CN118117118A - Proton exchange membrane fuel cell stack activation method based on ultrasonic atomization - Google Patents
Proton exchange membrane fuel cell stack activation method based on ultrasonic atomization Download PDFInfo
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Abstract
The invention discloses a proton exchange membrane fuel cell stack activation method based on ultrasonic atomization. A proton exchange membrane fuel cell stack activation method based on ultrasonic atomization comprises the following steps: after the proton exchange membrane fuel cell is pretreated, atomized liquid drops are introduced into the cathode side, and the fuel cell is activated by adopting a stepped circulation constant voltage discharge mode. The method provided by the invention can activate the fuel cell in a short time, effectively keep the proton exchange membrane moist, and ensure high water content in the electrolyte to improve proton conductivity. Under the action of atomized liquid drops, the current resistance is reduced, the overall efficiency of the PEMFC is improved, and a new method is provided for improving the activation effect of the PEMFC.
Description
Technical field:
The invention relates to the technical field of proton exchange membrane fuel cells, in particular to a proton exchange membrane fuel cell stack activation method based on ultrasonic atomization.
The background technology is as follows:
Before a Proton Exchange Membrane Fuel Cell (PEMFC) operates properly, a cell activation process is typically required to achieve a rated or optimal output performance of the fuel cell. Fuel cell activation is a process of testing and tuning a Membrane Electrode Assembly (MEA) and is not only a humidification process of a proton exchange membrane but also a complex process including the establishment of transport channels for electrons, protons, gas and water and reconstruction of an electrode microstructure.
Wherein, the activation of the membrane electrode assembly can comprise the following three parts:
(1) Humidification of a Proton Exchange Membrane (PEM); after the PEM is fully wetted, the proton transmission efficiency is improved, the ohmic resistance is reduced, and the output performance of the battery is improved;
(2) Establishing an electronic channel; the Catalyst Layer (CL) and the Gas Diffusion Layer (GDL) in the MEA are both good conductors of electrons, which are beneficial for reducing resistance by activation;
(3) Establishing a gas-liquid transmission channel; the water transport flow path can be promoted to be established by activation, and the gas transport channels are expanded, so that mass transfer is enhanced. In addition, the transfer of liquid water in the PEM, GDL and CL creates diffusion and the draining process gradually equilibrates and establishes transfer channels.
CN114883605A discloses a hydrogen fuel cell stack activation system and method, the method includes a stack, a self-checking module, a stack activation module and a stack protection unit; and detecting the voltage of the electric pile through the self-checking module, purifying and wetting air entering the electric pile by the electric pile protection unit, and activating the proton exchange membrane by the electric pile activation module. The three steps are used for carrying out self-checking and protection on the hydrogen fuel cell pile, and carrying out activation treatment on the pile with unqualified self-checking, so that the pile protection can reduce the pile proportion needing activation, and the three steps are tightly matched. However, the method has complex equipment, and the performance of the activated fuel cell is difficult to achieve the ideal effect, and in addition, the method has longer activation time period, wastes a great amount of time cost and has larger energy consumption, and the aim of high-efficiency activation is not achieved. However, in the existing PEMFC activation technology, an activation process exceeding 24 hours is frequently used, which results in consumption of a large amount of hydrogen fuel and time cost, severely reduces the production efficiency of the fuel cell, and increases the manufacturing cost of the fuel cell.
Before the PEMFC is put into use, an activation step is required, and the activation mode of the PEMFC is divided into pretreatment activation and in-situ activation. The pretreatment activation is performed before in-situ activation, so that the in-situ activation efficiency is improved, and the in-situ activation time is effectively shortened. In-situ activation refers to an operation of activating the assembled PEMFC stack on a test platform. The traditional in-situ activation step is complex, and the adopted activation scheme is unfavorable for quickly determining the optimal activation parameters when a plurality of control conditions exist, so that the research difficulty is increased.
Therefore, there is a need in the art for an efficient fuel cell activation method that maximizes fuel cell output performance in a short period of time, maintains a long operating time, and alleviates the aging problems of the fuel cell caused by repeated use.
