Electrolyte for electrolyzed water and preparation method thereof

Abstract

The invention relates to an electrolyte for electrolyzed water and a preparation method thereof. The electrolyte comprises K3 [Fe (CN) 6] serving as a redox medium, a mixture of sodium dihydrogen phosphate and disodium hydrogen phosphate serving as a buffering agent, an aqueous solvent and a pH regulator. The method comprises the following steps: S1, dissolving K3 [Fe (CN) 6], sodium dihydrogen phosphate (NaH2PO4) and disodium hydrogen phosphate (Na2HPO4) in the aqueous solvent to obtain an intermediate solution, and S2, adding the pH regulator into the intermediate solution to obtain the electrolyte. The electrolyte disclosed by the invention can be used for stably carrying out electrolytic reaction, and the volume ratio of hydrogen to oxygen can be accurately regulated and controlled by changing the concentration of an oxidation-reduction medium in the electrolyte. The method provided by the invention is simple and safe in process, can be repeatedly and stably carried out at low cost, and realizes large-scale production.

Description

Technical Field

[0001] The present invention relates to the technical field of water electrolysis, and in particular to an electrolyte for water electrolysis and a preparation method thereof, wherein the volume ratio of generated hydrogen and oxygen (hereinafter also referred to as "hydrogen-oxygen ratio") is controlled by adjusting the composition of the electrolyte. Background Art

[0002] The traditional technology of generating hydrogen-oxygen mixed gas (i.e., a mixture of hydrogen and oxygen) by electrolyzing water has always faced a fundamental chemical limitation - after the water molecules are decomposed, only a volume ratio of hydrogen to oxygen that strictly follows 2:1 can be obtained. This volume ratio, which is directly determined by the chemical reaction formula, requires additional gas separation devices and / or mixing devices when the volume ratio of hydrogen and oxygen gases needs to be adjusted in actual applications. The subsequent physical mixing process not only significantly increases the complexity of the equipment and energy consumption, but also introduces the risk of leakage or explosion due to the temporary storage of the gas, which seriously restricts the application of this technology in scenarios such as medical oxygen or hydrogen supply.

[0003] To solve this problem of fixed volume ratio, researchers have tried a variety of improvement plans. One solution is to develop a new catalyst to improve the efficiency of the electrode reaction. Although this can speed up the gas generation rate, it cannot change the volume ratio of the two gases. Another solution is to use electrical control methods such as pulsed current or partitioned power supply. However, due to the inherent differences in the generation dynamics of hydrogen and oxygen, the uneven charge distribution on the electrode surface leads to a slow control response and difficulty in achieving precise volume ratio control. Another solution is to use an external valve to adjust the volume ratio, but problems such as gas flow fluctuations and pipeline residues will cause the actual output gas volume ratio to continue to change. At the same time, external equipment greatly increases the system volume and maintenance costs.

[0004] In addition, the existing research on electrolyte systems mainly involves how to improve conductivity or extend service life, and has not yet achieved a stable and effective regulation of the volume ratio of hydrogen and oxygen gases by utilizing the chemical properties of the electrolyte. In an attempt to add a redox medium (potassium iodide) to the electrolyte, during the electrolysis reaction, potassium iodate (KIO3) generated by oxidation of potassium iodide (KI) easily clogs the pipeline, resulting in poor reaction stability of the resulting electrolyte, and the oxidation reaction is easily affected by manual operation and environmental factors. In this case, even if an electrolyte with the same composition is used, the resulting hydrogen-oxygen ratio may be different in different batches of electrolysis reactions.

[0005] In summary, existing technologies for producing hydrogen and oxygen mixed gases through water electrolysis have serious drawbacks in terms of safety, effectiveness, and stability of gas separation. Therefore, a new technology is needed to safely, effectively, and stably adjust the volume ratio of hydrogen to oxygen. Summary of the Invention

[0006] Technical issues A first object of the present invention is to provide an electrolyte for water electrolysis, wherein the electrolyte is capable of stably performing an electrolysis reaction and can precisely control the volume ratio of hydrogen to oxygen by varying the concentration of a redox medium therein. The electrolyte can be used as an electrolyte solution in an electrolytic cell.

[0007] The second object of the present invention is to provide a method for preparing an electrolyte, which is simple and safe, can be carried out stably and repeatedly at low cost, and can achieve large-scale production.

