Rapid activation method of functional modified catalyst layer of fuel cell

Abstract

The invention discloses a rapid activation method of a functional modified catalyst layer of a fuel cell, relates to the rapid activation method of the functional modified catalyst layer, and aims to solve the technical problem of long electrode activation time of the functional modified catalyst layer of the existing fuel cell. According to the method, ultrasonic pretreatment is combined with a dihydrovariable current density activation technology, the surface of the electrode is cleaned, the pore structure of the electrode is improved, the effective reaction surface area is increased, and the performance of the functional modified catalyst layer membrane electrode is rapidly improved in a short time. Meanwhile, H2 has reducibility, so that Pt is prevented from being oxidized into PtOx to be inactivated in a long process of a conventional activation method. According to the method, the whole activation process only consumes 35-60 minutes, the peak power density of the activated electrode is improved by 8%-40% compared with that of a conventional activation method, and the consumption of gas fuel is reduced. The invention can be used in fuel cell field.

Description

Technical Field

[0001] The present invention relates to a method for rapidly activating a functionalized modified catalyst layer, belonging to the technical field of fuel cells. Background Art

[0002] Proton exchange membrane fuel cells have high power density and environmental friendliness, and have broad application prospects in many fields such as transportation. However, there are still some deficiencies in the membrane electrode: ion cross-linked polymers are prone to degradation at low humidity, leading to an increase in resistance; the activity of the catalyst will decrease due to toxicity damage and structural changes; the electrode material is prone to corrosion and wear under high temperature and high humidity conditions, affecting the system life and long-term operation stability. By functionalizing and modifying the catalyst layer, the above problems existing in the membrane electrode of the proton exchange membrane fuel cell can be effectively solved, including regulating the catalyst structure and increasing the exposed number of active sites for the reaction of the catalyst with oxygen; preparing core-shell structure catalysts, such as Pt-Co alloy catalysts, Pt / C@PANI core-shell structure catalysts, etc., to increase the specific surface area of the catalyst and the exposed number of active sites; adding functional additives into the catalyst layer to improve the low humidity performance and weaken the poisoning effect of the ionomer; by adopting structural designs such as an ordered catalyst layer and a gradient catalyst layer, the utilization rate of the catalyst and the battery performance are improved. Although the above functionalized modified catalyst layer improves the power density and long-term stability of the battery, it also significantly prolongs the electrode activation time, usually requiring several hours, which not only increases the hydrogen consumption but also prolongs the production cycle. Summary of the Invention

[0003] The present invention aims to solve the technical problem of the long electrode activation time of the existing functionalized modified catalyst layer of the fuel cell, and provides a method for rapidly activating the functionalized modified catalyst layer of the fuel cell. The present invention utilizes ultrasonic pretreatment plus double-hydrogen variable current density activation technology to clean the electrode surface, improve the pore structure of the electrode, increase the effective reaction surface area, and rapidly improve the performance of the functionalized modified catalyst layer membrane electrode in a short period of time. At the same time, H 2 also has reducibility, avoiding the inactivation of Pt oxidized to PtO during the long process of the conventional activation method, x and improving the initial performance and durability of the membrane electrode.

[0004] The method for rapidly activating the functionalized modified catalyst layer of the fuel cell of the present invention is carried out according to the following steps:

[0005] 1. Immerse the functionalized modified catalyst layer membrane electrode in a solvent at a temperature of 60-80°C, treat it with an ultrasonic machine with a power of 80-100W for 5-10 minutes, and then place it in an oven and dry it at a temperature of 70-80°C for 5-10 minutes to complete the pretreatment;

[0006] 2. Assemble the pretreated functionalized modified catalyst layer membrane electrode into a single cell and perform airtightness detection;

[0007] III. Nitrogen with a relative humidity of 40% RH - 80% RH is introduced on both sides of the single cell, the gas flow rate is controlled at 0.3 - 0.5 L / min, and the gas is introduced for 3 - 5 min. The purpose is to discharge other gases in the single cell and achieve a pre - humidification effect;

