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  • B01D71/06—Organic material
  • B01D71/70—Polymers having silicon in the main chain, with or without sulfur, nitrogen, oxygen or carbon only
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  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
  • B01D67/0002—Organic membrane manufacture
  • B01D67/0006—Organic membrane manufacture by chemical reactions
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  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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  • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
  • B01D67/0039—Inorganic membrane manufacture
  • B01D67/0048—Inorganic membrane manufacture by sol-gel transition
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
  • B01D71/06—Organic material
  • B01D71/76—Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74
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  • C08G77/04—Polysiloxanes
  • C08G77/38—Polysiloxanes modified by chemical after-treatment
  • C08G77/382—Polysiloxanes modified by chemical after-treatment containing atoms other than carbon, hydrogen, oxygen or silicon
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  • C08J5/22—Films, membranes or diaphragms
  • C08J5/2206—Films, membranes or diaphragms based on organic and/or inorganic macromolecular compounds
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  • C08L83/00—Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon only; Compositions of derivatives of such polymers
  • C08L83/04—Polysiloxanes
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• • H—ELECTRICITY
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  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/10—Fuel cells with solid electrolytes
  • H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
  • H01M8/1018—Polymeric electrolyte materials
  • H01M8/102—Polymeric electrolyte materials characterised by the chemical structure of the main chain of the ion-conducting polymer
  • H01M8/1037—Polymeric electrolyte materials characterised by the chemical structure of the main chain of the ion-conducting polymer having silicon, e.g. sulfonated crosslinked polydimethylsiloxanes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/10—Fuel cells with solid electrolytes
  • H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
  • H01M8/1018—Polymeric electrolyte materials
  • H01M8/1069—Polymeric electrolyte materials characterised by the manufacturing processes
  • H01M8/1072—Polymeric electrolyte materials characterised by the manufacturing processes by chemical reactions, e.g. in situ polymerisation or in situ crosslinking
  • H01M8/1074—Sol-gel processes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2323/00—Details relating to membrane preparation
  • B01D2323/30—Cross-linking
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2325/00—Details relating to properties of membranes
  • B01D2325/26—Electrical properties
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2379/00—Characterised by the use of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen with or without oxygen, or carbon only, not provided for in groups C08J2361/00 - C08J2377/00
  • C08J2379/04—Polycondensates having nitrogen-containing heterocyclic rings in the main chain; Polyhydrazides; Polyamide acids or similar polyimide precursors
  • C08J2379/06—Polyhydrazides; Polytriazoles; Polyamino-triazoles; Polyoxadiazoles
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M2300/00—Electrolytes
  • H01M2300/0017—Non-aqueous electrolytes
  • H01M2300/0065—Solid electrolytes
  • H01M2300/0082—Organic polymers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M2300/00—Electrolytes
  • H01M2300/0088—Composites
  • H01M2300/0091—Composites in the form of mixtures
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/30—Hydrogen technology
  • Y02E60/50—Fuel cells
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
  • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

• the present invention relates to proton conducting materials, in particular to proton electrolyte membranes (PEMs) for fuel cells.
• PEMs proton electrolyte membranes
• Proton electrolyte membranes are a critical component in fuel cells, reforming/partial oxidation of hydrocarbon fuels, hydrogen separation/ purification, contaminant removal, gas sensing, and other processes relevant to energy storage and conversion.
• Membranes with high proton conductivity >0.01
• PBI-H 3 PO membranes have the best performance.
• PBI- H 3 PO membranes have high proton conductivity (>10 "2 S/cm in atmosphere with
• a composition of matter comprises a polymer network, including silicon atoms and oxygen atoms, a first organic side-chain attached to at least some silicon atoms within the polymer network comprising a flexible linking group and a terminal group, the terminal group including at least one atom providing a lone pair of electrons.
• the composition of matter can be used to form a proton-conducting membrane.
• the polymer network can be an organic-inorganic hybrid network and the terminal group can includes a nitrogen-containing heterocycle.
