Preparation method and application of flexible spherical copper composite ZIF-8 electrode

Abstract

The application belongs to the technical field of fuel cells, and discloses a preparation method of a flexible spherical copper composite ZIF-8 electrode and application thereof. The preparation method comprises the following steps: preparing boron-doped SiNWs, preparing a boron-doped SiNWs electrode, preparing a SiNWs@ZIF-8 electrode, performing heat annealing treatment on the SiNWs@ZIF-8 electrode, and depositing Cu balls by means of chronocoulometry. The application significantly reduces the preparation cost of the electrode, discards the dependence of a traditional ethylene glycol electrocatalytic electrode on noble metals, and does not need to compensate for performance defects by means of noble metal and non-noble metal doping, so that the preparation cost is greatly reduced from the material level.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell technology, specifically relating to a method for preparing a flexible spherical copper composite ZIF-8 electrode and its application. Background Technology

[0002] With the escalating global energy crisis and the growing prominence of plastic pollution, the development and utilization of clean energy and the high-value recycling of waste plastics have become dual research hotspots in the energy and environmental fields. Ethylene glycol (EG), as the core product of the alkaline hydrolysis recycling of polyethylene terephthalate (PET) plastic, is also a liquid fuel with high energy density, easy storage, and easy transportation. Using it as fuel for fuel cells to achieve the direct conversion of chemical energy into electrical energy can not only promote the industrial upgrading of waste plastic resource utilization but also enrich the fuel system of fuel cells, making up for the shortcomings of traditional fuels such as hydrogen and methanol in terms of storage, transportation, or cost. It has broad application prospects in portable power supplies, wearable electronic devices, and small power generation devices. Therefore, ethylene glycol fuel cells have become an important direction for the research and development of new fuel cells.

[0003] Electrode materials are a core component of ethylene glycol fuel cells, and their catalytic activity, electron conduction efficiency, and structural stability directly determine the fuel cell's output power and lifespan. Currently, the mainstream anode catalytic electrodes in ethylene glycol fuel cells are primarily based on noble metals. While these materials can achieve highly efficient electrocatalytic oxidation of ethylene glycol, they suffer from inherent drawbacks such as scarce raw materials and high costs. Furthermore, they are easily poisoned by intermediate species generated during the catalytic process, leading to rapid deactivation of active sites and a significant decrease in the long-term operational stability of the fuel cell. Non-noble metal-based catalysts, with transition metals such as copper and nickel as their core, have become a focus of alternative research due to their excellent catalytic activity towards alcohol molecules. However, it is worth noting that previous material selection for ethylene glycol electrocatalytic electrodes has typically been limited to noble metals or composite systems doped with both noble and non-noble metals. Research on ethylene glycol electrocatalysts using pure non-noble metals as the core active component is scarce, and mature technical solutions have not yet been developed. This research gap has prevented the full exploration of the application potential of non-noble metal materials in the field of ethylene glycol electrocatalysis. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, this invention provides a method for preparing a flexible spherical copper composite ZIF-8 electrode and its application. The prepared spherical copper composite ZIF-8 electrode exhibits excellent electrocatalytic activity for ethylene glycol and can be used to construct ethylene glycol fuel cells.

[0005] The above-mentioned objective of this invention is achieved through the following technical solution: a method for preparing a flexible spherical copper composite ZIF-8 electrode, comprising the following steps: 1. Spread SiNWs flat in a quartz boat, place it in a CVD reactor, introduce argon gas to purge air, raise the temperature, introduce a boron source while maintaining a mixed atmosphere of argon and hydrogen, keep the temperature, and allow it to cool naturally to obtain boron-doped SiNWs. 2. Boron-doped SiNWs were placed in a methanol solution and uniformly dispersed on a hydrophilically modified flexible substrate under ultrasonic conditions to prepare a boron-doped SiNWs electrode. 3. Disperse ZIF-8 in an ethanol solution, spray it onto the surface of a boron-doped SiNWs electrode, and allow it to dry to obtain a SiNWs@ZIF-8 electrode; 4. Perform thermal annealing on the SiNWs@ZIF-8 electrode; 5. The SiNWs@ZIF-8 electrode after thermal annealing was placed in a mixed electrolyte solution of H2SO4 and CuSO4, and electrochemical deposition was performed using the chronoamperometry method to obtain a spherical Cu-SiNWs@ZIF-8 electrode.

