Electrolytic cell and gas emission method thereof

Abstract

The invention provides an electrolytic tank. The electrolytic tank comprises a shell; an anode and a cathode; an exchange membrane; an anode gas diffusion layer, the housing defining an anode chamber surrounding the anode gas diffusion layer; and a cathode gas diffusion layer, the housing defining a cathode chamber surrounding the cathode gas diffusion layer; wherein at least one of the anode chamber and the cathode chamber is filled with water, bubbles are generated in the at least one chamber under the action of direct current, the at least one chamber is selectively communicated with the first gas circuit and the second gas circuit, and when accumulation of the bubbles reaches a critical state, the at least one chamber is communicated with the first gas circuit and the second gas circuit. The at least one chamber is switched from being communicated with the first gas loop to being communicated with the second gas loop and is switched again to be communicated with the first gas loop after a preset time, and the pressure of the first gas loop is higher than that of the second gas loop. The invention also provides a gas emission method for the electrolytic tank. According to the invention, bubbles can be quickly discharged, and the energy efficiency and the running current density are improved.

Description

Technical Field

[0001] The present application relates to the field of electrochemical cells, and in particular to an electrolytic cell that is conducive to gas emission and a gas emission method thereof. Background Art

[0002] With the development of new energy technologies, hydrogen energy, as a centralized renewable energy carrier, has attracted more and more attention due to its zero pollution, high energy, and wide sources. There are many ways to produce hydrogen at present, among which the use of electrolytic cells is the simplest, and the process is stable and reliable, the hydrogen purity is high, and it does not produce pollution, so it has become a research hotspot in the field of hydrogen production.

[0003] An electrolytic cell generally comprises an anode, a cathode, an exchange membrane located therebetween, and a gas diffusion layer located on the anode side and the cathode side, respectively, wherein the exchange membrane is generally a proton exchange membrane (PEM) or an anion exchange membrane (AEM). In an electrolytic cell, the anode, cathode, exchange membrane, and gas diffusion layer are generally made into a single component, called a membrane electrode.

[0004] For example, in an electrolytic cell using a proton exchange membrane, when direct current is supplied to the anode and cathode on both sides of the proton exchange membrane, water flowing through the anode gas diffusion layer is ionized, and the generated hydrogen ions pass through the proton exchange membrane into the cathode gas diffusion layer to generate hydrogen, and oxygen is generated in the anode gas diffusion layer. Since there is water in the anode gas diffusion layer, oxygen bubbles are formed. In addition, if there is also water in the cathode gas diffusion layer, hydrogen bubbles are also formed. Similarly, in an electrolytic cell using an anion exchange membrane, when direct current is supplied to the anode and cathode of the anion exchange membrane electrode, water flowing through the cathode gas diffusion layer is ionized, and the generated hydroxide ions pass through the anion exchange membrane into the anode gas diffusion layer to generate oxygen, and hydrogen is generated in the cathode gas diffusion layer, and since there is water in the cathode gas diffusion layer, hydrogen bubbles are formed. In addition, if there is also water in the anode gas diffusion layer, oxygen bubbles are also formed.

[0005] Since the anode, cathode and their gas diffusion layers are usually metal meshes or porous metals with a mesh size or pore size less than 1 mm, the generated gas will form bubbles and attach to the mesh or pores. As the gas is generated, the bubbles become more and more numerous and larger until they become large enough to be discharged under the action of buoyancy. However, the bubbles attached to the mesh or pores reduce the reaction area, block the path for water to reach the anode or cathode, and increase the resistance to water transport. As a result, the accumulation of bubbles leads to a decrease in the energy efficiency of the entire electrolytic cell and limits the operating current density.

[0006] Therefore, there is a need to improve the existing electrolytic cell and its gas discharge method to optimize the discharge of the gas generated in the electrolytic cell. Summary of the invention

[0007] The purpose of the present application is to provide an improved electrolytic cell and a gas discharge method thereof to overcome at least one of the above-mentioned technical problems.

