Multi-electron transfer polynuclear quinoxaline derivative and synthesis method and application thereof

Abstract

This application discloses a multi-electron transfer polynuclear quinoxaline derivative and its synthesis method and application, relating to the field of electrochemical energy storage. The method involves dissolving cyclohexanehexaone octahydrate and 4,5-dichloro-1,2-phenylenediamine or 4-chloro-1,2-phenylenediamine in a mixed solution of glacial acetic acid and anhydrous ethanol. The solution is refluxed and stirred at high temperature under N2 protection for 24 hours. The product is then refluxed and stirred at high temperature in dilute nitric acid for 3 hours to obtain intermediate products HATN-HC or HATN-TC. HATN-HC or HATN-TC, potassium tert-butoxide, mercaptopropionic acid, manganese dioxide, and 15-crown ether-5 are added to anhydrous ethanol. The mixture is stirred and reacted at 70°C under N2 protection for 24 hours. The product is filtered, washed, and acidified, then dried at 60°C in a vacuum oven to obtain HATN-HSPA or HATN-TSPA. The application of the multi-electron transfer polynuclear quinoxaline derivative in alkaline aqueous organic flow batteries is also discussed.

Description

Technical Field

[0001] This application relates to the field of electrochemical energy storage technology, specifically to a multi-electron transfer polynuclear quinoxaline derivative and its synthesis method and application. Background Technology

[0002] Advanced energy storage technology is key to addressing the challenges of clean energy sources such as solar and wind power, which suffer from spatiotemporal fluctuations. Aqueous organic flow batteries (AORFBs), as a novel energy storage technology, use aqueous solutions as electrolytes and organic active molecules as electroactive materials. They offer advantages such as energy / power decoupling design, rapid charge / discharge response, and flexible scalability, making them suitable for diverse applications. However, the capacity and energy density of AORFBs are generally low due to limitations in the low electron transfer number and low solubility of organic active molecules. According to the energy density equation (E = QV, where E is energy density, Q is charge per unit volume, and V is battery voltage), increasing the battery operating voltage is the most effective way to construct high-energy-density AORFBs. Similarly, increasing the solubility of organic materials is another common strategy to improve the energy density of AORFBs. Grafting water-soluble substituents and optimizing the electrolyte can increase the solubility of organic active molecules, allowing them to contain more molecules per unit volume, thus achieving a high electron number density. However, the resulting increase in viscosity affects battery life. Developing organic active molecules with high electron transfer can avoid this adverse effect. However, due to the existence of a large number of intermediate states resulting from the expansion of molecular structure, organic molecules must maintain relatively good stability in all redox states, which poses a design challenge for simultaneously achieving multiple electron transfers and high solubility.

[0003] Organic materials have shown great potential for development in molecules used in flow batteries. However, most organic active molecules involve single or two electron transfers, and their molecular structures need to be further improved through reasonable molecular engineering to achieve both high electron transfer numbers and high water solubility. Summary of the Invention

[0004] Technical problems to be solved: This application provides a multi-electron-transfer polynuclear quinoxaline derivative, its synthesis method and application. A strategy of thioalkylation side group modification was designed and used to synthesize polynuclear quinoxaline derivatives for alkaline aqueous organic flow batteries, which can solve the problems of low number of transferred electrons and low solubility of existing organic molecules. The water solubility and structural stability of most organic molecules still need to be further improved through reasonable molecular engineering.

[0005] The specific technical solution of this invention is as follows: A multi-electron-transfer polynuclear quinoxaline derivative, wherein the multi-electron-transfer polynuclear quinoxaline derivative is a mercaptopropionic acid-modified quinoxaline HATN-HSPA or HATN-TSPA, and the structural formula of the mercaptopropionic acid-modified quinoxaline HATN-HSPA or HATN-TSPA is as follows: .

[0006] Further, the mercaptopropionic acid-modified quinoxaline HATN-HSPA or HATN-TSPA is specifically: 3,3',3'',3''',3'''',3''''-(diquinoxalano[2,3-a:2',3'-c]phenazine-2,3,8,9,14,15-hexylhexathioetheryl)hexapropionic acid or 3,3',3''-(diquinoxalano[2,3-a:2',3'-c]phenazine-2,8,14-trimethyltrithioetheryl)tripropionic acid.