[0008] IV. The gases on both sides are switched to hydrogen with a relative humidity of 40% RH - 80% RH, and a direct - current power supply is used to apply a current density of J 1 = 180 - 300 mA / cm 2 to the single cell for 3 - 5 min; then the gases on both sides are switched to nitrogen with a relative humidity of 40% RH - 80% RH and run for 1 - 3 min. This is the first cycle;

[0009] V. The operation in step IV is cycled. When the nth cycle is carried out, the current density J n = J n-1 +(200 - 400), n≥2. The cycle is continued until the cell voltage remains stable, and the activation of the functionalized modified catalytic layer of the fuel cell is completed.

[0010] Preferably, the functionalized modified catalytic layer membrane electrode described in step I is a PtCo / C catalytic layer membrane electrode, a catalytic layer membrane electrode with hygroscopic COFs added, or a Pt catalytic layer membrane electrode supported on a sulfur - doped carbon carrier.

[0011] Preferably, the solvent described in step I is a mixed solution of isopropanol and deionized water with a volume ratio of (0.5 - 1):1.

[0012] Preferably, the frequency range of the ultrasonic machine described in step I is 40 - 50 KHz.

[0013] Preferably, the voltage remaining stable described in step V means that the last two decimal places of the cell voltage remain unchanged within 3 minutes during the activation process.

[0014] The present invention activates the membrane electrode by ultrasonic pretreatment and dual - hydrogen variable current. The ultrasonic pretreatment not only cleans the electrode surface, but also improves the pore structure of the electrode and increases the effective reaction surface area by removing non - bound particles inside the membrane electrode. The dual - hydrogen variable current activation process avoids the inactivation of Pt oxidized to PtO x during the long process of conventional activation methods, and improves the initial performance and durability of the membrane electrode. The entire activation process of the present invention only takes 35 - 60 min, reducing the activation time of the membrane electrode, enabling the membrane electrode to reach the highest performance in the shortest time. At the same time, compared with conventional activation, the peak power density of the electrode of the present invention is increased by 8% - 40% after activation, and the gas fuel consumption is reduced. It can be used in the field of fuel cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is the relationship diagram of the conventional potentiostatic cycling activation voltage and time of Comparative Example 1;

[0016] Figure 2 is the polarization performance comparison diagram of different activation methods of Example 1, Comparative Example 1, and Comparative Example 2;

[0017] Figure 3 is the polarization performance comparison diagram of different activation methods of Example 2, Comparative Example 3, and Comparative Example 4;

[0018] Figure 4 is the polarization performance comparison diagram of different activation methods of Example 3, Comparative Example 5, and Comparative Example 6. Detailed implementation manners

[0019] The beneficial effects of the present invention are verified by the following examples.

[0020] Example 1: The rapid activation method of the fuel cell functionalized modified catalytic layer in this example is carried out according to the following steps:

[0021] I. Immerse a single-piece 5 cm * 5 cm PtCo / C catalytic layer membrane electrode into a solvent formed by mixing isopropyl alcohol and deionized water at a volume ratio of 0.5:1 at a temperature of 60 °C, ultrasonically treat it with an ultrasonic machine with a power of 80 W and a frequency of 40 KHz for 10 min, and then put it into an oven and dry it at a temperature of 80 °C for 10 min to complete the pretreatment;

[0022] II. Assemble the pretreated PtCo / C catalytic layer membrane electrode into a single cell and perform airtightness detection;

[0023] III. Pass nitrogen with a relative humidity of 40% RH on both sides of the single cell, control the gas flow rate at 0.5 L / min, and ventilate for 5 min. The purpose is to discharge other gases in the single cell and achieve a pre-humidification effect;