• FIG. 1 shows a synthetic scheme for the synthesis of 2- triethoxysilylpropylthiomethyl-lH-benzimidazole (BISSi);
• FIG. 2 shows a synthetic scheme for the synthesis of 2-[(p-2- triethoxysilylethylene-phenylenemethyl)thio]- 1 H-imidazole (ImSSi);
• FIG 3 shows a synthetic scheme for the synthesis of 2-((3- triemoxysilylpropyl)thio)-lH-imidazole (ImSSib);
• FIG. 4 shows a synthetic scheme for the synthesis of 2- methyldiethoxysilyl-propylthiomethyl- 1 H-benzimidazole
• FIG. 5 shows a schematic representation of proton transport within a membrane
• FIG. 6 shows P NMR spectra of two hybrid inorganic-organic membranes with composition of (A) 2 M-3 T-l BiSSi - 3 P and (B) 2M-2Oc- lT-HmSSi - 5 P;
• FIG. 9 shows TGA curves of several membranes measured in dry air at a heating rate of 5°C / minute;
• FIG. 10 shows proton conductivity of 2 M-3 T-x ImSSi (ImSSib)-y P
• FIG. 13 shows cell voltage and power density versus current density of 2M-3T-lBISSi-7P at 100°C and 130°C under ambient pressure. (H 2 /O 2 bubbled with water vapor at room temperature);
• FIG. 14 shows an FTIR spectrum of OxImSSi
• FIG. 15 shows TGA curves of the new membranes with OxImSSi compared with that with ImSSi, using a rate of 5°C/min in dry air
• FIG. 16 shows proton conductivity of 2 MDSPPO-3 TEOS-1 OxImSSi- 5 H 3 PO 4 and 2 MDSPPO-3 TEOS-1 ImSSi-5 H 3 PO in anhydrous state;
• FIG. 17 shows proton conductivity of 2 MDSPPO-2 BTESO-1 TEOS-1 OxImSSi-5 H 3 P0 4 and 2 MDSPPO-2 BTESO-1 TEOS-1 ImSSi-5 H 3 PO 4 in the vapor of MgCl 2 saturated aqueous solution, the calculated relative humidity is about 26 % at 80°C and 22 % at 100 °C;
• FIG. 18 shows the molecular structure of membranes grafting -SO 3 H and benzimidazole rings
• FIG. 19 shows a TGA curve measured in dry air with a heating rate of 5 °C/min
• FIG. 20 shows proton conductivity of lM-2Oc-4S-4B in environments with different relative humidity (RH);
• FIG 21 shows proton conductivity dependence on relative humidity and temperature for the sample 2M-2Oc-4S-2BI.
• Novel proton conducting membranes were fabricated using a simple sol-gel process. Imidazole rings are attached to flexible branches grafted on an organic- inorganic copolymer network, allowing the imidazole rings to have high degree of local motion.
• the inorganic Si-O-Si network can absorb significant amount of H 3 PO 4 in the membranes.
• the membranes have excellent proton transport characteristics.
• silane precursors were synthesized, in which a terminal group was flexibly connected to a silane group through a flexible linking group.
• Alkoxysilanes derivatives terminated with imidazole rings were synthesized. Imidazole rings were attached to alkoxysilanes through a simple nucleophilic substitution reaction as described in the literature, e.g. T. Hamaguchi et al., Bioorg. Med. Chem. Lett., 10, 2657 (2000); U.S .Pat. 5,0914,15 to J. F. Patoiseau et al.
• the precursors can be synthesized from commercially available chemicals through a simple nucleophilic additive reaction or nucleophilic substitution reaction. A number of illustrative examples are given below.
• FIG. 1 further illustrates a scheme used to synthesize 2- triethoxysilylpropylthiomethyl-lH-benzimidazole (BISSi, triethoxy analog of example la)
• BISSi triethoxy analog of example la
• 1.9634g 3-mercaptopropyltrimethoxysilane (10 mmle) was dissolved in 10 ml of anhydrous ethanol, mixed with 0.84 g of potassium ethoxide (10 mmole, 24 % solution in ethyl alcohol), and then stirred for 10 minutes.
• 1.6661g of 2- (chloromethyl)benzimidazole (lOmmole) in 20 ml was added dropwise to the above mixture and stirred for about 12 hours. TLC was used to check if the reaction has been completed.
• the white precipitate KC1 was removed by filtration. About 2.2g of 2-triethoxysilylpropylthiomethyl-lH-benzimidazole was separated from the filtrate through a silicate gel column chromatography eluted with ethyl acetate and hexane (50/50 in volume) (60 % yield). It was a yellow oil-like liquid.
• ImSSi with KBr showed that the characteristic peaks of -CH 2 -C1 at 640 cm “1 of the reagents disappeared, and the peaks of -CH 2 -S-CH - in BiSSi at 693 cm “1 and -S-CH 2 - group in ImSSi at 596 cm “1 were observed, indicating that imidazole rings were attached on alkoxysilane through S-C bonds.
• Fig. 2 further illustrates a scheme used to synthesize 1.2 2-[(p- triethoxysilylethylphenylmethyl)thio]-lH-imidazole (ImSSi, triethoxy analog of example 2a)
• ImSSi was synthesized from 2-mercaptoimidazole and ((chloromethyl)phenylethyl)-trimethoxysilane with the same method as described above. 1.0001 g of 2-mercaptoimidazole (10 mmole) was dissolved in 20 ml anhydrous ethanol and mixed with 0.84 g of potassium ethoxide (10 mmole, 24 % solution in ethyl alcohol), and then stirred for 10 minutes. 2.7482 g of ((chloromethyl)phenylethyl)-triethoxysilane (10 mmole) was added dropwise to the mixture, and then stirred for 6 hours. The white precipitate KC1 was removed by filtration.
