CN110459789B - Single-strand electrolyte microfluidic fuel cell with co-current arrangement of cathode and anode - Google Patents

Abstract

The invention discloses a single-strand electrolyte microfluidic fuel cell with cathode and anode arranged in co-current flow, comprising a cathode cover plate, an air self-breathing cathode, a flow field plate, a permeable porous anode and a bottom plate; it is characterized in that: the cathode cover plate An electrolyte inlet and a cathode breathing hole are provided, and the cathode breathing hole is located behind the electrolyte inlet; the flow field plate is arranged under the cathode cover plate, and the flow field plate is provided with a main channel for the flow of the solution, and the main channel is communicated with the electrolyte inlet. The self-breathing cathode is placed on the flow field plate and is located below the cathode breathing hole; the permeable porous anode is arranged behind the self-breathing cathode and embedded in the flow channel; the bottom plate is provided with a fuel inlet, which is communicated with the main channel, and the electrolyte It flows into the main channel from the electrolyte inlet, first flows through the self-breathing cathode, then mixes with the fuel entering from the fuel inlet, enters the permeable anode together, and finally discharges from the outlet of the flow channel.

Description

Single-strand electrolyte microfluidic fuel cell with co-current arrangement of cathode and anode

technical field

The invention relates to a fuel cell, in particular to a single-strand electrolyte microfluidic fuel cell with cathodes and anodes arranged in parallel.

Background technique

In recent years, with the development of technology and the popularization of mobile Internet, the use of portable electronic devices has become more and more extensive. Existing portable electronic devices mostly use lithium batteries as power sources, but lithium batteries have significant disadvantages such as low energy density, short running time, and poor adaptability to ambient temperature. Compared with traditional lithium batteries, micro fuel cells have attracted extensive attention due to their high energy density, long-term operation, and easy integration.

Thanks to the development of microfabrication technology, microfluidic fuel cells use the property of fluid to form stable parallel laminar flow in microchannels to naturally separate oxidant and fuel, remove the proton exchange membrane in traditional micro fuel cells, and eliminate the membrane-induced The problems of membrane degradation and high cost are more conducive to the miniaturization and integration of fuel cells. Microfluidic fuel cells show greater flexibility in the selection of fuels and oxidants. Considering fuel safety, easy storage, and energy density, renewable organic small-molecule fuels (such as formic acid, methanol, etc.) are the first choice. Taking the air self-breathing cathode microfluidic fuel cell as an example, under alkaline conditions, sodium formate solution is used as fuel, potassium hydroxide solution is used as electrolyte, and the electrochemical reaction equation that occurs in the battery is:

Anodic reaction: 2HCOO ^- +6OH ^- →2CO ₃ ^2- +4H ₂ O+4e ^- , E ⁰ =-1.17V vs. SHE (1)

Cathodic reaction: O ₂ +2H ₂ O+4e ^- →4OH ^- , E ⁰ =0.40V vs. SHE (2)

Most current membraneless microfluidic fuel cells are based on parallel laminar flow in which the cathode and anode are arranged face-to-face, and ions are transferred laterally through the liquid-liquid interface to the counter electrode. However, a certain diffusion and mixing zone will be formed between the two parallel laminar flow fluids, and fuel permeation is more likely to occur. When the fuel concentration is high and the flow rate is too low, the fuel can be diffused and transported to the cathode to generate mixed potential and parasitic current, which seriously reduces the performance of the cell; and when the flow rate is too high, hydraulic instability will also occur, causing the fuel to be transported to the cathode and fuel permeation occurs. In addition, in a microfluidic fuel cell with parallel laminar flow, the fuel is mainly transported to the anode catalytic layer by diffusion and the oxidation reaction occurs, which leads to the formation of a fuel concentration boundary layer on the anode surface, and the concentration boundary layer gradually increases along the length of the electrode. large, severely limiting battery performance. Some researchers have changed the microfluidic fuel cell microchannel structure to inhibit fuel penetration or destroy the fuel concentration boundary layer. For example, Sun et al. introduced a third electrolyte fluid to avoid direct contact between fuel and oxidant and reduce fuel penetration. Kamil et al. proposed a disc-like Sequential-flow flow structure, but the assembly of the cell is complicated, and the fuel flow must be precisely controlled so that the fuel is completely oxidized when it passes through the anode, and the unreacted fuel and the oxidant are mixed and entered together The cathode, therefore, also failed to completely solve the problem of fuel permeation. Yoon et al. used a multi-inlet and multi-outlet flow channel structure to enhance the transport of fuel to the electrode surface to increase the fuel concentration on the anode surface, but the cell structure and assembly were complicated.