The invention comprises the following steps:
The invention solves the problems existing in the prior art, and provides a proton exchange membrane fuel cell stack activation method based on ultrasonic atomization. Under the action of atomized liquid drops, the current resistance is reduced, the overall efficiency of the PEMFC is improved, and a new method is provided for improving the activation effect of the PEMFC.
The invention aims to provide a proton exchange membrane fuel cell stack activation method based on ultrasonic atomization, which comprises the following steps: after the proton exchange membrane fuel cell is pretreated, atomized liquid drops are introduced into the cathode side of the fuel cell, and the fuel cell is activated by adopting a stepped circulation constant voltage discharge mode.
The proton exchange membrane fuel cell stack activation method specifically comprises the following steps:
S1, on a fuel cell test platform, enabling a fuel cell to be in an open circuit state, and preprocessing the anode side and the cathode side of the fuel cell;
S2, opening an electronic load, loading stack voltage step by step to enable the fuel cell to be heated to a normal working temperature, and feeding atomized droplet streams with different atomization amounts to the cathode side of the fuel cell;
s3, performing constant-voltage circulation test on the fuel cell, enabling the fuel cell to perform activation under the step-type voltage of 8.5-4.0V of atomized droplet streams with different atomization amounts, and stopping conveying the atomized droplet streams until activation is completed, so that activation of the fuel cell is completed.
The invention uses atomized air mixed air supply as an important means of activation. According to the invention, an ultrasonic atomization technology is introduced in the activation process of the fuel cell, and the performance of the fuel cell is effectively improved by improving the hydration degree of the proton exchange membrane; adopting non-continuous atomization operation, namely sending atomized liquid drops into a fuel cell for a period of time, stopping using, and then carrying out polarization characteristic test; after stopping the use of the atomizing device, the fuel cell performance can be further improved and can be maintained for a certain period of time.
The invention is mainly based on the innovation of the in-situ activation process, wherein the in-situ activation refers to the activation process of connecting the PEMFC to a fuel cell test bench and controlling the operating conditions such as voltage, current and the like to generate electricity. The activation time of the traditional in-situ activation process is more than 6 hours, and some of the traditional in-situ activation process is more than 24 hours. Ideally, it is desirable to have the fuel cell possess as high a power density as possible after activation at a minimum time cost.
Preferably, the specific steps of pretreatment of the anode and the cathode of the fuel cell in step S1 are as follows: the anode is purged with hydrogen for 4-8min, and the cathode is purged with air for 4-8min for pretreatment, wherein the relative humidity of the hydrogen is 100%, and the air does not need additional humidification. The purpose of the pretreatment is to remove air, hydrogen and other impurities remaining from the cathode and anode. The purge time is determined according to the actual purge effect, and the purge time is only required to remove other impurities such as residual air, hydrogen and the like.
Preferably, the fuel cell in the step S1 is formed by stacking n single-element exchange membrane fuel cells, wherein n is more than or equal to 10. For example: the fuel cell is formed by stacking 10 single-element exchange membrane fuel cells, the theoretical voltage is 1.23V 10, and the circulating voltage is 0.8-0.7-0.6-0.65-0.5-0.45-0.4-0.45-0.5-0.65 … … by taking single-cell voltage change as an example.
Preferably, the temperature of the galvanic pile in the step S2 is raised to 60 ℃, and the normal working temperature is 60 ℃.
Preferably, the atomized droplet stream in step S2 is an atomized droplet stream obtained by atomizing air using an ultrasonic atomizer.
In the step S2, an ultrasonic atomizer is opened to feed atomized liquid drops into a cathode airflow channel (cathode side) of the fuel cell, the cathode airflow channel (cathode side) of the fuel cell adopts an atomized air mixing air supply mode, humidification of air is replaced by the atomized liquid drops, and atomization amount is introduced to be Q s =25-100 mL/h; wherein the best battery cooling effect is obtained using an atomization amount of Q s =100 mL/h. Further preferably, the amount of atomization may be 25mL/h, 50mL/h, 75mL/h, or 100mL/h.
Preferably, the activating conditions described in step S3 are: changing the atomization amount Qs of the atomized droplet flow, wherein the range is Q s =25-100 mL/h, and the minimum change amount is 25mL/h; the voltage is 8.5-4.5V, the minimum variation is 0.5V, and the activation time is 2-3h.
