CN100344023C - Method of operating fuel cell - Google Patents
Method of operating fuel cell Download PDFInfo
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- CN100344023C CN100344023C CNB2005100625672A CN200510062567A CN100344023C CN 100344023 C CN100344023 C CN 100344023C CN B2005100625672 A CNB2005100625672 A CN B2005100625672A CN 200510062567 A CN200510062567 A CN 200510062567A CN 100344023 C CN100344023 C CN 100344023C
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract
An operation method for a fuel cell is provided. In the fuel cell, oxidation degradation of a catalyst in the cathode can be prevented even if a large volume of air instantaneously penetrates into the cell, and the fuel-cell characteristics also do not deteriorate even though starting-up, shutting-down and pausing operations are repeatedly performed. As a method of controlling a fuel cell system, hydrogen-containing fuel gas is supplied to the anode and oxidant gas is supplied to the cathode, an external load is connected between the anode and the cathode so that the fuel cell generates electric power, the external load is disconnected after the power generation, a resistor is connected between the anode and the cathode, supply of the oxidant gas is stopped, and then supply of the fuel gas is stopped after the potential at the cathode has dropped to equal to or lower than the potential at which hydrogen evolution starts, so as to pause the fuel cell.
Description
Technical field
The present invention relates to utilize the method for operation of fuel cell that electrochemical reaction is generated electricity, that for example on electric automobile etc., use.
Background technology
In the closing method of existing fuel cell; be controlled to; from making fuel gas or flowing at anode with the gas that an amount of inactive gas has diluted; make inactive gas only purify negative electrode; resistance is connected and controls the connection and the disconnection of this resistance with the output of fuel cell; cell voltage equates (for example, with reference to patent documentation 1) substantially with the electromotive force of the theoretical concentration cell of hydrogen.
＜patent documentation 1 〉
Japanese kokai publication hei 1-128362 communique (the 2nd page)
In the closing method of existing fuel cell; in order to control the connection and the disconnection of fuel cell resistance when taking care of; when keeping, only on negative electrode, exist inactive gas; therefore when moment has a large amount of air to invade; resistance connected up and before producing hydrogen on the negative electrode, to take time, can not prevent the oxidative degradation of the catalyst that on negative electrode, forms fully.In addition, make fuel cell repeat starting, shut down, when keeping is turned round,,, exist the problem that the electrochemical reaction characteristic slowly reduces so on catalyst surface, generate oxide owing to be exposed in the oxidizing atmosphere.The oxidative degradation of so-called cathod catalyst refers to constitute the catalysqt deactivation of cathode catalyst layer, specifically, this phenomenon is, when for example mounting platinum catalyst particle is as catalyst on carbon particle, the airborne oxygen of intrusion and carbon particle reaction, carbon particle becomes carbon monoxide and disappears, platinum particles and carbon particle break away from, platinum particles condenses each other, loses the conducting with negative electrode, can not work as catalyst.
Summary of the invention
The present invention proposes in order to solve above-mentioned problem just; its purpose is to obtain also can preventing the oxidative degradation of cathod catalyst when moment has a large amount of air to enter when keeping; even repeat starting, shut down, take care of action, the fuel cell that performance does not also reduce.
The method of operation of fuel cell of the present invention is, antianode is supplied with the fuel gas and the target that comprise hydrogen and is supplied with oxidant gas, external loading is being connected between anode and the negative electrode and after generating electricity, cut off the said external load, then, resistance is connected between anode and the negative electrode, stop to supply with oxidant gas, cathode potential is lower than after the generation current potential that equals hydrogen, stop fueling gas, take care of, wherein, voltage when fuel cell running is the A volt, the electric current that flows in the external loading is the B ampere, when the gas effciency of fuel gas was C%, resistance value R ohm of resistance satisfied following formula: R 〉=(A * C)/(B * 100).
In addition, the method of operation of another kind of fuel cell of the present invention is, antianode is supplied with the fuel gas and the target that comprise hydrogen and is supplied with oxidant gas, external loading is being connected between anode and the negative electrode and after generating electricity, is cutting off external loading, then, resistance is connected between anode and the negative electrode, stops to supply with oxidant gas, cathode potential is lower than after the generation current potential that equals hydrogen, with space that negative electrode is communicated with in dispose reducing agent, take care of.
Fuel cell of the present invention can make the space that is communicated with anode and negative electrode always in reducing atmosphere in keeping, even a large amount of air was sneaked in moment, hydrogen or reducing agent react with airborne oxygen, also can fall oxygen consumption.And, in keeping, can reduce the oxide of the catalyst surface that on negative electrode, forms, can activated catalyst.
Description of drawings
Fig. 1 is the ideograph of the general picture of the fuel cell of displaying embodiment of the present invention 1.
Fig. 2 tests the performance plot of the relation of fate and generating voltage for the DSS that shows embodiment of the present invention 1.
Fig. 3 tests the performance plot of the relation of fate and generating voltage for the DSS that shows embodiment of the present invention 1.
Fig. 4 is the ideograph of the general picture of the fuel cell of displaying embodiment of the present invention 3.
Fig. 5 is the ideograph of the general picture of the fuel cell of displaying embodiment of the present invention 5.
Fig. 6 is the ideograph of the general picture of the fuel cell of displaying embodiment of the present invention 6.
Fig. 7 is the ideograph of the general picture of the fuel cell of displaying embodiment of the present invention 7.
