Ultra-low-load Ga monatomic carbon carrier loaded Pd ethylene glycol oxidation reaction catalyst as well as preparation method and application of ultra-low-load Ga monatomic carbon carrier loaded Pd ethylene glycol oxidation reaction catalyst

Abstract

The invention relates to the technical field of Pd-based catalysts and preparation thereof, and discloses an ultra-low-loading Ga monatomic carbon carrier-loaded Pd ethylene glycol oxidation reaction catalyst and a preparation method and application thereof, the ultra-low-loading Ga monatomic carbon carrier-loaded Pd ethylene glycol oxidation reaction catalyst comprises an MOF-derived N-doped carbon carrier, Ga monatomic and Pd nanoparticles; ga single atoms and N atoms are synergistically anchored and loaded through defect sites on the surface of the carbon carrier, and Pd nanoparticles are dispersed on the surface of the carbon carrier and around the Ga single atoms. According to the scheme, Ga single atoms and Pd nano-particles are loaded on a carrier of the catalyst, the Ga single atoms and the Pd nano-particles form synergistic catalysis sites, the Ga single atoms regulate and control the d band center of Pd through the electron transfer effect, the adsorption energy barrier of ethylene glycol oxidation intermediates (such as acetaldehyde and acetic acid) and CO is reduced, meanwhile, desorption and conversion of the intermediates are promoted, and the catalytic activity of the catalyst is improved. The catalytic activity and the anti-poisoning capability are obviously improved.

Description

Technical Field

[0001] This invention relates to the field of Pd-based catalysts and their preparation technology, specifically to a Pd ethylene glycol oxidation catalyst supported on an ultra-low loading Ga single-atom carbon support, its preparation method, and its application. Background Technology

[0002] Under the "dual-carbon" strategy, green hydrogen production is key to energy transition. Traditional water electrolysis for hydrogen production suffers from slow kinetics and high overpotential of the anodic oxygen evolution reaction, resulting in high energy consumption and hindering large-scale application. Meanwhile, traditional treatment methods for the large amounts of ethylene glycol-containing waste generated by the polyester industry are energy-intensive, have low resource recovery rates, and easily lead to carbon waste and emissions. The core applications of ethylene glycol oxidation catalysts are: first, to replace the anodic oxygen evolution reaction in hydrogen electrolysis, reducing electrolysis voltage and hydrogen production energy consumption; and second, to realize the resource recovery of ethylene glycol waste, reducing carbon waste, thus possessing both energy and environmental value. Furthermore, it is also a core material for ethylene glycol fuel cells, directly determining the battery's energy conversion efficiency and lifespan, which is crucial for commercial applications.

[0003] Current research on ethylene glycol oxidation catalysts primarily focuses on noble metal-based methods, with Pd-based catalysts becoming the mainstream due to their superior catalytic activity. The core preparation approach is the supported method, which involves immobilizing the Pd active component on a support to improve utilization and stability. A common method is the direct reduction and loading of Pd nanoparticles onto a carbon support. Specifically, commercial carbon materials (such as Vulcan XC-72) are used as supports, and the catalyst is obtained through Pd precursor adsorption, chemical reduction, and post-treatment. To improve performance, existing technologies also explore optimizing the preparation process, constructing single-atom sites, or utilizing the support-metal synergistic effect, aiming to reduce the amount of noble metal used and improve catalytic performance.

[0004] However, existing Pd-based catalyst preparation technologies still have the following defects, which restrict industrial applications: (1) High noble metal loading and low atom utilization. Pd exists in the form of nanoparticles, and the internal atoms cannot participate in the reaction. It is necessary to increase the loading to ensure activity and increase costs; (2) Single active site and weak synergy. Single Pd nanoparticles have limited adaptability to the complex process of ethylene glycol oxidation, are easily poisoned by intermediate products (such as CO), and lack site synergy, which limits reaction efficiency; (3) Single support function and limited performance. Commercial carbon supports have small specific surface area and disordered pores, which leads to uneven dispersion of Pd particles and easy agglomeration, resulting in large mass transfer resistance and affecting catalytic efficiency. In summary, how to accurately design catalysts, significantly reduce Pd loading, construct multifunctional synergistic active centers and match them with high-performance supports to prepare highly active, highly selective and highly stable ethylene glycol oxidation catalysts is still a problem that needs to be solved in this field. Summary of the Invention

[0005] The present invention aims to provide a Pd ethylene glycol oxidation catalyst supported on an ultra-low loading Ga single-atom carbon support, its preparation method and application, in order to solve the technical problems of weak anti-poisoning ability and poor stability of Pd-based catalysts prepared by existing technologies.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a Pd ethylene glycol oxidation catalyst supported on an ultra-low loading Ga single-atom carbon support, comprising a MOF-derived N-doped carbon support, Ga single atoms, and Pd nanoparticles; wherein the Ga single atoms are anchored and loaded in synergy with N atoms through defect sites on the carbon support surface, and the Pd nanoparticles are dispersed on the carbon support surface and around the Ga single atoms.

[0007] Preferably, as an improvement, the loading of the Ga single atom is 0.04~0.08 wt% of the total mass of the catalyst.

[0008] Preferably, as an improvement, the loading of Pd nanoparticles is 3-5 wt% of the total mass of the catalyst, and the particle size of the Pd nanoparticles is 3-6 nm.

