Rough porous octahedral structure photosensitive air positive electrode material and preparation method and application thereof

Abstract

The invention relates to the technical field of electrodes, in particular to a rough porous octahedral structure photosensitive air positive electrode material and a preparation method and application thereof. The first purpose of the invention is to provide a rough porous octahedral structure photosensitive air positive electrode material, CuBTC is used as a template, a cobalt precursor is grown on the surface of the template by using a hydrothermal method, and further oxidation is performed to generate a composite metal oxide, namely the core-shell structure nanosphere photocatalytic material. The Co3O4-coated CuxO-based zinc-air battery has the advantages that the Co3O4-coated CuxO-based zinc-air battery is of an octahedral structure with a rough surface and a porous interior, the number of active sites can be increased due to the high specific surface area, efficient mass transfer in the electrochemical process is guaranteed due to the porous structure, the catalytic activity is further improved, and the discharge power density and the specific capacity of the Co3O4-coated CuxO-based zinc-air battery are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of electrode technology, and in particular to a rough porous octahedral structure photosensitive air cathode material, its preparation method, and its application. Background Art

[0002] Zinc-air batteries have become a widely watched energy conversion device in the field of electrocatalysis due to their advantages such as low cost, safety, environmental friendliness, and good stability. However, the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), which are the basic reactions in these devices, have extremely slow kinetic processes, resulting in low energy conversion efficiency and seriously hindering the large-scale application of zinc-air batteries and water electrolysis devices.

[0003] Cu2O, as an important indirect bandgap semiconductor material, has important applications in photocatalysis, optoelectronics and other fields. However, pure cuprous oxide has a short carrier diffusion distance and its photocorrosion limits its stability as a photoelectrode, which greatly limits its energy utilization and service life. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of the prior art by proposing a rough, porous octahedral structure photosensitive air cathode material, its preparation method, and its application.

[0005] The first objective of this invention is to provide a rough, porous, octahedral structure photosensitive air cathode material, which uses CuBTC as a template, grows a cobalt precursor on its surface using a hydrothermal method, and then further oxidizes it to generate a composite metal oxide, which is the core-shell structured nanosphere photocatalytic material.

[0006] Furthermore, in the composite metal oxide, the molar ratio of Cu to Co is 0.9 to 1.1:1.

[0007] A second objective of this invention is to provide a method for preparing the rough porous octahedral structure photosensitive air cathode material as described above, comprising the following steps:

[0008] CuBTC was dispersed in deionized water, and then cobalt nitrate methanol solution and 2-methylimidazolium methanol solution were added. After hydrothermal reaction, the mixture was centrifuged and dried to obtain the initial product with the rough octahedral structure. The centrifugation speed was 8000 r / min to 9000 r / min, and the centrifugation time was 3 min to 5 min.

[0009] The octahedral initial product was subjected to a graded sintering process in air to induce an oxidation reaction, resulting in the rough, porous octahedral photosensitive air cathode material.

[0010] Furthermore, the preparation method of CuBTC is as follows:

[0011] At room temperature, copper nitrate was added to deionized water as solution A, and trimethyl-1,3,5-benzenetricarboxylic acid and polyvinylpyrrolidone were dissolved in ethanol as solution B. Solution A was slowly poured into solution B and stirred until homogeneous. The mixture was then transferred to a reaction vessel and kept warm for a period of time before centrifugation with water and ethanol to obtain CuBTC.

[0012] Furthermore, the molar ratio of trimethyl-1,3,5-benzenetricarboxylic acid and polyvinylpyrrolidone is 1:0.95 to 1; the volume ratio of solution A to solution B is 1 to 1.5:1.

[0013] Furthermore, the concentration of the cobalt nitrate methanol solution is 0.4–0.6 mol / L and the concentration of the 2-methylimidazolium methanol solution is 0.4–0.5 mol / L.

[0014] Furthermore, the molar ratio of Cu in CuBT to cobalt in cobalt nitrate is 0.96 to 1.1:1.

[0015] Furthermore, the hydrothermal reaction was carried out under static conditions at 60–80°C for 8–9 hours; followed by centrifugation with methanol and drying. The drying temperature was 55–65°C, and the drying time was 12–24 hours.

[0016] Furthermore, the graded calcination involves first heating to 250–300°C and holding for 1.5–2 hours, then raising the temperature to 350–400°C and holding for 1–1.5 hours.

[0017] A third objective of this invention is to provide a photo-assisted zinc-air battery comprising the aforementioned rough, porous octahedral structure photosensitive air cathode material.

