CN100592563C - Membrane electrode assembly (MEA), method for its manufacturing and a method for preparing a membrane to be assembled in a MEA - Google Patents

Abstract

A method for preparing a membrane to be assembled in a membrane,electrode assembly is disclosed comprising the step of swelling an ion-conducting membrane in a liquid containing at least one solvent or to an atmosphere containing the vapor phase of at least one solvent by controlling the content of the solvent in the ion conducting membrane. Further, a method for manufacturing a membrane electrodeassembly using a ion conducting membrane is disclosed, comprising the steps of: providing a ion conducting membrane in a pre-swollen state; coating of the ion conducting membrane on both sides with an electrode layer to form a sandwich; and hot-pressing the sandwich to form an ion conducting bonding of the afore-mentioned layers of the sandwich. Furthermore, a membrane electrode assembly is disclosed comprising a hot pressed sandwich comprising an electrode layer, a ion conducting membrane and again an electrode layer, thereby using the ion conducting membrane in its pre-swollen status priorto the hot-pressing.

Description

Membrane electrode assembly (MEA), its preparation method and the preparation method who waits to be assembled into the film among the MEA

Technical field

The present invention relates to prepare the method for membrane electrode assembly and the method that preparation waits to be assembled into the film in the membrane electrode assembly.And, the present invention relates to membrane electrode assembly.

Background technology

People need prepare the quick straightforward procedure of the membrane electrode assembly (MEA) with optimization interface.As [J.Huslage such as Huslage, T.Rager, B.Schnyder andA.Tsukada, " Radiation-grafted membrane/electrode assemblies withimproved interface ", Electrochim.Acta 48 (2002) 247-254] discuss like that, prepare this and the optimization interface radiation grafting cross linking membrane is the never problem of solution of this area.Particularly, they notice that electrochemical interface forms and not good enoughly are characterised in that fuel battery performance instability, operation could obtain for a long time steady-state behaviour and even in the fuel cell test caudacoria of prolongation and the poor adhesion between the electrode.So obviously, the electrochemical interface optimization of MEA is quite important for obtain high-performance in fuel cells applications.For example, the optimization at this interface makes and adopts the equal fuel battery component that for example, film and electrode etc. can be realized better battery polarization performance and higher power density.

Described as Huslage etc., in the MEA of the radiation grafting cross linking membrane that contains low grafting degree, especially be difficult to obtain optimum electrochemical interface.It is quite important to solve this interface problem, because Huslage etc. and people such as Kuhn (H.Kuhn subsequently, L.Gubler, T.J.Schmidt, G.G.Schmidt, H.-P.Brack, K.Simbek, T.Rager and F.Geiger, " MEABased on Radiation-Grafted PSI-Membrane:Durability andDegradation Mechanisms ", Proceedings of the 2nd European PEFCForum, 2-6 day in July, 2003, ISBN 3-905592-13-4, the 69-77 page or leaf) verified that all this film can move thousands of hours in fuel cell under limit, and can not observe loss or film or the battery character or the performance decrease of fuel cell output.

At the document of above-mentioned Huslage etc. or in European patent EP 0667983B1 for example, the conventional preparation method of this radiation grafting film has been described.Usually, they are with the preparation of the thick FEP based polyalcohol of 25 μ m, and have adopted and contain the 10 volume % crosslinking agents of having an appointment, DVB, monomer solution.These films have the grafting degree of about 18-20 quality % usually, people such as Brack (H.-P.Brack, D.Fischer, M.Slaski, G.Peter and G ü nther G.Scherer, " CrosslinkedRadiation-Grafted Membranes; Proceedings of the 2nd European PEFCForum; 2-6 day in July, 2003, ISBN 3-905592-13-4,127-136 page or leaf ") reported their spectrum property and the ratios of the isomers of graft component.

Huslage etc. have reported by the restriction grafting degree and have improved the mechanical performance of film to quite low value, and the respective electrical conductance loss under low grafting degree can be compensated by improvement film/electrode interface.

Document according to Huslage etc. " passes through Nafion Coat film and hot-pressing technique have obtained to have the MEA that improves the interface between the gas-diffusion electrode at film and commercial can getting ".

Unfortunately, these progress can not successfully be duplicated.Passing through Nafion according to the instruction of Huslage etc.