[0007] This application also discloses a method for synthesizing any of the above-mentioned multi-electron transfer polynuclear quinoxaline derivatives, wherein the method for synthesizing HATN-HSPA includes the following steps: Step 1: 10 mmol of cyclohexanehexaone octahydrate and 30 mmol of 4,5-dichloro-1,2-phenylenediamine were added to 600 mL of glacial acetic acid and anhydrous ethanol solution to obtain a mixture. The mixture was refluxed and stirred at 140 °C for 24 hours under N2 protection and at a stirring speed of 500 rpm. The volume ratio of glacial acetic acid to anhydrous ethanol was 1:1. Step 2: After the mixture after reflux and stirring has cooled to room temperature, the mixture is filtered with a sand core filter and washed three times in sequence with glacial acetic acid, deionized water and anhydrous ethanol. The product is dried in a vacuum oven at 60°C to obtain a green solid precursor. Step 3: Add the green solid precursor to 400 mL of 30% nitric acid. Reflux the mixture at 140°C for 3 hours with a stirring speed of 500 rpm. Step 4: After cooling to room temperature, the mixture was filtered using a sand core filter and washed three times with deionized water and anhydrous ethanol in sequence to obtain the yellow-green intermediate 2,3,8,9,14,15-hexachlorodiquinoxalino[2,3-a:2',3'-c]phenazine, i.e., HATN-HC; Step 5: Add 2 mmol HATN-HC, 38.4 mmol potassium tert-butoxide, 14.4 mmol mercaptopropionic acid, 3 mmol manganese dioxide and 0.06 mmol 15-crown ether-5 to 100 mL of anhydrous ethanol to obtain a mixed solution. The mixed solution is stirred at 70 °C under N2 protection for 24 hours at a stirring speed of 500 rpm. Step 6: After the mixed solution has cooled to room temperature, add 100 mL of deionized water to the mixed solution and stir the mixture evenly at a speed of 500 rpm. Then, remove insoluble impurities by centrifugation and filtration to obtain the supernatant. Centrifuge at a speed of 5000 rpm and filter the mixture using a sand core filter. Step 7: Acidify the supernatant with 2 M HCl. After centrifugation, filtration and washing with 0.1 M dilute HCl, the precipitate is dried in a vacuum oven at 60°C to constant weight to obtain a black-green solid HATN-HSPA. The centrifugation speed is 5000 rpm. The mixture is filtered using a sand core filter.

[0008] Furthermore, the synthesis method of HATN-TSPA includes the following steps: Step 1: 10 mmol of cyclohexanehexaone octahydrate and 30 mmol of 4-chloro-1,2-phenylenediamine were added to 600 mL of glacial acetic acid and anhydrous ethanol solution to obtain a mixture. The mixture was refluxed and stirred at 140 °C for 24 hours under N2 protection and at a stirring speed of 500 rpm. The volume ratio of glacial acetic acid to anhydrous ethanol was 1:1. Step 2: After the mixture after reflux and stirring has cooled to room temperature, the mixture is filtered with a sand core filter and washed three times in sequence with glacial acetic acid, deionized water and anhydrous ethanol. The product is dried in a vacuum oven at 60°C to obtain a green solid precursor. Step 3: Add the green solid precursor to 400 mL of 30% nitric acid. Reflux the mixture at 140°C for 3 hours with a stirring speed of 500 rpm. Step 4: After cooling to room temperature, the mixture is filtered using a sand filter and washed three times with deionized water and anhydrous ethanol to obtain the yellow-green intermediate 2,8,14-trichlorodiquinoxalino[2,3-a:2',3'-c]phenazine, i.e., HATN-TC; Step 5: Add 2 mmol HATN-TC, 38.4 mmol potassium tert-butoxide, 14.4 mmol mercaptopropionic acid, 3 mmol manganese dioxide and 0.06 mmol 15-crown ether-5 to 100 mL of anhydrous ethanol to obtain a mixed solution. The mixed solution is stirred at 70 °C under N2 protection for 24 hours at a stirring speed of 500 rpm. Step 6: After the mixed solution has cooled to room temperature, add 100 mL of deionized water to the mixed solution and stir the mixture evenly at a speed of 500 rpm. Then, remove insoluble impurities by centrifugation and filtration to obtain the supernatant. Centrifuge at a speed of 5000 rpm and filter the mixture using a sand core filter. Step 7: Acidify the supernatant with 2 M HCl. After centrifugation, filtration and washing with 0.1 M dilute HCl, the precipitate is dried in a vacuum oven at 60°C to constant weight to obtain a black-green solid HATN-TSPA. The centrifugation speed is 5000 rpm. The mixture is filtered using a sand filter.

[0009] Furthermore, the synthetic route for the multi-electron-transfer polynuclear quinoxaline derivative HATN-HSPA is as follows: .

[0010] Furthermore, the synthetic route for the multi-electron-transfer polynuclear quinoxaline derivative HATN-TSPA is as follows: .

[0011] Furthermore, in the first step, the mass ratio of cyclohexanehexane octhydrate to 4,5-dichloro-1,2-phenylenediamine is cyclohexanehexane octhydrate: 4,5-dichloro-1,2-phenylenediamine = 3.13: 5.35.

[0012] Furthermore, in the first step, the mass ratio of cyclohexanehexane octahydrate to 4-chloro-1,2-phenylenediamine is cyclohexanehexane octahydrate: 4-chloro-1,2-phenylenediamine = 3.13: 4.28.

[0013] This application also discloses the application of any of the aforementioned multi-electron transfer polynuclear quinoxaline derivatives in aqueous flow batteries.

[0014] Furthermore, the aqueous flow battery is an alkaline aqueous organic flow battery.

