Layered MFI molecular sieve / reduced graphene oxide composite material as well as preparation method and application thereof
By preparing layered MFI molecular sieves with specific morphologies and combining them with graphene oxide to form a three-dimensional conductive network, the problem of easy stacking of graphene-based materials was solved, the specific capacitance and cycle stability of supercapacitors were improved, and high-efficiency electrochemical performance was achieved.
Patent Information
- Application Number
- CN202610211929.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-02-13
- Publication Date
- 2026-05-19
AI Technical Summary
The electrode materials of existing supercapacitors have reduced active area due to the easy interlayer recombination of graphene-based materials, which hinders the adsorption and intercalation of electrolyte ions. Furthermore, there is room for improvement in the specific capacitance and cycle stability of molecular sieve/reduced graphene oxide composite materials in a 6M KOH electrolyte system.
Layered MFI molecular sieves with an average length of 80-200 nm, a width of 40-100 nm, and a thickness of 10-20 nm were prepared using a seed-guided synthesis strategy. The surface charge of graphene oxide was adjusted by ammonium salt solution to promote the electrostatic interaction between the layered MFI molecular sieves and graphene oxide, forming a three-dimensional conductive network.
Significantly improved ion transport performance and cycling stability, the layered MFI molecular sieve/reduced graphene oxide composite material achieved a specific capacitance of 523.5 F·g⁻¹ at a current density of 0.5 A·g⁻¹, a capacitance retention of 80.1% after 10,000 cycles at 10 A·g⁻¹, and maintained an energy density of 20.67 Wh·kg⁻¹ at a power density of 2750 W·kg⁻¹.
Smart Images
Figure CN122067923A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of electrode material technology, and more specifically, to a layered MFI molecular sieve / reduced graphene oxide composite material, its preparation method, and its application. Background Technology
[0002] Supercapacitors, as novel energy storage devices, possess advantages such as rapid charge-discharge capability, high power density, extremely long charge-discharge cycle life, wide operating temperature range, excellent environmental friendliness, and high reliability, and hold great potential for large-scale energy storage in the future. However, the commercial deployment of supercapacitors is still hindered by relatively low specific capacitance and insufficient electrode stability. Therefore, improving electrochemical performance through the manufacture of advanced electrode materials is crucial.
[0003] Over the past decade, graphene oxide and reduced graphene oxide have proven to be excellent electrode materials due to their large specific surface area and inherent high conductivity. However, graphene-based materials are prone to interlayer recombination due to van der Waals forces, which reduces the active area and hinders the adsorption and intercalation of electrolyte ions. A common strategy to overcome this limitation is to insert spacers, such as organic compounds, inorganic particles, and polymer mixtures, between graphene sheets. However, using nanomaterials... rice The combination of advanced metal oxides with rGO still faces limitations, such as electrochemical dissolution and particle agglomeration, which lead to the re-stacking of graphene sheets.
[0004] In contrast, molecular sieves offer a promising alternative due to their low toxicity, cost-effectiveness, scalability, and ordered microporous structure with adjustable framework charge. Chinese patent CN106057479A discloses a molecular sieve / graphene composite supercapacitor electrode material, its preparation method, and a supercapacitor. This patent prepares the molecular sieve / graphene composite electrode material by mixing an aqueous mixture of graphene oxide and molecular sieve at a specific mass ratio, followed by calcination and cooling. In this composite electrode material, graphene is encapsulated on the surface of the molecular sieve, forming an encapsulated composite structure. Tests show that this material exhibits high performance at 4 A·g -1 The specific capacitance can reach 450 F·g at current density. -1 Furthermore, after 800 cycles at the same current density, the specific capacitance retention rate was 85.7%. However, it should be noted that the above performance data were obtained in a 6M KOH electrolyte system, and there is still room for further improvement in its specific capacitance and cycle stability.
[0005] Therefore, it is particularly important to develop a molecular sieve / reduced graphene oxide composite material with superior specific capacitance and cycling stability. Summary of the Invention
[0006] The primary objective of this invention is to overcome the problems and deficiencies in the prior art and to provide a layered MFI molecular sieve.
[0007] Another object of the present invention is to provide a method for preparing the above-mentioned layered MFI molecular sieve.
[0008] Another object of the present invention is to provide a layered MFI molecular sieve / reduced graphene oxide composite material.
[0009] Another object of the present invention is to provide a method for preparing the above-mentioned layered MFI molecular sieve / reduced graphene oxide composite material.
[0010] Another object of the present invention is to provide the application of the above-mentioned layered MFI molecular sieve / reduced graphene oxide composite material in the preparation of supercapacitors.
[0011] Another object of the present invention is to provide a supercapacitor electrode.
[0012] To achieve the above objectives, the present invention adopts the following technical solution: The present invention provides a layered MFI molecular sieve, wherein the layered MFI molecular sieve has an average length of 80~200nm, an average width of 40~100nm, an average thickness of 10~20nm, a pore size of 0.5~0.68nm, and a SiO2 / Al2O3 molar ratio of 10~30:1.