[0008] Technical Solution According to a first aspect of the present invention, there is provided an electrolyte for electrolyzing water, the electrolyte comprising: K3[Fe(CN)6] as a redox mediator, A mixture of sodium dihydrogen phosphate (NaH2PO4) and disodium hydrogen phosphate (Na2HPO4) as a buffer, aqueous solvent, and a pH adjuster.

[0009] In one embodiment, the aqueous solvent is at least one of ultrapure water, deionized water and distilled water. The pH adjuster is at least one of KOH and NaOH.

[0010] In one embodiment, the concentration of K3[Fe(CN)6] is 0.05-0.22 M, The total concentration of sodium dihydrogen phosphate and disodium hydrogen phosphate is 0.01-0.50 M. The molar ratio of sodium dihydrogen phosphate to disodium hydrogen phosphate is 1.0:1.0 to 1.0:3.0, The concentration of the pH adjuster is 0.005-0.015 M.

[0011] In one embodiment, the pH value of the electrolyte is 8.0-10.0.

[0012] According to a second aspect of the present invention, there is provided a method for preparing the above-mentioned electrolyte, the method comprising the following steps: S1: dissolving K3[Fe(CN)6], sodium dihydrogen phosphate (NaH2PO4) and disodium hydrogen phosphate (Na2HPO4) in the aqueous solvent to obtain an intermediate solution, and S2: adding the pH adjuster to the intermediate solution to obtain the electrolyte.

[0013] In one embodiment, the pH adjuster is added dropwise to the intermediate solution in the form of an aqueous solution.

[0014] Beneficial effects Compared with the existing technology, the present invention breaks through the stoichiometric limitation of the fixed volume ratio of hydrogen and oxygen (hydrogen-oxygen ratio) of 2:1 generated by traditional water electrolysis technology, and for the first time realizes in-situ regulation of the hydrogen-oxygen ratio through the intrinsic chemical properties of the electrolyte.

[0015] Specifically, the electrolyte of the present invention forms an electron transfer path that takes precedence over the oxygen evolution reaction in the anode (such as nickel) region of the electrolytic cell by using a synergistic system of a redox medium (potassium ferricyanide K3[Fe(CN)6]), a phosphate buffer, and a pH regulator, while simultaneously constructing a stable proton transfer microenvironment in the cathode (such as platinum) region. Furthermore, the electrolyte of the present invention uses redox media of varying concentrations to easily and stably control the hydrogen-oxygen ratio obtained by electrolysis of water within a range of 3:1 to 15:1, thereby eliminating the need for additional gas separation and / or mixing devices, thereby avoiding the explosion risk associated with them.

[0016] In addition, the traditional physical method of controlling the hydrogen-oxygen ratio has a hydrogen-oxygen ratio fluctuation of more than ±5% when repeating the same preparation process, while the preparation method of the present invention can achieve a stable output accuracy of ±0.3%. DETAILED DESCRIPTION

[0017] Hereinafter, the present invention will be described in detail.

[0018] Unless otherwise defined, all terms used herein, including technical or scientific terms, should be interpreted as having the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Therefore, unless explicitly defined, terms such as those defined in commonly used dictionaries should not be interpreted in an ideal or overly formal sense.

[0019] When the conditions and methods for measuring a property or parameter described in this specification are not specifically described, the property or parameter can be measured using measurement conditions and methods generally used by those skilled in the art.

[0020] Unless otherwise specified, "%" used herein refers to weight %.

[0021] Water electrolysis is a process that uses electricity to decompose water into hydrogen and oxygen. Its core principle is based on electrochemical reactions. Pure water has poor electrical conductivity, so an electrolyte (such as KOH or H2SO4) is typically added to enhance ion conduction, converting pure water into an electrolyte. When an external power source applies voltage to electrodes (including a cathode and an anode) immersed in the electrolyte, water molecules decompose under the influence of the electric field. During this process, water molecules undergo reduction and oxidation reactions at the cathode and anode surfaces, respectively. At the cathode, water molecules gain electrons, decomposing to produce hydrogen and release hydroxide ions; at the anode, hydroxide ions lose electrons to produce oxygen. The combined effect of these two half-reactions is the decomposition of water into hydrogen and oxygen in a volume ratio of 2:1. The entire process requires continuous electrical energy input, and energy efficiency is affected by factors such as electrolyte properties, voltage, and reaction kinetics. The key to this technology is the efficient production of hydrogen through controllable electrical energy input, providing an important approach for clean energy storage and conversion.

