbon nanotubes, the actual mass of Pt in each catalyst dispersion prepared in the electrocatalytic performance test is related to the amount of composite film broken by ultrasonic at the tip and the volume of anhydrous ethanol. It is necessary to adjust the volume of the dispersion dropped onto the electrode according to the actual ICP test results.

[0028] The design concept of this invention is as follows:

[0029] First, defect engineering is an effective means to improve the catalytic performance of catalysts. This includes utilizing abundant surface structures (e.g., edges, corners) and crystal defects terminating at the surface (e.g., interstitial sites, vacancies, dislocations, grain boundaries, twin boundaries, stacking faults, etc.). These optimize the intrinsic activity of the catalyst by adjusting the surface geometry and electronic structure. However, since defect formation is a high-energy process with thermodynamic instability, the controllable preparation of defect catalysts and the stable existence of defects during catalysis remain challenges. Carbon nanotubes, as carbon supports for catalysts, possess high conductivity and strong chemical stability. Furthermore, a unique, strong, symmetrical, periodic vdW interaction has been demonstrated between the supported nanocrystals and single-walled carbon nanotube bundles, with an energy potential hydrazine at the trenches, leading to anisotropic diffusion of nanocrystals and simultaneously securing the nanocrystals. Utilizing this property, when nanocrystals randomly distributed on single-walled carbon nanotube bundles recrystallize, adjacent nanocrystals undergo strong anisotropic vdW interactions when thermally diffused and connected. To adapt to orientation and positional mismatches, various crystal defects such as twins and stacking faults are generated, thus enabling the preparation of controllable defect catalysts. Furthermore, the one-dimensional nanoshell structure formed after annealing, which completely coats the carbon nanotubes, is less prone to detachment and aggregation compared to dispersed nanocrystals, exhibiting higher long-term stability. The nanoshell and carbon nanotubes are in interlocked contact, which greatly stabilizes the preservation of defect structures during the catalytic process, thereby improving catalyst stability.

[0030] Based on the above-mentioned advantages and main design principles, this invention successfully utilizes this characteristic of carbon nanotubes to prepare a one-dimensional serrated ultrathin Pt-based nanoshell catalyst with abundant defects, completely coated on carbon nanotubes. By adjusting relevant parameters through room temperature magnetron sputtering and annealing, the composition, thickness, coating integrity, edge smoothness, and crystal defect density of the nanoshell can be controlled, realizing the controllable preparation of defective catalysts. This maximizes the optimization of catalytic performance for methanol oxidation and ethanol oxidation, which is beneficial for large-scale catalyst synthesis and applicable to various fuel cell-related catalytic reactions.

[0031] The advantages and beneficial effects of this invention are as follows:

[0032] 1. This invention utilizes the strong anisotropic constraint effect of single-walled carbon nanotube bundles on the recrystallization process of nanocrystals. Through simple magnetron sputtering and annealing, a one-dimensional serrated ultrathin Pt-based nanoshell with rich surface structure (high-index edge steps) and a large number of crystal defects such as twins and stacking faults is prepared. The composition, thickness, morphology and density of crystal defects of the nanoshell catalyst can be controlled simultaneously. This method realizes the controllable preparation of Pt-based defect catalysts, greatly simplifies the experimental steps and improves the catalyst synthesis efficiency. This preparation method can also be extended to other nanocrystalline catalysts.

[0033] 2. The one-dimensional Pt-based nanoshell catalyst synthesized in this invention has a serrated edge composed of high-index steps, as well as a large number of crystal defects such as {111} twin boundaries and stacking faults. These structures contribute abundant active sites, and the twin boundaries and stacking faults lead to different degrees of lattice strain, which changes the geometric and electronic structure of the surface atoms, thereby optimizing the adsorption / desorption intensity of intermediates and thus affecting the catalytic activity. The mass activity and specific activity of the catalyst for catalytic methanol oxidation and ethanol oxidation are superior to the most advanced Pt-based catalysts currently available.

[0034] 3. The one-dimensional Pt-based nanoshell catalyst synthesized in this invention has good long-term durability. The one-dimensional nanoshell structure completely coated on carbon nanotubes is relatively more stable and less prone to detachment and aggregation. An interlocking contact is formed between the nanoshell and the carbon nanotube, which can firmly fix the nanocrystals and greatly stabilize the preservation of defect structures during the catalytic process, thereby improving the stability of the catalyst.