[0006] Furthermore, in step 1, the argon flow rate is 200-300 sccm, the ventilation time is 15-30 min, the temperature is raised to 800-1200℃, the boron source is B2H6, the flow rate is 1-3 sccm, and the temperature is maintained for 30-60 min.

[0007] Furthermore, in step 2, boron-doped SiNWs are placed in a methanol solution with a concentration of 3-8 mg / mL, an ultrasonic temperature of 20-35°C, and an ultrasonic time of 3-15 min.

[0008] Furthermore, in step 3, ZIF-8 is a type of metal-organic framework material formed by the coordination of zinc ions with 2-methylimidazole.

[0009] Furthermore, in step 3, ZIF-8 is dispersed in an ethanol solution at a concentration of 5-20 mg / mL, and the spraying volume is 50-300 μL.

[0010] Furthermore, in step 4, the SiNWs@ZIF-8 electrode is thermally annealed at a temperature of 200~350℃ for 20~40min, and the protective gas is nitrogen or argon.

[0011] Furthermore, in step 5, the concentration of H2SO4 is 0.05 ~ 1 mol / L, and the concentration of CuSO4 is 0.01 ~ 0.1 mol / L.

[0012] In a further preferred embodiment of the present invention, the concentration of H2SO4 in step 5 is 0.5 mol / L and the concentration of CuSO4 is 0.05 mol / L.

[0013] Furthermore, in step 5, electrochemical deposition is performed using a chronoamperometry method, wherein the deposition time is 200~3000s and the constant potential is -1~-0.05V.

[0014] In a further preferred embodiment of the present invention, the deposition time in step 5 is 500s and the constant potential is -0.3V.

[0015] This invention also protects the application of a flexible spherical copper composite ZIF-8 electrode in the construction of ethylene glycol fuel cells.

[0016] The method for constructing an ethylene glycol fuel cell is as follows: a flexible spherical Cu-SiNWs@ZIF-8 electrode is used as the anode and Pt / C is used as the cathode. A 3 mol / L KOH solution is added to the anode side as the electrolyte solution and a 0.5 mol / L ethylene glycol solution is added as the fuel. A 0.5 mol / L ethylene glycol solution is added to the cathode side and oxygen is introduced. The two parts are connected through an electrolyte chamber to construct an ethylene glycol fuel cell.

[0017] The specific testing method is as follows: using a spherical Cu-SiNWs@ZIF-8 electrode as the working electrode, Hg / Hg2Cl2 as the reference electrode, and a platinum mesh as the counter electrode, the three-electrode system is placed in a mixed electrolyte of potassium hydroxide and ethylene glycol. The potential is set to -0.7 ~ 0.3V, and cyclic voltammetry is performed on 0.2 ~ 1mol / L ethylene glycol solutions. The linear correlation curve between peak current density and ethylene glycol concentration is plotted to analyze the electrocatalytic reaction process of ethylene glycol.

[0018] The advantages of this invention compared to the prior art are: This invention significantly improves the catalytic performance of the electrode: spherical Cu nanoparticles are uniformly loaded on the SiNWs@ZIF-8 framework, while ZIF-8 particles are also attached to the surface of SiNWs and Cu nanospheres. This structure not only retains the active sites of spherical Cu, but also introduces the pore confinement and molecular enrichment effect of ZIF-8, which significantly increases the specific surface area of ​​the electrode and provides more reaction sites and mass transfer pathways for the electrocatalytic reaction of ethylene glycol.

