ELECTROLYSIS CELL AND ITS GAS SEPARATION METHOD

Abstract

The present application provides an electrolysis cell comprising: a housing; an anode and a cathode; an exchange membrane; an anode gas diffusion layer, wherein the housing encloses an anode chamber surrounding the anode gas diffusion layer; and a cathode gas diffusion layer, wherein the housing encloses a cathode chamber surrounding the cathode gas diffusion layer. At least one chamber of the anode chamber and at least one of the cathode chambers is filled with water, and gas bubbles are formed in at least one of the chambers by the action of the direct current.This at least one chamber is selectively connected to a first gas circuit and a second gas circuit, and when the accumulation of gas bubbles reaches a limit state, at least one chamber is switched from connection to the first gas circuit to connection to the second gas circuit and, after a predetermined time, switched back to connection to the first gas circuit, wherein the pressure of the first gas circuit is higher than the pressure of the second gas circuit. The present application further provides a gas separation method for the described electrolysis cell. According to the present application, gas bubbles can be separated rapidly, thereby increasing energy efficiency and operating current density.

Description

FIELD OF THE INVENTION

[0001] The present application relates to the field of electrochemical batteries, in particular to an improved gas separation of electrolysis cells and their gas separation processes. STATE OF THE ART

[0002] With the technological development of new energies, hydrogen energy is receiving increasing attention as a renewable energy source due to its characteristics such as zero environmental pollution, high energy output, and wide availability. Currently, there are numerous methods for producing hydrogen, with electrolysis cells being the simplest and the most stable and reliable. The high purity of the hydrogen and the absence of environmental pollution make it a key research focus in the field of hydrogen production.

[0003] Electrolysis cells typically comprise an anode, a cathode, an exchange membrane sandwiched between the two, and gas diffusion layers on both the anode and cathode sides. The exchange membrane is typically a proton exchange membrane (PEM) or an anion exchange membrane (AEM). In the electrolysis cell, the anode, cathode, exchange membrane, and gas diffusion layers are typically manufactured in a single component, the so-called membrane-electrode assembly.

[0004] For example, in an electrolysis cell with a proton exchange membrane, if the anode and cathode on either side of the proton exchange membrane are supplied with direct current, the water flowing through the anode gas diffusion layer is ionized. The generated hydrogen ions penetrate the proton exchange membrane into the cathode gas diffusion layer, generating hydrogen, and oxygen is generated in the anode gas diffusion layer. Since water is present in the anode gas diffusion layer, oxygen bubbles form. If water is also present in the cathode gas diffusion layer, hydrogen bubbles also form.Similarly, in an anion-exchange membrane electrolysis cell, when the anode and cathode of the anion-exchange membrane electrodes are supplied with direct current, ionization of the water flowing through the cathode gas diffusion layer occurs. The generated hydroxide ions penetrate the anion-exchange membrane into the anode gas diffusion layer and generate oxygen. Hydrogen is generated in the cathode gas diffusion layer. Since water is present in the cathode gas diffusion layer, hydrogen bubbles form. If water is also present in the anode gas diffusion layer, oxygen bubbles form.

[0005] Since the anodes, cathodes, and their gas diffusion layers are typically metal grids or perforated metal with grid sizes or pore widths of less than 1 mm, the generated gases form gas bubbles that adhere to the grid or hole. As the gases are generated, the gas bubbles become increasingly larger until they are large enough to escape due to the effect of buoyancy. However, the gas bubbles adhering to the grid or pores reduce the reaction surface, block the flow of water to the anode or cathode, and increase the water flow resistance. As a result, the accumulation of gas bubbles reduces the energy efficiency of the entire electrolysis cell and limits the operating current density.

[0006] Therefore, current electrolysis cells and their gas separation processes require improvement to optimize the separation of the gases generated in the electrolysis cells. DISCLOSURE OF THE INVENTION

[0007] The aim of the present application is to provide an improved electrolytic cell and its gas separation process to overcome at least one of the described technical problems.

[0008] To this end, according to one aspect of the present application, an electrolysis cell is provided comprising: a housing; an anode and a cathode located within the housing, the anode and the cathode being arranged opposite 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 the side of the anode facing away from the exchange membrane, the housing enclosing an anode chamber surrounding the anode gas diffusion layer; and a cathode gas diffusion layer located on the side of the cathode facing away from the exchange membrane, the housing enclosing 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 gas bubbles are formed in the at least one chamber by 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 gas bubbles reaches a limit state, the at least one chamber switches from a connection to the first gas circuit to a connection to the second gas circuit and, after a predetermined time, switches again to the connection to the first gas circuit, wherein the pressure of the first gas circuit is higher than the pressure of the second gas circuit;

[0009] According to one embodiment of the present application, the limit state is determined based on the voltage change or current change of the direct current or the limit state is set according to the operating time of the electrolysis cell.

