CN100433437C - Method for recovering performance of poisoned proton exchange membrane fuel cell - Google Patents

Abstract

The present invention relates to a proton exchange membrane fuel cell, specifically a method for restoring the performance of a poisoned proton exchange membrane fuel cell, wherein cyclic voltammetry is used for the proton exchange membrane fuel cell electrode that has been poisoned by impurity gases contained in the air, so that the impurities adsorbed on the electrocatalyst are oxidized and desorbed, and the catalytic activity is restored, thereby restoring the electrode performance; wherein: the cyclic voltammetry is to perform a cyclic scan on the two electrodes of the proton exchange membrane fuel cell within a certain potential range. The method of the present invention can restore the electrode performance, and can effectively solve the problem of performance degradation and shortened life of the fuel cell electrode after poisoning, thereby promoting the development of fuel cells.

Description

A method of restoring the performance of a poisoned proton exchange membrane fuel cell

technical field

The invention relates to a proton exchange membrane fuel cell, which is a method for restoring the performance of a proton exchange membrane fuel cell poisoned by a cathode impurity gas by applying voltage; specifically, it is a method for applying cyclic voltammetry to the poisoned impurities chemically adsorbed on the electrode. A method for recovering the performance of a proton exchange membrane fuel cell in which impurities adsorbed on electrodes are desorbed at higher voltages.

Background technique

Proton exchange membrane fuel cell (PEMFC) not only has the general characteristics of fuel cells, such as high energy conversion efficiency, environmental friendliness, etc., but also has the outstanding characteristics of rapid start-up at room temperature, no electrolyte loss, long life, high specific power and specific energy, etc. . Therefore, it can not only be used to build decentralized power stations, but also is particularly suitable for use as a mobile power source. It is one of the ideal candidate power sources for electric vehicles and air-independent submarines. It is a new type of mobile power source for military and civilian use. In the future hydrogen energy era with hydrogen as the main energy carrier, it is the best power source for households.

With the deepening of proton exchange membrane fuel cell research, the durability of the battery has been paid more and more attention by researchers, and the adaptability to the environment atmosphere is an important aspect. Since proton exchange membrane fuel cells use ambient air during operation, various impurity gases contained in the air are closely related to the performance and life of the cells.

NO, NO ₂ , H ₂ S, SO _{2 ,} etc. are the main pollutants in the atmosphere, mostly caused by industrial waste gas and vehicle exhaust emissions. Once the impurity gas in the air enters the battery, it will generate adsorption on the electrocatalyst. There are two kinds of adsorption, the adsorption of NO, NO ₂ etc. on the electrocatalyst is physical adsorption, and the adsorption of H ₂ S and SO ₂ on the electrocatalyst is chemical adsorption. Once the impurities are adsorbed on the electrocatalyst, they will occupy the active sites of Pt. When the adsorption reaches a certain level and the remaining active sites cannot meet the requirements of the hydrogen-oxygen catalytic reaction, the performance of the battery will decline. Once the performance of the battery drops, especially the performance attenuation caused by chemically adsorbed impurities, it will be difficult to recover through the battery itself.

There have been a few patent reports on the adsorption mechanism of cathode impurity gas on the electrocatalyst and the degree of influence on the battery. However, how to restore the performance of the poisoned electrode has not been reported yet.

Contents of the invention

In order to make up for the deficiencies of the prior art, the purpose of the present invention is to provide a method for recovering the performance of the proton exchange membrane fuel cell which can restore the performance of the fuel cell electrode after being poisoned and prolong the service life.

In order to achieve the above object, the technical solution of the present invention is: adopt cyclic voltammetry to apply a higher voltage to the electrode poisoned by the impurity gas contained in the air, so that the impurities adsorbed on the electrocatalyst are oxidized and desorbed, and the catalyst is restored. activity, thereby restoring electrode performance.

The specific steps of the method for proton exchange membrane fuel cell performance recovery are as follows:

(1) Nitrogen gas is passed into the cathode of the poisoned battery, and hydrogen gas is passed into the anode.

(2) After ventilating the poisoned battery for 60 minutes, perform a cyclic voltammetry scan after the voltage is stabilized.

Among them: the scanning range is: the cathode voltage is 0.05V ~ 1.45V, and the scanning rate is 5mV/s, 10mV/s, 15mV/s respectively; during the scanning process, the anode is still flowing with hydrogen, and the cathode is still flowing with nitrogen.

