Preparation method of high-activity foamy copper electrode for catalyzing aqueous flow battery
By subjecting copper foam to alcohol washing, acid washing, and electrochemical reconstruction, its surface crystal planes are controlled to be (100) or (110) crystal planes, which solves the problems of conductivity and charge transfer kinetics of copper-based catalysts in aqueous redox flow batteries, improves battery performance, and simplifies the processing.
Patent Information
- Application Number
- CN202510891677.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-30
- Publication Date
- 2025-10-28
AI Technical Summary
Existing copper-based catalysts suffer from poor conductivity and slow charge transfer kinetics in aqueous redox flow batteries, resulting in poor battery performance. Furthermore, existing processing methods are complex and difficult to preserve.
After alcohol washing, acid washing and ultrasonic treatment of copper foam, electrochemical reconstruction was carried out in sodium formate solution to adjust its surface crystal plane to (100) or (110) crystal plane, and a highly active catalytic electrode was prepared and applied to benzo[a]hydroxyphenazine-7/8-carboxylic acid/BHPC/K4[Fe(CN)6] aqueous organic flow battery.
It significantly improves the power density, energy efficiency, and capacity utilization of aqueous organic flow batteries, and is easy to operate and inexpensive, showing good prospects for industrial application.
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Figure CN120854571A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of new energy materials, specifically relating to a method for preparing a highly active foamed copper electrode for catalytic aqueous flow batteries. Background Technology
[0002] With population growth and the continuous consumption of fossil fuels, energy crises and environmental problems are becoming increasingly prominent. Renewable energy sources, such as solar, tidal, and wind power, offer significant opportunities to alleviate the potential energy crisis. However, the inherent intermittency of these renewable energy sources, influenced by weather and geographical conditions, poses a major challenge to grid operators. To buffer the impact of intermittency and improve grid quality, it is necessary to develop low-cost, large-scale energy storage systems.
[0003] Among various energy storage methods, redox flow batteries have been widely recognized as the only suitable energy storage device with low cost, high efficiency, and long cycle life. The key difference between redox flow batteries and other secondary batteries lies in their ability to flexibly design and scale up the electrolyte independently of electrochemical batteries, thereby achieving energy and power separation. Therefore, redox flow batteries can be easily scaled up to meet specific energy storage needs. Aqueous redox flow batteries, using water as a solvent, offer even higher safety and lower cost characteristics.
[0004] Phenrazine possesses high solubility, low redox potential, and two-electron transfer capability, along with a stable molecular structure. Therefore, phenrazine is considered one of the most promising core structures for organic anode electrolytes in aqueous redox flow batteries. However, compared to organic active molecules such as viologen, phenrazine exhibits slower charge transfer kinetics, resulting in poorer rate performance and efficiency.
[0005] As a key component of ARFBs (Advanced ARFBs), electrodes affect the ohmic polarization of the battery through their conductivity, and the electrochemical polarization of the battery is closely related to the active sites of the electrodes, thus directly influencing the battery's performance. Therefore, ideal electrode materials should possess high conductivity, abundant active sites, high chemical stability, and low cost.
[0006] Copper possesses excellent catalytic activity, high electrical conductivity, low resistivity, and significant stability, making it a promising catalytic material for redox processes. In recent years, considerable effort has been made to overcome the poor selectivity of copper-based catalysts, including methods such as interactions with second metals and heteroatom doping. However, these designs are complex, difficult to operate, and the prepared samples are not easily preserved. Therefore, developing a simple and efficient surface treatment method for copper-based materials is currently the main approach to solving the technical challenges of copper in industrial production. Summary of the Invention
[0007] This invention aims to improve the power density, energy efficiency and capacity utilization of BHPC-based aqueous organic flow batteries by constructing a catalytic electrode with high (100) and (110) crystal plane orientation through sodium formate modification of copper foam.
[0008] Specifically, the present invention provides an electrochemical treatment method for controlling the crystal surface of copper foam. This method uses pretreated copper foam as a catalytic electrode after electrochemical reconstruction in sodium formate solution, and applies it to a BHPC / / K4[Fe(CN)6] aqueous organic flow battery.