Reference numeral
1 fuel cell
2 polyelectrolyte membranes
3 anodes
4 negative electrodes
5,6 streams
7,8 dividing plates
9,10 sealing gland portions
11 oxidant gas services
12 fuel gas supply pipelines
13 oxidant gas discharge lines
14 fuel gas discharge lines
15 oxidant gas quantity delivered adjustment units
16 fuel gas supply amount adjustment units
17 oxidant gas discharge rate adjustment units
18 fuel gas supply amount adjustment units
19 external loadings
20 switches
21 resistance
22 gas bags
23 blanketing gas services
24 blanketing gas quantity delivered adjustment units
32 gas flow adjustment units
33 gas bags
34 reducing agents
35 gas flow adjustment units
Embodiment
(execution mode 1)
Fig. 1 is the ideograph that the fuel cell 1 that is used for implementing embodiments of the present invention 1 is shown.Among Fig. 1, on polyelectrolyte membrane 2 two-sided, have anode 3 and negative electrode 4, on the composition surface of each electrode and polyelectrolyte membrane 2, formed catalyst layer (not shown) as the electrochemical reaction field.Dividing plate 7,8 with gas flow path 5,6 is configured in the outside of each electrode.Around anode 3 and negative electrode 4, be provided with sealing gland portion 9,10.In sealing gland portion 9,10, be provided with to gas flow path 5,6 fueling gases or oxidant gas or from gas flow path 5,6 and discharge the manifold hole (not shown) of fuel gas or oxidant gas, oxidant gas service 11, fuel gas supply pipeline 12, oxidant gas discharge line 13 and fuel gas discharge line 14 are connected with this manifold hole.Oxidant gas service 11 is connected with the stream 6 that oxidant gas discharge line 13 and target 4 are supplied with oxidant gas, and fuel gas supply pipeline 12 is connected with the stream 5 of fuel gas discharge line 14 with antianode 3 fueling gases.Oxidant gas quantity delivered adjustment unit 15 is connected with oxidant gas service 11, so that can adjust the quantity delivered of oxidant gas; Fuel gas supply amount adjustment unit 16 is connected with fuel gas supply pipeline 12, so that can adjust the quantity delivered of fuel gas.In addition, oxidant gas discharge rate adjustment unit 17 and fuel gas discharge rate adjustment unit 18, be connected with fuel gas discharge line 14 with oxidant gas discharge line 13 respectively.
Use polymeric membrane as polyelectrolyte membrane 2, for example, can use the polyelectrolyte membrane that constitutes by perfluor owner chain and sulfonic group etc. with proton conductive, gas barrier and electrical insulating property.Catalyst layer is made of metal particle, the polymeric binder materials etc. such as for example platinum catalyst particle with catalyst activity of mounting on surfaces of carbon particles, can sneak into additives such as polymer particle as required.These additives are that purpose is used with the hydrophily of control catalyst layer or water proofing property or control porosity.Formation method as catalyst layer has: directly in the method that forms on the surface of polyelectrolyte membrane 2, after forming on another base material, transferring to polyelectrolyte membrane 2 lip-deep methods, on the surface of anode 3 and negative electrode 4, forming method that the back engages with polyelectrolyte membrane 2 etc.For supply to by stream 5,6 gas supplied diffusions catalyst layer comprehensively on, anode 3 and negative electrode 4 need gas permeability and conductivity, generally the carbon fiber by carbon paper or carbon cloth etc. constitutes. Dividing plate 7,8 uses for example carbon plate fine and close and that have conductivity, and is formed with groove so that constitute stream 5,6.
The method of operation of the fuel cell 1 that constitutes as described above is described.Fuel cell 1 is connected with resistance 21 between anode 3 and the negative electrode 4 by switch 20.At this moment, owing to for example carbon plate of dividing plate 7,8 by conductivity constitutes, so resistance 21 is connected at dividing plate stacked on the anode 37 and between dividing plate stacked on the negative electrode 8.Have, the effective area of anode 3 and negative electrode 4 (having formed the area of catalyst layer) is about 100cm again
2Then, fuel cell 1 is remained under 75 ℃ the state, is for example dew point that 70 ℃ hydrogen acts as a fuel gas with the flow (about 340ml/min) suitable with utilance 80% and so that the electrical current during generating is the mode of 25A, flows into anodes 3 from fuel gas supply pipeline 12 by stream 5; Be for example dew point 70 ℃ air as oxidant gas with the flow (about 970ml/min) suitable with utilance 50%, flow into negative electrodes 4 from oxidant gas service 11 by stream 6.Make fuel gas and oxidant gas in the reason of the state current downflow that comprises moisture be, have conductivity in order to make polyelectrolyte membrane 2, this polyelectrolyte membrane 2 must be moistening.At this, the utilance of so-called gas is defined by the ratio of the gas flow that utilizes in generating to gas delivery volume.At this moment, oxidant gas quantity delivered adjustment unit 15, fuel gas supply amount adjustment unit 16, oxidant gas discharge rate adjustment unit 17 and fuel gas discharge rate adjustment unit 18 are adjusted to fuel gas or oxidant gas are all flowed with essential gas flow.Then, switch to external loading 19 from resistance 21, make fuel cell 1 become the state of common running by switch 20.During the running beginning, the generating voltage of fuel cell 1 is 0.73V.
Running stops the generating of fuel cell 1 after 100 hours in the following order continuously.At first, use switch 20 that the load between anode 3 and the negative electrode 4 is switched to resistance 21 (30m Ω) from external loading 19, inaccessible oxidant gas quantity delivered adjustment unit 15 and oxidant gas discharge rate adjustment unit 17, making air mass flow is 0ml/min.At this moment because remaining airborne oxygen and H-H reaction generation water in the negative electrode 4, so with oxidant gas service 11 that negative electrode 4 is connected in have only nitrogen basically.Therefore, the current potential of negative electrode 4 slowly reduces, the increase of the concentration polarization that causes along with the diffusion rate of oxygen rule speed, and this current potential becomes≤0.1V.At this moment, the reaction shown in the following formula taking place on anode 3 and negative electrode 4, form the concentration cell of hydrogen/hydrogen, produces hydrogen.The generation current potential that the cathode potential of this moment is called hydrogen.