[0018] The octahedral precursor obtained in this invention undergoes an oxidation reaction during staged sintering in a muffle furnace in air, thereby forming the corresponding oxide from the precursor MOF without altering its morphology. Benefiting from the high specific surface area and porous structure derived from the MOF, the rough, porous structure formed after oxidation provides efficient transport and utilization of photogenerated electrons and holes, and significantly improves the discharge power density and specific capacity of zinc-air batteries. The rough, porous octahedral photosensitive air cathode material prepared in this invention uses CuO as its base material. x An octahedral core and a rough thin shell of Co3O4 nanoparticles, wherein the CuO x The side length is 400nm to 600nm; the thickness of the rough porous octahedral structure photosensitive air cathode material nanoparticles is 50nm to 150nm.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] 1. Aiming at efficient and low-cost utilization of visible light from solar energy, a cobalt precursor is grown on the surface of CuBTC using a hydrothermal method, and then further oxidized to generate a composite metal oxide. This oxide exhibits a rough surface and a porous internal octahedral structure. The high specific surface area increases the number of active sites, while the porous structure ensures efficient mass transfer during electrochemical processes, thereby increasing catalytic activity.

[0021] 2. Co3O4@Cu x O is an excellent bifunctional catalytic material in photo-assisted zinc-air batteries, benefiting from the high specific surface area and porous structure derived from MOF, and Cu x The composite material exhibits superior photoresponse properties and high electrocatalytic activity compared to Cu, and can fully utilize visible light energy to catalyze the decomposition of water molecules to produce oxygen and improve the energy density of zinc-air batteries. These properties significantly outperform those of Cu alone. x O, and can successfully capture visible light, further improving electrochemical activity. The discharge power density and specific capacity of the zinc-air battery based on Co3O4@CuxO are significantly improved. Attached Figure Description

[0022] Figure 1 This is a scanning electron microscope image of the initial product of the rough porous octahedral structure in Embodiment 1 of the present invention;

[0023] Figure 2 This is a scanning electron microscope image of the rough porous octahedral nanosphere photocatalytic material of Example 1 of the present invention;

[0024] Figure 3 The charging platform (a) and discharging platform (b) obtained under darkness and illumination at different current densities are shown.

[0025] Figure 4 Charge / discharge polarization curves at different current densities;

[0026] Figure 5 For 0.1mA cm -2 The following charge / discharge cycle is performed using the switching optical switch mode;

[0027] Figure 6 For 0.1mA cm -2 The long cycle curve obtained below;

[0028] Figure 7 To test the performance of 5 mA cm under both light and dark conditions. -2 Calculated specific capacity of ZAB (using Co3O4@CuxO as air photocathode); the inset shows the apparatus for electrochemical measurement of ZAB under light irradiation;

[0029] Figure 8 The discharge power density of the zinc-air battery with Co3O4@CuxO in darkness and light. Detailed Implementation

[0030] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0031] Example 1

[0032] Preparation of rough porous octahedral structure photosensitive air cathode material

[0033] Synthesis of CuBTC precursor: 875 mg Cu(NO3)2·3H2O was dissolved in 15 mL of water as solution A, and 420 mg H3BTC and 1 g PVP were dissolved in 15 mL of ethanol as solution B. After both solutions were thoroughly mixed, solution A was poured into solution B and stirring continued until clear. The solution was then transferred to a reaction vessel and placed in an oven at 100 °C for 12 h. After the reaction was complete, the solution was removed and centrifuged three times each with water and ethanol, and then transferred to a vacuum drying oven at 60 °C for 12 h.

[0034] Synthesis of ZIF67@CuBTC: 300 mg CuBTC was dissolved in 75 mL of methanol and sonicated for 30 min until the powder was uniformly dispersed. Then, 725 mg Co(NO3)2·6H2O was added to the above solution, and stirring was continued for 30 min. Simultaneously, 1231 mg 2-methylimidazole was added to 75 mL of methanol, fully dissolved, and then poured into the above solution. The mixture was stirred for an additional 30 min, and then allowed to stand at room temperature for 4 h. After the reaction was complete, the mixture was centrifuged three times with methanol and then transferred to a vacuum drying oven at 60 °C for 12 h.

[0035] Co3O4@Cu x O synthesis: ZIF67@CuBTC was transferred to a muffle furnace and sintered in stages. The temperature was raised to 300℃ and held for 2 hours, then raised to 400℃ and held for 1 hour. The heating rate was 2℃ / min for both times. -1 Thus, the corresponding oxidation product Co3O4@Cu is obtained. x O.

[0036] Figure 1 This is a scanning electron microscope image of the initial product of the rough porous octahedral structure in Example 1 of the present invention. As can be seen from the figure, CuBTC exhibits a classic octahedral structure with a very smooth surface and a relatively uniform particle size distribution, approximately between 1 and 1.5 μm.