[0009] Preferably, as an improvement, the specific surface area of ​​the MOF-derived N-doped carbon support is 1200~1300 m². 2 / g, the surface is rich in mesoporous structures and N doping sites, and the N content is 5~8 at%. Detailed test results are available in [link to test results]. Figure 4 .

[0010] Preferably, as an improvement, this solution also provides a method for preparing a Pd ethylene glycol oxidation catalyst supported on an ultra-low loading Ga single-atom carbon support, comprising the following steps: Step 1: Preparation of MOF precursor: Hexadecyltrimethylammonium bromide (CTAB), Zn(NO3)2·6H2O and gallium acetylacetonate were dissolved in deionized water and magnetically stirred until completely dissolved; then 2-methylimidazole was added and the mixture was stirred continuously at room temperature for 20 min to form a homogeneous suspension; after the reaction was completed, the solid product was collected by vacuum filtration, washed three times alternately with deionized water and anhydrous ethanol, and dried overnight in an oven at 65℃ to obtain the MOF precursor; Step 2: Preparation of Ga single-atom doped carbon support Ga_SA-NC: The MOF precursor was dispersed in an ethanol / deionized water mixture (volume ratio 1:1) and ultrasonically dispersed for 30 min to obtain a uniformly dispersed solution A; Dopamine hydrochloride, F-127, and trimethylbenzene were dissolved in an ethanol / deionized water mixture (volume ratio 1:1) and ultrasonically dispersed for 15 min to form a white microemulsion, which was used as solution B; Solution B was rapidly injected into solution A, and after vigorous stirring for 5 min, 25% ammonia water was added dropwise, and stirring was continued at room temperature for 2 h; The product was collected by vacuum filtration again, washed, and dried at 65℃ overnight; The dried sample was placed in a tube furnace and heated to 900℃ at a heating rate of 5℃ / min under N2 atmosphere, carbonized at this temperature for 2 h, and then naturally cooled to obtain the Ga_SA-NC support; Step 3: Preparation of the target catalyst using Pd-supported material: Weigh the Ga_SA-NC support and add it to a mixed system containing PdCl2 solution and deionized water. Disperse the mixture ultrasonically for 20 minutes to allow Pd to settle. 2+ The Pd plasmid was fully adsorbed onto the support surface; then, NaBH4 solution was slowly added dropwise at a rate of 1 mL / min, and the mixture was stirred continuously at room temperature for 12 h to complete the Pd plasmid adsorption process. 2+ The reduction was carried out; after the reaction was completed, the mixture was centrifuged at 9000 rpm, washed alternately with deionized water and anhydrous ethanol until the filtrate was neutral, and dried under vacuum at 60℃ for 8 h to obtain an ultra-low loading Ga single-atom carbon support for Pd catalyst.

[0011] Preferably, as an improvement, in step one, the ratio of CTAB, Zn(NO3)2·6H2O, gallium acetylacetonate, and 2-methylimidazole is 5 mg:(0.8~1.0 mmol):(0.6~1.0 mmol):55 mmol, and the amount of deionized water is 70 mL. This scheme ensures the uniform formation of the MOF precursor, laying the structural foundation for the subsequent uniform dispersion of Ga single atoms.

[0012] Preferably, as an improvement, in step two, the amount of MOF precursor in solution A is 500 mg, and the total solvent volume is 20 mL; the ratio of dopamine hydrochloride, F-127, and trimethylbenzene in solution B is 500 mg:0.5 g:2 mL, and the total solvent volume is 30 mL. This scheme utilizes the combination of dopamine hydrochloride and F-127 to regulate the functional groups and pore structure of the support surface, while trimethylbenzene acts as a porogen to further optimize the mesoporous distribution of the support. 2 mL of ammonia is used to adjust the pH of the reaction system, promoting the polymerization of dopamine and the anchoring of Ga ions. The carbonization process employs a high temperature of 900 °C and a slow heating rate of 5 °C / min to ensure the volatilization of Zn and the stable anchoring of Ga single atoms, while simultaneously forming a high specific surface area N-doped carbon support.

[0013] Preferably, as an improvement, in step three, the ratio of Ga_SA-NC support to PdCl2 solution is 0.1g:2mL, the concentration of PdCl2 solution is 50mmol / L, and the volume of deionized water is 10mL. The proportions used in this scheme allow for precise control of the Pd loading; NaBH4 solution, as a mild reducing agent, can achieve Pd loading... 2+ Uniform reduction is achieved to avoid Pd particle agglomeration, while not affecting the binding state of Ga single atoms with the support.

[0014] Preferably, as an improvement, the present invention also protects the application of the above-mentioned catalyst in the ethylene glycol oxidation reaction, wherein the catalyst is used as an anode catalyst in a direct ethylene glycol fuel cell in a 0.1 mol / L HClO4 and 1 mol / L ethylene glycol electrolyte. The catalyst prepared by this method exhibits excellent catalytic activity, resistance to CO poisoning, and long-term cycling stability, and its catalytic performance is superior to commercial Pd / C catalysts and Pd / carbon catalysts without Ga single-atom synergy. The principle of this scheme is: This scheme loads Ga and Pd onto a catalyst support, where Ga single atoms and Pd nanoparticles form synergistic catalytic sites. Ga single atoms regulate the d-band center of Pd through electron transfer, reducing the adsorption energy barrier of ethylene glycol oxidation intermediates (such as acetaldehyde and acetic acid) and CO, while promoting the desorption and transformation of intermediates, thus significantly improving catalytic activity and anti-poisoning ability.