Anode: H
2→ 2H
++ 2e
-
Negative electrode: 2H
++ 2e
-→ H
2
The current potential that begins to produce hydrogen determines that by the Nernst that shows down (Nernst) formula (1) this current potential is along with the variations such as hydrogen concentration of temperature, negative electrode.
E＝-(RT/2F)ln(P
H2-c/P
H2-a) (1)
(1) in the formula, E represents generating voltage, and R represents gas constant, and T represents temperature, and F represents Faraday constant, P
H2-cHydrogen partial pressure on the expression negative electrode, P
H2-aHydrogen partial pressure on the expression anode.In the present embodiment, the generation current potential of hydrogen is≤0.1V.For hydrogen is produced reliably, current potential is reduced to≤0.05V.At this moment, owing to supply with hydrogen, so fill the space that is communicated with anode by hydrogen by fuel gas supply pipeline 12.
According to said sequence, confirming after cathode side has produced hydrogen, inaccessible fuel gas supply amount adjustment unit 16 and fuel gas discharge rate adjustment unit 18, making hydrogen flowing quantity is 0ml/min.Therefore, each gas flow adjustment unit 15,16,17,18 of the gas supply/discharge line of inaccessible anode and negative electrode when keeping, space that is communicated with anode and the space that is communicated with negative electrode for closure respectively state, but, even just in case air sneak into the space that is communicated with anode or with space that negative electrode is communicated with in the time, according to present embodiment also can prevent air sneak into cause the oxidative degradation of electrode.That is, in the time of in the space that air is sneaked into negative electrode is communicated with, its airborne oxygen by be present in space that negative electrode is communicated with in hydrogen carry out redox reaction and be consumed.Be consumed and air when further having sneaked at this hydrogen, because resistance is two electrode electrical shorts, so hydrogen is oxidized to hydrogen ion on anode, this hydrogen ion moves to the airborne hydrogen reduction that the negative electrode handle is sneaked into by dielectric film.After having consumed air, hydrogen is moving in two interpolar electromigration by dielectric film, so that the difference of the hydrogen concentration on the two poles of the earth disappears.That is, for example in the hydrogen concentration on the negative electrode than the hydrogen concentration on the anode hour, hydrogen is oxidized to hydrogen ion on anode, this hydrogen ion moves by dielectric film and is reduced into hydrogen at negative electrode, to keep the balance of two interpolars.By this mechanism, in the two poles of the earth, become the state that always remains in the nitrogen atmosphere.After keeping under this state, carry out the starting of fuel cell.Have again, utilize the gas chromatography analysis to the electrode before at once will starting in atmosphere when investigating, hydrogen concentration is 70vol%.
In order to estimate the fuel cell performance in the present embodiment; repeating in 1 day time uninterruptable power generation in 100 day time made fuel cell shut down 16 hours test of keeping (every day starting and engine cut off test according to said sequence after 8 hours; be called for short " DSS test "), the generating voltage of having measured fuel cell is over time.Assay method is to be determined at the generating voltage of the fuel cell after 4 hours after beginning to generate electricity.Fig. 2 illustrates the variation of generating voltage of the fuel cell of DSS test, and generating voltage reduces hardly in 100 day time.
In the method for operation of the fuel cell that constitutes like this, in keeping air from the outside invade the space be communicated with anode or with space that negative electrode is communicated with in the time, because hydrogen always is present in inside, so airborne oxygen and hydrogen generation redox reaction and generate water, the oxygen of intrusion is consumed.Its result can prevent the carbon particle of catalyst layer to disappear, and can prevent the deterioration of electrode.
In addition, the negative electrode of fuel cell is a high potential in the running, is exposed in the oxidizing atmosphere, still, as present embodiment, by the current potential that reduces negative electrode hydrogen is produced when keeping, because this negative electrode of hydrogen that is generated becomes the state of reducing atmosphere.Therefore,, generating on the catalyst surface under the occasion of such oxide of making cathode catalyst layer reduce the electrochemical reaction characteristic etc., when keeping, reducing to handle and also have the effect that the catalyst that makes negative electrode activates once more even in the running.
And, on negative electrode, oxygen consumption fallen during running and generate water, because the water that generates focuses on downstream area by flowing of oxidant, so might be created in the skewness homogenize of water in the dielectric film.According to present embodiment, owing to the time stopping to supply with oxidant gas in keeping, making negative electrode become electronegative potential hydrogen is produced, so under the state that does not generate water humidification gas flow equably by anode surface, its result also has the effect of being evenly distributed that makes water in polyelectrolyte membrane.
In order to compare with present embodiment, when keeping, with space that anode is communicated with in fill hydrogen, with space that negative electrode is communicated with in the nitrogen of filling as inactive gas replace fuel gas, generating voltage with the potentiometer monitor fuel cell, carry out the connection of resistance and disconnection simultaneously so that the electromotive force of generating voltage and theoretical concentration cell, promptly on negative electrode, do not produce hydrogen voltage about equally, implemented DSS test same as described above.Fig. 3 represents the variation of the generating voltage of the fuel cell that this DSS test causes, voltage reduces 0.05V approximately in 50 day time.The disappearance that constitutes the carbon particle of cathod catalyst is irreversible, just can not restore in case disappeared, and in the DSS test, generating voltage reduces at leisure.On the other hand; in the present embodiment; in keeping; since hydrogen always be present in the space that is communicated with anode or with space that negative electrode is communicated with in; so in keeping, have the effect that catalyst is activated; even can access and repeat starting, shut down, take care of running, the fuel cell that performance does not also reduce.
