Method for solving catalyst poisoning and methanol permeation problems of direct methanol (ethanol) fuel cell

Abstract

The invention relates to a method for solving the problems of catalyst poisoning and methanol permeation of a direct methanol (ethanol) fuel cell. The direct methanol (ethanol) fuel cell belongs to one of proton exchange membrane fuel cells (PEMFC). The carbon monoxide poisoning problem of a positive platinum electrode of an existing direct methanol (ethanol) fuel cell and the methanol (ethanol) permeation of a proton exchange membrane are unsolvable problems, and the popularization and use of the direct methanol fuel cell are directly influenced. The method comprises the following steps: (1) the direct methanol fuel cell works for a period of time, an input port of methanol fuel and an input port of oxygen are exchanged, a negative electrode is filled with strong oxidants such as hydrogen peroxide, the strong oxidants enable a poisoned electrode to recover the catalyst function through oxidation of the strong oxidants, and the catalyst function is further recovered through further oxidation of the oxygen; the system comprises a battery current output rectifier bridge, a methanol fuel exchange three-way electromagnetic valve and an oxygen exchange three-way electromagnetic valve, and the methanol fuel exchange three-way electromagnetic valve and the oxygen exchange three-way electromagnetic valve are controlled by a PLC or a single-chip microcomputer. And (2) two proton exchange membranes are added between the two electrodes, and a molecular sieve membrane is filled between the two proton exchange membranes, so that methanol (ethanol) permeation can be prevented.

Description

Technical Field

[0001] The invention belongs to the technical field of fuel cells, and in particular relates to a solution to the carbon monoxide poisoning problem of a cathode catalyst of a direct methanol (ethanol) fuel cell and the methanol (ethanol) permeation problem of a proton exchange membrane. Background Art

[0002] Direct methanol (ethanol) fuel cells belong to a type of proton exchange membrane fuel cells (PEMFC). They directly use methanol (ethanol) aqueous solution or steam as a fuel supply source, without the need to reform methanol (ethanol) to produce hydrogen for power generation. At present, the existing direct methanol (ethanol) fuel cell positive electrode (platinum electrode) carbon monoxide poisoning problem and proton exchange membrane methanol (ethanol) permeation problem is an unsolvable problem, which directly affects the promotion and use of direct methanol (ethanol) fuel cells. Summary of the invention

[0003] The present invention aims to solve the carbon monoxide poisoning problem of direct methanol (ethanol) fuel cell catalyst and the methanol (ethanol) permeation problem of proton exchange membrane in the above-mentioned background technology.

[0004] The solution we adopted is: 1. After the direct methanol (ethanol) fuel cell has been working for a period of time, the input ports of methanol (ethanol) fuel and oxygen are swapped, and strong oxidants such as hydrogen peroxide are introduced into the negative electrode of the direct methanol (ethanol) fuel cell, so that the originally poisoned positive electrode is oxidized by the strong oxidant (hydrogen peroxide) to restore the catalyst function, and further oxidized by oxygen to further restore the catalyst function. The carbon monoxide adsorbed by the original positive electrode is oxidized by the strong oxidant and oxygen to generate carbon dioxide, eliminating the CO poisoning problem of the original positive electrode. The battery current output rectifier bridge, methanol (ethanol) fuel exchange three-way solenoid valve, oxygen exchange three-way solenoid valve, methanol (ethanol) fuel exchange three-way battery valve and oxygen exchange three-way solenoid valve are controlled by PLC or single-chip microcomputer; 2. The proton exchange membrane in the middle of the direct methanol (ethanol) fuel cell uses two proton exchange membranes, and a molecular sieve membrane is used between the two exchange membranes. The molecular sieve membrane can ensure that methanol (ethanol) will not penetrate between the two membranes.

[0005] Direct methanol (ethanol) fuel cells use liquid methanol (ethanol) instead of hydrogen. The methanol (ethanol) fuel is mixed with water and directly enters the anode of the fuel cell, where it is oxidized with the help of a catalyst layer to produce carbon dioxide, hydrogen ions (H+) and electrons. The electrons move through an external circuit as the power output of the fuel cell, and the positive ions (H+) are transported to the cathode through a molecular sieve membrane, where they react with oxygen to produce water, which is recycled and input together with the methanol (ethanol) fuel.