[0008] To this end, according to one aspect of the present application, an electrolytic cell is provided, comprising: a shell; an anode and a cathode located in the shell, the anode and the cathode being arranged opposite to each other and configured to receive direct current; an exchange membrane located between the anode and the cathode; an anode gas diffusion layer located on a side of the anode away from the exchange membrane, the shell defining an anode chamber surrounding the anode gas diffusion layer; and a cathode gas diffusion layer located on a side of the cathode away from the exchange membrane, the shell defining a cathode chamber surrounding the cathode gas diffusion layer; wherein at least one of the anode chamber and the cathode chamber is filled with water, and bubbles are generated in the at least one chamber under the action of the direct current, wherein the at least one chamber is selectively connected to a first gas circuit and a second gas circuit, and when the accumulation of the bubbles reaches a critical state, the at least one chamber is switched from being connected to the first gas circuit to being connected to the second gas circuit, and is switched to being connected to the first gas circuit again after a predetermined time, wherein the pressure of the first gas circuit is higher than the pressure of the second gas circuit.

[0009] According to an embodiment of the present application, the critical state is determined according to a voltage change or a current change of the direct current, or the critical state is set according to an operating time of the electrolytic cell.

[0010] According to an embodiment of the present application, the electrolytic cell further includes a direct current power supply, which is configured to be connected to the anode and the cathode to provide the direct current, and the direct current power supply is a constant current power supply or a constant voltage power supply.

[0011] According to one embodiment of the present application, when the at least one chamber is connected to the first gas circuit, the DC power supply provides a first operating current, and when the at least one chamber is connected to the second gas circuit, the DC power supply provides a second operating current, wherein the second operating current is less than the first operating current.

[0012] According to an embodiment of the present application, the electrolytic cell further comprises a three-way valve, an inlet end of the three-way valve is connected to the at least one chamber, and two outlet ends of the three-way valve are respectively connected to the first gas circuit and the second gas circuit.

[0013] According to an embodiment of the present application, the electrolytic cell further includes a control device configured to monitor the direct current and control the switching of the three-way valve.

[0014] According to an embodiment of the present application, the control device is configured to adjust the pressure of the second gas circuit.

[0015] According to an embodiment of the present application, the exchange membrane is a proton exchange membrane or an anion exchange membrane.

[0016] According to another aspect of the present application, a gas discharge method for the above-mentioned electrolytic cell is provided, comprising: monitoring whether the accumulation of bubbles generated in at least one chamber filled with water of the electrolytic cell reaches a critical state; when the critical state is reached, switching the at least one chamber from being connected to a first gas circuit to being connected to a second gas circuit, and after a predetermined time, switching it back to being connected to the first gas circuit, wherein the pressure of the first gas circuit is higher than the pressure of the second gas circuit.

[0017] According to one embodiment of the present application, the gas exhaust method also includes: providing a first operating current when the at least one chamber is connected to the first gas circuit, and providing a second operating current when the at least one chamber is connected to the second gas circuit, wherein the second operating current is less than the first operating current.

[0018] The electrolytic cell and the gas discharge method thereof of the present application can quickly discharge the gas generated in the electrochemical reaction and avoid the accumulation of bubbles, thereby improving the energy efficiency and operating current density of the electrolytic cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The exemplary embodiments of the present application will be described in detail below with reference to the accompanying drawings. It should be understood that the embodiments described below are only used to explain the present application, rather than to limit the scope of the present application. In the accompanying drawings:

[0020] Figure 1 is a schematic block diagram of an electrolytic cell according to an embodiment of the present application, wherein the electrolytic cell uses a proton exchange membrane;

[0021] Figure 2 is a schematic block diagram of an electrolytic cell according to another embodiment of the present application, wherein the electrolytic cell uses an anion exchange membrane;

[0022] Figure 3 is a schematic flow chart of a gas exhaust method for an electrolytic cell according to an embodiment of the present application. DETAILED DESCRIPTION

[0023] The preferred embodiments of the present application are described in detail below with reference to examples. It should be understood by those skilled in the art that these exemplary embodiments are not intended to limit the present application in any way. In addition, the features in the embodiments of the present application may be combined with each other unless they conflict. In different drawings, the same components are represented by the same reference numerals, and other components are omitted for brevity, but this does not mean that the electrolytic cell of the present application may not include other components, nor does it mean that the gas discharge method of the present application may not include other steps. It should be understood that the size, proportional relationship and number of components of the components in the drawings are not intended to limit the present application.