[0035] 4. The carbon nanotube network film used in this invention plays a variety of beneficial roles. On the one hand, it can be directly used as a carbon support for the catalyst, possessing high electrical conductivity and strong chemical stability, which is beneficial for electron conduction during the reaction process. On the other hand, it has a strong anisotropic restriction effect on the growth and diffusion of nanocrystals, leading to the generation of crystal defects. Finally, carbon nanotubes can firmly fix nanocrystals, greatly improving the long-term stability of the catalyst. Therefore, the use of carbon nanotubes has certain innovative significance, and it does not require an additional processing step of loading the catalyst onto the carbon support, thus improving the catalyst synthesis efficiency.

[0036] 5. The present invention allows for the transfer of self-supporting porous carbon nanotube films onto hollowed-out supports of various shapes and sizes for double-sided magnetron sputtering, which facilitates the uniform deposition of sputtered materials on each carbon nanotube bundle and is also beneficial for the large-area synthesis of catalysts.

[0037] 6. From the perspective of defect engineering, the Pt-based catalyst nanoparticles that are dense and uniformly distributed after room temperature magnetron sputtering do not generate a large number of defects. They need to be annealed. The annealing temperature is set at 270-300℃, with a large heating rate of 40℃ / min and a short holding time of 1-1.5h to ensure that the nanoparticles recrystallize but do not grow excessively, forming a nanoshell covering the carbon nanotubes. During the annealing process, when adjacent nanoparticles are heated and diffuse, they are subjected to strong anisotropic vdW interactions with the carbon nanotube bundle. In order to adapt to the mismatch in orientation and position between different nanoparticles, a large number of crystal defects such as twins and stacking faults are generated on the nanoshell.

[0038] 7. The lattice strain caused by edge steps and crystal defects in this invention contributes abundant active sites, giving the Pt-based nanoshell a large electrochemically active surface area and enhanced electrocatalytic activity for methanol and ethanol oxidation. Its mass activity and specific activity are superior to the most advanced Pt-based catalysts currently available. After 3000s CA testing and 500 potential cycles, the Pt-based nanoshell catalyst exhibits good long-term durability. It still retains edge steps, twins, and stacking faults after CA testing because the nanoshell and carbon nanotubes are in interlocked contact, which anchors the nanoparticles in the nanoshell and greatly stabilizes the defect structure.

[0039] 8. This invention controls the deposition time to ensure that the deposited nanoparticles are distributed to an appropriate degree on each carbon nanotube bundle. Too little deposition will not form a complete nanoshell, while too much deposition will result in an excessively thick nanoshell. The rapid annealing temperature should not be too high, the heating rate should be fast, and the holding time should be appropriate to ensure that adjacent nanoparticles are thermally diffused and connected together, but will not grow excessively. It also ensures that the high-index surface steps, twins, and stacking faults generated have not disappeared due to thermodynamic instability and reconstruction. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of a one-dimensional serrated ultrathin Pt-based nanoshell catalyst with abundant defects coated on carbon nanotubes. In the figure, 1 is a one-dimensional serrated ultrathin PtFe nanoshell, and 2 is a single-walled carbon nanotube bundle.

[0041] Figure 2 This is a flowchart illustrating the preparation process of a one-dimensional serrated ultrathin Pt-based nanoshell catalyst with abundant defects coated on carbon nanotubes.

[0042] Figure 3 These are transmission electron microscopy (TEM) images of dense and uniform PtFe nanoparticles deposited on carbon nanotube bundles by room-temperature magnetron sputtering. (a) is a low-magnification bright-field image; (b) is a high-resolution image.

[0043] Figure 4Transmission electron microscopy (TEM) images of one-dimensional serrated ultrathin PtFe nanoshells coated on carbon nanotubes after annealing. Among them, (a) is a low-magnification bright-field image; (b) is a high-resolution dark-field image of twins; and (c) is a high-resolution image of stacked faults. Detailed Implementation

