Activity recovery method for fuel cell platinum catalyst after carbon monoxide poisoning

Abstract

The invention discloses an activity recovery method for a fuel cell platinum catalyst after carbon monoxide poisoning, which comprises the following steps: periodically and alternately introducing oxidizing gas and reducing gas, and treating the anode of the fuel cell after carbon monoxide poisoning under the condition of low-temperature heating, the reducing gas is hydrogen or hydrogen-containing gas. According to the method, by controlling the switching time sequence of oxidizing gas and reducing gas, CO adsorbed on the surface of the catalyst is oxidized into CO2 and desorbed in the oxidation stage, formed Pt-O species are reduced into metallic platinum and surface residues are removed in the reduction stage, meanwhile, the surface of the platinum catalyst is induced to be dynamically reconstructed, and the surface of the platinum catalyst is subjected to dynamic reconstruction. The method has the advantages that lattice defects caused by poisoning can be repaired, the activity recovery rate of 90% or above can be achieved at the temperature of 80 DEG C, an external power source or additional complex equipment is not needed, and the method has the advantages of being easy and convenient to operate, low in energy consumption and free of influence on system operation and is suitable for online regeneration and maintenance of the proton exchange membrane fuel cell system.

Description

Technical Field

[0001] This invention relates to the field of fuel cells, and more particularly to a method for restoring the activity of a platinum catalyst in a fuel cell after carbon monoxide poisoning. Background Technology

[0002] As a highly efficient and clean energy conversion device, fuel cells suffer from the vulnerability of their core component, the platinum (Pt) catalyst, to carbon monoxide (CO) adsorption and poisoning during the anode reaction, leading to permanent deactivation of active sites. Statistics show that when the CO concentration in hydrogen fuel exceeds 10 ppm, CO adsorbs onto the Pt active sites, hindering fuel activation and reaction, resulting in a sharp decline in battery performance and severely impacting the long-term stable operation of the fuel cell. This problem significantly restricts the commercial application of fuel cells in vehicle power systems and distributed energy fields.

[0003] Traditional solutions mainly focus on three directions: (1) improving fuel purity, but hydrogen purification process greatly increases system cost; (2) developing Pt alloy catalysts, which improve their anti-poisoning performance, but usually accompanied by a decrease in catalytic activity; (3) high-temperature oxidation treatment, but may cause excessive oxidation of platinum and accelerate catalyst sintering.

[0004] In recent years, some studies have attempted to remove CO by oxidation through electrochemical pulse method or anodic potential cycle, but these methods usually rely on a single oxidation reaction pathway, resulting in limited regeneration efficiency (usually less than 80%). At the same time, their continuous reliance on external power source leads to high energy consumption and may cause carbon carrier corrosion. Summary of the Invention

[0005] The objective of this invention is to provide a method for restoring the activity of a platinum catalyst in a fuel cell after carbon monoxide poisoning. This method has high regeneration efficiency and low energy consumption, and can achieve efficient removal of CO from the poisoned platinum catalyst.

[0006] On one hand, the present invention provides a method for restoring the activity of a platinum catalyst in a fuel cell after carbon monoxide poisoning, which includes: periodically and alternately introducing an oxidizing gas and a reducing gas and treating the carbon monoxide poisoned anode of the fuel cell under low-temperature heating conditions, wherein the oxidizing gas is oxygen or an oxygen-containing gas, and the reducing gas is hydrogen or a hydrogen-containing gas.

[0007] Preferably, the oxidizing gas is a mixture of 1-10% oxygen and argon, and the reducing gas is pure hydrogen.

[0008] Preferably, the temperature range of the low-temperature heating is 80-120℃.

[0009] Preferably, the process includes the following steps:

[0010] (1) Oxidation stage: An oxidizing gas is introduced into the anode, the temperature is controlled at 80-120℃, the gas flow rate is 0.1-0.5L / min, and the duration is 0.5-5 minutes;

[0011] (2) Reduction stage: Stop the oxidizing gas from being introduced into the anode and switch to the reducing gas from being introduced into the anode. The gas flow rate is maintained at 0.1 to 0.5 L / min for 0.5 to 5 minutes, and the temperature is kept constant.

[0012] Repeat steps (1) and (2) several times to restore the activity of the platinum catalyst at the anode of the fuel cell that has been poisoned by carbon monoxide.