Have again, in the present embodiment, used air as oxidant gas, the gas that acts as a fuel has used hydrogen, but, can also use the mist of oxygen, inactive gas and oxygen etc. except air as oxidant gas, the gas that acts as a fuel can also use resulting modifications such as methyl alcohol or kerosene, as to comprise carbon dioxide hydrogen etc. except hydrogen.
In addition, in the present embodiment, utilization has illustrated method of operation by the fuel cell that a target shown in Figure 1 and anode constitute, but, the method of operation identical with present embodiment also can be applied on anode 3 one sides the dividing plate 7 that configuration is provided with the anode-side of the stream 5 that fuel gas uses, and configuration is provided with the dividing plate 8 of the cathode side of the stream 6 that oxidant gas uses on negative electrode 4 one sides, and is stacked and constitute in the fuel cell of stepped construction anode 3, dividing plate 7 and 8, negative electrode 4.
And, if having, external loading 19 is controlled to the load controlled function that fuel cell 1 can be generated electricity with the constant current of about 25A, just can holding current unconverted, the electricity generate function stablized.
(execution mode 2)
Fuel cell when shutting down, the space that is communicated with anode and with space that negative electrode is communicated with in hydrogen concentration when hanging down, the air of sneaking into from the outside is consumed hydrogen at short notice fully, exists the possibility of anodizing deterioration.In the execution mode 2, studied the space that is communicated with anode and with space that negative electrode is communicated with in hydrogen concentration to the influence of battery performance.When keeping, with space that anode is communicated with in and the space that is communicated with negative electrode be the mist of filling hydrogen and nitrogen so that the hydrogen concentration in this mist is 0,0.1,0.5,3.0,10.0vol% comes battery unit certainly for these five kinds.In order to estimate these fuel cell performance, similarly in 100 day time, repeated the DSS test with execution mode 1, studied generating voltage over time.The deterioration rate of each battery gathered be shown in table 1.The deterioration rate is illustrated in the reduction amount of DSS test front and back generating voltage.
[table 1]
| Hydrogen concentration (vol%) | 0 | 0.1 | 0.5 | 3.0 | 10.0 |
| Deterioration rate (mV/100 time) | 90 | 6 | 5 | ＜2 | ＜2 |
As can be seen from Table 1, if the hydrogen concentration 〉=0.1vol% in when keeping fuel cell just can prevent the reduction of the caused battery performance of anodizing.
(execution mode 3)
With space that anode is communicated with in the hydrogen amount that exists many more, just can adapt to more and prevent from when keeping, to sneak into caused electrode degradation from air outside.By being provided as that the pipeline different with the anodic gas service is provided with the increase and decrease fuel gas supplementary units, that be accompanied by internal pressure and the method for container of Free Transform, for example aluminum gas bag etc., the spatial volume that is communicated with anode is increased, fill the fuel gas that comprises hydrogen therein, thus, even, also can prevent anodizing when air has been sneaked in the outside.Fig. 4 is the ideograph that the fuel cell 1 in the execution mode 3 is shown.Among Fig. 4, the structure identical with execution mode 1 represented with identical Reference numeral.In the present embodiment, the mechanism as filling fuel gas is connected with fuel gas supply pipeline 12 the gas bag 22 of aluminum.
In the present embodiment, in order to ensure the space that is communicated with anode and with space that negative electrode is communicated with in hydrogen concentration 〉=0.1vol%, estimated the volume in the essential space that is communicated with anode.Below, illustrate tolerance that air is sneaked into and with space that anode is communicated with in the hydrogen amount and the space that is communicated with anode and with space that negative electrode is communicated with in the dependency relation of hydrogen concentration.
Air sneak into from the outside space that is communicated with anode or with space that negative electrode is communicated with in the time, suppose that its speed of sneaking into is α (ml/min).Suppose that the indoor hydrogen concentration that is communicated with anode is C when shutting down
H2-a(vol%), the volume in the space that is communicated with anode is V
a(ml), the volume in the space that is communicated with negative electrode is V
c(ml), the storage time before the fuel cell activation is T
R(min) time, the space that is communicated with anode and with space that negative electrode is communicated with in hydrogen concentration C
The H2-battery unitBy the expression of following formula (2) table.
C
The H2-battery unit=(V
a* C
H2-a-2 α * T
R)/(V
a+ V
c) (2)
Therefore, in (2) formula, other factor (C
The H2-battery unit, V
a, V
c, T
R) when being set at certain value,, can design V by the volume of suitable selection gas bag 22
aSo that the space that is communicated with anode and with space that negative electrode is communicated with in hydrogen concentration (during starting) C
The H2-battery unit〉=0.1vol%.
(execution mode 4)
In the execution mode 1, the gas flow adjustment unit that inaccessible target is supplied with/discharged falls oxidant consumption with unlimited increase oxidant utilance, but, can also enumerate the method for utilizing the inactive gas of oxygen-free agent to carry out gas displacement at cathode side as the method that improves the oxidant gas utilance.Used the fuel cell the same in the execution mode 4 with execution mode 1.
The running of the fuel cell in the present embodiment is described.Generating voltage when using the method identical with execution mode 1 to make generating is 0.73V.After turning round 100 hours continuously, stopped the generating of fuel cell 1 by following order.At first, use switch 20 that the load between anode 3 and the negative electrode 4 is switched to resistance 21 (30m Ω) from external loading 19, the oxidant gas of supplying with towards cathode side is switched to nitrogen from air.The utilance that by this operation can be common running the time be 50% oxidant gas is brought up to infinity, and oxygen consumption is fallen.As other method that improves the oxidant gas utilance,, just can adopt gas of utilizing the oxygen-free agent and composition thereof to dilute the method for oxidant gas if no problem on device and safety.As the gas of oxygen-free agent, except nitrogen, can be from inactive gass such as argon, carbon dioxide, select in the steam, the hydrocarbon compound of methane etc. etc.