[0019] This invention significantly reduces the manufacturing cost of electrodes: the flexible spherical Cu-SiNWs@ZIF-8 electrode uses non-noble metal Cu as the core active component, eliminating the dependence on noble metals in traditional ethylene glycol electrocatalytic electrodes and eliminating the need to compensate for performance defects through doping with noble and non-noble metals, thus greatly reducing manufacturing costs at the material level. It solves the problem of high process costs caused by the scarcity of raw materials and complex preparation of traditional noble metal-based and noble metal-non-noble metal doped electrodes, providing core support for the low-cost industrialization and promotion of ethylene glycol electrocatalysts. Attached Figure Description

[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Figure 1 SEM image of boron-doped SiNWs@ZIF-8 electrode; Figure 2 SEM image of a flexible spherical Cu-SiNWs@ZIF-8 electrode; Figure 3 XRD pattern of flexible spherical Cu-SiNWs@ZIF-8 electrode; Figure 4 CV curves for electrocatalysis of ethylene glycol using a flexible spherical Cu-SiNWs@ZIF-8 electrode; Figure 5 CV curves for catalysis of different concentrations of ethylene glycol by a flexible spherical Cu-SiNWs@ZIF-8 electrode; Figure 6 This is a standard curve of peak current density versus ethylene glycol concentration; Figure 7 Electrochemical stability testing of flexible spherical Cu-SiNWs@ZIF-8 electrodes; Figure 8 This is a schematic diagram of the apparatus for constructing an ethylene glycol fuel cell according to the present invention. Detailed Implementation

[0021] The present invention is described in detail below through specific embodiments, but this does not limit the scope of protection of the present invention. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can all be obtained commercially.

[0022] Example 1 The preparation method of flexible spherical Cu-SiNWs@ZIF-8 electrodes is as follows: Step 1: Preparation of boron-doped SiNWs: SiNWs were dispersed in a quartz boat and placed in a CVD reactor. Argon gas at 200 sccm was introduced for 30 min to purge air. The temperature was raised to 900℃, and 2 sccm of B2H6 was introduced under a mixed atmosphere of 150 sccm argon and 50 sccm hydrogen. The temperature was maintained for 45 min, and the boron-doped SiNWs were obtained after natural cooling.

[0023] Step 2: Preparation of boron-doped SiNWs electrode: 5 mg of boron-doped SiNWs powder was placed in 1 mL of methanol solution. 150 μL of the SiNWs methanol solution was then slowly added dropwise onto the surface of the hydrophilically modified flexible polyimide substrate. The material was placed in an ultrasonic cleaner with an ultrasonic power of 120 W, an ultrasonic frequency of 40 kHz, and a temperature of 25 °C. Ultrasonic dispersion was continued for 15 min, followed by drying at room temperature for one day after ultrasonication.

[0024] Step 3: Preparation of SiNWs@ZIF-8 electrode: Disperse 10 mg of ZIF-8 powder in 1 mL of ethanol solution. After the dispersion is uniform, spray 100 μL of the dispersion onto the surface of boron-doped SiNWs and let it stand to dry.

[0025] Step 4: Heat annealing of SiNWs@ZIF-8 electrodes: Using argon as a protective gas, heat the electrodes to 250℃ under vacuum conditions, hold for 25 minutes, and then allow them to cool naturally.

[0026] Step 5: Deposition of Cu spheres by chronoamperometry: Using the above-mentioned SiNWs@ZIF-8 electrode as the working electrode, a saturated calomel electrode as the reference electrode, and a platinum mesh as the counter electrode, a three-electrode system was formed. The system was placed in a mixed electrolyte containing 0.5 mol / L H2SO4 and 0.05 mol / L CuSO4, and Cu was deposited for 500 s at a constant potential of -0.3 V using an Autolab PGSTAT101 electrochemical workstation to obtain spherical Cu-SiNWs@ZIF-8 electrodes.

