CN101536237A

CN101536237A - Passive recovery of liquid water produced by fuel cells

Info

Publication number: CN101536237A
Application number: CNA2007800414471A
Authority: CN
Inventors: A·莫斯曼; B·威尔斯; R·巴顿; H·沃斯
Original assignee: PolyFuel Inc
Current assignee: PolyFuel Inc
Priority date: 2006-11-07
Filing date: 2007-11-06
Publication date: 2009-09-16

Abstract

Passive recovery of liquid water from the cathode side of a polymer electrolyte membrane through the design of layers on the cathode side of an MEA and through the design of the PEM, may be used to supply water to support chemical or electrochemical reactions, either internal or external to the fuel cell, to support the humidification or hydration of the anode reactants, or to support the hydration of the polymer electrolyte membrane over its major surface or some combination thereof. Such passive recovery of liquid water can simplify fuel cell power generators through the reduction or elimination of cathode liquid water recovery devices.

Description

The passive recovery of the aqueous water that fuel cell produced

The application is 60/864 according to the sequence number that 35U.S.C. § 119 (e) requires on November 7th, 2006 to submit to, the sequence number that on September 4th, 767 and 2007 submitted to is 60/969, the rights and interests of 890 U.S. Provisional Application are clearly incorporated described provisional application into this paper by reference.

Technical field

Disclose novel polyelectrolyte membrane and/or negative electrode, they can passively be recovered in the aqueous water that negative electrode produced of fuel cell.

Background of invention

At fuel cell, for example the existing well-known problem of using in the direct methanol fuel cell (DMFC) of polyelectrolyte membrane (PEM) is to the recovery from the water of negative electrode, described water not only is used for the hydration of PEM itself but also be used for being incorporated into the anode fuel reactant flow again, wherein for the situation of DMFC, it is used as the reactant and the diluent of methanol fuel simultaneously.Water is also as one of reactive material in the fuel reaction of the PEM fuel cell of other type, and these types are included in respond those or compound (as sodium borohydride) and the water reaction of (as the reformation of hydrocarbon fuel) of fuel cell outside and produce those of hydrogen.Water can also be used for the reactant gas flow in the anode chamber that enters fuel cell is carried out humidification.

Routine " initiatively " solution of this problem is comprised that condenser and liquid separator are placed on negative electrode discharges in the logistics (exhaust stream), so that collect aqueous water, returns this water metering to anode loop then.

Summary of the invention

The objective of the invention is to reclaim at least a portion in the following water: the water that is produced in the electrochemical reaction at (1) negative electrode place; (2) move to the water of cathode catalyst layer from anode along with the ion flow from the anode to the negative electrode; And/or (3) other form is present in the water of negative electrode, may come from the direct oxidation that strides across the fuel of (across) PEM from the anode-side diffusion.This water is called " negative electrode water " sometimes at this paper.Negative electrode water can be guided to anode itself, be used for reaction or be used for the fuel moisturization purpose, or it is guided to the fuel reaction chamber, to be used for fuel reaction.

Fuel cell membrane electrode assembly (MEA) contains the polyelectrolyte membrane of making from ionic conductive polymer (PEM).This PEM contains passage aisle between relative (opposite) surface at PEM through modification.These passages make aqueous water can flow to the anode-side of PEM from the cathode side of PEM under enough pressure.This PEM is called water penetration (water permeable) PEM sometimes

PEM has relative anode and cathode surface.To cause water migration (transport) by the needed pressure of PEM passage in order producing, to exist aqueous water to intercept (LWB) layer on the cathode side of PEM.This layer conducts electricity, and has high gas diffusibility, arrives cathode catalyst layer to allow oxygen, but liquid towards water flows and has tangible impedance.In operating process, this fuel cell produces water on the cathode side of PEM.In this embodiment, the LWB layer is enough to separately to reduce mobile that aqueous water flows from the negative electrode to the cathode oxidant, produce enough hydraulic pressure back pressures (hydraulic back pressure) thus, cause aqueous water to flow to the anode-side of PEM by the PEM passage from negative electrode.

In another embodiment, gaseous diffusion obstruct (GDB) layer is used in combination with the LWB layer.The GDB layer is a conductivity in many embodiments.Yet, in adopting the plane, do not need it to conduct electricity in some embodiments of (in-plane) electric current collection.The GDB layer can limit steam and flow to cathode oxidant stream.Yet it has enough diffusibilities of gases, arrives cathode catalyst layer to allow oxygen to pass it.

In some cases, there is liquid water distribution (LWD) layer between the cathode surface of PEM and the LWB layer.This layer is conductivity, and allow aqueous water in the plane upper side parallel with the cathode surface of PEM to moving.This layer can be used in and promote water to move to the PEM passage and/or be used to provide the side direction of residual water is collected (lateral collection).If catalyst is added in the LWD layer, then it also is used as the catalyst layer of cathodic oxygen reduction reaction or other cathode interface chemical reaction.

Calibrating gas diffusion layer (GDL) can with these layers in any one or all be used in combination, and generally place, to avoid and cathode oxidant stream interacts away from the PEM cathode surface.

The present invention also comprises combining with standard P EM or at water penetration PEM disclosed herein and is used for the negative electrode that control cathode water flows.

In one embodiment, negative electrode is from GDB layer and the preparation of LWB layer.In another embodiment, can prepare monolayer cathodes, it has the performance of GDB and LWB layer.This monolayer cathodes also can use with LWD layer and/or GDL.Perhaps, can use GDB/LWB printing ink on standard GDL surface, to form this individual layer.

In another embodiment, negative electrode is from GDL and the preparation of GDB layer.This negative electrode can further contain the LWB layer, and its position makes the GDB layer between GDL and LWB layer.This negative electrode also can comprise the LWD layer, and its position makes the LWB layer between LWD layer and GDB layer.

In another negative electrode embodiment, negative electrode contains LWB layer independent or that combine with GDL and LWD layer.

In another embodiment, replace using wherein anode and cathod catalyst to be applied over CCM on this film, these catalyst put on the gaseous diffusion layer assembly, then under pressure and temperature in conjunction with so that form mechanical bond with PEM.With regard to negative electrode, electrocatalyst for cathode is put on the layer of next-door neighbour PEM, described layer can be LWB layer or LWD layer.

Membrane electrode assembly (MEA) prepares the catalyst coated membrane (CCM) of self-contained polyelectrolyte membrane (PEM) and catalyst layer, and any above-mentioned negative electrode, or from being incorporated into the catalyst coat cathode assembly preparation of PEM.This PEM can be standard P EM or water penetration PEM disclosed herein.

Fuel cell contains above-mentioned MEA.

The fuel cell system that uses water penetration PEM is also disclosed.Water penetration PEM allows to use the fuel that highly concentrates, and as pure methyl alcohol, need not to provide water as diluent.In this type systematic, the enriched fuel source is communicated with the anode loop fluid, the latter and then be communicated with water penetration PEM fluid.The LWB layer is placed on the cathode side of water penetration PEM, so that generation causes that the migration of enough residual water is with the needed hydraulic pressure of the hydration of keeping anode reaction and/or PEM.Except the LWB layer, any or multiple passive recovery (passive recovery) that also can be used for promoting residual water in the above-mentioned layer.

The fuel cell system that adopts standard P EM is also disclosed.In these embodiments, suitable negative electrode is selected from those negative electrodes that above definite passive water of promotion reclaims.

The accompanying drawing summary

Figure 1A shows has a plurality of water penetration PEM that cross the flow channel of PEM from the negative electrode to the anode surface.

Figure 1B shows the MEA cross section that shows laser drill.The outlet diameter in hole is 2 microns.By under vacuum, using the epoxy resin backfill, and carry out follow-up polishing and prepare cross section; The part in hole shows that this hole partly filled by epoxy resin.

Fig. 2 shows water penetration PEM, and it has water penetration zone and waterproof zone.

Fig. 3 is can be individually or be used for being formed for the schematic diagram of various layers of the negative electrode of passive recycle-water in combination.

Fig. 4 shows the cross section of the cathode side of membrane electrode assembly.Aqueous water barrier layer and gas diffusion barrier limit liquid water and steam and flow to the cathode air circulation road from cathode catalyst layer.The aqueous water Distribution Layer is a water penetration, and be used for aqueous water away from the lateral flow of cathode catalyst layer to carry out lateral edge and collect or to be used for the water penetration zone of liquid water stream to PEM.

