CN111276722A

CN111276722A - Method for solving isopropanol poisoning problem in direct methanol fuel cell

Info

Publication number: CN111276722A
Application number: CN201811474399.1A
Authority: CN
Inventors: 孙公权; 孙雪敬; 孙海
Original assignee: Dalian Institute of Chemical Physics of CAS
Current assignee: Dalian Institute of Chemical Physics of CAS
Priority date: 2018-12-04
Filing date: 2018-12-04
Publication date: 2020-06-12

Abstract

A method of poisoning resistance of a direct methanol fuel cell using methanol having isopropanol as an impurity; in the operation process of the direct methanol fuel cell, the cathode gas is supplied in an intermittent supply mode, and a voltage of-0.2-0.05V (vs. RHE) is applied to the anode of the direct methanol fuel cell within the time range of stopping the supply of the cathode gas. The design of the invention can effectively solve the problem that the isopropanol contained in the industrial methanol causes catalyst poisoning and thus causes the performance attenuation of the battery. The method is simple to operate, and can realize operation in the battery operation process. The design operation mode of the invention can realize that the methanol containing isopropanol impurity with low price replaces expensive chromatographic pure methanol in the direct methanol fuel cell, thereby reducing the operation cost of the direct methanol fuel cell.

Description

Method for solving isopropanol poisoning problem in direct methanol fuel cell

Technical Field

The invention relates to the technical field of fuel cells, in particular to a method for resisting toxicity of a direct methanol fuel cell by using methanol containing isopropanol impurities as fuel.

Background

A fuel cell is a device that directly converts chemical energy stored in a compound fuel into electrical energy through a chemical reaction. Proton exchange membrane fuel cells are typically comprised of an anode, a cathode, and a proton exchange membrane. During the operation of the cell, fuel is oxidized on the surface of the anode catalyst to generate protons and electrons, the protons reach the cathode through the proton exchange membrane, oxygen and the protons are reduced on the surface of the cathode catalyst to generate water, and the electrons do work through an external circuit to reach the cathode.

The direct methanol fuel cell is one of proton exchange membrane fuel cells, which takes methanol water solution as anode fuel to generate methanol oxidation reaction on the surface of an anode catalyst to generate proton and carbon dioxide. In the actual operation process of the methanol fuel cell, chromatographic pure methanol is used as a fuel, and the methanol fuel cell is high in purity and therefore expensive. Industrial methanol has the advantage of low cost, but the industrial methanol usually contains isopropanol impurity which can cause catalyst poisoning and thus cause serious performance degradation of the battery during operation.

Disclosure of Invention

The invention provides an operation method for effectively solving the problem of cell performance attenuation caused by isopropanol in methanol, which aims to solve the problem that the cell performance is rapidly attenuated by methanol containing isopropanol impurities in the operation process of a direct methanol fuel cell.

The invention is realized by adopting the following specific modes:

the direct methanol fuel cell comprises two end plates and a single cell arranged between the two end plates, wherein the single cell comprises a bipolar plate and a membrane electrode, and the membrane electrode comprises an anode catalyst layer, a proton exchange membrane and a cathode catalyst layer.

The fuel used by the direct methanol fuel cell is methanol containing isopropanol impurities; in the operation process of the direct methanol fuel cell, the cathode gas is supplied in an intermittent supply mode, and a voltage of-0.2-0.05V (vs. RHE) is applied to the anode of the direct methanol fuel cell within the time range of stopping the supply of the cathode gas. Theoretically, the poisoning substance acetone is subjected to reduction reaction at a voltage of less than 0.05V to generate isopropanol, so that the coverage of the poisoning substance acetone on the active surface area of the catalyst is avoided, and further the rapid attenuation of the performance of the battery is avoided.

In the intermittent supply process of the cathode gas, the ratio of the adjacent continuous gas supply time length to the gas supply stopping time length is 1: 2-3600: 3, preferably 15: 0.5-30: 0.333, optimally 10: 0.5-20: 0.333.

the minimum time for stopping the gas supply is 3s, preferably 10s, and most preferably 20 s.

The voltage applied to the cathode of the direct methanol fuel cell is preferably in the range of-0.2 to 0.05V (vs. RHE); the optimal range is-0.1-0.0V (vs. RHE). The voltage is within the above range, and the effect is more remarkable.

The direct methanol fuel cell is a direct methanol fuel cell single cell, or a direct methanol fuel cell system.