[0015] The advantages of this solution are: 1. Innovative structural design with significant synergistic effect: The innovative construction of a ternary synergistic structure of "MOF-derived N-doped carbon support Ga single-atom Pd nanoparticles" allows Ga single atoms to be synergistically anchored to the support defects through N doping sites, which not only avoids self-aggregation but also forms strong electronic interactions with Pd, precisely controlling the d-band center of Pd. This fundamentally solves the defects of excessive adsorption and weak anti-poisoning ability of traditional Pd-based catalyst intermediates.

[0016] 2. Extremely low precious metal loading, resulting in significant cost advantages: Pd loading is only 1~5wt%, and Ga single atom loading is as low as 0.04~0.08wt%, which reduces the amount of precious metals used by more than 84% compared with commercial Pd / C catalysts (20wt% Pd loading), significantly reducing the cost of catalyst preparation and breaking through the economic bottleneck of dependence on precious metals.

[0017] 3. The preparation process is green, controllable, and easily scalable: the entire process uses an aqueous solution and low-toxicity solvent system, eliminating the need for extreme conditions such as high temperature and high pressure. The steps are simple and the parameters are easy to control. The regular structure of the MOF precursor and the porosizing effect of F-127 ensure that the specific surface area of ​​the carrier remains stable at 1200~1300m². 2 / g, achieving efficient exposure and uniform dispersion of active sites, suitable for mass production.

[0018] 4. Comprehensive performance surpasses traditional catalysts: The mesoporous structure of the support (pore size 2~50nm) accelerates the mass transfer process, and Ga-Pd electron synergy enhances reaction kinetics, enabling the catalyst to exhibit high activity in the ethylene glycol oxidation reaction (oxidation peak current density reaches 128mA / cm). 2 It exhibits high stability (86.2% current retention rate at 3000s) and strong resistance to poisoning (CO oxidation peak potential 0.52V vs. RHE), with overall performance superior to commercial Pd / C catalysts and Pd-based catalysts without Ga single-atom synergy.

[0019] 5. Strong adaptability to application scenarios: The catalyst exhibits excellent electrochemical performance in 0.1 mol / L HClO4 and 1 mol / L ethylene glycol electrolytes, and can be directly used as an anode catalyst for direct ethylene glycol fuel cells. It is suitable for energy conversion needs in portable power supplies, new energy vehicles and other fields, and has broad application prospects. Attached Figure Description Figure 1 The X-ray diffraction (XRD) patterns of the catalysts prepared in Examples 1, 1, and 5 of this invention are shown below (the red curve corresponds to the Pd-Ga / NC catalyst with Pd supported on an N-doped carbon support and Ga single atom in Example 1, the blue curve corresponds to the Pd / NC catalyst without Ga single atom doping in Example 1, and the gray curve corresponds to the Ga / NC catalyst with Ga single atom supported on an N-doped carbon support in Example 5).

[0020] Figure 2 This is a TEM image of the Pd catalyst supported on a Ga single-atom carbon support prepared in Example 1 of the present invention.

[0021] Figure 3 The image shows the elemental distribution mappings of the Ga single-atom carbon support Pd catalyst prepared in Example 1 of this invention (corresponding to C, Pd, and Ga elements respectively).

[0022] Figure 4 The elemental content EDS energy diagrams (corresponding to C, N, Pd, and Ga elements respectively) of the Ga single-atom carbon support-supported Pd catalyst prepared in Example 1 of this invention are shown.

[0023] Figure 5 Linear sweep voltammetry (LSV) spectra of the catalysts obtained in Example 1, Comparative Example 1, and Comparative Example 2 of this invention (red curve (Pd-Ga / NC) represents the catalyst with Pd supported on a Ga single-atom N-doped carbon support in Example 1; blue curve (Pd / NC) represents the catalyst with Pd nanoparticles without Ga single-atom doping directly supported on an N-doped carbon support in Comparative Example 1; gray curve (Pd / C) represents the commercial Pd / C catalyst in Comparative Example 2).

[0024] Figure 6 This is a schematic diagram of the morphology of the Ga single-atom carbon support for Pd catalyst prepared in Example 1 of the present invention, showing the coexistence of single atoms and Pd nanoparticles.

[0025] Figure 7 This is a TEM image of the Ga-free single-atom carbon support-supported Pd catalyst prepared in Comparative Example 1 of this invention.

[0026] Figure 8 The image shows the elemental distribution mappings (corresponding to C, Pd, and N elements) of the Ga-free single-atom carbon support-supported Pd catalyst prepared in Comparative Example 1 of this invention.

[0027] Figure 9 This is a schematic diagram of the morphology and structure of the Ga single-atom carbon support prepared in Comparative Example 5 of the present invention.

[0028] Figure 10 The image shows the elemental distribution mappings of the Ga single-atom carbon support prepared in Comparative Example 5 of this invention (corresponding to C, N, and Ga elements respectively).