Fig. 5 shows the fuel cell system that comprises methanol source, anode loop and fuel cell, and this fuel cell contains the MEA that fuel cell is divided into anode chamber and cathode chamber.When water penetration PEM was used in combination with the aqueous water barrier layer, aqueous water is directly from the cathode system anode, and was represented as arrow.Perhaps, standard P EM can be used for providing the side direction of water to collect, and it can be used for other purpose, transfers to anode loop as negative electrode water.

Fig. 6 shows disclosed fuel cell performance among the embodiment 2.

The fuel cell that Fig. 7 shows embodiment 2 is through the performance after 500 hours.

Detailed Description Of The Invention

The negative electrode of water penetration PEM and control cathode water migration is disclosed. This PEM and negative electrode can make together With, with produce can passive recycle-water MEA. Perhaps, they can use separately, in this feelings Water penetration PEM uses with standard cathode under the condition, and standard P EM makes with negative electrode disclosed herein With.

Cathode electrode comprises and has the liquid water and steam of restriction from the cathodic migration to the oxidant and/or cooling agent One or more layers of the performance of air stream. Along with the cathode side at PEM produces aqueous water, at the moon These layers in the utmost point electrode promote the generation of aqueous water pressure.

This water penetration PEM comprises and transform the integral passage (integral that has by PEM as Passageway) ion conductive polymer layer, this passage allow water from the cathodic migration of PEM to sun Utmost point side.

Fuel cell

Main purpose of the present invention provide to a part form in the fuel battery negative pole place aqueous water or The passive water that is migrated to the aqueous water of fuel battery negative pole reclaims. In some cases, with a part Recycle-water is transferred to anode loop, to promote anode electrochemical reaction (1 molecular water and 1 minute among the DMFC Sub-methyl alcohol reaction produces carbon dioxide, proton and electronics). The water yield that needs to reclaim preferably is equal to or greater than Following summation: the water yield that consumes in (1) anodic oxidation reactions, in the situation of DMFC Lower, it is 1/3rd of the water that produces from the electrochemical reaction of proton, electronics and oxygen on negative electrode; (2) Via diffusion or electro-osmosis hinder (electro-osmotic drag) or by alternate manner from polymer electrolytic The water yield of the anode-side migration of plasma membrane; (3) via gas-liquid separator (for example at DMFC In the situation, the separator of separating carbon dioxide from liquid fuel) can from anolyte fluid fuel stream, leave The water yield; (4) can be from fortune by alternate manner (such as the regular purging of the fuel flow in the hydrogen-air fuel cell) The water yield that consumes in the anode fuel stream that is turning to.

Its of employing polyelectrolyte membrane (PEM) and use hydrogen, organic-fuel or fuel blends The passive water that its fuel cell also will be benefited from from the negative electrode to the anode reclaims, because the ion guide of this type The known features of motor reason (polyelectrolyte membrane) is that electro-osmosis hinders (electro-osmotic drag), according to This and so that the proton ion that moves to negative electrode from anode typically carry out " hindering (drag) " or they and The hydrone of moving to negative electrode from anode combines. Although the definite mechanism of this " electro-osmosis obstruction " still So be main topic of discussion, but observe, exist and the proton that causes in the water consumption at anode place The water purification migration (net water transport) from the anode to the negative electrode that flux is relevant, described water consumption also Cause the consumption of water in the various piece of PEM. As everyone knows, has ionic conduction sulfonic group (ion Conducting sulfonate groups) needs hydrone among the PEM, in order to make PEM keep foot Enough ionic conductivities are to support required electrochemical reaction. If with the functionalized sulfonic group among the PEM The local concentration of the water that approaches descends significantly, and then the local ion electric conductivity of PEM also descends, and leads The part that causes performance (current density or the electrochemical reaction speed under given cell voltage) descends, this Be harmful to the performance of fuel cell itself and can cause infringement or unsafe operating condition (if this is at fuel Take place unevenly between the battery in the battery pile assembly (fuel cell stack assembly)). In addition, Industrially wish (for example, being illustrated by the U.S.'s DOE technical goal that is used for the PEM fuel cell) Reduce the amount of the additional water that offers fuel cell itself. This hope enters combustion by reducing operating period Humidification or the dividing potential drop of the steam of material battery represent. The passive recovery of negative electrode residual water promotes from the moon Extremely replenish anode-side water, this causes the improvement of performance and durability potentially, and may allow lower Operate under the entrance reactant gas humidity level. It promotes the water in the PEM to keep in addition, and Moisture on the plane domain of PEM is joined.

In addition, have the fuel cell of other type, wherein water is reactive material, but water is not at the fuel electricity In the pond itself, but water is used for the course of reaction of fuel cell outside. The fuel cell of these types Example is (reformed) methanol fuel cell of reforming, and wherein (higher temperature is urged at reformer for methyl alcohol and water Change the agent bed process) middle reaction, mainly produce carbon dioxide and hydrogen; And chemical hydride (its example is Sodium borohydride) fuel cell, wherein water is used as one of reactant with the chemical hydride reaction, to produce hydrogen Gas. The application of the invention, passage be collected and be conducted through to residual water can from the PEM fuel cell Or mobile mechanism arrives the course of reaction of this fuel cell outside. Water collecting manifold in the fuel cell can be used Work guides to a kind of mechanism of external fluid path with the residual water of the recovery in the fuel cell, as from fuel Battery is to pipeline or the pipeline of response location.

Passive water reclaims

Passive water reclaims the water recovery that refers to from the cathode side of fuel cell, and it is not involved in fuel cell itself Outside additional member (component) carry out from negative electrode waste liquid (exhaust) stream, collecting water (that is, Condenser, water collector, water pump or be used for this type of water is led back to anode fuel from the cathode oxidant waste liquid Other mechanism of stream). Via pipeline, pipeline, manifold, passage or have the resistance of flowing of enough low aqueous water The fluid of other mechanism of power connects the water that can be used for reclaiming and guides to desired location, and can not make water big Amount is lost to other position. The non-passive recovery of water normally needs the power of some form with collected Water guides to desired location, there water is used for electrochemical reaction or discharging (rejected) to environment In or collect for from now on use. It is further typically representing the extra heat of system load, make water from The condensation of steam attitude also guides to desired location with this water.

It is favourable that passive water reclaims for electric generator using fuel battery, because it simplifies the design of this system, Reduce size, weight and the cost of this system, and make fuel cell system have higher summation watt rating With weight power and volume energy density and weight energy density, all these are highly welcome spies Levy.

The present invention describes many modes, can realize reclaiming from negative electrode liquid at inside battery according to these modes Water, and reboot into anode, and the component of a system that need not to add. The present invention further describes many sides Formula can guide to the water that reclaims member outside the fuel cell itself according to these modes, thereby can Utilize this water.

All modification of this aqueous water take-back strategy can be used for having the current that run through the plane and collect In a kind of planar array or a kind of stack configuration of (through-plane current collection). They also can use with the oxidant-cooling agent strategy of associating, or with more conventional low discharge, hypoxemia Changing the oxidizer source of agent stoichiometric proportion and independent heat loss position (for example hands in the liquid heat of fuel circuit Parallel operation or independent liquid cooling loops) use together.

All modification of the present invention are utilized the key physical principle of the capillary pressure in the hydrophobicity hole, wherein liquid Attitude water will preferentially penetrate larger-diameter hole, make only gassy of small diameter hole network.

Water penetration PEM

In one embodiment, water penetration PEM has whole aquaporin, and this passage is from the sun of PEM The utmost point crosses PEM to cathode surface, as shown in fig. 1. Water penetration PEM has the group of following characteristics Close: wherein (1) on aspect of its surface, it have ionic conductivity, low fuel diffusivity, Low water penetration does not exist any flow channel that aqueous water uses and (2) another side on its surface On the face, it has high water permeability, through architectural feature (through features), for example phase Overall flow passage (or passage) between the effects on surface, it allows the aqueous water migration to stride across this film. Aqueous water Migrating channels can consist of the aperture among the PEM, can after making PEM, pass through machinery, static, Heat (such as laser) or alternate manner form these apertures. The aqueous water migrating channels also can be in the manufacturing of PEM Form by comprising pore former in the process, this pore former produces a surface from PEM to another The flow channel on surface. Can be little by producing with blend polymer in the formation of PEM Flow channel, wherein a kind of component of polymer has low permeability resistance for aqueous water, another kind of polymerization Thing has high permeability resistance for aqueous water. At least a in the above-mentioned polymer (preferably has high That of permeability resistance is a kind of) must have the ionic conduction ability. Blend polymer also can contain other and gather Compound, it can induce the function outside deionization or the aqueous water migration. Another embodiment is used poly-The carrier matrix of compound (such as EPTFE or other suitable material) makes the size stabilization of PEM, can The infiltration water structure can pass through one or more aforesaid way at the carrier base in the forming process of film Produce in the matter or produce flow channel after the PEM and in carrier matrix, produce by forming. Other is real The scheme of executing is used multilayer PEM, and wherein at least one deck of multilayer PEM has high and low penetration by liquid water concurrently The property architectural feature.