The fuel for the direct methanol fuel cell is methanol containing isopropanol impurity, wherein the content of isopropanol in the methanol is not higher than 0.5M. The isopropanol content is too high, so that the performance of the battery is attenuated too fast, and the application significance is avoided.

The cathode supply gas is air or oxygen.

According to the operation of the invention, the problem of battery performance attenuation caused by catalyst poisoning caused by organic impurity isopropanol can be effectively solved. The service life of the cell is prolonged, and the cost of the direct methanol fuel cell in the operation process is reduced. The method can effectively solve the problem of poisoning of isopropanol in industrial methanol, and when the chromatographic pure methanol is used as a fuel and an operation mode is adopted, the stability of the battery in the operation process can be effectively improved, the attenuation of the battery performance is slowed down, and the service life of the battery is prolonged. In addition, the operation method can realize the operation in the battery operation process, and the operation mode is adopted in the direct methanol fuel battery system without external facilities, so that the operation method is simple and convenient.

Drawings

FIG. 1 is a bipolar plate flow channel distribution diagram;

1. an end plate; 2. a flow channel; 3. an anode catalyst layer; 4. a proton exchange membrane; 5. a cathode catalyst layer; 6. bipolar plate

FIG. 2 is a fuel cell stack assembly view;

FIG. 3 is a view of a membrane electrode assembly MEA;

FIG. 4 shows the test results of one embodiment;

FIG. 5 shows the results of the test in example two.

Detailed Description

The following describes a specific embodiment of the present invention with reference to the drawings and the like.

The specific implementation mode comprises the following steps:

an end plate 1 for fluid distribution and collection; a flow channel 2, a flow channel for a reactant inside the fuel cell; an anode catalyst layer 3 that catalyzes an oxidation reaction of the fuel; the proton exchange membrane 4 is used for transferring protons and isolating cathode and anode reactants; a cathode catalyst layer 5 that catalyzes a reduction reaction of oxygen; bipolar plate 6, fluid distribution of the cathode and anode reactants.

The working principle is as follows:

in the operation process of the direct methanol fuel cell, the methanol aqueous solution generates oxidation reaction on the anode catalyst layer to generate protons and carbon dioxide, the protons are transmitted to the cathode through the proton exchange membrane, and the oxygen in the air generates reduction reaction on the cathode catalyst layer and the protons transmitted to the cathode to generate water. When industrial methanol is used as fuel on the anode side, organic impurity isopropanol in the industrial methanol is oxidized under the action of an anode catalyst to generate acetone, and the acetone has strong adsorption capacity on the surface of the catalyst, so that the acetone occupies the active site of the catalyst, the active surface area of the catalyst is reduced, and the performance of the battery is seriously attenuated.

By adopting the operation mode of the invention, when a reduction voltage is applied to the anode under the condition of gas cut-off, the oxidation reaction is carried out on the cathode side, so that the methanol permeating from the anode to the cathode through the proton exchange membrane is oxidized, the catalytic activity of the cathode side is partially improved, meanwhile, the reduction reaction is carried out on the anode side, the acetone adsorbed on the catalytic site of the anode is reduced to generate the isopropanol which is separated from the surface of the catalyst, the active site of the catalyst of the anode is exposed, and the catalytic activity of the catalyst of the anode is recovered.

In the test process, the battery is tested by adopting a single battery, the single battery is communicated with an external reference electrode through a Nafion membrane, the feeding concentration of the anode of the battery is 0.5M methanol water solution, the flow rate is 0.5mL/min, the cathode is air, and the air flow is 80 mL/min;

the specific implementation mode is as follows:

the first embodiment is as follows: this embodiment was tested using a mixture of 0.5M chromatographically pure methanol and 0.025M isopropanol as fuel.

Using the cell operating mode of the present invention (the cathode gas supply was stopped when the cell voltage decrement was 15% of the initial value, a potential of-0.2V was applied to the anode side compared to the reference electrode for 5s) and the conventional cell operating method at 100mA cm in the cell^-2And after the constant-current discharge operation is carried out for 35 hours, the performance attenuation comparison of the battery is carried out, and the voltage of the battery is respectively reduced by 0.017V and 0.114V. The data fully show that the operation mode of the direct methanol fuel cell can effectively solve the problem of attenuation of acetone generated by oxidizing isopropanol on the performance of the cell, improve the stability of the cell in the constant-current discharge operation process and prolong the service life of the cell.

Example two: the embodiment adopts industrial methanol (wherein the content of isopropanol impurities is relatively high, China middlings energy group, Inc.) as fuel to carry out the constant current discharge test of the cell.