[0013] Compared with the prior art, the present invention has the following beneficial technical effects:

[0014] 1. High regeneration efficiency and good recovery effect: By constructing an oxidation-reduction synergistic mechanism, not only is CO adsorbed on the catalyst surface effectively removed, but lattice defects are also repaired by inducing dynamic reconstruction of the platinum surface. The activity recovery rate of more than 90% can be achieved at a low temperature of 80℃, which is significantly better than the traditional method with a single oxidation path.

[0015] 2. No complex equipment required, low energy consumption: The method of this invention can directly use the fuel cell's own air intake system to switch the reaction gas, without relying on an external power source to provide high-potential pulses or additional heating devices, which greatly reduces the energy consumption and system complexity of the regeneration process.

[0016] 3. Easy to operate and integrate: The regeneration process is under mild conditions and is simple to operate, with good engineering applicability and market application prospects. It is especially suitable for vehicle-mounted power and distributed energy fields that are sensitive to cost, space and system complexity.

[0017] 4. Environmentally friendly, widely applicable and highly safe: No disassembly of the fuel cell system is required, no chemical waste is generated, it can be applied to most products on the market, and there are no safety hazards or product performance degradation issues caused by reassembly. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that these drawings are schematic and simplified diagrams, which only show the details necessary for understanding the present invention, while omitting other details.

[0019] Figure 1 The voltage, current, and power curves of a fuel cell under ideal operating conditions are shown.

[0020] Figure 2The voltage, current and power curves of a fuel cell after undergoing an accelerated CO poisoning experiment;

[0021] Figure 3 for Figure 2 The voltage, current, and power curves of the corresponding fuel cell after activity recovery using the method according to an embodiment of the present invention. Detailed Implementation

[0022] The embodiments and examples of the present invention will now be described in detail with reference to the accompanying drawings.

[0023] The scope of the invention will become apparent from the detailed description given below. However, it should be understood that while the detailed description and specific examples illustrate preferred embodiments of the invention, they are given for illustrative purposes only.

[0024] To achieve the objective of this invention, the technical solution is as follows: the anode of a fuel cell poisoned by carbon monoxide is treated by periodically and alternately introducing oxidizing gas and reducing gas under low-temperature heating conditions. The oxidizing gas is a mixture of 1-10% oxygen and argon (1-10% O2 / Ar) or pure oxygen, and the reducing gas is pure hydrogen (H2) or a hydrogen-containing gas.

[0025] In this embodiment, the temperature range of the low-temperature heating is 80-120°C.

[0026] In an embodiment, the process includes:

[0027] (1) Oxidation stage: Oxidizing gas is introduced into the poisoned anode, the temperature is controlled at 80-120℃, the gas flow rate is 0.1~0.5L / min, and the duration is 0.5~5 minutes;

[0028] (2) Reduction stage: Stop the oxidizing gas and switch to the reducing gas to be introduced into the anode. The gas flow rate is maintained at 0.1 to 0.5 L / min for 0.5 to 5 minutes, and the temperature is kept constant.

[0029] Depending on the degree of poisoning, the amount of platinum loaded on the catalyst, and the size of the catalyst particles, steps (1) and (2) are repeated several times to restore the activity of the platinum catalyst at the anode of the fuel cell that has been poisoned by carbon monoxide.

[0030] In the embodiments, steps (1) and (2) are repeated 5 to 20 times. The number of repetitions is affected by parameters such as temperature, time, flow rate, and gas composition. In principle, the higher the degree of poisoning, the higher the platinum loading of the catalyst, and the larger the catalyst particles, the higher the concentration of the oxygen-argon mixed gas, the higher the flow rate, the longer the duration, and the more repetitions (cycles) can be.

[0031] Theoretically, the higher the oxygen content in the oxidizing gas, the better the CO removal effect and the less time is required to restore activity. However, because hydrogen and oxygen are alternately introduced, using a high-oxygen mixture or pure oxygen under heating conditions poses a high risk of explosion. Using an oxygen-argon mixture can prevent the risk of explosion and side reactions. Oxidizing gases can also be mixtures of oxygen and other inert gases.

[0032] From a chemical reaction perspective, the higher the temperature, the faster the reaction rate, requiring a higher gas flow rate and a shorter single-stage duration.

