Asymmetric electrolyte supply space-time step-by-step hydrogen production system

Abstract

The invention discloses an asymmetric electrolyte supply space-time step-by-step hydrogen production system. The system comprises an electrochemical reaction module and an electrolyte circulation module. The electrochemical reaction module comprises an anode chamber, an ion exchange membrane, a cathode chamber and an external power supply; an anode catalytic electrode is arranged in the anode chamber; reducing the electrolyte containing trivalent vanadium ions into divalent vanadium ions in the cathode chamber to replace hydrogen evolution reaction for storing electrons; the electrolyte circulation module comprises a regeneration circulation pool, a hydrogen collection pool and a buffer pool; and the regeneration cycle pool is used for receiving the cathode electrode liquid which flows out of the cathode chamber and is subjected to reaction to form a cycle electrolyte solution, and the hydrogen product is generated by controlling the input of a catalyst in the pool. According to the invention, separation of hydrogen and oxygen in time and space can be realized, additional anolyte supply is not needed, and efficient production and continuous operation of the process can be realized at room temperature.

Description

Technical Field

[0001] This invention relates to the field of hydrogen production by water electrolysis, and specifically to an asymmetric electrolyte supply system for spatiotemporal stepwise hydrogen production. Background Technology

[0002] Hydrogen energy, as a secondary energy source, is considered one of the most promising green new energy sources due to its high calorific value and pollution-free characteristics, and has been widely applied in transportation, food, energy storage, and other fields. Currently, there are three main methods for producing hydrogen: water splitting, biomass hydrogen production, and hydrogen production using fossil fuels. Water splitting is further divided into electrocatalytic hydrogen production and photocatalytic hydrogen production. Both methods decompose water into hydrogen and oxygen without causing environmental pollution. Electrocatalytic hydrogen production, due to its high efficiency and ease of operation, has become a recognized green hydrogen production method.

[0003] However, traditional water electrolysis methods face numerous challenges. When producing hydrogen using an electrolyzer, the mixing of hydrogen and oxygen is almost unavoidable, and this mixing increases with pressure. High-pressure water electrolysis is virtually impossible using traditional methods, meaning the produced hydrogen needs to be pressurized before being transported and stored in cylinders, further increasing costs. Traditional water electrolysis uses a method where both the anode and cathode are supplied with liquid electrolytes and circulated. This electrolyte supply and circulation system leads to increased costs, and because the anode catalyst is often a precious metal oxide, prolonged exposure to acidic or alkaline environments shortens the electrode material's lifespan. Therefore, reducing costs and extending electrolysis lifespan are urgent problems that need to be addressed. Summary of the Invention

[0004] The purpose of this invention is to provide an asymmetric electrolyte supply system for spatiotemporal stepwise hydrogen production, which can solve the problems of hydrogen-oxygen mixing and low catalyst life in the existing water electrolysis process. It provides a method that greatly reduces costs and enables the spatiotemporal stepwise preparation of hydrogen (H2) and oxygen (O2), while achieving efficient production and continuous operation of the process at room temperature.

[0005] In one aspect of the invention, an asymmetric electrolyte supply spatiotemporal stepwise hydrogen production system is proposed. According to an embodiment of the invention, it includes:

[0006] An electrochemical reaction module includes an anode chamber, an ion exchange membrane, a cathode chamber, and an external DC power supply. The anode chamber houses an anode catalytic electrode and an anode current collector. The cathode chamber houses a cathode catalytic electrode, a cathode current collector, and a cathode electrode solution. The ion exchange membrane is disposed between the anode chamber and the cathode chamber, with a cathode catalyst and an anode catalyst loaded on both sides of the ion exchange membrane, respectively. The anode current collector is disposed between the anode chamber and the ion exchange membrane, and the cathode current collector is disposed between the cathode chamber and the ion exchange membrane.

[0007] An electrolyte circulation module includes a regeneration circulation tank, a hydrogen collection tank, and a buffer tank. The regeneration circulation tank receives the reacted electrolyte solution flowing out of the cathode chamber and forms a circulating electrolyte solution. A palladium-on-carbon catalyst is used to oxidize divalent vanadium ions in the reacted electrolyte solution flowing out of the cathode chamber to trivalent vanadium ions, generating hydrogen gas, thus achieving spatiotemporal separation of hydrogen and oxygen. The hydrogen collection tank collects the hydrogen gas released from the regeneration circulation tank. The buffer tank thoroughly mixes the circulating electrolyte solution in the regeneration circulation tank before recirculating it back to the cathode chamber of the electrochemical reaction module.