[0015] Explanation of the principle: This patent successfully synthesized two quinoxaline derivatives (HATN-HSPA and HATN-TSPA) through a thioalkylation side-group modification strategy, exhibiting both high water solubility and molecular stability. HATN-HSPA and HATN-TSPA have water solubilities of 1.26 and 0.48 M, respectively, making them ideal materials for basic AORFBs. Differential pulse voltammetry curves confirmed that HATN-HSPA and HATN-TSPA achieved six-electron transfer through a three-step redox process. HATN-HSPA possesses multiple highly polar hydrophilic groups and active sites, unlike traditional... O -or NUnlike other alkylation strategies, HATN-HSPA's molecular structure incorporates six propionic acid groups grafted onto sulfur atoms. Suitable solubilization sites further stabilize the large π-conjugated system, effectively suppressing molecular side reactions. Consequently, HATN-HSPA and HATN-TSPA exhibit excellent structural stability. Therefore, AORFBs based on 0.1 M HATN-HSPA||K4Fe(CN)6 and HATN-TSPA||K4Fe(CN)6 showed no significant capacity decay over 1200 cycles. The AORFB based on 0.5 M HATN-HSPA||K4Fe(CN)6 showed a capacity decay rate as low as 0.003% / cycle or 0.03% / day over 600 cycles. Furthermore, even at the extremely high concentration of 1.26 M, the AORFB of HATN-HSPA||K4Fe(CN)6 still maintained 150 Ah L / L. -1 and 187.5 Wh L -1 The HATN-HSPA exhibits ultra-high capacity and energy density, with a corresponding capacity decay rate of only 0.02% / day. Through theoretical calculations and a series of spectral analyses before and after cycling, the structural changes of HATN-HSPA during cycling were investigated. Density functional theory calculations showed that the Ar-SC bonds in the side chains of the HATN-HSPA molecule possess weak electrophilic properties. Furthermore, the isomerization barrier ΔG of HATN-HSPA is as high as 21.58. The kcal / mol value indicates that the appropriate solubilizing side chain position prevents the isomerization side reaction. Although HATN-HSPA exhibits trace side chain shedding during cycling, it does not affect the overall structural stability, and the presence of multiple carboxyl solubilizing groups ensures the molecule's water solubility. Furthermore, the natural large π-conjugated system of the HATN-HSPA molecule has significant structural advantages, effectively suppressing the destruction of the molecular conjugated structure and aromaticity by the isomerization reaction. The synergistic effect of these two factors gives the HATN-HSPA molecule excellent cycling stability. This patent demonstrates the great potential of the thioalkylation side group modification strategy in creating redox-reversible and electrochemically stable organic molecules, laying the technical foundation for the widespread application of large-scale and environmentally friendly energy storage systems.

[0016] The beneficial effects of this invention are: 1. This invention designs a quinoxaline derivative synthesized through a thioalkylation side-group modification strategy for use in alkaline aqueous organic flow batteries. Based on the thioalkylation side-group modification strategy, the quinoxaline structure with six-electron transfer capability is functionalized and modified. The synthesized HATN-HSPA and HATN-TSPA have water solubility of 1.26 and 0.48 M, respectively, and are ideal materials for AORFBs. 2. Differential pulse voltammetry curves confirmed that HATN-HSPA and HATN-TSPA achieved six-electron transfer through a three-step redox process; 3. The suitable solubilization position of HATN-HSPA further stabilizes the large π-conjugated system, thereby effectively suppressing the occurrence of molecular side reactions; 4. In addition, there is a small amount of side chain shedding, but it does not affect the stability of the overall structure, and the presence of multiple carboxyl solubilizing groups ensures the water solubility of the molecule. 5. The AORFBs of 0.1 M HATN-HSPA||K4Fe(CN)6 and HATN-TSPA||K4Fe(CN)6 did not show significant capacity decay throughout the entire 1200 cycles. The AORFB based on 0.5 M HATN-HSPA||K4Fe(CN)6 showed a capacity decay rate as low as 0.003% / cycle or 0.03% / day over 600 cycles. Furthermore, even at the limiting concentration of 1.26 M, the AORFB of HATN-HSPA||K4Fe(CN)6 still had 150 Ah L. -1 and 187.5 Wh L -1 Its ultra-high capacity and energy density correspond to a capacity decay rate of only 0.02% / day; 6. The structural changes of HATN-HSPA during cycling were investigated through theoretical calculations and a series of spectral analyses before and after cycling. Density functional theory calculations showed that the Ar-SC bonds in the side chains of the HATN-HSPA molecule exhibit weak electrophilic properties. The isomerization barrier ΔG of HATN-HSPA is as high as 21.58 kcal / mol, indicating that the appropriate solubilizing side chain positions prevent the isomerization side reaction. Although a small amount of side chain shedding occurs during cycling, it does not affect the overall structural stability, and the presence of multiple carboxyl solubilizing groups ensures the molecule's water solubility. Furthermore, the natural large π-conjugated conformation of the HATN-HSPA molecule has significant structural advantages, effectively suppressing the isomerization reaction from damaging the molecular conjugated structure and aromaticity. The synergistic effect of these two factors gives the HATN-HSPA molecule excellent cycling stability. 7. This patent demonstrates the great potential of the thioalkylation side-group modification strategy in creating redox-reversible and electrochemically stable organic molecules, laying the technical foundation for the widespread application of large-scale, environmentally friendly energy storage systems. Attached Figure Description

