CN1194435C

CN1194435C - Fuel cell adopting natural air as oxidant

Info

Publication number: CN1194435C
Application number: CNB011128623A
Authority: CN
Inventors: 胡里清
Original assignee: Shanghai Shen Li High Tech Co Ltd
Current assignee: Shanghai Shenli Technology Co Ltd
Priority date: 2001-05-11
Filing date: 2001-05-11
Publication date: 2005-03-23
Anticipated expiration: 2021-05-11
Also published as: CN1385916A

Abstract

The present invention relates to a fuel battery using natural air as an oxidant, which comprises membrane electrodes, a graphite plate which can lead in hydrogen gas, a heat-radiation airflow guiding plate and a connecting rod, wherein the front face and the reverse face of the graphite plate are respectively provided with a flow guiding slot and a seal ring; the top of the graphite plate is provided with a flow guiding hole; one graphite plate is clamped between two membrane electrodes, the heat-radiation airflow guiding plate is clamped at the external sides of the membrane electrodes, so a battery unit is formed. A fuel battery is formed by connecting the battery units in series. Compared with the prior art, the present invention has the advantages of convenient electrode manufacture, easy hydrogen diffusion, good seal performance and low cost.

Description

Fuel cell using natural air as oxidant

Technical Field

The present invention relates to electrochemical fuel cells, and more particularly to a fuel cell using natural air as an oxidant.

Background

An electrochemical fuel cell is a device that is capable of converting hydrogen fuel and an oxidant into electrical energy and reaction products. The inner core component of the device is a Membrane Electrode (MEA), which is composed of a proton exchange Membrane and two porous conductive materials sandwiched between two surfaces of the Membrane, such as carbon paper. The membrane contains a uniform and finely dispersed catalyst, such as a platinum metal catalyst, for initiating an electrochemical reaction at the interface between the membrane and the carbon paper. The electrons generated in the electrochemical reaction process can be led out by conductive objects at two sides of the membrane electrode through an external circuit to form a current loop.

At the anode end of the membrane electrode, fuel can permeate through a porous diffusion material (carbon paper) and undergo electrochemical reaction on the surface of a catalyst to lose electrons to form positive ions, and the positive ions can pass through a proton exchange membrane through migration to reach the cathode end at the other end of the membrane electrode. At the cathode end of the membrane electrode, a gas containing an oxidant (e.g., oxygen), such as air, forms negative ions by permeating through a porous diffusion material (carbon paper) and electrochemically reacting on the surface of the catalyst to give electrons. The anions formed at the cathode end react with the positive ions transferred from the anode end to form reaction products.

In a pem fuel cell using hydrogen as the fuel and oxygen-containing air as the oxidant (or pure oxygen as the oxidant), the catalytic electrochemical reaction of the fuel hydrogen in the anode region produces hydrogen cations (or protons). The proton exchange membrane assists the migration of positive hydrogen ions from the anode region to the cathode region. In addition, the proton exchange membrane separates the hydrogen-containing fuel gas stream from the oxygen-containing gas stream so that they do not mix with each other to cause explosive reactions.

In the cathode region, oxygen gains electrons on the catalyst surface, forming negative ions, which react with the hydrogen positive ions transported from the anode region to produce water as a reaction product. In a proton exchange membrane fuel cell using hydrogen, air (oxygen), the anode reaction and the cathode reaction can be expressed by the following equations:

and (3) anode reaction:

and (3) cathode reaction:

in a typical pem fuel cell, a Membrane Electrode Assembly (MEA) is typically placed between two conductive plates, and the surface of each conductive plate in contact with the MEA is die-cast, stamped, or mechanically milled to form at least one or more channels. The conductive plates can be plates made of metal materials or plates made of graphite materials. The flow guide pore canals and the flow guide grooves on the conductive polar plates respectively guide the fuel and the oxidant into the anode area and the cathode area on two sides of the membrane electrode. In the structure of a single proton exchange membrane fuel cell, only one membrane electrode is arranged, and a flow guide polar plate of anode fuel and a flow guide polar plate of cathode oxidant are respectively arranged on two sides of the membrane electrode. The flow guide polar plates are used as current collector plates and mechanical supports at two sides of the membrane electrode, and the flow guide grooves on the flow guide polar plates are also used as channels for fuel and oxidant to enter the surfaces of the anode and the cathode and as channels for taking away water generated in the operation process of the fuel cell.