[0010] According to an embodiment of the present application, the electrolysis cell further comprises a direct current source configured to be connected to the anode and the cathode to provide the direct current, wherein the direct current source is a constant current source or a constant voltage current source.

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

[0012] According to one embodiment of the present application, the electrolysis cell further comprises a three-way valve, the inlet of the three-way valve is connected to the at least one chamber, and the two outlets of the three-way valve are each connected to the first gas circuit and the second gas circuit.

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

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

[0015] According to one 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 venting method for an electrolysis cell as described above is provided, comprising: monitoring whether the accumulation of gas bubbles generated in the at least one chamber of the electrolysis cell filled with water reaches a limit state; when the limit state is reached, switching the at least one chamber from a connection to the first gas circuit to a connection to the second gas circuit and, after a predetermined time, switching again to the connection 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 an embodiment of the present application, the gas separation method further comprises the following: When the at least one chamber is connected to the first gas circuit, a first operating current is provided, and when the at least one chamber is connected to the second gas circuit, a second operating current is provided, wherein the second operating current is smaller than the first operating current.

[0018] With the electrolysis cell and its gas separation method of the present application, the gases generated during the electrochemical reaction can be rapidly separated and accumulation of gas bubbles is prevented, thereby increasing the energy efficiency and operating current density of the electrolysis cell. DESCRIPTION OF THE CHARACTERS

[0019] In the following, the exemplary embodiments of the present application are described in detail with reference to the figures, it being understood that the embodiments described below are only for the interpretation of the present application and do not limit the scope of the present application, wherein the figures apply: Fig. 1 is a schematic block diagram of an electrolysis cell according to an embodiment of the present application, the electrolysis cell using a proton exchange membrane; Fig. 2 is a schematic block diagram of an electrolysis cell according to another embodiment of the present application, wherein the electrolysis cell uses an anion exchange membrane; Fig. 3 a schematic flow diagram of a gas separation process for an electrolysis cell according to an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] In the following, preferred embodiments of the present application are described in detail using examples. Those skilled in the art should understand that these exemplary embodiments do not constitute any limitation of the present application. Furthermore, the features of the embodiments of the present application can be combined with one another if no conflicts exist. In different figures, identical components are designated by identical reference numerals, and for simplicity, other components have been omitted from the figures. However, this does not mean that the electrolysis cell of the present application may not include other components, nor does it mean that the gas separation method of the present application may not include further steps.It is understood that the dimensions and scale relationships of the individual components as well as the number of components in the figures do not represent a limitation of the present application.

[0021] In the following, with reference to Fig. 1 an electrolysis cell according to an embodiment of the present application is described. Fig. The electrolysis cell 100 shown in Figure 1 uses a proton exchange membrane. As shown in Fig. 1, the electrolysis cell 100 comprises a housing 10, an anode 11, a cathode 12, and an exchange membrane 13 (in this example, a proton exchange membrane) disposed within the housing 10, an anode gas diffusion layer 15 disposed on the anode 11 side, and a cathode gas diffusion layer 14 disposed on the cathode 12 side. The anode 11 and the cathode 12 are disposed opposite each other and configured to receive direct current from a direct current source 70. The exchange membrane 13 is disposed between the anode 11 and the cathode 12. The anode gas diffusion layer 15 is disposed on the side of the anode 11 opposite the exchange membrane 13, and the housing 10 encloses an anode chamber 17 surrounding the anode gas diffusion layer 15.The cathode gas diffusion layer 14 is located on the side of the cathode 12 facing away from the exchange membrane 13, and the housing 10 encloses an anode chamber 16 surrounding the cathode gas diffusion layer 14. It should be noted that the anode 11 and the anode gas diffusion layer 15 may collectively be referred to as the anode gas diffusion electrode, while the cathode 12 and the cathode gas diffusion layer 14 may collectively be referred to as the cathode gas diffusion electrode.