• FIG 3 illustrates a scheme used to synthesize 2-((3- triethoxysilylpropyl)thio)-lH-imidazole (ImSSib)
• ImSSib was synthesized from 2-mercaptoimidazole and 3-iodopropyl trieethoxysilane with the same method. 1.0001 g of 2-mercaptoimidazole (10 mmole) was dissolved in 20 ml anhydrous ethanol and mixed with 0.84 g of potassium ethoxide (10 mmole, 24 % solution in ethyl alcohol), and then stirred for
• FIG. 4 illustrates the scheme used to synthesize 2-methyldiethoxysilyl- propylthiomethyl- 1 H-benzimidazole 2-methyldiethoxysilylpropylthiomethyl-
• alkoxysilanes having an active -X or -SH group which can be used to synthesize the precursors, include: 3- mercaptopropylmethyldimethoxysilane, 3 -mercaptopropyltriethoxysilane, 3 - mercaptopropyltrimethoxysilane, 3-bromopropyltrimethoxysilane, 11- bromoundecyltrimethoxy silane, chloromethylmethyldiethoxysilane,
• the nucleophilic addition reaction can take place between an -SH group of a compound also containing a heterocycle, such as one having an imidazole ring, and alkoxysilyl-containing acrylate or methacrylate.
• the nucleophilic addition can take place in a basic solvent. For example, a small amount of KOH can be used as a catalyst. This reaction can complete in several minutes at room temperature.
• a nucleophilic substitution reaction can be written in the form:
• A can be an alkyloxysilane, and B a compound including a nitrogen-containing heterocycle, or vice-versa (A being a compound including a nitrogen-containing heterocycle and B being an alkyloxysilane).
• Examples of-SH group containing compounds include: 2- mercaptoimidazole, 2-mercaptobenzimidazole, 2-mercapto-5 -methylbenzimidazole, and derivatives thereof.
• the alkoxysilyl containing acrylate or methacrylate can be (3- acryloxypropyl)dimethylmethoxysilane, (3-acryloxypropyl)methyldimethoxysilane, (3-acryloxypropyl)trimethoxysilane, (methacryloxymethyl)dimethylethoxysilane, methacryloxymethyltriethoxysilane, methacryloxymethyltrimethoxysilane, meti ⁇ acryloxypropyldimethyle oxysilane, memacryloxypropyldimethylmethoxysilane, methacryloxypropylmethyldiethoxysilane, memacryloxypropylmemyldimethoxysilai e, methacryloxypropyltriethoxysilane, and the like.
• a sulfur atom is directly connected to an imidazole ring (or other nitrogen-containing heterocycle), it can be oxidized to sulfonyl (— S02-) groups via peroxide to increase the activity of a proton on the imidazole ring because the -SO2- group has a strong electron- withdrawing effect.
• Specific examples include 2-[(p-2-trimethoxysilylethylenephenylenemethyl)sulfonyl]-lH- imidazole and 2-[(3-methyldiethoxysilylpropyl propinyl)sulfonyl]-lH- imidazole. Further precursor examples are illustrated below:
• silane grafted polymers such as silane-grafted thermoplastics, which can also be used in preparing improved membranes according to the present invention, are also described in U.S. Provisional Application Serial Number 60/473,812, filed May 28, 2003, the entire contents of which are incorporated herein by reference.
• Precursors described herein can be used to form polymer chains or networks for use in improved proton conducting materials.
• PROTON CONDUCTING MEMBRANES A new series of proton conducting membranes based on hybrid inorganic- organic copolymers grafted imidazole rings as proton solvents instead of water were fabricated using a simple sol-gel process.
• imidazole rings are attached to flexible (short, organic) branches grafted on an organic-inorganic copolymer network, allowing imidazole rings to have high degree of local motion.
• the inorganic Si-O-Si network can absorb significant amount of H 3 PO 4 in the membranes. Accordingly, the protons can transport through the membrane by the so-called Grotthuss-type mechanism. Fig.
• FIG. 5 schematically shows the proton transport process that may occur between imidazole rings and H 3 PO 4 molecules within a membrane.
• the figure shows one nitrogen atom of the heterocycle receiving a proton from H 3 PO , the other nitrogen atom giving up a proton to the acid ion.
• the imidazole ring is flexibly attached to a network, such as an inorganic network or a hybrid inorganic- organic copolymer network.
• the previous section described synthesis of precursors, examples included where imidazole rings were grafted on alkoxysilane with a simple nucleophilic substitution reaction to facilitate the preparation of hybrid inorganic-organic copolymers.
• Proton electrolyte membranes (PEM) based on these co-polymers and H 3 P0 4 exhibit high proton conductivity in low relative humidity, excellent mechanical properties, and high thermal stability.
• the new membranes can possess high proton conductivity in the anhydrous state, so that they have proton conductivity independent of the presence of water. Also, because of the hybrid inorganic-organic copolymer network, the new membranes can have good mechanical properties and high thermal stability. They have great potential application in fuel cells and other electrochemical devices.
