Molecular simulation of mass transport in phosphoric acid doped poly(2,5-benzimidazole) polymer electrolyte membranes

Sun, Hong; Yu, Mingfu; Zhao, Xuenan; Almheiri, Saif

doi:10.1016/j.ijhydene.2015.11.008

Cited by 12 publications

(3 citation statements)

References 35 publications

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“…In this context, the molecular dynamics (MD) simulation technique was used to provide detailed information on polymer properties and electrode morphologies at various PTFE contents in this study. In addition, MD simulations are useful tools for elucidating detailed atomistic information when designing PEMFC components. − Note that most of the MD simulation used in HT-PEMFC studies have focused on the phosphoric acid and PBI in the membrane system, while the HT-PEMFC electrode has not been thoroughly simulated, even though establishing the structures and morphologies of the contents of the PTFE binder at the molecular level is important. Therefore, in this study, we investigated how the PTFE distribution changes with changing PTFE content on a Pt/C catalyst using full atomistic MD simulations.…”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Simulation to Reveal Effects of Binder Content on Pt/C Catalyst Coverage in a High-Temperature Polymer Electrolyte Membrane Fuel Cell

Kwon

Lee

Kim

et al. 2018

ACS Appl. Nano Mater.

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Full atomistic molecular dynamics simulations were performed to provide detailed information on the morphologies of Pt/C catalyst with varying poly(tetrafuoroethylene) (PTFE) binder contents. Changes in the surface configuration and PTFE coverage on Pt particles with changing binder content were examined on the molecular level; this coverage can affect the catalytic performance of Pt particles and PTFE binding. The PTFE binder content in the prepared solutions ranged from 4.0 to 35.1 wt %. From Pt-PTFE pair correlation analysis, the coordination number of this pair increased from 0.43 to 1.23 as the PTFE binder content increased from 4.0 to 35.1 wt %, with a concomitant 40.0 to 84.0% change in coverage over the Pt surface. At low PTFE content, the PTFE binder was dispersed between Pt particles and the carbons on the Pt/C surface to form a triple-phase boundary. Subsequently, Pt particles become increasingly covered by PTFE with increasing binder content. However, no significant changes were observed when the PTFE content exceeded 20.0 wt %; we expect that the catalytic performance of Pt will significantly decrease at PTFE binder contents greater than 20.0 wt %. Considering the Pt-retaining role of the binder, we conclude that the optimum PTFE binder content is less than 20.0 wt % for the ∼2.6 nm diameter Pt particle used in this study. This investigation provides detailed information on polymer properties and electrode morphologies for high-temperature polymer electrolyte membrane fuel cells applications at various PTFE binder contents.

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Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Simulation to Reveal Effects of Binder Content on Pt/C Catalyst Coverage in a High-Temperature Polymer Electrolyte Membrane Fuel Cell

Kwon

Lee

Kim

et al. 2018

ACS Appl. Nano Mater.

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“…PA molecules and the imidazole rings from PBI form proton wires along which protons hop by alternating cleavage and formation of hydrogen bonds. This hopping mechanism ensures the membrane performance under low RH …”

Section: Introductionmentioning

confidence: 91%

Pre‐Oxidized Acrylic Fiber Reinforced Ferric Sulfophenyl Phosphate‐Doped Polybenzimidazole‐Based High‐Temperature Proton Exchange Membrane

Sun

Liu

Jin

et al. 2017

Macro Materials & Eng

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Pre-oxidized acrylic fiber (POAF) and ferric sulfophenyl phosphate (FeSPP) are incorporated into polybenzimidazole (PBI) membrane for the first time to prepare high-temperature proton exchange membranes (PEMs). The strong hydrogen bonds formed between PBI/POAF and FeSPP lead to good dispersion of POAF and FeSPP, facilitate the construction of proton channels, and enhance the dimensional and mechanical stability of the membranes. PBI/FeSPP (30 wt%) shows good proton conductivity (5.43 × 10 −2 and 4.13 × 10 −2 S cm −1 at 180 °C at 50% and 0 relative humidity (RH), respectively) and improved dimensional and mechanical stability compared with pristine PBI. By incorporating 5 wt% POAF into PBI/FeSPP (30 wt%), the swelling ratios are halved and the mechanical strength is enhanced by almost 30% while the proton conductivity is slightly affected (3.84 × 10 −2 and 2.97 × 10 −2 S cm −1 at 180 °C at 50% and 0 RH for PBI/FeSPP (30 wt%)/POAF (5 wt%), respectively). This work offers a new route in the preparation of high-temperature PEMs with enhanced properties.

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“…MD simulations provide the opportunity to explore the underlying physical phenomena associated with fuel cell membranes at atomistic scales, and thereby elucidate detailed information regarding various membrane characteristics, which are difficult to be acquired through experiments. These techniques have been recently used to examine the various properties of water and water/methanol solvated Nafion and alternative PEMs . In spite of numerous experimental research studies directed toward the chitosan membranes , very few computational works have been reported in literature for hydrated chitosan, and to the best of our knowledge no researches have been published concerning the methanol crossover phenomenon in chitosan‐based DMFC polyelectrolyte.…”

Section: Introductionmentioning

confidence: 99%

Morphological and transport characteristics of swollen chitosan‐based proton exchange membranes studied by molecular modeling

2016

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Chitosan biopolymer has been extensively applied in direct methanol fuel cells (DMFCs) as a potential replacement to conventional Nafion membrane for its considerably reduced methanol crossover. Here, we computationally explored the influences of methanol concentration, temperature, and pH parameters upon the nanostructure and dynamics, particularly the methanol crossover, in chitosan proton-exchange membrane (PEM) through molecular dynamics simulations. Theoretical results demonstrated the increased swelling and radius of gyration of chitosan chains at higher concentrations. Structural examinations further revealed that an increase in methanol loading weakened the water interactions with chitosan functionalities (amineNH , hydroxylOH, and methoxyCH OH) whereas improved the methanol affinities toward chitosan, reflecting higher methanol sorption capability of chitosan at enhanced concentrations. Additionally, it was found that interactions between solvents and chitosan strengthened under acidic pH conditions on account of amine protonation. The water diffusivity inside the swollen chitosan diminished by increasing CH OH uptake, and in contrast diffusivity of methanol was noted to enhance. Furthermore, it was observed that an enhancement in temperature or a decrease in pH intensified solvent mobility. These insights imply that supplying methanol-concentrated and/or acidic feed solutions into DMFCs based on chitosan PEMs could lower membrane performance due to the significant methanol transport dynamics.

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Molecular simulation of mass transport in phosphoric acid doped poly(2,5-benzimidazole) polymer electrolyte membranes

Cited by 12 publications

References 35 publications

Molecular Dynamics Simulation to Reveal Effects of Binder Content on Pt/C Catalyst Coverage in a High-Temperature Polymer Electrolyte Membrane Fuel Cell

Molecular Dynamics Simulation to Reveal Effects of Binder Content on Pt/C Catalyst Coverage in a High-Temperature Polymer Electrolyte Membrane Fuel Cell

Pre‐Oxidized Acrylic Fiber Reinforced Ferric Sulfophenyl Phosphate‐Doped Polybenzimidazole‐Based High‐Temperature Proton Exchange Membrane

Morphological and transport characteristics of swollen chitosan‐based proton exchange membranes studied by molecular modeling

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