[0024] Refer to the following Figure 1 An electrolytic cell according to an embodiment of the present application is described. Figure 1 The electrolytic cell 100 shown in FIG. 1 uses a proton exchange membrane. Figure 1 As shown, the electrolytic cell 100 includes a housing 10, an anode 11 located in the housing 10, a cathode 12, an exchange membrane 13 (in this example, a proton exchange membrane), an anode gas diffusion layer 15 located on one side of the anode 11, and a cathode gas diffusion layer 14 located on one side of the cathode 12. The anode 11 and the cathode 12 are arranged opposite to each other and are configured to receive direct current, for example, direct current from a direct current power source 70. The exchange membrane 13 is located between the anode 11 and the cathode 12. The anode gas diffusion layer 15 is located on a side of the anode 11 away from the exchange membrane 13, and the housing 10 defines an anode chamber 17 surrounding the anode gas diffusion layer 15. The cathode gas diffusion layer 14 is located on a side of the cathode 12 away from the exchange membrane 13, and the housing 10 defines a cathode chamber 16 surrounding the cathode gas diffusion layer 14. It should be noted that the anode 11 and the anode gas diffusion layer 15 can be collectively referred to as an anode gas diffusion electrode, and the cathode 12 and the cathode gas diffusion layer 14 can be collectively referred to as a cathode gas diffusion electrode.

[0025] like Figure 1 As shown, the anode chamber 17 is filled with water through the water source 40, and under the action of direct current, the water is ionized to generate hydrogen ions H + , hydrogen ion H + Passing through the proton exchange membrane into the cathode chamber 16, hydrogen H2 is generated in the cathode chamber 16 and can be transported to the gas storage device 50, while oxygen O2 is generated in the anode chamber 17 and attached to the anode gas diffusion layer 15 in the form of bubbles 18. It should be noted that the water filled in the electrolytic cell 100 may include pure water, alkaline water, etc., and the generated gas is not limited to hydrogen and oxygen. For example, in an electrolytic cell using a proton exchange membrane, pure water can be filled, and in an electrolytic cell using an anion exchange membrane, alkaline water or pure water can be filled.

[0026] The anode chamber 17 is selectively connected to the first gas circuit 20 and the second gas circuit 30 through the three-way valve 80. The inlet end of the three-way valve 80 is connected to the anode chamber 17, and the two outlet ends of the three-way valve 80 are respectively connected to the first gas circuit 20 and the second gas circuit 30. The pressure of the first gas circuit 20 (also referred to as the high-pressure gas circuit) is higher than the pressure of the second gas circuit 30 (also referred to as the low-pressure gas circuit), so the anode chamber 17 that generates bubbles can switch between two gas circuits with different pressures. The first gas circuit 20 and the second gas circuit 30 can be storage tanks or pipelines, and the present application is not limited to this. It should be noted that the three-way valve 80 can be replaced by two separate valves without affecting the implementation of the embodiments of the present application.

[0027] As the electrolytic cell 100 operates, the bubbles 18 generated in the anode chamber 17 gradually accumulate. When the accumulation of the bubbles 18 reaches a critical state, the anode chamber 17 can be switched from being connected to the first gas circuit 20 to being connected to the second gas circuit 30, so that the pressure in the anode chamber 17 changes from high pressure to low pressure. Since the volume of the bubbles 18 is inversely proportional to the pressure, as the pressure decreases, according to the ideal gas law: pV=nRT, the bubbles 18 will expand and merge into large bubbles, so that they are easily discharged from the anode gas diffusion layer 15.

[0028] Therefore, by switching the anode chamber 17 that generates bubbles 18 between the high-pressure gas circuit and the low-pressure gas circuit, the bubbles generated during the operation of the electrolytic cell 100 can be quickly discharged to increase the reaction area and improve the water transport path, thereby improving energy efficiency and operating current density.