Confirmed that in 10 minutes, generating voltage changes to 0.06V from 0.73V, has produced hydrogen on negative electrode oxidant gas is switched to nitrogen from air after.Confirming after having produced hydrogen on the negative electrode, inaccessible oxidant gas quantity delivered adjustment unit 15 and oxidant gas discharge rate adjustment unit 17, making the nitrogen flow is 0ml/min, and, inaccessible fuel gas supply amount adjustment unit 15 and fuel gas discharge rate adjustment unit 18, making the hydrogen flow is 0ml/min.Therefore, when keeping,, under the state in airtight space that is communicated with anode and the space that is communicated with negative electrode, take care of by hydrogen gas flow adjustment unit 15,16,17,18 obturations of the gas supply/discharge line of anode and negative electrode.
In order to estimate the fuel cell performance in the present embodiment, equally with execution mode 1 in 100 day time, repeated the DSS test, the generating voltage of having measured fuel cell is over time.Its result, generating voltage reduces hardly in 100 day time.
In the method for operation of the fuel cell that constitutes like this, in keeping air from the outside invade the space be communicated with anode or with space that negative electrode is communicated with in the time, because hydrogen always is present in inside, so airborne oxygen and hydrogen generation redox reaction and generate water, the oxygen of intrusion is consumed.Its result can prevent the carbon particle of catalyst layer to disappear, and can prevent the deterioration of electrode.
In addition, the negative electrode of fuel cell is a high potential in the running, is exposed in the oxidizing atmosphere, still, as present embodiment, by the current potential that reduces negative electrode hydrogen is produced when keeping, because this negative electrode of hydrogen that is generated becomes the state of reducing atmosphere.Therefore,, generating on the catalyst surface under the occasion of such oxide of making cathode catalyst layer reduce the electrochemical reaction characteristic etc., when keeping, reducing to handle and also have the effect that the catalyst that makes negative electrode activates once more even in the running.
(execution mode 5)
In execution mode 1; by when shutting down, stopping to supply with oxidant gas; oxidant gas in the negative electrode is consumed and makes the hydrogen generation; but; in the space that is communicated with negative electrode by other pipeline and direct filling fuel gas are set; make with space that negative electrode is communicated with in form the method for nitrogen atmosphere, to sneak into aspect the caused electrode degradation also be effective to air when preventing keeping.Fig. 5 is the ideograph that the fuel cell 1 in the execution mode 5 is shown.Among Fig. 5, the structure identical with execution mode 1 represented with identical symbol.In the present embodiment,, blanketing gas service 23 is connected with oxidant gas service 11 by blanketing gas quantity delivered adjustment unit 24 for filling fuel gas.
In above-mentioned such fuel cell that constitutes 1, because electricity-generating method is identical with execution mode 1, so the method for shutting down and taking care of is described at this.When turning round usually, inaccessible blanketing gas quantity delivered adjustment unit 24.Running is after 100 hours continuously, at first use switch 20 that the load between anode 3 and the negative electrode 4 is switched to resistance 21 from external loading 19, inaccessible oxidant gas quantity delivered adjustment unit 15 and oxidant gas discharge rate adjustment unit 17, making air mass flow is 0ml/min.At this moment because remaining airborne oxygen and H-H reaction generation water in the negative electrode 4, so with oxidant gas service 11 that negative electrode 4 is connected in have only nitrogen basically, the generation current potential of hydrogen is about≤0.1V.Then, by adjusting blanketing gas quantity delivered adjustment unit 24, fuel gas is delivered to oxidant gas service 11 through blanketing gas service 23.At this moment, adjust fuel gas supply amount adjustment unit 16 and blanketing gas quantity delivered adjustment unit 24, fuel gas is filled into oxidant gas service 11 and fuel gas supply pipeline 12, fuel cell 1 is taken care of with the roughly equal pressure of atmospheric pressure.
In order to estimate the fuel cell performance in the present embodiment, equally with execution mode 1 in 100 day time, repeated the DSS test, the generating voltage of having measured fuel cell is over time.Its result, generating voltage reduces hardly in 100 day time.
In the method for operation of the fuel cell that constitutes like this, in keeping air from the outside invade the space be communicated with anode or with space that negative electrode is communicated with in the time, because hydrogen always is present in inside, so airborne oxygen and hydrogen generation redox reaction and generate water, the oxygen of intrusion is consumed.Its result can prevent the carbon particle of catalyst layer to disappear, and can prevent the deterioration of electrode.
In addition, the negative electrode of fuel cell is a high potential in the running, is exposed in the oxidizing atmosphere, still, as present embodiment, by the current potential that reduces negative electrode hydrogen is produced when keeping, because this negative electrode of hydrogen that is generated becomes the state of reducing atmosphere.Therefore,, generating on the catalyst surface under the occasion of such oxide of making cathode catalyst layer reduce the electrochemical reaction characteristic etc., when keeping, reducing to handle and also have the effect that the catalyst that makes negative electrode activates once more even in the running.
(execution mode 6)
Fig. 6 is the ideograph that the fuel cell 1 in the execution mode 6 is shown.Among Fig. 6, the structure identical with execution mode 1 represented with identical Reference numeral.In execution mode 5, fuel gas is filled in the oxidant gas service through the bypass gases service, fuel cell is taken care of, and in the present embodiment, gas bag 33 is connected with oxidant gas service 11 by gas flow adjustment unit 32.Reducing agent 34 is enclosed in the gas bag 33.Can use for example metallic zinc powder as reducing agent.
