Method for rapidly measuring mass transfer critical water stoichiometric ratio of proton exchange membrane electrolytic tank

Abstract

The invention provides a rapid measurement method for a mass transfer critical water stoichiometric ratio of a proton exchange membrane electrolytic cell, which comprises the following steps: carrying out electrolysis by the electrolytic cell at an initial voltage, increasing the voltage once every a period of time to carry out voltage forward scanning, and recording the current in the whole process. And when the current is reduced after the voltage is increased, the current is operated to be stable at the current. And taking the voltage as a reference, reducing the voltage once at set intervals for negative scanning, and recording a corresponding current value. When the current is kept stable instead of being increased due to reduction of the voltage, the voltage and the current at the moment are critical points at which the electrolytic tank starts to be limited by mass transfer, namely the mass transfer critical points. And calculating the mass transfer critical water stoichiometric ratio by using the current value of the mass transfer critical point and the water supply flow. According to the method, positive scanning and negative scanning of polarization curve voltage of electrolyzed water are combined, and rapid measurement of the mass transfer critical water stoichiometric ratio can be achieved under the condition that damage to a membrane electrode is extremely small.

Description

Technical Field

[0001] The 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] The water electrolysis cell converts electrical energy directly into chemical energy through electrochemical reactions and stores it in hydrogen. It has 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, and can be quickly converted with other forms of energy (especially electricity). It is the "link" for building a new energy system with renewable energy as the main body. At the same time, the production of hydrogen by electrolysis of water adapts to the volatile input of renewable electricity, and the large-scale production of "green hydrogen" using renewable energy "green electricity" is an effective way to achieve "grey hydrogen" substitution and help the low-carbon transformation of industry.

[0003] In order to maintain the efficient operation of the water electrolysis cell, it is necessary to reduce the influence of water vapor transmission on the electrolysis rate, prevent obvious mass transfer polarization, and enable the electrolysis cell to always maintain a stable state for electrolysis. The water stoichiometric ratio is an indicator that reflects the utilization rate of water in the electrolysis cell under a specific current. The water stoichiometric ratio at the critical point where the electrolysis cell begins to be limited by mass transfer, that is, the mass transfer critical water stoichiometric ratio, characterizes the utilization rate of water at the critical point of mass transfer in the electrolysis cell. At the same time, it can be used as a parameter to link the actual flow rate with the mass transfer critical current, and is used to indicate the critical water flow rate of the electrolysis cell that is not limited by mass transfer polarization under the corresponding current.

[0004] At present, the commonly used measurement method is to wait for the electrolytic cell to gradually become short of water and obvious mass transfer polarization to occur at a given voltage and current, and judge whether the electrolytic cell is in a state of mass transfer polarization limitation by the decrease of current. However, using this measurement method, on the one hand, it takes a long time to try different voltages and currents and spend a long time waiting for the electrolytic cell to become short of water. On the other hand, long-term short of water state will increase the damage to the membrane electrode in the electrolytic cell and shorten the service life of the electrolytic cell. Summary of the invention

[0005] According to the technical problem 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 the positive scanning and negative scanning 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.

[0006] The technical means adopted by 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, comprising:

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

[0009] S2, increase the voltage, perform a voltage forward 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 reduces the current during the constant voltage maintenance time t1 as V2, and operate at the 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 the 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 restricted by mass transfer;

[0013] S6. Calculate the critical water stoichiometric ratio of mass transfer when it is limited by mass transfer based on the current value at the critical point of mass transfer 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 ranges from 1 to 30 minutes.

[0017] Further, 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] Further, in step S2:

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

[0021] Further, 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] Further, 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] Further, in step S6, the formula for calculating the critical water stoichiometric ratio of mass transfer when subject to mass transfer limitation is as follows:

[0026]

[0027] Among them, ξ represents the critical water stoichiometry 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 electrolysis of water, 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 method for rapidly measuring the critical water stoichiometric ratio of mass transfer in a proton exchange membrane electrolytic cell. The method utilizes a positive voltage scan from low to high, combined with a relatively large step gradient |ΔE1|, so that the electrolytic cell quickly reaches the mass transfer polarization control region, and reaches a state where the current first decreases and then stabilizes under the influence of mass transfer polarization, making it easy to perform negative voltage scanning.

[0030] 2. The present invention provides a method for quickly measuring the critical water stoichiometric ratio of mass transfer in a proton exchange membrane electrolyzer. The method utilizes a negative scanning method of the voltage from high to low with a relatively small step gradient |ΔE2| to give play to the effect of increased current due to water filling after obvious mass transfer polarization occurs in the electrolytic cell, thereby reducing the stabilization time of obvious 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 judge 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 electrolyzer, which combines rapid positive voltage scanning with immediate negative voltage scanning after stabilization, thereby eliminating the long time required to wait for obvious mass transfer polarization to occur in the electrolyzer in conventional methods, and can measure the critical point of mass transfer polarization in a shorter time.