[0027] The morphology of the boron-doped SiNWs@ZIF-8 electrode and the spherical Cu-SiNWs@ZIF-8 electrode in Example 1 was characterized by scanning electron microscopy, as shown in the attached figure. Figure 1 and attached Figure 2 As shown, the three-dimensional conductive network of boron-doped SiNWs is clearly visible, with ZIF-8 particles uniformly distributed between the SiNWs framework. After Cu deposition, spherical Cu nanoparticles are uniformly loaded on the surface of the SiNWs@ZIF-8 framework, increasing the specific surface area of ​​the electrode.

[0028] Example 2: XRD testing of spherical Cu-SiNWs@ZIF-8 electrodes The electrode structure composition was analyzed using X-ray diffraction (XRD), as shown in the attached figure. Figure 3 As shown in the figure, characteristic diffraction peaks of Cu and ZIF-8 appear, confirming the successful loading of the two substances.

[0029] Example 3: Comparison of cyclic voltammetry curves of ethylene glycol solution and blank solution A spherical Cu-SiNWs@ZIF-8 electrode was used as the working electrode, Hg / Hg2Cl2 as the reference electrode, and a platinum mesh as the counter electrode. Cyclic voltammetry was employed to catalyze 1 mol / L ethylene glycol. The results are shown in the attached figure. Figure 4 As shown, a distinct oxidation peak appeared at a potential of -0.1V, with a peak current density of 22.4 mA cm⁻¹. -2Compared with the blank solution, the spherical Cu-SiNWs@ZIF-8 electrode exhibits a higher oxidation peak current density and a lower oxidation potential, indicating that the electrode has excellent electrocatalytic performance for ethylene glycol and can be applied in the field of ethylene glycol fuel cells.

[0030] Example 4: Cyclic voltammetric response of spherical Cu-SiNWs@ZIF-8 electrode to different concentrations of ethylene glycol Using the above three-electrode system, cyclic voltammetry tests were performed on EG solutions with concentrations of 0.2, 0.4, 0.6, 0.8, and 1 mol / L in 1 mol / L KOH solution. The results are attached. Figure 5 Appendix Figure 6 As shown, the oxidation peak current density of ethylene glycol further increases with increasing concentration, indicating that the increased reactant concentration provides more substrate for the electrocatalytic reaction, thereby effectively improving the catalytic reaction rate. Within the concentration range of 0.2 ~ 1 mol / L, there is a good linear relationship between the oxidation peak current density and the EG concentration, with the linear regression equation being y = 18.958x + 1.4966, R0. 2 =0.9965.

[0031] Example 5: Electrochemical stability test of spherical Cu-SiNWs@ZIF-8 electrode The chronoamperometry was used to test the spherical Cu-SiNWs@ZIF-8 electrode under the conditions of 1 mol / L KOH + 1 mol / L EG for 3600 s. The test potential was -0.2 V. The results are shown in the attached figure. Figure 7 As shown, the current density initially decreased rapidly, mainly due to the rapid adsorption of intermediates generated during the electro-oxidation of ethylene glycol on the electrode surface. Subsequently, the current density gradually stabilized and remained stable throughout the entire test period without significant decay, indicating that the electrode has good operational stability and resistance to poisoning.

[0032] Table 1 shows a comparison of the performance of the spherical Cu-SiNWs@ZIF-8 electrode from Comparative Example 1 with other reported ethylene glycol electrocatalysts: Compared with previously reported ethylene glycol electrocatalysts, the spherical Cu-SiNWs@ZIF-8 electrode of this invention uses non-precious metal Cu as the core active component, has a simple preparation process, does not require precious metals, and exhibits excellent ethylene glycol electrocatalytic activity through the synergistic effect of boron-doped SiNWs conductive network and ZIF-8. The peak current density is significantly higher than other electrocatalysts, and it also has good resistance to poisoning and long-term stability. Furthermore, it has lower cost and is suitable for emerging application scenarios such as flexible fuel cells, showing greater industrialization potential.

