Browsing by Author "Varshney, S.K."

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    Enhanced hydronium ion diffusion in proton exchange membranes reinforced with multilayer graphene oxide: new insights into water retention and ion mobility using molecular dynamics simulation
    (Royal Society of Chemistry, 2025) Varshney, S.K.; Koorata, P.K.
    Graphene oxide (GO) reinforced perfluorosulfonic acid (PFSA) based proton exchange membranes (PEMs) show enhanced ion diffusion resulting in elevated polymer electrolyte fuel cell (PEFC) performance. However, the mechanisms by which GO influences water dynamics and ion (hydronium) transport are relatively less explored in the literature. In addition, it is expected that the interlayer spacing of multilayer GO plays a crucial role in promoting ion mobility. To this end, this research article explores the possibility of providing new insights into the water/ion dynamics as well as identifying the impact of interlayer spacing of GO on the ion diffusion. Molecular dynamics (MD) simulation is implemented to elucidate the behaviour of multilayer-GO with PFSA structure and to examine the interactions between functional groups (epoxy and hydroxyl) on the GO surface with water molecules and hydronium ions. The retention of water molecules adjacent to the multilayer-GO plays a crucial role in forming transport channels that significantly enhance ion mobility within the membrane structure. The optimal interlayer spacing of 9.5 Å is identified as the critical threshold value where ion diffusion is observed at its peak. In comparison with pristine Nafion®, the ion (hydronium) diffusion coefficient in the multilayer-GO with PFSA polymer shows an improvement of ?17% and ?30% at 300 K and ?9% and ?12% at 350 K for hydration levels (?) of 13 and 20, respectively. This journal is © 2025 The Royal Society of Chemistry
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    Ultrafast molecular dynamics approach to quantify structural and transport properties of ion exchange polymer: a case study on perfluorinated sulfonic acid polymer
    (Royal Society of Chemistry, 2025) Varshney, S.K.; Koorata, P.K.
    A computationally efficient molecular dynamics (MD) simulation approach for evaluating the transport and structural properties of ion exchange polymers (IEPs) is proposed. Prediction of transport and structural properties of IEPs using MD simulation is beneficial in understanding structure-property relations and to design advanced tailor-made variants of such polymers. The IEP is a complex network of polymer chains with ionic end groups. Hence, computational robustness plays a key role, especially in large simulation cells, in avoiding iterative and often time-consuming process to arrive at definitive solutions in terms of physical properties. A novel and robust approach is presented in general and evaluated for perfluorosulfonic acid (PFSA) polymer structure as a case study. While prior researches have analysed transport and structural properties of such polymers using MD simulation in detail, there is a lack of information on the model standard and equilibration protocol. To this end, the present article compares the proposed algorithm to conventional approaches for structure equilibration and demonstrate that the variation in diffusion coefficients (water and hydronium ions) reduces as the number of chains increases, with significantly reduced errors observed in 14 and 16 chains models, even at elevated hydration. The proposed method to achieve equilibration is ?200% more efficient than conventional annealing and ?600% more efficient than the lean method. © 2025 The Royal Society of Chemistry.