Coat film and hot-pressing technique are by the work of the optimized MEA of radiation grafting film preparation aspect, obtained quite wonderful result: (1) Nafion-applies and these two steps of (2) hot pressing separately, can not obtain in fuel cell, having favourable electrochemical properties, such as low ohmic resistance or low charge transport resistance, the MEA that perhaps has advantageous property character.

In prior art research, the key breakthrough of finding the disclosed the article stress of Supramanium Srinivasan is to make the platinum heap(ed) capacity reduce 10 times, from about 4mg cm ^-2To 0.4mg cm ^-2Or below.For example, S.Srinivasan and P.Costamanga are at " Quantum jumps in thePEMFC science and Technology from the 1960s to the yeas 2000PartI.Fundamental scientific aspects ", J.Power Sources comments on this breakthrough among 102 (2001) 242-252.He thinks that this breakthrough is to come from the increase of the BET surface energy of (i) eelctro-catalyst and (ii) pass through to use proton conductive Nafion

Film immersion has been expanded 3 dimension electrochemical active regions in electrode.In same document, S.Srinivasan etc. claim " under the condition of temperature required (130-140 ℃), pressure (2000psi) and time (about 1 minute) ", with electrode hot pressing film forming.But unfortunately, S.Srinivasan etc. do not mention relevant preliminary treatment or the pre-adjustment to film before hot pressing fully.

In addition, they the instruction hot pressing should carry out near glass transformation temperature also indeterminate.Do not know that they are meant the glass transformation temperature of form membrane in the hot pressing, or the glass transformation temperature of other type preliminary treatment film.In addition, term " approaching " is not specialized, and can be meant one degree centigrade or several degrees centigrade.There is not explanation whether variant or preferred between the hot pressing that is lower than, is equal to or higher than glass transformation temperature yet.

So target of the present invention provides the method for preparing membrane electrode assembly, and the method for preparing wherein used film, and combination, life-span and the improved membrane electrode assembly of performance characteristics are provided.

Summary of the invention

Generally speaking, notion of the present invention is included in the water content of controlling diaphragm in the hot pressing, because verified this parameter is very important for obtaining optimized MEA interface and favourable electrochemical properties and fuel battery performance.To and put into practice to the present invention and various embodiment below is described, and can study it from claims.

So, under high pressure and/or hot conditions, will be in solvent swelling state lead ionic membrane and two electrodes combine, wherein said solvent swelling state be characterised in that this material have high relatively surface energy or and glassware for drinking water low contact angle is arranged.By the described ionic membrane of leading is exposed to one or more liquid fluxs or contains in the atmosphere of vapor phase of one or more solvents, be easy to change described solvent swelling state of leading ionic membrane.The not concrete restriction of the method for film swelling.The limiting examples of this solvent comprises water, ethylene glycol, propylamine, propyl alcohol, propionic acid, and propionic aldehyde, ethyl ketone, acetonitrile, the N-butyl glycolate, N, N '-di-n-butyl acetamide, diethoxyethane, diethyl carbonate, 1, the 3-dioxolanes, dimethylacetylamide, N, N '-amide dimethyl butyrate, dimethyl carbonate, N, N '-dimethyl decyl amide, dimethoxy-ethane, the dimethyl ethane sulphonamide, N, N '-dimethyl formamide, N, N '-dimethylpropylene urea, dimethyl sulfoxide (DMSO), the sulfurous acid dimethyl esters, 2, the 5-dimethoxy-tetrahydrofuran, ethyl acrylate, acrylic acid 2-ethoxy ethyl ester, ethylene carbonate (1,3-dioxy penta-2-ketone), ethyl glycolate, CH ₃OC ₄F ₉, CF ₃CF ₂CF ₂OCF (CF ₃) CF ₂OCHFCF ₃, gamma-butyrolacton, methyl acrylate, 2-(2-(2-methoxy ethoxy) ethyoxyl)-1,3-dioxolanes, methyl alcohol, methyl formate, methyl glycollate, methyl tertiary butyl ether(MTBE), N-butylamine, N-methylformamide, N-N-methyl-2-2-pyrrolidone N-, propylene carbonate, poly-(ethylene glycol), 4-(1-propenyloxy group methyl)-1,3-dioxy penta-2-ketone, sulfolane, TBuA, triethyl phosphate, oxolane and 3-methyl sydnone.In one embodiment, amberplex is in deionized water in about 80 ℃ Temperature Treatment about 4 or 5 hours.