In order to increase the total power of the whole proton exchange membrane fuel cell, two or more single cells can be connected in series to form a battery pack in a straight-stacked manner or connected in a flat-laid manner to form a battery pack. In the direct-stacking and serial-type battery pack, two surfaces of one polar plate can be provided with flow guide grooves, wherein one surface can be used as an anode flow guide surface of one membrane electrode, and the other surface can be used as a cathode flow guide surface of another adjacent membrane electrode, and the polar plate is called a bipolar plate. A series of cells are connected together in a manner to form a battery pack. The battery pack is generally fastened together into one body by a front end plate, a rear end plate and a tie rod.

A typical battery pack generally includes: (1) the fuel (such as hydrogen, methanol or hydrogen-rich gas obtained by reforming methanol, natural gas and gasoline) and the oxidant (mainly oxygen or air) are uniformly distributed in the diversion trenches of the anode surface and the cathode surface; (2) cooling fluid (such as water) is uniformly distributed into cooling channels in each battery pack through an inlet and an outlet of the cooling fluid and a flow guide channel, and heat generated by electrochemical exothermic reaction of hydrogen and oxygen in the fuel cell is absorbed and taken out of the battery pack for heat dissipation; (3) the outlets of the fuel gas and the oxidant gasand the corresponding flow guide channels can carry out liquid and vapor water generated in the fuel cell when the fuel gas and the oxidant gas are discharged. Typically, all fuel, oxidant, and cooling fluid inlets and outlets are provided in one or both end plates of the fuel cell stack.

The positive hydrogen ions in the anode region migrate through the proton exchange membrane and usually need to carry a large number of water molecules to pass through together, so that the water molecules must be kept on the two side surfaces of the membrane to ensure that the migration conductance of the positive hydrogen ions is not affected. Therefore, the fuel and oxidant gases must be humidified before they enter the active region of the fuel cell to react in order to ensure that the membrane in the membrane electrode is saturated with water.

The fuel cell uses hydrogen as fuel and air or pure oxygen as oxidant. In general, peripheral auxiliary devices of a fuel cell must force hydrogen or air to flow inside the fuel cell to carry water generated inside the fuel cell, such forced flow must be achieved by using compressed hydrogen or compressed air pressure higher than natural 1 atm, and in order to rapidly dissipate heat generated inside the fuel cell, a cooling water pump is generally used to force cooling water to flow inside the fuel cell. The external auxiliary operating facilities of such fuel cells, such as compressed hydrogen pumps, compressed air pumps or forced air flow fans, water pumps, etc., add significant complexity, volume and weight to the overall fuel cell system, and add significant cost.

In order to simplify the operation of the whole system of the fuel cell, forced flowing air, a water pump and the like can be removed, so that the fuel cell can adopt natural air as an oxidant, and the generated heat can be completely automatically dissipated by air flow. This technique is already mentioned in US Patent 5470671 (1995), as shown in fig. 1, 2 and 3. The design must adopt a bipolar electrode which is composed of thick carbon paper, an ion exchange membrane attached to two sides of the thick carbon paper and carbon paper attached to the outer side of the ion exchange membrane. This technique has a number of drawbacks: 1. this technical design must use bipolar electrodes, as shown in fig. 2, which are relatively cumbersome to manufacture because of the need for thicker carbon paper a; 2. after the bipolar electrode is adopted, the current extraction of the fuel end (negative end) is troublesome, for example, in fig. 2, metal wires A1 and A2 are required to be pressed into the electrode, on one hand, the metal wires are easy to pollute the electrode, if noble metals such as gold wires are used, the cost is too high, and after the metal extraction, the current and voltage losses are large due to the small size, small contact area with the electrode and large resistance; 3. after the bipolar electrode is adopted, fuel supply is difficult because fuel hydrogen must be uniformly diffused into thick-layer carbon paper, and the difficulty of sealing and preventing hydrogen leakage is increased; 4. the hydrogen supply diffusion resistance is large.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a fuel cell which adopts natural air as an oxidant, has convenient electrode manufacturing, easy hydrogen diffusion, good sealing performance and lower cost.

