Preparation of monatomic modified multi-element nano-alloy catalyst and application in methanol fuel cell

Abstract

The application belongs to the technical field of electrocatalysis, and particularly relates to a single-atom modified multi-element nano-alloy catalyst preparation and methanol fuel cell application. The application first synthesizes a chromium single-atom catalyst (Cr-SAC), then uses the Cr-SAC as a carrier substrate, and uses an electrochemical deposition method to load palladium (Pd), cobalt (Co) and nickel (Ni) metal precursors, and finally obtains a single-atom modified multi-element nano-alloy catalyst PdCoNi / Cr-SAC. The single-atom modified multi-element nano-alloy catalyst synthesized by the method has good conductivity, the single atoms and the multi-element nano-alloy are uniformly distributed on the substrate, the active sites are dense, the CO poisoning resistance is strong, and the catalytic activity and stability of the methanol oxidation reaction are improved, so that the direct methanol fuel cell with the PdCoNi / Cr-SAC catalyst as the anode has super-high energy conversion efficiency and long-term operation stability.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalysis technology, specifically relating to the preparation of a single-atom modified multi-component nano-alloy catalyst and its application in methanol fuel cells. Background Technology

[0002] Direct methanol fuel cells (DMFCs) are considered promising clean energy conversion devices due to their high energy density, convenient fuel storage and transportation, and low operating temperature. Methanol oxidation (MOR) is the core anode reaction in DMFCs. This reaction involves a 6-electron transfer process with slow kinetics, placing stringent demands on catalyst performance. Currently, precious metals such as platinum (Pt) and palladium (Pd) remain the mainstream materials for MOR catalysis; however, their high cost and poor stability severely hinder the large-scale commercialization of DMFCs. The core technical bottleneck in the MOR process lies in the strong adsorption of the reaction intermediate carbon monoxide (CO) on the surface of precious metals, which directly causes catalyst poisoning and deactivation.

[0003] To overcome the aforementioned technical limitations, researchers have developed nano-alloy catalysts incorporating non-precious metals. These catalysts can construct abundant coordination unsaturated sites, defect structures, and interfacial structures, synergistically enhancing the catalytic efficiency of methanol oxidation while effectively reducing the amount of precious metals required. Crucially, alloying transition metals with palladium significantly enhances the catalytic activity of methanol oxidation through a bifunctional mechanism: firstly, alloying induces a reconstruction of the electronic structure of palladium; secondly, it promotes the generation of adsorbed oxygen-containing species (OHads), thereby oxidizing and removing carbon monoxide that poisons the catalyst. Nevertheless, existing palladium-based nano-alloy catalysts still suffer from two major drawbacks: reduced electrochemical active area and continuous exposure of palladium-palladium sites. This not only limits the catalyst's mass activity but also fails to fundamentally solve the carbon monoxide poisoning problem. Therefore, an ideal catalyst design should focus on constructing a high density of palladium-transition metal (Pd-M) active sites on the palladium surface.

[0004] Single-atom catalysts (SACs), with their maximum atom utilization and tunable electronic structure, offer new insights for designing high-performance Pd-based nanoalloys. Combining single atoms with Pd nanoalloys promises to optimize the adsorption energy of key intermediates in the MOR process by controlling the electronic states of the alloy surface with single atoms, thereby achieving efficient six-electron transfer. However, achieving the controllable construction of single atoms on the Pd alloy surface to form a structure rich in active boundaries and Pd-M sites, while ensuring the stability of the catalyst during long-term operation, remains a critical technical challenge to be solved in this field. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention provides a method for preparing a single-atom modified multi-component nano-alloy catalyst. This method involves loading transition metal atomic sites onto a nitrogen-doped carbon framework and then depositing the multi-component nano-alloy by electrodeposition. By modifying the single-atom sites, the electronic structure of the multi-component nano-alloy is regulated, thereby effectively improving its tolerance and durability to CO, and enhancing its catalytic activity and stability in the methanol oxidation reaction.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of this invention provides a method for preparing a single-atom modified multi-component nano-alloy catalyst, the method comprising the following steps: S1. Preparation of Cr single-atom catalyst Cr-SAC by ball milling pyrolysis: Using chromium acetate, melamine, and L-alanine as raw materials, after ball milling, ethanol and hydrochloric acid are added for solvent modification. After collecting the solid product, Cr-SAC is synthesized by stepwise high-temperature sintering, acid washing, and annealing. This process can achieve high dispersion loading of Cr single atoms on carbon substrate, and Cr exists stably in the Cr-N4 coordination form without the formation of metal or metal oxide phases.