• a sol-gel process was used to synthesize the new hybrid inorganic-organic copolymer proton conducting membranes. All precursors were dissolved in a conventional solvent (such as ethanol, methanol, THF, ethyl acetate, or the like) and hydrolyzed by water with acid as a catalyst. After the sols are stirred for several hours, a pre-determined amount of H 3 PO 4 was added and further stirred for several hours. The resultant sols were then cast in Petri dishes made of polystyrene or glass, and dried oven at 60°C for several days to form gels and evaporate solvents. The solvent evaporation rate may be controlled, as it can substantially influence the mechanical properties of the membranes.
• a conventional solvent such as ethanol, methanol, THF, ethyl acetate, or the like
• the latter two species are known to be within 2 ppm of the undissociated H 3 PO signal.
• the weak peaks at ⁇ ⁇ -11 ppm and -24 ppm are attributed to the end unit of pyrophosphoric acid and tripolyphosphoric acid.
• these weak peaks may be assigned to the phosphates bound to one or two silicon atoms through P-O-Si bonds, which means that H 3 PO 4 was attached to the Si-O-Si network in the hybrid inorganic-organic copolymer.
• the integral of the two weak peaks is about 20 % of the total 31 P resonance peaks for the membrane. This suggests that about 80 % of the phosphoric acid is present in the free form, including undissociated H 3 PO 4 and dissociated species such as H 4 P0 4 + and H P0 " .
• TMSPBI 2-trimethoxysilylpropylthiomethyl-l H-benzimidazole
• the samples were labeled by their mole composition as x M - y T - z BI - m P, where x, y, and z refers to the moles of Si in MDSPPO, TEOS, and TMSPBI, respectively, and m refers to the moles of H 3 P0 4 .
• Fig. 7A shows the TGA and DSC curves versus temperature of samples with compositions of 2 M-3 T-l BI-x P (x ⁇ O, 3, 5, 7), indicating that the membrane is thermally stable up to 210°C.
• the samples had good mechanical properties. Gels were dried in a slow procedure by decreasing the gel contact area with air. Pressure was not controlled, but pressure control could be helpful in obtaining reproducible properties.
• Fig. 7B shows the proton conductivities of these samples as determined using impedance spectroscopy under anhydrous conditions.
• the proton conductivities at 125°C of samples 2 M-3 T-l BI-5 P and 2 M-3 T-l BI-7 P are 1.0 x 10 " S/cm and 1.5 x 10 " S/cm, respectively.
• the proton conductivities were obtained in dry Ar after the membranes were dried in Ar at 60°C for 5 hours and 80° for 2 hours to remove water and organic solvents.
• TMSPI 2-[(p-trimethoxysilylethylphenylmethyl)thio]-lH- imidazole
• BISSi, ImSSi, AND ImSSib The obtained BISSi, ImSSi, or ImSSib prepared as described above, was dissolved in ethanol together with bis(3 -methyldimethyoxysilyl)polypropylene oxide (MDSPPO, MW 600-900), l,4-bis(trimethoxysilylethyl)benzene (BTMSEB), bis(triethoxysilyl)octane (BTESO), and tetraethoxysilane (TEOS).
• MDSPPO bis(3 -methyldimethyoxysilyl)polypropylene oxide
• BTMSEB l,4-bis(trimethoxysilylethyl)benzene
• BTESO bis(triethoxysilyl)octane
• TEOS tetraethoxysilane
• the samples were labeled by their mole composition as x M - y B (or O)- z T - m BISSi (ImSSi/ImSSib) - n P, where x, y, z, and m refer to the moles of Si in MDSPPO, BTMSEB (or BTESO), TEOS, and BISSi (or ImSSi/ ImSSib), respectively, and n is the moles of H 3 P0 4 .
• compositions M for MDSPPO (bis(3-methyldimethyoxysilyl)polypropylene oxide), B for MDSPPO (bis(3-methyldimethyoxysilyl)polypropylene oxide), B for MDSPPO (bis(3-methyldimethyoxysilyl)polypropylene oxide), B for MDSPPO (bis(3-methyldimethyoxysilyl)polypropylene oxide), B for
• BTMSEB l,4-bis(trimethoxysilylethyl)benzene
• T for TEOS tetraethoxysilane
• P for phosphoric acid H 3 PO 4 .
• the proton conductivity of the hydrolyzed and condensed BISSi in anhydrous state was measured to be about 2 x 10 "7 S/cm at 80°C, and 7 x 10 "7 S/cm at 100°C, and that of the hydrolyzed and condensed ImS Si is 2 x 10 "7
• H 3 PO 4 in the membranes can be assigned to the good affinity of Si-0 network and the hydrogen bonds between H 3 P0 4 and
• X-ray diffraction spectra show that all the membranes as obtained are amorphous. After heating in dry Ar from 100°C to 140°C for total 6 hours, no peak observed in the XRD, indicating that no crystallization takes place between Si-O-Si network and H 3 PO 4 , as previously reported in inorganic Si- H 3 PO 4 gels.