[0008] The asymmetric electrolyte-supply water electrolysis stepwise hydrogen production system generates oxygen at the anode while simultaneously utilizing the divalent vanadium ions, a reaction product at the cathode, in a chemical reaction. This releases hydrogen while simultaneously generating trivalent vanadium ions. The reaction solution then re-enters the cathode chamber to participate in the electrochemical reaction, completing the cycle. This system achieves simultaneous, spatiotemporally separated water electrolysis for hydrogen production with a single-sided electrolyte supply, effectively solving the problem of mixing large quantities of anode electrolyte with products from both the anode and cathode.

[0009] In this invention, a vanadium reduction reaction occurs in the cathode chamber: Oxygen evolution reaction occurs in the anode chamber: The generated H + Under the influence of an electric field, the electrolyte moves through the membrane into the cathode chamber; the reaction solution in the anode chamber is obtained by permeating the cathode electrolyte through an ion exchange membrane.

[0010] In the regeneration cycle tank, divalent vanadium comes into contact with the catalyst to undergo a vanadium oxidation reaction, releasing hydrogen gas and simultaneously obtaining trivalent vanadium. The catalyst is palladium on carbon; the mass of the catalyst is preferably 5-50 mg, more preferably 10 mg.

[0011] In addition, the asymmetric electrolyte supply spatiotemporal stepwise hydrogen production system according to the above embodiments of the present invention may also have the following additional technical features:

[0012] In some embodiments of the present invention, the anode catalyst is iridium oxide; and / or, the cathode catalyst is carbon black or carbon felt; and / or, the cathode electrolyte is a sulfuric acid solution containing vanadium oxysulfate; and / or, the ion exchange membrane is a cation exchange membrane with a thickness of 220 μm, specifically a DuPont Nafion 117 cation exchange membrane.

[0013] In some embodiments of the present invention, the preparation of the ion exchange membrane includes the following steps:

[0014] The cathode catalyst slurry and the anode catalyst slurry are sprayed onto both sides of the membrane, respectively. The catalyst-sprayed portions on both sides of the membrane are covered with a heat-resistant film and then placed in a hot press for hot pressing.

[0015] In some embodiments of the present invention, the solvent in the cathode catalyst slurry is a mixture of isopropanol and perfluorosulfonic acid solution, wherein the mass fraction of the perfluorosulfonic acid solution is 5 wt% to 8 wt%, and the volume ratio of isopropanol to perfluorosulfonic acid solution is 50:1; the mass concentration of the cathode catalyst slurry is 5 to 10 mg / mL, more preferably 6.8 mg / mL, wherein the mass concentration represents the mass (mg) of the cathode catalyst contained in the solvent per unit volume (mL) of the cathode catalyst slurry; and the loading of the cathode catalyst is 0.5 to 2 mg / cm³. 2 The load capacity is expressed per unit area (cm²) 2 The mass (mg) of the cathode catalyst loaded on the cathode catalytic electrode; the method for preparing the cathode carbon black catalyst slurry preferably includes: dispersing the cathode catalyst carbon black in a solvent and ultrasonically treating it; the ultrasonic treatment time is preferably 40 min.

[0016] And / or, the solvent in the anode catalyst slurry is a mixture of isopropanol and perfluorosulfonic acid solution, wherein the mass fraction of the perfluorosulfonic acid solution is 5-8 wt%, and the volume ratio of the isopropanol to the perfluorosulfonic acid solution is 50:1; the mass concentration of the anode catalyst slurry is 5-10 mg / mL, and the loading of the anode catalyst is 0.5-2 mg / mL. 2 The preparation method of the anode catalyst slurry preferably includes: dispersing the anode catalyst in a solvent and ultrasonically treating it; the ultrasonic treatment time is preferably 1.5 h.