[0024] IV. Switch the gases on both sides to hydrogen with a relative humidity of 40% RH, and apply a current density of J 1 = 180 mA / cm 2 to the single cell using a DC power supply and run for 5 min; then switch the gases on both sides to nitrogen with a relative humidity of 40% RH and run for 3 min. This is the first cycle;

[0025] V. Switch the gases on both sides to hydrogen with a relative humidity of RH 40%, and apply a current density of J 2 = 380 mA / cm 2The current density is applied for 5 min; then the gases on both sides are switched to nitrogen with a relative humidity of 40% RH and run for 3 min. This is the second cycle;

[0026] VI. Switch the gases on both sides to hydrogen with a relative humidity of 40% RH, and apply a current density of J 3 = 580 mA / cm 2 to the single cell using a DC power supply and run for 5 min; then switch the gases on both sides to nitrogen with a relative humidity of 40% RH and run for 3 min. This is the third cycle;

[0027] VII. Switch the gases on both sides to hydrogen with a relative humidity of 40% RH, and apply a current density of J 3 = 780 mA / cm 2 to the single cell using a DC power supply and run for 5 min; at this time, the last two decimal places of the battery voltage remain unchanged within 3 minutes, that is, the voltage reaches stability; then switch the gases on both sides to nitrogen with a relative humidity of 40% RH and run for 3 min to complete the activation. The whole process takes 57 min.

[0028] After the activation is completed, then switch the anode and cathode to air and hydrogen, the anode-cathode stoichiometric ratio is 2.5 / 1.5, the anode-cathode back pressures are both 100 Kpa, the anode-cathode humidities are both RH 100%, the battery temperature is 80 °C, and pull the load from the open-circuit voltage to 0.2 V voltage to complete the polarization performance test.

[0029] Comparative Example 1: Using the same PtCo / C catalytic layer membrane electrode as in Example 1, after directly assembling it into a single cell, air and hydrogen are respectively introduced into the anode and cathode, the anode-cathode stoichiometric ratio is 2.5 / 1.5, the anode-cathode back pressures are both 100 Kpa, the anode-cathode relative humidities are both 100% RH, the battery temperature is 80 °C, and constant potential cycling activation is carried out. Steps: stay at 0.8 V for 10 min, stay at 0.6 V for 10 min, stay at 0.4 V for 10 min, stay at 0.2 V for 2 min, and cycle 6 times to complete the activation. The relationship diagram of the conventional constant potential cycling activation voltage and time for this comparative example is as Figure 1 shown, and the total activation time is 192 min. Then, the polarization performance test is carried out using the same method as in Example 1.

[0030] Comparative Example 2: The difference between this comparative example and Example 1 is that the pretreatment process in Step 1 is omitted, and the rest is the same as in Example 1 to complete the dual-hydrogen activation. Then, the polarization performance test is carried out using the same method as in Example 1.

[0031] The polarization performance curves obtained in Example 1, Comparative Example 1, and Comparative Example 2 are as Figure 2 shown. It can be seen from Figure 2 that for the method of ultrasonic + dual-hydrogen activation in Example 1, the peak power density of the electrode is 1.33 W / cm2 For the conventional activation method of Comparative Example 1, the peak power density of the electrode is only 1.19 W / cm 2 For Comparative Example 2 after only dihydrogen activation, the peak power density of the electrode is 1.24 W / cm 2 . It can be seen by comparison that compared with the conventional activation, the method of ultrasonic + dihydrogen activation in Example 1 not only greatly shortens the activation time, but also increases the peak power density by 11.8%.

