Understanding ion diffusion in anion exchange membranes; effects of morphology and mobility of pendant cationic groups

Rezayani, Mohammad; Sharif, Farhad; Makki, Hesam

doi:10.1039/d2ta04400e

Cited by 23 publications

(35 citation statements)

References 73 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…To gain more structural detail for diffusivity, we turn to look at the PLD variation as a function of spacer length for different membranes. The PLD is equal to the bottleneck size and is an essential parameter for diffusants to move from one pore to another . As shown in Figure c, all membranes show a PLD in the range of 0.5–0.6 nm.…”

Section: Resultsmentioning

confidence: 95%

“…The simulation procedure of this study is inspired by our previous works. , In summary, we used a GROMACS (2020-2) package with the OPLS-AA force field to describe polyelectrolyte interactions. The partial charges of polyelectrolytes, hydronium ions, and methanol are obtained from DFT calculations using Gaussian 16 software with B3LYP theory and 6-31G* basis set. , The partial charges of PES-C6S are shown in the ESI in Figure S1 and Table S2.…”

Section: Methodsmentioning

confidence: 99%

“…Our results revealed a substantial growth in anion mobility and relatively constant methanol diffusion coefficient as the cationic group moved toward the end of the long alkyl side-chain, while the distribution of water channel size remained unchanged. We explained this behavior by the faster dynamics of the cationic group at the head of the alkyl side-chain, which promotes hand-to-hand transport of water and anions while limiting the mobility of methanol due to the constant size of the water channel . However, a similar study showed an increase in the water channel size with an increase in the alkyl side-chain length in polymers containing a flexible aliphatic backbone …”

Section: Introductionmentioning

confidence: 99%

“…Their results demonstrated that ion and water diffusion coefficients increase substantially as the alkyl spacer length increases, while clustering of ion-conducting channels is insensitive to the length of the spacer and remains relatively intact. In our most recent work, 29 we studied the role of a relatively long alkyl side-chain (16 carbon unit) as the extender, spacer, and spacer + extender attached to the cationic groups on water, anion, and methanol diffusion coefficient in PPO-based membranes by MD simulations. Our results revealed a substantial growth in anion mobility and relatively constant methanol diffusion coefficient as the cationic group moved toward the end of the long alkyl side-chain, while the distribution of water channel size remained unchanged.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Role of Side-Chain Lengths on Hydronium Mobility in Sulfonated Poly(ether sulfone) Proton-Conducting Model Membranes

2023

Self Cite

View full text Add to dashboard Cite

Designing novel polymer architectures is a key to maintain high proton conductivity for proton-conducting membranes (PCMs) while reducing fuel permeability at a medium water content. Modifying anion exchange membranes with alkyl side-chains is a common strategy to improve the aforementioned membrane properties. This improvement is attributed to the flexibility and dynamics of alkyl side-chains, which speed up the hand-to-hand process of anion diffusion. In this study, we employed this strategy for PCMs and propose hypothetical model membranes to improve proton conduction. To this end, a series of model sulfonated poly(ether sulfone) block copolymers with sulfonate groups attached to the backbone with 0, 6, 10, and 16 carbon unit spacers have been made. Then, we analyzed the morphological properties of the membranes and dynamical properties of water, hydronium ions (H 3 O + ), and methanol by using molecular dynamics simulations. We find that the morphological parameters of the PCM and the hydrophilic domains are almost robust against alkyl side-chain lengths. Nevertheless, the diffusion coefficients of water and hydronium ions increase with a side-chain length of up to 10 carbon units (around 50%) and decrease for membranes with a spacer length of 16 carbons at λ = 15. Moreover, the methanol diffusion coefficient increase, despite the substantial improvement in sulfonate group mobility, remains marginal (below 15%) with a spacer length; hence, a considerably better membrane selectivity is achieved. The results put forward a new design strategy and produce a general understanding of the structure−function interplay for the new generation of PCMs.

show abstract

Section: Resultsmentioning

confidence: 95%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Role of Side-Chain Lengths on Hydronium Mobility in Sulfonated Poly(ether sulfone) Proton-Conducting Model Membranes