Used in the present invention film type is not specifically limited.Any can all be suitable at the organic or inorganic of object run temperature transmission proton or organic/inorganic or composite membrane.Described organic component can be polymerization in essence.The composition of film and chemical constitution are also without limits.Film is usually according to required film character, such as, conductance, dimensional stability, gas separations, methyl alcohol impenetrability or engineering properties are selected.Some non-limitative examples of ionomeric membrane comprise fluorinated monomer, such as the copolymer of tetrafluoroethene and diversion subtype or acidic comonomer or its precursor.The non-limitative example of this polymer is perfluorinated sulfonic acid (PFSA) the polymer Nafion of DuPont

Film is perhaps from Asahi Glass (Flemion membrane), the associated materials of AsahiChemical or Dow.These ionomer membrane material also can be used with composite form, such as the PRIMEA from Gore The situation of the compound little reinforced film among the MEA.The not concrete restriction of the composition of film, shape and form.These perfluorinated membranes before carrying out MEA assembling usually by cleaning with the processing of strong acid solution short time and becoming sour form fully.In one embodiment, their salpeter solutions with about 35 weight % before swelling were handled 1 hour.After acid treatment, wash this film by water usually and become neutrality and from the deacidification of getting on of this film up to flushing water.

In some cases, can be by in the MEA preparation, flooding this film with the volume of extending three-dimensional electrochemical active regions or improve the surperficial of film or, improve the chemical property of MEA and fuel cell in conjunction with character with the sub-polymer phase of another kind of diversion.Described dipping can be by means commonly known in the art, such as with the sub-polymer of diversion such as Nafion

Polymer or other ionomer fluoridized, partially fluorinated or that do not fluoridize spray or flood this film to be implemented.After having finished described impregnation technology, film can be in high temperature drying, for Nafion

Normally 100-140 ℃ in polymer is so that remove residual solvent and described ionomer is transformed into the form of insoluble solids.

In one embodiment, film is the radiation grafting film.The The Nomenclature Composition and Structure of Complexes of radiation grafting film is not specifically limited.Usually, compare with the primary quantity of membrane material, grafting degree is 10-40 mole %.For example, described radiation grafting film can be by multiple base polymer film preparation, and described base polymer film comprises fluoropolymer, comprises FEP, ETFE or PVDF such as PTFE and its copolymer, and perhaps polyolefin is such as polyethylene, polypropylene and its copolymer.The emission types that is used to prepare film is not specifically limited, comprise electromagnetic radiation such as UV or X ray or particle radiation such as electron beam.In some cases,, select vacuum or inertia radiation atmosphere in order to minimize the degraded of base polymer.The film grafting can with radiation process simultaneously, perhaps grafting can be carried out in the step after radiation.

If in subsequent step, carry out grafting, if the substrate of radiation can store at low temperatures and/or the unstable rule of reaction site can be under inert atmosphere.The physical form that is used for the monomer of grafting can be gas or liquid, and monomer can or pure, or with the dilution of solvent or inert substance, and/or be mixture with one or more other monomers.Any free radical activity monomer be can adopt, vinyl, phenylethylene or acrylic monomer comprised.Monomer can be selected according to the required character of film.For example, if desired film can diversion son, monomer or its precursor that then can select to have acidity, alkalescence, salt or both sexes degree of functionality.Non-limitative example with monomer of acidity, alkalescence, salt or both sexes degree of functionality comprises vinyl phosphonate, vinyl sulfonic acid, 3-[(2-acrylamido-2-methyl-propyl) dimethyl amido] propane sulfonic acid ester, Sodium styrene sulfonate, N-vinyl-2-Pyrrolidone, 4-vinylpridine.Can also adopt and can be used as the monomer that precursor is introduced acidity, alkalescence and amphiprotic group.Non-limitative example comprises styrene monomer, such as styrene, α, and α, β-trifluorostyrene, α-fluorobenzene ethene and vinyl chloride and its derivative.Cross-linking monomer well known in the art such as divinylbenzene or two (ethenylphenyl) ethane, can be used to change swelling, gas or liquid intersection character or the stability and the persistence of these films.The content of this cross-linking monomer in graft copolymer solution should be no more than 25% in the scope of certain percentage, preferably be no more than 20%.This solution can be added into styrene to 100%.The polystyrene chain of described grafting can adopt approach well known to derive to produce acidity, alkalescence or both sexes degree of functionality in this film subsequently.For example, can introduce anion exchange groups with aqueous hydroxide generation ion-exchange again by follow-up amination, can be by using strong acid, handle and introduce cation exchange group such as being dissolved in chlorosulfonic acid in the halogenated solvent or sulfuric acid or sulfur trioxide.The complete sour form of these films by at first handling with alkaline solution, is regenerated in acid usually then, and final rinse water obtains.In one embodiment, fresh sulfonated membranes is at first handled at least about 12 hours, then at 2M H with the NaOH of 0.1M ₂SO ₄The middle processing about 5 hours.