SUMMARY OF THE INVENTION

Aiming at the deficiencies of the prior art, the present invention proposes a single-strand electrolyte microfluidic fuel cell in which the cathode and anode are arranged in parallel.

The technical scheme of the present invention is: a single-strand electrolyte microfluidic fuel cell with cathode and anode arranged in co-current, comprising a cathode cover plate, an air self-breathing cathode, a flow field plate, a permeable porous anode and a bottom plate; it is characterized in that: the cathode The cover plate is provided with an electrolyte inlet and a cathode breathing hole, and the cathode breathing hole is located behind the electrolyte inlet; the flow field plate is arranged under the cathode cover plate, and a main channel for the flow of the solution is arranged on the flow field plate. The liquid inlets communicate with each other; the self-breathing cathode is placed on the flow field plate and is located below the cathode breathing holes; the permeable porous anode is arranged behind the self-breathing cathode and embedded in the flow channel; the bottom plate is provided with a fuel inlet, which is communicated with the main flow channel , and the fuel inlet is located between the self-breathing cathode and the permeable porous anode, and the fuel flows into the main channel slowly and evenly through the fuel inlet; the air self-breathing cathode and the permeable porous anode are arranged in a co-current arrangement, the air self-breathing cathode is located upstream, and the permeable porous anode is located upstream. The anode is located downstream; the electrolyte flows into the main channel from the electrolyte inlet, first flows through the self-breathing cathode, and then mixes with the fuel entering from the fuel inlet, enters the permeable anode together, and finally discharges from the outlet of the flow channel.

The invention starts from avoiding fuel permeation and strengthening fuel transmission, aiming at improving the performance of the battery, and adopts a downstream arrangement of cathode/anode, so that the electrolyte first flows through the air self-breathing cathode, and then permeates through the permeable porous hole after being mixed with the fuel. anode. The use of permeable porous anodes expands the anode reaction area and weakens the concentration boundary layer, thereby enhancing fuel transport and electrochemical reactions. Since the convective transport rate of the electrolyte is much greater than the countercurrent diffusion rate of the fuel, fuel permeation can be avoided to the greatest extent. In addition, the electrolyte flowing through the air self-breathing cathode is mixed with the fuel and continues to participate in the permeable porous anode reaction as the supporting electrolyte, removing the supporting electrolyte on the anode side of the conventional microfluidic fuel cell and realizing the dual utilization of the single-strand electrolyte. .

According to the preferred solution of the single-strand electrolyte microfluidic fuel cell in which the cathode and anode are arranged in co-current flow according to the present invention, the air self-breathing cathode is composed of a hydrophobic carbon paper, a leveling layer and a Pt catalytic layer.

The cathode uses hydrophobic carbon paper as the substrate, and the surface of the carbon paper facing the flow channel is sprayed with a Pt catalyst, and the oxygen in the air is diffused and transported to the surface of the cathode catalytic layer by natural convection, and electrochemically reacts with water molecules and electrons. Generate hydroxide ions.

According to the preferred solution of the single-strand electrolyte microfluidic fuel cell in which the cathode and anode are arranged in parallel according to the present invention, the permeable porous anode is composed of a hydrophilic carbon paper and a Pd catalytic layer.

The permeable porous anode uses hydrophilic carbon paper as a substrate, and electrochemically depositing a catalyst inside the three-dimensional porous carbon paper expands the anode reaction area and strengthens fuel transmission;

According to the preferred solution of the single-strand electrolyte microfluidic fuel cell in which the cathode and anode are arranged in parallel according to the present invention, the cathode cover plate, the flow field plate and the bottom plate are all composed of corrosion-resistant materials.

The beneficial effects of the single-strand electrolyte microfluidic fuel cell with the cathode and anode arranged in the downstream of the present invention are:

1) In this patent, the cathode and anode are arranged in a downstream flow, so that the electrolyte first flows through the air self-breathing cathode, and then permeates through the permeable porous anode after mixing with the fuel, because the convective transmission rate of the electrolyte is much greater than the countercurrent diffusion of the fuel. rate, it can effectively avoid fuel permeation.

2) The permeable porous anode is used to expand the anode reaction area and thin the concentration boundary layer, thereby enhancing the fuel transport and electrochemical reaction, and the air self-breathing cathode enhances the cathode oxygen mass transfer and improves the battery performance.