[0029] Figure 11 The linear sweep voltammetry (LSV) spectra of the catalysts obtained in Examples 2, 3, 3, and 4 of this invention are shown below. (The orange curve (Pd-Ga / NC-1) represents the catalyst in Example 2 with Pd supported on a Ga single-atom N-doped carbon support (Ga loading of 0.01 wt%); the pink curve (Pd-Ga / NC-2) represents the catalyst in Example 3 with Ga single-atom N-doped Pd nanoparticles directly supported on an N-doped carbon support (Ga loading of 0.09 wt%); the blue curve (Pd-Ga / NC-3) represents the catalyst in Comparative Example 3 with Pd supported on a Ga single-atom N-doped carbon support (Ga loading of 0.12 wt%); and the green curve (Pd-Ga / NC-4) represents the catalyst in Comparative Example 4 with Pd supported on a Ga single-atom N-doped carbon support without the addition of F127.)

[0030] Figure 12 This is a TEM image (scale bar is 100 nm) of the Pd / NC catalyst in Comparative Example 2 of the present invention.

[0031] Figure 13 This is a TEM image (scale bar is 50 nm) of the Pd / NC catalyst in Comparative Example 2 of the present invention.

[0032] Figure 14 This is an EDS image of the Pd / Ga alloy catalyst of Comparative Example 3 of this invention.

[0033] Figure 15This is a TEM image of the catalyst obtained in Comparative Example 4 of the present invention without the addition of F127.

[0034] Figure 16 The image shows the performance of the Pd / Ga_SA-NC catalyst obtained in Example 1 of this invention. Detailed Implementation

[0035] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto. Unless otherwise specified, the technical means used in the following embodiments and experimental examples are conventional means well known to those skilled in the art, and the materials and reagents used can all be obtained commercially.

[0036] Example 1 This embodiment provides a method for preparing an ultra-low loading Ga single-atom carbon support-supported Pd ethylene glycol oxidation catalyst (i.e., Pd / Ga_SA-NC-1 catalyst), which specifically includes the following steps: Step 1: Preparation of MOF precursors: 5 mg of cetyltrimethylammonium bromide (CTAB), 0.9 mmol of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and 0.8 mmol of gallium acetylacetonate were added sequentially to 70 mL of deionized water and stirred magnetically until completely dissolved. Then, 55 mmol of 2-methylimidazole was added and the mixture was stirred continuously at room temperature for 20 min to form a homogeneous suspension. After the reaction was completed, the solid product was collected by vacuum filtration, washed three times alternately with deionized water and anhydrous ethanol, and dried overnight in an oven at 65 °C to obtain the MOF precursor.

[0037] Step 2: Preparation of Ga single-atom doped carbon support (Ga_SA-NC): Take 500 mg of the above MOF precursor, add 20 mL of ethanol / deionized water mixed solution (volume ratio 1:1), and sonicate for 30 min to obtain a uniformly dispersed solution A; separately take 500 mg of dopamine hydrochloride, 0.5 g of F-127 and 2 mL of trimethylbenzene, add 30 mL of ethanol / deionized water mixed solution (volume ratio 1:1), and sonicate for 15 min to form a white microemulsion, which is solution B; rapidly inject solution B into solution A, stir vigorously for 5 min, then add 2 mL of ammonia water (mass fraction 25%) dropwise, and continue stirring at room temperature for 2 h; filter again to collect the product, wash and dry at 65 °C overnight; place the dried sample in a tube furnace, heat to 900 °C at a heating rate of 5 °C / min under N2 atmosphere, carbonize at this temperature for 2 h, and obtain the Ga_SA-NC support after natural cooling. Step 3: Preparation of Pd-supported target catalyst: Weigh 0.1 g of Ga_SA-NC support and add it to a mixture containing 2 mL of PdCl2 solution (50 mmol / L) and 10 mL of deionized water. Disperse the mixture ultrasonically for 20 min to allow Pd to disperse. 2+ The adsorption was fully achieved on the carrier surface; then 3 mL of 0.1 mol / L sodium borohydride (NaBH4) solution was slowly added dropwise at a rate of 1 mL / min, and the mixture was stirred continuously at room temperature for 12 h to complete the Pd process. 2+ The reduction was carried out; after the reaction was completed, the mixture was centrifuged at 9000 rpm, washed alternately with deionized water and anhydrous ethanol until the filtrate was neutral, and dried under vacuum at 60℃ for 8 h to obtain an ultra-low loading Ga single-atom carbon support Pd catalyst (denoted as Pd / Ga-NC). Experimental Results Detection 1: Determination and Characterization of Pd / Ga-NC Catalyst Inductively coupled plasma mass spectrometry (ICP-MS) revealed a Ga single-atom loading of 0.06 wt% and a Pd loading of 3.2 wt%. Transmission electron microscopy (TEM) images of the catalyst and a particle size distribution chart of 200 randomly selected Pd particles showed a Pd nanoparticle size of 4.2 ± 0.5 nm. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) confirmed the uniform dispersion of Ga in single-atom form. X-ray photoelectron spectroscopy (XPS) analysis of the catalyst surface chemical state spectrum showed strong interactions between Ga and N and C, and electron transfer between Ga and Pd. Nitrogen adsorption-desorption tests revealed a specific surface area of ​​1280 m². 2 / g, rich in mesoporous structure, experimental results are detailed in [link to experimental results]. Figures 1-6 The specific surface area of ​​the MOF-derived N-doped carbon support is 1200~1300 m². 2 / g, the surface is rich in mesoporous structures and N doping sites, and the N content is 5~8 at%. Detailed test results are available in [link to test results]. Figure 4 .