[0007] S2. Preparation of single-atom modified multi-component nanoalloy catalyst PdCoNi / Cr-SAC by electrochemical deposition: In a standard three-electrode testing system, Cr-SAC powder prepared in S1 was uniformly loaded onto the surface of a carbon-based electrode. Simultaneously, a mixed electrolyte containing potassium hydroxide (KOH) and three metal precursors—palladium, cobalt, and nickel—was prepared. Specific deposition potentials and scan rates were set, and after multiple cyclic scans, PdCoNi / Cr-SAC was obtained through cathodic deposition. This deposition process achieves uniform loading of PdCoNi ternary nanoalloys on a Cr-SAC substrate and induces the formation of defect structures rich in twins, vacancies, and lattice distortion, generating intrinsic lattice strain.

[0008] The method of this invention prepares PdCoNi / Cr-SAC. The composite structure formed by Cr-SAC and PdCoNi ternary nanoalloys enables strong d-orbital coupling, modulating the electronic structure of Pd and shifting the d-band center of Pd downwards. This effectively weakens the CO adsorption binding energy, completely suppresses the formation of CO poisoning intermediates in the methanol oxidation reaction, and achieves a CO-free methanol oxidation reaction pathway. Furthermore, the CO oxidation onset potential is as low as 0.41 V, significantly improving the catalyst's resistance to CO poisoning. Moreover, the single-atom modified PdCoNi ternary nanoalloy catalyst possesses high-density active sites and good conductivity. The electronic regulation of Cr single atoms and the defect strain of the PdCoNi nanoalloy synergistically lower the rate-determining energy barrier of the methanol oxidation reaction while promoting the formation of hydroxyl species. This catalyst exhibits ultra-high catalytic activity for methanol oxidation (12.62 A mg).Pd -1 ) and specific activity (49.32 mA·cm -2 This is far superior to traditional catalysts such as commercial Pd / C. Furthermore, a direct methanol fuel cell using PdCoNi / Cr-SAC as the anode catalyst, with 4.0 M methanol as the anode fuel and 6.0 M NaOH as the electrolyte, can achieve a maximum power density of 111.3 mW·cm⁻¹. -2 It is 3.8 times that of commercial Pt / C anodes and can achieve a current of 50 mA·cm⁻¹. -2 It exhibits stable discharge for 60 hours at a current density, demonstrating both high energy conversion efficiency and excellent long-term operational stability. Furthermore, this single-atom modified multi-element nanoalloy catalyst not only demonstrates highly efficient catalytic performance for methanol oxidation but also maintains a high activity retention rate after multiple cycles, showing promising potential for broad-spectrum electrocatalytic oxidation of alcohols.

[0009] Preferably, the mass ratio of chromium acetate, melamine, and L-alanine is 6–8:1100–1300:120–250.

[0010] Preferably, the ball milling is performed at a rotation speed of 300-500 rpm, alternating between clockwise and counterclockwise for 20-40 minutes.

[0011] Preferably, the stepwise high-temperature sintering involves first heating to 500-700℃ at a rate of 2-3℃ / min and holding for 100-150 minutes, then heating to 800-1000℃ and holding for 80-100 minutes.

[0012] Preferably, the volume ratio of ethanol to hydrochloric acid is 9-11:1-3.

[0013] Preferably, the pickling is performed by washing with 1-3 mol / L hydrochloric acid (HCl) at 70-90°C for 20-30 hours.

[0014] Preferably, the annealing is performed at 700–900°C in an inert gas atmosphere for 50–70 minutes.

[0015] Preferably, the mixed electrolyte contains 0.05–0.3 mol / L potassium hydroxide and equimolar amounts of palladium chloride (PdCl2), cobalt chloride (CoCl2), and nickel acetate tetrahydrate (Ni(OCOCH3)2·4H2O), with a total concentration of 800–1000 mmol / L.

[0016] Preferably, the carbon-based electrode includes a glassy carbon electrode and a graphite electrode; the loading of Cr-SAC powder on the surface of the carbon-based electrode is 0.3–0.5 mg / cm³. 2 .