The principle of the present invention is: take air containing H ₂ S impurities as an example. The battery performance was stable when running the battery on pure air. When switching to the air containing H ₂ S impurity gas to run the battery, the performance of the battery decreased sharply in a short time, indicating that the H ₂ S impurity gas had a significant poisoning effect on the PEMFC electrodes. After using cyclic voltammetry, in the process of cyclic voltammetry scanning, two obvious oxidation peaks appeared at 0.92V and 1.12V in the first circle in the range of anodic scanning potential above 0.9V, and at 1.12V The oxidation peak is the most prominent. This is due to the reaction of S on the Pt electrode as follows:

$h_{2}S-\mathrm{Pt}\⇒\mathrm{Pt}-S+h_2$ [1]

$h_{2}S+\mathrm{Pt}-h\⇒\mathrm{Pt}-S+3/2h_2$ [2]

In the second scan and several subsequent scans, these two peaks degenerate rapidly, and basically disappear in the fifth scan. It shows that the cyclic voltammetry can oxidize and desorb the impurities chemically adsorbed on the electrocatalyst, and the electrode performance is well restored.

The present invention has the following advantages:

1. Prolong the service life of fuel cell electrodes. The electrode performance can be recovered by adopting the method of the invention, which effectively solves the problems of performance degradation and life shortening of fuel cell electrodes after poisoning, thereby promoting the development of fuel cells.

2. The method is simple. The invention has the advantages of simple operation and rapid effect, and can completely restore the performance of the electrode in a short time.

3. Solve the environmental adaptability problem of PEMFC. The performance of PEMFC will drop significantly in harsh air environment. By adopting the method, the performance of the electrode can be quickly recovered, thereby better adapting to different environments.

Description of drawings

Fig. 1 is the change result figure of battery voltage with cumulative time under different operating conditions of the embodiment of the present invention;

Fig. 2 is a comparison diagram of polarization curves obtained under different conditions of the embodiment of the present invention;

Fig. 3 is a cyclic voltammogram obtained after injecting 200ppm H ₂ S in the embodiment of the present invention;

In the figure: Recover with air: recovery with air, CV: cyclic voltammetry, IVtest: polarization curve test, Accumulative running time: cumulative running time. Voltage: Voltage, Current density: Current density, Potential vs. SHE: Voltage relative to the standard hydrogen electrode.

Detailed ways:

Explanation: In this example, through accelerated experiments, the cathode is fed with air containing a relatively high concentration (200ppm) of H ₂ S, so that the battery is poisoned in a short time. Reintroduction of pure air does not restore battery performance on its own. At this time, the cyclic voltammetry method is used to apply a higher voltage to the electrodes, and the battery performance can be restored.

Example 1

1. Toxicity treatment test:

(1) Assemble a single cell: the anode reaction gas is pure hydrogen, and the cathode reaction gas is pure air.

Polarization curve test: ① Operate the battery for a period of time with pure air at a constant current density (700mA/cm ² ), and record the voltage-time curve (see Figure 1).

② Run the assembled battery above, and test the polarization curve after the battery performance is stable. Among them: when testing the polarization curve, the steady-state polarization method is adopted, and each test current density point is measured for about 5 minutes (see Figure 2).

(2) Poisoning single cell: the anode reaction gas is pure hydrogen, and the cathode reaction gas is air with 200ppm H ₂ S impurity gas.

Polarization curve test: ① Operate for a period of time with constant current density polarization in the air containing H ₂ S impurity gas, and also record the constant current density (700mA/cm ² ) polarization curve.

② After the battery performance is stable, use the steady state polarization method to test the polarization curve of the battery after H ₂ S poisoning (see Figure 2).

(3) Detection of poisoned single cells: the anode reaction gas is pure hydrogen, the cathode reaction gas is switched to pure air again, the battery is polarized at a constant current density and the polarization curve of the constant current density is recorded, and then the steady state polarization curve of the battery is measured again.

2. Recovery of battery performance by cyclic voltammetry

① Introduce nitrogen gas into the cathode of the above-mentioned poisoned battery, and hydrogen gas into the anode.

② After ventilating the poisoned battery for 60 minutes, perform cyclic voltammetry scanning on it after the voltage is stabilized.

Among them: the scanning range is: the cathode voltage is 0.05V ~ 1.45V, and the scanning rate is 10mV/s; during the scanning process, the anode is still flowing with hydrogen, and the cathode is still flowing with nitrogen.

The so-called cyclic voltammetry refers to applying a potential that gradually increases (or decreases) in certain steps on the electrode. When the desired maximum (or minimum) potential is reached, the direction of the "scan" is reversed. Measure the current at each step, then plot the current versus potential.