[0009] The electrocatalytic electrode of this invention is a three-electrode system, in which pretreated copper foam is used as the working electrode, a saturated calomel electrode is used as the reference electrode, and a platinum sheet electrode or a graphite electrode is used as the counter electrode. Cyclic voltammetry (CV) scanning is performed in sodium formate solution to obtain the catalytic electrode.
[0010] The specific steps of the pretreatment are as follows: the foamed copper is first subjected to alcohol washing and acid washing and ultrasonic treatment, and finally rinsed with ultrapure water and dried in a non-reactive atmosphere.
[0011] The alcohol used in alcohol washing is selected from at least one of isopropanol, ethanol, and methanol.
[0012] The acid used for pickling is selected from at least one of hydrochloric acid, sulfuric acid, and nitric acid, and the concentration of the acid solution is 1–3 mol / L.
[0013] The treatment conditions are as follows: first, soak the copper foam in alcohol and sonicate for 5-10 minutes, and then soak it in acid and sonicate for 5-10 minutes.
[0014] The gas in the inactive atmosphere is selected from at least one of nitrogen, argon, and hydrogen.
[0015] The purpose of electrochemical reconstruction is to reconstruct the surface of copper foam, transforming it from the original (111) crystal plane to at least partially (100) or (110) crystal plane, thereby improving the electrocatalytic performance of copper foam as a catalytic electrode.
[0016] When electrochemical reconstruction is performed using cyclic voltammetry, the preferred number of scan cycles is 2 to 10.
[0017] The concentration of the sodium formate solution used for electrochemical reconstruction is preferably any value in the range of 0.5 wt.% to 10 wt.% or between two values.
[0018] The preferred pH value for sodium formate used in electrochemical reconstruction is any value between 9 and 12 or a range between two values.
[0019] The above electrodes are used to prepare aqueous organic flow batteries. The negative electrode of the flow battery is a foamed copper electrode treated with sodium formate, and the positive electrode is a carbon felt electrode. The negative electrode active material of the flow battery is benzo[a]hydroxyphenazine-7 / 8-carboxylic acid (BHPC), and the positive electrode active material is potassium ferrocyanide K4[Fe(CN)6].
[0020] The redox active electrolytes for the positive and negative electrodes of the flow battery are stored in corresponding external storage tanks. The electrolytes circulate between the storage tanks and the flow battery via a peristaltic pump and undergo redox reactions as they flow over the surfaces of the positive and negative electrodes. The redox active electrolytes for the positive and negative electrodes are separated by a cation exchange membrane.
[0021] The negative and positive electrode active materials are dissolved in an alkaline aqueous solution containing 1 mol / L potassium hydroxide; the supporting electrolyte is 0.95 mol / L potassium chloride.
[0022] The beneficial effects of this invention are as follows: Treating copper foam with sodium formate promotes the formation of more (110) or (100) crystal planes, significantly improving the charge transfer kinetics of benzo[a]hydroxyphenazine-7 / 8-carboxylic acid (BHPC), the negative electrode active material in aqueous organic flow batteries, on the material surface. This effectively improves the power density, energy efficiency, and capacity utilization of BHPC-based aqueous organic flow batteries. Furthermore, this treatment method is simple to operate, low in cost, and has good prospects for industrial application. Attached Figure Description
[0023] Figure 1 The image shows a scanning electron microscope (SEM) image of a copper foam electrode obtained in Example 1 after treatment with cyclic voltammetry in a 1 wt.% sodium formate solution.
[0024] Figure 2 The XRD patterns are of the copper foam electrode in Comparative Example 1 that was not treated with sodium formate and the copper foam electrode in Example 1 that was treated with cyclic voltammetry in a 1 wt.% sodium formate solution.
[0025] Figure 3 The image shows a comparison of the copper foam electrode obtained in Example 1 after treatment with cyclic voltammetry in a 1 wt.% sodium formate solution for catalyzing the phenazine compound BHPC, with a scan rate of 25 mV / s.
[0026] Figure 4 The image shows a comparison of different numbers of cyclic voltammetry cycles performed in 1 wt.% sodium formate solution for catalyzing the phenazine compound BHPC using a foamed copper electrode in Example 1, with a scan rate of 25 V / s.