[0038] Example 2 This embodiment provides a method for preparing a Pd ethylene glycol oxidation catalyst supported on an ultra-low loading Ga single-atom carbon support (i.e., a Pd / Ga-NC-1 catalyst), which specifically includes the following steps: Step 1: Preparation of MOF precursor: Add 5 mg of CTAB, 0.9 mmol of Zn(NO3)2·6H2O and 0.6 mmol of gallium acetylacetonate to 70 mL of deionized water. The subsequent operations are the same as in Step 1 of Example 1 (i.e., the amount of 2-methylimidazole, washing and drying conditions are the same) to obtain MOF precursor. Step 2: Preparation of Ga single-atom doped carbon support (Ga_SA-NC): Dispersion, polymerization and carbonization were carried out according to the process in step 2 of Example 1 (the amount of each reagent and the reaction parameters were the same) to obtain Ga_SA-NC support with a Ga single-atom loading of 0.04wt%; Step 3: Preparation of Pd-supported target catalyst: Pd loading was carried out according to the process in Step 3 of Example 1 (PdCl2 solution concentration, NaBH4 amount and reaction conditions were the same) to obtain a catalyst with a Pd loading of 3.0 wt% (denoted as Pd / Ga-NC-1).

[0039] Experimental Results Detection 2: Determination and Characterization of Pd / Ga-NC-1 Catalyst Inductively coupled plasma mass spectrometry (ICP-MS) revealed a Ga single-atom loading of 0.04 wt% and a Pd loading of 3.0 wt%. Transmission electron microscopy (TEM) images of the catalyst and a particle size distribution chart of 200 randomly selected Pd particles showed uniform dispersion of the Pd nanoparticles. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images confirmed the absence of significant Ga single-atom aggregation. Nitrogen adsorption-desorption tests were used to obtain the specific surface area data of the support, verifying its mesoporous structure. Detailed experimental results are available in [link to experimental data]. Figure 11 .

[0040] Example 3 This embodiment provides a method for preparing a Pd ethylene glycol oxidation catalyst supported on an ultra-low loading Ga single-atom carbon support (i.e., a Pd / Ga-NC-2 catalyst), which specifically includes the following steps: Step 1: Preparation of MOF precursor: Add 5 mg of CTAB, 0.9 mmol of Zn(NO3)2·6H2O and 1.0 mmol of gallium acetylacetonate to 70 mL of deionized water. The subsequent operations are the same as in Step 1 of Example 1 to obtain the MOF precursor. Step 2: Preparation of Ga single-atom doped carbon support (Ga_SA-NC): Dispersion, polymerization and carbonization were carried out according to the process in step 2 of Example 1 to obtain Ga_SA-NC support with a Ga single-atom loading of 0.08wt%; Step 3: Preparation of Pd-supported target catalyst: Pd loading was carried out according to the process in step 3 of Example 1 to obtain a catalyst with a Pd loading of 3.3 wt% (denoted as Pd / Ga-NC-2). Experimental Results Detection 3: Determination and Characterization of Pd / Ga-NC-2 Catalyst Inductively coupled plasma mass spectrometry (ICP-MS) was used to determine the single-atom loading of Ga was 0.08 wt% and the single-atom loading of Pd was 3.3 wt%. Transmission electron microscopy (TEM) was used to obtain TEM images of the catalyst and a particle size distribution chart of 200 randomly selected Pd particles, recording the size and dispersion of Pd nanoparticles. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) was used to obtain images of Ga elemental distribution and observe the single-atom dispersion state of Ga. X-ray photoelectron spectroscopy (XPS) was used to analyze the elemental chemical state spectrum of the catalyst surface and explore the electronic interaction between Ga and Pd. Detailed experimental results are available in [link to experimental data]. Figure 11 .

[0041] Comparative Example 1 Preparation steps of Ga-free single-atom doped Pd / carbon catalyst (Pd / NC): Step 1: Take 0.1 g of porous carbon support (specific surface area 1200 m²) 2 / g), directly added to a mixture containing 2 mL of PdCl2 solution (concentration 50 mmol / L) and 10 mL of deionized water, and ultrasonically dispersed for 20 min, so that Pd 2+ It is fully adsorbed onto the carrier surface.

[0042] Step 2: Slowly add 3 mL of 0.1 mol / L sodium borohydride (NaBH4) solution at a dropping rate of 1 mL / min, and continue stirring at room temperature for 12 h to complete the Pd process. 2+ The restoration.

[0043] Step 3: After the reaction is complete, the mixture is centrifuged at 9000 rpm, washed alternately with deionized water and anhydrous ethanol until the filtrate is neutral, and dried under vacuum at 60℃ for 8 hours to obtain the Pd / NC catalyst.