3) After the electrolyte flowing through the air self-breathing cathode is mixed with the fuel, it continues to participate in the reaction in the permeable porous anode as a supporting electrolyte, removing the supporting electrolyte on the anode side of the conventional microfluidic fuel cell, and realizing the single-strand electrolyte. Double use.

4) The present invention has better flexibility, keeps the total flow rate of the flow channel unchanged, and can adjust the battery performance in real time by changing the respective flow rates of the electrolyte and the fuel.

5) The present invention strengthens anode fuel transmission and avoids fuel permeation. When the cell operates at a low reactant flow, it still has a high output power, so the reactant flow in the flow channel can be appropriately reduced to obtain higher cell performance and High fuel efficiency.

The invention can be widely used in the fields of energy and chemical industry.

Description of drawings

FIG. 1 is an exploded schematic diagram of the single-strand electrolyte microfluidic fuel cell with the cathode and anode arranged in co-current flow according to the present invention.

Figure 2 is a front view of a single-strand electrolyte microfluidic fuel cell with the cathode and anode arranged in co-current flow.

Figure 3 is a top view of a single-strand electrolyte microfluidic fuel cell with cathode and anode arranged in co-current flow.

FIG. 4 is a cathode-anode polarization curve diagram of a single-strand electrolyte microfluidic fuel cell with cathode and anode co-current arrangement according to the present invention under different fuel concentrations.

Detailed ways

The solution of the present invention will be described in further detail below with reference to the accompanying drawings and specific examples, but it should be pointed out that the present invention has various embodiments, which are not limited thereto.

Referring to FIGS. 1 to 3 , a single-strand electrolyte microfluidic fuel cell with cathodes and anodes arranged in co-current flow includes a cathode cover plate 1 , an air self-breathing cathode 4 , a flow field plate 5 , a permeable porous anode 7 and a bottom plate 9 ; It is characterized in that: the cathode cover plate 1 is provided with an electrolyte inlet 2 and a cathode breathing hole 3, and the cathode breathing hole 3 is located behind the electrolyte inlet 2; the flow field plate 5 is arranged under the cathode cover plate 1, and the flow field plate 5 is arranged on the There is a main channel 6 for the flow of the solution, and the main channel 6 is communicated with the electrolyte inlet 2; the self-breathing cathode 4 is placed on the flow field plate 5 and is located below the cathode breathing hole 3; the permeable porous anode 7 is arranged on the self-breathing cathode. 4 rear and embedded in the flow channel 6; the bottom plate 9 is provided with a fuel inlet 10, the fuel inlet 10 communicates with the main channel 6, and the fuel inlet 10 is located between the self-breathing cathode 4 and the permeable porous anode 7, and the fuel passes through the fuel inlet. 10 slowly and evenly flow into the main channel 6; the air self-breathing cathode 4 and the permeable porous anode 7 are arranged in a co-current flow, the air self-breathing cathode is located upstream, and the permeable porous anode 7 is located downstream; the electrolyte flows into the main channel 6 from the electrolyte inlet 2 , first flows through the self-breathing cathode 4 , and then mixes with the fuel entering from the fuel inlet 10 , enters the permeable anode 7 together, and finally discharges from the flow channel outlet 8 .

In a specific embodiment, the air self-breathing cathode 4 is composed of a hydrophobic carbon paper, a leveling layer and a Pt catalytic layer. Hydrophobic carbon paper can be used as the substrate, and Pt catalyst can be sprayed on the surface of the carbon paper facing the flow channel.

The permeable porous anode 7 is composed of hydrophilic carbon paper and Pd catalytic layer. Hydrophilic carbon paper can be used as the electrode substrate, and catalysts such as Pd can be electrochemically deposited inside the three-dimensional porous carbon paper.

The cathode cover plate 1 , the flow field plate 5 and the bottom plate 9 are all composed of corrosion-resistant materials.

In a specific example, both the cathode cover plate 1 and the bottom plate 9 are made of transparent organic glass plates. A laser cutting machine is used to machine an air breathing hole 3 and a circular hole as an electrolyte inlet 2 on the cathode cover plate. The bottom plate 9 is machined with circular holes as the fuel inlet 10 . The flow field plate 5 adopts a silicone gasket with a thickness of 0.18 mm, and a rectangular flow channel 6 is processed on it, and the flow channel height is 0.18 mm. The air self-breathing cathode 4 is placed above the flow channel, the size of the permeable porous anode 7 is embedded in the main flow channel 6, and the distance between it and the cathode is 2 mm.

