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Ion transport through electrolyte/polyelectrolyte multi-layers.

Femmer R, Mani A, Wessling M - Sci Rep (2015)

Bottom Line: Ion transport of multi-ionic solutions through layered electrolyte and polyelectrolyte structures are relevant in a large variety of technical systems such as micro and nanofluidic devices, sensors, batteries and large desalination process systems.EnPEn can robustly capture ion transport in sub-millimeter architectures with submicron polyelectrolyte layers.We proof the strength of EnPEn for three yet unsolved architectures: (a) selective Na over Ca transport in surface modified ion selective membranes, (b) ion transport and water splitting in bipolar membranes and (c) transport of weak electrolytes.

View Article: PubMed Central - PubMed

Affiliation: AVT Chemical Process Engineering, RWTH Aachen University, Turmstr. 46, 52064 Aachen, Germany.

ABSTRACT
Ion transport of multi-ionic solutions through layered electrolyte and polyelectrolyte structures are relevant in a large variety of technical systems such as micro and nanofluidic devices, sensors, batteries and large desalination process systems. We report a new direct numerical simulation model coined EnPEn: it allows to solve a set of first principle equations to predict for multiple ions their concentration and electrical potential profiles in electro-chemically complex architectures of n layered electrolytes E and n polyelectrolytes PE. EnPEn can robustly capture ion transport in sub-millimeter architectures with submicron polyelectrolyte layers. We proof the strength of EnPEn for three yet unsolved architectures: (a) selective Na over Ca transport in surface modified ion selective membranes, (b) ion transport and water splitting in bipolar membranes and (c) transport of weak electrolytes.

No MeSH data available.


Related in: MedlinePlus

a) Current-voltage behaviour of bipolar membranes depending on the junction thickness. The onset of water splitting at V = 20 Vth is common for all junction thicknesses, the current behaviour at higher potentials exhibits strong non-linear dependence on junction thickness. b) Concentration profile of Water over the domain at limiting current density. At the 2 nm junction water concentration is only slightly reduced.
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f5: a) Current-voltage behaviour of bipolar membranes depending on the junction thickness. The onset of water splitting at V = 20 Vth is common for all junction thicknesses, the current behaviour at higher potentials exhibits strong non-linear dependence on junction thickness. b) Concentration profile of Water over the domain at limiting current density. At the 2 nm junction water concentration is only slightly reduced.

Mentions: With respect to the analysis of the second limiting current density, the model can be used to investigate the effect of junction thickness for instance. Figure 5 indicates that features of the current voltage curves depend strongly on the junction thickness for high potential drops. The onset of the limiting current density moves with increasing junction thickness towards higher current densities and higher potentials. The total rate of H+ and OH− ion production in the junction layer is the integral of the reaction rate over the junction volume. Therefore, a larger volume explains a higher limiting current density. However, sustaining a large electric field over thicker junction layers also requires a larger overall potential drop. In the limit of vanishing a junction thickness, the potential drop will overlap with the membranes, however, behaving similarly to a 1 nm junction. Consequently, for a given production rate there exists an optimal junction layer thickness. In the example of Fig. 5 for current densities below 0.012, a junction thickness of 4–5 nm would minimize power consumption. The results show that the proposed autoprotolysis kinetics do not lead to a complete drying of the membrane junction. Here, the limiting current density stems from a slight decrease in available water ions. Concentration profiles, pH and the development of the corresponding iV curve are visualized in a supplementary video.


Ion transport through electrolyte/polyelectrolyte multi-layers.

Femmer R, Mani A, Wessling M - Sci Rep (2015)

a) Current-voltage behaviour of bipolar membranes depending on the junction thickness. The onset of water splitting at V = 20 Vth is common for all junction thicknesses, the current behaviour at higher potentials exhibits strong non-linear dependence on junction thickness. b) Concentration profile of Water over the domain at limiting current density. At the 2 nm junction water concentration is only slightly reduced.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4481379&req=5

f5: a) Current-voltage behaviour of bipolar membranes depending on the junction thickness. The onset of water splitting at V = 20 Vth is common for all junction thicknesses, the current behaviour at higher potentials exhibits strong non-linear dependence on junction thickness. b) Concentration profile of Water over the domain at limiting current density. At the 2 nm junction water concentration is only slightly reduced.
Mentions: With respect to the analysis of the second limiting current density, the model can be used to investigate the effect of junction thickness for instance. Figure 5 indicates that features of the current voltage curves depend strongly on the junction thickness for high potential drops. The onset of the limiting current density moves with increasing junction thickness towards higher current densities and higher potentials. The total rate of H+ and OH− ion production in the junction layer is the integral of the reaction rate over the junction volume. Therefore, a larger volume explains a higher limiting current density. However, sustaining a large electric field over thicker junction layers also requires a larger overall potential drop. In the limit of vanishing a junction thickness, the potential drop will overlap with the membranes, however, behaving similarly to a 1 nm junction. Consequently, for a given production rate there exists an optimal junction layer thickness. In the example of Fig. 5 for current densities below 0.012, a junction thickness of 4–5 nm would minimize power consumption. The results show that the proposed autoprotolysis kinetics do not lead to a complete drying of the membrane junction. Here, the limiting current density stems from a slight decrease in available water ions. Concentration profiles, pH and the development of the corresponding iV curve are visualized in a supplementary video.

Bottom Line: Ion transport of multi-ionic solutions through layered electrolyte and polyelectrolyte structures are relevant in a large variety of technical systems such as micro and nanofluidic devices, sensors, batteries and large desalination process systems.EnPEn can robustly capture ion transport in sub-millimeter architectures with submicron polyelectrolyte layers.We proof the strength of EnPEn for three yet unsolved architectures: (a) selective Na over Ca transport in surface modified ion selective membranes, (b) ion transport and water splitting in bipolar membranes and (c) transport of weak electrolytes.

View Article: PubMed Central - PubMed

Affiliation: AVT Chemical Process Engineering, RWTH Aachen University, Turmstr. 46, 52064 Aachen, Germany.

ABSTRACT
Ion transport of multi-ionic solutions through layered electrolyte and polyelectrolyte structures are relevant in a large variety of technical systems such as micro and nanofluidic devices, sensors, batteries and large desalination process systems. We report a new direct numerical simulation model coined EnPEn: it allows to solve a set of first principle equations to predict for multiple ions their concentration and electrical potential profiles in electro-chemically complex architectures of n layered electrolytes E and n polyelectrolytes PE. EnPEn can robustly capture ion transport in sub-millimeter architectures with submicron polyelectrolyte layers. We proof the strength of EnPEn for three yet unsolved architectures: (a) selective Na over Ca transport in surface modified ion selective membranes, (b) ion transport and water splitting in bipolar membranes and (c) transport of weak electrolytes.

No MeSH data available.


Related in: MedlinePlus