• FTIR spectra of the membranes with H 3 PO 4 showed the characteristic absorption of NH + groups around 2920 cm "1 , indicating that H 3 PO 4 in the new membranes protonated the imidazole rings. This is different from conventional PBI/H 3 PO 4 membranes where HsPO interacts with PBI with strong hydrogen bonds, but does not protonate imidazole groups.
• the thermal stability of the membranes was improved by the addition of BTMSEB and BTESO.
• the onset of decomposition of the membranes with BTMSEB and BTESO is at around 250°C.
• BISSi may enhance the thermal stability.
• the proton conductivity of all the membranes in anhydrous state was measured using a Solartron 1255 / 1286 impedance analyzer in the frequency range of 0.01 Hz - 5 MHz from room temperature (RT) to about 140°C. All the membranes were previously heated in dry Ar at 60°C for 6 hours, 80°C for
• the proton conductivity increases with temperature, reaching 10 "3 S/cm above 100°C when H 3 PO content in the membranes is larger than 5. It is 3.2 x 10 "3 S/cm at 110°C for the sample with a composition of 2 M-3 T-l ImSSi-7 P.
• the proton conductivity increases with H 3 PO 4 content, similar to conventional polymer-H 3 PO 4 materials reported, indicating that the protons from H 3 PO 4 self-dissociation are the main originate of the proton conductivity in the new membranes 9"13 .
• the new membranes Compared with conventional self-standing PBI-2.9 H 3 PO 4 , the new membranes have higher proton conductivity. This can be attributed to the fact that H 3 PO 4 in PBI membranes has a strong interaction with imidazole rings, but that in the new membranes exists mainly in free forms and protonates the imidazole rings as discussed above.
• Fig. 11 shows proton conductivity data for BISSi - P membranes, for various content of H 3 PO 4 . Comparing the imidazole-grafted membrane 2 M-3 T-l ImSSi-5 P to that with a composition of 2 M-3 T-5 P, we can find that the proton conductivity of the imidazole-grafted membrane is smaller, especially in lower temperature range. With increasing benzimidazole contents, the proton conductivity of the membranes decreased (see Fig.ll). One of the possible reasons is that the local mobility of imidazole rings was pressed because of the high viscosity of the membranes as observed in PBI-H 3 PO 4 -Imidazole system .
• the calculated relative humidity in the closed chamber with saturated MgCl 2 aqueous solution is 26 % at 70°C, about 22.5% at 100°C, and less than 15% at 120°C 23 .
• the samples were kept at each temperature for several hours until the measured proton conductivity values were stable.
• the proton conductivity of all the samples is larger than 0.01 S/cm above 100°C. It is 0.04 S/cm at 110°C for the sample 2 M-2 O -1 T-l BISSi-6 P.
• the much higher proton conductivity under wet conditions can be attributed to the higher mobility of H 3 O as a vehicle of proton.
• the membranes kept their mechanical properties after they were kept in the wet environments at 120 C for more than ten hours.
• Membranes according to the present invention can be used in a variety of applications.
• the membranes can be used in improved fuel cells.
• a membrane-electrodes assembly (MEA) with the new membrane 2M-3T-1BISS ⁇ -7P as the electrolyte and the commercially available Pt- loaded carbon paper (1 mg/cm 2 ) as electrodes was obtained by hot-pressing the membrane between the electrodes at 100°C under about 110 bar for 2 minutes.
• the new hybrid inorganic-organic copolymer membranes was tested in a fuel cell using H 2 as fuel and 0 2 as oxidant.
• the relative humidity of the inlet gases was calculated to be 2% at 100°C and 1 % at 130°C.
• the thickness of the membranes is about 200 ⁇ m.
• the fuel cell was run at atmospheric pressure.
• Fig. 13 shows the curves of voltage-current and power density - current at 100°C and 130°C with a membrane 2 M-3T-lBISSi-7 P as the electrolyte.
• the figure shows cell voltage and power density versus current density of 2M- 3T-lBISSi-7P at 100°C and 130°C under ambient pressure. (H 2 /O 2 bubbled with water vapor at room temperature).
• the open-circuit voltage is about 0.9 V and the power density is 3.2 mW/cm at 130°C.
• the power density is one or two orders of magnitude lower than that for fuel cells using PBI-H3P0 4 as electrolyte.
• OxImSSi 2-[(p-2-trimethoxysilylethylene- phenylenemethyl)sulfonyl]-l H-imidazole (OxImSSi, shown below) and fabrication of membranes with OxImSSi and HsPO .
• Fig. 16 shows the proton conductivity of 2 MDSPPO-3 TEOS-1 OxImSSi-5 H 3 P0 4 and 2 MDSPPO-3 TEOS-1 ImSSi-5 H 3 PO 4 in anhydrous state.