[0032] Example 2: The rapid activation method of the functionalized modified catalytic layer of the fuel cell in this example is carried out according to the following steps:

[0033] I. Immerse the Pt catalytic layer membrane electrode supported by a single-piece 5 cm * 5 cm sulfur-doped carbon support in a solvent composed of isopropanol and deionized water mixed at a volume ratio of 0.8:1 at a temperature of 80 °C, and ultrasonically treat it with an ultrasonic machine with a power of 90 W and a frequency of 50 KHz for 5 min, and then place it in an oven and dry it at a temperature of 80 °C for 10 min to complete the pretreatment;

[0034] II. Assemble the pretreated Pt catalytic layer membrane electrode supported by the sulfur-doped carbon support into a single cell and conduct an airtightness test;

[0035] III. Pass nitrogen with a relative humidity of 50% RH on both sides of the single cell, control the gas flow rate at 0.3 L / min, and ventilate for 4 min. The purpose is to discharge other gases in the single cell and achieve a pre-humidification effect;

[0036] IV. Switch the gases on both sides to hydrogen with a relative humidity of 60% RH, and apply a current density of J 1 = 240 mA / cm 2 to the single cell using a DC power supply and operate for 4 min; then switch the gases on both sides to nitrogen with a relative humidity of 50% RH and operate for 4 min. This is the first cycle;

[0037] V. Switch the gases on both sides to hydrogen with a relative humidity of 60% RH, and apply a current density of J 2 = 480 mA / cm 2 to the single cell using a DC power supply and operate for 4 min; then switch the gases on both sides to nitrogen with a relative humidity of 50% RH and operate for 4 min. This is the second cycle;

[0038] VI. Switch the gases on both sides to hydrogen with a relative humidity of 60% RH, and apply a current density of J 3 = 720 mA / cm 2 to the single cell using a DC power supply and operate for 4 min; then switch the gases on both sides to nitrogen with a relative humidity of 50% RH and operate for 4 min. This is the third cycle;

[0039] VII. Switch the gases on both sides to hydrogen with a relative humidity of 60% RH, and apply a current density of J 3 = 960 mA / cm 2 to the single cell using a DC power supply and operate for 4 minutes. At this time, the last two decimal places of the cell voltage remain unchanged within 3 minutes, that is, the voltage reaches stability; then switch the gases on both sides to nitrogen with a relative humidity of 50% RH and operate for 4 minutes to complete activation. The entire process takes 51 minutes.

[0040] After completion of activation, then switch the anode and cathode to air and hydrogen, with the anode-cathode stoichiometric ratio of 2.2 / 1.8, the back pressure of both the anode and cathode being 150 KPa, the relative humidity of both the anode and cathode being 100% RH, and the cell temperature being 80°C. Pull the load from the open circuit voltage to 0.2 V to complete the polarization performance test.

[0041] Comparative Example 3: Using the Pt catalytic layer membrane electrode supported by the same sulfur-doped carbon carrier as in Example 2, after directly assembling it into a single cell, air and hydrogen are respectively introduced into the anode and cathode, the anode-cathode stoichiometric ratio is 2.2 / 1.8, the back pressure of both the anode and cathode is 150 Kpa, the humidity of both the anode and cathode is 100% RH, and the cell temperature is 80°C. Use potentiostatic cycling activation, steps: stay at 0.8 V for 10 minutes, stay at 0.6 V for 10 minutes, stay at 0.4 V for 10 minutes, stay at 0.2 V for 2 minutes, cycle 6 times to complete activation, with a total time of 192 minutes. Then use the same method as in Example 2 to conduct the polarization performance test.

[0042] Comparative Example 4: The difference between this comparative example and Example 2 is that the pretreatment process in Step 1 is omitted, and the rest is the same as in Example 2 to complete the dual-hydrogen activation. Then use the same method as in Example 2 to conduct the polarization performance test.

[0043] The polarization performance curves obtained from Example 2, Comparative Example 3, and Comparative Example 4 are as Figure 3 shown. It can be seen from Figure 3 that for the method of ultrasonic + dual-hydrogen activation in Example 2, the peak power density of the electrode is 1.46 W / cm 2 , for the conventional activation method in Comparative Example 3, the peak power density of the electrode is only 1.35 W / cm 2 , and for Comparative Example 4 after only dual-hydrogen activation, the peak power density of the electrode is 1.4 W / cm 2 . By comparison, it can be known that compared with the conventional activation, the method of ultrasonic + dual-hydrogen activation in Example 2 not only greatly reduces the activation time, but also increases the peak power density by 8.1%.