[0022] As in Fig. 1, the anode chamber 17 is filled with water by means of a water source 40, and under the influence of the direct current, ionization of the water is effected, whereby hydrogen ions H + The hydrogen ions H +penetrate the proton exchange membrane into the cathode chamber 16. Hydrogen H2 is generated in the cathode chamber 16 and can be transported to a gas storage device 50, while oxygen O2 is generated in the anode chamber 17 and adheres as gas bubbles 18 in the anode gas diffusion layer 15. It should be noted that the water filled into the electrolytic cell 100 can include, among other things, pure water and alkaline water, and the generated gases are not limited to hydrogen and oxygen. For example, an electrolytic cell with a proton exchange membrane can be filled with pure water, while an electrolytic cell with an anion exchange membrane can be filled with alkaline water or pure water.

[0023] The anode chamber 17 is selectively connected to a first gas circuit 20 and a second gas circuit 30 via a three-way valve 80. The inlet of the three-way valve 80 is connected to the anode chamber 17, and the two outlets of the three-way valve 80 are each connected to the first gas circuit 20 and the second gas circuit 30. The pressure of the first gas circuit 20 (which can also be referred to as the high-pressure gas circuit) is higher than the pressure of the second gas circuit (which can also be referred to as the low-pressure gas circuit), which is why the gas bubble-generating anode chamber 17 can switch between the two gas circuits with different pressures. The first gas circuit 20 and the second gas circuit 30 can be storage containers or lines, which is not limited by the present application.It should be noted that the three-way valve 80 may be replaced by two separate valves without affecting the implementation of the embodiments of the present application.

[0024] During the operation of the electrolytic cell 100, the gas bubbles 18 generated in the anode chamber 17 gradually accumulate. When the accumulation of gas bubbles 18 reaches a limiting 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, causing the pressure in the anode chamber 17 to change from high pressure to low pressure. Since the volume of the gas bubbles 18 is inversely proportional to the pressure, according to the ideal gas law pV = nRT, the gas bubbles 18 expand with decreasing pressure and coalesce into large gas bubbles, allowing them to be easily separated from the anode gas diffusion layer 15.

[0025] Therefore, by switching between the high-pressure gas circuit and the low-pressure gas circuit of the anode chamber 17 generating gas bubbles 18, the gas bubbles generated during operation of the electrolytic cell 100 can be quickly separated to increase the reaction area and improve the flow distance of the water, thereby increasing the energy efficiency and the operating current density.

[0026] After a predetermined time of connection to the second gas circuit 30, the generated gas bubbles 18 have largely been separated, which is why it can be assumed that the gas separation is complete. At this point, the anode chamber 17 can be switched back to a connection to the first gas circuit 20, so that it returns to the high-pressure state of normal operation.

[0027] It should be noted that in the above-described embodiment of a proton exchange membrane electrolytic cell, water is only filled into the anode chamber 17. However, the present application is not limited to this, and water may also be filled into the cathode chamber 16. In such a case, gas bubbles are also generated in the cathode chamber 16, and the generated gas bubbles also adhere to the cathode gas diffusion layer 14 and are gradually accumulated. 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 may be further configured, so that the cathode chamber 16 can also switch between a high-pressure gas circuit and a low-pressure gas circuit, thereby quickly separating the gas bubbles generated in the cathode chamber 16.The high pressure gas circuit and the low pressure gas circuit connected to the cathode chamber 16 can be set up similarly to the method described above, which is why this will not be repeated here.

[0028] In the same way, when using an electrolytic cell with anion exchange membrane as in Fig. 2, the gas bubble generating cathode chamber 16 can also be optionally connected to the first gas circuit 20 and the second gas circuit 30, whereby the generated gas bubbles 18 are separated as quickly as possible. Specifically, the exchange membrane 13 is in Fig. 2 an anion exchange membrane, the cathode chamber 16 is filled with water, and under the effect of the direct current, ionization of the water is effected, whereby hydroxide ions OH - The hydroxide ions OH -penetrate through the anion exchange membrane into the anode chamber 17, in the anode chamber 17 oxygen O2 is generated and can be transported into a gas storage device 50, while in the cathode chamber 16 hydrogen H2 is generated and remains as gas bubbles 18 in the cathode gas diffusion layer 14. It should be noted that the remaining Fig. 2 shown components with the Fig. 1 are identical, so their respective descriptions are omitted here. Therefore, during operation of the Fig. In the electrolysis cell shown in Figure 2, by switching the gas bubble generating cathode chamber 16 between the high pressure gas circuit and the low pressure gas circuit, the gas bubbles are quickly separated, which in turn increases the energy efficiency and the operating current density.