Preferably, the conditions for completion of the activation in step S3 are: and monitoring the current and temperature change conditions generated by the fuel cell in a constant voltage mode in the process of activating the fuel cell until the current output is stable and does not change to 0-4A (for example, 0A, 1A, 2A, 3A and 4A) after a plurality of times of cyclic tests, and keeping the temperature of the electric pile constant, namely, completing activation.
Compared with the prior art, the invention has the following advantages:
1. The fuel cell stack activation method provided by the invention adopts a control strategy with higher relative humidity: 1) Under the action of atomized liquid drops, the water content in the battery is increased, and under the condition that the temperature of the battery does not need to be reduced, even if the water is evaporated by the high temperature generated in the running process of the battery, the water can be rapidly supplemented at the moment, so that a durable water film is provided for the catalyst layer and the proton exchange membrane, the conduction of protons is facilitated, and the electrochemical reaction rate is improved; 2) Under the action of atomized liquid drops, the fuel cell is reactivated, the output current is increased by 21.07%, and the performance of the cell when leaving the factory is nearly restored. The reason is that under high current density, the heat generated by the battery is rapidly increased, the temperature is too high, the moisture is rapidly evaporated, the membrane is dehydrated, at the moment, the water vapor partial pressure is increased by atomizing liquid drops, the water content and the water activity of the membrane are improved, the proton conduction efficiency is improved, and the latent heat generated by the liquid drop phase transition is beneficial to discharging the waste heat in the battery, so that the membrane is prevented from being broken due to the too high temperature; the injected atomized droplets supplement the evaporation of water and increase the output current.
2. The fuel cell stack activation method provided by the invention improves the stability of the fuel cell under high current output, improves the water activity required by catalytic reaction, enhances the cell reaction, reduces the activation loss of the cell, prevents flooding caused by water vapor accumulation due to the blowing of a fan at the cathode side, and improves the limit output power of the fuel cell.
3. The fuel cell stack activation method provided by the invention simplifies the fuel cell system and shortens the activation time of the fuel cell.
For the above reasons, the fuel cell stack activation method provided by the invention can be widely popularized in the field of fuel cells.
Description of the drawings:
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below make some embodiments of the invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic view of the structure of a fuel cell of the present invention;
Fig. 2 is a schematic view of the structure of the fuel cell of the present invention;
FIG. 3 is a schematic diagram of a proton exchange membrane fuel cell testing platform of the present invention;
FIG. 4 is the effect of the amount of fogging on the average temperature inside the battery in example 1 of the invention;
FIG. 5 is a polarization curve of the fuel cell stack of example 2 of the present invention activated by conventional means and activated by ultrasonic atomization;
FIG. 6 is a plot of current versus time for a stack constant voltage cycle test in example 2 of the present invention;
reference numerals illustrate: 1. the device comprises a hydrogen inlet, 2, a hydrogen outlet, 3, a fan housing, 4, a first end plate, 5, a fastener, 6, a cathode airflow channel (cathode side), 7, a second end plate, 8, a fan blade, 9, a fuel cell, 10, a fan, 11, 12V direct current power supply, 12, a temperature acquisition instrument, 13, a signal control and data acquisition instrument, 14, an electronic load, 15, an ultrasonic atomizer, 16, a bubbling humidifier, 17, a float flowmeter, 18, a hydrogen tank, 19, a high-precision regulating valve, 20, an air and atomized liquid drop channel, 21, a thermocouple, 22, a gas flow direction, 23 and atomized gas.
The specific embodiment is as follows:
The following examples are further illustrative of the invention and are not intended to be limiting thereof.
In order to make the objects, technical solutions and advantages of the present invention more apparent, examples and embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. It is apparent that the described embodiments are only some, not all, embodiments of the invention. The following description of at least one example is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to fall within the scope of the invention.
The invention provides a fuel cell stack activation method based on ultrasonic atomization, which comprises the steps of preprocessing a fuel cell, introducing atomized liquid drops into a cathode gas channel, and activating the fuel cell by adopting a stepped circulation constant voltage discharge mode.
The method specifically comprises the following steps:
S1, on a fuel cell testing platform, enabling the fuel cell to be in an open circuit state, and respectively purging hydrogen and air to an anode and a cathode to pretreat the fuel cell.