[0027] Figure 5The image shows the CV curves of the copper foam electrode obtained in Example 2 after 8 cycles of cyclic voltammetry in 5 wt.% sodium formate solutions at different pH values in 2 mmol / L BHPC and 1 mol / L KOH solutions, with a scan rate of 25 mV / s.
[0028] Figure 6 The figures for Example 2 are cyclic voltammograms of a copper foam electrode obtained after 8 cycles of cyclic voltammetry treatment in KHCO3 solution at different scan rates, using a 5wt% sodium formate solution at pH 10. The figures show (a) cyclic voltammograms and (b) graphs showing the relationship between current and scan rate at the median potential of the copper foam electrode obtained after cyclic voltammetry treatment in KHCO3 solution.
[0029] Figure 7 The image shows the CV curves of the foamed copper electrode obtained in Example 3 under the condition of scanning 8 times in a sodium formate solution with pH=10, with different mass fractions of sodium formate solution, in 2 mmol / L BHPC and 1 mol / L KOH solution, with a scan rate of 25 mV / s.
[0030] Figure 8 The CA curves of 1mM BHPC and 1mM BHPCH2 solutions dissolved in 1M KOH in Example 3 are shown at different overpotentials on (a) the original copper foam and (b) the Cuf-5wt% electrode. The entire experiment was conducted under nitrogen protection. (c) shows the relationship between the extrapolated absolute current value and the overpotential on the chronocurrent CA curves of the original copper foam electrode and (d) the Cuf-5wt% electrode at t=0s.
[0031] Figure 9 Comparative Examples 1 and 4, for the original foamed copper and CuF-5wt% electrodes, were tested at a current density of 80 mA / cm². 2 The following parameters are used to determine the (A) energy efficiency, coulombic efficiency, and (B) discharge capacity during the cycling process.
[0032] Figure 10 This is a cyclic voltammogram of the untreated copper foam electrode from Comparative Example 1 in a phenazine compound BHPC solution.
[0033] Figure 11 This is a scanning electron microscope (SEM) image of the copper foam electrode in Comparative Example 2 after being immersed in sodium formate solution.
[0034] Figure 12 (A) is the cyclic voltammogram of the copper foam electrode in KHCO3 solution at different scan rates in Comparative Example 2, and (B) is the corresponding current and scan rate graph.
[0035] Figure 13This is a cyclic voltammogram of a copper foam electrode treated with sodium formate in Comparative Example 2 in a phenazine compound BHPC solution. Detailed Implementation
[0036] The present invention will now be described in detail with reference to specific embodiments.
[0037] Example 1: Catalysis of phenazine compound BHPC by a foamed copper electrode obtained after treatment with cyclic voltammetry in a 1 wt.% sodium formate solution;
[0038] (1) A copper foam-based catalytic electrode was prepared in a 1 wt.% sodium formate solution at pH = 10 using cyclic voltammetry.
[0039] Take 1x1cm 2 Copper foam (thickness: 20 μm) was ultrasonically treated for 5 min in ethanol and 1 mol / L dilute hydrochloric acid solutions to remove surface organic matter and oxides. It was then washed with ultrapure water (until the copper electrode surface became shiny) and dried with nitrogen. A CHI660E electrochemical workstation was used as the electrochemical treatment device. The pretreated copper foam was used as the working electrode, a saturated calomel electrode as the reference electrode, and a platinum sheet electrode as the counter electrode, forming a three-electrode system. A 1 wt.% sodium formate aqueous solution was used as the electrolyte solution, with a pH of 10. Cyclic voltammetry was employed (scan rate: 10 mV / s, scan range: ...).
[0040] Scan the copper foil surface 2-10 times at room temperature (-1 to 0.5V), then clean the foamed copper surface again and dry it with nitrogen.
[0041] (2) Electrochemical performance of copper-based catalytic electrodes for BHPC was prepared using cyclic voltammetry in a 1 wt.% sodium formate solution at pH = 10.
[0042] The copper foam prepared by the cyclic voltammetry method described above was used as the working electrode, the mercury / mercury oxide electrode (MMO) as the reference electrode, and the graphite electrode as the counter electrode. The electrochemical performance was tested in a three-electrode system. The entire electrochemical test was conducted under nitrogen protection. The electrolyte used was a mixed solution of 2 mmol / L BHPC and 1 mol / L KOH.
