A method for rapid measurement of mass transfer critical water stoichiometry ratio of proton exchange membrane electrolytic cell

Abstract

The application provides a kind of proton exchange membrane electrolytic cell mass transfer critical water metering ratio fast measurement method, comprising: electrolytic cell is electrolyzed with initial voltage, increases voltage once every time interval to carry out voltage positive scanning, records the current in the whole process.When current decreases after increasing voltage, run to current stable at this time voltage. Again, as the voltage, reduces voltage once every time interval to carry out negative scanning, records corresponding current value. When current does not increase due to voltage reduction, but remains stable, the voltage and current at this time are the critical point when electrolytic cell starts to be mass transfer limited, i.e. mass transfer critical point. The mass transfer critical water metering ratio is calculated using the current value of the mass transfer critical point and the water supply flow. The method of the application combines the voltage positive scanning and negative scanning of the polarization curve of electrolytic water, which can realize the fast measurement of the mass transfer critical water metering ratio under the condition of minimal damage to the membrane electrode.

Description

Technical Field

[0001] The present invention relates to the technical field of water electrolysis cell testing, and in particular to a method for quickly measuring the critical water stoichiometric ratio of mass transfer in a proton exchange membrane electrolysis cell. Background Art

[0002] Water electrolysis cells use electrochemical reactions to convert electrical energy directly into chemical energy and store it in hydrogen. They have the advantages of high gas purity, fast response speed, high current density, low energy consumption, small size, and green environmental protection. The hydrogen and its derivatives produced by electrolysis can be stored across seasons and transported over long distances. They can be quickly converted with other forms of energy (especially electricity), and are the "link" for building a new energy system with renewable energy as the main body. At the same time, hydrogen production by electrolysis of water adapts to the fluctuating input of renewable electricity. The large-scale production of "green hydrogen" using renewable energy "green electricity" is an effective way to achieve "grey hydrogen" substitution and assist in the low-carbon transformation of industry.

[0003] To maintain efficient operation of a water electrolysis cell, it is necessary to minimize the impact of water vapor transport on the electrolysis rate, prevent significant mass transfer polarization, and enable the cell to consistently perform electrolysis in a stable state. The water stoichiometric ratio is an indicator of the cell's water utilization at a specific current. The water stoichiometric ratio at the critical point where the cell begins to be limited by mass transfer, known as the mass transfer critical water stoichiometric ratio, characterizes the cell's water utilization at that critical point. It can also serve as a parameter linking the actual flow rate to the critical mass transfer current, indicating the critical water flow rate at which the cell is not limited by mass transfer polarization at the corresponding current.

[0004] The commonly used measurement method currently is to wait for the electrolytic cell to gradually become dehydrated at a given voltage and current, resulting in significant mass transfer polarization. The decrease in current is then used to determine whether the cell is in a mass transfer polarization-limited state. However, this measurement method requires a long time to experiment with different voltages and currents, and it takes a long time to wait for the electrolytic cell to become dehydrated. Furthermore, prolonged dehydrated conditions can increase damage to the cell's membrane electrodes, shortening the cell's service life. Summary of the Invention

[0005] In response to the technical problems raised above, a method for rapidly measuring the critical water stoichiometric ratio of mass transfer in a proton exchange membrane electrolyzer is provided. The present invention combines positive and negative voltage sweeps of the polarization curve of electrolyzed water to achieve rapid measurement of the critical water stoichiometric ratio with minimal damage to the membrane electrode.

[0006] The technical means adopted in the present invention are as follows:

[0007] A method for rapidly measuring the critical water stoichiometric ratio of mass transfer in a proton exchange membrane electrolyzer comprises:

[0008] S1, set the circulating water flow rate Q and initial voltage V1, electrolyze the electrolytic cell according to the set water flow rate Q and initial voltage V1, and record the current during the constant voltage maintenance time t1;

[0009] S2. Increase the voltage, perform a forward voltage scan, record the corresponding current, and determine whether the recorded current decreases within the constant voltage maintenance time t1. If the current decreases, execute step S3; otherwise, repeat step S2 until the current decreases.

[0010] S3, record the voltage that causes the current to decrease during the constant voltage maintenance time t1 as V2, and operate at voltage V2 until the current stabilizes;

[0011] S4, reduce the voltage, perform a negative voltage scan, record the corresponding current value, and determine whether the recorded current remains stable within time t2. If the current remains stable, execute step S5; otherwise, repeat step S4 until the current no longer increases and remains stable;

[0012] S5, taking the voltage value that keeps the current stable and the output stable current value as the mass transfer critical point where the electrolytic cell begins to be limited by mass transfer;

[0013] S6. Calculate the critical water stoichiometric ratio of mass transfer when the mass transfer is limited based on the current value at the mass transfer critical point and the actual water flow rate entering the electrolytic cell.

