Functionalized mesoporous materials used as proton conductive additives for high temperature PEM fuel cell membranes

Marschall, Roland; Wark, Michael; Jeske, Michael; Wilhelm, Michaela; Grathwohl, Georg; Caro, Jürgen

doi:10.1016/s0167-2991(07)81028-7

Cited by 5 publications

(14 citation statements)

References 6 publications

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“…SANS measurements combined with H 2 O/D 2 O (42:58) adsorption on a Si-MCM-41 sample functionalized with MPMS by co-condensation, however, document a different situation (Figure ). Although obviously the quality of the mesoporous structure is slightly decreased compared to the samples functionalized by grafting, because the small diffraction signals have already disappeared in the pattern taken in vacuum, the presence of the strong main signal proves the existence of the mesoporous structure as also confirmed by nitrogen adsorption and X-ray diffraction measurements . Again, adsorption of the H 2 O/D 2 O molecules first smooth the inner pore walls and cause a slight increase in the intensity of the SANS diffraction signal.…”

Section: Resultsmentioning

confidence: 75%

“…Water sorption isotherms at 295 K were obtained by volumetric vapor adsorption on a BELSORP 18−3 (Bel Japan Inc.) measurement device using an equilibration time of 500 s. The samples were dried at 395 K in flowing argon for 24 h before measurement . To determine the proton conductivities, impedance spectroscopy measurements were performed on a Zahner electrochemical workstation IM6e in a frequency range from 1 to 10 6 Hz with an oscillating voltage of 100 mV.…”

Section: Syntheses and Characterizationmentioning

confidence: 99%

“…The samples synthesized by co-condensation exhibit higher proton conductivities along the whole temperature range (Table ). The obtained values make them attractive for use as additives in fuel cells membranes, because commercially used Nafion membranes mostly also exhibit proton conductivities around 10 −1 S/cm, whereas the conductivity drops down at temperatures above 373 K . On the basis of the synthesis procedure and theoretical models, this could be explained by assuming that in the case of co-condensation, the SO 3 H groups are more homogenously distributed along the pores, but an experimental proof is needed.…”

Section: Introductionmentioning

confidence: 99%

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Detection of Homogeneous Distribution of Functional Groups in Mesoporous Silica by Small Angle Neutron Scattering and in Situ Adsorption of Nitrogen or Water

et al. 2011

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The distribution of SO(3)H-functional groups attached to the ordered inner pore walls of mesoporous Si-MCM-41 materials based on SiO(2) was investigated by gas adsorption combined with in situ small angle neutron scattering (SANS). The functionalization was performed by two different methods, (i) grafting and (ii) co-condensation. The adsorbates N(2) at 77 K or a H(2)O/D(2)O mixture of 42:58 at 298 K possess neutron scattering length densities (SLD) similar to that of SiO(2) and therefore quench the diffraction signals of the nonmodified silica. SANS measurements show that N(2) matches completely not only with the pristine mesoporous Si-MCM-41 but also with Si-MCM-41-SO(3)H functionalized by grafting. Thus, full access of adsorbate into the entire length of the pores is proven. For the analysis of the distribution of functional groups within the pores in dependence on the used functionalization method, grafting or co-condensation, however, the more specific adsorbate H(2)O/D(2)O (42:58) is necessary, because it reacts more sensitively toward small changes in the SLD of the host material. For grafted Si-MCM-41-SO(3)H materials, an incomplete quenching was observed, indicating that only some regions, probably the pore mouths, have been modified. For a sample functionalized by co-condensation, almost no quenching of the neutron diffraction was found, indicating a very homogeneous distribution of the functional groups along the entire pores.

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Section: Resultsmentioning

confidence: 75%

Section: Syntheses and Characterizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Detection of Homogeneous Distribution of Functional Groups in Mesoporous Silica by Small Angle Neutron Scattering and in Situ Adsorption of Nitrogen or Water

et al. 2011

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“…The comparability is also questionable because our materials exhibit a rigid silica framework providing less degrees of freedom for the proton conduction. As compared to sulfonated MCM-41 materials formed by oxidation of grafted mercaptosilane species, the calculated average activation energies are significantly lower …”

Section: Discussionmentioning

confidence: 99%

Proton Conduction in Sulfonated Organic–Inorganic Hybrid Monoliths with Hierarchical Pore Structure

Lehr

Seidler

Taffa

et al. 2016

ACS Appl. Mater. Interfaces

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Porous organic-inorganic hybrid monoliths with hierarchical porosity exhibiting macro- and mesopores are prepared via sol-gel process under variation of the mesopore size. Organic moieties in the pore walls are incorporated by substituting up to 10% of the silicon precursor tetramethylorthosilicate with bisilylated benzene molecules. After functionalization with sulfonic acid groups, the resulting sulfonated hybrid monoliths featuring a bimodal pore structure are investigated regarding proton conduction depending on temperature and relative humidity. The hierarchical pore system and controlled mesopore design turn out to be crucial for sulfonation and proton conduction. These sulfonated hybrid hierarchical monoliths containing only 10% organic precursor exhibit higher proton conduction at different relative humidities than sulfonated periodic mesoporous organosilica made of 100% bisilylated precursors exhibiting solely mesopores, even with a lower concentration of sulfonic acid groups.

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“…This work deals with the proton transfer on propyl‐imidazole functionalised mesoporous silicon dioxide particles, which are e.g . used as additives to the polymer electrolyte membranes for fuel cell application 1–7. Here, the intrinsic proton transport ability of the surface under dry working conditions is studied.…”

Section: Introductionmentioning

confidence: 99%

Water free proton transport in imidazole functionalised silicon dioxide material: Calculation of free energy barrier dependent on the mCEC proton coordinate

Tölle

Köhler

2011

Physica Status Solidi (b)

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Free energy barriers are calculated using the modified centre of excess charge (mCEC) coordinate and the umbrella sampling formalism. Proton transport is described on propylimidazole functionalised silicon dioxide surfaces by a quantum mechanical-molecular mechanical coupling (QM/MM) coupling approach, coupling the density functional-based tight binding method (DFTB) to a classical force field. The proton transport between imidazole groups on the dry surface is shown to be favourable. Besides the comparison of competing transport mechanisms, we discuss the influence of the proton coordinate and the choice of the reaction coordinate.

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Functionalized mesoporous materials used as proton conductive additives for high temperature PEM fuel cell membranes

Cited by 5 publications

References 6 publications

Detection of Homogeneous Distribution of Functional Groups in Mesoporous Silica by Small Angle Neutron Scattering and in Situ Adsorption of Nitrogen or Water

Detection of Homogeneous Distribution of Functional Groups in Mesoporous Silica by Small Angle Neutron Scattering and in Situ Adsorption of Nitrogen or Water

Proton Conduction in Sulfonated Organic–Inorganic Hybrid Monoliths with Hierarchical Pore Structure

Water free proton transport in imidazole functionalised silicon dioxide material: Calculation of free energy barrier dependent on the mCEC proton coordinate

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