[0044] Experimental Result Detection 4: Structure and performance were determined following the characterization procedures outlined in Example 1. ICP-MS was used to test the Pd loading. Morphology and elemental distribution were analyzed using TEM and elemental mapping. The specific surface area of ​​the support was tested using nitrogen adsorption-desorption. Electrochemical performance testing was performed as described in Experimental Result Detection 1. Detailed experimental results are available in [link to experimental results]. Figure 1 , Figure 5 and Figures 7-8 .

[0045] Comparative Example 2 The preparation steps of commercial Pd / C catalysts are as follows: A commercially available 20wt% Pd / C catalyst (Pd particle size 5~8 nm) from Johnson-Matthey, UK, was selected, eliminating the need for additional preparation.

[0046] Experimental Results Detection 5: Structural and performance determinations were performed, following the characterization procedures outlined in Example 1. The actual Pd loading was tested using ICP-MS, and the particle morphology and size distribution were observed using TEM. The results are as follows: Figures 12-13 As shown; the electrochemical performance test results are the same as those in Experiment 1, and the experimental results are detailed in [link to Experiment 1]. Figure 5 .

[0047] Comparative Example 3 The preparation steps of Ga-supported Pd / Ga alloy / C catalyst are as follows: Step 1: Take 0.1 g of commercial porous carbon support and add it to a mixture containing 2 mL of PdCl2 solution (concentration 50 mmol / L), 0.8 mmol / L gallium acetylacetonate solution and 10 mL of deionized water, and sonicate for 20 min.

[0048] Step 2: Slowly add 3 mL of 0.1 mol / L NaBH4 solution and stir at room temperature for 12 h; after centrifugation, washing, and drying, calcine at 300 °C for 2 h under N2 atmosphere at a rate of 5 °C / min to obtain the Pd / Ga alloy / C catalyst (denoted as Pd / Ga-NC-3).

[0049] Experimental Results Detection 6: Structure and Performance Determination. ICP-MS was used to test the Ga and Pd loadings. The alloy structure and elemental distribution were analyzed using TEM, HAADF-STEM, and elemental mapping. Electrochemical performance testing was performed as described in Experimental Results Detection 1. See detailed experimental results below. Figure 11 and Figure 14 .

[0050] Comparative Example 4 The preparation steps of the Ga_SA-NC-4 supported Pd catalyst without the addition of F-127 are as follows: Step 1: Preparation of MOF precursor: 5 mg CTAB, 0.9 mmol Zn(NO3)2·6H2O and 0.8 mmol gallium acetylacetonate were added sequentially to 70 mL of deionized water and magnetically stirred until completely dissolved; 55 mmol 2-methylimidazole was added, and the mixture was stirred at room temperature for 20 min, then vacuum filtered, washed, and dried at 65 °C overnight to obtain the MOF precursor.

[0051] Step 2: Preparation of Ga single-atom doped carbon support: Take 500 mg of the above MOF precursor, add 20 mL of ethanol / deionized water mixed solution (volume ratio 1:1) and sonicate for 30 min (solution A); separately take 500 mg of dopamine hydrochloride and 2 mL of trimethylbenzene, add 30 mL of ethanol / deionized water mixed solution (volume ratio 1:1) and sonicate for 15 min (solution B); inject solution B into solution A, add 2 mL of ammonia water and stir for 2 h, wash and dry, and then carbonize at 900℃ for 2 h under N2 atmosphere to obtain Ga_SA-NC-4 support.

[0052] Step 3: Preparation of Pd support: Weigh 0.1 g of Ga_SA-NC-4 support and perform Pd loading according to the process in Step 3 of Example 1 to obtain a catalyst with a Pd loading of 3.3 wt% (denoted as Pd / Ga-NC-4).

[0053] Experimental Results Detection 7: Structure and performance were determined following the characterization procedures outlined in Example 1. ICP-MS was used to test the Ga and Pd loadings. TEM and elemental mapping were used to analyze particle dispersion and elemental distribution. Nitrogen adsorption-desorption was used to test the specific surface area of ​​the support. Electrochemical performance testing was performed as described in Experimental Results Detection 1. Detailed experimental results can be found in [link to experimental results]. Figure 11 and Figure 15 .

[0054] Comparative Example 5 Ga / NC catalyst supported on N-doped carbon support with Ga single atom Step 1: Preparation of MOF precursor: 5 mg CTAB, 0.9 mmol Zn(NO3)2·6H2O and 0.8 mmol gallium acetylacetonate were added sequentially to 70 mL of deionized water and magnetically stirred until completely dissolved; 55 mmol 2-methylimidazole was added, and the mixture was stirred at room temperature for 20 min, then vacuum filtered, washed, and dried at 65 °C overnight to obtain the MOF precursor.

[0055] Step 2: Preparation of Ga single-atom doped carbon support: Take 500 mg of the above MOF precursor, add 20 mL of ethanol / deionized water mixed solution (volume ratio 1:1) and sonicate for 30 min (solution A); separately take 500 mg of dopamine hydrochloride and 2 mL of trimethylbenzene, add 30 mL of ethanol / deionized water mixed solution (volume ratio 1:1) and sonicate for 15 min (solution B); inject solution B into solution A, add 2 mL of ammonia water and stir for 2 h, wash and dry, and then carbonize at 900℃ for 2 h under N2 atmosphere to obtain Ga / NC catalyst.