The planar surface region in the higher water penetration zone of PEM is preferably 0.000001～50%, and more preferably 0.000001～1%, most preferably 0.000001～0.001%.Yet, the selection of fluid power pore size (hydraulicpore size), contain the percentage on PEM surface of hole and the running parameter that fuel cell will be depended in their interval, and can use definite (re:150mA/cm2 that vide infra design) by rule of thumb at each.Preferably, the higher percent of PEM planar surface region has low infiltration and diffusion and less percentage that should the zone has higher penetration by liquid water performance, that is, the ratio of the cross section of the cross section of high permeability for liquids and low permeability for liquids is lower than 1.The thickness of PEM is usually less than 200 microns, preferably is lower than 100 microns, more preferably less than 25 microns.The effective hydraulic diameter (effective hydraulic diameter) that runs through this type of passage of described PEM is the 1-25 micron normally, preferred 2-10 micron, more preferably 2-5 micron.

The example of PEM with autonomous channel pattern has been shown among Figure 1A.Figure 1B shows one cross section in the passage that is formed by laser.This passage is 2 microns at the diameter of its stenosis.Diameter in the hole of laser entrance is about 7 microns.Part near the hole that enters the mouth is filled with epoxy resin, and this epoxy resin is used to make the cross section sample of using for microscopic analysis.Hydraulic diameter is the minimum diameter in given passage.In this case, hydraulic diameter is about 2 microns.Fig. 2 has the zone of water permeable and the plan view of PEM in zone shown in figure 2 not.

Negative electrode

The member of negative electrode is shown among Fig. 3 and Fig. 4.These members can combined in various manners, to form negative electrode of the present invention.

Negative electrode comprises a plurality of layers combination, and described layer has the liquid water and steam of restriction from the cathodic migration to the oxidant and/or the performance of flow of coolant air.Along with produce aqueous water on the cathode side of PEM, these layers in the cathode electrode promote the generation of aqueous water pressure.

(a) aqueous water barrier layer

Key element in the negative electrode is " aqueous water barrier layer " (LWB layer), and it is the layer in negative electrode, and this layer is conductivity, permeable gas (comprising oxygen and steam) to a certain extent, but aqueous water is impermeable basically.This liquid barrier can be characterized by wherein needs pressure to induce aqueous water to move through a kind of barrier layer of this layer.Above-mentioned pressure is enough to greater than the highest fuel pressure, adds that aqueous water penetrates the pressure loss of this PEM, adds the summation of liquid flow loss in the plane in the water Distribution Layer, makes aqueous water rationally be uniformly distributed in the whole surface of described PEM.This type of aqueous water pressure is usually more than or equal to 30kPa (4.35psi), but can be regulated by those skilled in the art of the present technique, and this depends on the design of fuel cell member.

The aqueous water barrier layer can form the conducting medium from porous, and for example the typical case uses it carbon and/or graphite powder, special teflon then as the carbon fiber paper of gas diffusion layers in the PEM fuel cell industries

(PTFE and/or FEP) and other liquid ink slurry composition dipping.Then with this carbon/special teflon

Slurry heats makes liquid evaporation, special teflon

Both can make carbon particle fixing in position, again because special teflon as binding agent Hydrophobic property and the impedance that can produce the liquid towards water permeability.Have several commercially available materials, they contain special teflon Binding agent is used for carbon and/or graphite powder are remained in the gas diffusion layers, but major part does not demonstrate the remarkable flow resistance of liquid towards water.Can use simple and easy moulding bed (simple jig) to measure this liquid water stream dynamic resistance, simple and easy moulding bed is measured the pressure with respect to the water of the flow velocity in a certain zone of passing material.This type of test typically shows, for the aqueous water barrier layer, require to have certain pressure before flowing through this material observing any measurable water, typically have the linear relationship between aqueous water flow velocity and the aqueous water pressure after this, this is that porous media flow is desired.Induce mobile initial pressure of water and aqueous water flow velocity that (relation curve) slope of water pressure all be can be used to select suitable material.In the present invention, use candidate's layer (material and manufacture method) of selecting to be used for the aqueous water barrier layer greater than the pressure of 30kPa water pressure with optimization.Characterize on the methodological principle that water flows through negative electrode LWB layer similar with the method for the water pressure that is used for characterizing the water-fast cloth (for example EN343) that is used to penetrate gas permeability.

The resistance that liquid towards water flows in the aqueous water barrier layer is mainly caused by the network of little hydrophobic pores.Flowing of these hole restriction water, this produces the hydraulic pressure that aqueous water is used on the interface of aqueous water barrier layer and cathode catalyst layer or in aqueous water Distribution Layer (seeing below) (if exist, it is between cathode catalyst layer and aqueous water barrier layer).This pressure directly guides to passage among the PEM with aqueous water, or guiding to some zones via the aqueous water Distribution Layer indirectly, water can move the plane of passing catalyst layer and the flow channel that passes with the Surface Vertical of PEM arrives anode chamber in these zones.The aqueous water pressure inducement aqueous water that is caused by liquid barrier flows.But the common deficiency of this pressure is so that the penetration by liquid water of real mass is crossed this aqueous water intercepts, and is not enough to also cause on those zones of the low penetration by liquid water of having of PEM surface that the penetration by liquid water of real mass passes this PEM itself.Yet, this pressure is enough to make liquid cathode water: (1) with the liquid Distribution Layer in the parallel plane plane of MEA on flow, (2) flow through catalyst layer, and (3) flow through PEM arrival anode-side via the zone (as the through-flow passage) of the high permeability for liquids among the PEM from cathode side.Situation for (3), also aqueous water might be guided to PEM and divide the flow channel of opening, and directly guide this water to the anode logistics, for example guide to the fluid manifold that is communicated with described fuel stream fluid or guide to can be outside fuel cell fuel treating equipment.The aqueous water barrier layer is not to intercept completely; But it has enough gas porositys so that gaseous material (as oxygen, nitrogen, steam, carbon dioxide and methyl alcohol etc.) can spread, thereby diffuses through it with the speed of the electrochemical reaction that can keep the negative electrode place.Yet its liquid towards water flows through the plane sizable resistance, and this can measure by the pressure of inducing this one deck of penetration by liquid water.

Usually be not enough to promote penetration by liquid water by aqueous water at the aqueous water pressure that accumulation produced on the liquid barrier and pass the conventional PEM film that thickness is 50～175 microns (measuring) under drying regime.Yet this pressure can be enough to cause that the water migration strides across thin film.In addition, liquid barrier can with perfluorinated membranes, use together as the Nafion that makes by E. I. Du Pont de Nemours and Co (E.I.du Pont de Nemours and Company), combine separately or with the formation that strides across the Nafion membrane channels.

(b) gas diffusion layers

Gas diffusion layers (GDL) is the layer of typical case's preparation from carbon fiber, and it has high-caliber porosity under non-compressed state, usually greater than 50%.It also prepares from conductive material in certain embodiments.The functional requirement of GDL is that it must allow this reactive material and reactor product material turnover collector plate or flow-field plate and pass in and out the electro-catalysis layer that reacts, and may pass the intermediate layer.In some embodiments, GDL also is a current collector, and electronics can ' in the plane ' be walked in GDL in this case.For carbon fiber type GDL, this fiber can be orientated, with the situation of weaving material (as carbon cloth), or randomly be orientated, for example for the situation of the carbon fiber paper mold product of making from the slurry of the carbon fiber of all lengths, and evaporation and make potentially in the slurry resin carbonation or even graphitization so that between carbon fiber, produce bonding, so that they are together adhering to each other.Also have other method to prepare carbon fiber type GDL, they are not described at this paper but are well known in the art.In addition, also can be used as the alternative materials of GDL in addition, for example the graphite material of woven wire and perforation with high porosity and suitable diffusion property.

