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Hans Wolfgang Spiess - One of the best experts on this subject based on the ideXlab platform.
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high resolution solid state nmr studies of poly vinyl Phosphonic Acid proton conducting polymer molecular structure and proton dynamics
Journal of Physical Chemistry B, 2007Co-Authors: Young Joo Lee, Bahar Bingol, Wolfgang H Meyer, Tatiana Murakhtina, Daniel Sebastiani, Gerhard Wegner, Hans Wolfgang SpiessAbstract:The structure and the local proton mobility of poly(vinyl Phosphonic Acid) were studied by solid-state NMR under fast magic-angle spinning. At elevated temperatures, the signature of the hydrogen-bonded P−OH protons is observed in 1H magic-angle spinning (MAS) NMR as a single resonance at 10.5 ppm. Both 1H double-quantum NMR and variable-temperature experiments demonstrate that P−OH protons are mobile and thus able to contribute to proton conductivity. Below room temperature, two different types of hydrogen-bonded P−OH resonances are observed at 10.5 and 15 ppm, and 1H double-quantum NMR demonstrates that these protons are immobile on the NMR time scale. By means of first-principles calculations of a model polymer, we have assigned the additional hydrogen-bonded species at lower temperatures to Phosphonic Acid anhydride and charged anhydride. Also, in the 31P MAS NMR spectrum, two distinct resonances appear, arising from “normal” Phosphonic Acid and Phosphonic Acid anhydride. 31P double-quantum NMR experi...
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intermediate temperature proton conductors for pem fuel cells based on Phosphonic Acid as protogenic group a progress report
Physical Chemistry Chemical Physics, 2007Co-Authors: Hanna Steininger, M. Schuster, Klaus-dieter Kreuer, Joachim Maier, Anke Kaltbeitzel, Bahar Bingol, Wolfgang H Meyer, Siri Schauff, Gunther Brunklaus, Hans Wolfgang SpiessAbstract:The melting behaviour and transport properties of straight chain alkanes mono- and difunctionalized with Phosphonic Acid groups have been investigated as a function of their length. The increase of melting temperature and decrease of proton conductivity with increasing chain length is suggested to be the consequence of an increasing ordering of the alkane segments which constrains the free aggregation of the Phosphonic Acid groups. However, the proton mobility is reduced to a greater extent than the proton diffusion coefficient indicating an increasing cooperativity of proton transport with increasing length of the alkane segment. The results clearly indicate that the “spacer concept”, which had been proven successful in the optimization of the proton conductivity of heterocycle based systems, fails in the case of Phosphonic Acid functionalized polymers. Instead, a very high concentration of Phosphonic Acid functional groups forming “bulky” hydrogen bonded aggregates is suggested to be essential for obtaining very high proton conductivity. Aggregation is also suggested to reduce condensation reactions generally observed in Phosphonic Acid containing systems. On the basis of this understanding, the proton conductivities of poly(vinyl Phosphonic Acid) and poly(meta-phenylene Phosphonic Acid) are discussed. Though both polymers exhibit a substantial concentration of Phosphonic Acid groups, aggregation seems to be constrained to such an extent that intrinsic proton conductivity is limited to values below σ = 10–3 S cm–1 at T = 150 °C. The results suggest that different immobilization concepts have to be developed in order to minimize the conductivity reduction compared to the very high intrinsic proton conductivity of neat Phosphonic Acid under quasi dry conditions. In the presence of high water activities, however, (as usually present in PEM fuel cells) the very high ion exchange capacities (IEC) possible for Phosphonic Acid functionalized ionomers (IEC >10 meq g–1) may allow for high proton conductivities in the intermediate temperature range (T ∼ 120 –160 °C).
Joachim Maier - One of the best experts on this subject based on the ideXlab platform.