[0006] Advantages of direct methanol (ethanol) fuel cells: 1. Direct methanol (ethanol) fuel cells do not require any preliminary fuel processing procedures, and can directly generate thermodynamic potential through a specific method by chemically reacting methanol (ethanol) and air; 2. It does not require moving parts, but generates current through electrochemical reactions, without combustion, so it is not limited by the thermal efficiency of the Carnot cycle; 3. No need to convert fuel storage back into hydrogen or expose hydrogen to proton exchange membranes; 4. Removed internal heating and cooling metal plates, water and thermal treatment systems, pressure balance and other equipment; 5. The production cost is low and it can be easily made of non-metallic materials; 6. High energy density, the product is lightweight and thin.

[0007] Disadvantages of direct methanol (ethanol) fuel cells: 1. The main technical problem of direct methanol (ethanol) fuel cells DMFC is the problem of anode catalyst. At present, the most commonly used anode catalyst for direct methanol (ethanol) fuel cells DMFC is Pt-based catalyst. However, Pt catalysts are easily poisoned by carbon monoxide, an intermediate product generated by the oxidation of methanol (ethanol) fuel, resulting in reduced electrocatalytic performance of Pt catalysts. 2. The problem of methanol (ethanol) permeation through the proton exchange membrane. Therefore, solving the problem of carbon monoxide poisoning of platinum electrodes and the problem of methanol (ethanol) permeation through the proton exchange membrane is the primary task for the commercialization of direct methanol (ethanol) fuel cells DMFC.

[0008] Figure 1 This is a structural diagram of a direct methanol (ethanol) fuel cell that can overcome carbon monoxide poisoning, such as Figure 1 3 and 4 are platinum electrodes. Figure 1 5 in the figure is the positive output terminal of the current. Figure 1 6 in the figure is the negative output terminal of the current. Figure 1 7 and 8 are the outlets for water and carbon dioxide. Figure 1 9 and 10 are the input ports of methanol (ethanol) and oxygen, Figure 1 1 and 2 are the switch ports for methanol (ethanol) fuel and oxygen. Figure 1 The 12-bit methanol (ethanol) input terminal in Figure 1 The 13-bit oxygen input port in Figure 1 11 is the molecular sieve membrane filler between two proton exchange membranes. Figure 1 14 and 15 are two proton exchange membranes.

[0009] when Figure 1 When 12 in the middle is connected to 1 on the left, methanol (ethanol) 12 enters the input port 9 through the left side 1 of the input port. Figure 1The oxygen 13 in the water enters the input port 10 through the right side 1 of the input port, the output port 7 on the left outputs carbon dioxide, and the output port 8 on the right outputs water. The electrode 3 is the positive electrode, the electrode 4 is the negative electrode, the output terminal 5 is the positive electrode for current output, and the output terminal 6 is the negative electrode for current output. When Figure 1 When 12 in the middle is connected to 2 on the left, methanol (ethanol) 12 enters the input port 10 through the left side 2 of the input port. Figure 1 The oxygen 13 in the input port enters the input port 9 through the right side 2 of the input port, the output port 8 on the right side outputs carbon dioxide, and the output port 7 on the left side outputs water. The electrode 3 is the negative electrode, the electrode 4 is the positive electrode, the output terminal 5 is the positive electrode for current output, and the output terminal 6 is the negative electrode for current output. The control of the methanol (ethanol) input port and the control of the oxygen input port are switched by the PLC or the single-chip microcomputer at a fixed time. Figure 1 11 in the figure is a filler filled with molecular sieve between two proton exchange membranes. Figure 1 14 and 15 are two proton exchange membranes.