[0017] Figure 1 This is the 1H NMR spectrum of the HATN-HSPA of this invention; Figure 2 This is the 1H NMR spectrum of the HATN-TSPA of this invention; Figure 3 In the figure, a represents the UV-Vis absorption spectra of HATN-HSPA at different concentrations in 1.0 M KOH, and c represents the UV-Vis absorption spectra of HATN-TSPA at different concentrations in 1.0 M KOH. Figure 3 In the figure, b is the absorbance-concentration fitting graph of HATN-HSPA solution, and d is the absorbance-concentration fitting graph of HATN-TSPA solution. Figure 4 The figures are cyclic voltammetry curves and differential pulse voltammetry curves of 4.0 mM HATN-HSPA, HATN-TSPA and K4Fe(CN)6 in 1.0 M KOH solution, where a is the cyclic voltammetry curve and b is the differential pulse voltammetry curve. Figure 5 This is an electrochemical performance diagram of 0.1 M HATN-HSPA||K4Fe(CN)6 and HATN-TSPA||K4Fe(CN)6AORFBs of the present invention. Figure 5 Figure 'a' shows the rate performance of 0.1 M HATN-HSPA||K4Fe(CN)6 at different current densities. Figure 5 Figure b shows the rate performance of 0.1 M HATN-TSPA||K4Fe(CN)6 at different current densities. Figure 5 The AORFB constant current and constant current-constant voltage cycling performance of HATN-HSPA||K4Fe(CN)6 with c = 0.1 M; Figure 5 The AORFB constant current and constant current-constant voltage cycling performance of HATN-TSPA||K4Fe(CN)6 with a d of 0.1M; Figure 6 In Figure 'a', the charge-discharge curves of 0.5 M HATN-HSPA||K4Fe(CN)6 AORFB at different current densities are shown. Figure 6 In the figure, b represents the coulombic efficiency, energy efficiency, and discharge capacity corresponding to HATN-HSPA||K4Fe(CN)6. Figure 6 In the figure, c represents the polarization curves and power density curves of HATN-HSPA||K4Fe(CN)6 AORFB at different concentrations. Figure 6 d is at 25 mA·cm -2 Long-term constant current cycling performance of 0.5 M HATN-HSPA||K4Fe(CN)6 AORFB Figure 6 In the middle, e represents 20 mA·cm -2 Long-term constant current cycling performance of 1.26M HATN-HSPA||K4Fe(CN)6 AORFB. Detailed Implementation

[0018] To make the objectives and advantages of this invention clearer, the invention will be specifically described below with reference to embodiments. It should be understood that the following text is merely used to describe one or more specific embodiments of the invention and does not strictly limit the scope of protection specifically claimed by the invention.

[0019] In this application, cyclohexanehexanone octahydrate, 4,5-dichloro-1,2-phenylenediamine, and 4-chloro-1,2-phenylenediamine were purchased from Shanghai Bide Pharmaceutical Technology Co., Ltd., with a purity of 98%. Mercaptopropionic acid, potassium tert-butoxide, manganese dioxide, and 15-crown ether-5 were purchased from Shanghai Mairui Chemical Technology Co., Ltd., with a purity of 98%.

[0020] Nitric acid was purchased from Sinopharm Chemical Reagent Co., Ltd., and was of analytical grade.

[0021] Example 1: A multi-electron-transfer polynuclear quinoxaline derivative, wherein the multi-electron-transfer polynuclear quinoxaline derivative is a mercaptopropionic acid-modified quinoxaline HATN-HSPA or HATN-TSPA, and the structural formula of the mercaptopropionic acid-modified quinoxaline HATN-HSPA or HATN-TSPA is as follows: .

[0022] The mercaptopropionic acid-modified quinoxaline HATN-HSPA or HATN-TSPA is specifically: 3,3',3'',3''',3'''',3'''''-(diquinoxalano[2,3-a:2',3'-c]phenazine-2,3,8,9,14,15-hexylhexathioetheryl)hexapropionic acid or 3,3',3''-(diquinoxalano[2,3-a:2',3'-c]phenazine-2,8,14-trimethyltrithioetheryl)tripropionic acid.

[0023] The method for synthesizing HATN-HSPA includes the following steps: Step 1: 10 mmol of cyclohexanehexaone octahydrate and 30 mmol of 4,5-dichloro-1,2-phenylenediamine were added to 600 mL of glacial acetic acid and anhydrous ethanol solution to obtain a mixture. The mixture was refluxed and stirred at 140 °C for 24 hours under N2 protection and at a stirring speed of 500 rpm. The volume ratio of glacial acetic acid to anhydrous ethanol was 1:1. Step 2: After the mixture after reflux and stirring has cooled to room temperature, the mixture is filtered with a sand core filter and washed three times in sequence with glacial acetic acid, deionized water and anhydrous ethanol. The product is dried in a vacuum oven at 60°C to obtain a green solid precursor. Step 3: Add the green solid precursor to 400 mL of 30% nitric acid. Reflux the mixture at 140°C for 3 hours with a stirring speed of 500 rpm. Step 4: After cooling to room temperature, the mixture was filtered using a sand filter and washed three times with deionized water and anhydrous ethanol to obtain the yellow-green intermediate 2,3,8,9,14,15-hexachlorodiquinoxalino[2,3-a:2',3'-c]phenazine, i.e., HATN-HC; Step 5: Add 2 mmol HATN-HC, 38.4 mmol potassium tert-butoxide, 14.4 mmol mercaptopropionic acid, 3 mmol manganese dioxide and 0.06 mmol 15-crown ether-5 to 100 mL of anhydrous ethanol to obtain a mixed solution. The mixed solution is stirred at 70 °C under N2 protection for 24 hours at a stirring speed of 500 rpm. Step 6: After the mixed solution has cooled to room temperature, add 100 mL of deionized water to the mixed solution and stir the mixture evenly at a speed of 500 rpm. Then, remove insoluble impurities by centrifugation and filtration to obtain the supernatant. Centrifuge at a speed of 5000 rpm and filter the mixture using a sand core filter. Step 7: Acidify the supernatant with 2 M HCl. After centrifugation, filtration and washing with 0.1 M dilute HCl, the precipitate is dried in a vacuum oven at 60°C to constant weight to obtain a black-green solid HATN-HSPA. The centrifugation speed is 5000 rpm. The mixture is filtered using a sand core filter.