[0037] Figure 2This is a scanning electron microscope (SEM) image of the rough porous octahedral nanosphere photocatalytic material of Example 1 of the present invention; as can be seen from the image, the Co3O4@Cu obtained after nanoparticle modification... x The O composite material is an octahedron with a rough and porous surface, although its spatial structure is similar to that of Cu. x Similar in appearance to O, but with significant changes in microstructure. Co3O4@Cu x The uniform porous structure of Cu allows it to have a larger specific surface area, providing more catalytic active sites. Furthermore, the complete octahedron structure, compared to the agglomerated particles of Cu... x O has better stability, and measurements have shown that CuO x The side length is 400nm to 600nm; the thickness of the rough porous octahedral structure photosensitive air cathode material nanoparticles is 50nm to 150nm.

[0038] Assembly of photo-charged zinc-air batteries

[0039] Photosensitive air cathode: First, the active material and acetylene black were mixed in a 6:1 ratio (actual mass 60mg, 10mg respectively) and added to a certain amount of ethanol. Then, 60μL of polytetrafluoroethylene emulsion was added dropwise, and the mixture was ground until the ethanol evaporated three times to obtain a dough-like mixture. Next, it was rolled into a thin sheet with a glass rod and then cut into 1.5×1.5cm pieces. 2 Small pieces. Finally, combine it with a waterproof and breathable membrane (2.5×2.5cm). 2 Nickel mesh current collector (2.5×6cm) 2 Stack them and place them on a tablet press, adjust the appropriate spacing and press them into a whole, which can be used as an air cathode for later use.

[0040] Zinc anode: A zinc sheet with a thickness of 0.5 mm (2.5 × 6 cm) is used. 2 The zinc sheet is placed on a punching machine to press out a 16mm diameter hole. The oxide layer on the surface of the zinc sheet is then sanded off with sandpaper to prepare it as a zinc anode.

[0041] Electrochemical testing

[0042] Rate testing refers to testing the charge and discharge plateaus of a battery under different current densities, observing the changes in charge and discharge voltages as the current changes, and thus judging the battery's charge and discharge performance. The chronopotential method was used with current densities of 0.1, 0.2, 0.3, 0.5, 0.8, 1.0, and 2.0 mA cm⁻¹. -2 Under certain conditions (current density is switched every 30 minutes), constant current charging and discharging are performed to obtain a rate ladder.

[0043] Charge-discharge curve testing refers to performing a linear sweep voltammetry test on the battery across its charging and discharging voltage ranges, and outputting a current-voltage curve to assess the battery's charge-discharge performance. Furthermore, the discharge power density curve can be obtained from the voltage and current values ​​on the discharge curve, further evaluating the battery's discharge performance. In this invention, the charging and discharging ranges are set to 1.3–2.5V and 1.6–0.4V, respectively, with a sweep rate of 5 mV / s. -1 .

[0044] Cyclic charge-discharge testing refers to periodically charging and discharging a battery at a specific current density and outputting corresponding voltage-time curves to assess the battery's cycle stability. In this project, a current density of 0.1 mA cm⁻¹ is set. -2 The constant current switches between charging and discharging states every 30 minutes, completing one cycle in 1 hour.

[0045] Specific capacity refers to the amount of electricity that a unit mass of Zn can provide during discharge, and it is commonly used as an indicator of battery discharge performance. This study uses the chronopotential method at 5 mA cm⁻¹. -2 Under certain conditions, the battery was discharged for an extended period, with a lower voltage limit of 0.5V set, and the voltage curve was observed to fluctuate over time. The specific capacity was obtained by calculating the ratio of the discharged capacity of the zinc-air battery to the difference in the mass of the zinc sheet before and after the test.

[0046] Figure 3 Figures show the charging and discharging plateaus (a) and (b) under different current densities in darkness and illumination; the figures show that at 0.1 mA cm⁻¹... -2 At a given current density, the battery's charging voltage in the dark was 1.837V, but dropped to 1.748V after the lights were switched on, a decrease of 89mV. As the current density gradually increased, the charging voltage plateau also rose, but the voltage after the lights were switched on remained lower than under dark conditions. When the current density increased from 2mA / cm²... -2 Switch to 0.1mA cm -2 At this time, the battery's charging plateau remains roughly the same as its initial value, with almost no degradation. The voltage plateau changes during discharge in the opposite way to during charging; as the current density increases, the battery's discharge plateau gradually decreases. However, regardless of the current density, the voltage plateau after switching on is always significantly higher than in the dark. At 0.1 mA cm⁻¹ -2 At the initial discharge current density, when the battery device switched from darkness to light conditions, the voltage plateau increased from 1.321V to 1.349V. Based on the above analysis, it can be concluded that Co3O4@Cu x Zinc-air batteries assembled with O-air cathodes exhibit good rate performance in both dark and light conditions.