[0017] And / or, the heat-resistant film is a polytetrafluoroethylene film with a thickness of 0.5 mm;

[0018] And / or, the pressure of the hot pressing operation is 0.5 to 15 MPa, more preferably 5 MPa; the temperature is 90 to 150°C, more preferably 135°C; and the time is 5 to 30 min, more preferably 15 min.

[0019] In some embodiments of the present invention, the cathode current collector is a carbon felt with a thickness of 5.4 mm, and the anode current collector is a titanium felt with a thickness of 0.25 to 0.35 mm, preferably 0.3 mm.

[0020] In some embodiments of the present invention, the electrolyte circulation module includes a peristaltic pump one, a peristaltic pump two, and a peristaltic pump three. The peristaltic pump one is used to pump the reacted electrolyte solution flowing out of the cathode chamber into the regeneration circulation tank; the peristaltic pump two is used to pump the circulating electrolyte solution from the regeneration circulation tank into the buffer tank; and the peristaltic pump three is used to pump the circulating electrolyte solution from the buffer tank into the cathode chamber of the electrochemical reaction module.

[0021] In some embodiments of the present invention, the electrolyte solution circulation rate of the peristaltic pump one, peristaltic pump two and peristaltic pump three is 20 to 100 mL / min, more preferably 80 mL / min; the electrolyte solution circulates into the cathode and then permeates a small amount into the anode region through the membrane.

[0022] In some embodiments of the present invention, an electrolyte heating unit is also included. The electrolyte heating unit is disposed at the bottom of the regeneration circulation tank and is used to heat the electrolyte in the regeneration circulation tank at a heating temperature of 25 to 70°C.

[0023] In some embodiments of the present invention, the hydrogen collection pool includes a drainage gas collection system connected to the regeneration circulation pool; the drainage gas collection system includes a container filled with water and a collection cylinder inverted in the container; the drainage collection system utilizes the accumulation of collected gas above the measuring cylinder to create a pressure difference between the waterless part and the water-filled part of the collection cylinder, thereby removing water and confirming the volume of collected gas.

[0024] In some embodiments of the present invention, the current density of the external DC power supply is -250 to -50 mA / cm². 2 .

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] 1) After the electrolyte solution of the present invention undergoes electrochemical conversion in an electrolytic cell, the product is oxidized in a regeneration cell (from divalent vanadium ions to trivalent vanadium ions). This allows for electrolyte regeneration and recycling. In the electrolytic cell, the anode electrode electrolyzes water permeating from the cathode electrolyte through a membrane into oxygen and protons. Simultaneously, trivalent vanadium ions in the cathode electrolyte are reduced to divalent vanadium ions. The divalent vanadium ions in the electrolyte solution after electrolysis are reduced to trivalent vanadium ions under the action of a catalyst, producing hydrogen gas. This effectively solves the hydrogen-oxygen mixing problem in water electrolysis systems, achieving spatiotemporal decoupling of hydrogen and oxygen. The membrane-free electrolytic cell system provided by this invention exhibits good stability, with a current density consistently maintained at approximately -250 mA / cm². 2 After 40 hours of continuous operation, the voltage of the electrolytic cell becomes relatively stable.

[0027] 2) In this invention, the electrolysis reaction is decoupled in time and space, so that the oxygen evolution reaction and the hydrogen evolution reaction are carried out in two different reaction vessels, and the hydrogen evolution reaction is a controllable reaction. Furthermore, hydrogen can be stored in the form of divalent vanadium, which enables safer hydrogen storage.

[0028] 3) This invention directly uses a vanadium-sulfuric acid solution as the electrolyte for water electrolysis. The hydrogen storage efficiency of vanadium reaches over 95% during the reaction. The anode and cathode of this system are separated by a cation exchange membrane to prevent direct contact between them. The electrolyte is circulated to the cathode by a peristaltic pump at a flow rate of 20-100 mL / min and then permeates through the membrane into the anode region.

[0029] 4) This invention adopts an electrolysis method in which the cathode electrolyte is supplied separately and the anode electrolyte is not supplied. Water that permeates from the cathode side is used for the anode reaction, which reduces costs and avoids long-term contact between the anode precious metal catalyst and the acidic electrolyte, thus extending the catalytic life of the anode catalyst.