2023

Self Cite

View full text Add to dashboard Cite

show abstract

“…Water sorption is a primary factor defining the water/salt transport properties of hydrated polymers and usually correlates with polymer backbone chemistry and functional groups. − Upon hydrophilization, water in the resulting hydrated polymers typically exists in three states: free water, intermediate water, and nonfreezable water. , Previous research indicates that only the freezable water (free water and intermediate water) in the polymer membrane has the solvation ability to dissolve salt, while the water permeability is pertinent to the total water uptake . Therefore, we speculate that tailoring the polymer molecular structure for the simultaneous enhancement of total water sorption and the nonfreezable water content is essential to increase the water/salt selectivity of the hydrated polymer membrane.…”

Section: Introductionmentioning

confidence: 95%

Molecular Design of Hydrophilized Polyethersulfone to Enhance Water/Salt Selectivity

et al. 2023

View full text Add to dashboard Cite

Understanding the relationship between the polymer chain structure and its water and salt transport structure− property is crucial for the development of hydrophilized polyethersulfone materials as candidates for high-performance desalination membranes. A series of novel hydrophilic polyethersulfone (HPES) copolymers were designed. Three hydrophilic molecules, thioglycolic acid, DL-cysteine hydrochloride, and 2-(dimethylamino) ethanethiol hydrochloride, were selected to modify allylcontaining polyethersulfone via thiol−ene click chemistry to prepare HPES-TGA, HPES-CYSAH, and HPES-DMAET with a controllable content of carboxyl, cysteine, and amino groups. Compared with the commercial sulfonated polysulfone (SPSF), the novel HPES polymers, especially HPES-CYSAH membranes, showed the best ideal desalting properties. The transport property measurements and simulation results show that HPES-CYSAH has the highest free volume fraction (FFV) and the strongest hydration capacity, which was also confirmed by the simulated state of the polymer in brine. This study suggests that the incorporation of bulky hydrophilic groups onto poly(arylene ether sulfone) backbone, especially zwitterionic groups, is expected to be an effective strategy for the preparation of chemically robust desalination membrane with high water permeability and high water/ salt selectivity.

show abstract

Durable Multiblock Poly(biphenyl alkylene) Anion Exchange Membranes with Microphase Separation for Hydrogen Energy Conversion

Ma,

Hu,

et al. 2023

Angewandte Chemie

View full text Add to dashboard Cite

Anion exchange membrane fuel cells (AEMFCs) and water electrolysis (AEMWE) show great application potential in the field of hydrogen energy conversion technology. However, scalable anion exchange membranes (AEMs) with desirable properties are still lacking, which greatly hampers the commercialization of this technology. Herein, we propose a series of novel multiblock AEMs based on ether‐free poly(biphenyl ammonium‐b‐biphenyl phenyl)s (PBPA‐b‐BPPs) that are suitable for use in high performance AEMFC and AEMWE systems because of their well‐formed microphase separation structures. The developed AEMs achieved outstanding OH− conductivity (162.2 mS cm−1 at 80 °C) with a low swelling ratio, good alkaline stability, and excellent mechanical durability (tensile strength >31 MPa and elongation at break >147 % after treatment in 2 M NaOH at 80 °C for 3750 h). A PBPA‐b‐BPP‐based AEMFC demonstrated a remarkable peak power density of 2.41 W cm−2 and in situ durability for 330 h under 0.6 A cm−2 at 70 °C. An AEMWE device showed a promising performance (6.25 A cm−2 at 2 V, 80 °C) and outstanding in situ durability for 3250 h with a low voltage decay rate (<28 μV h−1). The newly developed PBPA‐b‐BPP AEMs thus show great application prospects for energy conversion devices.

show abstract

Understanding ion diffusion in anion exchange membranes; effects of morphology and mobility of pendant cationic groups

Abstract: Anion Exchange membranes (AEM) are a promising low-cost alternative to cation exchange membranes (CEM) in fuel cells. Among them, poly(2, 6-dimethyl-1, 4-phenylene oxide) with pendant quaternary ammonium (PPO-QA) is one...

Cited by 23 publications

References 73 publications

Role of Side-Chain Lengths on Hydronium Mobility in Sulfonated Poly(ether sulfone) Proton-Conducting Model Membranes

Role of Side-Chain Lengths on Hydronium Mobility in Sulfonated Poly(ether sulfone) Proton-Conducting Model Membranes

Molecular Design of Hydrophilized Polyethersulfone to Enhance Water/Salt Selectivity

Durable Multiblock Poly(biphenyl alkylene) Anion Exchange Membranes with Microphase Separation for Hydrogen Energy Conversion

Contact Info

Product

Resources

About