[0013] This invention employs a seed-guided synthesis strategy to successfully prepare a layered MFI molecular sieve with an average length of 80-200 nm, an average width of 40-100 nm, an average thickness of 10-20 nm, and a pore size of 0.5-0.68 nm by reducing the silicon-to-aluminum ratio. The pore size of the prepared layered MFI molecular sieve is related to K... + (H2O) n The isohydrated electrolyte exhibits well-matched kinetic diameters of ions, effectively enhancing ion conductivity and selectivity, thereby significantly improving ion transport. The layered MFI molecular sieve framework contains abundant aluminum active sites, significantly improving the material's ionic conductivity. This provides a foundation for subsequent reversible cation intercalation / deintercalation reactions (pseudocapacitance) in the electrolyte. Furthermore, the nanoscale morphology and ultrathin thickness of this layered MFI molecular sieve facilitate its integration with reduced graphene oxide.
[0014] Preferably, the pore size of the layered MFI molecular sieve is 0.53~0.57 nm.
[0015] Preferably, the molar ratio of SiO2 / Al2O3 in the layered MFI molecular sieve is 10~20:1.
[0016] More preferably, the molar ratio of SiO2 / Al2O3 in the layered MFI molecular sieve is 20:1.
[0017] The preparation method of the above-mentioned layered MFI molecular sieve is also within the scope of protection of this invention, and includes the following steps: S1. Tetraethyl orthosilicate, tetrapropylammonium hydroxide and water are mixed and stirred to obtain a clear hydrolysate. The hydrolysate is then evaporated and hydrothermally aged to obtain a seed suspension. S2. Mix the seed crystal suspension, tetrapropylammonium hydroxide, tetrapropylammonium bromide and water, then add aluminum source and ammonium fluoride in sequence and stir to form a uniform gel. S3. Crystallize the gel, centrifuge and wash with water until neutral, then calcine to obtain the layered MFI molecular sieve.
[0018] Preferably, in step S1, the molar ratio of tetraethyl orthosilicate to tetrapropylammonium hydroxide to water is 1:0.32~0.40:7.5~9.0.
[0019] Preferably, in step S1, the stirring temperature is 30~35℃.
[0020] During seed crystal preparation, the hydrolysis of siloxanes generates alcohol byproducts. These alcohols alter the polarity of the seed crystal growth environment, thereby affecting the formation and growth kinetics of the crystal nucleus. Therefore, they need to be removed by rotary evaporation. Preferably, in step S1, the rotary evaporation temperature is below 55°C.
[0021] Preferably, in step S1, the temperature of the hydrothermal aging is 65~75℃.
[0022] Preferably, in step S1, the hydrothermal aging time is 55~65h.
[0023] Preferably, in step S2, the aluminum source is one or more of aluminum oxide hexahydrate, aluminum isopropoxide, or sodium aluminate.
[0024] Preferably, in step S2, the amount of seed suspension added is 50-70% of the amount of tetraethyl orthosilicate added.
[0025] Preferably, in step S2, the molar ratio of tetraethyl orthosilicate to tetrapropylammonium hydroxide to tetrapropylammonium bromide to water is 1:0.06~0.10:0.06~0.10:150~180.
[0026] More preferably, in step S2, the molar ratio of tetraethyl orthosilicate to tetrapropylammonium hydroxide to tetrapropylammonium bromide to water is 1:0.07:0.07:160.
[0027] Preferably, in step S2, the stirring and mixing time is 3 to 5 hours.
[0028] Preferably, in step S2, the temperature of the stirring and mixing is 30~40℃.
[0029] Preferably, in step S2, the molar ratio of ammonium fluoride to tetraethyl orthosilicate is 0.8~1.2:1.
[0030] Preferably, in step S2, the stirring speed of the stirring reaction is 600~800 rpm.
[0031] Preferably, in step S3, the crystallization time is 12-14 hours.
[0032] Preferably, in step S3, the crystallization temperature is 160~180℃.
[0033] Preferably, in step S3, the calcination temperature is 500~600℃.
[0034] Preferably, in step S3, the roasting time is 6-8 hours.
[0035] The present invention also provides a layered MFI molecular sieve / reduced graphene oxide composite material, wherein the layered MFI molecular sieve / reduced graphene oxide composite material comprises reduced graphene oxide and the above-mentioned layered MFI molecular sieve; the layered MFI molecular sieve is embedded in the wrinkled surface of the reduced graphene oxide.
[0036] The preparation method of the above-mentioned layered MFI molecular sieve / reduced graphene oxide composite material is also within the scope of protection of this invention, and includes the following steps: S1. Stir and mix the above-mentioned layered MFI molecular sieve, ammonium salt solution and graphene oxide dispersion to obtain a mixed suspension; S2. Freeze-dry the mixed suspension to obtain the precursor solid; S3. The precursor solid is heat-treated under an inert atmosphere to obtain the layered MFI molecular sieve / reduced graphene oxide composite material.
[0037] This invention introduces an ammonium salt solution to adjust the surface charge of graphene oxide, promoting stronger electrostatic interaction between graphene oxide and layered MFI molecular sieves with opposite charges, thus promoting interfacial bonding between the layered MFI molecular sieves and graphene oxide, and ultimately enabling the two to form a three-dimensional conductive network.
[0038] Preferably, the concentration of the ammonium salt solution is 0.5~2 mol / L.
[0039] More preferably, the concentration of the ammonium salt solution is 0.5 mol / L.
[0040] Preferably, the ammonium salt is one or more of ammonium chloride, ammonium sulfate, or ammonium trifluoromethanesulfonate.
[0041] Preferably, the mass ratio of the layered MFI molecular sieve to graphene oxide is 1:0.5~2.