[0056] Experimental Results Detection 8: Structure and performance were determined following the characterization procedures outlined in Example 1. ICP-MS was used to test the Ga loading. Particle dispersion and elemental distribution were analyzed using TEM and elemental mapping. The specific surface area of ​​the support was tested using nitrogen adsorption-desorption. Electrochemical performance testing was performed as described in Experimental Results Detection 1. Detailed experimental results can be found in [link to experimental results]. Figure 1 and Figures 9-10 .

[0057] Experimental Results and Comparison Summary: 1. XRD pattern: Figure 1 The red curve in the middle shows the characteristic diffraction peaks of the Pd-Ga / NC catalyst (i.e. the Pd / Ga-NC catalyst obtained in Example 1), indicating that Ga is combined with Pd in ​​an alloy form. Figure 1 The Pd / NC catalyst in the blue curve (obtained from Comparative Example 1) shows typical crystal plane diffraction peaks of Pd nanoparticles; Figure 1 The Ga / NC catalyst (obtained from Comparative Example 5) with the medium gray curve showed no diffraction peaks of elemental metal or alloy, confirming that Ga exists in single-atom form. Combined with the preparation process of Comparative Example 3 (calcination to form a Pd / Ga alloy) and... Figure 6 (Aberration diagram of the catalyst obtained in Example 1) further illustrates that in this invention, Ga is supported in the form of a single atom rather than an alloy, and the d-band center of Pd can be controlled by electron transfer. This is a key innovation that distinguishes it from the alloy structure of Comparative Example 3.

[0058] 2. SEM image of Ga_SA-NC vector: Figure 2 The outline of the carrier precursor of Example 1 is clearly shown. After carbonization, a uniform porous surface is formed with uniform pore size distribution and uniform Pd distribution, providing sufficient space for the dispersion of active sites.

[0059] 3. Element distribution mappings: Figure 3 The example in Example 1 shows that C, N, Ga, and Pd are uniformly distributed throughout the entire catalyst, with Ga distributed discretely in single-atom form and Pd aggregated at the nanoscale, which fits the synergistic catalytic structure design. In Comparative Example 1, only C and Pd are present in the catalyst, with Pd locally agglomerated (see reference). Figure 7 and Figure 8 The catalyst obtained in Comparative Example 2 showed no Ga element signal and uneven Pd distribution (e.g., ...). Figure 12 and Figure 13 As shown); in the catalyst obtained in Comparative Example 3, Ga and Pd elements highly overlap, exhibiting alloy-phase aggregation without single-atom dispersion characteristics, thus failing to achieve electronic synergistic regulation (as shown). Figure 14 (As shown).

[0060] 4. TEM image: Figure 2TEM images of the Ga single-atom carbon support-supported Pd catalyst prepared in Example 1 are shown. The results indicate that the Pd nanoparticles in Example 1 have a uniform particle size (4.2 ± 0.5 nm), are uniformly embedded in the mesoporous channels of the support, and exhibit strong structural stability; the Pd particles in the catalyst obtained in Comparative Example 1 have a particle size of 5–10 nm, are unevenly dispersed, and show significant agglomeration (e.g., ...). Figure 7 and Figure 8 In Comparative Example 2, the Pd particles in the catalyst exhibited severe agglomeration (5-8 nm) (e.g. Figure 12 and Figure 13 As shown); in the catalyst obtained in Comparative Example 4, the Pd particles had a particle size of 5-7 nm, and the poor dispersibility was due to insufficient support porosity (as shown). Figure 15 (As shown).

[0061] 5. Linear sweep voltammetry (LSV) spectrum: Figure 5 The images show the linear sweep voltammetry (LSV) spectra of the catalysts obtained in Examples 1, 1, and 2 of this invention. The red curve (Pd-Ga / NC) represents the catalyst in Example 1 with Pd supported on a Ga single-atom N-doped carbon support; the blue curve (Pd / NC) represents the catalyst in Comparative Example 1 with Pd nanoparticles without Ga single-atom doping directly supported on an N-doped carbon support; and the gray curve (Pd / C) represents the commercial Pd / C catalyst in Comparative Example 2.

[0062] In summary, the Pd / Ga_SA-NC catalyst of Example 1 of this scheme forms a porous support (1280 m) with a Ga single-atom loading of 0.06 wt% and a Pd loading of 3.2 wt%. 2 The synergistic structure of " / g) + Ga single atom uniform dispersion + Pd nanoparticle embedding" is as follows: Figure 16 As shown, the Pd / Ga_SA-NC catalyst obtained in Example 1 of this scheme exhibits a flux of 100 mA / cm². 2 The current density of the ethylene glycol oxidation peak ( Figure 16 (a) shows the current density and a charge transfer resistance of 6.52 Ω. Figure 16 (b) and long-term stability of 223 hours and Faraday efficiency greater than 90% Figure 16 (c)). However, each comparative example had structural defects due to either a lack of Ga single atoms (Comparative Example 1), excessive Pd loading (20wt%) (Comparative Example 2), Ga being in alloy form (Comparative Example 3), or insufficient porosity caused by the absence of F-127 on the support (Comparative Example 4). Their catalytic activity, stability, anti-poisoning ability, and electron transport efficiency were all significantly inferior, which fully demonstrates that the preparation process of Example 1 can achieve the unity of "low loading" and "high performance", and its comprehensive performance surpasses that of the comparative samples.