[0029] After being connected to the second gas circuit 30 for a predetermined time, the generated bubbles 18 have been basically discharged, so the gas discharge can be considered to be completed. At this time, the anode chamber 17 can be switched to be connected to the first gas circuit 20 again, so that it is back in a normal operating high pressure state.

[0030] It should be noted that in the above-mentioned electrolytic cell embodiment using a proton exchange membrane, water is only filled in the anode chamber 17, however, the present application is not limited thereto, and water can also be filled in the cathode chamber 16. In this case, bubbles will also be generated in the cathode chamber 16, and the generated bubbles will also adhere to the cathode gas diffusion layer 14 and gradually accumulate. Therefore, according to another embodiment of the present application, a high-pressure gas circuit and a low-pressure gas circuit connected to the cathode chamber 16 can also be provided, so that the cathode chamber 16 can also switch between the high-pressure gas circuit and the low-pressure gas circuit, so that the bubbles generated in the cathode chamber 16 can be quickly discharged. The high-pressure gas circuit and the low-pressure gas circuit connected to the cathode chamber 16 can be provided in a manner similar to that described above, and therefore will not be described repeatedly.

[0031] Similarly, in an electrolytic cell using an anion exchange membrane, Figure 2 As shown, the cathode chamber 16 where bubbles are generated can also be selectively connected to the first gas circuit 20 and the second gas circuit 30, so that the generated bubbles 18 can be discharged as quickly as possible. Figure 2 In the embodiment, the exchange membrane 13 is an anion exchange membrane, the cathode chamber 16 is filled with water, and under the action of direct current, the water is ionized to generate hydroxide ions OH - , hydroxide ion OH - Passing through the anion exchange membrane into the anode chamber 17, oxygen O2 is generated in the anode chamber 17 and can be transported to the gas storage device 50, while hydrogen H2 is generated in the cathode chamber 16 and attached to the cathode gas diffusion layer 14 in the form of bubbles 18. It should be noted that Figure 2 The other parts shown in Figure 1 Therefore, the corresponding description will be omitted. Figure 2 During operation of the electrolytic cell shown, by switching the cathode chamber 16 where bubbles are generated between a high-pressure gas circuit and a low-pressure gas circuit, the bubbles can be quickly discharged, thereby improving energy efficiency and operating current density.

[0032] It should be noted that in the above-mentioned electrolytic cell embodiment using an anion exchange membrane, water is only filled in the cathode chamber 16, however, the present application is not limited thereto, and water can also be filled in the anode chamber 17. In this case, bubbles will also be generated in the anode chamber 17, and the generated bubbles will also adhere to the anode gas diffusion layer 15 and gradually accumulate. Therefore, according to another embodiment of the present application, a high-pressure gas circuit and a low-pressure gas circuit connected to the anode chamber 17 can also be provided, so that the anode chamber 17 can also switch between the high-pressure gas circuit and the low-pressure gas circuit, so that the bubbles generated in the anode chamber 17 can be quickly discharged. The high-pressure gas circuit and the low-pressure gas circuit connected to the anode chamber 17 can be provided in a manner similar to that described above, and therefore will not be described repeatedly.

[0033] Depending on the configuration of the electrolytic cell (for example, anodes, cathodes, exchange membranes, anode gas diffusion layers and cathode gas diffusion layers with different structures), the types of water used and the operating parameters, the effects of the generated bubbles on energy efficiency or operating current density are different. For example, the critical state of the accumulation of bubbles produced by an electrolytic cell with an operating pressure of 30 MPa is obviously different from the critical state of the accumulation of bubbles produced by an electrolytic cell with an operating pressure of 15 MPa. Therefore, the critical state of the accumulation of bubbles can be calibrated by experiments or calculated by simulation software for a specific configuration. As an example, the critical state can be determined according to the voltage change or current change of the direct current used by the electrolytic cell 100. For example, when the direct current power supply 70 is a constant current power supply, the accumulation of bubbles will cause the voltage to increase, while when the direct current power supply 70 is a constant voltage power supply, the accumulation of bubbles will cause the current to decrease. Therefore, by monitoring the voltage or current change of the direct current, it can be determined whether the accumulation of bubbles reaches a critical state. Alternatively, the critical state can also be set according to the operating time of the electrolytic cell 100. For example, after the electrolytic cell 100 has been running for a period of time (the length of this period of time can be set according to the specific configuration and operating parameters of the electrolytic cell 100), it can be considered that the accumulation of bubbles has reached a critical state and the bubbles need to be discharged quickly.