The permeable porous anode 7 can oxidize the fuel sodium formate and combine with hydroxide ions to generate carbonate, water and electrons, and the generated electrons reach the cathode 4 through the external circuit load to generate electricity. The air self-breathing cathode 4 can reduce the oxygen in the air, the Pt catalyst sprayed on the leveling layer has a catalytic effect on the oxygen, and the oxygen is transported from the cathode breathing hole 3 to the cathode catalytic layer and electrochemically reacts with water molecules and electrons to generate hydroxide ions.

During operation, the electrolyte adopts potassium hydroxide solution, and enters the flow channel 6 from the cathode cover plate electrolyte inlet 2; the fuel adopts sodium formate solution to pass into the flow channel 6 from the fuel inlet 10 of the bottom bottom plate, and is mixed and diluted with the electrolyte from the cathode side, Then it enters the porous permeable anode 7 , the fuel is transported to the surface of the anode electrode catalytic layer by convection, and electrochemical reaction occurs, and the waste liquid is discharged from the flow channel outlet 8 to the fuel cell.

As shown in FIG. 4 , FIG. 4 is a cathode-anode polarization curve diagram of a single-strand electrolyte microfluidic fuel cell in which cathode and anode are arranged in a co-current flow according to the present invention under different fuel concentrations. It can be seen from Fig. 4 that as the fuel concentration continues to increase from 1M to 10M, the open circuit potential of the cathode remains stable, and there is no fuel permeation phenomenon.

Table 1 is a comparison table of the highest output power density of some microfluidic fuel cells. It can be seen that compared with other microfluidic fuel cells using renewable organic small molecule fuels (such as formic acid), the maximum power density of the battery of the present invention reaches 281mW/ cm ³ , reaching the international advanced level.

Table 1

Embodiments of the present invention have been shown and described above, and those of ordinary skill in the art will understand that various changes, modifications, substitutions and changes can be made to these embodiments without departing from the principles and spirit of the present invention. Variations, the scope of the invention is defined by the claims and their equivalents.

Claims (4)

1. A single-strand electrolyte microfluidic fuel cell with cathode and anode arranged in co-current, comprising a cathode cover plate (1), an air self-breathing cathode (4), a flow field plate (5), a permeable porous anode (7) and Bottom plate (9); It is characterized in that: the cathode cover plate (1) is provided with an electrolyte inlet (2) and a cathode breathing hole (3), and the cathode breathing hole (3) is located behind the electrolyte inlet (2), and the flow field plate (5) is arranged under the cathode cover plate (1), the flow field plate (5) is provided with a main channel (6) for the flow of the solution, and the main channel (6) is communicated with the electrolyte inlet (2); the air is self-breathing The cathode (4) is placed on the flow field plate (5) and is located below the cathode breathing hole (3); the permeable porous anode (7) is arranged behind the air self-breathing cathode (4) and is embedded in the main flow channel (6) The bottom plate (9) is provided with a fuel inlet (10), the fuel inlet (10) communicates with the main channel (6), and the fuel inlet (10) is located between the air self-breathing cathode (4) and the permeable porous anode (7). During the time, the fuel flows into the main channel (6) through the fuel inlet (10); the electrolyte flows into the main channel (6) from the electrolyte inlet (2), firstly flows through the air self-breathing cathode (4), and then flows into the main channel (6) from the electrolyte inlet (2). 10) The incoming fuels are mixed, enter the permeable porous anode (7) together, and are finally discharged from the flow channel outlet (8). 2. The single-strand electrolyte microfluidic fuel cell with cathode and anode arranged in co-current flow according to claim 1, characterized in that: the air self-breathing cathode (4) is composed of a hydrophobic carbon paper, a leveling layer and a Pt catalytic layer composition. 3 . The single-strand electrolyte microfluidic fuel cell with the cathode and anode arranged in parallel according to claim 1 , wherein the permeable porous anode ( 7 ) is composed of a hydrophilic carbon paper and a Pd catalytic layer. 4 . 4. The single-strand electrolyte microfluidic fuel cell with the cathode and anode arranged in parallel according to claim 1, wherein the cathode cover plate (1), the flow field plate (5) and the bottom plate (9) are all composed of Corrosion-resistant material composition.

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