[0030] 5) The asymmetric electrolyte supply system of the present invention provides a spatiotemporal stepwise hydrogen production system in which the vanadium concentration in the electrolyte is 0.5 mol / L and the current density is -100 mA / cm². 2 At a full-cell voltage of -2.75 V, an electrolyte circulation rate of 60 mL / min, and a temperature of 25 °C, a vanadium reduction Faraday efficiency of 96.7% can be achieved. It also maintains stable operation for 40 hours, demonstrating good stability. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the asymmetric electrolyte supply electrolysis stepwise hydrogen production system of the present invention. In the figure, 1 is the anode chamber, 2 is the anode catalytic electrode, 3 is the cation exchange membrane, 4 is the cathode catalytic electrode, 5 is the cathode chamber, 6 is the peristaltic pump one, 7 is the regeneration circulation tank, 8 is the peristaltic pump two, 9 is the buffer tank, 10 is the peristaltic pump three, 11 is the hydrogen collection tank, 12 is the measuring cylinder, and 13 is the heating platform.

[0032] Figure 2 The diagram shows the structure near the cation exchange membrane in this invention, the mass exchange and ion exchange on both sides of the membrane, and the reaction principles of the anode and cathode sides and the regeneration device.

[0033] Figure 3 This is a detailed diagram of the electrolytic cell assembly in this invention;

[0034] Figure 4 The diagram shows the performance of the electrolysis system in Examples 1-5 of this invention. The left diagram shows the amount of hydrogen released during the electrolysis process in Examples 1-5, and the right diagram shows the Faraday efficiency of vanadium reduction in Examples 1-5 during the electrolysis process.

[0035] Figure 5 The diagram shows the performance of the electrolysis system in Examples 1 and 6-9 of this invention. The left diagram shows the amount of hydrogen released during the electrolysis process in Examples 1 and 6-9, and the right diagram shows the Faraday efficiency of vanadium reduction during the electrolysis process in Examples 1 and 6-9.

[0036] Figure 6 The diagram shows the performance of the electrolysis system in Examples 1 and 10-13 of this invention. The left diagram shows the amount of hydrogen released during the electrolysis process in Examples 1 and 10-13, and the right diagram shows the Faraday efficiency of vanadium reduction during the electrolysis process in Examples 1 and 10-13.

[0037] Figure 7 This is a comparison diagram of the electrolytic cell voltages of Comparative Example 1, Example 1, and Examples 14-17 in this invention;

[0038] Figure 8 The graph shows the voltage change of the electrolyzer during 40 hours of continuous operation of the asymmetric electrolyte supply electrolysis step-by-step hydrogen production system of the present invention. Detailed Implementation

[0039] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0040] All reagents used in the following examples were purchased from McLean and were not further purified.

[0041] The electrochemical characterizations used in the following examples were performed using an electrochemical workstation CHI 1140D (DC power supply) and a commercial membrane electrode assembly cell (Shanghai Chuxi).

[0042] Example 1

[0043] like Figure 1 As shown, an asymmetric electrolyte supply spatiotemporally decoupled water electrolysis hydrogen production system is disclosed. The system includes an electrochemical reaction module, an electrolyte circulation module, and an electrolyte heating module.

[0044] The electrochemical reaction module includes an anode chamber 1, an ion exchange membrane 3, a cathode chamber 5, and an external DC power supply; the anode chamber houses an anode catalytic electrode 2; the cathode chamber houses a cathode catalytic electrode 2 and a cathode electrode solution; the ion exchange membrane is located between the anode chamber and the cathode chamber, and cathode catalyst and anode catalyst are respectively loaded on both sides of the ion exchange membrane.

[0045] The electrolyte circulation module includes a regeneration circulation tank 7, a hydrogen collection tank 11, and a buffer tank 9. The regeneration circulation tank is used to catalyze the regeneration of the circulating electrolyte solution and release hydrogen. The reacted electrolyte solution flowing out of the cathode chamber is circulated to the regeneration circulation tank 7 by a peristaltic pump 6. In this tank, a catalyst (palladium on carbon) is used to oxidize divalent vanadium ions to trivalent vanadium ions and generate hydrogen, realizing the spatial and temporal separation of hydrogen and oxygen. The hydrogen collection tank 11 is used to collect the hydrogen generated and released in the regeneration circulation tank 7. The buffer tank 9 is used to fully mix the circulating electrolyte solution in the regeneration circulation tank before circulating it to the cathode chamber of the electrochemical reaction module. The regenerated electrolyte in the buffer tank 9 is circulated to the cathode chamber 5 by a peristaltic pump 10.