Electrode shape, form, structure and composition are not specifically limited.Usually, they are electrical conductances, and in addition thereon or inside can have catalyst.Usually, they have some the regional ability at least that makes gaseous state or liquid reagent transmission or diffuse through its structure.The non-limitative example of electrode material comprises carbon cloth, carbon paper or carbon felt.For example, under the situation of fuel cell electrode,, can adopt other catalyst for catalytic electrochemical oxidation or reduction reaction.The non-limitative example of catalyst comprise carbon coating platinum, platinum black or with platinum alloy and Raney nickel and the carbon black of other metal such as ruthenium or metal oxide.Some these alloys can be used for helping making electrode surface to be minimized by the poisoning of CO and other material, and help to methyl alcohol, other alcohol matter or even the oxidation of hydrocarbon carry out catalysis.By flooding mutually with the sub-polymerization of diversion, can significantly improve the chemical property of electrode, MEA and fuel cell in electrode, to expand the volume of 3 dimension electrochemical active regions.Described dipping can be by means commonly known in the art, such as with the sub-polymer of diversion such as Nafion

Implement on the surface of polymer or other ionomer spraying fluoridized, partially fluorinated or that do not fluoridize, dipping or wetting described electrode.After having finished described impregnation technology, this electrode can be in high temperature drying, for Nafion

Normally 100-140 ℃ in polymer is so that remove residual solvent and described ionomer is transformed into the form of insoluble solids.

Membrane electrode assembly produced according to the present invention can be described below: lead ionic membrane pre-swelling in ratio of solvent such as water.Please note in the MEA packaging technology, make this film remain on swelling, plasticized condition, be characterised in that surface energy increases and more there is hydrophily on the surface.By selective solvent, can be easy to change the influence of swelling to the mechanical performance and the surface nature of film.

Therefore for example, polarity and hydrogen bonding solvent swell get better, and influence contains polarity and hydrogen bonding functional group engineering properties and the surface nature such as the film of acid, alkalescence or both sexes functional group more significantly.By means commonly known in the art, comprise selected solvent volatility, be exposed in the solvent time with and the method that exposes of concentration, solvent, film in atmosphere that exposes after the swelling and the described open-assembly time before MEA hot pressing, can be easy to the degree of swelling of controlling diaphragm.In one embodiment, before the MEA assembling, can on film, apply catalyst coat by spraying, dipping, sputter or other method well known in the art.

Usually, the film with the swelling form closely contacts placement with two electrodes subsequently, electrode of every side.This MEA interlayer is hot pressing a period of time under high pressure and high temperature subsequently.The not concrete restriction of accurate hot pressing condition, optimal conditions depends on film and electrode property to a certain extent, such as hardness, surface energy and machinery and chemical stability.Can carry out various combinations to temperature, pressure and time conditions.For example, adopt higher temperature to make it possible to adopt shorter hot pressing time or lower pressure usually.In another case, the higher pressure of employing makes it possible to adopt temperature and the short hot pressing time that hangs down some.Under another situation, adopt the long press time to make it possible to adopt lower temperature and pressure.Usually, can adopt the about 150 ℃ hot pressing temperature of about 60-.In one embodiment, temperature is about 110 ℃.Generally speaking, do not wish to adopt too high temperature because this may cause film dry or even decompose, especially under the situation of aerobic.The too low MEA that may cause of temperature is in conjunction with poor.Usually, can apply the hot pressing pressure of the about 30Mpa of about 2-.In one embodiment, institute's plus-pressure is the about 18MPa of about 5-.In addition, too high pressure may cause degraded, and too low pressure may cause in conjunction with poor.The time of hot-pressing processing can change between about 15 seconds-Yue 10 minutes.In one embodiment, the time is about 3 minutes.