[0017] Preferably, the deposition potential is controlled at -0.71 to -1.20V, the scan rate is 4-6 mV / s, and the number of cycles is 8-15.

[0018] The second aspect of the present invention also provides a single-atom modified multi-component nano-alloy catalyst prepared by the preparation method described in the first aspect.

[0019] The third aspect of the present invention also provides the application of the single-atom modified multi-component nanoalloy catalyst described in the second aspect in the preparation of direct methanol fuel cells (DMFC), that is, using the single-atom modified multi-component nanoalloy catalyst as an anode catalyst.

[0020] Compared with the prior art, the beneficial effects of the present invention are: This invention discloses a single-atom modified multi-component nanoalloy catalyst, PdCoNi / Cr-SAC, with methanol oxidation catalytic activity. The preparation process involves first synthesizing a chromium single-atom catalyst (Cr-SAC), then using this Cr-SAC as a support substrate to electrochemically deposit palladium (Pd), cobalt (Co), and nickel (Ni) metal precursors to obtain the target catalyst. This catalyst can be used as a highly efficient catalytic material in the cathode of direct methanol fuel cells.

[0021] Specifically, the present invention has the following advantages: (1) Cr single-atom modification can induce intrinsic strain in PdCoNi ternary nanoalloys, while simultaneously achieving electronic structure regulation of PdCoNi nanoalloys, forming strong d-orbital coupling, and shifting the d-band center of Pd downwards, thus optimizing the adsorption energy of catalytic intermediates; (2) PdCoNi / Cr-SAC single-atom modified multi-element nanoalloy catalysts have abundant crystal defects and active edge sites, significantly improving the catalytic activity of methanol oxidation reaction, exhibiting ultra-high mass activity (12.62 A mg). Pd -1 ) and specific activity (49.32 mA·cm - ²), far superior to commercial Pt / C, Pd / C and other catalysts; (3) PdCoNi / Cr-SAC catalyst can effectively weaken CO adsorption binding energy, completely inhibit the generation of CO poisoning intermediates, realize CO-free methanol oxidation reaction pathway, and the CO oxidation onset potential is as low as 0.41 V, significantly improving CO poisoning resistance and catalytic stability; (4) The synergistic effect of Cr single atoms and PdCoNi ternary nano-alloy reduces the rate-determining energy barrier of methanol oxidation reaction, while promoting the generation of hydroxyl species, accelerating the removal of toxic intermediates, and further improving catalytic efficiency; (5) The maximum power density of direct methanol fuel cell with PdCoNi / Cr-SAC catalyst as anode can reach 111.3 mW·cm -2It is 3.8 times that of commercial Pt / C and can reach 50 mA·cm⁻¹. -2 It can stably discharge for 60 hours at a current density, and has both high energy conversion efficiency and long-term operational stability; (6) The PdCoNi / Cr-SAC catalyst also exhibits excellent catalytic performance for the oxidation of alcohols such as ethylene glycol and glycerol, has broad-spectrum applicability for electrocatalytic oxidation of alcohols, and can still maintain a high activity retention rate after multiple cycles, with excellent structural and compositional stability. Attached Figure Description

[0022] Figure 1 (a) HAADF-STEM image of PdCoNi / Cr-SAC, where pink triangles, blue circles, green circles, and yellow circles represent twin boundaries (TB), stacking faults (SFs), vacancies, and lattice distortions, respectively; (b) Strain simulation based on the solid white area in (a), where colored bars represent strain intensity, with positive values ​​indicating tensile strain and negative values ​​indicating compressive strain; (c) Fast Fourier Transform (FFT) image of the pink triangular area in (a) showing the presence of twins, where triangles represent atomic alignment and pink spheres represent metal atoms; (d) Inverse FFT mode and intensity distribution mapping corresponding to the HAADF-STEM image.

[0023] Figure 2 This is the energy spectrum of the PdCoNi / Cr-SAC catalyst.

[0024] Figure 3 Electrocatalytic performance of PdCoNi / Cr-SAC catalyst; (a) in 1.0 M NaOH solution, at 20 mV·s -1 (a) Cyclic voltammogram of the electrocatalyst obtained by scanning; (b) In an Ar-saturated electrolyte containing 1.0 M NaOH and 1.0 M methanol, at 20 mV·s -1 (c) Mass-normalized CV curve obtained by scanning; In 1.0 M NaOH solution, at 20 mV·s -1 CO stripping curves of the catalyst obtained by scanning.