[0014] Furthermore, in step S1:

[0015] The magnitude of the initial voltage V1 is set according to the number of sections of the electrolytic cell. For a single-section electrolytic cell, the range of V1 is 1.4-2V;

[0016] The constant voltage maintaining time t1 is in the range of 1-30 minutes.

[0017] Furthermore, in step S2:

[0018] After the voltage increases, within the constant voltage maintaining time t1, the criterion for judging whether the current decreases after the voltage increases is that the current decrease amplitude is greater than 5%.

[0019] Furthermore, in step S2:

[0020] The amount of the increased voltage change is set as the step voltage |ΔE1| of the forward scan, and the range of |ΔE1| is 0.02-0.5V.

[0021] Furthermore, in step S4:

[0022] After the voltage decreases, within the time t2, the criterion for judging whether the current remains stable after the voltage decreases is that the fluctuation amplitude of the current is less than 2%.

[0023] Furthermore, in step S4:

[0024] The reduced voltage variation is set as the step voltage |ΔE2| of the negative scanning, and |ΔE2|<|ΔE1|, and the range of |ΔE2| is 5-50 mV.

[0025] Furthermore, in step S6, the formula for calculating the mass transfer critical water stoichiometric ratio when subject to mass transfer limitation is as follows:

[0026]

[0027] Wherein, ξ represents the critical water stoichiometric ratio for mass transfer; Q represents the actual circulating water flow rate; Q1 represents the theoretical water consumption rate when the current is completely used for water electrolysis, in mL / min; z represents the number of transferred charges in the water electrolysis reaction; F represents the Faraday constant; ρ represents the density of water; M represents the molar mass of water; and I represents the current value at the critical point of mass transfer.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] 1. The present invention provides a rapid measurement method for the critical water stoichiometric ratio of mass transfer in a proton exchange membrane electrolytic cell. The method utilizes a positive voltage sweep from low to high, combined with a large step gradient |ΔE1|, to enable the electrolytic cell to quickly reach the mass transfer polarization control region, achieving a state in which the current first decreases and then stabilizes under the influence of mass transfer polarization, making it easy to perform a negative voltage sweep.

[0030] 2. The present invention provides a method for rapidly measuring the critical water stoichiometric ratio of mass transfer in a proton exchange membrane electrolytic cell. The method utilizes a negative voltage scan from high to low with a relatively small step gradient |ΔE2| to take advantage of the increase in current due to water filling after significant mass transfer polarization occurs in the electrolytic cell, thereby reducing the stabilization time of significant mass transfer polarization in the electrolytic cell under high voltage. Measuring the critical point of mass transfer polarization using this method causes less damage to the membrane electrode of the electrolytic cell and can more accurately determine and measure the critical point of mass transfer polarization.

[0031] 3. The present invention provides a method for rapidly measuring the critical water stoichiometric ratio of mass transfer in a proton exchange membrane electrolytic cell. By combining rapid positive voltage scanning with immediate negative voltage scanning after stabilization, the conventional method eliminates the long waiting time required for significant mass transfer polarization to occur in the electrolytic cell, and enables the critical point of mass transfer polarization to be measured in a shorter time.

[0032] 4. The application provides a kind of proton exchange membrane electrolytic cell mass transfer critical water metering ratio fast measurement method, using the current value of mass transfer critical point, in combination with actual water flow, by water metering ratio calculation formula, the relationship between mass transfer critical water metering ratio and current and water flow can be obtained, the effect of judging the critical water flow of different current under the limitation of mass transfer polarization for the same electrolytic cell can be achieved.

[0033] Based on the above reasons, the application can be widely popularized in the field of water electrolysis cell test. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical scheme in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0035] Figure 1 The method flowchart of the present application.

[0036] Figure 2 The example polarization curve schematic diagram for measuring mass transfer critical water metering ratio quickly by using polarization curve provided by the present application. DETAILED DESCRIPTION

[0037] In order to enable those skilled in the art to better understand the present application scheme, the technical scheme in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should be within the scope of protection of the present application.