[0033] Application Example 1: Application of spherical Cu-SiNWs@ZIF-8 electrodes in the construction of ethylene glycol fuel cells A spherical Cu-SiNWs@ZIF-8 electrode is used as the anode, and a Pt / C electrode is used as the cathode. Ethylene glycol is added as fuel to the anode side, while oxygen is introduced to the cathode side through the gas inlet endplate. Ion transport is achieved in the electrolyte chamber, and electrolyte circulation is achieved through the inlet and outlet. Gaskets and endplates serve as seals and structural supports. The entire ethylene glycol fuel cell is assembled by bolts. A schematic diagram is attached. Figure 8 As shown.

[0034] The core innovation of this invention lies in constructing a spherical Cu-SiNWs@ZIF-8 electrode that combines flexibility, high catalytic activity, and stable operation, and applying it to the field of ethylene glycol fuel cells. In terms of material structure, a composite architecture is adopted, consisting of a boron-doped SiNWs three-dimensional conductive network, a ZIF-8 porous support, and spherical Cu active components. The pore confinement and molecular enrichment effect of ZIF-8, combined with the high active sites of spherical Cu, significantly improves the electrode's specific surface area and mass transfer efficiency. SiNWs ensure efficient electron transport, and the three synergistically optimize the electrocatalytic reaction kinetics of ethylene glycol. Regarding the preparation process, uniform loading of each component is achieved by controlling the SiNWs concentration, ZIF-8 coating amount, thermal annealing parameters, and electrochemical deposition conditions. The process is simple and controllable, requires no precious metals, and significantly reduces the catalyst preparation cost. In terms of application, the ethylene glycol fuel cell constructed by this invention uses ethylene glycol, a product of the alkaline hydrolysis of PET plastic, as fuel. It has the dual value of energy supply and resource utilization of waste plastics. Relying on a flexible substrate, the fuel cell achieves flexible and miniaturized design, breaking through the application scenario limitations of traditional rigid electrodes. At the same time, the electrode has excellent electrochemical stability and anti-poisoning ability, providing an economical, environmentally friendly and practical solution for the industrialization and promotion of ethylene glycol fuel cells.

[0035] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0036] References [1] Du H, Wang K, Tsiakaras P, et al. Excavated and Dendritic Pt-CoNanocubes as Efficient Ethylene Glycol and Glycerol OxidationElectrocatalysts[J]. Applied Catalysis B: Environmental, 2019, 258: 117951. [2] Wang Y, Zheng M, Sun H, et al. Catalytic Ru containing Pt 3 Mnnanocrystals enclosed with high-indexed facets: Surface alloyed Ru makes Ptmore active than Ru particles for ethylene glycol oxidation[J]. AppliedCatalysis B: Environmental, 2019. [3] Tang J X, Chen Q S, You L X, et al. Screw-like PdPt nanowires ashighly efficient electrocatalysts for methanol and ethylene glycol oxidation[J]. JOURNAL OF MATERIALS CHEMISTRY. A, 2018, 6(5): 2327-2336. [4] Zhang K, Xu H, Yan B, et al. Superior ethylene glycol oxidationelectrocatalysis enabled by hollow PdNi nanospheres[J]. Electrochimica Acta,2018: 383-391。

Claims

1. A method for preparing a flexible spherical copper composite ZIF-8 electrode, characterized in that, The steps are as follows: S1. SiNWs are spread out in a quartz boat, placed in a CVD reactor, argon gas is introduced to remove air, the temperature is raised, and a boron source is introduced under a mixed atmosphere of argon and hydrogen. The temperature is maintained and the boron-doped SiNWs are obtained after natural cooling. S2. Boron-doped SiNWs were placed in a methanol solution and uniformly dispersed on a hydrophilically modified flexible substrate under ultrasonic conditions to prepare a boron-doped SiNWs electrode. S3. Disperse ZIF-8 in an ethanol solution, spray it onto the surface of a boron-doped SiNWs electrode, and let it stand to dry to obtain a SiNWs@ZIF-8 electrode; S4. Perform thermal annealing on the SiNWs@ZIF-8 electrode; S5. The SiNWs@ZIF-8 electrode after thermal annealing was placed in a mixed electrolyte solution of H2SO4 and CuSO4, and electrochemical deposition was performed by chronoamperometry to obtain a spherical Cu-SiNWs@ZIF-8 electrode.