[0025] Figure 4 This is the in-situ attenuated total reflectance surface-enhanced infrared spectrum of PdCoNi / Cr-SAC.

[0026] Figure 5 The oxidation performance of PdCoNi / Cr-SAC catalyst for ethylene glycol and glycerol was tested; (a) in an Ar-saturated electrolyte of 1.0 M NaOH + 1.0 M ethylene glycol, at 20 mV·s -1(a) Cyclic voltammetry curves measured at the scan rate; (b) Comparison of mass-normalized CV curves of PdCoNi / Cr-SAC and Pd / C catalysts before and after 100 cyclic voltammetry scans in Ar-saturated 1.0 M NaOH + 1.0 M ethylene glycol electrolyte; (c) Cyclic voltammetry curves measured at the scan rate of Ar; (d) Cyclic voltammetry curves measured at the scan rate of Ar; (e ...b) Comparison of mass-normalized CV curves of PdCoNi / Cr-SAC and Pd / C catalysts before and after 100 cyclic voltammetry scans; (c) Cyclic voltammetry curves measured at the scan rate of Ar; (d) Cyclic voltammetry curves measured at the scan rate of -1 (d) Cyclic voltammetry curves obtained by scanning rate; (d) Comparison of mass-normalized CV curves of PdCoNi / Cr-SAC and Pd / C catalysts before and after 100 cyclic voltammetry scans in Ar-saturated 1.0 M NaOH + 1.0 M glycerol electrolyte to evaluate the electrochemical activity and stability of the catalysts.

[0027] Figure 6 Performance figures for a PdCoNi / Cr-SAC-based direct methanol fuel cell (DMFC); (a) discharge polarization curve and power density; (b) at 50 mA·cm⁻¹ -2 Durability test under current density. Detailed Implementation

[0028] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0029] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0030] This invention utilizes electrochemical deposition to successfully prepare a multi-component nanoalloy catalyst modified with transition metal single atoms on a nitrogen-doped carbon support. Experimental results show that the introduction of transition metal single atoms can effectively regulate the electronic structure of the catalyst, significantly enhance the kinetic rate of methanol oxidation, and simultaneously impart excellent stability to the catalyst. Furthermore, this preparation method is both simple and controllable, and the obtained catalyst is an ideal candidate material for DMFC anodes.

[0031] This invention synthesizes single-atom modified multi-component nanoalloy catalysts (taking PdCoNi / Cr-SAC as an example) through the following technical solution: First, a Cr single-atom catalyst (Cr-SAC) is synthesized. Then, using Cr-SAC as a substrate, Pd, Co, and Ni metal precursors are supported by electrochemical deposition to prepare PdCoNi / Cr-SAC. The single-atom modified multi-component nanoalloy catalyst synthesized by this method exhibits good electrical conductivity, uniform distribution of single atoms and multi-component nanoalloys on the substrate, dense active sites, and strong resistance to CO poisoning, which is beneficial for improving the catalytic activity and stability of the methanol oxidation reaction.

[0032] To fully and clearly present the technical solution and significant advantages of the present invention, the present invention will be described in detail below with reference to specific embodiments.

[0033] Example 1: Preparation of single-atom modified multi-component nanoalloy catalyst PdCoNi / Cr-SAC (1) Preparation of Cr-SAC by ball milling pyrolysis: A mixture of 68.70 mg chromium acetate, 12 g melamine, and 2 g L-alanine was placed in a ball mill jar and ball-milled at 350 rpm for 60 minutes, alternating between 30 minutes of clockwise milling and 30 minutes of counterclockwise milling. Then, 10 mL of anhydrous ethanol and 2 mL of concentrated hydrochloric acid (36%–38%) were added to the jar, and stirring was continued for 5 minutes. The solid product was then collected by centrifugation and dried overnight in a 60°C oven. Following this, sintering was performed under an argon atmosphere. The temperature was controlled to rise from 30°C to 600°C at a rate of 2.5°C / min and held at 600°C for 120 minutes. The temperature was then increased to 900°C and held for 90 minutes, finally cooled to room temperature. The resulting solid was then mixed with a 2 mol / L hydrochloric acid solution (w / v = 0.5 mg / L). After mixing (mL), the mixture was washed at 80°C for 24 hours, dried, and then annealed at 800°C for 60 minutes under an argon atmosphere to finally obtain Cr-SAC powder.