[0043] Figure 1 This is a scanning electron microscope (SEM) image of a copper foam electrode obtained after treatment with cyclic voltammetry in a 1 wt.% sodium formate solution. The high surface roughness of the copper foam electrode is beneficial for increasing the contact area between the copper electrode and the phenazine compound.
[0044] Figure 2The image shows the XRD pattern of a copper foam electrode obtained after cyclic voltammetry treatment in a 1 wt.% sodium formate solution. As can be seen from the image, the copper foam modified by cyclic voltammetry in sodium formate solution exhibits high (100) and (110) crystal plane orientations. Simultaneously, the increased full width at half maximum (FWHM) of the peaks after cyclic voltammetry treatment in sodium formate solution indicates a decrease in crystal size and an increase in roughness, suggesting that formate-induced surface reconstruction of the copper foam.
[0045] Figure 3 The image shows a comparison of copper foam electrodes treated with cyclic voltammetry in a 1 wt% sodium formate solution for catalyzing phenazine compound BHPC, with a scan rate of 25 mV / s. The electrochemically treated copper foam exhibits an oxidation potential of -0.89 V, a reduction potential of -0.96 V, a potential difference of 0.07 V, and a current density of 4 mA / cm². 2 The efficiency was twice that of the untreated copper foam (the copper foam electrode in Comparative Example 2, which was only immersed in sodium formate), and it effectively improved the transfer kinetics of BHPC on the electrode surface, which confirms the superiority of using electrochemical treatment of copper foam electrodes in sodium formate solution.
[0046] Figure 4 The figure shows a comparison of different numbers of cyclic voltammetry cycles performed in a 1 wt.% sodium formate solution for catalyzing phenazine compound BHPC using a copper foam electrode. The scan rate was 25 mV / s. As can be seen from the figure, the catalytic current reached its maximum of 4.8 mA / cm² after 8 cycles of cyclic voltammetry in the sodium formate solution using the copper foam electrode. 2 .
[0047] Example 2: Catalysis of phenazine compound BHPC by copper foam electrodes obtained after cyclic voltammetry treatment in 5 wt.% sodium formate solutions at different pH values;
[0048] (1) Preparation of copper foam-based catalytic electrode in sodium formate solution at pH=9
[0049] Take 1x1cm 2 Copper foam (thickness: 20 μm) was ultrasonically treated for 5 min in ethanol and 1 mol / L dilute hydrochloric acid solutions to remove surface organic matter and oxides. After washing with ultrapure water, it was dried under nitrogen. A CHI660E electrochemical workstation was used as the electrochemical treatment device. The pretreated copper foam was used as the working electrode, a saturated calomel electrode as the reference electrode, and a platinum sheet electrode as the counter electrode, forming a three-electrode system. A 5 wt% sodium formate aqueous solution was used as the electrolyte solution, with a pH of 9. Cyclic voltammetry (scan rate: 10 mV / s, scan range: -1 to 0.5 V) was used to scan the copper foil surface 8 times at room temperature. After treatment, the copper foam surface was washed again and dried under nitrogen.
[0050] (2) Preparation of copper foam-based catalytic electrode in sodium formate solution at pH=10
[0051] The pH of the electrolyte solution sodium formate aqueous solution was adjusted to 10, and the rest was the same as in Example 2(1).
[0052] (3) Preparation of copper-based catalytic electrodes in sodium formate solution at pH=11
[0053] The pH of the electrolyte solution sodium formate aqueous solution was adjusted to 11, and the rest was the same as in Example 2(1).
[0054] (4) Preparation of copper-based catalytic electrodes in sodium formate solution at pH=12
[0055] The pH of the electrolyte solution sodium formate aqueous solution was adjusted to 12, and the rest was the same as in Example 2(1).
[0056] The copper foam prepared by the cyclic voltammetry method described above was used as the working electrode, the mercury / mercury oxide electrode (MMO) as the reference electrode, and the graphite electrode as the counter electrode. The electrochemical performance was tested in a three-electrode system. The entire electrochemical test was conducted under nitrogen protection. The electrolyte used was a mixed solution of 2 mmol / L BHPC and 1 mol / L KOH.