Further, the anode was purged with hydrogen for 5min and the cathode was purged with air for 5min for pretreatment, wherein the relative humidity of hydrogen was 100%, and the air was not additionally humidified.
Further, a fuel cell model and a fuel cell test platform are schematically shown in FIGS. 1-3. The anode side of the fuel cell model is supplied with air from a hydrogen inlet 1 and exhausted from a hydrogen outlet 2, the air supply of the cathode side is supplied with air and atomized liquid drops along a gas flow direction 22 by an external fan 10 (comprising a fan housing 3 and a fan blade 8 arranged in the fan housing) which is supplied with power from a 12V direct current power supply 11 and enters a cathode gas flow channel 6; the fuel cell first end plate 4 and the second end plate 7 are connected using fasteners 5. There is no limitation in the choice of fuel cell, and the fuel cell used in the following examples is an air-cooled fuel cell stack consisting of 10 single element exchange membrane fuel cells (theoretical voltage 1.23v 10). The choice of the fastener 5 is not limited as long as it can connect the fixing elements of the first end plate and the second end plate.
During activation, atomized gas 23 enters the cathode gas flow channel 6 through the air and atomized liquid drop channel 20, and before activation, the normal operation and performance improvement of the battery are ensured by purging, firstly, the air in the anode channel of the battery is thoroughly removed, and the purpose of preventing oxyhydrogen mixing is to prevent; the gas is introduced in advance for a period of time to purify the impurities, so that the impurities are prevented from blocking the channel or pore structure, and the reaction is prevented from being uneven and the efficiency is prevented from being reduced. The purging time is 4-8min, the anode side hydrogen is supplied by a hydrogen tank 18, the hydrogen flow is controlled by a float flowmeter 17 and a high-precision regulating valve 19, and the hydrogen humidity is controlled by a bubbling humidifier 16.
S2, opening the electronic load 14, adjusting the temperature of the fuel cell to 60 ℃ by the temperature acquisition instrument 12, and connecting the temperature acquisition instrument 12 with the fuel cell 9 through the thermocouple 21. The humidification of the air is replaced by atomized droplets, and the ultrasonic atomizer 15 is turned on to feed a stream of atomized droplets of different atomization to the cathode side of the fuel cell, with Q s =25-100 mL/h.
Further, the activation process of the cell corresponds to the process of discharging to the outside, and the temperature of the fuel cell gradually increases to 60 ℃ as the electrochemical reaction proceeds.
Further, atomized droplet streams with an atomization amount of Q s＝25mL/h、Qs＝50mL/h、Qs＝75mL/h、Qs =100 mL/h were fed to the fuel cell cathode channels, respectively. At 5.0V, the average cell temperature was reduced by 10 ℃ using Q s = 100mL/h of nebulization versus no nebulization. The atomized flow of the atomized mixed air can be used for improving the water activity at different degrees to reduce the activation loss by humidifying the air by utilizing atomized liquid drops at different degrees, and the cathode side flooding caused by the excessive air relative humidity is avoided. Atomized liquid drops attached to the channel wall absorb heat at high temperature, and the atomization amount is Q s =100 mL/h, so that heat generated in the activation process can be taken away, and the temperature uniformity in the electric pile is improved.
S3, performing constant voltage cycle test on the fuel cell, and activating the fuel cell by adopting a signal control and data acquisition device 13 to enable the fuel cell to operate under constant voltage cycle of 8.5-4.5V.
Further, when the fuel cell is in low working voltage, the problems of heat generation increase and flooding are solved, and local overheating and uneven temperature are easily caused; the atomized droplet flow is introduced to increase the humidity of the proton exchange membrane, so that under the condition that the battery keeps normal working temperature, even if the water is evaporated by the high temperature generated in the running process of the battery, the water can be rapidly supplemented at the moment, thereby providing more water films for the catalyst layer and the proton exchange membrane, facilitating the conduction of protons and improving the electrochemical reaction rate; meanwhile, due to the evaporation heat absorption characteristic of atomized liquid drops, heat in the battery can be taken away, and the problem of local overheating is solved.
