Acidic CO2 electrolysis method

Abstract

The present invention discloses an acidic CO2 electrolysis method, which belongs to the field of electrochemical electrolysis technology. After adding tetramethylammonium salt to the acidic cathode electrolyte, it is dissolved and ionized to produce tetramethylammonium cation TMA. + The acidic electrolyte contacts the inflowing CO2 gas to form an electrolytic reaction system, and an electrocatalytic reduction reaction is carried out under the electrolytic conditions to generate carbon-based products. + Effective regulation of the double-layer interface in electrocatalytic CO2 reduction achieves efficient conversion of CO2 to target products and avoids salting out during long-term electrolysis. The operating life even exceeds 2600h at industrially relevant current densities, demonstrating excellent activity, selectivity and stability. This method not only redesigns the acidic electrolyte components of the electrocatalytic CO2 reduction system, but also provides new ideas for the future design of new alkali-metal-ion-mediated acidic CO2 electrolysis systems.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical electrolysis, and specifically relates to an acidic CO2 electrolysis method, and more particularly to a method for electrocatalytic CO2 reduction in an acidic medium mediated by tetramethylammonium cations. Background Art

[0002] CO2 is one of the main gases that cause the greenhouse effect. The greenhouse effect will lead to global temperature rise, ocean acidification, glacier melting and other problems, seriously hindering the sustainable development of human society. It is extremely necessary to actively formulate and implement a comprehensive carbon treatment plan to reduce CO2 emissions.

[0003] CO2 electrochemical reduction technology (CO2ER) is a method that converts CO2 into high-value-added energy fuels and chemical products driven by renewable energy (such as wind energy, hydropower, solar energy, etc.). It can also achieve long-term storage of intermittent renewable energy, providing a feasible solution to global climate warming and energy crisis. It has huge application potential and has therefore attracted widespread attention from technicians in this field.

[0004] Conventional CO2 electrolysis technology usually relies on alkaline / neutral solutions as electrolytes, but in alkaline and neutral reaction systems, CO2 easily reacts with hydroxide (OH - ) reaction to produce carbonates or bicarbonates, which causes CO2 loss and reduces the energy conversion efficiency and stability of the reaction system. CO2 electroreduction in acidic media can not only alleviate the problem of salt accumulation, but also improve the single-pass conversion rate of CO2 (often exceeding 50%) and the energy conversion efficiency of generating target products. Therefore, the development of electrocatalytic reduction of CO2 in acidic systems has attracted much attention in recent years. However, due to the H + The concentration of CO2 is very high, and the competitive reaction of water reduction hydrogen evolution (HER) will be more intense, which will cause the Faradaic efficiency of CO2 electroreduction to be lower than that of alkaline or neutral systems. Therefore, it is of great significance to design a catalytic reduction process with high selectivity and stability in an acidic environment.

[0005] Introducing alkali metal cations (such as K + 、Li + 、Cs +Alkali metal cations (e.g., alkali metal cations) can inhibit competitive reactions, promote proton transfer, and enhance electrocatalytic performance. Specifically, alkali metal cations physically adsorb on the electrode surface, regulating the double-layer electric field distribution on the electrode surface, thereby inhibiting the movement of hydronium ions, reducing competitive hydrogen evolution reactions, and thus improving the Faradaic efficiency of CO2 electrocatalytic reduction. In addition, alkali metal cations can stabilize CO2 reduction intermediates through electrostatic interactions or direct coordination, promoting CO2 activation to produce formic acid, CO, or multi-carbon compounds. However, over time, systems with alkaline metal cations often face the problem of salt precipitation on the gas diffusion electrode (GDE), mainly due to the local accumulation of metal cations combining with carbonate anions, resulting in the precipitation of bicarbonate. This precipitation can destroy the hydrophobicity of the electrode, thereby causing flooding, that is, the abnormal accumulation of electrolyte on the electrode surface, affecting the normal progress of the electrolysis process. In addition, when a proton exchange membrane is used to separate the anode and cathode electrolytes, alkali metal ions may also pass through the proton exchange membrane, causing the composition of the anode and cathode electrolytes to gradually change over time. This change will further affect the stability of the electrolysis system, reducing the controllability and repeatability of the electrolysis process.