[0034] In order to facilitate the rapid discharge of bubbles, the pressure of the second gas circuit 30 may have a large pressure difference with the pressure of the first gas circuit 20. For example, the pressure of the first gas circuit 30 may be half of the pressure of the first gas circuit 20. However, the present application is not limited thereto. Depending on the different configurations of the electrolytic cell 100 and the size of the bubbles generated, the pressure of the second gas circuit 30 may be greater or less than the percentages exemplified above. In addition, the pressure of the second gas circuit 30 may be adjustable so as to maintain a predetermined pressure difference between the second gas circuit 30 and the first gas circuit 20.

[0035] In the bubble generation chamber ( Figure 1 Anode chamber 17 or Figure 2 When the cathode chamber 16 in the anode and cathode is connected to the second gas circuit 30, the rapid escape of bubbles may cause local water shortage on the surface of the anode or cathode in a short period of time. At this time, if the previous current density is still maintained, local overheating may occur, causing damage to the anode or cathode and the corresponding gas diffusion layer. Therefore, when the chamber for generating bubbles is switched from being connected to the first gas circuit 20 to being connected to the second gas circuit 30, the operating current can also be reduced accordingly, thereby avoiding damage to the components of the electrolytic cell and reducing energy consumption. That is, when the chamber for generating bubbles is connected to the first gas circuit 20, the DC power supply 70 provides a first operating current, and when it is connected to the second gas circuit 20, the DC power supply 70 provides a second operating current, wherein the second operating current is less than the first operating current.

[0036] To facilitate the control of the switching of the gas circuit and the adjustment of the operating current, the electrolytic cell 100 further includes a control device 60, which is configured to control the switching of the three-way valve 80 and monitor the direct current provided by the direct current power supply 70. In addition, the control device 60 can also be configured to adjust the pressure of the second gas circuit 30 to adapt to different operating conditions.

[0037] Refer to the following Figure 3 To describe the gas discharge method for the electrolytic cell of the present application. Figure 3 As shown, at step 110, the electrolytic cell 100 starts to operate, and the chamber for generating bubbles is connected to the first gas circuit 20 (i.e., the high-pressure gas circuit). Then, at step 120, it is monitored and judged whether the accumulation of bubbles reaches a critical state. If it reaches a critical state, step 130 is performed, otherwise, monitoring and judging are continued. At step 130, the chamber for generating bubbles is switched from being connected to the first gas circuit 20 to being connected to the second gas circuit 30, and an optional step 150 (shown in dotted lines) can be performed at the same time, and the operating current of the electrolytic cell is adjusted from the first operating current to the second operating current at step 150. After a predetermined time, the bubbles have been basically discharged, and at this time, step 140 can be performed, and the chamber for generating bubbles is switched from being connected to the second gas circuit 30 to being connected to the first gas circuit 20 again, and an optional step 160 (shown in dotted lines) can be performed at the same time, and the operating current of the electrolytic cell is adjusted from the second operating current to the first operating current at step 160. Then, the entire operation process can return to step 120 to continue monitoring and determining whether the accumulation of bubbles has reached a critical state until the next switching cycle begins.

[0038] Therefore, by designing two gas circuits with different pressures, the bubble generating chamber of the electrolytic cell can be operated first while being connected to the high-pressure gas circuit. Then, when the accumulation of bubbles generated in the electrolytic cell reaches a critical state, the bubble generating chamber can be switched to be connected to the low-pressure gas circuit, so that the bubbles can expand rapidly and merge into large bubbles and be quickly discharged, thereby returning the energy efficiency and operating current density of the electrolytic cell to the initial state.