The same operation of the cell according to the invention was also carried out (the cathode gas supply was stopped at 10% of the initial value of the cell voltage decay, a potential of 0.05V was applied to the anode side compared to the reference electrode for a period of 30s) compared with the conventional constant current discharge operation of the cell at 100mA cm in the cell^-2And performing constant current discharge operation for 35 hours, and then performing cell performance attenuation comparison, wherein the cell voltage is respectively reduced by 0.002V and 0.127V. The data further proves that the operation mode of the direct methanol fuel cell can effectively solve the problem of attenuation of organic species in industrial methanol to the performance of the cell, and can completely realize the operation of the direct methanol fuel cell by using cheap industrial methanol containing isopropanol impurities to replace expensive chromatographic pure methanol as fuel, thereby reducing the cost of the direct methanol fuel cell in the operation process.

The design of the invention can effectively solve the problem that the isopropanol contained in the industrial methanol causes catalyst poisoning and thus causes the performance attenuation of the battery. The method is simple to operate, and can realize operation in the battery operation process. The design operation mode of the invention can realize that the cheap industrial methanol containing isopropanol replaces the expensive chromatographic pure methanol in the direct methanol fuel cell, thereby reducing the operation cost of the direct methanol fuel cell.

Claims

1. A method of poisoning resistance of a direct methanol fuel cell using methanol having isopropanol as an impurity; the method is characterized in that:

and in the operation process of the direct methanol fuel cell, arranging a reference electrode which is electrically communicated with the proton exchange membrane, stopping introducing a gas oxidant to the cathode side, and applying a voltage of-0.2-0.05V (vs. RHE) between the anode and the reference electrode of the direct methanol fuel cell within the time range of stopping supplying cathode gas so that the potential of the anode side is lower than the potential of the reference electrode for more than 2 seconds, preferably 15-30 seconds.

2. The direct methanol fuel cell poisoning method of claim 1, wherein: and the cathode gas is intermittently supplied, the operation process of the direct methanol fuel cell for resisting toxicity is carried out in the intermittent supply process, and the ratio of the adjacent continuous gas supply time length to the gas supply stopping time length is 1: 2-3600: 3.

3. the direct methanol fuel cell poisoning method of any of claims 1 to 2, wherein: the minimum time for stopping the gas supply is 3s, preferably 10s, and most preferably 20 s.

4. The direct methanol fuel cell poisoning method of claim 3, wherein: the maximum time for continuous gas supply is 60min, preferably 30min, and most preferably 15 min.

5. The direct methanol fuel cell poisoning method of claim 2, wherein: in the intermittent supply of the cathode gas, the ratio of the adjacent continuous gas supply time length to the gas supply stop time length is preferably 15: 0.5-30: 0.333.

6. the direct methanol fuel cell poisoning method of claim 2, wherein: in the intermittent supply process of the cathode gas, the ratio of the adjacent continuous gas supply time length to the gas supply stopping time length is optimally 10: 0.5-20: 0.333.

7. the direct methanol fuel cell poisoning method of claim 1, wherein: the direct methanol fuel cell is characterized in that a voltage of-0.2-0.05V (vs. RHE) is applied to the anode of the direct methanol fuel cell, namely, the anode of the direct methanol fuel cell is connected with the anode of a direct current power supply, the cathode of the direct methanol fuel cell is connected with the cathode of the direct current power supply, a reference electrode is introduced into the cell to serve as a counter electrode, and a voltage of-0.2-0.05V (vs. RHE) is applied between the anode of the direct methanol fuel cell and the reference electrode.

8. The direct methanol fuel cell poisoning method of claim 1 or 7, wherein: the preferred range of the applied voltage is-0.1-0.02V (vs. RHE), and the optimal range is-0.1-0.0V (vs. RHE).

9. The direct methanol fuel cell poisoning method of claim 1 or 7, wherein: the direct methanol fuel cell is a direct methanol fuel cell single cell, or a direct methanol fuel cell system.

10. The direct methanol fuel cell poisoning method of claim 1, wherein: the content of isopropanol in the methanol containing isopropanol impurities is 0.01-2% of the mass of the methanol;

introducing methanol fuel into the anode side, introducing air and/or oxygen serving as an oxidant into the cathode side, and operating the cell;

the fuel used by the direct methanol fuel cell is methanol containing isopropanol impurity or methanol water solution containing isopropanol impurity.