[0044] Example 3: The rapid activation method for the functionalized modified catalytic layer of the fuel cell in this example is carried out according to the following steps:

[0045] 1. Immerse the catalytic layer membrane electrode of a single piece of 2.25 cm * 2.25 cm with hygroscopic COFs added into a solvent composed of isopropyl alcohol and deionized water mixed at a volume ratio of 1:1 and at a temperature of 80 °C, and ultrasonically treat it for 10 min with an ultrasonic machine with a power of 100 W and a frequency of 50 KHz. Then place it in an oven and dry it at 80 °C for 5 min to complete the pretreatment;

[0046] 2. Assemble the pretreated catalytic layer membrane electrode with hygroscopic COFs added into a single cell and conduct an airtightness test;

[0047] 3. Pass nitrogen with a relative humidity of 80% RH on both sides of the single cell, control the gas flow rate at 0.5 L / min, and ventilate for 3 min. The purpose is to discharge other gases in the single cell and achieve a pre-humidification effect;

[0048] 4. Switch the gases on both sides to hydrogen with a relative humidity of 80% RH, and apply a current density of J 1 = 300 mA / cm 2 to the single cell using a DC power supply and run for 3 min. Then switch the gases on both sides to nitrogen with a relative humidity of 80% RH and run for 3 min. This is the first cycle;

[0049] 5. Switch the gases on both sides to hydrogen with a relative humidity of 80% RH, and apply a current density of J 2 = 700 mA / cm 2 to the single cell using a DC power supply and run for 3 min. Then switch the gases on both sides to nitrogen with a relative humidity of 80% RH and run for 3 min. This is the second cycle;

[0050] 6. Switch the gases on both sides to hydrogen with a relative humidity of 80% RH, and apply a current density of J 3 = 1100 mA / cm 2 to the single cell using a DC power supply and run for 3 min. At this time, the last two decimal places of the battery voltage remain unchanged within 3 min, that is, the voltage reaches stability. Then switch the gases on both sides to nitrogen with a relative humidity of 80% RH and run for 3 min to complete the activation. The whole process takes 36 min.

[0051] After the activation is completed, then switch the anode and cathode to air and hydrogen, the anode-cathode stoichiometric ratio is 2.5 / 1.5, the back pressure of both the anode and cathode is 100 Kpa, the relative humidity of both the anode and cathode is 40% RH, the battery temperature is 80 °C, and pull the load from the open circuit voltage to 0.2 V voltage to complete the polarization performance test.

[0052] Comparative Example 5: Using the same membrane electrode as in Example 3, after directly assembling it into a single cell, air and hydrogen were respectively introduced into the anode and cathode, the anode-cathode stoichiometric ratio was 2.5 / 1.5, the back pressures of both the anode and cathode were 100 Kpa, the humidities of both the anode and cathode were RH 40%, the battery temperature was 80 °C, and constant potential cycling activation was used. Steps: Stay at 0.8 V for 10 min, stay at 0.6 V for 10 min, stay at 0.4 V for 10 min, stay at 0.2 V for 2 min, cycle 6 times to complete activation, with a total time consumption of 192 min. Then, the polarization performance test was carried out using the same method as in Example 3.

[0053] Comparative Example 6: The difference between this comparative example and Example 3 is that the pretreatment process in Step 1 was omitted, and the others were the same as in Example 3 to complete the dual-hydrogen activation. Then, the polarization performance test was carried out using the same method as in Example 3.