[0057] Figure 5 The CV plots of the copper foam electrode obtained after 8 cycles of cyclic voltammetry treatment in 5 wt.% sodium formate solutions at different pH values in 2 mmol / L BHPC and 1 mol / L KOH solutions are shown, with a scan rate of 25 mV / s. It can be seen that, compared to the copper foam electrode in the comparative example that was soaked in sodium formate, the electrochemically treated copper foam electrode exhibits superior electrocatalytic performance for BHPC, and its effect is most significant at pH 10 of the sodium formate solution.
[0058] Figure 6 The figures show the cyclic voltammetry (CV) curves of a copper foam electrode prepared by cyclic voltammetry for 8 cycles in KHCO3 solution at different scan rates, obtained in a 5 wt% sodium formate solution at pH 10. As can be seen from the figures, at a scan rate of 100 mV / s, the area under the CV curve is larger than that of the copper foam electrode prepared by the immersion method alone, with a median current intensity of 0.6 mA and a double-layer capacitance of 6.3 F / cm². 2 Meanwhile, the CV plot is close to an ideal rectangle, indicating that the copper foam electrode obtained after cyclic voltammetry treatment has good capacitance performance.
[0059] Example 3: Catalysis of phenazine compound BHPC by a foamed copper electrode obtained after 8 cycles of cyclic voltammetry in sodium formate solutions of different concentrations at pH 10;
[0060] Take 1x1cm 2 Copper foam (thickness: 20 μm) was ultrasonically treated for 5 min in ethanol and 1 mol / L dilute hydrochloric acid solutions to remove surface organic matter and oxides. After washing with ultrapure water, it was dried under nitrogen. A CHI660E electrochemical workstation was used as the electrochemical treatment device. The pretreated copper foam was used as the working electrode, a saturated calomel electrode as the reference electrode, and a platinum sheet electrode as the counter electrode, forming a three-electrode system. A 0.5 wt.%–10 wt.% sodium formate aqueous solution was used as the electrolyte solution, with a pH of 10. Cyclic voltammetry (scan rate: 10 mV / s, scan range: -1 to 0.5 V) was used to scan the copper foil surface 8 times at room temperature. After treatment, the copper foam surface was washed again and dried under nitrogen.
[0061] The copper foam prepared by the cyclic voltammetry method described above was used as the working electrode, the mercury / mercury oxide electrode (MMO) as the reference electrode, and the graphite electrode as the counter electrode. The electrochemical performance was tested in a three-electrode system. The entire electrochemical test was conducted under nitrogen protection. The electrolyte used was a mixed solution of 2 mmol / L BHPC and 1 mol / L KOH.
[0062] Figure 7 The CV plots of copper foam electrodes obtained by controlling different mass fractions of sodium formate solution in 2 mmol / L BHPC and 1 mol / L KOH solution are shown in the figure. The scan rate was 25 mV / s. The figure shows that the copper foam electrode (Cuf-5wt%) obtained by scanning 8 times in 5.0 wt.% sodium formate solution exhibited the highest catalytic current and the best catalytic effect.
[0063] Figure 8 The CA diagrams of 1mM BHPC and 1mM BHPCH2 solutions dissolved in 1M KOH at different overpotentials are shown on (a) the original copper foam and (b) the Cuf-5wt% electrode. The entire experiment was conducted under nitrogen protection. Figure 8 Extrapolating the obtained CA curves (c and d) to t = 0 s yields the kinetic current I0 corresponding to the applied overpotential. Based on the chronoamperometry method, the exchange current I0 of the BHPC on the Cuf-5wt% electrode is calculated to be 30.72 mA, which is 2.2 times that of the original foamed copper electrode, demonstrating that the electrode treated with sodium formate has significantly improved charge transfer kinetic performance.
[0064] Example 4: Performance of the battery BHPC / / K4[Fe(CN)6] using CuF-5wt% as the catalytic electrode
[0065] Assembly and performance testing of an aqueous organic flow battery: In the battery test system, the catalytic electrode was CuF-5wt%. A 5cm sample was taken. 2 Copper foam was ultrasonically treated for 5 min in ethanol and 1 mol / L dilute hydrochloric acid solutions to remove surface organic matter and oxides. After washing with ultrapure water, it was dried under nitrogen. A CHI660E electrochemical workstation was used as the electrochemical treatment device. The cleaned copper foam was used as the working electrode, a saturated calomel electrode as the reference electrode, and a platinum sheet electrode as the counter electrode, forming a three-electrode system. A 5 wt% sodium formate aqueous solution (pH = 10) was used as the electrolyte solution. Cyclic voltammetry (scan rate: 10 mV / s, scan range: -1 to 0.5 V) was used to scan the copper foil surface 8 times at room temperature. After treatment, the copper foam surface was washed again and dried under nitrogen. The prepared catalytic electrode was used as the negative electrode of a BHPC / / K4[Fe(CN)6] battery.
