An integrated photochargeable zinc-ion supercapacitor and its preparation method

Abstract

This invention provides an integrated photochargeable zinc-ion supercapacitor, comprising a photoelectric positive electrode, a zinc negative electrode, and a gel electrolyte. The preparation method involves: spraying a TiO2 colloidal solution onto FTO glass to form a TiO2 mesoporous film; then spraying an Ag-np@MXene colloidal solution onto it to obtain a TiO2 / Ag-np@MXene photoelectric positive electrode; fixing a zinc sheet onto the conductive surface of another FTO glass; and sequentially stacking the zinc sheet, gel electrolyte, and TiO2 / Ag-np@MXene photoelectric positive electrode fixed on the FTO glass, and encapsulating them to obtain the integrated zinc-ion photochargeable capacitor. This invention significantly enhances the pseudocapacitive performance of MXene through silver nanoparticles and utilizes the synergistic effect of Ag-np and TiO2 to enhance the electrochemical energy storage capacity under illumination. The energy level matching between the composite electrode materials achieves efficient separation and photoelectric conversion of photogenerated carriers. This photocharged zinc-ion capacitor exhibits excellent photoelectrochemical performance, with a significantly increased specific capacitance under illumination, maintaining good light-assisted energy storage performance at high current densities, and stable light gain capability after long-term cycling.

Description

Technical Field

[0001] This invention belongs to the fields of supercapacitors and photoelectrochemical technology, specifically relating to an integrated photochargeable zinc-ion supercapacitor and its preparation method. Background Technology

[0002] In recent years, the rapid development of portable electronic devices and wearable devices has created an increasingly urgent demand for energy storage devices that combine high energy density, good flexibility, and multifunctional integration. While solar energy is a clean and renewable energy source, its intermittent nature severely restricts its large-scale, efficient utilization. Traditional solar cells can only achieve photoelectric conversion and lack long-term energy storage capabilities, typically requiring connection to rechargeable batteries, leading to system complexity and reduced efficiency. Integrated photovoltaic charging containers combine photoelectric conversion and electrochemical energy storage, directly capturing solar energy and converting it into electrical energy for storage, making them an ideal solution for self-powered systems. However, existing photovoltaic charging containers still face bottlenecks in light absorption efficiency, photogenerated carrier separation and transport capabilities, and energy storage capacity, necessitating breakthroughs through material innovation and structural design.

[0003] MXene, a novel two-dimensional transition metal carbide / nitride, possesses excellent metallic conductivity, a tunable layered structure, and abundant surface functional groups, demonstrating great potential in electrochemical energy storage. However, the specific capacitance of pure MXene mainly comes from the contribution of the electric double layer capacitance, resulting in limited capacity. Constructing heterostructures by compositing Faraday-reactive nanometals with MXene is an effective way to improve its energy storage performance. Silver nanoparticles (Ag-np) exhibit unique advantages in photovoltaic energy storage devices due to their excellent conductivity, reversible redox activity, and localized surface plasmon resonance (LSPR) effect. However, relying solely on the LSPR effect is insufficient to achieve efficient directional transport of photogenerated carriers. At the metal-semiconductor interface, the difference in work function naturally creates a built-in electric field pointing from the semiconductor to the metal. This electric field can drive the spatial separation of photogenerated electron-hole pairs and suppress recombination. Therefore, coupling the LSPR effect with the built-in electric field can achieve a synergistic mechanism of hot electron injection + electric field-driven separation, thereby maximizing the conversion efficiency of light energy to electrochemical energy. Based on this, the present invention provides an integrated photochargeable zinc-ion supercapacitor and its preparation method, aiming to provide a new technical solution for high-performance integrated photochargeable containers. Summary of the Invention

[0004] This invention addresses the problems existing in the prior art by providing an integrated photochargeable zinc-ion supercapacitor and its preparation method.