[0038] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above drawings are used to distinguish similar objects, and do not necessarily describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0039] As Figure 1As shown, the application provides a method for quickly measuring the mass transfer critical water metering ratio of a proton exchange membrane electrolysis cell, comprising:

[0040] S1, set the circulating water flow Q and the initial voltage V1, electrolyze the electrolysis cell according to the set water flow Q and the initial voltage V1, and record the current in the constant voltage maintaining time t1;

[0041] S2, on the basis of the initial voltage V1, increase the voltage, perform positive voltage scanning, record the corresponding current, and in the constant voltage maintaining time t1, judge whether the recorded current is reduced, if the current is reduced, execute step S3, otherwise repeat step S2 until the current is reduced;

[0042] S3, record the voltage that makes the current decrease in the constant voltage maintaining time t1 as V2, and run to the stable current with the voltage V2;

[0043] S4, on the basis of the voltage V2, decrease the voltage, perform negative voltage scanning, record the corresponding current value, and in t2 time, judge whether the recorded current is stable, if the current is stable, execute step S5, otherwise repeat step S4 until the current is no longer increased and stable;

[0044] S5, the voltage value and the stable current value that make the current stable are taken as the mass transfer critical point of the electrolysis cell starting to be mass transfer limited;

[0045] S6, according to the current value of the mass transfer critical point and the actual water flow into the electrolysis cell, calculate the mass transfer critical water metering ratio when mass transfer is limited.

[0046] In specific implementation, as a preferred embodiment of the application, in step S1:

[0047] The circulating water flow Q is in the range of 1-1000 mL / min;

[0048] The size of the initial voltage V1 is set according to the number of electrolysis cells, for single electrolysis cell, V1 is in the range of 1.4-2V;

[0049] The constant voltage maintaining time t1 is in the range of 1-30 min.

[0050] In this embodiment, the constant voltage maintaining time t1 is to ensure the stable state of the water electrolysis cell under constant voltage.

[0051] In specific implementation, as a preferred embodiment of the application, in step S2:

[0052] After the voltage is increased, the criterion for judging whether the current is reduced after the voltage is increased in the constant voltage maintaining time t1 is that the current reduction amplitude is greater than 5%.

[0053] In this embodiment, when the electrolytic cell is in the mass transfer polarization limitation due to the lack of water, the current of the electrolytic cell will be reduced due to the mass transfer polarization.

[0054] In the embodiment, in step S2, the voltage is increased by a step voltage |ΔE1|, and |ΔE1| is in the range of 0.02-0.5V.

[0055] The variation of the increased voltage is set as the step voltage |ΔE1| of the forward scanning, and |ΔE1| is in the range of 0.02-0.5V.

[0056] In the embodiment, in step S4, the voltage is decreased by a step voltage |ΔE2|, and |ΔE2| is in the range of 5-50mV.

[0057] After the voltage is decreased, in t2 time, the criterion for judging whether the current remains stable after the voltage is decreased is that the fluctuation amplitude of the current is less than 2%.

[0058] In this embodiment, under the constant voltage, when the electrolytic cell is recharged in the state of the lack of water, the current of the electrolytic cell will be increased. When the current no longer increases but remains stable, it is indicated that the electrolytic cell is out of the influence of the mass transfer polarization. At this time, the voltage value and the current value are the critical point when the electrolytic cell starts to be limited by the mass transfer, i.e. the mass transfer critical point.

[0059] In the embodiment, in step S4, the voltage is decreased by a step voltage |ΔE2|, and |ΔE2| is in the range of 5-50mV.

[0060] The variation of the decreased voltage is set as the step voltage |ΔE2| of the negative scanning, and |ΔE2| < |ΔE1|, and |ΔE2| is in the range of 5-50mV.

[0061] In this embodiment, the step voltage of the negative scanning needs to be less than the step voltage of the forward scanning, so as to ensure the measurement accuracy and precision in the negative scanning process.

[0062] In the embodiment, in step S6, the formula for calculating the mass transfer critical water metering ratio when the electrolytic cell is limited by the mass transfer is as follows:

[0063]

[0064] In the formula, ξ represents the mass transfer critical water metering ratio; Q represents the actual circulating water flow rate; Q1 represents the theoretical water consumption rate of the electrolytic water by the current, and the unit is mL / min; z represents the transfer charge number of the electrolytic water reaction; F represents the Faraday constant; ρ represents the density of water; M represents the molar mass of water; and I represents the current value of the mass transfer critical point.

[0065] In summary, the measurement method provided by the present invention combines the positive scan and negative scan of the polarization curve voltage of electrolyzed water, and can realize the rapid measurement of the critical water stoichiometric ratio of mass transfer under the condition of minimal damage to the membrane electrode. The specific measurement process is: first, the electrolytic cell is electrolyzed at an initial voltage, and the voltage is increased once at intervals to perform a positive voltage scan, and the current in the whole process is recorded. Secondly, when the current decreases after the voltage is increased, the voltage at this time is operated until the current stabilizes. Then, using this voltage as a reference, the voltage is reduced once at intervals to perform a negative scan, and the corresponding current value is recorded. Finally, when the current does not increase due to the voltage reduction, but remains stable, the voltage and current at this time are the critical point at which the electrolytic cell begins to be restricted by mass transfer, i.e., the mass transfer critical point. The mass transfer critical water stoichiometric ratio is calculated using the current value and water supply flow rate at this point.