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Proton conductivity and diffusion study of molten Phosphonic Acid H3PO3
Solid State Ionics, 2008Co-Authors: Michael Schuster, Hanna Steininger, Klaus-dieter Kreuer, Joachim MaierAbstract:Abstract Proton conductivity and diffusion in molten nominally dry Phosphonic Acid (H 3 PO 3 ) have been studied by 1 H PFG NMR (pulsed magnetic field gradient NMR) and ac impedance spectroscopy. The high intrinsic proton conductivity is found to be the result of fast structure diffusion of protonic defects (Grotthuss mechanism) which are present at high concentration (high degree of self-dissociation). The proton transport behavior is reminiscent to this of phosphoric Acid, but slightly higher correlations in the diffusion of protonic defects, as indicated by a higher Haven ratio (~ 2.5 compared to ~ 1.5), and the lower rate of structure diffusion (Grotthuss mechanism) compared to vehicle diffusion (~ 90% for Phosphonic Acid compared to ~ 98% for phoshoric Acid) are suggested to be the consequence of a “weaker” hydrogen bond network formed by Phosphonic Acid compared to phosphoric Acid. But contrary to phosphoric Acid, Phosphonic Acid may be immobilized to organic structures by stable P–C bonds. This opens a way to a new class of fully polymeric proton conducting materials, which are of paramount interest for PEM-fuel cell technology.
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intermediate temperature proton conductors for pem fuel cells based on Phosphonic Acid as protogenic group a progress report
Physical Chemistry Chemical Physics, 2007Co-Authors: Hanna Steininger, M. Schuster, Klaus-dieter Kreuer, Joachim Maier, Anke Kaltbeitzel, Bahar Bingol, Wolfgang H Meyer, Siri Schauff, Gunther Brunklaus, Hans Wolfgang SpiessAbstract:The melting behaviour and transport properties of straight chain alkanes mono- and difunctionalized with Phosphonic Acid groups have been investigated as a function of their length. The increase of melting temperature and decrease of proton conductivity with increasing chain length is suggested to be the consequence of an increasing ordering of the alkane segments which constrains the free aggregation of the Phosphonic Acid groups. However, the proton mobility is reduced to a greater extent than the proton diffusion coefficient indicating an increasing cooperativity of proton transport with increasing length of the alkane segment. The results clearly indicate that the “spacer concept”, which had been proven successful in the optimization of the proton conductivity of heterocycle based systems, fails in the case of Phosphonic Acid functionalized polymers. Instead, a very high concentration of Phosphonic Acid functional groups forming “bulky” hydrogen bonded aggregates is suggested to be essential for obtaining very high proton conductivity. Aggregation is also suggested to reduce condensation reactions generally observed in Phosphonic Acid containing systems. On the basis of this understanding, the proton conductivities of poly(vinyl Phosphonic Acid) and poly(meta-phenylene Phosphonic Acid) are discussed. Though both polymers exhibit a substantial concentration of Phosphonic Acid groups, aggregation seems to be constrained to such an extent that intrinsic proton conductivity is limited to values below σ = 10–3 S cm–1 at T = 150 °C. The results suggest that different immobilization concepts have to be developed in order to minimize the conductivity reduction compared to the very high intrinsic proton conductivity of neat Phosphonic Acid under quasi dry conditions. In the presence of high water activities, however, (as usually present in PEM fuel cells) the very high ion exchange capacities (IEC) possible for Phosphonic Acid functionalized ionomers (IEC >10 meq g–1) may allow for high proton conductivities in the intermediate temperature range (T ∼ 120 –160 °C).
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Intermediate temperature proton conductors based on Phosphonic Acid functionalized oligosiloxanes
Solid State Ionics, 2006Co-Authors: Hanna Steininger, M. Schuster, Klaus-dieter Kreuer, Joachim MaierAbstract:Abstract Fully immobilized Phosphonic Acid based proton conductors, where Phosphonic Acid groups are tethered to cyclic siloxanes via flexible alkane spacers, are synthesized. Unlike conventional hydrated ionomers containing sulfonic Acid groups, which are commonly used as separator material in PEM fuel cells, the proton conductivity of these materials occurs within a dynamical hydrogen bond network formed by the protogenic groups (Phosphonic Acid), which are present at very high concentrations. Conductivities of up to 2 · 10 − 3 S cm − 1 are obtained at T ≈ 130 °C and RH ≈ 37%. This is only slightly higher than the conductivity of similar imidazole based systems although neat Phosphonic Acid has a much higher proton conductivity compared to neat imidazole. The proton conductivity of Phosphonic Acid is more sensitive towards immobilization at cyclic siloxanes and the corresponding restrictions for hydrogen bond formation (aggregation).