Further, in the conventional activation process, as the electrochemical reaction proceeds, heat generation increases rapidly, the temperature of the battery increases, water evaporates rapidly, resulting in dehydration of the membrane, and at this time, atomized droplets introduced into the cathode side increase the partial pressure of water vapor, thereby increasing the water content and water activity of the membrane, and further improving the reaction intensity, and the temperature increases again, so that when the atomization amount introduced into the stack is insufficient to satisfy the evaporation rate of water, the output current decreases rapidly. Therefore, the atomization amount is increased to 100mL/h according to the temperature change of the galvanic pile, and if the atomization amount is increased too much, flooding occurs, and the water content of the membrane electrode or the combined water cannot be improved.
Further, the current output and the temperature change condition of the fuel cell in the constant voltage mode are monitored in the process of activating the fuel cell until the current output and the temperature are stable, which indicates that the fuel cell is completely activated. The activation time is 2-3 h, and the activation time is different for fuel cells with different sizes, but compared with the traditional in-situ activation mode, the activation time of the activation method provided by the invention is obviously shortened for the same fuel cell.
The fuel cell stack activation method provided by the invention can achieve a rapid humidification effect on the membrane electrode by utilizing atomized liquid drops, so that the air on the cathode side of the fuel cell is not required to be pre-humidified in the activation process, and the activation time is saved; the atomized liquid drops can take away part of waste heat in the electric pile, so that the membrane dehydration and rupture caused by the generation of local hot spots are avoided, meanwhile, the purpose of controlling the heat generating speed of the battery can be achieved by controlling the atomization amount, and the output power of the battery is improved.
The method for activating the membrane electrode of the fuel cell and the technical effects of the invention are described below with reference to specific examples.
Example 1
The fuel cell stack adopted in the embodiment is an air-cooled fuel cell stack, the fuel cell stack model is shown in fig. 1 and 2, the fuel cell stack is composed of 10 single-element exchange membrane cells (theoretical voltage is 1.23v×10), and air in a cathode airflow channel is supplied by a fan; hydrogen is input into the battery through a hydrogen supply pipeline, and atomization is generated by an ultrasonic atomizer and sent to the cathode side through a fan. During operation of the fuel cell stack, atomized droplets are drawn into the stack through the air duct for an experiment, the experimental platform being shown in fig. 3.
Before activation, the fuel cell is normally operated, hydrogen is introduced into the anode, air is introduced into the cathode, and the back pressure of the fuel cell is regulated to be the required pressure at the normal operating temperature of the fuel cell.
In this embodiment, the polarization characteristics of the fuel cell under different atomization amounts are studied, and the specific implementation steps are as follows:
S1, mounting a fuel cell on a test bench, and setting anode gas as hydrogen with the relative humidity of 100%; setting the cathode gas as air, and no additional humidification is required; hydrogen and air which are purged to the anode and the cathode respectively, wherein the gas flow is 18L/h, the purging time is 5min, and the fuel cell is pretreated;
S2, opening an electronic load, step-wise loading the voltage of a galvanic pile to enable the temperature of the fuel cell to rise to 60 ℃, ensuring that the cathode and the anode of the fuel cell do not have redundant impurities after pretreatment in the step S1, and opening an ultrasonic atomizer to respectively send atomized droplet streams with the atomization amount of qs=25-100 mL/h into a cathode channel of the fuel cell;
S3, respectively carrying out polarization characteristic test on the fuel cells with different atomization amounts, enabling the fuel cells to operate at 8.5-4.5V, and recording the change trend of current along with voltage and the temperature change condition of the fuel cells in the constant voltage discharge process until the polarization performance of the proton exchange membrane fuel cell stack is kept stable, so that the polarization characteristic test is completed.
In step S2, atomized droplet streams having atomization amounts of qs=25 mL/h, qs=50 mL/h, qs=75 mL/h, and qs=100 mL/h are fed to the fuel cell cathode channels, respectively. At low operating voltages, the gradual increase in heat generation rate causes an increase in internal temperature. And the evaporation heat absorption characteristic of atomized liquid drops ensures that the cooling effect is better when the atomization amount is increased.