[0032] 4. The present invention provides a method for quickly measuring the critical water stoichiometric ratio of mass transfer in a proton exchange membrane electrolytic cell. The method utilizes the current value at the critical point of mass transfer, combined with the actual water flow rate, and through the calculation formula of the water stoichiometric ratio, the relationship between the critical water stoichiometric ratio of mass transfer and the current and water flow rate can be obtained, so as to achieve the effect of judging the critical water flow rate that will be limited by mass transfer polarization under different currents for the same electrolytic cell.

[0033] Based on the above reasons, the present invention can be widely promoted in the fields of water electrolysis cell testing and the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0035] Figure 1 The figure is a flow chart of the method of the present invention.

[0036] Figure 2 A schematic diagram of an example polarization curve for rapidly measuring the critical water stoichiometric ratio of mass transfer using polarization curves provided by the present invention. DETAILED DESCRIPTION

[0037] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

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

[0039] like Figure 1As shown, the present invention provides a method for quickly measuring the critical water stoichiometric ratio of mass transfer in a proton exchange membrane electrolyzer, comprising:

[0040] S1, set the circulating water flow rate Q and the initial voltage V1, electrolyze the electrolytic cell according to the set water flow rate Q and the initial voltage V1, and record the current within the constant voltage maintenance time t1;

[0041] S2, based on the initial voltage V1, increase the voltage, perform a voltage forward 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;

[0042] S3, record the voltage that reduces the current during the constant voltage maintenance time t1 as V2, and operate at the voltage V2 until the current stabilizes;

[0043] S4, based on the voltage V2, reduce the voltage, perform a negative voltage scan, record the corresponding current value, and determine whether the recorded current remains stable within the time t2. If the current remains stable, execute step S5, otherwise repeat step S4 until the current no longer increases and remains stable;

[0044] 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 restricted by mass transfer;

[0045] S6. Calculate the critical water stoichiometric ratio of mass transfer when it is limited by mass transfer based on the current value at the critical point of mass transfer and the actual water flow rate entering the electrolytic cell.

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

[0047] The circulating water flow rate Q ranges from 1 to 1000 mL / min;

[0048] 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;

[0049] The constant voltage maintaining time t1 ranges from 1 to 30 minutes.

[0050] In this embodiment, the time t1 is maintained at a constant voltage to ensure that the state of the water electrolysis cell is stable at a constant voltage.

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

[0052] 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%.

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

[0054] In specific implementation, as a preferred embodiment of the present invention, in step S2:

[0055] The amount of change of the increased voltage is set as the step voltage |ΔE1| of the forward scan, and the range of |ΔE1| is 0.02-0.5V.

[0056] In specific implementation, as a preferred embodiment of the present invention, in step S4:

[0057] 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%.

[0058] In this embodiment, under constant voltage, when the electrolytic cell is refilled with water in a water-deficient state, the current of the electrolytic cell will increase. When the current no longer increases but remains stable, it means that the electrolytic cell is now free from the influence of mass transfer polarization. The voltage and current values ​​at this time are the critical points at which the electrolytic cell begins to be restricted by mass transfer, that is, the mass transfer critical point.

[0059] In specific implementation, as a preferred embodiment of the present invention, in step S4:

[0060] 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.

[0061] In this embodiment, the step voltage of the negative scan needs to be smaller than the step voltage of the positive scan to ensure the measurement precision and accuracy during the negative scan process.

[0062] In specific implementation, as a preferred embodiment of the present invention, in step S6, the formula for calculating the critical water stoichiometric ratio of mass transfer when subject to mass transfer limitation is as follows:

[0063]

[0064] Among them, ξ represents the critical water stoichiometry 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 electrolysis of water, 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.

[0065] In summary, the measurement method provided by the present invention combines the positive scanning of the polarization curve voltage of the electrolyzed water with the negative scanning, 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 with the initial voltage, and the voltage is increased once every period of time 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 is stable. Then, based on this voltage, the voltage is reduced once every period of time to perform a negative scan, and the corresponding current value is recorded. Finally, when the current does not increase due to the reduction in voltage, 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 critical water stoichiometric ratio of mass transfer 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 scanning and voltage negative scanning, 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 to |ΔE1| = 0.2 V to perform a voltage forward scan and record the corresponding current.

[0069] When the current decreases, the voltage V2 = 2.3 V is used to operate until the current stabilizes.

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

[0071] When the current no longer increases and becomes stable, 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 aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned 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 rapid measurement method for 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 the initial voltage V1, electrolyze the electrolytic cell according to the set water flow rate Q and the initial voltage V1, and record the current within the constant voltage maintenance time t1; S2, increase the voltage, perform a voltage forward 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 reduces the current during the constant voltage maintenance time t1 as V2, and operate at the 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 the 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 restricted by mass transfer; S6. Calculate the critical water stoichiometric ratio of mass transfer when it is limited by mass transfer based on the current value at the critical point of mass transfer and the actual water flow rate entering the electrolytic cell.

2. The rapid measurement method of 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 ranges from 1 to 30 minutes.

3. The rapid measurement method of 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 change of the increased voltage 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 critical water stoichiometric ratio of mass transfer when subject to mass transfer limitation is as follows: Among them, ξ represents the critical water stoichiometry 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 electrolysis of water, 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.

Images