[0039] The present application has been described in detail above in conjunction with specific embodiments. Obviously, the above description and the embodiments shown in the accompanying drawings should be understood as exemplary and do not constitute a limitation to the present application. For those skilled in the art, various modifications or changes can be made to the present application without departing from the spirit of the present application, and these modifications or changes do not depart from the scope of the present application.

Claims

1. An electrolytic cell (100), comprising: Housing (10); an anode (11) and a cathode (12) located in the housing (10), the anode (11) and the cathode (12) being arranged opposite to each other and configured to receive direct current; an exchange membrane (13) located between the anode (11) and the cathode (12); an anode gas diffusion layer (15) located on a side of the anode (11) away from the exchange membrane (13), the housing (10) defining an anode chamber (17) surrounding the anode gas diffusion layer (15); and A cathode gas diffusion layer (14) is located on a side of the cathode (12) away from the exchange membrane (13), and the shell (10) defines a cathode chamber (16) surrounding the cathode gas diffusion layer (14); At least one of the anode chamber (17) and the cathode chamber (16) is filled with water, and bubbles (18) are generated in the at least one chamber under the action of the direct current. The at least one chamber is selectively connected to a first gas circuit (20) and a second gas circuit (30), and when the accumulation of the bubbles (18) reaches a critical state, the at least one chamber switches from being connected to the first gas circuit (20) to being connected to the second gas circuit (30), and switches back to being connected to the first gas circuit (20) after a predetermined time, wherein the pressure of the first gas circuit (20) is higher than the pressure of the second gas circuit (30).

2. The electrolytic cell (100) according to claim 1, wherein: The critical state is determined according to a voltage change or a current change of the direct current, or the critical state is set according to an operating time of the electrolytic cell (100).

3. The electrolytic cell (100) according to claim 1, wherein: The electrolytic cell (100) further comprises a DC power supply (70) configured to be connected to the anode (11) and the cathode (12) to provide the DC power, wherein the DC power supply (70) is a constant current power supply or a constant voltage power supply.

4. The electrolytic cell (100) according to claim 3, wherein: When the at least one chamber is connected to the first gas circuit (20), the DC power supply (70) provides a first operating current, and when the at least one chamber is connected to the second gas circuit (20), the DC power supply (70) provides a second operating current, wherein the second operating current is less than the first operating current.

5. The electrolytic cell (100) according to claim 1, wherein: The electrolytic cell (100) further comprises a three-way valve (80), wherein an inlet end of the three-way valve (80) is connected to the at least one chamber, and two outlet ends of the three-way valve (80) are respectively connected to the first gas circuit (20) and the second gas circuit (30).

6. The electrolytic cell (100) according to claim 5, wherein: The electrolytic cell (100) further comprises a control device (60) configured to monitor the direct current and control the switching of the three-way valve (80).

7. The electrolytic cell (100) according to claim 6, wherein: The control device (60) is configured to adjust the pressure of the second gas circuit (30).

8. The electrolytic cell (100) according to claim 1, wherein: The exchange membrane is a proton exchange membrane or an anion exchange membrane.

9. A method for exhausting gas from an electrolytic cell (100) according to claim 1, comprising: monitoring whether the accumulation of bubbles (18) generated in at least one water-filled chamber of the electrolytic cell (100) reaches a critical state; When the critical state is reached, the at least one chamber is switched from being connected to the first gas circuit (20) to being connected to the second gas circuit (30), and after a predetermined time, is switched back to being connected to the first gas circuit (20), wherein the pressure of the first gas circuit (20) is higher than the pressure of the second gas circuit (30).

10. The gas exhaust method according to claim 9, wherein: The gas exhaust method further comprises: When the at least one chamber is connected to the first gas circuit (20), a first operating current is provided, and when the at least one chamber is connected to the second gas circuit (20), a second operating current is provided, wherein the second operating current is less than the first operating current.

Images