[0006] In order to achieve stable acidic CO2 electroreduction technology, the development of a new alkali-free metal ion electrolysis system for acidic CO2 electrolysis is key. However, from the perspective of publicly available alternatives, existing strategies are either unable to eliminate the carbonates produced at the interface of the electroreduction system, affecting stability during long-term operation (generally no more than 150 hours); or are unable to effectively suppress the violent hydrogen evolution side reaction that occurs during acidic electrocatalysis of CO2, resulting in a high selectivity for the hydrogen evolution side reaction. Through continuous research, it was found that if you want to achieve efficient acidic CO2 electrolysis, a feasible solution is to regulate the local microenvironment at the electrocatalytic double layer interface.

[0007] Organic cations, with their large ionic size, hydrophobicity, and unique solvation shell structure, are another important class of cations in electrochemistry. Compared to metal cations, organic cations offer more opportunities to modulate the interfacial microenvironment in the double layer through intermolecular interactions between their functional groups, water, and other active / inactive species. These properties make organic cations promising alternatives to traditional alkali metal cations as supporting electrolytes for acidic CO2 electrolysis processes. In principle, due to their cationic nature, organic cations in acidic electrolytes can screen the electric field from the cathode by accumulating at the Helmholtz plane, thereby inhibiting the migration of hydrogen ions and improving the selectivity of acidic CO2 electroreduction. However, to date, no relevant research has shown that adding organic cations to the electrolyte can drive acidic CO2 electrolysis alone. Although technicians in this field have tried to explore the feasibility of organic cations promoting acidic CO2 electrolysis, their understanding of how these organic cations affect the acidic CO2 electrolysis process at the molecular level lags far behind that of metal cations. This is mainly due to the more complex kinetic behavior of organic cations in the double layer. This complexity is related to their unique structure, which hinders the further development of the design of metal-free cation systems. The relevant processes and mechanisms of action need further in-depth exploration. Summary of the Invention

[0008] In response to the above-mentioned problems, the present invention aims to provide an acidic CO2 electrolysis method, which introduces tetramethylammonium cations into the acidic electrolyte to effectively regulate the double-layer interface of electrocatalytic CO2 reduction, thereby improving the activity, selectivity and stability of the reduction reaction.

[0009] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is as follows: an acidic CO2 electrolysis method, by adding tetramethylammonium salt to the acidic cathode electrolyte, dissolving it and ionizing it to produce tetramethylammonium cations, the acidic electrolyte contacts the inflowing CO2 gas to form an electrolytic reaction system, and an electrocatalytic reduction reaction is carried out under electrolysis conditions to generate carbon-based products.

[0010] Furthermore, the tetramethylammonium salt is selected from salts that can stably exist in an acidic electrolyte and ionize into tetramethylammonium cations, and the pH of the acidic electrolyte is less than 7.

[0011] Furthermore, the cathode electrolyte is a sulfuric acid aqueous solution, and the sulfuric acid concentration in the electrolyte is 0.01 to 1M.

[0012] Preferably, the tetramethylammonium salt is selected from one or more of tetramethylammonium chloride, tetramethylammonium hydroxide, tetramethylammonium phosphate and tetramethylammonium sulfate.

[0013] Furthermore, the voltage conditions for the electrocatalytic reduction reaction are -0.1V to -1.7V and the current is 0 to 300mAcm-2 .

[0014] Furthermore, the carbon-based product is one or more of carbon monoxide, formic acid, methanol, ethanol, and ethylene.

[0015] Furthermore, the concentration of tetramethylammonium cations in the acidic electrolyte is 0.1 to 5M.

[0016] Furthermore, the flow rate of the inflowing CO2 is 0.5 to 50 sccm.

[0017] Furthermore, the cathode catalyst is one of Au-based catalyst, Bi-based catalyst, Cu-based catalyst, Sn-based catalyst and In-based catalyst.

[0018] As can be seen from the examples, the present invention adds high concentration tetramethylammonium chloride molecules to the sulfuric acid solution to ionize TMA. + Under strong acidic conditions, CO2 is efficiently reduced to carbon monoxide, and the salting out phenomenon during long-term electrolysis is completely avoided. The reaction activity, selectivity and stability are significantly improved. It is speculated that TMA + It shows a different cation effect from traditional alkali metal cations. Alkali metal cations mainly play a role by reducing the driving force of proton electromigration. TMA + It inhibits HER mainly by disrupting the hydrogen bond network of proton shuttling.