[0066] BHPC, used as the negative electrode redox active material, was dissolved in 10 mL of a mixed solution of 0.95 mol / L KCl and 1 mol / L KOH to prepare a negative electrode active electrolyte with a concentration of 0.1 mol / L. Commercially available potassium ferrocyanide (0.2 mol / L) and potassium ferricyanide (0.05 mol / L) were dissolved together in 30 mL of 1 mol / L KOH to serve as the positive electrode active electrolyte. A Nafion 212 membrane was used as a separator to separate the positive and negative electrode active electrolytes. The flow rate of the positive and negative electrode active electrolytes was 60 mL / min.
[0067] The aforementioned CuF-5wt% catalytic electrode was used as the negative electrode in the flow battery, and carbon felt as the positive electrode. To prevent the redox active material of the negative electrode from being oxidized by oxygen in the air, the battery was placed in a glove box filled with nitrogen. Battery performance was tested using a Neware battery testing system, with constant current and constant voltage charging and discharging, and a voltage range of 1.0–1.6V.
[0068] Figure 9 The results of BHPC / / K4[Fe(CN)6] cells using CuF-5wt% negative electrode and carbon felt positive electrode respectively at 80 mA / cm are given. 2The following is a 100-cycle charge-discharge diagram, with detailed performance parameters shown in Table 1. The theoretical specific capacity of the negative electrode active electrolyte is 5.36 Ah / L. The efficiency, discharge specific capacity, and material utilization of the battery using the sodium formate-modified foamed copper negative electrode are significantly improved. Specifically, the flow battery using the Cuf-5wt% catalytic negative electrode has a coulombic efficiency of 99.98%, an energy efficiency of 77.0%, a discharge specific capacity of 4.93 Ah / L, and a material utilization of 91.88%, which is far superior to the performance of the flow battery using foamed copper as the negative electrode in comparison. Table 1 shows the BHPC / / K4[Fe(CN)6] battery using Cuf-5wt% as the negative electrode at 80 mA / cm². 2 Performance data for charge and discharge cycles.
[0069] negative electrode CE (%) EE (%) SDC(Ah / L) TC (Ah / L) UR (%) Cuf 99.92 71.75 4.83 5.36 89.80 Cuf-5wt% 99.98 77.0 4.93 5.36 91.88
[0070] Comparative Example 1: Catalysis of phenazine compound BHPC by the unused original foamed copper electrode;
[0071] The original copper foam electrode was placed in a phenazine compound BHPC, with a mercury / mercury oxide (MMO) electrode as the reference electrode and a graphite electrode as the counter electrode. Cyclic voltammetry was used to test its electrochemical performance in a three-electrode system. The entire electrochemical test was conducted under nitrogen protection. The electrolyte used was a mixed solution of 2 mmol / L BHPC and 1 mol / L KOH, and the scan rate was 25 mV / s.
[0072] Figure 10 This is a cyclic voltammogram of the original foamed copper electrode in a phenazine compound BHPC solution. The oxidation potential is -0.75V, the reduction potential is -1.05V, and the potential difference is 0.3V. The peak currents of the oxidation and reduction peaks are small (less than 2mA / cm), and the peak symmetry is weak.
[0073] Comparative Example 2: Catalysis of phenazine compound BHPC by copper foam electrode treated with sodium formate solution immersion
[0074] Take 1x1cm 2 Copper foam (thickness: 20 μm) was ultrasonically treated with ethanol and 1 mol / L dilute hydrochloric acid solution for 5 min to remove surface organic matter and oxides, then washed with ultrapure water and dried with nitrogen. The foam was then soaked in a 5 wt.% sodium formate aqueous solution for 1 hour, and the surface was washed again and dried with nitrogen.