[0044] In the specific implementation process, a self-supporting porous film composed of single-walled carbon nanotube bundles was used as the substrate. Dense and uniformly distributed Pt-based catalyst nanoparticles of different compositions were deposited on the substrate via room-temperature magnetron sputtering using a platinum target and other metal targets. Rapid annealing then caused the nanoparticles to recrystallize, grow, and interconnect, ultimately yielding a one-dimensional serrated ultrathin Pt-based nanoshell catalyst with abundant defects, completely coated on the carbon nanotube film. The one-dimensional serrated ultrathin Pt-based nanoshell uniformly coated the carbon nanotube film. Preparation method: Preparation of the self-supporting carbon nanotube film for magnetron sputtering and installation of the sample tray; magnetron sputtering deposition of Pt-based alloy nanoparticles; rapid annealing; preparation of a catalyst dispersion for electrocatalytic performance testing by tip-breaking of the catalyst film; and electrocatalytic performance testing of methanol oxidation and ethanol oxidation. Adjusting the relevant parameters of magnetron sputtering and annealing allowed for the control of the nanoshell composition, thickness, coating integrity, edge smoothness, and crystal defect density, thus optimizing the catalytic performance for methanol and ethanol oxidation.

[0045] The Pt-based (PtFe, PtCo, and PtNi) nanoshells are only 3–6 nm thick, and their serrated edges are composed of high-index steps such as {422}, {622}, {822}, and {1222}. During annealing, the diffusion motion of adjacent nanoparticles is constrained by the strong anisotropic vdW interaction of the carbon nanotube bundles. To accommodate the mismatch in orientation and position between different nanoparticles, numerous crystal defects such as twins and stacking faults are generated on the nanoshells. The twin boundaries are all coherent {111} twin boundaries, and these twin boundaries and stacking faults lead to varying degrees of lattice strain. These Pt-based nanoshells possess a large electrochemically active surface area, enhancing the electrocatalytic activity of methanol and ethanol oxidation reactions. Their mass activity and specific activity are superior to the most advanced Pt-based catalysts currently available. Furthermore, this Pt-based nanoshell catalyst exhibits excellent long-term durability, retaining edge steps, twins, and stacking faults even after stability testing. This is because the nanoshells and carbon nanotubes are in interlocked contact, which anchors the nanoparticles within the nanoshells and greatly stabilizes the defective structures.

[0046] This invention enables the controllable preparation of Pt-based defective catalysts, improving the catalytic efficiency and long-term stability of methanol and ethanol oxidation reactions. It also greatly simplifies experimental procedures, increases catalyst synthesis efficiency, and facilitates large-scale catalyst synthesis. This preparation method can also be extended to other nanocrystalline catalysts and can provide a reference for the design of catalysts in related fuel cell fields.

[0047] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0048] Example

[0049] In this embodiment, a method for preparing a one-dimensional serrated ultrathin PtFe nanoshell catalyst with abundant defects coated on carbon nanotubes is illustrated. For example... Figure 1 As shown, the catalyst uses a carbon nanotube film as a substrate, with a one-dimensional serrated ultrathin PtFe nanoshell 1 uniformly coated on the carbon nanotube film. The carbon nanotube film is a self-supporting porous film composed of stacked single-walled carbon nanotube bundles 2, with uniform pore distribution. The pore sizes vary depending on the thickness of the carbon nanotube film. The diameter of the single-walled carbon nanotube bundles used in the carbon nanotube film is 5–50 nm, the length of the single-walled carbon nanotubes is 5–50 μm, the thickness of the carbon nanotube film is 40–400 nm, and the average pore size is 10–50 nm. The one-dimensional serrated ultrathin PtFe nanoshell is only 3–6 nm thick. The serrated edges of the nanoshell consist of high-index steps, and the twin boundaries are all coherent {111} twin boundaries. Stacking faults terminating at {111} grain boundaries, along with the twin boundaries and stacking faults, lead to different degrees of lattice strain, with the maximum strain located at the twin boundaries and stacking faults.

[0050] Reference Figure 2 The preparation process is as follows: preparation of self-supporting carbon nanotube films → double-sided magnetron sputtering deposition of PtFe catalyst nanocrystals → rapid annealing → preparation of catalyst dispersion by tip-crushing composite catalyst films. The specific process is as follows:

[0051] (1) Preparation of self-supporting carbon nanotube thin films for magnetron sputtering:

[0052] First, use laser cutting to cut metal supports of different sizes and corresponding hollow sample trays. High-temperature resistant and high-thermal-conductivity metal materials are required, including molybdenum, tungsten, titanium, copper or 304 stainless steel alloys. Then, use acetone, anhydrous ethanol and deionized water to ultrasonically clean the metal supports in sequence to remove organic contaminants. Next, press the carbon nanotube film paper upside down on the metal supports, remove the paper, and obtain a suspended self-supporting carbon nanotube film.