[0019] The beneficial effects of the present invention are:

[0020] 1. This application discloses a tetramethylammonium cation (TMA) suitable for CO2 reduction. + )-mediated acidic CO2 electrolysis method, by adding a certain amount of tetramethylammonium salt to the acidic electrolyte to ionize TMA + , TMA + It can effectively regulate the double-layer interface of electrocatalytic CO2 reduction, achieving efficient conversion of CO2 to target products (nearly 100% Faradaic efficiency), with a single-pass carbon efficiency of 85.1%. It can also avoid salting out during long electrolysis processes, breaking the limitations of existing acidic CO2 electroreduction electrolyte application strategies.

[0021] 2. TMA proposed in this application + The mediated acidic CO2 electrolysis technology has the advantages of high Faradaic efficiency in generating products and no obvious salt precipitation phenomenon. The technology can be used at industrial relevant current density (100mAcm -2 ) has an operating life of more than 2600 hours, and this advantage of no salt precipitation during the reaction process has also been demonstrated in alkaline CO2 electrolysis technology, with long-term stability exceeding 1200 hours;

[0022] 3. TMA proposed in this application + The mediated acidic CO2 electrolysis system not only exhibits excellent activity, selectivity, and stability in the electrocatalytic conversion of CO2 to CO, but is also applicable in promoting the conversion of CO2ER to formic acid, with a selectivity of formic acid exceeding 80%.

[0023] 4. By adjusting TMA in acidic electrolyte + The concentration of CO2 and the flow rate of inflow CO2 can further regulate the Faradaic efficiency and single-pass carbon utilization rate of electrocatalytic CO2 reduction to generate target products, thereby maximizing the carbon utilization efficiency of the catalytic reaction;

[0024] 5. The acidic CO2 electrolysis method proposed in this application is not only a redesign of the acidic electrolyte components of the electrocatalytic reduction of CO2 system, but also provides a new idea for designing a new acidic CO2 electrolysis system without alkali metal ion mediation. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The Faradaic efficiency (FE) and local current density of different products generated at specific potentials when the electrocatalytic CO2 reduction test is performed based on the electrolysis system set up in Example 1;

[0026] Figure 2 This is the result of a long-term stability test on the electrolysis system set up in Example 1;

[0027] Figure 3 is the XRD spectrum of the cathode working electrode before and after the electrocatalytic test in Example 1;

[0028] Figure 4 is the Faradaic efficiency (FE) and local current density of the product produced during the electrocatalytic CO2 reduction test in Comparative Example 1 at a specific potential;

[0029] Figure 5 In Example 2, different TMA + The Faradaic efficiency (FE) and local current density of the products produced when the electrocatalytic CO2 reduction test is carried out in the electrolysis system with a concentration of 400 nm;

[0030] Figure 6 The Faraday efficiency (FE) and formic acid current density of different products produced at a specific potential when the electrocatalytic CO2 reduction test based on the Bi-based catalyst in Example 3 is performed;

[0031] Figure 7 The Faraday efficiency and single-pass carbon efficiency of the electrocatalytic CO2 reduction test at different carbon dioxide flow rates in Example 4;

[0032] Figure 8is the Faradaic efficiency (FE) and local current density of different products produced at specific potentials when the electrocatalytic CO2 reduction test was performed on Example 2;

[0033] Figure 9 This is the result of a long-term stability test on the electrolysis system set up in Comparative Example 2;

[0034] Figure 10 The Faraday efficiency and single-pass carbon efficiency of the electrocatalytic CO2 reduction test at different carbon dioxide flow rates based on the electrolysis system set up in Comparative Example 2;

[0035] Figure 11 The XRD spectra of the cathode working electrode before and after the electrocatalytic test based on the electrolysis system of Comparative Example 2 are shown;

[0036] Figure 12 is the Faradaic efficiency of the product produced during the electrocatalytic CO2 reduction test in Comparative Example 3 at a specific potential;

[0037] Figure 13 This is the result of a long-term stability test on the electrolysis system set up in Comparative Example 3. DETAILED DESCRIPTION

[0038] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0039] Example 1

[0040] This example addresses the limitations of existing acidic CO2 electroreduction electrolyte applications by developing a novel alkali-metal ion-free electrolysis system. Specifically, organic cations are introduced into the acidic electrolyte to regulate the proton concentration at the electrocatalytic double layer interface (to control the progress and product selectivity of the CO2 reduction reaction) and thermodynamically stabilize CO2-related intermediates (to improve the efficiency of the reduction reaction and product purity).