Hanna Steininger - One of the best experts on this subject based on the ideXlab platform.
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Proton conductivity and diffusion study of molten Phosphonic Acid H3PO3
Solid State Ionics, 2008Co-Authors: Michael Schuster, Hanna Steininger, Klaus-dieter Kreuer, Joachim MaierAbstract:Abstract Proton conductivity and diffusion in molten nominally dry Phosphonic Acid (H 3 PO 3 ) have been studied by 1 H PFG NMR (pulsed magnetic field gradient NMR) and ac impedance spectroscopy. The high intrinsic proton conductivity is found to be the result of fast structure diffusion of protonic defects (Grotthuss mechanism) which are present at high concentration (high degree of self-dissociation). The proton transport behavior is reminiscent to this of phosphoric Acid, but slightly higher correlations in the diffusion of protonic defects, as indicated by a higher Haven ratio (~ 2.5 compared to ~ 1.5), and the lower rate of structure diffusion (Grotthuss mechanism) compared to vehicle diffusion (~ 90% for Phosphonic Acid compared to ~ 98% for phoshoric Acid) are suggested to be the consequence of a “weaker” hydrogen bond network formed by Phosphonic Acid compared to phosphoric Acid. But contrary to phosphoric Acid, Phosphonic Acid may be immobilized to organic structures by stable P–C bonds. This opens a way to a new class of fully polymeric proton conducting materials, which are of paramount interest for PEM-fuel cell technology.
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intermediate temperature proton conductors for pem fuel cells based on Phosphonic Acid as protogenic group a progress report
Physical Chemistry Chemical Physics, 2007Co-Authors: Hanna Steininger, M. Schuster, Klaus-dieter Kreuer, Joachim Maier, Anke Kaltbeitzel, Bahar Bingol, Wolfgang H Meyer, Siri Schauff, Gunther Brunklaus, Hans Wolfgang SpiessAbstract:The melting behaviour and transport properties of straight chain alkanes mono- and difunctionalized with Phosphonic Acid groups have been investigated as a function of their length. The increase of melting temperature and decrease of proton conductivity with increasing chain length is suggested to be the consequence of an increasing ordering of the alkane segments which constrains the free aggregation of the Phosphonic Acid groups. However, the proton mobility is reduced to a greater extent than the proton diffusion coefficient indicating an increasing cooperativity of proton transport with increasing length of the alkane segment. The results clearly indicate that the “spacer concept”, which had been proven successful in the optimization of the proton conductivity of heterocycle based systems, fails in the case of Phosphonic Acid functionalized polymers. Instead, a very high concentration of Phosphonic Acid functional groups forming “bulky” hydrogen bonded aggregates is suggested to be essential for obtaining very high proton conductivity. Aggregation is also suggested to reduce condensation reactions generally observed in Phosphonic Acid containing systems. On the basis of this understanding, the proton conductivities of poly(vinyl Phosphonic Acid) and poly(meta-phenylene Phosphonic Acid) are discussed. Though both polymers exhibit a substantial concentration of Phosphonic Acid groups, aggregation seems to be constrained to such an extent that intrinsic proton conductivity is limited to values below σ = 10–3 S cm–1 at T = 150 °C. The results suggest that different immobilization concepts have to be developed in order to minimize the conductivity reduction compared to the very high intrinsic proton conductivity of neat Phosphonic Acid under quasi dry conditions. In the presence of high water activities, however, (as usually present in PEM fuel cells) the very high ion exchange capacities (IEC) possible for Phosphonic Acid functionalized ionomers (IEC >10 meq g–1) may allow for high proton conductivities in the intermediate temperature range (T ∼ 120 –160 °C).