[0046] The hydrogen collection tank 11 includes a drainage gas collection system connected to the regeneration circulation tank; the drainage gas collection system includes a container filled with water and a collection cylinder inverted in the container, specifically, the collection cylinder is a measuring cylinder 12; the drainage collection system utilizes the accumulation of collected gas above the measuring cylinder to create a pressure difference between the waterless part and the water-filled part of the collection cylinder, thereby removing water and confirming the volume of collected gas.

[0047] The electrolyte heating module includes a heating platform 13 for heating the regeneration circulation tank 7.

[0048] In this embodiment, the cathode electrolyte solvent is a 0.5 mol / L sulfuric acid solution, and the cathode electrolyte is vanadium oxysulfate with a vanadium concentration of 0.5 mol / L. In this embodiment, as... Figure 2 As shown, during electrolysis, the cathode electrolyte undergoes an electrochemical vanadium reduction reaction on the cathode catalytic electrode 4. Meanwhile, some of the electrolyte diffuses through the cation exchange membrane 3 into the anode chamber 1, where an oxygen evolution reaction occurs on the anode catalytic electrode 2. Protons generated in the anode chamber migrate through the cation exchange membrane 3 to the cathode chamber 5. After the electrochemical reaction, the cathode electrolyte flows from the cathode chamber 5 into the regeneration circulation tank 7 via the peristaltic pump 6, where the vanadium oxidation reaction occurs. Hydrogen gas is released simultaneously. The temperature of the heating platform 13 below the regeneration circulation tank 7 is 25°C. The released hydrogen gas enters the measuring cylinder 12 in the hydrogen collection tank 11, and the hydrogen gas produced is measured by water displacement. At the same time, the electrolyte flows from the regeneration circulation tank 7 into the buffer tank 9 via peristaltic pump 2, and then returns to the cathode electrolysis chamber via peristaltic pump 3 10.

[0049] In this embodiment, a cathode guide channel is provided on the cathode plate. The cathode guide channel is distributed in a serpentine shape from bottom to top. The serpentine groove and the cathode catalyst attached to it cooperate to form the cathode guide channel. The lower port of the cathode guide channel is inlet, and the upper port is open as the cathode liquid outlet. The cathode liquid enters the cathode guide channel after passing through the cathode catalyst, and then flows out from the upper port. The area of ​​the serpentine groove is 2cm×2cm.

[0050] In this real-time example, the cathode and anode chambers are made of 6.5 cm × 6.5 cm titanium plates. The electrochemical reaction module is assembled as follows: Figure 3 As shown, the PTFE gasket is used to prevent liquid leakage.

[0051] In this embodiment, the iridium oxide loading on the side of the DuPont Nafion 117 cation exchange membrane closest to the anode chamber is 1 mg cm⁻¹. -2 The carbon black loading on the side of the DuPont Nafion 117 cation exchange membrane closest to the cathode is 1 mg / cm³. 2 .

[0052] In this embodiment, the anode current collector has a thickness of 0.3 mm, an area of ​​2 cm × 2 cm, and is made of titanium felt; the cathode current collector has a thickness of 5.4 mm, an area of ​​2 cm × 2 cm, and is made of carbon felt.

[0053] In this embodiment, the temperature of the cathode electrolyte is 25°C.

[0054] In this embodiment, the electrolyte circulation rate in the system is 60 mL / min.

[0055] In this embodiment, the applied current density is 250 mA / cm². -2 The running time is 0.5 hours.

[0056] Example 2

[0057] An electrolyte circulation module is provided. The only difference between this embodiment and Embodiment 1 is that the electrolyte circulation rate tested is 20 mL / min, while the other conditions and steps are the same as in Embodiment 1.

[0058] Example 3

[0059] An electrolyte circulation module is provided. The only difference between this embodiment and Embodiment 1 is that the electrolyte circulation rate tested is 40 mL / min, while the other conditions and steps are the same as in Embodiment 1.

