Abstract:The morphology and transport properties of thin films of the ionomer Nafion, with thicknesses on the order of the bulk cluster size, have been investigated as a model system to explain the anomalous behaviour of catalyst/electrode-polymer interfaces in membrane-electrode assemblies. We have employed dissipative particle dynamics (DPD) to investigate the interaction of water and fluorocarbon chains with carbon and quartz as confining materials for a wide range of operational water contents and film thicknesses.… Show more
“…In order to clarify the origin of the interfacial resistance, Jinnouchi et al 24 and Kurihara et al 25 performed molecular dynamics (MD) simulations and showed that the interfacial resistance originates from the dense ionomer layer created at the ionomer/Pt interface. By contrast, a more significant bulk ionomer resistance was recently proposed on the basis of hydrogen pump experiments 26 and a mesoscopic CL model 27 assuming highly reduced transport in thin films compared to that in bulk ionomers because of confinement effects 28 or substrate interactions 29 . Fig.…”
In recent years, considerable research and development efforts are devoted to improving the performance of polymer electrolyte fuel cells. However, the power density and catalytic activities of these energy conversion devices are still far from being satisfactory for large-scale operation. Here we report performance enhancement via incorporation, in the cathode catalyst layers, of a ring-structured backbone matrix into ionomers. Electrochemical characterizations of single cells and microelectrodes reveal that high power density is obtained using an ionomer with high oxygen solubility. The high solubility allows oxygen to permeate the ionomer/catalyst interface and react with protons and electrons on the catalyst surfaces. Furthermore, characterizations of single cells and single-crystal surfaces reveal that the oxygen reduction reaction activity is enhanced owing to the mitigation of catalyst poisoning by sulfonate anion groups. Molecular dynamics simulations indicate that both the high permeation and poisoning mitigation are due to the suppression of densely layered folding of polymer backbones near the catalyst surfaces by the incorporated ring-structured matrix. These experimental and theoretical observations demonstrate that ionomerâs tailored molecular design promotes local oxygen transport and catalytic reactions.
“…In order to clarify the origin of the interfacial resistance, Jinnouchi et al 24 and Kurihara et al 25 performed molecular dynamics (MD) simulations and showed that the interfacial resistance originates from the dense ionomer layer created at the ionomer/Pt interface. By contrast, a more significant bulk ionomer resistance was recently proposed on the basis of hydrogen pump experiments 26 and a mesoscopic CL model 27 assuming highly reduced transport in thin films compared to that in bulk ionomers because of confinement effects 28 or substrate interactions 29 . Fig.…”
In recent years, considerable research and development efforts are devoted to improving the performance of polymer electrolyte fuel cells. However, the power density and catalytic activities of these energy conversion devices are still far from being satisfactory for large-scale operation. Here we report performance enhancement via incorporation, in the cathode catalyst layers, of a ring-structured backbone matrix into ionomers. Electrochemical characterizations of single cells and microelectrodes reveal that high power density is obtained using an ionomer with high oxygen solubility. The high solubility allows oxygen to permeate the ionomer/catalyst interface and react with protons and electrons on the catalyst surfaces. Furthermore, characterizations of single cells and single-crystal surfaces reveal that the oxygen reduction reaction activity is enhanced owing to the mitigation of catalyst poisoning by sulfonate anion groups. Molecular dynamics simulations indicate that both the high permeation and poisoning mitigation are due to the suppression of densely layered folding of polymer backbones near the catalyst surfaces by the incorporated ring-structured matrix. These experimental and theoretical observations demonstrate that ionomerâs tailored molecular design promotes local oxygen transport and catalytic reactions.
“…Other types of important polymeric materials are the hydrated selectively permeable membranes (particularly the Nafion membranes), which play a crucial role in fuel cells. Their study has represented a hot topic for experimentalists [266,267], theoreticians and computer scientists for several decades, and it is not surprising that several recent DPD studies have addressed the fuel cell membranes [124,253,[268][269][270][271][272][273]; the last two papers unfortunately study the electrically charged system without explicit electrostatics, which restricts their impact. On the other hand, the papers on hydrated membranes published by the Neimark group [124,271,273] are of special interest because they also contribute significantly to the methodological progress in DPD modelling.…”
Section: Experiment-inspired and Application-orientated Papersmentioning
This review article is addressed to a broad community of polymer scientists. We outline and analyse the fundamentals of the dissipative particle dynamics (DPD) simulation method from the point of view of polymer physics and review the articles on polymer systems published in approximately the last two decades, focusing on their impact on macromolecular science. Special attention is devoted to polymer and polyelectrolyte self- and co-assembly and self-organisation and to the problems connected with the implementation of explicit electrostatics in DPD numerical machinery. Critical analysis of the results of a number of successful DPD studies of complex polymer systems published recently documents the importance and suitability of this coarse-grained method for studying polymer systems.
“…Further applications involving dl meso dpd as the DPD simulation engine have made use of the same technique of parameterising conservative interactions by finding energies of mixing or Hildebrand solubility parameters using atomistic molecular dynamics or Monte Carlo simulations. These include systems involving carbon nanotubes [100,101], Nafion [102][103][104], block copolymers with poly(carboxybetaine) and poly(ethylene glycol) [105], poly(amido amine) (PANAM) dendrimers and single-stranded DNA [106], poly(methyl methacrylate-co-butyl acrylate-co-styrene) for strengthening fragile papers [107], channel membranes of polystyrene-block -poly(4-vinyl pyridine) block copolymer [108] and phase behaviour of sophorolipids [109].…”
Section: Work Carried Out Using DL Meso Dpdmentioning
dl meso is a highly-scalable general purpose software package for mesoscale modelling. Created and developed at Daresbury Laboratory for the UK Collaborative Computational Project CCP5, it was intended to be a companion package to the flagship molecular dynamics code dl poly. One of dl meso's component codes, dl meso dpd, is based on dissipative particle dynamics, a mesoscale modelling technique with many similarities to classical molecular dynamics. While this code and dl poly were created with different applications in mind, they share a significant amount of functionality and development history. This article gives an overview on how dl meso dpd has been developed, including its shared history with dl polyand information on its current performance, and a selection of applications for which the code has been used.
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