[0066] Example

[0067] The polarization curve test method in this example is as follows Figure 2 As shown, it includes two parts: voltage positive scan and voltage negative scan, specifically including:

[0068] The electrolytic cell was electrolyzed at a water flow rate of 3 mL / min and an initial voltage of V1 = 1.3 V, and the voltage was continuously increased by |ΔE1| = 0.2 V to perform a forward voltage scan and record the corresponding current.

[0069] When the current decreases, the circuit is operated at the voltage V2 = 2.3 V until the current stabilizes.

[0070] On the basis of 2.3V, reduce the voltage |ΔE2|=0.1V to perform a negative voltage scan and record the corresponding current value.

[0071] When the current no longer increases and stabilizes, the voltage V 临界 =1.9V and stable current value I 临界 =80A is the critical point where the electrolytic cell begins to be limited by mass transfer, which is called the mass transfer critical point.

[0072] Substitute the current value of the mass transfer critical point into the formula for calculating the mass transfer critical water stoichiometric ratio when the mass transfer is limited to obtain the mass transfer critical water stoichiometric ratio ξ 临界 =6.7.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for rapidly measuring the critical water stoichiometric ratio of mass transfer in a proton exchange membrane electrolyzer, characterized in that: include: S1, set the circulating water flow rate Q and initial voltage V1, electrolyze the electrolytic cell according to the set water flow rate Q and initial voltage V1, and record the current during the constant voltage maintenance time t1; S2. Increase the voltage, perform a forward voltage scan, record the corresponding current, and determine whether the recorded current decreases within the constant voltage maintenance time t1. If the current decreases, execute step S3; otherwise, repeat step S2 until the current decreases. S3, record the voltage that causes the current to decrease during the constant voltage maintenance time t1 as V2, and operate at voltage V2 until the current stabilizes; S4, reduce the voltage, perform a negative voltage scan, record the corresponding current value, and determine whether the recorded current remains stable within time t2. If the current remains stable, execute step S5; otherwise, repeat step S4 until the current no longer increases and remains stable; S5, taking the stable current value and the corresponding constant voltage value as the mass transfer critical point where the electrolytic cell begins to be limited by mass transfer; S6. Calculate the critical water stoichiometric ratio of mass transfer when the mass transfer is limited based on the current value at the mass transfer critical point and the actual water flow rate entering the electrolytic cell.

2. The method for rapidly measuring the critical water stoichiometric ratio of mass transfer in a proton exchange membrane electrolyzer according to claim 1, characterized in that: In step S1: The magnitude of the initial voltage V1 is set according to the number of sections of the electrolytic cell. For a single-section electrolytic cell, the range of V1 is 1.4-2V; The constant voltage maintaining time t1 is in the range of 1-30 minutes.

3. The method for rapidly measuring the critical water stoichiometric ratio of mass transfer in a proton exchange membrane electrolyzer according to claim 1, characterized in that: In step S2: After the voltage increases, within the constant voltage maintaining time t1, the criterion for judging whether the current decreases after the voltage increases is that the current decrease amplitude is greater than 5%.

4. The method for rapidly measuring the critical water stoichiometric ratio of mass transfer in a proton exchange membrane electrolyzer according to claim 1, characterized in that: In step S2: The amount of the increased voltage change is set as the step voltage |ΔE1| of the forward scan, and the range of |ΔE1| is 0.02-0.5V.

5. The method for rapidly measuring the critical water stoichiometric ratio of mass transfer in a proton exchange membrane electrolyzer according to claim 1, characterized in that: In step S4: After the voltage decreases, within the time t2, the criterion for judging whether the current remains stable after the voltage decreases is that the fluctuation amplitude of the current is less than 2%.

6. The method for rapidly measuring the critical water stoichiometric ratio of mass transfer in a proton exchange membrane electrolyzer according to claim 1, characterized in that: In step S4: The reduced voltage variation is set as the step voltage |ΔE2| of the negative scanning, and |ΔE2|<|ΔE1|, and the range of |ΔE2| is 5-50 mV.

7. The method for rapidly measuring the critical water stoichiometric ratio of mass transfer in a proton exchange membrane electrolyzer according to claim 1, characterized in that: In step S6, the formula for calculating the mass transfer critical water stoichiometric ratio when subject to mass transfer limitation is as follows: Wherein, ξ represents the critical water stoichiometric ratio for mass transfer; Q represents the actual circulating water flow rate; Q1 represents the theoretical water consumption rate when the current is completely used for water electrolysis, in mL / min; z represents the number of transferred charges in the water electrolysis reaction; F represents the Faraday constant; ρ represents the density of water; M represents the molar mass of water; and I represents the current value at the critical point of mass transfer.

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