• the membrane with composition of 2 MDSPPO-3 TEOS-1 OxImSSi-5 HsPO had a higher proton conductivity in the measured temperature range.
• the -SO 2 - groups increased the acidity of imidazole rings, and thus enhanced the proton conductivity of the membranes.
• Fig. 17 shows proton conductivity of 2 MDSPPO-2 BTESO-1 TEOS-1
• Membranes can be synthesized in which imidazole rings and acid groups are grafted on to a network.
• Acid groups can be organic acid groups (such as -COOH, and the like) or inorganic acid groups (such as -SO 3 H,
• Precursors can also be synthesized having grafted imidazole-ring terminated flexible chains, along with chains including -SO 3 H groups, -PO 3 H 2 groups, -COOH groups, and/or other acidic groups.
• Fig. 18 shows the molecular structure of an example membrane with grafted -SO3H and benzimidazole rings. The -SO 3 H groups were added to achieve a higher proton conductivity in the anhydrous state.
• 4BI was prepared through typical sol-gel process (TSPS: trihydroxy silylpropylsufonic acid, 30 wt % in water bought from Gelest). It was brittle in anhydrous state, but very flexible saturated with water.
• TSPS trihydroxy silylpropylsufonic acid
• Fig. 19 shows a TGA curve measured in dry air with a heating rate of
• the proton conductivity in anhydrous state is less than 10 "6 S/cm from RT to 140°C. This can attributed to the strong basic property of benzimidazole rings.
• the proton conductivity can be increased by substituting benzimidazole
• Fig. 21 shows the proton conductivity dependence on RH and temperature of a sample 2M-2O&4S-2BI.
• Two other membranes with compositions of 2MDSPPO-2BTESO- 4TSPS-2BI and 1MDSPPO-2BTESO-2 TSPS ⁇ IBI have been prepared.
• Imidazole rings have been attached to a hybrid inorganic-organic copolymer network through a flexible organic branch by simple and effective nucleophilic substitution reactions to provide improved proton conducting materials.
• New membranes made from imidazole ring terminated alkoxysilane and H 3 PG4 had good mechanical properties and high proton conductivity in the anhydrous state and in low relative humidity, and can be thermally stable up to at least 190°C.
• the proton conductivities are over 10 "2 S/cm under conditions with low relative humidity ( ⁇ 20 %) above 100°C, indicating that they have great potential for application in high temperature PEM fuel cells and other electrochemical devices.
• Proton electrolyte membranes (PEMs) described herein can be used in fuel cells, hydrogen separation/purification, reforming/partial oxidation of hydrocarbon fuels, contaminant removal, gas sensing, and other processes relevant to energy storage and conversion.
• a membrane can be formed by reacting a number of precursors, of different molecular structure, for example in a copolymerization reaction.
• Novel precursors according to the present invention include compounds of the general form: X - Y - Z where X is a terminal group, Y is a linking group, and Z is a reactive group.
• TERMINAL GROUPS Terminal groups can include a heterocycle, preferably a heterocycle including at least one atom that can provide a lone pair of electrons.
• Examples include nitrogen-containing heterocycles, such as nitrogen-containing heterocycles having two or more nitrogen atoms.
• Heterocycles include imidazole, and derivatives thereof.
• a heterocycle may include one or more nitrogen, sulfur and/or oxygen atoms, such as some combination of N, O, and/or S atoms.
• a heterocycle may be heteroaliphatic or heteroaromatic.
• Terminal groups may also include halogenated heterocycles, for example fluorinated imidazoles. Examples of fluorinated imidazoles are described in U.S. Prov. App. Ser. No. 60/539,641, the entire content of which is incorporated herein by reference.
• the terminal group may include one, two, three, or more interconnected connected and/or fused ring structures. If the terminal group contains more than one ring structure, one or more of the rings may be a heterocycle, such as a nitrogen-containing heterocycle. The terminal group may contain more than one heterocycle, which may have different structures.
• nitrogen containing heterocycles which may be included in the terminal group of compounds according to the present invention, include benzimidazole, phenylimidazole (e.g. 2-phenylimidazole, PI), vinylimidazole, 2-methyl 4-ethyl imidazole, imidazole-2-carboxaldehyde, pyrazole, oxazole, carbazole, indole, isoindole, dihydrooxazole, isooxazole, thiazole, benzothiazole, isothiazole, benzimidazole, imidazolidine, indazole, 4,5-dihydropyrazole, 1,2,3-oxadiazole, furazane, 1,2,3-thiadiazole, 1,2,4- thiadiazole, 1,2,3-triazole, benzotriazole, 1,2,4-triazole, tetrazole, pyrrole, pyrrolidine, and pyrazole,
• the terminal group may contain one or more atoms each providing a lone pairs of electrons, for example through one or more amino groups.