[0053] (2) Install metal brackets:

[0054] The metal support carrying the self-supporting carbon nanotube film in step (1) is installed in the hole position on the corresponding hollow sample plate, connected and fixed by screws, and irradiated under infrared baking lamp for 1 hour to remove surface adsorbed water vapor.

[0055] (3) Magnetron sputtering deposition of Pt-based alloy nanoparticles:

[0056] PtFe alloy nanoparticles were deposited by dual-target or triple-target co-sputtering in a magnetron sputtering deposition system. The deposition conditions were as follows: the sputtering targets were high-purity Pt and Fe targets (purity 99.99 wt%), and the background vacuum was 5 × 10⁻⁶. -7 torr~1×10 -8 High-purity argon gas (volume purity 99.999%) was used as the sputtering gas, with a flow rate of 20 sccm. The deposition temperature was room temperature, the sample disk rotation speed was 10 rpm, the metal target deposition power was 50 W for Pt target and 180 W for Fe target, and the deposition time was 56 s. After one side was deposited, the other side was deposited under the same deposition conditions, so that dense and uniform Pt-based nanoparticles were distributed on each carbon nanotube bundle.

[0057] (4) Rapid annealing:

[0058] The PtFe alloy nanoparticles deposited in step (3) were then annealed under the following conditions: annealing temperature of 300℃, heating rate of 40℃ / min, holding time of 1.5h, and annealing atmosphere of argon containing 5 vol% hydrogen. This formed a nanoshell covering the carbon nanotubes and produced a large number of crystal defects such as twins and stacking faults.

[0059] By changing the target material, Pt-based nanoshell catalysts with different compositions can be prepared, such as co-depositing Pt with elements such as Fe, Co, or Ni. Then, by controlling relevant parameters such as sputtering power, sputtering time, annealing temperature, heating rate, and holding time, ultrathin Pt-based nanoshells can be completely coated on carbon nanotube bundles. The serrated edges of the nanoshells are composed of high-index steps. Due to the strong anisotropic vdW interaction between adjacent nanoparticles and carbon nanotube bundles during the diffusion motion caused by heating during annealing, a large number of crystal defects such as twins and stacking faults are generated on the nanoshells in order to adapt to the mismatch of orientation and position between different nanoparticles, as well as lattice strain caused by twin boundaries and stacking faults.

[0060] The morphology of the one-dimensional serrated ultrathin PtFe nanoshell catalyst with abundant defects coated on carbon nanotubes prepared in the examples was characterized and its electrocatalytic performance in methanol oxidation and ethanol oxidation was tested. The process is as follows:

[0061] (S1) Micromorphological analysis of one-dimensional serrated ultrathin PtFe nanoshell catalyst with abundant defects coated on carbon nanotubes

[0062] like Figure 3 As shown, PtFe nanoparticles deposited on carbon nanotube bundles by room temperature magnetron sputtering were observed by transmission electron microscopy. The nanoparticles are densely and uniformly distributed on a single carbon nanotube bundle. The grain size is small, and no twins or atomic steps were observed. Stacking faults exist in a few grains.

[0063] like Figure 4 As shown in the transmission electron microscope (TEM) image, after annealing at 300℃ with a heating rate of 40℃ / min and a holding time of 1.5h, the room-temperature deposited nanoparticles underwent recrystallization and growth, with adjacent particles connecting to form a complete one-dimensional serrated ultrathin PtFe nanoshell encapsulated on carbon nanotubes. The nanoshell thickness is 3–6 nm, and the serrated edges consist of high-index steps. Figure 4 (a) shows the observed twins, and the twin boundaries are all coherent {111} twin boundaries. Figure 4 (b) shows the observed stacking fault, terminating at the {111} grain boundary.

[0064] (S2) Electrocatalytic performance testing of one-dimensional serrated ultrathin PtFe nanoshell catalysts with abundant defects coated on carbon nanotubes for methanol oxidation and ethanol oxidation.