[0029] It should be noted that in the above-described embodiment of an anion exchange membrane electrolytic cell, water is only filled into the cathode chamber 16. However, the present application is not limited to this, and water may also be filled into the anode chamber 17. In such a case, gas bubbles are also generated in the anode chamber 17, and the generated gas bubbles also adhere to the anode gas diffusion layer 15 and are gradually accumulated. 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 may be further configured, so that the anode chamber 17 can also switch between a high-pressure gas circuit and a low-pressure gas circuit, thereby quickly separating the gas bubbles generated in the anode chamber 17.The high pressure gas circuit and the low pressure gas circuit connected to the anode chamber 17 can be set up similarly to the method described above, so this will not be repeated here.

[0030] Depending on the configuration of the electrolysis cell (e.g., with differently designed anodes, cathodes, exchange membranes, anode gas diffusion layers, and cathode gas diffusion layers), differences in the type of water used, and differences in the operating parameters, the influence of the generated gas bubbles on the energy efficiency or the operating current density varies. For example, the limit state of gas bubble accumulation generated by an electrolysis cell with an operating pressure of 30 MPa differs from the limit state of gas bubble accumulation generated by an electrolysis cell with an operating pressure of 15 MPa. Therefore, the limit state of gas bubble accumulation can be calibrated experimentally for the specific configuration or calculated using simulation software.As an example, the limit state can be determined based on the voltage change or current change of the direct current used by the electrolytic cell 100. For example, if the direct current source 70 is a constant current source, the accumulation of gas bubbles leads to a voltage increase, and if the direct current source 70 is a constant voltage source, the accumulation of gas bubbles leads to a current decrease. Therefore, by monitoring the voltage or current change of the direct current, it can be determined whether the accumulation of gas bubbles has reached the limit state. Alternatively, the limit state can also be adjusted according to the operating time of the electrolytic cell 100.For example, after the electrolysis cell 100 has been in operation for a period of time (the length of time can be determined depending on the specific configuration and operating parameters of the electrolysis cell 100), it can be assumed that the accumulation of gas bubbles has reached the limit state and the gas bubbles must be quickly removed.

[0031] To facilitate the rapid separation of the gas bubbles, the pressure of the second gas circuit 30 and the pressure of the first gas circuit 20 can have a relatively large pressure difference. For example, the pressure of the second gas circuit 30 can be half the pressure of the first gas circuit 20, although this is not restricted by the present application. Depending on the different configurations of the electrolysis cell 100 and the dimensions of the generated gas bubbles, the pressure of the second gas circuit 30 can be greater or lesser than the percentage in the example mentioned. Furthermore, the pressure of the second gas circuit 30 can be adjustable so that a predetermined pressure difference is maintained between the second gas circuit 30 and the first gas circuit 20.

[0032] When the gas bubble generating chamber (the anode chamber 17 in Fig. 1 or the cathode chamber 16 in Fig. 2) is connected to the second gas circuit 30, the rapid deposition of gas bubbles can lead to a temporary partial lack of water on the anode or cathode surface. If the previous current density is maintained, partial overheating may occur, leading to damage to the anode or cathode and the corresponding gas diffusion layers. Therefore, when switching the gas bubble-generating chamber from the connection to the first gas circuit 20 to the second gas circuit 30, the operating current can also be reduced accordingly to avoid damage to the electrolysis cell components and reduce energy consumption.In other words, when the gas bubble generating chamber is connected to the first gas circuit 20, the DC power source 70 provides a first operating current and when connected to the second gas circuit 20, the DC power source 70 provides a second operating current, wherein the second operating current is smaller than the first operating current.

[0033] To facilitate switching the gas circuit and regulating the operating current, the electrolysis cell 100 further comprises a control device 60 configured to control the switching of the three-way valve 80 and to monitor the direct current provided by the direct current source 70. In addition, the control device 60 may be further configured to regulate the pressure of the second gas circuit 30 to adapt it to different operating conditions.