[0010] Embodiment 1: A direct methanol (ethanol) fuel cell disclosed in the present invention, as shown in 11 in FIG1 , includes a molecular sieve membrane filler between two proton exchange membranes located in the middle of the battery, an electrode catalyst 3 is on the left side of the leftmost proton exchange membrane 14, an electrode catalyst 4 is on the rightmost side of the rightmost proton exchange membrane 15, water and carbon dioxide outlets 7 and 8, methanol (ethanol) and oxygen inlets 9 and 10, methanol (ethanol) and oxygen switching switches left 1, right 1 and left 2, right 2, methanol (ethanol) inlet 12, oxygen inlet 13; when the methanol (ethanol) and oxygen switching switch is switched to 1, methanol (ethanol) enters the left inlet 9 through the switching port left 1, oxygen enters the right inlet 10 through the switching port right 1, methanol (ethanol) is oxidized by the electrode 3 to become carbon dioxide and output from the output port 7, oxygen reacts with protons to become water and output from the output port 8, Electrode 3 outputs electrons, which is equivalent to the positive electrode, and electrode 4 inputs electrons, which is equivalent to the negative electrode. Electrode 3 outputs positive electricity through the rectifier bridge and outputs positive electricity at the current output terminal 5. Electrode 4 outputs negative electricity through the rectifier bridge at the current output terminal 6. When the methanol (ethanol) and oxygen switching switches are switched to 2, methanol (ethanol) enters the right inlet 10 through the switching port 2 on the left, and oxygen enters the left inlet 9 through the switching port 2 on the right. Methanol (ethanol) is oxidized by electrode 4 to become carbon dioxide and output from the output port 8. Oxygen reacts with protons to become water and output from the output port 7. Electrode 4 outputs positive electricity through the rectifier bridge and outputs positive electricity at the output terminal 5. Electrode 3 outputs negative electricity through the rectifier bridge at the current output terminal 6.

[0011] The direct methanol (ethanol) fuel cell (DMFC) of the present invention is compared with various battery current densities such as phosphate battery (PAFC), solid oxide fuel cell (SOFC), proton exchange membrane battery (PEMFC), and molten carbonate battery (MCFC). The direct methanol (ethanol) fuel cell of the present invention has the highest density. In production, the material source is abundant, the price is low, and the cost performance is excellent, which is conducive to market promotion, thereby realizing the replacement of direct methanol (ethanol) fuel cells, conforming to the development direction of battery environmental protection, high efficiency, economy, durability, and energy saving, and has broad development prospects, especially breaking through the bottleneck of existing battery applications, and the development prospects are very optimistic.

[0012] The above description is only a specific embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and change of equivalent components made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present technical solution.

Claims

1. Claim 1: After the direct methanol (ethanol) fuel cell has been operated for a period of time, the input ports of methanol (ethanol) fuel and oxygen are swapped, and a strong oxidant such as hydrogen peroxide is filled into the negative electrode plate to oxidize the poisoned electrode and restore the catalytic function of the electrode. The catalytic function of the electrode is further restored by further oxidation with oxygen, and the carbon monoxide adsorbed by the original positive electrode is oxidized by the strong oxidant and the oxygen to generate carbon dioxide, thereby eliminating the CO poisoning problem of the original positive electrode. The battery current output rectifier bridge, the methanol (ethanol) fuel exchange three-way solenoid valve, the oxygen exchange three-way solenoid valve, the methanol (ethanol) fuel exchange three-way battery valve and the oxygen exchange three-way solenoid valve are controlled by a PLC or a single-chip microcomputer; the proton exchange membrane in the middle of the direct methanol (ethanol) fuel cell uses two proton exchange membranes, and the middle of the two exchange membranes is filled with a molecular sieve membrane filler, and the molecular sieve membrane can ensure that methanol (ethanol) will not penetrate between the two membranes.

2. The strong oxidant in claim 1 can be any of various strong oxidants.

3. The electrode in claim 1 can be made of any material having catalytic activity.

4. The two proton exchange membrane molecular sieve membrane fillers of claim 1, the size of the molecular sieve membrane can be adjusted according to the molecular size of methanol or ethanol, such as using a 3A molecular sieve membrane for methanol and a 4A molecular sieve membrane for ethanol.

5. The input ports of methanol (ethanol) fuel and oxygen in claim 1 are swapped, and a methanol (ethanol) fuel exchange three-way solenoid valve and an oxygen exchange three-way solenoid valve are used.

6. The methanol (ethanol) fuel exchange three-way solenoid valve and the oxygen exchange three-way solenoid valve in claim 1 are controlled by a PLC or a single-chip microcomputer.

7. The output terminal of the power supply in claim 1 is automatically controlled by a rectifier bridge. No matter whether the electrode is positive or negative, the output current is the same for both positive and negative electrodes.

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