[0041] When selecting cations, considering that organic cations should have both high solubility and minimum size in the corresponding carbonates to prevent salt precipitation and minimize HER kinetics, tetramethylammonium cation (TMA) was finally selected in this embodiment. + ) As an acidic supporting electrolyte, the solubility of tetramethylammonium cation-bicarbonate can reach ~12.4M, which is 3.4 times that of KHCO3 (20℃, 3.62M).

[0042] The process of CO2 electroreduction test based on catholyte with tetramethylammonium chloride added is as follows:

[0043] Step 1: Preparation of the cathode electrolyte: Weigh 548 g of tetramethylammonium chloride (McLean, AR, molecular weight 109.6) into a beaker, dissolve it in water, transfer it to a 1000 mL volumetric flask, and add sulfuric acid to complete the cathode electrolyte. The sulfuric acid concentration in the electrolyte is 0.05 M and the tetramethylammonium ion cation concentration is 5 M.

[0044] In the second step, 0.5M sulfuric acid was used as the anolyte, and the cathode catalyst was Au nanomaterial, which was loaded on carbon black at a ratio of 40wt% and then sprayed on the gas diffusion electrode as the working electrode. The anode electrocatalyst was IrO2 / Ti, and the reference electrode was Ag / AgCl (3.5M KCl).

[0045] The cathode catalyst was prepared as follows: 80 mg of HAuCl4·3H2O was dissolved in a mixed solvent of 2 mL of ethanol and 16 mL of oleylamine, heated to 150°C in an oil bath with the lid open for 10 minutes, then tightly closed and heated to 220°C for 30 minutes, cooled to room temperature, and centrifuged at 13500 rpm for 5 minutes to separate the solid product - gold nanoparticles supported on carbon (i.e., Au / C catalyst). 4 mg of Au / C catalyst was then added to 500 μL of ethanol, and 5 μL of Nafion was added and ultrasonicated for 40 minutes to obtain a uniform catalyst ink. The catalyst ink was evenly sprayed onto carbon paper (gas diffusion layer) and dried overnight.

[0046] The third step is to conduct electrocatalytic CO2 reduction tests at different potentials in a flow cell electrocatalytic device, analyze the gas products by gas chromatography, and analyze the liquid products by nuclear magnetic resonance spectroscopy.

[0047] Unless otherwise specified, the carbon dioxide input flow rate used was 50 sccm, the commercial carbon paper used was YLS-30T, and the back of the carbon paper was sprayed with a 1% polytetrafluoroethylene (PTFE) emulsion (1 cm -2 300 μL was sprayed on the surface and then dried under an infrared lamp).

[0048] The Faradaic efficiency and local current density of different products at specific potentials are as follows: Figure 1 As shown in the figure, when 5M TMA is added to the acidic medium + The Faradaic efficiency of CO generation can reach over 90% in a wide potential range, which is comparable to that of the reversible hydrogen electrode (V RHE ) compared to -1.20V RHE Maximum FE at CO It is 99.1%.

[0049] Based on the electrolysis system disclosed in this embodiment, the current density of the industry-related current (100mAcm -2 ) below -1.23V RHELong-term electrolysis to obtain long-term stability test results ( Figure 2 ), after 2600h of electrolysis, the catalytic system can still remain stable, surpassing most of the currently reported CO2 electrocatalytic reduction systems.

[0050] The XRD spectra of the cathode working electrode before and after the electrocatalytic test are shown in Figure 3 ,from Figure 3 It can be seen that no carbonate is precipitated on the cathode working electrode before and after the test.

[0051] Comparative Example 1

[0052] The only difference between this comparative example and Example 1 is that no tetramethylammonium chloride is added to the cathode electrolyte, and the concentration of sulfuric acid in the cathode acidic electrolyte is 0.05M.