The method of operation of above-mentioned such fuel cell that constitutes 1 is described.Because the electricity-generating method of fuel cell 1 is identical with execution mode 1, so the method for shutting down and taking care of is described at this.Have again, during generating, occlusion gas scale of construction adjustment unit 32.Running is after 100 hours continuously, at first use switch 20 that the load between anode 3 and the negative electrode 4 is switched to resistance 21 from external loading 19, inaccessible oxidant gas quantity delivered adjustment unit 15 and oxidant gas discharge rate adjustment unit 17, making air mass flow is 0ml/min.At this moment because remaining airborne oxygen and H-H reaction generation water in the negative electrode 4, so with oxidant gas service 11 that negative electrode 4 is connected in have only nitrogen basically, the generation current potential of hydrogen is about≤0.1V.Then, open gas flow adjustment unit 32 so that oxidant gas service 11 and gas bag 33 conductings, and, adjust fuel gas supply amount adjustment unit 16 and adjust fuel gas supply pipeline 12, so that come filling fuel gas supply pipe road 12 by the fuel gas that is roughly atmospheric pressure, fuel cell 1 taken care of.
In order to estimate the performance of the fuel cell 1 in the present embodiment, similarly in 100 day time, repeated the DSS test with execution mode 1, measured generating voltage over time.Its result, generating voltage reduces hardly in 100 day time.
In the method for operation of the fuel cell 1 that constitutes like this, when air is invaded oxidant service 11 from the outside in keeping,,, airborne oxygen consumes so being reduced agent 34 because oxidant service 11 is being connected with the gas bag 33 of having enclosed reducing agent 34.In addition, when air was invaded fuel gas supply pipeline 12, airborne oxygen and hydrogen reacted and are consumed.Its result can prevent the carbon particle of catalyst layer to disappear, and can prevent the deterioration of electrode.
In addition, the negative electrode of fuel cell is a high potential in the running, is exposed in the oxidizing atmosphere, still, as present embodiment, by the current potential that reduces negative electrode hydrogen is produced when keeping, because this negative electrode of hydrogen that is generated becomes the state of reducing atmosphere.Therefore,, generating on the catalyst surface under the occasion of such oxide of making cathode catalyst layer reduce the electrochemical reaction characteristic etc., when keeping, reducing to handle and also have the effect that the catalyst that makes negative electrode activates once more even in the running.
Have again, in the present embodiment, used the metallic zinc powder as reducing agent, still, so long as, also can use other material than the easy oxidation of electrode member.For example, also can use the solid of alkali metal powder such as magnesium metal powder, Li or Na etc., perhaps the liquid of oxalic acid aqueous solution etc., the perhaps gas of methane gas, hydrogen sulfide gas etc.
(execution mode 7)
Fig. 7 is the ideograph of the fuel cell 1 in the execution mode 7.In execution mode 6, the gas bag of having enclosed reducing agent only is connected with the oxidant gas service by the gas flow adjustment unit, but, in the present embodiment, as shown in Figure 7, gas bag 33 is connected with fuel gas supply pipeline 12 with oxidant service 11 by gas flow adjustment unit 32,35.Reducing agent 34 is enclosed in the gas bag 33.Can use for example metallic zinc powder as reducing agent 34.
In above-mentioned such fuel cell that constitutes 1, fuel cell 1 in the running, gas flow adjustment unit 32,35 is all by obturation.Fuel cell 1 is when shutting down; inaccessible fuel gas supply amount adjustment unit 15, oxidant gas quantity delivered adjustment unit 16, oxidant gas discharge rate adjustment unit 17 and fuel gas discharge rate adjustment unit 18; airtight fuel gas supply pipeline 11 and oxidant gas service 12; open gas flow adjustment unit 32,35; fuel gas supply pipeline 11 and oxidant gas service 12 and gas bag 33 conductings are taken care of thus.In such method of operation, when air is invaded oxidant service 11 or fuel gas supply pipeline 12 from the outside in keeping,,, airborne oxygen consumes so being reduced agent 34 because these pipelines are being connected with the gas bag 33 of having enclosed reducing agent 34.Its result can prevent the carbon particle of catalyst layer to disappear, and can prevent the deterioration of electrode.
In addition, the negative electrode of fuel cell is a high potential in the running, is exposed in the oxidizing atmosphere, still, as present embodiment, by the current potential that reduces negative electrode hydrogen is produced when keeping, because this negative electrode of hydrogen that is generated becomes the state of reducing atmosphere.Therefore,, generating on the catalyst surface under the occasion of such oxide of making cathode catalyst layer reduce the electrochemical reaction characteristic etc., when keeping, reducing to handle and also have the effect that the catalyst that makes negative electrode activates once more even in the running.
In addition, in execution mode 5 and execution mode 8, in keeping, owing to need fill oxidant service 11 or fuel gas supply pipeline 12 to be roughly atmospheric pressure with fuel gas, so though be micro-but want consume fuel gas, in the present embodiment, in keeping, owing to do not need filling fuel gas,, and be cheap so the keeping program is simple.
Have again, in the present embodiment, used the metallic zinc powder as reducing agent, but, also can use the solid of alkali metal powder such as magnesium metal powder, Li or Na etc. in addition, perhaps the liquid of oxalic acid aqueous solution etc., the perhaps gas of methane gas, hydrogen sulfide gas etc.
(execution mode 8)
The structure of execution mode 8 is to use the container of for example rubber system that has retractility, can be airtight airtightly to constitute gas bag 33 in execution mode 7, and has removed reducing agent 34.In the fuel cell that constitutes like this, fuel cell in gas flow adjustment unit 35 closing state, open under the state of gas flow adjustment unit 32 and generate electricity.At this moment, fuel gas supplies to gas bag 33 from fuel gas supply pipeline 12, and gas bag 33 with retractility becomes the state that internal capacity has increased under the supply pressure of fuel gas.Fuel cell is when shutting down; inaccessible fuel gas supply amount adjustment unit 15, oxidant gas quantity delivered adjustment unit 16, oxidant gas discharge rate adjustment unit 17 and fuel gas discharge rate adjustment unit 18; airtight fuel gas supply pipeline 11 and oxidant gas service 12; open gas flow adjustment unit 32,35; fuel gas supply pipeline 11 and oxidant gas service 12 and gas bag 33 conductings are taken care of thus.