[0022] However, certain application areas (such as medical treatment and smelting) require the use of specific hydrogen-to-oxygen ratios. Conventional methods achieve the desired hydrogen-to-oxygen ratio by mixing pure hydrogen and pure oxygen gases, which is inefficient and inconvenient. To overcome these shortcomings, the present invention uses a specific electrolyte instead of a conventional electrolyte and varies the concentration of the redox media contained in the specific electrolyte to achieve a precisely adjustable hydrogen-to-oxygen ratio within a range of 3:1 to 15:1. The above hydrogen-to-oxygen ratio range is the range commonly used in related fields.

[0023] The electrolyte for water electrolysis and the preparation method thereof of the present invention are described in detail below.

[0024] 1. Electrolyte for electrolyzed water According to a first aspect of the present invention, there is provided an electrolyte for electrolyzing water, the electrolyte comprising: K3[Fe(CN)6] as a redox mediator, A mixture of sodium dihydrogen phosphate and disodium hydrogen phosphate as a buffer, aqueous solvent, and a pH adjuster.

[0025] Each component is described in detail below.

[0026] Redox mediator The redox medium is used to consume part of the anode current and reduce the amount of O2 generated. If the redox medium is not added, the volume ratio of hydrogen to oxygen in the generated mixed gas is fixed at 2:1.

[0027] In the present invention, potassium ferricyanide K3[Fe(CN)6] is used as a redox medium. K3[Fe(CN)6] is a red crystal that is soluble in water and can produce ferrocyanide ions [Fe(CN)6] after dissolution.3- The oxidation potential of K3[Fe(CN)6] is slightly lower than the potential of the anodic oxygen evolution reaction (OER) during water electrolysis, so it is preferentially oxidized to K4[Fe(CN)6] at the anode, consuming part of the current and reducing the amount of oxygen generated, thereby changing the hydrogen-oxygen volume ratio.

[0028] In the electrolyte, the concentration of K3[Fe(CN)6] may be 0.05-0.0.22 M, or 0.07-0.20 M, or 0.09-0.15 M. By using the above concentrations, the hydrogen-oxygen volume ratio may be controlled within the range of 3:1 to 15:1.

[0029] If the concentration of K3[Fe(CN)6] is too low, it will not sufficiently inhibit the oxygen evolution reaction at the anode, and the hydrogen-oxygen ratio will drop to close to the theoretical value of 2:1, and the required hydrogen-oxygen ratio control cannot be achieved; if the concentration of K3[Fe(CN)6] is too high, the hydrogen-oxygen ratio will be out of control after exceeding 15:1, and the oxygen evolution reaction at the anode will be completely inhibited, resulting in anode passivation.

[0030] buffer In the present invention, a mixture of sodium dihydrogen phosphate and disodium hydrogen phosphate is used as a buffer (phosphate buffer). The buffer can be quickly dissolved in an aqueous solvent.

[0031] The buffer is H2PO4 - / HPO4 2- Balance, stabilize the pH of the cathode surface (such as Pt cathode) at 8.0-10.0, and enhance the hydrogen evolution activity of the cathode. If no buffer is added, the overall pH of the electrolyte will fluctuate greatly, the hydrogen and oxygen evolution performance will be unstable, and the resulting hydrogen-oxygen ratio will fluctuate.

[0032] In one embodiment, the total concentration of sodium dihydrogen phosphate and sodium hydrogen phosphate may be 0.01-0.50 M, or may be 0.05-0.45 M, or may be 0.10-0.40 M.

[0033] If the total concentration of sodium dihydrogen phosphate and disodium hydrogen phosphate is too low, the pH fluctuation in the cathode region may be more than ±1.0, and the stability of hydrogen and oxygen evolution will be greatly reduced; If the total concentration of sodium dihydrogen phosphate and disodium hydrogen phosphate is too high, phosphate crystals will precipitate and block the circulation pipeline.

[0034] The molar ratio of sodium dihydrogen phosphate to disodium hydrogen phosphate may be 1.0:1.0 to 1.0:3.0, or may be 1.0:1.5 to 1.0:2.5, or may be 1.0:1.8 to 1.0:2.0.