[0060] Example 4

[0061] An electrolyte circulation module is provided. The only difference between this embodiment and Embodiment 1 is that the electrolyte circulation rate tested is 80 mL / min, while the other conditions and steps are the same as in Embodiment 1.

[0062] Example 5

[0063] An electrolyte circulation module is provided. The only difference between this embodiment and Embodiment 1 is that the electrolyte circulation rate tested is 100 mL / min, while the other conditions and steps are the same as in Embodiment 1.

[0064] Example 6

[0065] An electrolyte heating module is provided. The only difference between this embodiment and Embodiment 1 is that the electrolyte temperature tested is 40°C, while the other conditions and steps are the same as in Embodiment 1.

[0066] Example 7

[0067] An electrolyte heating module is provided. The only difference between this embodiment and Embodiment 1 is that the electrolyte temperature tested is 50°C, while the other conditions and steps are the same as in Embodiment 1.

[0068] Example 8

[0069] An electrolyte heating module is provided. The only difference between this embodiment and Embodiment 1 is that the electrolyte temperature tested is 60°C, while the other conditions and steps are the same as in Embodiment 1.

[0070] Example 9

[0071] An electrolyte heating module is provided. The only difference between this embodiment and Embodiment 1 is that the electrolyte temperature tested is 70°C, while the other conditions and steps are the same as in Embodiment 1.

[0072] Example 10

[0073] An electrochemical reaction module, the only difference between this embodiment and Example 1 is that the tested current density is 50 mA / cm². 2 All other conditions and steps are the same as in Example 1.

[0074] Example 11

[0075] An electrochemical reaction module, the only difference between this embodiment and Example 1 is that the tested current density is 100 mA / cm². 2 All other conditions and steps are the same as in Example 1.

[0076] Example 12

[0077] An electrochemical reaction module, the only difference between this embodiment and Example 1 is that the tested current density is 150 mA / cm². 2 All other conditions and steps are the same as in Example 1.

[0078] Example 13

[0079] An electrochemical reaction module, the only difference between this embodiment and Example 1 is that the tested current density is 200 mA / cm². 2 All other conditions and steps are the same as in Example 1.

[0080] The vanadium reduction Faraday efficiency in Examples 1-13 was calculated based on the volume of hydrogen collected by the hydrogen collection system using the following formula:

[0081] Formula for calculating the Faraday efficiency of vanadium reduction: .

[0082] Where z is the number of electrons transferred during the reduction of H2O to hydrogen, V is the volume (mL) of hydrogen collected by the hydrogen collection system, F is the Faraday constant (96485 C / mol), and Q is the total amount of electricity input during the reaction.

[0083] To obtain the average value and error bars, all Faraday efficiency measurements were repeated three times. The results are as follows: Figure 4 As shown in Figures 5, 6, and 6, the specific results are summarized in Table 1.

[0084] Table 1. Vanadium reduction Faraday efficiency in Examples 1-13

[0085]

[0086] like Figure 4 As shown in the left figure, with the increase of electrolyte circulation rate, the volume of hydrogen gas released in the spatiotemporal distribution during vanadium reduction gradually increases, reaching a maximum of 206 mL at a circulation rate of 80 mL / min in Example 4. Simultaneously, as... Figure 4 As shown in the right figure, the Faraday efficiency of vanadium reduction in Examples 1-5 is all higher than 89.5%, and the Faraday efficiency of vanadium reduction is the highest at a circulation rate of 80 mL / min, reaching 98.6%, indicating high overall efficiency of the device.

[0087] like Figure 5As shown in the left figure, with the increase of electrolyte temperature, the volume change trend of hydrogen gas released during vanadium reduction is not obvious, and the amount of hydrogen gas released is consistently around 200 mL. Meanwhile, in Example 1, when the electrolyte temperature is 25 degrees Celsius, the highest amount of hydrogen gas released is 206 mL. Furthermore... Figure 5 As shown in the right figure, the Faraday efficiency of vanadium reduction in Examples 1 and 6-9 is higher than 95%, with Example 1 exhibiting the highest Faraday efficiency of 96.7%. This demonstrates that the asymmetric electrolyte supply spatiotemporal distribution water electrolysis system does not require additional heat input and can selectively release hydrogen at room temperature.