[0065] Since the density of carbon nanotube bundles in the carbon nanotube film is not completely uniform, and in order to more accurately control the Pt loading on the electrode during testing, the catalytic composite film needs to be pretreated. The specific steps are as follows:

[0066] (1) Sample preparation for electrocatalytic performance testing:

[0067] The prepared serrated ultrathin nanoshell catalyst film with abundant defects coated on carbon nanotubes was peeled off from the metal support and placed in anhydrous ethanol. A high-precision cell disruptor was used with a power of 200W for 1 hour. The volume was then adjusted to 2 mL to obtain a catalyst dispersion, which could be directly drop-coated onto a rotating disk electrode. 5 μL of the dispersion was taken each time and drop-coated multiple times. The number of drop-coatings was determined based on the accurate Pt loading measured by inductively coupled plasma mass spectrometry (ICP). Finally, 10 μL of a 1 wt% perfluorosulfonic acid resin solution was drop-coated.

[0068] (2) Electrocatalytic performance testing of methanol oxidation and ethanol oxidation:

[0069] The rotating disk after the catalyst dispersion was applied in step (2) was used as the working electrode, the platinum sheet as the counter electrode, and the saturated Ag / AgCl as the reference electrode. Cyclic voltammetry (CV) was first performed in a 0.1M HClO4 electrolyte saturated with N2 at a potential of 0.01–1.1 V vs RHE for 40 cycles, after which the catalyst electrode surface was cleaned. The activity tests for methanol oxidation and ethanol oxidation were conducted in N2-saturated 0.1M (molar concentration) HClO4 + 0.5M CH3OH and 0.1M HClO4 + 0.5M CH3CH2OH electrolytes, respectively, at a scan rate of 50 mV / s. -1 The potential range was 0.1–1.2 V vs RHE. CV scans were performed, and the mass activity and specific activity were obtained by normalizing to the Pt loading and electrochemical active surface area, respectively. For the stability tests of methanol oxidation and ethanol oxidation, CA (chronoamperometric) was used, maintaining a fixed potential of 0.65 V vs RHE for 3000 s and recording the current decay. The CO dissolution curve revealed the catalyst's resistance to CO poisoning. CO was continuously passed into a 0.1 M HClO4 electrolyte for 10 min, while maintaining the working electrode potential constant at 0.1 V vs RHE. Then, high-purity nitrogen (99.999% volume purity) was passed into the electrolyte for 15 min to remove excess CO gas. Afterward, the scan rate was 20 mV / s within the range of 0.05 V–0.1 V vs RHE.

[0070] The results of the examples show that the one-dimensional serrated ultrathin Pt-based nanoshell catalyst with abundant defects coated on carbon nanotubes prepared in this invention exhibits high electrocatalytic activity and stability for methanol oxidation and ethanol oxidation. The innovative use of carbon nanotubes as the carbon support for the catalyst provides high electrical conductivity and strong chemical stability, which is beneficial for electron conduction during the reaction process. More importantly, it strongly restricts the growth and diffusion of nanocrystals anisotropically, leading to the generation of crystal defects, optimizing the intrinsic activity of the catalyst, and significantly improving its long-term stability. This simplifies the experimental steps and improves the catalyst synthesis efficiency. This preparation method can also be extended to other nanocrystalline catalysts and can provide a reference for the design of catalysts in related fuel cell fields.

[0071] The preparation of the one-dimensional serrated ultrathin Pt-based nanoshell catalyst with abundant defects coated on carbon nanotubes, and the electrocatalytic performance testing of methanol oxidation and ethanol oxidation provided by this invention, have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make several improvements and modifications to this invention without departing from the principles of this invention, and these improvements and modifications also fall within the protection scope of the claims of this invention.

Claims

1. A one-dimensional serrated ultrathin Pt-based nanoshell catalyst with abundant defects coated on carbon nanotubes, characterized in that, The catalyst uses carbon nanotube films as a substrate. Dense and uniformly distributed Pt-based catalyst nanoparticles of different compositions are deposited on the substrate by room temperature magnetron sputtering of platinum targets and other metal targets. Then, rapid annealing is performed to allow the nanoparticles to recrystallize, grow and connect with each other, and finally obtain a one-dimensional serrated ultrathin Pt-based nanoshell catalyst with abundant defects that is completely coated on the carbon nanotube film.

2. The one-dimensional serrated ultrathin Pt-based nanoshell catalyst with abundant defects coated on carbon nanotubes according to claim 1, characterized in that, The carbon nanotube film used as the substrate is a self-supporting porous carbon nanotube film composed of overlapping single-walled carbon nanotube bundles. The pores are uniformly distributed, and the pore size varies with different thicknesses. The diameter of the single-walled carbon nanotube bundles in the carbon nanotube films used is 5–50 nm, the length of the single-walled carbon nanotubes is 5–50 μm, the thickness of the carbon nanotube film is 40–400 nm, and the average pore size is 10–50 nm.