[0042] More preferably, the mass ratio of the layered MFI molecular sieve to graphene oxide is 1:1.
[0043] Preferably, the concentration of the graphene oxide dispersion is 2-4 mg / mL. -1 .
[0044] The solvent in the graphene oxide dispersion described in this invention can be a solvent commonly used in the art, such as one or more of water, ethylene glycol, N,N-dimethylformamide, or N-methylpyrrolidone. Preferably, the solvent in the graphene oxide dispersion is water.
[0045] Preferably, the stirring speed for mixing is 400~600 rpm.
[0046] Preferably, the mixing time is 10-14 hours.
[0047] Preferably, the freeze-drying process involves first rapidly freezing the mixed suspension in liquid nitrogen, and then drying it in a freeze-drying agent for more than 72 hours.
[0048] Preferably, the heat treatment temperature is 300~400℃.
[0049] Preferably, the heat treatment time is 0.5 to 1.5 hours.
[0050] The above-mentioned layered MFI molecular sieve / reduced graphene oxide composite material is used in the preparation of supercapacitors.
[0051] The present invention provides a supercapacitor electrode comprising the above-mentioned layered MFI molecular sieve / reduced graphene oxide composite material, a conductive agent, and a binder.
[0052] Preferably, the mass ratio of the layered MFI molecular sieve / reduced graphene oxide composite material to the conductive agent to the binder is 80~90:8~12:3~7.
[0053] Compared with the prior art, the present invention has the following beneficial effects: This invention employs a seed-guided synthesis strategy to successfully prepare a layered MFI molecular sieve with a specific morphology by controlling the silicon-to-aluminum ratio. This layered molecular sieve exhibits a nanoscale morphology and ultrathin thickness, and its structural dimensions match the ionic kinetics of hydrated electrolytes, demonstrating excellent ion kinetic performance. Simultaneously, its framework contains abundant aluminum active sites, further enhancing its ionic conductivity and selectivity. Using this layered MFI molecular sieve and graphene oxide as raw materials, a layered MFI molecular sieve / reduced graphene oxide composite material was prepared under the action of ammonium salts. In this composite material, the layered MFI molecular sieve acts as a multifunctional spacer, embedded on the wrinkled surface of reduced graphene oxide, effectively inhibiting the recombination of the reduced graphene oxide layers and providing ordered channels for efficient ion transport. Furthermore, the layered MFI molecular sieve itself possesses pseudocapacitive properties, and under the action of ammonium salt solution, the layered MFI molecular sieve and graphene oxide undergo tight interfacial bonding, constructing a three-dimensional conductive network and accelerating the electron transport rate. Thanks to the above structure, the layered MFI molecular sieve / reduced graphene oxide composite material prepared in this invention exhibits high specific capacitance, excellent cycle stability, and rate performance. (At 0.5 A·g) -1 The specific capacitance at current density can reach 523.5 F·g -1 , in 10 A·g -1 After 10,000 cycles, the capacitance retention rate reached 80.1%.
[0054] The symmetric supercapacitor prepared using this composite material exhibits excellent and stable electrochemical performance at 2750 W·kg⁻¹. -1 It still maintains 20.67 Wh·kg at power density. -1 Energy density.
[0055] Furthermore, the preparation method of this composite material is simple to operate, highly controllable, and has low equipment requirements, making it very suitable for large-scale production and of significant application value. Attached Figure Description
[0056] Figure 1 The material structure characterization diagrams for ZG-1, MFI-1, and rGO are shown; where (a) is the X-ray diffraction pattern, (b) is the Fourier transform infrared spectrum, (c) is the Raman spectrum, and (d) is the N2 adsorption-desorption isotherm.
[0057] Figure 2 The images are SEM and TEM images of ZG-1, MFI-1, and rGO; where (a) is the TEM image of MFI-1, (bc) is the SEM image of MFI-1, (d) is the SEM image of rGO, and (ef) is the SEM image of ZG-1.
[0058] Figure 3The figures show the structural characterization of materials ZG-1, ZG-2, and ZG-3; where (a) is the X-ray diffraction pattern, (b) is the Fourier transform infrared spectrum, (c) is the N2 adsorption-desorption isotherm, (d) is the SEM image of ZG-1, (e) is the SEM image of ZG-2, and (f) is the SEM image of ZG-3.
[0059] Figure 4 The electrochemical performance test results for ZG-1, ZG-2, ZG-3, ZG-4, ZG-D1, ZG-D2, and ZG-D3 are shown; where (a) represents 30 mV·s. -1 Cyclic voltammetry curves of ZG-1, ZG-2, and ZG-3 at scan rates, (b) at 0.5 A·g -1 (c) Constant current charge-discharge curves of ZG-1, ZG-2, and ZG-3 at different current densities; (d) Specific capacitance data of ZG-1, ZG-2, and ZG-3 at different current densities; -1 Cyclic voltammetry curves of composite materials ZG-3, ZG-D1, and ZG-D2 at scan rate, (e) is 5 A·g -1 (f) Constant current charge-discharge curves of composite materials ZG-3, ZG-D1, and ZG-D2 at different current densities. (g) Specific capacitance data of composite materials ZG-3, ZG-D1, and ZG-D2 at different current densities. -1 Cyclic voltammetry curves of composite materials ZG-3, ZG-4, and ZG-D3 at scan rate (h) of 5 A·g -1 Constant current charge-discharge curves of composite materials ZG-3, ZG-4, and ZG-D3 under different current densities, (i) Specific capacitance data of composite materials ZG-3, ZG-4, and ZG-D3 under different current densities.