[0005] The present invention adopts the following technical solution:

[0006] (i) The present invention provides an integrated photochargeable zinc-ion supercapacitor, comprising a photoelectric positive electrode, a zinc negative electrode and a gel electrolyte; the photoelectric positive electrode comprises FTO glass, a TiO2 mesoporous membrane disposed on the FTO glass, and an Ag-np@MXene thin film disposed on the TiO2 mesoporous membrane; the zinc negative electrode comprises a zinc sheet; the gel electrolyte is disposed between the photoelectric positive electrode and the zinc negative electrode, serving as a separator and electrolyte.

[0007] (II) This invention also provides a method for preparing the integrated photochargeable zinc-ion supercapacitor described above, comprising the following steps: TiO2 colloidal solution was sprayed onto the conductive surface of FTO glass, heat-treated and annealed to obtain a TiO2 mesoporous film; Ag-np@MXene colloidal solution was sprayed onto the TiO2 mesoporous film to obtain a TiO2 / Ag-np@MXene photoelectrode; a zinc sheet was taken and fixed onto the conductive surface of another FTO glass using conductive silver paste; the zinc sheet, gel electrolyte and TiO2 / Ag-np@MXene photoelectrode fixed on the FTO glass were stacked sequentially, with the sprayed surface of the photoelectrode facing the gel electrolyte, and the whole assembly was encapsulated to obtain an integrated zinc ion photocharging device.

[0008] Furthermore, the method for preparing the TiO2 colloidal solution is as follows: mixing TiO2 slurry with ethanol solvent to obtain TiO2 colloidal solution; wherein, the mass ratio of TiO2 slurry to ethanol solvent is 1:7~15, preferably 1:10.

[0009] Furthermore, the TiO2 slurry is composed of terpineol, ethyl cellulose, TiO2 and lauric acid; wherein the mass of TiO2 is 15-25% of the total mass of the TiO2 slurry, preferably 20%.

[0010] Furthermore, the mass ratio of terpineol, ethyl cellulose, TiO2 and lauric acid is 70~75:4~8:15~25:1~2.

[0011] Furthermore, the heat treatment operation is as follows: sintering at 400~500℃ for 1~3 h, preferably sintering at 450℃ for 2 h.

[0012] Furthermore, the preparation method of the Ag-np@MXene colloidal solution is as follows: silver nitrate and MXene are mixed in a solvent, sonicated, and then allowed to stand to obtain the Ag-np@MXene colloidal solution.

[0013] Furthermore, the mass ratio of silver nitrate to MXene is 1:3 to 10, preferably 1:5.

[0014] Furthermore, the gel electrolyte is a polyacrylamide gel electrolyte soaked in a ZnCl2 solution; the concentration of the ZnCl2 solution is 0.5~3 mol / L, preferably 1 mol / L; the soaking time is 12~48 h, preferably 24 h.

[0015] Further, after spraying the Ag-np@MXene colloidal solution onto the TiO2 mesoporous membrane, it was heated on a hot plate at 80~120℃ for 10~40 min to obtain the TiO2 / Ag-np@MXene photoelectrode.

[0016] Furthermore, after the Ag-np@MXene colloidal solution was sprayed onto the TiO2 mesoporous membrane, it was heated at 100°C on a hot plate and held for 15 minutes to obtain the TiO2 / Ag-np@MXene photoelectrode.

[0017] The principle of this invention is as follows: This invention utilizes the excellent conductivity and reversible redox reaction of Ag-np to provide Faraday pseudocapacitance. Simultaneously, the localized surface of Ag-np exhibits a plasmon resonance effect, enabling the generation of high-energy hot electrons under visible light. TiO2, acting as a light-absorbing layer, forms a Schottky barrier with Ag-np. The difference in the interfacial work function naturally generates a built-in electric field pointing from TiO2 to Ag-np. This electric field drives the spatial separation of photogenerated electron-hole pairs. Hot electrons cross the barrier, inject into the conduction band of TiO2, and rapidly transport to the external circuit, while holes migrate to Ag-np to participate in the Faraday reaction. The synergistic effect of these two mechanisms—hot electron injection + electric field-driven separation—significantly improves the conversion efficiency of light energy to electrochemical energy. Furthermore, the high conductivity and layered structure of MXene provide a rapid electron transport channel, and the integrated hydrogel electrolyte encapsulation ensures the device's cycle stability.