[0035] If the amount of sodium dihydrogen phosphate is too low, the pH fluctuation range in the cathode area will expand, and a Ni(OH)2 passivation layer will form on the surface of the nickel anode due to the local high pH. If the amount of sodium dihydrogen phosphate is too high, the electrolyte ionic strength will be too high, and phosphate will precipitate NaH2PO4 at low temperature (<25°C) or high concentration. 4` 2H2O crystals (whose solubility is 90 g / 100 mL, 25°C) block the circulation pipeline.

[0036] The pH range of phosphate buffer is pH 6.0-12.0, which can fully cover the working pH range of the electrolyte of the present invention (8.0-10.0). In comparison, the pH range of conventional carbonate buffer is pH 9.2-10.8, which cannot cover the above working pH range.

[0037] In addition, phosphates have high thermal stability (decomposition temperature > 200°C) and do not release gases such as CO2, ensuring that the purity of the hydrogen and oxygen mixed gas is greater than 99.9%. Carbonates release CO2 gas at high temperatures (> 50°C) or low pH, requiring additional purification steps.

[0038] Therefore, the present invention chooses to use a phosphate buffer instead of a carbonate buffer.

[0039] Aqueous solvents Aqueous solvent is used to dissolve the redox mediator (K3[Fe(CN)6]) and buffer.

[0040] There is no particular limitation on the aqueous solvent, and it can be any aqueous solvent commonly used in the art. For example, the aqueous solvent can be at least one of ultrapure water, deionized water, and distilled water, preferably ultrapure water.

[0041] pH adjusters The pH regulator is used to adjust the pH of the electrolyte to 8.0-10.0, preferably 8.5-9.5. Within this pH range, the overall catalytic water electrolysis performance of the electrode system can be optimized.

[0042] If the pH of the electrolyte is too low, the phosphate buffer loses its buffering capacity. In addition, the nickel anode will corrode under acidic conditions, generating Ni 2+ Contaminated electrolyte, the anode reaction path turns to acidic oxygen evolution, causing the hydrogen-oxygen ratio to rebound to close to 2:1, and the control function is lost; If the pH of the electrolyte is too high, Fe(CN)6 3- It slowly hydrolyzes under strong alkaline conditions to produce Fe(OH)3 and CNO - (cyanate), loses its redox regulating function, and a dense Ni(OH)2 passivation layer is formed on the surface of the nickel anode.

[0043] The pH adjuster may be at least one of KOH and NaOH, preferably KOH.

[0044] In the electrolyte of the present invention, the concentration of the pH adjuster (such as KOH) can be 0.005 to 0.015 M, which is determined according to the desired pH of the electrolyte.

[0045] Working mechanism of electrolyte The present invention introduces a specific redox medium and a buffer on the basis of a traditional alkaline electrolyte system (aqueous solvent + a base such as KOH as an electrolyte), thereby obtaining a new electrolyte system capable of precisely controlling the hydrogen-oxygen ratio.

[0046] Specifically, the present invention constructs a synergistic system comprising a redox medium, a buffer, and a pH regulator, which exhibits reversible proton-coupled electron transfer properties and precisely regulates the proton concentration gradient at the electrode interface through valence state conversion of the redox medium. This not only achieves kinetic equilibrium control of the hydrogen / oxygen evolution reaction but also provides an electrochemical control window for precise regulation of the volume ratio of hydrogen and oxygen gases in the electrolysis product, thus overcoming the inherent thermodynamic limitation of the hydrogen-oxygen ratio in traditional electrolytes.

[0047] Specifically, when the concentration of potassium ferricyanide K3[Fe(CN)6] as a redox medium was adjusted in the range of 0.05-0.0.22M, Fe(CN)6 3- The oxidation reaction of Fe(CN)6 3- To reduced Fe(CN)6 4- The conversion of plays a "shunt" role in electron transfer. This reaction consumes the anode current and reduces the amount of oxygen generated as needed. In addition, the phosphate buffer suppresses local pH oscillations, and the concentration of the pH regulator (such as KOH) linearly regulates the bulk conductivity of the electrolyte, ultimately achieving a continuously adjustable hydrogen-oxygen ratio in the range of 3:1 to 15:1. Specifically, as needed, the hydrogen-oxygen ratio can range from 5:1 to 10:1, or 6:1 to 8:1.