[0063] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A catalyst for the oxidation of Pd ethylene glycol with ultra-low loading Ga single-atom carbon support, characterized in that: It includes a MOF-derived N-doped carbon support, Ga single atoms, and Pd nanoparticles; the Ga single atoms are anchored and loaded in synergy with N atoms through defect sites on the carbon support surface, and the Pd nanoparticles are dispersed on the carbon support surface and around the Ga single atoms.

2. The ultra-low loading Ga single-atom carbon support Pd ethylene glycol oxidation catalyst according to claim 1, characterized in that: The loading of Ga single atoms is 0.04~0.08 wt% of the total catalyst mass.

3. The ultra-low loading Ga single-atom carbon support Pd ethylene glycol oxidation catalyst according to claim 2, characterized in that: The loading of Pd nanoparticles is 3-5 wt% of the total mass of the catalyst, and the particle size of the Pd nanoparticles is 3-6 nm.

4. The ultra-low loading Ga single-atom carbon support Pd ethylene glycol oxidation catalyst according to claim 3, characterized in that: The specific surface area of ​​the MOF-derived N-doped carbon support is 1200~1300 m². 2 / g, the surface is rich in mesoporous structure and N doping sites, and the N content is 5~8 at.

5. The method for preparing a Pd ethylene glycol oxidation catalyst with ultra-low loading Ga single-atom carbon support according to any one of claims 1 to 4, characterized in that: Includes the following steps: Step 1: Preparation of MOF precursor: Hexadecyltrimethylammonium bromide, Zn(NO3)2·6H2O and gallium acetylacetonate were dissolved in deionized water and magnetically stirred until completely dissolved; then 2-methylimidazole was added and the mixture was stirred continuously at room temperature for 20 min to form a homogeneous suspension; after the reaction was completed, the solid product was collected by vacuum filtration, washed three times alternately with deionized water and anhydrous ethanol, and dried overnight in an oven at 65℃ to obtain the MOF precursor; Step 2: Preparation of Ga single-atom doped carbon support Ga_SA-NC: MOF precursor was dispersed in an equal volume mixture of ethanol and deionized water, and ultrasonically dispersed for 30 min to obtain a uniformly dispersed solution A. Dopamine hydrochloride, F-127, and trimethylbenzene were dissolved in an equal volume mixture of ethanol and deionized water, and ultrasonically dispersed for 15 min to form a white microemulsion, which was then used as solution B. Solution B was rapidly injected into solution A, and after vigorous stirring for 5 min, 25% ammonia solution was added dropwise. Stirring continued at room temperature for 2 h. The product was collected by filtration again, washed, and dried overnight at 65℃. The dried sample was placed in a tube furnace and heated to 900℃ at a rate of 5℃ / min under a N2 atmosphere, carbonized for 2 h, and then naturally cooled to obtain the Ga_SA-NC support. Step 3: Preparation of the target catalyst using Pd-supported material: Weigh the Ga_SA-NC support and add it to a mixed system containing PdCl2 solution and deionized water. Disperse the mixture ultrasonically for 20 minutes to allow Pd to settle. 2+ The Pd solution was fully adsorbed onto the support surface; then, NaBH4 solution was slowly added dropwise at a rate of 1 mL / min, and the mixture was stirred continuously at room temperature for 12 h to complete the Pd process. 2+ The reduction was carried out; after the reaction was completed, the mixture was centrifuged at 9000 rpm, washed alternately with deionized water and anhydrous ethanol until the filtrate was neutral, and dried under vacuum at 60℃ for 8 h to obtain an ultra-low loading Ga single-atom carbon support for Pd catalyst.

6. The method for preparing a Pd ethylene glycol oxidation catalyst supported on an ultra-low loading Ga single-atom carbon support according to claim 5, characterized in that: In step one, the ratio of CTAB, Zn(NO3)2·6H2O, gallium acetylacetonate and 2-methylimidazole is 5mg:(0.8~1.0mmol):(0.6~1.0mmol):55mmol, and the amount of deionized water is 70mL.

7. The method for preparing a Pd ethylene glycol oxidation catalyst supported on an ultra-low loading Ga single-atom carbon support according to claim 5, characterized in that: In step two, the amount of MOF precursor used in solution A is 500 mg, and the total amount of solvent used is 20 mL; the ratio of dopamine hydrochloride, F-127, and trimethylbenzene used in solution B is 500 mg: 0.5 g: 2 mL, and the total amount of solvent used is 30 mL.

8. The method for preparing a Pd ethylene glycol oxidation catalyst supported on an ultra-low loading Ga single-atom carbon support according to claim 5, characterized in that: In step three, the ratio of Ga_SA-NC support to PdCl2 solution was 0.1g:2mL, the concentration of PdCl2 solution was 50mmol / L, and the amount of deionized water used was 10mL.

9. The application of the catalyst according to any one of claims 1 to 4 or the catalyst prepared by the method according to any one of claims 5 to 8 in the ethylene glycol oxidation reaction, characterized in that: The catalyst is used as an anode catalyst in a direct ethylene glycol fuel cell in a 0.1 mol / L HClO4 and 1 mol / L ethylene glycol electrolyte.

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