(c) gaseous diffusion barrier layer

Preferably gaseous diffusion barrier layer (GDB) layer is inserted between liquid barrier and the cathode gas diffusion layer, though it can be inserted between gas diffusion layers and the oxidizer flow passage.Gas-barrier layer has low gas permeability, also can be hydrophobic.The purpose of this layer is to limit steam passes this layer arrival oxidant air stream from cathode catalyst layer diffusion rate to a certain extent, and make reactive material oxygen pass this one deck from oxidant air stream with enough diffusivitys, pass the aqueous water barrier layer, pass aqueous water Distribution Layer (if existence) and arrive cathode catalyst layer, to support and to keep this electrochemical reaction.Because the migration mechanism of steam and oxygen is a gaseous diffusion, the fuel battery operation temperature that the diffusion of gaseous diffusion barrier layer can about 45-60 degree centigrade is an in addition optimization of basis.The diffusion rate that gas passes the gaseous diffusion barrier layer is partly handled in adjusting to fuel battery temperature.Because electrochemical reaction of fuel battery is heat release, fuel cell utilizes cooling mechanism (arriving surrounding air as heat exchange) usually, to regulate the temperature of this fuel cell itself.The notion that gaseous diffusion intercepts has been disclosed in US patent 6 451470, in " Gas Diffusion Electrode with Reduced Diffusing Capacity for Waterand Polymer Electrolyte Membrane Fuel Cells ", Koschany etc., assignee: Magnet-Motor Gesellschaft f ü r Magnetmotorlsche Technik mbH (Germany).

The gaseous diffusion barrier layer can pass through to form the microporous layers of conductive particle (as carbon or graphite), and uses binding agent (for example one or more following material: PVDF, PTFE, FEP) to produce.The another kind of method that produces the gaseous diffusion barrier layer is to form thin conducting film, and this film has pore former to be included in wherein in forming process and this pore former can be removed after film forms, and keeps required diffusivity.Those skilled in the art can use other method to produce target diffusivity scope.

In some embodiments, GDB is put on GDL, this restriction gas is by its diffusion rate.Compare with GDL, it has extremely low diffusivity.This GDB can form by the mixture that applies carbon, graphite and PTFE, so that forms the sublayer (sublayer) of low pore fraction.

Flowing of GDB layer opposing steam, but allow oxygen to have enough diffusivitys to pass through this layer.The GDB layer has the diffusion relevant with operating temperature with required battery-operated current density, as shown in Table I:

Table I

In addition to the foregoing, the gross mass migration performance of gas-barrier layer (overall mass transportproperties) can be optimised in the 0.001-0.0015m/sec scope, based on about 50 degrees centigrade operation of fuel cells temperature.

Therefore, required system operation point (temperature, current density) is used for determining that the desired cathode gas diffusion that has intercepts the steam quality transport coefficient scope of (GDB) layer.

Foregoing has been described independent LWB and the use of GDB layer in making negative electrode.Yet the performance of these individual courses can be combined in the single layer.For example, LWB/GDB printing ink can form coating in the plastics test piece, has the single layer of the performance of LWD and GDB layer with preparation.Perhaps, this LWD/GDB printing ink can directly form coating on GDL.Embodiment 1 has described by apply the method for optimizing that this LWB/GDB printing ink forms this type of layer repeatedly on gas diffusion layers.

(c) aqueous water distributes (LWD) layer

Aqueous water Distribution Layer (if existence) is inserted between cathode catalyst layer and the liquid water barrier layer of negative electrode.Perhaps, it can be the intrinsic part of cathode catalyst layer itself.Typically, the aqueous water Distribution Layer is transparent for aqueous water, steam and gas (as oxygen), but has than lower porosity of above-mentioned GDB layer and the hydrophobicity of Geng Gao.The purpose of this one deck is to make aqueous water realize the combination than large diameter hole (combination) that fluid is communicated with by major part in the plane upper side of PEM to motion (flow resistance in low plane).This type of hole is dispersed in the matrix little, the high hydrophobicity hole (matrix) in this layer or in the flow channel, aqueous water moves in the zone of catalyst layer in view of the above, and these zones are among the zone line in the middle of the height water penetration zone of PEM.Negative electrode water flows through catalyst layer and PEM arrival anode chamber from the liquid Distribution Layer, and this aqueous water can participate in fuel oxidation reaction (for the situation of methyl alcohol) and may dilute fuel itself there.The aqueous water Distribution Layer be conductivity and have high diffusibility of gases, make the reactant gas material can move by this layer, to participate in electrochemical reaction to catalyst layer.This layer generally is hydrophobic, it make gas can diffuse through it, the interference networks (interconnected network) by the fine pore, and conducts liquid water to the network of the big weep hole of interconnection or passage (they have lower capillary sheet surface tension influence for aqueous water) and/or in this layer contained unitary side to flow channel.Flow channel also interconnects basically, and takes on the collection container (irrigation canals and ditches) of aqueous water.Effectively Test Liquid Permeability of Core should be 1 * 10 in the plane ^-8～2 * 10 ^-10Cc/sec Pa.Fig. 4 has shown an example of the mobile passage of LWD aqueous water that can produce in the forming process of LWD layer.Another case description of the notion of aqueous water Distribution Layer perforation (through) flow channel is in United States Patent (USP) 6,890,680 " Modified Diffusion Layer for Use in a FuelCell System " (Beckmann etc.) and United States Patent (USP) 7,179, among 501 " Modified DiffusionLayer for use in a Fuel Cell System " (Beckmann etc.), both have all transferred MTI MicroFuel Cells.

The distinguishing characteristics of LWD layer and LWB layer is to induce water to move through the size of the needed pressure of this layer itself.If a large amount of water pressure of this layer needs induces aqueous water to move, and do not have available path to move under this pressure for aqueous water, then pressure can run up to it and can induce water to flow through the degree of this layer.Such pressure is normally low-down for the LWD layer, and in fact can not be used to guide water to pass through PEM, by the path of engineering design, by this PEM itself or by other flow channel.In addition, this type of LWD layer has high diffusion or permeability usually, and it can fully not reduce the mobility of steam by this layer.On the contrary, the LWB layer needs higher aqueous water pressure to induce aqueous water to move through it.Reach enough pressure at aqueous water and promote its migration by before the LWB layer, this water is conducted through than the low flow resistance path, arrives anode by the LWD layer with by PEM.

The water infiltration is visibly different by normal PEM (as the Nafion film) with by the needed pressure of water penetration PEM disclosed herein.People such as Ren (WO 2004/093231) disclose and have worked as battery at 100mA/cm ²Under when operating, the pressure of 3.2 atmospheric pressure (about 50psi) is used for Nafion 112 (2 mils or 50 micron thickness films).In addition, people such as Ren also discloses 11.3 atmospheric pressure and is used for Nafion 117 (7 mils or 175 micron thickness films).We before for embodiment in the similar PEM of film observe 150mA/cm ²Operating current need the pressure of 100psi, be the basis with some outside tests (that is, not having actuating battery).These pressure may be unpractical for the fuel cell design of routine.

Otherwise, the needed hydrostatic pressure height of the enough current of acquisition from the negative electrode to the anode depends on the flow resistance and the current density (therefore the lower less current of electric current needs need lower resistance and lower pressure) of the size in hole, the distribution in hole (these spans how far), liquid Distribution Layer.

Table II has shown that the film that uses 20 micron thickness is at 150mA/cm ²Following hole and the pressure drop for various pitchs of holes for one group of various diameter.Can easily find out, more intensive needs lower hydrostatic pressure to stride across them to realize the required flow rate that passes through them than macropore, corresponding with the required current from the negative electrode to the anode (water that 1/3 electrochemical means produces adds that whole electro-osmosis hinder (Electro-Osmotic Drag) (EOD) water, ignore the water that is produced by the diffusion of the methyl alcohol from the anode to the negative electrode).

Table II

Table III has shown the flow blockage pressure loss in the highest plane of different pitchs of holes, depends on the plane intrinsic permeability.The spacing in hole is big more, and the pressure loss is high more.

Table III

For example, the MEA based on the DM-2 film in embodiment 2 has 2 microns holes and 2mm pitch of holes.At 150mA/cm ²Down, promoting enough water passes these holes and needs 33kPa (4.8psi).In addition, the plane intrinsic permeability of the aqueous water Distribution Layer of cracking is 1 * 10 ^-10/ (sec-Pa), without any the cracking the layer permeability be 1 * 10 ^-12Cc/ (sec-Pa) (more not preferred).Use 1 * 10 ^-11The intermediate value of cc/ (sec-Pa), the pressure loss that flows through LDL for the 2mm pitch of holes are 83kPa (12psi).The required hydrostatic pressure that promotes enough water adds up to 116kPa (16.8psi).