[0048] The electrolyte system of this invention is particularly suitable for portable medical water electrolysis systems, flexibly matching downstream medical needs for varying volume ratios of hydrogen and oxygen mixed gases (H2 / O2). Compared to traditional control methods that require complex membrane electrode assemblies, this invention achieves precise control of the hydrogen-oxygen ratio simply by adjusting the concentrations of the electrolyte components, providing a cost-effective solution for the intelligent transformation of large-scale water electrolysis hydrogen production systems.

[0049] 2. Method for preparing electrolyte According to a second aspect of the present invention, there is provided a method for preparing the above-mentioned electrolyte, the method comprising the following steps: S1: dissolving K3[Fe(CN)6], sodium dihydrogen phosphate (NaH2PO4) and disodium hydrogen phosphate (Na2HPO4) in the aqueous solvent to obtain an intermediate solution, and S2: adding the pH adjuster to the intermediate solution to obtain the electrolyte.

[0050] The above steps can be carried out by conventional technical means. The steps can be carried out at room temperature (such as 15-25°C), normal pressure (such as one atmosphere) and atmospheric atmosphere. For the description of each component, please refer to the above.

[0051] The following describes each step in detail. K3[Fe(CN)6], sodium dihydrogen phosphate (NaH2PO4) and sodium hydrogen phosphate (Na2HPO4) are dissolved in the aqueous solvent to obtain an intermediate solution.

[0052] In one embodiment, K3[Fe(CN)6] can be first added to ultrapure water and stirred to dissolve, and then sodium dihydrogen phosphate (NaH2PO4) and sodium hydrogen phosphate (Na2HPO4) are added thereto and stirred to dissolve to obtain an intermediate solution.

[0053] Alternatively, K3[Fe(CN)6], sodium dihydrogen phosphate (NaH2PO4), and disodium hydrogen phosphate (Na2HPO4) can be added to ultrapure water and stirred to dissolve to obtain an intermediate solution.

[0054] The dosage of the above components can be determined according to the required K3[Fe(CN)6] concentration.

[0055] There is no particular limitation on the method of stirring, as long as the various materials being stirred are uniformly mixed. For example, a stirrer can be used for mechanical stirring. The stirring time can generally be 1-10 minutes, preferably 2-5 minutes.

[0056] Step S2: Prepare electrolyte A pH adjuster is added to the intermediate solution to obtain the target electrolyte.

[0057] In one embodiment, similar to step S1, a pH adjuster may be added under stirring. Furthermore, the amount of the pH adjuster added may be determined based on the desired pH of the electrolyte (eg, 8.0-10.0).

[0058] Since the amount of the pH adjuster used is relatively small, it can be added dropwise in the form of an aqueous solution.

[0059] The obtained target electrolyte is in the form of a solution in which the components are uniformly mixed, that is, a homogeneous system.

[0060] Example Hereinafter, the present invention will be described in detail with reference to Examples to specifically describe the present invention. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention should not be interpreted as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely describe the present invention to those of ordinary skill in the art.

[0061] Unless otherwise specified, the experimental methods in the following examples are generally based on conventional conditions in the art or conditions recommended by the manufacturer; the raw materials and equipment used are all commercially available from conventional markets, unless otherwise specified.

[0062] Example 1 (Using low concentration potassium ferrocyanide as redox medium) Examples 1a, 1b and 1c The electrolyte for water electrolysis was prepared by the following steps.

[0063] S1: 0.6 mol of potassium ferricyanide K3[Fe(CN)6] as a redox medium, 1.2 mol of sodium dihydrogen phosphate (NaH2PO4) and disodium hydrogen phosphate (Na2HPO4) (phosphate buffer, the molar ratio of sodium dihydrogen phosphate to disodium hydrogen phosphate is 1.0:1.6) are dissolved in 10 L of ultrapure water under stirring to obtain an intermediate solution; S2: Add 10 ml of 1 M KOH aqueous solution to the intermediate solution and stir evenly to obtain a target electrolyte with a pH of 9.

[0064] The obtained electrolyte was divided into three equal parts and used as the electrolytes of Examples 1a, 1b and 1c, respectively.

[0065] Example 1d The electrolyte for water electrolysis was prepared by the same steps as in Example 1a, except that the amount of potassium ferricyanide K3[Fe(CN)6] in step S1 was changed to 0.5 mol.

[0066] Finally, an electrolyte with pH=9 was obtained.