The not concrete restriction of the application of these MEA.These MEA can be applied to various electrochemical process, battery and device, for example, and in fuel cell, electrolytic cell and battery pack.These electrochemical cells can use separately, and perhaps the kit form of connecting or being connected in parallel with a plurality of batteries uses.Fuel cell can adopt the pluralities of fuel of gaseous state or liquid form that energy is provided, described fuel ratio such as hydrogen, methyl alcohol or reformate, perhaps with pure form or with the form of mixtures of other component.Fuel cell can adopt oxidant various or gaseous state or liquid form, such as oxygen or air, perhaps with pure form or with the form of mixtures of other component, operate.

Description of drawings

Fig. 1 contains the representative cells polarization curve of the fuel cell of various MEA described in work embodiment and the comparative example.

Fig. 2 contains the typical consequence at the electrochemical impedance spectroscopy measurements of the fuel cell of the various MEA described in work embodiment and the comparative example.

Embodiment

The present invention at first by and the fuel cell seminar of electrochemistry experiment chamber and material II seminar (all belong to Paul Scherrer Institute, Villigen, cooperation Switzerland) and putting into practice.Prepared the radiation grafting film.They are by available from DuPont, Circleville, OH, FEP film (FEP 100A) preparation that the 25 μ m of USA are thick.Should be noted that the degree of depth of film should be 5-250 μ m, is preferably 20-200 μ m.Film is called the FEP-25 film in this article according to the method preparation of descriptions such as Huslage.Adopt the radiation dose of 3kGY and be 3.5h at 60 ℃ of the reaction times.Graft copolymer solution contains the crosslinking agent with respect to cinnamic 10 volume %, DVB.The film of acid form in the deionization water-bath in about 5 hours of 80 ℃ of swellings.The grafting degree of gained film is 18-20 quality %, and ion-exchange capacity is 1.25-1.35mEq/g.For relatively, bought Nafion from DuPont company

The N-112 film.This membrane material is at first at 1: the 1 (volume: volume) in solution, in 90 ℃ handle 1 hour of red fuming nitric acid (RFNA) (65%) in deionized water.Subsequently, Nafion Film is by carrying out till the water of reprocessing in described bath keeps neutrality in about 95 ℃ of swelling a few hours in a plurality of deionization water-baths.Described film has the water-soluble of the ion exchange capacity of about 0.9mEq/g and about 20 quality % and expands.

The membrane material of all swellings is stored in the deionized water, till it is handled in the process for preparing MEA by hot pressing.

Electrode among these work embodiment is the ELAT type carbon cloth base electrode from E-TEK, and the Pt heap(ed) capacity is 0.6mg cm ^-2Described electrode by with the Nafion solution spraying of 0.5 quality % then under vacuum in about 2 hours of 130 ℃ of dryings, carry out the Nafion coating.The amount of the Nafion that applies is about 0.6-0.7mg cm ^-2

The film of dipping Nafion in vacuum drying oven in 120 ℃ of dryings 1 hour.Then, film is immersed in the Nafion of 0.5 weight %

In the ionomer solution.After 1 hour, take out film, get rid of lip-deep solution gently, sample was placed in the fume hood in drying at room temperature about 1 hour.Subsequently, by film was solidified 2 hours in 120 ℃, make Nafion in vacuum drying oven

The ionomer coating becomes and does not dissolve.To be attached to film swelling again on the electrode with hygrometric state by making in the water that sample is immersed room temperature subsequently.

Use solubility Nafion

Another technology of ionomer dipping radiation grafting film makes film fragility after processing less.In the technology of this milder, film in vacuum drying oven in 60 ℃ of dryings at least 1 hour, preferred a few hours.Then, film is immersed in the Nafion of 0.5 weight %

Spend the night in the ionomer solution.Take out film, get rid of excessive solution gently.Made sample drying at room temperature in fume hood about 2 hours.Subsequently, with film in vacuum drying oven in 60 ℃ of dryings 2 hours.

Estimated four kinds of performances based on the MEA of FEP25 radiation grafting film, and with it with contain Nafion

112 standard MEA compares.Two samples use (Nafion of no use with the preparation state

The ionomer dipping).After the film preparation it is being preserved in water.

Work embodiment 1: in experiment V150, having adopted grafting degree is 19.1% FEP-25 film.This film is Nafion of no use before hot pressing

The ionomer dipping.Adopt the film of conventional hot-press condition (120 ℃/18MPa/3 minute) hot pressing solvent swelling state (FEP-hp (wetting)).Check the leakage situation of MEA, in following hydrogen/oxygen fuel cell testboard, test then.