DM-2 film with 5 microns holes of 2mm spacing needs 0.83kPa (0.12psi).If using the plane intrinsic permeability is 1 * 10 ^-10The LWD layer of the cracking of cc/ (sec-Pa) then needs other 8.3kPa (1.2psi).At 150mA/cm ²Operating point, these of total will need the hydrostatic pressure of 9.1kPa (1.32psi) to reach the enough current from the negative electrode to the anode.

Optimal mode uses 5 microns holes, has optimized LWD layer and pitch of holes, and the hydrostatic pressure that approximately need be no more than 10psi promotes the water migration and strides across PEM.

The MEA embodiment

In one embodiment, MEA has the cathode construction that comprises with the combination of lower member: (1) GDL; (2) gas barrier diffusion layer, it carries out balance with the arrival cathode catalyst layer with the oxygen diffusion of keeping required reaction to the water vapor diffusion restriction of leaving negative electrode; (3) aqueous water barrier layer; (4) Ren Xuan side direction aqueous water migrating layer; (5) cathode catalyst layer and (6) PEM.PEM is permeable, and has at least two zones, and one of them zone has high water-permeability, and another has low permeability, as shown in Figure 3.

In another embodiment, above-mentioned MEA can have and possess rationally penetration by liquid water and the conventional PEM that has the fluid passage that crosses this PEM uniformly, thereby make the water that produces at negative electrode be communicated with anode fuel loop fluid, for example as shown in Figure 6 via this type of passage.

In other embodiments, the fluid passage is communicated with external fuel reative cell (as apparatus for reforming of fuel) fluid.

In another embodiment, MEA comprises the combination with lower member: (1) PEM, and the zone that it has high and low penetration by liquid water has the anode and the cathode surface of (opposing) relatively; (2) the liquid water barrier layer of conductivity negative electrode; (3) cathode gas diffusion barrier layer and (4) cathode gas diffusion layer.In this embodiment, there is not foregoing negative electrode liquid Distribution Layer.PEM has the diffusible fully well distributed zone of height water in its surface, make aqueous water easily move to these zones: the hole in the catalyst layer by in following one or more, the near interface of liquid barrier and catalyst layer hole, and/or the hole at the interface of catalyst layer and liquid barrier.Cathode catalyst layer is inserted between the liquid barrier and cathode surface of PEM, and have enough gas permeabilities and a permeability for liquids, thereby can carry out gaseous diffusion to support electrochemical reaction, can make the plane and the high permeability zones territory of carrying out plane in infiltration arrival PEM of penetration by liquid water again by MEA, thereby pass PEM, to prevent aqueous water gathering on negative electrode.Similar with existing embodiment, the aqueous water barrier layer is inserted between catalyst layer and the gas-barrier layer; Gas-barrier layer is inserted between liquid barrier and the gas diffusion layers; Gas diffusion layers is inserted in the gaseous diffusion barrier layer and contains between the gas stream of oxidant reaction material.

In another embodiment, MEA comprises the combination with lower member: (1) PEM, and it has uniform relatively penetration by liquid water, has relative anode and cathode surface; (2) Ren Xuan negative electrode liquid Distribution Layer; (3) the liquid water barrier layer of conductivity negative electrode; (4) cathode gas diffusion layer and the fluid passage in cathode gas diffusion barrier layer and (5) cathode assembly, they are with section between negative electrode liquid barrier and PEM and anode fuel loop fluid is communicated with or be communicated with external fuel reative cell fluid.

In another embodiment, MEA comprises water penetration PEM (or standard P EM) and negative electrode, and this negative electrode comprises and has as discussed above and at the single layer of LWB described in the embodiment 1 and GDB performance.This negative electrode can further comprise GDL and/or LWD layer.

Moisture is joined (water distribution)

There are two kinds of approach aqueous water can be guided in MEA.These embodiments are divided into two classes: plane formula (through-plane) water that runs through that a) passes PEM reclaims, and b) flow through the side direction water that passage carried out of not crossing PEM by aqueous water and reclaim.Table III has been summed up and has been run through the embodiment that PEM formula water reclaims (through PEM water recovery).

Table III

Table IV has been summed up side direction water and has been reclaimed.

Table IV

Running through PEM formula aqueous water reclaims

The PEM film can be used for water directly from the cathode transport to the anode.Typical PEM permeability of the membrane is not enough to realize sufficient aqueous water transmission.Make special P EM film, wherein thin especially film or have high water-permeability can film can be used for providing the transmission channel of the water from the negative electrode to the anode.But this type of face faces challenge, because they also allow the infiltration of fuel from the anode to the negative electrode.Preferably have the PEM of low and high water permeability concurrently, more preferably a few surface zone of PEM has high permeance property.Further preferably, will have the PEM that hangs down with high water permeability is used in combination with the cathode construction that comprises aqueous water barrier layer and gas-barrier layer.

The high osmosis of PEM can be able to produce by variety of way.They can produce by the form of PEM itself, when its (PEM) performance and combination of manufacture method when making by polymer itself.They also can make second kind of polymer properties be present in a few surface zone by PEM polymer and the another kind of polymer mixed with higher water permeability are produced and make film forming.Another kind method can be to use pore former in the manufacturing of film, causes pore former to enter into solution in the solvent removing this type of pore former by film is exposed to after the film manufacturing.In some cases, in the pore former water soluble itself.Other method can be to use the manufacture method of the control porosity that causes PEM itself: for example when it contains high-caliber residual solvent in water this film of quenching, frozen polymerization thing form under opened state more thus.Can be in manufacture process that film is biaxial stretch-formed, to produce porosity.In addition, also have some modes, wherein can produce little flow channel or hole in the ad-hoc location of PEM, these class methods can comprise: static discharge, machine drilling, laser or other processing.Fig. 3 has shown that little flow channel hole is communicated with an example on two main surfaces of PEM.

This PEM can be used in combination with other PEM layer with different performance.The PEM that has high and low permeability layer concurrently can be with its permeance property not one or more layer use of the permeable characteristic of substantial effect PEM layer, for example disclosed adhesion-promoting layers in the US patent publications 2006/0068268.On the contrary, the PEM with high water permeability can be used in combination with one or more layers in the zone with low and high water penetration, and these multizone layers are controlled effective infiltration that water pass the structure of these layers in view of the above.

Penetration type PEM water recovery method can use side direction liquid Distribution Layer (though this is optional in some embodiments), moves to the zone of the high water penetration of having of PEM to promote water.Having flow channel to run through in the situation of PEM (from the negative electrode to the anode) itself, wishing has the lateral stream passage, arrives this and runs through PEM formula flow passage area to reduce flow resistance that aqueous water moves.This liquid Distribution Layer can be that independent layer or it can be one of catalyst layer or liquid barrier or the architectural feature among both (feature), or it can be the architectural feature at the interface between catalyst layer and the liquid barrier.

In another embodiment that runs through the recovery of PEM formula water, above-mentioned cathode construction can use with conventional PEM, described conventional PEM has only a high water-permeability district (together with the anode construction of implementing conditional fuel diffusion), or in operation strategy, wherein fuel concentration is kept enough low.In two kinds of selections, the strategy of this design or operation is to be restricted to certain level at anode-PEM fuel concentration at the interface, and fuel permeability or fuel diffusion rate are enough low in view of the above, so that the chemical property of fuel cell is not had significant adverse effect.

The side direction aqueous water reclaims

In side direction water recovery approach, liquid residual water at the cathode catalyst layer place is limited to leave by GDL and enters into the cathode oxidant air duct, but by the caused pressure of liquid barrier promote to flow to lower pressure section, pass liquid collection network in the plane, and further be guided through passage and be incorporated into anode loop again or be used for other purpose.This can intercept diffusion layer, GDL, PEM and catalyst layer with above-mentioned gas and combine.

Can use the structure shown in Fig. 4 to realize collecting via the side direction of LWD.Aqueous water occurs from cathode catalyst layer, preferentially penetrates in the macropore of aqueous water Distribution Layer, and arrives liquid barrier.Aqueous water is at first filled available macrovoid network, is stoped to leave by the aqueous water barrier layer to enter into cathode channel.In case aqueous water has been filled the macrovoid network in the LWD layer, it will raise and continue to fill subsequently smaller aperture along with fluid pressure, or it will flow out at the bleeding point (if providing) of LWD layer edge.The capillary pressure of aqueous water produces aqueous water pressure in the hydrophobicity aperture of aqueous water barrier layer.