[0034] (2) PdCoNi / Cr-SAC was prepared by electrochemical deposition: In the standard three-electrode test system, take the Cr-SAC powder prepared in step (1) at a concentration of 0.35 mg / cm³. 2A uniform coating of chromium oxide was applied to the surface of a glassy carbon electrode as the working electrode, an Hg / HgO electrode as the reference electrode, and a graphite electrode as the counter electrode. Simultaneously, a composite electrolyte was prepared, based on a 0.1 mol / L potassium hydroxide (KOH) system, with the addition of a metal precursor at a total concentration of 900 mmol / L. This metal precursor consisted of 300 mmol / L palladium chloride (PdCl2), 300 mmol / L cobalt chloride (CoCl2), and 300 mmol / L nickel acetate tetrahydrate (Ni(OCOCH3)2·4H2O) in a 1:1:1 molar ratio. During electrochemical deposition, the deposition potential range was set to -0.71 to -1.20 V, and the electrode was cyclically scanned 10 times at a scan rate of 5 mV / s. The PdCoNi / Cr-SAC composite material was prepared by cathodic deposition.

[0035] Figure 1 This is a high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) image of the sample (PdCoNi / Cr-SAC catalyst) synthesized in this embodiment; the image shows that PdCoNi / Cr-SAC has abundant crystal plane defects ( Figure 1 a); Geometric phase analysis (GPA) of the Pd(111) crystal plane in PdCoNi / Cr-SAC revealed a significant lattice strain effect. Figure 1 b); Meanwhile, high-density nanotwins are visible in PdCoNi / Cr-SAC in the HAADF-STEM image, and the twin boundary features are obvious ( Figure 1 c); The Pd (111) interplanar spacing of PdCoNi / Cr-SAC is 0.232 nm ( Figure 1 (d) It can be seen that lattice distortion and intrinsic strain were formed, which laid the foundation for the effective improvement of its catalytic activity.

[0036] Further analysis of the energy spectrum of the synthesized sample (PdCoNi / Cr-SAC catalyst) in this embodiment ( Figure 2 Analysis shows that Cr is uniformly distributed on the nitrogen-doped carbon substrate, and the main diameter of the ternary nano-alloy particles is 20 nm.

[0037] Comparative Example 1: Preparation of single-atom modified Pd catalyst Pd / Cr-SAC The difference from Example 1 is that the metal precursor in step (2) is 900 mmol / L palladium chloride (PdCl2).

[0038] Comparative Example 1: Preparation of Pd / NC The difference from Example 1 is that the electrochemical deposition operation in step (2) is not required, and the 68.70 mg chromium acetate in step (1) is replaced with 25 mg PdCl2.

[0039] Experimental Example 1: The test employed a three-electrode system with a loading of 0.35 mg·cm⁻¹. -2 The PdCoNi / Cr-SAC catalyst was tested using a glassy carbon electrode as the working electrode, a Hg / HgO electrode as the reference electrode, and a graphite electrode as the counter electrode. Electrolysis was performed in two electrolytes: 1 M NaOH and 1 M NaOH + 1 M methanol, with a scan rate set at 10 mV·s. -1 The test results are as follows: Figure 3 As shown: Throughout the test, the absolute value of the methanol oxidation reaction current of PdCoNi / Cr-SAC was higher than that of other catalysts; and its CO oxidation onset potential was as low as 0.41 V, significantly lower than that of other control catalysts. Figure 3 a) The above results indicate that PdCoNi / Cr-SAC exhibits significantly superior catalytic activity for methanol oxidation compared to other catalysts, while effectively weakening the CO adsorption binding energy and demonstrating excellent resistance to CO poisoning. Figure 3 According to the mass-normalized cyclic voltammetry (CV) curve calculation, the mass activity and specific activity of PdCoNi / Cr-SAC for methanol oxidation are as high as 12.62 A·mgPd. - ¹ and 49.32 mA·cm - ², far superior to traditional catalysts such as commercial Pd / C. Furthermore, Figure 3 c. The anti-poisoning ability of PdCoNi / Cr-SAC was revealed by CO stripping voltammetry. The CO oxidation onset potential was 0.41 V, which was lower than that of PdCo / Cr-SAC (0.43 V), PdNi / Cr-SAC (0.44 V), Pd / Cr-SAC (0.45 V), Pd / NC (0.48 V) and Pd / C (0.50 V).