[0034] In the following, with reference to Fig. 3 describes the gas separation process for an electrolysis cell of the present application. As in Fig.3, in step 110, the electrolysis cell 100 begins operation with the gas bubble generating chamber connected to the first gas circuit 20 (i.e., the high-pressure gas circuit). Subsequently, in step 120, monitoring and assessment are performed to determine whether the accumulation of gas bubbles has reached the limiting state. If the limiting state has been reached, step 130 is performed; otherwise, monitoring and assessment continue. In step 130, the gas bubble generating chamber is switched from the connection to the first gas circuit 20 to a connection to the second gas circuit 30. At the same time, optional step 150 (shown by a dashed line) may be performed. In step 150, the operating current of the electrolysis cell is adjusted from the first operating current to the second operating current.After a predetermined time, the gas bubbles have been substantially eliminated. Step 140 may be performed, in which the gas bubble-generating chamber is switched from the connection to the second gas circuit 30 back to a connection to the first gas circuit 20. At the same time, optional step 160 (shown by a dashed line) may be performed. In step 160, the operating current of the electrolysis cell is adjusted from the second operating current to the first operating current. The entire process may then return to step 120, where monitoring and assessment of whether the accumulation of gas bubbles has reached the limiting state continues until the next switching cycle begins.

[0035] This allows the gas bubble generating chamber of the electrolysis cell to be initially operated connected to the high pressure gas circuit by setting up gas circuits with two different pressures, and as soon as the accumulation of generated gas bubbles in the electrolysis cell reaches the limit state, the gas bubble generating chamber can be switched to a connection with the low pressure gas circuit, so that the gas bubbles expand rapidly, merge into large gas bubbles and are separated, which in turn returns the energy efficiency and the operating current density of the electrolysis cell to the initial level.

[0036] The present application has been described in detail above using specific embodiments. It is obvious that all descriptions and embodiments illustrated in the figures are to be understood as exemplary and do not represent a limitation of the present application. Those skilled in the art may, without departing from the spirit of the present application, make various variations or modifications thereto, which do not depart from the scope of the present application.

Claims

[1] Electrolytic cell (100) comprising: a housing (10); an anode (11) and a cathode (12) located in the housing (10), wherein the anode (11) and the cathode (12) are arranged opposite 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 the side of the anode (11) facing away from the exchange membrane (13), wherein the housing (10) encloses an anode chamber (17) surrounding the anode gas diffusion layer (15); and a cathode gas diffusion layer (14) located on the side of the cathode (12) facing away from the exchange membrane (13), wherein the housing (10) encloses a cathode chamber (16) surrounding the cathode gas diffusion layer (14); wherein at least one chamber below the anode chamber (17) and the cathode chamber (16) is filled with water and gas bubbles (18) are formed in at least one of these chambers by the effect of the direct current, wherein 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 gas bubbles (18) reaches a limit state, the at least one chamber switches from a connection to the first gas circuit (20) to a connection to the second gas circuit (30) and switches again to the connection 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] Electrolytic cell (100) according to claim 1, wherein the limit state is determined based on the voltage change or current change of the direct current or the limit state is set according to the operating time of the electrolytic cell (100). [3] The electrolytic cell (100) of claim 1, wherein the electrolytic cell (100) further comprises a direct current source (70) configured to be connected to the anode (11) and the cathode (12) to provide the direct current, wherein the direct current source (70) is a constant current source or a constant voltage current source. [4] Electrolysis cell (100) according to claim 3, wherein when the at least one chamber is connected to the first gas circuit (20), the direct current source (70) provides a first operating current and when the at least one chamber is connected to the second gas circuit (20), the direct current source (70) provides a second operating current, wherein the second operating current is smaller than the first operating current. [5] Electrolysis cell (100) according to claim 1, wherein the electrolysis cell (100) further comprises a three-way valve (80), the inlet of the three-way valve (80) is connected to the at least one chamber and the two outlets of the three-way valve (80) are each connected to the first gas circuit (20) and the second gas circuit (30). [6] The electrolytic cell (100) of 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] Electrolysis cell (100) according to claim 6, wherein the control device (60) is configured to regulate the pressure of the second gas circuit (30). [8] Electrolytic cell (100) according to claim 1, wherein the exchange membrane is a proton exchange membrane or an anion exchange membrane. [9] A gas separation method for an electrolytic cell (100) according to claim 1, comprising: Monitoring whether the accumulation of gas bubbles (18) generated in the at least one chamber of the electrolysis cell (100) filled with water reaches a limit state; when the limit state is reached, switching the at least one chamber from a connection to the first gas circuit (20) to a connection to the second gas circuit (30) and, after a predetermined time, switching again to the connection 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 separation method according to claim 9, wherein the gas separation 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 smaller than the first operating current.

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