Molecular dynamics simulation analysis of sulfonated polybenzimidazole/[DEMA+][NTf2-]: A potential polymer electrolyte membrane for high-temperature fuel cells

In this research work, the ionic conductivity performance of a prospective candidate polymer electrolyte membrane, sulfonated polybenzimidazole/[DEMA(+)][NTf2(-)], was investigated using the molecular dynamics simulation technique. At first, a unit cell consisting of three chains (each one consisting 30 monomers) of polybenzimidazole polymer was determined as the optimum amorphous unit cell by comparing the simulated solubility parameter and glass transition temperature with available experimental data. Furthermore, the behavior of the ionic self-diffusion coefficients was investigated using the mean square displacement curves. It was found that the diffusion of [DEMA(+)] and [NTf2(-)] depends on the degrees of sulfonation (DS) values: with increasing DS, the ionic self-diffusion coefficients enhance, which could be attributed to a reduction in [DEMA(+)][NTf2(-)] - polymer chains interactions. The results revealed that the simulated ionic conductivities of this ionic liquid-based membrane is comparable with other electrolyte membranes and would be suitable for high-temperature applications. In addition, the investigation was complemented with analysis of plausible proton conduction pathways by evaluating the radial/angular distribution function and cationic/anionic clusters. The results suggest that proton hopping through very short ionic bridges is possible but could not be dominated. This work would pave the way for further research into the new protic ionic liquid -doped sulfonated polybenzimidazole membranes for proton exchange membrane fuel cells. (C) 2022 Elsevier B.V. All rights reserved.

Automated summary

This research work investigated the ionic conductivity performance of a prospective polymer electrolyte membrane using molecular dynamics simulation. The results showed that with increasing sulfonation levels, the diffusion coefficients of ions increased, leading to enhanced ionic conductivity. The simulated ionic conductivities of the membrane were comparable to other electrolyte membranes, making it suitable for high-temperature applications.