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Intermediate temperature proton conductors based on Phosphonic Acid functionalized oligosiloxanes
Solid State Ionics, 2006Co-Authors: Hanna Steininger, M. Schuster, Klaus-dieter Kreuer, Joachim MaierAbstract:Abstract Fully immobilized Phosphonic Acid based proton conductors, where Phosphonic Acid groups are tethered to cyclic siloxanes via flexible alkane spacers, are synthesized. Unlike conventional hydrated ionomers containing sulfonic Acid groups, which are commonly used as separator material in PEM fuel cells, the proton conductivity of these materials occurs within a dynamical hydrogen bond network formed by the protogenic groups (Phosphonic Acid), which are present at very high concentrations. Conductivities of up to 2 · 10 − 3 S cm − 1 are obtained at T ≈ 130 °C and RH ≈ 37%. This is only slightly higher than the conductivity of similar imidazole based systems although neat Phosphonic Acid has a much higher proton conductivity compared to neat imidazole. The proton conductivity of Phosphonic Acid is more sensitive towards immobilization at cyclic siloxanes and the corresponding restrictions for hydrogen bond formation (aggregation).
Wolfgang H Meyer - One of the best experts on this subject based on the ideXlab platform.
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high resolution solid state nmr studies of poly vinyl Phosphonic Acid proton conducting polymer molecular structure and proton dynamics
Journal of Physical Chemistry B, 2007Co-Authors: Young Joo Lee, Bahar Bingol, Wolfgang H Meyer, Tatiana Murakhtina, Daniel Sebastiani, Gerhard Wegner, Hans Wolfgang SpiessAbstract:The structure and the local proton mobility of poly(vinyl Phosphonic Acid) were studied by solid-state NMR under fast magic-angle spinning. At elevated temperatures, the signature of the hydrogen-bonded P−OH protons is observed in 1H magic-angle spinning (MAS) NMR as a single resonance at 10.5 ppm. Both 1H double-quantum NMR and variable-temperature experiments demonstrate that P−OH protons are mobile and thus able to contribute to proton conductivity. Below room temperature, two different types of hydrogen-bonded P−OH resonances are observed at 10.5 and 15 ppm, and 1H double-quantum NMR demonstrates that these protons are immobile on the NMR time scale. By means of first-principles calculations of a model polymer, we have assigned the additional hydrogen-bonded species at lower temperatures to Phosphonic Acid anhydride and charged anhydride. Also, in the 31P MAS NMR spectrum, two distinct resonances appear, arising from “normal” Phosphonic Acid and Phosphonic Acid anhydride. 31P double-quantum NMR experi...
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intermediate temperature proton conductors for pem fuel cells based on Phosphonic Acid as protogenic group a progress report
Physical Chemistry Chemical Physics, 2007Co-Authors: Hanna Steininger, M. Schuster, Klaus-dieter Kreuer, Joachim Maier, Anke Kaltbeitzel, Bahar Bingol, Wolfgang H Meyer, Siri Schauff, Gunther Brunklaus, Hans Wolfgang SpiessAbstract:The melting behaviour and transport properties of straight chain alkanes mono- and difunctionalized with Phosphonic Acid groups have been investigated as a function of their length. The increase of melting temperature and decrease of proton conductivity with increasing chain length is suggested to be the consequence of an increasing ordering of the alkane segments which constrains the free aggregation of the Phosphonic Acid groups. However, the proton mobility is reduced to a greater extent than the proton diffusion coefficient indicating an increasing cooperativity of proton transport with increasing length of the alkane segment. The results clearly indicate that the “spacer concept”, which had been proven successful in the optimization of the proton conductivity of heterocycle based systems, fails in the case of Phosphonic Acid functionalized polymers. Instead, a very high concentration of Phosphonic Acid functional groups forming “bulky” hydrogen bonded aggregates is suggested to be essential for obtaining very high proton conductivity. Aggregation is also suggested to reduce condensation reactions generally observed in Phosphonic Acid containing systems. On the basis of this understanding, the proton conductivities of poly(vinyl Phosphonic Acid) and poly(meta-phenylene Phosphonic Acid) are discussed. Though both polymers exhibit a substantial concentration of Phosphonic Acid groups, aggregation seems to be constrained to such an extent that intrinsic proton conductivity is limited to values below σ = 10–3 S cm–1 at T = 150 °C. The results suggest that different immobilization concepts have to be developed in order to minimize the conductivity reduction compared to the very high intrinsic proton conductivity of neat Phosphonic Acid under quasi dry conditions. In the presence of high water activities, however, (as usually present in PEM fuel cells) the very high ion exchange capacities (IEC) possible for Phosphonic Acid functionalized ionomers (IEC >10 meq g–1) may allow for high proton conductivities in the intermediate temperature range (T ∼ 120 –160 °C).