In step S3, the polarization characteristic temperature change is as shown in fig. 4. At 5.0V, the cell was subjected to polarization property test without atomizing, and the maximum temperature of the cell was 45 ℃. The highest cell temperature was reduced by nearly 10 ℃ using 100mL/h of nebulization versus the test without nebulization. The highest temperature of the battery tested by using 25mL/h, 50mL/h and 75mL/h is respectively reduced by 5 ℃ and 7 ℃ compared with the highest temperature of the battery tested without physical and chemical treatment, so that the battery can be cooled more obviously by adopting the atomizing droplet flow with qs=100 mL/h. Subsequent activation experiments were performed with an atomized droplet stream having an atomization level of qs=100 mL/h, avoiding rupture of the membrane due to excessive temperatures.
Comparative example 1
The traditional in-situ activation mode comprises the following specific steps: step one, placing a proton exchange membrane fuel cell stack to be activated on a fuel cell test platform, respectively introducing hydrogen and oxygen with the relative humidity of 100% to the anode side and the cathode side of the cell for purging, wherein the gas flow is 18L/h, the purging time is 5min, and preprocessing the fuel cell. And step two, setting the normal working temperature of the fuel cell. And thirdly, after the proton exchange membrane fuel cell reaches a set temperature, keeping the gas of the anode and the cathode to be introduced, performing constant-pressure circulation test on the fuel cell to ensure that the fuel cell operates for 6 hours under a specified constant voltage, and performing cell performance test for 4 times until stable cell performance is obtained, wherein the activation time of the fuel cell is up to 24 hours.
Example 2
The fuel cell stack adopted in the embodiment is an air-cooled fuel cell stack, the fuel cell stack model is shown in fig. 1 and 2, the fuel cell stack is composed of 10 single-element exchange membrane cells (theoretical voltage is 1.23v×10), and air in a cathode airflow channel is supplied by a fan; hydrogen is input into the battery through a hydrogen supply pipeline, and atomization is generated by an ultrasonic atomizer and sent to the cathode side through a fan. In the operation process of the electric pile, atomized liquid drops are sucked into the electric pile through the air duct for experiment, and an experiment platform is shown in fig. 3.
Before activation, the fuel cell is normally operated, hydrogen is introduced into the anode side, air is introduced into the cathode side, and the back pressure of the fuel cell is adjusted to the required pressure at the normal operating temperature of the fuel cell.
The fuel cell stack activation method is adopted for activation, and specifically comprises the following steps:
S1, mounting a fuel cell on a test bench, and setting anode gas as hydrogen with the relative humidity of 100%; setting the cathode gas as air, and no additional humidification is required; hydrogen and air which are purged to the anode and the cathode respectively, wherein the gas flow is 18L/h, the purging time is 5min, and the fuel cell is pretreated;
S2, opening an electronic load, step-wise loading the voltage of a galvanic pile to enable the temperature of the fuel cell to rise to 60 ℃, ensuring that the cathode and the anode of the fuel cell do not have redundant impurities after pretreatment in the step S1, and opening an ultrasonic atomizer to send an atomized droplet flow with the atomization amount of Q s =100 mL/h to a cathode channel of the fuel cell;
S3, performing constant-voltage cycle test on the fuel cell to enable the fuel cell to operate under constant voltage of 8.5-4.5V, and activating the fuel cell; and observing the output current and temperature change condition of the fuel cell under constant voltage discharge in the activation process of the fuel cell until the polarization performance of the proton exchange membrane fuel cell stack is kept stable, which indicates that the fuel cell is completely activated, and the activation time of the fuel cell is 2h.
In step S3, a polarization performance curve of the fuel cell is obtained, as shown in fig. 5, and the result shows that compared with the fuel cell which does not use atomization, the output current is increased by 21.07% by using the atomization method to perform the cell activation experiment, and the performance of the fuel cell when the fuel cell leaves the factory is nearly restored, thereby realizing the reactivation of the fuel cell. It can be seen that the fuel cell stack activation method provided by the invention can obviously improve the current output and the performance of the cell.