In such method of operation, when air is invaded oxidant service 11 or fuel gas supply pipeline 12 from the outside in keeping, because these pipelines are being connected with gas bag 33, so the hydrogen that airborne oxygen is stored in the interior fuel gas of gas bag 33 consumes.Its result can prevent the carbon particle of catalyst layer to disappear, and can prevent the deterioration of electrode.
In addition, the negative electrode of fuel cell is a high potential in the running, is exposed in the oxidizing atmosphere, still, as present embodiment, by the current potential that reduces negative electrode hydrogen is produced when keeping, because this negative electrode of hydrogen that is generated becomes the state of reducing atmosphere.Therefore,, generating on the catalyst surface under the occasion of such oxide of making cathode catalyst layer reduce the electrochemical reaction characteristic etc., when keeping, reducing to handle and also have the effect that the catalyst that makes negative electrode activates once more even in the running.
In addition; because the container with retractility constitutes gas bag 33; even reduce and be in decompression state so fuel gas supply pipeline 11 and oxidant gas service 12 are accompanied by the temperature of fuel cell when shutting down; also, also has the effect that prevents that air from invading from the outside from gas bag 33 fueling gases.And, in execution mode 5 and execution mode 6, in keeping, owing to need under the pressure about atmospheric pressure, to fill oxidant service 11 or fuel gas supply pipeline 12 with fuel gas, so though be trace but want consume fuel gas, in the present embodiment, in keeping, owing to do not need filling fuel gas,, and be cheap so the keeping program is simple.
In the present embodiment; imagine in advance or be determined at fuel cell is shut down carry out the time of keeping, for example if the DSS test then is in time of 16 hours; invade the amount of the air in fuel gas supply pipeline 11 and the oxidant gas service 12, the internal capacity of gas bag 33 is set for can be preserved used up enough fuel gas in order to reduce this airborne oxygen of invading into.
Having, the example of not enclosing reducing agent among gas bag 33 has been shown in the present embodiment, still, also can be to enclose reducing agent to constitute.At this moment, the further consumption ability that increases at the oxygen of the air of in keeping, invading.In addition, in the present embodiment, to gas bag 33 fueling gases, still, except the fuel gas supply pipeline, also can wait and supply with from for example other hydrogen cylinder from the fuel gas supply pipeline.
(execution mode 9)
In execution mode 1, making makes the resistance change of resistance 21 become 15,25,30 (execution modes 1), 50 and the fuel cell of 80m Ω, with the DSS test of carrying out 100 day time with same generating of execution mode 1 and keeping method, measured the reduction amount of DSS test back generating voltage with comparing before the DSS test.At this moment, external loading has used and execution mode 1 the same load with load controlled function.Table 2 illustrates the resistance value of resistance 21 and the relation of generating voltage reduction amount.
[table 2]
| Resistance value (m Ω) | 15 | 25 | 30 | 50 | 80 |
| Reduced rate (mV) | 200 | 0.9 | 1.0 | 1.4 | 1.5 |
As can be seen from Table 2, if resistance value between 25～80m Ω then the voltage reduction amount≤2mV in the DSS of the 100 day time test.During the resistance value of resistance 21≤15m Ω, when shutting down, using switch 20 when external loading 19 switches to resistance 21, moment has excessive electric current to flow through in fuel cell.Specifically, when resistance value was 15m Ω, the electric current of about 37.5A flow through in the fuel cell, and the utilance of fuel gas is 120%, and fuel gas is deficiency state in the short time.Fuel cell is under the deficiency state when continuing generating at fuel gas, causes the oxide etch deterioration of the carbon particle that forms on anode catalyst layer.Because this deterioration, the electrochemical reaction characteristic of anode catalyst layer reduces, and causes that generating voltage reduces.
As described above, when shutting down, fuel cell must be set in the resistance value that will connect the resistance that switches to from external loading in the correct scope.The lower limit of resistance value is described.When resistance value reduced, the electric current that flows through when connecting resistance in the fuel cell increased.At this moment, if get final product because the utilance of fuel gas is no more than 100%, so fuel cell voltage was A (V) when supposition was turned round usually at the connection external loading, the electric current that flows through in the external loading is B (A), when the utilance of fuel gas is (1%), the resistance value R of resistance (Ω) 〉=(A/B) * (C/100) get final product.If resistance value 〉=this value, then connecting when external loading 19 switches to resistance 21, the gas effciency of fuel gas is no more than 100%, does not produce the deficiency state of fuel gas.
Promptly; when fuel cell is shut down; connecting when external loading 19 switches to resistance 21; the resistance value of resistance 21 is R (Ω) if R 〉=(A * C)/(B * 100); then fuel cell voltage is correct value when generation outage and keeping, can suppress the reduction of generating voltage in the running.
Claims (7)
1. the method for operation of a fuel cell, this fuel cell comprise that antianode is supplied with the fuel gas that comprises hydrogen, the gas supply pipe road that target is supplied with oxidant gas respectively, it is characterized in that:
Supply with above-mentioned fuel gas and above-mentioned oxidant gas, external loading is being connected between above-mentioned anode and the above-mentioned negative electrode and after generating electricity, cut off the said external load, then, resistance is connected between above-mentioned anode and the above-mentioned negative electrode, stops to supply with above-mentioned oxidant gas, after the current potential of above-mentioned negative electrode is lower than the generation current potential that equals hydrogen, stop to supply with above-mentioned fuel gas, take care of
Wherein, the voltage when fuel cell running is that the electric current that flows in A volt, the external loading is the gas effciency of B ampere, fuel gas when being C%, and resistance value R ohm of resistance satisfies following formula:
R≥(A×C)/(B×100)。
2. the method for operation of fuel cell according to claim 1 is characterized in that: in keeping, the hydrogen concentration in space that is communicated with anode and the space that is communicated with negative electrode is 〉=0.1vol%.