Oxygen can still diffuse through LWB layer and optional LWD layer, arrives cathode catalyst layer, because remain with the substantive interference networks of fine pore in liquid Distribution Layer and aqueous water barrier layer, this network is not filled water owing to need bigger capillary pressure.

Side direction is collected aqueous water and is required the liquid Distribution Layer of certain volume mark to be filled with water, and the residual volume mark can be used for gaseous diffusion.If this volume fraction is too big, then will limit oxygen diffusion to catalyst layer, cause the transmission loss of negative electrode quality.Can come to determine by rule of thumb this volume fraction according to the selection of material, the hydrophobicity degree of structure (liquid flow path transmits the capillary pressure of passage to gas), side direction aqueous water mobility and operating condition.

In some cases, can omit the liquid Distribution Layer, if but its function merger go among one of aqueous water barrier layer and catalyst layer or both.

To collect aqueous water but do not produce the fluid pressure of enough height with induced damage resistive MEA in order to go up in the several centimetres of scales (multi-centimeter scale) in actual battery zone, the aqueous water Distribution Layer must have permeability for liquids in the high relatively plane.In order to realize permeability for liquids in so high plane, the macroporous interference networks in this one deck are essential.This type of pore network can produce by several means:

A) design aqueous water Distribution Layer ink formulations and/or drying and processing specification are so that the LWD slabbing changes into mud bank (mud-flat) crack pattern.This crack produces useful big " hole " interference networks then.

B) printing LWD layer or catalyst layer or otherwise make the LWD layer or catalyst layer produces pattern is so that produce the network of major path, with conducts liquid water.

C) the LWD layer is carried out embossing or cut, to produce the network of major path.

D) use LWD layer, so that produce the interference networks in big space on the interface between LWD layer and the cathode catalyst layer with intrinsic big surface roughness.

In order to promote to collect aqueous water within the water Distribution Layer, what come in handy is to provide architectural feature at battery edge, and infiltration is essential in the shortest possible passage only in the plane of liquid like this.

The side direction liquid water collection architectural feature of cathode electrode assembly can be used for aqueous water guided to and runs through PEM high water-permeability zone.It also can be used for liquid is guided to the fluid passage, and described fluid passage is communicated with anode fuel stream fluid.It also can be used for guiding fluid to the fluid passage in addition, and described fluid passage is communicated with outside (outside fuel cell itself) fuel reaction device (aqueous water can participate in reaction there) fluid.

Ionic conductive polymer

Can be used in the ion-conducting copolymer of making the PEM that uses among the present invention and comprise the ion-conducting copolymer of representing by formula I:

Formula I

[{[{({Ar}_{1} - T)}_{i} - {Ar}_{1} - X -]}_{a}^{m} {[{Ar}_{2} - U - {Ar}_{2} - X -]}_{b}^{n} {[{({Ar}_{3} - V)}_{i} - {Ar}_{3} - X -]}_{c}^{o} {[{Ar}_{4} - W - {Ar}_{4} - X -]}_{d}^{p}]

Ar wherein ₁, Ar ₂, Ar ₃And Ar ₄Be the aromatics part, at least one Ar wherein ₁Comprise the ionic conduction group, and at least one Ar ₂Comprise the ionic conduction group;

T, U, V and W are the coupling parts;

X is independently-O-or-S-;

I and j are equal to or greater than 1 integer;

A, b, c and d are molar fractions, and wherein the summation of a, b, c and d is 1, and a is 0.3 at least, and at least one among b, c and the d is greater than 0; With

M, n, o and p are the integers of the quantity of different oligomer or monomer in the expression copolymer.

Being used to implement ion-conducting copolymer of the present invention also can be represented by formula II:

Formula II

[{[{({Ar}_{1} - T)}_{i} - {Ar}_{1} - X -]}_{a}^{m} {[{Ar}_{2} - U - {Ar}_{2} - X -]}_{b}^{n} {[{({Ar}_{3} - V)}_{i} - {Ar}_{3} - X -]}_{c}^{o} {[{Ar}_{4} - W - {Ar}_{4} - X -]}_{d}^{p}]

Wherein, Ar ₁, Ar ₂, Ar ₃And Ar ₄Be phenyl, substituted-phenyl, naphthyl, terphenyl, aryl nitrile and substituted aryl nitrile independently;

At least one Ar ₁Comprise the ionic conduction group;

At least one Ar ₂Comprise the ionic conduction group;

T, U, V and W be independently key ,-O-,-S-,-C (O)-,-S (O) ₂-,

Or

X is independently-O-or-S-;

I and j are equal to or greater than 1 integer;

M, n, o and p are the integers of the number of different oligomer or monomer in the expression copolymer.

R ₁And R ₂Be end-blocking monomer, wherein R ₁And R ₂In at least one be present in the described copolymer.

Being used to implement ion-conducting copolymer of the present invention can also be represented by formula III:

Formula III

[{[{({Ar}_{1} - T -)}_{i} - {Ar}_{1} - X -]}_{a}^{m} {[{Ar}_{2} - U - {Ar}_{2} - X -]}_{b}^{n} {[{({Ar}_{3} - V -)}_{i} - {Ar}_{3} - X -]}_{c}^{o} {[{Ar}_{4} - W - {Ar}_{4} - X -]}_{d}^{p}]

At least one Ar ₁Comprise the ionic conduction group;

At least one Ar ₂Comprise the ionic conduction group;

Wherein T, U, V and W are key O, S, C (O), S (O independently ₂), alkyl, branched alkyl, fluoro-alkyl, side chain fluoro-alkyl, cycloalkyl, aryl, substituted aryl or heterocycle;

X is independently-O-or-S-;

I and j are equal to or greater than 1 integer;

M, n, o and p are the integers of the quantity of different oligomer or monomer in the expression ion-conducting copolymer.

In exemplary, at least two among b, c and the d greater than 0.In some embodiments, c and d are greater than 0.In other embodiments, b and d are greater than 0.In another embodiment still, b and c are greater than 0.In other embodiments, each among b, c and the d is greater than 0.

Can be used for ion-conducting copolymer of the present invention comprises and is disclosed in US patent application No.10/438,186 (applications on May 13rd, 2003, title " sulfonated copolymer (SulfonatedCopolymer) ", publication No. No.US 2004-0039148 A1, on February 26th, 2004 published) and US patent application No.10/987,178 (applications on November 12nd, 2004, title " ion conductive random copolymers (Ion Conductive Random Copolymer) ") random copolymer in and be disclosed in US patent application No.10/438,299 (applications on May 13rd, 2003, title " sulfonated copolymer (Sulfonated Copolymers) ", announced publication No. No.2004-0126666 on July 1st, 2004) in block copolymer.Other ion-conducting copolymer comprises and is disclosed in US patent application No.10/987,951 (applications on November 12nd, 2004, title " ion-conducting copolymer (Ion Conductive Copolymers Containing One orMore Hydrophobic Monomers or Oligomers) that contains one or more hydrophobic monomers or oligomer "), US patent application No.10/988,187 (applications on November 11st, 2004, title " ion-conducting copolymer (Ion Conductive Copolymers Containing First andSecond Hydrophobic Oligomers) that contains the first and second hydrophobicity oligomer " and US patent application No.11/077,994 (applications on March 11st, 2005), title " ion-conducting copolymer (Ion Conductive Copolymers Containing One or More Ion ConductingOligomers) that contains one or more ionic conduction oligomer ") the oligomeric ionic conductive polymer in.By reference with whole above-mentioned patents and this paper.Other ion-conducting copolymer comprises US patent application No.60/684,412 (applications on May 24th, 2005, title " ion-conducting copolymer (Ion ConductiveCopolymers Containing Ion-Conducting Oligomers) that contains the ionic conduction oligomer "), US patent application No.60/685,300 (applications on May 27th, 2005, title " end-blocking of ion-conducting copolymer (EndCapping of Ion-Conductive Copolymers) "), US patent application No.60/686,757 (applications on June 1st, 2005, title " cross-linked ion-conductive copolymer (Cross-Linked Ion-Conductive Copolymers) "), US patent application No.60/686,663 (applications on June 1st, 2005, title " blend polymer (Polymer Blend Comprising Ion Conductive Polymerand Non-Conductive Polymers) that comprises ionic conductive polymer and non-conductive polymer "), US patent application No.60/686,755 (applications on June 1st, 2005, title " ion-conducting copolymer (Ion-ConductiveCopolymers Containing Pendant Ion Conducting Groups) that contains the ionic conduction side group ") and in the US patent ask No.60/687,408 (application on June 2nd, 2005, titles " anisotropy polyelectrolyte membrane (Anisotropic Polymer Electrolyte Membranes) ").