The comparative example 1: in test V203, be 19.5% FEP-25 film preparation MEA by grafting degree.This film is Nafion also of no use before hot pressing The ionomer dipping.This film hot pressing (FEP-hp) before in baking oven in 60 ℃ of dryings 1 hour (not having vacuum).All other MEA preparation conditions are with above-mentioned identical.

Work embodiment 2: in test V213, having adopted grafting degree is 19.1% FEP-25 film.This film Nafion

The ionomer dipping is as described in prosthomere.This sample is at room temperature carrying out in water under the condition that heavy swelling spends the night in hygrometric state (FEP-ni-hp (wetting)) hot pressing.Directly from water, take out film, blot lip-deep water with fabric.Then, film is contacted placement with two electrodes.Then, the MEA interlayer is placed in the hot pressing die fast, (110 ℃/5MPa/3 minute) lamination under softer condition ftractures easily because find the film that floods when employing standard hot pressing condition.Softer can not cause laminate quality observable deterioration to occur in conjunction with condition.

The comparative example 2: in experiment V211, be 17.9% FEP-25 film preparation MEA by grafting degree.Use Nafion The ionomer impregnated membranes, according to work embodiment 2 (V213) method prepare MEA, except in this comparative example in the Nafion coating after 120 ℃ of curing, (FEP-ni-hp), after sample took out from the baking oven that solidifies, described film was with the dry state combination, as mentioned above.

The comparative example 3: in test V208, from the Nafion of hygrometric state

112 films (N112-hp (wetting)) preparation MEA.

The MEA of table 1 pair preparation sums up.

Table 1, employing have 0.6mgpt cm ^-2The ETEK electrode, the preparation MEA film.

These MEA test in the testboard of the fuel battery of PSI.Fuel cell test has 30cm ²Carry out in the monocell of active area.Battery is at pure H ₂And O ₂Following operation, the gas flow rate of employing are 1.5 times of battery current aequum.Battery temperature is 80 ℃, and the reaction gas pressure in the exit is 1 crust _aIt is that 80 ℃ water becomes moistening that hydrogen passes temperature by bubbling, and oxygen need not to become moistening when supplying with battery.Between the starting period, battery is operated under the constant internal resistance of 0.05 Ω, up to the performance that reaches about 5W.Then, constant current (the 500mA cm that operator scheme is transferred to 14.6A ^-2).

The in-situ characterization of MEA:, then MEA is carried out in-situ characterization after startup by polarimetric test and electrochemical impedance spectroscopy in case MEA has carried out adjusting and having reached stability.Fig. 1 has provided the representative cells polarization curve of various MEA.For polarimetric test, battery current density progressively changes to maximum current density from open-loop voltage.The equilibration time of every bit is 20 seconds.Electrochemical impedance spectroscopy is at 500mA cm ^-2Constant battery current density under, adopt to derive from Zahner Elektrik (Kronach, impedance set of tools Germany) carries out.Forcing frequency changes between 100mHz-25kHz usually.Fig. 2 has provided the result that the MEA that describes is characterized in work embodiment and comparative example.The Ohmic resistance and the charge transport resistance that record by this electrochemical impedance spectroscopic method original position are summarised in the table 2.

The result sums up: Fig. 1 has provided the representative cells polarization curve of the fuel cell of the MEA that contains work embodiment and comparative example.If MEA adopt hot pressing simultaneously film be in solvent swelling state, the polarization property that then contains based on the battery of the MEA of radiation grafting film has obtained remarkable improvement.No matter whether film used Nafion before hot pressing Ionomer dipping (relatively work respectively embodiment 2 and comparative example 2, and relatively work embodiment 1 and comparative example 1), this improvement is all very remarkable.

Embodiment	The experiment number	RohmmOhm cm -2	RCT mOhm cm -2
				Work embodiment 1	V150	132	222
The comparative example 1	V203	132	358
				Work embodiment 2	V213	124	229
The comparative example 2	V211	129	297
				The comparative example 3	V208	101	195

The work embodiment of table 2 by electrochemical impedance spectroscopy in-site detecting and the summary of comparative example's MEA impedance

Fig. 1 contains the representative cells polarization curve of the fuel cell of various MEA described in work embodiment and the comparative example.After MEA has carried out after the startup adjusting and reached stability, about usually 100-150 hour, measure.V150 (FEP25-hp (wetting)) in fact measured after about 2350 hours, but compared with early measuring of this MEA, did not descend on the performance.