As the operating voltage decreases from 8.5-4.5V, the battery current increases from 0.5-4.0A. However, the lower the operating voltage, the less stable the current output. The fuel cell was operated at a constant voltage load of 70s, and was subjected to a voltage step-wise load-varying operation at intervals of 70s with a voltage change of 0.5V, to obtain a current-voltage change curve of the fuel cell with time at the time of constant voltage cycle test, as shown in fig. 6. The atomization method provided by the embodiment can quickly activate the fuel cell, the total activation time is 20/9h, and compared with the traditional in-situ activation mode in comparative example 1, the activation time is greatly shortened, as shown in fig. 6.
Example 3
The procedure was as in example 2, except that:
The activation conditions in step S2 are: the ultrasonic atomizer was turned on to feed an atomized droplet stream having an atomization amount of qs=25 mL/h to the fuel cell cathode channels.
The activation conditions in step S3 are: performing constant voltage cycle test on the fuel cell to enable the fuel cell to operate under constant voltage of 8.5-4.5V, and activating the fuel cell; and observing the output current and temperature change condition of the fuel cell under constant voltage discharge in the activation process of the fuel cell stack until the polarization performance of the proton exchange membrane fuel cell stack is kept stable, which indicates that the fuel cell is completely activated, and the activation time of the fuel cell is 3h.
In step S3, a polarization performance curve of the fuel cell is obtained, as shown in fig. 5, and the result shows that compared with the fuel cell which does not use atomization, the output current is increased and the performance of the fuel cell when the fuel cell leaves the factory is nearly restored, so that the reactivation of the fuel cell is realized. It can be seen that the fuel cell stack activation method provided by the invention can obviously improve the current output and the performance of the cell.
The above embodiments are only described to assist in understanding the technical solution of the present invention and its core idea, and it should be noted that it will be obvious to those skilled in the art that several improvements and modifications can be made to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.
Claims (8)
1. The proton exchange membrane fuel cell stack activation method based on ultrasonic atomization is characterized by comprising the following steps of: after the proton exchange membrane fuel cell is pretreated, atomized liquid drops are introduced into the cathode side of the fuel cell, and the proton exchange membrane fuel cell is activated by adopting a stepped circulation constant voltage discharge mode.
2. The method for activating a proton exchange membrane fuel cell stack according to claim 1, comprising the steps of:
S1, on a fuel cell test platform, enabling a fuel cell to be in an open circuit state, and preprocessing the anode side and the cathode side of the fuel cell;
S2, opening an electronic load, loading stack voltage step by step to enable the fuel cell to be heated to a normal working temperature, and feeding atomized droplet streams with different atomization amounts to the cathode side of the fuel cell;
S3, performing constant-voltage circulation test on the fuel cell, enabling the fuel cell to perform activation under the step-type voltage of 8.5-4.5V of atomized droplet streams with different atomization amounts, and stopping conveying the atomized droplet streams until activation is completed, so that activation of the fuel cell is completed.
3. The method for activating a proton exchange membrane fuel cell stack according to claim 2, wherein the specific steps of pretreating the anode and the cathode of the fuel cell in step S1 are as follows: the anode is purged with hydrogen for 4-8min, and the cathode is purged with air for 4-8min for pretreatment, wherein the relative humidity of the hydrogen is 100%, and the air does not need additional humidification.
4. The method according to claim 2, wherein the fuel cells in step S1 are stacked by n single-element-exchange-membrane fuel cells, where n is not less than 10.
5. The method of claim 2, wherein the stack temperature in step S2 is raised to 60 ℃.
6. The method of claim 2, wherein the atomized droplet stream in step S2 is an atomized droplet stream obtained by atomizing air using an ultrasonic atomizer.
7. The method of activating a proton exchange membrane fuel cell stack as claimed in claim 2, wherein the activating conditions in step S3 are: changing the atomization amount Qs of the atomized droplet flow, wherein the range is qs=25-100 mL/h, and the minimum change amount is 25mL/h; the voltage is 8.5-4.5V, the minimum variation is 0.5V, and the activation time is 2-3h.
8. The method of activating a proton exchange membrane fuel cell stack as claimed in claim 2, wherein the activation is completed in step S3 under the following conditions: and monitoring the current and temperature change conditions generated by the fuel cell in a constant voltage mode in the process of activating the fuel cell until the current output is stable and does not become 0-4A after a plurality of cyclic tests, and the temperature of the electric pile is kept constant, namely the activation is completed.
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