[0088] like Figure 6 As shown in the left figure, increasing the current density during electrolysis leads to an increase in the volume of hydrogen gas released in the spatiotemporal distribution during vanadium reduction. Meanwhile, as... Figure 6 As shown in the right figure, the Faraday efficiency of vanadium reduction in Examples 1 and 10-13 is higher than 90%, and the distribution of vanadium reduction Faraday efficiency generally exhibits a volcano-like distribution with increasing current density. In Example 13, the current density is 200 mA / cm². 2 Under certain conditions, the Faraday efficiency of vanadium reduction is 98.6%, which is the optimal performance.

[0089] Example 14

[0090] An electrochemical reaction module is described. The only difference between this embodiment and Example 1 is that the concentration of vanadium in the electrolyte used for testing is 0.1 mol / L. All other conditions and steps are the same as in Example 1.

[0091] Example 15

[0092] An electrochemical reaction module is described in this embodiment. The only difference between this embodiment and Example 1 is that the concentration of vanadium in the electrolyte used for testing is 0.25 mol / L. All other conditions and steps are the same as in Example 1.

[0093] Example 16

[0094] An electrochemical reaction module is described. The only difference between this embodiment and Example 1 is that the concentration of vanadium in the electrolyte used for testing is 1 mol / L. All other conditions and steps are the same as in Example 1.

[0095] Example 17

[0096] An electrochemical reaction module is described. The only difference between this embodiment and Example 1 is that the concentration of vanadium in the electrolyte used for testing is 1.5 mol / L. All other conditions and steps are the same as in Example 1.

[0097] Comparative Example 1

[0098] Compared with Example 1, the difference is that the cathode electrolyte contains only 0.5 mol / L sulfuric acid solution and does not contain vanadium.

[0099] The electrolytic cell voltages during the operation of Examples 1, 14-17, and Comparative Example 1 were obtained using an electrochemical workstation CHI1140D. To obtain the average value and error bars, all data were measured three times. The results are as follows: Figure 6 As shown.

[0100] Table 2 shows the tank pressure during the operation of Examples 1, Examples 14-17, and Comparative Example 1.

[0101]

[0102] like Figure 7 As shown, the cell voltage gradually decreases with increasing vanadium concentration in the electrolyte, reaching a minimum value of -2.59V when the vanadium concentration is 1.5mol / L.

[0103] Example 18

[0104] An electrochemical reaction module is described. The only difference between this embodiment and Embodiment 1 is that the test time is 40 hours, and the hydrogen released in the circulating regeneration tank during the test is no longer collected in the hydrogen collection system. All other conditions and steps are the same as in Embodiment 1.

[0105] Figure 8 This diagram shows the voltage variation of the electrolyzer in the asymmetric electrolyte supply-based stepwise hydrogen production system for water electrolysis after 40 hours of continuous operation. It was found that the system maintained good stability during the 40-hour applied current period, and the entire device did not exhibit overheating or a sudden increase in cell voltage. This indicates that the asymmetric electrolyte supply-based water electrolysis system possesses a certain degree of stability under long-term conditions.

[0106] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the present invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. An asymmetric electrolyte supply system for spatiotemporal stepwise hydrogen production, characterized in that, include: An electrochemical reaction module includes an anode chamber, an ion exchange membrane, a cathode chamber, and an external DC power supply. The anode chamber houses an anode catalytic electrode and an anode current collector. The cathode chamber houses a cathode catalytic electrode, a cathode current collector, and a cathode electrode solution. The ion exchange membrane is disposed between the anode chamber and the cathode chamber, with a cathode catalyst and an anode catalyst loaded on both sides of the ion exchange membrane, respectively. The anode current collector is disposed between the anode chamber and the ion exchange membrane, and the cathode current collector is disposed between the cathode chamber and the ion exchange membrane. An electrolyte circulation module includes a regeneration circulation tank, a hydrogen collection tank, and a buffer tank. The regeneration circulation tank receives the reacted electrolyte solution flowing out of the cathode chamber and forms a circulating electrolyte solution. A palladium-on-carbon catalyst is used to oxidize divalent vanadium ions in the reacted electrolyte solution flowing out of the cathode chamber to trivalent vanadium ions, generating hydrogen gas, thus achieving spatiotemporal separation of hydrogen and oxygen. The hydrogen collection tank collects the hydrogen gas released from the regeneration circulation tank. The buffer tank thoroughly mixes the circulating electrolyte solution in the regeneration circulation tank before recirculating it back to the cathode chamber of the electrochemical reaction module.