[0024] In the first step, the mass ratio of cyclohexanehexane octhydrate to 4,5-dichloro-1,2-phenylenediamine is cyclohexanehexane octhydrate: 4,5-dichloro-1,2-phenylenediamine = 3.13: 5.35.

[0025] The method for synthesizing HATN-TSPA includes the following steps: Step 1: 10 mmol of cyclohexanehexaone octahydrate and 30 mmol of 4-chloro-1,2-phenylenediamine were added to 600 mL of glacial acetic acid and anhydrous ethanol solution to obtain a mixture. The mixture was refluxed and stirred at 140 °C for 24 hours under N2 protection and at a stirring speed of 500 rpm. The volume ratio of glacial acetic acid to anhydrous ethanol was 1:1. Step 2: After the mixture after reflux and stirring has cooled to room temperature, the mixture is filtered with a sand core filter and washed three times in sequence with glacial acetic acid, deionized water and anhydrous ethanol. The product is dried in a vacuum oven at 60°C to obtain a green solid precursor. Step 3: Add the green solid precursor to 400 mL of 30% nitric acid. Reflux the mixture at 140°C for 3 hours with a stirring speed of 500 rpm. Step 4: After cooling to room temperature, the mixture is filtered using a sand filter and washed three times with deionized water and anhydrous ethanol to obtain the yellow-green intermediate 2,8,14-trichlorodiquinoxalino[2,3-a:2',3'-c]phenazine, i.e., HATN-TC; Step 5: Add 2 mmol HATN-HC, 38.4 mmol potassium tert-butoxide, 14.4 mmol mercaptopropionic acid, 3 mmol manganese dioxide and 0.06 mmol 15-crown ether-5 to 100 mL of anhydrous ethanol to obtain a mixed solution. The mixed solution is stirred at 70 °C under N2 protection for 24 hours at a stirring speed of 500 rpm. Step 6: After the mixed solution has cooled to room temperature, add 100 mL of deionized water to the mixed solution and stir the mixture evenly at a speed of 500 rpm. Then, remove insoluble impurities by centrifugation and filtration to obtain the supernatant. Centrifuge at a speed of 5000 rpm and filter the mixture using a sand core filter. Step 7: Acidify the supernatant with 2 M HCl. After centrifugation, filtration and washing with 0.1 M dilute HCl, the precipitate is dried in a vacuum oven at 60°C to constant weight to obtain a black-green solid HATN-TSPA. The centrifugation speed is 5000 rpm. The mixture is filtered using a sand filter.

[0026] In the first step, the mass ratio of cyclohexanehexane octhydrate to 4-chloro-1,2-phenylenediamine is cyclohexanehexane octhydrate: 4-chloro-1,2-phenylenediamine = 3.13: 4.28.

[0027] The synthetic route for the multi-electron-transfer polynuclear quinoxaline derivative HATN-HSPA is as follows: .

[0028] The synthetic route for the multi-electron-transfer polynuclear quinoxaline derivative HATN-TSPA is as follows: .

[0029] Figure 1 and Figure 2 The images show the 1H NMR spectra of HATN-HSPA and HATN-TSPA.

[0030] The application of two quinoxaline derivatives in aqueous flow batteries, wherein the aqueous flow battery is an alkaline aqueous organic flow battery.

[0031] Example 2, Solubility test of HATN-HSPA and HATN-TSPA: Standard concentrations of HATN-HSPA and HATN-TSPA solutions dissolved in 1.0 M KOH solution were prepared using a 10 mL graduated cylinder. The absorbance of these solutions was measured at 0.2 nm intervals within the wavelength range of 250 to 700 nm using a UV-Vis spectrophotometer. Concentration curves of the standard solutions were plotted based on the absorbance at their highest absorption peaks. Saturated solutions were prepared by stepwise addition of HATN-HSPA and HATN-TSPA solids to 1.0 mL of 1.0 M KOH solution followed by sonication until a small amount of precipitate appeared. Then, 100 μL of the saturated solution was pipetted and diluted to the appropriate factor using 1.0 M KOH solution. The maximum solubility of the solution was determined by plotting UV-Vis absorbance versus concentration.

[0032] like Figure 3 As shown, the solubility of HATN-HSPA and HATN-TSPA in 1.0 M KOH solution was tested by UV-Vis absorption spectroscopy. The solubilities of HATN-HSPA and HATN-TSPA were 1.26 M and 0.48 M, respectively. Figure 3 a and Figure 3 In Figure b, the UV-Vis absorption spectra of HATN-HSPA and HATN-TSPA at different concentrations in 1.0 M KOH are shown. Figure 3 c and Figure 3 In the figure, d represents the absorbance versus concentration fitting plot of HATN-HSPA and HATN-TSPA solutions.