[0067] Example 1e An electrolyte for water electrolysis was prepared by the same steps as in Example 1a, except that the amount of potassium ferricyanide K3[Fe(CN)6] in step S1 was changed to 0.7 mol.

[0068] Finally, an electrolyte with pH=9 was obtained.

[0069] Example 2 (using a medium concentration of potassium ferrocyanide and changing the amount of buffer and pH adjuster accordingly) Examples 2a, 2b and 2c The electrolyte for water electrolysis was prepared by the following steps.

[0070] S1: Dissolve 1.5 mol of potassium ferricyanide K3[Fe(CN)6] as a redox medium, 3.0 mol of sodium dihydrogen phosphate (NaH2PO4) and sodium hydrogen phosphate (Na2HPO4) (phosphate buffer, the molar ratio of sodium dihydrogen phosphate to sodium hydrogen phosphate is 1.0:2.2) in 10 L of ultrapure water to obtain an intermediate solution; S2: Add 15 ml of 1 M KOH aqueous solution to the intermediate solution to obtain a target electrolyte with a pH of 9.

[0071] The obtained electrolyte was divided into three equal parts and used as the electrolytes of Examples 2a, 2b and 2c, respectively.

[0072] Example 2d An electrolyte for water electrolysis was prepared by the same steps as in Example 2a, except that the amount of potassium ferricyanide K3[Fe(CN)6] in step S1 was changed to 1.4 mol.

[0073] Finally, an electrolyte with pH=9 was obtained.

[0074] Example 2e An electrolyte for water electrolysis was prepared by the same steps as in Example 2a, except that the amount of potassium ferricyanide K3[Fe(CN)6] in step S1 was changed to 1.6 mol.

[0075] Finally, an electrolyte with pH=9 was obtained.

[0076] Example 3 (Using high concentration potassium ferricyanide and changing the amount of buffer and pH adjuster accordingly) Examples 3a, 3b and 3c The electrolyte for water electrolysis was prepared by the following steps.

[0077] S1: Dissolve 2.1 mol of potassium ferricyanide K3[Fe(CN)6] as a redox medium, 4.0 mol of sodium dihydrogen phosphate (NaH2PO4) and sodium hydrogen phosphate (Na2HPO4) (phosphate buffer, the molar ratio of sodium dihydrogen phosphate to sodium hydrogen phosphate is 1.0:3.0) in 10 L of ultrapure water to obtain an intermediate solution; S2: Add 8 ml of 1 M KOH aqueous solution to the intermediate solution to obtain a target electrolyte with a pH of 9.

[0078] The obtained electrolyte was divided into three equal parts and used as the electrolytes of Examples 3a, 3b and 3c, respectively.

[0079] Example 3d An electrolyte for water electrolysis was prepared by the same steps as in Example 3a, except that the amount of potassium ferricyanide K3[Fe(CN)6] in step S1 was changed to 2.0 mol.

[0080] Finally, an electrolyte with pH=9 was obtained.

[0081] Example 3e An electrolyte for water electrolysis was prepared by the same steps as in Example 3a, except that the amount of potassium ferricyanide K3[Fe(CN)6] in step S1 was changed to 2.2 mol.

[0082] Finally, an electrolyte with pH=9 was obtained.

[0083] Comparative Example 1 (Using Low Concentration Potassium Iodide KI as Redox Medium) Comparative Examples 1a, 1b, and 1c The electrolyte for water electrolysis was prepared by the following steps.

[0084] S1: Dissolve 1.5 mol of potassium iodide (KI) as a redox medium, 2.5 mol of sodium dihydrogen phosphate (NaH2PO4) and disodium hydrogen phosphate (Na2HPO4) (phosphate buffer, the molar ratio of sodium dihydrogen phosphate to disodium hydrogen phosphate is 1.0:2.0) in 10 L of ultrapure water to obtain an intermediate solution; S2: Add 10 ml of 1 M KOH aqueous solution to the intermediate solution to obtain a target electrolyte with a pH of 9.

[0085] The obtained electrolyte solution was divided into three equal parts and used as electrolyte solutions of Comparative Examples 1a, 1b, and 1c, respectively.

[0086] Comparative Example 2 (Using High Concentration Potassium Iodide KI as Redox Medium) Comparative Examples 2a, 2b, and 2c The electrolyte for water electrolysis was prepared by the following steps.

