Hydration structure of trifluoromethanesulfonate studied by quantum chemical calculations

► We study hydration structure of Nafion ionomer with quantum chemical calculations. ► Trifluoromethanesulfonate (TFMS) uses as a model for Nafion ionomer. ► Hydration of TFMS induces deprotonation and formation of hydronium anion. ► Frequencies of O-H stretching modes increase, deformation modes decrease with number of H+(H2O)n. ► Hydration energies of TFMS decrease with increasing number of deprotonated anion.