[0018] The beneficial effects of this invention are: (1) The integrated photo-charged zinc-ion supercapacitor prepared by the present invention realizes the integration of photoelectric conversion and storage. Compared with the separate combination of traditional solar cells and energy storage devices, it can eliminate the need for transformers and connecting lines, effectively reduce space costs and improve photoelectric conversion efficiency. (2) This invention retains the high safety advantage of aqueous batteries, and at the same time, by combining Ag-np with MXene, the electrode specific capacitance is greatly improved compared with pure MXene, which significantly enhances the charge storage capacity. (3) This invention utilizes the Schottky barrier and localized surface plasmon resonance effect between TiO2 and Ag-np to significantly promote the separation and directional migration of photogenerated carriers. Under illumination, this photochargeable container exhibits significantly improved discharge performance and excellent areal capacity, and possesses stable light-assisted energy storage capability under high current density; (4) The present invention adopts an integrated hydrogel electrolyte and a stacked encapsulation structure, and still maintains nearly 55% of the photocapacitance after 750 cycles, demonstrating good cycle stability and system integration. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the zinc ion photocharging container in Embodiment 1 of the present invention; Figure 2 This is a SEM image of Ag nanoparticles reconstructed in situ on MXene in Example 1 of this invention; Figure 3 In Embodiment 1 of this invention, the zinc ion photocharger is tested under light and darkness at 1 mA cm⁻¹. -1 Comparison chart of constant current charge and discharge curves; Figure 4 In Embodiment 1 of this invention, the zinc ion photocharging container was tested under light and darkness for 2 A g. -1 The performance curve of cycling at current density. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] This invention provides an integrated photochargeable zinc-ion supercapacitor, such as... Figure 1 As shown, the device includes a photoelectric positive electrode, a zinc negative electrode, and a gel electrolyte. The photoelectric positive electrode comprises FTO glass, a TiO2 mesoporous membrane disposed on the FTO glass, and an Ag-np@MXene thin film disposed on the TiO2 mesoporous membrane. The zinc negative electrode comprises a zinc sheet. The gel electrolyte is disposed between the photoelectric positive electrode and the zinc negative electrode, serving as a separator and electrolyte. The preparation method includes the following steps: Step 1: Preparation of TiO2 / Ag-np@MXene photoelectrode TiO2 slurry was prepared, consisting of terpineol, ethyl cellulose, TiO2, and lauric acid in a mass ratio of 70-75:4-8:15-25:1-2. The TiO2 slurry was mixed with ethanol solvent at a mass ratio of 1:7-15 to obtain a TiO2 colloidal solution. Silver nitrate and MXene were mixed in ethanol solvent at a mass ratio of 1:3-10. After ultrasonication for 30 min and standing for 6 h, an Ag-np@MXene colloidal solution was obtained. FTO conductive glass was cut to dimensions determined by the material coating area, and then ultrasonically cleaned sequentially with a cleaning agent, deionized water, ethanol, and acetone, followed by drying. TiO2 colloidal solution was uniformly sprayed onto the conductive surface of FTO glass, sintered at 400~500℃ for 1~3 h, and annealed to obtain a TiO2 mesoporous film; Ag-np@MXene colloidal solution was sprayed onto the TiO2 mesoporous film, heated on a hot plate at 80~120℃ for 10~40 min to obtain a TiO2 / Ag-np@MXene photoelectrode.

[0022] Step 2: Preparation of zinc anode and gel electrolyte Cut the zinc sheet and fix it to the conductive surface of another FTO glass using conductive silver paste; The polyacrylamide gel was soaked in a 0.5-3 mol / L ZnCl2 solution for 12-48 h. After complete absorption, it was cut to obtain the polyacrylamide gel electrolyte.

[0023] Step 3: Assembly Zinc sheets, polyacrylamide gel electrolyte, and TiO2 / Ag-np@MXene photoelectrode fixed on FTO glass are stacked sequentially in a double-sided double-glass configuration, with the coated side of the photoelectrode facing the gel electrolyte. The entire assembly is then encapsulated to obtain an integrated zinc ion photocharging device.