• the terminal group may also include one or more substituents, such as an alkyl chain extending from a ring structure. Substituents can be included for various reasons, for example to adjust the electrochemical properties of the terminal group, improve mixing with other compounds, adjust thermal properties, and the like.
• LINKING GROUPS Linking groups may include alkyl chains, such as alkyl chains having 1 - 20 carbon atoms (such as 2-5 carbon atoms) in one or more alkyl groups.
• the linking group may also include one or more aromatic rings, such as a benzene ring, or one or more atoms such as oxygen (for example, in an ether or ester linkage) or sulfur.
• the linking group preferably provides a degree of mobility to the terminal group when reactive group (or polymerizable group) Z is reacted to form a network, such as a polymer or sol-gel derived network.
• Linking groups can include a sulfur atom, in particular if the precursor was synthesized by a nucleophilic substitution reaction between a thiol group and a halogen, for example between a compound including a halogen and a silane, and a compound including a thiol group and a heterocycle (or other terminal group).
• the reactive group Z (for example a polymerizable group) includes groups that can be reacted (e.g. polymerized or copolymerized with one or more other precursors or other compounds) to form a network, such as a polymer.
• the reactive group may be a silane group, such as a trialkyloxysilyl group.
• the reactive group may also be a conventional monomer group, such as vinyl, acrylate, and the like.
• a material can be formed from a mixture of precursors having different reactive groups, for example to form an inorganic (from silane) - organic hybrid network, organic copolymer network, and the like. Alternatively, different precursors can be used with the same reactive group, but different terminal and/or linking groups.
• precursors include silanes, such as trialkyloxysilanes of the form
• T is a terminal group
• L is a linking group
• R is an alkyl group, hydrogen, or other substituent.
• the R groups may be the same or different. The nature of the alkoxy groups attached to the silicon atom may not have a significant effect on the final membrane.
• a silane precursor may also have the form T - L - SiR x (OR) 3-x , where R may be an alkyl group or other substituent.
• the linking group (with or without omission of the silane group) or the silane group may be connected to a polymer backbone, such as a polysiloxane, polycarbonate, polyether, polyester, or other polymer such as polymers described elsewhere in this specification, or known in the polymer chemistry art.
• a flexible linking group can be grafted onto a pre- existing polymer chain so as to flexibly attach the terminal group to the preexisting polymer chain.
• a pre-existing polymer may have sites to which one or more sidechains can be attached, the sidechains for example including a terminal group such as a nitrogen-containing heterocycle.
• a preexisting polymer can be treated, for example with UV or ozone, to facilitate such a grafting process, for example as described in U.S. Prov. Pat. App. Ser.
• a proton-conducting membrane can also be formed by hydrolyzing a mixture of silane precursors to form a network comprising silicon atoms, with one or more heterocycles being flexibly attached to silicon atoms of the network. Acidic groups can also be attached to the network.
• an improved proton conductive membrane comprises a network formed from copolymerization of at least a first silane and a second silane, the first silane comprising a first silane group, a terminal group, and a linking group connecting the terminal group to the first silane group, the first terminal group including an atom providing a lone pair of electrons.
• the atom may be nitrogen, sulfur, or oxygen.
• the terminal group can be a heterocycle, for example a nitrogen containing heterocycle, such as a heterocycle having two nitrogen atoms, optionally non-adjacent atoms within the ring.
• the linking group can include a sulfur atom, for example if the precursor was formed in a nucleophilic reaction e.g. between a thiol containing compound and a halogen containing compound, one of the compounds including a silane group and the other the terminal group.
• the terminal group is flexibly attached to a silicon atom within the network.
• a linking group may include at least two or three carbon atoms. Acid groups can also be attached to the network.
• the proton electrolyte membrane may further include free acid molecules, such as an inorganic acid (e.g. phosphoric acid) or an inorganic acid (e.g. carboxylic acid).
• Membranes may be formed by copolymerization of one or more precursors according to the present invention, with or without other compounds present.
• a proton-conducting membrane can be formed by copolymerization of a first precursor including a first reactive group, a first linking group, and a first terminal group, with a second precursor including a second reactive group, a second linking group, and a second terminal group.
• the first terminal group may provide one, two, or more atoms providing a lone pair of electrons, for example a nitrogen-containing heterocycle.
• the second terminal group may provide an acid group, for example as described below.
• the first and second reactive groups may be trialkyloxysilanes, so that the copolymerization may be a sol-gel process.
• the silane group of the precursors include silane groups of the form -
• silane-containing precursors according to the present invention can be grafted to a thermoplastic polymer, the grafted polymer then being involved in a sol-gel reaction, for example with other silanes such as alkyloxysilanes or other silane precursors discussed herein.
• ACID GROUPS Acid group species can also be attached to the network, for example, inorganic acid groups such as sulfonic acid group (-SO3H), phosphoric acid groups (-PO 3 H), boronic acid (-B(OH) 2 ), and the like, and/or organic acid groups such as a carboxylic acid groups (-COOH).