The purpose of the invention can be realized by the following technical scheme: a fuel cell using natural air as oxidant includes membrane electrode, radiating air-guiding flow plate, connecting rod, and is characterized by that it also includes graphite plate capable of guiding in hydrogen gas, the front and back surfaces of said graphite plate are respectively equipped with flow-guiding groove, the periphery of said flow-guiding groove is equipped with sealing ring, the top of said graphite plate is equipped with flow-guiding hole capable of reaching front and back flow-guiding grooves, the described membrane electrode is formed from catalyst and porous carbon paper attached to two sides of proton exchange membrane, and two membrane electrodes are used to sandwich one graphite plate, and the radiating air-guiding flow plate is clamped on the outer side of membrane electrode so as to form a cell unit, and all the cell units are series-connected together by means of connecting rod, so that it can be formed into the fuel cell.

The membrane electrode assembly also comprises a sealing frame, wherein the sealing frame is arranged on the periphery of the membrane electrode.

The heat dissipation air guide flow plate is of a hollow frame structure.

The inner side of the heat dissipation air guide flow plate is vertically provided with a guide groove.

The outer side of the heat dissipation air guide flow plate is vertically provided with a heat dissipation sheet.

The air conditioner also comprises a fan, an air pump or a fan, wherein forced air flow generated by the fan, the air pump or the fan is led into the heat dissipation air guide flow plate, and the heat dissipation air guide flow plate is connected in series or in parallel and leads in forced flowing air flow.

The invention adopts the technical proposal that the electrode is formed by clamping a double-sided graphite plate with a diversion hole, a diversion groove and a sealing ring between two common three-in-one electrodes, thus having the following advantages:

1. the electrode is convenient and simple to manufacture, and special carbon paperis not needed;

2. the fuel supply is easy, the diffusion speed is high and uniform;

3. the sealing performance is good, and hydrogen cannot leak;

4. the graphite plate can be directly used as a flow guide plate without leading out metal wires, and the graphite plate has no pollution to electrodes and low cost.

Drawings

The invention is further described with reference to the following drawings and specific embodiments.

Fig. 1 is a schematic view of a structure of a prior art battery pack;

FIG. 2 is a cross-sectional view of a bipolar electrode of a prior art battery;

FIG. 3 is a schematic diagram of a prior art fuel cell;

fig. 4 is a schematic structural view of a battery pack according to the present invention;

FIG. 5 is a cross-sectional view of a membrane electrode and graphite plate of a battery of the present invention;

FIG. 6 is a schematic diagram of the membrane electrode structure of FIG. 5;

FIG. 7 is a schematic structural view of an active portion of the membrane electrode of FIG. 6;

fig. 8 is a schematic view of the structure of the graphite plate of fig. 5.

Detailed Description

Example 1

As shown in fig. 4 to 8, a fuel cell using natural air as an oxidant includes a membrane electrode 1, a graphite plate 2 into which hydrogen can be introduced, a heat dissipation air guide plate 3, and a connecting rod 4. The membrane electrode 1 is a common three-in-one electrode, namely an effective part of the membrane electrode is formed by a proton exchange membrane 11, catalysts 12 attached to two sides of the proton exchange membrane and carbon paper 13 attached to the outer sides of the catalysts respectively, and the membrane electrode also comprises a sealing frame 14, wherein the effective part of the membrane electrode is combined with the sealing frame 14 to form the membrane electrode; the front and back sides of the graphite plate 2 are provided with diversion trenches 21, the periphery of the diversion trenches 21 is provided with a sealing ring 22, the top of the graphite plate 2 is provided with diversion holes 23 which can reach the diversion trenches on the front and back sides, and the thickness of the graphite plate 2 is about 1-5 mm; the heat dissipation air guide flow plate 3 is also made of a graphite plate and is processed into a frame-shaped structure; a graphite plate 2 is clamped between two membrane electrodes 1, and a heat dissipation air guide flow plate 3 is clamped on the outer side of each membrane electrode 1 to form a battery unit, and the battery units are connected in series through connecting rods 4 to form the fuel battery.