[0060] Figure 5 The graphs show the electrochemical performance of electrodes prepared from ZG-1, MFI-1, and ZG-rGO; where (a) represents 30 mV·s. -1 Cyclic voltammetry curves at scan rate, (b) is 0.5 A·g -1 The constant current charge-discharge curves at current density are shown in Figure (c), which is the electrochemical impedance spectroscopy (the inset is a magnified view of the high-frequency region), and Figure (d) which is the electrochemical impedance spectroscopy of the electrode made from ZG-1 at 10 A·g⁻¹. -1 Cyclic stability test results at current density.
[0061] Figure 6The figures show the electrochemical performance test results of the ZG-1 / / ZG-1 symmetrical supercapacitor; (a) is a schematic diagram of the ZG-1 / / ZG-1 symmetrical supercapacitor, (b) is the cyclic voltammetry curve of the ZG-1 / / ZG-1 device at different scan rates, (c) is the constant current charge-discharge curve of the ZG-1 / / ZG-1 device at different current densities, (d) is the specific capacitance variation of the ZG-1 / / ZG-1 device at different current densities, (e) is the electrochemical impedance spectroscopy of the ZG-1 / / ZG-1 device (the inset is a magnified view of the high-frequency region), and (f) is the electrochemical impedance spectroscopy of the ZG-1 / / ZG-1 device at 10 A·g⁻¹. -1 Capacitance retention after 10,000 cycles at current density (the inset shows an application demonstration of the device lighting a pink LED).
[0062] Figure 7 This is a schematic diagram of the structure of ZG-1 / / ZG-1. Detailed Implementation
[0063] The present invention will be further described below with reference to embodiments and comparative examples. These embodiments are merely typical descriptions of the present invention, but the present invention is not limited thereto. Unless otherwise specified, the test methods used in the following embodiments and comparative examples are conventional methods, and the raw materials and reagents used are commercially available from conventional commercial sources.
[0064] Example 1 This embodiment provides a layered MFI molecular sieve / reduced graphene oxide composite material, abbreviated as ZG-1, whose preparation method includes the following steps: S1. Weigh 20 mg of layered MFI molecular sieve and 10 mL of graphene oxide aqueous dispersion (concentration 2 mg / mL). -1 Mix the ingredients together, then add 5 mL of ammonium chloride solution (concentration 0.5 mol / L), and stir at 500 rpm for 12 h at 25℃ to obtain a mixed suspension. S2. After freezing the mixed suspension with liquid nitrogen, transfer it to a freeze desiccant and dry for 72 hours to obtain the precursor solid; S3. Under a nitrogen atmosphere, the precursor solid is heat-treated at 350°C for 1 hour to obtain the layered MFI molecular sieve / reduced graphene oxide composite material.
[0065] The preparation method of the above-mentioned layered MFI molecular sieve, abbreviated as MFI-1, specifically includes the following steps: S1. According to the molar ratio of tetraethyl orthosilicate to tetrapropylammonium hydroxide to water of 1:0.36:8.2, 25g of tetraethyl orthosilicate and 35.35g of tetrapropylammonium hydroxide aqueous solution (the mass fraction of tetrapropylammonium hydroxide is 25wt%) were weighed and stirred at 35℃ for 6h to obtain a clear hydrolysate; then the hydrolysate was rotary evaporated at 55℃ for 1h to remove ethanol; finally, the solution was transferred to a polytetrafluoroethylene-lined reactor and statically hydrothermally aged at 70℃ for 60h to obtain Silicalite-1 seed suspension; S2. According to the molar ratio of tetraethyl orthosilicate to tetrapropylammonium hydroxide to tetrapropylammonium bromide to water of 1:0.07:0.07:160, weigh 2g of tetraethyl orthosilicate, 0.3425g of tetrapropylammonium hydroxide, 0.1789g of tetrapropylammonium bromide, 26.420g of deionized water and 2.4032g of Silicalite-1 seed suspension and stir and mix at 35°C for 4h. Then add 0.232g of aluminum trichloride hexahydrate and 0.2845g of ammonium fluoride in sequence, and then stir vigorously at 600rpm for 1h to form a uniform gel. S3. The gel was transferred to a high-pressure autoclave lined with polytetrafluoroethylene and crystallized at 170°C for 12 hours. The product was then centrifuged, washed with water until neutral, dried, and calcined at 550°C for 6 hours to obtain the layered MFI molecular sieve.
[0066] The molar ratio of SiO2 / Al2O3 in MFI-1 is 20:1.
[0067] Material structure characterization The MFI-1, rGO, and ZG-1 prepared in this embodiment were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, nitrogen adsorption-desorption, scanning electron microscopy (SEM), and transmission electron microscopy (TEM), respectively. The results are as follows: Figure 1 and Figure 2 As shown. The preparation method of rGO is as follows: graphene oxide is heat-treated at 350℃ for 1 hour.