[0024] Example 1 This invention provides an integrated photochargeable zinc-ion supercapacitor, the preparation of which includes the following steps: Step 1: Preparation of TiO2 / Ag-np@MXene photoelectrode A TiO2 slurry was prepared, consisting of terpineol, ethyl cellulose, TiO2, and lauric acid in a mass ratio of 71:7:20:2. The TiO2 slurry was mixed with ethanol solvent at a mass ratio of 1:10 to obtain a TiO2 colloidal solution. Silver nitrate and MXene were mixed in 5 mL of anhydrous ethanol solvent at a mass ratio of 1:5, sonicated for 30 min, and then allowed to stand for 6 h to obtain an Ag-np@MXene colloidal solution. The FTO conductive glass was cut, cleaned, and dried.

[0025] TiO2 colloidal solution was uniformly sprayed onto the conductive surface of FTO glass, with the spraying position being the center 1. A 1cm square region was formed, and then sintered in a muffle furnace at 450℃ for 2 h to obtain a TiO2 mesoporous membrane. Ag-np@MXene colloidal solution was sprayed onto the TiO2 mesoporous membrane and held on a hot plate at 100℃ for 15 min to obtain an Ag-np@MXene thin film. The TiO2 / Ag-np@MXene photoelectric cathode was thus prepared.

[0026] Step 2: Preparation of zinc anode and gel electrolyte Cut the zinc sheet, clean and dry it thoroughly, and fix the zinc sheet to the conductive surface of another FTO glass with conductive silver paste as the negative electrode; The polyacrylamide gel was immersed in a 1 mol / L ZnCl2 solution for 24 h. After complete absorption, it was cut to obtain the polyacrylamide gel electrolyte. Step 3: Assembly The zinc sheet, polyacrylamide gel electrolyte, and TiO2 / Ag-np@MXene photoelectrode, which are fixed on FTO glass, are stacked in sequence in a double-sided double-glass configuration and sealed with 3M waterproof adhesive to obtain an integrated zinc ion photocharging device.

[0027] Example 2 The performance of the integrated zinc-ion photocharger prepared in Example 1 was measured, as follows: 1. Verify the in-situ reconstruction effect of Ag nanoparticles in Ag-np@MXene.

[0028] Figure 2 This is a SEM image of Ag nanoparticles in Ag-np@MXene, prepared in Example 1, reconstructed in situ on MXene. (See image for reference.) Figure 2 As shown, Ag nanoparticles are uniformly distributed on the surface of the MXene layer, and the layered structure of MXene remains intact. Electrochemical test results show that the specific capacitance of the Ag-np@MXene composite material is increased by approximately 4.3 times compared to pure MXene, significantly improving the capacitance performance.

[0029] 2. Determine the light-enhanced energy storage performance of the integrated zinc-ion photocharger prepared in Example 1.

[0030] The integrated zinc-ion photochargeable capacitor was subjected to constant current discharge under both light and dark conditions.

[0031] The results are as follows Figure 3 As shown, at 1 mA cm -2 Under current, the specific capacity under illumination is 153.6 μWhcm higher than under dark conditions. -2 The increase was approximately 100%.

[0032] 3. Determine the long-cycle performance of the integrated zinc-ion photocharger prepared in Example 1.

[0033] The results are as follows Figure 4 As shown, in 2 A•g -1 After 750 cycles at a current density, the capacity gain under illumination remained at nearly 55%, and the discharge specific capacity remained at 148.7 mAh g⁻¹. -1 This integrated zinc-ion photochargeable capacitor exhibits excellent light gain stability during long-term cycling, and its cycle capacity retention capability can be continuously and significantly improved under illumination conditions.