[0075] The copper foam prepared by the cyclic voltammetry method described above was used as the working electrode, the mercury / mercury oxide electrode (MMO) as the reference electrode, and the graphite electrode as the counter electrode. The electrochemical performance was tested in a three-electrode system. The entire electrochemical test was conducted under nitrogen protection. The electrolyte used was a mixed solution of 2 mmol / L BHPC and 1 mol / L KOH.
[0076] Figure 11 This is a scanning electron microscope (SEM) image of a copper foam electrode that has been immersed in sodium formate solution. After immersion in sodium formate, the surface is smooth and some micropores appear.
[0077] Figure 12 The figures show the cyclic voltammetry and corresponding current-scan rate plots of the copper foam electrode in KHCO3 solution at different scan rates. As can be seen from the figures, even at a scan rate of 100 mV / s, the area under the curve in the CV plot is small, the median current intensity is only about 0.012 mA, and the double-layer capacitance is small, approximately 0.084 F / cm². 2 Meanwhile, the steep slope of the CV plot indicates that the resistance of the foamed copper electrode treated by immersion in sodium formate solution is relatively high.
[0078] Figure 13 This is a cyclic voltammogram of a copper foam electrode treated with sodium formate in a phenazine compound BHPC solution. The oxidation potential is -0.77 V, the reduction potential is -1.02 V, and the potential difference is 0.25 V. The peak currents of both oxidation and reduction are small (less than 2 mA / cm), and the symmetry and reversibility of the peaks are better than those of the copper foam electrode without sodium formate treatment. The copper foam electrode treated only with sodium formate solution has a very weak catalytic effect on BHPC, with a low current density and weak BHPC transfer kinetics on the electrode surface.
Claims
1. A method for preparing a highly active foamed copper electrode for a catalytic aqueous flow battery, characterized in that, The preparation method is as follows: first, the copper foam is pretreated, and then the copper foam is electrochemically reconstructed in sodium formate solution using cyclic voltammetry.
2. The method for preparing the highly active foamed copper electrode according to claim 1, characterized in that, The specific steps for pretreatment of copper foam are as follows: first, the copper foam is subjected to alcohol washing and ultrasonic treatment, then acid washing and ultrasonic treatment, then rinsed with ultrapure water, and finally dried in a non-reactive atmosphere.
3. The method for preparing the highly active foamed copper electrode according to claim 2, characterized in that, The alcohol used for alcohol washing is selected from at least one of isopropanol, ethanol, and methanol; the acid used for acid washing is selected from at least one of hydrochloric acid, sulfuric acid, and nitric acid, and the concentration of the acid solution is 1–3 mol / L.
4. The method for preparing a highly active foamed copper electrode according to claim 2, characterized in that, The ultrasonic treatment time for both alcohol washing and acid washing is 5-10 minutes; the gas in the inactive atmosphere is selected from at least one of nitrogen, argon, and hydrogen.
5. The method for preparing a highly active foamed copper electrode according to claim 1, characterized in that, During the electrochemical reconstruction of copper foam in sodium formate solution, the pH range of the sodium formate solution was 9–12, the mass fraction of the sodium formate solution ranged from 0.5 wt.% to 10 wt.%, and the number of scan cycles was 2–10.
6. An application of a highly active foamed copper electrode prepared according to claim 1, characterized in that, Highly active foamed copper electrodes are used to catalyze the redox reaction of phenazine-based active electrolyte benzo[a]hydroxyphenazine-7 / 8-carboxylic acid in aqueous flow batteries.
7. The application of the highly active foamed copper electrode according to claim 6, characterized in that, The negative electrode of the aqueous flow battery is the foamed copper electrode treated with sodium formate solution as described in claim 1, and the positive electrode is the carbon felt electrode.
8. The application of the highly active foamed copper electrode according to claim 6, characterized in that, The negative electrode active material of the aqueous flow battery is benzo[a]hydroxyphenazine-7 / 8-carboxylic acid, and the positive electrode active material is potassium ferrocyanide.
9. The application of the highly active foamed copper electrode according to claim 8, characterized in that, The negative and positive electrode electroactive materials are dissolved in an alkaline aqueous solution containing 1 mol / L potassium hydroxide, and the supporting electrolyte is 0.95 mol / L potassium chloride.