[0040] Meanwhile, the methanol oxidation process of PdCoNi / Cr-SAC was tested using in-situ attenuated total reflectance surface-enhanced infrared spectroscopy. Figure 4 The in-situ attenuated total reflectance surface-enhanced infrared spectrum of PdCoNi / Cr-SAC during the potential scan process from 0.1 to 1.0 V shows characteristic vibrational peaks of formate and carbon dioxide, with no adsorbed CO characteristic peaks. At the same time, a characteristic vibrational peak of hydroxyl groups was detected, indicating that the methanol oxidation catalyzed by PdCoNi / Cr-SAC follows a CO-free reaction pathway and can promote the formation of hydroxyl species, effectively removing toxic intermediates in the reaction.

[0041] In addition, the electrolyte was changed to 1 M NaOH + 1 M ethylene glycol or 1 M NaOH + 1 M glycerol, and the results were studied. The oxidation properties of PdCoNi / Cr-SAC for ethylene glycol and glycerol. For example... Figure 5 As shown, PdCoNi / Cr-SAC also exhibits excellent performance in the oxidation of ethylene glycol and glycerol, demonstrating broad applicability to the electrocatalytic oxidation of alcohols. In the ethylene glycol oxidation reaction (EGOR), the specific activity and mass activity of PdCoNi / Cr-SAC reached 33.04 mA·cm⁻¹, respectively. -2 and 8.46A·mg Pd -1 It surpasses commercial Pd / C catalysts (9.89 mA·cm⁻¹). -2 and 3.59 A·mg Pd -1 In the glycerol oxidation reaction (GOR), PdCoNi / Cr-SAC exhibits enhanced specific activity (17.77 mA·cm⁻¹). -2 ) and mass activity (4.54 A·mg Pd -1 Both are superior to commercial Pd / C (2.55 mA·cm⁻¹). -2 and 2.36 A·mg Pd -1 After 100 cyclic voltammetric scans, its mass activity in EGOR and GOR remained at 70.5% and 44.7% of the initial values, respectively, confirming its strong anti-poisoning properties and long-term stability.

[0042] Experimental Example 2: This experiment constructed a direct methanol fuel cell (DMFC). The battery system used a PdCoNi / Cr-SAC composite material supported on carbon cloth as the anode catalyst and platinum-carbon (Pt / C) powder as the cathode catalyst. The anode catalyst was prepared by ultrasonically mixing 10 mg of PdCoNi / Cr-SAC powder with 0.94 mL of isopropanol, 0.94 mL of deionized water, and 60 μL of 5wt% Nafion solution to form a homogeneous electrocatalyst slurry, which was then impregnated onto carbon paper. The catalyst loading was controlled at 1 mg / cm³. -2 The cathode catalyst was prepared by ultrasonically mixing 30 mg of Pt / C powder with 2.91 mL of isopropanol, 2.91 mL of deionized water, and 180 μL of 5 wt% Nafion solution to form a homogeneous slurry, which was then impregnated onto carbon paper. The Pt loading was 1.2 mg·cm³. -2 The overall catalyst loading of the cathode carbon paper is 6 mg·cm⁻¹. -2 .

[0043] The DMFC system uses a 4.0 M methanol solution as the anode fuel and a 6.0 M potassium hydroxide (NaOH) solution as the electrolyte. The proton exchange membrane is a pretreated potassium hydroxide-doped polybenzimidazole (PBI) membrane. The PBI membrane pretreatment process involves: first, treatment in 6 M NaOH solution at 60°C for 3 hours, then treatment at 40°C for 6 hours, and finally soaking in 6 M NaOH solution overnight to improve the membrane's ion transport performance. Simultaneously, to enhance the proton (H+) transport in Nafion... + To assess the exchange efficiency, the gas diffusion layer of the battery was immersed in 1 M NaOH solution overnight.

[0044] The prepared anode catalyst, pretreated potassium hydroxide-doped PBI proton exchange membrane, and cathode catalyst were assembled with current collectors, fuel tanks, and other components to form a complete DMFC. The anode chamber was filled with a mixed solution of 4 M methanol and 6 M NaOH, while the cathode chamber was supplied with 6 M NaOH solution and oxygen required for the reaction. The battery system was operated at 80°C. After the membrane electrode assembly (MEA) stabilized for about 1 hour and the open-circuit voltage reached a stable state, relevant tests such as battery polarization performance were carried out based on this system to verify the electrochemical performance of the DMFC system.