[0047] Figure 4 The figure shows the charging / discharging polarization curves under different current densities. As can be seen from the figure, the opening of the curve narrows after the light is switched on, indicating that when the same current density is reached, the charging and discharging voltage gap decreases, and the battery charging and discharging efficiency is correspondingly improved.

[0048] Figure 5 For 0.1mA cm -2 The following is a charge-discharge cycle performed using the switching light switch mode; as can be seen from the figure, there are significant changes in the charge-discharge curves of the battery between each two adjacent cycles, and the voltage gap between charge and discharge is significantly reduced after the light is switched on.

[0049] Figure 6 For 0.1mA cm -2 The long-cycle curves obtained are shown in the figure. It can be seen that the battery's charge and discharge voltage fluctuates slightly at certain points, but overall it exhibits excellent stability. After 160 consecutive cycles under illumination, the change in its charge and discharge voltage plateau is small, which strongly demonstrates its charge and discharge stability under long-term illumination.

[0050] Figure 7 To test the performance of 5 mA cm under both light and dark conditions. -2 Calculated ZAB (using Co3O4@Cu) x The specific capacity of the ZAB (using O as an air photocathode) is shown in the figure; the inset shows the apparatus for electrochemical measurements under light irradiation; as can be seen from the figure, the discharge plateau of the battery under light conditions is consistently higher than that under dark conditions. Furthermore, its discharge specific capacity reaches a high 759.12 mAh g⁻¹. -1 It improved by 7.24% compared to dark conditions.

[0051] Figure 8 The figure shows the discharge power density of the Co3O4@CuxO zinc-air battery under darkness and light. As can be seen from the figure, the peak power density is 58 mW cm⁻¹ when the light is off. -2 After the consecration ceremony, this value increased to 76mW cm⁻¹. -2 The improvement was as high as 31%, which further verifies the Co3O4@Cu x O composite materials exhibit excellent light response properties.

[0052] For any points not covered above, existing technologies shall apply.

[0053] Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the direction of the invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A rough, porous octahedral structure photosensitive air cathode material, characterized in that, Using CuBTC as a template, a cobalt precursor is grown on its surface using a hydrothermal method, and then further oxidized to generate a composite metal oxide, which is the rough porous octahedral structure photosensitive air cathode material.

2. A rough, porous octahedral structure photosensitive air cathode material, characterized in that, In the composite metal oxide, the molar ratio of Cu to Co is 0.9 to 1.1:

1.

3. A method for preparing a rough porous octahedral structure photosensitive air cathode material as described in claim 1 or 2, characterized in that, Includes the following steps: CuBTC was dispersed in deionized water, then cobalt nitrate methanol solution and 2-methylimidazolium methanol solution were added, and after hydrothermal reaction, the product was centrifuged and dried to obtain the initial product with the rough octahedral structure. The octahedral initial product was subjected to a graded sintering process in air to induce an oxidation reaction, resulting in the rough, porous octahedral photosensitive air cathode material.

4. The preparation method according to claim 3, characterized in that, The preparation method of CuBTC is as follows: At room temperature, copper nitrate was added to deionized water as solution A, and trimethyl-1,3,5-benzenetricarboxylic acid and polyvinylpyrrolidone were dissolved in ethanol as solution B. Solution A was slowly poured into solution B and stirred until homogeneous. The mixture was then transferred to a reaction vessel and kept warm for a period of time before centrifugation with water and ethanol to obtain CuBTC.

5. The preparation method according to claim 4, characterized in that, The molar ratio of trimethyl-1,3,5-benzenetricarboxylic acid and polyvinylpyrrolidone is 1:0.95-1; the volume ratio of solution A to solution B is 1-1.5:

1.

6. The preparation method according to claim 3, characterized in that, The concentrations of cobalt nitrate methanol solution and 2-methylimidazolium methanol solution were 0.4–0.6 mol / L and 0.4–0.5 mol / L, respectively.

7. The preparation method according to claim 3, characterized in that, The molar ratio of Cu in CuBT to cobalt in cobalt nitrate is 0.96 to 1.1:

1.

8. The preparation method according to claim 3, characterized in that, The hydrothermal reaction was carried out at a temperature of 60°C to 80°C for 8 to 9 hours; then the mixture was centrifuged with methanol and dried.

9. The preparation method according to claim 3, characterized in that, The graded calcination involves first heating to 250–300℃ and holding for 1.5–2 hours, then raising the temperature to 350–400℃ and holding for 1–1.5 hours.

10. A photo-assisted zinc-air battery, characterized in that, Including the rough porous octahedral structure photosensitive air cathode material as described in claim 1 or 2.

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