[0068] from Figure 1As shown in the XRD pattern (a), MFI-1 exhibits typical MFI crystal structure diffraction peaks at 7.9°, 8.8°, 23.2°, and 23.8°, consistent with the standard card PDF#47-0638. The sharpness of the diffraction peaks directly reflects the high regularity and periodicity of the internal crystal structure, while the precise correspondence of the peak positions confirms that its crystal framework is consistent with the standard MFI topology, indicating that the material does not contain impurities or obvious long-range structural defects. rGO shows a broadened diffraction peak at approximately 24°, corresponding to its (002) crystal plane. In the XRD pattern of ZG-1, all the characteristic diffraction peaks of MFI molecular sieve are clearly preserved, and the peak intensity near 24° is enhanced compared with MFI-1. This is attributed to the overlap between the diffraction signal of MFI molecular sieve at this position and the (002) diffraction peak of rGO. This phenomenon confirms that graphene oxide has been effectively thermally reduced to rGO, and the crystal structure of MFI molecular sieve remains intact after recombination. It also indicates that ZG-1 has a "uniform pore structure".
[0069] from Figure 1 The Fourier transform infrared spectrum (b) shows that rGO at 1560 cm⁻¹ -1 The absorption peaks that appear nearby belong to its sp 2 The carbon skeleton exhibits C=C stretching vibrations. MFI-1 occurs at 550, 795, 1073, and 1226 cm⁻¹. -1 The spectrum shows characteristic vibrational peaks of its skeletal structure. For ZG-1, the spectrum also shows C=C bond vibrations attributed to rGO (~1560 cm⁻¹). -1 ) and characteristic vibrational peaks attributable to the MFI molecular sieve framework (such as 550, 1073 cm⁻¹) -1 Furthermore, the typical COC (~1040 cm⁻¹) in graphene oxide was not observed. -1 ) and C-OH (~1415 cm) -1 The obvious signals of oxygen-containing functional groups such as GO and MFI-1 further confirm that GO in ZG-1 has been successfully reduced and that MFI-1 has been successfully embedded in the wrinkled surface of reduced graphene oxide.
[0070] from Figure 1 As shown in the Raman spectrum (c), MFI-1 and ZG-1 are at approximately 380 cm⁻¹. -1 Each region exhibits a characteristic peak, corresponding to the pentagonal ring vibration within the MFI framework. For ZG-1, the characteristic D and G bands of carbon appear at approximately 1317 and 1594 cm⁻¹, respectively. -1 The D-band originates from carbon lattice defects, contrasting with the G-band, which is caused by sp... 2This is due to the in-plane vibrations of hybrid carbon atoms. Therefore, the ID / IG intensity ratio can be used to assess the defect density and graphitization degree of a material. The calculated ID / IG value of ZG-1 is 1.50, higher than that of pristine graphite, indicating that ZG-1 contains a large number of structural defects that can provide additional active sites for electrochemical reactions.
[0071] from Figure 1 As shown in the N2 adsorption-desorption isotherm plot (d), the adsorption isotherm of MFI-1 exhibits a typical Type I curve, a characteristic feature of homogeneous microporous materials. Further analysis using the t-Plot method revealed that micropores contribute over 75% of the specific surface area, confirming that micropores are the dominant pore structure of the material. Furthermore, pore size distribution calculations based on density functional theory show that over 85% of the micropore volume in MFI-1 is concentrated in a narrow size range of 0.50 nm to 0.68 nm, exhibiting a sharp single peak near 0.55 nm, with a pore size of approximately 0.55 nm. The full width at half maximum (FWHM) of the pore size distribution curve is also very narrow (FWHM ≤ 0.20 nm). In contrast, rGO exhibits extremely low adsorption capacity at low relative pressures (P / P0) and displays a significant hysteresis loop in the relative pressure range of 0.49–1, which is related to the slit-like mesoporous structure formed by the stacking of rGO sheets. In ZG-1, MFI-1 is mainly distributed between rGO layers, occupying part of the stacked mesoporous space, thus exhibiting a high adsorption capacity even in the low P / P0 range. Furthermore, the abundant microporous structure in ZG-1 is beneficial for electrolyte ions (such as OH-). - The rapid embedding and extraction of ) imparts high specific capacitance to the material.
[0072] from Figure 2 TEM (a) and SEM (bc) images of MFI-1 show that the MFI-1 molecular sieve exhibits an ultrathin layered morphology with a thickness of approximately 20 nm. This facilitates rapid ion transport and reduces volume changes during electrochemical cycling measurements. Figure 2 As shown in the SEM image (d) of rGO, rGO exhibits a typical wrinkled, thin-film structure, primarily appearing as ultrathin, nearly transparent sheet-like morphology. From... Figure 2 The SEM image (ef) of ZG-1 shows that MFI-1 is firmly anchored on the wrinkled rGO surface, meaning that the wrinkled thin film structure of rGO is not destroyed, thus forming a stable three-dimensional conductive network with tight interfacial contact.
[0073] Example 2 This embodiment provides a layered MFI molecular sieve / reduced graphene oxide composite material, referred to as ZG-2. The difference between this embodiment and Example 1 is that the preparation process of the composite material is different. Specifically, the mass ratio of layered MFI molecular sieve to graphene oxide is different, that is, the amount of graphene oxide added is changed from 10 mL to 5 mL.
[0074] The layered MFI molecular sieve used in this embodiment is MFI-1, and its preparation method is the same as that in Example 1.
[0075] The ZG-2 prepared in this embodiment was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), nitrogen adsorption-desorption, scanning electron microscopy (SEM), and transmission electron microscopy (TEM), and the results are as follows. Figure 3 As shown.