[0087] S1: Dissolve 3.0 mol of potassium iodide (KI) as a redox medium, 4.0 mol of sodium dihydrogen phosphate (NaH2PO4) and sodium hydrogen phosphate (Na2HPO4) (phosphate buffer, the molar ratio of sodium dihydrogen phosphate to sodium hydrogen phosphate is 1.0:1.0) in 10 L of ultrapure water to obtain an intermediate solution; S2: Add 8 ml of 1 M KOH aqueous solution to the intermediate solution to obtain a target electrolyte with a pH of 9.

[0088] The obtained electrolyte solution was divided into three equal parts and used as electrolyte solutions of Comparative Examples 2a, 2b and 2c, respectively.

[0089] Comparative Example 3 (Conventional alkaline electrolyte, excluding potassium ferrocyanide and buffer) The electrolyte for water electrolysis is prepared by the following steps.

[0090] Take 10L of ultrapure water and add 1ml of 1M KOH to obtain the target electrolyte with pH = 9.

[0091] Comparative Example 4 (using carbonate buffer) An electrolyte for water electrolysis was prepared by the same steps as in Example 1a, except that the phosphate buffer in step S1 was replaced by 1.5 mol of sodium carbonate (Na2CO3) and sodium bicarbonate (NaHCO3) (the molar ratio of carbonate buffer, sodium carbonate to sodium bicarbonate was 1.0:1.8).

[0092] The target electrolyte solution with pH=9 was obtained.

[0093] Comparative Example 5 (Buffer Omitted) An electrolyte for water electrolysis was prepared by the same steps as in Example 1a, except that no phosphate buffer was used in step S1.

[0094] The target electrolyte solution with pH=9 was obtained.

[0095] Experimental Example 1 Electrolyte Reaction Stability Test Electrochemical tests were performed on the electrolytes of each embodiment and comparative example using an electrochemical workstation (manufactured by Shanghai Chenhua, model CHI 660E). Specifically, a three-electrode system (platinum mesh as working electrode (cathode), porous nickel plate as counter electrode (anode), and calomel electrode as reference electrode) was used, and the electrolyte was used as the electrolyte solution, with a constant current of 50 mA cm -2 , water conditions are 40℃, and run for 3h.

[0096] The gas was collected using the drainage method at one-hour intervals, and the volume ratio of hydrogen and oxygen gases (hereinafter referred to as the "hydrogen-oxygen ratio") was analyzed, as shown in Table 1 below.

[0097]

[0098] (1) Regarding electrolytes of different batches but having the same composition (Examples 1a-1c, Examples 2a-2c, Examples 3a-3c, Comparative Examples 1a-1c, and Comparative Examples 2a-2c) As can be seen from Table 1, Examples 1a-1c, Examples 2a-2c, and Examples 3a-3c, respectively, used different batches of electrolytes having the same composition for electrolysis, resulting in the same hydrogen-oxygen ratio and controlling the gas production fluctuation within a range of ±0.3%, demonstrating their suitability for small-scale stable gas supply for portable medical inhalation mixed gases. Furthermore, this indicates that normal experimental errors during the electrolysis process (including manual operating errors and environmental factors) do not affect the final hydrogen-oxygen ratio. The electrolyte containing potassium ferricyanide K3[Fe(CN)6] exhibits excellent reaction stability, allowing for easy and repeatable production of the same hydrogen-oxygen ratio.

[0099] In contrast, when comparative examples 1a-1c and 2a-2c (using low and high concentrations of potassium iodide KI as redox media, respectively) were electrolyzed using different batches of electrolytes with the same composition, the resulting hydrogen-oxygen ratios fluctuated significantly, indicating that normal experimental errors and environmental factors during the electrolysis process significantly affected the final hydrogen-oxygen ratio. This suggests that electrolytes containing potassium iodide KI have poor reaction stability, and even with electrolytes of the same composition, it is difficult to repeatedly obtain the same hydrogen-oxygen ratio.

[0100] In addition, the sensitivity of the electrolyte containing potassium iodide KI is significantly nonlinear, and the control accuracy drops sharply at high concentrations, making it unsuitable for applications such as gas therapy, which requires accurate and stable output of hydrogen and oxygen mixed gas within a certain period of time.

