Dependence of electroosmosis on polymer structure in proton exchange membranes

Mabuchi, Takuya; Tokumasu, Takashi

doi:10.1299/mej.17-00054

Cited by 12 publications

(12 citation statements)

References 59 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Most ionomer studies have focused on the solid membrane and thin-film state to clarify the relationship between the ionomer morphology and mass transport. , The morphological characteristics of ionomers have been studied extensively using experimental approaches, such as scattering experiments, − positron annihilation spectroscopy, , and neutron reflectivity measurements . Theoretical approaches, such as molecular dynamics (MD) simulations, have also been used to understand proton and oxygen transport at the nanoscale level within the morphology of PFSA ionomer membranes − and thin films. − …”

Section: Introductionmentioning

confidence: 99%

Influence of Ionomer Loading and Substrate Wettability on the Morphology of Ionomer Thin Films Using Coarse-Grained Solvent Evaporation Simulations

2020

Self Cite

View full text Add to dashboard Cite

Coarse-grained molecular dynamics simulations were performed to understand the evolution of ionomer morphologies in solutions during solvent evaporation. To reproduce experimental fabrication conditions, the simulation conditions, such as evaporation and sedimentation rate, were determined based on a dimensionless parameter, the Péclet number, providing a direct link between simulation results and experimental findings. The effects of ionomer loading and substrate wettability on the morphologies of ionomer thin films after drying were investigated extensively, which exhibit similar trends reported in experiments. At low ionomer loading, a discontinuous patchy film with a minimum thickness of ≈3 nm was formed on the hydrophobic substrate, whereas a high-coverage continuous film of ≈2 nm thickness was found on the hydrophilic substrate. At high ionomer loading, regardless of the substrate wettability, a lamellar-like morphology with multiple water-rich layers was observed, although the stability of the layer structures and the ionomer surface roughness differ between the substrate types because the substrate wettability strongly affects the adsorption behaviors of ionomers and water as the first layer in the interfacial region. Our findings of a decrease in the degree of phase segregation with increasing thickness suggest an eventual collapse of the lamellar structure at a certain thickness within a few tens of nanometers or even thinner.

show abstract

Section: Introductionmentioning

confidence: 99%

Influence of Ionomer Loading and Substrate Wettability on the Morphology of Ionomer Thin Films Using Coarse-Grained Solvent Evaporation Simulations

2020

Self Cite

View full text Add to dashboard Cite

show abstract

“… K drag values are found to increase almost linearly with increasing diameters, which is attributed to the increase in the free water volume, where water molecules can move freely without being trapped by sulfonate groups. In the case of Nafion membranes, K drag values obtained by experimental measurements and simulations are found in the range of 1.0–2.5, depending on the water content. We expect that these differences are mainly a result of the highly connected water nanochannels through the membranes.…”

Section: Resultsmentioning

confidence: 97%

“…Following our previous study, the electroosmotic drag coefficient, K drag , is defined as:

K_{drag} = \frac{J_{{normalH}_{2} O}}{J_{H^{+}}},

where

J_{{normalH}^{+}}

and

J_{H_{2} normalO}

are the mass fluxes of protons and water molecules along the axis, respectively. The mass flux J X can be obtained by multiplying the concentration of X and the mean velocity of X induced by the electric field.…”

Section: Resultsmentioning

confidence: 99%

“…To evaluate electroosmotic properties, an external electric field of E = 0.4 V/nm, which is equivalent to that used in the previous study of PEMs, was applied along the axis ( z direction) to obtain statistically reliable fluxes of protons while avoiding an ordered dipole orientation of water molecules by an excessive degree of external electric fields. On the basis of the report by Ren et al ., the disordered structure of water molecules can be retained at E ≤ 0.4 V/nm.…”

Section: Simulation Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Effects of water nanochannel diameter on proton transport in proton‐exchange membranes

Mabuchi

Tokumasu

2019

J Polym Sci B Polym Phys

Self Cite

View full text Add to dashboard Cite

The effects of water nanochannel diameter on proton transport pathways and properties have been studied using reactive molecular dynamics simulations. The proton distributions and diffusivities have been evaluated using the cylinder model of water domains at various diameters that is the most typical proposed morphological model in proton‐exchange membranes. The proton distributions are analyzed to clarify proton pathways by classifying the water channel into two regions in parallel: an inner channel (free water) and an outer channel (bound water). For all the water contents, the nonmonotonic trends that show a peak at a certain diameter are found to be observed in the proton diffusivity, which is dominated by the proton diffusivity in the free water region and has a strong correlation with the proton distribution that is controlled by the balance between the volume fraction of free water and the surface density of sulfonate groups. The electroosmotic drag coefficients are found to increase monotonically with increasing channel diameter as a result of the increase in the volume fraction of free water. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 867–878

show abstract

“…Although the types of macromolecules and ions are different in the present study, in our previous studies, we analyzed the ion transport phenomena in polymer electrolyte membranes and polymer thin films with thicknesses of several nanometers in polymer electrolyte fuel cells using MD simulations; further, we analyzed the correlation of the polymer structure with the vehicular ion diffusion [ 17 ], the structural ion diffusion [ 18 , 19 , 20 , 21 ], and the electroosmosis [ 22 ]. Based on these findings, the present study aimed to clarify the effect of nanoscale structural properties on the ion transport properties of the PEO-LiTFSI system and P(2EO-MO)-LiTFSI system.…”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Study of Ion Transport in Polymer Electrolytes of All-Solid-State Li-Ion Batteries

2021

Self Cite

View full text Add to dashboard Cite

Atomistic analysis of the ion transport in polymer electrolytes for all-solid-state Li-ion batteries was performed using molecular dynamics simulations to investigate the relationship between Li-ion transport and polymer morphology. Polyethylene oxide (PEO) and poly(diethylene oxide-alt-oxymethylene), P(2EO-MO), were used as the electrolyte materials, and the effects of salt concentrations and polymer types on the ion transport properties were explored. The size and number of LiTFSI clusters were found to increase with increasing salt concentrations, leading to a decrease in ion diffusivity at high salt concentrations. The Li-ion transport mechanisms were further analyzed by calculating the inter/intra-hopping rate and distance at various ion concentrations in PEO and P(2EO-MO) polymers. While the balance between the rate and distance of inter-hopping was comparable for both PEO and P(2EO-MO), the intra-hopping rate and distance were found to be higher in PEO than in P(2EO-MO), leading to a higher diffusivity in PEO. The results of this study provide insights into the correlation between the nanoscopic structures of ion solvation and the dynamics of Li-ion transport in polymer electrolytes.

show abstract

Dependence of electroosmosis on polymer structure in proton exchange membranes

Cited by 12 publications

References 59 publications

Influence of Ionomer Loading and Substrate Wettability on the Morphology of Ionomer Thin Films Using Coarse-Grained Solvent Evaporation Simulations

Influence of Ionomer Loading and Substrate Wettability on the Morphology of Ionomer Thin Films Using Coarse-Grained Solvent Evaporation Simulations

Effects of water nanochannel diameter on proton transport in proton‐exchange membranes

Molecular Dynamics Study of Ion Transport in Polymer Electrolytes of All-Solid-State Li-Ion Batteries

Contact Info

Product

Resources

About