• the dissociable proton may be replaced by another ion, such as an alkali metal ion, other metal ion, ammonium ion, or the like.
• Other species that can be attached to the network include amide groups, such as bissulfonylamide groups.
• a fuel cell according to the present invention includes a positive electrode, a negative electrode, and a proton-conducting membrane formed from proton conducting ma described elsewhere.
• Proton conducting materials can be produced in a form suitable for use as a membrane without further processing, or formed as a tape or sheet that can be cut to a desired shape, or further processed.
• Proton conducting materials can include or be disposed on one or more reinforcing sheets, such as a web material.
• a thermally stable material for example in the form of a web or grid, may be included within a membrane or on its surface so as to improve the mechanical properties of the membrane.
• a National grid may be included to reduce membrane brittleness.
• an example fuel cell according to the present invention includes a positive electrode, a negative electrode, and a membrane therebetween formed from a proton conducting material described herein.
• Proton electrolyte membranes (PEMs) or other forms of the polymer conducting materials described herein can be used in fuel cells, hydrogen separation/purification, reforming/partial oxidation of hydrocarbon fuels, contaminant removal, gas sensing, and other processes relevant to energy storage and conversion.
• Proton conducting materials according to the present invention can further include particles such as metal-containing particles (such as nanometer-sized hygroscopic metal oxides), polymers dispersed through the membrane for improved mechanical properties, main-chain polymers having electron lone pair providing atoms within the main chain, acid-group substituted polymers (such as polymers including inorganic acid groups such as -H 3 P0 4 ) and dopants such as proton-conductive inorganic compounds, such as Zr(HP0 4 ) 2 H 0, silicotungstic acid (Si0 '12W0 3 '26H 2 0), other compounds including acid groups (such as inorganic acids such as -S0 3 H, -P0 3 H 2 ), groups such as -S0 2 NHS0 2 CF 3 , and
• particles such as metal-containing particles (such as nanometer-sized hygroscopic metal oxides), polymers dispersed through the membrane for improved mechanical properties, main-chain polymers having electron lone pair providing atoms within the
• additional organosilanes such as two or more flexibly interconnected silane groups, for example two silane groups interconnected through an alkyl chain having 2 - 20 carbon atoms, can be used in preparation of the membrane, for example to improve mechanical properties.
• bisalkyloxysilyl terminated polymers including oligomers
• short organic chains can be used, for example silanes of the form Si(A 3- X B X ) - R - Si(A 3 _ x B x ), where A can be an alkyloxy group, hydrogen, or other substituent, and B can be an alkyl group, and where R is a flexible chain.
• Examples of flexible chains include polypropylene oxide, polytetraethylene oxide, poly(l-butene), polyethylene, polypropylene, polyvinylidene fluoride, polystyrene, polytetrafluoroethylene, polyvinylchloride, and polyvinylalcohol.
• examples include bis(alkyloxysilyl)- terminated polymer compounds.
• Other examples of flexible chains include straight chain alkyl groups with 2 -
• Proton conducting materials according to the present invention can further comprise small molecules analogous to the terminal groups discussed above in relation to silane precursors, such as imidazole and its derivatives (including 2- ethyl, 4-methylimidazole and benzimidazole), or other nitrogen-containing heterocycles and their derivatives. Such compounds can be added to improve the proton conductivity of the materials.
• silane precursors such as imidazole and its derivatives (including 2- ethyl, 4-methylimidazole and benzimidazole), or other nitrogen-containing heterocycles and their derivatives.
• Such compounds can be added to improve the proton conductivity of the materials.
• the resistance of a membrane to water induced degradation can be increased by including insoluble acid salts in the membrane, such as cesium hydrogen sulphate (CsHS0 4 ) or cesium hydrogen phosphate (CsH 2 P0 4 ).
• insoluble acid salts in the membrane such as cesium hydrogen sulphate (CsHS0 4 ) or cesium hydrogen phosphate (CsH 2 P0 4 ).
• Membranes formed from materials according to the present invention may further be include polymer fibers, such as National fibers, to improve properties such as mechanical properties. These fibers need not be chemically bonded to the remainder of an inorganic-organic hybrid network. Acid groups can be bound to the network by including acid-group including silanes in a sol-gel reaction. Examples include PETHS (PO(OH) - C2H 4 -Si(OH) 3 , phosphoryl ethyl trihydroxyl silane, and alkyloxy analogs), acid-substituted phenyl trialkyloxy silanes (such as SPS (Si(EtO) 3 -Ph-S0 2 OH), and the like.
• PETHS PO(OH) - C2H 4 -Si(OH) 3
• phosphoryl ethyl trihydroxyl silane and alkyloxy analogs
• acid-substituted phenyl trialkyloxy silanes such as SPS (Si(EtO) 3

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