2. The asymmetric electrolyte supply spatiotemporal stepwise hydrogen production system according to claim 1, characterized in that: The anode catalyst is iridium oxide; And / or, the cathode catalyst is carbon black or carbon felt; And / or, the cathode electrolyte is a sulfuric acid solution containing vanadium sulfate; And / or, the ion exchange membrane is a cation exchange membrane.

3. The asymmetric electrolyte supply spatiotemporal stepwise hydrogen production system according to claim 1, characterized in that, The preparation of the ion exchange membrane includes the following steps: The cathode catalyst slurry and the anode catalyst slurry are sprayed onto both sides of the membrane, respectively. The catalyst-sprayed portions on both sides of the membrane are covered with a heat-resistant film and then placed in a hot press for hot pressing.

4. The asymmetric electrolyte supply spatiotemporal stepwise hydrogen production system according to claim 1, characterized in that: The solvent in the cathode catalyst slurry is a mixture of isopropanol and perfluorosulfonic acid solution, wherein the perfluorosulfonic acid solution has a mass fraction of 5 wt% to 8 wt%, the mass concentration of the cathode catalyst slurry is 5 to 10 mg / mL, and the loading of the cathode catalyst is 0.5 to 2 mg / mL. 2 ; And / or, the solvent in the anode catalyst slurry is a mixture of isopropanol and perfluorosulfonic acid solution, wherein the mass fraction of the perfluorosulfonic acid solution is 5 wt% to 8 wt%, the mass concentration of the anode catalyst slurry is 5 to 10 mg / mL, and the loading of the anode catalyst is 0.5 to 2 mg / mL. 2 ; And / or, the heat-resistant film is a polytetrafluoroethylene film; And / or, the pressure of the hot pressing operation is 0.5 to 15 MPa, the temperature is 90 to 150 °C, and the time is 5 to 30 min.

5. The asymmetric electrolyte supply spatiotemporal stepwise hydrogen production system according to claim 1, characterized in that: The cathode current collector is a carbon felt, and the anode current collector is a titanium felt with a thickness of 0.25 to 0.35 mm.

6. The asymmetric electrolyte supply spatiotemporal stepwise hydrogen production system according to claim 1, characterized in that: The electrolyte circulation module includes a peristaltic pump one, a peristaltic pump two, and a peristaltic pump three. The peristaltic pump one is used to pump the reacted electrolyte solution flowing out of the cathode chamber into the regeneration circulation tank; the peristaltic pump two is used to pump the circulating electrolyte solution from the regeneration circulation tank into the buffer tank. The peristaltic pump three is used to pump the circulating electrolyte solution in the buffer tank into the cathode chamber of the electrochemical reaction module.

7. The asymmetric electrolyte supply spatiotemporal stepwise hydrogen production system according to claim 6, characterized in that: The electrolyte solution circulation rate of the peristaltic pumps 1, 2, and 3 is 20–100 mL / min.

8. The asymmetric electrolyte supply spatiotemporal stepwise hydrogen production system according to claim 1, characterized in that: It also includes an electrolyte heating unit, which is located at the bottom of the regeneration circulation tank and is used to heat the electrolyte in the regeneration circulation tank at a temperature of 25 to 70°C.

9. The asymmetric electrolyte supply spatiotemporal stepwise hydrogen production system according to claim 1, characterized in that: The hydrogen collection pool includes a drainage gas collection system connected to the regeneration circulation pool; the drainage gas collection system includes a container filled with water and a collection cylinder inverted in the container; the drainage collection system utilizes the accumulation of collected gas above the measuring cylinder to create a pressure difference between the waterless part and the water-filled part of the collection cylinder, thereby removing water and confirming the volume of collected gas.

10. The asymmetric electrolyte supply spatiotemporal stepwise hydrogen production system according to claim 1, characterized in that: The current density of the external DC power supply is -250 to -50 mA / cm². 2 .

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