3. The one-dimensional serrated ultrathin Pt-based nanoshell catalyst with abundant defects coated on carbon nanotubes according to claim 2, characterized in that, Porous carbon nanotube films are transferred onto hollowed-out supports of various shapes and sizes for double-sided magnetron sputtering, which facilitates the uniform deposition of sputtered materials on each carbon nanotube bundle and is beneficial for large-area catalyst synthesis.

4. The one-dimensional serrated ultrathin Pt-based nanoshell catalyst with abundant defects coated on carbon nanotubes according to claim 1, characterized in that, Pt is co-deposited with one or more of the elements Fe, Co, Ni, Cu, Zn, Ru, Rh, Ir, Sn, Au, and Ag. By changing the type of target material used in magnetron sputtering, Pt-based binary or ternary alloy nanoshell catalysts with different compositions can be prepared. These catalysts are suitable for various fuel cell-related catalytic reactions. Furthermore, by adjusting the sputtering power and sputtering time, the composition ratio and the deposition density of Pt-based nanoparticles on carbon nanotubes can be controlled.

5. The one-dimensional serrated ultrathin Pt-based nanoshell catalyst with abundant defects coated on carbon nanotubes according to claim 1, characterized in that, After room temperature magnetron sputtering, annealing is performed at a temperature of 270–300℃, a heating rate of 40℃±5℃ / min, and a holding time of 1–1.5h. This ensures that the nanoparticles recrystallize but do not grow excessively, forming a one-dimensional serrated ultrathin Pt-based nanoshell that coats the carbon nanotube film. During the annealing process, when adjacent nanoparticles undergo diffusion motion due to heating, they are subjected to strong anisotropic vdW interactions with the carbon nanotube bundle, resulting in crystal defects such as twins and stacking faults on the one-dimensional serrated ultrathin Pt-based nanoshell.

6. The one-dimensional serrated ultrathin Pt-based nanoshell catalyst with abundant defects coated on carbon nanotubes according to claim 1, characterized in that, One-dimensional serrated ultrathin Pt-based nanoshells are PtFe, PtCo, or PtNi nanoshells with a thickness of 3–6 nm. The serrated edges of the nanoshells are composed of high-index steps. The twin boundaries are coherent {111} twin boundaries, as well as stacking faults terminating at {111} grain boundaries. The twin boundaries and stacking faults lead to different degrees of lattice strain, and the lattice strain distribution is non-uniform. Tensile or compressive strain is distributed in different regions, and the maximum strain is located at the twin boundaries and stacking faults.

7. The one-dimensional serrated ultrathin Pt-based nanoshell catalyst with abundant defects coated on carbon nanotubes according to claim 6, characterized in that, The lattice strain caused by edge steps and crystal defects contributes abundant active sites, giving the one-dimensional serrated ultrathin Pt-based nanoshell a large electrochemically active surface area and enhanced electrocatalytic activity for methanol and ethanol oxidation. The one-dimensional serrated ultrathin Pt-based nanoshell and the carbon nanotube film are in interlocked contact, anchoring the nanoparticles in the one-dimensional serrated ultrathin Pt-based nanoshell and stabilizing the defect structure of edge steps, twins and stacking faults.