[0101] (2) Regarding the electrolytes of different concentrations of the present invention (Examples 1a, 1d, 1e, Examples 2a, 2d, 2e, and Examples 3a, 3d, 3e) In addition, it can be seen from Table 1 that the three groups of embodiments of the present invention with different concentrations (Examples 1a, 1d, 1e, Examples 2a, 2d, 2e, and Examples 3a, 3d, 3e) exhibit excellent hydrogen-oxygen ratio controllability through the gradient design of the redox medium concentration.

[0102] Specifically, the electrolytes in the three aforementioned embodiments each achieve a linear response characteristic with proportional adjustment around their concentrations by varying their concentrations by 0.01 M. Thus, when using an automatic rehydration system, the gas supply needs of large-scale gas usage scenarios, such as hospitals, can be met.

[0103] In addition, Example 3e uses a high concentration of 0.22 M K3[Fe(CN)6] to achieve an extremely high hydrogen-oxygen ratio of 15:1.

[0104] It can be seen from the above three groups of embodiments that the electrolyte of the present invention can be applied to various scenarios ranging from mixed gases in different proportions to special needs.

[0105] In addition, it can be seen from Table 1 that the hydrogen-oxygen ratio obtained by various electrolytes in Examples 1 to 3 (using different concentrations of potassium ferricyanide) during the operation of 3 hours is constant and does not change, which proves that they can stably generate hydrogen-oxygen mixed gas with the required hydrogen-oxygen ratio.

[0106] In addition, in Examples 1 to 3, the desired hydrogen-oxygen ratio can be obtained by adjusting the concentration of potassium ferricyanide.

[0107] (3) Comparison of Electrolytes Omitting the Redox Mediator or Buffer of the Present Invention and Changing the Buffer Type (Example 1a and Comparative Examples 3 to 5) Compared with Example 1a, The hydrogen-oxygen ratio obtained in Comparative Example 3 (conventional electrolyte, without potassium ferricyanide and buffer) during the 3-hour operation was fixed at 2:1, but it did not have the function of adjusting the hydrogen-oxygen ratio by changing the electrolyte composition.

[0108] The hydrogen-oxygen ratio obtained in Comparative Example 4 (using carbonate buffer) during the 3-hour operation was not constant, indicating that the carbonate buffer could not ensure that the pH of the electrolyte remained stable, and thus could not stabilize the electrolysis of water.

[0109] Comparative Example 5 (no buffer added) achieved an even more unstable hydrogen-oxygen ratio over a 3-hour run, making it unsuitable for applications such as gas therapy, which require a precise and stable output of a hydrogen-oxygen mixture over a certain period of time. This suggests that even when using potassium ferricyanide as a redox medium, a buffer is still required to ensure a stable hydrogen-oxygen ratio.

[0110] The above experimental results show that compared with the electrolyte of the comparative example, the electrolyte of the embodiment of the present invention can safely, effectively and stably control the hydrogen-oxygen ratio obtained by electrolysis of water within the range of 3:1 to 15:1 by adopting different concentrations of specific redox media K3[Fe(CN)6] in combination with a phosphate buffer.

[0111] Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

1. An electrolyte for electrolyzing water, the electrolyte comprising: K3[Fe(CN)6] as a redox mediator, A mixture of sodium dihydrogen phosphate and disodium hydrogen phosphate as a buffer, aqueous solvent, and a pH adjuster.

2. The electrolyte according to claim 1, wherein The aqueous solvent is at least one of ultrapure water, deionized water and distilled water, The pH adjuster is at least one of KOH and NaOH.

3. The electrolyte according to claim 1, wherein The concentration of K3[Fe(CN)6] is 0.05-0.22 M, The total concentration of sodium dihydrogen phosphate and disodium hydrogen phosphate is 0.01-0.50 M. The molar ratio of sodium dihydrogen phosphate to disodium hydrogen phosphate is 1.0:1.0 to 1.0:3.0, The concentration of the pH adjuster is 0.005-0.015 M. The electrolyte according to claim 1 , wherein the pH value of the electrolyte is 8.0-10.

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5. A method for preparing the electrolyte according to claim 1, comprising the steps of: S1: dissolving K3[Fe(CN)6], sodium dihydrogen phosphate and disodium hydrogen phosphate in the aqueous solvent to obtain an intermediate solution; S2: adding the pH adjuster to the intermediate solution to obtain the electrolyte. The method according to claim 5 , wherein the pH adjuster is added dropwise to the intermediate solution in the form of an aqueous solution.

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