[0053] The electrocatalytic CO2 reduction test was carried out in the same way, and the gas products were analyzed by gas chromatography. The Faradaic efficiency and local current density of the corresponding products at a specific potential were as follows: Figure 4 As shown, from Figure 4 It can be seen that in the absence of organic cations, the HER competitive reaction dominates in the electrocatalytic system, resulting in only H2 being produced and carbon dioxide not being effectively activated.

[0054] Example 2

[0055] The difference between this embodiment and embodiment 1 is that the concentration of tetramethylammonium chloride in the cathode electrolyte is changed to form different TMA + Concentration electrolytic system for studying TMA + The effect of concentration on acidic CO2 electrolysis. Specifically, the concentration of sulfuric acid in the cathode electrolyte was kept constant at 0.05M, and the TMA in different electrolysis systems + The concentrations of 0M, 0.1M, 0.5M, 1M, 2M and 5M were respectively, and the other settings of the electrolysis system remained unchanged. The electrocatalytic CO2 reduction test was carried out in the same manner as in Example 1 to detect TMA. + Selectivity and activity of electrocatalytic systems with different concentrations.

[0056] Test results see Figure 5 ,from Figure 5 It can be seen that the Faradaic efficiency of CO generation increases steadily with the increase of tetramethylammonium cation concentration, and the CO generation rate is positively correlated with the concentration of tetramethylammonium cation, confirming that tetramethylammonium cation plays a key role in promoting the kinetic conversion of CO2 to CO under strong acid conditions.

[0057] Example 3

[0058] The only difference between Example 3 and Example 1 is that the cathode catalyst used in Example 1 is replaced with a Bi nanosheet catalyst to electrocatalyze CO2 to produce formic acid, and other parameters and steps remain unchanged.

[0059] The synthesis method of Bi nanosheets is as follows: first disperse 20mL of ethylene glycol in 145mg of Bi(NO3)3·5H2O, then add 4mL of NaBH4 (2.25mg / mL) at a rate of 16mL / h, and a black precipitate is obtained at room temperature. The bismuth nanosheet catalyst is obtained by centrifugation and drying.

[0060] The electrocatalytic CO2 reduction test was carried out in the same manner as in Example 1. The test results are shown in Figure 6 ,from Figure 6 It can be seen that under the action of Bi-based catalyst, the selectivity of hydrogen production in the acidic CO2 electrolysis system mediated by tetramethylammonium chloride can also be suppressed to less than 1%, and the selectivity of formic acid production is maintained at a level greater than 80% within a wide potential range.

[0061] Example 4

[0062] The difference between this embodiment and embodiment 1 is that the flow rate of the inflowing carbon dioxide is changed to explore the effect of the flow rate of the carbon dioxide on the single-pass carbon utilization rate. The flow rate of the inflowing carbon dioxide is adjusted to 50, 30, 20, 10, 3, 1 and 0.5 sccm respectively. The other steps and parameters remain unchanged. The electrocatalytic CO2 reduction test is carried out in the same manner as in embodiment 1. The test results are shown in FIG. Figure 7 The results show that as the inflow CO2 flow rate decreases, the carbon utilization rate of CO2 gradually increases. When the CO2 input flow rate is 0.5 sccm, the carbon utilization rate reaches 85.1%, which means that more than 85% of the carbon dioxide can be converted into CO.

[0063] Comparative Example 2

[0064] The only difference between this comparative example and Example 1 is that potassium chloride is added to the cathode electrolyte instead of tetramethylammonium chloride, so that the sulfuric acid concentration in the electrolyte is 0.05M and the potassium ion concentration is 3M. ​​The electrocatalytic CO2 reduction test is carried out in the same manner as in Example 1 to detect the electrocatalytic CO2 reduction selectivity, activity and stability in the potassium ion-containing electrolyte system.

[0065] The Faradaic efficiency and local current density of the corresponding products at a specific potential are as follows: Figure 8 As shown, combined Figure 8 It can be seen that when there is 3M potassium ion in the cathode electrolyte, the CO2 electroreduction reaction is dominant in the electrocatalytic system, but the selectivity of CO generation does not exceed 90% at each potential, and the hydrogen selectivity is greater than 10%. Compared with TMA+ In terms of system, the selectivity of hydrogen evolution reaction in potassium ion system is still relatively high.