[0076] from Figure 3 The XRD pattern (a), Fourier transform infrared spectrum (b), and N2 adsorption-desorption isotherm (c) show that ZG-2 has a similar structure to ZG-1.
[0077] from Figure 3 As shown in the SEM image (e), when the loading of layered MFI molecular sieve is high, the layered MFI molecular sieve is prone to forming large aggregates at the folds of reduced graphene oxide, which is not conducive to the permeation of electrolyte and the diffusion of ions.
[0078] Example 3 This embodiment provides a layered MFI molecular sieve / reduced graphene oxide composite material, referred to as ZG-3. The difference between this embodiment and Example 1 is that the preparation process of the composite material is different. Specifically, the mass ratio of layered MFI molecular sieve to graphene oxide is different, that is, the amount of graphene oxide added is changed from 10 mL to 20 mL.
[0079] The layered MFI molecular sieve used in this embodiment is MFI-1, and its preparation method is the same as that in Example 1.
[0080] The ZG-3 prepared in this embodiment was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), nitrogen adsorption-desorption, scanning electron microscopy (SEM), and transmission electron microscopy (TEM), and the results are as follows. Figure 3 As shown.
[0081] from Figure 3 The XRD pattern (a), Fourier transform infrared spectrum (b), and N2 adsorption-desorption isotherm (c) show that ZG-3 has a similar structure to ZG-1.
[0082] from Figure 3As shown in the SEM image (f), when the loading of layered MFI molecular sieve is low, the reduced graphene oxide is prone to recombination, which is not conducive to the permeation of electrolyte and the diffusion of ions.
[0083] Example 4 This embodiment provides a layered MFI molecular sieve / reduced graphene oxide composite material, abbreviated as ZG-4. The difference between this embodiment and Example 3 lies in the preparation process of the composite material. Specifically, the concentration of the ammonium salt solution is different, that is, the ammonium chloride solution is changed from 0.5 mol / L to 2 mol / L.
[0084] The layered MFI molecular sieve used in this embodiment is MFI-1, and its preparation method is the same as that in Example 1.
[0085] Comparative Example 1 This comparative example provides a layered MFI molecular sieve / reduced graphene oxide composite material, abbreviated as ZG-D1, which differs from Example 3 in that it uses a different layered MFI molecular sieve. The layered MFI molecular sieve, abbreviated as MFI-2, is prepared by the following steps: S1. According to the molar ratio of tetraethyl orthosilicate to tetrapropylammonium hydroxide to water of 1:0.36:8.2, 25g of tetraethyl orthosilicate and 35.35g of tetrapropylammonium hydroxide aqueous solution (the mass fraction of tetrapropylammonium hydroxide is 25wt%) were weighed and stirred at 35℃ for 6h to obtain a clear hydrolysate; then the hydrolysate was rotary evaporated at 55℃ for 1h to remove ethanol; finally, the solution was transferred to a polytetrafluoroethylene-lined reactor and statically hydrothermally aged at 70℃ for 60h to obtain Silicalite-1 seed suspension; S2. According to the molar ratio of tetraethyl orthosilicate to tetrapropylammonium hydroxide to tetrapropylammonium bromide to water of 1:0.07:0.07:160, weigh 2g of tetraethyl orthosilicate, 0.3425g of tetrapropylammonium hydroxide, 0.1789g of tetrapropylammonium bromide, 26.420g of deionized water and 2.4032g of Silicalite-1 seed suspension, stir and mix at 35°C for 4h, then add 0.0464g of aluminum trichloride hexahydrate and 0.2845g of ammonium fluoride in sequence, and then stir vigorously at 600rpm for 1h to form a uniform gel; S3. The gel was transferred to a high-pressure autoclave lined with polytetrafluoroethylene and crystallized at 170°C for 12 hours. The product was then centrifuged, washed with water until neutral, dried, and calcined at 550°C for 6 hours to obtain the layered MFI molecular sieve.
[0086] The molar ratio of SiO2 to Al2O3 in MFI-2 is 100:1.
[0087] Comparative Example 2 This comparative example provides a layered MFI molecular sieve / reduced graphene oxide composite material, abbreviated as ZG-D2, which differs from Example 3 in that it uses a different layered MFI molecular sieve. The layered MFI molecular sieve, abbreviated as MFI-3, is prepared by the following steps: S1. According to the molar ratio of tetraethyl orthosilicate to tetrapropylammonium hydroxide to water of 1:0.36:8.2, 25g of tetraethyl orthosilicate and 35.35g of tetrapropylammonium hydroxide aqueous solution (the mass fraction of tetrapropylammonium hydroxide is 25wt%) were weighed and stirred at 35℃ for 6h to obtain a clear hydrolysate; then the hydrolysate was rotary evaporated at 55℃ for 1h to remove ethanol; finally, the solution was transferred to a polytetrafluoroethylene-lined reactor and statically hydrothermally aged at 70℃ for 60h to obtain Silicalite-1 seed suspension; S2. According to the molar ratio of tetraethyl orthosilicate to tetrapropylammonium hydroxide to tetrapropylammonium bromide to water of 1:0.07:0.07:160, weigh 2g of tetraethyl orthosilicate, 0.3425g of tetrapropylammonium hydroxide, 0.1789g of tetrapropylammonium bromide, 26.420g of deionized water and 2.4030g of Silicalite-1 seed suspension, stir and mix at 35°C for 4h, then add 0.0116g of aluminum trichloride hexahydrate and 0.2845g of ammonium fluoride in sequence, and then stir vigorously at 600rpm for 1h to form a uniform gel; S3. The gel was transferred to a high-pressure autoclave lined with polytetrafluoroethylene and crystallized at 170°C for 12 hours. The product was then centrifuged, washed with water until neutral, dried, and calcined at 550°C for 6 hours to obtain the layered MFI molecular sieve.