[0045] Figure 6 Figure a shows the discharge polarization curve and corresponding power density curve of the PdCoNi / Cr-SAC based DMFC. The test results show that the maximum power density of this battery can reach 111.3 mW·cm⁻¹. -2 It is 3.8 times that of commercially available Pt / C anode catalysts used in battery assembly. Figure 6 b is a PdCoNi / Cr-SAC based DMFC at 50 mA·cm -2 Durability test curves at current density. As shown in the figure, the battery can discharge stably for 60 hours, which is far superior to the stability of commercial Pt / C based batteries.

[0046] The above results demonstrate that the direct methanol fuel cell using PdCoNi / Cr-SAC as the anode catalyst exhibits both excellent energy conversion efficiency and long-term operational stability. This performance advantage stems from the synergistic effect of the electronic regulation effect of Cr single atoms and the defect strain effect of PdCoNi nanoalloys. This effect not only effectively lowers the energy barrier of the rate-determining step of the methanol oxidation reaction but also promotes the formation of hydroxyl species, thereby significantly improving the overall performance of the battery.

[0047] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A method for preparing a single-atom modified multi-component nanoalloy catalyst, characterized in that, Includes the following steps: S1. Preparation of Cr single-atom catalyst Cr-SAC by ball milling pyrolysis: Using chromium acetate, melamine and L-alanine as raw materials, after ball milling, ethanol and hydrochloric acid are added for solvent modification. After collecting the solid product, Cr-SAC is synthesized by stepwise high-temperature sintering, acid washing and annealing. S2. Preparation of single-atom modified multi-element nano-alloy catalyst PdCoNi / Cr-SAC by electrochemical deposition: In a standard three-electrode test system, the Cr-SAC powder prepared in S1 is uniformly loaded onto the surface of a carbon-based electrode. At the same time, a mixed electrolyte containing potassium hydroxide and three metal precursors, palladium, cobalt and nickel, is prepared. Then, a specific deposition potential and scan rate are set, and PdCoNi / Cr-SAC can be obtained by cathode deposition after multiple cycles of scanning.

2. The method for preparing a single-atom modified multi-component nano-alloy catalyst according to claim 1, characterized in that, The mass ratio of chromium acetate, melamine, and L-alanine is 6–8:1100–1300:120–250.

3. The method for preparing a single-atom modified multi-component nano-alloy catalyst according to claim 1, characterized in that, The stepwise high-temperature sintering process involves first heating the temperature at 2–3°C / min to 500–700°C and holding it for 100–150 minutes, then heating it to 800–1000°C and holding it for 80–100 minutes.

4. The method for preparing a single-atom modified multi-component nano-alloy catalyst according to claim 1, characterized in that, The pickling process involves washing with 1–3 mol / L hydrochloric acid at 70–90°C for 20–30 hours.

5. The method for preparing a single-atom modified multi-component nano-alloy catalyst according to claim 1, characterized in that, The annealing is performed at 700–900°C in an inert gas atmosphere for 50–70 minutes.

6. The method for preparing a single-atom modified multi-component nano-alloy catalyst according to claim 1, characterized in that, The mixed electrolyte contains 0.05–0.3 mol / L potassium hydroxide and palladium chloride, cobalt chloride, and nickel acetate tetrahydrate in an equimolar ratio, with a total concentration of 800–1000 mmol / L.

7. The method for preparing a single-atom modified multi-component nano-alloy catalyst according to claim 1, characterized in that, The carbon-based electrode includes a glassy carbon electrode and a graphite electrode; the loading of Cr-SAC powder on the surface of the carbon-based electrode is 0.3–0.5 mg / cm³. 2 .

8. The method for preparing a single-atom modified multi-component nano-alloy catalyst according to claim 1, characterized in that, The deposition potential is controlled at -0.71 to -1.20V, the scan rate is 4 to 6 mV / s, and the number of cycles is 8 to 15.

9. A single-atom modified multi-component nano-alloy catalyst prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the single-atom modified multi-component nano-alloy catalyst according to claim 9 in the preparation of direct methanol fuel cells, characterized in that, The single-atom modified multi-component nano-alloy catalyst was used as the anode catalyst.

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