[0033] Example 3: Based on Example 1, this example tests the electrochemical performance of HATN-HSPA and HATN-TSPA, as follows: Electrochemical parameters were measured using an electrochemical workstation. A three-electrode configuration was used for CV testing: a 3 mm diameter glassy carbon electrode as the working electrode, a saturated Ag / AgCl electrode as the reference electrode, and a platinum electrode as the counter electrode. The test solutions were 4 mM HATN-HSPA, HATN-TSPA, and 1 M KOH solutions of K₄Fe(CN)₆.

[0034] like Figure 4 As shown, the redox properties of HATN-HSPA, HATN-TSPA, and K4Fe(CN)6 in 1.0 MkOH solution were tested by cyclic voltammetry. Figure 4Cyclic voltammetry curves of HATN-HSPA, HATN-TSPA, and K4Fe(CN)6 in 1.0 M KOH solution are shown. The oxygen reduction potentials of HATN-HSPA, HATN-TSPA, and K4Fe(CN)6 are also shown. vs. The Ag / AgCl electrodes were -0.96 / -0.69, -0.92 / -0.66, and 0.29 V, respectively. Differential pulse voltammetry curves confirmed that HATN-HSPA and HATN-TSPA achieved six-electron transfer through a three-step redox process.

[0035] Flow battery performance testing: 1. By using 25 mA·cm under different charging states -2 The battery was charged at a specific current density and allowed to rest for 30 seconds before recording the OCV and measuring the SOC curve. The battery was charged to 100% SOC while maintaining a voltage of 1.7 V. Polarization curves were obtained using LSV at 25 mV·s at 20%, 50%, and 100% SOC. -1 The scan rate was measured.

[0036] 2. For the constant current cycling test of 0.1 M HATN-HSPA and HATN-TSPA, the negative electrode electrolyte was 0.04 M HATN-HSPA or HATN-TSPA dissolved in 5 mL of 1.0 M KOH solution, and the positive electrode electrolyte was 0.2 M K4Fe(CN)6 dissolved in 15.0 mL of 1.0 M KOH solution. The constant current cycling was performed at 25 mA·cm⁻¹ between 1.7 V and 0.5 V. -2 The constant current was used to conduct cyclic testing of the flow battery.

[0037] 3. For the constant current-constant voltage charge-discharge test of 0.1 M HATN-HSPA and HATN-TSPA in 1.0 M KOH solution, at 25 mA·cm⁻¹ -2 The current density is charged to 1.7V, and then this voltage is maintained until the current density drops to 5mA·cm. -2 It is then discharged to 0.5 V and maintained at that voltage until the current density drops to 5 mA·cm⁻¹. -2 .

[0038] 4. For the constant current cycling test of 0.5 M HATN-HSPA, the negative electrode electrolyte was 0.5 M HATN-HSPA dissolved in 4 mL of 1.0 M KOH solution, and the positive electrode electrolyte was 0.4 M K₄Fe(CN)₆ dissolved in 200.0 mL of 1.0 M KOH solution. The constant current cycling was performed at 25 mA·cm⁻¹ between 1.7 V and 0.5 V. -2The constant current was used to conduct cyclic testing of the flow battery.

[0039] Performance testing of flow batteries based on HATN-HSPA or HATN-TSPA: a. The constant current charge-discharge cycle (AORFB) of low-concentration HATN-HSPA and HATN-TSPA negative electrolytes, K4Fe(CN)6 positive electrolyte, and PBI membrane was investigated. The negative electrolyte was 0.04 M HATN-HSPA or HATN-TSPA dissolved in 5 mL of 1.0 M KOH solution, and the positive electrolyte was 0.2 M K4Fe(CN)6 dissolved in 15.0 mL of 1.0 M KOH solution. The constant current charge-discharge cycle was investigated at 10 to 60 mA·cm⁻¹. -2 Rate performance was tested within the current density range. Figure 5 a and Figure 5 (b) At 10 mA·cm -2 At that time, the capacities of HATN-HSPA||K4Fe(CN)6 and HATN-TSPA||K4Fe(CN)6 were 5.92 and 5.91 Ah·L, respectively. -1 The capacity utilization rates were 92.1% and 91.9%, respectively. As the current density increased, the energy density and capacity utilization rate of the battery decreased. When the current density reached 50 mA·cm⁻¹... -2 At that time, the capacity utilization rates of 0.1 M HATN-HSPA||K4Fe(CN)6 and HATN-TSPA||K4Fe(CN)6 AORFB were 62.5% and 61.9%, respectively, with corresponding energy efficiency values ​​of 59.8% and 54.8%.

[0040] b. At 25 mA cm -2 At the specified current density, the battery was cycled 1200 times in constant current mode. Figure 5 c and Figure 5 As shown in Figure d, the discharge capacity of AORFB for HATN-HSPA||K4Fe(CN)6 and HATN-TSPA||K4Fe(CN)6 remained essentially unchanged, demonstrating good capacity retention. Subsequently, 800 cycles of constant current-voltage constant voltage charge-discharge mode were performed at the same current density. During charging, the potential was maintained at 1.7 V until the current density dropped to 5 mA·cm⁻¹. -2 Similarly, the potential remains at 0.5 V during discharge until the current density drops to 5 mA·cm⁻¹. -2These conditions can induce near 100% redox activity in organic active molecules, thus aiding in the study of their electrochemical stability during complete charge-discharge processes. After 800 cycles, the AORFB capacity of HATN-HSPA||K4Fe(CN)6 and HATN-TSPA||K4Fe(CN)6 showed no significant decay.