[0033] In practical applications, temperature, flow rate, duration, and number of repetitions can be adjusted in a coordinated manner according to specific needs. For example, when there is a significant sacrifice in catalyst life but the performance needs to be restored in the shortest possible time, a parameter combination of high temperature, short time, high flow rate, and short cycle can be used to shorten the total treatment time and improve efficiency. As another example, in the case of routine maintenance for mild poisoning, a parameter combination of medium temperature, moderate time, low flow rate, and long cycle can be used.

[0034] In this embodiment, during the oxidation phase, oxygen is continuously supplied to the fuel cell cathode. During single-fuel cell operation, the gas flow rate to the cathode is typically 0.5 L / min. This means that the recovery process of the poisoned anode does not completely interrupt the reaction between the anode and cathode, and the cathode continues to be supplied with oxygen, supporting normal reduction reactions and fuel cell operation. Of course, if the fuel cell completely stops operating, oxygen can be withheld from the cathode without significantly affecting the performance recovery of the poisoned anode.

[0035] The principle of this invention is as follows:

[0036] During the oxidation stage, an oxidizing gas (1-10% O2 / Ar) is introduced to oxidize the CO adsorbed on the anode platinum catalyst into CO2, which then desorbs from the platinum catalyst surface, resulting in the following reaction:

[0037] Pt-CO+O2→Pt+CO2[1]

[0038] In the H2 reduction stage, a reducing gas (H2) is introduced to reduce the Pt-O oxide layer to active Pt, and further remove residual CO and O2, resulting in the following reaction:

[0039] Pt-O+H2→Pt+H2O [2]

[0040] H2+Pt-CO+O2→Pt+H2O+CO2[3]

[0041] This invention fully utilizes the synergistic effect of oxidation-reduction. By controlling the switching sequence of oxidizing gas (O2) and reducing gas (H2), a high recovery rate can be achieved at a lower temperature, resulting in efficient CO removal while avoiding excessive oxidation corrosion and platinum sintering caused by excessively high temperatures. Simultaneously, the Pt catalyst undergoes dynamic surface reconstruction during the oxidation-reduction cycle; under an oxidizing atmosphere, metastable PtO can form on the Pt surface. x Layer, and when switching to a reducing atmosphere, PtO x The reduction process induces surface atomic rearrangement, which not only removes adsorbed CO but also repairs lattice defects caused by long-term operation. Experiments have shown that this method can fully utilize the synergistic effect of reduction and oxidation, achieving an activity recovery rate of over 90% at relatively low temperatures (80–120°C). Furthermore, since the gas can be switched directly using the fuel cell's intake pipe without additional energy consumption or complex equipment, it has extremely high engineering application value.

[0042] The following provides some embodiments of the method of the present invention and illustrates the effectiveness of the method of the present invention through experimental tests.

[0043] Experimental preparation

[0044] 1. Operating under ideal conditions

[0045] Assemble a single cell: the anode reaction gas is pure hydrogen, and the cathode reaction gas is pure oxygen. Operate the cell with pure hydrogen gas (i.e., ideal operating conditions) for a period of time, and record the voltage, current, and power curves, as follows: Figure 1 As shown.

[0046] 2. Accelerate CO poisoning experiments

[0047] (1) Poisoning single cell: The anode reaction gas is a mixture of 5% CO and hydrogen, and the cathode reaction gas is pure oxygen. The operation time is 15 hours.

[0048] (2) Detection of poisoned single cells: The anode reaction gas is pure hydrogen, and the cathode reaction gas is pure oxygen. Record the voltage, current, and power curves, such as... Figure 2 As shown.

[0049] Depend on Figure 1 It is evident that the battery performance is stable when operating with pure hydrogen. From Figure 2 It is evident that after operating the fuel cell with a mixture of 5% CO and hydrogen, the battery performance dropped sharply by 35.3%, indicating the significant toxic effect of CO on battery performance.

[0050] As described above, the method of the present invention based on oxygen / hydrogen cycle reduction oxidation can effectively restore the performance of fuel cells by treating CO-poisoned anodes.

[0051] Example 1

[0052] (1) Pass 5% O2 / Ar into the anode of the above-mentioned poisoned battery, set the electrode temperature to 80°C, the flow rate to 0.3L / min, and maintain for 1 minute.

[0053] (2) Then close the oxygen channel of the battery cathode, introduce H2 at a flow rate of 0.3 L / min, maintain for 1 minute, and keep the temperature constant.