[0054] The polarization performance curves obtained from Example 3, Comparative Example 5, and Comparative Example 6 are as Figure 4 shown. It can be seen from Figure 4 that for the method of ultrasonic + dual-hydrogen activation in Example 3, the peak power density of the electrode is 1.05 W / cm 2 , for the conventional activation method in Comparative Example 6, the peak power density of the electrode is only 0.75 W / cm 2 , and for Comparative Example 5 after only dual-hydrogen activation, the peak power density of the electrode is 0.81 W / cm 2 . By comparison, it can be known that compared with the conventional activation, the method of ultrasonic + dual-hydrogen activation in Example 3 not only greatly reduces the activation time, but also increases the peak power density by 40%. Compared with the method of only dual-hydrogen activation in Comparative Example 6, the method of ultrasonic + dual-hydrogen activation in Example 3 also increases the peak power density by 29.6%.

[0055] The present invention adopts the ultrasonic pretreatment plus dual-hydrogen variable current density activation technology, which rapidly improves the initial performance of the functionalized modified catalytic layer membrane electrode, greatly reduces the activation time and reduces the gas fuel consumption, thereby significantly reducing the activation cost. Among them, the ultrasonic pretreatment not only cleans the electrode surface, but also improves the pore structure of the electrode and increases the effective reaction surface area by removing the non-bonded particles inside the membrane electrode. At the same time, H 2 also has reducibility, avoiding the inactivation of Pt oxidized to PtO x during the long process of the conventional activation method, and improving the initial performance and durability of the membrane electrode.

Claims

1. A method for rapid activation of a functional modified catalyst layer of a fuel cell, characterized in that: The method proceeds as follows:

1. Immerse the functionalized modified catalyst layer membrane electrode in a solvent at a temperature of 60 to 80°C, treat it with an ultrasonic machine with a power of 80 to 100W for 5 to 10 minutes, and then put it in an oven at a temperature of 70 to 80°C for 5 to 10 minutes to complete the pretreatment; 2. Assemble the pre-treated functionalized modified catalyst layer membrane electrode into a single cell and conduct air tightness test; 3. Nitrogen with a relative humidity of 40% RH to 80% RH is introduced into both sides of the single cell, and the gas flow rate is controlled at 0.3 to 0.5 L / min for 3 to 5 minutes, in order to discharge other gases in the single cell and achieve a pre-humidification effect; 4. Switch the gas on both sides to hydrogen with a relative humidity of 40% RH to 80% RH, and use a DC power supply to apply J1 = 180 ~ 300mA / cm 2 The current density is set to 3-5 minutes. Then the gas on both sides is switched to nitrogen with a relative humidity of 40% RH to 80% RH and the cycle is run for 1-3 minutes. This is the first cycle.

5. Cycle according to the operation of step 4. During the nth cycle, the current density J applied by the DC power supply to the single battery n =J n-1 +(200~400), n≥2, cycle until the battery voltage remains stable, and complete the activation of the functional modified catalytic layer of the fuel cell.

2. A method for rapid activation of a functional modified catalyst layer of a fuel cell according to claim 1, characterized in that: The functionalized modified catalyst layer membrane electrode described in step 1 is a PtCo / C catalyst layer membrane electrode, a catalyst layer membrane electrode with hygroscopic COFs added, or a Pt catalyst layer membrane electrode supported by a sulfur-doped carbon carrier.

3. A method for rapid activation of a fuel cell functional modified catalyst layer according to claim 1 or 2, characterized in that: The solvent described in step 1 is a mixed solution of isopropanol and deionized water in a volume ratio of (0.5-1):

1.

4. A method for rapid activation of a functional modified catalyst layer of a fuel cell according to claim 1 or 2, characterized in that: The frequency range of the ultrasound machine described in step 1 is 40 to 50 KHz.

5. A method for rapid activation of a fuel cell functional modified catalyst layer according to claim 1 or 2, characterized in that: The voltage stability described in step 5 means that the battery voltage remains unchanged to two decimal places within 3 minutes during the activation process.

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