[0088] The molar ratio of SiO2 / Al2O3 in MFI-3 is 400:1.
[0089] Comparative Example 3 This comparative example provides a layered MFI molecular sieve / reduced graphene oxide composite material, abbreviated as ZG-D3. The difference between this example and Example 3 is that the preparation process of the composite material is different, specifically: no ammonium salt solution is added in step S1.
[0090] The layered MFI molecular sieve used in this comparative example is MFI-1, and its preparation method is the same as that in Example 1.
[0091] Comparative Example 4 This comparative example provides a reduced graphene oxide material, abbreviated as ZG-rGO, whose preparation method includes the following steps: S1. Weigh 20 mL of graphene oxide aqueous dispersion (concentration 2 mg·mL). -1Mix the ingredients together, then add 5 mL of ammonium chloride solution (concentration 0.5 mol / L), and stir at 500 rpm for 12 h at 25℃ to obtain a mixed suspension. S2. After freezing the mixed suspension with liquid nitrogen, transfer it to a freeze desiccant and dry for 72 hours to obtain the precursor solid; S3. Under a nitrogen atmosphere, the precursor solid is heat-treated at 350°C for 1 hour to obtain the reduced graphene oxide material.
[0092] Performance testing of layered MFI molecular sieve / reduced graphene oxide composite materials (1) Preparation of load electrode sheet Following the above method for preparing the load electrode sheet, ZG-1 was fabricated into a load electrode sheet ZG-1.
[0093] Following the above method for preparing the load electrode sheet, ZG-2 was fabricated into a load electrode sheet ZG-2.
[0094] Following the above method for preparing the load electrode sheet, ZG-3 was fabricated into a load electrode sheet ZG-3.
[0095] Following the above method for preparing the load electrode sheet, ZG-4 was fabricated into a load electrode sheet ZG-4.
[0096] Following the above method for preparing the load electrode sheet, ZG-D1 was fabricated into a load electrode sheet ZG-D1.
[0097] Following the above method for preparing the load electrode sheet, ZG-D2 was fabricated into a load electrode sheet ZG-D2.
[0098] Following the above method for preparing the load electrode sheet, ZG-D3 was fabricated into a load electrode sheet ZG-D3.
[0099] Following the above method for preparing the loaded electrode sheet, ZG-rGO was fabricated into a loaded electrode sheet ZG-rGO.
[0100] (2) Performance testing A standard three-electrode system was used, with a platinum sheet as the counter electrode and a saturated calomel electrode as the reference electrode. Supported electrode plates ZG-1, ZG-2, ZG-3, ZG-4, ZG-D1, ZG-D2, ZG-D3, and ZG-rGO were used as working electrodes. Electrochemical performance was tested in a 0.5 M potassium hydroxide solution. The results are as follows: Figure 4 and Figure 5 As shown.
[0101] from Figure 4The cyclic voltammetry (a), constant current charge-discharge curve (b), and specific capacitance data at different current densities (c) show that ZG-1, ZG-2, and ZG-3 exhibit excellent electrochemical performance. When the layered MFI molecular sieve / reduced graphene oxide composite material is in its optimal structural configuration, it can effectively promote the interaction between the electrode and the electrolyte, thereby achieving enhanced surface-mediated redox reactions and bilayer capacitance, making ZG-1 exhibit superior electrochemical performance compared to ZG-2 and ZG-3.
[0102] from Figure 4 The cyclic voltammetry (d), galvanostatic charge-discharge curves (e), and specific capacitance data at different current densities (f) show that ZG-1 has a significantly lower silicon-to-aluminum ratio than ZG-D1 and ZG-D2. This lower ratio implies a higher aluminum content in its framework, resulting in a greater number of exchangeable protons and more abundant Brønsted acid sites. These acid sites contribute significant pseudocapacitance through surface redox reactions or reversible ion adsorption / desorption processes, leading to better electrochemical activity in ZG-1.
[0103] from Figure 4 The cyclic voltammetry (g), constant current charge-discharge curve (h), and specific capacitance data at different current densities (i) show that adding a certain concentration of ammonium salt during the preparation of the composite material helps improve its electrochemical performance. When the ammonium salt concentration is 0.5 M, it is more conducive to the formation of a loose, porous, and well-conducting three-dimensional network structure in the composite material, thus exhibiting excellent electrochemical performance. In contrast, when the ammonium salt concentration increases to 2 M, excessive neutralization of surface sites may lead to excessive interlayer attraction, resulting in partial agglomeration, which to some extent reduces the effective specific surface area and the number of active sites, leading to a slight decrease in specific capacitance.
[0104] from Figure 5 From the cyclic voltammetry (a), it can be seen that at 30 mV·s -1 At a scan rate of 0.4 V, ZG-1 exhibited a distinct redox peak within a potential window of -0.4 to 0.8 V, indicating its excellent charge storage capacity.