[0054] (3) Repeat steps (1) and (2) for 10 cycles. After that, the anode gas is pure hydrogen and the cathode gas is pure oxygen.

[0055] Example 2

[0056] (1) Pass 5% O2 / Ar through the above-mentioned poisoned battery anode, set the electrode temperature to 100℃, the flow rate to 0.3L / min, and maintain for 0.5 minutes.

[0057] (2) Then close the oxygen channel at the cathode of the battery, introduce H2 at a flow rate of 0.3 L / min, maintain for 0.5 minutes, and keep the temperature constant.

[0058] (3) Repeat steps (1) and (2) for a total of 20 cycles. After that, the anode gas is pure hydrogen and the cathode gas is pure oxygen.

[0059] Example 3

[0060] (1) Pass 5% O2 / Ar into the anode of the above-mentioned poisoned battery, set the electrode temperature to 80°C, the flow rate to 0.1L / min, and maintain for 3 minutes.

[0061] (2) Then close the oxygen channel of the battery cathode, introduce H2 at a flow rate of 0.1 L / min, maintain for 3 minutes, and keep the temperature constant.

[0062] (3) Repeat steps (1) and (2) for 15 cycles. After that, the anode gas is pure hydrogen and the cathode gas is pure oxygen.

[0063] from Figure 3 As can be seen, after treatment using the oxygen / hydrogen cycle redox method of the present invention, the battery performance was significantly improved, recovering to 96.8% of the performance before poisoning (test results of Example 1). This demonstrates that the method of the present invention effectively removes carbon monoxide adsorbed on the surface of the platinum catalyst at the anode and restores the activity of the platinum catalyst well.

[0064] The various embodiments described herein, or their specific features, structures, or characteristics, may be appropriately combined in one or more embodiments of the invention. Furthermore, in some cases, the order of steps described in the flowcharts and / or flow processing may be modified where appropriate, and they need not necessarily be performed in the exact order described.

[0065] Unless explicitly stated otherwise, the singular forms “a” and “the” used herein include the plural meaning (i.e., meaning “at least one”). It should be further understood that the terms “having,” “comprising,” and / or “including” as used in the specification indicate the presence of the described features, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The term “and / or” as used herein includes any and all combinations of one or more of the listed related items.

[0066] The foregoing has described some preferred embodiments of the present invention. However, it should be emphasized that the present invention is not limited to these embodiments, but can be implemented in other ways within the scope of the present invention. Those skilled in the art can make various modifications and variations to the present invention based on the inventive concept and without departing from the scope of the present invention, and such modifications or variations still fall within the protection scope of the present invention.

Claims

1. A method for recovering activity of a platinum catalyst of a fuel cell after carbon monoxide poisoning, characterized by, The method comprises: Periodically alternatingly feeding an oxidizing gas and a reducing gas to the anode of a fuel cell poisoned by carbon monoxide and heating at low temperature, wherein the oxidizing gas is oxygen or an oxygen-containing gas, and the reducing gas is hydrogen or a hydrogen-containing gas.

2. The method of claim 1, wherein: The oxidizing gas is a mixture of 1-10% oxygen and argon, and the reducing gas is pure hydrogen.

3. The method of claim 1, wherein: The low-temperature heating temperature ranges from 80-120°C.

4. The method of claim 1, wherein, The treatment comprises the following steps: (1) Oxidation stage: feeding the oxidizing gas to the anode, controlling the temperature at 80-120°C, the gas flow rate at 0.1-0.5 L / min, and the duration at 0.5-5 minutes; (2) Reduction stage: stopping feeding the oxidizing gas to the anode and switching to feeding the reducing gas to the anode, maintaining the gas flow rate at 0.1-0.5 L / min, the duration at 0.5-5 minutes, and the temperature unchanged; Repeating steps (1) and (2) for several times to complete the activity recovery of the platinum catalyst of the anode of the fuel cell poisoned by carbon monoxide.

5. The method of claim 4, wherein: The number of repetitions of step (1) and step (2) is 5-20 times.

6. The method of claim 4, wherein: In the oxidation stage, oxygen is continuously fed to the cathode of the fuel cell at a gas flow rate of 0.5 L / min.

7. The method of any one of claims 1-6, wherein: The method is performed on-line without disassembling the fuel cell system.

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