Bahar Bingol - One of the best experts on this subject based on the ideXlab platform.
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high resolution solid state nmr studies of poly vinyl Phosphonic Acid proton conducting polymer molecular structure and proton dynamics
Journal of Physical Chemistry B, 2007Co-Authors: Young Joo Lee, Bahar Bingol, Wolfgang H Meyer, Tatiana Murakhtina, Daniel Sebastiani, Gerhard Wegner, Hans Wolfgang SpiessAbstract:The structure and the local proton mobility of poly(vinyl Phosphonic Acid) were studied by solid-state NMR under fast magic-angle spinning. At elevated temperatures, the signature of the hydrogen-bonded P−OH protons is observed in 1H magic-angle spinning (MAS) NMR as a single resonance at 10.5 ppm. Both 1H double-quantum NMR and variable-temperature experiments demonstrate that P−OH protons are mobile and thus able to contribute to proton conductivity. Below room temperature, two different types of hydrogen-bonded P−OH resonances are observed at 10.5 and 15 ppm, and 1H double-quantum NMR demonstrates that these protons are immobile on the NMR time scale. By means of first-principles calculations of a model polymer, we have assigned the additional hydrogen-bonded species at lower temperatures to Phosphonic Acid anhydride and charged anhydride. Also, in the 31P MAS NMR spectrum, two distinct resonances appear, arising from “normal” Phosphonic Acid and Phosphonic Acid anhydride. 31P double-quantum NMR experi...
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intermediate temperature proton conductors for pem fuel cells based on Phosphonic Acid as protogenic group a progress report
Physical Chemistry Chemical Physics, 2007Co-Authors: Hanna Steininger, M. Schuster, Klaus-dieter Kreuer, Joachim Maier, Anke Kaltbeitzel, Bahar Bingol, Wolfgang H Meyer, Siri Schauff, Gunther Brunklaus, Hans Wolfgang SpiessAbstract:The melting behaviour and transport properties of straight chain alkanes mono- and difunctionalized with Phosphonic Acid groups have been investigated as a function of their length. The increase of melting temperature and decrease of proton conductivity with increasing chain length is suggested to be the consequence of an increasing ordering of the alkane segments which constrains the free aggregation of the Phosphonic Acid groups. However, the proton mobility is reduced to a greater extent than the proton diffusion coefficient indicating an increasing cooperativity of proton transport with increasing length of the alkane segment. The results clearly indicate that the “spacer concept”, which had been proven successful in the optimization of the proton conductivity of heterocycle based systems, fails in the case of Phosphonic Acid functionalized polymers. Instead, a very high concentration of Phosphonic Acid functional groups forming “bulky” hydrogen bonded aggregates is suggested to be essential for obtaining very high proton conductivity. Aggregation is also suggested to reduce condensation reactions generally observed in Phosphonic Acid containing systems. On the basis of this understanding, the proton conductivities of poly(vinyl Phosphonic Acid) and poly(meta-phenylene Phosphonic Acid) are discussed. Though both polymers exhibit a substantial concentration of Phosphonic Acid groups, aggregation seems to be constrained to such an extent that intrinsic proton conductivity is limited to values below σ = 10–3 S cm–1 at T = 150 °C. The results suggest that different immobilization concepts have to be developed in order to minimize the conductivity reduction compared to the very high intrinsic proton conductivity of neat Phosphonic Acid under quasi dry conditions. In the presence of high water activities, however, (as usually present in PEM fuel cells) the very high ion exchange capacities (IEC) possible for Phosphonic Acid functionalized ionomers (IEC >10 meq g–1) may allow for high proton conductivities in the intermediate temperature range (T ∼ 120 –160 °C).