8. The method for preparing a one-dimensional serrated ultrathin Pt-based nanoshell catalyst with abundant defects coated on carbon nanotubes according to any one of claims 1 to 7, characterized in that, First, a carbon nanotube film is transferred onto a hollowed-out metal scaffold. Then, Pt-based nanoparticles are deposited by double-sided magnetron sputtering, followed by rapid annealing. The specific steps are as follows: (1) Preparation of carbon nanotube thin films for magnetron sputtering: First, use laser cutting to cut metal supports of different sizes and corresponding hollow sample trays. High-temperature resistant and high-thermal-conductivity metal materials are required, including molybdenum, tungsten, titanium, copper or 304 stainless steel alloys. Then, use acetone, anhydrous ethanol and deionized water to ultrasonically clean the metal supports in sequence to remove organic contaminants. Next, press the carbon nanotube film paper upside down on the metal supports, remove the carbon nanotube film paper, and obtain a suspended self-supporting carbon nanotube film. (2) Install metal brackets: The metal support carrying the self-supporting carbon nanotube film in step (1) is installed in the hole position on the corresponding hollow sample plate, connected and fixed by screws, and irradiated under infrared baking lamp for 1 hour to remove surface adsorbed water vapor. (3) Magnetron sputtering deposition of Pt-based alloy nanoparticles: Pt-based alloy nanoparticles were deposited by dual-target or triple-target co-sputtering in a magnetron sputtering deposition system. The deposition conditions were as follows: high-purity sputtering targets and a background vacuum of 5 × 10⁻⁶. -7 torr~1×10 -8 Torr, high-purity argon gas was used as the sputtering gas, the gas flow rate was 15-30 sccm, the deposition temperature was room temperature, the sample disk rotation speed was 20 rpm, the metal target deposition power was 50-200 W, and the deposition time was 20-80 s. After one side was deposited, the other side was deposited under the same deposition conditions, so that dense Pt-based nanoparticles were uniformly distributed on each carbon nanotube bundle. (4) Rapid annealing: The composite film with Pt-based nanoparticles deposited in step (3) is then annealed. The annealing conditions are: annealing temperature of 270-300℃, heating rate of 40℃ / min, holding time of 1-1.5h, and annealing atmosphere of argon containing 5 vol% hydrogen. This forms a nanoshell covering the carbon nanotubes and generates crystal defects such as twins and stacking faults in the nanoshell. (5) Sample preparation for electrocatalytic performance testing: Since the density of carbon nanotube bundles in the carbon nanotube film is not completely uniform, in order to more accurately control the Pt loading on the electrode, the serrated ultrathin nanoshell catalyst film with abundant defects coated on the carbon nanotubes prepared in step (4) was peeled off from the metal support, placed in anhydrous ethanol, and a high-precision cell disruptor was used with a power of 200W and a disruption time of 1h. Then, the volume was adjusted to 2mL to obtain a catalyst dispersion, which was directly drop-coated onto the rotating disk electrode. Then, 5μL of the dispersion was taken each time and drop-coated multiple times. The number of drop-coatings was determined based on the accurate Pt loading measured by inductively coupled plasma mass spectrometry (ICP). Finally, 10μL of a 1wt% perfluorosulfonic acid resin solution was drop-coated. (6) Electrocatalytic performance test of methanol oxidation and ethanol oxidation.

9. The method for preparing a one-dimensional serrated ultrathin Pt-based nanoshell catalyst with abundant defects coated on carbon nanotubes according to claim 8, characterized in that, In step (6), the rotating disk after drop coating in step (5) is used as the working electrode, the platinum sheet as the counter electrode, and the saturated Ag / AgCl as the reference electrode. First, in a 0.1M HClO4 electrolyte saturated with N2, a CV scan is performed for 40 cycles at a potential of 0.01–1.1 V vs RHE to clean the catalyst electrode surface. The activity tests for methanol oxidation and ethanol oxidation are conducted in N2-saturated 0.1M HClO4 + 0.5M CH3OH and 0.1M HClO4 + 0.5M CH3CH2OH electrolytes, respectively, at a scan rate of 50 mV / s. -1 The potential range was 0.1–1.2 V vs RHE. CV scans were performed, and the mass activity and specific activity were obtained by normalizing to the Pt loading and electrochemical active surface area, respectively. For the stability tests of methanol oxidation and ethanol oxidation, the CA curve was obtained by maintaining a fixed potential of 0.65 V vs RHE for 3000 s and recording the current decay. The CO dissolution curve was used to determine the catalyst's resistance to CO poisoning. CO was continuously passed into a 0.1 M HClO4 electrolyte for 10 min, while maintaining the working electrode potential constant at 0.1 V vs RHE. Then, high-purity nitrogen was passed into the electrolyte for 15 min to remove excess CO gas. Afterwards, the scan rate was 20 mV / s within the range of 0.05 V–0.1 V vs RHE.

10. The method for preparing a one-dimensional serrated ultrathin Pt-based nanoshell catalyst with abundant defects coated on carbon nanotubes according to claim 8, characterized in that, In the electrocatalytic performance test, the actual mass of Pt in each catalyst dispersion prepared is related to the amount of composite film broken by ultrasonic tip and the volume of anhydrous ethanol. The volume of dispersion dropped onto the electrode needs to be adjusted according to the actual ICP test results.

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