Other ion-conducting copolymer and the monomer that can be used to prepare them comprise and are disclosed in U.S. Patent application No.09/872,770 (applications on June 1 calendar year 2001, publication No. No.US 2002-0127454 A1, on September 12nd, 2002 published), U.S. Patent application No.10/351,257 (applications on January 23rd, 2003, publication No. No.US 2003-0219640 A1, on November 27th, 2003 published), U. S. application No.10/449,299 (applications on February 20th, 2003, publication No. No.US 2003-0208038 A1, publication on November 6th, 2003) those in, this paper is incorporated in described each application by reference into.Can (as be used to prepare those monomers (U.S. Patent No. 5 of sulfonation trifluorostyrene from comonomer by other ion-conducting copolymer of end-blocking preparation, 773,480), Acid-Base polymer (U.S. Patent No. 6,300,381), poly (arylene ether) sulfone (U.S. Patent Publication No.US2002/0091225 A1); Grafted polystyrene (Macromolecules 35:1348 (2002)); Polyimides (U.S. Patent No. 6,586,561 and J.Membr.Sci.160:127 (1999)) and Japanese patent application No JP2003147076 and JP2003055457 clearly incorporate each piece of writing in them into this paper by reference.

Though the use in conjunction with arylene ether or disulfide polymer is described being used to implement ion-conducting copolymer of the present invention, but can be used to implement ionic conductive polymer of the present invention and can contain aliphatic series or perfluorinate aliphatic series main chain (for example Nafion), or contain polyphenylene, polyamide or polybenzimidazoles main chain.The ionic conduction group can be connected in skeleton or can side be hung on main chain, for example, is connected in main polymer chain via connecting base.Perhaps, the ionic conduction group part that can be used as the standard main chain of polymer forms.Referring to, for example, the U.S. 2002/018737781 (publication on December 12nd, 2002) incorporates it into this paper by reference.Any of these ionic conduction oligomer can be used for implementing the present invention.

The exemplary ion conduction block copolymer that is used for direct methanol fuel cell has following formula:

Wherein, m is about 10-about 500;

Each X is 0 or 1 integer independently;

Z is about 10-about 500; With

N is about 40-about 4000.

When only a kind of ionic conduction group was present in the comonomer, the mole percent of ionic conduction group was preferably 30%～70%, or is preferably 40%～60%, most preferably is 45%～55%.When being included in this ionic conduction monomer above a kind of conduction group, this type of percentage multiply by the sum of the ionic conduction group of each monomer.Therefore, for comprising two sulfonic monomers, sulphonation rate is 60-140% preferably, more preferably 80-120%, most preferably 90-110%.Perhaps, the amount of ionic conduction group can be measured by ion exchange capacity (IEC).As a comparison, Nafion

The ion exchange capacity that typically has 0.9meq/g (milliequivalent/gram).In the present invention preferably, IEC is 0.9～3.0meq/g, and more preferably 1.0～2.5meq/g most preferably is 1.6～2.2meq/g.In preferred embodiments, a is 0.7, and b is 0.3.

Polymer film can be by the solution casting manufactured of ion-conducting copolymer.Perhaps, polymer film can prepare by the blend of this ionic conductive polymer of solution casting and acid and alkali polymer.

Work as casting film-forming, when using in fuel cell, film thickness is preferably 0.1～10 mil, and more preferably 0.25～6 mil most preferably is lower than 2.5 mils, and it can be coated on the polymeric substrate.

As used herein, if proton flux greater than about 0.005S/cm, more preferably greater than 0.01S/cm, most preferably greater than 0.02S/cm, then film is permeable proton.

As used herein, be lower than the Nafion that strides across same thickness if stride across the methyl alcohol transportation of film with given thickness

The methyl alcohol of film transfers, and then film is impermeable methyl alcohol basically.In preferred embodiments, methanol permeability is preferably than Nafion

The methanol permeability of film is low by 50%, with Nafion

Film is compared, and is more preferably low by 75%, most preferably low greater than 80%.

Ion-conducting copolymer has formed after the film, and it can be used for preparing catalyst coated membrane (CCM).As used herein, when partially or even wholly scribbling catalyst, CCM comprises PEM when at least one side (preferred two opposite sides) of PEM.The layer that this catalyst preferably is made up of catalyst and ionomer.Preferred catalyst is Pt and Pt-Ru.Preferred ionomer comprises Nafion and other ionic conductive polymer.Usually, use the standard technique of fully establishment with on anode and this film of cathod catalyst paint.For direct methanol fuel cell, platinum/ruthenium catalyst typically uses on anode-side, and platinum catalyst is applied on the cathode side.For hydrogen/air or hydrogen/oxygen fuel cell, generally platinum is applied in anode and cathode side.Catalyst can randomly be supported on the either side or both sides of carbon.Catalyst is dispersed in (the 100mg catalyst of having an appointment in the 1g water) in a spot of water at first.The solution (0.25～0.75g) of ionomer in water/ethanol of adding 5% in this dispersion.Dispersions obtained can directly being coated on the polymer film.Perhaps, and the adding isopropyl alcohol (1～3g), dispersion is sprayed directly on the film.Can also be by being described in decalcomania transfer (decaltransfer) in the open source literature (Electrochimica Acta, 40:297 (1995)) with on the catalyst paint film.

Perhaps, can be directly on any or both with catalyst and ionomer paint anode and cathode construction, and use heat and pressure these can be combined with PEM, formation MEA.Catalyst and ionomer are selected for the expectation function of male or female according to them, and can be applied as previously described.

Depend on the concrete application of fuel cell, many battery combination can be obtained the output of suitable voltage and power.This type of application comprises the power source of dwelling house, industry, commercial power supply system, and can be used for locomotive electric power (as being used for automobile).Other application of the concrete purposes that the present invention finds comprises the use of fuel cell in portable electronic equipment (as mobile phone) and other communication equipment, video and audio frequency consumer-elcetronics devices, laptop computer, notebook computer, PDA(Personal Digital Assistant) and other computing equipment, GPS equipment etc.In addition, fuel cell can pile up (stacked) to improve the voltage and current capacity, is used for high-power application, as industry with the dwelling house sewer is powered or be used to vehicle that power is provided.This type of fuel cell structure comprises and is disclosed in US Patent No 6,416,895,6,413,664,6,106,964,5,840,438,5,773,160,5,750,281,5,547,776,5,527,363,5,521,018,5,514,487,5,482,680,5,432,021,5,382,478,5,300,370, those in 5,252,410 and 5,230,966.

This type of CCM and MEA generally are used for fuel cell, for example are disclosed in US Patent No 5,945,231,5,773,162,5,992,008,5,723,229,6,057,051,5,976,725,5,789,093,4,612,261,4,407,905,4,629,664,4,562,123,4,789,917,4,446,210,4,390,603,6,110,613,6,020,083,5,480,735,4,851,377,4,420,544,5,759,712,5,807,412,5,670,266,5,916,699,5,693,434,5,688,613, in 5,688,614 those are clearly incorporated each piece of writing in the described patent into this paper by reference.

CCM of the present invention and MEA also can be used in the hydrogen fuel cell known in the art.Example comprises 6,630,259; 6,617,066; 6,602,920; 6,602,627; 6,568,633; 6,544,679; 6,536,551; 6,506,510; 6,497,974,6,321,145; 6,195,999; 5,984,235; 5,759,712; 5,509,942 and 5,458,989, clearly incorporate each piece of writing in the described patent into this paper by reference.

Embodiment 1

(a) negative electrode LWB/GDB layer printing ink

Can make ins all sorts of ways prepares negative electrode.In one embodiment, use the barrier layer printing ink that is applied on the gas diffusion layers (as carbon fiber paper) to form negative electrode, this printing ink forms the barrier layer of the target property that has aqueous water barrier layer and gas diffusion barrier simultaneously.Below provided a kind of method of preparation LWB/GDB layer printing ink.Yet those skilled in the art can use the method and the material of alternative.

Use surfactant that nonpolar graphite granule is suspended in (polarity) aqueous solution.Graphite mixture is carried out sonicated, be broken to guarantee the agglomeration of particles body.After sonicated, add Teflon

And hydroxyethylcellulose, because the performance of these two kinds of compounds changes in the sonicated process potentially.