Fig. 2 contains the typical consequence at the electrochemical impedance spectroscopy measurements of the fuel cell of the various MEA described in work embodiment and the comparative example.After MEA has carried out after the startup adjusting and reached stability, about usually 100-150 hour, measure.V150 (FEP25-hp (wetting)) in fact measured after about 2350 hours, but compared with early measuring of this MEA, did not descend on the performance.

Claims (22)

1. one kind prepares the method for waiting to be assembled into the film in the membrane electrode assembly, be included in the liquid that contains at least a solvent or contain in the atmosphere of vapor phase of at least a solvent, make the described step of leading the ionic membrane swelling by controlling the content of described solvent in leading ionic membrane, and the described ionic membrane of leading is led ionic polymerization and is applied mutually, and the ionomer on the film is transformed into the form of insoluble solids, and before hot pressing, it is carried out swelling again.

2. the method for claim 1 is characterised in that the described ionic membrane of leading is the radiation grafting film.

3. the method for claim 2, the grafting degree that is characterised in that described radiation grafting film is 5-50 mole %.

4. the method for claim 3, the grafting degree that is characterised in that described radiation grafting film is 10-40 mole %.

5. claim 2,3 or 4 method are characterised in that the described ionic membrane of leading is by using graft copolymer solution radiation grafted, and described graft copolymer solution comprises cross-linking monomer, and the content of described cross-linking monomer is 5-25%.

6. the method for claim 5, the content that is characterised in that described cross-linking monomer is less than 20%.

7. claim 1 or 2 method were characterised in that before described swelling step,

A) described leading the time that ionic membrane was handled in strong acid solution 10-120 minute; With

B) use flushing water to wash the ionic membrane of leading of described processing like this.

8. the method for claim 7 was characterised in that before described swelling step,

A) described leading the time that ionic membrane was handled in strong acid solution 10-120 minute; With

That b) uses that flushing water washes described processing like this leads ionic membrane till described flushing water is as neutrality.

9. each method of claim 1-4 is characterised in that the described ionic membrane of leading is led ionic polymerization and flooded mutually.

10. an employing comprises the following steps: according to the method for the sub-film preparation membrane electrode assembly of diversion of aforementioned arbitrary claim preparation

A) provide the ionic membrane of leading that is in pre-solvent swelling state;

B) at described coating on both sides electrode layer of leading ionic membrane, to form interlayer; With

C) the described interlayer of hot pressing is with the ionic combination of leading of above-mentioned each layer of forming described interlayer.

11. the method for claim 10 is characterised in that the both sides of leading ionic membrane described, is provided with catalytic active layer between the ionic membrane at described electrode layer and described leading.

12. the method for claim 10 is characterised in that to adopt to be selected from one of carbon cloth, carbon paper and carbon felt as electrode layer.

13. the method for claim 12 is characterised in that to apply with the water seeking liquid form to be selected from one of carbon cloth, carbon paper and carbon felt as electrode layer.

14. the method for claim 13 is characterised in that to apply with polarity and hydrogen bonding solvent version to be selected from one of carbon cloth, carbon paper and carbon felt as electrode layer.

15. the method for claim 10, be characterised in that described hot pressing condition be selected from following condition one of at least:

A) temperature range is 70-150 ℃;

B) pressure limit is 2-30MPa; With

C) the duration scope of hot-pressing processing is 15-400 second.

16. the method for claim 15 is characterised in that described temperature range is 90-120 ℃.

17. the method for claim 15 is characterised in that described pressure limit is 5-18MPa.

18. the method for claim 15, the duration scope that is characterised in that described hot-pressing processing are 60-240 second.

19. the method for claim 10, be characterised in that described catalytic active layer comprise be selected from platinum, ruthenium, rhodium, rhenium, nickel, rare earth and transition metal and its mixture one of at least.

20. the membrane electrode assembly according to the arbitrary preparation of aforementioned claim 10-19, it comprises the hot pressing interlayer, and described interlayer comprises electrode layer, leads ionic membrane and another electrode layer, thereby adopts the described ionic membrane of leading that is in pre-solvent swelling state before described hot pressing.

21. the membrane electrode assembly of claim 20 is characterised in that described depth bounds of leading ionic membrane is 5-250 μ m.

22. the membrane electrode assembly of claim 21 is characterised in that described depth bounds of leading ionic membrane is 20-200 μ m.

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