Example 2

Referring to fig. 4 to 8, a fuel cell using natural air as an oxidant includes a membrane electrode 1, a graphite plate 2 capable of introducing hydrogen, a heat dissipation air guide plate 3, and a connecting rod 4. The membrane electrode 1 is a common three-in-one electrode, namely an effective part of the membrane electrode is formed by a proton exchange membrane 11, catalysts 12 attached to two sides of the proton exchange membrane and carbon paper 13 attached to the outer sides of the catalysts respectively, and the membrane electrode also comprises a sealing frame 14, wherein the effective part of the membrane electrode is combined with the sealing frame 14 to form the membrane electrode; the front and back sides of the graphite plate 2 are provided with diversion trenches 21, the periphery of the diversion trenches 21 is provided with a sealing ring 22, the top of the graphite plate 2 is provided with diversion holes 23 which can reach the diversion trenches on the front and back sides, the thickness of the graphite plate 2 is about 1-5mm, 2, the heat dissipation air diversion plate 3 also adopts a graphite plate, the inner side of the graphite plate is vertically provided with the diversion trenches (not shown), and the diversion trenches can conveniently guide air in; a graphite plate 2 is clamped between two membrane electrodes 1, and a heat dissipation air guide flow plate 3 is clamped on the outer side of each membrane electrode 1 to form a battery unit, and the battery units are connected in series through connecting rods 4 to form the fuel battery.

Example 3

Referring to fig. 4 to 8, a fuel cell using natural air as an oxidant includes a membrane electrode 1, a graphite plate 2 capable of introducing hydrogen, a heat dissipation air guide plate 3, and a connecting rod 4. The membrane electrode 1 is a common three-in-one electrode, namely an effective part of the membrane electrode is formed by a proton exchange membrane 11, catalysts 12 attached to two sides of the proton exchange membrane and carbon paper 13 attached to the outer sides of the catalysts respectively, and the membrane electrode also comprises a sealing frame 14, wherein the effective part of the membrane electrode is combined with the sealing frame 14 to form the membrane electrode; the front and back sides of the graphite plate 2 are provided with diversion trenches 21, the periphery of the diversion trenches 21 is provided with a sealing ring 22, the top of the graphite plate 2 is provided with diversion holes 23 which can reach the diversion trenches on the front and back sides,and the thickness of the graphite plate 2 is about 1-5 mm; the heat dissipation air guide flow plate 3 is also made of graphite plate, the inner side of the heat dissipation air guide flow plate is vertically provided with a guide groove (not shown) which can conveniently guide air in, the outer side of the heat dissipation air guide flow plate is also vertically provided with a radiating fin (not shown) which can timely take away heat generated by reaction of hydrogen and air, and the air guided by the heat dissipation air guide flow plate 3 can also be air flow generated by a forced fan, an air pump or a fan, so that the inner sides of all the heat dissipation air guide flow plates 3 are provided with the guide grooves and can be connected in series or parallel in a unified manner to guide the forced flowing air flow; a graphite plate 2 is clamped between two membrane electrodes 1, and a heat dissipation air guide flow plate 3 is clamped on the outer side of each membrane electrode 1 to form a battery unit, and the battery units are connected in series through connecting rods 4 to form the fuel battery.

Claims

1. A fuel cell using natural air as oxidant includes membrane electrode, heat radiation air guide flow plate, connecting rod, and is characterized by that it also includes graphite plate capable of leading in hydrogen, and the front and back surfaces of said graphite plate are respectively equipped with guide grooves, and the periphery of said guide grooves is equipped with sealing ring, and the top of said graphite plate is equipped with guide holes capable of reaching the guide grooves of front and back surfaces, and the described membrane electrode is formed from catalyst and porous carbon paper attached to two sides of proton exchange membrane, and two membrane electrodes are used to sandwich one graphite plate, and the heat radiation air guide flow plate is clamped on the outer side of membrane electrode so as to form a cell unit, and all the cell units are series-connected together by means of connecting rod, so that it can be formed into the fuel cell.

2. The fuel cell as claimed in claim 1, wherein the heat dissipating and air guiding plate has guiding grooves formed vertically on an inner side thereof.

3. The fuel cell of claim 1, wherein the heat sink air guide plate has heat dissipation fins on the outer side thereof.

4. The fuel cell of claim 2, further comprising a fan, a wind pump or a fan, wherein the fan, the wind pump or the fan generates a forced air flow to the heat sink air guide plates, and the heat sink air guide plates are connected in series or in parallel to introduce the forced air flow.