2. The method for preparing the flexible spherical copper composite ZIF-8 electrode according to claim 1, characterized in that, In step S1, the argon flow rate is 200-300 sccm, the ventilation time is 15-30 min, the temperature is raised to 800-1200℃, the boron source is B2H6, the flow rate is 1-3 sccm, and the temperature is maintained for 30-60 min.

3. The method for preparing the flexible spherical copper composite ZIF-8 electrode according to claim 1, characterized in that, In step S2, boron-doped SiNWs are placed in a methanol solution with a concentration of 3-8 mg / mL, an ultrasonic temperature of 20-35°C, and an ultrasonic time of 3-15 min.

4. The method for preparing the flexible spherical copper composite ZIF-8 electrode according to claim 1, characterized in that, In step S3, ZIF-8 is a type of metal-organic framework material composed of zinc ions coordinated with 2-methylimidazole. ZIF-8 is dispersed in an ethanol solution at a concentration of 5 to 20 mg / mL and the spraying amount is 50 to 300 μL.

5. The method for preparing the flexible spherical copper composite ZIF-8 electrode according to claim 1, characterized in that, In step S4, the SiNWs@ZIF-8 electrode is annealed at a temperature of 200-350°C for 20-40 minutes, and the protective gas is nitrogen or argon.

6. The method for preparing the flexible spherical copper composite ZIF-8 electrode according to claim 1, characterized in that, In step S5, the concentration of H2SO4 is 0.05 ~ 1 mol / L, and the concentration of CuSO4 is 0.01 ~ 0.1 mol / L.

7. The method for preparing the flexible spherical copper composite ZIF-8 electrode according to claim 1, characterized in that, In step S5, electrochemical deposition is performed using the chronoamperometry method, wherein the deposition time is 200 ~ 3000 s and the constant potential is -1 ~ -0.05 V.

8. The application of the flexible spherical copper composite ZIF-8 electrode prepared according to claim 1 in the construction of ethylene glycol fuel cells.

9. The application of the flexible spherical copper composite ZIF-8 electrode according to claim 8 in the construction of ethylene glycol fuel cells, characterized in that, The method for constructing an ethylene glycol fuel cell is as follows: a flexible spherical Cu-SiNWs@ZIF-8 electrode is used as the anode and Pt / C is used as the cathode. A 3 mol / L KOH solution is added to the anode side as the electrolyte solution and a 0.5 mol / L ethylene glycol solution is added as the fuel. A 0.5 mol / L ethylene glycol solution is added to the cathode side and oxygen is introduced. The two parts are connected through an electrolyte chamber to construct an ethylene glycol fuel cell.

10. The application of the flexible spherical copper composite ZIF-8 electrode according to claim 9 in the construction of ethylene glycol fuel cells, characterized in that, The ethylene glycol fuel cell testing method is as follows: using a spherical Cu-SiNWs@ZIF-8 electrode as the working electrode, Hg / Hg2Cl2 as the reference electrode, and a platinum mesh as the counter electrode, the three-electrode system is placed in a mixed electrolyte of potassium hydroxide and ethylene glycol. The potential is set to -0.7 ~ 0.3V, and cyclic voltammetry is performed on a 0.2 ~ 1 mol / L ethylene glycol solution. The linear correlation curve between peak current density and ethylene glycol concentration is plotted to analyze the ethylene glycol electrocatalytic reaction process.

Images