3. the method for operation of fuel cell according to claim 1 is characterized in that: the mechanism that replenishes above-mentioned fuel gas and the service of fuel gas are coupled together.
4. the method for operation of a fuel cell, this fuel cell comprise that antianode is supplied with the fuel gas that comprises hydrogen, the gas supply pipe road that target is supplied with oxidant gas respectively, it is characterized in that:
Supply with above-mentioned fuel gas and above-mentioned oxidant gas,, then, resistance be connected between above-mentioned anode and the above-mentioned negative electrode external loading being connected between above-mentioned anode and the above-mentioned negative electrode and after generating electricity, cutting off the said external load,
Stop to supply with above-mentioned oxidant gas, above-mentioned negative electrode is supplied with inactive gas, the current potential of above-mentioned negative electrode is lower than after the generation current potential that equals hydrogen, supplies with under the state of above-mentioned inactive gas and above-mentioned fuel gas stopping, taking care of,
Wherein, the voltage when fuel cell running is that the electric current that flows in A volt, the external loading is the gas effciency of B ampere, fuel gas when being C%, and resistance value R ohm of resistance satisfies following formula:
R≥(A×C)/(B×100)。
5. the method for operation of a fuel cell, this fuel cell comprise that antianode is supplied with the fuel gas that comprises hydrogen, the gas supply pipe road that target is supplied with oxidant gas respectively, it is characterized in that:
Supply with above-mentioned fuel gas and above-mentioned oxidant gas,, then, resistance be connected between above-mentioned anode and the above-mentioned negative electrode external loading being connected between above-mentioned anode and the above-mentioned negative electrode and after generating electricity, cutting off the said external load,
Stop to supply with above-mentioned oxidant gas, the current potential of above-mentioned negative electrode is lower than and equals to produce after the current potential of hydrogen, the space that is communicated with above-mentioned anode and with space that above-mentioned negative electrode is communicated with in fill above-mentioned fuel gas, take care of,
Wherein, the voltage when fuel cell running is that the electric current that flows in A volt, the external loading is the gas effciency of B ampere, fuel gas when being C%, and resistance value R ohm of resistance satisfies following formula:
R≥(A×C)/(B×100)。
6. the method for operation of a fuel cell, this fuel cell comprise that antianode is supplied with the fuel gas that comprises hydrogen, the gas supply pipe road that target is supplied with oxidant gas respectively, it is characterized in that:
Supply with above-mentioned fuel gas and above-mentioned oxidant gas,, then, resistance be connected between above-mentioned anode and the above-mentioned negative electrode external loading being connected between above-mentioned anode and the above-mentioned negative electrode and after generating electricity, cutting off the said external load,
Stop to supply with above-mentioned oxidant gas, the current potential of above-mentioned negative electrode is lower than and equals to produce after the current potential of hydrogen, with space that above-mentioned anode is communicated with in filling fuel gas, with space that above-mentioned negative electrode is communicated with in dispose reducing agent, take care of,
Wherein, the voltage when fuel cell running is that the electric current that flows in A volt, the external loading is the gas effciency of B ampere, fuel gas when being C%, and resistance value R ohm of resistance satisfies following formula:
R≥(A×C)/(B×100)。
7. the method for operation of a fuel cell, this fuel cell comprise that antianode is supplied with the fuel gas that comprises hydrogen, the gas supply pipe road that target is supplied with oxidant gas respectively, it is characterized in that:
Supply with above-mentioned fuel gas and above-mentioned oxidant gas,, then, resistance be connected between above-mentioned anode and the above-mentioned negative electrode external loading being connected between above-mentioned anode and the above-mentioned negative electrode and after generating electricity, cutting off the said external load,
Stop to supply with above-mentioned oxidant gas, the current potential of above-mentioned negative electrode is lower than and equals to produce after the current potential of hydrogen, stops to supply with above-mentioned fuel gas, the space that is communicated with above-mentioned anode and with space that above-mentioned negative electrode is communicated with in dispose reducing agent, take care of,
Wherein, the voltage when fuel cell running is that the electric current that flows in A volt, the external loading is the gas effciency of B ampere, fuel gas when being C%, and resistance value R ohm of resistance satisfies following formula:
R≥(A×C)/(B×100)。
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH01128362A (en) * | 1987-11-13 | 1989-05-22 | Hitachi Ltd | Operating method for fuel cell |
| US6399231B1 (en) * | 2000-06-22 | 2002-06-04 | Utc Fuel Cells, Llc | Method and apparatus for regenerating the performance of a PEM fuel cell |
| US6635369B2 (en) * | 2000-05-22 | 2003-10-21 | The Regents Of The University Of California | Method for improving fuel cell performance |
| CN1501537A (en) * | 2002-10-08 | 2004-06-02 | Nec东金株式会社 | Fuel regeneratable fuel cell, system and method for power generation, and fuel regenerating method |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH01128362A (en) * | 1987-11-13 | 1989-05-22 | Hitachi Ltd | Operating method for fuel cell |
| US6635369B2 (en) * | 2000-05-22 | 2003-10-21 | The Regents Of The University Of California | Method for improving fuel cell performance |
| US6399231B1 (en) * | 2000-06-22 | 2002-06-04 | Utc Fuel Cells, Llc | Method and apparatus for regenerating the performance of a PEM fuel cell |
| CN1501537A (en) * | 2002-10-08 | 2004-06-02 | Nec东金株式会社 | Fuel regeneratable fuel cell, system and method for power generation, and fuel regenerating method |
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