[0041] like Figure 5 The diagram shows the electrochemical performance of AORFB for 0.1 M HATN-HSPA||K4Fe(CN)6 and HATN-TSPA||K4Fe(CN)6. Figure 5 a and Figure 5 In the figure, b represents the coulombic efficiency, energy efficiency, and discharge capacity of 0.1 M HATN-HSPA||K4Fe(CN)6 and HATN-TSPA||K4Fe(CN)6 at different current densities. Figure 5 The AORFB constant current and constant current constant voltage cycling performance of HATN-HSPA||K4Fe(CN)6 with c = 0.1 M was evaluated. Figure 5 The AORFB constant current and constant current-constant voltage cycling performance of HATN-TSPA||K4Fe(CN)6 with d=0.1 M was evaluated.

[0042] Figure 6 In Figure 'a', the charge-discharge curves of AORFB of 0.5 M HATN-HSPA||K4Fe(CN)6 under different current densities are shown. Figure 6 In the figure, b represents the rate performance corresponding to HATN-HSPA||K4Fe(CN)6. Figure 6 In the figure, c represents the OCV value of HATN-HSPA||K4Fe(CN)6AORFB under different SOCs. Figure 6 d is at 25 mA·cm -2 Long-term constant current cycling performance of 0.5 M HATN-HSPA||K4Fe(CN)6 AORFB. Figure 6 In the middle, e represents 20 mA·cm -2 Long-term constant current cycling performance of 1.26 M HATN-HSPA||K4Fe(CN)6 AORFB.

[0043] like Figure 6 As shown, considering practical applications, this patent also investigated the electrochemical performance of 0.5 M HATN-HSPA||K4Fe(CN)6AORFB. For example... Figure 6 a and Figure 6 As shown in Figure b, at 20, 30, 40, 50, 60 and 80 mA·cm -2The rate performance of high-concentration HATN-HSPA||K4Fe(CN)6AORFB was measured at a current density of [value missing]. As the current density increased from 20 to 80 mA·cm⁻¹, [the following data was obtained]. -2 The capacity decreased from 53.89 to 43.95 Ah·L. -1 The energy density decreased from 85.35% to 63.21%. This result highlights the excellent rate performance of HATN-HSPA||K4Fe(CN)6 AORFB and verifies its great application potential in high-power energy storage scenarios. Figure 6 As shown in Figure c, the polarization curve and power density of 1.0 M HATN-HSPA||K4Fe(CN)6AORFB were obtained by linear sweep voltammetry. At 100% SOC, the peak power density was 253 mW·cm⁻¹. -2 .

[0044] like Figure 6 As shown in d, at 25 mA·cm -2 The constant-current cycling stability of 0.5 M high-concentration HATN-HSPA||K4Fe(CN)6 AORFB was tested at a current density. The capacity stabilized at 74.92 Ah·L⁻¹ during 600 cycles (60 days). -1 The corresponding capacity decay rate is 0.003% / cycle or 0.03% / day. For example... Figure 6 As shown in Figure e, the cycling performance of the HATN-HSPA negative electrode electrolyte with a near-saturation concentration (1.26 M) was tested at 20 mA cm⁻¹. -2 Under the given current density conditions, the 1.26 M HATN-HSPA||K4Fe(CN)6 AORFB exhibits excellent capacity performance. After 50 cycles (equivalent to 25 days), the capacity of the AORFB reaches 150 Ah L. -1 (187.5 Wh L) -1 The capacity retention rate is as high as 99.5%, corresponding to a daily capacity decay rate of only 0.02%.

[0045] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained in this invention are implemented according to conventional methods in the art unless otherwise specified or limited.

Claims

1. A polynuclear quinoxaline derivative with multi-electron transfer, characterized in that, The multi-electron-transfer polynuclear quinoxaline derivative is a mercaptopropionic acid-modified quinoxaline HATN-HSPA or HATN-TSPA, and the structural formula of the mercaptopropionic acid-modified quinoxaline HATN-HSPA or HATN-TSPA is as follows: 。 2. The polynuclear quinoxaline derivative with multi-electron transfer according to claim 1, characterized in that, The mercaptopropionic acid-modified quinoxaline HATN-HSPA or HATN-TSPA is specifically: 3,3',3'',3''',3'''',3'''''-(diquinoxalano[2,3-a:2',3'-c]phenazine-2,3,8,9,14,15-hexylhexathioetheryl)hexapropionic acid or 3,3',3''-(diquinoxalano[2,3-a:2',3'-c]phenazine-2,8,14-trimethyltrithioetheryl)tripropionic acid.

3. A method for synthesizing the polynuclear quinoxaline derivative with multi-electron transfer as described in claim 1, characterized in that, The method for synthesizing HATN-HSPA includes the following steps: Step 1: 10 mmol of cyclohexanehexaone octahydrate and 30 mmol of 4,5-dichloro-1,2-phenylenediamine were added to 600 mL of glacial acetic acid and anhydrous ethanol solution to obtain a mixture. The mixture was refluxed and stirred at 140 °C for 24 hours under N2 protection and at a stirring speed of 500 rpm. The volume ratio of glacial acetic acid to anhydrous ethanol was 1:

1. Step 2: After the mixture after reflux and stirring has cooled to room temperature, the mixture is filtered with a sand core filter and washed three times in sequence with glacial acetic acid, deionized water and anhydrous ethanol. The product is dried in a vacuum oven at 60°C to obtain a green solid precursor. Step 3: Add the green solid precursor to 400 mL of 30% nitric acid. Reflux the mixture at 140°C for 3 hours with a stirring speed of 500 rpm. Step 4: After cooling to room temperature, the mixture was filtered using a sand core filter and washed three times with deionized water and anhydrous ethanol in sequence to obtain the yellow-green intermediate 2,3,8,9,14,15-hexachlorodiquinoxalino[2,3-a:2',3'-c]phenazine, i.e., HATN-HC; Step 5: Add 2 mmol HATN-HC, 38.4 mmol potassium tert-butoxide, 14.4 mmol mercaptopropionic acid, 3 mmol manganese dioxide and 0.06 mmol 15-crown ether-5 to 100 mL of anhydrous ethanol to obtain a mixed solution. The mixed solution is stirred at 70 °C under N2 protection for 24 hours at a stirring speed of 500 rpm. Step 6: After the mixed solution has cooled to room temperature, add 100 mL of deionized water to the mixed solution and stir the mixture evenly at a speed of 500 rpm. Then, remove insoluble impurities by centrifugation and filtration to obtain the supernatant. Centrifuge at a speed of 5000 rpm and filter the mixture using a sand core filter. Step 7: Acidify the supernatant with 2 M HCl. After centrifugation, filtration and washing with 0.1 M dilute HCl, the precipitate is dried in a vacuum oven at 60°C to constant weight to obtain a black-green solid HATN-HSPA. The centrifugation speed is 5000 rpm. The mixture is filtered using a sand core filter.

4. The method for synthesizing polynuclear quinoxaline derivatives with multi-electron transfer according to claim 3, characterized in that, The method for synthesizing HATN-TSPA includes the following steps: Step 1: 10 mmol of cyclohexanehexaone octahydrate and 30 mmol of 4-chloro-1,2-phenylenediamine were added to 600 mL of glacial acetic acid and anhydrous ethanol solution to obtain a mixture. The mixture was refluxed and stirred at 140 °C for 24 hours under N2 protection and at a stirring speed of 500 rpm. The volume ratio of glacial acetic acid to anhydrous ethanol was 1:

1. Step 2: After the mixture after reflux and stirring has cooled to room temperature, the mixture is filtered with a sand core filter and washed three times in sequence with glacial acetic acid, deionized water and anhydrous ethanol. The product is dried in a vacuum oven at 60°C to obtain a green solid precursor. Step 3: Add the green solid precursor to 400 mL of 30% nitric acid. Reflux the mixture at 140°C for 3 hours with a stirring speed of 500 rpm. Step 4: After cooling to room temperature, the mixture is filtered using a sand filter and washed three times with deionized water and anhydrous ethanol to obtain the yellow-green intermediate 2,8,14-trichlorodiquinoxalino[2,3-a:2',3'-c]phenazine, i.e., HATN-TC; Step 5: Add 2 mmol HATN-TC, 38.4 mmol potassium tert-butoxide, 14.4 mmol mercaptopropionic acid, 3 mmol manganese dioxide and 0.06 mmol 15-crown ether-5 to 100 mL of anhydrous ethanol to obtain a mixed solution. The mixed solution is stirred at 70 °C under N2 protection for 24 hours at a stirring speed of 500 rpm. Step 6: After the mixed solution has cooled to room temperature, add 100 mL of deionized water to the mixed solution and stir the mixture evenly at a speed of 500 rpm. Then, remove insoluble impurities by centrifugation and filtration to obtain the supernatant. Centrifuge at a speed of 5000 rpm and filter the mixture using a sand core filter. Step 7: Acidify the supernatant with 2 M HCl. After centrifugation, filtration and washing with 0.1 M dilute HCl, the precipitate is dried in a vacuum oven at 60°C to constant weight to obtain a black-green solid HATN-TSPA. The centrifugation speed is 5000 rpm. The mixture is filtered using a sand filter.

5. The method for synthesizing polynuclear quinoxaline derivatives with multi-electron transfer according to claim 3, characterized in that, The synthetic route for the multi-electron-transfer polynuclear quinoxaline derivative HATN-HSPA is as follows: 。 6. The method for synthesizing polynuclear quinoxaline derivatives with multi-electron transfer according to claim 4, characterized in that, The synthetic route for the multi-electron-transfer polynuclear quinoxaline derivative HATN-TSPA is as follows: 。 7. The method for synthesizing polynuclear quinoxaline derivatives with multi-electron transfer according to claim 3, characterized in that, In the first step, the mass ratio of cyclohexanehexane octhydrate to 4,5-dichloro-1,2-phenylenediamine is cyclohexanehexane octhydrate: 4,5-dichloro-1,2-phenylenediamine = 3.13: 5.

35.

8. The method for synthesizing polynuclear quinoxaline derivatives with multi-electron transfer according to claim 4, characterized in that, In the first step, the mass ratio of cyclohexanehexane octhydrate to 4-chloro-1,2-phenylenediamine is cyclohexanehexane octhydrate: 4-chloro-1,2-phenylenediamine = 3.13: 4.

28.

9. The application of a multi-electron-transfer polynuclear quinoxaline derivative as described in claim 1 or 2 in an aqueous flow battery.

10. The application according to claim 9, characterized in that, The aqueous flow battery is an alkaline aqueous organic flow battery.

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