[0105] from Figure 5 As shown in the constant current charge-discharge curve (b), at 0.5 A·g -1 At a given current density, ZG-1 exhibits excellent discharge time, and calculations show that ZG-1 has a discharge time of 523.5 F·g. -1 Its specific capacity is much higher than that of ZG-rGO (164.3 F·g). -1 .from Figure 5As shown in the electrochemical impedance spectroscopy (c), ZG-1 exhibits the smallest semicircular diameter in the high-frequency region, corresponding to the lowest charge transfer resistance (Rct); in the low-frequency region, its curve slope is closer to vertical, indicating that it has more ideal capacitive behavior and a faster ion diffusion rate. Figure 5 As shown in the cyclic stability plot (d), ZG-1 at 10 A·g -1 After 10,000 cycles at high current density, the capacitance retention rate still reaches 80.1%, indicating excellent cycle stability.
[0106] Electrochemical performance testing of symmetrical supercapacitor devices Using ZG-1 loaded electrode as both the positive and negative electrodes, filter paper as the diaphragm, and 0.5 M KOH as the electrolyte, a coin-type symmetrical supercapacitor device (ZG-1 / / ZG-1 device) was assembled. Electrochemical performance tests were conducted, and the results are as follows: Figure 6 As shown. The overall structure of the device is as follows. Figure 7 As shown.
[0107] from Figure 6 As shown in the CV curve (b), ZG-1 induced a significant redox peak, which is a typical Faraday process. This phenomenon is caused by the oxygen-containing functional groups of rGO (surface redox) and the ordered microporous channels of the MFI-1 molecular sieve (ion intercalation). From... Figure 6 As shown in GCD curve (c), the ZG-1 / / ZG-1 device exhibits a low IR voltage drop during the discharge process, at 0.5 A·g. -1 A current density of 181.8 F·g was achieved. -1 Its maximum specific capacitance. Further calculations show that its energy density is at a power density of 2750 W·kg⁻¹. -1 It still maintains 20.67 Wh·kg at power density. -1 .from Figure 6 (d) It can be seen that even at 5A·g -1 It remains at 136.4 F·g. -1 This demonstrates significant rate performance. From Figure 6 From the EIS plot (e), we can see that Rct is 0.406 Ω·cm. 2 Rs is 1.345 Ω·cm 2 This indicates rapid ion transport and excellent interfacial conductivity. From Figure 6 As shown in the cyclic stability plot (f), the ZG-1 / / ZG-1 device is stable at 10 A·g -1After 10,000 cycles, the device retained 83.6% of its initial capacitance, demonstrating excellent cycle durability. To verify its practical applicability, two devices connected in series were charged for only 10 seconds and then used to light a pink LED for approximately 180 seconds (see [link to relevant documentation]). Figure 6 (f) illustration shows that the supercapacitor made from the layered MFI molecular sieve / redox graphene composite material provided by the present invention has excellent performance in charge storage.
[0108] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.
Claims
1. A layered MFI molecular sieve, characterized in that, The layered MFI molecular sieve has an average length of 80~200nm, an average width of 40~100nm, an average thickness of 10~20nm, a pore size of 0.5~0.68nm, and a SiO2 / Al2O3 molar ratio of 10~30:
1.
2. The layered MFI molecular sieve according to claim 1, characterized in that, The pore size of the layered MFI molecular sieve is 0.53~0.57 nm.
3. The method for preparing the layered MFI molecular sieve according to any one of claims 1 to 2, characterized in that, Includes the following steps: S1. Tetraethyl orthosilicate, tetrapropylammonium hydroxide and water are mixed and stirred to obtain a clear hydrolysate. The hydrolysate is then evaporated and hydrothermally aged to obtain a seed suspension. S2. Mix the seed crystal suspension, tetrapropylammonium hydroxide, tetrapropylammonium bromide and water, then add aluminum source and ammonium fluoride in sequence and stir to form a uniform gel. S3. Crystallize the gel, centrifuge and wash with water until neutral, then calcine to obtain the layered MFI molecular sieve.
4. The preparation method according to claim 3, characterized in that, In step S2, the amount of seed suspension added is 50-70% of the amount of tetraethyl orthosilicate added.
5. A layered MFI molecular sieve / reduced graphene oxide composite material, characterized in that, It includes reduced graphene oxide and the layered MFI molecular sieve of any one of claims 1 to 2; the layered MFI molecular sieve of any one of claims 1 to 2 is embedded in the wrinkled surface of the reduced graphene oxide.
6. The method for preparing the layered MFI molecular sieve / reduced graphene oxide composite material according to claim 5, characterized in that, Includes the following steps: S1. Stir and mix the layered MFI molecular sieve, ammonium salt solution, and graphene oxide dispersion as described in any one of claims 1 to 2 to obtain a mixed suspension; S2. Freeze-dry the mixed suspension to obtain the precursor solid; S3. The precursor solid is heat-treated under an inert atmosphere to obtain the layered MFI molecular sieve / reduced graphene oxide composite material.
7. The preparation method according to claim 6, characterized in that, The mass ratio of the layered MFI molecular sieve to graphene oxide is 1:0.5~2.
8. The preparation method according to claim 6, characterized in that, The concentration of the ammonium salt is 0.5~2 mol / L.
9. The application of the layered MFI molecular sieve / reduced graphene oxide composite material according to claim 5 in the preparation of supercapacitors.
10. A supercapacitor electrode, characterized in that, It includes the layered MFI molecular sieve / reduced graphene oxide composite material as described in claim 5, a conductive agent, and a binder.