[0034] This invention combines aqueous zinc-ion capacitors with metal-semiconductor photoelectrochemistry to develop an integrated zinc-ion photocharger. While MXene possesses excellent conductivity and a layered structure, it still suffers from limitations in capacitance performance and low utilization of active sites. This invention effectively enhances capacitance performance and endows the material with bifunctional properties by in-situ reconstructing Ag nanoparticles on the MXene surface. To fully utilize the localized surface plasmon resonance (LSPR) effect of nano-metal particles under illumination, this invention further introduces a wide-bandgap semiconductor TiO2 to synergize with Ag nanoparticles. The difference in work function at their interface creates a built-in electric field, achieving a hot electron injection combined with an electric field synergy mechanism, significantly promoting the separation and transport of photogenerated carriers. Photogenerated electrons are transported to the external circuit and stored at the negative electrode, while photogenerated holes migrate to the MXene surface, promoting double-layer formation and synergistically enhancing the overall capacitance, completing the conversion of light energy into chemical and electrical energy. This integrated zinc-ion photocharger exhibits significantly improved specific capacitance under illumination, with a maximum optical gain of 84.9%, demonstrating excellent photoelectrochemical performance.

[0035] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should be considered within the scope of protection of the present invention.

Claims

1. An integrated photochargeable zinc-ion supercapacitor, characterized in that, include: A photoelectric positive electrode, comprising FTO glass, a TiO2 mesoporous film disposed on the FTO glass, and an Ag-np@MXene thin film disposed on the TiO2 mesoporous film; Zinc negative electrode, including zinc sheet; A gel electrolyte is placed between the photoelectric positive electrode and the zinc negative electrode.

2. The method for preparing the integrated photochargeable zinc-ion supercapacitor according to claim 1, characterized in that, include: TiO2 colloidal solution was sprayed onto the conductive surface of FTO glass, and then heat-treated and annealed to obtain a TiO2 mesoporous film. The Ag-np@MXene colloidal solution was sprayed onto the TiO2 mesoporous membrane to obtain a TiO2 / Ag-np@MXene photoelectrode. Take a zinc sheet and fix it to the conductive surface of another FTO glass; A zinc sheet, a gel electrolyte, and a TiO2 / Ag-np@MXene photoelectrode fixed on an FTO glass are sequentially stacked, with the sprayed surface of the photoelectrode facing the gel electrolyte. The whole assembly is then encapsulated to form an integrated zinc ion photocharging device.

3. The method for preparing the integrated photochargeable zinc-ion supercapacitor according to claim 2, characterized in that, The method for preparing the TiO2 colloidal solution is as follows: TiO2 slurry was mixed with ethanol solvent to obtain TiO2 colloidal solution; The mass ratio of TiO2 slurry to ethanol solvent is 1:7~15.

4. The method for preparing the integrated photochargeable zinc-ion supercapacitor according to claim 3, characterized in that, The TiO2 slurry is composed of terpineol, ethyl cellulose, TiO2 and lauric acid; The mass of TiO2 is 15-25% of the total mass of TiO2 slurry.

5. The method for preparing the integrated photochargeable zinc-ion supercapacitor according to claim 4, characterized in that, In the TiO2 slurry, the mass ratio of terpineol, ethyl cellulose, TiO2 and lauric acid is 70~75:4~8:15~25:1~2.

6. The method for preparing the integrated photochargeable zinc-ion supercapacitor according to claim 2, characterized in that, The heat treatment process is as follows: sintering at 400~500℃ for 1~3 hours.

7. The method for preparing the integrated photochargeable zinc-ion supercapacitor according to claim 2, characterized in that, The preparation method of the Ag-np@MXene colloidal solution is as follows: Silver nitrate and MXene were mixed in a solvent, sonicated, and then allowed to stand to obtain an Ag-np@MXene colloidal solution.

8. The method for preparing the integrated photochargeable zinc-ion supercapacitor according to claim 7, characterized in that, The mass ratio of silver nitrate to MXene is 1:3~10.

9. The method for preparing the integrated photochargeable zinc-ion supercapacitor according to claim 2, characterized in that, The gel electrolyte is a polyacrylamide gel electrolyte that has been soaked in a ZnCl2 solution; The concentration of the ZnCl2 solution is 0.5~3 mol / L, and the soaking time is 12~48 h.

10. The method for preparing the integrated photochargeable zinc-ion supercapacitor according to claim 2, characterized in that, After spraying the Ag-np@MXene colloidal solution onto the TiO2 mesoporous membrane, the solution was kept at 80~120℃ for 10~40 min to obtain the TiO2 / Ag-np@MXene photoelectrode.

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