③ Polarization curve test: measure the polarization curve of the battery at constant current density and then measure the steady state polarization curve of the battery.

(3) Analysis of results:

It can be seen from Figure 1 that the performance of the battery is stable when the battery is operated in pure air. After switching to the air containing H ₂ S impurity gas, the battery performance decreased sharply in a short time, which indicated that H ₂ S impurity gas had obvious poisoning effect on PEMFC electrodes. However, after cyclic voltammetry, the battery performance almost returned to the original level.

It can be clearly seen from Fig. 2 that after the battery is operated in the air containing H ₂ S, the performance of the battery drops greatly, which once again shows that H ₂ S has a significant poisoning effect on the performance of the battery. After adopting cyclic voltammetry, the performance of the electrode is obviously improved.

It can be seen from Figure 3 that in the process of cyclic voltammetry scanning, two obvious oxidation peaks appeared at 0.92V and 1.12V in the first circle in the anodic scanning potential range above 0.9V, and at 1.12V The oxidation peak is most prominent. This is due to the reaction of S on the Pt electrode as follows:

$h_{2}S-\mathrm{Pt}\⇒\mathrm{Pt}-S+h_2$ [1]

$h_{2}S+\mathrm{Pt}-h\⇒\mathrm{Pt}-S+3/2h_2$ [2]

In the second scan and several subsequent scans, these two peaks degenerate rapidly, and basically disappear in the fifth scan. It shows that cyclic voltammetry can oxidize and desorb the impurities chemically adsorbed on the electrocatalyst very well. It can also be seen from Figure 1 and Figure 2 that the electrode performance has been well restored.

Example 2

The difference from Example 1 is:

1. Recovery of battery performance by cyclic voltammetry

① Introduce nitrogen gas into the cathode of the above-mentioned poisoned battery, and hydrogen gas into the anode.

② After ventilating the poisoned battery for 60 minutes, perform cyclic voltammetry scanning on it after the voltage is stabilized.

Among them: the scanning range is: the cathode voltage is 0.05V ~ 1.45V, and the scanning rate is 5mV/s; during the scanning process, the anode is still flowing with hydrogen, and the cathode is still flowing with nitrogen.

Example 3

The difference from Example 1 is:

1. Recovery of battery performance by cyclic voltammetry

① Introduce nitrogen gas into the cathode of the above-mentioned poisoned battery, and hydrogen gas into the anode.

② After ventilating the poisoned battery for 60 minutes, perform cyclic voltammetry scanning on it after the voltage is stabilized.

Among them: the scanning range is: the cathode voltage is 0.05V ~ 1.45V, and the scanning rate is 15mV/s; during the scanning process, the anode is still flowing with hydrogen, and the cathode is still flowing with nitrogen.

It can be seen from this example that when the PEMFC passes through areas with poor air quality and high H ₂ S content, the performance of the battery will be attenuated. Even returning to an area with clean air does not restore battery performance. At this time, by applying voltage, the impurities adsorbed on the electrode can be oxidized and desorbed, thereby restoring the activity of the electrocatalyst and the performance of the battery.

Claims (3)

1. method that the proton exchange film fuel battery performance that poisons is recovered, it is characterized in that: the proton exchange membrane fuel cell electrode that the foreign gas that is contained in the air is poisoned adopts cyclic voltammetry, make the oxidized desorption of the impurity that adsorbs on the eelctro-catalyst, recover catalytic activity, thereby recover electrode performance;

Wherein: described cyclic voltammetry is meant carries out scan round to electrode in certain potential range;

Adopt the cyclic voltammetry concrete steps to be:

(1) cell cathode that will have been poisoned feeds nitrogen, and anode feeds hydrogen;

(2) poison the battery ventilation after 60 minutes with described, treat that voltage is stable, it is carried out cyclic voltammetry scan;

Sweep limits is: cathode voltage is 0.05V～1.45V, and sweep speed is respectively 5mV/s, 10mV/s, 15mV/s; The still logical hydrogen of anode in the scanning process, the still logical nitrogen of negative electrode.

2. according to the described method that makes the proton exchange film fuel battery performance recovery that poisons of claim 1, its feature also is: described cyclic voltammetry is that the foreign gas of chemisorbed on the Pt catalyst in the proton exchange membrane fuel cell electrode is carried out the oxidation desorption.

3. according to the described method that makes the proton exchange film fuel battery performance recovery that poisons of claim 1, its feature also is: the foreign gas that contains in the described air is H ₂S, SO ₂, NO or NO ₂

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