The 3%TMN-100 surfactant solution of 50.0g (is preferably passed through to mix about 250g water and about 7.73g Tergitol

TMN-100 90% AQ solution and make) mix with the graphite of 14.03g.Use the spatula of cleaning to come broken graphite, even fully until mixture.Mixture is placed ice bath, at 100% power, carried out sonicated under 70% duty cycle 3 minutes with clavate ultrasonoscope (rod sonicator) (for example Hielscher UP200S).After sonicated, mixture is shifted out from ice bath.

(for example about 3.75cm is long, quality=9g) join in the ink mixture with magnetic stirring bar.By decantation from the 500ml jar, with Teflon

(23.38g) be added in the mixture.Mixture was stirred 5 minutes on the magnetic agitation plate.Add Natrosol

(0.254g), make Natrosol

Fine dust fall into this printing ink.Before using, stirred printing ink at least 30 minutes.

(b) printing ink applying on gas diffusion layers paper

Below be that negative electrode printing ink is applied in embodiment on the exposed carbon fiber paper (CFP).Can use other method such as the coating of silk screen printing or scraper with on the printing ink paint porous GDL material (as CFP).

GDL (for example SGL 24BA) carbon fiber paper is cut into the sample size of standard and weighs.

Use synthetic scrub-brush to press heavy coating (heavy coats) with on the printing ink paint GDL web.On brush, apply light pressure, equably applying coating.SGL 24BA carbon paper is unusual porous, and the first road coating of printing ink will be typically " infiltrate " CFP and arriving on the painted surface.After each sample reception one coat on the plate, it is transferred in the convection oven that is set in 70 ℃ placed at least 6 minutes.

More than coating step triplicate again, thereby each sample has four road ink coatings altogether.Between each road coating, sample is put in 70 ℃ of baking ovens dry.Then with on the stainless steel frame of sample transfer in the high temperature convection oven, to decompose and sintering.

After sample was in the baking oven, temperature slowly was increased to 300 ℃ and kept 30 minutes down at 300 ℃.Elevated temperature to 350 ℃ and kept 15 minutes down then at 350 ℃.Temperature is slowly reduced to about 50 ℃ then, take out sample.Sample has about 10mg/cm ²The printing ink capacity value.

Repeat decomposition/sintering operation.

Embodiment 2

Make up following fuel cell, and test was above 500 hours.

Battery design comprises:

(1) fuel cell technology monocell (Fuel Cell Technologies Single Cell), 26cm ²Effective area;

(2) PolyFuel DM-2-20-HB film;

(3) the negative electrode for preparing according to method described in the embodiment 1: JM HiSpec9000 catalyst, 1.62mg/cm with catalyst layer ²The Pt capacity value; With

(4) anode: JMFC anode P/N ELE0069.

Operating condition is 150mA/cm ²50C, fuel 1M methanol solution (being in 1.8ml/min); Air-flow 2 standard liters per minute kinds; Per 12 hours of every day stopped work 30 minutes.

Fig. 6 shows that the characteristic that passive water reclaims MEA is enough to be used in actual fuel cell system.Fig. 7 shows that this type of property feature keeps the stable duration of test runs that surpasses 500 hours.It is stable that the water mobility of measuring on right hand vertical axis keeps, and battery alternating-current resistance (HFR) is also like this.This battery comprises per 2 millimeters PEM that the interval has 2 microns laser drill.Ratio by the water that produces in water that leaves and the electrochemical reaction is measured, water purification mobility from negative electrode is 0.65, this provides enough passive water to reclaim, to allow anode reaction and, to comprise that the electro-osmosis of the water (combining with proton) from the anode to the negative electrode hinders from any additional water loss in the anode fuel loop.

Claims

1. comprise the polyelectrolyte membrane (PEM) of ionic conductive polymer, wherein said PEM has negative electrode and anode surface, and wherein said PEM further comprises the passage that extends to described anode surface from described cathode surface.

2. the PEM of claim 1, wherein said passage is in the precalculated position that strides across described PEM.

3. the PEM of claim 1, wherein said passage is substantially perpendicular to described negative electrode and anode surface.

4. the PEM of claim 1, wherein said PEM has the thickness of 10-200 micron.

5. the PEM of claim 1, wherein said passage has 10 microns or cross section still less.

6. the PEM of claim 1, wherein said passage has 5 microns or cross section still less.

7. the PEM of claim 1, the about 0.1-20 millimeter of wherein said passage each interval.

8. the PEM of claim 1, wherein said passage forms by laser.

9. the PEM of claim 1, wherein said passage is a frustoconical.

10. the catalyst coated membrane (CCM) that comprises the described PEM of claim 1.

11. comprise the membrane electrode assembly of the described PEM of claim 1.

12. comprise the fuel cell of the described MEA of claim 11.

13. negative electrode, it comprises:

(a) gaseous diffusion intercept (GDB) layer and

(b) aqueous water intercepts (LWB) layer

Wherein said GDB layer comprises the hydrophobicity hole, and optional is conductivity, and allows the diffusion of oxygen and stop flow of water vapor to stride across described layer; Wherein said LWB layer comprises the hydrophobicity hole, is conductivity, and allows oxygen diffusion also, stops aqueous water to flow and strides across described layer.

Have the negative electrode that gaseous diffusion intercepts the layer of (GDB) layer performance and aqueous water obstruct (LWB) layer performance 14. comprise, wherein said layer comprises the hydrophobicity hole, and optional is conductivity, and the permission oxygen diffusion strides across described layer, and stops flowing of liquid water and steam.

15. the negative electrode of claim 14, its further air inclusion diffusion layer (GDL).

16. the negative electrode of claim 13 or 14, it further comprises

(c) aqueous water that comprises the hydrophobicity hole distributes (LWD) layer, and wherein said layer is a conductivity, and allows aqueous water to flow to pass or stride across described layer.

17. negative electrode, it comprises:

(a) gas diffusion layers (GDL) and

(b) gaseous diffusion intercepts (GDB) layer,

Wherein said GDL is optional to be conductivity, and allows gas flow to stride across described layer, and wherein said GDB layer comprises the hydrophobicity hole, and optional is conductivity, allows oxygen diffusion also to stop flow of water vapor to stride across described layer.

18. the negative electrode of claim 17, it further comprises:

(c) aqueous water intercepts (LWB) layer,

Wherein said LWB layer comprises the hydrophobicity hole, is conductivity, allows oxygen diffusion and stop aqueous water to flow to stride across described layer.

19. the negative electrode of claim 18, it further comprises:

(d) aqueous water distributes (LWD) layer, and it is a conductivity, allows aqueous water to flow and passes or stride across described layer.

20. negative electrode, it comprises:

(a) aqueous water intercept (LWB) layer and

(b) aqueous water distributes (LWD) layer

Wherein said LWB layer comprises the hydrophobicity hole, is conductivity, and the permission oxygen diffusion strides across described layer and stops flowing of aqueous water; Wherein said LWD layer is a conductivity, allows aqueous water to flow and passes or stride across described layer.

21. negative electrode, it comprises each described negative electrode and catalyst layer among the claim 13-20.

22. membrane electrode assembly (MEA), it comprises:

(a) catalyst coated membrane (CCM), it comprises polyelectrolyte membrane (PEM) and catalyst layer; With

(b) each described negative electrode in the claim 13 to 20.

23. membrane electrode assembly (MEA), it comprises the negative electrode of PEM and claim 21.

24. the MEA of claim 22 or 23, wherein said PEM comprise the described PEM of claim 1.

25. fuel cell, it comprises claim 22,23 or 24 MEA.

26. electronic equipment, system, motor, power supply or vehicle, it comprises the fuel cell of claim 25.

27. fuel cell system, it comprises:

(a) fuels sources,

(b) fuel cell of claim 25 and

(c) anode loop that is communicated with the anode-side fluid of described fuels sources and described fuel cell.

28. the fuel system of claim 27, it further comprises the conduit that the regional fluid between the cathode surface with LWB layer and described PEM is communicated with.

29. the fuel cell system of claim 28, wherein institute's conduit also is communicated with described anode loop fluid.

30. the fuel cell system of claim 28, wherein said conduit also are communicated with the external reactors fluid.

31. prepare the method for water penetration polyelectrolyte membrane (PEM), it comprises PEM perforation, to form passage between the anode of described PEM and cathode surface.

32. make the method for water penetration polyelectrolyte membrane (PEM), it comprises from ionic conductive polymer and poragen and prepares PEM, handle formed PEM with the solvent that described poragen dissolves in wherein, between the anode of described PEM and cathode surface, to form passage.