[0066] The electrolytic system was tested at -1.07V RHE The long-term stability under Figure 9 As shown in the results, the long-term electrolysis in 3M potassium ion sulfuric acid electrolyte (pH ~ 0.7) only achieved 18h ​​stability, which is far less than TMA + Mediated acidic CO2 electrocatalytic reduction system.

[0067] The effect of CO2 flow rate on the single-pass carbon utilization rate during CO2 electrocatalytic reduction based on this electrolysis system was tested. The results are shown in Figure 10 ,from Figure 10 As the input CO2 flow rate decreases, the carbon utilization rate of CO2 gradually increases. However, when the CO2 flow rate is as low as 0.5 sccm, the carbon utilization rate is only 36.5%, which means that only 36.5% of the carbon dioxide can be converted into CO. Compared with TMA + For the acidic CO2 electrocatalytic reduction system mediated by HO, the CO2 single-pass utilization rate is at a low level.

[0068] Figure 11 This is the XRD spectrum of the cathode working electrode before and after CO2 electrocatalytic reduction based on this electrolytic system. The graphical results show that obvious potassium bicarbonate accumulates on the carbon paper after electrolytic reduction. This accumulated carbonate should be the reason for the instability of the electrolytic system.

[0069] Comparative Example 3

[0070] The difference between this comparative example and Example 1 is that the cathode electrolyte used in the example is replaced with 3M tetramethylammonium hydroxide, and the anolyte is replaced with 1M potassium hydroxide. The other steps and parameters remain unchanged. The electrocatalytic CO2 reduction test is carried out. The results are as follows Figure 12 As shown, from Figure 12 It can be seen that when the cathode electrolyte is an alkaline electrolyte system without potassium ions, the Faradaic efficiency of CO generation can reach more than 90% within a wide potential range.

[0071] The long-term stability of the electrolysis system was tested and the results were as follows: Figure 13 As shown, the alkaline system based on tetramethylammonium ions also achieved an electrolytic stability of more than 1200 hours, which is better than the catalytic durability test results of most potassium ion systems reported so far.

[0072] The above shows and describes the basic principles, main features, and advantages of the present invention. However, the above is only a specific embodiment of the present invention, and the technical features of the present invention are not limited thereto. Any other implementation methods derived by any person skilled in the art without departing from the technical solution of the present invention are intended to be within the scope of the present invention.

Claims

1. An acidic CO2 electrolysis method, characterized in that: Tetramethylammonium salt is added to the acidic cathode electrolyte to dissolve it and ionize tetramethylammonium cations. The cathode electrolyte contacts the inflowing CO2 gas to form an electrolytic reaction system. An electrocatalytic reduction reaction is carried out under electrolytic conditions to generate carbon-based products. The concentration of tetramethylammonium cations in the acidic electrolyte is 2~5 M.

2. The acidic CO2 electrolysis method according to claim 1, wherein: The tetramethylammonium salt is selected from salts that can stably exist in an acidic electrolyte and ionize into tetramethylammonium cations, and the pH of the acidic electrolyte is less than 7.

3. The acidic CO2 electrolysis method according to claim 2, wherein: The tetramethylammonium salt is selected from one or more of tetramethylammonium chloride, tetramethylammonium hydroxide, tetramethylammonium phosphate, and tetramethylammonium sulfate.

4. The acidic CO2 electrolysis method according to claim 1, wherein: The electrocatalytic reduction reaction was carried out under the voltage conditions of -0.1 V to -1.7 V and the current of 100 to 300 mA cm -2 .

5. The acidic CO2 electrolysis method according to claim 1, wherein: The carbon-based product is one or more of carbon monoxide, formic acid, methanol, ethanol, and ethylene.

6. The acidic CO2 electrolysis method according to claim 1, wherein: The flow rate of the inflowing CO2 is 0.5~50sccm.

7. The acidic CO2 electrolysis method according to claim 1, wherein: The cathode catalyst is one of Au-based catalyst, Bi-based catalyst, Cu-based catalyst, Sn-based catalyst and In-based catalyst.

8. The acidic CO2 electrolysis method according to claim 1, wherein: The cathode electrolyte is a sulfuric acid aqueous solution, and the sulfuric acid concentration in the electrolyte is 0.01~1 M.

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